1,351 research outputs found
Toward a history of the space shuttle. An annotated bibliography
This selective, annotated bibliography discusses those works judged to be most essential for researchers writing scholarly studies on the Space Shuttle's history. A thematic arrangement of material concerning the Space Shuttle will hopefully bring clarity and simplicity to such a complex subject. Subjects include the precursors of the Space Shuttle, its design and development, testing and evaluation, and operations. Other topics revolve around the Challenger accident and its aftermath, promotion of the Space Shuttle, science on the Space Shuttle, commercial uses, the Space Shuttle's military implications, its astronaut crew, the Space Shuttle and international relations, the management of the Space Shuttle Program, and juvenile literature. Along with a summary of the contents of each item, judgments have been made on the quality, originality, or importance of some of these publications. An index concludes this work
Master of Science
thesisThis study introduces a pipeline for the temporal dilation of canine cardiac signals following registration to human torsos. Performing registration of data attained from canine electrophysiology studies to human torso geometries allows for a larger database for the investigation of human-like arrhythmias that cannot be readily obtained otherwise. However, during registration, the canine cardiac signals must be adjusted to correct spatially dependent aspects of propagation, such as conduction velocity (CV), that are influenced by increased heart size. We refer to this correction process as "temporal dilation'' as it includes resampling of the cardiac signals. We acquired 10 canine cardiac recordings from electrodes built into socks that covered the epicardial surface of the ventricles. The sock geometries were registered to two human torsos. From this spatial transform, we calculated both global and local scaling factors needed to adjust the time signals. Signals were then dilated with both scaling types using linear and nonlinear techniques. The linear method homogeneously dilated the entire signal and the nonlinear technique dilated segments of the signals outside the QRS and T wave. Dilated cardiac signals were validated by comparison of calculated values of CV, total activation time (TAT), and activation recovery interval (ARI). Activation maps also served as a means of qualitative comparison. The observed ECG metrics of canine cardiac signals after temporal dilation using global scaling closely resembled those from human recordings in terms of CV, ARI, and TAT. Temporally dilated signals using local scaling, in contrast, caused the observed ECG metrics to no longer remain within a physiologically relevant range. A realistic activation pattern was maintained after temporal dilation using global scaling. Though temporal dilation using locally calculated scaling factors did not result in physiologically relevant cardiac signals to humans, homogenous temporal dilation could be used to correct the spatially dependent aspects of propagation after geometric registration of canine hearts to human torso geometries. Homogenous temporal dilation, therefore, is a technique that can be used to generate human-like cardiac signals useful for validation of devices used to diagnose, monitor, or intervene in cases of cardiac arrhythmias
Immediate disclosure or secrecy? The release of information in experimental asset markets
The Federal Reserve has made significant changes in its predisposition to release information over time. This paper reports the results of experimental asset markets designed to investigate how the public disclosure of uncertain information affects market and individual outcomes. In one set of markets, no information is released at the beginning of each trading year. In two other sets, an imperfect pre-announcement of the state of nature is disclosed. The reliability of the pre-announcement (60 percent and 90 percent) varies across treatments. Halfway through each trading year, the state of nature is revealed. By year-end, price deviations from Bayesian predictions are similar across all treatments; however, price volatility is significantly higher and allocational efficiency significantly lower with a pre-announcement that reflects substantial uncertainty. Furthermore, when the reliability of the pre-announcement is low (60 percent), the distribution in profit across traders is significantly greater even though the average profit is similar across treatments. Thus, in a highly uncertain environment better outcomes may actually result when information is withheld
Harsh Parenting and Food Insecurity in Adolescence: The Association with Emerging Adult Obesity
In the U.S., as of 2012, more than one in three youth were overweight or obese [1]. This is a critical health issue, as being overweight or obese (OW/OB) during adolescence increases the risk of adulthood diseases, including but not limited to cardiovascular and heart disease, diabetes, stroke, cancer, and osteoarthritis [2]. Understanding the pathways to obesity is critical for implementation of successful prevention and intervention programs. One of the pathways leading to OW/OB is through social and economic experiences within the family
Calcium dynamics and circadian rhythms in suprachiasmatic nucleus neurons
The hypothalamic suprachiasmatic nucleus (SCN) has a pivotal role in the mammalian circadian clock. SCN neurons generate circadian rhythms in action potential firing frequencies and neurotransmitter release, and the core oscillation is thought to be driven by "clock gene" transcription-translation feedback loops. Cytosolic Ca2+ mobilization followed by stimulation of various receptors has been shown to reset the gene transcription cycles in SCN neurons, whereas contribution of steady-state cytosolic Ca2+ levels to the rhythm generation is unclear. Recently, circadian rhythms in cytosolic Ca2+ levels have been demonstrated in cultured SCN neurons. The circadian Ca2+ rhythms are driven by the release of Ca2+ from ryanodine-sensitive internal stores and resistant to the blockade of action potentials. These results raise the possibility that gene translation/transcription loops may interact with autonomous Ca2+ oscillations in the production of circadian rhythms in SCN neurons
947-111 IkBlockade Selectively Eliminates Slow Antegrade Atrioventricular Nodal Conduction in the Rabbit
