6,019 research outputs found
Bank efficiency, ownership and market structure: Why are interest spreads so high in Uganda?.
Calibration of star formation rate tracers for short- and long-lived star formation episodes
To derive the history of star formation in the Universe a set of calibrated
star formation rate tracers at different wavelengths is required. The
calibration has to consistently take into account the effects of extinction,
star formation regime (short or long-lived) and evolutionary state to avoid
biases at different redshift ranges. We use evolutionary synthesis models
optimized for intense episodes of star formation in order to compute a
consistent calibration of the most usual star formation rate tracers at
different energy ranges, from X-ray to radio luminosities. Nearly-instantaneous
and continuous star formation regimes, and the effect of interstellar
extinction are considered, as well as the effect of metallicity on the
calibration of the different estimators. A consistent calibration of a complete
set of star formation rate tracers is presented, computed for the most usual
star-forming regions conditions: evolutionary state, star formation regime,
interstellar extinction and initial mass function. We discuss the validity of
the different tracers in different star formation scenarios and compare our
predictions with previous calibrations of general use. Nearly-instantaneous and
continuous star formation regimes must be distinguished. While the Star
Formation Strength (\msun) should be used for the former, the more common Star
Formation Rate (\msun yr) is only valid for episodes forming stars at a
constant rate during extended periods for time. Moreover, even for the latter,
the evolutionary state should be taken into account, since most SFR tracers
stabilize only after 100 Myr of evolution.Comment: Accepted for publication in A&A, webtool in
http://www.laeff.cab.inta-csic.es/research/sfr/, 19 pages, 10 figures, 14
tables. New version including language style revisio
Activity Identification and Local Linear Convergence of Douglas--Rachford/ADMM under Partial Smoothness
Convex optimization has become ubiquitous in most quantitative disciplines of
science, including variational image processing. Proximal splitting algorithms
are becoming popular to solve such structured convex optimization problems.
Within this class of algorithms, Douglas--Rachford (DR) and alternating
direction method of multipliers (ADMM) are designed to minimize the sum of two
proper lower semi-continuous convex functions whose proximity operators are
easy to compute. The goal of this work is to understand the local convergence
behaviour of DR (resp. ADMM) when the involved functions (resp. their
Legendre-Fenchel conjugates) are moreover partly smooth. More precisely, when
both of the two functions (resp. their conjugates) are partly smooth relative
to their respective manifolds, we show that DR (resp. ADMM) identifies these
manifolds in finite time. Moreover, when these manifolds are affine or linear,
we prove that DR/ADMM is locally linearly convergent. When and are
locally polyhedral, we show that the optimal convergence radius is given in
terms of the cosine of the Friedrichs angle between the tangent spaces of the
identified manifolds. This is illustrated by several concrete examples and
supported by numerical experiments.Comment: 17 pages, 1 figure, published in the proceedings of the Fifth
International Conference on Scale Space and Variational Methods in Computer
Visio
Some causes for porosity and leakage in non-ferrous castings
Non-ferrous copper base alloys find many applications in industry. Among these alloys one finds the tin bronzes rather widely used for many purposes, and by delving still farther one finds pressure castings as one of their important applications. In many foundries the percentage of rejections due to leakage or porosity is quite high. This is obviously very costly since leakage is generally only found after machining. It is with a view to determine the causes for leakage in pressure castings and to devise methods for its prevention that the work described in this thesis was undertaken. It is not intended to cover the subject completely. Furthermore, the author wishes to direct attention to the fact that the work was conducted primarily to increase the knowledge on the behavior of these alloys under certain controlled conditions and that no attempt was made to adhere to existing specifications other than chemical composition --Statement of Problem, page 1
Scattering of non-uniform incident fields by long cylinders
Copyright University of BremenWe investigate experimentally far-field scattering from cylinders with illumination non-uniform along the axis of the cylinder. Scattered intensity as a function of angle in two orthogonal directions is examined. Variation along the scattering angle is found to be little affected by the illumination profile. However, variation in the transverse direction follows closely the Fourier transform of the illumination pattern and reproduces the angular distribution of the incident wave. These finding apply to circular as well as hexagonal cross-section cylinders
Consistent structural linearisation in flexible-body dynamics with large rigid-body motion
