72 research outputs found
Shape Distortion by Irreversible Flux-Pinning-Induced Magnetostriction
Exact analytical results are obtained for the flux-pinning-induced
magnetostriction in cylindrical type-II superconductors placed in parallel
magnetic field. New modes of irreversible deformation are found: In contrast to
the circular cylinder where shape is conserved, it is shown that a square
cross-section deforms with considerable distortion. During a field cycle both
concave, convex, and even more complicated distortions are predicted. Strong
implications for dilatometric measurements on crystals are emphasized. The main
results are valid for any critical-state model, j_c = j_c(B).Comment: 4 pages, 4 graph
The composite picture of the charge carriers in La2-xSrxCuO4 (0.063 < x < 0.11) superconductors
Through far-infrared studies of La2-xSrxCuO4 single crystals for x = 0.063,
0.07, 0.09, and 0.11, we found that only ~ 0.2 % of the total holes
participated in the nearly dissipationless normal state charge transport and
superconductivity. We have also observed characteristic collective modes at w ~
18 cm-1 and 22 cm-1 due to the bound carriers in an electronic lattice (EL)
state and the free carriers are massively screened by the EL. Our findings lead
us to propose a composite picture of the charge system where the free carriers
are coupled to and riding on the EL. This unique composite system of charge
carriers may provide further insights into the understanding of the cuprate
physics.Comment: 10 pages, 4 figure
TEMPus VoLA: The timed Epstein multi-pressure vessel at low accelerations.
The field of planetary system formation relies extensively on our understanding of the aerodynamic interaction between gas and dust in protoplanetary disks. Of particular importance are the mechanisms triggering fluid instabilities and clumping of dust particles into aggregates, and their subsequent inclusion into planetesimals. We introduce the timed Epstein multi-pressure vessel at low accelerations, which is an experimental apparatus for the study of particle dynamics and rarefied gas under micro-gravity conditions. This facility contains three experiments dedicated to studying aerodynamic processes: (i) the development of pressure gradients due to collective particle-gas interaction, (ii) the drag coefficients of dust aggregates with variable particle-gas velocity, and (iii) the effect of dust on the profile of a shear flow and resultant onset of turbulence. The approach is innovative with respect to previous experiments because we access an untouched parameter space in terms of dust particle packing fraction, and Knudsen, Stokes, and Reynolds numbers. The mechanisms investigated are also relevant for our understanding of the emission of dust from active surfaces, such as cometary nuclei, and new experimental data will help interpreting previous datasets (Rosetta) and prepare future spacecraft observations (Comet Interceptor). We report on the performance of the experiments, which has been tested over the course of multiple flight campaigns. The project is now ready to benefit from additional flight campaigns, to cover a wide parameter space. The outcome will be a comprehensive framework to test models and numerical recipes for studying collective dust particle aerodynamics under space-like conditions
Comparison between reference values for FVC, FEV1, and FEV1/FVC ratio in White adults in Brazil and those suggested by the Global Lung Function Initiative 2012
Genome-wide gene expression profiling reveals renal genes regulated during metabolic acidosis
Production and excretion of acids are balanced to maintain systemic acid-base homeostasis. During metabolic acidosis (MA) excess acid accumulates and is removed from the body, a process achieved, at least in part, by increasing renal acid excretion. This acid-secretory process requires the concerted regulation of metabolic and transport pathways, which are only partially understood. Chronic MA causes also morphological remodeling of the kidney. Therefore, we characterized transcriptional changes in mammalian kidney during MA to gain insights into adaptive pathways. Total kidney RNA from control and 2- and 7-days NH(4)Cl treated mice was subjected to microarray gene profiling. We identified 4,075 transcripts significantly (P < 0.05) regulated after 2 and/or 7 days of treatment. Microarray results were confirmed by qRT-PCR. Analysis of candidate genes revealed that a large group of regulated transcripts was represented by different solute carrier transporters, genes involved in cell growth, proliferation, apoptosis, water homeostasis, and ammoniagenesis. Pathway analysis revealed that oxidative phosphorylation was the most affected pathway. Interestingly, the majority of acutely regulated genes after 2 days, returned to normal values after 7 days suggesting that adaptation had occurred. Besides these temporal changes, we detected also differential regulation of selected genes (SNAT3, PEPCK, PDG) between early and late proximal tubule. In conclusion, the mammalian kidney responds to MA by temporally and spatially altering the expression of a large number of genes. Our analysis suggests that many of these genes may participate in various processes leading to adaptation and restoration of normal systemic acid-base and electrolyte homeostasis
Modernisation and the practices of contemporary food shopping
This paper examines the relationship between modernisation, consumption, and society, challenging received ideas about the distinction between âmodernâ and âpremodernâ geographies of food consumption. While conventional accounts posit a historical progression from premodern to modern forms of consumption, associated with the rise of the supermarket and the demise of the corner store, we argue that such distinctions may, in fact, refer less to a historical process of transition than to a contrast between different forms of contemporary sociality, experienced simultaneously in different sites of consumption. By drawing critically on the work of AugĂ© and his contrast between places and nonplaces, these ideas are then put to work empirically in an examination of contemporary food shopping in Germany, focusing particularly on notions of consumer trust. A practice-based and ethnographically informed account of food shopping in Germany shows how distinctions between âtraditionalâ and âmodernâ forms of consumption involve historicised accounts of contemporary consumption spaces and their associated socialities rather than referring to historical differences per se
Ever-young sex chromosomes in European tree frogs.
Non-recombining sex chromosomes are expected to undergo evolutionary decay, ending up genetically degenerated, as has happened in birds and mammals. Why are then sex chromosomes so often homomorphic in cold-blooded vertebrates? One possible explanation is a high rate of turnover events, replacing master sex-determining genes by new ones on other chromosomes. An alternative is that X-Y similarity is maintained by occasional recombination events, occurring in sex-reversed XY females. Based on mitochondrial and nuclear gene sequences, we estimated the divergence times between European tree frogs (Hyla arborea, H. intermedia, and H. molleri) to the upper Miocene, about 5.4-7.1 million years ago. Sibship analyses of microsatellite polymorphisms revealed that all three species have the same pair of sex chromosomes, with complete absence of X-Y recombination in males. Despite this, sequences of sex-linked loci show no divergence between the X and Y chromosomes. In the phylogeny, the X and Y alleles cluster according to species, not in groups of gametologs. We conclude that sex-chromosome homomorphy in these tree frogs does not result from a recent turnover but is maintained over evolutionary timescales by occasional X-Y recombination. Seemingly young sex chromosomes may thus carry old-established sex-determining genes, a result at odds with the view that sex chromosomes necessarily decay until they are replaced. This raises intriguing perspectives regarding the evolutionary dynamics of sexually antagonistic genes and the mechanisms that control X-Y recombination
The influence of sample surface quality and grain boundaries on the electrical resistivity of metals
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