某工程混凝土异常膨胀的调查与分析

该文通过对某工程混凝土出现的冒气、膨胀、开裂现象的现场调查,结合原材料检测和XRD分析,揭示了该工程产生异常质量问题的机理和过程,为混凝土生产企业的质量控制提供参考。     

辉光放电清洗在同步辐射光束线上的应用

同步辐射光束线上存在的碳污染是影响光束线特别是软X光束线传输效率的重要原因,污染的生成与镜箱腔壁上存在有少量的油有关。为了获得更加洁净的真空室,通过辉光放电对镜箱真空室壁进行清洗,力争从源头上减少光学元件碳污染的产生。设计并搭建了一套应用在同步辐射光束线镜箱上的辉光放电清洗系统,并研究了装置在不同真空度下辉光的伏安特性。利用四极质谱对辉光放电前后及过程中镜箱内的残气进行分析。研究得出,真空室表面残留油分子的初步裂解产物主要是分子量为69的粒子。通过辉光放电清洗,真空室内残存的微量油大分子的(分子量为39,41,43,55,57,69,71)减少幅度达到50%。辉光放电清洗对真空腔体内表面油分子有明显的去除效果。本文研究的内容对于减少光束线站特别是软X射线光束线上碳污染具有重要意义。     

Dendrimer as nanocarrier for drug delivery

Dendrimers are novel three dimensional, hyperbranched globular nanopolymeric architectures. Attractive features like nanoscopic size, narrow polydispersity index, excellent control over molecular structure, availability of multiple functional groups at the periphery and cavities in the interior distinguish them amongst the available polymers. Applications of dendrimers in a large variety of fields have been explored. Drug delivery scientists are especially enthusiastic about possible utility of dendrimers as drug delivery tool. Terminal functionalities provide a platform for conjugation of the drug and targeting moieties. In addition, these peripheral functional groups can be employed to tailor-make the properties of dendrimers, enhancing their versatility. The present review highlights the contribution of dendrimers in the field of nanotechnology with intent to aid the researchers in exploring dendrimers in the field of drug delivery.     

Electroactive phases of poly(vinylidene fluoride): Determination,processing and applications

Poly(vinylidene fluoride), PVDF, and its copolymers are the family of polymers with the highest dielectric constant and electroactive response, including piezoelectric, pyroelectric and ferroelectric effects. The electroactive properties are increasingly important in a wide range of applications such as in biomedicine, energy generation and storage, monitoring and control, and include the development of sensors and actuators, separator and filtration membranes and smart scaffolds, among others. For many of these applications the polymer should be in one of its electroactive phases. This review presents the developments and summarizes the main characteristics of the electroactive phases of PVDF and copolymers, indicates the different processing strategies as well as the way in which the phase content is identified and quantified. Additionally, recent advances in the development of electroactive composites allowing novel effects, such as magnetoelectric responses, and opening new applications areas are presented. Finally, some of the more interesting potential applications and processing challenges are discussed.     

Enhancing the solubility and bioavailability of isoflavone by particle size reduction using a supercritical carbon dioxide-based precipitation process

Isoflavones are a group of small molecular compounds found in many plants. Genistein is the most well studied isoflavones because of its beneficial effects in reducing menopausal symptoms, anti-oxidant and anti-cancer. The major difficulty in developing isoflavone-based healthcare products is their low water solubility. In this study, the solubility and oral bioavailability of genistein were increased by reducing its particle size using supercritical CO₂ as an antisolvent in the precipitation process. The effects of various process parameters including type of solvent, pressure of precipitation, and concentration of genistein solution on particle formation were evaluated. We found that under optimized conditions: dissolving 4 mg/mL genistein in acetone and precipitating them with supercritical CO₂ under 100 bar at 40 °C, the size of genistein particles was reduced from its original width of 10–50 μm to ∼254 nm. The reduction of genistein particle size not only increased its water solubility by 2 fold but more importantly increased its 24 h-plasma concentration by 2.6 fold after orally administrated to rats. These results proof the concept of using supercritical CO₂ as an antisolvent in the precipitation process to reduce particle size of water insoluble compounds such as genistein and to improve its oral bioavailability.     

Processing and characterization of nano-magnetic Co0.5Ni0.5Fe2O4 system

Various techniques such as X-ray diffraction (XRD), infrared (IR) spectroscopy, scanning electron micrographs (SEM), energy dispersive X-ray (EDX) and a vibrating sample magnetometer (VSM) were used to investigate the structural, morphological, and magnetic properties of spinel Co_0.5Ni_0.5Fe₂O₄ system. XRD and IR analyses enabled us to determine the functional group and structural parameters of Co_0.5Ni_0.5Fe₂O₄. EDX measurements showed the concentrations of O, Ni, Fe, and Co species involved in Co_0.5Ni_0.5Fe₂O₄ specimen from the uppermost surface to the bulk layers. The magnetization and coercivity of the as synthesized composite were 77 emu/g and 128 Oe, respectively.     

