5,685 research outputs found
Local Behavior of the First-Order Gradient Correction to the Thomas-Fermi Kinetic Energy Functional
The first order gradient correction to the Thomas-Fermi functional, proposed
by Haq, Chattaraj and Deb (Chem. Phys. Lett. vol. 81, 8031, 1984) has been
studied by evaluating both the total kinetic energy and the local kinetic
energy density. For testing the kinetic energy density we evaluate its
deviation from an exact result through a quality factor, a parameter that
reflects the quality of the functionals in a better way than their relative
errors. The study is performed on two different systems: light atoms (up to
Z=18) and a noninteracting model of fermions confined in a Coulombic-type
potential. It is found than this approximation gives very low relative errors
and a better local behavior than any of the usual generalized gradient
approximation semilocal kinetic density functionals.Comment: 7 pages, 2 tables, 4 figure
Child Care and Work Challenges for Maine’s Parents of Children with Special Needs
Research by the authors with parents, child care providers, and other service providers found that parents of children with special needs face particular challenges trying to maintain stable employment while balancing work and family. These parents have more difficulty finding and keeping child care for children with special needs, and there is a lack of coordination of therapy with child care programs. Since the study was completed, Maine has taken several steps to begin to address these issue
English Language Learners in the State of Maine: Early Education Policy That Can Make a Difference
The authors discuss the increasing number of Maine children who are English language learners (ELL) or who are limited-English proficient (LEP), noting that insufficient attention has been paid to the preschool education of this group. The authors describe lessons learned from an Early Reading First Program in Portland, which enhanced the school-readiness of preschool ELL children
Gaussian-Charge Polarizable Interaction Potential for Carbon Dioxide
A number of simple pair interaction potentials of the carbon dioxide molecule
are investigated and found to underestimate the magnitude of the second virial
coefficient in the temperature interval 220 K to 448 K by up to 20%. Also the
third virial coefficient is underestimated by these models. A rigid,
polarizable, three-site interaction potential reproduces the experimental
second and third virial coefficients to within a few percent. It is based on
the modified Buckingham exp-6 potential, an anisotropic Axilrod-Teller
correction and Gaussian charge densities on the atomic sites with an inducible
dipole at the center of mass. The electric quadrupole moment, polarizability
and bond distances are set to equal experiment. Density of the fluid at 200 and
800 bars pressure is reproduced to within some percent of observation over the
temperature range 250 K to 310 K. The dimer structure is in passable agreement
with electronically resolved quantum-mechanical calculations in the literature,
as are those of the monohydrated monomer and dimer complexes using the
polarizable GCPM water potential. Qualitative agreement with experiment is also
obtained, when quantum corrections are included, for the relative stability of
the trimer conformations, which is not the case for the pair potentials.Comment: Error in the long-range correction fixed and three-body dispersion
introduced. 32 pages (incl. title page), 7 figures, 9 tables, double-space
Entanglement of distant optomechanical systems
We theoretically investigate the possibility to generate non-classical states
of optical and mechanical modes of optical cavities, distant from each other. A
setup comprised of two identical cavities, each with one fixed and one movable
mirror and coupled by an optical fiber, is studied in detail. We show that with
such a setup there is potential to generate entanglement between the distant
cavities, involving both optical and mechanical modes. The scheme is robust
with respect to dissipation, and nonlocal correlations are found to exist in
the steady state at finite temperatures.Comment: 12 pages (published with minor modifications
Thermodynamically consistent description of the hydrodynamics of free surfaces covered by insoluble surfactants of high concentration
In this paper we propose several models that describe the dynamics of liquid
films which are covered by a high concentration layer of insoluble surfactant.
First, we briefly review the 'classical' hydrodynamic form of the coupled
evolution equations for the film height and surfactant concentration that are
well established for small concentrations. Then we re-formulate the basic model
as a gradient dynamics based on an underlying free energy functional that
accounts for wettability and capillarity. Based on this re-formulation in the
framework of nonequilibrium thermodynamics, we propose extensions of the basic
hydrodynamic model that account for (i) nonlinear equations of state, (ii)
surfactant-dependent wettability, (iii) surfactant phase transitions, and (iv)
substrate-mediated condensation. In passing, we discuss important differences
to most of the models found in the literature.Comment: 31 pages, 2 figure
Service delivery interventions to increase uptake of voluntary medical male circumcision for HIV prevention: A systematic review.
BackgroundVoluntary medical male circumcision (VMMC) remains an essential component of combination HIV prevention services, particularly in priority countries in sub-Saharan Africa. As VMMC programs seek to maximize impact and efficiency, and to support World Health Organization guidance, specific uptake-enhancing strategies are critical to identify.MethodsWe systematically reviewed the literature to evaluate the impact of service delivery interventions (e.g., facility layout, service co-location, mobile outreach) on VMMC uptake among adolescent and adult men. For the main effectiveness review, we searched for publications or conference abstracts that measured VMMC uptake or uptake of HIV testing or risk reduction counselling within VMMC services. We synthesized data by coding categories and outcomes. We also reviewed studies assessing acceptability, values/preferences, costs, and feasibility.ResultsFour randomized controlled trials and five observational studies were included in the effectiveness review. Studies took place in South Africa, Tanzania, Uganda, Zambia, and Zimbabwe. They assessed a range of service delivery innovations, including community-, school-, and facility-based interventions. Overall, interventions increased VMMC uptake; some successfully improved uptake among age-specific subpopulations, but urban-rural stratification showed no clear trends. Interventions that increased adult men's uptake included mobile services (compared to static facilities), home-based testing with active referral follow-up, and facility-based HIV testing with enhanced comprehensive sexual education. Six acceptability studies suggested interventions were generally perceived to help men choose to get circumcised. Eleven cost studies suggested interventions create economies-of-scale and efficiencies. Three studies suggested such interventions were feasible, improving facility preparedness, service quality and quantity, and efficiencies.ConclusionsInnovative changes in male-centered VMMC services can improve adult men's and adolescent boys' VMMC uptake. Limited evidence on interventions that enhance access and acceptability show promising results, but evidence gaps persist due to inconsistent intervention definition and delivery, due in part to contextual relevance and limited age disaggregation
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