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With the recent discovery of a dozen dusty star-forming galaxies and around 30 quasars at z > 5 that are hyper-luminous in the infrared (μ LIR > 1013 L⊙, where μ is a lensing magnification factor), the possibility has opened up for SPICA, the proposed ESA M5 mid-/far-infrared mission, to extend its spectroscopic studies toward the epoch of reionisation and beyond. In this paper, we examine the feasibility and scientific potential of such observations with SPICA’s far-infrared spectrometer SAFARI, which will probe a spectral range (35–230 μm) that will be unexplored by ALMA and JWST. Our simulations show that SAFARI is capable of delivering good-quality spectra for hyper-luminous infrared galaxies at z = 5 − 10, allowing us to sample spectral features in the rest-frame mid-infrared and to investigate a host of key scientific issues, such as the relative importance of star formation versus AGN, the hardness of the radiation field, the level of chemical enrichment, and the properties of the molecular gas. From a broader perspective, SAFARI offers the potential to open up a new frontier in the study of the early Universe, providing access to uniquely powerful spectral features for probing first-generation objects, such as the key cooling lines of low-metallicity or metal-free forming galaxies (fine-structure and H2 lines) and emission features of solid compounds freshly synthesised by Population III supernovae. Ultimately, SAFARI’s ability to explore the high-redshift Universe will be determined by the availability of sufficiently bright targets (whether intrinsically luminous or gravitationally lensed). With its launch expected around 2030, SPICA is ideally positioned to take full advantage of upcoming wide-field surveys such as LSST, SKA, Euclid, and WFIRST, which are likely to provide extraordinary targets for SAFARI.
Measurements in the infrared wavelength domain allow direct assessment of the physical state and energy balance of cool matter in space, enabling the detailed study of the processes that govern the formation and evolution of stars and planetary systems in galaxies over cosmic time. Previous infrared missions revealed a great deal about the obscured Universe, but were hampered by limited sensitivity.
SPICA takes the next step in infrared observational capability by combining a large 2.5-meter diameter telescope, cooled to below 8 K, with instruments employing ultra-sensitive detectors. A combination of passive cooling and mechanical coolers will be used to cool both the telescope and the instruments. With mechanical coolers the mission lifetime is not limited by the supply of cryogen. With the combination of low telescope background and instruments with state-of-the-art detectors SPICA provides a huge advance on the capabilities of previous missions.
SPICA instruments offer spectral resolving power ranging from R ~50 through 11 000 in the 17–230 μm domain and R ~28.000 spectroscopy between 12 and 18 μm. SPICA will provide efficient 30–37 μm broad band mapping, and small field spectroscopic and polarimetric imaging at 100, 200 and 350 μm. SPICA will provide infrared spectroscopy with an unprecedented sensitivity of ~5 × 10−20 W m−2 (5σ/1 h)—over two orders of magnitude improvement over what earlier missions. This exceptional performance leap, will open entirely new domains in infrared astronomy; galaxy evolution and metal production over cosmic time, dust formation and evolution from very early epochs onwards, the formation history of planetary systems.
The mid-infrared range contains many spectral features associated with large molecules and dust grains such as polycyclic aromatic hydrocarbons and silicates. These are usually very strong compared to fine-structure gas lines, and thus valuable in studying the spectral properties of faint distant galaxies. In this paper, we evaluate the capability of low-resolution mid-infrared spectroscopic surveys of galaxies that could be performed by SPICA. The surveys are designed to address the question how star formation and black hole accretion activities evolved over cosmic time through spectral diagnostics of the physical conditions of the interstellar/circumnuclear media in galaxies. On the basis of results obtained with Herschel far-infrared photometric surveys of distant galaxies and Spitzer and AKARI near- to mid-infrared spectroscopic observations of nearby galaxies, we estimate the numbers of the galaxies at redshift z > 0.5, which are expected to be detected in the polycyclic aromatic hydrocarbon features or dust continuum by a wide (10 deg2) or deep (1 deg2) blind survey, both for a given observation time of 600 h. As by-products of the wide blind survey, we also expect to detect debris disks, through the mid-infrared excess above the photospheric emission of nearby main-sequence stars, and we estimate their number. We demonstrate that the SPICA mid-infrared surveys will efficiently provide us with unprecedentedly large spectral samples, which can be studied further in the far-infrared with SPICA.
