228 research outputs found

    Anomalous scaling behavior in Takens-Bogdanov bifurcations

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    A general algorithm is presented for estimating the nonlinear instability threshold, ŌÉc\sigma_c, for subcritical transitions in systems where the linearized dynamics is significantly non-normal (i.e. subcritical bifurcations of {\em Takens-Bogdanov} type). The NN-dimensional degenerate node is presented as an example. The predictions are then compared to numerical studies with excellent agreement.Comment: 6 page

    Gut microbiome transition across a lifestyle gradient in Himalaya

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    Published: November 15, 2018The composition of the gut microbiome in industrialized populations differs from those living traditional lifestyles. However, it has been difficult to separate the contributions of human genetic and geographic factors from lifestyle. Whether shifts away from the foraging lifestyle that characterize much of humanity's past influence the gut microbiome, and to what degree, remains unclear. Here, we characterize the stool bacterial composition of four Himalayan populations to investigate how the gut community changes in response to shifts in traditional human lifestyles. These groups led seminomadic hunting-gathering lifestyles until transitioning to varying levels of agricultural dependence upon farming. The Tharu began farming 250-300 years ago, the Raute and Raji transitioned 30-40 years ago, and the Chepang retain many aspects of a foraging lifestyle. We assess the contributions of dietary and environmental factors on their gut-associated microbes and find that differences in the lifestyles of Himalayan foragers and farmers are strongly correlated with microbial community variation. Furthermore, the gut microbiomes of all four traditional Himalayan populations are distinct from that of the Americans, indicating that industrialization may further exacerbate differences in the gut community. The Chepang foragers harbor an elevated abundance of taxa associated with foragers around the world. Conversely, the gut microbiomes of the populations that have transitioned to farming are more similar to those of Americans, with agricultural dependence and several associated lifestyle and environmental factors correlating with the extent of microbiome divergence from the foraging population. The gut microbiomes of Raute and Raji reveal an intermediate state between the Chepang and Tharu, indicating that divergence from a stereotypical foraging microbiome can occur within a single generation. Our results also show that environmental factors such as drinking water source and solid cooking fuel are significantly associated with the gut microbiome. Despite the pronounced differences in gut bacterial composition across populations, we found little differences in alpha diversity across lifestyles. These findings in genetically similar populations living in the same geographical region establish the key role of lifestyle in determining human gut microbiome composition and point to the next challenging steps of determining how large-scale gut microbiome reconfiguration impacts human biology.Aashish R. Jha, Emily R. Davenport, Yoshina Gautam, Dinesh Bhandari, Sarmila Tandukar, Katharine M. Ng, Gabriela K. Fragiadakis, Susan Holmes, Guru Prasad Gautam, Jeff Leach, Jeevan Bahadur Sherchand, Carlos D. Bustamante, Justin L. Sonnenbur

    Difference in countries' use of resources and clinical outcome for patients with cardiogenic shock after myocardial infarction: results from the GUSTO trial

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    BACKGROUND: Use of aggressive and invasive interventions is more common in the USA than in other countries. We have compared use of resources for patients with cardiogenic shock after myocardial infarction in the USA and in other countries, and assessed the association between use of resources and clinical outcomes. METHODS: We analysed data for patients with cardiogenic shock after myocardial infarction who were enrolled in the GUSTO-I trial (1891 treated in the USA, 1081 treated in other countries). Patients were randomly assigned combinations of streptokinase, heparin, and accelerated tissue-plasminogen activator (t-PA), then decisions about further interventions were left to the discretion of the attending physician. The interventions included in our analysis were: pulmonary-artery catheterisation, cardiac catheterisation, intravenous inotropic agents, ventilatory support, intra-aortic balloon counterpulsation (IABP), percutaneous transluminal coronary angioplasty (PTCA), and coronary bypass graft surgery (CABG). The primary outcome measure was death from any cause at 30 days of follow-up. FINDINGS: Patients who were treated in the USA were significantly younger than those treated elsewhere (median 68 [IQR 59-75] vs 70 [62-76], p < 0.001), a smaller proportion had anterior infarction (49 vs 53%, p < 0.001), and they had a shorter time to treatment (mean 3.1 vs 3.3 h, p < 0.001). Aggressive diagnostic and therapeutic procedures were used more commonly in the USA than in the other countries: cardiac catheterisation (58 vs 23%); IABP (35 vs 7%); right-heart catheterisation (57 vs 22%); and ventilatory support (54 vs 38%). 483 (26%) of the patients treated in the USA underwent PTCA, compared with 82 (8%) patients in oth

    Nuclear Level Density and the Determination of Thermonuclear Rates for Astrophysics

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    The prediction of cross sections for nuclei far off stability is crucial in the field of nuclear astrophysics. We discuss the model mostly employed for such calculations: the statistical model (Hauser-Feshbach). Special emphasis is put on the uncertainties arising from nuclear level density descriptions and an improved global description is presented. Furthermore, criteria for the applicability of the statistical model are investigated and a "map" for the applicability of the model to reactions of stable and unstable nuclei with neutral and charged particles is given.Comment: REVTeX paper + 7 B/W figures + 2 color figures; PRC, in press. Also available at http://quasar.physik.unibas.ch/preps.htm

    Error sources and data limitations for the prediction ofsurface gravity: a case study using benchmarks

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    Gravity-based heights require gravity values at levelled benchmarks (BMs), whichsometimes have to be predicted from surrounding observations. We use EGM2008 andthe Australian National Gravity Database (ANGD) as examples of model and terrestrialobserved data respectively to predict gravity at Australian national levelling network(ANLN) BMs. The aim is to quantify errors that may propagate into the predicted BMgravity values and then into gravimetric height corrections (HCs). Our results indicatethat an approximate ¬Ī1 arc-minute horizontal position error of the BMs causesmaximum errors in EGM2008 BM gravity of ~ 22 mGal (~55 mm in the HC at ~2200 melevation) and ~18 mGal for ANGD BM gravity because the values are not computed atthe true location of the BM. We use RTM (residual terrain modelling) techniques toshow that ~50% of EGM2008 BM gravity error in a moderately mountainous regioncan be accounted for by signal omission. Non-representative sampling of ANGDgravity in this region may cause errors of up to 50 mGals (~120 mm for the Helmertorthometric correction at ~2200 m elevation). For modelled gravity at BMs to beviable, levelling networks need horizontal BM positions accurate to a few metres, whileRTM techniques can be used to reduce signal omission error. Unrepresentative gravitysampling in mountains can be remedied by denser and more representative re-surveys,and/or gravity can be forward modelled into regions of sparser gravity
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