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University of Nebraska - Lincoln

2006

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Articles 1 - 30 of 675

Full-Text Articles in Physical Sciences and Mathematics

Measurement Of The BS0 Lifetime Using Semileptonic Decays, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration Dec 2006

Measurement Of The BS0 Lifetime Using Semileptonic Decays, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration

Kenneth Bloom Publications

We report a measurement of the Bs0 lifetime in the semileptonic decay channel Bs0 → Ds- μ+νX (and its charge conjugate), using approximately 0.4 fb-1 of data collected with the D0 detector during 2002–2004. Using 5176 reconstructed Ds- μ+ signal events, we have measured the Bs0 lifetime to be τ(Bs0) = 1.398 ± 0.044(stat) -0.025+0.028(syst) ps. This is the most precise measurement of the Bs0 lifetime to date.

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Thickness Profiles Through Fatigued Bulk Ceramic Lead Zirconate Titanate, Nina Balke, Doru C. Lupascu, Thomas Blair Dec 2006

Thickness Profiles Through Fatigued Bulk Ceramic Lead Zirconate Titanate, Nina Balke, Doru C. Lupascu, Thomas Blair

Alexei Gruverman Publications

Wedge-cut samples of fatigued ferroelectric lead zirconate titanate ceramics were investigated using piezoresponse force microscopy in conjunction with conventional electrical hysteresis measurements. The local clamping of domains is monitored at different depths in the sample. The coercive fields in grains near the electrodes differ for different materials and preparation methods of the electrodes. For silver, fatigue consistently generates a space charge in the depth of the sample. For platinum electrodes, the fatigue behavior scatters strongly. Microscopically, it either occurs directly underneath the electrodes or resembles the behavior of the silver electrodes in other samples.

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Responses Of Pond-Breeding Amphibians To Wildfire: Short-Term Patterns In Occupancy And Colonization, Blake R. Hossack, Paul Stephen Corn Dec 2006

Responses Of Pond-Breeding Amphibians To Wildfire: Short-Term Patterns In Occupancy And Colonization, Blake R. Hossack, Paul Stephen Corn

United States Geological Survey: Staff Publications

Wildland fires are expected to become more frequent and severe in many ecosystems, potentially posing a threat to many sensitive species. We evaluated the effects of a large, stand-replacement wildfire on three species of pond-breeding amphibians by estimating changes in occupancy of breeding sites during the three years before and after the fire burned 42 of 83 previously surveyed wetlands. Annual occupancy and colonization for each species was estimated using recently developed models that incorporate detection probabilities to provide unbiased parameter estimates. We did not find negative effects of the fire on the occupancy or colonization rates of the long-toed …

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Measurement Of BD Mixing Using Opposite-Side Flavor Tagging, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration Dec 2006

Measurement Of BD Mixing Using Opposite-Side Flavor Tagging, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration

Kenneth Bloom Publications

We report on a measurement of the Bd0 mixing frequency and the calibration of an opposite-side flavor tagger in the D0 experiment. Various properties associated with the b quark on the opposite side of the reconstructed B meson are combined using a likelihood-ratio method into a single variable with enhanced tagging power. Its performance is tested with data, using a large sample of reconstructed semileptonic B → μD0X and B → μD*X decays, corresponding to an integrated luminosity of approximately 1 fb-1. The events are divided into groups depending on …

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Fate Of Fish Production In A Seasonally Flooded Saltmarsh, Philip W. Stevens, Clay L. Montague, Kenneth J. Sulak Dec 2006

Fate Of Fish Production In A Seasonally Flooded Saltmarsh, Philip W. Stevens, Clay L. Montague, Kenneth J. Sulak

United States Geological Survey: Staff Publications

Although saltmarshes are thought to enhance the productivity of open estuarine water, the mechanism by which energy transfer occurs has been debated for decades. One possible mechanism is the transfer of saltmarsh production to estuarine waters by vagile fishes and invertebrates. Monthly estimates of fish standing stock, net fish ingress, and predation were used to develop a bio-mass budget to estimates annual production of fishes and the relative yield to predatory fish, birds, and direct migration to the estuary. Annual production of saltmarsh fishes was estimated to 31.0 gm-2 saltmarsh, which falls within the range of previously reported values …

