Physical Sciences and Mathematics Commons^™

Postulated Evolution Of Platte River And Related Drainages, V. L. Souders, J. B. Swinehart, V. H. Dreeszen

Conservation and Survey Division

No abstract provided.

Alternative Usages Of Wetlands Other Than Conventional Farming In Iowa, Kansas, Missouri, And Nebraska, Ellen Leventhal, Hubert H. Humphrey

United States Environmental Protection Agency: Staff Publications

Conversion of wetlands in Iowa, Kansas, Missouri, and Nebraska into agricultural dry lands in the past several decades has occurred as a means to obtain profit from what landowners would otherwise consider unprofitable land. This activity has resulted in substantial losses of wetlands valued for their unique ability to mitigate flood and storm damage, control erosion, discharge and recharge groundwater, improve water quality, and support a wide diversity of fish, wildlife, and vegetation.

Utilizing fish, wildlife, and vegetation from wetlands for profit is a way for wetland owners to recognize the value their wetlands add to their property. Landowners then …

Possible Conserved Quantity For The Henon-Heiles Problem, Paul Finkler, C. Edward Jones, Glenn A. Sowell

Paul Finkler Papers

We study a power-series expansion for a conserved quantity K in the case of the two-dimensional Henon-Heiles potential. An alternative technique to that of Gustavson [Astron. J. 71, 670 (1966)] is applied to find the coefficients in the expansion for K. The technique is used to determine twelve orders for the conserved quantity K, more than twice as many as that calculated by Gustavson. We investigate the degree of constancy of our truncated K in regions where the motion is known to be chaotic and also where it is nonchaotic.

Intracavity Frequency Doubling Of A Nd:Yag Laser With An Organic Nonlinear Optical Crystal, Stephen Ducharme, W.P. Risk, W.E. Moerner, Victor Y. Lee, R.J. Twieg, G.C. Bjorklund

Stephen Ducharme Publications

Your access to Appl. Phys. Lett. is provided through the subscription of Univ Nebraska-Lincoln Lib. What is this? Scitation Citing Articles | CrossRef Citing Articles | All Citing Articles [ Previous / Next Abstract | Issue Table of Contents | Bottom of Page ] Applied Physics Letters -- August 6, 1990 -- Volume 57, Issue 6, pp. 537-539 Full Text: [ PDF (639 kB) ] Order Rightslink Permissions for Reuse About Rightslink view MyArticles What is this? Select up to 20 articles at a time. Intracavity frequency doubling of a Nd:YAG laser with an organic nonlinear optical crystal Stephen Ducharme, …

Statics And Dynamics Of Organic Charge-Transfer Crystals: The Orientational Phase Transition In A-Tcnb, Karl-Heinz Brose, Tadeusz Luty, Craig J. Eckhardt

Craig J. Eckhardt Publications

Crystal potential energy calculations and lattice dynamical calculations are presented for the high-temperature and low-temperature phases of the charge-transfer complex crystal of anthracene with 1,2,4,5-tetracyanobenzene using the method of atom–atom potentials. For several different sets of the “exp-6'' potential parameters the crystal energy was minimized with respect to the lattice constants and orientations and positions of the molecules in the unit cell. These calculations show good agreement with the experimental values. The equilibrium crystal structures were used to calculate the lattice dynamics in the harmonic approximation for both crystal modifications. In the phonon dispersion curves lattice modes were discovered that …

The Probe, Issue 103 - August 1990

The Probe: Newsletter of the National Animal Damage Control Association

THE PROBE National Animal Damage Control Association
JULY 1990
APHIS Activity Report
DWRC in Trouble
Bear
Blackbirds
Cats
Cormorants
DRC-1339
Mountain Beaver
Pigeons
Yellow-Bellied Marmots
Animal Rights
Public Lands Improved, Not Harmed by Ranching
Fur
Prairie Dogs
“Telling Rat From Wrong Takes Time”
By-Products
Endangered Species

