106 research outputs found
The behavior of micro explosive charge underwater explosion near a rigid wall
The interactions between an underwater explosion and underwater structures is a research topic related to understanding strong impulsive forces for disaster preparation and prevention. This study is a part of series studying the behavior of underwater explosion bubbles near different boundaries and structures because understanding the boundary phases and the pulsation of bubbles could be a useful predictive tool. Micro explosive underwater explosions were conducted by detonating a very small amount of silver azide; the time evolution and attenuation of effects from the explosion were studied. Both numerical and experimental data were acquired and compared for underwater shock waves, gas bubbles and overpressures caused by the micro explosions
A first-principles study of tunneling magnetoresistance in Fe/MgAl2O4/Fe(001) magnetic tunnel junctions
We investigated the spin-dependent transport properties of Fe/MgAl2O4/Fe(001)
magnetic tunneling junctions (MTJs) on the basis of first-principles
calculations of the electronic structures and the ballistic conductance. The
calculated tunneling magnetoresistance (TMR) ratio of a Fe/MgAl2O4/Fe(001) MTJ
was about 160%, which was much smaller than that of a Fe/MgO/Fe(001) MTJ
(1600%) for the same barrier thickness. However, there was an evanescent state
with delta 1 symmetry in the energy gap around the Fermi level of normal spinel
MgAl2O4, indicating the possibility of a large TMR in Fe/MgAl2O4/Fe(001) MTJs.
The small TMR ratio of the Fe/MgAl2O4/Fe(001) MTJ was due to new conductive
channels in the minority spin states resulting from a band-folding effect in
the two-dimensional (2-D) Brillouin zone of the in-plane wave vector (k//) of
the Fe electrode. Since the in-plane cell size of MgAl2O4 is twice that of the
primitive in-plane cell size of bcc Fe, the bands in the boundary edges are
folded, and minority-spin states coupled with the delta 1 evanescent state in
the MgAl2O4 barrier appear at k//=0, which reduces the TMR ratio of the MTJs
significantly.Comment: 5 pages, 6 figures, 1 tabl
Electroproduction of psi' and polarized gluon distribution in a proton
In order to get information about the polarized gluon distribution in a
proton, we studied the electroproduction of \psi' in polarized electron and
polarized proton collisions in the framework of the NRQCD factorization
approach. The value of the cross section d\Delta\sigma / dp_T^2 for color-octet
mechanism is about 5 times larger than that for color-singlet one, and it might
be another test of the color-octet model if the polarized gluon distribution
\Delta g(x) is well known. Furthermore, we found that this reaction is quite
effective for testing the model of gluon polarization by measuring the double
spin asymmetry A_{LL} for the initial electron and proton. Though the shape of
p_T^2 distribution of A_{LL} is quite similar for the production mechanism with
color-octet and color-singlet, we can see a big difference in A_{LL} among
various models of the polarized gluon distribution function \Delta g(x).Comment: 9 pages, 6 figure
Theoretical studies on spin-dependent conductance in FePt/MgO/FePt(001) magnetic tunnel junctions
Structure of Mass Gap between Two Spin Multiplets
Studying our semirelativistic potential model and the numerical results,
which succeeds in predicting and reproducing recently discovered higher
resonances of , , , and , we find a simple expression for the
mass gap between two spin multiplets of heavy-light mesons, and
. The mass gap between chiral partners defined by and/or is given by in the limit of heavy
quark symmetry, and including corrections, we have with
MeV, a light quark mass , and a heavy quark
mass . This equation holds both for and heavy mesons. Our model
calculations for the and also follow this formula.Comment: 6 pages, 2 figure
Behavior of vascular resistance undergoing various pressure insufflation and perfusion on decellularized lungs
Bioengineering of functional lung tissue by using whole lung scaffolds has been proposed as a potential alternative for patients awaiting lung transplant. Previous studies have demonstrated that vascular resistance (Rv) could be altered to optimize the process of obtaining suitable lung scaffolds. Therefore, this work was aimed at determining how lung inflation (tracheal pressure) and perfusion (pulmonary arterial pressure) affect vascular resistance. This study was carried out using the lungs excised from 5 healthy male Sprague-Dawley rats. The trachea was cannulated and connected to a continuous positive airway pressure (CPAP) device to provide a tracheal pressure ranging from 0 to 15 cmH(2)O. The pulmonary artery was cannulated and connected to a controlled perfusion system with continuous pressure (gravimetric level) ranging from 5 to 30 cmH(2)O. Effective Rv was calculated by ratio of pulmonary artery pressure (P-PA) by pulmonary artery flow (V'(PA)). Rv in the decellularized lungs scaffolds decreased at increasing V'(PA), stabilizing at a pulmonary arterial pressure greater than 20 cmH(2)O. On the other hand, CPAP had no influence on vascular resistance in the lung scaffolds after being subjected to pulmonary artery pressure of 5 cmH(2)O. In conclusion, compared to positive airway pressure, arterial lung pressure markedly influences the mechanics of vascular resistance in decellularized lungs. (C) 2016 Elsevier Ltd. All rights reserved