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Structural Study Of Mn-Doped Zno Fi Lms By Tem, Xingzhong Li, Jun Zhang, David J. Sellmyer Dec 2006

Structural Study Of Mn-Doped Zno Fi Lms By Tem, Xingzhong Li, Jun Zhang, David J. Sellmyer

David Sellmyer Publications

The structural study of diluted magnetic semiconductors is important for interpreting the ferromagnetic behavior associated with the materials. In the present work, a series of low concentration Mn-doped ZnO thin films synthesized by pulsed laser deposition was studied by electron microscopy. All films show the wurtzite structure with (001) preferred growth orientation on the Si substrate. Electron diffraction experiments indicate the deterioration of the growth orientation in some areas of the films with increasing Mn concentration, and the existence of a secondary phase, of Mn2O3-type, in the films with larger Mn concentrations. High-resolution electron microscopy images …

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Collisions Of Red-Tailed Hawks (Buteo Jamaicensis), Turkey Vultures (Cathartes Aura), And Black Vultures (Coragyps Atratus) With Aircraft: Implications For Bird Strike Reduction, Bradley F. Blackwell, Sandra E. Wright Dec 2006

Collisions Of Red-Tailed Hawks (Buteo Jamaicensis), Turkey Vultures (Cathartes Aura), And Black Vultures (Coragyps Atratus) With Aircraft: Implications For Bird Strike Reduction, Bradley F. Blackwell, Sandra E. Wright

USDA Wildlife Services: Staff Publications

From 1990 through 2003, 52,493 wildlife collisions with aircraft were reported to the U.S. Federal Aviation Administration (FAA); 97% of these incidents involved birds. The approximate cost to the civil aviation industry in the U.S.A. due to collisions of birds with aircraft (hereafter referred to as bird strikes) was $163.51 million in direct monetary losses and associated costs for the 14 year period (Cleary et al. 2004). Strikes with raptors (Falconidae and Accipitridae; including vultures, Cathartidae)accounted for approximately 28% of reported aircraft down time resulting from known-species bird strikes (known species =182942 hr; total for all birds = 244510 hr) …

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Spatial And Temporal Variation In Cores From Lake Titicaca, Bolivia/Peru During The Last 13,000 Years, Sherilyn C. Fritz, P. A. Baker, P. Tapia, J. Garland Dec 2006

Spatial And Temporal Variation In Cores From Lake Titicaca, Bolivia/Peru During The Last 13,000 Years, Sherilyn C. Fritz, P. A. Baker, P. Tapia, J. Garland

Department of Earth and Atmospheric Sciences: Faculty Publications

We compared the stratigraphy of sediment cores that span the last 13,000 yrs from three sites in the main basin of Lake Titicaca, Boliva/Peru as indicators of regional paleoclimate. The cores show similar patterns of change after ~6,400 calendar yrs before present (cal yr BP) but differ before that time. Site NE98-PC2, which is near the Rio Illave and its delta, shows differences in diatom species composition and in calcium carbonate concentrations relative to cores from the other two sites, particularly during times of inferred high precipitation. In contrast, the carbon isotopic stratigraphy of the three sites is relatively similar. …

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Modulational Instability In A Layered Kerr Medium: Theory And Experiment, Martin Centurion, Mason A. Porter, Ye Pu, P. G. Kevrekidis, D. J. Frantzeskakis, Demetri Psaltis Dec 2006

Modulational Instability In A Layered Kerr Medium: Theory And Experiment, Martin Centurion, Mason A. Porter, Ye Pu, P. G. Kevrekidis, D. J. Frantzeskakis, Demetri Psaltis

Martin Centurion Publications

We present the first experimental investigation of modulational instability in a layered Kerr medium. The particularly interesting and appealing feature of our configuration, consisting of alternating glass-air layers, is the piecewise-constant nature of the material properties, which allows a theoretical linear stability analysis leading to a Kronig-Penney equation whose forbidden bands correspond to the modulationally unstable regimes. We find very good quantitative agreement between theoretical, numerical, and experimental diagnostics of the modulational instability. Because of the periodicity in the evolution variable arising from the layered medium, there are multiple instability regions rather than just one as in a uniform medium.