Measurement Of Parity Violation In The Elastic Scattering Of Polarized Electrons From 12C, P. A. Souder, R. Holmes, D. - H. Kim, K. S. Kumar, M. E. Schulze, K. Isakovich, G. W. Dodson, K. W. Dow, M. Farkhondeh, S. Kowalski, M. S. Lubell, J. Bellanca, M. Goodman, S. Patch, Richard Wilson, G. D. Cates, S. Dhawan, Timothy J. Gay, V. W. Hughes, A. Magnon, R. Michaels, H. R. Schaefer

Timothy J. Gay Publications

We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from ¹²C nuclei. Our result is A_expt=0.60±0.14±0.02 ppm, where the first error is statistical and the second is systematic. With a beam polarization of 0.37, we compute the isoscalar vector hadronic coupling constant γ̃ to be 0.136±0.032±0.009. The standard model predicts γ̃ =0.155 at the tree level, in agreement with our data.

Water Current, Volume 22, July 1990

Water Current Newsletter

Water Sciences Research Facility Open Here Soon
Water Center Director Comes Here From CSRS in Washington, D.C.
Water Sciences Laboratory
Drip Irrigation and Weather Modification Explained on Water Tour

The Probe, Issue 102 - July 1990

The Probe: Newsletter of the National Animal Damage Control Association

THE PROBE National Animal Damage Control Association
JULY 1990
Inhumane Torture
Car Bomb
The Animal Liberation Front
The Farm Animal and Research Facilities Protection Act
Canada’s Department of Agriculture
The Black-footed Ferret
World Championship Prairie Dog Shootout
The Elk Horn
Lyme Disease
The Anti-Apartheid Act of 1986
EPA
President’s Corner

Photodarkening Profiles And Kinetics In Chalcogenide Glasses, Stephen Ducharme, J. Hautala, P.C. Taylor

Stephen Ducharme Publications

The spatial and temporal evolution of photodarkening in chalcogenide glasses is simulated by a simple kinetic model and tested against experiments. In the model, photodarkening, a gradual decrease of the energy of the absorption edge caused by above-band-gap illumination, is the additional absorption at defects created by the absorbed light. The defect-creation rate is proportional to the rate at which photons are absorbed either directly at the defect site or, alternatively, at a neighboring site. The depletion of the incident light within the sample is included and the resulting equations cast into a universal form that is applicable to realistic …

Kerr Effect Of Two-Medium Layered Systems, Liang-Yao Chen, William A. Mcgahan, Z.S. Shan, David J. Sellmyer, John A. Woollam

David Sellmyer Publications

Detailed and practical expressions are given for the magneto-optical Kerr effect (MOKE) for various configurations of two media. One is a magneto-optic (MO) one, and the other is a nonmagnetic (NM) medium. For a system of two thick media with a single interface, with a first-order approximation in MOKE term Q, the Kerr function is determined by the product of a MOKE term Q and an optical term η. A second type of system includes a thin MO (or NM) layer deposited on a thick NM (or MO) substrate. For a MO/(NM-substrate) configuration, the Kerr function is related to …

Disappearance And Recoverability Of Songbird Carcasses In Fruit Orchards, Mark E. Tobin, Richard A. Dolbeer

USDA Wildlife Services: Staff Publications

Songbird mortality due to agricultural pesticides is often assessed by searching treated areas for carcasses. However, carcass removal by scavengers and the failure of searchers to find carcasses that are present may bias mortality estimates. We conducted two studies in 1987 and 1988 in New York to evaluate such biases at the time of fruit maturation in cherry and apple orchards. In the first study, mean survival times for carcasses were 8.2 d in cherry and 10.4 d in apple orchards. In the second study, searchers located an average of 75% of carcasses placed in orchards. Our results suggest that …

Two-Photon Ionization Of The Ar Atom And Detachment Of The F- Ionv, Cheng Pan, Bo Gao, Anthony F. Starace

