977 research outputs found
Structure And Dynamics Of Modulated Traveling Waves In Cellular Flames
We describe spatial and temporal patterns in cylindrical premixed flames in
the cellular regime, , where the Lewis number is the ratio of
thermal to mass diffusivity of a deficient component of the combustible
mixture. A transition from stationary, axisymmetric flames to stationary
cellular flames is predicted analytically if is decreased below a critical
value. We present the results of numerical computations to show that as is
further decreased traveling waves (TWs) along the flame front arise via an
infinite-period bifurcation which breaks the reflection symmetry of the
cellular array. Upon further decreasing different kinds of periodically
modulated traveling waves (MTWs) as well as a branch of quasiperiodically
modulated traveling waves (QPMTWs) arise. These transitions are accompanied by
the development of different spatial and temporal symmetries including period
doublings and period halvings. We also observe the apparently chaotic temporal
behavior of a disordered cellular pattern involving creation and annihilation
of cells. We analytically describe the stability of the TW solution near its
onset+ using suitable phase-amplitude equations. Within this framework one of
the MTW's can be identified as a localized wave traveling through an underlying
stationary, spatially periodic structure. We study the Eckhaus instability of
the TW and find that in general they are unstable at onset in infinite systems.
They can, however, become stable for larger amplitudes.Comment: to appear in Physica D 28 pages (LaTeX), 11 figures (2MB postscript
file
An a priori investigation of astrophysical false positives in ground-based transiting planet surveys
Astrophysical false positives due to stellar eclipsing binaries pose one of
the greatest challenges to ground-based surveys for transiting Hot Jupiters. We
have used known properties of multiple star systems and Hot Jupiter systems to
predict, a priori, the number of such false detections and the number of
genuine planet detections recovered in two hypothetical but realistic
ground-based transit surveys targeting fields close to the galactic plane (b~10
degrees): a shallow survey covering a magnitude range 10<V<13, and a deep
survey covering a magnitude range 15<V<19. Our results are consistent with the
commonly-reported experience of false detections outnumbering planet detections
by a factor of ~10 in shallow surveys, while in our synthetic deep survey we
find ~1-2 false detections for every planet detection. We characterize the
eclipsing binary configurations that are most likely to cause false detections
and find that they can be divided into three main types: (i) two dwarfs
undergoing grazing transits, (ii) two dwarfs undergoing low-latitude transits
in which one component has a substantially smaller radius than the other, and
(iii) two eclipsing dwarfs blended with one or more physically unassociated
foreground stars. We also predict that a significant fraction of Hot Jupiter
detections are blended with the light from other stars, showing that care must
be taken to identify the presence of any unresolved neighbors in order to
obtain accurate estimates of planetary radii. This issue is likely to extend to
terrestrial planet candidates in the CoRoT and Kepler transit surveys, for
which neighbors of much fainter relative brightness will be important.Comment: 33 pages, 7 figures, 4 tables; To be published in The Astrophysical
Journa
The clinical effectiveness of different parenting programmes for children with conduct problems : a systematic review of randomised controlled trials
Background
Conduct problems are common, disabling and costly. The prognosis for children with conduct problems is poor, with outcomes in adulthood including criminal behaviour, alcoholism, drug abuse, domestic violence, child abuse and a range of psychiatric disorders.
There has been a rapid expansion of group based parent-training programmes for the treatment of children with conduct problems in a number of countries over the past 10 years. Existing reviews of parent training have methodological limitations such as inclusion of non-randomised studies, the absence of investigation for heterogeneity prior to meta-analysis or failure to report confidence intervals.
The objective of the current study was to systematically review randomised controlled trials of parenting programmes for the treatment of children with conduct problems.
Methods
Standard systematic review methods were followed including duplicate inclusion decisions, data extraction and quality assessment. Twenty electronic databases from the fields of medicine, psychology, social science and education were comprehensively searched for RCTs and systematic reviews to February 2006.
Inclusion criteria were: randomised controlled trial; of structured, repeatable parenting programmes; for parents/carers of children up to the age of 18 with a conduct problem; and at least one measure of child behaviour. Meta-analysis and qualitative synthesis were used to summarise included studies.
Results
57 RCTs were included. Studies were small with an average group size of 21. Meta-analyses using both parent (SMD -0.67; 95% CI: -0.91, -0.42) and independent (SMD -0.44; 95% CI: -0.66, -0.23) reports of outcome showed significant differences favouring the intervention group. There was insufficient evidence to determine the relative effectiveness of different approaches to delivering parenting programmes.
