7,746 research outputs found
Detection of Dark Matter Concentrations in the Field of Cl 1604+4304 from Weak Lensing Analysis
We present a weak-lensing analysis of a region around the galaxy cluster Cl
1604+4304 (z=0.897) on the basis of the deep observations with the HST/WFPC2.
We apply a variant of Schneider's aperture mass technique to the observed WFPC2
field and obtain the distribution of weak-lensing signal-to-noise (S/N) ratio
within the field. The resulting S/N map reveals a clear pronounced peak located
about 1.7 arcmin (850h_{50}^{-1} kpc at z=0.897) southwest of the second peak
associated with the optical cluster center determined from the dynamical
analysis of Postman et al. A non-linear finite-field inversion method has been
used to reconstruct the projected mass distribution from the observed shear
field. The reconstructed mass map shows a super-critical feature at the
location of the S/N peak as well as in the cluster central region. Assuming the
redshift distribution of field galaxies, we obtain the total mass in the
observed field to be 1.0 h_{50}^{-1} 10^{15} M_sun for =1.0. The estimated
mass within a circular aperture of radius 280h_{50}^{-1} kpc centered on the
dark clump is 2.4h_{50}^{-1} 10^{14} M_sun. We have confirmed the existence of
the ` dark ' mass concentration from another deep HST observation with a
slightly different ~20 arcsec pointing.Comment: 7 pages, 3 figure
Ionic conductivity and relaxation dynamics in plastic-crystals with nearly globular molecules
We have performed a dielectric investigation of the ionic charge transport
and the relaxation dynamics in plastic-crystalline 1-cyano-adamantane (CNA) and
in two mixtures of CNA with the related plastic crystals adamantane or
2-adamantanon. Ionic charge carriers were provided by adding 1% of Li salt. The
molecules of these compounds have nearly globular shape and, thus, the
so-called revolving-door mechanism assumed to promote ionic charge transport
via molecular reorientations in other PC electrolytes, should not be active
here. Indeed, a comparison of the dc resistivity and the reorientational
alpha-relaxation times in the investigated PCs, reveals complete decoupling of
both dynamics. Similar to other PCs, we find a significant mixing-induced
enhancement of the ionic conductivity. Finally, these solid-state electrolytes
reveal a second relaxation process, slower than the alpha-relaxation, which is
related to ionic hopping. Due to the mentioned decoupling, it can be
unequivocally detected and is not superimposed by the reorientational
contributions as found for most other ionic conductors.Comment: 9 pages, 7 figure
Species- and organ-specificity of secretory proteins derived from human prostate and seminal vesicles
Polyclonal antibodies against semenogelin (SG) isolated from human seminal vesicle secretion and acid phosphatase (PAP), β‐microseminoprotein (β‐MSP), and Prostate‐Specific Antigen (PSA) derived from human prostatic fluid, as well as a monoclonal antibody against β‐MSP were used for immunocytochemical detection of the respective antigens in different organs from different species. SG immunoreactivity was detected in the epithelium of the pubertal and adult human and in monkey seminal vesicle, ampulla of the vas deferens, and ejaculatory duct. PAP, β‐MSP, and PSA immunoreactivities were detected in the pubertal and adult human prostate and the cranial and caudal monkey prostate. With the exception of a weak PSA immunoreactivity in the proximal portions of the ejaculatory duct, none of the latter antisera reacted with seminal vesicle, ampullary, and ejaculatory duct epithelium. Among the non‐primate species studied (dog, bull, rat, guinea pig) only the canine prostatic epithelium displayed a definite immunoreactivity with the PAP antibody and a moderate reaction with the PSA antibody. No immunoreaction was seen in bull and rat seminal vesicle and canine ampulla of the vas deferens with the SG antibody. The same was true for the (ventral) prostate of rat, bull, and dog for β‐MSP. The epithelium of the rat dorsal prostate showed a slight cross‐reactivity with the monoclonal antibody against β‐MSP and one polyclonal antibody against PSA. The findings indicate a rather strict species‐dependent expression of human seminal proteins which show some similarities in primates, but only marginal relationship to species with different physiology of seminal fluid
