Showing papers on "Energy (signal processing) published in 1991"

The effective mechanical properties of nonlinear isotropic composites

Abstract: A new variational structure is proposed that yields a prescription for the effective energy potentials of nonlinear composites in terms of the corresponding energy potentials for linear composites with the same microstructural distributions. The prescription can be used to obtain bounds and estimates for the effective mechanical properties of nonlinear composites from any bounds and estimates that may be available for the effective properties of linear composites. The main advantages of the procedure are the simplicity of its implementation, the generality of its applications and the strength of its results. The general prescription is applied to three special nonlinear composites : a porous material, a two-phase incompressible composite and a rigidly reinforced material. The results are compared with previously available results for the special case of power-law constitutive behavior.

Homogeneous compositions of microcrystalline semiconductor material, semiconductor devices and directly overwritable memory elements fabricated therefrom, and arrays fabricated from the memory elements

Abstract: A unique class of microcrystalline semiconductor materials which can be modulated, within a crystalline phase, to assume any one of a large dynamic range of different Fermi level positions while maintaining a substantially constant band gap over the entire range, even after a modulating field has been removed. A solid state, directly overwritable, electronic and optical, non-volatile, high density, low cost, low energy, high speed, readily manufacturable, multibit single cell memory based upon the novel switching characteristics provided by said unique class of semiconductor materials, which memory exhibits orders of magnitude higher switching speeds at remarkably reduced energy levels. The novel memory of the instant invention is in turn characterized, inter alia, by numerous stable and non-volatile detectable configurations of local atomic order, which configurations can be selectively and repeatably accessed by input signals of varying levels.

Observation of synchronous picosecond sonoluminescence

Abstract: SONOLUMINESCENCE1–13 is a non-equilibrium phenomenon in which the energy in a sound wave becomes highly concentrated so as to generate flashes of light in a liquid. We show here that these flashes, which comprise over 105 photons, are too fast to be resolved by the fastest photomultiplier tubes available. Furthermore, when sonoluminescence is driven by a resonant sound field, the bursts can occur in a continuously repeating, regular fashion. These precise 'clock-like' emissions can continue for hours at drive frequencies ranging from audible to ultrasonic. These bursts represent an amplification of energy by eleven orders of magnitude

Electron-energy-loss-spectroscopy near-edge fine structures in the iron-oxygen system.

Abstract: We report an electron-energy-loss-spectroscopy study of the characteristic oxygen K and iron ${\mathit{L}}_{2,3}$ edges in FeO, ${\mathrm{Fe}}_{3}$${\mathrm{O}}_{4}$, \ensuremath{\alpha}-${\mathrm{Fe}}_{2}$${\mathrm{O}}_{3}$, and \ensuremath{\gamma}-${\mathrm{Fe}}_{2}$${\mathrm{O}}_{3}$ thin films. Data have been processed for quantitative elemental analysis and for detailed comparison of the different fine structures (energy position and width as well as relative intensities). Oxygen edge profiles are sensitive to the local bonding and symmetry properties on the excited anion. The features of the prepeak at the onset are governed by the 3d components in the hybridized unoccupied pd wave functions. They can be described in a molecular-orbital scheme and depend on the first coordination shell. Oscillations at higher energies are interpreted in terms of backscattering from the next coordination shells. The intense white lines on the iron ${\mathit{L}}_{2,3}$ edges are due to strong 2${\mathit{p}}^{6}$3${\mathit{d}}^{\mathit{n}}$\ensuremath{\rightarrow}2${\mathit{p}}^{5}$3${\mathit{d}}^{\mathit{n}+1}$ excitations, and the recorded changes of relative intensity (or branching ratio) are predominantly governed by strong Coulomb and exchange interactions on the excited cation.

