Doctoral Thesis
Refine
Year of publication
- 2015 (50) (remove)
Document Type
- Doctoral Thesis (50) (remove)
Language
- English (50) (remove)
Is part of the Bibliography
- no (50)
Keywords
- Antikörper (2)
- Bach Ma Nationalpark (2)
- Biokatalyse (2)
- Enzym (2)
- Geopolymer (2)
- Karies (2)
- Kristallstruktur (2)
- Laserspektroskopie (2)
- Plasmaphysik (2)
- Pneumokokken (2)
Institute
- Institut für Physik (9)
- Abteilung für Mikrobiologie und Molekularbiologie (6)
- Institut für Geographie und Geologie (6)
- Institut für Biochemie (4)
- Zoologisches Institut und Museum (4)
- Institut für Mathematik und Informatik (3)
- Institut für Botanik und Landschaftsökologie & Botanischer Garten (2)
- Institut für Mikrobiologie - Abteilung für Genetik & Biochemie (2)
- Poliklinik für Zahnerhaltung, Parodontologie und Endodontologie (2)
- Institut für Epidemiologie u. Sozialmedizin (1)
- Institut für Geologische Wissenschaften (1)
- Institut für Immunologie u. Transfusionsmedizin - Abteilung Immunologie (1)
- Institut für Pharmazie (1)
- Institut für Psychologie (1)
- Interfakultäres Institut für Genetik und Funktionelle Genomforschung (UMG) (1)
- Klinik für Anästhesiologie und Intensivmedizin (1)
- Klinik und Poliklinik für Chirurgie Abt. für Unfall- und Wiederherstellungschirurgie (1)
- Klinik und Poliklinik für Frauenheilkunde u. Geburtshilfe (1)
- Klinik und Poliklinik für Mund-, Kiefer- und Gesichtschirurgie/Plastische Operationen (1)
- Poliklinik für Kieferorthopädie, Präventive Zahnmedizin und Kinderzahnheilkunde (1)
- Wirtschaftswissenschaften (1)
Streptococcus pneumoniae (pneumococci) are lancet-shaped, Gram-positive, alpha-hemolytic, facultative anaerobic human specific commensals of the upper and lower respiratory tract. Pneumococci may convert to pathogenic bacteria and spread to the lungs and blood. In different population groups, such as children, the elderly and immunocompromised individuals, pneumococci can cause local infections such as bronchitis, rhinitis, acute sinusitis, and otitis media as well as life-threatening invasive diseases such as community-acquired pneumonia, sepsis and meningitis. Pneumococci are surrounded by a rigid and complex exoskeleton, the peptidoglycan, also referred to as murein sacculus. The peptidoglycan (PNG) protects the cells from rupture by osmotic pressure and maintains their characteristic shape. The PNG is a heteropolymer made up of glycan strands that are cross-linked by short peptides and during growth the existing murein is continuously hydrolyzed by specific lytic enzymes to enable the insertion of new peptidoglycan. Bacterial cell-wall hydrolases are essential for peptidoglycan turnover and crucial to preserve cell shape. The D,D-carboxypeptidase DacA and L,D-carboxypeptidase DacB of Streptococcus pneumoniae function in a sequential manner. This study determined the crystal structure of the surface-exposed lipoprotein DacB, which differs considerably from the DacA structure. DacB contains a Zn2+ ion in its catalytic center located in the middle of a fully exposed, large groove. Two different conformations with differently arranged active site topology were identified. In addition the critical residues for catalysis and substrate specificity were identified. Deficiency in DacA or DacB resulted in a modified peptidoglycan peptide composition and led to an altered cell shape of the dac-mutants. In contrast, lgt-mutant lacking lipoprotein diacylglyceryl transferase activity required for proper lipoprotein maturation retained L,D-carboxypeptidase activity and showed an intact murein sacculus. Furthermore, this study demonstrated the pathophysiological effects of disordered DacA or DacB activities. Real-time bioimaging of intranasally infected mice indicated a substantially attenuated virulence of dacB- and dacAdacB-mutants pneumococci, while loss of function of DacA had no significant effect. In addition, uptake of these mutants by professional phagocytes was enhanced, while their adherence to lung epithelial cells was decreased. The second part of this study focused on the functional and structure determination of the soluble dimeric pneumococcal lipoprotein PccL. Because of its calycin fold and structural homology with the lipocalin YxeF from Bacillus subtilis, PccL was introduced as the first member of the lipocalin protein family in pneumococci and named “PccL” (Pneumococcal calycin fold containing Lipoprotein). Similar to other lipocalins, the distinct beta-barrel, which is open at one end, is significantly conserved in PccL. Moreover, the application of the in vivo acute pneumonia mouse infection model and the in vitro phagocytosis as well as adherence invasion studies revealed considerable differences in colonization and invasive infection between the wild-type D39 and the pccL-mutant. In conclusion, this study characterized the crucial role of pneumococcal carboxypeptidases DacA and DacB for PGN architecture, bacterial shape and pathogenesis. By applying in vivo and in vitro approaches, a close relationship between PGN metabolism and pathophysiological effects was discovered. In addition, the high resolution structure of DacB has been solved and analyzed and a structure model with a resolution of 2.0 Å is provided. Furthermore, analysis of the PGN composition was applied to indicate the impact of an impaired lipoprotein biogenesis pathway on localization and activity of DacB. The major impact of carboxypeptidases on cell shape and virulence proposes DacB as a promising target for the development of novel drugs or due to its surface exposition also as a promising vaccine candidate. PccL is the first pneumococcal lipocalin-like protein and this study indicated its contribution to pneumococcal virulence. However, the mechanism and the mode of action of PccL are still unknown and have to be deciphered in further studies.
