Conception et réalisation d'un récepteur composé de réseau d'antennes YAGI multicouches verticales et de composants en ondes millimétriques

RÉSUMÉ Les applications en ondes millimétriques telles que les réseaux sans-fils haute vitesse demandent des composants de hautes performances, faibles coûts de revient, modulaires et compacts. Ce mémoire présente la conception d’une chaine de démodulation en ondes millimétriques utilisant le concept du multicouche. Tout d’abord, une antenne Yagi multicouche est proposée et démontrée à 5.8 GHz. La structure utilise pour la première fois les éléments parasites des antennes Yagi dans une structure de substrats empilés verticalement. Cela permet d’atteindre un gain de 12 dBi. Deux configuration sont présentées : une première basée sur un dipôle et une deuxième basée sur un patch circulaire afin d’avoir une double polarisation. Les résultats mesurés montrent un très bon accord avec les simulations. Basé sur les principes démontrés précédemment, l’antenne est adaptée à 60 GHz, puis un réseau d’antennes Yagi verticales en ondes millimétriques est introduit pour la première fois exploitant les technologies multicouches. Une analyse est faite pour définir les limites du design. L’antenne élément mesurée atteint un gain de 11 dBi. Le réseau 4x4 a une taille 50x50x60 mm3, et atteint un gain mesuré de 18 dBi sur 7% de bande passante. Une autre configuration du réseau utilisant des antennes Yagi inclinées permet d’avoir une réduction des lobes secondaires tout en ayant un impact minimum sur le gain. Les antennes proposées sont d’excellents candidats pour des systèmes intégrés, faibles coûts, demandant une petite empreinte en ondes millimétriques. Finalement, un nouveau six-port double couche utilisant des Guides Intégrés au Substrats (GIS) est présenté et démontré. Celui-ci permet de faire la démodulation QPSK. Son architecture utilise des coupleurs multicouches, fournissant une grande surface de couplage à travers deux fentes ; un déphaseur inédit, large bande composé de deux stubs plan-H et une ligne de référence ; ainsi que de deux diviseurs de puissance. Les simulations et mesures montrent que le circuit fonctionne correctement sur toute la bande V. La démodulation QPSK complète est testée sous le logiciel de simulation ADS et montre les excellentes performances du système.----------ABSTRACT Millimeter wave applications such as high-speed wireless connections require modular, compact-size, low-cost and high-performance systems. In order to realize a complete receiver satisfying those requirements, compact stacked multilayered designs are presented in this thesis. First, high-gain compact stacked multilayered Yagi designs are proposed and demonstrated at 5.8 GHz. The structure makes use for the first time of vertically stacked Yagi-like parasitic director elements that allow easily obtaining a simulated gain of 12 dBi. Two different antenna configurations are presented, one based on dipole geometry for single polarization, and the other on a circular patch to achieve dual polarization. Measured results of the fabricated antenna prototypes are in good agreement with simulated results. Second, based on the above-demonstrated principle, the antenna is redesigned and adapted for 60 GHz applications, and a novel design showing for the first time an array of Yagi elements in millimeter wave stacked structure is presented. An analysis is performed to define the structure limits. The measured element attains 11 dBi of gain. The proposed 4x4 array has a size of 50x50x60 mm3, and reaches a measured gain of 18 dBi over 7% of bandwidth. An alternative configuration of the array using angled Yagi antenna elements allows for a significant improvement of the side lobe level without a visible impact on the gain. The proposed antennas present excellent candidates for integrated low-cost millimeter-wave systems that require small footprint. Third, a novel dual layered six-port front-end circuit using the Substrate Integrated Waveguide (SIW) technology is presented and demonstrated. The six-port architecture makes use of multilayer couplers, providing a wide coupling area through two slots; a new broadband SIW phase shifter composed of two H-plane stub lines and one reference line; and two SIW power dividers. Simulation and measurement results show that the proposed six-port circuit can easily operate at 60 GHz for V-band system applications. The complete QPSK demodulation is tested through the ADS simulation platform to prove the good performances of the designed circuits

