Thermally Activated Composite with Two-Way and Multi-Shape Memory Effects

The use of shape memory polymer composites is growing rapidly in smart structure applications. In this work, an active asymmetric composite called “controlled behavior composite material (CBCM)” is used as shape memory polymer composite. The programming and the corresponding initial fixity of the composite structure is obtained during a bending test, by heating CBCM above thermal glass transition temperature of the used Epoxy polymer. The shape memory properties of these composites are investigated by a bending test. Three types of recoveries are conducted, two classical recovery tests: unconstrained recovery and constrained recovery, and a new test of partial recovery under load. During recovery, high recovery displacement and force are produced that enables the composite to perform strong two-way actuations along with multi-shape memory effect. The recovery force confirms full recovery with two-way actuation even under a high load. This unique property of CBCM is characterized by the recovered mechanical work.     

Quadriplegic areflexic ICU illness: selective thick filament loss and normal nerve histology

Areflexic quadriplegia that occurs in the intensive care unit (ICU) is commonly ascribed to critical illness polyneuropathy based upon electrophysiology or muscle light microscopy. However, electron microscopy often documents a selective thick filament loss myopathy. Eight ICU patients who developed areflexic quadriplegia underwent biopsy. Seven patients had received steroids, and 2 had also received paralytic agents. Electrodiagnostic studies revealed absent or low-amplitude motor responses in 7. Sensory responses were normal in 5 of 6 and absent in 1. Initial electromyography revealed absent (n = 3), small (n = 3), or polyphasic (n = 1) motor unit potentials, and diffuse fibrillation potentials (n = 5). In all 8, light microscopy of muscle revealed numerous atrophic-angulated fibers and corelike lesions, and electron microscopy revealed extensive thick filament loss. Morphology of sural and intramuscular nerves, and, in one autopsied case, of the obturator nerve and multiple nerve roots, was normal. Although clinical, electrodiagnostic, and light microscopic features mimicked denervating disease, muscle electron microscopy revealed thick filament loss, and nerve histology was normal. This suggests that areflexic ICU quadriplegia is a primary myopathy and not an axonal polyneuropathy.     

新型纳米仿生骨植入材料的生物相容性的初步研究

  【目的】 研究新型纳米仿生骨植入材料的生物相容性? 【方法】 采用骨髓基质细胞体外培养技术,通过MTT法检测细胞相对增殖度,对材料的细胞毒性进行分级评价,并采用直接接触培养法,观察细胞在材料上的黏附与散布? 【结果】 材料的细胞毒性分级在0～1之间,骨髓基质细胞可紧密附着于材料表面,黏附生长,并有突起向材料的连通微孔内伸展?【结论】 新型纳米仿生骨植入材料对骨髓基质细胞无毒性作用,符合医用生物材料的安全要求?     

Coronal thick CT reconstruction: an alternative for initial chest radiography in trauma patients

It has been proposed that the imaging workup of trauma patients be accelerated by omitting the initial chest radiography (CR) and directly performing a computed tomography (CT); however, the baseline CR is then lacking. The purpose of this study was to assess if coronal thick reconstructions generated from chest CT could present an adequate alternative for CR. Sixty trauma patients underwent bedside CR and multidetector row chest CT in the emergency room. The image quality of thoracic anatomical structures, the diagnostic accuracy for chest pathology, and the depiction of indwelling devices were assessed on both modalities. Main pulmonary arteries and perihilar bronchi were equally visualized with both modalities. Central bronchi, retrocardial lung parenchyma, diaphragm, descending aorta, and vertebral pedicles were better visualized on thick CT reconstructions, whereas peripheral lung vessels were better depicted on CR (p<0.05). The accuracy to delineate various pathological findings did not differ between both modalities, except for a higher sensitivity to diagnose bronchial cuffing on CR (p<0.05). The location of indwelling devices was similarly and correctly depicted with both modalities. Coronal thick CT reconstructions provide a similar image quality and diagnostic accuracy compared with CR. These reconstructions may serve as an equivalent baseline image in trauma patients in whom emergency radiological evaluation has to be accelerated.     

