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1992

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Articles 1 - 30 of 1692

Full-Text Articles in Physical Sciences and Mathematics

A Theoretical Model For Biased Superlattice Devices, Michael Ferner Dec 1992

A Theoretical Model For Biased Superlattice Devices, Michael Ferner

Theses

A model describing the subband structures and tunneling characteristics of superlattices is presented. The model solves the envelope function equations by the transfer matrix technique. The results are codified in a Fortran program, and the model is applied to several structures.

Superlattice have been studied extensively, however many new structures await investigation.

This model is presented as a preliminary design tool. The program allows a designer to do preliminary calculations. This type of investigation guides a designer toward a goal by making possible a large number of calculations on many different structures.


Giant Suppression Of Flux-Flow Resistivity In Heavy-Ion Irradiated Tl2Ba2Ca2Cu3O10 Films: Influence Of Linear Defects On Vortex Transport, R.C. Budhani, M. Suenaga, Sy_Hwang Liou Dec 1992

Giant Suppression Of Flux-Flow Resistivity In Heavy-Ion Irradiated Tl2Ba2Ca2Cu3O10 Films: Influence Of Linear Defects On Vortex Transport, R.C. Budhani, M. Suenaga, Sy_Hwang Liou

Si-Hwang Liou Publications

A large shift of the onset of flux-flow resistivity and the irreversibility line Hirr (T) to higher temperatures is observed in Tl2Ba2Ca2Cu3O10 films containing linear defects created by Ag+21 ion irradiation. The Hirr(T), which has a characteristic ssL shape in highly anisotropic Tl and Bi based cuprates, becomes more like that of YBa2Cu3O7 in the presence of these defects. The Jc at 77 K also shows a large increase as a result of flux localization at the defects. The transport data ...


Performance Of Iterative Methods For Distributed Memory Processors, Dan C. Marintescu, John R. Rice, E. Vavallis Dec 1992

Performance Of Iterative Methods For Distributed Memory Processors, Dan C. Marintescu, John R. Rice, E. Vavallis

Department of Computer Science Technical Reports

No abstract provided.


The Elastic Moduli Of Simple Two-Dimensional Isotropic Composites: Computer Simulation And Effective Medium Theory, K. A. Snyder, E. J. Garboczi, Anthony Roy Day Dec 1992

The Elastic Moduli Of Simple Two-Dimensional Isotropic Composites: Computer Simulation And Effective Medium Theory, K. A. Snyder, E. J. Garboczi, Anthony Roy Day

Anthony Roy Day

An algorithm, combining digital-image with spring network techniques, has been developed that enables computation of the elastic moduli of random two-dimensional multiphase composites. This algorithm is used to study the case of isotropic, randomly centered, overlapping circular inclusions in an isotropic elastic matrix. The results of the algorithm for the few-inclusion limit, as well as the case where both phases have the same shear moduli, agree well with the exact results for these two problems. The case where the two phases have the same Poisson’s ratio, but different Young’s moduli, is also studied, and it is shown that ...


Measurement Of Ionization And Phonon Production By Nuclear Recoils In A 60 G Crystal Of Germanium At 25 Mk, Tom Shutt, B. Ellman, P. D. Barnes Jr., Alan Cummings, Angela Da Silva, John Emes, Y. Giraud-Héraud, Eugene E. Haller, Andrew E. Lange, Ron R. Ross, J. Rich, Bernard Sadoulet, G. Smith, W. Stockwell, C. Stubbs, N. Wang, S. White, Betty A. Young, D. Yvon Dec 1992

Measurement Of Ionization And Phonon Production By Nuclear Recoils In A 60 G Crystal Of Germanium At 25 Mk, Tom Shutt, B. Ellman, P. D. Barnes Jr., Alan Cummings, Angela Da Silva, John Emes, Y. Giraud-Héraud, Eugene E. Haller, Andrew E. Lange, Ron R. Ross, J. Rich, Bernard Sadoulet, G. Smith, W. Stockwell, C. Stubbs, N. Wang, S. White, Betty A. Young, D. Yvon

Physics

We report on the first measurement of the absolute phonon energy and the amount of ionization produced by the recoil of nuclei and electrons in a 60 g germanium cyrstal at a temperature of ≊25 mK. We find good agreement between our results and previous measurements of ionization yield from nuclear recoils in germanium. Our device achieves 10:1 discrimination between neutrons and photons in the few keV energy range, demonstrating the feasibility of this technique for large reductions of background in searches for direct interactions of weakly interacting massive particle dark matter.


