1,350 research outputs found

    Data analysis and archival

    Get PDF
    The purpose of this task is the acquisition, distribution, archival, and analysis of data collected during and in support of the Upper Atmospheric Research Program (UARP) field experiments. Meteorological and U2 data from the 1984 Stratosphere-Troposphere Exchange Project (STEP) was analyzed to determine characteristics of internal atmospheric waves. CDROM's containing data from the 1987 STEP, 1987 Airborne Antarctic Ozone Expedition (AAOE), and the 1989 Airborne Arctic Stratospheric Expedition (AASE) were produced for archival and distribution of those data sets. The AASE CDROM contains preliminary data and a final release is planned for February 1990. Comparisons of data from the NASA ER-2 Meteorological Measurement System (MMS) with radar tracking and radiosonde data show good agreement. Planning for a Meteorological Support Facility continues. We are investigating existing and proposed hardware and software to receive, manipulate, and display satellite imagery and standard meteorological analyses, forecasts, and radiosonde data

    Sonoelastography of the Common Flexor Tendon of the Elbow with Histologic Agreement: A Cadaveric Study.

    Get PDF
    Purpose To determine the correlation of the results of conventional B-mode ultrasonography (US) and compression sonoelastography with histologic results in common flexor tendons of the elbow in human cadavers. Materials and Methods Twenty-five common flexor tendons were evaluated in 16 fresh, unembalmed cadavers of 11 women with a median age of 85 years (range, 71-101 years) and five men with a median age of 78 years (range, 70-88 years). Informed consent was provided according to the last will of the donors. B-mode US results were classified as grade 1, normal tendon with homogeneous fibrillar pattern; grade 2, tendon thickening or hypoechoic areas and/or calcifications in less than 30% of the tendon; or grade 3, hypoechoic areas and/or calcifications greater than 30% of the tendon. Sonoelastographic results were grade 1, blue (hardest) to green (hard); grade 2, yellow (soft); and grade 3, red (softest). The intraclass correlation coefficient was calculated to determine agreement with histologic findings for each B-mode US, sonoelastographic, and combined B-mode US and sonoelastographic examination. Histologic results were grade 1, normal, with parallel fibrillar pattern; grade 2, mild tendinopathy, with cellular infiltration, angiogenesis, or fatty vacuoles; or grade 3, severe tendinopathy, with loss of parallel collagen structure and necrosis. Results Histologic alterations were detected in 44% (11 of 25) of biopsy specimens. Intraclass correlation with histologic results was 0.57 for B-mode US, 0.68 for sonoelastography, and 0.84 for the combination of the two approaches. Conclusion The addition of sonoelastography to B-mode US provided statistically significant improvement in correlation with histologic results compared with the use of B-mode US alone (P \u3c .02). (©) RSNA, 2016 Online supplemental material is available for this article

    Cloaking and imaging at the same time

    Full text link
    In this letter, we propose a conceptual device to perform subwavelength imaging with positive refraction. The key to this proposal is that a drain is no longer a must for some cases. What's more, this device is an isotropic omnidirectional cloak with a perfect electric conductor hiding region and shows versatile illusion optical effects. Numerical simulations are performed to verify the functionalities.Comment: 15 pages, 4 figure

    Super Weyl invariance: BPS equations from heterotic worldsheets

    Full text link
    It is well-known that the beta functions on a string worldsheet correspond to the target space equations of motion, e.g. the Einstein equations. We show that the BPS equations, i.e. the conditions of vanishing supersymmetry variations of the space-time fermions, can be directly derived from the worldsheet. To this end we consider the RNS-formulation of the heterotic string with (2,0) supersymmetry, which describes a complex torsion target space that supports a holomorphic vector bundle. After a detailed account of its quantization and renormalization, we establish that the cancellation of the Weyl anomaly combined with (2,0) finiteness implies the heterotic BPS conditions: At the one loop level the geometry is required to be conformally balanced and the gauge background has to satisfy the Hermitean Yang-Mills equations.Comment: 1+31 pages LaTeX, 5 figures; final version, discussion relation Weyl invariance and (2,0) finiteness extended, typos correcte