Direct dynamics calculations with neglect of diatomic differential overlap molecular orbital theory with specific reaction parameters

Abstract: The authors have calculated the {alpha}-deuterium secondary kinetic isotope effect and the heavy-water solvent kinetic isotope effect for the reaction Cl{sup {minus}}(H{sub 2}O){sub n} + CH{sub 3}Cl{prime} {yields} CH{sub 3}Cl + Cl{prime}{sup {minus}}(H{sub 2}O){sub n} with n = 0, 1, and 2. Instead of using an analytic potential energy function, they calculated the energy and gradient whenever they needed them by neglect of diatomic differential overlap (NDDO) molecular orbital theory with parameters adjusted specifically for these individual reactions. The interface of the molecular orbital calculations with the dynamics calculations was accomplished by the use of a new direct dynamics computer program MORATE. The results are compared in detail to previous calculations based on 18-, 27-, and 36-dimensional semiglobal analytic potential energy functions, and the correspondences between the kinetic isotope effects and their interpretation in terms of specific modes are very encouraging. They conclude that use of NDDO molecular orbital theory with specific reaction parameters should be a very useful technique for modeling potential energy surfaces for polyatomic reactions. 69 refs., 6 figs., 13 tabs.

Analysis of mismatch effects among A/D converters in a time-interleaved waveform digitizer

Abstract: High-speed A/D conversion can be achieved by employing a parallel array of M A/D converters interleaved in time, each working at 1/Mth of the sampling rate. Theoretically, the resolution of the structure is given by the resolution of the A/D converters in the array (subconverters). In practice, however, mismatches among the subconverters lead to a decrease in the resolution. The effect of such mismatches is analyzed in terms of a signal-to-noise ratio defined as the ratio between the energy of the input analog signal and the energy of the error signal due exclusively to these mismatches. The analysis shows that the distortion is comparable to that generated by nonuniform sample timing in the analog demultiplexer when converting a single high-speed signal into several low-speed sampled-and-held signals. The results of the analysis can be used to specify the degree of precision to be achieved in an actual monolithic implementation. >

Model for the reversible magnetization of high- kappa type-II superconductors: Application to high-Tc superconductors.

Abstract: A simple theoretical model is proposed for the reversible magnetization of type-II superconductors as a function of the applied field H for the entire field region between ${\mathit{H}}_{\mathit{c}1}$ and ${\mathit{H}}_{\mathit{c}2}$. For H\ensuremath{\simeq}${\mathit{H}}_{\mathit{c}1}$, the theory reduces to a variational model, from which ${\mathit{H}}_{\mathit{c}1}$ can be accurately computed in the Ginzburg-Landau regime. In calculating the free energy, we include, in addition to the supercurrent kinetic energy and the magnetic-field energy, the kinetic-energy and the condensation-energy terms arising from suppression of the order parameter in the vortex core. The model is further extended to include anisotropy by introducing an effective-mass tensor for the case when H is parallel to one of the principal axes. The theory is compared to reversible-magnetization data on a ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ single crystal. The method permits an accurate determination of ${\mathit{H}}_{\mathit{c}2}$ versus temperature from measurements of the magnetization versus temperature at fixed magnetic field and explains why the measurements have different slopes in different fields, contrary to what might have been expected from the linear Abrikosov formula near ${\mathit{H}}_{\mathit{c}2}$. The deduced ${\mathit{dH}}_{\mathit{c}2}$/dT is (-1.65\ifmmode\pm\else\textpm\fi{}0.23) T/K for H parallel to the c axis near ${\mathit{T}}_{\mathit{c}}$, implying ${\ensuremath{\xi}}_{\mathit{a}\mathit{b}}$(0)=(17\ifmmode\pm\else\textpm\fi{}1) \AA{}.

