Restoration of universality for the rod-to-coil transition scaling in the infinite-dimensionality limit: Exact results for directed walks

We derive scaling forms for the thermodynamic and correlation quantities for the turn-weighted fully and partially directed self-avoiding walks on the hypercubic lattices ind2. In the grand canonical (fixed fugacity per step) ensemble, the conformational rod-to-coil transition sets up in the regimew¯N=O(1), wherew is the weight of each 90° turn and¯N is the (fugacity-dependent) average number of steps. Contrary to the conventional critical phenomena wisdom, the scaling functions for the two different walk models, directed and partially directed, become universal only in the limitd.     

Unified quantum logic

Unified quantum logic based on unified operations of implication is formulated as an axiomatic calculus. Soundness and completeness are demonstrated using standard algebraic techniques. An embedding of quantum logic into a new modal system is carried out and discussed.On leave of absence from Department of Mathematics, University of Zagreb, Pot. Pret. 165, YU-41001 Zagreb, Yugoslavia.     

Electrocatalysis by foreign metal monolayers: Oxidation of formic acid on platinum

It was demonstrated that some foreign metal monolayers formed by underpotential deposition have pronounced catalytic effects on the oxidation of formic acid on platinum. The explanation of these effects was sought within the framewor of existing data on the formic acid oxidation and the underpotential deposition. It was found that the catalytic effect of foreign metal monolayers originates in the decrease of hydrogen adsorption thus preventing the formation of the main poisoning species COH. At the same time these experiments confirm the previously postulated mechanism of formation of the poisoning species involving adsorbed hydrogen.     

On the properties of surfactant aqueous solutions

Summary From studies of aqueous solutions of dodecylammoniumnitrate an association mechanism has been proposed involving multiequilibrium. In the concentration range considered we can differentiate between two aspects: ranges of marked qualitative and quantitative changes and formation of differently structured surfactant species.

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Zusammenfassung Aus der Untersuchung wäßriger Lösungen von Dodecylammoniumnitrat würde ein Assoziationsmechanismus abgeleitet, welcher ein Multiequilibrium beinhaltet. Im untersuchten Konzentrationsbereich können zwei Bereiche unterschieden werden: Bereiche mit ausgeprägten qualitativen und quantitativen Änderungen und Bereiche mit der Bildung von verschieden strukturierten oberflächenaktiven Spezies.

     

Viskosimetrische Untersuchung des Systems LiNO3−H2O

Zusammenfassung Die Temperaturabhängigkeit der Viskosität im System LiNO₃–H₂O und im Temperaturbereich 20–70°C wird in der Gleichung =A expB/T=T ₀ zusammengefaßt; aus der so erhaltenen Beziehung werden Rückschlüsse auf die Struktur der Lösungen gezogen.

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Temperature dependence of the viscosity in the system LiNO₃–H₂O is expressed by =A expB/T-T ₀ in the temperature range 20–70°C. Possible relations to structural changes in the solutions are considered.

     

Global Forcing Number of Benzenoid Graphs

A global forcing set in a simple connected graph G with a perfect matching is any subset S of E(G) such that the restriction of the characteristic function of perfect matchings of G on S is an injection. The number of edges in a global forcing set of the smallest cardinality is called the global forcing number of G. In this paper we prove several results concerning global forcing sets and numbers of benzenoid graphs. In particular, we prove that all catacondensed benzenoids and catafused coronoids with n hexagons have the global forcing number equal to n, and that for pericondensed benzenoids the global forcing number is always strictly smaller than the number of hexagons.     

Development and prevalidation of a method for phenol determination by solid-phase spectrophotometry

A simple, sensitive and rapid solid-phase spectrophotometric procedure was developed for the determination of traces of phenol with 4-aminoantipyrine as a reagent (AAP-SPS), and the optimal experimental conditions were established. This method was performed by sorption and direct absorbance measurements of the product phenol-AAP sorbed on the anion-exchanger Dowex 1-X4 (0.2 g) at 495 nm (absorption maximum) and 700 nm (non-absorption wavelength). The sensitivity offered by the AAP-SPS procedure was higher by a factor of 40 compared with the respective conventional spectrophotometric method. Metrological characteristics were established using a prevalidation strategy. The AAP-SPS procedure is characterized by a linear calibration function in the working range of 0.05–0.50 μmol, low standard deviation of procedure (±0.012), low limit of determination (0.021 μmol), and favorable random (±0.85 to ±11.27%) and systematic deviations (−4.55 to +11.50%). Moreover, the accuracy of the system investigated by the recovery test is acceptable (99–102%). Favorable working and performance characteristics make the new SPS method ideal for phenol monitoring in pharmaceutical preparations as well as other matrices.     

Cyclic chronopotentiometry of nickel(II) at mercury electrodes in acidic perchlorate solutions: Case of higher order nonregenerative reactions following electron transfer

The reduction of Ni²⁺ ions at mercury electrodes in acidic perchlorate solutions, at perchlorate concentrations below 0.2 M, is characterized by absence of kinetic control in the preceding step, and by a complex reaction mechanism following the electron transfer. This reaction sequence is known to involve intermetallic compound formation between Ni and Hg and is best described, as shown here, by a parallel second and third order kinetic scheme. Apparent rate coefficients for this kinetic scheme were determined using cyclic chronopotentiometric data and fitting by digital simulation. A linearization test of computed kinetic rate coefficients versus the number of transitions permits quantitative tests of validity of assumptions made.     

Mössbauer spectroscopic and X-ray diffraction study of the thermal decomposition of natural siderite and goethite

Thermal decomposition of natural siderite and goethite has been studied using Mössbauer spectroscopy and X-ray diffraction. Hematite and magnetite were the principal compounds formed during high temperature treatment of siderite. Natural goethite transformed to hematite at high temperatures. The crystal structures, stoichiometry and the nuclear magnetic properties of Fe-oxides formed are discussed.     

Comparative thermal analysis of commercial and low-grade bauxites

This paper presents qualitative and quantitative comparative results on the simultaneous TG-DTG DTA of five commercial and low-grade bauxites. The methodology of qualitative determination of the basic mineral forms contained in bauxites is currently being established. The weight losses relating to the steps in the TG curve allow determination of the contents of the basic minerals in bauxite. These are recalculated as percentages of Al₂O₃, SiO₂, CaO moisture and total volatiles. The final results are in accordance with the results of classical chemical analyses, and this jusitifies the use of this technique as a quick method for qualitative and quantitative determinations of both commercial and low-grade bauxites.

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Zusammenfassung Qualitative und quantitative Ergebnisse vergleichender simultaner TG-DTG-DTA-Untersuchungen an 5 kommerziellen und geringwertigen Bauxiten werden vorgestellt. Die Methodologie der qualitativen Bestimmung der wichtigsten im Bauxit enthaltenen Minerale wird ausgearbeitet. Die Gewichtsverluste bei den entsprechenden TG-Stufen erlauben die Berechnung der Gehalte an den wichtigsten Mineralen. Diese werden umgerechnet in die Anteile an Al₂O₃, SiO⁰², CaO, Feuchtigkeit und Glühverlust. Letztere Resultate stimmen mit denen klassisch-chemischer Analyse überein. Das erlaubt die Anwendung thermoanalytischer Methoden als Schnellverfahren für qualitative und quantitative Bestimmungen in kommerziellen und geringwertigen Bauxiten.

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