There has been much debate about whether shallow water diving , in the absence of neurological insult , can lead to cognitive deficits. The aim of this study was to investigate possible neuropsychological effects on two groups of divers , without any known history of decompression illness, who represent opposite ends of the spectrum of diving practice (rescue divers and sport divers) , and to compare them with a non-diving control group. 17 rescue divers , 17 non-diving controls and 15 sport divers were recruited. The groups were matched for age, but not for education. The two diving groups were comparable in terms of diving history. Results of neuropsychological testing indicated that the rescue diving group was not significantly different from the control group, suggesting that rescue diving under controlled conditions is comparatively safe. The sport diver group performed significantly worse than controls on a test of verbal reasoning (Comprehension, SAWAIS-R) and on a measure of word fluency (Controlled Oral Word Initiation Test), suggesting the possibility that risky diving practices may lead to decrements in frontal lobe functioning. Another possibility is that global decrements occur, but that the tests of frontal lobe functioning were more sensitive to mild deficits in functioning. This contention is tentative, and further research into frontal lobe functioning of divers should be conducted. Sport divers are recommended to follow safe diving practices and use dive profiles that avoid bubbling in order to prevent cognitive damage. VI / Thesis (M.A.)-University of Natal, Pietermaritzburg, 2002.

>Magister Scientiae - MSc / Antarctica is known for its pristine environments. A variety of unsuitable environmental conditions were once thought to render the continent unsuitable for sustaining life. However, metagenomic data have revealed a wealth of species diversity in a range of biotopes.Hypolithons, photosynthetic communities which live under translucent rocks in climatically extreme environments, are an important input source for both carbon (C) and nitrogen (N) in this hyperarid desert environment. Microbial contribution to biogeochemical cycling resulting in fixation of both C and N remains poorly understood. Moreover, there is a reported close interplay between both cycles, with nitrogen being reported to be a limiting factor in carbon assimilation.In this study the diversity of C and N fixing organisms was investigated by using the cbbL and nifH genes as phylogenetic and functional markers. High Molecular weight metagenomic DNA and RNA was extracted from hypolithons. PCR amplification was carried out using cbbL (800 bp for red-like, 1,100 bp for green-like) and nifH (360 bp) gene specific primers.Resultant PCR products were used to construct libraries which were screened for correct sized inserts. Restriction Fragment Length Polymorphism (RFLP) was used to de-replicate clones prior to sequencing. Phylogenetic positions from both clone libraries were established by aligning nucleotide sequences and constructing similarity trees using NJ clustering methods.BLASTn results indicated the presence of previously uncultured organisms which contain cbbL and nifH genes. BLASTn results were characterized by low percentages of maximum identity (typically <95%), a potential indicator of novel taxa. Sequences from respective libraries clustered with cyanobacteria such as Nostoc, Scytonema, and Tolypothrix and α-, β-, and γ-Proteobacteria such as Azotobacter, Agrobacterium and Mesorhizobium. Generally sequence results indicate a largely homogenous, being dominated by specific taxa. Each group may contain potential keystone species, essential for both biogeochemical cycling in oligotrophic environment.

I takt med en ökande individualism i samhället ställs nya krav på dagens organisationer, där medbestämmande och personlig utveckling önskas från medarbetare. Det kan dock innebära en paradox för militära organisationer när deras kärna så tydligt grundar sig i kollektivistiska värden och en anda av laget före jaget. Samtidigt finns höga förväntningar på militär personal att kunna påverka sig själva att agera och pusha sig igenom utmanande uppgifter, vilket är särskilt påtagligt i extrema miljöer som internationella insatser. Den här studien har undersökt om självledarskap är ett verktyg som militär personal använt för att kunna prestera under sina insatser. Trots att studier visat på positiva effekter av självledarskap i påfrestande förhållanden, har få studier undersökt huruvida det kan vara effektfullt i militära kontexter. Det kan samtidigt visa på att självledarskap inte nått militära organisationer än. Därmed har studien även undersökt synen på självledarskap hos Försvarsmaktens personal. Genom att ha intervjuat sex militärer som genomfört sin insats i Mali har studien kunnat visa på att flera strategier av självledarskap används i extrema miljöer. Den avvikelse som kunde urskiljas var att självmålsättning och självbelöning inte är lika synligt som övriga. Det kan delvis förklaras utifrån kollektivistiska värderingar där personalen redan motiveras av och känner stor tillhörighet till organisatoriska mål, men även att extrema miljöer medför hög arbetsbelastning och lite utrymme för återhämtning.