IR spectroscopy in the range 12–230 μm with the SPace IR telescope for Cosmology and Astrophysics (SPICA) will reveal the physical processes governing the formation and evolution of galaxies and black holes through cosmic time, bridging the gap between the James Webb Space Telescope and the upcoming Extremely Large Telescopes at shorter wavelengths and the Atacama Large Millimeter Array at longer wavelengths. The SPICA, with its 2.5-m telescope actively cooled to below 8 K, will obtain the first spectroscopic determination, in the mid-IR rest-frame, of both the star-formation rate and black hole accretion rate histories of galaxies, reaching lookback times of 12 Gyr, for large statistically significant samples. Densities, temperatures, radiation fields, and gas-phase metallicities will be measured in dust-obscured galaxies and active galactic nuclei, sampling a large range in mass and luminosity, from faint local dwarf galaxies to luminous quasars in the distant Universe. Active galactic nuclei and starburst feedback and feeding mechanisms in distant galaxies will be uncovered through detailed measurements of molecular and atomic line profiles. The SPICA’s large-area deep spectrophotometric surveys will provide mid-IR spectra and continuum fluxes for unbiased samples of tens of thousands of galaxies, out to redshifts of z ~ 6.
Our current knowledge of star formation and accretion luminosity at high redshift (z > 3–4), as well as the possible connections between them, relies mostly on observations in the rest-frame ultraviolet, which are strongly affected by dust obscuration. Due to the lack of sensitivity of past and current infrared instrumentation, so far it has not been possible to get a glimpse into the early phases of the dust-obscured Universe. Among the next generation of infrared observatories, SPICA, observing in the 12–350 µm range, will be the only facility that can enable us to trace the evolution of the obscured star-formation rate and black-hole accretion rate densities over cosmic time, from the peak of their activity back to the reionisation epoch (i.e., 3 < z ≲ 6–7), where its predecessors had severe limitations. Here, we discuss the potential of photometric surveys performed with the SPICA mid-infrared instrument, enabled by the very low level of impact of dust obscuration in a band centred at 34 µm. These unique unbiased photometric surveys that SPICA will perform will fully characterise the evolution of AGNs and star-forming galaxies after reionisation.
The physical processes driving the chemical evolution of galaxies in the last ~ 11Gyr cannot be understood without directly probing the dust-obscured phase of star-forming galaxies and active galactic nuclei. This phase, hidden to optical tracers, represents the bulk of the star formation and black hole accretion activity in galaxies at 1 < z < 3. Spectroscopic observations with a cryogenic infrared observatory like SPICA, will be sensitive enough to peer through the dust-obscured regions of galaxies and access the rest-frame mid- to far-infrared range in galaxies at high-z. This wavelength range contains a unique suite of spectral lines and dust features that serve as proxies for the abundances of heavy elements and the dust composition, providing tracers with a feeble response to both extinction and temperature. In this work, we investigate how SPICA observations could be exploited to understand key aspects in the chemical evolution of galaxies: the assembly of nearby galaxies based on the spatial distribution of heavy element abundances, the global content of metals in galaxies reaching the knee of the luminosity function up to z ~ 3, and the dust composition of galaxies at high-z. Possible synergies with facilities available in the late 2020s are also discussed.
The Fukushima Nuclear Energy Workers' Support (NEWS) Project Study previously showed that experiences related to the Fukushima nuclear disaster on 11 March 2011 had a great impact on psychological states, including post-traumatic stress response (PTSR) and general psychological distress (GPD), among the Fukushima nuclear plant workers. To determine the causal relationship between disaster-related experiences and levels of psychological states, we conducted a 3-year longitudinal study from 2011 to 2014.
PTSR and GPD of the nuclear plant workers were assessed by annual questionnaires conducted from 2011 to 2014. The present study included a total of 1417 workers who provided an assessment at baseline (2011). A total of 4160 observations were used in the present analysis. The relationship between disaster-related experiences and psychological states over time was analysed using mixed-effects logistic regression models.
A declining influence of disaster-related experiences on PTSR over time was found. However, the impact on PTSR remained significantly elevated even 3 years after the disaster in several categories of exposure including the experience of life-threatening danger, experiences of discrimination, the witnessing of plant explosion, the death of a colleague and home evacuation. The associations between GPD and disaster-related experiences showed similar effects.
The effects of disaster-related experiences on psychological states among the nuclear plant workers reduced over time, but remained significantly high even 3 years after the event.
