Z. A. Schelly

Explodator: A new skeleton mechanism for the halate driven chemical oscillators

In the first part of this work, some shortcomings in the present theories of the Belousov–Zhabotinskii oscillating reaction are discussed. In the second part, a new oscillatory scheme, the limited Explodator, is proposed as an alternative skeleton mechanism. This model contains an always unstable three‐variable Lotka–Volterra core (the ‘‘Explodator’’) and a stabilizing limiting reaction. The new scheme exhibits Hopf bifurcation and limit cycle oscillations. Finally, some possibilities and problems of a generalization are mentioned.

Solvent-jump relaxation kinetics of the association of rhodamine type laser dyes

Equilibrium spectral photometric and solvent-jump relaxation kinetic results of the monomer (M) — dimer (D) equilibrium

Electric field-induced transient birefringence and light scattering of synthetic liposomes

2M{H^{ + }}\underset{{{0^{{{K_{{ - 1}}}}}}}}{\overset{{{0^{{{K_1}}}}}}{\rightleftharpoons}} {D^{{ + + }}}

Structures of Silver Pyrazolates in Hydrocarbon Solutions via Vapor-Pressure Osmometry

(1) of aqueous and ethanolic rhodamine B, rhodamine 3B, rhodamine 6G, and rhodamine 110 (Fig. l) have been obtained, which indicate that, contrary to previous suggestions, association occurs in both solvents with the exception of rhodamine 3B and 6G in ethanol.

Cavitation as Artifact in Stopped Flow Experiments

Abstract The effects of surface tension and temperature on the nonlinear dynamics of the dripping faucet were investigated, through the introduction of high-resolution timing, temperature and continuously variable flow rate controls, and the addition of surfactant of the water. The continuously variable flow rate allows the recording of the novel “dripping spectrum” (drop intervals { t i } versus flow rate) over a wide range of flow rate in a single experiment. Lowering the surface tension dramatically changes the dynamics, sharpens the familiar dripping patterns previously found for water, and reveals the existence of novel single and multiple closed-loop patterns. Using dripping spectra, time-delay and time-series representations, the closed-loop patterns are shown to correspond to quasiperiodic states. Lowering the temperature reduces random noise and shifts the occurrence of characteristic patterns to higher flow rates.

Dynamics in water-in-oil microemulsions

The dynamics of electric field-induced transient birefringence Deltan(t) and light scattering (detected as turbidity) of 190 nm diameter unilamellar vesicles of dioleoylphosphatidylcholine are investigated as a function of applied field strength E, length of the square pulse Deltat, lipid concentration, mean hydrodynamic diameter , ionic strength, and temperature. Generally, induced birefringence exclusively is observed at low lipid concentration and below certain threshold values of E and Deltat, whereas concomitant induced turbidity appears at high lipid concentration and above thresholds values of E and Deltat. Turbidity is monitored through the change in transmitted intensity DeltaS parallel(t) and DeltaS perpendicular(t) of light polarized parallel and perpendicular to the applied field E. The field-induced structural changes are reflected in double-exponential forward relaxation and triple-exponential reverse relaxation of the positive birefringence, and in non-exponential relaxations of DeltaS parallel (t) and DeltaS perpendicular(t). Under the field, the associated physical events are interpreted as elongation of the spherical bilayer shells in the direction of E, linear chain formation (pearling) of the induced dipolar liposomes parallel to E, and partial fusion of adjoining vesicles within the chains. Under conditions where electroporation can be detected, pore opening succeeds the elongation of the vesicles. After termination of the field, the vesicles return to their original time average spherical shape, the oriented chains randomize and disintegrate, and the fused structures are converted either to unilamellar or multilamellar vesicles.

Synthesis and bandgap variation of molecular-size CdSe clusters via electroporation of vesicles

Abstract Dry reverse micellar systems are hygroscopic and the water-rich ones exhibit a water vapor pressure pw which can approach that of pure water. For these properties, conventional vapor pressure osmometry (VPO) cannot be used for the determination of the true mean aggregation number n of the surfactant because weate ris absorbed or lost by the sample in the osmometer chamber, with the concomitant changes of n during the measurement. The problem can be remedied by matching the water partical pressure pw,c in the osmometer chamber to the water vapor pressure pw of the sample. A new method that utilizes this the osmometer chamber to the water vapor pressure pw of the sample. A new method that utilizes this principle, controlled partial pressure—vapor pressure osmometry (CPP—VPO), is described and its use is demonstrated on the AOT/benzene/H2O system. CPP—VPO is ideally suited for the determination of n and pw of reverse micelles and W O microemulsions.

Electric birefringence of surfactant vesicles

Molecular weights of {[3,5-(CF 3) 2Pz]Ag} 3, {[3-(C 3F 7),5-( t-Bu)Pz]Ag} 3, and {[3,5-( i-Pr) 2Pz]Ag} 3 at various solution concentrations have been investigated using vapor-pressure osmometry. Depending on the concentration, the trinuclear {[3,5-(CF 3) 2Pz]Ag} 3 either dissociates into mono- and dinuclear moieties or remains trinuclear or aggregates to hexanuclear species in toluene. In contrast, {[3-(C 3F 7),5-( t-Bu)Pz]Ag} 3, which has a bulky and relatively electron-rich pyrazolate, retains the trinuclear form even at low concentrations in toluene. Both {[3,5-(CF 3) 2Pz]Ag} 3 and {[3,5-( i-Pr) 2Pz]Ag} 3 adopt trinuclear structures in heptane at low concentrations. At higher concentrations, {[3,5-( i-Pr) 2Pz]Ag} 3 forms hexanuclear species. The aggregation-segregation points are rather sharp and are reminiscent of the all-or-none character of phase transitions. Remarkably, at higher concentrations, the aggregation states of these silver pyrazolates are similar to those expected based on solid-state data.