Biochemical and morphological alterations of the extracellular matrix of chicken calcaneal tendon during maturation

The region in tendons that surrounds bone extremities adapts to compression forces, developing a fibrocartilaginous structure. During maturation, changes occur in the amount and organization of macromolecules of the extracellular matrix of tendons, changing the tissue morphology. To study the effect of maturation on tendons, Pedrês chickens were sacrificed at 1, 5, and 8 months old and had the calcaneal tendon (CT) divided into proximal region, submitted to tension/compression forces ( p ), and distal region submitted to tension force ( d ). Morphological analysis of the p region showed the presence of fibrocartilage in all ages. In the central part of the fibrocartilage, near a diminishment of the metachromasy, there was also a development of a probable fat pad that increased with the maturation. The activity of MMP‐2 and MMP‐9 was higher at 5 and 8 months old, in both regions, compared with 1‐month‐old animals. In SDS‐PAGE analysis, components with electrophoretic migration similar to decorin and fibromodulin increased with maturation, particularly in the d region. The Western blotting confirmed the increased amount of fibromodulin with maturation. In conclusion, our results show that process of maturation leads to the appearance of a probable fat pad in the center of the fibrocartilage of CT, with a reduced amount of glycosaminoglycans and an increased activity of MMPs. Microsc. Res. Tech. 78:949–957, 2015. © 2015 Wiley Periodicals, Inc.     

Polarization artefacts of an FTIR microscope and the consequences for intensity measurements on anisotropic materials

The infrared beam on both the main Nicolet Nexus bench and the attached Spectra‐Tech Continuum microscope has been shown to be partially polarized. The degree of polarization is ≈ 30%. Although the state of polarization of the infrared beam is of no consequence when measuring the spectra of isotropic materials (gases, liquids), there is a potential problem when considering the spectra of anisotropic materials. Single band intensities are particularly prone to error as small changes in sample thickness or orientation directly affect the intensity. Thickness effects can be overcome by measuring intensity ratios. However, because of the partially polarized nature of the infrared beam, even intensity ratios, illustrated here by the ratio amide I/II of collagen fibres, vary with sample orientation. If overlooked, this effect can be problematic when measuring infrared spectra with an FTIR microscope from samples that are anisotropic or contain anisotropic domains, even though they may appear isotropic on a macroscopic scale. Because dichroic ratios remain unaffected, the intensity ratio from two bands with different transition moments may be used to give a strong indication of the orientation of the sample. This work is illustrated by reference to the FTIR spectra of orientated polyethylene, collagen tape and human trabecular bone.     

Effect of the compression ratio on wear properties of slightly cross-linked ultra-high molecular weight polyethylene, crystallized under uniaxial compression

To improve wear properties of artificial joints, cross-linked ultra-high molecular weight polyethylene (UHMWPE) was crystallized under compression in a molten state. Slight cross-linking was created by γ-ray irradiation at a 0.5 Mrad dose under reduced pressure at room temperature before the compression. Next, the UHMWPE was melted at 200°C and compressed using two metal plates. The compression ratio (CR) is defined as the ratio of the final thickness to the original thickness of the sample. The molecular chain of the UHMWPE was orientated to the direction of deformation and was crystallized by cooling to room temperature while maintaining the deformation. The (2 0 0) crystalline plane was only orientated parallel to the compression plane in the CR=2 sample; however, in the case of the CR=5 sample, both the (2 0 0) and the (1 1 0) crystalline planes were orientated parallel to the compressed surface. The density and melting point of the sample depended on the compression ratio. The physical and the mechanical properties were increased in accordance with their compression ratio. The _c-peak of the loss modulus was shifted to a higher temperature compared with the non-compressed sample. Dimensional stability of the compressed sample by heating near 135°C was not found. It was confirmed that the wear factor also depended on the compression ratio based on the findings of pin-on-disc and pin-on-flat wear tests. The wear factor of the (CR=2) sample was similar to the non-compressed sample (CR=1); in contrast, that of the CR=5 sample was significantly smaller.     

对拉式挡风墙高度和位置对接触网的影响

新疆百里风区铁路电气化改造后,风通过挡风墙在接触网处形成的风速和上吹角影响不容忽视.挡风墙位置和高度发生变化时,将直接影响接触网处的风速和上吹角,较大的风速和上吹角将导致弓网故障.采用高雷诺数k-ε紊流模型进行模拟计算,得出对拉式挡风墙参数变化对接触网的影响,分析确定较好的挡风墙位置和高度参数,从而保证列车的正常运行....     

