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Topic: Electric field gradient

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	Electric field - Wikipedia, the free encyclopedia
		Electric fields are composed of photons and contain electrical energy with energy density proportional to the square of the field intensity.
		The electric field is a vector quantity, and the electric field strength is the magnitude of this vector.
		The electric field is equal to the negative gradient of the electric potential.
	en.wikipedia.org /wiki/Electric_field (902 words)

	Encyclopedia: Electric field gradient (Site not responding. Last check: 2007-10-16)
		Mathematically, the electric field gradient (EFG) is the hessian matrix (the matrix of the second derivatives) of the electrical potential V: In mathematics, the Hessian matrix is the square matrix of second partial derivatives of a scalar-valued function.
		Electrical potential is the potential energy per unit charge associated with a static (time-invariant) electric field, also called the electrostatic potential or the electric potential, typically measured in volts.
		The EFG is non-zero only if the charges surrounding the nucleus violate cubic symmetry and therefore generate an inhomogeneous electric field at the position of the nucleus.
	www.nationmaster.com /encyclopedia/Electric-field-gradient (488 words)

	Electric field - Encyclopedia.WorldSearch (Site not responding. Last check: 2007-10-16)
		The units of the electric field are Newtons/Coulomb or Volts/Meter (both are equivalent).
		The electric field is equal to minus the gradient of the electric potential.
		Electric Fields of the Brain: The Neurophysics of Eeg
	encyclopedia.worldsearch.com /electric_field.htm (590 words)

	MEASUREMENTS OF THE ELECTRIC FIELD GRADIENT IN A BLIZZARD
		When an electrically charged particle moves through an electric field, it is subject to a force which has a magnitude equal to the particles charge times the magnitude of the electric field.
		The electric field probe was mounted on a tripod equipped with a ten-turn potentiometer.
		The electric field probe was connected by 15-m fiber-optic cables to the receiver unit, housed in the mobile laboratory.
	www.avalanche.org /~moonstone/issw%2094'/measurements%20of%20the%20electric%20field%20gradient%20in%20a%20blizzard.htm (2099 words)

	Jiwaji University (Site not responding. Last check: 2007-10-16)
		Electric field gradient in dilute alloys of copper, Phys.
		Electric field gradient in dilute alloys of Aluminium, Phys.
		Electric field gradient in dilute transitional alloys of Cu and A1, Cand.
	www.jiwaji.edu /vc/publication.htm (2693 words)

	Gravity Electric field gradient (Site not responding. Last check: 2007-10-16)
		Note that a spherical capacitor is the perfect shape to generate a non linear electric field gradient between its centre electrode and its inner surface.
		By applying an electric field across a spherical capacitor filled with a dielectric liquid, a body force analogous to gravity is generated around the fluid.
		As illustrated above, a dielectric in space is always drawn from the weaker to the stronger field, and the force is proportional to the gradient of the square of the electric field.
	bel.150m.com /f-efield.htm (2785 words)

	Definition of Diffusion
		There is a concentration gradient in the balloon wall because the balloon was filled up with helium, and thus there is plenty of helium on the inside, but there is relatively little helium on the outside, because helium is not a major component of air.
		The rate of transport is governed by the electrical conductivity of the conductor and the electric field.
		The gradient in this case is between the liquid in contact with the surface (which isn't moving at all and has zero momentum) and the liquid far away from the wall, which has momentum proportional to the speed at which it is flowing.
	www.wordiq.com /definition/Diffusion (849 words)

