Multiple periodic solutions for a nonlinear suspension bridge equation

We investigate nonlinear oscillations in a fourth-order partialdifferential equation which models a suspension bridge. Previouswork establishes multiple periodic solutions when a parameterexceeds a certain eigenvalue. In this paper, we use Leray-Schauderdegree theory to prove that if the parameter is increased further,beyond a second eigenvalue, then additional solutions are created.     

Characterization of partially transesterified poly(beta-hydroxyalkanoate)s using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) was used for the characterization of a partially transesterified poly(beta-hydroxyalkanoate), PHA, polymer produced by the bacterial strain Alcaligenes eutrophus using saponified vegetable oils as the sole carbon sources. The transesterification was carried out separately under acidic and basic conditions to obtain PHA oligomers weighing less than 10 kDa. The intact oligomers were detected in their cationized [M + Na](+) and [M + K](+) forms by MALDI-TOFMS. A composition analysis, using the MALDI-TOF spectra, indicate that the oligomers obtained via acid catalysis were terminated with a methyl 3-hydroxybutyrate end group, and those obtained by base catalysis had a methyl crotonate (olefinic) termination. In addition to HB (hydroxy butyrate), the oligomers were found to contain a small percentage of HV (hydroxy valerate). This was independently confirmed using gas chromatography/mass spectrometry (GC/MS). In comparison, the analysis of a commercial PHA polymer, transesterified under identical conditions, only showed the presence of HB, i.e. a pure PHB homopolymer. Copyright 1999 John Wiley & Sons, Ltd.     

Enhanced para-xylene selectivity in the toluene alkylation reaction at ultralow contact time

Dramatic improvements in the para-xylene selectivity of the toluene alkylation reaction can be effected by operating the catalytic reaction at ultralow contact time. Unexpectedly, the rate of alkylation is sustained, while unwanted side reactions are suppressed. By demonstrating that contact time directly influences the fate of para-xylene, which is known to form and diffuse preferentially within the zeolite catalyst, we conclude that external mass transfer is a key parameter in controlling selectivity. Even non-optimized catalysts can be made to achieve near-perfect selectivity, without sacrificing conversion.     

On strongly exposed points and frechet differentiability

Using properties of convex functionals, it is shown that closed and bounded convex sets in a class of Banach spaces which includes separable conjugate spaces are the closed convex hulls of their strongly exposed points. This research was supported by the National Research Council of Canada, Grant A-3999.     

Exakte Reduktion Der Allgemeinrelativistischen Dirac-Gleichung Auf Eine Pauli-Typ-Gleichung. I

Acta physica Academiae Scientiarum Hungaricae - Im Teil I wird die allgemeinrelativistische Dirac-Gleichung mittels geeigneter Nullteiler exakt auf eine mit der Paulischen σ(a)-Algebra...     

Magnetohydrodynamic pressure drop in ducted two-phase flows

Two models are presented for predicting magnetohydrodynamic pressure drop in two phase gas—liquid flows of conducting fluids for large values of Hartmann number. The first of these models treats the gas—liquid mixture as a single homogeneous pseudofluid with averaged mixture properties. The second model assumes that the flow pattern is one where the liquid is displaced to the duct walls as a liquid film and the gas flows in the central core. It is shown that the two models do not differ significantly in their predictions of overall pressure drop for vaporising two-phase flow of potassium. There is little experimental data available for testing the models but very satisfactory agreement is found between measurements of magnetic pressure drop of NaK—nitrogen mixtures at low quality and the predictions of both models.     

Metal-organic framework from an anthracene derivative containing nanoscopic cages exhibiting high methane uptake

A microporous metal-organic framework, PCN-14, based on an anthracene derivative, 5,5'-(9,10-anthracenediyl)di-isophthalate (H4adip), was synthesized under solvothermal reaction conditions. X-ray single crystal analysis revealed that PCN-14 consists of nanoscopic cages suitable for gas storage. N2-adsorption studies of PCN-14 at 77 K reveal a Langmuir surface area of 2176 m2/g and a pore volume of 0.87 cm3/g. Methane adsorption studies at 290 K and 35 bar show that PCN-14 exhibits an absolute methane-adsorption capacity of 230 v/v, 28% higher than the DOE target (180 v/v) for methane storage.