@article{Linsenmair1979,
  author    = {Linsenmair, Karl Eduard},
  title     = {Untersuchungen zur Soziobiologie der W{\"u}stenassel Hemilepistus reaumuri und verwandter Isopodenarten (Isopoda, Oniscoidea): Paarbildung und Evolution der Monogamie},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-30854},
  year      = {1979},
  abstract  = {The desert isopod, Hemilepistus reaumuri, extremely common in the arid regions of North Africa and Asia Minor, depends upon the burrows it itself digs for survival during the hotter parts of the year. The dig-ging of new burrows is limited by chmatic conditions to a short period during the spring. Burrows must be constantly defendet - especially against roving eonspecifics. The decisive problem of a connnuous burrow defense is solved through cooperative behavior: the adult woodlice form monogamous pairs whose partners recognize one another individually. Here, questions on the binding of partners, especially the problem of the binding of male to female will be treated upon, along with questions on the evolution of monogamy, wherein the purely maternal families of Porcellio species will be taken as models for intermedi{\"a}re stages. At first, males olHemilepistus are not permitted to copulate at all; later, for a relatively long period, they are only permitted incomplete copulations, the females alone have control over the partunal ecdysis; they alone determine the moment of final copulations. Under the thermal conditions prevalent during the season of pair formation, a female irreversibly induces a parturial ecdysis only when it has spent a minimum of sev-eral days in her own burrow with a specific male. At higher average temperatures, the number of females which undergo parturial ecdyses without these preconditions increases sharply. Males cannot greatly lnrlu-ence the willingness of females to reproduce with the investment they make in the digging of burrows; the factors deciding this are the male's presence and its role as guard. The first condition necessary for the genesis of monogamy might have been the evolution of a stnc{\"u}y lo-cation-dependent copulatory behavior, which guaranteed the male exclusive mating pnveliges with the female whose location - the burrow - he acheived control of. A male must, under these conditions, serve guard duty in his own interest, and defend the burrow against competitors (Cf or 2) seeking an already-dug burrow. The decisive advantage for the female in the beginning of the development was probably that she could leave the burrow for extended feeding excursions, whereas alone it would have to either completely forego nourishment or, as is the case with the Porcellio species mentioned, must greatly restrict the spectrum of food that it can use (to that which is to be found only a short distance from the burrow and which can eas-ily be carried inside the burrow). This could be a disadvantage, especially during egg production. Necessary to the male's successful defense of the burrow is that he recognises his female. Studies of the Canary Island Porcellio species have shown over which pathways and under what selection pressures the recopinon of individuals, as is realized mHemilepistus, could have evolved. Females can bind males longer, the longer the period of their attraction is extended: Females olHemilepistus reaumuri have been proven to be al·ready att-ractive before they are ready to copulate and still remain attractive after they have copulated. The conse-quences of the last fact will be discussed. The question of why the males remain with the females after the parturial ecdysis will also be discussed: The great danger to the male's investment resulting from a tooi early abandoning, and the low probability of successfully finding another partner after a later abandomng should prevent a positive balance in the males' cost-effecriveness calculations.},
  language  = {de}
}
@article{BringmannZagstSchoeneretal.1991,
  author    = {Bringmann, Gerhard and Zagst, Rainer and Sch{\"o}ner, Bernd and Busse, Holger and Hemmerling, Martin and Burschka, Christian},
  title     = {Acetogenic Isoquinoline Alkaloids. XXIII. Structure of the Naphthyl Isoquinoline Alkaloid Dioncophylline A},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-31331},
  year      = {1991},
  abstract  = {No abstract available},
  subject      = {Chemie},
  language  = {en}
}
@article{AlbertBerningBurschkaetal.1981,
  author    = {Albert, Bernhard and Berning, Wilfried and Burschka, Christian and H{\"u}nig, Siegfried and Martin, Hans-Dieter and Prokschy, Frank,},
  title     = {Transanulare Wechselwirkung des Azo-Chromophors inisodrinanalogen Systemen},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-31328},
  year      = {1981},
  abstract  = {No abstract available},
  subject      = {Chemie},
  language  = {de}
}
@article{FialaLinsenmairMaschwitz1994,
  author    = {Fiala, Brigitte and Linsenmair, Karl Eduard and Maschwitz, Ulrich},
  title     = {Diversit{\"a}t von Interaktionen zwischen Ameisen und Pflanzen im s{\"u}dostasiatischen Regenwald},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32894},
  year      = {1994},
  abstract  = {Assoziationen von Ameisen mit Pflanzen (und oft noch mit pflanzensaugenden Insekten als drittem Partner) d{\"u}rften eine Ursache des Artenreichtums und der hohen Abundanzen tropischer Formicidae sein. Die von den Ameisen genutzten Pflanzen bieten entweder Nahrung an, {\"u}ber extraflorale Nektarien und/oder N{\"a}hrk{\"o}rperchen, oder aber - bei den eigentlichen Myrmekophyten - Nistraum und z.T. auch Nahrung. Diese Beziehungen zeichnen sich durch unterschiedliche Nutzungsweisen und Nutzungsintensit{\"a}ten und damit stark differierende Abh{\"a}ngigkeit der Partner voneinander aus. Ein besonders breites Spektrum von Ameisen-Pflanzen-Assoziationen finden wir in der pal{\"a}otropischen Baumgattung Macaranga (Euphorbiaceae), die sich daher als Modellsystem f{\"u}r vergleichende Untersuchungen hervorragend eignet. Die Grundfrage unserer Untersuchungen an diesem System lautet: Verl{\"a}uft aufgrund der ausgepr{\"a}gt mosaikartigen Verteilung der von den myrmekophilen Pflanzen angebotenen Nahrungs- und Nistraumressourcen die Neu- und Wiederbesiedlung von Habitaten durch die Ameisen in Form von Zufallsprozessen? Oder werden, im Gegenteil, durch diesen Umstand Spezialisierungen seitens der Ameisen gef{\"o}rdert und die Zusammensetzung der Lebensgemeinschaften dadurch st{\"a}rker deterministisch gepr{\"a}gt? Unsere bisherigen Untersuchungen zeigen, daß beide Prinzipien wirken. Bei der alleinigen Nutzung von Nahrungsressourcen fehlen spezialisierte Beziehungen weitgehend und stochastische Ereignisse d{\"u}rften sehr h{\"a}ufig die Pflanzen-Ameisen-Assoziation bestimmen. Bei den eigentlichen Myrmekophyten hingegen ist die Auswahl der assozierten Ameisen viel st{\"a}rker determiniert, ganz besonders dann, wenn der Wohnraum, den die Pflanze offeriert, nur durch aktives {\"O}ffnen seitens der Ameisen erschlossen werden kann.},
  language  = {de}
}
@article{ScheerSommervilleMueller1980,
  author    = {Scheer, Ulrich and Sommerville, John and M{\"u}ller, Ulrike},
  title     = {DNA is assembled into globular supranucleosomal chromatin structures by nuclear contents of amphibian oocytes},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39671},
  year      = {1980},
  abstract  = {The assembly of DNA into nucleosomal and supranucleosomal chromatin structures has been studied (i) by injection of circular DNA molecules (plasmids) into nuclei of Pleurodeles waltlii oocytes; and (ii) by in vitro incubation of plasmid molecules with the supernatant fraction from oocyte nuclei of Pleurodeles and Xenopus laevis, followed by purification of nucleoprotein structures formed with sucrose gradient centrifugation. [n both types of experiments , spread preparations of the newly assembled and transcriptionally inactive chromatin , examined by electron microscopy , show dense globular higher order (supranucleosomal) packing forms. Under partially relaxing (low salt) preparation conditions granular chromatin subunits of about 30 nm diameter can be seen either as widely spaced particles or in closely packed aggregates. The transcriptionally inactive endogenous chromatin of chromomeres of lampbrush chromosomes is arranged in similar higher order chromatin units. A correlation is found between the sizes of the DN A molecule probes used and the numbers of nucleosomes and higher order globules in the assembled chromatin structures. After prolonged dispersion in low salt buffers , these globular chromatin units unfold into chains of7-12 nucleosomes. The results support the concept that chromatin is arranged , under physiological ion concentrations as they are present in the nucleus , in supranucleosomal units of globular morphology.},
  language  = {en}
}
@article{HuegleHazanScheeretal.1985,
  author    = {H{\"u}gle, Barbara and Hazan, Rachel and Scheer, Ulrich and Franke, Werner W.},
  title     = {Localization of ribosomal protein S1 in the granular component of the interphase nucleolus and its distribution during mitosis},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39695},
  year      = {1985},
  abstract  = {Using antibodies to various nucleolar and ribosomal proteins, we define, by immunolocalization in situ, the distribution of nucleolar proteins in the different morphological nucleolar subcompartments. In the present study we describe the nucleolar localization of a specific ribosomal protein (51) by immunofluorescence and immunoelectron microscopy using a monoclonal antibody (R5 1-105). In immunoblotting experiments, this antibody reacts specifically with the largest and most acidic protein of the small ribosomal subunit (51) and shows wide interspecies cross-reactivity from amphibia to man. Beside its localization in cytoplasmic ribosomes, this protein is found to be specifically localized in the granular component of the nucleolus and in distinct granular aggregates scattered over the nucleoplasm. This indicates that ribosomal protein 51, in contrast to reports on other ribosomal proteins, is not bound to nascent pre-rRNA transcripts but attaches to preribosomes at later stages of rRNA processing and maturation. This protein is not detected in the residual nucleolar structures of cells inactive in rRNA synthesis such as amphibian and avian erythrocytes. During mitosis, the nucleolar material containing ribosomal protein 51 undergoes a remarkable transition and shows a distribution distinct from that of several other nucleolar proteins. In prophase, the nucleolus disintegrates and protein 51 appears in numerous small granules scattered throughout the prophase nucleus. During metaphase and anaphase, a considerable amount of this protein is found in association with the surfaces of all chromosomes and finely dispersed in the cell plasm. In telophase, protein 51-containing material reaccumulates in granular particles in the nucleoplasm of the newly formed nuclei and, finally, in the re-forming nucleoli. These observations indicate that the nucleolus-derived particles containing ribosomal protein 51 are different from cytoplasmic ribosomes and, in the living cell, are selectively recollected after mitosis into the newly formed nuclei and translocated into a specific nucleolar subcompartment, i.e ., the granular component. The nucleolar location of ribosomal protein 51 and its rearrangement du'ring mitosis is discussed in relation to the distribution of other nucleolar proteins.},
  subject      = {Cytologie},
  language  = {en}
}
@article{ScheerHinssenFrankeetal.1984,
  author    = {Scheer, Ulrich and Hinssen, Horst and Franke, Werner W. and Jockusch, Brigitte M.},
  title     = {Microinjection of actin-binding proteins and actin antibodies demonstrates involvement of nuclear actin in transcription of lampbrush chromosomes},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39706},
  year      = {1984},
  abstract  = {Nuclei of amphibian oocytes contain large amounts of actin, mostly in unpolymerized or short-polymer form. When antibodies to actin or actin-binding proteins (fragmin and the actin modulator from mammalian smooth muscle) are injected into nuclei of living oocytes of Pleurodeles waltlii, transcription of the lampbrush chromosomes, but not of the rRNA genes, is inhibited. When transcription is repressed by drugs or RNA is digested by microinjection of RNAase into oocyte nuclei, an extensive meshwork of actin filament bundles is seen in association with the isolated lampbrush chromosomes. These observations indicate a close relationship between the state of nuclear actin and transcriptional activity and suggest that nuclear actin may be involved in transcriptional events concerning protein-coding genes.},
  language  = {en}
}
@article{ScheerHansmannFalketal.1986,
  author    = {Scheer, Ulrich and Hansmann, Paul and Falk, Heinz and Sitte, Peter},
  title     = {Ultrastructural localization of DNA in two Cryptomonas species by use of a monoclonal DNA-antibody},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39746},
  year      = {1986},
  abstract  = {Immunogold cytochemistry - DNA localization - Cryptomonas nucleomorph The distribution and subcellular localization of DNA in the unicellular alga Cryptomonas has been investigated electron-microscopically by indirect immunocytochemistry, using a monoclonal DNA antibody and a gold-Iabeled secondary antibody. This technique proved to be very sensitive and entirely specific. DNA could be demonstrated in four different compartments (nucleus, nucleomorph, plastid, and mitochondrion). Within the plastid, DNA is concentrated in stroma regions that are localized preferentially around the center of the organelle. The mitochondrion contains several isolated DNA-containing regions (nucleoids). Within the nucleus, most of the DNA is localized in the 'condensed' chromatin. DNA was also detectable in small areas of the nucleolus, whereas the interchromatin space of the nucleus appeared almost devoid of DNA. Within the nucleomorph, DNA is distributed inhomogeneously in the matrix. DNA could furthermore be detected in restricted areas of the 'fibrillogranular body' of the nucleomorph, resembling the situation encountered in the nucleol us. The presence of DNA and its characteristic distribution in the nucleomorph provide additional, strong evidence in favour of the interpretation of that organelle as the residual nucleus of a eukaryotic endosymbiont in Cryptomonas.},
  subject      = {Cytologie},
  language  = {en}
}
@article{Scheer1978,
  author    = {Scheer, Ulrich},
  title     = {Changes of nucleosome frequency in nucleolar and non-nucleolar chromatin as a function of transcription: an electron microscopic study},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39750},
  year      = {1978},
  abstract  = {The morphology of nucleolar and non-nucleolar (Iampbrush chromosome loops) chromatin was studied in the electron microscope during states of reduced transcriptional activity in amphibian oocytes (Xenopus laevis, Triturus alpestris, T. cristatus). Reduced transcriptional activity was observed in maturing stages of oocyte development and after treatment with an inhibitor, actinomycin D. Strands of nucleolar chromatin appear smooth and thin, and contain only few, if any, nucleosomal particles in the transcribed units. This is true whether they are densely or only sparsely covered with lateral ribonucleoprotein fibrils. This smooth and non-nucleosomal character is also predominant in the interspersed, apparently nontranscribed rDNA spacer regions. During inactivation, however, nucleolar chromatin frequently and progressively assumes a beaded appearance in extended fibril-free-that is, apparently nontranscribed - regions. I n either fUll-grown 00- cytes or late after drug treatment, most of the nucleolar chromatin is no longer smooth and thin, but rather shows a beaded configuration indistinguishable from inactive non - nucleolar chromatin. In many chromatin strands, transitions of fibril-associated regions of smooth character into beaded regions wihout lateral fibrils are seen. Similarly, in the non-nucleolar chromatin of the retracting lampbrush chromosome loops, reduced transcriptional activity is correlated with a change from smooth to beaded morphology. Here, however, beaded regions are also commonly found interspersed between the more or less distant bases of the lateral fibrils, the putative transcriptional complexes. I n both sorts of chromatin, detergents (in particular Sarkosyl) that remove most of the chromatin proteins including histones from the DNA axis but leave the RNA polymerases of the transcriptional complexes attached were used to discriminate between polymerases and nucleosomal particles. The results suggest that nucleosomes are absent in heavily transcribed chromatin regions but are reformed after inactivation. In contrast to the findings with inactivated nucleolar genes, in lampbrush chromosome loops the beaded nucleosomal configuration appears to be assumed also in regions within transcriptional units that, perhaps temporarily, are not involved in transcription.},
