Global ETD Search

91	ROLE OF FDCs AND FDC ACTIVATION IN PROMOTING HUMORAL IMMUNITY INCLUDING RESPONSES TO T-DEPENDENT ANTIGENS IN THE ABSENCE OF T CELLS El, Sayed Rania 16 June 2009 (has links) Follicular dendritic cells (FDCs) reside in primary B-cell follicles and in the light zones of germinal centers (GCs) in secondary follicles, where their dendrites interdigitate forming extensive networks intimately interacting with B-cells. In GCs, FDCs can be found at the edges attached to the supporting reticular fibers. They trap and arrange immune complexes (ICs) in vivo and in vitro in a periodic manner with 200–500Å spacing and provide both antigen-specific and non-specific accessory signals to B-cells. FDCs exist in resting and activated states, with two characteristically different phenotypes. In their activated state, FDCs upregulate the expression of accessory molecules and cytokines important in the FDC-B cell interaction in GCs. We sought to determine the mechanisms influencing the transition of FDCs from a resting to an activated state in GCs and their impact on T-cell dependent (TD) and independent (TI)-GC reactions (GCRs). We found that IC-FDC interactions via FDC-FcgammaRIIB induce the upregulation of FDC-FcgammaRIIB, -ICAM-1, and -VCAM-1, at both the protein and mRNA levels. We also reported for the first time the expression of TLR-4 on FDCs. Moreover, engagement of FDC-TLR4 with LPS activated NF-kappaB, up-regulated expression of important FDC-accessory molecules, including FcgammaRIIB, ICAM-1, and VCAM-1, and enhanced FDC accessory activity in promoting recall IgG responses. Moreover, IC-activated FDCs produced IL-6 and FDC-IL-6 promoted GCRs, somatic hypermutation (SHM) and IgG production. Further, we reported that binding of FDCs to collagen coated surfaces induced restoration of their dendritic processes and networks in vitro. In addition, we designed an FDC-supported in vitro model capable of induction and assessment of primary human antibody responses to protein antigens characterized by class-switching and affinity maturation. Uniquely, we generated TI immune responses to TD protein Ags in the complete absence of T cell help in vivo and in vitro. In the presence of FDC-associated second signals such as BAFF and C4BP, FDC- FcgammaRIIB-periodically trapped-ICs induced the production of Ag-specific IgM, GC-development and plasmablast-differentiation in anti-Thy-1-pretreated nude mice. Purified murine and human B cells cultured in vitro with IC-bearing FDCs also showed the production of antigen–specific IgM within just 48 h. Follicular Dendritic Cells Humoral Immunity T-dependent Antigens Germinal Centers IL-6 FcgammaRIIB TLR-4 Immune Complexes Collagen type I IgG Somatic Hypermutation T-Independent In vitro Vaccine Assessment Primary Human Antibody Response Secondary Follicle Activation Accessory Activity Dendrites BAFF C4BP IgM Periodicity ICAM VCAM Medicine and Health Sciences
92	Reef fish spawning aggregation sites : the ecology of aggregating and resident species. / Zones d'agrégation de reproduction des poissons coralliens : Ecologie des espèces migrantes et résidentes Bijoux, Jude peter 07 May 2013 (has links) Les sites d'agrégation de ponte (AP) sont des zones où des poissons d'une même espèce se rassemblent pour frayer. En dépit de leur importance dans la reproduction de nombreuses espèces de poissons des récifs coralliens, bien peu de sites d'AP sont gérés. Le but de cette étude est d'améliorer la compréhension générale sur l'écologie des sites d'AP en vue de faciliter la gestion. L'étude, réalisée aux Seychelles, se concentre sur les individus regroupant sur les sites d'AP pour frayer et aussi sur ceux résidant sur ces sites. La télémétrie acoustique et le recensement visuel sous-marin ont, ici, été employé comme principaux outils d'observation des espèces formant des agrégations de reproduction (cordonnier (Siganus sutor), mérou camouflage (Epinephelus polyphekadion) et mérou marbré (E. fuscoguttatus)) et des espèces résidant sur les sites d'AP. Les détections acoustiques ont montré que les individus de S. sutor présentent une grande fidélité à leur