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Macroscopic physics in noncommutative models
No full textIt is expected that quantum gravitational effects at very small length scales lead to drastic modifications to the familiar notation of smooth spacetime. It is not clear, however, what effects this will have on macroscopic physics. Models based on noncommutative geometry can be used to study these effects. A particular striking result is the interplay of physics at very different length scales called UV/IR mixing. The topics of the thesis is to investigate modifications of macroscopic physics by noncommutative effects, in particular UV/IR mixing in noncommutative gauge theories defined via Seiberg-Witten maps, modifications to the long range Coulomb potential by UV/IR mixing and corrections to classcial solutions in a noncommutative version of general relativity. UV/IR mixing is an effect directly reflecting the nonlocal nature of spacetime in noncommutative quantum field theory. In noncommutative gauge theory defined via Seiberg-Witten map, which is nowadays widely used to develop noncommutative particle phenomenology models, the study of similar effects was for a long time impossible due to the expansion method used to construct these models. Here the existence of quadratically divergent UV/IR mixing terms in a noncommutative quantum electrodynamics model defined via Seiberg-Witten map is shown by explicit computation using a non-perturbative approach. The second topic of the thesis is to demonstrate the influence of UV/IR mixing on macroscopic physics in the case of a renormalizable massless noncommutative scalar field theory: The power-law nonrelativistic static potential of the commutative theory is modified to an exponentially decaying one. Thus imposing noncommutativity not only modifies physics at small scales but also macroscopic physics when quantum corrections are taken into account. The final topic discussed in the thesis is solutions to noncommutative gravity, in particular the flat Robertson-Walker metric and linear perturbations around it
Surface energetics of adsorbent-biomass interactions during expanded bed chromatography : implications for process performance
No full textCommon limitations encountered during the direct recovery of bioproducts from an unclarified feedstock are related to the presence of biomass in such processing systems. Biomass related effects can be described as biomass-to-support interaction and cell-to-cell aggregation. In the current thesis work biomass related effects were studied in an important integrated primary unit operation mode viz Expanded bed adsorption (EBA), which was proved to suffer from the detrimental effects by the presence of biomass.
Current work involves the investigation and understanding of the biomass interaction and aggregation onto various EBA process surfaces at local or molecular level. In doing so Streamline materialsTM of various chemistries were taken as process surface and intact yeast cell, yeast homogenates, and disrupted bacterial paste were employed as model colloids to understand their deposition and subsequent aggregation.
Deposition and aggregation was studied with surface energetics according to XDLVO theory. These predictions based on the application of XDLVO theory were confirmed by independent experimental methods, like biomass deposition experiments and laser diffraction spectroscopy.
Biomass components and beaded adsorbents were characterized by contact angle determinations with three diagnostic liquids and zeta potential measurements. Subsequently, free energy of interaction vs. distance profiles between interacting surfaces was calculated in aqueous media provided by its operating mobile phase. The effect of various chromatographic conditions based on the mode of operation was explored in relation to yeast interaction and aggregation.
Calculations indicated that the interaction and aggregation is mainly due to the existence of a reversible secondary energy minimum. The extent and depth of pocket varied based on the operating process conditions for different interacting pairs.
Understanding biomass-related effects will overcome or at least mitigate the process limitations. Exploring the effect of various types of additives for their ability to inhibit either biomass deposition, cell aggregation, or a combination of both effects, a non ionic polymer PVP 360 was found to alleviate biomass deposition on weak anion exchangers.
The predictions made by the XDLVO theory were well correlated with the physicochemical parameter α, in relation to ion exchangers where only interaction is happening. On the other hand a discrete modifications of XDLVO energies was observed with the lump parameter α for hydrophobic and pseudo affinity process surfaces where interaction and aggregation is taking place. Establishing a correlation defined a safe operational windows for EBA process when U ≤ |50| kT and α ≤ 0.15.
Fundamental knowledge which could predict feedstock behaviour during primary unit operations of downstream processing would alleviate the current bottleneck during processing of bioproducts
Studying complex metal-molecule interface with low temperature scanning tunneling microscope : from electronic structure to charge transport
No full textA fundamental understanding of complex metal-organic interfaces is widely considered to be a milestone on the way to successful realization of molecular-based electronic devices. In the context of interface studies, local tunneling methods, based on the ability of the scanning tunneling microscope (STM) to resolve surface structure as well as surface electronic and vibrational properties with atomic scale resolution, are considered to be very helpful. However, the potential of such methods as applied to cases of complex organic adsorption have not yet been exhaustively tested. In this thesis, a well-studied model case of complex organic adsorption was selected in order to apply a number of local STM methods aiming at a detailed characterization of the interface structural, electronic, vibrational and transport properties on the scale of a single metal-molecule contact. The main objective is twofold: On the one hand a fundamental analysis of the complex metal-organic interfaces is performed, especially the relation between their electronic structure and charge transport properties. On the other hand, we aim a detailed test of various STM-based techniques applied to the realistic problem of complex adsorption and transport measurements. Given that the chosen interface system is the best studied case of complex organic adsorption showing the highest degree of order and at the same time demonstrating very rich phenomenology one may expect that the results obtained on such a system will clearly demonstrate the potential and limitations of the experimental techniques applied
Trace element analyses in geological materials using low resolution inductively coupled plasma mass spectrometry (ICPMS)
No full textThe benefits of inductively coupled plasma mass spectrometry (ICPMS) for geochemical studies include excellent instrument sensitivity for determining a large number of elements (<40) with high precision, and the ability to analyze numerous samples relatively quickly (minutes per sample). This study describes the ICPMS methods employed within the Jacobs University Bremen (JUB) Geochemistry Lab for determining the concentrations of 32 trace metals in different geological materials. The quality of the analytical data is discussed in the context of repeated analyses of certified reference materials (CRMs) commonly used in geochemical research.
