Numerical calculations of diffraction losses in advanced interferometric gravitational wave detectors

Knowledge of the diffraction losses in higher-order modes of large optical cavities is essential for predicting three-mode parametric photon-phonon scattering, which can lead to mechanical instabilities in long-baseline gravitational wave detectors. We explore different numerical methods in order to determine the diffraction losses of the higher-order optical modes. Diffraction losses not only affect the power buildup inside the cavity but also influence the shape and frequency of the mode, which ultimately affect the parametric instability gain. Results depend on both the optical mode shape (order) and the mirror diameter. We also present a physical interpretation of these results

Evidence for an inflationary phase transition from the LSS and CMB anisotropy data

In the light of the recent Boomerang and Maxima observations of the CMB which show an anomalously low second acoustic peak, we reexamine the prediction by Adams et al (1997) that this would be the consequence of a 'step' in the primordial spectrum induced by a spontaneous symmetry breaking phase transition during primordial inflation. We demonstrate that a deviation from scale-invariance around $k\sim0.1h$~Mpc$^{-1}$ can simultaneously explain both the feature identified earlier in the APM galaxy power spectrum as well the recent CMB anisotropy data, with a baryon density consistent with the BBN value. Such a break also allows a good fit to the data on cluster abundances even for a critical density matter-dominated universe with zero cosmological constant.Comment: 4 pages with 3 figures, LaTeX file using espcrc2.sty to appear on the Proceedings of "Euroconference on Frontiers in Particle Astrophysics and Cosmology",Sant Feliu de Guixols,Spain,30th September-5th October of 200

EVALUATION OF THE ANTIOXIDANT ACTIVITY OF THE FLAVONOIDS ISOLATED FROM HELIOTROPIUM SINUATUM RESIN USING ORACFL, DPPH AND ESR METHODOLOGIES

Indexación: Web of Science; Scielo.The antioxidant capacity has been determined for a number of flavonoid compounds from Heliotropium sinuatum, a plant that grows in arid areas in the north of Chile. The methodologies used were: ORAC(FL) (oxygen radical absorbance capacity - fluorescein), DPPH (2,2-diphenyl-2-picrylhydrazyl) bleaching and electron spin resonance (ESR). These compounds were studied in homogeneous and heterogeneous media. The results showed that the 7-o-methyleriodictiol and 3-o-methylisorhamnetin are those with the highest antioxidant capacity.http://ref.scielo.org/m82cz

Interplay between the magnetic anisotropy contributions of Cobalt nanowires

We report on the magnetic properties and the crystallographic structure of the cobalt nanowire arrays as a function of their nanoscale dimensions. X-ray diffraction measurements show the appearance of an in-plane HCP-Co phase for nanowires with 50 nm diameter, suggesting a partial reorientation of the magnetocrystalline anisotropy axis along the membrane plane with increasing pore diameter. No significant changes in the magnetic behavior of the nanowire system are observed with decreasing temperature, indicating that the effective magnetoelastic anisotropy does not play a dominant role in the remagnetization processes of individual nanowires. An enhancement of the total magnetic anisotropy is found at room temperature with a decreasing nanowire diameter-to-length ratio (d/L), a result that is quantitatively analyzed on the basis of a simplified shape anisotropy model.Comment: 8 pages, 4 figure

The Poisson-exponential regression model under different latent activation schemes

In this paper, a new family of survival distributions is presented. It is derived by considering that the latent number of failure causes follows a Poisson distribution and the time for these causes to be activated follows an exponential distribution. Three different activationschemes are also considered. Moreover, we propose the inclusion of covariates in the model formulation in order to study their effect on the expected value of the number of causes and on the failure rate function. Inferential procedure based on the maximum likelihood method is discussed and evaluated via simulation. The developed methodology is illustrated on a real data set on ovarian cancer. Mathematical subject classification: 62N01, 62N99

Probing two topological surface bands of Sb2Te3 by spin-polarized photoemission spectroscopy

Using high resolution spin- and angle-resolved photoemission spectroscopy, we map the electronic structure and spin texture of the surface states of the topological insulator Sb2Te3. In combination with density functional calculations (DFT), we directly show that Sb2Te3 exhibits a partially occupied, single spin-Dirac cone around the Fermi energy, which is topologically protected. DFT obtains a spin polarization of the occupied Dirac cone states of 80-90%, which is in reasonable agreement with the experimental data after careful background subtraction. Furthermore, we observe a strongly spin-orbit split surface band at lower energy. This state is found at 0.8eV below the Fermi level at the gamma-point, disperses upwards, and disappears at about 0.4eV below the Fermi level into two different bulk bands. Along the gamma-K direction, the band is located within a spin-orbit gap. According to an argument given by Pendry and Gurman in 1975, such a gap must contain a surface state, if it is located away from the high symmetry points of the Brillouin zone. Thus, the novel spin-split state is protected by symmetry, too.Comment: 8 pages, 10 figure

Photoemission of Bi2_2Se3_3 with Circularly Polarized Light: Probe of Spin Polarization or Means for Spin Manipulation?

