A simple method for the optimization of the decay time in pulse polarography

1988 ◽  
Vol 53 (6) ◽  
pp. 1149-1155
Author(s):  
Jorge A. Bolzan
Keyword(s):  
Double Layer ◽  
Decay Time ◽  
Sampling Time ◽  
Simple Method ◽  
Faradaic Current ◽  
Maximum Value ◽  
Pulse Polarography ◽  
Null Value ◽  
Polarographic Current

A simple method for optimization of the minimum decay time, previous to the sampling time of the polarographic current, is described. The former should make compatible two requisites: it should be short enough for obtaining the maximum value of the faradaic current and long enough for the minimum or null value of the double layer decay current. The method is performed with the pulse polarograph only, without ancillary instruments, is fast and its accuracy is fairly comparable with earlier methods, which were more accurate but by far more involved to perform.

Evaluation of polydispersity index Mw/Mn by quasielastic light scattering

1987 ◽  
Vol 52 (5) ◽  
pp. 1235-1245 ◽  
Author(s):  
Petr Štěpánek ◽  
Zdeněk Tuzar ◽  
Čestmír Koňák
Keyword(s):  
Molecular Weight ◽  
Light Scattering ◽  
Decay Time ◽  
Sampling Time ◽  
Polydispersity Index ◽  
New Method ◽  
Molecular Weights ◽  
Quasielastic Light Scattering ◽  
Good Agreement

The response of quasielastic light scattering to the polydispersity of scattering objects has been investigated. A new method of the polydispersity index determination has been suggested, suitable for the range 1.02 ⪬ Mw/Mn ⪬ 2.0 and consisting in the measurement of the dependence of the apparent decay time on the correlator sampling time. The polydispersity index can be determined by comparing these dependences with the theoretical ones obtained using correlation curves simulated for various values of the polydispersity index, assuming lognormal and Schulz-Zimm distributions of molecular weights. The test measurements on polystyrene standards having molecular weights in the range 9 103 – 20.6 106 give polydispersity index values Mw/Mn that are in a good agreement with those given by the manufacturer. The polydispersity index for polystyrene having the molecular weight Mw = 20.6 106 thus determined was Mw/Mn = 1.35.

PRESTRESSING TENSEGRITY SYSTEMS — APPLICATION TO MULTIPLE SELFSTRESS STATE STRUCTURES

2004 ◽  
Vol 04 (04) ◽  
pp. 543-557 ◽  
Author(s):  
J. AVERSENG ◽  
B. CROSNIER
Keyword(s):  
Double Layer ◽  
Correct Order ◽  
Simple Method ◽  
Stress Control ◽  
Normal Forces ◽  
Tensegrity Systems ◽  
Stress Levels ◽  
Tension And Compression ◽  
Implementation Stage ◽  
Prestressed Structures

Stress control is a major issue in the development of prestressed structures like the tensegrity systems that gain from it equilibrium and stability. In this paper, we present a simple method for adjusting the whole set of normal forces in this kind of structure, based on a combination of influences determined from the unit variations of rest lengths for a reduced set of active cables. According to an elementary criterion, tension and compression forces are kept in a reduced domain during the implementation stage in order to avoid unwanted transitory stress levels. The process is then simulated to retrieve the modifications for actual lengths that are to be implemented in the correct order. Finally, we describe the application of this method on a 1:1 scale double layer tensegrity grid.

THE DISCRETENESS-OF-CHARGE EFFECT IN ELECTRIC DOUBLE LAYER THEORY

1962 ◽  
Vol 40 (3) ◽  
pp. 518-538 ◽  
Author(s):  
S. Levine ◽  
G. M. Bell ◽  
D. Calvert
Keyword(s):  
Adsorption Isotherm ◽  
Double Layer ◽  
Electric Double Layer ◽  
Surface Density ◽  
Aqueous Electrolyte ◽  
Solution Phase ◽  
Charge Effect ◽  
Adsorption Potential ◽  
Simple Method ◽  
Ion Size

The Stern–Grahame–Devanathan theory of the electrical double layer in aqueous systems is modified to include the so-called discreteness-of-charge effect of Esin and Shikov and Ershler. This provides an explanation of a number of phenomena which are at variance with the Stern theory. A simple method of incorporating the above effect into the Stern theory is suggested by the work of Grahame and is equivalent in principle to the discrete-ion approximation employed by the Russian authors. It is shown that the effect can be interpreted in terms of a 'self-atmosphere' potential at the counterions adsorbed in the Stern layer. This provides a new term in the energy of an adsorbed ion, which is very nearly proportional to the surface density of these ions and which had hitherto been included in the specific adsorption potential in the Stern adsorption isotherm. This energy is not small and accounts for the conclusion reached by Grahame that the adsorption potential varies strongly with the surface charge. Grahame found that the potential at the plane separating the compact and diffuse parts of the double layer in the solution phase (i.e. the outer Helmholtz plane) at the mercury –aqueous electrolyte interface displays a maximum as the potential across the interface is varied, and this property is reproduced by the theory. The effect of ion size on the adsorption isotherm is also considered.

Faradaic Admittance and Migration in the Diffuse Double-Layer: Effect on the Phase Angle

1963 ◽  
Vol 16 (4) ◽  
pp. 565 ◽  
Author(s):  
K Narayanan ◽  
SK Rangarajan
Keyword(s):  
Double Layer ◽  
Phase Angle ◽  
Theoretical Studies ◽  
Diffuse Double Layer ◽  
Faradaic Current ◽  
Layer Effect ◽  
And Migration ◽  
Modified Equation

The effect of migration in the diffuse double-layer on the phase angle between the alternating components of the faradaic current and voltage is discussed. It is shown that the cot � v. √ω relationship is nonlinear and the modified equation for this case (i.e. when migration is taken into account) is given. Equations derived already by Matsuda are discussed. Theoretical studies on the variation of ((Io)app/(Io)ms with Gouy potential are also reported.

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