Background: Restorative treatment for children’s teeth is still an important aspect of dentistry. In the light of an only moderate caries decline in the primary dentition and a persistently low care index in Germany during the past years [DAJ 2010], there is still a demand for further work on recent patterns and outcomes of restorative treatments in primary teeth placed in everyday practices under the Germany National Health System. Objectives: The present study aimed firstly to describe the prevalence of caries and restorations in the primary teeth in Berlin and Germany from the representative Germany surveys [DAJ 2010], secondly, to describe the frequency and distribution of restorative treatment in primary teeth performed in everyday dental practice in Berlin including children age groups from 1- to 13-years of age, thirdly, to evaluate the outcomes of restorative treatment performed in everyday dental practices in these children and finally to compare results of the present study with data from the German National Health System [KZBV 2011] and randomized community data on the longevity of restorations in primary teeth in Denmark [Qvist et al. 2010a]. Material and Methodology: In the first part of present study data from representative German surveys [DAJ 2010] were interpreted to describe and compare the prevalence of caries and restorations in the primary teeth in Berlin and Germany. For the second and third parts data generated from German National Health System in Berlin (KZV-Berlin) on fillings done in everyday practices in primary teeth of 1- to 13-year-olds during 2010/2011 were collected. This data included: distribution of children with dental treatment regardless of the type of intervention provided, of children who received restorative treatments in primary teeth during dental care visits including total number of fillings per child, the number of filled tooth surfaces, retreatment with another filling, stainless steel crowns, pulp involvement and extractions after prior filling therapy. Information on the age of the original fillings at the time of retreatment was also included. The collected data then were entered into a data base for descriptive and analytical analysis. The results were compared with equivalent data from the German National Health System [KZBV 2011] and randomized community data from Denmark [Qvist et al. 2010a]. Results: Result showed a high similarity in patterns of caries and restorative treatment in primary teeth in Berlin and all of Germany as reported in the representative German surveys [DAJ 2010]. About of 84% of 1-13-year-olds insured in the German National Health System in Berlin received dental care during 2010/2011, with considerably lower rates in very young children. Fillings in primary teeth were performed in 31.17% of all children attending the dentist. Most restorations were placed in 5-8-year-olds. In 1-13-year-olds mostly just one filling was placed, more than five fillings were per child were recorded on average for very young age groups (1-4-year-olds). 55.60% of all fillings in primary teeth were two-surface restorations, whereas more than three-surface restorations comprised 6.17% of all fillings and they were performed most frequently in young children of 1-4-years of age. Retreatment to fillings in primary teeth was 7.66% of fillings placed in 1-13-year-olds. Most retreatments took place from 5 to 9 years of age with a peak in 6-year-olds. In 1-3-year-old children fillings showed shorter mean age at the time of retreatment compared to 7-year-olds and above. Retreatment of fillings in primary teeth by stainless steel crowns was very limited with only 5.16% of all retreatments and it was preferred in children from 3 to 7 years of age. The retreatment with pulp involvement was 11.27% of all retreatments. Extractions were almost as often as retreatment as another filling (ratio 4:5), but they were preferred in older children due to the course of exfoliation. Conclusions: Under the conditions of this retrospective study, the restorative treatment with fillings performed within the National Health System in primary teeth in Berlin was very successful with low rates of retreatment and the fillings shows comparable results to data on the longevity of restorations in primary teeth in Denmark. The study highlighted the need to a structured program for prevention in primary teeth, especially for very young children with high caries activity and possibly also different treatment structures with specialized dentists in this field who can perform oral rehabilitations with pulpotomies and stainless steel crowns.
Background: Common to most theory-based intervention approaches is the idea of supporting intentions to increase the probability of behavior change. This principle works only if (a) intentions can be explained by the hypothesized socio-cognitive constructs, and (b) people actually do what they intend to do. The overall aim of this thesis was to test these premises using two health behavior theories applied to reducing at-risk alcohol use. Method: The three papers underlying this thesis were based on data of the randomized controlled “Trial Of Proactive Alcohol interventions among job-Seekers” (TOPAS). A total of 1243 job-seekers with at-risk alcohol use were randomized to stage tailored intervention (ST), non-stage tailored intervention (NST), or control group. The ST participants (n = 426) were analyzed in paper 1. Paper 2 was based on the baseline and 3-month data provided by the NST participants (n = 433). Paper 3 was based on baseline, 3-, 6-, and 15-month data provided by the control and ST group not intending to change alcohol use (n = 629). Latent variable modeling was used to investigate the associations of social-cognitive constructs and intentional stages (paper 1), the extent to which intentions were translated into alcohol use (paper 2), and the different trajectories of alcohol use among people not intending to change as well as the ST effect on the trajectories (paper 3). Results: Persons in different intentional stages differed in the processes of change in which they engaged, in the importance placed by them on the pros and cons of alcohol use, and in the perceived ability to quit (ps < 0.01). The association between intentions and alcohol use was weak. The magnitude of this intention-behavior gap depended on the extent to which normative expectations have changed over time (p < 0.01) and was reduced when controlling for the mediating effect of temporal stability of intentions. The gap was also present among people not intending to change: Even without intervention, 35% of the persons reduced the amount of alcohol use after 15 months (p < 0.05) and 2% achieved abstinence. Persons with heavier drinking (33%) and persons with low but frequent use (30%) did not change. Persons with frequent alcohol use seem to benefit less from ST than those with occasional use, although differences were not statistically significant. Conclusions: Intentions can be quite well explained by the hypothesized socio-cognitive constructs. In a sample of persons who were, as a whole, little motivated to change, the precision of how well intentions predict subsequent alcohol use was modest though. Time and socio-contextual influences should be considered.
Cancer is one of the leading causes of death in industrialized nations. Nowadays, cancer therapy mainly consists of surgery, radiation and chemotherapy. Thanks to intensive research alternative treatment strategies like gene therapy and especially immunotherapies are on the rise. Immunotherapies base on the idea of stimulating and supporting the patients immune system to generate an effective anti-tumor immune response. Dendritic Cells are perfect targets for this purpose, since these potent antigen-presenting immune cells influence the balance of the immune system by defining the route of action. Stimulation of these cells by activation of cellular signaling pathways results in maturation, upregulation of surface molecules and secretion of cytokines. A20 has been identified as a regulator of dendritic cell maturation and attenuator of their immune stimulating properties. Hence, the blockade of that natural inhibitor reveals an elegant way to activate cellular pathways of DCs. A siRNA against A20 obtains a functional blockade via RNA interference if it can be delivered into the cytoplasm of the target cells. CpG oligodeoxynucleotides can be used for this intracellular transport. CpGs contain DNA motifs similar to those found in bacteria. Innate immune cells can detect this DNA via the toll-like receptor 9 getting activated and stimulated. CpG oligodeoxynucleotides are already in clinical use as adjuvants in vaccines and in cancer therapy approaches. Linking A20-specific siRNA to CpG enables A20 regulation and cell stimulation selectively in toll-like receptor 9 expressing cells, like dendritic cells. Aim of this study was to investigate if these constructs trigger immune cell activation and if they are able to break immune-suppression in the tumor environment to enhance anti-tumor immunity. A long-term growth factor dependent bone marrow-derived dendritic cell culture has been established in order to analyze the CpG-siRNA A20 effects on murine dendritic cells. The constructs were internalized shortly after administration (1 hour) and led to cell stimulation/activation. The intraperitoneal treatment with the constructs induced local cellular activation and systemic IL-6, TNF-α cytokine production in healthy mice. Subcutaneous growing B16 melanoma tumors were treated peritumorally to analyse whether the observed immune-stimulation has effects on established tumors. The silencing of A20 enhances CpG-induced activation of NF-κB followed by elevated expression of IL-6, TNF-α and IL-12 in this tumor model. These changes led to enhanced anti-tumor immune responses manifested by increased numbers of tumor-specific cytotoxic T cells, high levels of tumor cell apoptosis and delayed tumor growth. New constructs were designed and tested on dendritic cells isolated from healthy donors in order to test whether the obtained results for the murine system are applicable to the human system. CpG-siRNA A20 constructs induced cell activation and cytokine expression (IL-6, TNF-α) significantly more than CpG alone. Even though responds of the donor DCs were variable, there are promising similarities to the results of the mouse experiments. The significant role of A20 in controlling the immune-stimulatory activity of DCs has been confirmed in this study. The novel CpG-siRNA A20 constructs provide a strategy for simultaneous A20 silencing and CpG-mediated cell stimulation directly in vivo. This therapeutic approach induces potent adaptive and innate immune responses against established tumors in mouse melanoma model leading to prolongation of survival. CpG-targeted A20 blockade is a new immune-stimulatory approach, which could be suitable for supplementation or optimization of clinical tumor treatments.
