Memorial University of Newfoundland

About: Memorial University of Newfoundland is a education organization based out in St. John's, Newfoundland and Labrador, Canada. It is known for research contribution in the topics: Population & Context (language use). The organization has 13818 authors who have published 27785 publications receiving 743594 citations. The organization is also known as: Memorial University & Memorial University of Newfoundland and Labrador.

Threshold Dynamics for Compartmental Epidemic Models in Periodic Environments

Abstract: The basic reproduction ratio and its computation formulae are established for a large class of compartmental epidemic models in periodic environments. It is proved that a disease cannot invade the disease-free state if the ratio is less than unity and can invade if it is greater than unity. It is also shown that the basic reproduction number of the time-averaged autonomous system is applicable in the case where both the matrix of new infection rate and the matrix of transition and dissipation within infectious compartments are diagonal, but it may underestimate and overestimate infection risks in other cases. The global dynamics of a periodic epidemic model with patch structure is analyzed in order to study the impact of periodic contacts or periodic migrations on the disease transmission.

Grade-12 Students' Misconceptions Relating to Fundamental Characteristics of Atoms and Molecules.

Abstract: An understanding of the concepts of atom and molecule is fundamental to the learning of chemistry. Any misconceptions and alternative conceptions that students harbor about these concepts will impede further learning. This article identifies misconceptions related to the fundamental characteristics of atoms and molecules which Grade-12 students hold. Data were obtained by administration of semistructured interviews to a stratified, random sample of 30 students of differing abilities and backgrounds in science. Fifty-two misconceptions were observed and are reported. These are grouped into 11 categories. Six relate to the structure, composition, size, shape, weight, bonding, and energy of molecules; five relate to the structure, shape, size, weight, and animistic perceptions of atoms. Some of the misconceptions identified parallel the historical development of scientific concepts.

Whole-genome sequencing of quartet families with autism spectrum disorder

Abstract: Autism spectrum disorder (ASD) is genetically heterogeneous, with evidence for hundreds of susceptibility loci. Previous microarray and exome-sequencing studies have examined portions of the genome in simplex families (parents and one ASD-affected child) having presumed sporadic forms of the disorder. We used whole-genome sequencing (WGS) of 85 quartet families (parents and two ASD-affected siblings), consisting of 170 individuals with ASD, to generate a comprehensive data resource encompassing all classes of genetic variation (including noncoding variants) and accompanying phenotypes, in apparently familial forms of ASD. By examining de novo and rare inherited single-nucleotide and structural variations in genes previously reported to be associated with ASD or other neurodevelopmental disorders, we found that some (69.4%) of the affected siblings carried different ASD-relevant mutations. These siblings with discordant mutations tended to demonstrate more clinical variability than those who shared a risk variant. Our study emphasizes that substantial genetic heterogeneity exists in ASD, necessitating the use of WGS to delineate all genic and non-genic susceptibility variants in research and in clinical diagnostics.

Individual understandings, perceptions, and engagement with climate change: insights from in-depth studies across the world

Abstract: Public understandings and perceptions of, as well as engagement with, climate change have garnered the interest of research and policy for almost three decades. A portion of this growing body of literature examines such perceptions in-depth, using largely qualitative methodologies, such as personal interviews, limited sample size surveys, focus groups, and case studies. This area of research has been conducted on different continents, with individuals of different cultural backgrounds and ethnic groups, and a variety of demographic characteristics. It has examined various aspects of the communication process, such as audience differences, influence of framing, messages and messengers, information processing, etc.). This paper focuses on this subset of the climate change literature, highlighting similarities and differences across cultural, social, and geographical landscapes. Apart from demographic and regional differences, this literature also offers more detailed insights into the effectiveness of different communication strategies and into the cognitive and psychological processes that underlie public opinions. These insights are generally not obtained through large-scale opinion surveys. Our review highlights great variation and sometimes direct contradiction between these pieces of research. This not only points to a need for further refinement in our knowledge of public understanding and engagement, but also simply to accept that no one theory will explain the variation in human experience of climate change and action in response to it. WIREs Clim Change 2011 2 547–569 DOI: 10.1002/wcc.120 For further resources related to this article, please visit the WIREs website

Norepinephrine ignites local hotspots of neuronal excitation: How arousal amplifies selectivity in perception and memory.

Abstract: Emotional arousal enhances perception and memory of high-priority information but impairs processing of other information. Here, we propose that, under arousal, local glutamate levels signal the current strength of a representation and interact with norepinephrine (NE) to enhance high priority representations and out-compete or suppress lower priority representations. In our "glutamate amplifies noradrenergic effects" (GANE) model, high glutamate at the site of prioritized representations increases local NE release from the locus coeruleus (LC) to generate "NE hotspots." At these NE hotspots, local glutamate and NE release are mutually enhancing and amplify activation of prioritized representations. In contrast, arousal-induced LC activity inhibits less active representations via two mechanisms: 1) Where there are hotspots, lateral inhibition is amplified; 2) Where no hotspots emerge, NE levels are only high enough to activate low-threshold inhibitory adrenoreceptors. Thus, LC activation promotes a few hotspots of excitation in the context of widespread suppression, enhancing high priority representations while suppressing the rest. Hotspots also help synchronize oscillations across neural ensembles transmitting high-priority information. Furthermore, brain structures that detect stimulus priority interact with phasic NE release to preferentially route such information through large-scale functional brain networks. A surge of NE before, during, or after encoding enhances synaptic plasticity at NE hotspots, triggering local protein synthesis processes that enhance selective memory consolidation. Together, these noradrenergic mechanisms promote selective attention and memory under arousal. GANE not only reconciles apparently contradictory findings in the emotion-cognition literature but also extends previous influential theories of LC neuromodulation by proposing specific mechanisms for how LC-NE activity increases neural gain.