  language  = {en}
}
@article{ScheerSommerville1981,
  author    = {Scheer, Ulrich and Sommerville, J.},
  title     = {Structural organization of nascent transcripts and hnRNA molecules in amphibian oocytes},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39765},
  year      = {1981},
  abstract  = {Comparisons ofrelative lengths oflampbrush loops, nascent RNP transcripts and hnRNA molecules from oocytes of amphibia with different C-values show that there is an increasing trend in loop, and transcriptional unit, length with increase in genome size but no increasing trend with respect to RN A contour length.The formation of duplex regions and circles in RNP fibrils indicates that RNA processing may occur within the nascent fibrils. The hnRNA molecules from oocytes of the various amphibia readily form intermolecular duplex structures. These complementary sequences have a low kinetic complexity and are transcribed from highly repetitive sequences distributed throughout the genome. Their possible function is considered.},
  language  = {en}
}
@article{ScheerSchmidtZachmannHuegleetal.1984,
  author    = {Scheer, Ulrich and Schmidt-Zachmann, Marion S. and H{\"u}gle, Barbara and Franke, Werner W.},
  title     = {Identification and localization of a novel nucleolar protein of a high molecular weight by a monoclonal antibody},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39786},
  year      = {1984},
  abstract  = {A monoclonal murine antibody (No-I 14) is described which reacts specifically with a polypeptide of molecular weight (M,) 180000 present in low-speed nuclear pellets from oocytes and somatic cells of Xenopus laevis and X. borealis and in isolated amplified nucleoli. Two-dimensional gel electrophoresis has revealed the acidic nature of this polypeptide (isoelectric at pH of ca 4.2 in the presence of 9.5 M urea). A relatively large proportion of the protein is extracted at elevated ionic strength( i.e., at 0.4-0.5 M alkali salt) in a form sedimenting at approx. 7-8S , compatible with a monomeric state. It is also extracted by digestion with RNase but not with DNase. In immunofluorescence microscopy, antibody No-114 stains intensely nucleoli of oocytes and all somatic cells examined , including the residual nucleolar structure of Xenopus erythrocytes which are transcriptionally inactive. During mitosis the antigen does not remain associated with the nucleolar organizer regions (NOR) of chromosomes but is released and dispersed over the cytoplasm until telophase when it re-associates with the reforming interphase nucleoli. At higher resolution the immunofluorescent region is often resolved into a number of distinct subnucleolar components of varied size and shape. Immunoelectron microscopy using colloidal gold-coupled secondary antibodies reveals that the M, 180000 protein is confined to the dense fibrillar component of the nucleolus. This conclusion is also supported by its localization in the fibrillar part of segregated nucleoli of cells treated with actinomycin D. We conclude that nucleoli contain a prominent protein of M, 180000 which contributes to the general structure of the dense fibrillar component of the interphase nucleolus , independent of its specific transcriptional activity.},
  language  = {en}
}
@article{Schuessler1988,
  author    = {Sch{\"u}ssler, Ulrich},
  title     = {Mobilisation einzelner Elemente in Amphiboliten aus der Umgebung der KTB-Lokation, Zone Erbendorf-Vohenstrauss, n{\"o}rdliche Oberpfalz},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39248},
  year      = {1988},
  abstract  = {No abstract available},
  subject      = {Mineralogie},
  language  = {de}
}
@article{ThiryScheerGoessens1991,
  author    = {Thiry, Marc and Scheer, Ulrich and Goessens, Guy},
  title     = {Localization of nucleolar chromatin by immunocytochemistry and in situ hybridization at the electron microscopic level},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39289},
  year      = {1991},
  abstract  = {Nucleoli are the morphological expression of the activity of a defined set of chromosomal segments bearing rRNA genes. The topological distribution and composition of the intranucleolar chromatin as well as the definition of nucleolar structures in which enzymes of the rDNA transcription machinery reside have been investigated in mammalian cells by various immunogold labelling approaches at the ultrastructural level. The precise intranucleolar location of rRNA genes has been further specified by electron microscopic in situ hybridization with a non-autoradiographic procedure. Our results indicate that the fibrillar centers are the sole nucleolar structures where rDNA, core histones, RNA polymerase I and DNA to po isomerase I are located together. Taking into account the potential value and limitations of immunoelectron microscopic techniques, we propose that transcription of the rRNA genes takes place within the confines of the fibrillar centers, probably close to the boundary regions to the surrounding dense fibrillar component.},
  language  = {en}
}
@article{GesslerKoenigArdenetal.1994,
  author    = {Gessler, Manfred and K{\"o}nig, A. and Arden, K. and Grundy, P. and Orkin, S. H. and Sallan, S. and Peters, C. and Ruyle, S. and Mandell, J. and Li, F. and Cavenee, W. and Bruns, G. A.},
  title     = {Infrequent mutation of the WT1 gene in 77 Wilms' Tumors},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-34308},
  year      = {1994},
  abstract  = {Homozygous deletions in Wilms' tumor DNA have been a key step in the identification and isolation of the WTI gene. Several additional loci are also postulated to contribute to Wilms' tumor formation. To assess the frequency of WTI alterations we have analyzed the WTI locus in a panel of 77 Wilms' tumors. Eight tumors showed evidence for large deletions of several hundred or thousand kilobasepairs of DNA, some of which were also cytogenetically detected. Additional intragenic mutations were detected using more sensitive SSCP analyses to scan all 10 WTI exons. Most of these result in premature stop codons or missense mutations that inactivate the remaining WTI allele. The overall frequency of WTI alterations detected with these methods is less than 15\%. While some mutations may not be detectable with the methods employed, our results suggest that direct alterations of the WTI gene are present in only a small fraction of Wilms' tumors. Thus, mutations at other Wilms' tumor loci or disturbance of interactions between these genes likely play an important role in Wilms' tumor development.},
  language  = {en}
}
@article{Ellgring1992,
  author    = {Ellgring, Johann Heinrich},
  title     = {Psychosoziale Aspekte des Morbus Parkinson},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-34052},
  year      = {1992},
  abstract  = {No abstract available},
  language  = {de}
}
@article{Koenig1984,
  author    = {K{\"o}nig, Dorothea},
  title     = {Materialien zu den Fragmenten des Mihanovic-Homiliars},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-38566},
  year      = {1984},
  abstract  = {No abstract available},
  language  = {ru}
}
@article{Koenig1986,
  author    = {K{\"o}nig, Dorothea},
  title     = {Materialien zu den Fragmenten des Mihanovic-Homiliars},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-38599},
  year      = {1986},
  abstract  = {No abstract available},
  language  = {ru}
}
@article{Koenig1974,
  author    = {K{\"o}nig, Dorothea},
  title     = {Notizen zum Wortschatz des Vatikanski Hrvatski Molitvenik},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-38740},
  year      = {1974},
  abstract  = {No abstract available},
  language  = {de}
}
@article{KoenigAitzetmueller1987,
  author    = {K{\"o}nig, Dorothea and Aitzetmueller, Rudolf},
  title     = {Die Slavistik an der Universit{\"a}t W{\"u}rzburg},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-38778},
  year      = {1987},
  abstract  = {No abstract available},
  language  = {de}
}
@article{Hee2009,
  author    = {Hee, Katrin},
  title     = {Nicht Tabu},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39075},
  year      = {2009},
  abstract  = {Dieser Artikel beschreibt eine Unterrichtssequenz f{\"u}r den Deutschunterricht im Bereich Deutsch als Fremdsprache und richtet sich an Lernende der Niveaustufe A2. Er zeigt, wie Lernende spielerisch sowohl rezeptive Sprachkenntnisse als auch aktive Sprachbeherrschung verbessern und ihren Wortschatz erweitern k{\"o}nnen. Ein besonders wichtiges Kriterium sind dabei der Spielcharakter und die Auflockerung des Unterrichts, sowie die M{\"o}glichkeit, individuell auf die Bed{\"u}rfnisse der Studenten eingehen zu k{\"o}nnen.},
  subject      = {Wortschatz},
  language  = {de}
}
@article{Hee2009,
  author    = {Hee, Katrin},
  title     = {Ein internationales Kochbuch},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39067},
  year      = {2009},
  abstract  = {In diesem Artikel wird eine Unterrichtssequenz beschrieben, die sich {\"u}ber einen Zeitraum von zirka 2 Wochen hinzieht und sich an Deutschlernende auf A1-Niveau richtet. Unterrichtsprojekt und Inhalt des Artikels ist ein internationales Kochbuch, das die Studenten selbst entwerfen. Das Projekt eignet sich besonders zur Binnendifferenzierung von großen Gruppen. Jedes Kapitel wird von einer Gruppe bearbeitet, so dass die Studenten je nach F{\"a}higkeiten und Lerntempo individuell ihr Wissen anwenden und erweitern k{\"o}nnen. Der Artikel gibt einen {\"U}berblick {\"u}ber die einzelnen Kapitel des Kochbuches, die jeweiligen Lernziele und allgemeine didaktische Hinweise in Bezug auf das Projekt.},
  subject      = {Projektarbeit},
  language  = {de}
}
@article{Apostoiu2009,
  author    = {Apostoiu, Nicoleta},
  title     = {Theater im Franz{\"o}sischunterricht: "Die ausgeflippte Familie"},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39089},
  year      = {2009},
  abstract  = {Das Hauptziel des Projekts war, internationale Studenten auf A1-Niveau zu motivieren, damit sie ihre kommunikative Kompetenz in Franz{\"o}sisch verbessern konnten. Da sich kein geeignetes Material f{\"u}r dieses Projekt fand, entwarf ich ein Projekt, um den Stoff vom gesamten Semesterkurs zu wiederholen.},
  subject      = {Projektarbeit},
  language  = {de}
}
@article{Ramos2009,
  author    = {Ramos, Carmen},
  title     = {Schl{\"u}sselbegriff: Handlungs- und Aufgabenorientierung},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39054},
  year      = {2009},
  abstract  = {Kurze Darstellung des Begriffs "Handlungsorientierung".},
  subject      = {Handlungsorientierung},
  language  = {de}
}
@article{RamosWildenauerJozsa2009,
  author    = {Ramos, Carmen and Wildenauer-J{\´o}zsa, Doris},
  title     = {Learning by doing: Eine handlungsorientierte Fortbildungsveranstaltung {\"u}ber Handlungsorientierung},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39049},
  year      = {2009},
  abstract  = {Der Artikel stellt Hintergr{\"u}nde, Ablauf und Ergebnisse eines als universit{\"a}re Dozentenfortbildung konzipierten Workshops zum Thema Handlungsorientierung vor.},
  subject      = {Handlungsorientierung},
  language  = {de}
}
@article{Karagiannakis2009,
  author    = {Karagiannakis, Evangelia},
  title     = {Projektorientierte Landeskunde im DaF-Unterricht - Eine Kooperation zwischen DaF-Lernern und Lehramtsstudierenden},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39031},
  year      = {2009},
  abstract  = {DaF-Unterricht an Hochschulen hat zum Ziel, nicht-deutschen Studierenden m{\"o}glichst z{\"u}gig die deutsche Sprache zu vermitteln. Da sie sich bereits im Zielsprachenland aufhalten und hier (f{\"u}r begrenzte Zeit) leben, ist es wichtig, auch landeskundliche Kenntnisse zu erwerben. Beides geschieht im universit{\"a}ren Sprachunterricht aufgrund von {\"a}ußeren Rahmenbedingungen oft sehr "kopflastig". Projektorientierte Methoden k{\"o}nnen hier Abhilfe schaffen, da jeder einzelne Lernerde sehr viel intensiver selbst aktiv werden muss als im herk{\"o}mmlichen Sprachunterricht. Besonders gewinnbringend werden Projekte, wenn sie in Kooperation mit deutschen Muttersprachlern, am besten k{\"u}nftigen DeutschlehrerInnen stattfinden. Diese sind nicht nur authentische Gespr{\"a}chspartner, sondern haben zudem auch (in unterschiedlich ausgepr{\"a}gtem Maße) didaktische Kenntnisse, die in die Projektarbeit einfließen. Sie selbst k{\"o}nnen in solchen Kooperationen wichtige Erfahrungen f{\"u}r ihren Lehrberuf sammeln. Wie dies in der Praxis aussehen kann, soll in diesem Beitrag exemplarisch vorgestellt werden.},
  subject      = {Projektarbeit},
  language  = {de}
}
@article{Holstein2009,
  author    = {Holstein, Silke},
  title     = {Web-Spaziergang - eine virtuelle Reise},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39029},
  year      = {2009},
  abstract  = {Im Artikel wird ein binationales Internet-Projekt beschrieben. Daran nahmen ein Deutschkurs der Universit{\"a}t Alcal{\´a} de Henares in Spanien und zwei Spanischkurse der Universit{\"a}t W{\"u}rzburg teil. Diese tauschten sich {\"u}ber einen Web-Blog aus. Das Ziel war, die jeweilige Stadt vorzustellen und so der anderen Seite einen virtuellen Besuch im Land der Zielsprache zu erm{\"o}glichen. Der Artikel beschreibt den didaktischen Umgang mit dem Blog und gibt Hinweise f{\"u}r Lehrende, die einen Blog im Unterricht einsetzen m{\"o}chten.},
  subject      = {Handlungsorientierung},
  language  = {de}
}
@article{FrankeScheer1970,
  author    = {Franke, Werner W. and Scheer, Ulrich},
  title     = {The ultrastructure of the nuclear envelope of amphibian oocytes: a reinvestigation. I. The mature oocyte},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32098},
  year      = {1970},
  abstract  = {1 n order to review the contradictory statements on the ultrast ructure of the nuclear envelope, a study was undertaken combining section and negat ive stai ning electron microscopy on manually isolated oocyte nuclei and nuclear envelopes from six amphibian species including Anura as well as Urodela. The a ppeara nce of the negatively stained iso lated nuclear envelopes is described in deta il and the dependence on the preparation co nditions used is emphas ized . Pore complex structures such as pore perimeter, central granule, an nul ar components, interna l fibrils, and annu lus-attached fibrils could be identified by both techniques, negat ive staining and sect ions. Comparative studies show that no marked diffe rences ex ist in the structural data of the nuclear envelope among the investigated amphibians and the significance of the structural components is discussed. A model of the nuclea r pore complex based on the findings of the present investigation is prese nted.},
  language  = {en}
}
@article{QuastSchmittSchaeferetal.1994,
  author    = {Quast, Helmut and Schmitt, Edeltraud and Sch{\"a}fer, Peter and Heller, Eberhard and Aldenkortt, Sven},
  title     = {Synthesis and Thermolysis of a Chiral, Non-Racemic Iminoaziridine},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-38298},
  year      = {1994},
