Volatile Chloro- and Chlorofluorocarbons in Lake Erie — 1977 and 1978

Water samples from the central and eastern basins of Lake Erie were analyzed for volatile chloro- and chlorofluorocarbons for a one-week period in each of 1977 and 1978. The following contaminants were observed with mean concentrations and standard deviations in 1978 with the corresponding values for 1977 in parentheses: Dichlorodifluoromethane (Freon 12) 76±38 (73±36) ng°L^?1; trichlorofluoromethane (Freon 11) 34±26 (46±40) ng·L^?1; chloroform 15±4 ng·L^?1; carbon tetrachloride 19±11 (37±20) ng·LT^?1; trichloroethylene 20±13 (11±9) ng·L^?1.Except for carbon tetrachloride and trichloroethylene, the distribution patterns appear to show little correlation with each other. Chloroform concentrations were relatively uniform, however the carbon tetrachloride and trichloroethylene concentrations appear to be point-source related with discharges along the south shore of Lake Erie. Freon 12 concentrations were generally higher in the eastern basin than in the central basin, while Freon 11 levels were high and relatively uniform throughout the study area.     

Study of PVC stabilization using capillary rheometry

Capillary rheometry allows monitoring of PVC thermal and shear stress degradations separately. Based on testing of PVC compounds with a capillary rheometer, stabilizers can be efficiently optimized to reduce both degradation processes. Capillary rheometry is an important tool for further improving productivity of PVC processing at high shear rates.     

Organochlorine Contaminants in a Sea Lamprey (Petromyzon Marinus) from Lake Ontario

A sea lamprey (Petromyzon marinus) specimen from Hamilton Beach, Lake Ontario, was analyzed for organochlorine pesticide and PCB residues. Contrary to the expectations, the residue levels observed were similar to those found in salmonid species. The concentrations of PCBs, DDT and metabolites, and mirex all exceeded the existing guidelines and proposed water quality objectives. Other organochlorine residues are below such limits, where existing. It is recommended to investigate organochlorine residues in sea lamprey from the Great Lakes in more detail.     

Two-Link Approximation Schemes for Loss Networks with Linear Structure and Trunk Reservation

Loss networks have long been used to model various types of telecommunication network, including circuit-switched networks. Such networks often use admission controls, such as trunk reservation, to optimize revenue or stabilize the behaviour of the network. Unfortunately, an exact analysis of such networks is not usually possible, and reduced-load approximations such as the Erlang Fixed Point (EFP) approximation have been widely used. The performance of these approximations is typically very good for networks without controls, under several regimes. There is evidence, however, that in networks with controls, these approximations will in general perform less well. We propose an extension to the EFP approximation that gives marked improvement for a simple ring-shaped network with trunk reservation. It is based on the idea of considering pairs of links together, thus making greater allowance for dependencies between neighbouring links than does the EFP approximation, which only considers links in isolation.     

Real-World Opportunities for Virtual- World Project Management

Virtual worlds provide technology capabilities that could transform education, communication and collaboration, and project management. Virtual spaces resemble the real world but without its physical limitations. Innovative companies and educational institutions are already finding ways to incorporate VW technology into their organizations. A VW research project conducted in Second Life highlights these new environments' unique technology capabilities. Such capabilities can provide richer, immersive, engaging environments to help overcome traditional barriers to virtual collaboration. By understanding this research, businesses interested in taking advantage of VWs can gain a greater appreciation of the opportunities and challenges involved.     

Accelerated test method for resistance of plastics to nitrogen dioxide

The discoloration produced by the exposure of plastics to a polluted atmosphere containing nitrogen oxides and other gases is well known. New formulations with increased resistance to such discoloration require reliable accelerated tests for characterization of additives and products. The new procedure is based on an exposure of plastics to an atmosphere with a controlled concentration of nitrogen dioxide and evaluation of subsequent discoloration by optical measurements.     

3-Arylaziridine-2-carboxylic Acid Derivatives and (3-Arylaziridin-2-yl)ketones: The Aziridination Approaches

Aziridination reactions represent a powerful tool in aziridine synthesis. Significant progress has been achieved in this field in the last decades, whereas highly functionalized aziridines including 3-arylated aziridine-2-carbonyl compounds play an important role in both medical and synthetic chemistry. For the reasons listed, in the current review we have focused on the ways to obtain 3-arylated aziridines and on the recent advances (mainly since the year 2000) in the methodology of the synthesis of these compounds via aziridination.     

Struktur und Reaktivität heterosubstituierter Nitrile. XVIII [1]. Kinetik und Mechanismus der Alkohol-Addition an Arylcyanate in Gegenwart tertiärer Amine

Structure and Reactivity of Heterosubstituted Nitriles. XVIII. Kinetics and Mechanism of the Addition of Alcohols to Aryl Cyanates in Presence of Tertiary Amines The mechanism of the carbonic acid arylester imide or carbamic acid arylester formation by the addition of alcohols or water to aryl cyanates in the presence of tertiary amines has been studied. After a slow formation of an autocatalyst, an intermediate is formed in a fast equilibrium between this one and a molecule of aryl cyanate and tertiary amine. This intermediate is slowly alcoholyzed to carbonimidic acid diester which in part is fragmented by the base to phenole and alkyl cyanate. The alkyl cyanate undergoes further reaction with the alcohol and the amine to dialkyl ether and trialkyl ammonium cyanate in the reaction mixture.     

Acylierung von Heterocyclen mit Kohlensäurederivaten. IV. Umsetzung von Benzoxazolin 2-thion mit Arylcyanaten. Kinetik und Mechanismus

Acylation of Heterocycles with Carbonic Acid Derivatives. IV. Reaction of Benzoxazolin-2-thione with Aryl Cyanates. Kinetics and Mechanism The arylcyanate benzoxazoline-2-thione ( 1 ) reaction in the presence and absence of the tertiary amines yields 1-aryloxyiminocarbonylbenzoxazoline-2-thione ( 2 ) and 2-thiocyanatobenzoxazole (4). A mechanism is proposed based on the influences of the reactants concentration, the concentration and basicity of tertiary amines, the solvent-water concentration, the arylcyanate substituents electronic effects on the reaction rate and the apparent activation parameters. This mechanism consists in the nucleophilic attack of the benzoxazoline-2-thione S-atom on the cyanate, followed by rearrangement through a four-center transition state.