The electron physics in the collisionless magnetic reconnection is studied using data from the Polar spacecraft. Among the types of discontinuities in space plasmas, the Electron Diffusion Region (EDR) at the center of the reconnection has the theoretically unique properties that its thickness is of order of the electron gyroradius, and in such a region electrons are demagnetized with a non-gyrotropic pressure tensor. These unusual properties of EDRs reflect the expected violation of guiding center theory for electrons and are exploited in this thesis. We use four dimensionless, diagnostic, single spacecraft observables derived from theoretical properties of EDRs to locate them. They are electron agyrotropy, out-of-interconnection-plane electron Mach number, and dimensionless thresholds for electric field strengths parallel and perpendicular to the magnetic field. These observables are constructible using the electron density, bulk velocity, pressure tensor, and the electromagnetic field data. With a 3-year survey using particle data from a slower version of Hydra's moment producing system, M3, the vast preponderance of these dimensionless parameters are below unity, which is consistent with the theoretical expectations for most space plasmas being strongly magnetized. The unusual outliers with the demagnetization parameters over unity (<1%) in the distribution are geophysically distributed near the magnetopause within 8-9 Re shells and collected as potential reconnection sites, although a number of other possibilities are also considered in this thesis such as data processing anomalies, systematic effects of data acquisition and aliasing. It is shown that plasma particle data with the highest time resolution possible are needed to improve the time aliasing issues, and to sense the rapidly changing and short scale current structure like the EDR. We use a recently developed algorithm G3/T1, which reduces the aliasing time of the 3D analysis of products of the Polar Hydra Hot Plasma Analyzer by a factor of 12. With this new technique, we have found that among these outliers some demagnetization signatures are ameliorated by higher time cadences and the ones caused by time aliasing effects are ruled out. The moment recoveries of G3/T1 at a 2.3 cadence are in excellent agreement with input distribution models over a considerably wide range of density, Mach number, electron anisotropy, and agyrotropy, provided that a suitable accurate inventory can be made in advance for the bulk velocity of these distributions. The 2 candidate reconnection events analyzed in this thesis by G3/T1 processing techniques demonstrate: (1) strong out-of-interconnection-plane electron flows along the separatrices also observed in 2D PIC simulations; (2) significant electron agyrotropy enhancements framing high thermal Mach number flow, proving excellent consistency with the agyrotropy islands predicted by PIC simulations of asymmetric reconnection geometry; and (3) measured thermal electron gyroscale current channels in patterns that are supported by PIC simulation models as resolved examples of EDRs with direct measures of the electron demagnetization.

