Magnetic field induced diamagnetic susceptibility of a hydrogenic donor in a GaN/AlGaN quantum dot

The binding energies of a hydrogenic donor in a GaN/AlGaN quantum dot are calculated in the influence of magnetic field. The calculations are carried out using the single-band effective mass approximation within a variational scheme. The magnetic field induced binding energy and diamagnetic susceptibility of the hydrogenic donor are obtained as a function of dot radius. Calculations have been carried out with and without the Zeeman effect through the energy-dependent effective mass. The diamagnetic shift of the hydrogenic donor is found for different dot radii. Our results show that (i) the binding energy is higher for smaller dot radii and the magnetic field effects are predominant for larger dot sizes, (ii) the binding energy is higher when the Zeeman effect is included for all the magnetic fields, (iii) the diamagnetic susceptibility increases with the magnetic field and is not pronounced for smaller dot radii and (iv) the diamagnetic shift has a good influence of larger dot radii.     

Fluorothiocarbonyl compounds. VI. Free-radical polymerization of thiocarbonyl fluoride

Thiocarbonyl fluoride, CF₂?S, and thiocarbonyl chlorofluoride, CFCl?S, undergo addition polymerization in free radical-initiated systems. In addition, both compounds copolymerize with various unsaturated compounds, including typical vinyl and vinylidene monomers. The chlorofluoride, because of its rapid polymerization rate, copolymerizes best with very active monomers, of which 2,3-dichloro-1,3-butadiene is an example. Thiocarbonyl fluoride polymerizes best at low temperatures. The trialkylborane—oxygen redox couple has been adapted to free-radical polymerizations and copolymerizations from ?60 to ?120°C. With such initiation CF₂?S has been copolymerized with terminal and internal olefins, vinyl compounds, allyl compounds, and acrylic esters. Copolymerization with propylene is unusual, in that it proceeds in a manner that strongly favors a product composed of two molecules of CF₂?S for each propylene. In other cases, product compositions are more responsive to the ratio of monomers charged.     

Parallel synthesis and in vitro activity of novel anthranilic hydroxamate-based inhibitors of the prostaglandin H2 synthase peroxidase activity

Currently available non-steroidal anti-inflammatory drugs (NSAIDs) such as aspirin are directed at the cyclooxygenase (COX) site, but not the peroxidase (POX) activity of prostaglandin H2 synthase (PGHS). They are thus unable to inhibit the free-radical induced tissue injury associated with PGHS peroxidase activity, which can occur independently of the COX site. A lead compound, anthranilic hydroxamic acid (AHA) was found to have significant PGHS-POX inhibitory activity (IC50= 72 microM). To define the critical parameters for PGHS-POX inhibition, we investigated 29 AHA derivatives, synthesised from their acid precursors, using solid phase synthesis. In vitro analysis demonstrated a ten-fold improvement in inhibition with 3,5-diiodoanthranilic hydroxamic acid (IC50= 7 microM).     

Laser Mass Spectrometry of Organophosphorus Pesticides and Related Compounds

Abstract

Laser mass spectra obtained for 20 organophosphorus (OP) compounds were systematically evaluated for groups containing analogous structural features. Variations in fragmentation can be understood based on simple organic reactions. While detailed mechanistic interpretations of the laser mass spectra (LMS) were not possible, the qualitative features in the LMS obtained from five compounds, not in the original set, could be predicted based on the characteristics of the other OP compounds studied. The success of the prediction lends credence to the qualitative models developed for rationalizing the LMS. A specific feature in the LMS of aromatic thionophosphates is a thiono-thiolo rearrangement. Detailed investigation into the phenomena involved comparison of LMS obtained from aromatic thionophosphates with spectra from electron impact, chemical ionization, field desorption, and secondary ion mass spectrometry. These results led to the conclusion that the rearrangement in laser mass spectrometry must occur during volatilization while the molecule/ion is in the “cloud” present immediately above the laser impact area.     

Exponentially and pre-exponentially correlated Gaussians for atomic quantum calculations

Explicitly correlated, n-electron, one-center s Gaussian (ECG) functions that depend on the interelectron distances in the exponent are combined with s ECGs which also depend on the interelectron separations through pre-exponential r(ij)(2) multipliers. The pre-exponentially r(ij)(2)-dependent ECGs are included in the basis to better describe the interelectron correlation and the interelectron cusps. The basis set is tested in the calculations of the ground state of the beryllium atom ((9)Be).     

