Describing the ground state of quantum systems through statistical mechanics

We present a statistical mechanics description to study the ground state of quantum systems. In this approach, averages for the complete system are calculated over the non-interacting energy levels. Taking different interaction parameter, the particles of the system fall into non-interacting microstates, corresponding to different occupation probabilities for these energy levels. Using this novel thermodynamic interpretation we study the Hubbard model for the case of two electrons in two sites and for the half-filled band on a one-dimensional lattice. We show that the form of the entropy depends on the specific system considered.Comment: 8 page

Generalizing Planck's distribution by using the Carati-Galgani model of molecular collisions

Classical systems of coupled harmonic oscillators are studied using the Carati-Galgani model. We investigate the consequences for Einstein's conjecture by considering that the exchanges of energy, in molecular collisions, follows the L\'evy type statistics. We develop a generalization of Planck's distribution admitting that there are analogous relations in the equilibrium quantum statistical mechanics of the relations found using the nonequilibrium classical statistical mechanics approach. The generalization of Planck's law based on the nonextensive statistical mechanics formalism is compatible with the our analysis.Comment: 10 pages, 3 figure

A simple model for magnetism in itinerant electron systems

A new lattice model of interacting electrons is presented. It can be viewed as a classical Hubbard model in which the energy associated to electron itinerance is proportional to the total number of possible electron jumps. Symmetry properties of the Hubbard model are preserved. In the half-filled band with strong interaction the model becomes the Ising model. The main features of the magnetic behavior of the model in the one-dimensional and mean-field cases are studied.Comment: 9 pages, 3 figures, to be published in Physica

Solar Neutrino Rates, Spectrum, and its Moments : an MSW Analysis in the Light of Super-Kamiokande Results

We re-examine MSW solutions of the solar neutrino problem in a two flavor scenario taking (a) the results on total rates and the electron energy spectrum from the 1117-day SuperKamiokande (SK) data and (b) those on total rates from the Chlorine and Gallium experiments. We find that the SMA solution gives the best fit to the total rates data from the different experiments. One new feature of our analysis is the use of the moments of the SK electron spectrum in a $\chi^2$ analysis. The best-fit to the moments is broadly in agreement with that obtained from a direct fit to the spectrum data and prefers a $\Delta m^2$ comparable to the SMA fit to the rates but the required mixing angle is larger. In the combined rate and spectrum analysis, apart from varying the normalization of the $^8$B flux as a free parameter and determining its best-fit value we also obtain the best-fit parameters when correlations between the rates and the spectrum data are included and the normalization of the $^8$B flux held fixed at its SSM value. We observe that the correlations between the rates and spectrum data are important and the goodness of fit worsens when these are included. In either case, the best-fit lies in the LMA region.Comment: 17 pages, 4 figure

Growing up in Portugal: Cape Verdean ancestry children exhibit low overweight and obesity compared to Portuguese in urban Lisbon

Portugal has one of the highest rates of childhood overweight and obesity (OW/OB) in Europe. However little is known about the health of ethnic minorities living in its capital city, Lisbon. The Cape Verdean community in Lisbon tend to have low educational levels, material deprivation and they struggle with discrimination and racism, factors that would likely be associated with a higher prevalence of OW/OB. Data for the Cape Verdean population were collected in three different time periods by three different research teams in 1993, 2009 and 2013 and included children from 6 to 12 years living in Cova da Moura neighbourhood, Great Lisbon Metro Area (GLMA). The Portuguese national survey was collected between 2009/2010 at public and private schools in mainland Portugal and included height, weight, skinfolds, arm, and waist circumferences. From these survey data body mass index (BMI) and the prevalence of stunting, (chronic malnutrition - low height-for-age) and underweight (low-weight-for-age) were calculated according to reference values proposed by Frisancho (2008). Overweight and obesity values were defined based on the references established by the International Obesity Task Force (IOTF). Results show that there are significant differences in height for boys and girls between Cape Verdean and Portuguese children. Generally, Cape Verdeans’ growth falls within the healthy range of International growth references across all of the survey data collected. Cape Verdean rates for combined overnutrition (overweight and obesity) in 2013 (9.8% for boys and 16.7% for girls) are lower than the Portuguese (33% for boys and 31.7% for girls). Logistic regression models showed that Cape Verdean children have a lower risk of being OW/OB when accounting for breastfeeding,birthweight,maternal education and occupation. Despite living in a deprived neighbourhood these Cape Verdean children seem to have grown more healthily than Portuguese ancestry children. The challenge for policy makers will be to support improvement of the poverty related living conditions of this community without creating a risky environment for increasing prevalence of overweight and obesity

