3,224 research outputs found
Multiple mechanisms of spiral wave breakup in a model of cardiac electrical activity
It has become widely accepted that the most dangerous cardiac arrhythmias are
due to re- entrant waves, i.e., electrical wave(s) that re-circulate repeatedly
throughout the tissue at a higher frequency than the waves produced by the
heart's natural pacemaker (sinoatrial node). However, the complicated structure
of cardiac tissue, as well as the complex ionic currents in the cell, has made
it extremely difficult to pinpoint the detailed mechanisms of these
life-threatening reentrant arrhythmias. A simplified ionic model of the cardiac
action potential (AP), which can be fitted to a wide variety of experimentally
and numerically obtained mesoscopic characteristics of cardiac tissue such as
AP shape and restitution of AP duration and conduction velocity, is used to
explain many different mechanisms of spiral wave breakup which in principle can
occur in cardiac tissue. Some, but not all, of these mechanisms have been
observed before using other models; therefore, the purpose of this paper is to
demonstrate them using just one framework model and to explain the different
parameter regimes or physiological properties necessary for each mechanism
(such as high or low excitability, corresponding to normal or ischemic tissue,
spiral tip trajectory types, and tissue structures such as rotational
anisotropy and periodic boundary conditions). Each mechanism is compared with
data from other ionic models or experiments to illustrate that they are not
model-specific phenomena. The fact that many different breakup mechanisms exist
has important implications for antiarrhythmic drug design and for comparisons
of fibrillation experiments using different species, electromechanical
uncoupling drugs, and initiation protocols.Comment: 128 pages, 42 figures (29 color, 13 b&w
The associations between autistic traits and disordered eating/drive for muscularity are independent of anxiety and depression in females but not males
Previous research has shown a positive correlation between autistic traits and eating disorder symptoms, and this relationship appears to be independent of co-occurring mental health status. The current study followed a pre-registered analysis plan with the aim to investigate a previously unconsidered factor in the relationship between autistic traits and disorders of eating and body image: the drive for muscularity. Participants (N = 1068) completed the Autism Spectrum Quotient (AQ), Hospital Anxiety and Depression Scale (HADS), Eating Attitudes Test-26 (EAT-26) and Drive for Muscularity Scale (DMS). Positive correlations between AQ and EAT-26 and AQ and DMS were observed. In females, AQ remained significantly correlated with EAT-26 and DMS when controlling for co-occurring anxiety and depression symptoms, but this was not the case in males. These findings demonstrate the moderating role of sex, and the need to consider autistic traits in individuals diagnosed with, or at a heightened risk for, disorders of eating and body image
Newspaper media framing of obesity during pregnancy in the UK: A review and framework synthesis
Two thirds of women report experiencing weight stigma during pregnancy. Newspaper media is powerful in framing health issues. This review synthesized UK newspaper media portrayal of maternal obesity. NexisUni was searched to identify newspaper articles, published January 2010 to May 2021, reporting content on obesity during pregnancy. Framework synthesis integrated quantitative and qualitative analysis of the content of articles. There were 442 articles included (59% tabloids and 41% broadsheets). Three overarching themes with interacting sub-themes were as follows: (1) Women were blamed for their weight, risks, and NHS impact. (2) Women were solely responsible for solving obesity, gendered from school age. (3) Women with obesity were a burden on individuals (e.g., themselves, their children, and health professionals), to society, and the NHS. Catastrophizing language framed the “problem,” “scale,” and “public health concern” of maternal obesity, emphasizing risk, and danger and was alarmist, aggressive, and violent as to elicit fear or devalue women. Articles platformed ‘expert’ voices rather than women's lived experiences. This review identified that UK newspaper media negatively frames and oversimplifies the topic of maternal obesity. Exposure to blaming and alarmist messaging could increase women's guilt, stigma, and internalized weight bias. The newspaper media should be harnessed to de-stigmatize maternal obesity and promote maternal well-being
