Dynamics of osmosis in a porous medium.

We derive from kinetic theory, fluid mechanics and thermodynamics the minimal continuum-level equations governing the flow of a binary, non-electrolytic mixture in an isotropic porous medium with osmotic effects. For dilute mixtures, these equations are linear and in this limit provide a theoretical basis for the widely used semi-empirical relations of Kedem & Katchalsky (Kedem & Katchalsky 1958 Biochim. Biophys. Acta 27, 229-246 (doi:10.1016/0006-3002(58)90330-5), which have hitherto been validated experimentally but not theoretically. The above linearity between the fluxes and the driving forces breaks down for concentrated or non-ideal mixtures, for which our equations go beyond the Kedem-Katchalsky formulation. We show that the heretofore empirical solute permeability coefficient reflects the momentum transfer between the solute molecules that are rejected at a pore entrance and the solvent molecules entering the pore space; it can be related to the inefficiency of a Maxwellian demi-demon.J.C. acknowledges the financial support of Spanish MICINN grant no. FIS2013-48444-C2-2-P, and thanks Pembroke College, Cambridge, for a visiting fellowship. This work was performed within the framework of the NASA Astrobiological Institute focus group on thermodynamics, disequilibrium and evolution (TDE).This is the final published version. It first appeared at http://rsos.royalsocietypublishing.org/content/1/3/140352

Increased methane emissions from deep osmotic and buoyant convection beneath submarine seeps as climate warms.

High speeds have been measured at seep and mud-volcano sites expelling methane-rich fluids from the seabed. Thermal or solute-driven convection alone cannot explain such high velocities in low-permeability sediments. Here we demonstrate that in addition to buoyancy, osmotic effects generated by the adsorption of methane onto the sediments can create large overpressures, capable of recirculating seawater from the seafloor to depth in the sediment layer, then expelling it upwards at rates of up to a few hundreds of metres per year. In the presence of global warming, such deep recirculation of seawater can accelerate the melting of methane hydrates at depth from timescales of millennia to just decades, and can drastically increase the rate of release of methane into the hydrosphere and perhaps the atmosphere

Association of sul genes and class 1 integron with trimethoprimsulfamethoxazole Resistance in Stenotrophomonas maltophilia clinical isolates in Zagazig University, Egypt

Background: Stenotrophomonas maltophilia (S.maltophilia) is an intrinsically drug resistant    opportunistic pathogen associated with serious infections in humans. Acquired resistance to   trimethoprim-sulfamethoxazole (SXT,co-trimoxazole), the main stay of therapy against S. maltophilia ,has made its treatment more problematic. Objectives: This work aimed to determine the occurrence  of SXT resistance among S. maltophilia isolated from Zagazig University Hospitals in Egypt and to   assess the association of sul genes and integron1 with SXT-resistant isolates.Material and Methods: Thirty-two S.maltophilia isolates were identified in this study during the   period from 2013 to 2015. Screening of SXT-resistant isolates was done by Kirby-Bauer method.  Minimum inhibitory concentration(MIC) values for SXT were determined by agar dilution. S. maltophilia isolates were tested for the presence of sul1, sul2, sul3, and int 1 genes by multiplex polymerase chain reaction.Results: Amongst the 32 S. maltophilia isolates, 12(37.5%) were resistant to SXT. All SXT-resistant isolates were found to harbor sul1 gene and integron1. One of these isolates had sul2 gene  (1/12,8.3%). Meanwhile, sul3 gene was not detected in any of the SXT-resistant isolates. Only 2 of the 20 SXT-susceptible isolates was found to yield positive PCR results for sul1 gene, one of them gave positive result for class 1 Integron. The association of sul genes and Integrin1 with resistance to SXT had a statistically significant difference( P<0.0001). Conclusion: Our study indicated a high frequency of SXT resistance among clinical S.maltophilia isolates from Zagazig University Hospitals, in which sul genes and class 1 integron were found to have a major role.Keywords: Stenotrophomonas maltophilia; Sulphamethoxazole-trimethoprim-resistant; Multiplex  PCR; sul genes; Integron

Performance characteristics of enzyme linked immunosorbent assay and rapid immunochromatographic test for routine screening of human norovirus

Noroviruses (NoV) are identified as the major cause of epidemic and sporadic acute gastroenteritis. Controlling the spread of the disease needs early recognition of NoV. This study investigated the  contribution of norovirus to sporadic cases of pediatric gastroenteritis in Zagazig University Hospitals and studied the performance characteristics of enzyme linked immunosorbent assay(EIA) and  immunochromatographic (ICT) assay for their ability to detect NoV. Two hundred stool specimens werecollected from pediatric patients with acute gastroenteritis. Samples were tested for Norovirus presence by reverse transcription PCR (RT-PCR), ICT kit and EIA. 27% of the samples showed the 338-bp portion of the RNA-dependent RNA polymerase (RdRp) gene of both Norovirus genogroups I and II by RT-PCR. The ICT assay showed high specificity (97.94%) and high sensitivity (85.18%). The EIA  showed high specificity (93.8%) but low sensitivity (64.8%). In conclusion, the high detection rate of NoV as the cause of diarrhea in children reported in this study supports their addition in screenings to  identify sporadic cases of acute gastroenteritis. The ICT and RIA Norovirus kits may be useful for rapid screening of stool samples from patients with acute gastroenteritis. However, RT-PCR should be  considered for negative samples to be confirmed.Key words: Norovirus, pediatric gastroenteritis, RNA-dependent RNA polymerase (RdRp) gene,  enzyme linked immunosorbent assay, immunochromatographic assay, Sensitivity, Specificity.Abbreviations: NoV , Noroviruses; EIA, enzyme linked immunosorbent assay; ICT,  immunochromatographic; RT-PCR, reverse transcription PCR; RdRp, RNA-dependent RNA polymerase; ORFs, open reading frames

On the differing growth mechanisms of black-smoker and Lost City-type hydrothermal vents.

