Science.gov

Sample records for gas assisted mechanical

  1. Direct droplet production from a liquid film: a new gas-assisted atomization mechanism

    NASA Astrophysics Data System (ADS)

    Snyder, Herman E.; Reitz, Rolf D.

    1998-11-01

    X-ray lithography and micro-machining have been used to study gas-assisted liquid atomization in which a liquid film was impinged by a large number of sonic micro-gas jets. Three distinct breakup regimes were demonstrated. Two of these regimes share characteristics with previously observed atomization processes: a bubble bursting at a free surface (Newitt et al. 1954; Boulton-Stone & Blake 1993) and liquid sheet disintegration in a high gas/liquid relative velocity environment (Dombrowski & Johns 1963). The present work shows that suitable control of the gas/liquid interface creates a third regime, a new primary atomization mechanism, in which single liquid droplets are ejected directly from the liquid film without experiencing an intermediate ligament formation stage. The interaction produces a stretched liquid sheet directly above each gas orifice. This effectively pre-films the liquid prior to its breakup. Following this, surface tension contracts the stretched film of liquid into a sphere which subsequently detaches from the liquid sheet and is entrained by the gas jet that momentarily pierces the film. After droplet ejection, the stretched liquid film collapses, covering the gas orifice, and the process repeats. This new mechanism is capable of the efficient creation of finely atomized sprays at low droplet ejection velocities (e.g. 20 [mu]m Sauter mean diameter methanol sprays using air at 239 kPa, with air-to-liquid mass ratios below 1.0, and droplet velocities lower than 2.0 m s[minus sign]1). Independent control of the gas and the liquid flows allows the droplet creation process to be effectively de-coupled from the initial droplet momentum, a characteristic not observed with standard gas-assisted atomization mechanisms.

  2. Dynamic and quasi-static lung mechanics system for gas-assisted and liquid-assisted ventilation.

    PubMed

    Alvarez, Francisco J; Gastiasoro, Elena; Rey-Santano, M Carmen; Gomez-Solaetxe, Miguel A; Publicover, Nelson G; Larrabe, Juan L

    2009-07-01

    Our aim was to develop a computerized system for real-time monitoring of lung mechanics measurements during both gas and liquid ventilation. System accuracy was demonstrated by calculating regression and percent error of the following parameters compared to standard device: airway pressure difference (Delta P(aw)), respiratory frequency (f(R) ), tidal volume (V(T)), minute ventilation (V'(E)), inspiratory and expiratory maximum flows (V'(ins,max), V'(exp,max)), dynamic lung compliance (C(L,dyn) ), resistance of the respiratory system calculated by method of Mead-Whittenberger (R(rs,MW)) and by equivalence to electrical circuits (R(rs,ele)), work of breathing (W(OB)), and overdistension. Outcome measures were evaluated as function of gas exchange, cardiovascular parameters, and lung mechanics including mean airway pressure (mP(aw)). Delata P(aw), V(T), V'(ins,max), V'(exp,max), and V'(E) measurements had correlation coefficients r = 1.00, and %error < 0.5%. f(R), C(L,dyn), R(rs,MW), R(rs,ele), and W(OB) showed r > or = 0.98 and %error < 5%. Overdistension had r = 0.87 and %error < 15%. Also, resistance was accurately calculated by a new algorithm. The system was tested in rats in which lung lavage was used to induce acute respiratory failure. After lavage, both gas- and liquid-ventilated groups had increased mP(aw) and W(OB), with decreased V(T), V'(E), C(L,dyn), R(rs,MW), and R(rs,ele) compared to controls. After 1-h ventilation, both injured group had decreased V(T), V'(E) , and C(L,dyn), with increased mP(aw), R(rs,MW), R(rs,ele), and W(OB) . In lung-injured animals, liquid ventilation restored gas exchange, and cardiovascular and lung functions. Our lung mechanics system was able to closely monitor pulmonary function, including during transitions between gas and liquid phases.

  3. The effect of gas assisted length on polymer melt extrusion based on the gas-assisted extrusion technique

    NASA Astrophysics Data System (ADS)

    Wan, B.; Ren, Z.; Liu, G. D.; Huang, X. Y.

