Characterizations and integral formulae for generalized m-quasi-Einstein metrics

The aim of this paper is to present some structural equations for generalized m-quasi-Einstein metrics (M ⁿ , g, ? f, λ), which was defined recently by Catino in [11]. In addition, supposing that M ⁿ is an Einstein manifold we shall show that it is a space form with a well defined potential f. Finally, we shall derive a formula for the Laplacian of its scalar curvature which will give some integral formulae for such a class of compact manifolds that permit to obtain some rigidity results.     

Various extraction methods for detection of bistrifluron residues in Asian pear using high‐performance liquid chromatography: application to dissipation patterns under open‐field conditions

The present study was carried out to develop an analytical method for the detection and quantification of bistrifluron, a benzoylphenylurea compound, in pear using high‐performance liquid chromatography with UV detection. Samples were extracted using conventional, AOAC and EN quick, easy, cheap, effective, rugged and safe ‘QuEChERS’ methods. As expected, conventional and EN‐QuEChERS methods gave higher recoveries than AOAC. In addition, interference around the analyte retention time was observed in the conventional method. Thus, the EN‐QuEChERS method was selected and validated by studying various parameters, including linearity, limit of detection, limit of quantification (LOQ), recovery and precision. Linearity was excellent, with a correlation coefficient of 0.9998. Recovery rates at three spiking levels (0.05, 0.2 and 1 mg/kg) ranged from 73.76 to 98.66%. Intra‐ and inter‐day precisions, expressed as relative standard deviations, were <6%. The LOQ of 0.05 mg/kg was considerably lower than the maximum residue limit (1 mg/kg) set by the Korean Ministry of Food and Drug Safety. The developed method was successfully applied to open‐field pear samples, in which the target analyte was slowly dissipated (55% decline) over 14 days with a half‐life of 10.19 days. Notably, the residue levels throughout the period of sample collection (14 days) were lower than the maximum residue limit, indicating that the residue was not hazardous for consumers. Copyright © 2016 John Wiley & Sons, Ltd.     

Production of 152,154Eu mixed sources for calibrations of gamma-ray spectrometers

Mixed gamma-ray point sources consisting of ¹⁵²Eu and ¹⁵⁴Eu were prepared from a solution of EuCl₃ containing both isotopes. Gamma-rays emitted from these isotopes were used to establish the relative efficiency curves of HPGe detector, which were converted to absolute ones using gamma-ray sources of well-known activities. Gamma-ray attenuation correction factors were taken into account. Accuracies of activity measurements of the prepared sources were checked by measuring other sources of well-known activities and confirmed by simulating the absolute efficiency curve at distance of 15?cm from the detector window using the DETEFF software. The prepared sources were then submitted to quality control tests.