Sublethal sanitizer stress and adaptive response of Escherichia coli O157:H7

The effect of sublethal exposure to peroxyacetic acid (PAA) sanitizer on adaptation to peroxidative stress and development of thermal cross-resistance was investigated in Escherichia coli O157:H7. Acute sublethal PAA sanitizer exposure was used to represent a contact scenario. Cultures were grown in Trypticase soy-yeast extract broth. Acute treatment cultures were pretreated with 0.1% PAA, then all cultures were challenged at either 80 mM H202 or 54 degrees C. Acute and peroxide control cultures showed substantially increased peroxidative tolerance (D80mM > 2 h) versus negative control cultures not exposed to sanitizer (D80mM = 0.19+/-0.03 h). The inactivation rate of the acetic acid control (D80mM = 0.21+/-0.05 h) was similar to the negative control rate. Acute (D54 degrees C = 0.55+/-0.07 h) cultures did not exhibit increased thermal resistance versus the control (D54 degrees C = 0.54+/-0.07 h). Thermal injury was determined as difference in D54 degrees C value (deltaD54 degrees c) obtained on pyruvate and deoxycholate media. Thermal-induced injury was not observed in either control (deltaD54 degrees C = 0.04 h) or acute (deltaD54 degrees C = 0.05 h) cultures.     

A fully bypassed six-issue integer datapath and register file on the Itanium-2 microprocessor

The six-issue integer datapath of the second-generation Itanium microprocessor is described. Pulse techniques enable a high-speed, 20-ported, 128-entry, 65 bit register file with only 12 wordlines per register. A four-stage operand bypass network achieves a fully bypassed design with operands sourced from 34 locations with 16 destinations. To control this network, over 280 bypass comparators are utilized. Using half a clock for execution and half a clock for bypass, each result is available for the next instruction. Functional units are pre-enabled, reducing power consumption by 15% while eliminating a stage of result mixing and improving performance. The part is fabricated in a six-layer 0.18 /spl mu/m process and operates at 1.0 GHz at 1.5 V, consuming less than 130 W in about 420 mm/sup 2/.     

Development of a Risk-Ranking Framework to Evaluate Potential High-Threat Microorganisms, Toxins, and Chemicals in Food

ABSTRACT:  Through a cooperative agreement with the U.S. Food and Drug Administration, the Institute of Food Technologists developed a risk-ranking framework prototype to enable comparison of microbiological and chemical hazards in foods and to assist policy makers, risk managers, risk analysts, and others in determining the relative public health impact of specific hazard–food combinations. The prototype is a bottom-up system based on assumptions that incorporate expert opinion/insight with a number of exposure and hazard-related risk criteria variables, which are propagated forward with food intake data to produce risk-ranking determinations. The prototype produces a semi-quantitative comparative assessment of food safety hazards and the impacts of hazard control measures. For a specific hazard–food combination the prototype can produce a single metric: a final risk value expressed as annual pseudo-disability adjusted life years (pDALY). The pDALY is a harmonization of the very different dose–response relationships observed for chemicals and microbes. The prototype was developed on 2 platforms, a web-based user interface and an Analytica® model (Lumina Decision Systems, Los Gatos, Calif., U.S.A.). Comprising visual basic language, the web-based platform facilitates data input and allows use concurrently from multiple locations. The Analytica model facilitates visualization of the logic flow, interrelationship of input and output variables, and calculations/algorithms comprising the prototype. A variety of sortable risk-ranking reports and summary information can be generated for hazard–food pairs, showing hazard and dose–response assumptions and data, per capita consumption by population group, and annual p-DALY.     

Emission characteristics of silicon vacuum triodes with fourdifferent gate geometries

Arrays of 10×10, 30×30, and 50×50 phosphorus-doped 0.005-0.025 Ω-cm, monocrystalline silicon field emitters have been fabricated with an emitter height of approximately 4.5 μm, a cone angle of 110°, and four gate openings ranging from 1.8 to 5.3 μm. The placement of the rims of the gates range from coplanar with the apexes of the emitters for the 1.8-μm devices to fully recessed for the 5.3-μm devices. The devices have been characterized in terms of geometry-dependent β factors, scaling of emission currents with array size, temperature dependency from room temperature to 48 K, pressure dependency from 2.5×10^-9 to 0.8×10^-5 torr, current fluctuations at room temperature and at 48 K, and image formation. All of the measurements have been performed by operating the devices in the gate-induced field emission mode     

Standardization of a method to determine the efficacy of sanitizers in inactivating human pathogenic microorganisms on raw fruits and vegetables.

The efficacy of sanitizers in killing human pathogenic microorganisms on a wide range of whole and fresh-cut fruits and vegetables has been studied extensively. Numerous challenge studies to determine the effects of storage conditions on survival and growth of pathogens on raw produce have also been reported. Results of these studies are often difficult to assess because of the lack of sufficient reporting of methods or, comparatively, because of variations in procedures for preparing and applying inocula to produce, conditions for treatment and storage, and procedures for enumerating pathogens. There is a need for a standard method to accurately determine the presence and populations of pathogenic microorganisms on produce. The adoption of standard, well-characterized reference strains would benefit a comparative assessment of a basic method among laboratories. A single protocol will not be suitable for all fruits and vegetables. Modifications of a basic method will be necessary to achieve maximum recovery of pathogens on various types of produce subjected to different sanitizer or storage treatments. This article discusses parameters that must be considered in the course of developing a basic standard method against which these modifications could be made.     

Hardware implementation of a `wired-once' neural net in thin-filmtechnology on a glass substrate

To prove the feasibility of implementing artificial neural networks on large inexpensive substrates, a net designed and fabricated on a glass wafer using hydrogenated-amorphous-silicon-based technology (a-Si:H) is discussed. The net functions as an autoassociative memory in which binary numbers corresponding to 28, 56, 112, and 224 are stored. Learning of the weight matrix is carried out with the associative memory algorithm using the delta rule. Phosphorus-doped microcrystalline silicon with a resistivity of 100 to 300 Ω-cm was used for the fabrication of the weight (synapse) resistors. Inverters with a beta of one were used to form negative-weight synapses, and inverters with a beta of 10 were used for the thresholding elements (neurons). The net functions surprisingly well; it filters both the learned numbers and some numbers of the form N=4k (with k an integer), and maps other random numbers to the closest one accepted, even though the experimental weight matrix is not identical to the theoretical one     

Atomically sharp silicon and metal field emitters

A method is described for forming atomically sharp silicon tips of less than 10-15° half-angle by utilizing a known oxidation inhibition at regions of high curvature; equally sharp silicon wedges are now made in a similar fashion. The sharp silicon tips serve as the starting point for forming sharp tips of W, β-W and gold. Field emission data from silicon emitters are compared with Fowler-Nordheim modelling and emission as a function of emitter-anode distance is described