3,405 research outputs found
Positron-molecule bound states and positive ion production
The interaction was studied of low energy positrons with large molecules such as alkanes. These data provide evidencce for the existence of long lived resonances and bound states of positrons with neutral molecules. The formation process and the nature of these resonances are discussed. The positive ions produced when a positron annihilates with an electron in one of these resonances were observed and this positive ion formation process is discussed. A review is presented of the current state of the understanding of these positron-molecule resonances and the resulting positive ion formation. A number of outstanding issues in this area is also discussed
Will Churches Respond to the Call? Religion, Civic Responsibility, and Social Service
Despite national calls for churches to become more involved in social service, many churches may not be willing or able to respond. Drawing on sociological theory, previous research, and interviews with pastors and parish social ministers from Catholic congregations in a large, urban city in Texas, we examine key factors linked to church-based social service efforts. Particulara ttention is given to church leadership,r ace/ethnicity,o rganizational characteristics, social and political networks, and the intersection of these factors in affecting service provision and advocacy. We then discuss the likely impacts of policies calling for religious organizations to increase their social service activities
Spectroscopy from 2 to 200 keV
The astrophysical processes responsible for line and continuum emission in the spectra range 2 keV to 200 keV are examined from the viewpoint of designing a spectrometer which would operate in this regime. Phenomena considered include fluorescent line radiation in X-ray binaries, magnetically shifted iron lines and cyclotron emission from neutron star surfaces, line emission from cosmically abundant elements in thermal plasmas, and nuclear deexcitation lines in fresh nucleosynthetically produced matter. An instrument consisting of a approximately 10 sq cm array of planar germanium detectors surrounded by a large sodium-iodide anticoincidence shield is described and projected background rates and sensitivities are considered. A sample observing program for a two-day shuttle-based mission is included as an example of the wide range of scientific questions which could be addressed by such an instrument
Inequality and Procedural Justice in Social Dilemmas
This study investigates the influence of resource inequality and the fairness
of the allocation procedure of unequal resources on cooperative behavior in
social dilemmas. We propose a simple formal behavioral model that incorporates
conflicting selfish and social motivations. This model allows us to predict how
inequality influences cooperative behavior. Allocation of resources is manipulated
by three treatments that vary in terms of procedural justice: allocating resources
randomly, based on merit, and based on ascription. As predicted, procedural
justice influences cooperation significantly. Moreover, gender is found to be an
important factor interacting with the association between procedural justice and
cooperative behavior.
INTEGRAL/IBIS search for e-e+ annihilation radiation from the Galactic Center Region
Electron-positron annihilation radiation from the Galactic Center region has
been detected since the seventies, but its astrophysical origin is still a
topic of a scientific debate. We have analyzed data of the gamma-ray imager
IBIS/ISGRI onboard of ESA's INTEGRAL platform in the ee line.