Finite-size scaling and monte carlo simulations of first-order phase transitions

Abstract: We develop a detailed finite-size-scaling theory at a general, asymmetric, temperature-driven, strongly first-order phase transition in a system with periodic boundary conditions. We compute scaling functions for various cumulants of energy in the form U(L,t)=${\mathit{U}}_{0}$(${\mathit{tL}}^{\mathit{d}}$)+${\mathit{L}}^{\mathrm{\ensuremath{-}}\mathit{d}}$${\mathit{U}}_{1}$(${\mathit{tL}}^{\mathit{d}}$) with t=1-${\mathit{T}}_{\mathit{c}}$/T. In particular, we consider the specific heat and Binder's fourth cumulant and show this has a minimum value of 2/3-(${\mathit{e}}_{1}$/${\mathit{e}}_{2}$-${\mathit{e}}_{2}$/${\mathit{e}}_{1}$${)}^{2}$/12+O(${\mathit{L}}^{\mathrm{\ensuremath{-}}\mathit{d}}$) at a temperature ${\mathit{T}}_{\mathit{c}}^{(2)}$(L)-${\mathit{T}}_{\mathit{c}}$=O(${\mathit{L}}^{\mathrm{\ensuremath{-}}\mathit{d}}$). Various other pseudocritical temperatures corresponding to extrema of other cumulants are evaluated. We compare these theoretical predictions with extensive Monte Carlo simulations of the nominally strong first-order transitions in the eight- and ten-state Potts models in two dimensions for system sizes L\ensuremath{\le}50. The ten-state simulations agree with theory in all details in contrast to the eight-state data, and we give estimates for the bulk specific heats at ${\mathit{T}}_{\mathit{c}}$ using all exactly known analytic results. A criterion is developed to estimate numerically whether or not system sizes used in a simulation of a first-order transition are in the finite-size-scaling regime.

Threshold production of heavy top quarks: QCD and the Higgs boson.

Abstract: We calculate the threshold cross section for ${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{\ensuremath{-}}}$\ensuremath{\rightarrow}tt\ifmmode\bar\else\textasciimacron\fi{} to leading-logarithmic order in QCD, using a nonrelativistic approximation suggested by Fadin and Khoze. We study the mass range 100\ensuremath{\le}${\mathit{m}}_{\mathit{t}}$\ensuremath{\le}250 GeV, and show that the cross section is an excellent measure of ${\mathrm{\ensuremath{\alpha}}}_{\mathit{s}}$ for the lower portion of the mass range, while for a heavier top quark it is sensitive to the mass and couplings of the Higgs boson. We argue that a precise determination of ${\mathit{m}}_{\mathit{t}}$ and a measurement of ${\mathrm{\ensuremath{\Gamma}}}_{\mathit{t}}$ are possible. We also show that nonperturbative effects are small, confirming that the tt\ifmmode\bar\else\textasciimacron\fi{} threshold is a detailed perturbative test of the standard model.

Luggage inspection device

Abstract: The invention provides an inspection system for closed containers, such as luggage, which applies radiant energy, such as x-rays, to a container and receives energy which is scattered, such as by Compton scattering, by objects in the container. The received energy is measured and a three-dimensional image of the objects in the container is constructed. The container may be moved relative to a fan-shaped primary x-ray beam, which illuminates a single slice of the container at a time. For example, the container may be moved by a conveyer belt, or, the container may be held stationary while the x-ray tube may comprise a steerable beam. A plurality of collimated x-ray sensors may receive energy which is scattered, at a fixed angle for each sensor, and transmits those measurements to a processor which reconstructs the three-dimensional image and displays that image for an operator. The processor may also search for, and raise an alarm if it detects, a sufficient volume of material with a mass density indicative of an explosive.

