Volume 39, Issue 4

In thin nematic liquid crystal films with homeotropic boundaries, surface forces are measured that are produced by an electric field induced flow. The sample is placed between two horizontal circular glass disks in a torsion viscosimeter, where a torque is exerted on the upper disk by these surface forces. The evolution of the induced flow is registered via this torque. The time constants of this evolution, the viscosity term γ 1 - α 2 2 /η c and the elastic constant K 3 are determined.

By Whitham’s shock dynamics, axially symmetric diffraction problems of plane shocks by cones are reduced to the integration of a system of ordinary differential equations. This paper gives a simpler approach. Approximating the Mach stems by circular arcs, the problems are reduced to the solution of algebraical equations, and the calculating is much simplified. In the cases of small or large cone angles the estimation is even easier.

A promising candidate for a near-term low-cost inertial confinement fusion driver is the magnetic booster target concept. In it a small high density magnetically confined plasma and which serves as booster stage, is compressed and ignited by hypervelocity impact. The energy released in the magnetic booster stage, after being transformed into black body radiation, ablatively implodes a high gain second stage target and which releases most of the thermonuclear energy. Alternatively, the energy released in the booster stage can be also used to compress and ignite a target as in impact fusion. The importance of this concept is that it permits to drive the booster stage with a mass accelerator at a velocity of a few 10 km/sec, which is small compared to the velocity required for pure impact fusion, even though it is more than one order of magnitude larger than what can be directly reached with ordinary guns or high explosives. The required velocities can probably be reached by magnetic guns and by fluid dynamic methods through the implosion of cylindrical or spherical shells driven by light gas gun fired projectiles. In comparison to laser- or charged particle beam drivers, the initial driver power is several orders of magnitude smaller and which should lead to a substantial reduction in the driver cost.

A variant to the well known Danziger-Elmergreen equation of hormonal regulation is analyzed geometrically by analytical methods. The new method of Poincaré half maps is employed. Several chaotic regimes are found.

Near equilibrium potential energy and dipole moment functions have been calculated for the electronic ground state of the XeH + ion from highly correlated SCEP/CEPA electronic wavefunctions. The following spectroscopic constants for 132 XeH + are obtained: R e = 1.611 ± 0.005 Å, ω e = 2313 ± 50cm -1 , ω e x e = 41 ± 5cm -1 and D 0 (Xe + + H) = 3.90 ± 0.1 eV. Infrared transition dipole matrix elements and probability coefficients for 132 XeH + and 132 XeD + are given. The electric dipole moment functions of the protonated rare gas atoms HeH + to XeH + are discussed.

We report on the first experiments with Fourier Transform technique in K-band. Due to the limited performance of some components frequencies up to 20.5 GHz only could be reached. Some T 2 -relaxation measurements are given.

Pb 2 P 2 Se 6 crystallizes in the monoclinic system, space group Pn (No. 13) with the lattice constants a = 974.2 (4) pm. b = 766.2 (3) pm. c = 689.8 (3) pm, β=91.44(5)°. The title compound is isotypic to the homologous Pb 2 P 2 S 6 . In the structure there are discrete P 2 Se 4- 6 anions. Far infrared, infrared and Raman spectra of this compound have been recorded. The observed frequencies are assigned on the basis of P 2 Se 4- 6 units with C 2h symmetry in the crystal. DTA-data have been determined and interpreted.

The temperatures and enthalpy changes pertinent to the fusion and clearing processes in the linear cesium alkanoates from tridecanoate to eicosanoate were measured by differential scanning calorimetry. The present information along with data previously taken on the lower homologs allows one to draw the boundaries of the region where cesium soaps can exist in the liquid crystal state.

