Safe and recyclable lithium-ion capacitors using sacrificial organic lithium salt.

Lithium-ion capacitors (LICs) shrewdly combine a lithium-ion battery negative electrode capable of reversibly intercalating lithium cations, namely graphite, together with an electrical double-layer positive electrode, namely activated carbon. However, the beauty of this concept is marred by the lack of a lithium-cation source in the device, thus requiring a specific preliminary charging step. The strategies devised thus far in an attempt to rectify this issue all present drawbacks. Our research uncovers a unique approach based on the use of a lithiated organic material, namely 3,4-dihydroxybenzonitrile dilithium salt. This compound can irreversibly provide lithium cations to the graphite electrode during an initial operando charging step without any negative effects with respect to further operation of the LIC. This method not only restores the low CO2 footprint of LICs, but also possesses far-reaching potential with respect to designing a wide range of greener hybrid devices based on other chemistries, comprising entirely recyclable components.

Proof of ion-pair structures in ammonium-based protic ionic liquids using combined NMR and DFT/PCM-based chemical shift calculations.

The self-assembly of triethylammonium bis(trifluoromethylsulfonyl)imide, i.e. [(C2H5)3NH][TFSI], in chloroform and aqueous solutions has been investigated using 1H NMR spectroscopy and computational (DFT/PCM prediction) methods. We have examined a number of ion pairs formed between the [(C2H5)3NH]+ cation with different conformations of alkyl substituents as well as various dispositions of the multi-site [TFSI]- anion. Based on the agreement between the calculated (DFT) and observed 1H NMR chemical shifts, [(C2H5)3NH][TFSI] in chloroform formed lipophilic complexes with effective N+-HN or N+-HO hydrogen bonding, whereas hydrophilic complexes with Cα-HO and Cα-HF hydrogen bonding are found in aqueous solutions. This study provides a new insight into the self-aggregation of ammonium PILs incorporating the widely used [TFSI]- anion and demonstrates the importance of solvent effects on chemical shifts. The simulations with explicit and implicit dielectric continuum solvents are found to be the most realistic method, yielding a representative ensemble of structures.

Effect of low water content in protic ionic liquid on ions electrosorption in porous carbon: application to electrochemical capacitors.

The effect of low water content (<20, 150, 1000, 10 000 ppm) in triethylammonium bis[(trifluoromethyl)sulfonyl]imide - [(C2H5)3N+H][TFSI-] - protic ionic liquid (PIL) on the performance of activated carbon (AC) electrodes as well as AC/AC electrochemical capacitors (ECs) is reported. Under negative polarization, hydrogen electrosorption onto carbon is enhanced along with the increase of water content in PIL, whereas the resulting desorption peaks are shifted to lower potential values, evidencing lower sorption energy when hydrogen is stored from moisture containing PIL. Cyclic voltammetry (CV) investigations on PIL-based ECs demonstrated that the evolution of the Stern layer nanostructure at positive and negative potentials is asymmetrical. The results revealed comparable electrochemical performance for PIL containing 150 and 1000 ppm of H2O, due to similar operation of the positive electrode, where [TFSI-] anions are adsorbed in the outer Helmholtz plane, and the negative one, where hydrogen is stored through the reduction of the intermediate hydronium cation. By contrast, a cell with "dry" PIL (<20 ppm of water) displayed a distinctive operation due to hydrogen electrosorption directly through reduction of the protonated cation, and selective adsorption of [TFSI-] anions, which occurs thanks to the high polarizability and image force (IF) created by their induced charge. Galvanostatic cycling with potential limitation (GCPL) showed comparable capacitance values whatever the water content in PILs up to 1000 ppm, yet electrochemical impedance spectroscopy (EIS) revealed higher capacitance as well as better retention at higher frequencies with the PIL containing 150 ppm of water. Hence, 150 ppm is reasoned to be an optimal value for diffusion and adsorption of ions. The nature of current collectors (aluminum or stainless steel) has a determining role in their polarization behavior, and consequently the potential range of electrodes as well as ion diffusion into the activated carbon porosity, influencing the observed capacitance values (CEIS/2.0V: 170 vs. 128 F g-1, for Al and SSt, respectively).

Sodium molybdate - an additive of choice for enhancing the performance of AC/AC electrochemical capacitors in a salt aqueous electrolyte.