Use of woven glass fibres to reinforce a composite veneer. A fracture resistance and acoustic emission study

The aim of this study was to investigate the possibility to reinforce the mechanically interlocked veneer of a porcelain-fused-to-metal (PFM) crown by woven glass fibre. A simulated situation to repair a fractured porcelain veneer was used in the experimental test set-up. A brass jig made into the shape of a framework of PFM maxillary central incisor crown with a retentive area at the palatal side of the incisal edge was used. A veneer were made with a restorative hybrid composite on the brass jig (control group). In the test groups, one or two layers of woven polymer pre-impregnated glass fibres (thickness: 0.06 mm/layer) were used by pressing the fibre weaves to the surface of the brass jig. Restorative hybrid composite was applied on the glass fibre weaves. Five veneers were made for all groups and the veneers were not cemented on the test jig. The veneers were loaded from the incisal edge until fracture occurred. The force was measured simultaneously with an acoustic emission analysis (AE) of the fracture propagation. Fracture force values for control veneers were 121 N and for those reinforced with one layer of glass fibres 399 N and for those reinforced with two layers of glass fibres 744 N ANOVA revealed significant difference between the mean values (P=0.003). The AE analysis showed different fracture propagation for the unreinforced and glass fibre reinforced veneers. The results of this study suggests that by placing two layers of woven glass fibres on the retentively shaped metal framework of the PFM crown before applying the restorative composite, considerably higher fracture resistance for the veneer could be obtained.     

Raman scattering determination of the depth of cure of light-activated composites: influence of different clinically relevant parameters

The purpose of this research was to determine the depth of cure of light-activated composites in relation with different clinically relevant parameters. A Raman spectroscopic method has been used. The measurement of cure is made on a relative basis by comparing the vibration band of the residual unpolymerized methacrylate C=C bond at 1640 cm-1 against the aromatic C=C stretching band at 1610 cm-1 used as an internal standard. The information gained draw attention to the importance of light transmission during the exposure. The influence of sample's thickness on the depth of cure is illustrated by a second order polynomial regression. The shade and translucency of the resin composite also modify the light transmission and thus have a significant influence on the degree of conversion. Moreover the light-source intensity and the distance from the curing tip are important parameters of influence. A significant reduction of the depth of cure is observed for all sample thickness of resin composite tested when using a light device with an intensity of 300 mW cm-2 as well as using a distance from the curing tip higher than 20 mm.     

Improved Mechanical and Tribological Properties of Metal-Matrix Composites Dispersion-Strengthened by Nanoparticles

Co- and Fe-based alloys produced by powder technology are being widely used as a matrix for diamond-containing composites in cutting, drilling, grinding pplications, etc. The severe service conditions demand that the mechanical and tribological properties of these alloys be improved. Development of metal-matrix composites (MMCs) and alloys reinforced with nanoparticles is a promising way to resolve this problem. In this work, we have investigated the effect of nano-sized WC, ZrO₂, Al₂O₃, and Si₃N₄ additives on the properties of sintered dispersion-strengthened Co- and Fe-based MMCs. The results show an increase in the hardness (up to 10 HRB), bending strength (up to 50%), wear resistance (by a factor of 2–10) and a decrease in the friction coefficient (up to 4-fold) of the dispersion-strengthened materials. The use of designed alloys as a binder of cutting diamond tools gave a 4-fold increment in the service life, without reduction in their cutting speed.     

10例先天性巨痣患儿行手术切除的围术期护理

总结先天性巨痣患儿手术切除治疗的围术期护理经验。10例先天性巨痣患儿,利用刃厚皮片切削法治疗7例,使用扩张器埋植、扩张皮瓣转移切除修复法治疗2例,1例使用刃厚皮片切削法＋扩张器埋植、扩张皮瓣转移切除修复法综合治疗。做好患儿及其家属围术期心理护理,以纠正患儿不良的心理状态、积极配合手术;由于创面面积大、边缘不规整,做好术区备皮;术后3～5 d为渗液出现的高峰期,注意患者渗液量和颜色;观察患儿扩张皮瓣和转移皮瓣的血运情况,监测皮瓣指压反应时间;做好扩张器注水护理,每次生理盐水注入20～40 ml,以不引起患儿疼痛等不适症状为宜;由于患儿的治疗周期长,做好治疗间隔的出院期间的出院治疗。本组患儿均取得了满意的治疗效果。     

Dielectric and Elastic Characterization of Nonlinear Heterogeneous Materials

This review paper deals with the dielectric and elastic characterization of composite materials constituted by dispersions of nonlinear inclusions embedded in a linear matrix. The dielectric theory deals with pseudo-oriented particles shaped as ellipsoids of revolution: it means that we are dealing with mixtures of inclusions of arbitrary aspect ratio and arbitrary non-random orientational distributions. The analysis ranges from parallel spheroidal inclusions to completely random oriented inclusions. Each ellipsoidal inclusion is made of an isotropic dielectric material described by means of the so-called Kerr nonlinear relation. On the other hand, the nonlinear elastic characterization takes into consideration a dispersion of nonlinear (spherical or cylindrical) inhomogeneities. Both phases are considered isotropic (actually it means polycrystalline or amorphous solids). Under the simplifying hypotheses of small deformation for the material body and of small volume fraction of the embedded phase, we describe a theory for obtaining the linear and nonlinear elastic properties (bulk and shear moduli and Landau coefficients) of the overall material.