TY - JOUR A1 - Tacke, Reinhold A1 - Lange, Hartwig A1 - Bentlage, Anke A1 - Sheldrick, William S. A1 - Ernst, Ludger T1 - 2.2.5.5-Tetraorganyl-1.4-dioxa-2.5-disilacyclohexane/2,2,5,5-Tetraorganyl-1,4-dioxa-2,5-disilacyclohexanes JF - Zeitschrift für Naturforschung B N2 - The 2,2,5,5-tetraorganyl-1,4-dioxa-2,5-disilacyclohexanes 2a-2c were prepared by condensation of the corresponding (hydroxymethyl)diorganylsilanes 1 a-1 c. The constitution of the heterocycles was confirmed by elemental analyses, cryoscopic measurements, mass spectrometry, and NMR-spectroscopic \((^1H, ^{13}C)\) investigations. The molecular structure of 2 b was determined by X-ray diffraction analysis. KW - 1,4-Dioxa-2 KW - 5-disila-cyclohexane ring system KW - synthesis KW - structure Y1 - 1983 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-128423 VL - 38 IS - 2 ER - TY - JOUR A1 - Brill, Michael A1 - Schwab, Frank T1 - A mixed-methods approach using self-report, observational time series data, and content analysis for process analysis of a media reception phenomenon JF - Frontiers in Psychology N2 - Due to the complexityof research objects, theoretical concepts, and stimuli in media research, researchers in psychology and communications presumably need sophisticated measures beyond self-report scales to answer research questions on media use processes. The present study evaluates stimulus-dependent structure in spontaneous eye-blink behavior as an objective, corroborative measure for the media use phenomenon of spatial presence. To this end, a mixed methods approach is used in an experimental setting to collect, combine, analyze, and interpret data from standardized participant self-report, observation of participant behavior, and content analysis of the media stimulus. T-pattern detection is used to analyze stimulus-dependent blinking behavior, and this structural data is then contrasted with self-report data. The combined results show that behavioral indicators yield the predicted results, while self-report data shows unpredicted results that are not predicted by the underlying theory. The use of a mixed methods approach offered insights that support further theory development and theory testing beyond a traditional, mono-method experimental approach. KW - presence KW - measurement KW - blinking KW - structure KW - mixed methods Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-201380 VL - 10 ER - TY - JOUR A1 - Latifi, Hooman A1 - Valbuena, Ruben T1 - Current trends in forest ecological applications of three-dimensional remote sensing: Transition from experimental to operational solutions? JF - Forests N2 - The alarming increase in the magnitude and spatiotemporal patterns of changes in composition, structure and function of forest ecosystems during recent years calls for enhanced cross-border mitigation and adaption measures, which strongly entail intensified research to understand the underlying processes in the ecosystems as well as their dynamics. Remote sensing data and methods are nowadays the main complementary sources of synoptic, up-to-date and objective information to support field observations in forest ecology. In particular, analysis of three-dimensional (3D) remote sensing data is regarded as an appropriate complement, since they are hypothesized to resemble the 3D character of most forest attributes. Following their use in various small-scale forest structural analyses over the past two decades, these sources of data are now on their way to be integrated in novel applications in fields like citizen science, environmental impact assessment, forest fire analysis, and biodiversity assessment in remote areas. These and a number of other novel applications provide valuable material for the Forests special issue “3D Remote Sensing Applications in Forest Ecology: Composition, Structure and Function”, which shows the promising future of these technologies and improves our understanding of the potentials and challenges of 3D remote sensing