Certification of Mass Fractions of Aflatoxin B1, B2, G1 and G2 in Peanut Butter, BCR-385R and BCR-401R

This report describes the preparation of peanut butter (BCR-385R and BCR-401R) matrix reference materials and the certification of their content (mass fraction) of aflatoxin B1, B2, G1 and G2. The preparation of the materials, the homogeneity and stability studies and the characterisation are described and the results are discussed. Uncertainties were calculated in compliance with the Guide to the Expression of Uncertainty in Measurement (GUM), including uncertainties due to possible heterogeneity and instability.JRC.D.2-Reference material

Distinct causal influences of parietal versus frontal areas on human visual cortex: evidence from concurrent TMS-fMRI

It has often been proposed that regions of the human parietal and/or frontal lobe may modulate activity in visual cortex, for example, during selective attention or saccade preparation. However, direct evidence for such causal claims is largely missing in human studies, and it remains unclear to what degree the putative roles of parietal and frontal regions in modulating visual cortex may differ. Here we used transcranial magnetic stimulation (TMS) and functional magnetic resonance imaging (fMRI) concurrently, to show that stimulating right human intraparietal sulcus (IPS, at a site previously implicated in attention) elicits a pattern of activity changes in visual cortex that strongly depends on current visual context. Increased intensity of IPS TMS affected the blood oxygen level–dependent (BOLD) signal in V5/MT+ only when moving stimuli were present to drive this visual region, whereas TMS-elicited BOLD signal changes were observed in areas V1–V4 only during the absence of visual input. These influences of IPS TMS upon remote visual cortex differed significantly from corresponding effects of frontal (eye field) TMS, in terms of how they related to current visual input and their spatial topography for retinotopic areas V1–V4. Our results show directly that parietal and frontal regions can indeed have distinct patterns of causal influence upon functional activity in human visual cortex. Key words: attention, frontal cortex, functional magnetic resonance imaging, parietal cortex, top--down, transcranial magnetic stimulatio

Studying the Role of Human Parietal Cortex in Visuospatial Attention with Concurrent TMS-fMRI

Combining transcranial magnetic stimulation (TMS) with concurrent functional magnetic resonance imaging (fMRI) allows study of how local brain stimulation may causally affect activity in remote brain regions. Here, we applied bursts of high- or low-intensity TMS over right posterior parietal cortex, during a task requiring sustained covert visuospatial attention to either the left or right hemifield, or in a neutral control condition, while recording blood oxygenation-level-dependent signal with a posterior MR surface coil. As expected, the active attention conditions activated components of the well-described "attention network,” as compared with the neutral baseline. Also as expected, when comparing left minus right attention, or vice versa, contralateral occipital visual cortex was activated. The critical new finding was that the impact of high- minus low-intensity parietal TMS upon these visual regions depended on the currently attended side. High- minus low-intensity parietal TMS increased the difference between contralateral versus ipsilateral attention in right extrastriate visual cortex. A related albeit less pronounced pattern was found for left extrastriate visual cortex. Our results confirm that right human parietal cortex can exert attention-dependent influences on occipital visual cortex and provide a proof of concept for the use of concurrent TMS-fMRI in studying how remote influences can vary in a purely top-down manner with attentional demand

Технология сборки и сварки труб диаметром 1420 мм.

Цель работы - разработка технологии и технико-экономического обоснования сборки и сварки магистрального трубопровода. В процессе работы был проведен сравнительный технико-экономический анализ сварки корневого слоя шва двумя способами сварки. Используемая технология, ручная дуговая сварка покрытыми электродами и предлагаемая – механизированная сварка в среде защитных газов.The work purpose - working out of technology and the feasibility report on assemblage and welding of two lashes of the main pipeline consisting of two one-tubes. In the course of work the comparative technical and economic analysis of procooking of a root layer of a seam has been carried out by two ways of welding. Used technology, manual arc welding by the covered electrodes and offered - the mechanised welding in the environment of protective gases

Optimized EPI for fMRI studies of the orbitofrontal cortex: compensation of susceptibility-induced gradients in the readout direction

Object Most functional magnetic resonance imaging (fMRI) studies record the blood oxygen leveldependent (BOLD) signal using gradient-echo echo-planar imaging (GE EPI). EPI can suffer from substantial BOLD sensitivity loss caused by magnetic field inhomogeneities. Here, BOLD sensitivity losses due to susceptibility- induced gradients in the readout (RO) direction are characterized and a compensation approach is developed

Correspondence: Reply to Professor Michael Thompson's Rebuttal

Mr. Thompson has sent a letter to the editor of Trends in Analytical Chemistry. The editor invited us to publish a reaction on this letter.JRC.D.2-Reference material

Limitations of the Application of the Horwitz Equation

The basic assumptions of the Horwitz equation are revisited using the example of mycotoxin assays. Prediction intervals from the Horwitz equation often span one order of magnitude and including this variation in the calculation of the Horrat values would lead to a range of values including those exceeding 2, which is often used as criterion to assess interlaboratory comparisons, questioning the suitability of the Horrat value for this purpose. In addition, available analytical data shows significant improvement in reliability over time, which casts serious doubts on the applicability of the Horwitz equation for current analytical methods. The use of the Horwitz equation in the analytical laboratory is discussed, and it is concluded that it is not suitable for estimating uncertainties as required by ISO 17025. The Horwitz equation can be a valuable summary of historical data of analytical performance. However, it should not be used as a performance criterion due to: the shortcomings of the basic model, the uncertainty in the values determined using the equation, and its incompatibility with accepted methods for the determination of measurement uncertainty as required by ISO 17025. Instead of using the Horwitz equation, a proper identification of all components of uncertainty of measurement and reasonable estimation as stipulated by the “Guide to the Expression of Uncertainty in Measurements” (GUM) is recommended.JRC.D.2-Reference material

Development of Certified Reference Materials for Mycotoxins (Invited Lecture)

Abstract not availableJRC.D-Institute for Reference Materials and Measurements (Geel

Certification of the Mass Fraction of Aflatoxin B1 in Acetonitrile (ERM-AC057), Aflatoxin B2 in Acetonitrile (ERM-AC058), Aflatoxin G1 in Actonitrile (ERM-AC059) and Aflatoxin G2 in Acetonitrile (ERM-AC060)

This report describes the preparation of aflatoxin B1, B2, G1 and G2 calibrants (ERM-AC057, ERM-AC058, ERM-AC059, ERM-AC060) and the certification of their content (mass fraction) in the solutions. The preparation of the calibrants, the homogeneity and stability studies and the characterisation with a discussion of the results is described hereafter. Uncertainties were calculated in compliance with the Guide to the Expression of Uncertainty in Measurement (GUM) (2) and include uncertainties due to the processing, purity assessment and possible instability.JRC.D.2-Reference material

Certification of Mass Fractions of Aflatoxin B1, B2, G1 and G2 in Peanut Meal Report, BCR-263R

This report describes the preparation of peanut meal (BRC-263R) matrix reference material and the certification of its aflatoxins B1, B2, G1 and G2 content (mass fraction).JRC.D.2-Reference material