Towards van der Waals Epitaxial Growth of GaAs on Si using a Graphene Buffer Layer

Van der Waals growth of GaAs on silicon using a two‐dimensional layered material, graphene, as a lattice mismatch/thermal expansion coefficient mismatch relieving buffer layer is presented. Two‐dimensional growth of GaAs thin films on graphene is a potential route towards heteroepitaxial integration of GaAs on silicon in the developing field of silicon photonics. Hetero‐layered GaAs is deposited by molecular beam epitaxy on graphene/silicon at growth temperatures ranging from 350 °C to 600 °C under a constant arsenic flux. Samples are characterized by plan‐view scanning electron microscopy, atomic force microscopy, Raman microscopy, and X‐ray diffraction. The low energy of the graphene surface and the GaAs/graphene interface is overcome through an optimized growth technique to obtain an atomically smooth low­ temperature GaAs nucleation layer. However, the low adsorption and migration energies of gallium and arsenic atoms on graphene result in cluster‐growth mode during crystallization of GaAs films at an elevated temperature. In this paper, we present the first example of an ultrasmooth morphology for GaAs films with a strong (111) oriented fiber‐texture on graphene/silicon using quasi van der Waals epitaxy, making it a remarkable step towards an eventual demonstration of the epitaxial growth of GaAs by this approach for heterogeneous integration.     

Influence of packaging method and length of chilled storage on microflora, tenderness and colour stability of venison loins

Sections of venison loins (LD) weighing approximately 300 g from 12 red deer (Cervus elaphus) were packaged using four packaging methods: (a) vacuum packaging, (b) CO₂ flushed using a nylon containment film (CO₂-Nylon), (c) CO₂ flushed using an ultra-high barrier containment film (CO₂-UHB), and (d) CO₂ flushed using an aluminium foil laminate containment film (CO₂-Foil) and stored for 1, 6, 12 and 18 weeks at 0°C. Meat pH values were lower in all CO₂ flushed meat packages (P<0·05) than in vacuum packaged meat. Lactic acid bacteria and total anaerobic counts increased over storage time in all packages regardless of treatment up to values of log₁₀ 7·8 and 7·6 g⁻¹, respectively. Tenderness tended to increase as meat was stored for up to 18 weeks. Colour scores taken during simulated retail display indicated that colour deteriorated more rapidly when meat was stored for 12 and 18 weeks than for 1 and 6 weeks. Vacuum packaging and gas flushing (CO₂-Foil) resulted in higher initial colour scores than venison packaged in the CO₂-Nylon or CO₂-UHB materials. Venison stored for 18 weeks also exhibited a higher proportion of packages containing off odours, lower flavour desirability and flavour intensity scores as well as higher off flavour scores than meat stored for shorter times. The implications of these effects are discussed. Although there were few significant differences in microbial growth and sensory characteristics due to packaging method or containment film, vacuum packaging appeared to be the most economic and produced meat of better colour stability.     

The thymol method for glucosinolate determination

This paper details experiments aimed at optimising the conditions for the determination of glucosinolates in rapeseed (Brassica napus L) using the colorimetric thymol procedure. Glucose could not be substituted for sinigrin when preparing a standard curve for glucosinolate determination unless a correction factor was employed. The value of this factor was found to depend on the concentration of sulphuric acid. Although the coloured complexes formed between thymol and either glucose or sinigrin were found to be unstable at 100°C, the sinigrin/ glucose colour ratio remained relatively constant for incubation times from 40 to 60 min. It was found necessary to increase the amount of thymol present to a final value of 0.23% to ensure complete reaction of glucosinolates. The revised method can be employed successfully for the analysis of glucosinolates in both seed and meal.     

An overview of molecular stress response mechanisms in Escherichia coli contributing to survival of Shiga toxin-producing Escherichia coli during raw milk cheese production

The ability of foodborne pathogens to survive in certain foods mainly depends on stress response mechanisms. Insight into molecular properties enabling pathogenic bacteria to survive in food is valuable for improvement of the control of pathogens during food processing. Raw milk cheeses are a potential source for human infections with Shiga toxin-producing Escherichia coli (STEC). In this review, we focused on the stress response mechanisms important for allowing STEC to survive raw milk cheese production processes. The major components and regulation pathways for general, acid, osmotic, and heat shock stress responses in E. coli and the implications of these responses for the survival of STEC in raw milk cheeses are discussed.     

Evaluation of patient improvement in a token economy treatment program.

