1,846 research outputs found
Hidden interaction in SBO galaxies
Galaxies, like plants, show a large variety of grafts: an individual of some type connects physically with a neighborhood of same or different type. The effects of these interactions between galaxies have a broad range of morphologies depending, among other quantities, on the distance of the closest approach between systems and the relative size of the two galaxies. A sketch of the possible situations is shown in tabular form. This botanical classification is just indicative, because the effects of interactions can be notable also at relatively large separations, when additional conditions are met, as for example low density of the interacting systems or the presence of intra-cluster gas. In spite of the large variety of encounters and effects, in the literature the same terms are often used to refer to different types of interactions. Analysis indicates that only few of the situations show evident signs of interaction. They appear to be most relevant when the size of the two galaxies is comparable. Bridges and tails, like the well known case of NGC 4038/39, the Antennae, are only observed for a very low percentage of all galaxies (approx. 0.38 percent, Arp and Madore 1977). In most cases of gravitational bond between two galaxies, the effects of interactions are not relevant or evident. For instance, the detection of stellar shells (Malin and Carter 1983), which have been attributed to the accretion of gas stripped from another galaxy or to the capture and disruption of a small stellar system (Quinn 1984), requires particular observing and reduction techniques. Besides these difficulties of detection, time plays an important role in erasing, within a massive galaxy, the effects of interactions with smaller objects. This can happen on a timescale shorter than the Hubble time, so the number of systems now showing signs of interaction suggests lower limits to the true frequency of interactions in the life-time of a stellar system
Differential cross section analysis in kaon photoproduction using associated legendre polynomials
Angular distributions of differential cross sections from the latest CLAS
data sets \cite{bradford}, for the reaction have been analyzed using associated Legendre polynomials. This
analysis is based upon theoretical calculations in Ref. \cite{fasano} where all
sixteen observables in kaon photoproduction can be classified into four
Legendre classes. Each observable can be described by an expansion of
associated Legendre polynomial functions. One of the questions to be addressed
is how many associated Legendre polynomials are required to describe the data.
In this preliminary analysis, we used data models with different numbers of
associated Legendre polynomials. We then compared these models by calculating
posterior probabilities of the models. We found that the CLAS data set needs no
more than four associated Legendre polynomials to describe the differential
cross section data. In addition, we also show the extracted coefficients of the
best model.Comment: Talk given at APFB08, Depok, Indonesia, August, 19-23, 200
Global-in-time solutions for the isothermal Matovich-Pearson equations
In this paper we study the Matovich-Pearson equations describing the process
of glass fiber drawing. These equations may be viewed as a 1D-reduction of the
incompressible Navier-Stokes equations including free boundary, valid for the
drawing of a long and thin glass fiber. We concentrate on the isothermal case
without surface tension. Then the Matovich-Pearson equations represent a
nonlinearly coupled system of an elliptic equation for the axial velocity and a
hyperbolic transport equation for the fluid cross-sectional area. We first
prove existence of a local solution, and, after constructing appropriate
barrier functions, we deduce that the fluid radius is always strictly positive
and that the local solution remains in the same regularity class. To the best
of our knowledge, this is the first global existence and uniqueness result for
this important system of equations
Fingerprint of dynamical charge/spin correlations in the tunneling spectra of colossal magnetoresistive manganites
We present temperature-dependent scanning tunneling spectroscopy measurements
on () films with different degrees of biaxial
strain. A depletion in normalized conductance around the Fermi level is
observed both above and below the insulator-to-metal transition temperature
, for weakly as well as highly-strained films. This pseudogap-like
depletion globally narrows on cooling. The zero-bias conductance decreases on
cooling in the insulating phase, reaches a minimum close to and
increases on cooling in the metallic phase, following the trend of macroscopic
conductivity. These results support a recently proposed scenario in which
dynamical short-range antiferromagnetic/charge order correlations play a
preeminent role in the transport properties of colossal magnetoresistive
manganites [R. Yu \textit{et al}., Phys. Rev. B \textbf{77}, 214434 (2008)].Comment: 9 pages, 4 figure
Future Detection of Supernova Neutrino Burst and Explosion Mechanism
Future detection of a supernova neutrino burst by large underground detectors
would give important information for the explosion mechanism of collapse-driven
supernovae. We studied the statistical analysis for the future detection of a
nearby supernova by using a numerical supernova model and realistic Monte-Carlo
simulations of detection by the Super-Kamiokande detector. We mainly discuss
the detectability of the signatures of the delayed explosion mechanism in the
time evolution of the \anue luminosity and spectrum. For a supernova at 10
kpc away from the Earth, we find that not only the signature is clearly
discernible, but also the deviation of energy spectrum from the Fermi-Dirac
(FD) distribution can be observed. The deviation from the FD distribution
would, if observed, provide a test for the standard picture of neutrino
emission from collapse-driven supernovae. For the = 50 kpc case, the
signature of the delayed explosion is still observable, but statistical
fluctuation is too large to detect the deviation from the FD distribution. We
also propose a method for statistical reconstruction of the time evolution of
\anue luminosity and spectrum from data, by which we can get a smoother time
evolution and smaller statistical errors than a simple, time-binning analysis.
