Fractional-Flow Theory for Non-Newtonian Surfactant-Alternating-Gas Foam Processes

Transport in Porous Media - Foam can improve sweep efficiency in gas-injection-enhanced oil recovery. Surfactant-alternating-gas (SAG) is a favored method of foam injection. Laboratory data...     

Bivariate Lagrange interpolation at the Padua points: the ideal theory approach

The Padua points are a family of points on the square [−1, 1]² given by explicit formulas that admits unique Lagrange interpolation by bivariate polynomials. Interpolation polynomials and cubature formulas based on the Padua points are studied from an ideal theoretic point of view, which leads to the discovery of a compact formula for the interpolation polynomials. The L ^p convergence of the interpolation polynomials is also studied. S. De Marchi and M. Vianello were supported by the “ex-60%” funds of the University of Padua and by the INdAM GNCS (Italian National Group for Scientific Computing). Y. Xu was partially supported by NSF Grant DMS-0604056.     

Suppression of CO2-plasticization by semiinterpenetrating polymer network formation

CO₂-induced plasticization may significantly spoil the membrane performance in high-pressure CO₂/CH₄ separations. The polymer matrix swells upon sorption of CO₂, which accelerates the permeation of CH₄. The polymer membrane looses its selectivity. To make membranes attractive for, for example, natural gas upgrading, plasticization should be minimized. In this article we study a polymer membrane stabilization by a semiinterpenetrating polymer network (s-ipn) formation. For this purpose, the polyimide Matrimid 5218 is blended with the oligomer Thermid FA-700 and subsequently heat treated at 265°C. Homogeneous films are prepared with different Matrimid/Thermid ratios and different curing times. The stability of the modified membrane is tested with permeation experiments with pure CO₂ as well as CO₂/CH₄ gas mixtures. The original membrane shows a minimum in its permeability vs. pressure curves, but the modified membranes do not indicating suppressed plasticization. Membrane performances for CO₂/CH₄ gas mixtures showed that the plasticizing effect indeed accelerates the permeation of methane. The modified membrane clearly shows suppression of the undesired methane acceleration. It was also found that just blending Matrimid and Thermid was not sufficient to suppress plasticization. The subsequent heat treatment that results in the s-ipn was necessary to obtain a stabilized permeability. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1547–1556, 1998     

Thermoplastic composites based on flax fibres and polypropylene: Influence of fibre length and fibre volume fraction on mechanical properties

Natural-fibre-mat-reinforced thermoplastic (NMT) composites based on flax fibre mats and a Polypropylene (PP) matrix were manufactured using (i) a film-stacking method and (ii) a paper making process. The influence of fibre length and fibre content on stiffness and strength is reported and compared with data for glass-mat-reinforced thermoplastic (GMT) composites, including the influence of using maleic-anhydride grafted PP. The data is also compared with existing micromechanical models like Kelly-Tyson and Cox-Krenchel for strength and stiffness, respectively. A good agreement was found between theory and experiment in case of stiffness while in case of strength the experimental values fall well below the theoretical predictions. Results indicated that NMTs are of interest for low-cost engineering applications and can compete with commercial GMTs, especially when a high stiffness per unit weight is desirable. Results also indicated that the key area for future development lies not only in improved adhesion but mainly in improving the fibre strength.     

An efficient stereospecific total synthesis of (±) terrein

Flash vacuum pyrolysis of functionalized tricyclo|5.2.1.0^2,3|decenone epoxide $\text{5}$, and acetals $\text{3}$ and $\text{4}$ affords cyclopentadienone epoxide $\text{6}$ and acetals $\text{10}$ and $\text{8}$, respectively. These epoxides are suitable precursors for the synthesis of (±) terrein.     

A facile synthesis of functionalized cyclopentadienone epoxides by flash thermolytic cycloreversion of tricyclopecenones

A practical synthesis of cyclopentadienone epoxides $\text{10}$ and their dimethyl acetals $\text{12}$ by thermal cycloreversion of appropriate tricyclo |l5.2.1.0^2,6| decenone epoxides is described.     

High-power dye laser in the near infrared

A tunable wavelength, laser beam of very high spectral luminance in the near infrared is obtained by amplification of a monochromatic laser line emitted by a tunable dye oscillator. Optical pumping of the oscillator and the four-stage amplifier is effected by a giant pulse ruby laser. The energy obtained with a solution of 3,3′ dimethyl 2,2′ oxatricarbocyanine iodide (D.O.T.C.) in dimethyl sulfoxyde is 1 J at 7699 Å. The laser pulse of spectral width Δλ = 0.065 Å is emitted at a rate of 0.1 Hz. The half-peak pulse duration is 15 ns.     

A comparison of different HPLC detector designs based on the dropping mercury electrode principle

Summary Different designs of dropping-mercury electrode (DME) detectors for HPLC were tested and compared to solid-state and UV detectors. The time constants and the corresponding response volumes were measured. A qualitative explanation for the flow pattern of these cells was attempted. With nitrobenzene as a test substance the detection limits and reproducibilities of the best DME detectors were comparable to those of a good UV detector. The linear dynamic ranges and response times for optimally designed electroanalytical cells are better than for UV detectors.

---

Zusammenfassung Vergleiche zwischen diesen Detektoren sowie einem Festkörperelektroden und einem UV-Detektorentyp wurden angestellt. Zeitkonstanten und Detektionsvolumen wurden gemessen und eine Erklärung für die Flußprofile gegeben. Die mit Nitrobenzol gemessenen Detektionsgrenzen und Reproduzierbarkeiten der besten Typen sind vergleichbar mit denen von guten UV-Detektoren. Der dynamisch lineare Bereich und die Ansprechzeit sind für optimal gebaute elektro-analytische Detektoren deutlich besser als für UV-Detektoren.

     

The interactions of mathematics and society in history some exploratory remarks

An exploration of the relations of mathematics and society in history, intended as a basis for general discussion. This includes an argument for doing social history of mathematics; a survey of themes, problems, and methods, structured by distinguishing different social forms of mathematics; and, finally, reference to some special themes.