6,629 research outputs found
Structures in the microwave background radiation
We compare the actual WMAP maps with artificial, purely statistical maps of
the same harmonic content to argue that there are, with confidence level 99.7
%, ring-type structures in the observed cosmic microwave background.Comment: 4 pages, 2 figure
The use of computer-generated color graphic images for transient thermal analysis
Color computer graphics techniques were investigated as a means of rapidly scanning and interpreting large sets of transient heating data. The data presented were generated to support the conceptual design of a heat-sink thermal protection system (TPS) for a hypersonic research airplane. Color-coded vector and raster displays of the numerical geometry used in the heating calculations were employed to analyze skin thicknesses and surface temperatures of the heat-sink TPS under a variety of trajectory flight profiles. Both vector and raster displays proved to be effective means for rapidly identifying heat-sink mass concentrations, regions of high heating, and potentially adverse thermal gradients. The color-coded (raster) surface displays are a very efficient means for displaying surface-temperature and heating histories, and thereby the more stringent design requirements can quickly be identified. The related hardware and software developments required to implement both the vector and the raster displays for this application are also discussed
Alternative experimental evidence for chiral restoration in excited baryons
Given existing empirical spectral patterns of excited hadrons it has been
suggested that chiral symmetry is approximately restored in excited hadrons at
zero temperature/density (effective symmetry restoration). If correct, this
implies that mass generation mechanisms and physics in excited hadrons is very
different as compared to the lowest states. One needs an alternative and
independent experimental information to confirm this conjecture. Using very
general chiral symmetry arguments it is shown that strict chiral restoration in
a given excited nucleon forbids its decay into the N \pi channel. Hence those
excited nucleons which are assumed from the spectroscopic patterns to be in
approximate chiral multiplets must only "weakly" decay into the N \pi channel,
(f_{N^*N\pi}/f_{NN\pi})^2 << 1. However, those baryons which have no chiral
partner must decay strongly with a decay constant comparable with f_{NN\pi}.
Decay constants can be extracted from the existing decay widths and branching
ratios. It turnes out that for all those well established excited nucleons
which can be classified into chiral doublets N_+(1440) - N_-(1535), N_+(1710) -
N_-(1650), N_+(1720) - N_-(1700), N_+(1680) - N_-(1675), N_+(2220) - N_-(2250),
N_+(?) - N_-(2190), N_+(?) - N_-(2600), the ratio is (f_{N^*N\pi}/f_{NN\pi})^2
~ 0.1 or much smaller for the high-spin states. In contrast, the only well
established excited nucleon for which the chiral partner cannot be identified
from the spectroscopic data, N(1520), has a decay constant into the N\pi
channel that is comparable with f_{NN\pi}. This gives an independent
experimental verification of the chiral symmetry restoration scenario.Comment: 4 pp. A new footnote with an alternative proof of impossibility of
parity doublet decay into pi + N is added. To appear in Phys. Rev. Let
The Nucleon Anapole Moment and Parity-Violating ep Scattering
Parity-violating (PV) interactions among quarks in the nucleon induce a PV
coupling, or anapole moment (AM). We compute electroweak
gauge-independent contributions to the AM through {\cal O}(1/\lamchis) in
chiral perturbation theory. We estimate short-distance PV effects using
resonance saturation. The AM contributions to PV electron-proton scattering
slightly enhance the axial vector radiative corrections, R_A^p, over the scale
implied by the Standard Model when weak quark-quark interactions are neglected.
We estimate the theoretical uncertainty associated with the AM contributions to
R_A^p to be large, and discuss the implications for the interpretation PV of ep
scattering.Comment: RevTex 29 pages + 8 PS figures, references and discussions added, to
appear in Phys. Rev.