    2017-02-01

    In this study, the gas-assisted technique was used into the process of polymer melt extrusion to overcome the extrudate swell problem. The gas length is an important factors in the gas-assisted extrusion technique. To ascertain the mechanism of the gas-assisted extrusion technique, and to determine the optimal gas length, the effect of gas length on the extrudate swell ratio of melt was numerically investigated. In finite element numerical simulation, PTT constitutive model and full slip boundary condition were used to achieve the gas-assisted mode. Compared with the traditional no gas-assisted extrusion, numerical results showed that the extrudate swell problem was well eliminated by the gas-assisted method. Moreover, the extrudate swell of melt decreased with the increasing of the gas length because the pressure and shear stress of melt were greatly decreased. Moreover, the flow velocity of melt is uniform at the die outlet.

  4. Mechanical cardiac assistance.

    PubMed

    Sezai, Y

    1998-08-01

    In our institute, we have intensively introduced both pulsatile and non-pulsatile mechanical cardiac assist devices, such as the pneumatic ventricular assist device (VAD) and percutaneous cardiopulmonary support (PCPS), using a centrifugal pump. From various kinds of clinical views, these cases were estimated and evaluated retrospectively according to the weaning results, long-term survival rate and cause of death. Based upon our experiences and clinical results, an alternate strategy of mechanical cardiac assistance for severe heart failure is suggested as follows. In the case of post-cardiotomy cardiogenic shock or low output syndrome, PCPS system should be applied firstly under intra-aortic balloon pumping (IABP) assist for a maximum of 2-3 days. If the native cardiac function does not recover and more long-term support is needed, several types of VAD, which are more powerful and durable devices should be introduced, according to end organ function and expected support duration. In order to obtain better clinical results, we have to select an appropriate device depending on the limited availability of supporting duration. Generally speaking, centrifugal pumps can support in short-term duration, while pulsatile devices cover the broad spectrum of the supporting period. Pneumatic VADs can cover short-term to long-term support up to a year, and electric VADs can cover over 1 year, and can be used as a bridge to heart transplantation.

  5. Dynamically Assisted Schwinger Mechanism

    SciTech Connect

    Schuetzhold, Ralf; Gies, Holger; Dunne, Gerald

    2008-09-26

    We study electron-positron pair creation from the Dirac vacuum induced by a strong and slowly varying electric field (Schwinger effect) which is superimposed by a weak and rapidly changing electromagnetic field (dynamical pair creation). In the subcritical regime where both mechanisms separately are strongly suppressed, their combined impact yields a pair creation rate which is dramatically enhanced. Intuitively speaking, the strong electric field lowers the threshold for dynamical particle creation--or, alternatively, the fast electromagnetic field generates additional seeds for the Schwinger mechanism. These findings could be relevant for planned ultrahigh intensity lasers.

  6. Assisted mechanical ventilation: the future is now!

    PubMed

    Kacmarek, Robert M; Pirrone, Massimiliano; Berra, Lorenzo

    2015-07-29

    Assisted ventilation is a highly complex process that requires an intimate interaction between the ventilator and the patient. The complexity of this form of ventilation is frequently underappreciated by the bedside clinician. In assisted mechanical ventilation, regardless of the specific mode, the ventilator's gas delivery pattern and the patient's breathing pattern must match near perfectly or asynchrony between the patient and the ventilator occurs. Asynchrony can be categorized into four general types: flow asynchrony; trigger asynchrony; cycle asynchrony; and mode asynchrony. In an article recently published in BMC Anesthesiology, Hodane et al. have demonstrated reduced asynchrony during assisted ventilation with Neurally Adjusted Ventilatory Assist (NAVA) as compared to pressure support ventilation (PSV). These findings add to the growing volume of data indicating that modes of ventilation that provide proportional assistance to ventilation - e.g., NAVA and Proportional Assist Ventilation (PAV) - markedly reduce asynchrony. As it becomes more accepted that the respiratory center of the patient in most circumstances is the most appropriate determinant of ventilatory pattern and as the negative outcome effects of patient-ventilator asynchrony become ever more recognized, we can expect NAVA and PAV to become the preferred modes of assisted ventilation!

  7. Natural gas-assisted steam electrolyzer

    DOEpatents

    Pham, Ai-Quoc; Wallman, P. Henrik; Glass, Robert S.