  abstract  = {The 2-halo imidoyl chlorides 7 are obtained from the amide 5 and the 2-halo amides 6 by the action of phosphorus pentachloride and thionyl chloride, respectively. Non-racemic (S)-6a is converted into 7a which is racemic, however. The reaction of Lawesson's reagent with 6a furnishes the diastereomeric 1,3.2-thiazaphospholidine derivatives 15. Treatment of (S)-6a (98\% eel with methyl triflate affords 2-chloro imidate 8 (95\% eel which reacts with methanamine in the presence of methanammonium chloride to yield the 2-chloro amidine (S)-9a (90\% eel. The 2-halo imidoyl halides 7a and b react with methanamine to produce the 2-halo amidines 9a and b. - Strong bases, e.g. potassium tert-butoxide or sodium hydride in the presence of catalytic amounts of tertbutyl alcohol, eliminate hydrogen chloride or bromide from the 2-halo amidines 9a and band (S)-9a to yield mixtures of Recently, we demonstrated that the formation of the chiral non-racemic aziridinone (R)-2 from the a-chloro amide (5)-1 by base-promoted dehydrochlorination[2) as well as the nucleophilic cleavage of the N-C(3) bond of (R)_2[3,4) occur with inversion of configuration, thus excluding the intervention of achiral (acyclic) intermediates. In the temperature range of lOO-170°C, however, slow racemization accompanies the thermolysis of (R)-2 and indicates the existence of an achiral or a racemic transient, e. g. (M)-3 + (P)-3. Indeed, high-level quantum-chemical calculations reveal that an activation energy of (170 ± 25) kJmol- 1 is required for the unimolecular ring opening of the parent aziridinone which affords a species of high diradical character[41. Subsequently, the unstable N-phenylaziridinone invoked in the decomposition of the (5)-2-bromopropananilide anion was shown to react with tert-butylamine or dimethylformamide with inversion of configuration at C(3)[51. Thus, the stereochemical evidence in the series of 3-alkylaziridinones excludes achiral (acyclic) aziridinone isomers as intermediates at low tempera tures [6J. Similar stereochemical studies are still missing in the related series of iminoaziridines. Therefore, we report on the synthesis and thermolysis of the diastereomeric chiral racemic (E)- and (Z)-(4)[71 and non-racemic iminoaziridines (E,R)- and (Z,R)-4. Racemic Iminoaziridines (E)- and (Z)-4 Though a photochemical route to the iminoaziridines (E)- and (Z)-4 has been devised more recently, i. e. the phothe 2-iminoaziridines (E)- and (Z)-4, and (E,R)- and (Z.R)-4 (83\% eel, respectively. The 1.3-elimination of hydrogen bromide from 9b is diastereoselective at -30 to -40°C [(E)-4:(Z)-4 = <10:>90). The diastereomers equilibrate at 36°C with (kEZ + k ZE) = (5.92 ± 0.08) . 10-5 S-I (K = kEZlkzE = 0.428 ± 0.013). - The thermolysis of (E)- and (Z)-4 in [D61benzene solution yields the imine 16 and methyl isocyanide (17). The decomposition follows the first-order rate law. The following Arrhenius and Eyring parameters are calculated from five rate constants obtained in the temperature range of 70-110°C: Ea = (115.2 ± 0.4) kJmol-t, IgA = (12.06 ± 0.28), AH* = (112.1 ± 0.4) kJmol- l , AS'" = (-23.9 ± 0.7) JK-I mol-I, AGj73K = 121 kJmol-1 . The enantiomeric excess of the surviving fraction of (E,R)- and (Z.R)-4 is unchanged after two half-lives at 80°C.},
  language  = {en}
}
@article{HellerHerdeis1993,
  author    = {Heller, Eberhard and Herdeis, Claus},
  title     = {Synthesis of 2S,5S- and 2R,5S-5-Hydroxypipecolic Acid via Amide-Methylenation of S-5-Hydroxy-2-piperidone with Dimethyltitanocene},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-38288},
  year      = {1993},
  abstract  = {A route to 2S,5S-and 2R,5S-hydroxypipecolic acid is presented, starting with the enantiopure 5S-5-hydroxy-piperidone 7. The key step of this reaction sequence is the chemoselsctive methylenation of the amide carbonyl group of 8 with dimethyltitanocene 9 to 10. The transformation of the exocyclic enecarbamate double bond to the carboxylic acid group is best accomplished via hydroboration/oxidation to the alcohol 11a,b. Separation and oxidation of the dlastereomers 11a,b, to 148. and 14b, and hydrolysis furnishes the diastereomeric pipecolic acids 15a and 15b in enantiopure form.},
  subject      = {Chemie},
  language  = {en}
}
@article{Ruhe1989,
  author    = {Ruhe, Ernstpeter},
  title     = {Erz{\"a}hlen nach der Avantgarde. Rachid Boudjedras Weiterentwicklung des modernen Romans},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-38266},
  year      = {1989},
  abstract  = {No abstract available},
  language  = {de}
}
@article{Ruhe1982,
  author    = {Ruhe, Ernstpeter},
  title     = {Du songe {\`a} la r{\´e}alit{\´e} ou de la r{\´e}alit{\´e} au songe? Die j{\"u}ngsten Romane Mongo Betis},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-38191},
  year      = {1982},
  abstract  = {No abstract available},
  language  = {de}
}
@article{ReimerRaskaScheeretal.1988,
  author    = {Reimer, Georg and Raska, Ivan and Scheer, Ulrich and Tan, Eng M.},
  title     = {Immunolocalization of 7-2-ribonucleoprotein in the granular component of the nucleolus},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33890},
  year      = {1988},
  abstract  = {Certain autoimmune sera contain antibodies against a nucleolar ribonucleoprotein particle associated with 7-2-RNA (R. Reddy et al. (1983) J. Bioi. Chem . 258, 1383; C. Hashimoto and J. A. Steitz (1983) J. Bioi. Chem. 258, 1379). In this study, we showed by immunofluorescence microscopy that antibodies reactive with 7-2-ribonucleoprotein immunolocalized in the granular regions of actinomycin D and 5,6-dichloro-I-j3-D-ribofuranosylbenzimidazole (DRB)-segregated nucleoli from Vero cells. By electron microscopic immunocytochemistry, antigen-antibody complexes were located in the granular component of transcriptionally active nucleoli from rat liver hepatocytes and HeLa cells. Anti-7- 2-RNP antibodies from two autoimmune sera immunoprecipitated a major protein of Mr 40,000 from e5S] methionine-Iabeled HeLa cell extract. The immunolocalization data suggest that 7-2-ribonucleoprotein may be involved in stages of ribosome biogenesis which take place in the granular component of the nucleolus, i.e., assembly, maturation, and/or transport of preribosomes},
  language  = {en}
}
@article{SommervilleScheer1982,
  author    = {Sommerville, John and Scheer, Ulrich},
  title     = {Transcription of complementary repeat sequences in amphibian oocytes},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33915},
  year      = {1982},
  abstract  = {Repeat sequences are transcribed in the germinal vesicles of amphibian oocytes. In the hnRNA population both complements of the repeats are found and can be readily detected because they form intermolecular duplex structures. The structure and formation of duplex regions have been studied in the hnRNA of Xenopus laevis, Triturus cristatus, Amphiuma means and Necturus maculosus, a series of amphibians of increasing genome size (C-value). In T. cristatus, the duplex structures are mostly 600- 1200 bp in length, whereas in X. laevis they are shorter and in N. maculosus they tend to be longer. Although the proportion of RNA sequence capable of rapidly forming duplex structures is different in different organisms, this property bears no relationship to C-value. However the sequence complexity of complementary repeats, as estimated from the rate of duplex formation, does show an increasing trend with C-value. The complementary repeats found in oocyte hnRNA are transcribed from families of DNA sequence that are each represented in the genome by thousands of copies. The extent of cross-species hybridization is low, indicating that the repeat sequences transcribed in different amphibian genera are not the same. In situ hybridization experiments indicate that the repeat sequences are spread throughout the genome. The evolution and possible function of complementary repeats are considered.},
  language  = {en}
}
@article{BenaventeRoseReimeretal.1987,
  author    = {Benavente, Ricardo and Rose, Kathleen M. and Reimer, Georg and H{\"u}gle-D{\"o}rr, Barbara and Scheer, Ulrich},
  title     = {Inhibition of nucleolar reformation after microinjection of antibodies to RNA polymerase I into mitotic cells},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33247},
  year      = {1987},
  abstract  = {The formation of daughter nuclei and the reformation of nucleolar structures was studied after microinjection of antibodies to RNA polymerase I into dividing cultured cells (PtK2). The fate of several nucleolar proteins representing the three main structural subcomponents of the nucleolus was examined by immunofluorescence and electron microscopy. The results show that the RNA polymerase I antibodies do not interfere with normal mitotic progression or the early steps of nucleologenesis, i.e. , the aggregation of nucleolar material into prenucleolar bodies. However,they inhibit the telophasic coalescence of the prenucleolar bodies into the chromosomal nucleolar organizer regions, thus preventing the formation of new nucleoli. These prenucleolar bodies show a fibrillar organization that also compositionally resembles the dense fibrillar component of interphase nucleoli . We conclude that during normal nucleologenesis the dense fibrillar component forms from preformed entities around nucleolar organizer regions, and that this association seems to be dependent on the presence of an active form of RNA polymerase I.},
  language  = {en}
}
@article{FrankeBergerFalketal.1974,
  author    = {Franke, Werner W. and Berger, S. and Falk, Heinz and Spring, H. and Scheer, Ulrich and Trendelenburg, Michael F. and Schweiger, H. G. and Herth, W.},
  title     = {Morphology of the nucleo-cytoplasmic interactions during the development of Acetabularia cells. I. The vegetative phase},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32363},
  year      = {1974},
  abstract  = {The ultrastructure of th e growin g and ma turing primary nucleus of Acetabularia medite rranea and Acetabularia major has been studied with the use of various fi xation procedures. Particular interest has been focused on the deta ils of the nuclear periphery and the perinuclear region. It is demonstrated that early in nuclear grow th a characteristic perinucl ear structura l complex is formed which is, among the eukaryotic cells, unique to Acetabularia and re lated genera. This perinuclear system consists essentially of a) the nuclear envelope with a very hi gh pore frequency and various pore complex assoc iat ion s w ith granular and/or threadlike structures some of which are continuous with the nucleolus; b) an approx imate ly 100 nm thick intermediate zone densely filled with a filam entOus material and occasional sma ll membraneous structures from which the typical cytOplasmic and nuclear organe lles and particles are excl ud ed ; c) an adjacent Iacunar labyrinthum which is interrupted by many plasmatic junction channels between the intermed iate zone and the free cytOplasm; d) numerous dense perinuclear bodies in the juxtanuclear cytOplasm which a re especia lly frequent at the junction channels and reveal a composition of aggregated fibrillar and granul ar structures; e) very dense exclusively fibrill ar agg regates which occur either in assoc iation with t he perinuclear region of the lacunar labyrinthum or, somewhat further out, in the cytOplasmic strands between the bra nches of the lacun ar labyrinthum in the form of slender, characteristic rods or "sausages".},
  language  = {en}
}
@article{Scheer1973,
  author    = {Scheer, Ulrich},
  title     = {Nuclear pore flow rate of ribosomal RNA and chain growth rate of its precursor during oogenesis of Xenopus laevis},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32178},
  year      = {1973},
  abstract  = {The number of ribosomal RNA molecules which are transferred through an average nuclear pore complex per minute into the cytoplasm (nuclear pore flow rate, NPFR) during oocyte growth of Xenopus laevis is estimated. The NPFR calculations are based on determinations of the increase of cytoplasmic rRNA content during defined time intervals and of the total number of pore complexes in the respective oogenesis stages. In the mid-la mpbrush stage (500:"700 I'm oocyte diameter) the NPFR is maximal with 2.62 rRNA molecules/ pore/ minute. Then it decreases to zero at the end of oogenesis. The nucleocytoplasmic RNA f10w rates determined are compared with corresponding values of other cell types. The molecular weight of the rRNA precursor transcribed in the extrachromosomal nucleoli of Xenopus lampbrush stage oocytes is determined by acrylamide gel electrophoresis to be 2.5 x 10· daltons. From the temporal increase of cytoplasmic rRNA (3.8 I'g per oocyte in 38 days) and the known number of simultaneously growing precursor molecules in the nucleus the chain growth rate of the 40 S precursor RNA is estimated to be 34 nucleotides per second.},
  language  = {en}
}
@article{ScheerFranke1969,
  author    = {Scheer, Ulrich and Franke, Werner W.},
  title     = {Negative staining and adenosine triphosphatase activity of annulate lamellae of newt oocytes},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32087},
  year      = {1969},
  abstract  = {Semi -iso la ted annul a te lamellae were prepared from single newt oocy tes (Triturus alpestris) by a modified Call a n-T omlin technique. Such preparations were examined with the electron mi croscope, and the negative sta ining a ppearance of th e a nnulate lamellae is described . The annul a te lamellae can be de tected either adhering to the nuclear envelope or being detached from it. Sometimes they a re obse rved to be connected with slender tubular-like structures interpreted as pa rts of the endoplasmic reti culum. The results obta ined from negativ e sta ining a re combined with those from sections. Especially, the structural data on th e a nnula te lamellae and the nuclear envelope of the very same cell were compa red . Evidence is presented th a t in the oocytes studied the two kinds of porous cisternae, n amely a nnul a te lamellae and nuclear envelope, a re markedly distinguished in that the annul a te lamellae ex hibit a much higher pore frequency (generally about twice tha t found for the corresponding nuclear envelope) and have al so a rela tive pore area occupying as much as 32 \% to 55 \% of th e cistern al surface (compa red with 13 \% to 22 \% in the nuclear envelopes). T he pore di ame ter a nd all other ultras tructural details of the pore complexes, however, a re equi valent in both kinds of porous cisternae. Like the annuli of the nuclear pore complexes of various a nimal and pl ant cells, the a nnuli of the a nnula te lamellae pores reveal al so an eightfold symmetry of their subunits in negatively stained as well as in ectioned ma teria l. Furthermore, th e a nnul a te lamellae a re shown to be a site of activity of the Mg-Na-Kstimul a ted ATPase.},
  language  = {en}
}
@article{RoseSzopaHanetal.1988,
  author    = {Rose, Kathleen M. and Szopa, Jan and Han, Fu-Sheng and Cheng, Yung-Chi and Richter, Arndt and Scheer, Ulrich},
  title     = {Association of DNA topoisomerase I and RNA polymerase I: A possible role for topoisomerase I in ribosomal gene transcription},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33901},
  year      = {1988},
  abstract  = {RNA polymerase I preparations purified from a rat hepatoma contained DNA topoisomerase activity. The DNA topoisomerase associated with the polymerase had an Mr of 110000, required Mg2+ but not ATP, and was recognized by anti-topoisomerase I antibodies. When added to RNA polymerase I preparations containing topoisomerase activity, anti-topoisomerase I antibodies were able to inhibit the DNA relaxing activity of the preparation as well as RNA synthesis in vitro. RNA polymerase II prepared by analogous procedures did not contain topoisomerase activity and was not recognized by the antibodies. The topoisomerase I: polymerase I complex was reversibly dissociated by column chromatography on Sephacryl S200 in the presence of 0.25 M (NH4hS04. Topoisomerase I was immunolocalized in the transcriptionally active ribosomal gene complex containing RNA polymerase I in situ. These data indicate that topoisomerase I and RNA polymerase I are tightly complexed both in vivo and in vitro, and suggest a role for DNA topoisomerase I in the transcription of ribosomal genes.},
  language  = {en}
}
@article{RoeschAtzmuellerSchaacketal.1994,
  author    = {R{\"o}sch, M. and Atzm{\"u}ller, R. and Schaack, G. and Becker, Charles R.},
  title     = {Resonant Raman scattering in a zero-gap semiconductor: Interference effects and deformation potentials at the E\(_1\) and E\(_1\) + \(\Delta_1\) gaps of HgTe},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-38062},
  year      = {1994},
  abstract  = {No abstract available},
  language  = {en}
}
@article{KrausBeckerScholletal.1993,
