3,551 research outputs found
The Milky Way's stellar halo - lumpy or triaxial?
We present minimum chi-squared fits of power law and Hernquist density
profiles to F-turnoff stars in eight 2.5 deg wide stripes of SDSS data: five in
the North Galactic Cap and three in the South Galactic cap. Portions of the
stellar Galactic halo that are known to contain large streams of tidal debris
or other lumpy structure, or that may include significant contamination from
the thick disk, are avoided. The data strongly favor a model that is not
symmetric about the Galaxy's axis of rotation. If included as a free parameter,
the best fit to the center of the spheroid is surprisingly approx 3 kpc from
the Galactic center in the direction of the Sun's motion. The model fits favor
a low value of the density of halo stars at the solar position. The alternative
to a non-axisymmetric stellar distribution is that our fits are contaminated by
previously unidentified lumpy substructure.Comment: 10 pages, 10 figs, to appear in proceedings of conference "Physics at
the end of the Galactic Cosmic Ray Spectrum", Journal of Physics: Conf.
series, eds. G. Thomson and P. Sokolsk
Prepotentials for local mirror symmetry via Calabi-Yau fourfolds
In this paper, we first derive an intrinsic definition of classical triple
intersection numbers of K_S, where S is a complex toric surface, and use this
to compute the extended Picard-Fuchs system of K_S of our previous paper,
without making use of the instanton expansion. We then extend this formalism to
local fourfolds K_X, where X is a complex 3-fold. As a result, we are able to
fix the prepotential of local Calabi-Yau threefolds K_S up to polynomial terms
of degree 2. We then outline methods of extending the procedure to non
canonical bundle cases.Comment: 42 pages, 7 figures. Expanded, reorganized, and added a theoretical
background for the calculation
Shocked Quartz in Polymict Impact Breccia from the Upper Cretaceous Yallalie Impact Structure in Western Australia
Yallalie is a ~12 km diameter circular structure located ~200 km north of Perth, Australia. Previous studies have proposed that the buried structure is a complex impact crater based on geophysical data. Allochthonous breccia exposed near the structure has previously been interpreted as proximal impact ejecta; however, no diagnostic indicators of shock metamorphism have been found. Here we report multiple (27) shocked quartz grains containing planar fractures (PFs) and planar deformation features (PDFs) in the breccia. The PFs occur in up to five sets per grain, while the PDFs occur in up to four sets per grain. Universal stage measurements of all 27 shocked quartz grains confirms that the planar microstructures occur in known crystallographic orientations in quartz corresponding to shock compression from 5 to 20 GPa. Proximity to the buried structure (~4 km) and occurrence of shocked quartz indicates that the breccia represents either primary or reworked ejecta. Ejecta distribution simulated using iSALE hydrocode predicts the same distribution of shock levels at the site as those found in the breccia, which supports a primary ejecta interpretation, although local reworking cannot be excluded. The Yallalie impact event is stratigraphically constrained to have occurred in the interval from 89.8 to 83.6 Ma based on the occurrence of Coniacian clasts in the breccia and undisturbed overlying Santonian to Campanian sedimentary rocks. Yallalie is thus the first confirmed Upper Cretaceous impact structure in Australia
Far-Infrared Emission From E and E/S0 Galaxies
Studies of cold material through IRAS 60um and 100um observations indicated
that half of ordinary E and E/S0 galaxies were detected above the 3 sigma
level, indicating that cold gas is common, although no correlation was found
between the optical and far- infrared fluxes. Most detections were near the
instrumental threshold, and given an improved understanding of detection
confidence, we reconsider the 60um and 100um detection rate. After excluding
active galactic nuclei, peculiar systems, and background contamination, only 15
non-peculiar E and E/S0 galaxies from the RSA catalog are detected above the
98% confidence level, about 12% of the sample. An unusually high percentage of
these 15 galaxies possess cold gas (HI, CO) and optical emission lines
(Halpha), supporting the presence of gas cooler than 10E4 K. The 60um to 100um
flux ratios imply a median dust temperature for the sample of 30 K, with a
range of 23-38 K.
These detections define the upper envelope of the optical to far-infrared
relationship, F_fir propto F_B^0.24+/-0.08, showing that optically bright
objects are also brighter in the infrared, although with considerable
dispersion. A luminosity correlation is present with L_fir propto
L_B^1.65+/-0.28, but the dust temperature is uncorrelated with luminosity.
