Mesobenthic amphipods (2-15 mm) constitute an important faunal component of coastal ecosystems, and often represent a major trophic link between primary producers and fishes. However, obtaining basic demographic data on these taxa is often hindered by a lack of suitable non-destructive, quantitative, collection techniques. Although artificial substrates have been advocated for collecting data at these lower trophic levels, recent studies suggest that they may not accurately represent the natural benthic assemblage. This study evaluated how a structurally-complex artificial substrate (3-dimensional) simulated the natural substrate of a shallow Acropora reef environment. Assemblage development was followed on a series of artificial substrate units (ASUs) at 2-week intervals over a 14-week period; adjacent natural substrate was sampled monthly. Multivariate analyses were applied to determine the (dis)similarity of assemblages between the two substrate types. Statistical analyses showed significant differences in assemblage structure between artificial and natural substrates. However, no significant differences were found between sites or habitats within substrate type. Samples from the ASUs were dominated by Elasmopus balkomanus, Bemlos kunkelae, Neomegamphopus kalanii, and Ericthonius punctatus. Taxa abundant on the natural substrate, but numerically poor on the ASUs, included Chevalia carpenteri, Apolochus sp., Gammaropsis atlantica, and Globosolembos smithi. Assemblage dissimilarities depended chiefly on differences in species composition and relative abundance largely contributed to the dissimilarity between the two substrates.

La gestion de l’irrigation et de la fertilisation dans les systèmes de production hors sol est particulièrement cruciale afin de limiter tous risques d’asphyxie racinaire, de lessivage d’éléments minéraux, voire de développement de pathogènes liés à une irrigation excédentaire, ou, à l’inverse, de réhumectation délicate et de stress hydrique de la plante dans des conditions limitantes en eau. Ayant pour finalité d’améliorer l’efficience de l’eau pour les plantes cultivées sur substrats, les travaux développés dans cette thèse ont visé à analyser l’évolution des propriétés hydrauliques de différents substrats au cours de laculture, en se focalisant tout particulièrement sur les effets combinés du développement racinaire et de la gestion de l’irrigation.Des essais culturaux ont été menés sur tourbe, fibres de coco, fibres de bois et écorce, prenant pour plante modèle utilisée le rosier Knock Out®. Des mesures de biomassesracinaires et aériennes, ainsi que celles des propriétés de rétention en eau et en air, de conductivité hydraulique, de diffusivité des gaz et de mouillabilité ont été effectuées surchaque substrat soumis à des régimes d’irrigation différents (variant d’un optimum hydrique à des conditions de stress hydrique). Les résultats montrent d'importantes modifications aufil du temps, principalement en raison de l'histoire hydrique. Cela conduit à des modifications(1) de la distribution et de la taille des pores, traduite par une réduction de leur tortuositéqui génère une augmentation de la diffusion gazeuse dans le milieu, ainsi que (2) unediminution de / Precise irrigation management of substrates is of vital importance in horticultural soilless systems to avoid root asphyxia, nutrient leaching, and plant disease in case of excessive watering; as well as, nutrient and water deficiency, and then plant physiological stress in the driest conditions. The study presented here aimed to improve water efficiency for plants grown in pots or containers, focusing on the evolution of hydraulic properties of substratesdue to root development and irrigation strategies during plant growth. Crop trials were performed on peat, coir, wood fiber and pine bark, using the rose Radrazz Rosa x hybrida as plant model.Shoot and roots biomasses, air and water retention properties, hydraulic conductivity, relative gas diffusivity and wettability were measured on each substrate, managed with different irrigation strategies (from an optimal water content to hydric stress conditions). Results showed significant changes over time, mainly due to the hydric history. This led to changes (1) in pore distribution and size, and then a decrease in pore tortuosity generating an increase in relative gas diffusivity in the substrates, and (2) a decrease in substrates’ wettability according to the intensity of drying. Although they were with weaker amplitude to those resulting of the hydric history, filling of macroporosity by the root system led to limit substrates’ consolidation due to drying/wetting cycles, and moreoverto amplify pore connectivity and then relative gas diffusivity and to limit degradation inwettability.

No description available.

