415 research outputs found
Factorizations of Elements in Noncommutative Rings: A Survey
We survey results on factorizations of non zero-divisors into atoms
(irreducible elements) in noncommutative rings. The point of view in this
survey is motivated by the commutative theory of non-unique factorizations.
Topics covered include unique factorization up to order and similarity, 2-firs,
and modular LCM domains, as well as UFRs and UFDs in the sense of Chatters and
Jordan and generalizations thereof. We recall arithmetical invariants for the
study of non-unique factorizations, and give transfer results for arithmetical
invariants in matrix rings, rings of triangular matrices, and classical maximal
orders as well as classical hereditary orders in central simple algebras over
global fields.Comment: 50 pages, comments welcom
Multiwavelength Observations of Pulsar Wind Nebulae
The extended nebulae formed as pulsar winds expand into their surroundings
provide information about the composition of the winds, the injection history
from the host pulsar, and the material into which the nebulae are expanding.
Observations from across the electromagnetic spectrum provide constraints on
the evolution of the nebulae, the density and composition of the surrounding
ejecta, the geometry of the central engines, and the long-term fate of the
energetic particles produced in these systems. Such observations reveal the
presence of jets and wind termination shocks, time-varying compact emission
structures, shocked supernova ejecta, and newly formed dust. Here I provide a
broad overview of the structure of pulsar wind nebulae, with specific examples
from observations extending from the radio band to very-high-energy gamma-rays
that demonstrate our ability to constrain the history and ultimate fate of the
energy released in the spin-down of young pulsars.Comment: 20 pages, 11 figures. Invited review to appear in Proc. of the
inaugural ICREA Workshop on "The High-Energy Emission from Pulsars and their
Systems" (2010), eds. N. Rea and D. Torres, (Springer Astrophysics and Space
Science series
Methodological criteria for the assessment of moderators in systematic reviews of randomised controlled trials : a consensus study
Background: Current methodological guidelines provide advice about the assessment of sub-group analysis within
RCTs, but do not specify explicit criteria for assessment. Our objective was to provide researchers with a set of
criteria that will facilitate the grading of evidence for moderators, in systematic reviews.
Method: We developed a set of criteria from methodological manuscripts (n = 18) using snowballing technique,
and electronic database searches. Criteria were reviewed by an international Delphi panel (n = 21), comprising
authors who have published methodological papers in this area, and researchers who have been active in the
study of sub-group analysis in RCTs. We used the Research ANd Development/University of California Los Angeles
appropriateness method to assess consensus on the quantitative data. Free responses were coded for consensus
and disagreement. In a subsequent round additional criteria were extracted from the Cochrane Reviewers’
Handbook, and the process was repeated.
Results: The recommendations are that meta-analysts report both confirmatory and exploratory findings for subgroups
analysis. Confirmatory findings must only come from studies in which a specific theory/evidence based apriori
statement is made. Exploratory findings may be used to inform future/subsequent trials. However, for
inclusion in the meta-analysis of moderators, the following additional criteria should be applied to each study:
Baseline factors should be measured prior to randomisation, measurement of baseline factors should be of
adequate reliability and validity, and a specific test of the interaction between baseline factors and interventions
must be presented.
Conclusions: There is consensus from a group of 21 international experts that methodological criteria to assess
moderators within systematic reviews of RCTs is both timely and necessary. The consensus from the experts
resulted in five criteria divided into two groups when synthesising evidence: confirmatory findings to support
hypotheses about moderators and exploratory findings to inform future research. These recommendations are
discussed in reference to previous recommendations for evaluating and reporting moderator studies
A close examination of double filtering with fold change and t test in microarray analysis
<p>Abstract</p> <p>Background</p> <p>Many researchers use the double filtering procedure with fold change and <it>t </it>test to identify differentially expressed genes, in the hope that the double filtering will provide extra confidence in the results. Due to its simplicity, the double filtering procedure has been popular with applied researchers despite the development of more sophisticated methods.</p> <p>Results</p> <p>This paper, for the first time to our knowledge, provides theoretical insight on the drawback of the double filtering procedure. We show that fold change assumes all genes to have a common variance while <it>t </it>statistic assumes gene-specific variances. The two statistics are based on contradicting assumptions. Under the assumption that gene variances arise from a mixture of a common variance and gene-specific variances, we develop the theoretically most powerful likelihood ratio test statistic. We further demonstrate that the posterior inference based on a Bayesian mixture model and the widely used significance analysis of microarrays (SAM) statistic are better approximations to the likelihood ratio test than the double filtering procedure.</p> <p>Conclusion</p> <p>We demonstrate through hypothesis testing theory, simulation studies and real data examples, that well constructed shrinkage testing methods, which can be united under the mixture gene variance assumption, can considerably outperform the double filtering procedure.</p
Allergic Rhinitis and its Associated Co-Morbidities at Bugando Medical Centre in Northwestern Tanzania; A Prospective Review of 190 Cases.
