4,458 research outputs found
The subzero microbiome: Microbial activity in frozen and thawing soils
No full textMost of the Earth's biosphere is characterized by low temperatures (<5 °C) and cold-adapted microorganisms are widespread. These psychrophiles have evolved a complex range of adaptations of all cellular constituents to counteract the potentially deleterious effects of low kinetic energy environments and the freezing of water. Microbial life continues into the subzero temperature range, and this activity contributes to carbon and nitrogen flux in and out of ecosystems, ultimately affecting global processes. Microbial responses to climate warming and in particular, thawing of frozen soils are not yet well understood although the threat of microbial contribution to positive feedback of carbon flux is substantial. To date, several studies have examined microbial community dynamics in frozen soils and permafrost due to changing environmental conditions, and some have undertaken the complicated task of characterizing microbial functional groups and how their activity changes with changing conditions, either in situ or by isolating and characterizing macromolecules. With increasing temperature and wetter conditions microbial activity of key microbes and subsequent efflux of greenhouse gases also increase. In this review, we aim to provide an overview of microbial activity in seasonally frozen soils and permafrost. With a more detailed understanding of the microbiological activities in these vulnerable soil ecosystems, we can begin to predict and model future expectations for carbon release and climate change.Peer reviewe
Measurement of the time-dependent CP asymmetry in B0 -> J/ψ KS0 decays
No full textThis Letter reports a measurement of the CP violation observables SJ/ψK0S and CJ/ψK0S in the decay channel B0→J/ψK0S performed with 1.0 fb−1 of pp collisions at s√=7 TeV collected by the LHCb experiment. The fit to the data yields SJ/ψK0S=0.73±0.07(stat)±0.04(syst) and CJ/ψK0S=0.03±0.09(stat)±0.01(syst). Both values are consistent with the current world averages and within
expectations from the Standard Model
Status of the MAX-lab injector project
No full textThe status of the new injector system for MAX-lab is presented. The electron source is a thermionic RF-gun that has been designed at MAX-lab. The new injector will consist of two linac structures equipped with SLED cavities. This will produce an electron beam with an energy of 250 MeV. This beam will be recirculated in order to obtain a 500 MeV beam
Status of the MAX-lab injector project
No full textThe status of the new injector system for MAX-lab is presented. The electron source is a thermionic RF-gun that has been designed at MAX-lab. The new injector will consist of two linac structures equipped with SLED cavities. This will produce an electron beam with an energy of 250 MeV. This beam will be recirculated in order to obtain a 500 MeV beam
Evidence for the decay B0→J/ψω and measurement of the relative branching fractions of meson decays to J/ψη and J/ψη′
No full textFirst evidence of the B 0 → J / ψ ω decay is found and the B s 0 → J / ψ η and B s 0 → J / ψ η ′ decays are studied using a dataset corresponding to an integrated luminosity of 1.0 fb -1 collected by the LHCb experiment in proton-proton collisions at a centre-of-mass energy of sqrt(s) = 7 TeV. The branching fractions of these decays are measured relative to that of the B 0 → J / ψ ρ 0 decay:frac(B (B 0 → J / ψ ω), B (B 0 → J / ψ ρ 0)) = 0.89 ± 0.19 (stat) - 0.13 + 0.07 (syst),frac(B (B s 0 → J / ψ η), B (B 0 → J / ψ ρ 0)) = 14.0 ± 1.2 (stat) - 1.5 + 1.1 (syst) - 1.0 + 1.1 (frac(f d, f s)),frac(B (B s 0 → J / ψ η ′), B (B 0 → J / ψ ρ 0)) = 12.7 ± 1.1 (stat) - 1.3 + 0.5 (syst) - 0.9 + 1.0 (frac(f d, f s)), where the last uncertainty is due to the knowledge of f d / f s, the ratio of b-quark hadronization factors that accounts for the different production rate of B 0 and B s 0 mesons. The ratio of the branching fractions of B s 0 → J / ψ η ′ and B s 0 → J / ψ η decays is measured to befrac(B (B s 0 → J / ψ η ′), B (B s 0 → J / ψ η)) = 0.90 ± 0.09 (stat) - 0.02 + 0.06 (syst)
Measurement of the ratio of prompt χ c to J / ψ production in pp collisions at √s = 7 TeV
No full textThe prompt production of charmonium χ c and J / ψ states is studied in proton-proton collisions at a centre-of-mass energy of √s = 7 TeV at the Large Hadron Collider. The χ c and J / ψ mesons are identified through their decays χ c → J / ψ γ and J / ψ → μ + μ - using 36 pb - 1 of data collected by the LHCb detector in 2010. The ratio of the prompt production cross-sections for χ c and J / ψ, σ (χ c → J / ψ γ) / σ (J / ψ), is determined as a function of the J / ψ transverse momentum in the range 2 < p T J / ψ < 15 GeV / c. The results are in excellent agreement with next-to-leading order non-relativistic expectations and show a significant discrepancy compared with the colour singlet model prediction at leading order, especially in the low p T J / ψ region
