Dark Energy Accretion onto black holes in a cosmic scenario

In this paper we study the accretion of dark energy onto a black hole in the cases that dark energy is equipped with a positive cosmological constant and when the space-time is described by a Schwarzschild-de Sitter metric. It is shown that, if confronted with current observational data, the results derived when no cosmological constant is present are once again obtained in both cases.Comment: 7 pages, 3 figure

Role of inert gas in the Cvd-graphene synthesis over polycrystalline nickel foils

The role of the inert gas during CVD-graphene growth over polycrystalline nickel foils is reported. Nitrogen, hydrogen and methane were used as inert, reduction and carbonaceous gases, respectively. Graphene samples were characterized by using Optical Microscopy, Raman Spectroscopy and SEM equipped with EDX. Four different colors were distinguished over the optical microscope images. These colors were analyzed by Raman Spectroscopy and correlated to each type of graphene deposited over the foil (monolayer, bilayer, few-layers and multilayer). An Excel-VBA application was developed, which was used for computing the percentage of each type of graphene, resulting in an estimation of the graphene quality value. It was verified that the incorporation of the inert gas in the reaction step during CVD-graphene synthesis greatly influenced the quality of the obtained graphene. Different temperatures and percentages of nitrogen were studied in order to define the optimal reaction conditions. A factorial design study was performed to find the best experimental conditions leading to the highest quality graphene value, which resulted to be the following ones: 947 °C and 13 vol % of nitrogen in the feed stream, 1 min of reaction time, a relation between CH4 and H2 of 0.07 v/v, and a total flow of gases of 80 Nml/min.Se informa sobre el papel del gas inerte durante el crecimiento de CVD-grafeno sobre láminas de níquel policristalino . Se utilizaron nitrógeno, hidrógeno y metano como gases inertes, de reducción y carbonosos, respectivamente. Las muestras de grafeno se caracterizaron utilizando Microscopía Óptica, Espectroscopía Raman y SEM equipado con EDX .. Se distinguieron cuatro colores diferentes sobre las imágenes del microscopio óptico. Estos colores se analizaron mediante espectroscopia Raman y se correlacionaron con cada tipo de grafeno depositado sobre la lámina (monocapa, bicapa, pocas capas y multicapa). Se desarrolló una aplicación Excel-VBA, la cual se utilizó para calcular el porcentaje de cada tipo de grafeno, dando como resultado una estimación del valor de la calidad del grafeno. Se comprobó que la incorporación del gas inerte en el paso de reacción durante la síntesis de CVD-grafeno influyó mucho en la calidad del grafeno obtenido. Se estudiaron diferentes temperaturas y porcentajes de nitrógeno para definir las condiciones óptimas de reacción. Se realizó un estudio de diseño factorial para encontrar las mejores condiciones experimentales que conduzcan al valor de grafeno de mayor calidad, las cuales resultaron ser las siguientes:4 y H 2 de 0,07 v/v, y un caudal total de gases de 80 Nml/min

Dark Matter and Higgs Sector

The inert doublet model is an extension of the Standard Model of Elementary Particles that is defined by the only addition of a second Higgs doublet without couplings to quarks or leptons. This minimal framework has been studied for many reasons. In particular, it has been suggested that the new degrees of freedom contained in this doublet can account for the Dark Matter of the Universe.Comment: 6 pages, 3 figures,To appear in the Proceedings of the sixth International Workshop on the Dark Side of the Universe (DSU2010) Leon, Guanajuato, Mexico 1-6 June 201

The translation of cell-based therapies:clinical landscape and manufacturing challenges

Cell-based therapies have the potential to make a large contribution toward currently unmet patient need and thus effective manufacture of these products is essential. Many challenges must be overcome before this can become a reality and a better definition of the manufacturing requirements for cell-based products must be obtained. The aim of this study is to inform industry and academia of current cell-based therapy clinical development and to identify gaps in their manufacturing requirements. A total of 1342 active cell-based therapy clinical trials have been identified and characterized based on cell type, target indication and trial phase. Multiple technologies have been assessed for the manufacture of these cell types in order to facilitate product translation and future process development

Different strategies to simultaneously N-doping and reduce graphene oxide for electrocatalytic applications

