Film Worlds:Zur Neukonzeption von filmischer Repräsentation, Temporalität und Reflexivität

109120

Validity of dietary data in young populations and implications of measurement errors

Abstract: A high number of relationships between dietary intakes and health outcomes has been suggested and investigated during the last decades (Ezzati & Riboli, 2012; Vargas & Thompson, 2012; Alinia et al., 2009; Howarth et al., 2005; Kushi, 1992). Diet is of special interest as it is a modifiable risk factor. However, to date little is known with certainty on the complex relations between diet and specific diseases as respective research requires accurate, quantitative information on dietary intakes. Hence, the description of dietary intakes is one of the main tasks of dietary monitoring surveys and epidemiological studies. Assessment of dietary intakes is challenging due to changes in diet during life as well as due to the day-to-day variation that characterizes dietary intakes in general. In addition, the estimation of long-term consumption frequencies and amounts is difficult for most people as it relies on long-term memory and the capability of correct averaging. Strictly spoken, dietary intakes cannot be measured without error and will presumably never be. Researchers investigating associations between diet and specific diseases or distributions of dietary intakes need to account for various measurement errors to avoid drawing erroneous conclusions. The nature and magnitude of measurement errors in dietary data depend on the study population under investigation as well as on the assessment instrument. To date, there are only few recommendations available for measuring dietary intakes among children. As young children do not have the cognitive ability to report their dietary intakes themselves, usually parents are asked to proxy-report their child's intakes. This means that additional problems emerge from meals that are not under parents' control like e.g. school meals leading to unintentional misreporting. Little is known about the validity of proxy-reported dietary data, potential determinants of misreporting and additional sources of measurement errors in young populations yet. Therefore, this thesis aimed to investigate the extent and effects of measurement errors when assessing and modeling dietary data in young children. Special emphasis was put on differential measurement errors resulting from misreporting where different methods to counteract attenuation or distortion of risk estimates were encountered and evaluated. In summary, differences in the determinants of misreporting were found for proxy-reported dietary data compared to those previously reported for self-reported data where the problem of misreporting seemed to be even more severe in case of proxy-reports. Misreporting strongly affected effect estimates of associations between diet and overweight/obesity. Results strongly depended on the chosen statistical model where even reversed signs were observed when accounting or not-accounting for reporting errors. These findings suggest that studies on diet-disease associations based on proxy-reported dietary data are problematic as there is still no formal way to handle differential measurement errors caused by misreporting. In the absence of objective validation data, the true effects remain unknown. A large number of associations reported so far in epidemiological studies may be biased due to the application of models relying on the assumption of non-differential measurement errors only

Advanced CPTu and laboratory investigation of geotechnically critical on-shore and near-shore soft sediments in Germany and New Zealand

The integrated Coastal Zone and Shelf Sea Research (INTERCOAST) organization, a cooperative German and New Zealand multidisciplinary research program, concentrates on scientific issues in social and natural science disciplines in the both countries. INTERCOAST 4 (IC4) Ph.D. program tackled geotechnically problematic soft soils such as peat, clay and clayey silts which have posed considerable challenges to geotechnical engineers in all parts of the world during design and construction process. In Germany, peat is one of the prevailing groups of soil which is present in both off-shore and on-shore areas and exhibit properties such as high compressibility and low shear strength; these properties may cause complications such as differential settlement or failure in structures built on such soils. Removal or stabilization are the most important methods used to overcome geotechnical problems related to peat soilsâ engineering characteristics. In New Zealand, many off-shore and on-shore areas of the North Island are covered by volcanic ash, and weathering of this material has resulted in formation of clay minerals. Dredging of volcanic ash layers often causes major turbidity in the water column and poses risks to wildlife and humans. Due to very low effective shear strength and high sensitivity of volcanic ash, these sediments are not considered to be appropriate for off-shore construction and installation purposes. On-shore weathered volcanic ash having low permeability acts as a barrier to fluid flow, for example infiltration of rainfall, and prevents pore pressure from dissipating. This special characteristic may lead to failure of slopes with volcanic ash materials because increases in pore pressure lowers the effective normal (vertical) stress, and therefore shear strength. The aim of this dissertation is to utilize in-situ and laboratory measurements in order to (i) present soil mechanical intervention for stabilization of peat using cost-effective and environmentally-friendly stabilization method and focus on a comparison between mechanical characteristics of undisturbed and stabilized peat, (ii) investigate geological setting, lithology and depositional history of off-shore sub-seafloor volcanic soils and determine geotechnical properties of near-surface sediments and (iii) look into the role of volcanic soils in occurrence of on-shore landslides

Role of Mixed Layer Depth and Subduction Processes for the Southern Ocean Carbon and Nutrient Cycles