	Electric field gradient excited liquid crystal cell having bistability - Patent 4617646
		More specifically, the field configuration involved with the first state of the cell, is a non-uniform or "fringe" electric field; while the additional application of a voltage pulse to the third electrode results in a uniform field because of the configuration of the third electrode.
		The reason for this capability is because of the different electric fields that are applied to the liquid crystal material; specifically, a fringe field, or non-uniform field, is selectively applied by appropriate selection of voltage pulses supplied to the separate electrodes; also, a uniform field is applied at appropriate times.
		The electric field generated by the column voltage pulse on the clear state is screened by the mesh row electrodes.
	www.freepatentsonline.com /4617646.html (4392 words)

	efm
		Electric and magnetic modes work similar to the fashion of tapping mode, but rather than from a physical obstruction on the surface of the sample, the tip’s oscillations are changed due to an electric or magnetic force emanating from the sample.
		The first images electric field gradients on the surface of the sample, and the second images the surface potential of the sample.
		As the tip moves over an attractive electric field gradient, it is pulled toward the sample, which increases the amplitude of the oscillations and decreases the resonance frequency.
	members.cox.net /scottygilmore/afm/efm.html (1644 words)

	Electric field Article, Electricfield Information (Site not responding. Last check: 2007-10-16)
		In physics, an electric field is an effect produced by an electric charge that exerts a force on objects in its vicinity.
		If more than one charge is present, the total electric field at any pointis equal to the vector sum of the respective electric fields that each objectwould create in the absence of the others.
		The electric field can also be thought of as the gradient of the electric potential.
	www.anoca.org /charge/equation/electric_field.html (420 words)

	Gradient
		Gradient is a mathematical concept to measure the change of a scalar function over a specified distance and along a given direction.
		The gradient of the gravitational or electrical potential is the field, which is equal to the force by multiplying an appropriate coupling conatant.
		The gradient of the electric potential defines the electric field: E = -dV/dr n.
	www.universe-review.ca /R10-11-gradient.htm (479 words)

	Experiment 1 (Site not responding. Last check: 2007-10-16)
		Results of this experiment show that when an asymmetric field of 20kV is supplied across 40mm, a change in permeability of -0.03% relative to that of air is generated within the electric field lines, and is maintained as long as the electric field is present.
		Dielectrophoresis is the term used to describe the polarisation and associated motion induced in particles by a non-uniform electric field.
		Thus if one considers the electric field gradient in a lifter, with its high electric field gradient near the top wire, one would measure an increase in K in the region very near the wire, but an overall lower K in the rest of the lower electric field gradient.
	bel.150m.com /exp01.htm (1928 words)

	Electric Field from Voltage (Site not responding. Last check: 2007-10-16)
		One of the values of calculating the scalar electric potential (voltage) is that the electric field can be calculated from it.
		The component of electric field in any direction is the negative of rate of change of the potential in that direction.
		If the differential voltage change is calculated along a direction ds, then it is seen to be equal to the electric field component in that direction times the distance ds.
	hyperphysics.phy-astr.gsu.edu /hbase/electric/efromv.html (143 words)

	College of Physical and Mathematical Sciences : Spring Research Presentation (Site not responding. Last check: 2007-10-16)
		Electric field gradient focusing (EFGF) is an equilibrium-gradient separation technique in which an electric field gradient and an opposing hydrodynamic flow are used to separate and concentrate analytes.
		The ionically conductive polymer hydrogel is cast into a thin slab with a changing cross-section (wide at the low field end and narrow at the high field end) normal to the direction of current flow.
		The concentration gradients produced steeper than expected electric field gradients and degraded the separation performance.
	cpms.byu.edu /springresearch/abstractentry.php?id=84 (251 words)

	Does a non-linear electric field generate gravity
		The downward ionic current is that part of the ionosphere-earth current contributed by the electrical conduction of the atmosphere itself in fair weather conditions.
		Specifically, he saw that a directionalised Grad E produces an acceleration field, similar in all respects to gravitational field, and that this field, when superimposed on a gravitational acceleration field, will either add up or reduce the observed gravitational effect on the masses contained therein.
		Applying this directly to electric lines of force, we can clearly visualize the resulting force, which results in a force on a dielectric which tends towards the highest electric field gradient, independently of the polarity.
	www.blazelabs.com /f-efield.asp (3292 words)

