626 research outputs found
Paving the Way: The Influence of Early Research and Development Programs on Apollo, Saturn, and Legacy System Development
As we celebrate the 50th anniversary of the first successful human landings on the surface of the Moon in 1969, it is insightful to review the many historic accomplishments that contributed to this astounding human achievement. While the Apollo Program officially began following the charge by United States President John F. Kennedy in 1961, much of the foundation for Apollo was already underway with early research and development that began as early as the close of the second World War. Innovations and key decisions prior to the formal initiation of the Apollo Program, and even prior to the formation of the National Aeronautics and Space Administration (NASA), enabled the relatively rapid development of the Saturn V rocket, the Apollo capsule, and the Lunar Lander systems needed to achieve the goal of landing humans on the Moon and returning them safely to Earth by the close of the 1960s
Transverse electric scattering widths for strips-Fourier transform technique
A technique which is based on Fourier transformations is introduced for predicting scattering widths. For a strip it is shown that explicit determination of the linear current density is not necessary for bistatic or monostatic scattering width calculations. Comparisons of the predictions of the technique are made with the integral equation technique predictions, which do not require explicit evaluations of linear current densities
An analysis of the effects of secondary reflections on dual-frequency reflectometers
The error-producing mechanism involving secondary reflections in a dual-frequency, distance measuring reflectometer is examined analytically. Equations defining the phase, and hence distance, error are derived. The error-reducing potential of frequency-sweeping is demonstrated. It is shown that a single spurious return can be completely nullified by optimizing the sweep width
Electronic compensation for reflector surface distortion to improve radiation pattern characteristics of antennas
A simple procedure is described for determining the excitation coefficients of an array feed which compensates for the surface distortion of a reflector antenna to improve the radiation pattern in such a way as to approximate the performance of the undistorted antenna. A computer simulation for a practical feed array is presented as an example of compensation for the distortion of an actual antenna
Development of electromagnetic analysis methods for large aperture antennas
Both deterministic and statistical analysis methods for investigating large aperture antenna radiation patterns are examined. The effects of surface errors on radiation patterns are discussed
Precise targeted integration by a chimaeric transposase zinc-finger fusion protein
Transposons of the Tc1/mariner family have been used to integrate foreign DNA stably into the genome of a large variety of different cell types and organisms. Integration is at TA dinucleotides located essentially at random throughout the genome, potentially leading to insertional mutagenesis, inappropriate activation of nearby genes, or poor expression of the transgene. Here, we show that fusion of the zinc-finger DNA-binding domain of Zif268 to the C-terminus of ISY100 transposase leads to highly specific integration into TA dinucleotides positioned 6-17 bp to one side of a Zif268 binding site. We show that the specificity of targeting can be changed using Zif268 variants that bind to sequences from the HIV-1 promoter, and demonstrate a bacterial genetic screen that can be used to select for increased levels of targeted transposition. A TA dinucleotide flanked by two Zif268 binding sites was efficiently targeted by our transposase-Zif268 fusion, suggesting the possibility of designer ‘Z-transposases’ that could deliver transgenic cargoes to chosen genomic locations
Quantifying the Relationship between Capability and Health in Older People: Can't Map, Won't Map
BACKGROUND: Intuitively, health and capability are distinct but linked concepts. This study aimed to quantify the link between a measure of health status (EQ-5D-3L) and capability (ICECAP-O) using regression-based methods. METHODS: EQ-5D-3L and ICECAP-O data were collected from a sample of older people ( n = 584), aged over 65 years, requiring a hospital visit and/or care home resident, and recruited to one of 3 studies forming the Medical Crisis in Older People (MCOP) program in England. The link of EQ-5D-3L with 1) ICECAP-O tariff scores were estimated using ordinary least squares (OLS) or censored least absolute deviation (CLAD) regression models; and 2) ICECAP-O domain scores was estimated using multinomial logistic (MNL) regression. Mean absolute error (MAE), root mean squared error (RMSE), absolute difference (AD) between mean observed and estimated values, and the R(2) statistic were used to judge model performance. RESULTS: In this sample of older people ( n = 584), higher scores on the EQ-5D-3L were shown to be linked with higher ICECAP-O scores when using linear regression. An OLS-regression model was identified to be the best performing model with the lowest error statistics (AD = 0.0000; MAE = 0.1208; MSE = 0.1626) and highest goodness of fit ( R(2) = 0.3532); model performance was poor when predicting the lower ICECAP-O tariff scores. The three domains of the EQ-5D-3L showing a statistically significant quantifiable link with the ICECAP-O tariff score were self-care, usual activities, and anxiety/depression. CONCLUSION: A quantifiable, but weak, link between health (EQ-5D-3L) and capability (ICECAP-O) was identified. The findings from this study add further support that the ICECAP-O is providing complimentary information to the EQ-5D-3L. Mapping between the 2 measures is not advisable and the measures should not be used as direct substitutes to capture the impact of interventions in economic evaluations
Global Emergency Medicine: A Review of the Literature From 2012
