7,271 research outputs found
Superfluid Optomechanics: Coupling of a Superfluid to a Superconducting Condensate
We investigate the low loss acoustic motion of superfluid He
parametrically coupled to a very low loss, superconducting Nb, TE
microwave resonator, forming a gram-scale, sideband resolved, optomechanical
system. We demonstrate the detection of a series of acoustic modes with quality
factors as high as . At higher temperatures, the lowest
dissipation modes are limited by an intrinsic three phonon process. Acoustic
quality factors approaching may be possible in isotopically purified
samples at temperatures below 10 mK. A system of this type may be utilized to
study macroscopic quantized motion and as an ultra-sensitive sensor of
extremely weak displacements and forces, such as continuous gravity wave
sources
Ultra-high Q Acoustic Resonance in Superfluid 4He
We report the measurement of the acoustic quality factor of a gram-scale,
kilo-hertz frequency superfluid resonator, detected through the parametric
coupling to a superconducting niobium microwave cavity. For temperature between
400mK and 50mK, we observe a temperature dependence of the quality
factor, consistent with a 3-phonon dissipation mechanism. We observe Q factors
up to , consistent with the dissipation due to dilute He
impurities, and expect that significant further improvements are possible.
These experiments are relevant to exploring quantum behavior and decoherence of
massive macroscopic objects, the laboratory detection of continuous wave
gravitational waves from pulsars, and the probing of possible limits to
physical length scales.Comment: 5 pages, 2 figure
Results from new fungus-tolerant grapevine varieties for Organic Viticulture
Two red and three white new fungus-tolerant grape varieties were tested within a period of five years. REGENT, RONDO, JOHANNITER and Gf 48-12 show a better wine quality than PINOT NOIR or SILVANER and can be recommended for Organic Viticulture as well as for the conventional viticulture to reduce copper and fungicide applications
Comparison of secondary flows predicted by a viscous code and an inviscid code with experimental data for a turning duct
A comparison of the secondary flows computed by the viscous Kreskovsky-Briley-McDonald code and the inviscid Denton code with benchmark experimental data for turning duct is presented. The viscous code is a fully parabolized space-marching Navier-Stokes solver while the inviscid code is a time-marching Euler solver. The experimental data were collected by Taylor, Whitelaw, and Yianneskis with a laser Doppler velocimeter system in a 90 deg turning duct of square cross-section. The agreement between the viscous and inviscid computations was generally very good for the streamwise primary velocity and the radial secondary velocity, except at the walls, where slip conditions were specified for the inviscid code. The agreement between both the computations and the experimental data was not as close, especially at the 60.0 deg and 77.5 deg angular positions within the duct. This disagreement was attributed to incomplete modelling of the vortex development near the suction surface
Anisotropic conductivity of disordered 2DEGs due to spin-orbit interactions
We show that the conductivity tensor of a disordered two-dimensional electron
gas becomes anisotropic in the presence of both Rashba and Dresselhaus
spin-orbit interactions (SOI). This anisotropy is a mesoscopic effect and
vanishes with vanishing charge dephasing time. Using a diagrammatic approach
including zero, one, and two-loop diagrams, we show that a consistent
calculation needs to go beyond a Boltzmann equation approach. In the absence of
charge dephasing and for zero frequency, a finite anisotropy \sigma_{xy}
e^2/lhpf arises even for infinitesimal SOI.Comment: 6+ page
Sum rules for spin-Hall conductivity cancelation
It has been shown recently that the universal dc spin conductivity of
two-dimensional electrons with a Rashba spin-orbit interaction is canceled by
vertex corrections in a weak scattering regime. We prove that the zero bulk
spin conductivity is an intrinsic property of the free-electron Hamiltonian and
scattering is merely a tool to reveal this property in terms of the
diagrammatic technique. When Zeeman energy is neglected, the zero dc
conductivity persists in a magnetic field. Spin conductivity increases
resonantly at the cyclotron frequency and then decays towards the universal
value.Comment: 4 pages, 1 figur
Thermus aquaticus and You: Biodiversity, human health, and the interpretive challenge