Integrating restoration and scheduling decisions for disrupted interdependent infrastructure systems

We consider the problem faced by managers of critical civil interdependent infrastructure systems of restoring essential public services after a non-routine event causes disruptions to these services. In order to restore the services, we must determine the set of components (or tasks) that will be temporarily installed or repaired, assign these tasks to work groups, and then determine the schedule of each work group to complete the tasks assigned to it. These restoration planning and scheduling decisions are often undertaken in an independent, sequential manner. We provide mathematical models and optimization algorithms that integrate the restoration and planning decisions and specifically account for the interdependencies between the infrastructure systems. The objective function of this problem provides a measure of how well the services are being restored over the horizon of the restoration plan, rather than just focusing on the performance of the systems after all restoration efforts are complete. We test our methods on realistic data representing infrastructure systems in New York City. Our computational results demonstrate that we can provide integrated restoration and scheduling plans of high quality with limited computational resources. We also discuss the benefits of integrating the restoration and scheduling decisions.     

Restoring infrastructure systems: An integrated network design and scheduling (INDS) problem

We consider the problem of restoring services provided by infrastructure systems after an extreme event disrupts them. This research proposes a novel integrated network design and scheduling problem that models these restoration efforts. In this problem, work groups must be allocated to build nodes and arcs into a network in order to maximize the cumulative weighted flow in the network over a horizon. We develop a novel heuristic dispatching rule that selects the next set of tasks to be processed by the work groups. We further propose families of valid inequalities for an integer programming formulation of the problem, one of which specifically links the network design and scheduling decisions. Our methods are tested on realistic data sets representing the infrastructure systems of New Hanover County, North Carolina in the United States and lower Manhattan in New York City. These results indicate that our methods can be used in both real-time restoration activities and long-term scenario planning activities. Our models are also applied to explore the effects on the restoration activities of aligning them with the goals of an emergency manager and to benchmark existing restoration procedures.     

Weighted Aumann-Shapley pricing

Cost allocation problems arise in many contexts in economics and management science. In a typical problem that we have in mind, a decision maker must decide how to allocate the joint cost of production among several commodities using prices. Furthermore, these prices must satisfy certain reasonable postulates among which is the requirement that total revenue associated with these prices must cover total cost. In this paper, we investigate a generalization of Aumann-Shapley pricing, called Weighted Aumann-Shapley pricing, that allows for asymmetric pricing of commodities even when those commodities affect costs in a symmetric fashion. Weighted AS pricing is a natural extension of (symmetric) Aumann-Shapley pricing, and may be considered a non-atomic analogue of Owen's modified diagonal formula (with respect to the multilinear extension) for the weighted TU Shapley Value. Received December 1993/Revised version June 1998     

Investigation of porphyrins and metalloporphyrins by liquid matrix-assisted laser desorption mass spectrometry

Laser desorption mass spectrometry with liquid matrix-assistance has been used to study a series of selected porphyrins and metalloporphyrins. This work presents the results of using a liquid matrix with fibrous material as the substrate for liquid matrix assisted laser desorption of porphyrins and metalloporphyrins. The liquid matrices used for porphyrin studies were o-nitrophenyl octyl ether (NPOE) and 15-crown-5. The use of a liquid matrix with soft laser ionization enhances molecular ion formation. We also have investigated the use of NPOE as a liquid matrix for identifying mixtures of up to six porphyrins in a single shot spectrum without prior separation. The (M + H)⁺ peak of each metalloporphyrin component in the mixture is clearly indicated in the spectra and no obvious interference effects were observed.     

Intercalation of Toluidines into α-Zirconium Hydrogenphosphate

Intercalates of o-, m-, and p-toluidine into α-Zr(HPO₄)₂ · H₂O were prepared and characterized by powder X-ray diffraction, thermogravimetric analysis and infrared spectroscopy. As follows from IR, toludine molecules are protonated in the interlayer space. Toluidine molecules are arranged in a bimolecular way in the intercalates containing more than 1.5 toluidine molecules per Zr atom. On the other hand, a monolayer of the toluidine molecules is supposed in the intercalates with less than one toluidine molecule per Zr atom.