482 research outputs found
Dust in Hot Plasma of Nearby Dusty Elliptical Galaxies Observed with the Spitzer Space Telescope
We report on mid- and far-IR Spitzer observations of 7 nearby dusty
elliptical galaxies by using the Multiband Imaging Photometer (MIPS) and
Infrared Spectrograph (IRS). Our sample galaxies are known to contain an
excessive amount of interstellar dust against sputtering destruction in hot
plasma filling the interstellar space of elliptical galaxies. In order to study
the origin and the properties of the excess dust in the hot plasma, we selected
galaxies with a wide range of X-ray luminosities but similar optical luminos
ities for our Spitzer Guest Observers (GO1) program. The 7 galaxies are
detected at the MIPS 24 um, 70 um, and 160 um bands; the far- to mid-IR flux
ratios of relatively X-ray-bright elliptical galaxies are lower than those of
X-ray-faint galaxies. From the IRS spectra, polycyclic aromatic hydrocarbon
(PAH) emission features are detected significantly from 5 of the 7 galaxies; t
he emission intensities are weaker as the X-ray luminosity of the galaxy is
larger. We have found a correlation between the far- to mid-IR flux ratio and
the equivalent width of the PAH emission feature. We have obtained apparent
spatial correspondence between mid-IR and X-ray distributions in the outer
regions for the three X-ray-brightest galaxies in our sample. Possible
interpretations for our observational results are discussed.Comment: 25 pages, 7 figures, accepted for publication in Publications of the
Astronomical Society of Japa
Characterization and Improvement of the Image Quality of the Data Taken with the Infrared Camera (IRC) Mid-Infrared Channels onboard AKARI
Mid-infrared images frequently suffer artifacts and extended point spread
functions (PSFs). We investigate the characteristics of the artifacts and the
PSFs in images obtained with the Infrared Camera (IRC) onboard AKARI at four
mid-infrared bands of the S7 (7{\mu}m), S11 (11{\mu}m), L15 (15{\mu}m), and L24
(24 {\mu}m). Removal of the artifacts significantly improves the reliability of
the ref- erence data for flat-fielding at the L15 and L24 bands. A set of
models of the IRC PSFs is also constructed from on-orbit data. These PSFs have
extended components that come from diffraction and scattering within the
detector arrays. We estimate the aperture correction factors for point sources
and the surface brightness correction factors for diffuse sources. We conclude
that the surface brightness correction factors range from 0.95 to 0.8, taking
account of the extended component of the PSFs. To correct for the extended PSF
effects for the study of faint structures, we also develop an image
reconstruction method, which consists of the deconvolution with the PSF and the
convolution with an appropriate Gaussian. The appropriate removal of the
artifacts, improved flat-fielding, and image reconstruction with the extended
PSFs enable us to investigate de- tailed structures of extended sources in IRC
mid-infrared images.Comment: 35 pages, 15 figures, accepted for publication in PAS
Properties of polycyclic aromatic hydrocarbons in local elliptical galaxies revealed by the Infrared Spectrograph on Spitzer
We performed mid-infrared spectroscopic observations of 18 local dusty
elliptical galaxies by using the Infrared Spectrograph (IRS) on board Spitzer.
We have significantly detected polycyclic aromatic hydrocarbon (PAH) features
from 14 out of the 18 galaxies, and thus found that the presence of PAHs is not
rare but rather common in dusty elliptical galaxies. Most of these galaxies
show an unusually weak 7.7 um emission feature relative to 11.3 um and 17 um
emission features. A large fraction of the galaxies also exhibit H2 rotational
line and ionic fine-structure line emissions, which have no significant
correlation with the PAH emissions. The PAH features are well correlated with
the continuum at 35 um, whereas they are not correlated with the continuum at 6
um. We conclude that the PAH emission of the elliptical galaxies is mostly of
interstellar origin rather than of stellar origin, and that the unusual PAH
interband strength ratios are likely to be due to a large fraction of neutral
to ionized PAHs.Comment: 26 pages, 6 figures, accepted for publication in the Ap
Fluorescent ampicillin analogues as multifunctional disguising agents against opsonization
Cancer nanomedicines are opening new paradigms in cancer management and recent research points to how they can vastly improve imaging and therapy through multimodality and multifunctionality. However, challenges to achieving optimal efficacy are manifold starting from processing materials and evaluating their intended effectiveness on biological tissue, to developing new strategies aimed at improving transport of these materials through the biological milieu to the target tissue. Here, we report a fluorescent derivative of a beta-lactam antibiotic, ampicillin (termed iAmp) and its multifunctional physicobiochemical characteristics and potential as a biocompatible shielding agent and an effective dispersant. Carbon nanotubes (CNTs) were chosen to demonstrate the efficacy of iAmp. CNTs are known for their versatility and have been used extensively for cancer theranostics as photothermal and photoacoustic agents, but have limited solubility in water and biocompatibility. Traditional dispersants are associated with imaging artifacts and are not fully biocompatible. The chemical structure of iAmp is consistent with a deamination product of ampicillin. Although the four-membered lactam ring is intact, it does not retain the antibiotic properties. The iAmp is an