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Physics

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1980

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Articles 31 - 60 of 87

Full-Text Articles in Physical Sciences and Mathematics

Inversion Of The Nonlinear Equations Of Reflection Ellipsometry For Uniaxial Crystals In Symmetrical Orientations, M. Elshazly-Zaghloul, R. M.A. Azzam Jul 1980

Inversion Of The Nonlinear Equations Of Reflection Ellipsometry For Uniaxial Crystals In Symmetrical Orientations, M. Elshazly-Zaghloul, R. M.A. Azzam

Electrical Engineering Faculty Publications

The complex ordinary (No) and extraordinary (Ne) refractive indices of an absorbing uniaxial crystal can be determined using reflection ellipsometry. The measurements are taken with the optic axis parallel and perpendicular to the crystal’s surface. The equations obtained are solved without resort to iterative methods; No and Ne are determined separately. Sixteen solution sets (No, Ne) are obtained and the correct solution can be easily identified. We present an optimum angle of incidence that minimizes the relative errors in No and Ne.

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Automation Of A Popular Monochromator, David C. Look, J. W. Farmer, R. N. Ely Jul 1980

Automation Of A Popular Monochromator, David C. Look, J. W. Farmer, R. N. Ely

Physics Faculty Publications

A wavelength‐scan and intensity‐control system for a widely‐used, high‐intensity monochromator is described. The wavelength scan is bidirectional and variable speed, and may be controlled manually or by TTL logic from a computer. The intensity control is effected by use of a programmable dc power supply and D–A converter. Various filters are described which allow an intensity of up to 2×1014 photons/cm2 s to be achieved in a 1 cm×3 cm area over a wavelength range 0.76–2.50 μm, at 0.07 μm bandwidth, with a single grating. (A lesser intensity is available to 3.4 μm.) This wide range is made …

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Effect Of Hydrostatic Pressure On The Incommensurate Phase Of K2Seo4, W. Press, C. F. Majkrzak, J. D. Axe, John R. Hardy, N. E. Massa, F. G. Ullman Jul 1980

Effect Of Hydrostatic Pressure On The Incommensurate Phase Of K2Seo4, W. Press, C. F. Majkrzak, J. D. Axe, John R. Hardy, N. E. Massa, F. G. Ullman

John R. Hardy Papers

A neutron scattering study of the effect of hydrostatic pressure on the incommensurate phase transformation in K2SeO4 was performed in order to obtain information concerning the nature of the competing forces that give rise to a structural instability at a general wave vector. It was found that an increase in pressure lowers the transition temperature (dTi/dPi = - 6.5 K/kbar) and results in a smaller value of the initial incommensurate wave vector. The pressure dependence of the incommensurate to ferroelectric phase transition was also investigated (dTc/dPc = …

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Addendum To "Ab Initio Treatment Of Final-State Spin-Orbit Interactions: Photoionization Of The 6s Electron In Cesium", Keh-Ning Huang, Anthony F. Starace Jul 1980

Addendum To "Ab Initio Treatment Of Final-State Spin-Orbit Interactions: Photoionization Of The 6s Electron In Cesium", Keh-Ning Huang, Anthony F. Starace

Anthony F. Starace Publications

A previous calculation of the cesium 6s→εp photoionization cross section is extended to include interchannel coupling to the 5p→εd photoionization channels. For photon energies in the range 0.35 a.u.≲ℏω≲1.12 a.u., i.e., just above the near-threshold cross-section minimum, the 6s photoionization cross section is found to be dominated by 5p→5d resonance transitions. No experimental data exist for this energy region.

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Pressure Dependence Of Fluorescent And Photolytic Interferences In Ho Detection By Laser-Excited Fluorescence, Thomas M. Hard, Robert J. O'Brien, T. B. Cook Jul 1980

Pressure Dependence Of Fluorescent And Photolytic Interferences In Ho Detection By Laser-Excited Fluorescence, Thomas M. Hard, Robert J. O'Brien, T. B. Cook

Chemistry Faculty Publications and Presentations

In the measurement of HO concentrations by laser-excited fluorescence, expansion of the sampled air offers a way to reduce fluorescent and photolytic interference by other species. The decrease in [HO] upon expansion is balanced by an increase in HO fluorescence yield over a wide range of pressures. Background air fluorescence is reduced if the responsible species have fluorescence yields higher than those of HO. Preliminary experiments indicate that most of the fluorescence observed in laboratory air is due to such species. Upon expansion, the suppression of fluorescent interference can be no greater than the reduction in pressure, whereas the suppression …

