Ocorrência e estudos electrono-microscópicos do vírus do mosaico do trigo, transmitido pelo solo, no estado do Rio Grande do Sul.

Resumos

Produtividade de soja e eficiência no uso de potássio em sucessão a Urochloa brizantha cultivada na entressafra.

O objetivo deste estudo foi avaliar o uso de Urochloa brizantha na entressafra sobre a dinâmica de potássio e produtividade de soja cultivada em sucessão. O ensaio foi conduzido em blocos casualizados, com quatro repetições, em parcelas subsubdivididas 2x2x4. Na parcela principal foram alocados os tipos de correção do solo: total inicial e parcelada anual, nas subparcelas, foram implantados os tipos de cobertura de segunda safra: pousio e cultivo de U. brizantha e na subsubparcela foi avaliado as doses de 0, 20, 40 e 60 kg ha-1 de K2O aplicados à lanço e aos 20 dias após a emergência da soja. A U. brizantha foi semeada em 02/2011. A soja M7211 RR foi semeado em 10/2011. A coleta foliar de U. brizantha foi realizada em setembro de 2011 antes da dessecação para o plantio de soja. A correção total inicial proporcionou maior produção de matéria seca (14 Mg ha-1) e acúmulo de potássio nas folhas (121 kg ha-1) de U. brizantha. A utilização dessa forrageira na entressafra proporcionou incremento na produção de soja, além de maiores teores de potássio na parte aérea, nos grãos e consequentemente maior exportação desse nutriente. As doses de potássio proporcionaram incremento nos teores foliares desse nutriente, porém isso não se refletiu na produtividade. Apesar disso, o aumento crescente das doses de potássio contribuiu para a ocorrência de menores valores negativos no balanço de potássio

Estabilidade de agregados em sistemas de cultivo da soja em sucessão à Urochloa sp.

O uso da Urochloa sp. como cobertura vegetal do solo na entressafra tem ocasionado o aumento do rendimento da soja em sucessão. O objetivo deste trabalho foi avaliar a estabilidade dos agregados, densidade do solo, porosidade do solo, matéria orgânica do solo e o rendimento da soja em um Latossolo Vermelho sob quatro sistemas de cultivo de entressafra em Rio Verde - GO, dentre os quais dois sistemas incluíram a Urochloa sp. O delineamento foi em blocos ao acaso, com quatro repetições, em parcelas subdivididas 2x4 (as formas de correção do solo parcelada anual e total inicial e os tipos de cobertura de solo Urochloa brizantha, milho + U. ruziziensis, milho solteiro e pousio). A cultura da soja foi implantada em toda a área na safra 2011/2012. Durante a floração da soja realizou-se as amostragens de solo, na profundidade de 0 a 10 cm, para as determinações da estabilidade de agregados em água, densidade do solo, porosidade do solo e matéria orgânica do solo. Ao final do ciclo determinou-se o rendimento dos grãos de soja. O uso de U. brizantha em sucessão à soja, favorece o aumento da agregação entre 4,76 e 2,00 mm e reduz a densidade do solo, na camada de 0 a 10 cm de profundidade, quando comparado com as sucessões com milho + U. ruziziensis, milho solteiro e pousio. Isso provavelmente auxilia no maior rendimento da soja em sucessão à U. brizantha

Temperature effects on dislocation core energies in silicon and germanium

Temperature effects on the energetics of the 90-degree partial dislocation in silicon and germanium are investigated, using non-equilibrium methods to estimate free energies, coupled with Monte Carlo simulations. Atomic interactions are described by Tersoff and EDIP interatomic potentials. Our results indicate that the vibrational entropy has the effect of increasing the difference in free energy between the two possible reconstructions of the 90-degree partial, namely, the single-period and the double-period geometries. This effect further increases the energetic stability of the double-period reconstruction at high temperatures. The results also indicate that anharmonic effects may play an important role in determining the structural properties of these defects in the high-temperature regime.Comment: 8 pages in two-column physical-review format with six figure

A meteorological overview of the MILAGRO field campaigns

International audienceWe describe the large-scale meteorological conditions that affected atmospheric chemistry over Mexico during March 2006 when several field campaigns were conducted in the region. In-situ and remote-sensing instrumentation was deployed to obtain measurements of wind, temperature, and humidity profiles in the boundary layer and free atmosphere at four primary sampling sites in central Mexico. Several models were run operationally during the field campaign to provide forecasts of the local, regional, and synoptic meteorology as well as the predicted location of the Mexico City pollutant plume for aircraft flight planning purposes. Field campaign measurements and large-scale analyses are used to define three regimes that characterize the overall meteorological conditions: the first regime prior to 14 March, the second regime between 14 and 23 March, and the third regime after 23 March. Mostly sunny and dry conditions with periods of cirrus and marine stratus along the coast occurred during the first regime. The beginning of the second regime was characterized by a sharp increase in humidity over the central plateau and the development of late afternoon convection associated with the passage of a weak cold surge on 14 March. Over the next several days, the atmosphere over the central plateau became drier so that deep convection gradually diminished. The third regime began with the passage of a strong cold surge that lead to humidity, afternoon convection, and precipitation over the central plateau that was higher than during the second regime. The frequency and intensity of fires, as determined by satellite measurements, also diminished significantly after the third cold surge. The synoptic-scale flow patterns that govern the transport of pollutants in the region are described and compared to previous March periods to put the transport into a climatological context. The complex terrain surrounding Mexico City produces local and regional circulations that govern short-range transport; however, the mean synoptic conditions modulate the thermally-driven circulations and on several days the near-surface flow is coupled to the ambient winds aloft

Acute Hepatitis B in a patient previously positive for antibody to surface antigen (anti-HBs) determined by radioimmunoassay: case report and review of the literature

The determination of anti-HBs as a screening test before vaccination has been advisable in order to encounter immune individuals that don't need to receive vaccine protection. A case-report is presented and three other cases are reviewed from the literature. Anti-HBs was positive in these health-care personnels that developped typical acute B hepatitis. Different subtyping involving the d/y determinants were found in the first case, but false-positive anti-HBs even with high titres, determined by RIA, were found in the other cases. Concomitant determination of anti-HBc or absence of screening tests seem to be more reasonable policies until a low-cost and risk-free vaccine is produced

Human Immunodeficiency Virus Envelope Protein Gp120 Induces Proliferation but Not Apoptosis in Osteoblasts at Physiologic Concentrations

Patients with HIV infection have decreased numbers of osteoblasts, decreased bone mineral density and increased risk of fracture compared to uninfected patients; however, the molecular mechanisms behind these associations remain unclear. We questioned whether Gp120, a component of the envelope protein of HIV capable of inducing apoptosis in many cell types, is able to induce cell death in bone-forming osteoblasts. We show that treatment of immortalized osteoblast-like cells and primary human osteoblasts with exogenous Gp120 in vitro at physiologic concentrations does not result in apoptosis. Instead, in the osteoblast-like U2OS cell line, cells expressing CXCR4, a receptor for Gp120, had increased proliferation when treated with Gp120 compared to control (P<0.05), which was inhibited by pretreatment with a CXCR4 inhibitor and a G-protein inhibitor. This suggests that Gp120 is not an inducer of apoptosis in human osteoblasts and likely does not directly contribute to osteoporosis in infected patients by this mechanism