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In the various groups of social bees, different systems of communication about food sources occur. These communication systems are different solutions to a common problem of social insects: efficiently allocating the necessary number of workers first to the task of foraging and second to the most profitable food sources. The solution chosen by each species depends on the particular ecological circumstances as well as the evolutionary history of that species. For example, the outstanding difference between the bumble bee and the honey bee system is that honey bees can communicate the location of profitable food sources to nestmates, which bumble bees cannot. To identify possible selection pressures that could explain this difference, I have quantified the benefits of communicating location in honey bees. I show that these strongly depend on the habitat, and that communicating location might not benefit bees in temperate habitats. This could be due to the differing spatial distributions of resources in different habitats, in particular between temperate and tropical regions. These distributions may be the reason why the mostly temperate-living bumble bees have never evolved a communication system that allows them to transfer information on location of food sources, whereas most tropical social bees (all honey bees and many stingless bees) are able to recruit nestmates to specific points in their foraging range. Nevertheless, I show that in bumble bees the allocation of workers to foraging is also regulated by communication. Successful foragers distribute in the nest a pheromone which alerts other bees to the presence of food. This pheromone stems from a tergite gland, the function of which had not been identified previously. Usage of a pheromone in the nest to alert other individuals to forage has not been described in other social insects, and might constitute a new mode of communicating about food sources. The signal might be modulated depending on the quality of the food source. Bees in the nest sample the nectar that has been brought into the nest. Their decision whether to go out and forage depends not only on the pheromone signal, but also on the quality of the nectar they have sampled. In this way, foraging activity of a bumble bee colony is adjusted to foraging conditions, which means most bees are allocated to foraging only if high-quality food sources are available. In addition, foraging activity is adjusted to the amount of food already stored. In a colony with full honeypots, no new bees are allocated to foraging. These results help us understand how the allocation of workers to the task of food collection is regulated according to external and internal nest conditions in bumble bees.
S=N versus S+-N-
(2002)
The main aim of this thesis was to characterise structurally four sulfur-nitrogen compounds in terms of their experimental electron density distribution: Sulfurdiimide S(NtBu)2 (I), sulfurtriimide S(NtBu)3 (II), methyl(diimido)sulfinic acid H(NtBu)2SMe (III) and methylene-bis(triimido)sulfonic acid CH2{S(NtBu)2(HNtBu)}2 (IV). The electron density was determined by multipole refinements on high-resolution X-ray data at low temperatures. The refined densities were analysed by means of Bader’s theory of ‘Atoms in Molecules’ to get information about the bonding types (shared/ closed shell), bond strengths, and the extent of polarisation. The distributions of the static deformation densities, which already showed the most important electronical features as lone-pairs and bonding densities, were calculated for all compounds. The spatial distributions provided a first impression about the bonding properties. The nitrogen lone-pair densities were found to be inclined towards the electropositive sulfur atoms. In II, III and IV the spatial distributions already suggested sp3 hybridisation of the nitrogen atoms. In I gradual differences between the E/Z and Z/Z oriented NtBu groups were visualised. The charge density distribution was analysed along the bond paths, which showed some of the S,N bonds to be considerably bent. In the central part of the thesis detailed topological analyses of the electron density distributions were performed. All BCPs and the related electronical properties as the electron density, the negative Laplacian, the eigenvalues of the Hessian matrix, and several values, which can be deduced from these, were calculated. Due to the low number of comparable published compounds, internal scaling facilitated by III and IV led to system-specific ranking of the S-N and S-C bonds in terms of bond type (shared vs. closed shell), bond order, and bond strength. To quantify bond polarisation a criterion was developed which relates shifts in the BCPs to electron transfer from the electropositive to the electronegative bonding partner. The distributions of the Laplacian were determined for all S-E (E = N, C) bonds because of their fundamental importance for the classification of atomic interactions. Furthermore, the spatial distribution of the negative Laplacian with respect to all important bonds was determined around the central sulfur and nitrogen atoms. The analyses led to detailed information about the S,N interactions. A calculation of the reactive surfaces where the Laplacian equals zero revealed possible reaction pathways of nucleophilic attacks to the central sulfur atoms. All nitrogen atoms in H(NtBu)2SMe (III) as well as in CH2{S(NtBu)2(HNtBu)}2 (IV) are predominantly sp3 hybridised. The S,N bonds should therefore be formulated as S+–N– single bonds, strengthened and shortened by electrostatic reinforcement. In S(NtBu)2 (I) the sp2 hybridisation of the nitrogen atoms was verified. All topological criteria unearthed the inequality of the formally equivalent S=N double bonds. The differences were assigned to the molecular E/Z conformation in the solid state. Interaction between the in-plane lone-pair density of the nitrogen and the sulfur atom located at the same side causes the non-bonding charge concentration at the sulfur atom to be dislocated into the second S–N bond. The existence of a delocalised 3-centres-2-electrons system within the planar SN2 core was assumed to be formed by non-hybridised p-orbitals. An effective delocalisation was found to be possibly disturbed by a weak intermolecular S...S interaction. The interpretation of the S,N interaction in S(NtBu)3 (II) was not straightforward, since the electron density distribution showed both, indicators for multiple bonding as well as for sp3 hybridisation of the nitrogen atoms, which verifies the formulation of a S+–N– bonding mode. The bonding situation in S(NtBu)3 was identified as an intermediate state between that of a delocalised 4-centres-6-electrons system formed by non-hybridised p-orbitals within the planar SN3 unit and that of a S+–N– system.
