2,514 research outputs found
Local cluster aggregation models of explosive percolation
We introduce perhaps the simplest models of graph evolution with choice that
demonstrate discontinuous percolation transitions and can be analyzed via
mathematical evolution equations. These models are local, in the sense that at
each step of the process one edge is selected from a small set of potential
edges sharing common vertices and added to the graph. We show that the
evolution can be accurately described by a system of differential equations and
that such models exhibit the discontinuous emergence of the giant component.
Yet, they also obey scaling behaviors characteristic of continuous transitions,
with scaling exponents that differ from the classic Erdos-Renyi model.Comment: Final version as appearing in PR
Environmental and genetic influences on neurocognitive development: the importance of multiple methodologies and time-dependent intervention
Genetic mutations and environmental factors dynamically influence gene expression and developmental trajectories at the neural, cognitive, and behavioral levels. The examples in this article cover different periods of neurocognitive development—early childhood, adolescence, and adulthood—and focus on studies in which researchers have used a variety of methodologies to illustrate the early effects of socioeconomic status and stress on brain function, as well as how allelic differences explain why some individuals respond to intervention and others do not. These studies highlight how similar behaviors can be driven by different underlying neural processes and show how a neurocomputational model of early development can account for neurodevelopmental syndromes, such as autism spectrum disorders, with novel implications for intervention. Finally, these studies illustrate the importance of the timing of environmental and genetic factors on development, consistent with our view that phenotypes are emergent, not predetermined
A Crystallographic Basis for Critically Evaluating the Mechanisms for Secondary Grain Formation During Directional Solidification
Is Early Bilingual Experience Associated with Greater Fluid Intelligence in Adults?
Emerging evidence suggests that early bilingual experience constrains the development of attentional processes in infants, and that some of these early bilingual adaptations could last into adulthood. However, it is not known whether the early adaptations in the attentional domain alter more general cognitive abilities. If they do, then we would expect that bilingual adults who learned their second language early in life would score more highly across cognitive tasks than bilingual adults who learned their second language later in life. To test this hypothesis, 170 adult participants were administered a well-established (non-verbal) measure of fluid intelligence: Raven’s Advanced Progressive Matrices (RAPM). Fluid intelligence (the ability to solve novel reasoning problems, independent of acquired knowledge) is highly correlated with numerous cognitive abilities across development. Performance on the RAPM was greater in bilinguals than monolinguals, and greater in ‘early bilinguals’ (adults who learned their second language between 0–6 years) than ‘late bilinguals’ (adults who learned their second language after age 6 years). The groups did not significantly differ on a proxy of socioeconomic status. These results suggest that the difference in fluid intelligence between bilinguals and monolinguals is not a consequence of bilingualism per se, but of early adaptive processes. However, the finding may depend on how bilingualism is operationalized, and thus needs to be replicated with a larger sample and more detailed measures
Real-Time Synthesis is Hard!
We study the reactive synthesis problem (RS) for specifications given in
Metric Interval Temporal Logic (MITL). RS is known to be undecidable in a very
general setting, but on infinite words only; and only the very restrictive BRRS
subcase is known to be decidable (see D'Souza et al. and Bouyer et al.). In
this paper, we precise the decidability border of MITL synthesis. We show RS is
undecidable on finite words too, and present a landscape of restrictions (both
on the logic and on the possible controllers) that are still undecidable. On
the positive side, we revisit BRRS and introduce an efficient on-the-fly
algorithm to solve it
Transmission of infection among health care personnel performing surgical tracheostomies on COVID-19 patients
Background: Staff and patient safety are of paramount importance while performing a surgical tracheostomy(ST) during the corona virus disease(COVID-19) pandemic. The aim was to assess the incidence of COVID-19 infection among the healthcare personnel(HCP) performing ST on COVID-19 patients. /
Methods: One hundred and twenty-two HCP participating in 71 ST procedures performed at our institution between 26th March 2020 and 27th May 2020 were identified. A COVID-19 health questionnaire was distributed among staff with their consent. Data related to the presence of COVID-19 symptoms(new onset continuous cough, fever, loss of taste and/or loss of smell) among HCP involved in ST as well as patient related data were collected. /
Results: Of the HCP who responded, eleven(15%,11/72) reported key COVID-19 symptoms and went into self-isolation. Ten members from this group underwent a COVID-19 swab test and three tested positive. Only one HCP attended hospital for symptomatic treatment, none required hospitalisation. Sixty percent(43/72) of the responders had a COVID-19 antibody test with a positive rate of 18.6%(8/43).
