232 research outputs found
Australia\u27s Most Extreme Case : A New Alternative for U.S. Medical Malpractice Liability Reform
The United States currently confronts a severe increase in medical costs and a simultaneous decrease in the availability of health care services. A nearly identical situation recently emerged in the Commonwealth of Australia. This phenomenon, often labeled the medical malpractice crisis, results in part from an increasing litigious trend spurred on by the appeal of potentially enormous damage awards. More lawsuits filed and increased award amounts raise the liability of health care providers and generate uncertainty in the medical malpractice insurance market. This in turn drives up the costs of insurance policy premiums and ultimately forces health care providers to diminish their delivery of health services. In response, many states implement reform initiatives that cap the maximum amount recoverable for an injured patient\u27s non-economic loss. Australian jurisdictions, by contrast, take a more comprehensive approach to liability reform that incorporates a minimum loss requirement and a calculation scheme that proportions non-economics damage awards based on a hypothetical most extreme case. The Australian approach not only limits the quantum of damages available to plaintiffs, but also produces more consistent damage awards than the U.S. cap approach. That is, Australian-style reform reduces the uncertainty posed to insurers in estimating their policyholders\u27 liability. In turn, insurers can more accurately set rates. The reform model followed by Australia is appropriate for the United States. If implemented, it would alleviate inefficiencies created by certain features unique to the U.S. legal system, including civil jury trials and contingency fee agreements. The regulation of non-economic damage awards in a manner consistent with Australia\u27s reform thus presents a desirable model for U.S. policymakers, state legislatures, and the federal government to emulate in the current medical malpractice crisis
Axisymmetric Magnetorotational Instability in Viscous Accretion Disks
Axisymmetric magnetorotational instability (MRI) in viscous accretion disks
is investigated by linear analysis and two-dimensional nonlinear simulations.
The linear growth of the viscous MRI is characterized by the Reynolds number
defined as , where is the Alfv{\'e}n
velocity, is the kinematic viscosity, and is the angular
velocity of the disk. Although the linear growth rate is suppressed
considerably as the Reynolds number decreases, the nonlinear behavior is found
to be almost independent of . At the nonlinear evolutionary stage,
a two-channel flow continues growing and the Maxwell stress increases until the
end of calculations even though the Reynolds number is much smaller than unity.
A large portion of the injected energy to the system is converted to the
magnetic energy. The gain rate of the thermal energy, on the other hand, is
found to be much larger than the viscous heating rate. Nonlinear behavior of
the MRI in the viscous regime and its difference from that in the highly
resistive regime can be explained schematically by using the characteristics of
the linear dispersion relation. Applying our results to the case with both the
viscosity and resistivity, it is anticipated that the critical value of the
Lundquist number for active turbulence
depends on the magnetic Prandtl number in
the regime of and remains constant when , where and is the magnetic diffusivity.Comment: Accepted for publication in ApJ -- 18 pages, 9 figures, 1 tabl
Nonaxisymmetric Magnetorotational Instability in Proto-Neutron Stars
We investigate the stability of differentially rotating proto-neutron stars
(PNSs) with a toroidal magnetic field. Stability criteria for nonaxisymmetric
MHD instabilities are derived using a local linear analysis. PNSs are expected
to have much stronger radial shear in the rotation velocity compared to normal
stars. We find that nonaxisymmetric magnetorotational instability (NMRI) with a
large azimuthal wavenumber is dominant over the kink mode () in
differentially rotating PNSs. The growth rate of the NMRI is of the order of
the angular velocity which is faster than that of the kink-type
instability by several orders of magnitude. The stability criteria are
analogous to those of the axisymmetric magnetorotational instability with a
poloidal field, although the effects of leptonic gradients are considered in
our analysis. The NMRI can grow even in convectively stable layers if the
wavevectors of unstable modes are parallel to the restoring force by the
Brunt-V\"ais\"al\"a oscillation. The nonlinear evolution of NMRI could amplify
the magnetic fields and drive MHD turbulence in PNSs, which may lead to
enhancement of the neutrino luminosity.Comment: 24pages, 7figures, Accepted for publication in the Astrophysical
Journal (December 12, 2005
The Effect of Neutrino Radiation on Magnetorotational Instability in Proto-Neutron Stars
Neutrino radiation takes a major role in the momentum, heat, and lepton
transports in proto-neutron stars (PNSs). These diffusive processes affect the
growth of magnetorotational instability (MRI) in PNSs. We perform a local
linear analysis for the axisymmetric and nonaxisymmetric MRI including the
effects of neutrino transports and ohmic dissipation. We find that the MRI can
grow even in the multi-diffusive situations that are realized in neutrino
loaded PNSs. When the toroidal magnetic component dominates over the poloidal
one, nonaxisymmetric MRI modes grow much faster than axisymmetric modes. These
results suggest the importance of the nonaxisymmetric MRI in PNSs. Thus the
understandings of three-dimensional nonlinear evolutions of the MRI are
necessary to reveal the explosion mechanism of core-collapse supernovae.Comment: Accepted for publication in ApJ, 24 pages,6 figure
Vaughan-Jackson-like syndrome as an unusual presentation of Kienböck's disease: a case report
