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Articles 1 - 30 of 134
Full-Text Articles in Physics
Hydrodynamic Forces And Band Formation In Swimming Magnetotactic Bacteria, D. C. Guell, H. Brenners, Richard B. Frankel, H. Hartman
Hydrodynamic Forces And Band Formation In Swimming Magnetotactic Bacteria, D. C. Guell, H. Brenners, Richard B. Frankel, H. Hartman
Physics
Dense suspensions of magnetotactic bacteria form long, thin, stable bands perpendicular to the common, net direction of motion of the cells in a magnetic field. A mechanism for this phenomenon is proposed in which the hydrodynamic coupling between two swimming cells is described in terms of an approximate, far-field solution for the flow around one swimming cell. The calculated hydrodynamic interaction force and torque based upon this analysis are of the correct orders of magnitude and in the right directions to provide a reasonable explanation for band formation and stability.
Microstructure Of Epitaxial Ybba2Cu3O7 Superconducting Films Grown By A New Liquid-Gas-Solidification Technique, C.H. Chen, H.S. Chen, Sy_Hwang Liou
Microstructure Of Epitaxial Ybba2Cu3O7 Superconducting Films Grown By A New Liquid-Gas-Solidification Technique, C.H. Chen, H.S. Chen, Sy_Hwang Liou
Sy-Hwang Liou Publications
We have studied the microstructures of epitaxial YbBa2Cu3O7 superconducting films grown on SrTiO3 [100] and [110] substrates by a new liquid-gas-solidification processing technique. Films grown on SrTiO3 [100] and [110] substrates are epitaxially oriented with [001] and [110] axes normal to the film surface. Twinned domains of ~200 Å in size are observed in the [001] oriented films. Most defects observed can be attributed to the presence of stacking faults along the c axis. The presence of Cu-O bilayer defects is also observed. Rapid oxygen diffusion in the liquid phase is found to …
Nuclear-Spin Relaxation In Molecular Solids With Reorienting Methyl And T-Butyl Groups: The Spectral Density And The State Of The Solid, Peter A. Beckmann, Audrey I. Hill, Ellen B. Kohler, Hong Yu
Nuclear-Spin Relaxation In Molecular Solids With Reorienting Methyl And T-Butyl Groups: The Spectral Density And The State Of The Solid, Peter A. Beckmann, Audrey I. Hill, Ellen B. Kohler, Hong Yu
Physics Faculty Research and Scholarship
There are two solid phases which either have a large hysteresis of at least 90 K, or are both stable below 200 K. The sample melts at 262 K. We interpret the high-temperature phase R-versus-T-1 data with three models. First, we adopt a one-correlation-time model using a Davidson-Cole spectral density which suggests that there is a distribution of correlation times, or, equivalently, a distribution of activation energies for t-butyl and methyl group reorientation. In this case, the methyl and t-butyl reorientation is characterized by a cutoff activation energy of 17±1 kJ/mol which is to be compared with 18±1 kJ/mol in …
On The Possibility Of Quasi-Static Convection In The Quiet Magnetotail, Margaret G. Kivelson, Harlan E. Spence
On The Possibility Of Quasi-Static Convection In The Quiet Magnetotail, Margaret G. Kivelson, Harlan E. Spence
Physics & Astronomy
Abstract
The magnetotail is known to serve as a reservoir of energy transferred into the terrestrial magnetosphere from the solar wind. In principle, the stored energy can be dissipated impulsively, as in a substorm, or steadily through the process of steady adiabatic plasma convection. However, some theoretical arguments have suggested that quasi-static adiabatic convection cannot occur throughout the magnetotail because of the structure of the magnetic field. Here we reexamine the question. We show that in a magnetotail of finite width, downtail pressure gradients depend strongly on the ratio of the potential across half the tail to the ion temperature …
