5,984 research outputs found
Study of the modifications needed for effective operation NASTRAN on IBM virtual storage computers
The necessary modifications were determined to make NASTRAN operational under virtual storage operating systems (VS1 and VS2). Suggested changes are presented which will make NASTRAN operate more efficiently under these systems. Estimates of the cost and time involved in design, coding, and implementation of all suggested modifications are included
Operative versus nonoperative treatment of acute Achilles tendon ruptures: A pilot economic decision analysis
Background: The operative treatment of Achilles tendon ruptures has been associated with lower rerupture rates and better function but also a risk of surgery-related complications compared with nonoperative treatment, which may provide improved outcomes with accelerated rehabilitation protocols. However, economic decision analyses integrating the updated costs of both treatment options are limited in the literature.
Purpose: To compare the cost-effectiveness of operative and nonoperative treatment of acute Achilles tendon tears.
Study Design: Economic and decision analysis; Level of evidence, 2.
Methods: An economic decision model was built to assess the cost-utility ratio (CUR) of open primary repair versus nonoperative treatment for acute Achilles tendon ruptures, based on direct costs from the practices of sports medicine and foot and ankle surgeons at a single tertiary academic center, with published outcome probabilities and patient utility data. Multiway sensitivity analyses were performed to reflect the range of data.
Results: Nonoperative treatment was more cost-effective in the average scenario (nonoperative CUR, US1995), but crossover occurred during the sensitivity analysis (nonoperative CUR range, US2079; operative CUR range, US8380). Operative treatment cost an extra average marginal CUR of US$1475 compared with nonoperative treatment, assuming uneventful healing in both treatment arms. The sensitivity analysis demonstrated a decreased marginal CUR of operative treatment when the outcome utility was maximized, and rerupture rates were minimized compared with nonoperative treatment.
Conclusion: Nonoperative treatment was more cost-effective in average scenarios. Crossover indicated that open primary repair would be favorable for maximized outcome utility, such as that for young athletes or heavy laborers. The treatment decision for acute Achilles tendon ruptures should be individualized. These pilot results provide inferences for further longitudinal analyses incorporating future clinical evidence
Simultaneous Red - Blue Lidar and Airborne Impactor Measurements
Simultaneous two-color (0.6943 micrometers and 0.3472 micrometers) LIDAR measurements were made in the troposphere and lower stratosphere over Boulder, Colorado during March 1973. In addition, on the evening of March 26, airborne single-stage impactor measurements were made at four altitudes-- 10,500, 25,000, 33,000 and 43,000 feet MSL. These data were integrated at constant altitude for 15,45, 45, and 60 minutes respectively. The LIDAR data were taken with Langley's 48" LIDAR using a dichroic beamsplitter to separate the return at 0.6943 micrometers and 0.3472 micrometers. The analog waveforms for both colors were digitized simultaneously; one on an NCAR data acquisition system and the other on the 48" Langley data acquisition system. A discussion of the preliminary results from these measurements will be presented
Natural Cycles, Gases
The major gaseous components of the exhaust of stratospheric aircraft are expected to be the products of combustion (CO2 and H2O), odd nitrogen (NO, NO2 HNO3), and products indicating combustion inefficiencies (CO and total unburned hydrocarbons). The species distributions are produced by a balance of photochemical and transport processes. A necessary element in evaluating the impact of aircraft exhaust on the lower stratospheric composition is to place the aircraft emissions in perspective within the natural cycles of stratospheric species. Following are a description of mass transport in the lower stratosphere and a discussion of the natural behavior of the major gaseous components of the stratospheric aircraft exhaust
Tropospheric Transmissivity Measurements Using the Raman Nitrogen Lidar Technique
LIDAR measurements in Azusa, California, during October 1972, were made in which the backscattered Raman-shifted nitrogen return was ratioed at different altitudes in order to obtain transmissivity. Rawinsonde data from nearby El Monte were used to determine the temperature and nitrogen number density altitude profiles. These data and other meteorological data are compared to the vertical aerosol and transmissivity structure determined by LIDAR. Also data analysis techniques are shown for obtaining q2 (transmissivity) and beta (attenuation coefficient) as a function of altitude
Optimizing end-labeled free-solution electrophoresis by increasing the hydrodynamic friction of the drag-tag
We study the electrophoretic separation of polyelectrolytes of varying
lengths by means of end-labeled free-solution electrophoresis (ELFSE). A
coarse-grained molecular dynamics simulation model, using full electrostatic
interactions and a mesoscopic Lattice Boltzmann fluid to account for
hydrodynamic interactions, is used to characterize the drag coefficients of
different label types: linear and branched polymeric labels, as well as
transiently bound micelles.
