bluuebunny/crossref_metadata_2025 huggingface dataset:
Second Virial Coefficients of Polar Gas Mixtures
Authors: Stockmayer W. H.
Published: January 2005

An empirical equation used by Keyes to represent the second virial coefficients of several polar gases is compared to a theoretical expression for the same quantity. The constants appearing in this equation are discussed in terms of intermolecular forces, and their relationship to analogous constants in the Beattie-Bridgeman equation for non-polar gases is examined. These considerations permit the construction of simple rules by means of which the second virial coefficient of any gas mixture may be calculated if the second virial coefficients and dipole moments of the pure component gases are known. The success of these rules is demonstrated by comparison with data on H2O–CO2, N2–NH3, and N2–H2O systems. In the case of N2–H2O mixtures (vapor-liquid equilibrium data) the agreement is not satisfactory at the higher temperatures. A rough method of including the effect of higher virial coefficients reduces, but does not remove, this discrepancy.
Dissociation Treatment of Condensing Systems—IV
Authors: Ch'eng C. , Tseng T. P. , Feng S. K. , Band W.
Published: January 2005

The more exact dissociation theory of Part II, is applied to eighteen different gases and vapors, ranging in molecular weight from H2 to Xe. Interaction energies per molecule in clusters formed during condensation of the saturated vapors are found as functions of temperature. From the differences between surface energy and measured surface tension, which remain finite at Tc, estimates are made of the numbers of heavy clusters maintained in the saturated vapor over the liquid surface, also as functions of temperature. In the case of eight vapors, the theory predicts measurable differences between the two critical points, Tc at which the meniscus blurs, and Tr at which the densities equalize; the largest differences being for water, 6.5°K; methyl alcohol, 5.1°K; and nitrous oxide, 4.1°K. True critical volumes at Tr are calculated.
Negative Ion Formation in Iodine Vapor by Electron Impacts
Authors: Buchdahl Rolf
Published: January 2005

Using an apparatus similar to the one used by Lozier, the negative ion formation in I2 vapor was investigated as a function of the electron velocity (0–7 ev). The following reaction is responsible for negative ion formation at these velocities: I2+e→I—+I. Measurements of the kinetic energy of the ions for different electron energies show that all the ions are formed by the same reaction. The variation of the yield as a function of the velocity of the electrons can be understood with the help of a potential-curve diagram, by considering transitions from the ground state of the I2 molecule to the ground state of the I2— molecule. The probability that an electron colliding with an I2 molecule forms a negative ion varies between 10—4 and 10—3. With the aid of an energy cycle one can calculate the electron-affinity of the iodine atom, if one knows the dissociation energy of the neutral molecule, the kinetic energy of the incoming electron, and the kinetic energy of the ions. The value of the electron affinity obtained by this method is 3.0±0.2 ev, which is in agreement with other determinations.
A Note on Bethe-Kirkwood's Partition Function for a Binary Solid Solution
Authors: Chang T. S.
Published: January 2005

A symmetrical method of finding the Thiele semi-invariants λn in the partition function for a binary solid solution is described. In addition to the first four λ's already known, λ5 and λ6 are calculated.
Granulation, Phase Change, and Microstructure Kinetics of Phase Change. III
Authors: Avrami Melvin
Published: January 2005

The theory of the preceding papers is generalized and the notation simplified. A cluster of molecules in a stable phase surrounded by an unstable phase is itself unstable until a critical size is reached, though for statistical reasons a distribution of such clusters may exist. Beyond the critical size, the cluster tends to grow steadily. The designation ``nuclei'' or ``grains'' is used according as the clusters are below or above the critical size. It is shown that a comprehensive description of the phenomena of phase change may be summarized in Phase Change, Grain Number and Microstructure Formulas or Diagrams, giving, respectively, the transformed volume, grain, and microstructure densities as a function of time, temperature, and other variables. To facilitate the deduction of formulas for these densities the related densities of the ``extended'' grain population are introduced. The extended population is that system of interpenetrating volumes that would obtain if the grains granulated and grew through each other without mutual interference. The extended densities are much more readily derivable from an analysis of the fundamental processes of granulation and growth. It is shown that, under very general circumstances, the densities of the actual grain population may be expressed simply in terms of the extended population.
Spectroscopic Studies of the Simpler Porphyrins II. The Absorption Spectra of Porphine and Isoporphine, ms-Tetravanillinporphine and ms-Tetravanillinisoporphine, ms-Tetrapropylporphine and ms-Tetrapropylisoporphine, ms-Tetra-n-butylporphine and ms-Tetraisobutylporphine
Authors: Knorr H. V. , Albers V. M.
Published: January 2005

The molecular absorption coefficients of porphine and two aliphatic ms-tetrasubstituted porphines and one aromatic ms-tetrasubstituted porphine, together with their corresponding isomers have been measured for a portion of the visible region of the spectrum. The curves representing the absorptions coefficient as a function of wave-length are shown. In porphine and the aromatic ms-tetrasubstituted porphine a displacement in the spectrum toward the red region and a decrease in the magnitude of the absorption coefficients was observed, when the two isomers were compared. The aliphatic ms-tetrasubstituted porphine showed very little shift in the spectrum but a large increase in the value of the absorption coefficients for the case where the isomerism was in the fundamental ring of porphine. The shift was small and the value of the absorption coefficients nearly equal when the isomerism was in the side chain in the meso-position.
Spectroscopic Evidence for Hydrogen Bonds: Comparison of Proton-Attracting Properties of Liquids. IV
Authors: Gordy Walter
Published: January 2005