Surface science at MAX-LAB
No full textThe 550 MeV storage ring at MAX-LAB provides synchrotron radiation for a large community of users. An important part of the scientific program is photoelectron spectroscopy studies of semiconductor and metal surfaces and interfaces. Here is a brief review of some of the experimental efforts obtained in this area. Results are shown for the Ge(100)2×1:As, Si(111):Au, Mo(110):Yb and Mo(110):Sm systems
A protective antiarrhythmic role of ursodeoxycholic acid in an in vitro rat model of the cholestatic fetal heart
No full textIntrahepatic cholestasis of pregnancy may be complicated by fetal arrhythmia, fetal hypoxia, preterm labor, and, in severe cases, intrauterine death. The precise etiology of fetal death is not known. However, taurocholate has been demonstrated to cause arrhythmia and abnormal calcium dynamics in cardiomyocytes. To identify the underlying reason for increased susceptibility of fetal cardiomyocytes to arrhythmia, we studied myofibroblasts (MFBs), which appear during structural remodeling of the adult diseased heart. In vitro, they depolarize rat cardiomyocytes via heterocellular gap junctional coupling. Recently, it has been hypothesized that ventricular MFBs might appear in the developing human heart, triggered by physiological fetal hypoxia. However, their presence in the fetal heart (FH) and their proarrhythmogenic effects have not been systematically characterized. Immunohistochemistry demonstrated that ventricular MFBs transiently appear in the human FH during gestation. We established two in vitro models of the maternal heart (MH) and FH, both exposed to increasing doses of taurocholate. The MH model consisted of confluent strands of rat cardiomyocytes, whereas for the FH model, we added cardiac MFBs on top of cardiomyocytes. Taurocholate in the FH model, but not in the MH model, slowed conduction velocity from 19 to 9 cm/s, induced early after depolarizations, and resulted in sustained re-entrant arrhythmias. These arrhythmic events were prevented by ursodeoxycholic acid, which hyperpolarized MFB membrane potential by modulating potassium conductance. Conclusion: These results illustrate that the appearance of MFBs in the FH may contribute to arrhythmias. The above-described mechanism represents a new therapeutic approach for cardiac arrhythmias at the level of MFB.Michele Miragoli, Siti H. Sheikh Abdul Kadir, Mary N. Sheppard, Nicoló Salvarani, Matilda Virta, Sarah Wells, Max J. Lab, Viacheslav O. Nikolaev, Alexey Moshkov, William M. Hague, Stephan Rohr, Catherine Williamson and Julia Goreli
Linearly polarized photon beam at MAX-lab
No full textA linearly polarized photon beam has been produced at MAX-lab using the coherent bremsstrahlung of electrons with an energy of 192.6 MeV in a 0.1 mm thick diamond crystal. The intensity and shape of the coherent maxima and their dependence on the crystal orientation are similar to the features observed at higher electron energies (~ 1 GeV) and are well described by coherent bremsstrahlung theory. The linear polarization of the uncollimated beam at the coherent peak energy ≈50–60 MeV is about 20% and can be increased to 40–45% if collimation of half the characteristic angle is used. At present the degree of polarization is high enough to allow the study of polarization observables in photo-nuclear reactions at MAX-lab in the energy range from Giant Dipole Resonance up to ≈80 MeV
Nuclear physics program at MAX-lab
No full textThe upgrade of the MAX-lab Injector and the construction of MAX III, provided the opportunity for upgrading the tagged-photon facility and thus lead to the possibility of more extensive program in nuclear physics research This upgrade increased the injected electron energy to all eventual maximum of 250 MeV and allows for the extraction of electrons from the MAX I ring operated in the stretcher mode The first stretched bean was delivered in September 2005. The tagged-photon facility was commissioned in parallel with the commissioning of new experimental equipment. The PAC approved experimental program is current in progress, including measurement of pion photoproduction below the Delta(1232) The efforts at the tagged photon-facility are pursed within all international collaboration with around fifty member
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