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Improving assessment and modelling of climate change impacts on global terrestrial biodiversity
No full textUnderstanding how species and ecosystems respond to climate change has become a major focus of ecology and conservation biology. Modelling approaches provide important tools for making future projections, but current models of the climate-biosphere interface remain overly simplistic, undermining the credibility of projections. We identify five ways in which substantial advances could be made in the next few years: (i) improving the accessibility and efficiency of biodiversity monitoring data, (ii) quantifying the main determinants of the sensitivity of species to climate change, (iii) incorporating community dynamics into projections of biodiversity responses, (iv) accounting for the influence of evolutionary processes on the response of species to climate change, and (v) improving the biophysical rule sets that define functional groupings of species in global model
Ribozyme catalysis with a twist: active state of the twister ribozyme in solution predicted from molecular simulation
No full textWe present results from molecular dynamics simulations and free energy calculations of the twister ribozyme at different stages along the reaction path to gain insight into its mechanism. The results, together with recent biochemical experiments, provide support for a mechanism involving general-acid catalysis by a conserved adenine residue in the active site. Although adenine has been previously implicated as a general acid acting through the N1 position in other ribozymes such as the hairpin and VS ribozymes, in the twister ribozyme there may be a twist. Biochemical experiments suggest that general acid catalysis may occur through the N3 position, which has never before been implicated in this role; however, currently, there is a lack of a detailed structural model for the active state of the twister ribozyme in solution that is consistent with these and other experiments. Simulations in a crystalline environment reported here are consistent with X-ray crystallographic data, and suggest that crystal packing contacts trap the RNA in an inactive conformation with U-1 in an extruded state that is incompatible with an in-line attack to the scissile phosphate. Simulations in solution, on the other hand, reveal this region to be dynamic and able to adopt a conformation where U-1 is stacked with G33. In this state, the nucleophile is in line with the scissile phosphate, and the N1 position of G33 and N3 position of A1 are poised to act as a general base and acid, respectively, as supported by mutational experiments. Free energy calculations further predict the electrostatic environment causes a shift of the microscopic pKa at the N3 position of A1 toward neutrality by approximately 5 pKa units. These results offer a unified interpretation of a broad range of currently available experimental data that points to a novel mode of general acid catalysis through the N3 position of an adenine nucleobase, thus expanding the repertoire of known mechanistic strategies employed by small nucleolytic ribozymes.Peer reviewe
Lytic activity by temperate phages of Pseudomonas aeruginosa in long-term cystic fibrosis chronic lung infections
Get PDFPseudomonas aeruginosa is the most common bacterial pathogen infecting the lungs of cystic
fibrosis (CF) patients. The transmissible Liverpool epidemic strain (LES) harbours multiple inducible
prophages (LESu2; LESu3; LESu4; LESu5; and LESu6), some of which are known to confer a
competitive advantage in an in vivo rat model of chronic lung infection. We used quantitative PCR
(Q-PCR) to measure the density and dynamics of all five LES phages in the sputa of 10 LES-infected
CF patients over a period of 2 years. In all patients, the densities of free-LES phages were positively
correlated with the densities of P. aeruginosa, and total free-phage densities consistently exceeded
bacterial host densities 10–100-fold. Further, we observed a negative correlation between the phageto-
bacterium ratio and bacterial density, suggesting a role for lysis by temperate phages in
regulation of the bacterial population densities. In 9/10 patients, LESu2 and LESu4 were the most
abundant free phages, which reflects the differential in vitro induction properties of the phages.
These data indicate that temperate phages of P. aeruginosa retain lytic activity after prolonged
periods of chronic infection in the CF lung, and suggest that temperate phage lysis may contribute
to regulation of P. aeruginosa density in vivo
Le désert
No full textPoesie de M. A. Colin. Musique de Felicien DavidOrnée du portrait de F. David. - Mit LibrettoVorlageform des Erscheinungsvermerks: MAYENCE ANVERS ET BRUXELLES chez les fils de B. Schott. paris au Bureau Central de Musique. Londres, chez Chappell et Beale..
Public Policy in a Private Arena: The Case of Vocational Education and Training
Get PDFM.21586-1998 Colin Crouch. 30 cm. This paper is based on a seminar that he presented at the Center for Advanced Study in the Social Sciences of the Juan March Institute, Madrid, on 9 May 1995, entitled Diversity in Modern Capitalism: Examples from Vocational Education." -- T.p. Includes bibliographical references (p. 35-37
Orbit design for future SpaceChip swarm missions in a planetary atmosphere
No full textThe effect of solar radiation pressure and atmospheric drag on the orbital dynamics of satellites-on-a-chip (SpaceChips) is exploited to design equatorial long-lived orbits about the oblate Earth. The orbit energy gain due to asymmetric solar radiation pressure, considering the Earth's shadow, is used to balance the energy loss due to atmospheric drag. Future missions for a swarm of SpaceChips are proposed, where a number of small devices are released from a conventional spacecraft to perform spatially distributed measurements of the conditions in the ionosphere and exosphere. It is shown that the orbit lifetime can be extended and indeed selected through solar radiation pressure and the end-of-life re-entry of the swarm can be ensured, by exploiting atmospheric drag
Vascular healing : cell biology and rheologic factors
No full textIssued as Progress report summary, Project E-25-M44 (continued by E-25-M80)Progress report summary has author: Colin J. Schwart
Vascular healing : cell biology and rheologic factors
No full textIssued as Progress report summary, Project no. E-25-M80 (continued by E-25-M44; continues E-25-614)Progress report summary has author: Colin J. Schwart
Trends and themes in African Ornithology
Get PDFOrnithology in Africa has a long history. I review trends in the ornithological literature since 1990 within the context of the 14th Pan-African Ornithological Congress. Using full text searches of papers on PubMed® and abstracts from main ornithological journals I found that most papers referencing African bird species are focused on medicalrelated research questions. Restricting the literature search to journals African ornithologists are most likely to publish in, I found 2 279 relevant papers. These describe work on 29% of African bird species from 82% of African bird families, in all but two African countries. Overall output has increased slightly over time, with more papers tackling more research topics. Most popular research topics were demography, conservation and climate, with disease ecology, physiology and ecological processes the least researched topics. I found that while many authors with African affiliations publish papers, outside of South Africa very few African-based authors reliably publish in the international research literature, perhaps indicating difficulties in establishing a productive research career in much of Africa. I conclude with a call to overseas ornithologists working in Africa and to organisations funding research in Africa to work together to build capacity outside of the few established research centres
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