14,405 research outputs found
Technological learning: towards an integrated model
The acquisition and growth of technological knowledge is fundamental to competitive advantage in the emerging knowledge economy. This article explores the notion of technological learning as a means of developing the capabilities that underpin long term sustainable innovation. The research project was designed to identify new ways of understanding learning in the context of technology-driven SMEs, so the methods employed were essentially inductive in nature. This has resulted in the development of a comprehensive framework comprising four inter-related knowledge categories (Identity, Direction, Capability, and Relationship), each of which has an associated learning process (learning by reflecting, learning by strategising, learning by doing, and learning by interacting). We argue that it is the interaction between these knowledge categories that generates the new insights that are essential to technological learning
A Powerful New Quantitative Genetics Platform, Combining Caenorhabditis elegans High-Throughput Fitness Assays with a Large Collection of Recombinant Strains.
The genetic variants underlying complex traits are often elusive even in powerful model organisms such as Caenorhabditis elegans with controlled genetic backgrounds and environmental conditions. Two major contributing factors are: (1) the lack of statistical power from measuring the phenotypes of small numbers of individuals, and (2) the use of phenotyping platforms that do not scale to hundreds of individuals and are prone to noisy measurements. Here, we generated a new resource of 359 recombinant inbred strains that augments the existing C. elegans N2xCB4856 recombinant inbred advanced intercross line population. This new strain collection removes variation in the neuropeptide receptor gene npr-1, known to have large physiological and behavioral effects on C. elegans and mitigates the hybrid strain incompatibility caused by zeel-1 and peel-1, allowing for identification of quantitative trait loci that otherwise would have been masked by those effects. Additionally, we optimized highly scalable and accurate high-throughput assays of fecundity and body size using the COPAS BIOSORT large particle nematode sorter. Using these assays, we identified quantitative trait loci involved in fecundity and growth under normal growth conditions and after exposure to the herbicide paraquat, including independent genetic loci that regulate different stages of larval growth. Our results offer a powerful platform for the discovery of the genetic variants that control differences in responses to drugs, other aqueous compounds, bacterial foods, and pathogenic stresses
Event Horizons in Numerical Relativity I: Methods and Tests
This is the first paper in a series on event horizons in numerical
relativity. In this paper we present methods for obtaining the location of an
event horizon in a numerically generated spacetime. The location of an event
horizon is determined based on two key ideas: (1) integrating backward in time,
and (2) integrating the whole horizon surface. The accuracy and efficiency of
the methods are examined with various sample spacetimes, including both
analytic (Schwarzschild and Kerr) and numerically generated black holes. The
numerically evolved spacetimes contain highly distorted black holes, rotating
black holes, and colliding black holes. In all cases studied, our methods can
find event horizons to within a very small fraction of a grid zone.Comment: 22 pages, LaTeX with RevTeX 3.0 macros, 20 uuencoded gz-compressed
postscript figures. Also available at http://jean-luc.ncsa.uiuc.edu/Papers/
Submitted to Physical Review
Strain-induced magnetic phase transition in SrCoO thin films
It has been well established that both in bulk at ambient pressure and for
films under modest strains, cubic SrCoO () is a
ferromagnetic metal. Recent theoretical work, however, indicates that a
magnetic phase transition to an antiferromagnetic structure could occur under
large strain accompanied by a metal-insulator transition. We have observed a
strain-induced ferromagnetic to antiferromagnetic phase transition in
SrCoO films grown on DyScO substrates, which provide a large
tensile epitaxial strain, as compared to ferromagnetic films under lower
tensile strain on SrTiO substrates. Magnetometry results demonstrate the
existence of antiferromagnetic spin correlations and neutron diffraction
experiments provide a direct evidence for a G-type antiferromagnetic structure
with Ne\'el temperatures between and depending on the oxygen content of the samples. Therefore, our
data experimentally confirm the predicted strain-induced magnetic phase
transition to an antiferromagnetic state for SrCoO thin films
under large epitaxial strain.Comment: 6 pages, 4 figure
Phases of massive scalar field collapse
We study critical behavior in the collapse of massive spherically symmetric
scalar fields. We observe two distinct types of phase transition at the
threshold of black hole formation. Type II phase transitions occur when the
radial extent of the initial pulse is less than the Compton
wavelength () of the scalar field. The critical solution is that
found by Choptuik in the collapse of massless scalar fields. Type I phase
transitions, where the black hole formation turns on at finite mass, occur when
. The critical solutions are unstable soliton stars with
masses \alt 0.6 \mu^{-1}. Our results in combination with those obtained for
the collapse of a Yang-Mills field~{[M.~W. Choptuik, T. Chmaj, and P. Bizon,
Phys. Rev. Lett. 77, 424 (1996)]} suggest that unstable, confined solutions to
the Einstein-matter equations may be relevant to the critical point of other
matter models.Comment: 5 pages, RevTex, 4 postscript figures included using psfi
Potential mechanical loss mechanisms in bulk materials for future gravitational wave detectors
Low mechanical loss materials are needed to further decrease thermal noise in
upcoming gravitational wave detectors. We present an analysis of the
contribution of Akhieser and thermoelastic damping on the experimental results
of resonant mechanical loss measurements. The combination of both processes
allows the fit of the experimental data of quartz in the low temperature region
(10 K to 25 K). A fully anisotropic numerical calculation over a wide
temperature range (10 K to 300 K) reveals, that thermoelastic damping is not a
dominant noise source in bulk silicon samples. The anisotropic numerical
calculation is sucessfully applied to the estimate of thermoelastic noise of an
advanced LIGO sized silicon test mass.Comment: 7 pages, 3 figures, submitted to Journal of Physics: Conference
Series (AMALDI8
The Evolution of Distorted Rotating Black Holes II: Dynamics and Analysis
We have developed a numerical code to study the evolution of distorted,
rotating black holes. This code is used to evolve a new family of black hole
initial data sets corresponding to distorted ``Kerr'' holes with a wide range
of rotation parameters, and distorted Schwarzschild black holes with odd-parity
radiation. Rotating black holes with rotation parameters as high as
are evolved and analyzed in this paper. The evolutions are generally carried
out to about , where is the ADM mass. We have extracted both the
even- and odd-parity gravitational waveforms, and find the quasinormal modes of
the holes to be excited in all cases. We also track the apparent horizons of
the black holes, and find them to be a useful tool for interpreting the
numerical results. We are able to compute the masses of the black holes from
the measurements of their apparent horizons, as well as the total energy
radiated and find their sum to be in excellent agreement with the ADM mass.Comment: 26 pages, LaTeX with RevTeX 3.0 macros. 27 uuencoded gz-compressed
postscript figures. Also available at http://jean-luc.ncsa.uiuc.edu/Papers/
Submitted to Physical Review
Transverse-Longitudinal Coupling by Space Charge in Cyclotrons
A method is presented that enables to compute the parameters of matched beams
with space charge in cyclotrons with emphasis on the effect of the
transverse-longitudinal coupling. Equations describing the
transverse-longitudinal coupling and corresponding tune-shifts in first order
are derived for the model of an azimuthally symmetric cyclotron. The
eigenellipsoid of the beam is calculated and the transfer matrix is transformed
into block-diagonal form. The influence of the slope of the phase curve on the
transverse-longitudinal coupling is accounted for. The results are generalized
and numerical procedures for the case of an AVF cyclotron are presented. The
algorithm is applied to the PSI Injector II and Ring cyclotron and the results
are compared to TRANSPORT.Comment: 8 pages, 2 figure
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