A system model for the utilization of mineral resources

A multiobjective dynamic optimization model is described for the optimal utilization of mineral resources. The special forms of the objective functions, state-transition relations, and additional constraints satisfy the conditions for using a special dynamic multiobjective programming method. A case study is also outlined.     

Kinetics of polymerization initiated by peroxides containing heterocyclic groups. I. Kinetics of bulk polymerization of styrene and vinyl acetate initiated by difuroyl peroxide

The rate and degree of bulk polymerization of styrene and vinyl acetate initiated by difuroyl peroxide and, for comparison, by dilauroyl and dibenzoyl peroxides were measured at several temperatures as a function of the initiator concentration. Also the rates of initiation were determined by the inhibition method with Banfield's radicals. The rate of polymerization initiated by difuroyl peroxide appears to be lower than could be expected from the rate of initiation determined by the inhibition method and from the decomposition of difuroyl peroxide. In the case of polymerization of vinyl acetate there are significant deviations from the proportionality between R_p and the square root of the initiator concentration, which follows from the conventional kinetic scheme. The degrees of polymerization are also low, and the plots of P _n^?1 versus R_p are not linear. These deviations can be accounted for by postulating a retardation effect of the furan cycle and chain transfer to difuroyl peroxide.     

On the way to formal accreditation

The Radiochemical Laboratory participated in the Technical Co-operation (TC) Project on Quality Control and Quality Assurance for Nuclear Analytical Techniques RER/2/004 organized by the International Atomic Energy Agency (IAEA) during the period June 1999 and September 2001. Motivations, major goals of participation in the project, milestones of implementation of the project, establishing the quality system, improvements fulfilling both technical and management requirements as well as major achievements for future activities of the laboratory with respect to technical and financial conditions are discussed in detail.     

Low-energy electron-excited nanoluminescence studies of GaN and related materials

We have used low-energy electron-excited nanoluminescence (LEEN) spectroscopy combined with ultrahigh vacuum surface analysis techniques to obtain electronic bandgap, confined state and deep-level trap information from III nitride compound semiconductor surfaces and their buried interfaces on a nanometer scale. Localized states are evident at GaN/InGaN quantum wells, GaN ultrathin films, AlGaN/GaN pseudomorphic heterostructures, and GaN/Al₂O₃ interfaces that are sensitive to the chemical composition, bonding and atomic structure near interfaces, and in turn to the specifics of the epitaxial growth process. Identification of electrically active defects in these multilayer nanostructures provides information to optimize interface growth and control local electronic properties.     

Reduction of temazepam to diazepam and lorazepam to delorazepam during enzymatic hydrolysis

It has been previously reported that treatment of urinary oxazepam by commercial β-glucuronidase enzyme preparations, from Escherichia coli, Helix pomatia and Patella vulgata, results in production of nordiazepam (desmethyldiazepam) artefact. In this study, we report that this unusual reductive transformation also occurs in other benzodiazepines with a hydroxyl group at the C3 position such as temazepam and lorazepam. As determined by liquid chromatography-mass spectrometry analysis, all three enzyme preparations were found capable of converting urinary temazepam into diazepam following enzymatic incubation and subsequent liquid–liquid extraction procedures. For example, when H. pomatia enzymes were used with incubation conditions of 18 h and 50 °C, the percentage conversion, although small, was significant—approximately 1% (0.59–1.54%) in both patient and spiked blank urines. Similarly, using H. pomatia enzyme under these incubation conditions, a reductive transformation of urinary lorazepam into delorazepam (chlordesmethyldiazepam) occurred. These findings have both clinical and forensic implications. Detection of diazepam or delorazepam in biological samples following enzyme treatment should be interpreted with care.     

Parametric continuation algorithm for time-delay systems and bifurcation caused by multiple characteristic roots

Nonlinear Dynamics - Stability analysis has been always a key issue in nonlinear dynamics and engineering applications, and it is still a challenging task for time-delay control systems when tuning...