Although the Pleistocene deposits exposed in the steep coastal cliffs of Mecklenburg-Vorpommern have been studied for more than a century, the depositional conditions of many lithostratigraphic units remain unclear. There is, in particular, a question whether the individual tills (locally more than 9 successive till units) are mainly subglacial deposits or resedimented (mass flows) in origin (at least in part). The Pleistocene deposits preserve information concerning the former glacial depositional processes. Detailed micromorphological analysis of these deposits can provide key information regarding these processes and thereby aid in the reconstruction of former glacial environments. The island of Rügen is located on the southwestern Baltic Sea coast and was situated in the marginal zone of the Scandinavian Ice Sheet during the last glacial period (Weichselian). Therefore, the region is considered as an ideal area for reconstructing the complex fluctuations in the position of the margin of this ice sheet as it expanded across the Baltic Sea and into northern Germany. Successive glacial advances and retreats of the ice sheet can be reconstructed by specific glacial sedimentation processes and flow-direction criteria derived from a variety of glacial deposits. The investigation area is located near Sassnitz on Rügen, where an imbricated and folded Weichselian succession disconformably overlies Maastrichtian chalk bedrock. The individual till units were sampled for micromorphological analyses to identify the former depositional conditions. Detailed description of the sedimentology and variation in facies, the description of macroscale deformation structures provides the context for the detailed micromorphology study. The three dimensional analysis of the microfabrics is based on the microstructural mapping methodology which enables the identification and interpretation of polyphase deformation within subglacial sediments.
This work focuses the glycoprotein H of PrV which was analysed by structure-based functional analyses by targeted site-directed mutagenesis. Disulfid bridges were introduced at specific sites and the effects on the fusion mechanism investigated. A revertant was obtained and characterised during the studies, as well as chimeric glycoprotein H proteins were constructed, combining the different domains of the glycoproteins Hs of PrV and HSV1.
The following work is describing the development of two innovative biosensors for the detection of biologically relevant molecules in the field of ecology and medical diagnostics. Biosensors have the particularity to possess a biological partner which recognizes the target molecule and a physical detection method responsible for the transformation of this biological interaction into measurable information. In the present case, both biosensors are designed following the same strategy and use a recombinant produced human receptor as biological partner and the surface plasmon resonance (SPR) technique to transform the biological interaction in quantitative information. The progesterone biosensor is aimed to detect and quantify substances with affinity to the human progesterone receptor. The recent discoveries that some chemicals present in low quantities in the ecosystem called endocrine disrupting chemicals (EDCs) have a negative impact on the aquatic life fitness raised concerns about the effects of these same molecules to the human health. In order to assess the effects of these EDCs, the use of classical analytical detection methods like high performance liquid chromatography (HPLC) or gas chromatography (GC) is not sufficient as these techniques only quantify a defined molecule without giving information about its biological activity. By integrating a recombinant human progesterone receptor, the progesterone biosensor can determine the biological activity of an unknown molecule or of a mixture of molecules in a real sample. In this work, two different yeasts – one methylotrophic (Hansenula polymorpha) and one non-methylotrophic (Arxula adeninivorans) - were selected as host for the recombinant protein production and their performances were compared. Different purification strategies were assayed and the binding activity of the purified progesterone receptor was then confirmed by enzyme like receptor assay (ELRA) and SPR. This led to the design of a first version of the biosensor with the immobilization of a progesterone-BSA ligand to the surface of a SPR chip and the use of a progesterone receptor mixed with the target molecule as sample. This competitive assay format was successfully utilized with a commercial progesterone-BSA ligand as target molecule and the next step will be the adaptation of this biosensor for real samples measurements. The HER-2 biosensor was developed as an answer for one of the most critical issue in the field of breast cancer diagnostics. In approximately 30 % of cancer cases, the transmembrane protein HER-2 can be found in large amount at the surface of the carcinoma cells and these cases are known to be particularly aggressive. Based on the amount of HER-2 protein at the surface of the cells, the pathologists established a scale with four levels to adapt the treatment to each patient. Although effective therapies have been developed to treat the HER-2 positive breast cancer, one of the major challenges remains the classification of breast sample in this scale as the only accepted determination methods are immunohistochemistry (IHC) and fluorescent in situ hybridization (FISH) which are only qualitative. In this work, a biosensor has been designed to quantify the amount of the HER-2 protein in a crude cell extract from a breast cancer tissue sample. To achieve this, the strategy is to utilize an antibody specifically targeted against the HER-2 protein and bound to a SPR chip. As the development of this biosensor necessitated the use of large amount of purified HER-2 protein, it was decided to produce recombinant full-length HER-2 in two different yeasts and to purify it by chromatography. This recombinant protein production required particular attention due to the membrane localization of HER-2. The structural integrity of the recombinant protein was confirmed by Western Blot and ELISA and different antibodies were bound to SPR chips in order to detect the HER-2 protein. After finding the conditions giving an optimal SPR signal, a protocol was developed to extract native HER-2 from breast tissue sample and the biosensor was assayed with this crude cell extract.
