1,650 research outputs found
Deep-Focus Diagnostics of Sunspot Structure
In sequel to Moradi et al. [2009, ApJ, 690, L72], we employ two established
numerical forward models (a 3D ideal MHD solver and MHD ray theory) in
conjunction with time-distance helioseismology to probe the lateral extent of
wave-speed perturbations produced in regions of strong, near-surface magnetic
fields. We continue our comparisons of forward modeling approaches by extending
our previous surface-focused travel-time measurements with a common midpoint
deep-focusing scheme that avoids the use of oscillation signals within the
sunspot region. The idea is to also test MHD ray theory for possible
application in future inverse methods.Comment: 8 pages, 4 figures, published in the conference proceedings "Magnetic
Coupling between the Interior and Atmosphere of the Sun", edited by S.S.
Hasan and R.J. Rutten; Astrophysics and Space Science Proceeding
A Product Formula for the Normalized Volume of Free Sums of Lattice Polytopes
The free sum is a basic geometric operation among convex polytopes. This note
focuses on the relationship between the normalized volume of the free sum and
that of the summands. In particular, we show that the normalized volume of the
free sum of full dimensional polytopes is precisely the product of the
normalized volumes of the summands.Comment: Published in the proceedings of 2017 Southern Regional Algebra
Conferenc
Assessing Professionalism: A theoretical framework for defining clinical rotation assessment criteria
Although widely accepted as an important graduate competence, professionalism is a challenging outcome to define and assess. Clinical rotations provide an excellent opportunity to develop student professionalism through the use of experiential learning and effective feedback, but without appropriate theoretical frameworks, clinical teachers may find it difficult to identify appropriate learning outcomes. The adage “I know it when I see it” is unhelpful in providing feedback and guidance for student improvement, and criteria that are more specifically defined would help students direct their own development. This study sought first to identify how clinical faculty in one institution currently assess professionalism, using retrospective analysis of material obtained in undergraduate teaching and faculty development sessions. Subsequently, a faculty workshop was held in which a round-table type discussion sought to develop these ideas and identify how professionalism assessment could be improved. The output of this session was a theoretical framework for teaching and assessing professionalism, providing example assessment criteria and ideas for clinical teaching. This includes categories such as client and colleague interaction, respect and trust, recognition of limitations, and understanding of different professional identities. Each category includes detailed descriptions of the knowledge, skills, and behaviors expected of students in these areas. The criteria were determined by engaging faculty in the development of the framework, and therefore they should represent a focused development of criteria already used to assess professionalism, and not a novel and unfamiliar set of assessment guidelines. The faculty-led nature of this framework is expected to facilitate implementation in clinical teaching
N=1 SQCD-like theories with N_f massive flavors from AdS/CFT and beta functions
We study new supergravity solutions related to large-
supersymmetric gauge field theories with a large number of massive
flavors. We use a recently proposed framework based on configurations with
color D5 branes and a distribution of flavor D5 branes, governed by
a function . Although the system admits many solutions, under
plausible physical assumptions the relevant solution is uniquely determined for
each value of . In the IR region, the solution smoothly
approaches the deformed Maldacena-N\'u\~nez solution. In the UV region it
approaches a linear dilaton solution. For the gauge coupling
function computed holographically is negative definite, in the UV approaching
the NSVZ function with anomalous dimension
(approaching )), and with in
the IR. For , has a UV fixed point at strong coupling,
suggesting the existence of an IR fixed point at a lower value of the coupling.
We argue that the solutions with describe a "Seiberg dual" picture where
flips sign.Comment: 18 pages, 10 figure
A large age for the pulsar B1757-24 from an upper limit on its proper motion
The "characteristic age" of a pulsar usually is considered to approximate its true age, but this assumption has led to some puzzling results, including the fact that many pulsars with small characteristic ages have no associated supernova remnants. The pulsar B1757-24 is located just beyond the edge of a supernova remnant; the properties of the system indicate that the pulsar was born at the centre of the remnant, but that it has subsequently overtaken the expanding blast-wave. With a characteristic age of 16,000 yr, this implies an expected proper motion by the pulsar of 63-80 milliarcsec per year. Here we report observations of the nebula surrounding the pulsar which limit its proper motion to less than 25 mas/yr, implying a minimum age of 39,000 yr. A more detailed analysis argues for a true age as great as 170,000 yr, significantly larger than the characteristic age. From this result and other discrepancies associated with pulsars, we conclude that characteristic ages seriously underestimate the true ages of pulsars
Concurrent acute illness and comorbid conditions poorly predict antibiotic use in upper respiratory tract infections: a cross-sectional analysis
