关键词： 种植体周围炎   光动力疗法   机械清创   翻瓣术   Meta分析  

摘要： 目的采用Meta分析方法系统评价光动力疗法(PDT)辅助机械清创(MD)或翻瓣清创术(OFD)治疗种植体周围炎的短期临床疗效。方法计算机检索PubMed、The Cochrane Library、Embase、中国知网、万方及维普等数据库,检索PDT辅助MD或OFD治疗种植体周围炎临床疗效观察的随机对照试验(RCTs),检索时限从建库至2019年6月1日。由2名评价员根据纳入排除标准独立筛选文献,进行文献质量评价、提取数据并交叉核对,采用Revman5.3软件进行统计学分析。结果共纳入9篇RCTs,研究对象544例。Meta分析结果显示,与单独的MD或OFD相比,辅助应用PDT种植体周围炎患者的探诊深度(PD)减少[MD=0.52,95%CI(0.13,0.92),P=0.010]、临床附着丧失(CAL)获得[MD=0.36,95%CI(0.11,0.61),P=0.004]、探诊出血指数(BOP)减少[MD=4.96,95%CI(1.87,8.06),P=0.002]、改良龈沟出血指数(m SBI)降低[MD=0.53,95%CI(0.32,0.73),P<0.00001]更加显著,差异有统计学意义(P<0.05),而改良菌斑指数(m PLI)降低[MD=0.05,95%CI(-0.12,0.22),P=0.55]差异无统计学意义。与辅助局部用药(LDD)相比,辅助应用PDT患者各临床指标差异均无统计学意义(P>0.05)。结论 PDT的辅助应用较单独的机械清创或翻瓣清创治疗种植体周围炎的临床疗效更佳,其效果与局部用药相当。

关键词： 气囊-旋转机械系统   限位器   冲击激励   非线性动力学  

摘要： 主要研究了冲击激励下含限位器的气囊-旋转机械系统的动力学特性。首先,考虑了轴承的非线性油膜力和转子的不平衡力等因素,建立了在冲击激励下气囊-旋转机械系统的非线性动力学模型;然后,采用数值模拟的方法分析了冲击激励下,限位器对气囊-旋转机械系统动力学特性的影响,讨论了在限位器不同刚度比、安装间隙、阻尼比等参数下气囊-旋转机械系统的动力学响应。结果表明:限位器的刚度和安装间隙对冲击激励下系统的最大相对位移和绝对加速度有较大影响,而阻尼对其影响会随着刚度比的增大而减小。

关键词： Adaptive neuro fuzzy inference system modeling   mechanical properties   moisture absorption   natural fibre composites  

摘要： Natural fibres possess low density, less abrasiveness, good strength and sound absorption capacity and its significance lies in being renewable and biodegradable. The mechanical characteristics and moisture absorption of pineapple fibres reinforced with polypropylene resin are focused in this study. Chopped fibres and unidirectional fibre mats of pineapple were reinforced with polypropylene resin to make pineapple fibre/polypropylene composites. The length of the pineapple fibres and the orientation of the layup of the fibre mats are varied to make composite specimens and the mechanical properties are tested. Moisture absorption studies were carried out and it was confirmed to follow Fickian diffusion. A total of 384 samples were tested and it was observed that all the samples reached its saturation in moisture absorption before 720 h and the strength was inversely proportional to the moisture absorbed. Specimens reinforced with unidirectional fibre mats of alternate orientation possessed high strength irrespective of the moisture absorbed when compared to the specimens reinforced with chopped fibres of random orientation. Neuro fuzzy modelling using ANFIS tool box in MATLAB was used to correlate the static mechanical properties of pineapple fibre-reinforced polymer under different moisture conditions, fibre orientations, fibre volume percentage, fibre size, etc.

关键词： Unstable pelvic ring injuries   Hemodynamically unstable   Polytrauma   Temporary pelvic fixation  

