4,407 research outputs found

    Extratropical Cyclogenesis and Frontal Waves on Mars: Influences on Dust, Weather and the Planet's climate

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    Between late autumn and early spring, middle and high latitudes on Mars exhibit strong equatortopole mean temperature contrasts (i.e., "baroclinicity"). Data collected during the Viking era and observations from both the Mars Global Surveyor (MGS) and Mars Reconnaissance Orbiter (MRO) indicate that this strong baroclinicity supports vigorous, large-scale eastward traveling weather systems (i.e., transient synoptic periodwaves) [1,2]. For a rapidly rotating, differentially heated, shallow atmosphere such as on Earth and Mars, these large-scale, extratropical weather disturbances are critical components of the global circulation. The wavelike disturbances act as agents in the transport of heat and momentum between low and high latitudes of the planet. Through cyclonic/anticyclonic winds, intense shear deformations, contractions-dilatations in temperature and density, and sharp perturbations amongst atmospheric tracers (i.e., dust, volatiles (e.g., water vapor) and condensates (e.g., water-ice cloud particles)), Mars extratropical weather systems have significant subsynoptic scale ramifications by supporting atmospheric frontal waves (Fig. 1)

    Compounding the Results: The Integration of Virtual Worlds With the Semantic Web

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    Over the past 20 years, governmental use of Web-base information and technologies has continually expanded taking advantage of the Web's vast, ever- expanding volumes of browser-accessible information. Now, it infuses two new technologies, the first one espousing a world where semantic-powered applications become knowledgeable assistants for Web users. The second new technology takes a perceivably flat two-dimensional approach to presenting current Web-content and adds a three-dimensional perspective to the presentation. Welcome to the Semantic Web as seen through the eyes of a Virtual World participant, an environment where Web users no longer are browsing for information that is largely static, where Web users interact through their proxies (avatars) query applications (Web agents) soliciting them to collect, filter, verify, correlate and present answers to their queries often in a more visually palatable three-dimensional format. Following a brief overview of these two technologies, this article presents several of the key force drivers behind their evolution and the benefits gleaned from their collective use. Further discussion identifies new methods for visualizing semantic content in virtual worlds. Finally, as with any technological evolution, the merge of these two technologies brings on a whole new set of challenges from a Web userÕs perspective as well as perspectives from technology developers both in academia and government

    Examining Seasonal Trends of the Martian Polar Warming with the NASA Ames Mars Global Climate Model

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    The presented work focuses on polar warming as a diagnostic of the mean circulation to increase our understanding of processes that control the mean meridional circulation and transport in the Mars middle atmosphere. The NASA Ames Mars Global Climate Model is utilized to isolate physical processes to determine their impact on polar warming and its seasonal trends

    Rotational Evolution During Type I X-Ray Bursts

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    The rotation rates of six weakly-magnetic neutron stars accreting in low-mass X-ray binaries have most likely been measured by Type I X-ray burst observations with RXTE. The nearly coherent oscillations detected during the few seconds of thermonuclear burning are most simply understood as rotational modulation of brightness asymmetries on the neutron star surface. We show that, as suggested by Strohmayer and colleagues, the frequency changes of 1-2 Hz observed during bursts are consistent with angular momentum conservation as the burning shell hydrostatically expands and contracts. We calculate how vertical heat propagation through the radiative outer layers of the atmosphere and convection affect the coherence of the oscillation. We show that the evolution of the rotational profile depends strongly on whether the burning layers are composed of pure helium or mixed hydrogen/helium. Our results help explain the absence (presence) of oscillations from hydrogen-burning (helium-rich) bursts that was found by Muno and collaborators. We investigate angular momentum transport within the burning layers and the recoupling of the burning layers with the star. We show that the Kelvin-Helmholtz instability is quenched by the strong stratification, and that mixing between the burning fuel and underlying ashes by the baroclinic instability does not occur. However, the baroclinic instability may have time to operate within the differentially rotating burning layer, potentially bringing it into rigid rotation.Comment: To appear in The Astrophysical Journal; minor corrections made to tables and figure

    Met Receptor Inhibitor SU11274 Localizes in the Endoplasmic Reticulum

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    We discovered that SU11274, a class I c-Met inhibitor, fluoresces when excited by 488 nm laser light and showed rapid specific accumulation in distinct subcellular compartments. Given that SU11274 reduces cancer cell viability, we exploited these newly identified spectral properties to determine SU11274 intracellular distribution and accumulation in human pancreatic cancer cells. The aim of the studies reported here was to identify organelle(s) to which SU11274 is trafficked. We conclude that SU11274 rapidly and predominantly accumulates in the endoplasmic reticulum

    Falling down a flight of stairs: the impact of age and intoxication on injury pattern and severity

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    Background Falling down a flight of stairs is a common injury mechanism in major trauma patients, but little research has been undertaken into the impact of age and alcohol intoxication on the injury patterns of these patients. Objectives The objective of this study was to compare the impact of age and alcohol intoxication on injury pattern and severity in patients who fell down a flight of stairs. Methods This was a retrospective observational study of prospectively collected trauma registry data from a major trauma centre in the United Kingdom comparing older and younger adult patients admitted to the Emergency Department following a fall down a flight of stairs between July 2012 and March 2015. Results Older patients were more likely to suffer injuries to all body regions, and sustained more severe injuries to the spine (AIS 2[IQR 2 – 3] vs AIS 2 [IQR 2 – 2] p<0.001). They were also more likely to suffer polytrauma (23.6% vs 10.6%; p<0.001). Intoxicated patients were more likely to suffer injuries to the head and neck (42.9% vs 30.5%; p=0.006) and were significantly younger than sober patients (53 years vs 69 years; p<0.001). Conclusion Older patients who fall down a flight of stairs are significantly different from their younger counterparts, with a different injury pattern and a greater likelihood of polytrauma. In addition, alcohol intoxication also affects injury pattern in people who have fallen down a flight of stairs, increasing the risk of traumatic brain injury. Both age and intoxication should be considered when managing these patients

    Upper Boundary Extension of the NASA Ames Mars General Circulation Model

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    Extending the NASA Ames Mars General Circulation Model (MGCM) upper boundary will expand our understanding of the connection between the lower and upper atmosphere of Mars through the middle atmosphere. The extension's main requirements is incorporation of Non-local thermodynamic equilibrium (NLTE) heating (visible) and cooling (infrared). NLTE occurs when energy is exchanged more rapidly with the radiation field (or other energy sources) rather than collisions with other molecules. Without NLTE above approximately 80km/approximately 60km in Mars' atmosphere the IR/visible heating rates are overestimated. Currently NLTE has been applied successfully into the 1D RT code and is in progress for the 3D application
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