Comparison on Tensile Characteristics of Plain C–Mn Steel with Ultrafine Grained Ferrite/Cementite Microstructure and Coarse Grained Ferrite/Pearlite Microstructure

This work investigated the tensile characteristics of plain C–Mn steel with an ultrafine grained ferrite/cementite (UGF/C) microstructure and coarse-grained ferrite/pearlite (CGF/P) microstructure. The tensile tests were performed at temperatures between 77 K and 323 K. The lower yield and the ultimate tensile strengths were significantly increased when the microstructure was changed from the CGF/P to the UGF/C microstructures, but the total elongation and the uniform elongation decreased. A microstructural change from the CGF/P microstructure to the UGF/C microstructure had an influence on the athermal component of the lower yield and the ultimate tensile strengths but not on the thermal component. The UGF/C microstructure with a higher carbon content provided a higher strength without losing ductility because cementite particles restrained necking.     

Effect of Cu Content on Performance of Sn-Zn-Cu Lead-Free Solder Alloys Designed by Cluster-Plus-Glue-Atom Model

The mechanical properties of solder alloys are a performance that cannot be ignored in the field of electronic packaging. In the present study, novel Sn-Zn solder alloys were designed by the cluster-plus-glue-atom (CPGA) model. The effect of copper (Cu) addition on the microstructure, tensile properties, wettability, interfacial characterization and melting behavior of the Sn-Zn-Cu solder alloys were investigated. The Sn₂₉Zn_4.6Cu_0.4 solder alloy exhibited a fine microstructure, but the excessive substitution of the Cu atoms in the CPGA model resulted in extremely coarse intermetallic compound (IMC). The tensile tests revealed that with the increase in Cu content, the tensile strength of the solder alloy first increased and then slightly decreased, while its elongation increased slightly first and then decreased slightly. The tensile strength of the Sn₂₉Zn_4.6Cu_0.4 solder alloy reached 95.3 MPa, which was 57% higher than the plain Sn-Zn solder alloy, which is attributed to the fine microstructure and second phase strengthening. The spreadability property analysis indicated that the wettability of the Sn-Zn-Cu solder alloys firstly increased and then decreased with the increase in Cu content. The spreading area of the Sn₂₉Zn_0.6Cu_0.4 solder alloy was increased by 27.8% compared to that of the plain Sn-Zn solder due to Cu consuming excessive free state Zn. With the increase in Cu content, the thickness of the IMC layer decreased owing to Cu diminishing the diffusion force of Zn element to the interface.     

Process–Structure–Property Relationships of Copper Parts Manufactured by Laser Powder Bed Fusion

The process–structure–property relationships of copper laser powder bed fusion (L-PBF)-produced parts made of high purity copper powder (99.9 wt %) are examined in this work. A nominal laser beam diameter of 100 μm with a continuous wavelength of 1080 nm was employed. A wide range of process parameters was considered in this study, including five levels of laser power in the range of 200 to 370 W, nine levels of scanning speed from 200 to 700 mm/s, six levels of hatch spacing from 50 to 150 μm, and two layer thickness values of 30 μm and 40 μm. The influence of preheating was also investigated. A maximum relative density of 96% was obtained at a laser power of 370 W, scanning speed of 500 mm/s, and hatch spacing of 100 μm. The results illustrated the significant influence of some parameters such as laser power and hatch spacing on the part quality. In addition, surface integrity was evaluated by surface roughness measurements, where the optimum Ra was measured at 8 μm ± 0.5 μm. X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDX) were performed on the as-built samples to assess the impact of impurities on the L-PBF part characteristics. The highest electrical conductivity recorded for the optimum density-low contaminated coils was 81% IACS.     

Characterization of the microtubule-binding activity of kinesin-like calmodulin binding protein from Dunaliella salina

Although the C-terminal motor and the N-terminal myosin-like domains of KCBP in Dunaliella salina (DsKCBP) are implicated in interaction with the microtubules, its microtubule binding property has not been addressed. It has been shown that several calmodulin isoforms suppress the microtubule binding activity of KCBP, but whether the calmodulin-like protein (CLP) has this ability remains unknown. The results of our previous study showed that there are two microtubule binding sites in DsKCBP, motor domain at the C-terminus and MyTH4-FREM at the N-terminus. In the present study, MyTH4, without the companion of FERM, was identified as the minimal domain responsible for interaction with the microtubules in the N-terminal of DsKCBP. CLP interacted with the calmodulin-binding domain of DsKCBP in the presence of Ca²⁺, and inhibited the microtubule-binding activity of motor domain but not MyTH4 domain. Furthermore, MyTH4 domain in the N-terminus of DsKCBP was responsible for binding to the microtubules, and had 10-fold weaker affinity to the microtubules than the motor domain.     

Regulation of intracellular metabolism by biodegradable polyrotaxanes

Cellular response to our designed biodegradable polyrotaxanes was investigated in terms of changes in cytoplasmic calcium levels in platelets. The polyrotaxanes regulated thrombin-induced calcium increase in platelets although constituent molecules of the polyrotaxanes showed fewer effects on the intracellular metabolism. Further, an increase in membrane fluidity of red blood cell ghosts was significantly observed by the addition of the polyrotaxanes. Static light scattering study revealed that the polyrotaxanes formed a supramolecular association state in relation to the molecular weight of PEG: a loosely packed association with a specific molecular shape. From these characteristics, it is suggested that supramolecular level interactions between the polyrotaxanes and cell membranes regulate the intracellular metabolism. It is concluded that these biodegradable polyrotaxanes can be feasible as temporarily-controlled bioactivator.     

