Physical Sciences and Mathematics Commons^™

Degree Spectra Of The Successor Relation Of Computable Linear Orderings, Jennifer Chubb, Andrey Frolov, Valentina Harizanov

Mathematics

We establish that for every computably enumerable (c.e.) Turing degree b, the upper cone of c.e. Turing degrees determined by b is the degree spectrum of the successor relation of some computable linear ordering. This follows from our main result, that for a large class of linear orderings, the degree spectrum of the successor relation is closed upward in the c.e. Turing degrees.

Generalized Helmholtz-Kirchhoff Model For Two-Dimensional Distributed Vortex Motion, Raymond J. Nagem, Guido Sandri, David Uminsky, C. Eugene Wayne

Mathematics

The two-dimensional Navier-Stokes equations are rewritten as a system of coupled nonlinear ordinary differential equations. These equations describe the evolution of the moments of an expansion of the vorticity with respect to Hermite functions and of the centers of vorticity concentrations. We prove the convergence of this expansion and show that in the zero viscosity and zero core size limit we formally recover the Helmholtz-Kirchhoff model for the evolution of point vortices. The present expansion systematically incorporates the effects of both viscosity and finite vortex core size. We also show that a low-order truncation of our expansion leads to the …

Cooperation In An Evolutionary Prisoner's Dilemma On Networks With Degree-Degree Correlations, Stephen Devlin, T Treloar

Mathematics

We study the effects of degree-degree correlations on the success of cooperation in an evolutionary prisoner's dilemma played on a random network. When degree-degree correlations are not present, the standardized variance of the network's degree distribution has been shown to be an accurate analytical measure of network heterogeneity that can be used to predict the success of cooperation. In this paper, we use a local-mechanism interpretation of standardized variance to give a generalization to graphs with degree-degree correlations. Two distinct mechanisms are shown to influence cooperation levels on these types of networks. The first is an intrinsic measurement of base-line …

Evolution Of Cooperation Through The Heterogeneity Of Random Networks, Stephen Devlin, T Treloar

Mathematics

We use the standardized variance (nu_{st}) of the degree distribution of a random network as an analytic measure of its heterogeneity. We show that nu_{st} accurately predicts, quantitatively, the success of cooperators in an evolutionary prisoner's dilemma. Moreover, we show how the generating functional expression for nu_{st} suggests an intrinsic interpretation for the heterogeneity of the network that helps explain local mechanisms through which cooperators thrive in heterogeneous populations. Finally, we give a simple relationship between nu_{st} , the cooperation level, and the epidemic threshold of a random network that reveals an appealing connection between epidemic disease models and the …

Soil Ph In Northern And Southern Areas Of The Wa Wheatbelt, Chris Gazey, Joel Andrew

Bulletins 4000 -

More than 80% of the topsoils sampled fall below the critical surface pHCaCl2 of 5.5 in the northern and southern wheatbelt study areas, with more in the south than the north. These results confirm soil acidity is a serious concern throughout the WA wheatbelt when considered in conjunction with the more intensive analysis of current soil pH throughout the Avon River Basin (2005–2008).

With low topsoil pH, it is likely that subsurface acidity is also a problem. For soil acidity to be managed, subsurface pH also needs to be known. In the Avon River Basin study, about half of the …

Survey Of Western Australian Agricultural Lime Sources, Chris Gazey, Dave Gartner

Bulletins 4000 -

As a service to WA wheatbelt farmers, to assist with cost effective management of soil acidity, a survey of agricultural lime availability and quality was conducted by the Department of Agriculture and Food, Western Australia.

The quality of agricultural lime surveyed varied widely between pits. High quality lime is available from limes and, limestone and dolomite sources. Twice as much of the lowest neutralising value lime surveyed would need to be applied compared to the highest to achieve the same increase in soil pH. Limes also varied in the distribution of particle sizes. Selecting limes with a high proportion of …

The Lookup Technique To Replace Nested-If Formulas In Spreadsheet Programming, Thomas A. Grossman Jr., O Ozluk, J Gustavson

Business Analytics and Information Systems

Spreadsheet programmers often implement contingent logic using a nested-IF formula even though this technique is difficult to test and audit and is believed to be risky. We interpret the programming of contingent logic in spreadsheets in the context of traditional computer programming. We investigate the “lookup technique” as an alternative to nested-IF formulas, describe its benefits for testing and auditing, and define its limitations. The lookup technique employs four distinct principles: 1) make logical tests visible; 2) make outcomes visible; 3) make logical structure visible; and 4) replace a multi-function nested-IF formula with a single-function lookup formula. It can be …

