6,611 research outputs found
Mesoscale dynamics on the Sun's surface from HINODE observations
Aims: The interactions of velocity scales on the Sun's surface, from
granulation to supergranulation are still not understood, nor are their
interaction with magnetic fields. We thus aim at giving a better description of
dynamics in the mesoscale range which lies between the two scales mentioned
above. Method: We analyse a 48h high-resolution time sequence of the quiet Sun
photosphere at the disk center obtained with the Solar Optical Telescope
onboard Hinode. The observations, which have a field of view of 100
\arcsec 100 \arcsec, typically contain four supergranules. We monitor
in detail the motion and evolution of granules as well as those of the radial
magnetic field. Results: This analysis allows us to better characterize Trees
of Fragmenting Granules issued from repeated fragmentation of granules,
especially their lifetime statistics. Using floating corks advected by measured
velocity fields, we show their crucial role in the advection of the magnetic
field and in the build up of the network. Finally, thanks to the long duration
of the time series, we estimate that the turbulent diffusion coefficient
induced by horizontal motion is approximately . Conclusions: These results demonstrate that the long living
families contribute to the formation of the magnetic network and suggest that
supergranulation could be an emergent length scale building up as small
magnetic elements are advected and concentrated by TFG flows. Our estimate for
the magnetic diffusion associated with this horizontal motion might provide a
useful input for mean-field dynamo models.Comment: to appear in A&A - 8 pages, 13 figures (degraded quality) - Full
resolution version available @
http://www.ast.obs-mip.fr/users/rincon/hinode_roudier_aa09.pd
Dissipative collapse of the adiabatic piston
An adiabatic piston, separating two granular gases prepared in the same
macroscopic state, is found to eventually collapse to one of the sides. This
new instability is explained by a simple macroscopic theory which is
furthermore in qualitative agreement with hard disk molecular dynamics.Comment: 7 pages, 5 figure
Metabolic factors in obesity
Obesity has a rising prevalence in children and adolescents, affecting 30% of the paediatric population in Portugal. Leptin is an important hormone involved in the pathogenesis of obesity and has been under investigation as a risk marker for future complications.
AIMS:
1. To evaluate the relation between serum leptin levels and body mass index (BMI) and height. 2. To compare leptin levels in obese and non-obese children. 3. To evaluate the relation between leptin levels and insulin resistance index.
METHODS:
Cross-sectional study, using a sample of 70 obese children and a control group of 53 non-obese children. Obesity was defined as BMI standard deviation > 2 for age and sex. In the obese group we assessed sex, age, BMI SDS and height SDS for age and sex, and serum levels of glucose, insulin and leptin. In the control group were obtained BMI SDS and height SDS for age and sex and leptin levels. Data were analysed using SPSS 12.
RESULTS:
The mean age of obese and non-obese children was 10.3 +/- 2.9 versus 10.9 +/- 3.5 years. In the obese group, 32 (45.7%) were boys versus 18 (31.0%) in the non-obese group. BMI SDS in the obese group was 3.12 +/- 0.60 versus 0.20 +/- 0.99 in the non-obese group (p < 0.001). Leptin levels showed a positive correlation with BMI SDS (r = 0.69; p < 0.001) and height SDS (r = 0.31; p < 0.001). When comparing leptin levels between obese and non-obese groups, we found a significant difference in boys (50.7 +/- 27.3 versus 7.0 +/- 6.8 ng/ml; p < 0.001) and in girls (57.6 +/- 25.5 versus 16.5 +/- 10.3 ng/ml; p < 0.001). In the nonobese group, leptin levels were lower in boys. This difference was not seen in the obese group. Leptin showed a positive correlation with insulin resistance index in boys (r = 0.45, p = 0.05), but not in girls.