A quantitative model of groundwater flows contributing to the Goblenz state water scheme at the north-western fringe of the Kalahari was developed within this study. The investigated area corresponds to the Upper Omatako basin and encompasses an outer mountainous rim and sediments of the Kalahari sand desert in the centre. This study revealed the eminent importance of the mountainous rim for the water balance of the Kalahari, both in terms of surface and ground water. A hydrochemical subdivision of groundwater types in the mountain rim around the Kalahari was derived from cluster analysis of hydrochemical groundwater data. The western and south-western secondary aquifers within rocks of the Damara Sequence, the Otavi Mountain karst aquifers of the Tsumeb and Abenab subgroups as well as the Waterberg Etjo sandstone aquifer represent the major hydrochemical groups. Ca/Mg and Sr/Ca ratios allowed to trace the groundwater flow from the Otavi Mountains towards the Kalahari near Goblenz. The Otavi Mountains and the Waterberg were identified as the main recharge areas showing almost no or only little isotopic enrichment by evaporation. Soil water balance modelling confirmed that direct groundwater recharge in hard-rock environments tends to be much higher than in areas covered with thick Kalahari sediments. According to the water balance model average recharge rates in hard-rock exposures with only thin sand cover are between 0.1 and 2.5 % of mean annual rainfall. Within the Kalahari itself very limited recharge was predicted (< 1 % of mean annual rainfall). In the Upper Omatako basin the highest recharge probability was found in February in the late rainfall season. The water balance model also indicated that surface runoff is produced sporadically, triggering indirect recharge events. Several sinkholes were discovered in the Otavi Foreland to the north of Goblenz forming short-cuts to the groundwater table and preferential recharge zones. Their relevance for the generation of indirect recharge could be demonstrated by stable isotope variations resulting from observed flood events. Within the Kalahari basin several troughs were identified in the pre-Kalahari surface by GIS-based analyses. A map of saturated thickness of Kalahari sediments revealed that these major troughs are partly saturated with groundwater. The main trough, extending from south-west to north-east, is probably connected to the Goblenz state water scheme and represents a major zone of groundwater confluence, receiving groundwater inflows from several recharge areas in the Upper Omatako basin. As a result of the dominance of mountain front recharge the groundwater of the Kalahari carries an isotopic composition of recharge at higher altitudes. The respective percentages of inflow into the Kalahari from different source areas were determined by a mixing-cell approach. According to the mixing model Goblenz receives most of its inflow (70 to 80 %) from a shallow Kalahari aquifer in the Otavi Foreland which is connected to the Otavi Mountains. Another 15 to 10 % of groundwater inflow to the Kalahari at Goblenz derive from the Etjo sandstone aquifer to the south and from inflow of a mixed component. In conclusion, groundwater abstraction at Goblenz will be affected by measures that heavily influence groundwater inflow from the Otavi Mountains, the Waterberg, and the fractured aquifer north of the Waterberg.