Role Of Phytoplankton In Mercury Cycling In The San Francisco Bay Estuary, Allison C. Luengen, A. Russell Flegal

Environmental Science

To study the role of phytoplankton in mercury cycling, we measured methylmercury (MeHg) and total mercury (Hg_T) in surface waters during the spring 2003 phytoplankton bloom in San Francisco Bay. Conditions that described the peak of the bloom, the amount of sorbent, and decay of the bloom were summarized by principal component analysis (PCA). Multivariate analyses conducted with the PCA factors demonstrated that the bloom accounted for a significant (p = 0.03) decrease in dissolved (-1 and was unaffected when chlorophyll a concentrations nearly tripled, indicating that bloom dilution could occur as a result of a limited …

Effects Of Magnetic Field Orientation On Optical Decoherence In Er3+: Y2 Sio5, Thomas Böttger, C W. Thiel, R L. Cone, Y Sun

Physics and Astronomy

The influence of the anisotropic Zeeman effect on optical decoherence was studied for the 1.54 μm telecom transition in Er3+:Y2SiO5 using photon echo spectroscopy as a function of applied magnetic field orientation and strength. The decoherence strongly correlates with the Zeeman energy splittings described by the ground- and excited-state g factor variations for all inequivalent Er3+ sites, with the observed decoherence times arising from the combined effects of the magnetic dipole-dipole coupling strength and the ground- and excited-state spin-flip rates, along with the natural lifetime of the upper level. The decoherence time was maximized along a preferred magnetic field orientation …

Discovery Of An Unusual Optical Transient With The Hubble Space Telescope, K Barbary, Ks Dawson, K Tokita, G Aldering, R Amanullah, Nv Connolly, M Doi, L Faccioli, V Fadeyev, As Fruchter, G Goldhaber, A Goobar, A Gude, Xiaosheng Xiaosheng Huang, Y Ihara, K Konishi, M Kowalski, C Lidman, J Meyers, T Morokuma, P Nugent, S Perlmutter, D Rubin, D Schlegel, Al Spadafora, N Suzuki, Hk Swift, N Takanashi, Rc Thomas, N Yasuda, Supernova Cosmology Project

Physics and Astronomy

We present observations of SCP 06F6, an unusual optical transient discovered during the Hubble Space Telescope Cluster Supernova Survey. The transient brightened over a period of ~;;100 days, reached a peak magnitude of ~;;21.0 in both i_775 and z_850, and then declined over a similar timescale. There is no host galaxy or progenitor star detected at the location of the transient to a 3 sigma upper limit of i_775 = 26.4 and z_850 = 26.1, giving a corresponding lower limit on the flux increase of a factor of ~;;120. Multiple spectra show five broad absorption bands between 4100 AA and …

An Intensive Hst Survey For Z>1 Supernovae By Targeting Galaxy Clusters, K S. Dawson, G Aldering, R Amanullah, K Barbary, L F. Barrientos, M Brodwin, N Connolly, A Dey, M Doi, M Donahue, P Eisenhardt, E Ellingson, L Faccioli, V Fadeyev, H K. Fakhouri, A S. Fruchter, D G. Gilbank, M D. Gladders, G Goldhaber, A H. Gonzalez, A Goobar, A Gude, T Hattori, H Hoekstra, Xiaosheng Huang, Y Ihara, B T. Jannuzi, D Johnston, K Kashikawa, B Koester, K Konishi, M Kowalski, C Lidman, E V. Linder, L Lubin, J Meyers, T Morokuma, F Munshi, C Mullis, T Oda, N Panagia, S Perlmutter, M Postman, T Pritchard, J Rhodes, P Rosati, D Rubin, D J. Schlegel, A Spadafora, S A. Stanford, V Stanishev, D Stern, M Strovink, N Suzuki, N Takanashi, K Tokita, M Wagner, L Wang, N Yasuda, H. K. C. Yee, Supernova Cosmology Project

Physics and Astronomy

We present a new survey strategy to discover and study high redshift Type Ia supernovae (SNe Ia) using the Hubble Space Telescope (HST). By targeting massive galaxy clusters at 0.9<zHST field survey and a factor of three improvement in the total yield of SN detections in relatively dust-free red-sequence galaxies. In total, sixteen SNe were discovered at z>0.95, nine of which were in galaxy clusters. This strategy provides a SN sample that can be used to decouple the effects of host galaxy extinction and intrinsic color in high redshift SNe, thereby reducing one of the …

Development Of A Healthy Farm Index To Assess Ecological, Economic, And Social Function On Organic And Sustainable Farms In Nebraska's Four Agroecoregions., James R. Brandle

School of Natural Resources: Faculty Publications

No abstract provided.

