Swapping trajectories: a new wall-induced cross-streamline particle migration mechanism in a dilute suspension of spheres

Binary encounters between spherical particles in shear flow are studied for a system bounded by a single planar wall or two parallel planar walls under creeping flow conditions. We show that wall proximity gives rise to a new class of binary trajectories resulting in cross-streamline migration of the particles. The spheres on these new trajectories do not pass each other (as they would in free space) but instead they swap their cross-streamline positions. To determine the significance of the wall-induced particle migration, we have evaluated the hydrodynamic self-diffusion coefficient associated with a sequence of uncorrelated particle displacements due to binary particle encounters. The results of our calculations quantitatively agree with the experimental value obtained by \cite{Zarraga-Leighton:2002} for the self-diffusivity in a dilute suspension of spheres undergoing shear flow in a Couette device. We thus show that the wall-induced cross-streamline particle migration is the source of the anomalously large self-diffusivity revealed by their experiments.Comment: submited to JF

HESS J1632-478: an energetic relic

HESS J1632-478 is an extended and still unidentified TeV source in the galactic plane. In order to identify the source of the very high energy emission and to constrain its spectral energy distribution, we used a deep observation of the field obtained with XMM-Newton together with data from Molonglo, Spitzer and Fermi to detect counterparts at other wavelengths. The flux density emitted by HESS J1632-478 peaks at very high energies and is more than 20 times weaker at all other wavelengths probed. The source spectrum features two large prominent bumps with the synchrotron emission peaking in the ultraviolet and the external inverse Compton emission peaking in the TeV. HESS J1632-478 is an energetic pulsar wind nebula with an age of the order of 10^4 years. Its bolometric (mostly GeV-TeV) luminosity reaches 10% of the current pulsar spin down power. The synchrotron nebula has a size of 1 pc and contains an unresolved point-like X-ray source, probably the pulsar with its wind termination shock.Comment: A&A accepted, 9 pages, 5 figures, 4 table

Financial Crisis, Health Outcomes and Aging: Mexico in the 1980s and 1990s

We study the impact of economic crisis on health in Mexico. There have been four wide-scale economic crises in Mexico in the past two decades, the most recent in 1995-96. We find that mortality rates for the very young and the elderly increase or decline less rapidly in crisis years as compared with non-crisis years. In late 1995-96 crisis, mortality rates were about 5 to 7 percent higher in the crisis years compared to the years just prior to the crisis. This translates into a 0.4 percent increase in mortality for the elderly and a 0.06 percent increase in mortality for the very young. We find tentative evidence that economic crises affect mortality by reducing incomes and possibly by placing a greater burden on the medical sector, but not by forcing less healthy members of the population to work or by forcing primary caregivers to go to work.

A Review Of Implementing Adc In Rfid Sensor

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)The general considerations to design a sensor interface for passive RFID tags are discussed. This way, power and timing constraints imposed by ISO/IEC 15693 and ISO/IEC 14443 standards to HF RFID tags are explored. A generic multisensor interface is proposed and a survey analysis on the most suitable analog-to-digital converters for passive RFID sensing applications is reported. The most appropriate converter type and architecture are suggested. At the end, a specific sensor interface for carbon nanotube gas sensors is proposed and a brief discussion about its implemented circuits and preliminary results is made.Region Rhone-Alpes (France)CNPq (Brazil)INCT/NAMITEC (Brazil)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

The internal dynamical equilibrium of HII regions: a statistical study

We present an analysis of the integrated Halpha emission line profiles for the HII region population of the spiral galaxies NGC 1530, NGC 6951 and NGC 3359. We show that 70% of the line profiles show two or three Gaussian components. The relations between the Halpha luminosity and non-thermal line width for the HII regions of the three galaxies are studied and compared with the relation found taken all the HII regions of the three galaxies as a single distribution. A clearer envelope in non-thermal line width is found when only those HII regions with non-thermal line width bigger than 13kms are considered. The linear fit for the envelope is logL=36.8+2.0*log(sigma). The masses of the HII regions on the envelope using the virial theorem and the mass estimates from the Halpha luminosity are comparable, which offers evidence that the HII regions on the envelope are virialized systems, while the remaining regions, the majority, are not in virial equilibrium.Comment: 19 pages, 10 figures,accepted for publication in A&

Probing Clumpy Stellar Winds in SFXTs

Quantitative constraints on the wind clumping of massive stars can be obtained from the study of the hard X-ray variability of SFXTs. In these systems, a large fraction of the hard X-ray emission is emitted in the form of flares with typical duration of 3 ksec, frequency of 7 days and luminosity of $10^{36}$ ergs/s. Such flares are most probably emitted by the interaction of a compact object orbiting at $\sim10$ R$_*$ with wind clumps ($10^{22-23}$ g). The density ratio between the clumps and the inter-clump medium is $10^{2-4}$ . The parameters of the clumps and of the inter-clump medium are in good agreement with macro-clumping scenario and line-driven instability simulations.Comment: 3 pages, A Population Explosion: The Nature and Evolution of X-ray Binaries in Diverse Environment