In north-western Namibia the fills of the Karoo-Etendeka depositories can be subdivided into (1) a Carboniferous-Permian, (2) a Triassic-Jurassic and (3) a Cretaceous megasequence, each recording extensional periods related to successive rifting phases in the evolving South Atlantic. The tectonic environment of the depositories in north-western Namibia changes successively from the coast towards the continental interior, which is reflected by the facies distribution and the position of time-stratigraphic gaps. Close to the present-day coastline synsedimentary listric faults, trending parallel to the South Atlantic rift (N-S), caused the formation of wedge shaped sediment bodies. Here, the Karoo Supergroup is only represented by the Permian succession in the Huab area. A hiatus within the Permian can be recognised by the correlation with the main Karoo Basin in South Africa and the Brazilian Paraná Basin. This stratal gap correlates with a pre-Beaufort Group unconformity in the main Karoo Basin that might be related to an orogenic pulse in the Cape Fold Belt. The Permian succession itself is unconformably overlain by the Lower Cretaceous Etendeka Group. This hiatus extending from the Upper Permian to the Lower Cretaceous has probably been induced by a combination of rift shoulder uplift and additional crustal doming associated with Etendeka flood volcanism. The enhanced tectonism during the Early Cretaceous controlled accommodation space for the alluvial-fluvial and aeolian deposits of the lower Etendeka Group. Disconformities within those deposits and the overlying lava succession attribute to distinct phases of tectonic and volcanic activity heralding the South Atlantic breakup. Towards the south-east, the Karoo succession becomes successively more complete. In the vicinity of Mt. Brandberg Early Triassic strata (Middle Omingonde Formation) follow disconformably above the Upper Permian/Lowermost Triassic Doros Formation. The sedimentation there was essentially controlled by the SW-NE trending Damaraland Uplift. South of the Damaraland Uplift the SW-NE trending Waterberg-Omaruru Fault zone is interpreted as a sinistral oblique-slip fault that compartmentalised the South Atlantic rift. This fault controlled accommodation space of the entire Triassic Omingonde Formation and the Early Jurassic Etjo Formation in its associated pull-apart and transtension structures. A locally well developed angular unconformity defines a hiatus between the two formations. Correlation with the main Karoo Basin in South Africa confirms that this gap is of a regional extent and not only a local, fault induced feature. Furthermore, it might also correlate with an orogenic pulse of the Cape Fold Belt. In general, the Mesozoic megasequences record the long-lived history of the southern Atlantic rift evolution. Rifting has been controlled by orogenic pulses derived from the Samfrau active margin throughout the Mesozoic. The associated intracratonic E-W extension caused the formation of grabens and conjugated oblique-slip zones. The generation of voluminous flood basalts marks the climax of intracratonic extension that was accompanied by enhanced uplift of the rift shoulders.
Clinical evaluation of novel methods to determine dialysis parameters using conductivity cells
(2002)
Eine die letzten beiden Jahrzehnte anhaltende Diskussion über die erforderliche Dosis Dialyse, die ein Patient benötigt, ergab, daß der Harnstoff-basierte Kt/V-Wert signifikant mit der Morbidität von ‚end stage renal deasease' (ESRD)- Patienten korreliert. Wenn auch nicht vollständig akzeptiert, so scheint es doch zunehmende Übereinkunft zwischen Nephrologen, daß eine angemessene Dialysebehandlung von Patienten ohne Restdiurese im Rahmen eines 3x4 Stunden pro Woche- Schemas mindestens einen Kt/V-Wert von 1.2 bis 1.3 ergeben sollte, um auf lange Sicht die Lebensqualität zu sichern und die Morbidität und Mortalität niedrig zu halten. K ist die vom Dialysesystem