Optical absorption spectroscopy of one-dimensional silicon nanostructures

a b s t r a c t During the last decade there has been a great development in nanoscience and nanotechnology. The technology of nanostructures synthesis and characterization has grown rapidly and optical spectroscopy has become a very useful characterization technique, since it provides information on the structural, electronic, optical and dynamical properties of materials. Nanostructures have unique physical properties that are different from bulk materials. A wealth of interesting and new phenomena are associated with nanometer-sized structures, such as size-dependent emission or excitation, metallic and semiconductor behavior, etc. Here we present an overview of the linear optical response of one-dimensional silicon nanostructures. In particular, we make a theoretical study of the effects of the size and shape of onedimensional silicon structures on the absorption spectrum, focusing on the calculation of the linear optical response of clean and hydrogen-adsorbed armchair (6,6) silicon nanotubes. We discuss the changes of the absorption spectrum of silicon nanowires with different diameters and analyze the behavior of the band gap as we go from bulk silicon to one-dimensional silicon nanostructures with nanometer-size diameters

Deep and fast live imaging with two-photon scanned light-sheet microscopy

We implemented two-photon scanned light-sheet microscopy, combining nonlinear excitation with orthogonal illumination of light-sheet microscopy, and showed its excellent performance for in vivo, cellular-resolution, three-dimensional imaging of large biological samples. Live imaging of fruit fly and zebrafish embryos confirmed that the technique can be used to image up to twice deeper than with one-photon light-sheet microscopy and more than ten times faster than with point-scanning two-photon microscopy without compromising normal biology

Combined analysis of three genome-wide association studies on vWF and FVIII plasma levels

<p>Abstract</p> <p>Background</p> <p>Elevated levels of factor VIII (FVIII) and von Willebrand Factor (vWF) are well-established risk factors for cardiovascular diseases, in particular venous thrombosis. Although high, the heritability of these traits is poorly explained by the genetic factors known so far. The aim of this work was to identify novel single nucleotide polymorphisms (SNPs) that could influence the variability of these traits.</p> <p>Methods</p> <p>Three independent genome-wide association studies for vWF plasma levels and FVIII activity were conducted and their results were combined into a meta-analysis totalling 1,624 subjects.</p> <p>Results</p> <p>No single nucleotide polymorphism (SNP) reached the study-wide significance level of 1.12 × 10^-7that corresponds to the Bonferroni correction for the number of tested SNPs. Nevertheless, the recently discovered association of <it>STXBP5</it>, <it>STX2</it>, <it>TC2N </it>and <it>CLEC4M </it>genes with vWF levels and that of <it>SCARA5 </it>and STAB2 genes with FVIII levels were confirmed in this meta-analysis. Besides, among the fifteen novel SNPs showing promising association at p < 10^-5with either vWF or FVIII levels in the meta-analysis, one located in <it>ACCN1 </it>gene also showed weak association (<it>P </it>= 0.0056) with venous thrombosis in a sample of 1,946 cases and 1,228 controls.</p> <p>Conclusions</p> <p>This study has generated new knowledge on genomic regions deserving further investigations in the search for genetic factors influencing vWF and FVIII plasma levels, some potentially implicated in VT, as well as providing some supporting evidence of previously identified genes.</p

A Constitutional Translocation t(1;17)(p36.2;q11.2) in a Neuroblastoma Patient Disrupts the Human NBPF1 and ACCN1 Genes

