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Articles 3751 - 3780 of 3783

Full-Text Articles in Physical Sciences and Mathematics

Rotationally Inelastic Molecular Scattering. Computational Tests Of Some Simple Solutions Of The Strong Coupling Problem, Thomas P. Tsien, Gregory A. Parker, Russell T. Pack Nov 1973

Rotationally Inelastic Molecular Scattering. Computational Tests Of Some Simple Solutions Of The Strong Coupling Problem, Thomas P. Tsien, Gregory A. Parker, Russell T. Pack

Faculty Publications

Partial cross sections (opacity functions) for rotational transitions in atom-diatom collisions are computed in the infinite-order sudden (IOS) approximation and compared with accurate close-coupling (CC) calculations. Agreement is good in the dominant coupling (small total angular momentum J) region. Simple methods for calculating integral inelastic cross sections are discussed, and it is found that accurate cross sections can often be computed very simply, even when large numbers of channels are coupled together, by using IOS or first-order sudden (FOS) approximations for small J and CC or exponential Born (EBDW) methods for large J.

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The Role Of Mannosyl-Phosphoryl-Dihydropolyisoprenol In The Synthesis Of Mammalian Glycoproteins, John W. Baynes, An-Fei Hsu, Edward C. Heath Aug 1973

The Role Of Mannosyl-Phosphoryl-Dihydropolyisoprenol In The Synthesis Of Mammalian Glycoproteins, John W. Baynes, An-Fei Hsu, Edward C. Heath

Faculty Publications

A mouse myeloma tumor was used as a model system to study the biochemical steps involved in the incorporation of mannose into glycoproteins. This tumor, MOPC-46B, synthesizes a K-type immunoglobulin light chain (K-46) which is a glycoprotein with a single oligosaccharide side chain containing mannose as one of its constituent sugars. MOPC-46B microsomal preparations contain enzymes which transfer mannose from the sugar nucleotide, GDPmannose, to endogenous lipid and protein acceptors. Formation of the mannolipid proceeds by the reversible transfer of mannose from GDP-mannose to an endogenous phospholipid. The mannolipid was purified and characterized by chemical methods and mass spectrometry as …

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Nonlinear Stochastic Integral-Equation Of Hammerstein Type, William J. Padgett May 1973

Nonlinear Stochastic Integral-Equation Of Hammerstein Type, William J. Padgett

Faculty Publications

No abstract provided.

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Observation Of A Second-Order Phase Transition And Its Associated P - T Phase Diagram In Liquid He3, Richard A. Webb, T. J. Greytak, R. T. Johnson, J. C. Wheatley Feb 1973

Observation Of A Second-Order Phase Transition And Its Associated P - T Phase Diagram In Liquid He3, Richard A. Webb, T. J. Greytak, R. T. Johnson, J. C. Wheatley

Faculty Publications

A specific-heat "discontinuity" is observed in liquid He3 from 241 lb/in.2 to the melting pressure in the temperature range 2-3 mK.

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On Improved Wkb (Uniform Asymptotic) Quantum Conditions, Dunham Corrections, The Langer Modification, And Rkr Potentials, Russell T. Pack Dec 1972

On Improved Wkb (Uniform Asymptotic) Quantum Conditions, Dunham Corrections, The Langer Modification, And Rkr Potentials, Russell T. Pack

Faculty Publications

An improvement to the WKB quantum condition for the rotation-vibration levels of diatomic molecules, known empirically to give RKR potentials of increased accuracy and to account for the Dunham correction Y00, is derived using uniform asymptotic methods. The role of the Langer transformation in this problem is also discussed.

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Nonnegative Matrices Whose Inverses Are M-Matrices, Thomas L. Markham Dec 1972

Nonnegative Matrices Whose Inverses Are M-Matrices, Thomas L. Markham

Faculty Publications

A characterization of a class of totally nonnegative matrices whose inverses are M-matrices is given. It is then shown that if A is nonnegative of order n and A^-1 is an M-matrix, then the almost principal minors of A of all orders are nonnegative.

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Stochastic Integro-Differential Equations Of Volterra Type, William J. Padgett, Chris P. Tsokos Dec 1972

Stochastic Integro-Differential Equations Of Volterra Type, William J. Padgett, Chris P. Tsokos

Faculty Publications

No abstract provided.

