541 research outputs found
Una comparación de los modernos sistemas de calcinación de cal
Not availableLa producción de cal en Estados Unidos durante el año de 1969 fue de unos 19,7 millones de toneladas y en 1970 se espera sobrepasar esta cifra. La cal tiene muchas aplicaciones en la construcción, industrias químicas y del acero, estabilización de suelos, etc. Las exigencias del producto, tanto físicas como químicas, cubren un amplio margen, y no es sorprendente que estas exigencias de calidad tan variables hayan creado gran número de sistemas diferentes de producción
Non-gapped Fermi surfaces, quasiparticles and the anomalous temperature dependence of the near- electronic states in the CMR oxide LaSrMnO with
After years of research into colossal magnetoresistant (CMR) manganites using
bulk techniques, there has been a recent upsurge in experiments directly
probing the electronic states at or near the surface of the bilayer CMR
materials LaSrMnO using angle-resolved photoemission
or scanning probe microscopy. Here we report new, temperature dependent, angle
resolved photoemission data from single crystals with a doping level of
. The first important result is that there is no sign of a pseudogap in
the charge channel of this material for temperatures below the Curie
temperature . The second important result concerns the temperature
dependence of the electronic states. The temperature dependent changes in the
Fermi surface spectra both at the zone face and zone diagonal regions in
-space indicate that the coherent quasiparticle weight disappears for
temperatures significantly above , and that the -dependence of the
T-induced changes in the spectra invalidate an interpretation of these data in
terms of the superposition of a `universal' metallic spectrum and an insulating
spectrum whose relative weight changes with temperature. In this sense, our
data are not compatible with a phase separation scenario.Comment: 6 pages, 4 figure
Characteristics and robustness of Agulhas leakage estimates: an inter-comparison study of Lagrangian methods
The inflow of relatively warm and salty water from the Indian Ocean into the South Atlantic via Agulhas leakage is important for the global overturning circulation and the global climate. In this study, we analyse the robustness of Agulhas leakage estimates as well as the thermohaline property modifications of Agulhas leakage south of Africa. Lagrangian experiments with both the newly developed tool Parcels and the well established tool Ariane were performed to simulate Agulhas leakage in the eddy-rich ocean–sea-ice model INALT20 (1/20∘ horizontal resolution) forced by the JRA55-do atmospheric boundary conditions. The average transport, its variability, trend and the transit time from the Agulhas Current to the Cape Basin of Agulhas leakage is simulated comparably with both Lagrangian tools, emphasizing the robustness of our method. Different designs of the Lagrangian experiment alter in particular the total transport of Agulhas leakage by up to 2 Sv, but the variability and trend of the transport are similar across these estimates. During the transit from the Agulhas Current at 32∘ S to the Cape Basin, a cooling and freshening of Agulhas leakage waters occurs especially at the location of the Agulhas Retroflection, resulting in a density increase as the thermal effect dominates. Beyond the strong air–sea exchange around South Africa, Agulhas leakage warms and salinifies the water masses below the thermocline in the South Atlantic
Geometric Universality of Currents
We discuss a non-equilibrium statistical system on a graph or network.
