Low acoustic attenuation silicone rubber lens for medical ultrasonic array probe

Effects of heavy density (p = 9.2 x 10³ kg/m³) Yb²O³ fine dopant (16 nm in diameter) on the acoustic properties of a high-temperature-vulcanization (HTV) silicone rubber have been investigated, to develop a new acoustic lens material with a low acoustic attenuation (alpha) for the medical array probe application. The HTV silicone rubber has advantages in that it shows a lower alpha than that of a room-temperature-vulcanization (RTV) silicone rubber and it can be mixed by applying shear stress, using roll-milling equipment. Roll-milling time dependence of the HTV silicone rubber indicates that the alpha is closely affected by the dispersion of nanopowders in the rubber matrix. The 8 vol% Yb²O³-doped HTV silicone rubber mixed for 30 min showed the lowest alpha of 0.73 dB/mmMHz with an acoustic impedance [AI = sound speed (c) times density (p)] of 1.43 times 106 kg/m²s at 37degC. Moreover, simulation results reveal that a 5 MHz linear probe using the HTV silicone rubber doped with Yb²O³ powder showed relative sensitivity around 2.6 to 3.0 dB higher than a probe using RTV silicone rubber doped with Yb²O³ powder or SiO²-doped conventional silicone rubber for the ultrasonic medical application.     

Child restraint seat use behavior and attitude among Japanese mothers

OBJECTIVES: The purpose of the study was to assess associations between child restraint seat use and attitudes among Japanese mothers. MATERIALS AND METHODS: Mothers whose children were under 6 years of age were recruited through 11 kindergartens located in Kanagawa prefecture, Japan. Questions were developed based on the Health Belief Model and the Theory of Reasoned Action. Past use and future intentions to use, perceived risk of injury, knowledge of safety, attitudes toward use, subjective norms, and safety values related to safety seats were asked. RESULTS: A total of 552 complete questionnaires was obtained. Of 500 car owning households, 54.2% used child restraint seats inconsistently on short drives, and 36.4% did so on long drives. Three variables were associated with inconsistent use on short drives: frequent child resistance to sitting in a restraint seat; mothers' feeling hassled by child restraint seat use; and, mothers' agreement with the lack of need to use a restraint seat when another adult is in a car. Two variables were associated with inconsistent use on long drives: lower subjective norm of husband and frequent child resistance. CONCLUSIONS: In-car environmental modification and parent education need to be considered to increase child restraint seat use among Japanese households.     

Torsional Oscillator measurements of multiply connected monolayer 4He films under high speed rotation up to 4.0 rev./s

No Heading We are studying the physical phenomena of superfluid thin films adsorbed on multiply connected surface of porous glasses under high speed rotation. The combination of thin superfluid ⁴He films on large pore porous surfaces and high-speed rotation gives rise to a new quantum vortex excitation, where vortex lines are pinned on the center of pores and have the core at the pore. This excitation has been predicted and named as a pore vortex. We are trying to measure the behavior of pore vortices using the Torsional Oscillator (TO) technique and we have succeeded in making measurements up to the high-speed rotation of 4.0 rev./s. Here we report the actual design of the TO set up.PACS numbers: 67.40.Vs, 67.57.Fg, 67.70+n, 67.40.Rp.     

A series of double disruptants for protein phosphatase genes in Saccharomyces cerevisiae and their phenotypic analysis

Thirty-two protein phosphatase (PPase) genes were identified in Saccharomyces cerevisiae based on the nucleotide sequences of the entire genome. In an effort to understand the role of PPases and their functional redundancy in the cellular physiology of one of the reference eukaryotic organisms, a series of single and double PPase gene disruptants were constructed in the W303 strain background. Two single disruptants for the CDC14 and GLC7 genes were lethal. Double disruptants for 30 non-essential PPase genes were constructed in all possible 435 combinations. No double disruptant showed synthetic lethality. Several phenotypes of the viable 30 single and 435 double disruptants were examined; temperature-sensitive growth, utilization of carbon sources and sensitivity to cations and drugs. Four double disruptants exhibited synthetic phenotypes in addition to eight single ones: the pph21 pph22 double disruptant showed slow growth on complete medium, as did the sit4 and yvh1 single ones. In addition to the ptc1, ynr022c and ycr079w single disruptants, the ppz1 ppz2 double disruptant showed temperature-sensitive slow growth. The msg5 ptp2 double disruptant, like the ynr022c single one, did not grow on complete medium containing 0.3 M CaCl(2). The double msg5 ptc2 disruptant failed to grow on medium containing 1.0 M NaCl and, like the ynr022c single deletion, also could not grow on medium containing 0.3 M CaCl(2). The synthetic phenotypes in the two latter cases where each of the PPases is categorized in a different phosphatase family led us to discuss the novel mechanism involved in the functional redundancy of the PPases.     

Discrepancy in bicycle helmet use among college students between two bicycle use purposes: Commuting and recreation

Objectives

The purpose of the study was to examine associations between bicycle helmet use and attitudes among U.S. college students. Bicycle helmet use was assessed for two different bicycle use purposes: commuting to school and recreation.