Improved techniques for power system voltage stability assessment using energy methods

Abstract: An improved method of assessing power system voltage stability using energy techniques is presented. The concept of an energy function providing a localized measure of voltage security in a particular portion of the system is developed. A crucial factor in the use of the energy function method is the ability to rapidly determine the appropriate low-voltage solution to use in the energy measure calculation. Also, an improved method of locating power alternative solutions with low associated energy measures is presented. Techniques are demonstrated on the IEEE 118 bus system and a 415-bus system. >

How to observe the elusive resonances in H or D + H2 → H2 or HD + H reactive scattering

Abstract: Short-lived collision complexes in H or D + H{sub 2} (v = j = 0) {yields} H{sub 2} or HD ({nu}{prime},j{prime}) + H reactive scattering give rise to broad resonance structure Though this structure is not observable in the energy dependence of the integral cross section, it is readily seen in the energy dependence in the differential cross section {sigma}({theta},E), as a peak along a line in the E-{theta} plane The equation of this resonance line is E = E{sub r}(J({theta})), where E{sub r}(J) is the resonance energy as a function of total angular momentum J (ie, the rotational quantum number of the complex) and J({theta}) is the inverse function of {Theta}(J), the effective classical deflection function for the transition Observation of this resonance structure requires cross section to individual final ({nu}{prime}, j{prime}) states; it is quenched by summing over j{prime} The results reported are all from rigorous three-dimensional quantum mechanical reactive scattering calculations for these cross sections

Christodoulou's nonlinear gravitational wave memory: Evaluation in the quadrupole approximation

Abstract: Christodoulou has found a new nonlinear contribution to the net change in the wave form caused by the passage of a burst of gravity waves ("memory of the burst"). We argue that this effect is nothing but the gravitational wave form generated by the stress energy in the burst itself. We derive an explicit formula for this effect in terms of a retarded-time integral of products of time derivatives of wave-zone gravitational wave forms. The resulting effect corresponds in size to a correction 2.5 post-Newtonian orders [$O({(\frac{\mathrm{Gm}}{r{c}^{2}})}^{\frac{5}{2}})=O({(\frac{v}{c})}^{5})$] beyond the quadrupole approximation, and is therefore negligible for all but the most relativistic of systems. For gravitational bremsstrahlung from two stars moving at 3000 km ${\mathrm{s}}^{\ensuremath{-}1}$, the effect is much less than ${10}^{\ensuremath{-}10}$ of the usual linear quadrupole wave form, while for a system of coalescing binary compact objects we estimate that the effect is of order ${10}^{\ensuremath{-}1}$ for two neutron stars.

Pedagogic notes on Thomas-Fermi theory (and on some improvements): atoms, stars, and the stability of bulk matter

Abstract: In the more than half century since the semiclassical Thomas-Fermi theory of the atom was introduced, there have been literally thousands of publications based on that theory; they encompass a broad range of atomic bound-state and scattering problems. (The theory has also been applied to nuclear physics and solid-state problems.) We will concentrate here on the essence of the theory, namely, its implementation of the uncertainty and exclusion principles and of the Coulomb or Newton force law. Since we are often far more interested in physical concepts than in numerical accuracy or rigor, we will sometimes consider the implementation in a qualitative rather than quantitative fashion. The theory is then capable of giving only qualitative information about a system---one obtains the dependence of the total ground-state binding energy $E$ and radius $R$ of an atom on the nuclear charge $Z$, for example, but one obtains only rough estimates of the numerical coefficients; in compensation, the calculations are often literally trivial, very much simpler than the already simple Thomas-Fermi calculations. A point to be emphasized is that in the course of obtaining an estimate of $E$ and $R$ of an atom in a Thomas-Fermi approach, one also obtains an estimate of the electronic density, and, particularly if the analysis is more than simply qualitative, an electronic-density estimate can be very useful in a wide variety of problems. We include a short comment on alternative formulations of Thomas-Fermi theory in a $D$-dimensional space. We will review the applications of the theory, from both qualitative and (Thomas-Fermi) quantitative viewpoints, to heavy atoms, where we are concerned with a Coulomb interaction, and to neutron stars and white dwarfs, where we are concerned with a gravitational interaction and with gravitational-plus-Coulomb interactions, respectively. In the latter case, the first two Coulomb corrections are evaluated. Very rough (relativistic) estimates are made of the conditions under which heavy atoms, neutron stars, and white dwarfs collapse. A one-dimensional Thomas-Fermi-like theory also exists for heavy atoms in a uniform strong magnetic field $B$, of the order of the field believed to exist at the surface of a neutron star. Here, too, the qualitative picture immediately gives some of the main results, namely, the dependence of $E$ and $R$ on $B$ and $Z$. We also comment briefly on some relatively recent and very recent developments in Thomas-Fermi theory. These include a proof of the stability of matter. Though it was first proved by Dyson and Lenard, we consider the Lieb-Thirring proof, both because it is much simpler and because it makes extensive use of Thomas-Fermi theory, including a no-molecular-binding theorem that follows in the Thomas-Fermi approximation: Teller proved that, in that approximation, atoms could not form molecular bound states. These developments also include (a) the Lieb-Simon proof that the prediction of the theory that $E=\ensuremath{-}{c}_{7}{Z}^{\frac{7}{3}}$, with ${c}_{7}$ a specified coefficient, becomes exact at $Z\ensuremath{\sim}\ensuremath{\infty}$, (b) the Scott-${c}_{6}{Z}^{\frac{6}{3}}$ correction term, with ${c}_{6}$ specified and now known also to be exact, and (c) the Schwinger estimate of the coefficient ${c}_{5}$ of the ${Z}^{\frac{5}{3}}$ term, which there is good reason to believe is exact. The many digressions include comments on QED, on lower bounds on the ground-state energy of a system, and on mini-boson stars.

