On resumming periodic orbits in the spectra of integrable systems

Spectral determinants have proven to be valuable tools for resumming the periodic orbits in the Gutzwiller trace formula of chaotic systems. We investigate these tools in the context of integrable systems to which these techniques have not been previously applied. Our specific model is a stroboscopic map of an integrable Hamiltonian system with quadratic action dependence, for which each stage of the semiclassical approximation can be controlled. It is found that large errors occur in the semiclassical traces due to edge corrections which may be neglected if the eigenvalues are obtained by Fourier transformation over the long time dynamics. However, these errors cause serious harm to the spectral approximations of an integrable system obtained via the spectral determinants. The symmetry property of the spectral determinant does not generally alleviate the error, since it sometimes sheds a pair of eigenvalues from the unit circle. By taking into account the leading order asymptotics of the edge corrections, the spectral determinant method makes a significant recovery

Much or More? Experiments of Rationality and Spite with School Children

Copyright © 2014 North American Journal of Pyschology.In a competitive environment the maximization of self-interest and the minimization of the other's interest can be seen as the two faces of the same coin. However, these motivations can lead to very different behaviors. In order to understand how these are expressed, we designed an experiment to measure the ability of children and teenagers to react to stimuli that induce behavior to act as a rational player (maximization of self interest) or as a spiteful player (minimization of other's interest). Each player faced the following dilemma: maximizing pay-off and incurring the risk of having a lower pay-off; or alternatively guaranteeing one’s own pay-off was not smaller than the opponent’s pay-off. A prize was attributed proportionally to the pay-off (Treatment 1) or to the player with highest pay-off (Treatment 2), which meant that the optimal behavior was different for each treatment. We performed experiments with 398 Portuguese children and teenagers and found evidence that younger children tended to be maximizers (in both variants) and that teenagers tended towards rational behavior when it was best for them and towards spiteful behavior when the latter was more advantageous

Type of diet modulates the metabolic response to sleep deprivation in rats

<p>Abstract</p> <p>Background</p> <p>Evidence suggests that sleep loss is associated with an increased risk of obesity and diabetes; however, animal models have failed to produce weight gain under sleep deprivation (SD). Previous studies have suggested that this discrepancy could be due to more extreme SD conditions in experimental animals, their higher resting metabolic rate than that of humans, and the decreased opportunity for animals to ingest high-calorie foods. Thus, our objective was to determine whether diets with different textures/compositions could modify feeding behavior and affect the metabolic repercussions in SD in rats.</p> <p>Methods</p> <p>Three groups of male rats were used: one was designated as control, one was sleep deprived for 96 h by the platform technique (SD-96h) and one was SD-96h followed by a 24-h recovery (rebound). In the first experiment, the animals were fed chow pellets (CPs); in the second, they received high-fat diet and in the third, they were fed a liquid diet (LD).</p> <p>Results</p> <p>We observed that SD induces energy deficits that were related to changes in feeding behavior and affected by the type of diet consumed. Regardless of the diet consumed, SD consistently increased animals' glucagon levels and decreased their leptin and triacylglycerol levels and liver glycogen stores. However, such changes were mostly avoided in the rats on the liquid diet. SD induces a wide range of metabolic and hormonal changes that are strongly linked to the severity of weight loss.</p> <p>Conclusions</p> <p>The LD, but not the CP or high-fat diets, favored energy intake, consequently lessening the energy deficit induced by SD.</p

Association of increased levels of homocysteine and peripheral arterial disease in a Japanese-Brazilian population

