3,437 research outputs found
On the origin of central abundance drops in the intracluster medium of galaxy groups and clusters
A central drop of ICM Fe abundance has been observed in several cool-core
clusters. It has been proposed that this abundance drop may be due, at least
partially, to the depletion of Fe into dust grains in the central, high-density
regions. According to this scenario, noble gas elements such as Ar and Ne are
not expected to be depleted into dust, and therefore should not show any drop,
but follow the general increase of metal abundance toward the center. In this
work, we test this scenario by measuring with {\sl Chandra} data the radial
profiles of Ar and Ne in a sample of 12 groups and clusters where a central
drop in Fe abundance has been detected. We confirm the presence of the Fe drop
in 10 out of 12 clusters at more than 2 c.l., and 4 Ar drops with
similar significance. We also find 4 Ne drops, with the caveat that Ne
abundance measurement from CCD spectra suffers from systematics not completely
under control. Our results are consistent with an abundance drop common to the
three elements. When comparing the profiles, we find that, on average, the
abundance profiles of Ar and Ne are significantly higher than Fe and steeper
toward the center, while they all gradually become consistent with solar
composition at . We also check that Si and S profiles are
mostly consistent with Fe. This result confirms a scenario in which some
fraction of Fe is depleted into dust grains in the inner regions, although the
global central abundance drop is mostly due to mechanical processes, like the
displacement of metal-rich ICM from the very center to larger radii by
AGN-driven feedback. Finally, we report the detection of an Fe drop in the
cluster MACSJ1423.8+2404 at , showing that this feature appears early
on in cool-core clusters.Comment: To appear in MNRA
Convergence analysis of a weak Galerkin finite element method on a Shishkin mesh for a singularly perturbed fourth-order problem in 2D
We consider the singularly perturbed fourth-order boundary value problem
on the unit square , with boundary conditions on
, where is a small parameter. The
problem is solved numerically by means of a weak Galerkin(WG) finite element
method, which is highly robust and flexible in the element construction by
using discontinuous piecewise polynomials on finite element partitions
consisting of polygons of arbitrary shape. The resulting WG finite element
formulation is symmetric, positive definite, and parameter-free. Under
reasonable assumptions on the structure of the boundary layers that appear in
the solution, a family of suitable Shishkin meshes with elements is
constructed ,convergence of the method is proved in a discrete norm for
the corresponding WG finite element solutions and numerical results are
presented
Tolerability and effectiveness of (S)-amlodipine compared with racemic amlodipine in hypertension: A systematic review and meta-analysis
AbstractBackground: Amlodipine is a calcium channel blocker prescribed for the management of angina and hypertension. As a racemic mixture, amlodipine contains (R)- and (S)-amlodipine isomers, but only (S)-amlodipine as the active moiety possesses therapeutic activity. Based on pharmacologic research, it remains uncertain if (S)-amlodipine alone has similar efficacy and fewer associated adverse events (AEs) compared with the racemic mixtures.Objective: The aim of this systematic review and meta-analysis was to determine the effectiveness and tolerability of (S)-amlodipine compared with that of racemic amlodipine.Methods: A systematic literature search was performed using MEDLINE (1966–2009), EMBASE (1966–2009), the Cochrane Central Register of Controlled Trials (issue 3, 2009), the Chinese Biomedical Database (1978–2009), and the China National Knowledge Internet (1980–2009). All randomized controlled trials (RCTs) comparing (S)-amlodipine 2.5 mg and racemic amlodipine 5.0 mg in the treatment of hypertension were included in the review. The outcome measures to be collected were cardiovascular events, systolic blood pressure (SBP), diastolic BP (DBP), and AEs. Quality assessments of clinical trials were conducted using a modified Jadad Scale, with trials being rated as low quality (score 0–3) or high quality (score 4–7). Meta-analysis of the included studies was performed using RevMan software.Results: Of the 229 references identified, 214 were excluded after screening the titles, abstracts, or full texts. Fifteen RCTs were included, of which 13 were