Allergic rhinitis is one of the commonest atopic diseases which contribute to significant morbidity world wide while its epidemiology in Tanzania remains sparse. There was paucity of information regarding allergic rhinitis in our setting; therefore it was important to conduct this study to describe our experience on allergic rhinitis, associated co-morbidities and treatment outcome in patients attending Bugando Medical Centre. This was descriptive cross-sectional study involving all patients with a clinical diagnosis of allergic rhinitis at Bugando Medical Centre over a three-month period between June 2011 and August 2011. Data was collected using a pre-tested coded questionnaire and analyzed using SPSS statistical computer software version 17.0. A total of 190 patients were studied giving the prevalence of allergic rhinitis 14.7%. The median age of the patients was 8.5 years. The male to female ratio was 1:1. Adenoid hypertrophy, tonsillitis, hypertrophy of inferior turbinate, nasal polyps, otitis media and sinusitis were the most common co-morbidities affecting 92.6% of cases and were the major reason for attending hospital services. Sleep disturbance was common in children with adenoids hypertrophy (χ2 = 28.691, P = 0.000). Allergic conjunctivitis was found in 51.9%. The most common identified triggers were dust, strong perfume odors and cold weather (P < 0.05). Strong perfume odors affect female than males (χ2 = 4.583, P = 0.032). In this study family history of allergic rhinitis was not a significant risk factor (P =0.423). The majority of patients (68.8%) were treated surgically for allergic rhinitis co morbidities. Post operative complication and mortality rates were 2.9% and 1.6% respectively. The overall median duration of hospital stay of in-patients was 3 days (2 - 28 days). Most patients (98.4%) had satisfactory results at discharge. The study shows that allergic rhinitis is common in our settings representing 14.7% of all otorhinolaryngology and commonly affecting children and adolescent. Sufferers seek medical services due to co-morbidities of which combination of surgical and medical treatment was needed. High index of suspicions in diagnosing allergic rhinitis and early treatment is recommended
Tipping Points for Norm Change in Human Cultures
Humans interact with each other on a daily basis by developing and
maintaining various social norms and it is critical to form a deeper
understanding of how such norms develop, how they change, and how fast they
change. In this work, we develop an evolutionary game-theoretic model based on
research in cultural psychology that shows that humans in various cultures
differ in their tendencies to conform with those around them. Using this model,
we analyze the evolutionary relationships between the tendency to conform and
how quickly a population reacts when conditions make a change in norm
desirable. Our analysis identifies conditions when a tipping point is reached
in a population, causing norms to change rapidly.Comment: SBP-BRiMS 201
SDSS-IV MaNGA: A serendipitous observation of a potential gas accretion event
The nature of warm, ionized gas outside of galaxies may illuminate several key galaxy evolutionary processes. A serendipitous observation by the MaNGA survey has revealed a large, asymmetric H complex with no optical counterpart that extends ≈8″ (≈6.3 kpc) beyond the effective radius of a dusty, starbursting galaxy. This H extension is approximately three times the effective radius of the host galaxy and displays a tail-like morphology. We analyze its gas-phase metallicities, gaseous kinematics, and emission-line ratios and discuss whether this H extension could be diffuse ionized gas, a gas accretion event, or something else. We find that this warm, ionized gas structure is most consistent with gas accretion through recycled wind material, which could be an important process that regulates the low-mass end of the galaxy stellar mass function.Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of Science, and the Participating Institutions. SDSS-IV acknowledges support and resources from the Center for High-Performance Computing at the University of Utah. SDSS-IV is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS Collaboration. D.B. is supported by grant RSCF-14-22-00041. A.W. acknowledges support from a Leverhulme Early Career Fellowship. J.H.K. acknowledges financial support from the Spanish Ministry of Economy and Competitiveness (MINECO) under grant number AYA2013-41243-P and thanks the Astrophysics Research Institute of Liverpool John Moores University for their hospitality, and the Spanish Ministry of Education, Culture and Sports for financial support of his visit there, through grant number PR2015-00512
