Processing of diamond-particle-dispersed silver-matrix composites in solid–liquid co-existent state by SPS and their thermal conductivity

Diamond-particle-dispersed silver (Ag) matrix composite was fabricated in a unique fabrication method, where solid–liquid coexistent state of the powder mixture of diamond, pure Ag and pure Si was designed to create during spark plasma sintering (SPS) process. The composite is well consolidated in a temperature range between 1113 K and 1188 K and no reaction was detected by scanning electron microscopy at the interface between diamond particles and the Ag matrix. The relative packing density of the diamond–Ag composite fabricated was 95–97% in a volume fraction range of diamond between 40% and 50%. The thermal conductivity of the diamond–Ag composite containing 50 vol.% (v/o) diamond reached 717 W/mK, approximately 80% the theoretical thermal conductivity calculated by Maxwell–Eucken’s equation. This result suggests that the solid–liquid co-existent state during SPS consolidation is very effective not only for rapid densification of the composite but also for producing strong bonding between the diamond particles and the Ag matrix.     

Scanning tunnelling microscopy imaging of symmetry-breaking structural distortion in the bismuth-based cuprate superconductors

A complicating factor in unravelling the theory of high-temperature (high-T(c)) superconductivity is the presence of a 'pseudogap' in the density of states, the origin of which has been debated since its discovery. Some believe the pseudogap is a broken symmetry state distinct from superconductivity, whereas others believe it arises from short-range correlations without symmetry breaking. A number of broken symmetries have been imaged and identified with the pseudogap state, but it remains crucial to disentangle any electronic symmetry breaking from the pre-existing structural symmetry of the crystal. We use scanning tunnelling microscopy to observe an orthorhombic structural distortion across the cuprate superconducting Bi(2)Sr(2)Ca(n-1)Cu(n)O(2n+4+x) (BSCCO) family tree, which breaks two-dimensional inversion symmetry in the surface BiO layer. Although this inversion-symmetry-breaking structure can impact electronic measurements, we show from its insensitivity to temperature, magnetic field and doping, that it cannot be the long-sought pseudogap state. To detect this picometre-scale variation in lattice structure, we have implemented a new algorithm that will serve as a powerful tool in the search for broken symmetry electronic states in cuprates, as well as in other materials.     

Target cattle age of post-slaughter testing for bovine spongiform encephalopathy and infectivity entering the human food chain in Japan

A model of possible outcomes of bovine spongiform encephalopathy (BSE)-infected cattle in Japan was constructed, and the expected proportion of BSE-infected cattle entering the human food chain and the expected infectivity remaining in edible meat per capita by breed variety and sex were calculated, while changing target ages of BSE testing. As widely accepted, BSE testing for all ages could reduce the proportion of infected cattle entering the human food chain and their infectivity. It was especially effective among female dairy cattle, but the resulting reduction was quite limited. The effectiveness of BSE testing on food safety hardly differs between the target age of 21 months and all ages.     

Zel’dovich-Starobinsky Effect in Atomic Bose-Einstein Condensates: Analogy to Kerr Black Hole

We consider circular motion of a heavy object in an atomic Bose-Einstein condensate (BEC) at T=0 K. Even if the linear velocity of the object is smaller than the Landau critical velocity, the object may radiate quasiparticles and thus experience the quantum friction. The radiation process is similar to Zel’dovich-Starobinsky (ZS) effect—the radiation by a rotating black hole. This analogy emerges when one introduces the effective acoustic metric for quasiparticles. In the rotating frame this metric has an ergosurface, which is similar to the ergosurface in the metric of a rotating black hole. In a finite size BEC, the quasiparticle creation takes place when the ergosurface is within the condensate and occurs via quantum tunneling from the object into the ergoregion. The dependence of the radiation rate on the position of the ergosurface is investigated.      

Heterogeneous nucleation of hydroxyapatite on protein: structural effect of silk sericin.

Acidic proteins play an important role during mineral formation in biological systems, but the mechanism of mineral formation is far from understood. In this paper, we report on the relationship between the structure of a protein and hydroxyapatite deposition under biomimetic conditions. Sericin, a type of silk protein, was adopted as a suitable protein for studying structural effect on hydroxyapatite deposition, since it forms a hydroxyapatite layer on its surface in a metastable calcium phosphate solution, and its structure has been reported. Sericin effectively induced hydroxyapatite nucleation when it has high molecular weight and a beta sheet structure. This indicates that the specific structure of a protein can effectively induce heterogeneous nucleation of hydroxyapatite in a biomimetic solution, i.e. a metastable calcium phosphate solution. This finding is useful in understanding biomineralization, as well as for the design of organic polymers that can effectively induce hydroxyapatite nucleation.     

Biochemical and molecular biological analyses of space-flown nematodes in Japan, the first international caenorhabditis elegans experiment (ICE-First)

The first International Caenorhabditis elegans Experiment (ICE-First) was carried out using a Russian Soyuz spacecraft from April 19–30, 2004. This experiment was apart of the program of the DELTA (Dutch Expedition for Life science Technology and Atmospheric research) mission, and the space agencies that participate in the International Space Station (ISS) program formed international research teams. A Japanese research team that conducted by Japan aerospace Exploration Agency (JAXA) investigated the following aspects of the organism: (1) whether meiotic chromosomal dynamics and apoptosis in the germ cells were normal under microgravity conditions, (2) the effect of the space flight on muscle cell development, and (3) the effect of the space flight on protein aggregation. In this article, we summarize the results of these biochemical and molecular biological analyses.     

