452 research outputs found
Potential time-cost benefits from use of orbital-height photographic data in cartographic programs
Cost effectiveness of mapping using satellite- borne photograph
Anharmonic force field and vibrational frequencies of tetrafluoromethane (CF) and tetrafluorosilane (SiF)
Accurate quartic anharmonic force fields for CF and SiF have been
calculated using the CCSD(T) method and basis sets of quality. Based on
the {\it ab initio} force field with a minor empirical adjustment, the
vibrational energy levels of these two molecules and their isotopomers are
calculated by means of high order Canonical Van Vleck Perturbation Theory(CVPT)
based on curvilinear coordinates. The calculated energies agree very well with
the experimental data. The full quadratic force field of CF is further
refined to the experimental data. The symmetrization of the Cartesian basis for
any combination bands of group molecules is discussed using the circular
promotion operator for the doubly degenerate modes, together with tabulated
vector coupling coefficients. The extraction of the spectroscopic constants
from our second order transformed Hamiltonian in curvilinear coordinates is
discussed, and compared to a similar procedure in rectilinear coordinates.Comment: (submitted to J. Chem. Phys.
A Local Mode Study of Ring Puckering Effects in the Infrared Spectra of Cyclopentane
We report and interpret recently recorded high-resolution infrared spectra for the fundamentals of the CH2 scissors and CH stretches of gas phase cyclopentane at −26.1 and −50 ○C, respectively. We extend previous theoretical studies of this molecule, which is known to undergo barrierless pseudorotation due to ring puckering, by constructing local mode Hamiltonians of the stretching and scissor vibrations for which the frequencies, couplings, and linear dipoles are calculated as functions of the pseudorotation angle using B3LYP/6-311++(d,p) and MP2/cc-pVTZ levels of theory. Symmetrization (D5h) of the vibrational basis sets leads to simple vibration/pseudorotation Hamiltonians whose solutions lead to good agreement with the experiment at medium resolution, but which miss interesting line fractionation when compared to the high-resolution spectra. In contrast to the scissor motion, pseudorotation leads to significant state mixing of the CH stretches, which themselves are Fermi coupled to the scissor overtones
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Studies of offshore petroleum leases using a cartoraphic data base system
An innovative system combining techniques of computer graphics and data base management has been developed at the Los Alamos Scientific Laboratory for the United States Geological Survey (USGS). The system is based on a CODASYL-type network data base management system. An interactive query language has been developed to allow standard data base retrievals as well as cartographic display of retrieval results. Map displays include both real-time display on a CRT terminal (such as a Tektronix 4014) and postprocessed full-color display on computer output microfilm. Since the system became operational early in 1978, it has been used in a number of ongoing studies for both the USGS and the Department of Energy (DOE). The primary application to date has been verification of the Lease, Production, and Revenue data (LPR) amassed by the USGS as part of its regulatory responsibility. Over 150 color-coded maps of offshore areas in the Gulf of Mexico have been produced for comparison with hand-drawn originals. This has proved to be an effective verification procedure, because differences between the maps are readily visible. Other current applications include provisions of both data and displays for statistical studies of bidding behavior of oil companies for both USGS and DOE projects
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Extubation and the Risks of Coughing and Laryngospasm in the Era of Coronavirus Disease-19 (COVID-19).
The coronavirus disease-19 (COVID-19) pandemic has prompted new interest among anesthesiologists and intensivists in controlling coughing and expectoration of potentially infectious aerosolized secretions during intubation and extubation. However, the fear of provoking laryngospasm may cause avoidance of deep or sedated extubation techniques which could reduce coughing and infection risk. This fear may be alleviated with clear understanding of the mechanisms and effective management of post-extubation airway obstruction including laryngospasm. We review the dynamic function of the larynx from the vantage point of head-and-neck surgery, highlighting two key concepts: 1. The larynx is a complex organ that may occlude reflexively at levels other than the true vocal folds; 2. The widely held belief that positive-pressure ventilation by mask can "break" laryngospasm is not supported by the otorhinolaryngology literature. We review the differential diagnosis of acute airway obstruction after extubation, discuss techniques for achieving smooth extubation with avoidance of coughing and expectoration of secretions, and recommend, on the basis of this review, a clinical pathway for optimal management of upper airway obstruction including laryngospasm to avoid adverse outcomes
A study of navigation in virtual space
In the physical world, man has developed efficient methods for navigation and orientation. These methods are dependent on the high-fidelity stimuli presented by the environment. When placed in a virtual world which cannot offer stimuli of the same quality due to computing constraints and immature technology, tasks requiring the maintenance of position and orientation knowledge become laborious. In this paper, we present a representative set of techniques based on principles of navigation derived from real world analogs including human and avian navigation behavior and cartography. A preliminary classification of virtual worlds is presented based on the size of the world, the density of objects in the world, and the level of activity taking place in the world. We also summarize an informal study we performed to determine how the tools influenced the subjects' navigation strategies and behavior. We conclude that principles extracted from real world navigation aids such as maps can be seen to apply in virtual environments
The Effect of Online Quizzing on Understanding of Key Concepts in an Introduction to Psychology Course
Students enrolled in Introduction to Psychology were required to complete online chapter-review quizzes as part of their course. Using a within-subjects experimental design, we compared the students’ understanding of key concepts during a week when they were required to take an online review quiz to their understanding of key concepts during a week when an online review quiz was not offered. Results suggest that online quizzing improves understanding of key chapter concepts
High energy vibrational excitations of nitromethane in liquid water
The pathways and timescales of vibrational energy flow in nitromethane are investigated in both gas and condensed phases using classical molecular mechanics, with a particular focus on relaxation in liquid water. We monitor the flow of excess energy deposited in vibrational modes of nitromethane into the surrounding solvent. A marked energy flux anisotropy is found when nitromethane is immersed in liquid water, with a preferential flow to those water molecules in contact to the nitro group. The factors that permit such anisotropic energy relaxation are discussed, along with the potential implications on the molecule's non-equilibrium dynamics. In addition, the energy flux analysis allows us to identify the solvent motions responsible for the uptake of solute energy, confirming the crucial role of water librations. Finally, we also show that no anisotropic vibrational energy relaxation occurs when nitromethane is surrounded by argon gas.A.J.R. acknowledges the financial support from the Departament de Recerca i Universitats de la Generalitat de Catalunya. C.C. acknowledges support from Spanish Grant No. PID2021-124297NB-C31, funded by MCIN/AEI/10.13039/501100011033 and “ERDF A way of making Europe.” E.L.S. gratefully acknowledges support from the NSF via Grant No. CHE-1900095. A.J.R. and R.R. acknowledge support from Grant No. PID2021-124297NB-C32, funded by MCIN/AEI/10.13039/501100011033 and FEDER, and from the Generalitat de Catalunya (Grant No. 2021 SGR 01411).Peer ReviewedPostprint (published version
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