An Evaporation Estimation Method Based On The Coupled 2-D Turbulent Heat And Vapor Transport Equations, Jozsef Szilagyi, Janos Jozsa

School of Natural Resources: Faculty Publications

The analytical solution of the coupled turbulent diffusion equations of heat and vapor transport across a moisture discontinuity under near-neutral atmospheric conditions and constant energy available at the evaporating surface yields a simple equation (i.e., the wet-surface equation [WSE]) that relates the change in surface temperature to the change in the land surface moisture content as the environment dries. With the help of percent possible sunshine, air temperature, and humidity measurements at selected weather stations as well as land surface temperature values from MODIS data, monthly, warm-season evaporation rates were estimated for five rectangular regions across the contiguous U.S. employing …

Complementary Relationship Of Evaporation And The Mean Annual Water-Energy Balance, Jozsef Szilagyi, Janos Jozsa

School of Natural Resources: Faculty Publications

By combining the complementary relationship of evaporation with the coupled long-term water-energy balance of Porporato et al. (2004) in a Budyko-type framework, one can, from atmospheric measurements alone, derive important ecosystem characteristics, such as the mean effective relative soil moisture and the maximum soil water storage, as well as predict changes in the rooting depth of vegetation as a response to climate variations.

Comment On ‘‘Power Law Catchment-Scale Recessions Arising From Heterogeneous Linear Small-Scale Dynamics’’ By C. J. Harman, M. Sivapalan, And P. Kumar, Jozsef Szilagyi

School of Natural Resources: Faculty Publications

It is demonstrated that a near-linear subsurface runoff response from a short and relatively steep slope segment and a nonlinear response at the watershed scale may primarily arise from geometry rather than from an assumed linear nature of the subsurface runoff response from the hillslope, as Harman et al. [2009] employed for the Panola Mountain Research (PMR) catchment in Georgia. The authors caution in their paper that hydraulic theory (exemplified by the study of Brutsaert and Nieber [1977]) cannot generally account for the heterogeneity in the watershed scale and therefore should be used with certain reservation when employing it for …

Movements, Distribution, And Abundance Of Great Argus Pheasants (Argusianus Argus) In A Sumatran Rainforest, Nurul L. Winarni, Timothy G. O'Brien, John P. Carroll, Margaret F. Kinnaird

School of Natural Resources: Faculty Publications

We used radiotelemetry, habitat sampling, camera trapping, and line-transect surveys to explore movement patterns, distribution, and abundance of Great Argus Pheasants (Argusianus argus) in Sumatra, Indonesia. We radiotracked six adult and one subadult males. Territories averaged 14.5 ± 8.5 ha, and home-range size did not vary by month or by relative abundance of selected plant foods. Daily travel distance (849 ± 211 m) varied significantly between months but did not reflect changes in plant foods. Territories were used almost exclusively by resident males. Males preferentially used undisturbed forest (habitat I). Vegetation structure at male display sites and random points indicated …

A Phylogenetic Supertree Of The Fowls (Galloanserae, Aves), Soo Hyumg Eo, Olaf R.P. Bininda-Emonds, John P. Carroll

School of Natural Resources: Faculty Publications

The fowls (Anseriformes and Galliformes) comprise one of the major lineages of birds and occupy almost all biogeographical regions of the world. The group contains the most economically important of all bird species, each with a long history of domestication, and is an ideal model for studying ecological and evolutionary patterns. Yet, despite the relatively large amount of systematic attention fowls have attracted because of their socio-economic and biological importance, the species-level relationships within this clade remain controversial. Here we used the supertree method matrix representation with parsimony to generate a robust estimate of species-level relationships of fowls. The supertree …

Modeling Lakes And Reservoirs In The Climate System, M. D. Mackay, P. J. Neale, C. D. Arp, L. N. De Senerpont Domis, X. Fang, G. Gal, K. D. Johnk, G. Kirillin, J. D. Lenters, E. Litchman, S. Macintyre, P. Marsh, J. Melack, W. M. Mooij, F. Peeters, A. Quesada, S. G. Schladow, M. Schmid, C. Spence, S. L. Stokes