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Optical And X-Ray Variability Of Agns, C. Martin Gaskell Dec 2006

Optical And X-Ray Variability Of Agns, C. Martin Gaskell

C. Martin Gaskell Publications

I present new comparisons of AGN optical, UV, and X-ray variations. These reveal complex relationships between the different passbands that can change with time in a given object. While there is evidence from several objects that X-ray and optical activity levels are correlated on long timescales, variations on shorter timescales can occur independently. It is proposed that the combination of correlated and uncorrelated short-timescale variability is a consequence of anisotropic high-energy emission. It is also argued that the correlation between X-ray and optical variability on long timescales must be due to a common underlying factor and not to reprocessing of …

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Optical Variability Of The Three Brightest Nearby Quasars, C. Martin Gaskell, Andrew J. Benker, Jeffrey S. Campbell, Thomas A. George, Cecilia H. Hedrick, Mary E. Hiller, Elizabeth S. Klimek, Joseph P. Leonard, Shoji Masatoshi, Bradley W. Peterson, Kelly S. Peterson, Kelly M. Sanders Dec 2006

Optical Variability Of The Three Brightest Nearby Quasars, C. Martin Gaskell, Andrew J. Benker, Jeffrey S. Campbell, Thomas A. George, Cecilia H. Hedrick, Mary E. Hiller, Elizabeth S. Klimek, Joseph P. Leonard, Shoji Masatoshi, Bradley W. Peterson, Kelly S. Peterson, Kelly M. Sanders

C. Martin Gaskell Publications

We report on the relative optical variability of the three brightest nearby quasars, 3C 273, PDS 456, and PHL 1811. All three have comparable absolute magnitudes, but PDS 456 and PHL 1811 are radio quiet. PDS 456 is a broadline object, but PHL 1811 could be classified as a high-luminosity Narrow-Line Seyfert 1 (NLS1). Both of the radio-quiet quasars show significant variability on a timescale of a few days. The seasonal rms V-band variability amplitudes of 3C 273 and PDS 456 are indistinguishable, and the seasonal rms variability amplitude of PHL 1811 was only exceeded by 3C 273 once in …

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The Origin Of Wavelength-Dependent Continuum Delays In Agns – A New Model, C. Martin Gaskell Dec 2006

The Origin Of Wavelength-Dependent Continuum Delays In Agns – A New Model, C. Martin Gaskell

C. Martin Gaskell Publications

A model of wavelength-dependent lags in optical continuum variability of AGNs is proposed which avoids the problems of the popular “lamppost” model. Rather than being due to reprocessing of high-energy radiation from a hypothetical source above the accretion disk, the wavelength-dependent delays observed from the B to I bands are instead due to contamination of an intrinsically coherently variable continuum with the Wien tail of the thermal emission from the hot dust in the surrounding torus. The new model correctly gives the size, wavelength dependence, and luminosity dependence of the lags, and quantitatively predicts observed color hysteresis. The model also …

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A Handheld Neutron-Detection Sensor System Utilizing A New Class Of Boron Carbide Diode, Kevin Osberg, Nathan Schemm, M. Susan Hallbeck, Sina Balkir, Peter A. Dowben, Jennifer I. Brand, Michael W. Hoffman Dec 2006

A Handheld Neutron-Detection Sensor System Utilizing A New Class Of Boron Carbide Diode, Kevin Osberg, Nathan Schemm, M. Susan Hallbeck, Sina Balkir, Peter A. Dowben, Jennifer I. Brand, Michael W. Hoffman

Peter Dowben Publications

A handheld neutron-detection sensor application is described in this paper. The sensor system utilizes a new class of boron carbide diode that interacts with incoming neutrons. To interface with the boron carbide diode, an integrated front end is designed in a 1.5-μm standard CMOS technology. With the diode and front-end microchip, a handheld neutron-detection system was realized with an embedded microcontroller for real-time processing. The handheld detector operation was then tested with a plutonium–beryllium neutron source. Test and measurement results confirm the validity of the approach and the functionality of the design.

