We combine small-angle x-ray scattering (SAXS) and wide-angle x-ray scattering (WAXS) with aerodynamic levitation techniques to study in situ phase transitions in the liquid state under contactless ...conditions. At very high temperatures, yttria-alumina melts show a first-order transition, previously inferred from phase separation in quenched glasses. We show how the transition coincides with a narrow and reversible maximum in SAXS indicative of liquid unmixing on the nanoscale, combined with an abrupt realignment in WAXS features related to reversible shifts in polyhedral packing on the atomic scale. We also observed a rotary action in the suspended supercooled drop driven by repetitive transitions (a polyamorphic rotor) from which the reversible changes in molar volume (1.2 ± 0.2 cubic centimeters) and entropy (19 ± 4 joules mole⁻¹ kelvin⁻¹) can be estimated.
The structure of liquid alumina at a temperature ~2400 K near its melting point was measured using neutron and high-energy x-ray diffraction by employing containerless aerodynamic-levitation and ...laser-heating techniques. The measured diffraction patterns were compared to those calculated from molecular dynamics simulations using a variety of pair potentials, and the model found to be in best agreement with experiments was refined using the reverse Monte Carlo method. The resultant model shows that the melt is composed predominantly of AlO sub(4) and AlO sub(5) units, in the approximate ratio of 2:1, with only minor fractions of AlO sub(3) and AlO sub(6) units. The majority of Al-O-Al connections involve corner-sharing polyhedra (83%), although a significant minority involve edge-sharing polyhedra (16%), predominantly between AlO sub(5) and either AlO sub(5) or AlO sub(4) units. Most of the oxygen atoms (81%) are shared among three or more polyhedra, and the majority of these oxygen atoms are triply shared among one or two AlO sub(4) units and two or one AlO sub(5) units, consistent with the abundance of these polyhedra in the melt and their fairly uniform spatial distribution.
ObjectivesInfections in primary care are often treated with non-steroidal anti-inflammatory drugs (NSAIDs). This study evaluates whether NSAID prescribing is associated with adverse outcomes for ...respiratory (RTIs) or urinary track (UTI) infections.ObjectivesTo determine whether there is an association between NSAID prescribing and the rate of adverse outcomes for infections for individual consulting in primary care.DesignCohort study of electronic health records.Setting87 general practices in the UK Clinical Practice Research Datalink GOLD.Participants142 925 patients consulting with RTI or UTI.Primary and secondary outcome measuresRepeat consultations, hospitalisation or death within 30 days of the initial consultation for RTI or UTI. Poisson models estimated the associations between NSAID exposure and outcome. Rate ratios were adjusted for gender, age, ethnicity, deprivation, antibiotic use, seasonal influenza vaccination status, comorbidities and general practice. Since prescribing variations by practice are not explained by case mix—hence, less impacted by confounding by indication—both individual-level and practice-level analyses are included.ResultsThere was an increase in hospital admission/death for acute NSAID prescriptions (RR 2.73, 95% CI 2.10 to 3.56) and repeated NSAID prescriptions (6.47, 4.46–9.39) in RTI patients, and for acute NSAID prescriptions for UTI (RR 3.03; 1.92 to 4.76). Practice-level analysis, controlling for practice population characteristics, found that for each percentage point increase in NSAID prescription, the percentages of hospital admission/death within 30 days increased by 0.32 percentage points (95% CI 0.16 to 0.47).ConclusionsIn this non-randomised study, prescription of NSAIDs at consultations for RTI or UTIs in primary care is infrequent but may be associated with increased risk of hospital admission. This supports other observational and limited trial data that NSAID prescribing might be associated with worse outcomes following acute infection and should be prescribed with caution.
A combination of in situ high-pressure neutron diffraction at pressures up to 17.5(5) GPa and molecular dynamics simulations employing a many-body interatomic potential model is used to investigate ...the structure of cold-compressed silica glass. The simulations give a good account of the neutron diffraction results and of existing x-ray diffraction results at pressures up to ~60 GPa. On the basis of the molecular dynamics results, an atomistic model for densification is proposed in which rings are "zipped" by a pairing of five- and/or sixfold coordinated Si sites. The model gives an accurate description for the dependence of the mean primitive ring size ⟨n⟩ on the mean Si-O coordination number, thereby linking a parameter that is sensitive to ordering on multiple length scales to a readily measurable parameter that describes the local coordination environment.
Following observations of survival of microbes and other life forms in deep subsurface environments it is necessary to understand their biological functioning under high pressure conditions. Key ...aspects of biochemical reactions and transport processes within cells are determined by the intracellular water dynamics. We studied water diffusion and rotational relaxation in live Shewanella oneidensis bacteria at pressures up to 500 MPa using quasi-elastic neutron scattering (QENS). The intracellular diffusion exhibits a significantly greater slowdown (by -10-30%) and an increase in rotational relaxation times (+10-40%) compared with water dynamics in the aqueous solutions used to resuspend the bacterial samples. Those results indicate both a pressure-induced viscosity increase and slowdown in ionic/macromolecular transport properties within the cells affecting the rates of metabolic and other biological processes. Our new data support emerging models for intracellular organisation with nanoscale water channels threading between macromolecular regions within a dynamically organized structure rather than a homogenous gel-like cytoplasm.
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