Relations for the standard potential of the cell H,(Pt)IHClIAgCl-Ag in various aqueous organic media, based on the Born equation, are briefly reviewed, and the limitations of this method noted. A new stoicheiometric relationship is developed, based on a simple treatment of ion solvation in liquid mixtures. The resulting equation shows that a plot of the standard potential E," on the molar scale should be linearly related to the logarithm of the volume fraction #w of water in the solvent medium. The correlation achieved experimentally is considerably better than anything obtained with plots based on the Born equation, and is free from marked solvent effects. Certain observed deviations are discussed.FOLLOWING work on aqueous ketone and glycol solutions (cf. J., 1957, 2284), we can discuss the standard potentials of the cell H,(Pt)[HClIAgCl-Ag in a large number of aqueous solutions of the comrnoner water-soluble organic substances, particularly where the water content is high.In Table 1 are given all the available standard potentials of the cell for such systems on the molal (Em'), molar (E," = Emo + 2k log do), and mole fractional [EN' = Emo -2k log (lOOO/M,,)] scales ( k = 2.3026 RTIF, do = density of pure solvent mixture M , = lOO/[X/M, + (100 -X)/My] = mean molecular weight of solvent ( X = weight yo of organic substance of molecular weight Mx, and M y = molecular weight of water). Values of the dielectric constant E, and of the density do of each mixture are recorded. Where not given by the original author, the values of E are taken from Hikerlof's data,l and the do values from International Critical Tables or from GriEths's data.2*3 The mole fraction of water, N,, has been calculated for each mixture.The difference between the standard potentials, "E" in water and "E" in another solvent, is related to a freeenergy difference AG by the equations Discussion of the CeU H,(Pt) 1 HClI AgCl-Ag.-AG = F("E' -*E") = -2RT In aJa, = -2RT In flcl/f2c, AG is the difference in solvation energies of hydrogen chloride in the two solvents, referred to standard conditions in the gas phase and the standard state in the given solvent, andf. are mean ion-activity coefficients referred to a standard state of unity at infinite dilution in pure water, i.e., fi = 1. By the definition of standard potential, interionic attractions are eliminated, and we are concerned solely with ion-solvent interactions.It would be convenient to choose the standard state such that the work done in transferring the ions, considered uncharged, is zero; in other words, that terms of the type 2RT In cl}c, vanish. Classically this is assumed to be the case if the mole fraction of
BackgroundIncreasing the number of patients participating in research studies is a current priority in the National Health Service (NHS) in the United Kingdom. The role of specialist nurses in inviting patients to participate is important, yet little is known about their experiences of doing so. The aim of this study was to explore the perceptions of barriers and facilitators held by specialist nurses with experience of inviting adult NHS patients to a wide variety of research studies.MethodsA cross-sectional qualitative descriptive study was conducted between March and July 2015. Participants were 12 specialist nurses representing 7 different clinical specialties and 7 different NHS Trusts. We collected data using individual semi-structured interviews, and analysed transcripts using the Framework method to inductively gain a descriptive overview of barriers and facilitators.ResultsBarriers and facilitators were complex and interdependent. Perceptions varied among individuals, however barriers and facilitators centred on five main themes: i) assessing patient suitability, ii) teamwork, iii) valuing research, iv) the invitation process and v) understanding the study. Facilitators to inviting patients to participate in research often stemmed from specialist nurses’ attitudes, skills and experience. Positive research cultures, effective teamwork and strong relationships between research and clinical teams at the local clinical team level were similarly important. Barriers were reported when specialist nurses felt they were providing patients with insufficient information during the invitation process, and when specialist nurses felt they did not understand studies to their satisfaction.ConclusionOur study offers several new insights regarding the role of specialist nurses in recruiting patients for research. It shows that strong local research culture and teamwork overcome some wider organisational and workload barriers reported in previous studies. In addition, and in contrast to common practice, our findings suggest research teams may benefit from individualising study training and invitation procedures to specialist nurses’ preferences and requirements. Findings provide a basis for reflection on practice for specialist nurses, research teams, policymakers, and all with an interest in increasing patient participation in research.Electronic supplementary materialThe online version of this article (doi:10.1186/s12874-016-0204-5) contains supplementary material, which is available to authorized users.
Background Process evaluations are increasingly conducted within pragmatic randomised controlled trials (RCTs) of health services interventions and provide vital information to enhance understanding of RCT findings. However, issues pertaining to process evaluation in this specific context have been little discussed. We aimed to describe the frequency, characteristics, labelling, value, practical conduct issues, and accessibility of published process evaluations within pragmatic RCTs in health services research. Methods We used a 2-phase systematic search process to (1) identify an index sample of journal articles reporting primary outcome results of pragmatic RCTs published in 2015 and then (2) identify all associated publications. We used an operational definition of process evaluation based on the Medical Research Council’s process evaluation framework to identify both process evaluations reported separately and process data reported in the trial results papers. We extracted and analysed quantitative and qualitative data to answer review objectives. Results From an index sample of 31 pragmatic RCTs, we identified 17 separate process evaluation studies. These had varied characteristics and only three were labelled ‘process evaluation’. Each of the 31 trial results papers also reported process data, with a median of five different process evaluation components per trial. Reported barriers and facilitators related to real-world collection of process data, recruitment of participants to process evaluations, and health services research regulations. We synthesised a wide range of reported benefits of process evaluations to interventions, trials, and wider knowledge. Visibility was often poor, with 13/17 process evaluations not mentioned in the trial results paper and 12/16 process evaluation journal articles not appearing in the trial registry. Conclusions In our sample of reviewed pragmatic RCTs, the meaning of the label ‘process evaluation’ appears uncertain, and the scope and significance of the term warrant further research and clarification. Although there were many ways in which the process evaluations added value, they often had poor visibility. Our findings suggest approaches that could enhance the planning and utility of process evaluations in the context of pragmatic RCTs. Trial registration Not applicable for PROSPERO registration
The conductances of solutions of picric acid in various ketones and nitriles have been measured over a concentration range from 0.04 x 10-3 to 100 x 10-3 g-equiv./l., the temperatures employed being 15", 25", and 40°C. A new conductance equation is developed on the assumption that triple ions of one type only are formed. The experimental results of the present investigation are examined on the basis of ion pair, triple ion, and modified (unilateral) triple ion formation. It is shown that the preferential formation of one type of triple ion can best explain the variation of conductance with concentration in these systems.
Davidson and French. 191 38. The Xynthesis and Structure of Aromatic BoronCompounds.
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