Equilibrium budding and vesiculation in the curvature model of fluid lipid vesicles

Abstract: According to a model introduced by Helfrich [Z. Naturforsch. 28c, 693 (1973)], the shape of a closed lipid vesicle is determined by minimization of the total bending energy at fixed surface area and enclosed volume. We show that, in the appropriate regime, this model predicts both budding (the eruption of a satellite connected to the parent volume via a neck) and vesiculation (the special case when the neck radius goes to zero). Vesiculation occurs when the minimum is located at a boundary in the space of configurations. Successive vesiculations produce multiplets, in which the minimum-energy configuration consists of several bodies coexisting through infinitesimal necks. We study the sequence of shapes and shape transitions followed by a spherical vesicle of radius ${\mathit{R}}_{\mathit{V}}$, large on the scale ${\mathit{R}}_{0}$ set by the spontaneous curvature, as its area A increases at constant volume V=4\ensuremath{\pi}${\mathit{R}}_{\mathit{V}}^{3}$/3. Such a vesicle periodically sheds excess area into a set of smaller spheres with radii comparable to ${\mathit{R}}_{0}$. We map out this (shape) phase diagram at large volume. In this region the phase diagram is dominated by multiplets and reflects the details of the shedding process. The overall effect of successive vesiculations is to reduce the energy from a quantity of order ${\mathit{R}}_{\mathit{V}}^{2}$ down to zero or near zero when the area reaches 3V/${\mathit{R}}_{0}$; however, the decrease is not uniform and the energy E(A,V) is not convex.

System and method for monitoring and analyzing energy characteristics

Abstract: A system for monitoring various, diverse energy characteristics of an energy consuming system is shown. The system includes a data gathering device that accumulates data representing each of the sensed energy characteristics in real time, the data representing magnitude of the sensed energy characteristic as well as the time at which the magnitude is sensed. The data that is accumulated for each of the sensed energy characteristics is periodically transmitted to a remote analysis station. The remote analysis station performs a detailed analysis of the sensed energy characteristics and generates reports containing summaries of the sensed data in the form of listings of compressed data as well as graphs such as histograms and graphs correlating different energy characteristics of the energy consuming system.

Two-dimensional spin-1/2 Heisenberg antiferromagnet: A quantum Monte Carlo study.