    2000-01-01

    An efficient method of producing hydrogen by high temperature steam electrolysis that will lower the electricity consumption to an estimated 65 percent lower than has been achievable with previous steam electrolyzer systems. This is accomplished with a natural gas-assisted steam electrolyzer, which significantly reduces the electricity consumption. Since this natural gas-assisted steam electrolyzer replaces one unit of electrical energy by one unit of energy content in natural gas at one-quarter the cost, the hydrogen production cost will be significantly reduced. Also, it is possible to vary the ratio between the electricity and the natural gas supplied to the system in response to fluctuations in relative prices for these two energy sources. In one approach an appropriate catalyst on the anode side of the electrolyzer will promote the partial oxidation of natural gas to CO and hydrogen, called Syn-Gas, and the CO can also be shifted to CO.sub.2 to give additional hydrogen. In another approach the natural gas is used in the anode side of the electrolyzer to burn out the oxygen resulting from electrolysis, thus reducing or eliminating the potential difference across the electrolyzer membrane.

  8. Chemically assisted mechanical refrigeration process

    DOEpatents

    Vobach, A.R.

    1987-11-24

    There is provided a chemically assisted mechanical refrigeration process including the steps of: mechanically compressing a refrigerant stream which includes vaporized refrigerant; contacting the refrigerant with a solvent in a mixer at a pressure sufficient to promote substantial dissolving of the refrigerant in the solvent in the mixer to form a refrigerant-solvent solution while concurrently placing the solution in heat exchange relation with a working medium to transfer energy to the working medium, said refrigerant-solvent solution exhibiting a negative deviation from Raoult's Law; reducing the pressure over the refrigerant-solvent solution in an evaporator to allow the refrigerant to vaporize and substantially separate from the solvent while concurrently placing the evolving refrigerant-solvent solution in heat exchange relation with a working medium to remove energy from the working medium to thereby form a refrigerant stream and a solvent stream; and passing the solvent and refrigerant stream from the evaporator. 5 figs.

  9. Chemically assisted mechanical refrigeration process

    DOEpatents

    Vobach, A.R.

    1987-06-23

    There is provided a chemically assisted mechanical refrigeration process including the steps of: mechanically compressing a refrigerant stream which includes vaporized refrigerant; contacting the refrigerant with a solvent in a mixer at a pressure sufficient to promote substantial dissolving of the refrigerant in the solvent in the mixer to form a refrigerant-solvent solution while concurrently placing the solution in heat exchange relation with a working medium to transfer energy to the working medium, said refrigerant-solvent solution exhibiting a negative deviation from Raoult's Law; reducing the pressure over the refrigerant-solvent solution in an evaporator to allow the refrigerant to vaporize and substantially separate from the solvent while concurrently placing the evolving refrigerant-solvent solution in heat exchange relation with a working medium to remove energy from the working medium to thereby form a refrigerant stream and a solvent stream; and passing the solvent and refrigerant stream from the evaporator. 5 figs.

  10. Chemically assisted mechanical refrigeration process

    DOEpatents

    Vobach, Arnold R.

    1987-01-01

    There is provided a chemically assisted mechanical refrigeration process including the steps of: mechanically compressing a refrigerant stream which includes vaporized refrigerant; contacting the refrigerant with a solvent in a mixer (11) at a pressure sufficient to promote substantial dissolving of the refrigerant in the solvent in the mixer (11) to form a refrigerant-solvent solution while concurrently placing the solution in heat exchange relation with a working medium to transfer energy to the working medium, said refrigerant-solvent solution exhibiting a negative deviation from Raoult's Law; reducing the pressure over the refrigerant-solvent solution in an evaporator (10) to allow the refrigerant to vaporize and substantially separate from the solvent while concurrently placing he evolving refrigerant-solvent solution in heat exchange relation with a working medium to remove energy from the working medium to thereby form a refrigerant stream and a solvent stream; and passing the solvent and refrigerant stream from the evaporator.

  11. Chemically assisted mechanical refrigeration process

    DOEpatents

    Vobach, Arnold R.

    1987-01-01

    There is provided a chemically assisted mechanical refrigeration process including the steps of: mechanically compressing a refrigerant stream which includes vaporized refrigerant; contacting the refrigerant with a solvent in a mixer (11) at a pressure sufficient to promote substantial dissolving of the refrigerant in the solvent in the mixer (11) to form a refrigerant-solvent solution while concurrently placing the solution in heat exchange relation with a working medium to transfer energy to the working medium, said refrigerant-solvent solution exhibiting a negative deviation from Raoult's Law; reducing the pressure over the refrigerant-solvent solution in an evaporator (10) to allow the refrigerant to vaporize and substantially separate from the solvent while concurrently placing the evolving refrigerant-solvent solution in heat exchange relation with a working medium to remove energy from the working medium to thereby form a refrigerant stream and a solvent stream; and passing the solvent and refrigerant stream from the evaporator.

