Simple Interaction Model Research Articles

Valence Charge Fluctuations in Tl2-x-zBa2Ca2+xCu3O10-y System

Systematic XPS core level studies and wet chemical analysis in the Tl2-x-zBa2Ca2+xCu3O10-y system have been carried out for the "as synthesized" samples. Broadening of Ca 2p core level and ionic radii considerations suggest that calcium substitutes at the Tl site. The valence state of thallium in Tl2223 is between +3 and +1, and substitution of calcium at thallium site oxidizes thallium to Tl(III) to optimize the hole concentration and maximize Tc. Origin of holes in this system is discussed in terms of charge transfer between Tl (or Tl, Ca) and CuO2 layers. The Cu 2p3/2 core level shows that the relative intensity of satellite, the energy separation between main line and the satellite and binding energy of main line varies in a systematic way. The observed variations are explained with a simplified configuration interaction model. An increase in charge transfer energy and a decrease in hybridization strength is predicted for higher Ca substitution.

Separation of enantiomers by affinity electrokinetic chromatography using avidin.

Avidin, a basic protein isolated from egg white, was employed as a chiral selector in affinity electrokinetic chromatography (EKC) for the separation of acidic enantiomers. Optical isomers of vanilmandelic acid, warfarin, ibuprofen, ketoprofen, flurbiprofen, and folinic acid were successfully resolved within 20 min with 25 microM avidin in a linear polyacrylamide-coated capillary under weakly acidic conditions. The effects of pH, the concentration of avidin, addition of an organic solvent such as ethanol and 2-propanol, and temperature on enantioselectivity were investigated. The choice of pH and the organic solvent additive was critical to improve the separation. Some general considerations about affinity EKC are also described, based on a simple one-site interaction model.

Earthquake Response Estimation and Control of Equipment Supported by Frames

Dynamic interaction between industrial equipment and its supporting frames should be taken into account in the aseismic design of complex industrial structures such as blast furnaces, chemical reactor vessels, towers, or stacks. This paper aims to examine the effects of dynamic interaction on the maximum base shear distribution between two kinds of sructural components, that is, the equipment and its supporting frames, and on the vibratory energy consumption of the damping devices placed between these two structural components. The random vibration theory is applied to obtain the average peak responses of simplified interaction models placed on a base which is stimulated by ground acceleration having the standard power spectrum. The expected ratio of the maximum rocking moment shared between the two structural components of the dynamic model is obtained as a function of the dynamic characteristics of each constituent component and the interaction spring, and the maximum response is reduced by the intermediate damping devices. These results are presented garaphically for convenience so as to determine the rational aseismic design forces for each structural component.

Relation of magneto-optical properties of free excitons to spin alignment of Mn 2+ ions in Cd1− xMnxTe

A direct comparison of the splitting of free exciton states with the magnetic moment of the Mn 2+ ion system shows excellent agreement with simple exchange interaction model throughout the composition range studied (0.005 < x < 0.3) at liquid helium temperature in magnetic field up to 5.6 T. Measurements of magnetic moments up to 15.5 T at 1.5 K show paramagnetic behaviour of samples with low manganese contents. With increasing amount of manganese mile fraction, strong influence of interaction of antiferromagnetic type between Mn 2+ ions is observed. Comparison of optical and magnetic data yields refined values of exchange integrals of Mn 2+ ions with conduction and valence electrons: 0.22 and -0.88 eV, respectively.

Thermodynamics and transport properties of n-butane computed by molecular dynamics using a rigid interaction model.

With a simple rigid four-center interaction model we computed the thermodynamics and transport properties of liquid n-butane by equilibrium molecular dynamics. Unlike previous works, which investigated only one state near the boiling point with semiflexible models, this work considers six states ranging from the boiling point to the triple point. In contrast to the studies based on semiflexible potential models, our calculations give good agreement with experiment for states near the boiling-point state. Reasonable agreement with experiment was achieved for the pressure and the shear viscosity at denser states near the triple point. The equilibrium time-correlation functions were computed for different shapes of the model molecules. Their time dependence leads to interesting conclusions concerning the anisotropic behavior of the molecules in the liquid state. Unlike the correlation functions, the transport coefficients were found to be nearly independent of the molecule shape. This explains partially why our rigid potential model is successful.

