Dynamic structure factor of ultracold Bose and Fermi gases in optical lattices

We investigate the dynamic structure factor of atomic Bose and Fermi gases in one-dimensional optical lattices at zero temperature. The focus is on the generic behaviour of S(k,omega) as function of filling and interaction strength with the aim of identifying possible experimental signatures for the different quantum phase transitions. We employ the Hubbard or Bose-Hubbard model and solve the eigenvalue problem of the Hamiltonian exactly for moderate lattice sizes. This allows us to determine the dynamic structure factor and other observables directly in the phase transition regime, where approximation schemes are generally not applicable. We discuss the characteristic signatures of the various quantum phases appearing in the dynamic structure factor and illustrate that the centroid of the strength distribution can be used to estimate the relevant excitation gaps. Employing sum rules, these quantities can be evaluated using ground state expectation values only. Important differences between bosonic and fermionic systems are observed, e.g., regarding the origin of the excitation gap in the Mott-insulator phase.Comment: 15 pages, 7 figure

Periodic behaviors in the observed vertical column abundances of atmospheric hydroxyl

The data base for the vertical column abundance of atmospheric hydroxyl (OH) for Fritz Peak Observatory, Colorado (40 N, 105 W), now extends from 1976 through 1988 and is composed of 8849 independent data sets, averaging about 15 percent uncertainty and 20-minute time resolution each. The dominant solar zenith angle (chi) dependence of the OH abundance is characterized by an empirical curve, N(88), which has been updated from N(82) to include all valid data from 1980 through 1988. The chi-dependence of the OH abundance has been, to a first order, removed from the data base by a normalization procedure in which each data point is divided by the N(88,AM) value for the corresponding solar zenith angle. The resulting normalized OH values may then be examined for other systematic effects, particularly for periodic variations. Observations have also been made at Boca Raton, Florida (26 N, 80 W) and at Truk, Federated States of Micronesia (7 N, 152 E). These data bases are much less extensive and, as such, are less amenable to analysis for periodic behaviors. Some comparisons with the Colorado data may be made, however

BCS Theory for Trapped Ultracold Fermions

We develop an extension of the well-known BCS-theory to systems with trapped fermions. The theory fully includes the quantized energy levels in the trap. The key ingredient is to model the attractive interaction between two atoms by a pseudo-potential which leads to a well defined scattering problem and consequently a BCS-theory free of divergences. We present numerical results for the BCS critical temperature and the temperature dependence of the gap. They are used as a test of existing semi-classical approximations.Comment: 4 pages, 3 figures, submitted to PR

21st century social work: reducing re-offending - key practice skills

This literature review was commissioned by the Scottish Executive’s Social Work Services Inspectorate in order to support the work of the 21st Century Social Work Review Group. Discussions in relation to the future arrangements for criminal justice social work raised issues about which disciplines might best encompass the requisite skills for reducing re-offending in the community. Rather than starting with what is known or understood about the skills of those professionals currently involved in such interventions, this study sought to start with the research evidence on effective work with offenders to reduce re-offending and then work its way back to the skills required to promote this outcome

A study of the intensity of the self-broadened fundamental band of hydrogen chloride

Intensity study of self-broadened fundamental band of hydrogen chlorid

Dynamic Optimization of Nitrogen Use in Agriculture

Agricultural production is highly dependent on inorganic substances including fertilizers. High-yielding crop varieties, such as corn, require large amounts of primary nutrients including nitrogen, phosphorus and potassium. Farmers often add a surplus of nutrients to crops to maximize yields. Utilization of primary nutrients has increased by more than 300% while that of nitrogen alone has increased by more than 600% between 1960 and 2007 (USDA, 2009). From 1964 to 2007, the use of nitrogen in the corn sector alone increased from 1,623,000 to 5,714,000 nutrient tons (USDA, 2009). While increasing production, increased fertilizer use can potentially create negative externalities in the form of nitrate-nitrogen contamination in groundwater. Groundwater is the source of drinking water for about half the total U.S. population and nearly all of the rural population, and it provides over 50 billion gallons per day for agricultural needs (USGS, 2009). In the U.S. the main source of nitrate pollution in the groundwater results from the actions of farmers through the use of fertilizers and other chemicals (Haller, et al. 2009). Nitrogen-nitrate contamination can have adverse human affects including methemoglobinemia or ―blue-baby‖ syndrome (Majumdar, 2003). The potential for nitrate contamination in corn production is especially problematic as corn alone accounts for over 90% of feed grains produced in the U.S. (USDA, 2009). The USDA estimates that approximately 80 million acres of land is planted to corn, with the majority in the Heartland region (the Midwest) of the U.S. (2009). The Heartland region is primarily rural and much of the population there derives its drinking water from groundwater. Therefore, the potential for groundwater contamination is greatly increased in this region.Environmental Economics, Nitrogen/Nitrate Contamination, Dynamic Optimization, Agriculture, Agricultural and Food Policy, Demand and Price Analysis, Environmental Economics and Policy, C61, C63, Q10, Q51, Q53,

Dynamic Optimization of Nitrogen Use in Agriculture

Agricultural and Food Policy, Crop Production/Industries,

Police Militarization And Overuse of Force: An Analysis of the Efficacy of Paramilitary Units And Society

The role of the police is to maintain social order and safety through the enforcement of law. They investigate, prevent, and detect criminal activity. However, the problem with police protection today is overuse of force which often comes through the term militarism regarding agency tenets and dogma. Also, social media has focused on police overuse of force, exacerbating race riots and retaliatory police killings. Because of this, police reform has become a significant concern, not only in the United States but also abroad. The methodological approach for this dissertation is a quantitative analysis, data used is secondary, statistical procedure is chi square (cross tabulation) and multiple linear regression. This dissertation’s expected findings are to answer whether there is a statistically significant difference in police overuse of force by race and geographic areas; is there a relationship between DHS 1033 Program and violent crimes and property crimes; how accurately can a DHS 1033 Program index be predicted from a linear combination of crime rates