Formation of microporous polymeric materials by microemulsion polymerization of methyl methacrylate and 2-hydroxyethyl methacrylate

The investigated microemulsion system consisted of methyl methacrylate, 2-hydroxyethyl methacrylate and water using sodium dodecyl sulphate as surfactant. Ethylene glycol dimethacrylate acting as a cross-linker was also incorporated to enhance the mechanical strengths of the microporous polymeric materials. The polymerization was carried out at room temperature using a reactive redox initiator comprising ammonium persulphate and N,N,N′,N′-tetramethylethylene diamine. The conductivities of the microemulsion samples were monitored during the course of polymerization. The conductivities for a bicontinuous microemulsion before and after polymerization were found to be very similar. In addition, the transformation of microstructures was also examined using a transmission as well as a field emission scanning electron microscope. It is evidenced from the micrographs that microporous polymeric materials prepared from bicontinuous microemulsion polymerization are attributed to numerous coagulations of spherical particles. A possible mechanism for the microstructural transformation is discussed based on the information of conductivity measurements and electron micrographs. © 1996 John Wiley & Sons, Inc.     

Application of GDQ scheme to simulate natural convection in a square cavity

The global method of generalized differential quadrature (GDQ) was applied to simulate the natural convection in a square cavity. Numerical results demonstrated that accurate solutions can be obtained using just a few grid points and requiring much less computational effort and storage.     

Contributing to sustainability: addressing the core problems

Clean Technologies and Environmental Policy -     

O6-alkylguanine-DNA alkyltransferase inactivation by ester prodrugs of O6-benzylguanine derivatives and their rate of hydrolysis by cellular esterases

To modulate the bioavailability and perhaps improve the tumor cell selectivity of O6-alkylguanine-DNA alkyltransferase (AGT) inactivators, pivaloyloxymethyl ester derivatives of O6-benzylguanine (BG) were synthesized and tested as AGT inactivators and as substrates for cellular esterases. The potential prodrugs examined were the 7- and 9-pivaloyloxymethyl derivatives of O6-benzylguanine (7- and 9-esterBG), and of 8-aza-O6-benzylguanine (8-aza-7-esterBG and 8-aza-9-esterBG) and the 9-pivaloyloxymethyl derivative of 8-bromo-O6-benzylguanine (8-bromo-9-esterBG). The benzylated purines were all potent inactivators of the pure AGT and of the AGT activity in HT29 cells and cell extracts. Each ester was at least 75 times less potent than the corresponding benzylated purine against the pure human AGT. In contrast, the activities of esters and their respective benzylated purine were similar in crude cell extracts and in intact cells. The increase in potency of esters in cellular extracts could be explained by a conversion of the respective prodrug to the more potent benzylated purine in the presence of cellular esterases. The apparent catalytic activity (Vmax/Km) of liver microsomal esterase for 8-azaBG ester prodrugs was 70-130 times greater than for BG prodrugs and 10-20 times greater than for 8-bromo-9-esterBG. Tumor cell hydrolysis of the esters varied considerably as a function of cell type and prodrug structure. These data suggest that these or related prodrugs may be advantageous for selective AGT inactivation in certain tumor types.     

Evaluation of nefazodone as a serotonin uptake inhibitor and a serotonin antagonist in vivo

Nefazodone (2-[3-[4-(3-chlorophenyl)-1-piperazinyl]propyl]-5-ethyl- 2,4-dihydro-4-(2-phenoxyethyl)-3H-1,2,4-triazol-3-one) has been reported to be effective in the treatment of depression. Antagonism of serotonin type 2A (5HT2A) receptors, as well as inhibition of the serotonin (5HT) uptake carrier, has been suggested to contribute to the antidepressant action of nefazodone in vivo (Eison et al., 1990). Nefazodone weakly antagonized the quipazine-induced rise in rat serum corticosterone levels and the quipazine-induced increase in rat hypothalamic 3-methoxy-4-hydroxy-phenylglycol sulfate, suggesting blockade of 5HT2A receptors in vivo. Nefazodone, however, failed to antagonize the p-chloroamphetamine-induced depletion of mouse or rat brain 5HT, displaying a lack of effect on the 5HT uptake carrier. These data extend previous in vitro and in vivo data (Eison, et al. 1990) reporting nefazodone to be an antagonist at 5HT2A receptors, but fail to show inhibition of the 5HT uptake carrier in the same dose range.     

A concise synthesis and in vitro cytotoxicity of new labdane diterpenes

A new series of labdane-related diterpenes have been synthesized from (-)-sclareol and assayed in vitro cytotoxicity against mouse and human cancer cells. A key intermediate, homodrimane and furanolabdane derivatives show good in vitro cytotoxicity comparable to those of mitomycin C and adriamycin.     

An analytical method for selecting the optimal nozzle external geometry for fluid dynamic gauging

Fluid dynamic gauging (FDG) was developed to measure, in situ and in real time, the thickness of a soft deposit layer immersed in a liquid without contacting the surface of the layer. An analysis based on the lubrication assumption for the flow patterns in the space between the nozzle and the surface being gauged yielded analytical expressions for the relationships between the main flow variables and system parameters. Nozzle shapes for particular pressure, pressure gradient and shear stress profiles could then be identified. The effect of flow rate, nozzle geometry and nozzle position on the pressure beneath the nozzle and shear stress on the gauged surface showed very good agreement with computational fluid dynamics (CFD) simulations. Case studies presented include nozzle shapes for uniform pressure and shear stress profiles, which are useful for measuring the strength of soft deposit layers.     

A Fragrance Prediction Model for Molecules Using Rough Set-based Machine Learning

In this work, a novel machine learning based methodology was developed to predict fragrance from the molecular structure and the effect of the subjects attributes on odour perception. As fragrance is linked to the molecular structure and interactions, topological indices are used to develop a predictive model. Rough set-based machine learning is used to generate rule-based models that link the topology of fragrant molecules and dilution to their respective odour characteristics. The results show that the generated models are effective in determining the odour characteristic of molecules.     

Intrusive probes in riser applications

Many of the probes used to understand hydrodynamics in circulating fluidized bed risers intrude into the environment they are measuring, although assumptions are typically asserted that the intrusive probes do not affect the data collected. This could be a poor assumption in some cases and conditions. We found that intrusive fiber‐optic probe measurements consistently mis‐predicted the solids concentration compared to the nonintrusive pressure drop measurements outside the fully developed flow region of a riser containing fluid catalytic cracking catalyst or glass bead particles. The discrepancy was sensitive to superficial gas velocity, solid circulation rate, probe position, and flow direction. Barracuda VR? computational fluid dynamics simulations confirmed this, and indicated that particle momentum was lost at the leading edge of the probe and particles were spilling over to the probe tip. Accordingly, new probe designs were proposed to mitigate the intrusiveness of a fiber‐optic probe for more accurate characterization. © 2017 American Institute of Chemical Engineers AIChE J, 63: 5361–5374, 2017     

Influence of Fillers on Sizing Efficiency and Hydrolysis of Alkyl Ketene Dimer

The influence of various fillers on sizing efficiency, adsorption and hydrolysis of alkyl ketene dimer (AKD) has been investigated. Results indicated that the precipitated calcium carbonate (PCC) improved AKD retention, both bound and unbound. The sizing efficiency was reduced as PCC contents increased, which might be attributed to the decrease in the relative AKD dosage to fibres and AKD hydrolysis promoted by PCC. Less amount of AKD was adsorbed on PCC, compared with calcined clay and TiO₂ fillers under the same conditions. Hydrolysis studies indicated that PCC had a more detrimental effect on AKD hydrolysis than clay and TiO₂.