Search results for "electrostatic"
showing 10 items of 134 documents
Towards controlling PCDD/F production in a multi-fuel fired BFB boiler using two sulfur addition strategies. Part I: Experimental campaign and results
2014
Abstract Levels of PCDD/F production in a 140 MW th bubbling fluidized bed boiler were measured. The boiler uses solid recovered fuel, bark and sludge. Homologue distribution patterns suggest the de novo mechanism is the main pathway for the generation of dioxin and furans in the post combustion zones of the boiler. Two modes of sulfur addition were tested to induce the deactivation of Cu which has been identified as the prime catalyst of this mechanism. First, S-pellet promoted Cu sulfation as supported by aerosol sampling data and resulted in a decrease in PCDD/F levels. The second approach was adding sulfur through peat; this resulted in an increase in PCDD/F concentration. Factors such …
Strong N−X⋅⋅⋅O−N Halogen Bonds: A Comprehensive Study on N‐Halosaccharin Pyridine N ‐Oxide Complexes
2019
A study of the strong N-X⋅⋅⋅- O-N+ (X=I, Br) halogen bonding interactions reports 2×27 donor×acceptor complexes of N-halosaccharins and pyridine N-oxides (PyNO). DFT calculations were used to investigate the X⋅⋅⋅O halogen bond (XB) interaction energies in 54 complexes. A simplified computationally fast electrostatic model was developed for predicting the X⋅⋅⋅O XBs. The XB interaction energies vary from -47.5 to -120.3 kJ mol-1 ; the strongest N-I⋅⋅⋅- O-N+ XBs approaching those of 3-center-4-electron [N-I-N]+ halogen-bonded systems (ca. 160 kJ mol-1 ). 1 H NMR association constants (KXB ) determined in CDCl3 and [D6 ]acetone vary from 2.0×100 to >108 m-1 and correlate well with the calculat…
Lennard-Jones Parameters for B3LYP/CHARMM27 QM/MM Modeling of Nucleic Acid Bases.
2015
Combined quantum mechanics/molecular mechanics (QM/MM) methods allow computations on chemical events in large molecular systems. Here, we have tested the suitability of the standard CHARMM27 forcefield Lennard-Jones van der Waals (vdW) parameters for the treatment of nucleic acid bases in QM/MM calculations at the B3LYP/6-311+G(d,p)-CHARMM27 level. Alternative parameters were also tested by comparing the QM/MM hydrogen bond lengths and interaction energies with full QM [B3LYP/6-311+G(d,p)] results. The optimization of vdW parameters for nucleic acid bases is challenging because of the likelihood of multiple hydrogen bonds between the nucleic acid base and a water molecule. Two sets of optim…
An AC-assisted single-nanowire electromechanical switch
2013
A unique two-source controlled nanoelectromechanical switch has been assembled from individual, single-clamped Ge nanowires. The switching behaviour was achieved by superimposing the control signals of specific frequencies to the electrostatic potential of the output terminals, eliminating the need for an additional gate electrode. Using an in situ manipulation technique inside a scanning electron microscope, we demonstrate that the pull-out force required to overcome adhesion at the contact can be significantly reduced by exciting mechanical resonant modes within the nanowire.
Neutral one-dimensional metal chains consisting of alternating anionic and cationic rhodium complexes.
2012
The metallophilic interactions were investigated within chains of oppositely charged rhodium carbonyl complexes. The cationic [Rh(CO)(2)(L)](+) (L = 2,2'-bipyridine and 1,10-phenanthroline) and anionic [RhCl(2)(CO)(2)](-) units were self-assembled into one dimensional rhodium chains supported by electrostatic interactions. The array of Rh centers in {[Rh(CO)(2)(2,2'-bpy)][RhCl(2)(CO)(2)]}(n) was found to be nearly linear with a Rh···Rh···Rh angle of 170.927(11)° and Rh···Rh distances of 3.3174(5) Å and 3.4116(5) Å. The crystal structure of {[Rh(CO)(2)(1,10-phen)][RhCl(2)(CO)(2)]} consisted of two sets of crystallographically independent chains with slightly different Rh···Rh···Rh angles (17…
Collision induced fragmentations of multiply charged sodium bis(2-ethylhexyl)-sulfosuccinate aggregates in gas phase: neutral loss versus charge sepa…
2016
Abstract Stability and fragmentation patterns of multicharged aggregates of sodium bis(2-ethylhexyl)-sulfosuccinate (NaAOT) in gas phase have been investigated by ion mobility mass spectrometry (IM-MS) and tandem mass spectrometry (MS-MS). Positively doubly charged NaAOT aggregates show at low collision energy a preference for the loss of NaAOT molecules, whereas fragmentation through charge separation process is favored at higher collision energy. By increasing the charge state of the aggregates, the fragmentation through charge separation tends to predominate especially at low aggregation number and only charge separation fragmentation is observed for positively quadruply charged species.…
Self-consistent continuum solvation (SCCS): the case of charged systems.
2013
The recently developed self-consistent continuum solvation model (SCCS) [O. Andreussi, I. Dabo, and N. Marzari, J. Chem. Phys. 136, 064102 (2012)] is applied here to charged species in aqueous solutions. Describing ions in solution represents a great challenge because of the large electrostatic interactions between the solute and the solvent. The SCCS model is tested over 106 monocharged species, both cations and anions, and we demonstrate its flexibility, notwithstanding its much reduced set of parameters, to describe charged species in solution. Remarkably low mean absolute errors are obtained with values of 2.27 and 5.54 kcal/mol for cations and anions, respectively. These results are co…
Measuring electrostatic double-layer forces on HOPG at high surface potentials
1999
Abstract The aim of this study was to investigate surface forces in aqueous electrolyte solutions between surfaces with high electric potentials. Therefore the force between a surface of highly oriented pyrolytic graphite (HOPG) and a silicon nitride tip of an atomic force microscope was measured. Various electric potentials by a counter electrode were applied to the HOPG, which served as working electrode. As predicted by the Poisson–Boltzmann theory the electrostatic double-layer force changed only in a narrow potential range of ≈300 mV. At high negative sample potentials, where the negatively charged tip was repelled from the sample, the force saturated. At positive potentials an attract…
Single-molecule switching with non-contact atomic force microscopy
2011
We report upon controlled switching of a single 3,4,9,10-perylene tetracarboxylic diimide derivative molecule on a rutile TiO(2)(110) surface using a non-contact atomic force microscope at room temperature. After submonolayer deposition, the molecules adsorb tilted on the bridging oxygen row. Individual molecules can be manipulated by the atomic force microscope tip in a well-controlled manner. The molecules are switched from one side of the row to the other using a simple approach, taking benefit of the sample tilt and the topography of the titania substrate. From density functional theory investigations we obtain the adsorption energies of different positions of the molecule. These adsorp…
Apolipoprotein CI is a physiological regulator of cholesteryl ester transfer protein activity in human plasma but not in rabbit plasma
2009
Plasma cholesteryl ester transfer protein (CETP) activity is high in rabbits, intermediate in humans, and nondetectable in rodents. Human apolipoprotein CI (apoCI) was found to be a potent inhibitor of CETP. The aim of this study was to compare the ability of rabbit and human apoCI to modulate the interaction of CETP with HDLs and to evaluate to which extent apoCI contributes to plasma cholesteryl ester transfer rate in normolipidemic humans and rabbits. Rabbit apoCI gene was cloned and sequenced, rabbit and human apoCI were purified to homogeneity, and their ability to modify the surface charge properties and the CETP inhibitory potential of HDL were compared. It is demonstrated that unlik…