Crystal structure, electron density and chemical bonding in inorganic compounds studied by the Electric Field Gradient

The goal of solid state physics and chemistry is to gain deeper understanding of the basic principles of condensed matter. This ongoing process is achieved by the combination of experimental methods and theoretical models. One theoretical approach are the so-called first-principles calculations, which are based on the concept of density functional theory (DFT). In order to test the reliability of a band structure calculation, its results have to be compared with experiments. Since the electron density, the main constituent of DFT codes, cannot be directly determined experimentally with sufficient accuracy (e.g., by X-ray diffraction), other experimentally available properties are needed for the comparison with the calculation. A quantity that can be measured with high accuracy and that provides indirect information about the electron density is the electric field gradient (EFG). The EFG reflects local structural symmetry properties of the charge distribution surrounding a nucleus: the EFG is nonzero if the density deviates from cubic symmetry and therefore generates an inhomogeneous electric field at the nucleus. Since the EFG is highly sensitive to structural parameters and to disorder, it is a valuable tool to extract structural information. Furthermore, the evaluation of the EFG can provide valuable insight into the chemical bonding. Whereas the experimental determination of the quadrupole frequency and the closely related EFG has been possible for more than 70 years, reliable values for calculated EFGs could not be obtained before 1985, when an EFG module was implemented in the full-potential, linearised-augmented-plane-wave code WIEN. Since the full-potential local-orbital minimum-basis scheme FPLO is numerically very efficient and its local-orbital scheme allows an easy analysis of the different contributions to the EFG, one goal of this work was the implementation of an EFG module within the FPLO code. The newly implemented EFG module was applied to different systems: starting from simple metals, then approaching more complex systems and finally tackling strongly correlated oxides. Simultaneously, the EFGs for the studied compounds were determined experimentally by NMR spectroscopists. This close collaboration enables the comparison of the calculated EFGs with the experimental observations, which makes it possible to extract more physical and chemical information from the measured values regarding structural relaxation, distortion, the chemical bond or the relevance of electron correlation. In the last part of this work, the importance of corrections that go beyond the EFG are discussed. Such corrections arise for any multipole order of the hyperfine interactions, and are due to electron penetration into the nucleus. A correction similar to the isomer shift, coined here the "quadrupole shift" is examined in detail

Novel evasion strategies of Staphylococcus aureus against the human innate immune response

There is an ongoing competition between the human host and pathogenic microbes. The immune system, especially the immediately acting innate response, recognizes pathogens, prevents their spreading, and eliminates them. By contrast, certain microbes have developed sophisticated strategies to evade and suppress the host immune response. This thesis focuses on the functions of the plasma proteins apolipoprotein E (apoE)and plasmin in the interactions between the human host and the pathogen Staphylococcus aureus. Here, it is shown that antimicrobial peptides (AMPs) were generated from apoE upon cleavage by neutrophil elastase. The bactericidal activity was located to the heparin-binding site of the LDL-receptor-binding domain of apoE (SHL14). Full-length apoE had no antibacterial, but opsonic activity. Additionally, a new function of plasmin is reported. The serine protease degraded the AMPs C3a and SHL14. Thereby plasmin terminated bactericidal activity and may facilitate clearance of no longer needed effector molecules. Plasminogen, the precursor of plasmin, is bound by S. aureus. Here, a novel type of plasminogen-binding proteins, unique for S. aureus, is shown. Sbi and Efb recruited plasminogen together with the complement component C3. Plasminogen, fixed in these complexes, remained accessible to its activators uPa and staphylokinase. In the presence of Sbi or Efb, plasmin-mediated degradation of C3(C3b) was accelerated, likely due to conformational changes in C3(C3b). Thus, S. aureus efficiently inactivates complement activity. Plasmin and the metalloprotease aureolysin were also used by S. aureus to degrade the AMP SHL14 and inactivate the anti-opsonic activity of apoE. Taken together, apoE and plasmin have different functions in the interactions between host and pathogen. ApoE is part of the immune response against S. aureus and thus degraded by the pathogen. By contrast, plasmin restricts immune reactions and its activity is therefore exploited by S. aureus

Identification and analysis of Dictyostelium discoideum microtubule associated proteins

