Low-temperature anharmonicity and symmetry breaking in the sodalite

©2018 Walter de Gruyter GmbH, Berlin/Boston 2018. The aluminosilicate iodide sodalite |Na8I2|[AlSiO4]6 was examined by temperature-dependent neutron time-of-flight powder diffraction from 5 K to 290 K and X-ray diffraction from 298 K to 1200 K. The temperature-dependent properties of the mean structure in space group P4 3n were obtained by Rietveld analysis. A negative slope for the thermal expansion coefficient below 50 K could be observed, and the displacement parameters of the iodide ions indicate anharmonic effects. Local structure models (8×8×8 super cells) were refined against pair-distribution functions calculated from total scattering data collected at 5 K, 165 K and 240 K. The results indicate isotropic displacements for all atoms except for I-atoms, showing the effects of an anharmonic potential around this anion at very low temperatures

Radar plots: A novel modality for displaying disparate data on the efficacy of eluxadoline for the treatment of irritable bowel syndrome with diarrhea

BackgroundPatients with irritable bowel syndrome with diarrhea (IBS‐D) experience a range of abdominal and bowel symptoms; successful management requires alleviation of this constellation of symptoms. Eluxadoline, a locally active mixed μ‐ and κ‐opioid receptor agonist and δ‐opioid receptor antagonist, is approved for the treatment of IBS‐D in adults based on the results of 2 Phase 3 studies. Radar plots can facilitate comprehensive, visual evaluation of diverse but interrelated efficacy endpoints.MethodsTwo double‐blind, placebo‐controlled, Phase 3 trials (IBS‐3001 and IBS‐3002) randomized patients meeting Rome III criteria for IBS‐D to twice‐daily eluxadoline 75 or 100 mg or placebo. Radar plots were prepared showing pooled Weeks 1‐26 response rates for the primary efficacy composite endpoint (simultaneous improvement in abdominal pain and stool consistency), stool consistency, abdominal pain, urgency‐free days, and adequate relief, and change from baseline to Week 26 in IBS‐D global symptom score, abdominal discomfort, abdominal pain, abdominal bloating, and daily number of bowel movements.Key ResultsThe studies enrolled 2428 patients. Eluxadoline increased Weeks 1‐26 responder proportions vs placebo for the composite endpoint, stool consistency, abdominal pain, urgency‐free days, and adequate relief. Changes from baseline to Week 26 in IBS‐D global symptom score, abdominal discomfort, abdominal pain, abdominal bloating, and number of bowel movements were greater with eluxadoline vs placebo.Conclusions and InferencesData presentation in radar plot format facilitates interpretation across multiple domains, demonstrating that eluxadoline treatment led to improvements vs placebo across 13 endpoints representing the range of symptoms experienced by patients with IBS‐D.Data presentation in radar plot format can facilitate evaluation of the diverse array of symptoms and outcomes that are relevant to a symptom‐based condition like irritable bowel syndrome with diarrhea (IBS‐D). In 2 Phase 3 trials, eluxadoline treatment improved stool consistency and frequency, abdominal pain, bloating and discomfort, feelings of urgency, global symptom score, and adequate relief. Radar plots provide a visual demonstration of improvements with eluxadoline across 13 endpoints encompassing the diverse constellation of symptoms experienced by patients with IBS‐D.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/145265/1/nmo13331_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/145265/2/nmo13331.pd

Condensation of a tetrahedra rigid-body libration mode in HoBaCo4O7 : the origin of phase transition at 355 K

Rietveld profiles, Moessbauer spectra and x-ray absorption fine structure (XAFS) were analyzed through the structural phase transition at Ts = 355 K in HoBaCo4O7. Excess of the oxygen content over O7 was avoided via annealing the samples in argon flow at 600 degree C. Space groups (S.G.) Pbn21c and P63mc were used to refine the structure parameters in the low- and high-temperature phases, respectively. Additionally, the Cmc21 symmetry was considered as a concurrent model of structure of the low-temperature phase. In the high-temperature phase, severe anisotropy of thermal motion of the major part of the oxygen atoms was observed. This anisotropic motion turns to be quenched as the sample is cooled below Ts. The variation of quadrupole splitting near Ts is not similar to a steplike anomaly frequently seen at the charge-ordering transition. We observe instead a dip-like anomaly of the average quadrupole splitting near Ts. Narrow distribution of the electric field gradient (EFG) over different cobalt sites is observed and explained on the basis of point-charge model. XAFS spectra show no evidence of significant difference between YBaCo4O7 (T > Ts) and HoBaCo4O7 (T < Ts). The origin of the transition at Ts is ascribed to the condensation of the libration phonon mode associated with the rigid-body rotational movements of the starlike tetrahedral units, the building blocks of kagome network. It is shown that the condensation of the libration mode is not compatible with translation symmetry for the hexagonal S.G., but compatible for the orthorhombic S.G. The orthorhombic lattice parameters and EFG components (Vxx, Vyy, Vzz) vary smoothly with temperature at approaching Ts and closely follow each other.Comment: 13 figure