A consistent linearisation, using perturbation methods, is obtained for the structural degrees of freedom of flexible slender bodies with large rigid-body motions. The resulting system preserves all couplings between rigid and elastic motions and can be projected onto a few vibration modes of a reference configuration. This gives equations of motion with cubic terms in the rigid-body degrees of freedom and constant coefficients which can be pre-computed prior to the time-marching simulation. Numerical results are presented to illustrate the approach and to show its advantages with respect to mean-axes approximations
Dynamic Load Alleviation in Wake Vortex Encounters
This paper introduces an integrated approach for flexible-aircraft timedomain
aeroelastic simulation and controller design suitable for wake encounter
situations. The dynamic response of the vehicle, which may be
subject to large wing deformations in trimmed flight, is described by a
geometrically-nonlinear finite-element model. The aerodynamics are modeled
using the unsteady vortex lattice method and include the arbitrary
time-domain downwash distributions of a wake encounter. A consistent
linearization in the structural degrees of freedom enables the use of balancing
methods to reduce the problem size while retaining the nonlinear
terms in the rigid-body equations. Numerical studies on a high-altitude,
long-endurance aircraft demonstrate the reduced-order modeling approach
for load calculations in wake vortex encounters over a large parameter space. Closed-loop results finally explore the potential of combining feedforward/feedback
Hâ control and distributed control surfaces to obtain
significant load reductions
The functional subdivision of the visual brain : Is there a real illusion effect on action? A multi-lab replication study
Acknowledgements We thank Brian Roberts and Mike Harris for responding to our questions regarding their paper; Zoltan Dienes for advice on Bayes factors; Denise Fischer, Melanie Römer, Ioana Stanciu, Aleksandra Romanczuk, Stefano Uccelli, Nuria Martos SĂĄnchez, and Rosa MarĂa Beño Ruiz de la Sierra for help collecting data; Eva Viviani for managing data collection in Parma. We thank Maurizio Gentilucci for letting us use his lab, and the Centro Intradipartimentale Mente e Cervello (CIMeC), University of Trento, and especially Francesco Pavani for lending us his motion tracking equipment. We thank Rachel Foster for proofreading. KKK was supported by a Ph.D. scholarship as part of a grant to VHF within the International Graduate Research Training Group on Cross-Modal Interaction in Natural and Artificial Cognitive Systems (CINACS; DFG IKG-1247) and TS by a grant (DFG â SCHE 735/3-1); both from the German Research Council.Peer reviewedPostprin
Improving the nutritive value of rice seeds: elevation of cysteine and methionine contents in rice plants by ectopic expression of a bacterial serine acetyltransferase
With the aim of increasing the cysteine level in rice (Oryza sativa L.) and thus improving its nutritional quality, transgenic rice plants were generated expressing an Escherichia coli serine acetyltransferase isoform (EcSAT), the enzyme synthesizing O-acetylserine, the precursor of cysteine. The gene was fused to the transit peptide of the Arabidopsis Rubisco and driven by a ubiquitin promoter to target the enzyme to plastids. Twenty-two transgenic plants were examined for transgene protein expression, and five lines with a high expression level and enzymatic activity, respectively, were selected for further analysis. In these lines, the contents of cysteine and glutathione increased 2.4-fold and 2-fold, respectively. More important is the increase in free methionine and methionine incorporated into the water-soluble protein fraction in seeds. Free methionine increased in leaves up to 2.7-fold, in seeds up to 1.4-fold, and bound to seed proteins up to 4.8-fold, respectively, while the bound methionine level remained constant or even decreased in leaves. Notably, the transgenic lines exhibited higher isoleucine, leucine, and valine contents (each up to 2-fold depending on tissue, free, or bound), indicating a potential conversion of methionine via methionine -lyase to isoleucine. As the transgenic rice plants overexpressing EcSAT had significantly higher levels of both soluble and protein-bound methionine, isoleucine, cysteine, and glutathione in rice they may represent a model and target system for improving the nutritional quality of cereal crops
A light scattering instrument for investigating cloud ice microcrystal morphology
We describe an optical scattering instrument designed to assess the shapes and sizes of microscopic atmospheric cloud particles, especially the smallest ice crystals that can profoundly affect cloud processes and radiative properties yet cannot be seen clearly using in situ cloud particle imaging probes. The new instrument captures high-resolution spatial light scattering patterns from individual particles down to ~1 ÎŒm in size passing through a laser beam. Its significance lies in the ability of these patterns to provide morphological data for particle sizes well below the optical resolution limits of current probes
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