1,676 research outputs found

    Duo-check valve, 2-inch mission valve and Pump Company part number 15BVFCC1C, NASA DRAWING number 75Mo4406 PCV-2 Test report

    Get PDF
    Testing and evaluation of 2-inch duo-check valve for Saturn IB progra

    Specific requirements for MRE foundation analysis

    Get PDF
    PublishedMarine Renewable Energy (MRE) systems involve single or arrays of devices that are secured to the seafloor via foundations and/or anchors. These MRE devices will transmit long-term cyclic loads to the seafloor sediment or rock, which may affect seafloor material properties and hence the overall physical performance of the MRE system. The response of seafloor sediments or rock formations is uncertain for the novel MRE systems and especially large arrays of 10s to >1000s of devices. This report summarizes critical inputs and tools for the design and analysis of foundations, anchors, and the response of the seafloor materials. Followed by an introduction in Section 1, Section 2 reviews the offshore structure and MRE literature to highlight current approaches and needed inputs for assessing interactions between foundations or anchors and seafloor materials, including potential environmental impacts. Section 3 addresses relevant marine geological settings that control key geotechnical engineering properties. Data collection activities are described, including in-situ site surveys and laboratory testing. Section 4 considers the unique interactions between MRE systems and seafloor materials, particularly cyclic loading and sediment response. Section 5 describes analytical and numerical tools and associated inputs for the design process of MRE foundations and anchors. Constitutive models are key to simulating sediment response and thus are discussed in detail. Important summary tables relate key variables of geology, geotechnical parameters, foundation or anchor type, and quantitative assessment tools including numerical analysis. Section 5 also addresses the incorporation of the geotechnical analysis into system-level tools to support decision making for MRE arrays. Section 6 presents conclusions and recommendations for future work.European Commission’s 7th Framework; Grant agreement number: 60859

    Bifurcations and chaos in semiconductor superlattices with a tilted magnetic field

    Full text link
    We study the effects of dissipation on electron transport in a semiconductor superlattice with an applied bias voltage and a magnetic field that is tilted relative to the superlattice axis.In previous work, we showed that although the applied fields are stationary,they act like a THz plane wave, which strongly couples the Bloch and cyclotron motion of electrons within the lowest miniband. As a consequence,the electrons exhibit a unique type of Hamiltonian chaos, which creates an intricate mesh of conduction channels (a stochastic web) in phase space, leading to a large resonant increase in the current flow at critical values of the applied voltage. This phase-space patterning provides a sensitive mechanism for controlling electrical resistance. In this paper, we investigate the effects of dissipation on the electron dynamics by modifying the semiclassical equations of motion to include a linear damping term. We demonstrate that even in the presence of dissipation,deterministic chaos plays an important role in the electron transport process. We identify mechanisms for the onset of chaos and explore the associated sequence of bifurcations in the electron trajectories. When the Bloch and cyclotron frequencies are commensurate, complex multistability phenomena occur in the system. In particular, for fixed values of the control parameters several distinct stable regimes can coexist, each corresponding to different initial conditions. We show that this multistability has clear, experimentally-observable, signatures in the electron transport characteristics.Comment: 14 pages 11 figure

    Magnescope: Applications in nondestructive evaluation

    Get PDF
    This paper describes recent results obtained with the Magnescope, which has been used on location in industrial environments and has successfully detected impending fatigue failure, creep damage, applied stress, and microstructural differences. It is concluded that the device provides a useful nondestructive method for evaluating the mechanical properties of materials through the measurement of their structure sensitive magnetic properties

    A Feasibility Study of Quantifying Longitudinal Brain Changes in Herpes Simplex Virus (HSV) Encephalitis Using Magnetic Resonance Imaging (MRI) and Stereology.

    Get PDF
    OBJECTIVES: To assess whether it is feasible to quantify acute change in temporal lobe volume and total oedema volumes in herpes simplex virus (HSV) encephalitis as a preliminary to a trial of corticosteroid therapy. METHODS: The study analysed serially acquired magnetic resonance images (MRI), of patients with acute HSV encephalitis who had neuroimaging repeated within four weeks of the first scan. We performed volumetric measurements of the left and right temporal lobes and of cerebral oedema visible on T2 weighted Fluid Attenuated Inversion Recovery (FLAIR) images using stereology in conjunction with point counting. RESULTS: Temporal lobe volumes increased on average by 1.6% (standard deviation (SD 11%) in five patients who had not received corticosteroid therapy and decreased in two patients who had received corticosteroids by 8.5%. FLAIR hyperintensity volumes increased by 9% in patients not receiving treatment with corticosteroids and decreased by 29% in the two patients that had received corticosteroids. CONCLUSIONS: This study has shown it is feasible to quantify acute change in temporal lobe and total oedema volumes in HSV encephalitis and suggests a potential resolution of swelling in response to corticosteroid therapy. These techniques could be used as part of a randomized control trial to investigate the efficacy of corticosteroids for treating HSV encephalitis in conjunction with assessing clinical outcomes and could be of potential value in helping to predict the clinical outcomes of patients with HSV encephalitis

