Tachio Takano

Effects of the freezing and thawing process on biomechanical properties of the human skull.

The aim of this study was to determine if biomechanical investigations of skull samples are reliable after skulls have been subjected to a freezing and thawing process. The skulls were obtained from 105 Japanese cadavers (66 males, 39 females) of known age that were autopsied in our department between October 2012 and June 2013. We obtained bone specimens from eight sites (four bilaterally symmetrical pairs) of each skull and measured the mass of each specimen. They were then classified into three groups (A, B, C) based on the duration of freezing of the experimental samples. The left-side samples were subjected to frozen storage (experimental group). The corresponding right-side samples were their controls. Bending tests were performed on the controls immediately after they were obtained. The experimental samples were preserved by refrigeration at -20 °C for 1 day (group A), 1 month (group B), or 3 months (group C). Following refrigeration, these samples were placed at 37 °C to thaw for 1 h and then were subjected to bending tests using a three-point-bending apparatus attached to a Handy force gauge. The device recorded the fracture load automatically when the specimen fractured. Statistical analyses revealed that there were no significant differences in sample fracture loads between the frozen preserved/thawed samples and the unfrozen controls for each of the cryopreservation intervals. We eliminated any possible sample mass bias by using controls from the same skull in each case. The results suggest that the freezing/thawing process has little effect on the mechanical properties of human skulls. Thus, frozen storage for up to 3 months is a good method for preserving human skulls.

Statistical analysis of biomechanical properties of the adult skull and age-related structural changes by sex in a Japanese forensic sample.

The purpose of this research was to investigate the biomechanical properties of the adult human skull and the structural changes that occur with age in both sexes. The heads of 94 Japanese cadavers (54 male cadavers, 40 female cadavers) autopsied in our department were used in this research. A total of 376 cranial samples, four from each skull, were collected. Sample fracture load was measured by a bending test. A statistically significant negative correlation between the sample fracture load and cadaver age was found. This indicates that the stiffness of cranial bones in Japanese individuals decreases with age, and the risk of skull fracture thus probably increases with age. Prior to the bending test, the sample mass, the sample thickness, the ratio of the sample thickness to cadaver stature (ST/CS), and the sample density were measured and calculated. Significant negative correlations between cadaver age and sample thickness, ST/CS, and the sample density were observed only among the female samples. Computerized tomographic (CT) images of 358 cranial samples were available. The computed tomography value (CT value) of cancellous bone which refers to a quantitative scale for describing radiodensity, cancellous bone thickness and cortical bone thickness were measured and calculated. Significant negative correlation between cadaver age and the CT value or cortical bone thickness was observed only among the female samples. These findings suggest that the skull is substantially affected by decreased bone metabolism resulting from osteoporosis. Therefore, osteoporosis prevention and treatment may increase cranial stiffness and reinforce the skull structure, leading to a decrease in the risk of skull fractures.

Measurement of 3D sound field formed by orthogonal three lines speaker array

This paper describes actual measurement of 3D sound field which is formed by multiple lines speaker array. In order to realize a novel hands-free sound interface for human-machine systems, the authors are studying multiple lines speaker array. A technique to transmit sound towards a specified direction by speaker array of one straight line is known as beam forming. The authors propose an idea that two and three orthogonal lines speaker array can form spot-like small area of higher sound pressure level. We conduct simulation of two and three lines speaker array. Simulation results support feasibility of the proposed idea. Based upon the results, the authors construct 32 by 2 lines array and 32 by 3 lines array. And we actually measure 3D distribution of sound pressure level by the constructed speaker arrays. Results of the measurement also support the feasibility of our idea.

Differences in biomechanical properties and thickness among frontal and parietal bones in a Japanese sample

The aim of this study was to assess the mechanical properties and thickness of adult frontal and parietal bones. The heads of 114 Japanese cadavers (78 male cadavers and 36 female cadavers) of known age and sex were used. A total of 912 cranial samples, 8 from each skull, were collected. Samples were imaged using multidetector computed tomography to measure sample thickness. The fracture load of each sample was measured using a bending test with calculation of flexural strength. Statistical analyses demonstrated no significant bilateral difference in either the mechanical properties or thickness of frontal or parietal bones. The mechanical properties and thicknesses of frontal bones were significantly greater than those of parietal bones regardless of sex. Therefore, the skull may have a great ability to resist frontal impacts compared with parietal impacts. In female samples, parietal bones were found to have a more uniform structure when compared with male samples. Male parietal bones were found to be thicker at medial sites than at lateral sites. This study also revealed parietal bones at lateral sites in female samples were thicker than in male samples. No strong association was observed between age and flexural strength of frontal or parietal bones. However, the fracture load was negatively correlated with age most likely due to the reduction of thickness.

