1,562 research outputs found
Constraining multiple systems with GAIA
GAIA will provide observations of some multiple asteroid and dwarf systems.
These observations are a way to determine and improve the quantification of
dynamical parameters, such as the masses and the gravity fields, in these
multiple systems. Here we investigate this problem in the cases of Pluto's and
Eugenia's system. We simulate observations reproducing an approximate planning
of the GAIA observations for both systems, as well as the New Horizons
observations of Pluto. We have developed a numerical model reproducing the
specific behavior of multiple asteroid system around the Sun and fit it to the
simulated observations using least-square method, giving the uncertainties on
the fitted parameters. We found that GAIA will improve significantly the
precision of Pluto's and Charon's mass, as well as Petit Prince's orbital
elements and Eugenia's polar oblateness.Comment: 5 pages, accepted by Planetary and Space Science, Gaia GREAT-SSO-Pis
Uncertainties in determining parton distributions at large x
We critically examine uncertainties in parton distribution functions (PDFs)
at large x arising from nuclear effects in deuterium F2 structure function
data. Within a global PDF analysis, we assess the impact on the PDFs from
uncertainties in the deuteron wave function at short distances and nucleon
off-shell effects, the use of relativistic kinematics, as well as the use of
less a restrictive parametrization of the d/u ratio. We find that in particular
the d-quark and gluon PDFs vary significantly with the choice of nuclear model.
We highlight the impact of these uncertainties on the determination of the
neutron structure function, and on W boson production and parton luminosity at
the Tevatron and the LHC. Finally, we discuss prospects for new measurements
sensitive to the d-quark and gluon distributions but insensitive to nuclear
corrections.Comment: 37 pages, 13 figures. Final published versio
New parton distributions from large-x and low-Q^2 data
We report results of a new global next-to-leading order fit of parton
distribution functions in which cuts on W and Q are relaxed, thereby including
more data at high values of x. Effects of target mass corrections (TMCs),
higher twist contributions, and nuclear corrections for deuterium data are
significant in the large-x region. The leading twist parton distributions are
found to be stable to TMC model variations as long as higher twist
contributions are also included. The behavior of the d quark as x-->1 is
particularly sensitive to the deuterium corrections, and using realistic
nuclear smearing models the d-quark distribution at large x is found to be
softer than in previous fits performed with more restrictive cuts.Comment: 31 pages, 8 figures. Minor corrections. References added. To appear
in Phys.Rev.
The scale and persistence of soil moisture anomalies as simulated in a global model
Short term variability of climate is intimately connected with soil moisture variability. Soil moisture provides the storage and subsequent return to the atmosphere, through evaporation and transpiration, of precipitation anomalies over land. Global Circulation Model (GCM) simulations enable consistent identification of correlations and dynamical connections between the hydrologic variables, many of which are incompletely observed. One way to facilitate understanding with these increasingly intricate models is to perform sensitivity studies in which a boundary condition or process is prescribed. In this study we will report on a sensitivity study in which a GCM with a sophisticated land surface representation is used to investigate soil moisture variability in the model climate. The simulations to be used in this study were made at R15 resolution (approximately 4.5 deg latitude x 7.5 deg longitude) with prescribed sea surface temperatures (SST) in the GENESIS model (Thompson and Pollard, 1994), which is coupled to a Land Surface Transfer model (LSX) at 2 deg x 2 deg resolution (Pollard and Thompson, 1994). All the results represented here were taken from the monthly averages of the model results. The LSX model accounts for the physical effects of vegetation with two layers specified at each grid point. Vegetation attributes such as leaf area indices, fractional cover, leaf albedos, etc., were taken from the global dataset in Dorman and Sellers (1989). A six-layer soil model extends from the surface to 4.25 m depth. SST's were prescribed in two ten year experiments using monthly SST values with the daily value being interpolated from the nearest two months. In the first experiment monthly climatological values were used, and in the second, the Atmospheric Model Intercomparison Project (AMIP) observed SST's for the years 1979 through 1988 were used (Gates, 1992). Thus, the former experiment gives a measure of the intrinsic model variability, to be compared with that of the latter experiment, which includes month-to-month variability due to ocean forcing