High dietary energy density (ED) has been associated with weight gain. However, little is known about the long-term effects of ED on weight changes among free-living subjects, particularly in Japanese and other Asian populations. In this study, we assessed dietary habits and weight changes in participants (5778 males and 7440 females, 35–69 years old) of the Takayama study. ED was estimated using a validated FFQ at baseline only. Information on body weight (BW) was obtained by self-administered questionnaires at baseline and follow-up. Mean BW difference in 9·8 years was 17 (se 4221) g for men and −210 (se 3889) g for women. In men, ED was positively associated with BW at follow-up after controlling for age, BW, height, physical activity score, alcohol consumption, energy intake, years of education at the baseline and change of smoking status during the follow-up. On average, men in the highest quartile of ED (>5·322 kJ/g (>1·272 kcal/g)) gained 138 (se 111) g, whereas men in the lowest ED (<1·057) lost 22 (se 111) g (Pfor trend=0·01). The association between ED and BW gain was stronger in men with normal weight. In women, the association between ED and weight change was not statistically significant. In conclusion, contrary to some studies that report an association between ED and weight gain in the overweight only, our data suggest that high-ED diets may be associated with weight gain in the lean population as well, at least in male subjects.
The kinetics of Ge lateral overgrowth on SiO2 with line-shaped Si seeds is examined. The growth process is described by the difference between the growth rates of Ge on (100) planes (GR100) and <311> facets (GR311). The theoretical calculations well reproduce the growth kinetics. It is shown that narrowing the line-seeds helps Ge coalescence and flat film formation.
We performed a couple of balloon experiments to measure the size and the location of Cyg-X-1 using the techniques of the modulation collimator . The angular periods of the modulation collimator were 26′ and 10′ for the respective flights corresponding to the approximate angular resolutions of the size determination and location, 3′ and 1′ respectively. Preliminary results of the experiment with 3′ resolution are reported here.
A Compact Planar Magnetron Plasma Sputtering Deposition Device (CPM-PSDD) has been used to deposit TiO2 on silicon, glass and cotton cloth. An 80 mm diameter Ti target was placed at the cathode and was sputtered by argon-oxygen plasma with 10-20 mA discharge current and -300 V to -450 V discharge potential. Reactive oxygen gas fed into the system at 13:1 Ar:O2 sccm ratio for the deposition durations between one to four hours. The deposited films exhibited both anatase and rutile phases. Cotton cloths were dipped in methyl blue to evaluate the photocatalytic activity of the film.
Thin-film silicon solar cells have been attracted a lot of intention as low-cost solar cells. One of the most important technologies for improving their performances is light trapping. We have demonstrated the high potential of double-textured zinc oxide (ZnO) thin films used as front transparent conductive oxide (TCO) films due to further enhancement of their light-trapping effects. Although the laser scribing method has already been well established for low-cost thin-film silicon solar cell module manufacturing, laser scribing technique on double-textured ZnO is new and still a challenging issue. In this study, we firstly demonstrated the availability of laser scribing for amorphous silicon (a-Si) solar cells fabricated on double-textured ZnO substrates. It is general to utilize lasers with wavelength of 1.06 μm and 532 nm for scribing of TCO and silicon layer, respectively. Here we attempted to scribe both of TCO and silicon layers using a 532 nm wavelength laser (green laser) for process simplifying.
The 7-valent pneumococcal conjugate vaccine (PCV7) is reported to decrease the incidence of community-acquired pneumonia (CAP) in children. To determine the annual incidence of CAP before the introduction of PCV7, we counted the number of children hospitalized with CAP between 2008 and 2009 in Chiba City, Japan. We investigated serotype and multilocus sequence typing (MLST) for Streptococcus pneumoniae isolates in CAP cases. The annual incidence of hospitalized CAP in children aged <5 years was 17·6 episodes/1000 child-years. In 626 episodes, S. pneumoniae was dominant in 14·7% and 0·8% of sputum and blood samples, respectively. The most common serotypes were 6B, 23F and 19F. The coverage rates of PCV7 were 66·7% and 80% in sputum samples and blood samples, respectively. MLST analysis revealed 37 sequence types. Furthermore, 54·1% of the sputum isolates and 40% of the blood isolate were related to international multidrug-resistant clones.
Japanese Disaster Medical Assistance Team (DMAT) has important duties to support and reinforce functionally insufficient key disaster hospitals in the large-scale disasters. However, it is difficult for Japanese DMAT to fulfill these duties in the current circumstances, because the DMAT consists of individual institutions and Teams have less experience to work in the other institutions. To resolve the issues, disaster drills for some DMATs which consist of several institutions have been held since 2008. We evaluated the effectiveness of the drills and educational system.
