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Harsh Conditions (harsh + condition)
Selected AbstractsRecent advances in the biogeography and genecology of symbiotic Frankia and its host plantsPHYSIOLOGIA PLANTARUM, Issue 3 2007David R. Benson Molecular phylogenetic approaches have begun to outline the origin, distribution and diversity of actinorhizal partners. Geographic isolation of Frankia and its host plants resulting from shifting continents and dispersal patterns have apparently led to the development of Frankia genotypes with differing affinities for host genera, even within the same plant family. Actinorhizal plant genera of widespread global distribution tend to nodulate readily even outside their native ranges. These taxa may maintain infective Frankia populations of considerable diversity on a broad scale. Arid environments seem to have distinctive actinorhizal partnerships, with smaller and more specific sets of Frankia symbionts. This has led to the hypothesis that some host families have taxa that are evolving towards narrow strain specificity, perhaps because of drier habitats where fewer Frankia strains would be able to survive. Harsh conditions such as water-saturated soils near lakes, swamps or bogs that are typically acidic and low in oxygen may similarly lessen the diversity of Frankia strains present in the soil, perhaps limiting the pool of frankiae available for infection locally and, at a larger scale, for natural selection of symbiotic partnerships with host plants. Recent molecular ecological studies have also provided examples of Frankia strain sorting by soil environment within higher order cluster groupings of Frankia host specificity. Future frontiers for ecological research on Frankia and actinorhizal plants include the soil ecosystem and the genome of Frankia and its hosts. [source] From protozoa to mammalian cells: a new paradigm in the life cycle of intracellular bacterial pathogensENVIRONMENTAL MICROBIOLOGY, Issue 3 2000Minireview It is becoming apparent that several intracellular bacterial pathogens of humans can also survive within protozoa. This interaction with protozoa may protect these pathogens from harsh conditions in the extracellular environment and enhance their infectivity in mammals. This relationship has been clearly established in the case of the interaction between Legionella pneumophila and its protozoan hosts. In addition, the adaptation of bacterial pathogens to the intracellular life within the primitive eukaryotic protozoa may have provided them with the means to infect the more evolved mammalian cells. This is evident from the existence of several similarities, at both the phenotypic and the molecular levels, between the infection of mammalian and protozoan cells by L. pneumophila. Thus, protozoa appear to play a central role in the transition of bacteria from the environment to mammals. In essence, protozoa may be viewed as a ,biological gym', within which intracellular bacterial pathogens train for their encounters with the more evolved mammalian cells. Thus, intracellular bacterial pathogens have benefited from the structural and biochemical conservation of cellular processes in eukaryotes. The interaction of intracellular bacterial pathogens and protozoa highlights this conservation and may constitute a simplified model for the study of these pathogens and the evolution of cellular processes in eukaryotes. Furthermore, in addition to being environmental reservoirs for known intracellular pathogens of humans and animals, protozoa may be sources of emerging pathogenic bacteria. It is thus critical to re-examine the relationship between bacteria and protozoa to further our understanding of current human bacterial pathogenesis and, possibly, to predict the appearance of emerging pathogens. [source] Age-Related Microhabitat Segregation in Willow Tit Parus montanus Winter FlocksETHOLOGY, Issue 11 2000Lluís Brotons It is expected that through flexibility in behaviour, flock living birds respond to the asymmetries in resource access derived from dominance relationships. We analysed the microhabitat use of willow tits in winter flocks and assessed possible factors which shape habitat segregation between adults and juveniles in different temperature regimes. When foraging in mild conditions (ambient temperature >,0°C), flocks split up into subgroups with adults foraging in inner parts of trees more often than juveniles. However, no differences were recorded in the vertical position occupied in trees. In harsh conditions (< , 4°C), flocks re-united and juveniles further moved to outer parts of trees, increasing horizontal segregation between age classes. In mild conditions, vigilance behaviour was not related to the position of birds in trees, but in harsh conditions, scanning frequency was higher in outer parts of trees only for adults. In mild weather, juvenile position in trees was associated with body size and mass. The foraging microhabitat segregation detected in harsh conditions fits the age-related hoarding distribution previously described in the same population. This supports the hypothesis that hoarded food is important in determining future foraging habitat use. Adult preference and intraspecific competition for safer or richer inner parts of trees as foraging sites during harsh conditions seems to determine the habitat segregation between adults and juveniles. Furthermore, we suggest that in mild weather, when foraging in the absence of adults, juveniles balance the costs of using a potentially dangerous microhabitat