Ion and solvent transfer discrimination at a nickel hydroxide film exposed to LiOH by combined electrochemical quartz crystal microbalance (EQCM) and probe beam deflection (PBD) techniques

A combined electrochemical quartz crystal microbalance (EQCM) and probe beam deflection (PBD) instrument was used to monitor the mobile species transfers associated with the redox processes of thin (Γ100–150 nmol cm⁻²) α- and β-nickel hydroxide films exposed to aqueous LiOH solution. A comparison of the measured PBD signal with the predicted PBD profiles, calculated by temporal convolution analysis of the current and mass responses, enabled the contributions to redox switching of anion (OH⁻) and solvent (H₂O) transfers to be discriminated quantitatively. The responses from the combined instrument are reconciled in terms of H⁺ deintercalation/intercalation within the nickel hydroxide structure as OH⁻ ions enter/exit the film. Hydroxide ion movement is associated with a counterflux of water. Thin nickel hydroxide films show a gradual α→β phase transformation with continuous voltammetric cycling, especially when the films are exposed to high concentrations of electrolyte. α-Films are characterised by OH⁻ transfers that dominate the H⁺ and H₂O movements; β-films are characterised by an increased participation of water and protons to the exchange dynamics.     

Determination of water compartments in rat myocardium using combined D-T1 and T1-T2 experiments

We have used combined D-T1 and T1-T2 correlation experiments to explore water compartments in rat heart tissue (myocardium). The results show that two main compartments can be identified, which we assign to extracellular (ec) and intracellular (ic) water. The exchange rate of water across the cell membrane was found to be on the order of 0.1 Hz. In addition, the T1-T2 correlation measurements indicate that the ic compartment contain two T2 populations.     

A novel microstep device for the size separation of cells

We report on a series of preliminary experiments investigating the applicability of a novel method for the size separation of nano- and microsized particles and cells. The working principle is based on the application of a shear-driven flow through stepwise tapered micro- or nanochannels. Size separations of mixtures of 0.5 and 1.0 microm carboxylated polystyrene beads as well as of binary mixtures of Staphylococcus aureus and Saccharomyces cerevisiae cells and of S. cerevisiae and Escherichia coli cells are demonstrated.     

Viscosity of two-dimensional suspensions

Over a range of conditions, lipid and surfactant monolayers exhibit coexistence of discrete solid domains in a continuous liquid. The surface shear viscosity, mu(s), of such monolayers collapses onto a single curve: mu(s)/mu(so) = [1-(A/A(c))](-1), in which mu(so) is the viscosity of the liquid phase, A is the area fraction of the solid phase measured by fluorescence microscopy, and A(c) is a critical solid phase fraction. This scaling relationship is directly analogous to that of three-dimensional dispersion of spheres in a solvent with long-range repulsive interactions, with area fraction replacing volume fraction.     

Shallow Flows Over a Permeable Medium: The Hydrodynamics of Submerged Aquatic Canopies

Aquatic flow over a submerged vegetation canopy is a ubiquitous example of flow adjacent to a permeable medium. Aquatic canopy flows, however, have two important distinguishing features. Firstly, submerged vegetation typically grows in shallow regions. Consequently, the roughness sublayer, the region where the drag length scale of the canopy is dynamically important, can often encompass the entire flow depth. In such shallow flows, vortices generated by the inflectional velocity profile are the dominant mixing mechanism. Vertical transport across the canopy–water interface occurs over a narrow frequency range centered around f _v (the frequency of vortex passage), with the vortices responsible for more than three-quarters of the interfacial flux. Secondly, submerged canopies are typically flexible, coupling the motion of the fluid and canopy. Importantly, flexible canopies can exhibit a coherent waving (the monami) in response to vortex passage. This waving reduces canopy drag, allowing greater in-canopy velocities and turbulent stresses. As a result, the waving of an experimental canopy reduces the canopy residence time by a factor of four. Finally, the length required for the set-up and full development of mixing-layer-type canopy flow is investigated. This distance, which scales upon the drag length scale, can be of the same order as the length of the canopy. In several flows adjacent to permeable media (such as urban canopies and reef systems), patchiness of the medium is common such that the fully developed condition may not be representative of the flow as a whole.     

Influence of turning radius on wheeled military vehicle induced rut formation

A rut is a depression or groove formed into the ground by the travel of wheels and tracks. Ruts can cause severe influences on soil and vegetation, and reduce vehicle mobility. In this paper, rut depth and rut width were used as the main indicators to quantify a rut. A new indicator, rut index, was proposed, combining rut depth and rut width. A Light Armored Vehicle (LAV) and a High Mobility Multi-purpose Wheeled Vehicle (HMMWV) were used for testing the influence of turning radius on rut depth, rut width and rut index. The LAV and the HMMWV were operated in spiral patterns at different speeds. Differential GPS data for the vehicles were collected every second during the spiral. Rut measurements were manually taken every 4-7 m along each of the spiral tracks. The results of field tests indicate that rut depth, rut width and rut index increase with the decrease of turning radius, especially when turning radius is less than 20 m. Velocity influences rut formation for the LAV but not HMMWV.     

Fractionation of cadmium in tobacco and cigarette smoke condensate using XANES and sequential leaching with ICP-MS/MS

Analytical and Bioanalytical Chemistry - Fractionation data for cadmium in tobacco products, as obtained by sequential leaching of cadmium species with ICP-MS/MS analysis, and separately by X-ray...     

Bias effects on the electronic spectrum of a molecular bridge

In this paper the effect of bias and geometric symmetry breaking on the electronic spectrum of a model molecular system is studied. Geometric symmetry breaking can either enhance the dissipative effect of the bias, where spectral peaks are disabled, or enable new excitations that are absent under zero bias conditions. The spectral analysis is performed on a simple model system by solving for the electronic response to an instantaneously impulsive perturbation in the dipole approximation. The dynamical response is extracted from the electronic equations of motion as expressed by the Keldysh formalism. This expression provides for the accurate treatment of the electronic structure of a bulk-coupled system at the chosen model Hamiltonian electronic structure level.