Black smokers and Lost City-type springs are varieties of hydrothermal vents on the ocean floors that emit hot, acidic water and cool, alkaline water, respectively. While both produce precipitation structures as the issuing fluid encounters oceanic water, Lost City-type hydrothermal vents in particular have been implicated in the origin of life on the Earth. We present a parallel-velocity flow model for the radius and flow rate of a cylindrical jet of fluid that forms the template for the growth of a tube precipitated about itself and we compare the solution with previous laboratory experimental results from growth of silicate chemical gardens. We show that when the growth of the solid structure is determined by thermal diffusion, fluid flow is slow at the solid-liquid contact. However, in the case of chemical diffusive transport, the fluid jet effectively drags the liquid in the pores of the solid precipitate. These findings suggest a continuum in the diffusive growth rate of hydrothermal vent structures, where Lost City-type hydrothermal vents favour contact between the vent fluid and the external seawater. We explore the implications for the road to life

Childhood secondhand smoke exposure and pregnancy loss in never smokers: The Guangzhou Biobank Cohort Study

published_or_final_versio

On The Phase Structure and Thermodynamic Geometry of R-Charged Black Holes

We study the phase structure and equilibrium state space geometry of R-charged black holes in $D = 5$, 4 and 7 and the corresponding rotating $D3$, $M2$ and $M5$ branes. For various charge configurations of the compact black holes in the canonical ensemble we demonstrate new liquid-gas like phase coexistence behaviour culminating in second order critical points. The critical exponents turn out to be the same as that of four dimensional asymptotically AdS black holes in Einstein Maxwell theory. We further establish that the regions of stability for R-charged black holes are, in some cases, more constrained than is currently believed, due to properties of some of the response coefficients. The equilibrium state space scalar curvature is calculated for various charge configurations, both for the case of compact as well as flat horizons and its asymptotic behaviour with temperature is established.Comment: 1 + 33 pages, LaTeX, 25 figures. References adde

Exploding Chemical Gardens: A Phase-Change Clock Reaction.

Chemical gardens and clock reactions are two of the best-known demonstration reactions in chemistry. Until now these have been separate categories. We have discovered that a chemical garden confined to two dimensions is a clock reaction involving a phase change, so that after a reproducible and controllable induction period it explodes

Hydrodynamics of a 5D Einstein-dilaton black hole solution and the corresponding BPS state

We apply the potential reconstruction approach to generate a series of asymptotically AdS (aAdS) black hole solutions, with a self-interacting bulk scalar field. Based on the method, we reproduce the pure AdS solution as a consistency check and we also generate a simple analytic 5D black hole solution. We then study various aspects of this solution, such as temperature, entropy density and conserved charges. Furthermore, we study the hydrodynamics of this black hole solution in the framework of fluid/gravity duality, e.g. the ratio of the shear viscosity to the entropy density. In a degenerate case of the 5D black hole solution, we find that the c function decreases monotonically from UV to IR as expected. Finally, we investigate the stability of the degenerate solution by studying the bosonic functional energy of the gravity and the Witten-Nester energy $E_{WN}$. We confirm that the degenerate solution is a BPS domain wall solution. The corresponding superpotential and the solution of the killing spinor equation are found explicitly.Comment: V2: 23 pages, no figure, minor changes, typos corrected, new references and comments added, version accepted by JHE

Functional organisation for verb generation in children with developmental language disorder

Developmental language disorder (DLD) is characterised by difficulties in learning one's native language for no apparent reason. These language difficulties occur in 7% of children and are known to limit future academic and social achievement. Our understanding of the brain abnormalities associated with DLD is limited. Here, we used a simple four-minute verb generation task (children saw a picture of an object and were instructed to say an action that goes with that object) to test children between the ages of 10–15 years (DLD N = 50, typically developing N = 67). We also tested 26 children with poor language ability who did not meet our criteria for DLD. Contrary to our registered predictions, we found that children with DLD did not have (i) reduced activity in language relevant regions such as the left inferior frontal cortex; (ii) dysfunctional striatal activity during overt production; or (iii) a reduction in left-lateralised activity in frontal cortex. Indeed, performance of this simple language task evoked activity in children with DLD in the same regions and to a similar level as in typically developing children. Consistent with previous reports, we found sub-threshold group differences in the left inferior frontal gyrus and caudate nuclei, but only when analysis was limited to a subsample of the DLD group (N = 14) who had the poorest performance on the task. Additionally, we used a two-factor model to capture variation in all children studied (N = 143) on a range of neuropsychological tests and found that these language and verbal memory factors correlated with activity in different brain regions. Our findings indicate a lack of support for some neurological models of atypical language learning, such as the procedural deficit hypothesis or the atypical lateralization hypothesis, at least when using simple language tasks that children can perform. These results also emphasise the importance of controlling for and monitoring task performance