Ellipsoidal analysis of coordination polyhedra

The idea of the coordination polyhedron is essential to understanding chemical structure. Simple polyhedra in crystalline compounds are often deformed due to structural complexity or electronic instabilities so distortion analysis methods are useful. Here we demonstrate that analysis of the minimum bounding ellipsoid of a coordination polyhedron provides a general method for studying distortion, yielding parameters that are sensitive to various orders in metal oxide examples. Ellipsoidal analysis leads to discovery of a general switching of polyhedral distortions at symmetry-disallowed transitions in perovskites that may evidence underlying coordination bistability, and reveals a weak off-centre ‘d(5) effect' for Fe(3+) ions that could be exploited in multiferroics. Separating electronic distortions from intrinsic deformations within the low temperature superstructure of magnetite provides new insights into the charge and trimeron orders. Ellipsoidal analysis can be useful for exploring local structure in many materials such as coordination complexes and frameworks, organometallics and organic molecules

The association between failed quit attempts and increased levels of psychological distress in smokers in a large New Zealand cohort

<p>Abstract</p> <p>Background</p> <p>Although the association between smoking status and poorer mental health has been well documented, the association between quit status and psychological distress is less clear. The aim of the present study is to investigate the association of smoking status and quit status with psychological distress.</p> <p>Methods</p> <p>Data for this study is from a single year of the Survey of Families, Income and Employment (SoFIE) conducted in New Zealand (2004/05) (n = 18,525 respondents). Smoking status and quit status were treated as exposure variables, and psychological distress (Kessler-10) was treated as the outcome variable. Logistic regression analyses were performed to determine the association of smoking with psychological distress in the whole adult population and quit status with psychological distress in the ex- and current-smoking population.</p> <p>Results</p> <p>Current smokers had higher rates of high and very high psychological distress compared to never smokers (adjusted odds ratio (aOR) = 1.45; 95% CI: 1.24-1.69). Unsuccessful quitters had much higher levels of high to very high levels of psychological distress (16%) than any other group. Moreover, compared to long-term ex-smokers, unsuccessful quitters had a much higher odds of high to very high levels of psychological distress (aOR = 1.73; 95% CI: 1.36-2.21).</p> <p>Conclusion</p> <p>These findings suggest that the significant association between smoking and psychological distress might be partly explained by increased levels of psychological distress among current smokers who made a quit attempt in the last year. This issue needs further study as it has implications for optimising the design of quitting support.</p

Recalculation of the friction constant and transport coefficients of liquid argon from the Rice-Allnatt theory

The linear trajectory approximation of the ?soft? friction constant in the Rice-Allnatt theory of transport has been computed with specific attention to the lower limit of the integral. The results are significantly different from the Palyvos-Davis values for ζS in the dense gas region but agree within 2% in the liquid region. The Rice- Allnatt expressions for the coefficients of shear viscosity and thermal conductivity have been simplified and a correction of a numerical error in the collisional contributions to momentum and heat transfer is made. The coefficients D, η, and λ have been calculated for the corrected ζS and related expressions. No significant change in D is obtained, but a worsening of agreement with experimental viscosities and thermal conductivities occurs. Conversely, a better prediction of the ratio mλ/kη is obtained. More recent viscosity data for liquid argon indicate the theory is less satisfactory than has previously been considered. These results suggest that any improvement of this class of theory can only come through the use of a better representation of the radial distribution function. </jats:p

Kirkwood Theory of Shear Viscosity in a Simple Dense Fluid

The molecular theory of momentum transport in dense fluids developed by Kirkwood is examined for the case of the Lennard-lones (12,6) fluid. The radial distribution functions and one-particle friction constants used are based on molecular dynamics studies. Shear viscosity coefficients calculated with elk = 120 K and 0' = 3.405x10- 10 m vary from one-third to two-thirds of comparable experimental data for argon. The significance of an approximate relationship between the pair friction tensor and the one-particle friction constant is discussed.</jats:p

The Electrical Resistance of the Lower Consolute System 2,6-Lutidine?Water

The one-phase electrical resistance of the lower consolute system 2,6-lutidine-water has been measured in the reduced temperature range 2x 10-6 &lt; 8 &lt; 0�11. Particular attention has been given to the drift in resistance and separation temperature caused by the leaching of ' ions during long contact with glass surfaces. When correction is made for this effect, no contribution to the electrical resistance due to critical fluctuations is observed. The effect of the leaching of ions has not been taken into account in previously published studies which have observed, and attempted to characterize, a weak divergence in the electrical resistance of critical binary mixtures.</jats:p