407 research outputs found
The impact of correlated projections on weak lensing cluster counts
Large-scale structure projections are an obstacle in converting the shear
signal of clusters detected in weak-lensing maps into virial masses. However,
this step is not necessary for constraining cosmology with the shear-peak
abundance, if we are able to predict its amplitude. We generate a large
ensemble of N-body simulations spanning four cosmological models, with total
volume V~1 (Gpc/h)^3 per model. Variations to the matter density parameter and
amplitude of fluctuations are considered. We measure the abundance of peaks in
the mass density projected in ~100 Mpc/h slabs to determine the impact of
structures spatially correlated with the simulation clusters, identified by the
3D friends-of-friends algorithm. The halo model shows that the choice of the
smoothing filter for the density field is important in reducing the
contribution of correlated projections to individual halo masses. Such
contributions are less than 2% in the case of the optimal, compensated filter
used throughout this analysis. We measure the change in the mass of peaks when
projected in slabs of various thicknesses. Peaks in slabs of 26 Mpc/h and 102
Mpc/h suffer an average mass change of less than 2% compared to their mass in
slabs of 51 Mpc/h. We then explore the cosmology dependence of the
projected-peak mass function, and find that, for a wide range of slab
thicknesses (<500 Mpc/h), it scales with cosmology in exactly the same way as
the 3D friends-of-friends mass function and the Sheth-Tormen formula. This
extends the earlier result of Marian et al. (2009). Finally, we show that for
all cosmological models considered, the low and intermediate mass bins of the
peak abundance can be described using a modified Sheth-Tormen functional form
to within 10%-20% accuracy.Comment: 19 pages, 14 figures, accepted for publication in the Astrophysical
Journa
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A Comparison of Two Types of Home Project Report Forms
The purpose of the present study is to compare two forms of home project reports and to determine the preferred form
Ring Current Development During Storm Main Phase
The development of the ring current ions in the inner magnetosphere during the main phase of a magnetic storm is studied. The temporal and spatial evolution of the ion phase space densities in a dipole field are calculated using a three dimensional ring current model, considering charge exchange and Coulomb losses along drift paths. The simulation starts with a quiet time distribution. The model is tested by comparing calculated ion fluxes with Active Magnetospheric Particle Tracer Explorers/CCE measurement during the storm main phase on May 2, 1986. Most of the calculated omnidirectional fluxes are in good agreement with the data except on the dayside inner edge (L less than 2.5) of the ring current, where the ion fluxes are underestimated. The model also reproduces the measured pitch angle distributions of ions with energies below 10 keV. At higher energy, an additional diffusion in pitch angle is necessary in order to fit the data. The role of the induced electric field on the ring current dynamics is also examined by simulating a series of substorm activities represented by stretching and collapsing the magnetic field lines. In response to the impulsively changing fields, the calculated ion energy content fluctuates about a mean value that grows steadily with the enhanced quiescent field
How particles emerge from decaying classical fields in heavy ion collisions: towards a kinetic description of the Glasma
We develop the formalism discussed previously in hep-ph/0601209 and
hep-ph/0605246 to construct a kinetic theory that provides insight into the
earliest ``Glasma'' stage of a high energy heavy ion collision. Particles
produced from the decay of classical fields in the Glasma obey a Boltzmann
equation whose novel features include an inhomogeneous source term and new
contributions to the collision term. We discuss the power counting associated
with the different terms in the Boltzmann equation and outline the transition
from the field dominated regime to the particle dominated regime in high energy
heavy ion collisions.Comment: 29 pages, 16 postscript figures, some typos correcte
Successive Solar Flares and Coronal Mass Ejections on 2005 September 13 from Noaa Ar 10808
We present a multiwavelength study of the 2005 September 13 eruption from
NOAA 10808 that produced total four flares and two fast coronal mass ejections
(CMEs) within 1.5 hours. Our primary attention is paid to the fact that these
eruptions occurred in close succession in time, and that all of them were
located along an S-shaped magnetic polarity inversion line (PIL) of the active
region. In our analysis, (1) the disturbance created by the first flare
propagated southward along the PIL to cause a major filament eruption that led
to the first CME and the associated second flare underneath. (2) The first CME
partially removed the overlying magnetic fields over the northern Delta spot to
allow the third flare and the second CME. (3) The ribbon separation during the
fourth flare would indicate reclosing of the overlying field lines opened by
the second CME. It is thus concluded that this series of flares and CMEs are
interrelated to each other via magnetic reconnections between the expanding