背压对脱水除油一体式液液分离旋流器流场及分离性能影响的研究

应用FLUENT流体动力分析软件,对脱水除油一体式液液分离旋流器进行了数值模拟,分析了底流背压、溢流背压对旋流器速度分布、流量分率及分离效率的影响。结果表明,底流背压和溢流背压对旋流器流量分率的影响可归结为压降比的影响;底流背压和溢流背压对旋流器分离效率的影响可归结为底流分率的影响;牛顿效率比传统的除油效率和脱水效率更能全面地表征旋流器油水分离的性能。随着底流分率的增大,牛顿效率先升高再降低,存在一个最佳操作点。研究结果及新的表征方法对旋流器的研究和实际应用具有指导意义。     

Effect of carbon fiber content on the friction and wear performance of paper-based friction materials

In order to get homogeneous pores distribution of friction materials, four kinds of micron-level carbon fibers reinforced paper-based friction materials were prepared. Experimental results showed that the porosity of samples decreased with the increase of carbon fiber content. Pores formed in micrometer-level fibers reinforced friction materials were more regular than friction materials reinforced by millimeter-level fibers. The tensile strength of samples decreased with the increase of carbon fiber content. The wear rate of samples increased with the increase of carbon fiber content. The sample with 55% carbon fibers exhibited the best friction stability and anti-shudder performance under oil lubricated conditions.     

Effect of copper content on the mechanical and sliding wear properties of monotectoid-based zinc-aluminium-copper alloys

One binary zinc-aluminium monotectoid and five ternary zinc-aluminium-copper alloys were produced by permanent mould casting. Their wear properties were examined using a block-on-ring test machine. Hardness, tensile strength and percentage elongation of the alloys were also determined and microhardness of aluminium-rich α phase was measured.It was observed that the hardness of the alloys increased continuously with increasing copper content up to 5%. Their tensile strength also increased with increasing copper content up to 2%, but above this level the strength decreased as the copper content increased further. Microhardness of the aluminium-rich α phase was also affected by the copper content in a manner similar to that of the tensile strength. It was found that the wear loss of the alloys decreased with increasing copper content and reached a minimum at 2% Cu for a sliding distance of 700 km. However, the coefficient of friction and temperature due to frictional heating were found to be generally less for the copper containing alloys than the one without the element. The effect of copper on the wear behaviour of the alloys was explained in terms of their microstructure, hardness, tensile strength, percentage elongation and microhardness of the α phase.     

Effect of Reynolds number and boundary layer thickness on the performance of V-cone flowmeter using CFD

The effect of Reynolds number and boundary layer thickness on the performance of V-cone flowmeter has been evaluated using computational fluid dynamics (CFD). The shear stress transport k-ω (SST k-ω) turbulence model has been adopted for closure. The performance of two V-cone flowmeters with different beta ratios (β) viz., 0.6 and 0.7 for a fixed vertex angle (ϕ) of 60° has been analysed as a function of Reynolds number (Re). The results show that the coefficient of discharge (C_d) increases with Reynolds number in the laminar and transition flow regimes whereas it is nearly constant in turbulent flow regime. From the results, it can be concluded that C_d is independent of Re for values equal to 4000 and beyond. Further, it is also seen that the performance of the V-cone flowmeter is not affected by the upstream boundary layer thickness if the velocity profiles having different boundary layer thickness are extracted from an axial distance of 10D and more are fed at 5D upstream of the meter. However, the meter is sensitive to the extracted velocity profile from an axial distance of 5D and uniform velocity profile being fed at 5D upstream. The value of C_d may be sensitive as a result of the pressure variation due to the obstruction.     

预变形量和机械训练对形状记忆合金回复率的影响

利用废钢和生铁为原料,采用特殊保护剂,在大气中熔炼出Fe-Mn-Si-C形状记忆合金;利用应力诱发马氏体相变对Fe-Mn-Si-C合金实现形状记忆效应,探讨了预变形量和机械训练对Fe-Mn-Si-C合金回复率的影响规律.结果表明:在600℃的回复温度下,在一定的变形范围内,回复率随着预变形量的增大而降低;在机械训练过程中,合金的回复率随机械训练次数增加逐渐上升,训练超过一定次数后合金的回复率略有降低.     