erbrachte Clearance, t die Behandlungszeit und V das Harnstoff-Verteilungsvolumen, welches dem Gesamt-Körperwasser nahezu gleicht. Kt/V wird in der Dosiseinheit (ml Medikament pro ml Körperwasser) ausgedrückt und daher auch häufig als Dialyse-‚Dosis' bezeichnet, auch wenn darüber wegen der Zusammenfassung in nur einer Harnstoff-korrelierten Zahl konträr diskutiert wird. Diese Arbeit besitzt eine eher technische Prämisse und möchte sich nicht an dieser Diskussion beteiligen. Sie möchte dem interessierten Nephrologen lediglich eine patientenfreundliche, präzise, kostenneutrale und leicht zu handhabende technische Lösung an die Hand geben, um kontinuierlich die in Kt/V ausgedrückte Dialysedosis zu überwachen. Natürlich ist damit auch die Hoffnung verbunden, daß die Langzeit-Sterblichkeit verringert werden kann, wenn eine flächendeckende, zeitnahe Erfolgskontrolle der Dialyse ermöglicht wird. Die gewählte technische Lösung basiert auf der Äquivalenz der Diffusionskoeffizienten von gelöstem Harnstoff und Natriumchlorid. Es ist das zentrale Anliegen dieser Studie, festzustellen, ob das Diffusionsverhalten von NaCl und Harnstoff beim Durchtritt durch die Membran des Dialysefilters gleich ist. Der entscheidende Vorteil, der das Verfahren so leicht handhabbar macht, besteht darin, daß NaCl-Konzentrationen sehr genau durch die ohnehin in großer Zahl in Dialysegeräten verwendeten Leitfähigkeitsmeßzellen bestimmt werden können. Um die NaCl-Massenbilanz über den Dialysefilter zu bestimmen, benötigt man lediglich eine weitere Meßzelle, die stromab des Filters zu installieren ist. Die Messung von Harnstoff, die indirekt über die enzymatische Zerlegung in Ammonium-Ionen und das anschließende Erzeugen eines hoch zu verstärkenden elektrischen Potentials an einer Membran geschieht, ist komplizierter. Zudem ist eine geschlossene Kühlkette für das Enzym sicher zu stellen. Um eine leitfähigkeitsbasierte technische Lösung abzusichern, wurden zwei klinische Studien durchgeführt. In der ersten Studie wurde die Leitfähigkeit in Form von konstanten Stufenprofilen variiert. Sie wurde ausgehend von der Grundlinie für 7 min erhöht und anschließend für 7 min erniedrigt. Das Prinzip einer solchen Messung wurde erstmals 1982 in einer Patentschrift beschrieben. In einer Sequenz von 494 solchen Messungen in 206 automatisch aufgezeichneten Dialysesitzungen an 22 Patienten wurde gefunden, daß sich die Harnstoff- Clearance elektrolytisch mit einer Genauigkeit von -1.46+/-4.75% (Fehler+/-Standardabweichung) messen ließ. Die Messung von Kt/V gemäß dem Ein-Kompartment-Modell ergab eine ähnliche Genauigkeit von 2.88+/-4.15%. Obgleich diese Ergebnisse in Übereinstimmung mit anderen Studien stehen, wurde ein Effekt bemerkt, der nicht in Einklang mit der zunächst bestehenden Theorie zu bringen war. Dieser Effekt besteht darin, daß die Genauigkeit der elektrolytischen Clearancemessung vom beim Patienten vorhandenen Harnstoff-Verteilungsvolumen abhängig war. Weiter war es nicht bedeutungslos, welchen Teil des dreiteiligen Stufenprofils man zur Auswertung heranzog: Den Grundlinie-Hoch- Übergang, den von der Grundlinie zum Niedrig-Nieveau oder den Hoch-Niedrig- Übergang. Dies deutete auf einen Mangel an theoretischem Verständnis hin. Eine genaue weitere Untersuchung führte zu dem Ergebnis, daß unerwünschter NaCl-Transfer vom und zum Patienten die Ursache für die Abhängigkeit vom Verteilungsvolumen war. Es wurde daraufhin die Theorie dahingehend erweitert, daß dieser Effekt korrekt und plausibel beschrieben werden konnte. Aus dieser Erweiterung ergab sich die neue Forderung, den NaCl-Transfer bei der Messung weitestgehend zu minimieren. Die Benutzung von Stufenprofilen stellte hier jedoch an sich eine Limitierung dar, da in der zum Einnehmen eines stabilen Zustandes erforderlichen Zeit zuviel NaCl über die Membran transferiert wurde. Die Konsequenz war, von den Stufenprofilen auf kurze, dynamische Leitfähigkeitsboli überzugehen, die erlaubten, die