Quasidegenerate Variational Perturbation Theory And The Calculation Of First‐Order Properties From Variational Perturbation Theory Wave Functions, Robert J. Cave, Ernest R. Davidson
Quasidegenerate Variational Perturbation Theory And The Calculation Of First‐Order Properties From Variational Perturbation Theory Wave Functions, Robert J. Cave, Ernest R. Davidson
All HMC Faculty Publications and Research
In previous work on the treatment of correlation in molecular systems we have applied a multireference version of second‐order Hylleraas variational perturbation theory. The choice made for the partitioning of H treated the interactions between the correlating functions to infinite order and gave the corrections to the wave function to first order. The method was shown to be accurate in many cases, but became less so when near degeneracies occurred between the reference energy and other eigenvalues of H0. In this article we introduce an effective Hamiltonian method that is analogous to variational perturbation theory, but which is significantly more …
Tunneling Characteristics Of Internal Josephson Junctions In Yba2Cu3O7-Δ Thin Films, W.S. Brocklesby, Don Monroe, M. Hong, Sy_Hwang Liou, J. Kwo, G.J. Fisanick, P.M. Mankiewich, R.E. Howard
Tunneling Characteristics Of Internal Josephson Junctions In Yba2Cu3O7-Δ Thin Films, W.S. Brocklesby, Don Monroe, M. Hong, Sy_Hwang Liou, J. Kwo, G.J. Fisanick, P.M. Mankiewich, R.E. Howard
Sy-Hwang Liou Publications
We have measured detailed I-V characteristics of small areas of YBa2Cu3O7-δ films, which exhibit structure associated with individual Josephson junctions within the film. Both hysteretic and nonhysteretic junctions are seen. A simple model relating the voltage steps to the junction properties is developed. The temperature dependence of lc for the hysteretic junctions fits that predicted for quasiparticle tunneling junctions between conventional superconductors.
Cooperative Effects Among Partial Waves In Mie Scattering, James A. Lock
Cooperative Effects Among Partial Waves In Mie Scattering, James A. Lock
Physics Faculty Publications
Observations of an illuminated water droplet at a close distance are described mathematically by the Fourier transform of the Mie-scattering amplitude convolved with the aperture function of the observer’s eye. Most of the sharp enhancements found in the Fourier transform correspond to geometrical rays associated with the various terms in the Debye-series expansion of the Mie amplitude. However, there are some enhancements that cannot be ascribed to any individual Debye-series term. Instead, they arise from a constructive interference cooperation of the phase of a scattering resonance in a single partial wave with the region of the stationary phase corresponding to …
Spin-Polarized ³He Nuclear Targets And Metastable 4he Atoms By Optical Pumping With A Tunable, Nd:Yap Laser, C. L. Bohler, Laird D. Schearer, M. Leduc, P. J. Nacher, L. Zachorowski, R. G. Milner, R. D. Mckeown, C. E. Woodward
Spin-Polarized ³He Nuclear Targets And Metastable 4he Atoms By Optical Pumping With A Tunable, Nd:Yap Laser, C. L. Bohler, Laird D. Schearer, M. Leduc, P. J. Nacher, L. Zachorowski, R. G. Milner, R. D. Mckeown, C. E. Woodward
Physics Faculty Research & Creative Works
Several Nd:YAP lasers were constructed which could be broadly tuned in the 1083-nm region which includes the helium 23S-23P transition, using a Lyot filter and thin, uncoated etalons within the laser cavity. 1 W of power could be extracted at 1083 nm through a 1% transmitting output coupler. This laser beam was used to optically pump metastable 4He and 3He 23S helium atoms in a weak discharge cell, spin polarizing the metastable ensemble. In a 3He cell the polarization is transferred to the nuclear spin system. A 3He target cell at 0.3 …