Anthony F. Starace Publications

Theoretical calculations of the two-photon ionization cross section of argon and of the two-photon detachment cross section of the negative fluorine ion are presented for the energy region from threshold to the single-photon ionization or detachment threshold. Detailed analyses are presented of the effects of various kinds of electron correlations, whose contributions to the two-photon transition amplitudes are evaluated using variationally stable procedures to sum implicitly over intermediate states. These variationally stable procedures enable us to give much more reliable predictions in the region of the first few intermediate-state resonances in argon than were provided by previous calculations of one …

The Prairie Naturalist Volume 22, No. 2. June 1990

The Prairie Naturalist

Paul B. Kannowski, Editor

Nikki R. Seabloom, Assistant Editor

Douglas H. Johnson, Book Review Editor

CONTENTS

BREEDING BIOLOGY OF THE BLACK-TAILED PRAIRIE DOG IN NORTH DAKOTA ▪ R. W. Seabloom and P. W. Theisen

PATTERNS OF RESOURCE USE IN A LIZZARD COMMUNITY IN THE NEBRASKA SAND HILLS PRAIRIE ▪ R. E. Ballinger, S. M. Jones, and J. W. Nietfeldt

A THIRTEEN-YEAR SURVEY OF THE APHIDOPHAGOUS INSECTS OF ALFALFA ▪ N. C. Elliott and R. W. Kieckhefer

STATUS AND DISTRIBUTION OF PLAINS SHARP-TAILED GROUSE IN COLORADO ▪ A. W. Hoag and C. E. Braun

CHRISTMAS BIRD COUNTS FOR NORTH DAKOTA - …

Interactions Between Plains Pocket Gophers And Two Varieties Of Dryland Alfalfa, James C. Luchsinger

School of Natural Resources: Dissertations, Theses, and Student Research

No abstract provided.

Evaluation Of Monofilament Lines To Prevent Damage By Birds, Danilo A. Aguero

School of Natural Resources: Dissertations, Theses, and Student Research

No abstract provided.

The Probe, Issue 101 - May/June 1990

The Probe: Newsletter of the National Animal Damage Control Association

Contents:
APHIS Activity Report
Reading Material
Letters to the Editor
Personnel
Practical Tips from the Field
All the News that’s Print to Fit
Editorial
New Academic Endeavor
Graduate Assistantships in ADM

Magnetism And Anisotropy Of Tb/Fe Multilayers, Z.S. Shan, David J. Sellmyer

David Sellmyer Publications

Studies of the layer-thickness dependence of hysteresis loops for Tb/Fe compositionally modulated films (CMF) are reported. The characteristics of magnetic properties, such as magnetization and uniaxial anisotropy, which depend on the FE layer thickness, can be interpreted in terms of the compositional dependence of magnetic properties of the constituent subnetworks and the spatial distribution of the constituent atoms. The magnetic properties of Tb/Fe CMF are analyzed with a micromagnetic model, and the behavior of the anisotropy and constituent magnetization near the compensation point is discussed. Journal of Applied Physics is copyrighted by The American Institute of Physics.

Magnetic And Structural Properties Of Cocrta Films And Multilayers With Cr, David J. Sellmyer, D. Wang, J.A. Christner

David Sellmyer Publications

We report our studies of epitaxial growth of CoCrTa films on Cr underlayers and the properties of CoCrTa/Cr multilayers. The coercivity, H_c, strongly depends on Ta composition, sputtering conditions, and the thicknesses of the magnetic layer and Cr underlayer. An H_cvalue of 1300 Oe was obtained for a Ta composition of 2 at. %, a Cr underlayer thickness of 4000 Å, and a magnetic layer thickness of 400 Å. The x-ray data show that the high H_c occurs when crystallites of the Cr underlayer and CoCrTa layer are aligned with the Cr (200) and CoCrTa …

The Structure And Magneto-Optic Properties Of Mnal-Based Thin Films, J.X. Shen, Roger D. Kirby, David J. Sellmyer

Roger Kirby Publications

We have measured the magnetization and magneto-optic Kerr rotation of sputtered thin films of Mn-Al-Cu ternary alloys over a wide composition range and for substrate temperatures between 25 and 450 °C. Magnetization and x-ray diffraction measurements suggest that our films are a mixture of the ferromagnetic kappa (κ) phase of MnAl and a highly paramagnetic amorphous phase. Room-temperature magneto-optic measurements on these films show a saturation polar Kerr rotation of up to 0.12° with little wavelength dependence.

