Evaluation of a four-channel multiplexed electrospray triple quadrupole mass spectrometer for the simultaneous validation of LC/MS/MS methods in four different preclinical matrixes

A four-channel multiplexed electrospray interface on a triple quadrupole mass spectrometer was evaluated for the simultaneous validation of LC/MS/MS methods for the quantitation of loratadine and its metabolite, descarboethoxyloratadine, in four different biological matrixes. The assays were performed in rat, rabbit, mouse, and dog plasma from 1 to 1000 ng/mL using 96-well solid-phase extraction for sample preparation. The limit of quantitation of 1 ng/mL corresponded to 5.56 pg of each analyte injected on-column. For the drug, quality control samples (n = 6 at four concentrations) had precision ranging from 0.967 to 16.0% and accuracy ranging from -8.44 to 10.5% across all four species. For the metabolite, the precision ranged from 0.684 to 11.0% and the accuracy was between 6.36 and -9.06%. Intersprayer cross talk for the multiplexed electrospray ion source was evaluated as a function of analyte concentration and was less than 0.08% at concentrations as high as 1000 ng/mL. These results demonstrate the feasibility of using parallel analysis to reduce the time required for method validation and to increase sample throughput in drug development studies.     

Towards Deeper Understanding of the Search Interfaces of the Deep Web

Many databases have become Web-accessible through form-based search interfaces (i.e., HTML forms) that allow users to specify complex and precise queries to access the underlying databases. In general, such a Web search interface can be considered as containing an interface schema with multiple attributes and rich semantic/meta-information; however, the schema is not formally defined in HTML. Many Web applications, such as Web database integration and deep Web crawling, require the construction of the schemas. In this paper, we first propose a schema model for representing complex search interfaces, and then present a layout-expression based approach to automatically extract the logical attributes from search interfaces. We also rephrase the identification of different types of semantic information as a classification problem, and design several Bayesian classifiers to help derive semantic information from extracted attributes. A system, WISE-iExtractor, has been implemented to automatically construct the schema from any Web search interfaces. Our experimental results on real search interfaces indicate that this system is highly effective.     

The synthesis,swelling behaviour and rheological properties of chemically crosslinked thermosensitive copolymers based on <Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide

In this contribution thermosensitive polymer matrices based on N-isopropylacrylamide have been developed. The hydrogels were prepared by photopolymerisation of N-isopropylacrylamide and 1-vinyl-2-pyrrolidinone in appropriate amounts of distilled water. The monomers were cured using a UV-light sensitive initiator called 1-hydroxycyclohexylphenylketone. These copolymers were crosslinked using ethylene glycol dimethacrylate and poly(ethylene glycol) dimethacrylate with molecular weights 600 and 1,000, at 0.1 wt% of the total monomer content. The chemical structure of the xerogels was characterised by means of Fourier transform infrared spectroscopy (FTIR) and the transition temperature of the hydrogels was determined using modulated differential scanning calorimetry (MDSC). By altering the feed ratio, hydrogels were synthesised to have lower critical solution temperatures (LCST) around 37 °C. This ability to shift the phase transition temperature of the gels provides excellent flexibility in tailoring transitions for specific uses. The samples synthesised with PEG1000DMA crosslinking agents absorbed over 18 times their weight in water, while maintaining good gel integrity thus falling marginally short of being characterised as superabsorbent. Each of the samples showed similar deswelling behaviour at 37 °C. Rheological studies showed that increasing the molecular weight of the crosslinking agent caused an increase in hydrogel strength.     

Computational Models for Simulating Multicomponent Aerosol Evaporation in the Upper Respiratory Airways

An effective model for predicting multicomponent aerosol evaporation in the upper respiratory system that is capable of estimating the vaporization of individual components is needed for accurate dosimetry and toxicology analyses. In this study, the performance of evaporation models for multicomponent droplets over a range of volatilities is evaluated based on comparisons to available experimental results for conditions similar to aerosols in the upper respiratory tract. Models considered include a semiempirical correlation approach as well as resolved-volume computational simulations of single and multicomponent aerosol evaporations to test the effects of variable gas-phase properties, surface blowing velocity, and internal droplet temperature gradients. Of the parameters assessed, concentration-dependent gas-phase specific heat had the largest effect on evaporation and should be taken into consideration for respiratory aerosols that contain high volatility species, such as n-heptane, at significant concentrations. For heavier droplet components or conditions below body temperatures, semiempirical estimates were shown to be appropriate for respiratory aerosol conditions. In order to reduce the number of equations and properties required for complex mixtures, a resolved-volume evaporation model was used to identify a twelve-component surrogate representation of potentially toxic JP-8 fuel based on comparisons to experimentally reported droplet evaporation data. Due to the relatively slow evaporation rate of JP-8 aerosols, results indicate that a semiempirical evaporation model in conjunction with the identified surrogate mixture provide a computationally efficient method for computing droplet evaporation that can track individual toxic markers. However, semiempirical methodologies are in need of further development to effectively compute the evaporation of other higher volatility aerosols for which variable gas-phase specific heat does play a significant role.     

