Small-Scale X-ray Variability in the Cassiopeia A Supernova Remnant

A comparison of X-ray observations of the Cassiopeia A supernova remnant taken in 2000, 2002, and 2004 with the Chandra ACIS-S3 reveals the presence of several small scale features (<= 10 arcsec) which exhibit significant intensity changes over a 4 year time frame. Here we report on the variability of six features, four of which show count rate increases from ~ 10% to over 90%, and two which show decreases of ~ 30% -- 40%. While extracted 1-4.5 keV X-ray spectra do not reveal gross changes in emission line strengths, spectral fits using non-equilibrium ionization, metal-rich plasma models indicate increased or decreased electron temperatures for features showing increasing or decreasing count rates, respectively. Based on the observed count rate changes and the assumption that the freely expanding ejecta has a velocity of ~ 5000 km/s at the reverse shock front, we estimate the unshocked ejecta to have spatial scale variations of 0.02 - 0.03 pc, which is consistent with the X-ray emitting ejecta belonging to a more diffuse component of the supernova ejecta than that seen in the optically emitting ejecta, which have spatial scales ~ 0.001 pc.Comment: 9 pages, 8 figures, to be published in Astronomical Journa

Ultraviolet modifications of dispersion relations in effective field theory

The existence of a fundamental ultraviolet scale, such as the Planck scale, may lead to modifications of the dispersion relations for particles at high energies, in some scenarios of quantum gravity. We apply effective field theory to this problem and identify dimension 5 operators that do not mix with dimensions 3 and 4 and lead to cubic modifications of dispersion relations for scalars, fermions, and vector particles. Further we show that, for electrons, photons and light quarks, clock comparison experiments bound these operators at 10^{-5}/Mpl.Comment: Version to appear in Phys.Rev.Let

Tobacco Use and Health Insurance Literacy Among Vulnerable Populations: Implications for Health Reform

Background: Under the Affordable Care Act (ACA), millions of Americans have been enrolling in the health insurance marketplaces. Nearly 20% of them are tobacco users. As part of the ACA, tobacco users may face up to 50% higher premiums that are not eligible for tax credits. Tobacco users, along with the uninsured and racial/ethnic minorities targeted by ACA coverage expansions, are among those most likely to suffer from low health literacy – a key ingredient in the ability to understand, compare, choose, and use coverage, referred to as health insurance literacy. Whether tobacco users choose enough coverage in the marketplaces given their expected health care needs and are able to access health care services effectively is fundamentally related to understanding health insurance. However, no studies to date have examined this important relationship.Methods: Data were collected from 631 lower-income, minority, rural residents of Virginia. Health insurance literacy was assessed by asking four factual questions about the coverage options presented to them. Adjusted associations between tobacco use and health insurance literacy were tested using multivariate linear regression, controlling for numeracy, risk-taking, discount rates, health status, experiences with the health care system, and demographics.Results: Nearly one third (31%) of participants were current tobacco users, 80% were African American and 27% were uninsured. Average health insurance literacy across all participants was 2.0 (SD 1.1) out of a total possible score of 4. Current tobacco users had significantly lower HIL compared to non-users (−0.22, p \u3c 0.05) after adjustment. Participants who were less educated, African American, and less numerate reported more difficulty understanding health insurance (p \u3c 0.05 each.)Conclusions: Tobacco users face higher premiums for health coverage than non-users in the individual insurance marketplace. Our results suggest they may be less equipped to shop for plans that provide them with adequate out-of-pocket risk protection, thus placing greater financial burdens on them and potentially limiting access to tobacco cessation and treatment programs and other needed health services

A practical low-boom overpressure signature based on minimum sonic boom theory

A brief resume of sonic boom minimization methods is given to provide a background for a new, empirical modification of the Seebass and George minimum-nose-shock sonic boom F-function and signature. The new 'hybrid' F-function has all the inherent flexibility of application found with the Darden-modified Seebass and George F-function. In addition, it has enhanced this flexibility and applicability with neglegible increase in nose and/or tail shock strength. A description of this 'hybrid' F-function and signature is provided, and the benefits of using them to design high-performance, low-boom aircraft are discussed

Pressurization and expulsion of cryogenic liquids: Generic requirements for a low gravity experiment

Requirements are presented for an experiment designed to obtain data for the pressurization and expulsion of a cryogenic supply tank in a low gravity environment. These requirements are of a generic nature and applicable to any cryogenic fluid of interest, condensible or non-condensible pressurants, and various low gravity test platforms such as the Space Shuttle or a free-flyer. Background information, the thermophysical process, preliminary analytical modeling, and experimental requirements are discussed. Key parameters, measurements, hardware requirements, procedures, a test matrix, and data analysis are outlined

Advertising Expenditures in U.S. Manufacturing Industries, 1967 and 1982

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Geomagnetic model investigations for 1980 - 1989: A model for strategic defense initiative particle beam experiments and a study in the effects of data types and observatory bias solutions

Two suites of geomagnetic field models were generated at the request of Los Alamos National Lab. concerning Strategic Defense Initiative (SDI) research. The first is a progression of five models incorporating MAGSAT data and data from a sequence of batches as a priori information. The batch sequence is: post 1979.5 observatory data, post 1980 land survey and selected aeromagnetic and marine survey data, a special White Sands (NM) area survey by Project Magnet with some additional post 1980 marine survey data, and finally DE-2 satellite data. These models are of 13th deg and order in their main field terms, and deg and order 10 in their first derivative temporal terms. The second suite consists of four models based solely upon post 1983.5 observatory and survey data. They are of deg and order 10 in main field and 8 in a first deg Taylor series. A comprehensive error analysis was applied to both series, which accounted for error sources such as the truncated core and crustal fields, and the neglected Sq and low deg crustal fields. Comparison of the power spectrum of the MGST (10/81) model with those of this series show good agreement

Montane lakes (lagoons) of the New England Tablelands Bioregion

The vegetation of montane lagoons of the New England Tablelands Bioregion, New South Wales is examined using flexible UPGMA analysis of frequency scores on all vascular plant taxa, charophytes and one liverworts. Seven communities are described: 1. Hydrocotyle tripartita – Isotoma fluviatilis – Ranunculus inundatus – Lilaeopsis polyantha herbfield; 2. Eleocharis sphacelata – Potamogeton tricarinatus sedgeland; 3. Eleocharis sphacelata – Utricularia australis – Isolepis fluitans, herbfield; 4. Utricularia australis – Nitella sonderi herbfield; 5. Eleocharis sphacelata – Utricularia australis – Ricciocarpus natans sedgeland; 6. Carex gaudichaudiana – Holcus lanatus – Stellaria angustifolia sedgeland; 7. Cyperus sphaeroides – Eleocharis gracilis – Schoenus apogon – Carex gaudichaudiana sedgeland. 58 lagoons were located and identified, only 28% of which are considered to be intact and in good condition. Two threatened species (Aldovandra vesiculosa and Arthaxon hispidus) and three RoTAP-listed taxa were encountered during the survey