Hajime Kawahara

Immunohistochemical demonstration of bone morphogenetic protein-2 and transforming growth factor-β in the ossification of the posterior longitudinal ligament of the cervical spine

To clarify the mechanism of ossification of the posterior longitudinal ligament, immunohistochemical localization of bone morphogenetic protein-2 and transforming growth factor-β was examined using surgical specimens of ligament tissues from an affected patient. Two poly-clonal antibone morphogenetic protein-2 antibodies and an anti-human transforming growth factor-β antibody were used as primary antibodies. Bone morphogenetic protein-2 and transforming growth factor-β were present in ossified matrix and chondrocytes of adjacent cartilaginous areas of ossification of the posterior longitudinal ligament. Although immunostaining with antibone morphogenetic protein-2 antibodies also was observed in mesenchymal cells with fibroblastic features in the immediate vicinity of the cartilaginous areas, no staining could be detected with anti-human transforming growth factor-β antibody in these cells. The presence of these factors were specific for the ossified ligament because no immunostaining was observed after using antibodies in the posterior longitudinal ligament at unossified levels from the same patient. It is suggested that bone morphogenetic protein-2 and transforming growth factor-β play important roles in the development of ossification of the posterior longitudinal ligament and that bone morphogenetic protein-2 may act as an initiating factor in the development of ossification of the posterior longitudinal ligament by stimulating differentiation of mesenchymal progenitor cells. Transforming growth factor-β may stimulate bone formation at a later stage of the process of ectopic ossification.

Probing the extreme planetary atmosphere of WASP-12b

We report near-infrared measurements of the terminator region transmission spectrum and dayside emission spectrum of the exoplanet WASP-12b obtained using the HST WFC3 instrument. The disk-average dayside brightness temperature averages about 2900 K, peaking to 3200 K around 1.46 μm. Both the dayside and terminator region spectra can be explained in terms of opacity due to the metal hydrides CrH and TiH together with a dayside temperature inversion with a deep tropopause. Although our measurements do not constrain the C/O ratio, the combination of TiH and high temperatures could imply the atmosphere of WASP-12b may be significantly metal poor. The dayside flux distribution reconstructed from the ingress light-curve shape shows indications of a hotspot. If located along the equatorial plane, the possible hot spot is near the sub-stellar point, indicating the radiative time scale may be shorter than the advection time scale. We also find the near-infrared primary eclipse light curve is consistent with small amounts of prolate distortion. The likely picture of WASP-12b that emerges is that this gas giant is powerfully influenced by the parent star to the extent that the planet’s dayside atmosphere is star-like in terms of temperature, opacity, and the relative importance of radiation over advection. As part of the calibration effort for these data, we conducted a detailed study of instrument systematics using 65 orbits of WFC3-IR grims observations. The instrument systematics are dominated by detector-related affects, which vary significantly depending on the detector readout mode. The 256×256 subarray observations of WASP-12 produced measurements within 15% of the photon-noise limit using a simple calibration approach. Residual systematics are estimated to be ≤70 parts per million.

Inhibition of Bone Resorption by Pamidronate Cannot Restore Normal Gain in Cortical Bone Mass and Strength in Tail‐Suspended Rapidly Growing Rats