We studied the effects of an Ikblocker, risotilide (R) on the dynamic properties of perfused rabbit AV nodes using intermittent right atrial premature pacing and bipolar surface electrograms. R was serially perfused with 1, 3 and6× 10–6M R for 15 minutes following pre-drug measurements.ResultsTypical changes in the antegrade recovery curve produced by R are shown in the figure. There was a concentration dependent decrease in Δ.AH from the pre-drug value of 56±15 ms to 29.2±16.9 ms and 13.7±5.9 ms by 3 and6× 10-6M respectively (n = 6). A reciprocal increase in the AV node effective refractory period was observed from 91±15 ms (pre-drug) to 139±16 ms (3×10-6M) and 170±16 ms (6 × 10-6M). AH∝ was unchanged at any concentration of R.ConclusionsThese results suggest that class III antiarrhythmic agents may increase action potential duration and the refractory period of the structure(s) limiting AV conduction and thereby eliminate a majority of the “slow” AV node conduction. These findings may have important implications for a pharmacologic approach to the treatment of AV node reentry tachycardias
Assessing landscape dust emission potential using combined ground‐based measurements and remote sensing data
Modeled estimates of aeolian dust emission can vary by an order of magnitude due to the spatiotemporal heterogeneity of emissions. To better constrain location and magnitude of emissions, a surface erodibility factor is typically employed in models. Several landscape-scale schemes representing surface dust-emission potential for use in models have recently been proposed, but validation of such schemes has only been attempted indirectly with medium-resolution remote sensing of mineral aerosol loadings and high-resolution land-surface mapping. In this study, we used dust-emission source points identified in Namibia with Landsat imagery together with field-based dust-emission measurements using a Portable In-situ Wind Erosion Laboratory (PI-SWERL) wind tunnel to assess the performance of schemes aiming to represent erodibility in global dust-cycle modeling. From analyses of the surface and samples taken at the time of wind tunnel testing, a Boosted Regression Tree analysis identified the significant factors controlling erodibility based on PI-SWERL dust flux measurements and various surface characteristics, such as soil moisture, particle size, crusting degree and mineralogy. Despite recent attention to improving the characterisation of surface dust-emission potential, our assessment indicates a high level of variability in the measured fluxes within similar geomorphologic classes. This variability poses challenges to dust modelling attempts based on geomorphology and/or spectral-defined classes. Our approach using high-resolution identification of dust sources to guide ground-based testing of emissivity offers a valuable means to help constrain and validate dust-emission schemes. Detailed determination of the relative strength of factors controlling emission can provide further improvement to regional and global dust-cycle modeling
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Draft principles, policy, and acceptance criteria for decommissioning of U.S. Department of Energy contaminated surplus facilities and summary of international decommissioning programs
Decommissioning activities enable the DOE to reuse all or part of a facility for future activities and reduce hazards to the general public and any future work force. The DOE Office of Environment, Health and Safety has prepared this document, which consists of decommissioning principles and acceptance criteria, in an attempt to establish a policy that is in agreement with the NRC policy. The purpose of this document is to assist individuals involved with decommissioning activities in determining their specific responsibilities as identified in Draft DOE Order 5820.DDD, ``Decommissioning of US Department of Energy Contaminated Surplus Facilities`` (Appendix A). This document is not intended to provide specific decommissioning methodology. The policies and principles of several international decommissioning programs are also summarized. These programs are from the IAEA, the NRC, and several foreign countries expecting to decommission nuclear facilities. They are included here to demonstrate the different policies that are to be followed throughout the world and to allow the reader to become familiar with the state of the art for environment, safety, and health (ES and H) aspects of nuclear decommissioning
Ornamental plants, 1985: a summary of research
Field transplant survival of Amelanchier liners produced by tissue culture / Daniel K. Struve and R. Daniel Lineberger -- An evaluation of strawdust - an alternative growing media / Elton M. Smith and Sharon A. Treaster -- Growth of container grown nursery stock produced in composted municipal sludge amended media / Elton M. Smith and Sharon A. Treaster -- Soil temperature effects on root regeneration of scarlet oak seedlings / Daniel K. Struve arid Bruno C. Moser -- Lighting Viburnum opulus 'Nanum' cuttings to increase winter survival / Elton M. Smith and Sharon A. Treaster -- Treatments of etiolated dormant rose shoots / Elton M. Smith and Sharon A. Treaster -- Evaluation of flowering crabapple susceptibility to apple scab in Ohio – 1984 / Elton M. Smith and Sharon A. Treaster -- Tolerance of azalea, cotoneaster, and euonymus to Devrinol, Goal, and Goal Combinations / Elton M. Smith and Sharon A. Treaster -- Micropropagation of chimeral african violets / R. Daniel Lineberger and Mark Druckenbrod -- capital requirements of overwintering structures for nurseries in Ohio - 1984 / Reed D. Taylor, Daryl T. Gillette, and Elton M. Smith -- annual fixed costs of overwintering plants in nurseries differentiated by type of structure for Ohio - 1984 / Daryl T. Gillette, Reed D. Taylor, and Elton M. Smith -- Comparative costs of overwintering plants in nurseries differentiated by system for Ohio - 1984 / Reed D. Taylor, Daryl T. Gillette, and Elton M. Smit
Molecular and Subcellular-Scale Modeling of Nucleotide Diffusion in the Cardiac Myofilament Lattice
AbstractContractile function of cardiac cells is driven by the sliding displacement of myofilaments powered by the cycling myosin crossbridges. Critical to this process is the availability of ATP, which myosin hydrolyzes during the cross-bridge cycle. The diffusion of adenine nucleotides through the myofilament lattice has been shown to be anisotropic, with slower radial diffusion perpendicular to the filament axis relative to parallel, and is attributed to the periodic hexagonal arrangement of the thin (actin) and thick (myosin) filaments. We investigated whether atomistic-resolution details of myofilament proteins can refine coarse-grain estimates of diffusional anisotropy for adenine nucleotides in the cardiac myofibril, using homogenization theory and atomistic thin filament models from the Protein Data Bank. Our results demonstrate considerable anisotropy in ATP and ADP diffusion constants that is consistent with experimental measurements and dependent on lattice spacing and myofilament overlap. A reaction-diffusion model of the half-sarcomere further suggests that diffusional anisotropy may lead to modest adenine nucleotide gradients in the myoplasm under physiological conditions
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