in practical forest ecology worldwide. KW - 3D remote sensing KW - composition KW - forest ecology KW - function KW - structure Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-193282 SN - 1999-4907 VL - 10 IS - 10 ER - TY - JOUR A1 - Butt, Elke A1 - Howard, Cory M. A1 - Raman, Dayanidhi T1 - LASP1 in cellular signaling and gene expression: more than just a cytoskeletal regulator JF - Cells N2 - LIM and SH3 protein 1 was originally identified as a structural cytoskeletal protein with scaffolding function. However, recent data suggest additional roles in cell signaling and gene expression, especially in tumor cells. These novel functions are primarily regulated by the site-specific phosphorylation of LASP1. This review will focus on specific phosphorylation-dependent interaction between LASP1 and cellular proteins that orchestrate primary tumor progression and metastasis. More specifically, we will describe the role of LASP1 in chemokine receptor, and PI3K/AKT signaling. We outline the nuclear role for LASP1 in terms of epigenetics and transcriptional regulation and modulation of oncogenic mRNA translation. Finally, newly identified roles for the cytoskeletal function of LASP1 next to its known canonical F-actin binding properties are included. KW - LASP1 KW - AKT KW - CXCR4 KW - structure KW - cytoskeleton KW - phosphorylation KW - transcriptional regulation KW - epigenetics KW - nucleus Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-297447 SN - 2073-4409 VL - 11 IS - 23 ER - TY - JOUR A1 - Greefrath, Gilbert A1 - Oldenburg, Reinhard A1 - Siller, Hans-Stefan A1 - Ulm, Volker A1 - Weigand, Hans-Georg T1 - Mathematics students’ characteristics of basic mental models of the derivative JF - Journal für Mathematik-Didaktik N2 - The concept of derivative is characterised with reference to four basic mental models. These are described as theoretical constructs based on theoretical considerations. The four basic mental models—local rate of change, tangent slope, local linearity and amplification factor—are not only quantified empirically but are also validated. To this end, a test instrument for measuring students’ characteristics of basic mental models is presented and analysed regarding quality criteria. Mathematics students (n = 266) were tested with this instrument. The test results show that the four basic mental models of the derivative can be reconstructed among the students with different characteristics. The tangent slope has the highest agreement values across all tasks. The agreement on explanations based on the basic mental model of rate of change is not as strongly established among students as one would expect due to framework settings in the school system by means of curricula and educational standards. The basic mental model of local linearity plays a rather subordinate role. The amplification factor achieves the lowest agreement values. In addition, cluster analysis was conducted to identify different subgroups of the student population. Moreover, the test results can be attributed to characteristics of the task types as well as to the students’ previous experiences from mathematics classes by means of qualitative interpretation. These and other results of students’ basic mental models of the derivative are presented and discussed in detail. N2 - Der Begriff der Ableitung wird anhand von vier Grundvorstellungen charakterisiert. Diese werden als theoretische Konstrukte beschrieben, die auf theoretischen Überlegungen beruhen. Die vier Grundvorstellungen – lokale Änderungsrate, Tangentensteigung, lokale Linearität und Verstärkungsfaktor – werden empirisch quantifiziert und validiert. Zu diesem Zweck wird ein Testinstrument zur Messung der Charakteristika dieser Grundvorstellungen von Lernenden erstellt, bzgl. Gütekriterien ausgewertet und an Mathematikstudierenden (n = 266) getestet. Die Ergebnisse zeigen, dass die vier Grundvorstellungen der Ableitung bei den Lernenden mit unterschiedlichen Merkmalen rekonstruiert