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Ones Used (ones + used)

Distribution by Scientific Domains

Earth and Environmental Science	40%

Selected Abstracts

Sale, price and valuation in Galicia and Castile,León in the tenth century

EARLY MEDIEVAL EUROPE, Issue 2 2002
Wendy Davies
The number of sale transactions recorded by northern Spanish charters of the tenth century is very striking, especially in the 930s to 960s. A record of price paid was a consistent element of such documents, although words used to express price varied from silver solidi to goats, shirts and grain. Valuations, in solidi and in other units of account such as cattle, were often stated when objects were used as payment. While it looks as if some silver was really used in deals in urban León and its hinterland, using pieces of silver called argenzos, argenteos etc., elsewhere this was rare. Comparing the transactions in the three very different monastic collections of Celanova in the north,west, Sahagún in the central meseta and Cardeña in the foothills of the sierras in the north,east, regional difference is also striking. Sahagún is notable for the volume and early date of its sales and for increasing use of silver,based expressions of price and value. Round Celanova, by contrast, although there were also many sales, people used several modes of valuation simultaneously, but metal,based notions very rarely. Round Cardeña, close to urban Burgos, far fewer sales are recorded, and they come later in the century, but silver,based notions of value were the only ones used. This latter sub,urban context seems to have been much less commercially active than that of León and Sahagún, with exchange by gift and countergift a more prominent characteristic. [source]

Factors affecting fluid flow in strike,slip fault systems: coupled deformation and fluid flow modelling with application to the western Mount Isa Inlier, Australia

GEOFLUIDS (ELECTRONIC), Issue 1 2009
A. FORD
Abstract Deformation and focused fluid flow within a mineralized system are critical in the genesis of hydrothermal ore deposits. Dilation and integrated fluid flux due to coupled deformation and fluid flow in simple strike,slip fault geometries were examined using finite difference analysis in three dimensions. A series of generic fault bend and fault jog geometries consistent with those seen in the western Mount Isa Inlier were modelled in order to understand how fault geometry parameters influence the dilation and integrated fluid flux. Fault dip, fault width, bend/jog angle, and length were varied, and a cross-cutting fault and contrasting rock types were included. The results demonstrate that low fault dips, the presence of contrasts in rock type, and wide faults produce highest dilation and integrated fluid flux values. Increasing fault bend lengths and angles increases dilation and integrated fluid flux, but increasing fault jog length or angle has the opposite effect. There is minimal difference between the outputs from the releasing and restraining fault bend and jog geometries. Model characteristics producing greater fluid flows and/or gradients can be used in a predictive capacity in order to focus exploration on regions with more favorable fault geometries, provided that the mineralized rocks had Mohr,Coulomb rheologies similar to the ones used in the models. [source]

Calcium supplementation of breeding birds: directions for future research

IBIS, Issue 4 2004
S. James Reynolds
Calcium is an essential nutrient for avian reproduction. Calcium-rich foods are consumed by breeding birds for production of eggshells and for provisioning chicks that are mineralizing skeletal tissues. A number of studies have documented calcium-limited reproduction, and calcium supplementation has been employed over the last decade to demonstrate degrees, causes and consequences of calcium limitation. However, supplementation studies have produced equivocal findings resulting from an absence of calcium limitation in the study species, a poorly designed supplementation procedure or both. Prior to effective calcium supplementation, many factors need to be considered. Calcium-limited breeding in birds can only be detected by monitoring breeding attempts for more than one year and by ensuring that the measured breeding parameters are sensitive to calcium availability. Natural calcium availability needs to be estimated, and daily calcium budgets for the appropriate reproductive stages determined for the study species. Most crucially, if calcium limitation of breeding is caused by secondary calcium limitation (e.g. through heavy metal toxicity), calcium supplementation will probably be ineffective. Effective calcium supplementation will then be achieved through careful planning , a study over several years using appropriate supplements (i.e. naturally occurring ones used by breeding birds), applied at the appropriate time of year (i.e. prelaying and/or chick-rearing phases) and using a response variable that is highly sensitive to calcium availability. If properly planned and performed, calcium supplementation is a cost-effective and potent tool for the study of bird breeding biology. [source]

On the hardness of range assignment problems

NETWORKS: AN INTERNATIONAL JOURNAL, Issue 4 2008
Bernhard Fuchs
Abstract We investigate the computational hardness of the connectivity, the strong connectivity, and the broadcast type of range assignment problems in ,2 and ,3. We present new reductions for the connectivity problem, which are easily adapted to suit the other two problems. All reductions are considerably simpler than the technically quite involved ones used in earlier works on these problems. Using our constructions, we can for the first time prove NP-hardness of these problems for all real distance-power gradients , > 0 (resp. , > 1 for broadcast) in 2D, and prove APX-hardness of all three problems in 3D for all , > 1. Our reductions yield improved lower bounds on the approximation ratios for all problems where APX-hardness was known before already. In particular, we derive the overall first APX-hardness proof for broadcast. This was an open problem posed in earlier work in this area, as was the question whether (strong) connectivity remains NP-hard for , = 1. In addition, we give the first hardness results for so-called well-spread instances. On the positive side, we prove that two natural greedy algorithms are 2-approximations for (strong) connectivity, and show that the factor 2 is tight in ,2 for , > 1. We also analyze the performance guarantee of the well-known MST-heuristic as a function of the input size. © 2008 Wiley Periodicals, Inc. NETWORKS, 2008 [source]

The interaction between model resolution, observation resolution and observation density in data assimilation: A one-dimensional study

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 582 2002
Z.-Q. Liu
Abstract In this paper, the optimal configurations of model resolution, observation resolution and observation density are investigated in a simple one-dimensional framework. In this context, the representativeness error is formalized and estimated before being used in the analysis-error formulation. Some optimal and suboptimal assimilation-schemes, differing from different approximations of observation-error covariance and observation operator, are compared. The optimal observation-extent is determined as a function of model resolution. Increasing the observation density is usually beneficial, except for suboptimal schemes similar to the ones used in operational practice. The impact of thinning the observations with correlated error is also studied from a suboptimal viewpoint. Copyright © 2002 Royal Meteorological Society [source]