Germanene: a novel two-dimensional Germanium allotrope akin to Graphene and Silicene

Using a gold (111) surface as a substrate we have grown in situ by molecular beam epitaxy an atom-thin, ordered, two-dimensional multi-phase film. Its growth bears strong similarity with the formation of silicene layers on silver (111) templates. One of the phases, forming large domains, as observed in Scanning Tunneling Microscopy, shows a clear, nearly flat, honeycomb structure. Thanks to thorough synchrotron radiation core-level spectroscopy measurements and advanced Density Functional Theory calculations we can identify it to a $\sqrt{3}$x$\sqrt{3}$R(30{\deg}) germanene layer in coincidence with a $\sqrt{7}$x$\sqrt{7}$R(19.1{\deg}) Au(111) supercell, thence, presenting the first compelling evidence of the birth of a novel synthetic germanium-based cousin of graphene.Comment: 16 pages, 4 figures, 1 tabl

A retarded coupling approach to intermolecular interactions

A wide range of physical phenomena such as optical binding and resonance energy transfer involve electronic coupling between adjacent molecules. A quantum electrodynamical description of these intermolecular interactions reveals the presence of retardation effects. The clarity of the procedure associated with the construction of the quantum amplitudes and the precision of the ensuing results for observable energies and rates are widely acknowledged. However, the length and complexity of the derivations involved in such quantum electrodynamical descriptions increase rapidly with the order of the process under study. Whether through the use of time-ordering approaches, or the more expedient state-sequence method, time-consuming calculations cannot usually be bypassed. A simple and succinct method is now presented, which provides for a direct and still entirely rigorous determination of the quantum electrodynamical amplitudes for processes of arbitrarily high order. Using the approach, new results for optical binding in two- and three-particle systems are secured and discussed

La respuesta de la comunidad epilítica intermareal natural e impactada por las aguas residuales del Atlántico SO a pulsos (antes/después del verano) y descargas crónicas de aguas residuales en el período 1997 - 2014

Until 2014 Mar del Plata city discharged its untreated sewage effluents to the intertidal sector. This city has a marked seasonality in the urban discharge, varying between 2.8 and 3.5 m3.sec.-1 of effluents before/after summer. The effect on the intertidal benthic community was evaluated in both spatially, in sewage-impacted and reference sites, and temporarily in both the short term, before/after summer, and in long term along nine periods between 1997 - 2014. The bivalve Brachidontes rodriguezii, the ecosystem engineer, reach the maximum dominance and frequency in reference areas. Spatially the presence of opportunistic and tolerant species characterized the impacted areas, while in reference sites sensitive species were prevalent. The opportunistic polychaete species Capitella "capitata" sp. and Alitta succinea were dominant near the sewage discharge in firsts periods. In other periods the indicator species were Rhynchospio glutaea or Boccardia spp. From 2008 the invader Boccardia proboscidea characterized the sewage-impacted sites building massive reefs. The crustaceans Jassa falcata and Caprella sp. were very abundant at intermediate distances from the sewage discharge, while Monocorophium insidiosum was very abundant in sewage-impacted areas. The tolerant and opportunistic species are favored after the summer due to the extra organic matter input. All community parameters showed lower values after the summer, and also a trend to diminish along the studied period.Hasta el año 2014 la ciudad de Mar del Plata descargaba sus efluentes cloacales sin tratamiento al sector intermareal. Esta ciudad tiene una marcada estacionalidad en sus descargas, variando el caudal entre 2,8 a 3,5 m3.seg-1 antes/después del verano. El efecto sobre la comunidad bentónica intermareal fue evaluado en la escala espacial, en sitios de referencia y sitios impactados, y también temporalmente en el corto período de tiempo, antes/después del verano, y a lo largo de nueve períodos entre 1997 - 2014. El bivalvo Brachidontes rodriguezii, el ingeniero ecosistémico, alcanza su máxima dominancia y frecuencia en áreas de referencia. Espacialmente la presencia de especies oportunistas y tolerantes caracterizó los sitios impactados, mientras que en sitios de referencia las especies sensibles son prevalentes. En los primeros períodos el poliqueto oportunista Capitella “capitata” sp. fue dominante cerca de la descarga cloacal, y también Alitta succinea. En periodos posteriores las especies indicadoreas fueron Rhynchospio glutaea o Boccardia spp. Desde 2008 el poliqueto invasor Boccardia proboscidea caracterizó los sitios impactados por la descarga por masivos arrecifes. Los crustáceos Jassa falcata y Caprella sp. fueron muy abundantes a distancias intermedias de la descarga, mientras que Monocorophium insidiosum fue muy abundante en el àrea impactada por la descarga cloacal. Las especies tolerantes u oportunistas se vieron favorecidas después del verano debido al aporte extra de materia orgánica. Todos los parámetros comunitarios mostraron valores menores después del verano, y también se observa una tendencia a disminuir a lo largo de los períodos estudiados

