87 research outputs found
Multi-Color Coronagraph Experiment in a Vacuum Testbed with a Binary Shaped Pupil Mask
We conducted a number of multi-band coronagraph experiments using a vacuum
chamber and a binary-shaped pupil mask which in principle should work at all
wavelengths, in the context of the research and development on a coronagraph to
observe extra-solar planets (exoplanets) directly. The aim of this work is to
demonstrate that subtraction of Point Spread Function (PSF) and multi-band
experiments using a binary-shaped pupil mask coronagraph would help improve the
contrast in the observation of exoplanets. A checkerboard mask, a kind of
binary-shaped pupil mask, was used. We improved the temperature stability by
installing the coronagraph optics in a vacuum chamber, controlling the
temperature of the optical bench, and covering the vacuum chamber with thermal
insulation layers. We evaluated how much the PSF subtraction contributes to the
high contrast observation by subtracting the images obtained through the
coronagraph. We also carried out multi- band experiments in order to
demonstrate a more realistic observation using Super luminescent Light Emitting
Diodes (SLEDs) with center wavelengths of 650nm, 750nm, 800nm and 850nm. A
contrast of 2.3x10-7 was obtained for the raw coronagraphic image and a
contrast of 1.3x10-9 was achieved after PSF subtraction with a He-Ne laser at
632.8nm wavelength. Thus, the contrast was improved by around two orders of
magnitude from the raw contrast by subtracting the PSF. We achieved contrasts
of 3.1x10-7, 1.1x10-6, 1.6x10-6 and 2.5x10-6 at the bands of 650nm, 750nm,
800nm and 850nm, respectively, in the multi-band experiments. The results show
that contrast within each of the wavelength bands was significantly improved
compared with non-coronagraphic optics. We demonstrated PSF subtraction is
potentially beneficial for improving contrast of the coronagraph, and this
coronagraph produces a significant improvement in contrast with multi-band
light sources.Comment: 14 pages, 7 figures, accepted for publication in PAS
Effect of the angiotensin-converting enzyme inhibitor imidapril on reactive hyperemia in patients with essential hypertension: relationship between treatment periods and resistance artery endothelial function
AbstractOBJECTIVESThe purpose of this study was to evaluate the effects of the angiotensin-converting enzyme (ACE) inhibitor imidapril and the calcium antagonist amlodipine on endothelial function before and after 2, 4, 8, 12, 24 and 48 weeks of treatment.BACKGROUNDThere are limited data on whether and how long endothelial function is improved after initiation of ACE inhibitor treatment and how the grade of endothelial function further progresses after improvement of endothelial dysfunction in patients with essential hypertension.METHODSThe forearm blood flow (FBF) was measured in 25 patients with essential hypertension and in 25 normotensive subjects by using strain-gauge plethysmography during reactive hyperemia (RH) (280 mm Hg for 5 min) and after sublingual administration of nitroglycerin (NTG, 0.3 mg).RESULTSThe FBF of patients with essential hypertension during RH was significantly less than that of normotensive subjects. The increase in FBF after sublingual NTG was similar in both groups. Both imidapril (n = 13) and amlodipine (n = 12) significantly reduced systolic blood pressure and diastolic after eight weeks of treatment from the pretreatment values. Forearm vascular resistance was significantly decreased after two weeks of treatment. Imidapril significantly augmented RH after 12 weeks of treatment from the pretreatment values (31.6 ± 5.7 to 38.2 ± 6.0 ml/min per 100 ml tissue, p < 0.05), whereas amlodipine did not alter RH for each treatment period. The ability of imidapril to improve RH was maintained throughout the 48-week treatment period. There was no significant difference in RH at 12, 24 and 48 weeks. The increase in FBF after sublingual administration of NTG was similar in all treatment periods for the two groups. The infusion of NG-monomethyl-L-arginine, a nitric oxide (NO) synthase inhibitor, abolished the enhancement of RH in hypertensive patients treated with imidapril.CONCLUSIONSThese findings suggest that the ACE inhibitor imidapril augments RH after 12 weeks of treatment in patients with essential hypertension and that this ACE inhibitor-induced augmentation of RH may be due to an increase in NO
Flight Performance of the AKARI Cryogenic System
We describe the flight performance of the cryogenic system of the infrared
astronomical satellite AKARI, which was successfully launched on 2006 February
21 (UT). AKARI carries a 68.5 cm telescope together with two focal plane
instruments, Infrared Cameras (IRC) and Far Infrared Surveyor (FIS), all of
which are cooled down to cryogenic temperature to achieve superior sensitivity.
