Analysis of Fluctuations in the Early Universe Using Fokker-Planck Formalism

The thesis begins with a review of basic elements of general theory of relativity (GTR) which forms the basis for the theoretical interpretation of the observations in cosmology. The first chapter also discusses the standard model in cosmology, namely the Friedmann model, its predictions and problems. We have also made a brief discussion on fractals and inflation of the early universe in the first chapter. In the second chapter we discuss the formulation of a new approach to cosmology namely a stochastic approach. In this model, the dynam ics of the early universe is described by a set of non-deterministic, Langevin type equations and we derive the solutions using the Fokker—Planck formalism. Here we demonstrate how the problems with the standard model, can be eliminated by introducing the idea of stochastic fluctuations in the early universe. Many recent observations indicate that the present universe may be approximated by a many component fluid and we assume that only the total energy density is conserved. This, in turn, leads to energy transfer between different components of the cosmic fluid and fluctuations in such energy transfer can certainly induce fluctuations in the mean to factor in the equation of state p = wp, resulting in a fluctuating expansion rate for the universe. The third chapter discusses the stochastic evolution of the cosmological parameters in the early universe, using the new approach. The penultimate chapter is about the refinements to be made in the present model, by means of a new deterministic model The concluding chapter presents a discussion on other problems with the conventional cosmology, like fractal correlation of galactic distribution. The author attempts an explanation for this problem using the stochastic approach.

Zur Adsorption und Reaktion von Stickstoffmonoxid an Aktivkohle

Die Verwendung von Aktivkohlen und -koksen stellt eine Alternative zu herkömmlichen Prozessen zur Verminderung der NOx-Emissionen in Rauchgasen dar. An diesen Materialien wird Stickstoffmonoxid adsorbiert und katalytisch zu N2 reduziert. Eine einheitliche Erklärung über die ablaufenden Vorgänge und die Reaktionsmechanismen gibt es noch nicht. Die Ergebnisse der bisher veröffentlichten wissenschaftlichen Arbeiten sind sehr unterschiedlich, wenn nicht sogar widersprüchlich. In dieser Arbeit wird, anhand der Messung von NO-Durchbruchskurven und thermischen Desorptionsspektren, die Adsorption und Reaktion von Stickstoffmonoxid an Aktivkohlen und -koksen in Anwesenheit von Sauerstoff und Wasserdampf untersucht. Zur Durchführung der experimentellen Untersuchungen wird eine Versuchsanlage, bestehend aus einer Vorrichtung zur Gasgemischaufbereitung, einem Festbettreaktor und einer Gasanalytik, konzipiert und aufgebaut. Die Untersuchungen erfolgen bei Temperaturen zwischen 100 und 150 °C. Die NO-, O2- und H2O-Konzentrationen werden anhand der Rauchgaszusammensetzung kohlegefeuerter Kraftwerke gewählt. Die experimentellen Untersuchungen konzentrieren sich auf die Verwendung einer Aktivkohle aus Ölpalmschalen, die in einem Drehrohrreaktor am Institut für Thermische Energietechnik der Universität Kassel hergestellt wurde. Die experimentellen Ergebnisse zeigen, dass während des Prozesses NO-Adsorption, -Reduktion und -Oxidation, NO2-Bildung, -Adsorption und -reduktive Desorption, H2O-Adsorption sowie O2-Vergasung gleichzeitig stattfinden. Bei niedrigen Temperaturen werden die NO2-Bildung und die Adsorption bevorzugt. Die NO-Reduktion läuft über adsorbiertes NO mit CO2- und CO-Bildung. Durch O2-Vergasung werden aktive freie Cf-Plätzen für die NO-Reaktion und -Adsorption gebildet. Wasserdampf wird an der Aktivkohle adsorbiert und belegt aktive Plätze für diese Prozesse. Aus den experimentellen Ergebnissen werden kinetische und Gleichgewichtsparameter der NO-Sorption bestimmt. Ein vereinfachtes mathematisches Modell des Festbettreaktors, das zur Berechnung der NO-Durchbruchskurven bei unterschiedlichen Temperaturen dient, wird aufgestellt.

