Synthesis of ethyl propionate catalyzed by poly(N‐AEAAm‐co‐AAc)‐cl‐MBAm hydrogel‐immobilized lipase of Bacillus coagulans MTCC‐6375

A purified alkaline thermotolerant bacterial lipase of Bacillus coagulans MTCC‐6375 was efficiently immobilized onto poly(N‐AEAAm‐co‐AAc‐cl‐MBAm)‐hydrogel at pH 8.5 and at temperature 55°C in 16 h. The hydrogel‐bound matrix possessed 1.04 U/g (matrix) lipase activity with a specific activity of 1.8 U/mg of protein. The immobilized lipase resulted in formation of 52.5 mM of ethyl propionate (52% conversion) at 55°C in 9 h in n‐nonane. Ethanol and propionic acid when used in a ratio of 300 : 100 mM, respectively, in n‐nonane along with 10 mg of hydrogel‐bound lipase resulted in optimal synthesis of ethyl propionate (82.5 mM). Addition of molecular sieves (3 Å, 0.7 g/reaction volume) further enhanced the conversion rate to 82.4% resulting in 83.5 mM of ethyl propionate. Incubation temperature below or above 55°C had a marked effect on the synthesis of ethyl propionate. However, esterification performed in n‐heptane at 65°C resulted in 87.5 mM of ethyl propionate with a conversation rate of 89.3%. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Preparation and Crystal Structure of KFeCl3 and KFeBr3

The preparation and crystal structures of anhydrous KFeCl₃ and KFeBr₃ are described. X-ray diffraction data obtained at room temperature indicate that the two compounds belong to the orthorhombic system, space group Pnma and z = 4. Unit cell parameters are a = 8.712 Å, b = 3.845 Å, c = 14.15 Å for KFeCl₃ and a = 9.220 Å, b = 4.026 Å, c = 14.899 Å for KFeBr₃. Atomic positions were determined.     

Effect of Precursor and Solvent on Morphology of Zirconia Nanoparticles Produced by Combustion Aerosol Synthesis

Zirconia nanoparticles were synthesized using a flame-based system involving spray droplet combustion of different precursor solutions. The characteristics of the feed were varied by varying the precursor compound, precursor concentration, and solvent type, and by using droplets of different mean sizes. When large droplets were used, agglomerated particles were formed when an organometallic precursor was used and large cenospheric particles were produced when an inorganic precursor was used. Reduction of the droplet size to a number-mean droplet diameter of 3.2 μm resulted in the production of solid spherical particles regardless of the precursor type. When an inertial impactor was used to eliminate droplets larger than 2.3 μm, the large particles in the final product were eliminated and uniformly sized solid zirconia particles having a smaller mean size were produced. The final particle size did not vary with the concentration of the precursor, indicating that multiple ceramic particles resulted from each precursor-containing droplet.     

Prediction of Experimental Methanol Decomposition Rates on Platinum from First Principles

A microkinetic model for methanol decomposition on platinum is presented. The model incorporates competitive decomposition pathways, beginning with both O–H and C–H bond scission in methanol, and uses results from density functional theory (DFT) calculations [Greeley and Mavrikakis, J. Am. Chem. Soc. 124 (2002) 7193, Greeley and Mavrikakis, J. Am. Chem. Soc. 126 (2004) 3910]. Results from reaction kinetics experiments show that the rate of H₂ production increases with increasing temperature and methanol concentration in the feed and is only nominally affected by the presence of CO or H₂ with methanol. The model, based on the values of binding energies, pre-exponential factors and activation energy barriers derived from first principles calculations, accurately predicts experimental reaction rates and orders. The model also gives insight into the most favorable reaction pathway, the rate-limiting step, the apparent activation energy, coverages, and the effects of pressure. It is found that the pathway beginning with the C–H bond scission (CH₃OH→H₂COH→HCOH→CO) is dominant compared with the path beginning with O–H bond scission. The cleavage of the first C–H bond in methanol is the rate-controlling step. The surface is highly poisoned by CO, whereas COH appears to be a spectator species.     

Melt‐processable rubber: Chlorinated waste tire rubber‐filled polyvinyl chloride

Chlorinated ground rubber tire (Cl‐GRT) particles were used as filler in a plasticized polyvinylchloride (PVC) to develop a melt‐processable rubber composition. Physical properties of the Cl‐GRT‐filled PVC compound showed improvement compared to the nonchlorinated counterpart. Interaction between Cl‐GRT and PVC was examined on the basis of results of stress relaxation, dynamic mechanical thermal analysis, and solvent swelling studies. The Cl‐GRT could be loaded upto 40 parts per hundred parts of PVC, and the composition still retains the elastomeric characteristics. The Cl‐GRT‐filled composite was found to be reprocessable like the unfilled PVC compound. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 622–631, 2002; DOI 10.1002/app.10352     

高速公路施工区车辆强制换道耗时生存模型

为研究高速公路施工区车辆强制换道行为及其影响因素,采用生存分析中的半参数分析方法建立强制换道耗时的乘法风险率模型.通过无人机拍摄采集高速公路施工区的车辆换道耗时及其影响因素数据,最终确立换道耗时Cox比例风险模型,对换道耗时数据进行Cox回归建模分析.结果表明:近77%的换道车辆在10 s内完成换道;小型车和中型车经养护施工区的换道耗时未发现显著性差别;对于相同的换道耗时,平峰期的累积生存率明显低于高峰期和过渡时期,而高峰期的累积生存率最高.建立的强制换道耗时生存模型可有效的定量分析车型和交通时段对高速公路施工区车辆换道行为的影响,可为高速公路施工区交通管理控制及车辆换道行为建模及仿真奠定一定的理论基础.     

