Comprehensively characterizing heterogeneous and transversely isotropic properties of femur cortical bones.

Comprehensive characterization of the transversely isotropic mechanical properties of long bones along both the longitudinal and circumferential gradients is crucial for developing accurate mathematical models and studying bone biomechanics. In addition, mechanical testing to derive elastic, plastic, and failure properties of bones is essential for modeling plastic deformation and failure of bones. To achieve these, we machined a total of 336 cortical specimens, including 168 transverse and 168 longitudinal specimens, from four different quadrants of seven different sections of 3 bovine femurs. We conducted three-point bending tests of these specimens at a loading rate of 0.02 mm/s. Young's modulus, yield stress, tangential modulus, and effective plastic strain for each specimen were derived from correction equations based on classical beam theory. Our statistical analysis reveals that the longitudinal gradient has a significant effect on the Young's modulus, yield stress, and tangential modulus of both longitudinal and transverse specimens, whereas the circumferential gradient significantly influences the Young's modulus, yield stress, and tangential modulus of transverse specimens only. The differences in Young's modulus and yield stress between longitudinal specimens from different sections are greater than 40%, whereas those between transverse specimens are approximately 30%. The Young's modulus and yield stress of transverse specimens in the anterior quadrant were 18.81%/15.46% and 18.34%/14.88% higher than those in the posterior and lateral quadrants, respectively. There is no significant interaction between the longitudinal gradient and the circumferential gradient. Considering the transverse isotropy, it is crucial to consider loading direction when investigating the impact of circumferential gradients in the anterior, lateral, medial, and posterior directions. Our findings indicate that the conventional assumption of homogeneity in simulating the cortical bone of long bones may have limitations, and researchers should consider the anatomical position and loading direction of femur specimens for precise prediction of mechanical responses.

Study on the Effect of Sample Temperature on the Uniaxial Compressive Mechanical Properties of the Brain Tissue.

Craniocerebral injury has been a research focus in the field of injury biomechanics. Although experimental endeavors have made certain progress in characterizing the material behavior of the brain, the temperature dependency of brain mechanics appears to be inconclusive thus far. To partially address this knowledge gap, the current study measured the brain material behavior via unconstrained uniaxial compression tests under low strain rate (0.0083 s-1) and high strain rate (0.83 s-1) at four different sample temperatures (13°C, 20°C, 27°C, and 37°C). Each group has 9~12 samples. One-way analysis of variance method was used to study the influence of sample temperature on engineering stress. The results show that the effect of sample temperature on the mechanical properties of brain tissue is significant under the high strain rate, especially at low temperature (13°C), in which the hardening of the brain tissue is very obvious. At the low strain rate, no temperature dependency of brain mechanics is noted. Therefore, the current results highlight that the temperature of the brain sample should be ensured to be in accordance with the living subject when studying the biomechanical response of living tissue.

[Development of Axial Resolution Testing Device for Optical Coherence Tomograph for the Posterior Segment of the Human Eye and Measurement Uncertainty Analysis].

Based on the analysis of the theoretical calculation model of axial resolution of optical coherence tomograph for the posterior segment of the human eye, a set of testing device for measuring its axial resolution is designed and developed. In view of a commercial ophthalmic optical coherence tomograph in clinical use, its axial resolution is calculated to be 5.07 µm theoretically, and the actual measurement value is 5.45 µm. The uncertainty of the detection device is evaluated and the result is (5.45±0.10) µm. The measurement error introduced by the testing device is very small. Meanwhile, the axial resolution measured by the testing device meets the requirements of the instrument(≤ 6 µm).

[A Simplifed Model Eye for Testing Fundus Imaging Device].

Based on the Gullstrand I model eye, a simplified model eye for testing fundus imaging device is designed. The model eye can reach the following requirements:(1) The refractive characteristics of the ocular refractive tissue are simulated, and the equivalent focal length in air is 17 mm; (2) The differences between relative refractive index differences of the adjacent materials of the simplified model eye and relative refractive index differences of any adjacent two layers (cornea and aqueous humor, aqueous humor and lens, lens and vitreous body) of the Gullstrand I model eye are not more than 1%; (3) In the case of the incident aperture diameter of 3 mm, the differences of radii of the diffuse spots formed by the paraxial light and the axial light are not more than 15%; (4) The differences of angles of chief ray and tangent line of the fundus are not more than 1°; (5) In the case of the incident aperture diameter of 3 mm, the differences of MTF values of the near axis light are not more than 0.1. The simplified model eye can be expected to be used for testing fundus imaging device instead of the test method in ISO 10940:2009 Ophthalmic instruments-Fundus cameras.

