3,889 research outputs found
Digging Deeper into Hardin\u27s Pasture: The Complex Institutional Structure of The Tragedy of the Commons
The institutional and ecological structure of Hardin’s “tragedy of the commons” appears deceptively simple: the open-access pasture eventually will be overexploited and degraded unless (i) it is privatized, (ii) the government regulates access and use, or (iii) the users themselves impose a common-property regime to regulate their own access and use. In this paper, we argue that the institutional structure of the “Herder Problem” (as it is known to game theorists) is far more complicated than it is usually portrayed. Specifically, it is not just about the pasture. It is equally about the grass that grows on the pasture and the cattle that consume the grass. Even Elinor Ostrom — a scholar known for embracing complexity — presented an overly simplistic portrayal of Hardin’s open-access pasture when she described its governance system as a null set of institutions. A more careful assessment of the situation, employing Ostrom’s Social-Ecological System (SES) framework, broadens the focus from the res communes omnium pasture to incorporate the res nullius grass that grows upon it and the res private cattle grazing there. The “tragedy” arises from the combination and interactions of the resources and their governing institutions, not just from the absence of property in the pasture. If the grass was not subject to appropriation, the cattle were not privately owned, or if property- and contract-enforcement institutions supporting market exchange were absent, the “tragedy of the commons” probably would not arise regardless of the pasture’s open-access status
Digging Deeper into Hardin\u27s Pasture: The Complex Institutional Structure of The Tragedy of the Commons
The institutional and ecological structure of Hardin’s “tragedy of the commons” appears deceptively simple: the open-access pasture eventually will be overexploited and degraded unless (i) it is privatized, (ii) the government regulates access and use, or (iii) the users themselves impose a common-property regime to regulate their own access and use. In this paper, we argue that the institutional structure of the “Herder Problem” (as it is known to game theorists) is far more complicated than it is usually portrayed. Specifically, it is not just about the pasture. It is equally about the grass that grows on the pasture and the cattle that consume the grass. Even Elinor Ostrom — a scholar known for embracing complexity — presented an overly simplistic portrayal of Hardin’s open-access pasture when she described its governance system as a null set of institutions. A more careful assessment of the situation, employing Ostrom’s Social-Ecological System (SES) framework, broadens the focus from the res communes omnium pasture to incorporate the res nullius grass that grows upon it and the res private cattle grazing there. The “tragedy” arises from the combination and interactions of the resources and their governing institutions, not just from the absence of property in the pasture. If the grass was not subject to appropriation, the cattle were not privately owned, or if property- and contract-enforcement institutions supporting market exchange were absent, the “tragedy of the commons” probably would not arise regardless of the pasture’s open-access status
The Nature of the Halo Population of NGC 5128 Resolved with NICMOS on the Hubble Space Telescope
We present the first infrared color-magnitude diagram (CMD) for the halo of a
giant elliptical galaxy. The CMD for the stars in the halo of NGC 5128
(Centaurus A) was constructed from HST NICMOS observations of the WFPC2 CHIP-3
field of Soria et al. (1996) to a 50% completeness magnitude limit of
[F160W]=23.8. This field is located at a distance of 08'50" (~9 kpc) south of
the center of the galaxy. The luminosity function (LF) shows a marked
discontinuity at [F160W]=20.0. This is 1-2 mag above the tip of the red giant
branch (TRGB) expected for an old population (~12 Gyr) at the distance modulus
of NGC 5128. We propose that the majority of stars above the TRGB have
intermediate ages (~2 Gyr), in agreement with the WFPC2 observations of Soria
et al. (1996). Five stars with magnitudes brighter than the LF discontinuity
are most probably due to Galactic contamination. The weighted average of the
mean giant branch color above our 50% completeness limit is
[F110W]-[F160W]=1.22+-0.08 with a dispersion of 0.19 mag. From our
artificial-star experiments we determine that the observed spread in color is
real, suggesting a real spread in metallicity. We estimate the lower and upper
bounds of the stellar metallicity range by comparisons with observations of
Galactic star clusters and theoretical isochrones. Assuming an old population,
we find that, in the halo field of NGC 5128 we surveyed, stars have
metallicities ranging from roughly 1% of solar at the blue end of the color
spread to roughly solar at the red end, with a mean of [Fe/H]=-0.76 and a
dispersion of 0.44 dex.Comment: Accepted for publication in AJ, 23 pages of text, 13 figures, uses
aastex v5.