werden können. Die Tangentensteigung weist über alle Aufgaben hinweg die höchsten Übereinstimmungswerte auf. Die Übereinstimmung bei Erklärungen, die auf der Grundvorstellung der lokalen Änderungsrate beruhen, ist bei den Studierenden nicht so stark ausgeprägt, wie man es aufgrund der Rahmenbedingungen im Schulsystem durch Lehrpläne und Bildungsstandards erwarten würde. Die Grundvorstellung der lokalen Linearität spielt eine eher untergeordnete Rolle. Der Verstärkungsfaktor erzielt die geringsten Übereinstimmungswerte. Darüber hinaus wurde eine Clusteranalyse durchgeführt, um verschiedene Untergruppen der Schülerpopulation zu identifizieren. Die Testergebnisse können mittels qualitativer Interpretation auf Merkmale der Aufgabentypen sowie auf die Vorerfahrungen der Studierenden aus dem Mathematikunterricht zurückgeführt werden. Diese und weitere Ergebnisse zu den grundlegenden mentalen Modellen der Studierenden zur Ableitung werden ausführlich dargestellt und diskutiert. KW - derivative KW - basic mental models KW - structure KW - test instrument KW - Ableitung KW - Grundvorstellung KW - Struktur KW - Testinstrument Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-324317 SN - 0173-5322 VL - 44 IS - 1 ER - TY - THES A1 - Krüger, Reinhard T1 - Pyrolyse- und Sinterverhalten Sol-Gel-abgeleiteter Al2O3-YAG-Fasern T1 - Pyrolysis and Sintering Behavior of Sol–Gel-Derived Al2O3-YAG Fibers N2 - Nichtwäßrige Sol-Gel-Vorstufen, die zu einem Mischgefüge aus Al2O3 und YAG führen (Volumenverhältnis 45 : 55), wurden zu Fasern versponnen, in unterschiedlichen Atmosphären pyrolysiert und abschließend gesintert. Die strukturelle Ent-wicklung während der Pyrolyse der Gel-Fasern wurde in Abhängigkeit von Pyrolysetemperatur (200-850 °C) und -atmosphäre beschrieben. Die Zusammenhänge zwischen den mittels der Pyrolyseparameter variierten amorphen Strukturen und dem daraus resultierenden Kristallisations- und Sinterverhalten sowie den mechanischen Fasereigenschaften wurden gezeigt. Die isotropen Gel-Fasern sind frei von Poren und weisen lokal regelmäßig angeordnete, organische Domänen mit mittleren Abständen von 2 nm innerhalb des anorganischen Matrixgerüsts auf. Während der Pyrolyse auftretende Strukturveränderungen hängen stark von der Atmosphäre und der Temperatur ab. In Luft- und Sauerstoffatmosphäre trat ab 600 °C innerhalb der Fasern lokal eine Kristallisation von YAG und Korund in Form kugeliger Bereiche auf, die zum Bruch der Fasern bereits während der Pyrolyse führten. Die Abgabe organischer Bestandteile erfolgte bei Pyrolyse in Stickstoff im wesentlichen zwischen 300 °C und 500 °C, blieb jedoch auch bei höheren Temperaturen unvollständig. In Wasserdampf-Atmosphäre kam es durch Hydrolysereaktionen zwischen 250 °C und 385 °C zu einer verbesserten Abgabe der organischen Bestandteile. Der Kohlenstoffgehalt sinkt bei 385 °C unter 2 Masse-%. Werden dem Wasserdampf saure Gase wie z.B. Stickoxide zugesetzt, wird um 200 °C die Hydrolyse und Abgabe der Organik zusätzlich verstärkt. Nach Pyrolyse in Stickstoff oder wasserhaltigen Atmosphären blieben die Fasern amorph. Bei Pyrolyse in Stickstoff war die Struktur der Fasern porenfrei, wobei die organischen Pyrolysatreste wie in den Gel-Fasern als regelmäßig angeordnete, isolierte Bereiche innerhalb einer anorganischen Matrix vorlagen. In Wasserdampf bildete sich ab 250 °C aus den organischen Domänen eine geordnete Porenstruktur, die sich mit ansteigender Temperatur vergröberte. Auch in der aus verdampfter Salpetersäure erzeugten Atmosphäre bildeten sich Poren. Die Porendurchmesser und spezifischen Oberflächen der Fasern blieben jedoch geringer als in reinem Wasserdampf. In dem anorganischen Matrixgerüst änderten sich durch die Pyrolyse die Koordinationsverhältnisse der Al-Ionen. Ausgehend von der mehrheitlich 6-fachen Koordination in den Gel-Fasern kam es zunehmend zur Umlagerung in die 4- und 5-fache Koordination. Bei Pyrolyse in reinem Wasserdampf war diese Koordinationsveränderung deutlich