b \rightarrow s \gamma AND Z \rightarrow b \overline{b} IN TECHNICOLOR WITH SCALARS
We consider the radiative decay , and the correction
to the vertex in technicolor models with scalars. In these
models, the scalar develops a vacuum expectation value when the technifermions
condense, and the ordinary fermions develop masses via Yukawa couplings. Since
the symmetry breaking sector involves both a fundamental scalar doublet and an
isotriplet of composite scalars (the technipions), the phenomenology associated
with the charged scalars is similar to that found in a type-I two-Higgs doublet
model. We show that the correction to the vertex is small over
the allowed parameter space of the model in the two limits that we consider,
and that there can be large, potentially observable, contributions to the
branching fraction.Comment: 9pp. LaTeX, 4 figures in a uuencoded compressed .ps file We remove
nonstandard LaTeX fonts from the previous versio
Effects of Dexamethasone on Mesenchymal Stromal Cell Chondrogenesis and Aggrecanase Activity: Comparison of Agarose and Self-Assembling Peptide Scaffolds
Objective: Dexamethasone (Dex) is a synthetic glucocorticoid that has pro-anabolic and anticatabolic effects in cartilage tissue engineering systems, though the mechanisms by which these effects are mediated are not well understood. We tested the hypothesis that the addition of Dex to chondrogenic medium would affect matrix production and aggrecanase activity of human and bovine bone marrow stromal cells (BMSCs) cultured in self-assembling peptide and agarose hydrogels. Design: We cultured young bovine and adult human BMSCs in (RADA)[subscript 4] self-assembling peptide and agarose hydrogels in medium containing TGF-β1±Dex and analyzed extracellular matrix composition, aggrecan cleavage products, and the effects of the glucocorticoid receptor antagonist RU-486 on proteoglycan content, synthesis, and catabolic processing. Results: Dex improved proteoglycan synthesis and retention in agarose hydrogels seeded with young bovine cells but decreased proteoglycan accumulation in peptide scaffolds. These effects were mediated by the glucocorticoid receptor. Adult human BMSCs showed minimal matrix accumulation in agarose, but accumulated ~50% as much proteoglycan and collagen as young bovine BMSCs in peptide hydrogels. Dex reduced aggrecanase activity in (RADA)[subscript 4] and agarose hydrogels, as measured by anti-NITEGE Western blotting, for both bovine and human BMSC-seeded gels. Conclusions: The effects of Dex on matrix production are dependent on cell source and hydrogel identity. This is the first report of Dex reducing aggrecanase activity in a tissue engineering culture system.National Science Foundation (U.S.). Graduate Research FellowshipNational Institutes of Health (U.S.) (Grant EB003805
Carotid Atheroinflammation Is Associated With Cerebral Small Vessel Disease Severity.
Background: Atherosclerosis is a systemic inflammatory disease, with common inflammatory processes implicated in both atheroma vulnerability and blood-brain barrier disruption. This prospective multimodal imaging study aimed to measure directly the association between systemic atheroma inflammation ("atheroinflammation") and downstream chronic cerebral small vessel disease severity. Methods: Twenty-six individuals with ischemic stroke with ipsilateral carotid artery stenosis of >50% underwent 18fluoride-fluorodeoxyglucose-positron emission tomography within 2 weeks of stroke. Small vessel disease severity and white matter hyperintensity volume were assessed using 3-tesla magnetic resonance imaging also within 2 weeks of stroke. Results: Fluorodeoxyglucose uptake was independently associated with more severe small vessel disease (odds ratio 6.18, 95% confidence interval 2.1-18.2, P < 0.01 for the non-culprit carotid artery) and larger white matter hyperintensity volumes (coefficient = 14.33 mL, P < 0.01 for the non-culprit carotid artery). Conclusion: These proof-of-concept results have important implications for our understanding of the neurovascular interface and potential therapeutic exploitation in the management of systemic atherosclerosis, particularly non-stenotic disease previously considered asymptomatic, in order to reduce the burden of chronic cerebrovascular disease
Risk factors for eating disorder symptoms at 12 years of age: A 6-year longitudinal cohort study