Among the patients undergoing a ST, 67%(37/55) required a direct intensive care unit(ICU) admission; the mean age was 58 years(29-78) with a male preponderance(65.5%). The median time from intubation to ST was 15 days (range 5-33,IQR=9). The overall mortality was 11%(6/55). /
Conclusions: ST can be carried out safely with strict adherence to both, personnel protective equipment and ST protocols which are vital to mitigate the potential transmission of COVID-19 to the HCP
Influence of Bath Composition at Acidic pH on Electrodeposition of Nickel-Layered Silicate Nanocomposites for Corrosion Protection
Nickel-layered silicates were electrochemically deposited from acidic bath solutions. Citrate was used as a ligand to stabilize nickel (II) ions in the plating solution. The silicate, montmorillonite, was exfoliated by stirring in aqueous solution over 24 hours. The plating solutions were analyzed for zeta-potential, particle size, viscosity, and conductivity to investigate the effects of the composition at various pHs. The solution particles at pH 2.5 (−22.2 mV) and pH 3.0 (−21.9 mV) were more stable than at pH 1.6 (−10.1 mV) as shown by zeta-potential analysis of the nickel-citrate-montmorillonite plating solution. Ecorr for the films ranged from −0.32 to −0.39 V with varying pH from 1.6 to 3.0. The films were immersed in 3.5% NaCl and the open circuit potential monitored for one month. The coatings deposited at pH 3.0 were stable 13 days longer in the salt solution than the other coatings. X-ray diffraction showed a change in the (111)/(200) ratio for the coatings at the various pHs. The scanning electron microscopy and hardness results also support that the electrodeposition of nickel-montmorillonite at pH 3.0 (234 GPa) had improved hardness and morphology compared to pH 2.5 (174 GPa) and pH 1.6 (147 GPa)
Predictive value of respiratory symptoms and bronchial hyperresponsiveness to diagnose asthma in New Zealand
SummaryRespiratory symptoms are often used as the only diagnostic criteria for asthma in epidemiological surveys and the clinical diagnosis of asthma relies primarily on a detailed history. The aim of this study is to predict the diagnostic value of 11 different respiratory symptoms to diagnose asthma, and to determine if bronchial hyperresponsiveness (BHR) improves the predictive value of these respiratory symptoms.A random sample of 1257 subjects aged 20–44 years old in 3 different areas of New Zealand were selected between March 1991 and December 1992 to answer the European Community Respiratory Health Survey questionnaire on respiratory symptoms. Of these, 784 underwent bronchial challenge with methacholine. The prevalence of current doctor diagnosed asthma (DDA) defined as asthma confirmed by a physician and an asthma attack in the last 12 months was 8.3%. Wheezing with dyspnoea is the single best predictor of diagnosed asthma with a sensitivity of 82%, a specificity of 90% and a Youden's index of 0.72. Wheezing alone is more sensitive (94%) but less specific (76%), with a Youden's index of 0.70. The addition of BHR to asthma symptoms decreases sensitivity and increases specificity with a small increase in Youden's index to 0.75. In New Zealand adults, a history of wheezing with BHR best predicts a diagnosis of asthma but wheezing alone or with dyspnoea are the two best symptoms for predicting asthma
Teachers developing assessment for learning: impact on student achievement
While it is generally acknowledged that increased use of formative assessment (or assessment for learning) leads to higher quality learning, it is often claimed that the pressure in schools to improve the results achieved by students in externally-set tests and examinations precludes its use. This paper reports on the achievement of secondary school students who worked in classrooms where teachers made time to develop formative assessment strategies. A total of 24 teachers (2 science and 2 mathematics teachers, in each of six schools in two LEAs) were supported over a six-month period in exploring and planning their approach to formative assessment, and then, beginning in September 1999, the teachers put these plans into action with selected classes. In order to compute effect sizes, a measure of prior attainment and at least one comparison group was established for each class (typically either an equivalent class taught in the previous year by the same teacher, or a parallel class taught by another teacher). The mean effect size was 0.32
Strongly discontinuous explosive percolation with multiple giant components
We generalize the random graph evolution process of Bohman, Frieze, and
Wormald [T. Bohman, A. Frieze, and N. C. Wormald, Random Struct. Algorithms,
25, 432 (2004)]. Potential edges, sampled uniformly at random from the complete
graph, are considered one at a time and either added to the graph or rejected
provided that the fraction of accepted edges is never smaller than a decreasing
function asymptotically approaching the value alpha = 1/2. We show that
multiple giant components appear simultaneously in a strongly discontinuous
percolation transition and remain distinct. Furthermore, tuning the value of
alpha determines the number of such components with smaller alpha leading to an
increasingly delayed and more explosive transition. The location of the
critical point and strongly discontinuous nature are not affected if only edges
which span components are sampled.Comment: Final version appearing in PR
- …