1,517 research outputs found
The Economic Foundations of Institutional Stagnation in Commodity-Exporting Countries
Many poor countries are plagued with growth-impeding institutions. We develop a three-sector general equilibrium model linking economic stagnation in these countries to poor export terms of trade. We examine the extent to which changes in the terms of trade affect private agents’ incentive to coalesce to oppose the adoption of growth-promoting institutions. We show that under certain conditions, below a threshold terms of trade level, private agents gain from coalescing to oppose the adoption of growth-promoting institutions. Above this threshold, gains from coalescing disappear, fostering institutional change.Terms of trade, primary commodities, institutions, general equilibrium
Outcomes of Endoluminal Re-intervention for Recurrent Disease after Percutaneous Iliac Angioplasty and Stenting
Spatial variation in the effects of size and age on reproductive dynamics of common coral trout Plectropomus leopardus
The effects of size and age on reproductive dynamics of common coral trout Plectropomus leopardus populations were compared between coral reefs open or closed (no-take marine reserves) to fishing and among four geographic regions of the Great Barrier Reef (GBR), Australia. The specific reproductive metrics investigated were the sex ratio, the proportion of vitellogenic females and the spawning fraction of local populations. Sex ratios became increasingly male biased with length and age, as expected for a protogyne, but were more male biased in southern regions of the GBR (Mackay and Storm Cay) than in northern regions (Lizard Island and Townsville) across all lengths and ages. The proportion of vitellogenic females also increased with length and age. Female P. leopardus were capable of daily spawning during the spawning season, but on average spawned every 4·3 days. Mature females spawned most frequently on Townsville reserve reefs (every 2·3 days) and Lizard Island fished reefs (every 3·2 days). Females on Mackay reefs open to fishing showed no evidence of spawning over 4 years of sampling, while females on reserve reefs spawned only once every 2–3 months. No effect of length on spawning frequency was detected. Spawning frequency increased with age on Lizard Island fished reefs, declined with age on Storm Cay fished reefs, and declined with age on reserve reefs in all regions. It is hypothesized that the variation in P. leopardus sex ratios and spawning frequency among GBR regions is primarily driven by water temperature, while no-take management zones influence spawning frequency depending on the region in which the reserve is located. Male bias and lack of spawning activity on southern GBR, where densities of adult P. leopardus are highest, suggest that recruits may be supplied from central or northern GBR. Significant regional variation in reproductive traits suggests that a regional approach to management of P. leopardus is appropriate and highlights the need for considering spatial variation in reproduction where reserves are used as fishery or conservation management tools
Geology of the Llanidloes district : British Geological Survey Sheet 164
This Sheet Explanation provides a summary of the geology of the district covered by Geological 1:50 000 Series
Map Sheet 164 (Llanidloes), published in 2010 as a Bedrock and Superficial Deposits edition. The district mostly
lies within the county of Powys, but includes small parts of Ceredigion in the extreme west and south-west. Much of
the western part of the district is occupied by the deeply dissected uplands of the Cambrian Mountains, a designated
Area of Outstanding Natural Beauty. In this area the land rises to 740 m on the flanks of Plynlimon (Pumlumon
Fawr), the highest summit in the range. It falls away towards the eastern part of the district into rolling countryside
that includes the important catchment of the River Severn (Afon Hafren) and its tributaries, the largest of which are
the rivers Carno, Trannon, Cerist, Clywedog and Dulas. A major reservoir (Llyn Clywedog) occupies the upper
reaches of the Clywedog valley, its purpose being to regulate river discharge and groundwater levels within the
catchment. The south-western part of the district is drained by the River Wye (Afon Gwy) and its tributaries, that
flow south-eastwards via Llangurig. The sources of both the Severn and Wye are situated on the eastern flanks of
Plynlimon within the western part of the district.
The town of Llanidloes is the main centre of population, with smaller settlements at Llangurig, Carno, Trefeglwys,
Caersws and Staylittle; the Newtown conurbation impinges on the eastern part of the district. Much of the district is
given over to beef and dairy farming, although sheep are reared in the remote upland areas in the west and extensive
forestry plantations have been developed in places. The Ordovician and Silurian rocks of the district have been
exploited locally, in the past, as a source of building material and, recently, commercial quantities of sandstone
aggregate have been excavated at Penstrowed Quarry [SO 0680 9100]. The district includes part of the Central
Wales Mining Field from which substantial volumes of lead and zinc ore were extracted during the 19th and early
20th centuries. A number of former mine sites are still visible, notably along the Van, Nant-y-ricket, Dylife,
Dyfngwm and Llanerchyraur lodes (Jones, 1922[1]; IGS, 1974), and the historic Bryntail Mine, below the Clywedog
Dam has been restored as a site of industrial archaeological interest.
