11,144 research outputs found
The question of âalternativesâ within food and drink markets and marketing: introduction to the special issue
The question of 'alternatives' within food and drink markets and marketing: introduction to the special issu
Optical Spectroscopy and Nebular Oxygen Abundances of the Spitzer/SINGS Galaxies
We present intermediate-resolution optical spectrophotometry of 65 galaxies
obtained in support of the Spitzer Infrared Nearby Galaxies Survey (SINGS). For
each galaxy we obtain a nuclear, circumnuclear, and semi-integrated optical
spectrum designed to coincide spatially with mid- and far-infrared spectroscopy
from the Spitzer Space Telescope. We make the reduced, spectrophotometrically
calibrated one-dimensional spectra, as well as measurements of the fluxes and
equivalent widths of the strong nebular emission lines, publically available.
We use optical emission-line ratios measured on all three spatial scales to
classify the sample into star-forming, active galactic nuclei (AGN), and
galaxies with a mixture of star formation and nuclear activity. We find that
the relative fraction of the sample classified as star-forming versus AGN is a
strong function of the integrated light enclosed by the spectroscopic aperture.
We supplement our observations with a large database of nebular emission-line
measurements of individual HII regions in the SINGS galaxies culled from the
literature. We use these ancillary data to conduct a detailed analysis of the
radial abundance gradients and average HII-region abundances of a large
fraction of the sample. We combine these results with our new integrated
spectra to estimate the central and characteristic (globally-averaged)
gas-phase oxygen abundances of all 75 SINGS galaxies. We conclude with an
in-depth discussion of the absolute uncertainty in the nebular oxygen abundance
scale.Comment: ApJS, in press; 52 emulateapj pages, 12 figures, and two appendices;
v2: final abundances revised due to minor error; conclusions unchange
HB 438, Relating to Watershed Management, House Committee on Water and Land Use, Public Hearing, February 9, 1999, 9:00 A.M., Room 312, State Capitol
Searching for Star Formation Beyond Reionization
The goal of searching back in cosmic time to find star formation during the
epoch of reionization will soon be within reach. We assess the detectability of
high-redshift galaxies by combining cosmological hydrodynamic simulations of
galaxy formation, stellar evolution models appropriate for the first
generations of stars, and estimates of the efficiency for Lyman alpha to escape
from forming galaxies into the intergalactic medium. Our simulated observations
show that Lyman alpha emission at z ~ 8 may be observable in the near-infrared
with 8-meter class telescopes and present-day technology. Not only is the
detection of early star-forming objects vital to understanding the underlying
cause of the reionization of the universe, but the timely discovery of a z > 7
star-forming population -- or even an interesting upper limit on the emergent
flux from these objects -- will have implications for the design of the next
generation of ground- and space-based facilities.Comment: 4 pages, submitted to ApJ Letter
The Radial Structure of SNR N103B
We report on the results from a Chandra ACIS observation of the young,
compact, supernova remnant N103B. The unprecedented spatial resolution of
Chandra reveals sub-arcsecond structure, both in the brightness and in spectral
variations. Underlying these small-scale variations is a surprisingly simple
radial structure in the equivalent widths of the strong Si and S emission
lines. We investigate these radial variations through spatially resolved
spectroscopy using a plane-parallel, non-equilibrium ionization model with
multiple components. The majority of the emission arises from components with a
temperature of 1 keV: a fully ionized hydrogen component; a high ionization
timescale (n_e*t > 10^12 s cm^-3) component containing Si, S, Ar, Ca, and Fe;
and a low ionization timescale (n_e*t ~ 10^{11} s cm^-3) O, Ne, and Mg
component. To reproduce the strong Fe Kalpha line, it is necessary to include
additional Fe in a hot (> 2 keV), low ionization (n_e*t ~ 10^10.8 s cm^-3)
component. This hot Fe may be in the form of hot Fe bubbles, formed in the
radioactive decay of clumps of 56Ni. We find no radial variation in the
ionization timescales or temperatures of the various components. Rather, the Si
and S equivalent widths increase at large radii because these lines, as well as
those of Ar and Ca, are formed in a shell occupying the outer half of the
remnant. A shell of hot Fe is located interior to this, but there is a large
region of overlap between these two shells. In the inner 30% of the remnant,
there is a core of cooler, 1 keV Fe. We find that the distribution of the
ejecta and the yields of the intermediate mass species are consistent with
model prediction for Type Ia events.Comment: 34 pages, including 7 tables and 7 figures, Accepted by Ap
Biology and Conservation of Horseshoe Crabs
We dedicate this book to Drs. Carl N. Shuster, Jr. and Koichi Sekiguchi for their life-long contributions to the biology and conservation of the magnificent horseshoe crab
AN OVERVIEW OF THE CLASSIFICATION AND EVOLUTION OF THE MAJOR SCARAB BEETLE CLADES (COLEOPTERA: SCARABAEOIDEA) BASED ON PRELIMINARY MOLECULAR ANALYSES
We present a preliminary overview of our molecular phylogenetics research on the superfamily Scarabaeoidea. The molecular data consists of 28S ribosomal DNA sequences (mainly D2 and D3 expansion regions) for over 600 taxa and 18S ribosomal DNA sequences (mainly E17 to E35 expansion regions) for over 150 representative taxa within the lineages sampled. Based on our preliminary molecular phylogenetic results, Scarabaeoidea includes three major groups: 1) Geotrupidae, Passalidae, and Pleocomidae; 2) Lucanidae, Diphyllostomatidae, Trogidae, and Glaresidae; and 3) Hybosoridae, Ochodaeidae, Glaphyridae, and Scarabaeidae. The broad evolutionary patterns within the Scarabaeoidea are discussed with respect to phylogeny and evolution
Development and evaluation of a regression-based model to predict cesium-137 concentration ratios for saltwater fish
Development of a MassTag PCR Assay for the Syndromic Detection of Pathogens that can Cause Encephalitis
Direct and cross elasticities for freight distribution access charges
The interest in reform of road user charges for freight distribution in many countries continues unabated, linked to a desire to improve economic efficiency as well as recognition of the declining revenue base from traditional sources, especially fuel excise. A critical input into the assessment framework used to identify the impact of alternative access charges on freight vehicle utilisation, by vehicle class, is a suite of direct and cross elasticities. This paper uses data collected in Australia in 2010- 11 on alternative access charge regimes obtained from a stated choice experiment, used in estimation of mixed logit models calibrated on vehicle market shares, to derive matrices of direct and cross access charging elasticities that represent the relationship between an access charge (defined by combinations of distance, mass, and location), vehicle class choice, total kilometres, and tonne-kilometres carried in the vehicle class segments. The elasticities can be used to estimate the response of heavy vehicle operators (and shippers) to price signals under the different access charging schemes
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