102 research outputs found
Advance care planning for patients with end-stage kidney disease on dialysis: narrative review of the current evidence, and future considerations
Patients with end-stage kidney disease (ESKD) have a high symptom-burden and high rates of morbidity and mortality. Despite this, evidence has shown that this patient group does not have timely discussions to plan for deterioration and death, and at the end of life there are unmet palliative care needs. Advance care planning is a process that can help patients share their personal values and preferences for their future care and prepare for declining health. Earlier, more integrated and holistic advance care planning has the potential to improve access to care services, communication, and preparedness for future decision-making and changing circumstances. However, there are many barriers to successful implementation of advance care planning in this population. In this narrative review we discuss the current evidence for advance care planning in patients on dialysis, the data around the barriers to advance care planning implementation, and interventions that have been trialled. The review explores whether the concepts and approaches to advance care planning in this population need to be updated to encompass current and future care. It suggests that a shift from a problem-orientated approach to a goal-orientated approach may lead to better engagement, with more patient-centred and satisfying outcomes
ESR investigations on Ca perovskite
Electron spin resonance studies on fine powders of La0.65Ca0.35MnO3, performed in the X band, are reported. The coexistence of paramagnetic and ferromagnetic phases, in a narrow temperature range close to the Curie temperature, is observed. The electron spin resonance measurements do not support the presence of bipolarons above the Curie temperature. Temperature dependence of the ESR linewidth is governed by the hopping of polarons and the corresponding activation energy is about 150 meV above Tc
Fast strain wave induced magnetization changes in long cobalt bars: Domain motion versus coherent rotation
A high frequency (88 MHz) traveling strain wave on a piezoelectric substrate is shown to change the magnetization direction in 40 lm wide Co bars with an aspect ratio of 103. The rapidly alternating strain wave rotates the magnetization away from the long axis into the short axis direction, via magnetoelastic coupling. Strain-induced magnetization changes have previously been demonstrated in ferroelectric/ferromagnetic heterostructures, with excellent fidelity between the ferromagnet and the ferroelectric domains, but these experiments were limited to essentially dc frequencies. Both magneto-optical Kerr effect and polarized neutron reflectivity confirm that the traveling strain wave does rotate the magnetization away from the long axis direction and both yield quantitatively similar values for the rotated magnetization. An investigation of the behavior of short axis magnetization with increasing strain wave amplitude on a series of samples with variable edge roughness suggests that the magnetization reorientation that is seen proceeds solely via coherent rotation. Polarized neutron reflectivity data provide direct experimental evidence for this model. This is consistent with expectations that domain wall motion cannot track the rapidly varying strain
Surface superconductivity and order parameter suppression in UPt
We show that a recent measurement of surface superconductivity in UPt
(Keller {\it et. al.}, Phys. Rev. Lett. {\bf 73}, 2364 (1994)) can be
understood if the superconducting pair wavefunction is suppressed
anisotropically at a vacuum to superconductor interface. Further measurements
of surface superconductivity can distinguish between the various
phenomenological models of superconducting UPt.Comment: 4 pages, latex, 2 Figures available upon request
([email protected]
Effects of Magnetic Order on the Upper Critical Field of UPt
I present a Ginzburg-Landau theory for hexagonal oscillations of the upper
critical field of UPt near . The model is based on a
representation for the superconducting order parameter,
, coupled to an in-plane AFM order parameter,
. Hexagonal anisotropy of arises from the weak in-plane
anisotropy energy of the AFM state and the coupling of the superconducting
order parameter to the staggered field. The model explains the important
features of the observed hexagonal anisotropy [N. Keller, {\it et al.}, Phys.
Rev. Lett. {\bf 73}, 2364 (1994).] including: (i) the small magnitude, (ii)
persistence of the oscillations for , and (iii) the change in
sign of the oscillations for and (the temperature at the
tetracritical point). I also show that there is a low-field crossover
(observable only very near ) below which the oscillations should vanish.Comment: 9 pages in a RevTex (3.0) file plus 2 postscript figures (uuencoded).