Models that contain large dust grains composed of amorphous carbon plus
silicates come close to reproducing the typical 60um to 100um flux ratios, the
far-infrared luminosity, and the L_fir - L_B relationship.Comment: 10 postscript pages, 2 tables, and 2 figure
Reasons for current E -cigarette use among U.S. adults
E-cigarette use has increased rapidly among U.S. adults. However, reasons for use among adults are unclear. We assessed reasons for e-cigarette use among a national sample of U.S. adults. Data were collected via online surveys among U.S. adults aged 18 or older from April through June 2014. Descriptive and multivariate regression analyses were conducted to assess reasons for e-cigarette use among 2448 current e-cigarette users, by sociodemographic characteristics and product type. Assessed reasons included cessation/health, consideration of others, convenience, cost, curiosity, flavoring, and simulation of conventional cigarettes. Among current e-cigarette users, 93% were also current cigarette smokers. The most common reasons for e-cigarette use were cessation/health (84.5%), consideration of others (71.5%), and convenience (56.7%). The prevalence of citing convenience (adjusted prevalence ratio [aPR] = 1.49) and curiosity (aPR = 1.54) as reasons for e-cigarette use were greater among current cigarette smokers than nonsmokers (P < 0.05). The prevalence of citing flavoring as a reason for use was greater among adults aged 18 to 24 (aPR = 2.02) than 55 or older (P < 0.05). Tank use was associated with greater prevalence of citing every assessed reason except convenience and curiosity. Cessation- and health-related factors are primary reasons cited for e-cigarette use among adults, and flavorings are more commonly cited by younger adults. Efforts are warranted to provide consumers with accurate information on the health effects of e-cigarettes and to ensure that flavoring and other unregulated features do not promote nicotine addiction, particularly among young adults
Reproductive Phenophases and Clutch Characteristics of Selected Arkansas Amphibians
Seasonal reproductive phenomena in 13 species of salamanders and 16 species of anurans from Arkansas were investigated. Most specimens were collected during a span of 6 years (1985-1990). Clutch characteristics, including mensural and meristic data, were determined from gravid females. In some species, the size of egg masses was also documented. Among the plethodontid salamanders, average clutch size (in parentheses) was greatest in Eurycea lucifuga (77.7) and smallest in Plethodon serratus (7.0). One of 2 ambystomatid salamanders (Ambystoma texanum) averaged 545.4 eggs per clutch; the other species (Ambystoma tigrinum) averaged 1 30.5. Siren intermedia nettingi (one of 3 large salamanders examined) had the greatest mean clutch size (851.3). Among anurans, Rana catesbeiana had the largest clutch size and mass (43,073 eggs and 55.9 g), whereas clutches of Acris crepitans blanchardi averaged the smallest (264.1 eggs and 0.1382 g). Multiple clutch production may be the rule in some amphibians (e.g., Desmognathus brimleyorum, A. c. blanchardi, Pseudacris triseriata feriarum, and P. streckeri streckeri); however, partial clutch deposition remains a possibility in these species. By knowing the synchrony between male and female reproductive cycles, a clarification of the onset, timing, and duration of reproductive phenophases (e.g., courtship, breeding, egg laying, etc.) was documented in many species
Production Quality Video Over Broadband Networks: A Description of the System and Two Interactive Applications
The Washington University MultiMedia eXplorer (MMX) is a complete, host-independent multimedia system capable of transmitting and receiving JPEG-compressed video, CD-quality audio, and high-resolution radiographic images over the Washington University broadband ATM network. If the host is equipped with an ATM interface card, normal network traffic can be supported via an ATM extension port on the MMX. The major components of the MMX are an ATMizer and three multimedia channels. The ATMizer implements the host interface, the interface to the ATM network, and hte interface to the three multimdeia channels. This paper describes the architecture of the MMX, the software used with the system, and two applications which have been developed to demonstrate the capability of broadband ATM networks for multimedia applications
Experimental stylo accessions produce higher yields than commercial pasture legume varieties on light textured soils in southern Queensland.
Pasture legumes are the best long-term option to increase productivity of grass pastures for large areas of Australia, however there are no commercially available, summer-growing legume varieties that are well adapted to sandy and loamy textured soils in the frost prone sub-tropics. A recently completed eight-year project collected 40 accessions of legumes from old pasture evaluation trial sites that were sown more than 20 years ago, as well as two roadside locations. These accessions were compared to 10 commercial varieties and three previously shortlisted accessions across six trial sites (three districts and two soil types) in southern Queensland between 2016 – 2019, during drought years. The five highest yielding accessions of stylos were
from two species (Stylosanthes scabra and S. seabrana) and had 39 – 67% higher yields than the best performing commercial variety when averaged across all trials. These accessions also had good disease tolerance and formed effective nodules with commercial rhizobia. The five highest yielding accessions have been shortlisted for release as new varieties due to their potential to significantly improve productivity for the grazing industries in the sub-tropics of Australia
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