site de ponte et une périodicité liée à la période de pleine lune. Par ailleurs, les agrégations de ponte d'E. fuscoguttatus et E. polyphekadion se chevauchent spatialement et temporellement avec une forte périodicité liée à la nouvelle lune. La formation d'AP de E. fuscoguttatus et E. polyphekadion provoque des changements complexes dans l'assemblage de poissons résidents sur le site. L'effet de la phase lunaire sur les assemblages de poissons résidant sur les sites d'AP de S. Sutor apparait être dépendant de l'échelle considérée. Les informations sur la dynamique spatiale et temporelle des espèces étudiée sont utilisées pour proposer des mesures de gestion susceptibles d'améliorer la protection des sites d'AP. / Fish spawning aggregation (FSA) sites are areas where repeated concentration of conspecific fish gathers for the purpose of spawning. Despite of their importance in the reproduction of many coral reef fishes, few FSA sites are actively managed. The aim of this study, conducted in the Seychelles, was to improve general understanding on the ecology of FSA sites to facilitate their management. It focuses on both the individuals that aggregate at FSA sites to spawn and those that are resident at FSA sites. Acoustic telemetry and underwater visual census were used to study three species that form spawning aggregations (spinefoot shoemaker (Siganus sutor), Camouflage grouper (Epinephelus polyphekadion) and Brown-marbled grouper (E. fuscoguttatus)) and the resident fish assemblages at FSA sites. Acoustic detections found individual S. sutor to have high fidelity to individual FSA sites and to show significant periodicity with the full moon period in the timing of their arrival and departure from FSA sites. Conversely, spawning aggregations of E. fuscoguttatus and E. polyphekadion overlapped spatially and temporally, with strong periodicity for spawning aggregation to form with the new moon period. The formation of E. fuscoguttatus and E. polyphekadion FSAs caused complex changes in the fish assemblage that is resident at the FSA site. The effect of lunar phase on the resident fish assemblages at S. sutor FSA sites appeared to be scale-dependent, having greater impact at the larger than the smaller FSA site. Information on the spatial and temporal dynamics of aggregating and resident fish species is used to propose management actions to improve the protection of FSA sites. Agrégation de ponte de poissons Assemblages de poissons résidents Fidélité Cycle lunaire Poissons des récifs coralliens Mobilité Changement de la biodiversité Télémétrie acoustique Recensement visuel sous-marin Resident fish assemblages Site fidelity Lunar periodicity Coral reef fishes, Mobility Biodiversity change Acoustic telemetry Underwater visual census 577
93	Mathematical modelling of virus RSV: qualitative properties, numerical solutions and validation for the case of the region of Valencia Arenas Tawil, Abraham José 24 May 2010 (has links) El objetivo de esta memoria se centra en primer lugar en la modelización del comportamiento de enfermedades estacionales mediante sistemas de ecuaciones diferenciales y en el estudio de las propiedades dinámicas tales como positividad, periocidad, estabilidad de las soluciones analíticas y la construcción de esquemas numéricos para las aproximaciones de las soluciones numéricas de sistemas de ecuaciones diferenciales de primer orden no lineales, los cuales modelan el comportamiento de enfermedades infecciosas estacionales tales como la transmisión del virus Respiratory Syncytial Virus (RSV). Se generalizan dos modelos matemáticos de enfermedades estacionales y se demuestran que tiene soluciones periódicas usando un Teorema de Coincidencia de Jean Mawhin. Para corroborar los resultados analíticos, se desarrollan esquemas numéricos usando las técnicas de diferencias finitas no estándar desarrolladas por Ronald Michens y el método de la transformada diferencial, los cuales permiten reproducir el comportamiento dinámico de las soluciones analíticas, tales como positividad y periocidad. Finalmente, las simulaciones numéricas se realizan usando los esquemas