1,653 research outputs found
Swing-out rail system separates overhead crane rails
Swing-out rail system separates and reconnects the overhead traveling crane rails of a building to provide for the passage of a thick concrete radiation shield sliding door through the rails. In the swing-out position, the rail cantilevered from an axial shaft
Obstetrics and Gynecology at the University of Iowa: Three leaders and 51 years
In his history of the Department of Obstetrics and Gynecology of the University of Iowa College of Medicine, William C. Keettel traced the evolution of the department from its origin in 1870 until 1980. This article will focus on a particular segment of the departmentâs history, that from 1926 to 1977, in which the department grew and developed to a position of national stature. During this 51-year period, departmental leadership was provided by three individuals, E. D. Plass (1926-1951), John H. Randall (1952-1959), and William C. Keettel (1959-1977) and this paper will consider these three men and their contributions to the departmentâs growth and development. The 1980 department history provided most of the basis of the article, although a small amount of the Randall section and a substantial amount of the Keettel section reflect my personal perspective and recollections
Advanced technologies for future ground-based, laser-interferometric gravitational wave detectors
We present a review of modern optical techniques being used and developed for the field of gravitational wave detection. We describe the current state-of-the-art of gravitational waves detector technologies with regard to optical layouts, suspensions and test masses. We discuss the dominant sources and noise in each of these subsystems and the developments that will help mitigate them for future generations of detectors. We very briefly summarise some of the novel astrophysics that will be possible with these upgraded detectors
Searching for gravitational waves from the Crab pulsar - the problem of timing noise
Of the current known pulsars, the Crab pulsar (B0531+21) is one of the most
promising sources of gravitational waves. The relatively large timing noise of
the Crab causes its phase evolution to depart from a simple spin-down model.
This effect needs to be taken in to account when performing time domain
searches for the Crab pulsar in order to avoid severely degrading the search
efficiency. The Jodrell Bank Crab pulsar ephemeris is examined to see if it can
be used for tracking the phase evolution of any gravitational wave signal from
the pulsar, and we present a method of heterodyning the data that takes account
of the phase wander. The possibility of obtaining physical information about
the pulsar from comparisons of the electromagnetically and a gravitationally
observed timing noise is discussed. Finally, additional problems caused by
pulsar glitches are discussed.Comment: 5 pages, 1 figure, Proceedings of the 5th Amaldi Conference on
Gravitational Waves, Pisa, Italy, 6-11 July 200
Wind Energy Opposition in Vermont: Perspectives on the State\u27s Energy Future
Due to its high levels of concern and awareness of environmental issues, rural character, and sparse population, Vermont would at first glance appear to possess the ideal recipe to become a national leader in renewable energy development. Renewable initiatives have focused primarily on wind energy, as over a dozen wind farms have been proposed in the last few years across the state. However, in spite of the widely held belief in Vermontâs wind energy future, its proponents have run into vehement opposition at every proposed site, often successfully impeding the planned developments.
