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Articles 33991 - 34020 of 36548

Full-Text Articles in Physical Sciences and Mathematics

Comment On "Molecular Description Of Two-Electron Atoms", Anthony F. Starace, Joseph H. Macek Jun 1987

Comment On "Molecular Description Of Two-Electron Atoms", Anthony F. Starace, Joseph H. Macek

Anthony F. Starace Publications

Molecular Description of Two-Electron Atoms

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Some Aspects Of The Isogroup Of The Self-Dual Yang-Mills System, C. J. Papachristou, B. Kent Harrison Jun 1987

Some Aspects Of The Isogroup Of The Self-Dual Yang-Mills System, C. J. Papachristou, B. Kent Harrison

Faculty Publications

A generalized isovector formalism is used to derive the isovectors and isogroup of the self-dual Yang-Mills (SDYM) equation in the so-called J formulation. In particular, the infinitesimal "hidden symmetry'' transformation, a linear system, and a well-known Backlund transformation of the SDYM equation are derived in the process. Thus symmetry and integrability aspects of the SDYM system appear in natural relationship to each other within the framework of the isovector approach.

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Length-Independent Voltage Fluctuations In Small Devices, A. Benoit, C. P. Umbach, R. B. Laibowitz, Richard A. Webb Jun 1987

Length-Independent Voltage Fluctuations In Small Devices, A. Benoit, C. P. Umbach, R. B. Laibowitz, Richard A. Webb

Faculty Publications

Conductance fluctuations in one-dimensional lines of length L shorter than the phase-coherence length Lφ are not universal but diverge as L-2. Using the Onsager relations and voltage additivity, we show that the voltage fluctuations are independent of the distance between voltage probes. The antisymmetric (Hall-type) contribution to the voltage fluctuations is constant for all values of L. Measurements of the voltage fluctuations and correlation function between different regions in Au and Sb lines confirm these results.

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Synthetic Aperture Multi-Telescope Tracker Apparatus, Richard A. Carreras, Salvatore J. Cusumano, Morton B. Jenks, Robert I. Suizu May 1987

Synthetic Aperture Multi-Telescope Tracker Apparatus, Richard A. Carreras, Salvatore J. Cusumano, Morton B. Jenks, Robert I. Suizu

AFIT Patents

A plurality of telescopes provide output return signals which are applied both directly and in sampled form to a photo-detector cell. The detected signals from the photo-detector will represent the constant and transient errors of the telescope system. A low pass filter insures that the tracker provides only the constant or D.C. component of the error, while a high pass filter insures that the existing measuring devices for each telescope beam provide only the transient or A.C. component of the error. The A.C. and D.C. error signals are summed together with the appropriate applied gains on each channel such that …

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Reduced-Mass Fock-Tani Representations For A+ + (B+C-) --> (A+C-) + B+ And First-Order Results For {Abc} = {Ppe, Epe, Μpμ, Μdμ, And Μtμ}, Jack C. Straton May 1987

Reduced-Mass Fock-Tani Representations For A+ + (B+C-) --> (A+C-) + B+ And First-Order Results For {Abc} = {Ppe, Epe, Μpμ, Μdμ, And Μtμ}, Jack C. Straton

Physics Faculty Publications and Presentations

The Fock-Tani transformation in the Jacobi three ⟶ two-body reduced-mass system is carried out and the first-order T matrix is found to be identical to that for the full three-body transformation. The Fock-Tani transformation in the reduced-mass system in which particle b is fixed at the origin is found to give a first-order T matrix with an error of mc /mb in the initial momentum wave function. First-order differential and total cross sections are calculated for a+ + (b+c-)⟶(a+c-) + b+ where |abc|= { …

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On The Height Variation Of The Equatorial F-Region Vertical Plasmadrifts, J. E. Pingree, Bela G. Fejer May 1987

On The Height Variation Of The Equatorial F-Region Vertical Plasmadrifts, J. E. Pingree, Bela G. Fejer