The average analytical precision of the concentration measurements for all rock types discussed, reported as percent relative standard deviation, is better than ±3% for eleven elements (Ti, Co, Sr, Y, Zr, Ba, La, Ce, Pr, Nd, Pb), between ±3-5% for sixteen elements (Sc, Ni, Rb, Nb, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Th, U), and between ±5-8% for only five elements (Mo, Cs, Hf, Ta, W). The analytical accuracy of the data, determined from comparisons between measured elemental concentrations in various CRMs with published reference values, is considered excellent for 31 of 32 elements, with the exception being accurate measurements of Ti at high concentrations in the analytical solution (>10 mg/kg). However, some elements suffer from interferences due to the major element content of particular rock types, and are unlikely to be quantifiable when present at low concentrations. This includes Co in carbonate rocks, and Nb in Fe-rich rock types. The concentrations of many trace metals in some CRMs are poorly constrained, and early published datasets appear to frequently overestimate the abundances of these elements
Empirical research on aging workforce management : secondary data, grounded theory, and case study findings with particular consideration of the automobile industry
No full textThe demographic change in many western industrialized societies' populations points to one of the most negative future scenarios in business management: The increasing average age mirrored in the workforce and labor pool. In an industry that relies on physical work performance as an important input factor, such as automobile mass production, this will lead to a workforce that is limited in terms of employability and is thus more expensive, since organizations have to cover absenteeism and/or the loss of value creation on production lines. Empirical evidence demonstrates that increased costs, a lack of flexibility, as well as increased global demands in terms of productivity have resulted in a potential threat to sustainable competitiveness. The successful management of an aging workforce is an evolving field of research that has to date provided little on which advanced studies could be built. This dissertation therefore aims to approach the topic of aging workforce management in the automobile industry in an exploratory manner, clarifying fundamental concepts that have been neglected by managerial sciences, but that are, in fact, elementary and crucial for the development of sound research in future. To achieve this aim, this dissertation presents the cumulated results of three articles, that 1. identify the status quo of the aging workforce management from a management science perspective in theory and practice, 2. provide answers regarding how the aging workforce challenge as a topic and the elements that constitute its management can be defined, and 3. evaluate the effectiveness of applied aging workforce measures in practice
Laser-induced electron transport through molecular junctions and DNA
No full textThe goal of this thesis is to investigate the electron transport through molecular junctions or wires which have recently attracted much attention experimentally as well as theoretically. Under the influence of a bias voltage and the coupling to the leads which act as electron source and drain, a current through the molecular junction is established. When an external time-dependent field, such as a laser field or an additional AC voltage is applied to the molecular junction, new features can be observed. One phenomenon is the well-known photon-assisted tunneling (PAT) which means that an external field periodic in time with frequency can induce inelastic tunneling events when the electrons exchange energy quanta with the external field. Another important effect is the famous phenomenon of coherent destruction of tunneling (CDT) which exhibits the unusual effect of quenching the tunneling dynamics at specific values of the field amplitude. In the present thesis the theoretical foundation for these investigations is a density matrix formalism where the full system is partitioned into a relevant part, i.e. the molecular junctions and fermionic reservoirs mimicking the leads. By using a perturbative approach in the system-reservoir coupling strength, it is possible to establish a quantum master equation (QMEs) for the population dynamics of the wire states and an equation for the current through the wire. By combining the theory of optimal control and assuming a predefined target current, a laser field can be obtained which does generate a predefined current pattern. The same technique can be applied to minimize the shot noise. Besides of using QMEs to study electron transport through molecular junctions with the affection of a coupling to leads, it is also possible to apply QMEs to investigate the electron transfer through DNA which is coupled to a phonon-bath
Coordinated regulation of gene expression by E.coli chromatin proteins FIS and H-NS