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An Apparatus For Measuring The Thermal Conductivity Of Cast Insulation Materials, Christine A. Wilkins, Robert L. Ash Jul 1980

An Apparatus For Measuring The Thermal Conductivity Of Cast Insulation Materials, Christine A. Wilkins, Robert L. Ash

Mechanical & Aerospace Engineering Faculty Publications

A steady-state apparatus has been developed for measuring the thermal conductivity of cast materials. The design has employed a novel thermal symmetry arrangement which can permit total electrical isolation of the test material from its surroundings. © 1980 American Institute of Physics

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Studies Of H₂O On Ss-Agi Surfaces: An Effective Pair Potential Model, Barbara N. Hale, Jerry Kiefer Jul 1980

Studies Of H₂O On Ss-Agi Surfaces: An Effective Pair Potential Model, Barbara N. Hale, Jerry Kiefer

Physics Faculty Research & Creative Works

Effective pair potential functions are used to study the adsorption of a water molecule on surfaces of β-AgI. The water molecule is represented by a rigid point charge ST-2 model and the AgI substrate by an array of point atoms with effective charge ±0.6e, Lennard-Jones cores, and ionic polarizabilities. Maximal binding energy surfaces and optimal H2O configurations are generated for the water molecule adsorbed on the rigid and unrelaxed basal and prism AgI faces. Adsorption of the H2O above a two layer ledge, an iodine vacancy, and an H2O trapped in the …

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Ionospheric Irregularities, Bela G. Fejer, M. C. Kelley Jun 1980

Ionospheric Irregularities, Bela G. Fejer, M. C. Kelley

Bela G. Fejer

Extensive experimental and theoretical research has been performed in the last decade to study ionospheric irregularities. These studies have shown that plasma instabilities play a major role in the generation of the irregularities. In this work we describe in detail the recent experimental studies of the E and F region irregularities and also the extensive work on plasma instability theories developed to explain them. We also describe both radio wave and spacecraft-borne experimental techniques to allow a common ground for the understanding of the data from ground-based and in situ experiments. To date, theoretical work has been mostly concentrated on …

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Supralinearity Of Peak 5 And Peak 6 In Tld-700, Michael P. R. Waligórski, Robert Katz Jun 1980

Supralinearity Of Peak 5 And Peak 6 In Tld-700, Michael P. R. Waligórski, Robert Katz

Robert Katz Publications

Track theory has been applied to an earlier suggestion, that the supralinearity of TLDs at high gamma-ray doses is due to pre-existing 1-hit and 2-hit trap structures, to calculate high-LET response. Measured 60Co dose responses for peaks 5 and 6 in LiF (TLD- 700) were decomposed to yield parameters characterizing each peak as a two-component c-hit mixture. One value of “trap radius” was assigned to each two-component representation, different for peak 5 and for peak 6, to calculate their responses for H, He, C, O, and Ne bombardments. Calculations reproduce experimental features of the heavy ion response of TLD-700, and …

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Influence Of Las Vegas Wash Density Current On Nutrient Availability And Phytoplankton Growth In Lake Mead, John R. Baker, Larry J. Paulson Jun 1980

Influence Of Las Vegas Wash Density Current On Nutrient Availability And Phytoplankton Growth In Lake Mead, John R. Baker, Larry J. Paulson

Publications (WR)

Density currents are commonly formed in reservoirs because of temperature or salinity induced density differences between inflowing and receiving waters. Anderson and Pritchard (1951) were among the first to demonstrate this in their investigations of density currents in Lake Mead. They found that the Colorado River formed an underflow in Lake Mead during the winter, an overflow in the spring and an interflow in the summer and fall. Wunderlich and Elder (1973) have since described the hydromechanics of these types of flow patterns, and density currents have been reported for several other large reservoirs (Carmack et al. 1979, Johnson and …

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Nature Of Iron Deposits On The Cardiac Walls In Β-Thalassemia By Mössbauer Spectroscopy, K. S. Kaufman, G. C. Papaefthymiou, Richard B. Frankel, A. Rosenthal May 1980

Nature Of Iron Deposits On The Cardiac Walls In Β-Thalassemia By Mössbauer Spectroscopy, K. S. Kaufman, G. C. Papaefthymiou, Richard B. Frankel, A. Rosenthal

Physics

An identification of the nature and an estimation of the particle size distribution of the iron deposits on thalassemic heart tissue is carried out by variable temperature Mössbauer spectroscopy. Comparison of Mössbauer spectra obtained for the thalassemic heart tissue (I) with those of normal heart tissue (II) and of horse spleen ferritin (III) identifies the iron deposits to be small, superparamagnetic particles of ferritin and/or hemosiderin, two closely related iron storage proteins containing an iron core of (FeOOH)8(FeO · OPO3H2). The dependence of the superparamagnetic relaxation time, τ2, of magnetically ordered fine …