School of Natural Resources: Faculty Publications

Modeling studies examining the effect of lakes on regional and global climate, as well as studies on the influence of climate variability and change on aquatic ecosystems, are surveyed. Fully coupled atmosphere–land surface–lake climate models that could be used for both of these types of study simultaneously do not presently exist, though there are many applications that would benefit from such models. It is argued here that current understanding of physical and biogeochemical processes in freshwater systems is sufficient to begin to construct such models, and a path forward is proposed. The largest impediment to fully representing lakes in the …

First Record Of Pseudorabies In Feral Swine In Nebraska, Sam Wilson, Alan R. Doster, Justin D. Hoffman, Scott E. Hygnstrom

School of Natural Resources: Faculty Publications

In 2007, two new populations of feral swine were discovered in Nance and Valley counties, Nebraska, USA. Necropsies and serologic testing was done on two individuals from the Nance County herd. Results indicated that a lactating sow had positive antibodies for pseudorabies virus (PRV). Investigations conducted by Nebraska Game and Parks Commission Law Enforcement division confirmed that the infected individual was transported illegally to Nebraska, USA, from Texas, USA. All domestic swine herds located within an 8 km radius of the infected individual tested negative for antibodies to PRV. Our results provide a clear example of how diseases can spread …

A Modified Advection-Aridity Model Of Evapotranspiration, Jozsef Szilagyi, Michael T. Hobbins, Janos Jozsa

School of Natural Resources: Faculty Publications

No abstract provided.

Analytical Solution Of The Coupled 2-D Turbulent Heat And Vapor Transport Equations And The Complementary Relationship Of Evaporation, Jozsef Szilagyi, Janos Jozsa

School of Natural Resources: Faculty Publications

No abstract provided.

Estimating Spatially Distributed Monthly Evapotranspiration Rates By Linear Transformations Of Modis Daytime Land Surface Temperature Data, J. Szilagyi, J. Jozsa

School of Natural Resources: Faculty Publications

No abstract provided.

The Nasa Land-Cover/Land-Use Change (Lcluc) Program’S Support Of The Northern Eurasia Earth Science Partnership Initiative (Neespi): Focus On Non-Boreal Europe, Garik Gutman

United States National Aeronautics and Space Administration: Publications

Currently, the Northern Eurasia Earth Science Partnership Initiative (NEESPI) includes over 120 international projects involving more than 200 scientific institutions from over 30 countries. The program involves national government agencies, academia and private organizations in the U.S., Europe, Japan and Northern Eurasia (Gutman 2007). The NEESPI science is directed at evaluating the role of anthropogenic impacts on the Northern Eurasia ecosystems, the hemispheric-scale interaction and assessing how future human actions would affect the global climate and ecosystems of the region. Projections of the consequences of global changes for regional environment in Northern Eurasia are also in the center of the …

Nutrient Uptake And Mineralization During Leaf Decay In Streams – A Model Simulation, J. R. Webster, J. D. Newbold, Steven A. Thomas, P. J. Mulholland

School of Natural Resources: Faculty Publications

We developed a stoichiometrically explicit computer model to examine how heterotrophic uptake of nutrients and microbial mineralization occurring during the decay of leaves in streams may be important in modifying nutrient concentrations. The simulations showed that microbial uptake can substantially decrease stream nutrient concentrations during the initial phases of decomposition, while mineralization may produce increases in concentrations during later stages of decomposition. The simulations also showed that initial nutrient content of the leaves can affect the stream nutrient concentration dynamics and determine whether nitrogen or phosphorus is the limiting nutrient. Finally, the simulations suggest a net retention (uptake > mineralization) of …

Characterizing The Seasonal Dynamics Of Plant Community Photosynthesis Across A Range Of Vegetation Types, Lianhong Gu, Wilfred M. Post, Dennis D. Baldocchi, T. Andrew Black, Andrew E. Suyker, Shashi Verma, Timo Vesala, Steve C. Wofsy

School of Natural Resources: Faculty Publications

The seasonal cycle of plant community photosynthesis is one of the most important biotic oscillations to mankind. This study built upon previous efforts to develop a comprehensive framework to studying this cycle systematically with eddy covariance flux measurements. We proposed a new function to represent the cycle and generalized a set of phenological indices to quantify its dynamic characteristics. We suggest that the seasonal variation of plant community photosynthesis generally consists of five distinctive phases in sequence each of which results from the interaction between the inherent biological and ecological processes and the progression of climatic conditions and reflects the …

Spring Home Ranges Of White Bass In Irrigation Reservoirs Of The Republican River Basin, Nebraska, D. R. Martin, Larkin A. Powell, Kevin L. Pope

