Probing the electrochemical double layer of an ionic liquid using voltammetry and impedance spectroscopy: a comparative study of carbon nanotube and glassy carbon electrodes in [EMIM](+)[EtSO(4)](-).

Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) are compared as techniques for analyzing double layer capacitances of ionic liquids (ILs) at the surfaces of two carbon-based electrodes. These systems are relevant for energy storage supercapacitors and often are associated with unconventional electrochemical properties. Certain theoretical and experimental aspects of CV and EIS necessary for quantitative evaluation of the capacitance characteristics of such systems are explored. The experiments use 1-ethyl-3-methyl imidazolium ethylsulfate as a model IL electrolyte in combination with a porous electrode of carbon nanotubes (CNTs). The results are compared with those obtained with a nonporous glassy carbon (GC) electrode. The time is constant, and hence the power delivery characteristics of the experimental cell are affected by the electrolyte resistance and residual faradaic reactions of the IL, as well as by the spatially inhomogeneous electrode surfaces. It is shown that adequate characterization of these IL-electrode systems can be achieved by combining CV with EIS. A phenomenological framework for utilizing this combination is discussed.

D.C. voltammetry of ionic liquid-based capacitors: effects of Faradaic reactions, electrolyte resistance and voltage scan speed investigated using an electrode of carbon nanotubes in EMIM-EtSO4.

Carbon nanotube (CNT) electrodes in combination with ionic liquid (IL) electrolytes are potentially important for energy storage systems. We report electrochemical investigation of such a system involving a paper-electrode of multi-wall CNT (MWCNT) in the IL of 1-ethyl-3-methyl imidazolium ethylsulfate (EMIM-EtSO(4)). Our study concentrates on the analytical aspects of cyclic voltammetry (CV) to probe the double layer capacitance of these relatively unconventional systems (that involve rather large charge-discharge time constants). Both theoretical and experimental aspects of CV for such systems are discussed, focusing in particular, on the effects of Faradaic side-reactions, electrolyte resistance and voltage scan speeds. The results are analyzed using an electrode equivalent circuit (EEC) model, demonstrating a method to account for the typical artifacts expected in CV of CNT-IL interfaces.

The superosmic phenomenon.

BACKGROUND: Olfaction studies in the institution of Department of Otorhinolaryngology at Leicester Royal Infirmary have detected a previously unreported, variable phenomenon--'superosmia'--in which subjects' olfaction threshold concentrations are up to 100,000 smaller than the average value. OBJECTIVES: The aim of this report is to define and quantify this phenomenon. METHODS: Two hundred and thirty subjects, who had been screened for active nasal pathology (age range 20-60 years), underwent individual olfactory threshold tests for phenylethyl alcohol or eucalyptol, using a computer-driven olfactometer in a controlled laboratory setting. Some tests were single tests and others were repeated on a small cohort. RESULTS: Two per cent of subjects demonstrated the superosmic phenomenon on single testing, and 10 per cent demonstrated this phenomenon on variable occasions during repeated testing. The superosmic phenomenon was defined by: (1) confident olfactory perception of a threshold at least equal to if not greater than three threshold levels below the subject's average threshold; (2) repeated perception of the odour at this level for at least 10 responses (1:1024 probability of chance finding); and (3) (where time permitted) a sudden, rapid loss of superosmia. CONCLUSIONS: Superosmia is a distinct phenomenon, the stimulus or mechanism of which is currently the subject of further research. The enhancement of olfactory ability may be possible through activation of an accessory pathway or modulation of the existing olfactory apparatus.

Use of intranasal corticosteroids in sinonasal infection and after surgery.

The use of intranasal steroids by otolaryngologists in the treatment of patients with infective rhinosinusitis and after endonasal surgery, particularly endoscopic sinus surgery, is unlicensed, as stated in the British National Formulary and in the manufacturers' leaflets supplied with nasal steroid medications. However, despite this, nasal steroids continue to be prescribed in these circumstances. Debate continues as to the exact role of intranasal steroids in sinonasal infection and after sinonasal surgery and whether their use in these circumstances should still be unlicensed. This article reviews the current medical literature regarding this topic and aims to clarify whether intranasal steroid usage in these circumstances should be recommended.

