Key Engineering Materials Vols. 326-328

Abstract: The conversion of chemical energy into mechanical forces that powers cell movements is a ubiquitous theme across biology. Besides molecular motors such as kinesin-microtubule and actin-myosin complexes, biological springs and ratchets can also store and release energy to rectify motion. The acrosome reaction of horseshoe crab sperm is a simple example of a biological spring where a 60!μm-long crystalline bundle of actin filaments, tightly cross-linked by actin bundling protein scruin, straightens from a coiled conformation and extends from the cell to penetrate an egg in about five seconds. To identify the basis and mechanism for this movement, we examine the possible sources of chemical and mechanical energy and show that the stored elastic energy alone is sufficient to drive the reaction. We also provide an estimate of the maximum force generated during the uncoiling by stalling the bundle using an agarose gel to show the reaction produces enough force to penetrate the egg.

Abstract: In generally, it is known that structures of living thing are optimized. The wings of a dragonfly are thin and light. Although it is having the structure of bearing the load produced in the case of an advanced flight such as “Flapping flight”, “Glide”, and “Hovering”. The wings of a dragonfly are made by veins and membranes. In addition, the wings of a dragonfly have some characteristic structures, such as “Nodus”. Thus, the wings of dragonfly have many complicated structures. The configuration of costal vein of the wings is different from them of other insects. So, we paid attention to the configuration of costal vein of the wings. Therefore, in this study, we researched about the effect of costal vein. As a result, it was showed that the configuration of costal vein became bending and torsional deformation small. In addition, it was showed that the configuration of costal vein related to nodus. In this study, several 3-D models of the dragonfly’s wing were made and calculated by the 3-D finite element method.

Abstract: This paper concerns a mechanics of interactions of helical structures in proteins. Helices are the most important secondary structures of proteins and contribute the formation of a more complex 3-D structure, and so the analysis of interactions of helices is quite critical. We examine 1290 protein structures that have 2.0 Å or better resolutions and less than 20 percent of their sequences in common. Interactions between helices are represented by two parameters: the distance and angle. Assuming that helices are slender rigid rods with finite length, we define three different mechanisms of interactions: (1) line-on-line contact; (2) endpoint-to-line contact; and (3) endpointto- endpoint contact. In this paper, interactions for the first case are expressed with the 3-D relative rigid-body motion (position and orientation) and the unique volume element for correctly integrating over rigid-body motions are determined using six parameters. The results are extremely useful for the correct analysis of interactions in terms of distance and angle without the statistical biases inherent in the three data sets.

Abstract: The inner ear hair cells, the receptors sensing mechanical stimuli such as acoustic vibration and acceleration, achieve remarkably high sensitivity to miniscule stimuli by selectively amplifying small inputs. The gating springs hypothesis proposes that a phenomenon called negative stiffness is responsible for the nonlinear sensitivity. According to the hypothesis, the bundle becomes more sensitive in certain region as its stiffness changes due to the opening or closing of transduction channels, which in turn exert force in the same direction of the bundle’s displacement. In this study, we developed a conceptual model of an inertial sensor inspired by the inner ear hair cells, focusing on the hair cell’s amplifying mechanism known as negative stiffness. The negative stiffness was applied to a simple mass-spring-damper system with nonlinear spring derived from gating springs hypothesis. Sinusoidal stimuli of 0.1Hz~10Hz with magnitude of 1pN to 1000pN were applied to the system to match the dynamic range of vestibular organs. Simulation on this nonlinear model was performed on MATLAB, and power transfers and sensitivities in both transient and steady states were obtained and compared with those from the system with linear spring. Parameters were chosen in relation to those of the hair bundle to reproduce operating conditions of both the hair cells and micro inertial sensors. The suggested model displayed compressive nonlinear sensitivity resulting from selective amplification of smaller stimuli despite the energy loss due to large viscous damping typical in micro systems.

Abstract: This study focused on the treatment performance of membrane bioreactor (MBR) coupled with intermittent ozone bubbling for the effective recovery of dissolved organics from coagulated fresh sewage sludge. Intermittent ozone bubbling was effective in the prevention of permeation resistance increase caused by particle accumulation on membrane surface, which result in keeping high permeation flux. MBR with intermittent ozone bubbling is believed to be an effective system for the recovery of organic matter usefully utilized in biological denitrification as well as membrane fouling reduction.

