Objectives
The purpose of this study was to assess the prevalence and prognosis of sarcopenic dysphagia in patients who require dysphagia rehabilitation.
Design
Prospective cohort study.
Setting
...Tertiary-care acute general hospital.
Participants
One hundred and eight patients referred to the Department of Rehabilitation Medicine for dysphagia rehabilitation.
Measurements
The Food Intake Level Scale (FILS), a 5-step diagnostic algorithm for sarcopenic dysphagia.
Results
The study included 72 males and 36 females (mean age, 76±7 years). Comorbid diseases included brain and nervous system disease (36%), cardiovascular disease (25%), respiratory disease (14%), and cancer (11%). Median energy intake was 1159 kcal (interquartile range: 648, 1502). Median FILS at admission and discharge was 4 (interquartile range: 2, 7) and 8 (interquartile range: 5, 8), respectively. Sarcopenic dysphagia was observed in 35 patients (32%). Sarcopenic dysphagia was associated with lower FILS at referral and discharge, lower calf circumference, lower handgrip strength, lower body mass index, lower serum albumin, and higher C-reactive protein at referral. Tongue pressure, energy intake, and Barthel index did not differ significantly between patients with or without sarcopenic dysphagia. Ordered logistic regression analysis of the FILS at discharge adjusted for presence of sarcopenic dysphagia, age, sex, and the FILS at admission revealed that presence of sarcopenic dysphagia (β=-1.603, 95% confidence intervals= -2.609, -0.597, p=0.002), sex, and the FILS at admission were independently associated with the FILS at discharge.
Conclusions
The prevalence of sarcopenic dysphagia in patients who require dysphagia rehabilitation was quite high. Sarcopenic dysphagia was independently associated with poor swallowing function at discharge.
ABSTRACT Using three-dimensional general relativistic radiation-magnetohydrodynamics simulations of accretion flows around stellar mass black holes, we report that the relatively cold disk ( ) is ...truncated near the black hole. Hot and less dense regions, of which the gas temperature is and more than 10 times higher than the radiation temperature (overheated regions), appear within the truncation radius. The overheated regions also appear above as well as below the disk, sandwiching the cold disk, leading to the effective Compton upscattering. The truncation radius is for , where are the gravitational radius, mass accretion rate, Eddington luminosity, and light speed, respectively. Our results are consistent with observations of a very high state, whereby the truncated disk is thought to be embedded in the hot rarefied regions. The truncation radius shifts inward to with increasing mass accretion rate , which is very close to an innermost stable circular orbit. This model corresponds to the slim disk state observed in ultraluminous X-ray sources. Although the overheated regions shrink if the Compton cooling effectively reduces the gas temperature, the sandwich structure does not disappear at the range of . Our simulations also reveal that the gas temperature in the overheated regions depends on black hole spin, which would be due to efficient energy transport from black hole to disks through the Poynting flux, resulting in gas heating.
By performing 2.5-dimensional general relativistic radiation magnetohydrodynamic simulations, we demonstrate supercritical accretion onto a non-rotating, magnetized neutron star, where the magnetic ...field strength of dipole fields is 1010 G on the star surface. We found the supercritical accretion flow consists of two parts: the accretion columns and the truncated accretion disk. The supercritical accretion disk, which appears far from the neutron star, is truncated at around 3 R* (R* = 106 cm is the neutron star radius), where the magnetic pressure via the dipole magnetic fields balances with the radiation pressure of the disks. The angular momentum of the disk around the truncation radius is effectively transported inward through magnetic torque by dipole fields, inducing the spin up of a neutron star. The evaluated spin-up rate, ∼−10−11 s s−1, is consistent with the recent observations of the ultraluminous X-ray pulsars. Within the truncation radius, the gas falls onto a neutron star along the dipole fields, which results in a formation of accretion columns onto the northern and southern hemispheres. The net accretion rate and the luminosity of the column are 66 LEdd/c2 and 10 LEdd, where LEdd is the Eddington luminosity and c is the light speed. Our simulations support a hypothesis whereby the ultraluminous X-ray pulsars are powered by the supercritical accretion onto the magnetized neutron stars.
