A semi-analytical theory of coastal upwelling and jet

The general forms of the conservation of momentum, temperature and potential vorticity of coastal ocean are obtained in the x-z plane for the nonlinear ocean circulation of Boussinesq fluid, and a elliptic type partial differential equations of second order are derived. Solution of the partial differential equations are obtained under the conditions that the fluid moves along the topography. The numerical results show that there exist both upwelling and downwelling along coastline that mainly depends on the large scale ocean condition. Numerically results of the upwelling (downwelling), coastal jet and temperature front zone are favorable to the observations.

Density-dependent effects on seston dynamics and rates of filtering and biodeposition of the suspension-cultured scallop Chlamys farreri in a eutrophic bay (northern China): An experimental study in semi-in situ flow-through systems

Effects of stocking density on seston dynamics and filtering and biodeposition by the suspension-cultured Zhikong scallop Chlamys farreri Jones et Preston in a eutrophic bay (Sishili Bay, northern China), were determined in a 3-month semi-field experiment with continuous flow-through seawater from the bay. Results showed that the presence of the scallops could strongly decrease seston and chlorophyll a concentrations in the water column. Moreover, in a limited water column, increasing scallop density could cause seston depletion due to scallop's filtering and biodeposition process, and impair scallop growth. Both filtration rate and biodeposition rate of C. farreri showed significant negative correlation with their density and positive relationship with seston concentration. Calculation predicts that the daily removal of suspended matter from water column by the scallops in Sishili Bay ecosystem can be as high as 45% of the total suspended matter; and the daily production of biodeposits by the scallops in early summer in farming zone may amount to 7.78 g m(-2), with daily C, N and P biodeposition rates of 3.06 x 10(-1), 3.86 x 10(-2) and 9.80 x 10(-3) g m(-2), respectively. The filtering and biodeposition by suspension-cultured scallops could substantially enhance the deposition of total suspended particulate material, suppress accumulation of particulate organic matter in water column, and increase the flux of C, N and P to benthos, strongly enhancing pelagic-benthic coupling. It was suggested that the filtering-biodeposition process by intensively suspension-cultured bivalve filter-feeders could exert strong top-down control on phytoplankton biomass and other suspended particulate material in coastal ecosystems. This study also indicated that commercially suspension-cultured bivalves may simultaneously and potentially aid in mitigating eutrophication pressures on coastal ecosystems subject to anthropogenic N and P loadings, serving as a eutrophic-environment bioremediator. The ecological services (e.g. filtering capacity, top-down control, and benthic-pelagic coupling) functioned by extractive bivalve aquaculture should be emphasized in coastal ecosystems. (c) 2005 Elsevier B.V. All rights reserved.

Genetic diversity of the subterranean Gansu zokor in a semi-natural landscape

We studied the relationship between genetic diversity of the subterranean Gansu zokor Myospalax cansus and habitat variability in the Loess Plateau, Qinghai Province, China. We used a combination of geographic information systems and molecular techniques to assess the impact of habitat composition and human activities on the genetic diversity of zokor populations in this semi-natural landscape. Although they occurred relatively infrequently in the landscape, woodland and high-coverage grassland habitats were the main positive contributors to the genetic diversity of zokor populations. Rural residential land, plain agricultural land and low-coverage grassland had a negative effect on genetic diversity. Hilly agricultural land and middle-coverage grassland had little impact on zokor genetic diversity. There were also interactions between some habitat types, that is, habitat types with relatively better quality together promoted conservation of genetic diversity, while the interaction between (among) bad habitat types made situations worse. Finally, habitat diversity, measured as patch richness and Shannon's diversity index, was positively correlated with the genetic diversity. These results demonstrated that: (1) different habitat types had different effects on the genetic diversity of zokor populations and (2) habitat quality and habitat heterogeneity were important in maintaining genetic diversity. Habitat composition was closely related to land use thus emphasizing the importance of human activities on the genetic diversity of subterranean rodent populations in this semi-natural landscape. Although the Gansu zokor was considered to be a pest species in the Loess Plateau, our study provides insights for the management and conservation of other subterranean rodent species.

