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Dissecting the C-DI-GMP Signaling Pathways : Tools and TalesSharma, Indra Mani January 2014 (has links) (PDF)
Evaluating aerodynamic noise from aircraft engines is a design stage process, so that it conform to regulations at airports. Aerodynamic noise is also a principal source of structural vibration and internal noise in short/vertical take off and landing and rocket launches. Acoustic loads may be critical for the proper functioning of electronic and mechanical components. It is imperative to have tools with capability to predict noise generation from turbulent flows. Understanding the mechanism of noise generation is essential in identifying methods for noise reduction.
Lighthill (1952) and Lighthill (1954) provided the first explanation for the mechanism of aerodynamic noise generation and a procedure to estimate the radiated sound field. Many such procedures, known as acoustic analogies are used for estimating the radiated sound field in terms of the turbulent fluid flow properties. In these methods, the governing equations of the fluid flow are rearranged into two parts, the acoustic sources and the propagation terms. The noise source terms and propagation terms are different in different approaches. A good description of the turbulent flow field and the noise sources is required to understand the mechanism of noise generation.
Computational aeroacoustics (CAA) tools are used to calculate the radiated far field noise. The inputs to the CAA tools are results from CFD simulations which provide details of the turbulent flow field and noise sources. Reynolds-Averaged Navier Stokes (RANS) solutions can be used as inputs to CAA tools which require only time-averaged mean quantities. The output of such tools will also be mean quantities. While complete unsteady turbulent flow details can be obtained from Direct Numerical Simulation (DNS), the computation is limited to low or moderate Reynolds number flows. Large eddy simulations (LES) provide accurate description for the dynamics of a range of large scales. Most of the kinetic energy in a turbulent flow is accounted by the large-scale structures. It is also the large-scale structures which accounts for the maximum contribution towards the radiated sound field. The results from LES can be used as an input to a suitable CAA tool to calculate the sound field.
Numerical prediction of turbulent flow field, the acoustic sources and the radiated sound field is at the focus of this study. LES based on explicit filtering method is used for the simulations. The method uses a low-pass compact filter to account for the sub-grid scale effects. A one-parameter fourth-order compact filter scheme from Lele (1992) is used for this purpose. LES has been carried out for four different flow situations: (i) round jet (ii) plane jet (iii) impinging round jet and (iv) impinging plane jet. LES has been used to calculate the unsteady flow evolution of these cases and the Lighthill’s acoustic sources. A compact difference scheme proposed by Hixon & Turkel (1998) which involves only bi-diagonal matrices are used for evaluating spatial derivatives. The scheme provides similar spectral resolution as standard tridiagonal compact schemes for the first spatial derivatives. The scheme is computationally less intensive as it involves only bi-diagonal matrices. Also, the scheme employs only a two-point stencil.
To calculate the radiated sound field, the Helmholtz equation is solved using the Green’s function approach, in the form of the Kirchhoff-Helmholtz integral. The integral is performed over a surface which is present entirely in the linear region and covers the volume where acoustic sources are present. The time series data of pressure and the normal component of the pressure gradient on the surface are obtained from the CFD results. The Fourier transforms of the time series of pressure and pressure gradient are then calculated and are used as input for the Kirchhoff-Helmholtz integral.
The flow evolution for free jets is characterised by the growth of the instability waves in the shear layer which then rolls up into large vortices. These large vortical structures then break down into smaller ones in a cascade which are convected downstream with the flow. The rms values of the Lighthill’s acoustic sources showed that the sources are located mainly at regions immediately downstream of jet break down. This corresponds to the large scale structures at break down.
The radiated sound field from free jets contains two components of noise from the large scales and from the small scales. The large structures are the dominant source for the radiated sound field. The contribution from the large structures is directional, mainly at small angles to the downstream direction. To account for the difference in jet core length, the far field SPL are calculated at points suitably shifted based on the jet core length. The peak value for the radiated sound field occurs between 30°and 35°as reported in literature.