NaCl-Gabe auf das Maß zu verringern, welches aufgrund der technischen Auflösung erforderlich war. Hierzu mußten jedoch die notwendigen mathematischen Algorithmen neu zugeschnitten werden. Nach diesem Schritt wurde eine weitere klinische Studie gestartet, die den Zweck verfolgte, das neue Verfahren am Patienten zu verifizieren. In dieser Studie mit 10 Patienten und 93 Dialysesitzungen, 264 Stufenprofil- und 173 Bolus-Dialysancemesssungen wurde gefunden, daß die Bolus-Messungen ihre zugehörigen blutseitigen Referenzmessungen mit außergewöhnlicher Genauigkeit von 0.06+/-4.76% trafen. Student's t-Test für gepaarte Daten ergab, daß sich die Datensätze nicht signifikant unterschieden (p=0.87). Die blutseitige Kt/V-Referenz auf der Basis des equilibrierten Einkompartment-Modells mit variablem Volumen wurde mit 5.32+/-3.9% getroffen, wobei eine Korrelation von 0.98 erzielt wurde. Die verbleibende Differenz von 5.32% wird der Vernachlässigung der Harnstoff-Erzeugung während der Messung zugeschrieben. Auch das Stufenprofil zeigte trotz seiner Abhängigkeit vom Verteilungsvolumen gegenüber dem gleichen Modell einen mittleren Fehler von 0.05+/-5% bei einer Korrelation von 0.96. Jedoch konnte es die Vernachlässigung der Harnstoff-Erzeugung nicht korrekt abbilden. Die kontinuierlich aufgenommenen Daten wurden auch nach dem 2-pool Modell untersucht, welches auch die Harnstoff-Erzeugung enthält sowie eine innere Kompartimentierung des Patienten annimmt und damit die tatsächlichen Verhältnisse besser beschreibt. Danach weicht das Bolus-Meßprinzip -3.04+/-14.3% von der Referenz ab (n.s.,p=0.13). Die relativ hohe Standardabweichung wird mit der Komplexität des Modells erklärt. Weiter ist aus der Theorie zum Na-Transfer eine vereinfachende Methode zur Messung des Na-Verteilungsvolumens abgeleitet worden. Diese Methode wurde in-vitro gegen ein Behältnis mit einer bekannten Menge an Dialysat geprüft. Es wurde ein mittlerer Fehler von -19.9+/-34% gefunden. Die Korrelation war 0.92 (n.s., p=0.916). Die gleiche Prüfung fand in-vivo gegen das Harnstoff-Verteilungsvolumen statt und ergab einen mittleren Fehler von -7.4+/-23.2% (r=0.71, n.s., p=0.39). Es hat den Anschein, als würden sich gemäß der Theorie der Dilution die Verteilungsvolumina für Natrium und für Harnstoff scheinbar nur wenig unterscheiden, obwohl sie sich absolut natürlich deutlich unterscheiden. In Anbetracht der erheblichen Vereinfachungen, die bei der Ableitung dieses Ansatzes gemacht wurden, scheint es ausgesprochen ermutigend, auf diesem Weg möglicherweise ein Verfahren entwickeln zu können, welches auf rein elektrolytischem Wege nun nicht mehr nur K, sondern auch V und damit alle zur Quantifizierung gesuchten Größen analytisch ermitteln kann. Weiter wurde im Rahmen dieser Arbeit anhand der analytisch ermittelten Volumina verglichen, ob man mit Hilfe anthropometrischer Formeln zur Ermittlung des Harnstoff-Verteilungsvolumens zu einer guten Abschätzung kommen kann. Es wurde gefunden, daß man das Ergebnis der Watson-Formel um ca. 13% vermindern kann und dann zu einem recht guten Wert für das tatsächliche Harnstoff-Verteilungsvolumen gelangt. Dies ist jedoch mit Vorsicht und Erfahrung zu tun, da sich damit Kt/V rechnerisch zum Nachteil des Patienten verändert. Auch ein elektrolytisches Verfahren mit empirischen Komponenten zur Ermittlung des Plasma-Natriums des Patienten wurde erprobt und konnte mit einer Genauigkeit von 4.3+/-1.2% den Laborwert vorhersagen. Zusammenfassend kann gesagt werden, daß sich im Rahmen dieser Arbeit die leitfähigkeitsbasierten Methoden zur Messung von einigen wichtigen Dialyseparametern als sehr nützlich für die klinische Praxis erwiesen haben und zudem mit keinem Zusatzaufwand für die Beteiligten verbunden sind. Das Ergebnis dieser Arbeit ist mittlerweile in größeren Stückzahlen in frei erhältliche Dialysegeräte implementiert worden. Die Erfahrung der ersten Zeit zeigt, daß das verwendete Prinzip von den Klinikern gut angenommen wird.
