3,728 research outputs found
From Frictional to Viscous Behavior: Three Dimensional Imaging and Rheology of Gravitational Suspensions
We probe the three dimensional flow structure and rheology of gravitational
(non-density matched) suspensions for a range of driving rates in a
split-bottom geometry. We establish that for sufficiently slow flows, the
suspension flows as if it were a dry granular medium, and confirm recent
theoretical modeling on the rheology of split-bottom flows. For faster driving,
the flow behavior is shown to be consistent with the rheological behavior
predicted by the recently developed "inertial number approaches for suspension
flows.Comment: 5 pages, 4 figures, accepted for Phys. Rev. E. (R
GRHydro: a new open-source general-relativistic magnetohydrodynamics code for the Einstein toolkit
We present the new general-relativistic magnetohydrodynamics (GRMHD) capabilities of the Einstein toolkit, an open-source community-driven numerical relativity and computational relativistic astrophysics code. The GRMHD extension of the toolkit builds upon previous releases and implements the evolution of relativistic magnetized fluids in the ideal MHD limit in fully dynamical spacetimes using the same shock-capturing techniques previously applied to hydrodynamical evolution. In order to maintain the divergence-free character of the magnetic field, the code implements both constrained transport and hyperbolic divergence cleaning schemes. We present test results for a number of MHD tests in Minkowski and curved spacetimes. Minkowski tests include aligned and oblique planar shocks, cylindrical explosions, magnetic rotors, Alfvén waves and advected loops, as well as a set of tests designed to study the response of the divergence cleaning scheme to numerically generated monopoles. We study the code's performance in curved spacetimes with spherical accretion onto a black hole on a fixed background spacetime and in fully dynamical spacetimes by evolutions of a magnetized polytropic neutron star and of the collapse of a magnetized stellar core. Our results agree well with exact solutions where these are available and we demonstrate convergence. All code and input files used to generate the results are available on http://einsteintoolkit.org. This makes our work fully reproducible and provides new users with an introduction to applications of the code
An equivalence framework for an age-structured multi-stage representation of the cell cycle
We develop theoretical equivalences between stochastic and deterministic models for populations of individual cells stratified by age. Specifically, we develop a hierarchical system of equations describing the full dynamics of an age-structured multi-stage Markov process for approximating cell cycle time distributions. We further demonstrate that the resulting mean behaviour is equivalent, over large timescales, to the classical McKendrick-von Foerster integro-partial differential equation. We conclude by extending this framework to a spatial context, facilitating the modelling of travelling wave phenomena and cell-mediated pattern formation. More generally, this methodology may be extended to myriad reaction-diffusion processes for which the age of individuals is relevant to the dynamics
Modulation of the Intestinal Microbiota Alters Colitis-Associated Colorectal Cancer Susceptibility
It is well established that the intestinal microbiota plays a key role in the pathogenesis of Crohn's disease (CD) and ulcerative colitis (UC) collectively referred to as inflammatory bowel disease (IBD). Epidemiological studies have provided strong evidence that IBD patients bear increased risk for the development of colorectal cancer (CRC). However, the impact of the microbiota on the development of colitis-associated cancer (CAC) remains largely unknown. In this study, we established a new model of CAC using azoxymethane (AOM)-exposed, conventionalized-Il10â/â mice and have explored the contribution of the host intestinal microbiota and MyD88 signaling to the development of CAC. We show that 8/13 (62%) of AOM-Il10â/â mice developed colon tumors compared to only 3/15 (20%) of AOM- wild-type (WT) mice. Conventionalized AOM-Il10â/â mice developed spontaneous colitis and colorectal carcinomas while AOM-WT mice were colitis-free and developed only rare adenomas. Importantly, tumor multiplicity directly correlated with the presence of colitis. Il10â/â mice mono-associated with the mildly colitogenic bacterium Bacteroides vulgatus displayed significantly reduced colitis and colorectal tumor multiplicity compared to Il10â/â mice. Germ-free AOM-treated Il10â/â mice showed normal colon histology and were devoid of tumors. Il10â/â; Myd88â/â mice treated with AOM displayed reduced expression of Il12p40 and Tnfα mRNA and showed no signs of tumor development. We present the first direct demonstration that manipulation of the intestinal microbiota alters the development of CAC. The TLR/MyD88 pathway is essential for microbiota-induced development of CAC. Unlike findings obtained using the AOM/DSS model, we demonstrate that the severity of chronic colitis directly correlates to colorectal tumor development and that bacterial-induced inflammation drives progression from adenoma to invasive carcinoma
Pre-Emptive Endoluminal Negative Pressure Therapy at the Anastomotic Site in Minimally Invasive Transthoracic Esophagectomy (the preSPONGE Trial): Study Protocol for a Multicenter Randomized Controlled Trial
Introduction: Anastomotic leakage (AL) accounts for a significant proportion of morbidity following oesophagectomy. Endoluminal negative pressure (ENP) therapy via a specifically designed polyurethane foam (EsoSpongeÂź, B.Braun Medical, Melsungen, Germany) has become the standard of care for AL in many specialized centres. The prophylactic (pENP) application of this technique aims to reduce postoperative morbidity and is a novel approach which has not yet been investigated in a prospective study. The aim of this study is therefore to assess the effect of pENP at the anastomotic site in high-risk patients undergoing minimally invasive transthoracic Ivor Lewis oesophagectomy.