implementados y parámetros deducidos de datos clínicos De La Región de Valencia de personas infectadas con el virus RSV. Se confrontan con las que arrojan los métodos de Euler, Runge Kutta y la rutina de ODE45 de Matlab, verificándose mejores aproximaciones para tamaños de paso mayor a los que usan normalmente estos esquemas tradicionales. / Arenas Tawil, AJ. (2009). Mathematical modelling of virus RSV: qualitative properties, numerical solutions and validation for the case of the region of Valencia [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/8316 / Palancia Seasonal diseases Systems of differential equations Jean mawhin's theorem of coincidence Numerical schemes Non-standard finite difference Differential transformation method Numerical simulations MATEMATICA APLICADA 12 - Matemáticas 1206 - Análisis numérico 120602 - Ecuaciones diferenciales
94	Generická analýza toků v počítačových sítích / Generic Flow Analysis in Computer Networks Jančová, Markéta January 2020 (has links) Tato práce se zabývá problematikou popisu síťového provozu pomocí automaticky vytvořeného modelu komunikace. Hlavním zaměřením jsou komunikace v řídicích systémech , které využívají speciální protokoly, jako je například IEC 60870-5-104 . V této práci představujeme metodu charakteristiky síťového provozu z pohledu obsahu komunikace i chování v čase. Tato metoda k popisu využívá deterministické konečné automaty , prefixové stromy a analýzu opakovatelnosti. Ve druhé části této diplomové práce se zaměřujeme na implementaci programu, který je schopný na základě takového modelu komunikace verifikovat síťový provoz v reálném čase.
95	Steigerung der Effektivität repetitiver Doppelpuls-TMS mit I-Wellen-Periodizität (iTMS) durch individuelle Adaptation des Interpulsintervalls Sewerin, Sebastian 01 November 2012 (has links) Die transkranielle Magnetstimulation (TMS) ist ein nichtinvasives Hirnstimulationsverfahren, mit welchem sowohl die funktionelle Untersuchung umschriebener kortikaler Regionen als auch die Modulation der Erregbarkeit ebendieser sowie die Induktion neuroplastischer Phänomene möglich ist. Sie wurde in der Vergangenheit insbesondere bei der Erforschung des humanen zentralmotorischen Systems angewandt. Dabei zeigte sich, dass ein einzelner über dem primärmotorischen Areal (M1) applizierter TMS-Puls multiple deszendierende Erregungswellen im Kortikospinaltrakt induzieren kann. Von diesen Undulationen besitzt die D-Welle (direkte Welle) die kürzeste Latenz und sie rekurriert auf eine direkte Aktivierung kortikospinaler Neurone, wohingegen I-Wellen (indirekte Wellen) längere Latenzen besitzen und durch transsynaptische Aktivierung dieser Zellen entstehen. Bemerkenswert ist das periodische Auftreten der letztgenannten Erregungswellen mit einer Periodendauer von etwa 1,5 ms. Zwar sind die genauen Mechanismen noch unbekannt, welche der Entstehung dieser I-Wellen sowie dem Phänomen der I-Wellen-Fazilitierung, das sich in geeigneten TMS-Doppelpulsprotokollen offenbart, zugrunde liegen, jedoch existieren hierzu verschiedene Erklärungsmodelle. Im Mittelpunkt der vorliegenden Arbeit steht die repetitive Anwendung eines TMS-Doppelpulsprotokolls, bei dem das Interpulsintervall (IPI) im Bereich der I-Wellen-Periodizität liegt (iTMS) und das gleichsam durch eine Implementierung der I-Wellen-Fazilitierung in der repetitiven TMS charakterisiert ist. Da gezeigt werden konnte, dass iTMS mit einem IPI von 1,5 ms (iTMS_1,5ms) die kortikospinale Erregbarkeit signifikant intra- und postinterventionell zu steigern vermag, und die I-Wellen-Periodizität interindividuellen Schwankungen unterliegt, wurde in der hier vorgestellten Studie an Normalprobanden der Einfluss einer individuellen Anpassung des IPIs (resultierend in der iTMS_adj) auf die intrainterventionelle kortikospinale Erregbarkeit untersucht. In der Tat stellte sich heraus, dass die iTMS_adj der iTMS_1,5ms diesbezüglich überlegen ist. Dieses Ergebnis unterstreicht das Potential einer Individualisierung der interventionellen TMS für erregbarkeitsmodulierende Effekte und macht dasjenige der ohnehin auf physiologische Prozesse abgestimmten iTMS explizit, was insbesondere für klinische Anwendungen relevant sein mag. info:eu-repo/classification/ddc/612 ddc:612
