4,420 research outputs found
On the robust determination of eigenmodes in 2D stratified wave guiding systems with Berenger-type PML's.
A contour integration method is presented to determine the eigenmodes in a layered structure closed with PML layers at the boundaries of the computational window. Improvements are provided to ensure the accuracy of contour integration and to assure that all the encircled eigenvalues are determined. Numerical examples are presented to test the accuracy of the method
Opportunity for development or necessary nuisance? The case for viewing working with interpreters as a bonus in therapeutic work
This paper explores the central role a language interpreter can play in the process of the therapeutic relationship. Although others have described the changes to the therapeutic dyad that the presence of a third party (an interpreter) brings, little attention has been paid to the advantages and additional opportunities of this altered therapeutic situation. This paper details these gains and further argues that clinicians who are willing to gain experience of working with interpreters will find that benefits accrue at the micro and macro levels: at the micro level, through enhancement of their work with individual non English speaking clients, and at the macro level through learning about different cultural perspectives, idioms of distress and the role of language in the therapeutic endeavour. This is in addition to developing skills to fulfil legal and professional requirements relating to equity of service provision. Some ideas are offered to explain the negative slant than runs throughout the literature in this area and tends to colour the overall discussion of therapeutic work with interpreters and, before the final section, makes some specific suggestions which may help maximise the gains possible in such work while reducing difficulties
First detection of galaxy-galaxy-galaxy lensing in RCS. A new tool for studying the matter environment of galaxy pairs
The weak gravitational lensing effect, small coherent distortions of galaxy
images by means of a gravitational tidal field, can be used to study the
relation between the matter and galaxy distribution. In this context, weak
lensing has so far only been used for considering a second-order correlation
function that relates the matter density and galaxy number density as a
function of separation. We implement two new, third-order correlation functions
that have recently been suggested in the literature, and apply them to the
Red-Sequence Cluster Survey. We demonstrate that it is possible, even with
already existing data, to make significant measurements of third-order lensing
correlations. We develop an optimised computer code for the correlation
functions. To test its reliability a set of tests are performed. The
correlation functions are transformed to aperture statistics, which allow easy
tests for remaining systematics in the data. In order to further verify the
robustness of our measurement, the signal is shown to vanish when randomising
the source ellipticities. Finally, the lensing signal is compared to crude
predictions based on the halo-model. On angular scales between roughly 1 arcmin
and 11 arcmin a significant third-order correlation between two lens positions
and one source ellipticity is found. We discuss this correlation function as a
novel tool to study the average matter environment of pairs of galaxies.
Correlating two source ellipticities and one lens position yields a less
significant but nevertheless detectable signal on a scale of 4 arcmin. Both
signals lie roughly within the range expected by theory which supports their
cosmological origin.[ABRIDGED]Comment: 15 pages, 12 figures, accepted by A&A; minor change
Stable Food Crops Turning Into Commercial Crops: Case Studies Of Teff, Wheat And Rice In Ethiopia
Teff, wheat and rice are becoming important market oriented crops in Ethiopia. This study aims at measuring the level of market orientation of households in these crops, identifying the important market places and market outlets used by producers, and analyzing the determinants of market orientation in these crops. Results are based on analysis of data collected from community (peasant association) and household surveys in three districts in three regional states of the country in 2005. Analysis of descriptive information and econometric analysis are used. About 65 - 77% of households produce these market oriented commodities in the study areas, on about 27 â 44% of the total cultivated land. About 47 â 60% of the produce of these market oriented commodities is sold. The important market places for producers of these commodities are the district town markets and markets located at the peasant associations within the district. Wholesalers and retailers are the most important buyers from producers. Average distance to market places for these commodities is about two walking hours. Econometric analyses show that market orientation of households is affected by a host of factors related to household demographics, household endowments of human and physical capital, access to institutional services, and village level factors. Size of cultivable land and traction power, and household labor supply are important factors that induce households to be market oriented. While household size tends to favor food security objectives, number of dependents is associated with market orientation. Population control measures could contribute to market orientation through their effect of reducing household subsistence requirements. Our results also imply that interventions to improvements markets operations in order to benefit producers need to consider the operation of district level markets. Improving the operations of factor markets of land, traction and farm labor could contribute to enhancing market orientation of farm households. Special attention is needed to female headed households in the process of commercial transformation of subsistence agriculture. The development and institutionalization of marketing extension warrants due consideration
Intrinsic galaxy shapes and alignments II: Modelling the intrinsic alignment contamination of weak lensing surveys
Intrinsic galaxy alignments constitute the major astrophysical systematic of
forthcoming weak gravitational lensing surveys but also yield unique insights
into galaxy formation and evolution. We build analytic models for the
distribution of galaxy shapes based on halo properties extracted from the
Millennium Simulation, differentiating between early- and late-type galaxies as
well as central galaxies and satellites. The resulting ellipticity correlations
are investigated for their physical properties and compared to a suite of
current observations. The best-faring model is then used to predict the
intrinsic alignment contamination of planned weak lensing surveys. We find that
late-type galaxy models generally have weak intrinsic ellipticity correlations,
marginally increasing towards smaller galaxy separation and higher redshift.