The microtubule cytoskeleton and its dynamic ends are crucial for many cellular functions throughout the whole cell cycle. Microtubule associated proteins (MAPs) are known to interact with other proteins to fulfill these complex functions in balancing the dynamic instability of microtubules as well as anchoring microtubules at the cell cortex, guiding transport along them and controlling mitosis at the centrosome. Deficient function of these proteins leads to severe defects, including cancer. A major part of our understanding of these processes is knowing the proteins associated with the complexes at either end of microtubules. To identify new members of these complexes, interactors of well characterized and conserved proteins of the EB1 and XMAP215 family of MAPs were searched for in the model organism Dictyostelium discoideum. DdEB1 and the Dictyostelium member of the XMAP215 protein family, DdCP224, are known to be part of complexes at the microtubule tips as well as at the centrosome. DdCP224 is involved in centrosome duplication and cytokinesis, whereas DdEB1 assists in spindle formation. At the microtubule tip these two proteins are part of a complex that is thought to link microtubules to the cell cortex. In this study, two approaches were selected screen for novel interactors. Employment of the yeast two hybrid system yielded five putative interactors of DdEB1 and DdCP224 that could not be verified by other means. Tandem affinity purification (TAP) is a method originally established in yeast to isolate highly purified protein complexes in a very gentle and efficient way. In this study TAP was modified for Dictyostelium applications and proved to be a useful method to specifically isolate and identify microtubule-associated protein (MAP) complexes. Employing TAP and mass spectrometry the interaction between DdEB1 and DdCP224 was confirmed. Additionally, among several interactions that remain to be confirmed by other methods, an interaction between DdCP224 and a TACC-family protein could be shown for the first time in Dictyostelium and was confirmed by colocalization and co-immunoprecipitation analyses. Similar to findings in other species, the TACC domain is sufficient for the centrosomal localization of the protein and the interaction with the XMAP215 orthologue. Based on the results presented, DdTACC, the only member of this protein family present in Dictyostelium discoideum, was considered to be an essential gene product

A Wide-Field View of Leo II -- A Structural Analysis Using the SDSS

Using SDSS I data, we have analysed the stellar distribution of the Leo II dwarf spheroidal galaxy (distance of 233 kpc) to search for evidence of tidal deformation. The existing SDSS photometric catalogue contains gaps in regions of high stellar crowding, hence we filled the area at the centre of Leo II using the DAOPHOT algorithm applied to the SDSS images. The combined DAOPHOT-SDSS dataset contains three-filter photometry over a 4x4 square degree region centred on Leo II. By defining a mask in three-filter colour-magnitude space, we removed the majority of foreground field stars. We have measured the following Leo II structural parameters: a core radius of r_c = 2.64 +/- 0.19 arcmin (178 +/- 13 pc), a tidal radius of r_t = 9.33 +/- 0.47 arcmin (632 +/- 32 pc) and a total V-band luminosity of L_V = (7.4 +/- 2.0) times 10^5 L_sun (M_V = -9.9 +/- 0.3). Our comprehensive analysis of the Leo II structure did not reveal any significant signs of tidal distortion. The internal structure of this object contains only mild isophotal twisting. A small overdensity was discovered appoximately 4.5 tidal radii from the Leo II centre, however we conclude it is unlikely to be material tidally stripped from Leo II based on its stellar population, and is most likely a foreground overdensity of stars. Our results indicate that the influence of the Galactic graviational field on the structure of Leo II has been relatively mild. We rederived the mass-to-light ratio of this system using existing kinematic data combined with our improved structural measurements, and favour the scenario in which Leo II is strongly dominated by dark matter with (M/L)_V ~ 100 in solar units.Comment: 41 pages, 15 figures, accepted for publication in the Astronomical Journa

Der Bestandsaufbau Öffentlicher Bibliotheken im Spiegel der Zeitschrift „Buch und Bibliothek“ seit 1948

Diese Diplomarbeit zeigt die Entwicklung des Bestandsaufbaus Öffentlicher Bibliotheken von der Volksbücherei über die Informationsbibliothek bis zu den heutigen Bibliotheken mit Profil auf. Dabei wird sowohl auf die zeitlich relevanten Problemstellungen der Bestandspolitik, als auch auf die Bestandskonzepte und Methoden des Bestandsaufbaus in den verschiedenen Entwicklungsstufen der Öffentlichen Bücherei eingegangen. Desweiteren werden die Probleme und Entwicklungen, welche die jeweils „Neuen Medien“ erzeugten, dargestellt. Da dieses Thema im Spiegel der Fachzeitschrift „Buch und Bibliothek“ aufbereitet wurde, wird sie zusammen mit ihrem ehemaligen Besprechungsdienst vorgestellt

