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The fine structures of proteins, such as the positions of hydrogen atoms, distributions of valence electrons and orientations of bound waters, are critical factors for determining the dynamic and chemical properties of proteins. Such information cannot be obtained by conventional protein X-ray analyses at 3.0-1.5 Å resolution, in which amino acids are fitted into atomically unresolved electron-density maps and refinement calculations are performed under strong restraints (1,2). Therefore, we usually supplement the information on hydrogen atoms and valence electrons in proteins with preexisting common knowledge obtained by chemistry in small molecules. However, even now, computational calculation of such information with quantum chemistry also tends to be difficult, especially for polynuclear metalloproteins (3). Here we report a charge-density analysis of the high-potential iron-sulfur protein from the thermophilic purple bacterium Thermochromatium tepidum using X-ray data at an ultra-high resolution of 0.48 Å. Residual electron densities in the conventional refinement are assigned as valence electrons in the multipolar refinement. Iron 3d and sulfur 3p electron densities of the [Fe.sub.4] [S.sub.4] cluster are visualized around the atoms. Such information provides the most detailed view of the valence electrons of the metal complex in the protein. The asymmetry of the iron-sulfur cluster and the protein environment suggests the structural basis of charge storing on electron transfer. Our charge-density analysis reveals many fine features around the metal complex for the first time, and will enable further theoretical and experimental studies of metalloproteins., Fine structural information, including the positions of hydrogen atoms and distributions of valence electrons, is essential for understanding the full properties of protein molecules; in particular, of electron transfer metalloproteins [...]

The quantum condensate of Cooper pairs forming a superconductor was originally conceived as being translationally invariant. In theory, however, pairs can exist with finite momentum Q, thus generating a state [...]

We address the electrostatic problem of a thin, curved, and cylindrical conductor (a conducting filament) and show that the corresponding linear charge density slowly tends to uniformity as the inverse of the logarithm of a characteristic parameter, which is the ratio of the diameter to the smaller of the length and minimum radius of curvature of the filament. An alternative derivation of this result based on energy minimization is given. These results follow from a general asymptotic analysis of the electric field components and potential near a charged filament in the limit of vanishing diameter. It is found that the divergent parts of the radial and azimuthal electric field components are determined by the local charge density, while the axial component is determined by the local dipole density. For a straight filament our results reduce to those known for conducting needles. For curved filaments, the configuration of charges and fields is no longer azimuthally symmetric, and there is an additional length scale arising from the finite radius of curvature of the filament. The basic uniformity result survives the added complications, which include an azimuthal variation in the surface charge density of the filament. As with the variations in linear charge density along the filament, the azimuthal variations vanish with the characteristic parameter, only more rapidly. These findings allow us to derive an asymptotic formula for the capacitance of a curved filament that generalizes a result first obtained by Maxwell. The examples of a straight filament with uniform and linearly varying charge densities and a circular filament with a uniform charge distribution are treated analytically and found to agree with the general analysis. Numerical calculations illustrating the slow convergence of linear charge distribution to uniformity for an elliptical filament are presented. An interactive computer program implementing and animating the numerical calculations is available. [DOI: 10.1119/1.3231081]

In this paper the distribution of electrification current flowing across a pipe, for alternating charge near a surface, is presented. A distribution of charge density was arbitrarily assumed compatible to the Stern theory. Assuming that the velocity distribution is parabolic (in laminar regime) or logarithmic (in turbulent regime), the convective current density can be obtained. The distribution of current density shows changes of sign at different distances from the boundary. This may be the reason for the change of total electrification current sign that is often observed during experimental measurements. Index Terms--Streaming electrification, flow electrification, electrostatic charging.

The molecular system of 1,2-diphenylacetylene was examined by experimental and theoretical studies. The experimental charge density analysis shows that the acetylenic linker exhibits a noncylindrical density reminiscent of the strong conjugation present in the molecule and theoretical calculations show that the [pi]-orbitals of the triple bond can give enough scope to the molecule to sustain a range of conjugation lengths.

The physics of an asymmetric single dielectric barrier plasma actuator is explained and the effect of different control parameters like the applied voltage, the rf frequency and the charge density on the induced force field is studied. The motion of electrons and ions results in charge separation and generation of an electrostatic electric field.

A comparative study on acid and hydrothermal methods as ways to reduce interlamellar charge is carried out on a vermiculite. It is shown that the application of hydrothermal treatment is a new route to obtain the porous material with a particular interest as heterogeneous catalysts, starting from mineral clays with a high density of charge.

An approach to capacitance modeling that is simple, relies on few assumptions and is computationally efficient is described. It has to do with the inversion charge at the source and drain, and the modified saturation charge.