This method is useful especially when the available number of events is
relatively small, e.g., a supernova in the LMC or SMC. Neutronization burst of
's produces about 5 scattering events when = 10 kpc and this signal
is difficult to distinguish from \anue p events.Comment: 28 pages including all figures. Accepted by Astrophys.
Molecular Gas in Elliptical Galaxies: Distribution and Kinematics
I present interferometric images (approx. 7" resolution) of CO emission in
five elliptical galaxies and nondetections in two others. These data double the
number of elliptical galaxies whose CO emission has been fully mapped. The
sample galaxies have 10^8 to 5x10^9 solar masses of molecular gas distributed
in mostly symmetric rotating disks with diameters of 2 to 12 kpc. Four out of
the five molecular disks show remarkable alignment with the optical major axes
of their host galaxies. The molecular masses are a few percent of the total
dynamical masses which are implied if the gas is on circular orbits. If the
molecular gas forms stars, it will make rotationally supported stellar disks
which will be very similar in character to the stellar disks now known to be
present in many ellipticals. Comparison of stellar kinematics to gas kinematics
in NGC 4476 implies that the molecular gas did not come from internal stellar
mass loss because the specific angular momentum of the gas is about three times
larger than that of the stars.Comment: 47 pages, 6 tables, 27 figures. Accepted by AJ, scheduled for August
200
Di(2-ethylhexyl)phthalate (DEHP) and di-n-butylphthalate (DBP) exposure through diet in hospital patients.
Ready-to-eat packed meals intended to hospital patients were studied over a two-weeks period to measure the contents of di-(2-ethylhexyl) phthalate (DEHP) and di-n-butylphthalate (DBP) and to evaluate their daily intake by total diet. The packaging consisted of polyethylene terephthalate (PET) dishes sealed with polypropylene (PP) foil. The DEHP mean concentrations in total meals varied from 0.061 ± 0.028 to 0.307 ± 0.138 μg/g. wet. weight (wet wt.); the DBP mean levels varied from 0.025 ± 0.018 to 0.174 ± 0.091 μg/g. wet. wt. Highest levels of concentration for DEHP and DBP were found in bread with mean values of 0.307 ± 0.138 μg/g. wet. wt. and 0.174 ± 0.091 μg/g. wet. wt. for DEHP and DBP, respectively. The daily intake for DEHP was 3.1 ± 0.9 μg/kg. bw and 1.5 ± 0.5 μg/kg. bw for DBP.The mean ± sd incidence of DEHP and DBP intake via hospital meals on the respective EFSA TDI was 6 ± 2% (range 4-11%), and 15 ± 5% (range 8-24%), respectively. Even if for hospital patients the major route of exposure may be represented by medical devices, the influence of the diet could have a significant value on TD
Neuroprotective potential of isothiocyanates in an in vitro model of neuroinflammation
Isothiocyanates (ITCs), present as glucosinolate precursors in cruciferous vegetables, have shown anti-inflammatory, antioxidant
and anticarcinogenic activities. Here, we compared the effects of three different ITCs on ROS production and on
the expression of matrix metalloproteinase (MMP)-2 and -9, which represent important pathogenetic factors of various
neurological diseases. Primary cultures of rat astrocytes were activated by LPS and simultaneously treated with different
doses of Allyl isothiocyanate (AITC), 2-Phenethyl isothiocyanate (PEITC) and 2-Sulforaphane (SFN). Results showed
that SFN and PEITC were able to counteract ROS production induced by H2O2.
The zymographic analysis of cell culture
supernatants evidenced that PEITC and SFN were the most effective inhibitors of MMP-9, whereas, only SFN significantly
inhibited MMP-2 activity. PCR analysis showed that all the ITCs used significantly inhibited both MMP-2 and MMP-9
expression. The investigation on the mitogen-activated protein kinase (MAPK) signaling pathway demonstrated that ITCs
modulate MMP transcription by inhibition of extracellular-regulated protein kinase (ERK) activity. Results of this study
suggest that ITCs could be promising nutraceutical agents for the prevention and complementary treatment of neurological
diseases associated with MMP involvement
- …