Renormalized waves and thermalization of the Klein-Gordon equation: What sound does a nonlinear string make?

We study the thermalization of the classical Klein-Gordon equation under a u^4 interaction. We numerically show that even in the presence of strong nonlinearities, the local thermodynamic equilibrium state exhibits a weakly nonlinear behavior in a renormalized wave basis. The renormalized basis is defined locally in time by a linear transformation and the requirement of vanishing wave-wave correlations. We show that the renormalized waves oscillate around one frequency, and that the frequency dispersion relation undergoes a nonlinear shift proportional to the mean square field. In addition, the renormalized waves exhibit a Planck like spectrum. Namely, there is equipartition of energy in the low frequency modes described by a Boltzmann distribution, followed by a linear exponential decay in the high frequency modes.Comment: 13 pages, 13 figure

Tachyonic preheating using 2PI-1/N dynamics and the classical approximation

We study the process of tachyonic preheating using approximative quantum equations of motion derived from the 2PI effective action. The O(N) scalar (Higgs) field is assumed to experience a fast quench which is represented by an instantaneous flip of the sign of the mass parameter. The equations of motion are solved numerically on the lattice, and the Hartree and 1/N-NLO approximations are compared to the classical approximation. Classical dynamics is expected to be valid, since the occupation numbers can rise to large values during tachyonic preheating. We find that the classical approximation performs excellently at short and intermediate times, even for couplings in the larger region currently allowed for the SM Higgs. This is reassuring, since all previous numerical studies of tachyonic preheating and baryogenesis during tachyonic preheating have used classical dynamics. We also compare different initializations for the classical simulations.Comment: 32 pages, 21 figures. Published version: Some details added, section added, references added, conclusions unchange

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

Physical origin of third order NLO properties of TTF –based self assembled molecular corners and polygons

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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

Third order NLO properties of TTF-based self assembled molecular corners and polygons (poster presentation)

International audienc

Third order nonlinearities of TTF-based self-assembled molecular corners (oral presentation)

Date du colloque&nbsp;: 04/2010</p

Zinc deficiency: a frequent and underestimated complication after bariatric surgery

BACKGROUND: Although zinc deficiency is common after bariatric surgery, its incidence is underestimated. The objective was to monitor zinc and nutritional status before and 6, 12 and 24 months (M6, M12 and M24) after gastric bypass (Roux-en-Y gastric bypass), sleeve gastrectomy and biliopancreatic diversion with duodenal switch (DS) in patients receiving systematised nutritional care. METHODS: Data for 324 morbidly obese patients (mean body mass index 46.2 ± 7.3 kg/m(2)) were reviewed retrospectively. The follow-up period was 6 months for 272 patients, 12 months for 175, and 24 months for 70. Anthropometric, dietary and serum albumin, prealbumin, zinc, iron and transferrin saturation measures were determined at each timepoint. RESULTS: Nine percent of patients had zinc deficiency pre-operatively. Zinc deficiency was present in 42.5% of the population at M12 and then remained stable. Zinc deficiency was significantly more frequent after DS, with a prevalence of 91.7% at M12. Between M0 and M6, variation in plasma prealbumin, surgery type and zinc supplementation explained 27.2% of the variance in plasma zinc concentration. Surgery type explained 22.1% of this variance between M0 and M24. Mean supplemental zinc intake was low (22 mg/day). The percentage of patients taking zinc supplementation at M6, M12 and M24 was 8.9%, 20.6% and 29%, respectively. CONCLUSIONS: Reduced protein intake, impaired zinc absorption and worsening compensatory mechanisms contribute to zinc deficiency. The mechanisms involved differ according to the type of surgery and time since surgery. Zinc supplementation is necessary early after bariatric surgery, but this requirement is often underestimated or is inadequate

Third order nonlinear optical response of self-assembled molecular corners

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