Youichirou Iwashita

Application to Vacuum Gauge of Marx's Composite Oscillator Method

By automated Marxs composite oscillator method, changes of internal friction with the pressure of nitrogen, oxygen, and argon were measured. The range of the measurement was from a pressure of 103 mbar to 10-5 mbar. An application to a wide range vacuum gauge was discussed.

Overtone-Drive in Marx's Composite Oscillator Method

We developed Marxs composite oscillator method to an automatic control system to keep the strain amplitude constant at fundamental and third overtone frequency. Stability of this control system is analyzed by an automatic control theory in the measurement of internal friction with varying strain amplitude, temperature, and external field. It is applied to measurement of a relaxation peak at a fundamental frequency of 50 kHz and overtone 150 kHz of the same specimen to study the relaxation process of AgCl.

Image of Ion Beam Excited Acoustic Microscope of the Teeth

The ion beam excited acoustic microscope (IAM) is a new microscope which provides visual representations of the elastic waves caused by localized chopping ion energy. Topographs and images of ultrasonic attenuation and local elastic variation were obtained by measuring frequency and amplitude at a composite resonant point between transducer and sample. Acoustic images of the teeth were measured by IAM. The elasticity of the hydroxyapatite crystal of the teeth was examined.

Ion Beam Excited Acoustic Image and Specific Element Image of Teeth

The ion beam excited acoustic microscope (IAM) is a new microscope which provides visual representations of the elastic waves caused by localized chopping ion energy. Topographs of ultrasonic attenuation and local elastic variations were obtained by measuring frequency and amplitude at a composite resonant point between transducer and sample. Specific ion images were also obtained from the same measurement. In this paper, the IAM and observed topographs and intensity modulated images of the specific ions are described. The elasticity of the hydroxyapatite crystal of the teeth is examined.

Interpretation of distant focal accumulations revealed by bone scintigraphy using Tc-99m HMDP in patients with oral malignant tumors

ObjectiveFocal accumulations in the skeleton were analyzed in order evaluate the usefulness of bone scintigraphy in the detection of distant skeletal metatases originating from malignant oral tumors.Study designOf 350 patients who underwent bone scintigraphy, 62 patients who showed distant focal accumulations in the skeleton were selected. Observations were performed on 12 skeletal regions: the skull, facial bone, clavicle, rib, scapula, sternum, cervical spine, thoracic spine, lumbar spine, pelvis, upper, and lower extremities. Distant focal accumulations were classified into 3 degrees: very hot, moderately hot and warm. A diagnosis of metastatic focal accumulation was made with reference to the CT, MR, X-ray and Ga-67 images, clinical features, and laboratory data.ResultsFour of the 350 cases showed skeletal metastases (1.1%). Sixty-two of the 350 patients showed 106 distant focal accumulations, with 10 accumulations proving to be skeletal metastases. The common sites of the skeletal metastases were the lumbar spine, rib, cervical spine, and sternum. Patients with skeletal metastases had a tendency to show distant focal accumulations of very hot images in some skeletal sites, and these focal accumulations were usually accompanied by severe pain. The most common cause of distant focal accumulations except metastasis was traumatic injury.ConclusionThe results in the present study indicate that the distant focal accumulations accompanied by severe pain and simultaneously observed in more than one skeletal site can be interpreted as skeletal metastases.Focal accumulations in the skeleton were analyzed in order evaluate the usefulness of bone scintigraphy in the detection of distant skeletal metatases originating from malignant oral tumors. Of 350 patients who underwent bone scintigraphy, 62 patients who showed distant focal accumulations in the skeleton were selected. Observations were performed on 12 skeletal regions: the skull, facial bone, clavicle, rib, scapula, sternum, cervical spine, thoracic spine, lumbar spine, pelvis, upper, and lower extremities. Distant focal accumulations were classified into 3 degrees: very hot, moderately hot and warm. A diagnosis of metastatic focal accumulation was made with reference to the CT, MR, X-ray and Ga-67 images, clinical features, and laboratory data. Four of the 350 cases showed skeletal metastases (1.1%). Sixty-two of the 350 patients showed 106 distant focal accumulations, with 10 accumulations proving to be skeletal metastases. The common sites of the skeletal metastases were the lumbar spine, rib, cervical spine, and sternum. Patients with skeletal metastases had a tendency to show distant focal accumulations of very hot images in some skeletal sites, and these focal accumulations were usually accompanied by severe pain. The most common cause of distant focal accumulations except metastasis was traumatic injury. The results in the present study indicate that the distant focal accumulations accompanied by severe pain and simultaneously observed in more than one skeletal site can be interpreted as skeletal metastases.

Behavior of Hydrogen at Charged Dislocation in NaCl.

To study the structure of an edge dislocation core in an ionic crystal, we measured the amplitude dependence of internal friction by the automated Marxs composite oscillator method and the vibrational current caused by charged dislocations in a hydrogen-absorbed NaCl single crystal. The change of the sign of dislocation charge at the strain amplitude of 10-6 disappeared with absorption of hydrogen, while it was preserved using helium. These findings suggest that hydrogen exists as a positive ion in the dislocation core.

Analysis of Internal Friction Peaks in the Intermediate Temperature Range of NaCl

We measured internal friction, Youngs modulus, ionic conductivity corresponding to the density of vacancies and the dielectric loss corresponding to the dipole density at the same time by an automated Marxs composite oscillator method, in order to investigate the internal friction peaks of NaCl single crystal around 90°C. We observed peaks for both internal friction and dielectric loss, and interpreted the peaks to reflect relaxation by dipole reorientation.

Behavior of Dislocation Core in AgCl Single Crystal

To study the behavior of dislocation core in AgCl, we measured the amplitude dependence of internal friction by automated Marxs composite oscillator method and the vibrational current caused by charged dislocations, which are driven with the frequency of external force, fR=50 kHz. We obtained the association energy between vacancy and metallic impurity as EA=0.96 eV and the binding energy between dislocation and vacancy as Eb=0.66 eV combining ionic conductivity measurements.

An Attempt to Observe Nuclear Fusion in Titanium by Internal Friction

Internal friction and Youngs modulus were measured in a deuterium-absorbed titanium rod during the heating process from liquid nitrogen temperature, but no change was observed at 30 °C, the point at which neutrons were detected by a Los Alamos group. An internal friction peak was observed at -70 °C.

Measurement of Vibrational Current by Charged Dislocation in NaCl Crystal

To study the structure of the core of an edge dislocation in ionic crystal, we measured the amplitude dependence of internal friction by automated Marxs composite oscillator method and the vibrational current caused by charged dislocations. The phase angle between vibrational current and strain suddenly changed by 180 degrees at a strain amplitude of 10-6. From this fact we discuss the structure of the dislocation core.