Switching electrostatic

We mentioned the MORE apparatus which offers some of the features of pulsed beam data collection for continuous beams. The acronym MORE stands for Muons On REquest. Its basic feature is a fast-switching electrostatic beam deflector (for surface muons only) which extracts one muon out of the beam and sends it towards a pSR spectrometer. After 10T i the system is ready for the next muon to be extracted. This ensrues that at any time only one muon is in the sample and the muon gate circuitry is not needed. Time resolution is not blurred by a finite pulse width when compared to a pulsed beam, but count rates are lower. The system runs parasitically on a beam line which delivers sruface muons to a conventional spectrometer when the beam deflector is off (which is most of the time). 

Caution C omparing the shifted constant dielectric to a constant dielectric function without a cutoff shows that the sh ifted dielectric, iin like a switch in g fun ction, perturbs the en tire electrostatic energy curve, not only the region near the cnioff. 

In an attempt to remedy truncation problems, a shifting potential multiplies the nonbonded electrostatic potential by a function that goes to zero. That is, the potential is shifted to zero at the cutoff Roff. Unlike the switching function, the shifted potential does not apply to van der Waals interactions. 

The switching function used by HyperChem, called switch below, alters the nonbonded energy (van der Waals, hydrogen bond, and electrostatic) in the following way ... 

Display electrostatic potential maps for water, ethanol, formic acid and propanoic acid, and examine the value of the electrostatic potential at the most electron-poor site. What causes a larger change in electrostatic potential, switching the alkyl group for H, or changing the structure of the acidic functional group ... 

Zebiihr et al. (29) developed an automated system for determining PAHs, PCBs and PCDD/Fs by using an aminopropyl silica column coupled to a porous graphitic carbon column. This method gives five fractions, i.e. aliphatic and monoaromatic hydrocarbons, polycyclic aromatic hydrocarbons, PCBs with two or more ortho-chlorines, mono-ort/io PCBs, and non-ortho PCBs and PCDD/Fs. This method employed five switching valves and was successfully used with extracts of sediments, biological samples and electrostatic filter precipitates. 

Figure 35. Schematic representation of the reversible variation of volume associated with the electrochemical switching of polypyrrole. Changes in free volume are mainly due to two effects electrostatic repulsions between fixed positive charges and exchange of cations, anions, and solvent molecules between the polymer and the solution. (Reprinted from T. F. Otero, H.-J. Grande, and J. Rodriguez, J. Phys. Chem. 101, 3688, 1997, Figs. 1, 3,6, 7, 13. Copyright 1997. Reprinted with the permission of the American Chemical Society.)...

How is the mobility of the Rieske cluster within the bci complex and the switch between different positional states related to (and controlled by) the electrostatic properties of the Rieske cluster ... 

In the present work, we shall investigate the problem of the amount of correlation accounted for in the DF formalism by comparing the molecular electrostatic potentials (MEPs) and dipole moments of CO and N2O calculated by DF and ab initio methods. It is indeed well known that the calculated dipole moment rf these compounds is critically dependent on the level of theory implemented and, in particular, that introduction of correlation is essential for an accurate prediction [13,14]. As the MEP property reflects reliably the partial charges distribution on the atoms of the molecule, it is expected that the MEP will exhibit a similar dependence and that its gross features correlate with the changes in the value of dipole moment when switching from one level of theory to the other. Such a behavior has indeed been reported recently by Luque et al. [15], but their study is limited to the ab initio method and we found it worthwhile to extend it to the DF formalism. Finally, the proton affinity and the site of protonation of N2O, as calculated by both DF and ab initio methods, will be reported. 

Switched van der Waals and electrostatic functions, with switching... 

McLaughlin, S., and Aderem, A. (1995). The myristoyl-electrostatic switch a modulator of reversible protein-membrane interactions. Trends Biochem. Sci. 20, 272—276. 

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