Bela G. Fejer

We have used improved incoherent scatter radar measurements at the Jicamarca Radio Observatory to study the height variation of the F region vertical plasma drift velocity (driven by the zonal electric field) during moderately quiet conditions. Preliminary results indicate a nearly linear change of the vertical drift velocity with altitude between 200 and 700 km, but with considerable day-to-day variations in the value of the slope. On the average, the velocity gradients are positive in the late night and morning periods and negative during the afternoon and evening hours. Simultaneous vertical and zonal drift measurements confirm that the measured height …

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University Of Missouri--Rolla Cloud Simulation Facility: Proto Ii Chamber, Daniel R. White, James L. Kassner, John C. Carstens, Donald E. Hagen, John L. Schmitt, Darryl J. Alofs, Alfred Raymond Hopkins, Max B. Trueblood, Max W. Alcorn, William L. Walker May 1987

University Of Missouri--Rolla Cloud Simulation Facility: Proto Ii Chamber, Daniel R. White, James L. Kassner, John C. Carstens, Donald E. Hagen, John L. Schmitt, Darryl J. Alofs, Alfred Raymond Hopkins, Max B. Trueblood, Max W. Alcorn, William L. Walker

Physics Faculty Research & Creative Works

The Graduate Center for Cloud Physics Research at UMR has developed a cloud simulation facility to study phenomena occurring in terrestrial clouds and fogs. The facility consists of a pair of precision cooled-wall expansion chambers along with extensive supporting equipment. The smaller of these chambers, described in this article, is fully operational, and is capable of simulating a broad range of in-cloud thermodynamic conditions. It is currently being used to study water drop growth and evaporation for drops nucleated (activated) on well-characterized aerosol particles. Measurements have been made not only for continuous expansions (simulated updraft) but also for cyclic conditions, …

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Variational Principles Of Fluid Mechanics And Electromagnetism: Imposition And Neglect Of The Lin Constraint, Ross Roundy Allen Jr. May 1987

Variational Principles Of Fluid Mechanics And Electromagnetism: Imposition And Neglect Of The Lin Constraint, Ross Roundy Allen Jr.

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Variational principles in classical fluid mechanics and electromagnetism have sprinkled the literature since the eighteenth century. Even so, no adequate variational principle in the Eulerian description of matter was had until 1968 when an Eulerian variational principle was introduced which reproduces Euler's equation of fluid dynamics. Although it successfully produces the appropriate equation of motion for a perfect fluid, the variational principle requires imposition of a constraint which was not fully understood at the time the variational principle was introduced. That constraint is the Lin constraint. The Lin constraint has subsequently been utilized by a number of authors who have …

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Magnetic Transitions And Scaling In Anisotropic Rare-Earth Glasses, Kevin M. Lee, Michael J. O'Shea, David J. Sellmyer Apr 1987

Magnetic Transitions And Scaling In Anisotropic Rare-Earth Glasses, Kevin M. Lee, Michael J. O'Shea, David J. Sellmyer

David Sellmyer Publications

We report studies of the magnetic critical behavior as a function of anisotropy strength in rare-earth-rich glasses. Anisotropy is induced in Gd-Co by alloying with Tb. The system studied is Gd65-xTbxCo35 and the random magnetic anisotropy (RMA) strength may be increased by increasing x. The x=0 alloy of this series has been shown to exhibit standard critical behavior expected for a second-order phase transition. With increasing x we find deviations from this behavior due to the presence of RMA. We present detailed results for the alloy with composition x=50 at. % and …

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Magnetic Properties Of Fe/Nd Multilayer Films, David J. Sellmyer, Z.R. Zhao, Z.S. Shan, S. Nafis Apr 1987

Magnetic Properties Of Fe/Nd Multilayer Films, David J. Sellmyer, Z.R. Zhao, Z.S. Shan, S. Nafis

David Sellmyer Publications

Measurements are reported on the relationship between magnetic properties and microstructure in thin amorphous and crystalline Fe/Nd multilayer films. The samples, denoted by (XÅFe/YÅNd) ( X/Y), were prepared in a multiple-gun sputtering chamber with a microprocessor-controlled rotating table. For X and Y values less than about 20 Å an amorphous compositionally modulated structure is obtained, with magnetic properties characterized by speromagnetic ordering associated with strong Nd random anisotropy. The net magnetization in general lies in the plane of the film. The temperature and composition dependence of the coercivity, magnetization, and transition temperatures are …