CONCLUSIONS:
This study has confirmed a positive correlation between leptin levels and BMI SDS. In obese children elevated leptin is associated with central resistance to its action. The positive correlation of leptin with insulin resistance index may suggest a major role of leptin in insulin resistance.info:eu-repo/semantics/publishedVersio
Heterogeneous Dynamics, Marginal Stability and Soft Modes in Hard Sphere Glasses
In a recent publication we established an analogy between the free energy of
a hard sphere system and the energy of an elastic network [1]. This result
enables one to study the free energy landscape of hard spheres, in particular
to define normal modes. In this Letter we use these tools to analyze the
activated transitions between meta-bassins, both in the aging regime deep in
the glass phase and near the glass transition. We observe numerically that
structural relaxation occurs mostly along a very small number of
nearly-unstable extended modes. This number decays for denser packing and is
significantly lowered as the system undergoes the glass transition. This
observation supports that structural relaxation and marginal modes share common
properties. In particular theoretical results [2, 3] show that these modes
extend at least on some length scale where
corresponds to the maximum packing fraction, i.e. the jamming
transition. This prediction is consistent with very recent numerical
observations of sheared systems near the jamming threshold [4], where a similar
exponent is found, and with the commonly observed growth of the rearranging
regions with compression near the glass transition.Comment: 6 pages, improved versio
The pasta phase within density dependent hadronic models
In the present paper we investigate the onset of the pasta phase with
different parametrisations of the density dependent hadronic model and compare
the results with one of the usual parametrisation of the non-linear Walecka
model. The influence of the scalar-isovector virtual delta meson is shown. At
zero temperature two different methods are used, one based on coexistent phases
and the other on the Thomas-Fermi approximation. At finite temperature only the
coexistence phases method is used. npe matter with fixed proton fractions and
in beta-equilibrium are studied. We compare our results with restrictions
imposed on the the values of the density and pressure at the inner edge of the
crust, obtained from observations of the Vela pulsar and recent isospin
diffusion data from heavy-ion reactions, and with predictions from spinodal
calculations.Comment: 15 pages, 11 figures and 7 table
The Ecological and Ethical Consumption Development Prospects in Poland Compared with the Western European Countries
An overview of the Western European literature shows that one of the most distinct trends in consumption that has been noted in the recent years is globally increasing environmental and social awareness. The issue of consumers' behaviours and attitudes towards "socially responsible products" has been gaining importance in Polish economy as well. This article evaluates the development prospects of ethical and ecological consumption in Poland vis-à-vis Western European countries. The comparative analysis being part of the article utilizes primary sources of information, i.e. interviews with a representative sample of Polish adults, as well as secondary sources of information. A factor analysis or, more precisely, a principal component analysis, allowed dividing Polish consumers into groups that were typologically homogeneous in respect of their sensitivity to various aspects of business ethics and ecology.Przegląd literatury zachodnio-europejskiej pozwala stwierdzić, że jednym z najbardziej zauważalnych trendów w sferze konsumpcji w ostatnich latach jest coraz większa świadomość ekologiczna i społeczna w wymiarze globalnym. Problematyka zachowań i postaw konsumentów wobec produktów "społecznie odpowiedzialnych" nabiera coraz większego znaczenia także w polskiej gospodarce. Celem artykułu jest ocena perspektyw rozwoju etyczneji ekologicznej konsumpcji w Polsce na tle krajów zachodnio-europejskich. Analizę porównawczą prowadzono bazując na źródłach wtórych jak i badaniach pierwotnych realizowanych na reprezentatywnej próbie losowej dorosłych mieszkańców Polski. W oparciu o analizę czynnikową, a dokładniej metodę analizy głównych składowych, dokonano także podziału polskich konsumentów na jednorodne grupy typologiczne pod względem ich wrażliwości na różne aspekty związane z ekologią i etyką
Qualidade do leite armazenado em tanques coletivos.
Importância da refrigeração do leite ; Tanques coletivos; Pesquisa sobre a qualidade do leite de tanques coletivos; Uma segunda pesquisa: maio de 2007 a junho de 2008.bitstream/item/65295/1/CT-99-Qualid-leite-armaz-tanq-coletivos.pd
- …