Chaotic Interaction of Langmuir Solitons and Long Wavelength Radiation

In this work we analyze the interaction of isolated solitary structures and ion-acoustic radiation. If the radiation amplitude is small solitary structures persists, but when the amplitude grows energy transfer towards small spatial scales occurs. We show that transfer is particularly fast when a fixed point of a low dimensional model is destroyed.Comment: LaTex + 4 eps file

Shock-Like Dynamics of Inelastic Gases

We provide a simple physical picture which suggests that the asymptotic dynamics of inelastic gases in one dimension is independent of the degree of inelasticity. Statistical characteristics, including velocity fluctuations and the velocity distribution are identical to those of a perfectly inelastic sticky gas, which in turn is described by the inviscid Burgers equation. Asymptotic predictions of this continuum theory, including the t^{-2/3} temperature decay and the development of discontinuities in the velocity profile, are verified numerically for inelastic gases.Comment: 4 pages, 5 figures, revte

Three-dimensional lattice-Boltzmann simulations of critical spinodal decomposition in binary immiscible fluids

We use a modified Shan-Chen, noiseless lattice-BGK model for binary immiscible, incompressible, athermal fluids in three dimensions to simulate the coarsening of domains following a deep quench below the spinodal point from a symmetric and homogeneous mixture into a two-phase configuration. We find the average domain size growing with time as $t^\gamma$, where $\gamma$ increases in the range $0.545 < \gamma < 0.717$, consistent with a crossover between diffusive $t^{1/3}$ and hydrodynamic viscous, $t^{1.0}$, behaviour. We find good collapse onto a single scaling function, yet the domain growth exponents differ from others' works' for similar values of the unique characteristic length and time that can be constructed out of the fluid's parameters. This rebuts claims of universality for the dynamical scaling hypothesis. At early times, we also find a crossover from $q^2$ to $q^4$ in the scaled structure function, which disappears when the dynamical scaling reasonably improves at later times. This excludes noise as the cause for a $q^2$ behaviour, as proposed by others. We also observe exponential temporal growth of the structure function during the initial stages of the dynamics and for wavenumbers less than a threshold value.Comment: 45 pages, 18 figures. Accepted for publication in Physical Review

Childhood Obesity among Puerto Rican Children: Discrepancies Between Child’s and Parent’s Perception of Weight Status

Public concern about childhood obesity and associated health problems calls for the identification of modifiable factors that could halt this epidemic. Parental perceptions of their children’s weight status could be associated to how parents influence children’s eating patterns. We aimed to identify the perceptions Puerto Rican parents have of their children’s weight and children’s own perceptions of weight status as compared to real weight. A cross sectional survey was performed in a representative sample of 1st–6th grade students. Only half of the children correctly identified their weight, and only 62.4% of the parents correctly classified their children’s weight. Most obese/overweight children did not perceive themselves as such. Almost half of obese/overweight children were identified by the parents as normal weight while over half of the underweight children were perceived by their parents at normal weight. More girls than boys perceived themselves as obese/overweight and more parents of girls than of boys perceived them as such. Higher-educated parents were better at recognizing overweight/obesity among their children compared to less-educated parents. This study suggests an influence of parents’ SES characteristics on their perceptions of children’s weight status as well as on children’s own perceptions of their weight status

Theory and applications of atomic and ionic polarizabilities

Atomic polarization phenomena impinge upon a number of areas and processes in physics. The dielectric constant and refractive index of any gas are examples of macroscopic properties that are largely determined by the dipole polarizability. When it comes to microscopic phenomena, the existence of alkaline-earth anions and the recently discovered ability of positrons to bind to many atoms are predominantly due to the polarization interaction. An imperfect knowledge of atomic polarizabilities is presently looming as the largest source of uncertainty in the new generation of optical frequency standards. Accurate polarizabilities for the group I and II atoms and ions of the periodic table have recently become available by a variety of techniques. These include refined many-body perturbation theory and coupled-cluster calculations sometimes combined with precise experimental data for selected transitions, microwave spectroscopy of Rydberg atoms and ions, refractive index measurements in microwave cavities, ab initio calculations of atomic structures using explicitly correlated wave functions, interferometry with atom beams, and velocity changes of laser cooled atoms induced by an electric field. This review examines existing theoretical methods of determining atomic and ionic polarizabilities, and discusses their relevance to various applications with particular emphasis on cold-atom physics and the metrology of atomic frequency standards.Comment: Review paper, 44 page