Les communautés microbiennes de sédiments de subsurface ont été décrites jusqu’à 1922 mbsf (meters below the seafloor) et pourraient représenter 0,6% de la biomasse totale. Largement incultivées, ces communautés comprennent des groupes endémiques aux environnements de subsurface et des généralistes retrouvés dans des environnements contrastés, appartenant aux 3 domaines du vivant (Bacteria, Eukarya and Archaea). Bien que jouant un rôle majeur dans les grands cycles géochimiques, l’écologie microbienne des sédiments de subsurface reste peu connue. Les conditions hostiles de ces sédiments contrastent avec la présence d’activité et de viabilité microbiennes. Dans ce contexte, de nombreuses questions sur les modes de vie et les métabolismes des microorganismes enfouis demeurent. L’objectif de cette thèse était de mieux comprendre quelles stratégies adaptatives pouvaient être mises en place par les communautés microbiennes de subsurface et de caractériser leur potentiel physiologique. Pour cela, 3 approches ont été utilisées.(1) Une approche culturale a permis de décrire 2 nouvelles espèces bactériennes sédimentaires (Halomonas lionensis, ungénéraliste versatile, et Phaeobacter leonis, une bactérie marine typique). L’étude de la résistance aux conditions de subsurface de ces deux espèces et de la bactérie Sunxiuqinia faeciviva, isolée à 247 mbsf, a ensuite été étudiée. (2) Par une étude de génomique comparée et structurale, la plasticité physiologique de H. lionensis a été analysée. (3) Enfin, le potentiel fonctionnel de communautés microbiennes enfouies à 31 et 136 mbsf dans le bassin de Canterbury a été étudié, en analysant les 2métagénomes correspondants. Les résultats culturaux et génomiques montrent que H. lionensis et S. faeciviva résistent mieux aux stress de subsurface que P. leonis et, dans le cas de H. lionensis, ceci impliquerait des propriétés physiologiques variées pouvant expliquer le succès écologique du genre Halomonas. Les données de métagénomique indiquent que les diversités phylogénétique et fonctionnelle de subsurface du bassin de Canterbury sont distinctes de celles d’environnements de surface et suggèrent que des métabolismes comme la fermentation, la méthanogenèse ou la β-oxydation pourraient être importants. La présence de gènes d’importance écologique et évolutive a permis d’émettre des hypothèses sur les modes de vie de ces microorganismes et des évènements de recombinaison génomique de groupes toujours incultivés ont aussi pu être décrits / Microbial communities inhabiting marine subsurface sediments were described up to 1922 mbsf (meters below the sea floor) andcould represent 0.6% of the total biomass. This microbial diversity, remaining elusive to cultivation, comprises groups specific to subsurface environments and groups of generalists found in contrasted habitats, all belonging to the 3 domains of life (Bacteria,Eukarya and Archaea). Although playing a major role in global geochemical cycles, the microbial ecology of the subseafloor remains largely unknown. The hostile conditions of subsurface sediments contrast with the descriptions of microbial activity andviability in the subseafloor. In this context, many questions related to the microbial physiology and the lifestyles of buried communities remain to be answered. The objective of this thesis was to better understand which adaptive strategies could be deployed by subseafloor microbial communities and to characterize their physiological potential. In that aim, 3 approaches were used.(1) A cultural approach enabled describing 2 novel sedimentary bacterial species (Halomonas lionensis, a versatile generalist and Phaeobacter leonis a typical marine bacterium). The survival of these 2 species to subseafloor conditions and of the subsurface bacteria Sunxiuqinia faeciviva, isolated at 247 mbsf, was then studied. (2) Using a structural and comparative genomic approach, the physiological plasticity of H. lionensis was investigated. (3) Finally, the functional potential of the microbial communities buried at 31 and 136 mbsf in the Canterbury Basin was analyzed, by studying the 2 corresponding metagenomes. Cultural and genomics results showed that H. lionensis and S. faeciviva are more resistant to subsurface constrains than P. leonis and, in the case of H. lionensis, this may involve various physiological properties, maybe explaining thee cological success of the genus Halomonas. Metagenomic data showed that the functional and the phylogenetic diversity of the subseafloor are distinct from the ones from surface environments and highlighted the importance of metabolic pathways like fermentation, methanogenesis and β-oxidation. Genes of ecological and evolutionary interests enabled speculating about lifestyles of buried microorganisms and analyses of genomic fragments highlighted recombination events of still uncultivated microbial groups

