2,5-Dihydroxyacetophenone oxime as an analytical reagent for the amperometric determination of copper,palladium, and nickel

Summary Copper, palladium and nickel can be titrated amperometrically with 2,5-dihydroxyacetophenone oxime at –0.15, –0.4 and, –1.2 V vs. S. C. E. respectively, the optimum p_H values being 4.6, 4.0, and 9.0. Alkali and alkaline earth metals, Al, Bi, Cd, Co, Cr. Fe(II), Hg, Mn, Ni, Pb, Th, Zn, UO, W, and Zr do not interfere with the estimation of copper and palladium. The interferences due to the presence of silver and iron(III) can be eliminated by adding excess of KCl and KF respectively. Most heavy metals interfere with the estimation of nickel and should be eliminated before titration.

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Zusammenfassung Kupfer, Palladium und Nickel können mit 2,5-Dihydroxyaeetophenonoxim bei –0,15, –0,4 bzw. –1,2 V gegen eine gesättigte Kalomelelektrode amperometrisch titriert werden, wobei man das p_H am besten auf 4,6, 4,0 bzw. 9,0 hält. Alkalimetalle, Erdalkalien, Al, Bi, Cd, Co, Cr, Fe(II), Hg, Mn, Ni, Pb, Th, Zn, UO₂, W und Zr stören die Bestimmung des Kupfers und des Palladiums. Silber und Eisen können mit Kaliumchlorid gefällt bzw. mit Kaliumfluorid maskiert werden. Die meisten Schwermetalle stören die Nickelbestimmung und müssen daher vor der Titration entfernt werden.

     

The order parameter model for structural relaxation in glass

The order parameter model assumes that the state of a glass or liquid depends on T, P and a number of order parameters Z_i. Structural relaxation is due to the kinetically impeded evolution of the order parameters following a rapid change in T or P. The linear relaxation function for the evolution of property Q (V or H) in response to a change in X (T or P) is of the form φ_QX = Σ_igⁱ_QX exp(?tτ_i). Expressions are derived for the qeighting coefficients gⁱ_QX in terms of the dependences of V and H on the various order parameters. It is shown that gⁱ_VT = gⁱ_HP and that gⁱ_VTgⁱ_HP/gⁱ_VPgⁱ_HT = II, where II is the Prigogine-Defay ratio. The corresponding relations among the relaxation functions are φ_VT = φ_HP and φ_VTφ_HP/φ_VPφ_HT ? II. The predictions of the order parameter model for structural relaxation are compared with and found generally to agree with existing literature data. A number of suggestions for future investigations to test this model are made.     

A variational principle for fully developed laminar heat transfer in uniform channels I

Summary A variational principle for forced convection in laminar flow in uniform channels is formulated. The concepts of thermal potential, dissipation function and thermal force have been introduced and a Lagrangian formulation of the thermal flow field using generalized coordinates is given. Special consideration is given to heat transfer in plug flow when the thermal field is a linear function of the generalized coordinates. The concept of normal and ignorable coordinates is introduced. An example showing the use of Lagrangian equations is worked out.     

Development,In-Vitro Characterization and Preclinical Evaluation of Esomeprazole-Encapsulated Proniosomal Formulation for the Enhancement of Anti-Ulcer Activity

Objective: The present study aimed to develop and optimize esomeprazole loaded proniosomes (EZL-PNs) to improve bioavailability and therapeutic efficacy. Method: EZL-PNs formulation was developed by slurry method and optimized by 33 box-Bhekhen statistical design software. Span 60 (surfactant), cholesterol, EZL concentration were taken as independent variables and their effects were evaluated on vesicle size (nm), entrapment efficiency (%, EE) and drug release (%, DR). Furthermore, optimized EZL-PNs (EZL-PNs-opt) formulation was evaluated for ex vivo permeation, pharmacokinetic and ulcer protection activity. Result: The EZL-PNs-opt formulation showed 616 ± 13.21 nm of vesicle size, and 81.21 ± 2.35% of EE. EZL-PNs-opt exhibited negative zeta potential and spherical confirmed scanning electron microscopy. EZL-PNs-opt showed sustained release of EZL (95.07 ± 2.10% in 12 h) than pure EZL dispersion. The ex-vivo gut permeation result exhibited a significantly (p < 0.05) enhanced flux than pure EZL. The in vivo results revealed 4.02-fold enhancement in bioavailability and 61.65% protection in ulcer than pure EZL dispersion (43.82%). Conclusion: Our findings revealed that EZL-PNs formulation could be an alternative delivery system of EZL to enhance oral bioavailability and antiulcer activity.     

A production system with two job classes,changeover times and revisitation

This paper, motivated by the need to predict performance of production systems with random arrivals, setup times and revisitation, presents an imbedded Markov chain analysis of the underlyingM/G/1 queue with two customer classes, changeover times and instantaneous Bernoulli feedback. It is assumed that jobs are scheduled according to the exhaustive alternative priority queue discipline. Expressions for the mean waiting time and the nonsaturation condition are derived under two different priority assignments to the repeat customers. Sojourn times under these priority assignments are shown to possess a convex ordering. Results of the study are also applicable to data communication networks that operate under cyclic switching mechanisms. Research supported in part by Natural Sciences and Engineering Research Council of Canada.     

An Incremental Algorithm for the Maximum Flow Problem

An incremental algorithm may yield an enormous computational time saving to solve a network flow problem. It updates the solution to an instance of a problem for a unit change in the input. In this paper we have proposed an efficient incremental implementation of maximum flow problem after inserting an edge in the network G. The algorithm has the time complexity of O((n)² m), where n is the number of affected vertices and m is the number of edges in the network. We have also discussed the incremental algorithm for deletion of an edge in the network G.     

Representing the mean residual life in terms of the failure rate

In survival or reliability studies, the mean residual life or life expectancy is an important characteristic of the model. Whereas the failure rate can be expressed quite simply in terms of the mean residual life and its derivative, the inverse problem—namely that of expressing the mean residual life in terms of the failure rate—typically involves an integral of a complicated expression. In this paper, we obtain simple expressions for the mean residual life in terms of the failure rate for certain classes of distributions which subsume many of the standard cases. Several results in the literature can be obtained using our approach. Additionally, we develop an expansion for the mean residual life in terms of Gaussian probability functions for a broad class of ultimately increasing failure rate distributions. Some examples are provided to illustrate the procedure.     

Analysis of anharmonic and thermoelastic properties of non-centrosymmetric crystals

In the present paper an analytical potential form is used for overlap repulsive energy, derived by Harrison from quantum mechanical considerations, along with the composite effect of three-body forces and intersublattice displacement. The short-range overlap parameters in Harrison's potential form have direct correlation with the valence state energies for outermost electrons. The potential model is applied to calculate the third and fourth order elastic constants, first and second pressure derivatives of second order elastic constants, Grüneisen parameter and its volume dependence, Anderson parameter, and thermal expansion coefficient for three non-centrosymmetric crystals, viz. CaF₂, SrF₂ and BaF₂. The calculated values of various physical quantities are found to be in good agreement with experimental data.The authors are grateful to Dr. Mansour Khalef, the Head of Physics Department, TNRC, Tajura (Tripoli) for the facilities and encouragements.