8 research outputs found
Spin torque contribution to the a.c. spin Hall conductivity
Using the recently proposed definition of a conserved spin-current operator
[J. Shi et al., Phys. Rev. Lett. 96, 076604 (2006)] we explore the frequency
dependent spin Hall conductivity for a two-dimensional electron gas with Rashba
and Dresselhaus spin-orbit interaction in response to an oscillating electric
field. We show that the optical spectrum of the spin Hall conductivity exhibit
remarkable changes when the new definition of spin current is applied. Such
behavior is mainly due to a significant contribution of the spin torque term
which is absent in the conventional form of the spin current. In addition, it
is observed that the magnitude and direction of the dynamic spin Hall current
strongly depends on the electric field frequency as with the interplay of the
spin-orbit coupling strengths.Comment: 8 pages, 4 figures, pape
Hot-electron dynamics at noble metal surfaces
The dynamics of excited electronic states at Ag surfaces is studied by evaluating the quasiparticle self-energy within the GW approximation. The screened Coulomb interaction W is shown to be sensitive to the spatial variation of s-d screening near the surface. In the region of s-electron spill-out electronic damping is stronger than in the bulk due to the reduced s-d polarization, giving rise to shorter surface-state lifetimes. The lifetime of Ag image states is expected to be strongly reduced due to decay into surface plasmons
Inclusion of Mannan-Oligosaccharides in Diets for Tropical Gar <i>Atractosteus tropicus</i> Larvae: Effects on Growth, Digestive Enzymes, and Expression of Intestinal Barrier Genes
Mannan-oligosaccharides (MOS) are non-digestible carbohydrates, and their use in aquaculture as prebiotics is well documented. The objective of this work was to test whether MOS supplemented in the diet of A. tropicus larvae (2, 4, and 6 g kgâ1) influence growth parameters, the activity of digestive enzymes, and the expression of genes related to the intestinal barrier. The highest total length was observed in larvae fed 6 g kgâ1 MOS compared to control larvae. Trypsin activity increased with the addition of MOS to the diets, but leucine aminopeptidase activity only increased with 6 g kgâ1 MOS. Lipase and α-amylase activities increased in larvae fed with 2 and 4 g kgâ1 MOS. The expression of zo-2 was higher with the 6 g kgâ1 MOS treatment. The cl-3 transcripts were lower with 2 g kgâ1 MOS but higher with 6 g kgâ1 MOS. All tested concentrations of MOS increased the expression of muc-2. In this study, incorporating mannan-oligosaccharides into the diet of A. tropicus larvae had a positive effect, and the concentration of 6 g kgâ1 produced the best results. Therefore, including this prebiotic in the diets for the culture of A. tropicus larvae is suitable
Incorporation of Fructooligosaccharides in Diets Influence Growth Performance, Digestive Enzyme Activity, and Expression of Intestinal Barrier Function Genes in Tropical Gar (<i>Atractosteus tropicus</i>) Larvae
This study was conducted to investigate the effects of dietary fructooligosaccharides (FOS) on the growth, survival rate, digestive enzyms activity, and the expression of intestinal barrier function genes in tropical gar (Atractosteus tropicus) larvae. A total of 960 larvae (0.030 ± 0.006 g) were fed three diets supplemented with increasing FOS concentrations (2.5, 5, and 7.5 g kgâ1) and a control diet for 15 days. Results revealed that a 7.5 g kgâ1 FOS supplementation improved weight gain, specific growth rate, and survival rate (p â1 FOS supplementation increased alkaline protease and amylase activities and induced an upregulation of the claudin-17 gene expression (p â1 FOS induced the upregulation of mucin 2 (muc-2), and the tight junction genes zo-2 and claudin-3 (p â1 FOS promoted the downregulation of the claudin-15 gene expression (p il-8 expression. We can conclude that 7.5 g kgâ1 FOS supplementation improves growth performance, survival rate, and digestive capacity, and could contribute to the reinforcement of the intestinal barrier function of Tropical gar larvae