The Role of Penning Collisions in Hollow Cathode Helium Cadmium Lasers

The excitation mechanisms leading to the formation of the 5s² ²D5/2 level, the upper level of the 4416 Å transition of Cd+, have been investigated. Experiments were carried out in both a helium cadmium discharge and corresponding afterglow. A self absorption technique was used to measure the variation, with current, pressure and oven temperature, of the densities of selected excited helium levels and the cadmium ion ground state. A comparison of the parametric behaviour of the Penning collision rate with the 4416 Å spontaneous emission provided good evidence that Penning ionization was the dominant mechanism leading to laser oscillation at 4416 Å. Gas temperature effects were found to have a significant influence on the interpretation of the experimental results. Signal averaging techniques were employed to record the pressure, current and oven temperature dependence of the 4416 Å spontaneous decay in the hollow cathode helium cadmium afterglow. The decay was more complex than anticipated but was eventually attributed to the temporal evolution of the helium triplet metastable species in the afterglow. A simplified model of the afterglow was developed and, using the available excited state densities and estimates of the electron and helium ion densities and electron collision rates, the system of coupled differential rate equations was solved and found to be in reasonable agreement with the experimentally observed trends of the 4416 Å decay. Taken as a whole, the results of the study of the helium cadmium d.c. discharge and afterglow show beyond doubt that Penning ionization is the dominant excitation mechanism of the 5s² ²D5/2 level of Cd II

Towards an Efficient Finite Element Method for the Integral Fractional Laplacian on Polygonal Domains

We explore the connection between fractional order partial differential equations in two or more spatial dimensions with boundary integral operators to develop techniques that enable one to efficiently tackle the integral fractional Laplacian. In particular, we develop techniques for the treatment of the dense stiffness matrix including the computation of the entries, the efficient assembly and storage of a sparse approximation and the efficient solution of the resulting equations. The main idea consists of generalising proven techniques for the treatment of boundary integral equations to general fractional orders. Importantly, the approximation does not make any strong assumptions on the shape of the underlying domain and does not rely on any special structure of the matrix that could be exploited by fast transforms. We demonstrate the flexibility and performance of this approach in a couple of two-dimensional numerical examples

Virtual Electrode Recording Tool for EXtracellular potentials (VERTEX): Comparing multi-electrode recordings from simulated and biological mammalian cortical tissue

Local field potentials (LFPs) sampled with extracellular electrodes are frequently used as a measure of population neuronal activity. However, relating such measurements to underlying neuronal behaviour and connectivity is non-trivial. To help study this link, we developed the Virtual Electrode Recording Tool for EXtracellular potentials (VERTEX). We first identified a reduced neuron model that retained the spatial and frequency filtering characteristics of extracellular potentials from neocortical neurons. We then developed VERTEX as an easy-to-use Matlab tool for simulating LFPs from large populations (>100 000 neurons). A VERTEX-based simulation successfully reproduced features of the LFPs from an in vitro multi-electrode array recording of macaque neocortical tissue. Our model, with virtual electrodes placed anywhere in 3D, allows direct comparisons with the in vitro recording setup. We envisage that VERTEX will stimulate experimentalists, clinicians, and computational neuroscientists to use models to understand the mechanisms underlying measured brain dynamics in health and disease.Comment: appears in Brain Struct Funct 201

Rebuilding relationships on coral reefs: Coral bleaching knowledge-sharing to aid adaptation planning for reef users: Bleaching emergence on reefs demonstrates the need to consider reef scale and accessibility when preparing for, and responding to, coral bleaching

Coral bleaching has impacted reefs worldwide and the predictions of near-annual bleaching from over two decades ago have now been realized. While technology currently provides the means to predict large-scale bleaching, predicting reef-scale and within-reef patterns in real-time for all reef users is limited. In 2020, heat stress across the Great Barrier Reef underpinned the region's third bleaching event in 5 years. Here we review the heterogeneous emergence of bleaching across Heron Island reef habitats and discuss the oceanographic drivers that underpinned variable bleaching emergence. We do so as a case study to highlight how reef end-user groups who engage with coral reefs in different ways require targeted guidance for how, and when, to alter their use of coral reefs in response to bleaching events. Our case study of coral bleaching emergence demonstrates how within-reef scale nowcasting of coral bleaching could aid the development of accessible and equitable bleaching response strategies on coral reefs. Also see the video abstract here: https://youtu.be/N9Tgb8N-vN0

Same old song and dance: An exploratory study of portrayal of physical activity in television programmes aimed at young adolescents

