657 research outputs found
Quantum Monte Carlo study of the Ne atom and the Ne+ ion
We report all-electron and pseudopotential calculations of the
ground-stateenergies of the neutral Ne atom and the Ne+ ion using the
variational and diffusion quantum Monte Carlo (DMC) methods. We investigate
different levels of Slater-Jastrow trial wave function: (i) using Hartree-Fock
orbitals, (ii) using orbitals optimized within a Monte Carlo procedure in the
presence of a Jastrow factor, and (iii) including backflow correlations in the
wave function. Small reductions in the total energy are obtained by optimizing
the orbitals, while more significant reductions are obtained by incorporating
backflow correlations. We study the finite-time-step and fixed-node biases in
the DMC energy and show that there is a strong tendency for these errors to
cancel when the first ionization potential (IP) is calculated. DMC gives highly
accurate values for the IP of Ne at all the levels of trial wave function that
we have considered
Crossbred dairy cattle productivity in Arsi region, Ethiopia
Presents results of analyses carried out on a range of performance traits and productivity estimates for indigenous Arsi & Zebu cattle and their crosses with Jersey & Friesian, maintained for milk production at Asela station & on smallholder farms in the Arsi region of Ethiopia; includes data on age at first calving, calving interval, breeding efficiency, milk yield & composition and body weight
Accurate structure factors from pseudopotential methods
Highly accurate experimental structure factors of silicon are available in
the literature, and these provide the ideal test for any \emph{ab initio}
method for the construction of the all-electron charge density. In a recent
paper [J. R. Trail and D. M. Bird, Phys. Rev. B {\bf 60}, 7863 (1999)] a method
has been developed for obtaining an accurate all-electron charge density from a
first principles pseudopotential calculation by reconstructing the core region
of an atom of choice. Here this method is applied to bulk silicon, and
structure factors are derived and compared with experimental and Full-potential
Linear Augmented Plane Wave results (FLAPW). We also compare with the result of
assuming the core region is spherically symmetric, and with the result of
constructing a charge density from the pseudo-valence density + frozen core
electrons. Neither of these approximations provide accurate charge densities.
The aspherical reconstruction is found to be as accurate as FLAPW results, and
reproduces the residual error between the FLAPW and experimental results.Comment: 6 Pages, 3 figure
Diffusion quantum Monte Carlo study of three-dimensional Wigner crystals
We report diffusion quantum Monte Carlo calculations of three-dimensional
Wigner crystals in the density range r_s=100-150. We have tested different
types of orbital for use in the approximate wave functions but none improve
upon the simple Gaussian form. The Gaussian exponents are optimized by directly
minimizing the diffusion quantum Monte Carlo energy. We have carefully
investigated and sought to minimize the potential biases in our Monte Carlo
results. We conclude that the uniform electron gas undergoes a transition from
a ferromagnetic fluid to a body-centered-cubic Wigner crystal at r_s=106+/-1.
The diffusion quantum Monte Carlo results are compared with those from
Hartree-Fock and Hartree theory in order to understand the role played by
exchange and correlation in Wigner crystals. We also study "floating" Wigner
crystals and give results for their pair-correlation functions
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Preliminary site report for the 2005 ICDP-USGS deep corehole in the Chesapeake Bay impact crater
First report for the ICDP-USGS 1.7-km-deep corehole drilled into the central part of the Chesapeake Bay impact crater during 2005
Downscaling a Global Climate Model to Simulate Climate Change Impacts on U.S. Regional and Urban Air Quality
Climate change can exacerbate future regional air pollution events by making conditions more favorable to form high levels of ozone. In this study, we use spectral nudging with WRF to downscale NASA earth system GISS modelE2 results during the years 2006 to 2010 and 2048 to 2052 over the continental United States in order to compare the resulting meteorological fields from the air quality perspective during the four seasons of five-year historic and future climatological periods. GISS results are used as initial and boundary conditions by the WRF RCM to produce hourly meteorological fields. The downscaling technique and choice of physics parameterizations used are evaluated by comparing them with in situ observations. This study investigates changes of similar regional climate conditions down to a 12km by 12km resolution, as well as the effect of evolving climate conditions on the air quality at major U.S. cities. The high resolution simulations produce somewhat different results than the coarse resolution simulations in some regions. Also, through the analysis of the meteorological variables that most strongly influence air quality, we find consistent changes in regional climate that would enhance ozone levels in four regions of the U.S. during fall (Western U.S., Texas, Northeastern, and Southeastern U.S), one region during summer (Texas), and one region where changes potentially would lead to better air quality during spring (Northeast). We also find that daily peak temperatures tend to increase in most major cities in the U.S. which would increase the risk of health problems associated with heat stress. Future work will address a more comprehensive assessment of emissions and chemistry involved in the formation and removal of air pollutants
Unrestricted Hartree-Fock theory of Wigner crystals
We demonstrate that unrestricted Hartree-Fock theory applied to electrons in
a uniform potential has stable Wigner crystal solutions for in
two dimensions and in three dimensions. The correlation energies
of the Wigner crystal phases are considerably smaller than those of the fluid
phases at the same density.Comment: 4 pages, 5 figure
Multistate Hepatitis A Outbreak: Vaccination of Food Service Workers as Part of the Kentucky Outbreak Response
Background: In August 2017, a local outbreak of Hepatitis A was identified among homeless individuals in Louisville, Kentucky. This marked the first cases in what has now become recognized as the largest Hepatitis A outbreak in the US. When infection was identified in a Food Service Worker (FSW), vaccination efforts were expanded to target this group.
Objective: The purpose of this study was to describe: 1) the processes used to provide access to Hepatitis A vaccine for FSWs, 2) results from the immunization activities, and 3) lessons learned from the outcomes.
Methods: Through a partnership between the Louisville Metro Department of Public Health and Wellness (LMDPHW) and the University of Louisville Division of Infectious Diseases, a novel approach to vaccination was implemented. Access to vaccine was provided via on-site immunization in 66 restaurants and subsequent availability in a pop-up vaccination clinic. Data were collected using the LMDPHW data collection form and included demographics, risk factors for Hepatitis A, and vaccine documentation. Results for those vaccinated March-December 2018 were analyzed using descriptive statistics.
Results: On-site vaccination was provided to 1337 FSW at 66 restaurants during the seven (7) week period from March 28-May 15, 2018. This process involved a team of 42 including Advanced Practice Registered Nurses, Registered and Licensed Practical Nurses, Physicians, and UL team members. During the 35 weeks the walk-in clinic has been in operation (May 16-December 31, 2018), 3068 additional FSW were vaccinated for a total of 4405 FSWs vaccinated as part of the outbreak response. Critical partners included the Kentucky Restaurant Association and the Kentucky Nurses Association.
Conclusions: This study demonstrated a successful model for vaccination of a novel population during an infectious disease outbreak and the importance of expanding partnership networks to ensure success. The outcomes emphasized the importance of the resources available in the academic community for reliable and consistent public health emergency response
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