Precipitation polymerization in mixed monomer–solvent droplets

This contribution reports the precipitation copolymerization of lauryl methacrylate–divinylbenzene (LMA–DVB) in stable isolated droplets dispersed in water. The droplets contain either n‐hexadecane (HD) or HD–toluene (HD–T) or toluene as a nonsolvent for the resulting P(LMA–DVB) copolymer. The polymerization proceeds smoothly with an appreciably high content of DVB without the formation of coagulum and thus proves the quite high stability of the droplet reactors. The differences in the interaction between the nonsolvent–copolymer combinations allow the variation of the internal morphology of the particles between core and shell type, highly porous, and solid sphere. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41881.     

Blends of aliphatic polyesters. IV. Morphology,swelling behavior,and surface and bulk properties of blends from hydrophobic poly(L-lactide) and hydrophilic poly(vinyl alcohol)

Blend films were prepared from hydrophobic poly(L -lactide) (PLLA) and hydrophilic poly(vinyl alcohol) (PVA) with different PLLA contents [X_PLLA (w/w) = PLLA/(PVA + PLLA)] by solution casting and melt quenching. Their morphology, swelling behavior, and surface and bulk properties were investigated. Polarizing optical microscopy, scanning electron microscopy, differential scanning calorimetry, X-ray diffractometry, and tensile testing revealed that PLLA and PVA were phase separated in these blend films and the PLLA-rich and PVA-rich phases both formed a continuous domain in the blend film of X_PLLA = 0.5. The water absorption of the blend films was higher for the blend films of low X_PLLA values when compared at the same immersion time, and it was larger than expected from those of nonblended PLLA and PVA films. The dynamic contact angles of the blend films were linearly increased with an increase in X_PLLA. The tensile strength and Young's modulus of the dry blend films decreased with a rise in X_PLLA, but this dependence was reversed because of the large decreases in tensile strength and Young's modulus for the blend films having high X_PLLA values after immersion in water. The elongation at break was higher for the wet blend film than for the dry blend film when compared at the same X_PLLA and that of the dry and wet blend films decreased with an increase in X_PLLA. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2151–2160, 2001     

Effect of apex cone shape on fine particle classification of gas-cyclone

The purpose of this paper is to study the effects of apex cone shape on particle separation performance of gas-cyclones by experiment and CFD studies. It is found that the optimum apex cone angle is 70°. The minimum 50% cut size was obtained by use of this special apex cone. From the flow visualization method by use of soap foam, the upward flow and downward flow coexisted on the surface of this special apex cone. The clear interface between upward flow and downward flow was detected on the apex cone angle of 70°. The effect of the apex cone angle on particle separation performance decreases under high inlet velocity conditions, because most particles are moving in the area away from the apex cone.The particle separation performance and flow visualization results qualitatively supported the 3-dimensional CFD simulation based on the direct method.     

Development of a chlorine‐resistant polyamide nanofiltration membrane and its field‐test results

For the development of chlorine‐resistant nanofiltration membranes, a thin‐film‐composite membrane was prepared by the interfacial polymerization of N‐phenylethylenediamine and 1,3,5‐benzenetricarbonyl trichloride on a microporous polysulfone support substrate. The polymerization on the substrate surface was confirmed by Fourier transform infrared measurements, and membrane surface properties such as the roughness and ζ potential were characterized. Rejections of NaCl and isopropyl alcohol of the prepared membrane were 95 and 50%, respectively. The membrane showed much higher chlorine resistance than a commercial polyamide membrane when the membranes were immersed in an aqueous NaOCl solution. A field test was carried out with a spiral‐type membrane module. Tap water was treated by this module for more than 70 days under the condition of continuous NaOCl injection. The prepared membrane module was quite stable, and no distinguished change in the rejection and flux was recognized. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Conductivity of Tazheranite Ceramics Synthesized by Controlling Composition

Tazheranite ceramics with controlled compositions were synthesized by solid-phase reaction, and their conductivity was measured using the complex impedance method. The CaO content in tazheranite compositions showed the highest conductivity at around 15 mol%. In particular, Ca_0.81Ti_0.04O_y sintered bodies revealed the highest conductivity, and this value agreed very closely with that of 15 mol% CaO-stabilized ZrO₂.     