Nd:Lna Laser Optical Pumping Of ⁴He: Application To Space Magnetometers, R. E. Slocum, Laird D. Schearer, P. Tin, R. Marquedant
Nd:Lna Laser Optical Pumping Of ⁴He: Application To Space Magnetometers, R. E. Slocum, Laird D. Schearer, P. Tin, R. Marquedant
Physics Faculty Research & Creative Works
We have observed Hanle signals and n=0, p=1 parametric resonances of 23S1 metastable helium atoms in a discharge cell by optically pumping the helium atoms with a tunable Nd:LNA laser. These resonances were used to construct a sensitive magnetometer for the measurement of very small magnetic fields. Since magnetometer sensitivity is proportional to the slope of the parametric resonance signal (signal amplitude divided by linewidth), the slopes for single-line laser pumping were compared with similar quantities obtained from conventional helium lamp pumping. Laser pumping yielded 45 times greater slopes with comparable power requirements, thus establishing the potential for …
Superconducting Tl-Ba-Ca-Cu-O Films By Sputtering, M. Hong, Sy_Hwang Liou, D.D. Bacon, G.S. Grader, J. Kwo, A.R. Kortan, B.A. Davidson
Superconducting Tl-Ba-Ca-Cu-O Films By Sputtering, M. Hong, Sy_Hwang Liou, D.D. Bacon, G.S. Grader, J. Kwo, A.R. Kortan, B.A. Davidson
Sy-Hwang Liou Publications
Superconducting Tl-Ba-Ca-Cu-O thin films 0.2–1.0 µm thick have been prepared on MgO(100) and SrTiO3 (100) substrates by dc diode sputtering using a single oxide target. Films containing primarily the Tl2Ba2Ca1Cu2O8 phase were obtained with a Tc (R =0) at 102 K and a transport Jc of 104 A/cm2 at 90 K. For the nearly pure phase Tl2Ba2Ca2Cu3O10 films, the Tc's (R =0) are higher at 116 K and the transport Jc's …
A Current Algebra For Some Gauge Theory Amplitudes, V. Parameswaran Nair
A Current Algebra For Some Gauge Theory Amplitudes, V. Parameswaran Nair
Publications and Research
The classical amplitude for scattering of two positive helicity and n-2 negative helicity (or the other way) gauge bosons is shown to be generated by a Wess-Zumino-Witten (WZW) model for N= 4 supersymmetric gauge theory; i.e. the current algebra of the WZW model (with central charge k= 1 ) gives a Kac-Moody algebra as the symmetry behind these amplitudes.
Magnetic And Structural Properties Of Melt-Spun Rare-Earth Transition-Metal Intermetallics With Thmn12 Structure, E.W. Singleton, J. Strzeszewski, George C. Hadjipanayis, David J. Sellmyer
Magnetic And Structural Properties Of Melt-Spun Rare-Earth Transition-Metal Intermetallics With Thmn12 Structure, E.W. Singleton, J. Strzeszewski, George C. Hadjipanayis, David J. Sellmyer
David Sellmyer Publications
The magnetic and structural properties of melt-spun R8Fe84Ti8 with R=Nd, Sm, Dy, Gd and R8 (Fe,Co) 76 [V(Mo)] 16 with R=Nd, Sm have been studied with x-ray diffraction, transmission electron microscopy, and magnetic measurements. The tetragonal ThMn12-type structure was found in all alloys after annealing at about 700 °C. The Curie temperature (Tc) of the as-spun amorphous samples was in the range of 40–100 °C. Crystallized Nd8 (Fe1-xCox)84Ti8 samples with the 1:12 structure have a Tc around 250 °C for …
Structure And Magnetic Properties Of Nanostructured Dy/Transition-Metal Multilayered Films, Z.S. Shan, David J. Sellmyer
Structure And Magnetic Properties Of Nanostructured Dy/Transition-Metal Multilayered Films, Z.S. Shan, David J. Sellmyer
David Sellmyer Publications
We report the results of magnetic and microstructural studies for T/Dy (T=Fe, Co, Ni) compositionally modulated films prepared in a multiple-gun sputtering system. The perpendicular anisotropy and magnetization were measured systematically for X-Å Fe/Y-Å Dy and X-Å Co/Y-Å Dy films. The layer-thickness dependence of the magnetization for Co/Dy and Fe/Dy was interpreted in terms of the antiparallel coupling between transition-metal and Dy magnetic moments. For Co/Dy films the ranges of X and Y required for perpendicular anisotropy were determined. A comparision of the structural and magnetic properties of Ni/Dy, Co/Dy, and Fe/Dy is given and the origin of the perpendicular …
