Untersuchung der Zustandsdiagramme der Systeme Ag2Se0,5Te0,5?Ag2S und Ag2S0,5Te0,5 −Ag2Se

Investigation of the State Diagrams of the Systems Ag₂Se_0.5Te_0.5? Ag₂S and Ag₂S_0.5Te_0.5? Ag₂Se The Systems Ag₂Se_0.5Te_0.5? Ag₂S and Ag₂S_0.5Te_0.5? Ag₂Se were investigated by the methods of DTA, X-ray and microstructure analysis and measuring of the conductivity. It was found, that the systems are polythermic sections of the ternary diagram Ag₂Te? Ag₂Se? Ag₂S. In all regions from 0 till 100 Mol.-% Ag₂S, resp. Ag₂Se, except the phases with composition Ag₂Se_0.5Te_0.5 and Ag₂S_0.5Te_0.5 mixed crystals are formed. The structure of the observed interphases was not investigated. The state diagrams of the systems Ag₂Se_0.5Te_0.5 ?Ag₂S and Ag₂S_0.5Te_0.5? Ag₂Se are characterized with peritectical destruction at 140°C for the first and eutectical destructions at 70°C for both systems. In the systems Ag₂Se_0.5Te_0.5? Ag₂S a peritectical reaction at 780°C is observed.     

Preparation and physicochemical characterization of novel chlorambucil-loaded nanoparticles of poly(butylcyanoacrylate)

The aim of the present study is the preparation and physicochemical characterization of chlorambucil-loaded poly(butylcyanoacrylate) nanoparticles. Chlorambucil is a lipophilic drug, which is used clinically against chronic lymphocytic leukemia, lymphomas, and other types of malignant diseases. However, the chlorambucil use is limited by its chemical instability and toxic side effects. A promising approach to circumvent these drawbacks is the entrapment of chlorambucil in a suitable nanosized carrier. Toward this goal, poly(butylcyanoacrylate) nanoparticles meet the requirements for a drug carrier system due to their biocompatibility, biodegradability, low toxicity, and ability to overcome the multidrug resistance in cancer cells. We prepared chlorambucil-loaded poly(butylcyanoacrylate) nanoparticles, which are characterized for chemical composition, particle size, drug content, and drug release. It is expected that the utilization of poly(butylcyanoacrylate) nanoparticles as a drug carrier system will pave the way toward more effective use of chlorambucil in the treatment of cancer.     

Untersuchung des Systems Silbertellurid—Silbersulfid

The system Ag₂Te–Ag₂S has been investigated by differentialthermal, X-ray phase and micro-structural analysis within the concentration range from 0 to 100 mole% silver telluride. Equilibrium samples obtained by tempering for 1000 hours at 120°C were used. The system Ag₂Te–Ag₂S represents a solid solution with a minimum, with complicated solid phase interactions at temperatures under the solidus line.

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Electrochemical characterization and analytical application of arsenopyrite mineral in non-aqueous solutions by voltammetry and potentiometry

Based on the cyclic voltammetric method, in the present study we have employed carbon paste for arsenopyrite mineral characterization in non-aqueous solution. Arsenopyrite yields well-defined cyclic voltammetric responses with well-defined oxidation (in the potential region from −0.7 to 0.7 V, versus Ag/AgCl) and reduction (from −1.0 to 0.8 V) peaks using this electrode. In addition, arsenopyrite mineral was studied as a new indicator electrode for the potentiometric titrations of acids (benzoic, anthranilic and salicylic acids) and bases (N,N′-diphenylguanidine, tributylamine and collidine) in acetonitrile and propionitrile. Potassium hydroxide, tetrabutylammonium hydroxide (TBAH) and perchloric acid proved to be very suitable titrating agents for these titrations.The investigated electrode showed a linear dynamic response for p-toluenesulfonic acid concentrations in the range 0.1-0.001 M, with a Nernstian slope of 38.5 mV in acetonitrile and 44.6 mV in propionitrile. The electrode showed a relatively fast response time and can be used without any time limit or without considerable divergence in potentials. The response time of the electrode was less than 10 s in both solvents. The standard deviation of the determination of the investigated acids and bases was less than 0.6% from those obtained with a glass electrode.The advantages of the electrodes are long-term stability, fast response and reproducibility, while the sensors are easy to prepare and are of low cost.     

Potentiometric determination of ascorbic acid in water–acetonitrile solution using pyrite and chalcopyrite electrodes

Journal of Solid State Electrochemistry - Performance characteristics of the solid-state potentiometric sensors, based on natural sulfide minerals pyrite and chalcopyrite, are assayed in aqueous...     

Über Herstellung und Thermostabilität der Chalkogenate von Antimon und Wismut, 4. Mitt.: Herstellung und Untersuchung der Thermostabilität von Wismutselenat

A method of obtaining bismuth(III) selenate Bi₂(SeO₄)₃ will be described. The thermal dissociation in air was studied by means of thermal, thermogravimetric, X-ray and chemical analysis. The probable scheme of the thermal dissociation of the compound will be discussed.

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DOIT: a program to calculate thermal rate constants and mode‐specific tunneling splittings directly from quantum‐chemical calculations

In this contribution we discuss computational aspects of a recently introduced method for the calculation of proton tunneling rate constants, and tunneling splittings, which has been applied to molecules and complexes, and should apply equally well to bulk materials. The method is based on instanton theory, adapted so as to permit a direct link to the output of quantum‐chemical codes. It is implemented in the DOIT (dynamics of instanton tunneling) code, which calculates temperature‐dependent tunneling rate constants and mode‐specific tunneling splittings. As input, it uses the structure, energy, and vibrational force field of the stationary configurations along the reaction coordinate, computed by conventional quantum‐chemical programs. The method avoids the difficult problem of calculating the exact least‐action trajectory, known as the instanton path, and instead focusses on the corresponding instanton action, because it governs the dynamic properties. To approximate this action for a multidimensional system, the program starts from the one‐dimensional instanton action along the reaction coordinate, which can be obtained without difficulty. It then applies correction terms for the coupling to the other vibrational degrees of freedom, which are treated as harmonic oscillators (transverse normal modes). The couplings are assumed linear in these modes. Depending on the frequency and the character of the transverse modes, they may either decrease or increase the action, i.e., help or hinder the transfer. A number of tests have shown that the program is at least as accurate as alternative programs based on transition‐state theory with tunneling corrections, and is also much less demanding in computer time, thus allowing application to much larger systems. An outline of the instanton formalism is presented, some new developments are introduced, and special attention is paid to the connection with quantum‐chemical codes. Possible sources of error are investigated. To show the program in action, calculations are presented of tunneling rates and splittings associated with triple proton transfer in the chiral water trimer. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 787–801, 2001     

Poly(ethyl cyanoacrylate) colloidal particles tagged with Rhodamine 6G: preparation and physicochemical characterization

This paper describes the preparation and characterization of poly(ethyl cyanoacrylate) colloidal particles loaded with the organic fluorophore Rhodamine 6G. We studied the physicochemical properties of the colloidal particles: morphology, size-distribution, ζ-potential, fluorescent properties and photobleaching upon UV-light illumination. The properties of the obtained colloidal particles, as well as the dye loading efficiency, were found to depend on the concentrations of ethyl cyanoacrylate monomer and Rhodamine 6G in the polymerization medium. The fluorophore release from the colloidal particles in aqueous buffer is also studied.