20,819 research outputs found
Tearing Out the Income Tax by the (Grass)Roots
Landscapes are increasingly fragmented, and conservation programs have started to look at network approaches for maintaining populations at a larger scale. We present an agent-based model of predator–prey dynamics where the agents (i.e. the individuals of either the predator or prey population) are able to move between different patches in a landscaped network. We then analyze population level and coexistence probability given node-centrality measures that characterize specific patches. We show that both predator and prey species benefit from living in globally well-connected patches (i.e. with high closeness centrality). However, the maximum number of prey species is reached, on average, at lower closeness centrality levels than for predator species. Hence, prey species benefit from constraints imposed on species movement in fragmented landscapes since they can reproduce with a lesser risk of predation, and their need for using anti-predatory strategies decreases.authorCount :
Performance of Hybrid NbTiN-Al Microwave Kinetic Inductance Detectors as Direct Detectors for Sub-millimeter Astronomy
In the next decades millimeter and sub-mm astronomy requires large format
imaging arrays and broad-band spectrometers to complement the high spatial and
spectral resolution of the Atacama Large Millimeter/sub-millimeter Array. The
desired sensors for these instruments should have a background limited
sensitivity and a high optical efficiency and enable arrays thousands of pixels
in size. Hybrid microwave kinetic inductance detectors consisting of NbTiN and
Al have shown to satisfy these requirements. We present the second generation
hybrid NbTiN-Al MKIDs, which are photon noise limited in both phase and
amplitude readout for loading levels fW. Thanks to the
increased responsivity, the photon noise level achieved in phase allows us to
simultaneously read out approximately 8000 pixels using state-of-the-art
electronics. In addition, the choice of superconducting materials and the use
of a Si lens in combination with a planar antenna gives these resonators the
flexibility to operate within the frequency range THz. Given
these specifications, hybrid NbTiN-Al MKIDs will enable astronomically usable
kilopixel arrays for sub-mm imaging and moderate resolution spectroscopy.Comment: 7 pages, 3 figures. Presented at SPIE Astronomical Telescopes and
Instrumentation 2014: Millimeter, Submillimeter, and Far-Infrared Detectors
and Instrumentation for Astronomy VI
Photon noise limited radiation detection with lens-antenna coupled Microwave Kinetic Inductance Detectors
Microwave Kinetic Inductance Detectors (MKIDs) have shown great potential for
sub-mm instrumentation because of the high scalability of the technology. Here
we demonstrate for the first time in the sub-mm band (0.1...2 mm) a photon
noise limited performance of a small antenna coupled MKID detector array and we
describe the relation between photon noise and MKID intrinsic
generation-recombination noise. Additionally we use the observed photon noise
to measure the optical efficiency of detectors to be 0.8+-0.2.Comment: The following article has been submitted to AP
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