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

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

Multivariate restricted maximum likelihood estimation of genetic parameters for production traits in three selected turkey strains

Genetic parameters related to growth, carcass composition and egg production were estimated on three (two female and one male) commercial strains of turkey using the method of restricted maximum likelihood (REML). In order to account for the sexual dimorphism in turkeys, body weight (BW, measured at 12 and 16 weeks of age) was considered as a sex-limited trait. As many as seven traits were analyzed simultaneously in one strain. Egg numbers were normalized using a Box-Cox transformation. Three different genetic models were used. The first one was a linear mixed model with a direct genetic effect. Model 2 accounted in addition for a dam’s environmental effect, while model 3 introduced a maternal genetic effect. The heritability estimates of BW were very high, especially for female traits (0.77 for female BW16 and 0.68 for male BW16 in strain B). Sexual dimorphism was less heritable (0.23, 0.16, and 0.14 for the 16 weeks body weight sex difference in the three strains considered). One of the female strains exhibited a strongly negative genetic correlation (-0.5) between female BW and egg number. The elevated values of the estimates probably originated from the method used, which accounted for the bias due to the sequential selection that had been carried out, and from the choice of the base population. Use of models 2 and 3 resulted in slightly lower heritability estimates than model 1, due to low maternal effects. The latter, however, offered a reasonable compromise between quality and computational cost of the evaluations.Les paramètres génétiques de caractères relatifs à la croissance (poids corporels à 12 et 16 semaines), la teneur en gras (mesure ultrasonique) et la ponte ont été estimés à l’aide de la méthode du maximum de la vraisemblance restreinte (REML) dans trois souches de dindes sélectionnées. Les caractères de poids ont été séparés selon les sexes, afin de rendre compte du dimorphisme sexuel important dans l’espèce et jusqu’à sept caractères ont ainsi été analysés simultanément dans une des souches. Les données de ponte ont été normalisées à l’aide d’une transformation de Box-Cox. Trois modèles génétiques différents ont été utilisés. Le premier est un modèle linéaire mixte incluant la valeur génétique additive individuelle comme effet aléatoire. Dans les autres on ajoute un effet maternel d’abord considéré comme un effet essentiellement de milieu (modèle 2) puis uniquement génétique (modèle 3). Les héritabilités sont très fortes pour les poids corporels, plus élevées pour les poids femelles que pour les poids mâles (0,77 pour les femelles à 16 semaines dans la lignée B contre 0,68 pour les mâles). Le dimorphisme sexuel est un caractère plus faiblement héritable (0,23; 0,16; et 0,14 pour la différence de poids entre mâles et femelles à 16 semaines dans les trois lignées). Dans une des lignées femelles, la corrélation génétique est fortement négative (-0,5) entre le poids des femelles et le nombre d’oeufs pondus. Les valeurs élevées des paramètres génétiques s’expliquent probablement par la méthode employée qui permet de prendre en compte le biais important lié à la sélection de type séquentiel. Le choix de la population de base permet également d’expliquer ces valeurs inhabituelles. Les modèles 2 et 3 donnent des estimées légèrement moins élevées pour les héritabilités que le modèle 1, à cause de la faiblesse des effets maternels. Le modèle 1 permet néanmoins un bon compromis entre simplicité des calculs et qualité de la description

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

A Bright Future for Fluorescence Imaging of Fungi in Living Hosts

Funding: The PhD studentship (A.C.) was funded by the National Centre for the Replacement, Refinement and Reduction of Animals in Research (NC3Rs), grant number NC/N002482/1. We would also like to acknowledge the support of the Medical Research Council Centre for Medical Mycology at the University of Aberdeen (MR/N006364/1).Peer reviewedPublisher PD

Multivariate restricted maximum likelihood estimation of genetic parameters for production traits in three selected turkey strains

Genetic parameters related to growth, carcass composition and egg production were estimated on three (two female and one male) commercial strains of turkey using the method of restricted maximum likelihood (REML). In order to account for the sexual dimorphism in turkeys, body weight (BW, measured at 12 and 16 weeks of age) was considered as a sex-limited trait. As many as seven traits were analyzed simultaneously in one strain. Egg numbers were normalized using a Box-Cox transformation. Three different genetic models were used. The first one was a linear mixed model with a direct genetic effect. Model 2 accounted in addition for a dam’s environmental effect, while model 3 introduced a maternal genetic effect. The heritability estimates of BW were very high, especially for female traits (0.77 for female BW16 and 0.68 for male BW16 in strain B). Sexual dimorphism was less heritable (0.23, 0.16, and 0.14 for the 16 weeks body weight sex difference in the three strains considered). One of the female strains exhibited a strongly negative genetic correlation (-0.5) between female BW and egg number. The elevated values of the estimates probably originated from the method used, which accounted for the bias due to the sequential selection that had been carried out, and from the choice of the base population. Use of models 2 and 3 resulted in slightly lower heritability estimates than model 1, due to low maternal effects. The latter, however, offered a reasonable compromise between quality and computational cost of the evaluations.Les paramètres génétiques de caractères relatifs à la croissance (poids corporels à 12 et 16 semaines), la teneur en gras (mesure ultrasonique) et la ponte ont été estimés à l’aide de la méthode du maximum de la vraisemblance restreinte (REML) dans trois souches de dindes sélectionnées. Les caractères de poids ont été séparés selon les sexes, afin de rendre compte du dimorphisme sexuel important dans l’espèce et jusqu’à sept caractères ont ainsi été analysés simultanément dans une des souches. Les données de ponte ont été normalisées à l’aide d’une transformation de Box-Cox. Trois modèles génétiques différents ont été utilisés. Le premier est un modèle linéaire mixte incluant la valeur génétique additive individuelle comme effet aléatoire. Dans les autres on ajoute un effet maternel d’abord considéré comme un effet essentiellement de milieu (modèle 2) puis uniquement génétique (modèle 3). Les héritabilités sont très fortes pour les poids corporels, plus élevées pour les poids femelles que pour les poids mâles (0,77 pour les femelles à 16 semaines dans la lignée B contre 0,68 pour les mâles). Le dimorphisme sexuel est un caractère plus faiblement héritable (0,23; 0,16; et 0,14 pour la différence de poids entre mâles et femelles à 16 semaines dans les trois lignées). Dans une des lignées femelles, la corrélation génétique est fortement négative (-0,5) entre le poids des femelles et le nombre d’oeufs pondus. Les valeurs élevées des paramètres génétiques s’expliquent probablement par la méthode employée qui permet de prendre en compte le biais important lié à la sélection de type séquentiel. Le choix de la population de base permet également d’expliquer ces valeurs inhabituelles. Les modèles 2 et 3 donnent des estimées légèrement moins élevées pour les héritabilités que le modèle 1, à cause de la faiblesse des effets maternels. Le modèle 1 permet néanmoins un bon compromis entre simplicité des calculs et qualité de la description

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