Investigation was performed by surveillance questionnaires to 129 participants in the drill (staffs from DMATs, Red Cross and local government, and sham patients). The questionnaires are: A. Was the cooperative medical practice performed smoothly? B. Was the support for hospitals conducted effectively?, C. Was the medical record for wide-area transportation completed? (for our staffs only), D. Was our activity enough? (for participants excluding us), and E. Was the drill beneficial?
85 participants including 30 staffs in our institution answered the questionnaires (65.9%). The number of participants who answered ‘Yes’ was as follows: A. 48 (56.5%), B. 64 (75.3%), C. 8 (26.7%), D. 44 (83.0%) and E. 81 (95.3%).
Although the cooperative medical practice was not so smooth, it was recognized that members in DMATs got mutual trust by their high knowledge and skills. And it was suggested that DMAT could not command and control the hospital staffs without their understanding the equipments and documentations used by DMAT. And it is ideal to change the mindset of hospital top managements towards the disaster medicine through the repeated drills.
The repeated disaster drills at the local area is essential to make DMAT function sufficiently.
Defect formation in Si by B10H14 (decaborane) ion implantation has been investigated with photoluminescence measurement. An intense W-line was observed at photon energy of 1.018eV from as-implanted FZ-Si by 30keV B10H14+ implantation. W-line center is considered as an interstitial aggregate and usually observed after ion implantation with subsequent low-temperatureannealing in the case of atomic ion implantation. As W-line is observed from as-implanted Si, the defect formation with B10H14 is expected to be different from that of B+ implantation with the same energy per atom. The energy dependence of W-line intensity is similar to that of diffusivity enhancement after rapid thermal annealing. Molecular dynamics simulation and Rutherford backscattering spectrometry channeling experiment suggest that one B10H14 implantation creates a larger number of dislocated Si atoms than that of B+ implantation with the same energy per atom. This characteristic of B10H14 implantation may cause the different defect reactions in subsequent annealing process.
Silicon self–diffusion coefficients were measured in intrinsic and extrinsic silicon from870 to 1070°C using isotopically pure 30Si layer. 30Si diffusion profiles are determined by secondary ion mass spectrometry. The temperature dependence of intrinsic diffusion coefficient in bulk Si isobtained. Comparing it in heavily As-doped or B-doped Si, it is found that Si self-diffusion is entirely mediated by interstitialcy mechanism at lower temperatures below 870°C.
Tin oxide (SnO2) thin films have been grown on Si (100) and Al2O3 substrates by pulsed Nd:YAG (532nm) and KrF excimer (248 nm) laser deposition methods using SnO2 targets. X-ray diffraction measurement showed that the almost amorphous microstructure transformed into a crystalline SnO2 phase and preferred orientation varied from (101) to (110) on Si (100) with increasing oxygen gas pressure. This result suggests that oxygen gas pressure affects the phase formation, crystalline structure and preferred orientation of the films. Gas sensing properties of SnO2 thin films by PLD method were also investigated over the temperature range 300 – 600°C, using 0.31vol%H2 as a test gas. The oxygen gas pressure results in a notable change in gas sensing properties of SnO2 thin films.
We identified two causes of source/drain (S/D) series resistance (Rs) in bottom-contact (BC) pentancene thin-film transistors (TFTs). One is mixed-phase pentacene grown in the blurred- edge region of Au electrodes and the other is the semi-insulating pentacene region between the Au electrode and the carrier-accumulating layer. A novel Au S/D electrode structure with a self-assembled monolayer (SAM) adhesion layer enables direct injection of carriers into the accumulating layer and markedly reduces Rs for unit gate width (RsW) to 6 Mωμ[.proportional]m. BC TFTs with this electrode structure showed extrinsic field-effect mobility as high as 1.1 cm2/Vs.
Enhanced light output is observed from a light-emitting diode (LED) structure containing a two-dimensional (2D) photonic crystal. The capture of emitted light into planar waveguide modes reduces the extraction efficiency of LEDs. Here, 2D photonic crystals are utilized to: 1) enhance the extraction of light in the vertical direction from an LED and 2) enhance optical pumping by directly coupling light from a pump laser into the LED structure. Spatially and spectrally-resolved photoluminescence (PL) is used to characterize the enhancements. A 100-fold enhancement in extraction for a single wavelength into the vertical direction is obtained without the photonic crystal penetrating the active material.