457 research outputs found
Identifications and SEDs of the detected sources from the AKARI Deep Field South
In order to find counterparts of the detected objects in the AKARI Deep Field
South (ADFS) in all available wavelengths, we searched public databases (NED,
SIMBAD and others). Checking 500 sources brighter than 0.0482 Jy in the AKARI
Wide-S band, we found 114 sources with possible counterparts, among which 78
were known galaxies. We present these sources as well as our first attempt to
construct spectral energy distributions (SEDs) for the most secure and most
interesting sources among them, taking into account all the known data together
with the AKARI measurements in four bands.Comment: 4 pages, 10 figures, To appear in: the proceedings of the conference
"AKARI, a light to illuminate the misty Universe", February 16-19 2009, Toky
Finite spin-glass transition of the XY model in three dimensions
A three-dimensional XY spin-glass model is investigated by a
nonequilibrium relaxation method. We have introduced a new criterion for the
finite-time scaling analysis. A transition temperature is obtained by a
crossing point of obtained data. The scaling analysis on the relaxation
functions of the spin-glass susceptibility and the chiral-glass susceptibility
shows that both transitions occur simultaneously. The result is checked by
relaxation functions of the Binder parameters and the glass correlation lengths
of the spin and the chirality. Every result is consistent if we consider that
the transition is driven by the spin degrees of freedom.Comment: 11 pages, 8 figures, incorrect arguments are delete
Far-infrared imaging of post-AGB stars and (proto)-planetary nebulae with the AKARI Far-Infrared Surveyor
By tracing the distribution of cool dust in the extended envelopes of
post-AGB stars and (proto)-planetary nebulae ((P)PNe) we aim to recover, or
constrain, the mass loss history experienced by these stars in their recent
past. The Far-Infrared Surveyor (FIS) instrument on board the AKARI satellite
was used to obtain far-infrared maps for a selected sample of post-AGB stars
and (P)PNe. We derived flux densities (aperture photometry) for 13 post-AGB
stars and (P)PNe at four far-infrared wavelengths (60, 90, 140, and 160 um).
Radial (azimuthally averaged) profiles are used to investigate the presence of
extended emission from cool dust. No (detached) extended emission is detected
for any target in our sample at levels significant with respect to background
and cirrus emission. Only IRAS 21046+4739 reveals tentative excess emission
between 30 and 130". Estimates of the total dust and gas mass from the obtained
maps indicate that the envelope masses of these stars should be large in order
to be detected with the AKARI FIS. Imaging with higher sensitivity and higher
spatial resolution is needed to detect and resolve, if present, any cool
compact or extended emission associated with these evolved stars.Comment: accepted for publication in The Astronomical Journal (16 pages, 3
figures and 4 tables
Detection of the Cosmic Far-Infrared Background in the AKARI Deep Field South
We report the detection and measurement of the absolute brightness and
spatial fluctuations of the cosmic infrared background (CIB) with the AKARI
satellite. We have carried out observations at 65, 90, 140 and 160 um as a
cosmological survey in AKARI Deep Field South (ADF-S), which is one of the
lowest cirrus regions with contiguous area on the sky. After removing bright
galaxies and subtracting zodiacal and Galactic foregrounds from the measured
sky brightness, we have successfully measured the CIB brightness and its
fluctuations across a wide range of angular scales from arcminutes to degrees.
The measured CIB brightness is consistent with previous results reported from
COBE data but significantly higher than the lower limits at 70 and 160 um
obtained with the Spitzer satellite from the stacking analysis of 24-um
selected sources. The discrepancy with the Spitzer result is possibly due to a
new galaxy population at high redshift obscured by hot dust. From power
spectrum analysis at 90 um, three components are identified: shot noise due to
individual galaxies; Galactic cirrus emission dominating at the largest angular
scales of a few degrees; and an additional component at an intermediate angular
scale of 10-30 arcminutes, possibly due to galaxy clustering. The spectral
shape of the clustering component at 90 um is very similar to that at longer
wavelengths as observed by Spitzer and BLAST. Moreover, the color of the
fluctuations indicates that the clustering component is as red as
Ultra-luminous infrared galaxies (ULIRGs) at high redshift, These galaxies are
not likely to be the majority of the CIB emission at 90 um, but responsible for
the clustering component. Our results provide new constraints on the evolution
and clustering properties of distant infrared galaxies.Comment: 50 pages, 15 figures, submitted to Ap
Polyamine metabolism is involved in adipogenesis of 3T3-L1 cells
Polyamines spermidine and spermine are known to be required for mammalian cell proliferation and for embryonic development. Alpha-difluoromethylornithine (DFMO), an inhibitor of ornithine decarboxylase (ODC) a limiting enzyme of polyamine biosynthesis, depleted the cellular polyamines and prevented triglyceride accumulation and differentiation in 3T3-L1 cells. In this study, to explore the function of polyamines in adipogenesis, we examined the effect of polyamine biosynthesis inhibitors on adipocyte differentiation and lipid accumulation of 3T3-L1 cells. The spermidine synthase inhibitor trans-4-methylcyclohexylamine (MCHA) increased spermine/spermidine ratios, whereas the spermine synthase inhibitor N-(3-aminopropyl)-cyclohexylamine (APCHA) decreased the ratios in the cells. MCHA was found to decrease lipid accumulation and GPDH activity during differentiation, while APCHA increased lipid accumulation and GPDH activity indicating the enhancement of differentiation. The polyamine-acetylating enzyme, spermidine/spermine N1-acetyltransferase (SSAT) activity was increased within a few hours after stimulus for differentiation, and was found to be elevated by APCHA. In mature adipocytes APCHA decreased lipid accumulation while MCHA had the opposite effect. An acetylpolyamine oxidase and spermine oxidase inhibitor MDL72527 or an antioxidant N-acetylcysteine prevented the promoting effect of APCHA on adipogenesis. These results suggest that not only spermine/spermidine ratios but also polyamine catabolic enzyme activity may contribute to adipogenesis
Reversible Electric-Field-Driven Magnetic Domain-Wall Motion
Control of magnetic domain-wall motion by electric fields has recently attracted scientific attention because of its potential for magnetic logic and memory devices. Here, we report on a new driving mechanism that allows for magnetic domain-wall motion in an applied electric field without the concurrent use of a magnetic field or spin-polarized electric current. The mechanism is based on elastic coupling between magnetic and ferroelectric domain walls in multiferroic heterostructures. Pure electric-field-driven magnetic domain-wall motion is demonstrated for epitaxial Fe films on BaTiO3 with in-plane and out-of-plane polarized domains. In this system, magnetic domain-wall motion is fully reversible and the velocity of the walls varies exponentially as a function of out-of-plane electric-field strength.Peer reviewe
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