The polymerase chain reaction: Applications for the detection of foodborne pathogens

Faster methods for the detection of foodborne microbial pathogens are needed. The polymerase chain reaction (PCR) can amplify specific segments of DNA and is used to detect and identify bacterial genes responsible for causing diseases in humans. The major features and requirements for the PCR are described along with a number of important variations. A considerable number of PCR‐based assays have been developed, but they have been applied most often to clinical and environmental samples and more rarely for the detection of foodborne microorganisms. Much of the difficulty in implementing PCR for the analysis of food samples lies in the problems encountered during the preparation of template DNAs from food matrices; a variety of approaches and considerations are examined. PCR methods developed for the detection and identification of particular bacteria, viruses, and parasites found in foods are described and discussed, and the major features of these reactions are summarized.     

A note on the lactation performance of twin-bearing cows

Seven pairs of cows were chosen at parturition. In each pair, 1 member had had a twin pregnancy (T) and the other was a comparable cow with a single calf pregnancy (S). All cows were offered the same amount of feed over the first 28 weeks of lactation. In early lactation, intakes were equal; in mid-lactation the T group ate more. The T cows had a lower peak yield of milk than the S cows, but rates of decline in yield in mid-lactation were equal for the 2 groups. Lactose concentrations in the milk were equal throughout lactation, but the fat and protein concentrations were greater for the T group in early lactation. The T group yielded smaller amounts of milk solids. The T group lost less weight in early lactation and gained more weight subsequently. Three of the T group, but only 1 of the S group, did not conceive during the test lactation.     

Avalanche multiplication characteristics ofAl0.8Ga0.2As diodes

The avalanche multiplication characteristics of Al_0.8Ga _0.2As have been investigated in a series of p-i-n and n-i-p diodes with i-region widths, w, varying from 1 μm to 0.025 μm. The electron ionization coefficient, α, is found to be consistently higher than the hole ionization coefficient, β, over the entire range of electric fields investigated. By contrast with Al_xGa _1-xAs (x⩽0.6) a significant difference between the electron and hole initiated multiplication characteristics of very thin Al_0.8Ga_0.2As diodes (w=0.025 μm) was observed. Dead space effects in the diodes with w⩽0.1 μm were found to reduce the multiplication at low bias below the values predicted from bulk ionization coefficients. Effective α and β that are independent of w have been deduced from measurements and are able to reproduce accurately the multiplication characteristics of diodes with w⩾0.1 μm and breakdown voltages of all diodes with good accuracy. By performing a simple correction for the dead space, the multiplication characteristics of even thinner diodes were also predicted with reasonable accuracy     

An efficient algorithm for the three-dimensional analysis ofpassive microstrip components and discontinuities for microwave andmillimeter-wave integrated circuits

A numerical technique for the full-wave analysis of shielded, passive microstrip components on a two-layer substrate is presented. The distinct feature of the technique is an efficient formulation for establishing the system matrix in the moment method procedure which allows the derivation of the elements of any large matrix by a linear combination of elements in a precomputed index table. The table is obtained from a two-dimensional discrete fast Fourier transform. In the moment method procedure, the two-dimensional surface current is represented by locally defined rooftop functions. The effect of the resonant modes associated with the metallic enclosure on the numerical procedure is examined. In order to demonstrate the features and the accuracy of the technique, numerical results for a microstrip open end and for a right-angle bend with and without the compensated corner are computed by using the resonant technique and are compared with other published computational and experimental data     

The natural food grade inhibitor, lacticin 3147, reduced the incidence of mastitis after experimental challenge with Streptococcus dysgalactiae in nonlactating dairy cows.