Convection of acoustic sources causes the radiated sound field to be altered due to Doppler effect. Lighthills sources along the shear layer were examined in the form of (x, t) plots and phase velocity pattern in (ω, k) plots to analyse for their convective speeds. These revealed that there is no unique convective speeds for the acoustic sources. The median convective velocity Uc of the acoustic sources in the shear layer is proportional to the jet velocity Uj at the center of the nozzle as Uc ≈ 0.6Uj.
Simulations of the round jet at Mach number 0.9 were used for validating the LES approach. Five different cases of the round jet were used to understand the effect of Reynolds number and inflow perturbation on the flow, acoustic sources and the radiated sound field. Simulations were carried out for an Euler and LES at Reynolds number 3600 and 88000 at two different inflow perturbations. The LES results for the mean flow field, turbulence profiles and SPL directivity were compared with DNS of Freund (2001) and experimental data available in literature. The LES results showed that an increase in inflow forcing and higher Reynolds number caused the jet core length to reduce. The turbulent energy spectra showed that the energy content in smaller scale is higher for higher Reynolds number.
LES of plane jets were carried out for two different cases, one with a co-flow and one without co-flow. LES of plane jets were carried out to understand the effect of co-flow on the sound field. The plane jets were of Mach number 0.5 and Reynolds number of 3000 based on center-line velocity excess at the nozzle. This is similar to the DNS by Stanley et al. (2002). It was identified that the co-flow leads to a reduction in turbulence levels. This was also corroborated by the turbulent energy spectrum plots. The far field radiation for the case without co-flow is higher over all angles. The contribution from the low frequencies is directional, mainly towards the downstream direction. The range of dominant convective velocities of the acoustic sources were different along shear layers and center-line.
The plane jet results were also used to bring out a qualitative comparison of flow and the radiation characteristics with round jets. For the round jet, the center-line velocity decays linearly with the stream-wise distance. In the plane jet case, it is the square of the center-line velocity excess which decays linearly with the stream-wise distance. The turbulence levels at any section scales with the center-line stream-wise velocity. The decay of turbulence level is slower for the plane jet and hence the acoustic sources are present for longer distance along the downstream direction.
Subsonic impinging jets are composed of four regions, the jet core, the fully developed jet, the impingement zone and the wall jet. The presence of the second region (fully developed free jet) depends on the distance of the wall from the nozzle and the length of the jet core. In impinging jets, reflection from the wall and the wall jet are additional sources of noise compared to the free jets. The results are analysed for the contribution of the different regions of the flow towards the radiated sound field. LES simulations of impinging round jets and impinging plane jet were carried out for this purpose. In addition, the results have been compared with equivalent free jets. The directivity plots showed that the SPL levels are significantly higher for the impinging jets at all angles. For free jets, a typical time scale for the acoustic sources is the ratio of the nozzle size to the jet velocity. This is ro/Uj for round jets and h/Uj for plane jets. For impinging jets, the non-dimensionlised rms of Lighthill’s source indicates that the time scale for acoustic sources is the ratio of the height of the nozzle from the wall to the jet velocity be L/Uj.
LES of impinging round jets was carried out for two cases with different inflow perturbations. The jets were at Reynolds number of 88000 and Mach number of 0.9, same as the free jet cases. The impingement wall was at a distance L = 24ro from the nozzle exit. For impinging round jets, the SPL levels are found to be higher than the equivalent free jets. From the SPL levels and radiated noise spectra it was shown that the contribution from the large scale structures and its reflection from the wall is directional and at small angles to the wall normal. The difference in the range of angles where the radiation from the large scale structures were observed shows the significance of refraction of sound waves inside the flow. The rms values of the Lighthill’s sources indicate two dominant regions for the sources, just downstream of jet breakdown and in the impingement zone.
The LES of impinging plane jet was done for a jet of Mach number 0.5 and Reynolds number of 6000. The impingement wall was at a distance L = 10h from the nozzle exit. The radiated sound field appears to emanate from this impingement zone. The directivity and the spectrum plots of the far field SPL indicate that there is no preferred direction of radiation from the impingement zone. The Lighthill’s sources are concentrated mainly in the impingement zone. The rms values of the sources indicate that the peak values occur in the impingement zone.