Abstract: Spin-1/2 nearest-neighbor Heisenberg antiferromagnet on a square lattice is studied via a large-scale quantum Monte Carlo simulation. We developed a fast and efficient multispin coding algorithm on a parallel supercomputer, based on the Suzuki-Trotter transformation. We performed high-statistics simulations on lattices as large as 128\ifmmode\times\else\texttimes\fi{}128 spins, in the temperature range from 0.25J to 2.5J. We calculated energy, specific heat, uniform and staggered susceptibility, and staggered correlation function, from which we deduce the correlation length. For temperatures higher than J, the results are in excellent agreement with high-temperature series expansion. At low temperatures the long-wavelength behavior is essentially classical. Our data show that the correlation length and staggered susceptibility are quantitatively well described by the renormalized classical picture at the two-loop level of approximation. From the divergence of correlation length, we deduce the value of quantum-renormalized spin stiffness, ${\mathrm{\ensuremath{\rho}}}_{\mathit{s}}$/J=0.199(2). We give evidence that the correlation function is of Ornstein-Zernike type. By comparing the largest measured correlation lengths with neutron scattering experiments on ${\mathrm{La}}_{2}$${\mathrm{CuO}}_{4}$, we deduce the value of effective exchange coupling J=1450\ifmmode\pm\else\textpm\fi{}30 K.

Systematic errors in free energy perturbation calculations due to a finite sample of configuration space: sample-size hysteresis

Abstract: Although the free energy perturbation procedure is exact when an infinite sample of configuration space is used, for finite sample size there is a systematic error resulting in hysteresis for forward and backward simulations. The qualitative behavior of this systematic error is first explored for a Gaussian distribution, then a first-order estimate of the error for any distribution is derived. To first order the error depends only on the fluctuations in the sample of potential energies, {Delta}E, and the sample size, n, but not on the magnitude of {Delta}E. The first-order estimate of the systematic sample-size error is used to compare the efficiencies of various computing strategies. It is found that slow-growth, free energy perturbation calculations will always have lower errors from this source than window-growth, free energy perturbation calculations for the same computing effort. The systematic sample-size errors can be entirely eliminated by going to thermodynamic integration rather than free energy perturbation calculations. When {Delta}E is a very smooth function of the coupling parameter, {lambda}, thermodynamic integration with a relatively small number of windows is the recommended procedure because the time required for equilibration is reduced with a small number of windows. These results give a method of estimatingmore » this sample-size hysteresis during the course of a slow-growth, free energy perturbation run. This is important because in these calculations time-lag and sample-size errors can cancel, so that separate methods of estimating and correcting for each are needed. When dynamically modified window procedures are used, it is recommended that the estimated sample-size error be kept constant, not that the magnitude of {Delta}E be kept constant. Tests on two systems showed a rather small sample-size hysteresis in slow-growth calculations except in the first stages of creating a particle, where both fluctuations and sample-size hysteresis are large.« less

Intermittency in a cascade model for three-dimensional turbulence

Abstract: We discuss a possible mechanism for intermittency of the energy dissipation in a model for three-dimensional fully developed turbulence. We compute the structure functions for the velocity field and show that their behavior can be described in the context of a multifractal approach. We also compute the instantaneous maximum Lyapunov exponent and the corresponding (stability) eigenvector. Violent bursts of energy dissipation are related to a sudden increase of the instantaneous Lyapunov exponent, and simultaneous localization of its eigenvector on the high wave numbers at the end of the inertial range. In particular, we relate the correction to the ${\mathit{k}}^{\mathrm{\ensuremath{-}}5/3}$ Kolmogorov law for the energy spectrum to the fractal dimension extracted by temporal sequences both of the instantaneous Lyapunov exponent and of the eigenvector.