    Enlightened defense: The national security *policy of Thomas Jefferson

    Get PDF
    The triumph of Thomas Jefferson and the Democratic Republicans in 1800 left the deposed Federalists aghast at what this Francophile, anti nationalist, reputedly atheistic president might do to the country. Despite Jefferson\u27s impulses toward pacifism, national isolation, the diffusion of political power, and healing faction, the eight years of his two administrations were destined to be as calm as a hurricane. The turbulent situation in Europe had already made a mockery of Washington\u27s advice to avoid entanglement, and during Jefferson\u27s presidency, the dangers only increased.;Jefferson\u27s ideas on national security were diametrically opposed to those of Alexander Hamilton and the Federalists. Jefferson was an advocate of states\u27 rights, but Hamilton of centralized power. Jefferson wanted to avoid debt, while Hamilton thought debt was a positive and unifying factor. Jefferson believed in maintaining a minuscule standing military in favor of state militias, whereas Hamilton called for a huge, regular army and a sea-going navy. The debate was not an academic one: the young nation was literally surrounded by enemies and potential enemies. Spain had a stranglehold on New Orleans, and the slightest pressure there could (and sometimes did) throttle the entire economy of the American west. Britain, with a firm hold on Canada and total domination of the high seas, bullied the Americans with seemingly unfair commercial practices. When Napoleon began to restrict trade as well, Jefferson and his countrymen faced economic calamity and the threat of wars they would not likely win.;Jefferson introduced legislation that altered the structure of both the army and navy, established the military academy at West Point, and changed the political constitution of the defense establishment. He fought a long, frustrating war with Tripoli, fended off insults from Europe, and struggled to formulate an Indian policy that would protect native Americans while dealing with the reality and inevitability of white domination of the continent. Jefferson also pulled off the most spectacular land deal in history: the Louisiana Purchase---an accretion that doubled the size of the young republic and sowed the seeds for the eventual triumph of Jefferson\u27s strategic calculations.;By the end of his second term, however, Jefferson\u27s initial successes had been eclipsed by the disappointing results of his embargo against Great Britain. Historians roundly condemn the embargo as both ineffective and a direct violation of Jefferson\u27s own ideas on governance. His handling of the military has also been criticized, particularly in the light of America\u27s martial mediocrity in the War of 1812---shortfalls that can be partially attributed to Jefferson\u27s underfunding of the army and navy.;This essay looks critically at the military and national security policies of Thomas Jefferson with a view to penetrating beyond traditional interpretations. By examining closely the political, economic, social, and military context of the times---especially the delicate domestic situation---it is possible to see Jefferson\u27s policies with a new appreciation of how enlightened and ultimately effective they really were

    Ice Nucleation and Dehydration in the Tropical Tropopause Layer

    Get PDF
    Optically thin cirrus near the tropical tropopause regulate the humidity of air entering the stratosphere, which in turn has a strong influence on the Earth's radiation budget and climate. Recent highaltitude, unmanned aircraft measurements provide evidence for two distinct classes of cirrus formed in the tropical tropopause region: (i) vertically extensive cirrus with low ice number concentrations, low extinctions, and large supersaturations (up to approx. 70%) with respect to ice; and (ii) vertically thin cirrus layers with much higher ice concentrations that effectively deplete the vapor in excess of saturation. The persistent supersaturation in the former class of cirrus is consistent with the long time-scales (several hours or longer) for quenching of vapor in excess of saturation given the low ice concentrations and cold tropical tropopause temperatures. The low-concentration clouds are likely formed on a background population of insoluble particles with concentrations less than 100 L1 (often less than 20 L1), whereas the high ice concentration layers (with concentrations up to 10,000 L1) can only be produced by homogeneous freezing of an abundant population of aqueous aerosols. These measurements, along with past high-altitude aircraft measurements, indicate that the low-concentration cirrus occur frequently in the tropical tropopause region, whereas the high-concentration cirrus occur infrequently. The predominance of the low-concentration clouds means cirrus near the tropical tropopause may typically allow entry of air into the stratosphere with as much as approx. 1.7 times the ice saturation mixing ratio
    corecore