Cascade capture of charge carriers in highly doped semiconductors

We analyze the cascade capture of charge carriers due to the interaction with acoustic phonons in highly doped semiconductors using a model that describes the recombination of photo-ionized carriers as a continuous relaxation of carriers in the energy space at both positive and negative energies in the field of a set of impurity ions. Such description enables simultaneous calculation of non-equilibrium carrier distribution formed by interaction with acoustic phonons in the presence of impurity traps, and the time of recombination in a wide range of concentrations of capture centers and phonon temperatures. Additionally, we calculated the time of cascade recombination in the presence of fast scattering processes forming a Maxwellian distribution of free carriers. We show that experimentally observed concentration and temperature dependence of carrier life times in highly doped semiconductors can be described within the model of the cascade capture to uniformly spaced capture centers, and the main factor that determines the regime of cascade capture is the ratio of the thermal energy and the energy of the overlap of impurity potentials

Liver phospholipids fatty acids composition in response to different types of diets in rats of both sexes

Background: Dietary intake influence changes in fatty acids (FA) profiles in liver which plays a central role in fatty acid metabolism, triacylglycerol synthesis and energy homeostasis. We investigated the effects of 4-weeks treatment with milk-and fish-based diet, on plasma biochemical parameters and FA composition of liver phospholipids (PL) in rats of both sexes. Methods: Adult, 4 months old, Wistar rats of both sexes, were fed with different types of diets: standard, milk-based and fish-based, during 4 weeks. Analytical characterization of different foods was done. Biochemical parameters in plasma were determined. Fatty acid composition was analyzed by gas-chromatography. Statistical significance of FA levels was tested with two-way analysis of variance (ANOVA) using the sex of animals and treatment (type of diet) as factors on logarithmic or trigonometric transformed data. Results: Our results showed that both, milk-and fish-based diet, changed the composition and ratio of rat liver phospholipids FA, in gender-specific manner. Initially present sex differences appear to be dietary modulated. Although, applied diets changed the ratio of total saturated fatty acids (SFA), monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA), and effects were gender specific. Milk-based diet lowered SFA and elevated MUFA in males and increased PUFA in females vs. standard diet. The same diet decreased n-3, increased n-6 and n-6/n-3 ratio in males. Fish-based diet increased n-3, decreased n-6 and n-6/n-3 ratio vs. standard and milk-based diet in females. However, the ratio of individual FA in liver PL was also dietary-influenced, but with gender specific manner. While in females fish-based diet decreased AA (arachidonic acid) increased level of EPA (eicosapentaenoic acid), DPA (docosapentaenoic acid) and DHA (docosahexaenoic acid), the same diet elevated only DHA levels in males. Conclusion: Gender related variations in FA composition of rat liver PL were observed, and results have shown that those initial differences could be significantly modulated by the type of diet. Furthermore, the modulatory effects of milk-and fish-based diets on liver phospholipids FA profiles appeared to be sex-specific

Graduate employability: a review of conceptual and empirical themes

The purpose of this paper is to provide an overview of some of the dominant empirical and conceptual themes in the area of graduate employment and employability over the past decade. The paper considers the wider context of higher education and labour market change, and the policy thinking towards graduate employability. It draws upon various studies to highlight the different labour market perceptions, experiences and outcomes of graduates in the UK and other national contexts. It further draws upon research that has explored the ways in which students and graduates construct their employability and begin to manage the transition from higher education to work. The paper explores some of the conceptual notions that have informed understandings of graduate employability, and argues for a broader understanding of employability than that offered by policy-makers