To clarify how the changes in bone formation and resorption affect bone volume and strength after mechanical unloading, the effect of inhibition of bone resorption by a potent bisphosphonate, pamidronate, on bone mineral density (BMD), histology, and strength of hind limb bones was examined using tail‐suspended growing rats. Tail suspension for 14 days reduced the gain in the BMD of the femur at both the metaphysis rich in trabecular bone and the diaphysis rich in cortical bone. Treatment with pamidronate increased the total BMD as well as that of the metaphysis of the femur but had almost no effect on the BMD of the diaphysis in both control and tail‐suspended rats. Histological examinations revealed that 14‐day tail suspension caused a loss of secondary cancellous bone with a reduction in the trabecular number and thickness in comparison with control rats. In the femoral diaphysis, the diameter and cortical bone thickness increased to a lesser degree in tail‐suspended rats when compared with rats without tail suspension, and a marked reduction in bone formation and the layers of alkaline phosphatase–positive cells was observed at the periosteal side. Pamidronate treatment increased secondary cancellous bone but could not restore normal growth‐induced periosteal bone apposition and bone strength. Because the material strength of the femoral diaphysis at the tissue level was not affected by pamidronate treatment, the inability of pamidronate to prevent the reduction in physical strength of the femoral diaphysis does not appear to be due to a change in the quality of newly formed bone. These results demonstrate that tail suspension reduces the growth‐induced periosteal modelling drift and that the antiresorptive agent pamidronate is unable to restore normal periosteal bone apposition.

Systematic X-ray Analysis of Radio Relic Clusters with SUZAKU

We perform a systematic X-ray analysis of six giant radio relics in four clusters of galaxies using the Suzaku satellite. The sample includes CIZA 2242.8-5301, Zwcl 2341.1-0000, the South-East part of Abell 3667 and previously published results of the North-West part of Abell 3667 and Abell 3376. Especially we first observed the narrow (50 kpc) relic of CIZA 2242.8-5301 by Suzaku satellite, which enable us to reduce the projection effect. We report X-ray detections of shocks at the position of the relics in CIZA2242.8-5301 and Abell 3667 SE. At the position of the two relics in ZWCL2341.1-0000, we do not detect shocks. From the spectroscopic temperature profiles across the relic, we find that the temperature profiles exhibit significant jumps across the relics for CIZA 2242.8-5301, Abell 3376, Abell 3667NW, and Abell 3667SE. We estimated the Mach number from the X-ray temperature or pressure profile using the Rankine-Hugoniot jump condition and compared it with the Mach number derived from the radio spectral index. The resulting Mach numbers (M=1.5-3) are almost consistent with each other, while the Mach number of CIZA2242 derived from the X-ray data tends to be lower than that of the radio observation. These results indicate that the giant radio relics in merging clusters are related to the shock structure, as suggested by previous studies of individual clusters.

Colors of a Second Earth: Estimating the fractional areas of ocean, land, and vegetation of Earth-like exoplanets

Characterizing the surfaces of rocky exoplanets via their scattered light will be an essential challenge in investigating their habitability and the possible existence of life on their surfaces. We present a reconstruction method for fractional areas of different surface types from the colors of an Earth-like exoplanet. We create mock light curves for Earth without clouds using empirical data. These light curves are fitted to an isotropic scattering model consisting of four surface types: ocean, soil, snow, and vegetation. In an idealized situation where the photometric errors are only photon shot noise, we are able to reproduce the fractional areas of those components fairly well. The results offer some hope for detection of vegetation via the distinct spectral feature of photosynthesis on Earth, known as the red edge. In our reconstruction method, Rayleigh scattering due to the atmosphere plays an important role, and for terrestrial exoplanets with an atmosphere similar to our Earth, it is possible to estimate the presence of oceans and an atmosphere simultaneously.

MAPPING EARTH ANALOGS FROM PHOTOMETRIC VARIABILITY: SPIN-ORBIT TOMOGRAPHY FOR PLANETS IN INCLINED ORBITS

Aiming at obtaining detailed information on the surface environment of Earth analogs, Kawahara & Fujii proposed an inversion technique of annual scattered light curves named spin-orbit tomography (SOT), which enables us to sketch a two-dimensional albedo map from annual variation of the disk-integrated scattered light, and demonstrated the method with a planet in a face-on orbit. We extend it to be applicable to general geometric configurations, including low-obliquity planets like the Earth in inclined orbits. We simulate light curves of the Earth in an inclined orbit in three photometric bands (0.4-0.5 μm, 0.6-0.7 μm, and 0.8-0.9 μm) and show that the distribution of clouds, snow, and continents is retrieved with the aid of the SOT. We also demonstrate the SOT by applying it to an upright Earth, a tidally locked Earth, and Earth analogs with ancient continental configurations. The inversion is model independent in the sense that we do not assume specific albedo models when mapping the surface, and hence applicable in principle to any kind of inhomogeneity. This method can potentially serve as a unique tool to investigate the exohabitats/exoclimes of Earth analogs.