Journal ArticleImagine being imprisoned for a crime you didn?t commit. How would it affect your physical, mental, and emotional health? How would it affect the health of your family and friends? Imagine your sense of helplessness when everyone who should have helped set you free? eyewitnesses, investigators, police, and attorneys?all conspired instead to build a strong case against you. After your trial and sentencing, imagine how you would feel after more than a decade behind bars for something you didn?t do
Tripping and Falling into the Future: An Eolithic Perspective
Thirty years ago, Dustin and McAvoy (1984) published an essay in Environmental Ethics titled Toward Environmental Eolithism. The article compared and contrasted two distinct orientations to environmental planning and management: the design mentality and the eolithic mentality. The authors concluded that the more popular design mentality lacked sufficient flexibility and adaptability to maximize performance, and that the more obscure eolithic mentality was a superior orientation to environmental planning and management. In this article we extend the logic of that Environmental Ethics essay to criticize a popular offshoot of the design mentality strategic planning as it is commonly conducted in the park and recreation administration, and then discuss how an eolithic perspective might complement the strategic planning process. We begin by describing the similarities between strategic planning and the design mentality as well as the shortcomings of strategic planning in a rapidly changing world. We then consider the eolithic mentality\u27s yin to strategic plannings yang. We stress the futility of planning for a future that cannot be predicted, and, consequently, how important it is for park and administrators to keep an open mind, be opportunistic,and take risks in a work world characterized by serendipity the discover of valuable but unforeseen opportunities that strategic planning, by its very nature, cannot anticipate. Finally, we conclude the article by discussing the management implications of both the design and eolithic orientations to park and recreation administration. We anchor our thinking in the management writings of Drucker (2001), Mintzberg\u27s critique of strategic planning (1994), the systems thinking of Meadows (2008) and Ackoff (1983, 1979), and the contributions of other forward-looking theorists renowned for their entrepreneurial spirit and proclivity for proactive leadership
Bat Activity Patterns and Roost Selection in Managed Forests
The recent introduction and subsequent westward spread of white-nose syndrome (WNS) has decimated hibernating bat populations in eastern North America and created an urgent need for scientists to understand basic information about bat ecology, especially during the winter season. White-nose syndrome has killed between 5 and 7 million bats and continues to spread westward from the eastern U.S. and southern Canada, primarily affecting bats during hibernation. Acoustic monitoring has been suggested as a potential surveillance tool for detecting WNS; however, baseline information must first be collected to test this technique. We initiated a pilot project in June 2014 by deploying 2 remote acoustic monitoring stations in western Montana’s managed forests collecting baseline acoustic information. We also conducted radio telemetry to determine characteristics of roosts used by bats during the fall season. Thus far we have recorded 11 of Montana’s 15 bat species, and observed extremely high activity levels during the summer. We radio-tagged 5 bats of 3 different species (California myotis, Western small-footed myotis, Silver-haired bat) and tracked them in late October and early November. Identifying the characteristics of roost sites used during the pre-hibernation period, and the annual activity patterns determined from acoustic monitoring, begin to form the foundation for understanding basic aspects of bat ecology during the season when Montana bats will be most susceptible to WNS
Reflections on lnter-Species Parasitism: A Rejoinder to Gibson, Howard, McDonald, Wellman, and Rea
We read the reactions to our Kirrland\u27s Warbl r article with great interest, and we thank professors Gibson, Howard, McDonald, Wellman, and Rea for their thoughtful responses to it. We will continue employing the Kirtland\u27s warbler analogy in this rejoinder and organize our comments under four sub-headings: I) Birds of a Feather? 2) Feathering our own Nests? 3) Species Invasion and Succession? and 4) Bluebird of Happiness? Our intent is not so much to insist that the respondents are wrong about this matter, burro encourage the reader to ponder the implications if it turns out they are
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