During the first year of the missions Galactic Center Deep Exposure no evidence
for point sources at 511 keV has been found in the ISGRI data; the
upper limit for resolved single point sources is estimated to be .Comment: 6 pages, 3 figures; Cospar 2004. To be published in: Advances in
Space Researc
The Role of Canids in Ritual and Domestic Contexts: New Ancient DNA Insights from Complex Hunter-Gatherer Sites in Prehistoric Central California
This study explores the interrelationship between the genus Canis and hunterâgatherers through a case study of prehistoric Native Americans in the San Francisco Bay-Sacramento Delta area. A distinctive aspect of the region\u27s prehistoric record is the interment of canids, variously classified as coyotes, dogs, and wolves. Since these species are difficult to distinguish based solely on morphology, ancient DNA analysis was employed to distinguish species. The DNA study results, the first on canids from archaeological sites in California, are entirely represented by domesticated dogs (including both interments and disarticulated samples from midden deposits). These results, buttressed by stable isotope analyses, provide new insight into the complex interrelationship between humans and canids in both ritual and prosaic contexts, and reveal a more prominent role for dogs than previously envisioned
A comparison of the illness beliefs of people with angina and their peers: a questionnaire study
BACKGROUND: What people believe about their illness may affect how they cope with it. It has been suggested that such beliefs stem from those commonly held within society . This study compared the beliefs held by people with angina, regarding causation and coping in angina, with the beliefs of their friends who do not suffer from angina. METHODS: Postal survey using the York Angina Beliefs Questionnaire (version 1), which elicits stress attributions and misconceived beliefs about causation and coping. This was administered to 164 people with angina and their non-cohabiting friends matched for age and sex. 132 people with angina and 94 friends completed the questionnaire. RESULTS: Peers are more likely than people with angina to believe that angina is caused by a worn out heart (p <0.01), angina is a small heart attack (p = 0.02), and that it causes permanent damage to the heart (p <0.001). Peers were also more likely to believe that people with angina should take life easy (p <0.01) and avoid exercise (p = 0.04) and excitement (p <0.01). CONCLUSIONS: The beliefs of the peer group about causation and coping in angina run counter to professional advice. Over time this may contribute to a reduction in patient concordance with risk factor reduction, and may help to create cardiac invalids
Spectral analysis of the Galactic e+e- annihilation emission
We present a spectral analysis of the e+e- annihilation emission from the
Galactic Centre region based on the first year of measurements made with the
spectrometer SPI of the INTEGRAL mission. We have found that the annihilation
spectrum can be modelled by the sum of a narrow and a broad 511 keV line plus
an ortho-Ps continuum. The broad line is detected with a flux of
(0.35+/-0.11)e-3 s-1 cm-2. The measured width of 5.4+/-1.2 keV FWHM is in
agreement with the expected broadening of 511 keV photons emitted in the
annihilation of Ps that are formed by the charge exchange process of slowing
down positrons with H atoms. The flux of the narrow line is (0.72+/-0.12)e-3
s-1 cm-2 and its width is 1.3+/-0.4 keV FWHM. The measured ortho-Ps continuum
flux yields a fraction of Ps of (96.7+/-2.2)%. To derive in what phase of the
interstellar medium positrons annihilate, we have fitted annihilation models
calculated for each phase to the data. We have found that 49(+2,-23)% of the
annihilation emission comes from the warm neutral phase and 51(+3,-2)% from the
warm ionized phase. While we may not exclude that less than 23% of the emission
might come from cold gas, we have constrained the fraction of annihilation
emission from molecular clouds and hot gas to be less than 8% and 0.5%,
respectively. We have compared our knowledge of the interstellar medium in the
bulge and the propagation of positrons with our results and found that they are
in good agreement if the sources are diffusively distributed and if the initial
kinetic energy of positrons is lower than a few MeV. Despite its large filling
factor, the lack of annihilation emission from the hot gas is due to its low
density, which allows positrons to escape this phase.Comment: 12 pages, 6 figures, accepted in A&
Long-Term X-ray Monitoring of 1E 1740.7-2942 and GRS 1758-258
We report on long-term observations of the Galactic-bulge black hole
candidates 1E 1740.7-2942 and GRS 1758-258 with the Rossi X-Ray Timing
Explorer. 1E 1740.7-2942 has been observed 77 times and GRS 1758-258 has been
observed 82 times over the past 1000 days. The flux of each object has varied
by no more than a factor of 2.5 during this period, and the indices of the
energy spectra have varied by no more than 0.4. The power spectra are similar
to other black-hole candidates: flat-topped noise, breaking to a power law.
Each object has exhibited a brightening that lasted for several months, and we
have a found a time lag between the photon power-law index and the count rate.
In both sources, the spectrum is softest during the decline from the
brightening. This behavior can be understood in the context of thin-disk and
advection-dominated accretion flows coexisting over a wide range of radii, with
the implication that both sources have low-mass companions and accrete via
Roche-lobe overflow.Comment: Accepted for publication in The Astrophysical Journa
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