Der Synaptonemalkomplex (SC) ist eine hochkonservierte Proteinstruktur. Er weist eine dreiteili-ge, leiterähnliche Organisation auf und ist für die stabile Paarung der homologen Chromosomen während der Prophase der ersten meiotischen Teilung verantwortlich, die auch als Synpase be-zeichnet wird. Fehler während der Synpase führen zu Aneuploidie oder Apoptose der sich entwi-ckelnden Keimzellen. Seit 1956 ist der SC Gegenstand intensiver Forschung. Seine Existenz wurde in zahlreichen Orga-nismen von der Hefe bis zum Menschen beschrieben. Seine Struktur aus zwei parallel verlaufen-den Lateralelementen (LE), die durch eine Vielzahl von sogenannten Transversalfilamenten (TF) verbunden werden und dem Zentralen Element (CE) in der Mitte des SC ist dabei offensichtlich über die Millionen von Jahren der Evolution erhalten geblieben. Einzelne Proteinkomponenten des SC wurden jedoch nur in wenigen Modelorganismen charakterisiert, darunter Saccharomyces cerevisiae, Arabidopsis thaliana, Drosophila melanogaster, Ceanorhabditis elegans und Mus mus-culus. Unerwarteter Weise gelang es bei dieser Charakterisierung nicht, eine evolutionäre Ver-wandtschaft, d.h. eine Homologie zwischen den Proteinsequenzen der verschiedenen SCs nach-zuweisen. Diese Tatsache sprach gegen die grundsätzliche Annahme, dass der SC in der Evolution nur einmal entstanden sei. Diese Arbeit hat sich nun der Aufgabe gewidmet, die Diskrepanz zwischen der hochkonservierten Struktur des SC und seiner augenscheinlich nicht-homologen Proteinzusammensetzung zu lösen. Dabei beschränkt sie sich auf die Analyse des Tierreichs. Es ist die erste Studie zur Evolution des SC in Metazoa und demonstriert die Monophylie der Säuger SC Proteinkomponenten im Tierreich. Die Arbeit zeigt, dass mindestens vier von sieben SC Proteinen der Maus spätestens im letzten gemeinsamen Vorfahren der Gewebetiere (Eumetazoa) enstanden sind und auch damals Teil ei-nes ursprünglichen SC waren, wie er heute in dem Nesseltier Hydra zu finden ist. Dieser SC weist die typische Struktur auf und besitzt bereits alle notwendigen Komponenten, um die drei Domä-nen – LE, TF und CE – zu assemblieren. Darüber hinaus ergaben die einzelnen Phylogenien der verschiedenen SC Proteine der Maus, dass der SC eine sehr dynamische Evolutionsgeschichte durchlaufen hat. Zusätzliche Proteine wurden während der Entstehung der Bilateria und der Wir-beltiere in den SC integriert, während andere ursprüngliche Komponenten möglicherweise Gen-Duplikationen erfuhren bzw. besonders in der Linie der Häutungstiere verloren gingen oder sich stark veränderten. Es wird die These aufgestellt, dass die auf den ersten Blick nicht-homologen SC Proteine der Fruchtfliege und des Fadenwurms tatsächlich doch von den ursprünglichen Prote-inenkomponenten abstammen, sich aber aufgrund der rasanten Evolution der Arthropoden und der Nematoden bis zu deren Unkenntlichkeit diversifizierten. Zusätzlich stellt die Arbeit Hydra als alternatives wirbelloses Modellsystem für die Meiose- und SC-Forschung zu den üblichen Modellen D. melanogaster und C. elegans vor. Die kürzlich gewon-nenen Erkenntnisse über den Hydra SC sowie der Einsatz der Standard-Methoden in diesem Orga-nismus werden in dem abschließenden Kapitel zusammengefasst und diskutiert. / The synaptonemal complex (SC) is a highly conserved structure in sexually reproducing organism. It has a tripartite, ladder-like organization and mediates the stable pairing, called synapsis, of the homologous chromosomes during prophase of meiosis I. Failure in homolog synapsis result in aneuploidy and/or apoptosis of the developing germ cells. Since 1956, the SC is subject of intense research and its presence was described in various species from yeast to human. Its structure was maintained during millions of years of evolution consist-ing of two parallel lateral elements (LEs), joined by numerous transverse filaments (TFs) which run perpendicular to the LEs and an electron dense central element (CE) in the middle of the SC. Individual protein components, however, were characterized only in few available model organ-isms, as for example Saccharomyces cerevisiae, Arabidopsis thaliana, Drosophila melanogaster, Ceanorhabditis elegans and Mus musculus. Rather unexpectedly, these characterizations failed to detect an evolutionary homology between the protein components of the different SCs. This fact challenged the general idea of a single origin of the SC in the evolution of meiosis and sexual reproduction. This thesis now addressed itself to the task to unravel the discrepancy between the high conser-vation of the SC structure and its diverse and apparently non-homologous protein composition, focusing on the animal kingdom. It is the first study dealing with the evolution of the SC in Meta-zoa and demonstrates the monophyly of the mammalian SC components in metazoan species. The thesis demonstrates that at least four out of seven murine SC proteins emerged in Eumeta-zoa at the latest and have been likewise part of an ancient SC as it can be found in the present-day cnidarian species Hydra. This SC displays the common organization and already possesses the minimal protein kit corresponding to the three different structural domains: LEs, TFs and the CE. Additionally, the individual phylogenies of the murine SC proteins revealed the dynamic evolu-tionary history of the ancient SC. Further components were added during the diversification of Bilateria and vertebrates while ancestral proteins likely duplicated in the vertebrate lineage and diversified or got lost in the branch leading to ecdysozoan species. It is hypothesized that the apparently non-homologous SC proteins in D. melanogaster and C. elegans actually do derive from the ancient SC proteins but diversified beyond recognition during the fast evolution of Ar-thropoda and Nematoda. The study proposes Hydra as an alternative invertebrate model system for meiosis and SC re-search to the standard organisms D. melanogaster and C. elegans. Recent results about the cni-darian SC as well as the possible application of standard methods is discussed and summarized in the concluding section.