Geopolymers (GPs) are inorganic binders created by adding alkaline solution (e.g. KOH) to silicates such as furnace slag, fly ash or clay to dissolve Si and Al that polymerises and precipitates to form an inorganic binder material while hardening. GP properties are similar to ordinary Portland cement regarding their high compressive strength or low shrinkage but they are particularly notable for a high resistance to acid and fire. However, the most significant advantage of GP cements is their low CO2 footprint. The most common clay used as GP raw material is kaolin. The aim of this study is to investigate the suitability of illitic clays as a cheaper alternative to kaolin and determine the necessary preparation steps required to produce effective GP binder materials. Three clays dominated by dioctahedral 2:1 layer silicates, in particular interstratifications of mica and smectite were investigated: (1) Illitic clay from Friedland, Northern Germany, containing an irregularly stacked illite-smectite interstratification (R0 I-S), (2) rectorite from Arkansas, USA, as a regular interstratification of mica and smectite, and (3) clay stated as “sárospatakite” from Füzérradvány clay deposit, Northern Hungary, containing a long range ordered I-S (R3). The three types of I-S interstratification-rich clays were extensively characterised and the Friedland clay, as the most probable raw material for GP production, was studied in more detail including several size fraction analyses. These results are used to investigate and determine the parameters necessary to produce suitable precursors for GP binders. Different approaches of clay activation to yield a highly reactive material by milling and heating were examined. Milling was found to be suitable as a preparation step after heating breaking up sintering aggregates to create pathways for the alkaline solution, but not as a substitute for heating. Important parameters for the precursor design such as temperature, time, and heating rate are determined and discussed. Geopolymerisation is considered to be a multi-parameter system and is influenced strongly by the degree of dehydroxylation, Si:Al ratio, or amount of 5-fold coordinated Al. However, in contrast to kaolin-based systems, none of these parameters explain why the illitic Friedland clay heated to 875 °C was found to be most suitable for GP binders. Based on leaching experiments and specific surface area (AS) measurements of the heated Friedland clay, a conceptual model is presented to explain the observed relationship between the heating temperature and the subsequent compressive strength of the GP cement. An optimum between the counteracting reactions of decreasing AS (fewer particles must be covered with GP phase) and decreasing Si+Al dissolved (less GP phase created) is necessary, which exists at 875 °C for the Friedland clay. In this state enough GP phase is created to bind all remaining sintering aggregates to form a cement with high compressive strength. This relationship can be expressed as (Si+Al) / AS (sum of dissolved Si and Al divided by the surface area of grains that must be covered with GP phase), and can be used as a predictive tool for determining the optimal heating temperature. The results presented in this thesis indicate that illitic clays are suitable raw materials as GP binders if the necessary preparation steps of dehydroxylation, sintering and grinding are made. Proxies used to evaluate the optimal conditions for making GP binders are determined including the (Si+Al) / AS ratio as a key relationship that controls the cementation process and determines its ultimate hardness.
The aim of this thesis is to concentrate on the investigation of these ROS&RNS composition distribution and their production pathways in the gas phase produced by a plasma jet. By understanding the physical mechanisms behind the generation of the ROS&RNS a precise tuning and design of the composition distribution in the gas phase can be achieved. One crucial physical parameter is the dissipated power inside the plasma. Only if this parameter is known a meaningful comparison of different feed gas settings is possible. Therefore, a concept for measuring the dissipated power inside the plasma for the modified micro-scaled atmospheric pressure plasma jet( µAPPJ) is designed. Additionally, due to achievements within this thesis it is now possible to ignite a homogeneous discharge in argon and helium within the geometry of the µAPPJ. The used feed gas is a determining factor concerning the electron energy distribution function and consequently influencing the production mechanism of the ROS&RNS. First of all, the electrical characterisation of the modified µAPPJ was performed including the alpha-to-gamma transition. It is shown that the alpha-to-gamma transition power is increasing with increasing frequency. For the first time it is now feasible to investigate the influence of the dissipated power on the neutral gas temperature, the metastable atom densities and the ROS&RNS production for the modified µAPPJ with argon and helium as feed gas. Due to the possibility of changing the feed gas and controlling the dissipated power a fundamental insight into the production mechanism of the ROS&RNS generated by the plasma jet is achieved. With rising dissipated power the temperature and the metastable densities as well as the ozone and nitrogen dioxide concentrations are increasing. By adding molecular oxygen and nitrogen to the feed gas of a plasma jet the ROS&RNS composition can be tuned. However, also the dissipated power is changed by the small amount of admixtures. Due to the developed dissipated power measurements within this thesis it was possible to disentangle the influence of the admixture on the power and on the ROS&RNS production. If the dissipated power is fixed for the µAPPJ with argon and helium feed gas, respectively, the highest amount of ozone was measured with oxygen admixture in an argon discharge, the highest amount of dinitrogen pentoxide with nitrogen admixture in an argon discharge and the highest amount of nitrogen dioxide with nitrogen admixture in a helium discharge. Beyond the influence of the dissipated power and the molecular admixture on the ROS&RNS production the feed gas temperature is a crucial parameter for the corresponding chemical reactions. By changing this parameter the distribution of ozone and nitrogen dioxide can be tuned precisely in such a way that with increasing temperature the ozone density goes down and the nitrogen dioxide density rises. Another determinant for the ROS&RNS composition produced by an atmospheric pressure plasma jet is the influence of ambient air. If the ambient air is changing from pure nitrogen to pure oxygen atmosphere the ozone density produced by the plasma jet is increasing. For the same conditions the nitrogen dioxide has a maximum at an oxygen-to-nitrogen ratio of 1:1. To avoid the influence of the ambient air on the reactive species production the afterglow of the µAPPJ was prolonged with a glass tube. By increasing the amount of molecular admixtures to the feed gas with each in equal quantities a totally different ROS&RNS composition can be obtained compared without the glass tube. It figures out that for small molecular admixtures the reactive species composition is nitrogen dominated and for higher admixtures it is oxygen dominated. Consequently, by shielding the ambient air from the active effluent and by admixing molecular oxygen and nitrogen the ROS&RNS composition can be designed.
Because heavy metal ions prefer to bind sulfur, inspired by molybdopterin the main goal of this work was combining dithiolene binding moieties with optically active substituents with the aim to detect/capture metal ions, which could preferably bind to the dithiolene moiety of for instance MPT. Therefore a number of dithiolene based molecules mimicking the natural immediate coordination sphere composition of Mo and W dependent oxidoreductase enzymes were synthesized and characterized by NMR, MS, IR, X-ray crystallography, UV-Vis, EPR and electrochemical methods. In order to work at the lowest possible base concentration due to potentially base sensitive substituents and reaction partners, the procedure for the de-protection of the ligand precursors and the in situ complexation reaction was first optimized in course of the work and interim we explored the surprising fact that the ring opening reaction of the 1,3- dithiol-2-one system is fully reversible and can be controlled simply by adjusting the pH-value of the solution. Then, the coordination behavior of the de-protected ligands towards different metal ions, including biologically relevant ions like Cu+, Cu2+, Fe3+ was tested. As the optically active substituents necessarily possess interesting electronic properties, a second focus of this work was to utilize the developed ligand systems for MoCo and WCo models and to investigate their potential catalytic activity in the model oxotransfer reaction between DMSO and PPh3 in order to evaluate the substituent’s effect on the dithiolene binding moiety.
