Deacetylation behavior of binary blend films of cellulose acetate and various polymers

For binary blend films of cellulose acetate (CA) and various polymers, the elution behavior of the polymers from the CA films in different environments (i.e., soil, water) was examined. For the CA film containing poly(ethylene glycol) (PEG), the PEG eluted to the periphery of the film completely. On the other hand, polyvinylpyrrolidone blended with CA remained in the CA film. A CA film containing acrylic acid was prepared, and this film was heated. The elution of acrylic acid was inhibited by its polymerization. These results suggested that the internal polymers were capable of remaining in the CA film by polymer entanglement. Second, we examined the deacetylation and biodegradation behavior of CA films containing polymers with a phosphoric acid moiety in the side chain, such as poly(2‐hydroxyethyl methacrylate phosphoric acid ester) [poly(HEMA‐P)]. Poly(HEMA‐P) had the ability to deacetylate the CA, and the biodegradation rate of the CA films containing poly(HEMA‐P) increased in comparison with that of the nonadditive CA films. The elution of internal 2‐hydroxyethyl methacrylate phosphoric acid ester was inhibited by the copolymerization with 2‐hydroxyethyl methacrylate or crosslinking. In the case of both 2‐hydroxyethyl methacrylate phenyl phosphoric acid ester and 10‐methacryloyloxydecyl dihydrogen phosphate, the acetone‐soluble polymers were obtained by radical polymerization in a mixture of acetone and water. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1816–1823, 2006     

Inevitable generation of primary alcohols during reduction of oxidized lipids with sodium borohydride

This report deals with the fluorometric determination of fatty alcohols generated by the reduction of the ester linkage of lipids with NaBH₄, and with the limitations of the reduction method for assaying oxidized lipids. Optimum conditions for the fluorometric analysis of primary and secondary alcohols using 1-anthroyl nitrile were obtained. After reduction with NaBH₄ in MeOH or in MeOH/benzene (8∶2, v/v), the formation of 1-hexadecanol from a variety of palmitic acid esters was measured fluorometrically by reverse-phase high-performance liquid chromatography (HPLC): From glycerides and methyl palmitate, 1–3% (w/w) 1-hexadecanol was produced and a trace was produced from cholesteryl palmitate (10 min, 21°C). 1-Hexadecanol was never generated from palmitic acid. Although considerable improvement occurred with the choice of the solvent for the NaBH₄ reduction, the generation of primary alcohols from ester lipids usually seems inevitable.     

A conservative and monotone mixed-hybridized finite element approximation of transport problems in heterogeneous domains

In this article, we discuss the numerical approximation of transport phenomena occurring at material interfaces between physical subdomains with heterogenous properties. The model in each subdomain consists of a partial differential equation with diffusive, convective and reactive terms, the coupling between each subdomain being realized through an interface transmission condition of Robin type. The numerical approximation of the problem in the two-dimensional case is carried out through a dual mixed-hybridized finite element method with numerical quadrature of the mass flux matrix. The resulting method is a conservative finite volume scheme over triangular grids, for which a discrete maximum principle is proved under the assumption that the mesh is of Delaunay type in the interior of the domain and of weakly acute type along the domain external boundary and internal interface. The stability, accuracy and robustness of the proposed method are validated on several numerical examples motivated by applications in biology, electrophysiology and neuroelectronics.     

Cavitation damage prediction for spallation target vessels by assessment of acoustic vibration

Liquid-mercury target systems for MW-class spallation neutron sources are being developed around the world. Proton beams are used to induce the spallation reaction. At the moment the proton beam hits the target, pressure waves are generated in the mercury because of the abrupt heat deposition. The pressure waves interact with the target vessel leading to negative pressure that may cause cavitation along the vessel wall. In order to estimate the cavitation erosion, i.e. the pitting damage formed by the collapse of cavitation bubbles, off-beam tests were performed by using an electric magnetic impact testing machine (MIMTM), which can impose equivalent pressure pulses in mercury. The damage potential was defined based on the relationship between the pitting damage and the time-integrated acoustic vibration induced by impact due to the bubble collapses. Additionally, the damage potential was measured in on-beam tests carried out by using the proton beam at WNR (Weapons Neutron Research) facility in Los Alamos Neutron Science Center (LANSCE). In this paper, the concept of the damage potential, the relationship between the pitting damage formation and the damage potential both in off-beam and on-beam tests is shown.     

