Tri-axial sensors and actuators made of a single piezoelectric cylindrical shell

Electromechanical transducers for sensing and actuating disturbances or vibrations have been used in many fields of applications. There have been transducers of different configuration developed for the unidirectional transduction. This paper demonstrates a single element transducer for tri-axial components made of a piezoelectric cylindrical shell. The separation of the tri-axial transductions is achieved by devising a proper electrode arrangement. The structure and the fundamental idea are first presented, and then the numerical analysis by means of the finite element modeling follows, and their characteristics and behaviors are then experimentally verified.     

Application of gene gun for local-regional cancer

We studied the in vivo gene transfusion using a gene gun, formerly used in plants and culture cells. The hand-held type gene gun (Helios Gene Gun System) is simple and convenient for effective gene transfection in living animals. This method has some advantages in that there is no need for use of viral vector, independence on the cell cycle and local inducement of plural genes. There is a great possibility for application to local-regional cancer.     

Electromagnetic shielding of HF lamps using wire structures:simulation and measurement

High-frequency (HF) operated lamps, such as HF fluorescent lamps, have several advantages over conventional ones but they contaminate the environment with their EM field emissions. The shielding of the electromagnetic emission should be realized without much effect on the emission of the light. Enclosing the lamps in a housing made of widely spaced thin wires could be an appropriate way to shield the electromagnetic field. The paper studies the effectiveness of some wire structures for shielding the electromagnetic emission from HF fluorescent lamps. An analytical study, method of moments (MoM), and measurements have been carried out to evaluate the strength of the near-field and the shielding effectiveness of the structures     

Right atrial contractile performance in patients with myocardial infarction

To evaluate right atrial (RA) contractile performance in patients with myocardial infarction, we validated a cineangiographic method of RA volume measurement, and investigated RA volume change in 'normal' individuals and patients with a previous myocardial infarction. Sixteen silicone rubber RA casts made from human cadavers were filmed in the postero-anterior and left lateral projections. The cast volumes calculated following Simpson's rule were in good agreement with those measured by water replacement (r = 0.992, P < 0.01). At cardiac catheterization, biplane RA cineangiography was performed in 19 'normal' individuals (N group), in 14 patients with a previous antero-septal infarction (AMI group) and in seven patients with a previous inferior infarction (IMI group). The RA volume-time curve was constructed at 20-40 ms intervals for one cardiac cycle. RA volume at the beginning of the atrial contraction (RAVd), which was defined as the 'preload' of the RA, tended to be larger in both the AMI and IMI groups compared with 'normal' individuals. The RA ejection volume was significantly larger in both the AMI (18.4 +/- 2.1 ml.m-2, P < 0.01) and IMI groups (19.4 +/- 2.8, P < 0.01) than in the N group (14.5 +/- 1.9), even for a comparable level of RAVd (range from 26 to 36 ml.m-2) (18.6 +/- 2.1, P < 0.01, 18.2 +/- 2.0, P < 0.01, 14.7 +/- 1.9, respectively). These results suggest that RA contraction increases in patients with myocardial infarction by increasing both the 'preload' and 'contractility' of the RA.     

Time-dependent deformation in an enhanced SiC/SiC composite

Time-dependent deformation in an enhanced SiC/SiC composite has been studied under constant load at high temperatures of 1200 °C, 1300 °C, and 1400 °C. Creep damage evolution was evaluated by a Young’s-modulus change of partial unloading and microscopic observation. The addition of the glassy phase in the matrix is very effective for protecting the composite from oxidation. The transient creep is dominant in creep life at all the temperatures. An empirical equation is proposed to describe creep behavior of the composite. It is found that creep activation energy increases with creep time at stresses lower than matrix cracking stress, but the activation energy remains constant at stresses higher than the matrix cracking stress. The creep strain rate of the composite is considered to be controlled by creep of fibers based on examining the time, strain, stress, and temperature dependencies of creep strain rates.     

Pixel design of pulsed CMOS image sensor for retinal prosthesis with digital photosensitivity control

A newly designed pulse frequency modulation photosensor for use in retinal prosthesis is proposed and demonstrated. The pixel converts the intensity of incident light into biphasic current pulses at frequencies suitable for the electrical stimulation of retinal neurons. Experimental results showed that the device was sensitive over a dynamic range of input light of about 120 dB, and that photosensitivity could be varied from 0 dB to around -40 dB.     

Development of a new advanced process for manufacturing polyacetal resins. Part III. End-capping during polymerization for manufacturing acetal homopolymer and copolymer

Conventionally, acetal homopolymer or copolymer is obtained by the polymerization of formaldehyde or trioxane, following the end-capping using acetic anhydride or unzipping of the unstable polymer end fraction. First, Asahi Chemical developed a new process to obtain an end-capped polymer during polymerization of highly purified formaldehyde using acetic anhydride as the chain-transfer agent. Use of highly purified formaldehyde and endcapping during polymerization using acetic anhydride as a chain-transfer agent or an endcapping agent will provide a simple process for manufacturing acetal homopolymer. The polymerization mechanism was confirmed by infrared spectroscopy analysis and proton NMR analysis of the polymer obtained. Second, for the acetal copolymer, purified trioxane was copolymerized with ethylene oxide in the presence of methylal, which gave an endcapped polymer with high thermal stability. Two new intermediates from the initiation reaction of the copolymerization, 1,3,5,7-tetraoxacyclononane (TOCN) and 1,3,5,7,10-pentaoxacyclododecane (POCD), were isolated and a new initiation mechanism was proposed. © 1993 John Wiley & Sons, Inc.     

A wide-bandwidth low-noise InGaAsP-InAlAs superlattice avalanchephotodiode with a flip-chip structure for wavelengths of 1.3 and 1.55μm

The authors reports the fabrication of a flip-chip InGaAsP-InAlAs superlattice avalanche photodiode using gas source molecular beam epitaxy. The incident light reaches the InGaAs photoabsorption layer through the InP substrate and an InGaAsP-InAlAs superlattice multiplication region which are transparent for wavelengths of 1.55 and 1.3 μm. The light reflection by the electrode enables the absorption layer to be as thin as 0.8 μm without significantly reducing the quantum efficiency. A maximum bandwidth of 17 GHz was obtained at a low multiplication factor because the transit time through the absorption layer is reduced