3,582 research outputs found

    Method for producing edge geometry superconducting tunnel junctions utilizing an NbN/MgO/NbN thin film structure

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    A method for fabricating an edge geometry superconducting tunnel junction device is discussed. The device is comprised of two niobium nitride superconducting electrodes and a magnesium oxide tunnel barrier sandwiched between the two electrodes. The NbN electrodes are preferably sputter-deposited, with the first NbN electrode deposited on an insulating substrate maintained at about 250 C to 500 C for improved quality of the electrode

    Edge geometry superconducting tunnel junctions utilizing an NbN/MgO/NbN thin film structure

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    An edge defined geometry is used to produce very small area tunnel junctions in a structure with niobium nitride superconducting electrodes and a magnesium oxide tunnel barrier. The incorporation of an MgO tunnel barrier with two NbN electrodes results in improved current-voltage characteristics, and may lead to better junction noise characteristics. The NbN electrodes are preferably sputter-deposited, with the first NbN electrode deposited on an insulating substrate maintained at about 250 to 500 C for improved quality of the electrode

    A study of the optimal sequencing of multicomponent distillation trains

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    The process design of chemical processes may be divided into two broad phases: one, a synthesis phase, is all activities associated with the selection of the process route or configuration together with the selection of the type of process units required for a given processing function; the other is an analysis phase in which the design and optimisation of each unit within a given configuration or process scheme is established. Historically, the discipline of chemical engineering has been concerned primarily with the analysis phase of process design; in that it pioneered the concept of breaking down processes into unique processing steps or 'unit operations'. Most of these unit operations have now been developed to a very high degree of sophistication. However, the synthesis phase has not received the same degree of attention. For example, the selection of the optimal process route for a given process function from among a number of possible process routes has been made to a certain extent upon the process designer's experience and/or intuition, there being no formal techniques available to assist in the selection. Process synthesis has been regarded more or less as an art and consequently it has received very little attention in chemical engineering research. [Continues.

    Effect of Photobiomodulation on Vinblastine-Poisoned Murine HERS Cells

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    Objective: The aim of this study was to investigate the effect of near-infrared (NIR) photobiomodulation on the proliferation and glutathione levels in murine Hertwig\u27s epithelial root sheath (HERS) cells after poisoning with vinblastine. Background: Photobiomodulation has been shown to improve wound healing in a number of animal models. There have been no studies on the effect of photobiomodulation on cancer-related chemotherapy injury to the cells that initiate tooth root growth. Materials and Methods: Control groups consisted of murine HERS cells without vinblastine (VB−) and cells with vinblastine at 10, 20, and 30 ng/mL (VB10, VB20, and VB30). Experimental groups consisted of these same groups with light therapy (VB-L, VB10L, VB20L, and VB30L). The cells were exposed to vinblastine for 1 h. Photobiomodulation consisted of a 75-cm2 gallium-aluminum-arsenide light-emitting diode (LED) array at an energy density of 12.8 J/cm2, delivered with 50 mW/cm2 power over 256 s. Results: Vinblastine alone significantly decreased HERS cell proliferation and glutathione levels at all concentrations (VB10 [−55%, p \u3c 1.0 × 10−8]; VB20 [−72%, p \u3c 1.0 × 10−9]; VB30 [−80%, p \u3c 1.0 × 10−10]; and VB10 [−36%, p \u3c 0.0001]; VB20 [−49%, p \u3c 1.0 × 10−6]; VB30 [−53%, p \u3c 1.0 × 10−7] respectively). Photobiomodulation significantly increased cell proliferation at all levels of vinblastine exposure (VB10L [+50%, p \u3c 0.0001]; VB20L [+45%, p \u3c 0.05]; VB30 [+39%, p \u3c 0.05]) but not of the control (+22%, p  = 0.063). The photobiomodulation significantly increased glutathione production in all concentrations of vinblastine except 20 ng/mL (VB10L [+39%, p = 0.007]; VB20L [+19%, p = 0.087]; VB30 [+14%, p = 0.025]) and the control (+12%, p = 0.13). Conclusions: Photobiomodulation demonstrated an improvement in proliferation and glutathione levels in vinblastine-poisoned murine HERS cells

    Two Suns in The Sky: Stellar Multiplicity in Exoplanet Systems

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    We present results of a reconnaissance for stellar companions to all 131 radial-velocity-detected candidate extrasolar planetary systems known as of July 1, 2005. CPM companions were investigated using the multi-epoch DSS images, and confirmed by matching the trigonometric parallax distances of the primaries to companion distances estimated photometrically. We also attempt to confirm or refute companions listed in the Washington Double Star Catalog, the Catalogs of Nearby Stars, in Hipparcos results, and in Duquennoy & Mayor (1991). Our findings indicate that a lower limit of 30 (23%) of the 131 exoplanet systems have stellar companions. We report new stellar companions to HD 38529 and HD 188015, and a new candidate companion to HD 169830. We confirm many previously reported stellar companions, including six stars in five systems that are recognized for the first time as companions to exoplanet hosts. We have found evidence that 20 entries in the Washington Double Star Catalog are not gravitationally bound companions. At least three, and possibly five, of the exoplanet systems reside in triple star systems. Three exoplanet systems have potentially close-in stellar companions ~ 20 AU away from the primary. Finally, two of the exoplanet systems contain white dwarf companions. This comprehensive assessment of exoplanet systems indicates that solar systems are found in a variety of stellar multiplicity environments - singles, binaries, and triples; and that planets survive the post-main-sequence evolution of companion stars.Comment: 52 pages, 7 figures, Accepted for publication in Ap