Statistical analysis of biomechanical properties of the adult sagittal suture using a bending method in a Japanese forensic sample

This study examined the mechanical properties of the adult sagittal suture compared with surrounding parietal bones using bending tests and investigated the association between the mechanical properties of the suture and age. We used the heads of 116 Japanese cadavers (76 male cadavers and 40 female cadavers) of known age and sex. A total of 1160 cranial samples, 10 from each skull, were collected. The samples were imaged using multidetector computed tomography, and the sample thickness at the center of each sample (ST) was measured. The failure stress of each sample (FS) was measured by a bending test, and the ratio of failure stress to the square of sample thickness (FS/ST(2)) was calculated. Statistical analyses revealed that the FS and FS/ST(2) values were significantly lower at all suture sites than at all bone sites regardless of sex. There were not significant but slight positive correlations between age and FS and FS/ST(2) values at any suture site in male samples. In female samples, age had significant positive correlations with FS and FS/ST(2) values at the middle suture sites, whereas there were not significant but slight positive correlations between age and FS and FS/ST(2) values at the edges of the suture. Statistical analyses also demonstrated that FS and FS/ST(2) values were significantly greater in male samples than in female samples at the middle suture sites. These findings suggest that the bending strength of the adult sagittal suture is significantly lower than that of surrounding parietal bones. Therefore, avoiding direct impact on cranial sutures may be important for preventing skull fractures and severe complications that can cause death. The results of this study also revealed that the bending strength of the middle sagittal suture significantly increases with age in only female samples, whereas the bending strength is significantly higher in male samples than in female samples at the middle suture sites, indicating the possibility of sex difference in the bony interdigitation of the sutures during childhood.

Development of a System for Analyzing Common Laceration Generation Mechanisms

Lacerations occur frequently in numerous common environments, but the mechanisms by which they are generated remain unclear. This makes it difficult for designers to create products that can prevent such injuries. Although a significant number of studies have dealt with injury prevention from the standpoint of avoiding bone fractures, lacerations have yet to be thoroughly investigated and a scientific approach to laceration prevention is urgently required. In this paper, we describe a system for analyzing the dynamic characteristics of human-skin like materials, such as pigskin, in an effort to understand laceration generation mechanisms. The system consists of a high speed camera and a drop impact device. Additionally, we developed a finite element model (FEM) for use in determining the inner behavior of materials via computer simulation. According to statistical analysis using injury surveillance data, a typical situation involves a collision between a victims head and the edge of an object, such as a table, chair, bathtub, or other such item. Accordingly, we conducted experiments aimed at determining the dynamic characteristic of pigskin, which is a substitute for human skin, when it collides with various materials. This paper reports our experimental results and discusses laceration generation mechanisms in order to obtain scientific knowledge that can be used when designing product safety features.

Software‐centered implementation of 128 channel huge speaker array with stock PC

A huge speaker array system of 128 loudspeakers was constructed and experimented. It was implemented as ‘‘software‐centered’’ style utilizing stock loudspeakers and a PC. No dedicated hardware nor DSP was utilized. Spot forming, instead of beam forming, could be realized by 32 by 4 square layout of the array. Spot means small area of higher sound pressure level. Number of the spot was not limited to one. In the experiment, within 3 m by 3 m area, four spots of different sounds could be simultaneously formed. This spot forming was confirmed by actually measured spatial distribution of sound pressure level. The effect of the spot was also confirmed auditorily. Since the system was software‐centered, it was dynamic. By simply changing software parameters, location of the spot can be easily moved even while the system was running. This movability of the spot was intended to be basis for visual steering. To realize the system, a simultaneous 128 channel 14‐bit DA converter PCI board was developed. 44.1 kHz sam...