Development and validation of rapid multiresidue and multi-class analysis for antibiotics and anthelmintics in feed by ultra-high-performance liquid chromatography coupled to tandem mass spectrometry

A new multi-residue method for the analysis of veterinary drugs, namely amoxicillin, chlortetracycline, colistins A and B, doxycycline, fenbendazole, flubendazole, ivermectin, lincomycin, oxytetracycline, sulfadiazine, tiamulin, tilmicosin and trimethoprim, was developed and validated for feed. After acidic extraction, the samples were centrifuged, purified by SPE and analysed by ultra-high-performance liquid chromatography coupled to tandem mass spectrometry. Quantitative validation was done in accordance with the guidelines laid down in European Commission Decision 2002/657/CE. Matrix-matched calibration with internal standards was used to reduce matrix effects. The target level was set at the authorised carryover level (1%) and validation levels were set at 0.5%, 1% and 1.5%. Method performances were evaluated by the following parameters: linearity (0.986 < R² < 0.999), precision (repeatability < 12.4% and reproducibility < 14.0%), accuracy (89% < recovery < 107%), sensitivity, decision limit (CCα), detection capability (CCβ), selectivity and expanded measurement uncertainty (k = 2).This method has been used successfully for three years for routine monitoring of antibiotic residues in feeds during which period 20% of samples were found to exceed the 1% authorised carryover limit and were deemed non-compliant.     

Effects of low temperature on the mechanical properties of glass fibre–epoxy composites: static tension,compression, R = 0.1 and R =− 1 fatigue of ±45° laminates

Effects of cold climate exposure on structures made of composite materials are scarcely documented. As a result, even if exceptional wind conditions prevail in some cold regions, uncertainties related to composite materials durability at low temperatures may hinder development of wind energy projects in those regions. Therefore, as part of the Wind Energy Strategic Network (WESNet) of the Natural Sciences and Engineering Research Council (NSERC) of Canada, efforts were made to evaluate the effects of cold climate exposure on the mechanical properties of glass–epoxy composites. Tensile and compressive quasi‐static tests as well as tensile (R = 0.1) and fully reversed (R =? 1) fatigue tests were performed on vacuum‐infused [±45]_2s glass–epoxy composites at ?40°C and 23°C. Results for quasi‐static tests show an increase of tensile, compressive and shear strengths and moduli at low temperatures. It is also demonstrated that for the stress range under scrutiny, fatigue performance is improved at ?40°C for both the R = 0.1 and R =? 1 loading cases. Moreover, the failure mode for R =? 1 fatigue changed from compressive failure due to buckling of delaminated plies to tensile failure, suggesting a more efficient use of the material. However, if R =? 1 fatigue results at low temperature are extrapolated towards the very low stresses that are also part of wind turbine blades fatigue load spectrum, fatigue life may be degraded compared with that at ambient temperature. Finally, evidence of visco‐elastic behaviour leading to changes in s ? N curve slope parameter are reported. Copyright © 2015 John Wiley & Sons, Ltd.     

A DNA microarray for fission yeast: minimal changes in global gene expression after temperature shift

Completion of the fission yeast genome sequence has opened up possibilities for post-genomic approaches. We have constructed a DNA microarray for genome-wide gene expression analysis in fission yeast. The microarray contains DNA fragments, PCR-amplified from a genomic DNA template, that represent > 99% of the 5000 or so annotated fission yeast genes, as well as a number of control sequences. The GenomePRIDE software used attempts to design similarly sized DNA fragments corresponding to gene regions within single exons, near the 3'-end of genes that lack homology to other fission yeast genes. To validate the design and utility of the array, we studied expression changes after a 2 h temperature shift from 25 degrees C to 36 degrees C, conditions widely used when studying temperature-sensitive mutants. Obligingly, the vast majority of genes do not change more than two-fold, supporting the widely held view that temperature-shift experiments specifically reveal phenotypes associated with temperature-sensitive mutants. However, we did identify a small group of genes that showed a reproducible change in expression. Importantly, most of these corresponded to previously characterized heat-shock genes, whose expression has been reported to change after more extreme temperature shifts than those used here. We conclude that the DNA microarray represents a useful resource for fission yeast researchers as well as the broader yeast community, since it will facilitate comparison with the distantly related budding yeast, Saccharomyces cerevisiae. To maximize the utility of this resource, the array and its component parts are fully described in On-line Supplementary Information and are also available commercially.     

