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The search for life in the Universe is a fundamental problem of astrobiology and modern science. The current progress in the detection of terrestrial-type exoplanets has opened a new avenue in the characterization of exoplanetary atmospheres and in the search for biosignatures of life with the upcoming ground-based and space missions. To specify the conditions favourable for the origin, development and sustainment of life as we know it in other worlds, we need to understand the nature of global (astrospheric), and local (atmospheric and surface) environments of exoplanets in the habitable zones (HZs) around G-K-M dwarf stars including our young Sun. Global environment is formed by propagated disturbances from the planet-hosting stars in the form of stellar flares, coronal mass ejections, energetic particles and winds collectively known as astrospheric space weather. Its characterization will help in understanding how an exoplanetary ecosystem interacts with its host star, as well as in the specification of the physical, chemical and biochemical conditions that can create favourable and/or detrimental conditions for planetary climate and habitability along with evolution of planetary internal dynamics over geological timescales. A key linkage of (astro)physical, chemical and geological processes can only be understood in the framework of interdisciplinary studies with the incorporation of progress in heliophysics, astrophysics, planetary and Earth sciences. The assessment of the impacts of host stars on the climate and habitability of terrestrial (exo)planets will significantly expand the current definition of the HZ to the biogenic zone and provide new observational strategies for searching for signatures of life. The major goal of this paper is to describe and discuss the current status and recent progress in this interdisciplinary field in light of presentations and discussions during the NASA Nexus for Exoplanetary System Science funded workshop ‘Exoplanetary Space Weather, Climate and Habitability’ and to provide a new roadmap for the future development of the emerging field of exoplanetary science and astrobiology.
NUMO and JAEA have been conducting a joint research since FY2011, which is aimed
to enhance the methodology of repository design and performance assessment in
preliminary investigation stage for the deep geological disposal of high-level
radioactive waste. As a part of this joint research, we have been developing
glass dissolution models which include various processes derived from
glass-overpack-bentonite buffer interaction, considering the precipitation of
Fe-silicates associated with steel overpack corrosion, and Si transport through
altered layer of glass. The objective of this modeling work is to show
comprehensively the lifetime of the vitrified waste due to glass matrix
dissolution timescales through sensitivity analysis, and to identify the
feature/process that most strongly influences the lifetime, and to identify
future R&D issues that would help to improve the nuclide transport
analysis with confidential value and the safety case in future. The sensitivity
analysis suggested that the duration of the glass dissolution might be predicted
in the ranges from 3.8×103 to 1.9×105
years. Also, the results indicated that the precipitation of
Fe–silicate has the strongest influence on the long-team behavior of
CIGS thin films were irradiated with 100 or 250 keV electrons to reveal the radiation defect by analyzing PL measurement. The PL intensity decreased due to non-radiative recombination defects induced by electron irradiation. Furthermore, the intensity 0.8 eV peak of the PL spectrum was observed from CIGS films irradiated with 250 eV electrons and is said to correspond to In-antisite defects in CIGS materials. The defects can usually change into InCu-VCu complex defects combined with VCu, since the formation energy of the complex defect is lower than that of each defect. Cu interstitial defects induced by 250 keV electron irradiation would diffuse to VCu of the complex defect, whereupon the complex defect might become an In-antisite defect due to 250 keV electron irradiation.
A seroprevalence survey on measles, mumps, rubella and varicella was conducted on healthcare workers (HCWs) at Shimane University Hospital, Japan utilizing an enzyme immunoassay. Of 1811 HCWs tested, 91·8% were seropositive to measles, 92·1% to mumps, 89·5% to rubella and 96·3% to varicella. Sex-related differences in seroprevalence were found in rubella (males vs. females: 84·7 vs. 92·2%, P < 0·001). Moreover, males aged 30–39 years were most susceptible to rubella (22·4%), which may be attributed to the design of childhood immunization programmes in Japan. Individuals aged ⩽29 years were more susceptible to measles (14·3%) and mumps (10·9%), compared to other age groups. There were no significant sex- and age-related differences in varicella seroprevalence. The physician occupational group was more susceptible to rubella, but no significant occupational-related difference was observed in the other diseases. Susceptible subjects, with negative or equivocal serological results were given a vaccine which induced seroconversion in most vaccinees. Seroconversion occurred more frequently in the equivocal group than in the negative group. These findings provide a new insight for the seroprevalence survey of vaccine-preventable diseases in Japanese HCWs with special reference to vaccine efficacy.