96	Efficient Computation of Electrostatic Interactions in Particle Systems Based on Nonequispaced Fast Fourier Transforms Nestler, Franziska 27 August 2018 (has links) The present thesis is dedicated to the efficient computation of electrostatic interactions in particle systems, which is of great importance in the field of molecular dynamics simulations. In order to compute the therefor required physical quantities with only O(N log N) arithmetic operations, so called particle-mesh methods make use of the well-known Ewald summation approach and the fast Fourier transform (FFT). Typically, such methods are able to handle systems of point charges subject to periodic boundary conditions in all spatial directions. However, periodicity is not always desired in all three dimensions and, moreover, also interactions to dipoles play an important role in many applications. Within the scope of the present work, we consider the particle-particle NFFT method (P²NFFT), a particle-mesh approach based on the fast Fourier transform for nonequispaced data (NFFT). An extension of this method for mixed periodic as well as open boundary conditions is presented. Furthermore, the method is appropriately modified in order to treat particle systems containing both charges and dipoles. Consequently, an efficient algorithm for mixed charge-dipole systems, that additionally allows a unified handling of various types of periodic boundary conditions, is presented for the first time. Appropriate error estimates as well as parameter tuning strategies are developed and verified by numerical examples. / Die vorliegende Arbeit widmet sich der Berechnung elektrostatischer Wechselwirkungen in Partikelsystemen, was beispielsweise im Bereich der molekulardynamischen Simulationen eine zentrale Rolle spielt. Um die dafür benötigten physikalischen Größen mit lediglich O(N log N) arithmetischen Operationen zu berechnen, nutzen sogenannte Teilchen-Gitter-Methoden die Ewald-Summation sowie die schnelle Fourier-Transformation (FFT). Typischerweise können derartige Verfahren Systeme von Punktladungen unter periodischen Randbedingungen in allen Raumrichtungen handhaben. Periodizität ist jedoch nicht immer bezüglich aller drei Dimensionen erwünscht. Des Weiteren spielen auch Wechselwirkungen zu Dipolen in vielen Anwendungen eine wichtige Rolle. Zentraler Gegenstand dieser Arbeit ist die Partikel-Partikel-NFFT Methode (P²NFFT), ein Teilchen-Gitter-Verfahren, welches auf der schnellen Fouriertransformation für nichtäquidistante Daten (NFFT) basiert. Eine Erweiterung dieses Verfahrens auf gemischt periodische sowie offene Randbedingungen wird vorgestellt. Außerdem wird die Methode für die Behandlung von Partikelsystemen, in denen sowohl Ladungen als auch Dipole vorliegen, angepasst. Somit wird erstmalig ein effizienter Algorithmus für gemischte Ladungs-Dipol-Systeme präsentiert, der zusätzlich die Behandlung sämtlicher Arten von Randbedingungen mit einem einheitlichen Zugang erlaubt. Entsprechende Fehlerabschätzungen sowie Strategien für die Parameterwahl werden entwickelt und anhand numerischer Beispiele verifiziert. info:eu-repo/classification/ddc/518 ddc:518 Teilchen-Gitter-Methode
97	Multispectral imaging of Sphagnum canopies: measuring the spectral response of three indicator species to a fluctuating water table at Burns Bog Elves, Andrew 02 May 2022 (has links) Northern Canadian peatlands contain vast deposits of carbon. It is with growing urgency that we seek a better understanding of their assimilative capacity. Assimilative capacity and peat accumulation in raised bogs are linked to primary productivity of resident Sphagnum species. Understanding moisture-mediated photosynthesis of Sphagnum spp. is central to understanding peat production rates. The relationship between depth to water table fluctuation and spectral reflectance of Sphagnum moss was investigated using multispectral imaging at a recovering raised bog on the southwest coast of British Columbia, Canada. Burns Bog is a temperate oceanic ombrotrophic