The strengths of deuterium bridges formed between heavy water and forty-two different basic solvents are compared by measurements of the perturbations which the solvents produce on the OD vibrational band of heavy water which occurs at 3.59 μ in heavy water vapor and at 4.00 μ in liquid heavy water. The solvents were selected from the following classes: ketones, ethers, esters, glycols, nitriles, amides, ketoximes and amines. The proton-attracting properties of twenty-five solvents are compared by measurement of the strengths of the hydrogen bonds which they form by sharing the proton of hydrogen chloride. Heavy water was found more satisfactory for strong and moderately weak bases; hydrogen chloride, for extremely weak bases. The shifts which the different liquids produce upon the D2O band and the HCl band are compared with the shifts which the same solvents produce on the OD vibrational band of CH3OD. A linear relation was found in each case, with frequent but small variations from linearity. Basicity constants were known from other measurements for nineteen of the solvents used with D2O. The shifts which these solvents produce on the D2O band were found to be directly proportional to the logarithms of their basicity constants. The method used here promises to be practical for comparing basicities of numerous types of compounds. The close relation existing between the hydrogen bond theory and modern theories of acids and bases is discussed.
On the Recombination of Iodine and Bromine Atoms
Authors: Rice O. K.
Published: January 2005

The data on the rate of recombination of iodine and of bromine atoms in the presence of an inert gas have been used, together with the equilibrium data, to calculate the rate of dissociation of I2 and Br2. The results have been used to obtain effective collision radii for the collision of I2 and Br2 molecules with the inert gas molecules. If the inert gas is a monatomic, or sufficiently simple, molecule, these effective radii turn out to be of the order of magnitude of ordinary kinetic theory radii, provided proper allowance is made for the density of energy levels in excited I2 and Br2. The interpretation of abnormally large radii, obtained in some cases, has been discussed.
Infra-Red and Raman Spectra of Polyatomic Molecules XIII. Nitromethane
Authors: Wells A. J. , Wilson E. Bright
Published: January 2005

The infra-red spectrum of gaseous nitromethane has been studied over the wave-length range from 3 to 25 μ. The Raman work of Pendl, Reitz and Sabathy has been checked. These data together with a partial normal coordinate treatment enable us to make an assignment of the observed lines and bands which accounts for all the fundamental frequencies except the torsion around the C–N bond. The fundamental frequencies for the gas are 476, 599, 647, 921, 1097, 1153, 1384, 1413, 1449, 1488, 1582, 2965, 3048 (2). No decision regarding the potential barrier restricting the internal rotation of the methyl group can be made until at least one thermo dynamic quantity has been measured. The present results are compatible with the usual structure CH3NO2.
The Normal Vibrations of Molecules with Internal Torsional Motions
Authors: Crawford Bryce L. , Wilson E. Bright
Published: January 2005

The vibrational problem has been treated for molecules consisting of a framework to which are attached any number of symmetrical tops, such as methyl groups. Nitromethane, methyl alcohol, neopentane, etc. are examples. The vibrational problem can be separated from the internal torsional and over-all rotation if the potential function is restricted so that the vibrational frequencies are independent of the torsion angles. The separation is effected by carrying out the normal coordinate treatment in the usual manner using however the value zero for all force constants involving torsion angles. The frequencies will not depend on the particular equilibrium orientation assumed for the tops. Furthermore the secular equation for the vibrational problem can frequently be factored to a greater extent than is indicated by the symmetry of the rigid molecule. The vibrational selection rules are also discussed and shown to be similar to those for normal molecules.
Induction and Dipole Moment in Chloro- and Nitroparaffins
Authors: Wiswall R. H. , Smyth C. P.
Published: January 2005

The dielectric constants of the vapors of the butyl chlorides, methyl chloroform, nitromethane, α- and β-nitropropane, and 2-methyl-2-nitropropane have been measured over a range of temperature and pressure and used to calculate the dipole moments of the molecules of these substances. The dipole moment increases from normal to secondary to tertiary butyl chloride much less than indicated by the apparent moments previously measured in solution, it being shown that the apparent solution values for the primary and secondary compounds are lowered by solvent effect. The moments found for α- and β-nitropropane and 2-methyl-2-nitropropane are indistinguishable from one another, but are slightly larger than that of nitromethane. Examination of the molecular models shows that the moment differences found are approximately those to be expected from the inductive effects, with the exception of the large difference between chloroform and methyl chloroform where it can only be said that induction is a major cause of the difference.
Hindered Rotation in Halogenated Ethanes
Authors: Glockler George , Sage Charles
Published: January 2005