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Effective Force Constant Ratios: Iron In Iridium And Rhodium, Dennis Munsterman May 1980

Effective Force Constant Ratios: Iron In Iridium And Rhodium, Dennis Munsterman

Dissertations and Theses

Classical methods of analyzing heat capacity data for the characteristic moments of the frequency distribution are applied to iridium and rhodium. Impurity moments are determined from high and low temperature f values. These moments are combined by modern theory to estimate the magnitude of the host-host to host-impurity force constant ratio. Ratios of the various host moments are also examined.

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Fluid-Structure-Factor Measurements In 4he For 5.5<=T<=7.0 K, Robert Hallock, D. A. Ewen, H. N. Robkoff May 1980

Fluid-Structure-Factor Measurements In 4he For 5.5<=T<=7.0 K, Robert Hallock, D. A. Ewen, H. N. Robkoff

Robert Hallock

We report precise measurements of the structure factor S(k) as a function of the momentum transfer k for 4He at T=5.5 and 6.5 K in the density range 10<~ρ<~155 kg/m3. No theoretical predictions that can be tested against the data are available. The recent theoretical work by Bruch et al. at T=7.0 K, ρ=69.6 kg/m3 is in only limited agreement with our experimental data at T=7.0 K, ρ=69.0 kg/m3.

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Third Sound And The Decay Of Persistent Currents In Unsaturated 3he-4he Films, Robert Hallock May 1980

Third Sound And The Decay Of Persistent Currents In Unsaturated 3he-4he Films, Robert Hallock

Robert Hallock

We report the observation of metastable currents in unsaturated 3He-4He-mixture films. The decay rate of these currents is found to be an increasing function of 3He concentration in the film. A simple model for the role of the 3He, adequate to explain our observations of the concentration dependence of the third-sound velocity, does not agree with the measured decay rates.

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Very-Long-Lived Metastable Vibrational States Of Ba2++ , Stanley J. Sramek, J.A. Macek, Gordon A. Gallup May 1980

Very-Long-Lived Metastable Vibrational States Of Ba2++ , Stanley J. Sramek, J.A. Macek, Gordon A. Gallup

Gordon Gallup Publications

Potential-energy curves for the 1 Σg+ states of Ba2++ are exhibited. The ground-state curve shows a local minimum lying 0.0562 a.u. above the energy at infinite separation, and a local maximum lying at 0.0618. These features form a potential well in which metastable vibrational states can exist. The lifetimes are estimated as high as 10197 sec, using the WKB method. Considerations regarding experimental formation and detection of bound Ba2++ are discussed.

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Electron Irradiation Defects In N-Type Gaas, J. W. Farmer, David C. Look Apr 1980

Electron Irradiation Defects In N-Type Gaas, J. W. Farmer, David C. Look

Physics Faculty Publications

We have studied the production and annealing of defects produced by 1-MeV electron irradiation of n-type GaAs. Two of these defects lie at 0.15 and 0.31 eV from the conduction band, respectively; in addition, there is at least one acceptor much closer to the valence band. The carrier-removal rate depends upon sample purity but is independent of the irradiation flux. The removal rate is also highly dependent upon the position of the the Fermi level, an effect which is considered in some detail. At about 200°C, the defects recover in two stages, with the respective recovery rates given by λ …

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Studies Of The Reorientational Relaxation Of Pyridine In Water By Depolarized Rayleigh Light Scattering, C. H. Wang, Scott L. Whittenburg, P. A. Lund, D. H. Christensen Apr 1980

Studies Of The Reorientational Relaxation Of Pyridine In Water By Depolarized Rayleigh Light Scattering, C. H. Wang, Scott L. Whittenburg, P. A. Lund, D. H. Christensen

Chemistry and Biochemistry Faculty Publications

The depolarized Rayleigh spectra of aqueous solutions of pyridine have been studied using a high‐finesse Fabry–Perot interferometer as a function of temperature and concentration. The Rayleigh relaxation times are found to have a complex concentration and viscosity dependence. The classical Stokes–Einstein–Debye equation for molecular reorientation breaks down in this system. The Rayleigh relaxation time of pyridine molecules is not determined by the macroscopic shear viscosity of the solution. The specific interaction due to the formation of hydrogen bonds between pyridine and water molecules plays a very important role in affecting the relaxation time. At a fixed temperature the plot of …

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Partial Chemical Equilibrium In Fluid Dynamics, John D. Ramshaw Apr 1980