Changes in wind forcing in the Southern Ocean exert a large impact on the dynamics of the surface mixed layer and subduction processes. Over the last two decades, the index of the Southern Annular Mode (SAM) has experienced a trend towards its positive phase, which is characterized by stronger westerly winds. The positive trend in the SAM index results from the complex interaction between the steady increase of atmospheric CO2 concentration due to anthropogenic emissions and the stratospheric ozone depletion. Co-occurring with the wind signal is the global warming effect driven by the increase in atmospheric CO2. Increased wind forcing alone would lead to a deepening of the mixed layer and enhance the supply of carbon and nutrients to the euphotic zone. In contrast, the surface ocean warming alone would lead to more surface stratification, and therefore to a shoaling of the mixed layer. The main objective of this PhD thesis is to answer the question: How did the combined changes in atmospheric forcing affect the surface mixed layer and the carbon and nutrient subduction rates on the timescale of interannual to decadal variability? In the first part of my thesis, I assessed the impact of the recent changes in atmospheric temperature and zonal wind speed on the summer mixed-layer depth (MLD) in the SO (south of 30AAA S) from observations and a set of model sensitivity experiments over the period of 2002-2011. The study showed that summer MLD changes in response to recent atmospheric forcing were zonally asymmetric. Summer MLD increased in the Antarctic Zone of the Atlantic and the Indian Ocean sectors. Overall, the effect of recent changes in wind forcing dominated over temperature-induced changes in summer MLD. In the second part of this thesis, I examined the decadal variability in nutrient and dissolved inorganic carbon (DIC) concentrations in the Antarctic Intermediate Water of the Atlantic sector of the Southern Ocean between 1990 and 2014 using cruise data sampled along the Prime Meridian. The results showed a positive trend in DIC and nitrate concentrations along with a negative trend in temperature and salinity. These observations support a scenario of an increase in the upper-ocean overturning circulation probably linked to the positive trend in the SAM index. The third part of this thesis focused on the SAM impact on the inter-annual variability of carbon and nutrient subduction rates across the base of the winter mixed layer between 1958 and 2016 using a coupled physical-biogeochemical general circulation model. The study showed that the variations in SAM led to large-scale anomalies in carbon and nutrient subduction and obduction rates that are zonally symmetric. More obduction occured south of the Antarctic Polar Front (APF) and more subduction occurred where the MLD gradient is strongest in response to the positive trend in the SAM index. Also, I found that the annual mean carbon and nutrient subduction rates varied by around 10% around the long-term mean on interannual to decadal time scales with a stronger positive trend since 1990 leading to an approximately 20% increase in DIC and nitrate subduction rates between 1990 and 2016. My findings (parts I, II and III) suggest that the positive trend of the SAM index (wind intensification) has profoundly affected the surface mixed layer, and increased upwelling of carbon and nutrient-rich deep water. The increased upwelling is driven by the Ekman divergence and is balanced by the stronger northward Ekman transport across the APF. North of the APF these water masses subduct as mode and intermediate waters. While today changes in the wind forcing play a larger role than atmospheric temperature changes, this might reverse in the future

Experimental evolution of Paracoccus denitrificans in anoxic chemostats

Natural microbial communities play a central role in ecosystems and global cycles of elements. The microbial community compositions, functions as well as interactions between species and the environment have been studied with increasing effort. However, it is challenging to understand which parameters determine for the success of individual species to survive in a specific habitat. The often highly diverse microbial communities are continuously subjected to environmental stress such as biotic and abiotic fluctuations that cannot be completely tracked. To investigate the influence of different parameters on the ability of microorganisms to adapt to the environment, simple microbial communities, often single species are cultivated in the laboratory under strictly controlled conditions with reduced complexity. Such long-term experiments provide insight into the association between genetic and phenotypic alterations that evolve over hundreds or even thousands of generations. The availability of nutrients often affects microbial growth. This thesis describes the experimental evolution of Paracoccus denitrificans Pd1222, a model denitrifying soil bacterium, to study the adaptation on acetate or nitrate limitation. Initially, nutrient limitation for the anaerobic growth of P. denitrificans was addressed with focus on trace elements (Chapter 2). New trace element solutions were designed based on previous reports and tested to exclude growth limitation or inhibition by these nutrients during long-term cultivation. Improved generation times of 4.4 hours were achieved with a chelated trace element solution and lower concentrations than frequently used media. Chapter 3 describes the adaptive responses of P. denitrificans to acetate and nitrate limitation during experimental evolution in chemostats. In the course of at least 800 generations of P. denitrificans under denitrifying conditions the metabolic conversions of substrates were monitored. For deeper insights into different adaptive mechanisms of P. denitrificans under both conditions we investigated the transcriptomes and genome variations. Throughout the experiment the different treatments led to significantly different substrate conversion rates and transcriptomic profiles. Specifically, in nitrate limited cultures genes of the citric acid cycle and the nitrogen metabolism showed higher transcriptional activities than in acetate limited cultures. In the latter the transcription of genes encoding regulators and transporters was more pronounced. Additionally, more changes in transcriptional activities and in metabolism were observed over time than under nitrate limitation. Most notably, denitrification became more efficient resulting in the depletion of nitrite that accumulated in the culture during the first 500 generations. Although numerous mutations were detected in DNA obtained from this culture, they could not be related to the observed phenotypic changes. In all cultures the types and numbers of genetic variations did not considerably differ. The study indicated that P. denitrificans had a stronger potential to adapt to acetate limitation than to nitrate limitation and underlines the capacity of this bacterium to improve denitrification even in absence of environmental fluctuations. The possible explanation that phenotypic changes may have been independent of genetic variations is discussed in Chapter 4. The relevance of the insights gained in this study for natural, in particular denitrifying communities is presented and future studies towards the understanding of natural microbial community functions are suggested

