Carbon—hydrogen stretching vibrations in fluorocyclohexanes

For perfluorocyclohexane derivatives in which not more than one fluorine at each carbon atom is replaced by a hydrogen atom, it is established that C---H groups with an axial hydrogen show infra-red absorption at 2980 cm⁻¹ and with equatorial hydrogen at 2974 cm⁻¹. With 1H/2H-, 1H:2H/- and 1H:3H/-decafluorocyclohexane the frequencies are reduced somewhat. When the C---H groups are adjacent to a double bond the absorption is at 2961 cm⁻¹, while olefinic C---H groups absorb near 3095 cm⁻¹ in the fluorocarbon series. The C---H absorption is at 3102 cm⁻¹ in pentafluorobenzene.     

Effects of preparation method on properties of lithium salt-poly(ethylene oxide) polymer electrolytes

The effects of using different sources of precursor poly(ethylene oxide) (PEO) and acetonitrile solvent on the physical and electrochemical properties of lithium salt-PEO polymer electrolytes were investigated. Although no differences were found due to the use of different types of PEO, the purity of the acetonitrile solvent was found to be critical in controlling the properties of the polymer product. Acetonitrile of nominally relatively low purity produced polymer electrolytes exhibiting largely crystalline type behaviour while the use of nominally high purity solvents gave polymers which were apparently completely amorphous at temperatures above about 50°C. Transport number measurements gave values for the lithium ions of 0.4 at 132°C for the largely crystalline materials and 0.3 at 112°C for the amorphous polymers. Analysis of the acetonitrile solvents revealed the presence of water in the nominally high purity grades and it has been confirmed that water contamination is responsible for the production of the low melting temperature form of the polymer complex.     

The vibrational force field of halogenated aromatic molecules: In-plane vibrations of benzene and fluorobenzenes

The force fields for the in-plane vibrations of benzene and its fluoro derivatives are determined using the overlay technique. Between 36 and 39 parameters were allowed to vary in different fields and in all cases convergence on the experimental frequencies was smooth and rapid. Only one solution could be found. This solution agrees extremely well with the benzene field of Duinker and Mills. The variation of diagonal force constants in an internal valence coordinate basis set with fluorine substitution in the coordinate environment is determined. The variation in certain force constants is considerable. Thus for the CF stretching constant it is 12% for replacement of two hydrogens by two fluorines. Attempts are made to interpret these variations. Various aspects of the force constant problem for benzene are discussed.     

A rapid colorimetric method for the determi nation of aluminium in cu-al alloys

Aluminium is determined colorimetrically using Eriochrome cyanine. 'I'he application in this paper is to copper-aluminium alloys. The red colour obeys the Beer-Lambert law and the maximum absorption is at a wavelength of 550 mm     

The Use of a Modified Resin for Studying the Internal Structure of Microcrystalline Cellulose Particles

The use of a modified resin which allows the study of the internal structure of microcrystalline cellulose is described. Electron probe microanalysis and elemental X-ray mapping suggest that it is possible to identify cellulose within cross-sectioned microcrystalline cellulose particles.     

Effect of coiling in a cochlear model

Transformation of the three-dimensional equations of fluid motion into cylindrical coordinates allowed analysis of a coiled cochlear model by the WKB technique. The model includes a single transverse mode of basilar membrane deflection and inviscid fluid. The results calculated using realistic parameters for the guinea pig show no significant difference in the basilar membrane amplitude and phase between the straight and coiled models. Some differences exist in the fluid pressure found in the scala. The conclusion is that the macromechanical response is not significantly affected by coiling.     

Magnetic plasmon propagation along a chain of connected subwavelength resonators at infrared frequencies

A one-dimensional magnetic plasmon propagating in a linear chain of single split ring resonators is proposed. The subwavelength size resonators interact mainly through exchange of conduction current, resulting in stronger coupling as compared to the corresponding magneto-inductive interaction. Finite-difference time-domain simulations in conjunction with a developed analytical theory show that efficient energy transfer with signal attenuation of less then 0.57 dB/microm and group velocity higher than 1/4c can be achieved. The proposed novel mechanism of energy transport in the nanoscale has potential applications in subwavelength transmission lines for a wide range of integrated optical devices.     

Advances in methods and algorithms in a modern quantum chemistry program package

Advances in theory and algorithms for electronic structure calculations must be incorporated into program packages to enable them to become routinely used by the broader chemical community. This work reviews advances made over the past five years or so that constitute the major improvements contained in a new release of the Q-Chem quantum chemistry package, together with illustrative timings and applications. Specific developments discussed include fast methods for density functional theory calculations, linear scaling evaluation of energies, NMR chemical shifts and electric properties, fast auxiliary basis function methods for correlated energies and gradients, equation-of-motion coupled cluster methods for ground and excited states, geminal wavefunctions, embedding methods and techniques for exploring potential energy surfaces.     

Force-torque correlations

The equilibrium force-torque correlation ?Nf? is studied, first for a general fluid in which the intermolecular potential is expanded in generalized spherical harmonics, and then for the specific case of homonuclear diatomic molecules. If coordinate axes are taken with z axis parallel to the 12 intermolecular vector, it is shown that two (and only two) elements of the tensor are non-zero : ?n_x (12)f_y (12)? = -?n_y (12)f_x (12)?. For the linear molecule, these elements are evaluated in the limit of zero density for the atom-atom model of the potential. Example calculations are done, numerically for finite L (where L is the length of the diatomic molecule) and analytically in the limit of small L.