There is general concern whether human exposure to selected Canadian bottled waters and the chemicals which may leach from them, could potentially cause deleterious effects. This research was designed to determine whether exposures to bottled water and plastic leachates caused toxicity to the freshwater Cnidarian Hydra viridissima (green hydra). Three chemicals used in the production of polycarbonate and polyethylene plastics, bisphenol A (BPA) and two phthalate esters: dibutyl phthalate (DBP) and bis (2- ethylhexyl) phthalate (DEHP) along with one type of commercial bottled water were investigated. One brand of bottled water was analyzed over four months (stored in light and dark conditions) along with lab water similarly stored in glass, polycarbonate and polyethylene bottles. Following 2, 4, 8 and 16 weeks in each of the two treatments, hydra bioassays were conducted. Chronic toxicity tests were also conducted on the two phthalates and BPA. The chronic toxicity tests showed that BPA caused effects on hydra morphology and population at low doses and DBP and DEHP both showed signs of hormesis.

The "DNA Damage Hypothesis" pertaining to the evolution of sex was tested using Hydra littoralis. DNA damage was produced by irradiating whole live hydra with ultraviolet light. A curve of uv light dosage vs. survival was constructed. Estimations of threshold fluence and LD50 were made from the survival curve. In four separate experiments, using various combinations of environmental temperatures, uv doses, and number of doses, frequencies of asexual and sexual reproduction were observed and compared. The hydra that received uv treatments did not show an increase in the consequent amount of sexual reproduction, and actually showed a decrease. An increase in the amount of sexual reproduction following DNA damage is predicted by the DNA damage hypothesis, therefore these results do not support this theory. The data was also used to make contradictory observations regarding the "stress hypothesis" for the occurrence of sexual reproduction in hydra.

University, Diss., 2003--Kiel.

University, Diss., 2004--Kiel.

L’objectif de ce travail a consisté à évaluer différents effets écotoxiques, cytotoxique et le potentiel androgénique de 14 produits pharmaceutiques: la clomipramine, la fluoxétine, la fluvoxamine, la paroxétine, la sertraline et la venlafaxine (antidépresseurs), l’amphotéricine B, l’éconazole, le kétoconazole et le miconazole (antifongiques), la clarithromycine (antibiotique), l’acébutolol (ß-bloquants), le gabapentine (antiépileptiques) et la cétirizine (antihistaminiques), à l’aide d’études in vivo et in vitro. Les tests d’écotoxicité aiguë (96h) sur le cnidaire d’eau douce Hydra attenuata ont montré un effet délétère sur la survie des hydres adultes, la morphologie et le développement des embryons pour l’ensemble d’antidépresseurs et des antifongiques testés. Les valeurs de CE50 calculées ont révélé que l’éconazole, le miconazole et la sertraline sont les molécules les plus toxiques. Les tests d’écotoxicité chronique sur les hydres adultes (10 jours) et les embryons (14 jours) ont mis en évidence que la plus part des molécules d’antidépresseurs testées sont des embryotoxiques et tératogènes puisque ils induisent des malformations chez les embryons contrairement aux antifongiques qui présentent des anomalies seulement chez les adultes. Ces tests ont montré aussi que les molécules d’antidépresseurs testées seules sont moins toxiques que lorsqu’elles sont testées en mélange. En effet, le mélange de molécules antidépresseurs testées présente une toxicité plus élevée sur les adultes que sur les embryons, avec une concentration minimale induisant des effets significatifs de l’ordre de ng L-1, concentrations proches de celles retrouvées dans l’environnement. De plus, les résultats d’écotoxicité chronique sur plusieurs générations d’hydres ont montré que la morphologie des individus de la première génération (F0) ainsi que ceux de la deuxième génération (F1) été affectée de la même manière, démontrant une sensibilité du même ordre vis-à-vis de la sertraline ou du mélange d’antidépresseurs, tandis que les individus issus de la troisième génération (F2) apparaissent moins sensibles lors de l'exposition à la sertraline. Par contre, la reproduction des hydres exposées à la sertraline est diminué de plus en plus dans chaque génération, avec une toxicité plus importante pour les individus de la troisième génération. Le mélange d’antidépresseurs affecte la reproduction des hydres de la deuxième génération F1 à des concentrations environnementales. Les essais in vitro conduits sur les mêmes molécules pharmaceutiques, testées seules et en mélange, sur les cellules MDA-Kb2 n'ont révélé aucun effet androgénique et cytotoxique sur les cellules à des concentrations environnementales / The objective of this work was to evaluate different ecotoxic, cytotoxic and androgenic effects of 14 pharmaceutical compounds: clomipramine, fluoxetine, fluvoxamine, paroxetine, sertraline and venlafaxine, amphotericin B, éconazole, ketoconazole and miconazole, clarithromycin, the acebutolol, gabapentin and cetirizine, using in vivo and in vitro studies. The acute ecotoxicity tests (96h) on the freshwater cnidarian Hydra attenuata showed deleterious effects on adult survival, morphology and embryo development for all tested antidepressants and antifungals drug. The values of EC50 concentrations revealed that econazole, miconazole and sertraline are the most toxic molecules. The chronic ecotoxicity tests on hydras adults (10 days) and embryos (14 days) revealed that most of the molecules tested antidepressants are embryotoxic and teratogenic as they cause malformations in embryos contrary to antifungal which display abnormalities in adults only. These tests also showed that antidepressants tested individually are less toxic than when tested as a mixture. This mixture has a higher toxicity on adults than on embryos, with significant effects concentrations around ng L-1 which are close to measured environmental concentrations. In addition, chronic ecotoxicity results over several generations of hydras have shown identical sensitivity of both first and second generation on morphology of individuals. No more toxicity was observed on the third generation of hydra. Concerning the reproduction of hydras, this parameters was strongly decreased in all generations with an increasing sensitivity of individuals along the generations. Moreover, the mixture of antidepressants affect reproduction of hydras for the second generation at environmental concentrations. In vitro tests conducted on MDA-KB2 cells with the same pharmaceuticals revealed that these compounds tested did not exert any androgenic and cytotoxic effect on cells in culture at environmental concentrations