Point-by-point inscription of apodized fiber Bragg gratings
We demonstrate apodized fiber Bragg gratings inscribed with a point-by-point
technique. We tailor the grating phase and coupling amplitude through precise
control over the longitudinal and transverse position of each laser-inscribed
modification. This method of apodization is facilitated by the
highly-localized, high-contrast modifications generated by focussed IR
femtosecond laser inscription. Our technique provides a simple method for the
design and implementation of point-by-point fiber Bragg gratings with complex
apodization profiles.Comment: 6 pages, 4 figures, article in revie
The Winter Camp of the Viking Great Army, AD 872–3, Torksey, Lincolnshire
This paper presents the results of a multidisciplinary project that has revealed the location, extent
and character of the winter camp of the Viking Great Army at Torksey, Lincolnshire, of AD 872–3.
The camp lay within a naturally defended area of higher ground, partially surrounded by marshes
and bordered by the River Trent on its western side. It is considerably larger than the Viking camp of
873–4 previously excavated at Repton, Derbyshire, and lacks the earthwork defences identified
there. Several thousand individuals overwintered in the camp, including warriors, craftworkers and
merchants. An exceptionally large and rich metalwork assemblage was deposited during the Great
Army’s overwintering, and metal processing and trading was undertaken. There is no evidence for a
pre-existing Anglo-Saxon trading site here; the site appears to have been chosen for its strategic
location and its access to resources. In the wake of the overwintering, Torksey developed as an
important Anglo-Saxon borough with a major wheel-thrown pottery industry and multiple churches
and cemeteries. The Torksey evidence allows for a radical reappraisal of the character of Viking
winter camps, and the legacy of the Viking Great Army for Anglo-Saxon England
Automated speckle tracking algorithm to aid on-axis imaging in echocardiography
Obtaining a “correct” view in echocardiography is a subjective process in which an operator attempts to obtain images conforming to consensus standard views. Real-time objective quantification of image alignment may assist less experienced operators, but no reliable index yet exists. We present a fully automated algorithm for detecting incorrect medial/lateral translation of an ultrasound probe by image analysis. The ability of the algorithm to distinguish optimal from sub-optimal four-chamber images was compared to that of specialists—the current “gold-standard.” The orientation assessments produced by the automated algorithm correlated well with consensus visual assessments of the specialists (r=0.87r=0.87) and compared favourably with the correlation between individual specialists and the consensus, 0.82±0.09. Each individual specialist’s assessments were within the consensus of other specialists, 75±14% of the time, and the algorithm’s assessments were within the consensus of specialists 85% of the time. The mean discrepancy in probe translation values between individual specialists and their consensus was 0.97±0.87  cm, and between the automated algorithm and specialists’ consensus was 0.92±0.70  cm. This technology could be incorporated into hardware to provide real-time guidance for image optimisation—a potentially valuable tool both for training and quality control
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Simulating the Cranfield geological carbon sequestration project with high-resolution static models and an accurate equation of state
Bureau of Economic Geolog
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Microcraters in aluminum foils exposed by Stardust
We will present preliminary results on the nature and size frequency distribution of microcraters that formed in aluminum foils during the flyby of comet Wild 2 by the Stardust spacecraft
Aerogel Track Morphology: Measurement, Three Dimensional Reconstruction and Particle Location using Confocal Laser Scanning Microscopy
The Stardust spacecraft returned the first undoubted samples of cometary dust, with many grains embedded in the silica aerogel collector . Although many tracks contain one or more large terminal particles of a wide range of mineral compositions , there is also abundant material along the track walls. To help interpret the full particle size, structure and mass, both experimental simulation of impact by shots and numerical modeling of the impact process have been attempted. However, all approaches require accurate and precise measurement of impact track size parameters such as length, width and volume of specific portions. To make such measurements is not easy, especially if extensive aerogel fracturing and discoloration has occurred. In this paper we describe the application and limitations of laser confocal imagery for determination of aerogel track parameters, and for the location of particle remains
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