A study of the charge density of crystalline pentafluorobenzoic acid which his focused on the polar C (sp (super 2))-F bond, hydrogen bond, and the nonbonding interactions F...F and F...O also a topological analysis of the experimental and theoretical electron density using high resolution x-ray diffraction data collected at 110 K is presented. The results show that charge density studies with topological analysis are worthwhile to get quantitative parameters for characterizing bonds and nonbonding interactions from experimental data.

A relation is presented that provides the inversion charge density in the channel of metal oxide semiconductor (MOS) transistors as a function of saturation voltage and channel voltage. The relation is valid from subthreshold to strong inversion.

The inversion-layer centroid and its effects on the performance of double-gate (DG) MOSFETs are discussed with consideration of overall advantages /disadvantages of DG-MOSFETs over conventional counterparts. The minority-carrier distribution has been found to be even closer to the interfaces in volume-inversion transistors with very thin films. Some assumptions about advantages were found to be unjustifed.

Research is presented demonstrating the use of Hartree-Fock calculations to ascertain the total and orbital density difference contours for three systems: Ne2 (R = 3.80 bohr), Ne, and Ne6+ polarized by a +1 charge at 4.66 bohr.

The effect of charge density in a polymer on the structure of a monolayer on water and on the thickness of the adsorption layer has been investigated. The interplay of interactions in the headgroup and the tail regions is one of the significant factors for the structure formation in a lipid monolayer.

A thin-film patterning technology for a charge-density-wave (CDW) conductor, Rb0.30MoO3, was developed. The patterning of Rb0.30MoO3 was carried out by the use of near-ultraviolet photolithography. The thin-film CDW devices were realized by contacting the wires with submicron Au contacts with spacings down to 100 nm. The good CDW properties suggest that the patterning process has not substantially affected the Rb0.30MoO3 material.

Research was conducted to examine the space charge distribution of organic-molecular-beam-deposition titanylphthalocyanine (TiOPc) films on metal electrodes using surface potential calculation. A spectrometer and an atomic force microscopy were used to investigate the profile and thickness of the TiOPc films. Results indicate that the space charges are excessive electrons transferred from metals and 90% of them concentrate on the metal-TiOPc interface at a range of 10 nm.

A new method of quantitative convergent-beam electron diffraction has been linked with X-ray diffraction to map the charge-density distribution in the simple oxide Cu2O. It was shown that ambiguities in previous X-ray investigations of the charge density of Cu2O (cuprite) are attributable to large extinction effects on the strong low-order reflections. It is possible to estimate the population of the outer valence shells from the multipole model coefficients using the characteristic and localized distortion around Cu.

Some important features of semiconductor detectors (pulse height, energy resolution, photopeak efficiency) are strongly affected by charge collection efficiency; therefore low charge mobility and trapping/detrapping phenomena can more or less degrade the CdTe based detectors performance, depending on the distance between the charge formation location and the collecting electrodes. Using a narrow photon beam, obtained by a 20 mm thick tungsten collimator, we have studied the response of a small sample of CdTe(Cl) planar detectors. In particular we have investigated the behavior of the above parameters vs. the charge formation position induced by the incoming radiation irradiating the detectors perpendicularly to the electric field and performing a Free scanning of the inter-electrode region [1]. For comparison the detectors were irradiated also with a non collimated beam both perpendicularly and in the classical configuration (through the cathode).

Research was conducted to examine the charge distribution in an uncomplexed proton sponge compound through low-temperature, high-resolution X-ray and neutron diffraction methods. A small degree of asymmetry of the naphthalene moiety, which was induced by weak, asymmetric intermolecular interactions, was observed. Results demonstrate that protonation affects the atomic charges and structural parameters such as C-C, C-N and C-H bond lengths.

A measurement of the membrane potentials across cation- and anion-exchange membranes for five LiBr-various solvent systems found good agreement between theoretical predictions and experimental data. The solvents used were water, dimethyl sulfoxide, ethylene glycol, methanol and n-propanol. The Donnan equilibrium and the Nernst-Planck equation of ion flux were the basis of analysis of experimental data, with the effect of ion pairing of the electrolyte in the external solution taken into account.

The chemical bonds in bis(diiminosuccinonitrilo)nickel were investigated by X-ray diffraction analysis and molecular orbital calculations. Topological analysis showed the asphericity in electron density around the Ni ion with density accumulation in the d(pi) direction and density depletion along the d(sigma) (Ni-N) direction. The Ni-N bond has been classified as a closed-shell interaction with some covalent character.

The ability to control individual electrons in an electronic conductor would pave the way for novel quantum technologies. Single electrons emerging from a sea of their fellows in a nanoscale electrode can now be generated. SEE LETTER P.659, Splashing water in the bath usually leads to small waves, splashes and droplets. Similarly, applying a voltage pulse to the sea of electrons in a nanoscale electrode produces a complex [...]