Comment on “Comparison of observed and calculated implanted ion distributions outside comet Halley's bow shock” by T. I. Gombosi, M. Neugebauer, A. D. Johnstone, A. J. Coates, and D. E. Huddleston

It is argued that the formulation used by Gombosi (1991) does not distinguish between two fundamental types of resonant interactions (those between cometary pickup ions and LF electromagnetic waves). Two problems arise from using their overly simplified expressions. The wave polarization of the solar wind Alfven wave is not purely right-handed, and values from alpha sub com and alpha sub sw are not well known, nor are the 'polarizations' of the 'backward'-going waves in either case. Gombosi et al. discuss the antisunward vs the sunward propagating solar wind Alfven wave, and assume a reasonable value of 0.2 for alpha sub sw. However, alpha sub com is totally unknown. It is concluded that a more correct analysis of wave polarization can lead to significant changes in the formulation and results from Gombosi et al. In his reply Gombosi argues that his simplified wave-particle interaction model is consistent with Giotto observations and plasma kinetic simulations and it leads to a reasonable approximation of the implanted ion transport coefficients. The more complicated approach suggested by Tsurutani & Thorne (1993) requires the introduction of several ad hoc parameters and it does not lead to any change of the energy diffusion coefficient.

A pseudo-spin model for poly(vinylidene fluoride-trifluoroethylene) copolymers

We propose a simple four-particle interaction model to describe the phase transition in the poly(vinylidene fluoride—trifluoroethylene) [P(VDF-TrFE)] system. The mean field treatment of this model displays the main qualitative behaviour of the copolymer by predicting a tricritical point for an equimolar VDF-TrFE sample and the thermal evolution of the order parameter for the different sample compositions.

Investigation of the Electronic Structure of Oxocuprates by Photoelectron Spectroscopy

The oxocuprates Y2BaCuO5 and Bi2CuO4 the crystal structures of which contain discrete CuO5 and CuO4 units, respectively, have been investigated by angle integrated photoelectron spectroscopy. The Cu 2p core level and Cu L3VV Auger spectra are analysed within a simple cluster configuration interaction model. The experimental data and model parameters, namely the charge transfer energy Δ, the transfer integral T, and the correlation energy U as well as the main valence band features are similar as for oxocuprates with extended copper oxygen network.

Interacting with structure-oriented editors

Why have structure-oriented editors failed to attract a wider audience? Despite their obviously good qualities, they have almost exclusively been used for education and for experimental purposes in universities and research labs. In this paper a number of common objections raised against structure-oriented editors are quoted and commented upon. Many objections concern the interaction of such editors. Therefore the aspect of interaction in structure-oriented editors in analysed in more detail. We pin down the differences between interacting with text and structure-oriented editors, thus obtaining a deeper understanding of how structure-oriented editors can be improved to suit both naive and expert users. An analysis based on Norman's model for user activities is presented both for text editing and structure-oriented editing of programming languages. The analysis illustrates the trade-offs between structure-oriented editing and text editing of programs. It is also used to suggest some improvements to structure-oriented editor interaction in order to minimize the mental and physical effort required. The interaction problems have earlier been dealt with in hybrid editors, which combine structure-oriented editing and text editing in one system. This approach is also commented upon and discussed. Conceptual models are presented and compared for text editors. structure-oriented editors and hybrid editors. An interaction model for structure-oriented editors based on direct manipulation is suggested. The model is examined in terms of semantic distance, articulatory distance, and engagement as suggested by Hutchins et al. It is also related to the analysis of user activities and the discussion of conceptual models. The direct manipulation model aims at obtaining a simple but powerful interaction model for “pure” structure-oriented editors that may be appreciated by different user categories. Finally, some objections against structure-oriented editors not concerning interaction issues are commented upon, and some directions for future research are outlined.

An analysis of Sigma -hypernuclear spectra using a simplified model

The (K, pi ) Sigma -hypernuclear spectrum is studied, using a simple interaction model with a square-well central part and a delta function spin-orbit Sigma -nuclear core interaction. With this simplified model the general features of the spectrum are explained. A comparison is made between the theoretical results and the in-flight (K, pi +) experimental data for Sigma 12C and Sigma 16O. A shallow potential, with a central potential depth of Vc=(-5-115) MeV and a spin-orbit depth of Vso=15 MeV, gives a satisfactory representation of the CERN and BNL in-flight data.