Growing need for application of electronics at temperatures beyond their rated limit, (usually > 150 °C) and the non availability of high temperature compatible electronics necessitates thermal management solutions that should be compact, scalable, reliable and be able to work in environments characterized by high temperature (150 -250 °C), mechanical shock and vibrations. In this backdrop the proposed research aims at realization of an adsorption cooling system for evaporator temperatures in the range of 140 °C-150 °C, and condenser temperature in the range of 160 °C-200 °C. Adsorption cooling systems have few moving parts (hence less maintenance issues), and the use of Thermo-Electric (TE) devices to regenerate heat of adsorption in between adsorbent beds enhances the compactness and efficiency of the overall 'ThermoElectric-Adsorption' (TEA) system. The work presented identifies the challenges involved and respective solutions for high temperature application. An experimental set up was fabricated to demonstrate system operation and mathematical models developed to benchmark experimental results. Also, it should be noted that TEA system comprises TE and adsorption chillers. A TE device can be a compact cooler in its own right. Hence a comparison of the performance of TEA and TE cooling systems has also been presented.

The objective of proposed research is to investigate the potential of strained silicon and silicon-germanium (SiGe) based devices for RF/mixed-signal applications. Different device topologies, namely strained buried channel modulation doped field effect transistor (MODFET) and silicon-on-insulator (SOI) based MOSFETs, are studied in this context. Our preliminary results on SiGe MODFETs indicate strong dependence of device performance on displacement damage, which is critical for extreme environment applications. This research will be an effort towards understanding the physics of these devices in extreme environment conditions.

Les archées halophiles sont des procaryotes vivant dans des conditions d’extrême salinité. Ces micro-organismes colonisent les environnements hypersalins et synthétisent des peptides antimicrobiens appelés halocines, qui pourraient leur conférer un avantage sélectif sur leurs compétiteurs. Parmi les peptides antimicrobiens d’archées halophiles décrits, on distingue l’halocine C8, initialement purifiée à partir de la souche halophile Natrinema sp. AS7092. Ce travail de thèse a permis de montrer que la production d’halocine C8 était conservée chez plusieurs archées halophiles appartenant aux genres : Natrinema, Haloterrigena, Haloferax et Halobacterium. Une activité antimicrobienne associée des particules supérieures à 100 kDa non infectieuses suggère que l’halocine C8 pourrait être localisée dans des vésicules membranaires. Ce travail présente des résultats qui déboucheront sur une meilleure compréhension des compétitions microbiennes dans les environnements hypersalins et du rôle écologique des halocines. / Halophilic archaea are prokaryotes living in extremely high salinity conditions. Those microorganisms thrive in hypersaline environments and produce antimicrobial peptides named halocins, which may confer them a selective advantage over competitors. Among the known antimicrobial peptides produced by halophilic archaea, halocin C8 had been initially purified from the halophilic strain Natrinema sp. AS7092. This work demonstrates that halocin C8 production is conserved among several halophilic archaea belonging to genera Natrinema, Haloterrigena, Haloferax and Halobacterium. An antimicrobial activity has been associated with non-infectious particles larger than 100 kDa, suggesting that halocin C8 could be localized in membrane vesicles. Results obtained from this work will lead to a better understanding of microbial competitions arising in hypersaline environments and the ecological role of halocins

