Self-consistent Coulomb effects and charge distribution of quantum dot arrays

This paper considers the self-consistent Coulomb interaction within arrays of self-assembled InAs quantum dots (QDs) which are embedded in a pn structure. Strong emphasis is being put on the statistical occupation of the electronic QD states which has to be solved self-consistently with the actual three-dimensional potential distribution. A model which is based on a Green's function formalism including screening effects is used to calculate the interaction of QD carriers within an array of QDs, where screening due to the inhomogeneous bulk charge distribution is taken into acount. We apply our model to simulate capacitance-voltage (CV) characteristics of a pn structure with embedded QDs. Different size distributions of QDs and ensembles of spatially perodic and randomly distributed arrays of QDs are investigated.Comment: submitted to pr

Magnetotelluric Imaging of the Lithosphere Across the Variscan Orogen (Iberian Autochthonous Domain, NW Iberia)

A new magnetotelluric (MT) survey comprising 17 MT soundings throughout a 30 km long N30°W transect in the Iberian autochthons domain of NW Iberia (Central Iberian Zone) is presented. The 2-D inversion model shows the resistivity structure of the continental crust up to 10 km depth, heretofore unavailable for this region of the Variscan Orogen. The MT model reveals a wavy structure separating a conductive upper layer underlain by a resistive layer, thus picturing the two main tectonic blocks of a large-scale D2 extensional shear zone (i.e., Pinhel shear zone). The upper layer represents a lower grade metamorphic domain that includes graphite-rich rocks. The lower layer consists of high-grade metamorphic rocks that experienced partial melting and are associated with granites (more resistive) emplaced during crustal thinning. The wavy structure is the result of superimposed crustal shortening responsible for the development of large-scale D3 folds (e.g., Marofa synform), later deflected and refolded by a D4 strike-slip shear zone (i.e., Juzbado-Penalva do Castelo shear zone). The later contribution to the final structure of the crust is marked by the intrusion of postkinematic granitic rocks and the propagation of steeply dipping brittle fault zones. Our study demonstrates that MT imaging is a powerful tool to understand complex crustal structures of ancient orogens in order to design future prospecting surveys for mineral deposits of economic interest

Elastase-2, a tissue alternative pathway for angiotensin II generation, plays a role in circulatory sympathovagal balance in mice

In vitro and ex vivo experiments indicate that elastase-2 (ELA-2), a chymotrypsin-serine protease elastase family member 2A, is an alternative pathway for angiotensin II (Ang II) generation. However, the role played by ELA-2 in vivo is unclear. We examined ELA-2 knockout (ELA-2KO) mice compared to wild-type (WT) mice and determined whether ELA-2 played a role in hemodynamics [arterial pressure (AP) and heart rate (HR)], cardiocirculatory sympathovagal balance and baroreflex sensitivity. The variability of systolic arterial pressure (SAP) and pulse interval (PI) for evaluating autonomic modulation was examined for time and frequency domains (spectral analysis), whereas a symbolic analysis was also used to evaluate PI variability. In addition, baroreflex sensitivity was examined using the sequence method. Cardiac function was evaluated echocardiographically under anesthesia. The AP was normal whereas the HR was reduced in ELA-2KO mice (425 ± 17 vs. 512 ± 13 bpm from WT). SAP variability and baroreflex sensitivity were similar in both strains. The LF power from the PI spectrum (33.6 ± 5 vs. 51.8 ± 4.8 nu from WT) and the LF/HF ratio (0.60 ± 0.1 vs. 1.45 ± 0.3 from WT) were reduced, whereas the HF power was increased (66.4 ± 5 vs. 48.2 ± 4.8 nu from WT) in ELA-2KO mice, indicating a shift toward parasympathetic modulation of HR. Echocardiographic examination showed normal fractional shortening and an ejection fraction in ELA-2KO mice; however, the cardiac output, stroke volume, and ventricular size were reduced. These findings provide the first evidence that ELA-2 acts on the sympathovagal balance of the heart, as expressed by the reduced sympathetic modulation of HR in ELA-2KO mice

Altered glucose homeostasis and hepatic function in obese mice deficient for both kinin receptor genes