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Magnetic And Thermometric Properties Of Na3[Ce(C7h3no4)3] ·15h2o In The Millikelvin Range, Richard A. Webb, J. C. Wheatley Oct 1972

Magnetic And Thermometric Properties Of Na3[Ce(C7h3no4)3] ·15h2o In The Millikelvin Range, Richard A. Webb, J. C. Wheatley

Faculty Publications

Measurements of the 16-Hz susceptibility of a powdered Na3[Ce(C7H3NO4)3] · 15H2O (CDP) sample, in the shape of a right-circular cylinder with diameter equal to height, have been made as a function of the Johnson noise temperature TJ of a resistor in the range 2 to 20 mK. Pure liquid 3He was used for thermal contact between the CDP and the noise thermometer in a demagnetization cell. The results are compared with similar data for cerium magnesium nitrate (CMN). CDP appears, like CMN, to have an anomalously …

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X-Ray Diffraction Studies On Liquids At Very High Pressures Along The Melting Curve. I. Methods And Techniques, Keith H. Brown, J. Dean Barnett Sep 1972

X-Ray Diffraction Studies On Liquids At Very High Pressures Along The Melting Curve. I. Methods And Techniques, Keith H. Brown, J. Dean Barnett

Faculty Publications

A technique using the tetrahedral anvil high-pressure x-ray system has been developed to extract coherent x-ray intensity patterns of liquids near melting from measured scattering curves in the presence of high-background counts. Radial distribution functions for liquids along the melting curve to pressures of at least 50 kbar can be obtained. At each pressure scattering curves are recorded for the liquid and solid on opposite sides of the melting curve and a subtraction is made to eliminate background and incoherent scattering. Theoretical estimates of the thermal diffuse scattering from the solid are added to the appropriately corrected difference patterns to …

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X-Ray Diffraction Studies On Liquids At Very High Pressures Along The Melting Curve Ii. Sodium, Keith H. Brown, J. Dean Barnett Sep 1972

X-Ray Diffraction Studies On Liquids At Very High Pressures Along The Melting Curve Ii. Sodium, Keith H. Brown, J. Dean Barnett

Faculty Publications

Coherent x-ray diffraction patterns for liquid Na have been extracted from measured patterns at 0.5, 7.5, 17, and 43 kbar along the melting curve. The experimentally determined liquid structure factor and resulting radial distribution function are given at each pressure. The position of the principal x-ray intensity peak is reproducible to within 0.5% and shows shifts of the order of 12%. The resulting nearest neighbor distance in the radial distribution function also shifts 12% but is reproducible only to approximately 2%. The distribution functions obtained at points along the melting curve suggest a simple dimensional compression or scaling; however, a …

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Β-Delayed Proton Decay Of 9c, David D. Allred, John E. Esterl, J. C. Hardy, R. G. Sextro, Joseph Cerny Jul 1972

Β-Delayed Proton Decay Of 9c, David D. Allred, John E. Esterl, J. C. Hardy, R. G. Sextro, Joseph Cerny

Faculty Publications

The delayed-proton spectrum following the β decay of 9C (t1/2=126.5±1.0 msec) was found to consist primarily of a continuum extending from 13 to 1.5 MeV, the latter being the lowest energy observed. In addition to the previously observed peaks at 9.28 and 12.30 MeV (C.M.), possible peaks between 3 and 7 MeV have been tentatively identified.

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On The Mechanism Of Low-Temperature Termolecular Atomic Recombination, Russell T. Pack, Richard L. Snow, Wesley D. Smith Jan 1972

On The Mechanism Of Low-Temperature Termolecular Atomic Recombination, Russell T. Pack, Richard L. Snow, Wesley D. Smith

Faculty Publications

A simple theory of gas-phase termolecular atomic recombination kinetics is presented which treats the bound-complex (BC) mechanism in a fashion which parallels the Roberts, Bernstein, and Curtiss resonance theory of the energy-transfer (ET) mechanism. The ET rate constant has a low temperature maximum, but the BC rate constant does not. The contributions of the two mechanisms to the low-temperature recombination of hydrogen atoms, with He, Ar, and H2 as third bodies, are estimated and compared. The presence (absence) of a low-temperature maximum in the observable total rate constant is determined by absence (presence) of bound vibrational levels of the hydrogen-third …

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Isopiestic Studies Of Some Aqueous Electrolyte Solutions At 80°C, John T. Moore Jan 1972

Isopiestic Studies Of Some Aqueous Electrolyte Solutions At 80°C, John T. Moore

Faculty Publications

No abstract provided.