<p>Abstract</p> <p>Introduction</p> <p>Kienböck's disease is a condition of osteonecrosis of the lunate bone in the hand, and most patients present with a painful and sometimes swollen wrist with a limited range of motion in the affected wrist. Vaughan-Jackson syndrome is characterized by the disruption of the digital extensor tendons, beginning on the ulnar side with the extensor digiti minimi and extensor digitorum communis tendon of the small finger. It is most commonly associated with rheumatoid arthritis. We describe a case of a patient with an unusual presentation of Kienböck's disease with symptoms similar to those of Vaughan-Jackson syndrome.</p> <p>Case presentation</p> <p>A 40-year-old man of Indian ethnic origin with no known history of trauma presented to our clinic with a ten-day history of an inability to extend his right little and ring fingers with associated pain in his right wrist. He was being treated with long-term steroids but had no other significant medical history. His examination revealed an inability to extend the metacarpal and phalangeal joints of the right ring and little fingers with localized tenderness over the lunate bone. Spontaneous disruption of the extensor tendons was diagnosed clinically and, after radiological investigation, was confirmed to be secondary to dorsal extrusion of the fragmented lunate bone. The patient underwent surgical repair of the tendons and had a full recovery afterward.</p> <p>Conclusion</p> <p>Kienböck's disease, though rare, is an important cause of spontaneous extensor tendon rupture. The original description of Vaughan-Jackson syndrome was of rupture of the extensor tendons of the little and ring fingers caused by attrition at an arthritic inferior radioulnar joint. We describe a case of a patient with Kienböck's disease that first appeared to be a Vaughan-Jackson-like syndrome.</p
Dead Zone Formation and Nonsteady Hyperaccretion in Collapsar Disks : A Possible Origin of Short-Term Variability in the Prompt Emission of Gamma-Ray Bursts
The central engine of gamma-ray bursts (GRBs) is believed to be a hot and
dense disk with hyperaccretion onto a few solar-mass black hole. We investigate
where the magnetorotational instability (MRI) actively operates in the
hyperaccretion disk, which can cause angular momentum transport in the disk.
The inner region of hyperaccretion disks can be neutrino opaque, and the
energy- and momentum-transport by neutrinos could affect the growth of the MRI
significantly. Assuming reasonable disk models and a weak magnetic field , it is found that the MRI is strongly suppressed by
the neutrino viscosity in the inner region of hyperaccretion disks. On the
other hand, the MRI can drive active MHD turbulence in the outer
neutrino-transparent region regardless of the field strength. This suggests
that the baryonic matter is accumulated into the inner dead zone where the MRI
grows inactively and the angular momentum transport is inefficient. When the
dead zone gains a large amount of mass and becomes gravitationally unstable,
intense mass accretion onto the central black hole would occur episodically
through the gravitational torque. This process can be a physical mechanism of
the short-term variability in the prompt emission of GRBs. Finally, the origin
of flaring activities in the X-ray afterglow is predicted in the context of our
episodic accretion scenario.Comment: 11pages, 4figures. Accepted for publication in the Astrophysical
Journa
A variable absorption feature in the X-ray spectrum of a magnetar
Soft gamma-ray repeaters (SGRs) and anomalous X-ray pulsars (AXPs) are slowly
rotating, isolated neutron stars that sporadically undergo episodes of
long-term flux enhancement (outbursts) generally accompanied by the emission of
short bursts of hard X-rays. This behaviour can be understood in the magnetar
model, according to which these sources are mainly powered by their own
magnetic energy. This is supported by the fact that the magnetic fields
inferred from several observed properties of AXPs and SGRs are greater than -
or at the high end of the range of - those of radio pulsars. In the peculiar
case of SGR 0418+5729, a weak dipole magnetic moment is derived from its timing
parameters, whereas a strong field has been proposed to reside in the stellar
interior and in multipole components on the surface. Here we show that the
X-ray spectrum of SGR 0418+5729 has an absorption line, the properties of which
depend strongly on the star's rotational phase. This line is interpreted as a
proton cyclotron feature and its energy implies a magnetic field ranging from
2E14 gauss to more than 1E15 gauss.Comment: Nature, 500, 312 (including Supplementary Information
Direct dark matter search by annual modulation in XMASS-I
A search for dark matter was conducted by looking for an annual modulation
signal due to the Earth's rotation around the Sun using XMASS, a single phase
liquid xenon detector. The data used for this analysis was 359.2 live days
times 832 kg of exposure accumulated between November 2013 and March 2015. When
we assume Weakly Interacting Massive Particle (WIMP) dark matter elastically
scattering on the target nuclei, the exclusion upper limit of the WIMP-nucleon
cross section 4.310cm at 8 GeV/c was obtained and we
exclude almost all the DAMA/LIBRA allowed region in the 6 to 16 GeV/c range
at 10cm. The result of a simple modulation analysis, without
assuming any specific dark matter model but including electron/ events,
showed a slight negative amplitude. The -values obtained with two
independent analyses are 0.014 and 0.068 for null hypothesis, respectively. we
obtained 90\% C.L. upper bounds that can be used to test various models. This
is the first extensive annual modulation search probing this region with an
exposure comparable to DAMA/LIBRA.Comment: 5 pages, 4 figure
How to avoid complications of distraction osteogenesis for first brachymetatarsia
Background and purpose Distraction osteogenesis may be used for the treatment of brachymetatarsia. However, few reports have been published on first metatarsal lengthening by this method. We evaluated the complications of distraction osteogenesis for first brachymetatarsia and here we provide a solution
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