A Robust Classification of Galaxy Spectra: Dealing with Noisy and Incomplete Data

Over the next few years new spectroscopic surveys (from the optical surveys of the Sloan Digital Sky Survey and the 2 degree Field survey through to space-based ultraviolet satellites such as GALEX) will provide the opportunity and challenge of understanding how galaxies of different spectral type evolve with redshift. Techniques have been developed to classify galaxies based on their continuum and line spectra. Some of the most promising of these have used the Karhunen and Loeve transform (or Principal Component Analysis) to separate galaxies into distinct classes. Their limitation has been that they assume that the spectral coverage and quality of the spectra are constant for all galaxies within a given sample. In this paper we develop a general formalism that accounts for the missing data within the observed spectra (such as the removal of sky lines or the effect of sampling different intrinsic rest wavelength ranges due to the redshift of a galaxy). We demonstrate that by correcting for these gaps we can recover an almost redshift independent classification scheme. From this classification we can derive an optimal interpolation that reconstructs the underlying galaxy spectral energy distributions in the regions of missing data. This provides a simple and effective mechanism for building galaxy spectral energy distributions directly from data that may be noisy, incomplete or drawn from a number of different sources.Comment: 20 pages, 8 figures. Accepted for publication in A

Accounting for the Decline in AFDC Caseloads: Welfare Reform or Economic Growth?

Nationwide, AFDC caseloads have decreased by about 18 percent since March 1994, while some states, such as Wisconsin, Indiana, and Oregon, have seen declines of 40 percent or more. Two factors are frequently suggested as possible causes: state-level experiments with welfare reform and strong economic growth. In this paper, we use state-level monthly panel data from 1987 to 1996 to assess the importance of each of these factors by estimating a model of AFDC caseloads as a dynamic function of time-dependent state welfare reform variables (welfare waivers) and economic variables such as per capita employment. Our results from the dynamic model suggest that the decline in per capita AFDC caseloads is attributable largely to the economic growth of states and not to waivers from federal welfare policies. In the 26 states experiencing at least a 20 percent decline in per capita AFDC caseloads between 1993 and 1996, we attribute 78 percent of the decline to business-cycle factors and 6 percent to welfare waivers.

The Statistical Approach to Quantifying Galaxy Evolution

Studies of the distribution and evolution of galaxies are of fundamental importance to modern cosmology; these studies, however, are hampered by the complexity of the competing effects of spectral and density evolution. Constructing a spectroscopic sample that is able to unambiguously disentangle these processes is currently excessively prohibitive due to the observational requirements. This paper extends and applies an alternative approach that relies on statistical estimates for both distance (z) and spectral type to a deep multi-band dataset that was obtained for this exact purpose. These statistical estimates are extracted directly from the photometric data by capitalizing on the inherent relationships between flux, redshift, and spectral type. These relationships are encapsulated in the empirical photometric redshift relation which we extend to z ~ 1.2, with an intrinsic dispersion of dz = 0.06. We also develop realistic estimates for the photometric redshift error for individual objects, and introduce the utilization of the galaxy ensemble as a tool for quantifying both a cosmological parameter and its measured error. We present deep, multi-band, optical number counts as a demonstration of the integrity of our sample. Using the photometric redshift and the corresponding redshift error, we can divide our data into different redshift intervals and spectral types. As an example application, we present the number redshift distribution as a function of spectral type.Comment: 40 pages (LaTex), 21 Figures, requires aasms4.sty; Accepted by the Astrophysical Journa

A Consumer Test of Canned Seasoned Salad Tomatoes

Consumer, Canned Tomatoes, Salad Tomatoes, Seasoned Tomatoes, Consumer/Household Economics, Food Consumption/Nutrition/Food Safety,

ASPIRE-2-PREVENT: a survey of lifestyle, risk factor management and cardioprotective medication in patients with coronary heart disease and people at high risk of developing cardiovascular disease in the UK.

OBJECTIVE: To determine in patients with coronary heart disease (CHD) and people at high risk of developing cardiovascular disease (CVD) whether the Joint British Societies' guidelines on CVD prevention (JBS2) are followed in everyday clinical practice. DESIGN: A cross-sectional survey was undertaken of medical records and patient interviews and examinations at least 6 months after the recruiting event or diagnosis using standardised instruments and a central laboratory for measurement of lipids and glucose. SETTINGS: The ASPIRE-2-PREVENT survey was undertaken in 19 randomly selected hospitals and 19 randomly selected general practices in 12 geographical regions in England, Northern Ireland, Wales and Scotland. PATIENTS: In hospitals, 1474 consecutive patients with CHD were identified and 676 (25.6% women) were interviewed. In general practice, 943 people at high CVD risk were identified and 446 (46.5% women) were interviewed. RESULTS: The prevalence of risk factors in patients with CHD and high-risk individuals was, respectively: smoking 14.1%, 13.3%; obesity 38%, 50.2%; not reaching physical activity target 83.3%, 85.4%; blood pressure ≥130/80 mm Hg (patients with CHD and self-reported diabetes) or ≥140/85 mm Hg (high-risk individuals) 46.9%, 51.3%; total cholesterol ≥4 mmol/l 52.6%, 78.7%; and diabetes 17.8%, 43.8%. CONCLUSIONS: The potential among patients with CHD and individuals at high risk of developing CVD in the UK to achieve the JBS2 lifestyle and risk factor targets is considerable. CVD prevention needs a comprehensive multidisciplinary approach, addressing all aspects of lifestyle and risk factor management. The challenge is to engage and motivate cardiologists, physicians and other health professionals to routinely practice high quality preventive cardiology in a healthcare system which must invest in prevention

Nanopercolation

We investigate through direct molecular mechanics calculations the geometrical properties of hydrocarbon mantles subjected to percolation disorder. We show that the structures of mantles generated at the critical percolation point have a fractal dimension $d_{f} \approx 2.5$. In addition, the solvent access surface $A_{s}$ and volume $V_{s}$ of these molecules follow power-law behavior, $A_{s} \sim L^{\alpha_A}$ and $V_{s} \sim L^{\alpha_V}$, where $L$ is the system size, and with both critical exponents $\alpha_A$ and $\alpha_V$ being significantly dependent on the radius of the accessing probing molecule, $r_{p}$. Our results from extensive simulations with two distinct microscopic topologies (i.e., square and honeycomb) indicate the consistency of the statistical analysis and confirm the self-similar characteristic of the percolating hydrocarbons. Due to their highly branched topology, some of the potential applications for this new class of disordered molecules include drug delivery, catalysis, and supramolecular structures.Comment: 4 pages, 5 figure