1,312 research outputs found
Photometric observations of Southern Abell Cluster Redshifts Survey Clusters: Structure of galaxies in the inner region of clusters of galaxies
We analyze photometric properties of 1384 cluster galaxies as a function of
the normalized distance to cluster center. These galaxies were selected in the
central region ( 0.8) of 14 southern Abell clusters chosen from
the Southern Abell Cluster Redshifts Survey (SARS). For 507 of these galaxies
we also obtained their luminosity profiles. We have studied the
morphology-clustercentric distance relation on the basis of the shape parameter
of the S\'ersic's law. We also have analyzed the presence of a possible
segregation in magnitude for both, the galaxy total luminosity and that of
their components (i.e. the bulge and the disk).
Results show a marginal ( level) decrease of the total luminosity as
a function of normalized radius. However, when bulges are analyzed separately,
a significant luminosity segregation is found ( and for
galaxies in projection and member galaxies respectively). The fraction of
bulges brighter than is three times larger in the core of
clusters than in the outer region. Our analysis of the disk component suggests
that disks are, on average, less luminous in the cluster core than at
. In addition, we found that the magnitude-size relation as
a function of indicates (at level) that disks are smaller
and centrally brighter in the core of clusters. However, the Kormendy relation
(the bulge magnitude-size relation) appears to be independent of environment.Comment: To appear in the A
Interaction-induced charge and spin pumping through a quantum dot at finite bias
We investigate charge and spin transport through an adiabatically driven,
strongly interacting quantum dot weakly coupled to two metallic contacts with
finite bias voltage. Within a kinetic equation approach, we identify
coefficients of response to the time-dependent external driving and relate
these to the concepts of charge and spin emissivities previously discussed
within the time-dependent scattering matrix approach. Expressed in terms of
auxiliary vector fields, the response coefficients allow for a straightforward
analysis of recently predicted interaction-induced pumping under periodic
modulation of the gate and bias voltage [Phys. Rev. Lett. 104, 226803 (2010)].
We perform a detailed study of this effect and the related adiabatic Coulomb
blockade spectroscopy, and, in particular, extend it to spin pumping. Analytic
formulas for the pumped charge and spin in the regimes of small and large
driving amplitude are provided for arbitrary bias. In the absence of a magnetic
field, we obtain a striking, simple relation between the pumped charge at zero
bias and at bias equal to the Coulomb charging energy. At finite magnetic
field, there is a possibility to have interaction-induced pure spin pumping at
this finite bias value, and generally, additional features appear in the pumped
charge. For large-amplitude adiabatic driving, the magnitude of both the pumped
charge and spin at the various resonances saturate at values which are
independent of the specific shape of the pumping cycle. Each of these values
provide an independent, quantitative measurement of the junction asymmetry.Comment: 17 pages, 8 figure
On booms that never bust: ambiguity in experimental asset markets with bubbles
We study the effect of ambiguity on the formation of bubbles and crashes in experimental asset markets à la Smith, Suchanek, and Williams (1988) by allowing for ambiguity in the fundamental value of the asset. Although bubbles form in both the ambiguous and the risky environments we find that asset prices tend to be lower when the fundamental value is ambiguous than when it is risky. Bubbles do not crash in the ambiguous case whereas they do so in the risky one. These findings, regarding depressed prices and the absence of crashes in the presence of ambiguity, are in line with recent theoretical work stressing the crucial role of ambiguity to account for surprisingly low equity prices (high returns) as well as herding in asset markets
Structure and dynamics of the Shapley Supercluster
We present results of our wide-field redshift survey of galaxies in a 285
square degree region of the Shapley Supercluster (SSC), based on a set of 10529
velocity measurements (including 1201 new ones) on 8632 galaxies obtained from
various telescopes and from the literature. Our data reveal that the main plane
of the SSC (v~ 14500 km/s) extends further than previous estimates, filling the
whole extent of our survey region of 12~degrees by 30~degrees on the sky (30 x
75~h-1 Mpc). There is also a connecting structure associated with the slightly
nearer Abell~3571 cluster complex (v~ 12000km/s. These galaxies seem to link
two previously identified sheets of galaxies and establish a connection with a
third one at V= 15000 km/s near R.A.= 13h. They also tend to fill the gap of
galaxies between the foreground Hydra-Centaurus region and the more distant
SSC. In the velocity range of the Shapley Supercluster (9000 km/s < cz < 18000
km/s), we found redshift-space overdensities with b\_j < 17.5 of ~5.4 over the
225 square degree central region and ~3.8 in a 192 square degree region
excluding rich clusters. Over the large region of our survey, we find that the
intercluster galaxies make up 48 per cent of the observed galaxies in the SSC
region and, accounting for the different completeness, may contribute nearly
twice as much mass as the cluster galaxies. In this paper, we discuss the
completeness of the velocity catalogue, the morphology of the supercluster, the