The results from the different flow situations demonstrates the capability of LES with explicit filtering method in predicting the turbulent flow and radiated noise field. The method is robust and has been successfully used for moderate Reynolds number and an Euler simulation. An important feature is that LES can be used to identify acoustic sources and its convective speeds. It has been shown that the Lighthill source calculations, the calculated sound field and the observed radiation patterns agree well. An explanation for these based on the different turbulent flow structures has also been provided.
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Etude de nouveaux biomarqueurs de toxicité induite par des micropolluants (benzo(a)pyrène et phtalate de bis(2-ethylhexyle)) sur des modèles de placenta humain / New biomarkers of toxicity induced by micropollutants (benzo(a)pyrene and di(2-ethylhexyle)phthalate) on human placental modelsWakx, Anaïs 28 November 2014 (has links)
L’exposition prénatale à différents agents toxiques est généralement étudiée en considérant le placenta comme une barrière entre la mère et le fœtus ; nous le considérons en tant qu’organe cible des agents toxiques. Pour ce faire, nous avons sélectionné un modèle cellulaire de trophoblastes adapté aux études toxicologiques. En clinique, des pathologies de la grossesse sont associées à des modifications de la sécrétion de l’hormone placentaire lactogène hPL et de l’hormone gonadotrope chorionique hCG. Nos travaux in vitro ont permis de faire le lien entre une exposition à des micropolluants (le mono(2-ethylhexyl) phtalate, un perturbateur endocrinien, et le benzo(a)pyrene, un carcinogène) et ces observations cliniques. Les biomarqueurs de sécrétion hormonale (hPL et hCG hyperglycosylée) et de dégénérescence (activation du purinorécepteur P2X7) que nous avons identifiés permettent de détecter l’exposition et le risque suite à une exposition à des polluants. / Prenatal exposure to pollutants is commonly evaluated using placenta as a barrier between mother and fetus. Here, we consider placenta as a target organ for toxic agents. To achieve this, we selected a trophoblastic cell model, which is adapted to toxicological studies. In clinical studies, pregnancy pathologies are associated to changes in human placental lactogen (hPL) and human chorionic gonadotropin (hCG) secretions. Our in vitro work links exposure to micropollutants (mono(2-ethylhexyl)phthalate, an endocrine disruptor, and benzo(a)pyrene, a carcinogen) and clinical observations. We identified biomarkers of hormonal secretion (hPL and hyperglycosylated hCG) and degeneration (P2X7 receptor activation), which enable the evaluation of exposure and risk attached to exposure to pollutants.
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Étude mécanistique computationnelle des réactions d’amination catalysées par des dimères de rhodiumAzek, Emna 01 1900 (has links)
Catalytic amination reactions are a powerful tool in organic synthesis. They aim to introduce nitrogen atom to alkane, alkene or thioether moieties, giving rise to amine products that have various medical and industrial applications. The Lebel group has developed catalytic amination reactions in the presence of rhodium dimers using N-sulfonyloxycarbamates as nitrene precursors. In the presence of a base, N-sulfonyloxycarbamates presumably afforded rhodium nitrenes which underwent C-H insertions, C=C additions or reactions with the sulfur atom of thioethers resulting in acyclic and cyclic carbamates, aziridines and sulfilimines respectively. In addition, good diastereoselectivities were observed in the presence of a chiral N-sulfonyloxycarbamate reagent and a chiral rhodium dimer for all three reactions.
In this dissertation, we are interested in the mechanistic aspects of these amination reactions. Given the absence of experimental proofs of in-situ generated rhodium nitrene species, playing the role of the amination agent, nor of its precomplex, the rhodium nitrenoid, the different amination reactions mechanisms remain uncertain. Our approach is based on the scan of the potential energy surfaces of different mechanistic paths, for each of the amination reactions, well established on the experimental level, by resorting to the Functional Theory of Density (DFT).