    High temperature and ion implantation-induced phase transformations in novel reduced activation Si-Fe-V-Cr (-Mo) high entropy alloys

    Get PDF
    For fusion to be realized as a safe, sustainable source of power, new structural materials need to be developed which can withstand high temperatures and the unique fusion radiation environment. An attractive aspect of fusion is that no long-lived radioactive wastes will be produced, but to achieve this structural materials must comprise reduced activation elements. Compositionally complex alloys (CCAs) (also called high entropy alloys, HEAs) are promising candidates for use in extreme environments, including fusion, but few reported to date have low activation. To address these material challenges, we have produced novel, reduced activation, HEAs by arc-melting, and investigated their thermal stability, and radiation damage resistance using 5 MeV Au2+ ion implantation. Whilst the alloys were designed to form single phase BCC, using room temperature and non-ambient in situ X-ray diffraction we have revealed the thermodynamically stable structure of these alloys is in fact a sigma phase. We propose that a BCC phase is formed in these alloys, but at high temperatures (>1000°C). A BCC phase was also formed during heavy ion implantation, which we propose to be due to the rapid heating and cooling that occurs during the thermal spike, effectively freezing in the BCC phase produced by an implantation induced phase transformation. The BCC phase was found to have high hardness and a degree of ductility, making these new alloys attractive in the development of reduced activation HEAs for nuclear applications

    An Experimental Approach To Evaluate the Impact of Impaired Transport Function on Hepatobiliary Drug Disposition Using Mrp2-Deficient TR – Rat Sandwich-Cultured Hepatocytes in Combination with Bcrp Knockdown

    Get PDF
    Breast cancer resistance protein (BCRP) and multidrug resistance-associated protein 2 (MRP2) are members of the ATP binding cassette (ABC) transporter family located in the canalicular membrane of hepatocytes that mediate biliary excretion of many drugs and endogenous compounds. BCRP and MRP2 have overlapping substrate profiles. Predicting drug disposition in the setting of altered transport function has important clinical significance. This investigation was designed to establish an in vitro model system to evaluate the impact of impaired Mrp2 and Bcrp function on hepatobiliary drug disposition. To achieve Bcrp knockdown by RNA interference (RNAi), sandwich-cultured hepatocytes (SCH) from Mrp2-deficient (TR–) and wild-type (WT) rats were infected with adenoviral vectors to express shRNA targeting Bcrp (Ad-siBcrp) at multiplicity of infection (MOI) of 1–10. MOI of 5 was identified as optimal. At MOI of 5, viral infection as well as WT or TR– status was statistically significant predictors of the rosuvastatin (RSV) biliary excretion index (BEI), consistent with the known role of Bcrp and Mrp2 in the biliary excretion of RSV in vivo in rats. Relative to WT rat SCH, marginal mean BEI (%) of RSV in TR– rat SCH decreased by 28.6 (95% CI: 5.8–51.3). Ad-siBcrp decreased marginal mean BEI (%) of RSV by 13.3 (7.5–9.1) relative to SCH infected with adenoviral vectors expressing a nontargeting shRNA (Ad-siNT). The BEI of RSV was almost ablated in TR– rat SCH with Bcrp knockdown (5.9 ± 3.0%) compared to Ad-siNT-infected WT rat SCH (45.4 ± 6.6%). These results demonstrated the feasibility of Bcrp knockdown in TR– rat SCH as an in vitro system to assess the impact of impaired Bcrp and Mrp2 function. At MOI of 5, viral infection had minimal effects on RSV total accumulation, but significantly decreased marginal mean taurocholate total accumulation (pmol/mg of protein) and BEI (%) by 9.9 (7.0–12.8) and 7.5 (3.7–11.3), respectively, relative to noninfected SCH. These findings may be due to off-target effects on hepatic bile acid transporters, even though no changes in protein expression levels of the hepatic bile acid transporters were observed. This study established a strategy for optimization of the knockdown system, and demonstrated the potential use of RNAi in SCH as an in vitro tool to predict altered hepatobiliary drug disposition when canalicular transporters are impaired
    • …
    corecore