The Glass Transition in Driven Granular Fluids: A Mode-Coupling Approach

We consider the stationary state of a fluid comprised of inelastic hard spheres or disks under the influence of a random, momentum-conserving external force. Starting from the microscopic description of the dynamics, we derive a nonlinear equation of motion for the coherent scattering function in two and three space dimensions. A glass transition is observed for all coefficients of restitution, epsilon, at a critical packing fraction, phi_c(epsilon), below random close packing. The divergence of timescales at the glass-transition implies a dependence on compression rate upon further increase of the density - similar to the cooling rate dependence of a thermal glass. The critical dynamics for coherent motion as well as tagged particle dynamics is analyzed and shown to be non-universal with exponents depending on space dimension and degree of dissipation.Comment: 16 pages, 9 figure

A Qualitative Case Study Of Novice Kenyan Primary School Teachers What Messages Transmitted By The Teacher Training Colleges Are Internalized And Applied?

The method of instruction and the formal curriculum within two Kenyan teacher training colleges were studied in order to discover which messages regarding pedagogical practice are internalized within novice Kenyan primary school teachers and then actualized within their classrooms. An educational connoisseurship approach was utilized to give descriptive, interpretive, evaluative, and thematic insight. Three data streams were collected through interview, observation, and design evaluation in order to establish structural corroboration and internal validity. The study found that the method of instruction by the teacher training college faculty was teacher-centered and utilized lower order cognitive methodology. Though the formal curriculum design was strong, it too promoted lower cognitive processes. These two messages, teacher-centered pedagogies and lower cognitive processes, are being internalized and applied by the novice teachers and maybe affecting the quality of education in Kenyan schools. The results of this study suggest that pedagogical skills promoting higher cognitive levels should be developed through in-service training in Kenyan training colleges and primary schools as a way to improve the quality of education in this country

Partitioning of energy in highly polydisperse granular gases

A highly polydisperse granular gas is modeled by a continuous distribution of particle sizes, a, giving rise to a corresponding continuous temperature profile, T(a), which we compute approximately, generalizing previous results for binary or multicomponent mixtures. If the system is driven, it evolves towards a stationary temperature profile, which is discussed for several driving mechanisms in dependence on the variance of the size distribution. For a uniform distribution of sizes, the stationary temperature profile is nonuniform with either hot small particles (constant force driving) or hot large particles (constant velocity or constant energy driving). Polydispersity always gives rise to non-Gaussian velocity distributions. Depending on the driving mechanism the tails can be either overpopulated or underpopulated as compared to the molecular gas. The deviations are mainly due to small particles. In the case of free cooling the decay rate depends continuously on particle size, while all partial temperatures decay according to Haff's law. The analytical results are supported by event driven simulations for a large, but discrete number of species.Comment: 10 pages; 5 figure

Eating late in the evening is associated with childhood obesity in some age groups but not in all children: the relationship between time of consumption and body weight status in U.S. children

<p>Abstract</p> <p>Background</p> <p>Some studies in adults indicate a positive correlation between eating later in the day and overall energy intake as well as body weight status. Thus, the time of food intake may be a risk factor in childhood obesity. This study was designed to describe the proportion of energy consumed in the time from 4 pm to midnight measured in two-hour increments and to determine a potential association between the time of proportion of energy consumed and body weight status.</p> <p>Methods</p> <p>Dietary, anthropometric, and socio-demographic data of 2–18 year olds (N = 11,072) of the National Health and Nutrition Examination Survey (NHANES) 1999–2004 was examined to describe the proportion of total energy consumed within two-hour time periods between 4 pm and midnight. To examine the potential association between eating later in the day and body weight status, generalized estimating equations (GEE) models were used to quantify the effect of time trends (proportion of total energy consumed in each 2-hour time period from 4 pm to 11.59 pm) on body weight status. Analysis was conducted in the total sample and in subgroups stratified by sex, ethnic group (Non-Hispanic white, Non-Hispanic black, Mexican American, Other Hispanic, and Other Race including multi-racial) and age group (2–5, 6–11, and 12–18 year olds). Complex sample survey analysis were used to assess differences at a significance level of p-value < 0.05.</p> <p>Results</p> <p>Proportion of energy consumed varied by sex, ethnic group, and age groups between 4 pm and 11.59 pm. Compared to healthy weight children, overweight school-age children consumed significantly higher while overweight adolescents consumed significantly lower proportions of total daily energy with each advancing two-hour time increment.</p> <p>Conclusion</p> <p>The association between the circadian rhythm of eating and body weight status needs to be investigated further to examine the effect of time of consumption on the risk of childhood obesity. Especially longitudinal studies in diverse child populations would help elucidate the importance of time of eating on obesity.</p

Benchmarking high fidelity single-shot readout of semiconductor qubits

Determination of qubit initialisation and measurement fidelity is important for the overall performance of a quantum computer. However, the method by which it is calculated in semiconductor qubits varies between experiments. In this paper we present a full theoretical analysis of electronic single-shot readout and describe critical parameters to achieve high fidelity readout. In particular, we derive a model for energy selective state readout based on a charge detector response and examine how to optimise the fidelity by choosing correct experimental parameters. Although we focus on single electron spin readout, the theory presented can be applied to other electronic readout techniques in semiconductors that use a reservoir.Comment: 19 pages, 8 figure