Configurable/adaptive digital FIR filter

En este trabajo de obtención de grado se describe el proceso de diseño y posterior implementación en silicio de un filtro digital de respuesta finita adaptativo que, a la vez, puede ser un filtro configurable.ITESO, A. C

Interactions between spherical nanoparticles optically trapped in Laguerre-Gaussian modes

When a Laguerre-Gaussian (LG) laser mode is used to trap nanoparticles, the spatial disposition of the particles about the beam axis is determined by a secondary mechanism that engages the input radiation with the interparticle potential. This analysis, based on the identification of a range-dependent laser-induced energy shift, elicits and details features that arise for spherical nanoparticles irradiated by a LG mode. Calculations of the absolute minima are performed for LG beams of variable topological charge, and the results are displayed graphically. It is shown that more complex ordered structures emerge on extension to three- and four-particle systems and that similar principles will apply to other kinds of radially structured optical mode. © 2005 Optical Society of America

Raman scattering mediated by neighboring molecules

Raman scattering is most commonly associated with a change in vibrational state within individual molecules, the corresponding frequency shift in the scattered light affording a key way of identifying material structures. In theories where both matter and light are treated quantum mechanically, the fundamental scattering process is represented as the concurrent annihilation of a photon from one radiation mode and creation of another in a different mode. Developing this quantum electrodynamical formulation, the focus of the present work is on the spectroscopic consequences of electrodynamic coupling between neighboring molecules or other kinds of optical center. To encompass these nanoscale interactions, through which the molecular states evolve under the dual influence of the input light and local fields, this work identifies and determines two major mechanisms for each of which different selection rules apply. The constituent optical centers are considered to be chemically different and held in a fixed orientation with respect to each other, either as two components of a larger molecule or a molecular assembly that can undergo free rotation in a fluid medium or as parts of a larger, solid material. The two centers are considered to be separated beyond wavefunction overlap but close enough together to fall within an optical near-field limit, which leads to high inverse power dependences on their local separation. In this investigation, individual centers undergo a Stokes transition, whilst each neighbor of a different species remains in its original electronic and vibrational state. Analogous principles are applicable for the anti-Stokes case. The analysis concludes by considering the experimental consequences of applying this spectroscopic interpretation to fluid media; explicitly, the selection rules and the impact of pressure on the radiant intensity of this process

Metodologia do teste de imunofluorescência indireta para o diagnóstico da tripanosomose eqüina.

A tripanosomose causada pelo Trypanosoma evansi tem uma distribuição geográfica extremamente ampla. Ela ocorre no norte da África, Índia, Malásia, Indonésia, China, Rússia, Filipinas, América Central e América do Sul. O T. evansi causa a tripanosomose equina também conhecida no nordeste da Argentina e Pantanal como "mal de cadeiras". O T. evansi infecta uma ampla variedade de mamíferos e no Pantanal ele tem sido encontrado em cavalos, quoatis (Nasua nasua), cães, capivaras (Hydrochaeris hydrochaeris) e pequenos roedores (Oryzomys sp.). No Pantanal tripanosomose eqüina causa centenas de mortes todo ano. Esta publicação tem como objetivo descrever a metodologia do TIFI utilizada no Laboratório de Sanidade Animal da Embrapa Pantanal.bitstream/item/37539/1/CT39.pd

Métodos de diagnósticos parasitológicos das tripanosomoses bovinas e eqüinas.

