4,663 research outputs found
Southern Arizona riparian habitat: Spatial distribution and analysis
The objectives of this study were centered around the demonstration of remote sensing as an inventory tool and researching the multiple uses of riparian vegetation. Specific study objectives were to: (1) map riparian vegetation along the Gila River, San Simon Creek, San Pedro River, Pantano Wash, (2) determine the feasibility of automated mapping using LANDSAT-1 computer compatible tapes, (3) locate and summarize existing mpas delineating riparian vegetation, (4) summarize data relevant to Southern Arizona's riparian products and uses, (5) document recent riparian vegetation changes along a selected portion of the San Pedro River, (6) summarize historical changes in composition and distribution of riparian vegetation, and (7) summarize sources of available photography pertinent to Southern Arizona
Use of Earth Resources Technological Satellite (ERTS) data in a natural resource inventory
There are no author-identified significant results in this report
Elastic cavitation, tube hollowing, and differential growth in plants and biological tissues
Elastic cavitation is a well-known physical process by which elastic materials under stress can open cavities. Usually, cavitation is induced by applied loads on the elastic body. However, growing materials may generate stresses in the absence of applied loads and could induce cavity opening. Here, we demonstrate the possibility of spontaneous growth-induced cavitation in elastic materials and consider the implications of this phenomenon to biological tissues and in particular to the problem of schizogenous aerenchyma formation
A new array for the study of ultra high energy gamma-ray sources
The design and operation of a 32 x 1 10 to the 15th power sq m array of scintillation detectors for the detection of 10 to the 15th power eV cosmic rays is described with an expected angular resolution of 1 deg, thus improving the present signal/background ratio for gamma ray sources. Data are recorded on a hybrid CAMAC, an in-house system which uses a laser and Pockel-Cell arrangement to routinely calibrate the timing stability of the detectors
Network governance for largeāscale natural resource conservation and the challenge of capture
Largeāscale natural resource conservation initiatives are increasingly adopting a network governance framework to respond to the ecological, social, and political challenges of contemporary environmental governance. A network approach offers new modes of management that allow resource managers and others to transcend a single institution, organization, resource, or landscape and engage in conservation that is multiāspecies and multiājurisdictional. However, there are challenges to network governance in largeāscale conservation efforts, which we address by focusing on how special interests can capture networks and shape the goals, objectives, and outcomes of initiatives. The term ānetwork captureā is used here to describe an array of strategies that direct the processes and outcomes of largeāscale initiatives in ways that advance a group\u27s positions, concerns, or economic interests. We outline how new stakeholders emerge from these management processes, and how the ease of information sharing can blur stakeholder positions and lead to competing knowledge claims. We conclude by reasserting the benefits of network governance while acknowledging the unique challenges that networks present
The Computational Complexity of Symbolic Dynamics at the Onset of Chaos
In a variety of studies of dynamical systems, the edge of order and chaos has
been singled out as a region of complexity. It was suggested by Wolfram, on the
basis of qualitative behaviour of cellular automata, that the computational
basis for modelling this region is the Universal Turing Machine. In this paper,
following a suggestion of Crutchfield, we try to show that the Turing machine
model may often be too powerful as a computational model to describe the
boundary of order and chaos. In particular we study the region of the first
accumulation of period doubling in unimodal and bimodal maps of the interval,
from the point of view of language theory. We show that in relation to the
``extended'' Chomsky hierarchy, the relevant computational model in the
unimodal case is the nested stack automaton or the related indexed languages,
while the bimodal case is modeled by the linear bounded automaton or the
related context-sensitive languages.Comment: 1 reference corrected, 1 reference added, minor changes in body of
manuscrip
On Love-type waves in a finitely deformed magnetoelastic layered half-space
In this paper, the propagation of Love-type waves in a homogeneously and finitely deformed layered half-space of an incompressible non-conducting magnetoelastic material in the presence of an initial uniform magnetic field is analyzed. The equations and boundary conditions governing linearized incremental motions superimposed on an underlying deformation and magnetic field for a magnetoelastic material are summarized and then specialized to a form appropriate for the study of Love-type waves in a layered half-space. The wave propagation problem is then analyzed for different directions of the initial magnetic field for two different magnetoelastic energy functions, which are generalizations of the standard neo-Hookean and MooneyāRivlin elasticity models. The resulting wave speed characteristics in general depend significantly on the initial magnetic field as well as on the initial finite deformation, and the results are illustrated graphically for different combinations of these parameters. In the absence of a layer, shear horizontal surface waves do not exist in a purely elastic material, but the presence of a magnetic field normal to the sagittal plane makes such waves possible, these being analogous to BleusteināGulyaev waves in piezoelectric materials. Such waves are discussed briefly at the end of the paper
Alfalfa Insect Management Studies 1971-77
Three tests in southwestern Nebraska during 1971 and 1972 evaluated insecticides against the army cutworm. Adult alfalfa weevils did not damage new second growth alfalfa in a small plot study during a 3-year period (1973-1975) at Gothenburg, NE. However, excellent control of larval alfalfa weevils was obtained. These results indicated a need to establish economic threshold levels for the alfalfa weevil in Nebraska to prevent unnecessary use of insecticides. Four tests to control the alfalfa weevil with registered insecticides verified the efficacy of these materials under Nebraska conditions. A series of tests conducted during 1975 at the Mead Field Laboratory were designed to evaluate plant resistance, cultural practices and insecticides. The use of alfalfa varieties with resistance to various insect pests of alfalfa appeared to be an ideal control method. During 1975-1977, a test was conducted each year at the Mead Field Laboratory to evaluate new experimental insecticides against the alfalfa weevil and other pest insects of alfalfa grown for forage. A number of the new insecticides showed promise against the alfalfa weevil and the pea aphid
Alfalfa Insect Management Studies 1971-77
Three tests in southwestern Nebraska during 1971 and 1972 evaluated insecticides against the army cutworm. Adult alfalfa weevils did not damage new second growth alfalfa in a small plot study during a 3-year period (1973-1975) at Gothenburg, NE. However, excellent control of larval alfalfa weevils was obtained. These results indicated a need to establish economic threshold levels for the alfalfa weevil in Nebraska to prevent unnecessary use of insecticides. Four tests to control the alfalfa weevil with registered insecticides verified the efficacy of these materials under Nebraska conditions. A series of tests conducted during 1975 at the Mead Field Laboratory were designed to evaluate plant resistance, cultural practices and insecticides. The use of alfalfa varieties with resistance to various insect pests of alfalfa appeared to be an ideal control method. During 1975-1977, a test was conducted each year at the Mead Field Laboratory to evaluate new experimental insecticides against the alfalfa weevil and other pest insects of alfalfa grown for forage. A number of the new insecticides showed promise against the alfalfa weevil and the pea aphid
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