摘要： In polytrauma patients with unstable pelvic ring injuries, pelvic binders interfere with femoral arterial access and are frequently removed for emergent endovascular and abdominal procedures. The 'trochanteric C-clamp' (T-clamp) is a novel technique described for rapid stabilization of the pelvis without fluoroscopic imaging, while ensuring adequate access to the groin. This case series reports the feasibility and safety following T-clamp application for unstable pelvic ring injuries in patients requiring simultaneous endovascular intervention. Between May 2018 - May 2019, seventeen patients with unstable pelvic ring injuries were treated with a T-clamp in conjunction with other emergent endovascular or intra-abdominal procedures. Nine presented with unstable APC injuries, seven with unstable LC injuries and one with a vertical shear pattern. Complications related to the T-clamp were prospectively collected. Following T-clamp application, there were two cases of intraoperative over-reduction, one of which required exchange for an anterior external fixator. This was the result of a concomitant acetabulum fracture leading to iatrogenic acetabular protrusion secondary to the T-clamp. Twelve cases maintained the T-clamp fixation postoperatively ranging from 1-3 days. One postoperative loss of reduction was noted and required exchange for anterior external fixator. In hemodynamically unstable patients who require emergent endovascular procedures, such as pelvic angiography and REBOA, T-clamp application offers a reasonably safe and effective method for expeditious stabilization of the pelvis while allowing unimpeded access to the abdomen, groin and pelvis. Caution should also be applied in patients with concomitant acetabulum fracture for risk of malreduction. Additionally, its prolonged postoperative use should be limited to patients who are not immediately suitable for fixation of the pelvis. (C) 2020 Elsevier Ltd. All rights reserved.

关键词： Viscoelastic properties   Palm oil   Hazelnut oil   Crystallization kinetics   Avrami model   Oscillation rheology  

摘要： Fat crystal networks result from a crystallization process, forming interlinked crystal aggregates of viscoelastic character. Palm oil-based fat crystal networks, such as chocolate and nougat spreads, often show liquid oil separation during storage because the fat crystal network is too weak to retain the liquid oils trapped within its structure. To explore the relationship between crystallization kinetics and subsequent mechanical properties, i) palm oil from three different geographical origins and with diverging crystallization properties, ii) mixtures of Ghanaian palm oil with gradually increasing additions of hazelnut oil, and iii) blends of Ecuadorian palm oil with palm stearin as a tripalmitin (PPP)-rich fraction were investigated. Kinetic parameters were acquired from an extended Avrami model by isothermal differential scanning calorimetry measurements, and the results combined with the elastic properties measured by oscillation rheology since studying crystallization kinetics alone insufficiently informs about the mechanical/structural properties needed to overcome liquid oil separation. Rate constants of all investigated fats followed bell-shaped curves, with curve progression strongly dependent on the lipid composition. Ameliorating crystallization properties entailed enhanced elastic properties. The higher the maximum rate constants, the higher the elastic modulus and the gel rigidity of the respective fats. However, two different linear regions of elastic modulus versus PPP or solid fat content resulted, depending on whether palm oil was diluted with hazelnut oil or blended with a PPP-rich fraction. Hazelnut oil strongly diluted crystallizable portions of the structuring fat, thereby decreasing the mechanical properties in a power-law fashion, because the fat crystal network became less connected between fat crystal aggregates.

关键词： Bombyx mori   silk fibroin   Biomaterial   Molecular dynamics   Computational materials science   Nanoscale mechanics   beta-Sheet crystallite  

摘要： Bombyx mori silk fibroin (B. mori SF) is a promising biopolymer for use in biomedical applications such as tissue engineered grafts and as a load bearing biopolymer with biocompatible and bioresorbable properties. B. mori SF is a hierarchical bio- macro-molecule made up of amino acid (residue) chains consisting of a crystalline phase and an amorphous phase arranged in a specific order. Understanding about the mechanical behavior of B. mori SF at multiple length scales is of importance when developing tissue grafts, which requires a deeper understanding of the mechanics of its nanostructure. Four phenomenological models of B. mori SF nanostructures were developed, based on crystalline and amorphous phase connectivity. Tensile loading based mechanical behavior analysis of these models were performed using molecular dynamics (MD) simulations and compared with existing results from literature for selection of best performing model. Elastic modulus of similar to 7.4GPa and tensile strength of similar to 340 MPa were obtained for this model. Analysis of results reveals that deformation mechanisms in B. mori SF at nanoscale are a combination of tensile and shear deformations, wherein, the tensile deformation of amorphous region results into excessive extension of B. mori SF, whereas, shear deformation of crystalline region results into a high tensile strength. Overall, this work is instrumental in development of a right computational nanoscale model of SF nanostructure and provides deeper insights into the mechanistic interactions and mechanisms between amorphous and crystalline regions of B. mori SF, which would be useful for further studies of silk based biomaterials.

