Enhancement of dielectric constant of polyimide by doping with modified silicon dioxide@titanium carbide nanoparticles.

Electrode materials used in supercapacitors must have a high dielectric constant and a low dielectric loss along with good mechanical properties. In this study, the dielectric constant of polyimide (PI) was improved by preparing a PI/SiO2@TiC composite. A homogeneous dispersion of SiO2@TiC nanoparticles was obtained by the hydrolyzation of tetraethyl orthosilicate, which resulted in the formation of a thin layer of SiO2 on TiC particles. Polyamic acid was doped with the modified SiO2@TiC nanoparticles by mechanical blending to synthesize the PI/SiO2@TiC composite, and its dielectric properties were investigated. Scanning electron microscopy studies confirmed that the SiO2@TiC particles were homogeneously dispersed in the PI matrix and did not exhibit agglomeration. An increase in the SiO2@TiC filler content increased the dielectric constant and the dielectric loss of the composite, but decreased its breakdown strength and deteriorated its mechanical properties. Thus, the addition of SiO2@TiC particles to PI is suitable for improving its dielectric properties while maintaining its flexibility.

Three-dimensional analysis of cervical spine segmental motion in rotation.

INTRODUCTION: The movements of the cervical spine during head rotation are too complicated to measure using conventional radiography or computed tomography (CT) techniques. In this study, we measure three-dimensional segmental motion of cervical spine rotation in vivo using a non-invasive measurement technique. MATERIAL AND METHODS: Sixteen healthy volunteers underwent three-dimensional CT of the cervical spine during head rotation. Occiput (Oc) - T1 reconstructions were created of volunteers in each of 3 positions: supine and maximum left and right rotations of the head with respect to the bosom. Segmental motions were calculated using Euler angles and volume merge methods in three major planes. RESULTS: Mean maximum axial rotation of the cervical spine to one side was 1.6° to 38.5° at each level. Coupled lateral bending opposite to lateral bending was observed in the upper cervical levels, while in the subaxial cervical levels, it was observed in the same direction as axial rotation. Coupled extension was observed in the cervical levels of C5-T1, while coupled flexion was observed in the cervical levels of Oc-C5. CONCLUSIONS: The three-dimensional cervical segmental motions in rotation were accurately measured with the non-invasive measure. These findings will be helpful as the basis for understanding cervical spine movement in rotation and abnormal conditions. The presented data also provide baseline segmental motions for the design of prostheses for the cervical spine.

Biomechanical evaluation of a novel total cervical prosthesis in a single-level cervical subtotal corpectomy model: an in vitro human cadaveric study.

BACKGROUND: Anterior cervical subtotal corpectomy and fusion provides extensive decompression in the treatment of cervical myelopathy. However, early adjacent segment degeneration may arise due to the abnormal kinematics. To the best of our knowledge, this is the first report on a newly-designed total cervical prosthesis (TCP) to preserve the normal kinematics of cervical spine. The purpose of this study was to compare the cervical range of motion (ROM) of TCP with anterior cervical plating (ACP) in a single-level cervical subtotal corpectomy model. STUDY DESIGN: An in vitro biomechanical study of a novel total cervical prosthesis (TCP) using a cadaveric model. MATERIALS AND METHODS: After evaluation of the ROM of the 14 human cadaveric cervical spines (C(2)-T(1)) (intact group), single-level subtotal corpectomy models at the C(5) levels were performed. All specimens were randomized, instrumented with ACP (n = 7) and TCP (n = 7) from C(4) to C(6). All specimens were tested for flexion/extension, lateral bending, and axial rotation loading. The ROM of implanted segments (C(4)-C(6)) and adjacent segments (C(3)/C(4) and C(6)/C(7)) were monitored, respectively. RESULTS: TCP was found to accurately recapitulate the preoperative ROM both in the adjacent segments (C(3)/C(4) and C(6)/C(7)) and the implanted segments (C(4)-C(6)). In the adjacent segments, no significant difference was found in ROM(C3/C4) between the TCP group and the intact group in flexion, extension, and lateral bending. In the implanted segments, TCP preserved well the ROM(C4-C6), with 5.29° in flexion, 12.27° in extension, 8.95° in right lateral bending, and 7.50° in left lateral bending. In contrast, the mean ROM(C4-C6) in the ACP group was lower than those in the TCP group and the intact group significantly in all directions (P < 0.05). In addition, compared with the ACP group, the mean ROM(C3-C7) in TCP group increased by 32.6% (P = 0.034) in flexion, 62.9% (P = 0.008) in extension, 24.8% (P > 0.05) in lateral bending, and 36.0% (P < 0.01) in rotation. Compared with the intact group, the TCP group showed moderate decrease in flexion and moderate increases in extension, lateral bending, and rotation. But no significant differences were detected (P > 0.05). CONCLUSIONS: Biomechanical analyses suggest that TCP preserves ROM in the implanted segments after cervical subtotal corpectomy. TCP will not induce compensatory motion in the adjacent segments, thus may possibly help prevent adjacent segment degeneration.