29,846 research outputs found
Angular Momentum Distribution Function of the Laughlin Droplet
We have evaluated the angular-momentum distribution functions for finite
numbers of electrons in Laughlin states. For very small numbers of electrons
the angular-momentum state occupation numbers have been evaluated exactly while
for larger numbers of electrons they have been obtained from Monte-Carlo
estimates of the one-particle density matrix. An exact relationship, valid for
any number of electrons, has been derived for the ratio of the occupation
numbers of the two outermost orbitals of the Laughlin droplet and is used to
test the accuracy of the MC calculations. We compare the occupation numbers
near the outer edges of the droplets with predictions based on the chiral
Luttinger liquid picture of Laughlin state edges and discuss the surprisingly
large oscillations in occupation numbers which occur for angular momenta far
from the edge.Comment: 11 pages of RevTeX, 2 figures available on request. IUCM93-00
The Large Area Crop Inventory Experiment (LACIE)
A Large Area Crop Inventory Experiment (LACIE) was undertaken to prove out an economically important application of remote sensing from space. The experiment focused upon determination of wheat acreages in the U.S. Great Plains and upon the development and testing of yield models. The results and conclusions are presented
Calculus on surfaces with general closest point functions
The Closest Point Method for solving partial differential equations (PDEs) posed on surfaces was recently introduced by Ruuth and Merriman [J. Comput. Phys. 2008] and successfully applied to a variety of surface PDEs. In this paper we study the theoretical foundations of this method. The main idea is that surface differentials of a surface function can be replaced with Cartesian differentials of its closest point extension, i.e., its composition with a closest point function. We introduce a general class of these closest point functions (a subset of differentiable retractions), show that these are exactly the functions necessary to satisfy the above idea, and give a geometric characterization this class. Finally, we construct some closest point functions and demonstrate their effectiveness numerically on surface PDEs
Inference in complex biological systems with Gaussian processes and parallel tempering
Parameter inference in mathematical models of complex biological
systems, expressed as coupled ordinary differential equations (ODEs), is a challenging problem. These depend on kinetic parameters, which cannot all be measured and have to be ascertained a different way. However, the computational
costs associated with repeatedly solving the ODEs are often staggering, making
many techniques impractical. Therefore, aimed at reducing this cost, new concepts using gradient matching have been proposed. This paper combines current
adaptive gradient matching approaches, using Gaussian processes, with a parallel tempering scheme, in order to compare 2 different paradigms using the same
nonlinear regression method. We use 2 ODE systems to assess our technique,
showing an improvement over the recent method in Calderhead et al. (2008)
Differences in opinions of occupational physicians on the required competencies by field of practice: results of an international Delphi study
Background:
The activities and work demands of medical professionals, including occupational physicians (OPs), fall into three categories: clinical, academic, and administrative. Work demands of an OP consist of these three categories and additional specialty specific roles and competencies. Research on the core competencies and skills required for OPs have identified high levels of consensus amongst OPs internationally, however these opinions have not been examined between areas of practice specific groups. Furthermore, it has been identified that to a large extent academics are often the group who define the skills required of OPs. The aim of this study is to compare the opinions of OPs grouped by field of practice on the common core competencies required for occupational health (OH) practice using results from an international survey.
Methods:
An international modified Delphi study conducted among OPs, completed in two rounds (Rating-Round 1; Ranking-Round 2) using developed questionnaires based on the specialist training syllabus of a number of countries and expert discussions. Respondents were categorised as Physician, Manager/Physician, and Academic/Physician, based on self-reported job titles and place of work.
Results:
There was good agreement between the Physician and Manager/Physician groups, with the Academic/Physician group deviating the most. The top three and bottom three principle domains (PDs) were in good agreement across all groups. The top three were clinically based and would be considered core OH activities. The PDs with considerable intergroup variance were Environmental Issues Related to Work Practice and Communication Skills, categories which may reflect direct relevance and relative importance to the job tasks of respective groups.
Conclusion:
This study demonstrated general agreement between the three occupational groups. Academic/Physician opinions deviate the most, while good agreement is depicted between the Physician and Manager/Physician groups. The findings of this study can help identify potential gaps in training requirements for OPs and be used as a stepping stone to developing training programmes that are reflective of practice and tailored for those predominantly undertaking these specific roles
Solving eigenvalue problems on curved surfaces using the Closest Point Method
Eigenvalue problems are fundamental to mathematics and science. We present a
simple algorithm for determining eigenvalues and eigenfunctions of the
Laplace--Beltrami operator on rather general curved surfaces. Our algorithm,
which is based on the Closest Point Method, relies on an embedding of the
surface in a higher-dimensional space, where standard Cartesian finite
difference and interpolation schemes can be easily applied. We show that there
is a one-to-one correspondence between a problem defined in the embedding space
and the original surface problem. For open surfaces, we present a simple way to
impose Dirichlet and Neumann boundary conditions while maintaining second-order
accuracy. Convergence studies and a series of examples demonstrate the
effectiveness and generality of our approach
The large area crop inventory experiment: A major demonstration of space remote sensing
Strategies are presented in agricultural technology to increase the resistance of crops to a wider range of meteorological conditions in order to reduce year-to-year variations in crop production. Uncertainties in agricultral production, together with the consumer demands of an increasing world population, have greatly intensified the need for early and accurate annual global crop production forecasts. These forecasts must predict fluctuation with an accuracy, timeliness and known reliability sufficient to permit necessary social and economic adjustments, with as much advance warning as possible
Thematic mapper data quality and performance assessment in renewable resource/agricultural remote sensing
A "quick look" investigation of the initial LANDSAT-4, thematic mapper (TM) scene received from Goddard Space Flight Center was performed to gain early insight into the characteristics of TM data. The initial scene, containing only the first four bands of the seven bands recorded by the TM, was acquired over the Detroit, Michigan, area on July 20, 1982. It yielded abundant information for scientific investigation. A wide variety of studies were conducted to assess all aspects of TM data. They ranged from manual analyses of image products to detect obvious optical, electronic, or mechanical defects to detailed machine analyses of the digital data content for evaluation of spectral separability of vegetative/nonvegetative classes. These studies were applied to several segments extracted from the full scene. No attempt was made to perform end-to-end statistical evaluations. However, the output of these studies do identify a degree of positive performance from the TM and its potential for advancing state-of-the-art crop inventory and condition assessment technology
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