Screening Methodology for the Efficient Pairing of Ionic Liquids and Carbonaceous Electrodes Applied to Electric Energy Storage

A model is presented that correlates the measured electric capacitance with the energy that comprises the desolvation, dissociation and adsorption energy of an ionic liquid into carbonaceous electrode (represented by single-wall carbon nanotubes). An original methodology is presented that allows for the calculation of the adsorption energy of ions in a host system that does not necessarily compensate the total charge of the adsorbed ions, leaving an overall net charge. To obtain overall negative (favorable) energies, adsorption energies need to overcome the energy cost for desolvation of the ion pair and its dissociation into individual ions. Smaller ions, such as BF4 −, generally show larger dissociation energies than anions such as PF6 − or TFSI−. Adsorption energies gradually increase with decreasing pore size of the CNT and show a maximum when the pore size is slightly greater than the dimensions of the adsorbed ion and the attractive van der Waals forces dominate the interaction. At smaller pore diameters, the adsorption energy sharply declines and becomes repulsive as a result of geometry deformations of the ion. Only for those diameters where the adsorption reaches maximum values is the adsorption energy sufficiently negative to balance the positive dissociation and desolvation energies. We present for each ion (and ionic liquid) what the most adequate electrode pore size should be for maximum capacitance

Reaction Kinetics of a Selected Number of Elementary Processes Involved in the Thermal Decomposition of 9-Methylphenanthrene Using Density Functional Theory

With the use of general transition state theory and density functional theory, six reference reactions that are thought to play an essential role in the thermal cracking process of 9-methylphenanthrene have been studied. At the uB3LYP/6-31G(d,p) level, the transition state structures could be located on the 0 K potential energy surface for the three propagation reactions which induce no net creation/annihilation of radicals, and the calculated activation energies and preexponential frequency factor generally correspond well to experimental values. The transition states for two termination reactions were determined by replacement of a phenanthrenic by a phenylic aromatic moiety; it followed that such model reactions represent well systems with larger aromatic units. Only for the initiation reaction the transition state could not be located; in this case the activation energy was approximated by the change in overall enthalpy

Long-term survival and secondary procedures after open or endovascular repair of abdominal aortic aneurysms

Objective: Randomized trials have shown an initial survival benefit of endovascular over conventional open abdominal aortic aneurysm repair but no long-term difference up to 6 years after repair. Longer follow-up may be required to demonstrate the cumulative negative impact on survival of higher reintervention rates associated with endovascular repair. Methods: We updated the results of the Dutch Randomized Endovascular Aneurysm Management (DREAM) trial, a multicenter, randomized controlled trial comparing open with endovascular aneurysm repair, up to 15 years of follow-up. Survival and reinterventions were analyzed on an intention-to-treat basis. Causes of death and secondary interventions were compared by use of an events per person-year analysis. Results: There were 178 patients randomized to open and 173 to endovascular repair. Twelve years after randomization, the cumulative overall survival rates were 42.2% for open and 38.5% for endovascular repair, for a difference of 3.7 percentage points (95% confidence interval, -6.7 to 14.1; P = .48). The cumulative rates of freedom from reintervention were 78.9% for open repair and 62.2% for endovascular repair, for a difference of 16.7 percentage points (95% confidence interval, 5.8-27.6; P = .01). No differences were observed in causes of death. Cardiovascular and malignant disease account for the majority of deaths after prolonged follow-up. Conclusions: During 12 years of follow-up, there was no survival difference between patients who underwent open or endovascular abdominal aortic aneurysm repair, despite a continuously increasing number of reinterventions in the endovascular repair group. Endograft durability and the need for continued endograft surveillance remain key issues