Analytical formulas for calculating the thermal diffusivity of cylindrical shell and spherical shell samples

Calculating the thermal diffusivity of solid materials is commonly carried out using the laser flash experiment. This classical experiment considers a small (usually thin disc-shaped) sample of the material with parallel front and rear surfaces, applying a heat pulse to the front surface and recording the resulting rise in temperature over time on the rear surface. Recently, Carr and Wood [Int J Heat Mass Transf, 144 (2019) 118609] showed that the thermal diffusivity can be expressed analytically in terms of the heat flux function applied at the front surface and the temperature rise history at the rear surface. In this paper, we generalise this result to radial unidirectional heat flow, developing new analytical formulas for calculating the thermal diffusivity for cylindrical shell and spherical shell shaped samples. Two configurations are considered: (i) heat pulse applied on the inner surface and temperature rise recorded on the outer surface and (ii) heat pulse applied on the outer surface and temperature rise recorded on the inner surface. Code implementing and verifying the thermal diffusivity formulas for both configurations is made available.Comment: 12 pages, 5 figure

Simplified models of diffusion in radially-symmetric geometries

We consider diffusion-controlled release of particles from $d$-dimensional radially-symmetric geometries. A quantity commonly used to characterise such diffusive processes is the proportion of particles remaining within the geometry over time, denoted as $P(t)$. The stochastic approach for computing $P(t)$ is time-consuming and lacks analytical insight into key parameters while the continuum approach yields complicated expressions for $P(t)$ that obscure the influence of key parameters and complicate the process of fitting experimental release data. In this work, to address these issues, we develop several simple surrogate models to approximate $P(t)$ by matching moments with the continuum analogue of the stochastic diffusion model. Surrogate models are developed for homogeneous slab, circular, annular, spherical and spherical shell geometries with a constant particle movement probability and heterogeneous slab, circular, annular and spherical geometries, comprised of two concentric layers with different particle movement probabilities. Each model is easy to evaluate, agrees well with both stochastic and continuum calculations of $P(t)$ and provides analytical insight into the key parameters of the diffusive transport system: dimension, diffusivity, geometry and boundary conditions.Comment: 22 pages, 3 figures, submitte

Measuring the Faraday effect in olive oil using permanent magnets and Malus' law

We present a simple permanent magnet set-up that can be used to measure the Faraday effect in gases, liquids and solids. By fitting the transmission curve as a function of polarizer angle (Malus' law) we average over short-term fluctuations in the laser power and can extract phase shifts as small as ± 50 μrads. We have focused on measuring the Faraday effect in olive oil and find a Verdet coefficient of V = 192 ± 1 deg T-1 m-1 at approximately 20 °C for a wavelength of 659.2 nm. We show that the Verdet coefficient can be fit with a Drude-like dispersion law A / (λ2 - λ0 2) with coefficients A = 7.9 ± 0.2 × 107 deg T-1 m-1 nm2 and λ0 = 142 ± 13 nm

Viral metagenomics of aphids present in bean and maize plots on mixed-use farms in Kenya reveals the presence of three dicistroviruses including a novel Big Sioux River virus-like dicistrovirus

Background: Aphids are major vectors of plant viruses. Common bean (Phaseolus vulgaris L.) and maize (Zea mays L.) are important crops that are vulnerable to aphid herbivory and aphid-transmitted viruses. In East and Central Africa, common bean is frequently intercropped by smallholder farmers to provide fixed nitrogen for cultivation of starch crops such as maize. We used a PCR-based technique to identify aphids prevalent in smallholder bean farms and next generation sequencing shotgun metagenomics to examine the diversity of viruses present in aphids and in maize leaf samples. Samples were collected from farms in Kenya in a range of agro-ecological zones. Results: Cytochrome oxidase 1 (CO1) gene sequencing showed that Aphis fabae was the sole aphid species present in bean plots in the farms visited. Sequencing of total RNA from aphids using the Illumina platform detected three dicistroviruses. Maize leaf RNA was also analysed. Identification of Aphid lethal paralysis virus (ALPV), Rhopalosiphum padi virus (RhPV), and a novel Big Sioux River virus (BSRV)-like dicistrovirus in aphid and maize samples was confirmed using reverse transcription-polymerase chain reactions and sequencing of amplified DNA products. Phylogenetic, nucleotide and protein sequence analyses of eight ALPV genomes revealed evidence of intra-species recombination, with the data suggesting there may be two ALPV lineages. Analysis of BSRV-like virus genomic RNA sequences revealed features that are consistent with other dicistroviruses and that it is phylogenetically closely related to dicistroviruses of the genus Cripavirus.Work was funded by a grant from the Sustainable Crop Production Research for International Development programme funded by the UK Biotechnology and Biological Sciences Research Council (BBSRC) with co-funding from the UK Department for International Development, the Bill & Melinda Gates Foundation, the Department of Biotechnology of India’s Ministry of Science and Technology, and the Indian Council of Agricultural Research (BB/J011762/1) and a Global Challenges Research Fund Foundation Award (BB/P023223/1). LAB was funded by a Cambridge BBSRC doctoral training programme studentship