The Medio Creek Site (41BX1421): National Register Test Excavations, Bexar County Texas
During April 2001, the Center for Archaeological Research of The University of Texas at San Antonio conducted National Register of Historic Places eligibility testing for archeological site 41BX1421, located in southwest Bexar County, Texas, under contract with the Texas Department of Transportation. The investigations were conducted under Texas Antiquities Permit Number 2569. The Phase II testing fieldwork consisted of excavation of five test units across the site to investigate cultural deposits encountered during the previous survey phase. A single sheet midden consisting of burned limestone cobbles was encountered across the majority of the site. In concert with the archeological field investigations, the following special analyses and studies were performed to aid the determination of site integrity and eligibility: radiocarbon, lithic, aboriginal ceramic, vertebrate faunal. and magnetic sediment susceptibility. The synthesis of these analyses has provided adequate data to determine 41BX1421 ineligible for the National Register of Historic Places. It is therefore recommended that the Loop 1604 improvements proceed without further cultural resources investigations
Multi-Magnon Scattering in the Ferromagnetic XXX-Model with Inhomogeneities
We determine the transition amplitude for multi-magnon scattering induced
through an inhomogeneous distribution of the coupling constant in the
ferromagnetic XXX-model. The two and three particle amplitudes are explicitely
calculated at small momenta. This suggests a rather plausible conjecture also
for a formula of the general n-particle amplitude.Comment: 21 pages, latex, no figure
An Effective Field Theory Calculation of the Parity Violating Asymmetry in n+p -> d+gamma
Weak interactions are expected to induce a parity violating pion-nucleon
coupling, h_{\pi NN}^{(1)}. This coupling should be measurable in a proposed
experiment to study the parity violating asymmetry A_\gamma in the process \vec
n + p \to d+\gamma. We compute the leading dependence of A_\gamma on the
coupling h_{\pi NN}^{(1)} using recently developed effective field theory
techniques and find an asymmetry of A_\gamma = +0.17 h_{\pi NN}^{(1)} at
leading order. This asymmetry has the opposite sign to that given by
Desplanques, Donoghue and Holstein.Comment: 7 pages, 2 figures from 3 eps files, late
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Pro-tobacco marketing and anti-tobacco campaigns aimed at vulnerable populations: A review of the literature.
INTRODUCTION:We reviewed research literature on pro-tobacco marketing and anti-tobacco campaigns targeting eight vulnerable populations to determine key findings and research gaps. Results can inform tobacco policy and control efforts and the design of public education campaigns for these groups. METHODS:Five journal databases in medicine, communication, and science, were used to identify 8875 peer-reviewed, original articles in English, published in the period 2004-2018. There were 144 articles that met inclusion criteria on pro-tobacco marketing or anti-tobacco campaigns aimed at eight US groups: women of reproductive age, racial/ethnic minority groups (African American, Hispanic/Latino, Asian/Pacific Islander and American Indian/Alaska Native), Lesbian/Gay/Bisexual/Transgender (LGBT) populations, groups with low socioeconomic status, rural/inner city residents, military/veterans, and people with mental health or medical co-morbidities. We summarized the number of articles for each population, type of tobacco, and pro-tobacco or anti-tobacco focus. Narrative summaries were organized by population and by pro-tobacco or anti-tobacco focus, with key strategies and gaps by group. RESULTS:There were more studies on pro-tobacco marketing rather than anti-tobacco campaigns, and on cigarettes rather than other tobacco products. Major gaps included studies on Asian Americans, American Indian/Alaska Natives, pregnant women, LGBT populations, and those with mental health or medical co-morbidities. Gaps related to tobacco products were found for hookah, snus, and pipe/roll-your-own tobacco in the pro-tobacco studies, and for all products except cigarettes in anti-tobacco studies. Common tobacco industry methods used were tailoring of product and package design and messages that were used to reach and appeal to different sociodemographic groups. Studies varied by research design making it difficult to compare results. CONCLUSIONS:We found major research gaps for specific groups and tobacco products. Public education campaigns need a stronger foundation in empirical studies focused on these populations. Research and practice would benefit from studies that permit comparisons across studies
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