2,984 research outputs found
Magnetic reconnection and stochastic plasmoid chains in high-Lundquist-number plasmas
A numerical study of magnetic reconnection in the large-Lundquist-number
(), plasmoid-dominated regime is carried out for up to . The
theoretical model of Uzdensky {\it et al.} [Phys. Rev. Lett. {\bf 105}, 235002
(2010)] is confirmed and partially amended. The normalized reconnection rate is
\normEeff\sim 0.02 independently of for . The plasmoid flux
() and half-width () distribution functions scale as and . The joint distribution of and
shows that plasmoids populate a triangular region ,
where is the reconnecting field. It is argued that this feature is due to
plasmoid coalescence. Macroscopic "monster" plasmoids with % of the
system size are shown to emerge in just a few Alfv\'en times, independently of
, suggesting that large disruptive events are an inevitable feature of
large- reconnection.Comment: 5 pages, 6 figures, submitted for publicatio
Manager's effort and endogenous economic discrimination
Vamos assumir que a oferta de trabalho consiste de dois tipos de trabalhadores, 1 e 2. Ambos os trabalhadores são igualmente produtivos e exibem funções de oferta com a mesma elasticidade. Consideramos uma firma (empresário ou acionistas), a qual é competitiva no mercado de produtos e monopsonista nos mercados de insumos. A firma usa os serviços de um gerente quem tem um alto capital humano e cujo salário é dado pelo mercado. Suponhamos que o gerente não gosta de trabalhar com um tipo de trabalhador, digamos o tipo 1. Se permitirmos que o esforço do gerente seja um insumo adicional sem nenhum custo extra (além de seu salário), a decisão de salários será diferente para ambos os trabalhadores. Isto é, haverá um diferencial de salários e, em conseqüência, uma discriminação econômica1 endógena nos mercados de trabalho.Assume a labor supply consisting of two types of workers, 1 and 2. Both workers are equally productive and exhibit supply functions with the same elasticity. We consider a firm (entrepreneur or shareholders) that is competitive in the output market and monopsonistic in input markets. The firm uses the services of a manager who has a high human capital and whose wage is given by the market. It is supposed that the manager does not like to work with one type of worker, say type 1. If we allow the manager's effort to be an additional input without any extra (in addition to his salary) cost for the firm, then the firm's pricing decision will be different for both workers. That is, there will be a wage differential and therefore endogenous economic discrimination2 in the labor markets
Effect of explosive characteristics on the explosive welding of stainless steel to carbon steel in cylindrical configuration
The aim of this research is to study the influence of explosive characteristics on the weld interfaces of stainless steel AISI 304L to low alloy steel 51CrV4 in a cylindrical configuration. The effect of ammonium nitrate-based emulsion, sensitized with different quantities and types of sensitizing agents (hollow glass microballoons or expanded polystyrene spheres) and Ammonium Nitrate Fuel Oil (ANFO) explosives on the interface characteristics is analyzed. Research showed that the type of explosive and the type and proportion of explosive sensitizers affect the main welding parameters, particularly collision point velocity. The morphology of the wavy weld interfaces, chiefly the amplitude and length of the waves, is affected both by the impact velocity and the type and particle size of the explosive sensitizers, and increases with particle size. All the weld interfaces, except welds done with ANFO, displayed localized melted and solidified regions, whose chemical composition resulted from the contribution of both flyer and base metal
Effect of current corrugations on the stability of the tearing mode
The generation of zonal magnetic fields in laboratory fusion plasmas is
predicted by theoretical and numerical models and was recently observed
experimentally. It is shown that the modification of the current density
gradient associated with such corrugations can significantly affect the
stability of the tearing mode. A simple scaling law is derived that predicts
the impact of small stationary current corrugations on the stability parameter
. The described destabilization mechanism can provide an explanation
for the trigger of the Neoclassical Tearing Mode (NTM) in plasmas without
significant MHD activity.Comment: Accepted to Physics of Plasma
A technical note on the phase transformation in furnace container material after a periodic thermo-chemical treatment
The aim of this work is to investigate the metallurgical changes in the wall of cylindrical containers, fabricated by welding from AISI 310 steel, used in the thermal and chemical treatment of spindle chains for the automotive industry, for an in-service period of over 1000 h. In order to identify the phases originated during this in-service period, several etchants were used in the structural study, together with X-ray diffraction and 57Fe Mössbauer spectroscopy analysis. The metallographic technique demonstrates some limitations in the complete identification of the phases produced in the wall of the containers. The structure of the wall of the containers, after the referred to working period, is composed of an austenitic matrix, whose grain size is about 212 and 238 [mu]m, near the internal and external faces of the wall, respectively. These show numerous precipitates inside the grains and at the grain boundaries. The density of the precipitates decreases from the internal to the external surface. The precipitates are nitrides (Cr, Mo)12 (Fe,Ni)8-x N4-z near the internal surface, and carbides (Cr, Fe, Mo)23C6 on the other zones of the wall.http://www.sciencedirect.com/science/article/B6TGJ-4502Y49-G/1/4e6ae31d16e053b40c961bebbfda1e0