schwächer ausgeprägt als in Stickstoff oder der Atmosphäre aus verdampfter Salpetersäure. Während der Sinterung treten intermediär gamma-Al2O3 und hexagonales YAlO3 als metastabile Phasen vor der Kristallisation von YAG auf. Mit der Kristallisation von Korund schließt die Phasenbildung der Al2O3-YAG-Fasern je nach vorangegangener Pyrolysebehandlung zwischen 1275 °C und 1315 °C ab. Die Abweichungen in der Kristallisationstemperatur bzw. Keimbildungsdichte von Korund und im Sinterverhalten ließen sich auf die Unterschiede in den amorphen Strukturen der pyrolysierten Fasern zurückführen. Hohe Anteile 6-fach koordinierter Al-Ionen und eine zu hohen spezifischen Oberflächen führende, feine Porosität erwiesen sich als günstige Strukturmerkmale für pyrolysierte Fasern. Die dabei entstandenen feinkörnigen, homogenen Gefüge konnten dicht gesintert werden und hatten die höchsten Festigkeiten und E-Moduln. Kohlenstoffgehalte bis zu 2 Masse-% wirkten sich in den offenporigen Zwischenprodukten nicht negativ auf das Sinterverhalten aus. In dieser Arbeit wurde gezeigt, daß die Kristallisation der Sol-Gel-abgeleiteten Fasern und damit auch die Ausbildung der keramischen Gefüge in entscheidendem Maße von den Pyrolysebedingungen abhängen. Bei einheitlicher Synthese der Gel-Fasern lassen sich durch die Pyrolysebehandlung unterschiedliche Strukturen in den amorphen Zwischenprodukten einstellen, die durch ihre spezifisches Kristallisations- und Sinterverhalten zu unterschiedlichen keramischen Gefügen in den Fasern führen. Die Optimierung der Gefüge vorstufenabgeleiteter Keramiken durch Zusatz von Keimen ("Seeding") ist seit längerem bekannt. In Ergänzung dazu bietet die gezielte Wahl der Pyrolysebedingungen eine weitere Möglichkeit zur Steuerung der Gefügeausbildung in Sol-Gel-Keramiken. N2 - Ceramic fibers of Al2O3-YAG composition (volume ratio 45 : 55) were prepared by spinning non-aqueous sol-gel precursors to fibers which were then pyrolyzed in various atmospheres and finally sintered. Structural development of the gel fibers upon pyrolysis at temperatures between 200 °C and 850 °C was described for different atmospheres. Variation of pyrolysis conditions lead to different amorphous structures. A correlation between the amorphous structures and their crystallization and sintering behavior as well as mechanical fiber properties could be established. The gel fibers have an isotropic, pore-free structure which is characterized by an inorganic matrix that contains organic domains in a locally ordered arrangement with mean distances of 2 nm. Alteration of this structure strongly depends on the type of atmosphere and temperature during pyrolysis. In air and oxygen above 600 °C local, spherulitic crystallization of YAG and corundum occurs within the fibers and leads to fracture of the fibers. In nitrogen, organic constituents are mainly removed between 300 and 500 °C, but residues remain even at higher temperatures. Water vapor hydrolyses organic constituents and enhances their release at 200-385 °C. Thus carbon contents drops below 2 wt.-% at 385 °C. Additional acceleration of hydrolysis at ~200 °C can be achieved by addition of acidic gases like nitric oxide to the moist atmosphere. The structure of fibers pyrolysed in nitrogen or moist atmospheres remains amorphous. After pyrolysis in nitrogen the fibers are pore-free and the organic residues still appear as locally ordered domains within an inorganic matrix. In water vapor from 250 °C on, the release of organics leads to the formation of ordered micropores that coarsen with further increasing temperature. In the atmosphere of evaporated nitric acid, pores form too, but pore sizes and specific surface areas of the fibers are lower than in pure water vapor. The coordination of Al-ions in the inorganic network is altered by pyrolysis. Gel fibers mainly contain 6-fold coordinated Al-ions. With increasing temperature a rearrangement of part of the octahedrally coordinated Al-ions to 4- and 5-fold