1,939 research outputs found
Could natural selection change the geographic range limits of light brown apple moth (Lepidoptera, Tortricidae) in North America?
We artificially selected for increased freeze tolerance in the invasive light brown apple moth. Our results suggest that, by not accounting for adaptation to cold, current models of potential geographic distributions could underestimate the areas at risk of exposure to this species
An assessment and validation study of nuclear reactors for low power space applications
The feasibility and safety of six conceptual small, low power nuclear reactor designs was evaluated. Feasibility evaluations included the determination of sufficient reactivity margins for seven years of full power operation and safe shutdown as well as handling during pre-launch assembly phases. Safety evaluations were concerned with the potential for maintaining subcritical conditions in the event of launch or transportation accidents. These included water immersion accident scenarios both with and without water flooding the core. Results show that most of the concepts can potentially meet the feasibility and safety requirements; however, due to the preliminary nature of the designs considered, more detailed designs will be necessary to enable these concepts to fully meet the safety requirements
A 14-day ground-based hypokinesia study in nonhuman primates: A compilation of results
A 14 day ground based hypokinesia study with rhesus monkeys was conducted to determine if a spaceflight of similar duration might affect bone remodeling and calcium homeostatis. The monkeys were placed in total body casts and sacrificed either immediately upon decasting or 14 days after decasting. Changes in vertebral strength were noted and further deterioration of bone strength continued during the recovery phase. Resorption in the vertebrae increased dramatically while formation decreased. Cortical bone formation was impaired in the long bones. The immobilized animals showed a progressive decrease in total serum calcium which rebounded upon remobilization. Most mandibular parameters remained unchanged during casting except for retardation of osteon birth or maturation rate and density distribution of matrix and mineral moieties
The Color-Sharing Bonus:Roles of Perceptual Organization and Attentive Processes in Visual Working Memory
Color repetitions in a visual scene boost memory for its elements, a phenomenon known as the color-sharing effect. This may occur because improved perceptual organization reduces information load or because the repetitions capture attention. The implications of these explanations differ drastically for both the theoretical meaning of this effect and its potential value for applications in design of visual materials. If repetitions capture attention to the exclusion of other details, then use of repetition in visual displays should be confined to emphasized details, but if repetitions reduce the load of the display, designers can assume that the nonrepeated information is also more likely to be attended and remembered. We manipulated the availability of general attention during a visual memory task by comparing groups of participants engaged in meaningless speech or attention-demanding continuous arithmetic. We also tracked eye movements as an implicit indicator of selective attention. Estimated memory capacity was always higher when color duplicates were tested, and under full attention conditions this bonus spilled over to the unique colors too. Analyses of gazes showed that with full attention, participants tended to glance earlier at duplicate colors during stimulus presentation but looked more at unique colors during the retention interval. This pattern of results suggests that the color-sharing bonus reflects efficient perceptual organization of the display based on the presence of repetitions, and possibly strategic attention allocation when attention is available.<br/
MEASURING GAINS IN OPERATIONAL EFFICIENCY FROM INFORMATION TECHNOLOGY: A STUDY OF THE POSITRAN DEPLOYMENT AT HARDEE'S INC.
This paper presents a new approach to measuring the input productivity
gains from information technology (IT) in complex managerial environments. The
approach is illustrated in the context of a study of a pilot deployment at Hardee's Inc.
of a new cash register point-of-safe and order-coordination technology called âPositran."
The method employs data envelopment analysis (DEA) and nonparametric
production frontier hypothesis testing to determine whether the performance of
restaurants that have deployed Positran is better, on average, than for those that have
not. The design of the study is of special interest because it approximates a controlled
experiment. Our results show that Positran helped to reduce input materials costs, since
restaurants that deployed the technology were less likely to be inefficient It is further
possible to characterize the class of restaurants for which the relationship holds.
Operational efficiency measures such as the ones we have developed provide managers
with the opportunity to implement deployment strategies for new ITs in order to
maximize value.Information Systems Working Papers Serie
MEASURING INPUT PRODUCTIVITY GAINS FROM INFORMATION TECHNOLOGY
This paper proposes a new method to measure the input productivity gains from information technology in
complex managerial environments. The method employs a production function which maps output and
relating moderating variables in the managerial environment into input resource consumption, with a
random inefficiency component which can be affected by IT deployment. Sample hypotheses and a sketch
of the F-tests used to identify reductions in input inefficiency are presented, and then illustrated for a new
information technology which has recently been deployed in fast food restaurants.Information Systems Working Papers Serie
Study of resonance light scattering for remote optical probing
Enhanced scattering and fluorescence processes in the visible and UV were investigated which will enable improved remote measurements of gas properties. The theoretical relationship between scattering and fluorescence from an isolated molecule in the approach to resonance is examined through analysis of the time dependence of re-emitted light following excitation of pulsed incident light. Quantitative estimates are developed for the relative and absolute intensities of fluorescence and resonance scattering. New results are obtained for depolarization of scattering excited by light at wavelengths within a dissociative continuum. The experimental work was performed in two separate facilities. One of these utilizes argon and krypton lasers, single moded by a tilted etalon, and a 3/4 meter double monochromator. This facility was used to determine properties of the re-emission from NO2, I2 and O3 excited by visible light. The second facility involves a narrow-line dye laser, and a 3/4 meter single monochromator. The dye laser produces pulsed light with 5 nsec pulse duration and 0.005 nm spectral width
Calculating quasinormal modes of Schwarzschild anti-de Sitter black holes using the continued fraction method
We investigate the scalar, gravitational, and electromagnetic quasinormal
mode spectra of Schwarzschild anti-de Sitter black holes using the numerical
continued fraction method. The spectra have similar, almost linear structures.
With a few exceptions, the low overtone quasinormal modes are consistent with
previously obtained results in the literature that use other numerical
techniques. The intermediate and high overtone quasinormal modes, in comparison
to the Schwarzschild case, converge very quickly to the asymptotic formulas
previously obtained by analytic monodromy techniques. We also determine one of
the purely imaginary modes in the gravitational spectrum to be algebraically
special. In addition, we find a connection between the analytic asymptotic
formulas and the purely imaginary modes. In particular, these formulas can be
used to predict the bifurcation of the lowest damped electromagnetic modes.
Finally, we find no high overtone quasinormal modes with high oscillation
frequency and low damping, which had been previously predicted.Comment: 20 pages, 6 figures, regular article, some typos correcte
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