1,164 research outputs found
Non-Newtonian fluid flow through three-dimensional disordered porous media
We investigate the flow of various non-Newtonian fluids through
three-dimensional disordered porous media by direct numerical simulation of
momentum transport and continuity equations. Remarkably, our results for
power-law (PL) fluids indicate that the flow, when quantified in terms of a
properly modified permeability-like index and Reynolds number, can be
successfully described by a single (universal) curve over a broad range of
Reynolds conditions and power-law exponents. We also study the flow behavior of
Bingham fluids described in terms of the Herschel-Bulkley model. In this case,
our simulations reveal that the interplay of ({\it i}) the disordered geometry
of the pore space, ({\it ii}) the fluid rheological properties, and ({\it iii})
the inertial effects on the flow is responsible for a substantial enhancement
of the macroscopic hydraulic conductance of the system at intermediate Reynolds
conditions. This anomalous condition of ``enhanced transport'' represents a
novel feature for flow in porous materials.Comment: 5 pages, 5 figures. This article appears also in Physical Review
Letters 103 194502 (2009
Editorial foreword: Angiogenesis: Cells, tissues and organs
On the occasion of his 90th birthday, this Special Issue is dedicated to Professor Robert Auerbach. Born 1929 in Berlin, Germany, he and his family escaped Nazi Germany in 1939 and emigrated to the United States, where he became a zoologist and ultimately Professor and Director of the Developmental Biology Training Program at the Department of Zoology, Madison, University of Wisconsin, USA. In Auerbach's laboratory, students and scientists of many different nations, including politically persecuted ones, harmoniously worked together on different aspects of angiogenesis. One of the hallmarks of Auerbach's career as a scientist was and is his generosity towards others, sharing his equipment and ideas freely, his integrity and his collegiality. His significant contributions to angiogenesis and tumour research include the finding that angiogenesis in tumours can occur even after their irradiation (Auerbach, Arensman, Kubai, & Folkman, 1975) and an explanation of organ selectivity in the spread of metastasizing cancer cells (Auerbach, 1988). Through his outstanding papers on in vitro methods in angiogenesis research, he also supported animal welfare (Alby & Auerbach, 1984; Auerbach, Lewis, Shinners, Kubai, & Akhtar, 2003; Gumkowski, Kaminska, Kaminski, Morrissey, & Auerbach, 1987; Obeso, Weber, & Auerbach, 1990)
Elevational richness patterns of sphingid moths support area effects over climatic drivers in a nearâglobal analysis
Not sure if this is the pre-refereed or final submitted version.Aim
We test hypotheses on the environmental control of elevational richness patterns of sphingid moths for their global applicability and generality. Specifically, we compare effects of area with climateârelated drivers, such as primary productivity and temperature, while also considering direct effects of precipitation.
Major taxa
Sphingid moths (Lepidoptera).
Location
Eightyâsix mountain ranges of the Old World and the Australia/Pacific region, from Scandinavia and Siberia through the African and Australasian tropics to South Africa and Southern Australia.
Methods
We used a large compilation of point locality records for 744 species, in addition to fineâgrained range maps derived from species distribution modelling of these records, to characterize the elevational pattern of species richness in 86 customâdelineated mountain regions. For both types of data, we compared the effects of environmental drivers on richness by comparing standardized coefficients of multivariate models for pooled data after accounting for betweenâregion variation in richness.
Results
We observed varying patterns of elevational richness across the research region, with a higher prevalence of midpeaks in arid regions. We found overwhelming support for area as a main determinant of richness, modulated by temperature and productivity, whereas we detected no effect of precipitation.
Main conclusions
Area, productivity and temperature are the main environmental predictors explaining a large proportion of variability in sphingid richness. This is consistent not only with other elevational studies, but also with empirical and theoretical biodiversity research in a nonâelevational context (with the caveat of some unresolved issues in elevational area effects). However, distinct differences in elevational patterns remain even within the same mountain ranges when comparing with other Lepidoptera, that is, geometrid moths, which highlights the importance of understanding higher clade differentiation in ecological responses, within insects and in other groups.© 2019 John Wiley & Sons Ltd. This is the pre-peer reviewed version of the following article: BĂ€rtschi, F, McCain, CM, BallesterosâMejia, L, Kitching, IJ, Beerli, N, Beck, J. Elevational richness patterns of sphingid moths support area effects over climatic drivers in a nearâglobal analysis. Global Ecol Biogeogr. 2019; 28: 917â 927. https://doi.org/10.1111/geb.12903, which has been published in final form at doi:10.1111/geb.12903. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.
Tryptophan Degradation in Women with Breast Cancer: A Pilot Study
Altered tryptophan metabolism and indoleamine 2,3-dioxygenase activity are linked to cancer development and progression. In addition, these biological factors have been associated with the development and severity of neuropsychiatric syndromes, including major depressive disorder. However, this biological mechanism associated with both poor disease outcomes and adverse neuropsychiatric symptoms has received little attention in women with breast cancer. Therefore, a pilot study was undertaken to compare levels of tryptophan and other proteins involved in tryptophan degradation in women with breast cancer to women without cancer, and secondarily, to examine levels in women with breast caner over the course of chemotherapy
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Choice consequences: salinity preferences and hatchling survival in the mangrove rivulus (Kryptolebias marmoratus).