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High-Pressure Equation Of State For Nacl, Kcl, And Cscl, Daniel L. Decker Jul 1971

High-Pressure Equation Of State For Nacl, Kcl, And Cscl, Daniel L. Decker

Faculty Publications

A calculation of the equation of state for NaCl from a Mie-Grüneisen equation was repeated using more accurate values of the zero-pressure compressibility. It was also extended to KCl and CsCl. An analysis of this approach to pressure calibration indicates that it will yield pressures with about the same accuracy as can be presently achieved by experimental measurements above 25 kbar, and thus furnishes a temporary practical pressure scale.

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Lamb-Mössbauer Factor Of Sodium Ferrocyanide, Daniel L. Decker, L. E. Lortz Feb 1971

Lamb-Mössbauer Factor Of Sodium Ferrocyanide, Daniel L. Decker, L. E. Lortz

Faculty Publications

Using a set of commercially prepared sodium ferrocyanide absorbers enriched to 91.2% Fe57 the Lamb-Mössbauer factor was measured to be 0.28±0.03. The thickness of Fe57 for these absorbers was measured using x-ray absorption techniques and was found to be considerably smaller than that advertised by the manufacturer even after correcting for the size of the ferrocyanide particles in the absorbers.

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A Variable Coeficient Of Restitution Experiment On A Linear Air Track, R. Gruebel, James C. Dennis, L. Choate Jan 1971

A Variable Coeficient Of Restitution Experiment On A Linear Air Track, R. Gruebel, James C. Dennis, L. Choate

Faculty Publications

A system consisting of two pendula attached to an air cart is mathematically analyzed, and the coefficient of restitution is shown to pass through a deep minimum. The solution to the small angle equation of motion is transcendental and provides an exercise in graphical methods for the beginning mechanics student.

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High-Pressure Phase Studies On Sodium–Potassium Alloys, D. Ray Anderson, J. Bevan Ott, Rex J. Goates, H. Tracy Hall Jan 1971

High-Pressure Phase Studies On Sodium–Potassium Alloys, D. Ray Anderson, J. Bevan Ott, Rex J. Goates, H. Tracy Hall

Faculty Publications

The solid–liquid phase diagrams were investigated to 60 kbar for elemental sodium, potassium, and various sodium–potassium alloys. The data for Na and K are in general agreement with those of earlier workers. In the alloy system the temperatures of both the peritectic and eutectic halts increase as the pressure increases, but with different slopes, so that the two invariant points merge at approximately 35 kbar. Above this pressure, two halts are again observed. One increases with increasing pressure, and the other decreases with increasing pressure up to 55 kbar, where it abruptly starts increasing again. Melting points for samples in …

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Rayleigh Hysteresis Shape: Its Relationship To Displacement Distance Of A Single Domain Wall In 50% Ni–Fe, R. C. Woodbury, M. R. Hunt Mar 1970

Rayleigh Hysteresis Shape: Its Relationship To Displacement Distance Of A Single Domain Wall In 50% Ni–Fe, R. C. Woodbury, M. R. Hunt

Faculty Publications

The need to measure the displacement distance of domain walls from equilibrium for very weak alternating fields (H ≪ coercive force) in bulk magnetic material has prompted a study of the possible use of the opening of the Rayleigh hysteresis loop to indicate the amount of wall displacement. This paper contains (1) a review of the theoretical relationship between hysteresis shape and the displacement distance of a domain wall, based upon defect-energy models of Rodbell and Bean, and Baldwin; and (2) an experimental approach which provides a measure of the wall displacements versus hysteresis shape for 50% Ni–Fe tape. Discrepancies …

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Asymptotic Evaluation Of Wkb Matrix Elements. Ii. Use Of Langer's Uniform Asymptotic Wavefunctions, Wesley D. Smith, Russell T. Pack Feb 1970

Asymptotic Evaluation Of Wkb Matrix Elements. Ii. Use Of Langer's Uniform Asymptotic Wavefunctions, Wesley D. Smith, Russell T. Pack

Faculty Publications

An improvement in a previous procedure for the analytic asymptotic evaluation of integrals arising in the quantum-mechanical theory of inelastic molecular collisions is presented. The integrals are evaluated using Langer's uniform asymptotic wavefunctions and the higher-order saddle-point or steepest-descents method. It is found that the Langer functions give no better results than WKB functions, but the higher-order steepest-descents corrections produce a marked improvement. The result is a simple method for evaluating a large class of integrals with an error of 0.1%-2.1%.

