187 research outputs found
Physicians' attitudes about artificial feeding in older patients with severe cognitive impairment in Japan: a qualitative study
<p>Abstract</p> <p>Background</p> <p>The question of whether to withhold artificial nutrition and hydration (ANH) from severely cognitively impaired older adults has remained nearly unexplored in Japan, where provision of ANH is considered standard care. The objective of this study was to identify and analyze factors related to the decision to provide ANH through percutaneous endoscopic gastrostomy (PEG) in older Japanese adults with severe cognitive impairment.</p> <p>Methods</p> <p>Retrospective, in-depth interviews with thirty physicians experienced in the care of older, bed-ridden, non-communicative patients with severe cognitive impairment. Interview content included questions about factors influencing the decision to provide or withhold ANH, concerns and dilemmas concerning ANH and the choice of PEG feeding as an ANH method. The process of data collection and analysis followed the Grounded Theory approach.</p> <p>Results</p> <p>Data analysis identified five factors that influence Japanese physicians' decision to provide ANH through PEG tubes: (1) the national health insurance system that allows elderly patients to become long-term hospital in-patients; (2) legal barriers with regard to limiting treatment, including the risk of prosecution; (3) emotional barriers, especially abhorrence of death by 'starvation'; (4) cultural values that promote family-oriented end-of-life decision making; and (5) reimbursement-related factors involved in the choice of PEG. However, a small number of physicians did offer patients' families the option of withholding ANH. These physicians shared certain characteristics, such as a different perception of ANH and repeated communication with families concerning end-of-life care. These qualities were found to reduce some of the effects of the factors that favor provision of ANH.</p> <p>Conclusion</p> <p>The framework of Japan's medical-legal system unintentionally provides many physicians an incentive to routinely offer ANH for this patient group through PEG tubes. It seems apparent that end-of-life education should be provided to medical providers in Japan to change the automatic assumption that ANH must be provided.</p
Non-Fermi-Liquid Scaling in Ce(Ru_{0.5}Rh_{0.5})_2Si_2
We study the temperature and field dependence of the magnetic and transport
properties of the non-Fermi-liquid compound Ce(Ru_{1-x}Rh_x)_2Si_2 at x=0.5.
For fields 0.1T the experimental results show signatures of the
presence of Kondo-disorder, expected to be large at this concentration. For
larger fields, however, magnetic and transport properties are controlled by the
coupling of the conduction electrons to critical spin-fluctuations. The
temperature dependence of the susceptibility as well as the scaling properties
of the magnetoresistance are in very good agreement with the predictions of
recent dynamical mean-field theories of Kondo alloys close to a spin-glass
quantum critical point.Comment: 4 pages, 4 figures. Improved discussion. To appear in Phys. Rev. Let
Susceptibility Inhomogeneity and Non-Fermi-Liquid Behavior in Ce(Ru_{0.5}Rh_{0.5})_2Si_2
Magnetic susceptibility and muon spin rotation (\muSR) experiments have been
carried out to study the effect of structural disorder on the non-Fermi-liquid
(NFL) behavior of the heavy-fermion alloy Ce(Ru_{0.5}Rh_{0.5})_2Si_2. Analysis
of the bulk susceptibility in the framework of disorder-driven Griffiths-phase
and Kondo-disorder models for NFL behavior yields relatively narrow
distributions of characteristic spin fluctuation energies, in agreement with
\muSR linewidths that give the inhomogeneous spread in susceptibility. \muSR
and NMR data both indicate that disorder explains the "nearly NFL" behavior
observed above \sim2 K, but does not dominate the NFL physics found at low
temperatures and low magnetic fields.Comment: 6 pages, 4 figures, REVTeX, submitted to Phys. Rev.
