Yohsuke Kinouchi

Theoretical analysis of magnetic field interactions with aortic blood flow

The flow of blood in the presence of a magnetic field gives rise to induced voltages in the major arteries of the central circulatory system. Under certain simplifying conditions, such as the assumption that the length of major arteries (e.g., the aorta) is infinite and that the vessel walls are not electrically conductive, the distribution of induced voltages and currents within these blood vessels can be calculated with reasonable precision. However, the propagation of magnetically induced voltages and currents from the aorta into neighboring tissue structures such as the sinuatrial node of the heart has not been previously determined by any experimental or theoretical technique. In the analysis presented in this paper, a solution of the complete Navier-Stokes equation was obtained by the finite element technique for blood flow through the ascending and descending aortic vessels in the presence of a uniform static magnetic field. Spatial distributions of the magnetically induced voltage and current were obtained for the aortic vessel and surrounding tissues under the assumption that the wall of the aorta is electrically conductive. Results are presented for the calculated values of magnetically induced voltages and current densities in the aorta and surrounding tissue structures, including the sinuatrial node, and for their field-strength dependence. In addition, an analysis is presented of magnetohydrodynamic interactions that lead to a small reduction of blood volume flow at high field levels above approximately 10 tesla (T). Quantitative results are presented on the offsetting effects of oppositely directed blood flows in the ascending and descending aortic segments, and a quantitative estimate is made of the effects of assuming an infinite vs. a finite length of the aortic vessel in calculating the magnetically induced voltage and current density distribution in tissue.

New water disinfection system using UVA light-emitting diodes

Aim:  To evaluate the ability of high‐energy ultraviolet A (UVA) light‐emitting diode (LED) to inactivate bacteria in water and investigate the inactivating mechanism of UVA irradiation.

Studies on the Sm-Co Magnet as a Dental Material

The Sm-Co magnet has superior and convenient magnetic properties as compared with conventional ones used hitherto in prosthesis, and even very small pieces can provide the force necessary in dentistry. Also, the magnet has high corrosion resistance and is innocuous to tissues. Therefore, it can be used as a dental material, overcoming the limitations in past applications.

Artificial neural networks for source localization in the human brain

SummarySource localization in the brain remains an ill-posed problem unless further constraints about the type of sources and the head model are imposed. Human head is modeled in various ways depending critically on the computing power available and/or the required level of accuracy. Sophisticated and truly representative models may yield more accurate results in general, but at the cost of prohibitively long computer times and huge memory requirements. In conventional source localization techniques, solution source parameters are taken as those which minimize an index of performance, defined relative to the model-generated and clinically measured voltages. We propose the use of a neural network in the place of commonly employed minimization algorithms such as the Simplex Method and the Marquardt algorithm, which are iterative and time consuming. With the aid of the error-backpropagation technique, a neural network is trained to compute source parameters, starting from a voltage set measured on the scalp. Here we describe the methods of training the neural network and investigate its localization accuracy. Based on the results of extensive studies, we conclude that neural networks are highly feasible as source localizers. A trained neural networks independence of localization speed from the head model, and the rapid localization ability, makes it possible to employ the most complex head model with the ease of the simplest model. No initial parameters need to be guessed in order to start the calculation, implying a possible automation of the entire localization process. One may train the network on experimental data, if available, thereby possibly doing away with head models.

Growth of human cultured cells exposed to a non-homogenous static magnetic field generated by SmCo magnets

A static magnetic field, with a strong spatial gradient, was established on the surface of cell culture dishes by use of a gilded iron needle set vertically above an Sm-Co magnet. The calculated magnetic flux density was more than 1.5 T at the center of the needle tip, and the products of the flux density and its gradient were about 200 and 60 T2/m at distances of 0.1 and 0.3 mm, respectively, from the center. The DNA content, DNA synthesis and labeling index of cultured cells located within 0.1 mm from the center of the needle, and the growth rate of cells located within 0.3 mm from the center, were measured. HeLa cells grew at a normal rate for 96 h in the magnetic field and showed no significant change in shape, detectable by scanning electron microscopy. The growth of HeLa cells was not influenced by exposure to the magnetic field. Similarly, exposure for 48 h to the magnetic field had no effect on growth of normal human gingival fibroblasts (Gin-1). The DNA content, assayed by microfluorometry of the nuclei of both types of cells stained by the Feulgen reaction, was not significantly different from that of controls. Moreover, exposure to the magnetic field had no effect on DNA synthesis or the labeling index of HeLa cells assayed by autoradiography of incorporated [3H]thymidine. It is concluded that a non-homogeneous magnetic field of the intensity and the gradient used in this study does not significantly influence the growth of HeLa cells or Gin-1 cells.

