Molecular-scale observation of formation of nuclei in soap-free polymerization of styrene

To clarify the mechanism of the nucleation process in the soap-free polymerization of styrene in water, the polymerization process of styrene mainly at a temperature 46 degrees C was investigated on a molecular scale using an atomic force microscope (AFM) as well as a scanning electron microscope (SEM) and a dynamic light scattering apparatus (DLS). A cationic initiator was employed to make polymerized styrene adsorb electrostatically on the negatively charged mica plate with molecular-scale smoothness, and the mechanism was estimated from their AFM measurements in situ in water. The following was found. There exist two streams to produce PSL particles in the polymerization: one is the polymerization in monomer droplets fragmented by mixing from the main monomer reservoir floating above the solution, and the other is the polymerization of monomers dissolved in the solution by initiators. The former is normally neglected or not recognized because of the small contribution. The latter is the main production process of PSL particle, which is investigated in detail on a molecular scale, and a possible mechanism was proposed.     

Chiral separation of phenylalanine in ultrafiltration through DNA-immobilized chitosan membranes

Ultrafiltration experiments for the chiral separation of racemic phenylalanine were performed with DNA-immobilized chitosan membranes having various pore sizes. Atomic analysis on the membranes showed that the chitosan membranes covalently bound six times more DNA than the cellulose membranes used in our previous study [A. Higuchi, Y. Higuchi, K. Furuta, B.O. Yoon, M. Hara, S. Maniwa, M. Saitoh, K. Sanui, Chiral separation of phenylalanine by ultrafiltration through immobilized DNA membranes, J. Membr. Sci. 221 (2003) 207–218]. d-Phenylalanine preferentially permeated through DNA-immobilized chitosan membranes with a pore size <6.4 nm [molecular weight cut-off (MWCO) <67,000]. The binding affinity of a specific enantiomer due to the pore size of the DNA-immobilized membranes regulated the preferential permeation of the enantiomer through the membranes. l-Phenylalanine was adsorbed on the DNA-immobilized chitosan membranes with a pore size <6.4 nm (MWCO < 67,000), while there was little difference between the adsorption of d-phenylalanine and l-phenylalanine on the membranes with a pore size >6.4 nm (MWCO > 67,000). The DNA-immobilized chitosan membranes were categorized as channel type membranes.     

Raman spectroscopy of isotopically pure (<Superscript>12</Superscript>C, <Superscript>13</Superscript>C) and isotopically mixed (<Superscript>12.5</Superscript>C) diamond single crystals at ultrahigh pressures

The Raman scattering by isotopically pure ¹²C and ¹³C diamond single crystals and by isotopically mixed ^12.5C diamond single crystals is studied at a high accuracy. The studies are performed over a wide pressure range up to 73 GPa using helium as a hydrostatic pressure-transferring medium. It is found that the quantum effects, which determine the difference between the ratio of the Raman scattering frequencies in the ¹²C and ¹³C diamonds and the classical ratio (1.0408), increase to 30 GPa and then decrease. Thus, inversion in the sign of the quantum contribution to the physical properties of diamond during compression is detected. Our data suggest that the maximum possible difference between the bulk moduli of the ¹²C and ¹³C diamonds is 0.15%. The investigation of the isotopically mixed ^12.5C diamond shows that the effective mass, which determines the Raman frequency, decreases during compression from 12.38 au at normal pressure to 12.33 au at 73 GPa.     

Catalytic chain-breaking pyridinol antioxidants

When assayed for their capacity to inhibit azo-initiated peroxidation of linoleic acid in a water/chlorobenzene two-phase system, tellurium-containing 3-pyridinols were readily regenerable by N-acetylcysteine contained in the aqueous phase. The best inhibitors quenched peroxyl radicals more efficiently than alpha-tocopherol, and the duration of inhibition was limited only by the availability of the thiol reducing agent. The compounds were also found to catalyze reduction of hydrogen peroxide in the presence of thiol reducing agent.     