X-ray total scattering study of regular and magic-size nanoclusters of cadmium sulphide

Four kinds of magic-size CdS clusters and two different regular CdS quantum dots have been studied by x-ray total scattering technique and pair distribution function method. Results for the regular CdS quantum dots could be modelled as a mixed phase of atomic structures based on the two bulk crystalline phases, which is interpreted as representing the effects of stacking disorder. However, the results for the magic-size clusters were significantly different. On one hand, the short-range features in the pair distribution function reflect the bulk, indicating that these structures are based on the same tetrahedral coordination found in the bulk phases (and therefore excluding new types of structures such as cage-like arrangements of atoms). But on the other hand, the longer- range atomic structure clearly does not reflect the layer structures found in the bulk and the regular quantum dots. We compare the effects of two ligands, phenylacetic acid and oleic acid, showing that in two cases the ligand has little effect on the atomic structure of the magic-size nanocluster and in another it has a significant effect

Symbiodinium biogeography tracks environmental patterns rather than host genetics in a key Caribbean reef-builder, Orbicella annularis

This is the final version of the article. Available from the Royal Society via the DOI in this record.The physiological performance of a reef-building coral is a combined outcome of both the coral host and its algal endosymbionts, Symbiodinium While Orbicella annularis-a dominant reef-building coral in the Wider Caribbean-is known to be a flexible host in terms of the diversity of Symbiodinium types it can associate with, it is uncertain how this diversity varies across the Caribbean, and whether spatial variability in the symbiont community is related to either O. annularis genotype or environment. Here, we target the Symbiodinium-ITS2 gene to characterize and map dominant Symbiodinium hosted by O. annularis at an unprecedented spatial scale. We reveal northwest-southeast partitioning across the Caribbean, both in terms of the dominant symbiont taxa hosted and in assemblage diversity. Multivariate regression analyses incorporating a suite of environmental and genetic factors reveal that observed spatial patterns are predominantly explained by chronic thermal stress (summer temperatures) and are unrelated to host genotype. Furthermore, we were able to associate the presence of specific Symbiodinium types with local environmental drivers (for example, Symbiodinium C7 with areas experiencing cooler summers, B1j with nutrient loading and B17 with turbidity), associations that have not previously been described.This project was funded primarily by an NERC grant, no. NE/E010393/1 (J.R.S. and P.J.M.), European Union FP7 project Future of Reefs in a Changing Environment (FORCE) under grant agreement no. 244161 (P.J.M. and J.R.S.) and a University of Exeter studentship (E.V.K.)

On the Absorption of X-rays in the Interstellar Medium

We present an improved model for the absorption of X-rays in the ISM intended for use with data from future X-ray missions with larger effective areas and increased energy resolution such as Chandra and XMM, in the energy range above 100eV. Compared to previous work, our formalism includes recent updates to the photoionization cross section and revised abundances of the interstellar medium, as well as a treatment of interstellar grains and the H2molecule. We review the theoretical and observational motivations behind these updates and provide a subroutine for the X-ray spectral analysis program XSPEC that incorporates our model.Comment: ApJ, in press, for associated software see http://astro.uni-tuebingen.de/nh

Systematic review of clinical practice guidelines for acne vulgaris published between January 2017 and July 2021

