Crystallographic Studies of Iodide-Containing Quasi-One-Dimensional Conductors

The crystal structures of three iodide-containing quasi-one-dimensional conductors, (tetrathiotetracene)2(iodide)3 (high disorder), tetrathiotetracene-iodide, and (hexamethylenetetraselenofulvalene)-(iodide)x were solved by single crystal X-ray diffraction methods. These three iodides are single charge-carrier conductors and allow a comparison of such competing effects as disorder, interchain coupling, and overlap. The crystal structure of metallic (tetrathiotetracene)2(iodide)3 (high disorder), TTT2I3 (h.d.), was solved at room temperature (~294° K), 164° K, 74° K, and at 19° K. At all four temperatures the lattice symmetry remained orthorhombic and the structures were successfully refined in the space group Cmca. During slow cooling the diffuse layer lines were also carefully monitored. In contrast to TTFC10.67, even with slow cooling the iodide chains do not three-dimensionally order, and there are no distortions in the TTT lattice to 19° K. A model of the iodide chains is presented which explains the positions and intensities of the diffuse layer lines and also explains why three-dimensional ordering at low temperatures is not observed. The structure of semiconducting tetrathiotetracene-iodide (TTTI) was studied at room temperature. The structure consists of two ordered lattices which are incommensurate along →c, the stacking axis. The unit cell dimensions for Lattice 1 (triclinic, C-l) are a = 13.028(2), b = 16.445(2), c = 3.643(1) Å and α = 90.81(1)°, β = 96.11(1)°, and γ = 91 .11(1)°. For Lattice 2, c ≃ 4.78 Å. The positions of all of the layer lines, including the two “sixth” layer lines, which are observed on X-ray oscillation photographs of crystals of TTTI rotated about →c, can be explained by the presence of two lattices. The measured density dm ≃ 2.09 g/cm3 and refinement of the [001] projection (hk0 reflections) confirmed that the overall stoichiometry is TTTI (1:1). For a complete data set collected with copper Kα radiation, the refinement of Lattice 1 converged to R = 0.102. For the 1132 reflections with Fo2 > 3σ(Fo2), R = 0.081. The overlap between adjacent TTT cations in the same stack in TTTI is significantly different from that observed in TTT2I3 (h.d.). There is also very little interchain coupling in TTTI. Hexamethylenetetraselenofulvalene-iodide, HMTSF-Ix, is triclinic, P-l, with the unit cell parameters a = 8.056(4), b = 12.740(4), c = 8.016(3) Å and α = 81.72(4)°, β = 67.73(5)°, and γ = 102.64(4)°. For a complete data set of 4213 reflections collected with monochromatized molybdenum Kα radiation to 2θ = 60° the structure refined to R = 0.097. For 2042 reflections with Fo2 > 3σ(Fo2), R = 0.051. The hydrogen atoms were not located. There is disordered iodide and solvent at 1/2,1/2,1/2. The HMTSF cations stack along →a. A new type of alternating overlap between adjacent HMTSF molecules was observed. The magnitude of the d.c. electrical conductivity at room temperature suggests that this phase of HMTSF-Ix is semiconducting. These iodide-containing structures show three different types of iodide behavior in quasi-one-dimensional conductors. In TTT2I3 (h.d.) the slip-stacking and large interchain coupling favor formation of a metallic state at high temperatures. At low temperatures the disordered iodide chains have a major effect on the transport properties by allowing states to exist in the semiconductor band gap. In TTTI the iodides are no longer disordered but still dominate the physical properties by causing a modulation of the TTT lattice. There is very little interchain coupling in TTTI. In HMTSF-Ix the iodide is probably of minor importance.</p

New genetic loci link adipose and insulin biology to body fat distribution.

