1,521 research outputs found
Convergence in a multidimensional randomized Keynesian beauty contest
We study the asymptotics of a Markovian system of particles in
in which, at each step in discrete time, the particle farthest from
the current centre of mass is removed and replaced by an independent random particle. We show that the limiting configuration contains
coincident particles at a random location . A key tool
in the analysis is a Lyapunov function based on the squared radius of gyration
(sum of squared distances) of the points. For d=1 we give additional results on
the distribution of the limit , showing, among other things, that it
gives positive probability to any nonempty interval subset of , and
giving a reasonably explicit description in the smallest nontrivial case, N=3.Comment: 26 pages, 4 figure
A Comprehensive Review and Synthesis of Open Source Research
The open source movement has grown steadily and matured in recent years, and this growth has been mirrored by a rise in open source related research. The objective of this paper is to pause and reflect on the state of the field. We start by conducting a comprehensive literature review of open source research, and organize the resulting 618 peer-reviewed articles into a taxonomy. Elements of this taxonomy are defined and described. We then draw on a number of existing categorization schemes to develop a framework to situate open source research within a wider nomological network. Building on concepts from systems theory, we propose a holistic framework of open source research. This framework incorporates current research, as represented by the taxonomy, identifies gaps and areas of overlap, and charts a path for future work
Comparative use of active searches and artificial refuges to detect amphibians in terrestrial environments
Artificial refuges (cover boards) are commonly used to survey and monitor herpetofauna in many parts of the world. Despite the extensive use of artificial refuges in mesic environments, their effectiveness for detecting amphibians in temperate zones has rarely been examined. We compared amphibian detection probabilities between two survey methods; active searches of natural habitat and artificial refuges of three different types (corrugated steel, roofing tiles and timber railway sleepers). Our study area included five bioregions encompassing a 1,180 km latitudinal gradient across a modified, temperate eucalypt woodland vegetation community in south-eastern Australia. We deployed 14,778 artificial refuges in terrestrial environments, within patches of remnant vegetation, and collected presence and abundance data on herpetofauna between 1999 and 2017. We used Bayesian logistic regression to identify the most effective survey method for detecting frog species across all bioregions. We modelled frog detections by fitting survey method, time since refuge deployment, and rainfall prior to each survey. We detected 3970 individuals from 18 frog species. Overall, we found active searches and timber substrates most effective for detecting a broad range of species, although detection rates were driven by the numerically abundant spotted marsh frog Limnodynastes tasmaniensis. Timber refuges were effective for detecting several burrowing species, whereas active searches were effective at detecting habitat generalists. Quadratic effects of rainfall prior to survey as opposed to linear effects of time since artificial refuge placement was important in explaining frog detection rates in some bioregions. Active searches, timber railway sleepers and sheets of corrugated steel provide complimentary survey methods for detecting amphibians, although detection rates are influenced by rainfall patterns. Artificial refuges provide a time-effective and standardised method for studying amphibians in their non-breeding terrestrial environment and should be incorporated into future surveys and biodiversity monitoring programs.The work was funded by the Australian Govern-ment's Caring for Our Country Initiative, the National Environmental Science Program's Threatened Species Recovery Hub and the Australian Research Council, and is supported by the Murray Local Land Services, Riverina Local land Services, Central Tablelands Local land Services, North East Catchment Management Authority, Goulburn Broken Catchment Management Authority, NSW Environment Trust, Ian Potter Foundation and the Vincent Fairfax Family Foundation
Antitrust: Will it Change the Lives of Telecommunications Executives?