in Chinese and 2 in English. Based on the Jadad Scale score, 3 of the RCTs were classified as high quality (score 5 or 6) and the remaining 12 as low quality (score 1–3). None of the trials evaluated cardiovascular events beyond 40 weeks. Meta-analysis of the 15 trials indicated that (S)-amlodipine was not significantly different from racemic amlodipine in the effect on BP. When only high-quality studies were included, after 4 weeks' treatment, the weighted mean difference (WMD) of SBP and DBP decrease (1 study) was −2.84 (95% CI, −6.42 to 0.74) with (S)-amlodipine and −1.71 (95% CI, −3.48 to 0.06) with racemic amlodipine. After 8 weeks' treatment, the WMD of SBP and DBP decrease (2 studies) was −1.13 (95% CI, −5.29 to 3.03) and −1.34 (95% CI, −2.67 to −0.01), respectively. The risk difference (RD) for the number of patients who experienced AEs with (S)-amlodipine and racemic amlodipine was found to be −0.04 (95% CI, −0.06 to −0.02). When all the trials were included, (S)-amlodipine treatment was associated with significantly less edema than racemic amlodipine (RD, −0.02; 95% CI, −0.03 to 0.00); however, when only high-quality studies (2 studies) were included, no difference was found between the 2 groups (RD, 0.01; 95% CI, −0.02 to 0.03). One high-quality study found significant differences in increases in aspartate and alanine aminotransferase activities in the 2 groups (RD, 0.08; 95% CI, 0.01 to 0.05). No significant differences between the 2 groups were found in the incidence of headache (RD, 0.00; 95% CI, −0.02 to 0.01) or flushing (RD, −0.01; 95% CI, −0.02 to 0.00).Conclusions: The majority of the clinical trials comparing (S)-amlodipine and racemic amlodipine treatment were low quality (12/15 [80%]). According to the limited evidence, there were no significant differences between (S)-amlodipine 2.5 mg and racemic amlodipine 5.0 mg in controlling BP. When all the trials were considered, (S)-amlodipine treatment was associated with significantly less edema than racemic amlodipine; however, when only high-quality trials were included, no significant difference was found. More long-term, high-quality RCTs with cardiovascular events as the primary outcome are needed to compare the safety and efficacy of (S)-amlodipine and racemic amlodipine
Optimal pricing strategy for green products under salience theory
Environmental pressures and people’s demands for green consumption have prompted manufacturers to engage in the
research and development of green products. Manufacturers
need to consider the price and greenness of products when making production decisions. This paper analyzes the level of greenness and price competition of duopoly manufacturers in the
consumer market in which both green-sensitive consumers (salience to greenness) and price-sensitive consumers (salience to
price) exist simultaneously according to salience theory. We find
that the regular manufacturer will enter the green market when
all consumers’ average degree of price responsiveness is small or
in a moderate part of the region. In addition, this paper also discusses the influence of salience on manufacturers’ level of greenness and pricing strategy choice. We find that the degree of
salient thinking of consumers influences optimal pricing, optimal
greenness and profits under the uniform pricing and price discrimination mechanisms
MedDM:LLM-executable clinical guidance tree for clinical decision-making
It is becoming increasingly emphasis on the importance of LLM participating
in clinical diagnosis decision-making. However, the low specialization refers
to that current medical LLMs can not provide specific medical advice, which are
more like a medical Q\&A. And there is no suitable clinical guidance tree data
set that can be used directly with LLM. To address this issue, we first propose
LLM-executavle clinical guidance tree(CGT), which can be directly used by large
language models, and construct medical diagnostic decision-making dataset
(MedDM), from flowcharts in clinical practice guidelines. We propose an
approach to screen flowcharts from medical literature, followed by their
identification and conversion into standardized diagnostic decision trees.
Constructed a knowledge base with 1202 decision trees, which came from 5000
medical literature and covered 12 hospital departments, including internal
medicine, surgery, psychiatry, and over 500 diseases.Moreover, we propose a
method for reasoning on LLM-executable CGT and a Patient-LLM multi-turn
dialogue framework
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