Weak Lensing Analysis of the z~0.8 cluster CL 0152-1357 with the Advanced Camera for Surveys
We present a weak lensing analysis of the X-ray luminous cluster CL 0152-1357
at z~0.84 using HST/ACS observations. The unparalleled resolution and
sensitivity of ACS enable us to measure weakly distorted, faint background
galaxies to the extent that the number density reaches ~175 arcmin^-2. The PSF
of ACS has a complicated shape that also varies across the field. We construct
a PSF model for ACS from an extensive investigation of 47 Tuc stars in a
modestly crowded region. We show that this model PSF excellently describes the
PSF variation pattern in the cluster observation when a slight adjustment of
ellipticity is applied. The high number density of source galaxies and the
accurate removal of the PSF effect through moment-based deconvolution allow us
to restore the dark matter distribution of the cluster in great detail. The
direct comparison of the mass map with the X-ray morphology from Chandra
observations shows that the two peaks of intracluster medium traced by X-ray
emission are lagging behind the corresponding dark matter clumps, indicative of
an on-going merger. The overall mass profile of the cluster can be well
described by an NFW profile with a scale radius of r_s =309+-45 kpc and a
concentration parameter of c=3.7+-0.5. The mass estimates from the lensing
analysis are consistent with those from X-ray and Sunyaev-Zeldovich analyses.
The predicted velocity dispersion is also in good agreement with the
spectroscopic measurement from VLT observations. In the adopted WMAP cosmology,
the total projected mass and the mass-to-light ratio within 1 Mpc are estimated
to be 4.92+-0.44 10^14 solar mass and 95+-8 solar mass/solar luminosity,
respectively.Comment: Accepted for publication in Astrophysical Journal. 58 pages, 26
figures. Figures have been degraded to meet size limit; a higher resolution
version available at http://acs.pha.jhu.edu/~mkjee/ms_cl0152.pd
Hubble Space Telescope weak lensing study of the z=0.83 cluster MS 1054-03
We have measured the weak gravitational lensing signal of MS 1054-03, a rich
and X-ray luminous cluster of galaxies at a redshift of z=0.83, using a
two-colour mosaic of deep WFPC2 images. The small corrections for the size of
the PSF and the high number density of background galaxies obtained in these
observations result in an accurate and well calibrated measurement of the
lensing induced distortion. The strength of the lensing signal depends on the
redshift distribution of the background galaxies. We used photometric redshift
distributions from the Northern and Southern Hubble Deep Fields to relate the
lensing signal to the mass. The predicted variations of the signal as a
function of apparent source magnitude and colour agrees well with the observed
lensing signal. We determine a mass of (1.2+-0.2)x10^15 Msun within an aperture
of radius 1 Mpc. Under the assumption of an isothermal mass distribution, the
corresponding velocity dispersion is 1311^{+83}_{-89} km/s. For the
mass-to-light ratio we find 269+-37 Msun/Lsun. The errors in the mass and
mass-to-light ratio include the contribution from the random intrinsic
ellipticities of the source galaxies, but not the (systematic) error due to the
uncertainty in the redshift distribution. However, the estimates for the mass
and mass-to-light ratio of MS 1054-03 agree well with other estimators,
suggesting that the mass calibration works well. The reconstruction of the
projected mass surface density shows a complex mass distribution, consistent
with the light distribution. The results indicate that MS 1054-03 is a young
system. The timescale for relaxation is estimated to be at least 1 Gyr.
Averaging the tangential shear around the cluster galaxies, we find that the
velocity dispersion of an Lstar galaxy is 203+-33 km/s.Comment: 21 pages, Latex, with 27 figures (3 figures bitmapped), ApJ, in
press. Version (with non-bitmapped figures) available at
http://www.astro.rug.nl/~hoekstra/papers.htm
Electromechanical Reliability Testing of Three-Axial Silicon Force Sensors
This paper reports on the systematic electromechanical characterization of a
new three-axial force sensor used in dimensional metrology of micro components.
