861 research outputs found
South Atlantic response to El Niño–Southern Oscillation induced climate variability in an ocean general circulation model
[1] The response of the South Atlantic Ocean to El Niño-Southern Oscillation (ENSO) is investigated by means of an ocean general circulation model (ORCA2) forced with National Centers for Environmental Prediction (NCEP) reanalyses for the 1948–1999 period. Seasonal ENSO composites suggest that the ENSO-induced wind anomalies play a major role in driving upper ocean temperatures by altering the net surface heat fluxes, the meridional Ekman heat transport, and Ekman pumping. Model diagnostics indicate that the Ekman heat transport changes are in better agreement with the upper ocean temperature anomalies during the first half of the ENSO event whereas, in the latter half, the surface heat flux anomalies agree better. In general, the atmospheric forcing tends to lead to a coherent ocean response with a time lag of about one season. Subsurface temperatures evolve more slowly in response to ENSO forcing than the upper ocean. They receive time-filtered ENSO signals from mainly Ekman pumping (suction) and variations in thermocline depth that result in the poleward and equatorward margins of the subtropical gyre exhibiting temperature anomalies of the same sign but opposite to those in the central regions of the gyre
Peculiar Velocities of Galaxy Clusters
We investigate the peculiar velocities predicted for galaxy clusters by
theories in the cold dark matter family. A widely used hypothesis identifies
rich clusters with high peaks of a suitably smoothed version of the linear
density fluctuation field. Their peculiar velocities are then obtained by
extrapolating the similarly smoothed linear peculiar velocities at the
positions of these peaks. We test these ideas using large high resolution
N-body simulations carried out within the Virgo supercomputing consortium. We
find that at early times the barycentre of the material which ends up in a rich
cluster is generally very close to a high peak of the initial density field.
Furthermore the mean peculiar velocity of this material agrees well with the
linear value at the peak. The late-time growth of peculiar velocities is,
however, systematically underestimated by linear theory. At the time clusters
are identified we find their rms peculiar velocity to be about 40% larger than
predicted. Nonlinear effects are particularly important in superclusters. These
systematics must be borne in mind when using cluster peculiar velocities to
estimate the parameter combination .Comment: 8 pages, 4 figures; submitted to MNRA
Physical Activity/Exercise and Diabetes: A Position Statement of the American Diabetes Association
The adoption and maintenance of physical activity are critical foci for blood glucose management and overall health in individuals with diabetes and prediabetes. Recommendations and precautions vary depending on individual characteristics and health status. In this Position Statement, we provide a clinically oriented review and evidence-based recommendations regarding physical activity and exercise in people with type 1 diabetes, type 2 diabetes, gestational diabetes mellitus, and prediabetes. Physical activity includes all movement that increases energy use, whereas exercise is planned, structured physical activity. Exercise improves blood glucose control in type 2 diabetes, reduces cardiovascular risk factors, contributes to weight loss, and improves well-being (1,2). Regular exercise may prevent or delay type 2 diabetes development (3). Regular exercise also has considerable health benefits for people with type 1 diabetes (e.g., improved cardiovascular fitness, muscle strength, insulin sensitivity, etc.) (4). The challenges related to blood glucose management vary with diabetes type, activity type, and presence of diabetes-related complications (5,6). Physical activity and exercise recommendations, therefore, should be tailored to meet the specific needs of each individual
Direct cosmological simulations of the growth of black holes and galaxies
We investigate the coupled formation and evolution of galaxies and their
embedded supermassive black holes using state-of-the-art hydrodynamic
simulations of cosmological structure formation. For the first time, we
self-consistently follow the dark matter dynamics, radiative gas cooling, star
formation, as well as black hole growth and associated feedback processes,
starting directly from initial conditions appropriate for the LambdaCDM
cosmology. Our modeling of the black hole physics is based on an approach we
have developed in simulations of isolated galaxy mergers. Here we examine: (i)
the predicted global history of black hole mass assembly (ii) the evolution of
the local black hole-host mass correlations and (iii) the conditions that allow
rapid growth of the first quasars, and the properties of their hosts and
descendants today. We find a total black hole mass density in good agreement
with observational estimates. The black hole accretion rate density peaks at
lower redshift and evolves more strongly at high redshift than the star
formation rate density, but the ratio of black hole to stellar mass densities
shows only a moderate evolution at low redshifts. We find strong correlations
between black hole masses and properties of the stellar systems, agreeing well
with the measured local M_BH-sigma and M_BH -M_* relationships, but also
suggesting (dependent on the mass range) a weak evolution with redshift in the
normalization and the slope. Our simulations also produce massive black holes
at high redshift, due to extended periods of exponential growth in regions that
collapse early and exhibit strong gas inflows. These first supermassive BH
systems however are not necessarily the most massive ones today, since they are
often overtaken in growth by quasars that form later. (abridged)Comment: 22 pages, 17 figures, submitted to Ap
Measurement of Spin Correlation Parameters A, A, and A_ at 2.1 GeV in Proton-Proton Elastic Scattering
At the Cooler Synchrotron COSY/J\"ulich spin correlation parameters in
elastic proton-proton (pp) scattering have been measured with a 2.11 GeV
polarized proton beam and a polarized hydrogen atomic beam target. We report
results for A, A, and A_ for c.m. scattering angles between
30 and 90. Our data on A -- the first measurement of this
observable above 800 MeV -- clearly disagrees with predictions of available of
pp scattering phase shift solutions while A and A_ are reproduced
reasonably well. We show that in the direct reconstruction of the scattering
amplitudes from the body of available pp elastic scattering data at 2.1 GeV the
number of possible solutions is considerably reduced.Comment: 4 pages, 4 figure
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