3,133 research outputs found
Bibliometric cartography of information retrieval research by using co-word analysis
The aim of this study is to map the intellectual structure of the field of Information Retrieval (IR) during the period of 1987-1997. Co-word analysis was employed to reveal patterns and trends in the IR field by measuring the association strengths of terms representative of relevant publications or other texts produced in IR field. Data were collected from Science Citation Index (SCI) and Social Science Citation Index (SSCI) for the period of 1987-1997. In addition to the keywords added by the SCI and SSCI databases, other important keywords were extracted from titles and abstracts manually. These keywords were further standardized using vocabulary control tools. In order to trace the dynamic changes of the IR field, the whole 11-year period was further separated into two consecutive periods: 1987-1991 and 1992-1997. The results show that the IR field has some established research themes and it also changes rapidly to embrace new themes
Dynamic reasoning in a knowledge-based system
Any space based system, whether it is a robot arm assembling parts in space or an onboard system monitoring the space station, has to react to changes which cannot be foreseen. As a result, apart from having domain-specific knowledge as in current expert systems, a space based AI system should also have general principles of change. This paper presents a modal logic which can not only represent change but also reason with it. Three primitive operations, expansion, contraction and revision are introduced and axioms which specify how the knowledge base should change when the external world changes are also specified. Accordingly the notion of dynamic reasoning is introduced, which unlike the existing forms of reasoning, provide general principles of change. Dynamic reasoning is based on two main principles, namely minimize change and maximize coherence. A possible-world semantics which incorporates the above two principles is also discussed. The paper concludes by discussing how the dynamic reasoning system can be used to specify actions and hence form an integral part of an autonomous reasoning and planning system
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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
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
A novel route to phase formation of cobalt oxyhydrates using KMnO4 as an oxidizing agent
We have first succeefully synthesized the sodium cobalt oxyhydrate
superconductors using KMnO4 as a de-intercalating and oxidizing agent. It is a
novel route to form the superconductive phase of NaxCoO2.yH2O without resorting
to the commonly used Br2/CH3CN solution. The role of the KMnO4 is to
de-intercalate the Na+ from the parent compound Na0.7CoO2 and oxidize the Co
ion as a result. The higher molar ratio of KMnO4 relative to the sodium content
tends to remove more Na+ from the parent compound and results in a slight
expansion of the c-axis in the unit cell. The superconducting transition
temperature is 4.6-3.8 K for samples treated by the aqueous KMnO4 solution with
the molar ratio of KMnO4 relative to the sodium content in the range of 0.3 and
2.29.Comment: 10 pages, 3 figure
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
Synthesis and characterization of Na03RhO206H2O - a semiconductor with a weak ferromagnetic component
We have prepared the oxyhydrate Na03RhO206H2O by extracting Na+ cations from
NaRhO2 and intercalating water molecules using an aqueous solution of Na2S2O8.
Synchrotron X-ray powder diffraction, thermogravimetric analysis (TGA), and
energy-dispersive x-ray analysis (EDX) reveal that a non-stoichiometric
Na03(H2O)06 network separates layers of edge-sharing RhO6 octahedra containing
Rh3+(4d6, S=0) and Rh4+ (4d5, S=1/2). The resistivities of NaRhO2 and
Na03RhO206H2O (T < 300) reveal insulating and semi-conducting behavior with
activation gaps of 134 meV and 7.8 meV, respectively. Both Na03RhO206H2O and
NaRhO2 show paramagnetism at room temperature, however, the sodium-deficient
sample exhibits simultaneously a weak but experimentally reproducible
ferromagnetic component. Both samples exhibit a temperature-independent Pauli
paramagnetism, for NaRhO2 at T > 50 K and for Na03RhO206H2O at T > 25 K. The
relative magnitudes of the temperature-independent magnetic susceptibilities,
that of the oxide sample being half that of the oxyhydrate, is consistent with
a higher density of thermally accessible electron states at the Fermi level in
the hydrated sample. At low temperatures the magnetic moments rise sharply,
providing evidence of localized and weakl -ordered electronic spins.Comment: 15 fages 5 figures Solid State Communications in prin
Magnetic and Metal-Insulator Transitions in beta-Na0.5CoO2 and gamma-K0.5CoO2 -NMR and Neutron Diffraction Studies-
Co-oxides beta-Na0.5CoO2 and gamma-K0.5CoO2 have been prepared by the Na
de-intercalation from alpha-NaCoO2 and by the floating-zone method,
respectively. It has been found that successive phase transitions take place at
temperatures Tc1 and Tc2 in both systems. The appearance of the internal
magnetic field at Tc1 with decreasing temperature T indicates that the
antiferromagnetic order exists at T < Tc1, as in gamma-Na0.5CoO2. For
beta-Na0.5CoO2, the transition temperatures and the NMR parameters determined
from the data taken for magnetically ordered state are similar to those of
gamma-Na0.5CoO2, indicating that the difference of the stacking ways of the
CoO2 layers between these systems do not significantly affect their physical
properties. For gamma-K0.5CoO2, the quantitative difference of the physical
quantities are found from those of beta- and gamma-Na0.5CoO2. The difference
between the values of Tci (i = 1 and 2) of these systems might be explained by
considering the distance between CoO2 layers.Comment: 8 pages, 14 figures, 1 Tabl
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