It is shown analytically and experimentally that, when significant densities of positive and/or negative charge are trapped in the bulk of the oxide, standard thermally stimulated current (TSC) measurements at negative gate bias may not provide accurate estimates of MOS oxide-trap charge densities. Combining TSC measurements at negative bias with capacitance-voltage (C-V) measurements allows useful, self-consistent estimates of trapped electron densities in the oxide to be obtained. However, unless one can determine whether most of the trapped electrons lie in the bulk of the oxide or in border traps, unambiguous estimates of trapped positive charge densities cannot be obtained with negative or positive bias TSC, with or without C-V measurements. Implications are discussed for charge trapping in radiation-hardened thermal oxides, SIMOX buried oxides, and bipolar base oxides.

The cationic and anionic hydrogen bonds in 'proton sponge' complex was examined using a charge density analysis. Results revealed that the charge density distribution in crystals of the 1,2-dichloro hydrogen maleate salt can be obtained by using high resolution X-ray and neutron diffraction. The hydrogen bonds paths has multicenter characters with only minimal contibutions from an oxygen atom.

The concept of an equilibrium continuous charge density on a conducting line, although in some ways unphysical, does provide useful physical insight into needlelike conductors. It is shown that the charge density on such a line must be uniform. A simple method is developed for calculating the charge density on long, thin conductors with circular cross section. Also, the equilibrium distribution of N equal charges on a line is shown to approach equal spacing (except near the ends) as the number of charges grows.

The braking force acting on a conducting disk rotating under the influence of an external magnetic field of axial symmetry is calculated in a quasi-static approximation and the role played by the charge distributions induced in the disk is shown. The two cases of infinite and finite radius are considered to analyze the influence of edge effects and we obtain a general expression for the braking torque when the magnetic field has axial symmetry. The particular case of a uniform external magnetic field is used to show the working of a simplified model of a cylindrical battery. Analytical results are compared with those obtained by other authors.

The nested k-vector method used for studying nondefective LaSe2 and K0.33Ba0.67AgTe2 lattice structures was applied to examine charge density waves in defective lattice structures. Specifically, the nested Fermi surface of unperturbed crystal substructures was applied to the four-square superstructures La10Se19, RbDy3Se8, Cs3Te22 and Dy65.3Se120. This was achieved by modifying the band filling from the actual electron band filling to an effective band filling.

The charge-density integral method is used to analyse a triode gun which will inject electrons into a standing wave electron linac. The effect of space charge on the gun output beam parameters is estimated. The beam dynamics of the entire linac system is studied. The energy spectrum, beam size and divergence at the end of the linac are evaluated neglecting space charge.

Electronic band structure studies analyze the scanning tunneling and atomic force microscopic (STM and AFM) images of the charge density wave chalcogenides 1T-TaX2 (X = S, Se). Partial and total electron density calculations show that the observed height amplitude differences simply reflect the difference in the electron density plots. The bright spots arise from the pattern of six-chalcogen-atom triangles at the surface, splitting into three-atom clusters in the STM images. Other aspects of the STM and AFM images are also explained in terms of surface topography.

The collective charge density excitations in two-dimensional semiconductor superlattices were investigated. The results showed that the surface charge density excitations featured a broken degeneracy in the retarded limit. This occured when the plasma branch was positioned within the gap between two bulk bands. In addition, the bloch wave vector edge of the bulk bands featured a splitting of the dispersion curve at a frequency greater than the cyclotron frequency.

Cherenkov-type frequency doubling in an optical channel waveguide was investigated using three-dimensional calculations obtained by slicing the lateral profile of the interacting fields into a several small segments. The method allowed lateral field variations of the harmonic signal to be neglected. The unidirectional-radiation model predicted the optimum configuration and conversion efficiency of miniaturized frequency doublers that use guided-to-radiation-mode interactions in nonlinear channel waveguides.

The electronic structures of the inorganic transition-metal oxide Sr3V2O7 and the organic conducting salts (BEDT-TTF)2ReO4 and (BEDT-TTF)4Pt(C2O4)2 were investigated to study the conditions resulting in hidden Fermi surface nesting in low-dimensional systems. The inorganic materials exhibiting hidden nested Fermi surfaces revealed metal-oxygen layers of MO6 octahedra with partially filled t2g-blockedbands. The organic salts, on the other hand, exhibited weak bonds between donor molecules and between donor molecules and anions.

Molecular orbital calculations of the structures and energies of ethyl, vinyl, isopropyl and cyclopropyl derivatives reveal the effects of various substituents on their charge distibutions. The study shows electronegative substituents preferring the isopropyl group and the electropositive ones preferring the cyclopropyl group. The charge correlation is not as clear-cut between the ethyl and vinyl groups, although the bond path angles for all four correlate with substituent electronegativities. Substituents have little effect on the unsubstituted carbons while their effects on the substituted carbons show linear dependence on their atomic charge.