magnetic structure and the nearby magnetic fields. These results complement
previous works made on this event with the suggested causal relationship among
the successive eruptions.Comment: 11 pages, 8 figures, 2 tables, accepted to The Astrophysical Journa
Entanglement between motional states of a single trapped ion and light
We propose a generation method of Bell-type states involving light and the
vibrational motion of a single trapped ion. The trap itself is supposed to be
placed inside a high- cavity sustaining a single mode, quantized
electromagnetic field. Entangled light-motional states may be readily generated
if a conditional measurement of the ion's internal electronic state is made
after an appropriate interaction time and a suitable preparation of the initial
state. We show that all four Bell states may be generated using different
motional sidebands (either blue or red), as well as adequate ionic relative
phases.Comment: 4 pages, LaTe
Bjorken Flow, Plasma Instabilities, and Thermalization
At asymptotically high energies, thermalization in heavy ion collisions can
be described via weak-coupling QCD. We present a complete treatment of how
thermalization proceeds, at the parametric weak-coupling level. We show that
plasma instabilities dominate the dynamics, from immediately after the
collision until well after the plasma becomes nearly in equilibrium. Initially
they drive the system close to isotropy, but Bjorken expansion and increasing
diluteness makes the system again become more anisotropic. At time \tau ~
\alpha^(-12/5) Q^(-1) the dynamics become dominated by a nearly-thermal bath;
and at time \tau ~ \alpha^(-5/2) Q^(-1)$ the bath comes to dominate the energy
density, completing thermalization. After this time there is a nearly isotropic
and thermal Quark-Gluon Plasma.Comment: 22 pages, 5 figure
QCD Plasma Instabilities and Isotropization
We study the coupled Wong Yang-Mills equations for both U(1) and SU(2) gauge
groups and anisotropic particle momentum distributions numerically on a
lattice. For weak fields with initial energy density much smaller than that of
the particles we confirm the existence of plasma instabilities and exponential
growth of the fields which has been discussed previously. Also, the SU(2) case
is qualitatively similar to U(1), and we do find strong ``abelianization'' of
the non-Abelian fields during the period of exponential growth. However, the
effect nearly disappears when the fields are strong. This is because of the
very rapid isotropization of the particle momenta by deflection in a strong
field on time scales comparable to that for the development of Yang-Mills
instabilities. This happens without entropy production which makes it very
interesting for the phenomenology of high-energy heavy-ion collisions.Comment: version3: 8 pages, 9 figures, revised discussion of entropy
production, a few additional references, supplement: 3 figures showing the
dependence on the lattice spacing and on the number of test-particles; to
appear in PL
Prophylactic antibiotics in the prevention of infection after operative vaginal delivery (ANODE): a multicentre randomised controlled trial
Background Risk factors for maternal infection are clearly recognised, including caesarean section and operative vaginal birth. Antibiotic prophylaxis at caesarean section is widely recommended because there is clear systematic review evidence that it reduces incidence of maternal infection. Current WHO guidelines do not recommend routine antibiotic prophylaxis for women undergoing operative vaginal birth because of insufficient evidence of effectiveness. We aimed to investigate whether antibiotic prophylaxis prevented maternal infection after operative vaginal birth. Methods In a blinded, randomised controlled trial done at 27 UK obstetric units, women (aged ≥16 years) were allocated to receive a single dose of intravenous amoxicillin and clavulanic acid or placebo (saline) following operative vaginal birth at 36 weeks gestation or later. The primary outcome was confirmed or suspected maternal infection within 6 weeks of delivery defined by a new prescription of antibiotics for specific indications, confirmed systemic infection on culture, or endometritis. We did an intention-to-treat analysis. This trial is registered with ISRCTN, number 11166984, and is closed to accrual. Findings Between March 13, 2016, and June 13, 2018, 3427 women were randomly assigned to treatment: 1719 to amoxicillin and clavulanic acid, and 1708 to placebo. Seven women withdrew, leaving 1715 in the amoxicillin and clavulanic acid group and 1705 in the placebo groups. Primary outcome data were missing for 195 (6%) women. Significantly fewer women allocated to amoxicillin and clavulanic acid had a confirmed or suspected infection (180 [11%] of 1619) than women allocated to placebo (306 [19%] of 1606; risk ratio 0·58, 95% CI 0·49–0·69; p<0·0001). One woman in the placebo group reported a skin rash and two women in the amoxicillin and clavulanic acid reported other allergic reactions, one of which was reported as a serious adverse event. Two other serious adverse events were reported, neither was considered causally related to the treatment. Interpretation This trial shows benefit of a single dose of prophylactic antibiotic after operative vaginal birth and guidance from WHO and other national organisations should be changed to reflect this
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