We presented the prevalence of MIH in Dubai/UAE for the first time, which represents a developed Middle Eastern city and compared it to results obtained from Greifswald/Germany, which represents a developed European city. The results have shown that the prevalence of MIH in Dubai/UAE is higher than Greifswald/Germany. However, in comparison to the literature, the prevalence of MIH in Dubai is lower than other Middle Eastern cities. Furthermore, we have shown that there is a higher caries level associated with MIH in Dubai. This is also true in Greifswald, Germany and other international studies. In addition, we have reported the prevalence of caries and fluorosis in Dubai and compared them to Greifswald and the previous studies in Dubai. Nevertheless, caries values presented in this study and previous studies indicate that strong attention is required from health authority to this topic. This research provides a strong and comparable source of information on the prevalence of MIH in Dubai for other studies, since it followed strictly all methodological and clinical standards suggested for the assessment and diagnosis of MIH, which are the EAPD criteria. The findings presented in this study require particular attention from the local health authorities and general practitioners for such developmental defect to facilitate early and adequate diagnosis and treatment. This could be achieved by implementing continuing education courses on MIH detection, diagnosis, and treatment for general practitioners. Furthermore, this study has the potential to trigger new studies that would help in understanding the MIH etiology.
The current work is focused on the study of two surface modification plasma processes, (i) the active screen plasma nitriding (ASPN) and nitrocarburizing (ASPNC) for the hardening of ferrous surfaces and (ii) the microwave plasma assisted chemical vapor deposition (MW-PACVD) for the synthesis of single crystal and doped diamond. Conventional and active screen plasma nitriding processes have been investigated in a cylindrical, industrial scale ASPN reactor with a volume of about 1 m3, using low-pressure pulsed dc H2-N2 plasmas with admixtures of CH4 or CO2. The experiments were carried out (i) with the plasma at an internal model probe, (ii) with the plasma at the active screen (floated model probe) and (iii) with the plasma at the active screen and an additional plasma at the biased model probe. For deeper insights in ASPN and ASPNC processes, a laboratory scale plasma nitriding monitoring reactor, PLANIMOR, has been constructed. The main feature of this reactor is the linear configuration of the electrode setup combined with a tubular glass vessel, overcoming the experimental disadvantages of cylindrical laboratory scale ASPN reactors. With the help of infrared laser absorption spectroscopy (IRLAS) the rotational temperature of the stable molecules in the gas phase and the concentrations of the precursor, CH4, and the reaction products (NH3, HCN, C2H2, C2H4, CO, CH3) could be determined in both reactors, depending on the plasma power, the gas mixture, the plasma at the model probe and the admixture of CH4. Furthermore, the admixture of CO2 as the carbon containing precursor has been studied in the ASPN reactor leading to an additional reaction product H2O. The concentration of the molecular species has been found being in a range of 1012 to 1016 molecules cm-3. Also optical emission spectroscopy (OES) has been applied during the studies for analyzing the emission of the plasmas in the nitriding and nitrocarburizing processes. A similar behavior of the plasma chemistry in PLANIMOR comparing to that in the ASPN reactor has been found. Beside the plasma chemical investigations, both reactors have been used for the treatment of C15 steel samples. These samples have been analyzed with the help of GDOES resulting in the elements profile of the treated surfaces. It has been found that samples treated in PLANIMOR reach comparable nitriding results as samples treated in the ASPN reactor. Another focus of interest during the investigations about plasma nitrocarburizing has been the application of a carbon containing screen electrode as carbon source. For this purpose the carbon containing precursor and the steel screen have been substituted by a meshed carbon electrode, acting as the active screen. This change of the setup leads to a decrease of the NH3 production by a factor of 2.5 and an increase of the concentrations of HCN by a factor of 30 and of C2H2 by a factor of 70. The investigations of MW-PACVD processes used for diamond layer deposition have been carried out in a jacketed stainless steel reactor (JR), dedicated to the deposition of single crystalline diamond under high pressure and plasma power conditions. Using H2-plasmas with admixtures of CH4 and B2H6, the experiments were carried out in order to analyze the dependence of the plasma chemistry on several parameters, such as plasma power, pressure and gas mixture, in a wide pressure (p = 25…270 mbar) and power range (P = 0.6…4 kW). Using IRLAS the concentrations of six molecular species (B2H6, CH4, C2H2, C2H4, C2H6, CH3) have been monitored. With the help of OES the concentration of atomic boron could be determined. The concentrations of the detected molecular and atomic species were found to be in a range of 1010 to 1017 cm-3. With the help of the line-ratio-method the rotational temperature of the stable molecules has been determined. The temperature increased with pressure and power from 340 to 425 K. Using the Doppler broadening of the absorption line of CH3 at ν = 612,413 cm-1, the gas temperature has found to be Tg = (2000 ± 200) K under lower pressure and power conditions. For the H2-CH4 gas mixture, the experimental obtained molecular densities have been compared to those of a 1D-radial thermochemical model. The calculated radial densities have been integrated axially. For the same range the chemical processes in JR have been compared with those in a bell-jar (BJ) reactor. The hydrocarbon chemistry in JR has found to be similar to that in a BJ reactor.
Using geopolymers can reduce significant amounts of CO2-emissions during the production compared to Portland cement. Although illite/smectite clays are very abundant on earths crust and rich in SiO2 and Al2O3, studies of their geopolymerization potential are rare. Thus, the illite/smectite clay of Friedland (NE Germany) was calcined (850 °C) and ground to form a reactive metaclay and then mixed with synthetic gibbsite (to test the effect of Al-concentration) and 6 molar NaOH or KOH, in order to study their geopolymerization at 25, 50 and 75 °C within 28 days. The raw clay, the precursors, and the geopolymers were characterized by XRF, XRD, SEM-EDX, Flame-AAS, nitrogen adsorption and compressive strength test. 25 °C was too low to initiate the geopolymerization of illite/smectite. Increasing the curing temperature increased the reactivity of meta-illite/smecite. Si and Al dissolution was confined to the first 24 h, followed by the hardening of the geopolymers within 28 days. At 50°C, KOH-activation formed amorphous and mesoporous aluminosilicates, which significantly cemented the particles and agglomerates of the metaclay. Consequently, geopolymers with high compression strength (~38 N/mm2) were formed. Adding 10 wt% Gibbsite (precursor Si/Al = 2.1) to the metaclay strengthened the formation of amorphous aluminosilicates and increased the compression strength of the geopolymer by 20 % from 38 - 45 N/mm2. At 75 °C, the reactivity of the metaclay in NaOH was higher than in KOH. NaOHactivation at that temperature formed geopolymers with high compression strength (~30 N/mm2) due to the cementation by microporous phillipsite (K-, Na-zeolite) crystals. Thus, alkali-activation of the calcined and ground meta-illite/smectite from Friedland form high strength geopolymers under hydrothermal conditions.