The district is underlain by a succession of Late Ordovician (Ashgill) to Silurian sedimentary rocks, over 5 km thick,
deposited between 450 and 420 million years ago in the Early Palaeozoic Welsh Basin (Figure P930911). The basin
developed on a fragment of the ancient supercontinent of Gondwana, known as Eastern Avalonia (e.g. Pickering et
al., 1988[2]), that drifted northwards to collide with the continents of Baltica and Laurentia during the Late
Ordovician and Silurian (Soper and Hutton, 1984[3]; Soper and Woodcock, 1990[4]; Woodcock and Strachan,
2000[5]). To the east and the south of the basin lay the Midland Platform, a relatively stable shallow marine shelf that
was subject to periodic emergence. The basinal sediments are predominantly deep marine turbiditic facies that were
introduced into the district by density currents from southerly, south-easterly and north-westerly quadrants. Coeval
shallower-water ‘shelfal’ sediments were deposited north and east of the district, and locally impinge on its northern
margins. Thickness variations within the major sedimentary units suggest that, at times, syndepositional fault
movements were an important control on their distribution. During late Silurian (Ludlow) times, shallowing of the
basin occurred, and sandstones, variably interpreted as a turbiditic (Cave and Hains, 2001[6]) or storm-generated
facies (Tyler and Woodcock, 1987[7]), were laid down over the eastern part of the district and adjacent areas. The
shallowing was a result of tectonic reconfiguration of the basin, a precursor to the late Caledonian (Acadian)
Orogeny that affected the region during the late Early Devonian, around 400 million years ag
Factorization in integrable systems with impurity
This article is based on recent works done in collaboration with M. Mintchev,
E. Ragoucy and P. Sorba. It aims at presenting the latest developments in the
subject of factorization for integrable field theories with a reflecting and
transmitting impurity.Comment: 7 pages; contribution to the XIVth International Colloquium on
Integrable systems, Prague, June 200
Particle-Field Duality and Form Factors from Vertex Operators
Using a duality between the space of particles and the space of fields, we
show how one can compute form factors directly in the space of fields. This
introduces the notion of vertex operators, and form factors are vacuum
expectation values of such vertex operators in the space of fields. The vertex
operators can be constructed explicitly in radial quantization. Furthermore,
these vertex operators can be exactly bosonized in momentum space. We develop
these ideas by studying the free-fermion point of the sine-Gordon theory, and
use this scheme to compute some form-factors of some non-free fields in the
sine-Gordon theory. This work further clarifies earlier work of one of the
authors, and extends it to include the periodic sector.Comment: 17 pages, 2 figures, CLNS 93/??
Law, politics and the governance of English and Scottish joint-stock companies 1600-1850
This article examines the impact of law on corporate governance by means of a case study of joint-stock enterprise in England and Scotland before 1850. Based on a dataset of over 450 company constitutions together with qualitative information on governance practice, it finds little evidence to support the hypothesis that common-law regimes such as England were more supportive of economic growth than civil-law jurisdictions such as Scotland: indeed, levels of shareholder protection were slightly stronger in the civil-law zone. Other factors, such as local political institutions, played a bigger role in shaping organisational forms and business practice
Free Boson Realization of
We construct a realization of the quantum affine algebra
of an arbitrary level in terms of free boson fields.
In the limit this realization becomes the Wakimoto
realization of . The screening currents and the vertex
operators(primary fields) are also constructed; the former commutes with
modulo total difference, and the latter creates the
highest weight state from the vacuum state of the boson
Fock space.Comment: 24 pages, LaTeX, RIMS-924, YITP/K-101
Manifestation of ageing in the low temperature conductance of disordered insulators
We are interested in the out of equilibrium phenomena observed in the
electrical conductance of disordered insulators at low temperature, which may
be signatures of the electron coulomb glass state. The present work is devoted
to the occurrence of ageing, a benchmark phenomenon for the glassy state. It is
the fact that the dynamical properties of a glass depend on its age, i.e. on
the time elapsed since it was quench-cooled. We first critically analyse
previous studies on disordered insulators and question their interpretation in
terms of ageing. We then present new measurements on insulating granular
aluminium thin films which demonstrate that the dynamics is indeed age
dependent. We also show that the results of different relaxation protocols are
related by a superposition principle. The implications of our findings for the
mechanism of the conductance slow relaxations are then discussed
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