[Study on the Photoelectric Performance Indicators of Medical Electronic Endoscope].

OBJECTIVE: To establish a method for measuring the photoelectric performance index (luminance response characteristic and luminance tolerance) of medical electronic endoscope. METHODS: Based on the clinical application and product features of medical electronic endoscope, the umbrella grayscale test chart and the adjustable gray scale test chart are designed and made from two aspects of distribution and density differential. RESULTS: The influence of gray scale arrangement, background illumination intensity and illumination spectrum on photoelectric performance measurement of electronic endoscope is verified by test. CONCLUSIONS: It is a reference for the design analysis, evaluation and modification of electronic endoscope product photoelectric part, whether it is suitable for fast detection of umbels and more accurate gray scale test chart.

[Application of EDXRF in Detection of Impurity Elements in Anodic Oxide Layer of Surgical Implants].

This paper established a qualitative and semi-quantitative analysis detection method of the micro-arc oxidation titanium and titanium alloy layer of Na, Si, P, S and other impurity elements by X-ray fluorescence. At the same time, from the angle of technological process, we analyzed the impurity element types and sources, and verify the reliability of this method. The locking plates superficial layer contained P element, the average was 1.01%. The occipital plate superficial layer contained Si element, the average was 1.39%. The advantages of this detection method were convenient and fast, and the sample without pretreatment and so forth. So this detection method was the ideal method of qualitative and semi-quantitative analysis to the micro-arc oxidation of surgical implants.

[Feasibility Research of Determined Oxygen Permeability of Finished Soft Contact Lens].

OBJECTIVE: A method for determined oxygen permeability (Dk) of finished soft contact lens. METHODS: Oxygen permeability(Dk) of 10 group finished soft contact lens was determined by polarographic method, and the values were linearly calibrated using the measured and established Dk values of the specified reference materials. RESULTS: Only one Dk value fell outside of the requirement of GB 11417.3-2012 tolerance for Dk (± 20%). CONCLUSION: It is great practicability when determined the oxygen permeability (Dk) of finished soft contact lens by polarographic method which were linearly calibrated using the measured and established Dk values of the specified equal thickness reference materials without the measured lens customized 4 different thickness.

[Method to Calculate the Yield Load of Bone Plate in Four-point Bending Test].

This paper developed a calculation method to acquire the yield load P of bone plate during four-point bending test. This method is based on the displacement--force (δ-F) curve function f(M)(δ) obtained from the test, each slope of the curve was calculated using piecewise smooth function and the line segment in f(M)(δ) elastic deformation area was searched by setting the minimum slope T. Slope S was obtained through linear fit so as to build parallel displacement function f(L)(δ). Then, approximating intersection point of f(M)(δ) and f(L)(δ) was obtained through linear interpolation. Thus, yield load P was acquired. The method in the paper was loyal to YY/T 0342-2002 regulation and was liable to program calculation. The calculating process was nothing to do with whether the initial point during the test was preloaded or unloaded, and there was no need to correct the original point. In addition, T was set in an ideal fitting level guaranteed by the fitting coefficient of determination R2, and thus S was very close to the real value, and P was with a high accuracy.

[A testing method of assessing the protein-removing effect of the contact lenses' protein -removing care solution].

OBJECTIVE: Testing the protein-removing effect of the protein-removing care solution on the protein precipitation of the soft contact lenses. METHOD: Soak the lenses into the artificial-tears to simulate the protein absorption, test the absorbency of cleaned protein at the wavelength of 280 nm by UV spectrophotometer, and compute the percentage of protein. RESULT: Testing results of the percentage of the cleaned protein are repeatable. CONCLUSION: This experimental method can be used to evaluate the cleaning effect of the protein- removing care solution, but still needs much improvements.