982 research outputs found
Testing Bekenstein's Relativistic MOND gravity with Lensing Data
We propose to use multiple-imaged gravitational lenses to set limits on
gravity theories without dark matter, specificly TeVeS (Bekenstein 2004), a
theory which is consistent with fundamental relativistic principles and the
phenomenology of MOdified Newtonian Dynamics (MOND) theory. After setting the
framework for lensing and cosmology, we derive analytically the deflection
angle for the point lens and the Hernquist galaxy profile, and fit
galaxy-quasar lenses in the CASTLES sample. We do this with three methods,
fitting the observed Einstein ring sizes, the image positions, or the flux
ratios. In all cases we consistently find that stars in galaxies in MOND/TeVeS
provide adequate lensing. Bekenstein's toy function provides more
efficient lensing than the standard MOND function. But for a handful of
lenses [indicated in Table 2,3, fig 16] a good fit would require a lens mass
orders of magnitude larger/smaller than the stellar mass derived from
luminosity unless the modification function and modification scale
for the universal gravity were allowed to be very different from what spiral
galaxy rotation curves normally imply. We discuss the limitation of present
data and summarize constraints on the MOND function. We also show that
the simplest TeVeS "minimal-matter" cosmology, a baryonic universe with a
cosmological constant, can fit the distance-redshift relation from the
supernova data, but underpredicts the sound horizon size at the last
scattering. We conclude that lensing is a promising approach to differentiate
laws of gravity (see also astro-ph/0512425).Comment: reduced to 17p, 16 figs, discussed cosmology and constraints on
mu-function, MNRAS accepte
Factors associated with mortality in patients with tuberculosis
<p>Abstract</p> <p>Background</p> <p>Known risk factors for death following a diagnosis of tuberculosis may not be applicable to current U.S. cases. We evaluated the factors associated with all-cause mortality in patients with tuberculosis in Washington State.</p> <p>Methods</p> <p>Using data from the Tuberculosis Information Management System of Washington State, we conducted a cohort study of all residents diagnosed with tuberculosis from 1993 through 2005. Death from any cause was ascertained through the Washington State Death Certificate Data Files. Proportional hazards models were used to estimate the independent effect on all-cause mortality of demographic, clinical, and behavioral characteristics.</p> <p>Results</p> <p>During a median follow-up of 6 years in 3451 patients treated for tuberculosis, there were 417 deaths. Mortality was independently associated with increasing age, male gender, HIV-coinfection, and U.S. birth. Within 1 year of tuberculosis diagnosis, treatment by a private provider and the use of directly observed therapy were also independently associated with increased mortality. In addition, an interaction term of private provider times directly observed therapy was also significantly associated with mortality.</p> <p>Conclusions</p> <p>We identified factors independently associated with increased all-cause mortality following a diagnosis of tuberculosis. The associations between mortality and provider type should be evaluated with more thorough adjustment for severity of illness, but suggest important directions for future research.</p
Continuum and CO/HCO+ Emission from the Disk Around the T Tauri Star LkCa 15
We present OVRO Millimeter Array lambda = 3.4 - 1.2 mm dust continuum and
spectral line observations of the accretion disk encircling the T Tauri star
LkCa 15. The 1.2 mm dust continuum emission is resolved, and gives a minimum
diameter of 190 AU and an inclination angle of 57+/-5 degrees. There is a
noticeable, but at present poorly constrained, decrease in the continuum
spectral slope with frequency that may result from the coupled processes of
grain growth and dust settling. Imaging of the fairly intense emission from the
lowest rotational transitions of CO, 13CO and HCO+ reveals a rotating disk and
emission extends to 750 AU and the characteristic radius of the disk is
determined to be around 425 AU (HWHM) based on model fits to the CO velocity
field. The disk mass derived from the CO isotopologues with ``typical'' dense
cloud abundances is still nearly two orders of magnitude less than that
inferred from the dust emission, which is probably due to extensive molecular
depletion in the cold, dense disk midplane. N2H+ 1-0 emission has also been
detected which, along with HCO+, sets a lower limit to the fractional
ionization of 10^{-8} in the near-surface regions of protoplanetary disks. This
first detection of N2H+ in circumstellar disks has also made possible a
determination of the N2/CO ratio (~2) that is at least an order of magnitude
larger than those in the envelopes of young stellar objects and dense clouds.