The AKARI cryogenic system is a unique hybrid system, which consists of cryogen
(liquid helium) and mechanical coolers (2-stage Stirling coolers). With the
help of the mechanical coolers, 179 L (26.0 kg) of super-fluid liquid helium
can keep the instruments cryogenically cooled for more than 500 days. The
on-orbit performance of the AKARI cryogenics is consistent with the design and
pre-flight test, and the boil-off gas flow rate is as small as 0.32 mg/s. We
observed the increase of the major axis of the AKARI orbit, which can be
explained by the thrust due to thermal pressure of vented helium gas.Comment: 19 pages, 10 figures, and 6 tables. Accepted for publication in the
AKARI special issue of the Publications of the Astronomical Society of Japa
Constraint on the giant planet production by core accretion
The issue of giant planet formation by core instability (CI) far from the
central star is rather controversial because the growth of massive solid core
necessary for triggering the CI can take longer than the lifetime of the
protoplanetary disk. In this work we assess the range of separations at which
the CI may operate by (1) allowing for arbitrary (physically meaningful) rate
of planetesimal accretion by the core and (2) properly taking into account the
dependence of the critical mass for the CI on the planetesimal accretion
luminosity. This self-consistent approach distinguishes our work from similar
studies in which only a specific planetesimal accretion regime was explored
and/or the critical core mass was fixed at some arbitrary level. We demonstrate
that the largest separation at which the CI can occur within 3 Myr corresponds
to the surface density of solids in the disk higher than 0.1 g cm^{-2} and is
40-50 AU in the minimum mass Solar nebula. This limiting separation is achieved
when the planetesimal accretion proceeds at the fastest possible rate, even
though the high associated accretion luminosity increases the critical core
mass delaying the onset of the CI. Our constraints are independent of the mass
of the central star and vary only weakly with the core density and its
atmospheric opacity. We also discuss various factors which can strengthen or
weaken our limits on the operation of the CI.Comment: 8 pages, 1 figure, submitted to Ap
Low body mass index is a risk factor forimpaired endothelium-dependent vasodilation in humans: role of nitric oxide and oxidative stress
AbstractObjectivesThe purpose of this study was to evaluate the relationship between body mass index (BMI), including low BMIs, and endothelial function.BackgroundEpidemiologic study has demonstrated that not only obesity but also a low BMI may be a risk factor for cardiovascular disease.MethodsThe forearm blood flow (FBF) response to acetylcholine (ACh) and isosorbide dinitrate (ISDN) was measured in 87 healthy young men (15 low BMI, 51 normal, 14 obese, and 7 extremely obese).ResultsPlasma concentrations of 8-hydroxy-2′-deoxyguanosine and serum concentrations of malondialdehyde-modified low-density lipoprotein were higher in low BMI, obese, and extremely obese subjects than in normal subjects and were similar among the low BMI, obese, and extremely obese groups. The FBF response to ACh was greater in the normal group than in the other groups (p < 0.001), and was lower in the extremely obese group as compared with the other groups (p < 0.001). The ACh-stimulated vasodilation was similar between the low BMI group and the obese group. The ISDN-stimulated vasodilation was similar in all four groups. There were no significant differences in ACh-stimulated vasodilation between the four groups after the nitric oxide (NO) synthase inhibitor NG-monomethyl-L-arginine infusion. Co-infusion of vitamin C augmented the FBF response to ACh in low BMI, obese, and extremely obese groups—but not in normal BMI group.ConclusionsThese findings suggest that not only obesity but also a low BMI may be a risk factor for impaired endothelium-dependent vasodilation through the increased oxidative stress, leading to the reduced bioavailability of NO
SPICA infrared coronagraph for the direct observation of exo-planets
We present a MIR coronagraph to target the direct observation of extrasolar
planets for SPICA, in which a coronagraph is currently regarded as an option of
the focal plane instruments. The primary target of the SPICA coronagraph is the
direct observation of Jovian exo-planets. A strategy of the baseline survey and
the specifications for the coronagraph instrument for the survey are introduced
together. The main wavelengths and the contrast required for the observations
are 3.5-27um, and 10^{-6}, respectively.Laboratory experiments were performed
with a visible laser to demonstrate the principles of the coronagraphs. In an
experiment using binary-shaped pupil coronagraphs, a contrast of 6.7x10^{-8}
was achieved, as derived from the linear average in the dark region and the
core of the PSF. A coronagraph by a binary-shaped pupil mask is a baseline
solution for SPICA because of its feasibility and robustness. On the other
