Nanoscale potassium niobate crystal structure and phase transition

Nanoscale potassium niobate (KNbO3) powders of orthorhombic structure were synthesized using the sol-gel method. The heat-treatment temperature of the gels had a pronounced effect on KNbO3 particle size and morphology. Field emission scanning electron microscopy and transmission electron microscopy were used to determine particle size and morphology. The average KNbO3 grain size was estimated to be less than 100 nm, and transmission electron microscopy images indicated that KNbO3 particles had a brick-like morphology. Synchrotron X-ray diffraction was used to identify the room-temperature structures using Rietveld refinement. The ferroelectric orthorhombic phase was retained even for particles smaller than 50 nm. The orthorhombic to tetragonal and tetragonal to cubic phase transitions of nanocrystalline KNbO3 were investigated using temperature-dependent powder X-ray diffraction. Differential scanning calorimetry was used to examine the temperature dependence of KNbO3 phase transition. The Curie temperature and phase transition were independent of particle size, and Rietveld analyses showed increasing distortions with decreasing particle size

The Critical Richardson Number and Limits of Applicability of Local Similarity Theory in the Stable Boundary Layer

Measurements of atmospheric turbulence made over the Arctic pack ice during the Surface Heat Budget of the Arctic Ocean experiment (SHEBA) are used to determine the limits of applicability of Monin-Obukhov similarity theory (in the local scaling formulation) in the stable atmospheric boundary layer. Based on the spectral analysis of wind velocity and air temperature fluctuations, it is shown that, when both of the gradient Richardson number, Ri, and the flux Richardson number, Rf, exceed a 'critical value' of about 0.20 - 0.25, the inertial subrange associated with the Richardson-Kolmogorov cascade dies out and vertical turbulent fluxes become small. Some small-scale turbulence survives even in this supercritical regime, but this is non-Kolmogorov turbulence, and it decays rapidly with further increasing stability. Similarity theory is based on the turbulent fluxes in the high-frequency part of the spectra that are associated with energy-containing/flux-carrying eddies. Spectral densities in this high-frequency band diminish as the Richardson-Kolmogorov energy cascade weakens; therefore, the applicability of local Monin-Obukhov similarity theory in stable conditions is limited by the inequalities Ri < Ri_cr and Rf < Rf_cr. However, it is found that Rf_cr = 0.20 - 0.25 is a primary threshold for applicability. Applying this prerequisite shows that the data follow classical Monin-Obukhov local z-less predictions after the irrelevant cases (turbulence without the Richardson-Kolmogorov cascade) have been filtered out.Comment: Boundary-Layer Meteorology (Manuscript submitted: 16 February 2012; Accepted: 10 September 2012

Mining the human phenome using allelic scores that index biological intermediates

J. Kaprio ja M-L. Lokki työryhmien jäseniä.It is common practice in genome-wide association studies (GWAS) to focus on the relationship between disease risk and genetic variants one marker at a time. When relevant genes are identified it is often possible to implicate biological intermediates and pathways likely to be involved in disease aetiology. However, single genetic variants typically explain small amounts of disease risk. Our idea is to construct allelic scores that explain greater proportions of the variance in biological intermediates, and subsequently use these scores to data mine GWAS. To investigate the approach's properties, we indexed three biological intermediates where the results of large GWAS meta-analyses were available: body mass index, C-reactive protein and low density lipoprotein levels. We generated allelic scores in the Avon Longitudinal Study of Parents and Children, and in publicly available data from the first Wellcome Trust Case Control Consortium. We compared the explanatory ability of allelic scores in terms of their capacity to proxy for the intermediate of interest, and the extent to which they associated with disease. We found that allelic scores derived from known variants and allelic scores derived from hundreds of thousands of genetic markers explained significant portions of the variance in biological intermediates of interest, and many of these scores showed expected correlations with disease. Genome-wide allelic scores however tended to lack specificity suggesting that they should be used with caution and perhaps only to proxy biological intermediates for which there are no known individual variants. Power calculations confirm the feasibility of extending our strategy to the analysis of tens of thousands of molecular phenotypes in large genome-wide meta-analyses. We conclude that our method represents a simple way in which potentially tens of thousands of molecular phenotypes could be screened for causal relationships with disease without having to expensively measure these variables in individual disease collections.Peer reviewe

Development of a practical guide for the early recognition for malignant melanoma of the foot and nail unit

Background: malignant melanoma is a rare but potentially lethal form of cancer which may arise on the foot. Evidence suggests that due to misdiagnosis and later recognition, foot melanoma has a poorer prognosis than cutaneous melanoma elsewhere.Methods: a panel of experts representing podiatry and dermatologists with a special interest in skin oncology was assembled to review the literature and clinical evidence to develop a clinical guide for the early recognition of plantar and nail unit melanoma.Results: a systematic review of the literature revealed little high quality data to inform the guide. However a significant number of case reports and series were available for analysis. From these, the salient features were collated and summarised into the guide. Based on these features a new acronym "CUBED" for foot melanoma was drafted and incorporated in the guide.Conclusions: the use of this guide may help clinicians in their assessment of suspicious lesions on the foot (including the nail unit). Earlier detection of suspicious pedal lesions may facilitate earlier referral for expert assessment and definitive diagnosis. The guide is currently being field tested amongst practitioner