Abstract
We present a general relativistic radiative transfer code
RAIKOU
(来光) for multiwavlength studies of spectra and images including the black hole shadows around Kerr black holes. Important ...radiative processes in hot plasmas around black holes, i.e., (cyclo-)synchrotron, bremsstrahlung emission/absorption, and Compton/inverse-Compton scattering, are incorporated. The Maxwell–Jüttner and single/broken power-law electron distribution functions are implemented to calculate the radiative transfer via both thermal and nonthermal electrons. Two calculation algorithms are implemented for studies of the images and broadband spectra. An observer-to-emitter ray-tracing algorithm, which inversely solves the radiative transfer equation from the observer screen to emitting plasmas, is suitable for an efficient calculations of the images, e.g., the black hole shadows observed by the Event Horizon Telescope, and spectra without Compton effects. On the other hand, an emitter-to-observer Monte Carlo algorithm, by which photons are transported with a Monte Carlo method including the effects of Compton/inverse-Compton scatterings, enables us to compute multiwavelength spectra, with their energy bands broadly ranging from radio to very high energy gamma-ray. The X-ray black hole shadows, which are formed via synchrotron emission and inverse-Compton scattering processes and will be observed in the future X-ray interferometry missions, can be also computed with this algorithm. The code is generally applicable to accretion flows around Kerr black holes with relativistic jets and winds/coronae with various mass accretion rates (i.e., radiatively inefficient accretion flows, super-Eddington accretion flows, and others). We demonstrate an application of the code to a radiatively inefficient accretion flow onto a supermassive black hole.
We develop a general relativistic radiation magnetohydrodynamics (GR-RMHD) code inazuma in which the time-dependent radiation transfer equation (frequency-integrated Boltzmann equation) is solved in ...curved spacetime. The Eddington tensor is derived from the specific intensity, and we solve the zeroth and first moment equations in order to update the radiation fields. Therefore, our code can solve the radiation field around relativistic compact objects more appropriately than an approximation method like the M1 closure scheme. The numerical scheme of magnetohydrodynamics is the same as that of our previous code. In some test calculations for propagating radiation and radiation hydrodynamics in flat spacetime, our code shows similar results to our previous work. Radiation propagation in curved spacetime is also properly solved for. We also show the radiation transport from the super-Eddington accretion disk around the black hole. The disk structure, such as the density, velocity, and temperature, is fixed by the model obtained using the GR-RMHD simulation with the M1 method. We found that the difference between our scheme and the M1 method appears in the optically thin outflow region around the rotation axis while the radiation field is almost the same in the optically thick disk region.
ABSTRACT
The impact of the magnetic field on post-bounce supernova dynamics of non-rotating stellar cores is studied by performing 3D magnetohydrodynamics simulations with spectral neutrino ...transport. The explodability of strongly and weakly magnetized models of 20 and 27 M⊙ pre-supernova progenitors are compared. We find that although the efficiency for the conversion of the neutrino heating into turbulent energy including magnetic fields in the gain region is not significantly different between the strong and weak field models, the amplified magnetic field due to the neutrino-driven convection on large hot bubbles just behind stalled shock results in a faster and more energetic explosion in the strongly magnetized models. In addition, by comparing the difference between the 2nd- and 5th-order spatial accuracy of the simulation in the strong field model for 27 M⊙ progenitor, we also find that the higher order accuracy in space is beneficial to the explosion because it enhances the growth of neutrino-driven convection in the gain region. Based on our results of core-collapse supernova simulations for the non-rotating model, a new possibility for the origin of the magnetic field of the protoneutron star (PNS) is proposed. The magnetic field is accumulated and amplified to magnetar level, that is, $\mathcal {O}(10^{14})$ G, in the convectively stable shell near the PNS surface.
Abstract
By performing two-dimensional axisymmetric general relativistic radiation magnetohydrodynamics simulations with spin parameter
a
* varying from −0.9 to 0.9, we investigate the dependence on ...the black hole spin of the energy flow from a supercritical accretion disk around a stellar mass black hole. It is found that optically and geometrically thick disks form near the equatorial plane, and a part of the disk matter is launched from the disk surface in all models. The gas ejection is mainly driven by the radiative force, but magnetic force cannot be neglected when ∣
a
*∣ is large. The energy outflow efficiency (total luminosity normalized by
M
̇
in
c
2
;
M
̇
in
and
c
are the mass-accretion rate at the event horizon and the light speed) is higher for rotating black holes than for nonrotating black holes. This is 0.7% for
a
* = −0.7, 0.3% for
a
* = 0, and 5% for
a
* = 0.7 for
M
̇
in
∼
100
L
Edd
/
c
2
(
L
Edd
is the Eddington luminosity). Furthermore, although the energy is mainly released by radiation when
a
* ∼ 0, the Poynting power increases with ∣
a
*∣ and exceeds the radiative luminosity for models with
a
* ≥ 0.5 and
a
* ≤ −0.7. The faster the black hole rotates, the higher the power ratio of the kinetic luminosity to the isotropic luminosity tends to be. This implies that objects with a high (low) power ratio may have rapidly (slowly) rotating black holes. Among ultraluminous X-ray sources, IC342 X-1, is a candidate with a rapidly rotating black hole.
