182 research outputs found
Time Evolution of Relativistic Force-Free Fields Connecting a Neutron Star and its Disk
We study the magnetic interaction between a neutron star and its disk by
solving the time-dependent relativistic force-free equations. At the initial
state, we assume that the dipole magnetic field of the neutron star connects
the neutron star and its equatorial disk, which deeply enters into the
magnetosphere of the neutron star. Magnetic fields are assumed to be frozen to
the star and the disk. The rotation of the neutron star and the disk is imposed
as boundary conditions. We apply Harten-Lax-van Leer (HLL) method to simulate
the evolution of the star-disk system. We carry out simulations for (1) a disk
inside the corotation radius, in which the disk rotates faster than the star,
and (2) a disk outside the corotation radius, in which the neutron star rotates
faster than the disk. Numerical results indicate that for both models, the
magnetic field lines connecting the disk and the star inflate as they are
twisted by the differential rotation between the disk and the star. When the
twist angle exceeds pi radian, the magnetic field lines expand with speed close
to the light speed. This mechanism can be the origin of relativistic outflows
observed in binaries containing a neutron star.Comment: 10 pages, 6figures, accepted for publication in PAS
A Comparative Study of Neural Network Approach and Linear Regression for Analysis of Multivariate Data of the Defect Color on the Color CRT Displays
Mental deterioration in childhood epilepsy
Mental retardation is detected in 20-30% of children with epilepsy at hospitals specializing in treatment of childhood epilepsy. However, the incidence of mental deterioration in childhood epilepsy is not high. In this study, mental deterioration was found in 52 (1.8%) of the 2,880 children with epilepsy at Okayama University Hospital. The patients showing mental deterioration mostly suffered from specific epileptic syndromes, such as West syndrome, Lennox-Gastaut syndrome, severe myoclonic epilepsy in infancy and epilepsy with continuous spike-waves during slow wave sleep. These types of epilepsy show generalized electroencephalographic (EEG) abnormalities. It is presumed that mental deterioration is caused by the total effects of prolonged diffuse EEG abnormalities and the age of the patients. Antiepileptic drugs exert a relatively minor effect on mental deterioration.</p
Proton Magnetic Resonance Spectroscopy in Patients with Migration Disorders
Proton Magnetic Resonance Spectroscopy (1H-MRS) can be used to detect cerebral metabolites including N-acetylaspartate (NAA),creatine (Cr) and choline (Ch). Hence,clinical applications of this method for neuropediatric diseases can be expected. However,regarding neuronal migration disorders,there have been only a few reported studies. We therefore examined the lH-MRS in six patients with migration disorders,ages ranged
from 8months to 28years 10months with a mean of 10years 10months. Investigation was performed using Magnetom H15 (Siemens) with a repetition time of 1500 msec and an echo time of 270msec. The ratio of NAA/Cr,Ch/Cr were examined. The volume of interest with the size of 2 × 2 × 2 ~ 3 × 3 × 5cm3 was chosen in the area including lesions,and a contralateral area without lesions was also investigated. Results were as follows. 1) The ratio of NAA/Cr was low in the area with lesions in all 6cases; 1.41,1.95,2.27 and 1.71 in cases with heterotopic gray matter,0.99 in one case with polymicrogyria,an d 1.30 in one
case with hemimegalencephaly,contrasted with a contralataral area without lesions: 1.89,
2.89,2.87,2.55,3.26,2.03,respectively. 2) The ratio of Ch/Cr showed no consistent difference
between the area including lesions and contralataral area without lesions. Our
findings of a decreased NAA/Cr ratio can be inferred to reflect the decreased numbers of
neuronal cell population,or reduced metabolism in the lesions
Special Relativistic Magnetohydrodynamic Simulation of Two-Component Outflow Powered by Magnetic Explosion on Compact Stars
The nonlinear dynamics of outflows driven by magnetic explosion on the
surface of a compact star is investigated through special relativistic
magnetohydrodynamic simulations. We adopt, as the initial equilibrium state, a
spherical stellar object embedded in hydrostatic plasma which has a density
and is threaded by a dipole magnetic field. The
injection of magnetic energy at the surface of compact star breaks the
equilibrium and triggers a two-component outflow. At the early evolutionary
stage, the magnetic pressure increases rapidly around the stellar surface,
initiating a magnetically driven outflow. A strong forward shock driven outflow
is then excited. The expansion velocity of the magnetically driven outflow is
characterized by the Alfv\'en velocity on the stellar surface, and follows a
simple scaling relation . When the
initial density profile declines steeply with radius, the strong shock is
accelerated self-similarly to relativistic velocity ahead of the magnetically
driven component. We find that it evolves according to a self-similar relation
, where is the Lorentz
factor of the plasma measured at the shock surface . Purely
hydrodynamic process would be responsible for the acceleration mechanism of the
shock driven outflow. Our two-component outflow model, which is the natural
outcome of the magnetic explosion, can provide a better understanding of the
magnetic active phenomena on various magnetized compact stars.Comment: Accepted for publication in ApJ. 15 pages, 2 tables, 17 figure
The development of fears of compassion scale Japanese version.