The large N2/CO ratio indicates that our observations probe disk layers in
which CO is depleted but some N2 remains in the gas phase. Such differential
depletion can lead to large variations in the fractional ionization with height
in the outer reaches of circumstellar disks, and may help to explain the
relative nitrogen deficiency observed in comets.Comment: Submitted to ApJ, 28 pages, 7 figure
Evaluating the Benefits of Restricted Grazing to Protect Wet Pasture Soils in Two Dairy Regions of New Zealand
Many dairy farms in the Manawatu and Southland regions of New Zealand have poorly drained soils that are prone to treading damage, an undesirable outcome on grazed pastures during the wetter months of the year. Removing cows to a stand-off pad during wet conditions can reduce damage, but incurs costs. The objective of this study was to evaluate the impact of different levels of restricted grazing (from 0 to 10 hours grazing time/day for lactating cows) on pasture yield, damage and wastage, feed and stand-off expenses, and farm operating profit. A simulated farm from each region was used in a farm systems model. This model simulated pasture-cow-management interactions, using site-specific climate data as inputs for the soil-pasture sub-models. Days to recover previous yield potential for damaged paddocks can vary widely. A sensitivity analysis (40 to 200 days to recover) was conducted to evaluate the effect of this parameter on results. Full protection when there is risk of damage (0 grazing hours/day) appeared to be less profitable compared with some level of grazing, because the advantages of reduced damage were outweighed by the disadvantages of managing infrequently grazed pastures. The differences in operating profit between full protection and some level of grazing became less as the recovery time increased, but for both regions grazing durations of 6-8 hours/day when a risk of damage is present appeared to be a sensible strategy irrespective of recovery time
IMOST: A database for non-marine ostracods in the Iberian Peninsula, the Balearic Islands and Macaronesia
Ostracods are common microcrustaceans in inland waters, widely used as (palaeo-) environmental indicators. Information on their species distribution worldwide is extremely fragmentary, and usually biased towards some regions, hampering attaining a general view of their biogeography. The Iberian Peninsula, the Balearic Islands and Macaronesia are considered biodiversity hotspots as part of the Mediterranean Region, whose non-marine ostracod fauna was reviewed in the 1990s accounting for 88 species. Most of these data were included in the NODE database (Non-marine Ostracod Distribution in Europe). Here, we present IMOST (Ibero-Balearic and Macaronesian OSTracod database), a non-marine ostracod database for the Iberian Peninsula and the Balearic and Macaronesian islands, incorporating data included in NODE plus many new records from recently published studies and new unpublished observations. Our database stores data in separated and standardised spreadsheets, one for each data source. Moreover, the database also offers updated, reviewed and accurate coordinates of the cited occurrence and taxonomic identification. According to the data compiled in IMOST, we updated the list of non-marine ostracods in the studied region from 88 to 118 species. Nevertheless, we expect that the actual number of species for the included regions should be higher, considering other Mediterranean countries with smaller areas but more extensive surveys (e.g. 152 species in Italy). The updated database is instrumental for our understanding of the biodiversity and biogeographic patterns of these organisms in this hotspot, as well as for analysing their species-environment relationships in a context of global change
3,7,7a-Tri-epi-casuarine pentaacetate
The relative stereochemistry at six contiguous centres in an analogue of the natural product casuarine, viz. 3,7,7a-tri-epi-casuarine pentaacetate, C18H25NO10, has been established by an analysis of a crystalline pentaacetate. © 2006 International Union of Crystallography All rights reserved
Probable detection of starlight reflected from the giant exoplanet orbiting tau Bootis
Giant planets orbiting stars other than the Sun are clearly detectable
through precise radial-velocity measurements of the orbital reflex motion of
the parent star. In the four years since the discovery of the companion to the
star 51 Peg, similar low-amplitude ``Doppler star wobbles'' have revealed the
presence of some 20 planets orbiting nearby solar-type stars. Several of these
newly-discovered planets are very close to their parent stars, in orbits with
periods of only a few days. Being an indirect technique, however, the
reflex-velocity method has little to say about the sizes or compositions of the
planets, and can only place lower limits on their masses. Here we report the
use of high-resolution optical spectroscopy to achieve a probable detection of
the Doppler-shifted signature of starlight reflected from one of these objects,
the giant exoplanet orbiting the star tau Bootis. Our data give the planet's
orbital inclination i=29 degrees, indicating that its mass is some 8 times that
of Jupiter, and suggest strongly that the planet has the size and reflectivity
expected for a gas-giant planet.Comment: 15 pages, 4 figures. (Fig 1 and equation for epsilon on p1 para 2
revised; changed from double to single spacing
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