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Nesting Success Of Grassland And Savanna Birds On Reclaimed Surface Coal Mines Of The Midwestern United States, Edward W. Galligan, Travis L. Devault, Steven L. Lima Dec 2006

Nesting Success Of Grassland And Savanna Birds On Reclaimed Surface Coal Mines Of The Midwestern United States, Edward W. Galligan, Travis L. Devault, Steven L. Lima

USDA Wildlife Services: Staff Publications

Reclaimed surface coal mines in southwestern Indiana support many grassland and shrub/ savanna bird species of conservation concern. We examined the nesting success of birds on these reclaimed mines to assess whether such ‘‘unnatural’’ places represent productive breeding habitats for such species. We established eight study sites on two large, grassland-dominated mines in southwestern Indiana and classified them into three categories (open grassland, shrub/savanna, and a mixture of grassland and shrub/savanna) based on broad vegetation and landscape characteristics. During the 1999 and 2000 breeding seasons, we found and monitored 911 nests of 31 species. Daily nest survival for the most …

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Raccoon Predation As A Potential Limiting Factor In The Success Of The Green Iguana In Southern Florida, Henry T. Smith, Walter E. Meshaka Jr., Richard M. Engeman, Steven M. Crossett, Mark E. Foley, Gary Bush Dec 2006

Raccoon Predation As A Potential Limiting Factor In The Success Of The Green Iguana In Southern Florida, Henry T. Smith, Walter E. Meshaka Jr., Richard M. Engeman, Steven M. Crossett, Mark E. Foley, Gary Bush

USDA Wildlife Services: Staff Publications

The Green Iguana, Iguana iguana, is a well established, large-bodied, exotic species in Florida (Meshaka et al. 2004a. The Exotic Amphibians and Reptiles of Florida, Krieger Publishing Company, Malabar, Florida. 155 pp.; Meshaka et al. 2004b. Iguana 11:154-161). Limiting factors of populations and causes of Green Iguana mortality in Florida are poorly understood and the only documented predators are the domestic dog (Canus familiaris) (Meshaka et al. 2004a), Yellow-crowned Night-heron (Nyctanassa violacea) (Engeman et al. 2005. Herpetol. Rev. 36:320), Florida Burrowing Owl (Athene cunicularia floridana) (McKie et al. 2005. Florida Field Nat. 33:125-127), …

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A Long-Term Perspective On Drought In The Great Plains And West, Sherilyn C. Fritz Nov 2006

A Long-Term Perspective On Drought In The Great Plains And West, Sherilyn C. Fritz

Nebraska Water Center: Faculty Publications

Management of water resources requires an understanding of the full range of natural variability and its consequences. The weather record, which spans the last 100 years or so, provides a snapshot of the contemporary history of drought and its impacts, but this record is relatively short and is inadequate for understanding long-term trends or for evaluating the magnitude of human impacts. A variety of so-called paleoclimatic records - such as tree rings, lake sediments, and sand dunes - record the history of the environment and can be used to extend the record of climatic variation to older intervals of time. …

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The Public Interest Test For Water Appropriations, Sandi Zellmer Nov 2006

The Public Interest Test For Water Appropriations, Sandi Zellmer

Nebraska Water Center: Faculty Publications

Nebraska, like most states, imposes a “public interest” review on applications for water appropriations, changes and transfers. However, Nebraska statutes do not provide any specific public interest criteria for use in evaluating applications for new water appropriations or intra-basin transfers. Under Neb. Rev. Stat. § 46-234, an application for a water appropriation may be refused when denial is demanded by the public interest. The director of the Department of Natural Resources (DNR) has the duty of determining whether the public interest demands the denial of a water appropriation, but is given no express statutory criteria to provide assistance in making …

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Instream Flow Legislation, Sandi Zellmer Nov 2006

Instream Flow Legislation, Sandi Zellmer

Nebraska Water Center: Faculty Publications

In the west, state law historically considered water left in the stream to be wasted. Western states, which rely heavily on diversions to meet their water needs, have encouraged full appropriation of rivers and streams. In many cases, however, diversions have resulted in the depletion of stream flow reliant ecosystems and adversely affected fish, wildlife, recreation and river navigation.