By 79,81 Br and 127 I NQR spectroscopy 4-(CH 3 )C 6 H 4 NH ⊕ 3 X ⊖ , X = Br and I, and 4-(CH 3 )C 6 H 4 ND ⊕ 3 I ⊖ were studied in the temperature range 77 ≦ TK ⪅ 340. The three compounds experience phase transitions, most likely of higher order. Two reversible transitions are observed for the para-toluidinium iodide. 7~i-n being in the temperature range 247 ⪅ T/K ⪅ 258. T II ⇌ III in the range 174 ⪅ T/K ⪅ 179. The deuterated compound shows slight shift of the transition temperatures compared to the protonated one. whereas the 127 I-NQR resonance frequencies are considerably lowered as is the nuclear quadrupole coupling constant. The asymmetry parameter η, however, increases through deuteration of the NH 3 group. The room temperature phase of the iodide crystallizes with an orthorhombic space group (Pmmn or Pmn2 1 , Z = 2). Temperature dependence of the 79 BrNQR spectrum of p-toluidinium bromide indicates a phase transition near T = 281 K.

The magnetic susceptibilities of diaquabis(phenoxyacetato)manganese(II), diaquabis(p-chlorophenoxyacetato) manganese(II), and diaquabis(phenoxyacetato)cobalt(II) were determined in a temperature region below 77 K. The temperature dependence of the magnetic susceptibility observed for the first two manganese(II) complexes shows a broad maximum near 2 K. which can be interpreted as arising from two-dimensional Heisenberg antiferromagnets with S = 5/2. The magnetic susceptibility of the cobalt(II) complex obeys the Curie-Weiss law showing the presence of a ferromagnetic interaction between neighboring cobalt(II) ions. For diaquabis( phenoxyacetato)manganese(II), a magnetic phase transition from a disordered to an antiferromagnetic ordered state was located at 1.633 ± 0.005 K from the sharp maximum of the magnetic susceptibility.

Ab initio MO calculations on solvated NaCl adducts are presented. They provide insight into effects to be expected upon oligomerisation of NaCl in aqueous solution or, vice versa, during the last step of the dissolution/solvation process in water. Extrapolation of the data obtained predict the minimal nucleation size for the formation of NaCl crystals to be represented by a (NaCl) ~100 aggregate.

The highly regiospecific electrophilic substitution of Benzo[1,3]dioxole leads only to the β-substitution products. Quantumchemical calculations with the semiempirical MNDO- and MINDO/3-methods including the influence of the solvent however suggest that there might be a critical value of the dielectric constant of the solvent above which the α-σ-complex formed by the attack of an electrophil (H + or Cl + ) should be energetically more favoured than the corresponding β-σ-complex.

Semiempirical MNDO calculations with optimization of geometry were carried out for several polycyano derivatives of some unsaturated hydrocarbons and benzene. The results show that the MNDO method overestimates the AEA s (adiabatic electron affinity) by about 0.575 eV. as is seen from the equation AEA exp = 0.998 AEA MNDO - 0.575; R = 0.9995. It was found that there exists a linear correlation between the energies of LUMO and the AEA's of the investigated compounds: AEA = - 1078 LUMO + 0.387; R = 0.9979 for 40 points. MNDO does not show a linear correlation of AEA with IP (ionization potential). Generally, with increasing number of cyano substituents in unsaturated hydrocarbons the energy of HOMO and LUMO decreases, but this may not necessarily be true for higher molecular orbitals.

The kinetica energy released on the loss of CNO 2 from nitrobenzene and deuterated nitrobenzene ions in the second field-free region shows that this loss does not occur as a single-step process. The apparent heat of formation of the C 6 H + 5 ion is found to be 270.85 kcal mol -1 , which is consistent with the ion having the cyclic structure.

We construct a formal second integral of motion in a bisymmetrical potential field describing the motion on the plane of symmetry of a triaxial galaxy. We also check the constancy of the second integral adding higher-order terms which are found using a computer program.

The variation of intensity of the benzophenone-sensitized naphthalene phosphorescence with naphthalene concentration is different in a hydrocarbon or ethanol-ether glass, respectively. The naphthalene phosphorescence quenching observed in the hydrocarbon glass at higher naphthalene concentrations is assumed to result from the formation of non-phosphorescent naphthalene aggregates in benzophenone microcrystals.

Quantitative absorption spectroscopy in the infrared and near-infrared region enables kinetic and thermodynamic investigations to be performed on systems at high temperatures and pressures. The technique is illustrated for the ethylene polymerization. From spectroscopic experiments up to 3 kbar at maximum temperatures of 250 °C, the rate equations of the thermally, of the photochemically, and of the chemically initiated polymerization are determined.