If it is assumed on the basis of available evidence that the ``staggered'' form of the molecule is more stable than the ``eclipsed'' one, then the eight haloethanes investigated by means of the Raman effect show the following number of forms: CCl3CF3 and CCl3CHFCl one form (13 and 18 lines); CF2ClCF2Cl, CF2BrCF2Br, CF2ClCF2H and CF2ClCFCl2 two forms (23, 22, 21 and 24 lines) and CF2ClCHFCl and CF2BrCFClBr three forms (29 and 28 lines). These forms are considered to be distinct rotational isomers.
Electric Polarization of Carboxylic Acids in Dilute Solutions of Nonpolar Solvents I. The Relation of Electric Polarization to the Association of Carboxylic Acids in Hydrocarbon Solvents
Authors: Pohl Herbert A. , Hobbs Marcus E. , Gross Paul M.
Published: January 2005

The association and polar character of various carboxylic acids have been studied in the solvents benzene and heptane by means of measurements of the electric polarization in very dilute solutions. The data have been analyzed by assuming an equilibrium between dimers and monomers of the acid molecules. A rather large anomalous contribution to the polarization of the dimer has been found. Possible origins of this polarization have been briefly considered.
Electric Polarization of Carboxylic Acids II. Polarization of Heavy Acetic Acid and of the Three Fluorobenzoic Acids in Benzene and the Anomalous Polarization of the Dimer
Authors: Maryott Arthur A. , Hobbs Marcus E. , Gross Paul M.
Published: January 2005

The electric polarizations of acetic acid-d and o- m- and p-fluorobenzoic acids have been determined in benzene solution at concentrations ranging from approximately 10—5 to 10—2 mole fraction of solute. On the assumption of a monomer-dimer equilibrium, the polarization of the monomer and of the dimer molecules and the equilibrium constant have been calculated. The unexpectedly high polarization of the dimer is best interpreted on the basis of the assumption of an atomic polarization of about 20 cc.
Spectroscopic Studies of the Simpler Porphyrins III. The Absorption Spectra of ms-Tetraphenylporphine and a Series of Its Metal Complex Salts
Authors: Albers V. M. , Knorr H. V.
Published: January 2005

The molecular absorption coefficients of ms-tetraphenylporphine and the Cu, Ag2, Mg, Zn, Cd, Hg, SnCl2, Pb, MnCl, FeCl, Co and Ni complex salts have been measured over the visible region of the spectrum. The curves representing the absorption coefficients as a function of the wave-length are shown. The variations in the spectra of the metal salts of this one ms-tetrasubstituted porphine are much greater than those which have been found in the spectra of the different ms-tetrasubstituted porphines which so far have been studied.
Helium Repulsive Potential from Collision Cross Section Measurements
Authors: Amdur I. , Pearlman H.
Published: January 2005

Total collision cross sections have been measured for fast helium atoms, having velocities corresponding to 300–1000 electron volts, scattered in room temperature helium gas. Using classical theory, attempts were made to find a repulsive intermolecular potential which could account for the experimental results. A hard sphere model or a Lennard-Jones type potential were both unsatisfactory, whereas exponential type potentials of the form V(r)=A exp (−arn) seemed promising. For the distances involved in the scattering experiments, 0.55 to 1.05A, the specific repulsive potential which predicted total collision cross sections within the experimental error was V(r)=11.3 exp (−4.63r12)×10−10erg.
The Spreading of Oils on Water Part I. Ionized Molecules Having Only One Polar Group
Authors: Zisman W. A.
Published: January 2005

The spreading phenomena on water of drops of mineral oils containing a wide variety of organic acids and amines having but one polar group have been studied under conditions where dissociation at the oil-water interface could most readily occur. Particular emphasis is placed on the homologous series as an aid in separating the variables involved. Various phenomena of edge diffusion are described and a qualitative theory is presented. Edge diffusion is shown not to be a serious source of error in measuring the cross-sectional areas of the adsorbed molecules if there are over 13 carbon atoms per straight chain. The different types of film spreading and break-up effects are described and the various physical and chemical factors involved are discussed. The changes in the spreading effects due to varying the pH and to the presence in the water of Ca++, Cu++, Pb++, Fe+++, Al+++, La+++, and Th++++ on the interfacial film are described. It is shown that only the long chain monobasic saturated acids form rigid films when affected by metallic ions, while other acids are either condensed somewhat or are unaffected. Short chain metallic salts of these fatty acids are often oil soluble and have brief lifetimes of adsorption. An experimental proof is given that dissociated long chain acids and amines have infinite lifetimes of adsorption. Evidence is given for concluding that the lifetime is short for molecules having less than 14 carbon atoms. The effect of Ca++ on the spreading of oleic-stearic acid mixtures is given in some detail and also a theory of the results. Reasons are given for concluding that the adsorbed acid molecules form two-dimensional film complexes with hydrocarbon molecules derived from the oil.
Semi-Empirical Calculations of Activation Energies
Authors: Hirschfelder Joseph O.
Published: January 2005

The predictions of the Eyring semi-empirical scheme for calculating activation energies are compared with the existing experimental data. It is found that in most cases this agreement is satisfactory. However, the experimental data are not sufficiently accurate to make this scheme appear unique. The experimental activation energies seem to be functions only of the binding energies and do not depend in an important way on either the size of the atoms or on the diatomic force constants. If the reaction a+bc→ab+c is exothermic, it is found that the activation energy is 0.055D′bc, where D′bc is the energy of the bond bc. This formula is derived from the semi-empirical scheme on the assumption that the attraction between the distant atoms a and c is zero. For exothermic four atom reactions ab+cd→ac+bd, it is found that the activation energy is 0.28(D′ab+D′cd). The numerical factor was adjusted to fit the H2+I2 reaction and although, in most cases, this gives activation energies in agreement with the semiempirical values no mathematical connection has been made.
The Production of Concentrated Carbon (13) by Thermal Diffusion
Authors: Nier Alfred O. , Bardeen John
Published: January 2005