with the benefits of building energetically cheap and large food reserves through hoarding. The expected patterns of microhabitat segregation may differ in parids, depending on whether predation risk or other factors such as food availability are the main factors controlling habitat quality. [source] Environmental variation and experience-related differences in the demography of the long-lived black-browed albatrossJOURNAL OF ANIMAL ECOLOGY, Issue 1 2007MARIE NEVOUX Summary 1It has been largely demonstrated that demographic performances of animals increase with age or experience as a result of an improvement of foraging skills, an increasing reproductive effort or a selection process. However, little is known about the age or experience-related response of populations to environmental variations. Theoretical studies consider that age-related variations of the performances are greater under more restricting conditions, but this has rarely been tested. 2We tested this hypothesis on a long-lived species, black browed albatross Thalassarche melanophrys Temminck, using a long-term capture,mark,recapture data set. We investigated the responses of a population to climate, by studying the effects of climatic factors and breeding experience on survival and breeding success. 3First-time breeders appear to be poorer performers compared with experienced adults, with lower reproductive success and lower survival. In addition, interannual variations of demographic traits were partly explained by climatic indices, reflecting environmental variations. The survival probability of black-browed albatrosses varied with experience and climate, and differences being greater under harsh conditions. By contrast, the reproductive success of inexperienced individuals was affected by climatic fluctuations in the same way as the experienced ones. 4First breeding event acts as a strong selective process on the highly heterogeneous class of inexperienced individuals, suggesting the increase in survival and breeding success with experience may mainly reflect a reduction in the heterogeneity among individual qualities. [source] Hydrothermal processing of rice husks: effects of severity on product distributionJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2008Rodolfo Vegas Abstract BACKGROUND: Treatment in aqueous media (hydrothermal or autohydrolysis reactions) is an environmentally friendly technology for fractionating lignocellulosic materials. Rice husks were subjected to hydrothermal processing under a variety of operational conditions to cause the selective breakdown of xylan chains, in order to assess the effects of reaction severity on the distribution of reaction products. RESULTS: The effects of severity (measured by the severity factor, R0) on the concentrations of the major autohydrolysis products (monosaccharides, xylo- and glucooligosaccharides, xylooligosaccharide substituents, acetic acid, acid-soluble lignin and elemental nitrogen) were assessed. The interrelationship between the severity of treatment and molecular weight distribution was established by high-performance size-exclusion chromatography. Selected samples were subjected to refining treatments as ethyl acetate extraction and ion exchange for refining purposes, and the concentrates were assayed by high-performance anion-exchange chromatography and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. CONCLUSIONS The protein equivalent of the products present in liquors accounted for 43 to 51% of the protein present in the raw rice husks. The concentrations of glucose (derived from starchy material) and arabinose (split from the xylan backbone) were fairly constant with severity. Even in treatments at low severity, high molecular weight compounds derived from xylan accounted for a limited part of the stoichiometric amount. Operating under harsh conditions, about 50% of the total xylan-derived compounds corresponded to fractions with a degree of polymerization (DP) < 9. After refining, saccharides accounted for more than 90% of the non-volatile components of the sample. The refined products showed a series of xylose oligomers up to about DP 13, and a series of acetylated xylose oligomers up to about DP 15. Copyright © 2008 Society of Chemical Industry [source] Synthesis and ring-opening (co)polymerization of L -lysine N -carboxyanhydrides containing labile side-chain protective groupsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2003Juan Rodríguez Hernández Abstract This contribution describes the synthesis and ring-opening (co)polymerization of several L -lysine N -carboxyanhydrides (NCAs) that contain labile protective groups at the ,-NH2 position. Four of the following L -lysine NCAs were investigated: N, -trifluoroacetyl- L -lysine N -carboxyanhydride, N, -(tert -butoxycarbonyl)- L -lysine N -carboxyanhydride, N, -(9-fluorenylmethoxycarbonyl)- L -lysine N -carboxyanhydride, and N, -(6-nitroveratryloxycarbonyl)- L -lysine N -carboxyanhydride. In contrast to the harsh conditions that are required for acidolysis of benzyl carbamate moieties, which are usually used to protect the ,-NH2 position of L -lysine during NCA polymerization, the protective groups of the L -lysine NCAs presented here can be removed under mildly acidic or basic conditions or by photolysis. As a consequence, these monomers may allow access to novel peptide hybrid materials that cannot be prepared from ,-benzyloxycarbonyl- L -lysine N -carboxyanhydride (Z-Lys NCA) because of side reactions that accompany the removal of the Z groups. By copolymerization of these L -lysine NCAs with labile protective groups, either with each other or with ,-benzyl- L -glutamate N -carboxyanhydride or Z-Lys NCA, orthogonally side-chain-protected copolypeptides with number-average degrees of polymerization ,20 were obtained. Such copolypeptides, which contain different side-chain protective groups that can be removed independently, are interesting for the synthesis of complex polypeptide architectures or can be used as scaffolds for the preparation of synthetic antigens or protein mimetics. