4,251 research outputs found
Design and Performance of Arena Dam
Arena Dam is located in north-central Trinidad, West Indies. The dam forms a 35,000-acre-foot reservoir, which serves as the main raw water storage facility for Trinidad. The 1.6-million-cubic-yard earthfill embankment has a crest elevation 80 feet above the original streambed. The upstream-sloping core is composed of dispersive clay. The shells are composed of compacted fine sand and silty fine sand. The dam is founded on deep, stiff, fissured clay deposits interbedded with sand. The project is located approximately 12 miles from the El Pilar Fault, a major Caribbean fault with seismic activity comparable to that of the San Andreas Fault in the United States. Important design concerns included the dispersive clay core, residual strength properties of the foundation, embankment and control structure settlement, and the seismic environment. This paper discusses the design criteria and approach, and field performance data from foundation and embankment piezometers and survey monuments in the outlet conduit
Inference with interference between units in an fMRI experiment of motor inhibition
An experimental unit is an opportunity to randomly apply or withhold a
treatment. There is interference between units if the application of the
treatment to one unit may also affect other units. In cognitive neuroscience, a
common form of experiment presents a sequence of stimuli or requests for
cognitive activity at random to each experimental subject and measures
biological aspects of brain activity that follow these requests. Each subject
is then many experimental units, and interference between units within an
experimental subject is likely, in part because the stimuli follow one another
quickly and in part because human subjects learn or become experienced or
primed or bored as the experiment proceeds. We use a recent fMRI experiment
concerned with the inhibition of motor activity to illustrate and further
develop recently proposed methodology for inference in the presence of
interference. A simulation evaluates the power of competing procedures.Comment: Published by Journal of the American Statistical Association at
http://www.tandfonline.com/doi/full/10.1080/01621459.2012.655954 . R package
cin (Causal Inference for Neuroscience) implementing the proposed method is
freely available on CRAN at https://CRAN.R-project.org/package=ci
Timing of larval release by two Caribbean demosponges
The timing of larval release has important implications for a larva's potential vulnerability to predators and environmental stresses. For larvae with planktonic periods of only minutes to hours, timing of larval release also determines the light levels that larvae experience, which can strongly influence their settlement behavior. We placed larval traps over colonies of 2 common Caribbean sponges and found that both species released larvae during daylight hours. Niphates digitalis generally releases its larvae between 07:00 and 11:00 h, while Callyspongia vaginalis releases its larvae later in the day. Of 17 captured N. digitalis larvae released 0.5 to i m above the substrate, 13 remained near the bottom, and 8 of these 13 contacted the substrate within 10 min. For shortlived larvae, daytime release and their photonegative behavior at settlement should drive them to settle in shaded microhabitats that protect juveniles from predators and Solar UV radiation. Larvae of N. digitalis and C. vaginalis are distasteful to potential predators; thus they can remain near the bottom with fishes and yet not be consumed. These data support a general co-occurrence of daytime spawning of conspicuous, short-lived larvae and larval distastefulness that previously had been noted only for tropical ascidians
Effects of Wet Corn Gluten Feed and Roughage Inclusion Levels in Finishing Diets Containing Modified Distillers Grains Plus Solubles
A finishing trial evaluated wet corn gluten feed (WCGF) and roughage inclusion levels in diets containing 30% modified distillers grains plus solubles (MDGS, DM basis) using a 3 x 3 factorial treatment structure. No significant WCGF x roughage level interactions were observed. There was a quadratic response due to WCGF level for dry matter intake (DMI) and average daily gain (ADG), which were lowest for cattle fed 30% WCGF; however, feed-gain ratio (F:G) increased linearly with increasing WCGF. Gain responded quadratically and was lowest for cattle fed 0% corn silage. F:G and DMI increased linearly with increasing corn silage. Feedlot performance was improved by feeding 0% or 15% WCGF compared to 30% WCGF in finishing diets containing 30% MDGS. The optimal level was 7.5% corn silage in diets containing 30% MDGS with or without WCGF
Capture Velocity for a Magneto-Optical Trap in a Broad Range of Light Intensity
In a recent paper, we have used the dark-spot Zeeman tuned slowing technique
[Phys. Rev. A 62, 013404-1, (2000)] to measure the capture velocity as a
function of laser intensity for a sodium magneto optical trap. Due to technical
limitation we explored only the low light intensity regime, from 0 to 27
mW/cm^2. Now we complement that work measuring the capture velocity in a
broader range of light intensities (from 0 to 400 mW/cm^2). New features,
observed in this range, are important to understant the escape velocity
behavior, which has been intensively used in the interpretation of cold
collisions. In particular, we show in this brief report that the capture
velocity has a maximum as function of the trap laser intensity, which would
imply a minimum in the trap loss rates.Comment: 2 pages, 2 figure
Bulk gravitons from a cosmological brane
We investigate the emission of gravitons by a cosmological brane into an Anti
de Sitter five-dimensional bulk spacetime. We focus on the distribution of
gravitons in the bulk and the associated production of `dark radiation' in this
process. In order to evaluate precisely the amount of dark radiation in the
late low-energy regime, corresponding to standard cosmology, we study
numerically the emission, propagation and bouncing off the brane of bulk
gravitons.Comment: 27 pages, 5 figures, minor corrections. Final versio
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