    Stroke-related Effects on Maximal Dynamic Hip Flexor Fatigability and Functional Implications

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    Introduction: Stroke-related changes in maximal dynamic hip flexor muscle fatigability may be more relevant functionally than isometric hip flexor fatigability. Methods: Ten chronic stroke survivors performed 5 sets of 30 hip flexion maximal dynamic voluntary contractions (MDVC). A maximal isometric voluntary contraction (MIVC) was performed before and after completion of the dynamic contractions. Both the paretic and nonparetic legs were tested. Results: Reduction in hip flexion MDVC torque in the paretic leg (44.7%) was larger than the nonparetic leg (31.7%). The paretic leg had a larger reduction in rectus femoris EMG (28.9%) between the first and last set of MDVCs than the nonparetic leg (7.4%). Reduction in paretic leg MDVC torque was correlated with self-selected walking speed (r2 = 0.43), while reduction in MIVC torque was not (r2 = 0.11). Conclusions: Reductions in maximal dynamic torque of paretic hip flexors may be a better predictor of walking function than reductions in maximal isometric contractions

    Real-Time Molecular Imaging of Tricarboxylic Acid Cycle Metabolism in Vivo by Hyperpolarized 1-^(13)C Diethyl Succinate

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    The Krebs tricarboxylic acid cycle (TCA) is central to metabolic energy production and is known to be altered in many disease states. Real-time molecular imaging of the TCA cycle in vivo will be important in understanding the metabolic basis of several diseases. Positron emission tomography (PET) with FDG-glucose (2-[^(18)F]fluoro-2-deoxy-d-glucose) is already being used as a metabolic imaging agent in clinics. However, FDG-glucose does not reveal anything past glucose uptake and phosphorylation. We have developed a new metabolic imaging agent, hyperpolarized diethyl succinate-1-^(13)C-2,3-d_2 , that allows for real-time in vivo imaging and spectroscopy of the TCA cycle. Diethyl succinate can be hyperpolarized via parahydrogen-induced polarization (PHIP) in an aqueous solution with signal enhancement of 5000 compared to Boltzmann polarization. ^(13)C magnetic resonance spectroscopy (MRS) and magnetic resonance imaging (MRI) were achieved in vivo seconds after injection of 10–20 μmol of hyperpolarized diethyl succinate into normal mice. The downstream metabolites of hyperpolarized diethyl succinate were identified in vivo as malate, succinate, fumarate, and aspartate. The metabolism of diethyl succinate was altered after exposing the animal to 3-nitropropionate, a known irreversible inhibitor of succinate dehydrogenase. On the basis of our results, hyperpolarized diethyl succinate allows for real-time in vivo MRI and MRS with a high signal-to-noise ratio and with visualization of multiple steps of the TCA cycle. Hyperpolarization of diethyl succinate and its in vivo applications may reveal an entirely new regime wherein the local status of TCA cycle metabolism is interrogated on the time scale of seconds to minutes with unprecedented chemical specificity and MR sensitivity

    Clean-Fuel e-VTOL Air Mobility Vehicles for Unmanned and Manned Operations

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    Imagine for a moment, having your very own safe, affordable, clean-fuel, point-to-any point vehicle for travel in the 21st-century 3-dimensional airspace system. Your ultra-reliable e-VTOL allows commuters to leave behind the constraints of hub-and-spoke airports, and the congestion of interstates, turnpikes and freeways. Facilitating Inter- and Intra-urban travel, such as downtown-to-airport, or metropolis-to-metropolis, or home-to-work. Perfect for dense urban environments worldwide. And all while offering the clean power of hydrogen for zero-emission travel. This vision for efficient, clean, delay-free mobility has been talked about for decades, but always waived aside as some kind of futurist vision. This future requires tackling hard problems in propulsion, airspace management, regulatory satisfaction and (not the least) technologies that seemed out of reach. Well, the future is upon us. What’s at stake? Serious impact on climate change. Affordable transportation. Widely available medical-flights. Timely disaster relief and recovery. Autonomous transport and delivery. On-Demand air taxis. Efficient emergency response. Ubiquitous border security. Economical bulk commodity deliveries. Simplified off-shore deliveries. Sustainable fleet support. NASA, FAA and industry have been laying the foundations for decades, starting with the NASA AGATE and SATS programs of the 1990’s to 2000’s, and the industrial initiatives in On-Demand Mobility such as DayJet, SATSair, LinearAir and many others. Now, some 20 years later, we’re poised to build and deliver e-VTOL, powered by clean, reliable hydrogen fuel cells, operated with more reliable simplified vehicle operations, and in more automated airspace capabilities. This paper summarizes the core strategy, progress and challenges in the certification program for a hydrogen fuel-cell powered e-VTOL having redundant power sources, redundant motors, redundant auto-pilots, and an airframe parachute. The authors believe the implications to operator training for safe and reliable transportation services for the public are central to strategies and industrial vision
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