Cografting kinetics of styrene and ethyl acrylate onto polyethylene

Kinetic studies of cografting reactions of styrene (St) and ethyl acrylate (EA) onto preirradiated polyethylene (PE) have been investigated by means of bromine labeling and infrared spectroscopy. Kinetic data obtained from these methods, that is, the percent grafting, the number of graft chains, and growing rates, were obtained at temperatures of 0, 20, 40, and 50°C. The graft percent was virtually influenced by the degree of swelling. At 0°C, the mixing ratio of ethyl acrylate and styrene monomer before the beginning of the reaction was equal to the existence ratio in the graft chains after the reaction. Therefore, this reaction is considered to be diffusion-controlled. On the contrary, at 20 and 40°C, the existence ratio in graft chains after the reaction. Therefore, this reaction is considered to be diffusion-controlled. On the contrary, at 20 and 40°C, the existence ratio in graft chains agreed with the theoretical curve calculated from monomer reactivity ratio. The number of active graft chains for given times were 3～5 × 10^?7 mole/g PE and it decreased with temperature; 0 > 20 > 50°C. While the total number of graft chains is 5～15 × 10^?7 mole/g PE and it increased with temperature; 0 < 20 < 50°C. The growing rate were 1～5 monomer/site/sec for 0°C, 2～15 for 20°C.     

A competitive immunochromatographic assay for testosterone based on electrochemical detection

An immunochromatographic assay using nitrocellulose membrane was combined with electrochemical detection using an electrode chip in order to quantitatively detect testosterone as a model analyte. The electrode chip consisted of a gold working electrode, a counter electrode and a pseudo-reference electrode, all fabricated on the bottom of a 3.2 mm × 3.2 mm well. Competitive immunoreactions on the membrane were initiated by flowing a solution containing testosterone and horseradish peroxidase (HRP)-labeled testosterone (a competitor) over the membrane. Prepared membrane was placed in a solution containing ferrocenemethanol (FcOH) and H₂O₂ in the well of the electrode chip, and the enzyme reaction was detected by amperometry. Labeled HRP captured on the membrane catalyzed the oxidation of FcOH to the oxidized form FcOH⁺, which was reduced electrochemically by the electrode chip. The electrochemical response of the reduction current decreased with increasing concentration of testosterone over the range 1–625 ng/ml.     

Mechanism of stereoregular polymerization of butadiene by homogeneous Ziegler-Natta catalysts. II. Effects of the nature of bases and halogens

The effects of the addition of various bases to metal acetylacetonate–diethylaluminum chloride catalyst systems were investigated. Generally speaking, the cis content of polybutadiene decreases as the basicity of bases in a homologous series increases. The effects were more prominent for the cobalt and the titanium catalysts than for the nickel and the vanadium catalysts. The effects of the species of halogens on the microstructure of polybutadiene were also discussed. In conclusion, the decrease of the cis content was ascribed to the decrease of the electron density of dπ orbitals of the transition metal atoms.     

Structures of beta-FeOOH particles formed in the presence of Ti(IV), Cr(III), and Cu(II) ions

beta-FeOOH particles were prepared by aging aqueous FeCl3 solutions containing Ti(IV), Cr(III), and Cu(II) at room temperature for 360 days. The structures of the formed particles were investigated by various techniques including TEM, XRD, XAFS, and adsorption of N2 and H2O. Ti(IV) markedly impeded the crystallization and particle growth of beta-FeOOH by coprecipitation with Fe(III) and disturbing the short-range structure of beta-FeOOH particles. In the presence of a large amount of Ti(IV), it was pronounced that the hydrolysis of Ti(IV) impeded beta-FeOOH formation by reducing the solution pH, whereas Cr(III) and Cu(II), which were hardly involved in the products, gave rise to no noticeable effects on the formation of beta-FeOOH particles. The knowledge obtained in this study can be available for interpretation of the anti-corroding function of Ti alloyed with steels in a Cl- -containing environment.     

Interpretation of the difference of optimal Mo density in MoS<Subscript>2</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and MoS<Subscript>2</Subscript>-TiO<Subscript>2</Subscript> HDS catalysts