Effect of Pressure on Tiny Antiferromagnetic Moment in the Heavy-Electron Compound URu_2Si_2
We have performed elastic neutron-scattering experiments on the
heavy-electron compound URu_2Si_2 for pressure P up to 2.8 GPa. We have found
that the antiferrmagnetic (100) Bragg reflection below T_m ~ 17.5 K is strongly
enhanced by applying pressure. For P < 1.1 GPa, the staggered moment mu_o at
1.4 K increases linearly from ~ 0.017(3) mu_B to ~ 0.25(2) mu_B, while T_m
increases slightly at a rate ~ 1 K/GPa, roughly following the transition
temperature T_o determined from macroscopic anomalies. We have also observed a
sharp phase transition at P_c ~ 1.5 GPa, above which a 3D-Ising type of
antiferromagnetic phase (mu_o ~ 0.4 mu_B) appears with a slightly reduced
lattice constant.Comment: RevTeX, 4 pages, 4 eps figures, accepted for publication in Phys.
Rev. Let
Effects of Uniaxial Stress on Antiferromagnetic Moment in the Heavy Electron Compound URu_2Si_2
We have performed the elastic neutron scattering experiments under uniaxial
stress \sigma along the tetragonal [100], [110] and [001] directions for
URu2Si2. For \sigma // [100] and [110], the antiferromagnetic moment \mu_o is
strongly enhanced from 0.02 \mu_B (\sigma=0) to 0.22 \mu_B (\sigma=2.5 kbar) at
1.5 K. The rate of increase d\mu_o/d\sigma is roughly estimated to be ~ 0.1
\mu_B/kbar, which is much larger than that for the hydrostatic pressure (~
0.025 \mu_B/kbar). Above 2.5 kbar, \mu_o shows a tendency to saturate similar
to the behavior in the hydrostatic pressure. For \sigma // [001], on the other
hand, \mu_o shows only a slight increase to 0.028 \mu_B (\sigma = 4.6 kbar)
with a rate of ~ 0.002 \mu_B/kbar. The observed anisotropy suggests that the
competition between the hidden order and the antiferromagnetic state in URu2Si2
is strongly coupled with the tetragonal four-fold symmetry and the c/a ratio,
or both.Comment: 3 pages, 3 eps figures, Proceedings of Int. Conf. on Strongly
Correlated Electrons with Orbital Degrees of Freedom (Sendai, Japan,
September 11-14, 2001
Neutron Scattering Study on Competition between Hidden Order and Antiferromagnetism in U(Ru_{1-x}Rh_x)_2Si_2 (x <= 0.05)
We have performed elastic and inelastic neutron scattering experiments on the
solid solutions U(Ru_{1-x}Rh_x)_2Si_2 for the Ru rich concentrations: x=0,
0.01, 0.02, 0.025, 0.03, 0.04 and 0.05. Hidden order is suppressed with
increasing x, and correspondingly the onset temperature T_m (~ 17.5 K at x=0)
of weak antiferromagnetic (AF) Bragg reflection decreases. For x=0.04 and 0.05,
no magnetic order is detected in the investigated temperature range down to 1.4
K. In the middle range, 0.02 <= x <= 0.03, we found that the AF Bragg
reflection is strongly enhanced. At x=0.02, this takes place at ~ 7.7 K (=T_M),
which is significantly lower than T_m (~ 13.7 K). T_M increases with increasing
x, and seems to merge with T_m at x=0.03. If the AF state is assumed to be
homogeneous, the staggered moment \mu_o estimated at 1.4 K increases from
0.02(2) \mu_B/U (x=0) to 0.24(1) \mu_B/U (x=0.02). The behavior is similar to
that observed under hydrostatic pressure (\mu_o increases to ~ 0.25 \mu_B/U at
1.0 GPa), suggesting that the AF evolution induced by Rh doping is due to an
increase in the AF volume fraction. We also found that the magnetic excitation
observed at Q=(1,0,0) below T_m disappears as T is lowered below T_M.Comment: 4 pages, 4 figures, submitted to J. Phys. Soc. Jp
Resonant X-Ray Scattering from URu_{2}Si_{2}
Based on a localized crystal electric field model for the U^{4+} in the
(5f)^2-configuration, we analyze the resonant x-ray scattering spectra around U
M_{IV} and M_{V} edges in URu_{2}Si_{2}, taking full Coulomb and spin-orbit
interactions into account. We consider two level schemes, a singlet model of
Santini and Amoretti and a doublet model of Ohkawa and Shimizu, and assume the
antiferroquadrupolar order and the antiferromagnetic order as candidates for
