7,329 research outputs found
Thunderstorm/environment interactions that affect subsequent convection
Mesoscale kinematics and thermodynamics of severe thunderstorm-baroclinic zone interactions, and the development and evolution of mesoscale pressure systems associated with strong convective storms, are being studied in an ongoing research project
The environments of intermediate-redshift QSOs: 0.3 < z < 0.7
An angular correlation of low significance (2 sigma) is observed between 0.3
< z < 0.5 QSOs and V < 23 galaxies. Overall, the cross-correlation function
between 82 intermediate-redshift (0.3 < z < 0.7), X-ray selected QSOs and V <
24 galaxies is investigated, but no signal is detected for the z > 0.5 QSOs.
After converting to an excess of galaxies physically associated with the QSO,
this lack of strong correlation is shown to be consistent with the clustering
of normal galaxies at the same moderate redshifts. Combined with previous
observations, these results imply that the environments of radio-quiet QSOs do
not undergo significant evolution with respect to the galaxy population over a
wide range of redshifts (0 < z < 1.5). This is in marked contrast to the rapid
increase in the richness of the environments associated with radio-loud QSOs
over the same redshift range.Comment: 12 pages, 8 figures, MNRAS TeX macro, to appear to MNRA
Angular correlations between LBQS and APM: Weak Lensing by the Large Scale Structure
We detect a positive angular correlation between bright, high-redshift QSOs
and foreground galaxies. The QSOs are taken from the optically selected LBQS
Catalogue, while the galaxies are from the APM Survey. The correlation
amplitude is about a few percent on angular scales of over a degree. It is a
function of QSO redshift and apparent magnitude, in a way expected from weak
lensing, and inconsistent with QSO-galaxy correlations being caused by physical
associations, or uneven obscuration by Galactic dust. The correlations are
ascribed to the weak lensing effect of the foreground dark matter, which is
traced by the APM galaxies. The amplitude of the effect found here is compared
to the analytical predictions from the literature, and to the predictions of a
phenomenological model, which is based on the observed counts-in-cells
distribution of APM galaxies. While the latter agree reasonably well with the
analytical predictions (namely those of Dolag & Bartelmann 1997, and Sanz et
al. 1997), both under-predict the observed correlation amplitude on degree
angular scales. We consider the possible ways to reconcile these observations
with theory, and discuss the implications these observations have on some
aspects of extragalactic astronomy.Comment: 9 pages; MNRAS, in pres
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A casein kinase 1 prevents expulsion of the oocyte meiotic spindle into a polar body by regulating cortical contractility.
During female meiosis, haploid eggs are generated from diploid oocytes. This reduction in chromosome number occurs through two highly asymmetric cell divisions, resulting in one large egg and two small polar bodies. Unlike mitosis, where an actomyosin contractile ring forms between the sets of segregating chromosomes, the meiotic contractile ring forms on the cortex adjacent to one spindle pole, then ingresses down the length of the spindle to position itself at the exact midpoint between the two sets of segregating chromosomes. Depletion of casein kinase 1 gamma (CSNK-1) in Caenorhabditis elegans led to the formation of large polar bodies that contain all maternal DNA, because the contractile ring ingressed past the spindle midpoint. Depletion of CSNK-1 also resulted in the formation of deep membrane invaginations during meiosis, suggesting an effect on cortical myosin. Both myosin and anillin assemble into dynamic rho-dependent cortical patches that rapidly disassemble in wild-type embryos. CSNK-1 was required for disassembly of both myosin patches and anillin patches. Disassembly of anillin patches was myosin independent, suggesting that CSNK-1 prevents expulsion of the entire meiotic spindle into a polar body by negatively regulating the rho pathway rather than through direct inhibition of myosin
The Environment of HII Galaxies revisited
We present a study of the close (< 200 kpc) environment of 110 relatively
local (z< 0.16) HII galaxies, selected from the Sloan Digital Sky Survey (SDSS;
DR7). We use available spectroscopic and photometric redshifts in order to
investigate the presence of a close and possibly interacting companion galaxy.
Our aim is to compare the physical properties of isolated and interacting HII
galaxies and investigate possible systematic effects in their use as
cosmological probes. We find that interacting HII galaxies tend to be more
compact, less luminous and have a lower velocity dispersion than isolated ones,
in agreement with previous studies on smaller samples. However, as we verified,
these environmental differences do not affect the cosmologically important
L_{H{\beta}}-{\sigma} correlation of the HII galaxies.Comment: 5 pages, accepted for publication in A&
Quantum initial value representations using approximate Bohmian trajectories
Quantum trajectories, originating from the de Broglie-Bohm (dBB) hydrodynamic
description of quantum mechanics, are used to construct time-correlation
functions in an initial value representation (IVR). The formulation is fully
quantum mechanical and the resulting equations for the correlation functions
are similar in form to their semi-classical analogs but do not require the
computation of the stability or monodromy matrix or conjugate points. We then
move to a {\em local} trajectory description by evolving the cumulants of the
wave function along each individual path. The resulting equations of motion are
an infinite hierarchy, which we truncate at a given order. We show that
time-correlation functions computed using these approximate quantum
trajectories can be used to accurately compute the eigenvalue spectrum for
various potential systems.Comment: 7 pages, 6 figure
Multiparameter vision testing apparatus
Compact vision testing apparatus is described for testing a large number of physiological characteristics of the eyes and visual system of a human subject. The head of the subject is inserted into a viewing port at one end of a light-tight housing containing various optical assemblies. Visual acuity and other refractive characteristics and ocular muscle balance characteristics of the eyes of the subject are tested by means of a retractable phoroptor assembly carried near the viewing port and a film cassette unit carried in the rearward portion of the housing (the latter selectively providing a variety of different visual targets which are viewed through the optical system of the phoroptor assembly). The visual dark adaptation characteristics and absolute brightness threshold of the subject are tested by means of a projector assembly which selectively projects one or both of a variable intensity fixation target and a variable intensity adaptation test field onto a viewing screen located near the top of the housing
Politics, Deception, and Being Self-Deceived
A review of Anna Elisabeth Galeotti's "Political Self-Deception
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