Background: Acne is very common, can cause considerable negative impact on quality of life and there is increasing concern over the use of long courses of oral antibiotics for this condition. Objectives: (1) To critically appraise reporting in acne guidelines and compare this with previous systematic review of acne guidelines. (2) Examine acne treatment guidance on pre-specified acne treatments of interest and compare between acne guidelines. Methods: Searches for new or updated guidelines were carried out in MEDLINE, Embase, Google Scholar, LILACS from 1 January 2017 to 31 July 2021, supplemented by searching a guideline-specific depository and checking for updates to guidelines included in previous review. We included guidelines, consensus statements or care protocols on the medical treatment of acne vulgaris in adults and/or children and excluded those that focused on a single intervention or subgroup of acne, regional adaptations of guidelines or guidelines included in previous review. AGREE II checklist was applied to critically appraise reporting of guidelines. Results were synthesised narratively. Results: Of 807 abstracts identified nine guidelines were identified that were eligible for inclusion. All guidelines had AGREE II scores above average in at least one domain and reporting was substantially improved compared to the systematic review of acne carried out 5 years previously. There was consensus between guidelines on the key role of topical treatments as first-line acne treatment and most recommended continuing topical treatments as maintenance therapy. There was considerable variation between guidelines on classification of severity, indications for commencing oral antibiotics and on maximum duration of oral antibiotics. However, there was consensus on the need for co-prescription of a non-antibiotic topical treatment when using oral antibiotics. There were notable differences on recommendations regarding provision of information for patients on how to use topical treatments or how to mitigate against side effects. Conclusions: Substantial differences in classification of acne severity hampered comparisons between guidelines. Although development and reporting of guidelines has improved over the past 5 years, differences in key recommendations remain, possibly reflecting uncertainties in the underlying evidence base. Differences between guidelines could have substantial implications for prevalence of antibiotic prescribing for acne

Dual-barrel conductance micropipet as a new approach to the study of ionic crystal dissolution kinetics

A new approach to the study of ionic crystal dissolution kinetics is described, based on the use of a dual-barrel theta conductance micropipet. The solution in the pipet is undersaturated with respect to the crystal of interest, and when the meniscus at the end of the micropipet makes contact with a selected region of the crystal surface, dissolution occurs causing the solution composition to change. This is observed, with better than 1 ms time resolution, as a change in the ion conductance current, measured across a potential bias between an electrode in each barrel of the pipet. Key attributes of this new technique are: (i) dissolution can be targeted at a single crystal surface; (ii) multiple measurements can be made quickly and easily by moving the pipet to a new location on the surface; (iii) materials with a wide range of kinetics and solubilities are open to study because the duration of dissolution is controlled by the meniscus contact time; (iv) fast kinetics are readily amenable to study because of the intrinsically high mass transport rates within tapered micropipets; (v) the experimental geometry is well-defined, permitting finite element method modeling to allow quantitative analysis of experimental data. Herein, we study the dissolution of NaCl as an example system, with dissolution induced for just a few milliseconds, and estimate a first-order heterogeneous rate constant of 7.5 (±2.5) × 10–5 cm s–1 (equivalent surface dissolution flux ca. 0.5 μmol cm–2 s–1 into a completely undersaturated solution). Ionic crystals form a huge class of materials whose dissolution properties are of considerable interest, and we thus anticipate that this new localized microscale surface approach will have considerable applicability in the future

Spin-Atomic Vibration Interaction and Spin-Flip Hamiltonian of a Single Atomic Spin in a Crystal Field

We derive the spin-atomic vibration interaction $V_{\rm SA}$ and the spin-flip Hamiltonian $V_{\rm SF}$ of a single atomic spin in a crystal field. We here apply the perturbation theory to a model with the spin-orbit interaction and the kinetic and potential energies of electrons. The model also takes into account the difference in vibration displacement between an effective nucleus and electrons, \Delta {{\boldmath r}}. Examining the coefficients of $V_{\rm SA}$ and $V_{\rm SF}$, we first show that $V_{\rm SA}$ appears for \Delta {{\boldmath r}}$\ne$0, while $V_{\rm SF}$ is present independently of \Delta {{\boldmath r}}. As an application, we next obtain $V_{\rm SA}$ and $V_{\rm SF}$ of an Fe ion in a crystal field of tetragonal symmetry. It is found that the magnitudes of the coefficients of $V_{\rm SA}$ can be larger than those of the conventional spin-phonon interaction depending on vibration frequency. In addition, transition probabilities per unit time due to $V_{\rm SA}$ and $V_{\rm SF}$ are investigated for the Fe ion with an anisotropy energy of $-|D|S_Z^2$, where $D$ is an anisotropy constant and $S_Z$ is the $Z$ component of a spin operator.Comment: 55 pages, 17 figures, to be published in J. Phys. Soc. Jpn. 79 (2010) No. 11, typos correcte