	Microsystem Application Example - Micro TIP Field Emitter
		A circular anode ring is placed in proximity to the tip so that when a potential difference of a few in the range 10 -100V DC is applied an extremely large electric field gradient is produced at the tip The electric field gradient is proportional to the sharpness of the tip.
		For this device the tip is so small, a large enough field gradient is produced to cause electrons in the bulk material of the tip to be physically "stripped off".
		Once the electrons are "out" of the tip the electrostatic field exerts a force causing the electrons to follow extended trajectories away from the cathode.
	www.ansys.com /industries/mems/mems-application-field-emitter.asp (716 words)

	Electric field gradient at the nucleus, nuclear quadrupole coupling constant
		Electric field gradient at the nucleus, nuclear quadrupole coupling constant
		For comparison with experimental data derived from the hyperfine structure of rotational spectra, tensor components defined in the principal axes of inertia system should be used.
		It is proportional to EFG, a preceding analysis (Total non-diagonalized EFG Tensor, EFG Principal axis) may be printed if needed.
	folk.uio.no /michalj/node29.html (223 words)

	Research Publication
		Here we analyze whether this error is systematic or not by comparing DFT electric field gradients for a number of diatomic compounds MX.
		From experimental nuclear quadrupole coupling data and electric field gradient calculations for each of the three sets (ScX, CuX and GaX) the nuclear quadrupole moment at the metal can be deduced at a specific DFT level.
		Using this modified B3LYP functional we obtain reasonable results for the copper electric field gradient in CuF3, a case where the Cu(3d) core is strongly polarized by the fluorine ligands.
	www.che.auckland.ac.nz /research/abstract.aspx?pubid=1712 (263 words)

	Drift mechanisms [Oulu] (Site not responding. Last check: 2007-10-16)
		Both drifts are perpendicular to B, and in addition the gradient drift is perpendicular to the field gradient, and the curvature drift to the plane in which the magnetic field is curved.
		Closely related to the gradient drift is the fact that, when magnetic field has longitudinal variation (i.e., convergence or divergence of the field lines), both positively and negatively charged particles are accelerated in the direction of decreasing magnetic field.
		When the frequency of the changing electric field is the same as the particle's cyclotron frequency, a cyclotron resonance is created.
	www.oulu.fi /~spaceweb/textbook/drift.html (553 words)

	Optical Frequency Standards and Metrology at NPL: Quadrupole shift in 88Sr+ (Site not responding. Last check: 2007-10-16)
		are the dc and ac components of the electric quadrupole field gradient respectively.
		includes not only the quadrupole field gradient arising from the voltages applied to the outer endcap electrodes, but also stray electric field gradients due to contact potentials arising from strontium metal deposited on the trap electrodes, or due to dc voltages applied to the compensation electrodes.
		The relationship between mean endcap voltage and dc quadrupole field gradient can be expected to change slowly over timescales of several months, due to changes in contact potentials arising from strontium metal deposits and the radial compensation electrode voltages required to minimize the micromotion of the ion.
	www.npl.co.uk /optical_frequency_standards/npl_research/ion_trapping/strontium_quadrupole.html (611 words)

	AC Electrokinetics: Applications for Nanotechnology (Site not responding. Last check: 2007-10-16)
		Due to the inhomogeneous nature of the electric field, the force is greater in the side facing the point than that on the side facing the plane, and there is net motion towards the point electrode.
		This results in non-zero angle between field and dipole, which induces a torque in the body and causes it to rotate asynchronously with the field; the rotation can be with or against the direction of rotation of the field, depending of whether the lag is less or more than 180°.
		Firstly, the relationship with the electric field is as a function of the square of the electric field rather than of the gradient of the square of the electric field.
	www.foresight.org /Conferences/MNT7/Papers/Hughes (5717 words)