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Enhanced Magnetism In Amorphous Fe-Based Alloys, Sy_Hwang Liou, S.H. Ge, J.N. Taylor, C.L. Chien Apr 1987

Enhanced Magnetism In Amorphous Fe-Based Alloys, Sy_Hwang Liou, S.H. Ge, J.N. Taylor, C.L. Chien

Sy-Hwang Liou Publications

Systematic investigations of binary amorphous Fe–T alloys (T=an early transition-metal elements Ti, Zr, Nb, Hf, Ta...) over wide composition ranges reveal depressed magnetic properties with anomalously low magnetic ordering temperature and magnetization. We show in this work, via a prototype amorphous Fe70Ti30 alloy, the substitution of Fe by Co, Ni, or Cu greatly enhances the magnetic ordering temperature and the magnetization. Our results indicate that this is primarily caused by the increased Fe moment upon alloying.

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Magnetic Granular Fe-(Sio2) Solids, C.L. Chien, Gang Xiao, Sy_Hwang Liou, J.N. Taylor, A. Levy Apr 1987

Magnetic Granular Fe-(Sio2) Solids, C.L. Chien, Gang Xiao, Sy_Hwang Liou, J.N. Taylor, A. Levy

Sy-Hwang Liou Publications

We have synthesized a series of granular Fe-SiO2 solids consisting of Fe metal granules of nanometer sizes embedded in an insulating SiO2 matrix. The ultrafine microstructures, revealed by TEM, are achieved by using a high-rate magnetron sputtering system. The magnetic properties of such solids are determined by the granular size and the metal volume fraction. Below the percolation threshold, isolated single-domain particles having large magnetic coercivity in the blocked state exhibit superparamagnetic relaxation, which has been studied by using SQUID magnetometry and Mössbauer spectroscopy. Above the percolation threshold, magnetic coercivity drops dramatically and the magnetic properties approach that …

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Magnetic Characteristics Of Ultrafine Fe Particles Reduced From Uniform Iron Oxide Particles, K. Bridger, J. Watts, M. Tadros, Gang Xiao, Sy_Hwang Liou, C.L. Chien Apr 1987

Magnetic Characteristics Of Ultrafine Fe Particles Reduced From Uniform Iron Oxide Particles, K. Bridger, J. Watts, M. Tadros, Gang Xiao, Sy_Hwang Liou, C.L. Chien

Sy-Hwang Liou Publications

Uniform, cubic 0.05-µm iron oxide particles were formed by forced hydrolysis of ferric perchlorate. These particles were reduced to α-Fe by heating in hydrogen at temperatures between 300 and 500 °C. The effect of reduction temperature and various prereduction treatments on the microstructure of the iron particles will be discussed. Complete reduction to α-Fe was established by 57Fe Mössbauer spectroscopy and x-ray diffraction. Magnetic measurements on epoxy and polyurethane films containing these particles with various mass fractions gave coercivities as high as 1000 Oe. The relationship between the magnetic measurements and the microstructure will be discussed. Na2SiO …

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Mössbauer Study Of Spin Reorientation In Y1.8Er0.2Fe14B, M. Abe , Sy_Hwang Liou, C.L. Chien, N.C. Koon, B.N. Das, E. Callen Apr 1987

Mössbauer Study Of Spin Reorientation In Y1.8Er0.2Fe14B, M. Abe , Sy_Hwang Liou, C.L. Chien, N.C. Koon, B.N. Das, E. Callen

Sy-Hwang Liou Publications

Fe57 Mössbauer spectra were taken from 300 K down to 4.2 K for two single-crystal samples of Y1.8Er0.2Fe14B, one cut with its [001] axis normal to the surface, the other with its diagonal of [100], [010], and [001] axes normal to the surface. The former sample has shown that the angle between the Fe spin and the [001] increases continuously below ~90 K. This qualitatively agrees with the spin reorientation (i.e., the easy axis of magnetization rotates away from the [001] toward [100] on cooling below ~90 K) which have already been observed …