Development of UPS-SMES as a protection from momentary voltage drop
We have been developing the UPS-SMES as a protection from momentary voltage drop and power failure. The superconducting system is suitable as electric power storage for large energy extraction in a short time. The most important feature of superconducting coil system for the UPS-SMES is easy handling and maintenance-free operation. We have selected low temperature superconducting (LTS) coils instead of high temperature superconducting (HTS) coils from the viewpoint of cost and performance. However, it is difficult for the conventional LTS coils to fulfill maintenance-free operation since the cooling methods are either pool boiling with liquid helium or forced flow of supercritical helium. Thus, a conduction cooled LTS pulse coil has been designed as a key component of the UPS-SMES. The development program of 1 MW, 1 sec UPS-SMES is explained
Preventive effect of statin pretreatment on contrast-induced acute kidney injury in patients undergoing coronary angioplasty: Propensity score analysis from a multicenter registry
BackgroundThe prophylactic benefit of statins in reducing the incidence of contrast-induced acute kidney injury (CI-AKI) has been investigated in several studies with conflicting results. We sought to investigate whether statin pretreatment prevents CI-AKI in coronary artery disease (CAD) patients undergoing percutaneous coronary intervention (PCI).MethodsA total of 2198 CAD patients who underwent PCI, except for those undergoing dialysis or who died within 7 days after angioplasty, were analyzed from the ICAS (Ibaraki Cardiovascular Assessment Study) multicenter registry. Analyzed subjects were divided into 2 groups according to statin pretreatment: statin pretreatment (n = 839) and non-statin pretreatment (n = 1359). Selection bias of statin pretreatment was adjusted by propensity score-matching method: pretreatment statin (n = 565) and non-statin pretreatment (n = 565). CI-AKI was defined as an increase in serum creatinine of â„ 25% or 0.5 mg/dl from baseline within 1 week of contrast medium exposure.ResultsA total of 192 (8.7%) patients developed CI-AKI. No significant differences were observed in baseline patient characteristics between the statin and non-statin pretreatment groups after propensity score matching. In the propensity score-matched groups, the incidence of CI-AKI was significantly lower in patients with statin pretreatment than in those without statin pretreatment (3.5% vs.10.6%, odds ratio [OR]: 0.31, 95% confidence interval [CI]: 0.18â0.52, P < 0.001). Multivariate logistic regression analysis showed that statin pretreatment remained an independent negative predictor of CI-AKI (OR: 0.31, 95% CI: 0.18â0.53, P < 0.001) among propensity score-matched subjects.ConclusionsStatin pretreatment was associated with a significant decrease in the risk of CI-AKI in CAD patients undergoing PCI in the ICAS Registry
Spectral evolution of GRB 060904A observed with Swift and Suzaku -- Possibility of Inefficient Electron Acceleration
We observed an X-ray afterglow of GRB 060904A with the Swift and Suzaku
satellites. We found rapid spectral softening during both the prompt tail phase
and the decline phase of an X-ray flare in the BAT and XRT data. The observed
spectra were fit by power-law photon indices which rapidly changed from to within a few hundred
seconds in the prompt tail. This is one of the steepest X-ray spectra ever
observed, making it quite difficult to explain by simple electron acceleration
and synchrotron radiation. Then, we applied an alternative spectral fitting
using a broken power-law with exponential cutoff (BPEC) model. It is valid to
consider the situation that the cutoff energy is equivalent to the synchrotron
frequency of the maximum energy electrons in their energy distribution. Since
the spectral cutoff appears in the soft X-ray band, we conclude the electron
acceleration has been inefficient in the internal shocks of GRB 060904A. These
cutoff spectra suddenly disappeared at the transition time from the prompt tail
phase to the shallow decay one. After that, typical afterglow spectra with the
photon indices of 2.0 are continuously and preciously monitored by both XRT and
Suzaku/XIS up to 1 day since the burst trigger time. We could successfully
trace the temporal history of two characteristic break energies (peak energy
and cutoff energy) and they show the time dependence of while the following afterglow spectra are quite stable. This fact
indicates that the emitting material of prompt tail is due to completely
different dynamics from the shallow decay component. Therefore we conclude the
emission sites of two distinct phenomena obviously differ from each other.Comment: 19 pages, 9 figures, accepted for publication in PASJ (Suzaku 2nd
Special Issue
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