A method to fabricate hydroxyapatite/poly(lactic acid) microspheres intended for biomedical application

The interaction between organic and inorganic materials enables one to fabricate inorganic/organic microsphere composites. In a novel microemulsion method, we have prepared surfactant-free poly(lactic acid) (PLA)/hydroxyapatite (HAp) microspheres by using the interfacial interaction between inorganic and organic materials, because surfactants are undesireble materials for biomedical applications due to their non-biodegradability. The studies that varied the ion concentrations in oil/water microemulsions revealed that HAp was nucleated at the end group PLA, COOH, and the array of the PLA end groups determined the crystal phase of the calcium phosphate as HAp under the low ion concentration condition. PLA induced the nucleation and precipitation of HAp at the oil/water interface, simultaneously, the precipitated HAp stabilized the microemulsion without surfactants. This novel process made surfactants unnecessary for organic/inorganic microsphere fabrications.     

超声冲击对高速列车转向架焊接十字接头超高周疲劳性能的影响

针对高速列车转向架在实际运用中出现的疲劳问题,利用HJ-Ⅲ型超声冲击处理装置,对高速列车转向架用SAM490BW钢十字接头焊趾进行超声冲击处理,并对处理后接头的超高周疲劳性能进行研究。结果表明,原始焊态试样和超声冲击态试样的S-N曲线均出现了传统意义上的水平段。超声冲击处理试样的疲劳强度相比于未处理试样提高了25%。经过超声冲击处理后,疲劳裂纹源的数量由多个变为单个,焊接接头焊趾处的应力集中系数下降了32.4%,降低了裂纹萌生概率;超声冲击降低了焊趾区域的残余拉应力,并诱发产生残余压应力,高达-255.5 MPa;焊趾表层晶粒得到细化,晶粒平均尺寸小于100nm;裂纹在塑性变形区扩展路径变长。     

稀土Ce对激光熔覆高硼贝氏体涂层性能的影响

利用激光熔覆制备了不同Ce含量的高硼贝氏体涂层.采用扫描电镜对不同Ce含量的涂层组织进行表征;利用显微硬度计检测熔覆层显微硬度;通过万能拉伸机测试熔覆涂层的断裂韧性;用往复摩擦磨损试验机测试涂层的磨损性能.结果表明:经稀土Ce改性后,初生奥氏体晶粒尺寸减小,晶间网格状硼化物形态得到改善,呈现断网或颗粒状.三点弯曲断裂韧...     

Identification of variety cycles in food choices: Its’ impact on state-dependence coefficients

In food products, the demand for variety is satisfied in purchasing cycles, and different products are demanded and consumed in each cycle, until the acceptable and/or available variety is depleted. The presentation of the variety cycle concept constitutes the basic contribution of this research; it allows us to be able to explain different purchasing behaviours by consumers. Our study also points out some research implications by providing a further explanation to the dynamics of state-dependence coefficients, inertia and variety seeking, of individuals, in addition to their experience or their tendency to seek variety.     

Investigation on in situ Al0.5FeSi0.5/Al composites prepared by transient liquid phase sintering

In situ Al_0.5FeSi_0.5/Al composites were prepared by transient liquid-phase sintering. The hardness and wear resistance of the composites were investigated with an XHV-1000 microhardness tester and an M-2000 wear tester. Results show that with increased sintering temperature and holding time, the in situ needle-like reinforcement is transformed into short, bar-like, massive particles. At a sintering temperature of 510 °C and holding time of 4 h, the reinforcement consists of short, bar-like Al_0.5FeSi_0.5; moreover, the hardness of the in situ Al_0.5FeSi_0.5/Al composites peaks to a value eight times that of pure aluminum and 2.5 times that of Al–Si alloy. Accordingly, the wear resistance of the composites is the highest, i.e., 6.6 that of pure Al and 4.5 times that of Al–Si alloy.     