coordination was observed. While this rearrangement was only weakly pronounced for fibers pyrolysed in water vapor, in nitrogen or the atmosphere that was derived from evaporated nitric acid a significantly higher proportion of 6-fold coordinated Al-ions rearranged to lower coordination numbers. During the sintering process gamma-Al2O3 and hexagonal YAlO3 are formed as intermediate metastable phases prior to the crystallization of YAG. Formation of crystalline phases in the Al2O3-YAG fibers completes with the crystallization of corundum at 1275 to 1315 °C depending on pyrolysis conditions. Differences in crystallization temperature and nucleation density of corundum were put down the structural features of pyrolysed, amorphous fibers. A high proportion of 6-fold coordinated Al-ions and a high specific surface caused by fine pores revealed as favorable characteristics of low corundum crystallization temperature and high nucleation density. Such fibers could be fully densified resulting in the highest strength and Young's moduli in the ceramic fibers. Carbon contents up to 2 wt.-% were not deleterious to the densification of pyrolysed fibers with an open porous structure. The results presented in this study show that crystallization and microstructural evolution of sol-gel derived ceramic fibers critically depend on pyrolysis conditions. Different amorphous structures that lead to altered ceramic microstructures can be obtained from uniformly synthesized gel fibers by variation of pyrolysis conditions. Seeding is a well known process for the microstructural optimization of precursor derived ceramics. As a supplement the choice of suitable pyrolysis conditions is a further tool for the microstructure control in sol-gel ceramics. KW - Keramikfaser KW - Sol-Gel-Verfahren KW - Pyrolyse KW - Kristallisation KW - Sintern KW - Mechanische Eigenschaft KW - Korund KW - YAG KW - Mikrostruktur KW - Pyrolyse KW - Struktur KW - Sol-Gel KW - Faser KW - Al2O3 KW - pyrolysis KW - structure KW - sol-gel KW - fiber KW - Al2O3 Y1 - 2002 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-6827 ER - TY - THES A1 - Qiu, Liyan T1 - Structural and functional analysis of crossveinless 2 / BMP-2 /Chordin interaction N2 - No abstract available KW - structure KW - protein KW - BMP Y1 - 2008 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-29249 ER - TY - JOUR A1 - Kaltdorf, Martin A1 - Srivastava, Mugdha A1 - Gupta, Shishir K. A1 - Liang, Chunguang A1 - Binder, Jasmin A1 - Dietl, Anna-Maria A1 - Meir, Zohar A1 - Haas, Hubertus A1 - Osherov, Nir A1 - Krappmann, Sven A1 - Dandekar, Thomas T1 - Systematic Identification of Anti-Fungal Drug Targets by a Metabolic Network Approach JF - Frontiers in Molecular Bioscience N2 - New antimycotic drugs are challenging to find, as potential target proteins may have close human orthologs. We here focus on identifying metabolic targets that are critical for fungal growth and have minimal similarity to targets among human proteins. We compare and combine here: (I) direct metabolic network modeling using elementary mode analysis and flux estimates approximations using expression data, (II) targeting metabolic genes by transcriptome analysis of condition-specific highly expressed enzymes, and (III) analysis of enzyme structure, enzyme interconnectedness (“hubs”), and identification of pathogen-specific enzymes using orthology relations. We have identified 64 targets including metabolic enzymes involved in vitamin synthesis, lipid, and amino acid biosynthesis including 18 targets validated from the literature, two validated and five currently examined in own genetic experiments, and 38 further promising novel target proteins which are non-orthologous to human proteins, involved in metabolism and are highly ranked drug targets from these pipelines. KW - metabolism KW - targets KW - antimycotics KW - modeling KW - structure KW - interaction KW - fungicide Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-147396 VL - 3 ER -