482 research outputs found
Evolution of Multiphase Hot Interstellar Medium in Elliptical Galaxies
We present the results of a variety of simulations concerning the evolution
of multiphase (inhomogeneous) hot interstellar medium (ISM) in elliptical
galaxies. We assume the gases ejected from stars do not mix globally with the
circumferential gas. The ejected gas components evolve separately according to
their birth time, position, and origin. We consider cases where supernova
remnants (SNRs) mix with local ISM. The components with high metal abundance
and/or high density cool and drop out of the hot ISM gas faster than the other
components because of their high metal abundance and/or density. This makes the
average metal abundance of the hot ISM low. Furthermore, since the metal
abundance of mass-loss gas decreases with radius, gas inflow from outer region
makes the average metal abundance of the hot ISM smaller than that of mass-loss
gas in the inner region. As gas ejection rate of stellar system decreases, mass
fraction of mass-loss gas ejected at outer region increases in a galaxy. If the
mixing of SNRs is ineffective, our model predicts that observed [Si/Fe] and
[Mg/Fe] should decrease towards the galactic center because of strong iron
emission by SNRs. In the outer region, where the cooling of time of the ISM is
long, the selective cooling is ineffective and most of gas components remain
hot. Thus, the metal abundance of the ISM in this region directly reflects that
of the gas ejected from stars. Our model shows that supernovae are not
effective heating sources in the inner region of elliptical galaxies, because
most of the energy released by them radiates. Therefore, cooling flow is
established even if the supernova rate is high. Mixing of SNRs with ambient ISM
makes the energy transfer between supernova explosion and ambient ISM more
effective.Comment: 21 pages (AASTeX), 14 figures, accepted for publication in The
Astrophysical Journa
Formation of Sub-galactic Clouds under UV Background Radiation
The effects of the UV background radiation on the formation of sub-galactic
clouds are studied by means of one-dimensional hydrodynamical simulations. The
radiative transfer of the ionizing photons due to the absorption by HI, HeI and
HeII, neglecting the emission, is explicitly taken into account. We find that
the complete suppression of collapse occurs for the clouds with circular
velocities typically in the range V_c \sim 15-40 km/s and the 50% reduction in
the cooled gas mass with V_c \sim 20-55 km/s. These values depend most
sensitively on the collapse epoch of the cloud, the shape of the UV spectrum,
and the evolution of the UV intensity. Compared to the optically thin case,
previously investigated by Thoul & Weinberg (1996), the absorption of the
external UV photon by the intervening medium systematically lowers the above
threshold values by \Delta V_c \sim 5 km/s. Whether the gas can contract or
keeps expanding is roughly determined by the balance between the gravitational
force and the thermal pressure gradient when it is maximally exposed to the
external UV flux. Based on our simulation results, we discuss a number of
implications on galaxy formation, cosmic star formation history, and the
observations of quasar absorption lines. In Appendix, we derive analytical
formulae for the photoionization coefficients and heating rates, which
incorporate the frequency/direction-dependent transfer of external photons.Comment: 38 pages, 16 figures, accepted for publication in Ap
Single-longitudinal mode laser structure based on a very narrow filtering technique
A narrow filtering technique based on the spectral overlapping of two uniform FBGs and applied to obtain a Single Longitudinal Mode (SLM) laser is proposed and demonstrated in this work. The two FBGs are spectrally detuned to reduce their coincident reflection response narrowing the equivalent filter bandwidth. A proof-of-concept linear laser has been built and tested exhibiting SLM operation even with temperature and strain variations.The authors are grateful to the Spanish government project TEC2010-20224-C02, to the Spanish Ministry of Education and Culture, and to the grant AP2009-1403
Cholangiohepatitis in broiler chickens in Japan: histopathological, immunohistochemical and microbiological studies of spontaneous disease
Forty-five broiler arcasses from 6 different flocks were condemned due to liver lesions at processing meat inspection, and collected for pathological and bacterial examination. All affected chickens showed liver enlargement with distrahepatic bile ducts contained yellow inspissated cream-coloured material. Histopathologically, extensive proliferation of bile ductules with fibrosis was observed in interlobular connective tissue, and it spread to form bridges with adjoining triads. Destruction and obstruction of portal bile ducts with multiple granulomas due to bacterial infection and outflow of the bile were frequently observed.Many-Gram-positive bacilli were seen in the lesions, and they were identified asClostridium perfringensby indirect immunofluores en ecstaining technique.Clostridium perfringenswas isolated from affected livers. These findings are consistent with cholangiohepatitis. Therefore, it is suggested thatC. perfringensmight be important in the pathogenesis of cholangiohepatitis in broiler chickens
Hypoxia induces expression and activation of AMPK in rat dental pulp cells
博士(歯学)・第1721号(甲第1004号)・平成20年3月31日http://jdr.iadrjournals.org/cgi/content/full/86/9/90
A Groundbased Imaging Study of Galaxies Causing DLA, subDLA, and LLS Absorption in Quasar Spectra
We present results from a search for galaxies that give rise to damped Lyman
alpha (DLA), subDLA, and Lyman limit system (LLS) absorption at redshifts 0.1
~< z ~< 1 in the spectra of background quasars. The sample was formed from a
larger sample of strong MgII absorbers (W_0^(2796) >= 0.3 A) whose HI column
densities were determined by measuring the Ly-alpha line in HST UV spectra.
Photometric redshifts, galaxy colors, and proximity to the quasar sightline, in
decreasing order of importance, were used to identify galaxies responsible for
the absorption. Our sample includes 80 absorption systems for which the
absorbing galaxies have been identified, of which 54 are presented here for the
first time. The main results of this study are: (i) the surface density of
galaxies falls off exponentially with increasing impact parameter, b, from the
quasar sightline relative to a constant background of galaxies, with an
e-folding length of ~46 kpc. Galaxies with b >~ 100 kpc calculated at the
absorption redshift are statistically consistent with being unrelated to the
absorption system. (ii) log N(HI) is inversely correlated with b at the 3.0
sigma level of significance. DLA galaxies are found systematically closer to
the quasar sightline, by a factor of two, than are galaxies which give rise to
subDLAs or LLSs. The median impact parameter is 17.4 kpc for the DLA galaxy
sample, 33.3 kpc for the subDLA sample, and 36.4 kpc for the LLS sample. (iii)
Absorber galaxy luminosity relative to L*, L/L*, is not significantly
correlated with W_0^(2796), log N(HI), or b. (iv) DLA, subDLA, and LLS galaxies
comprise a mix of spectral types, but are inferred to be predominantly late
type galaxies based on their spectral energy distributions. The implications of
these results are discussed. (Abridged)Comment: Accepted for publication in MNRA
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