Dysregulation of the high mobility group AT-hook 2 (HMGA2) gene in human tumours

The high mobility group AT-hook 2 (HMGA2) gene is expressed during embryogenesis but silenced in adult tissues. It often is reactivated for varying reasons depending on tissue type in a variety of malignant and benign tumours contributing to tumour growth. In this thesis, causes for dysregulation in various human tissues were investigated. A potential HMGA2 increase upon growth factor incubation was investigated in the epithelial prostate cancer cell line PC-3 as well as in human umbilical vein endothelial cells. The underlying mechanism for HMGA2 silencing in the prostate cancer cell line LNCaP was examined as well as effects of HMGA2 on cell viability. Furthermore, a small subset of uterine leiomyomas was tested by high-resolution array-based comparative genomic hybridisation to detect microdeletions potentially related to the breakpoints accompanying the typical translocation responsible for HMGA2 reactivation. An HMGA2 increase in PC-3 cells upon growth factor and FBS incubation was not detected, whereat it was shown in HUVECs upon growth factor incubation. HMGA2 in non-expressing LNCaP cells was found to be detectable after incubation with a demethylating agent, but not after silencing of DICER1, pointing rather to the involvement of DNA methylation than of miRNAs in HMGA2 silencing. Furthermore, HMGA2 incubation was associated with reduced cell viability. In two of the three uterine leiomyomas, small deletions that may be associated with the translocation were identified upstream of the HMGA2 locus. The results obtained herein underline the versatility of HMGA2 in regulation and function supporting the need for individual consideration for the development of potential therapeutic applications

Integral Equation Methods for Ocean Acoustics with Depth-Dependent Background Sound Speed

Time-harmonic acoustic wave propagation in an ocean with depth-dependent background sound speed can be described by the Helmholtz equation in an infinite, two- or three-dimensional waveguide of finite height. A crucial subproblem for the anayltic and numeric treatment of associated wave propagation problems is a Liouville eigenvalue problem that involves the depth-dependent contrast. For different types of background sound speed profiles, we discuss discretization schemes for the Liouville eigenvalue problem arising in the vertical variable. Due to variational theory in Sobolev spaces, we then show well-posedness of weak solutions to the corresponding scattering problem from a bounded inhomogeneity inside such an ocean: We introduce an exterior Dirichlet-to-Neumann operator for depth-dependent sound speed and prove boundedness, coercivity, and holomorphic dependence of this operator in suitable function spaces adapted to our weak solution theory. Analytic Fredholm theory then implies existence and uniqueness of solution for the scattering problem for all but a countable sequence of frequencies. Introducing the Green's function of the waveguide, we prove equivalence of the source problem for the Helmholtz equation with depth-dependent sound speed profile, Neumann boundary condition on the bottom and Dirichlet boundary condition on the top surface, to the Lippmann-Schwinger integral equation in dimensions two and three. Next, we periodize the Lippmann-Schwinger integral equation in dimensions two and three. The periodized version of the Lippmann-Schwinger integral equation and an interpolation projection onto a space spanned by finitely many eigenfunctions in the vertical variable and trigonometric polynomials in the horizontal variables, two different collocation schemes are derived. A result of Sloan [J.Approx Theory, 39:97-117,1983] on non-polynomial interpolation yields both converge and algebraic convergence rates depending on the smoothness of the inhomogeneity and the source of both schemes. Using one collocation scheme we present numerical results in dimension two. We further present an optimization technique of the vertical transform process, when the height of the obstacle is small compared to the finite height of the ocean, which makes computation in dimension three possible. If several scatters are present in the waveguide, this discretization technique leads to one computational domain containing all scatterers. For a three dimensional waveguide, we reformulate the Lippmann-Schwinger integral equation as a coupled system in an union of several boxes, each containing one part of the scatter