global overdensity, and some properties of the individual galaxy clusters in
the Supercluster.Comment: Accepted for publication in Astronomy and Astrophysic
In-vitro toxoplasmacidal activity of cationic electron carriers
Exposing murine macrophages infected th the protozoan parasite Toxoplasma gondii to micromolar concentrations of some cationic electron carriers (dyes), resulted in complete killing of the intracellular parasites at concentrations at which these compounds did not seem toxic for the macrophages. The 50% inhibitory concentrations (with 95% confidence limits) were calculated as 0·26 (0·18-0·37), 1·35 (1-2·25), 0·45 (0·13-1·50), and 1·52 (0·91-2·53) μM for crystal violet, phenazine methosulphate, methylene blue and brilliant cresyl blue, respectively. The effects of these electron carriers did not appear to be the result of an enhancement of the natural antitoxoplasmic activity of the macrophages. None of the tested compounds was active against extracellular Tox. gondii as measured by ability to reinfect murine macrophages; thus, these dyes seem to act primarily on actively metabolizing, intracellular, Tox. gondii. Our data also suggest that the killing effect of the electron carriers was not related to the generation of reactive oxygen intermediates as judged by the inability of scavengers of these intermediates to block the activity against intracellular Tox. gondii. Further studies with related redox compounds would have an interesting chemotherapeutic perspective for treating toxoplasma infection
Wavelength calibration of the JWST-MIRI medium resolution spectrometer
We present the wavelength and spectral resolution characterisation of the
Integral Field Unit (IFU) Medium Resolution Spectrometer for the Mid-InfraRed
Instrument (MIRI), to fly onboard the James Webb Space Telescope in 2014. We
use data collected using the Verification Model of the instrument and develop
an empirical method to calibrate properties such as wavelength range and
resolving power in a portion of the spectrometer's full spectral range (5-28
microns). We test our results against optical models to verify the system
requirements and combine them with a study of the fringing pattern in the
instrument's detector to provide a more accurate calibration. We show that
MIRI's IFU spectrometer will be able to produce spectra with a resolving power
above R=2800 in the wavelength range 6.46-7.70 microns, and that the unresolved
spectral lines are well fitted by a Gaussian profile.Comment: 12 pages, submitted to SPIE Proceedings vol. 7731, Space Telescopes
and Instrumentation 2010: Optical, Infrared, and Millimeter Wav
Activity of roxithromycin against Toxoplasma gondii in murine models
Investigations into the activity of roxithromycin against murine toxoplasma infections are reviewed. Roxithromycin is an active drug against murine toxoplasmosis after intraperitoneal challenge with the RH strain of Toxoplasma gondii. Roxithromycin protected 100% of mice after five daily doses of 540 mg per kg administered by gavage. The cure rate after treatment of peritoneal infections seemed to be related to the length of the therapy. Roxithromycin also decreased the number of toxoplasma cysts, after intracerebral infection with the C56 strain and showed synergistic activity when combined with gamma interferon. Thus, roxithromycin could be a worthwhile alternative to current therapy against toxoplasma infections. Clinical studies on its activity and safety, especially in pregnancy, are warrante
Activity of spiramycin against Toxoplasma gondii in vitro, in experimental infections and in human infection
The in-vitro, experimental and clinical activities of spiramycin against Toxoplasma gondii have been reviewed. In mammalian cells infected by T. gondii as in various experimental models, spiramycin definitively exerts an inhibitory antitoxoplasmic effect which, clinically, seems useful for preventing congenital toxoplasma infection during pregnancy or for reducing the inflammation in toxoplasmic chorioretinitis. However, spiramycin does not kill the parasite efficiently, and cannot be recommended for eradicating the most severe forms of toxoplasmosi
Effects of ampicillin, ceftriaxone, chloramphenicol, pefloxacin and trimethoprim-sulphamethoxazole on Salmonella typhi within human monocyte-derived macrophages
The killing effect of various antimicrobial agents used in the therapy of Salmonella typhi infection was tested against Salm. typhi strain Ty2 after phagocytosis by human monocyte-derived macrophages. The macrophages, cultured in 96-well microtitre plates, were infected for 1 h at 37°C by opsonized Salm. typhi Ty2 at a bacteria-cell ratio of 9:1. When added to the infected macrophage monolayers, at one and ten times the MIC, ampicillin, ceftriaxone and pefloxacin appeared to be highly bactericidal (< 0.25 logl0 cfu/well after 20 h, against 4 log10 cfu/well in antibiotic-free controls). Trimethoprim-sulphamethoxazole was bactericidal at ten times the MIC, but not at the MIC. Chloramphenicol was mostly bacteriostatic at the concentrations tested. As a control, gentamicin (10mg/l) did not exhibit any significant antibacterial effect, indicating that most or all the bacteria recovered from lyied cells were intracellular. Other controls for phagocytosis were also performed with heat-killed Candida albicans. Our results seem to correlate with the known clinical effect of some antimicrobials in human Salm. typhi infection. The in-vitro assay described here may be useful for assessing the activity of antimicrobial agents against Salm. typhi infectio
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