Comprehensive determination of the high-pressure structural behaviour of BaTiO₃

We have mapped the phase diagram of BaTiO3 more extensively than previous attempts using high-pressure neutron-powder diffraction. The mapping of the phase diagram has been performed using isothermal compression at fixed temperatures (175, 225, 290, 480 K) within each of the known crystallographic phases, up to ∼6 GPa using a large volume press. The crystallographic structure of each phase has been measured, and the determined absolute atomic displacements of all atoms within the cell have provided detailed information on the order of the phase transitions observed, and the behaviour of the ferroelectric dipole moment.Publisher PDFPeer reviewe

Low-intermediate-temperature, high-pressure thermoelastic and crystallographic properties of thermoelectric clausthalite (PbSe-I)

The thermoelastic properties of the rock-salt structured thermoelectric lead selenide (clausthalite, PbSe-I) have been determined using neutron powder diffraction techniques for the temperature interval 10 - 500 K at ambient pressure, and 0 - 5.2 GPa at 298, and 150 K. Within this temperature range, lead selenide can be described using the same selfconsistent phenomenological model developed for the isostructural phases lead sulfide (PbS) and lead telluride (PbTe) in which the cations and anions behave as independent Debye oscillators (vibrational Debye temperatures of PbSe-I: Pb 111(1) K, Se 205(1) K). Simultaneous fitting of the unit cell volume and isochoric heat capacity to a two-term Debye internal energy function gives characteristic temperatures of 104(3) K and 219(5) K in excellent agreement with the two vibrational Debye temperatures derived from fitting the individual atomic displacement parameters. Grüneisen constants for the two term fits are 1.79 and 2.28 for the lower and upper characteristic temperature respectively. The calculated thermodynamic Grüneisen parameter increases monotonically from 2.03 at 10 K, to a maximum 2.22 at 100 K before decreasing back to 2.00 at 298 K and is broadly in agreement with the average of the two Grüneisen parameters associated with the two-term internal energy function. Despite the simplicity of the model, the calculated phonon density of states that is implicit within the two-term Debye model is found to show fair agreement with the full and partial vibrational densities of states derived from density functional theory (DFT). The bulk modulus and its pressure derivative at 298 K are 47.9(4) GPa and 5.4(2) respectively by fitting the pressure dependence of the unit cell volume to a 3rd order Birch- Murnaghan equation-of-state. For lower temperatures (T < 300 K) the high-pressure transition to PbSe-II is associated with a steep initial Clapeyron slope of 151 K GPa-1

A cross-sectional survey investigating women's information sources, behaviour, expectations, knowledge and level of satisfaction on advice received about diet and supplements before and during pregnancy

Background The reported long-term effects of poor maternal nutrition and uptake of recommended supplements before and during pregnancy was the impetus behind this study. Our objectives were to investigate and understand women’s expectations, knowledge, behaviour and information sources used regarding the use of nutrition and vitamin supplements before and during pregnancy. Methods A cross-sectional survey using a self-administered questionnaire was undertaken. A purposive sampling technique was used. Women attending the antenatal clinic at Croydon University Hospital during 2015 were invited to take part in the study. The data was analysed using descriptive statistics, paired sample T-tests and Chi-squared tests, with the level of significance set at 5% (p < 0.05). Results A total of 133 pregnant women completed the survey. Analysis of the results showed that women are currently using electronic resources (33%, n = 42) rather than healthcare professionals (19%, n = 25) as an information source before pregnancy. Women who sourced information through the internet were significantly more likely to take folic acid (p = 0.006) and vitamin D (p = 0.004) before pregnancy. Women preferred to receive information from the antenatal clinic (62%, n = 83), internet (46%, n = 61) and from mobile applications (27%, n = 36). Although women believed they had sufficient knowledge (60%, n = 80) and had received adequate advice (53%, n = 70) concerning the correct supplements to take, this was not demonstrated in their behaviour, with only a small number of women (37%, n = 49) taking a folic acid supplement before pregnancy. Women mistakenly perceived the timing of supplement advice as correct, with only a small number of women (18%, n = 23) considering the advice on supplements as too late. Conclusions Despite the small sample size, this study demonstrated that women did not receive timely and/or accurate advice to enable them to take the recommended supplements at the optimal time. Women had the misconception that they understood the correct use of pregnancy supplements. This misunderstanding may be prevented by providing women intending to become pregnant with a structured, approved electronic source of information that improves their supplements uptake