Previous work on Jurassic bivalves from the Iberian Range is reviewed, whereby emphasis is placed on Callovian-Kimmeridgian species. The taxonomy, distribution pattern and ecology of the bivalve fauna occurring in Middle and Upper Jurassic rocks of the Aragonian Branch of the Iberian Range have been analysed. For this purpose 14 sections and 5 additional outcrops, selected according to the abundance of bivalves, were measured in detail and sampled. The rocks studied belong to the Chelva, Yátova, Sot de Chera and Loriguilla formations of Callovian-Kimmeridgian age. The distribution of species of bivalves is given for each section. More than 3000 specimens of bivalves representing 83 species that belong to 46 genera and subgenera of the subclasses Palaeotaxodonta, Pteriomorphia, Isofilibranchia. Palaeoheterodonta, Heterodonta and Anomaldesmata have been used for the taxonomic analysis. One species is new: Plagiostoma fuersichi from the Callovian of the Chelva Fm. The autecology (trophic group and life habit) of each bivalve has been discussed. 49 samples of four sections habe been selected for a quantitative palaeoecological analysis of the bivalve fraction of the benthic fauna. Five bivalve associations and two assemblages are recognised by a Q-mode hierarchical cluster analysis (Ward method). The main environmental factors controlling bivalve associations are thought to be substrate, water energy and distribution of organic matter. The bivalves exhibit a distinct spatial and temporal distribution pattern within the Aragonian Branch. Four of the bivalve associations occur in the Upper Oxfordian (Sot de Chera Fm) and one association in the Lower Callovian (Chelva Fm). In the Sot de Chera and Loriguilla formations, the abundance of bivalves decreases from NW to SE i.e., from relatively close to the shore line towards the distal-most part of the carbonate platform. In the Chelva Fm. bivalves are abundant in the Ariño region, interpreted as a palaeogeographic high. The distribution of bivalves might have been largely controlled by the availability of nutrients.
The present studies which have been performed in the work-group C-2 (Prof. W. Kiefer) within the program of the Sonderforschungsbereichs 347, deal with the FT-Raman and –IR spectroscopy on new organometallic complexes, synthesized in the work-groups B-2 (Prof. W. Malisch), B-3 (Prof. W. A. Schenk), D-1 (Prof. H. Werner) and D-4 (Prof. D. Stalke). The FT-Raman spectra recorded at 1064 nm led to very useful and interesting information. Furthermore, the DFT calculations which are known to offer promise of obtaining accurate vibrational wavenumbers, were successfully used for the assignment of the vibrational spectra. For the first time it has been possible to ascribe exactly the n(RhC) stretching mode in the vinylidene rhodium(I) complex trans-[RhF(=C=CH2)(PiPr3)2] by using isotopic substitution, in conjunction with theoretical calculations. This is also true for the complexes trans-[RhF(CO)(PiPr3)2], trans-[RhF(C2H4)(PiPr3)2], trans-[RhX(=C=CHPh)(PiPr3)2] (X = F, Cl, Br, I, Me, PhCºC) and trans-[RhX(CN-2,6-xylyl)(PiPr3)2] (X = F, Cl, Br, I, CºCPh). In addition, the comparison between the n(RhC) wavenumbers of the complexes trans-[RhF(=13C=13CH2)(PiPr3)2] and trans-[RhF(CO)(PiPr3)2], containing the isoelectronic ligands 13C=13CH2 and CO, which have the same reduced mass, indicated that the Rh-C bond is stronger in the carbonyl than in the vinylidene complex. Besides, the n(RhF) stretching mode, which has been observed at higher wavenumbers in the FT-Raman and -IR spectra of trans-[RhF(CO)(PiPr3)2], showed that the carbonyl ligand is a better p-acceptor and a less effective s-donor than the vinylidene one. Moreover, the comparison of the n(CºC) and n(Rh-C) modes from the FT-Raman spectrum of the complexes trans-[Rh(CºCPh)(L)(PiPr3)2] (L = C=CHPh, CO, CN-2,6-xylyl) point out that the p-acceptor ability of the ligand trans to CºCPh should rise in the order C=CH2 < CO < CN-2,6-xylyl £ C=CHPh. The investigated sensitivity of the n(RhC), n(CC), n(CO) and n(CN) vibrational modes to the electronic modifications occuring in the vinylidene, carbonyl, ethylene and isonitrile complexes, should allow in the future the examination of the p-acceptor or p-donor properties of further ligands. Likewise, we were able