Methods and analysis: The study design is a prospective, multi-centre, two-arm, parallel-group, randomised controlled trial and will be conducted in two phases. Phase one is a randomised feasibility and safety pilot trial involving 40 consecutive patients. After definitive sample size calculation, additional patients will be included accordingly during phase two. The primary outcome of the study will be the postoperative length of hospitalization until reaching previously defined âfit for discharge criteriaâ. Secondary outcomes will include postoperative morbidity, mortality and postoperative AL-rates based on 90-day follow-up. A confirmatory analysis based on intention-to-treat will be performed.
Ethics and dissemination: The ethics committee of the University of Zurich approved this study (2019-00562), which has been registered with ClinicalTrials.gov on 14.11.2019 (NCT04162860) and the Swiss National Clinical Trials Portal (SNCTP000003524). The results of the study will be published and presented at appropriate conferences
Phylloquinone (vitamin K 1 ) biosynthesis in plants: two peroxisomal thioesterases of lactobacillales origin hydrolyze 1,4âdihydroxyâ2ânaphthoylâcoa
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92396/1/TPJ_4972_sm_FigS3.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/92396/2/TPJ_4972_sm_TableS1.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/92396/3/TPJ_4972_sm_FigS2.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/92396/4/TPJ_4972_sm_TableS4.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/92396/5/TPJ_4972_sm_FigS6.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/92396/6/j.1365-313X.2012.04972.x.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/92396/7/TPJ_4972_sm_FigS1.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/92396/8/TPJ_4972_sm_TableS3.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/92396/9/TPJ_4972_sm_FigS5.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/92396/10/TPJ_4972_sm_TableS2.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/92396/11/TPJ_4972_sm_FigS4.pd
Anti-motility and reductions in the concentrations of gut electrolytes: Mechanisms for the anti-spasmodic use of the seeds of avocado (Persea americana Mill) in folk medicine
The seeds of avocado (Persea americana Mill) are used in traditional medicine to treat, allay or prevent some spasm-related disorders, for instance, diarrhoea. The chloroform and methanol fractions of the chloroform-methanol extract of the seeds of P. americana were investigated for their qualitative and quantitative phytochemical constituents as well as effects on gastro-intestinal motility (transit) and castor oil-induced intestinal fluid sodium ion (Na+) and potassium ion (K+) concentrations in Wistar rats. The qualitative and quantitative phytochemical studies of the chloroform and methanol fractions showed the presence and amounts of alkaloids (2.92 ± 0.14 g/100 g and 2.81 ± 0.08 g/100 g respectively), flavonoids (3.43 ± 0.19 g/100 g and 3.11 ± 0.16 g/100 g, respectively), tannins (2.64 ± 0.13 g/100 g and 2.85 ± 0.14 g/100 g, respectively), steroids (1.51 ± 0.07 g/100 g and 1.27 ± 0.04 g/100 g, respectively), saponins (2.35 ± 0.08 % and 2.47 ± 0.09%, respectively), terpenoids, proteins and carbohydrates in both fractions. Fats and oil were present only in the chloroform fraction. At the two doses (100 and 200 mg/kg body weight), the chloroform and methanol fractions produced significant (p<0.05) and dose-related decreases in the gastro-intestinal motility and concentration of the intestinal fluid potassium ions but only the chloroform fraction at the dose of 200 mg/kg body weight significantly (p<0.05) decreased the concentration of the intestinal fluid sodium ions. Results of the fractions were comparable with those of the standard anti-diarrhoeal drug, hyoscine butylbromide (3 mg/kg body weight). The results indicate that the chloroform-methanol extract of the seeds of P. americana contains compounds with anti-spasmodic effect.Keywords: Persea americana, spasm-related, castor oil, gastro-intestinal motility and electrolytesAfrican Journal of Biotechnology Vol. 12(37), pp. 5610-561
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Exploring uncertainties in global crop yield projections in a large ensemble of crop models and CMIP5 and CMIP6 climate scenarios
Concerns over climate change are motivated in large part because of their impact on human society. Assessing the effect of that uncertainty on specific potential impacts is demanding, since it requires a systematic survey over both climate and impacts models. We provide a comprehensive evaluation of uncertainty in projected crop yields for maize, spring and winter wheat, rice, and soybean, using a suite of nine crop models and up to 45 CMIP5 and 34 CMIP6 climate projections for three different forcing scenarios. To make this task computationally tractable, we use a new set of statistical crop model emulators. We find that climate and crop models contribute about equally to overall uncertainty. While the ranges of yield uncertainties under CMIP5 and CMIP6 projections are similar, median impact in aggregate total caloric production is typically more negative for the CMIP6 projections (+1% to â19%) than for CMIP5 (+5% to â13%). In the first half of the 21st century and for individual crops is the spread across crop models typically wider than that across climate models, but we find distinct differences between crops: globally, wheat and maize uncertainties are dominated by the crop models, but soybean and rice are more sensitive to the climate projections. Climate models with very similar global mean warming can lead to very different aggregate impacts so that climate model uncertainties remain a significant contributor to agricultural impacts uncertainty. These results show the utility of large-ensemble methods that allow comprehensively evaluating factors affecting crop yields or other impacts under climate change. The crop model ensemble used here is unbalanced and pulls the assumption that all projections are equally plausible into question. Better methods for consistent model testing, also at the level of individual processes, will have to be developed and applied by the crop modeling community
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