Simultaneous High Resolution Meausurement Of Phonons And Ionization Created By Particle Interactions In A 60 G Germanium Crystal At 25 Mk, Tom Shutt, N. Wang, B. Ellman, Y. Giraud-Héraud, C. Stubbs, Peter D. Barnes Jr., A. Cummings, Angela Da Silva, John Emes, Eugene E. Haller, Andrew E. Lange, J. Rich, R. R. Ross, B. Sadoulet, G. Smith, W. Stockwell, S. White, Betty A. Young, D. Yvon Dec 1992

Simultaneous High Resolution Meausurement Of Phonons And Ionization Created By Particle Interactions In A 60 G Germanium Crystal At 25 Mk, Tom Shutt, N. Wang, B. Ellman, Y. Giraud-Héraud, C. Stubbs, Peter D. Barnes Jr., A. Cummings, Angela Da Silva, John Emes, Eugene E. Haller, Andrew E. Lange, J. Rich, R. R. Ross, B. Sadoulet, G. Smith, W. Stockwell, S. White, Betty A. Young, D. Yvon

Physics

We demonstrate simultaneous high energy resolution (rms≊800 eV) measurements of ionization and phonons created by particle interactions in a semiconductor crystal of macroscopic size (60 g germanium) at 25 mK. We present first studies of charge collection at biases below 1 V/cm, and find that, contrary to commonly held opinion, the full recoil energy of particle interactions is recovered as phonons when charge trapping is negligible. We also report an unanticipated correlation between charge collection and phonon energy at very low bias, and discuss this effect in terms of charge trapping.


The Weakest Bond: Experimental Observation Of Helium Dimer, Fei Luo, George C. Mcbane, Geunsik Kim, Clayton F. Giese, W. Ronald Gentry Dec 1992

The Weakest Bond: Experimental Observation Of Helium Dimer, Fei Luo, George C. Mcbane, Geunsik Kim, Clayton F. Giese, W. Ronald Gentry

Peer Reviewed Articles

Helium dimer ion was observed after electron impact ionization of a supersonic expansion of helium with translational temperature near 1 mK. The dependence of the ion signal on source pressure, distance from the source, and electron kinetic energy was measured. The signal was determined to arise from ionization of neutral helium dimer.


Solidification And Morphology Of Submarine Lavas: A Dependence On Extrusion Rate, Ross W. Griffiths, Jonathan H. Fink Dec 1992

Solidification And Morphology Of Submarine Lavas: A Dependence On Extrusion Rate, Ross W. Griffiths, Jonathan H. Fink

Geology Faculty Publications and Presentations

The results of recent laboratory experiments with wax extruded beneath relatively cold water may be extrapolated to predict the surface morphology of submarine lavas as a function of the extrusion rate and melt vIscosity. The experiments with solidifying wax indicated that the surface morphology was controlled by a single parameter, the ratio of the time taken for the surface to solidify, and a time scale for lateral flow. For submarine basalts a solution of the cooling problem (which is dominated by conduction in the lava but convective heat transfer in the water) and estimates of lava viscosities place this parameter ...


The Morphology Of Lava Flows In Planetary Environments: Predictions From Analog Experiments, Ross W. Griffiths, Jonathan H. Fink Dec 1992

The Morphology Of Lava Flows In Planetary Environments: Predictions From Analog Experiments, Ross W. Griffiths, Jonathan H. Fink

Geology Faculty Publications and Presentations

The rates of surface cooling and lateral spreading are evaluated for lava flows on the surface of Earth, Venus, Mars, the Moon, and 10. Differences between the flow morphologies expected in these environments are then predicted under the assumption that the results of recent laboratory simulations oflavas using wax extruded beneath cold water (Fink and Griffiths, 1990) can be carried over. These experiments involved the spreading of viscous liquid under gravity in the presence of a solidifying surface crust and revealed a set of four distinct surface morphologies. Transitions from one morphology to the next occurred in a well-defined sequence ...