Macrodisco y glaucoma en individuos estudiados con tomografía óptica coherente

Introducción: El glaucoma representa la tercera causa de ceguera a nivel mundial y un diagnóstico oportuno requiere evaluar la excavación del nervio óptico que está relacionada con el área del mismo. Existen reportes de áreas grandes (macrodiscos) que pueden ser protectoras, mientras otros las asocian a susceptibilidad para glaucoma. Objetivo: Establecer si existe asociación entre macrodisco y glaucoma en individuos estudiados con Tomografía Optica Coherente (OCT ) en la Fundación Oftalmológica Nacional. Métodos: Estudio transversal de asociación que incluyó 25 ojos con glaucoma primario de ángulo abierto y 74 ojos sanos. A cada individuo se realizó examen oftalmológico, campo visual computarizado y OCT de nervio óptico. Se compararon por grupos áreas de disco óptico y número de macrodiscos, definidos según Jonas como un área de la media más dos desviaciones estándar y según Adabache como área ≥3.03 mm2 quien evaluó población Mexicana. Resultados: El área promedio de disco óptico fue 2,78 y 2,80 mm2 glaucoma Vs. sanos. De acuerdo al criterio de Jonas, se observó un macrodisco en el grupo sanos y según criterio de Adabache se encontraron ocho y veinticinco macrodiscos glaucoma Vs. sanos. (OR=0,92 IC95%=0.35 – 2.43). Discusión: No hubo diferencia significativa (P=0.870) en el área de disco entre los dos grupos y el porcentaje de macrodiscos para los dos grupos fue similar, aunque el bajo número de éstos no permitió concluir en términos estadísticos sobre la presencia de macrodisco y glaucoma.

Calibrating flood inundation models: identifying and addressing uncertainty in satellite observed flood extents

Improvements in the resolution of satellite imagery have enabled extraction of water surface elevations at the margins of the flood. Comparison between modelled and observed water surface elevations provides a new means for calibrating and validating flood inundation models, however the uncertainty in this observed data has yet to be addressed. Here a flood inundation model is calibrated using a probabilistic treatment of the observed data. A LiDAR guided snake algorithm is used to determine an outline of a flood event in 2006 on the River Dee, North Wales, UK, using a 12.5m ERS-1 image. Points at approximately 100m intervals along this outline are selected, and the water surface elevation recorded as the LiDAR DEM elevation at each point. With a planar water surface from the gauged upstream to downstream water elevations as an approximation, the water surface elevations at points along this flooded extent are compared to their ‘expected’ value. The pattern of errors between the two show a roughly normal distribution, however when plotted against coordinates there is obvious spatial autocorrelation. The source of this spatial dependency is investigated by comparing errors to the slope gradient and aspect of the LiDAR DEM. A LISFLOOD-FP model of the flood event is set-up to investigate the effect of observed data uncertainty on the calibration of flood inundation models. Multiple simulations are run using different combinations of friction parameters, from which the optimum parameter set will be selected. For each simulation a T-test is used to quantify the fit between modelled and observed water surface elevations. The points chosen for use in this T-test are selected based on their error. The criteria for selection enables evaluation of the sensitivity of the choice of optimum parameter set to uncertainty in the observed data. This work explores the observed data in detail and highlights possible causes of error. The identification of significant error (RMSE = 0.8m) between approximate expected and actual observed elevations from the remotely sensed data emphasises the limitations of using this data in a deterministic manner within the calibration process. These limitations are addressed by developing a new probabilistic approach to using the observed data.

