Addition of dianions of carboxylic acids to imines. Influence of the acid in the outcome of the reaction

The addition of different carboxylic acids dianions to N-benzylidenebenzeneamine have been studied. The outcome of the reaction depends on the acid. Saturated ones lead to β-aminoacids with good yields and syn-selectivity whereas α,β-unsaturated ones lead to α− and γ− regioisomers with a regioselectivity that depends on the steric hindrance around the reactive centre. From some of these unsaturated acids, polyunsaturated carboxylic acids can be obtained as a change in the reaction conditions lead to the in situ elimination of aniline. From o-methyl aromatic acids δ-aminoacids are isolated with uneven results. Those derived from six member arene carboxylic acids give, on standing, dihydro-2-pyridones as the sole product.Gil Grau, Salvador, [email protected], Parra Alvarez, Margarita, [email protected], Rodriguez Abad, Pablo, [email protected]

Efficient low-power terahertz generation via on-chip triply-resonant nonlinear frequency mixing

Achieving efficient terahertz (THz) generation using compact turn-key sources operating at room temperature and modest power levels represents one of the critical challeges that must be overcome to realize truly practical applications based on THz. Up to now, the most efficient approaches to THz generation at room temperature -- relying mainly on optical rectification schemes -- require intricate phase-matching set-ups and powerful lasers. Here we show how the unique light-confining properties of triply-resonant photonic resonators can be tailored to enable dramatic enhancements of the conversion efficiency of THz generation via nonlinear frequency down-conversion processes. We predict that this approach can be used to reduce up to three orders of magnitude the pump powers required to reach quantum-limited conversion efficiency of THz generation in nonlinear optical material systems. Furthermore, we propose a realistic design readily accesible experimentally, both for fabrication and demonstration of optimal THz conversion efficiency at sub-W power levels

Efficient Terahertz Generation in Triply Resonant Nonlinear Photonic Crystal Microcavities

We propose a scheme for efficient cavity-enhanced nonlinear THz generation via difference-frequency generation (DFG) processes using a triply resonant system based on photonic crystal cavities. We show that high nonlinear overlap can be achieved by coupling a THz cavity to a doubly-resonant, dual-polarization near-infrared (e.g. telecom band) photonic-crystal nanobeam cavity, allowing the mixing of three mutually orthogonal fundamental cavity modes through a chi(2) nonlinearity. We demonstrate through coupled-mode theory that complete depletion of the pump frequency - i.e., quantum-limited conversion - is possible in an experimentally feasible geometry, with the operating output power at the point of optimal total conversion efficiency adjustable by varying the mode quality (Q) factors.Comment: 8 pages, 3 figure

Difference-frequency generation with quantum-limited efficiency in triply-resonant nonlinear cavities

We present a comprehensive study of second-order nonlinear difference frequency generation in triply resonant cavities using a theoretical framework based on coupled-mode theory. We show that optimal quantum-limited conversion efficiency can be achieved at any pump power when the powers at the pump and idler frequencies satisfy a critical relationship. We demonstrate the existence of a broad parameter range in which all triply-resonant DFG processes exhibit monostable conversion. We also demonstrate the existence of a geometry-dependent bistable region.Comment: 10 pages, 3 figure

¿Puede el ejercicio físico moderado durante el embarazo actuar como un factor de prevención de la Diabetes Gestacional?

El presente trabajo pretendió conocer la eficacia de un programa de ejercicio físico moderado desarrollado durante todo el embarazo en el control de la excesiva ganancia de peso materno, la tolerancia materna a la glucosa y el desarrollo de la Diabetes Gestacional (DG). Se realizó un ensayo clínico, aleatorizado, no apareado, no enmascarado mediante una colaboración entre el Servicio de Ginecología y Obstetricia del Centro de Salud de Torrelodones y la Universidad Politécnica de Madrid. 55 gestantes sin contraindicaciones obstétricas fueron estudiadas, (edad=32,9±3,9 años), todas ellas caucásicas, 25 en el grupo de tratamiento y 30 en el de control. Se desarrolló un programa de ejercicio físico (seco/agua) durante todo el embarazo con una frecuencia de tres sesiones semanales. Nuestros resultados muestran que grupo de tratamiento presentó una menor ganancia de peso materno que en el de control (12,8±3,6 kg y 14,7±3,4 kg respectivamente, p=0,03), los valores en el Test de O'Sullivan (sobrecarga oral de glucosa) fueron inferiores en el grupo de tratamiento que en el de control 102,9±17,7 gr/dL vs 125,6±30,8 gr/dL respectivamente, p=0,002). No se diagnosticó ningún caso de DG en el grupo de tratamiento mientras que en el grupo de control se diagnosticaron 2 casos. El ejercicio físico desarrollado durante el embarazo reduce la ganancia de peso materno, los valores del Test de O'Sullivan y actúa aparentemente como un factor de prevención de la DG

Utilización de bolsas ANKOM® en la determinación de la digestibilidad de la materia seca in vitro en conejos.