Partial Chemical Equilibrium In Fluid Dynamics, John D. Ramshaw

Physics Faculty Publications and Presentations

An analysis is given for the flow of a multicomponent fluid in which an arbitrary number of chemical reactions may occur, some of which are in equilibrium while the others proceed kinetically. The primitive equations describing this situation are inconvenient to use because the progress rates ω [subscript s] for the equilibrium reactions are determined implicitly by the associated equilibrium constraint conditions. Two alternative equivalent equation systems that are more pleasant to deal with are derived. In the first system, the ω [subscript s] are eliminated by replacing the transport equations for the chemical species involved in the equilibrium reactions …

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Photoionization Of The 5S Subshell Of Xenon: A Multichannel K-Matrix Calculation Including Spin-Orbit Interactions, Keh-Ning Huang, Anthony F. Starace Mar 1980

Photoionization Of The 5S Subshell Of Xenon: A Multichannel K-Matrix Calculation Including Spin-Orbit Interactions, Keh-Ning Huang, Anthony F. Starace

Anthony F. Starace Publications

Ab initio theoretical calculations are presented for the cross section, angular distribution, and spin polarization of photoelectrons for the 5s subshell of xenon. Starting from an initial basis of nonrelativistic Hartree-Fock wave functions, the authors treat the effect of final-state spin-orbit interaction in the Breit-Pauli approximation exactly. Electrostatic correlations between the 5s and 5p subshells are also included. Good agreement is obtained with experiment in the case of the photoionization cross section, but only qualitative agreement with experiment and with other theoretical calculations is obtained in the case of the photoelectron angular distribution due to the difficulty …

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Angular Differential Cross Sections For Excitation Of Atomic Hydrogen To The N=2 Level By Proton Impact, John T. Park, Judith E. Aldag, Jerry Peacher, Jacob M. George Mar 1980

Angular Differential Cross Sections For Excitation Of Atomic Hydrogen To The N=2 Level By Proton Impact, John T. Park, Judith E. Aldag, Jerry Peacher, Jacob M. George

Physics Faculty Research & Creative Works

Differential cross sections for 15-145-keV proton impact excitation of atomic hydrogen to the n=2 level have been determined for center-of-mass scattering angles 0 to 1.2 mrad. The cross sections were obtained from an analysis of the angular distribution of protons which had lost an energy corresponding to the excitation of atomic hydrogen to its n=2 level. The differential cross sections obtained are in rather good agreement with available coupled-state calculations as well as the simpler Glauber-approximation calculations. However, at the larger scattering angles the cross sections obtained from the theoretical treatments appear to decrease more rapidly than the experimental data.

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Potential Use Of Chemical Spot Test Method For Submicron Aerosol Sizing, Paul C. Yue, Josef Podzimek Mar 1980

Potential Use Of Chemical Spot Test Method For Submicron Aerosol Sizing, Paul C. Yue, Josef Podzimek

Physics Faculty Research & Creative Works

A submicron particle, which is too small to be observed in an optical microscope, may form an observable spot on a chemically prepared substrate of the collector. The size of the spot or "Liesegang circle" is related to the aerodynamic diameter of the particle through a magnification factor. This paper presents the experimental results of the study of this factor using sodium chloride aerosol in the size range of 0.5 to 2 pm which has not previously been studied. We calibrated a cylindrical centrifuge with known sized latex particles. A relationship between the aerodynamic diameter and the deposition length is …

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Four-Color And Hβ Photometry Of Stars In The Galactic Cluster Ngc 6087, Edward G. Schmidt Feb 1980

Four-Color And Hβ Photometry Of Stars In The Galactic Cluster Ngc 6087, Edward G. Schmidt

Edward Schmidt Publications

Four-color and Hβ photometry has been obtained for 16 stars in the open cluster NGC 6087. Based on this photometry the membership of these stars in the cluster is discussed. Using stars which appear to be members a color excess of E(b – y) = 0m.23 and a distance modulus of (V0 – Mv) = 9m.60 are derived. This distance modulus is about 0m.4 less than previous values and indicates a lower luminosity for the Cepheid member, S Nor, than is currently accepted.

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Navigational Compass In Magnetic Bacteria, Richard B. Frankel, R. P. Blakemore Jan 1980

Navigational Compass In Magnetic Bacteria, Richard B. Frankel, R. P. Blakemore

Physics

Magnetotactic bacteria that orient and swim in a preferred direction in the geomagnetic field contain sufficient single domain magnetite to constitute a biomagnetic compass.