  author    = {Kraus, M. M. and Becker, Charles R. and Scholl, S. and Wu, Y. S. and Yuan, S. and Landwehr, G.},
  title     = {Infrared photoluminescence on molecular beam epitaxially grown Hg\(_{1-x}\)Cd\(_x\)Te layers},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-38053},
  year      = {1993},
  abstract  = {No abstract available},
  language  = {en}
}
@article{HeBeckerBicknellTassiusetal.1993,
  author    = {He, L. and Becker, Charles R. and Bicknell-Tassius, R. N. and Scholl, S. and Landwehr, G.},
  title     = {Molecular beam epitaxial growth of (100) Hg\(_{0.8}\)Cd\(_{0.2}\)Te on Cd\(_{0.96}\)Zn\(_{0.04}\)Te},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-38044},
  year      = {1993},
  abstract  = {No abstract available},
  language  = {en}
}
@article{WuBeckerWaagetal.1993,
  author    = {Wu, Y. S. and Becker, Charles R. and Waag, A. and von Schierstedt, K. and Bicknell-Tassius, R. N. and Landwehr, G.},
  title     = {Surface sublimation of zinc blende CdTe},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-37829},
  year      = {1993},
  abstract  = {The surface sublimation of Cd and Te atoms from the zinc blende (111)A CdTe surface has been investigated in detail by reflection high energy electron diffraction and x-ray photoelectron spectroscopy. These experiments verify that Te is much easier to evaporate than Cd. The experimental value for the Te activation energy from a Te stabilized (111)A CdTe surface is 1.41 ±0.1O eV, which is apparently inconsistent with recent theoretical results.},
  language  = {en}
}
@article{WuBeckerWaagetal.1992,
  author    = {Wu, Y. S. and Becker, Charles R. and Waag, A. and Bicknell-Tassius, R. N. and Landwehr, G.},
  title     = {Thermal effects on (100) CdZnTe substrates as studied by x-ray photoelectron spectroscopy and reflection high energy electron diffraction},
  issn      = {0003-6951},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-37801},
  year      = {1992},
  abstract  = {The influence of different CdZnTe substrate treatments prior to II-VI molecular beam epitaxial growth on surface stoichiometry, oxygen, and carbon contamination has been studied using x-ray photoelectron spectroscopy and reflection high energy electron diffraction. Heating the substrate at 300 °C can eliminate oxygen contamination, but cannot completely remove carbon from the surface. Heating at higher temperatures decreases the carbon contamination only slightly, while increasing the Zn-Cd ratio on the surface considerably. The magnitude of the latter effect is surprising and is crucial when one is using lattice matched CdZnTe (Zn 4\%) substrates.},
  language  = {en}
}
@article{WuBeckerWaagetal.1991,
  author    = {Wu, Y.S. and Becker, Charles R. and Waag, A. and Kraus, M. M. and Bicknell-Tassius, R. N. and Landwehr, G.},
  title     = {Correlation of the Cd-to-Te ratio on CdTe surfaces with the surface structure},
  isbn      = {0163-1829},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-37789},
  year      = {1991},
  abstract  = {We report here that reconstruction on (100), (1lIlA, and (1l1lB CdTe surfaces is either C(2X2), (2X2), and (l X I) or (2X I), (l X I), and (l X I) when they are Cd or Te stabilized, respectively. There is a mixed region between Cd and Te stabilization in which the reflected high-energy electron-diffraction (RHEED) patterns contain characteristics of both Cd- and Te-stabilized surfaces. We have also found that the Cd-to-Te ratio of the x-ray photoelectron intensities of their 3d\(_{3/ 2}\) core levels is about 20\% larger for a Cd-stabilized (1lIlA, (1lIlB, or (100) CdTe surface than for a Te-stabilized one. According to a simple model calculation, which was normalized by means of the photoelectron intensity ratio of a Cd-stabilized (lll)A and aTe-stabilized (1l1lB CdTe surface, the experimental data for CdTe surfaces can be explained by a linear dependence of the photoelectron-intensity ratio on the fraction of Cd in the uppermost monatomic layer. This surface composition can be correlated with the surface structure, i.e., the corresponding RHEED patterns. This correlation can in turn be employed to determine Te and Cd evaporation rates. The Te reevaporation rate is increasingly slower for the Te-stabilized (Ill) A, (l1l)B, and (100) surfaces, while the opposite is true for Cd from Cd-stabilized (Ill) A and (Ill)B surfaces. In addition, Te is much more easily evaporated from all the investigated surfaces than is Cd, if the substrate is kept at normal molecular-beam-epitaxy growth temperatures ranging from 2oo·C to 300 ·C.},
  subject      = {Festk{\"o}rperphysik},
  language  = {en}
}
@article{QiuHeLietal.1993,
  author    = {Qiu, Yueming and He, Li and Li, Jie and Yuan, Shixin and Becker, Charles R. and Landwehr, G.},
  title     = {Infrared photoconductor fabricated with HgTe/CdTe superlattice grown by molecular beam epitaxy},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-37772},
  year      = {1993},
  abstract  = {An infrared photoconductor fabricated with a HgTe/CdTe superlattice grown on a GaAs substrate by molecular beam epitaxy is described here for the first time. The growth procedure, device fabrication, and measurement results are described. The results show that the device has relatively high uniformity and 1000 K black-body detectivity 2.4 X 10\(^9\) cm Hz\(^{1/2}\) W\(^{-1}\) . The photoconductivity decay method was used for determining carrier lifetime of the HgTe/CdTe superlattice, the measured lifetime is 12\(\mu\)s at 77 K, which is the longest lifetime ever reported for HgTe/CdTe superlattices and we believe that the increase of lifetime is mainly due to the reduction of dimensions.},
  language  = {en}
}
@article{ToenniesBacherForcheletal.1994,
  author    = {T{\"o}nnies, D. and Bacher, G. and Forchel, Alfred and Waag, A. and Litz, Th. and Hommel, D. and Becker, Charles R. and Landwehr, G. and Heuken, M. and Scholl, M.},
  title     = {Optical study of interdiffusion in CdTe and ZnSe based quantum wells},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-37750},
  year      = {1994},
  abstract  = {No abstract available},
  language  = {en}
}
@article{BeckerHeRegnetetal.1993,
  author    = {Becker, Charles R. and He, L. and Regnet, M. M. and Kraus, M.M. and Wu, Y. S. and Landwehr, G. and Zhang, X. F. and Zhang, H.},
  title     = {The growth and structure of short period (001) Hg\(_{1-x}\)Cd\(_x\)Te-HgTe superlattices},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-37858},
  year      = {1993},
  abstract  = {Molecular beam epitaxially grown short period (001) Hg\(_{1_x}\)Cd\(_x\)Te-HgTe superlattices have been systematically investigated. Several narrow well widths were chosen, e.g., 30, 35 and 40 {\AA}, and the barrier widths were varied between 24 and 90 {\AA} for a particular well width. Both the well width and the total period were determined directly by means of x-ray diffraction. The well width was determined by exploiting the high reflectivity from HgTe and the low reflectivity from CdTe for the (002) Bragg reflection. Knowing the well and barrier widths we have been able to set an upper limit on the average Cd concentration of the barriers, \(\overline x_b\), by annealing several superlattices and then measuring the composition of the resulting alloy. \(\overline x_b\) was shown to decrease exponentially with decreasing barrier width. The structure of a very short period superlattice, i.e., 31.4 {\AA}, was also investigated by transmission electron microscopy, corroborating the x-ray diffraction results.},
  language  = {en}
}
@article{WuBeckerWaagetal.1993,
  author    = {Wu, Y. S. and Becker, Charles R. and Waag, A. and Schmiedl, R. and Einfeldt, S. and Landwehr, G.},
  title     = {Oxygen on the (100) CdTe surface},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-37869},
  year      = {1993},
  abstract  = {We have investigated oxygen on CdTe substrates by means of x-ray photoelectron spectroscopy (XPS) and reflection high-energy electron diffraction (RHEED). A Te oxide layer that was at least 15 A thick was found on the surface of as-delivered CdTe substrates that were mechanically polished. This oxide is not easily evaporated at temperatures lower than 350°C. Furthermore, heating in air, which further oxidizes the CdTe layer, should be avoided. Etching with HCI acid (15\% HCl) for at least 20 s and then rinsing with de-ionized water reduces the Te oxide layer on the surface down to 4\% of a monoatomic layer. However, according to XPS measurements of the 0 Is peak, 20\%-30\% of a monoatomic layer of oxygen remains on the surface, which can be eliminated by heating at temperatures ranging between 300 and 340 cC. The RHEED patterns for a molecular beam epitaxially (MBE)-grown CdTe film on a (lOO) CdTe substrate with approximately one monoatomic layer of oxidized Te on the surface lose the characteristics of the normal RHEED pattems for a MBE-grown CdTe film on an oxygen-free CdTe substrate.},
  language  = {en}
}
@article{KrausRegnetBeckeretal.1992,
  author    = {Kraus, M. M. and Regnet, M. M. and Becker, Charles R. and Bicknell-Tassius, R. N. and Landwehr, G.},
  title     = {Comparison of band structure calculations and photoluminescence experiments on HgTe/CdTe superlattices grown by molecular beam epitaxy},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-37878},
  year      = {1992},
  abstract  = {We have grown HgTe/CdTe superlattices by molecular beam epitaxy; barrier thicknesses were in the range from 15 to 91 {\AA} and the well thickness was maintained at a constant value of 30 {\AA}. The infrared photoluminescence was investigated by means of Fourier transform infrared spectroscopy in the temperature range from 4.2 to 300 K. All superlattices showed pronounced photoluminescence at temperatures up to 300 K. To gain more detailed insight into the band structure of the HgTe/CdTe superlattices, band structure calculations were performed. The concept of the envelope function approximation was followed. Employing the transfer matrix method, the calculations were completed taking into account an eight band k·p model. An important parameter in these calculations is the natural valence band offset (VBO) between the well and barrier materials. As a general trend, the value for the direct gap decreases with increasing VBO. The experimentally determined energies of the band gap are in reasonable agreement with the values obtained by the theoretical calculations. A comparison between theory and experiment shows that the observed transition energies are closer to calculations employing a large offset (350 meV) as opposed to a small VBO (40 meV).},
  language  = {en}
}
@article{HerrmannHappMoellmannetal.1993,
  author    = {Herrmann, K. H. and Happ, M. and M{\"o}llmann, K.-P. and Tomm, J. W. and Becker, Charles R. and Kraus, M. M. and Yuan, S. and Landwehr, G.},
  title     = {A new model for the absorption coefficient of narrow gap (Hg,Cd)Te that simultaneously considers band tails and band filling},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-37894},
  year      = {1993},
  abstract  = {A semiempirical model is presented that correlates the broadening of the absorption edge with both transitions below the energy gap and with transitions by the Kane band model. This model correctly fits both the absorption and luminescence spectra of narrow-gap (Hg,Cd)Te samples that have been grown by the traveling heater method as well as by molecular-beam epitaxy. The accuracy of the band-gap determination is enhanced by this model.},
  language  = {en}
}
@article{WaagHeinkeScholletal.1993,
  author    = {Waag, A. and Heinke, H. and Scholl, S. and Becker, Charles R. and Landwehr, G.},
  title     = {Growth of MgTe and Cd\(_{1-x}\)Mg\(_x\)Te thin films by molecular beam epitaxy},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-37917},
  year      = {1993},
  abstract  = {We report on the growth of the compound semiconductor MgTe as weil as the ternary alloy Cd\(_{l-x}\)Mg, Te by molecular hcam cpitaxy. This is to our knowkdgc thc first time that this material has heen grown by any epitaxial technique. Bulk MgTe, which is hygroscopic, has a band gap of 3.0 eV and crystallizcs usually in thc wurtzite structure. Pseudomorphic films were grown on zincblende Cd Te suhstrates for a MgTe thickness helow a critical layer thickncss of approximately 500 nm. In addition, Cd\(_{l_x}\),Mg\(_x\)Te epilayers were grown with a Mg concentration between 0 and 68\%, which corresponds to a band gap betwcen 1.5 and 2.5 eV at room temperature. The crystalline quality of thc layers is comparabk to CdTc thin films as long as they are fully strained. The lauice constant of zincblende MgTe is slightly smaller than that of CdTe, and the lattice mismatch is as low as O.7\%. In addition highly n-type CdMgTe layers were fabricatcd by hromine doping. The tunability of the band gap as weil as the rather good laUice match with CdTc makes the matcrial interesting for optoelectronic device applications for the entire visible range.},
  language  = {en}
}
@article{ShanjiaXinzhangGreineretal.1992,
  author    = {Shanjia, Xu and Xinzhang, Wu and Greiner, P. and Becker, Charles R. and Geick, R.},
  title     = {Microwave transmission and reflection of stratified lossy dielectric segments partially filled waveguide},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-37958},
  year      = {1992},
  abstract  = {The microwave transmission and reßection is evaluated for stratified lossy dielectric segments partially filling the rectangular waveguide by the method which combines the multimode network theory with the rigorous mode matching procedure. As an example, we investigate in detail the microwave scattering properties of II-VI-epitaxial layer on a lossy dielectric substrate inserted in the rectangular waveguide. The experimental data verify the accuracy and the effectiveness of the present method. Extensive numerical results are presented to establish useful guidelines for the contactless microwave measurement of the conductivity of the epitaxiallayer.},
  language  = {en}
}
@article{ShanjiaXinzhangBoegeetal.1993,
  author    = {Shanjia, Xu and Xinzhang, Wu and Boege, P. and Sch{\"a}fer, H. and Becker, Charles R. and Geick, R.},
  title     = {Scattering characteristics of 3-D discontinuity consisting of semiconductor sample filled in waveguide with gaps},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-37964},
  year      = {1993},
  abstract  = {No abstract available},
  language  = {en}
}
@article{HeBeckerBicknellTassiusetal.1993,
  author    = {He, L. and Becker, Charles R. and Bicknell-Tassius, R. N. and Scholl, S. and Landwehr, G.},
  title     = {Molecular beam epitaxial growth and evaluation of intrinsic and extrinsically doped (100) Hg\(_{0.8}\)Cd\(_{0.2}\)Te on (100) Cd\(_{0.96}\)Zn\(_{0.04}\)Te},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-37885},
  year      = {1993},
  abstract  = {No abstract available.},
  language  = {en}
}
@article{SchikoraHausleitnerEinfeldtetal.1994,
  author    = {Schikora, D. and Hausleitner, H. and Einfeldt, S. and Becker, Charles R. and Widmer, T. and Giftige, C. and Lischka, K. and von Ortenburg, M. and Landwehr, G.},
  title     = {Epitaxial overgrowth of II-VI compounds on patterned substrates},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-37985},
  year      = {1994},
  abstract  = {The selected area epitaxial overgrowth of narrow gap HgTe as well as wide gap CdTe and ZnTe on CdTe/GaAs substrates, which had been structured by dry etching techniques, has been investigated. A plasma etching process using a barrel reactor with CH\(_4\)-CH\(_2\) gases has been employed to prepare stripes with a width of about 1 μm with anisotropic as well as isotropic etching profiles. It has been found, that the selected area HgTe overgrowth takes place with a high local selectivity to the low index planes of the patterned surface. In contrast, the selected area overgrowth of the wide gap CdTe and ZnTe is controlled by anisotropic growth kinetics provided that the substrate temperature is not lower than 220°C and the starting surface consists of well developed low index crystallographic planes.},
  language  = {en}
}
@article{EinfeldtHeinkeBehringeretal.1994,
  author    = {Einfeldt, S. and Heinke, H. and Behringer, M. and Becker, Charles R. and Kurtz, E. and Hommel, D. and Landwehr, G.},