La metodología de digestibilidad in vitro de la materia seca (DMSiv) desarrollada por Ramos et al. (1992) para predecir la digestibilidad de la materia seca y valor nutricional de diferentes alimentos comúnmente utilizados en la alimentación de conejos, ha sido estandarizada y validada por diferentes laboratorios (Villamide et al. 2008 y Carabaño et al. 2008), demostrándose su fiabilidad, reproducibilidad y repetibilidad. Uno de los puntos críticos de las metodologías gravimétricas es la filtración con crisol, ya que las propiedades físicas junto con la composición química de diversas materias primas dificultan este proceso y aumentan la variabilidad en los resultados (Mertens, 2002). Por otra parte la digestión individual de las muestras limita la capacidad de análisis. Con la finalidad de corregir estas limitaciones se propuso como alternativa el uso de bolsas ANKOM ® , ya utilizadas en el análisis secuencial de Van Soest (Kenneth et al., 1999), digeridas colectivamente en un mismo recipiente. Además de la utilización de bolsas, como novedad se incluyó al final de la digestibilidad un lavado adicional de las bolsas. El objetivo de este trabajo fue determinar la validez de esta modificación en la digestibilidad in vitro ileal (dos pasos) y fecal (tres pasos

Wave-front phase-modulation control and focusing of second-harmonic light generated in transparent nonlinear random structures

We theoretically investigate how phase-only spatial light modulation can enable controlling and focusing the second-harmonic light generated in transparent nonlinear random structures. The studied structures are composed of domains with random sizes and antiparallel polarization, which accurately model widely used ferroelectric crystals such as strontium barium niobate. Using a first-principles Green-function formalism, we account for the effect that spatial light modulation of the fundamental beam introduces into the second-order nonlinear frequency conversion occurring in the considered class of structures. This approach provides a complete description of the physical origin of the second-harmonic light generation in the system, as well as the optimization of the light intensity in any arbitrary direction. Our numerical results show how the second-harmonic light is influenced by both the disorder in the structure and the boundaries of the crystal. Particularly, we find that the net result from the interplay between disorder and boundary effects is strongly dependent on the dimensions of the crystal and the observation direction. Remarkably, our calculations also show that although in general the maximum possible enhancement of the second-order light is the same as the one corresponding to linear light scattering in turbid media, in the Cerenkov phase matching direction the enhancement can exceed the linear limit. The theoretical analysis presented in this work expands the current understanding of light control in complex media and could contribute to the development of a new class of imaging and focusing techniques based on nonlinear frequency mixing in random optical materials.Peer ReviewedPostprint (published version

Evolution Of Fair Business Performance As A Tool Of Marketing In Spain

Although the distance communication systems have been developed in the last years thanks to the development of communication and information technologies, recent studies argue that simple ways of communication like fairs maintain and increase their weigh cause of their profitability. In this way the fairs represent an important communication platform, whose use is generalized in the all economic areas. The aim of this paper is analyze the evolution of fair business in Spain, in the period 2002-2009, to solve two important questions which revolve about the efficiency of this communication tool and its power to maintain and establish new business relationship. For this, this paper analyzes the main characteristics or indicators of fair business, such as number of celebrated events, areas of interest, number of exhibitors or the number of attendees, from the information of Spanish Association of Fairs

Impact of obstructive sleep apnea on the levels of placental growth factor (PlGF) and their value for predicting short-term adverse outcomes in patients with acute coronary syndrome

Background Placental growth factor (PlGF) induces angiogenesis and promotes tissue repair, and plasma PlGF levels change markedly during acute myocardial infarction (AMI). Currently, the impact of obstructive sleep apnea (OSA) in patients with AMI is a subject of debate. Our objective was to evaluate the relationships between PlGF levels and both the severity of acute coronary syndrome (ACS) and short-term outcomes after ACS in patients with and without OSA. Methods A total of 538 consecutive patients (312 OSA patients and 226 controls) admitted for ACS were included in this study. All patients underwent polygraphy in the first 72 hours after hospital admission. The severity of disease and short-term prognoses were evaluated during the hospitalization period. Plasma PlGF levels were measured using an electrochemiluminescence immunoassay. Results Patients with OSA were significantly older and more frequently hypertensive and had higher BMIs than those without OSA. After adjusting for age, smoking status, BMI and hypertension, PlGF levels were significantly elevated in patients with OSA compared with patients without OSA (19.9 pg/mL, interquartile range: 16.6–24.5 pg/mL; 18.5 pg/mL, interquartile range: 14.7–22.7 pg/mL; p<0.001), and a higher apnea-hypopnea index (AHI) was associated with higher PlGF concentrations (p<0.003). Patients with higher levels of PlGF had also an increased odds ratio for the presence of 3 or more diseased vessels and for a Killip score>1, even after adjustment. Conclusions The results of this study show that in patients with ACS, elevated plasma levels of PlGF are associated with the presence of OSA and with adverse outcomes during short-term followup. Trial Registration ClinicalTrials.gov NCT0133508