Objectives The Global Emergency Medicine Literature Review ( GEMLR ) conducts an annual search of peer‐reviewed and grey literature relevant to global emergency medicine ( EM ) to identify, review, and disseminate the most important new research in this field to a worldwide audience of academics and clinical practitioners. Methods This year, our search identified 4,818 articles written in six languages. These articles were distributed among 20 reviewers for initial screening based on their relevance to the field of global EM . Two additional reviewers searched and screened the grey literature. A total of 224 articles were deemed appropriate by at least one reviewer and were approved by their editor for formal scoring of overall quality and importance. Results Of the 224 articles that met our predetermined inclusion criteria, 56% were categorized as Emergency Care in Resource‐limited Settings, 18% as EM development, and 26% as Disaster and Humanitarian Response. A total of 28 articles received scores of 16 or higher and were selected for formal summary and critique. Inter‐rater reliability for two reviewers using our scoring system was good, with an intraclass correlation coefficient of 0.625 (95% confidence interval = 0.512 to 0.711). Conclusions In 2012 there were more disaster and humanitarian response articles than in previous years. As in prior years, the majority of articles addressed the acute management of infectious diseases or the care of vulnerable populations such as children and pregnant women. Resumen Medicina de Urgencias y Emergencias Global: Una Revisión de la Literatura de 2012 Objetivos La revisión de la literatura publicada en Medicina de Urgencias y Emergencias ( MUE ) global comporta una búsqueda anual de los trabajos relevantes para la MUE global, tanto publicados tras revisión por pares como corresponedientes a literatura gris. La finalidad es identificar, revisar y diseminar las investigaciones novedosas más importantes en este campoa médicos clínicos y universitarios de todo el mundo. Metodología Este año, nuestra búsqueda identificó 4.818 artículos escritos en seis lenguas. Estos artículos se distribuyeron entre 20 revisores para el despistaje inicial basándose en su relevancia para el campo de la MUE global. Dos revisores adicionales buscaron y filtraron la literatura gris. Un total de 224 artículos se consideraron apropiados por al menos un revisor, y se aprobaron por su editor para la puntuación formal de la calidad e importancia totales. Resultados De los 224 artículos que cumplieron nuestros criterios de inclusión predeterminados, un 56% se clasificaron como atención de urgencias y emergencias en ámbitos de recursos limitados, un 18% como desarrollo de la MUE y un 26% como catástrofes y respuesta humanitaria. Un total de 28 artículos recibieron una puntuación de 16 o más y se seleccionaron para el resumen y la crítica formal. La fiabilidad interobservador para los 2 revisores usando nuestro sistema de puntuación fue buena, con un coeficiente de correlación intraclase de 0,625 ( IC 95% = 0,512 a 0,711). Conclusiones En 2012 hubo más artículos sobre catástrofes y respuesta humanitaria que en años anteriores. Como en los años previos, la mayoría de los artículos valoraron el manejo agudo de enfermedades infecciosas o la atención de poblaciones vulnerables como los niños y las mujeres embarazadas.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/99685/1/acem12173.pd
Superconductors with Magnetic Impurities: Instantons and Sub-gap States
When subject to a weak magnetic impurity potential, the order parameter and
quasi-particle energy gap of a bulk singlet superconductor are suppressed.
According to the conventional mean-field theory of Abrikosov and Gor'kov, the
integrity of the energy gap is maintained up to a critical concentration of
magnetic impurities. In this paper, a field theoretic approach is developed to
critically analyze the validity of the mean field theory. Using the
supersymmetry technique we find a spatially homogeneous saddle-point that
reproduces the Abrikosov-Gor'kov theory, and identify instanton contributions
to the density of states that render the quasi-particle energy gap soft at any
non-zero magnetic impurity concentration. The sub-gap states are associated
with supersymmetry broken field configurations of the action. An analysis of
fluctuations around these configurations shows how the underlying supersymmetry
of the action is restored by zero modes. An estimate of the density of states
is given for all dimensionalities. To illustrate the universality of the
present scheme we apply the same method to study `gap fluctuations' in a normal
quantum dot coupled to a superconducting terminal. Using the same instanton
approach, we recover the universal result recently proposed by Vavilov et al.
Finally, we emphasize the universality of the present scheme for the
description of gap fluctuations in d-dimensional superconducting/normal
structures.Comment: 18 pages, 9 eps figure
Integrated Testing Approaches for the NASA Ares I Crew Launch Vehicle
The Ares I crew launch vehicle is being developed by the U.S. National Aeronautics and Space Administration (NASA) to provide crew and cargo access to the International Space Station (ISS) and, together with the Ares V cargo launch vehicle, serves as a critical component of NASA's future human exploration of the Moon. During the preliminary design phase, NASA defined and began implementing plans for integrated ground and flight testing necessary to achieve the first human launch of Ares I. The individual Ares I flight hardware elements - including the first stage five segment booster (FSB), upper stage, and J-2X upper stage engine - will undergo extensive development, qualification, and certification testing prior to flight. Key integrated system tests include the upper stage Main Propulsion Test Article (MPTA), acceptance tests of the integrated upper stage and upper stage engine assembly, a full-scale integrated vehicle ground vibration test (IVGVT), aerodynamic testing to characterize vehicle performance, and integrated testing of the avionics and software components. The Ares I-X development flight test will provide flight data to validate engineering models for aerodynamic performance, stage separation, structural dynamic performance, and control system functionality. The Ares I-Y flight test will validate ascent performance of the first stage, stage separation functionality, validate the ability of the upper stage to manage cryogenic propellants to achieve upper stage engine start conditions, and a high-altitude demonstration of the launch abort system (LAS) following stage separation. The Orion 1 flight test will be conducted as a full, un-crewed, operational flight test through the entire ascent flight profile prior to the first crewed launch
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