Thermodynamic properties of mixing for SnCl 4 dissolved in supercritical CO 2: a combined experimental and molecular dynamics study

Giles, N.F., Oscarson, J.L., Rowley, R.L., Tolley, W.K. and Izatt R.M., 1992. Thermodynamic properties of mixing for SnCl 4 dissolved in supercritical CO 2: a combined experimental and molecular dynamics study. Fluid Phase Equilibria, 73: 267-284. Enthalpies and volumes of mixing were measured as a function of composition for mixtures of SnCl 4 in supercritical CO 2 at two temperatures (313.15 and 348.15 K) above the critical temperature of pure CO 2 and at four pressures (6.29, 8.36, 10.44 and 12.50 MPa) spanning the critical pressure of CO 2. Molecular dynamics simulations were performed at the same conditions, modeling SnCl 4 as a Lennard-Jones fluid and CO 2 as a two-site fluid interacting with Lennard-Jones potentials. Quite simple molecular interaction models are capable of reproducing the large pressure dependence observed in both the mixing volume and enthalpy data in the critical region of pure CO 2. Additionally, Widom's method was used to obtain the excess free energies of the mixtures. Simulated vapor-liquid equilibrium for conditions below the mixture critical locus is in qualitative agreement with phase boundaries obtained from the experimental heat of mixing data.

Dynamic Interaction and Base Shear Distribution Between Equipment and its Supporting Frames.

Dynamic interaction between industrial equipment and its supporting frames during earthquakes should be taken into account for earthquake-resistant design of complex industrial structures such as blast furnaces, chemical reactor vessels or towers, certain kinds of stacks, and so on. In the first stage of the current aseismic design of these structures, the maximum base shear transmitted to each component is assumed in advance in order to obtain a precise stress analysis of each one. It is significantly important, therefore, to provide well-grounded base shear distribution in place of the conventional values which are decided via a static analysis at most. This paper aims to examine the effects of dynamic interaction on the base shear distribution between equipment and its supporting frames during earthquakes. The random vibration theory is applied to obtain the average peak responses of simplified interaction models placed on a base which is being stimulated by ground acceleration having the standard power spectrum. The expected maximum values of the rocking moment distribution are obtained as the function of dynamic characteristics of both components and the interaction spring. These results are presented graphically for convenience so as to determine the rational base shear distribution of structures composed of equipment and its supporting framed.

Fish and Nutrients Interplay Determines Algal Biomass: A Minimal Model

An analysis is presented of a simple zooplankton-phytoplankton interaction model, accounting for the effects of nutrients and planktivorous fish. The overall behaviour is shown to be analogous to that of the cusp catastrophe model with nutrients and fish as control variables. Predictions that emerge are : gradual change in fish density can lead to discontinuous changes in zooplankton and phytoplankton density under eutrophic conditions; planktivorous fish tends to damp zooplankton-phytoplankton oscillations; enrichment in the absence of fish enhances zooplankton density, but has no effect on algal density, whereas in the presence of a high fish stock the opposite applies. These and other predicted patterns are demonstrated to be present indeed in much field data and experimental results

The electronic structure of the [CuO5]8? unit: A photoemission study of Y2BaCuO5

A photoemission study of the ‘green phase’ Y2BaCuO5, including core level spectra of the elements, CuL3VV Auger, and XPS and UPS valence band spectra has been performed. The crystal structure of Y2BaCuO5 contains discrete [CuO5]8− units with divalent copper. The surface status of the Y2BaCuO5 samples is discussed with respect to the problems encountered in photoemission studies of the YBaCuO superconductors. The photoemission data are analysed within a simple cluster configuration interaction model by considering in addition previously reported optical spectra. Y2BaCuO5 is a charge transfer insulator with the charge transfer energy Δ≈0.5 eV being much smaller than thed−d Coulomb interaction energyU≈6eV. Cluster model parameters and valence band shapes of Y2BaCuO5 are compared with those of Nd2CuO4 the structure of which contains divalent copper within an extended copper-oxygen network. More detailed cluster and impurity models for cuprates described in literature are discussed in view of the present results.

Electronic surface states on Pd(110): Theory and comparison with experiment

A relativistic Green function formalism has been applied to calculate layer-projected densities of states on Pd(110). In particular, we obtained unoccupied surface states and their dispersion relations along two directions in the surface Brillouin zone. Good agreement with recent inverse photoemission data is reached by using an energy-dependent “dynamical” surface potential barrier, which is based on a simple electron-plasmon interaction model, instead of a “static” surface barrier.

An Illustrative Model of Seasonal and Interannual Variations of the Stratospheric Circulation

Abstract A simple wave-zonal flow interaction model, originally developed by Holton and Mass, is used to illustrate a rudimentary conception of seasonal and interannual variations of the stratospheric circulation. The radiative heating is varied periodically with an annual component to investigate the response of the circulation (i.e., the seasonal variation) to the periodic forcing. The response is qualitatively different depending on the wave forcing from the troposphere. The difference resembles that of the climatological seasonal march between the Northern and the Southern hemispheres. No example of interannual variations (namely, nonperiodic responses) was obtained for the periodic annual forcing. Interannual variation of external conditions is necessary in the present model to obtain interannual variations. A finite range of year-to-year variations of the wave forcing can produce large interannual variability as in the Northern Hemisphere.

