A Particle-Mesh Method for the Shallow Water Equations Near Geostrophic Balance

In this paper we outline a new particle-mesh method for rapidly rotating shallow water flows based on a set of regularized equations of motion. The time-stepping method uses an operator splitting of the equations into an Eulerian gravity wave part and a Lagrangian advection part. An essential ingredient is the advection of absolute vorticity by means of translated radial basis functions. We show that this implies exact conservation of enstrophy. The method is tested on two model problems based on the qualitative features of the solutions obtained (i.e., dispersion or smoothness of potential vorticity contours) as well as on the increase in mean divergence level.     

Behaviors of the positive temperature coefficient of resistance of poly(styrene‐co‐n‐butylacrylate) filled with Ni‐plated core‐shell polymeric particles

Conductive composite films of poly(styrene‐co‐n‐butylacrylate) copolymers filled with low‐density, Ni‐plated core‐shell polymeric particles were prepared and their behaviors of positive temperature coefficient of resistance (PTCR) were investigated. When the conductive fillers in the composite film were loaded beyond the critical volume, 10 up to 25 vol %, composite films exhibited a unique electrical resistant transition behavior, which the electrical resistance rapidly increased by several orders of magnitude at the critical temperature. The PTCR transition temperature, in general, occurred before the glass transition temperature of polymer matrix. Further increased the conductive filler loading to 30 vol %, the overpacked conduction paths were formed in the entire composite and the PTCR effects became blurred. While the composite film treated with thermal cycle several times from room temperature up to 120 °C, the electrical resistivity increased accompanied with the shift of the PTCR transition to lower temperature. The reason might have been caused by the formed interfacial cracks within the composite film. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 322–329, 2007     

Determination of limonene oxidation products using SPME and GC-MS

Limonene is a common component found in consumer goods ranging from beverages to cleaning compounds. Limonene oxidation products, however, have a less desirable flavor and fragrance. Early detection of limonene oxide formation would aid quality control. A method is developed to determine the concentration of limonene oxide in essential oils and beverages using solid-phase microextraction (SPME). A headspace sampling technique is used to reduce or eliminate the presence of less volatile components. Several different SPME fibers are tested, varying in polymer thickness, polymer cross-linking and bonding, and polarity of the polymer. For each fiber tested, the sampling time is optimized for reproducible results. The 7-microm-thick bonded poly(dimethylsiloxane) fiber provides the best results. External standards are used for quantitation.     

The effect of the anion on the physical properties of trihalide-based N,N-dialkylimidazolium ionic liquids

Low viscosity, high density trihalide-based 1-n-butyl-3-methylimidazolium ionic liquids have been prepared and characterised. Key physical properties (density, conductivity, melting point, refractive index, surface tension and diffusion coefficient) of the ionic liquids have been determined and are compared with those of other 1,3-dialkylimidazolium molten salts. The relationship between anion identity and the physical properties of the ionic liquids under investigation is discussed.     

Derivatives of pentamidine designed to target the Leishmania lipophosphoglycan

The Leishmania lipophosphoglycan (LPG) is the most abundant cell surface glycoconjugate of a family of infectious protozoa. Pentamidine, a common drug used in the treatment of Leishmania infections, has been modified with boronic acids so that it might bind more selectively to the phosphodisaccharide repeating unit of the LPG. This could serve to target the drug to the protozoan surface and increase its efficacy in vivo.     

A hexacyclic ent-trachylobane diterpenoid possessing an oxetane ring from Mitrephora glabra

[chemical reaction: see text]. Three new ent-trachylobane diterpenoids (1-3) were isolated and structures elucidated from Mitrephora glabra Scheff. (Annonaceae). Mitrephorone A (1) possesses a hexacyclic ring system with adjacent ketone moieties and an oxetane ring, both of which are unprecedented among trachylobanes. All compounds were evaluated for cytotoxicity against a panel of cancer cells, where 1 displayed the most potent and broadest activity, and against a battery of antimicrobial assays, where all compounds were approximately equipotent.     

Second Dissociation Constants of 4-[N-morpholino]butanesulfonic Acid and N-[2-hydroxyethyl]piperazine-N′-4-butanesulfonic Acid from 5 to 55°C

The values of the second dissociation constant, pK ₂, for the dissociation of the NH⁺ charge center of the zwitterionic buffer compounds 4-(N-morpholino)butanesulfonic acid (MOBS), and N-(2-hydroxyethyl)piperazine-N-4-butanesulfonic acid (HEPBS) have been determined from 5 to 55°C, including, 37°C at intervals of 5°C. The electromotive-force (emf) measurements have been made utilizing hydrogen electrodes and silver–silver chloride electrodes. The value of pK ₂ for MOBS was found to be 7.702 ± 0.0005, and 8.284 ± 0.0004 for HEPBS, at 25°C, respectively. The related thermodynamic quantities, G ^o, H ^o, S ^o, and C _p ^o for the dissociation processes of MOBS and HEPBS have been derived from the temperature coefficients of pK ₂. Both the MOBS and HEPBS buffer materials are useful as primary pH standards for the control of pH 7.3 to 8.6 in the region close to that of physiological fluids.     

Rotationally resolved electronic spectra of 1,2-dimethoxybenzene and the 1,2-dimethoxybenzene-water complex

Rotationally resolved S(1) <-- S(0) electronic spectra of 1,2-dimethoxybenzene (DMB) and its water complex have been observed and assigned. The derived values of the rotational constants show that the bare molecule has a planar heavy-atom structure with trans-disposed methoxy groups in its ground and excited electronic states. The transition of DMB is polarized along the b-axis bisecting the methoxy groups, demonstrating that its S(1) state is an (1)L(b) state. Higher energy bands of DMB are also polarized along the b-axis and have been tentatively assigned to different vibrational modes of the (1)L(b) state. The water complex origin appears 127 cm(-1) to the blue of the bare molecule origin. Analyses of the high resolution spectra of DMB/H(2)O and DMB/D(2)O suggest that the water molecule is attached via two O-H...O hydrogen bonds to the methoxy groups in both electronic states. A tunneling motion of the attached water molecule is revealed by a splitting of these spectra into two subbands. Potential barriers to this motion have been determined.