132 research outputs found
Dust properties in the cold and hot gas phases of the ATLAS3D early-type galaxies as revealed by AKARI
The properties of the dust in the cold and hot gas phases of early-type
galaxies (ETGs) are key to understand ETG evolution. We thus conducted a
systematic study of the dust in a large sample of local ETGs, focusing on
relations between the dust and the molecular, atomic, and X-ray gas of the
galaxies, as well as their environment. We estimated the dust temperatures and
masses of the 260 ETGs from the ATLAS3D survey, using fits to their spectral
energy distributions primarily constructed from AKARI measurements. We also
used literature measurements of the cold (CO and HI) and X-ray gas phases. Our
ETGs show no correlation between their dust and stellar masses, suggesting
inefficient dust production by stars and/or dust destruction in X-ray gas. The
global dust-to-gas mass ratios of ETGs are generally lower than those of
late-type galaxies, likely due to dust-poor HI envelopes in ETGs. They are also
higher in Virgo Cluster ETGs than in group and field ETGs, but the same ratios
measured in the central parts of the galaxies only are independent of galaxy
environment. Slow-rotating ETGs have systematically lower dust masses than
fast-rotating ETGs. The dust masses and X-ray luminosities are correlated in
fast-rotating ETGs, whose star formation rates are also correlated with the
X-ray luminosities. The correlation between dust and X-rays in fast-rotating
ETGs appears to be caused by residual star formation, while slow-rotating ETGs
are likely well evolved, and thus exhausting their dust. These results appear
consistent with the postulated evolution of ETGs, whereby fast-rotating ETGs
form by mergers of late-type galaxies and associated bulge growth, while
slow-rotating ETGs form by (dry) mergers of fast-rotating ETGs. Central cold
dense gas appears to be resilient against ram pressure stripping, suggesting
that Virgo Cluster ETGs may not suffer strong related star formation
suppression.Comment: 18 pages, 7 figures, accepted for publication in A&
Near- to mid-infrared spectroscopy of the heavily obscured AGN LEDA 1712304 with AKARI/IRC
Context. Although heavily obscured active galactic nuclei (AGNs) have been
found by many observational studies, the properties of the surrounding dust are
poorly understood. Using AKARI/IRC spectroscopy, we discover a new sample of a
heavily obscured AGN in LEDA 1712304 which shows a deep spectral absorption
feature due to silicate dust. Aims. We study the infrared (IR) spectral
properties of circumnuclear silicate dust in LEDA 1712304. Methods. We perform
IR spectral fitting, considering silicate dust properties such as composition,
porosity, size and crystallinity. Spectral energy distribution (SED) fitting is
also performed to the flux densities in the UV to sub-millimeter range to
investigate the global spectral properties. Results. The best-fit model
indicates 0.1 m-sized porous amorphous olivine (; ) with crystalline pyroxene. The optical
depth is , while the total IR luminosity and stellar
mass are estimated to be and
, respectively. In such low
and ranges, there are few galaxies which show that
large . Conclusions. The silicate dust in the AGN torus of
LEDA 1712304 has properties notably similar to those in other AGNs as a whole,
but slightly different in the wing shape of the absorption profile. The
porosity of the silicate dust suggests dust coagulation or processing in the
circumnuclear environments, while the crystallinity suggests that the silicate
dust is relatively fresh.Comment: 9 pages, 6 figures, accepted for publication in A&
Liquefaction Case Study of Volcanic Gravel Layer during 1993 Hokkaido-Nansei-Oki Earthquake
During the Hokkaido-Nansei-Oki Earthquake, a high-land area around the foot of the volcano, Mt. Komagatake, in Hokkaido in Northern Japan experienced liquefaction phenomena inflicting damages of differential settlement in some tens of houses in the area. Several kinds of geotechnical site investigations were carried out to study the cause of the damage in a typical liquefaction site. Trenching and geological survey disclosed that Holocene debris avalanche deposit containing a plenty of large rocks actually liquefied. The undrained cyclic triaxial test was carried out on large intact samples taken out by the in-situ freezing sampling. The stress ratio measured in the test was in accordance with the seismic induced stress ratio estimated from the maximum acceleration in the area
Soil Investigation and FVT Analysis in Hualien LSST SSI Research
An international joint research program, Large-Scale Seismic Test (LSST) Program at Hualien, Taiwan, is ongoing, where a large-scale model structure partly embedded in gravelly layer was constructed, in-depth site soil geotechnical investigation was performed at every one of four construction stages, that is, before excavation, after excavation before structure construction, after structure construction before backfill, and after backfill, forced vibration tests (FVTs) of the model structure before backfill (FVT-1) and after backfill (FVT-2) were performed, and seismic observation of the dynamic SSI (soil-structure interaction) system is underway. This paper describes the change of the shear wave velocity (Vs) accompanied by the construction stage progress, and predictive and correlative FVT analyses, taking above-mentioned Vs change into account
Interpretation from large-scale shake table tests on piles undergoing lateral spreading in liquefied soils
doi: 10.1016/j.soildyn.2005.02.018Results from a benchmark test on full-scale piles are used to investigate the response of piles to lateral spreading. In the experiment, two single piles, a relatively flexible pile that moves together with the surrounding soil and a relatively stiff pile that does not follow the ground movement have been subjected to large post-liquefaction ground displacement simulating piles in laterally spreading soils. The observed response of the piles is first presented and then the results are used to examine the lateral loads on the pile from a non-liquefied soil at the ground surface and to evaluate the stiffness characteristics of the spreading soils. The measured ultimate lateral pressure from the crust soil on the stiff pile was about 4.5 times the Rankine passive pressure. The back-calculated stiffness of the liquefied soil was found to be in the range between 1/30 and 1/80 of the initial stiffness of the soil showing gradual decrease in the course of lateral spreading
Dynamic Properties of Mixtures of Waste Materials
The stockpiling of waste mining by-products, i.e. steel furnace slag (SFS) and coal wash (CW) has brought significant environmental hazard and attracted research attention to reuse them in a more innovative way. In recent years, SFS+CW mixtures have been successfully applied in geotechnical projects, while the inclusion of rubber crumb (RC, from waste tyres) will extend them into dynamic projects. Thus the investigation of the geotechnical properties of SFS+CW+RC mixtures under dynamic loading is in urgent need. In this paper, the dynamic properties (i.e. shear modulus and damping ratio) have been explored based on extensive drained cyclic triaxial tests. The influences of number of loading cycles, RC contents, shear strain level, and the effective confining pressure have been presented. The dynamic properties of SFS+CW +RC mixtures presented in this paper will be essential for the application of the mixtures in the seismic isolation projects or railway foundation
The Baculovirus Uses a Captured Host Phosphatase to Induce Enhanced Locomotory Activity in Host Caterpillars
The baculovirus is a classic example of a parasite that alters the behavior or physiology of its host so that progeny transmission is maximized. Baculoviruses do this by inducing enhanced locomotory activity (ELA) that causes the host caterpillars to climb to the upper foliage of plants. We previously reported that this behavior is not induced in silkworms that are infected with a mutant baculovirus lacking its protein tyrosine phosphatase (ptp) gene, a gene likely captured from an ancestral host. Here we show that the product of the ptp gene, PTP, associates with baculovirus ORF1629 as a virion structural protein, but surprisingly phosphatase activity associated with PTP was not required for the induction of ELA. Interestingly, the ptp knockout baculovirus showed significantly reduced infectivity of larval brain tissues. Collectively, we show that the modern baculovirus uses the host-derived phosphatase to establish adequate infection for ELA as a virion-associated structural protein rather than as an enzyme
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