Uncertainty from sampling in measurements of aflatoxins in animal feedingstuffs: application of the Eurachem/CITAC guidelines

The duplicate method for estimating uncertainty from measurement including sampling is presented in the Eurachem/CITAC guide. The applicability of this method as a tool for verifying sampling plans for mycotoxins was assessed in three case studies with aflatoxin B(1) in animal feedingstuffs. Aspects considered included strategies for obtaining samples from contaminated lots, assumptions about distributions, approaches for statistical analysis, log(10)-transformation of test data and applicability of uncertainty estimates. The results showed that when duplicate aggregate samples are formed by interpenetrating sampling, repeated measurements from a lot can be assumed to approximately follow a normal or lognormal distribution. Due to the large variation in toxin concentration between sampling targets and sometimes very large uncertainty arising from sampling and sample preparation (U(rel) ≥ 50%), estimation of uncertainty from log(10)-transformed data was found to be a more generally applicable approach than application of robust ANOVA.     

Attaining persistent field-free control of open and closed quantum systems

Persistent quantum control (PQC) aims to maintain an observable objective value over a period of time following the action of an applied field. This paper assesses the feasibility of achieving PQC for arbitrary finite-level systems and observables. The analysis is carried out independent of the particular method used for state preparation. The PQC behavior is optimized over the set of physically accessible prepared states for both open and closed systems. The quality of observable value persistence in the postcontrol period was found to vary with the required duration of persistence, the system temperature, the chosen observable operator, and the energy levels of the system. The alignment of a rigid diatomic rotor is studied as a model system. The theoretical estimates of PQC behavior are encouraging and suggest feasible exploration in the laboratory using currently available technology.     

Developments in Direct C?H Arylation of (Hetero)Arenes under Microwave Irradiation

This minireview describes the progress made in the development of direct C? H arylation approaches through the application of focused microwave irradiation. The synergistic combination of microwave‐assisted techniques with the rapidly evolving domain of C? H arylation has opened new vistas in the efficient synthesis of a diverse array of biologically important (hetero)arenes.     

UV‐curable acrylate‐based nanocomposites: effect of polyaniline additives on the curing performance

Composites of nanostructured polyaniline (PANI) conducting polymer in a polyester acrylate (PEA) formulation were made to provide conductive organic coatings. The effect of the presence and amount of PANI on the photocuring performance of the ultraviolet (UV)‐curable acrylate system has been investigated employing real‐time Fourier transform infrared spectroscopy as the main technique. Longer initial retardation of the radical polymerization and lower rates of cross‐linking reactions were observed for dispersions containing PANI of higher than 3wt.%. The PEA/PANI samples were more affected than the neat PEA resin by the changes in UV light intensity and oxygen accessibility during UV curing. Samples with higher PANI content, of up to 10wt.%, were tested and could be partially cured even at UV light intensities as low as 2 mW cm^?2 when the oxygen replenishment into the system was inhibited. Thermal analysis revealed that the presence of PANI did not induce any significant change in Tg of the cured system, meaning that early decrease in mobility and vitrification is not the reason for lower ultimate conversion of the dispersions with higher PANI content compared with the neat PEA resin. Curing under strong UV lamps, of 1.5 W cm^?2 intensity, made it possible to reach high degrees of conversion on films with similar mechanical properties independent of the PANI content. Copyright © 2013 John Wiley & Sons, Ltd.     

N-Glycosylamine-mediated isotope labeling for mass spectrometry-based quantitative analysis of N-linked glycans

N-Linked glycosylation is a major protein modification involved in many essential cellular functions. Methods capable of quantitative glycan analysis are highly valuable and have been actively pursued. Here we describe a novel N-glycosylamine-based strategy for isotopic labeling of N-linked glycans for quantitative analysis by use of mass spectrometry (MS). This strategy relies on the primary amine group on the reducing end of freshly released N-linked glycans for labeling, and eliminates the need for the harsh labeling reaction conditions and/or tedious cleanup procedures required by existing methods. By using NHS-ester amine chemistry we used this strategy to label N-linked glycans from a monoclonal antibody with commercially available tandem mass tags (TMT). Only duplex experiments can be performed with currently available TMT reagents, because quantification is based on the intensity of intact labeled glycans. Under mild reaction conditions, greater than 95 % derivatization was achieved in 30 min and the labeled glycans, when kept at ?20 °C, were stable for more than 10 days. By performing glycan release, TMT labeling, and LC–MS analysis continuously in a single volatile aqueous buffer without cleanup steps, we were able to complete the entire analysis in less than 2 h. Quantification was highly accurate and the dynamic range was large. Compared with previously established methods, N-glycosylamine-mediated labeling has the advantages of experimental simplicity, efficient labeling, and preserving glycan integrity.