Near infrared light-induced disassembly of polymeric micelles based on methylene blue conjugated polyethylene glycol

Light-sensitive drug delivery systems are considered ideal for applications in the biomedical fields for their ability to release the payload in an on-demand spatiotemporal controlled manner through the manipulation of the light source. Among the broad radiation spectrum, near infrared (NIR) light is considered advantageous compared to UV and visible light, due to its inherently lower photodamage to normal tissues and deeper penetration to lesion areas. In this study, we report a successful synthesis of a polymer capable of undergoing partial degradation upon irradiation with NIR light by conjugating 10-N-carbamoyl linkage methylene blue (MB) moiety, a NIR photocleavable ligand, with polyethylene glycol (PEG). Through effective coupling of MB, a hydrophobic moiety, to the hydrophilic PEG molecule, an amphiphilic polymer was synthesized, as demonstrated by a lowered surface tension (55 mN/m at 0.1% wt/vol). Subsequently, photo-induced reversal of surface activity associated with self-assembled structure disruption, was displayed by surface tension measurements, size distribution analysis, and burst release profile of paclitaxel (PTX) from polymeric micelles upon the exposure to NIR irradiation.     

Preparation and cell-materials interactions of plasma sprayed strontium-containing hydroxyapatite coating

The use of strontium-containing hydroxyapatite (Sr-HA) as a biomaterial has been reported recently. In vitro and in vivo studies have shown that Sr-HA promotes osteoblast response and stimulates new bone formation. In order to extend its usage to major load-bearing applications, such as artificial hip replacement, it has been proposed that the material could be used in the form of a coating on implant surfaces. This paper reports a preliminary study of biocompatibility of plasma sprayed Sr-HA coatings on a metallic substrate. Coatings of Sr-HA containing 10 mol% Sr²⁺ was produced on titanium alloy substrates. The coating exhibited good bonding with the substrate. The bioactivity of Sr-HA coating was evaluated in vitro by immersion in simulated body fluid (SBF). After immersion in SBF, Sr-HA coating exhibited great ability to induce apatite precipitation on its surface. The possible effects of cell-materials interactions of Sr-HA coating were examined by culturing osteoprecursor cells (OPC1) on coating surfaces. The effect of Sr-HA was also compared to a hydroxyapatite (HA) coating, which is widely used in orthopedics and dentistry. The results indicated that Sr-HA coating had good biocompatibility with human osteoblasts. OPC1 cells survived and proliferated well on the surface of coating. Sr-HA coating promoted OPC1 cells attachment, and more local contacts were produced on the surface. The presence of Sr stimulated OPC1 cell differentiation and ALP expression. No deleterious effect on ECM formation and mineralization was found with Sr-HA coating. The results indicated that Sr-HA coating had good mechanical properties and bioactivity in vitro.     

Multi-objective reactive power market clearing in competitive electricity market using HFMOEA

This paper presents an application of a hybrid fuzzy multi-objective evolutionary algorithm (HFMOEA) for solving a highly constraint, mixed integer type, complex multi-objective reactive power market clearing (RPMC) problem for the competitive electricity market environment. In HFMOEA based multi-objective optimization approach, based on the output of a fuzzy logic controller crossover and mutation probabilities are varied dynamically. It enhances stochastic search capabilities of HFMOEA. In multi-objective RPMC optimization framework, two objective functions namely the total payment function (TPF) for reactive power support from generators and synchronous condensers and the total real transmission loss (TRTL) are minimized simultaneously for clearing the reactive power market. The proposed HFMOEA based multi-objective RPMC scheme is tested on a standard IEEE 24 bus reliability test system and its performance is compared with five other multi-objective evolutionary techniques such as MOPBIL, NSGA-II, UPS-EMOA and SPEA-2 and a new extended form of NSGA (ENSGA-II). Applying all these six evolutionary techniques, a detailed statistical analysis using T-test and boxplots is carried out on three performance metrics (spacing, spread and hypervolume) data for RPMC problem. The obtained simulation results confirm the overall superiority of HFMOEA to generate better Pareto-optimal solutions with higher convergence rate as compared to above mentioned algorithms. Further, TPF and TRTL values corresponding to the best compromise solutions are obtained using said multi-objective evolutionary techniques. These values are compared with one another to take better market clearing decisions in competitive electricity environment.