Polarization observables in p-d scattering below 30 MeV

Differential and total breakup cross sections as well as vector and tensor analyzing powers for p-d scattering are studied for energies above the deuteron breakup threshold up to E(lab)=28 MeV. The p-d scattering wave function is expanded in terms of the correlated hyperspherical harmonic basis and the elastic S-matrix is obtained using the Kohn variational principle in its complex form. The effects of the Coulomb interaction, which are expected to be important in this energy range, have been rigorously taken into account. The Argonne AV18 interaction and the Urbana URIX three-nucleon potential have been used to perform a comparison to the available experimental data.Comment: 31 pages, 8 figure

Melatonin Membrane Receptors in Peripheral Tissues: Distribution and Functions

Many of melatonin’s actions are mediated through interaction with the G-protein coupled membrane bound melatonin receptors type 1 and type 2 (MT1 and MT2, respectively) or, indirectly with nuclear orphan receptors from the RORα/RZR family. Melatonin also binds to the quinone reductase II enzyme, previously defined the MT3 receptor. Melatonin receptors are widely distributed in the body; herein we summarize their expression and actions in non-neural tissues. Several controversies still exist regarding, for example, whether melatonin binds the RORα/RZR family. Studies of the peripheral distribution of melatonin receptors are important since they are attractive targets for immunomodulation, regulation of endocrine, reproductive and cardiovascular functions, modulation of skin pigmentation, hair growth, cancerogenesis, and aging. Melatonin receptor agonists and antagonists have an exciting future since they could define multiple mechanisms by which melatonin modulates the complexity of such a wide variety of physiological and pathological processes

A cluster randomised trial testing an intervention to improve parents' recognition of their child's weight status: study protocol Health behavior, health promotion and society

Background: Parents typically do not recognise their child's weight status accurately according to clinical criteria, and thus may not take appropriate action if their child is overweight. We developed a novel visual intervention designed to improve parental perceptions of child weight status according to clinical criteria for children aged 4-5 and 10-11 years. The Map Me intervention comprises age- and sex-specific body image scales of known body mass index and supporting information about the health risks of childhood overweight. Design: This cluster randomised trial will test the effectiveness of the Map Me intervention. Primary schools will be randomised to: paper-based Map Me; web-based Map Me; no information (control). Parents of reception (4-5 years) and year 6 (10-11 years) children attending the schools will be recruited. The study will work with the National Child Measurement Programme which measures the height and weight of these year groups and provides feedback to parents about their child's weight status. Before receiving the feedback, parents will complete a questionnaire which includes assessment of their perception of their child's weight status and knowledge of the health consequences of childhood overweight. The control group will provide pre-intervention data with assessment soon after recruitment; the intervention groups will provide post-intervention data after access to Map Me for one month. The study will subsequently obtain the child height and weight measurements from the National Child Measurement Programme. Families will be followed-up by the study team at 12 months. The primary outcome is any difference in accuracy in parental perception of child weight status between pre-intervention and post-intervention at one month. The secondary outcomes include differences in parent knowledge, intention to change lifestyle behaviours and/or seek advice or support, perceived control, action planning, coping planning, and child weight status at 12 month follow-up. Discussion: The Map Me tool has potential to make a positive impact on children's health at a population level by introducing it into current intervention programmes to improve accuracy of parental perception of child's weight status. This trial will inform the action of researchers, educators, health professionals and policy makers. Trial registration: Current Controlled Trials ISRCTN91136472. Registered 3 May 2013