2,038 research outputs found
A model of human event detection in multiple process monitoring situations
It is proposed that human decision making in many multi-task situations might be modeled in terms of the manner in which the human detects events related to his tasks and the manner in which he allocates his attention among his tasks once he feels events have occurred. A model of human event detection performance in such a situation is presented. An assumption of the model is that, in attempting to detect events, the human generates the probability that events have occurred. Discriminant analysis is used to model the human's generation of these probabilities. An experimental study of human event detection performance in a multiple process monitoring situation is described and the application of the event detection model to this situation is addressed. The experimental study employed a situation in which subjects simulataneously monitored several dynamic processes for the occurrence of events and made yes/no decisions on the presence of events in each process. Input to the event detection model of the information displayed to the experimental subjects allows comparison of the model's performance with the performance of the subjects
Pilot interaction with automated airborne decision making systems
An investigation was made of interaction between a human pilot and automated on-board decision making systems. Research was initiated on the topic of pilot problem solving in automated and semi-automated flight management systems and attempts were made to develop a model of human decision making in a multi-task situation. A study was made of allocation of responsibility between human and computer, and discussed were various pilot performance parameters with varying degrees of automation. Optimal allocation of responsibility between human and computer was considered and some theoretical results found in the literature were presented. The pilot as a problem solver was discussed. Finally the design of displays, controls, procedures, and computer aids for problem solving tasks in automated and semi-automated systems was considered
Classification of Very Red Stars Using Narrowband Colors
A classification technique for faint, very red stars is described, based on two composite colors, derived from flux measurements in six narrowbands in the visual and red parts of the spectrum. One of the composite colors, ST, is an M spectral type indicator, common to both dwarfs and giants. It can be used to predict the spectral types to within half a class. The other color, DG, is a dwarf-giant discriminator for spectral types later than about M4, and whose power increases for the later types, where most other methods fail. It reflects the differences in blanketing between the late-M type dwarfs and the giants. The method can be generalized to other, similar colors, depending on the data and task at hand. It should be useful in surveys for extreme low-mass dwarfs, or alternatively, for luminous red giants, or other kinds of objects. We illustrate the application of the method on an example of a very red star identified earlier by Blair and Long, and show it to be a distant red giant
Teaching and understanding of quantum interpretations in modern physics courses
Just as expert physicists vary in their personal stances on interpretation in
quantum mechanics, instructors vary on whether and how to teach interpretations
of quantum phenomena in introductory modern physics courses. In this paper, we
document variations in instructional approaches with respect to interpretation
in two similar modern physics courses recently taught at the University of
Colorado, and examine associated impacts on student perspectives regarding
quantum physics. We find students are more likely to prefer realist
interpretations of quantum-mechanical systems when instructors are less
explicit in addressing student ontologies. We also observe contextual
variations in student beliefs about quantum systems, indicating that
instructors who choose to address questions of ontology in quantum mechanics
should do so explicitly across a range of topics.Comment: 18 pages, references, plus 2 pages supplemental materials. 8 figures.
PACS: 01.40.Fk, 03.65.-
EPR before EPR: a 1930 Einstein-Bohr thought experiment revisited
In 1930 Einstein argued against consistency of the time-energy uncertainty
relation by discussing a thought experiment involving a measurement of mass of
the box which emitted a photon. Bohr seemingly triumphed over Einstein by
arguing that the Einstein's own general theory of relativity saves the
consistency of quantum mechanics. We revisit this thought experiment from a
modern point of view at a level suitable for undergraduate readership and find
that neither Einstein nor Bohr was right. Instead, this thought experiment
should be thought of as an early example of a system demonstrating nonlocal
"EPR" quantum correlations, five years before the famous
Einstein-Podolsky-Rosen paper.Comment: 11 pages, revised, accepted for publication in Eur. J. Phy
J.S. Bell's Concept of Local Causality
John Stewart Bell's famous 1964 theorem is widely regarded as one of the most
important developments in the foundations of physics. It has even been
described as "the most profound discovery of science." Yet even as we approach
the 50th anniversary of Bell's discovery, its meaning and implications remain
controversial. Many textbooks and commentators report that Bell's theorem
refutes the possibility (suggested especially by Einstein, Podolsky, and Rosen
in 1935) of supplementing ordinary quantum theory with additional ("hidden")
variables that might restore determinism and/or some notion of an
observer-independent reality. On this view, Bell's theorem supports the
orthodox Copenhagen interpretation. Bell's own view of his theorem, however,
was quite different. He instead took the theorem as establishing an "essential
conflict" between the now well-tested empirical predictions of quantum theory
and relativistic \emph{local causality}. The goal of the present paper is, in