Combining impedance spectroscopy with cyclic voltammetry: measurement and analysis of kinetic parameters for faradaic and nonfaradaic reactions on thin-film gold.

The technique of time-resolved impedance spectroscopy can be combined with dc cyclic voltammetry (CV) to study mechanisms and kinetics of electrochemical reactions at solid-liquid interfaces. Utilization of these techniques in a combined framework, however, is based on a number of specific considerations of measurement procedures and data analysis. The present work discusses certain essential elements of this topic, focusing primarily on the analysis of time-resolved impedance spectra where interdependent dc and ac effects of parallel faradaic and nonfaradaic reactions are present under potentiodynamic conditions. A thin gold film is used as a model experimental system where oxidation and reduction of the sample surface is voltage-controlled both in the presence and in the absence of specifically adsorbing Cl- ions in neutral background electrolytes of NaF. Impedance spectra are recorded under transient conditions of CV, and kinetic parameters based on electrode-equivalent circuit models are obtained as functions of CV scans.

Double-blind comparison of the variability in spontaneous recovery of cisatracurium- and vecuronium-induced neuromuscular block in adult and elderly patients.

BACKGROUND: This study was designed to compare variability in the offset of two neuromuscular blocking agents with different elimination pathways. METHODS: The spontaneous recovery profiles of cisatracurium and vecuronium were compared in adult (18-64 years) and elderly (> or =65 years) patients receiving N2O/O2/fentanyl/propofol anaesthesia. Patients were randomised to receive an initial bolus dose and maintenance doses of 3xED95, respectively, 0.6xED95 for cisatracurium (0.15 and 0.03 mg.kg-1) or 2xED95, respectively, and 0.4xED95 for vecuronium (0.1 and 0.02 mg.kg(-1)), as recommended in their prescribing information. Administration of the study drugs was double-blinded, and neuromuscular transmission was monitored using mechanomyography of the evoked response of the adductor pollicis, following ulnar nerve stimulation. RESULTS: The clinically effective duration (minutes) of the initial bolus dose, defined as the mean time to 25% T1 recovery (+/-SD), for the adult and elderly patients was 53.5+/-9.8 and 57.3+/-11.5 for cisatracurium, respectively, and 34.1+/-9.0 and 47.5+/-14.4 for vecuronium, respectively. The duration of spontaneous sufficient recovery (SSR), defined as the mean (+/-SD) time interval in minutes from 25% T1 recovery to a T4:T1 ratio > or =0.8 after the last bolus dose, for the adult, respectively, elderly patients was 28.3+/-8.0 and 31.7+/-10.0 for cisatracurium and 38.5+/-13.2 and 60.3+/-26.1 for vecuronium. CONCLUSION: Whereas both the clinically effective duration and the duration of SSR are comparable between the adult and the elderly patients receiving cisatracurium, they differ substantially between these two age groups for vecuronium. Furthermore, the variability in offset is significantly lower in patients receiving cisatracurium, especially in the elderly, which may be of particular clinical interest.

The maximum depth of an atracurium neuromuscular block antagonized by edrophonium to effect adequate recovery.

