Significance of the detection of staphylococcal enterotoxin A gene in low fat milk which caused a serious outbreak of food poisoning

In June 2000, there was a large-scale outbreak of food poisoning after consumption of Snow Brand low fat milk. In the evening of a day the incident made public, some cartons of low fat milk were brought to our laboratory for examination. Next day, we detected only staphylococcal enterotoxin (SE) A gene among SE (A-E) genes by PCR in left-over milk samples or samples from the same lots that patients had consumed. We presumed that the outbreak was caused by the intake of SEA. We subsequently confirmed the presence of SEA in these samples. To investigate the existence of SE (A-E) genes in milk, we examined 100 samples of commercial low fat milk and milk by PCR, but none of the genes was detected. We estimated the detection limit of SEA gene in low fat milk by PCR. Four strains of SEA-producing Staphylococcus aureus cultures were serially diluted in low fat milk. The SEA gene was detected at levels of 5.5 x 10(2) to 1.6 x 10(4) cfu/mL of S. aureus. These amounts of S. aureus are higher than the values in raw milk reported previously. Therefore we consider that SE genes in low fat milk should usually be undetectable by our PCR. This study shows that quick detection of SE genes by PCR is very helpful to analyze outbreaks, especially if no significant bacterium can be cultured.     

Parallel processing of an object space for image synthesis using ray tracing

This paper presents a novel parallel processing system for image synthesis using ray tracing. An object space is divided into parts (subspaces), each of which is allocated to a processor. The processor detects, simultaneously the intersections of the surfaces of each object and a fixed number of rays over the whole space, and calculates the local intensity on an object in each subspace. The global intensities of pixels on a screen are calculated by the other kind of processors simultaneously. We also present the optimal data structure, based on an adaptive division algorithm, for parallel processing of the object space.     

Fatigue crack growth behavior of Sn-Pb and Sn-based lead-free solders

Solder alloys of lead-rich composition have been commonly used as joining materials in electronic package. However, because of environmental concerns, lead-free solders will replace lead-rich solders more and more in the future. The fatigue characteristics of the solders used are most important in assessing the reliability of joints in electronic packaging. In the present study, the fatigue crack growth (FCG) behavior of a wide variety of solders of both lead-rich and lead-free types has been investigated under a range of mean stresses and frequencies. Both time dependent and time independent (cyclic dependent) behaviors were observed. In the cyclic dependent crack growth regime, the FCG rates could be expressed as a function of either ΔK_eff or ΔJ. Further, the lead-free solders were found to have a higher resistance to FCG than did the lead-rich solders. In the time dependent crack growth regime, the FCG rates were found to be a function of C∗. The point of transition between time dependent and time independent behavior was found to depend on the homologous temperature and strength of the alloys.     

Cryo-transfer TEM study of vacancy cluster formation in thin films of aluminum and copper elongated at low temperature

Kiritani et al. encountered a large number of vacancy clusters in heavily deformed thin metal films at room temperature. In the present work, thin films of aluminum and copper were loaded to fracture in liquid nitrogen and transferred directly to the TEM without warming up (Cryo-transfer TEM). In thin films of Al and Cu deformed at 78 K, many defect clusters were observed at 120 K. In thin Al films, small defect clusters disappeared by the 120 keV electron irradiation. Upon isochronal annealing, some of the dislocation loops grew in their size, which is much larger than those observed at 120 K. However, in regions that were not exposed to electron irradiation at 120 K, only a large number of stacking fault tetrahedra were observed after room temperature annealing. In copper, the 200 keV electron beam did not significantly change the defect clusters observed at 120 K.     

A new shear technique: Semi Continuous Shear Flow (SCSF) in medium and ultra high molecular weight Polyhydroxybutyrate blends

In MMWT/UHMWT PHB blends (99.5/0.5), (99/1), (98/2) and (97/3) we demonstrate that by applying our new shear technique, “semi continuous shear flow”, copious fibre formation is guaranteed, irrespective of the ultra high molecular weight composition. The shishes formed via this technique are extremely stable being able to maintain their stability for at least 5–10 min. When this technique was applied to MMWT/UHMWT PHB blends of compositions (95/5), (90/10) and (85/15) disorientated fibres were observed in the flow direction. On increasing the UHMWT component, distinct unordered and intertwining of fibres resulted and with severe shearing orientation occurred, however shish formation was limited. We propose the optimum conditions for shish formation and the critical molecular weight necessary for entanglement.     

The Creep and Thermal Stability Characteristics of a Unidirectionally Solidified Al2O3/YAG Eutectic Composite

Compressive creep characteristics at 1773, 1873, and 1973 K, oxidation resistance over 1000 h at a temperature of 1973 K in ambient air, and the thermal stability characteristics at 1973 K in ambient air of a unidirectionally solidified Al2O3/YAG eutectic composite were evaluated. At a test temperature of 1873 K and a strain rate of 10–4/s, the compressive creep strength of a eutectic composite manufactured by the unidirectional solidification method is approximately 13 times higher than that of a sintered composite with the same chemical composition. The insite eutectic composite also showed greater thermal stability, with no change in mass after an exposure of 1000 hours at 1973 K in ambient air. The superior high-temperature characteristics are closely related to such factors as (1) the in-situ eutectic composite having a microstructure, in which single crystal Al2O3 and single crystal YAG are three-dimensionally and continuously connected and finely entangled without grain boundaries and (2) no amorphous phase is formed at the interface between the Al2O3 and the YAG phases.     

Parameter estimation of radiocardiogram using a minicomputer

Radiocardiography has been widely used as a method for the quantification of cardiac output by applying the principle of the dye dilution method. This paper deals with an automatic analyzing system of radiocardiograms and a parameter estimation procedure using a linear system made up of four compartments with two time delays as a model of transport process in the blood circulatory system. The parameter estimation procedure named the window method in frequency domain is very effective for shortening the computing time and can be easily performed using a minicomputer. Parameter sensitivity analysis is also applied to study behavior of parameters on the model. Some analyzed results of radiocardiograms are shown and it is verified that the procedure is sufficiently useful and efficient for routine clinical use.     

The crystallization and formation of cluster of ethylene ionomer during physical aging

The effect of the physical aging of ethylene ionomers was studied for the samples with the acid content of 5.4 mol%, and the degree of neutralization, 0%, 60% Na, 60% Zn, and 90% Zn. The information about the crystal and the cluster part of the physically aged ionomers was obtained by differential scanning calorimetry and by dynamic viscoelastic measurements, respectively. The degree of crystallinity and the dynamic modulus for the ionomers of the degree of neutralization 0%, 60% Na and 60% Zn increased gradually with the aging time; on the other hand, the crystallinity of 90% Zn remained constant and the modulus at 100°C increased to a certain value up to a period of 100 h, but thereafter the crystallinity increased remarkably and the modulus remained. These facts indicate that the crystallization of neutralized ethylene ionomer starts after clustering and the clustering would finish at early stage of the physical aging for intermediately neutralized ethylene ionomer. The physical aging effect of the ethylene ionomers was, thus, found to be important to material design.