A comparison of Nebraska law to the water law of other western states demonstrates that Nebraska’s existing instream flow legislation is quite narrow. Nebraska statutes impose a variety of restrictions on instream flow appropriations, many of which are unique and even …

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Water As Property, Sandi Zellmer Nov 2006

Water As Property, Sandi Zellmer

Nebraska Water Center: Faculty Publications

The issue of whether water is or should be characterized as property under the law raises considerable controversy. In the western United States, water is typically viewed as a form of property, while in the east it is not. Whether water should be treated as property has been the subject of an extensive body of scholarship. Proponents argue that establishing legally protected, secure private property rights encourages maximum utilization of resources. Also, exclusivity and surety of possession can foster wise investment of labor and stewardship. Conversely, the absence of legally protected interests in property ownership can result in a “tragedy …

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The Republican, The Platte And Pumpkin Creek: Current Nebraska Water Policy Issues, J. David Aiken Nov 2006

The Republican, The Platte And Pumpkin Creek: Current Nebraska Water Policy Issues, J. David Aiken

Nebraska Water Center: Faculty Publications

Potential conflicts between surface water users and ground water users are posing perplexing challenges to Nebraska policy makers. Surface water law is the rule of priority, "first in time is first in right," as administered by the Nebraska Department of Natural Resources (DNR). Ground water is primarily the rule of correlative rights, as administered by local natural resources districts (NRDs). Traditionally ground water irrigators have been subject to few restrictions on drilling new wells or how much water could be used (except in the Upper Republican NRD in southwest Nebraska). Now the DNR can ban new wells in overappropriated and …

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Multiwalled Ice Helixes And Ice Nanotubes, Jaeil Bai, Jun Wang, Xiao Cheng Zeng Nov 2006

Multiwalled Ice Helixes And Ice Nanotubes, Jaeil Bai, Jun Wang, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

We report six phases of high-density nano-ice predicted to form within carbon nanotubes (CNTs) at high pressure. High-density nano-ice self-assembled within smaller-diameter CNT (17,0) exhibits a double-walled helical structure where the outer wall consists of four double- stranded helixes, which resemble a DNA double helix, and the inner wall is a quadruple-stranded helix. Four other double-walled nano-ices, self-assembled respectively in two larger-diameter CNTs (20,0 and 22,0), display tubular structure. Within CNT (24,0), the confined water can freeze spontaneously into a triple-walled helical nanoice where the outer wall is an 18-stranded helix and the middle and inner walls are hextuple-stranded helixes.

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The All Boron Carbide Diode Neutron Detector: Comparison With Theory, A. N. Caruso, Peter A. Dowben, S. Balkir, Nathan Schemm, Kevin Osberg, R.W. Fairchild, Oscar Barrios Flores, Snjezana Balaz, A.D. Harken, Brian W. Robertson, Jennifer I. Brand Nov 2006

The All Boron Carbide Diode Neutron Detector: Comparison With Theory, A. N. Caruso, Peter A. Dowben, S. Balkir, Nathan Schemm, Kevin Osberg, R.W. Fairchild, Oscar Barrios Flores, Snjezana Balaz, A.D. Harken, Brian W. Robertson, Jennifer I. Brand

Peter Dowben Publications

A boron carbide diode detector, fabricated from two different polytypes of semiconducting boron carbide, will detect neutrons in reasonable agreement with theory. Small deviations from the model calculations occur due to the detection efficiencies of the 10B capture products Li plus α sum signal differing somewhat from expectation in the thin diodes. The performance of the all boron carbide neutron detector does depart from the behavior of devices where a boron rich neutron capture layer is distinct from the diode charge collection region (i.e. a conversion layer solid state detector), as is expected.

