3,095 research outputs found
Superconductivity Phase Diagram of Na(x)CoO(2).1.3H(2)O
Although the microscopic origin of the superconductivity in high Tc copper
oxides remains the subject of active inquiry, several of their electronic
characteristics are well established as universal to all the known materials,
forming the experimental foundation that all theories must address. The most
fundamental of those characteristics is the dependence of the superconducting
transition temperature on the degree of electronic band filling. Since the
discovery of cuprate superconductivity in 1986 (1), the search for other
families of superconductors that might help shed light on the superconducting
mechanism of the cuprates has been of great interest. The recent report of
superconductivity near 4K in the triangular lattice, layered sodium cobalt
oxyhydrate, Na0.35CoO2.1.3H2O, is the best indication that superconductors
related to the cuprates may be found (2). Here we show that the superconducting
transition temperature of this compound displays the same kind of band-filling
behavior that is observed in the cuprates. Specifically, that the optimal
superconducting Tc occurs in a narrow range of band filling, and decreases for
both underdoped and overdoped materials, in dramatic analogy to the phase
diagram of the cuprate superconductors. Our results suggest that
characterization of the detailed electronic and magnetic behavior of these new
materials may help establish which of the many special characteristics of the
cuprates is fundamental to their high Tc superconductivity.Comment: revised, publication information adde
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Patient-Related Barriers to Timely Dialysis Access Preparation: A Qualitative Study of the Perspectives of Patients, Family Members, and Health Care Providers
Rational & Objective
A key aspect of smooth transition to dialysis is the timely creation of a permanent access. Despite early referral to kidney care, initiation onto dialysis is still suboptimal for many patients, which has clinical and cost implications. This study aimed to explore perspectives of various stakeholders on barriers to timely access creation.
Study Design
Qualitative study.
Setting & Participants
Semi-structured interviews with 96 participants (response rate, 67%), including patients with stage 4 chronic kidney disease (n = 30), new hemodialysis patients with (n = 18) and without (n = 20) permanent access (arteriovenous fistula), family members (n = 19), and kidney health care providers (n = 9).
Analytical Approach
Thematic analysis.
Results
Patients reported differential levels of behavioral activation toward access creation: avoidance/denial, wait and see, or active intention. 6 core themes were identified: (1) lack of symptoms, (2) dialysis fear and practical concerns (exaggerated fear, pain, cost, lifestyle disruptions, work-related concerns, burdening their families), (3) evaluating value against costs/risks of access creation (benefits, threat of operation, viability, prompt for early initiation), (4) preference for alternatives, (5) social influences (hearsay, family involvement, experiences of others), and (6) health care provider interactions (mistrust, interpersonal tension, lack of clarity on information). Themes were common to all groups, whereas nuanced perspectives of family members and health care providers were noted in some subthemes.
Limitations
Response bias.