  title     = {The growth of HgSe by molecular beam epitaxy for ohmic contacts to p-ZnSe},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-38001},
  year      = {1994},
  abstract  = {The structural properties of HgSe grown by molecular beam epitaxy (MBE) are investigated for different lattice mismatches to the substrate and various growth conditions. The growth rate is shown to depend strongly on the growth temperature above lOO°C as well as on the Hg/Se flux ratio. It has been found that the crystalline perfection and the electrical properties are mainly determined by the layer thickness, especially for the growth on highly lattice mismatched substrates. Changes in the surface morphology are related to growth parameters. Differences between the electrical behavior of MBE-grown and bulk HgSe are discussed. The electrical properties of HgSe contacts on p-ZnSe are investigated as a function of different annealing procedures.},
  language  = {en}
}
@article{WuBeckerWaagetal.1993,
  author    = {Wu, Y. S. and Becker, Charles R. and Waag, A. and Bicknell-Tassius, R. N. and Landwehr, G.},
  title     = {Removal of oxygen and reduction of carbon contamination on (100) Cd\(_{0.96}\)Zn\(_{0.04}\)Te},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-38014},
  year      = {1993},
  abstract  = {No abstract available},
  language  = {en}
}
@article{ZhangBeckerZhangetal.1994,
  author    = {Zhang, X. F. and Becker, Charles R. and Zhang, H. and He, L. and Landwehr, G.},
  title     = {Investigation of a short period (001) HgTe-Hg\(_{0.6}\)Cd\(_{0.4}\)Te superlattice by transmission electron microscopy},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-38029},
  year      = {1994},
  abstract  = {No abstract available},
  language  = {en}
}
@article{BeckerMartin1972,
  author    = {Becker, Charles R. and Martin, T. P.},
  title     = {Infrared absorption by Impurity-pair resonant modes in NaCl:F},
  isbn      = {1098-0121},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-37840},
  year      = {1972},
  abstract  = {New resonant-mode infrared absorption lines have been observed in NaCl with high concentrations of fluorine impurities. The quadratic concentration dependence of the strength of these lines indicates that they are due to pairs of fluorine impurities. At the resonant frequencies, the motion of some host ions appears to be as important as the motion of the impurities themselves.},
  subject      = {Festk{\"o}rperphysik},
  language  = {en}
}
@article{BeckerNath1970,
  author    = {Becker, Charles R. and Nath, G.},
  title     = {Optical properties of LiIO\(_3\) in the far infrared},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-37905},
  year      = {1970},
  abstract  = {No abstract available},
  language  = {en}
}
@article{RoederSteinleinSchmidetal.1993,
  author    = {R{\"o}der, G. and Steinlein, C. and Schmid, M. and Linsenmair, Karl Eduard},
  title     = {Karyotype and chromosome banding in the Turkish desert woodlouse Desertellio elongatus (Crustacea, Isopoda, Oniscidea)},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-30989},
  year      = {1993},
  abstract  = {The karyotype of D. elongatus was investigated by means of C-banding, silver staining, and mithramycinand quinacrine fluorescent staining. The diploid chromosome number is 2n = 50. C-banding shows pericentromerically localized constitutive heterochromatin in every chromosome. Two of the chromosome pairs carry two telomeric nucleolus organizer regions each. No heteromorphic sex chromosomes were found.},
  language  = {en}
}
@article{Linsenmair1984,
  author    = {Linsenmair, Karl Eduard},
  title     = {Comparative studies on the social behaviour of the desert isopod Hemilepistus reaumuri and of a Porcellio species},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-30846},
  year      = {1984},
  abstract  = {Behavioural adaptations have made the desert isopod Hemilepistus reaumuri the most successful herbivore and detritivore of the macrofauna of many arid areas in North Africa and Asia Minor. For survival and reproduction Hemilepistus is dependent on burrows. New burrows can only be dug during spring. With the time-consuming digging of a burrow, Hemilepistus has only made the first step towards solving its ecological problems. The burrows are vital and have to be continuously defended against competitors. This requirement is met by co-operation of individuals within the framework of a highly developed social behaviour. In spring adults form monogamous pairs in which partners recognize each other individually and later form, with their progeny, strictly closed family communities. Hemilepistus is compared with a Porcellio' sp. which has developed, convergently, a social behaviour which resembles that of Hemilepistus in many respects, but differs essentially in some aspects, partly reflecting differences in ecological requirements. This and a few other Porcellio species demonstrate some possible steps in the evolution of the social behaviour of Hemilepistus. The female Hemilepistus is-in contrast to Porcellio sp. - semelparous and the selective advantages of monogamy in its environment are not difficult to recognize. This chapter discusses how this mating system could have evolved and especially why monogamous behaviour is also the best method for the Hemilepistus male to maximize its reproductive success. The cohesion of pairs and of family communities in Hemilepistus is based on a highly developed chemical communication system. Individual- and family-specific badges owe their specificity to genetically determined discriminating substances. The nature of the badges raises a series of questions: e.g. since alien badges release aggression, how do parents avoid cannibalizing their young? Similar problems arise from the fact that family badges are mixtures of chemical compounds of very low volatility with the consequence that they can only be transferred by direct contact and that during moulting all substances are lost which an individual does not produce itself. It is shown that in solving these problems inhibiting properties (presumably substances) and learning play a dominant role.},
  language  = {en}
}
@article{Linsenmair1985,
  author    = {Linsenmair, Karl Eduard},
  title     = {Individual and family recognition in subsocial arthropods, in particular in the desert isopod Hemilepistus reaumuri},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33957},
  year      = {1985},
  abstract  = {Individual recogmtlon in the non-eusocial arthropods is, according to our present knowledge, predominantly found in the frame of permanent or temporary monogamy. In some cases, e. g. in stomatopods and possibly other marine crustaceans too, individual recognition may serve to allow identification of (i) individuals within dominance hierarchies or (ii) neighbours in territorial species thus helping to avoid the repetition of unnecessary and costly fights. Kin recognition is experimentally proven only in some isopod species (genera Hemilepistus and Porcel/io) and in the primitive cockroach (termite?) Cryptocercus. The «signatures» or «discriminators» used in the arthropods are chemical. It is assumed that the identifying substances are mainly genetically determined and in this paper I shall discuss possible evolutionary origins. The main part of this account is devoted to the presentation of some aspects of the highly developed individual and kin identification and recognition system in the desert isopod Hemilepistus reaumuri - a pure monogamous species in which pairs together with their progeny form strictly exclusive family units. Amongst other things problems of (i) mate choice, (ii) learning to recognize a partner, (iii) avoiding the un adaptive familiarization with aliens are treated. Monogamy under present conditions is for both sexes the only suitable way of maximizing reproductive success; an extremely strong selection pressure must act against every attempt to abandon monogamy under the given ecological conditions. The family «badges» which are certainly always blends of different discriminator substances are extremely variable. This variability is mainly due to genetical differences and is not environmentally caused. It is to be expected that intra-family variabiliry exists in respect of the production of discriminator substances. Since the common badge of a family is the result of exchanging and mixing individual substances, and since the chemical nature of these discriminators requires direct body contacts in order to acquire those substances which an individual does not produce itself, problems must arise with molting. These difficulties do indeed exist and they are aggravated by the fact that individuals may produce substances which do not show up in the common family badge. An efficient learning capability on the one hand and the use of inhibiting properties of newly molted isopods help to solve these problems. In the final discussion three questions are posed and - partly at least - answered; (i) why are families so strictly exclusive, (ii) how many discriminator substances have to be produced to provide a variability allowing families to remain exclusive under extreme conditions of very high population densities, (iii) what is the structure of the family badge and what does an individual have to learn apart from the badge in order not to mistake a family member for an alien or vice versa.},
  language  = {en}
}
@article{LinsenmairLinsenmair1971,
  author    = {Linsenmair, Karl Eduard and Linsenmair, Christa},
  title     = {Paarbildung und Paarzusammenhalt bei der monogamen W{\"u}stenassel Hemilepistus reaumuri (Crustacea, Isopoda, Oniscoidea)},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33937},
  year      = {1971},
  abstract  = {No abstract available},
  language  = {de}
}
@article{GrafeLinsenmair1989,
  author    = {Grafe, U. and Linsenmair, Karl Eduard},
  title     = {Protogynous sex change in the Reed Frog: Hyperolius viridiflavus},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-30990},
  year      = {1989},
  abstract  = {Observations on captive reed frogs Hyperolius viridijlavus ommatostictus showed that seven out of 24 females changed into males. Sex change occurred without any hormone treatment and resulted in completely functional males. The adaptive value is discussed in terms of maximizing life-time reproductive success. Hyperolius r. ommatostictus is the first amphibian known to show functional sex reversal.},
  language  = {en}
}
@article{SchmuckGeiseLinsenmair1994,
  author    = {Schmuck, R. and Geise, W. and Linsenmair, Karl Eduard},
  title     = {Life cycle strategies and physiological adjustments of Reedfrog Tadpoles (Amphibia, Anura, Hyperoliidae) in relation to environmental conditions.},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-31009},
  year      = {1994},
  abstract  = {The relationship between different degrees of intraspecific crowding of reedfrog tadpoles and their physiological responses to a deterioration of the natal pond water quality was examined under laboratory conditions. Tadpoles that were reared at a lower density metamorphosed significantly earlier than those raised at a higher density. As density increases, the average body length at metamorphosis decreases. However, at low tadpole density, a significantly higher diversity of body size classes among freshly metamorphosed froglets was observed than under more crowded conditions. Mortality increased during metamorphic climax and was inversely correlated with the tadpole density. In ephemeral ponds, an accumulation of nitrogenous wastes from metabolic processes and/or a concentration by evaporation in prolonged rainless periods can pose a considerable chemical stress to reedfrog tadpoles. Hyperolius viridiflavus ommatostictus responded to an increasing ammonia concentration with an activity increase of the ornithine cycle (intensified urea synthesis). hi contrast, Hyperolius marmoratus taeniatus exhibited a strong tolerance against high ammonia levels. A deterioration of the natal pond water quality caused H. v. ommatostictus and H. v. nitidulus tadpoles to adjust to harsher climatic conditions at the time of metamorphosis. This physiological preadjustment enabled the froglets to start feeding and growing immediately after metamorphosis even at low air humidity and rare precipitation events. In contrast, froglets that were raised in daily refreshed water exhibited high mortality rates if subjected to identical conditions. As one possible indicator of the actual climatic conditions prevailing in the surrounding terrestrial habitat, fluctuations in the water ammonia level are discussed.},
  language  = {en}
}
@article{TackeSchuberthBeckeretal.1982,
  author    = {Tacke, M. and Schuberth, W. and Becker, Charles R. and Haas, L. D.},
  title     = {The dielectric constant of PbTe at 4.2 K and \(\tilde ν\)=84.15 cm\(^{-1}\), 96.97 cm\(^{-1}\), 103.60 cm\(^{-1}\)},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-30821},
  year      = {1982},
  abstract  = {The dielectric constant of a PbTe epitaxial layer has been measured by surface wave spectroscopy using an optically pumped far-infrared laser and the technique of attenuated total reflection.},
  language  = {en}
}
@article{GeisGeickBeckeretal.1977,
  author    = {Geis, G. and Geick, R. and Becker, Charles R. and Wagner, V.},
  title     = {Antiferromagnetic resonance in CoO/NiO mixed crystals},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-31239},
  year      = {1977},
  abstract  = {We have studied the lowest magnetic excitation of Ni\(_{1-x}\)Co\(_x\)O mixed crystals for 0.94 \(\leq\) x \(\leq\) 1. Together with previous results for 0.02 \(\leq\) x \(\leq\) 0.07 and neutron data for x = 0.14 and x = 0.30, the results are discussed by means of a model, especially the variation of AFMR frequency and preferred spin direction with Co concentration x.},
  language  = {en}
}
@article{Becker1970,
  author    = {Becker, Charles R.},
  title     = {Impurity-induced absorption in or near the phonon gap of KI},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-30757},
  year      = {1970},
  abstract  = {In or near the phonon gap of KI a single weak line due to OW (OD\(^-\)) at 69.7 (69.3) cm\(^{-1}\) has been observed. A second and much stronger line at 94.1 cm\(^{-1}\) was shown not to be related to OH\(^-\), but instead is thought to be due to CO\(_3\).},
  language  = {en}
}
@article{KoehlerBecker1974,
  author    = {K{\"o}hler, H. and Becker, Charles R.},
  title     = {Optically active lattice vibrations in Bi\(_2\)Se\(_3\)},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-31296},
  year      = {1974},
  abstract  = {The preparation of Bi2Sea single crystals with low free carrier densities allowed an investigation of the lattice vibrations to be carried out from the reflectivity of cleavage planes at nearly normal incidence of the radiation (E ~ c). The experimental results ean be explained with two classical oscillators, whose eigenfrequencies oceur at 92 and 69.5 cm-I. The static dielectric constant was determined to be 100 ± 10 for E ~ c.},
  language  = {en}
}
@article{KlitzingBecker1976,
  author    = {Klitzing, K. von and Becker, Charles R.},
  title     = {Far infrared photoconductivity of residual acceptors in pure tellurium},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-31278},
  year      = {1976},
  abstract  = {The photoconductivity of both undeformed and deformed Te samples has been investigated at liquid He temperature by means of a Fourier spectrometer. Three peaks were usually found in the spectra of undeformed samples at 11, 24 and 46 cm\(^{-1}\). These are shown to be due to three different chemical impurities. The deformed samples are characterized by additional structure at higher frequencies.},
  language  = {en}
}
@article{Becker1971,
  author    = {Becker, Charles R.},
  title     = {Evidence for a quasi-phonon gap in CsCl},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-30767},
  year      = {1971},
  abstract  = {The observed impurity induced far-infrared absorption in CsCl : Rb\(^+\) and CsCl : K\(^+\) is compared with a calculated density of acoustic phonon states in CsCl. The absorption due to CsCl : Rb\(^+\) displays a minimum between the acoustic and optic phonon bands. A narrow line is observed in CsCl: K\(^+\) at 85.8 cm\(^{-1}\) which falls in this quasi-phonon gap.},