A thermal diffusion column 74 feet long and employing methane is being used for the concentration of C13. Every 48 hours 308 milligrams of methane are removed in which the C13/C12 ratio has been increased 11.5 times. The power consumption is 6490 watts and six liters/minute of cooling water is used. An expenditure of 156 kw-hr. of energy thus results in a transport of 13.5 mg of C13 per 24 hours. The measured output is in good agreement with the value computed from the theory.
Vorticity probes and the characterization of vortices in the Kelvin–Helmholtz instability in the large plasma device experiment
Authors: Horton W. , Perez Jean C. , Carter Troy , Bengtson Roger
Published: January 2005

A new five-pin probe design called the vorticity probe is presented that explicitly measures the vorticity in the E×B flow from floating potentials, independent of any absolute calibration errors. The five Tantalum probe tips are arranged in a diamond pattern with 5mm tip spacing. The fluctuating floating potential at each tip is measured and used to compute a finite-difference approximation of the E×B vorticity. The probe is tested in the large plasma device (LAPD) [W. Gekelman et al., Rev. Sci. Instrum. 62, 2875 (1991)], operated with a variable bias between the anode and the chamber wall that creates a sharply localized Er profile at 30cm from the axis of the 100cm diameter chamber. The fluctuations are peaked in the shear flow layer and are correlated with theoretical calculations of the Kelvin–Helmholtz instability for this plasma. The spectrum at 15–30kHz matches the theoretical prediction from the measured dEr∕dr gradient that reaches 17kV∕m2 in the B=0.075T axial magnetic field.
Precision tracking of driving wave forms for inertial reaction devices
Authors: Zou Qingze , Giessen Clint Vander , Garbini Joseph , Devasia Santosh
Published: January 2005

Inertial reaction devices (also referred to as impact drive, or slip-stick devices) enable nano/micro resolution positioning over macroscopic ranges. Such positioning devices are characterized by the displacement of a mass by utilizing stick-slip phenomena between the mass and the device’s actuators. The displacement of the actuator (i.e., the driving wave form) is chosen such that the mass sticks to the actuator and is displaced with the actuator during the first tracking phase, and the mass slips with respect to the actuator during the second retrace phase during which the actuator’s position is reset. However, as the driving wave form’s frequency is increased to operate an inertial-reaction device at high speed, induced mechanical vibrations prevent accurate actuator positioning and thereby, limit the maximum achievable operating speed. In this article, the actuator dynamics is modeled and iteratively inverted to find the input that compensates for the induced mechanical vibrations. This inversion-based input allows the actuator to track high-frequency driving wave forms without exciting mechanical vibrations, and thereby, allows the inertial reaction device to operate at higher operating speeds. The method is applied to a rotational inertial-reaction device, and experimental results show that the use of the inversion-based iterative approach enables tracking of the desired wave form at an order-of-magnitude higher frequency.
Sightline optimization of the multichannel laser interferometer for W7-X
Authors: Airila M. I. , Dumbrajs O. , Hirsch M. , Geiger J. , Neuner U. , Hartfuss H.-J.
Published: January 2005

A multichannel CO2 laser interferometer is planned for electron density profile measurements in the Wendelstein 7-X stellarator under construction. This article describes the mathematical methods used to find the optimum orientation of the various sightlines. The problem of reconstructing local densities from line integrated density measurements can be formulated as a matrix inversion. The quality of the reconstruction is largely determined by the condition number of the matrix describing the problem, which has to be minimized, i.e., the sightlines have to be chosen such that the information content of different channels is maximally distinct. For the W7-X interferometer four- and eight-sightline arrangements are investigated and their orientations are optimized for standard conditions of magnetic configuration and density profile. The optimized arrangements are tested by simulating the inversion of hypothetical reference density profiles in a number of different magnetic configurations. In the ideal case the error of a reconstruction using four sightlines is typically a few times larger than that with eight sightlines. The robustness of the optimization is demonstrated by a variation of the position of the whole interferometer, and the influence of noisy phase data on the reconstructed profiles is investigated. These factors significantly narrow the difference between the four- and eight-beam setups. Finally, the use of regularization methods for the analysis of experimental data is briefly discussed.
Apparatus for Seebeck coefficient and electrical resistivity measurements of bulk thermoelectric materials at high temperature
Authors: Zhou Zhenhua , Uher Ctirad
Published: January 2005

A high temperature Seebeck coefficient and electrical resistivity measurement apparatus has been designed and built for measuring advanced thermoelectric materials. The apparatus covers the range of temperatures from 300to1300K. Different sources of errors involved in the two measurements are discussed. The accuracy of the electrical resistivity measurement is estimated to be better than ±1% by measuring standard graphite sample from NIST.
Direct numerical simulations of turbulent flow over a permeable wall using a direct and a continuum approach
Authors: Breugem W. P. , Boersma B. J.
Published: January 2005

