[Study on the Measurement and Optimization of Soybean Oil Optical Spectrum in THz Range].

Terahertz time-domain spectroscopy is an effective technique that applies spectral measurements by using an ultra fast femtosecond laser. These unique properties of terahertz waves make it an effective nondestructive testing technology. Currently, it has been applied in many fields. However, when we calculate the optical parameters of the sample especially for liquids, from data obtained with time-domain spectroscopy, a common problem occurred is spurious oscillation, which is caused by the Fabry-Perot effect in sample, containers and optical elements. In order to obtain high frequency resolution and accurate sample optical parameters, it is necessary to use some signal processing techniques properly. In this paper, we improved de-convolution algorithm and presented a simple algorithm based on the traditional optical parameter calculation model. Considering the nonlinear absorption of THz wave by samples, containers, emitters or detectors, a THz time-domain trace containing echo signals can be represented as a convolution of the primary peak, some delta functions and nonlinear transfer functions. By analyzing equations，spurious oscillations in the THz spectra result from echo signals can be removed or reduced effectively. The use of the method is discussed and the transmission spectrum of soybean oil in 0.2~2.0 THz range is measured accurately by terahertz time-domain spectroscopy. Experiments show that, this method can effectively remove the frequency oscillation caused by echoes. This algorithm is not affected by the tested object, and is equally applicable to other liquid measurements in THz range. What's more, compared with the traditional method of main pulse interception, this algorithm under the same experimental conditions can effectively improve frequency resolution of soybean oil in 0.2~2.0 THz region, from 50 GHz to less than 10 GHz. At the end of this paper, the causation of remaining oscillation in sample spectrum and absorption spectrum were deeply analyzed.

Do stress fractures induce hypertrophy of the grafted fibula? A report of three cases received free vascularized fibular graft treatment for tibial defects / 中华创伤杂志(英文版)

The presence of large segmental defects of the diaphyseal bone is challenging for orthopedic surgeons. Free vascularized fibular grafting (FVFG) is considered to be a reliable reconstructive procedure. Stress fractures are a common complication following this surgery, and hypertrophy is the main physiological change of the grafted fibula. The exact mechanism of hypertrophy is not completely known. To the best of our knowledge, no studies have examined the possible relationship between stress fractures and hypertrophy. We herein report three cases of patients underwent FVFG. Two of them developed stress fractures and significant hypertrophy, while the remaining patient developed neither stress fractures nor significant hypertrophy. This phenomenon indicates that a relationship may exist between stress fractures and hypertrophy of the grafted fibula, specifically, that the presence of a stress fracture may initiate the process of hypertrophy.

Advances in clinical application and biomechanical studies of the posterior dynamic transpedicular screw fixation system / 医用生物力学

It is known that rigid pedicle screw fixation may cause abnormal stress concentration on the posterior part of the spine, which may lead to stress concentration on the fixation device; meanwhile, due to the motion limitation to the fixed segment, the excessive motion at the adjacent segment may further fortify the disc degeneration. To solve these issues, the dynamic fixation is used in clinic, and many studies have investigated the biomechanical mechanism and clinical outcome of the dynamic fixation. The ideal dynamic fixation should meet the following conditions: offering enough stabilization for the fixed segment; reducing the load on the fixation device through enhancing the strain on the anterior vertebral bodies; preventing the degeneration at the adjacent segment; controlling the horizontal shear force at the fixed segment. In this article, the biomechanical properties and clinical application of the posterior dynamic fixation were reviewed and the biomechanical mechanisms of different dynamic fixations were compared.