Sodium molybdate (Na2MoO4) has been used as an additive to 1 mol L(-1) lithium sulfate electrolyte for electrochemical capacitors based on activated carbon (AC) electrodes, in order to reduce the corrosion of stainless steel current collectors. We demonstrate that the MoO4(2-) anions improve the overall capacitance owing to pseudofaradaic processes. In a two-electrode cell, capacitance values of 121 F g(-1) have been achieved up to 1.6 V using 1 mol L(-1) Li2SO4 + 0.1 mol L(-1) Na2MoO4, as compared to 103 F g(-1) when 1 mol L(-1) Li2SO4 is used. Further, by using a two-electrode setup equipped with a reference electrode, we could demonstrate that, at 1.6 V, the positive electrode potential reaches a value of 0.96 V vs. NHE in 1 mol L(-1) Li2SO4, crossing the thermodynamic potential limit of oxygen evolution (Eox = 0.846 V vs. NHE), and the pitting potential, Epit = 0.95 V vs. NHE. By contrast, in 1 mol L(-1) Li2SO4 + 0.1 mol L(-1) Na2MoO4, the pseudofaradaic contribution occurring at -0.05 V vs. NHE due to MoO4(2-) anions drives the positive electrode to reach only 0.798 V vs. NHE. Hence, the oxidation of the AC and corrosion of the stainless steel current collector at the positive electrode are unlikely in Li2SO4 + Na2MoO4 when the capacitor operates at 1.6 V. During potentiostatic floating of the capacitor at 1.6 V for 120 hours in Li2SO4 + Na2MoO4, the capacitance and resistance remain constant at 125 F g(-1) and ~1.0 Ω, respectively, while the resistance increases from 1.4 Ω to 3.1 Ω in Li2SO4. Overall, the addition of MoO4(2-) anions to Li2SO4 aqueous electrolyte allows the capacitance to be enhanced, corrosion of the positive stainless steel current collector to be inhibited and the AC/AC electrochemical capacitor to demonstrate stable performance up to 1.6 V.

Determination of the space between closed multiwalled carbon nanotubes by GCMC simulation of nitrogen adsorption.

We present a new determination method of the porosity created by the adsorption space between closed multiwalled carbon nanotubes. Using the grand canonical Monte Carlo (GCMC) simulation of nitrogen adsorption at 77 K and applying the "Karolina" algorithm, local isotherms were simulated for different distances between parallel nanotubes and finally the equation of the global adsorption isotherm was solved. This methodology leads to a satisfactory description of the experimental nitrogen adsorption data showing that the distance between nanotubes is in the range between 4 and 14 nm.

Thermodynamic and neutron scattering study of hydrogen adsorption in two mesoporous ordered carbons.

Two mesoporous ordered carbon materials (MOCs) have been synthesized from silica templates by using sucrose as the carbon precursor. The textural characterization using Ar, N2, and CO2 adsorption combined with neutron diffraction showed that the two samples exhibit a significant microporous volume close to 0.5 cm3/g and an ordered network of mesopores. For both MCM48 and SBA15 templated carbons, adsorption first proceeds with the filling of micropores and then by the filling of mesopores with an adsorption energy close to the enthalpy of vaporization of bulk hydrogen. The hydrogen isosteric heat of adsorption in the micropores (6-8 kJ/mol) is significantly larger than that on the graphite surface (approximately 4 kJ/mol) but still too small for a reasonable use of these MOCs as hydrogen adsorbents for storage at room temperature. The neutron scattering study showed that the structure at 10 K of the adsorbed deuterium phase is poorly organized; it exhibits short and medium range orders of about 13 angstroms in micropores and about 20 angstroms in mesopores, respectively. The average distance between adsorbed molecules decreases with coverage by about 10%. In the mesopores, the diffracted line is consistent with a pseudohexagonal packing.

Using Global Initiative for Asthma guidelines to assess asthma severity in populations.

The classification of asthmatics into severity categories is a crucial issue for assessing the asthma burden within a community, in which a proportion of patients is currently treated. There is no epidemiological method currently available. The Global Initiative for Asthma (GINA) was used to classify 4,362 patients aged 16-45 yrs (49% males, 42% taking inhaled corticosteroids), enrolled by 545 chest specialists in France with short standardized questionnaires including forced expiratory volume in one second (FEV1) measurements. Two independent GINA classifications were combined, one based only on symptoms and FEVI, and the other based only on current medication, to construct a final "symptom-FEV1 medication" classification. Almost 40% of the patients classed as step 1, 30% of those classed as step 2 and 13% of those classed as step 3 in the initial symptom-FEV1-classification, were allocated to categories of higher severity in the final classification. The approach was validated by showing that the proportions of: 1) patients considered by the physicians as having severe or moderately severe asthma; 2) patients with a history of hospital admission for asthma; and 3) patients with a history of emergency department visits for asthma, increased with severity steps in the final classification, for each step of the two initial independent classifications. The treatment manage plan in the Global Initiative for Asthma was not developed for assessing severity of asthma but rather to describe the recommended therapy for asthma with different severity. This is the first attempt to assess the severity of asthma in a large population of asthmatics mostly taking treatment, based on the Global Initiative for Asthma guidelines. The authors propose this simple and pragmatic procedure for a potential classification which should be put to the test in other studies.

[Asthma in private pneumology practice]. / Asthme en pneumologie libérale.

