4,675 research outputs found
Measured limits to contamination of optical surfaces by elastomers in vacuum
We have monitored the reflectivity of mirrors that were exposed to a fluoroelastomer (3M-Fluorel 2176) and a room-temperature vulcanizing silicone rubber (RTV-615) in vacuum. The 95% confidence limit on the decrease of mirror reflectivities was less than 0.35 ppm/week for Fluorel and <0.29 ppm@week for RTV-615
Shot Noise in Gravitational-Wave Detectors with Fabry-Perot Arms
Shot-noise-limited sensitivity is calculated for gravitational-wave interferometers with FabryâPerot arms, similar to those being installed at the Laser Interferometer Gravitational-Wave Observatory (LIGO) and the ItalianâFrench Laser Interferometer Collaboration (VIRGO) facility. This calculation includes the effect of nonstationary shot noise that is due to phase modulation of the light. The resulting formula is experimentally verified by a test interferometer with suspended mirrors in the 40-m arms
The Random Bit Complexity of Mobile Robots Scattering
We consider the problem of scattering robots in a two dimensional
continuous space. As this problem is impossible to solve in a deterministic
manner, all solutions must be probabilistic. We investigate the amount of
randomness (that is, the number of random bits used by the robots) that is
required to achieve scattering. We first prove that random bits are
necessary to scatter robots in any setting. Also, we give a sufficient
condition for a scattering algorithm to be random bit optimal. As it turns out
that previous solutions for scattering satisfy our condition, they are hence
proved random bit optimal for the scattering problem. Then, we investigate the
time complexity of scattering when strong multiplicity detection is not
available. We prove that such algorithms cannot converge in constant time in
the general case and in rounds for random bits optimal
scattering algorithms. However, we present a family of scattering algorithms
that converge as fast as needed without using multiplicity detection. Also, we
put forward a specific protocol of this family that is random bit optimal ( random bits are used) and time optimal ( rounds are used).
This improves the time complexity of previous results in the same setting by a
factor. Aside from characterizing the random bit complexity of mobile
robot scattering, our study also closes its time complexity gap with and
without strong multiplicity detection (that is, time complexity is only
achievable when strong multiplicity detection is available, and it is possible
to approach it as needed otherwise)
Motional sidebands and direct measurement of the cooling rate in the resonance fluorescence of a single trapped ion
Resonance fluorescence of a single trapped ion is spectrally analyzed using a
heterodyne technique. Motional sidebands due to the oscillation of the ion in
the harmonic trap potential are observed in the fluorescence spectrum. From the
width of the sidebands the cooling rate is obtained and found to be in
agreement with the theoretical prediction.Comment: 4 pages, 4 figures. Final version after minor changes, 1 figure
replaced; to be published in PRL, July 10, 200
Auditory reafferences: The influence of real-time feedback on movement control
© 2015 Kennel, Streese, Pizzera, Justen, Hohmann and Raab. Auditory reafferences are real-time auditory products created by a person's own movements. Whereas the interdependency of action and perception is generally well studied, the auditory feedback channel and the influence of perceptual processes during movement execution remain largely unconsidered. We argue that movements have a rhythmic character that is closely connected to sound, making it possible to manipulate auditory reafferences online to understand their role in motor control. We examined if step sounds, occurring as a by-product of running, have an influence on the performance of a complex movement task. Twenty participants completed a hurdling task in three auditory feedback conditions: a control condition with normal auditory feedback, a white noise condition in which sound was masked, and a delayed auditory feedback condition. Overall time and kinematic data were collected. Results show that delayed auditory feedback led to a significantly slower overall time and changed kinematic parameters. Our findings complement previous investigations in a natural movement situation with non-artificial auditory cues. Our results support the existing theoretical understanding of action-perception coupling and hold potential for applied work, where naturally occurring movement sounds can be implemented in the motor learning processes
How Much Is Winning a Matter of Luck? A Comparison of 3 Ă 3 and 5v5 Basketball
Background: The comparison of team sports based on luck has a long tradition and remains unsolved. A contrast between the new Olympic format three-on-three (3 Ă 3) and five-on-five (5v5) forms of basketball has never been analyzed and provides a comparison within the same form of sports. Methods: We developed a new method to calculate performance indicators for each team and invented the Relative Score Difference Index, a new competitive balance indicator that allows the comparison of luck in the two basketball forms for both men and women. We collected game-level data about 3 Ă 3 and 5v5 from the World Cups held between 2010 and 2019 (N = 666). Luck was defined as the difference between the expected and the actual outcomes of games. Using the basketball World Cup data, we applied the Surprise Index, ran probit regression models, and compared the basketball forms on the goodness-of-fit of the models. Results: As we predicted, there are differential effects of luck between game formats and sex, such that the 3 Ă 3 form depends more on luck and womenâs games are less influenced by luck when compared to menâs games. Conclusion: Coaches may better understand the differences between the two forms and sexes regarding luck if they are aware that the 3 Ă 3 and menâs competitions are usually more influenced by luck. The findings provide a leverage point for testing new performances and competition balance indicators and will acknowledge the number of games we enjoy watching