International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / This paper is a follow up to a paper presented at ITC 2002 entitled “Wireless Local Area Network for Data Telemetry from Fast Moving Nodes” by R. J. Bamberger, G. R. Barrett, R. A. Nichols, and J. L. Burbank of the Johns Hopkins University Applied Physics Laboratory, and M. H. Lauss of the Yuma Test Center at the U.S. Army Yuma Proving Ground (YPG). In that paper, network-centric data telemetry systems, specifically those based on commercial off- the-shelf (COTS) technologies such as the IEEE 802.11b Wireless Local Area Network (WLAN), were offered as an improvement over traditional frequency modulated (FM) data telemetry systems. The feasibility study of using WLANs for data telemetry considered both the radio frequency (RF) link over extended ranges and the effect due to Doppler shift. This paper describes an experiment designed to test those previous analyses.

Techn. Universiẗat, Diss., 2003--Darmstadt. / Dateien im PDF-Format.

Este trabalho apresenta uma generalização do modelo mínimo de movimento coletivo de Vicsek-Gregoire adaptado para a descrição da dinâmica celular de organismos pluricelulares de dois tipos de tecidos, como encontrado na Hydra Vulgaris. O trabalho se divide em duas partes. Na primeira é feita uma revisão histórica dos experimentos biológicos sobre o assunto assim como dos principais modelos matemáticos usados para descrever o problema. Ao final é apresentado o novo modelo mínimo de movimento coletivo (modelo de animóides) que será usado no restante da dissertação. Na segunda parte é feita uma exploração dos aspectos do modelo. Primeiro é construído um diagrama de fases para uma população homogênea de animóides (partículas), na qual se encontrou quatro fases distintas: gasosa, líquida, sólida e a de movimento coletivo. Também foi feito um estudo mais detalhado da difusão interna dos animóides dentro de um agregado, incluindo casos heterogêneos, onde se encontrou a existência de uma aparente superdifusão, assim como tempos de confinamento, para certos conjuntos de parâmetros. Finalmente ao final da segunda parte o modelo foi aplicado à simulação da segregação celular a partir de dois tecidos misturados. Além de se obter resultados que concordam perfeitamente com a principal hipótese biológica sobre o fenômeno, também foi estudado o papel que o movimento coletivo das células desempenha na segregação dos tecidos. / This work presents a generalization of the minimal collective movement model of Vicsek-Gregoire adapted for the description of the dynamics of multi-cellular organisms with two kinds of tissues, like Hydra Vulgaris. This work is composed of two main parts. In the first one an historical review is made about the biological experiments concerning the subject and also about the main mathematical models used for de description of the problem. At the end a new minimal collective movement model (boids model), which will be used in the rest of this dissertation, is presented. In the second part the model is explored in a more systematically way. First a phase diagram is build for an homogeneous population of boids (particles) where is found the existence of four distinct phases: gas, liquid, solid and also the collective movement phase. A study of the internal diffusion of boids inside a cluster is also made for both homogeneous and heterogeneous cases. An apparent super-diffusion, as also a trap time, is founded for certain sets of parameters. Finally, at the end of the second part the model is used for the simulation of the tissue segregation phenomena. The results obtained are in perfect agreement with the main biological hypothesis, and a study of the role of the collective movement in the segregation dynamics is also made.