Fabrication Of Ferromagnetic And Antiferromagnetic Chromium Oxides By Organometallic Chemical Vapor Deposition, Peter A. Dowben, Yoon Gi Kim, S. Baral-Tosh, G.O. Ramseyer, Chanyong Hwang, M. Onellion

Peter Dowben Publications

We have been able to fabricate CrO₂ and Cr₂O₃ from ultraviolet photolytic and plasma-assisted decomposition of Cr(CO) ₆ in an oxygen carrier gas. The composition of these films is uniform in composition and contains little contamination. Using magneto-optic Kerr effect measurements, we have been able to demonstrate that the CrO₂ films are ferromagnetic.

The Chemistry Of The Gadolinium-Nickel Interface, D. Lagraffe, Peter A. Dowben, M. Onellion

Peter Dowben Publications

Gadolinium overlayers on Ni(111) have been studied by angle resolved photoemission, angle resolved AES, LEED, and RHEEB. We have observed pronounced interdiffusion of nickel with the gadolinium overlayer at temperatures as low as 150 K. This is in marked contrast with gadolinium overlayers on Cu(108) where substantial interdiffusion is not observed until 360 K, but is consistent with studies of ytterbium on nickel. [A. Nilsson, B Eriksson, N. Martenssom, J. N. Andersen, and J. Onsgaard, Phys. Rev. B 38,10357, ( 1988) and I. Chorkendorff, K. Onsgaard, J. Schmidt-May and R. Nyholm, Surf. Sci. 160, 587, (1985) .] There is a …

Ordering Of Metal Overlayers On Metal Substrates Studied Using Atom Beam Scattering, G. Vidali, C.W. Hutchings, Peter A. Dowben, M. Karimi, C. Moses, M. Foresti

Peter Dowben Publications

We will illustrate how atom beam scattering (ABS) can be used to study the growth and ordering of adsorption of Hg on Cu(001). At low coverage (less than 2% of a monolayer), we obtain that the scattering cross section of He with (adsorbed) Hg is about 50 Ų. We find that mercury forms two stable phases on Cu(001) in the temperature range between 200 and 330 K, a c (2 x 2) and a high density c (4 x 4) phase. From ABS diffraction data, we can deduce the corrugation of the surface electron charge density of the …

The Effect Of Lateral Interactions On The Thermal Desorption Of N2 From Ni(100), Shikha Varma, Peter A. Dowben

Peter Dowben Publications

We have investigated the desorption of N₂ from Ni(100) using thermal desorption spectroscopy (TDS). A modified Polanyi-Wigner equation has been used to obtain the desorption energy and the preexponential factor, both of which depend on the coverage of the adsorbate. We show that there is a large lateral interaction among the adlayer molecules when N₂ goes down as ordered c (2 X 2) on Ni. In addition, the overlayer ordering, in the thermal desorption process, is observed to affect the thermal desorption spectra.

Selective Area Deposition Of Conducting Palladium Films On Polyimide Resins, Yoon-Gi Kim, S. Bialy, R.W. Miller, J.T. Spencer, Peter A. Dowben, Saswati Datta

Peter Dowben Publications

We have demonstrated that the selective area deposition of palladium on polyimide substrates i s possible through the U.V. photolysis of (π - a l l y 1) (π –cyclopentadieny1) palladium. This photolytic deposition process did not result in any apparent damage to either the Ultem 1000 (polyetherimide) or Kapton substrates (polyimide substrates). The resistivity of the palladium films (< 0.1 um) suggests that the films are porous.

