8,149 research outputs found
On the dependence of the avalanche angle on the granular layer thickness
A layer of sand of thickness h flows down a rough surface if the inclination
is larger than some threshold value theta which decreases with h. A tentative
microscopic model for the dependence of theta with h is proposed for rigid
frictional grains, based on the following hypothesis: (i) a horizontal layer of
sand has some coordination z larger than a critical value z_c where mechanical
stability is lost (ii) as the tilt angle is increased, the configurations
visited present a growing proportion $_s of sliding contacts. Instability with
respect to flow occurs when z-z_s=z_c. This criterion leads to a prediction for
theta(h) in good agreement with empirical observations.Comment: 6 pages, 2 figure
Characterization of a rare analphoid supernumerary marker chromosome in mosaic
Abstract publicado em: Chromosome Research. 2015;23(Suppl 1):67-8. doi:10.1007/s10577-015-9476-6Analphoid supernumerary marker chromosomes (SMCs) are a rare subclass of SMCs C-band-negative
and devoid of alpha-satellite DNA. These marker chromosomes cannot be identified unambiguously by conventional banding techniques alone being necessary to apply molecular cytogenetic methods in favour of a detailed characterization. In this work we report an analphoid SMC involving the terminal long arm of chromosome 7, in 9 years-old boy with several dysmorphic features and severe development delay.
Cytogenetic analysis revealed a mosaic karyotype with the presence of an extra SMC, de novo, in 20 %
of lymphocytes and 73 % of fibroblast cells. FISH analysis with alpha-satellite probes for all chromosomes, whole chromosome painting probe for chromosome 7, and D7S427 and TelVysion 7q probes, allowed
establishing the origin of the SMC as an analphoidmarker resulting of an invdup rearrangement of 7q36-qter region. Affimetrix CytoScan HD microarray analysis, redefined the SMC to arr[hg19] 7q35(143696249-159119707)×2~3, which correspond to a gain of 15.42 Mb and encloses 67 OMIM genes, 16 of which are associated to disease. This result, combined with detailed clinical description, will provide an important means for better genotype-phenotype correlation and a more suitable genetic counselling to the patient and his parents, despite the additional difficulty resulting from being a mosaic (expression varies in different tissues). Analphoid SMCs derived from chromosome 7 are very rare, with only three cases reported so far. With this case we hope contribute to a better understanding of this type of chromosome rearrangements which are difficult for genetic counselling
Identificação de 'outliers' em levantamentos amostrais.
O objetivo deste trabalho é apresentar uma sequência de procedimentos que levam à identificação de ?outliers? em um levantamento amostral cuja variável-resposta tem distribuição normal
Dissipative collapse of the adiabatic piston
An adiabatic piston, separating two granular gases prepared in the same
macroscopic state, is found to eventually collapse to one of the sides. This
new instability is explained by a simple macroscopic theory which is
furthermore in qualitative agreement with hard disk molecular dynamics.Comment: 7 pages, 5 figure
Chemical abundances for 11 bulge stars from high-resolution, near-IR spectra
It is debated whether the Milky Way bulge has the characteristics of a
classical bulge sooner than those of a pseudobulge. Detailed abundance studies
of bulge stars is a key to investigate the origin, history, and classification
of the bulge. The aim is to add to the discussion on the origin of the bulge
and to study detailed abundances determined from near-IR spectra for bulge
giants already investigated with optical spectra, the latter also providing the
stellar parameters which are very significant for the results of the present
study. Especially, the important CNO elements are better determined in the
near-IR. High-resolution, near-infrared spectra in the H band are recorded
using the CRIRES spectrometer on the Very Large Telescope. The CNO abundances
can all be determined from the numerous molecular lines in the wavelength range
observed. Abundances of the alpha elements are also determined from the near-IR
spectra. [O/Fe], [Si/Fe] and [S/Fe] are enhanced up to metallicities of at
least [Fe/H]=-0.3, after which they decline. This suggests that the Milky Way
bulge experienced a rapid and early star-formation history like that of a
classical bulge. However, a similarity between the bulge trend and the trend of
the local thick disk seems present. Such a similarity could suggest that the
bulge has a pseudobulge origin. Our [C/Fe] trend does not show any increase
with [Fe/H] which could have been expected if W-R stars have contributed
substantially to the C abundances. No "cosmic scatter" can be traced around our
observed abundance trends; the scatter found is expected, given the
observational uncertainties.Comment: Accepted for publication in A&
Atualização da rede de drenagens e inserção de sua nomenclatura no Estado do Mato Grosso do Sul.
O Projeto GeoMS visa à identificação, à caracterização e ao mapeamento das áreas desmatadas, à cobertura vegetal e ao uso da terra, para auxiliar a implantação de projetos estratégicos, promover a preservação e a conservação ambiental, além de um desenvolvimento sustentável do Estado do Mato Grosso do Sul (PROJETO GEOMS, 2011). O projeto é dividido basicamente em três áreas: o desenvolvimento do Sistema Interativo de Suporte ao Licenciamento Ambiental (Sisla) (SISLA, 2011); o levantamento e mapeamento de áreas degradadas e cobertura vegetal e uso da terra; e o ajuste da drenagem e delimitação das bacias hidrográficas. Um dos objetivos dessa terceira parte é a atualização das drenagens do Estado do Mato Grosso do Sul
Nontrivial temporal scaling in a Galilean stick-slip dynamics
We examine the stick-slip fluctuating response of a rough massive
non-rotating cylinder moving on a rough inclined groove which is submitted to
weak external perturbations and which is maintained well below the angle of
repose. The experiments presented here, which are reminiscent of the Galileo's
works with rolling objects on inclines, have brought in the last years
important new insights into the friction between surfaces in relative motion
and are of relevance for earthquakes, differing from classical block-spring
models by the mechanism of energy input in the system. Robust nontrivial
temporal scaling laws appearing in the dynamics of this system are reported,
and it is shown that the time-support where dissipation occurs approaches a
statistical fractal set with a fixed value of dimension. The distribution of
periods of inactivity in the intermittent motion of the cylinder is also
studied and found to be closely related to the lacunarity of a random version
of the classic triadic Cantor set on the line.Comment: 7 pages including 6 figure
Fatores de risco envolvidos na dermatite necrótica dos frangos de corte.
Projeto/Plano de Ação: 16.00.30.004
Confining potential in a color dielectric medium with parallel domain walls
We study quark confinement in a system of two parallel domain walls
interpolating different color dielectric media. We use the phenomenological
approach in which the confinement of quarks appears considering the QCD vacuum
as a color dielectric medium. We explore this phenomenon in QCD_2, where the
confinement of the color flux between the domain walls manifests, in a scenario
where two 0-branes (representing external quark and antiquark) are connected by
a QCD string. We obtain solutions of the equations of motion via first-order
differential equations. We find a new color confining potential that increases
monotonically with the distance between the domain walls.Comment: RevTex4, 5 pages, 1 figure; version to appear in Int. J. Mod. Phys.
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