Development of a Cherenkov light imaging system for studying the dynamics of radiocesium in plants

High-resolution images of radiocesium (¹³⁷Cs) distribution are required to study cesium kinetics in plants. A Cherenkov light imaging system can visualize fine distributions of radionuclides emitting beta particles using an optical camera. To evaluate the linearity of the system, an imaging test was performed with point sources of ¹³⁷Cs, with a radioactivity of 10–2000 kBq. The results indicated that the system has a good linearity between the image intensity and the radioactivity of ¹³⁷Cs. We developed an imaging system for plants using this system to study radiocesium movement in intact plants. To demonstrate the ability to image radiocesium in a plant, an experiment was performed with an intact soybean plant for four days. The root of an 11-day-old soybean plant was dipped in 20 mL of a culture solution containing ¹³⁷Cs with a radioactivity of 10 MBq without potassium. After one day, the solution was replaced with one with potassium but no ¹³⁷Cs. The soybean plant was in healthy condition in the system, and the high-resolution serial images indicated that ¹³⁷Cs was transported to the shoot and accumulated in the node. Therefore, Cherenkov light imaging is promising for imaging radiocesium in intact plants.     

Efficacy of acidified sodium chlorite treatments in reducing Escherichia coli O157:H7 on Chinese cabbage

Efficacy of acidified sodium chlorite for reducing the population of Escherichia coli O157:H7 pathogens on Chinese cabbage leaves was evaluated. Washing leaves with distilled water could reduce the population of E. coli O157:H7 by approximately 1.0 log CFU/g, whereas treating with acidified chlorite solution could reduce the population by 3.0 log CFU/g without changing the leaf color. A similar level of reduction was achieved by washing with sodium chlorite solution containing various organic acids. However, acidified sodium chlorite in combination with a mild heat treatment reduced the population by approximately 4.0 log CFU/g without affecting the color, but it softened the leaves. Moreover, the efficacy of the washing treatment was similar at low (4 degrees C) and room (25 degrees C) temperatures, indicating that acidified sodium chloride solution could be useful as a sanitizer for surface washing of fresh produce.     

Effectiveness of irradiation treatments in inactivating Listeria monocytogenes on fresh vegetables at refrigeration temperature

Ionizing radiation can be effective in controlling the growth of food spoilage and foodborne pathogenic bacteria. This study reports on an investigation of the effectiveness of irradiation treatment to eliminate Listeria monocytogenes on laboratory-inoculated broccoli, cabbage, tomatoes, and mung bean sprouts. Irradiation of broccoli and mung bean sprouts at 1.0 kGy resulted in reductions of approximately 4.88 and 4.57 log CFU/g, respectively, of a five-strain cocktail of L. monocytogenes. Reductions of approximately 5.25 and 4.14 log CFU/g were found with cabbage and tomato, respectively, at a similar dose. The appearance, color, texture, taste, and overall acceptability did not undergo significant changes after 7 days of postirradiation storage at 4 degrees C, in comparison with control samples. Therefore, low-dose ionizing radiation treatment could be an effective method for eliminating L. monocytogenes on fresh and fresh-cut produce.     

Effect of Impurity and Pretreatment Conditions on the Catalytic Activity of Au Powder for CO Oxidation

Recent X-ray photoelectron spectrometer(XPS) analysis of Au powder synthesized by evaporating high purity gold metal (> 99. 99%) in an inert gas detected impurity metals such as Ag and In at levels which far exceed those expected from the impurity levels of raw gold metal. Several samples of Au powder containing different amount of impurity metals were prepared to examine whether the activity of the Au powder for CO oxidation depends upon the impurity or not. The activity of the powder showed a strong correlation with the surface concentration of Ag.     

Thermogravimetry of wood treated with water-insoluble retardants and a proposal for development of fire-retardant wood materials

The combustion of wood and methods for the fire retardacy of wood are reviewed briefly first, and then a study on thermogravimetry (TG) and derivative thermogravimetry (DTG) of water-insoluble retardants and wood treated with retardants is presented. In the review of the flaming combustion of wood supported by cellulose, three categories of fire-retardant methods, namely (1) chemical modification of the wood pyrolysis, (2) inhibition of the flaming combustion in the gas phase, and (3) thermal effects to restrain the increase in the temperature of wood and assumed temperature profiles in the heated wood are described. The results of TG and DTG, discussed in terms of kinetics, indicate three kinds of action of the retardant tested: (1) acceleration of dehydration and carbonization, (2) thermal stabilization of the chemical structure of cellulose, and (3) inhibition of the flaming combustion by halogen products. In conclusion, models of fire-retardant wood materials for interior and exterior use are proposed, which contain retardants for the dehydration and the stabilization in the outer layer and those for the inhibition in the inner layer, respectively.     

A circuit technology for sub-10-ns ECL 4-Mb BiCMOS DRAM's

The feasibility of realizing an emitter-coupled-logic (ECL) interface 4-Mb dynamic RAM (DRAM) with an access time under 10 ns using 0.3-μm technology is explored, and a deep submicrometer BiCMOS VLSI using this technology is proposed. Five aspects of such a DRAM are covered. They are the internal power supply voltage scheme using on-chip voltage limiters, an ECL DRAM address buffer with a reset function and level converter, a current source for address buffers compensated for device parameter fluctuation, an overdrive rewrite amplifier for realizing a fast cycle time, and double-stage current sensing for the main amplifier and output buffer. Using these circuit techniques, an access time of 7.8 ns is expected with a supply current of 198 mA at a 16-ns cycle time     

A long-term evaluation of a Bj?rk-Shiley valve prosthesis--eighteen year follow-up

We evaluated the long-term (18 years) results in 356 patients undergoing valve replacement with Bj?rk-Shiley valve prosthesis (aortic, 212; mitral 120; double valve, 24) between 1970 and 1988. Actuarial survival rates of AVR and MVR were 90% (18 years) and 98% (8 years) respectively. Actuarial event free rates (including valve failure, thromboembolism, reoperation and prosthetic valve endocarditis) were 82% (18 years) for AVR and 95% (8 years) for MVR. There were no significant differences among spherical disc, convexo-concave disc and monostrut valve in actuarial survival rates and actuarial event free rates. In conclusion, this study demonstrated that Bj?rk-Shiley valve showed a low incidence of postoperative events. These results endorse our choice of the Bj?rk-Shiley valve prosthesis.