Submitted to Physical Review B (December 20, 1994)
Staggered Pairing Phenomenology for UPd_2Al_3 and UNi_2Al_3
We apply the staggered-pairing Ginzburg-Landau phenomenology to describe
superconductivity in UPd_2Al_3 and UNi_2Al_3. The phenomenology was applied
successfully to UPt_3 so it explains why these materials have qualitatively
different superconducting phase diagrams although they have the same
point-group symmetry. UPd_2Al_3 and UNi_2Al_3 have a two-component
superconducting order parameter transforming as an H-point irreducible
representation of the space group. Staggered superconductivity can induce
charge-density waves characterized by new Bragg peaks suggesting experimental
tests of the phenomenology.Comment: 4 pages, REVTeX, 2 Postscript figure
Possible Pairing Symmetry of Three-dimensional Superconductor UPt -- Analysis Based on a Microscopic Calculation --
Stimulated by the anomalous superconducting properties of UPt, we
investigate the pairing symmetry and the transition temperature in the
two-dimensional(2D) and three-dimensional(3D) hexagonal Hubbard model. We solve
the Eliashberg equation using the third order perturbation theory with respect
to the on-site repulsion . As results of the 2D calculation, we obtain
distinct two types of stable spin-triplet pairing states. One is the
-wave(B) pairing around and in a small region, which is
caused by the ferromagnetic fluctuation. Then, the other is the (or
)-wave(E) pairing in large region far from the half-filling () which is caused by the vertex corrections only. However, we find that the
former -wave pairing is destroyed by introduced 3D dispersion. This is
because the 3D dispersion breaks the favorable structures for the -wave
pairing such as the van Hove singularities and the small pocket structures.
Thus, we conclude that the ferromagnetic fluctuation mediated spin-triplet
state can not explain the superconductivity of UPt. We also study the case
of the pairing symmetry with a polar gap. This -wave(A) is stabilized
by the large hopping integral along c-axis . It is nearly degenerate with
the suppressed (or )-wave(E) in the best fitting parameter region
to UPt (). These two p-wave pairing states exist in
the region far from the half-filling, in which the vertex correction terms play
crucial roles like the case in SrRuO.Comment: 15 pages, 12 figure
High frequency sound in superfluid 3He-B
We present measurements of the absolute phase velocity of transverse and
longitudinal sound in superfluid 3He-B at low temperature, extending from the
imaginary squashing mode to near pair-breaking. Changes in the transverse phase
velocity near pair-breaking have been explained in terms of an order parameter
collective mode that arises from f-wave pairing interactions, the so-called
J=4- mode. Using these measurements, we establish lower bounds on the energy
gap in the B-phase. Measurement of attenuation of longitudinal sound at low
temperature and energies far above the pair-breaking threshold, are in
agreement with the lower bounds set on pair-breaking. Finally, we discuss our
estimations for the strength of the f-wave pairing interactions and the Fermi
liquid parameter, F4s.Comment: 15 pages, 8 figures, accepted to J. Low Temp. Phy
Lattice-stiffening transition in copolymer films of vinylidene fluoride (70%) with trifluoroethylene (30%)
We report the discovery of a compressibility phase transition at 160 K in crystalline copolymer films of vinylidene fluoride (70%) with trifluoroethylene (30%). This phase transition is distinct from the known bulk ferroelectric-paraelectric phase transition at 353 K and surface ferroelectric phase transition at 295 K. The new phase transition is characterized by an increase in the effective Debye temperature from 48 to 245 K along the 〈010〉 direction as the temperature falls below 160 K. This phase transition is evident in neutron scattering, x-ray diffraction, angle-resolved photoemission, and in the dipole active phonon modes in electron energy-loss spectroscopy. © 1999 The American Physical Society
Unconventional Pairing in Heavy Fermion Metals
The Fermi-liquid theory of superconductivity is applicable to a broad range
of systems that are candidates for unconventional pairing. Fundamental
differences between unconventional and conventional anisotropic superconductors
are illustrated by the unique effects that impurities have on the
low-temperature transport properties of unconventional superconductors. For
special classes of unconventional superconductors the low-temperature transport
coefficients are {\it universal}, i.e. independent of the impurity
concentration and scattering phase shift. The existence of a universal limit
depends on the symmetry of the order parameter and is achieved at low
temperatures , where is the bandwidth
of the impurity induced Andreev bound states. In the case of UPt thermal
conductivity measurements favor an or ground state.
Measurements at ultra-low temperatures should distinguish different pairing
states.Comment: 8 pages in a LaTex (3.0) file plus 5 Figures in PostScript. To appear
in the Proceedings of the XXI International Conference on Low Temperature
Physics held in Prague, 8-14 August 199
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