Pneumatic drying of cassava starch: Numerical analysis and guidelines for the design of efficient small-scale dryers

In a number of tropical countries, the expansion of cassava processing is tied to the development of small-scale, energy-efficient pneumatic dryers used to dry flour and starch. To facilitate this development, in this study a model of the pneumatic drying of starch particles was developed, to be fitted to measurements taken from large cassava processing factories. After that, numerical simulations were performed to analyze the effects of geometry and operating conditions on the energy efficiency and pipe length required to dry the product. The results clarified the influence of processing capacity, air inlet conditions, and starch particle size, emphasizing that air velocity as well as the dilution of the starch should be minimized. In light of the findings described here, we offer guidelines for the design of efficient small-capacity flash dryers

Lifetimes of Confined Acoustic Phonons in Ultra-Thin Silicon Membranes

We study the relaxation of coherent acoustic phonon modes with frequencies up to 500 GHz in ultra-thin free-standing silicon membranes. Using an ultrafast pump-probe technique of asynchronous optical sampling, we observe that the decay time of the first-order dilatational mode decreases significantly from \sim 4.7 ns to 5 ps with decreasing membrane thickness from \sim 194 to 8 nm. The experimental results are compared with theories considering both intrinsic phonon-phonon interactions and extrinsic surface roughness scattering including a wavelength-dependent specularity. Our results provide insight to understand some of the limits of nanomechanical resonators and thermal transport in nanostructures

Thickness-dependent thermal properties of amorphous insulating thin films measured by photoreflectance microscopy

In this work, we report on the measurement of the thermal conductivity of thin insulating films of SiO2 obtained by thermal oxidation, and Al2O3 grown by atomic layer deposition (ALD), both on Si wafers. We used photoreflectance microscopy to determine the thermal properties of the films as a function of thickness in the 2 nm to 1000 nm range. The effective thermal conductivity of the Al2O3 layer is shown to decrease with thickness down to 70% for the thinnest layers. The data were analyzed upon considering that the change in the effective thermal conductivity corresponds to an intrinsic thermal conductivity associated to an additional interfacial thermal resistance. The intrinsic conductivity and interfacial thermal resistance of SiO2 were found to be equal to 0.95 W/m·K and 5.1 × 10− 9 m2K/W respectively; those of Al2O3 were found to be 1.56 W/m·K and 4.3 × 10− 9 m2K/W

Shape-dependence of near-field heat transfer between a spheroidal nanoparticle and a flat surface

We study the radiative heat transfer between a spheroidal metallic nanoparticle and a planar metallic sample for near- and far-field distances. In particular, we investigate the shape dependence of the heat transfer in the near-field regime. In comparison with spherical particles, the heat transfer typically varies by factors between 1/2 and 2 when the particle is deformed such that its volume is kept constant. These estimates help to quantify the deviation of the actual heat transfer recorded by a near-field scanning thermal microscope from the value provided by a dipole model which assumes a perfectly spherical sensor

The Distance to the Soft Gamma Repeater SGR 1627-41

We report millimeter observations of the line of sight to the recently discovered Soft Gamma Repeater, SGR 1627-41, which has been tentatively associated with the supernova remnant SNR G337.0-0.1 Among the eight molecular clouds along the line of sight to SGR 1627-41, we show that SNR G337.0-0.1 is probably interacting with one of the most massive giant molecular clouds (GMC) in the Galaxy, at a distance of 11 kpc from the sun. Based on the high extinction to the persistent X-ray counterpart of SGR 1627-41, we present evidence for an association of this new SGR with the SNR G337.0-0.1; they both appear to be located on the near side of the GMC. This is the second SGR located near an extraordinarily massive GMC. We suggest that SGR 1627-41 is a neutron star with a high transverse velocity (~ 1,000 \kms) escaping the young (~ 5,000 years) supernova remnant G337.0-0.1Comment: 17 pages, including 2 figures. Accepted for publication in the Astrophysical Journal Letter

Safety and efficacy of recombinant human erythropoietin treatment of anaemia associated with multiple myeloma in haemodialysed patients

