Studies on the pathogenesis and survival of different culture forms of Listeria monocytogenes to pulsed UV-light irradiation after exposure to mild-food processing stresses

The effects of mild conventional food-processing conditions on Listeria monocytogenes survival to pulsed UV (PUV) irradiation and virulence-associated characteristics were investigated. Specifically, this study describes the inability of 10 strains representative of 3 different culture forms or morphotypes of L. monocytogenes to adapt to normally lethal levels of PUV-irradiation after exposure to sub-lethal concentrations of salt (7.5% (w/v) NaCl for 1 h), acid (pH 5.5 for 1 h), heating (48 °C for 1 h) or PUV (UV dose 0.08 μJ/cm(2)). Findings showed that the order of increasing sensitivity of L. monocytogenes of non-adapted and stressed morphotypes to low pH (pH 3.5 for 5 h, adjusted with lactic), high salt (17.5% w/v NaCl for 5 h), heating (60 °C for 1 h) and PUV-irradiation (100 pulses at 7.2 J and 12.8 J, equivalent to UV doses of 2.7 and 8.4 μJ/cm(2) respectively) was typical wild-type smooth (S/WT), atypical filamentous rough (FR) and atypical multiple-cell-chain (MCR) variants. Exposure of L. monocytogenes cells to sub-lethal acid, salt or heating conditions resulted in similar or increased susceptibility to PUV treatments. Only prior exposure to mild heat stressing significantly enhanced invasion of Caco-2 cells, whereas subjection of L. monocytogenes cells to combined sub-lethal salt, acid and heating conditions produced the greatest reduction in invasiveness. Implications of these findings are discussed. This constitutes the first study to show that pre-exposure to mild conventional food-processing stresses enhances sensitivity of different culture morphotypes of L. monocytogenes to PUV, which is growing in popularity as an alternative or complementary approach for decontamination in the food environment.     

Acid-insoluble ash as a marker compound for use in digestibility studies with humans

The study aimed to evaluate acid-insoluble ash, in the form of added celite (a diatomaceous earth), as an indigestible marker compound for use in digestibility studies with humans. The study comprised two parts. First, the recovery of dietary acid-insoluble ash in the faeces was determined in a controlled 10-day metabolism study involving five 6-week-old male pigs receiving food consisting of ingredients commonly eaten by humans. Secondly, the faecal recovery of dietary acid-insoluble ash was determined with six adult humans following a set diet which maintained their normal levels of daily food intake for 7 days. The mean (±SE) recoveries of dietary acid-insoluble ash in the faeces of the pigs and human subjects were 90·0 (±2·24) and 92·1 (±4·59)%, respectively. The mean apparent faecal digestibility coefficients for dietary dry matter were not significantly different (P > 0·05) when determined by total faeces collection or by reference to the marker, in both species. It was concluded that celite is a potentially useful dietary marker compound for use in human digestibility studies involving collection of faeces. The marker was readily accepted by the human subjects and can be determined chemically using simple gravimetric analysis.     

Electron cyclotron emission diagnostic for ITER

Electron temperature measurements and electron thermal transport inferences will be critical to the nonactive and deuterium phases of ITER operation and will take on added importance during the alpha heating phase. The diagnostic must meet stringent criteria on spatial coverage and spatial resolution during full field operation. During the early phases of operation, it must operate equally well at half field. The key to the diagnostic is the front end design. It consists of a quasioptical antenna and a pair of calibration sources. The radial resolution of the diagnostic is less than 0.06 m. The spatial coverage extends at least from the core to the separatrix with first harmonic O-mode being used for the core and second harmonic X-mode being used for the pedestal. The instrumentation used for the core measurement at full field can be used for detection at half field by changing the detected polarization. Intermediate fields are accessible. The electron cyclotron emission systems require in situ calibration, which is provided by a novel hot calibration source. The critical component for the hot calibration source, the emissive surface, has been successfully tested. A prototype hot calibration source has been designed, making use of extensive thermal and mechanical modeling.     

An integrated charge exchange recombination spectroscopy/beam emission spectroscopy diagnostic for Alcator C-Mod tokamak

A novel integrated charge exchange recombination spectroscopy (CXRS)/beam emission spectroscopy (BES) system is proposed for C-Mod, in which both measurements are taken from a shared viewing geometry. The supplementary BES system serves to quantify local beam densities and supplants the common calculation of beam attenuation. The new system employs two optical viewing arrays, 20 poloidal and 22 toroidal channels. A dichroic filter splits the light between two spectrometers operating at different wavelengths for impurity ion and beam neutrals emission. In this arrangement, the impurity density is inferred from the electron density, measured BES and CXRS spectral radiances, and atomic emission rates.     