Conclusion
Parenting programmes are an effective treatment for children with conduct problems. The relative effectiveness of different parenting programmes requires further research
The effect of an emollient containing urea, ceramide NP, and lactate on skin barrier structure and function in older people with dry skin
Xerosis affects up to 75% of older people and develops as a result of a skin barrier defect. Emollients are widely used to treat xerosis; however, there is limited understanding of the differences between them and their effects on the skin barrier in older people. This study aimed to compare the effect of a commercially available emollient containing 5% urea, ceramide NP and lactate (test emollient) to an alternative emollient without these additives (control emollient) on the properties of the skin barrier in older people. Two cohorts of 21 volunteers aged 60+ years with dry skin were recruited. The first applied the test emollient to one forearm and no treatment to the other for 28-days. The second compared the test emollient to the control emollient observing the same parameters. Effects on the skin barrier were determined by measuring skin barrier function, hydration, skin surface pH and by analyzing FTIR spectra before and after treatment. A third cohort of 6 young adults was recruited to investigate the effect of a single treatment with the test emollient on the molecular structure of the skin barrier at greater depths by employing the tape-stripping technique. The test emollient hydrated the skin to a significantly greater extent and for a longer period of time compared to the control emollient, an effect associated with a significant elevation of carboxylate groups (a marker of NMF content) within the stratum corneum. Furthermore, the test emollient imparted additional benefits to the structure and function of the skin barrier not exhibited by the control emollient. In conclusion the test emollient addressed the pathological features of xerotic aged skin, supporting its use as first-line therapy for xerotic skin conditions in this population
Relationships between central corneal thickness and optic disc topography in eyes with glaucoma, suspicion of glaucoma, or ocular hypertension
Pinakin Gunvant1, Lucia Porsia2, Russell J Watkins3, Henrietta Bayliss-Brown2, David C Broadway21Department of Research, Southern College of Optometry, Memphis, TN, USA; 2Department of Ophthalmology, Norfolk and Norwich University Hospital NHS Trust, Norwich, UK; 3Department of Pathology, Algernon Firth Buildings, Leeds General Infirmary, Leeds, UKPurpose: To identify relationships between central corneal thickness (CCT) and optic disc topography, as determined by scanning laser ophthalmoscopy (SLO), for patients seen in a specialist glaucoma service.Methods: 272 eyes of 144 patients with primary open angle glaucoma (POAG; n = 71), normal tension glaucoma (NTG; n = 50), ocular hypertension (OH; n = 48) and those considered to be suspicious for glaucoma (GS; n = 103) underwent ultrasonic pachymetry and optic disc topography by SLO. Correlations between CCT and SLO parameter values were identified. A Bonferroni correction for multiple comparisons was performed and a p value of 0.0042 was considered significant.Results: Mean CCT values were 533 &mu;m (POAG), 530 &mu;m (NTG), 550 &mu;m (GS), and 565 &mu;m (OH). As a group the GS and OH eyes had signifi cantly thicker CCT values than eyes with POAG. In addition, the NTG eyes had signifi cantly thinner CCT values than GS and OH eyes. Overall multiple SLO parameters correlated with CCT even after accounting for co-variance with age, refraction and inclusion of both eyes. Sub-group analysis indicated that &lsquo;optic disc rim area&rsquo; positively correlated with CCT (r = 0.378) and &lsquo;cup to disc area ratio&rsquo; negatively correlated with CCT (r = &minus;0.370) in the POAG group. In the GS group the parameter &lsquo;area below reference&rsquo; (a measure of cup volume) and &lsquo;mean cup depth&rsquo; had negative correlations with CCT (r = &minus;0.297 and &minus;0.323) indicating that eyes with thinner than average corneal thickness measurements had larger and deeper cups.Conclusion: Thinner corneas appear to be associated with larger and deeper optic disc cups in the eyes of patients seen in a specialist glaucoma service.Keywords: central corneal thickness, optic disc topography, optic disc compliance, glaucom
Annual Variation in Atmospheric 14C between 1700 BC and 1480 BC
In 2018 Pearson et al. published a new sequence of annual radiocarbon (14C) data derived from oak (Quercus sp.) trees from Northern Ireland and bristlecone pine (Pinus longaeva) from North America across the period 1700–1500 BC. The study indicated that the more highly resolved shape of an annually based calibration dataset could improve the accuracy of 14C calibration during this period. This finding had implications for the controversial dating of the eruption of Thera in the Eastern Mediterranean. To test for interlaboratory variation and improve the robustness of the annual dataset for calibration purposes, we have generated a replicate sequence from the same Irish oaks at ETH Zürich. These data are compatible with the Irish oak 14C dataset previously produced at the University of Arizona and are used (along with additional data) to examine inter-tree and interlaboratory variation in multiyear annual 14C time-series. The results raise questions about regional 14C offsets at different scales and demonstrate the potential of annually resolved 14C for refining subdecadal and larger scale features for calibration, solar reconstruction, and multiproxy synchronization
Exo70-Mediated Recruitment of Nucleoporin Nup62 at the Leading Edge of Migrating Cells is Required for Cell Migration
Nucleoporin Nup62 localizes at the central channel of the nuclear pore complex and is essential for nucleocytoplasmic transport. Through its FG-repeat domain, Nup62 regulates nuclear pore permeability and binds nuclear transport receptors. Here, we report that Nup62 interacts directly with Exo70 and colocalizes with Exo70 at the leading edge of migrating cells. Nup62 binds the N-terminal domain of Exo70 through its coiled-coil domain but not through its FG-repeat domain. Selective inhibition of leading edge Nup62 using RNA interference significantly reduces cell migration. Furthermore, Exo70 recruits Nup62 at the plasma membrane and at filopodia. Removal of the Exo70-binding domain of Nup62 prevents leading edge localization of Nup62. Analogous to Exo70, Nup62 cycles between the plasma membrane and the perinuclear recycling compartment. Altogether, we propose that Nup62 not solely regulates access to the cell nucleus, but additionally functions in conjunction with Exo70, a key regulator of exocytosis and actin dynamics, at the leading edge of migrating cells
The effectiveness and cost-effectiveness of parent training/education programmes for the treatment of conduct disorder, including oppositional defiant disorder, in children
Objectives: To assess the clinical and cost-effectiveness of parent training programmes for the treatment of children with conduct disorder ( CD) up to the age of 18 years.