Liposome-assisted activity of superoxide dismutase under oxidative stress

A biological membrane is the front line of defense for cells against various environmental stresses such as heat and reactive oxygen species (ROS) and is expected to play an important role in the antioxidant system with antioxidant enzymes, similarly to its chaperone-like function in cooperation with heat shock proteins. The oxidative stress response of superoxide dismutase (SOD), which is known to catalyze the dismutation of O(2)(-) to H(2)O(2), was investigated in the presence of artificial membranes, liposomes, in order to obtain fundamental information on the biological ROS scavenging system. SOD lost its activity in the presence of H(2)O(2) and was found to have two loops including one which contains an alpha-helix which presents the substrate O(2)(-) to the activity center of SOD (Cu(II)). From circular dichroism analysis of SOD in the presence of H(2)O(2), the contents of the alpha-helix in SOD were found to decrease in correspondence with the inactivation and conformational change of SOD, suggesting that the conformation of the alpha-helix loops affects SOD activity. In the presence of liposomes composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), SOD was not inactivated in the presence of H(2)O(2) although the contents of its alpha-helix structure were decreased. The oxidized SOD was found to interact with the liposome surface under oxidative stress using dielectric dispersion analysis. Based on these results, a possible mechanism of SOD protection against ROS on liposomes was presented.     

Preparation of porous membrane by combined use of thermally induced phase separation and immersion precipitation

By immersion in the cooled nonsolvent, PMMA porous membrane was prepared by the combined use of thermally induced phase separation (TIPS) and immersion precipitation. As nonsolvent, water with low mutual affinity with cyclohexanol (diluent) and methanol with high affinity were used. In the case of water, the porous structure was formed by TIPS immediately after the immersion. Near the top surface contacted with the nonsolvent, the thin skin layer was formed due to the outflow of the diluent. After the long immersion period, macrovoids were formed near the top surface due to the penetration of the nonsolvent. Thus, TIPS and the immersion precipitation occurred serially. On the contrary, TIPS and the immersion precipitation occurred simultaneously in the case of methanol because the inflow of methanol was fast. Therefore, the membrane obtained after the short immersion period had the larger pores near the top surface due to the nonsolvent induced phase separation and the smaller pores near the bottom surface due to TIPS. These two modes of the phase separations were confirmed by the changes in light transmittance through the polymer solutions.     

Identification of continuous-time systems with multiple unknown time delays by global nonlinear least-squares and instrumental variable methods

This paper considers the identification problem of multiple input single output (MISO) continuous-time systems with unknown time delays of the inputs, from sampled input-output data. An iterative global separable nonlinear least-squares (GSEPNLS) method which estimates the time delays and transfer function parameters separably is derived to significantly reduce the possibility of convergence to a local minimum, by using the stochastic global-optimization techniques. Furthermore, the GSEPNLS method is modified to a novel global separable nonlinear instrumental variable (GSEPNIV) method to remove the biases of the estimates in the presence of high measurement noise. Simulation results show that the proposed algorithms work quite well.     

The compaction of soot particles generated by spark discharge in the propene ozonolysis system

The compaction of soot aggregates generated by spark discharge is reported in the propene ozonolysis experiment. Since propene is not an organic aerosol precursor, the compaction cannot be explained by an earlier hypothesis attributing the compaction to the capillary forces of condensed organic matter in the small angle cavities of the aggregates [Saathoff, Naumann et al. (2003). Coating of soot and (NH₄)₂ SO₄ particles by ozonolysis products of alpha-pinene. Journal of Aerosol Science, 34, 1297–1321]. Several species among the gas-phase products from propene ozonolysis are proposed to contribute to the structural change of soot particles. As the compaction would directly change the morphology and the size distribution of soot particles, it is expected to induce important changes to the soot particles’ physical and chemical properties, which in turn would have significant atmospheric implications.