Free Radical-Catalyzed Synthesis Of Benzoprostacyclins, Richard C. Larock, Nam H. Lee Dec 1992

Free Radical-Catalyzed Synthesis Of Benzoprostacyclins, Richard C. Larock, Nam H. Lee

Iowa State University Patents

A method is provided for preparing benzoprostacyclins by the free-radical-catalyzed tandem alkene insertion into a 1,4-bisoxy-substituted cyclopent-2-ene intermediate.


Translational Correlations In The Vortex Array At The Surface Of A Type-Ii Superconductor, M. Cristina Marchetti, David R. Nelson Dec 1992

Translational Correlations In The Vortex Array At The Surface Of A Type-Ii Superconductor, M. Cristina Marchetti, David R. Nelson

Physics

We discuss the statistical mechanics of magnetic flux lines in a finite-thickness slab of type-II superconductor. The long wavelength properties of a flux-line liquid in a slab geometry are described by a hydrodynamic free energy that incorporates the boundary conditions on the flux lines at the sample's surface as a surface contribution to the free energy. Bulk and surface weak disorder are modeled via Gaussian impurity potentials. This free energy is used to evaluate the two-dimensional structure factor of the flux-line tips at the sample surface. We find that surface interaction always dominates in determining the decay of translational ...


Icon: A Interpreter-Based Approach, Dong Wei Dec 1992

Icon: A Interpreter-Based Approach, Dong Wei

Computer Science Technical Reports

This paper introduces the Icon programming language in a simplified form using a lisp-like syntax to represent an interesting subset of the language. The paper also discusses the semantics and implementation of some of Icon's advanced features with emphasis on generators and goal-directed evaluation. The organization of the paper resembles a chapter in the book ``Programming Languages: An Interpreter-Based Approach'' by Samuel Kamin. This paper can serve as a supplement to that book, allowing comparative programming language instructors who use the Kamin text to efficiently teach the Icon programming language


Digital Soil Maps For Iowa, Gerald A. Miller, Robert C. Mortensen Dec 1992

Digital Soil Maps For Iowa, Gerald A. Miller, Robert C. Mortensen

Proceedings of the Integrated Crop Management Conference

The Iowa Cooperative Soil Survey (ICSS) initiated a program in 1987 to transfer printed soil maps in each county soil survey report to an electronic database. The purpose of this cooperative project is to provide a computerized database of the county soil maps to support federal, state, local and private sector decision-making concerning use and management of Iowa's soil resources.


What's With The Weather?, S. Elwynn Taylor Dec 1992

What's With The Weather?, S. Elwynn Taylor

Proceedings of the Integrated Crop Management Conference

Most crops are well adapted to the prevailing climate. Nevertheless, weather remains the most significant factor in successful crop production. Weather-wise management of production and marketing can greatly reduce the risk of crop loss and of fmancial failure in crop production. The cyclic nature of midwest weather, the relationship of potential yield to soil moisture, and the effects of temperature on the development of crops and crop pests should be understood by the farmer and by the farm service representative. Com yield in Iowa and Illinois improved slowly during the first half of the 20th century. There was considerable yield ...


Reducing Pesticide Movement To Surface Water, Margaret A. Smith Dec 1992

Reducing Pesticide Movement To Surface Water, Margaret A. Smith

Proceedings of the Integrated Crop Management Conference

Pesticides (largely herbicides) can be detected in Iowa surface waters---but when found, are usually at very low concentrations (ppb). Concentrations and total herbicide losses to surface waters are often highest in the spring after chemical applications and heavy rains. Many management practices can be used to help minimize pesticides in Iowa waters. Farmers, dealers, and pesticide applicators may address the issue by focusing only on herbicide management. Other crop management tools are as important and should be considered before changing pest control strategies. The following checklist may be helpful for farm advisors reviewing options for reducing pesticides in surface waters.


Spray-Wind-Inversion, S. Elwynn Taylor Dec 1992

Spray-Wind-Inversion, S. Elwynn Taylor

Proceedings of the Integrated Crop Management Conference

Wind, clouds, humidity, stability--there are numerous properties of the atmosphere that influence effective application of agricultural chemicals. Whenever a material is dispersed in the atmosphere, some of it will, inevitably not reach the intended target. The responsibility of the applicator is to minimize drift that is to apply at a time and in a manner that will not result in the movement of significant concentrations of material away from the target zone: Drift can result from wind carry, from high concentrations of fine mist suspended in the air, and from vapor drift. Drift may be hazardous to nontarget crops, to ...


