INFLUENCE OF SHAMPOO ON THE MECHANICAL PROPERTIES OF HUMAN HAIRS1)

头发的弹性和抵抗意外拉断的能力是人们非常关注的指标。为了迎合这一需求,有些厂商推出了具有所谓“强韧”发质功效的洗发水,但其实并不清楚是否真能使头发变“强韧”。为此,针对市场上常见的一种标称具有“强韧”功效的洗发水,通过拉伸力学实验对头发洗护前后的力学性能进行了对比研究。结果表明,用洗发水处理后的头发,屈服应力下降,意味着头发更容易过早进入塑性变形;抗拉强度、最大应变减小,意味着头发抵抗外力拉断的能力下降;杨氏模量下降,说明头发抵抗弹性变形的能力变差。综上,所研究的洗发水对“强韧”发质没有帮助。 关键词: 头发,洗发水,力学性能,强度,韧性     

考虑塑性变形发展程度系数的RC梁开裂弯矩改进计算公式

针对RC梁开裂荷载计算方法尚未统一的现状，首先，结合18根RC梁试验数据对比了已有的6种RC梁开裂弯矩计算公式，发现开裂弯矩理论计算值与试验值的偏差大小和混凝土强度有关；然后，通过提出塑性变形发展程度系数k，推导新的RC梁开裂弯矩计算公式，并进一步基于k值和塑性影响系数计算值γ_k进行改进；最后，选取12根RC试验梁验证改进公式的准确性，证明改进公式的计算值与试验值吻合更好且偏于安全。     

生物活性牙科复合树脂的研究进展

牙科复合树脂由于色泽美观,在口腔临床上具有广泛的应用。但其仍然存在边缘缝隙的问题,从而导致继发龋的发生。再矿化复合树脂中的生物活性填料会释放能够再矿化的钙、磷离子,促使材料表面形成矿化层,能够抑制二次龋的发生。本文介绍了不同种类、含量、粒径大小和表面改性的生物活性填料对复合树脂物理、机械性能的影响,分析了再矿化复合树脂的再矿化行为,提出了再矿化复合树脂亟待解决的问题和研究难点,展望了复合树脂的研究方向。     

纳米银改性树脂基托机械性能的初步研究

采用磁控溅射技术在聚甲基丙烯酸甲酯(PMMA)树脂基托表面沉积一层纳米银(Ag NPs)涂层.研究了纳米银改性PMMA树脂基托的机械性能,为改性材料的临床应用提供理论基础.根据国际标准ISO2409:2007描述的划格法对涂层与基底的附着力强度进行测试,各组试件的接触角采用静态液滴法测量,三点弯曲法检测试件的弯曲强度.结果显示,各组涂层与PMMA基底材料结合良好,各组试件的表面润湿性变化不大,其中PMMA-Ag NPs80s组疏水性略有提高,各组试件的弯曲强度均符合国家标准.     

Anchoring Mechanism of ZnO Nanoparticles on Graphitic Carbon Nanofiber Surfaces through a Modified Co‐Precipitation Method to Improve Interfacial Contact and Photocatalytic Performance

A facile three‐step co‐precipitation method is developed to synthesize graphitic carbon nanofibers (CNFs) decorated with ZnO nanoparticles (NPs). By interchanging intermediate steps of the reaction processes, two kinds of nanohybrids are fabricated with stark morphological and physicochemical differences. The morphologies differ because of the different chemical environments of the NP/nanocluster formation. The hybrid with larger and non‐uniform ZnO nanocluster size is formed in liquid phase and resulted in considerable interfacial defects that deteriorate the charge‐transfer properties. The hybrid with smaller and uniform ZnO NPs was formed in a dry solid phase and produced near‐defect‐free interfaces, leading to efficient charge transfer for superior photocatalytic performance. The results broaden the understanding of the anchoring/bonding mechanism in ZnO/CNF hybrid formation and may facilitate further development of more effective exfoliation strategies for the preparation of high‐performance composites/hybrids.     

Optimizing gradient conditions in online comprehensive two‐dimensional reversed‐phase liquid chromatography by use of the linear solvent strength model

The linear solvent strength model was used to predict coverage in online comprehensive two‐dimensional reversed‐phase liquid chromatography. The prediction model uses a parallelogram to describe the separation space covered with peaks in a system with limited orthogonality. The corners of the parallelogram are assumed to behave like chromatographic peaks and the position of these pseudo‐compounds was predicted. A mix of 25 polycyclic aromatic compounds were used as a test. The precision of the prediction, span 0–25, was tested by varying input parameters, and was found to be acceptable with root mean square errors of 3. The accuracy of the prediction was assessed by comparing with the experimental coverages. Less than half of experimental coverages were outside prediction ± 1 × root mean square error and none outside prediction ± 2 × root mean square error. Accuracy was lower when retention factors were low, or when gradient conditions affected parameters not included in the model, e.g. second dimension gradient time affects the second dimension equilibration time. The concept shows promise as a tool for gradient optimization in online comprehensive two‐dimensional liquid chromatography, as it mitigates the tedious registration and modeling of all sample constituents, a circumstance that is particularly appealing when dealing with complex samples.     

