Dynamic covalent hydrazine chemistry as a selective extraction and cleanup technique for the quantification of the Fusarium mycotoxin zearalenone in edible oils

A novel, cost-efficient method for the analytical extraction of the Fusarium mycotoxin zearalenone (ZON) from edible oils by dynamic covalent hydrazine chemistry (DCHC) was developed and validated for its application with high performance liquid chromatography-fluorescence detection (HPLC-FLD). ZON is extracted from the edible oil by hydrazone formation on a polymer resin functionalised with hydrazine groups and subsequently released by hydrolysis. Specifity and precision of this approach are superior to liquid partitioning or gel permeation chromatography (GPC). DCHC also extracts zearalanone (ZAN) but not α-/β-zearalenol or -zearalanol. The hydrodynamic properties of ZON, which were estimated using molecular simulation data, indicate that the compound is unaffected by nanofiltration through the resin pores and thus selectively extracted. The method's levels of detection and quantification are 10 and 30 μg/kg, using 0.2 g of sample. Linearity is given in the range of 10–20,000 μg/kg, the average recovery being 89%. Bias and relative standard deviations do not exceed 7%. In a sample survey of 44 commercial edible oils based on various agricultural commodities (maize, olives, nuts, seeds, etc.) ZON was detected in four maize oil samples, the average content in the positive samples being 99 μg/kg. The HPLC-FLD results were confirmed by HPLC–tandem mass spectrometry and compared to those obtained by a liquid partitioning based sample preparation procedure.     

TASS: The Toolkit for Accurate Scientific Software

The Toolkit for Accurate Scientific Software (TASS) is a suite of integrated tools for the formal verification of programs used in computational science, including numerically-intensive message-passing-based parallel programs. While TASS can verify a number of standard safety properties (such as absence of deadlocks and out-of-bound array indexing), its most powerful feature is the ability to establish that two programs are functionally equivalent. These properties are verified by performing an explicit state enumeration of a model of the program(s). In this model, symbolic expressions are used to represent the inputs and the values of variables. TASS uses novel techniques to simplify the symbolic representation of the state and to reduce the number of states explored and saved. The TASS front-end supports a large subset of C, including (multi-dimensional) arrays, structs, dynamically allocated data, pointers and pointer arithmetic, functions and recursion, and other commonly used language constructs. A number of experiments on small but realistic numerical programs show that TASS can scale to reasonably large configurations and process counts. TASS is open source software distributed under the GNU Public License. The Java source code, examples, experimental results, and reference materials are all available at .     

Improving the 1H indirect dimension resolution of 2D CRAMPS NMR spectra: a simulation and experimental investigation

An experimental and simulation investigation regarding the effect of various CRAMPS parameters (delays interleaved with the decoupling shape, z-rotation symmetry and offset frequency) on the DUMBO decoupling performance is presented using two model compounds, glycine and tyrosine·HCl. Although the conclusions of this work may be extended to the other homonuclear-decoupling schemes, this work focuses essentially on the effect of adding interleaved delays to DUMBO decoupling during the indirect dimension using different 2D pulse-scheme architectures. While the simulations revealed an increasing loss of the spectral resolution with longer delays (from 0 to 6 μs), the experimental 2D (1)H DUMBO NMR correlation spectra revealed that the inclusion of delays, during the indirect dimension, improves the (1)H resolution whether the z-rotation symmetry was used or not. The best experimental spectra are obtained when z-rotation symmetry and windows are combined.     

Modeling of astigmatic-elliptical beam shaping during fs-laser waveguide writing including beam truncation and diffraction effects

In this work, we report a model for accurately calculating the focal volumes corresponding to astigmatic elliptical beams used in fs-laser waveguide writing. The model is based on the use of the ABCD matrix formalism for the propagation of a Gaussian beam. The code includes the effects of propagation on the astigmatic elliptical beam, and the effects of beam truncation and diffraction at the entrance pupil of the focusing objective due to beam clipping when overfilling the pupil. The results predict that for a given astigmatism value and propagation distance it is possible to efficiently suppress the astigmatic focus closer to the surface. This explains previous experimental results where single structure waveguides with controllable aspect-ratio were fabricated using astigmatic-elliptical beams. Furthermore, we investigate the respective roles of astigmatism and beam propagation, as well as the strong impact of truncation and diffraction effects caused by clipping the beam at the pupil of the focusing optics. Finally, based on the results from our model, we present some practical considerations in terms of beam propagation and phase wrapping constraints.     