Les lymphocytes T jouent un rôle central dans la réponse immunitaire adaptative. par l'intermédiaire d'un récepteur distinctif - le RCT (Récepteur des Cellules T), qui est responsable de la reconnaissance spécifique de peptides étrangers dans le corps. Les interactions moléculaires entre le RCT et son ligand, présenté par des cellules spécialisées (CPA cellules présentatrices d'antigène) sont suivies par un processus d'adhésion et d'étalement cellulaire caractérisé par d'importantes réorganisations à l'échelle supramoléculaire et cellulaire. Le rôle des propriétés physiques des cellules à ces échelles est encore mal compris. Dans cette thèse, nous nous sommes intéressés aux événements suivant cette reconnaissance en mimant la CPA par des substrats artificiels contrôlés exploitant plusieurs techniques de microscopie avancé. Nous avons réalisé une étude systématique de la dynamique d'étalement ainsi que de la morphologie (en terme d'aire d'adhésion et d'organisation de l'actine) des lymphocytes T humains de la lignée Jurkat sur des substrats présentant des anti-CD3 (un ligand spécifique du RCT) mobiles ou non. L'étalement des LT est fortement réduit sur les ligands mobiles par rapport aux ligands fixes. De plus le blocage de la myosine-II ou l'inclusion d'ICAM (le ligand des intégrines LFA-1) sur les substrats permettent de compenser ces différences. Nous proposons un modèle, inspiré de ceux sur la migration ou la croissance du cône neuronal , qui lie la dynamique du front d'étalement des lymphocytes T à la friction générée au niveau de la surface en tirant ou en fixant les ligands. / T- cells play a central role in cell mediated adaptive immune response. They are a class of lymphocytes that carry distinctive receptors - the TCRs (T cell receptor), which are responsible for specific recognition of foreign peptides in the body. Molecular interactions between the TCR complex and its ligand is followed by cell adhesion and spreading accompanied by dramatic changes at molecular and cellular scale. In this thesis we focus on the events that immediately follow recognition. I report a systematic study of the spreading dynamics and morphology (in terms of adhesion area and actin organization) of T lymphocytes on substrates with mobile or immobilized anti-CD3 (a ligand targeting the TCR complex). The spreading behaviour is seen to be dramatically different on the two types of substrates. Interestingly, on blocking myosin-II or by inclusion of ICAM (ligand of LFA1 integrins) on the substrate, these differences tend to disappear. We propose a model, partially inspired by earlier models of neuronal growth cones and filopodia, that links the dynamics of the leading edge of the spreading T cell to the friction generated at the surface by dragging or pinning of the ligands. I also report studies on T cells interacting with substrates decorated with nano-scale islands of anti-CD3 in a sea of repulsive PEG or a supported lipid bilayer. Dramatic differences in adhesion, organization of actin, and receptor distribution are observed on different geometries. I report advances in multi channel RICM towards the reconstruction of not only the topography of the proximal membrane of the T cell with high level of confidence but also the distal surface of lamellipodia.

Slot dipole antennas fed by coplanar waveguide (CPW) on substrates consisting of a single dielectric layer exhibit various attractive qualities, including significantly wider impedance bandwidth than comparable microstrip patch antennas. For applications that call for unidirectional radiation, such as antennas on airframes, a conducting back plane is needed. A CPW on a conductor-backed single-dielectric-layer substrate will always experience power leakage into the TEM parallel-plate mode. On the other hand, it is possible to design CPW lines on conductor-backed two-layer substrates that are free from leakage into the substrate. However, once the CPW is used as feed line to a slot dipole, power leakage into the TM0 substrate mode caused by the transition between the CPW and the radiating slot, and by the radiating slot itself, may still severely compromise radiation efficiency. This study has two main contributions to offer. First, a paucity of work on CPW-fed slot antennas on conductor-backed two-layer substrates is alleviated by providing a fuller characterization of single-slot behaviour on two-layer parallel-plate substrates than is currently available, and by systematically investigating a practically feasible minimum antenna configuration, namely broadside twin slots, that is not debilitated by the problem of substrate mode leakage. Results obtained with the moment-method-based electromagnetic simulator IE3D that emphasize the trade-off between radiation efficiency and impedance bandwidth are presented; they can be used for design purposes. For instance, with respect to single slots on a substrate with an electrically thin top dielectric layer and an air bottom layer, it is shown that radiation efficiency increases and bandwidth decreases as height of the bottom substrate layer increases. For broadside twin slots, it is demonstrated that spacing close to half a wavelength of the two-layer parallel-plate TM0 mode apart can yield a large improvement in radiation efficiency over that of a single slot (a reduction in bandwidth however occurs). The second main contribution is the development of an approach for finding the mutual admittance Y12 between CPW-fed slots on conductor-backed two-layer substrates that can be more readily incorporated in an iterative array design procedure than a moment-method-based technique, yet is of comparable accuracy; it is built on a standard reciprocity-based expression. As an initial step, the mutual admittance between CPW-fed slots on a conductor-backed two-layer substrate with an air bottom layer is characterized using IE3D. This involves presenting curves for Y12 between twin slots against slot separation d along standard paths for slot half-lengths in the vicinities of the first and second resonant half-lengths of the corresponding isolated slots (such data might be used towards a first-order array design), and a study of the effect of back plane distance (i.e., bottom layer height) on mutual coupling. The bulk of the thesis however is devoted to the above reciprocity-expression approach. Simplifying assumptions are outlined that make it possible to determine Y12 against d by performing a once-only moment-method analysis of each slot in isolation, and then calculating external and internal reaction integrals at each value of d. This is significantly more economical than carrying out a full moment-method analysis of the whole twin-slot structure at every instance of d. Evaluation of the internal reaction integral requires the appropriate component of the spatial-domain Green’s function for the substrate, which is derived in a form containing Sommerfeld-type integrals; treatment of singularities is discussed. The reciprocity-expression approach is verified by comparing Y12 against d curves for twin slots and non-identical slot pairs on a variety of conductor-backed two-layer substrates to IE3D simulations. A procedure that involves judicious selection of reference planes is introduced by which agreement between the methods for the special case of twin slots with the same half-length as the corresponding isolated second-resonant slot can be even further improved. A measurement is provided that validate theoretical calculations. / Thesis (PhD)--University of Pretoria, 2008. / Electrical, Electronic and Computer Engineering / unrestricted