the ambient pressure phase and the high pressure phase. It is found that the
spectral shapes as a function of photon energy are independent of the assumed
level scheme, but are quite different between the antiferroquadrupole and
antiferromagnetic phases, This may be useful to determine the character of the
ordered phase.Comment: 8 pages, 5 figures, submitted to JPS
Evolution of Heterogeneous Antiferromagnetic State in URu2Si2: Study of Hydrostatic-Pressure, Uniaxial-Stress and Rh-Dope Effects
We have investigated the nature of the competition between hidden order and
antiferromagnetic (AF) order in URu_2Si_2 by performing the neutron scattering
experiments under hydrostatic-pressure P, uniaxial-stress sigma, and
Rh-substitution conditions. Hidden order observed at ambient pressure in pure
URu_2Si_2 is found to be replaced by the AF order by applying P, sigma along
the tetragonal basal plane, and by doping Rh. We discuss these experimental
results on the basis of the crystalline strain calculations, and suggest that
this phase transition is generated by the 0.1% increase of the tetragonal c/a
ratio. We have also found that the magnetic excitation observed in the hidden
order phase vanishes in the AF phase. We show that this variation can be
qualitatively explained by assuming the hidden order parameter to be
quadrupole.Comment: 4 pages, 4 figures, proceedings of workshop on Novel Pressure-Induced
Phenomena In Condensed Matter Systems, 2006 Fukuok
Real spin glasses relax slowly in the shade of hierarchical trees
The Parisi solution of the mean-field spin glass has been widely accepted and
celebrated. Its marginal stability in 3d and its complexity however raised the
question of its relevance to real spin glasses. This paper gives a short
overview of the important experimental results which could be understood within
the mean-field solution. The existence of a true phase transition and the
particular behaviour of the susceptibility below the freezing temperature,
predicted by the theory, are clearly confirmed by the experimental results. The
behaviour of the complex order parameter and of the Fluctuation Dissipation
ratio are in good agreement with results of spontaneous noise measurements. The
very particular ultrametric symmetry, the key feature of the theory, provided
us with a simple description of the rejuvenation and memory effects observed in
experiment. Finally, going a step beyond mean-field, the paper shortly
discusses new analyses in terms of correlated domains characterized by their
length scales, as well as new experiments on superspin glasses which compare
well with recent theoretical simulations.Comment: To appear in the proceedings of "Wandering with Curiosity in Complex
Landscapes", a scientific conference in honour of Giorgio Parisi for his 60th
birthday, Roma, September 8-10 2008 (submitted for the special issue of the
Journal of Statistical Physics, 2009
Specific Heat of URuSi in Fields to 42 T: Clues to the 'Hidden Order'
The large C observed at 17.5 K in URuSi is inconsistent
with the small, 0.04 moment measured for the antiferromagnetism
observed starting (perhaps coincidentally) at the same temperature. We report
measurements of this specific heat transition, thought to be due to some
'hidden order', in magnetic fields between 24 and 42 T, i. e. through the field
region where three metamagnetic transtions are known to occur at 35.8, 37.3,
and 39.4 T. The response of C in single crystal URuSi to
magnetic field, which includes a change to C being possibly associated
with a first order phase transition for high fields, is analyzed to shed
further light on the possible explanations of this unknown ordering process. At
fields above 35 T, a new high field phase comes into being; the connection
between this high field phase revealed by the specific heat and earlier
magnetization data is discussed
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