Kinetic theory and rheology of dilute polymer solutions

Summary A summary is given of some recent attempts to relate the results of the kinetic theory of rigid and flexible macromolecules to continuum mechanics results.With 1 table     

A simple salt-enhanced surface-tension technique for detection of trace surfactants in water

A simple, relatively inexpensive DuNoy tensiometer can be used to detect small amounts of surfactants in water (at the μg l^-1 level in many cases). The surfactant must be salted-out to produce the desired effect. Addition of salt to pure water produces a reproducible increase in surface tension, whereas addition of salt to a water sample containing traces of surfactant produces a distinct, reproducible decrease. For pure surfactant solutions, calibration curves can be constructed for quantitative work.     

The anodic dissolution of silver into silver rubidium iodide — Impedance measurements

A.c. impedance measurements have been made on the Ag/Ag₄RbI₅ interphase at anodic potentials less than 50 mV vs. Ag/Ag⁺, using an automatic frequency response analyser.At overpotentials between 10 and 35 mV a high frequency semicircle and a low frequency inductive shape were seen. Spectra at these low overpotentials can be interpreted in terms of rate determining two-dimensional nucleation and growth of holes in the metal surface. The number of atoms in the critical nucleus at various overpotentials have been calculated from both steady state and impedance measurements.     

Axisymmetric vibration of prestressed non-uniform cantilever cylindrical shells

The extended Galerkin method has been used in the investigation of axially loaded clamped-free homogeneous, isotropic and elastic cylindrical shells. Both mass and stiffnesses are considered to vary along the longitudinal direction. Legendre polynomials have been used as shape functions which lead to a simple and systematic procedure in determining the natural frequencies and mode shapes. Some numerical results are presented.     

Theoretical investigation of paramagnetic diazabutadiene gallium(III)-pnictogen complexes: insights into the interpretation and simulation of electron paramagnetic resonance spectra

The electronic structures and the spin density distributions of the paramagnetic gallium 1,4-diaza(1,3)butadiene (DAB) model systems [((t)Bu-DAB)Ga(I)[Pn(SiH3)2]]* and the related dipnictogen species [((t)Bu-DAB)Ga[Pn(SiH3)2]2]* (Pn = N, P, As) were studied using density functional theory. The calculations demonstrate that all systems share a qualitatively similar electronic structure and are primarily ligand-centered pi-radicals. The calculated electron paramagnetic resonance (EPR) hyperfine coupling constants (HFCCs) for these model systems were optimized using iterative methods and were used to create accurate spectral simulations of the parent radicals [((t)Bu-DAB)Ga(I)[Pn(SiMe3)2]]* (Pn = N, P, or As) and [((t)Bu-DAB)Ga[Pn(SiMe3)2]2]* (Pn = P or As), the EPR spectra of which had not been simulated previously due to their complexity. Excellent agreement was observed between the calculated HFCCs and the optimum values, which can be considered the actual HFCCs for these systems. The computational results also revealed inconsistencies in the published EPR data of some related paramagnetic group 13-DAB complexes.