BACKGROUND: The inability of edrophonium to rapidly reverse a deep nondepolarizing neuromuscular block may be due to inadequate dosage or a ceiling effect to antagonism of neuromuscular block by edrophonium. A ceiling effect means that only a certain level of neuromuscular block could be antagonized by edrophonium. Neuromuscular block greater than this could not be completely antagonized irrespective of the dose of edrophonium administered. The purpose of this study was to determine whether a ceiling effect occurred for antagonism of an atracurium-induced neuromuscular block by edrophonium and, if so, the maximum level of block that could be antagonized by edrophonium. METHODS: In 30 adult patients, atracurium was administered to maintain a constant neuromuscular block. The level of block varied between patients. Evoked adductor pollicis twitch tension was monitored. Incremental doses of edrophonium were administered while the infusion of atracurium continued. Increments were given until adequate recovery occurred, as defined by a train-of-four (TOF) ratio > or = 70%, or until no further antagonism of the block could be achieved. The probability of being able to effect adequate recovery by antagonism with edrophonium was determined using a logistic regression model. Cumulative dose-response curves were constructed using the logit transformation of the neuromuscular effect versus the logarithm of the cumulative dose of edrophonium. RESULTS: In 14 patients with a block of 25-77% depression of the first twitch response, antagonism by edrophonium to a TOF ratio > or = 70% was possible, whereas in 16 patients with a 60-92% depression of T1, a TOF ratio > or = 70% was not achievable, indicating that a ceiling effect for antagonism by edrophonium occurred. A block of 67 +/- 3% (mean +/- SE) had a 50% probability of adequate antagonism. In patients in whom block was antagonized to a TOF ratio < 70%, 95% of the peak antagonistic effect occurred with an edrophonium dose of 0.8 +/- 0.33 mg.kg-1 (mean +/- SD). CONCLUSIONS: There is a maximum level of neuromuscular block that can be antagonized by edrophonium to effect adequate recovery. The level corresponds approximately to the reappearance of the fourth response to TOF stimulation. It is probably safest to wait until this level of block occurs before edrophonium is given for reversal. Earlier administration will not hasten recovery.

Pharmacokinetics of alcuronium in children with acyanotic and cyanotic cardiac disease undergoing cardiopulmonary bypass surgery.

The aim of this study was to determine the pharmacokinetic parameters for alcuronium in children with cyanotic or acyanotic congenital cardiac disease undergoing cardiopulmonary bypass surgery and to compare these parameters with previously reported values in children and adults with normal cardiac function. Seven children with acyanotic disease and seven with cyanotic disease were studied. Alcuronium (base) was administered in an initial dosage of 0.25 mg.kg-1 with additional doses as needed to maintain paralysis. Using time averaged data, cyanotic children had lower mean clearance, elimination half-life and volume of distribution at steady state than the acyanotic children; none of these differences was, however, statistically significant. In this study, children with acyanotic and cyanotic cardiac disease undergoing bypass, had a diminished clearance (P < 0.05) and a smaller volume of distribution (P < 0.05) than normal children and a shorter elimination half-life (P < 0.05) than adults. Onset of cardiopulmonary bypass caused an immediate marked decrease in alcuronium plasma concentrations which remained low in the acyanotic children at the completion of bypass.

Delayed onset of alcuronium effect in children with cyanotic congenital heart disease.

The effect of alcuronium dichloride (0.3 mg/kg) was studied in seven normal children (Group A), nine with acyanotic congenital heart disease (Group B) and eight with cyanotic disease (Group C). The onset of action was recorded using an integrated electromyograph and blood samples taken for later estimation of plasma concentrations of the drug. The mean time (SD) taken to 75% suppression of twitch height was 1.3(0.8), 1.7(1.0) and 3.8(2.8) minutes, respectively, in each of the three groups. This was significantly slower in Group C compared with both other groups (P < 0.05). While six of the Group A patients and seven from Group B reached 95% paralysis within ten minutes, only two of the cyanosed children achieved this level of relaxation. However, if times to 95% relaxation were extrapolated, there was no significant difference between the groups at 4.5(3.9), 5.8(5.7) and 10.9(6.5) minutes respectively. There was a weak but statistically significant relationship between haematocrit and time to 75% blockade. Maximum twitch depression was similar in all three groups with plasma concentrations at this time being 1.6(0.7), 1.8(0.5) and 2.3(1.4) micrograms/ml respectively. Again, there was no statistically significant difference between these values. These results confirm that the clinical onset of relaxation is delayed in children with cyanotic congenital heart disease, possibly because of delayed distribution of alcuronium.