Depression of net ecosystem CO2 exchange in semi-arid Leymus chinensis steppe and alpine shrub

Uptake and release of carbon in grassland ecosystems is very critical to the global carbon balance and carbon storage. In this study, the dynamics of net ecosystem CO2 exchange (FNEE) of two grassland ecosystems were observed continuously using the eddy covariance technique during the growing season of 2003. One is the alpine shrub on the Tibet Plateau, and the other is the sem-arid Leymus chinensis steppe in Inner Mongolia of China. It was found that the FNEE of both ecosystems was significantly depressed under high solar radiation. Comprehensive analysis indicates that the depression of FNEE in the L. chinensis steppe was the results of decreased plant photosynthesis and increased ecosystem respiration (R-eco) under high temperature. Soil water stress in addition to the high atmospheric demand under the strong radiation was the primary factor limiting the stomatal conductance. In contrast, the depression of FNEE in the alpine shrub was closely related to the effects of temperature on both photosynthesis and ecosystem respiration, coupled with the reduction of plant photosynthesis due to partial stomatal closure under high temperature at mid-day. The R,c of the alpine shrub was sensitive to soil temperature during high turbulence (u* > 0.2 m s(-1)) but its FNEE decreased markedly when the temperature was higher than the optimal value of about 12 degrees C. Such low optimal temperature contrasted the optimal value (about 20 degrees C) for the steppe, and was likely due to the acclimation of most alpine plants to the long-term low temperature on the Tibet Plateau. We inferred that water stress was the primary factor causing depression of the FNEE in the semi-arid steppe ecosystem, while relative high temperature under strong solar radiation was the main reason for the decrease of FNEE in the alpine shrub. This study implies that different grassland ecosystems may respond differently to climate change in the future. (c) 2006 Elsevier B.V All rights reserved.

Meat characteristics of Qinghai yak and semi-wild yak

Six domestic yaks aged 6 years, comprising three culling male and three culling female yaks, from the Qinghai Lake area and three male semi-wild yaks aged 6 months from Datong Yak Farm were used to detect the levels of amino acids, mineral elements, residual heavy metals and pesticides in yak meat. The results showed that there was little difference in amino acid levels for different types of yak by age and sex. The meat of the adult male yak was 7.35 mg/kg higher in calcium (P < 0.05) and 124 mg/kg higher in phosphorus (P < 0.01) than that of the adult female yak. There was an obvious difference in zinc content, and there was also a significant difference for copper and sulfur between adult male and female yaks (P < 0.01). Iron was 8.85 mg/kg higher in semi-wild yaks than in domestic yaks, but there were no differences for other minerals. The levels of residual heavy metals and residual pesticides were well within those allowed by the National Standard of China. Furthermore, the data showed that introducing wild yak's blood did not result in a quality change in the domestic yak meat. Yak meat from Qinghai Plateau has the characteristics of being non-polluted and rich in amino acids in comparison with local yellow cattle meat.

Characterization of polyethylene glycol-modified proteins by semi-aqueous capillary electrophoresis

A new program to characterize polyethylene glycol-modified (PEGylated) proteins is outlined using capillary zone electrophoresis (CZE). PEGylated ribonuclease A and lysozyme were selected as examples. Five separation procedures were compared to select out the mixed buffer of acetonitrile-water (1:1, v/v) at pH 2.5 as the best to characterize the PEGylated proteins without sample pretreatment. Polyethylene oxide (PEO) with a high molecular mass of 8X10(6) was applied to rinse the capillary to form a dynamic coating which would decrease the undesirable proteins adsorbed to the inner wall of the silica. The electroosmotic flow (EOF) mobility of the five procedures was determined, respectively. It is found that acetonitrile is mainly responsible for the good resolution of PEGylated proteins with the help of PEO coating in the semi-aqueous system. The low EOF mobility and current in the semi-aqueous system might also have some responsibility for the high resolution. The semi-aqueous procedure described in this paper also demonstrates higher resolution of natural proteins than aqueous ones. (C) 2001 Elsevier Science B.V. All rights reserved.

Sistema simplificado para melhoria da qualidade da água consumida nas comunidades rurais do semi-árido do Brasil.