Ark or park: the need to predict relative effectiveness of ex situ and in situ conservation before attempting captive breeding
1. When species face extinction, captive breeding may be appropriate. However, captive breeding may be unsuccessful, while reducing motivation and resources for in situ conservation and impacting wild source populations. Despite such risks, decisions are generally taken without rigorous evaluation. We develop an individual-based, stochastic population model to evaluate the potential effectiveness of captive-breeding and release programmes, illustrated by the Critically Endangered Ardeotis nigriceps Vigors great Indian bustard. 2. The model was parameterized from a comprehensive review of captive breeding and wild demography of large bustards. To handle uncertainty in the standards of captive-breeding performance that may be achieved we explored four scenarios of programme quality: âfull-rangeâ (parameters sampled across the observed range), âbelow-averageâ, âabove-averageâ and âbest possibleâ (performance observed in exemplary breeding programmes). Results are evaluated examining i) the probability of captive population extirpation within 50 years and ii) numbers of adult females subsequently established in the wild following release, compared to an alternative strategy of in situ conservation without attempting captive breeding. 3. Successful implementation of captive breeding, involving permanent retention of 20 breeding females and release of surplus juveniles, required collection of many wild eggs and consistent âbest possibleâ performance across all aspects of the programme. Under âfull-rangeâ and âabove-averageâ scenarios captive population extirpation probabilities were 73â88% % and 23â51%% respectively, depending on egg collection rates. 4. Although most (73â92%) âbest possibleâ programmes supported releases, re-establishment of free-living adults also required effective in situ conservation. Incremental implementation of effective conservation measures over the initial 10 years resulted in more free-living adults within 35 years if eggs were left in the wild without attempting captive breeding. 5. Synthesis and applications. For the great Indian bustard Ardeotis nigriceps, rapid implementation of in situ conservation offers a better chance to avoid extinction than captive breeding. Demographic modelling should be used to examine whether captive breeding is likely to bring net benefits to conservation programmes
Der Finowboden - ein lokaler PalÀoboden?
Der auf den sandigen Substraten der Weichseleiszeit in Mitteleuropa mehrfach beschriebene Finowboden wird, zusammen mit dem aus den Niederlanden beschriebenen UsseloâBoden, als stratigraphischer Marker verwendet. Der unter jĂŒngeren Sedimenten begrabene Usselo-Boden ist in der Regel von Humusanreicherung gekennzeichnet und weist oft auch Bleichungsmerkmale auf, die einer initialen Podsolierung Ă€hneln. Dagegen wird der Finowboden als von jĂŒngeren Ă€olischen Sedimenten fossilisierter und von Verbraunung und Verlehmung geformter Unterbodenhorizont beschrieben. Eine komplette Horizontsequenz des Finowbodens bestehend aus Ober- und Unterboden ist bisher noch nicht beschrieben worden. Um die pedogenetischen Prozesse der Finowbodenbildung zu klĂ€ren, wurden im Rahmen der Untersuchungen drei Standorte aufgesucht, an denen diese fossilisierte Böden in der Literatur beschrieben waren (GlashĂŒtte und JĂ€nschwalde in
Brandenburg und Ufer der Wda, Polen). FĂŒr die drei Standorte liegen publizierte Alter der Sedimente vor, die mittels optisch stimulierter Lumineszenz bestimmt worden sind. Die Sedimentation des Ausgangssubstrates des Finowbodens und dessen Fossilisierung waren demnach an den drei Standorten am Ăbergang der JĂŒngeren Dryas zum HolozĂ€n.
Unsere mikromorphologischen Untersuchungen an den drei Standorten widerlegen, dass die Finowböden mittels in-situ Verlehmung oder Verbraunung gebildet wurden. Vielmehr lĂ€sst sich nachweisen, dass die Horizontmerkmale v.a. durch Lessivierung entstanden sind . Ein klassischer Eluvialhorizont ist an keinem der drei Standorte vorhanden. An den drei untersuchten Standorten hangen 3 bis 30 dm mĂ€chtige DĂŒnensande ĂŒber den Illuvialhorizonten, aufgrund der Textur der Sande ist die Perkolation von tonhaltigen Suspensionen aus dem Hangenden naheliegend. Die Stratigraphie der Sedimente und Horizonte belegen in Verbindung mit den Datierungen, dass der Finowboden an den drei Standorten keineswegs einen eigenstĂ€ndigen Bodentyp darstellt. Damit ist die Eignung von fossilen und vermeintlich gekappten Illuvialhorizonten als stratigraphische Marker, nicht nur in sandigen Substraten, sondern generell kritisch zu hinterfragen
Multipole nonlinearity of metamaterials
We report on the linear and nonlinear optical response of metamaterials
evoked by first and second order multipoles. The analytical ground on which our
approach bases permits for new insights into the functionality of
metamaterials. For the sake of clarity we focus here on a key geometry, namely
the split-ring resonator, although the introduced formalism can be applied to
arbitrary structures. We derive the equations that describe linear and
nonlinear light propagation where special emphasis is put on second harmonic
generation. This contribution basically aims at stretching versatile and
existing concepts to describe light propagation in nonlinear media towards the
realm of metamaterials.Comment: 7 pages, 3 figure
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