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Magnetism And Microstructure Of Compositionally Modulated Disordered Fe/Ta Films, Z.S. Shan, Z.R. Zhao, J.G. Zhao, David J. Sellmyer Apr 1987

Magnetism And Microstructure Of Compositionally Modulated Disordered Fe/Ta Films, Z.S. Shan, Z.R. Zhao, J.G. Zhao, David J. Sellmyer

David Sellmyer Publications

Results are presented on compositionally modulated disordered magnetic films of the form (XÅFe/YÅTa), as a function of the modulation wavelength λ≡X+Y. Magnetization, ac susceptibility, torque magnetometry, x-ray diffraction, and Mössbauer measurements are used to probe magnetic transitions and microstructure. For X and Y values less than about 12 Å the structure is amorphous within the layers and compositionally modulated in the direction perpendicular to the film. Films with ultrathin individual layers (1–3 atomic diameters) exhibit perpendicular anisotropy while the thicker ones have in-plane magnetization. Spin-glass and ferromagnetic transitions are observed and are …

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Radiosensitivity Parameters For Neoplastic Transformations In C3h10t1/2 Cells, M. P. R. Waligorski, G. L. Sinclair, Robert Katz Apr 1987

Radiosensitivity Parameters For Neoplastic Transformations In C3h10t1/2 Cells, M. P. R. Waligorski, G. L. Sinclair, Robert Katz

Robert Katz Publications

We have evaluated radiosensitivity parameters for cellular transformation from published experimental data on neoplastic transformations induced in C3H10T1/2 cells by BEVALAC ions. The measured RBE values are well reproduced by a track theory calculation using sets of m-target parameters with either m = 2 or m = 3, suggesting a quadratic or cubic extrapolation to low doses of γ rays. Using track theory one is thus able to predict transformation frequencies in those cells after an arbitrary radiation field, under known or assumed conditions of exposure, in a manner shown earlier for cellular survival. Extension of these calculations to interpret …

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Science And Society Test X: Energy Conservation, David W. Hafemeister Apr 1987

Science And Society Test X: Energy Conservation, David W. Hafemeister

Physics

United States energy consumption has remained essentially constant at about 80 exajoules/year (75 quads/year) since the oil embargo of 1973–1974, while the GNP in constant dollars has increased by about 30%. This article will discuss the physics behind some of these improvements in end-use efficiency in such areas as: (i) buildings (scaling laws, "free-heat,'' superinsulated houses, thermal storage in large buildings, off-peak cooling), (ii) solar energy (passive, photovoltaics), (iii) utility load management ("smart meters,'' capital recovery fees, voltage control), (iv) appliances (life-cycle costs, refrigerators), and (v) lighting (isotopic enhancement).

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Search For An Instability On A Quenched-Liquid Interface, Steven N. Rauseo, Nalini Easwar, James V. Maher Apr 1987

Search For An Instability On A Quenched-Liquid Interface, Steven N. Rauseo, Nalini Easwar, James V. Maher

Physics: Faculty Publications

We searched for signs of an instability on the interface between the two phases of a binary-liquid mixture, isobutyric acid and water, after the mixture was quenched further into the two-phase region. Such an instability would be the liquid-liquid analog of the Mullins-Sekerka instability seen in quenched alloys. Never is any dramatic growth observed, but under conditions of small dimensionless quench depth (theta<1.5×10−3), the intensity of light scattered from the interface grows for small values of the momentum transfer k.

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The Breakdown Of Hund's Rule In Systems Of Fourfold Symmetry, Gordon A. Gallup Apr 1987

The Breakdown Of Hund's Rule In Systems Of Fourfold Symmetry, Gordon A. Gallup

Gordon Gallup Publications

The lowest energies of molecular systems with fourfold symmetry can violate Hund's multiplicity rule. We derive relationships between two electron integrals that in favorable cases allow one to predict when this will happen. These relationships result in a fairly simple inequality as a criterion. The systematics of the phenomenon are illustrated with a series of calculations on model systems consisting of hydrogen atoms. These are rings of three, four, five, six, seven, and eight members as well as octahedral and square planar arrangements. These show how the results and simple ideas of molecular orbital theory can be qualitatively modified when …