A Pentanucleotide ATTTC Repeat Insertion in the Non-coding Region of DAB1, Mapping to SCA37, Causes Spinocerebellar Ataxia
Advances in human genetics in recent years have largely been driven by next-generation sequencing (NGS); however, the discovery of disease-related gene mutations has been biased toward the exome because the large and very repetitive regions that characterize the non-coding genome remain difficult to reach by that technology. For autosomal-dominant spinocerebellar ataxias (SCAs), 28 genes have been identified, but only five SCAs originate from non-coding mutations. Over half of SCA-affected families, however, remain without a genetic diagnosis. We used genome-wide linkage analysis, NGS, and repeat analysis to identify an (ATTTC)n insertion in a polymorphic ATTTT repeat in DAB1 in chromosomal region 1p32.2 as the cause of autosomal-dominant SCA; this region has been previously linked to SCA37. The non-pathogenic and pathogenic alleles have the configurations [(ATTTT)7-400] and [(ATTTT)60-79(ATTTC)31-75(ATTTT)58-90], respectively. (ATTTC)n insertions are present on a distinct haplotype and show an inverse correlation between size and age of onset. In the DAB1-oriented strand, (ATTTC)n is located in 5' UTR introns of cerebellar-specific transcripts arising mostly during human fetal brain development from the usage of alternative promoters, but it is maintained in the adult cerebellum. Overexpression of the transfected (ATTTC)58 insertion, but not (ATTTT)n, leads to abnormal nuclear RNA accumulation. Zebrafish embryos injected with RNA of the (AUUUC)58 insertion, but not (AUUUU)n, showed lethal developmental malformations. Together, these results establish an unstable repeat insertion in DAB1 as a cause of cerebellar degeneration; on the basis of the genetic and phenotypic evidence, we propose this mutation as the molecular basis for SCA37.info:eu-repo/semantics/publishedVersio
Advanced FE models of stiffened cleat angle connections
Congreso celebrado en la Escuela de Arquitectura de la Universidad de Sevilla desde el 24 hasta el 26 de junio de 2015.In this paper, the development of reliable 3D FE models of stiffened angle connections is dealt with. These advanced models will permit to obtain the assessment of the 3D deformational response of some future tests. Abaqus® finite element code was used to carry the 3D finite element analyses out. Symmetry was considered for these numerical analyses so a quarter of the geometry was modelled. The results obtained are compared with those from the analysis of the analogous specimens but without the top angle stiffener, showing an important increase in the initial connection stiffness. At the same time, the stress increment in the column panel zone due to the presence of the angle stiffener has been discussed
ARPES Study of the Metal-Insulator Transition in Bismuth Cobaltates
We present an angle-resolved photoemission spectroscopy (ARPES) study of a
Mott-Hubbard-type bismuth cobaltate system across a metal-insulator transition.
By varying the amount of Pb substitution, and by doping with Sr or Ba cation, a
range of insulating to metallic properties is obtained. We observe a systematic
change in the spectral weight of the coherent and incoherent parts, accompanied
by an energy shift of the incoherent part. The band dispersion also shows the
emergence of a weakly dispersing state at the Fermi energy with increasing
conductivity. These changes correspond with the changes in the
temperature-dependent resistivity behavior. We address the nature of the
coherent-incoherent parts in relation to the peak-dip-hump feature seen in
cuprates superconductors
Ensayos comparativos a escala real de cubierta formada por correas Z conformadas en frÃo
The use of cold formed Z purlins is common in industrial construction. However, due to the high uncertainty of such structures and elements, and their tendency to suffer local instability phenomena, it is very interesting to have actual test results.
In this article, the results of two tests of full-scale roofs are provided. The roofs are loaded with water pool until the collapse of the structure, thereby determining its ultimate strength and behavior up to this point, and comparing the results with those obtained using different standard methodologies in the field of structural engineering.
It is concluded that the behavior in the linear range during testing is very similar to the predicted analytically, and a very high ultimate strength is observed until the collapse of the structure in both tests.<br><br>La utilización de correas Z conformadas en frio es muy habitual en construcción industrial. No obstante, debido al alto grado de incertidumbre de este tipo de estructuras y elementos, y a su tendencia a sufrir fenómenos de inestabilidad local, resulta muy interesante contar con resultados de ensayos reales.
En este artÃculo, se aportan los resultados de dos ensayos de cubiertas Deck a escala real. La cubierta se carga mediante balsa de agua hasta llegar al colapso de la estructura, determinando tanto su resistencia última, como el comportamiento hasta este punto. Adicionalmente se comparan los resultados de los ensayos con los obtenidos mediante diferentes metodologÃas habituales en el ámbito de la ingenierÃa estructural.
Se concluye que el comportamiento en el rango lineal durante los ensayos es muy similar al predicho analÃticamente, y se observa una muy alta resistencia última hasta el colapso de la estructura en ambos ensayos
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