Genetic Variation in the Androgen Receptor and Measures of Plasma Testosterone Levels Suggest Androgen Dysfunction in Alzheimer’s Disease

Alzheimer’s disease (AD) prevalence varies by sex, suggesting that sex chromosomes, sex hormones and/or their signaling could potentially modulate AD risk and progression. Low testosterone levels are reported in men with AD. Further, variation in the androgen receptor (AR) gene has been associated with AD risk and cognitive impairment. We assessed measures of plasma testosterone levels as a biomarker of AD in male participants from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) cohort. Baseline testosterone levels were significantly different between clinical diagnosis groups [cognitively normal controls, mild cognitive impairment (MCI), or AD], with the lowest testosterone levels in men with AD. Lower baseline testosterone levels were associated with higher baseline clinical severity. Change in testosterone levels between baseline and 1-year follow-up varied by diagnosis; MCI had the greatest decreases in testosterone levels between baseline and 1-year follow-up. Despite differences by clinical diagnosis, there was no association between plasma testosterone and CSF biomarkers of AD pathology. We also tested single nucleotide polymorphisms (SNPs) in AR for association with AD risk in a separate cohort from ADNI and found 26 SNPs associated with risk for AD. The top associated SNP is predicted to be an expression quantitative trait locus for AR in multiple tissues, including brain, with the AD-associated risk allele predicted to confer lower AR expression. Our findings suggest a link between the androgen pathway and AD through Aβ/tau independent pathways. These effects may be most pronounced during conversion from MCI to dementia

Cohort Profile: The United Kingdom Research study into Ethnicity and COVID-19 outcomes in Healthcare workers (UK-REACH)

The UK-REACH cohort was established to understand why ethnic minority healthcare workers (HCWs) are at risk of poorer outcomes from COVID-19 when compared with their White ethnic counterparts in the UK. Through study design, it contains a uniquely high percentage of participants from ethnic minority backgrounds about whom a wide range of qualitative and quantitative data have been collected. A total of 17 891 HCWs aged 16–89 years (mean age: 44) have been recruited from across the UK via all major healthcare regulators, individual National Health Service hospital trusts and UK HCW membership bodies who advertised the study to their registrants/staff to encourage participation in the study. Data available include linked healthcare records for 25 years from the date of consent and consent to obtain genomic sequencing data collected via saliva. Online questionnaires include information on demographics, COVID-19 exposures at work and home, redeployment in the workforce due to COVID-19, mental health measures, workforce attrition and opinions on COVID-19 vaccines, with baseline (n = 15 119), 6 (n = 5632) and 12-month follow-up (n = 6535) data captured. Request data access and collaborations by following documentation found at https://www.uk-reach.org/main/data_sharing

Low temperature electronic properties of Sr_2RuO_4 II: Superconductivity

The body centered tetragonal structure of Sr_2RuO_4 gives rise to umklapp scattering enhanced inter-plane pair correlations in the d_{yz} and d_{zx} orbitals. Based on symmetry arguments, Hund's rule coupling, and a bosonized description of the in-plane electron correlations the superconducting order parameter is found to be a orbital-singlet spin-triplet with two spatial components. The spatial anisotropy is 7%. The different components of the order parameter give rise to two-dimensional gapless fluctuations. The phase transition is of third order. The temperature dependence of the pair density, specific heat, NQR, Knight shift, and susceptibility are in agreement with experimental results.Comment: 20 pages REVTEX, 3 figure

Healthcare workers’ views on mandatory SARS-CoV-2 vaccination in the UK: A cross-sectional, mixed-methods analysis from the UK-REACH study