Investigated various indices of improvement in 20 female chronic mental patients (mean age = 36 yrs) who were randomly assigned to a token economy treatment ward as compared with 20 control patients who received typical custodial treatment. All Ss were given standardized interviews consisting of 5 experimental tasks. Segments of the interviews were video-recorded and rated by naive raters on a 20-item questionnaire. Results indicate that the token-economy Ss were better oriented, had more skill in making business purchases and discriminations, and were better able to follow commands. Token economy Ss were rated as being more cooperative and communicative, more socially desirable, more appropriate in mood, and as exhibiting less psychotic behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Distribution and identification of culturable airborne microorganisms in a Swiss milk processing facility

Airborne communities (mainly bacteria) were sampled and characterized (concentration levels and diversity) at 1 outdoor and 6 indoor sites within a Swiss dairy production facility. Air samples were collected on 2 sampling dates in different seasons, one in February and one in July 2012 using impaction bioaerosol samplers. After cultivation, isolates were identified by mass spectrometry (matrix-assisted laser desorption/ionization-time-of-flight) and molecular (sequencing of 16S rRNA and rpoB genes) methods. In general, total airborne particle loads and total bacterial counts were higher in winter than in summer, but remained constant within each indoor sampling site at both sampling times (February and July). Bacterial numbers were generally very low (<100 cfu/m³ of air) during the different steps of milk powder production. Elevated bacterial concentrations (with mean values of 391 ± 142 and 179 ± 33 cfu/m³ of air during winter and summer sampling, respectively; n = 15) occurred mainly in the “logistics area,” where products in closed tins are packed in secondary packaging material and prepared for shipping. However, total bacterial counts at the outdoor site varied, with a 5- to 6-fold higher concentration observed in winter compared with summer. Twenty-five gram-positive and gram-negative genera were identified as part of the airborne microflora, with Bacillus and Staphylococcus being the most frequent genera identified. Overall, the culturable microflora community showed a composition typical and representative for the specific location. Bacterial counts were highly correlated with total airborne particles in the size range 1 to 5 µm, indicating that a simple surveillance system based upon counting of airborne particles could be implemented. The data generated in this study could be used to evaluate the effectiveness of the dairy plant’s sanitation program and to identify potential sources of airborne contamination, resulting in increased food safety.     

Development and Characterization of Monoclonal and Polyclonal Antibodies Against Salmonella enterica Typhimurium for Biosensor Detection

ABSTRACT: For the construction of a biosensor to specifically and effectively detect Salmonella enterica Typhimurium, a monoclonal antibody (mAb) 1B4 and a polyclonal antibody (pAb) S48 were developed against purified outer membrane proteins (OMPs) of Salmonella enterica Typhimurium. Gel electrophoresis data indicated that the apparent molecular weight of the main OMP was 55 kD. The mAb 1B4 strongly reacted to Salmonella enterica Typhimurium and Salmonella enterica Paratyphi and had no cross-reaction to other gram-negative and gram-positive bacteria that were tested. The pAb S48 also showed high reactivity to Salmonella enterica Typhimurium, but had cross-reactivity with other tested bacteria. Because of the high specificity and sensitivity of 1B4 against S. enterica Typhimurium, it was immobilized onto a sensor platform to capture bacteria. The captured bacteria were visualized byalight microscope fortheir detection. The detection limit of the biosensorwas 1 × 10² colony forming units/mL in bacterial culture and in a milk sample, and no other bacteria interfered with the binding of targeted cells. Therefore, a biosensor was developed that would rapidly detect Salmonella in the laboratory and in a food processing plant.     

Fast Fluorescence Spectroscopy Methodology to Monitor the Evolution of Extra Virgin Olive Oils Under Illumination

Detailed regions of excitation and emission wavelengths for extra virgin olive oil samples have been extracted from three dimensional front-face fluorescence spectra. Information was applied to establish a right-angle fluorescence procedure. A right-angle device was assembled and tested with simultaneous excitation from 200 to 400 nm and registration of the fluorescence signal emitted from 400 to 850 nm. A principal component analysis was performed on the signal ranging from 400 to 550 nm from spectra of olive oils officially categorized as extra virgin in order to model the expected variability of compounds related to oxidative processes. Such model was useful to monitor the spectral evolution of extra virgin olive oil samples acquired at retail markets, which were exposed to indirect light during 2 months, through the analysis of the effect on their scores. Three relevant peaks characterized such evolution, with local maxima at around 434 to 437, 464 to 469 and 510 to 518 nm. Polynomial relationship was found between the evolution of those peaks and that of the chlorophyll, at around 670 to 673 nm, with R ² values of 0.98 and 0.99.     

The extraction of a glucomannan polysaccharide from konjac corms (elephant yam,Amorphophallus rivierii)

Abstract : A process for the micropropagation of Amorphophallus rivierii (elephant yam or konjac) and for the extraction and purification of the glucomannan polysaccharide from fresh konjac plant corms has been developed. This process involves extraction with 2-propanol, which has the additional benefit of extracting carotenoids as a potentially valuable side-product. Starch granules with an unusually high and homogeneous gelatinisation temperature range are normally present in the corms, particularly immature ones, and this greatly reduces the strength of gels formed using the glucomannan. Therefore, the extraction process also involves the selective hydrolysis of the starch, by α- and β-amylases that have been specially selected for an absence of contaminating β-mannanase or β-glucanase activity that would depolymerise the glucomannan and render it nonfunctional. Bacillus lichenformis α-amylase was preferred. Using this process pure glucomannan could be extracted which, when mixed with K -carrageenan, forms a gel almost twice as strong as locust bean gum-K -carrageenan gels of the same concentration.