Two different approaches to simultaneously introduce nitrogen atoms within the graphene framework and, reduce graphene oxide nanoplatelets (GO), have been explored in order to improve the electrocatalytic activity of the resulting materials. Thus, a facile hydrothermal method using 2-chloroethylamine under conditions at 180 °C and, another one, based in the formation of polypyrrole (PPy) on graphene oxide nanoplatelets by in situ polymerization of pyrrole monomer in the presence of GO, were compared through a deep characterization of the final materials by SEM, RAMAN, FTIR, XPS, Zeta potential, XRD and TGA analysis. Physico-chemical properties of the graphene-based materials were subsequently related with their electron transfer efficiency and electrocatalytic activity. The as prepared rGO prepared by the PPy method showed an N content quite superior (~6–8%) than the rGO prepared by the hydrothermal one (~1%) being an important part of their nitrogen state pyridinic type. The electrocatalytic results showed that GO exhibited higher specific capacitance than rGO materials due to its intrinsic higher porosity. However, the presence of N species seems to have a positive effect on the ORR activity, although the N incorporation through the PPy-rGO synthesis method seems to be the preferred one according for the complete ORR pathway.Se han explorado dos enfoques diferentes para introducir simultáneamente átomos de nitrógeno dentro del marco de grafeno y reducir las nanoplaquetas de óxido de grafeno ( GO) con el fin de mejorar la actividad electrocatalítica de los materiales resultantes. Así, se comparó un método hidrotermal fácil usando 2-cloroetilamina en condiciones a 180 °C y otro, basado en la formación de polipirrol (PPy) sobre nanoplaquetas de óxido de grafeno por polimerización in situ del monómero pirrol en presencia de GO. una caracterización profunda de los materiales finales por SEM, RAMAN, FTIR, XPS , potencial Zeta , XRD yanálisis TGA . Las propiedades fisicoquímicas de los materiales a base de grafeno se relacionaron posteriormente con su eficiencia de transferencia de electrones y su actividad electrocatalítica. El rGO preparado por el método PPy mostró un contenido de N bastante superior (~6–8%) que el rGO preparado por el hidrotermal (~1%) siendo una parte importante de su estado nitrogenado de tipo piridínico. Los resultados electrocatalíticos mostraron que GO exhibió una capacitancia específica más alta que los materiales rGO debido a su mayor porosidad intrínseca. Sin embargo, la presencia de especies de N parece tener un efecto positivo sobre la actividad de ORR, aunque la incorporación de N a través del método de síntesis de PPy-rGO parece ser el preferido según la vía completa de ORR

Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV

A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7 TeV is presented. The data were collected at the LHC, with the CMS detector, and correspond to an integrated luminosity of 4.6 inverse femtobarns. No significant excess is observed above the background expectation, and upper limits are set on the Higgs boson production cross section. The presence of the standard model Higgs boson with a mass in the 270-440 GeV range is excluded at 95% confidence level.Comment: Submitted to JHE

Measurement of the t t-bar production cross section in the dilepton channel in pp collisions at sqrt(s) = 7 TeV

The t t-bar production cross section (sigma[t t-bar]) is measured in proton-proton collisions at sqrt(s) = 7 TeV in data collected by the CMS experiment, corresponding to an integrated luminosity of 2.3 inverse femtobarns. The measurement is performed in events with two leptons (electrons or muons) in the final state, at least two jets identified as jets originating from b quarks, and the presence of an imbalance in transverse momentum. The measured value of sigma[t t-bar] for a top-quark mass of 172.5 GeV is 161.9 +/- 2.5 (stat.) +5.1/-5.0 (syst.) +/- 3.6(lumi.) pb, consistent with the prediction of the standard model.Comment: Replaced with published version. Included journal reference and DO

Search for anomalous t t-bar production in the highly-boosted all-hadronic final state

A search is presented for a massive particle, generically referred to as a Z', decaying into a t t-bar pair. The search focuses on Z' resonances that are sufficiently massive to produce highly Lorentz-boosted top quarks, which yield collimated decay products that are partially or fully merged into single jets. The analysis uses new methods to analyze jet substructure, providing suppression of the non-top multijet backgrounds. The analysis is based on a data sample of proton-proton collisions at a center-of-mass energy of 7 TeV, corresponding to an integrated luminosity of 5 inverse femtobarns. Upper limits in the range of 1 pb are set on the product of the production cross section and branching fraction for a topcolor Z' modeled for several widths, as well as for a Randall--Sundrum Kaluza--Klein gluon. In addition, the results constrain any enhancement in t t-bar production beyond expectations of the standard model for t t-bar invariant masses larger than 1 TeV.Comment: Submitted to the Journal of High Energy Physics; this version includes a minor typo correction that will be submitted as an erratu

Anisotropic Confinement, Electronic Coupling and Strain Induced Effects Detected by Valence-Band Anisotropy in Self-Assembled Quantum Dots

A method to determine the effects of the geometry and lateral ordering on the electronic properties of an array of one-dimensional self-assembled quantum dots is discussed. A model that takes into account the valence-band anisotropic effective masses and strain effects must be used to describe the behavior of the photoluminescence emission, proposed as a clean tool for the characterization of dot anisotropy and/or inter-dot coupling. Under special growth conditions, such as substrate temperature and Arsenic background, 1D chains of In0.4Ga0.6 As quantum dots were grown by molecular beam epitaxy. Grazing-incidence X-ray diffraction measurements directly evidence the strong strain anisotropy due to the formation of quantum dot chains, probed by polarization-resolved low-temperature photoluminescence. The results are in fair good agreement with the proposed model