Skeletal maturation in relation to ethnic background in children of school age: The Generation R Study

Ethnicity is a well-established determinant of pediatric maturity, but the underlying genetic and environmental contributions to these ethnic differences are poorly comprehended. We aimed to evaluate the influence of ethnicity on skeletal age (SA), an assessment of pediatric maturation widely used in clinical settings. We included children from the Generation R Study, a multiethnic population-based pregnancy cohort, assessed at a mean age of 9.78 (±0.33) years. SA was evaluated by a trained observer on hand DXA scans using the Greulich and Pyle method. Ethnic background was defined as geographic ancestry (questionnaire-based assessment) (N = 5325) and genetic ancestry (based on admixture analysis) (N = 3413). Associations between the ethnic background and SA were investigated separately in boys and girls, using linear regression models adjusted for age, height and BMI. Based on geographic ancestry, 84% of the children were classified as European, 6% as Asian and 10% as African. Children of European background had on average younger SA than those of Asian or African descent. Asian boys had 0.46 (95% CI 0.26–0.66, p-value < 0.0001) and African boys 0.36 years (95% CI 0.20–0.53, p-value < 0.0001) older SA as compared to European boys. Similarly, Asian girls showed 0.64 (95% CI 0.51–0.77, p-value < 0.0001) and African girls 0.38 years (95% CI 0.27–0.48, p-value < 0.0001) older SA as compared to European girls. A similar pattern was observed in the analysis with genetically-defined ancestry. Furthermore, an increase in the proportion of Asian or African component was associated with older SA in both boys (log[Non-European/European]proportion = 0.10, 95% CI 0.06–0.13, p-value < 0.0001) and girls (log[Non-European/European]proportion = 0.06, 95% CI 0.04–0.08, p-value < 0.0001). In summary, children of Asian and African backgrounds have on average older SA as compared to children of European descent, partially explained by a genetic com

Is there still room to explore cyclodextrin glycosyltransferase-producers in Brazilian biodiversity?

In the present work, different Brazilian biomes aiming to identify and select cyclodextrin glycosyltransferase-producer bacteria are explored. This enzyme is responsible for converting starch to cyclodextrin, which are interesting molecules to carry other substances of economic interest applied by textile, pharmaceutical, food, and other industries. Based on the enzymatic index, 12 bacteria were selected and evaluated, considering their capacity to produce the enzyme in culture media containing different starch sources. It was observed that the highest yields were presented by the bacteria when grown in cornstarch. These bacteria were also characterized by sequencing of the 16S rRNA region and were classified as Bacillus, Paenibacillus, Gracilibacillus and Solibacillus.publishersversionpublishe

Genetic and clinical determinants of abdominal aortic diameter: genome-wide association studies, exome array data and Mendelian randomization study

Progressive dilation of the infrarenal aortic diameter is a consequence of the ageing process and is considered the main determinant of abdominal aortic aneurysm (AAA). We aimed to investigate the genetic and clinical determinants of abdominal aortic diameter (AAD). We conducted a meta-analysis of genome-wide association studies in 10 cohorts (n = 13 542) imputed to the 1000 Genome Project reference panel including 12 815 subjects in the discovery phase and 727 subjects [Partners Biobank cohort 1 (PBIO)] as replication. Maximum anterior–posterior diameter of the infrarenal aorta was used as AAD. We also included exome array data (n = 14 480) from seven epidemiologic studies. Single-variant and gene-based associations were done using SeqMeta package. A Mendelian randomization analysis was applied to investigate the causal effect of a number of clinical risk factors on AAD. In genome-wide association study (GWAS) on AAD, rs74448815 in the intronic region of LDLRAD4 reached genome-wide significance (beta = −0.02, SE = 0.004, P-value = 2.10 × 10(−8)). The association replicated in the PBIO1 cohort (P-value = 8.19 × 10(−4)). In exome-array single-variant analysis (P-value threshold = 9 × 10(−7)), the lowest P-value was found for rs239259 located in SLC22A20 (beta = 0.007, P-value = 1.2 × 10(−5)). In the gene-based analysis (P-value threshold = 1.85 × 10(−6)), PCSK5 showed an association with AAD (P-value = 8.03 × 10(−7)). Furthermore, in Mendelian randomization analyses, we found evidence for genetic association of pulse pressure (beta = −0.003, P-value = 0.02), triglycerides (beta = −0.16, P-value = 0.008) and height (beta = 0.03, P-value < 0.0001), known risk factors for AAA, consistent with a causal association with AAD. Our findings point to new biology as well as highlighting gene regions in mechanisms that have previously been implicated in the genetics of other vascular diseases