Instant conversion of air to a clathrate hydrate: CO(2) hydrates directly from moist air and moist CO(2)(g)

The rapid conversion of vapor mixtures containing the gases CO(2), H(2)S, and HCN to clathrate hydrates was reported recently. The novel method is based on the pulsing of warm vapor mixtures, including a carrier gas, into a cold condensation chamber. With cooling, the vapors, which also include ～1% water and either tetrahydrofuran or trimethylene oxide as a catalyst, nucleate aqueous solution nanodroplets that, on a millisecond time scale, crystallize as hydrate nanoparticles that consume 100% of the water. Humid air approximates the content of mixtures used successfully in the vapor-to-hydrate conversions. FTIR spectra are examined for gas hydrates formed directly from air and air enriched with CO(2), as well as hydrate particles for which CO(2)(g) serves as both guest and aerosol medium. In each instance all of the water in the condensed phase converts to a clathrate hydrate. The subsecond ether-catalyzed formation of the hydrates near 230 K requires only a few percent of the CO(2) pressure used in conventional processes that yield fractional amounts of gas hydrates on an hour time scale in the same temperature range.     

Synthesis of statistical glycidyl methacrylate‐n‐vinyl pyrrolidone copolymers and their reaction with naproxen

Free‐radical copolymerization of glycidyl methacrylate (GMA) with N‐vinylpyrrolidone (VPD) was carried out at 50 °C using 3.0 mol · L^?1 of N,N′‐dimethylformamide solution and 9.0 · 10^?3 mol · L^?1 of 2,2′‐azobisisobutyronitrile as an initiator. The modification reaction of GMA‐VPD copolymers with a model bioactive carboxylic acid, 6‐methoxy‐α‐methyl‐2‐naphthaleneacetic acid (naproxen), was studied in the homogeneous phase using basic catalysts. The influence of the type of catalyst and the GMA content was evaluated. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1192–1199, 2002     

High precision delta(17)O isotope measurements of oxygen from silicates and other oxides: method and applications

The use of infrared laser-assisted fluorination to release oxygen from milligram quantities of silicates or other oxide mineral grains is a well-established technique. However, relatively few studies have reported the optimisation of this procedure for oxygen-17 isotope measurements. We describe here details of an analytical system using infrared (10 μm) laser-assisted fluorination, in conjunction with a dual inlet mass spectrometer of high resolving power ( approximately 250) to provide (17)O and (18)O oxygen isotope measurements from 0.5-2 mg of silicates or other oxide mineral grains. Respective precisions (1) of typically 0.08 and 0.04 per thousand are obtained for the complete analytical procedure. Departures from the mass-dependent oxygen isotope fractionation line are quantified by Delta(17)O; our precision (1) of such measurements on individual samples is shown to be +/-0.024 per thousand. In turn, this permits the offset between parallel, mass-dependent fractionation lines to be characterised to substantially greater precision than has been possible hitherto. Application of this system to investigate the (17)O versus (18)O relationship for numerous terrestrial whole-rock and mineral samples, of diverse geological origins and age, indicates that the complete data set may be described by a single, mass-dependent fractionation line of slope 0.5244+/- 0.00038 (standard error). Copyright 1999 John Wiley & Sons, Ltd.     

Molecular quadrangle formation from a diuranium μ-η6,η6-toluene complex

A new inverted sandwich of a μ-η(6),η(6)-toluene diuranium complex reacted with quinoxaline to form a tetranuclear macrocycle with ferrocene diamide uranium(IV) vertices and reduced quinoxaline edges.     

Far-infrared optical absorption due to surface phonon excitations in small metal particles

In this paper, the role played by the excitation of surface phonons in the far infrared optical absorption of small metallic spheres is explored. We find that for frequencies ranging between 100 cm^-3 and 200 cm^-1 this absorption mechanism is dominating over the ones coming from considering electronic excitations or the Joule heating.     

An approach formulated in terms of conserved variables for the characterisation of propellant combustion in internal ballistics

A model formulated in terms of conserved variables is proposed for its use in the study of internal ballistic problems of pyrotechnical mixtures and propellants. It is a transient two‐phase flow model adapted from the non‐conservative Gough model. This conversion is mathematically attractive because of the wide range of numerical methods for this kind of systems that may be applied. We propose the use of the AUSM+, AUSM + up and Rusanov schemes as an efficient alternative for this type of two‐phase problem. A splitting technique is applied, which solves the system of equations in several steps. A second‐order approach based on Monotonic Upstream‐Centred Scheme for Conservation Laws (MUSCL) is also used. Some tests are used to validate the code, namely a shock wave test, a contact discontinuity problem and an internal ballistics problem. In this last case, one‐dimensional numerical results are compared with experimental data of 155‐mm gunshots. Copyright © 2015 John Wiley & Sons, Ltd.     

The dyadic integral means spectrum for Bloch functions

An analogue of the universal integral means spectrum is definedfor Bloch functions, and is computed by using a suitable dyadicnorm.     

Extremal solutions of Nevanlinna-Pick problems and certain classes of inner functions

Consider a scaled Nevanlinna-Pick interpolation problem and let ∏ be the Blaschke product whose zeros are the nodes of the problem. It is proved that if ∏ belongs to a certain class of inner functions, then the extremal solutions of the problem or most of them are in the same class. Three different classical classes are considered: inner functions whose derivative is in a certain Hardy space, exponential Blaschke products and the well-known class of α-Blaschke products, for 0 < α < 1.