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Measurement Of The Top Quark Mass In The Lepton +Jets Final State With The Matrix Element Method, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration Nov 2006

Measurement Of The Top Quark Mass In The Lepton +Jets Final State With The Matrix Element Method, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration

Kenneth Bloom Publications

We present a measurement of the top quark mass with the matrix element method in the lepton +jets final state. As the energy scale for calorimeter jets represents the dominant source of systematic uncertainty, the matrix element likelihood is extended by an additional parameter, which is defined as a global multiplicative factor applied to the standard energy scale. The top quark mass is obtained from a fit that yields the combined statistical and systematic jet energy scale uncertainty. Using a data set of 0.4 fb-1 taken with the D0 experiment at Run II of the Fermilab Tevatron Collider, the …

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Using Baits To Deliver Pharmaceuticals To Feral Swine In Southern Texas, Tyler A. Campbell, Steven J. Lapidge, David B. Long Nov 2006

Using Baits To Deliver Pharmaceuticals To Feral Swine In Southern Texas, Tyler A. Campbell, Steven J. Lapidge, David B. Long

USDA Wildlife Services: Staff Publications

Few studies have evaluated oral delivery systems of pharmaceuticals (e.g., vaccines, fertility control agents, and toxicants) to feral swine (Sus scrofa) in the United States. Our objective was to assess, through a field trial, the percentage of feral swine and non-target animals that remove and consume baits intended to transport pharmaceuticals to feral swine in southern Texas, USA. We hand-placed 1,178 iophenoxic acid (IA)–marked baits distributed over 1,721 ha (68 baits/km2) in April 2005 and monitored species-specific bait removal and consumption using track stations, automated camera systems, and serum IA values from captured animals. Ninety percent …

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Domain Overlap In Antiferromagnetically Coupled [Co/Pt]/Nio/ [Co/Pt] Multilayers, Andrew Baruth, Lu Yuan, John D. Burton, Karolina Janicka, Evgeny Y. Tsymbal, Sy_Hwang Liou, Shireen Adenwalla Nov 2006

Domain Overlap In Antiferromagnetically Coupled [Co/Pt]/Nio/ [Co/Pt] Multilayers, Andrew Baruth, Lu Yuan, John D. Burton, Karolina Janicka, Evgeny Y. Tsymbal, Sy_Hwang Liou, Shireen Adenwalla

Sy-Hwang Liou Publications

Antiferromagnetically coupled magnetic thin films with perpendicular anisotropy exhibit domain overlap regions originating from magnetostatic stray fields localized in the vicinity of the domain walls. Using high resolution magnetic force microscopy, the authors investigate these overlap regions in [Co/Pt] /NiO/ [Co/Pt] multilayers with various strengths of the interlayer exchange coupling. They develop a simple model that provides a quantitative explanation of the formation of these regions and the relationship between the domain overlap width and the coupling strength. Their results are important for application of magnetic layered structures with perpendicular anisotropy in advanced magnetoresistive devices.

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The Biology Of Introduced Norway Rats On Kiska Island, Alaska, And An Evaluation Of An Eradication Approach, Gary W. Witmer, Patrick Burke, Susan Jojola, Peter Dunlevy Nov 2006

The Biology Of Introduced Norway Rats On Kiska Island, Alaska, And An Evaluation Of An Eradication Approach, Gary W. Witmer, Patrick Burke, Susan Jojola, Peter Dunlevy

USDA Wildlife Services: Staff Publications

Introduced, invasive rats can cause substantial damage to native flora and fauna, including ground-nesting seabirds, when they become established on islands. We tested a control method for introduced Norway rats on Kiska Island, Alaska, during April-May, 2004, by hand-broadcasting rodenticide pellets (0.005% diaphacinone) over a 4-ha area at the rate of 28 kg/ha. We also gathered data on aspects of rat ecology and distribution, although rats were difficult to detect and capture. The rodenticide bait pellets seemed to have been effective in reducing the Norway rat population, however, this is based on a limited observation of rat sign and captures. …

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High-Resolution Imaging Of Proteins In Human Teeth By Scanning Probe Microscopy, Alexei Gruverman, D. Wu, B. J. Rodriguez, Sergei V. Kalinin, S. Habelitz Nov 2006

High-Resolution Imaging Of Proteins In Human Teeth By Scanning Probe Microscopy, Alexei Gruverman, D. Wu, B. J. Rodriguez, Sergei V. Kalinin, S. Habelitz