Background: Several countries now have mandatory SARS-CoV-2 vaccination for healthcare workers (HCWs) or the general population. HCWs’ views on this are largely unknown. Using data from the nationwide UK-REACH study we aimed to understand UK HCW's views on improving SARS-CoV-2 vaccination coverage, including mandatory vaccination. // Methods: Between 21st April and 26th June 2021, we administered an online questionnaire via email to 17 891 UK HCWs recruited as part of a longitudinal cohort from across the UK who had previously responded to a baseline questionnaire (primarily recruited through email) as part of the United Kingdom Research study into Ethnicity And COVID-19 outcomes in Healthcare workers (UK-REACH) nationwide prospective cohort study. We categorised responses to a free-text question “What should society do if people do not get vaccinated against COVID-19?” using qualitative content analysis. We collapsed categories into a binary variable: favours mandatory vaccination or not, using logistic regression to calculate its demographic predictors, and its occupational, health, and attitudinal predictors adjusted for demographics. // Findings: Of 5633 questionnaire respondents, 3235 answered the free text question. Median age of free text responders was 47 years (IQR 36–56) and 2705 (74.3%) were female. 18% (n = 578) favoured mandatory vaccination (201 [6%] participants for HCWs and others working with vulnerable populations; 377 [12%] for the general population), but the most frequent suggestion was education (32%, n = 1047). Older HCWs (OR 1.84; 95% CI 1.44–2.34 [≥55 years vs 16 years to <40 years]), HCWs vaccinated against influenza (OR 1.49; 95% CI 1.11–2.01 [2 vaccines vs none]), and with more positive vaccination attitudes generally (OR 1.10; 95% CI 1.06–1.15) were more likely to favour mandatory vaccination, whereas female HCWs (OR= 0.79, 95% CI 0.63–0.96, vs male HCWs) and Black HCWs (OR=0.46, 95% CI 0.25–0.85, vs white HCWs) were less likely to. // Interpretation: Only one in six of the HCWs in this large, diverse, UK-wide sample favoured mandatory vaccination. Building trust, educating, and supporting HCWs who are hesitant about vaccination may be more acceptable, effective, and equitable

Access to personal protective equipment in healthcare workers during the COVID-19 pandemic in the United Kingdom: results from a nationwide cohort study (UK-REACH)

BACKGROUND: Healthcare workers (HCWs) are at high risk of SARS-CoV-2 infection. Effective use of personal protective equipment (PPE) reduces this risk. We sought to determine the prevalence and predictors of self-reported access to appropriate PPE (aPPE) for HCWs in the UK during the COVID-19 pandemic. METHODS: We conducted cross sectional analyses using data from a nationwide questionnaire-based cohort study administered between December 2020-February 2021. The outcome was a binary measure of self-reported aPPE (access all of the time vs access most of the time or less frequently) at two timepoints: the first national lockdown in the UK in March 2020 (primary analysis) and at the time of questionnaire response (secondary analysis). RESULTS: Ten thousand five hundred eight HCWs were included in the primary analysis, and 12,252 in the secondary analysis. 35.2% of HCWs reported aPPE at all times in the primary analysis; 83.9% reported aPPE at all times in the secondary analysis. In the primary analysis, after adjustment (for age, sex, ethnicity, migration status, occupation, aerosol generating procedure exposure, work sector and region, working hours, night shift frequency and trust in employing organisation), older HCWs and those working in Intensive Care Units were more likely to report aPPE at all times. Asian HCWs (aOR:0.77, 95%CI 0.67-0.89 [vs White]), those in allied health professional and dental roles (vs those in medical roles), and those who saw a higher number of COVID-19 patients compared to those who saw none (≥ 21 patients/week 0.74, 0.61-0.90) were less likely to report aPPE at all times. Those who trusted their employing organisation to deal with concerns about unsafe clinical practice, compared to those who did not, were twice as likely to report aPPE at all times. Significant predictors were largely unchanged in the secondary analysis. CONCLUSIONS: Only a third of HCWs in the UK reported aPPE at all times during the first lockdown and that aPPE had improved later in the pandemic. We also identified key determinants of aPPE during the first UK lockdown, which have mostly persisted since lockdown was eased. These findings have important implications for the safe delivery of healthcare during the pandemic