Magnetic Ordering Of Tb Overlayers On Ni(Ll1), D. Lagraffe, A. Miller, Peter A. Dowben, M. Onellion

Peter Dowben Publications

The 5p_3/2 to 5p_1/2 shallow core level branching ratios in different - photoemission geometries provide a measure of the magnetic ordering in rare earth overlayers as a result of final state effects in photoemission. This 5p level anisotropy can be used to probe magnetic ordering across the Tb Curie temperature as well as magnetic ordering induced by a ferromagnetic substrate in Results are shown for paramagnetic Tb overlayers on Ni(111). The Ginsberg-Landau theory can be used to accurately model terbium thin films for T>T_c.

Magnetic And Structural Properties Of High-Coercivity Pr2Fe14Bpr Cosputtered Films, K.D. Aylesworth, David J. Sellmyer, George C. Hadjipanayis

David Sellmyer Publications

The results of structural and magnetic measurements on a series of films produced by cosputtering Pr₂₁Fe₇₂B₇ and Pr are reported. The materials were deposited serially, 10–200 Å at a time, onto 700 °C Ta substrates attached to a computer-controlled stepping motor. The structure of the resulting films was examined by large- and small-angle x-ray diffraction, scanning electron microscopy, and by microprobe analysis. Magnetic measurements were made at temperatures from 4.2 to 300 K, in fields up to 80 kOe in a vibrating sample magnetometer. The films appear to consist of 1-µm grains of Pr_{2 …}

Enhancement Of Magneto-Optical Kerr Effects, Liang-Yao Chen, William A. Mcgahan, Z.S. Shan, David J. Sellmyer, John A. Woollam

David Sellmyer Publications

A general expression for the magneto-optical polar Kerr effect is given for a bilayered configuration in which the optical constants of the two media differ. The equation shows that a giant enhancement of the Kerr effect in magneto-optical/metallic bilayers can be expected if the dielectric constants of the two materials are low or are matched well to the other. An explicit equation is also given to calculate the spectral enhancement due to a dielectric overcoating on magnetic substrates. An example is given for SiO-coated Dy/Co compositionally modulated alloys, yielding a good comparison to the experimental results in both the transparent …

Magnetic And Structural Studies In Sm-Fe-Ti Magnets, Y. Wang, George C. Hadjipanayis, A. Kim, N.C. Liu, David J. Sellmyer

David Sellmyer Publications

The effects of vanadium substitution on the magnetic properties of Sm-Fe-Ti-V melt-spun ribbons and the magnetic properties and microstructure of sintered Sm-Fe-Ti based magnets are reported. The highest coercivity, H_c =10.65 kOe, was obtained in a heat-treated melt-spun Sm₈ Fe_75.5 Ga_0.5 Ti₈ V₈ alloy. This is the highest value of the coercivities reported in alloys with the ThMn₁₂ -type structure. Bulk magnets were prepared by the usual powder metallurgy technique. However, their highest coercivity (~2 kOe) was much less than that of the corresponding ribbons. The low coercivity of sintered magnets has been …

Electronic Structure And Magnetic Properties Of Fe-Rich Ternary Compounds: Yfe10V2 And Yfe10Cr2, Sitaram Jaswal, Y.G. Ren, David J. Sellmyer

David Sellmyer Publications

These compounds are prototypes of the Fe-rich ternary systems of ThMn₁₂ structure which are of considerable current interest as permanent magnet materials. The electronic structure of YFe₁₀V₂ and YFe₁₀Cr₂ have been studied with photoemission and spin-polarized calculations. The Fe d states dominate the calculated density of states (DOS) near the Fermi energy and there is a good correspondence between the DOS and the experimental spectra. The calculated magnetization is in very good agreement with the experimental data. The calculations give a magnetic moment of ~1 µ_B at the V or Cr site …