Data sources: Electronic databases.
Review methods: For the effectiveness review, relevant studies were identified and evaluated. A quantitative synthesis of behavioural outcomes across trials was also undertaken using two approaches: vote counting and meta-analysis. The economic analysis consisted of reviewing previous economic/cost evaluations of parent training/education programmes and the economic information within sponsor's submissions; carrying out a detailed exploration of costs of parent training/education programmes; and a de novo modelling assessment of the cost-effectiveness of parent training/education programmes. The potential budget impact to the health service of implementing such programmes was also considered.
Results: Many of the 37 randomised controlled trials that met the review inclusion and exclusion criteria were assessed as being of poor methodological quality. Studies were clinically heterogeneous in terms of the population, type of parent training/education programme and content, setting, delivery, length and child behaviour outcomes used. Both vote counting and meta-analysis revealed a consistent trend across all studies towards short-term effectiveness ( up to 4 months) of parent training/education programmes ( compared with control) as measured by a change in child behaviour. Pooled estimates showed a statistically significant improvement on the Eyberg Child Behaviour Inventory frequency and intensity scales, the Dyadic Parent - Child Interaction Coding System and the Child Behaviour Checklist. No studies reported a statistically significant result favouring control over parent training/education programmes. There were few statistically significant differences between different parent training/education programmes, although there was a trend towards more intensive interventions ( e. g. longer contact hours, additional child involvement) being more effective. The cost of treating CD is high, with costs incurred by many agencies. A recent study suggested that by age 28, costs for individuals with CD were around 10 times higher than for those with no problems, with a mean cost of 70,019 pound. Criminality incurs the greatest cost, followed by educational provision, foster and residential care and state benefits. Only a small proportion of these costs fall on health services. Using a 'bottom-up' costing approach, the costs per family of providing parent training/education programmes range from 629 pound to 3839 pound depending on the type and style of delivery. Using the conservative assumption that there are no cost savings from treatment, a total lifetime quality of life gain of 0.1 would give a cost per quality-adjusted life-year of between 38,393 pound and 6288 pound depending on the type of programme delivery and setting.
Conclusions: Parent training/education programmes appear to be an effective and potentially cost-effective therapy for children with CD. However, the relative effectiveness and cost-effectiveness of different models ( such as therapy intensity and setting) require further investigation. Further research is required on the impact of parent training/education programmes on the quality of life of children with CD and their parents/carers, as well as on longer term child outcomes
Missed opportunities: unnecessary medicine use in patients with lung cancer at the end of life: an international cohort study
Aims The aims of the current study were: (i) to examine the prescribing of preventative medication in a cohort of people with advanced lung cancer on hospital admission and discharge across different healthcare systems; and (ii) to explore the factors that influence preventative medication prescribing at hospital discharge. Methods A retrospective cohort study was conducted across two centres in the UK and the US. The prescribing of preventative medication was examined at hospital admission and discharge for patients who died of lung cancer. A zero‐inflated negative binomial regression model was used to examine the association between preventative medications at discharge and patient‐ and hospital‐based factors. The classes of preventative medication prescribed included were: vitamins and minerals, and antidiabetic, antihypertensive, antihyperlipidaemic and antiplatelet medications. Results In the UK site (n = 125), the mean number of preventative medications prescribed was 1.9 [standard deviation (SD) 1.7) on admission, and 1.7 (SD 1.7) on discharge, and in the US site (n = 191) the mean was 2.6 (SD 2.2) on admission and 1.9 (SD 2.2) on discharge. The model found a significant association between the number of preventative drugs prescribed on admission and the number on discharge; it also found a significant association between the total number of drugs prescribed on discharge and the number of preventative medications on discharge. Other indicators related to patient and hospital factors were not significantly associated with the number of preventative medications supplied on discharge. Conclusions The use of preventative medication was common in lung cancer patients, despite undergoing discharge. Patient‐ and hospital‐based factors did not influence the prescribing of preventative medication
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