Application of polymerase chain reaction for the correlation of Salmonella serovars recovered from greyhound feces with their diet

The polymerase chain reaction was employed to correlate Salmonella serovars isolated from fecal material of greyhounds suffering from gastroenteritis with those isolated from the diet fed to the greyhounds prior to onset of diarrhea. Kennels around the Abilene, Kansas, area were contacted and supplied with materials needed to collect a portion of the diet each day. With the onset of diarrhea, the kennels were instructed to ship the fecal material and diet from the previous 10 days to the laboratory for testing. Forty-one fecal samples and corresponding diets were screened for Salmonella, Clostridium perfringens, Campylobacter jejuni, Staphylococcus aureus, Staphylococcus intermedius, and pathogenic (piliated) Escherichia coli by direct culture using standard procedures. The fecal material was also screened for coronavirus and parvovirus using electron microscopy. Thirty-five "normal" fecal samples were screened for all of the above mentioned microorganisms as a control. In addition, the fecal material was screened for E. coli verotoxins I and II and clostridial enterotoxins. A total of 61 Salmonella isolates were recovered from the 41 samples of feces and diet submitted for testing; 31 were recovered from the feces and 30 from the diet. Four Salmonella isolates were recovered from the normal fecal samples. Results obtained by PCR, plasmid profiles, antigenic analysis, and antibiogram profiles indicated that 16 of the 31 isolates recovered from the fecal material were the same strain as that recovered from the diet.     

Machine vision applied to vehicle guidance

Research on the semiautonomous operation of mobile robots in typical pathways is described. The image of the pathway will consist of two nearly vertical lines bounding a region with little texture (the pathway) after correction for perspective. In order to identify pathway boundaries, regions in the image space are examined using an edge detection algorithm, edges between regions are determined by the algorithm, and those corresponding to straight or nearly straight lines with large slope (path boundaries) are identified by means of the Hough transform. Once the path boundaries are identified, the horizontal distance from camera to road edge is determined. Next, a method to detect cubics in the roadway (i.e., obstacles) is presented. The region of interest in the roadway (from the camera to some predetermined distance in front of it) is known from the path boundary algorithm. The interior of this region is examined for edges. If edges are detected, it means that obstacles or shadows are present. A method to separate obstacles from shadows using stere vision is then presented.     

Influence of Pluronic coating formulation on iron oxide nanoparticle transport in natural and oil-impacted sandy aquifer media

Targeted delivery of nanoparticles has the potential to enhance remediation and characterization of sites contaminated with non-aqueous phase liquids (NAPLs) by ensuring delivery of treatment or contrast agents to the NAPL/water interface. For a targeted delivery technique to be successful, nanoparticles must be capable of transporting through porous media and binding to NAPLs under relevant geological conditions. In this study, successful targeted delivery of nanoparticles to sandy aquifer material mixed with crude oil was achieved using an active targeting technique based on an amphiphilic polymer coating. It was determined that the molecular structure and concentration of the nanoparticle coating greatly influenced the recovery of nanoparticles injected into saturated columns. Coatings with longer polymer molecules and lower polymer concentrations reduced recovery, and the nanoparticle coating formulation could be adjusted to improve transport while maintaining targeted binding behaviour. This study demonstrated that nanoparticle retention in oil-impacted sand exceeded that of clean sand in flow through experiments, indicating that a nanoparticle targeted delivery strategy for soil contaminated with LNAPLs such as crude oil is possible under the experimental conditions explored.     

A theoretical model for single-phase silicon-controlled rectifier systems

A linear model for use in determining stability, relative stability, and dynamic response of phase-angle modulated SCR systems is presented. The model is based on sampled-data control theory and assumes 1) a system bandwidth that is small relative to sampling frequency, and 2) limited excursion of the SCR triggering angle. These assumptions are justified for practical systems. The theory leads to a simple equivalent transport-lag representation. If the triggering angle varies over a relatively wide range, a "worst-case" analysis is necessary using the linear model. An example is included to illustrate use of the model for system design and is supported by experimental data.     

E-商务-改变公司营销的途径

电子商务在商业贸易中逐渐被人们认识并接受，在信息时代高速发展的今天，其作用愈来愈明显、重要。     

A multilayered self-organizing artificial neural network forinvariant pattern recognition

An artificial neural network that self-organizes to recognize various images presented as a training set is described. One application of the network uses multiple functionally disjoint stages to provide pattern recognition that is invariant to translations of the object in the image plane. The general form of the network uses three stages that perform the functionally disjoint tasks of preprocessing, invariance, and recognition. The preprocessing stage is a single layer of processing elements that performs dynamic thresholding and intensity scaling. The invariance stage is a multilayered connectionist implementation of a modified Walsh-Hadamard transform used for generating an invariant representation of the image. The recognition stage is a multilayered self-organizing neural network that learns to recognize the representation of the input image generated by the invariance stage. The network can successfully self-organize to recognize objects without regard to the location of the object in the image field and has some resistance to noise and distortions     

Simulations of a ring resonator free-electron laser

A relatively high gain (≈25 to 40%) free-electron laser (FEL) with an optical ring resonator is simulated using the code FELEX. The laser system corresponds to the `burst mode' FEL. The ring consists of paraboloids, grazing incidence hyperboloids, and a grating rhomb. The wiggler is 5 m in length and has an adjustable taper, while the electron beam is produced by an RF linac. The optical elements of the ring together with the FEL interaction in the wiggler are modeled in three spatial dimensions to investigate the system from start-up to saturation. Both single-frequency and finite-pulse simulations are performed     

An experimental printed circuit board drilling system automated by pattern recognition

The two-dimensional image processing necessary for closed-loop control of automated printed circuit board drilling and a mechanical prototype capable of drilling simulated printed-circuit boards are described. A single closed-loop correction of position permits correction of errors introduced by vidicon camera positional nonlinearity, noise, irregular lighting, inaccuracy of transformational constants, and mechanical slippage. These errors are corrected to an acceptable degree and in a short enough time that automatic drilling may present a challenge to manual drilling labor costs.