The Ernzerhof research group is expert on the development of exchange-correlation functionals, therefore relevant strict criteria have been considered when choosing and validating the theoretical model used during the mechanistic studies. The correlation exchange functional developed by Perdew-Burke-Ernzerhof (PBE) was established as the best to study reactions involving rhodium dimers where the electronic correlation is strong. We studied the formation and reactivity of rhodium nitrene species considering their two lower energy spin states. Singlet rhodium nitrenes appeared to be the most reactive intermediates for the C-H amination reaction. In addition, singlet rhodium nitrenes were shown responsible for the formation of secondary products such as carbonyls and primary carbamates derived from the corresponding N-mesyloxycarbamates. In sharp contrast, in the aziridination reaction, both singlet and triplet rhodium nitrene species acted as aminating agents in a process involving an intersystem spin crossover. To further rationalize the asymmetric induction of catalytic aziridination reactions, we have undertaken the calculation of the diastereoselectivity ratios in the presence of the chiral catalyst Rh2[(S)-nttl]4. An exhaustive study was performed and it revealed that the asymmetric induction was due to a reactive conformation of rhodium nitrene species in which the ligand adopts C4 symmetry.
Up to now, no mechanistic study involving DFT calculations have been reported in the literature for the amination of thioethers, no matter what catalytic system is used. To study catalytic sulfimidation reactions, we calculated the different mechanistic paths of rhodium catalyzed thioanisole imidation with and without DMAP and bis(DMAP)CH2Cl2 additives. The study showed a 'classical' insertion mechanism of rhodium nitrene species into the thioether in absence of bis(DMAP)CH2Cl2. In the presence of the latter, the mechanism diverged to a thioether insertion/salt (bis(DMAP)CH2Cl-OMs) elimination reaction where the rhodium nitrenoid complex was, henceforth, the imidation reagent. / Les réactions d’amination catalytiques sont un outil très efficace en synthèse organique.
Elles consistent à introduire un azote sur différents composés organiques, permettant de
synthétiser des produits aminés qui peuvent être utilisés pour différentes applications
médicales et industrielles. Le groupe de recherche du Pr Lebel a développé des réactions
d’amination faisant appel aux dimères de rhodium comme catalyseurs et en utilisant les Nsulfonyloxycarbamates,
comme précurseurs de nitrènes métalliques. En effet, en présence
d’une base, les N-sulfonyloxycarbamates forment possiblement un intermédiaire de type
nitrène de rhodium qui peuvent s’insérer dans un lien C-H, s’additionner sur un lien C=C ou
réagir avec un atome de soufre d’un thioéther. On peut ainsi préparer des carbamates cycliques
et acycliques, des aziridines et des sulfilimines respectivement. Dans le cas où les réactions
d’amination sont catalysées par des dimères de rhodium chiraux, on obtient de bonnes
diastéréosélectivités en présence d’un réactif N-sulfonyloxycarbamate chiral.
Dans cette dissertation, nous nous sommes intéressés aux aspects mécanistiques de ces
réactions d’amination. À défaut de preuves expérimentales solides pour prouver la génération
in-situ des espèces nitrènes de rhodium, lesquelles sont les agents d’amination clés, ni de celle
du pré-complexe, nitrénoïde de rhodium, des incertitudes subsistaient toujours concernant les
mécanismes des différentes réactions d’amination. Notre approche se base sur l’étude des
surfaces d’énergies potentielles de différents chemins mécanistiques possibles pour chacune
des réactions d’amination, bien établie sur le plan expérimental, en faisant recours à la Théorie
des Fonctionnelles de la Densité (DFT).
Le groupe de recherche du Pr Ernzerhof est expert dans le développement des
fonctionnelles d’échange-corrélation. Pour ce, des critères strictes et pertinents ont été pris en
compte lors du choix et de la validation du modèle théorique utilisé dans ces études
mécanistiques. La fonctionnelle d’échange corrélation développée par Perdew–Burke–
Ernzerhof (PBE) s’est révélé être la meilleure pour décrire ces systèmes réactionnels faisant
intervenir les dimères de rhodium dont la corrélation électronique est forte. À l’aide de cette
fonctionnelle pure, nous avons étudié la formation et la réactivité des espèces nitrènes de
rhodium en fonction de leurs deux états de spin de plus basse énergie. Les nitrènes de rhodium
singulet se sont révélés être les intermédiaires les plus réactifs dans l`amination de liens C-H.