The relative basicities of the six external oxygen sites of the (V10O28)6- ion were examined using an ab initio self-consistent field wave function derived from the ground state of the decavanadate ion. The topological study characterized the distribution and behavior of the electrostatic potentials (ESP) and the charge concentrations associated with the oxygen sites. The results indicated that most of the ESP minima were positioned within the area of a specific oxygen atom. The angular position of the ESP minima correlated with the proposed charge concentration values.

The properties of a molecule are determined by the distribution of its electrons. This distribution can be described by the charge density, which is readily obtained from the wave functions [...]

This year marks the 50th anniversary of the preparation of the first transuranium elements, neptunium and plutonium though thus losing pride of place in the Periodic Table, uranium still has secrets to reveal. This article describes efforts to characterize the extremely subtle series of distortions that appears at low temperature in the element. Our understanding of these distortions require some of the latest ideas in diffraction physics, so that the story is a continuously evolving one. Uranium is the only element (so far) that has been found to have a spontaneous charge-density wave.

Two oppositely charged particles moving nonrelativistically in a two-particle Coulomb bound state produce a charge distribution that is equivalent to that of two single-particle bound states of opposite charge moving in separate external potentials. With examples, we show that this is unlikely to be true if the binding force is not pure Coulombic.

Electron-phonon coupling produces a charge density wave (CDW) at the surface of a lead/germanium (111) crystal. The CDW is reversible, induced by temperature and its stability depends on electron-electron interactions. Periodic redistribution of valence charge, metal-nonmetal transition and lattice displacement occur during CDW formation. The reversible transition to the CDW state occurs at an onset temperature lower than that for structural transitions. With enhanced lattice distortion due to electron-electron interaction, the stability of the low-temperature phase increases.

In the lab frame the total linear charge density of a current-carrying wire must be zero, while in the rest frame of the electrons making up the current the total volume charge density must be zero. These two pieces of information enable the determination of the volume, surface, and linear charge densities of such a wire in both of these frames using only straightforward relativistic length contractions and simple mathematics.

A new method for reducing the interface charge between CdTe substrates and CdTe epilayers grown by metalorganic chemical vapor deposition was presented. The photothermal in situ surface pretreatment required that the substrate be first held at 450 degrees celsius in a hydrogen atmosphere and simultaneously exposed to ultraviolet radiation prior to actual growth. The pretreatment effectively reduced the charge density to a negligible value.

Incommensurate charge density waves (CDWs) in some materials form domains within which the CDWs may be commensurate. However, two questions have remained controversial: What is the geometrical structure of these [...]

The concept of hidden Fermi surface nesting was introduced to explain the general observation that certain low-dimensional metals with several partially filled bands exhibit charge density wave (CDW) instabilities, although [...]

A study was conducted to examine the experimental and theoretical charge densities in the binculear complexes [[Cu.sub.2][(ap).sub.2][(L).sub.2] (ap = 3-aminopropanolate) (L = nitrite, nitrate, or formate) which contain the same centrosymmetric alkoxy-bridged motif. The topological analyses indicated the lack of any direct Cu...O interaction and the coupling between the two Cu(II) centers are strongly antiferromagnetic.

The energetic analysis of the association between [Na.sup.+] and [K.sup.+] with chloride and dimethylphosphate anions was performed to gain additional microscopic insights into the mechanisms of specificity on ionic associations. The results obtained shed light on a number of experiments on electrolyte solutions of monovalent salts and 16-mer DNA oligomer.

The structural determination of the incommensurate charge density wave (CDW) states in [Sm.sub.2][Te.sub.5] is described and the existence of two coexisting CDW states in a single material is confirmed. The new phenomenon has provided valuable structural and physical properties for developing theory of two-dimensional CDW systems.

It is shown that the surface charge density on a spherical conductor (spherical in the lab frame) is uniform, regardless of its velocity.

The charge density waves (CDWs) in AMRE[Te.sub.4] (A = K, Na, M = Cu, Ag and RE = La, Ce) is described and compared with those of the parent RE[Te.sub.3] compounds. The results have shown that interactions along the third, cross-plane dimension in the quasi-two-dimensional systems of AMRE[Te.sub.4] and RE[Te.sub.3] have played a vital role on defining the CDW modulations.

The characterization of mechanical properties and the electron charge density of the laser host single crystal material YV[O.sub.4] which were carried out by using first principles calculations is presented. The anisotropic property of elastic stiffness constants is attributed to lattice structure and electron-charge density distribution of YV[O.sub.4].