Conclusions
Individual, interpersonal, and psychosocial factors compromise dialysis preparation and contribute to suboptimal dialysis initiation. Our findings support the need for interventions to improve patient and family engagement and address emotional concerns and misperceptions about preparing for dialysis
Indoor Air Quality and Office Property Value
Urbanization and technological advancement have resulted in many urbanites working in window-sealed high-rise office buildings. Many researchers have found that indoor air quality (IAQ) affects tenantlandlord relationships, workers’ health and productivity, and building elements and systems. This may imply that IAQ could affect, positively or negatively, the value of buildings. This paper examines the impact of IAQ on the value of office buildings in Singapore. The results show that the return on investment in IAQ could be substantial (78.56%) while property values could increase by 1.28% to 3.85%. The findings could be of interest and usefulness to valuers and investors in office properties in Singapore and thus, help to promote sustainability in office property developments
IL-33 ameliorates Alzheimer’s disease-like pathology and cognitive decline
Alzheimer’s disease (AD) is a devastating condition with no known effective treatment. AD is characterized by memory loss as well as impaired locomotor ability, reasoning, and judgment. Emerging evidence suggests that the innate immune response plays a major role in the pathogenesis of AD. In AD, the accumulation of β-amyloid (Aβ) in the brain perturbs physiological functions of the brain, including synaptic and neuronal dysfunction, microglial activation, and neuronal loss. Serum levels of soluble ST2 (sST2), a decoy receptor for interleukin (IL)-33, increase in patients with mild cognitive impairment, suggesting that impaired IL-33/ST2 signaling may contribute to the pathogenesis of AD. Therefore, we investigated the potential therapeutic role of IL-33 in AD, using transgenic mouse models. Here we report that IL-33 administration reverses synaptic plasticity impairment and memory deficits in APP/PS1 mice. IL-33 administration reduces soluble Aβ levels and amyloid plaque deposition by promoting the recruitment and Aβ phagocytic activity of microglia; this is mediated by ST2/p38 signaling activation. Furthermore, IL-33 injection modulates the innate immune response by polarizing microglia/macrophages toward an antiinflammatory phenotype and reducing the expression of proinflammatory genes, including IL-1β, IL-6, and NLRP3, in the cortices of APP/PS1 mice. Collectively, our results demonstrate a potential therapeutic role for IL-33 in AD
Interface relaxation in electrophoretic deposition of polymer chains: Effects of segmental dynamics, molecular weight, and field
Using different segmental dynamics and relaxation, characteristics of the
interface growth is examined in an electrophoretic deposition of polymer chains
on a three (2+1) dimensional discrete lattice with a Monte Carlo simulation.
Incorporation of faster modes such as crankshaft and reptation movements along
with the relatively slow kink-jump dynamics seems crucial in relaxing the
interface width. As the continuously released polymer chains are driven (via
segmental movements) and deposited, the interface width grows with the
number of time steps , (--,
which is followed by its saturation to a steady-state value . Stopping the
release of additional chains after saturation while continuing the segmental
movements relaxes the saturated width to an equilibrium value ().
Scaling of the relaxed interface width with the driving field , remains similar to that of the steady-state width. In
contrast to monotonic increase of the steady-state width , the relaxed
interface width is found to decay (possibly as a stretched exponential)
with the molecular weight.Comment: 5 pages, 7 figure
59Co-NMR Knight Shift of Superconducting Three-Layer NaxCoO2.yH2O
The superconducting state of NaxCoO2.yH2O with three CoO2 layers in a unit
cell has been studied by 59Co-NMR. The Knight shift measured for a peak of the
NMR spectra corresponding to the external magnetic field H along one of the
principal directions within the CoO2 plane, exhibits a rapid decrease with
decreasing temperature T below the superconducting transition temperature Tc,
indicating that the spin susceptibility is suppressed in the superconducting
phase, at least, for this field direction. Because differences of the
superconducting properties are rather small between this three-layer
NaxCoO2.yH2O and previously reported NaxCoO2.yH2O with two CoO2 layers within a
unit cell, the present result of the Knight shift studies indicates that the
Cooper pairs of the former system are in the singlet state as in the latter,
