Volume 34, Issue 8

Spatially homogeneous chemical reaction systems with one or two intermediate reaction pro-ducts and with autocatalytic reactionsteps are considered. Because of their non-linearities, such open systems show already primitive forms of self-organization. In order to express the "information" contained in the structures occuring, a theory is developped for measuring that quantity by help of a fictive detector: In treating the stochastic reaction kinetics in the Fokker-Planck-equation approximation, expressions are derived for the averaged amount of information one gets by doing a measurement with the detector and for the temporal conservation of the message being detected. This concept is applied to a one-component reaction scheme that exhibits a non-equilibrium phase transition of second order resulting in bistability of the steady state. When pushing this reaction system from the near equilibrium side through its critical region to bi-stability, a certain amount of information becomes quasi conserved, thus giving rise to a definition of the degree of order of a self-organizating system. The problem of how the reaction system can be integrated into a greater chemical network as a "bit"-generator, is discussed. To explain what is necessary for the onset of a hard mode instability giving birth to limit-cycle behaviour, a two-component reaction scheme is constructed by superposing onto reaction steps causing conservative concentration oscillations those reactions of the former model system which are responsible for the instability occuring there. By applying the information formalism, again, a quasi-conservation of information is indicated, but with respect to a much smaller time scale. The consequences for using oscillating reaction models as an information pump within a network, and the necessity of a feed-back mechanism in order to get real information storage, are shortly mentioned. Finally, a one-component reaction scheme is outlined that shows successive phase transitions, each of these instabilities bringing out a higher degree of organization.

Longitudinal nuclear magnetic relaxation rates of 25 Mg 2+ have been measured in aqueous solutions of MgCl 2 and Mg(NO 3 ) 2 as a function of concentration. The value of 1/T 1 , extrapolated for infinite dilution has been compared with the "electrostatic theory" of Hertz. It turned out that the relaxation rate reflects the high cubic symmetry of the first hydration sphere of 25 Mg 2+ . Using the 1 H and 25 Mg 2+ relaxation rates at finite salt concentration the "ion-ion contributions" to the 25 Mg 2+ relaxation rates have been determined. They are compared with those in aqueous LiCl solutions. A big change in the 25 Mg 2+ relaxation rate in MgCl 2 solution was found when a little amount of sodium citrate was added.

Deuterium magnetic relaxation measurements are reported for two samples of specifically labeled dipalmitoyl lecithin bilayers in the temperature range 0° to 60 °C. While the liquid-crystalline phase shows a "dynamic gradient" along the alkane chains, which is already known from 13 C-investigations, there is no such gradient in the gel phase at least between the second and tenth methylene group. Moreover there is a common T 1 -minimum compatible with that observed in studies of the (non-specific) proton relaxation. Deuterium signals from the gel phase could only be detected by a combined spin-locking / echo method allowing to substract spurious signals arising from magneto-acoustic ringing typical for low-frequency / high-field pulse experiments in iron magnets.

A normal coordinate treatment of chlorofluoromethane has been performed in the Urey-Bradley force field model using the centrifugal distortion constants and the vibrational frequencies. Since the molecule has only one plane of symmetry (C s ), the symmetrized internal coordinates have not been used in the calculation. The effect of the angular redundancy has been rigorously treated and the derived force constants are in good agreement with those of other halogenated methane.

Results of calculations on pellet-plasma interaction that take into account transport phenomena inherent in tokamak plasmas are analyzed. It is shown that the results obtained by different authors on the optimum pellet penetration depth and required pellet injection frequencies, which are partly contradictory, can be explained by means of the different transport processes taken into account or neglected in the calculations concerned.

In refinement of a previous study made by Hayward and Packer, the self-diffusion coefficients D of the nematogen liquid crystals MBBA and EBBA were remeasured in the isotropic phase by means of the NMR pulsed field gradient technique. In particular, the diffusion measurements were made for the first time at different Larmor frequencies. A comparison with results obtained recently on the same samples by NMR T 1 relaxation analysis reveals a severe discrepancy. Since the gradient method gives results in essential agreement with optical spectroscopies, the observed discrepancy must be attributed to shortages of the relaxation analysis (incorrect models, insufficient experimental accuracy). It is also shown that D depends more strongly on the molecular weight m than m -1/2 .