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Proposed Thermodynamic Pressure Scale For An Absolute High-Pressure Calibration, Daniel L. Decker, J. Dean Barnett Feb 1970

Proposed Thermodynamic Pressure Scale For An Absolute High-Pressure Calibration, Daniel L. Decker, J. Dean Barnett

Faculty Publications

The field of high pressure has developed rapidly over the past few years to a point where relatively sophisticated experiments are being attempted. In many experiments it is no longer sufficient to qualitatively estimate the pressure or to base conclusions on experimental results tied to an empirical pressure parameter. One desires to accurately know the pressure dependence of physical quantities related to a true thermodynamic scale.

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Quasilattice Interpretation Of The Thermodynamic Properties Of Mixing Of Binary Alkali-Metal Systems, J. Bevan Ott, J. Rex Goates Nov 1969

Quasilattice Interpretation Of The Thermodynamic Properties Of Mixing Of Binary Alkali-Metal Systems, J. Bevan Ott, J. Rex Goates

Faculty Publications

Quasilattice theory was applied to heats of mixing in the six systems formed from the binary combinations of Na, K, Rb, and Cs. The alkali-metal systems are particularly well suited for a critical test of the quasi-crystalline assumption since the theoretical model for these systems is relatively simple and the thermodynamic data are fairly complex. Very good fits of the heat-of-mixing data were achieved by assuming that the larger atom in the binary system covered multiple sites on the quasilattice. The values of the empirically determined constants appear to fit the physical significance accorded to them by the quasilattice model. …

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Expectation Values Of Simple Correlated Helium-Atom Wavefunctions, Thomas P. Tsien, Russell T. Pack Nov 1968

Expectation Values Of Simple Correlated Helium-Atom Wavefunctions, Thomas P. Tsien, Russell T. Pack

Faculty Publications

In this Note we present the results of a calculation of the expectation values of a number of one- and two electron properties of the ground-state helium atom using two very simple correlated wavefunctions.

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New Solutions Of The Einstein-Maxwell Equations From Old, B. Kent Harrison Nov 1968

New Solutions Of The Einstein-Maxwell Equations From Old, B. Kent Harrison

Faculty Publications

Methods are discussed with which one may derive theorems which allow one to generate new solutions of the Einstein-Maxwell equations from old ones. The old solutions used to generate new ones must admit at least one nonnull Killing vector and may be required to satisfy other conditions, depending on the theorem derived. Examples of derivable theorems are shown; these theorems are used in turn to show how generation of new solutions is accomplished. Examples of the latter are shown, such as generation of Brill or electrified NUT space from the Schwarzschild solution, generation of a new twisted Melvin universe from …

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Actomyosin-Like Protein Isolated From Mammalian Brain, Donald Dudley Clarke Phd, S. Berl, S. Puszkin, Elena Puszkin Jul 1968

Actomyosin-Like Protein Isolated From Mammalian Brain, Donald Dudley Clarke Phd, S. Berl, S. Puszkin, Elena Puszkin

Faculty Publications

A protein with characteristics similar to actomyosin has been isolated from whole brain of rat and cat. It is soluble in 0.6 molar potassium chloride and insoluble in 0.1 molar potassium chloride. It superprecipitates with magnesium ions and adenosine triphosphate. It has adenosine triphosphatase activity stimulated by either magnesium or calcium ions. Both superprecipitation and adenosine triphosphatase activity are inhibited by p-chloromercuribenzoate and Mersalyl but not by ouabain.