A cautionary perspective regarding the isolation and serial propagation of SARS-CoV-2 in Vero cells

Abstract An array of SARS-CoV-2 virus variants have been isolated, propagated and used in in vitro assays, in vivo animal studies and human clinical trials. Observations of working stocks of SARS-CoV-2 suggest that sequential propagation in Vero cells leads to critical changes in the region of the furin cleavage site, which significantly reduce the value of the working stock for critical research studies. Serially propagating SARS-CoV-2 in Vero E6 cells leads to rapid increases in genetic variants while propagation in other cell lines (e.g. Vero/hSLAM) appears to mitigate this risk thereby improving the overall genetic stability of working stocks. From these observations, investigators are urged to monitor genetic variants carefully when propagating SARS-CoV-2 in Vero cells

Antiviral Screening of Multiple Compounds against Ebola Virus

In light of the recent outbreak of Ebola virus (EBOV) disease in West Africa, there have been renewed efforts to search for effective antiviral countermeasures. A range of compounds currently available with broad antimicrobial activity have been tested for activity against EBOV. Using live EBOV, eighteen candidate compounds were screened for antiviral activity in vitro. The compounds were selected on a rational basis because their mechanisms of action suggested that they had the potential to disrupt EBOV entry, replication or exit from cells or because they had displayed some antiviral activity against EBOV in previous tests. Nine compounds caused no reduction in viral replication despite cells remaining healthy, so they were excluded from further analysis (zidovudine; didanosine; stavudine; abacavir sulphate; entecavir; JB1a; Aimspro; celgosivir; and castanospermine). A second screen of the remaining compounds and the feasibility of appropriateness for in vivo testing removed six further compounds (ouabain; omeprazole; esomeprazole; Gleevec; D-LANA-14; and Tasigna). The three most promising compounds (17-DMAG; BGB324; and NCK-8) were further screened for in vivo activity in the guinea pig model of EBOV disease. Two of the compounds, BGB324 and NCK-8, showed some effect against lethal infection in vivo at the concentrations tested, which warrants further investigation. Further, these data add to the body of knowledge on the antiviral activities of multiple compounds against EBOV and indicate that the scientific community should invest more effort into the development of novel and specific antiviral compounds to treat Ebola virus disease

Development of a Seafloor Community Classification for the New Zealand Region Using a Gradient Forest Approach

To support ongoing marine spatial planning in New Zealand, a numerical environmental classification using Gradient Forest models was developed using a broad suite of biotic and high-resolution environmental predictor variables. Gradient Forest modeling uses species distribution data to control the selection, weighting and transformation of environmental predictors to maximise their correlation with species compositional turnover. A total of 630,997 records (39,766 unique locations) of 1,716 taxa living on or near the seafloor were used to inform the transformation of 20 gridded environmental variables to represent spatial patterns of compositional turnover in four biotic groups and the overall seafloor community. Compositional turnover of the overall community was classified using a hierarchical procedure to define groups at different levels of classification detail. The 75-group level classification was assessed as representing the highest number of groups that captured the majority of the variation across the New Zealand marine environment. We refer to this classification as the New Zealand “Seafloor Community Classification” (SCC). Associated uncertainty estimates of compositional turnover for each of the biotic groups and overall community were also produced, and an added measure of uncertainty – coverage of the environmental space – was developed to further highlight geographic areas where predictions may be less certain owing to low sampling effort. Environmental differences among the deep-water New Zealand SCC groups were relatively muted, but greater environmental differences were evident among groups at intermediate depths in line with well-defined oceanographic patterns observed in New Zealand’s oceans. Environmental differences became even more pronounced at shallow depths, where variation in more localised environmental conditions such as productivity, seafloor topography, seabed disturbance and tidal currents were important differentiating factors. Environmental similarities in New Zealand SCC groups were mirrored by their biological compositions. The New Zealand SCC is a significant advance on previous numerical classifications and includes a substantially wider range of biological and environmental data than has been attempted previously. The classification is critically appraised and considerations for use in spatial management are discussed.