Magnetic And Structural Properties Of Nd2Fe14B Permanent-Magnet Films And Multilayers With Fe And Ag, K.D. Aylesworth, Z.R. Zhao, David J. Sellmyer, George C. Hadjipanayis
Magnetic And Structural Properties Of Nd2Fe14B Permanent-Magnet Films And Multilayers With Fe And Ag, K.D. Aylesworth, Z.R. Zhao, David J. Sellmyer, George C. Hadjipanayis
David Sellmyer Publications
The effects of sputtering conditions on the structure and magnetic properties of Nd2 (Fe0.9Co0.1)14B films and multilayers are reported. The samples were sputtered onto temperature-controlled mica and Ta substrates, at temperatures between 20 and 620 °C. X-ray diffraction results indicate that films deposited directly onto 500–600 °C substrates with Fe buffer layers are nearly single-phase materials with the c axis of the grains largely perpendicular to the film plane. Room-temperature magnetization measurements to 17.4 kOe indicate that these films have strong perpendicular anisotropy with coercivities in excess of 10 kOe and magnetizations greater …
Electronic Structure And Surface Reactivity Of Nd2Fe14B And Related Compounds, Sitaram Jaswal, Marjorie Langell, Y.G. Ren, M.A. Engelhardt, David J. Sellmyer
Electronic Structure And Surface Reactivity Of Nd2Fe14B And Related Compounds, Sitaram Jaswal, Marjorie Langell, Y.G. Ren, M.A. Engelhardt, David J. Sellmyer
David Sellmyer Publications
Studies of electronic and magnetic structure and surface reactivity are reported for R2T14B compounds where R=Y, Nd, Gd, and T=Fe, Co. The calculations employed the self-consistent, spin-polarized linear-muffin-tin orbital method. Experiments included ultraviolet, x-ray, and Auger electron spectroscopy. Comparisons are made between the calculated and measured electronic densities of states, and the reactions of the surfaces with O2, H2, and CO gases are studied. The effects of heat treatment on surface segregation are also reported. Journal of Applied Physics is copyrighted by The American Institute of Physics.
Ferromagnetism In Metastable 304 Stainless Steel With Bcc Structure, J. Childress, Sy_Hwang Liou, C.L. Chien
Ferromagnetism In Metastable 304 Stainless Steel With Bcc Structure, J. Childress, Sy_Hwang Liou, C.L. Chien
Sy-Hwang Liou Publications
We have studied the consequence of structure on the magnetic properties of 304 stainless steel in two distinct crystalline states. Ordinary 304 stainless steel has an fcc structure and is nonmagnetic at room temperature. By using a vapor quenching method, we have fabricated single-phase metastable bcc 304 stainless steel which is strongly ferromagnetic. Films a few µm thick have been made by high-rate sputter deposition onto substrates at room temperature or liquid-nitrogen temperature. Vibrating sample magnetometry and 57Fe Mössbauer spectroscopy reveal that the bcc phase has a magnetization of 130 emu/g, due largely to the Fe moment. The Curie …
Transport Critical Current And Magnetization Measurements Of Melt-Processed Yba2cu3o7-X, A. H. Hermann, Z. Z. Sheng, W. Kiehl, D. Marsh, A. Elali, Paul D. Hambourger, C. Almasan, J. Estrada, T. Datta
Transport Critical Current And Magnetization Measurements Of Melt-Processed Yba2cu3o7-X, A. H. Hermann, Z. Z. Sheng, W. Kiehl, D. Marsh, A. Elali, Paul D. Hambourger, C. Almasan, J. Estrada, T. Datta
Physics Faculty Publications