Laser Ranging Interferometry for Future Gravity Missions : Instrument Design, Link Acquisition and Data Calibration

The presented study aims to improve the design solution adopted for the Laser Ranging Instrument of the GRACE Follow-On mission in terms of instrument layout, algorithms for the laser link acquisition and techniques for mitigating the range measurement noise. The first part of this work describes viable layout solutions of a heterodyne interferometer employed for intra-satellite range metrology and the major noise contributions which degrade the overall accuracy of the instrument. Together with the optical layout of the instrument, novel design concepts of the instrumenta s subsystems are also analyzed and tested. Precisely, a phasemeter designed to autonomously acquire and track a heterodyne signal with low signal-to-noise ratio in a frequency band that spans from 1MHz to 25MHz is presented. Particular attention is also dedicated to the mathematical modeling of the steering mirror dynamics and to the enhancement of its pointing performance by means of feedforward control. In the second part of this work, solutions for autonomously acquiring a laser signal buried in noise are analyzed and put in relation with the boundary constraints of the acquisition problem. The acquisition algorithms presented and the robustness of their design is verified mainly using numerical simulations. Experimental tests have also been performed for validating the simulation hypothesis and verifying their compliancy to a realistic mission scenario. The last part of this work describes a calibration algorithm which has been developed for minimizing, during data post-processing, the noise due to the tilt-to-piston coupling which represents one of the highest contributors to the overall measurement noise

Impact of mangroves and an agriculture-dominated hinterland on the carbon and nutrient biogeochemistry in the Segara Anakan Lagoon, Java, Indonesia.

The Segara Anakan Lagoon on Java, Indonesia, is mainly threatened by sedimentation and mangrove tree logging. The lagoon size decreased by >50% since the 1970´s due to high sedimentation loads from the Citanduy River and therefore the agriculture-dominated hinterland. The nutrient concentrations were significantly higher during the rainy season and mainly derived from the Citanduy River. Also mangrove leaves leached high amounts of nutrients into the system. However, the nutrient concentrations were low to moderate on a global scale. Nutrient sinks in the SAL were outwelling, assimilation by mangrove and shrub species, consumption by microbes and phytoplankton. A further shift from true mangrove tree species to shrub species due to logging can alter the carbon and nutrient inventory in the lagoon. Shrub species leached significantly more nutrients than true mangrove tree species which might accelerate the nutrient turnover rates in the lagoon and therefore affect the whole food web

Characterization of chitosan using triple detection size-exclusion chromatography and 13C-NMR spectroscopy

The biopolymer chitosan has shown a great potential for a tremendous number of applications despite the fact that typical chitosan preparations are always mixtures of different chemical entities, natural impurities and process-induced impurities. Chitosan preparations described in the literature or offered on the market are analytically highly undefined which prevents a detailed structure-activity-relationship (SAR) analysis. The aim of this thesis is to accomplish the prerequisites necessary for a sophisticated study of the polymers chitin/chitosan. Within this thesis a SAR guided multi-dimensional analysis is proposed including a physicochemical description (molecular weight (MW), polydispersity (MW/MN), fraction of acetylation (FA), and determination of the purity content combined to biological effects on two different bacteria (Escherichia coli, Vibrio fischeri ). Results are obtained by methods such as triple detection size-exclusion chromatography (refractive index, light scattering (90° and 7°), viscometry), inhibition assays and transmission electron microscopy (TEM). Furthermore, an improved method to determine the pattern of acetylation PA from heterogeneously as well as homogeneously prepared chitosan is shown. No link between the different production processes and the formation of a specific pattern of acetylation was found. For all investigated sample a random-dominated pattern was found. The obtained PA values include also calculated inter-day and inter-analyst variations of the carbon nuclear magnetic resonance technique (13C-NMR). The conformational analysis of chitosan, again achieved with the triple detection SEC, revealed an interesting behavior. Using different theoretical models (Benoit-Doty, Odijk-Houwart, Bohdanecky) different Kuhn segment lengths (lK) were found for the two different samples. While the first approached linear chain behavior, the second showed similarity to dextran, a branched polysaccharide. Dissolution studies on chitin and chitosan showed positive results in 18 cases (chitosan) and 6 cases (chitin), respectively, by testing 58 different ionic liquid samples in total. In case of chitin, ionic liquids may be promising candidates for future dissolution studies of this biopolymer. However, chitin behaves completely different in dissolution assays than its relative cellulose which may based on three different dissolution mechanism each for chitosan, chitin and cellulose, respectively