School of Natural Resources: Faculty Publications

Fishery biologists have documented small home ranges, relative to available habitat, for many littoral freshwater fishes. Home ranges for pelagic species, such as white bass Morone chrysops, are generally not well described, yet are thought to be large. We studied white bass movement using acoustic telemetry in two irrigation reservoirs of the Republican River basin in south-western Nebraska. Acoustic transmitters were implanted in fall of the previous year and tracking occurred a minimum of once per week throughout spring (mid-March to May) 2007 and 2008. Linear home ranges were calculated from observed locations of individual fish. Twelve of the …

Latitudinal Patterns Of Magnitude And Interannual Variability In Net Ecosystem Exchange Regulated By Biological And Environmental Variables, Wenping Yuan, Yiqi Luo, Andrew D. Richardson, Ram Oren, Sebastiaan Luyssaert, Ivan A. Janssens, Reinhart Ceulemans, Xuhui Zhou, Thomas Grünwald, Marc Aubinet, Christian Berhofer, Dennis D. Baldocci, Jiquan Chen, Allison L. Dunn, Jared L. Deforest, Danilo Dragoni, Allen H. Goldstein, Eddy Moors, J. William William Munger, Russell K. Monson, Andrew E. Suyker, Gregory Starr, Russell L. Scott, John Tenhunen, Shashi Verma, Timo Vesala, Steven C. Wofsy

School of Natural Resources: Faculty Publications

Over the last two and half decades, strong evidence showed that the terrestrial ecosystems are acting as a net sink for atmospheric carbon. However the spatial and temporal patterns of variation in the sink are not well known. In this study, we examined latitudinal patterns of interannual variability (IAV) in net ecosystem exchange (NEE) of CO₂ based on 163 site-years of eddy covariance data, from 39 northern-hemisphere research sites located at latitudes ranging from ~29°N to ~ 64°N. We computed the standard deviation of annual NEE integrals at individual sites to represent absolute interannual variability (AIAV), and the corresponding …

Seasonal Changes In Depth Of Water Uptake For Encroaching Trees Juniperus Virginiana And Pinus Ponderosa And Two Dominant C4 Grasses In A Semiarid Grassland, Kathleen D. Eggemeyer, Tala Awada, F. Edwin Harvey, David A. Wedin, Xinhua Zhou, C. William Zanner

School of Natural Resources: Faculty Publications

We used the natural abundance of stable isotopic ratios of hydrogen and oxygen in soil (0.05–3 m depth), plant xylem and precipitation to determine the seasonal changes in sources of soil water uptake by two native encroaching woody species (Pinus ponderosa P. & C. Lawson, Juniperus virginiana L.), and two C₄ grasses (Schizachyrium scoparium (Michx.) Nash, Panicum virgatum L.), in the semiarid Sandhills grasslands of Nebraska. Grass species extracted most of their water from the upper soil profile (0.05–0.5 m). Soil water uptake from below 0.5 m depth increased under drought, but appeared to be minimal in …

Landscape Structure Control On Soil Co2 Efflux Variability In Complex Terrain: Scaling From Point Observations To Watershed Scale Fluxes, Diego Andrés Riveros-Iregui, Brian L. Mcglynn

School of Natural Resources: Faculty Publications

We investigated the spatial and temporal variability of soil CO₂ efflux across 62 sites of a 393-ha complex watershed of the northern Rocky Mountains. Growing season (83 day) cumulative soil CO₂ efflux varied from ~300 to ~2000 g CO₂ m^—2, depending upon landscape position, with a median of 879.8 g CO₂ m^—2. Our findings revealed that highest soil CO₂ efflux rates were observed in areas with persistently high soil moisture (riparian meadows), whereas lower soil CO₂ efflux rates were observed on forested uplands (98% of watershed area). Furthermore, upslope accumulated …

Differential Soil Respiration Responses To Changing Hydrologic Regimes, Vincent J. Pacific, Brian L. Mcglynn, Diego Andrés Riveros-Iregui, Howard E. Epstein, Daniel J. Welsch

School of Natural Resources: Faculty Publications

Soil respiration is tightly coupled to the hydrologic cycle (i.e., snowmelt and precipitation timing and magnitude). We examined riparian and hillslope soil respiration across a wet (2005) and a dry (2006) growing season in a subalpine catchment. When comparing the riparian zones, cumulative CO₂ efflux was 33% higher, and peak efflux occurred 17 days earlier during the dry growing season. In contrast, cumulative efflux in the hillslopes was 8% lower, and peak efflux occurred 10 days earlier during the drier growing season. Our results demonstrate that soil respiration was more sensitive to drier growing season conditions in wet (riparian) …