Full Eulerian simulations of biconcave neo-Hookean particles in a Poiseuille flow

For a given initial configuration of a multi-component geometry represented by voxel-based data on a fixed Cartesian mesh, a full Eulerian finite difference method facilitates solution of dynamic interaction problems between Newtonian fluid and hyperelastic material. The solid volume fraction, and the left Cauchy–Green deformation tensor are temporally updated on the Eulerian frame, respectively, to distinguish the fluid and solid phases, and to describe the solid deformation. The simulation method is applied to two- and three-dimensional motions of two biconcave neo-Hookean particles in a Poiseuille flow. Similar to the numerical study on the red blood cell motion in a circular pipe (Gong et al. in J Biomech Eng 131:074504, 2009), in which Skalak’s constitutive laws of the membrane are considered, the deformation, the relative position and orientation of a pair of particles are strongly dependent upon the initial configuration. The increase in the apparent viscosity is dependent upon the developed arrangement of the particles. The present Eulerian approach is demonstrated that it has the potential to be easily extended to larger system problems involving a large number of particles of complicated geometries.     

A Biomimetic Approach to Taxol: Stereoselective Synthesis of a 12-Membered Ring Ene-Epoxide

The stereoselective synthesis of a taxol intermediate via a biomimetic route is described. Aldol condensation of γ-butyrolactone and citral derivatives generated three stereogenic centers at positions C1, C2, and C11 corresponding to taxol. Intramolecular alkylation of the cyanohydrin ether efficiently formed the 12-membered ring system in which stereoselective reduction, followed by directed epoxidation, afforded the key intermediate epoxide.     

Direct determinations of the unperturbed dimensions of linear polyethylene molecules

Light scattering measurements were carried out on three linear polyethylene samples in diphenyl at 127.5°C, i.e., under theta conditions. The unperturbed molecular dimensions and hence the characteristic ratio C_n were directly determined without recourse to theory for the excluded volume effect. It was found that the values of C_n were 8.7 to 10.5 in this theta solvent. These values suggest that the parameters, assigned to agree with the C_n value of 6.7, should be re-examined for the refinement of theory.     

Effect of anodic oxidation of coal tar pitch-based carbon fibre on adhesion in epoxy matrix: Part 2. Comparative study of three alkaline solutions

Anodic oxidation of coal tar pitch-based carbon fibre was performed in various alkaline solutions, such as NaOH, NaHCO₃ and Na₂CO₃, to examine the effect of various kinds of electrolytes on the surface chemical nature of treated fibres and the adhesive strength between treated fibres and epoxy resin. Evaluation of the oxygen concentration and surface functional groups of the carbon fibre surface was conducted by X-ray photoelectron spectroscopy (XPS). A fragmentation test was adopted for evaluation of the adhesive strength between the carbon fibre and epoxy matrix. As a result, it was shown that the highest O_1S/C_1S value was obtained in NaOH aqueous solution, and the highest interfacial shear strength (IFSS) was also obtained from the carbon fibre oxidized in NaOH solution. It was recognized that the IFSS values increase with increasing of O_1S/C_1S in every solution at the initial stage of oxidation below 1.0 × 10⁻³ C mm⁻². However, above this level of electrical charge in NaOH solution, decreasing IFSS values may occur, regardless of an increasing O_1S/C_1S value. SEM analysis inferred that in the case of the fibre treated in NaOH solution, grooves on the carbon fibre surfaces had become deeper over 1.0 × 10⁻³ C mm⁻². Presumably, the amorphous part of the carbon fibres could be oxidized intensively, and the remaining graphite layer become very thin and easy to break when a shear stress is loaded on its interface.     

Sintering behaviour of the diamond-cobalt system at high temperature and pressure

A powder mixture of diamond—8.9 vol % Co was consolidatedin situ on a WC-10 wt % Co base at temperatures of 1300 to 1500° C under a pressure of 5.8 GPa. The sintered body obtained at 1300° C, which is below the diamond—cobalt eutectic point, was not hard, and the surface of the diamond particle was partially graphitized. On the other hand, the sintered body obtained at 1400 to 1500° C was fairly hard. A strong correlation was also observed between hardness and the cobalt content found in the sintered body. The cobalt content in the harder sintered body was clearly lower compared with that of the softer one. The surface graphitization of the diamond particles is necessary to the transfer of cobalt during the sintering of diamond. In sintering the diamond-cobalt system, the sinterability of diamond was closely related to the feasibility of transformation from diamond to graphite.