Why Are Ring Galaxies Interesting?

Compared with ordinary spirals, the ISM in ring galaxies experiences markedly different physical conditions and evolution. As a result, ring galaxies provide interesting perspectives on the triggering/quenching of large scale star formation and the destructive effects of massive stars on molecular cloud complexes. We use high resolution radio, sub-millimeter, infrared, and optical data to investigate the role of gravitational stability in star formation regulation, factors influencing the ISM's molecular fraction, and evidence of peculiar star formation laws and efficiencies in two highly evolved ring galaxies: Cartwheel and the Lindsay-Shapley ring.Comment: 6 pages with 4 figures (2 color). To appear in the conference proceedings for "Galaxy Wars: Stellar Populations and Star Formation in Interacting Galaxies"

Rise time of pulsed parametric oscillators

General relations are derived that describe the rise time of the output power of parametric oscillators driven by a time-dependent pump. Both singly resonant and doubly resonant oscillators are discussed. Results of computer calculations using a Gaussian time envelope for the pump pulse are presented and, in the case of the doubly resonant oscillator, are compared to predictions of a steady-state analysis. Agreement between calculated rise times and published values is good

A Simple Pendulum Determination of the Gravitational Constant

We determined the Newtonian Constant of Gravitation G by interferometrically measuring the change in spacing between two free-hanging pendulum masses caused by the gravitational field from large tungsten source masses. We find a value for G of (6.672 34 +/- 0.000 14) x 10^-11 m^3 kg^-1 s^-2. This value is in good agreement with the 1986 Committee on Data for Science and Technology (CODATA) value of (6.672 59 +/- 0.000 85) x 10^-11 m^3 kg^-1 s^-2 [Rev. Mod. Phys. 59, 1121 (1987)] but differs from some more recent determinations as well as the latest CODATA recommendation of (6.674 28 +/- 0.000 67) x 10^-11 m^3 kg^-1 s^-2 [Rev. Mod. Phys. 80, 633 (2008)].Comment: 10 pages, 2 figure

Zoom-Whirl Orbits in Black Hole Binaries

Zoom-whirl behavior has the reputation of being a rare phenomenon. The concern has been that gravitational radiation would drain angular momentum so rapidly that generic orbits would circularize before zoom-whirl behavior could play out, and only rare highly tuned orbits would retain their imprint. Using full numerical relativity, we catch zoom-whirl behavior despite dissipation. The larger the mass ratio, the longer the pair can spend in orbit before merging and therefore the more zooms and whirls seen. Larger spins also enhance zoom-whirliness. An important implication is that these eccentric orbits can merge during a whirl phase, before enough angular momentum has been lost to truly circularize the orbit. Waveforms will be modulated by the harmonics of zoom-whirls, showing quiet phases during zooms and louder glitches during whirls.Comment: Replaced with published versio

Dual-topology insertion of a dual-topology membrane protein.

Some membrane transporters are dual-topology dimers in which the subunits have inverted transmembrane topology. How a cell manages to generate equal populations of two opposite topologies from the same polypeptide chain remains unclear. For the dual-topology transporter EmrE, the evidence to date remains consistent with two extreme models. A post-translational model posits that topology remains malleable after synthesis and becomes fixed once the dimer forms. A second, co-translational model, posits that the protein inserts in both topologies in equal proportions. Here we show that while there is at least some limited topological malleability, the co-translational model likely dominates under normal circumstances

Avoiding chronic and transitory poverty

This paper uses a panel data of 347 households in Egypt to measure changes in household consumption between 1997 and 1999 and to identify causes behind the changes. Per capita consumption decreased for the households during this time and, while not dramatic, it occurred at all points along the distribution. Over the two-year period, the number of households that fell into poverty was over twice as large as the number of households that climbed out of poverty. About two-thirds of overall poverty was chronic (average consumption over time was below the poverty line), and almost half of all poor were always poor. We use quantile regression methods to identify the factors that explain total, chronic, and transitory poverty. While our analysis ably documents the extent of transitory poverty, it does not explain well the determinants of this type of poverty. The predominantly chronic nature of poverty in the sample, and our ability to identify associated characteristics, strengthens the case for targeting antipoverty interventions such as food subsidies.Household consumption. ,Poverty Egypt. ,Poverty Research Methodology. ,Poverty alleviation Egypt. ,Subsidies Egypt. ,Food relief Egypt. ,Households Egypt. ,

Avoiding chronic and transitory poverty

This paper uses a panel data of 347 households in Egypt to measure changes in household consumption between 1997 and 1999 and to identify causes behind the changes. Per capita consumption decreased for the households during this time and, while not dramatic, it occurred at all points along the distribution. Over the two-year period, the number of households that fell into poverty was over twice as large as the number of households that climbed out of poverty. About two-thirds of overall poverty was chronic (average consumption over time was below the poverty line), and almost half of all poor were always poor. We use quantile regression methods to identify the factors that explain total, chronic, and transitory poverty. While our analysis ably documents the extent of transitory poverty, it does not explain well the determinants of this type of poverty. The predominantly chronic nature of poverty in the sample, and our ability to identify associated characteristics, strengthens the case for targeting antipoverty interventions such as food subsidies.Household consumption. ,Poverty Egypt. ,Poverty Research Methodology. ,Poverty alleviation Egypt. ,Subsidies Egypt. ,Food relief Egypt. ,Households Egypt. ,

Theoretical Study of Sodium and Potassium Resonance Lines Pressure Broadened by Helium Atoms

We perform fully quantum mechanical calculations in the binary approximation of the emission and absorption profiles of the sodium $3s$-$3p$ and potassium $4s$-$4p$ resonance lines under the influence of a helium perturbing gas. We use carefully constructed potential energy surfaces and transition dipole moments to compute the emission and absorption coefficients at temperatures from 158 to 3000 K. Contributions from quasi-bound states are included. The resulting red and blue wing profiles agree well with previous theoretical calculations and with experimental measurements.Comment: 16 figure

The Genetic and Environmental Etiology of Schizophrenia in Palau

Schizophrenia is a chronic, severe, and disabling brain disorder that has been affecting people throughout the world. There is an established worldwide 1% average prevalence of schizophrenia; however there are high degrees of variability between different regions. Palau, an oceanic nation located in Micronesia, has an abnormally high prevalence rate of schizophrenia at 1.99%. When separated by gender, women have abnormal prevalence rate of 1.24%, while the men have a high prevalence rate of 2.77%, which is over twice the average worldwide. There has been a plethora of research conducted over the years to determine the genetic and environmental etiology of schizophrenia in Palau. Palau’s somewhat isolated and small population offer the advantage of a valuable insular population for the study of genetic etiology of schizophrenia because there may be fewer susceptibility genes for schizophrenia than in heterogeneous populations throughout the world. Recent studies have highlighted that schizophrenia in Palau is a complex genetic disease, yet is also greatly influenced by certain environmental factors. As part of the research, blood and tissue samples from 160 schizophrenic Palauan patients were sampled. In addition, 400 relatives of the patients were reviewed and shown as unaffected by the disease; although there were first and second-degree relatives who were affected. The patients were also interviewed frequently about relevant matters, such as their diet and daily activities. By examining these studies, I was able to determine that many environmental factors may be involved with the disease, such as exposure to viruses, heavy marijuana use, malnutrition before birth, and other not yet known psychosocial factors. Because of Palau’s intricately, interconnected families and small population and isolation, it has a high prevalence rate of schizophrenia