Masayoshi Iwahara

Compatible solutes protect against chaotrope (ethanol)-induced, nonosmotic water stress.

ABSTRACT Water stress is one of the major stresses experienced by cellular systems and can take a number of distinct forms. In response to turgor-related osmotic stress, cells produce compatible solutes that are macromolecule protectants and also counteract the outflow of water from stressed cells. In this report we show that the germination of conidia of Aspergillus nidulans, a sensitive indicator of water stress, in the presence of ethanol is correlated with the intracellular concentration of the compatible solutes glycerol and erythritol, which protect against both osmotic and nonturgor forms of water stress.

Investigation of Printed Wiring Board Testing By Using Planar Coil Type ECT Probe

A new application of eddy current testing techniques for investigating trace defects on printed circuit boards is proposed. A test probe consisting of a meander type exciting coil is used to induce eddy currents. The following three experiments are conducted: measuring the induced signal when a circuit trace is cut; measuring the induced signal for a number of traces placed in parallel and with a cut in the centre trace; measuring the induced signal for two back to back right angle traces. The experimental results reveal that it is possible to clearly detect defects and that the signal response obtained is strongly associated with a particular defect pattern. The signals obtained from a high density patterned board have a complicated signal signature and are therefore difficult to interpret. This complexity can be avoided by comparing the signal signature of a known good board with a defective board. The difference signal gives a clear indication of a trace defect.

Built-in electrodialysis batch culture, a new approach to release of end product inhibition

Abstract Electrodialysis fermentation (ED-F) was carried out to study the kinetic analysis of the release of end product inhibition in l -lactate fermentation. The l -lactate was continuously extracted by a dialyzer as it was being produced, and removed from the culture system so that the l -lactate concentration in the broth was maintained at a level as low as about 10 g/ l . In spite of such a low concentration, however, the release of end product inhibition was not as great as the release level expected from the lactate concentration in the broth. In a culture with a low initial sugar concentration of 50 g/ l , the fermentation rate was not stimulated by electrodialysis, while the fermentation rate for ED-F at a high initial sugar concentration of 85 g/ l was stimulated, resulting in a reduction of the fermentation time. The reason for this contradiction was explained by computer simulation. It was assumed that the fermentation rate was regulated by the lactate concentration in the culture system, which has a concentration gradient across the cell membrane. The lactate gradient is greater in the early and the middle stages of batch culture, so the effect of dialysis did not develop at low initial sugar concentrations. The lactate gradient gradually became smaller as the fermentation proceeded, thus permitting the effect of dialysis to develop at high initial sugar concentrations. The kinetic analysis using computer simulation, and the fact that the lactate concentration calculated with kinetic data from ED-F agreed well with the lactate concentration observed, supported this assumption.

Modeling and control of a new horizontal-shaft hybrid-type magnetic bearing

This paper reports on the development of a new horizontal-shaft hybrid-type magnetic bearing system. The bearing system will be used for a horizontal-shaft machine. The rotor is levitated due to the repulsive force between a stator and a rotor permanent magnet (PM). A lower cost and higher radial stiffness have been achieved by using a strontium-ferrite magnet on the rotor and an Nd-Fe-B PM above and below the rotor magnet. A finite-element analysis was performed to calculate the levitation force and radial stiffness. An upper stator magnet subtending an angle of 45/spl deg/ provides the best compromise between a large levitation force and radial stiffness. A model for the horizontal-shaft hybrid magnetic bearing system has been developed and includes the effect of the rotor dynamics and the electromagnetic forces. An integral servocontroller was designed to stabilize the axial position. The controller has been implemented in a digital signal processor. Experimental results performed on a prototype system are in agreement with the theoretical results.

Eddy current testing probe composed of planar coils

This paper presents a new eddy-current probe composed of a micro-planar mesh coil and meander coil. The probe can be used to detect the existence and the size of cracks in metallic structures. Experimental results for the sensed output voltage of this device are presented. The output signal is shown to have a discrete nature. Also, the results show that the signal strength is weak and that an offset voltage exists. Improved probe characteristics are obtained by connecting two mesh coils in series, stacking the coils on top of each other and orienting the two coils 180/spl deg/ apart.

Eddy-current testing probe with spin-valve type GMR sensor for printed circuit board inspection

This paper proposes an eddy-current testing (ECT) probe composed of a spin-valve giant magnetoresistance (SV-GMR) sensor and a meander coil for the inspection of bare printed circuit board. The SV-GMR sensor serves as a magnetic sensor for the ECT probe to sense the variation of the magnetic field distribution occurred on the printed circuit board. The SV-GMR sensor is used specifically to detect the changing magnetic field distribution occurred at the defect point. The characteristics of the proposed probe are discussed in this paper. The comparisons of signal-to-noise ratios obtained from ECT probe with SV-GMR sensor and with solenoid coil verify that the applying of SV-GMR sensor to the ECT probe can improve the PCB inspection results.

Novel eddy current testing sensor for the inspection of printed circuit boards

This paper presents a novel eddy-current testing (ECT) sensor for the inspection of printed circuit board (PCB), which detects trace damages on PCB conductors. The sensor is composed of a meander-exciting coil and three solenoid pick-up coils. Application of three pick-up coils increases the speed of the inspection process. Information about defects can be extracted either from an amplitude or a phase of a signal obtained during the inspection. A visualization process was provided using the amplitude data. The structure of the ECT sensor and principles of detection, as well as experimental results, are presented.

Defect images by planar ECT probe of meander-mesh coils

This paper presents results pertaining to image data obtained from a planar meander-mesh coupled coil type ECT probe. The image data makes it possible to detect not only the existence of a defect but also to extract detailed information regarding the nature of the defect, such as its position, shape, length, and direction. In order to recognize a defect distinctly, we have fabricated the high sensitive planar coil which can be used to image a 2-D representation of the ECT signal. The relationships between the image pattern and defect shape are discussed.

Wavelet-based processing of ECT images for inspection of printed circuit board

This paper presents a wavelet-based image processing technique, which analyzes eddy-current testing (ECT) images derived by scanning printed circuit boards (PCBs) with an ECT probe and automatically detects the existence and location of the defect. First, the undesired components contained in probe output are removed through two types of wavelet filtering. Then the comparison of two images obtained from reference and tested PCBs are carried out to extract the signal due to the defect. In this paper, one-dimensional (1-D) wavelet is used only in the horizontal direction considering that the scanning of the probe is along that direction. In addition, the square norm of difference between original and processed signal is proposed as a criterion to keep the waveform of the defect peak as possible. The application examples of sample PCBs reveal the effectiveness and problems of the given approach.

A novel compact magnetic current limiter for three phase applications

The fabrication and development of a novel compact three phase magnetic current limiter consisting of permanent magnets (PM) and saturable cores is described in this paper. Simulation results using the tableau approach are presented for varying operating conditions. Experimental results are in good agreement with the simulation results. The proposed current limiter has potential in moderately low voltage applications.