De plus, les nitrènes de rhodium à l’état singulet sont responsables de la formation des
produits secondaires tels que les carbonyles et les carbamates primaires dérivés des Nmésyloxycarbamates
correspondants. Dans la réaction d’aziridination, les espèces nitrènes de
rhodium à l’état singulet et triplet peuvent toutes les deux agir comme agents d'amination et
les processus font intervenir un croisement intersystème de spin. Afin de rationaliser
l’induction asymétrique des réactions d’aziridination catalytiques, nous avons entrepris le
calcul des ratios de diastéréosélectivités en présence du catalyseur chiral Rh2[(S)-nttl]4.
L’étude exhaustive de cette réaction a permis de déterminer que l’induction asymétrique
provient d’une conformation réactive de l’espèce nitrène de rhodium de symétrie C4.
Aucune étude mécanistique s’appuyant sur la chimie computationnelle n’a été rapportée
dans la littérature pour la réaction d’amination de thioéthers et ce peu importe le système
catalytique. Afin d’étudier les réactions de sulfimidation catalytiques, nous avons calculé les
différents chemins mécanistiques de l’imidation du thioanisole catalysée par un complexe de
rhodium avec et sans les additifs DMAP et bis(DMAP)CH2Cl2. L’étude montre que le
mécanisme procède via une insertion ‘classique’ des espèces nitrènes de rhodium dans le
thioéther en absence de bis(DMAP)CH2Cl2. En présence de ce dernier, le mécanisme diverge
vers une réaction d’insertion du thioéther/élimination d’un sel (bis(DMAP)CH2Cl-OMs) où le
complexe nitrénoïde de rhodium devient, désormais, l’agent d’imidation.
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Frenkel and Charge-Transfer Excitons in Quasi-One-Dimensional Molecular Crystals with Strong Intermolecular Orbital OverlapHoffmann, Michael 19 December 2000 (has links)
We present a theoretical and experimental study on the lowest electronically excited states in quasi-one-dimensional molecular crystals. The specific calculations and the experiments are performed for the model compounds MePTCDI (N-N'-dimethylperylene-3,4:9,10-dicarboximide) and TCDA(3,4:9,10-perylenetetracarboxylic dianhydride). The intermolecular interactions between nearest neighbors are quantum chemically analyzed on the basis of semi-empirical (ZINDO/S) Hartree-Fock calculations and a singly excited configuration interaction scheme. Supermolecular dimer states are projected onto a basis set of localized excitations. The nature of the lowest states is then completely explained as a superposition of molecular and low lying charge-transfer excitations. The CT excitations show a significant intrinsic transition dipole, which is oriented approximately parallel to the molecular planes and has a large component along the molecular M-axis. The exciton states in the one-dimensional stacks are described by a model Hamiltonian that includes interactions between three vibronic levels of the lowest molecular excitation and nearest-neighbor CT excitations. The three-dimensional crystal structure is considered by Frenkel exciton transfer between arbitrary molecules. This model is compared to polarized absorption spectra. With a small set of parameters, we can describe the key features of the absorption spectra, the polarization behavior, and the Davydov splitting. The variation of the polarization ratio for the various exciton states is analyzed as a direct qualitative proof for the mixing between Frenkel and charge-transfer excitons.
