Stress Waves and Dynamic Characteristics of Rocks under Detonator's Attack

The experiments have been carried out to investigate the characteristics of the stress waves induced in rocks when they are attacked by an explosion of a detonator and also to study some mechanical properties of rocks under such an impulsive load. To obtain the shape of a stress wave which is induced in a cylindrical bar specimen by an impulsive load, a method utilizing the displacement of the free end face of the specimen was used in this study and it was recognized that this method was simpler and more convenient than the pellet method developed by J. S. Rinehart. The change in the propagation velocity of the stress wave with distance from the shot point was studied in detail and it was found that even in the case of detonator's attack a plastic wave or a shock wave seemed to be generated in the limited region near the shot point. The dynamic stress-strain relationship and the dynamic strengths for compression and tension were determined for three kinds of rock specimens and these results were compared with those obtained by the conventional static test

Stress Waves in Rocks and their Effects on Rock Breakage

In these experimental studies the authors have chiefly investigated the characteristics of the stress waves in rocks caused by detonators or explosives. The research consisted of two parts. In the first part, we have treated mainly the phenomena which accompany the detonator's attack and have discussed the dynamic characteristics of rocks under such impulsive loadings. The following results were obtained from this part of the investigation. The values of Young's moduli for rocks obtained dynamically are about two or three times greater than those obtained statically. The dynamic strengths of rocks are also greater than the static ones, but the difference seems to be not so great as in the case of metals. Moreover, it is an interesting result that various shock effects appear in accordance with the physical properties of rocks. In the second part we advanced to a study of the phenomena accompanying an explosive's attack and observed chiefly the changes in the propagation velocities of the induced stress waves near the explosion point. The results obtained can be summarized as follows. From the results obtained concerning the changes in the velocity of propagation of the stress waves with distance, a plastic wave of higher order seems to exist in the region very near the point of explosion and the appearance of the plastic wave seems to depend not only on the physical characteristics of the rocks but also on the brisance of the explosives. The compressibility of a rock under impulsive high pressure is peculiar to the physical properties of the rock, and it has no relation to the natures of the explosive. The peak pressure of the wave front decreases very rapidly with distance, and only within a few centimeters of the point of explosion do the explosives develop a different high pressure in proportion to their brisances

New Identification of the Mixed-Morphology Supernova Remnant G298.6-0.0 with Possible Gamma-ray Association

We present an X-ray analysis on the Galactic supernova remnant (SNR) G298.6-0.0 with Suzaku. The X-ray image shows a center-filled structure inside the radio shell, implying this SNR is categorized as a mixed-morphology (MM) SNR. The spectrum is well reproduced by a single temperature plasma model in ionization equilibrium, with a temperature of 0.78 (0.70-0.87) keV. The total plasma mass of 30 solar mass indicates that the plasma has interstellar medium origin. The association with a GeV gamma-ray source 3FGL J1214.0-6236 on the shell of the SNR is discussed, in comparison with other MM SNRs with GeV gamma-ray associations. It is found that the flux ratio between absorption-corrected thermal X-rays and GeV gamma-rays decreases as the MM SNRs evolve to larger physical sizes. The absorption-corrected X-ray flux of G298.6-0.0 and the GeV gamma-ray flux of 3FGL J1214.0-6236 closely follow this trend, implying that 3FGL J1214.0-6236 is likely to be the GeV counterpart of G298.6-0.0.Comment: 11 pages, 6 figures, PASJ, in pres

Discovery of X-ray Emission from the Galactic Supernova Remnant G32.8-0.1 with Suzaku

We present the first dedicated X-ray study of the supernova remnant (SNR) G32.8-0.1 (Kes 78) with Suzaku. X-ray emission from the whole SNR shell has been detected for the first time. The X-ray morphology is well correlated with the emission from the radio shell, while anti-correlated with the molecular cloud found in the SNR field. The X-ray spectrum shows not only conventional low-temperature (kT ~ 0.6 keV) thermal emission in a non-equilibrium ionization state, but also a very high temperature (kT ~ 3.4 keV) component with a very low ionization timescale (~ 2.7e9 cm^{-3}s), or a hard non-thermal component with a photon index Gamma~2.3. The average density of the low-temperature plasma is rather low, of the order of 10^{-3}--10^{-2} cm^{-3}, implying that this SNR is expanding into a low-density cavity. We discuss the X-ray emission of the SNR, also detected in TeV with H.E.S.S., together with multi-wavelength studies of the remnant and other gamma-ray emitting SNRs, such as W28 and RCW 86. Analysis of a time-variable source, 2XMM J185114.3-000004, found in the northern part of the SNR, is also reported for the first time. Rapid time variability and a heavily absorbed hard X-ray spectrum suggest that this source could be a new supergiant fast X-ray transient.Comment: 20 pages, 14 figures, ApJ, in pres

Suzaku Observation of the Anomalous X-ray Pulsar 1E 1841-045

We report the results of a Suzaku observation of the anomalous X-ray pulsar (AXP) 1E 1841-045 at a center of the supernova remnant Kes 73. We confirmed that the energy-dependent spectral models obtained by the previous separate observations were also satisfied over a wide energy range from 0.4 to ~70 keV, simultaneously. Here, the models below ~10 keV were a combination of blackbody (BB) and power-law (PL) functions or of two BBs wit h different temperatures at 0.6 - 7.0 keV (Morii et al. 2003), and that above ~20 keV was a PL function (Kuiper Hermsen Mendez 2004). The combination BB + PL + PL was found to best represent the phase-averaged spectrum. Phase-resolved spectroscopy indicated the existence of two emission regions, one with a thermal and the other with a non-thermal nature. The combination BB + BB + PL was also found to represent the phase-averaged spectrum well. However, we found that this model is physically unacceptable due to an excessively large area of the emission region of the blackbody. Nonetheless, we found that the temperatures and radii of the two blackbody components showed moderate correlations in the phase-resolved spectra. The fact that the same correlations have been observed between the phase-averaged spectra of various magnetars (Nakagawa et al. 2009) suggests that a self-similar function can approximate the intrinsic energy spectra of magnetars below ~10 keV.Comment: Accepted for publication in the PAS

In vitro nonalcoholic fatty liver disease model with cyclo-olefin-polymer-based microphysiological systems

Nonalcoholic fatty liver disease (NAFLD) is one of the most common chronic liver conditions, and its treatment involves curing the patients without liver transplantation. Understanding the mechanism of NAFLD initiation and progression would enable the development of new diagnostic tools and drugs; however, until now, the underlying mechanisms of this condition remain largely unknown owing to the lack of experimental settings that can simplify the complicated NAFLD process in vitro. Microphysiological systems (MPSs) have long been used to recapture human pathophysiological conditions in vitro for applications in drug discovery. However, polydimethylsiloxane (PDMS) is used in most of these MPSs as the structural material; it absorbs hydrophobic molecules, such as free fatty acids (FFAs), which are the key components that initiate NAFLD. Therefore, the current PDMS-based MPSs cannot be directly applied to in vitro NAFLD modeling. In this work, we present an in vitro NAFLD model with an MPS made of cyclo-olefin polymer (COP), namely COP-MPS, to prevent absorption of FFAs. We demonstrated the induction of NAFLD-like phenotype in HepaRG hepatocyte-like cells cultured in the COP-MPS by treatment with FFAs. The FFAs induced lipid accumulation in the HepaRG cells, resulting in inactivation of the apoptotic cells. We believe that the proposed COP-MPS can contribute toward the investigation of NAFLD mechanisms and identification of new drugs to prevent the progression of liver disease and thus avoid liver transplantation