<p>Cyclobutane pyrimidine dimers (CPD) are the predominant DNA lesions formed upon exposure of this biopolymer to sunlight. Given the potentially dire biological consequences of DNA lesions, there is a need to fully characterize their behaviour, with an eye towards understanding their complete reactivity and as a possible means to detect and quantify their presence in the genome. The work described in this dissertation describes studies of the alkaline reactivity of CPD lesions generated within dinucleotide & polynucleotide strands. It was found that CPD-TpT is generally inert under alkaline conditions at room temperature, which is in agreement with earlier studies on alkaline hydrolysis of CPD-thymine and CPD-thymidine. However, a re-evaluation of the same reaction in the presence of ¹⁸O labelled water demonstrated that, similar to other UV-induced DNA lesions containing a saturated pyrimidine ring, CPD undergoes a water addition at the C4=O group of the nucleobase leading to the formation of a hemiaminal intermediate. This intermediate, however, does not lead to hydrolysis products and completely reverts to starting material under those same conditions. Moreover, the two C4=O groups present on 3′ and 5′-thymines in a CPD molecule show different chemical reactivities, with the 3′ C4=O group having greater affinity towards water addition as compared to the one on 5′ end, a fact reflected in different rates of exchange with the incoming nucleophile leading to the hemiaminal intermediate. The ¹⁸O labelling reaction was also investigated in CPD lesions generated within oligonucleotides to probe the cause of asymmetry between the 3′ <i>vs</i> 5′ C4=O groups; ultimately, it was determined that the asymmetric reactivity observed to occur between the two C4=O groups was an intrinsic property of the CPD molecule and did not arise as a result of asymmetry in a dinucleotide setting.</p><p><br></p> <p>In addition to the above studies, during the course of the investigation of the nucleophilic reactivity of CPD, a chemical reaction was observed leading to what appeared to be the rapid and total chemical reversal of CPD lesions to the original TpT (thymine-thymine dinucleotide)! This “repair” reaction occurred when CPD reacted with hydrazine, and appears facilitated by an inert atmosphere under which it rapidly proceeds to completion at room temperature.</p><br>

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22776号 / 工博第4775号 / 新制||工||1747(附属図書館) / 京都大学大学院工学研究科材料工学専攻 / (主査)教授 杉村 博之, 教授 邑瀬 邦明, 教授 宇田 哲也 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Carotenoids are naturally occurring pigments produced by bacteria, yeasts, filamentous fungi and plants. They exhibit significant biological effects and are widely used in the food industry, pharmacy and cosmetics. The aim of this diploma thesis proposed as a comparative study was regulation of carotenoid and ergosterol production in red yeasts using several waste substrates as whey, corn germs, wheat, apple fiber and pasta. To selected production media extracellular hydrolytic enzymes degrading polysaccharide were added. These enzymes were obtained from the cultivation media of four fungal strains. In this study three carotenogenic yeast strains were used: Rhodotorula glutinis, Sporobolomyces roseus and Cystofilobasidium capitatum. All strains were cultivated simultaneously and changes in biomass and carotenoid production in different production media were monitored and compared. As the best waste substrate apple fiber was utilized, particularly in Rhodotorula glutinis, which exhibited mainly biomass production increase. In Sporobolomyces roseus increased production of biomass and carotenoids have been reported in media with hydrolyzed fiber and pasta as well. Beta-carotene production in this strain reached 4776,38 mg/g of dry weight. The strain Cystofilobasidium capitatum exhibited in waste media a decerase of biomass production accompanied with increased production of carotenoids, especially in wheat mush and pasta medium hydrolyzed by enzyme preparative from Aureobasidium pullulan. It can be concluded that hydrolyzed waste substrates are very hopeful as cheap nutrient sources for yeast strains producing carotenoids and ergosterol. Nevertheless, further study of substrate processing for individual strains is needed.