general, to make Bell's own views more widely known and, in particular, to
explain in detail Bell's little-known mathematical formulation of the concept
of relativistic local causality on which his theorem rests. We thus collect and
organize many of Bell's crucial statements on these topics, which are scattered
throughout his writings, into a self-contained, pedagogical discussion
including elaborations of the concepts "beable", "completeness", and
"causality" which figure in the formulation. We also show how local causality
(as formulated by Bell) can be used to derive an empirically testable Bell-type
inequality, and how it can be used to recapitulate the EPR argument.Comment: 19 pages, 4 figure
Towards More Accurate Molecular Dynamics Calculation of Thermal Conductivity. Case Study: GaN Bulk Crystals
Significant differences exist among literature for thermal conductivity of
various systems computed using molecular dynamics simulation. In some cases,
unphysical results, for example, negative thermal conductivity, have been
found. Using GaN as an example case and the direct non-equilibrium method,
extensive molecular dynamics simulations and Monte Carlo analysis of the
results have been carried out to quantify the uncertainty level of the
molecular dynamics methods and to identify the conditions that can yield
sufficiently accurate calculations of thermal conductivity. We found that the
errors of the calculations are mainly due to the statistical thermal
fluctuations. Extrapolating results to the limit of an infinite-size system
tend to magnify the errors and occasionally lead to unphysical results. The
error in bulk estimates can be reduced by performing longer time averages using
properly selected systems over a range of sample lengths. If the errors in the
conductivity estimates associated with each of the sample lengths are kept
below a certain threshold, the likelihood of obtaining unphysical bulk values
becomes insignificant. Using a Monte-Carlo approach developed here, we have
determined the probability distributions for the bulk thermal conductivities
obtained using the direct method. We also have observed a nonlinear effect that
can become a source of significant errors. For the extremely accurate results
presented here, we predict a [0001] GaN thermal conductivity of 185 at 300 K, 102 at 500 K, and 74
at 800 K. Using the insights obtained in the work, we have achieved a
corresponding error level (standard deviation) for the bulk (infinite sample
length) GaN thermal conductivity of less than 10 , 5 , and 15 at 300 K, 500 K, and 800 K respectively
Vitamins A & D Inhibit the Growth of Mycobacteria in Radiometric Culture
The role of vitamins in the combat of disease is usually conceptualized as acting by modulating the immune response of an infected, eukaryotic host. We hypothesized that some vitamins may directly influence the growth of prokaryotes, particularly mycobacteria. complex).Vitamins A and D cause dose-dependent inhibition of all three mycobacterial species studied. Vitamin A is consistently more inhibitory than vitamin D. The vitamin A precursor, β-carotene, is not inhibitory, whereas three vitamin A metabolites cause inhibition. Vitamin K has no effect. Vitamin E causes negligible inhibition in a single strain.We show that vitamin A, its metabolites Retinyl acetate, Retinoic acid and 13-cis Retinoic acid and vitamin D directly inhibit mycobacterial growth in culture. These data are compatible with the hypothesis that complementing the immune response of multicellular organisms, vitamins A and D may have heretofore unproven, unrecognized, independent and probable synergistic, direct antimycobacterial inhibitory activity
Intravitreal bevacizumab injections for diabetic macular edema - predictors of response: a retrospective study
BACKGROUND: Outcomes of intravitreal antivascular endothelial growth factor injections are variable among patients with diabetic macular edema (DME). The aim of this study was to determine the ocular and systemic predictors of DME response to intravitreal bevacizumab (IVB). METHODS: Retrospective review over 2 years of 78 eyes from 54 patients. An anatomical response to IVB was defined as a 20% reduction in central macula thickness after the first course (three injections) of IVB. RESULTS: Twenty-eight percent of patients had an anatomical response after the first course of IVB. Systemic hypertension (odds ratio, 95% confidence interval: 12.1, 0.7-21) was a statistically significant predictor (P=0.025) of a good response to IVB, whereas previous macular laser was a statistically significant (P=0.0005) predictor of a poor response (0.07, 0.01-0.32). Sixty-eight percent of eyes underwent subsequent treatment for DME after the first course of IVB. The visual acuity gain at 24 months in hypertensive (0.7±3.6 letters) and nonhypertensive (5.2±3.7 letters) patients was not significantly different (P=0.41). CONCLUSION: Hypertension and previous macular laser were positive and negative predictors of response to IVB, respectively. However, long-term visual acuity changes were not significantly different between eyes with and without systemic hypertension
Infrared photometry and spectroscopy of the brown dwarf candidate PC0025+0447
We have obtained I, J, H, Kf and L' photometry and infrared spectroscopy (λ/Δλ ≃ 100) from 1.2-2.4 µm of the unusual emission line M star PC0025+0447. The near infrared photometry shows that this star has infrared colors which are comparable to the latest M dwarf stars such as LHS 2924 and LHS 2065. The infrared colors of PC0025+0447 establish that this star is a dwarf and not a distant giant. The infrared spectrum is dominated by strong H_2O absorption bands, and these bands are the
strongest measured in any dwarf. Since H_2O band strength increases with decreasing temperature it is very likely that PC0025-f 0447 is substantially cooler than any of the stars calibrated by Berriman & Reid [MNRAS, 227, 315 (1987)], i.e. T_(eff) 10^9 yr) H burning star, with M ≃ 0.08 M_☉, or a younger brown dwarf
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