Objectives Cultivation of compassion is a useful way to treat mental problems, but some individuals show resistance. Fears of compassion can be an obstacle for clinicians when providing psychotherapy, and for clients when engaging in interpersonal relationships. Despite its importance, a Japanese version of fears of compassion scales (for others, from others, and for self) has not yet been developed. This study developed a Japanese version of the Fears of Compassion Scales and tested its reliability and validity. Design This study used a cross-sectional design, and a self-report procedure for collecting data. Methods A total of 485 students (121 males and 364 females) answered self-report questionnaires, including the draft Fears of Compassion Scales—Japanese version. Results There were distinctive factor structures for fear of compassion from others, and for self. The fear of compassion from others scale consisted of concern about compassion from others and avoidance of compassion from others. All scales had good internal consistency, test-retest reliability, face validity, and construct validity. Discrimination and difficulty were also calculated. Conclusions These results indicate that the Fears of Compassion Scales—Japanese version is a well-constructed and useful measure to assess fears of compassion and the existence of cultural differences in fears of compassion.This study was supported by JSPS KAKENHI Grant Number15K17289 (https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15K17289/)
Development of the external and internal shame scale: Japanese version
Shame contains external and internal aspects. However, a Japanese language scale for simultaneously assessing both aspects of shame has not been developed to date. This study aimed to standardize the Japanese version of the External and Internal Shame Scale (EISS-J). An online survey was conducted among university students (N = 203) at six universities in Japan (Study 1). A retest questionnaire was sent to the participants by email three weeks after the first survey (Study 2). Study 1 examined the internal consistency, factor structure, and criterion-related validity of the EISS-J, while Study 2 examined its test-retest reliability. Moreover, an additional study was conducted to examine the criterion-related validity of the scale. Study 1 demonstrated the high internal consistency of the EISS-J. Moreover, confirmatory factor analysis indicated a two-factor model: external and internal shame. However, exploratory factor analysis indicated a three-factor structure. Study 2 confirmed the test-retest reliability of the scale. Furthermore, both studies indicated correlations between the EISS-J and fear of compassion, anger, humiliation, depression, anxiety, and stress. In addition, the study established the criterion-related validity of the scale. These results confirmed adequate reliability and validity of the EISS-J.This work was supported by JSPS KAKENHI (Grant Number JP19K14412)
Relativistic Expansion of Magnetic Loops at the Self-similar Stage II: Magnetized outflows interacting with the ambient plasma
We obtained self-similar solutions of relativistically expanding magnetic
loops by assuming axisymmetry and a purely radial flow. The stellar rotation
and the magnetic fields in the ambient plasma are neglected. We include the
Newtonian gravity of the central star. These solutions are extended from those
in our previous work (Takahashi, Asano, & Matsumoto 2009) by taking into
account discontinuities such as the contact discontinuity and the shock. The
global plasma flow consists of three regions, the outflowing region, the post
shocked region, and the ambient plasma. They are divided by two
discontinuities. The solutions are characterized by the radial velocity, which
plays a role of the self-similar parameter in our solutions. The shock Lorentz
factor gradually increases with radius. It can be approximately represented by
the power of radius with the power law index of 0.25.