Porous poly(<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide) gels polymerized in mixed solvents of water and <Emphasis Type="Italic">N,N</Emphasis>-dimethylformamide

The structures of gels polymerized using a mixed solvent that induces cononsolvency during the free radical polymerization were investigated.N,N -isopropylacrylamide (NIPA) gels were polymerized in water and N,N-dimethylformamide (DMF) mixtures. The NIPA gels can have homogeneous/heterogeneous structures depending on the mole fraction of DMF, x_D. The NIPA gel synthesized at x_D = ca. 0.25 was opaque in appearance, and its porous structure was observed by the SEM micrograph; the porous structure is formed as the aggregates of microgels phase-separated due to the cononsolvency. The porous NIPA gels achieve a very rapid shrinking rate in response to the temperature jump, which are desirable for their applications.     

Anomalous dissolution property enhancement of naringenin from spray-dried particles with α-glucosylhesperidin

Spray-dried particles were prepared with α-glucosyl hesperidin (Hsp-G), a hesperidin derivative with enhanced water solubility, to improve the solubility profile of naringenin (NRG). Naringenin was used as a model hydrophobic polyphenol. The spray-dried sample of NRG in the presence of Hsp-G formed 3–4 μm spherical particles. Those particles showed a halo pattern in powder X-ray diffractometry, indicating the amorphous state of NRG in the solid dispersion with Hsp-G. Interestingly, the obtained powders dissolved immediately into the aqueous media and demonstrated dramatically high apparent solubility, over 60-fold greater than NRG crystals, when the loading ratio of NRG/Hsp-G was 1/20. The apparent solubility of NRG increased in proportion to the amount of Hsp-G loaded (R² > 0.99). These results suggested that a specific molecular interaction, a micelle-like structure in which NRG was incorporated with Hsp-G molecules, was formed in spray-dried particles, resulting in the anomalous enhancement in the solubility of NRG.     

Penetration of Escherichia coli O157:H7 into lettuce as influenced by modified atmosphere and temperature.

The effects of temperature and atmospheric oxygen concentration on the respiration rate of iceberg lettuce and Escherichia coli O157:H7 cells attachment to and penetration into damaged lettuce tissues were evaluated. Respiration rate of lettuce decreased as the temperature was reduced from 37 to 10 degrees C. Reducing the temperature further to 4 degrees C did not affect the respiration rate of lettuce. Respiration rate was also reduced by lowering the atmospheric oxygen concentration. Lettuce was submerged in E. coli O157:H7 inoculum at 4, 10, 22, or 37 degrees C under 21 or 2.7% oxygen. Attachment and penetration of E. coli O157:H7 were not related to the respiration rate. The greatest numbers of E. coli O157:H7 cells attached to damaged lettuce tissues at 22 degrees C at both oxygen concentrations. More cells were attached under 21% oxygen than under 2.7% oxygen at each temperature, but this difference was small. Penetration of E. coli O157:H7 into lettuce tissue was determined by immunostaining with a fluorescein isothiocyanate-labeled antibody. Under 21% oxygen, E. coli O157:H7 cells showed greatest penetration when lettuce was held at 4 degrees C, compared to 10, 22. or 37 degrees C, and were detected at an average of 101 microm below the surfaces of cut tissues. However, under 2.7% oxygen, there were no differences in degree of penetration among four incubation temperatures. The degree of E. coli O157:H7 penetration into lettuce tissue at 4 or 22 degrees C was greater under 21% oxygen than under 2.7% oxygen; however, no difference was observed at 37 degrees C. Conditions that promote pathogen penetration into tissue could decrease the effectiveness of decontamination treatments.     

Confocal microscopy and microbial viability detection for food research.

Confocal microscopy offers several advantages over other conventional microscopic techniques as a tool for studying the interaction of bacteria with food and the role of food microstructure in product quality and safety. When using confocal microscopy, samples can be observed without extensive preparation processes, which allows for the evaluation of food without introducing artifacts. In addition, observations can be made in three dimensions without physically sectioning the specimen. The confocal microscope can be used to follow changes over a period of time, such as the development of the food structure or changes in microbial population during a process. Microbial attachment to and detachment from food and food contact surfaces with complex three-dimensional (3-D) structures can be observed in situ. The fate of microbial populations in food system depends on processing, distribution, and storage conditions as well as decontamination procedures that are applied to inactivate and remove them. The ability to determine the physiological status of microorganisms without disrupting their physical relationship with a food system can be useful for determining the means by which microorganisms survive decontamination treatments. Conventional culturing techniques can detect viable cells; however, these techniques lack the ability to locate viable cells in respect to the microscopic structures of food. Various microscopic methods take advantage of physiological changes in bacterial cells that are associated with the viability to assess the physiologic status of individual cells while retaining the ability to locate the cell within a food tissue system. This paper reviews the application of confocal microscopy in food research and direct observation of viable bacteria with emphasis on their use in food microbiology.