Formation of cereulide and enterotoxins by Bacillus cereus in fermented African locust beans

Afitin, iru and sonru are three spontaneously fermented African locust bean Benin condiments. The fermentation processes are exothermic, with temperatures mostly being above 40 °C. A total of 19 predominant Bacillus cereus isolates from afitin, iru and sonru, were investigated. The enterotoxin genes nhe (A, B, C) were present in all 19 isolates, the hbl (A, C, D) in one (afitin), and the cytK gene in three isolates (afitin). Levels of cytotoxicity to Vero cells and NheA production in BHI-broth was within the range of known diarrheal outbreak strains. Autoclaved cooked African locust beans inoculated with emetic (cereulide producing) B. cereus Ba18H2/RIF supported growth at 25, 30 and 40 °C with highly different maximum cereulide productions of 6 ± 5, 97 ± 3 and 0.04 ± 0.02 μg/g beans, respectively (48 h). For non-autoclaved cooked beans inoculated with 2, 4 and 6 log₁₀B. cereus Ba18H2/RIF spores/g beans, cereulide production was 5 ± 4, 64 ± 8 and 69 ± 34 μg/g beans, respectively at 24 h, while it was 70 ± 43, 92 ± 53 and 99 ± 31 μg/g at 48 h of fermentation at 30 °C. Even though high toxin levels were observed, to date there are no known reports on diarrhea or vomiting due to the consumption or afitin, iru and sonru in Benin, which also according to the present study is likely to be expected from the low levels of cereulide produced at 40 °C.     

Characterization of marama bean (Tylosema esculentum) by comparative spectroscopy: NMR, FT-Raman, FT-IR and NIR

The marama bean from Southern Africa has proven to be a source for production of various healthy food products. In order to exploit its commercial potential, it is important to know its chemical composition in more detail. In this study, marama beans from different geographical sites and harvest years were analyzed by use of infrared, near infrared, Raman, and ¹H as well as ¹³C nuclear magnetic resonance spectroscopy. These techniques can measure single beans in a rapid and non-destructive manner. By comparative application, the qualitative composition of the marama bean was explored in detail, revealing large amounts of protein, dietary fiber and unsaturated fat. The carbohydrate fraction was largely present as pectins and a minor fraction of smaller water soluble carbohydrates were tentatively assigned to raffinose. It is characteristic that the beans do not contain starch or ??-glucans and that the water soluble part of the proteins/peptides have a high content of the aromatic amino acid tyrosine.     

Analysis of secondary plant metabolites by indirect desorption electrospray ionization imaging mass spectrometry

Secondary metabolites in plant material can be imaged in a simple and robust way by creating an imprint of the plant material on a porous Teflon surface. The Teflon surface serves to extract compounds from the plant material for enhanced desorption electrospray ionization imaging analysis, while maintaining the spatial information of the sample. The method, which remedies for limitations in mass spectrometry imaging of compounds embedded in plant material, was demonstrated on leaves and petals of Hypericum perforatum and leaves of Datura stramonium.     

Versatile flow-injection amperometric ion detector based on an interface between two immiscible electrolyte solutions: numerical and experimental characterization

The present paper describes a flexible thin layer electrochemical flow cell for ultrasensitive amperometric detection at a supported interface between immiscible electrolyte solutions. Nanomolar detection limits were demonstrated using the cell design, and 3D finite element simulations allowed a detailed characterization of the flow cell. The cell design employed in the present work allowed the sensing oil membrane and the aqueous reference electrode to be placed in close contact, thereby minimizing cell resistance. The adjustable cell volume means that the same cell design can be used for different application with different requirement for detection limits and dynamic range. A disposable membrane was employed which reduces the need for surface cleaning and prevents sample carryover between different applications. For the lowest cell volumes the detection chamber approaches a thin layer electrochemical flow cell detector with a large surface to volume ratio.     

Noctilucent clouds: modern ground-based photographic observations by a digital camera network

Noctilucent, or "night-shining," clouds (NLCs) are a spectacular optical nighttime phenomenon that is very often neglected in the context of atmospheric optics. This paper gives a brief overview of current understanding of NLCs by providing a simple physical picture of their formation, relevant observational characteristics, and scientific challenges of NLC research. Modern ground-based photographic NLC observations, carried out in the framework of automated digital camera networks around the globe, are outlined. In particular, the obtained results refer to studies of single quasi-stationary waves in the NLC field. These waves exhibit specific propagation properties--high localization, robustness, and long lifetime--that are the essential requisites of solitary waves.     

Effect of Grain Boundaries and Grain Orientation on Structure and Properties

The evolution of deformation microstructures in metals follows a universal pattern of grain subdivision. However, the structure in the grain boundary region may be different from that in the grain interior, although a characteristic region cannot be identified for polycrystals with medium to high stacking fault energy. In the grain interior, the dislocation structure is predominantly composed of almost planar boundaries (geometrically necessary boundaries) and cell boundaries (incidental dislocation boundaries) forming a cell block structure. For grains with grain sizes reaching down to about 4 μm deformed in tension and by rolling, a clear correlation has been established between the characteristics of the deformation structure and the orientation of the grain in which it evolves. A similar correlation is observed for single crystals of different orientations. Such correlations form the basis for a general analysis of active slip systems and for modeling of the flow stress and flow stress anisotropy of polycrystalline samples.     

Sampling Bias on Cup Anemometer Mean Winds

The cup anemometer signal can be sampled in several ways to obtain the mean wind speed. Here we discuss the sampling of series of mean wind speeds from consecutive rotor rotations, followed by unweighted and weighted averaging. It is shown that the unweighted averaging creates a positive bias on the long‐term mean wind speed, which is at least one order of magnitude larger than the positive bias from the weighted averaging, also known as the sample‐and‐hold method. For a homogeneous, neutrally stratified flow the first biases are 1%–2%. For comparison the biases due to fluctuations of the three wind velocity components and due to calibration non‐linearity are determined under the same conditions. The largest of these is the v‐bias from direction fluctuations. The calculations pertain to the Risø P2546A model cup anemometer. Copyright © 2003 John Wiley & Sons, Ltd.     

Strength prediction and failure modes of concrete specimens subjected to the split test

This paper deals with modelling and test of concrete specimens subjected to the Brazilian split test. Based on the fictitious crack concept, a simple model for the crack propagation process in the splitting plane is developed. From the model, it is possible to determine the distribution of residual tensile strength as crack propagation take place. The residual tensile strength is thereafter used in a rigid plastic analysis of the splitting failure. Based on this combined approach, the ultimate load may either be governed by crack propagation or by a plastic failure, which then terminates the crack growth process. It is shown that the model is able to replicate a number of experimental observations. This includes size effect and influence of loading width.