A direct numerical simulation (DNS) has been performed of turbulent channel flow over a three-dimensional Cartesian grid of 30×20×9 cubes in, respectively, the streamwise, spanwise, and wall-normal direction. The grid of cubes mimics a permeable wall with a porosity of 0.875. The flow field is resolved with 600×400×400 mesh points. To enforce the no-slip and no-penetration conditions on the cubes, an immersed boundary method is used. The results of the DNS are compared with a second DNS in which a continuum approach is used to model the flow through the grid of cubes. The continuum approach is based on the volume-averaged Navier–Stokes (VANS) equations [S. Whitaker, “The Forchheimer equation: a theoretical development,” Transp. Porous Media 25, 27 (1996)] for the volume-averaged flow field. This method has the advantage that it requires less computational power than the direct simulation of the flow through the grid of cubes. More in general, for complex porous media one is usually forced to use the VANS equations, because a direct simulation would not be possible with present-day computer facilities. A disadvantage of the continuum approach is that in order to solve the VANS equations, closures are needed for the drag force and the subfilter-scale stress. For porous media, the latter can often be neglected. In the present work, a relation for the drag force is adopted based on the Irmay [“Modèles théoriques d’écoulement dans les corps poreux,” Bulletin Rilem 29, 37 (1965)] and the Burke–Plummer model [R. B. Bird, W. E. Stewart, and E. N. Lightfoot, Transport Phenomena (Wiley, New York, 2002)], with the model coefficients determined from simulations reported by W. P. Breugem, B. J. Boersma, and R. E. Uittenbogaard [“Direct numerical simulation of plane channel flow over a 3D Cartesian grid of cubes,” Proceedings of the Second International Conference on Applications of Porous Media, edited by A. H. Reis and A. F. Miguel (Évora Geophysics Center, Évora, 2004), p. 27]. The results of the DNS with the grid of cubes and the second DNS in which the continuum approach is used, agree very well.
Statistics of particle transport in a two-dimensional dusty plasma cluster
Authors: Ratynskaia S. , Knapek C. , Rypdal K. , Khrapak S. , Morfill G.
Published: January 2005

Statistical analysis is performed on long time series of dust particle trajectories in a two-dimensional dusty plasma cluster. Particle transport is found to be superdiffusive on all time scales until the range of particle displacements approaches the size of the cluster. Analysis of probability distribution functions and rescaled range analysis of the position increments show that the signal is non-Gaussian self-similar with Hurst exponent H=0.6, indicating that the superdiffusion is caused by long-range dependencies in the system. Investigation of temporal and spatial characteristics of persistent particle slips demonstrates that they are associated with collective events present on all time scales and responsible for the non-Gaussianity and long-memory effects.
Apparatus for nonresonant rf power absorption studies in high Tc superconductors and CMR materials using rf oscillators
Authors: Sarangi S. , Bhat S. V.
Published: January 2005

The design, fabication, and performance of an apparatus for measurement of nonresonant rf power absorption (NRRA) in superconducting and CMR samples are described. The system consists of an effective self-resonant LC tank circuit driven by a NOT gate (Logic gate). The samples under investigation are placed in the core of an inductive coil and nonresonant power absorption is determined from the measured shift in total current supplies to the whole oscillator circuit. A customized low temperature insert is used to integrate the experiment with a commercial oxford cryostat and temperature controller. The system makes use of a sensitive digital multimeter (Keithley 2002 model) and is capable of measuring NRRA in superconducting and colossal magnetoresistance samples of volume as small as 1×10−3cm3 with a signal to noise ratio of 10. Further increase in the sensitivity of the experimental setup can be obtained by summing the results of repeated measurements obtained in the same temperature interval. The system has been tested for an IC 74LS04 oscillator at frequencies between 1MHz and 25MHz in the temperature range from 4.2Kto400K and in magnetic field from 0to1.4T. The system performance is evaluated by measuring the NRRA in YBa2Cu3O7 (YBCO) superconducting sample and La0.7Sr0.3MnO3 (LSMO) colossal magnetoresistive (CMR) manganite samples at different rf frequencies. During a measurement all operation are controlled automatically by computer from a menu-driven software system, with user input required only on initiation of measurement sequence.
Retention properties of fully integrated (Bi,La)4Ti3O12 capacitors and their lateral size effects
Authors: Kim D. J. , Jo J. Y. , So Y. W. , Kang B. S. , Noh T. W. , Yoon Jong-Gul , Song T. K. , Noh K. H. , Lee S.-S. , Oh S.-H. , Lee K.-N. , Hong S.-K. , Park Y.-J.
Published: January 2005

We investigated the retention characteristics of (Bi,La)4Ti3O12 (BLT) capacitors and their lateral size effects in a fully integrated device structure. Unlike the commonly used Pb(Zr,Ti)O3 capacitors for ferroelectric random access memories (FeRAMs), which have poor opposite-state retention characteristics, BLT capacitors showed very stable characteristics in both the same- and the opposite-state retention tests. These good retention properties were closely related to the small amount of imprint in the BLT capacitors. In addition, the retention characteristics of BLT capacitors showed no practical degradation due to the size reduction, down to 0.49×0.64μm2, which could be used for highly integrated FeRAMs of 32MB density.
SSIOD: The next generation
Authors: Kury P. , Grabosch T. , Horn-von Hoegen M.
Published: January 2005