  12. Excitation Mechanism of H, He, C, and F Atoms in Metal-Assisted Atmospheric Helium Gas Plasma Induced by Transversely Excited Atmospheric-Pressure CO2 Laser Bombardment

    NASA Astrophysics Data System (ADS)

    Lie, Zener Sukra; Khumaeni, Ali; Kurihara, Kazuyoshi; Kurniawan, Koo Hendrik; Lee, Yong Inn; Fukumoto, Ken-ichi; Kagawa, Kiichiro; Niki, Hideaki

    2011-12-01

    To clarify the excitation mechanism of hydrogen in transversely excited atmospheric-pressure (TEA) CO2 laser-induced helium gas plasma, atomic emission characteristics of H, C, F, and He were studied using a Teflon sheet (thickness of 2 mm) attached to a metal subtarget. The TEA CO2 laser (750 mJ, 200 ns) was focused on the Teflon sheet in the surrounding He gas at 1 atm. Atomic emissions of H, C, F, and He occurred with a long lifetime, a narrow spectrum width, and a low-background spectrum. The correlation emission intensity curves of H--He and F--He indicated a parabolic functions. To explain the emission characteristics, we offered a model in which helium metastable atoms (He*) play an important role in the excitation processes; namely, atoms collide with helium metastable atoms (He*) to be ionized by the Penning effect, and then recombine with electrons to produce excited states, from which atomic emissions occur.

  13. Excitation Mechanism of H, He, C, and F Atoms in Metal-Assisted Atmospheric Helium Gas Plasma Induced by Transversely Excited Atmospheric-Pressure CO2 Laser Bombardment

    NASA Astrophysics Data System (ADS)

    Sukra Lie, Zener; Khumaeni, Ali; Kurihara, Kazuyoshi; Hendrik Kurniawan, Koo; Inn Lee, Yong; Fukumoto, Ken-ichi; Kagawa, Kiichiro; Niki, Hideaki

    2011-12-01

    To clarify the excitation mechanism of hydrogen in transversely excited atmospheric-pressure (TEA) CO2 laser-induced helium gas plasma, atomic emission characteristics of H, C, F, and He were studied using a Teflon sheet (thickness of 2 mm) attached to a metal subtarget. The TEA CO2 laser (750 mJ, 200 ns) was focused on the Teflon sheet in the surrounding He gas at 1 atm. Atomic emissions of H, C, F, and He occurred with a long lifetime, a narrow spectrum width, and a low-background spectrum. The correlation emission intensity curves of H-He and F-He indicated a parabolic functions. To explain the emission characteristics, we offered a model in which helium metastable atoms (He*) play an important role in the excitation processes; namely, atoms collide with helium metastable atoms (He*) to be ionized by the Penning effect, and then recombine with electrons to produce excited states, from which atomic emissions occur.

  14. Computer Assisted Introduction to Mechanics.

    ERIC Educational Resources Information Center

    Huggins, Elisha R.

    These six chapters provide an introduction to Newtonian mechanics, based on a coordinated use of text material, laboratory work, and the computer. The material is essentially self-contained so that it can serve as a short text on mechanics or as a text supplement in a regular physics course. Chapter 1 is a brief introduction to the computer…

  15. Aerosol assisted chemical vapour deposition of gas sensitive SnO2 and Au-functionalised SnO2 nanorods via a non-catalysed vapour solid (VS) mechanism

    PubMed Central

    Vallejos, Stella; Selina, Soultana; Annanouch, Fatima Ezahra; Gràcia, Isabel; Llobet, Eduard; Blackman, Chris

    2016-01-01

    Tin oxide nanorods (NRs) are vapour synthesised at relatively lower temperatures than previously reported and without the need for substrate pre-treatment, via a vapour-solid mechanism enabled using an aerosol-assisted chemical vapour deposition method. Results demonstrate that the growth of SnO2 NRs is promoted by a compression of the nucleation rate parallel to the substrate and a decrease of the energy barrier for growth perpendicular to the substrate, which are controlled via the deposition conditions. This method provides both single-step formation of the SnO2 NRs and their integration with silicon micromachined platforms, but also allows for in-situ functionalization of the NRs with gold nanoparticles via co-deposition with a gold precursor. The functional properties are demonstrated for gas sensing, with microsensors using functionalised NRs demonstrating enhanced sensing properties towards H2 compared to those based on non-functionalised NRs. PMID:27334232