Identical particles are injected, interact with each other, traverse, and leave
the graph in a stochastic manner described in terms of Poisson rates, possibly
dependent on time and instantaneous occupation numbers at the nodes of the
graph. We show that under the assumption of constancy of the relative rates,
the system demonstrates a profound statistical symmetry, resulting in geometric
universality of the statistics of the particle currents. This phenomenon
applies broadly to many man-made and natural open stochastic systems, such as
queuing of packages over the internet, transport of electrons and
quasi-particles in mesoscopic systems, and chains of reactions in bio-chemical
networks. We illustrate the utility of our general approach using two enabling
examples from the two latter disciplines.Comment: 15 pages, 5 figure
Statistics of galaxy warps in the HDF North and South
We present a statistical study of the presence of galaxy warps in the Hubble
deep fields. Among a complete sample of 45 edge-on galaxies above a diameter of
1.''3, we find 5 galaxies to be certainly warped and 6 galaxies as good
candidates. In addition, 4 galaxies reveal a characteristic U-warp. Compared to
statistical studies of local warps, and taking into account the strong bias
against observing the outer parts of galaxies at high redshift, these numbers
point towards a very high frequency of warps at z \sim 1: almost all galaxy
discs might be warped. Furthermore, the amplitude of warps are stronger than
for local warps. This is easily interpreted in terms of higher galaxy
interactions and matter accretion in the past. This result supports these two
mechanisms as the best candidates for the origin of early warps. The mean
observed axis ratio of our sample of edge-on galaxies is significantly larger
in the high-z sample than is found for samples of local spiral galaxies. This
might be due to disk thickening due to more frequent galaxy interactions.Comment: 9 pages, 7 figures, accepted in A and
Double photo-ionization of He near a polarizable surface
We calculate the differential cross-section of the direct double
photo-ionization of He physisorbed on a polarizable surface. By including the
influence of the surface potential in the correlated two-electron final state
wavefunction, we show that the differential cross-section carries detailed
information on the electronic correlations at the surface. In particular,
photo-emission along opposite directions, which is prohibited in the free
space, is allowed if the surface potential is long-ranged.Comment: To appear in Phys. Rev. B - Rapid Comm. - 4 pages, 2 PostScript
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Model simulations on the long-term dispersal of 137Cs released into the Pacific Ocean off Fukushima
A sequence of global ocean circulation models, with horizontal mesh sizes of 0.5°, 0.25° and 0.1°, are used to estimate the long-term dispersion by ocean currents and mesoscale eddies of a slowly decaying tracer (half-life of 30 years, comparable to that of 137Cs) from the local waters off the Fukushima Dai-ichi Nuclear Power Plants. The tracer was continuously injected into the coastal waters over some weeks; its subsequent spreading and dilution in the Pacific Ocean was then simulated for 10 years. The simulations do not include any data assimilation, and thus, do not account for the actual state of the local ocean currents during the release of highly contaminated water from the damaged plants in March–April 2011. An ensemble differing in initial current distributions illustrates their importance for the tracer patterns evolving during the first months, but suggests a minor relevance for the large-scale tracer distributions after 2–3 years. By then the tracer cloud has penetrated to depths of more than 400 m, spanning the western and central North Pacific between 25°N and 55°N, leading to a rapid dilution of concentrations. The rate of dilution declines in the following years, while the main tracer patch propagates eastward across the Pacific Ocean, reaching the coastal waters of North America after about 5–6 years. Tentatively assuming a value of 10 PBq for the net 137Cs input during the first weeks after the Fukushima incident, the simulation suggests a rapid dilution of peak radioactivity values to about 10 Bq m−3 during the first two years, followed by a gradual decline to 1–2 Bq m−3 over the next 4–7 years. The total peak radioactivity levels would then still be about twice the pre-Fukushima values
Ranaviruses and reptiles
Ranaviruses can infect many vertebrate classes including fish, amphibians and reptiles, but for the most part, research has been focused on non-reptilian hosts, amphibians in particular. More recently, reports of ranaviral infections of reptiles are increasing with over 12 families of reptiles currently susceptible to ranaviral infection. Reptiles are infected by ranaviruses that are genetically similar to, or the same as, the viruses that infect amphibians and fish; however, physiological and ecological differences result in differences in study designs. Although ranaviral disease in reptiles is often influenced by host species, viral strain and environmental differences, general trends in pathogenesis are emerging. More experimental studies using a variety of reptile species, life stages and routes of transmission are required to unravel the complexity of wild ranavirus transmission. Further, our understanding of the reptilian immune response to ranaviral infection is still lacking, although the considerable amount of work conducted in amphibians will serve as a useful guide for future studies in reptiles
Work restructuring and changing craft identity: the Tale of the Disaffected Weavers (or what happens when the rug is pulled from under your feet)
This article explores the changes in worker identity that can occur during manufacturing restructuring – specifically those linked to the declining status of craft work – through an in-depth case study of Weaveco, a UK carpet manufacturer. An analysis of changes in the labour process is followed by employee reactions centred on the demise of the traditional craft identity of male carpet weavers. The voices of the weavers dramatize the tensions involved in reconstructing their masculine identity, and we consider the implications this has for understanding gendered work relations
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