The immune system of all vertebrates primarily is responsible to maintain the organisms homeostasis by either eliminating neoplastic or altered body cells and to protect against foreign invaders (viruses, bacteria, fungi, parasites) (Murphy 2012). It is a highly regulated network of innate and adaptive mechanisms between humoral factors and leukocytes. The successful elimination or protection is crucially based on differentiation of self from non-self. Pathogens and altered body cells are recognized by different receptor complexes on immune cells. Expressed pathogen- or danger-associated molecular patterns (PAMPs or DAMPs, respectively) are bound by pattern recognition receptors (PRR) (Takeuchi and Akira 2010). Missing major histocompatibility (MHC) class I molecules or non-self (e.g. allogeneic or xenogeneic cells) MHC are recognized by natural killer cell receptors (Fischer, Koppang and Nakanishi 2013, Raulet 2006). Foreign non-self peptides are presented through MHC class I (intracellular) or through MHC class II (extracellular) to B- cell or T cell receptor complexes. This initial activation is regulated by humoral factors or cellular interactions (receptor-ligand interactions) resulting in the activation, proliferation and effector function within an immune response. Some of the cellular receptors are permanently expressed on all leukocytes on a high level (MHC class I), whereas others only are expressed during certain developmental or activation stages or on certain leukocyte populations (monocytes, granulocytes, NK cells, lymphocytes) (Murphy 2012, Biosciences 2010). For different mammals (man, mouse, rat, but also swine, cattle, dog), a system of characterized leukocyte surface molecules primarily based on the recognition of these molecules by specific monoclonal antibodies (mabs) was summarized at international workshops as clusters of differentiation (CD) (Cobbold and Metcalfe 1994, Hopkins, Ross and Dutia 1993, Haverson et al. 2001, Mason et al. 2001). Using these mabs, it is not only possible to characterize the developmental and functional stage of different leukocyte subpopulations but also to define the interactions between these populations. For bony fish, such a system does not exist. Only a limited number of mabs against leukocyte surface molecules is available and most of them are strongly specific for species (Köllner et al. 2004, Köllner et al. 2001, Zhang et al. 2010, Ramirez-Gomez et al. 2012, Wen et al. 2011, DeLuca, Wilson and Warr 1983, Toda et al. 2011, Toda et al. 2009, Takizawa et al. 2011a, Hetland et al. 2010, Araki et al. 2008). The goal of this PhD work, therefore, was to develop monoclonal antibodies against surface markers of rainbow trout (Oncorhynchus mykiss) T cell population (chapter 2). The lymphocytes are characterized by the expression of a T cell receptor complex composed of TCR chains (α and β) and CD3 chains (α, β, γ, δ, ε and ζ). Cytotoxic T lymphocytes (CTLs) binds to MHC class I bound peptide on the infected host cell using their T cell receptor (TCR) and its co-receptor CD8 resulting in specific killing. Th cells recognize peptides through their T cell receptor (TCR) and their co-receptor CD4 after extracellular antigens uptake, processing and presentation via MHC class II by professional antigen presenting cells (macrophages, dendritic cells and B cells). During recent years, genes encoding MHC class I and II, TCR and their co-receptors CD8 and CD4 have been cloned in several fish species and antibodies have been developed to study protein expression in morphological and functional contexts. However, mabs specific for TCR or CD3 have not been established yet. Therefore, using pan-T cell marker specific mabs, the activation and kinetics of T cell subpopulation should be investigated (chapter 2). Moreover, a flow cytometry method was established using different lineage marker specific mabs to measure different leukocyte populations and their involvement in immune mechanisms of trout using a single tube assay (chapter 3). The first line of defense against altered body cells or pathogens is provided by evolutionarily ancient macrophages and natural killer (NK) cells. These innate mechanisms are well developed in bony fish. Two types of NK cell homologues have been described in fish: non-specific cytotoxic cells and NK-like cells (Shen et al. 2002, Shen et al. 2003, Shen et al. 2004, Fischer et al. 2013). Functional assays for innate and adaptive lymphocyte responses have been developed in only a few fish species. However, there are no tools available until now in trout to follow these cells directly in the immune response. The molecular characteristics and the expression on leukocyte subpopulations of CD56 were therefore analyzed. Furthermore, a mab that is specific for a molecule expressed only in NK cells but with uncommon expression kinetics was established (chapter 4). Overall, the established tools and methods allow a more detailed characterization of cellular immune mechanisms against intracellular pathogens in rainbow trout.
This thesis investigated dielectric barrier discharges (DBDs) in N2-O2 gas mixtures at atmospheric pressure, with a focus on the gas discharge physics. The main goal was to evaluate whether possible control mechanisms exist that can manipulate the breakdown and the development of DBDs, especially for pulsed operation. To examine the pre-breakdown phase, the actual breakdown and the main DBD development, DBDs in a double-sided, single filament arrangement with a 1 mm discharge gap were investigated by means of electrical and optical diagnostics with high resolutions. Spectrally- and temporally-resolved iCCD pictures (2D in space), spectrally- and spatio-temporally-resolved streak camera and CCS images (1D in space) were simultaneously recorded accompanied by a full electrical characterisation with fast voltage and current probes. Sinusoidal- and pulsed-driven DBDs were found to have a qualitatively similar spatio-temporal development, i.e. a cathode-directed ionisation front (v ~ 10^6 m/s, positive streamer mechanism), followed by a transient glow-like phase in the gap. For sinusoidal operation, the slope of the applied voltage is flat (dU/dt ~ 1 V/ns) compared to pulsed operation (dU/dt ~ 100 V/ns). Thus, during the longer pre-phase of the sine-driven DBD, many more charge carriers were generated, in contrast to the pulsed-driven DBDs, where the pre-phase is limited by the short voltage rise time. Consequently, just before the breakdown occurs, the charge carrier density is higher for sine-driven DBDs, i.e. the positive streamer starts in a highly pre-ionised environment, which leads to a lower propagation velocity. In addition to limiting the pre-phase (lower pre-ionisation), the steep voltage slope of the pulsed DBD amplifies the streamer breakdown because the applied voltage rises significantly during its propagation. Therefore, the transferred electrical charge and the electrical power of a single DBD can be controlled by the applied voltage amplitude, but only in pulsed operation. In addition to the effects of different voltage slope steepness, the pulse width is an excellent parameter in the pulsed operation to set the pre-ionisation, by shifting the DBDs into the after-glow of the previous discharge using asymmetrical HV pulse waveforms. The subsequent DBDs ignite in different pre-ionised conditions, defined by the residual charge carrier densities in the gap that originated from the previous DBD. The breakdown characteristics of these DBDs could be controlled down to the fundamental level. This thesis has described for the first time four different breakdown regimes in single filament DBDs for 0.1 vol% N2 in O2 and connected them to the processes during their pre-phases. The “classic” DBD development (a cathode-directed streamer followed by a transient glow discharge) could be controlled in a certain range, followed by a transition first to a breakdown regime featuring a simultaneous propagation of a cathode- and an anode-directed streamer, and finally to a reignition of the previous DBDs without any propagation, just by reducing the pulse width (time between two subsequent DBDs), i.e. increasing the pre-ionisation level. All differences between the DBDs at rising and falling slopes could be explained by the different pre-conditions in the gap. The O2 concentration in the N2-O2 gas mixtures offers another way of controlling the pre-ionisation. Due to the electron attachment as a consequence of the electronegativity of oxygen, the electron density decreases for higher O2 admixtures. Furthermore, the differences in the first Townsend ionisation coefficient and in the photo-ionisation between N2 and O2 influence the DBD behaviour as well. To some extent, some of the reported effects achieved by varying the pulse width at a fixed O2/N2 ratio were also observed for a fixed pulse width and changing O2 concentration. Hence, the response of the DBD properties to changing pre-ionisation levels seems to be a general principle of DBD control. Additional effects of the O2/N2 ratio, such as an increasing DBD inception jitter or higher streamer velocities, were also reported. Finally, a reverse of the effects induced by the O2 admixture such as DBD emission duration or DBD inception delay, was observed for O2 concentrations below 0.01 vol%, and were especially pronounced at a pressure of 0.5 bar. For 0.1 vol% O2 in N2, a minimal electron recombination rate was found, which can be explained by the different decay and recombination rates of positive nitrogen and oxygen ions. These different rates effect the charge carrier dynamics and consequently, the pre-ionisation in the gap. In conclusion, this investigation has highlighted the importance of volume memory processes on the breakdown and development of single filament DBDs at elevated pressures.