Gibbs free energies of reaction in the systems Te-TeX 4 (X = Cl, Br, I) were determined from e.m.f. measurements of solid state galvanic cells using silver halides as auxiliary electrolytes. From the temperature dependence of the e.m.f. the standard entropies and enthalpies of formation S 0 (298.15 K) and ⊿H f 0 (298.15 K) have been calculated for α-TeI, TeI 4 , Te 2 Br, TeBr 4 , Te 3 Cl 2 and TeCl 4 . The specific heats of α-Tel and Te 2 Br were determined from 1.5 K to 300 K by adiabatic and differential scanning calorimetry.

Raman spectra of some solid and molten PCl5- -SnCl4- mixtures have been recorded. According to the stoichiometry SnCl 5 - and additional SnCl 6 2- complex ions are present in the solid state. The 1 : 1 melt is built up by PCl 4 + and SnCl 5 - ions. PCl 5 rich melts contain PCl 5 molecules in addition, but almost no SnCl 6 2- . SnCl 4 rich melt mixtures are composed of PCl 4 + , SnCl 5 - and SnCl 4 .

The two-photon excitation spectra of gas phase pyrazine-h 4 and -d 4 in the region of the S 1 ←S 0 transition are presented. The two-photon absorption which is electronically forbidden is induced by-various vibrations of ungerade parity. Because of the different selection rules for two-photon transitions hitherto unknown vibrational frequencies in the excited state 1 B 3u have been determined.

A model for a new kind of one-dimensional conductors is presented. The compounds consist of square-planar metal complexes MX 4 which are polymerised via bridging ligands L to linear chains. The bidentate ligand L, e.g. C 2 2- , leads to the formation of a linear π-system along the chain, which is essential for the conductivity. The square-planar complex can be, for example, a metal phthalocyanine. MO-calculations show that this kind of polymer gives rise to a suitable energy band structure. An advantage of the new one-dimensional conductors is their flexibility; different combinations of the square-planar ligand system, the bridging ligand, and the central metal atom can be used. First experimental studies show that the preparation of the proposed conductors is possible.

The co-ordination polymer of tetrazaporphin (TAP) with a transition metal, say Fe II , in its center and acetylide anion, C 2 2⊖ , as an axial bidentate bridging ligand is taken as a model sub-stance for the new type of one-dimensional conductors introduced in the preceding communication of this series. Although the monomer shows D 4h symmetry, this is reduced to C 4v for arbitrary k z -values of the Bloch functions of the first Brillouin zone. From the irreducible representations a 1 , a 2 , b 1 , b 2 , and e only a 1 and e have contributions from all components, namely TAP 2⊖ , Fe 2⊕ and C 2 2⊖ , so that for these races broad energy bands can be expected. The a 2 , b 1 , and b2 MOs of the TAP-Fe II subunits are separated fairly well and have no counterparts in the C 2 2⊖ bridges so that very narrow bands should arise. This is confirmed by an EH calculation. Unexpectedly the a 1 bonds which have contributions from the σ-MOS of C 2 2⊖ are broader than the e-bands which contain the two crossed π-MO systems of C 2 2⊖ . The quantitative results of the nearly self-consistent iterative EH calculation indicate overlap of the energy bands near the Fermi level and fulfill thus one necessary condition for metal-like electrical conductivity.

Pair and triplet distribution functions of the NaCl-type lattice and MD-simulated molten KCl are compared. Some similarities in the arrangement of the nearest neighbours are observed.

The magnetic behaviour of the normal-temperature-form of CsTmO 2 (NT-CsTmO 2 ) has been studied in the temperature range between 2.9 and 251.3 K. In order to interpret the magnetic data a method applying the angular overlap model has been established to assess the crystal-field (CF) parameters of NT-CsTmO 2 (CF symmetry: D 3d ) from the known CF parameters for Tm 3+ substituted in YVO 4 (CF symmetry: D 2d )-With these CF parameters the observed magnetic properties of NT-CsTmO 2 can be satisfactorily simulated. The calculation of the paramagnetic principal susceptibilities yields a high magnetic anisotropy, especially at low temperatures. The energy values of the CF levels of the 3 H 6 ground state are calculated.

