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The thermochemical behavior of α-Al2O3 corundum in the whole temperature range 0–2317 K (melting point) and under pressures up to 12 GPa is predicted by applying ab initio methods based on the density functional theory (DFT), the use of a local basis set and periodic-boundary conditions. Thermodynamic properties are treated both within and beyond the harmonic approximation to the lattice potential. In particular, a recent implementation of the quasi-harmonic approximation, in the Crystal program, is here shown to provide a reliable description of the thermal expansion coefficient, entropy, constant-volume and constant-pressure specific heats, and temperature dependence of the bulk modulus, nearly up to the corundum melting temperature. This is a remarkable outcome suggesting α-Al2O3 to be an almost perfect quasi-harmonic crystal. The effect of using different computational parameters and DFT functionals belonging to different levels of approximations on the accuracy of the thermal properties is tested, providing a reference for further studies involving alumina polymorphs and, more generally, quasi-ionic minerals.

We report accurate ab initio theoretical predictions of the elastic, seismic, and structural anisotropy of the orthorhombic Mg2SiO4 forsterite crystal at high pressures (up to 20 GPa) and temperatures (up to its melting point, 2163 K), which constitute earth’s upper mantle conditions. Single-crystal elastic stiffness constants are evaluated up to 20 GPa and their first- and second-order pressure derivatives reported. Christoffel’s equation is solved at several pressures: directional seismic wave velocities and related properties (azimuthal and polarization seismic anisotropies) discussed. Thermal structural and average elastic properties, as computed within the quasi-harmonic approximation of the lattice potential, are predicted at high pressures and temperatures: directional thermal expansion coefficients, first- and second-order pressure derivatives of the isothermal bulk modulus, and P-V-T equation-of-state. The effect on computed properties of five different functionals, belonging to three different classes of approximations, of the density functional theory is explicitly investigated.

Hairy vetch (Vicia villosa Roth, HV) is widely grown as a legume cover crop throughout the U.S.A., with biological nitrogen fixation (BNF) through symbiosis with Rhizobium leguminosarum biovar viciae (Rlv) being one of the most sought after benefits of its cultivation. This study determined if HV cultivation history and plant genotype affect genetic diversity of resident Rlv. Soil samples were collected from within farmers’ fields at Graham, Cedar Grove and Ivanhoe sites in North Carolina and pairs of genetically similar hairy vetch genotypes used as trap hosts. A total of 519 Rlv strains were isolated from six paired field soils, three with and three without histories of HV cultivation. A total of 46 strains failed to PCR-amplify the nifH gene; however nodC PCR amplification of these nifH-negative strains resulted in amplification of 22 of the strains. Repetitive element polymerase chain reaction (rep-PCR) with BOX-A1R primer and redundancy analysis showed rhizobial diversity to vary greatly within and between fields, with over 30 BOX banding patterns obtained across the six fields. Cluster analysis of BOX-PCR banding patterns resulted in 36 genetic groups of Rlv at a similarity level of 70%, with 15 of the isolates from fields with HV history not belonging to any of the clusters. Site was found to be the main driver of isolate diversity overall, explaining 57%, of the total variation among rhizobia occupying HV nodules, followed by history of hairy vetch cultivation. Evidence of a HV host genotype influence on the populations of rhizobia that infect hairy vetch was also observed, with plant genotype explaining 12.7% of the variation among all isolates. Our results show that second to site, HV cultivation history was the most important driver of rhizobial nodule community structure and increases the genetic diversity of resident Rlv in soils.

The efficacy of the nasobuccal thermistor (NT) was compared with the nasal pressure cannula (NC) and the calibrated, time-differentiated respiratory inductance plethysmography sum signal (DS) in the detection of obstructive events in children during polysomnography (PSG). The overnight PSG of 20 consecutive referrals were selected for analysis. Obstructive events were scored in each study three times by one operator using a blinded procedure whereby either the NT, the NC or the DS was visible. The standard PSG channels were also visible. SPSS software was used for statistical analysis. Twenty patients aged 5 weeks to 16 years were studied. Agreement in obstructive apnoea-hypopnoea index (OAHI) was highest between the NT and NC, and the NC and DS. The NC signal was significantly more likely to be uninterpretable than the NT (P = 0.02) and this did not correlate with age. Event detection by the NT was significantly improved by the addition of either the NC (P = 0.01) or the DS (P = 0.001), while the NC stood alone unless the DS was added (P = 0.02). There was no significant difference in OAHI by the NC versus the DS. The NC detected significantly more OA than the NT or the DS (P = 0.04), while the DS trended towards detecting more OH. There was no significant difference in OAHI between any combination pair. The nasal cannula and differentiated sum signal perform better as measures of paediatric airflow than the NT. To optimize the detection of obstructive events in children we recommend using at least one, if not both these methods in paediatric sleep laboratories. © 2005 European Sleep Research Society.

In 2007 the American Academy of Sleep Medicine (AASM) published a new manual for the recording and scoring of sleep and associated events including guidelines for paediatric sleep. In 2011 a panel of experienced paediatric sleep practitioners and sleep scientists drawn from the Australasian Sleep Technologist Association (ASTA) and the Australasian Sleep Association (ASA) reviewed the applicability of the AASM guidelines in the Australasian context and produced the 'ASTA/ASA addendum to AASM guidelines for the recording and scoring of paediatric sleep'. This document provides recommendations for the application of the AASM guidelines as well as clarifications, minor modifications and additional or optional guidelines for conducting clinical polysomnography in Australasian paediatric sleep laboratories. While adoption of the majority of the AASM scoring rules is endorsed the following additional or alternative modifications are highlighted: (i) Technical and recording specifications: a number of additional recording parameters to provide further confirmatory diagnostic information are optional. (ii) Visual rules: an alternative rule is to extend the upper age limit at which the Anders infant sleep criteria can be applied; application of the R&K criteria for terminating N2 following a cortical arousal is optional; an alternative rule is to retain the R&K classification of movement epochs (iii) Arousal rules: additional criteria to classify arousal types and to define temporal associations are recommended; sub-cortical arousal criteria are provided with reporting of a sub-cortical arousal index optional. (iv) Respiratory rules: if adult respiratory rules are applied to children (> 13 years) then the AASM 'alternative' hypopnoea rule must be used; calibrated respiratory inductance plethysmography may be used as an alternative sensor for scoring hypopnoeas; the use of additional signals to sub-classify hypopnoeas is optional; the definition of respiratory effort-related

We report the observation of magnetic circular dichroism (MCD) in two-photon photoemission (2PPE). The Heusler alloys Ni2MnGa and Co2FeSi were investigated by excitation with femtosecond laser light, showing MCD asymmetries of A = (3.5 +/- 0.5) x 10(-3) for Ni2MnGa and of A = (2.1 +/- 1.0) x 10(-3) for Co2FeSi, respectively. A theoretical explanation is provided based on local spin-density calculations for the magnetic dichroic response; the computed 2PPE MCD agrees well with the experiment. The observed 2PPE magnetic contrast represents an interesting alternative for future time-resolved photoemission studies on surface magnetism practicable in the laboratory.

We report on a type of surface structuring after short pulse laser ablation of a binary alloy. We observe the emergence of a concentric ring structure with changing elemental composition. The composition changes are interpreted by condensation of the ambient ablation vapor due to stress wave excitations in the ablation spot.