This thesis delves into some very important scientific challenges for the stellarator concept as a whole and W7-X in particular, namely, how one effectively interfaces the hot plasma with the material walls of the experiment, in special how the plasma heat and particle fluxes are controlled. The fundamental concept that will be used in W7-X for particle and heat exhaust is the island divertor. A number of theoretical and numerical studies have been performed to guide the design of the divertor components. The actual divertor components are in series production at this time, and are largely compatible with the expected heat loads. However, with the sophisticated codes now available, it has become clear that there are some, otherwise very attractive, operational scenarios that could lead to overloading of the W7-X divertors. At least one mitigation strategy was proposed but was until now not analyzed in sufficient detail. In this thesis, state-of-the-art codes are used to analyze this previously proposed mitigation strategy; they are also used to develop several alternative mitigation schemes, which may in the end be advantageous. The work performed here shows not only that it is conceivable to solve this already identified problem in new and arguably better ways but also that the W7-X coil set has enough degrees of freedom that many important long-pulse plasma effects can be effectively mimicked in short-pulse operation. This opens up a rich research program in the early phases of operation and may therefore lead to a significant acceleration of the scientific program to control and optimize the divertor operation in W7-X. The main scientific challenge for the island divertor operation in W7-X is that, since the divertor geometry is now fixed, the magnetic field structure must be adjusted to the divertor geometry, or additional plasma-facing components must be manufactured and installed. Well before this thesis work was done, such additional plasma-facing components were proposed. These are called scraper elements (SEs). As a part of this work, computer simu- lations were performed in order to obtain a better knowledge base regarding the SEs. To analyze the effect of the SE, edge plasma physics simulation code EMC3-Eirene, was used, in combination with state-of-the-art magneto hydrodynamic (MHD) equilibrium codes. This combination was computationally non-trivial and new, and it has led to important insights. One main result of this study is that the SEs significantly reduce the particle exhaust capabilities in steady state operation; this is a concern for W7-X. To test and further quantify this deleterious effect, physics experiments with a prototype SE should be performed as soon as possible, ideally in the first operation campaigns before the approximately two-year break needed to complete W7-X for steady-state operation. In 3 this first operation phase, however, the necessary combination of plasma parameters, heating power, and achievable pulse length is not accessible. This means, on the one hand, that the problem described will not be present in the first operation phase; on the other hand, the physics implications of installing an SE would appear not to be experimentally testable in that phase. One major finding of this thesis is that the coil system of W7-X is flexible enough to allow such an early experimental test. Different stages of high performance long-pulse discharge can be effectively mimicked in the experiment by a targeted use of the available coil sets. Thus, even in the early phases of the W7-X program one can assess both the protection capabilities of the SEs and their effects on particle exhaust and plasma performance in general. These mimic scenarios also have the potential to test other possibilities for divertor pro- tection besides the SE. Such strategies are addressed in this thesis. The two most promising strategies identified here can be classified as plasma shift and iota control. Both adjust the edge magnetic field to better fit the divertor geometry. This is done slowly but dynamically — i.e. during a long plasma discharge.
In the last decade a new domain has developed in plasma physics: plasma medicine. Despite the successes that have already been achieved in this exciting new field, the interaction of plasmas with “biological materials” is not yet fully understood. Further investigations in particular with respect to the properties of the applied plasmas sources are therefore essential in order to decode this complex interaction process. Currently, a great variety of different discharge types are used in plasma medical investigation which are generally are operated in noble gases like helium and argon or with dry air. In the present work, the main focuses is on the diagnostics of reactive oxygen and nitrogen species (RONS) resulting from the plasma chemistry of an argon radio-frequency (RF) atmospheric pressure plasma jet (APPJ) and its interaction with the ambient atmosphere. To conduct this study, a commercially available plasma device, so-called kinpen is used due to its technical development maturity and its accessibility on the market. As a method of choice, diagnostic techniques are based on optical spectroscopy known to be a reliable tool to investigate plasmas. Consequently, three complementary optical laser diagnostics, namely quantum cascade laser absorption spectroscopy (QCLAS), laser induced fluorescence (LIF) and planar single shot LIF (PLIF), have been successfully applied to the plasma jet itself or its effluent. All of these diagnostics offer a high species selectivity and an excellent spatial and temporal resolution. They are used in this work for i) the characterization of the plasma chemical dynamics with respect to the generation of biological active RONS – in particular for the case of N2 and O2 admixtures. ii) the measurement of the NO density profile in the plasma effluent iii) the investigation of the flow characteristics of the neutral gas component (laminar vs. turbulent) and its influence on the plasma chemistry. Numerical analysis have been carried out in collaboration with PLASMANT (University of Antwerp) via kinetic simulations of the entire plasma chemistry. Expectingly, atomic oxygen (O) and nitric oxide (NO) turn out to be precursors of ozone (O3) and nitric dioxide (NO2). However, it was intriguing to unveil that atomic oxygen and nitrogen metastable (N2(A)) play together a key part --as intermediate species-- in the generation of more stable RONS, e.g. NO. The absolute density of NO space resolved was measured by LIF and absolutely calibrated molecular beam mass spectrometer. LIF was used to determine relative density of OH radical in the plasma plume. 2D-LIF was used to investigate the gas flow pattern with OH as a flow tracer. The results are discussed in details and show different operating mode of the jet, e.g. laminar or turbulent and that the plasma influences these regimes. The first detection and relative measurement by LIF of nitrogen metastable (N2(A)) produced by an argon APPJ is also shortly reported in this work. The outcome of this thesis will bring new insights in the field of argon APPJs chemistry and its interaction with the ambient atmosphere which can be valuable to support plasma modelling and to consider for the applications in plasma medicine.