Effect of heat treatment on the microstructure and properties of Ni based soft magnetic alloy

A Ni‐based alloy was heat treated by changing the temperature and ambient atmosphere of the heat treatment. Morphology, crystal structure, and physical performance of the Ni‐based alloy were characterized via SEM, XRD, TEM, and PPMS. Results show that due to the heat treatment process, the grain growth of the Ni‐based alloy and the removal of impurities and defects are promoted. Both the orientation and stress caused by rolling are reduced. The permeability and saturation magnetization of the alloy are improved. The hysteresis loss and coercivity are decreased. Higher heat treatment temperature leads to increased improvement of permeability and saturation magnetization. Heat treatment in hydrogen is more conducive to the removal of impurities. At the same temperature, the magnetic performance of the heat‐treated alloy in hydrogen is better than that of an alloy with heat treatment in vacuum. The Ni‐based alloy shows an excellent magnetic performance on 1,373 K heat treatment in hydrogen atmosphere. In this process, the µ_m, B_s, P_u, and H_c of the obtained alloy are 427 mHm^?1, 509 mT, 0.866 Jm^?3, and 0.514 Am^?1, respectively. At the same time, the resistivity of alloy decreases and its thermal conductivity increases in response to heat treatment.     

企业变革中管理者诚信的影响及对策的探讨

企业变革是常态。在利益的驱动下，企业变革中管理者的诚信问题，对企业变革的最终成败具有重大影响。造成不诚信的原因有伦理道德层面的诚信自省缺乏和法律层面的外部约束不足。解决的对策是通过建立诚信的企业文化和诚信制度，使企业在道德与法律的双重约束与驱动下，实现企业市场利益最大化。     

Effect of Ca addition on the microstructure and mechanical properties of as‐cast Mg–Sm alloys

This study investigated the effect of Ca addition on the microstructure and mechanical properties of as‐cast Mg–4Sm alloys. The addition of 1.0 wt% Ca led to a significant grain refinement of Mg–4.0Sm alloys owing to the formation of rod‐like Mg2Ca phases that acted as active nucleates for the Mg matrix. The as‐cast Mg–4.0Sm–1.0Ca alloy showed the smallest grain size at 45 μm. Furthermore, the Mg–4.0Sm–1.0Ca alloy exhibited greater hardness, higher tensile strength, and higher yield tensile strength and elongation than the other two alloys with different Ca contents. These results were attributed to the grain refinement and precipitation strengthening of the Mg2Ca and Mg41Sm5 phases. Microsc. Res. Tech. 79:707–711, 2016. © 2016 Wiley Periodicals, Inc.     

Effect of pressure and temperature on the molecular interaction of polar lubricant containing oleic acid in polypropylene glycol observed by infrared spectroscopy

In this work, we have investigated the infrared spectra of polar lubricant in order to explore the molecular interaction under high pressure and temperature conditions using diamond anvil cell. Polypropylene glycol and oleic acid were used as base oil and additive, respectively. Stretching vibration mode of polar functional groups, such as ν _O–H and ν _C═O, was found to be sensitive to pressure and temperature. The peak positions of the vibration mode were shifted clearly to lower wavenumber as pressure increases, and temperature increase induced a slight shift to higher wavenumber. These results indicate that hydrogen bonding between lubricant molecules of base oil and additive was influenced by pressure and temperature. And furthermore, the dependency of the peak shift was discontinuous and affected mainly by pressure. These results imply a structural change on the basis of the molecular interaction of the lubricating molecules at elastohydrodynamic lubrication contacts. Copyright © 2013 John Wiley & Sons, Ltd.     

Effect of the structure and metal atom of dialkyldithiophosphate derivatives on the wear behaviour in steel‐zirconia contacts

Wear investigations concerning the different structures and metal atoms of metal dialkyldithiophosphates (MeDTPs) were conducted using a ball‐on‐disc apparatus. Steel ball bearings (3.175 mm in diameter) and counterface discs, made of hot pressed ZrO₂ partially stabilised by Y₂O₃, were used. The synthesised MeDTPs were made up of primary linear aliphatic alcohols with hydrocarbon lengths varying from 8 to 16 carbon atoms, and contained the following metals: zinc(II), iron(III), gallium(III), antimony(III), and copper(II). Tests were performed at room temperature. The sliding speed was set to a constant 0.03 m/s, and a constant 30 N load was used. The additives investigated were used as solutions in n‐hexadecane. The study also focused on the influence of additive concentration on wear. It was found that the effectiveness in reducing wear depends both on the metal atom and on the length of the hydrocarbon chain in the additive's molecules. The lowest wear volumes were observed for additives with n‐octyl and n‐tetradecyl hydrocarbon chains. The worst antiwear performance was observed for n‐dodecyl derivatives. For almost all additives, more concentrated solutions resulted in less wear. Some friction coefficient results are also presented.     