The Kallikrein-Kinin System (KKS) has been implicated in several aspects of metabolism, including the regulation of glucose homeostasis and adiposity. Kinins and des-Arg-kinins are the major effectors of this system and promote their effects by binding to two different receptors, the kinin B2 and B1 receptors, respectively. To understand the influence of the KKS on the pathophysiology of obesity and type 2 diabetes (T2DM), we generated an animal model deficient for both kinin receptor genes and leptin (obB1B2KO). Six-month-old obB1B2KO mice showed increased blood glucose levels. Isolated islets of the transgenic animals were more responsive to glucose stimulation releasing greater amounts of insulin, mainly in 3-month-old mice, which was corroborated by elevated serum C-peptide concentrations. Furthermore, they presented hepatomegaly, pronounced steatosis, and increased levels of circulating transaminases. This mouse also demonstrated exacerbated gluconeogenesis during the pyruvate challenge test. The hepatic abnormalities were accompanied by changes in the gene expression of factors linked to glucose and lipid metabolisms in the liver. Thus, we conclude that kinin receptors are important for modulation of insulin secretion and for the preservation of normal glucose levels and hepatic functions in obese mice, suggesting a protective role of the KKS regarding complications associated with obesity and T2DM

Effects of α-tocopherol and ternatin antioxidants on morphology and activation of goat preantral follicles in vitro cultured

Os efeitos do α-tocoferol e da ternatina sobre morfologia, ativação e crescimento de folículos pré-antrais caprinos cultivados in vitro, por um ou cinco dias, foram avaliados. Os fragmentos ovarianos foram imediatamente fixados (controle não-cultivado) ou cultivados in vitro, por um ou cinco dias, em Meio Essencial Mínimo (MEM) com ou sem suplementação com α-tocoferol ou ternatina nas concentrações de 5, 10 ou 15M, formando os tratamentos MEM, TOC5, TOC10, TOC 15, TER5, TER10, TER15. O percentual de folículos pré-antrais normais no controle não-cultivado foi de 73,2%, depois de cinco dias de cultivo, houve redução desse percentual em todos os tratamentos, quando comparados com o controle não-cultivado (P<0,05). O cultivo por cinco dias aumentou a ativação folicular em todos os tratamentos (P<0,05). A análise ultra-estrutural não mostrou folículos pré-antrais íntegros após cinco dias de cultivo em meio contendo antioxidantes. Concluiu-se que o α -tocoferol e a ternatina podem promover a ativação folicular, no entanto a adição desses antioxidantes nas concentrações testadas reduziu a viabilidade folicular após o cultivo in vitro. ______________________________________________________________________________________________________________ ABSTRACTThe effects of α-tocopherol and ternatin on the morphology, activation, and growth of goat preantral follicles in vitro cultured, for one or five days, were evaluated. Ovarian fragments were immediately fixed (non-cultured control) or in vitro cultured for one or five days in Minimum Essential Medium (MEM) with or without α-tocopherol or ternatin supplementation, both at concentrations of 5, 10, or 15M, corresponding to the following treatments: MEM, TOC5, TOC10, TOC 15, TER5, TER10, and TER15. The percentages of morphologically normal preantral follicles in non-cultured ovarian tissue (control) was 73.2% and after five days of culture, there was a decrease on these percentages in all treatments (P<0.05) when compared with non-cultured control. Culture of ovarian cortex for five days increased the percentages of follicular activation in all treatments (P<0.05). Ultrastructural analysis did not confirm the integrity of caprine preantral follicles cultured for five days in medium containing antioxidants. This study demonstrated that α-tocopherol and ternatin can promote follicular activation; however, addition of these antioxidants in the tested concentrations reduced the follicular viability after in vitro culture

Histological and ultrastructural feature and nitrite production of caprine preantral follicles in vitro cultured in the presence or absence of serum