We also carried out magnetohydrodynamic simulations of the evolution of
magnetic loops to study the stability and the generality of our analytical
solutions. We used the analytical solutions as the initial condition and the
inner boundary conditions. We confirmed that our solutions are stable over the
simulation time and that numerical results nicely recover the analytical
solutions. We then carried out numerical simulations to study the generality of
our solutions by changing the power law index \delta of the ambient plasma
density \rho_0 \propto r^{-\delta}. We alter the power law index \delta from
3.5 in the analytical solutions. The analytical solutions are used as the
initial conditions inside the shock in all simulations. We observed that the
shock Lorentz factor increases with time when \delta is larger than 3, while it
decreases with time when \delta is smaller than 3. The shock Lorentz factor is
proportional to t^{(\delta-3)/2}. These results are consistent with the
analytical studies by Shapiro (1979).Comment: 19 pages, 13 figures, Accepted for publication in MNRA
Association between Serum Soluble Klotho Levels and Mortality in Chronic Hemodialysis Patients
Klotho is a single-pass transmembrane protein predominantly expressed in the kidney. The extracellular domain of Klotho is subject to ectodomain shedding and is released into the circulation as a soluble form. Soluble Klotho is also generated from alternative splicing of the Klotho gene. In mice, defects in Klotho expression lead to complex phenotypes resembling those observed in dialysis patients. However, the relationship between the level of serum soluble Klotho and overall survival in hemodialysis patients, who exhibit a state of Klotho deficiency, remains to be delineated. Here we prospectively followed a cohort of 63 patients with a mean duration of chronic hemodialysis of 6.7±5.4 years for a median of 65 months. Serum soluble Klotho was detectable in all patients (median 371 pg/mL, interquartile range 309–449). Patients with serum soluble Klotho levels below the lower quartile (<309 pg/mL) had significantly higher cardiovascular and all-cause mortality rates. Furthermore, the higher all-cause mortality persisted even after adjustment for confounders (hazard ratio 4.14, confidence interval 1.29–13.48). We conclude that there may be a threshold for the serum soluble Klotho level associated with a higher risk of mortality
VLBI Detections of Parsec-Scale Nonthermal Jets in Radio-Loud Broad Absorption Line Quasars
We conducted radio detection observations at 8.4 GHz for 22 radio-loud broad
absorption line (BAL) quasars, selected from the Sloan Digital Sky Survey
(SDSS) Third Data Release, by a very-long-baseline interferometry (VLBI)
technique. The VLBI instrument we used was developed by the Optically ConnecTed
Array for VLBI Exploration project (OCTAVE), which is operated as a subarray of
the Japanese VLBI Network (JVN). We aimed at selecting BAL quasars with
nonthermal jets suitable for measuring their orientation angles and ages by
subsequent detailed VLBI imaging studies to evaluate two controversial issues
of whether BAL quasars are viewed nearly edge-on, and of whether BAL quasars
are in a short-lived evolutionary phase of quasar population. We detected 20
out of 22 sources using the OCTAVE baselines, implying brightness temperatures
greater than 10^5 K, which presumably come from nonthermal jets. Hence, BAL
outflows and nonthermal jets can be generated simultaneously in these central
engines. We also found four inverted-spectrum sources, which are interpreted as
Doppler-beamed, pole-on-viewed relativistic jet sources or young radio sources:
single edge-on geometry cannot describe all BAL quasars. We discuss the
implications of the OCTAVE observations for investigations for the orientation
and evolutionary stage of BAL quasars.Comment: 10 pages, no figure, 3 tables, accepted for publication in PAS
- …