Beneficial Microorganisms In Low-Input Agriculture, Thomas E. Loynachan Dec 1992

Beneficial Microorganisms In Low-Input Agriculture, Thomas E. Loynachan

Proceedings of the Integrated Crop Management Conference

The overall involvement of microorganisms in crop production still remains much of a mystery. Because of their distribution and size, most studies have been done in the laboratory and the implications of these studies referred back to the field. With this approach, unfortunately, much remains unknown, not only about the growth of individual organisms, but certainly the interactions of organisms in nature. Several "nontraditional" soil amendments have been marketed over the years that capitalize on our lack of understanding of soil microbial processes. Terms such as soil activators, soil enhancers, and enzyme stimulators have been used, claiming to improve soil ...


Agricultural Contribution Of Nitrate-N To The Des Moines River: 1945 Vs. 1980, Dennis R. Keeney, Thomas H. Deluca Dec 1992

Agricultural Contribution Of Nitrate-N To The Des Moines River: 1945 Vs. 1980, Dennis R. Keeney, Thomas H. Deluca

Proceedings of the Integrated Crop Management Conference

Recently, intensive water quality monitoring has demonstrated the presence of nitrate (N03-N) in surface and groundwater throughout the Midwestern U.S. (Hallberg, 1989).


Fall Vs Spring Application Of Nitrogen, Gyles W. Randall Dec 1992

Fall Vs Spring Application Of Nitrogen, Gyles W. Randall

Proceedings of the Integrated Crop Management Conference

Fall application of nitrogen (N) has been a way-of-life for many Upper Midwest farmers for a number of years. The primary advantages of fall compared to spring application are: (1) spread out the work load for both the farmer and dealer, (2) reduce potential soil compaction by eliminating another field operation in the spring, and (3) slight price advantages for fall application. But with the eight-month period between application and the time of greatest N uptake by com, the potential loss of N from the soil system increases. These potential losses lead to poorer economic return and contamination of surface ...


The Research Basis For Wisconsin's Legume Nitrogen Credits, K. A. Kelling, L. G. Bundy, R. P. Wolkowski Dec 1992

The Research Basis For Wisconsin's Legume Nitrogen Credits, K. A. Kelling, L. G. Bundy, R. P. Wolkowski

Proceedings of the Integrated Crop Management Conference

The ability of legumes to supply nitrogen to succeeding crops has been recognized for many years. The amount of actual N available will depend on the amount of N in the alfalfa and its availability, and any additional soil N that may be released due to the growth of the legume. From a practical standpoint, however, it is not the amount of N added to the system that is of primary importance. Much more important is the amount of N not needed by the com when the com is grown following the legume. This approach, commonly called the nitrogen fertilizer ...


Royal Institute Of Technology: Department Of Polymer Technology, Otto Vogl, Ann Christine Albertsson Dec 1992

Royal Institute Of Technology: Department Of Polymer Technology, Otto Vogl, Ann Christine Albertsson

Emeritus Faculty Author Gallery

No abstract provided.


70. Obituary, Herman F. Mark, Otto Vogl Dec 1992

70. Obituary, Herman F. Mark, Otto Vogl

Emeritus Faculty Author Gallery

No abstract provided.


The Probe, Issue 128 - December 1992 Dec 1992

The Probe, Issue 128 - December 1992

The Probe: Newsletter of the National Animal Damage Control Association

Contents:

Reflections On An Onerous Deed
CALENDAR OF UPCOMING EVENTS
Coyote Urine Translocated by Flora
PETA Indictments Expected Soon
Plague Claims Bobcat Hunter
Colorado Voters Ban Spring Hunt; Arizonans Defeat Trapping Ban
Charter Member Says Good-Bye
Probe Should Be Advocate for ADC Activities
Bill Fitzwater III
Next Issue Jan/Feb
NADCA Renewals and Donations
New Logo Chosen for NADCA!


