4,341 research outputs found
Rapid Separable Analysis of Higher Order Correlators in Large Scale Structure
We present an efficient separable approach to the estimation and
reconstruction of the bispectrum and the trispectrum from observational (or
simulated) large scale structure data. This is developed from general CMB
(poly-)spectra methods which exploit the fact that the bispectrum and
trispectrum in the literature can be represented by a separable mode expansion
which converges rapidly (with terms). With an
effective grid resolution (number of particles/grid points
), we present a bispectrum estimator which requires only
operations, along with a
corresponding method for direct bispectrum reconstruction. This method is
extended to the trispectrum revealing an estimator which requires only operations. The complexity in
calculating the trispectrum in this method is now involved in the original
decomposition and orthogonalisation process which need only be performed once
for each model. However, for non-diagonal trispectra these processes present
little extra difficulty and may be performed in
operations. A discussion of how the methodology may be applied to the
quadspectrum is also given. An efficient algorithm for the generation of
arbitrary nonGaussian initial conditions for use in N-body codes using this
separable approach is described. This prescription allows for the production of
nonGaussian initial conditions for arbitrary bispectra and trispectra. A brief
outline of the key issues involved in parameter estimation, particularly in the
non-linear regime, is also given
Palliation and life quality in lung cancer; how good are clinicians at judging treatment outcome?
A recent trial by the MRC Lung Cancer Working Party used physician assessments to compare two palliative schedules of radiotherapy in lung cancer. A prospective study has been undertaken on a subset of these trial patients to see how physician assessments of symptomatic relief and general condition correlate with patient perception of therapeutic response. In 40 patients followed up monthly from presentation until close to death, good agreement was found between doctors and patients on change in specific physical symptoms and overall physical condition. Doctors were poor judges of life quality at presentation but appeared able to identify relative improvement or deterioration in overall quality of life. In conclusion, physician assessments may constitute valid end-points for radiotherapy trials comparing palliative schedules in lung cancer
The Mass Inflow Rate in the Barred Galaxy NGC 1530
Mass inflow in barred galaxies has been invoked to account for a wide variety
of phenomena, but until now direct evidence for inflow has been lacking. We
present Fabry-Perot H-alpha observations of the barred spiral galaxy NGC 1530
from which we determine velocities of the ionized gas for the entire region
swept by the bar. We compare the velocity field to models of gas flow in barred
spirals and show that it is well reproduced by ideal gas hydrodynamic models.
Inspection of the models and observations reveals that gas entering the bar
dust lanes streams directly down the dust lanes toward the 2 kpc radius nuclear
ring. The models predict that approximately 20% of the gas flowing down the
dust lane enters the nuclear ring; the remaining gas sprays around the ring to
the other bar dust lane. The fraction of the gas entering the ring is
relatively insensitive to the shape or size of the bar. Our observations of the
velocity field and dust optical depth yield a mass inflow rate into the nuclear
ring of 1 solar mass per year.Comment: 13 pages, 3 figures, aastex 4.0, accepted for publication in Ap J
Letter
Emerging Infections and Pregnancy
Immunologic changes of pregnancy may increase susceptibility to certain intracellular pathogens
Microscopic Surface Structure of Liquid Alkali Metals
We report an x-ray scattering study of the microscopic structure of the
surface of a liquid alkali metal. The bulk liquid structure factor of the
eutectic K67Na33 alloy is characteristic of an ideal mixture, and so shares the
properties of an elemental liquid alkali metal. Analysis of off-specular
diffuse scattering and specular x-ray reflectivity shows that the surface
roughness of the K-Na alloy follows simple capillary wave behavior with a
surface structure factor indicative of surface induced layering. Comparison of
thelow-angle tail of the K67Na33 surface structure factor with the one measured
for liquid Ga and In previously suggests that layering is less pronounced in
alkali metals. Controlled exposure of the liquid to H2 and O2 gas does not
affect the surface structure, indicating that oxide and hydride are not stable
at the liquid surface under these experimental conditions.Comment: 12 pages, 3 figures, published in Phys. Rev.
The suppression of superconductivity in MgCNi3 by Ni-site doping
The effects of partial substitution of Cu and Co for Ni in the intermetallic
perovskite superconductor MgCNi3 are reported. Calculation of the expected
electronic density of states suggests that electron (Cu) and hole (Co) doping
should have different effects. For MgCNi3-xCux, solubility of Cu is limited to
approximately 3% (x = 0.1), and Tc decreases systematically from 7K to 6K. For
MgCNi3-xCox, solubility of Co is much more extensive, but bulk
superconductivity disappears for Co doping of 1% (x = 0.03). No signature of
long range magnetic ordering is observed in the magnetic susceptibility of the
Co doped material.Comment: submitted, Solid State Communication
Tetrahedral Symmetry in Ground- and Low-Lying States of Exotic A ~ 110 Nuclei
Recent theoretical calculations predict a possible existence of nuclei with
tetrahedral symmetry: more precisely, the mean-field hamiltonians of such
nuclei are symmetric with respect to double point-group Td. In this paper, we
focus on the neutron-rich Zirconium isotopes as an example and present
realistic mean-field calculations which predict tetrahedral ground-state
configurations in 108,110Zr and low-lying excited states of tetrahedral
symmetry in a number of N > 66 isotopes. The motivations for focusing on these
nuclei, as well as a discussion of the possible experimental signatures of
tetrahedral symmetry are also presented.Comment: Accepted in Phys. Rev. C - Rapid Communication
- …