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1167,1187, 2003 [source] Biodiversity in microbial communities: system scale patterns and mechanismsMOLECULAR ECOLOGY, Issue 7 2009J. JACOB PARNELL Abstract The relationship between anthropogenic impact and the maintenance of biodiversity is a fundamental question in ecology. The emphasis on the organizational level of biodiversity responsible for ecosystem processes is shifting from a species-centred focus to include genotypic diversity. The relationship between biodiversity measures at these two scales remains largely unknown. By stratifying anthropogenic effects between scales of biodiversity of bacterial communities, we show a statistically significant difference in diversity based on taxonomic scale. Communities with intermediate species richness show high genotypic diversity while speciose and species-poor communities do not. We propose that in species-poor communities, generally comprising stable yet harsh conditions, physiological tolerance and competitive trade-offs limit both the number of species that occur and the loss of genotypes due to decreases in already constrained fitness. In species-rich communities, natural environmental conditions result in well-defined community structure and resource partitioning. Disturbance of these communities disrupts niche space, resulting in lower genotypic diversity despite the maintenance of species diversity. Our work provides a model to inform future research about relationships between species and genotypic biodiversity based on determining the biodiversity consequences of changing environmental context. [source] Structural stability and heat-induced conformational change of two complement inhibitors: C4b-binding protein and factor HPROTEIN SCIENCE, Issue 5 2004Lena Kask C4BP, C4b-binding protein; FH, factor H; CCP, complement control protein; CD, circular dichroism; FTIR, Fourier transform-infrared spectroscopy; PT, prothrombin; VCP, vaccinia virus complement control protein Abstract The complement inhibitors C4b-binding protein (C4BP) and factor H (FH) both consist of complement control protein (CCP) domains. Here we examined the secondary structure of both proteins by circular dichroism and Fourier-transform infrared technique at temperatures ranging from 30°C,90°C. We found that predominantly ,-sheet structure of both proteins was stable up to 70°C, and that a reversible conformational change toward ,-helix was apparent at temperatures ranging from 70°C to 90°C. The ability of both proteins to inhibit complement was not impaired after incubation at 95°C, exposure to extreme pH conditions, and storage at room temperature for several months. Similar remarkable stability was previously observed for vaccinia virus control protein (VCP), which is also composed of CCP domains; it therefore seems to be a general property of CCP-containing proteins. A typical CCP domain has a hydrophobic core, which is wrapped in ,-sheets and stabilized by two disulphide bridges. How the CCP domains tolerate harsh conditions is unclear, but it could be due to a combination of high content of prolines, hydrophobic residues, and the presence of two disulphide bridges within each domain. These findings are of interest because CCP-containing complement inhibitors have been proposed as clinical agents to be used to control unwanted complement activation that contributes to many diseases. [source] Birth seasonality and interbirth interval of captive Rhinopithecus bietiAMERICAN JOURNAL OF PRIMATOLOGY, Issue 5 2006Liang-Wei Cui Abstract This study, which is based on 10 years of birth records, shows that black-and-white snub-nosed monkeys (Rhinopithecus bieti) in captivity display marked birth seasonality. The birth season starts in December and ends in June, with a peak from March to May, and a median birth date of April 10. More male infants than female ones are born in captivity. More males were born at the Kunming Institute of Zoology (KIZ) than at the Kunming Zoo (KZ). Of 17 interbirth intervals (IBIs), 29% were from females that had lost an infant at <1 year of age or experienced stillbirth, and 71% were from females whose infant survived more than 1 year. The mean IBI for the former group (428±SD 87 days) was significantly shorter than that for the latter group (706±71 days), in agreement with reports of other Colobine species. Infant mortality was lower in captivity than in the field, which may reflect the relatively stable food availability and climate in captivity compared to the harsh conditions in the wild. Am. J. Primatol. 