Vitamin D and folate are associated with decreased colorectal cancer risk and their association with colorectal cancer prognosis is under investigation. We assessed the levels of plasma 25-hydroxyvitamin D3 (25(OH)D3), folate and vitamin B12 in an international pilot study in order to determine variability of these biomarkers based on geographical location. Plasma 25(OH)D3, folate and vitamin B12 concentrations were measured in 149 invasive, newly diagnosed colorectal cancer cases from Heidelberg (Germany), Seattle (WA, USA), and Tampa (FL, USA) and in ninety-one age- and sex-matched controls. Their associations with potential predictors were assessed using multivariate linear regression analyses. Plasma 25(OH)D3, folate and vitamin B12 concentrations differed by location. Other predictors were season for 25(OH)D3 and tumour stage (vitamin B12). Season-corrected average 25(OH)D3 concentrations were higher in Heidelberg (31·7 ng/ml; range 11·0–83·0 ng/ml) than in Seattle (23·3 ng/ml; range 4·0–80·0 ng/ml) and Tampa (21·1 ng/ml; range 4·6–51·6 ng/ml). In Heidelberg, a strong seasonal variation was observed. Folate (11·1 ng/ml) and vitamin B12 (395 pg/ml) concentrations in Heidelberg were lower than those in Seattle (25·3 ng/ml and 740 pg/ml, respectively) and Tampa (23·8 ng/ml and 522 pg/ml, respectively). Differences in plasma 25(OH)D3 and folate concentrations between Heidelberg and the US sites were observed, probably reflecting variation in outdoor activities and sun-avoidance behaviour during summer as well as in folic acid fortification and supplement use. Intra-site differences at each study location were greater than between-location variability, suggesting that individual health behaviours play a significant role. Nevertheless, the intra-site differences we observed may be due to chance because of the limited sample size. Our pilot study illustrates the value of an international cohort in studying colorectal cancer prognosis to discern geographical differences in a broad range of exposures.
We present an overview of recent astrometric results with VERA. Since 2004, we have been conducting astrometry of tens of Galactic maser sources with VERA, and recently obtained trigonometric parallaxes for several sources, with distances ranging from 180 pc to 5.3 kpc. In this paper, we briefly summarize the results for Galactic star-forming regions, including S269, Orion-KL, NGC 1333, ρ-oph, NGC 281 and others.
VERA aims at astrometric observations using phase referencing VLBI techniques, whose goal is a 10 micro arc-second accuracy for annual parallax measurements. VERA has four 20-m diameter VLBI radio telescopes in Japanese archipelago with the maximum baseline length of 2,300 km. They have the two-beam observing system, which makes simultaneous observations of two objects possible. This leads to very accurate phase referencing VLBI observations. An important science goal is to make a 3-dimensional map of the Galaxy and reveal its dynamics. In order to achieve this, VERA has the 22GHz and 43GHz bands for H2O and SiO maser objects, respectively. Maser objects are compact and suitable for astrometry observations. VERA's construction was started in 2000 and the array became operational in 2004. We have already measured annual parallaxes and proper motions of some galactic objects. In the future, VERA will collaborate with Korean and Chinese VLBI stations.
Parallax measurements of the Galactic Mira variables with VERA have started since 2004 to establish their Period-Luminosity (PL) relationship in the Galaxy. Multi-epoch VLBI observations of a semiregular variable S Crt yielded an accurate parallax of 2.27±0.14 mas corresponding to the distance of 441+29−24 pc. In addition to the distance, we obtained physical properties of S Crt. Temperature of the photosphere was found to be ~3000 K by fitting the infrared spectrum with a blackbody radiation. The stellar radius was obtained based on the distance, apparent magnitude, and the temperature. Internal proper motions of circularly-arranged maser spots in S Crt were detected for the first time. Observations of the other Mira variables, such as R UMa, SY Scl, AP Lyn, and WX Psc are in progress.
We present the results of a mm wavelength methanol maser survey towards massive star forming regions. We have carried out Class II methanol maser observations at 86.6 GHz, 86.9 GHz and 107.0 GHz, simultaneously, using the Nobeyama 45 m telescope. We selected 108 6.7 GHz methanol maser sources with declinations above −25 degrees and fluxes above 20 Jy. The detection limit of maser observations was ~3 Jy. Of the 93 sources surveyed so far, we detected methanol emission in 25 sources (27%) and “maser” emission in nine sources (10%), of which thre “maser” sources are new detections. The detection rate for maser emission is about half that of a survey of the southern sky (Caswell et al. 2000). There is a correlation between the maser flux of 107 GHz and 6.7 GHz/12 GHz emission, but no correlation with the “thermal” (non maser) emission. From results of other molecular line observations, we found that the sources with methanol emission show higher gas temperatures and twice the detection rate of SiO emission. This may suggest that dust evaporation and destruction by shock are responsible for the high abundance of methanol molecules, one of the required physical conditions for maser emission.