  language  = {en}
}
@article{ReimerScheerPetersetal.1986,
  author    = {Reimer, Georg and Scheer, Ulrich and Peters, Jan-Michael and Tan, Eng M.},
  title     = {Immunolocalization and partial characterization of a nucleolar autoantigen (PM-Scl) associated with polymyositis / scleroderma overlap syndromes.},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33191},
  year      = {1986},
  abstract  = {Precipitating anti-PM-Sel antibodies are present in sera from patients with polymyositis. scleroderma. and polymyositis/scleroderma overlap syndromes. By indirect immunofluorescence microscopy. anti-PM-Scl antibodies stained the nucleolus in cells of different tissues and species. suggesting that the antigen is highly conserved. By electron microscopy, anti-PM-Scl antibodies reacted primarily with the granular component of the nuc1eolus. Drugs that inhibit rRNA synthesis had a marked effect on the expression of PM-Scl antigen. In actinomycin D-treated cells, immunofluorescence staining by anti-PM-Scl was sign{\"u}icantly reduced with residual staining restricted to the granular regions of nuc1eoli. Treatment with 5,6-dichloro-beta-D- ribofuranosylbenzimidazole (DRB) also selectively reduced nuc1eolar staining. On a molecular level, anti-PM-Sel antibodies precipitated 11 polypeptides with molecular weights (Mr) ranging from 110,000 to 20,000. The Mr 80,000 and 20.000 polypeptides were phosphorylated. Evidence suggests that the PM-Scl antigen complex may be related to a prerlbosomal particle.},
  language  = {en}
}
@article{ScheerSommervilleBustin1979,
  author    = {Scheer, Ulrich and Sommerville, John and Bustin, M.},
  title     = {Injected histone antibodies interfere with transcription of lampbrush chromosome loops in oocytes of Pleurodeles},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33166},
  year      = {1979},
  abstract  = {Antibodies to calf thymus histone H2B were purified by chromatography on DEAE-cellulose and injected into oocyte nuclei of Pleurodeles waltlii. As shown by indirect immunofluorescence these antibodies cross-reacted strongly with corresponding histones associated with lampbrush chromosomes. Shortly after injection the lateral loops of the chromosomes retracted into the chromomeres and by 3 h postinjection the 'lampbrush' appearance was completely lost and the chromosomes appeared in light-microscopic preparations as rod-like structures consisting of 10ngitudina11y coalesced chromomeres. In control oocytes injected with non-immune immunoglobulins or antibodies against a ubiquitous transcript-associated protein no morphological alterations of the lampbrush chromosomes could be observed. Electron microscopic spreads of chromosomes prepared at various times after injection of anti-H2B revealed a progressive loss of transcriptional complexes from the loop axes. Finally, higher-order chromatin configurations, like supranuc1eosomal globules (' superbeads ') or cable-like chromatin strands 50- 60 nm thick predominated, indicating complete transcriptional inactivation of a11 chromosomal regions. The results indicate that H2B antibodies react specifically with his tones associated with the transcribed DNA of lateral loops in their native state. The resulting antigenantibody complexes seem to inhibit progression of the R A polymerases along the template, thus causing the premature release of transcripts, a process analogous to the stripping effect of actinomycin D. The demonstration of histones associated with heavily transcribed regions, which are not compacted into nucleosomes but largely extended, supports the current concept that unfolding of nucleosomes to a110w transcription of the DNA does not involve dissociation of histones. In contrast, amplified ribosomal RNA genes are unaffected by injected HzB antibodies. This does not necessarily indicate absence of his tones from nucleolar chromatin, since we do not know whether it is accessible in vivo to antibodies or whether the histone antigenie determinants are masked by the presence of other proteins. The technique of injecting specific antibodies should be widely applicable when analysing the in vivo distribution of chromosomal components at the electron-microscopic level and when studying complex metabolie processes, like the cleavage and modification of RNA, by selective inhibition of defined enzymic steps.},
  language  = {en}
}
@article{ReimerRoseScheeretal.1987,
  author    = {Reimer, Georg and Rose, Kathleen M. and Scheer, Ulrich and Tan, Eng M.},
  title     = {Autoantibody to RNA polymerase I in scleroderma sera},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-34294},
  year      = {1987},
  abstract  = {Autoantibodies to components of the nucleolus are a unique serological feature of patients with scleroderma. There are autoantibodies of several specificities; one type produces a speckled pattern of nucleolar staining in immunofluorescence. In actinomycin D and 5,6-dichloro-{j-D-ribofuranosylbenzimidazoletreated Vero cells, staining was restricted to the fibrillar and not the granular regions. By double immunofluorescence, specific rabbit anti-RNA polymerase I antibodies stained the same fibrillar structures in drug-segregated nucleoli as scleroderma sera. Scleroderma sera immunoprecipitated 13 polypeptides from (35S)methionine-labeled HeLa cell extract with molecular weights ranging from 210,000 to 14,000. Similar polypeptides were precipitated by rabbit anti-RNA polymerase I antibodies, and their common identities were confirmed in immunoabsorption experiments. Microinjection of purified IgG from a patient with speckled nucleolar staining effectively inhibited ribosomal RNA transcription. Autoantibodies to RNA polymerase I were restricted to certain patients with scleroderma and were not found in other autoimmune diseases.},
  language  = {en}
}
@article{ReinhardHalbrueggeScheeretal.1992,
  author    = {Reinhard, Matthias and Halbr{\"u}gge, Maria and Scheer, Ulrich and Wiegand, Christiane and Jockusch, Brigitte M. and Walter, Ulrich},
  title     = {The 46/50 kDa phosphoprotein VASP purified from human platelets is a novel protein associated with actin filaments and focal contacts},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-34246},
  year      = {1992},
  abstract  = {Vasoactive agents which elevate either cGMP or cAMP inhibit platelet activation by pathways sharing at least one component, the 46/50 kDa vasodilator-stimulated phosphoprotein (V ASP). V ASP is stoichiometrically phosphorylated by both cGMP-dependent and cAMPdependent protein kinases in intact human platelets, and its phosphorylation correlates very well with platelet inhibition caused by cGMP- and cAMP-elevating agents. Here we report that in human platelets spread on glass, V ASP is associated predominantly with the distal parts of radial micro filament bundles and with microfilaments outlining the periphery, whereas less V ASP is associated with a central microfilamentous ring. V ASP is also detectable in a variety of different cell types including fibroblasts and epithelial cells. In fibroblasts, V ASP is concentrated at focal contact areas, along microfilament bundles (stress fibres) in a punctate pattern, in the periphery of protruding lamellae, and is phosphorylated by cGMP- and cAMP-dependent protein kinases in response to appropriate stimuli. Evidence for the direct binding of V ASP to F -actin is also presented. The data demonstrate that V ASP is a novel phosphoprotein associated with actin filaments and focal contact areas, i.e. transmembrane junctions between microfilaments and the extracellular matrix.},
  language  = {de}
}
@article{ScheerDabauvalleMerkertetal.1988,
  author    = {Scheer, Ulrich and Dabauvalle, Marie-Christine and Merkert, Hilde and Benavente, Ricardo},
  title     = {The nuclear envelope and the organization of the pore complexes},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-34275},
  year      = {1988},
  abstract  = {No abstract available},
  language  = {en}
}
@article{SchubertKrausKenkliesetal.1992,
  author    = {Schubert, D.W. and Kraus, M.M and Kenklies, R. and Becker, Charles R. and Bicknell-Tassius, R.N.},
  title     = {Composition and wavelength dependence of the refractive index in Cd\(_{1-x}\)Mn\(_x\)Te epitaxial layers},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-37716},
  year      = {1992},
  abstract  = {We have investigated Cd\(_{1-x}\)Mn\(_x\)Te thin films with Mn concentrations of x=0.12, 0.18, 0.30, 0.52, and 0.70. These single crystal layers were grown by molecular beam epitaxy on [001] CdTe substrates. The real part of the refractive index, n, was determined below the band-gap Eo in the range of 0.5-2.5 eV at T=300 K. The parallel reOectivity was measured near the Brewster angle at the YAG laser wavelength of 1.064 J.Lm (hv= 1.165 eV). Combining these results with the optical pathlength results (nd) of reOection measurements in a Fourier spectrometer we have determined n(x,v) over a wide spectral range by utilizing a three parameter fit. The accuracy of these results for n should improve waveguide designs based on this material.},
  language  = {en}
}
@article{BellDabauvalleScheer1992,
  author    = {Bell, Peter and Dabauvalle, Marie-Christine and Scheer, Ulrich},
  title     = {In vitro assembly of prenucleolar bodies in Xenopus egg extract},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-34233},
  year      = {1992},
  abstract  = {Nuclei assembled in Xenopus egg extract from purified DNA or chromatin resemble their natural counterparts in a number of structural and functional features. However, the most obvious structural element of normal interphase nuclei, the nucleolus, is absent from the in vitro reconstituted nuclei. By EM, cytological silver staining, and immunofluorescence microscopy employing antibodies directed against various nucleolar components we show that nuclei assembled in vitro contain numerous distinct aggregates that resemble prenucleolar bodies (PNBs) by several criteria. Formation of these PNB-like structures requires pore complex-mediated nuclear transport of proteins but is independent of the genetic content of the in vitro nuclei as well as transcriptional and translational events. Our data indicate that nuclei assembled in vitro are capable of initiating early steps of nucleologenesis but that the resulting PNBs are unable to fuse with each other, probably due to the absence of a functional nucleolus organizer. With appropriate modifications, this experimental system should be useful to define and analyze conditions promoting the site-specific assembly of PNBs into a coherent nucleolar body.},
  language  = {en}
}
@article{Scheer1981,
  author    = {Scheer, Ulrich},
  title     = {Identification of a novel class of tandemly repeated genes transcribed on lampbrush chromosomes of Pleurodeles waltlii},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33153},
  year      = {1981},
  abstract  = {Electron microscope preparations of lampbrush chromosomes from oocytes of Pleurodeles waltl;; have revealed a new class of tandemly repeated genes. These genes are highly active, as judged by the close spacing of nascent transcripts. They occur in clusters of >100 copies and are transcribed in units containing roughly 940 base pairs of DNA that are separated by nontranscribed spacers of an estimated DNA content of 2,410 base pairs. The size and the pattern of arrangement of these transcription units can not be correlated with any of the repetitious genes so far described.},
  language  = {en}
}
@article{FrankeKleinschmidtSpringetal.1981,
  author    = {Franke, Werner W. and Kleinschmidt, J{\"u}rgen A. and Spring, Herbert and Krohne, Georg and Grund, Christine and Trendelenburg, Michael F. and St{\"o}hr, Michael and Scheer, Ulrich},
  title     = {A nucleolar skeleton of protein filaments demonstrated in amplified nucleoli of Xenopus laevis},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33130},
  year      = {1981},
  abstract  = {The amplified, extrachromosomal nucleoli of Xenopus oocytes contain a meshwork of -4-nm-thick filaments, which are densely coiled into higher-order fibrils of diameter 30-40 nm and are resistant to treatment with high- and low-salt concentrations, nucleases (DNase I, pancreatic RNase, micrococcal nuclease), sulfhydryl agents, and various nonionic detergents. This filamentous "skeleton" has been prepared from manually isolated nuclear contents and nucleoli as weil as from nucleoli isolated by fluorescence-activated particle sorting. The nucleolar skeletons are observed in light and electron microscopy and are characterized by ravels of filaments that are especially densely packed in the nucleolar cortex. DNA as weil as RNA are not constituents of this structure, and precursors to ribosomal RNAs are completely removed from the extraction-resistant filaments by treatment with high-salt buffer or RN ase. Fractions of isolated nucleolar skeletons show specific enrichment of an acidic major protein of 145,000 mol wt and an apparent pi value of -6.15, accompanied in some preparations by various amounts of minor proteins. The demonstration of this skeletal structure in "free" extrachromosomal nucleoli excludes the problem of contaminations by nonnucleolar material such as perinucleolar heterochromatin normally encountered in studies of nucleoli from somatic cells. It is suggested that this insoluble protein filament complex forms a skeleton specific to the nucleolus proper that is different from other extraction-resistant components of the nucleus such as matrix and lamina and is involved in the spatial organization of the nucleolar chromatin and its transcriptional products. In studies of the organization of the interphase nucleus, considerable progress has been made in the elucidation of the arrangement of chromatin components and transcriptional products. However, relatively little is known about the composition and function of another category of nuclear structures, the nonnucleoproteinaceous architectural components that are insoluble in solutions of low and high ionic strength, despite numerous studies dedicated to this problem. Such structures include (a) the nuclear envelope and its pore complexes (I, 15, 18, 23, 37, 41), (b) a peripheral layer of insoluble protein ("lamina"; I, 15, 22, 23, 59), (e) certain skeletal proteins related to the chromosome "scaffold" described by Laemmli and coworkers (see references 2 and 3), and (d) ill-defined tangles of fibrillar structures of the nuclear interior that are collectively described as residual "matrix" (6, 21 ; for reviews, see references THE JOURNAL OF CEll BrOlOGY . VOlUME 90 AUGUST 1981 289-299 © The RockefeIler University Press · 0021 -9525/ 81 / 08/ 0289/ 11 \$1 .00 4 and 12). The latter, preparatively},
  language  = {en}
}
@article{FrankeScheerKrohneetal.1981,
  author    = {Franke, Werner W. and Scheer, Ulrich and Krohne, Georg and Jarasch, Ernst-Dieter},
  title     = {The nuclear envelope and the architecture of the nuclear periphery},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33108},
  year      = {1981},
  abstract  = {No abstract available},
  language  = {en}
}
@article{BonaScheerBautz1981,
  author    = {Bona, Marion and Scheer, Ulrich and Bautz, Ekkehard K. F.},
  title     = {Antibodies to RNA polymerase II (B) inhibit transcription in lampbrush chromosomes after microinjection into living amphibian oocytes},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33128},
  year      = {1981},
  abstract  = {Antibodies directed against RNA polymerase II (B) from Drosophila melanogaster were obtained from rabbit sera and, as monoclonal immunoglobulins, from mouse hybridomas and shown to cross-react with the amphibian enzyme protein. Localization by indirect immunofluorescence microscopy revealed the association of this enzyme with chromatin of interphase nuclei of amphibian cells and its absence in nucleoli. Purified immunoglobulins were microinjected in to nuclei ofliving vitellogenic oocytes of Ple1lrodeles waltlii and X enopus laevis and their effects on transcriptional processes were monitored by biochemical and light and electron microscopic stud ies. RNA polymerase II antibodies from rabbit sera caused a rapid and almost complete release of nascent transcripts from the chromatin axis of the loops of lampbrush chromosomes, followed by collapse of the loops and their retraction on the main chromosome axis. Monoclonal murine antibodies to the Iarge RNA polymerase II subunits also inhibited transcription in chromosome Ioops but appeared to inhibit initiation rather than elongation events. Activities of class land III RNA polymerases were not significantly affected by injection of antibodies to polymerase II, indicating immunological differences between the three RNA polymerases. The potential value of the in vitro test system described , as a very sensitive assay for detecting proteins involved in transcription in living cells, is discussed. 1},
