EFFECT OF CHILLING AND FREEZING ON SURVIVAL OF VIBRIO PARAHAEMOLYTICUS ON FISH FILLETS1

Vibrio parahaemolyticus is a foodborne pathogen isolated from coastal waters of the United States, and from seafoods including fish. No information is available on the viability of V. parahaemolyticus on raw, chilled and frozen fish. A three‐strain mixture of V. parahaemolyticus was inoculated on fish fillets (pH 6.4) to obtain a bacterial load of 10⁴ (high) or 10³ (low) CFU/fillet, and stored at 4C or 8C for 9 days or at – 18C for seven weeks. At 4C and 8C, and at both levels of inoculation, V. parahaemolyticus survived on the fillets for the entire duration of the study. However, there was a significant reduction (P < 0.01) in V. parahaemolyticus population on the fillets by 9 days of storage. In the frozen fillets, there was a sharp decline (P < 0.01) in the population of V. parahaemolyticus by day 5 of storage. Although chilling and freezing significantly (P < 0.01) inactivated high numbers of V. parahaemolyticus on fish, they cannot be relied upon as a method to reduce V. parahaemolyticus on fish, since the time and magnitude of reduction depends on the initial load of the pathogen and the storage temperature.     

化学镀Ni-P-Cr2O3和Ni-P-SiO2复合镀层的研究

本文对化学镀镍及化学镀镍磷基质中SiO2与Cr2O3的共沉积进行了研究.微粒在不断生长的膜层中共沉积引起了新的化学复合镀层的出现,这些复合镀层许多都具有优异的耐磨及耐蚀性能.通过选取镀层合金/复合微粒/金属基体的组分可改进镀层,获得所需的性能,以满足特别的需求.在对这些复合镀层的应用需求正在迫近与增长的同时,其市场正在迅速扩张.本文开发出了一种合适的复合化学镀镍液,并通过维氏硬度法对化学复合镀镍层进行了表征.采用动电位极化及交流阻抗法测定了镀层的Taber耐磨性能及耐蚀性能.采用SEM及XRD对复合镀层的表面形貌进行了分析.     

A variable speed light chopper using a feedback controlled DC motor

A variable speed mechanical light chopper having a chopping frequency range from 10 to 2000 Hz using two chopping blades is described. A small DC motor whose speed can be varied ten fold was used and its speed was maintained constant by feedback control. The chopper has better than 0.l per cent stability and negligible temperature drift. The circuit is simple, inexpensive, and reliable.     

Study of Friction and Transfer Layer Formation in Copper-Steel Tribo-System: Role of Surface Texture and Roughness Parameters

In the present investigation, experiments were conducted on a tribological couple—copper pin against steel plate—using an inclined pin-on-plate sliding tester to understand the role of surface texture and roughness parameters of the plate on the coefficient friction and transfer layer formation. Two surface characteristics of the steel plates—roughness and texture–were varied in the tests. It was observed that the transfer layer formation and the coefficient of friction along with its two components, namely, the adhesion and plowing, are controlled by the surface texture of the plate. The plowing component of friction was highest for the surface texture that promotes plane strain conditions while it was lowest for the texture that favors plane stress conditions at the interface. Dimensionless quantifiable roughness parameters were formulated to describe the degree of plowing and hence the plane strain/stress type deformations taking place at the asperity level.     

Synthesis,growth, optical,mechanical and electrical properties of <Emphasis Type="Italic">L</Emphasis>-lysine <Emphasis Type="Italic">L</Emphasis>-lysinium dichloride nitrate (<Emphasis Type="Italic">L</Emphasis>-LLDN) single crystal

Semi-organic nonlinear optical material, L-lysine L-lysinium dichloride nitrate (2C₆H₁₅N₂O₂⁺_{2}^{+} · H⁺ · NO₃^-_{3}^{-} · 2Cl⁻) was synthesized at room temperature. Single crystals of L-LLDN were grown by slow cooling solution growth technique. The grown crystal was confirmed by powder X-ray diffraction analysis. The crystalline perfection of the grown single crystal was characterized by high-resolution X-ray diffraction (HRXRD) studies. The cut-off wavelength was determined by UV-vis transmission spectral analysis. The frequency doubling of the grown crystal was confirmed by powder second harmonic generation (SHG) measurement. The refractive index and birefringence of the crystal were determined using He–Ne laser source. Mechanical property of the crystal was determined by Vickers hardness tester. The frequency and temperature dependence of dielectric constant (ε _r), dielectric loss (tan δ) and a.c. conductivity (σ _ac) were also measured.     

