9,133 research outputs found
We haven't got a seat on the bus for you or All the seats are mine: Narratives and career transitions in professional golf
In this article we explore how the stories an athlete tells throughout life in sport affect her career transition experiences. We base our enquiry on a social constructionist conception of narrative theory which holds that storytelling is integral to the creation and maintenance of identity and sense of self. Life stories were gathered through interviews with two professional women golfers (Christiana and Kandy) over a six‐year period. Through a narrative analysis of structure and form we explored each participant’s stories of living in and withdrawing from professional golf. We suggest Christiana told monological performance‐oriented stories which, while aligning with the culture of elite sport, resulted in an exclusive athletic identity and foreclosure of alternative selves and roles. On withdrawal, Christiana experienced narrative wreckage, identity collapse, mental health difficulties and considerable psychological trauma. In contrast, Kandy told dialogical discovery‐oriented stories which, while being in tension with the dominant performance narrative, created and sustained a multidimensional identity and self. Her stories and identity remained intact, authentic and continuous on withdrawal from tournament golf and she experienced few psychological problems
Detection of Crab Giant Pulses Using the Mileura Widefield Array Low Frequency Demonstrator Field Prototype System
We report on the detection of giant pulses from the Crab Nebula pulsar at a
frequency of 200 MHz using the field deployment system designed for the Mileura
Widefield Array's Low Frequency Demonstrator (MWA-LFD). Our observations are
among the first high-quality detections at such low frequencies. The measured
pulse shapes are deconvolved for interstellar pulse broadening, yielding a
pulse-broadening time of 670100 s, and the implied strength of
scattering (scattering measure) is the lowest that is estimated towards the
Crab nebula from observations made so far. The sensitivity of the system is
largely dictated by the sky background, and our simple equipment is capable of
detecting pulses that are brighter than 9 kJy in amplitude. The brightest
giant pulse detected in our data has a peak amplitude of 50 kJy, and the
implied brightness temperature is K. We discuss the giant pulse
detection prospects with the full MWA-LFD system. With a sensitivity over two
orders of magnitude larger than the prototype equipment, the full system will
be capable of detecting such bright giant pulses out to a wide range of
Galactic distances; from 8 to 30 kpc depending on the frequency.
The MWA-LFD will thus be a highly promising instrument for the studies of giant
pulses and other fast radio transients at low frequencies.Comment: 10 pages, 6 figures, Accepted for publication in the Astrophysical
Journa
Chaotic Loss Cones, Black Hole Fueling and the M-Sigma Relation
In classical loss cone theory, stars are supplied to a central black hole via
gravitational scattering onto low angular momentum orbits. Higher feeding rates
are possible if the gravitational potential near the black hole is
non-axisymmetric and the orbits are chaotic. Motivated by recently published,
self-consistent models, we evaluate rates of stellar capture and disruption in
triaxial nuclei. Rates are found to substantially exceed those in
collisionally-resupplied loss cones, as long as an appreciable fraction of the
orbits are centrophilic. The mass captured by a black hole after a given time
in a steep nucleus scales as the fifth power of the velocity dispersion, and
the accumulated mass in 10^10 yr is of the correct order to reproduce the
M-sigma relation. Triaxiality can solve the "final parsec problem" of decaying
black hole binaries by increasing the flux of stars into the binary's loss
cone.Comment: 29 pages, 6 figure
Resource-Bound Quantification for Graph Transformation
Graph transformation has been used to model concurrent systems in software
engineering, as well as in biochemistry and life sciences. The application of a
transformation rule can be characterised algebraically as construction of a
double-pushout (DPO) diagram in the category of graphs. We show how
intuitionistic linear logic can be extended with resource-bound quantification,
allowing for an implicit handling of the DPO conditions, and how resource logic
can be used to reason about graph transformation systems
Time Variable Gravity modeling for Precise Orbits Across the TOPEX/Poseidon, Jason-l and Jason-2 Missions