Alignment of a model amyloid peptide fragment in bulk and at a solid surface

The alignment of model amyloid peptide YYKLVFFC is investigated in bulk and at a solid surface using a range of spectroscopic methods employing polarized radiation. The peptide is based on a core sequence of the amyloid beta (A beta) peptide, KLVFF. The attached tyrosine and cysteine units are exploited to yield information on alignment and possible formation of disulfide or dityrosine links. Polarized Raman spectroscopy on aligned stalks provides information on tyrosine orientation, which complements data from linear dichroism (LD) on aqueous solutions subjected to shear in a Couette cell. LD provides a detailed picture of alignment of peptide strands and aromatic residues and was also used to probe the kinetics of self-assembly. This suggests initial association of phenylalanine residues, followed by subsequent registry of strands and orientation of tyrosine residues. X-ray diffraction (XRD) data from aligned stalks is used to extract orientational order parameters from the 0.48 nm reflection in the cross-beta pattern, from which an orientational distribution function is obtained. X-ray diffraction on solutions subject to capillary flow confirmed orientation in situ at the level of the cross-beta pattern. The information on fibril and tyrosine orientation from polarized Raman spectroscopy is compared with results from NEXAFS experiments on samples prepared as films on silicon. This indicates fibrils are aligned parallel to the surface, with phenyl ring normals perpendicular to the surface. Possible disulfide bridging leading to peptide dimer formation was excluded by Raman spectroscopy, whereas dityrosine formation was probed by fluorescence experiments and was found not to occur except under alkaline conditions. Congo red binding was found not to influence the cross-beta XRD pattern.

Canonical description of the perspective projections

A unique parameterization of the perspective projections in all whole-numbered dimensions is reported. The algorithm for generating a perspective transformation from parameters and for recovering parameters from a transformation is a modification of the Givens orthogonalization algorithm. The algorithm for recovering a perspective transformation from a perspective projection is a modification of Roberts' classical algorithm. Both algorithms have been implemented in Pop-11 with call-out to the NAG Fortran libraries. Preliminary monte-carlo tests show that the transformation algorithm is highly accurate, but that the projection algorithm cannot recover magnitude and shear parameters accurately. However, there is reason to believe that the projection algorithm might improve significantly with the use of many corresponding points, or with multiple perspective views of an object. Previous parameterizations of the perspective transformations in the computer graphics and computer vision literature are discussed.

Generation, description and storage of dendritic morphology data

It is generally assumed that the variability of neuronal morphology has an important effect on both the connectivity and the activity of the nervous system, but this effect has not been thoroughly investigated. Neuroanatomical archives represent a crucial tool to explore structure–function relationships in the brain. We are developing computational tools to describe, generate, store and render large sets of three–dimensional neuronal structures in a format that is compact, quantitative, accurate and readily accessible to the neuroscientist. Single–cell neuroanatomy can be characterized quantitatively at several levels. In computer–aided neuronal tracing files, a dendritic tree is described as a series of cylinders, each represented by diameter, spatial coordinates and the connectivity to other cylinders in the tree. This ‘Cartesian’ description constitutes a completely accurate mapping of dendritic morphology but it bears little intuitive information for the neuroscientist. In contrast, a classical neuroanatomical analysis characterizes neuronal dendrites on the basis of the statistical distributions of morphological parameters, e.g. maximum branching order or bifurcation asymmetry. This description is intuitively more accessible, but it only yields information on the collective anatomy of a group of dendrites, i.e. it is not complete enough to provide a precise ‘blueprint’ of the original data. We are adopting a third, intermediate level of description, which consists of the algorithmic generation of neuronal structures within a certain morphological class based on a set of ‘fundamental’, measured parameters. This description is as intuitive as a classical neuroanatomical analysis (parameters have an intuitive interpretation), and as complete as a Cartesian file (the algorithms generate and display complete neurons). The advantages of the algorithmic description of neuronal structure are immense. If an algorithm can measure the values of a handful of parameters from an experimental database and generate virtual neurons whose anatomy is statistically indistinguishable from that of their real counterparts, a great deal of data compression and amplification can be achieved. Data compression results from the quantitative and complete description of thousands of neurons with a handful of statistical distributions of parameters. Data amplification is possible because, from a set of experimental neurons, many more virtual analogues can be generated. This approach could allow one, in principle, to create and store a neuroanatomical database containing data for an entire human brain in a personal computer. We are using two programs, L–NEURON and ARBORVITAE, to investigate systematically the potential of several different algorithms for the generation of virtual neurons. Using these programs, we have generated anatomically plausible virtual neurons for several morphological classes, including guinea pig cerebellar Purkinje cells and cat spinal cord motor neurons. These virtual neurons are stored in an online electronic archive of dendritic morphology. This process highlights the potential and the limitations of the ‘computational neuroanatomy’ strategy for neuroscience databases.