A primary care, multi-disciplinary disease management program for opioid-treated patients with chronic non-cancer pain and a high burden of psychiatric comorbidity
BACKGROUND: Chronic non-cancer pain is a common problem that is often accompanied by psychiatric comorbidity and disability. The effectiveness of a multi-disciplinary pain management program was tested in a 3 month before and after trial. METHODS: Providers in an academic general medicine clinic referred patients with chronic non-cancer pain for participation in a program that combined the skills of internists, clinical pharmacists, and a psychiatrist. Patients were either receiving opioids or being considered for opioid therapy. The intervention consisted of structured clinical assessments, monthly follow-up, pain contracts, medication titration, and psychiatric consultation. Pain, mood, and function were assessed at baseline and 3 months using the Brief Pain Inventory (BPI), the Center for Epidemiological Studies-Depression Scale scale (CESD) and the Pain Disability Index (PDI). Patients were monitored for substance misuse. RESULTS: Eighty-five patients were enrolled. Mean age was 51 years, 60% were male, 78% were Caucasian, and 93% were receiving opioids. Baseline average pain was 6.5 on an 11 point scale. The average CESD score was 24.0, and the mean PDI score was 47.0. Sixty-three patients (73%) completed 3 month follow-up. Fifteen withdrew from the program after identification of substance misuse. Among those completing 3 month follow-up, the average pain score improved to 5.5 (p = 0.003). The mean PDI score improved to 39.3 (p < 0.001). Mean CESD score was reduced to 18.0 (p < 0.001), and the proportion of depressed patients fell from 79% to 54% (p = 0.003). Substance misuse was identified in 27 patients (32%). CONCLUSIONS: A primary care disease management program improved pain, depression, and disability scores over three months in a cohort of opioid-treated patients with chronic non-cancer pain. Substance misuse and depression were common, and many patients who had substance misuse identified left the program when they were no longer prescribed opioids. Effective care of patients with chronic pain should include rigorous assessment and treatment of these comorbid disorders and intensive efforts to insure follow up
Radio emission from Supernova Remnants
The explosion of a supernova releases almost instantaneously about 10^51 ergs
of mechanic energy, changing irreversibly the physical and chemical properties
of large regions in the galaxies. The stellar ejecta, the nebula resulting from
the powerful shock waves, and sometimes a compact stellar remnant, constitute a
supernova remnant (SNR). They can radiate their energy across the whole
electromagnetic spectrum, but the great majority are radio sources. Almost 70
years after the first detection of radio emission coming from a SNR, great
progress has been achieved in the comprehension of their physical
characteristics and evolution. We review the present knowledge of different
aspects of radio remnants, focusing on sources of the Milky Way and the
Magellanic Clouds, where the SNRs can be spatially resolved. We present a brief
overview of theoretical background, analyze morphology and polarization
properties, and review and critical discuss different methods applied to
determine the radio spectrum and distances. The consequences of the interaction
between the SNR shocks and the surrounding medium are examined, including the
question of whether SNRs can trigger the formation of new stars. Cases of
multispectral comparison are presented. A section is devoted to reviewing
recent results of radio SNRs in the Magellanic Clouds, with particular emphasis
on the radio properties of SN 1987A, an ideal laboratory to investigate
dynamical evolution of an SNR in near real time. The review concludes with a
summary of issues on radio SNRs that deserve further study, and analyzing the
prospects for future research with the latest generation radio telescopes.Comment: Revised version. 48 pages, 15 figure
- …