Voltage drop in mesoscopic systems : a numerical study using a quantum kinetic equation

Abstract: In this paper, we present a numerical method for evaluating the full Wigner function throughout a device by solving a steady-state quantum kinetic equation in two dimensions, in the linear-response regime. This method has two advantages over conventional treatments of mesoscopic devices. First, dissipative processes can be included within the device, thus allowing a smooth transition from the quantum to the semiclassical regime. Second, the contacts are treated in the same manner as in semiclassical device analysis. A short phase-breaking time can be used in the contact regions so that oscillations in the electron density due to interference effects die out quickly; this is particularly useful when obtaining self-consistent solutions with the Poisson equation. Any quantity of interest, such as electron density or current density per unit energy, can be computed throughout the entire device. We will first show that under low-bias, low-temperature conditions, the diagonal elements of the Wigner function can be used to define a local electrochemical potential (\ensuremath{\mu}) that lends insight into the internal transport physics. We show that separate electrochemical potentials ${\mathrm{\ensuremath{\mu}}}_{\mathit{L}}$ and ${\mathrm{\ensuremath{\mu}}}_{\mathit{R}}$ for left- and right-moving electrons show unphysical behavior when defined in a local sense. But sensible results are obtained when these potentials are defined in an average sense over regions the size of a de Broglie wavelength. We then examine the difficulties associated with measuring \ensuremath{\mu}, with numerical examples. Next, we use the local electrochemical potential profile to clarify the nature of the spreading resistance associated with the narrowing of a current lead. Finally, we show that the electrostatic potential (\ensuremath{\varphi}) can be viewed as a convolution of \ensuremath{\mu} with a screening function and present example computations of \ensuremath{\varphi}.

Surface feature mapping using high resolution c-scan ultrasonography

Abstract: An ultrasonic system and method for imaging a surface wherein a C-mode ultrasonic scan is performed over a fixed area of the surface and range gating is applied to that area to a given depth below the surface. For use of the system and method in fingerprint imaging, a live finger is placed upon a sensitive surface, the portion of the finger on the surface is scanned using the ultrasonic energy, and ultrasonic energy returned from the finger portion is received to capture an electronic image of the pattern of ridges and valleys of the fingerprint. The ultrasonic imaging system comprises a probe for providing a directed output ultrasonic beam to scan the surface and to receive ultrasonic echos from the surface, a pulser-receiver to cause the probe to provide the output beam and to provide signals in response to the returned ultrasonic echos, a signal processing circuit for detecting and processing return echo signals from the pulser-receiver and a computer for storing and displaying information contained in signals from the processing circuit and for controlling operation of the processing circuit. The probe scans the surface along one direction, and then along another direction, the two directions preferably being orthogonal.

Energy deposition in small cylindrical targets by monoenergetic electrons.

Abstract: SummaryCalculations of energy deposition in cylindrical target volumes of diameter and height 1–100 nm, including those similar to the dimensions of biological molecules and structures such as DNA, nucleosomes and chromatin fibre, have been made. The calculations used the Monte Carlo track structure program MOCA8B for electrons of initial energy 0·1–100 keV. Details of the calculation are presented, as well as a selection of results. The frequency distributions of energy deposition events per gray per target, placed at random in a homogeneous aqueous medium, are given for uniform irradiation with monoenergetic electrons of various energies. The frequency distributions have been used to predict the initial biophysical parameters such as relative effectiveness for initial damage. These suggest that the final biological effects which depend on complex local damage may show substantial variations in biological effectiveness for different low linear energy transfer radiations, whereas those that depend on simp...

Finite-size scaling for critical films.

Abstract: The universal scaling function of the fine-size contribution to the free energy of O(N) symmetric systems confined between two parallel plates at distance L is calculatd by field-theoretical methods close to ${\mathit{T}}_{\mathit{c},\mathrm{b}\mathrm{u}\mathrm{l}\mathrm{k}}$ and for five different boundary conditions. The asymptotic behavior for large L of the specific heat at ${\mathit{T}}_{\mathit{c},}$b is computed explicitly, thus allowing quantitative experimental tests. We discuss the implications of our results for surface forces and wetting films. Universal amplitudes for the surface free energy are also presented.