This report develops a wide-level framework of the motivations of and complaints presented by wind opposition groups around the state, followed by an analysis of opposition strategies commonly employed. These are contrasted with the tactics used by wind developers and their supporters to remediate or overcome this opposition. Next, this essay will offer a view of the state and local institutional settings in which these battles take place, and finally conclude with a brief analysis of various alternatives to utility-scale wind, offering suggestions for windâs role in the future of energy in Vermont
Dynamic input to determine hip joint moments, power and work on the prosthetic limb of transfemoral amputees: ground reactions vs knee reactions
Study Design: Comparative analysis\ud
Background: Calculations of lower limbs kinetics are limited by floor-mounted force-plates.\ud
Objectives: Comparison of hip joint moments, power and mechanical work on the prosthetic limb of a transfemoral amputee calculated by inverse dynamics using either the ground reactions (force-plates) or knee reactions (transducer).\ud
Methods: Kinematics, ground reactions and knee reactions were collected using a motion analysis system, two force-plates and a multi-axial transducer mounted below the socket, respectively.\ud
Results: The inverse dynamics using ground reactions under-estimated the peaks of hip energy generation and absorption occurring at 63 % and 76 % of the gait cycle (GC) by 28 % and 54 %, respectively. This method over-estimated a phase of negative work at the hip (from 37 %GC to 56 %GC) by 24%. It under-estimated the phases of positive (from 57 %GC to 72 %GC) and negative (from 73 %GC to 98 %GC) work at the hip by 11 % and 58%, respectively.\ud
Conclusions: A transducer mounted within the prosthesis has the capacity to provide more realistic kinetics of the prosthetic limb because it enables assessment of multiple consecutive steps and a wide range of activities without issues of foot placement on force-plates
The declining representativeness of the British party system, and why it matters
In a recent article, Michael Laver has explained âWhy Vote-Seeking Parties May Make Voters Miserableâ. His model shows that, while ideological convergence may boost congruence between governments and the median voter, it can reduce congruence between the party system and the electorate as a whole. Specifically, convergence can increase the mean distance between voters and their nearest party. In this article we show that this captures the reality of todayâs British party system. Policy scale placements in British Election Studies from 1987 to 2010 confirm that the pronounced convergence during the past decade has left the Conservatives and Labour closer together than would be optimal in terms of minimising the policy distance between the average voter and the nearest major party. We go on to demonstrate that this comes at a cost. Respondents who perceive themselves as further away from one of the major parties in the system tend to score lower on satisfaction with democracy. In short, vote-seeking parties have left the British party system less representative of the ideological diversity in the electorate, and thus made at least some British voters miserable
Gravitational wave detection using pulsars: status of the Parkes Pulsar Timing Array project
The first direct detection of gravitational waves may be made through
observations of pulsars. The principal aim of pulsar timing array projects
being carried out worldwide is to detect ultra-low frequency gravitational
waves (f ~ 10^-9 to 10^-8 Hz). Such waves are expected to be caused by
coalescing supermassive binary black holes in the cores of merged galaxies. It
is also possible that a detectable signal could have been produced in the
inflationary era or by cosmic strings. In this paper we review the current
status of the Parkes Pulsar Timing Array project (the only such project in the
Southern hemisphere) and compare the pulsar timing technique with other forms
of gravitational-wave detection such as ground- and space-based interferometer
systems.Comment: Accepted for publication in PAS
The Sensitivity of the Parkes Pulsar Timing Array to Individual Sources of Gravitational Waves
We present the sensitivity of the Parkes Pulsar Timing Array to gravitational
waves emitted by individual super-massive black-hole binary systems in the
early phases of coalescing at the cores of merged galaxies. Our analysis
includes a detailed study of the effects of fitting a pulsar timing model to
non-white timing residuals. Pulsar timing is sensitive at nanoHertz frequencies
and hence complementary to LIGO and LISA. We place a sky-averaged constraint on
the merger rate of nearby () black-hole binaries in the early phases
of coalescence with a chirp mass of 10^{10}\,\rmn{M}_\odot of less than one
merger every seven years. The prospects for future gravitational-wave astronomy
of this type with the proposed Square Kilometre Array telescope are discussed.Comment: fixed error in equation (4). [13 pages, 6 figures, 1 table, published
in MNRAS
Report on the first round of the Mock LISA Data Challenges
The Mock LISA Data Challenges (MLDCs) have the dual purpose of fostering the
development of LISA data analysis tools and capabilities, and demonstrating the
technical readiness already achieved by the gravitational-wave community in
distilling a rich science payoff from the LISA data output. The first round of
MLDCs has just been completed: nine data sets containing simulated
gravitational wave signals produced either by galactic binaries or massive
black hole binaries embedded in simulated LISA instrumental noise were released
in June 2006 with deadline for submission of results at the beginning of
December 2006. Ten groups have participated in this first round of challenges.
Here we describe the challenges, summarise the results, and provide a first
critical assessment of the entries.Comment: Proceedings report from GWDAW 11. Added author, added reference,
clarified some text, removed typos. Results unchanged; Removed author, minor
edits, reflects submitted versio
- âŠ