742 resultados para Virtual communities of practice
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[by Joseph Herman Hertz]
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Background Tools to explore large compound databases in search for analogs of query molecules provide a strategically important support in drug discovery to help identify available analogs of any given reference or hit compound by ligand based virtual screening (LBVS). We recently showed that large databases can be formatted for very fast searching with various 2D-fingerprints using the city-block distance as similarity measure, in particular a 2D-atom pair fingerprint (APfp) and the related category extended atom pair fingerprint (Xfp) which efficiently encode molecular shape and pharmacophores, but do not perceive stereochemistry. Here we investigated related 3D-atom pair fingerprints to enable rapid stereoselective searches in the ZINC database (23.2 million 3D structures). Results Molecular fingerprints counting atom pairs at increasing through-space distance intervals were designed using either all atoms (16-bit 3DAPfp) or different atom categories (80-bit 3DXfp). These 3D-fingerprints retrieved molecular shape and pharmacophore analogs (defined by OpenEye ROCS scoring functions) of 110,000 compounds from the Cambridge Structural Database with equal or better accuracy than the 2D-fingerprints APfp and Xfp, and showed comparable performance in recovering actives from decoys in the DUD database. LBVS by 3DXfp or 3DAPfp similarity was stereoselective and gave very different analogs when starting from different diastereomers of the same chiral drug. Results were also different from LBVS with the parent 2D-fingerprints Xfp or APfp. 3D- and 2D-fingerprints also gave very different results in LBVS of folded molecules where through-space distances between atom pairs are much shorter than topological distances. Conclusions 3DAPfp and 3DXfp are suitable for stereoselective searches for shape and pharmacophore analogs of query molecules in large databases. Web-browsers for searching ZINC by 3DAPfp and 3DXfp similarity are accessible at www.gdb.unibe.ch webcite and should provide useful assistance to drug discovery projects.
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INTRODUCTION External beam radiotherapy (EBRT), with or without androgen deprivation therapy (ADT), is an established treatment option for nonmetastatic prostate cancer. Despite high-level evidence from several randomized trials, risk group stratification and treatment recommendations vary due to contradictory or inconclusive data, particularly with regard to EBRT dose prescription and ADT duration. Our aim was to investigate current patterns of practice in primary EBRT for prostate cancer in Switzerland. MATERIALS AND METHODS Treatment recommendations on EBRT and ADT for localized and locally advanced prostate cancer were collected from 23 Swiss radiation oncology centers. Written recommendations were converted into center-specific decision trees, and analyzed for consensus and differences using a dedicated software tool. Additionally, specific radiotherapy planning and delivery techniques from the participating centers were assessed. RESULTS The most commonly prescribed radiation dose was 78 Gy (range 70-80 Gy) across all risk groups. ADT was recommended for intermediate-risk patients for 6 months in over 80 % of the centers, and for high-risk patients for 2 or 3 years in over 90 % of centers. For recommendations on combined EBRT and ADT treatment, consensus levels did not exceed 39 % in any clinical scenario. Arc-based intensity-modulated radiotherapy (IMRT) is implemented for routine prostate cancer radiotherapy by 96 % of the centers. CONCLUSION Among Swiss radiation oncology centers, considerable ranges of radiotherapy dose and ADT duration are routinely offered for localized and locally advanced prostate cancer. In the vast majority of cases, doses and durations are within the range of those described in current evidence-based guidelines.