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A Study Of The Direct Capture Process Of Protons By 27Al, Rozana Hussain Apr 1987

A Study Of The Direct Capture Process Of Protons By 27Al, Rozana Hussain

Masters Theses

An experimental investigation of the 27Al(p,γ)28Si reaction was made for protons in the energy range 550- to 1785-keV and at angles of 0, 20, 55, 90 and 118 degrees. Four angular distributions at Ep = 845-, 1055-, 1135-, and 1618-keV were selected for detailed study. These angular distributions were fit with theoretical calculations employing a directcapture model. These fits permitted the extraction of spectroscopic factors for the population of the first excited-state in 28Si by proton transfer.

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Testing Of Beam Line For Charge Exchange Measurements, Mohd. Noor Ali Apr 1987

Testing Of Beam Line For Charge Exchange Measurements, Mohd. Noor Ali

Masters Theses

The atomic physics beam line in the Western Michigan University accelerator laboratory was tested for the first time for making atomic charge-exchange experiments. Cross sections obtained for single electron capture and loss for 25 MeV oxygen ions incident on a helium gas target are in reasonable agreement with previous measurements. These results indicate that the system is operating properly. An attempt to observe a nuclear resonance effect on electron capture and/or loss was not successful. However, it was determined that additional collimation is necessary for such measurements.

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Separated Resonances In Simultaneous Capture And Excitation Of S¹⁵⁺ In H₂ Observed By K-X-Ray K-X-Ray Coincidences, Michael Schulz, Edson L B Justiniano, Reinhold S. Schuch, Paul H. Mokler, S. Reusch Apr 1987

Separated Resonances In Simultaneous Capture And Excitation Of S¹⁵⁺ In H₂ Observed By K-X-Ray K-X-Ray Coincidences, Michael Schulz, Edson L B Justiniano, Reinhold S. Schuch, Paul H. Mokler, S. Reusch

Physics Faculty Research & Creative Works

We have measured cross sections for the correlated emission of two K x rays following the collision of hydrogenlike sulfur ions with H2 in the energy range between 70 and 160 MeV. The observation of the two correlated x rays is interpreted as a resonant capture of a target electron accompanied by simultaneous excitation of the projectile in the collision (RTE). By our distinguishing between Kα and Kβ lines, contributions from KLL and KLn (n≥M) resonances could be determined independently.

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Semiclassical Analysis Of A Detuned Ring Laser With A Saturable Absorber: New Results For The Steady States, D. E. Chyba, N. B. Abraham, Alfonso M. Albano Apr 1987

Semiclassical Analysis Of A Detuned Ring Laser With A Saturable Absorber: New Results For The Steady States, D. E. Chyba, N. B. Abraham, Alfonso M. Albano

Physics Faculty Research and Scholarship

This paper presents new results for the steady states of a detuned ring laser with a saturable absorber. We employ a semiclassical model which assumes homogeneously broadened two-level atoms. We proceed by solving the Maxwell-Bloch equations for the longitudinal dependence of the steady states of this system, and then simplify our solution by use of the uniform-field approximation. We present uniform-field results for squared electric field versus operating frequency, and for each of these versus cavity tuning and laser excitation. Various cavity linewidths and both resonant and nonresonant amplifier and absorber line-center frequencies are considered. The most notable finding is …

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On A Moving Boundary Problem Of Transitional Ballistics, Jen-Ing G. Hwang Apr 1987

On A Moving Boundary Problem Of Transitional Ballistics, Jen-Ing G. Hwang

Mathematics & Statistics Theses & Dissertations

A major problem which arises in computer simulation of the firing of a gun weapon is the development of numerical schemes which effectively account for the physics of projectile motion. The chief difficulty is that away from the projectile the calculation is ordinarily accomplished on a fixed numerical grid, whereas due to projectile movement some cells of the grid near the projectile undergo volume changes as the calculation proceeds. A local finite volume scheme is developed which accounts for the expansion or compression of cells fore-and-aft of the projectile. Through the process of numerical experiment, the effectiveness of the scheme …