Objectives. Our aim was to evaluate the possible association between homocysteine levels and peripheral arterial disease (PAD) in a population-based study of Japanese-Brazilians.Materials and methods. This cross-sectional study was derived from a population-based survey on the prevalence of diabetes and associated diseases conducted in Japanese-Brazilians. A total of 1330 male and female subjects aged >= 30 years were submitted to clinical examination and laboratory procedures including homocysteine measurement. the ankle-brachial index (ABI) was calculated, subjects with ABI values <0.9 were diagnosed with PAD. the evaluable population included 1008 subjects. Logistic regression was used taking PAD as the dependent variable.Results. Mean age of the population was 56.5 years and overall prevalence of PAD was 20%. A worse cardiovascular profile was found in male patients, including significantly higher homocysteine levels (11.9 +/- 1.8 vs. 9.1 +/- 1.1 mu mol/L, p < 0.001). Men with PAD had higher prevalence rates of hyperhomocysteinemia compared to women (22.7% vs 7.6%). Univariate analysis showed an odds ratio of hyperhomocysteinemia for PAD of 1.51 [1.02-2.25] in men and 1. 69 [1.06-2.68] in women. After adjustment for other cardiovascular risk factors, higher levels of homocysteine were only significantly related to PAD in men.Conclusion. in a Japanese-Brazilian population, elevated levels of homocysteine are associated with PAD in men. Prospective studies are necessary to confirm this finding.Universidade Federal de São Paulo, Dept Surg, Postgrad Course Cardiac Vasc & Thorac Surg, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Surg, Div Vasc Surg, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Pediat, São Paulo, BrazilUniv São Paulo, Sch Publ Hlth, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Surg, Postgrad Course Cardiac Vasc & Thorac Surg, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Surg, Div Vasc Surg, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Pediat, São Paulo, BrazilWeb of Scienc

Associations between sleep conditions and body composition states: results of the EPISONO study.

Evidence suggests anthropometric indicators of obesity are associated with changes in sleep quality and quantity, and the presence of obstructive sleep apnoea (OSA). Investigations including diverse and objective evaluations of sleep and body composition are scarce. We aimed to evaluate the associations between indicators of sleep impairment and body composition states in a sample from a population-based study. Participants of the first follow-up of the EPISONO (São Paulo, Brazil) &gt;50 years were cross-sectionally evaluated. Sleep was assessed through questionnaires, actigraphy, and polysomnography. Body composition was evaluated by bioelectrical impedance analysis. Appendicular skeletal muscle mass adjusted for body mass index defined sarcopenia (men &lt;0.789 and women &lt;0.512). Total body fat defined obesity (men &gt;30% and women &gt;40%). The overlap between both conditions defined sarcopenic obesity (SO). Final results were obtained by multinomial logistic regression analysis. Three hundred fifty-nine adults [mean (standard deviation) age, 61 (8.8) years; 212 (59.1%) female] were enrolled. Obesity was detected in 22.6% of the sample, sarcopenia in 5.6%, and SO in 16.2%. After controlling for covariates, OSA was associated with SO [odds ratio = 3.14, 95% confidence interval (CI) = 1.49-6.61]. Additionally, nocturnal hypoxaemia was associated with both obesity (adjusted odds ratio = 2.59, 95% CI = 1.49-4.49) and SO (odds ratio = 2.92, 95% CI = 1.39-6.13). Other indicators of poor sleep/sleep disorders were not associated with body composition states. Sarcopenic obesity but not obesity alone was associated with OSA. Both obesity and SO but not sarcopenia were associated with nocturnal hypoxaemia. The findings suggest a complex pathophysiologic relationship between adverse body composition states and OSA. Upcoming research on risk factors and therapeutic interventions for OSA should target synchronically the lean and adipose body tissues

Enhancement of titanate nanotubes dispersion for reinforcement of nylon-II nanocomposites

The purpose of the present study was to investigate the effect of titanate nanotubes (TINTs) dispersion in the mechanical properties of Nylon 11 (polyamide 11) polymer. According ,to the existing literature small amounts of TTNTs used as reinforcement in polymer matrix improve properties such as tensile strength and stiffness. However, the addition of these nanoparticles may also lead to a decrease of strength of the composite if the nanotubes are not well dispersed in the polymer matrix. In this work two different routes were investigated to enhance the disl?ersion of TTNTs used as a reinforcement of nylon matrix nanocomposites: (1) chemical functionalization with 3-arninopropyltriethoxysilane; and (2) treatment with 2 kinds of surfactant - a cationic (CTAB) and an anionic (SDS). Characterization of the nanotubes was done by infrared spectroscopy, CHN elemental analysis, measurement of the specific surface area, thermogravimetric analysis, scanning electron microscopy and transmission electron microscopy. Nylon-II matrix nanocomposites were manufactured by microextrusion-microinjection and reinforced with 0.5 to 2.0 wt.-% of functionalized and surfactant treated nanotubes. Finally, mechanical and thermal properties as well as the microstructure of the nanocomposites were evaluated. The presentation will discuss the results and potential applications of these materials