We report magnetic field dependence of the transport critical current and dc magnetic susceptibility measurements on YBa2Cu3O7−x superconductors formed by melt-solid reactions at 950 °C between Ba-Cu-O (or Tb-Ba-Cu-O) and solid nonstoichiometric Y-Ba-Cu-oxide. Four-probe dc critical current measurements at 77, 64, and 4.2 K show strong depression of the critical current density with increasing magnetic field in agreement with a model of weakly linked superconducting regions. Diamagnetic shielding and Meissner flux expulsion measurements in the temperature range 10–300 K show about one third volume fraction of perfect superconductivity. Both shielding and flux expulsion were observed to be approximately temperature independent …
Resonant Transfer And Excitation In Li-Like F Colliding With H₂, Michael Schulz, Reinhold S. Schuch, Sheldon Datz, Edson L B Justiniano, Philip D. Miller, Harald Schone
Resonant Transfer And Excitation In Li-Like F Colliding With H₂, Michael Schulz, Reinhold S. Schuch, Sheldon Datz, Edson L B Justiniano, Philip D. Miller, Harald Schone
Physics Faculty Research & Creative Works
We have measured coincidences between x rays and projectiles that have captured one electron in F6+ + H2 collisions at projectile energies between 15 and 33 MeV. The cross sections for capture and simultaneous x-ray emission as a function of projectile energy show clear structures. Indications of an unexpectedly high population of high-n states predominantly formed by resonant transfer and excitation (RTE) were found. Above the Kln (n>1) RTE resonance energies another maximum was observed.
A Mössbauer Effect Study Of Y₂Fe₁₄B And Its Aluminum Solid Solutions, Dwayne E. Tharp, Gary J. Long, Oran Allan Pringle, Gaya Kanishka Marasinghe, William Joseph James, Fernande Grandjean
A Mössbauer Effect Study Of Y₂Fe₁₄B And Its Aluminum Solid Solutions, Dwayne E. Tharp, Gary J. Long, Oran Allan Pringle, Gaya Kanishka Marasinghe, William Joseph James, Fernande Grandjean
Chemistry Faculty Research & Creative Works
The Mössbauer spectra of Y2Fe14B have been measured from 85 to 296 K. Analysis of the spectra indicates that the near-neighbor rare-earth atoms directly influence the orientation of the principal axis of the electric field gradient. The hyperfine parameters are very similar to those of Nd2Fe14B, but the internal fields are somewhat smaller at room temperature in the yttrium compound. The Mösssbauer spectra of Y2(Fe1-xAlx) 14B, where x equals 0.00, 0.02, 0.04, 0.06, and 0.08, have been measured at 85 K. The average internal hyperfine …
Roughness-Induced Resonance For Molecular Fluorescence Near A Corrugated Metallic Surface, P.T. Leung, Young Sik Kim, Thomas F. George
Roughness-Induced Resonance For Molecular Fluorescence Near A Corrugated Metallic Surface, P.T. Leung, Young Sik Kim, Thomas F. George
Physics Faculty Publications and Presentations
Based on a dynamical energy-transfer theory for the molecular decay rate near a rough metallic surface, a new resonance structure is predicted which is mediated by the roughness and which is absent in the static image theory. The implication of this new resonance structure to other phenomena, such as electron-energy-loss spectrum and cross coupling in thin films, is pointed out.
Excitation Of The Lowest Autoionizing Levels In Lithiumlike Ions By Electron Impact, Rajesh C. Srivastava, Don H. Madison
Excitation Of The Lowest Autoionizing Levels In Lithiumlike Ions By Electron Impact, Rajesh C. Srivastava, Don H. Madison
Physics Faculty Research & Creative Works
We present theoretical, differential, and total cross sections for electron impact excitation of the lowest autoionizing levels of various lithiumlike ions (viz., Be+, B2+, C3+, O5+, and Ne7+). For these ions, the autoionizing level of interest results from excitation of an inner-shell electron. A distorted-wave Born approximation (with exchange) is used for the calculation. The present results are compared with previous theoretical calculations and it is concluded that the Coulomb-Born approach is unreliable, particularly near threshold.