Percolation with long-range correlated disorder

Long-range power-law correlated percolation is investigated using Monte Carlo simulations. We obtain several static and dynamic critical exponents as function of the Hurst exponent $H$ which characterizes the degree of spatial correlation among the occupation of sites. In particular, we study the fractal dimension of the largest cluster and the scaling behavior of the second moment of the cluster size distribution, as well as the complete and accessible perimeters of the largest cluster. Concerning the inner structure and transport properties of the largest cluster, we analyze its shortest path, backbone, red sites, and conductivity. Finally, bridge site growth is also considered. We propose expressions for the functional dependence of the critical exponents on $H$

the case of South Africa

Das Engagement und somit auch der Einfluss multinationaler Firmen in Entwicklungs- und Schwellenländern sind oftmals umstritten. In Hinblick auf umweltschädliche Auswirkungen gibt es vielfältige Belege dafür, dass Firmen schwache staatliche Regulierung im Umweltbereich ausnutzen; häufig mit verheerenden Folgen. Im Rahmen von freiwilligen CSR-Standards sind in letzter Zeit zunehmend Anstrengungen unternommen worden, um solchen Entwicklungen entgegenzuwirken. In unserer Recherche untersuchen wir das Wechselspiel freiwilliger CSRNormen mit öffentlicher Regulierung in Ländern begrenzter Staatlichkeit. Wir gehen dabei von folgender Frage aus: Fördern multinationale Unternehmen, die sich zu internationalen CSR-Normen verpflichtet haben, diese Standards auch aktiv in den Ländern, in denen sie operieren? Anhand der Situation im Bereich Umweltpolitik in Südafrika und beispielhaft anhand der Bergbau-, und Lebensmittelindustrie sollen zwei Fragen beantwortet werden: Erstens, bringen sich Firmen, die freiwillige Umweltstandards unterzeichnet haben, aktiv in die Förderung kollektiver Umweltregulierung ein und unter welchen Bedingungen? Und zweitens, falls sie dies tun, welche Modelle setzen sich durch: engagieren sich Firmen durch Einflussnahme auf den Staat, durch private Selbstregulierung oder in Formen öffentlich-privater Koregulierung

Perception Of Cultural Competence in Nurse Practitioners

Purpose: Nurse practitioners are at the forefront in providing quality care to diverse populations and must become cognizant of the importance of cultural competence in caring for diverse patients. The purpose of this study was to examine perceptions of cultural competence and its integration in the delivery of health care in nurse practitioners practicing in a Mexican-American region of South Texas. Methodology: A descriptive, qualitative design using grounded theory and purposive sampling was utilized for this study. Sixteen nurse practitioners, fourteen females and two males, participated in the study. Qualitative data collection was elicited through individual interviews and a focus group. The selected participants included nurse practitioners who were employed for at least eight hours per week in a primary or acute care setting. The study included a demographic questionnaire and a nine-item interview guide created by the researchers to elicit thoughtful reflection on the participants’ perceptions of cultural competence and how cultural competence is integrated in their practice. Main findings: Data analysis involved grouping of response similarities until no new categories emerged. Affinity among the categories resulted in linkage into four distinct core categories or emerging themes. These themes provided a summary of what the nurse practitioners working with a Mexican-American population perceived as cultural competence and its integration in the delivery of health care. The four emerging themes include: 1) Culture as multifaceted; 2) Communication as empowerment; 3) Cultural dissonance; 4) Influence of myths, traditions, and complementary modalities. Principle conclusions: The study findings highlight the importance of advanced practice nurses’ efforts to continue to learn and increase their knowledge base and sensitivities to the culture of their clients in all dimensions of health care. The findings also support previous research and strengthen the understanding of the importance of cultural competency in the delivery of care to minority populations

Dark matter within high surface brightness spiral galaxies

We present results from a detailed dynamical analysis of five high surface brightness, late type spirals, studied with the aim to quantify the luminous-to-dark matter ratio inside their optical radii. The galaxies' stellar light distribution and gas kinematics have been observed and compared to hydrodynamic gas simulations, which predict the 2D gas dynamics arising in response to empirical gravitational potentials, which are combinations of differing stellar disk and dark halo contributions. The gravitational potential of the stellar disk was derived from near-infrared photometry, color-corrected to constant (M/L); the dark halo was modelled by an isothermal sphere with a core. Hydrodynamic gas simulations were performed for each galaxy for a sequence of five different mass fractions of the stellar disk and for a wide range of spiral pattern speeds. These two parameters mainly determine the modelled gas distribution and kinematics. The agreement between the non-axisymmetric part of the simulated and observed gas kinematics permitted us to conclude that the galaxies with the highest rotation velocities tend to possess near-maximal stellar disks. In less massive galaxies, with v_max<200 km/s, the mass of the dark halo at least equals the stellar mass within 2-3 R_disk. The simulated gas morphology provides a powerful tool to determine the dominant spiral pattern speed. The corotation radius for all galaxies was found to be constant at R_corotation ~ 3 R_disk and encloses the strong part of the stellar spiral in all cases.Comment: 28 pages, 7 figures; to appear in the Astrophysical Journal, Vol. 586, March 200