As hemoparasitoses constituem enfermidades amplamente distribuídas em toda a América Latina e Caribe causando efeitos negativos na saúde dos rebanhos animais e principalmente sobre a produção e rentabilidade dos sistemas de produção animal estabelecidos nas diferentes regiões do continente (Tamasaukas, 2000). Dentre os hemopar·sitos que causam importantes enfermidades nos animais domésticos e silvestres na América do Sul, destacam-se os Trypanosoma evansi e T. vivax. No Pantanal o T. evansi causa tripanosomose eqüina também conhecida como "mal de cadeira". É uma das doenças causadas por protozoários mais importantes do Pantanal. O objetivo deste trabalho foi descrever os métodos parasitológicos utilizados no Laboratório de Sanidade Animal da Embrapa Pantanal.bitstream/item/37534/1/CT41.pd

Metodologia da criopreservação dos Trypanosomas evansi e Trypanosoma vivax.

Várias espécies do gênero Trypanosoma causam doenças parasitárias de considerável importância médica e veterinária em todas as partes da África, Ásia e as Américas. Estes parasitas exibem considerável diversidade genética intraespecífica, variação que tem complicado sua classificação taxonômica. Esta diversidade e variação podem ser definidas em ambos níveis: do genoma e genes individuais. Em razão desta diversidade genética tem se discutido muito sobre a representatividade das cepas mantidas em laboratório quando comparadas com os isolados de campo (Deane et al., 1984). Aparentemente existe uma adaptação do parasita na troca de hospedeiro. Sabe-se que um isolado de campo pode estar constituído por uma população heterogênea de tripanosomas. Nos estudos realizados pelo Laboratório de Sanidade Animal da Embrapa Pantanal foram encontradas variações na infectividade das cepas de T. evansi. Estas foram pouco infectivas em animais de laboratório quando recém isoladas do hospedeiro natural, apresentando um período prepatente de 12 a 43 dias e baixa parasitemia. Após algumas passagens, elas se mostraram mais infectivas com um período prepatente de 2 a 4 dias e uma parasitemia mais alta. Também foram observadas variações biométricas deste parasita nas passagens. Verificou-se que este parasita sofreu alterações morfométricas durante as passagens como provável conseqüência da adaptação ao novo hospedeiro ou seleção de algumas subpopulações. As características biométricas das passagens foram sempre maiores que as do isolado primário (Dávila et al., 1998). As amostras de campo diferiram significativamente dos isolados após várias passagens em animais de laboratório, sendo que quanto maior o número de passagens mais acentuação das diferenças morfológicas. A criopreservação pode contribuir para que sejam mantidas amostras com variabilidade genética original da cepa. Esse trabalho tem por objetivo descrever o método de criopreservação utilizado no Laboratório de Sanidade Animal da Embrapa Pantanal.bitstream/item/37530/1/CT40.pd

Biases in Multi-Year Management Financial Forecasts: Evidence From Private Venture-Backed U.S. Companies

This paper studies the properties and determinants of managers’ multi-year financial forecasts. Using one- to five-year-ahead forecasts reported by private venture-backed firms, we ask whether, by how much, and why biases in managers’ forecasts of revenues, expenses and profits depend on the forecasting horizon and the verifiability of assets. We find that profitability forecasts contain a strategic component, in that [1] one-year-ahead revenue (expense) forecasts are slightly and asymmetrically pessimistic (optimistic), while five-year-ahead forecasts are hugely and asymmetrically optimistic (pessimistic); and [2] biases in revenue and expense forecasts are larger, the harder to verify or more intangible-intensive are firms’ assets