Colors of a Second Earth. II. Effects of Clouds on Photometric Characterization of Earth-like Exoplanets

As a test bed for future investigations of directly imaged terrestrial exoplanets, we present the recovery of the surface components of the Earth from multi-band diurnal light curves obtained with the EPOXI spacecraft. We find that the presence and longitudinal distribution of ocean, soil, and vegetation are reasonably well reproduced by fitting the observed color variations with a simplified model composed of a priori known albedo spectra of ocean, soil, vegetation, snow, and clouds. The effect of atmosphere, including clouds, on light scattered from surface components is modeled using a radiative transfer code. The required noise levels for future observations of exoplanets are also determined. Our model-dependent approach allows us to infer the presence of major elements of the planet (in the case of the Earth, clouds, and ocean) with observations having signal-to-noise ratio (S/N) 10 in most cases and with high confidence if S/N 20. In addition, S/N 100 enables us to detect the presence of components other than ocean and clouds in a fairly model-independent way. Degradation of our inversion procedure produced by cloud cover is also quantified. While cloud cover significantly dilutes the magnitude of color variations compared with the cloudless case, the pattern of color changes remains. Therefore, the possibility of investigating surface features through light-curve fitting remains even for exoplanets with cloud cover similar to Earths.

Mapping Clouds and Terrain of Earth-like Planets from Photometric Variability: Demonstration with Planets in Face-on Orbits

We develop an inversion technique of annual scattered light curves to sketch a two-dimensional albedo map of exoplanets in face-on orbits. As a test bed for future observations of extrasolar terrestrial planets, we apply this mapping technique to simulated light curves of a mock Earth-twin at a distance of 10 pc in a face-on circular orbit. A primary feature in recovered albedo maps traces the annual mean distribution of clouds. To extract information of other surface types, we attempt to reduce the cloud signal by taking the difference of two bands. We find that the inversion of reflectivity difference between 0.8-0.9 and 0.4-0.5 μm bands roughly recovers the continental distribution, except for high latitude regions persistently covered with clouds and snow. The inversion of the reflectivity difference across the red edge (0.8-0.9 and 0.6-0.7 μm) emphasizes the vegetation features near the equator. The planetary obliquity and equinox can be estimated simultaneously with the mapping under the presence of clouds. We conclude that the photometric variability of the scattered light will be a powerful means for exploring the habitat of a second Earth.

Magnetic resonance imaging and histopathology in femoral head necrosis

We correlated preoperative magnetic resonance (MR) images and histopathology of eight femoral heads from patients with osteonecrosis. The signal intensity of the MR image was low in the area where fibrovascular tissue, disintegrated fibrovascular tissue, or amorphous necrotic material occupied the medullary space. On the other hand, the necrotic marrow without revascularization showed high signal intensity. Osteonecrosis can be detected by MR imaging as soon as a certain amount of bone marrow is replaced by fibrovascular tissue.

The Axis Ratio Distribution of X-ray Clusters Observed by XMM-Newton

We derive the axis ratio distribution of X-ray clusters using the XMM-Newton catalog. By fitting the contour lines of the X-ray image by ellipses, we confirm that the X-ray distribution is well approximated by the elliptic distribution with a constant axis ratio and direction. We construct a simple model describing the axis ratio of the X-ray gas assuming the hydrostatic equilibrium embedded in the triaxial dark matter halo model proposed by Jing & Suto and the hydrostatic equilibrium. We find that the observed probability density function of the axis ratio is consistent with this model prediction.