Some aspects of bias current tuning of W-band IMPATT diodes mounted in a reduced-height waveguide circuit

The bias current tuning of W-band IMPATTs in reduced-height waveguide circuits have been discussed in details. The measured tuning response can be increasing, decreasing or practically insensitive with bias current depending on the device and circuit parameters. The observed results are explaine with a simple device-circuit interaction model.

Influence of the water content on the kinetics of counter-ion transport in perfluorosulphonic membranes

The high frequency electrical resistance of a Nafion ® 117 perfluorosulphonic membrane has been measured by means of the ac impedance technique. Using a mercury cell, the variations of the membrane conductance as a function of the degree of swelling and of the nature of the counter-ion have been determined. The variations of the conductance with the water content have two different origins: the first is a change in the rate constant of the elementary ion transfer reaction due to interactions between the mobile ions and the fixed sites, and the second is related to a change in the microstructure of the membrane material. An analysis of the membrane conductance on the basis of the absolute rate theory is proposed. It enables one to explain the shape of the impedance diagrams and shows that the variations of the membrane conductance with its water content cannot be accounted for by geometric considerations alone. On the basis of a simple electrostatic interaction model, the energy barrier of the elementary ion transfer jump can be related to the hydration radius of the cation.

Trace element and isotope geochemistry of zoned calcite cements, Lake Valley Formation (Mississippian, New Mexico): insights from water-rock interaction modelling

Regionally extensive, pre-Pennsylvanian, meteoric zoned calcite cements from the Mississippian age Lake Valley Formation (New Mexico) comprise three major zones, zones 1, 2, and 3, each with a distinct isotope and trace element geochemistry. Zone 1 has the highest Mg, 18O, and 13C contents, zone 2 intermediate values and greatest Mn and Fe, and zone 3 has the lowest trace element, 18O, and 13C values. Covariation of C and O isotopes for the three zones define an inverted “L”-shaped trend, and covariations of Mg-Mn and Mg-Fe define “L”-shaped trends, all suggestive of rock evolution curves resulting from water-rock interaction. These covariant trends were the impetus for quantitative mass balance modelling of water-rock interaction. Iterative mass balance modelling of covariations of stable isotopes (C and O) and trace elements (Mg, Mn, Fe) of these zoned cements implies that water-rock interaction progressively decreased (water/rock ratios increased) during precipitation. Cementing waters for the oldest cement zone (zone 1) resulted from water/rock ratios in the range of tens to a few hundred, whereas the youngest cement (zone 3) resulted from water/rock ratios in the 100's to 1000's. The modelling also implies that differences in geochemistry of the cement zones cannot be explained solely by changes in water/rock ratios, but require greater 18O, and greater Ca and Mg concentrations in input waters that evolved to zone 1 precipitational waters than those for zones 2 and 3. Zones 2 and 3 can reasonably be modelled using input waters with the same isotopic compositions, the same Ca concentration, and for some zone 2 cement the same Mg concentrations. The minimum Mg/Ca ratios in input waters is constrained by the lower Mg “plateau” in Mg-Mn space, and is about the same for all three zones, about 1/25. The maximum Mg/Ca ratios (about 1 20 ) occurred in zone 2 input waters. Mn-Fe covariations also show an “L”-shaped trend, a trend whch fits neither a simple water-rock interaction model, nor a simple Eh model. A model is proposed in which Eh and limited Mn sources determine the amount of Fe and Mn available in solution to partake in water-rock interaction. Water-rock interaction modelling provides one useful approach to quantitatively interpreting isotopic and trace element data from diagenetic carbonates to gain a clearer understanding of evolution of diagenetic fluids.

Interactions in SMA‐SAN blends

AbstractStyrene/maleic anhydride (SMA) and styrene/acrylonitrile (SAN) copolymers have previously been shown to form miscible blends when the MA and AN contents do not differ too greatly. It is shown here that this is the result of a weak exothermic interaction between the MA and AN units by measuring the heats of mixing for appropriate liquid analogs of the various monomer units. The region of copolymer compositions for miscibility of SMA‐SAN blends is predicted from the Sanchez‐Lacombe mixture theory using net interaction parameters calculated from the analog calorimetry results via a simple binary interaction model for copolymers. Lower critical solution temperature behavior was observed for blends of copolymers having compositions near the edge of the miscibility region. Various glass transition, volumetric, and FTIR results are discussed in terms of the interactions observed.