Studies on poly (iso-butene oxide): 3. Elastic hard fibre of poly (iso-butene oxide)

Poly(iso-butene oxide), a highly crystalline polyether, gives an ‘elastic hard fibre’, having excellent elastic recovery, on melt-spinning under appropriate drafting conditions. The interrelation between fabricating conditions and elastic recovery has been studied and the mechanism of the appearance of the elastic recovery is discussed. The mechanical, thermal and chemical properties of the fibre have been investigated.     

Bias-corrected realized variance under dependent microstructure noise

The aim of this study is to develop a bias-correction method for realized variance (RV) estimation, where the equilibrium price process is contaminated with market microstructure noise, such as bid-ask bounces and price-change discreteness. Although RV constitutes the simplest estimator of daily integrated variance, it remains strongly biased, and many estimators proposed in previous studies require prior knowledge about the dependence structure of microstructure noise to ensure unbiasedness and consistency. The dependence structure is unknown however, and needs to be estimated. A bias-correction method based on statistical inference from the general noise dependence structure is thus proposed. The results of Monte Carlo simulation indicate that the new approach is robust with respect to changes in the dependence of microstructure noise.     

Genetic and chemical diversity of Eleutherococcus senticosus and molecular identification of Siberian ginseng by PCR-RFLP analysis based on chloroplast trnK intron sequence

Siberian ginseng (SG), the rhizome and root of Eleutherococcus senticosus, has been used as a tonic and anti-fatigue agent in northeastern Asia from ancient time. In recent years, SG has been becoming fairly popular as dietary supplements and health foods worldwide. In order to establish a convenient and sensitive method for authentication, chloroplast trnK intron sequences of 6 Eleutherococcus species were determined and compared. Genetic polymorphism, representing by 14 types of trnK intron sequence, in E. senticosus was observed. However, characteristic nucleotide markers stable within this species enabled clear discrimination of it from other congeners. A PCR-RFLP method was further developed, which was demonstrated to be efficient for authentication of crude drugs as well as health foods. Quantitative evaluation of three main bioactive constituents indicated chemical diversity in E. senticosus collected from northeast China and the results suggested good producing areas of SG. The chemical data clearly revealed that E. sessliflorus was unsuitable to be used as SG.     

A thermally-stable self-mending polymer networked by Diels-Alder cycloaddition

A novel self-mending polymer with high thermal stability is developed based on the DA reaction between anthracene and maleimide. A network polymer, PEAA₂M₃ is prepared by the DA reaction of anthryl-telechelic poly(ethylene adipate) and a tris-maleimide. While the forward DA (addition) reaction is favored at room temperature, the reverse DA (dissociation) reaction is induced by mechanical stress. This mechanochemical reversibility allows the autonomous mending of cracks in PEAA₂M₃ at room temperature. It is well known that the thermal dissociation of the DA reaction occurs only at very high temperatures at which organic polymers degrades significantly. Therefore, thermal stability is successfully combined with self-mending ability in PEAA₂M₃.     

A New Formulation Approach for Location-Routing Problems

A Location-Routing Problem (LRP) combines two difficult problems, facility location and vehicle routing, and as such it is inherently hard to solve. In this paper, we propose a different formulation approach than the common arc-based product-flow (Arc-BPF) approach in the literature. We associate product amounts to the nodes of the network resulting in a node-based product-flow (Node-BPF) formulation. Our main objective is to develop LRP models with fewer constraints and variables, which can be solved more efficiently. To introduce the proposed approach, we reformulate a complex four-index Arc-BPF LRP model from the literature as a three-index Node-BPF model, which computationally outperforms the former. We then introduce a heuristic method.     

Impact of surfactant selection on the formulation and characterization of microparticles for pulmonary drug delivery

The effect of suspension stabilizers, internal aqueous phase volume and polymer amount were investigated for the production of protein loaded poly(d,l?lactide-co-glycolide) (PLGA) microparticles suitable for pulmonary drug delivery. PLGA microparticles were produced adopting water-in-oil-in-water (W/O/W) solvent evaporation technique and were investigated for surface morphology, particle size, encapsulation efficiency (EE%) and in-vitro release profile. Porous surface morphologies with a narrow size distribution were observed when employing 0.5?ml internal aqueous phase; 23.04?µm (±0.98), 15.05?µm (±0.27) and 22.89?µm (±0.41) for PVA, Tween 80 and oleic acid. Porous microparticles exhibited increased size and reduction in EE% with increasing internal aqueous phase, with non-porous microparticles produced when adopting 2.0?ml internal aqueous phase. The selection of stabilizer influences the size of the pores formed thus offers potential for the aerodynamic properties of the microparticles to be manipulated to achieve suitable aerosolization characteristics for pulmonary delivery of proteins.     

Quantitative determination of colored oily soil adhering to metal surface using digital image data

A method for calculating the amount of colored soil on a flat metal surface from digital image data was examined. Round samples cut out of SUS tape were soiled with oily soil mixed with sudan III, placed in sample bottles, and washed using a tube rotator. Images of the samples before and after the washing process were captured using a CCD camera and the image data were processed by a computer. The shine from the metallic surface was controlled by using indirect lighting. It was necessary to diminish the effect of the substrate's color, and to this end, we attempted to apply linear and non-linear color correction procedures. We found that the use of gamma correction after linear correction to remove the effect of the metal surface color was the most accurate quantitative method. Additionally, we conducted a washing test with commercial detergents using this quantitative method for image data and found that the removal process for the greasy soil from the metal surface could be expressed as a first-order reaction.