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Der Lotzdorfer Kirchsteig - Kirchgang zwischen Seelenheil, Pflicht und GeschäftSchönfuß-Krause, Renate 01 July 2021 (has links)
Untersuchungen über die Entstehung der einstigen Kirchsteige sind bisher kaum vorhanden. Ein interessantes Thema in Verbindung mit Kirchenentwicklung. Die Bedeutung dieser Straßen- und Wegeverläufe sind in den Erinnerungen der Menschen heute bereits vergessen, keiner denkt mehr über die Entstehungsgeschichte nach, warum die Straßen zumeist bewusst, auf kürzestem Weg, zu einer Kirche führten, die früher für die Bewohner eine große kulturelle, wirtschaftliche und sozialgeschichtliche Komponente besaßen. Unser heutiges, zumeist befestigtes Straßennetz beruht noch zu einem Großteil auf diesen lokalen, seit Jahrhunderten bestehenden Wegeverbindungen, die durchaus als historisches Erbe unserer Vorfahren anzusehen und zu erleben sind. Diese Wege spielten, besonders im Leben der Landbevölkerung, eine wichtige Rolle, wenn die Dörfer fernab der Kirchen lagen, in denen sie eingepfarrt waren. Der Lotzdorfer Kirchsteig wurde zum Ausgangspunkt der Recherchen, er ist teilweise durch historische Karten noch rekonstruierbar. Auf ihm gingen die Einwohner der Dörfer Lotzdorf und Liegau in vergangenen Zeiten zum Gottesdienst in die Radeberger Kirche.
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Militärakademie 'Friedrich Engels' der Nationalen Volksarmee der DDR: 1959 bis 1990: Eine DokumentationDemmer, Wolfgang, Haueis, Eberhard 09 November 2018 (has links)
Dokumentarische Darstellung der Geschichte der Gründung und Entwicklung der Militärakademie ´Friedrich Engels´ als höchster Lehreinrichtung der Nationalen Volksarmee der DDR (Dresden 2008).
In die vorliegende Online-Version sind mit Stand Mai 2012 Ergänzungen und Berichtigungen eingearbeitet. Eine zusammenfassende Übersicht dazu befindet
sich am Ende dieser Schrift.:Die Autoren.
Abkürzungsverzeichnis.
Vorwort der Autoren.
1. Gründung der Militärakademie und ihrer Fakultäten.
2. Kurzbiographien der Kommandeure/Chefs der Militärakademie.
3. Status der Militärakademie und ihrer Lehrstühle.
4. Stellvertreterbereiche zur Organisation und Sicherstellung von Lehre und Forschung an der Militärakademie.
5. Sektionen der Militärakademie.
6. Studienjahr 1989/90 im Zeichen politischer Umwälzungen.
Statt eines Nachwortes -
Bilanz nach über 30-jähriger Hochschultätigkeit.
Anhänge und Anlagen.
Literaturverzeichnis.
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ALD of Copper and Copper Oxide Thin Films For Applications in Metallization Systems of ULSI DevicesWaechtler, Thomas, Oswald, Steffen, Roth, Nina, Lang, Heinrich, Schulz, Stefan E., Gessner, Thomas 15 July 2008 (has links)
As a possible alternative for growing seed layers required for electrochemical Cu deposition of metallization systems in ULSI circuits, the atomic layer deposition (ALD) of Cu is under consideration. To avoid drawbacks related to plasma-enhanced ALD (PEALD), thermal growth of Cu has been proposed by two-step processes forming copper oxide films by ALD which are subsequently reduced.
This talk, given at the 8th International Conference on Atomic Layer Deposition (ALD 2008), held in Bruges, Belgium from 29 June to 2 July 2008, summarizes the results of thermal ALD experiments from [(<sup><i>n</i></sup>Bu<sub>3</sub>P)<sub>2</sub>Cu(acac)] precursor and wet O<sub>2</sub>. The precursor is of particular
interest as it is a liquid at room temperature and thus easier to handle than frequently utilized solids such as Cu(acac)<sub>2</sub>,
Cu(hfac)<sub>2</sub> or Cu(thd)<sub>2</sub>. Furthermore the substance is non-fluorinated, which helps avoiding a major source of adhesion issues repeatedly observed in Cu CVD.