The effect of saturation fluctuations on droplet growth

In the atmosphere the saturation ratio of water vapour varies as a function of time and space. In the present study we have investigated the effects of fluctuations of saturation ratio on droplet (cloud condansation nuclei) growth by stochastic approach employing an advanced growth model for cloud droplets. In saturated mean conditions growth of cloud droplets is accelerated by the fluctuations of saturation ratio, and our results indicate that due to fluctuations some droplets are able to grow in undersaturated conditions. Stochastic fluctuations of saturation ratio result in appearance of bimodal particle-size distribution and this is one of the possible explanations for the observed two modal cloud droplet distribution.     

Studies of the esterification of dextran: routes to bioactive polymers and graft copolymers

Problems associated with the esterification of dextran as a means of coupling bioactive molecules or introduction of functionality suitable for graft polymerization are considered. In particular, the importance of eliminating side-reactions which incorporate into dextran unwanted residues, e.g. groups containing nitrogen, is emphasized and practical techniques for minimizing this are described. We have developed a formamide-based solvent suitable for esterification with the aid of dicyclohexyl carbodiimide (DCC) and carbonyl di-imidazole (CDI) as coupling agents. The preferred catalyst is p-pyrrolidinopyridine. CDI has the advantage of enabling dimethylsulphoxide to be used as solvent for dextran and other hydroxylic polymers without inducing oxidation of hydroxyl groups. This coupling agent is flexible and offers a choice of two routes to esterification, each having its merits. We have optimized conditions for coupling by use of butyric acid as model. Esterification of dextran has been employed in the preparation of soluble bioactive macromolecules by coupling the anti-platelet agent (I) and also in the synthesis of graft copolymers via introduction of 2-bromopropionate groups. Crosslinking of dextran and the polymerization of dipyridamole have been effected by use of CDI.     

The mechanisms of collisional activation of ions in mass spectrometry

This article is a review of the mechanisms responsible for collisional activation of ions in mass spectrometers. Part I gives a general introduction to the processes occurring when a projectile ion and neutral target collide. The theoretical background to the physical phenomena of curve‐crossing excitation (for electronic and vibrational excitation), impulsive collisions (for direct translational to vibrational energy transfer), and the formation of long‐lived collision intermediates is presented. Part II highlights the experimental and computational investigations that have been made into collisional activation for four experimental conditions: high (>100 eV) and intermediate (1–100 eV) center‐of‐mass collision energies, slow heating collisions (multiple low‐energy collisions) and collisions with surfaces. The emphasis in this section is on the derived post‐collision internal energy distributions that have been found to be typical for projectile ions undergoing collisions in these regimes. © 2009 Wiley Periodicals, Inc., Mass Spec Rev 28:608–639, 2009     

Wind turbine performance under icing conditions

The wind energy market is in full growth in Quebec but technical difficulties due to cold climate conditions have occurred for most of the existing projects. Thus, icing simulations were carried out on a 0.2 m NACA 63 415 blade profile in the refrigerated wind tunnel of the Anti‐icing Materials International Laboratory (AMIL). The shapes and masses of the ice deposits were measured, as well as the lift and drag forces of the iced profiles. Scaling was carried out based on the 1.8 MW–Vestas V80 wind turbine technical data, for three different radial positions and two in‐fog icing conditions measured at the Murdochville wind farm in the Gaspé Peninsula. For both icing events, the mass of ice accumulated on the blade profile increased with an increase in the radial position. In wet regime testing (first icing event), glaze formed mostly near the leading edge and on the pressure side. It also accumulated by run‐off on the trailing edge of the outer half of the blade. In dry‐regime testing (second icing event), rime mostly accreted on the leading edge and formed horns. For both icing events, when glaze or rime accreted on the blade profile, lift decreased and drag increased. A load calculation using the blade element theory shows that drag force on the entire blade becomes too large compared to lift, leading to a negative torque and the stop of the wind turbine. Torque reduction is more significant on the outer third of the blade. Setting up a de‐icing system only on the outer part of the blade would enable significant decrease of heating energy costs. Copyright © 2007 John Wiley & Sons, Ltd.