68,006 research outputs found
Ranking relations using analogies in biological and information networks
Analogical reasoning depends fundamentally on the ability to learn and
generalize about relations between objects. We develop an approach to
relational learning which, given a set of pairs of objects
,
measures how well other pairs A:B fit in with the set . Our work
addresses the following question: is the relation between objects A and B
analogous to those relations found in ? Such questions are
particularly relevant in information retrieval, where an investigator might
want to search for analogous pairs of objects that match the query set of
interest. There are many ways in which objects can be related, making the task
of measuring analogies very challenging. Our approach combines a similarity
measure on function spaces with Bayesian analysis to produce a ranking. It
requires data containing features of the objects of interest and a link matrix
specifying which relationships exist; no further attributes of such
relationships are necessary. We illustrate the potential of our method on text
analysis and information networks. An application on discovering functional
interactions between pairs of proteins is discussed in detail, where we show
that our approach can work in practice even if a small set of protein pairs is
provided.Comment: Published in at http://dx.doi.org/10.1214/09-AOAS321 the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Detrital zircon from a late Paleozoic accretionary complex of SW Iberia (Variscan Belt): History of crustal growth and recycling at the Rheic convergent margin
In this study we present new U-Pb ages of detrital zircons from
greywackes and quartzites of the Pulo do Lobo Anticline (PLA) that have
been interpreted to represent a Late Paleozoic accretionary complex in SW
Iberia. The PLA separates the Ossa Morena Zone, which has a North-
Gondwana affinity throughout Late Ediacaran and Early Paleozoic times,
from the South Portuguese Zone, which is considered to be underlain by
Laurussia basement. The PLA stratigraphy most likely represents a
synorogenic basin that records the closure of the Late Paleozoic Rheic
Ocean and the amalgamation of Pangaea. The youngest formations of the
PLA contain upper Devonian microfossils.The results obtained indicate that the detrital zircons from the PLA
represent a wide range of Precambrian and Paleozoic crystallization ages.
Recycling of older sedimentary units of the Late Ediacaran active margin
(Cadomian/Pan-African orogenies) as well as of the Early Paleozoic rifting
and passive margin (Rheic Ocean) stages, accounts for the older
populations with North-Gondwana affinity (Cambrian, Neoproterozoic,
Paleoproterozoic and Archean, with a gap of Mesoproterozoic-age).
However, the Mesoproterozoic detrital zircon ages found in the
greywackes of the Pulo do Lobo Formation (< 7%) that do not correspond
to any substantial source within North-Gondwana, could come from
recycled sedimentary deposits or from denudation of Grenville-age
basement (Laurussia?). The more recent formations present in the northern
limb (Ferreira-Ficalho Group) of the PLA show a significant age cluster in
the upper Devonian (c. 378 Ma), whereas on the southern limb (Chança
Group), samples have from base to top of the stratigraphic sequence: a
minor age cluster in the middle Devonian (c. 390 Ma), a significant age
cluster in upper Devonian (c. 380 Ma) and very significant age cluster in
the upper Devonian (c. 372 Ma). The presence of middle-upper Devonian
detrital zircons in combination with very low abundances of
Mesoproterozoic detrital zircon suggests that the PLA sedimentary rocks
were not derived from exotic sources but rather have a North-Gondwanan
origin. The zircon population in the interval c. 390-380 Ma has no
identified corresponding magmatic or stratigraphic source in SW Iberia.
Considering that, during the development of the upper Devonian basins of
SW Iberia, Laurussia basement was not exposed and that there was no
magmatic arc on the North-Gondwana margin, we suggest that the c. 390-
380 Ma detrital zircons are most probably derived from denudation of a
(intra-oceanic) magmatic arc related to the closure of the Rheic Ocean
Capital requirements and business cycles with credit market imperfections
The business cycle effects of bank capital regulatory regimes are examined in a New Keynesian model with credit market imperfections and a cost channel of monetary policy. Key features of the model are that bank capital increases incentives for banks to monitor borrowers, thereby reducing the probability of default, and excess capital generates benefits in terms of reduced regulatory scrutiny. Basel I and Basel II-type regulatory regimes are defined, and the model is calibrated for a middle-income country. Simulations of supply and demand shocks show that, depending on the elasticity that relates the repayment probability to the capital-loan ratio, a Basel II-type regime may be less procyclical than a Basel I-type regime.Banks&Banking Reform,Debt Markets,Access to Finance,Economic Theory&Research,Emerging Markets
Symbolic Sequences and Tsallis Entropy
We address this work to investigate symbolic sequences with long-range
correlations by using computational simulation. We analyze sequences with two,
three and four symbols that could be repeated times, with the probability
distribution . For these sequences, we verified that
the usual entropy increases more slowly when the symbols are correlated and the
Tsallis entropy exhibits, for a suitable choice of , a linear behavior. We
also study the chain as a random walk-like process and observe a nonusual
diffusive behavior depending on the values of the parameter .Comment: Published in the Brazilian Journal of Physic
The impact of inappropriate soil management on river water quality: a case study in the Kurundu Oya Sub-catchment of the Upper Mahaweli Catchment, Sri Lanka
The results of many studies have revealed that intensive farming on steep slopes, coupled with over application of fertilizers and accumulation of nutrients in downstream water bodies due to soil erosion, have contributed to environmental hazards in the Upper Mahaweli Catchment Area (UMCA) of Sri Lanka. The encroachment of riparian zones for exotic vegetable cultivation has aggravated this situation. In view of this, a study was conducted in the Kurundu Oya catchment, a micro-catchment of the UMCA, to investigate the soil management practices within the farming systems and their impacts on river water quality. Three villages were selected along the Kurundu Oya: Mahakudugala, Kumbalgamuwa and Batagolla. The study consisted of a survey of 150 households in 2007 and 2008, to gather information on the characteristics of householders and on soil management practices. A soil survey was carried out to analyze the soil fertility of farmlands. Water quality parameters were measured periodically in different sections of a selected stream. The results revealed that nearly 50 % of the riparian zones in the upper catchment of the Kurundu Oya stream are encroached to cultivate potato and other exotic vegetables. In addition, it was observed that over application of fertilizers on the vegetable plots was causing nutrient accumulation and the plots also recorded high levels of phosphorous (P) (above 75 ppm). Results of the water quality analysis showed that nitrate and available P levels were within the standard limits, but nitrate nitrogen (NO3-N) levels were close to the upper level of the standard limit. Therefore, in order to minimize water pollution, it is strongly recommended that fertilizer application is based on soil tests. In addition, encroachment of sensitive lands has to be addressed. Priority should be given to strengthening institutional capacity in order to facilitate the implementation of existing environmental legislation.Length: pp.49-60Soil managementSoil degradationCatchment areasErosionSedimentationWater pollutionFertilizer applicationNitrogenVegetable growing
Globally controlled universal quantum computation with arbitrary subsystem dimension
We introduce a scheme to perform universal quantum computation in quantum
cellular automata (QCA) fashion in arbitrary subsystem dimension (not
necessarily finite). The scheme is developed over a one spatial dimension
-element array, requiring only mirror symmetric logical encoding and global
pulses. A mechanism using ancillary degrees of freedom for subsystem specific
measurement is also presented.Comment: 7 pages, 1 figur
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