Synthesis of cadmium sulfide nanosheets for smart photocatalytic and sensing applications

Herein, we report the synthesis, characterizations, photocatalytic and sensing applications of ultra-wide cadmium sulfide (CdS) nanosheets. The CdS nanosheets were prepared by a simple solution process at low-temperature using cetyltrimethyl ammonium bromide (CTAB) as a stabilizing agent. The synthesized CdS nanosheets were characterized by several techniques which confirmed large-scale growth, well-crystallinity and hexagonal crystal phase of the prepared nanosheets. The synthesized nanosheets were used as effective photocatalyst for the photocatalytic degradation of harmful toxic dye, i.e. methyl orange. The photocatalytic activities were evaluated by measuring the photodegradation rate of MO in presence of CdS nanosheets under UV light irradiation. Interestingly, over 90% degradation of MO dye was achieved in 75 min using 0.15 g of photocatalyst, i.e. CdS nanosheets. Further, the synthesized nanosheets were used as efficient scaffold to fabricate highly sensitive, selective and reproducible fluorescent sensor for the detection of Picric Acid (PA). The observed detection of limit for the fabricated sensor was ~2.46 μM. Moreover, the interfering studies confirmed that the developed sensor possesses very good selectivity towards PA as it detect selectively even in the presence of several other coexisting aromatic compounds such as phenol, benzaldehyde, benzoic acid and aniline.     

Magnetic lamellar nanohydroxyapatite as a novel nanocarrier for controlled delivery of 5-fluorouracil

Magnetic nanoparticles are attractive carriers for drug delivery and layered materials intercalated by drug molecules exhibit improved safety and effectiveness of drug delivery. In this work, we report the loading of a model anticancer drug, 5-fluorouracil (5FU), into a magnetic layered nanohydroxyapatite (ML-HAP) by intercalation technique. The as-prepared ML-HAP nanoparticles with loaded 5FU were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and vibrating sample magnetometer. We find that, within a certain drug concentration, the drug molecules can be intercalated into the gallery of ML-HAP without breaking its lamellar structure. The drug loading capacity of ML-HAP is extremely large. The drug release profiles display pH-dependent behavior and the drug release mechanisms are a combination of drug diffusion and HAP dissolution. Furthermore, ML-HAP/5FU shows strong superparamagnetism and good biocompatibility. The ML-HAP can be an efficient platform for targeted anticancer drug delivery.     

Surface amination and hydrolyzation of carbon fibers treated with triethylene tetramine in supercritical water/ethanol system

To improve the interfacial properties between carbon fibers and epoxy matrix, the fibers were treated by an ammoniac medium, which consisted of supercritical water, ethanol and triethylene tetramine. The images of atomic force microscopy and scanning electron microscope indicate that coating layers are formed on the surfaces of treated fibers. The results of X-ray photoelectron spectroscopy demonstrate that N content on the surfaces of carbon fibers increases and the main ammoniac groups of the coating layers are amino and imino groups. The mechanical measurements indicate that both interlaminar and interface shear strength of carbon fibers are significantly increased after amination.     

轧制工艺对薄带铸轧无取向硅钢组织性能的影响

利用光学显微镜、XRD、EBSD等研究了轧制工艺对薄带铸轧无取向硅钢组织、织构和磁性能的影响。研究表明,随热轧压下率增大,冷轧组织变形储能及剪切带的比例逐渐降低,冷轧板中α织构减弱,γ织构增强。退火板晶粒尺寸随热轧压下率增大而增加。热轧压下率为17%及40%时,退火织构以强的Goss织构及相对弱的{100}织构为主,热轧压下率达到55%后,退火织构为强的{115}<110>和{114}<371>织构,Goss织构和{100}组分明显减弱。随热轧压下率增大,退火板磁感值先升高后降低,铁损值先减小后增加。热轧压下率为40%时,退火板综合磁性能最优。     

Arc erosion behavior of a nanocomposite W-Cu electrical contact material

The erosion behavior of a nanocomposite W-Cu material under arc breakdown was investigated. The arc erosion rates of the material were determined, and the eroded surfaces and arc erosion mechanisms were studied by scanning electron microscopy. It is concluded that the nanocomposite W-Cu electrical contact material shows a characteristic of spreading arcs. The arc breakdown of a commercially used W-Cu alloy was limited in a few areas, and its average arc erosion rate is twice as large as that of the former. Furthermore, it is also proved that the arc extinction ability and arc stability of the nanocomposite W-Cu material are excellent, and melting is the major failure modality in the make-and-break operation of arcs.