Materials and methods

Student bicycle riders were recruited on the campus of a large public university in Colorado. Questionnaire development was guided by the Theory of Reasoned Action and Health Belief Model. Bicycle use and helmet use for the two purposes, attitudes toward helmet use and bicycle helmet regulations on campus, perceived risk of bicycle-related injury, subjective norms were asked. Bicycle helmet use was defined by current behaviors and intentions for the future, based on the Stages of Change model.

Results

A total of 192 questionnaires collected from students who rode bicycles for both commuting and recreation was used for the analysis. Bicycle helmet use differed depending on purposes of bicycle riding: 9.4% of bicycle riders wore bicycle helmets every time for commuting, while 36.5% did so for recreation. Different variables were associated with bicycle helmet use for commuting and recreation in logistic regression models, suggesting that psychosocial structures behind bicycle helmet use behaviors might differ between two bicycle use purposes, commuting and recreation.     

Energy‐saving house utilizing photovoltaic system

To study the efficient use of the housing and photovoltaic, we constructed housing which has adequate airtightness, adequate heat insulating efficiency, concrete floors, multiple window glasses for seasonal weather changes, and much more safety. We built a house in which two people can live (160 m²) and which needs only 4.9 kW of energy. We did data analysis while they were actually living there. As a result, we could create a comfortable environment in which to live, keeping the temperature in summer between 28.5 and 30 °C and the humidity 50% (moisture removal) and the temperature in winter between 22 and 24 °C and the humidity 50% (moisture addition). Because overdrying of the air was restricted, dew condensation was prevented. Of 4240 kWh, 2940 kWh (70%) became surplus electric power and the rest (30%) was consumed for a comfortable living environment. It was demonstrated that we could save 42% of electric power expenses compared with that of general housing (4‐person household, 160 m²) and that we could reduce by more than 60% the cooling and heating capacity. © 2000 Scripta Technica, Electr Eng Jpn, 130(4): 45–57, 2000     

Spectrum analysis and vector representation of SRAM bit failures

We present a method for analyzing several common cell failures in SRAM's, i.e., failures caused by defects produced during VLSI processing. Faults, in 64 k-bit CMOS SRAM's with six-transistor type cells used in this study, are classified in terms of the number of faulty cells. Single-cell and adjacent cell faults, which are dominant, are due to blocked contact holes, aluminum 1 short-circuit defects and blocked via holes. A vector plot showing the relation between single-cell and adjacent-cell failure probabilities suggests that blocked contact holes, aluminum 1 short-circuit defects, and blocked via holes can be isolated. This vector representation is useful in monitoring and improving fabrication yields of VLSI circuits. Vector representations are also given for three and four-cell failure probabilities     

Semiconductor thermoelectric-energy conversion systems working at low temperature differences

The present thermoelectric semiconductor integrated into the commercially available thermoelectric units are not designed elaborately for low temperature difference operation. Those elements available in the room-temperature range are usually applicable for the temperature difference around 60 K with relatively poor coefficient of performance. For air-conditioning purposes, it is expected that the thermoelectric energy conversion will have a high coefficient of performance as well as economical advantage because of the low temperature difference operation. This paper describes basic and analytical considerations for low temperature-difference operation, and also the new design systems desired from viewpoints of the effective and economical use of environmental energy. An appropriate design allows a drastic economy in the material and also a drastic improvement in the coefficient of performance, and it is possible to put the material, with the presently available figure of merit, in practical use. The availability of a simple cascade connection is discussed for the operation under some increased temperature difference. The concept of the cooling or heating systems using thermoelectric units driven by a solar-cell array will also be proposed and experimental results will be illustrated.     

Effects of fine metal oxide particle dopant on the acoustic properties of silicone rubber lens for medical array probe

The effects of fine metal oxide particles, particularly those of high-density elements (7.7 to 9.7 x 10(3) kg/m3), on the acoustic properties of silicone rubber have been investigated in order to develop an acoustic lens with a low acoustic attenuation. Silicone rubber doped with Yb2O3 powder having nanoparticle size of 16 nm showed a lower acoustic attenuation than silicone rubber doped with powders of CeO2, Bi2O3, Lu2O3 and HfO2. The silicone rubber doped with Yb2O3 powder showed a sound speed of 0.88 km/s, an acoustic impedance of 1.35 x 10(6) kg/m2s, an acoustic attenuation of 0.93 dB/mmMHz, and a Shore A hardness of 55 at 37 degrees C. Although typical silicone rubber doped with SiO2 (2.6 x 10(3) kg/m3) shows a sound speed of about 1.00 km/s, heavy metal oxide particles decreased the sound velocities to lower than 0.93 km/s. Therefore, an acoustic lens of silicone rubber doped with Yb2O3 powder provides increased sensitivity because it realizes a thinner acoustic lens than is conventionally used due to its low sound speed. Moreover, it has an advantage in that a focus point is not changed when the acoustic lens is pressed to a human body due to its reasonable hardness.