Avaliou-se o efeito da adição de diferentes tipos e concentrações de soro sobre o desenvolvimento e a sobrevivência de folículos ovarianos pré-antrais (FOPA) caprinos in vitro. Além disso, verificou-se a relação entre as concentrações de nitrito presentes no meio de cultivo e a viabilidade folicular. Cada par ovariano foi dividido em 29 fragmentos, sendo um destinado ao controle. Os fragmentos foram cultivados por um ou sete dias em meio essencial mínimo suplementado (MEM+) ou MEM+ com diferentes concentrações (10 ou 20%) de soro fetal bovino (SFB), soro de cabra em estro (SCE) ou soro de cabra em diestro (SCD). Na análise morfológica após sete dias, apenas o tratamento com 10% de SFB apresentou percentual de FOPA normais similar ao MEM+ (P>0,05). A análise ultra-estrutural dos folículos cultivados por sete dias com MEM+ ou MEM+ com 10% de SFB mostrou danos oocitários, porém células da granulosa normais. A análise do meio de cultivo revelou correlação positiva entre a viabilidade folicular e a produção de nitrito. A suplementação com soro não melhorou a viabilidade de FOPA e a concentração de nitrito no meio de cultivo funcionou como um indicador da viabilidade das células da granulosa de FOPA caprinos cultivados in vitro. ______________________________________________________________________________________________________________ ABSTRACTThe effect of the addition of different types and concentrations of sera on the viability and development of caprine preantal follicles (PAF) in vitro cultured was analyzed. In addition, it was evaluated the correlation between nitrite concentrations in culture medium and folicular viability. Each ovarian pair was divided in 29 fragments and one was used as control. The fragments were cultured for one or seven days in minimal essential medium (MEM+) or MEM+ with different concentrations of (10 or 20%) bovine fetal serum (BFS), estrous goat serum (EGS), or diestrous goat serum (DGS). After seven days, the morphological analysis showed that only the treatment with 10% BFS maintained the percentage of normal PAF similar to MEM+ (P>0.05). The ultrastructural analysis of follicles cultured for seven days in MEM+ or MEM+ with 10% BFS showed some oocyte damage, although the granulosa cells were normal. Analysis of culture medium revealed a positive correlation between follicular viability and nitrite production. Supplementation with serum did not improve the viability of PAF and nitrite levels in culture medium served as an indicator of viability of granulose cells from caprine PAF in vitro cultured

Agricultura familiar e programas de desenvolvimento rural no Alto Jequitinhonha.

Os regimes agrários peculiares e os baixos níveis relativos dos indicadores sócio-econômicos fizeram com que a região do alto Jequitinhonha, nordeste de Minas Gerais, fosse considerada uma das mais complexas do Brasil. Por isso, vários governos orientaram para lá programas de desenvolvimento rural. Mas esses esforços não produziram bons resultados. Este artigo analisa as relações entre programas públicos e agricultura familiar, fazendo um balanço dos métodos e resultados das últimas três décadas. Conclui pela necessidade de incorporar as especificidades de história, ambientes e sociedade aos programas, que deveriam partir das experiências das organizações da região e se ajustar às ações e à cultura desses agricultores

Adubos verdes e seus efeitos no rendimento da cana-de-açúcar em sistema de plantio direto.

O objetivo deste trabalho foi avaliar adubos verdes e seus efeitos no rendimento da cana-de-açúcar em sistema de plantio direto (SPD). O trabalho foi realizado em Campos dos Goytacazes (RJ), no período de dezembro de 2003 a julho de 2005. O delineamento experimental foi em blocos casualizados, com quatro repetições. Os tratamentos foram: feijão-de-porco (Canavalia ensiformis), mucuna-preta(Mucuna aterrimum), crotalária (Crotalária juncea) em plantio direto e vegetação espontânea em preparo convencional (testemunha). Com crotalária aos 35 dias após emergência (DAE) houve maior taxa de cobertura do solo – 87% – e, aos 92 DAE produziu 17.852 kg ha-1 de matéria seca, respectivamente, 41%, 78% e 407% superior ao feijão-de-porco, mucuna e vegetação espontânea, além de superá-las em acúmulos de K, Mg, S, Zn e Fe. O feijão-de-porco e a mucuna proporcionaram o maior teor de N na parte aérea. Com feijão-de-porco, os teores de P e Ca foram maiores que a crotalária e a mucuna. Com vegetação espontânea, o maior teor de K foi na parte aérea. As leguminosas acumularam maiores quantidades de N e Cu do que a vegetação espontânea. A crotalária e o feijão-de-porco acumularam 66% a mais de P na parte área que a mucuna. O SPD utilizando a adubação verde contribuiu significativamente para a maior produtividade de cana-de-açúcar, 135.863 kg ha-1, sendo 37% superior ao PC com a vegetação espontânea