As result of the ALD experiments, we obtained composites of metallic and oxidized Cu on Ta and TaN, which was determined by angle-resolved XPS analyses. While smooth, adherent films were grown on TaN in an ALD window up to about 130°C, cluster-formation due to self-decomposition of the precursor was observed on Ta. We also recognized a considerable dependency of the growth on the degree of nitridation of the TaN. In contrast, smooth films could be grown up to 130°C on SiO<sub>2</sub>and Ru, although in the latter case the ALD window only extends to about 120°C. To apply the ALD films as seed layers in subsequent electroplating processes, several reduction processes are
under investigation. Thermal and plasma-assisted hydrogen treatments are studied, as well as thermal treatments in vapors of isopropanol, formic acid, and aldehydes. So far these attempts were most promising using formic acid at temperatures between 100 and 120°C, also offering the benefit of avoiding agglomeration of the very thin ALD films on
Ta and TaN. In this respect, the process sequence shows potential for depositing ultra-thin, smooth Cu films at temperatures below 150°C.
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Lotzdorf, Pauline und die 1000-Flammen-KugelSchönfuß-Krause, Renate 21 June 2021 (has links)
Der Gasthof Lotzdorf bei Radeberg, erbaut und geführt von Wilhelm Riemer und Pauline Riemer, war eine Legende. Die Biografie beschreibt die Lebensleistung der Familie Riemer, den Aufstieg und Untergang des Gasthof Lotzdorf bzw. Riemers Gasthof mit Gasthaus, Ballsaal, Gästegarten, unzähligen großen und kleinen Veranstaltungen und der berühmten, bereits 1927 installierten '1000-Flammen-Kugel'. Einer damaligen Besonderheit.
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<strong>OH LIPIDS, THE PLACES WE HAVE GONE</strong>De'Shovon M Shenault (16650516) 27 July 2023 (has links)
<p>The development of a novel charge inversion ion/ion reaction in conjunction with a mass spectrometry technique (collisional induced dissociation (CID)) to induce fragmentation of selected ions species in the gas-phase. The utility of this experiment allows identification of varying saturated and unsaturated classes of glycerophospholipids (GPLs) in a biological matrix. In this work, we are able to characterize GPLs species at the subclass, headgroup, fatty acyl sum compositional levels, leaving the location(s) of carbon-carbon single bond (C-C), carbon-carbon double bond (C=C), cyclopropane moiety, branching site and differentiate isomeric species. </p>
<p><br></p>
<p>All data were collected on modified a Sciex QTRAP4000 hybrid triple quadrupole/linear ion trap mass spectrometer. Briefly, alternately, pulsed nano-electrospray ionization (nESI) was used for ion generation. Deprotonated lipid anions were generated via negative ion mode nESI, mass selected during transit through Q1, and transferred to q2 for storage. Next, the charge inversion (IIRXN) reagent doubly charged magnesium complex cations, were generated via positive ion mode nESI. To facilitate the ion/ion reaction, magnesium complex dictations and lipid anions were simultaneously stored in q2, resulting in the formation of charge-inverted lipid cations. Ion-trap CID of charge-inverted isomers resulted in distinctive fragmentation, facilitating differentiation of isomeric and localization of unsaturation sites in acyl chain constituents. </p>
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Four Essays on Banks, Firms and Real Effects of Bank LendingBednarek, Peter 26 August 2022 (has links)
This dissertation collects four essays on banks, firms and real effects of bank lending. Owing to the appliance of different econometric methods on several datasets, insights in the behav-ior of and the impacts from financial markets and market participants are generated.
In the first chapter, our results uncover a so far undocumented ability of the interbank market to distinguish between banks of different quality in times of aggregate distress. We show empirical evidence that during the 2007 financial crisis the inability of some banks to roll over their interbank debt was not due to a failure of the interbank market per se but rather to bank-specific shocks affecting banks’ capital, liquidity and credit quality as well as revised bank-level risk perceptions. Relationship banking is not capable of containing these frictions, as hard information seems to dominate soft information. In detail, we explore determinants of the formation and resilience of interbank lending relationships by analyzing an extensive da-taset comprising over 1.9 million interbank relationships of more than 3,500 German banks between 2000 and 2012.