Além da quantidade, a qualidade da água também é uma questão que preocupa. A má qualidade da água consumida é a maior responsável pelas doenças endêmicas nos países em desenvolvimento, como por exemplo, hepatite, cólera, febre tifóide, entre outras. Falta de acesso à água de boa qualidade e ao saneamento resulta em centenas de milhões de casos de doenças de veiculação hídrica. No Brasil, de acordo com pesquisa do Censo 2000, 5,9% dos domicílios brasileiros lançam seus esgotos em valas, rios, lagos ou no mar. Dessa proporção, a maior parte ocorre nas áreas rurais (10%) do que nas urbanas (5%). Já os domicílios que não possuem instalações sanitárias chegam a 8,3% do total do país, sendo mais freqüentes nas regiões rurais (35,3%). Essa situação torna-se gritante na área rural da Região Nordeste (60,5%), num contraste brutal com as áreas rurais da Região Sul (7,4%) (IBGE, 2002). Na região do Semi-Árido do Brasil, a população de algumas comunidades rurais, devido à escassez é obrigada a percorrer grandes distâncias para a obtenção de água, na maioria das vezes de péssima qualidade e de turbidez muito elevada. Entre os objetivos deste trabalho, estão a proposição de sistemas simplificados, econômicos, práticos e viáveis para a melhoria da qualidade da água consumida nas comunidades rurais do semi-áridodo Brasil; a comprovação da viabilidade de aplicação desses sistemas; e a apresentação dos resultados obtidos a partir da aplicação desses sistemas.

Irrigação da mangueira nas condições semi-áridas do Nordeste.

A irrigação constitui uma tecnologia indispensável no processo de produção da mangueira tanto em regiões semi-áridas, como em regiões de déficit hídrico prolongado. Entretanto, tem sido adotada por produtores, muitas vezes despreparados, que, por falta de orientação, não praticam seu manejo adequado, com perdas na produção potencial da cultura e nos custos com água e energia. O efeito potencial da irrigação contribui para os dois pontos mais importantes de uma economia globalizada: promove o aumento da produtividade e melhora a qualidade do produto. Este trabalho procura atualizar os conhecimentos sobre irrigação da mangueira, em condições Semi-áridas. O trabalho faz abordagem sobre aspectos de interesse direto do produtor, tais como sistemas de irrigação, necessidades hídricas da cultura e manejo de irrigação.

(Semi-)Predictive Discretization During Model Selection

In this paper, we present an approach to discretizing multivariate continuous data while learning the structure of a graphical model. We derive the joint scoring function from the principle of predictive accuracy, which inherently ensures the optimal trade-off between goodness of fit and model complexity (including the number of discretization levels). Using the so-called finest grid implied by the data, our scoring function depends only on the number of data points in the various discretization levels. Not only can it be computed efficiently, but it is also independent of the metric used in the continuous space. Our experiments with gene expression data show that discretization plays a crucial role regarding the resulting network structure.

DIVULGAÇÃO de cultivares e tecnologias para a produção de sorgo no semi-árido brasileiro.

2010

Barragem Subterrânea: uma opção de sustentabilidade para a agricultura familiar do semi-árido do Brasil.

2007

Caracterização de atributos do solo em áreas de barragem subterrânea no semi-árido brasileiro.

2008

Adensamento e compactação de solos irrigáveis da zona semi-árida do Nordeste brasileiro.

2007

Relação entre pressão e volume para implantação da técnica in vitro semi-automática de produção de gases na Embrapa Cerrados.

2008

Sistemas agrícolas sustentáveis para regiões semi-áridas.

Resumo: A maioria dos sistemas de produção em prática no trópico semi-árido brasileiro pela agricultura familiar apresenta baixa ou nenhuma sustentabilidade, devido ao uso de tecnologias quase sempre agressivas ao ecossistema. Como consequência, observa-se, nos sertões nordestinos degradação ambiental generalizada, baixa produtividade das atividades agrícolas, pastoris e madeireiras, inviabilização da agricultura, queda da qualidade devida e êxodo rural acentuado. Urge, pois, que se forneça ao agricultor alternativas de sistemas de produção sustentáveis que atendam a quatro objetivos, quais sejam, a fixação da agricultura migratória, a adequação do manejo pastoril, a racionalização da produção de madeira e a uma forte integração dessas atividades. Para tanto, deve-se: excluir as queimadas, substituir o desmatamento pelo raleamento da vegetação lenhosa, manter um aporte substancial de matéria orgânica, utilizar Ieguminosas como fonte de adubo verde, ajustar a carga animal para a capacidade de suporte da área e adotar-se o corte seletivo e manejo da rebrota na exploração madeireira. A adoção dessas tecnologias na certa contribuirá: para a viabilização ecológica, social e econômica da agricultura familiar nos serões nordestinos, para a sustação dos processos de degradação ambiental, para a melhoria da qualidade de vida da população e para a redução do êxodo rural.