effective dispersant and simultaneously serves as a fluorescent label for single-walled CNTs (SWNTs) with minimal photobleaching. The iAmp also enables bioconjugation of SWNTs to bio-ligands such as antibodies through functional carboxyl groups. Viability tests show that iAmp-coated SWNTs have minimal toxicity. Bio-stability tests under physiological conditions reveal that iAmp coating not only remains stable in a biologically relevant environment with high protein and salt concentrations, but also renders SWNTs transparent against nonspecific protein adsorption, also known as protein corona. Mammalian tissue culture studies with macrophages and opsonins validate that iAmp coating affords immunological resistance to SWNTs. Furthermore, iAmp coating offers protection to SWNTs against their nonspecific adsorption across disparate cell types, which has precluded a targeted strategy, and enables selective molecular targeting. The iAmp can therefore be used as an efficient dispersant, a photostable fluorescent agent, and a biocompatible disguising agent, alleviating CNTs' drawbacks and rendering them suitable for nanotheranostic and drug delivery applications.1111Ysciescopu
Protein and sensory quality of a food supplement formulated for the elderly
This study aimed to evaluate the composition, the protein quality, and the acceptability of a powder dietary supplement formulated for elderly people. The centesimal composition was analysed according to A.O.A.C. methods and the protein quality was assessed in weaning rats, by comparing Protein Efficiency Ratio (PER), Net Protein Ratio (NPR), and True Digestibility (TD) of the supplement with a casein-control based on AIN-93G diet. For the acceptance test samples of four flavours of the supplement dissolved in whole milk were offered to each judge, in monadic form. To assess the overall acceptability a scale of seven points was used. The sensory panel was composed of 121 Brazilian panellists, with mean age of 68.28±5.78 years. The supplement is promising in reaching the nutritional demands of the elderly, providing high content of protein and fibre and low content of fat. The values found for PER and NPR were shown to be superior to the control group of casein (P<0.05) and the digestibility was higher than 90%, showing that the supplement presented characteristics of a high nutritional value protein source. The supplements with banana, vanilla, and strawberry flavour were the most accepted and did not differ significantly for the overall acceptability
ESR investigation on the Breather mode and the Spinon-Breather dynamical crossover in Cu Benzoate
A new elementary-excitation, the so called "breather excitation", is observed
directly by millimeter-submillimeter wave electron spin resonance (ESR) in the
Heisenberg quantum spin-chain Cu benzoate, in which a field-induced gap is
found recently by specific heat and neutron scattering measurements. Distinct
anomalies were found in line width and in resonance field around the "dynamical
crossover" regime between the gap-less spinon-regime and the gapped
breather-regime. When the temperature becomes sufficiently lower than the
energy gap, a new ESR-line with very narrow line-width is found, which is the
manifestation of the breather excitation. The non-linear field dependence of
the resonance field agrees well with the theoretical formula of the first
breather-excitation proposed by Oshikawa and Affleck. The present work
establishes experimentally for the first time that a sine-Gordon model is
applicable to explain spin dynamics in a S=1/2 Heisenberg spin chain subjected
to staggered field even in high fields.Comment: Revtex, 4 pages, 4 figures, submitted to Phys. Rev. Let
Multi-wavelength analysis of 18um-selected galaxies in the AKARI/IRC monitor field towards the North Ecliptic Pole
We present an initial analysis of AKARI 18um-selected galaxies using all 9
photometric bands at 2-24um available in the InfraRed Camera (IRC), in order to
demonstrate new capabilities of AKARI cosmological surveys. We detected 72
sources at 18um in an area of 50.2 arcmin^2 in the AKARI/IRC monitor field
towards the North Ecliptic Pole (NEP). From this sample, 25 galaxies with
probable redshifts z>~ 0.5 are selected with a single colour cut (N2-N3>0.1)
for a detailed SED analysis with ground-based BVRi'z'JK data. Using an SED
radiative transfer model of starbursts covering the wavelength range UV --
submm, we derive photometric redshifts from the optical-MIR SEDs of
18um-selected galaxies. From the best-fit SED models, we show that the IRC
all-band photometry is capable of tracing the steep rise in flux at the blue
side of the PAH 6.2um emission feature. This indicates that the IRC all-band
photometry is useful to constrain the redshift of infrared galaxies,
specifically for dusty galaxies with a less prominent 4000A break. Also, we
find that the flux dip between the PAH 7.7 and 11.2um emission feature is
recognizable in the observed SEDs of galaxies at z~1. By using such a colour
anomaly due to the PAH and silicate absorption features, unique samples of
ULIRGs at z~1, `silicate-break' galaxies, can be constructed from large
cosmological surveys of AKARI towards the NEP, i.e. the NEP-Deep and NEP-Wide
survey. This pilot study suggests the possibility of detecting many interesting
galaxy properties in the NEP-Deep and Wide surveys, such as a systematic
difference in SEDs between high- and low-z ULIRGs, and a large variation of the
PAH inter-band strength ratio in galaxies at high redshifts. [abridged]Comment: Accepted for publication in PASJ, AKARI special issu
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