The role of anticipated regret and health beliefs in HPV vaccination intentions among young adults
Although cognitions have predicted young adults' human papillomavirus (HPV) vaccine decision-making, emotion-based theories of healthcare decision-making suggest that anticipatory emotions may be more predictive. This study examined whether anticipated regret was associated with young adults' intentions to receive the HPV vaccine above and beyond the effects of commonly studied cognitions. Unvaccinated undergraduates (N = 233) completed a survey assessing Health Belief Model (HBM) variables (i.e., perceived severity of HPV-related diseases, perceived risk of developing these diseases, and perceived benefits of HPV vaccination), anticipatory emotions (i.e., anticipated regret if one were unvaccinated and later developed genital warts or HPV-related cancer), and HPV vaccine intentions. Anticipated regret was associated with HPV vaccine intentions above and beyond the effects of HBM variables among men. Among women, neither anticipated regret nor HBM variables showed consistent associations with HPV vaccine intentions. Findings suggest that anticipatory emotions should be considered when designing interventions to increase HPV vaccination among college men
A Preference for a Sexual Signal Keeps Females Safe
Predation is generally thought to constrain sexual selection by female choice and limit the evolution of conspicuous sexual signals. Under high predation risk, females usually become less choosy, because they reduce their exposure to their predators by reducing the extent of their mate searching. However, predation need not weaken sexual selection if, under high predation risk, females exhibit stronger preferences for males that use conspicuous signals that help females avoid their predators. We tested this prediction in the fiddler crab Uca terpsichores by increasing females' perceived predation risk from crab-eating birds and measuring the attractiveness of a courtship signal that females use to find mates. The sexual signal is an arching mound of sand that males build at the openings of their burrows to which they attract females for mating. We found that the greater the risk, the more attractive were males with those structures. The benefits of mate preferences for sexual signals are usually thought to be linked to males' reproductive contributions to females or their young. Our study provides the first evidence that a female preference for a sexual signal can yield direct survival benefits by keeping females safe as they search for mates
Transcriptional profiling reveals extraordinary diversity among skeletal muscle tissues
Skeletal muscle comprises a family of diverse tissues with highly specialized functions. Many acquired diseases, including HIV and COPD, affect specific muscles while sparing others. Even monogenic muscular dystrophies selectively affect certain muscle groups. These observations suggest that factors intrinsic to muscle tissues influence their resistance to disease. Nevertheless, most studies have not addressed transcriptional diversity among skeletal muscles. Here we use RNAseq to profile mRNA expression in skeletal, smooth, and cardiac muscle tissues from mice and rats. Our data set, MuscleDB, reveals extensive transcriptional diversity, with greater than 50% of transcripts differentially expressed among skeletal muscle tissues. We detect mRNA expression of hundreds of putative myokines that may underlie the endocrine functions of skeletal muscle. We identify candidate genes that may drive tissue specialization, including Smarca4, Vegfa, and Myostatin. By demonstrating the intrinsic diversity of skeletal muscles, these data provide a resource for studying the mechanisms of tissue specialization
A precise extraction of the induced polarization in the 4He(e,e'p)3H reaction
We measured with unprecedented precision the induced polarization Py in
4He(e,e'p)3H at Q^2 = 0.8 (GeV/c)^2 and 1.3 (GeV/c)^2. The induced polarization
is indicative of reaction-mechanism effects beyond the impulse approximation.
Our results are in agreement with a relativistic distorted-wave impulse
approximation calculation but are over-estimated by a calculation with strong
charge-exchange effects. Our data are used to constrain the strength of the
spin independent charge-exchange term in the latter calculation.Comment: submitted to Physical Review Letter
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