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Magnetic Properties Of [Fe4S4(Sr)4]3- Clusters, G. C. Papaefthymiou, Richard B. Frankel, S. Foner, E. J. Laskowski, R. H. Holm Jan 1980

Magnetic Properties Of [Fe4S4(Sr)4]3- Clusters, G. C. Papaefthymiou, Richard B. Frankel, S. Foner, E. J. Laskowski, R. H. Holm

Physics

No abstract provided.

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Electronic Properties Of Molybdenum-Iron-Sulfur-Clusters: Approaches To The Molybdenum Site In Nitrogenase, Richard B. Frankel, T. E. Wolff, P. P. Power, R. H. Holm Jan 1980

Electronic Properties Of Molybdenum-Iron-Sulfur-Clusters: Approaches To The Molybdenum Site In Nitrogenase, Richard B. Frankel, T. E. Wolff, P. P. Power, R. H. Holm

Physics

No abstract provided.

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Solid State Phase Transitions And Molecular Reorientation In Ortho-Carborane And Para-Carborane: An Isomer Effect, Peter A. Beckmann, Amos J. Leffler Jan 1980

Solid State Phase Transitions And Molecular Reorientation In Ortho-Carborane And Para-Carborane: An Isomer Effect, Peter A. Beckmann, Amos J. Leffler

Physics Faculty Research and Scholarship

The proton nuclear spin-lattice relaxation times at 30 MHz have been measured for ortho- and paracarborane between 170 and 310 K and between 210 and 320 K, respectively. Para-carborane undergoes solid-solid transitions at about 300 and 238 K while the ortho isomer shows only one transition at about 265 K. The details of the phase transitions are discussed and molecular reorientation in the isomers is compared.

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Proton Spin-Lattice Relaxation In Meta-Carborane, Peter A. Beckmann, Armin Wendel Jan 1980

Proton Spin-Lattice Relaxation In Meta-Carborane, Peter A. Beckmann, Armin Wendel

Physics Faculty Research and Scholarship

No abstract provided.

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A Deuterium Nuclear Magnetic Resonance Study Of Chain Disorder In Lamellar Potassium Palmitate: The Effect Of Long And Short Chain Guests, Peter A. Beckmann, E. E. Burnell, M. A. Heldman, K. R. Northey, T. P. Higgs Jan 1980

A Deuterium Nuclear Magnetic Resonance Study Of Chain Disorder In Lamellar Potassium Palmitate: The Effect Of Long And Short Chain Guests, Peter A. Beckmann, E. E. Burnell, M. A. Heldman, K. R. Northey, T. P. Higgs

Physics Faculty Research and Scholarship

The deuterium magnetic resonance spectra of lamellar phases of host perdeuterated potassium palmitate mixed with varying amounts of guest protiated potassium octanoate and behenate and 86.3 mol% D2O are reported. At higher temperatures, the short chain guests give rise to more fluidity and the long chain guests give rise to less fluidity towards the end of the host chain. At low temperatures there are changes in the interaction between the polar head group and the water which depend on sample composition. The transition from the lamellar phase to the low temperature gel phase is investigated and in some …

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The Effects On Grain-Boundary Processes Of The Steps In The Boundary Plane Associated With The Cores Of Grain-Boundary Dislocations, Alexander H. King, D. A. Smith Jan 1980

The Effects On Grain-Boundary Processes Of The Steps In The Boundary Plane Associated With The Cores Of Grain-Boundary Dislocations, Alexander H. King, D. A. Smith

Alexander H. King

The contribution of the associated steps to the properties of grain-boundary dislocations are investigated. Two methods of step-height determination are given and it is shown that the step height, like the Burgers vector, must be conserved during the reactions of grain-boundary dislocations: this is not always automatic and additional coherent steps must take part in some reactions. The energies associated with steps have been estimated and compared with the elastic energies of grain-boundary dislocations; these comparisons suggest that (a) the reduction of elastic energy alone may not be a sufficient criterion for the progress of a reaction and (b) that …

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Thermodynamic Model And Sum Rules For Three-Phase Coexistence Near Thetricritical Point In A Liquid Mixture, Miron Kaufman, K. K. Bardhan, Robert B. Griffiths Jan 1980

Thermodynamic Model And Sum Rules For Three-Phase Coexistence Near Thetricritical Point In A Liquid Mixture, Miron Kaufman, K. K. Bardhan, Robert B. Griffiths

Miron Kaufman

Two sum rules for order-parameter susceptibilities are derived for the classical theory of the three-phase region near a tricritical point in ordinary liquid mixtures. The classical theory can also be fitted in a quantitative way to the composition data of Lang and Widom near the tricritical point in the mixture ethanol+ benzene+ water + ammonium sulfate.

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