Good afternoon. This is the last panel of the afternoon. I would like to introduce myself. I\u27m Deborah Ellenberg, one of the hearing examiners at the State Corporation Commission, and I might add, who has a heightened appreciation for the Virginia Commission\u27s wise decision to handle those arbitrations. I am sure on behalf of Howard, Glenn and myself, we thank you for that decision
Investigations of air-sea gas exchange in the CoOP Coastal Air-Sea Chemical Exchange project
Author Posting. © Oceanography Society, 2008. This article is posted here by permission of Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 21, 4 (2008): 34-45.The exchange of CO2 and other gases across the ocean-air interface is an extremely
important component in global climate dynamics, photosynthesis and respiration, and the absorption of
anthropogenically produced CO2. The many different mechanisms and properties that control the air-sea
flux of CO2 can have large spatial and temporal variability, particularly in the coastal environment. The need
for making short-time-scale and small-spatial-scale estimates of gas transfer velocity, along with the physical
and chemical parameters that affect it, provided a framework for the field experiments of the Coastal Ocean
Processes Program (CoOP) Coastal Air-Sea Chemical Exchange (CASCEX) program. As such, the CASCEX
project provided an opportunity to develop some of the first in situ techniques to estimate gas fluxes using
micrometeorological and thermal imagery techniques. The results reported from the CASCEX experiments
represent the first step toward reconciling the indirect but widely accepted estimates of gas exchange with
these more direct, higher-resolution estimates over the coastal ocean. These results and the advances in
sensor technology initiated during the CASCEX project have opened up even larger regions of the global
ocean to investigation of gas exchange and its role in climate change.Funding for this work was provided
by the National Science Foundation
(NSF) CoOP program under grants
OCE-9410534 and OCE-9711285
The Post-Common Envelope and Pre-Cataclysmic Binary PG 1224+309
We have made extensive spectroscopic and photometric observations of PG
1224+309, a close binary containing a DA white dwarf primary and an M4+
secondary. The H alpha line is in emission due to irradiation of the M-star by
the hot white dwarf and is seen to vary around the orbit. From the radial
velocities of the H alpha line we derive a period of P = 0.258689 +/- 0.000004
days and a semi-amplitude of K_Halpha = 160 +/- 8 km/s. We estimate a
correction Delta_K = 21 +/- 2 km/s, where K_M = K_Halpha + Delta_K. Radial
velocity variations of the white dwarf reveal a semi-amplitude of K_WD = 112
+/- 14 km/s. The blue spectrum of the white dwarf is well fit by a synthetic
spectrum having T_eff = 29,300 K and log(g) = 7.38. The white dwarf contributes
97% of the light at 4500 Angstroms and virtually all of the light blueward of
3800 Angstroms. No eclipses are observed. The mass inferred for the white dwarf
depends on the assumed mass of the thin residual hydrogen envelope: 0.40 < M_WD
< 0.45 solar masses for hydrogen envelope masses of 0 < M_H < 4.0E-4 solar
masses. We argue that the mass of the white dwarf is closer to 0.45 solar
masses, hence it appears that the white dwarf has a relatively large residual
hydrogen envelope. The mass of the M-star is then M_M = 0.28 +/- 0.05 solar
masses, and the inclination is i = 77 +/- 7 degrees. We discuss briefly how PG
1224+309 may be used to constrain theories of close binary star evolution, and
the past and future histories of PG 1224+309 itself. The star is both a
``post-common envelope'' star and a ``pre-cataclysmic binary'' star. Mass
transfer by Roche-lobe overflow should commence in about 10 Gyr.Comment: 17 pages, 8 figures, AAS LaTeX, to appear in AJ, March 199
Synthesis of β,β-Disubstituted Styrenes via Trimethylsilyl Trifluoromethanesulfonate-Promoted Aldehyde-Aldehyde Aldol Addition-Deformylative Elimination.
In the presence of trimethylsilyl trifluoromethanesulfonate (TMSOTf) and 2,6-lutidine, α,α-disubstituted aldehydes condense with electron-rich aromatic aldehydes to yield β, β- disubstituted styrenes. More electron-rich aromatic aldehydes react more rapidly and in higher yield. Preliminary results suggest that the reaction may proceed via the ionization and formal deformylation of an aldol intermediate
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