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Articles 1111 - 1132 of 1132
Full-Text Articles in Physics
Fluid Mechanics In The Elementary Laboratory, James C. Dennis
Fluid Mechanics In The Elementary Laboratory, James C. Dennis
Faculty Publications
No abstract provided.
Experiments On Dynamic Parallel Magnetism In Superfluid 3he, Richard A. Webb, R. L. Kleinberg, J. C. Wheatley
Experiments On Dynamic Parallel Magnetism In Superfluid 3he, Richard A. Webb, R. L. Kleinberg, J. C. Wheatley
Faculty Publications
Observations are reported of the ringing of parallel magnetization in superfluid 3He when an incremental magnetic field parallel to a steady field is suddenly turned off.
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
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.
Magnetic And Thermometric Properties Of Na3[Ce(C7h3no4)3] ·15h2o In The Millikelvin Range, Richard A. Webb, J. C. Wheatley
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 …
X-Ray Diffraction Studies On Liquids At Very High Pressures Along The Melting Curve Ii. Sodium, Keith H. Brown, J. Dean Barnett
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 …
X-Ray Diffraction Studies On Liquids At Very High Pressures Along The Melting Curve. I. Methods And Techniques, Keith H. Brown, J. Dean Barnett
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 …
Β-Delayed Proton Decay Of 9c, David D. Allred, John E. Esterl, J. C. Hardy, R. G. Sextro, Joseph Cerny
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.
High-Pressure Equation Of State For Nacl, Kcl, And Cscl, Daniel L. Decker
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.
Lamb-Mössbauer Factor Of Sodium Ferrocyanide, Daniel L. Decker, L. E. Lortz
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.
A Variable Coeficient Of Restitution Experiment On A Linear Air Track, R. Gruebel, James C. Dennis, L. Choate
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.
Rayleigh Hysteresis Shape: Its Relationship To Displacement Distance Of A Single Domain Wall In 50% Ni–Fe, R. C. Woodbury, M. R. Hunt
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 …
Proposed Thermodynamic Pressure Scale For An Absolute High-Pressure Calibration, Daniel L. Decker, J. Dean Barnett
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.
New Solutions Of The Einstein-Maxwell Equations From Old, B. Kent Harrison
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 …
A Method For Measuring Magnetization To High Pressures, C. R. Johansen, Mark H. Nelson, J. H. Gardner
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 …
Very High Pressure Effects Upon The Epr Spectrum Of Ruby, H. Mark Nelson, D. B. Larson, J. H. Gardner
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 …
Equation Of State Of Sodium Chloride, Daniel L. Decker
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 …
Model Of Electron Correlation In Solids, Everett G. Larson, Walter R. Thorson
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 …
Pressure Calibration To 100 Kbar Based On The Compression Of Nacl, R. N. Jeffrey, J. Dean Barnett, H. B. Vanfleet, H. Tracy Hall
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, …
X-Ray Diffraction Studies On Tin To 100 Kilobars, J. Dean Barnett, Vern E. Bean, H. Tracy Hall
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.
Equation Of State Of Nacl And Its Use As A Pressure Gauge In High-Pressure Research, Daniel L. Decker
Equation Of State Of Nacl And Its Use As A Pressure Gauge In High-Pressure Research, Daniel L. Decker
Faculty Publications
The pressure as a function of lattice parameter and temperature has been calculated for NaCl over a pressure range of 0 to 500 kbar for temperatures between 0degrees and 1500degrees C. The calculation used the Mie-Gruneisen equation of state with Born-Mayer type repulsion terms between first and second nearest neighbors. The Gruneisen constant was expanded about its value at room temperature and atmospheric pressure; the first coefficient in the expansion being evaluated by forcing the calculated thermal expansion at atmospheric pressure to fit the experimental results of Enck. The two empirical parameters in the repulsion terms were evaluated using the …
Diffraction Of Spherical Scalar And Vector Waves At Axial Points Of A Circular Aperture And Disk, Keith Leon Mcdonald
Diffraction Of Spherical Scalar And Vector Waves At Axial Points Of A Circular Aperture And Disk, Keith Leon Mcdonald
Faculty Publications
The following work treats Kottler's saltus problem of diffraction of electromagnetic waves emitted by a Hertzian oscillator source and the analogous Kirchhoff's scalar problem of waves emitted by a point source. The medium is a homogeneous isotropic dielectric. In the vector case a new exact solution of the basic integrals is presented, at axial points only, (a) behind a circular aperture in a "black'' screen, and (b) behind its complementary "black'' disk. The relative time-averaged intensity of energy flow is plotted for the disk only. It is shown that the scalar theory predicts considerably larger values than the electromagnetic theory …
A Note On K-Commutative Matrices, D. W. Robinson
A Note On K-Commutative Matrices, D. W. Robinson
Faculty Publications
Let A and B be square matrices over a field in which the minimum polynomial of A is completely reducible. It is shown that A is k commutative with respect to B for some non-negative integer k if and only if B commutes with every principal idempotent of A. The proof is brief, simplifying much of the previous study of k-commutative matrices. The result is also used to generalize some well-known theorems on finite matrix commutators that involve a complex matrix and its transposed complex conjugate.