Prediction of ionic liquid properties. I. Volumetric properties as a function of temperature at 0.1 MPa

The prediction of molar volumes and densities of several ionic liquids has been achieved using a group contribution model as a function of temperature between (273 and 423) K at atmospheric pressure. It was observed that the calculation of molar volumes or densities could be performed using the "ideal" behavior of the molar volumes of mixtures of ionic liquids. This model is based on the observations of Canongia Lopes et al. (J. Phys. Chem. B 2005, 109, 3519-3525) which showed that this ideal behavior is independent of the temperature and allows the molar volume of a given ionic liquid to be calculated by the sum of the effective molar volume of the component ions. Using this assumption, the effective molar volumes of ions constituting more than 220 different ionic liquids were calculated as a function of the temperature at 0.1 MPa using more than 2150 data points. These calculated results were used to build up a group contribution model for the calculation of ionic liquid molar volumes and densities with an estimated repeatability and uncertainty of 0.36% and 0.48%, respectively. The impact of impurities (water and halide content) in ionic liquids as well as the method of determination were also analyzed and quantified to estimate the overall uncertainty. © 2008 American Chemical Society.

Liquid-liquid miscibility and volumetric properties of aqueous solutions of ionic liquids as a function of temperature

The volumetric properties of seven {water + ionic liquid} binary mixtures have been studied as a function of temperature from (293 to 343) K. The phase behaviour of the systems was first investigated using a nephelometric method and excess molar volumes were calculated from densities measured using an Anton Paar densimeter and fitted using a Redlich-Kister type equation. Two ionic liquids fully miscible with water (1-butyl-3-methylimidazolium tetrafluoroborate ([CCIm][BF]) and 1-ethyl-3-methylimidazolium ethylsulfate ([CCIm][EtSO])) and five ionic liquids only partially miscible with water (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([CCIm][NTf]), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([CCIm][NTf]), 1-butyl-3-methylimidazolium hexafluorophosphate ([CCIm][PF]), 1-butyl-3-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([CCPyrro][NTf]), and butyltrimethylammonium bis(trifluoromethylsulfonyl)imide ([N][NTf])) were chosen. Small excess volumes (less than 0.5 cm · mol at 298 K) are obtained compared with the molar volumes of the pure components (less than 0.3% of the molar volume of the pure ionic liquid). For all the considered systems, except for {[CCIm][EtSO] + water}, positive excess molar volumes were calculated. Finally, an increase of the non-ideality character is observed for all the systems as temperature increases. © 2009 Elsevier Ltd. All rights reserved.

Bit error rate performance enhancement of a retrodirective array over a conventional fixed beam array in a dynamic multipath environment

In this paper, we provide experimental evidence to show that enhanced bit error rate (BER) performance is possible using a retrodirective array operating in a dynamically varying multipath environment. The operation of such a system will be compared to that obtained by a conventional nonretrodirective array. The ability of the array to recover amplitude shift keyed encoded data transmitted from a remote location whose position is not known a priori is described. In addition, its ability to retransmit data inserted at the retrodirective array back to a spatially remote beacon location whose position is also not known beforehand is also demonstrated. Comparison with an equivalent conventional fixed beam antenna array utilizing an identical radiating aperture arrangement to that of the retrodirective array are given. These show that the retrodirective array can effectively exploit the presence of time varying multipath in order to give significant reductions in BER over what can be otherwise achieved. Additionally, the retrodirective system is shown to be able to deliver low BER regardless of whether line of sight is present or absent.

A finite element solution scheme for an elastic–viscoplastic soil model

A Newton–Raphson solution scheme with a stress point algorithm is presented for the implementation of an elastic–viscoplastic soilmodel in a finite element program. Viscoplastic strain rates are calculated using the stress and volumetric states of the soil. Sub-incrementsof time are defined for each iterative calculation of elastic–viscoplastic stress changes so that their sum adds up to the time incrementfor the load step. This carefully defined ‘iterative time’ ensures that the correct amount of viscoplastic straining is accumulated overthe applied load step. The algorithms and assumptions required to implement the solution scheme are provided. Verification of the solutionscheme is achieved by using it to analyze typical boundary value problems.

Real-time error detection but not error correction drives automatic visuomotor adaptation

We investigated the role of visual feedback of task performance in visuomotor adaptation. Participants produced novel two degrees of freedom movements (elbow flexion-extension, forearm pronation-supination) to move a cursor towards visual targets. Following trials with no rotation, participants were exposed to a 60A degrees visuomotor rotation, before returning to the non-rotated condition. A colour cue on each trial permitted identification of the rotated/non-rotated contexts. Participants could not see their arm but received continuous and concurrent visual feedback (CF) of a cursor representing limb position or post-trial visual feedback (PF) representing the movement trajectory. Separate groups of participants who received CF were instructed that online modifications of their movements either were, or were not, permissible as a means of improving performance. Feedforward-mediated performance improvements occurred for both CF and PF groups in the rotated environment. Furthermore, for CF participants this adaptation occurred regardless of whether feedback modifications of motor commands were permissible. Upon re-exposure to the non-rotated environment participants in the CF, but not PF, groups exhibited post-training aftereffects, manifested as greater angular deviations from a straight initial trajectory, with respect to the pre-rotation trials. Accordingly, the nature of the performance improvements that occurred was dependent upon the timing of the visual feedback of task performance. Continuous visual feedback of task performance during task execution appears critical in realising automatic visuomotor adaptation through a recalibration of the visuomotor mapping that transforms visual inputs into appropriate motor commands.