Surface stress induced optical deflection (SSIOD) is a bending sample method for the in situ determination of the surface stress with a typical resolution of about 0.15N∕m. Here we present the latest version of SSIOD with major improvements concerning the sample shape and clamping, the laser system and the position detectors. With these modifications SSIOD becomes an easily applicable method to most UHV systems and can be combined with other surface analytical methods like SPA-LEED, Auger-CMA, XPS, UPS or maybe even with microscopy such as the flange-on LEEM. The presented modifications also improve the resolution of the method to below 0.01N∕m.
Comparison of hysteric and adhesive coefficient of friction for rubbers sliding onto self-affine rough surfaces
Authors: Palasantzas George
Published: January 2005

In this paper we investigate the influence of both the hysteric and adhesive friction for rubber surfaces sliding on self-affine rough surfaces. This type of roughness is described by the roughness amplitude w, the in-plane correlation length ξ, and the roughness exponent H that characterizes the degree of surface irregularity at short length scales (<ξ). It is shown that beyond the typical roughness parameters w and ξ, which are usually used in describing rough surfaces, the influence of the roughness exponent H should be taken carefully into account in order to properly gauge the contributing frictional mechanisms. Indeed, it is shown that for large roughness exponents (H∼1) and/or small roughness ratios w∕ξ<10−2, the adhesive friction becomes significant at relatively high sliding velocities beyond the maximum of the hysteric component.
Rapid thermal bonding of optical fiber interconnect
Authors: Bennett Ted D. , Farrelly Mark B. , Pasta Igor , Poulikakos D.
Published: January 2005

A model is developed and implemented using the finite element method to investigate the rapid thermal bonding of an optical fiber interconnect. The model is based on evaluating the elastic and plastic strain fields coupled with thermodynamic and fictive temperature fields. It is experimentally determined that the fiber bonding process leaves the material region below the bond pad in a significantly weakened state. The model is used to illustrate that a concentration of residual tensile stress occurs below the bond pad as a result of a steep gradient in fictive temperature (microstructure). It is found that bonds can be strengthened by furnace annealing, which equilibrates the fictive temperature below the bond pad.
Time-dependent current-voltage relation in electron guns
Authors: Weon Byung Mook , Je Jung Ho
Published: January 2005

We studied mathematical models for degradation behaviors of current and voltage in electron guns especially using oxide cathodes. We found that the current and the voltage, I(t) and V(t), follow the stretched exponential decay in oxide cathodes. On this basis, we derived a general expression for the time-dependent current–voltage relation as I(t)=p(t)V(t)δ(t), where δ(t) is a time-dependent exponent and the perveance, p(t), is a function of δ(t). The exponent δ(t) indicates the deviation of the classical Child–Langmuir relation (I=pV3∕2). This deviation is attributed to the gradual change of the electron gun geometry over time.
Simulation of oxygen vacancy induced phenomena in ferroelectric thin films
Authors: Li Kwok Tung , Lo Veng Cheong
Published: January 2005

The role of oxygen vacancy in lead–titanate–zirconate ferroelectric thin film has been numerically simulated using the two-dimensional four-state Potts model. On one hand, the presence of an oxygen vacancy in a perovskite cell strongly influences the displacement of the Ti4+ ion. Hence the vacancy–dipole coupling must be considered in the switching mechanism. On the other hand, a space charge layer is established by the inhomogeneous distribution of oxygen vacancies through trapping charge carriers. Consequently, the thickness dependence of the coercive field and remanent polarization are reproduced in the presence of this oxygen vacancy distribution. Frequency, temperature, and driving voltage-dependent polarization fatigue behaviors are also simulated.
Comparison of nanometer-thick films by x-ray reflectivity and spectroscopic ellipsometry
Authors: Kohli Sandeep , Rithner Christopher D. , Dorhout Peter K. , Dummer Ann M. , Menoni Carmen S.
Published: January 2005

Films of tantalum pentoxide (Ta2O5) with thickness of 10–100 nm were deposited on Si wafers and have been compared using spectroscopic ellipsometry (SE) and x-ray reflectivity (XRR). (Ta2O5) was chosen for comparison work based on various criterions for material selection outlined in this article. Measurements were performed at six positions across the sample area to take into consideration thickness and composition inhomogeneity. SE and XRR fitted curves required the incorporation of a linearly graded interface layer. SE systematically measured higher values of film thickness as compared to XRR. A linear equation was established between the thickness measurements using SE and XRR. The slope of the linear equation established was found to be 1.02±0.01. However, the intercepts were found to be 1.7±0.2 and 2.6±0.3 when the interface was excluded and included, respectively. These differences in the values of intercepts were attributed to the uncertainties in the determination of the interface layer.
P-assisted growth of molecular wires on Si(001)-2×1
Authors: Wang Yun , Hwang Gyeong S.
Published: January 2005