Topological insulators are characterized by Dirac cone surface states with electron spins aligned in the surface plane and perpendicular to their momenta. Recent theoretical and experimental work implied that this specific spin texture should enable control of photoelectron spins by circularly polarized light. However, these reports questioned the so far accepted interpretation of spin-resolved photoelectron spectroscopy. We solve this puzzle and show that vacuum ultraviolet photons (50-70 eV) with linear or circular polarization probe indeed the initial state spin texture of Bi$_2$Se$_3$ while circularly polarized 6 eV low energy photons flip the electron spins out of plane and reverse their spin polarization. Our photoemission calculations, considering the interplay between the varying probing depth, dipole selection rules and spin-dependent scattering effects involving initial and final states explain these findings, and reveal proper conditions for light-induced spin manipulation. This paves the way for future applications of topological insulators in opto-spintronic devices.Comment: Submitted for publication (2013

Competição de cultivares de milho no Pará.

bitstream/item/60127/1/CPATU-PA26.pd

Principales nemátodos fitoparasitos asociados con cultivos de plátano (Musa AAb y Musa ABB) en cuatro regiones de Colombia

Se realizó un reconocimiento general de nemátodos ecto y endoparásitos prevalentes en 4 zonas de producción de plátano. Los géneros de mayor diseminación fueron Helicotylenchus, Pratylenchus y Meloidogyne. De estos el que causa mayores daños es el nemátodo de la lesión radical, generalmente la especie P. coffeae, el cual en las zonas bananeras de la Costa Atlántica se encuentra en niveles altos de parasitismo. Los géneros Meloidogyne y Helicotylenchus fueron más prevalentes con altos niveles de población, en la región cafetera del Quindió donde posiblemente pueden causar pérdidas en producción de fruta. Radopholus similis se observó también en las regiones de la Costa, especialmente en la zona de Urabá, donde puede estar causando daños de importancia. Hoplolaimus seinhorsti fue identificado frecuentemente en la zona bananera de Santa Martha. R. similis no fue detectado en las 2 zonas del interior, sólo de material introducido al Quindió de la región de Urabá, lo cual implica un peligro potencial para ésta importante zona de producción del interior del paísEl plátano (Musa AÁAB y ARB) es considerado como uno de Jos alimentos basicós del pueblo colombiano, por lo: cuul: se cultiva en todas fas reglenes del pais desde las llanuras de lus costas, en arillos océanos, hasta os valles interandinos y las vertientes de las Cordilleras. donde generelmente se encuentra intercalado con útros. cultivos Importentes, como el cate, el cecao, la yuca y al malz. Es asi como para 1975, se colculuba, ul área de este quibvóo en superior a las 385,000 hectáreas con una produeción estimada de 1.300 000 toneladas métricas de frila (8). Sin embargo, debido a que tragficionalmente el cultivo del plátano ha sido: una actividad de producción para constimo interno. hasta la, presente no há existido una atención prioritaria para aplicar tecnologia con el lin de mejorar el cultivo e ¡dentificar los printipales probiemas fitosanitarioqsu:e lo efectán, Dentro de estos problemas pcupa especial importencia el relacionado. cen el parasitismo de nemétodos, a los cuales el plátano presenta un alto grado de susceptibilidad. El presente trabajo: tuvo: como objetivo principal etectuar un réconocimiento de. nernátodos en algubas de las principales zonas de producción de pláteno del a con el fin de conocer Ja Iiiportancia rejativa Uel problema y sugerir algunas medidas dé control para evitar la: dispersión de algunos grupos de nenátados firoparásitos. que puedan considerarse ¡como Ung arrenaza potencial para ciertes zones de producción de plátano.Plátano-Musa sapientu

Listado de las arañas de Colombia (Arachnida: Araneae)

The present list reviews 914 species of spiders that occur in Colombia. The information was obtained and compiled from two hundred seventy-three scientific documents which provided the valid name of the species, distribution in the Americas and Colombia, elevation range of specimens, and the collections where specimens were deposited. The aim of this list is to be a quick reference tool for those interested in the existing arachnofauna of Colombia.Este listado contiene 914 especies de arañas citadas en localidades colombianas. Información recogida y compilada de 273 documentos científicos, que aportan el nombre válido de la especie, su distribución en América y en Colombia, así como el intervalo altitudinal en el cual han sido colectados, el museo en el que se encuentran depositados. Este listado pretende ser una herramienta de consulta rápida y eficaz para aquellos interesados en la aracnofauna existente en Colombia