Lacticin 3147 is a broad-spectrum bacteriocin produced by the food-grade organism Lactococcus lactis. Lacticin 3147 is active at a neutral pH and has been shown to be bactericidal to streptococci and staphylococci in vitro. The effectiveness of an intramammary teat seal formulation, and a teat seal containing lacticin 3147 was evaluated at drying off in 68 uninfected quarters of 18 cows. Following infusion of either teat seal or lacticin 3147 combined with teat seal, a deliberate infection challenge of Streptococcus dysgalactiae (approximately equal to 1.5 x 10(4) cfu per teat) was administered by direct inoculation into the teat sinus. During an 8-d experimental period following inoculation, 61% of control quarters and 6% of the treatment quarters either developed clinical mastitis or were shedding the challenge organism. Randomly amplified polymorphic DNA polymerase chain reaction genetic typing was used to confirm that both the new infections and the bacteria surviving in the teats at the end of the experiment were the challenge strain. The combination of teat seal and lacticin 3147 was well tolerated within the udder and elicited only a temporary increase in somatic cell count to 5.7 x 10(5)/ml (88 h after infusion) in a previously uninfected lactating udder quarter. Therefore, we concluded that this nonantibiotic approach to mastitis prevention may contribute to a reduction in the routine application of antibiotics at drying off in the future.     

利用视频套件加速FPGA上的视频开发

处理器友好型视频开发的新方法,无须VHDL或Verilog知识即可生成高度优化的结果 随着下一代视频压缩标准问世,行业从基本视频处理向更复杂的集成处理解决方案转移,达使得系统的要求超越了独立DSP力所能及的视频性能.FPGA以不到30美元的价格提供20GMACs以上的DSP性能,从而为成本敏感型军事、汽车、医疗、消费、工业和安全应用填补了这一空白.只有FPGA能够为整套端对端视频解决方案提供逻辑、嵌入式处理、OS支持和驱动器.     

Attack Vulnerability of Complex Communication Networks

The Internet has been studied as a typical example of real-world complex networks. In this brief, we study the traffic performance of the Internet when it encounters a random or intentional attack. Different from previous approaches, the congestion control protocols are considered so that the bandwidth can be reallocated among flows. In this way, cascading breakdown is less likely to happen. The flow rates are adjusted when a node is attacked and out of function. Consequently, the traffic utility and the utilization ratio of bandwidth are affected. We compare the real Internet data with the classic random graph and scale-free network models. The simulated results also show that the ldquorobust yet fragilerdquo property previously observed in the study of cascading failures in the scale-free networks is still valid in this scenario.     

Optimal construction of synchronizable coding for railway trackcircuit data transmission

A new application using synchronizable error-control coding for train detection and track-train data transmission with audio frequency railway track circuits is described, with algorithms for quasi-optimal code construction and performance assessment. A new coding format is presented for frequency-shift-keying-modulated track circuits with which a fixed-duration-message telegram is transmitted. Only two-track-circuit separation frequencies are required, and although there exists a maximum rate of transmission for a given track-circuit parameter set, the data transmission capability is in general limited only by the telegram length. The problem addressed is that of assigning codes within the message to satisfy target safety and reliability criteria. The proposed telegram-type code comprises a synchronization sequence followed by message data bits arranged as three blocks and terminated by error-control bits with a final parity check. Data encoding is by conventional Hamming codes. Several hundred messages are available for typical track-circuit parameter sets     

Propagation along a two-wire line located at the air-Earthinterface

A simple quasi-static expression for the propagation constant of a two-wire transmission line located at the air-Earth interface is derived. A numerical solution of the mode equation shows that the quasi-static approximation is valid when the wire separation is much less than a free-space wavelength. The quasi-static approximation can be used to determine the complex dielectric constant of the Earth from measurements of either the propagation constant or the characteristic impedance of the transmission line     

A Study of Permittivity Measurement Reproducibility Utilizing the Agilent 4291B

In the analysis and design of electrical package and printed circuit board structures, engineers frequently rely on measured values of relative permittivity (epsiv_r). Typically, these measurements are performed using off-the-shelf instruments provided by a range of manufacturers. One instrument that is commonly used for measuring epsiv_r over the 1 MHz-1 GHz range is the Agilent 4291B. Using this instrument and Agilent's associated dielectric measurement fixture, a study of epsiv_r measurement reproducibility was performed. This study included five trained operators measuring nine material samples over three days. The material samples included both stacked and unstacked materials, hard and soft materials, and thin and thick materials. With this study, it was possible to estimate the ability of a typical laboratory to reproduce measurements of dielectric constant. In this case, our study showed that the Agilent 4291B system can be used by multiple operators and at different times to measure samples of ABF and FR5 to tolerances between 6% and 12%. Results for other material samples and measurement frequency effects are discussed