68:1,7, 2006. © 2005 Wiley-Liss, Inc. [source] The Crisis of Social Reproduction among Migrant Workers: Interrogating the Role of Migrant Civil SocietyANTIPODE, Issue 1 2010Nina Martin Abstract:, Transformations in urban economies are leading to the growth of jobs where labor and employment laws are routinely violated. Workers in these jobs are subject to harsh conditions such as low wages, hazardous work sites, and retaliation for speaking up. Many of these workers are undocumented migrants who are in a weak position to make demands on their employers or to request government assistance. These workers often turn to migrant civil society organizations for help with the multiple conflicts they face at work. Drawing on case studies of nonprofit organizations in Chicago, this paper focuses on the role of such organizations in the social reproduction of the migrant workforce. I posit that such organizations are integral to the functioning of the informal economy because the wide range of programs and services that they provide are essential to the social reproduction of migrant workers. [source] Homogeneous Stabilization of Pt Nanoparticles in Dendritic Core,Multishell Architectures: Application in Catalytic Hydrogenation Reactions and RecyclingCHEMCATCHEM, Issue 7 2010Juliane Keilitz Abstract Core,multishell architectures are a new approach to homogeneously stabilize metal nanoparticles for harsh conditions. Herein, we present the synthesis and stabilization of Pt nanoparticles in dendritic core,multishell polymers and their application in hydrogenation reactions. The successful recycling of the catalyst was demonstrated for the hydrogenation of methyl crotonate 1 and was either achieved by ultrafiltration or in a two-phase system for at least 14,cycles. Thereby, the total turnover number (TON) was increased to 22,000. In the recycling experiments, low metal leaching into the product (as low as 0.3,ppm) was detected. Additionally, the selective hydrogenation of isophorone 3 was investigated and selectivities of 99:1 for CC versus CO hydrogenation were achieved. [source] Novel Process Windows , Gate to Maximizing Process Intensification via Flow ChemistryCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 11 2009V. Hessel Abstract Driven by the economics of scale, the size of reaction vessels as the major processing apparatus of the chemical industry has became bigger and bigger [1, 2]. Consequently, the efforts for ensuring mixing and heat transfer have also increased, as these are scale dependent. This has brought vessel operation to (partly severe) technical limits, especially when controlling harsh conditions, e.g., due to large heat releases. Accordingly, processing at a very large scale has resulted in taming of the chemistry involved in order to slow it down to a technically controllable level. Therefore, reaction paths that already turned out too aggressive at the laboratory scale are automatically excluded for later scale-up, which constitutes a common everyday confinement in exploiting chemical transformations. Organic chemists are barely conscious that even the small-scale laboratory protocols in their textbooks contain many slow, disciplined chemical reactions. Operations such as adding a reactant drop by drop in a large diluted solvent volume have become second nature, but are not intrinsic to the good engineering of chemical reactions. These are intrinsic to the chemical apparatus used in the past. In contrast, today's process intensification [3,12] and the new flow-chemistry reactors on the micro- and milli-scale [13,39] allow such limitations to be overcome, and thus, enable a complete, ab-initio type rethinking of the processes themselves. In this way, space-time yields and the productivity of the reactor can be increased by orders of magnitude and other dramatic performance step changes can be achieved. A hand-in-hand design of the reactors and process re-thinking is required to enable chemistry rather than subduing chemistry around the reactor [40]. This often leads to making use of process conditions far from conventional practice, under harsh environments, a procedure named here as Novel Process Windows. [source] Chancen und Grenzen der Mikroverkapselung in der modernen LebensmittelverarbeitungCHEMIE-INGENIEUR-TECHNIK (CIT), Issue 11 2003B. Kunz Prof. Dr. Abstract Die Mikroverkapselung ist in der Lebensmittelindustrie immer bedeutender geworden, besonders im Bereich der funktionellen Lebensmittel und der Nahrungsergänzungsmittel. Die Verkapselung dient dem Schutz des eingeschlossenen Materials vor schädlichen Einflüssen. Das Verfahren birgt ein großes Potenzial für die Entwicklung neuer Produkte. Der Einschluss von ernährungsphysiologisch positiv zu bewertenden Substanzen führt zu Produkten mit einem zusätzlichen gesundheitlichen Nutzen (Added Value). Obwohl die Mikroverkapselung sich erst am Anfang ihrer Entwicklung befindet, ist es sinnvoll, die Chancen und Risiken dieser vielversprechenden Technologie abzuschätzen. Der Beitrag gibt einen Überblick über die Möglichkeiten der Mikroverkapselung in der Lebensmittelindustrie und zeigt zugleich die Grenzen der neuen Technologie auf. Chances and Limits of Microencapsulation in Progressive Food Industry Microencapsulation has gained importance in food technology especially in coevolution with the developments in functional food and dietary supplements. The aim of microencapsulation is to protect the core material from harsh conditions, so that it keeps its nutritional value. Although microencapsulation is in an early state of development, it seems to be necessary to evaluate the chances and risks of this technology. Because of the effects which can be reached by using the microencapsulation process there seems to be a great potential for the developments of new products or products with an added value. This contribution reviews the chances of microencapsulation in the food industry and tries to present and evaluate the limits of this new technology. [source] | |||||||||||||