Alexei Gruverman Publications

High-resolution studies of dental tissues are of considerable interest for biomedical engineering and clinical applications. In this paper, we demonstrate the application of piezoresponse force microscopy (PFM) to nanoscale imaging of internal structure of human teeth by monitoring the local mechanical response to an electrical bias applied via a conductive tip. It is shown that PFM is capable of detecting dissimilar components of dental tissues, namely, proteins and calcified matrix, which have resembling morphology but different piezoelectric properties. It is demonstrated that collagen fibrils revealed in chemically treated intertubular dentin exhibit high piezoelectric activity and can be visualized in PFM …

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Evidence For Two Kinematically Distinct Broad Emission Line Producing Regions In Active Galactic Nuclei, Stephanie A. Snedden, C. Martin Gaskell Nov 2006

Evidence For Two Kinematically Distinct Broad Emission Line Producing Regions In Active Galactic Nuclei, Stephanie A. Snedden, C. Martin Gaskell

C. Martin Gaskell Publications

We present the results of an analysis of line profiles of high- and low-ionization broad emission lines in 8 AGNs observed by the Hubble Space Telescope. We derive the physical conditions in the gas as a function of velocity. We find no evidence for a separate intermediate line region. For the broad line region as a whole we find a major contradiction between the velocity dependencies of conditions deduced from the major high-ionization lines and those deduced from the hydrogen lines alone if they are assumed to come from the same gas clouds. The hydrogen lines imply that the density …

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X-Ray/Ultraviolet Observing Campaign Of The Markarian 279 Active Galactic Nucleus Outflow: A Close Look At The Absorbing/Emitting Gas With Chandra-Letgs, E. Constantini, Jelle S. Kaastra, Nahum Arav, Gerard A. Kriss, K.C. Steenbrugge, Jack R. Gabel, F. Verbunt, Ehud Behar, C. Martin Gaskell, Kirk T. Korista, Daniel Proga, Jessica Kim-Quijano, J.E. Scott, Elizabeth S. Klimek, C.H. Hedrick Nov 2006

X-Ray/Ultraviolet Observing Campaign Of The Markarian 279 Active Galactic Nucleus Outflow: A Close Look At The Absorbing/Emitting Gas With Chandra-Letgs, E. Constantini, Jelle S. Kaastra, Nahum Arav, Gerard A. Kriss, K.C. Steenbrugge, Jack R. Gabel, F. Verbunt, Ehud Behar, C. Martin Gaskell, Kirk T. Korista, Daniel Proga, Jessica Kim-Quijano, J.E. Scott, Elizabeth S. Klimek, C.H. Hedrick

C. Martin Gaskell Publications

We present a Chandra-LETGS observation of the Seyfert 1 galaxy Mrk 279. This observation was carried out simultaneously with HST-STIS and FUSE, in the context of a multiwavelength study of this source. The Chandra pointings were spread over ten days for a total exposure time of ~360 ks. The maximal continuum flux variation is of the order of 30%. The spectrum of Mrk 279 shows evidence of broad emission features, especially at the wavelength of the O VII triplet. We quantitatively explore the possibility that this emission is produced in the broad line region (BLR). We modeled the broad …

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Nondipole Effects In Double Photoionization Of He, A.Y. Istomin, N. L. Manakov, A. V. Meremianin, Anthony F. Starace Nov 2006

Nondipole Effects In Double Photoionization Of He, A.Y. Istomin, N. L. Manakov, A. V. Meremianin, Anthony F. Starace

Anthony F. Starace Publications

Lowest-order nondipole effects are studied in double photoionization (DPI) of the He atom. Ah initio parametrizations of the quadrupole transition amplitude for DPI from the 1S0state are presented in terms of the exact two-electron reduced matrix elements. Parametrizations for the dipole-quadrupole triply differential cross section (TDCS) and doubly differential cross section (DDCS) are presented in terms of polarization-independent amplitudes for the case of an elliptically polarized photon. Expressions for the DDCS in terms of the reduced two-electron matrix elements are also given. A general analysis of retardation-induced asymmetries of the TDCS including the circular dichroism effect at …

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