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Photophysiological processes as well as uptake characteristics of iron and inorganic carbon were studied in inshore phytoplankton assemblages of the Western Antarctic Peninsula (WAP) and offshore assemblages of the Drake Passage. Chlorophyll a concentrations and primary productivity decreased from in- to offshore waters. The inverse relationship between low maximum quantum yields of photochemistry in PSII (Fv/Fm) and large sizes of functional absorption cross sections (sigma PSII) in offshore communities indicated iron-limitation. Congruently, the negative correlation between Fv/Fm values and iron uptake rates across our sampling locations suggest an overall better iron uptake capacity in iron-limited pelagic phytoplankton communities. Highest iron uptake capacities could be related to relative abundances of the haptophyte Phaeocystis antarctica. As chlorophyll a-specific concentrations of humic-like substances were similarly high in offshore and inshore stations, we suggest humic-like substances may play an important role in iron chemistry in both coastal and pelagic phytoplankton assemblages. Regarding inorganic carbon uptake kinetics, the measured maximum short-term uptake rates (Vmax(CO2)) and apparent half-saturation constants (K1/2(CO2)) did not differ between offshore and inshore phytoplankton. Moreover, Vmax(CO2) and K1/2(CO2) did not exhibit any CO2-dependent trend over the natural pCO2 range from 237 to 507 µatm. K1/2(CO2) strongly varied among the sampled phytoplankton communities, ranging between 3.5 and 35.3 µmol/L CO2. While in many of the sampled phytoplankton communities, the operation of carbon-concentrating mechanisms (CCMs) was indicated by low K1/2(CO2) values relative to ambient CO2 concentrations, some coastal sites exhibited higher values, suggesting down-regulated CCMs. Overall, our results demonstrate a complex interplay between photophysiological processes, iron and carbon uptake of phytoplankton communities of the WAP and the Drake Passage.
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There are high levels of uncertainty about how coastal ecosystems will be affected by rapid ocean acidification caused by anthropogenic CO2, due to a lack of data. The few experiments to date have been short-term (< 1 year) and reveal mixed responses depending on the species examined and the culture conditions used. It is difficult to carry out long-term manipulations of CO2 levels, therefore areas with naturally high CO2 levels are being used to help understand which species, habitats and processes are resilient to the effects of ocean acidification, and which are adversely affected. Here we describe the effects of increasing CO2 levels on macroalgal communities along a pH gradient caused by volcanic vents. Macroalgal habitat differed at taxonomic and morphological group levels along a pH gradient. The vast majority of the 101 macroalgal species studied were able to grow with only a 5% decrease in species richness as the mean pH fell from 8.1 to 7.8. However, this small fall in species richness was associated with shifts in community structure as the cover of turf algae decreased disproportionately. Calcitic species were significantly reduced in cover and species richness whereas a few non-calcified species became dominant. At mean pH 6.7, where carbonate saturation levels were < 1, calcareous species were absent and there was a 72% fall in species richness. Under these extremely high CO2 conditions a few species dominated the simplified macroalgal assemblage and a very few exhibited enhanced reproduction, although high CO2 levels seemed to inhibit reproduction in others. Our data show that many macroalgal species are tolerant of long-term elevations in CO2 levels but that macroalgal habitats are altered significantly as pH drops, contributing to a scant but growing body of evidence concerning the long-term effects of CO2 emissions in vegetated marine systems. Further study is now needed to investigate whether the observed response of macroalgal communities can be replicated in different seasons and from a range of geographical regions for incorporation into global modelling studies to predict effects of CO2 emissions on Earth's ecosystems.
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The present study analysed the megabenthic diversity in subtidal soft bottoms and assessed the main environmental drivers of megabenthic community organisation along the Algarve coast (southern Portugal). We tested the hypothesis that megabenthic communities respond to the same environmental drivers than macrofauna. We found that similar to macrofauna, megafaunal communities were organised in relation to the depth of closure, light reaching the bottom, and the hydrodynamic conditions related with exposure within the shallower areas. The influence of the main river outflow prevailed over other drivers, but only up to 9 m depth. We found that seven different spatial units should be considered, each characterised by different indicator species. Additionally, among a total of 412 taxa collected between 4 and 50 m depth, we provide the characteristics of the 64 commonest species in terms of occurrence, frequency, distribution, abundance, bathymetric and sedimentary preferences, which constitutes most valuable information for ecosystem modelling. Megabenthic alpha diversity decreased with depth, contrary to evenness and was higher in the proximity of the river Guadiana and in highly exposed shores. We conclude that the megafauna, which is significantly quicker to collect and analyse, can provide an accurate alternative to macrofauna sampling, as their communities are shaped by the same drivers.
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Zonal plant communities of the Ribesalbes-Alcora basin (La Rinconada mine, eastern Spain) during the early Miocene