The second chapter examines the relationship between central bank funding and credit risk-taking. Employing bank-firm-level data from the German credit registry during 2009:Q1-2014:Q4, we find that banks borrowing from the central bank rebalance their portfolios to-wards ex-ante riskier firms. We further establish that this effect is driven by the ECB’s maturi-ty extensions and that the risk-taking sensitivity of banks borrowing from the ECB is inde-pendent of idiosyncratic bank characteristics. Finally, we show that these shifts in bank lend-ing are associated with an increase in firm-level investment and employment, but also with a deterioration of bank balance sheet quality in the following year.
Once we analyze the relationship of banks as lenders vis-à-vis banks as borrowers and banks as lenders vis-à-vis non-financial companies as borrowers, we enlarge the understand-ing of non-financial companies not only in terms of being simply borrowers, respectively sub-jects exhibiting of credit risks. Instead, we try to understand the inner working of those com-panies more generally and analyze their quality not only in terms of a bank’s risk assessment but also in terms of the overall market assessment. However, this in turn can generate infor-mation useable to assess the quality of a bank’s credit portfolio in dimensions that so far are not taken into account by the current regulatory framework. Moreover, a better understanding of banks and non-banks beyond the standard lens of the banking and corporate finance litera-ture might promote new scopes for future research connecting those discrete subjects. In this regard, the third chapter analyzes the dependence of price reactions to corporate insider trad-ing on several measures of corporate governance quality. Our results strongly support the view that first, higher corporate governance levels seem to prevent or discourage insiders from engaging in insider trading as means of opportunistic rent extraction. Second, results confirm the notion of buy and sell trades not being just two sides of the same coin. That is, a higher level of corporate governance leads to a better pre-event information environment which results in less positive abnormal returns after insider buy trades as the incremental posi-tive information revealed by the trade is smaller. In contrast, sell trades in firms with better corporate governance are perceived to convey more valuable and most importantly negative information to the capital market so that prices adjust more for companies with better govern-ance schemes. Third, we show that institutional ownership even on an aggregate level is a sufficient measure to proxy a company’s corporate governance level. Hence, as information on companies’ bylaws and on investors’ investment dedication and type for example are scarce, respectively associated with higher costs because one has to gather that information one can refrain from that and instead proxy the governance level with the aggregate measure of institutional ownership. The latter result is important for carrying out future analyses merg-ing and extending the findings of the first two chapters.
Last, the fourth chapter abstracts from borrowers as subjects of credit risk, as well, and most importantly extends the analysis of banks, firms and their interactions effecting each other by a macroeconomic perspective of the real effects of bank lending. That is, as capital flows and real estate are pro-cyclical, and real estate has a substantial weight in economies’ income and wealth Chapter 4 studies the role of real estate markets in the transmission of bank flow shocks to output growth across German cities. In this regard, real sector firms play a central role in the transmission mechanism we uncover. More specifically, the empirical analysis relies on a new and unique matched data set at the city level and the bank-firm level. To measure bank flow shocks, we show that changes in sovereign spreads of Southern Eu-ropean countries (the so-called PIGS spread) can predict German cross-border bank flows. To achieve identification by geographic variation, in addition to a traditional supply-side varia-ble, we use a novel instrument that exploits a policy assigning refugee immigrants to munici-palities on an exogenous basis. We find that output growth responds more to bank flow shocks in cities that are more exposed to tightness in local real estate markets. We estimate that, during the 2009-2014 period, for every 100-basis point increase in the PIGS spread, the most exposed cities grow 15-2 basis points more than the least exposed ones. Moreover, the differential response of commercial property prices can explain most of this growth differen-tial. When we unpack the transmission mechanism by using matched bank-firm-level data on credit, employment, capital expenditure and TFP, we find that firm real estate collateral as measured by tangible fixed assets plays a critical role. In particular, bank flow shocks in-crease the credit supply to firms and sectors with more real estate collateral. Higher credit supply then leads firms to hire and invest more, without evidence of capital misallocation.
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