1,932 research outputs found

    Diffeomorphisms, Noether Charges and Canonical Formalism in 2D Dilaton Gravity

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    We carry out a parallel study of the covariant phase space and the conservation laws of local symmetries in two-dimensional dilaton gravity. Our analysis is based on the fact that the Lagrangian can be brought to a form that vanishes on-shell giving rise to a well-defined covariant potential for the symplectic current. We explicitly compute the symplectic structure and its potential and show that the requirement to be finite and independent of the Cauchy surface restricts the asymptotic symmetries.Comment: 14 pages, latex with psfig macro, one figur

    Harmonized cross-sectional surveys focused on fluid intake in children, adolescents and adults: The Liq.In7 initiative

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    Objective: To assess the intake of water and all other beverages in children, adolescents and adults. Methods: Three thousand six hundred eleven children (8 ± 2 years), 8, 109 adolescents (13 ± 2 years) and 16, 276 adults (40 ± 14 years) (47% men) were recruited in 15 cross-sectional surveys (liquid intake across 7 days, Liq.In7 study) and completed a 7-day fluid-specific record to assess total fluid intake (TFI), where TFI was defined as the sum of drinking water and other type of beverages. Results: The median TFI was 1.2, 1.2 and 1.8 liters/day in children, adolescents and adults respectively, with important differences observed between countries. Only 39% of children, 25% of adolescents and 51% of adults met the European Food Safety Authority adequate intake (AI) recommendations of water from fluids. In the surveys of Spain, France, Belgium, Germany, Turkey, Iran, Indonesia and China, water was the major contributor (47-78%) to TFI. In the adult surveys of UK, Poland, Japan and Argentina, hot beverages were the highest contributor to TFI. The fluid intake of children and adolescents in Mexico, Brazil, Argentina and Uruguay was characterized by a contribution of juices and sweet beverages that was as important as the contribution of water to TFI. Conclusion: Given that a relatively high proportion of subjects, especially children and adolescents, failed to meet the recommended AI of water from fluids and that water intake was not the highest contributor to TFI in all countries, undertaking actions to increase water intake are warranted

    Planetary nebulae abundances and stellar evolution II

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    Context: In recent years mid- and far infrared spectra of planetary nebulae have been analysed and lead to more accurate abundances. It may be expected that these better abundances lead to a better understanding of the evolution of these objects. Aims: The observed abundances in planetary nebulae are compared to those predicted by the models of Karakas (2003) in order to predict the progenitor masses of the various PNe used. The morphology of the PNe is included in the comparison. Since the central stars play an important role in the evolution, it is expected that this comparison will yield additional information about them. Methods: First the nitrogen/oxygen ratio is discussed with relation to the helium/hydrogen ratio. The progenitor mass for each PNe can be found by a comparison with the models of Karakas. Then the present luminosity of the central stars is determined in two ways: first by computing the central star effective temperature and radius, and second by computing the nebular luminosity from the hydrogen and helium lines. This luminosity is also a function of the initial mass so that these two values of initial mass can be compared. Results: Six of the seven bipolar nebulae can be identified as descendants of high mass stars (4Msun - 6Msun) while the seventh is ambiguous. Most of the elliptical PNe have central stars which descend from low initial mass stars, although there are a few caveats which are discussed. There is no observational evidence for a higher mass for central stars which have a high carbon/oxygen ratio. The evidence provided by the abundance comparison with the models of Karakas is consistent with the HR diagram to which it is compared. In the course of this discussion it is shown how `optically thin' nebulae can be separated from those which are 'optically thick'.Comment: 12 pages, 4 tables, 4 figures. Accepted for publication in A&

    A comparison of drinking behavior using a harmonized methodology (Liq.In 7) in six countries