Construction of the Pauli potential, Pauli energy, and effective potential from the electron density

Abstract: The Kohn-Sham (KS) one-electron Schr\"odinger equations assume the existence of a one-body effective potential ${\mathit{v}}_{\mathrm{eff}}$(x), defined to generate the correct electron density \ensuremath{\rho}(x) of the ground state. This paper returns to the electron-density description of an N-fermion system. It is best thought of as starting from a given \ensuremath{\rho}(x), ideally to be obtained from diffraction experiments. A method is then set up that focuses predominantly on the way the ``correct'' ${\mathit{v}}_{\mathrm{eff}}$(x) can be ``recovered,'' if it exists, from such an experimental density. Certainly the method has associated with it one practical disadvantage in common with the KS procedure; an order of N Euler equations have to be solved, with input information \ensuremath{\rho}(x), though the ``unknown'' potential ${\mathit{v}}_{\mathrm{eff}}$(x) does not now appear. In this program, we have found it most helpful to work with the Pauli potential and energy, which enable the N-fermion problem to be converted to a boson problem for the density amplitude [\ensuremath{\rho}(x)${]}^{1/2}$. The way the above-mentioned Euler equations determine the Pauli potential and energy is worked out explicitly. Examples that embrace the important area of atomic central-field calculations are presented to illustrate the method. As a by-product, the theory developed can afford a direct test as to whether a given electron density is, in fact, representable via a one-body potential ${\mathit{v}}_{\mathrm{eff}}$(x).

Proton transfer in mixed water-organic solvent solutions: correlation between rate, equilibrium constant, and the proton free energy of transfer

Abstract: We demonstrate that the proton dissociation reaction of excited 1-aminopyrene follows a simple structure-reactivity correlation in water-methanol, water-DMSO, water-dioxane, and water-acetonitrile binary mixtures.

Energy extension in three-dimensional atomic imaging by electron emission holography.

Abstract: A method is introduced joining together forward-scattering diffraction data taken in a small angular window at different photoelectron energies. This method extends the usable range in phase space for three-dimensional image reconstruction. Examples based on theoretical simulations demonstrate that a spatial resolution of \ensuremath{\le}1 \AA{} is achievable. We also show that using a small angular window in the backscattering geometry eliminates splittings in the reconstructed image.

Energy amount control device

Abstract: An energy amount control device having a pulse energy generating source which produces pulse energy with a predetermined range of energy fluctuations per oscillation, and adjusting voltage applied to the energy generating source to thereby control an energy amount of the pulse energy, the energy amount control device comprising a storage unit for storing information about the relation between predetermined voltage to produce pulse energy in the energy generating source and an energy amount of the pulse energy emitted from the energy generating source under the predetermined voltage; an energy amount measuring unit for detecting the energy amount of the pulse energy actually emitted from the energy generating source; an arithmetic unit for updating the information stored in the storage unit at predetermined timing based on the predetermined voltage to produce the pulse energy in the energy generating source and the energy amount detected by the energy amount measuring unit; and decision unit for determining the predetermined voltage corresponding to the energy amount of the pulse energy to be next emitted, based on the information updated by the arithmetic unit.

Coulomb blockade and nonperturbative ground-state properties of ultrasmall tunnel junctions.

Abstract: We present a nonperturbative calculation of the ground-state energy of a normal tunnel junction. The junction with a large conductance shows Coulomb blockade of tunneling provided the external charge ${\mathit{Q}}_{\mathit{x}}$ is less than e/4. For ${\mathit{Q}}_{\mathit{x}}$ge/4, the band is flat and the junction behaves like an Ohmic resistor. We predict a phase transition between insulating and conducting behavior of the junction controlled by an external Ohmic resistance. We plot the corresponding zero-temperature phase diagram and calculate the junction effective resistance.