	Electric field gradient -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-10-16)
		Mathematically, the electric field gradient (EFG) is the (Click link for more info and facts about hessian matrix) hessian matrix (the matrix of the second derivatives) of
		The EFG is non-zero only if the charges surrounding the nucleus violate cubic symmetry and therefore generate an inhomogeneous (A field of force surrounding a charged particle) electric field at the position of the nucleus.
		field surrounding it, thus the electric field gradient can be
	www.absoluteastronomy.com /encyclopedia/e/el/electric_field_gradient.htm (171 words)

	deMon-NMR1p2 User Manual: Electric Field Gradient Module (Site not responding. Last check: 2007-10-16)
		To run EFG calculations for a close-shell system, you have to have the line NMROUT POTNUM ON EXCNUM OFF in your deMon input (exactly as for chemical shift calculations).
		If this file is empty, all parameters are taken by default, that is a close-shell system is assumed; EGF is calculated for all nuclei, the NQM values are taken from the "default" table.
		The EFG and NQC tensors are printed in both molecular (GENERAL) axis and principal axis.
	www.demon-software.com /public_html/NMR/EFT.html (425 words)

	Dielectrophoretic dynamic light-scattering (DDLS) spectroscopy -- Halaka 100 (18): 10164 -- Proceedings of the National ... (Site not responding. Last check: 2007-10-16)
		field gradient thus is influenced by intrinsic and external
		An electric field gradient was generated by displacing the electrode tips (Inset, details arrangement).
		For media with high electrical conductivity, a terminating resistor was used in series with the cell.
	www.pnas.org /cgi/content/full/100/18/10164 (3336 words)

	Electrodeless Dielectrophoresis of Single- and Double-Stranded DNA -- Chou et al. 83 (4): 2170 -- Biophysical Journal (Site not responding. Last check: 2007-10-16)
		2 is due to the force a polarizable object feels in a field gradient.
		DNA at pH 7 are electrically neutral in the absence of an external
		on a polyelectrolyte in the presence of a electric field is proportional
	www.biophysj.org /cgi/content/full/83/4/2170 (5452 words)

	Electrostatics Explains the Shift in VDAC Gating with Salt Activity Gradient -- Levadny et al. 82 (4): 1773 -- ...
		gradient is the cause of the shift in the open-state probability
		The double-ended arrow shows the shift of the peak along the voltage axis as the salt gradient was increased from 10- to 20-fold.
		Redistribution of the electric field within the pore contributes to the voltage dependence of mitochondrial porin channel.
	www.biophysj.org /cgi/content/full/82/4/1773 (5441 words)

	Materials and Surface Characterization
		The Frank elastic constants* are determined by applying an external field to the liquid crystal cell in a direction perpendicular to the director orientation fixed by surface anchoring forces.
		The electric field technique requires that wires be placed in the planar cell perpendicular to the rubbing direction.
		If the magnetic field is parallel to the pretilt angle at the surface, there will be no change in the properties of the liquid crystal in the cell, hence no change in the measured retardation.
	www.lci.kent.edu /Characterization/MSC.html (1792 words)

	ELECTRIC FIELD INDUCED SELF ASSEMBLY
		A dielectric fluid placed in between to conductive plates experiences a force in an applied electric field gradient across the plates, which can induce a diffusive surface instability and self construction of the fluid surface.
		Finite element modeling of the electrical potential distribution and the minimum wavelength of the surface features was conducted.
		The capacitor structure was quenched to observe the structures using optical microscopy and atomic force microscopy.
	www.nsti.org /Nanotech2003/showabstract.html?absno=296 (543 words)

	Math Forum - Ask Dr. Math
		The gradient vector is (df/dx, df/dy), where the "d" should really be the symbol for partial derivative.
		There are lots of mathematical techniques to "follow the gradient" on a surface to find local maxima (or you can go in the opposite direction to find the minimun).
		If the surface represents the strengh of an electric field, then the gradient represents the direction and magnitude of force that a charged particle in that field will experience.
	www.mathforum.org /library/drmath/view/53584.html (273 words)

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