Spectator understanding of error in performance

The development of computer-based devices for music control has created a need to study how spectators understand new performance technologies and practices. As a part of a larger project examining how interactions with technology can be communicated to spectators, we present a model of a spectator's understanding of error by a performer. This model is broadly applicable throughout HCI, as interactions with technology are increasingly public and spectatorship is becoming more common.

Microsatellite standardization and evaluation of genotyping error in a large multi-partner research programme for conservation of Atlantic salmon (Salmo salar L.).

Microsatellite genotyping is a common DNA characterization technique in population, ecological and evolutionary genetics research. Since different alleles are sized relative to internal size-standards, different laboratories must calibrate and standardize allelic designations when exchanging data. This interchange of microsatellite data can often prove problematic. Here, 16 microsatellite loci were calibrated and standardized for the Atlantic salmon, Salmo salar, across 12 laboratories. Although inconsistencies were observed, particularly due to differences between migration of DNA fragments and actual allelic size ('size shifts'), inter-laboratory calibration was successful. Standardization also allowed an assessment of the degree and partitioning of genotyping error. Notably, the global allelic error rate was reduced from 0.05 ± 0.01 prior to calibration to 0.01 ± 0.002 post-calibration. Most errors were found to occur during analysis (i.e. when size-calling alleles; the mean proportion of all errors that were analytical errors across loci was 0.58 after calibration). No evidence was found of an association between the degree of error and allelic size range of a locus, number of alleles, nor repeat type, nor was there evidence that genotyping errors were more prevalent when a laboratory analyzed samples outside of the usual geographic area they encounter. The microsatellite calibration between laboratories presented here will be especially important for genetic assignment of marine-caught Atlantic salmon, enabling analysis of marine mortality, a major factor in the observed declines of this highly valued species.

Temporal characterization and in vitro comparison of cell survival following the delivery of 3D-conformal, intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT)

A phantom was designed and implemented for the delivery of treatment plans to cells in vitro. Single beam, 3D-conformal radiotherapy (3D-CRT) plans, inverse planned five-field intensity-modulated radiation therapy (IMRT), nine-field IMRT, single-arc volumetric modulated arc therapy (VMAT) and dual-arc VMAT plans were created on a CT scan of the phantom to deliver 3 Gy to the cell layer and verified using a Farmer chamber, 2D ionization chamber array and gafchromic film. Each plan was delivered to a 2D ionization chamber array to assess the temporal characteristics of the plan including delivery time and 'cell's eye view' for the central ionization chamber. The effective fraction time, defined as the percentage of the fraction time where any dose is delivered to each point examined, was also assessed across 120 ionization chambers. Each plan was delivered to human prostate cancer DU-145 cells and normal primary AGO-1522b fibroblast cells. Uniform beams were delivered to each cell line with the delivery time varying from 0.5 to 20.54 min. Effective fraction time was found to increase with a decreasing number of beams or arcs. For a uniform beam delivery, AGO-1552b cells exhibited a statistically significant trend towards increased survival with increased delivery time. This trend was not repeated when the different modulated clinical delivery methods were used. Less sensitive DU-145 cells did not exhibit a significant trend towards increased survival with increased delivery time for either the uniform or clinical deliveries. These results confirm that dose rate effects are most prevalent in more radiosensitive cells. Cell survival data generated from uniform beam deliveries over a range of dose rates and delivery times may not always be accurate in predicting response to more complex delivery techniques, such as IMRT and VMAT.

Volumetric properties and enthalpies of solution of alcohols CkH2k+1OH (k = 1, 2, 6) in 1-methyl-3-alkylimidazolium bis(trifluoromethylsulfonyl)imide {[C1CnIm][NTf2] n = 2, 4, 6, 8, 10} ionic liquids

We present a study on the effect of the alkyl chain length of the imidazolium ring in 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquids, [C1CnIm][NTf2] (n = 2 to 10), on the mixing properties of (ionic liquid + alcohol) mixtures (enthalpy and volume). We have measured small excess molar volumes with highly asymmetric curves as a function of mole fraction composition (S-shape) with more negative values in the alcohol-rich regions. The excess molar volumes increase with the increase of the alkyl-chain length of the imidazolium cation of the ionic liquid. The values of the partial molar excess enthalpy and the enthalpy of mixing are positive and, for the case of methanol, do not vary monotonously with the length of the alkyl side-chain of the cation on the ionic liquid – increasing from n = 2 to 6 and then decreasing from n = 8. This non-monotonous variation is explained by a more favourable interaction of methanol with the cation head group of the ionic liquid for alkyl chains longer than eight carbon atoms. It is also observed that the mixing is less favourable for the smaller alcohols, the enthalpy of mixing decreasing to less positive values as the alkyl chain of the alcohol increases. Based on the data from this work and on the knowledge of the vapour pressure of {[C1CnIm][NTf2] + alcohol} binary mixtures at T = 298 K reported in the literature, the excess Gibbs free energy, excess enthalpy and excess entropy could be then calculated and it was observed that these mixtures behave like the ones constituted by a non-associating and a non-polar component, with its solution behaviour being determined by the enthalpy.

Entanglement production by quantum error correction in the presence of correlated environment

We analyze the effect of a quantum error correcting code on the entanglement of encoded logical qubits in the presence of a dephasing interaction with a correlated environment. Such correlated reservoir introduces entanglement between physical qubits. We show that for short times the quantum error correction interprets such entanglement as errors and suppresses it. However, for longer time, although quantum error correction is no longer able to correct errors, it enhances the rate of entanglement production due to the interaction with the environment.