14,692 research outputs found
What motivates African-American charitable giving: findings from a national sample
Given the growing wealth of minority families in America, including that of African-American families, the potential for charitable donations from these households is much greater. The purpose of this secondary analysis is to examine those variables that may influence African-American charitable giving patterns. This study uses the Panel Study of Income Dynamics (PSID) data to analyze the effects of multiple factors on the giving habits of African-Americans. Based on this study\u27s findings, social workers employed as executive directors or fund-raisers in private nonprofit organizations may want to identify and cultivate individual African-American donors directly, instead of relying on United Way and other federated campaigns
Ideal, Defective, and Gold--Promoted Rutile TiO2(110) Surfaces: Structures, Energies, Dynamics, and Thermodynamics from PBE+U
Extensive first principles calculations are carried out to investigate
gold-promoted TiO2(110) surfaces in terms of structure optimizations,
electronic structure analyses, ab initio thermodynamics calculations of surface
phase diagrams, and ab initio molecular dynamics simulations. All computations
rely on density functional theory in the generalized gradient approximation
(PBE) and account for on-site Coulomb interactions via inclusion of a Hubbard
correction, PBE+U, where U is computed from linear response theory. This
approach is validated by investigating the interaction between TiO2(110)
surfaces and typical probe species (H, H2O, CO). Relaxed structures and binding
energies are compared to both data from the literature and plain PBE results.
The main focus of the study is on the properties of gold-promoted titania
surfaces and their interactions with CO. Both PBE+U and PBE optimized
structures of Au adatoms adsorbed on stoichiometric and reduced TiO2 surfaces
are computed, along with their electronic structure. The charge rearrangement
induced by the adsorbates at the metal/oxide contact are also analyzed and
discussed. By performing PBE+U ab initio molecular dynamics simulations, it is
demonstrated that the diffusion of Au adatoms on the stoichiometric surface is
highly anisotropic. The metal atoms migrate either along the top of the
bridging oxygen rows, or around the area between these rows, from one bridging
position to the next along the [001] direction. Approximate ab initio
thermodynamics predicts that under O-rich conditions, structures obtained by
substituting a Ti5c atom with an Au atom are thermodynamically stable over a
wide range of temperatures and pressures.Comment: 20 pages, 12 figures, accepted for publication in Phys. Rev.
P02.85. A prospective patient-centered data collection program at an acupuncture and Oriental medicine teaching clinic
Singular components of spectral measures for ergodic Jacobi matrices
For ergodic 1d Jacobi operators we prove that the random singular components
of any spectral measure are almost surely mutually disjoint as long as one
restricts to the set of positive Lyapunov exponent. In the context of extended
Harper's equation this yields the first rigorous proof of the Thouless' formula
for the Lyapunov exponent in the dual regions.Comment: to appear in the Journal of Mathematical Physics, vol 52 (2011
Alternative axiomatics and complexity of deliberative STIT theories
We propose two alternatives to Xu's axiomatization of the Chellas STIT. The
first one also provides an alternative axiomatization of the deliberative STIT.
The second one starts from the idea that the historic necessity operator can be
defined as an abbreviation of operators of agency, and can thus be eliminated
from the logic of the Chellas STIT. The second axiomatization also allows us to
establish that the problem of deciding the satisfiability of a STIT formula
without temporal operators is NP-complete in the single-agent case, and is
NEXPTIME-complete in the multiagent case, both for the deliberative and the
Chellas' STIT.Comment: Submitted to the Journal of Philosophical Logic; 13 pages excluding
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Suppression of insect activity due to gunpowder residue on decomposing remains
Estimation of time since death is an important variable when investigating legal cases involving decomposing human remains; however it has been sparsely studied in controlled environments. Decomposition rates are largely influenced by external factors with temperature being the most critical factor. The decomposition rates can also be influenced by insect infestation, chemical residues, and burial, yet little research has been conducted to document how various factors alter the rate and process of decomposition. A common occurrence at human remains recovery sites is the deposit of residues from criminal activities such as gunpowder and explosives. This experiment will look at gunpowder residue’s effects on porcine remains and the insect infestation after exposure. This study was conducted in
two phases: the 1st experiment being conducted in the late spring and the 2nd in the early fall. For each experiment two carcasses were covered with gunpowder residue while one carcass served as a control (no residue). The physical decomposition processes as well as ambient temperature were documented for each carcass. The results for the study showed variable findings between the control and experimental subjects. The insect infestation of the remains was consistent with the data from previous entomological studies conducted from areas of similar climate and terrain. Factors that may have influenced the results are discussed in reference to the effects of the gunpowder residue on the decomposing remains
DESIGNED EXPERIMENTS IN THE PRESENCE OF SPATIAL CORRELATION
Soil heterogeneity is generally the major cause of variation in plot yield data and the difficulty of its interpretation. If a large degree of variability is present at a test site, some method of controlling it must be found. Controlling experimental variability can be achieved either by good experimental design or by analysis procedures which account for the spatial correlation. Classical designs are only moderately equipped to adjust for spatially correlated data. More complex designs including nearest neighbor designs, Williams designs, and certain restricted Latin square designs are developed for field experimentation when spatial correlation causes classical designs to be less desirable
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The designs, both classical and nearest neighbor type designs, are analyzed using the classical statistical analysis approach and a strategy using general linear mixed models which takes into account that there is spatial correlation present. The results indicate that properly designed experiments may be analyzed either by the usual statistical techniques or more complex methods which adjust for spatial correlation. However, if no serious thought is used in constructing the design of the experiment then the usual analysis techniques are no longer valid
Parameterized Approximation Schemes using Graph Widths
Combining the techniques of approximation algorithms and parameterized
complexity has long been considered a promising research area, but relatively
few results are currently known. In this paper we study the parameterized
approximability of a number of problems which are known to be hard to solve
exactly when parameterized by treewidth or clique-width. Our main contribution
is to present a natural randomized rounding technique that extends well-known
ideas and can be used for both of these widths. Applying this very generic
technique we obtain approximation schemes for a number of problems, evading
both polynomial-time inapproximability and parameterized intractability bounds
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