Conformational analysis of TMC114, a novel HIV-1 protease inhibitor

TMC114, a potent novel HIV-1 protease inhibitor, remains active against a broad spectrum of mutant viruses. In order to bind to a variety of mutants, the compound needs to make strong, preferably backbone, interactions and have enough conformational flexibility to adapt to the changing geometry of the active site. The conformational analysis of TMC114 in the gas phase yielded 43 conformers in which five types of intramolecular H-bond interactions could be observed. All 43 conformers were subject to both rigid and flexible ligand docking in the wild-type and a triple mutant (L63P/V82T/I84V) of HIV-1 protease. The largest binding energy was calculated for the conformations that are close to the conformation observed in the X-ray complexes of TMC114 and HIV-1 protease.     

Synthesis and biological evaluation of (S)-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acids: a novel series of PPAR gamma agonists

A novel series of 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid derivatives were synthesized and biologically evaluated. (S)-2-Benzyl-7-[2-(5-methyl-2-phenyloxazol-4-yl)ethoxy]-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (10, KY-021) was identified as a novel peroxisome proliferators-activated receptor (PPAR) gamma agonist, which showed potent activity in human PPAR gamma (EC50=11.8 nM). KY-021 reduced plasma glucose and triglyceride levels at 3 mg/kg/d for 7 d in male KK-Ay mice. KY-021 also decreased plasma triglyceride levels at 0.3-3 mg/kg/d for 6 d, and improved oral glucose tolerance at 1 and 3 mg/kg/d for 7 d in male Zucker fatty rats. Maximal plasma concentration of KY-021 after oral administration at 10 mg/kg was 6.6 microg/ml and 2.1 microg/ml in male ICR mice and male SD rats, respectively. Repeated oral administration of KY-021 at 30 mg/kg/d for 10 weeks had little toxicity in male SD rats. These results demonstrated that KY-021 has great potential as an efficacious and safe drug for diabetes.     

A network flow procedure for project crashing with penalty nodes

In this paper a procedure is developed to obtain the project-cost curve when there are linear penalty costs for delays of certain key events in a project in addition to crashing costs for activities. A linear programming formulation is given. From primal dual considerations, the optimality conditions are derived and a network flow interpretation to the problem on a modified network is developed. The treatment is similar to that of Fulkerson [7] except that provision for flow drainage from penalty nodes is made, and the notion of auxiliary sources is introduced to satisfy the modified optimality conditions. The solution procedure based on network flow arguments proceeds in two phases. In phase 1, the global minimum of the project-cost is obtained, whereas in phase 2, the entire project cost-duration efficient frontier is generated. An example problem illustrating the procedure is also presented.     

Macroporous zirconia particles prepared by subcritical water in batch and flow processes

Porous zirconia particles were synthesized through a low-temperature hydrothermal synthesis process. Under hydrothermal conditions, water can control the direction of crystal growth, morphology, particle size, and size distribution because thermodynamics and transport properties can be controlled by pressure and temperature. In a batch process, the hydrothermal synthesis was conducted at 200–300 °C and 30 MPa with an SUS-304 tube as the reactor. At the same reaction pressure, experiments were also performed for a flow process with temperatures of 180–200 °C. The synthesized products were calcined and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The results showed that the macroporous zirconia particles that were formed had pore diameters around 419 nm. The XRD pattern indicated that the products were composed of zirconium oxide particles with monoclinic, tetragonal, and cubic structures.     

Correlation study among oxygen permeability,molecular mobility,and amorphous structure change of poly(ethylene‐vinylalcohol copolymers) by moisture

Oxygen permeability and the free‐volume hole size (cavity size) of ethylene‐vinylalcohol copolymers (EVOH) indicate abnormal humidity dependence, that is, they have minimum values in the range of around 20–40% RH, not showing a monotonic increase with humidity. To clarify this abnormal phenomenon, we investigated its molecular mobility and amorphous structure change by means of solid‐state NMR and temperature‐modulated differential scanning calorimetry (TMDSC). The glass transition temperature (T_g) decreased with humidity. Specimens stored at 15–60% RH showed large enthalpy relaxation, and it was found that the amorphous structure became more compact and the molecular conformation became more stable by ageing within this range of humidity. Under these conditions, solid‐state NMR measurement showed a component with intermediate relaxation time in the amorphous region. The results obtained by TMDSC and solid‐state NMR showed a reduction in molecular mobility by densifying in the amorphous region under the condition of 15–60% RH. The fact that the oxygen permeability and the cavity size of EVOH indicate minimum values at low humidity are attributed to the reduction in molecular mobility by enthalpy relaxation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1181–1191, 2009