Influence of the coupling between center of mass and internal degrees of freedom on the binding energy of magnetotrions

We present the effects of the center-of-mass dynamics on the negatively charged exciton bound states in the presence of longitudinal magnetic and electric fields. We consider an idealized GaAs/Al0.3Ga0.7As quantum well in the low-field limit and use the configuration interaction method to build up the two-particle basis set. Our results show that the dynamics of the charged exciton center of mass has to be taken into account for a realistic description of the bound states.67

Exciton center-of-mass dispersion in semiconductor quantum wells

We discuss the results of the calculation of the exciton center-of-mass dispersion in a semiconductor quantum well. Strong nonparabolicity arises due to the coupling among the excitons related to the heavy and light holes. We consider the effects of the coupling in the exciton dynamics by calculating the exciton average mass and spin.5642094210

Interacting valence holes in p-type SiGe quantum disks in a magnetic field

The interaction of holes in p-type SiGe quantum disks in a magnetic field is studied. The holes are described by a Luttinger Hamiltonian, with parity replacing spin as a good quantum number. The interaction Hamiltonian separates into charge-charge and parity-parity parts. The effect of parity mediated hole-hole interactions is illustrated by numerical calculations of the energy and capacitance spectra for up to two holes in a quantum disk for parameters corresponding to a SiGe system.5523156941570

Electron-spin polarization near the Fermi level in n-type modulation-doped semiconductor quantum wells

We study the spin polarization of optically created electrons near the Fermi energy in an n-type modulation-doped single quantum well. In our system the Fermi level is slightly above the second confined conduction subband. The results reveal that electrons optically created close to the Fermi level partially conserve their spin polarization, despite the presence of the electron gas. Data obtained by changing the excitation intensity show that exchange interaction among optically created electrons and holes dominates the spin flip processes in the vicinity of the Fermi edge. [S0163-1829(99)51412-4].5912R7813R781

Enhanced magneto-optical oscillations from two-dimensional hole-gases in the presence of Mn ions

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)We investigated the effects of nearby Mn ions on the optical properties of two-dimensional hole-gases confined in InGaAs/GaAs quantum wells. We observed energy oscillations on both the averaged emission and the spin-splitting energies, whereas the first one presents maxima at all integer filling factors, and the second one, solely at odd-filling factors. The strength of the oscillations clearly increases with the Mn concentration. Furthermore, considering the relatively low-mobility of our structures, the oscillations are surprisingly strong and robust, persisting up to relatively high temperatures and excitation intensities. (C) 2011 American Institute of Physics. [doi:10.1063/1.3601477]9825Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Ministry of Education and Science of Russian Federation [RNP 2.2.2.2/4737, 2.2.2.2/11107]Civilian Research and Development Foundation [RUXO-001-NN-06/BP1M01]Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Ministry of Education and Science of Russian Federation [RNP 2.2.2.2/4737, 2.2.2.2/11107]Civilian Research and Development Foundation [RUXO-001-NN-06/BP1M01

Analysis of a viral metagenomic library from 200 m depth in Monterey Bay, California constructed by direct shotgun cloning

<p>Abstract</p> <p>Background</p> <p>Viruses have a profound influence on both the ecology and evolution of marine plankton, but the genetic diversity of viral assemblages, particularly those in deeper ocean waters, remains poorly described. Here we report on the construction and analysis of a viral metagenome prepared from below the euphotic zone in a temperate, eutrophic bay of coastal California.</p> <p>Methods</p> <p>We purified viruses from approximately one cubic meter of seawater collected from 200m depth in Monterey Bay, CA. DNA was extracted from the virus fraction, sheared, and cloned with no prior amplification into a plasmid vector and propagated in <it>E. coli </it>to produce the MBv200m library. Random clones were sequenced by the Sanger method. Sequences were assembled then compared to sequences in GenBank and to other viral metagenomic libraries using BLAST analyses.</p> <p>Results</p> <p>Only 26% of the 881 sequences remaining after assembly had significant (E ≤ 0.001) BLAST hits to sequences in the GenBank nr database, with most being matches to bacteria (15%) and viruses (8%). When BLAST analysis included environmental sequences, 74% of sequences in the MBv200m library had a significant match. Most of these hits (70%) were to microbial metagenome sequences and only 0.7% were to sequences from viral metagenomes. Of the 121 sequences with a significant hit to a known virus, 94% matched bacteriophages (Families <it>Podo</it>-, <it>Sipho</it>-, and <it>Myoviridae</it>) and 6% matched viruses of eukaryotes in the Family <it>Phycodnaviridae </it>(5 sequences) or the Mimivirus (2 sequences). The largest percentages of hits to viral genes of known function were to those involved in DNA modification (25%) or structural genes (17%). Based on reciprocal BLAST analyses, the MBv200m library appeared to be most similar to viral metagenomes from two other bays and least similar to a viral metagenome from the Arctic Ocean.</p> <p>Conclusions</p> <p>Direct cloning of DNA from diverse marine viruses was feasible and resulted in a distribution of virus types and functional genes at depth that differed in detail, but were broadly similar to those found in surface marine waters. Targeted viral analyses are useful for identifying those components of the greater marine metagenome that circulate in the subcellular size fraction.</p

