Glycoconjugated polymer 6. Synthesis of poly[styrene-<Emphasis Type="Italic">block</Emphasis>-(styrene-<Emphasis Type="Italic">graft</Emphasis>-amylose)] via potato phosphorylase-catalyzed polymerization

Summary The potato phosphorylase-catalyzed polymerization of α-D-glucose-1-phosphate (G-1-P) onto poly[styrene-block-(4-vinylbenzyl maltohexaoside)] (1) was performed at the molar ratios of [G-l-P]₀ and [maltohexaose]₀ of 35, 80, and 250. The product was found to be soluble in dimethyl sulfoxide, which was a good solvent for amylose, and showed the complex-formation with iodine, indicating that the product was assignable to poly[styrene-block-(styrene-graft-amylose)] (2). The quantitative analysis of the liberated phosphoric acid gave the average degree of polymerization o f the glucose unit (n) as 27, 5 1, and 180 for 2-I, 2-II, and 2-III, respectively. Received: 29 November 2002/Accepted: 22 December 2002 Correspondence to Toyoji Kakuchi     

Determination of three dimensional in situ stress from core discing based on analysis of principal tensile stress

To determine all of the components of in situ stress from core discing, both the directions and magnitudes of the principal in situ stresses must be determined for a disc of a given thickness. In this study, we analyzed the direction and magnitude of tensile stress below an HQ core stub for 11 core lengths using stress conditions under which core discing is likely to occur. First, based on an analysis of the direction of tensile stress below the core stub, we propose a method for determining directions of in situ stress from the height distribution at the periphery of the end surface of a disc. This method can be used with a disc of any thickness. Next, based on an analysis of the magnitude of tensile stress in the central part of a core, we propose a linear criterion for core discing, which can be applied to a core of any length. This criterion was in good agreement with an empirical formula obtained previously in laboratory experiments. By combining information on the direction of in situ stress and the linear criterion for core discing, we propose a method for determining all of the components of in situ stress from core discing under the assumption that vertical stress is given by the overburden stress. Finally, these methods were applied to discs obtained from a field where hydraulic fracturing was performed to measure horizontal stresses. The results showed that the azimuths of the principal stresses estimated from core discing were consistent with those of the principal horizontal stresses determined by hydraulic fracturing and that while the magnitudes of the principal horizontal stresses estimated from core discing showed a large scatter, they were similar to those determined by hydraulic fracturing.     

Thermodynamic Regularities in Perovskite and K2NiF4 Compounds

It has been found that the enthalpy of formation of perovskite compounds, Δ_fH° (ABO₃, B = transition metais), from binary oxides can be well characterized in terms the tolerance factor, t≡(r_A+ r_o)√2 (r_B+ r_o), where r_A and r_B are the radii of A-site ions with 12-coordination and B-site ions with 6-coordination, respectively, and Δ_fH°=−168 + 270(1 − t) kJ·mol⁻¹ for A^IB^VO₃, Δ_fH°=−125 + 1000(1 − t) kJ·mol⁻¹ for A^IIB^IVO₃, and Δ_fH°=− 90 + 720(1 − t) kJ·mol⁻¹ for A^IIIB^IIIO₃. Although the thermodynamic data of K₂NiF₄ compounds are not extensive, a similar regularity can be found when use is made of the radii of A-site ions with 9-coordination for the K₂NiF₄ compounds. These correlations will be quite useful in predicting.     

Fate of the chlorine and fluorine in a sub-bituminous coal during pyrolysis and gasification

The fate of the chlorine and fluorine present in a sub-bituminous coal from Indonesia during pyrolysis and gasification has been studied with fixed and entrained bed reactors. The rate profile for HCl evolved in the temperature programmed pyrolysis exhibits the main and shoulder peaks at 480 and 600 °C, respectively. Model experiments and subsequent Cl 2p XPS measurements show that HCl reacts with metal impurities and carbon active sites at 500 °C to be retained as inorganic and organic chlorine forms, from which HCl evolves again at elevated temperatures. It is suggested that the HCl observed in the coal pyrolysis may originate from the above-mentioned chlorine functionalities formed by secondary reactions involving the nascent char. In the CO₂ gasification of the 900 °C char at 1000 °C and 2.5 MPa, any measurable amounts of HCl and HF could not be detected even at a high conversion of 75 wt% (daf), suggesting the accumulation of these halogens in the residual char. When the coal is injected into an O₂-blown, entrained bed gasifier at 1200-1400 °C under 2.6 MPa, the partial oxidation proceeds to a larger extent at a higher O₂/coal ratio, whereas the chlorine and fluorine are enriched in the remaining char, and the extent of the enrichment at the latter stage of gasification is larger with the fluorine. The XPS measurements of the chars reveal the presence of the broad F 1 s peak, which can cover a wide range of binding energies attributable to inorganic and organic fluorine. The halogen enrichment during gasification is discussed in terms of secondary reactions of HCl and HF with char.     