Yeasts are like other organisms constantly exposed to environmental influences. Their survival depends on the skills to adapt to environmental changes, including the ability to use various alternative sources of nutrients. In presented PhD thesis carotenogenic yeast belonging to the genera Rhodotorula, Sporobolomyces and Cystofilobasidium were tested for ability to use of selected waste substrates, and also subjected to several types of exogenous stress effects and mutations in order to increase the production of microbial biomass enriched with specific metabolites. As alternative nutrient sources derived from waste substrates from agricultural and farm production apple peel, pulp, corn germ and more were tested. Yeasts were also exposed to osmotic, oxidative and combined stress (benefits of various concentrations of NaCl and H2O2 to the culture media), followed by metal ions of selenium and chromium in concentrations of 0.01 mM, 0.1 mM and 1 mM. The effect of mutagen methanesulfonic acid ethyl ester was tested too. In all experiments the adaptivity of cells, morphological changes, color pigments produced by the media while some important fungal metabolites production and changes in chromosomal DNA fragmentation were analyzed. In order to evaluate potential changes in the yeast genome after treatment with mutagen and stress factors methods for isolation of intact chromosomal DNA and DNA analysis by pulsed field gel electrophoresis was optimized. The amount of produced metabolites was mainly analyzed by RP-HPLC with UV/VIS and MS detection. The work has been shown that most strains are able to use waste substrates and produced selected target metabolites. Biomass, for example, in R. aurantiaca on apple fiber was about 7 g/l and in C. capitatum cultivated on modified whey reached to 9 g/l. Amount of produced carotenoids by R. aurantiaca cultivated on wheat germ and maize after enzymatic hydrolysis by F. solani was 1.01 mg/g and S. roseus on pasta 4.3 mg/g. The values of ergosterol synthesis in R. aurantiaca are on the apple shells around 4.8 mg/g, in S. roseus on pasta with the enzymatic hydrolysis of P. chrysosporium 8.9 mg/g. The best substrate for biomass production and induction of carotenoids are waste substartes containing a mixture of simple and complex carbohydrates enriched with the addition of nitrogen compounds. Potential cytotoxic effect of stress factors of low concentrations was demonstrated. Red yeast genome was able to distribute by optimized PFGE, the karyotype of tested yeasts contain 11 or more chromosomes with visible differences between yeast species and genera. During exchange internship the ability of recombinant yeast S. cerevisiae to convert xylose to xylitol, which would be achieved by increasing the production of bioethanol as alternative fuel sources was studied. It turned out that both ligninocellulose materials to bioethanol production, as well as various waste substrates for microbial synthesis of carotenoids would reduce costs for industrial production of yeast metabolites, as well as to reduce the negative burden on the environment.

Carotenoids are naturally occurring pigments of plants also produced in many bacteria, and fungi. They represent one of the widest group of natural antioxidants with significant biological effects and numerous of industrial applications. There is an increased interest in carotenoids as natural antioxidants for their ability to reduce chronic diseases, various pathological stages and aging. The area of their application concerns mainly food industry; however, they are used in chemical, pharmaceutical, and cosmetics industry as well. One possibility is study of potential of red yeasts that are able to convert various substrates into carotenoid pigments. In presented thesis carotenogenic yeast belonging to the genus Rhodotorula, Sporobolomyces and Cystofilobasidium were tested for ability to use of selected waste substrates and also random mutagenesis in order to increase the production of biomass and specific metabolites – carotenoids and other lipid-soluble substances. As alternative nutrient sources derived from waste substrates from agricultural and food production (rapeseed substrate, rice, wheat, apple fiber, pasta and lignocellusic materials) were tested. To selected production media extracellular hydrolytic enzymes or commercial enzymes degrading polysaccharide were added. All tested red yeast strains were able to utilize these substrates as the only carbon source and simultaneous produce carotenoid enriched biomass. In this work, characterization of carotenogenic yeast using molecular techniques was studied. For this usage, interspecific variables of strongly conserved sequences of genomic DNA, especially rDNA D1/D2 large ribosomal subunit and ITS1 and 5,8-ITS2 rDNA regions were amplified. These sequences were subjected analysed by DGGE method to compare differences of carotenogenic yeasts. Isolation procedure of the intact DNA were optimized for caryotypic yeast characterization by pulsed field gel electrophoresis (PFGE). The karyotype of tested yeasts contain visible differences between yeast species and genera.