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    Purpose: To assess drinking occasions (volume and type) according to consumption with food in or outside meals, and location, for six countries. Methods: A total of 10, 521 participants aged 4–65 years from Argentina, Brazil, China, Indonesia, Mexico and Uruguay completed a validated 7-day fluid intake record. For each drinking event, the volume consumed, the fluid type, the location of intake, and whether the drink was accompanied by food (meal or snack) or not, was recorded. Results: Similar drinking behaviors were found in Mexico and Argentina; fluid intake during meals was 48 and 45% of total fluid intake (TFI), respectively. In Brazil (55%), Indonesia (58%) and China (66%) most fluid was consumed without food. In Uruguay, 34% of TFI was with a main meal, 31% with food between meals and 35% without food. Indonesia had the highest median (25–75th percentile) TFI; 2520 (1750–3347) mL/day, and China the lowest 1138 (818–3347) mL/day. Water was consumed with meals for 37% of Chinese and 87% of Indonesian participants, while the four Latin-American American countries showed a preference for sweet drinks; 54% in Mexico, 67% in Brazil, 55% in Argentina and 59% in Uruguay. Diversity in fluid type was noted when drinking with food between meals. Apart from China, most drinking occasions (> 75%) occurred at home. Conclusions: Three distinct drinking behaviors were identified, namely, drinking with meals, drinking as a stand-alone activity, and a type of ‘grazing’ (i.e., frequent drinks throughout the day) behavior. Most drinking occasions occurred at home

    Relevance of assessment methods for fluid intake

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    Reliable data at population level are essential to firmly establish links between fluid intake, hydration and health, investigate dose-response relationships and develop meaningful public health strategies or reference intake values. However, limited research exists regarding the most appropriate methodology for assessing beverage or total fluid intake (TFI). To date, methodologies have been developed to assess food and nutrient intake without due consideration of water or fluid intake behavior. A recent crossover study showed that a 24-hour food recall significantly underestimated mean TFI by 382 ml (95% CI 299-465) compared with a fluid specific 7-day record. The authors postulated that this average difference was mainly the result of missed drinking acts between meals a 24-hour recall was used. Using a 7-day record administered in paper form or on-line has also been shown to lead to a significantly different mean TFI of 129 ml. Therefore, the choice of methodology might result in measurement errors that limit between-survey or between-country comparisons. Such errors may contribute to variations in estimates of TFI that cannot be explained by differences in climate, physical activity or cultural habits. A recent survey confirmed the variation in methodologies used in European national dietary surveys. Since these surveys form the basis for setting adequate intakes for total water intake, measurement error between surveys should be limited, highlighting the need for the development of a consistent methodology that is validated for water and TFI estimation

    Weather-based models for predicting grape powdery mildew (Uncinula necator (Schwein) Burrill) epidemics

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    El oídio de la vid (Vitis vinifera L.), causado por Uncinula necator (Schwein) Burrill, es una enfermedad fúngica relevante en viñedos de la provincia de Mendoza, ocasionando pérdidas de producción y degradación de la calidad del fruto cosechado. Durante seis campañas agrícolas (2001/02; 2002/03; 2005/06; 2007/08; 2008/09; 2009/10), en un parral del cultivar susceptible Chenín (EEA INTA Mendoza, Luján de Cuyo), se observó la evolución de la incidencia del oídio en racimos (como tasa de incremento epidémica diaria), desde floración hasta envero. A partir de registros térmico-hídricos horarios (monitoreados con sensores ubicados en la parte superior del canopeo) se calcularon variables meteorológicas en los 15 días previos a cada observación del progreso de la epidemia. Con variables que integran efectos de la temperatura, humedad del aire y frecuencia de precipitaciones ligeras sobre el incremento de la enfermedad en función del tiempo, se ajustaron modelos de regresión logística para estimar las probabilidades de ocurrencia de tasas epidémicas categorizadas (severa, moderada y nula), logrando una precisión de predicción máxima de 92,5% (modelo bivariado, N=40). Las predicciones del modelo univariado (seleccionado por "Stepwise"; precisión de predicción: 87,5%) se validaron satisfactoriamente con la curva epidémica observada en 2000/2001. Los valores estimados por estos modelos podrían complementar a las observaciones epidémicas y emitir alarmas regionales que sustenten la toma de decisión de control químico.Powdery mildew, caused by Uncinula necator (Schwein) Burrill is one of the most damaging disease affecting grapevines (Vitis vinifera L.) in Mendoza and worldwide, reducing yield and fruit quality. Throughout six growing seasons (2001/02; 2002/03; 2005/06; 2007/08; 2008/09; 2009/10), powdery mildew incidence values (expressed as daily epidemic increment rates) were observed in clusters from flowering to onset of ripening (change of color of the grape berries), in a grapevine planted with the susceptible Chenin cultivar at the EEA INTA Mendoza (Luján de Cuyo). From hourly values of thermal-moisture elements recorded by upper canopy sensors, meteorological variables were calculated in the 15 previous days of each epidemic observation. Using variables which integrate the effects of air temperature and humidity and frequency of light precipitations over the epidemic progress, logistic models were adjusted for estimating the probability of occurrrence of severe, moderate and nil epidemic increment rates, reaching maximum prediction accuracy of 92.5% (two variable models, N=40). Predicted values by the univariate model (selected by Stepwise procedure; prediction accuracy: 87.5%) were validated with the epidemic curve observed during 2000/2001 growing season. These model predictions could complement epidemic observations, giving regional scale to warning systems for improving the decision making process regarding disease chemical control.Fil: Oriolani, Enrique J. A.. Instituto Nacional de Tecnología Agropecuaria (Argentina). Estación Experimental Agropecuaria Mendoza.Fil: Moschini, Ricardo C.. Instituto de Clima y Agua. CIRN. INTA Castelar.Fil: Salas, Sergio. Instituto Nacional de Tecnología Agropecuaria (Argentina). Estación Experimental Agropecuaria Mendoza.Fil: Martinez, Malvina I.. Instituto de Clima y Agua. CIRN. INTA Castelar.Fil: Banchero, Santiago. Instituto de Clima y Agua. CIRN. INTA Castelar