for which the spin susceptibility is suppressed for both directions of H
parallel and perpendicular to the CoO2 plane.Comment: 5 page
23Na NMR study of non-superconducting double-layer hydrate NaxCoO2.yH2O
We report 23Na NMR studies of the polycrystalline samples of double-layer
hydrated cobalt oxides NaxCoO2.yH2O (x ~ 0.35 and y ~ 1.3) with the
superconducting transition temperatures Tc < 1.8K and ~4.5K, and the dehydrated
NaxCoO2 (x ~ 0.35). The hyperfine field and the electric field gradient at the
Na sites in the non-hydrated Na0.7CoO2 and the dehydrated Na0.35CoO2 are found
to be significantly reduced by the hydration, which indicates a strong
shielding effect of the intercalated water molecules on the Na sites. The
temperature dependence of 23 Na nuclear spin-lattice relaxation rate 1/23T1 of
the non-superconducting double-layer hydrate NaxCoO2.yH2O is found to be
similar to that of the non-hydrated Na0.7CoO2, whose spin dynamics is
understood by A-type (intra-layer ferromagnetic and inter-layer
antiferromagnetic) spin fluctuations. The superconducting phase is located
close to the quantum critical point with the A-type magnetic instability.Comment: 4 pages, 4 figure
Novel phase diagram of superconductor NaxCoO2-yH2O in a 75 % relative humidity
We succeeded in synthesizing the powder samples of bilayer-hydrate sodium
cobalt oxide superconductors NaxCoO2-yH2O with Tc = 0 ~ 4.6 K by systematically
changing the keeping duration in a 75 % relative humidity atmosphere after
intercalation of water molecules. From the magnetic measurements, we found that
the one-day duration sample does not show any superconductivity down to 1.8 K,
and that the samples kept for 2 ~ 7 days show superconductivity, in which Tc
increases up to 4.6 K with increasing the duration. Tc and the superconducting
volume fraction are almost invariant between 7 days and 1month duration. The
59Co NQR spectra indicate a systematic change in the local charge distribution
on the CoO2 plane with change in duration.Comment: 4 pages, 5 figures, submitted to Journal of the Physical Society of
Japa
Transport and Magnetic Studies on the Spin State Transition of Pr1-xCaxCoO3 up to High Pressure
Transport and magnetic measurements and structural and NMR studies have been
carried out on (Pr1-yR'y)1-xAxCoO3 {R'=(rare earth elements and Y); A=(Ca, Ba
and Sr)} at ambient pressure or under high pressure. The system exhibits a
phase transition from a nearly metallic to an insulating state with decreasing
temperature T, where the low spin (LS) state of Co3+ is suddenly stabilized.
For y=0, we have constructed a T-x phase diagram at various values of the
external pressure p. It shows that the (T, x) region of the low temperature
phase, which is confined to a very narrow region around x=0.5 at ambient
pressure, expands as p increases, suggesting that the transition is not due to
an order-disorder type one. For the occurrence of the transition, both the Pr
and Ca atoms seem to be necessary. The intimate relationship between the local
structure around the Co ions and the electronic (or spin) state of Co3+ ions is
discussed: For the smaller unit cell volume or the smaller volume of the CoO6
octahedra and for the larger tilting angle of the octahedra, the temperature of
the transition becomes higher. The role of the carriers introduced by the
doping of the A atoms, is also discussed. By analyzing the data of 59Co-NMR
spectra and magnetic susceptibilities of Pr1-xCaxCoO3 the energy separations
among the different spin states of Co3+ and Co4+ are roughly estimated.Comment: 15 pages, 15 figures, 2 tables, submitted to J. Phys. Soc. Jp
Thermal and Electrical Properties of gamma-NaxCoO2 (0.70 < x < 0.78)
We have performed specific heat and electric resistivity measurements of
NaCoO (-0.78). Two anomalies have been observed in the
specific heat data for , corresponding to magnetic transitions at
K and K reported previously. In the electrical
resistivity, a steep decrease at and a bending-like variation at
(=120K for ) have been observed. Moreover, we have investigated
the -dependence of these parameters in detail. The physical properties of
this system are very sensitive to , and the inconsistent results of previous
reports can be explained by a small difference in . Furthermore, for a
higher value, a phase separation into Na-rich and Na-poor domains occurs as
we previously proposed, while for a lower value, from characteristic
behaviors of the specific heat and the electrical resistivity at the
low-temperature region, the system is expected to be in the vicinity of the
magnetic instability which virtually exists below .Comment: 4 pages (3 figures included) and an extra figure (gif), to be
published in J. Phys. Soc. Jpn. 73 (9) with possible minor revision
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