Recombinant human erythropoietin (rHuEpo) was used to treat the anaemia of four haemodialysed patients (3 males, 1 female) with advanced multiple myeloma; the type of serum M component was IgG kappa in all cases. During the 6-month period preceding rHuEpo therapy the patients received multiple blood transfusions (range 4-22 units of packed red cells per patient). After the first month of treatment haematocrit increased from 23±3 (SD) to 32±4% and during the last 3 months the maintenance dose of rHuEpo was 143±37 U/kg per week to achieve a mean haematocrit of 35±1%. After introduction of rHuEpo, blood transfusions were no longer required and the patients reported an improvement in wellbeing. No apparent worsening of multiple myeloma has been observed over the treatment period ranging from 5 to 34 months (cumulative duration of treatment 55 months). Anti-hypertensive therapy was started in one case and increased in two patients. We conclude that rHuEpo appears to be effective and safe in treating anaemia associated with multiple myeloma in patients requiring haemodialysi

Hereditary sensory and autonomic neuropathy type IV and orthopaedic complications

SummaryHereditary sensory and autonomic neuropathy type IV (HSAN-IV) is a very rare autosomal recessive disorder characterized by recurrent episodes of unexplained fever, extensive anhidrosis, total insensitivity to pain, hypotonia, and mental retardation. The most frequent complications of this disease are corneal scarring, multiple fractures, joint deformities, osteomyelitis, and disabling self-mutilations. We reported the case of a 12-year-old boy. The goal was to discuss our decision-making and compare this case with cases described in the literature

A Amazônia pode se tornar uma grande região de pecuária bovina sustentável?

A biblioteca possui o trabalho completo, copiado de CD-ROM (SP 4937

Influence of contact angle on slow evaporation in two-dimensional porous media

We study numerically the influence of contact angle on slow evaporation in two-dimensional model porous media. For sufficiently low contact angles, the drying pattern is fractal and can be predicted by a simple model combining the invasion percolation model with the computation of the diffusive transport in the gas phase. The overall drying time is minimum in this regime and is independent of contact angle over a large range of contact angles up to the beginning of a transition zone. As the contact angle increases in the transition region, the cooperative smoothing mechanisms of the interface become important and the width of the liquid gas interface fingers that form during the evaporation process increases. The mean overall drying time increases in the transition region up to an upper bound which is reached at a critical contact angle \Theta_c. The increase in the drying time in the transition region is explained in relation with the diffusional screening phenomenon associated with the Laplace equation governing the vapor transport in the gas phase. Above \Theta_c the drying pattern is character- ized by a flat traveling front and the mean overall drying time becomes independent of the contact angle. Drying time fluctuations are studied and are found to be important below \Theta_c, i.e., when the pattern is fractal. The fluctuations are of the same order of magnitude regardless of the value of contact angle in this range. The fluctuations are found to die out abruptly at \Theta_c as the liquid gas interface becomes a flat front

L' Amazonie Pâturée.

En passant de 4-5 à près de 100 millions de bovins en quatre décennies, l’Amazonie se positionne comme un acteur majeur de la production animale à l’échelle mondiale. Cette très forte croissance est étroitement liée à la colonisation de la grande forêt mise en œuvre par les pouvoirs publics des états amazoniens. A partir d’une information collectée sur une quinzaine d’années, les auteurs tentent d’expliquer les combinaisons de facteurs sociaux, économiques, politiques, techniques et culturel sconduisant à la transformation des écosystèmes forestiers naturels en pâturage. Pour tous les colons, grands et petits, l’acquisition de foncier est la principale motivation, d’autant plus que les états, notamment au Brésil, ont été généreux et pe u regardants sur les modalités d’attribution des terres. Malgré les disparités, la climatologie associant forte pluviométrie, forte température et fort ensoleillement, ainsi que l’absence de pathologie spécifique offre des conditions favorables à l’élevage bovin avec des coûts de production très bas. Un effort significatif a été fait pour mettre au point des systèmes adaptés. Le marché international des produits animaux semble vouloir continuer à absorber l’augmentation de la production agricole sud-américaine boostée par l’agriculture amazonienne