Modeling of the Time Variable Gravity (TVG) is believed to constitute one of the the largest remaining source of orbit error for altimeter satellite POD. The GSFC operational TVG model consists of forward modeling the atmospheric gravity using ECMWF 6-hour pressure data, a GRACE derived 20x20 annual field to account for changes in the hydrology and ocean water mass, and linear rates for C20, C30, C40, based on 17 years of SLR data analysis (IERS 2003) using the EIGEN-GL04S1 (a GRACE+Lageos-based geopotential solution). Although the GSFC Operational model can be applied from 1987, there may be long-term variations not captured by these linear models, and more importantly the linear models may not be consistent with more recent surface mass trends due to global climate change, We have evaluated the impact of TVG in two different wavs: (1) by using the more recent EIGEN-6S gravity model developed by the GFZ/GRGS tearm, which consists of annual, semi-annual and secular changes in the coefficients to 50x50 determined over 8(?) years of GRACE+Lageos+GOCE data (2003-200?): (2) Application of 4x4 solutions developed from a multi satellite SLR+DORIS solution based on GGM03S that span the period from 1993 to 2011. We have evaluated the recently released EIGEN6s static and time-varying gravity field for Jason-2 (J2). Jason-I (J1), and TOPEX/Posiedon (TP) Precise Orbit Determination (POD) spanning 1993-2011. Although EIGEN6s shows significant improvement for J2POD spanning 2008 - 2011, it also shows significant degradation for TP POD from 1992. The GSFC 4x4 time SLR+DORIS-based series spans 1993 to mid 2011, and shows promise for POD. We evaluate the performance of the different TVG models based on analysis of tracking data residuals use of independent data such as altimeter crossovers, and through analysis of differences with internally-generated and externally generated orbits
GSFC OSTM, Jason-l and TOPEX POD Update
The OSTM (Jason-2) has been in orbit for three years (since June 2008), and the full suite of altimeter data from TOPEX/Poseidon, Jason-I and Jason-2 now span nearly twenty years since the launch of TOPEX in 1992. Issues that affect the stability of the orbits through time and the orbit accuracy include the reference frame, the radiation pressure models for the altimeter satellites and the fidelity of the dynamic force model, including time-variable gravity, as well as the performance of the individual tracking systems. We have conducted detailed analyses of the new ITRF2008 reference frame and find only a small effect on global mean sea level compared to ITRF2005, although we note an improvement in POD quality over the most recent time periods for Jason-2. In the past year we have developed a new time series of orbits for TOPEX/Poseidon, Jason-I, and Jason-2 based on the ITRF2008 reference frame using SLR and DORIS data and for Jason-2 using GPS data. In addition, we have continued to experiment with improvements to the radiation pressure model for the altimeter satellites in particular the Jason satellites since these nonconservative force model errors now rank as the most outstanding source of error on altimeter satellite POD. In the previous (ITRF2005-based) and current (ITRF2008-based) orbits we have relied on a simplified time-variable gravity (TVG) model, derived from GRACE solutions. We have recently experimented with improvements using higher fidelity TVG models (both temporally and spatially) and report on the results. We have computed a time series of GPS-only reduced-dynamic orbits at GSFC, and used these in conjunction with the SLR-DORIS dynamic and reduced-dynamic orbits to assess reference fiame stability with respect to the different tracking systems for both ITRF2005 and ITRF2008. We show through internal (GSFConly) and external comparisons (with other analysis centers) that the radial orbit accuracy for Jason-2 remains at I cm
Panel: OASIS in the mirror: reflections on the impacts and research of IFIP WG 8.2
What has IFIP contributed to the field of information systems and organizations through the activities of Working Group 8.2, its central working group in information systems? What has WG 8.2 delivered to its constituents? What have the results and impacts of the WG 8.2 been on the larger community? This panel will not shy away from controversy as it discusses the history, contributions, and unrealized potential of research spawned by this working group over the past 30 years.The past and the future of information systems: 1976-2006 and beyondRed de Universidades con Carreras en Informática (RedUNCI
The Effect of Geocenter Motion on Jason-2 and Jason-1 Orbits and the Mean Sea Level
We have investigated the impact of geocenter motion on Jason-2 orbits. This was accomplished by computing a series of Jason-1, Jason-2 GPS-based and SLR/DORIS-based orbits using ITRF2008 and the IGS repro1 framework based on the most recent GSFC standards. From these orbits, we extract the Jason-2 orbit frame translational parameters per cycle by the means of a Helmert transformation between a set of reference orbits and a set of test orbits. The fitted annual and seasonal terms of these time-series are compared to two different geocenter motion models. Subsequently, we included the geocenter motion corrections in the POD process as a degree-1 loading displacement correction to the tracking network. The analysis suggested that the GSFC's Jason-2 std0905 GPS-based orbits are closely tied to the center of mass (CM) of the Earth whereas the SLR/DORIS std0905 orbits are tied to the center of figure (CF) of the ITRF2005 (Melachroinos et al., 2012). In this study we extend the investigation to the centering of the GPS constellation and the way those are tied in the Jason-1 and Jason-2 POD process. With a new set of standards, we quantify the GPS and SLR/DORIS-based orbit centering during the Jason-1 and Jason-2 inter-calibration period and how this impacts the orbit radial error over the globe, which is assimilated into mean sea level (MSL) error, from the omission of the full term of the geocenter motion correction
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