It is specifically shown that the label's drag coefficient is determined by
its hydrodynamic size, and that the drag per label monomer is largest for
linear labels. However, the addition of side chains to a linear label offers
the possibility to increase the hydrodynamic size, and therefore the label
efficiency, without having to increase the linear length of the label, thereby
simplifying synthesis. The third class of labels investigated, transiently
bound micelles, seems very promising for the usage in ELFSE, as they provide a
significant higher hydrodynamic drag than the other label types.
The results are compared to theoretical predictions, and we investigate how
the efficiency of the ELFSE method can be improved by using smartly designed
drag-tags.Comment: 32 pages, 11 figures, submitted to Macromolecule
Closed-Loop Perching and Spatial Guidance Laws for Bio-Inspired Articulated Wing MAV
This paper presents the underlying theoretical developments and successful experimental demonstrations of perching of an aerial robot. The open-loop lateral-directional dynamics of the robot are inherently unstable because it lacks a vertical tail for agility, similar to birds. A unique feature of this robot is that it uses wing articulation for controlling the flight path angle as well as the heading. New guidance algorithms with guaranteed stability are obtained by rewriting the flight dynamic equations in the spatial domain rather than as functions of time, after which dynamic inversion is employed. It is shown that nonlinear dynamic inversion naturally leads to proportional-integral-derivative (PID) controllers, thereby providing an exact method for tuning the gains. The effectiveness of the proposed bio-inspired robot design and its novel closed-loop perching controller has been successfully demonstrated with perched landings on a human hand
Extracting non-linear integrate-and-fire models from experimental data using dynamic I–V curves
The dynamic I–V curve method was recently introduced for the efficient experimental generation of reduced neuron models. The method extracts the response properties of a neuron while it is subject to a naturalistic stimulus that mimics in vivo-like fluctuating synaptic drive. The resulting history-dependent, transmembrane current is then projected onto a one-dimensional current–voltage relation that provides the basis for a tractable non-linear integrate-and-fire model. An attractive feature of the method is that it can be used in spike-triggered mode to quantify the distinct patterns of post-spike refractoriness seen in different classes of cortical neuron. The method is first illustrated using a conductance-based model and is then applied experimentally to generate reduced models of cortical layer-5 pyramidal cells and interneurons, in injected-current and injected- conductance protocols. The resulting low-dimensional neuron models—of the refractory exponential integrate-and-fire type—provide highly accurate predictions for spike-times. The method therefore provides a useful tool for the construction of tractable models and rapid experimental classification of cortical neurons
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Training experience at Experimental Breeder Reactor II
The EBR-II Training Group develops, maintains,and oversees training programs and activities associated with the EBR-II Project. The group originally spent all its time on EBR-II plant-operations training, but has gradually spread its work into other areas. These other areas of training now include mechanical maintenance, fuel manufacturing facility, instrumentation and control, fissile fuel handling, and emergency activities. This report describes each of the programs and gives a statistical breakdown of the time spent by the Training Group for each program. The major training programs for the EBR-II Project are presented by multimedia methods at a pace controlled by the student. The Training Group has much experience in the use of audio-visual techniques and equipment, including video-tapes, 35 mm slides, Super 8 and 16 mm film, models, and filmstrips. The effectiveness of these techniques is evaluated in this report
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