    Abundances of Planetary Nebula M1-42

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    The spectra of the planetary nebula M1-42 is reanalysed using spectral measurements made in the mid-infrared with the Spitzer Space Telescope. The aim is to determine the chemical composition of this object. We also make use of ISO, IUE and ground based spectra. Abundances determined from the mid- and far-infrared lines, which are insensitive to electron temperature, are used as the basis for the determination of the composition, which are found to substantially differ from earlier results. High values of neon, argon and sulfur are found. They are higher than in other PN, with the exception of NGC6153, a nebula of very similar abundances. The high values of helium and nitrogen found indicate that the second dredge-up and hot bottom burning has occurred in the course of evolution and that the central star was originally more massive than 4Msun. The present temperature and luminosity of the central star is determined and at first sight may be inconsistent with such a high mass.Comment: 9 pages, 8 tables, 1 figure. Accepted for publication in A&

    Holography, degenerate horizons and entropy

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    We show that a realization of the correspondence AdS_2/CFT_1 for near extremal Reissner-Nordstrom black holes in arbitrary dimensional Einstein-Maxwell gravity exactly reproduces, via Cardy's formula, the deviation of the Bekenstein-Hawking entropy from extremality. We also show that this mechanism is valid for Schwarzschild-de Sitter black holes around the degenerate solution dS_2xS^n. These results reinforce the idea that the Bekenstein-Hawking entropy can be derived from symmetry principles.Comment: LaTex file, 23 pages, 1 figure; several corrections, to appear in Nucl. Phys.

    Fluid intake of Latin American children and adolescents: results of four 2016 LIQ.IN 7 National Cross-Sectional Surveys

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    Purpose: The primary aim of this survey was to report total fluid intake (TFI) and different fluid types for children (4–9 years) and adolescents (10–17 years) in Mexico, Brazil, Argentina and Uruguay. The second aim was to compare TFI with the adequate intake (AI) of water from fluids as recommended by the USA Institute of Medicine. Methods: Data were collected using a validated liquid intake 7-day record (Liq.In7). Participants’ characteristics, including age, sex and anthropometric measurements were recorded. Results: A total of 733 children and 933 adolescents were recruited. Over 75% of children in Uruguay met the IOM’s recommended intake. Fewer children in Argentina (64–72%) and Brazil (41–50%) obtained AI and the lowest values were recorded in Mexico (33–44%), where 16% of boys and 14% girls drank 50% or less of the AI. More adolescents in Argentina (42%) met the AIs than other countries; the lowest was in Mexico (28%). Children and adolescents in Mexico and Argentina drank more sugar sweetened beverages than water. Conclusions: Large numbers of children and adolescents did not meet AI recommendations for TFI, raising concerns about their hydration status and potential effects on mental and physical well-being. Given the negative effects on children’s health, the levels of SSB consumption are worrying
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