Understanding distributions of chess performances

This paper presents evidence for several features of the population of chess players, and the distribution of their performances measured in terms of Elo ratings and by computer analysis of moves. Evidence that ratings have remained stable since the inception of the Elo system in the 1970’s is given in several forms: by showing that the population of strong players fits a simple logistic-curve model without inflation, by plotting players’ average error against the FIDE category of tournaments over time, and by skill parameters from a model that employs computer analysis keeping a nearly constant relation to Elo rating across that time. The distribution of the model’s Intrinsic Performance Ratings can hence be used to compare populations that have limited interaction, such as between players in a national chess federation and FIDE, and ascertain relative drift in their respective rating systems.

Conformational analysis of oriented non-crystalline polymers using wide angle X-ray scattering

A procedure is presented for obtaining conformational parameters from oriented but non-crystalline polymers. This is achieved by comparison of the experimental wide angle X-ray scattering with that calculated from models but in such a way that foreknowledge of the orientation distribution function is not required. X-ray scattering intensity values for glassy isotactic poly(methylmethacrylate) are analysed by these techniques. The method could be usefully applied to other oriented molecular systems such as liquid crystalline materials.

Measurement of molecular orientation in thermotropic liquid crystalline polymers

Procedures for obtaining molecular orientational parameters from wide angle X-ray scattering patterns of samples of thermotropic liquid crystalline polymers are presented. The methods described are applied to an extrusion-aligned sample of a random copolyester of poly(ethylene terephthalate) (PET) and p-acetoxybenzoic acid. Values of the orientational parameters are obtained from both the interchain and intrachain maxima in the scattering pattern. The differences in the values so derived suggest some level of local rotational correlation

Observations of nonthermal plasmas at different aspect angles

Data are presented from the EISCAT (European Incoherent Scatter (Facility)) CP-3-E experiment which show large increases in the auroral zone convection velocities (>2 km s−1) over a wide range of latitudes. These are larger than the estimated neutral thermal speed and allow a study of the plasma in a nonthermal state over a range of observing angles. Spectra are presented which show a well-defined central peak, consistent with an ion velocity distribution function which significantly departs from a Maxwellian form. As the aspect angle decreases, the central peak becomes less obvious. Simulated spectra, derived using theoretical expressions for the O+ ion velocity distribution function based on the generalized relaxation collision model, are compared with the observations and show good first-order, qualitative agreement. It is shown that ion temperatures derived from the observations, with the assumption of a Maxwellian distribution function, are an overestimate of the true ion temperature at large aspect angles and an underestimate at low aspect angles. The theoretical distribution functions have been included in the “standard” incoherent scatter radar analysis procedure, and attempts have been made to derive realistic ionospheric parameters from nonthermal plasma observations. If the expressions for the distribution function are extended to include mixed ion composition, a significant improvement is found in fitting some of the observed spectra, and estimates of the ion composition can be made. The non-Maxwellian analysis of the data revealed that the spectral shape distortion parameter, D*, was significantly higher in this case for molecular ions than for atomic ions in a thin height slab roughly 40 km thick. This would seem unlikely if the main molecular ions present were NO+. We therefore suggest that N2+ formed a significant proportion of the molecular ions present during these observations.

Cloud information content analysis of multi-angular measurements in the oxygen A-band: application to 3MI and MSPI