Using first principles quantum mechanics (DFT/GGA with pseudopotentials) calculations, we propose a mechanism for the P-assisted auto-catalyzed chain reaction of alkene molecules on a monohydride Si(001)-2×1–H surface. This study shows that surface-incorporated P atoms can serve as an initiator and a terminator for the self-directed growth of one-dimensional molecular wires on Si(001). We first present reaction paths and energetics for creation of single Si dangling bonds by (P-associated) selective H2 desorption on the P-incorporated Si(001)–H surface, with comparison to associative H2 desorption on the clean Si(001)–H surface. The (Si-dangling bond mediated) growth of styrene molecular lines is then compared between the P-incorporated and clean Si(001) surfaces.
Einstein oscillator in highly-random-packed bulk metallic glass
Authors: Tang M. B. , Bai H. Y. , Pan M. X. , Zhao D. Q. , Wang W. H.
Published: January 2005

Metallic glasses have often been regarded as ideal model systems of dense random packing with strong interaction among their components. Here we report direct evidence for the presence of the Einstein oscillator with an Einstein temperature θE of 74 K, which induces the boson peak at 4.9 meV in bulk metallic glass Zr46.75Ti8.25Cu7.5Ni10Be27.5. The presence of an Einstein oscillator suggests the existence of the vibrations of loose atoms in an independent localized harmonic mode in the highly random packed metallic glasses.
The effect of oxygenation on the superconducting properties of MgB2 thin films
Authors: Yates K. A. , Lockman Z. , Kursumovic A. , Burnell G. , Stelmashenko N. A. , MacManus Driscoll J. L. , Blamire M. G.
Published: January 2005

The effects of oxygen on the superconducting properties of thin films of MgB2 have been studied. It is found that after annealing for short times in flowing O2 at 400°C, complex oxides of Mgx(ByO)z are formed that cause a “two-step” behavior in the resistively determined superconducting transition. These oxides are not stable at room temperature and decay into MgO and B2O3 precipitates. As the complex oxides decay so the original Tc behavior of the films is restored to its preoxygenation level.
Stable and efficient electrophosphorescent organic light-emitting devices grown by organic vapor phase deposition
Authors: Zhou Theodore X. , Ngo Tan , Brown Julie J. , Shtein Max , Forrest Stephen R.
Published: January 2005

An electrophosphorescent organic light-emitting device (PHOLED™) employing fac-tris(2-phenylpyridine)iridium [Ir(ppy)3] as the green emitting phosphor has been fabricated using a pilot-production organic vapor phase deposition (OVPD™) system. Highly controlled mass transport of the organic vapor to the substrate results in deposition rates of over 10Å∕s and spatial uniformity better than ±2% across a 150mm×150mm substrate with less than ±2% run-to-run variations. The device current–voltage, luminous efficiency, and operational lifetime performances are compared to those of a similar device grown by conventional vacuum thermal evaporation (VTE). The green OVPD-grown PHOLED exhibits a maximum external quantum efficiency of (7.0±0.1)% at a luminance of 1000cd∕m2, comparable to the VTE device performance. The operational lifetime of the OVPD-grown devices was found to be comparable to or even somewhat longer than the lifetime achieved by VTE. Furthermore, PHOLEDs with emissive layers deposited at 4.8 and 10.8Å∕s are compared, and demonstrate equivalent performance.
Atomistic processes during nanoindentation of amorphous silicon carbide
Authors: Szlufarska Izabela , Kalia Rajiv K. , Nakano Aiichiro , Vashishta Priya
Published: January 2005

Atomistic mechanisms of nanoindentation of a-SiC have been studied by molecular dynamics simulations. The load displacement curve exhibits a series of load drops, reflecting the short-range topological order similar to crystalline 3C–SiC. In contrast to 3C–SiC, the load drops are irregularly spaced and less pronounced. The damage is spatially more extended than in 3C–SiC, and it exhibits long-range oscillations consistent with the indenter size. Hardness is ∼60% lower than in 3C–SiC and is in agreement with experiment. The onset of plastic deformation occurs at depth ∼75% lower than in 3C–SiC.
Terahertz wave generation and propagation in thin-film lithium niobate produced by crystal ion slicing
Authors: Ward David W. , Statz Eric R. , Nelson Keith A. , Roth Ryan M. , Osgood Richard M.
Published: January 2005

Terahertz phonon-polariton generation and real-space imaging with femtosecond optical pulses are demonstrated in a 10-μm-thick film of single-crystalline lithium niobate that was generated through crystal ion slicing. The film dispersion properties were characterized throughout the polariton wavelength range of 5–100μm, revealing substantial slab waveguide behavior at the longer wavelengths.
Radiation efficiency of water-window Cherenkov sources using atomic-shell resonances
Authors: Kaplan A. E. , Shkolnikov P. L.
Published: January 2005

A simple evaluation of the yield of Cherenkov radiation generated by relativistic electrons in the vicinity of atomic-shell resonances located in the water window x-ray domain is developed and applied to all the promising elements, including L-shell resonances explored recently by Knulst et al. [Appl. Phys. Lett. 83, 4050 (2003)], and K-shell resonance in liquid nitrogen proposed here. Our theoretical results compare favorably with experimental data. The feasibility of a related Cherenkov laser is also studied.
Multifocal flat lens with left-handed metamaterial
Authors: Wilson Jeffrey D. , Schwartz Zachary D.
Published: January 2005

