Position broadening effect in hot-electron transport

We utilize the Kadanoff-Baym-Keldysh methods to develop a formalism appropriate for high, homogeneous fields. The aim is to derive a spectral density model which can account for both the energy dependence of the collision rate and the intracollisional field effect in a relatively simple and rigorous way. We solve the appropriate Dyson's equation in the first Born approximation for the case of scattering mechanisms described by a momentum-independent self-energy. We obtain an analytical expression for the spectral density and derive an integral equation for the correlation function G^<, which is proportional to the density of particles. We show that the field, acting in conjunction with the phonons, leads to an effective quantization of the energy in the direction of the electric field suggesting the presence of a novel quantum effect consisting in a discontinuous trajectory of the electron along this direction.     

Bio-transformed sawdust by white rot fungi used as a carrier for plant growth-promoting bacteria

This study assessed the bio-transformation of sawdust wood waste by a white rot fungi consortium and explores the use of the final product as a carrier for plant growth-promoting bacteria. During 75 days, Tabebuia roseae and Eucalyptus pellita (1:1) sawdust wood were used as growing substrates for Ganoderma lucidum, Pleurotus ostreatus, Trametes versicolor and Phanerochaete chrysosporium. Then, bio-transformed sawdust was evaluated as carrier of two strains of Enterobacter sp. and one strain of Stenotrophomonas maltophilia. Biologic activity and viability were determined at two storage temperatures (23–4 °C) for 60 days. Sawdust mixture was bio-transformed by white rot fungi. After 45 days, the carbon/nitrogen ratio was reduced up to 46 %, and 4.8 mg/g of CO₂ of residue was produced. Enzymatic activities attained a peak of 36.7 and 0.8 U g^?1 for laccase and manganese peroxidase, respectively in 45 days. Population of plant growth-promoting bacteria immobilized in bio-transformed sawdust wood decreased to 10⁵ CFU g^?1. However, this concentration and its biologic activity remained stable at 23 °C.     

Concentrations of condensed tannins and anthocyanins in common bean seed coats

Seed coat colour in common bean (Phaseolus vulgaris L.) is determined by activity of the flavonoid biosynthetic pathway resulting in the presence or absence of specific anthocyanins, tannins and glycosidic flavanols. These secondary metabolites have anti-oxidant properties in the case of anthocyanins and glycosidic flavonols and strongly influence dietary mineral bioavailability in the case of tannins. The modification of tannin content is a goal of biofortification breeding programs, while almost all bean improvement considers seed colour in selection priorities as this affects consumer preference and food quality. In the present study, we analyzed condensed tannins, tannin monomers and anthocyanin levels in an inter-genepool population derived from the cross DOR364 × G19833 using HPLC and spectrophotometric methods. The overall average for condensed tannins expressed as percentage in seed coats was 20.04%. The ranges were between 8.0% and 27.9% for soluble tannins (ST), 1.5% and 5.4% for insoluble tannins (IT), and 10.7% and 30.9% for total tannins (TT). Anthocyanins in seed coats averaged 0.08% (0.013–0.21% range) expressed as delphinidin-3-glucoside equivalents for the population with the distribution biased towards low content. All traits had large variability between genotypes and showed transgressive segregation, indicating quantitative inheritance for tannin content and oligogenic control of anthocyanins. Condensed tannins in the genotypes were mainly composed of catechin (60.3%), gallocatechin (25%), and afzelechin (14.7%) as monomeric units.     

Difficulties of fishing at Lake Naivasha,Kenya: is community participation in management the solution?

Unlike other lakes in tropical regions, Lake Naivasha exhibits low fish species diversity. The fishery is based on introduced fish species that are not native to the lake. The lake ecosystem is very fragile, as reflected in its fluctuating fish catches. The fishery almost completely collapsed in 2001, due partly to mismanagement and ignorance about needed conservation measures. The Kenyan government, like many governments around the world, recognized the need to involve fishers and other stakeholders, in order to ensure better management of the lake fisheries resources. Also referred to as collaborative management (co-management), this management approach provides the opportunity to share responsibility for managing the fishery resources between the government and the community. A total ban on fishing was imposed in February 2001, lasting for 1 year, to allow lake fish stocks to recover. This study analyses the co-management process for Lake Naivasha, and discusses the role played by the community during the fishing ban, as well as the successes and challenges encountered, and the tribulations and perceptions of the fishers regarding the new management strategy. It also comprises the first documentation of community participation in fisheries management begun for Lake Naivasha in the year 2001.