Water flux,DSC, and cytotoxicity characterization of membranes of cellulose acetate produced from sugar cane bagasse,using PEG 600

Summary In this article, cellulose acetate produced through the homogeneous acetylation of sugar cane bagasse cellulose was used to produce membranes, using poly(ethyleneglycol) 600 (PEG 600) as an admixture. The membranes were characterized using water flux measurements (Payne’s cup), differential scanning calorimetry (DSC) and neutral red uptake (cytotoxicity). The results showed that PEG 600 acts as a crystallinity inductor and/or pore former in the cellulose acetate matrix. The induction of crystallinity is important for this system since it had not been reported on the literature yet. The results also demonstrated that the studied membranes present a nontoxic behavior.     

Formation of Bromate Ion Through a Radical Pathway in a Continuous Flow Reactor

The contribution of ozone and hydroxyl radical to the formation of bromate ion was investigated in a continuous flow reactor. Experiments were conducted under a wide range of ozone dose (0.7 ～ 3.8 mgL), pH (6.5 ～ 8.5), and t-butanol concentration (0 ～ 0.5 mM). The formation of bromate ion was found to depend on radical reaction pathway, because the amount of bromate ion formed increased with pH and decreased with t-butanol, a radical scavenger, even when dissolved ozone concentrations were almost the same. In fact, the amount of bromate ion formed was reduced by 90% in the presence of t-butanol. Furthermore, the formation of bromate ion occurred even when dissolved ozone was not significantly detected in the presence of organic matter (TOC of 1 mgCL). The second-order reaction rate constant of hydroxyl radical with bromide ion, k _HO,Br^? of 1.7 × 10⁹ (M^?1s^?1), was obtained on the assumption that the reactions of bromide ion and t-butanol with hydroxyl radical were competitive with each other in the presence of t-butanol and that the formation of bromate ion depended on the reaction of bromide ion with hydroxyl radical. Therefore, it is concluded that the reaction of bromide ion with hydroxyl radical dominated in the overall reaction from bromide ion to bromate ion in the continuous flow reactor.     

Synthesis of Hard Materials by Field Activation: The Synthesis of Solid Solutions and Composites in the TiB2–WB2–CrB2 System

The synthesis of solid solutions of (Ti,W,Cr)B₂ from elemental reactants using the field-activated, pressure-assisted synthesis method and employing the SPS apparatus was investigated. The nature of the products depended on temperature; they were nearly pure solid solutions at 1900°C with minor amounts of β-WB. The product density and microhardness depended on the temperature of synthesis for the same value of applied pressure (64 MPa). Samples with the highest density (94%) corresponded to a hardness of 22.7 GPa. When annealed at 1500°C, the solid solutions decomposed, precipitating a (W,Ti,Cr)B₂ phase in a spinodal form. In addition, β-WB precipitates in the form of thin (0.4–5.3 nm) layers were observed. They existed in a 60°/120° orientation to the (Ti,W,Cr)B₂ matrix, in agreement with previous observations. Highly faceted, small (nanosized) pores associated with the β-WB precipitates were also observed.     

Synthesis of polyamide-hydroxyapatite nanocomposites

Simultaneous one-pot syntheses of PA66 and HAp were carried out by extracting H₂O and CO₂ from PA66 monomers and HAp raw materials, respectively, resulting in the formation of a polyamide (PA) 66-hydroxyapatite (HAp) nanocomposite. During the process, a spherical nano-sized HAp particle was precipitated following dissolution of micro-sized CaHPO₄・2H₂O. The PA66 monomers were subsequently adsorbed onto the generated HAp product. Some of the adsorbed PA66 monomers formed a bound polymer on HAp, and an increase in the adhesiveness of the PA66-HAp interface was observed as the polymerization progressed. During this process, the synthesis of a nanocomposite from a micro-sized raw material and creation of an autonomous strong interface between the matrix and filler was achieved. In addition, the shape of the resultant HAp was controllable and could be modified to needle shape by the addition of F⁻ and Mg²⁺ ions to the raw material. HAp could also be changed to plate shape via octa-calcium phosphate (OCP). Notably, during the synthesis, the filler shape of the nanocomposite could be controlled to 0D (particle), 1D (needle), and 2D (plate).     

Synthesis and Photocrosslinking Reaction of N-Allylcarbamoylmethyl Cellulose Leading to Hydrogel

Summary The reaction of the carboxymethyl cellulose sodium salt (Na-CMC) (degrees of substitution (DS) = 1.2) with N-hydroxysuccinimide (Su-OH) in the presence of 1-hydroxybenzotriazole and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) was carried out in water to obtain the Su-OH ester of carboxymethyl cellulose, Su-CMC, with the DS values of 0.19 – 1.04. N-Allylcarbamoylmethyl cellulose (Allyl-CMC), which was prepared from the reaction of Su-CMC with an excess amount of allylamine, was crosslinked by UV-irradiation. In addition, the photocrosslinked Allyl-CMC film was swollen with water to form a hydrogel having a relatively high water-swelling property, e.g., the degree of swelling (ds) was ca. 360% for Allyl-CMC with the DS of 0.93.