40 research outputs found
Effect of Side Chain Length on Segregation of Squalane between Smectic Layers Formed by Rod-Like Polysilanes
The segregation of spherical molecules (squalane) between the smectic layers of rod-like polymers (polysilanes) with narrow molecular weight distributions were investigated by synchrotron radiation small-angle X-ray scattering (SR-SAXS), atomic force microscopy (AFM) observations, and molecular dynamics simulations to elucidate the effect of the polymer side chain length on the segregation. It has been theoretically predicted that the smectic phase of the rod-like particles will be stabilized by inserting the spherical particles into the interstitial region between the smectic layers when the diameter of the spherical particles is smaller than that of the rod-like particles whose length is sufficiently long. We found that the segregation of squalane was unaffected by the molecular weight (Mw) of the polysilane in the range of 9,200-44,100 g/mol, and the diameter of the polysilane showed the optimal size of 5.64 nm for the segregation of squalane whose diameter is 6.57 nm although the origin of these inconsistencies between theory and experiment is currently not clear
AKARI Infrared Camera Survey of the Large Magellanic Cloud. I. Point Source Catalog
We present a near- to mid-infrared point source catalog of 5 photometric
bands at 3.2, 7, 11, 15 and 24 um for a 10 deg2 area of the Large Magellanic
Cloud (LMC) obtained with the Infrared Camera (IRC) onboard the AKARI
satellite. To cover the survey area the observations were carried out at 3
separate seasons from 2006 May to June, 2006 October to December, and 2007
March to July.
The 10-sigma limiting magnitudes of the present survey are 17.9, 13.8, 12.4,
9.9, and 8.6 mag at 3.2, 7, 11, 15 and 24 um, respectively. The photometric
accuracy is estimated to be about 0.1 mag at 3.2 um and 0.06--0.07 mag in the
other bands. The position accuracy is 0.3" at 3.2, 7 and 11um and 1.0" at 15
and 24 um. The sensitivities at 3.2, 7, and 24 um are roughly comparable to
those of the Spitzer SAGE LMC point source catalog, while the AKARI catalog
provides the data at 11 and 15 um, covering the mid-infrared spectral range
contiguously. Two types of catalog are provided: a Catalog and an Archive. The
Archive contains all the detected sources, while the Catalog only includes the
sources that have a counterpart in the Spitzer SAGE point source catalog. The
Archive contains about 650,000, 140,000, 97,000, 43,000, and 52,000 sources at
3.2, 7, 11, 15, and 24 um, respectively. Based on the catalog, we discuss the
luminosity functions at each band, the color-color diagram, and the
color-magnitude diagram using the 3.2, 7, and 11 um band data. Stars without
circumstellar envelopes, dusty C-rich and O-rich stars, young stellar objects,
and background galaxies are located at distinct regions in the diagrams,
suggesting that the present catalog is useful for the classification of objects
towards the LMC.Comment: 59 pages, 12 figures, accepted for the Astronomical Journa
AKARI Near Infrared Spectroscopy: Detection of H2O and CO2 Ices toward Young Stellar Objects in the Large Magellanic Cloud
We present the first results of AKARI Infrared Camera near-infrared spec-
troscopic survey of the Large Magellanic Cloud (LMC). We detected absorption
features of the H2O ice 3.05 um and the CO2 ice 4.27 um stretching mode toward
seven massive young stellar objects (YSOs). These samples are for the first
time spectroscopically confirmed to be YSOs. We used a curve-of-growth method
to evaluate the column densities of the ices and derived the CO2/H2O ratio to
be 0.45 pm 0.17. This is clearly higher than that seen in Galactic massive YSOs
(0.17 pm 0.03). We suggest that the strong ultraviolet radiation field and/or
the high dust temperature in the LMC may be responsible for the observed high
CO2 ice abundance.Comment: 11 pages, 1 table, 2 figure
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
AKARI IRC survey of the Large Magellanic Cloud: Outline of the survey and initial results
We observed an area of 10 deg^2 of the Large Magellanic Cloud using the
Infrared Camera on board AKARI. The observations were carried out using five
imaging filters (3, 7, 11, 15, and 24 micron) and a dispersion prism (2 -- 5
micron, 20) equipped in the IRC. This paper
describes the outline of our survey project and presents some initial results
using the imaging data that detected over 5.9x10^5 near-infrared and 6.4x10^4
mid-infrared point sources. The 10 detection limits of our survey are
about 16.5, 14.0, 12.3, 10.8, and 9.2 in Vega-magnitude at 3, 7, 11, 15, and 24
micron, respectively. The 11 and 15 micron data, which are unique to AKARI IRC,
allow us to construct color-magnitude diagrams that are useful to identify
stars with circumstellar dust. We found a new sequence in the color-magnitude
diagram, which is attributed to red giants with luminosity fainter than that of
the tip of the first red giant branch. We suggest that this sequence is likely
to be related to the broad emission feature of aluminium oxide at 11.5 micron.
The 11 and 15 micron data also indicate that the ([11] - [15]) micron color of
both oxygen-rich and carbon-rich red giants once becomes blue and then turns
red again in the course of their evolution, probably due to the change in the
flux ratio of the silicate or silicon carbide emission feature at 10 or 11.3
micron to the 15 micron flux.Comment: Accepted for publication in PASJ AKARI special issue. High resolution
version is available at:
http://www-irc.mtk.nao.ac.jp/yita/lmc20080822.ps.gz (8.9MB
Time-resolved serial femtosecond crystallography reveals early structural changes in channelrhodopsin
X線自由電子レーザーを用いて、光照射によるチャネルロドプシンの構造変化の過程を捉えることに成功. 京都大学プレスリリース. 2021-03-26.Channelrhodopsins (ChRs) are microbial light-gated ion channels utilized in optogenetics to control neural activity with light . Light absorption causes retinal chromophore isomerization and subsequent protein conformational changes visualized as optically distinguished intermediates, coupled with channel opening and closing. However, the detailed molecular events underlying channel gating remain unknown. We performed time-resolved serial femtosecond crystallographic analyses of ChR by using an X-ray free electron laser, which revealed conformational changes following photoactivation. The isomerized retinal adopts a twisted conformation and shifts toward the putative internal proton donor residues, consequently inducing an outward shift of TM3, as well as a local deformation in TM7. These early conformational changes in the pore-forming helices should be the triggers that lead to opening of the ion conducting pore
Thalassionema bifurcum sp. nov., a new stratigraphically important diatom from Pliocene subantarctic sediments
Effect of Side Chain Length on Segregation of Squalane between Smectic Layers Formed by Rod-Like Polysilanes
The segregation of spherical molecules (squalane) between the smectic layers of rod-like polymers (polysilanes) with narrow molecular weight distributions were investigated by synchrotron radiation small-angle X-ray scattering (SR-SAXS), atomic force microscopy (AFM) observations, and molecular dynamics simulations to elucidate the effect of the polymer side chain length on the segregation. It has been theoretically predicted that the smectic phase of the rod-like particles will be stabilized by inserting the spherical particles into the interstitial region between the smectic layers when the diameter of the spherical particles is smaller than that of the rod-like particles whose length is sufficiently long. We found that the segregation of squalane was unaffected by the molecular weight (Mw) of the polysilane in the range of 9,200-44,100 g/mol, and the diameter of the polysilane showed the optimal size of 5.64 nm for the segregation of squalane whose diameter is 6.57 nm although the origin of these inconsistencies between theory and experiment is currently not clear