Effect of clay content on the morphological,thermo-mechanical and chemical resistance properties of propionic anhydride treated jute fiber/polyethylene/nanoclay nanocomposites

Nanoclay is considered potential nanofiller for the manufacturing of natural fiber nanocomposites. The hydrophilic nature of natural fibers affects negatively its adhesion to hydrophobic polymer matrix. In the present study, propionic anhydride (PA) treated jute were used for the manufacturing of jute/polyethylene/nanoclay nanocomposites. Different amount (wt%) of montmorillonite (MMT) were used as nanofiller in order to optimize the nanoclay in the composite system. Finally, the nanocomposites were prepared using hot press machine at 5, 10, 15, and 20 wt% fiber loadings. Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), tensile tests, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and chemical resistance test were used to evaluate the morphological, thermo-mechanical and chemical resistance properties of the composites.     

Effect of the third-body particles on the tool–chip contact and tool-wear behaviour during dry cutting of aeronautical titanium alloys

In machining process, a major limitation of the tool life is due to wear phenomena that occur at the tool–chip interface. Wear influences the surface quality and dimensional accuracy of the finished product by degrading the shape and efficiency of the tool cutting edge. The basic mechanisms of wear are controlled by the mechanical and physico-chemical properties of the tool and workpiece materials. The cutting conditions such as the cutting speed, the feed rate, and the tool geometry also have an important effect on the tool-wear behaviour. Several basic causes of tool wear have been previously investigated; some of the most important are: abrasion and adhesion wear. During the chip formation, particles are removed from the tool and/or the chip surface and are carried away by the flow of the work material along the contact. It is very hard to understand physical phenomena at the tool–chip interface using only experimental means since the contact between the tool and the machined material occurs under extreme mechanical and thermal loading. The situation is more complicated by the presence of the third body, which generates different wear mechanisms.In the present work, the discrete element method (DEM) based on molecular dynamics is used as a helpful tool to understand the behaviour of the third-body particles and their interactions with the tool and workpiece materials in the contact. Both tool and chip materials are defined as discrete particles connected by solid joints. The tool material (first body) is assumed to be degradable granular material and flows along the second material under a combination of pressure and sliding velocity. A parametric study on the transient phenomenon of the tool degradation has been carried out according to the contact conditions, which strongly depend on the machining parameters. The results show that the tribological parameters can be qualitatively evaluated by conducting both calibration–cutting experiments and DEM simulations.     

Effect of different irrigation protocols on the radicular dentin interface and bond strength with a metacrylate‐based endodontic sealer

This study assessed the influence of different endodontic chemical substances on the adhesion of the Epiphany SE/Resilon system (with and without resinous solvent) to radicular dentin walls, using the push‐out test and scanning electron microscopy (SEM). Forty‐eight root canals of human canines were prepared biomechanically with ProTaper rotary files (crown‐down technique) and the radicular dentin was treated with either 17% EDTA, 2% chlorhexidine gel (CHX) or 2.5% NaOCl (control). The root canals were filled with Resilon cones and Epiphany SE sealer with and without resinous solvent. Six groups of eight canals each had their roots sectioned transversally to obtain 1‐mm thick slices. Data were subjected to statistical analysis by ANOVA and Tukey's tests. The specimens treated with 17% EDTA (1.59 ± 0.91) presented higher bond strength (P < 0.05) than those treated with 2.5% NaOCl (0.93 ± 0.27) and 2% CHX (0.92 ± 0.22). Significantly higher bond strength (P < 0.05) was observed when the Epiphany SE was prepared with (1.37 ± 0.78) than without (0.92 ± 0.33) solvent. Adhesive failures were predominant in all groups. SEM analysis showed greater homogeneity of the filling mass when the solvent was added to the sealer. Treatment of root canal walls with 17% EDTA, and addition of a resinous solvent to Epiphany SE produced the highest adhesion to radicular dentin. Microsc. Res. Tech. 77:446–452, 2014. © 2014 Wiley Periodicals, Inc.