Materials Science Cytotoxicity of Pd-Co Dental Casting Ferromagnetic Alloys

The biocompatibility of three kinds of Pd-Co dental casting ferromagnetic alloys was assessed in a toxicity test in vitro. The test showed that the Pd-Co binary alloy may have weak cytotoxicity, while the Pd-Co-Cr and Pd-Co-Ni ternary alloys may be less cytotoxic. The Pd-Co-Ni alloy was least cytotoxic of the three.The biocompatibility of three kinds of Pd-Co dental casting ferromagnetic alloys was assessed in a toxicity test in vitro. The test showed that the Pd-Co binary alloy may have weak cytotoxicity, while the Pd-Co-Cr and Pd-Co-Ni ternary alloys may be less cytotoxic. The Pd-Co-Ni alloy was least cytotoxic of the three.

Neural networks for event extraction from time series: a back propagation algorithm approach

This paper presents a relatively new event detection method using neural networks for time series analysis. Such method can capture homeostatic dynamics of the system under the influence of exogenous event. The results show that financial time series include both predictable deterministic and unpredictable random components. Neural networks can identify the properties of homeostatic dynamics and model the dynamic relation between endogenous and exogenous variables in financial time series input-output system. We explore the signaling mechanisms that transfer information in such dynamic system and investigate the impact of the number of model inputs and the number of hidden layer neurons on financial analysis.

A new method for noninvasive measurement of multilayer tissue conductivity and structure using divided electrodes

This paper outlines a new method for measuring multilayer tissue conductivity and structure by using divided electrodes, in which current electrodes are divided into several parts. Our purpose is to estimate the multilayer tissue structure and the conductivity distribution in a cross section of the local tissue by using bioresistance data measured noninvasively. The effect of the new method is assessed by computer simulations using a typical two-dimensional (2-D) model. In this paper, the conductivity distribution in the model is analyzed based on a finite difference method (FDM) and a steepest descent method (SDM). Simulation results show that the conductivity values of skin, fat, and muscle layers can be estimated with an error of less than 0.1%. When random noise at various levels is added to the measured resistance values, estimates of the conductivity values for skin, fat, and muscle layers are still reasonably precise: their root mean square errors are about 1.06%, 1.39%, and 1.61% for 10% noise. In a 2-D model, increasing the number of divided electrodes permits simultaneous estimates of tissue structure and conductivity distribution. Optimal configuration for divided electrodes is examined in terms of dividing pattern.

Blood flow velocity in the common carotid artery in humans during graded exercise on a treadmill

Cerebral blood volume flow and flow velocity have been reported to increase during dynamic exercise, but whether the two increase in parallel and whether both increases occur as functions of exercise intensity remain unsettled. In this study, blood flow velocity in the common carotid artery was measured using the Doppler ultrasound method in eight healthy male students during graded treadmill exercise. The exercise consisted of stepwise progressive increases and decreases in exercise intensity. The peak intensity corresponded to approximately 85% of maximal oxygen consumption. During this exercise, the heart rate (fc), mean blood pressure (BP) in the brachial artery and mean blood flow velocity (νcc) in the common carotid artery increased as functions of exercise intensity. At the peak exercise intensity, (fc), BP and νcc increased by 134.5%, 20.5% and 51.8% over the control levels before exercise (P < 0.01), respectively. The resistance index (RI) and pulsatility index (PI) were determined from the velocity profile and were expected to reflect the distal cerebral blood flow resistance. The RI and PI increased during the graded exercise, but tended to decrease at the highest levels of exercise intensity. As νcc increased with increases in exercise intensity it would be expected that cerebral blood flow would also increase at these higher intensities. It is also suggested that blood flow velocity in the cerebral artery does not proportionately reflect the cerebral blood flow during dynamic exercise, since the cerebral blood flow resistance changes.

Pd-Co Dental Casting Ferromagnetic Alloys

Three kinds of Pd-Co alloys have been newly developed. Their magnetic and physical properties and corrosion resistances have been examined. As a result, it was found that they are available as the dental casting ferromagnetic alloy which can be used in combination with Sm-Co magnets, overcoming such problems as non-castability and brittleness.