In heterogeneous environments, mobile species should occupy habitats in which their fitness is maximized. Mangrove rivulus fish inhabit mangrove ecosystems where salinities range from 0 to 65â
ppt, but are most often collected from areas with salinities of âŒ25â
ppt. We examined the salinity preference of mangrove rivulus in a lateral salinity gradient, in the absence of predators and competitors. Fish could swim freely for 8â
h throughout the gradient with chambers containing salinities ranging from 5 to 45â
ppt (or 25â
ppt throughout in the control). We defined preference as the salinity in which the fish spent most of their time, and also measured preference strength, latency to begin exploring the arena, and number of transitions between chambers. To determine whether these traits were repeatable, each fish experienced three trials. Mangrove rivulus spent a greater proportion of time in salinities lower (5-15â
ppt) than they occupy in the wild. Significant among-individual variation in the (multivariate) behavioral phenotype emerged when animals experienced the gradient, indicating strong potential for selection to drive behavioral evolution in areas with diverse salinity microhabitats. We also showed that mangrove rivulus had a significantly greater probability of laying eggs in low salinities compared with control or high salinities. Eggs laid in lower salinities also had higher hatching success compared with those laid in higher salinities. Thus, although mangrove rivulus can tolerate a wide range of salinities, they prefer low salinities. These results raise questions about factors that prevent mangrove rivulus from occupying lower salinities in the wild, whether higher salinities impose energetic costs, and whether fitness changes as a function of salinity
Choice consequences: salinity preferences and hatchling survival in the mangrove rivulus (Kryptolebias marmoratus).
In heterogeneous environments, mobile species should occupy habitats in which their fitness is maximized. Mangrove rivulus fish inhabit mangrove ecosystems where salinities range from 0 to 65â
ppt, but are most often collected from areas with salinities of âŒ25â
ppt. We examined the salinity preference of mangrove rivulus in a lateral salinity gradient, in the absence of predators and competitors. Fish could swim freely for 8â
h throughout the gradient with chambers containing salinities ranging from 5 to 45â
ppt (or 25â
ppt throughout in the control). We defined preference as the salinity in which the fish spent most of their time, and also measured preference strength, latency to begin exploring the arena, and number of transitions between chambers. To determine whether these traits were repeatable, each fish experienced three trials. Mangrove rivulus spent a greater proportion of time in salinities lower (5-15â
ppt) than they occupy in the wild. Significant among-individual variation in the (multivariate) behavioral phenotype emerged when animals experienced the gradient, indicating strong potential for selection to drive behavioral evolution in areas with diverse salinity microhabitats. We also showed that mangrove rivulus had a significantly greater probability of laying eggs in low salinities compared with control or high salinities. Eggs laid in lower salinities also had higher hatching success compared with those laid in higher salinities. Thus, although mangrove rivulus can tolerate a wide range of salinities, they prefer low salinities. These results raise questions about factors that prevent mangrove rivulus from occupying lower salinities in the wild, whether higher salinities impose energetic costs, and whether fitness changes as a function of salinity
Quantification of habitat fragmentation reveals extinction risk in terrestrial mammals
Although habitat fragmentation is often assumed to be a primary driver of extinction, global patterns of fragmentation and its relationship to extinction risk have not been consistently quantified for any major animal taxon. We developed high-resolution habitat fragmentation models and used phylogenetic comparative methods to quantify the effects of habitat fragmentation on the world's terrestrial mammals, including 4,018 species across 26 taxonomic Orders. Results demonstrate that species with more fragmentation are at greater risk of extinction, even after accounting for the effects of key macroecological predictors, such as body size and geographic range size. Species with higher fragmentation had smaller ranges and a lower proportion of high-suitability habitat within their range, andmost high-suitability habitat occurred outside of protected areas, further elevating extinction risk. Our models provide a quantitative evaluation of extinction risk assessments for species, allow for identification of emerging threats in species not classified as threatened, and provide maps of global hotspots of fragmentation for the world's terrestrial mammals. Quantification of habitat fragmentation will help guide threat assessment and strategic priorities for global mammal conservation
Connexin43 ablation in foetal atrial myocytes decreases electrical coupling, partner connexins, and sodium current
Aims Remodelling and regional gradients in expression of connexins (Cx) are thought to contribute to atrial electrical dysfunction and atrial fibrillation. We assessed the effect of interaction between Cx43, Cx40, and Cx45 on atrial cell-to-cell coupling and inward Na current (INa) in engineered pairs of atrial myocytes derived from wild-type mice (Cx43+/+) and mice with genetic ablation of Cx43 (Cx43â/â). Methods and results Cell pairs were engineered by microcontact printing from atrial Cx43+/+ and Cx43â/â murine myocytes (1 day before birth, 3-5 days in culture). Dual and single voltage clamp were used to measure intercellular electrical conductance, gj, and its dependence on transjunctional voltage, Vj, single gap junction channel conductances, and INa. 3D reconstructions of Cx43, Cx40, and Cx45 immunosignals in gap junctions were made from confocal slices. Full genetic Cx43 ablation produced a decrease in immunosignals of Cx40 to 62 ± 10% (mean ± SE; n= 17) and Cx45 to 66 ± 8% (n= 16). Gj decreased from 80 ± 9 nS (Cx43+/+, n= 17) to 24 ± 2 nS (Cx43â/â, n= 35). Single channel analysis showed a shift in the main peak of the channel histogram from 49 ± 1.7 nS (Cx43+/+) to 67 ± 1.8 nS (Cx43â/â) with a second minor peak appearing at 27 ± 1.5 pS. The dependence of gj on Vj decreased with Cx43 ablation. Importantly, peak INa decreased from â350 ± 44 pA/pF (Cx43+/+) to â154 ± 28 pA/pF (Cx43â/â). Conclusions The dependence of Cx40, Cx45, and INa on Cx43 expression indicates a complex interaction between connexins and INa in the atrial intercalated discs that is likely to be of relevance for arrhythmogenesi
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