The first part of this paper deals with the morphology of the MoS₂ phase and its oxide precursor, the MoO₃ phase, mainly from a geometrical point of view. After giving a brief review of the literature describing the structure of these compounds, Mo densities in both phases were calculated along various crystallographic planes. Further, using structural models recently proposed by others, Mo densities in MoS₂ were also calculated in the case of an epitactic growth on γ-Al₂O₃ and TiO₂ model surfaces. Then, the calculated Mo densities were compared with experimental results (Mo density when HDS activity is maximal) previously obtained for catalysts constituted of MoS₂ supported on a low SSA TiO₂, a high SSA TiO₂ and a conventional γ-alumina. It was suggested that either on alumina or titania the MoS₂ phase is growing as (100) MoS₂ planes. However, while on the alumina the optimal MoS₂ phase might be constituted of dispersed MoS₂ slabs covering only a part of the alumina surface (2.9–3.9 Mo atoms/nm²), on titania the optimal MoS₂ phase might be constituted of a uniform MoS₂ monolayer (5.2 atoms/nm² for the high SSA titania, which is equal to the Mo density of a perfect MoS₂ (100) plane). This difference may originate in the creation of a 'TiMoS' phase enhancing the S atoms mobility over Mo/TiO₂-sulfided catalysts. Indeed, while in the case of a γ-alumina carrier the active sites (labile S atoms) are located on the edge of MoS₂ slabs making the ratio Mo_edge/Mo_total a crucial parameter for the catalytic performances, in the case of a titania carrier the labile sulfur atoms might be statistically distributed all over the TiMoS active phase. Further, the higher Mo density observed over the high SSA titania (5.2 atoms/nm²) when compared to that over the low SSA titania (4.2 atoms/nm²) was supposedly due to the pH-swing method advantageously used to prepare the former carrier. Indeed, this method allows giving a solid with enhanced mechanical properties providing a good stability to the derived catalysts under experimental conditions. In addition, this TiO₂ carrier exhibits a great homogeneity, with a surface structure substantially uniform, which might be adequate for a long-range growth of (100) MoS₂ slabs.     

6S,8R-Stereochemistry of the C27- and C29-alkane-6,8-diols isolated from three compositae flowers

The Deltadelta (deltaS-deltaR) values for the C-1 methyl 1H signals in the 1H-NMR spectroscopy of the bis-MTPA esters of four synthetic stereoisomers of alkane-6,8-diols, viz., bis-MTPA esters of (6S,8R)-C27- (1a) and C29- (3a) (Deltadelta = -0.05 ppm), (6R,8S)-C27- (2a) and C29- (4a) (Deltadelta = +0.05 ppm), (6S,8S)-C27- (5a) (Deltadelta = -0.01 ppm), and (6R,8R)-C27- (6a) (Deltadelta = +0.01 ppm) alkane-6,8-diols, made it possible to differentiate unequivocally among the four stereoisomers. This allowed the determination of the (6S,8R)-stereochemistry (Deltadelta = -0.05 ppm for the bis-MTPA esters) for the natural C27- and C29-alkane-6,8-diols isolated from the flowers of three Compositae plants, Carthamus tinctorius, Cynara cardanclus, and Taraxacum platycarpum.     

Estimation of surface free energies and hamaker constants for fibrous solids by wetting force measurements

Wetting force at three-phase line was measured by the Wilhelmy technique using fibrous solids/liquid/liquid systems. Advancing and receding contact angles were calculated from the wetting forces during fiber immersion and emersion. The obtained results showed that contact angle hysteresis was due to the heterogeneity of the fiber surfaces. The dispersive and polar components of surface free energies of the fibers were determined from the advancing and receding contact angles, respectively. The Hamaker constants of the fibers were estimated from the dispersive components of their surface free energies.     

Anti to syn isomerization of oxacalix[4]arene bearing two methyl groups at the intra-annular distal positions

The thermal isomerization of anti to syn stereoisomers of oxacalix[4]arene bearing two methyl groups at the intra-annular distal positions was investigated by temperature-dependent NMR spectroscopy. The conversion followed a first-order kinetics, and very slowly proceeded at 473 K in nitrobenzene-d₅ with a half-life of 7.2 h. The free energy of activation (ΔG^≠ 139 kJ mol⁻¹) is much higher than those for the ring inversion of related calix[4]arene derivatives.     

Ordered nanopore boring in silicon: Metal-assisted etching using a self-aligned block copolymer Au nanoparticle template and gravity accelerated etching

Metal-assisted etching into Si (1 0 0) surfaces can be performed in a highly defined and regular arrangement using self-organized patterns of single-size gold catalyst particles that are block polymer templated on Si surfaces. We show that small size catalyst particles (diameter ≈10 nm) can be forced to maintain straight etch tracks perpendicular to the surface using adequate centrifugal gravity force. This allows the creation of highly ordered uniform and synchronized pore boring into the substrate with single pore diameters in the 10 nm range.     

Determination of the Apparent Michaelis Constant of Glucose Oxidase Immobilized on a Microelectrode with Respect to Oxygen

We report determination of the apparent Michaelis constant of glucose oxidase (GOx) immobilized on a microelectrode with respect to oxygen. We used a GOx‐modified microelectrode as a probe for scanning electrochemical microscopy. We detected hydrogen peroxide generated by the enzyme reaction at the microelectrode under controlling the oxygen concentration using water electrolysis at an interdigitated array (IDA) electrode. The response depends on the oxygen concentration, which is regulated by the microelectrode position and the potential applied to the IDA electrode. We estimated the apparent Michaelis constant with respect to oxygen in this experimental condition to be about 0.28 mM.