1,556 research outputs found
El valor de la conservación forestal para la protección de la calidad del agua
Forests protect water quality by reducing soil erosion, sedimentation, and pollution; yet there is little information about the economic value of conserving forests for water quality protection in much of the United States. To assess this value, we conducted a meta-analysis of willingness-to-pay (WTP) for protecting unimpaired waters, and econometrically determined several significant drivers of WTP: type of conservation instrument (tool), aquatic resource type, geographic context, spatial scale, time, and household income. Using a benefit transfer to two highly forested sites, we illustrate the importance of these factors on WTP for water quality protection programs, forest conservation and policy design
LightBox: a multiwell plate illumination system for photoactive molecule characterization
Multiwell plates (MWPs) are the workhorses of the life sciences. However, biophotonics research with MWPs is limited, in part due to the lack of equipment suitable for photo‐irradiation of photoactive molecules in a MWP‐suitable, high‐throughput manner, either commercially or through open‐source MWP systems. Here we present “LightBox”, a calibrated controllable MWP illumination system with broad applications including screening of photoactive molecules and characterization of photocatalytic chemicals. LightBox is a high intensity, accurately controllable, uniform illumination system designed for MWPs with electronics and a control unit that provides a simple and intuitive interface. LightBox can reach intensities of 0.23 mW/mm2 at wavelengths of 405 nm with variance between well sites of <5%. The usefulness of LightBox is demonstrated by assessing the IC50 of a photosensitizing compound using a live/dead assay following simultaneous irradiation of the sample at a range of concentrations, eliminating uncontrolled variables between concentrations and drastically increasing assessment speed
Decay of quantised vorticity by sound emission
It is thought that in a quantum fluid sound generation is the ultimate sink
of turbulent kinetic energy in the absence of any other dissipation mechanism
near absolute zero. We show that a suitably trapped Bose-Einstein condensate
provides a model system to study the sound emitted by accelerating vortices in
a controlled way.Comment: 6 pages, 3 figure
Power amplifier for 1083nm using ytterbium-doped fibre
We have demonstrated a power amplifier for a single-frequency signal at 1088nm as required in spectroscopic applications. It is based on a ytterbium doped silica fibre which was pumped by a MOPA semiconductor laser at 978nm. In a preliminary experiment we achieved 14 dB gain and 60 mW of amplified signal. We discuss the design considerations, the possibility of significant improvements of output power and gain, and the relevance of the amplifier for high resolution spectroscopy
The use of the white cell count and haemoglobin in combination as an effective screen to predict the normality of the full blood count
The views of five participating undergraduate students of the Student Associates Scheme in England
This paper reports findings from a study which explored undergraduate perceptions of the Student Associates Scheme in England (SAS). The scheme was established by the Training and Development Agency for Schools in an attempt to increase the number of graduates entering the teaching profession, particularly in shortage subjects such as the physical sciences and mathematics. The scheme places undergraduate students on short-term placements in secondary schools throughout England to provide them with experiences that may encourage them to consider teaching as a career option. Findings show that the SAS school placements were a positive experience for the students participating in this study. However, a question emerged as to whether or not the scheme is targeting students who have yet to decide upon teaching as a career or just reinforcing the existing aspirations of students who have already decided to teach. As the scheme is attempting to increase the number of teachers entering the profession this question has important implications for this study and further work which will focus on undergraduates who think that their career ambitions would not be fulfilled by teaching
Renormalization of composite operators
The blocked composite operators are defined in the one-component Euclidean
scalar field theory, and shown to generate a linear transformation of the
operators, the operator mixing. This transformation allows us to introduce the
parallel transport of the operators along the RG trajectory. The connection on
this one-dimensional manifold governs the scale evolution of the operator
mixing. It is shown that the solution of the eigenvalue problem of the
connection gives the various scaling regimes and the relevant operators there.
The relation to perturbative renormalization is also discussed in the framework
of the theory in dimension .Comment: 24 pages, revtex (accepted by Phys. Rev. D), changes in introduction
and summar
Compaction of Rods: Relaxation and Ordering in Vibrated, Anisotropic Granular Material
We report on experiments to measure the temporal and spatial evolution of
packing arrangements of anisotropic, cylindrical granular material, using
high-resolution capacitive monitoring. In these experiments, the particle
configurations start from an initially disordered, low-packing-fraction state
and under vertical vibrations evolve to a dense, highly ordered, nematic state
in which the long particle axes align with the vertical tube walls. We find
that the orientational ordering process is reflected in a characteristic, steep
rise in the local packing fraction. At any given height inside the packing, the
ordering is initiated at the container walls and proceeds inward. We explore
the evolution of the local as well as the height-averaged packing fraction as a
function of vibration parameters and compare our results to relaxation
experiments conducted on spherically shaped granular materials.Comment: 9 pages incl. 7 figure
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