hand, a laboratory experiment of the phase induced amplitude
apodization/binary-mask hybrid coronagraph has been executed to obtain an
option of higher performance, and a contrast of 6.5x10^{-7} was achieved with
active wavefront control.Potentially important by-product of the instrument,
transit monitoring for characteization of exo-planets, is also described. We
also present recent progress of technology on a design of a binary-shaped pupil
mask for the actual pupil of SPICA, PSF subtraction, the development of
free-standing binary masks, a vacuum chamber, and a cryogenic deformable
mirror. Considering SPICA to be an essential platform for coronagraphs and the
progress of key technologies, we propose to develop a mid-infrared coronagraph
instrument for SPICA and to perform the direct observation of exo-planets with
it.Comment: 37th COSPAR Scientific Assembly; Montreal, Canada 13-20 July
2008/Submitted to AS
Hot debris dust around HD 106797
Photometry of the A0 V main-sequence star HD 106797 with AKARI and
Gemini/T-ReCS is used to detect excess emission over the expected stellar
photospheric emission between 10 and 20 micron, which is best attributed to hot
circumstellar debris dust surrounding the star. The temperature of the debris
dust is derived as Td ~ 190 K by assuming that the excess emission is
approximated by a single temperature blackbody. The derived temperature
suggests that the inner radius of the debris disk is ~ 14 AU. The fractional
luminosity of the debris disk is 1000 times brighter than that of our own
zodiacal cloud. The existence of such a large amount of hot dust around HD
106797 cannot be accounted for by a simple model of the steady state evolution
of a debris disk due to collisions, and it is likely that transient events play
a significant role. Our data also show a narrow spectral feature between 11 and
12 micron attributable to crystalline silicates, suggesting that dust heating
has occurred during the formation and evolution of the debris disk of HD
106797.Comment: Accepted to ApJ Letters, 8 pages, 2 figure
Iroquois homeobox 3 regulates odontoblast proliferation and differentiation mediated by Wnt5a expression
Iroquois homeobox (Irx) genes are TALE-class homeobox genes that are evolutionarily conserved across species and have multiple critical cellular functions in fundamental tissue development processes. Previous studies have shown that Irxs genes are expressed during tooth development. However, the precise roles of genes in teeth remain unclear. Here, we demonstrated for the first time that Irx3 is an essential molecule for the proliferation and differentiation of odontoblasts. Using cDNA synthesized from postnatal day 1 (P1) tooth germs, we examined the expression of all Irx genes (Irx1-Irx6) by RT-PCR and found that all genes except Irx4 were expressed in the tooth tissue. Irx1-Irx3 a were expressed in the dental epithelial cell line M3H1 cells, while Irx3 and Irx5 were expressed in the dental mesenchymal cell line mDP cells. Only Irx3 was expressed in both undifferentiated cell lines. Immunostaining also revealed the presence of IRX3 in the dental epithelial cells and mesenchymal condensation. Inhibition of endogenous Irx3 by siRNA blocks the proliferation and differentiation of mDP cells. Wnt3a, Wnt5a, and Bmp4 are factors involved in odontoblast differentiation and were highly expressed in mDP cells by quantitative PCR analysis. Interestingly, the expression of Wnt5a (but not Wnt3a or Bmp4) was suppressed by Irx3 siRNA. These results suggest that Irx3 plays an essential role in part through the regulation of Wnt5a expression during odontoblast proliferation and differentiation
The Ganymede Laser Altimeter (GALA) for the Jupiter Icy Moons Explorer (JUICE): Mission, science, and instrumentation of its receiver modules
The Jupiter Icy Moons Explorer (JUICE) is a science mission led by the European Space Agency, being developed for launch in 2023. The Ganymede Laser Altimeter (GALA) is an instrument onboard JUICE, whose main scientific goals are to understand ice tectonics based on topographic data, the subsurface structure by measuring tidal response, and small-scale roughness and albedo of the surface. In addition, from the perspective of astrobiology, it is imperative to study the subsurface ocean scientifically. The development of GALA has proceeded through an international collaboration between Germany (the lead), Japan, Switzerland, and Spain. Within this framework, the Japanese team (GALA-J) is responsible for developing three receiver modules: the Backend Optics (BEO), the Focal Plane Assembly (FPA), and the Analog Electronics Module (AEM). Like the German team, GALA-J also developed software to simulate the performance of the entire GALA system (performance model). In July 2020, the Proto-Flight Models of BEO, FPA, and AEM were delivered from Japan to Germany. This paper presents an overview of JUICE/GALA and its scientific objectives and describes the instrumentation, mainly focusing on Japan’s contribution
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