Kinder über Kindermuseen: eine empirische Studie zu Qualitätskriterien

"Kindermuseen wollen mit ihren Angeboten Kinder ansprechen und ihnen vielfältige Erfahrungen ermöglichen. Doch es sind die Erwachsenen, die entscheiden, welche Inhalte, Methoden und Vermittlungsformen für die Kinder im Kontext der Museumsarbeit die richtigen sind. Mit der vorliegenden Studie wurden Kinder nach ihren Einschätzungen der Kindermuseen befragt. 405 Schüler im Alter von sechs bis zehn Jahren füllten nach einem Besuch in einem von vier Kindermuseen einen Satzergänzungstest zu ihren Erlebnissen aus. Es zeigte sich z.B., dass die Kinder es schätzen, selbstständig etwas zu tun und sich kreativ zu beschäftigen. Aus den Antworten wurden Qualitätskriterien für die pädagogische Arbeit in Kindermuseen - aus der Perspektive von Kindern - entwickelt." (Autorenreferat)"Children's museums target children with their exhibitions and offer a multifaced array of experiences, but adults are the ones who decide on the content and its presentation. In this study, children were asked about exhibitions they had visited. 405 elementary school children between 6 and 10 years of age filled out a small questionnaire about their experiences in one of four children's museums. Results indicated that children enjoy being active, doing things on their own, and engaging in creative activities. Criteria for the quality of children's museums were derived from the children's answers." (author's abstract

The herbal extract EPs® 7630 increases the antimicrobial airway defense through monocyte-dependent induction of IL-22 in T cells

The phytotherapeutic compound EPs® 7630, an extract manufactured from Pelargonium sidoides roots, is frequently used for the treatment of airway infections. Nevertheless, the knowledge of the mode of action of EPs® 7630 is still sparse. Our study aimed at further elucidating the underlying pharmacological mechanisms by focusing on antimicrobial defense mechanisms of EPs® 7630. While investigating the influence of EPs® 7630 on lymphokine production by PBMCs, we found that EPs® 7630 is a novel inducer of IL-22 and IL-17. This cytokine-inducing effect was most pronounced for IL-22 and clearly dose-dependent starting from 1 μg/ml of the extract. Furthermore, EPs® 7630 pretreatment selectively enhanced the IL-22 and IL-17 production capacity of CD3/28-activated PBMCs while strongly limiting the IFN-γ production capacity of innate lymphoid cells. The relevance of EPs® 7630-induced IL-22 production was proven in vitro and in vivo, where IL-22 provoked a strong increase of the antimicrobial protein S100A9 in lung epithelial cells and pulmonary tissue, respectively. A detailed analysis of IL-22 induction modi revealed no direct influence of EPs® 7630 on the basal or anti-CD3/CD28 antibody-induced IL-22 production by CD4+ memory T cells. In fact, EPs® 7630-induced IL-22 production by CD4+ memory T cells was found to be essentially dependent on soluble mediators (IL-1/IL-23) as well as on direct cellular contact with monocytes. In summary, our study reveals a new immune-modulating function of EPs® 7630 that might confer IL-22 and IL-17-induced protection from bacterial airway infection. KEY MESSAGES: EPs® 7630 selectively strengthens IL-22 and IL-17 production of memory T cells. EPs® 7630 limits the IFN-y production capacity of innate lymphoid cells. EPs® 7630-caused IL-22 production by T cells is essentially dependent on monocytes. IL-22 increase antimicrobial proteins (AMPs) in airway epithelium. EPs® 7630 might protect against airway infection by induction of AMP-inducers

Challenges for Preventive Digital Stress Management Systems - Identifying Requirements by Conducting Qualitative Interviews

Personal health depends on physical factors as well as on the subject’s behavior and lifestyle. Stress is the cause of numerous diseases unless it is in balance with sufficient relaxation and rest. Nowadays, continuous stress and, as a consequence, a burnout are steadily increasing, thus the need for prevention and stress management is growing too. Digital technologies allow for new methods of stress management to prevent burnout. However, the requirements for such systems remain largely unexplored. This work closes this research gap by offering a qualitative requirement survey and its analysis. For this purpose, 15 semi-structured interviews were conducted from four different perspectives (health insurance companies, care providers, private sector and users), which allowed to derive the requirements for successful digital stress management systems. These can be divided into three categories: Human Centricity, Medicine and Technology