A DNA damage signal is required for p53 to activate gadd45

We provide direct evidence that overexpression of p53 is not sufficient for robust p53-dependent activation of the endogenous gadd45 gene. When p53 was induced in TR9-7 cells in the absence of DNA damage, waf1/p21 and mdm2 mRNA levels were increased, but a change in gadd45 mRNA was barely detectable. Activation of the gadd45 gene was observed when camptothecin was added to cells containing p53 in the absence of a further increase in the p53 level. Phosphorylation of p53 at serine 15 and acetylation at lysine 382 were detected after drug treatment. It has been suggested that p53 posttranslational modification is critical during activation. However, inhibition of these modifications by wortmannin was not sufficient to block the transactivation of gadd45. Interestingly, after camptothecin treatment, increased DNase I sensitivity was detected at the gadd45 promoter, suggesting that an undetermined DNA damage signal is involved in inducing chromatin remodeling at the gadd45 promoter while cooperating with p53 to activate gadd45 transcription

11-2001 Newsletter

Minnesota State University, Mankato, Library Services Newsletter for November 2001

Localization Properties of the Chalker-Coddington Model

The Chalker Coddington quantum network percolation model is numerically pertinent to the understanding of the delocalization transition of the quantum Hall effect. We study the model restricted to a cylinder of perimeter 2M. We prove firstly that the Lyapunov exponents are simple and in particular that the localization length is finite; secondly that this implies spectral localization. Thirdly we prove a Thouless formula and compute the mean Lyapunov exponent which is independent of M.Comment: 29 pages, 1 figure. New section added in which simplicity of the Lyapunov spectrum and finiteness of the localization length are proven. To appear in Annales Henri Poincar

Singlet oxygen generation as a major cause for parasitic reactions during cycling of aprotic lithium-oxygen batteries

Non-aqueous metal–oxygen batteries depend critically on the reversible formation/decomposition of metal oxides on cycling. Irreversible parasitic reactions cause poor rechargeability, efficiency, and cycle life, and have predominantly been ascribed to the reactivity of reduced oxygen species with cell components. These species, however, cannot fully explain the side reactions. Herewe showthat singlet oxygen forms at the cathode of a lithium–oxygen cell during discharge and from the onset of charge, and accounts for the majority of parasitic reaction products. The amount increases during discharge, early stages of charge, and charging at higher voltages, and is enhanced by the presence of tracewater. Superoxide and peroxide appear to be involved in singlet oxygen generation. Singlet oxygen traps and quenchers can reduce parasitic reactions effectively. Awareness of the highly reactive singlet oxygen in non-aqueous metal–oxygen batteries gives a rationale for future research towards achieving highly reversible cell operation

Deciphering the genome structure and paleohistory of _Theobroma cacao_

We sequenced and assembled the genome of _Theobroma cacao_, an economically important tropical fruit tree crop that is the source of chocolate. The assembly corresponds to 76% of the estimated genome size and contains almost all previously described genes, with 82% of them anchored on the 10 _T. cacao_ chromosomes. Analysis of this sequence information highlighted specific expansion of some gene families during evolution, for example flavonoid-related genes. It also provides a major source of candidate genes for _T. cacao_ disease resistance and quality improvement. Based on the inferred paleohistory of the T. cacao genome, we propose an evolutionary scenario whereby the ten _T. cacao_ chromosomes were shaped from an ancestor through eleven chromosome fusions. The _T. cacao_ genome can be considered as a simple living relic of higher plant evolution

The response of perennial and temporary headwater stream invertebrate communities to hydrological extremes

