1,953 research outputs found
Fluctuation-induced Distributed Resonances in Oscillatory Networks
Self-organized network dynamics prevails for systems across physics, biology
and engineering. How external signals generate distributed responses in
networked systems fundamentally underlies their function, yet is far from fully
understood. Here we analyze the dynamic response patterns of oscillatory
networks to fluctuating input signals. We disentangle the impact of the signal
distribution across the network, the signals' frequency contents and the
network topology. We analytically derive qualitatively different dynamic
response patterns and find three frequency regimes: homogeneous responses at
low frequencies, topology-dependent resonances at intermediate frequencies, and
localized responses at high frequencies. The theory faithfully predicts the
network-wide collective responses to regular and irregular, localized and
distributed simulated signals, as well as to real input signals to power grids
recorded from renewable-energy supplies. These results not only provide general
insights into the formation of dynamic response patterns in networked systems
but also suggest regime- and topology-specific design principles underlying
network function.Comment: 7 pages, 4 figure
The AUGER experiment - status and results
The Auger experiment was designed to study the high-energy cosmic rays by
measuring the properties of the showers produced in the atmosphere. The
Southern Auger Observatory has taken data since January 2004. Results on mass
composition, energy spectrum and anisotropy of the arrival directions are
presented. The most important result is the recent observation of correlations
with nearby extragalactic objects.Comment: Conferenc
New results from the Pierre Auger Observatory
Recent results from the Auger Observatory on the energy spectrum of high-energy cosmic rays and on the search for correlation with extragalactic objects are presented and discussed. The excess of high-energy events with arrival
direction pointing to the region of Centaurus A is discussed in some detail
Total cross section and luminosity
The measurement of the total cross section and of the machine luminosity is the first objective of the experiment TOTEM [1] [2]. The total cross section will be measured with the luminosity independent method based on the simultaneous measurement of low momentum transfer elastic scattering and of the rate of inelastic interactions with fully inclusive trigger. Elastic scattering events will be detected with the Roman pot technique using a suitable machine optics obtained by properly tuning the quadrupoles in the intersection region. The measurement of the total cross section will be followed in due course by the study of elastic scattering at large momentum transfer and of diffractive processes
The use of bio-telemetry for studying squirrel population dynamics and behavior
A full understanding of the ecology and behavior of any animal requires a knowledge of the animal\u27s movements. Historically, data from natural events involving any animal under natural conditions have been obtained from such methods as trapping, marking, recapture and visual observations. In the 1950\u27s and early 1960\u27s however, major breakthroughs in data gathering techniques were made when biologists began developing telemetering devices with which to monitor animal movement and to a limited degree, physiological parameters. Wild animals were being tracked for days, weeks and even months, continuously telemetering such events as temperature, daily and seasonal movement patterns, dispersal and behavior. Radio-telemetry, may be defined as the use of a miniature radio transmitter attached to a free roaming, wild animal, without use of restraining harnesses or wires, and capable of emitting a signal at a given frequency, which when received by a remote receiving station provides continuous data of a specific nature
Wetlands in environmental education
Wetlands are one of the most useful resources the environmentally oriented educator has at his disposal. They are his best teaching facility. Most wetlands allow active use. They provide rapid and easy direct contact study of their components. Because one can get an overall perspective, it is often easier to observe the animal populations and to sample the plant communities. Whether the wetland is a wet cattail marsh, sedge meadow, woodland swamp or acid bog the student can see it, feel it and appreciate it as a reservoir for living things. The wetland is not only easy to observe and comprehend but also provides an excellent opportunity to teach basic ecological principles and concepts, those of the ecosystem; of energy and the biogeochemical cycles; of limiting factors and of community and population organization. The wetland offers the opportunity to witness with relative simplicity the processes of orderly change we call succession. Wetlands illustrate the natural relationships of organisms to each other as well as how those organisms relate to their physical environment. Likewise, in wetlands all trophic levels from producer to carnivore are readily observed
Change in the urban-rural ecotone
Conversion of the rural Wisconsin landscape from farms to housing poses serious wildlife management and utilization problems. The problems are aggravated by the unregulated and unplanned nature of the land use changes. Purchase of farms for future development often results in removal of the entire farm from crop production. Occasionally the choicest tillable acres are rented or leased to a neighboring farmer, but even so, the remaining land is allowed to lie fallow and undergo old field succession. In a few cases pine plantations or wildlife food patches may be established or a pond constructed
Island biogeography in Southeastern Wisconsin: a progress report.
Ecosystems develop as a result of interactions between the biotic and abiotic components in the environment. Natural systems are diverse and stable when interactions between the community and the supersystem are in balance. Change or perturbation in the supersystem will effect a commensurate change in the natural subsystems. Urbanization results in the remaining natural systems becoming isolated within the urban system-a supersystem quite unlike that which gave rise to the natural system. As a result, the natural subsystem must change in the way in which it interacts with its new supersystem to reach equilibrium. A mechanism for such change in natural systems is succession. Successional patterns as a result of urban influences may be quite different than those expected under natural conditions. In order to evaluate these successional patterns, it is necessary to first assess the forest biotic communities when they are embedded and isolated from each other in a non-forest matrix. Crowell (1975) and others, point out that any discontinuous habitat becomes an island. In this context, isolated forested woodlots, embedded in the agro-urban matrix, are islands. This study attempts to explain how these forest islands function as a regional forest ecosystem. It will also examine the effects of urbanization on these wildland island communities
A theorem on the real part of the high-energy scattering amplitude near the forward direction
We show that if for fixed negative (physical) square of the momentum transfer
t, the differential cross-section tends to zero and if the
total cross-section tends to infinity, when the energy goes to infinity, the
real part of the even signature amplitude cannot have a constant sign near t =
0.Comment: 7 pages, late
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