The human 1p36 region is deleted in many different types of tumors, and so it probably harbors one or more tumor suppressor genes. In a Belgian neuroblastoma patient, a constitutional balanced translocation t(1;17)(p36.2;q11.2) may have led to the development of the tumor by disrupting or activating a gene. Here, we report the cloning of both translocation breakpoints and the identification of a novel gene that is disrupted by this translocation. This gene, named NBPF1 for Neuroblastoma BreakPoint Family member 1, belongs to a recently described gene family encoding highly similar proteins, the functions of which are unknown. The translocation truncates NBPF1 and gives rise to two chimeric transcripts of NBPF1 sequences fused to sequences derived from chromosome 17. On chromosome 17, the translocation disrupts one of the isoforms of ACCN1, a potential glioma tumor suppressor gene. Expression of the NBPF family in neuroblastoma cell lines is highly variable, but it is decreased in cell lines that have a deletion of chromosome 1p. More importantly, expression profiling of the NBPF1 gene showed that its expression is significantly lower in cell lines with heterozygous NBPF1 loss than in cell lines with a normal 1p chromosome. Meta-analysis of the expression of NBPF and ACCN1 in neuroblastoma tumors indicates a role for the NBPF genes and for ACCN1 in tumor aggressiveness. Additionally, DLD1 cells with inducible NBPF1 expression showed a marked decrease of clonal growth in a soft agar assay. The disruption of both NBPF1 and ACCN1 genes in this neuroblastoma patient indicates that these genes might suppress development of neuroblastoma and possibly other tumor types

The Interaction between the First Transmembrane Domain and the Thumb of ASIC1a Is Critical for Its N-Glycosylation and Trafficking

Acid-sensing ion channel-1a (ASIC1a), the primary proton receptor in the brain, contributes to multiple diseases including stroke, epilepsy and multiple sclerosis. Thus, a better understanding of its biogenesis will provide important insights into the regulation of ASIC1a in diseases. Interestingly, ASIC1a contains a large, yet well organized ectodomain, which suggests the hypothesis that correct formation of domain-domain interactions at the extracellular side is a key regulatory step for ASIC1a maturation and trafficking. We tested this hypothesis here by focusing on the interaction between the first transmembrane domain (TM1) and the thumb of ASIC1a, an interaction known to be critical in channel gating. We mutated Tyr71 and Trp287, two key residues involved in the TM1-thumb interaction in mouse ASIC1a, and found that both Y71G and W287G decreased synaptic targeting and surface expression of ASIC1a. These defects were likely due to altered folding; both mutants showed increased resistance to tryptic cleavage, suggesting a change in conformation. Moreover, both mutants lacked the maturation of N-linked glycans through mid to late Golgi. These data suggest that disrupting the interaction between TM1 and thumb alters ASIC1a folding, impedes its glycosylation and reduces its trafficking. Moreover, reducing the culture temperature, an approach commonly used to facilitate protein folding, increased ASIC1a glycosylation, surface expression, current density and slowed the rate of desensitization. These results suggest that correct folding of extracellular ectodomain plays a critical role in ASIC1a biogenesis and function

Simposio I. Controversias en la úlceras de la extremidad inferior

Las úlceras vasculares de las extremidades inferiores (EEII) ocasionan un problema sanitario importante con gran consumo de recursos humanos y materiales. Estas úlceras se manifiestan, generalmente, en personas de edad avanzada y conducen, con frecuencia, a una limitación de su autonomía funcional, ya de por sí disminuida, lo que origina una sobrecarga del entorno familiar y para los centros de asistencia sociosanitaria. Cuando revisamos los artículos publicados y la situación de la asistencia en nuestro entorno, nos encontramos con numerosos interrogante que se plantearán y desarrollarán a lo largo de la exposición. A modo de introducción, se revisan algunas cuestiones

Photophysical Study of Polymer-Based Solar Cells with an Organo-Boron Molecule in the Active Layer

Our group previously reported the synthesis of four polythiophene derivatives (P1–P4) used for solar cells. The cells were prepared under room conditions by spin coating, leading to low efficiencies. However, after the addition of 6-nitro-3-(E)-3-(4-dimethylaminophenyl)allylidene)-2,3-dihydrobenzo[d]-[1,3,2] oxazaborole (M1) to their active layers, the efficiencies of the cells showed approximately a two-fold improvement. In this paper, we study this enhancement mechanism by performing ultrafast transient absorption (TA) experiments on the active layer of the different cells. Our samples consisted of thin films of a mixture of PC61BM with the polythiophenes derivatives P1–P4. We prepared two versions of each sample, one including the molecule M1 and another without it. The TA data suggests that the efficiency improvement after addition of M1 is due not only to an extended absorption spectrum towards the infrared region causing a larger population of excitons but also to the possible creation of additional channels for transport of excitons and/or electrons to the PC61BM interface