to characterize the influence of various X ligands on the RhC bond by using the n(RhC) stretching mode as a probe for the weakening of this. The calculated wavenumbers of the n(RhC) for the vinylidene complexes trans-[RhX(=C=CHR)(PiPr3)2], where R = H or Ph, suggested that the strength of the Rh=C bond increases along the sequence X = CºCPh < CH3 < I < Br < Cl < F. For the series of carbonyl compounds trans-[RhX(CO)(PiPr3)2], where X = F, Cl, Br and I, analogous results have been obtained and confirmed from the model compounds trans-[RhX(CO)(PMe3)2]. Since, the calculated vibrational modes for the ethylene complex trans-[RhF(C2H4)(PiPr3)2] were in good agreement with the experimental results and supported the description of this complex as a metallacyclopropane, we were interested in getting more information upon this class of compounds. In this context, we have recorded the FT-Raman and -IR spectra of the thioaldehyde complexes mer-[W(CO)3(dmpe)(h2-S=CH2)] and mer-[W(CO)3(dmpe)(h2-S=CD2)] which have been synthezised by B-3. The positions of the different WL vibrational modes anticipated by the DFT calculations, were consistent with the experimental results. Indeed, the analysis of the band shifts in the FT-Raman and –IR spectra of the isotopomer mer-[W(CO)3(dmpe)(h2-S=CD2)] confirmed our assignment. The different stereoisomers of complex mer-[W(CO)3(dmpe)(h2-S=CH2)] were investigated too, since RMN and IR-data have shown that complex mer-[W(CO)3(dmpe)(h2-S=CH2)] lead in solution to an equilibrium. Since the information on the vibrational spectra of the molybdenum and tungsten complexes Cp(CO)2M-PR2-X (M = Mo, W; R = Me, tBu, Ph; X = S, Se) is very scarce, we extended our research work to this class of compounds. We have tried to elucidate the bonding properties in these chalcogenoheterocycle complexes by taking advantage of the mass effect on the different metal atoms (W vs. Mo). Thus, the observed band shifts allowed to assign most of the ML fundamental modes of these complexes. This project and the following one were a cooperation within the work-group B-2. The Raman and IR spectra of the matrix isolated photoproducts expected by the UV irradiation of the iron silyl complex Cp(CO)2FeSiH2CH3 have been already reported by Claudia Fickert and Volker Nagel in their PhD-thesis. Since no exact assignment was feasible for these spectra, we were interested in the study of the reaction products created by irradiation of the carbonyl iron silyl complex Cp(CO)2FeCH2SiH3. Although the calculated characteristic vibrational modes of the metal ligand unit for the various photoproducts are significantly different in constitution, they are very similar in wavenumbers, which did not simplify their identification. However, the theoretical results have been found to be consistent with the earlier experimental results. Finally, the last part of this thesis has been devoted to the (2-Py)2E- anions which exhibit a high selectivity toward metal-coordination. All di(2-pyridyl) amides and -phosphides which were synthesized by D-4, coordinate the R2Al+ fragment via both ring nitrogen atoms. This already suggests that the charge density in the anions is coupled into the rings and accumulated at the ring nitrogen atoms, but the Lewis basicity of the central nitrogen atom in Et2Al(2-Py)2N is still high enough to coordinate a second equivalent AlEt3 to form the Lewis acid base adduct Et2Al(2-Py)2NAlEt3. Due to the higher electronegativity of the central nitrogen atom in Me2Al(2-Py)2N, Et2Al(2-Py)2N and Et2Al(2-Py)2NAlEt3, compared to the bridging two coordinated phosphorus atom in Me2Al(2-Py)2P and Et2Al(2-Py)2P, the di(2-pyridyl)amide is the hardest Lewis base. In the phosphides merely all charge density couples into the rings leaving the central phosphorus atom only attractive for soft metals. These results were confirmed by using DFT and MP2 calculations. Moreover, a similar behaviour has been observed and described for the benzothiazolyl complex [Me2Al{Py(Bth)P}], where complementary investigations are to be continued. The DFT calculations carried out on the model compounds analysed in these studies supply very accurate wavenumbers and molecular geometries, these being in excellent agreement with the experimental results obtained from the corresponding isolated complexes.
