Development of a quantitative method for the analysis of tobacco-specific nitrosamines in mainstream cigarette smoke using isotope dilution liquid chromatography/electrospray ionization tandem mass spectrometry

An improved method has been developed for the determination of the four major tobacco-specific nitrosamines (TSNA) in mainstream cigarette smoke. The new method offers decreased sample preparation and analysis time as compared to traditional methodologies. This method uses isotope dilution liquid chromatography coupled to a tandem mass spectrometer with electrospray ionization and is significantly more sensitive than traditional methods. It also shows no evidence of artifactual formation of TSNA. Sample concentrations were determined for four TSNA in mainstream smoke using two isotopically labeled TSNA analogues as internal standards. Mainstream smoke was collected on an industry standard 44-mm Cambridge filter pad, extracted with an aqueous buffer solution, and analyzed without further sample cleanup. This method has been validated through intra- and interlaboratory studies and has shown excellent recoveries, sensitivity, and repeatability. The limits of detection of each TSNA varied from 0.01 to 0.1 ng/mL, and the linear calibration range of the instrument in sample matrix spanned 0.5-200 ng/ mL, which allowed for the determination of the TSNA levels in cigarettes with a wide range of deliveries. Data are also reported from two commercially available industry reference cigarettes and show excellent agreement and reproducibility over a six-month time period (n > 50).     

On the performance of OnLive thin client games

Computer games stand to benefit from “cloud” technology by doing heavy-weight, graphics-intensive computations at the server, sending only the visual game frames down to a thin client, with the client sending only the player actions upstream to the server. However, computer games tend to be graphically intense with fast-paced user actions necessitating bitrates and update frequencies that may stress end-host networks. Understanding the traffic characteristics of thin client games is important for building traffic models and traffic classifiers, as well as adequately planning network infrastructures to meet future demand. While there have been numerous studies detailing online game traffic and streaming video traffic, this paper provides the first detailed study of the network characteristic of OnLive, a commercially available thin client game system. Carefully designed experiments measure OnLive game traffic for several game genres, analyzing the bitrates, packet sizes and inter-packet times for both upstream and downstream game traffic, and analyzing frame rates for the games. Results indicate OnLive rapidly sends large packets downstream, similar but still significantly different than live video. Upstream, OnLive less frequently sends much smaller packets, significantly different than upstream traditional game client traffic. OnLive supports only the top frame rates with high-capacity end-host connections, but provides good frame rates with moderate end-host connections. The results should be a useful beginning to building effective traffic models and traffic classifiers and for preparing end-host networks to support this upcoming generation of computer games.     

Improving the Productivity of Volunteer Computing by Using the Most Effective Task Retrieval Policies

Volunteer computing projects have been used to make significant advances in knowledge since the 1990s. These projects use idle CPU cycles donated by people to solve computationally intensive problems in medicine, the sciences and other disciplines. It is important to use the donated cycles as efficiently as possible because participation in volunteer computing is low and the number of volunteer computing projects keeps increasing. Task retrieval policies, policies describing when a volunteered computer requests additional work from a server, can have an effect on the number of wasted CPU cycles and consequently, the number of tasks completed by clients. We present the results of simulating different task retrieval policies for clients under realistic conditions, including clients running on computers with one single-core CPU, clients running on computers with multi-core CPUs, and clients running on computers that are put into a power save mode by environmentally conscious owners.     