A concept study on non-targeted screening for chemical contaminants in food using liquid chromatography–mass spectrometry in combination with a metabolomics approach

A generic method to screen for new or unexpected contaminants at ppm levels in food has been developed. The method comprises an acidic acetonitrile extraction, detection with ultra-high-pressure liquid chromatography coupled to electrospray ionisation time-of-flight mass spectrometry and statistical evaluation using a metabolomics approach comparing suspected contaminated food with uncontaminated foods. The method was tested for 26 model contaminants from 100 μg/g down to 0.4 μg/g in three brands of fresh orange juice. Blinded statistical evaluation revealed signals from all added contaminants detectable by liquid chromatography–electrospray ionisation using positive ionisation mode, while only two false-positive signals were reported. The method is primarily intended to be used for investigation of food samples suspected to be contaminated with unknown substances. Additionally it could be used to continuously monitor for appearance of new food contaminants as a complement to the specific targeted analysis that is today’s foundation of food safety analysis.     

First Synthesis of Azachlorins and Azacorrins with a N‐Atom in β‐Pyrrolic Positions

Azachlorins 7 and 11 , and azahexadehydrocorrin rac‐ 10 are novel structural types of tetrapyrrolic macrocycles. Synthesis of the target structures bearing N‐atoms in the β‐periphery of the macrotetracycles could be achieved by attaching an imidazole moiety 4 to the tricyclic Ni complex rac‐ 5 , followed by cyclization. Depending on the central metal ion of the bilin intermediates rac‐ 6a and rac‐ 6b , chlorin‐ or corrin‐type structures were formed by cyclization.     

Optimization of ELFSE DNA sequencing with EOF counterflow and microfluidics

We present a nonlinear optimization study of different implementations of the DNA electrophoretic method “End‐labeled Free‐solution Electrophoresis” in commercial capillary electrophoresis systems and microfluidics to improve the time required for readout. Here, the effect of electro‐osmotic counterflows and snap‐shot detection are considered to allow for detection of peaks soon after they are electorphoretically resolved. Using drag tags available in micelle form, we identify a design capable of sequencing 600 bases in 2.8 min.     

Rate of convergence to stationarity of the system <Emphasis Type="Italic">M</Emphasis>/<Emphasis Type="Italic">M</Emphasis>/<Emphasis Type="Italic">N</Emphasis>/<Emphasis Type="Italic">N</Emphasis>+<Emphasis Type="Italic">R</Emphasis>

We consider the M/M/N/N+R service system, characterized by N servers, R waiting positions, Poisson arrivals and exponential service times. We discuss representations and bounds for the rate of convergence to stationarity of the number of customers in the system, and study its behaviour as a function of R, N and the arrival rate λ, allowing λ to be a function of N.     

Urban road traffic noise and annoyance: the effect of a quiet façade

Road traffic noise in urban areas is a major source of annoyance. A quiet fac?ade has been hypothesized to beneficially affect annoyance. However, only a limited number of studies investigated this hypothesis, and further quantification is needed. This study investigates the effect of a relatively quiet fac?ade on the annoyance response. Logistic regression was performed in a large population based study (GLOBE, N~18,000), to study the association between road traffic noise exposure at the most exposed dwelling fac?ade (L(den)) and annoyance in: (1) The subgroup with a relatively quiet fac?ade (large difference in road traffic noise level between most and least exposed fac?ade (Q>10 dB); (2) the subgroup without a relatively quiet fac?ade (Q<10 dB). Questionnaire data were linked to individual exposure assessment based on detailed spatial data (GIS) and standard modeling techniques. Annoyance was less likely (OR(Q) (>10)相似文献