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A Method For Measuring Magnetization To High Pressures, C. R. Johansen, Mark H. Nelson, J. H. Gardner Mar 1968

A Method For Measuring Magnetization To High Pressures, C. R. Johansen, Mark H. Nelson, J. H. Gardner

Faculty Publications

A partially successful attempt has been made to measure the magnetic moment per unit volume of ferromagnetic materials as a function of pressure to the 100-kbar region. The apparatus, an early version of which has been described previously, consists basically of two opposed Bridgman flat anvils of alumina. One anvil also acts as a dielectric-filled microwave resonant cavity for an x-band spectrometer, allowing electron spin resonance studies to be made to high pressure. The sample to be studied is placed in contact with the anvil-cavity and covered with a pressure-transmitting medium which in turn is encircled by a flat pyrophyllite …

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Very High Pressure Effects Upon The Epr Spectrum Of Ruby, H. Mark Nelson, D. B. Larson, J. H. Gardner Sep 1967

Very High Pressure Effects Upon The Epr Spectrum Of Ruby, H. Mark Nelson, D. B. Larson, J. H. Gardner

Faculty Publications

The variation in the electron paramagnetic resonance (EPR) spectrum of ruby as a function of pressure has been observed to beyond 70 kbar for a magnetic field orientation parallel to the crystalline c axis. The data can be interpreted in terms of the usual spin Hamiltonian, where the spectroscopic splitting factor g|| has the same value as at ambient pressures, but where the zero-field splitting deltaincreases in a linear fashion from 0.38 to 0.43 cm. The experimental apparatus has been described previously, although important improvements in the pressure seal and in the pressure calibration have been made and are described …

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Equation Of State Of Sodium Chloride, Daniel L. Decker Dec 1966

Equation Of State Of Sodium Chloride, Daniel L. Decker

Faculty Publications

Because of many requests, I wish to publish the following numerical table of results for the equation of state of NaCl as calculated in an earlier paper1 along with a few comments on various proposed equations for NaCl. Table I gives the pressure in kilobars at the corresponding values of t.a/ao and temperature in the appropriate row and column. The parameter t.a/ao is the fractional compression of the lattice parameter where the standard value ao is the appropriate lattice parameter at zero pressure and 25°C. The increments between the values given in the table were chosen such that one can …

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Model Of Electron Correlation In Solids, Everett G. Larson, Walter R. Thorson Sep 1966

Model Of Electron Correlation In Solids, Everett G. Larson, Walter R. Thorson

Faculty Publications

The usual Hartree-Fock model (energy-band theory) does not always give an adequate description of electronic structure in a solid, because it ignores the effects of electron correlation. It was shown first by Wigner that such a situation always develops in an electron ''gas'' at sufficiently low density; a solid structure described by ''resonance'' of Heitler-London pair bonds between electrons localized on neighboring atoms is then a good model of the system.The transition from a Bloch-type state to such a highly correlated state as a function of electron density (lattice parameter) is a problem of considerable interest for the theory of …

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Pressure Calibration To 100 Kbar Based On The Compression Of Nacl, R. N. Jeffrey, J. Dean Barnett, H. B. Vanfleet, H. Tracy Hall Jul 1966

Pressure Calibration To 100 Kbar Based On The Compression Of Nacl, R. N. Jeffrey, J. Dean Barnett, H. B. Vanfleet, H. Tracy Hall

Faculty Publications

An independent determination has been made of the transformation pressures assigned to the high-pressure transformations in Ba and Bi which are generally used for calibration points. The metals were imbedded in NaCl, and the transitions were detected by the resistance change of the metal while the NaCl lattice parameter was simultaneously measured by x-ray diffraction. The NaCl compression values determined at the fixed points were related to pressure by reference to the semiempirical compression curve of Decker. The Ba I-II and Bi III-V transformations at room temperature were assigned thermodynamic equilibrium values of 53.3 ±1.2 kbar and 73.8 ±1.3 kbar, …

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X-Ray Diffraction Studies On Tin To 100 Kilobars, J. Dean Barnett, Vern E. Bean, H. Tracy Hall Feb 1966

X-Ray Diffraction Studies On Tin To 100 Kilobars, J. Dean Barnett, Vern E. Bean, H. Tracy Hall

Faculty Publications

The high-pressure equilibrium phase diagram of tin is investigated, and the crystal structure of Sn II at 98 kbar and 25degrees C is shown to be body-centered tetragonal with a=3.70 Angstroms, c=3.37 Angstroms, c/a=0.91, and with two atoms per unit cell. The linear compressibility of white tin is given at 25degrees C up to the high-pressure transformation at 92 kbar, and the latent heat of the transformation is measured as 225 cal/g-atom.

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