The interaction of the quinoline derivatives with CoQ 10 is studied both experimentally, using Polarographie and spectrophotometric techniques, and theoretically, applying the perturbation molecular orbital theory. The E 1/2 potentials of a series of 1:1 solution mixtures of quinoline derivatives with CoQ 10 are measured and compared with E 1/2 of the coenzyme alone (0.52 V). An increase in the E 1/2 -magnitude of the coenzyme is detected (⊿E 1/2 ≈ 0.03-0.13 V). Simple perturbation molecular orbital treatment shows an increase in the energy of the lowest unoccuppied molecular orbital of the coenzyme due to the same interaction, in agreement with the Polarographie results. The complexation constants of the same quinoline derivatives, as well as the antimalarials quinine, primaquine and chloroquine, with CoQ 10 are determined spectrophotometrically and found to be in the order of 10 5 . The K value for each complex is determined at 10 different wavelengths and 7 different constituent concentrations of the solution. The complexation enthalpies are all small and positive (0.98-4.53 kcal/mol), the entropies are big and positive (29-41 cal/deg.mol). The big entropy change suggests an increase in the internal motion of the complexing molecules. It is suggested that the increase in the internal motion is due to the increase in the motion of the isoprenoid side chain of the coenzyme.

The positive column of the hollow cathode arc consists of a highly ionized ( > 90%) and -magnetized (ω ei τ i,i > 1) plasma. In order to obtain as much as possible information about this plasma its parameters were measured as functions of radius, r, and axial distance, z. They were varied by changing the discharge parameters - arc current I , gas feed Q, magnetic field strength B, arc length L and core diameter d. Generally the discharge was fed with Argon, but Neon, Helium, Nitrogen and Hydrogen were also used. - The radial plasma density distribution, n e (r), is approximately Gaussian for 0 ≦ r < 4 cm (n e (0)≅ 2 X 10 14 part./cm 3 ); in axial direction the plasma density does not vary much. -The ion temperature, T i , is constant with radius, contrary to the electron temperature, T e , which drops sharply near the core of the arc. In axial direction T i drops by a factor ten from the cathode to the anode (T i ≅ 1- 30 eV). T i (z = 0) increases with arc length L. - The whole plasma moves in axial direction from the cathode towards the anode ( υ z ≅ 6 X 10 4 cm/s); the angular mass velocity (Ω ≅ some 10 5 rad/s) is strongly sheared and decreases with temperature. - The axial electrical field is small (0.1 to 0.2 V/cm) corresponding to a normal electrical conductivity. The radial electrical field points inwardly and varies strongly with radius (0 ≧ E r ≳ - 10 V/cm). - Strong (nonlinear) low frequency oscillations (υ ≅ 15 kHz) are generated spontaneously in the plasma; these oscillations are due to the Kelvin-Helmholtz instability. As is shown in Part II of this investigation, the observed behaviour of the plasma column may be satisfactorily explained by the two fluid model with MHD ordering. Due to viscous effects (i, i collisions) the sheared plasma rotation has big consequences for the transport of particles and energy.

It is shown that the behaviour of the highly ionized and magnetized plasma in the positive column of the hollow cathode arc (described in Part I of this investigation) may be well explained with the macroscopic equations on basis of the MHD ordering (eE r ⪢ ⊿p/n e ). In particular the rotation of the plasma column around its axis is properly described by an equation for the electrical potential. Viscous effects (due to ion-ion collisions) play an important role in the transport of particles, momentum and energy. The strong shear in the plasma rotation goes along with an inwardly directed ion flux, oppositely to the "classical" outward ion flux (due to ion-electron collisions), thus leading to an improved confinement of the ions. As the electron viscosity is negligible, the electrons move outward with the "classical" velocity. The resulting non-ambipolar plasma transport leads to an inwardly directed current and the corresponding j X B force drives the plasma rotation against the friction of the ions (ion-ion and ion-neutral collisions). The stationary power balance is well fulfilled by the ions, and within a factor two also by the electrons. Most of the power is handled by the electrons.

The nuclear magnetic resonance of 67 Zn in hexagonal close-packed Zn metal has been observed at 4.2 K by pulsed NMR with three different frequencies. The spin echo profile showed a well resolved powder pattern due to electric quadrupole interaction. The quadrupole coupling constant was determined to be e 2 q Q/h = 12.0 (4) MHz. The spin-spin and spin-lattice-relaxation times were measured to be T 2 = 58 ± 2 ms and T 1 = 0.45 ± 0.2 s, respectively. The isotropic Knight shift is found to have the value K iso = 0.1 ± 0.05%.

From selective reflection (SR) measurements as a function of temperature it has been shown that cholesteryl myristate exhibits two "blue phases" (BP) between the isotropic and the cholesteric state. The SR of the two BP shows the same angular dependence as found in the cor-responding cholesteric state. From our results a model of the BP is proposed with the molecular axes inclined to the helix axis by a critical angle of 54.74° explaining the absence of birefringence as well as the cholesteric-like optical properties.

Extrapolation of the experimentally determined energies of the longest wavelength transition in the polymethinestreptocyanine series yields a value of 1.0 eV for the energy gap.