Evaluation of shiga toxin-producing Escherichia coli (STEC) method for the detection and identification of STEC O104 strains from sprouts

Protocols for Shiga toxin-producing Escherichia coli (STEC) typically focus on the detection and recovery of E. coli O157:H7; however, the prevalence of outbreaks associated with non-O157 STEC are increasing and the efficacy of current testing strategies have not been fully evaluated. Non-O157 STEC are a very diverse group whose pathogenic characteristics and clinical significance have not been well established. During an outbreak situation, the rapid dissemination of specific strain characteristics can provide information needed to verify standard laboratory methodology and identify potentially effective tests to detect and recover the outbreak strain from foods. This study validated the use of a standard method to detect and recover two strains of E. coli O104 STEC at a level of approximately 1 CFU/g from sprouts. The use of additional serotype-specific real-time PCR assays and supplemental chromogenic media to assist the detection and recovery of these organisms were also evaluated.     

Optically transparent magnetic nanocomposites based on encapsulated Fe(3)O(4) nanoparticles in a sol-gel silica network

Composite Fe(3)O(4)-SiO(2) materials were prepared by the sol-gel method with tetraethoxysilane and aqueous-based Fe(3)O(4) ferrofluids as precursors. The monoliths obtained were crack free and showed both optical and magnetic properties. The structural properties were determined by infrared spectroscopy, x-ray diffractometry and transmission electron microscopy. Fe(3)O(4) particles of 20?nm size lie within the pores of the matrix without any strong Si-O-Fe bonding. The well established silica network provides effective confinement to these nanoparticles. The composites were transparent in the 600-800?nm regime and the field dependent magnetization curves suggest that the composite exhibits superparamagnetic characteristics.     

Self-assembled one-dimensional nanostructure arrays

A range of proposed devices relies on the electronic, optical or magnetic properties of one-dimensional (1D) chains of nanoparticles. Here, well-controlled 1D arrays have been formed by templating a spherical-morphology block copolymer within a narrow groove. Significantly, the domains are distorted into ellipses with aspect ratio and major axis orientation controlled by the groove width. This technique gives unprecedented control over the period, particle size, aspect ratio, and orientation of nanoparticles in 1D arrays, making it valuable for creating self-assembled masks for the fabrication of novel devices.     

A counter-current parallel-plate membrane denuder for the non-specific removal of trace gases

In this paper we present a counter-current parallel-plate membrane diffusion denuder for the non-specific removal of trace gases from an air flow. In this design, gaseous pollutants are removed by diffusing from a sample channel to two purge channels by crossing microporous membranes. In the laboratory, at a sample flow rate of 5 L/min and purge flow rates of 5 L/min each, gas removal efficiencies ranged from 84% for CO to 72% for SF6. Removal efficiencies increased with lower sample flow rate, a higher sample to purge flow rate ratio, a longer channel length, and using molecules with higher diffusion coefficient. Removal efficiencies were, however, not affected by the sample channel height. In addition, gas penetration was exponentially associated with the product of channel length, diffusion coefficient, and the inverse of sample flow rate. Particle losses were significant (10-25% losses) only for particles smaller than 50 nm. In a field evaluation, the denuder's performance was tested with an aerosol produced in a photochemical chamber. The denuder's performance was similar to that observed in the laboratory and was stable over time. Finally, the denuder was tested with a semivolatile organic aerosol. Particle mass losses due to volatilization were about 30%.     

Simplified 3D Fading Channels Adopted in MIMO Beamforming Schemes

A simplified three-dimension (3D) fading channel model deployed in a multi-input multi-output (MIMO) beamforming system is explored in this article. Both angle of arrival (AoA) and angle of departure (...     

Glass Fiber-Reinforced Composites: From Formulation to Application

Glass fiber-reinforced composite materials are attractive because their properties can be tailored to meet the specific needs of a variety of applications. The mechanical and thermal properties of a composite generally follow the rule of mixtures. As glass fiber is the major component at 70–75% by weight (50–60% by volume), selection of the correct glass product is critical. Glass fiber reinforcement is available in many forms, including continuous rovings, chopped fibers, fabrics, and nonwoven mats. In addition to form, selection of a reinforcement product involves choosing a glass type, chemistry on the glass (sizing) filament diameter, and tex. Glass formulation or type governs mechanical, thermal, and corrosion properties, whereas sizing protects the glass during handling and gives compatibility with the resin system. Filament diameter and strand tex are chosen to balance physical properties and manufacturing efficiency. A significant amount of tensile strength, up to 50%, may be lost from a pristine single filament to a multi-filament roving. To minimize this degradation, the utmost care and consistency must be exercised in the fiber forming process. This, coupled with selection of a high-performance glass formulation, enables use of composites in highly demanding applications, such as pressure vessels and ballistic armor.     

Portability,predictability and performance for parallel computing: BSP in practice

We report on practical experience using the Oxford BSP Library to parallelize a large electromagnetic code, the British Aerospace finite-difference time-domain code EMMA T:FD3D. The Oxford BS Library is one of the first realizations of the Bulk Synchronous Parallel computational model to be targeted at numerically intensive scientific (typically Fortran) computing. The BAe EMMA code is one of the first large-scale applications to be parallelized using this library, and it is an important demonstration of the cost effectiveness of the BSP approach. We illustrate how BSP cost-modelling techniques can be used to predict and optimize performance for single-source programs across different parallel platforms. We provide predicted and observed performance figures for an industrial-strength, single-source parallel code for a variety of real parallel architectures: shared memory multiprocessors, workstation clusters and massively parallel platforms.