902 research outputs found
Effects of okadaic acid on the activities of two distinct phosphatidate phosphohydrolases in rat hepatocytes
AbstractIncubation of hepatocytes with okadaic acid displaced the N-ethylmaleimide-sensitive phosphatidate phosphohydrolase from the membrane fraction into the cytosol and partially prevented the oleate-induced movement of phosphohydrolase from cytosol to membranes. However, higher concentrations of oleate still caused translocation and activation of the phosphohydrolase. This enzyme is stimulated by Mg2+, and is probably involved in glycerolipid synthesis. Okadaic acid also decreased the concentration of diacylglycerol within the hepatocytes. Okadaic acid had no observable effect on the activity of an N-ethylmaleimide-insensitive phosphatidate phosphohydrolase which remained firmly attached to membranes. This activity is not stimulated by Mg2+ and is probably involved in signal transduction by the phospholipase D pathway
Minerales de Mn-Co-Ni en las lateritas De Cuba oriental: resultados preliminares
En los yacimientos de lateritas niquelĂferas, el Ni y Co pueden ser incorporados en Ăłxidos e hidrĂłxido s de Mn, donde han precipitados mediante reacciones redox (Elias et al., 1981). AdemĂĄs de asbolanas (ricas en Ni y ricas en Co), otros minerales que contienen Co son heterogenita y litioforita (Chukhrov et al., 1 983; Manceau et al., 1987; Llorca y Monchoux, 1991)
GraXe, graphene and xenon for neutrinoless double beta decay searches
We propose a new detector concept, GraXe (to be pronounced as grace), to
search for neutrinoless double beta decay in Xe-136. GraXe combines a popular
detection medium in rare-event searches, liquid xenon, with a new,
background-free material, graphene.
In our baseline design of GraXe, a sphere made of graphene-coated titanium
mesh and filled with liquid xenon (LXe) enriched in the Xe-136 isotope is
immersed in a large volume of natural LXe instrumented with photodetectors.
Liquid xenon is an excellent scintillator, reasonably transparent to its own
light. Graphene is transparent over a large frequency range, and impermeable to
the xenon. Event position could be deduced from the light pattern detected in
the photosensors. External backgrounds would be shielded by the buffer of
natural LXe, leaving the ultra-radiopure internal volume virtually free of
background.
Industrial graphene can be manufactured at a competitive cost to produce the
sphere. Enriching xenon in the isotope Xe-136 is easy and relatively cheap, and
there is already near one ton of enriched xenon available in the world
(currently being used by the EXO, KamLAND-Zen and NEXT experiments). All the
cryogenic know-how is readily available from the numerous experiments using
liquid xenon. An experiment using the GraXe concept appears realistic and
affordable in a short time scale, and its physics potential is enormous.Comment: 17 pages, 4 figures, 2 tables. Several typos and a reference
corrected. Version accepted for publication in the Journal of Cosmology and
Astroparticle Physics (JCAP
Universal scaling of magnetoconductance in magnetic nanocontacts (Invited)
We present results of half-metallic ferromagnets formed by atomic nanocontact of CrO2â CrO2 and
CrO2âNi that show as much as 400% magnetoconductance. Analysis of the magnetoconductance
versus conductance data for all materials known to exhibit so-called ballistic magnetoresistance
strongly suggests that the magnetoconductance of nanocontacts follows universal scaling. If the
maximum magnetoconductance is normalized to unity and the conductance is scaled to the
resistivity of the material, then all data points fall into a universal curve that is independent of the
contact material and the transport mechanism. The analysis was applied to all available
magnetoconductance data of magnetic nanocontacts in the literature, and the results agree with
theory that takes into account the spin scattering within a magnetic domain wall
Risky business: A mixed methods study of decision-making regarding COVID-19 risk at a public university in the United States
IntroductionUntil vaccines became available in late 2020, our ability to prevent the spread of COVID-19 within countries depended largely on voluntary adherence to mitigation measures. However, individual decision-making regarding acceptable COVID-19 risk is complex. To better understand decision-making regarding COVID-19 risk, we conducted a qualitative substudy within a larger Berkeley COVID-19 Safe Campus Initiative (BCSCI) during the summer of 2020, and completed a mixed-methods analysis of factors influencing decision-making.Materials and methodsWe interviewed 20 participants who tested positive for SARS-CoV-2 and 10 who remained negative, and analyzed quantitative survey data from 3,324 BCSCI participants. The BCSCI study enrolled university-affiliated