The presented work shows the analysis of the correlation between the spatial and temporal expression pattern of NtAQP1 and its function in water relation in planta. In situ immunological studies indicated NtAQP1-protein accumulation in the root exodermis and endodermis, in the cortex, close to vascular bundles, in the xylem parenchyma and in cells of the stomatal cavities. The aquaporin was also found to be abundant in longitudinal cell-rows in the petioles. Expression studies with generated transgenic plants (Ntaqp1-promoter::gus or luc) confirmed the Ntaqp1 accumulation in the root, stem and petioles but also revealed further localization in pollen grains, adventitious roots and leaf glandular hairs. Ntaqp1-expression was induced during growth processes, like stem bending after gravistimulation or photostimulation, seed germination and hypocotyl elongation as well as during the comparatively fast circadian leaf movement. The expression was further stimulated by phytohormones, especially gibberellic acid (GA) and osmotic stress. Further analysis displayed a diurnal and even circadian expression of Ntaqp1 in roots and petioles. The functional analysis of the aquaporin was accomplished by reverse genetics and biophysical studies. The antisense technique was used to reduce NtAQP1-expression in tobacco plants. The antisense (AS) plants exhibited a severe reduction of Ntaqp1-mRNA, less reduction of the highly homologous NtPIP1a RNA and no effect on expression of other aquaporin family genes (PIP2, TIP). The function of NtAQP1 at the cellular level was investigated by a newly developed experimental setup to record the osmotically induced increase in protoplast volume. The reduction of NtAQP1 by the antisense expression decreased the overall cellular waterpermeability Pos for more than 50 %. Function of NtAQP1 at the whole plant level was e.g. measured by the “high-pressure flow meter method”. Those measurements revealed that the root hydraulic conductivity per unit root surface area (KRA) of roots from the AS-lines was reduced by more than 50 %. KRA displayed a strong diurnal and circadian variation with a maximum in the middle of the light period, similar to the expression pattern of Ntaqp1 in roots. Gas exchange-, stem (Ystem) and leaf (Yleaf) water potential measurement gave dissimilar values in AS and control plants under well-watered conditions. Under a water-limiting environment the Y of AS-plants remained at more negative water values, even though a further decrease in transpiration of AS-plants was detected. Quantitative analysis displayed a much stronger wilting reaction in the AS than in the control plants. Quantitative studies of the leaf movement in AS compared to control plants exhibited a dramatic reduction in velocity and also in the extent of the process. The following conclusions can be drawn. NtAQP1 was expressed at sites of anticipated high water fluxes from and to the apoplast or symplast. Additionally, the specific distribution pattern and temporal expression of NtAQP1 in petioles and the bending stem strongly indicate a role in transcellular movement of water. The reduction of NtAQP1 by the antisense expression decreased the overall cellular Pos. Conclusively, NtAQP1-function increases membrane water permeability of tobacco root protoplasts. The decrease of the specific root hydraulic conductivity (KRA) was in the same order of magnitude as the mean cellular water permeability reduction, indicating that aquaporin expression is essential in maintaining a natural root hydraulic conductance. Reduction of KRA in AS plants might be the first definitive proof that the pathway of water uptake from the root surface to the xylem involves passage across membranes. The absence of NtAQP1 resulted in a water stress signal, causing a certain stomatal closure. NtAQP1 seems to contribute to water stress avoidance in tobacco. NtAQP1 plays an essential role in fast plant movements and transcellular water shift.
Network planning has come to great importance during the past decades. Today's telecommunication, traffic systems, and logistics would not have been evolved to the current state without careful analysis of the underlying network problems and precise implementation of the results obtained from those examinations. Graphs with node and arc attributes are a very useful tool to model realistic applications, while on the other hand they are well understood in theory. We investigate network design problems which are motivated particularly from applications in communication networks and logistics. Those problems include the search for homogeneous subgraphs in edge labeled graphs where either the total number of labels or the reload cost are subject to optimize. Further, we investigate some variants of the dial a ride problem. On the other hand, we use node and edge upgrade models to deal with the fact that in many cases one prefers to change existing networks rather than implementing a newly computed solution from scratch. We investigate the construction of bottleneck constrained forests under a node upgrade model, as well as several flow cost problems under a edge based upgrade model. All problems are examined within a framework of multi-criteria optimization. Many of the problems can be shown to be NP-hard, with the consequence that, under the widely accepted assumption that P is not equal to NP, there cannot exist efficient algorithms for solving the problems. This motivates the development of approximation algorithms which compute near-optimal solutions with provable performance guarantee in polynomial time.