Erosion resistance of CO2 corrosion scales formed on API P110 carbon steel

The erosion resistance of CO₂ corrosion scales formed on carbon steel was investigated in water–sand two-phase flow utilizing weight loss test, scanning electron microscopy, and X-ray diffraction. The effects of CO₂ partial pressure, stirring speed, test time, and grain size on the erosion resistance of the scales were analysed. Results show that several characteristics of CO₂ corrosion scales are key factors affecting erosion resistance. Cubic polynomials are used to fit the erosion rate data, and effectively evaluate the ability of CO₂ corrosion scales to resist erosion. An erosion mechanism, based on fluid dynamics and CO₂ corrosion scales characteristics, is discussed.     

Fermentation and heat-moisture treatment induced changes on the physicochemical properties of foxtail millet (Setaria italica) flour

This research intends to verify the effect of Lactobacillus paracasei Fn032 fermentation and heat-moisture treatment (HMT) on the physicochemical properties of foxtail millet (Setaria italica) flour. The results obtained showed a significant (P < 0.05) increase in protein content (12.02–20.54%), total starch (15.78–51.01%) and starch fractions after fermentation and HMT. Differential scanning calorimetry (DSC) analysis showed high decomposition temperature (T_d) trend of 180.59 and 189.82 °C after HMT. However, there was significant (P < 0.05) enthalpy (ΔH) decrease. Flour digestion resulted in variation of slow digestible starch (SDS) and resistant starch (RS) count from 6.83 to 18.42% and 7.61 to 22.68% respectively, after fermentation and HTM. Following this observation, it was ascertained that in X-ray diffraction; pasting viscosity and fluorescence spectrophotometry show greater HMT influenced on the flour components. Findings from the scanning electron microscopy (SEM) analysis showed microstructure differences of the flours samples. Fermentation and heat moisture treatment methods present a possible way of changing or improving the physicochemical properties and add nutritional value to foxtail millet meal.     

Copper substituted nickel ferrite nanoparticles anchored onto the graphene sheets as electrode materials for supercapacitors fabrication

Nickel ferrites with high theoretical capacitance value as compared to the other metal oxides have been applied as electrode material for energy storage devices i.e. batteries and supercapacitors. High tendency towards aggregation and less specific surface area make the metal oxides poor candidate for electrochemical applications. Therefore, the improvements in the electrochemical properties of nickel ferrites (NiFe₂O₄) are required. Here, we report the synthesis of graphene nano-sheets decorated with spherical copper substituted nickel ferrite nanoparticles for supercapacitors electrode fabrication. The copper substituted and unsubstituted NiFe₂O₄ nanoparticles were prepared via wet chemical co-precipitation route. Reduced graphene oxide (rGO) was prepared via well-known Hummer's method. After structural characterization of both ferrite (Ni_1-xCu_xFe₂O₄) nanoparticles and rGO, the ferrite particles were decorated onto the graphene sheets to obtain Ni_1-xCu_xFe₂O₄@rGO nanocomposites. The confirmation of preparation of these nanocomposites was confirmed by scanning electron microscopy (SEM). The electrochemical measurements of nanoparticles and their nanocomposites (Ni_0.9Cu_0.1Fe₂O₄@rGO) confirmed that the nanocomposites due to highly conductive nature and relatively high surface area showed better capacitive behavior as compared to bare nanoparticles. This enhanced electrochemical energy storage properties of nanocomposites were attributed to the graphene and also supported by electrical (I-V) measurements. The cyclic stability experiments results showed ~65% capacitance retention after 1000 cycles. However this retention was enhanced from 65% to 75% for the copper substituted nanoparticles (Ni_0.9Cu_0.1Fe₂O₄) and 65–85% for graphene based composites. All this data suggest that these nanoparticles and their composites can be utilized for supercapacitors electrodes fabrication.     

Comparative study of La0.5Nd0.2Ca0.3–xKxMnO3 (x = 0.0 and 0.05) nanoparticles: Effect of A-cation size and calcination temperature

In order to study the effect of sintering temperature and A-site cation radius on the structural, magnetic and transport properties, a systematic investigation of La_0.5Nd_0.2Ca_0.3–xK_xMnO₃ (x = 0.0 and 0.05) nanoparticles has been undertaken. Rietveld analysis of X-ray diffraction data confirmed the presence of orthorhombic symmetry with Pbnm space group for all the samples. A paramagnetic-ferromagnetic transition is shown by all our investigated compounds. The materials exhibit semiconducting behavior and the metal-semiconductor transition temperatures (T_MS) are found to be close to Curie temperatures (T_c), indicating a strong correlation between their electrical and magnetic properties. Both T_c and T_MS of K-doped samples were found to be higher than their undoped counterparts at same calcination temperatures. In the high temperature region, it was observed that the resistivity data was best fitted by SPH model.