We assessed asthma severity in patients attending private practice chest specialists, studied the factors related to classification by physicians, and described medications prescribed. 545 chest specialists scattered throughout France, included the patients examined from 3 to 28 May 1993 (N = 14,865). Besides a classification of asthma severity in four classes (mild, moderate, moderately severe, and severe), questionnaires included 20 questions on the history and characteristics of asthma, lung function level and medications prescribed. The proportion of mild asthmatics was 55% among the 3,620 children (aged 6 to 15 years), 42% among the 6,479 young adults (aged 16 to 45 years), and 18% among the 4,766 older adults (aged 46 to 75 years). Followed-up patients were considered more severe than new patients among adults, but not among children. The factors related to asthma severity were impaired FEV1, history of hospitalization, critical care and emergency visits for asthma, limitation of physical activities, and, to a latter extent, symptoms between exacerbations, frequent asthma attacks and daily use of beta 2-agonists. Anti-inflammatory drugs were prescribed to practically all patients from grade 2 (moderate): steroids increased whereas sodium cromoglycate and nedocromil decreased with increasing severity. This study provides a valuable estimate of the classification and medications prescribed to asthmatic patients examined by 50% of private practice chest specialists in France.

Is intrapartum vibratory acoustic stimulation a valid alternative to fetal scalp pH determination?

OBJECTIVES: To determine the association between fetal heart rate accelerations, whether spontaneous or induced by vibratory acoustic stimulation, and subsequent scalp pH values in presence of a suspicious intrapartum fetal heart rate tracing, and thereby assess the ability of accelerations to predict a concurrent normal fetal scalp blood pH. DESIGN: Prospective observational study of 253 labours involving 421 pH samples. SETTING: Tertiary care university hospital of Genoeva. INTERVENTION: Vibratory acoustic stimulation through the maternal abdominal wall for five seconds prior to fetal blood sampling. MAIN OUTCOME MEASURES: Spontaneous fetal heart rate reactivity (accelerations) in the 10 min preceding vibratory acoustic stimulation, vibratory acoustic-induced reactivity prior to fetal blood sampling, and scalp pH value. RESULTS: The positive predictive value of a reactive fetal heart rate response after vibratory acoustic stimulation was 78% (95% CI 73-84%) and 97% (95% CI 94-99%) for scalp pH values of > 7.25 and > or = 7.20, respectively. Similar observations occurred with spontaneous reactivity. Of concern, 7 out of 31 (23%) occasions where the scalp blood pH was less than 7.20 appeared to be associated with a normal fetal heart rate response to vibratory acoustic stimulation. CONCLUSION: Fetal heart rate acceleration induced by vibratory acoustic stimulation was significantly associated with a normal scalp blood pH higher than 7.25. However, vibratory acoustic stimulation offers no advantage over observation of spontaneous fetal heart rate tracings and cannot safely replace fetal blood sampling during labour.

Nonclosure of the visceral and parietal peritoneum at caesarean section: a randomised controlled trial.

OBJECTIVE: To assess the short term morbidity of nonclosure of the peritoneum at caesarean section. DESIGN: Women undergoing a lower segment caesarean section were randomly allocated to either closure or nonclosure of the visceral and parietal peritoneum. SETTING: Tertiary Care University Hospital of Geneva. MAIN OUTCOME MEASURES: Length of post-operative hospital stay. Other outcomes include maternal pain as assessed by both a visual analogue scale and the amount of post-operative analgesics administered, post-operative ileus, and febrile morbidity. Operative time was recorded. RESULTS: We allocated 137 women to the nonclosure group and 143 to the closure group. Population characteristics were similar between groups. The mean length of hospital stay was 6.5 (SD 1.9) days for the nonclosure group and 6.8 (SD 2.2) days for the closure group (P = 0.21). No differences were found in the level of post-operative pain, the number of analgesic doses given, nor in the proportion with febrile morbidity. Post-operative ileus resolved later in the closure group (P = 0.006). The mean operative time was shorter by 6 min (P = 0.006) in the nonclosure group. CONCLUSIONS: Short term post-operative morbidity and maternal pain are not increased by a shorter and more simple surgical procedure in which the peritoneum is left unsutured.

Successful term pregnancy after Mustard operation for transposition of the great arteries.

Transposition of the great arteries is a complex cardiac malformation with poor prognosis without surgical correction. Since the introduction of surgical procedures such as the intra-auricular reorientation of the venous return (Mustard procedure), an increasing number of patients may reach adulthood and experience pregnancy. Because long-term complications after the Mustard operation include systemic heart failure, arrhythmias, venous return stenosis and pulmonary edema, hemodynamic changes during pregnancy and delivery may potentially engender life-threatening complications in these patients. We report the case of a 24-year-old primigravida who underwent a Mustard procedure at the age of 2 years for transposition of the great vessels, and who carried out a full-term pregnancy. The pregnancy was uneventful until the 34th week, when the woman developed signs of moderate right ventricular failure and frequent episodes of accelerated junctional rhythm. Digitalisation improved symptoms and elicited return to normal sinus rhythm. The patient delivered at term by elective cesarean section, under close hemodynamic monitoring.