L'approche écologique est une des stratégies de recherche de substances actives. Cette approche porte sur les plantes extrêmophiles, incluant les plantes halophytes et xérophytes, végétaux natifs des biotopes salins et arides. De par leur capacité à subsister dans un environnement contraignant, qui se traduit, entre autres, par l'acquisition d'un système antioxydant puissant, elles se révèlent être des réservoirs en biomolécules, notamment en composés phénoliques. Dans cette étude, nous nous sommes ainsi intéressés à huit plantes halophytes et xérophytes Tunisiennes pouvant avoir des activités biologiques en santé humaine et en santé du végétal. Limonium virgatum (Willd.) Fourr. (Plumbaginaceae), plante halophyte, a montré des activités antioxydantes et antibactériennes intéressantes qui se trouvent respectivement liées à un contenu en polyphénols élevé et à la présence de phénylpropanoïdes. Cirsium scabrum (Poir.) Bonnet & Barratte (Asteraceae), plante xérophyte, a montré une activité cytotoxique selective envers la lignée cancéreuse J774 mettant en avant l'efficacité de triterpènes de type cycloartane ; mais également un pouvoir antibactérien sur des souches de Dermabacter hominis, qui serait lié à la présence de flavones glycosylées. Juncus maritimus Lam. (Juncaceae), plante halophyte, s'est montrée être une source de dérivés phénanthréniques à activités originales. Le juncunol, a montré une activité prometteuse sur une souche de Streptococcus pyogenes résistante à l'amoxicilline. L'effusol actif sur le pathogène de la septoriose du blé (Zymoseptoria tritici), serait stimulé dans les rhizomes de la plante en conditions de salinité élevées. Enfin, le dehydrojuncusol s'est montré être un nouvel inhibiteur de la réplication du virus de l'hépatite C, capable d'agir sur des formes de résistance à certains traitement disponibles sur le marché. / Research strategies of active natural products include ecological approaches. Extremophile plants, and in particular, halophytes and xerophytes, salt and drought-resistant plants, are a case in point. As they develop an arsenal of adaptation responses, including a powerful antioxidant system, they prove to be a promising source of biomolecules, especially in phenolic compounds. In this study, an assessment of biological activities was carried out on eight Tunisian halophyte and xerophyte plants that would offer new applications in public health-care, as well as in agriculture. Limonium virgatum (Willd.) Fourr. (Plumbaginaceae), a halophyte plant, showed interesting antioxidant and antibacterial activities in accordance to a high polyphenol content and to the presence of phenylpropanoides, respectively. Cirsium scabrum (Poir.) Bonnet & Barratte (Asteraceae), a xerophyte plant, revealed a cytotoxic potential involving cycloartane-type triterpenes, and a promising activity against Dermabacter hominis strains which is linked to the presence of glycosylated flavones. Juncus maritimus Lam. (Juncaceae), a halophyte plant, should be referred to a source of phenanthrene derivativeswith original biological activities. Juncunol showed a high activity against an amoxicillin-resistant strain of Streptococcus pyogenes. Effusol was highly active against the wheat pathogen (Zymoseptoria tritici), for which high salinity conditions would stimulate its activity in the rhizomes of the plant. Most interestingly, dehydrojuncusol, has been introduced as a novel inhibitor of hepatitis C virus replication that is effective against resistant mutants for which some treatments available on the market became ineffective.

No description available.

This thesis evaluates the suitability of silicon-germanium technology for electronic systems intended for extreme environments, such as ambient temperatures outside of military specification (-55 degC to 125 degC) range and intense exposures to ionizing radiation. Silicon-germanium devices and circuits were characterized at cryogenic and high-temperatures (up to 300 degC) and exposed to ionizing radiation, providing empirical evidence that silicon-germanium is an excellent platform for terrestrial and space-based electronic applications.