Key Engineering Materials Vols. 321-323

Abstract: Self-oscillating gel is designed by copolymerizing the catalyst for the Belousov- Zhabotinsky (BZ) reaction with thermosensitive polymer. The cylindrical-shaped specimens of NIPAAm-co-(Ru(bpy)3 gel were prepared by copolymerizing (Ru(bpy)3) monomer as catalyst with NIPAAm as thermosensitive polymer. Tensile tests were performed with cross-head speed of 10 )m/s in pure water at 20°C. Stress-strain curves were plotted using tensile load measured by semiconductor gauge and strains calculated from observation of the gel. Fracture strain and Young’s modulus were obtained from these curves. Also Poisson’s ratio was estimated from the ratio of strains in longitudinal and radial directions.

Abstract: A near-field scanning microwave microscope (NSMM) is used to study the physical properties of DNA strands with a specific sequence and image lamda-DNA bundles. After the hybridization process between target and capture sequences, specific DNA binding events leads to microwave reflection coefficient (S11) changes of the NSMM. These changes are caused by a modification of the physical dielectric constant due to sequence specific DNA binding. This study demonstrates significant potential of the NSMM as a nondestructive and noncontact tool to detect DNA strands without a target-probe amplification process and as a valuable technique to understand the physical property of DNA.

Abstract: The temperature at the surface of the bony recipient site during drilling for orthodontic micro-implant placement was monitored using infrared thermography. The primary objective was to identify proper drilling conditions to allow efficient drilling without raising the bone temperature above the threshold temperature of 44oC to 47oC. Bovine ribs were selected to provide cortical bone of a similar quality to the human mandible. Four drilling conditions combining 2 motor speeds (600 and 1200 rpm) and 2 pressure loads (500 g and 1000 g) were established based on clinical practice. Much care was taken to duplicate an oral environment, although no irrigation was used to allow the infrared radiation to transmit without being hindered by cooling water. Thermal images were recorded using a Thermovision 900 system (Amega, Danderryd, Sweden). The results showed that the temperature rise relys significantly on the drilling speed and pressure. When both the drilling speed and the pressure were low, the cortical bone could not be cut. However, increasing either the speed or the pressure resulted in a temperature increase. Drill speed of 600 rpm at the pressure load 1000g produced more or less the same temperature, 40- 45 o C, as when the drill speed was increased to 1200 rpm while keeping the load at 500g. Yet, a temperature as high as 62.4 o C was recorded when combining the high motor speed and high pressure. Most of the temperature rise took place during the initial 5-10 seconds of drilling, indicating that intermittent irrigation at an interval of 5 seconds or less would be of particular importance to minimize possible thermal trauma.

Abstract: We observed the glucose concentration of solutions using a near-field microwave microprobe (NFMM). Instead of the usual invasive technique, we take the advantage of the noncontact and noninvasive evaluation capabilities of an NFMM. The NFMM with a high Q dielectric resonator allows observation of small variations of the permittivity due to changes in the glucose concentration. By measuring the reflection coefficient we could observe the concentration of glucose with a detectable resolution to 0.5 mg/ml (0.05 %). The glucose biosensor using a NFMM provides an unique approach for glucose monitoring for diabetes.

Abstract: In order to develop a cost-effective digital X-ray imaging system, we considered a CMOS (complementary metal-oxide-semiconductor) photodiode array in conjunction with a scintillation screen. Imaging performance was evaluated in terms of MTF (modulation-transfer function), NPS (noise-power spectrum) and DQE (detective quantum efficiency). The presampled MTF was measured using a slanted-slit method. The NPS was determined by 2-dimensional Fourier analysis. Both the measured MTF and NPS, and a self-developed computational model for the X-ray spectral analysis were used to determine the spatial frequency-dependent DQE. From the measured MTF, the spatial resolution was found to be about 10.5 line pairs per millimeter (lp/mm). For a 45-kVp tungsten spectrum, the measured DQE around zero spatial frequency was about 40%.

Abstract: Terbium-doped gadolinium oxysulfide (Gd2O2S:Tb) phosphor screen is the most popular X-ray converter in diagnostic radiology. We have investigated the fundamental imaging performance of Gd2O2S:Tb screens in terms of X-ray sensitivity and MTF (modulation-transfer function). The measurements were performed for a wide range of coverages (34 – 135 mg/cm2) by using a conventional film radiographic method. In addition, CsI:Tl having columnar structure was also investigated.

Abstract: We have designed a computational tool for generating X-ray photon spectra for a range of applications both in diagnostic radiology and mammography. As a library, we have adapted the spectral data based on the interpolating polynomials methods by Boone et al [5,6] as well as the computer data files given by Cranley et al [8]. The attenuated spectra for element or compound materials can be calculated based on the mass-attenuation coefficients from NIST (National Institute of Science and Technology), which were also incorporated as a database. Furthermore, a function that a user can generate any filter material by editing the NIST data has been implemented. Parameters related to the beam quality, such as mean photon energy, fluence, exposure, half-value layer (HVL), etc., are considered as important outputs. All of functions and database are integrated in a form of graphical user interface (GUI) by using Microsoft Visual C++TM. This self-developed spectrum-generating code can be usefully served to design X-ray sensors. In this study, we have applied the code to estimate quantum efficiency and charge collection efficiency in various detector materials.

Abstract: In the present clinical fields, medical doctors mainly use Modified Ashworth Scale (MAS) to evaluate spasticity. However, MAS is manual and qualitative method and results depend on doctors. The purpose of this paper is to propose a method to quantitatively evaluate spasticity using a neuro-musculo-skeletal model. The proposed model consisted of the muscular activation model, variable viscoelastic model of the muscles, musculoskeletal model, muscle spindle model and alpha motoneuron model. This model could represent spasticity patient’s knee pendulum well. A parameter related with sensitivity of the muscle spindle was a factor to evaluate spasticity quantitatively.

Abstract: This study investigates micro-structural and mechanical properties of trabecular bone in human femoral head with and without osteoporosis using a micro-CT and a finite element model. 15 cored trabecular bone specimens with 20
of diameter were obtained from femoral heads with osteoporosis resected for total hip arthroplasty, and 5 specimens were removed from femoral head of cadavers, which has no history of musculoskeletal diseases. A high-resolution micro-CT system was used to scan each specimen to obtain histomorphometry indexes. Based on the micro-images, a FE-model was created to determine mechanical property indexes. While the non-osteoporosis group had increases the trabecular thickness, the bone volume, the bone volume fraction, the degree of anisotropy and the trabecular number compared with those of osteoporotic group, the non-osteoporotic group showed decreases in trabecular separation and structure model index. Regarding the mechanical property indexes, the reaction force and the Young's modulus were lower in the osteoporotic group than in non-osteoporotic group. Our data shows salient deteriorations in trabecular micro-structural and mechanical properties in human femoral head with osteoporosis.

Abstract: Tofu was suggested as Tissue Mimicking Materials (TMMs) due to its low cost, availability, gelatinous nature, and shape flexibility. However, the similarity in acoustic properties of the different packets of Tofu and acorn curd (Muk) is critical for TMMs but not fully investigated yet. In order to improve the accuracy for time-consuming and multi-stepped measurements of acoustic properties, an automated measurement system was developed. Using the automated system, the acoustic properties Tofu and Muk were measured to know whether they are similar among the different samples. In conclusion, the acoustic properties were measured to be similar among the different packets of Tofu and Muk, suggesting them as potential TMMs.