Commodification of accelerations for the Karp and Miller Construction

Karp and Miller’s algorithm is based on an exploration of the reachability tree of a Petri net where, the sequences of transitions with positive incidence are accelerated. The tree nodes of Karp and Miller are labeled with ω-markings representing (potentially infinite) coverability sets. This set of ω-markings allows us to decide several properties of the Petri net, such as whether a marking is coverable or whether the reachability set is finite. The edges of the Karp and Miller tree are labeled by transitions but the associated semantic is unclear which yields to a complex proof of the algorithm correctness. In this work we introduce three concepts: abstraction, acceleration and exploration sequence. In particular, we generalize the definition of transitions to ω-transitions in order to represent accelerations by such transitions. The notion of abstraction makes it possible to greatly simplify the proof of the correctness. On the other hand, for an additional cost in memory, which we theoretically evaluated, we propose an “accelerated” variant of the Karp and Miller algorithm with an expected gain in execution time. Based on a similar idea we have accelerated (and made complete) the minimal coverability graph construction, implemented it in a tool and performed numerous promising benchmarks issued from realistic case studies and from a random generator of Petri nets.

     

Polydimethylsilalkylene-dimethylsiloxanes as advanced membrane materials for thermopervaporative recovery of oxygenates from aqueous reaction media

Polydimethylsildimethylene-dimethylsiloxane (PSDMS) and polydimethylsiltrimethylenedimethylsiloxane (PSTMS) have been first studied as pervaporation membrane materials for the recovery of butanol from aqueous media. New synthesis procedures that make it possible to obtain the monomers 2,2,5,5-tetramethyl-1-oxa-2,5-disilacyclopentane (1) and 2,2,6,6-tetramethyl-1-oxa-2,6-disilacyclohexane (2) in high yields and with high purity required for subsequent polymerization have been developed. The optimum concentration of the crosslinking agent (tetraethoxysilane (TEOS)) of 5% has been found, which provides the maximum degree of crosslinking without sacrificing high values of separation factor and permeate flux. It has been shown that the permselectivity of PSDMS or PSTMS for butanol–water is higher by a factor of 1.5 or- almost 2, respectively, than the selectivity of the industrial membrane polymer, PDMS, at comparable values of the butanol permeability coefficient.     

The role of occupational complexity in trajectories of cognitive aging before and after retirement.

We examined the association between complexity of the main lifetime occupation and changes in cognitive ability in later life. Data on complexity of work with data, people, and things and on 4 cognitive factors (verbal, spatial, memory, and speed) were available from 462 individuals in the longitudinal Swedish Adoption/Twin Study of Aging. Mean age at the first measurement wave was 64.3 years (SD = 7.2), and 65% of the sample had participated in at least three waves of data collection. Occupational complexity with people and data were both correlated with cognitive performance. Individuals with more complex work demonstrated higher mean performance on the verbal, spatial, and speed factors. Latent growth curve analyses indicated that, after correcting for education, only complexity with people was associated with differences in cognitive performance and rate of cognitive change. Continued engagement as a result of occupational complexity with people helped to facilitate verbal function before retirement, whereas a previous high level of complexity of work with people was associated with faster decline after retirement on the spatial factor. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interindividual–intergroup discontinuity reduction through the anticipation of future interaction.

Consistent with the role of a long-term perspective in reducing the tendency of intergroup relations to be more competitive than interindividual relations in the context of noncorrespondent outcomes, an experiment demonstrated that anticipated future interaction reduced intergroup but not interindividual competitiveness. Further results indicated that the effect was present only for groups composed of members high in abstractness (Openness–Intellect on the Big 5 Inventory and Intuition on the Myers–Briggs Type Inventory) who trusted their opponents. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Synthesis of energetic compounds via the metathesis reaction of 4-methylenespiro[2,3]hexane

Transformations of methylenespiro[2,3]hexane (MSH) on a heterogeneous rhenium-alumina metathesis (disproportionation) catalyst were studied. It was found that, owing to a significant difference in the stability of carbenic complexes of methylene and disubstituted carbenes, MSH undergoes isomerization to 4-methylspiro[2,3]hex-4-ene followed by their cometathesis yielding bis(spiro[2,3]hexylidene-4). The feasibility of selective cometathesis of MSH and dicyclobutylidene on the rhenium-alumina catalyst resulting in the formation of 4-cyclobutylidenespiro[2,3]hexane was shown.