The siliconbased sensor system consists of piezoresistive mechanicalstress
transducers integrated in thin membrane hinges supporting a suspended flexible
cross structure. The mechanical behavior of the fragile micromechanical
structure isanalyzed for both static and dynamic load cases. This work
demonstrates that the silicon microstructure withstands static forces of 1.16N
applied orthogonally to the front-side of the structure. A statistical Weibull
analysis of the measured data shows that these values are significantly reduced
if the normal force is applied to the back of the sensor. Improvements of the
sensor system design for future development cycles are derived from the
measurement results.Comment: Submitted on behalf of TIMA Editions
(http://irevues.inist.fr/tima-editions
Rank 3 permutation characters and maximal subgroups
In this paper we classify all maximal subgroups M of a nearly simple
primitive rank 3 group G of type L=Omega_{2m+1}(3), m > 3; acting on an L-orbit
E of non-singular points of the natural module for L such that 1_P^G <=1_M^G
where P is a stabilizer of a point in E. This result has an application to the
study of minimal genera of algebraic curves which admit group actions.Comment: 41 pages, to appear in Forum Mathematicu
Is Task-Irrelevant Learning Really Task-Irrelevant?
In the present study we address the question of whether the learning of task-irrelevant stimuli found in the paradigm of task-irrelevant learning (TIPL) [1]–[9] is truly task irrelevant. To test the hypothesis that associations that are beneficial to task-performance may develop between the task-relevant and task-irrelevant stimuli, or the task-responses and the task-irrelevant stimuli, we designed a new procedure in which correlations between the presentation of task-irrelevant motion stimuli and the identity of task-targets or task-responses were manipulated. We found no evidence for associations developing between the learned (task-irrelevant) motion stimuli and the targets or responses to the letter identification task used during training. Furthermore, the conditions that had the greatest correlations between stimulus and response showed the least amount of TIPL. On the other hand, TIPL was found in conditions of greatest response uncertainty and with the greatest processing requirements for the task-relevant stimuli. This is in line with our previously published model that suggests that task-irrelevant stimuli benefit from the spill-over of learning signals that are released due to processing of task-relevant stimuli
Is Task-Irrelevant Learning Really Task-Irrelevant?
In the present study we address the question of whether the learning of task-irrelevant stimuli found in the paradigm of task-irrelevant learning (TIPL) [1]–[9] is truly task irrelevant. To test the hypothesis that associations that are beneficial to task-performance may develop between the task-relevant and task-irrelevant stimuli, or the task-responses and the task-irrelevant stimuli, we designed a new procedure in which correlations between the presentation of task-irrelevant motion stimuli and the identity of task-targets or task-responses were manipulated. We found no evidence for associations developing between the learned (task-irrelevant) motion stimuli and the targets or responses to the letter identification task used during training. Furthermore, the conditions that had the greatest correlations between stimulus and response showed the least amount of TIPL. On the other hand, TIPL was found in conditions of greatest response uncertainty and with the greatest processing requirements for the task-relevant stimuli. This is in line with our previously published model that suggests that task-irrelevant stimuli benefit from the spill-over of learning signals that are released due to processing of task-relevant stimuli
Weak Lensing by High-Redshift Clusters of Galaxies - I: Cluster Mass Reconstruction
We present the results of a weak lensing survey of six high-redshift (z >
0.5), X-ray selected clusters of galaxies. We have obtained ultra-deep R-band
images of each cluster with the Keck Telescope, and have measured a weak
lensing signal from each cluster. From the background galaxy ellipticities we
create two-dimensional maps of the surface mass density of each cluster. We
find that the substructure seen in the mass reconstructions typically agree
well with substructure in both the cluster galaxy distributions and X-ray
images of the clusters. We also measure the one-dimensional radial profiles of
the lensing signals and fit these with both isothermal spheres and "universal"
CDM profiles. We find that the more massive clusters are less compact and not
as well fit by isothermal spheres as the less massive clusters, possibly
indicating that they are still in the process of collapse.Comment: 43 pages, 15 figures, uses aastex, submitted to ApJ 4 color plates
produced here as jpg's, larger versions of the jpgs can be found at
http://www.mpa-garching.mpg.de/~clow
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