3,855 research outputs found
Seismometer designed for remote operation in random orientation
Portable seismometer mounted in a rugged housing can be placed in inaccessible locations and operate efficiently in other than a vertically upright position. The instrument housing contains an amplifier, transmitter, and antenna to relay measurement data to a receiving station
Estimating the final spin of a binary black hole coalescence
We present a straightforward approach for estimating the final black hole
spin of a binary black hole coalescence with arbitrary initial masses and
spins. Making some simple assumptions, we estimate the final angular momentum
to be the sum of the individual spins plus the orbital angular momentum of a
test particle orbiting at the last stable orbit around a Kerr black hole with a
spin parameter of the final black hole. The formula we obtain is able to
reproduce with reasonable accuracy the results from available numerical
simulations, but, more importantly, it can be used to investigate what
configurations might give rise to interesting dynamics. In particular, we
discuss scenarios which might give rise to a ``flip'' in the direction of the
total angular momentum of the system. By studying the dependence of the final
spin upon the mass ratio and initial spins we find that our simple approach
suggests that it is not possible to spin-up a black hole to extremal values
through merger scenarios irrespective of the mass ratio of the objects
involved.Comment: 9 pages, 8 figure
Estimating the Accuracy of Automated Classification Systems Using Only Expert Ratings that are Less Accurate than the System
A method is presented to estimate the accuracy of an automated classification system based only on expert ratings on test cases, where the system may be substantially more accurate than the raters. In this method an estimate of overall rater accuracy is derived from the level of inter-rater agreement, Bayesian updating based on estimated rater accuracy is applied to estimate a ground truth probability for each classification on each test case, and then overall system accuracy is estimated by comparing the relative frequency that the system agrees with the most probable classification at different probability levels. A simulation analysis provides evidence that the method yields reasonable estimates of system accuracy under diverse and predictable conditions
Detection of Interstellar C_2 and C_3 in the Small Magellanic Cloud
We report the detection of absorption from interstellar C_2 and C_3 toward
the moderately reddened star Sk 143, located in the near 'wing' region of the
SMC, in optical spectra obtained with the ESO VLT/UVES. These detections of C_2
(rotational levels J=0-8) and C_3 (J=0-12) absorption in the SMC are the first
beyond our Galaxy. The total abundances of C_2 and C_3 (relative to H_2) are
similar to those found in diffuse Galactic molecular clouds -- as previously
found for CH and CN -- despite the significantly lower average metallicity of
the SMC. Analysis of the rotational excitation of C_2 yields an estimated
kinetic temperature T_k ~ 25 K and a moderately high total hydrogen density n_H
~ 870 cm^-3 -- compared to the T_01 ~ 45 K and n_H ~ 85-300 cm^-3 obtained from
H_2. The populations of the lower rotational levels of C_3 are consistent with
an excitation temperature of about 34 K.Comment: accepted to MNRAS; 10 pages, 6 figure
Biodiversity and Foraging Preferences of Bee Communities at Pinnacles National Park Over Time
Bees are considered to be the most important animal pollinator, providing billions of dollars in pollination services each year. Despite their importance in both natural and agricultural settings, the status of most native bees is unknown. Native bees are subject to a variety of threats including habitat loss, pesticide use, and climate change. Yet, monitoring programs have been implemented in few natural areas. Pinnacles National Park, PNP, in California is one of the only natural areas to have a large historical dataset on bees across decades with surveys conducted in 1996, 1997, 1998, 1999, 2002, 2011, and 2012. These surveys have found PNP to house an exceptionally diverse community of bees. To determine how the bee community at PNP has changed over time we returned to survey bees in 2020 and compare the current collection to historical collections. We found that overall diversity levels remained at similar levels across years, but community composition changed among years, suggesting that the bee community experiences species turnover, but has not experienced over diversity losses. Using our bee survey as a framework, we discuss some issues with current bee monitoring practices and recommend creative solutions. To provide better techniques for site selection or monitoring monolectic species habitat we used Ceratina sequoiae Michener abundance at PNP, as a framework to model suitable habitat using citizen science records. We selected six topographic factors to model in conjunction with the required floral and nesting resources of C. sequoiae. The suitability modeling indicated that considering elevation in addition to the required floral and nesting resources could better predict C. sequoiae abundance. Throughout the duration of our bee survey at PNP, we also observed a novel foraging behavior. We discovered tens of bees feeding on aphid-produced pine honeydew, a seemingly rare behavior among native bees. The culmination of our findings highlight the importance of long term pollinator monitoring studies, not only to detect diversity shifts over time, but also to determine the diversity of behaviors exhibited by bees
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