Yujiro Naruse

Metal/amorphous silicon multilayer radiation detectors

A multilayer structure is described for use in a number of radiation detectors. The structure consists of alternating layers of metal and amorphous silicon (a-Si). The absorption of radiation mainly occurs in the metal layers, while electron-hole pairs are generated in the a-Si layers by the emitted secondary particles from the metal layers. The fundamental applicability of this novel detector for X-ray detection was confirmed by Monte Carlo computer simulations as well as by results for an experimental five-layer Ta(0.5 mu m)/a-Si(3 mu m)/Mo(0.5 mu m) X-ray sensor fabricated on a 1.5-cm*4-cm glass plate. The authors have confirmed that the detector has rectifying characteristics, with the Mo and Ta layers forming Schottky barrier and ohmic contacts respectively. >

A NOVEL QUANTUM CELLULAR AUTOMATA LOGIC WITH LOOP STRUCTURES

The effects of additional cells on the circuit operation of quantum cellular automata (QCA) logic, proposed by Lent et al., are numerically studied using the extended Hubbard model self-consistently. We investigate the differences in logic circuit operation between Lents inverter and our original 4-cell one characterized by a loop structure in the cases of 4 and 5 quantum dot cells (QDC). We find that the 4-cell inverter with loop structure composed of 4-QDC exhibits favorable characteristics in QCA logic operation.

Mechanical vibration model for chromosomes in metaphase of mitosis and possible application to the interruption of cell division

The behavior of chromosomes subjected to external mechanical vibration in metaphase of mitosis is modeled, and its possible applications to the interruption of cell divisions is investigated. The modeling is based on a mass and string coupled system where the mass and the string correspond to the condensed chromosome and the kinetochore microtubule, respectively. After establishing the motion of equation for a chromosome, the frequency response to the forced vibration from the outside of the cell is formulated. This will lead to an efficient method for kinetic energy transfer to chromosomes by finding the resonant frequencies of the cell system. There is a possibility that the increased kinetic energy in one chromosome will affect the cell as a whole, thereby interrupting the mitosis by the mechanisms that are discussed in this report. Rough calculation shows that the vibration in the frequency range of 22-50 kHz is effective for controlling the mitosis of human cells.

Multichannel Semiconductor Detectors for X-Ray Transmission Computed Tomography

Multichannel semiconductor detectors for X-ray transmission computed tomography (XCT) have been developed using surface-barrier diodes fabricated from high-purity n-type silicon. X-rays are detected directly by the semiconductor detectors in the operational mode, non-biasing in conjunction with current to voltage converters (I/V converters). In addition to the image reconstruction test, the fundamental properties of the detector have been studied theoretically as well as experimentally.

Theoretical Concept of Physical Antibiotics Using Nanoparticles

The concept of physical antibiotics using nanoparticles is proposed and a feasibility study is performed theoretically. The core operating principle is based on the temperature increase of nanoparticles adhering to an infected area (bacteria colony or biofilm) induced by applying an external magnetic field and electromagnetic waves. In the first phase, the magnetic field increases the temperature of the nanoparticles after their capture by the infection area. In the next phase, the nanoparticles form distributed dipole antennas that will absorb electromagnetic waves efficiently. The high-temperature nanoparticles will drill into the cell walls of the bacteria and consequently destroy the bacteria. There is a possibility that these physical antibiotics will solve the current problems related to conventional antibiotics.

Effect of static magnetic fields on the budding of yeast cells.

The effect of static magnetic fields on the budding of single yeast cells was investigated using a magnetic circuit that was capable of generating a strong magnetic field (2.93 T) and gradient (6100 T²  m⁻¹). Saccharomyces cerevisiae yeast cells were grown in an aqueous YPD agar in a silica capillary under either a homogeneous or inhomogeneous static magnetic field. Although the size of budding yeast cells was only slightly affected by the magnetic fields after 4 h, the budding angle was clearly affected by the direction of the homogeneous and inhomogeneous magnetic fields. In the homogeneous magnetic field, the budding direction of daughter yeast cells was mainly oriented in the direction of magnetic field B. However, when subjected to the inhomogeneous magnetic field, the daughter yeast cells tended to bud along the axis of capillary flow in regions where the magnetic gradient, estimated by B(dB/dx), were high. Based on the present experimental results, the possible mechanism for the magnetic effect on the budding direction of daughter yeast cells is theoretically discussed.

MEMS optical microphone with electrostatically controlled grating diaphragm

A new optical microphone was developed based on complementary metal–oxide–semiconductor (CMOS)—microelectromechanical systems (MEMS) micromachining techniques. One of the outstanding features of this microphone is that the output signal is obtained as a vibration of diffraction pattern from the grating diaphragm which is electrostatically actuated. The electronic signal actuates the diaphragm at an arbitrary frequency by electrostatic force and simultaneously detects sound using light waves. From the verification experiment, this microphone was able to perform advanced functions, such as the frequency selection and the detection of the sound wave phase information. Based on the theoretical model, experimental data are discussed and potential applications of this microphone are also proposed.

Mechanical Vibration Model for Proteins and Nanoparticles Coupling with the Cell Membrane and its Application to Cell Treatment

The behaviors of proteins and nanoparticles coupling with the cell membrane were analyzed using an external mechanical vibration model. This model was based on a one-dimensional seismic vibration system. A simple equation was derived for the relationship between the amplitude of cell vibration and the amplitude of mobile protein or nanoparticle vibration in the cell membrane. Using this equation, the optimal frequency for the efficient vibration of mobile proteins or nanoparticles was found in the applications of in vivo and in vitro cell treatments.

200 Channel Semiconductor Detectors for X-Ray Computed Tomography

Prototype 200 channel semiconductor detectors for third generation X-ray computed tomography have been developed using surface-barrier diodes fabricated from high-purity n-type silicon. The image reconstruction test was successful, and the relationship between the image quality and the detector characteristics has been studied.

Micromachined Thermal Effect Array by Joule Heating for Bio Applications

We have developed a micro local heating device for bio applications using micro-electro-mechanical systems (MEMS) technology. The device has a two-dimensional microdish array, which contains a series of diodes. The microdish array is fabricated by means of a combination of complementary metal–oxide–semiconductor (CMOS) technology and MEMS post-processing. The microdish array has a miniature cavity for thermal separation from substrate. These microdish arrays can be generated by a large forward current based on Joule heating. In this paper, we describe the direct heating of the whole microdish array and just an arbitrary portion of the microdish consisting of the device by Joule heating. In the localized selective heating, the highest temperature, 62.6 °C, from all the dishes was confirmed. More than twice the heat effect was achieved in heating an arbitrary portion compared with heating the whole microdish.