Spin hydrodynamic generation Takahashi, R; Matsuo, M; Ono, M ...
Nature physics,
01/2016, Letnik:
12, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Magnetohydrodynamic generation is the conversion of fluid kinetic energy into electricity. Such conversion, which has been applied to various types of electric power generation, is driven by the ...Lorentz force acting on charged particles and thus a magnetic field is necessary. On the other hand, recent studies of spintronics have revealed the similarity between the function of a magnetic field and that of spin-orbit interactions in condensed matter. This suggests the existence of an undiscovered route to realize the conversion of fluid dynamics into electricity without using magnetic fields. Here we show electric voltage generation from fluid dynamics free from magnetic fields; we excited liquid-metal flows in a narrow channel and observed longitudinal voltage generation in the liquid. This voltage has nothing to do with electrification or thermoelectric effects, but turned out to follow a universal scaling rule based on a spin-mediated scenario. The result shows that the observed voltage is caused by spin-current generation from a fluid motion: spin hydrodynamic generation. The observed phenomenon allows us to make mechanical spin-current and electric generators, opening a door to fluid spintronics.
Abstract
We perform general relativistic radiation magnetohydrodynamics simulations of super-Eddington accretion flows around a neutron star with a dipole magnetic field for modeling the Galactic ...ultraluminous X-ray source exhibiting X-ray pulsations, Swift J0243.6+6124. Our simulations show the accretion columns near the magnetic poles, the accretion disk outside the magnetosphere, and the outflows from the disk. It is revealed that the effectively optically thick outflows, consistent with the observed thermal emission at ∼10
7
K, are generated if the mass accretion rate is much higher than the Eddington rate
M
̇
Edd
and the magnetospheric radius is smaller than the spherization radius. In order to explain the blackbody radius (∼100–500 km) without contradicting the reported spin period (9.8 s) and spin-up rate (
P
̇
=
−
2.22
×
10
−
8
s
s
−
1
), a mass accretion rate of
(
200
–
1200
)
M
̇
Edd
is required. Since the thermal emission was detected in two observations with
P
̇
of −2.22 × 10
−8
s s
−1
and −1.75 × 10
−8
s s
−1
but not in another with
P
̇
=
−
6.8
×
10
−
9
s
s
−
1
, the surface magnetic field strength of the neutron star in Swift J0243.6+6124 is estimated to be between 3 × 10
11
G and 4 × 10
12
G. From this restricted range of magnetic field strength, the accretion rate would be
(
200
–
500
)
M
̇
Edd
when the thermal emission appears and
(
60
–
100
)
M
̇
Edd
when it is not detected. Our results support the hypothesis that the super-Eddington phase in the 2017–2018 giant outburst of Swift J0243.6+6124 is powered by highly super-Eddington accretion flows onto a magnetized neutron star.
ABSTRACT
We study the effects of the magnetic field on the dynamics of non-rotating stellar cores by performing 2D, magnetohydrodynamic (MHD) simulations. To this end, we have updated our ...neutrino-radiation-hydrodynamics supernova code to include MHD employing a divergence cleaning method with both careful treatments of finite volume and area reconstructions. By changing the initial strength of the magnetic field, the evolution of 15.0, 18.4, and $27.0\,\rm M_\odot$ pre-supernova progenitors is investigated. An intriguing finding in our study is that the neutrino-driven explosion occurs regardless of the strength of the initial magnetic field. For the 2D models presented in this work, the neutrino heating is the main driver for the explosion, whereas the magnetic field secondary contributes to the pre-explosion dynamics. Our results show that the strong magnetic field weakens the growth of the neutrino-driven turbulence in the small scale compared to the weak magnetic field. This results in the slower increase of the turbulent kinetic energy in the post-shock region, leading to the slightly delayed onset of the shock revival for models with the stronger initial magnetic field.
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