The headwaters of karst rivers experience considerable hydrological variability, including spates and streambed drying. Extreme summer flooding on the River Lathkill (Derbyshire, UK) provided the opportunity to examine the invertebrate community response to unseasonal spate flows, flow recession and, at temporary sites, streambed drying. Invertebrates were sampled at sites with differing flow permanence regimes during and after the spates. Following streambed drying at temporary sites, dewatered surface sediments were investigated as a refugium for aquatic invertebrates. Experimental rehydration of these dewatered sediments was conducted to promote development of desiccation-tolerant life stages. At perennial sites, spate flows reduced invertebrate abundance and diversity, whilst at temporary sites, flow reactivation facilitated rapid colonisation of the surface channel by a limited number of invertebrate taxa. Following streambed drying, 38 taxa were recorded from the dewatered and rehydrated sediments, with Oligochaeta being the most abundant taxon and Chironomidae (Diptera) the most diverse. Experimental rehydration of dewatered sediments revealed the presence of additional taxa, including Stenophylax sp. (Trichoptera: Limnephilidae) and Nemoura sp. (Plecoptera: Nemouridae). The influence of flow permanence on invertebrate community composition was apparent despite the aseasonal high-magnitude flood events

Exploring Gusev Crater with spirit: Review of science objectives and testable hypotheses

Gusev Crater was selected as the landing site for the Mars Exploration Rover (MER) Spirit mission. Located at the outlet of Ma'adim Vallis and 250 km south of the volcano Apollinaris Patera, Gusev is an outstanding site to achieve the goals of the MER mission. The crater could have collected sediments from a variety of sources during its 3.9 Ga history, including fluvial, lacustrine, volcanic, glacial, impact, regional and local aeolian, and global air falls. It is a unique site to investigate the past history of water on Mars, climate and geological changes, and the potential habitability of the planet, which are central science objectives of the MER mission. Because of its complex history and potential diversity, Gusev will allow the testing of a large spectrum of hypotheses with the complete suite of MER instruments. Evidence consistent with long-lived lake episodes exist in the landing ellipse area. They might offer a unique opportunity to study, for the first time, Martian aqueous sediments and minerals formed in situ in their geological context. We review the geological history and diversity of the landing site, the science hypotheses that can be tested during the MER mission, and the relevance of Gusev to the MER mission objectives and payload

Genomic, Pathway Network, and Immunologic Features Distinguishing Squamous Carcinomas

This integrated, multiplatform PanCancer Atlas study co-mapped and identified distinguishing molecular features of squamous cell carcinomas (SCCs) from five sites associated with smokin

Ten-year chemical signatures associated with long-range transport observed in the free troposphere over the central North Atlantic

Ten-year observations of trace gases at Pico Mountain Observatory (PMO), a free troposphere site in the central North Atlantic, were classified by transport patterns using the Lagrangian particle dispersion model, FLEXPART. The classification enabled identifying trace gas mixing ratios associated with background air and long- range transport of continental emissions, which were defined as chemical signatures. Comparison between the chemical signatures revealed the impacts of natural and anthropogenic sources, as well as chemical and physical processes during long transport, on air composition in the remote North Atlantic. Transport of North American anthropogenic emissions (NA-Anthro) and summertime wildfire plumes (Fire) significantly enhanced CO and O3 at PMO. Summertime CO enhancements caused by NA-Anthro were found to have been decreasing by a rate of 0.67 ± 0.60 ppbv/year in the ten-year period, due possibly to reduction of emissions in North America. Downward mixing from the upper troposphere and stratosphere due to the persistent Azores-Bermuda anticyclone causes enhanced O3 and nitrogen oxides. The d [O3]/d [CO] value was used to investigate O3 sources and chemistry in different transport patterns. The transport pattern affected by Fire had the lowest d [O3]/d [CO], which was likely due to intense CO production and depressed O3 production in wildfire plumes. Slightly enhanced O3 and d [O3]/d [CO] were found in the background air, suggesting that weak downward mixing from the upper troposphere is common at PMO. Enhancements of both butane isomers were found during upslope flow periods, indicating contributions from local sources. The consistent ratio of butane isomers associated with the background air and NA-anthro implies no clear difference in the oxidation rates of the butane isomers during long transport. Based on observed relationships between non-methane hydrocarbons, the averaged photochemical age of the air masses at PMO was estimated to be 11 ± 4 days