Temperature effect on Listeria monocytogenes growth in the event of contamination of cooked pork products

The aim of this study was to describe the effect of temperature on the growth of Listeria monocytogenes in the event of postprocess contamination of packaged pork meats. This study was carried out in two steps. In the first step, the effect of temperature on L. monocytogenes growth rates was determined in duplicates at 13 temperatures between 2 and 43 degrees C by turbidimetric methods and adjusted by a quantitative secondary model. Then, seven sets of growth kinetics were collected by challenge testing in white pudding and roulade, both cooked pork products prepared according to an industrial process and stored at suboptimal temperatures ranging from 2 to 20 degrees C. In the second step, objectives were to (i) collect direct information on the temperature effect of L. monocytogenes on the two pork products, (ii) compare the two products regarding L. monocytogenes exposure, and (iii) compare results given by modeling (step i) with results obtained independently and then evaluate the model application domain. Each kinetic was built with at least 10 experimental data and two replicates. Comparison between L. monocytogenes behavior at 4 degrees C on white pudding and roulade indicated that both meat products were affected by food safety problems. Indeed, after contamination and storage for 10 days at 4 degrees C, the bacterial population increased by 2 log CFU/g in both products. Comparison between growth kinetic simulations and experimental data obtained separately gave satisfactory conclusions; the difference between observed and predicted bacterial population values was always less than 1 log CFU/g and a bias factor of 1.18 when growth rates were compared. These results applied to L. monocytogenes contamination of white pudding or roulade can now be used either in the management of optimal process and distribution networks or in risk assessment (exposure assessment).     

增强型低功率AC负载通—断控制器件

1.前言 交流电流开关(ACS)嵌在一个集成化驱动器、一个钳位结构和一个双向晶闸管式开关内(如图1所示)。最初,这些新器件因电感性负载过高而受到批评,其串联电感可达到十几亨利,在关断操作时,很可能就会引起问题。在本文的第二节,将详细介绍在不使用任何外部钳位器件(如金属氧化物变阻器)的情况下,ACS的钳位特性是如何直接驱动一个电感性负载的,以及它怎样     

Mesh coding: Application to texture and scalable 3D scene coding

This article examines the problem of 3D scalable mesh and texture coding. The triangular mesh topology is encoded by an edge-based conquest strategy, while positions are encoded using a multiple prediction method associated with an adaptive arithmetic coder. Moreover, scalability is obtained on the positions via a bitplane coding technique, adapted to float numbers. Then, texture is approximated by a hybrid technique mixing affine interpolation and discrete cosinus transform applied to the triangles of a hierarchical nested mesh.     

Visuospatial working memory in learning from multimedia systems

Abstract  Multimedia systems involve the association of various types of information: verbal information presented visually or auditorily, static or dynamic pictorial information, and sound information. In a cognitive approach, integrating this information involves complex processes constrained by properties of the learner's cognitive system, and especially by the capacity of working memory. This paper, reports on an experiment focused on the integration of verbal and pictorial information when students learn a series of physics concepts. The involvement of the visuo-spatial working memory was investigated by means of a dual-task paradigm. Results show that pictorial information enhances the learning process. They also suggest that the visual and the spatial components of visuospatial working memory should be considered separately. Finally, they emphasise the need to consider the limitations in cognitive resources available to the learner.     

One-Pot Microwave-Assisted Synthesis of Graphene/Layered Double Hydroxide (LDH) Nanohybrids

Nano-Micro Letters - A facile and rapid method to synthesize graphene/layered double hydroxide (LDH) nanohybrids by a microwave technique is demonstrated. The synthesis procedure involves...