FEVS: A Functional Equivalence Verification Suite for High-Performance Scientific Computing

Scientific computing poses many challenges to formal verification, including the facts that typical programs: (1) are numerically-intensive, (2) are highly-optimized (often by hand), and (3) often employ parallelism in complex ways. Another challenge is specifying correctness. One approach is to provide a very simple, sequential version of an algorithm together with the optimized (possibly parallel) version. The goal is to show the two versions are functionally equivalent, or provide useful feedback when they are not. We present a new verification suite consisting of pairs of programs of this form. The suite can be used to evaluate and compare tools that verify functional equivalence. The programs are all in C and the parallel versions use the Message Passing Interface. They are simpler than codes used in practice, but are representative of real coding patterns (e.g., manager-worker parallelism, loop tiling) and present realistic challenges to current verification tools. The suite includes solvers for the 1-d and 2-d diffusion equations, Jacobi iteration schemes, Gaussian elimination, and N-body simulation.     

Certification of reference materials for ochratoxin A analysis in coffee and wine

Mycotoxins are important non-anthropogenic food and feed contaminants, which can be present on almost every agricultural commodity. Effective consumer protection therefore essentially depends on food surveillance by reliable quantitative analysis enabled by appropriate quality control. Certified (matrix) reference materials (CRMs) are versatile tools to support quality assurance. However, in the case of ochratoxin A (OTA), a hepato- and nephrotoxic mycotoxin, which is regulated in various foods, there is a lack of suitable CRMs. This lack has now been overcome by the development of two European Reference Materials (ERM^?) for the determination of OTA in roasted coffee (ERM^?-BD475) and red wine (ERM^?-BD476). This article discusses the material preparation process as well as the results of homogeneity and stability testing. Furthermore, the results of the in-house certification studies carried out at BAM Federal Institute for Materials Research and Testing are presented and discussed. Interlaboratory comparison studies involving selected expert laboratories with documented expertise in the field of mycotoxin analysis were conducted to confirm the certified values determined by BAM. The certified ochratoxin A values and their corresponding expanded uncertainties (k?=?2) were assigned in full compliance with the requirements of ISO Guide 35 and are as follows: (6.0?±?0.6)???g?kg^?1 for roasted coffee, ERM^?-BD475, and (0.52?±?0.11)???g?L^?1 for red wine, ERM^?-BD476.     

Evolution of material voids for highly anisotropic surface energy

In this paper we consider the evolution by surface diffusion of material voids in a linearly elastic solid, focusing on the evolution of voids with large surface energy anisotropy. It is well known that models for the time evolution of similar material surfaces can become mathematically ill-posed when the surface energy is highly anisotropic. In some cases, this ill-posedness has been associated with the formation of corners along the interface. Here the ill-posedness is removed through a regularization which incorporates higher order terms in the surface energy. Spectrally accurate numerical simulations are performed to calculate the steady-state solution branches and time-dependent evolution of voids, with a particular emphasis on inferring trends in the zero regularization (c→0) limit. For steady voids with large anisotropy we find that apparent corners form as c→0. In the presence of elastic stresses σ the limiting corner angles are most often found to differ from angles found on the (σ=0) Wulff shape. For large elastic stresses we find that steady solutions no longer exist; instead the void steadily lengthens via a filamenting instability referred to as tip streaming.     

Synthesis and Intracellular Redox Cycling of Natural Quinones and Their Analogues and Identification of Indoleamine‐2,3‐dioxygenase (IDO) as Potential Target for Anticancer Activity

Natural quinones, often linked with cellular oxidation processes, exhibit pronounced biological activity. In particular, the structurally unique isothiazolonaphthoquinone aulosirazole, isolated from blue‐green alga, possesses selective antitumor cytotoxicity, although its mechanism of action is unknown. The first synthesis of aulosirazole uses a route centered upon a late‐stage regioselective Diels–Alder reaction. The structurally related natural product pronqodine A, an inhibitor of prostaglandin release, and analogues thereof, were also prepared for comparison. Biological evaluation of the compounds identified one potential target as the immunoregulatory enzyme indoleamine‐2,3‐dioxygenase (IDO). The isothiazoloquinones are also efficient substrates for the human quinone reductase NQO1, and undergo intracellular NQO1‐dependent redox cycling resulting in the generation of reactive oxygen species, and at lower doses have the potential to alter the ratio of intracellular oxidized to reduced pyridine nucleotides.