The vertical distribution of cloud cover has a significant impact on a large number of meteorological and climatic processes. Cloud top altitude and cloud geometrical thickness are then essential. Previous studies established the possibility of retrieving those parameters from multi-angular oxygen A-band measurements. Here we perform a study and comparison of the performances of future instruments. The 3MI (Multi-angle, Multi-channel and Multi-polarization Imager) instrument developed by EUMETSAT, which is an extension of the POLDER/PARASOL instrument, and MSPI (Multi-angles Spectro-Polarimetric Imager) develoloped by NASA's Jet Propulsion Laboratory will measure total and polarized light reflected by the Earth's atmosphere–surface system in several spectral bands (from UV to SWIR) and several viewing geometries. Those instruments should provide opportunities to observe the links between the cloud structures and the anisotropy of the reflected solar radiation into space. Specific algorithms will need be developed in order to take advantage of the new capabilities of this instrument. However, prior to this effort, we need to understand, through a theoretical Shannon information content analysis, the limits and advantages of these new instruments for retrieving liquid and ice cloud properties, and especially, in this study, the amount of information coming from the A-Band channel on the cloud top altitude (CTOP) and geometrical thickness (CGT). We compare the information content of 3MI A-Band in two configurations and that of MSPI. Quantitative information content estimates show that the retrieval of CTOP with a high accuracy is possible in almost all cases investigated. The retrieval of CGT seems less easy but possible for optically thick clouds above a black surface, at least when CGT > 1–2 km.

CMB and LSS constraints on a single-field model of inflation

A new inflationary scenario whose exponential potential V (Phi) has a quadratic dependence on the field Phi in addition to the standard linear term is confronted with the five-year observations of the Wilkinson-Microwave Anisotropy Probe and the Sloan Digital Sky Survey data. The number of e-folds (N), the ratio of tensor-to-scalar perturbations (r), the spectral scalar index of the primordial power spectrum (n(s)) and its running (dn(s)/d ln k) depend on the dimensionless parameter a multiplying the quadratic term in the potential. In the limit a. 0 all the results of the exponential potential are fully recovered. For values of alpha not equal 0, we find that the model predictions are in good agreement with the current observations of the Cosmic Microwave Background (CMB) anisotropies and Large-Scale Structure (LSS) in the Universe. Copyright (C) EPLA, 2008.

Cohabitation with a B16F10 melanoma-bearer cage mate influences behavior and dendritic cell phenotype in mice

This study evaluated the effects of cohabitation with a B16F10 melanoma-bearer cage mate on behavior and immune functions in mice. Five different experiments were conducted. In each of them, the female mice were divided into two groups: control and experimental. One mouse of each control pair was kept undisturbed and called ""companion of health partner"" (CHP). One mouse of each experimental pair was inoculated with B16FI0 cells and the other, the subject of this study, was called ""companion sick partner"" (CSP). On Day 20 of cohabitation, behavior and immune parameters from CHP and CSP mice were analyzed. In comparison to the CHP, the CSP mice: (1) presented an increased general locomotion in the open field and a decreased exploration time and number of entries in the plus-maze open arms; (2) had an enhanced expression of the CD80 costimulatory molecule on Iab(+)CD11c(+) spleen cells, but no differences were found on lymph nodes cells; (3) presented an altered differentiation of bone marrow cells in the presence of GM-CSF, IL-4, and LPS in vitro, resulting in a lower percentage of Iab(+)CD80(+) cells; (4) had a deficit in the establishment of a Delayed Type of Hypersensitivity to ovalbumin, which was associated to an in vitro proliferation of an IL-10-producing lymphocyte subpopulation after ovalbumin stimulation. Corticosterone levels detected on Day 20 of cohabitation were similar in CHP and CSP mice. It is shown here that DCs phenotype in mice is affected by conditions associated with behavioral alterations indicative of an anxiety-like state induced by the cohabitation with a tumor-bearer conspecific. This phenomenon occurred probably through a nondependent corticosterone mechanism. (C) 2009 Elsevier Inc. All rights reserved.

The imprint of the interaction between dark sectors in galaxy clusters

Based on perturbation theory, we study the dynamics of how dark matter and dark energy in the collapsing system approach dynamical equilibrium when they are in interaction. We find that the interaction between dark sectors cannot ensure the dark energy to fully cluster along with dark matter. When dark energy does not trace dark matter, we present a new treatment on studying the structure formation in the spherical collapsing system. Furthermore we examine the cluster number counts dependence on the interaction between dark sectors and analyze how dark energy inhomogeneities affect cluster abundances. It is shown that cluster number counts can provide specific signature of dark sectors interaction and dark energy inhomogeneities.