Monte Carlo Studies of the Intrinsic Second Hyperpolarizability

The hyperpolarizability has been extensively studied to identify universal properties when it is near the fundamental limit. Here, we employ the Monte Carlo method to study the fundamental limit of the second hyperpolarizability. As was found for the hyperpolarizability, the largest values of the second hyperpolarizability approaches the calculated fundamental limit. The character of transition moments and energies of the energy eigenstates are investigated near the second hyperpolarizability's upper bounds using the missing state analysis, which assesses the role of each pair of states in their contribution. In agreement with the three-level ansatz, our results indicate that only three states (ground and two excited states) dominate when the second hyperpolarizability is near the limit.Comment: 8 pages, 7 figure

Maximizing the hyperpolarizability of one-dimensional systems

Previous studies have used numerical methods to optimize the hyperpolarizability of a one-dimensional quantum system. These studies were used to suggest properties of one-dimensional organic molecules, such as the degree of modulation of conjugation, that could potentially be adjusted to improve the nonlinear-optical response. However, there were no conditions set on the optimized potential energy function to ensure that the resulting energies were consistent with what is observed in real molecules. Furthermore, the system was placed into a one-dimensional box with infinite walls, forcing the wavefunctions to vanish at the ends of the molecule. In the present work, the walls are separated by a distance much larger than the molecule's length; and, the variations of the potential energy function are restricted to levels that are more typical of a real molecule. In addition to being a more physically-reasonable model, our present approach better approximates the bound states and approximates the continuum states - which are usually ignored. We find that the same universal properties continue to be important for optimizing the nonlinear-optical response, though the details of the wavefunctions differ from previous result.Comment: 10 pages, 5 figure

Experimental verification of a self-consistent theory of the first-, second-, and third-order (non)linear optical response

We show that a combination of linear absorption spectroscopy, hyper-Rayleigh scattering, and a theoretical analysis using sum rules to reduce the size of the parameter space leads to a prediction of the two-photon absorption cross-section of the dye AF455 that agrees with two-photon absorption spectroscopy. Our procedure, which demands self-consistency between several measurement techniques and does not use adjustable parameters, provides a means for determining transition moments between the dominant excited states based strictly on experimental characterization. This is made possible by our new approach that uses sum rules and molecular symmetry to rigorously reduce the number of required physical quantities.Comment: 10 pages, 9 figure

Cardiometabolic and Cardiovascular Complications of Obesity in Children

The rise in obesity in both children and adults has made obesity one of the biggest public health problems of this century. Obesity along with other factors such as hypertension, insulin resistance, dyslipidemia and diabetes mellitus are risk factors for the development of cardiovascular diseases. Overweight and/or obesity during childhood and its maintenance until adult life has been associated with early stages of cardiovascular disease. For this reason, the aim of this study is to revise the state of the art of cardiometabolic and cardiovascular complications related with overweight and/or obesity in children and adolescents. The first consequence of weight gain is an increase in adipose tissue, with different distribution depending on the sex. The excess of fat mass entails dysfunction of adipose tissue with an altered secretion of adipokines and instauration of a proinflammatory environment, which may derive in metabolic syndrome condition. The increase of adipose tissue along with an increase in sympathetic nervous system, triggers an increased left ventricular mass and with a reduced diastolic function. Therefore, obesity should be prevented from the early stages of life, in order to avoid obesity itself and the metabolic disturbances that could undermine quality of life further on

An Assessment of Available Models for the Design of Schottky-Based Multipliers Up to THz Frequencies

[EN]This paper evaluates the ranges of application and physical limitations of lumped equivalent circuits and drift-diffusion models for the design of THz circuits. The predictions of these models have been compared with aMonte Carlo model, which was considered as a reference, and with measurements from doublers and triplers designed and fabricated by the Jet Propulsion Laboratory. Additionally, the usefulness of Schottky diodes as frequency multipliers above 3 THz is analyzed with the Monte Carlo model.European Commision (EC). Funding FP7/SP1/SPA. Project Code: 242334European Commision (EC). Funding FP7/SP1/ICT. Project Code: 24384

Banks’ Net Interest Margin in the 2000s: A Macro-Accounting International Perspective

This paper re-examines the determinants of Net Interest Margin (NIM) in the banking industries of 15 developed and emerging economies. It presents three main contributions with respect to previous studies: first, we analyze the determinants of NIM in the years leading to the 2008 financial crisis; second, we account for the role of different accounting standards across countries; third, we use multi-way cluster estimation methodologies which control for cross-sectional and time-series dependence in macroeconomic and banking variables. We find that the introduction of International Financial Reporting Standards (IFRSs) contributed to lower NIM variations unexplained by standard accounting variables. Interest rate volatility is found to be positively and strongly related to NIM dynamics, whereas inflation risk is often found to be a relevant driver of NIM crosscountry differences

Análisis del infrarregistro de la mortalidad perinatal y sus factores asociados en una región sanitaria de Cataluña

ResumenObjetivosEvaluar la magnitud del infrarregistro de las muertes perinatales de la Región Sanitaria «Centre» (RSC) (Cataluña). Estimar las tasas de mortalidad reales y analizar los factores asociados al infrarregistro.MétodosEstudio observacional retrospectivo del infrarregistro de la mortalidad perinatal durante el período 1991–1992 en la RSC. Mediante una recogida activa se han identificado las muertes perinatales de peso igual o superior a 500 gr o de 22 semanas o más, ocurridas en los hospitales del RSC, comparándolas, mediante un apareamiento informático, con las muertes perinatales del registro oficial de mortalidad. Las variables de apareamiento utilizadas han sido: nombre y apellidos del recién nacido, sexo, municipio y fecha de la defunción. Se ha aplicado el análisis de regresión logística para detectar los factores asociados al infrarregistro.ResultadosLa mortalidad perinatal en la RSC en el período 1991–92 se ha infraestimado en un 34% (IC 95%: 26%–42%). La mayor parte de las muertes no declaradas corresponde a muertes fetales y/o recién nacidos de muy bajo peso o de gran prematuridad que mueren a las pocas horas de vida. Durante el fin de semana el infrarregistro es unas cuatro veces mayor. Una vez recogida, la tasa de mortalidad perinatal en la RSC para los años 1991–1992 pasa de 6,3 por 1.000 nacimientos a 9,6 por 1.000 nacimientos.ConclusionesPara disponer de una información precisa de las necesidades de salud de las mujeres en edad fértil y de los recién nacidos de la RSC, y de cada uno de sus sectores, debe mejorarse la declaración de las muertes perinatales.SummaryObjectivesTo assess the degree of undereporting of perinatal deaths in the «Centre» Region (CR) during 1991 and 1992.MethodsObservational retrospective study of the undereporting of perinatal deaths in the CR during 1991 and 1992. Perinatal deaths above 499 grams or 21 weeks of gestation which occurred in the hospitals of the CR were identified by reviewing hospital records, and then compared through linkage with perinatal deaths recorded in vital statistics. The following variables were used for the matching: name and surname, sex, county and date of death. Logistic regression was used to identify factors associated with undereporting.ResultsThe degree of undereporting of perinatal deaths in the CR during 1991–1992 was 34% [95% CI: (26%–42%)]. Most undereported perinatal deaths corresponded to fetal deaths, or very low birthweight or preterm livebirths that died shortly after birth. Over the weekend, undereporting increases by four-fold. The official perinatal mortality rate for the CR, 6.3 per 1,000 births, increased to 9.6 per 1,000 births, after taking into account undereporting.ConclusionsIn order to have valid information of the health needs of mothers and newborns reporting of perinatal deaths must be improved