A Neutron Diffraction And Mössbauer Spectral Study Of The Structure And Magnetic Properties Of The Y₂Fe₁₄₋ₓsiₓb Solid Solutions, Gaya Kanishka Marasinghe, Oran Allan Pringle, Gary J. Long, William B. Yelon, Fernande Grandjean
A Neutron Diffraction And Mössbauer Spectral Study Of The Structure And Magnetic Properties Of The Y₂Fe₁₄₋ₓsiₓb Solid Solutions, Gaya Kanishka Marasinghe, Oran Allan Pringle, Gary J. Long, William B. Yelon, Fernande Grandjean
Physics Faculty Research & Creative Works
A neutron diffraction and Mössbauer spectral study of Y2Fe14-xSixB shows that silicon preferentially occupies the 4c, and to a lesser extent, the 8j1 sites in Y2Fe14-xSixB. The trend in the site occupancy is the same as in Nd2Fe14-xSixB. The Curie temperature of Y2Fe14-xSixB increases with increasing silicon content. Neutron diffraction data show that the increase in Curie temperature is accompanied by a contraction of the unit cell. Wigner-Seitz cell calculations, using the Y2Fe …
Magnetism And Superconductivity In (Er₀.₁₆Ho₀.₈₄)Rh₄B₄, Oran Allan Pringle, Herbert A. Mook, Steven E. Lambert, M. Brian Maple
Magnetism And Superconductivity In (Er₀.₁₆Ho₀.₈₄)Rh₄B₄, Oran Allan Pringle, Herbert A. Mook, Steven E. Lambert, M. Brian Maple
Physics Faculty Research & Creative Works
The superconducting and ferromagnetic phase boundaries in the (Er1-xHox)Rh4B4 mixed ternary alloy system meet in a multicritical point at xcr ≈ 0.9. For xcr, the compounds first become superconducting as the temperature is lowered, and then lose superconductivity in a transition to ferromagnetism. The coexistence of superconductivity and ferromagnetism for alloys near the erbium-rich end of the phase diagram is well established. It has also been suggested that ferromagnetism and superconductivity coexist in alloys with x just below xcr. We have carried out neutron-diffraction, ac magnetic susceptibility, and heat-capacity …
Redox Reactivity Of Bacterial And Mammalian Ferritin: Is Reductant Entry Into The Ferritin Interior A Necessary Step For Iron Release?, G. D. Watt, D. Jacobs, Richard B. Frankel
Redox Reactivity Of Bacterial And Mammalian Ferritin: Is Reductant Entry Into The Ferritin Interior A Necessary Step For Iron Release?, G. D. Watt, D. Jacobs, Richard B. Frankel
Physics
Both mammalian and bacterial ferritin undergo rapid reaction with small-molecule reductants, in the absence of Fe2+ chelators, to form ferritins with reduced (Fe2+) mineral cores. Large, low-potential reductants (flavoproteins and ferredoxins) similarly react anaerobically with both ferritin types to quantitatively produce Fe2+ in the ferritin cores. The oxidation of Fe2+ ferritin by large protein oxidants [cytochrome c and Cu(II) proteins] also occurs readily, yielding reduced heme and Cu(I) proteins and ferritins with Fe3+ in their cores. These latter oxidants also convert enthetically added Fe2+, bound in mammalian or bacterial apo- or holo-ferritin, …
Testimony On The Verification And Compliance Of Nuclear Testing Treaties, David W. Hafemeister
Testimony On The Verification And Compliance Of Nuclear Testing Treaties, David W. Hafemeister
Physics
No abstract provided.