<p>Abstract</p> <p>Background</p> <p>Inappropriate antibiotic use promotes resistance. Antibiotics are generally not indicated for upper respiratory infections (URIs). Our objectives were to describe patterns of URI treatment and to identify patient and provider factors associated with antibiotic use for URIs.</p> <p>Methods</p> <p>This study was a cross-sectional analysis of medical and pharmacy claims data from the Pennsylvania Medicaid fee-for-service program database. We identified Pennsylvania Medicaid recipients with a URI office visit over a one-year period. Our outcome variable was antibiotic use within seven days after the URI visit. Study variables included URI type and presence of concurrent acute illnesses and chronic conditions. We considered the associations of each study variable with antibiotic use in a logistic regression model, stratifying by age group and adjusting for confounders.</p> <p>Results</p> <p>Among 69,936 recipients with URI, 35,786 (51.2%) received an antibiotic. In all age groups, acute sinusitis, chronic sinusitis, otitis, URI type and season were associated with antibiotic use. Except for the oldest group, physician specialty and streptococcal pharyngitis were associated with antibiotic use. History of chronic conditions was not associated with antibiotic use in any age group. In all age groups, concurrent acute illnesses and history of chronic conditions had only had fair to poor ability to distinguish patients who received an antibiotic from patients who did not.</p> <p>Conclusion</p> <p>Antibiotic prevalence for URIs was high, indicating that potentially inappropriate antibiotic utilization is occurring. Our data suggest that demographic and clinical factors are associated with antibiotic use, but additional reasons remain unexplained. Insight regarding reasons for antibiotic prescribing is needed to develop interventions to address the growing problem of antibiotic resistance.</p
Stochastic Seismic Emission From Acoustic Glories and the Quiet Sun
Abstract. Helioseismic images of multipolar active regions show enhanced seismic emission in 5-mHz oscillations in a halo surrounding the active region called the ‘acoustic glory’. The acoustic glories contain elements that sustain an average seismic emission 50 % greater than similar elements in the quiet Sun. The most intense seismic emitters tend to form strings in non-magnetic regions, sometimes marking the borders of weak magnetic regions and the separation between weak magnetic regions of opposite polarity. This study compares the temporal character of seismic emission from acoustic glories with that from the quiet Sun. The power distribution of quiet-Sun seismic emission far from solar activity is exponential, as for random Gaussian noise, and therefore not perceivably episodic. The distribution of seismic power emanating from the most intense elements that comprise the acoustic glories is exponential out to approximately 4 times the average power emitted by the quiet Sun. Above this threshold the latter distribution shows significant saturation, suggesting the operation of a hydromechanical non-linearity that sets limits on the acoustic power generated by the convection zone. This could give us considerable insight into the physical mechanism of seismic emission from the near subphotosphere. 1
Development of Trust in an Online Breast Cancer Forum: A Qualitative Study
Background: Online health forums provide peer support for a range of medical conditions, including
life-threatening and terminal illnesses. Trust is an important component of peer-to-peer support,
although relatively little is known about how trust forms within online health forums.
Objective: The aim of this paper is to examine how trust develops and influences sharing among
users of an online breast cancer forum.
Methods: An interpretive qualitative approach was adopted. Data were collected from forum posts
from 135 threads on nine boards on the UK charity, Breast Cancer Care (BCC). Semi-structured
interviews were conducted with 14 BCC forum users. Both datasets were analysed thematically using
Braun and Clarke’s [2006] approach and combined to triangulate analysis.
Results: Trust operates in three dimensions, structural, relational and temporal, which intersect with
each other and do not operate in isolation. The structural dimension relates to how the affordances
and formal rules of the site affected trust. The relational dimension refers to how trust was
necessarily experienced in interactions with other forum users: it emerged within relationships and
was a social phenomenon. The temporal dimension relates to how trust changed over time and was
influenced by the length of time users spent on the forum.
Conclusions: Trust is a process that changes over time, and which is influenced by structural features
of the forum and informal but collectively understood relational interactions among forum users.
The study provides a better understanding of how the intersecting structural, relational and
temporal aspects that support the development of trust facilitate sharing in online environments.
These findings will help organisations developing online health forums
Epigenome-wide association study (EWAS) on lipids: the Rotterdam Study
Background DNA methylation is a key epigenetic mechanism that is suggested to be associated with blood lipid levels. We aimed to identify CpG sites at which DNA methylation levels are associated with blood levels of triglycerides, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and total cholesterol in 725 participants of the Rotterdam Study, a population-based cohort study. Subsequently, we sought replication in a non-overlapping set of 760 participants. Results Genome-wide methylation levels were measured in whole blood using the Illumina Methylation 450 array. Associations between lipid levels and DNA methylation beta values were examined using linear mixed-effect models. All models were adjusted for sex, age, smoking, white blood cell proportions, array number, and position on array. A Bonferroni-corrected p value lower than 1.08 × 10−7 was considered statistically significant. Five CpG sites annotated to genes including DHCR24, CPT1A, ABCG1, and SREBF1 were identified and replicated. Four CpG sites were associated with triglycerides, including CpG sites annotated to CPT1A (cg00574958 and cg17058475), ABCG1 (cg06500161), and SREBF1 (cg11024682). Two CpG sites were associated with HDL-C, including ABCG1 (cg06500161) and DHCR24 (cg17901584). No significant associations were observed with LDL-C or total cholesterol. Conclusions We report an association of HDL-C levels with methylation of a CpG site near DHCR24, a protein-coding gene involved in cholesterol biosynthesis, which has previously been reported to be associated with other metabolic traits. Furthermore, we confirmed previously reported associations of methylation of CpG sites within CPT1A, ABCG1, and SREBF1 and lipids. These results provide insight in the mechanisms that are involved in lipid metabolism
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