Body fat distribution is a heritable trait and a well-established predictor of adverse metabolic outcomes, independent of overall adiposity. To increase our understanding of the genetic basis of body fat distribution and its molecular links to cardiometabolic traits, here we conduct genome-wide association meta-analyses of traits related to waist and hip circumferences in up to 224,459 individuals. We identify 49 loci (33 new) associated with waist-to-hip ratio adjusted for body mass index (BMI), and an additional 19 loci newly associated with related waist and hip circumference measures (P < 5 × 10(-8)). In total, 20 of the 49 waist-to-hip ratio adjusted for BMI loci show significant sexual dimorphism, 19 of which display a stronger effect in women. The identified loci were enriched for genes expressed in adipose tissue and for putative regulatory elements in adipocytes. Pathway analyses implicated adipogenesis, angiogenesis, transcriptional regulation and insulin resistance as processes affecting fat distribution, providing insight into potential pathophysiological mechanisms

The revised Approved Instructional Resources score:An improved quality evaluation tool for online educational resources

BACKGROUND: Free Open-Access Medical education (FOAM) use among residents continues to rise. However, it often lacks quality assurance processes and residents receive little guidance on quality assessment. The Academic Life in Emergency Medicine Approved Instructional Resources tool (AAT) was created for FOAM appraisal by and for expert educators and has demonstrated validity in this context. It has yet to be evaluated in other populations.OBJECTIVES: We assessed the AAT's usability in a diverse population of practicing emergency medicine (EM) physicians, residents, and medical students; solicited feedback; and developed a revised tool.METHODS: As part of the Medical Education Translational Resources: Impact and Quality (METRIQ) study, we recruited medical students, EM residents, and EM attendings to evaluate five FOAM posts with the AAT and provide quantitative and qualitative feedback via an online survey. Two independent analysts performed a qualitative thematic analysis with discrepancies resolved through discussion and negotiated consensus. This analysis informed development of an initial revised AAT, which was then further refined after pilot testing among the author group. The final tool was reassessed for reliability.RESULTS: Of 330 recruited international participants, 309 completed all ratings. The Best Evidence in Emergency Medicine (BEEM) score was the component most frequently reported as difficult to use. Several themes emerged from the qualitative analysis: for ease of use-understandable, logically structured, concise, and aligned with educational value. Limitations include deviation from questionnaire best practices, validity concerns, and challenges assessing evidence-based medicine. Themes supporting its use include evaluative utility and usability. The author group pilot tested the initial revised AAT, revealing a total score average measure intraclass correlation coefficient (ICC) of moderate reliability (ICC = 0.68, 95% confidence interval [CI] = 0 to 0.962). The final AAT's average measure ICC was 0.88 (95% CI = 0.77 to 0.95).CONCLUSIONS: We developed the final revised AAT from usability feedback. The new score has significantly increased usability, but will need to be reassessed for reliability in a broad population.</p

The Social Media Index as an Indicator of Quality for Emergency Medicine Blogs: A METRIQ Study

Study objective: Online educational resources such as blogs are increasingly used for education by emergency medicine clinicians. The Social Media Index was developed to quantify their relative impact. The Medical Education Translational Resources: Indicators of Quality (METRIQ) study was conducted in part to determine the association between the Social Media Index score and quality as measured by gestalt and previously derived quality instruments. Methods: Ten blogs were randomly selected from a list of emergency medicine and critical care Web sites. The 2 most recent clinically oriented blog posts published on these blogs were evaluated with gestalt, the Academic Life in Emergency Medicine Approved Instructional Resources (ALiEM AIR) score, and the METRIQ-8 score. Volunteer raters (including medical students, emergency medicine residents, and emergency medicine attending physicians) were identified with a multimodal recruitment methodology. The Social Media Index was calculated in February 2016, November 2016, April 2017, and December 2017. Pearson's correlations were calculated between the Social Media Index and the average rater gestalt, ALiEM AIR score, and METRIQ-8 score. Results: A total of 309 of 330 raters completed all ratings (93.6%). The Social Media Index correlated moderately to strongly with the mean rater gestalt ratings (range 0.69 to 0.76) and moderately with the mean rater ALiEM AIR score (range 0.55 to 0.61) and METRIQ-8 score (range 0.53 to 0.57) during the month of the blog post's selection and for 2 years after. Conclusion: The Social Media Index's correlation with multiple quality evaluation instruments over time supports the hypothesis that it is associated with overall Web site quality. It can play a role in guiding individuals to high-quality resources that can be reviewed with critical appraisal techniques