Differential Cross Sections For Secondary Electron Production By 1.5-Kev Electrons In Water Vapor, K. W. Hollman, G. W. Kerby, Iii, M. Eugene Rudd, J. H. Miller, S. T. Manson
Differential Cross Sections For Secondary Electron Production By 1.5-Kev Electrons In Water Vapor, K. W. Hollman, G. W. Kerby, Iii, M. Eugene Rudd, J. H. Miller, S. T. Manson
M. Eugene Rudd Publications
Discrepancies between previous experimental values of differential cross sections for electron-impact ionization of water vapor and recent model calculations have been largely resolved. A new measurement with improved suppression of spurious electrons has removed most of the discrepancy in the midrange of detected electron energies. A second discrepancy at secondary energies just below the primary energy has been explained by a more accurate accounting for electrons scattered at angles between zero and the minimum angle of the experimental apparatus. The improved data show more clearly the oxygen K-shell edge in the spectra at small angles and the Bethe ridge at …
Temperature And Supersaturation Dependent Nucleation Rates Of Water By Molecular Cluster Model Calculations, Sung-Ho Suck Salk, Chen K. Lutrus, Donald E. Hagen
Temperature And Supersaturation Dependent Nucleation Rates Of Water By Molecular Cluster Model Calculations, Sung-Ho Suck Salk, Chen K. Lutrus, Donald E. Hagen
Physics Faculty Research & Creative Works
Using a microphysical approach to nucleation, we present an extensive study of water nucleation rates for wide ranges of both temperature and supersaturation ratio. Based on the fundamental molecular properties of clusters instead of bulk properties, the microphysical approach is demonstrated to predict good agreement with measured nucleation rates over this broad range of conditions. Predicted critical sizes for nucleation are found to be relatively small, and are in the molecular cluster size regime rather than in a size regime that should be characterized by bulk values. Estimated sticking coefficient values cover the range of ~0.9 to ~0.2 for the …
Scanning Electron Microscope Identification Of Weak Links In Superconducting Thin Films, Don Monroe, W.S. Brocklesby, R.C. Farrow, M. Hong, Sy_Hwang Liou
Scanning Electron Microscope Identification Of Weak Links In Superconducting Thin Films, Don Monroe, W.S. Brocklesby, R.C. Farrow, M. Hong, Sy_Hwang Liou
Sy-Hwang Liou Publications
We have used a pulsed electron beam in a scanning electron microscope to produce highly localized (~1 µm) changes in the electrical properties of a heterogeneous thin film of YBa2Cu3O7-δ . The predominant effect of the beam is to locally heat the film, producing a measurable shift in the current-voltage characteristic. In particular, we have precisely located the part of the film responsible for a sharp feature in the current-voltage characteristic corresponding to a single Josephson junction. The technique should also be useful more generally in identifying specific weak links in superconducting thin films.
A Novel Algorithm For Calculating The Time Evolution Of The Electron Energy Distribution Function In Gaseous Discharges, P J. Drallos, J M. Wadehra
A Novel Algorithm For Calculating The Time Evolution Of The Electron Energy Distribution Function In Gaseous Discharges, P J. Drallos, J M. Wadehra
Physics and Astronomy Faculty Research Publications
We are presenting a novel numerical technique for obtaining the time evolution of the electron velocity and electron energy distribution functions in the presence of a uniform electric field. Using this technique, the various swarm parameters can be evolved for sufficiently long times so that equilibrium can be reached without incurring any numerical instabilities. Results are presented for electron swarms in gaseous neon for various values of E/N.
News Release, Fermi National Accelerator Laboratory
News Release, Fermi National Accelerator Laboratory
Documents
Dr. Leon M. Lederman, Director of Fermi National Accelerator Laboratory (Fermilab) in Batavia, Illinois, has been named one of three recipients of the 1988 Nobel Prize for physics. Sharing the prize with Dr. Lederman are Dr. Melvin Schwartz and Dr. Jack Steinberger. The three have been cited for their discovery, in 1962, of a second neutrino, an elementary subatomic particle. Fermilab is operated by the Universities Research Association, Inc., under contract with the United States Department of Energy (DOE).