We have started a VLBI monitoring program for Asymptotic Giant Branch (AGB) stars at 22 and 43 GHz as part of a project of the VLBI Exploration of Radio Astrometry (VERA) for precisely obtaining the period-luminosity (PL) relation of Galactic Mira variables. Using accurate distances measured with VERA, we reveal PL relation in the Galaxy based on the absolute magnitudes of the sources. We selected the sources for VLBI monitoring so that they have a good coverage of various pulsation periods. Photometry in the infrared J, H, and K bands for over 600 AGB stars has also started since 2003 with the 1m telescope of Kagoshima University to obtain the pulsation periods and magnitudes. Current analysis of the phase referencing VLBI observations of S Crt shows that the parallax of 2.3±0.2 milliarcsec (mas) corresponds to a distance of 435+41−35 pc. From the infrared monitoring data, pulsation periods and magnitudes in K band for 248 sources were obtained.
We present VLBA observation towards the nucleus of a nearby radio galaxy NGC 1052. In NGC 1052, two-sided jet structure and a dense plasma circumnuclear torus with a radius of 0.7 pc have been found around the central mass. It emits a H2O megamaser, which is redshifted with respect to the systemic velocity of the galaxy (1491 kms−1) with a large velocity width of 100 kms−1 (FWHM). The maser gas is found at the inner jet components of both the approaching and receding jets. The maser gas is positionally coincident with a plasma torus. The maser gas in NGC 1052 could be explained as a circumnuclear torus or disk, as found for the nucleus of NGC 4258.
Sorption of selenium (Se) was studied by batch technique by using sedimentary rock samples andcorresponding saline groundwater from Horonobe underground research laboratory (URL)site under reducing condition. Spectroscopic analyses were performed by X-ray absorption near-edge structure (XANES) afterthe sorption experiments to identify the oxidation states of Se on the sedimentary rock. It issuggested thatthe dominant parameters affecting the Se sorption are iron-bearing minerals, especially exchangeable Fe and pyrite, and organic matters. Most of the Se sorbed on the sedimentary rock was Se(0) inthe case of natural saline groundwater, at least at relatively high Se concentration, while only part of the Se was Se(0) in caseof the synthetic groundwater, which contains no organic matters. Incorporationinto pyrite could be the sorption mechanism of Se(0).
Extended abstract of a paper presented at the Pre-Meeting Congress: Materials Research in an Aberration-Free Environment, at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, July 31 and August 1, 2004.
Characterizations of transparent Schottky barrier GaN and AlGaN UV detectors in the vacuum UV (VUV) and soft X-ray (SX) region using synchrotron radiation are described. In the GaN UV detectors, the responsivity achieved about 0.05 A/W at 95 eV (13 nm). Thus, their device performance is shown between 3.4 and 100 eV (10 and 360 nm). Furthermore, the high responsivity spectra were realized by using AlGaN Schottky UV detectors consisting of Al0.5Ga0.5N on AlN epitaxial layer.
Excitonic resonance energies in a C-plane AlN epilayer on the (0001) sapphire substrate grown by low-pressure metalorganic vapor phase epitaxy were determined as a function of temperature by means of optical reflectance (OR) and cathodoluminescence (CL) measurements. The OR spectra exhibited distinct reflectance anomalies at the photon energies just above the multiple internal reflection fringes, and the spectral lineshape was fitted considering A (???u7v7c) and BC (???9v,???17v7c) exciton transitions. The energies of them at 0 K were obtained to be 6.211 and 6.266 eV, giving the crystal field splitting (Δcr) of approximately 55 meV. The AlNfilm exhibited an excitonic emission even at 300 K, which is due to the small Bohr radius of excitons and large longitudinal optical phonon energies. The Einstein characteristic temperature Q E was estimated to be 580 K.
Since the discovery of fading X-rays from Gamma-Ray Bursts (GRBs) with BeppoSAX (Piro et al. 1997, Costa et al. 1997), world-wide follow-up observations in optical band have achieved the fruitful results. The case of GRB 970228, there was an optical transient, coincides with the BeppoSAX position and faded (Paradijs et al. 1997, Sahu et al. 1997). These optical observations also confirmed the extended component, which was associated with the optical transient. The new transient are fading with a power-law function in time and the later observation of HST confirmed the extended emission is stable (Fruchter et al. 1997). This extended object seems to be a distant galaxy and strongly suggests to be the host.