  language  = {en}
}
@article{TrendelenburgScheerZentgrafetal.1976,
  author    = {Trendelenburg, Michael F. and Scheer, Ulrich and Zentgraf, Hanswalter and Franke, Werner W.},
  title     = {Heterogeneity of spacer lengths in circles of amplified ribosomal DNA of two insect species, Dytiscus marginalis and Acheta domesticus},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33055},
  year      = {1976},
  abstract  = {No abstract available},
  language  = {en}
}
@article{EmmrichMollSimon1985,
  author    = {Emmrich, F. and Moll, Heidrun and Simon, Markus M.},
  title     = {Recombinant human interleukin 2 acts as a B cell growth and differentiation promoting factor},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-34132},
  year      = {1985},
  abstract  = {Human B cells appropriately activated by a B cell mitogen are rendered susceptible to human Interleukin 2 (IL-2) as demonstrated with recombinant human IL-2 (rec. h IL-2). They show increased proliferation and drastically enhanced immunoglobulin secretion. Susceptibility to IL-2 is accompanied with the expression of the IL-2 receptor (Tac antigen) on B cells. The data suggest that IL-2 is one of the lymphokines directly involved in the activation of B lymphocytes.},
  language  = {en}
}
@article{MollEmmrichSimon1985,
  author    = {Moll, Heidrun and Emmrich, F. and Simon, Markus M.},
  title     = {Recombinant human interleukin 2 directly provides signals for the proliferation and functional maturation of murine B lymphocytes},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-34090},
  year      = {1985},
  abstract  = {In this study the effect of recombinant human interleukin 2 (rec.hIL-2) on the proliferation and maturation of B lymphocytes was investigated. It was found that the presence of rec.hIL 2 results in proliferation of mitogen (LPS)-activated B cell blasts. In addition, it is shown that highly enriched murine B cells can be induced by rec.hIL-2 to proliferate and to develop into antibody-secreting cells (PFC) in the presence of antigen (SRBC). When tested for its effect on B cell preparations enriched for resting (small) or activated (blasted) B lymphocytes, it was found that rec.hIL 2 provides signals for both B cell populations to develop into PFC. In contrast, induction of proliferation by the same lymphokine source was only seen in blasted B cells. The data indicate that IL 2 is involved in the generation of B effector cells by directly acting on their precursors thereby providing differentiation as well as proliferation signals.},
  language  = {en}
}
@article{SimonMollPresteretal.1984,
  author    = {Simon, Markus M. and Moll, Heidrun and Prester, Marlot and Nerz, Gaby and Eichmann, Klaus},
  title     = {Immunoregulation by mouse T-cell clones. I. Suppression and amplification of cytotoxic responses by cloned H-Y-specific cytolytic T lymphocytes.},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-30892},
  year      = {1984},
  abstract  = {H-Y-specific and H-2Db-restricted, Lyt-1 "2+ T-cell clones (CTLL) with graded specific cytotoxic activities on male C57BL/6 (B6) target cells (1E3, +++; 2C5, ++; 2A5, +, 3E6, ±) were tested for their capacity to inhibit the generation of H-Y-specific cytotoxic T lymphocytes (CTL) in vitro. Addition of irradiated lymphocytes of CTLL 1E3 and CTLL 3E6 but not those of CTLL 2A5 or CTLL 2C5 abolished the generation of CTL from in vivo primed H-Y-specific precursor cells (CTLP) when added to fresh mixed-lymphocyte cultures (MLC). Exogenous sources of T-cell growth factors (TCGF) did not overcome suppression. Rather the presence of TCGF resulted in a further enhancement of suppressive activities in CTLL 1E3 and 3E6 and the induction of similar activities in cells from CTLL 2A5 and 2C5, which by themselves were not inhibitory. Moreover when added to similar MLC on Day 1 instead of Day 0, only irradiated cells of CTLL 3E6 but not those of the other three CTLL were suppressive. Induction of suppressive activities in H-Y-specific CTLL was independent of the appropriate male stimulator cells since it was also observed in MLC induced by irrelevant antigens (H-2, trinitrophenol). Furthermore at low cell numbers, irradiated lymphocytes from any of the CTLL consistently enhanced CTL activities generated from H-Y-specific CTLP. This augmenting activity, which was not TCGF, could be transferred by soluble mediators present in antigen-sensitized CTLL cultures. Thus, these data indicate (i) that cytotoxic effector cells can function as suppressor cells in the generation of CTL, (ii) that the cytotoxic activity of cloned CTL does not correlate with their capacity to suppress CTL responses, (iii) that the inhibition of CTL responses by CTLL is not due to simple consumption of T-cell growth factors produced in MLC, and (iv) that different CTL clones may interfere with the generation of CTL at different stages of their maturation. Moreover, the experiments suggest an antigen-independent enhancement of suppression by the interaction of CTL with lymphokines. Together with the augmenting activity evoked by cloned CTL the data provide strong evidence for the expression of multiple immunological functions by one particular subset of T cells and suggest that cytotoxic effector cells can differentially regulate the maturation and/or clonal expression of their precursor cells.},
  language  = {en}
}
@article{MollEichmannSimon1985,
  author    = {Moll, Heidrun and Eichmann, K. and Simon, M. M.},
  title     = {Immunoregulation by mouse T-cell clones. II. The same H-Y-specific T helper clone can provide help for the generation of cytotoxic lymphocytes and of antibody-secreting cells.},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-30903},
  year      = {1985},
  abstract  = {Mouse H-Y-specific and I-Ab restricted T-cell clones have been established and compared for their helper effects in the differentiation ofboth T and B Iymphocytes. The results demonstrate that three individual T -cell clones and one subclone could help in the antigen-driven induction of cytotoxic Iymphocytes (CTL) from their precursor cells (CTL-P), and were able to activate B cells to develop into antibody-secreting cells (PFC) in the presence of SRBC, provided the cloned T cells were restimulated by H-Y antigen on antigen-presenting cells. In addition, antigen or lectin could induce the same H -Y -specific T -cell clones to secrete factor(s) expressing helper activities similar to that ofthe cloned T cells. Furthermore, it is shown that the T cell-derived soluble mediator(s) was distinct from T-cell growth factor (TCGF) and from immune interferon (lFN-y). The data reveal a new type ofT cell with helper potential for the activation ofCTL-P and B Iymphocytes, and suggest the existence of distinct T helper cells which can provide help for both cytotoxic and antibody responses by virtue of different Iymphokine activities.},
  language  = {en}
}
@article{FrischholzRoellinghoffMoll1994,
  author    = {Frischholz., S. and R{\"o}llinghoff, M. and Moll, Heidrun},
  title     = {Cutaneous leishmaniasis: Co-ordinate expression of granzyme A and lymphokines by CD4\(^+\) T cells from susceptible mice.},
  series = {Immunology},
  volume    = {82},
  journal   = {Immunology},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-30954},
  pages     = {255 -- 260},
  year      = {1994},
  abstract  = {We have recently demonstrated that the frequency ofT cells expressing granzyme A is significantly higher in skin lesions and spleens of susceptible BALB/c mice compared with resistant C57BL/6 mice infected with Leishmania major, a cause of human cutaneous leishmaniasis. In the present study, we have performed in vitro studies to characterize the subpopulation, the antigen responsiveness and the lymphokine production pattern of granzyme A-expressing T cells in L. major-infected mice. Using a limiting dilution system for functional analysis of selected T cells at the clonallevel, we could show that granzyme A activity in infected BALB/c mice can be assigned to L. major-reactive CD4\(^+\) T cells secreting interleukin-2 (IL-2) and IL-4. Granzyme A production was most pronounced in the early phase of infection. On the other hand, granzyme A expression could not be detected in C57BL/6-derived T cells responding to L. major. The da ta support the suggestion that granzyme A is produced by L. major-responsive CD4\(^+\) T cells facilitating lesion formation and the dissemination of infection.},
  language  = {en}
}
@article{FialaGrunskyMaschwitzetal.1994,
  author    = {Fiala, Brigitte and Grunsky, Harald and Maschwitz, Ulrich and Linsenmair, Karl Eduard},
  title     = {Diversity of ant-plant interactions: Protective efficacy in Macaranga species with different degrees of ant-association.},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32905},
  year      = {1994},
  abstract  = {The pioneer tree Macaranga in SE Asia has developed manyfold associations with ants. The genus comprises all stages of interaction with ants, from facultative relationships to obligate myrmecophytes. Only myrmecophytic Macaranga offer nesting space for ants and are associated with a specific ant partner. The nonmyrmecophytic species are visited by a variety of different ant species which are attracted by extrafloral nectaries (EFN) and food bodies. Transitional Macaranga species like M. hosei are colonized later in their development due to their stem structure. Before the colonization by their specific Crematogaster partner the young plants are visited by different ant species attracted by EFN. These nectaries are reduced and food body production starts as soon as colonization becomes possible. We demonstrated earlier that obligate ant partners can protect their Macaranga plants against herbivore damage and vine cover. In this study we focused on nonspecific interactions and studied M. tanarius and M. hosei, representing a non-myrmecophyte and a transitional species respectively. In ant exclusion experiments both M. tanarius and M. hosei suffered significantly higher mean leaf damage than controls, 37\% versus 6\% in M. hosei, 16\% versus 7\% in M. tanarius. M. tanarius offers both EFN and food bodies so that tests for different effects of these two food rewards could be conducted. Plants with food bodies removed but with EFN remaining had the lowest mean increase of herbivore damage of all experimental groups. Main herbivores on M. hosei were mites and caterpillars. Many M. tanarius plants were infested by a shootborer. Both Macaranga species were visited by various ant species. Crematogaster spp. being the most abundant. We found no evidence for any specific relationships. The results of this study strongly support the hypothesis that non-specific, facultative associations with ants can be advantageous for Macaranga plants. Food bodies appear to have lower attractive value for opportunistic ants than EFN and may require a specific dietary adaptation. This is also indicated by the fact that food body production in the transitional M. hosei does not start before stem structure allows a colonization by the obligate Crematogaster species. M. hosei thus benefits from facultative association with a variety of ants until it produces its first domatia and can be colonized by its obligate mutualist.},
  language  = {en}
}
@article{FialaMaschwitz1990,
  author    = {Fiala, Brigitte and Maschwitz, Ulrich},
  title     = {Studies on the south east asian ant-plant association Crematogaster borneensis / Macaranga: adaptations of the ant partner.},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32689},
  year      = {1990},
  abstract  = {C. borneensis (Myrmicinae) lives in dose association with several myrmecophytic species of the South East Asian pioneer tree genus Macaranga (Euphorbiaceae). The ants are adapted to the plants so dosely that they do not survive away from it. The only food they utilize is provided as food bodies by the plant and honeydew from specific scale insects kept inside the hollow internodes. The anatomy of the digestive tract is also adapted to life on the host plant: the crop is very sm all and can store only minute food quantities. C. borneensis exdusively colonizes certain Macaranga species. Queens as weIl as workers are able to recognize their host plant species, probably by chemical cues. Colony founding queens swarm throughout the year, mostly during darkness. There is strong competition among queens for host plants. Queens do not carry scale insects on their nuptial flight. Worker ants are active day and night. Most of them patrol and collect food bodies on the younger parts of the host plant. An important characteristic is their deaning behaviour, which results in removal of aIl foreign objects. Even though they are rather smalI, workers respond very aggressively to certain kinds of disturbance of the host plant. The ants attack most phytophagous insects and are especially effective in killing and removing smalI, softbodied herbivores (e.g. caterpillars). They do not possess a functional sting, but apply defensive secretion and-once biting an intruder-will not let go. Their effective alarm system results in a mass attack, which provides adequate defence for the colony and the host plant. A comparison with another Crematogaster species further illustrated the special adaptations of C. borneensis to its host plant.},
  language  = {en}
}
@article{ErnsbergerSendtnerRohrer1989,
  author    = {Ernsberger, Uwe and Sendtner, Michael and Rohrer, Hermann},
  title     = {Proliferation and differentiation of embryonic chick sympathetic neurons: Effects of ciliary neurotropic factor.},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-31721},
  year      = {1989},
  abstract  = {At early developmental stages (embryonic day 7, E7), chick paravertebral sympathetic ganglia contain a cell population that divides in culture while expressing various neuronal properties. In an attempt to identify factors that control neuronal proliferation, we found that ciliary neurotrophic factor (CNTF) specifically inhibits the proliferation of those cells expressing neuronal markers. In addition, CNTF affects the differentiation of sympathetic ganglion cells by inducing the expression of vasoactive intestinal peptide immunoreactivity (VIP-IR). After 1 day in culture, tyrosine hydroxylase immunoreactivity (TH-I R) was expressed by about 86\% of the cells whereas VIP-IR was virtually absent. In the presence of CNTF, 50\%-60\% of the cells expressed VIP-IR after 4 days in culture; however, none of the cells expressed VIP-IR in the absence of CNTF. These results, and the demonstration of cells that express both VIP and TH-IR, indicate that VIP is induced in cells that initially express tyrosine hydroxylase. The findings suggest a potential role for CNTF as a factor affecting the proliferation and differentiation of developing sympathetic neurons.},
  language  = {en}
}
@article{Sendtner1993,
  author    = {Sendtner, Michael},
  title     = {Neurotrophic factors and their action on motoneuron survival: Implications for neuromuscular disorders},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-31149},
  year      = {1993},