The signal for early-type models at fixed halo mass strongly increases by three
orders of magnitude over two decades in galaxy separation, and by one order of
magnitude from z=0 to z=2. The intrinsic alignment strength also depends
strongly on halo mass, but not on galaxy luminosity at fixed mass, or galaxy
number density in the environment. We identify models that are in good
agreement with all observational data, except that all models over-predict
alignments of faint early-type galaxies. The best model yields an intrinsic
alignment contamination of a Euclid-like survey between 0.5-10% at z>0.6 and on
angular scales larger than a few arcminutes. Cutting 20% of red foreground
galaxies using observer-frame colours can suppress this contamination by up to
a factor of two.Comment: 23 pages, 14 figures; minor changes to match version published in
MNRA
Metal-insulator transition in YHx: scaling of the sub-THz conductivity
The established scaling laws of the conductivity with temperature and doping
are strong indications for the quantum nature of the metal-insulator transition
in YH. Here we report the first results on the frequency scaling of the
conductivity. Samples were brought from the insulating to the metallic phase by
carrier doping via illumination. In the metallic phase, the sub-terahertz
conductivity coincides with the dc data. These results do not agree with the
simplest picture of a quantum-phase transition.Comment: 4 pages, accepted to PR
A framework for multi-scale modelling
We review a methodology to design, implement and execute multi-scale and multi-science numerical simulations. We identify important ingredients of multi-scale modelling and give a precise definition of them. Our framework assumes that a multi-scale model can be formulated in terms of a collection of coupled single-scale submodels. With concepts such as the scale separation map, the generic submodel execution loop (SEL) and the coupling templates, one can define a multi-scale modelling language which is a bridge between the application design and the computer implementation. Our approach has been successfully applied to an increasing number of applications from different fields of science and technology
Multiscale modelling and simulation: a position paper
We argue that, despite the fact that the field of multiscale modelling and simulation has enjoyed significant success within the past decade, it still holds many open questions that are deemed important but so far have barely been explored. We believe that this is at least in part due to the fact that the field has been mainly developed within disciplinary silos. The principal topics that in our view would benefit from a targeted multidisciplinary research effort are related to reaching consensus as to what exactly one means by âmultiscale modellingâ, formulating a generic theory or calculus of multiscale modelling, applying such concepts to the urgent question of validation and verification of multiscale models, and the issue of numerical error propagation in multiscale models. Moreover, we believe that this would, in principle, also lay the foundation for more efficient, well-defined and usable multiscale computing environments. We believe that multidisciplinary research to fill in the gaps is timely, highly relevant, and with substantial potential impact on many scientific disciplines
Land, water and carbon footprints of circular bioenergy production systems
Renewable energy sources can help combat climate change but knowing the land, water and carbon implications of different renewable energy production mixes becomes a key. This paper systematically applies land, water and carbon footprint accounting methods to calculate resource appropriation and CO 2eq GHG emissions of two energy scenarios. The â100% scenarioâ is meant as a thinking exercise and assumes a complete transition towards bioenergy, mostly as bioelectricity and some first-generation biofuel. The âSDS-bio scenarioâ is inspired by IEA's sustainable development scenario and assumes a 9.8% share of bioenergy in the final mix, with a high share of first-generation biofuel. Energy inputs into production are calculated by differentiating inputs into fuel versus electricity and exclude fossil fuels used for non-energy purposes. Results suggest that both scenarios can lead to emission savings, but at a high cost of land and water resources. A 100% shift to bioenergy is not possible from water and land perspectives. The SDS-bio scenario, when using the most efficient feedstocks (sugar beet and sugarcane), would still require 11â14% of the global arable land and a water flow equivalent to 18â25% of the current water footprint of humanity. In comparative terms, using sugar or starchy crops to produce bioenergy results in smaller footprints than using oil-bearing crops. Regardless of the choice of crop, converting the biomass to combined heat and power results in smaller land, water and carbon footprints per unit of energy than when converting to electricity alone or liquid biofuel
Finding halo streams with a pencil-beam survey: new wraps in the Sagittarius stream
We use data from two CFHT-MegaCam photometric pencil-beam surveys in the g'
and the r' bands to measure distances to the Sagittarius, the Palomar 5 and the
Orphan stream. We show that, using a cross-correlation algorithm to detect the
turnoff point of the main sequence, it is possible to overcome the main
limitation of a two-bands pencil-beam survey, namely the lack of adjacent
control-fields that can be used to subtract the foreground and background stars
to enhance the signal on the colour-magnitude diagrams (CMDs). We describe the
cross-correlation algorithm and its implementation. We combine the resulting
main sequence turnoff points with theoretical isochrones to derive photometric
distances to the streams. Our results (31 detections on the Sagittarius stream
and one each for the Palomar 5 and the Orphan streams) confirm the findings by
previous studies, expand the distance trend for the Sagittarius faint southern
branch and, for the first time, trace the Sagittarius faint branch of the
northern-leading arm out to 56 kpc. In addition, they show evidence for new
substructure: we argue that these detections trace the continuation of the
Sagittarius northern-leading arm into the southern hemisphere, and find a
nearby branch of the Sagittarius trailing wrap in the northern hemisphere.Comment: 16 pages, 15 figures, 2 table
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