We show experimental results demonstrating multiple focal lengths at microwave frequencies in a flat lens constructed of left-handed metamaterial (LHM). In contrast to conventional lenses, which are constructed of materials with positive index and require a curved surface or inhomogeneous structures to focus light or other electromagnetic radiation, no curvature is needed with a LHM because of a negative effective index of refraction. Such a flat lens has the advantage of being capable of changing the focal length by simply changing the distance between the electromagnetic source and the lens.
Direct comparison of field-effect and electrochemical doping in regioregular poly(3-hexylthiophene)
Authors: Shimotani Hidekazu , Diguet Gildas , Iwasa Yoshihiro
Published: January 2005

We have measured carrier mobility of regioregular poly(3-hexylthiophene) films by both field-effect and electrochemical doping on identical devices, which allowed us a direct comparison between the two doping processes. The carrier mobility of electrochemical doping at low doping levels was lower than that of field-effect doping by two orders of magnitudes, while that of electrochemical doping steeply increased with doping levels, reaching comparable or higher values than that of field-effect doping. These results are attributable to carrier trapping by the Coulomb potentials of dopant anions at low doping levels, demonstrating a significant difference between field-effect and chemical doping.
Coincidence fractional Fourier transform with entangled photon pairs and incoherent light
Authors: Cai Yangjian , Lin Qiang , Zhu Shi-Yao
Published: January 2005

The coincidence fractional Fourier transforms with entangled photon pairs and with incoherent light are introduced. Optical systems for implementing the two coincidence fractional Fourier transforms are designed. The difference between the two coincidence fractional Fourier transforms is discussed.
Laser emission from unprocessed cleavage microchip
Authors: Chen Y. J. , Huang Y. D. , Lin X. Q. , Tan Q. G. , Luo Z. D. , Lin Y. F.
Published: January 2005

A method utilizing an unprocessed cleavage microchip as the solid-state laser gain medium is proposed. Pumped by a Ti:sapphire laser at 871 nm, 1060 nm continuous-wave laser emission with slope efficiency of 23% has been achieved in an unprocessed microchip directly obtained from a cleavage Nd3+:LaB3O6 crystal. Based on this method, it is possible to avoid the difficulty of the microchip gain medium processing and largely lower the cost of solid-state lasers.
Role of thioredoxin in the response of normal and transformed cells to histone deacetylase inhibitors
Authors: Ungerstedt J. S. , Sowa Y. , Xu W.-S. , Shao Y. , Dokmanovic M. , Perez G. , Ngo L. , Holmgren A. , Jiang X. , Marks P. A.
Published: January 2005

This study examines the basis of resistance and sensitivity of normal and transformed cells to histone deacetylase inhibitor (HDACi)-induced cell death, specifically the role of caspases and thioredoxin (Trx). An important attribute of HDACis is that they induce cancer cell death at concentrations to which normal cells are relatively resistant, making them well suited for cancer therapy. The mechanism underlying this selectivity has not been understood. In this study we found that the HDACi suberoylanilide hydroxamic acid (SAHA) and MS-275, a benzamide, cause an accumulation of reactive oxygen species (ROS) and caspase activation in transformed but not normal cells. Inhibition of caspases does not block HDACi-induced cell death. These studies provide a possible mechanism that can explain why normal but not certain transformed cells are resistant to HDACi-induced cell death. The HDACi causes an increase in the level of Trx, a major reducing protein for many targets, in normal cells but not in transformed cells. The SAHA-induced increase in Trx activity in normal cells is associated with no increase in ROS accumulation. Transfection of transformed cells with Trx small interfering RNA caused a marked decrease in the level of Trx protein with an increase in ROS, a decrease in cell proliferation, and an increase in sensitivity to SAHA-induced cell death. Thus, Trx, independent of the caspase apoptotic pathway, is an important determinant of resistance of cells to HDACi-induced cell death.
Kinetic equivalence of the heat and cold structural transitions of λ
6–85
Authors: Yang Wei Y. , Gruebele Martin
Published: January 2005

Heat– and cold–denatured proteins are considered separate thermodynamic states because temperature tuning requires the protein to pass through two ‘soft’ first–order phase transitions. When both pressure and temperature changes are allowed, the heat– and cold–denatured states of proteins can be interconverted without going through the native state. This raises the question of whether these states are distinguished from one another by their folding kinetics. For the Tyr22Trp/Ala37Gly/Ala49Gly mutant of the 80 residue five–helix bundle protein
λ
6−85
, we show that viscosity–corrected folding rates do not distinguish the cold– and heat–denatured states. We attribute this to a folding mechanism dominated by hydrophobic collapse. Our ‘temperature–symmetric’ approach offers an alternative to viscosity tuning with solvent additives in such cases.
An evaluation of external factors in the decision of UK industrial firms to enter a new non‐domestic market: an exploratory study
Authors: Whitelock Jeryl , Jobber David
Published: January 2005

A study of key decision makers in a sample of large international companies explored the non‐domestic market entry decision. A literature review revealed five broad external domains which held the potential to affect that decision. A series of statements was factor analysed to reveal ten more specific variables. An analysis of which variables discriminated between the decision to enter and not enter a new non‐domestic market demonstrated that geocultural/political similarity, developed economy, attractive market, good market information and governmental attitude significantly affected the decision. The findings supported a marketing‐strategy based theory of market entry.