HPMC (Hydroxypropylmethylcellulose) based hydrophilic gel matrix tablets are one of the most commonly used monolithic extended release dosage forms used in the pharmaceutical industry. Drug release from the hydrated HPMC matrix is generally controlled by either diffusion or erosion, or a combination of both. Several studies have shown that for HPMC-based matrices with a high amount of poorly water-soluble additives, erosion is the predominant release mechanism. Erosion rates of these formulations vary significantly with changes in the matrix composition. Depending on the erosion rate, the drug delivery might occur over a shorter or longer time span and thus to different sites of action that are proximal or distal gastrointestinal tract (GIT). Erosion rates of HPMC-based matrices can be modulated by changing the amount and molecular weight of the HPMC. In the present study, four different HPMC-based hydrophilic matrix formulations developed by AstraZeneca R&D, Sweden, were investigated for in vitro as well as in vivo erosion behavior. Formulations F1, F2, and F3 consist of 40% HPMC, which is a mixture of two different HPMC viscosity grades (Methocel K100LV and Methocel K4M). Formulations F1, F2, and F3 contained 23%, 10%, and 0% of Methocel K4M, respectively, while formulation F4 was composed of 20% Methocel K100LV. Calcium hydrogen phosphate dihydrate (a poorly water-soluble compound) was used as the filling excipient. The in vitro HPMC release from the matrices was investigated using a USP dissolution apparatus II equipped with a stationary basket in a phosphate buffer (PB) pH 6.8 and simulated gastric fluid without pepsin (SGFsp) pH 1.2 at various rotation speeds. The HPMC concentration in the dissolution samples were analyzed using size exclusion chromatography coupled with multiangle light scattering and refractive index detectors (SEC-MALS/RI). In order to establish a correlation function between the magnetic moment and HPMC release, the formulations were tested in a magnetic moment dissolution tester (MMDT), a modified in vitro dissolution apparatus equipped with a magnetometer. The in vivo gastrointestinal imaging and erosion behavior of the tablets were investigated by magnetic marker monitoring (MMM) using a superconducting quantum interference devices (SQUIDs) sensor system in five healthy male volunteers at Physikalisch-Technische Bundesanstalt (PTB), Berlin. All formulations were administered after an overnight fast of at least 10 hours. However, formulations 3 and 4 were also administered 30 minutes after a standard FDA breakfast. The in vivo HPMC release was calculated using the correlation function from the recorded in vivo magnetic moment data. A linear correlation function was not observed, since the decrease of the magnetic signal was driven by both erosion and diffusion. The in vitro and in vivo erosion-time profiles show that erosion was strongly dependent on the composition of the formulation. The formulations containing a larger proportion of high molecular weight HPMC, or a higher content of HPMC, exhibited relatively slower erosion rates and vice versa. However, unlike in vitro erosion rates, the in vivo erosion rates for different formulations did not always significantly differ from each other. In vivo erosion rates of the investigated formulations were significantly higher under postprandial administration than under fasted state administration. No rapid disintegration of any of the formulations (that is, formulation failure that can potentially cause dose dumping) was observed. A good linear (point-to-point) correlation between the in vitro HPMC release at 50 rpm in PB pH 6.8 and the in vivo HPMC release was observed for all formulations in the individual volunteers for both administration conditions. The predictability of the in vivo HPMC release for all formulations in fasting as well as postprandial administrations was better with phosphate buffer pH 6.8 at 50 rpm in comparison to SGFsp pH 1.2 or higher stirring rate in phosphate buffer pH 6.8. In postprandial administrations, the gastric emptying time was significantly delayed compared to fasting administrations. For postprandial administrations, the localized erosion rate in the distal stomach was significantly higher than in the proximal stomach. The in vivo HPMC release of the investigated formulations under both intake conditions was not dependent on the motility of the tablet in the gastrointestinal tract. The in vivo HPMC release for all the investigated formulations when administered under fasting conditions was underestimated, while under postprandial conditions, the HPMC release was overestimated by the in vitro dissolution method in PB pH 6.8 at 50 rpm.
Modulation of emotional episodic memory in humans. Evidence from event-related potential studies.
(2015)
In the dissertation, own research on the modulation of emotional episodic long-term memory, especially on recognition memory performance and encoding- and retrieval-related event-related potentials (ERPs), is presented. Three ERP studies were conducted. The first study investigated spontaneous remembering of emotional events. In the second experiment, a crossover design for memory recognition studies was tested. The third study explored the noradrenergic influences on emotional memory. Next to discussing the results in the light existing findings and concepts (natural selective attention by Bradley & Lang and neuromodulation hypothesis by McGaugh), the obtained results are put in a broader context of emotional episodic long-term memory and the possible implications for clinical research are indicated.
Next Generation Sequencing (NGS)-technologies developed very fast in recent years and is used widely in current research areas. The aim of this study was to use NGS (i) for the identification of pathogens in outbreaks and (ii) for the identification of virulence-relevant sequencepolymorphisms when comparing whole genome sequences. Therefore, a previous developed workflow was used to identify a new virus of the family Bornaviridae. The generation of whole genome sequences elucidated the molecular epidemiological connection of infection of variegated squirrels (Sciurus variegatoides) and three human cases of fatal encephalitis. By generating the whole genome sequence of a Porcine Epidemic Diarrhea Virus (PEDV) in Germany it was possible to find difference compared to circulating high virulent strains in the USA. This led to potential virulence marker to distinguish strain in the USA and Germany. Connections between sequence variation and virulence were further investigated for the bovine viral diarrhea virus 2c (BVDV-2c), cowpox viruses (CPXV) and classical swine fever virus (CSFV). Here, for a highly virulent BVDV-2c strain a mixture of different genome structure variants could be found. The majority of these genomes harbors a duplication within the p7/NS2 coding region and might cause a high virulence. For CPXV virus isolated of different hosts were analyzed and a correlation between genome sequence and the A-type inclusion body phenotype could be found. Furthermore, several deletion/insertion events were detected which might influence the virulence of these strains. Finally, the virus population of CSFV strains in pigs was characterized. However, the population of the inoculum as well as of acute-lethal and chronically infected animals gave no indication that the virus itself causes the different types of disease outcome. In conclusion, this thesis shows the great potential of NGS for virus identification and characterization. Furthermore, it makes the identification of potential virulence marker possible which subsequently can be analyzed by reverse genetics.