Star-shaped PCL/PLLA blended fiber membrane via electrospinning

Electrospun fiber mesh has been a candidate for guided bone regeneration membrane. However, its poor mechanics property has been limited in clinical application. In this study, various star-shaped poly(ε-caprolactones) (PCLs) are successfully synthesized by ring-opening polymerization and mixed with poly(l-lactide) (PLLA) to be made into blended membranes through electrospinning. Their corresponding properties are evaluated including morphology, thermodynamics, mechanics, and cytotoxicity. The blended fibers show smooth surface and well-distributed structure, which have slight differences in morphology with the change of arm number of star-shaped PCL. Crystallization of the fibrous membrane is influenced by star-shaped PCLs. Glass temperature drops from 64.23 °C for pure PLLA membrane to 53.62–49 °C for the blended membranes. The membranous tensile strength is depended strongly on star-shaped PCLs. The tensile strength goes up with arm number increasing; on the contrary, at the same arm number, the mechanics strength decreases with molecular weight increasing. And the fibrous membrane containing 20 wt.% star-shaped PCL shows better mechanics property compared to the other membranes. The star-shaped PCL/PLLA fiber membrane is not cytotoxicity.     

Grafting antibiofilm polymer hydrogel film onto catheter by SARA SI-ATRP

Abstract

Catheters are widely used and play an important role in medicine. However, catheter-associated infection is prevalent even under stringent sterile conditions. Biofilms are formed when bacteria populate the surfaces of catheters. This makes the biofilm resistant to antibiotics. Hence, it is imperative for there to be an inherently antifouling and anti-bacterial catheter to mitigate the formation of biofilm. This paper aims to outline the synthesis of non-leachable anti-biofilm and anti-bacterial cationic film coatings through direct polymerization using supplemental activator and reducing agent surface initiated atom transfer radical polymerization (SARA SI-ATRP). Three crosslinked cationic coatings comprising of Diallyl dimethyl ammonium chloride (DADMAC), or ε-poly-L-lysine HCl methacrylic acid (EPL-MA) together with a crosslinker (polyethylene glycol dimethacrylate, PEGDMA) were investigated. These non-leachable covalently linked coatings with DADMAC can achieve more than 2 log reduction (99.0%) with Methicillin-resistant Staphylococcus aureus (MRSA) and 1.25 log reduction (94.4%) with Vancomycin resistant Enterococcus (VRE) in in vitro studies.     

Division of family property in Taiwan

Since property ownership affords the elderly some control over resources and perhaps even support and respect from potential caretakers, examination of the decision to transfer property to children can help us gain insight into the underlying dynamics of intergenerational exchanges between the elderly and their children. In this paper we use data from the 1989 Survey of Health and Living Status of the Elderly in Taiwan to explore the demographic and social characteristics associated with pre-mortem property division. From both bivariate and multivariate analyses, we find that the likelihood of property division is positively related to age, widowhood, natality in Taiwan, rural residence, and the number of living children, and negatively related to education. After controlling for other characteristics, our results show that widows are more than twice as likely as widowers to have divided all their property. These results lend statistical support to findings in the ethnographic literature on the Chinese family.     

各向异性松质骨弹性性能有限元分析

骨质疏松会导致松质骨细化从而降低松质骨力学性能。为了评估椎体松质骨的力学特性,文中采用有限元参数化建模,利用十四面体模型模拟棒状小梁骨的微结构,对各向异性松质骨的弹性性能进行了计算分析。通过控制输入参数Tb.Th、Tb.Sp、E0模拟不同骨质疏松程度的松质骨。计算结果表明,松质骨模量与骨体积分数呈平方律关系;随着各向异性比的增加,松质骨纵、横向模量间的比值呈线性增加,而横向两个模量保持基本一致。结果说明该微结构模型较好地反映了松质骨的横观各向同性性质,并能较好地反映受载松质骨的应力分布。     

Sesamin as a co-initiator for unfilled dental restorations

A natural component, sesamin (SA), was used to replace conventional amine as co-initiator for dental composite. A combination of camphorquinone (CQ) and SA was employed to initiate the photopolymerization of 2-2-bis[4-(2-hydroxy-3-methacryloxyprop-1-oxy)phenyl] propane/triethylene glycol dimethacrylate (70/30 wt.%). The kinetics was recorded by real-time Fourier transform infrared spectroscopy. The mechanical properties were measured by dynamic mechanical analysis, the cell toxicity was investigated by MTT assay and a mixture of CQ and ethyl 4-N,N-dimethylaminobenzoate (EDMAB) was used as control in the same photocuring condition. The results indicated that the addition of SA as co-initiator greatly improved the rate of polymerization and final double-bond conversion (DC) when compared with the system initiated by CQ alone. Compared with EDMAB, the final DC of the CQ/SA system (71%) was slightly lower than that of CQ/EDMAB (76%); SA resulted in approximately the same storage modulus at around 37 °C, but a slightly higher glass transition temperature. SA produced lower yellowing effect and good in vitro biocompatibility. The water sorption and solubility for two mixtures were very close and within the range of the ISO 4049 specification. These results suggest that SA is an effective alternative co-initiator to conventional amine. The natural compound characteristics of SA make it more promising than amine in dental resin formulations.