  abstract  = {Motoneuron diseases represent a m\&jor challenge to modern neurology, yet their clinical manifestations ware first described more than hundred years ago, and despite many studies the etiology of these diseases ramd,ns obscure with no effective treatments having been reported. Although progress has been made in establishing genetic linkage in the rare inherited for.ms of these diseases such as familial amyotrophic lateral scleriosisl , spinal mDscular atrophy and X-linked bulbo-spinal-mDscular atrophy, this new information has not yet affected therapeutic techniques. During the last few years several important steps have been taken concerning the physiological mechanisms involved in motoneuron survival during development, after lesion and in animal models of degenerative diseases, the molecular clOning of several new neurotrophic factors (brain-derived neurotrophic factor (BDNP), neurotrophin-3 and-4 (NT-3 and NT-4) and ciliary neurotrophic factor (CNTP)); the identification of a gene family of receptor molecules for same of these factors, progress in the understanding of the effects of polypeptide growth factors on muscle cell differentiation, neuronal sprouting (insulin-like growth factor-I and -11 (IGF-I and IGF-II), and in vitro motoneuronal survival (CNTF, IGF-I and -II and basic FGF). These findings have raised new hopes in that they could lead to a better understanding of the pathophysiological processes underlying these diseases, and that the pharmacological use of same of these newly characterized neurotrophic factors could present new possibilities for the treatment of these diseases.},
  language  = {en}
}
@article{Schuessler1990,
  author    = {Sch{\"u}ssler, Ulrich},
  title     = {Petrographie, Geochemie und Metamorphosealter von Metabasiten im KTB-Zielgebiet Oberpfalz},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-31694},
  year      = {1990},
  abstract  = {An Metabasiten der Zone Erbendorf-Vohenstrauß, der Erbendorfer Gr{\"u}nschieferzone und der Zone Tirschenreuth-M{\"a}hring wurden petrographische, geochemische und phasenpetrologische Untersuchungen sowie K-Ar-Mineraldatierungen durchgef{\"u}hrt. In der Zone Erbendorf-Vohenstrauß treten in regionaler Abh{\"a}ngigkeit drei Haupttypen von Metabasiten auf: 1. Flaseramphibolite mit der Paragenese Hornblende + Oligoklas/ Andesin + Granat ± Salit und mit Plagioklas- und / oder Kalksilikat-reichen Flasern findet man haupts{\"a}chlich im n{\"o}rdlichen und zentralen Teil der Zone Erbendorf-Vohenstrauß. Geochemisch zeigen sie eine deutliche Anreicherung der inkompatiblen Elemente und der leichten Seltenerdelemente und sind vergleichbar mit modernen Tholeiiten von ozeanischen Inseln oder anomalen Abschnitten mittelozeanischer R{\"u}kken. Ein kontinentaler Intraplatten-Charakter scheint nicht gegeben. In der Kontaktaureole von Windisch-Eschenbach wurde ein Teil der Flaseramphibolite kontaktmetamorph {\"u}berpr{\"a}gt. 2. Schiefrige, teils streifige Amphibolite mit der Paragenese Hornblende + Andesin / Labrador ± Salit dominieren im S{\"u}d teil der Zone Erbendorf-Vohenstrauß, erscheinen aber in einzelnen Ausstrichen auch im Norden. Die Streifung entsteht durch Plagioklas- und / oder Kalksilikat-reiche Zwischenlagen. Geochemisch sind diese Amphibolite bei flachen Spurenelement- und Seltenerdelement- Mustern vergleichbar mit modernen Tholeiiten von normalen Abschnitten mittelozeanischer R{\"u}cken. Sowohl Flaseramphibolite als auch schiefrige, teils streifige Amphibolite zeigen {\"U}berg{\"a}nge zu massigen, homogenen Amphiboliten. 3. Metagabbros mit der Paragenese Hornblende + Plagioklas ± Biotit und einer grobk{\"o}rnigen, gabbro iden Textur treten haupts{\"a}chlich im Bereich der Schuppenzone Michldorf-Kaimling (VOLL 1960) auf. Geochemisch nehmen sie bei einer schwachen Anreicherung der inkompatiblen Elemente eine Zwischenstellung zwischen Flaseramphiboliten und schiefrigen, teils streifigen Amphiboliten ein. In der Erbendorfer Gr{\"u}nschieferzone treten Metagabbros und schiefrige, teils gestreifte Amphibolite mit der Paragenese Hornblende + Oligoklas ± Epidot ± Chlorit auf. Die Amphibolite wurden z. T. stark retrograd {\"u}berpr{\"a}gt und dabei auch deformiert. Dies wird auf gr{\"o}ßere, post-regionalmetamorphe, tektonische Bewegungen, m{\"o}glicherweise Decken{\"u}berschiebungen zur{\"u}ckgef{\"u}hrt. Geochemisch sind die Metabasite der Erbendorfer Gr{\"u}nschieferzone mit modernen tholeiitischen bis kalkalkalischen, subduktionsgebundenen Basalten vergleichbar. Sie unterscheiden sich damit v{\"o}llig von den s{\"u}dlich angrenzenden Flaseramphiboliten der Zone Erbendorf-Vohenstrauß und den n{\"o}rdlich benachbarten Amphiboliten des Fichtelgebirges. Dies unterstreicht die Stellung der Erbendorfer Gr{\"u}nschieferzone als eigenst{\"a}ndige tektonische Einheit. Im Vergleich mit dem M{\"u}nchberger Komplex zeigt die Erbendorfer Gr{\"u}nschieferzone große {\"A}hnlichkeit mit der Prasinit-Phyllit-Serie hinsichtlich der tektonischen Stellung, der Lithologie und insbesondere des geochemischen Charakters der Metabasite. Zwischen der Zone Erbendorf-Vohen-strauß und den M{\"u}nchberger Serien konnten bez{\"u}glich der Metabasite dagegen keine Parallelen festgestellt werden. Schiefrige, teils streifige Amphibolite der Zone Tirschenreuth-M{\"a}hring mit der Paragenese Hornblende + Andesin ± Salit (± Granat) und hellen Plagioklas- oder Kalksilikat-reichen Lagen sind geochemisch mit modernen Basalten normaler mittel ozeanischer R{\"u}cken vergleichbar. Die untersuchten Metabasite d{\"u}rften die Zusammensetzung des basaltischen Ausgangsmaterials zumindest ann{\"a}hernd wiedergeben. In einigen F{\"a}llen wurde jedoch eine sekund{\"a}re Mobilisation von Elementen festgestellt: Die kontaktmetamorphe {\"U}berpr{\"a}gung eines Teils der Flaseramphibolite in der Kontaktaureole von Windisch-Eschenbach f{\"u}hrte zu einer deutlichen Anreicherung von Rb, Li und K und zu einer Abreicherung von Ca, Sr und V, insbesondere aber von Cr und Ni. Die sog. immobilen Elemente Nb, Ce, (P), Zr, Ti, Y, Sc streuen in einem deutlich breiteren Bereich als bei den nicht kontaktmetamorphen Flaseramphiboliten. In einer Probe sind die Seltenerdelemente insgesamt angereichert. Eine Mobilisation von P20 S und den leichten Seltenerdelementen in einigen schiefrigen, teils streifigen Amphiboliten der Zone Erbendorf-Vohenstrauß und in einigen kontaktmetamorphen Flaseramphiboliten wird auf einen Abbau von Apatit im Zuge einer post-regionalmetamorphen, m{\"o}glicherweise postgranitischen, hydrothermalen {\"U}berpr{\"a}gung zur{\"u}ckgef{\"u}hrt. Mineralchemische Untersuchungen ergaben f{\"u}r die Zusammensetzung der Hornblenden aus Amphiboliten der Zone Erbendorf-Vohenstrauß deutliche regionale Unterschiede, die weitgehend unabh{\"a}ngig von der regionalen Verteilung der einzelnen Metabasit-Haupttypen sind. Vergleichende Untersuchungen an Granat untermauern eine vermutete, fr{\"u}here, eklogitfazielle {\"U}berpr{\"a}gung eines Granatamphibolits vom Nordrand der Zone Erbendorf-Vohenstrauß bei Hauxdorf. K-Ar-Altersdatierungen an Hornblende- und Glimmerkonzentraten belegen, daß das letzte, (Mitteldruck-) metamorphe Ereignis im Westteil der Zone Erbendorf-Vohenstrauß vor etwa 380 Ma beendet war. Dieses Alter wird korreliert mit einer letzten Metamorphose der h{\"o}hermetamorphen Serien des M{\"u}nchberger Komplexes zur gleichen Zeit. Im Ostteil der Zone Erbendorf-Vohenstrauß treten j{\"u}ngere Altersdaten mit einem Schwerpunkt bei 324 Ma auf, die entweder auf einen Einfluß der etwa gleichalten Niederdruck-Metamorphose im unmittelbar benachbarten Moldanubikum i. e. S. oder auf die Intrusion des 324 Ma alten (K{\"O}HLER et al. 1974) Leuchtenberger Granits zur{\"u}ckzuf{\"u}hren sind. Im {\"U}bergangsbereich vom Saxothuringikum zum Moldanubikum bei M{\"a}hring zeigen Altersdaten um 320Ma das Ende der letzten (Niederdruck-)Metamorphose an.},
  language  = {de}
}
@article{ScheerZentgrafSauer1981,
  author    = {Scheer, Ulrich and Zentgraf, Hanswalter and Sauer, Helmut W.},
  title     = {Different chromatin structures in Physarum polycephalum: a special form of transcriptionally active chromatin devoid of nucleosomal particles},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33148},
  year      = {1981},
  abstract  = {Nonnucleolar chromatin from interphase nuclei of Physarum polycephalum plasmodia occurs in two different structural configurations as seen in electron microscopic spread preparations. While the majority of the chromatin is devoid of nascent ribonucleoprotein (RNP) fibrils and compacted into nucleosomal particles, a minor proportion (10- 20\%) is organized differently and reveals a smooth contour. It is this form of smooth chromatin which is rich in transcription units (mean length: 1.36±0.21 11m). Only occasionally are solitary nascent RNP fibrils observed which are associated with beaded strands of chromatin. In transcribed smooth chromatin nucleosomal particles are not only absent from the transcription units but also from their nontranscribed flan king regions, indicating that this special structural aspect is not merely a direct consequence of the transcriptional process. The existence of ca. 10- 20\% of Physarum chromatin in the smoothly contoured form is discussed in relation to reports of a preferential digestibility of a similar proportion of Physarum chromatin by DNAse I (Jalouzot et al. , 1980) and to the altered configuration of "peak A" chromatin subunits after micrococcal nuclease digestion (Johnson et al., 1978a, b).},
  language  = {en}
}
@article{ScheerZentgraf1978,
  author    = {Scheer, Ulrich and Zentgraf, Hanswalter},
  title     = {Nucleosomal and supranucleosomal organization of transcriptionally inactive rDNA circles in Dytiscus oocytes},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33188},
  year      = {1978},
  abstract  = {Oocytes of the water beetle, Dytiscus marginalis, contain large amounts of rDNA most of which is present in the form of rings containing one or several pre-rRNA genes. Electron microscopy of spread preparations of vitellogenic oocytes has shown that the rDNA is extended in chromatin rings with transcribed pre- rRNA genes and is not packed into nucleosomes (Trendelenburg eta!. , 1976). When similar preparations are made from previtellogenic ooytes in which a large proportion of the nuc1eolar chromatin is transcriptionally inactive, a different morphological form of this chromatin is recognized. In contrast to the transcribed chromatin rings the inactive nucleolar chromatin circles show the characteristic beaded configuration, indicative of nucleosomal packing. Nuc1eosomal packing is also indicated by the comparison of the lengths of these chromatin rings with both iso lated rDNA circ1es and transcribed chromatin rings. In addition, these inactive nuc1eofilaments often appear to be compacted into globular higher order structures of diameters from 21 to 34nm, each composed of an aggregate of 6-9 nuc1eosomes. While the estimated reduction of the overall length of rDNA, as seen in our preparations, is, on the average, only 2.2 - 2.4 fold in the nuc1eosomal state it is 10- 13 fold when supranuc1eosomal globules are present. These data show that the extrachromosomal rDNA of these oocytes goes through a cycle of condensation and extensio n, as a function of the specific transcriptional activity, and that the beaded state described here is exc1usively found in the non-transcribed state.},
  language  = {en}
}
@article{ScheerTrendelenburgKrohneetal.1977,
  author    = {Scheer, Ulrich and Trendelenburg, Michael F. and Krohne, Georg and Franke, Werner W.},
  title     = {Lengths and patterns of transcriptional units in the amplified nucleoli of oocytes of Xenopus laevis},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33069},
  year      = {1977},
  abstract  = {Transcriptionally active chromatin from peripheral amplified nuc1eoli of lampbrush-chromosome stage oocytes of Xenopus laevis was dispersed and spread in various solutions of low salt concentrations (incIuding some with additions of detergents) and examined by electron microscopy. Nucleolar material from oocytes of animals with normal (2-nu) and mutant (I-nu) genetical constitution of nucleolus organizers was compared. Histograms showing the distributions of the lengths of matrix units, apparent spacer intercepts, and the total repeating units of the rDNA containing chromatin axes revealed a significant degree of heterogeneity, with indications of subclasses and predominant repeat unit size c1asses of 3.3 and 3.8 11m length. The correspondence of matrix unit length to the molecular weight of the first stable product of rDNA transcription was studied using gel electrophoresis of labelIed pre-rRNA under non-denaturing and denaturing conditions. Evaluations of individual strands of nucleolar chromatin furt her demonstrated the existence of both (i) strands with obviously homogeneous repeating units and (ii) strands with intra-axial heterogeneity of rDNA subunits. " Preludecomplexes ", i.e. groups of transcriptional complexes in apparent spacer intercepts, were not infrequently noted. The data are compared with the measurements of lengths of repeating units in fragments of rDNA obtained by digestion with EcoRI endonuclease as described by Morrow et al. (1974) and Wellauer et al. (1974, 1976a, b). The results are discussed in relation to problems of variations in the modes of arrangement of the pre-rRNA genes, the state of packing of rDNA during transcription, and possible mechanisms of the amplification process.},
  language  = {en}
}
@article{ZentgrafMuellerScheeretal.1981,
  author    = {Zentgraf, H. and M{\"u}ller, U. and Scheer, Ulrich and Franke, W. W.},
  title     = {Evidence for the existence of globular units in the supranucleosomal organization of chromatin},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-34123},
  year      = {1981},
  abstract  = {No abstract available},
  language  = {en}
}
@article{SchuesslerHenjesKunst1994,
  author    = {Sch{\"u}ssler, Ulrich and Henjes-Kunst, Friedhelm},
  title     = {Petrographical and Geochronological Investigations on a Garnet-Tourmaline Pegmatite from Ringgold Knoll, Oates Coast, Antarctica},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-31789},
  year      = {1994},
  abstract  = {The Ringgold Knoll pegmatite, a late-stage member of the Granite Harbour Intrusives, crosscuts high-grade Wilson gneisses of the Oates Coast, which forms the westernmost part of the Wilson Terrane at the Pacific end of the Cambro-Ordovician Ross orogenic belt in West Antarctica. The pegmatite mineral assemblage consists of K-feldspar, plagioclase, quartz, garnet (almandinespessartine-pyrope), dark tourmaline (schorl-dravite), muscovite, apatite, monazite, zircon, blue AI-rich tourmaline and dumortierite in order of decreasing abundances. Major, minor and rare earth elements are reported for the greater part of the mineral assemblage. The time of pegmatite emplacement is constrained by Rb-Sr and Sm-Nd isochron ages of 492 ± 8 (2a) Ma and 500 ± 40 (2a) Ma, respectively. High initial 87Sr/86Sr of 0.7315 ± 0.0003 and low E Nd,t of -8.7 ± 1.2 strongly support an origin of the magma from highly evolved crustal source rocks. K-Ar and Ar-Ar model ages of about 470 to 475 Ma for igneous muscovite indicate that the pegmatite together with its wall rocks spent a prolonged period at elevated temperatures before final cooling below about 350 °C. The muscovite dates may give an estimate for the time of exhumation of the Oates Coast crystalline basement along two major late Ross orogenic detachment zones within the Wilson Terrane i.e. the Wilson and the Exiles thrusts (c.f. FL{\"O}TTMANN and KLEINSCHMIDT, 1991).},
  language  = {en}
}
@article{FialaMaschwitz1992,
  author    = {Fiala, Brigitte and Maschwitz, Ulrich},
  title     = {Domatia as most important adaptations in the evolution of myrmecophytes in the paleotropical tree genus Macaranga (Euphorbiacae)},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32935},
  year      = {1992},
  abstract  = {The paleotropical tree genus Macaranga (Euphorbiaceae) comprises all stages of interaction with ants, from facultative associations to obligate myrmecophytes. In SE.-Asia food availability does not seem to be the limiting factor for the development of a close relationship since all species provide food for ants in form of extrafloral nectar and/or food bodies. Only myrmecophytic Macaranga species offer nesting space for ants (domatia) inside intern odes which become hollow due to degeneration of the pith. Non-myrmecophytic species have a solid stem with a compact and wet pith and many resin ducts. The stem interior of some transitional species remains solid, but the soft pith can be excavated. The role of different ant-attracting attributes for the development of obligate ant-plant interactions is discussed. In the genus Macaranga, the provision of nesting space seems to be the most important factor for the evolution of obligate myrmecophytism.},
  language  = {en}
}