Eating disorders pose risks to health and wellbeing in young adolescents, but prospective studies of risk factors are scarce and this has impeded prevention efforts. This longitudinal study aimed to examine risk factors for eating disorder symptoms in a population-based birth cohort of young adolescents at 12 years. Participants from the Gateshead Millennium Study birth cohort (n = 516; 262 girls and 254 boys) completed self-report questionnaire measures of eating disorder symptoms and putative risk factors at age 7 years, 9 years and 12 years, including dietary restraint, depressive symptoms and body dissatisfaction. Body mass index (BMI) was also measured at each age. Within-time correlates of eating disorder symptoms at 12 years of age were greater body dissatisfaction for both sexes and, for girls only, higher depressive symptoms. For both sexes, higher eating disorder symptoms at 9 years old significantly predicted higher eating disorder symptoms at 12 years old. Dietary restraint at 7 years old predicted boys' eating disorder symptoms at age 12, but not girls'. Factors that did not predict eating disorder symptoms at 12 years of age were BMI (any age), girls’ dietary restraint at 7 years and body dissatisfaction at 7 and 9 years of age for both sexes. In this population-based study, different patterns of predictors and correlates of eating disorder symptoms were found for girls and boys. Body dissatisfaction, a purported risk factor for eating disorder symptoms in young adolescents, developed concurrently with eating disorder symptoms rather than preceding them. However, restraint at age 7 and eating disorder symptoms at age 9 years did predict 12-year eating disorder symptoms. Overall, our findings suggest that efforts to prevent disordered eating might beneficially focus on preadolescent populations
Transmission of Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) from pre and asymptomatic infected individuals: a systematic review
Background
The role of SARS-Cov-2-infected persons who develop symptoms after testing (presymptomatics) or not at all (asymptomatics) in the pandemic spread is unknown.
Objectives
To determine infectiousness and probable contribution of asymptomatic persons (at the time of testing) to pandemic SARS-CoV-2 spread.
Data sources
LitCovid, medRxiv, Google Scholar, and WHO Covid-19 databases (to 31 March 2021) and references in included studies.
Study eligibility criteria
Studies with a proven or hypothesized transmission chain based either on serial PCR cycle threshold readings and/or viral culture and/or gene sequencing, with adequate follow-up.
Participants
People exposed to SARS-CoV-2 within 2–14 days to index asymptomatic (at time of observation) infected individuals.
Interventions
Reliability of symptom and signs was assessed within contemporary knowledge; transmission likelihood was assessed using adapted causality criteria.
Methods
Systematic review. We contacted all included studies' corresponding authors requesting further details.
Results
We included 18 studies from a diverse setting with substantial methodological variation (this field lacks standardized methodology). At initial testing, prevalence of asymptomatic cases was 12.5–100%. Of these, 6–100% were later determined to be presymptomatic, this proportion varying according to setting, methods of case ascertainment and population. Nursing/care home facilities reported high rates of presymptomatic: 50–100% (n = 3 studies). Fourteen studies were classified as high risk of, and four studies as at moderate risk of symptom ascertainment bias. High-risk studies may be less likely to distinguish between presymptomatic and asymptomatic cases. Six asymptomatic studies and four presymptomatic studies reported culturing infectious virus; data were too sparse to determine infectiousness duration. Three studies provided evidence of possible and three of probable/likely asymptomatic transmission; five studies provided possible and two probable/likely presymptomatic SARS-CoV-2 transmission.
Conclusion
High-quality studies provide probable evidence of SARS-CoV-2 transmission from presymptomatic and asymptomatic individuals, with highly variable estimated transmission rates
Current Bounds on Technicolor with Scalars
Technicolor with scalars is the simplest dynamical symmetry breaking model
and one in which the predicted values of many observables may be readily
calculated. This letter applies current LEP, Tevatron, CESR, and SLAC data from
searches for neutral and charged scalars and from studies of b-quark physics to
obtain bounds on technicolor with scalars. Expectations for how upcoming
measurements will further probe the theory's parameter space are also
discussed.Comment: 9 pages, 2 figures, LaTe
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