Abstract: In this work a method to characterize soft tissue properties for mechanical modeling is presented. Attention is especially focused on developing a model of the lower esophagus to be used in a surgical simulation, which shows a promise as a training method for medical personnel. The viscoelastic properties of the lower esophageal junction are characterized using data from animal experiments and an inverse FE parameter estimation algorithm. Utilizing the assumptions of quasilinear- viscoelastic theory, the viscoelastic and hyperelastic material parameters are estimated to provide a physically based simulation of tissue deformations in real time. To calibrate the parameters to the experimental results, a three dimensional FE model that simulates the forces at the indenter and an optimization program that updates new parameters and runs the simulation iteratively are developed. It was possible to reduce the time and computation resources by decoupling the viscoelastic part and elastic part in a tissue model. The comparison of the simulation and the experimental behavior of pig esophagus are presented to provide validity to the tissue model using the proposed approach.

Abstract: This paper presents a microbiochip which can detect an antigen-antibody reaction through an electrical signal in real time with high sensitivity and low sample volume by using nanogold particle and silver enhancement. A filtration method using the microbead is adopted for sample immobilization. The chip is composed of an inexpensive and biocompatible Polydimethylsiloxane (PDMS) layer and Pyrex glass substrate. Platinum microelectrodes for electric signal detection were fabricated on the substrate and microchannel and pillar-type microfilters were formed in the PDMS layer. Successively introducing polystyrene microbeads precoated with protein A, anti-protein A (which was the first antibody) and the second antibody conjugated with nanogold particles into the microchannel, the resulting antigen-antibody complex was fixed on the bead surface. The injection of silver enhancer increased the size of nanogold particles tagged with the second antibody. As a result, microbeads were connected to each other and formed an electrical bridge between microelectrodes. Resistance measured through the electrodes showed a difference of two orders of magnitude between specific and nonspecific immunoreactions. The developed immunoassay chip reduced the time necessary for an antigen-antibody reaction to 10 min, thus shortening the overall analysis time from 3 hours to 50 min. The immunoassay chip reduces analysis time for clinical diagnoses, is simple, and has high sensitivity.

Abstract: Most ultrasound diagnosing systems for osteoporosis lack diagnostic precision due to the measurement of specific regions of interest (ROI). As well as using the existing ROI measurement method, this study introduced the concept of analyzing the distribution patterns of bone quality. Linear scanning and ultrasound transmission techniques were used to obtain the broadband ultrasound attenuation (BUA) images of the calcaneus. A 13mm-diameter ROI was selected as the position of minimum BUA value locally in the posterior calcaneus. Mean values of BUA and speed of sound (SOS) at the ROI, as well as the osteoporosis index (OI), by their linear combination, were defined. For a more accurate diagnosis of osteoporosis, OI and images of the bone quality distribution of the calcaneus were utilized together. The calcaneus is inhomogeneous and, furthermore, its images are not perpendicular to the direction of the ultrasound beam. Hence, the mean values of BUA and SOS for the entire calcaneus do not have any significant meaning. Accordingly, four image patterns of other OI in the calcaneus were defined in order to increase the correlation between diagnostic parameter and age. The results revealed a higher correlation between the bone quality index and age (r=0.75, p<0.0001), for which the pattern index was reflected on OI, than that (r=0.65, p<0.0001) of OI merely at ROI. This result confirmed the possibility of a new osteoporosis diagnostic method using the BUA distribution images of the entire calcaneus.

Abstract: Melt processable plasticized cellulose diacetate (CDA) was prepared using triacetin (TA) as a plasticizer and its mechanical properties were characterized. The processability of the plasticized CDA was further enhanced by using a small amount of epoxidized soybean oil as a secondary plasticizer. The glass transition temperature of the plasticized CDA was observed at 50°C lower than that of the virgin CDA and the incorporation of 5 % of ESO also resulted in an additional 20°C decrease in the Tg value. In order to obtain practical processing conditions, a plasticizer content of more than 20 wt % should be used.

Abstract: In this study, the change of the natural frequencies in mouse femurs with osteoporosis was investigated based on a vibration test and a finite element. Three groups of the femurs include the osteoporotic group, the treated group and the normal group. In the vibration test, the natural frequencies were measured by the mobility test. For the finite element analysis, the micro finite element model of the femur was reconstructed using the Micro-CT images and the Voxel mesh generation algorithm. From the results, the averaged natural frequencies in the osteoporotic group were the highest, followed by those in the treated group. The finite element models were validated within 15% errors by comparing the natural frequencies in the finite element analysis with those in the vibration test. The developed Micro-CT system, the Voxel mesh generation algorithm, the presented finite element analysis, and vibration test could be useful for the investigation of the structural change of the bone tissue, and the diagnosis and the treatment in the osteoporosis.