Evolutionary optimization of TCO/mesh electrical contacts in CIGS solar cells

State of the art solar cells often require a combination of TCO and metallic grid to efficiently transport the generated current to an external circuit. Optimization of these complex contacts based on several materials with different conductivities and geometries is often still based on a traditional approach consisting of simple analytical formulas and empirical knowledge in spite of the complexity. An evolutionary algorithm combined with an electrical 2D+1D FEM model is used to optimize the shape of the metallic contact considering the material conductivities, the geometry and shadowing. The performance of two automatically designed contacts is compared with experimental results of CIGS solar cells prepared with two different TCO thicknesses

Scanning tunneling microscopy of monoatomic gold chains on vicinal Si(335) surface: experimental and theoretical study

We study electronic and topographic properties of the Si(335) surface, containing Au wires parallel to the steps. We use scanning tunneling microscopy (STM) supplemented by reflection of high energy electron diffraction (RHEED) technique. The STM data show the space and voltage dependent oscillations of the distance between STM tip and the surface which can be explained within one band tight binding Hubbard model. We calculate the STM current using nonequilibrium Keldysh Green function formalism.Comment: 6 pages, 4 figure

Standard and Light-Cycler PCR methods for animal DNA species detection in animal feedstuffs

In this work four species-specific primers and probes were designed and evaluated for the detection and quantification of bovine, ovine, swine and chicken mitochondrial DNA in feeds. PCR primers were optimized using conventional and Real Time PCR, to detect short species-specific sequences amplifiable from heat treated material. Both methods confirmed the high specificity of the primers designed. Real time quantitative PCR assay allowed the detection of as few as 0.01 ng and 0.05 ng of ovine and bovine genomic DNA, respectively. The detection limit for swine and chicken genomic DNA was 0.5 ng. Sensitivity levels observed in DNA extracted from meat samples processed according to EU legislation were different compared to those in genomic DNAs previously described. They resulted in swine 5 fg of MBM DNA, in chicken 25 ng, in ovine and bovine 50 ng. We confirmed the efficiency and specificity of primers in RT-PCR to detect 0.5% of bovine, ovine, swine and chicken MBM in contaminated feedstuffs. (C) 2007 Elsevier Ltd. All rights reserved

Spontaneous magnetization of aluminum nanowires deposited on the NaCl(100) surface

We investigate electronic structures of Al quantum wires, both unsupported and supported on the (100) NaCl surface, using the density-functional theory. We confirm that unsupported nanowires, constrained to be linear, show magnetization when elongated beyond the equilibrium length. Allowing ions to relax, the wires deform to zig-zag structures with lower magnetization but no dimerization occurs. When an Al wire is deposited on the NaCl surface, a zig-zag geometry emerges again. The magnetization changes moderately from that for the corresponding unsupported wire. We analyse the findings using electron band structures and simple model wires.Comment: submitted to PHys. Rev.

Two-domains bulklike Fermi surface of Ag films deposited onto Si(111)-(7x7)

Thick metallic silver films have been deposited onto Si(111)-(7x7) substrates at room temperature. Their electronic properties have been studied by using angle resolved photoelectron spectroscopy (ARPES). In addition to the electronic band dispersion along the high-symmetry directions, the Fermi surface topology of the grown films has been investigated. Using ARPES, the spectral weight distribution at the Fermi level throughout large portions of the reciprocal space has been determined at particular perpendicular electron-momentum values. Systematically, the contours of the Fermi surface of these films reflected a sixfold symmetry instead of the threefold symmetry of Ag single crystal. This loss of symmetry has been attributed to the fact that these films appear to be composed by two sets of domains rotated 60$^o$ from each other. Extra, photoemission features at the Fermi level were also detected, which have been attributed to the presence of surface states and \textit{sp}-quantum states. The dimensionality of the Fermi surface of these films has been analyzed studying the dependence of the Fermi surface contours with the incident photon energy. The behavior of these contours measured at particular points along the Ag $\Gamma$L high-symmetry direction puts forward the three-dimensional character of the electronic structure of the films investigated.Comment: 10 pages, 12 figures, submitted to Physical Review

Progetto per Milano Bovisa : l'idea, il rigore, l'immaginazione

LAUREA MAGISTRAL

Resurgence of Sleeping Sickness in Tambura County, Sudan

Endemic foci of human African trypanosomiasis are present in southern Sudan. In 1996 and 1997, trypanosomiasis increased sharply in Tambura County. To define the magnitude and geographic distribution of the outbreak, we conducted a prevalence survey using population-based cluster sampling in 16 villages: 1,358 participants answered questions about routine activities and tsetse fly contact and received serologic testing. Seroprevalence in the surveyed area was 19.4% (95% confidence interval = 16.9%, 21.8%). We confirmed infection in 66% of seropositive persons who received one parasitologic examination and in 95% of those who had serial examinations of lymph node fluid and blood. Activities related to the civil war, such as temporary migration, were not associated with seropositive status. Since the previous population screening in 1988, the trypanosomiasis prevalence increased two orders of magnitude, and the proportion of villages affected increased from 54% to 100%. Our results suggest that there may be 5,000 cases in Tambura County. The absence of trypanosomiasis control for nearly a decade is a factor in the resurgence of the disease

Listeria monocytogenes in Ready-to-Eat Seafood and Potential Hazards for the Consumers

The risk of exposure to Listeria monocytogenes (L. monocytogenes) when consuming Ready-to-Eat (RTE) seafood was assessed in the Veneto Region (Italy). Thirty-eight samples were analyzed, each sample consisted of three subunits belonging to the same batches. The first of the three units was examined immediately, the second was stored at +4°C (for all of its shelf-life) and the third at +10°C (for the latter third of its shelf-life) before the analysis. Chemical-physical and microbiological parameters were tested simultaneously. Culture results showed the presence of viable L. monocytogenes in 9 (23,68%) of the 38 samples analysed, 3 (33,33%) of which with a concentration >100 cfu/g. PCR tests yielded 12 L. monocytogenes positive samples. Semipreserves with aw (water activity) and pH values that favour L. monocytogenes growth were the only ones to result positive to microbiological and PCR tests. Temperature proved to be an important factor as it limits the growth of L. monocytogenes, including products with potentially high competitive microbial charges. Four different serotypes were recovered and ribotyping has helped to highlight the genomic variability of L. monocytogenes strains in food. This supports the hypothesis that L. monocytogenes continues to evolve genetically to the detriment of phenotypic conservation

Hyperhidrosis treatment with bornaprine in the acute phase of spinal cord-injured patients

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