No full textBacteria posses impressive ability to adapt to their environment. Adaptation is accomplished mainly by adjustment of the gene expression pattern. Studies on transcript profiling in E.coli demonstrated the existence of direct correlations between the global gene expression patterns and different phases. Previous work indicated that in E.coli the transcription is controlled by a global regulatory network whose main components are - DNA topoisomerases, chromatin proteins and the RNA polymerase. Aim of this project was to understand the structural mechanism of interaction of the components (DNA supercoiling and chromatin proteins) and the underlying functional coordination of gene expression in E.coli. To understand the molecular mechanism of the interplay, the problem was approached at two levels of complexity (1) global - using a novel DNA microarray-based approach combining mutations in the genes of chromatin proteins with directional changes of DNA superhelicity and (2) local - at the level of individual gene promoter, using tyrT promoter system. The study has led us to propose that the global transcription is spatiotemporally coordinated by the differential distribution of two types of information, 'analog' and 'digital'. The digital or discontinuous property of information is manifest in the pattern of expressed genes depending on the distribution of the analog component - DNA supercoiling - in different parts of the genome. The analog component is continuously converted in the pattern of expressed genes and vice versa, thereby modulating the physiology to a dynamic equilibrium. On the example of tyrT promoter we demonstrate how the sequence organization of the promoter determines the supercoiling sensitivity of the promoters. We also show that the transcription from a strong promoter, like tyrT, is a consequence of the local effect of binding of chromatin protein FIS at the promoter and the general effect of FIS on the average superhelical density of the DNA
Identification of time-frequency localized operators
No full textWe consider identification of operator families defined via a time-frequency series expansion of the operator spreading function. The identification problem is transformed into an infinite-dimensional linear algebra problem. Our aim is to establish a connection between the identifiability of the operator family and a density measure of the time-frequency index set. In this way, the identification problem can be compared to the classical density condition for existence of Gabor frames. The conclusion is that the relationship between identifiability of such operator families and the critical density is highly intricate because of the presence of additional conditions. Criteria for identifiability are developed for families of time-frequency localized operators defined via time-frequency series expansions of the spreading function based on the Gaussian function
Particle-mesh and meshless methods for a class of barotropic fluids
No full textRecently, the Hamiltonian Particle-Mesh (HPM) method was proposed by J.Frank, G.Gottwald and S.Reich. It incorporates the procedure of artificial smoothing over a regular grid into the classical Smoothed Particle Hydrodynamics (SPH) formalism to improve the long-time stability of the method. HPM was applied to numerical solution of Shallow Water Equations (SWE), which are extensively used to simulate geophysical processes. So far, little research has been done to analyze and optimize HPM. The primary focus of our work is on the convergence of HPM method to solutions of a class of barotropic fluid equations. The convergence is investigated as smoothing scales vanish and as the number of particles grows unboundedly. The aim is to find an explicit relationship between these parameters to provide the best rate of convergence. For that purpose we adapt the convergence result for SPH obtained by K. Oelschläger. We consider HPM applied to the fluid model including SWE as a partial case and generalize the result to a self-gravitating fluid. Two new high-order meshfree methods for two-dimensional rotating shallow flows are proposed. They combine the conservation of Ertel potential vorticity with adaptive quadrature weights or moving least square approach for interpolation of scattered data. Generalizations for three-dimensional flows are discussed
The packaging of peptide-receptive MHC class I molecules from the endoplasmic reticulum in COPII vesicles
No full textMHC class I molecules are proteins are central to the defence of the body against viruses. They pick up fragments of proteins (peptides) from the inside of a cell and present them at the cell surface so that the immune system (cytotoxic T lymphocytes) can detect and kill them. Most class I molecules that appear at the cell surface are loaded with specific peptides, however, some empty (peptide-receptive) class I molecules are able to escape the ER QC. This raises the question whether these peptide-receptive class molecules cycle between the ER and cis-Golgi or whether they are retained in the ER. To address this question, I used radiolabeled mammalian ER membranes to generate COPII vesicles in vitro. From these vesicles, I investigated the packaging of different forms of class I molecules using specific antibodies. I found that peptide-receptive class I molecules are packaged into COPII vesicles that are generated from wild type lymphocytes as well as from TAP deficient lymphocytes. This is interesting, since for the first time we are able to look at the empty class I molecules in a situation similar to that of the living cell. Using my established in vitro vesicle generation system (budding assay) is advantageous for looking at the packaging of proteins that escape the ER QC, and their characteristics. I used the same system to study the trafficking of the peptide loading complex (PLC) in the COPII vesicles to find out whether the PLC proteins (which are chaperones that help in class I peptide binding) are packaged into COPII vesicles. My results indicate that the TAP peptide transporter and calreticulin are present in the COPII vesicles, and that these molecules may be retrieved from the ERGIC in COPI transport vesicles. This finding indicates that the PLC cycles between the ER and post ER compartments and the cycling may play a role in the retrieval of empty class I molecules