Photolithographic patterning of conducting polyaniline films via flash welding

In this work, two significant advances in photolithographic patterning of polyaniline (PANI) films are reported. Firstly, flash welding was enhanced through the use of polymeric substrates, enabling complete penetration of the welding of PANI films with thicknesses ranging from 5 to over 14 μm, significantly thicker than reported previously. Masking of parts of the PANI films during flash welding enabled the formation of adjacent conducting and insulating regions as the welding changes the electrical properties of the film. Raman spectroscopy was used to determine the sharpness of these edges, and indicated that the interface between the flash welded and masked regions of the PANI films was typically less than 15 μm wide. Secondly, using longpass filters, light with a wavelength less than 570 nm was found not to contribute to the welding process. This was confirmed by the use of a 635 nm laser diode for welding the PANI films. This novel approach enabled patterning of PANI films using a direct writing technique with a narrow wavelength light source.     

声色饕餮——解析创新X-Fi音频处理器

上期为大家介绍了X-Fi的前瞻。随着X-Fi同我们的日益临近,本期我们将深入X-Fi处理器,为大家解析这一期待已久的音频处理器的新特性。规格分析下面先来看看X-Fi的芯片规格。可说X-Fi芯片的制造工艺都已达到了目前CPU和GPU的水平。与目前顶级的GPU相比,下面的规格表也许不会让你太吃惊,但你要记得X-Fi可     

Effect of enalapril therapy on left ventricular mass and volumes in asymptomatic chronic, severe mitral regurgitation secondary to mitral valve prolapse

Pleomorphic xanthoastrocytoma (PXA) is a rare cerebral tumor of young adults with a slow growth and a good prognosis. Due to its peculiar histopathological findings, the tumor resemble to the lytic phase of progressive multifocal leukoencephalopathy (PML), a JC Virus (JCV) induced disease. For these reasons, the presence of JCV genoma and viral particles were searched for by means of nested polymerase chain reaction (nPCR) and electron microscopy (EM) in a 9-year-old child with PXA. Although EM did not reveal any viral particles, nPCR did reveal genomic sequences of the LT, R, and VP1 regions of JCV. Sequence analysis showed that the R region was mutated with respect to the archetypal form thus yielding the Mad 4 variant of JCV previously reported as being oncogenic in animals. We suggest that JCV may have played a role in the development of this tumor.     

现代服务器平台介绍——CPU篇

随着互联网络全球化的步代,大到广域的主干网络,小到公司部门的局城网络,现代服务器的任务越来越繁重。服务器要完成大型数据库的检索任务,要支持百万人的同时在线访问,要执行大量的科学运算,更要求服务器24小时不间断的稳定工作。因此对服务器品质的要求越来越高。本文将详细介绍包括Intel的Itanium、HP的PA8700、Alpha、MIPS、SUN公司的UltraSPARC还有IBM的Power4等世界顶级的服务器技术。     

Pulsed electric field inactivation of spoilage microorganisms in alcoholic beverages

In recent years, a number of new applications have emerged where pulsed power is being used in the treatment of waste and effluent, foodstuffs and beverages. One of these emerging applications is pulsed electric field (PEF) inactivation of microorganisms in liquid media. This involves the generation of electric fields of the order of 30 kV/cm across liquids contaminated with microorganisms. This induces a relatively large transmembrane potential that can lead to irreversible electroporation and consequently cell lysis. The nature of the PEF pulse profile is the subject of extensive study, and it has been reported that bipolar square waves provide superior inactivation when compared to monopolar pulses. A previous study, however, has challenged this view, and results will be presented demonstrating that more effective inactivation of bacteria can be achieved using the monopolar pulse. Results will also be given on the effect of monopolar pulse PEF applied to alcoholic beverages containing known spoilage microorganisms. This will highlight an apparent synergistic inactivation effect when microorganisms in alcoholic beverages are exposed to PEF.     

Supramolecular command surfaces for liquid crystal alignment

Devices based on liquid crystal display technology, ranging from watches to flat panel displays, have proliferated over the past few decades and can now be found in all conceivable aspects of everyday life. It is surprising that a crucial part in the construction of such displays, namely the alignment layer, which dictates the surface alignment of mesogenic molecules, relies essentially on a mechanical rubbing process which was invented 100 years ago. In this paper, recent developments in the construction of alignment layers (also called command layers) based on the self‐assembly of molecular and macromolecular components are discussed. Two topics are highlighted: (i) tuneable layers formed by hierarchical assembly of siloxane oligomers and phthalocyanine dyes on indium‐tin‐oxide surfaces and (ii) command layers formed by self‐assembly of porphyrin trimers. Copyright © 2007 Society of Chemical Industry