bog. Three ecohydrological indicator species of moss were chosen for monitoring: S. capillifolium, S. papillosum, and S. cuspidatum. Three spectral vegetation indices (SVIs) were used to characterize Sphagnum productivity: the normalized difference vegetation index 660, the chlorophyll index, and the photochemical reflectance index. In terms of spectral sensitivity and the appropriateness of SVIs to species and field setting, we found better performance for the normalized difference vegetation index 660 in the discrimination of moisture mediated species-specific reflectance signals. The role that spatiotemporal scale and spectral mixing can have on reflectance signal fidelity was tested. We were specifically interested in the relationship between changes in the local water table and Sphagnum reflectance response, and whether shifting between close spatial scales can affect the statistical strength of this relationship. We found a loss of statistical significance when shifting from the species-specific cm2 scale to the spectrally mixed dm2 scale. This spatiospectral uncoupling of the moisture mediated reflectance signal has implications for the accuracy and reliability of upscaling from plot based measurements. In terms of species-specific moisture mediated reflectance signals, we were able to effectively discriminate between the three indicator species of Sphagnum along the hummock-to-hollow gradient. We were also able to confirm Sphagnum productivity and growth outside of the vascular growing season, establishing clear patterns of reflectance correlated with changes in the local moisture regime. The strongest relationships for moisture mediated Sphagnum productivity were found in the hummock forming species S. capillifolium. Each indicator Sphagnum spp. of peat has distinct functional traits adapted to its preferred position along the ecohydrological gradient. We also discovered moisture mediated and species-specific reflectance phenologies. These phenospectral characteristics of Sphagnum can inform future monitoring work, including the creation of a regionally specific phenospectral library. It’s recommended that further close scale multispectral monitoring be carried out incorporating more species of moss, as well as invasive and upland species of concern. Pervasive vascular reflectance bias in remote sensing products has implications for the reliability of peatland modelling. Avoiding vascular bias, targeted spectral monitoring of Sphagnum indicator species provides a more reliable measure for the modelling of peatland productivity and carbon assimilation estimates. / Graduate peatland peatland restoration peatland monitoring peatland modelling peat peat moss multispectral multispectral imaging multicamera array multitemporal multiple linear regression linear mixed effects Sphagnum sphagna Sphagnum capillifolium Sphagnum papillosum Sphagnum cuspidatum spatiospectral uncoupling near-sensing remote sensing phenospectral phenology phenologies phenospectral bias phenospectral libraries carbon assimilation carbon dioxide carbon dynamics carbon emissions carbon geographies carbon mineralization carbon sequestration carbon source carbon sink carbon storage irrecoverable carbon climate forcing methane Ecological Restoration restoration ecology ecohydrology ecohydrological restoration hydrology ecohydrological gradients ecological integrity reflectance nature based solutions ombrotrophic moss raised peatland mires mires photochemical reflectance index normalized difference vegetation index chlorophyll index climate change climate forcing climate envelope climatope nonvascular vascular bias plant functional type plant functional types structure equation models spectral vegetation indices hummock hollow acrotelm catotelm diplotelmic biocrusts organic soil periodicity moisture deficit senescence rejuvenescence productivity photosynthesis light use efficiency photosynthetic function photosynthetically active radiation water table hydrology rewetting depth to water table landscape change landscape degradation peat subsidence Burns Bog

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