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A Numerical Study Of Three-Dimensional Vortex Breakdown, Robert Edward Spall Apr 1987

A Numerical Study Of Three-Dimensional Vortex Breakdown, Robert Edward Spall

Mechanical & Aerospace Engineering Theses & Dissertations

A numerical simulation of vortex breakdown using the time-dependent Navier-Stokes equations was performed. Unlike previous studies, the numerical algorithm, formulated in terms of the velocity and vorticity, was not restricted to axisymmetric flows. Prototype vortices were parameterized in terms of their Reynolds number and Rossby number. Two cases were studied extensively. In one case, a vortex was imbedded in a uniform free stream. In the other case, the axial velocity of the free stream was decelerated in the streamwise direction. For both cases breakdown occurred when the Rossby number was below a critical value. Vortex lines, particle traces and velocity …

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Studies Of Radiation Effects In Three High Polymers, Heidi Rene-Mitchell Ries Apr 1987

Studies Of Radiation Effects In Three High Polymers, Heidi Rene-Mitchell Ries

Physics Theses & Dissertations

Three high polymers, Mylar®, Ultem®, and Kapton®, were irradiated to total doses of 1, 5, and 9.5 gigarad using 1-MeV electrons. The glass transition temperatures (Tg) of the materials before and after irradiation were measured using an AC electrical dissipation factor technique. From the Tg data, it was found that the electron radiation at these total doses results in net chain scissioning in Mylar and net crosslinking in Ultem, while self-mending is predominant in Kapton. The dielectric constant was measured before and after irradiation, but no significant changes due to irradiation were observed. Electron paramagnetic resonance (EPR) …

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Inactivation Of Dry Enzymes And Viruses By Energetic Heavy Ions, M. P. R. Waligorski, Kim Sun Loh, Robert Katz Mar 1987

Inactivation Of Dry Enzymes And Viruses By Energetic Heavy Ions, M. P. R. Waligorski, Kim Sun Loh, Robert Katz

Robert Katz Publications

A newly developed corrected formula for the radial distribution of dose (RDD) has been used to calculate cross sections for the inactivation of dry enzymes and viruses by heavy ions ranging from 42He to 4018 Ar of energies ca. 10 MeV/a.m.u., spanning a range of LET of ca. 5–2,000 Me V cm2 g–1. In comparison with earlier “point-target” calculations of Butts and Katz where a linear range-energy relationship for electrons (δ-rays) was used, and with “extended-target” calculations of Zhang, Dunn, and Katz, where a power range-energy law and an “uncorrected” RDD formula …

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Binding Of Fe2+ By Mammalian Ferritin, Richard B. Frankel, G. C. Papaefthymiou, G. D. Watt Mar 1987

Binding Of Fe2+ By Mammalian Ferritin, Richard B. Frankel, G. C. Papaefthymiou, G. D. Watt

Physics

An average of 140 Fe2+ ions bind to mammalian ferritin that has an average core content of 1876 Fe3+ ions per molecule. The Fe2+ ions enter the protein interior and exchange electrons with the core Fe3+ ions. A non-homogeneous model for the iron-containing core of ferritin is proposed.

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Comparison Of Low-Energy Seismic Sources In Till, Paul J. Wolfe, B. H. Richard, Dale V. Dailey, James R. Plomer Mar 1987

Comparison Of Low-Energy Seismic Sources In Till, Paul J. Wolfe, B. H. Richard, Dale V. Dailey, James R. Plomer

Physics Faculty Publications

No abstract provided.

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Multicritical Susceptibility Sum Rules, Miron Kaufman, Michael Ma Mar 1987

Multicritical Susceptibility Sum Rules, Miron Kaufman, Michael Ma

Physics Faculty Publications

Asymptotically close to the Nth-order multicritical point of an N-phase system, there are N-1 sum rules involving the mean-field susceptibilities measured in each of the coexisting phases. These sum rules provide the experimentalist a convenient and stringent test of the theory. In particular, they facilitate the detection of nonclassical effects, especially valuable for N>3 where the fluctuation effect is dominated by the classical contribution for three-dimensional systems.

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