Effect of atomic-hydrogen irradiation on reduction of residual carrier concentration in β-FeSi2 films grown on Si substrates by atomic-hydrogen-assisted molecular beam epitaxy

β-FeSi2 films were epitaxially grown by atomic-hydrogen-assisted molecular beam epitaxy (MBE) on high-resistive n-type floating-zone (FZ) Si(1 1 1) (ρ>1000 Ω cm). They showed n-type conduction with a reduced electron concentration of an order of 1016 cm−3 at room temperature (RT). In contrast, β-FeSi2 films prepared without atomic hydrogen or prepared with molecular hydrogen showed p-type conduction with a large hole density of over 1018 cm−3. These results show that the atomic-hydrogen irradiation is an effective means to reduce the residual carrier concentration in undoped β-FeSi2 films

Small satellites with MEMS x-ray telescopes for x-ray astronomy and solar system exploration

Toward a new era of X-ray astronomy, next generation X-ray optics are indispensable. To meet a demand for telescopes lighter than the foil optics but with a better angular resolution less than 1 arcmin, we are developing micropore X-ray optics based on micromaching technologies. Using sidewalls of micropores through a thin silicon wafer, this type can be the lightest X-ray telescope ever achieved. Two new Japanese missions ORBIS and GEOX will carry this optics. ORBIS is a small X-ray astronomy mission to monitor supermassive blackholes, while GEO-X is a small exploration mission of the Earth's magnetosphere. Both missions need a ultra light-weight (<1 kg) telescope with moderately good angular resolution (<10 arcmin) at an extremely short focal length (<30 cm). We plan to demonstrate this optics in these two missions around 2020, aiming at future other astronomy and exploration missions

Photoinduced Structural Phase Transitions in Polyacene

There exist two types of structural instability in polyacene: double bonds in a cis pattern and those in a trans pattern. They are isoenergetic but spectroscopically distinct. We demonstrate optical characterization and manipulation of Peierls-distorted polyacene employing both correlated and uncorrelated Hamiltonians. We clarify the phase boundaries of the cis- and trans-distorted isomers, elucidate their optical-conductivity spectra, and then explore their photoresponses. There occurs a photoinduced transformation in the polyacene structure, but it is one-way switching: The trans configuration is well convertible into the cis one, whereas the reverse conversion is much less feasible. Even the weakest light irradiation can cause a transition of uncorrelated electrons, while correlated electrons have a transition threshold against light irradiation.Comment: 14 pages with 15 figures embedde

The Comet Interceptor Mission

Here we describe the novel, multi-point Comet Interceptor mission. It is dedicated to the exploration of a little-processed long-period comet, possibly entering the inner Solar System for the first time, or to encounter an interstellar object originating at another star. The objectives of the mission are to address the following questions: What are the surface composition, shape, morphology, and structure of the target object? What is the composition of the gas and dust in the coma, its connection to the nucleus, and the nature of its interaction with the solar wind? The mission was proposed to the European Space Agency in 2018, and formally adopted by the agency in June 2022, for launch in 2029 together with the Ariel mission. Comet Interceptor will take advantage of the opportunity presented by ESA’s F-Class call for fast, flexible, low-cost missions to which it was proposed. The call required a launch to a halo orbit around the Sun-Earth L2 point. The mission can take advantage of this placement to wait for the discovery of a suitable comet reachable with its minimum ΔV capability of 600 ms-1. Comet Interceptor will be unique in encountering and studying, at a nominal closest approach distance of 1000 km, a comet that represents a near-pristine sample of material from the formation of the Solar System. It will also add a capability that no previous cometary mission has had, which is to deploy two sub-probes – B1, provided by the Japanese space agency, JAXA, and B2 – that will follow different trajectories through the coma. While the main probe passes at a nominal 1000 km distance, probes B1 and B2 will follow different chords through the coma at distances of 850 km and 400 km, respectively. The result will be unique, simultaneous, spatially resolved information of the 3-dimensional properties of the target comet and its interaction with the space environment. We present the mission’s science background leading to these objectives, as well as an overview of the scientific instruments, mission design, and schedule

Inhibition of the Soleus H-Reflex during Dorsiflexion is Dependent on Individual Differences in Maximal Soleus H-Reflex as a Test Reflex

The quantitative differences among individuals in the natural reciprocal inhibition of the soleus H-reflex during dorsiflexion were examined, in conjunction with the maximal H-reflex as the test reflex size in each individual. Maximal H-reflex was expressed relative to the maximal M-response (Hmax) when compared among individuals. Analysis showed that with increases in Hmax at rest in each individual, the inhibitory effect was first enhanced, then reached a peak, and was finally alleviated. This pattern was similar to the intraindividual pattern of the inhibitory effect induced by specific conditioning stimulus as a function of the test reflex size. </jats:p