Hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 ; HAp) is one of inorganic components of bone and teeth, and has an osteoconductivity and execellent biocompatibility. Thus, the HAp has been used as biomaterials for bone graftings. Clinically-used HAp cements are set on the basis of the acid-base reaction of Ca 4 O(PO 4 ) 2 and CaHPO 4 . This mechanism accompany the changes of pH during hardening, leading to inflammation around tissues, together with slow setting time. We have succeeded to develop novel HAp cement, which is created by mixing the HAp powder modified with inositol phosphate (IP6) and water. The present IP6-HAp cement is set based on the chelate-bonding of IP6 without the acid-base reaction. The IP6 is not only biocompatible but also has able to chelate to some metal ions as strongly as EDTA. In the present study, we fabricated four kinds of IP6-HAp cements using commercially-available HAp powders with diferent morphology and specific surface area (SSA): HAp-100 (fine particle), HAp-200 (hexagonal shape), HAp-400 (plate shape), and s-HAp (spherical shape). Among the cement specimens examined, the IP6/HAp-100 cement derived from HAp-100 powder had maximum compressive strength of 10 MPa under following condition: Powder/Liquid (P/L) ratio＝1/0.45[w/w]. The HAp-100 powder was composed of microcrystals with the highest SSA of 62.4 m 2 ･g -1 among the HAp powder used in the present work. On the other hand, the compressive strength of the IP6/HAp-200 cements showed the lowest value of 2 MPa under following condition: P/L ratio＝1/0.35[w/w]. The HAp-200 powder of a starting material was composed of hexagonal-shaped crystals, and had the lowest SSA of 7.0 m 2 ･g -1 . These results indicate that the compressive strength of novel IP6/HAp cements was affected by powder properties, especially, the morphology and SSA of starting HAp powders.

We report MAXI and Swift observations of short-term spectral softenings of the Galactic black hole X-ray binary Swift J1753.5−0127 in the low/hard state. These softening events are characterized by a simultaneous increase of soft X-rays (2–4 keV) and a decrease of hard X-rays (15–50 keV) lasting for a few tens of days. The X-ray energy spectra during the softening periods can be reproduced with a model consisting of a multi-color disk blackbody and its Comptonized component. The fraction of the Comptonized component decreased from 0.30 to 0.15 when the spectrum became softer; meanwhile the inner disk temperature (Tin) increased from 0.2 to 0.45 keV. These results imply that the softening events are triggered by a short-term increase of the mass accretion rate. During the observed spectral softening events, the disk flux (Fdisk) and Tin did not obey the Fdisk ∝ (Tin )4 relation, suggesting that the inner disk radius does not reach the innermost stable circular orbit.

We present observations of a transient He-like Fe K α absorption line in Suzaku observations of the black hole binary Cygnus X-1 on 2011 October 5 near superior conjunction during the high/soft state, which enable us to map the full evolution from the start and the end of the episodic accretion phenomena or dips for the first time.We model the X-ray spectra during the event and trace their evolution. The absorption line is rather weak in the first half of the observation, but instantly deepens for ∼10 ks, and weakens thereafter. The overall change in equivalent width is a factor of ∼ 3, peaking at an orbital phase of ∼ 0.08. This is evidence that the companion stellar wind feeding the black hole is clumpy. By analyzing the line with a Voigt profile, it is found to be consistent with a slightly redshifted Fe XXV transition, or possibly a mixture of several species less ionized than Fe XXV . The data may be explained by a clump located at a distance of ∼ 10 10−12 cm with a density of ∼ 10 (−13)−(−11) g cm −3 , which accretes onto and/or transits the line-of-sight to the black hole, causing an instant decrease in the observed degree of the ionization and/or an increase in density of the accreting matter. Continued monitoring for individual events with future X-ray calorimeter missions such as ASTRO-H and AXSIO will allow us to map out the accretion environment in detail and how it changes between the various accretion states.

Polarimetry is a powerful tool for astrophysical observations that has yet to be exploited in the X-ray band. For satellite-borne and sounding rocket experiments, we have developed a photoelectric gas polarimeter to measure X-ray polarization in the 2-10 keV range utilizing a time projection chamber (TPC) and advanced micro-pattern gas electron multiplier (GEM) techniques. We carried out performance verification of a flight equivalent unit (1/4 model) which was planned to be launched on the NASA Gravity and Extreme Magnetism Small Explorer (GEMS) satellite. The test was performed at Brookhaven National Laboratory, National Synchrotron Light Source (NSLS) facility in April 2013. The polarimeter was irradiated with linearly-polarized monochromatic X-rays between 2.3 and 10.0 keV and scanned with a collimated beam at 5 different detector positions. After a systematic investigation of the detector response, a modulation factor ≥35% above 4 keV was obtained with the expected polarization angle. At energies below 4 keV where the photoelectron track becomes short, diffusion in the region between the GEM and readout strips leaves an asymmetric photoelectron image. A correction method retrieves an expected modulation angle, and the expected modulation factor, ∼20% at 2.7 keV. Folding the measured values of modulation through an instrument model gives sensitivity, parameterized by minimum detectable polarization (MDP), nearly identical to that assumed at the preliminary design review (PDR).