people living in the local area during summer of 2020, collected data on behaviors and attitudes toward COVID-19, and conducted SARS-CoV-2 testing at baseline and endline.ResultsAt baseline, 1362 students (57.5%) and 285 non-students (35.1%) said it had been somewhat or very difficult to comply with COVID-19-related mandates. Most-cited reasons were the need to go out for food/essentials, difficulty of being away from family/friends, and loneliness. Eight interviewees explicitly noted they made decisions partially because of others who may be at high risk. We did not find significant differences between the behaviors of students and non-students.DiscussionDespite prevailing attitudes about irresponsibility of college students during the COVID-19 pandemic, students in our study demonstrated a commitment to making rational choices about risk behavior, not unlike non-students around them. Decision-making was driven by perceived susceptibility to severe disease, need for social interaction, and concern about risk to others. A harm reduction public health approach may be beneficial
A Search for Sigma^0_5, N^0_5 and Theta^++ Pentaquark States
A high-resolution (sigma_instr. = 1.5 MeV) search for narrow states (Gamma <
10 MeV) with masses of M_x approx 1500-1850 MeV in ep -> e'K^+ X, e'K^- X and
e' pi^+ X electroproduction at small angles and low Q^2 was performed. These
states would be candidate partner states of the reported Theta^+(1540)
pentaquark. No statistically significant signal was observed in any of the
channels at 90% C.L. Upper limits on forward production were determined to be
between 0.7% and 4.2% of the Lambda(1520) production cross section, depending
on the channel and the assumed mass and width of the state.Comment: 5 pages, 5 figures, to appear in Phys. Rev. C, update with responses
to referee suggestion
Characterization of Microbialites and Microbial Mats of the Laguna Negra Hypersaline Lake (Puna of Catamarca, Argentina)
Microbial carbonates provide an invaluable tool to understand biogeochemical processes in aqueous systems, especially in lacustrine and marine environments. Lakes are strongly sensitive to climatically driven environmental changes, and microbialites have recently been shown to provide a record of these changes. Unraveling physicochemical and microbiological controls on carbonates textures and geochemistry is necessary to correctly interpret these signals and the microbial biosphere record within sedimentary carbonates. The Laguna Negra is a high-altitude hypersaline Andean lake (Puna of Catamarca, Argentina), where abundant carbonate precipitation takes place and makes this system an interesting example that preserves a spectrum of carbonate fabrics reflecting complex physical, chemical, and biological interactions. The extreme environmental conditions (high UV radiation, elevated salinity, and temperature extremes) make the Laguna Negra a good analogue to some Precambrian microbialites (e.g., Tumbiana Fm., Archean, Australia). In addition, the discovery of ancient evaporating playa-lake systems on Marsâ surface (e.g., ShalbatanaVallis, Noachian, Mars) highlights the potential of Laguna Negra to provide insight into biosignature preservation in similar environments, in both terrestrial and extraterrestrial settings, given that microbial processes in the Laguna Negra can be studied with remarkable detail.Fil: Boidi, Flavia Jaquelina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - CĂłrdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de CĂłrdoba. Facultad de Ciencias Exactas FĂsicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Mlewski, Estela Cecilia. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - CĂłrdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de CĂłrdoba. Facultad de Ciencias Exactas FĂsicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Gomez, Fernando Javier. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - CĂłrdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de CĂłrdoba. Facultad de Ciencias Exactas FĂsicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: GĂ©rard, Emmanuelle. Centre National de la Recherche Scientifique; Franci
Deeply Virtual Compton Scattering off the neutron
The present experiment exploits the interference between the Deeply Virtual
Compton Scattering (DVCS) and the Bethe-Heitler processes to extract the
imaginary part of DVCS amplitudes on the neutron and on the deuteron from the
helicity-dependent D cross section measured at =1.9
GeV and =0.36. We extract a linear combination of generalized parton
distributions (GPDs) particularly sensitive to , the least constrained
GPD. A model dependent constraint on the contribution of the up and down quarks
to the nucleon spin is deduced.Comment: Published in Phys. Rev. Let
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