Reliability evaluation of III-V concentrator solar cells

Concentrator solar cells have been proposed as an interesting way of reducing the cost of photovoltaic electricity. However, in order to compete with conventional solar modules it is necessary not only to reduce costs but also to evaluate and increase the present reliability. Concentrator solar cells work at higher temperature, solar radiation and current stress than conventional solar cells and a carefully reliability analysis is needed. In this paper a reliability analysis procedure, that is being developed, is presented

Remediation of metal-contaminated soils with the addition of materials - Part II: Leaching tests to evaluate the efficiency of materials in the remediation of contaminated soils

The effect of the addition of materials on the leaching pattern of As and metals (Cu, Zn, Ni, Pb, and Cd) in two contaminated soils was investigated. The examined materials included bentonites, silicates and industrial wastes, such as sugar foam, fly ashes and a material originated from the zeolitization of fly ash. Soil+material mixtures were prepared at 10% doses. Changes in the acid neutralization capacity, crystalline phases and contaminant leaching over a wide range of pHs were examined by using pH stat leaching tests. Sugar foam, the zeolitic material and MX-80 bentonite produced the greatest decrease in the leaching of pollutants due to an increase in the pH and/or the sorption capacity in the resulting mixture. This finding suggests that soil remediation may be a feasible option for the reuse of non-hazardous wastes.Ministerio de Educación y Ciencia CTQ2010-14874, CTM2008-01147Ministerio de Medio Ambiente A536/2007/3-01.2, 300/PC/08/3-01.

Brenneria quercina and Serratia spp. isolated from Spanish oak trees: molecular characterization and PCR development

Brenneria quercina has been reported as one of the causal agents of oak decline in Spain. To investigate the bacterial variability of this pathogen from different Spanish oak forests, a collection of 38 bacterial isolates from seven geographic locations and from different oak species was analysed by sequencing 16S rDNA and rep-PCR fingerprinting. All Spanish isolates of B. quercina were grouped by rep-PCR into a homogenous cluster that differed significantly from B. quercina reference strains from California. 16S rDNA analysis revealed that 34 out of 38 isolates were Brenneria . However, four isolates belonged to the genus Serratia , suggesting that this bacterium could cause cankers in oak trees. The information obtained by rep-PCR fingerprint analysis was used to develop PCR primers for the sensitive and specific detection of B. quercina from infected plant tissues. Pathogenicity tests performed with Brenneria and Serratia isolates showed that both were able to grow and cause cankers in oak trees

Towards new insights in the phylogeny of the Spermacoce clade: an integrative taxonomic approach using morphology, anatomy, ecology and phylogenetics reveáis the new genus Leonoria

Phylogenetic inference analyses o f two nuclear and four plastid DNA markers from 82 accessions representing 19 genera o f the Spermacoce clade (Spermacoceae-Rubiaceae) confirm that the Brazilian genus Denscantia is biphyletic. By the analyses o f reproductive morphological characters, foliar morpho-anatomy and histochemical, geographical distribution ranges, and ecological niche derived from climatic space, Denscantia caldcóla is shown as a distinct lineage from the other Denscantia species, indicating its taxonomic segregation into a new monospecific genus Leonoria. Significant morphological diíferences o f Leonoria with Denscantia were found in inflorescence organization, stigma shape, fruit dehiscence, and pollen morphology. Morphoanatomical variation among leaf traits were found in epidemial cells, occurrence o f trichomes, mesophyll histochemical, and vascular organization. Analysis o f occurrence records o f 205 specimens demonstrates a clear ecological distinction between o f Denscantia s.s. and Leonoria, which is ecologically confined to limestone outcrops associated with seasonally dry forests. The current study demonstrates the importance of an integrative taxonomic approach - in which múltiple disciplines are combined - to the unravel complex taxonomic pattems within Rubiaceae. The genus Leonoria, to be newly described, is dedicated to Professor Elsa Leonor Cabral

Clinical utility of intralesional methotrexate to distinguish crateriform keratinocytic tumors before surgery

Clinical utility of intralesional methotrexate to distinguish crateriform keratinocytic tumors before surgeryDear Editors,Keratoacanthoma (KA) and cutaneous squamous cell carci-noma (CSCC) may adopt an identical crateriform morpho-logy. Nowadays, the debate about whether KA is a distinct entity, or a low-grade variant of cutaneous squamous cell carcinoma (CSCC) still persists. Since CSCC is a more ag-gressive neoplasm, misdiagnosing crateriform lesions may have a negative impact on the patient's prognosis. Evaluating a partial biopsy is extremely challenging to confidently dis-tinguish KA from CSCC [1]. No distinctive gene expression profiles have been identified and no pathognomonic criteria to unequivocally differentiate between KA and CSCC exist [2]. Consequently, the surgical approach remains the gold standard in the management of crateriform tumors, especi-ally those arising on the face

La función matemática como contenido implícito en el aprendizaje de conceptos de la mecánica newtoniana

El trabajar un contenido físico(contrataintuitivo) que en sí mismo encierra una relación de variables, a través de la función matemática, facilitará la generalización del mismo en otros contextos. Esta hipótesis se fundamenta en que para alcanzar la comprensión de conceptos como peso específico, presión, velocidad y aceleración se requiere de un concepto matemático como lo es el de proporcionalidad, lo cual necesita un tratamiento didáctico que contemple no sólo el análisis cualitativo sino también el de cálculo que es a la vez geométrico y numérico. De esta manera, lo conceptual y procedimental se integran en la construcción de nociones físicas.Departamento de Ciencias de la Educació

La función matemática como contenido implícito en el aprendizaje de conceptos de la mecánica newtoniana

El trabajar un contenido físico(contrataintuitivo) que en sí mismo encierra una relación de variables, a través de la función matemática, facilitará la generalización del mismo en otros contextos. Esta hipótesis se fundamenta en que para alcanzar la comprensión de conceptos como peso específico, presión, velocidad y aceleración se requiere de un concepto matemático como lo es el de proporcionalidad, lo cual necesita un tratamiento didáctico que contemple no sólo el análisis cualitativo sino también el de cálculo que es a la vez geométrico y numérico. De esta manera, lo conceptual y procedimental se integran en la construcción de nociones físicas.Departamento de Ciencias de la Educació

Case study in failure analysis of accelerated life tests (ALT) on III-V commercial triple-junction concentrator solar cells

In this work the failure analysis carried out in III-V concentrator multijunction solar cells after a temperature accelerated life test is presented. All the failures appeared have been catastrophic since all the solar cells turned into low shunt resistances. A case study in failure analysis based on characterization by optical microscope, SEM, EDX, EQE and XPS is presented in this paper, revealing metal deterioration in the bus bar and fingers as well as cracks in the semiconductor structure beneath or next to the bus bar. In fact, in regions far from the bus bar the semiconductor structure seems not to be damaged. SEM images have dismissed the presence of metal spikes inside the solar cell structure. Therefore, we think that for these particular solar cells, failures appear mainly as a consequence of a deficient electrolytic growth of the front metallization which also results in failures in the semiconductor structure close to the bus bars