Binding Characteristics Study of DNA based Aptamers for E. coli O157:H7

E. coli O157:H7 is a pathogenic bacterium producing verotoxins that could lead to serious complications such as hemolytic uremia syndrome. Fast detection of such pathogens is important. For rapid detection, aptamers are quickly gaining traction as alternative biorecognition molecules besides conventional antibodies. Several DNA aptamers have been selected for E. coli O157:H7. Nonetheless, there has not been a comparative study of the binding characteristics of these aptamers. In this work, we present a comprehensive analysis of binding characteristics including binding affinity (K_d) and binding capacity (B_max) of DNA-based aptamers for E. coli O157:H7 using qPCR. Our results show that aptamer E18R has the highest binding capacity to E. coli 157:H7 and the highest specificity over non-pathogenic E. coli strains K12 and DH5α. Our study also finds that the common biotin-tag modification at 5′ end typically changes the binding capacity significantly. For most of the selected aptamers, the binding capacity after a biotin-tag modification decreases. There exists a discrepancy in the binding capability between the selected aptamer and the aptamer used for detection. Our study also shows that a lower concentration of Mg²⁺ ions in the binding buffer leads to a decrease in the binding capacity of E17F and E18R, while it does not affect the binding capacity of S1 and EcoR1.     

Influence of Carbon Nanotubes on Phase Composition,Thermal and Post-Heating Behavior of Cementitious Composites

This paper experimentally investigates the influence of carbon nanotubes (CNTs) on phase composition, microstructure deterioration, thermal behavior, and residual mechanical strengths of cementitious composites exposed to elevated temperatures. Cement mortars with small dosages of CNTs, 0.05% and 0.2% by weight of cement, were prepared and then heated at 25 °C, 150 °C, 200 °C, 450 °C, and 600 °C for two hours before being tested. The results show positive impact of the CNTs on the hydration process of cement mortar at room temperature and at higher temperatures up to 200 °C. Decomposition of the hydration products is obvious at 450 °C, whereas sever deterioration in the microstructure occurs at 600 °C. The nano reinforcement and bridging effect of the CNTs are obvious up to 450 °C. Thermal behavior characterization shows that CNTs incorporation enhances the thermal conductivity of the unheated and heat-treated mortar specimens. The decomposition of the hydration products needs more heat in the presence of CNTs. Finally, presence of CNTs significantly enhances the residual compressive and flexural strengths of heated mortar specimens for all studied temperatures.     

Enhanced Physical and Mechanical Properties of Nitrile-Butadiene Rubber Composites with N-Cetylpyridinium Bromide-Carbon Black

The physical and mechanical properties of nitrile–butadiene rubber (NBR) composites with N-cetylpyridinium bromide-carbon black (CPB-CB) were investigated. Addition of 5 parts per hundred rubber (phr) of CPB-CB into NBR improved the tensile strength by 124%, vulcanization rate by 41%, shore hardness by 15%, and decreased the volumetric wear by 7% compared to those of the base rubber-CB composite.     

The mosaic structure design to improve the anchoring strength of SiOx@C@Graphite anode

Silicon oxide (SiO_x)-based anodes have aroused great interest as the most promising alternative anode in the practical application of high-performance lithium-ion batteries. However, the electrochemical performance is inhibited because of the large volume change, and the electrode structure deteriorates during the cycling process, which hinders their practical application. In this article, a novel fabrication method for the synthesis of high-performance SiO_x@C@Graphite composites is presented. SiO_x particles are anchored on the graphite surface by chemical vapor deposition and compression molding. This structure makes up the shortcomings of poor electrical conductivity and poor bonding strength between SiO_x and graphite particles. It is beneficial to form a stable solid electrolyte interface and helps to maintain the structural integrity of electrode materials. As a result, the synthetic SiO_x@C@Graphite anode shows a high reversible capacity (2698.8 mA h), excellent cycle stability (about 76.9% capacity retention for 500 cycles) and a superior rate ability. Our research hopes to provide a new idea for improving the bonding strength of the surface coating.