Coastal Rehabilitation Manual, Veronica P M Oma, D M. Clayton, J. B. Broun, C D M. Keating Dec 1992

Coastal Rehabilitation Manual, Veronica P M Oma, D M. Clayton, J. B. Broun, C D M. Keating

Bulletins 4000 -

Provides an overview of the coastal environment to ensure that the natural environment and coastal processes are considered properly. Describes how to develop a successful coastal rehabilitation strategy and detail rehabilitation techniques applicable to Western Australia. Lists sources of further advice and information.


Water Current, Volume 24, December 1992 Dec 1992

Water Current, Volume 24, December 1992

Water Current Newsletter

Seminar Series to Feature Global Perspective
Report from the Director
Argentina, Brazil Toured by Group from Nebraska
Czech Water Specialists Enumerate Contamination Problems
UNL Environmental Specialists Impressed by Hungarians
Foreign Influences on Nebraska Water Law
Trade, Environment, and Development, Tied Together in U.S. Trade Policy
Slovakian Grad Student Studies Aquaculture Here; Wants to Establish Fish Farm in Czechoslovakia
EARTH with Nebraska Connections Trains Agriculturists
La Mancha Plateau Aquifer Stressed by Intensive Irrigation
Hungarian Research Says Their Nitrogen Fertilizer Use Down
What's New?
Irrigation Association Centennial Spawns State Water-History Chronicle
Director of International Drought Information Center Receives Award
Dates ...


Vertex Coloring For Weighted Graphs With Application To Timetabling, Lynn Kiaer, Jay Yellen Dec 1992

Vertex Coloring For Weighted Graphs With Application To Timetabling, Lynn Kiaer, Jay Yellen

Mathematical Sciences Technical Reports (MSTR)

This paper applies the methods of vertex coloring to timetabling problems


The Influence Of Alfalfa Root Structure On Plains Pocket Gopher Damage And Behavior, Bruce A. Jasch Dec 1992

The Influence Of Alfalfa Root Structure On Plains Pocket Gopher Damage And Behavior, Bruce A. Jasch

Dissertations & Theses in Natural Resources

No abstract provided.


Stream Of Consciousness (1992), Alliance For Aquatic Resource Monitoring (Allarm) Dec 1992

Stream Of Consciousness (1992), Alliance For Aquatic Resource Monitoring (Allarm)

Stream of Consciousness

Stream of Consciousness is a publication from the Alliance for Aquatic Resource Monitoring (ALLARM) at Dickinson College.

Table of Contents

The Clean Air Act Made Simple / by Jennifer Sloan

Monitor Contribution: Sewage Treatment Plants of the 90's / by Andrew Saul

How Does the Weather Affect Acid Deposition? / by Cristin Tighe

Volunteer Spotlight: Ron Comstock / by Matt Franke

Carmen's Corner / by Carmen Irizarry

Classification of Streams Monitored by ALLARM Volunteers (1987-1992)

Did You Know? / by Cristin Tighe

Matt's Helpful Hints / by Matt Franke

Duquesne: Lighting the Way to Interstate Power? / by Jennifer Sloan

Four, Fix, and Six Year ...


Geology Newsletter- 1992, Department Of Geology Dec 1992

Geology Newsletter- 1992, Department Of Geology

Geological and Environmental Sciences News

Vol.1, No. 17

  • Faculty News
  • Alumni/ Friends/ Former Faculty Notes
  • New Alumni
  • Awards and Scholarships
  • Geology Development and Scholarship Donations
  • Service Staff News
  • Grand Canyon Raft Adventure


The Multiple Admission Factor (Maf) In Small Area Variation Analysis, Kevin Cain, Paula Diehr Dec 1992

The Multiple Admission Factor (Maf) In Small Area Variation Analysis, Kevin Cain, Paula Diehr

UW Biostatistics Working Paper Series

Small area variation analysis are often based on area-level data such as the total number of hospital admissions within an area, rather than person-level data. Such analysis often make the assumption that the number of admissions within a small area follow a Poisson distribution. This may not be a reasonable assumption when multiple admissions per person are possible. In this case, the multiple admission factor (MAF) can be used to adjust for the extra variance introduced by multiple admissions. In this article, data from Washington State are used to estimate the multiple admission rate and the MAF for each modifed ...