关键词： Gene regulation   Genomic instability   Long non-coding RNAs   RNA decay  

摘要： Much of the mammalian genome is transcribed, generating long non-coding RNAs (lncRNAs) that can undergo post-transcriptional surveillance whereby only a subset of the non-coding transcripts is allowed to attain sufficient stability to persist in the cellular milieu and control various cellular functions. Paralleling protein turnover by the proteasome complex, lncRNAs are also likely to exist in a dynamic equilibrium that is maintained through constant monitoring by the RNA surveillance machinery. In this Review, we describe the RNA surveillance factors and discuss the vital role of lncRNA surveillance in orchestrating various biological processes, including the protection of genome integrity, maintenance of pluripotency of embryonic stem cells, antibody-gene diversification, coordination of immune cell activation and regulation of heterochromatin formation. We also discuss examples of human diseases and developmental defects associated with the failure of RNA surveillance mechanisms, further highlighting the importance of lncRNA surveillance in maintaining cell and organism functions and health. Mammalian genomes generate long non-coding RNAs, which are degraded by the RNA surveillance machinery. This regulated degradation is vital for various processes, including for genome integrity, stem cell pluripotency and immune cell activation. Consequently, defects in RNA surveillance cause human diseases and developmental disorders.

关键词： Deposition   Nanoindentation   Nanoscratching   Heat   Germanium   Silicon  

摘要： Molecular dynamics (MD) simulations are performed to study the mechanical behavior of SiGe thin film during nanoindentation and nanoscratching processes. The MD simulations of deposition and annealing process are conducted to create the Si80Ge20 thin film deposited on Si(0 0 1) substrate. MD simulations of nanoindentation and nanoscratching processes are carried out to study the influence of the temperature on deformation behaviors and mechanical properties of this material. Moreover, the influences of the scratching depth, tool velocity, and temperature on the deformation behavior during nanoscratching process are also surveyed. It is found that the elastic and plastic deformations occur and the shear transformation zones (STZs) are independently developed in the contact region. The force, hardness, and Young's modulus of the Si80Ge20 thin film deposited on the Si substrate decrease as increasing the temperature during the indentation process. The pile-up, friction force, and normal force grow as increasing the scratching depth. As increasing the scratching speed, the pile-up increase while the normal force and the friction force reduce due to the effect of heat and strain rate are more efficient than the effect of the pile-up. As increasing the temperature, the height of pile-up increases while the normal force and the friction force decrease as a result of a higher temperature leads to softening the workpiece because the thermal expansion causes a reduction of the bonding strength of atoms.

关键词： Perfluorooctanoic acid   Peroxymonosulfate   Photocatalysis   Sulfate radicals   Visible light  

摘要： The global occurrence and adverse environmental impacts of perfluorooctanoic acid (PFOA) have attracted wide attention. This study focused on the PFOA photodegradation by using photocatalyst TiO2 with peroxymonosulfate (PMS) activation. Aqueous PFOA (50 mg L-1) at the pH 3 was treated by TiO2/ PMS under 300 W visible light (400-770 nm) or 32 W UV light (254 nm and 185 nm). The addition of PMS induced a significant degradation of PFOA under powerful visible light compared with sole TiO2. Under visible light, 0.25 g L-1 TiO2 and 0.75 g L-1 PMS in the solution with the initial pH 3 provided optimum condition which achieved 100% PFOA removal within 8 h. Under UV light irradiation at 254 nm and 185 nm wavelength, TiO2/PMS presented excellent performance of almost 100% removal of PFOA within .1.5 h, attributed to the high UV absorbance by the photocatalyst The intermediates analysis showed that PFOA was degraded from a long carbon chain PFOA to shorter chain intermediates in a stepwise manner. Furthermore, scavenger experiments indicated that SO(4)(.-)radicals from PMS and photogenerated holes from TiO2 played an essential role in degrading PFOA. The presence of organic compounds in real wastewater reduced the degradation efficacy of PFOA by 18-35% in visible/TiO2/PMS system. In general, TiO2/PMS could be an ideal and effective photocatalysis system for the degradation of PFOA from wastewater using either visible or UV light source. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： Oxidation   Iron(II)   Oxygen   Catalysis   Copper(II)  

摘要： The results of this comparative study have shown that in 1M acid solutions, the differences in reactivity of iron (II) for reduction of oxygen are within about an order of magnitude of each other for the systems studied at 40 degrees C. This applies to both the uncatalysed and copper(II) catalysed systems. The exception is the chloride system in which the rate can be significantly increased by increasing the chloride concentration. The other main conclusion is that although catalysis by copper(II) ions can be significant there exist conditions (iron(II) and (III) concentrations) for which the effect is not that important. Rate equations for both the uncatalysed and catalysed reactions have been derived that apply equally to all the systems studied. Values for the various rate constants have been obtained by analysis of extensive kinetic data in 1M acid solutions at 40 degrees C. A limited electrochemical study has been used to derive values for the equilibrium constant for the reaction involving the iron(III)/iron(II) and copper(II)/copper(I) couples. An attempt has been made to compare relevant constants with previously published data and to derive a mechanism that is consistent with the kinetic results. This study has shown that the use of methanesulfonic acid as an oxidative leaching medium does not offer any advantages and is the least reactive of the systems studied.