Enhancement of titanate nanotubes dispersion for reinforcement of nylon-II nanocomposites

The purpose of the present study was to investigate the effect of titanate nanotubes (TINTs) dispersion in the mechanical properties of Nylon 11 (polyamide 11) polymer. According ,to the existing literature small amounts of TTNTs used as reinforcement in polymer matrix improve properties such as tensile strength and stiffness. However, the addition of these nanoparticles may also lead to a decrease of strength of the composite if the nanotubes are not well dispersed in the polymer matrix. In this work two different routes were investigated to enhance the disl?ersion of TTNTs used as a reinforcement of nylon matrix nanocomposites: (1) chemical functionalization with 3-arninopropyltriethoxysilane; and (2) treatment with 2 kinds of surfactant - a cationic (CTAB) and an anionic (SDS). Characterization of the nanotubes was done by infrared spectroscopy, CHN elemental analysis, measurement of the specific surface area, thermogravimetric analysis, scanning electron microscopy and transmission electron microscopy. Nylon-II matrix nanocomposites were manufactured by microextrusion-microinjection and reinforced with 0.5 to 2.0 wt.-% of functionalized and surfactant treated nanotubes. Finally, mechanical and thermal properties as well as the microstructure of the nanocomposites were evaluated. The presentation will discuss the results and potential applications of these materials

Retrievals of Antarctic aerosol characteristics using a Sun-sky radiometer during the 2001-2002 austral summer campaign

In order to characterize the Antarctic aerosol and to analyze the effect of katabatic winds on the properties of suspended particles, measurements of solar direct and diffuse irradiance were carried out at the Italian Terra Nova Bay station in Antarctica, during the 2001-2002 austral summer campaign. Measurements were performed by the ground-based PREDE sky radiometer and processed by using the Skyrad inversion code. Aerosol optical thickness at 500 nm was found to vary between 0.01 and 0.02. The volume size distribution curves showed bimodal features with the two modes located within 0.1-0.3 μm and 5-7 μm radius intervals, respectively. The real part of the refractive index characterizing the Antarctic aerosol was found to have a mean value of 1.40. During the katabatic event the analysis indicated that the advection of larger and drier fresh particles, together with the removal of marine suspended particles, caused the decrease in aerosol optical thickness

The neural basis of fatigue in multiple sclerosis: A multimodal MRI approach

BACKGROUND: Fatigue is a frequent disabling symptom in multiple sclerosis (MS), but its pathophysiology remains incompletely understood. This study aimed to explore the underlying neural basis of fatigue in patients with MS. METHODS: We enrolled 60 consecutive patients with MS and 60 healthy controls (HC) matched on age, sex, and education. Fatigue was assessed using the Portuguese version of the Modified Fatigue Impact Scale (MFIS). All participants underwent 3T brain MRI (conventional and diffusion tensor imaging [DTI] sequences). White matter (WM) focal lesions were identified and T1/T2 lesion volumes were computed. Tract-based spatial statistics were applied for voxel-wise analysis of DTI metrics fractional anisotropy and mean diffusivity (MD) on normal-appearing WM (NAWM). Using Freesurfer software, total and regional volumes of cortical and subcortical gray matter (GM) were calculated. RESULTS: Compared to HC, patients with MS scored significantly higher on MFIS (33.8 ± 19.7 vs 16.5 ± 15.1, p < 0.001). MFIS scores were not significantly correlated with T1/T2 lesion volumes, total GM volume, or any regional volume of cortical and subcortical GM. Significant correlations were found between global scores of MFIS and MD increase of the NAWM skeleton, including corona radiata, internal capsule, external capsule, corticospinal tract, cingulum, corpus callosum, fornix, superior longitudinal fasciculus, superior fronto-occipital fasciculus, sagittal stratum, posterior thalamic radiation, cerebral peduncle, and uncinate fasciculus. CONCLUSIONS: In this study, fatigue was associated with widespread NAWM damage but not with lesion load or GM atrophy. Functional disconnection, caused by diffuse microstructural WM damage, might be the main neural basis of fatigue in MS.info:eu-repo/semantics/publishedVersio