Multiple mechanisms controlling fatigue crack growth

Recognizing that fatigue is a two‐parameter problem requiring two load parameters to define cyclic loads unambiguously, a unified approach has been developed to account for crack growth behaviour in terms of ΔK and K_max . Since both driving forces govern the crack growth rate, any analysis based on either ΔK or K_max will provide only partial information about the fatigue behavior of materials. It is shown that ΔK–K_max plots and the associated crack growth trajectory maps reflect the basic mechanisms that contribute to crack growth in a material. These plots also provide a convenient basis to recognize the changes in the micromechanisms that can occur as a function of load ratio or crack growth rate, or both. Taking examples from the literature, crack growth trajectory maps are provided showing such changes in the governing mechanisms of crack growth. It is shown that the ΔK–K_max approach is not an alternative to crack closure models, but it reflects the intrinsic material behaviour that must be understood before reliable crack prediction models can be developed.     

基于运动矢量细化的帧率上变换与HEVC结合的视频压缩算法

将帧率变换技术与新型视频压缩编码标准HEVC相结合有利于提升视频的压缩效率。针对直接利用HEVC码流信息中的低帧率视频的运动矢量进行帧率上变换时效果不理想的问题,文中提出了一种基于运动矢量细化的帧率上变换与HEVC结合的视频压缩算法。首先,在编码端对原始视频进行抽帧,降低视频帧率;其次,对低帧率视频进行HEVC编解码;然后,在解码端与从HEVC码流中提取出的运动矢量相结合,利用前向-后向联合运动估计对其进行进一步的细化,使细化后的运动矢量更加接近于对象的真实运动;最后,利用基于运动补偿的帧率上变换技术将视频序列恢复至原始帧率。实验结果表明,与HEVC标准相比,所提算法在同等视频质量下可节省一定的码率。同时,与其他算法相比,在节省码率相同的情况下,所提算法重建视频的PSNR值平均可提升0.5 dB。     

HEAT INACTIVATION OF ESCHERICHIA COLI 0157:H7 IN APPLE CIDER IN THE PRESENCE OF GLYCEROL MONOLAURATE AND A SYNTHETIC ANTIMICROBIAL PEPTIDE, PR-26

The effect of moderate temperatures in combination with glycerol monolaurate and an antimicrobial peptide, PR-26 on E. coli 0157:H7 in apple cider was determined. A five-strain mixture of E. coli 0157:H7 was inoculated into apple cider (pH 3.53) containing 0.01% PR-26 or 0.02% glycerol monolaurate or a combination of 0.01% PR-26 and 0.02% glycerol monolaurate. The apple cider was incubated at 40, 45 or 50C for 30 s, 5 min, 10 min, and 15 min. At each of the specified time intervals, the surviving population of E. coli 0157:H7 was determined. At all the three temperatures, there was no significant difference (P > 0.05) between the E. coli 0157:H7 populations of the control and the treatment containing PR-26. However, the treatments containing glycerol monolaurate alone or combination of glycerol monolaurate and PR-26 resulted in significant reductions (P < 0.05) in E. coli 0157:H7 counts. Results indicate that addition of glycerol monolaurate (0.02%) to apple cider and heating at 50C for 5 min can reduce E. coli 0157:H7 by 5.0 log CFU/mL.     

Effect of solvent on formation characteristics of sol-gel aluminium titanate

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

Development and characterization of new phosphorus based flame retardant tetraglycidyl epoxy nanocomposites for aerospace application

A study was made in the present investigation on the development and characterization of triphenyl phosphine oxide based phosphorus tetraglycidyl epoxy nanocomposites denoted as ??C?? and to find out its suitability for use in high performance applications. The synthesized resin was characterized by Fourier transform infrared spectra (FT?CIR) and ¹H, ¹³C nuclear magnetic resonance (NMR) spectra. Nanoclay and POSS-amine nano-reinforcements denoted as N1 and N2 were incorporated into the synthesized epoxy resin. Curing was done with diaminodiphenylmethane (DDM) and bis(3-aminophenyl) phenylphosphine oxide (BAPPO) curing agents denoted as X and Y, respectively. Mechanical, thermal, flame retardant, water absorption behaviour and electrical properties of the epoxy nanocomposites were studied and the results are discussed.