Sex differences in basal hypothalamic anorectic and orexigenic gene expression and the effect of quantitative and qualitative food restriction

Abstract Background Research into energy balance and growth has infrequently considered genetic sex, yet there is sexual dimorphism for growth across the animal kingdom. We test the hypothesis that in the chicken, there is a sex difference in arcuate nucleus neuropeptide gene expression, since previous research indicates hypothalamic AGRP expression is correlated with growth potential and that males grow faster than females. Because growth has been heavily selected in some chicken lines, food restriction is necessary to improve reproductive performance and welfare, but this increases hunger. Dietary dilution has been proposed to ameliorate this undesirable effect. We aimed to distinguish the effects of gut fullness from nutritional feedback on hypothalamic gene expression and its interaction with sex. Methods Twelve-week-old male and female fast-growing chickens were either released from restriction and fed ad libitum or a restricted diet plus 15% w/w ispaghula husk, a non-nutritive bulking agent, for 2 days. A control group remained on quantitative restriction. Hypothalamic arcuate nucleus neuropeptides were measured using real-time PCR. To confirm observed sex differences, the experiment was repeated using only ad libitum and restricted fed fast-growing chickens and in a genetically distinct breed of ad libitum fed male and female chickens. Linear mixed models (Genstat 18) were used for statistical analysis with transformation where appropriate. Results There were pronounced sex differences: expression of the orexigenic genes AGRP (P < 0.001) and NPY (P < 0.002) was higher in males of the fast-growing strain. In genetically distinct chickens, males had higher AGRP mRNA (P = 0.002) expression than females, suggesting sex difference was not restricted to a fast-growing strain. AGRP (P < 0.001) expression was significantly decreased in ad libitum fed birds but was high and indistinguishable between birds on a quantitative versus qualitative restricted diet. Inversely, gene expression of the anorectic genes POMC and CART was significantly higher in ad libitum fed birds but no consistent sex differences were observed. Conclusion Expression of orexigenic peptides in the avian hypothalamus are significantly different between sexes. This could be useful starting point of investigating further if AGRP is an indicator of growth potential. Results also demonstrate that gut fill alone does not reduce orexigenic gene expression

Política Nacional de Saúde Integral da População Negra: implementação, conhecimento e aspectos socioeconômicos sob a perspectiva desse segmento populacional

A Política Nacional de Saúde Integral da População Negra tem o objetivo de garantir a equidade na atenção à saúde para esse segmento populacional. Tal medida possui um caráter compensatório em virtude das discriminações raciais existentes ao longo da história do Brasil. A população negra apresenta maior vulnerabilidade social e econômica, o que reflete uma menor expectativa de vida e maior susceptibilidade a agravos. O objetivo do estudo é investigar o conhecimento da população negra acerca da política, seus potenciais benefícios e as dificuldades de acesso à saúde. Trata-se de uma pesquisa transversal, descritiva e quantitativa. Foram realizadas entrevistas estruturadas com 391 indivíduos negros, usuários do SUS, da cidade de Juiz de Fora. A amostra foi estratificada de acordo com raça (preto e pardo), renda e escolaridade. Cerca de 90% dos entrevistados relataram desconhecer a existência de uma política de saúde para a população negra e 53% declararam uma possível discriminação racial. Observou-se também associação positiva entre discriminação e menor escolaridade e renda. Apesar de desconhecerem a existência da PNSIPN, a maioria dos entrevistados aprovou seus objetivos, mesmo relatando a possibilidade de discriminação dela advinda