Staying Thermal with Hartree Ensemble Approximations

We study thermal behavior of a recently introduced Hartree ensemble approximation, which allows for non-perturbative inhomogeneous field configurations as well as for approximate thermalization, in the $\phi^4$ model in 1+1 dimensions. Using ensembles with a free field thermal distribution as out-of-equilibrium initial conditions we determine thermalization time scales. The time scale for which the system stays in approximate quantum thermal equilibrium is an indication of the time scales for which the approximation method stays reasonable. This time scale turns out to be two orders of magnitude larger than the time scale for thermalization, in the range of couplings and temperatures studied. We also discuss simplifications of our method which are numerically more efficient and make a comparison with classical dynamics.Comment: 19 pages latex; extensively rewritten to improve presentation, data essentially unchanged, analysis sharpened and one table adde

Finite Temperature Simulations from Quantum Field Dynamics?

We describe a Hartree ensemble method to approximately solve the Heisenberg equations for the \phi^4 model in 1+1 dimensions. We compute the energies and number densities of the quantum particles described by the \phi field and find that the particles initially thermalize with a Bose-Einstein distribution for the particle density. Gradually, however, the distribution changes towards classical equipartition. Using suitable initial conditions quantum thermalization is achieved much faster than the onset of this undesirable equipartition. We also show how the numerical efficiency of our method can be significantly improved.Comment: Lattice 2000 (Finite Temperature), 4 pages, 5 figures; title correcte

A practical approach to estimate resting energy expenditure in frail elderly people

Objectives: Some prediction equations of resting energy expenditure (REE) are available and can be used in clinical wards to determine energy requirements of patients. The aim of the present study was to assess the accuracy of those equations in sick elderly patients, using the Bland & Altman methods with our database of 187 REE measurements.Design: The 3 equations tested were Harris & Benedict equation of 1919, WHO/FAO/UNU equation of 1985 and Fredrix et al. equation of 1990. In addition, three models developed from the present data were tested.Results: The present study shows that the Fredrix et al equation gave an accurate prediction of REE without significant bias along the whole range of REE. It also shows that under-weight sick elderly patients (BMI ≤ 21 kg/m2) had a greater weight-adjusted REE than their normal weight counterparts.Conclusion: A simple formula using a factor multiplying body weight, i.e. 22 kcal/kg/d in under-weight and 19 kcal/kg/d in normal weight sick elderly was accurate to predicting REE and bias was not influenced by the level of REE. This model included half of the group in the range of ±10% of the difference between predicted REE and measured REE, but the confidence interval of the bias was ±400 kcal/d. Conversely, the Harris & Benedict and WHO formulae did accurately predict REE

Electrochemical M2+ recognition by an amidopyridyl-tetrathiafulvalene derivative

A tetrathiafulvalene-based redox-responsive receptor incorporating amide and pyridyl coordinating units exhibits an original multi-wave electrochemical recognition behaviour towards Cd(II)

Extraskeletal effects of vitamin D: Facts, uncertainties, and controversies

Vitamin D was long viewed as a hormone acting chiefly to regulate calcium-phosphate metabolism and bone mineralization. Over the last decade, however, basic science and clinical researchers have produced a bewildering amount of information on the extraskeletal effects of vitamin D. This article is a review of the clinical and biological actions of vitamin D including effects on the immune system, auto-immune diseases, infections, cancer, metabolic syndrome, fall risk, cognitive function, and muscle function

Les effets extra-osseux de la vitamine D : faits, questions et controverses

La vitamine D a été longtemps considérée comme une hormone utile pour réguler le métabolisme phosphocalcique et la minéralisation osseuse. Depuis dix ans, la progression des connaissances fondamentales et cliniques sur son influence pluritissulaire est vertigineuse. Les auteurs passent en revue les effets biologique et clinique de la vitamine D en particulier sur le système immunitaire, les maladies auto-immunes, les infections, le cancer, le syndrome métabolique, le risque de chute, les fonctions cognitives et le fonctionnement musculaire

Early postoperative undernutrition following aortic valve replacement surgery

Background Experiencing loss of appetite after cardiac surgery is often noted during daily care and has been described by several studies. However, no information is available on either energy needs or spontaneous food intake following aortic valve replacement surgery. The goal of this study was to assess the risk of early postoperative undernutrition following aortic valve replacement in a group of patients who were preoperatively well-nourished. Methods Anthropometrics data (body mass index, fat free mass index, albuminemia and prealbuminemia, extracellular water), energy balance and appetite were assessed in a cross-over prospective observational study. . Each subject was enrolled in two procedures: surgery and routine coronary angiograms which were used for control matched assessment. Data were assessed during the pre-procedure period (d-15 to d-1) and the post-procedure period (d0 to d+4). Energy expenditure was determined by indirect calorimetry. Results 15 patients median aged 73 years old [65–77] were included in the study. In post-surgery period, weight and extracellular water were increased and correlated (r2 = 0.571, p = 0.003). CRP was increased from 2 [2;3] to 91 [73;138] (p = 0.001). Ingested calories decreased from 1451 [1272–1640] kcal to 372 [22–528] kcal (p = 0.001) while energy expenditure was increased from 1358 [1180–1559] kcal to 1613 [1472–1670] kcal (p = 0.002). A severe loss of appetite was noted (p = 0.011). None of these changes were observed in the control phase. Conclusion Energy balance was strongly negative after cardiac surgery. Cardiac surgery increased endogenous metabolism by 20% and a severe loss of appetite decrease food intake by 75%, which does not make it possible to compensate for the increase in resting energy expenditure

Supramolecular chemistry of helical foldamers at the solid-liquid interface: self-assembled monolayers and anion recognition

The synthesis of a redox-active helical foldamer and its immobilization onto a gold electrode are described. These large molecular architectures are grafted in a reproducible manner and provide foldamer-based self-assembled monolayers displaying recognition properties

Bark beetle population dynamics in the Anthropocene: Challenges and solutions

Tree-killing bark beetles are the most economically important insects in conifer forests worldwide. However, despite N200 years of research, the drivers of population eruptions and crashes are still not fully understood and the existing knowledge is thus insufficient to face the challenges posed by the Anthropocene. We critically analyze potential biotic and abiotic drivers of population dynamics of an exemplary species, the European spruce bark beetle (ESBB) (Ips typographus) and present a multivariate approach that integrates the many drivers governing this bark beetle system. We call for hypothesis-driven, large-scale collaborative research efforts to improve our understanding of the population dynamics of this and other bark beetle pests. Our approach can serve as a blueprint for tackling other eruptive forest insects