Abstract Objective Exposure to health-related behaviours on television has been shown to influence smoking and drinking in young people, but little research has been conducted on the portrayal physical activity. The aim of the current project was to explore the portrayal of physical activity in television programmes aimed specifically at adolescent females. Content analysis of 120 episodes of four popular adolescent television programmes was performed. Information on the type and context of physical activity, motivating factors and characters involved was recorded. Results Physical activity was portrayed 122 times, for a duration of 1 h and 31 min (3.2% of total viewing time). Physical activity was mainly portrayed as part of an informal activity as part of a group activity. Over half (53.2%) of scenes portrayed activity been carried out by teenagers. The types of activities portrayed were mostly of vigorous intensity (76.2%), for recreational purposes (78.7%) such as dancing (54.1%) and running (11.5%), and motivated by enjoyment. This study highlights that physical activity is portrayed infrequently, and often with a skewed representation of type of activity. There may be an opportunity to influence physical activity in young adolescents through the positioning of positive images of an active lifestyle in the media

Using Point-of-Choice Prompts to Reduce Sedentary Behavior in Sit-Stand Workstation Users

Introduction: Desk-based office workers are at occupational risk for poor health outcomes from excessive time spent sitting. Sit-stand workstations are used to mitigate sitting, but lack of workstation usage has been observed. Point-of-choice (PoC) prompts offer a complementary strategy for office workers to break up their sitting time.Study purpose: The purpose of this study was to examine the preliminary efficacy, preference, and acceptability of a theory-driven (i.e., 40 unique prompts encompassing social cognitive theory; TD-PoC) and an atheoretical basic reminder PoC prompt intervention (R-PoC) on reducing sedentary behavior in office workers with self-reported low sit-stand workstation usage (≤4 h per day).Methods: In a cross-over design, participants (N = 19, 78.9% female, 39.4 ± 10.7 years of age) completed a 5-days no-prompt control condition followed by a random and counterbalanced assignment to one of the TD-PoC and R-PoC active conditions with a 1-week washout period between. Preliminary efficacy was assessed during work hours with the activPAL micro accelerometer. Preference was assessed prior to each active condition and acceptability was assessed following each active condition via questionnaire.Results: The R-PoC prompt condition significantly decreased sitting time (b[se] = −49.0 [20.8], p = 0.03) and increased standing time (b[se] = 49.8 [19.7], p = 0.02) and displayed a significant increase in sit-stand transitions (b[se] = 2.3 [1.1], p = 0.04), relative to no-prompt control. Both the R-PoC and TD-PoC prompt conditions significantly decreased time spent in prolonged sitting bouts at b[se] = −68.1 [27.8], (p = 0.02), (b[se] = −76.7 [27.1], p = 0.008) relative to no-prompt control. Overall, the TD-PoC prompt condition displayed higher preference and acceptability ratings; however, these differences were not significant (p's > 0.05).Conclusion: While the R-PoC prompt condition was slightly more efficacious than the TD-PoC prompt condition, the TD-PoC prompt condition was rated with higher preference and acceptability scores. Large variations between participants in preference, acceptability, and intervention feedback may indicate need for tailored messaging which may facilitate sustained use in the long-term

Model validation for a noninvasive arterial stenosis detection problem

Copyright @ 2013 American Institute of Mathematical SciencesA current thrust in medical research is the development of a non-invasive method for detection, localization, and characterization of an arterial stenosis (a blockage or partial blockage in an artery). A method has been proposed to detect shear waves in the chest cavity which have been generated by disturbances in the blood flow resulting from a stenosis. In order to develop this methodology further, we use both one-dimensional pressure and shear wave experimental data from novel acoustic phantoms to validate corresponding viscoelastic mathematical models, which were developed in a concept paper [8] and refined herein. We estimate model parameters which give a good fit (in a sense to be precisely defined) to the experimental data, and use asymptotic error theory to provide confidence intervals for parameter estimates. Finally, since a robust error model is necessary for accurate parameter estimates and confidence analysis, we include a comparison of absolute and relative models for measurement error.The National Institute of Allergy and Infectious Diseases, the Air Force Office of Scientific Research, the Deopartment of Education and the Engineering and Physical Sciences Research Council (EPSRC)

New scientific discoveries : plants and fungi

Scientific discovery, including naming new taxa, is important because without a scientific name, a species is invisible to science and the possibilities of researching its ecology, applications and threats, and conserving it, are greatly reduced. We review new scientific discoveries in the plant and fungal kingdoms, based largely on new names of taxa published in 2019 and indexed in the International Plant Names Index and Index Fungorum. Numbers of new species in both kingdoms were similar with 1942 new species of plant published and 1882 species of fungi. However, while >50% of plant species have likely been discovered, >90% of fungi remain unknown. This gulf likely explains the greater number of higher order taxa for fungi published in 2019: three classes, 18 orders, 48 families and 214 genera versus one new family and 87 new genera for plants. We compare the kingdoms in terms of rates of scientific discovery, globally and in different taxonomic groups and geographic areas, and with regard to the use of DNA in discovery. We review species new to science, especially those of interest to humanity as new products, and also by life‐form. We consider where future such discoveries can be expected. We recommend an urgent increase in investment in scientific discovery of plant and fungal species, while they still survive. Priorities include more investment in training taxonomists, in building and equipping collections‐based research centers for them, especially in species‐rich, income‐poor countries where the bulk of species as yet unknown to science are thought to occur