  16. Plasma Assisted Combustion Mechanism for Small Hydrocarbons

    DTIC Science & Technology

    2015-01-01

    Andrey Starikovskiy Nickolay Aleksandrov PRINCETON University Plasma Assisted Combustion  Mechanism for Small  Hydrocarbons Report Documentation Page...COVERED 00-00-2015 to 00-00-2015 4. TITLE AND SUBTITLE Plasma Assisted Combustion Mechanism for Small Hydrocarbons 5a. CONTRACT NUMBER 5b...Kinetics of ignition of saturated  hydrocarbons  by nonequilibrium plasma: C2H6‐ to C5H12‐containing mixtures. Combustion and Flame 156  (2009) 221–233

  17. Final Report. SFAA No. DEFC02-98CH10961. Technical assistance for joint implementation and other supporting mechanisms and measures for greenhouse gas emissions mitigation

    SciTech Connect

    Knight, Denise

    2001-10-15

    IIEC, a division of CERF, has developed an extensive base of experience implementing activities that support climate action by developing USIJI projects in transitional countries within Asia, Latin America, Central and Eastern Europe, and southern Africa. IIEC has been able to provide a range of technical and policy assistance to governments and industry in support of sustainable energy use. IIEC continues to work in key countries with local partners to develop and implement energy efficiency policies and standards, develop site-specific projects, and assist governing bodies to establish national priorities and evaluation criteria for approving GHG-mitigation projects. As part of this project, IIEC focused on promoting a series of activities in Thailand and South Africa in order to identify GHG mitigation projects and work within the national approval process of those countries. The sections of this report outline the activities conducted in each country in order to achieve that goal.

  18. Mechanical Serial-Sectioning Data Assistant

    SciTech Connect

    Poulter, Gregory A.; Madison, Jonathan D.

    2015-11-17

    Mechanical Serial-Sectioning Data Assistant (MECH-SSDA) is a real-time data analytics software with graphical user-interface that: 1) tracks and visualizes material removal rates for mechanical serial-sectioning experiments using at least two height measurement methods 2) tracks process time for specific segments of the serial-sectioning experiment and 3) alerts the user to anomalies in expected removal rate, process time or unanticipated operational pauses

  19. New modes of assisted mechanical ventilation.

    PubMed

    Suarez-Sipmann, F

    2014-05-01

    Recent major advances in mechanical ventilation have resulted in new exciting modes of assisted ventilation. Compared to traditional ventilation modes such as assisted-controlled ventilation or pressure support ventilation, these new modes offer a number of physiological advantages derived from the improved patient control over the ventilator. By implementing advanced closed-loop control systems and using information on lung mechanics, respiratory muscle function and respiratory drive, these modes are specifically designed to improve patient-ventilator synchrony and reduce the work of breathing. Depending on their specific operational characteristics, these modes can assist spontaneous breathing efforts synchronically in time and magnitude, adapt to changing patient demands, implement automated weaning protocols, and introduce a more physiological variability in the breathing pattern. Clinicians have now the possibility to individualize and optimize ventilatory assistance during the complex transition from fully controlled to spontaneous assisted ventilation. The growing evidence of the physiological and clinical benefits of these new modes is favoring their progressive introduction into clinical practice. Future clinical trials should improve our understanding of these modes and help determine whether the claimed benefits result in better outcomes.

  20. Determination of gas length for gas-assisted extrusion forming of polymer melt

    NASA Astrophysics Data System (ADS)

    Ren, Z.; Huang, X. Y.

    2017-02-01

    To determine the optimal gas length for the gas-assisted etrusion forming of melt, numerical investigations about the gas length on the extrudate swell of melt were performed by using the finite element method. Meanwhile, the geometric model of gas-assistd extrusion forming was established. The full slip boundary condition was used as the gas-assisted condition. Numerical results show that the gas length should be shortened with increasing of the inlet volumme flow rate of melt. In addition, under the given inlet volume flow rate of melt, the extrudate swell ratio, X velocity and shear stress of melt greatly decreases with increasing the gas length. Accroding to the numerical results and experiences reported past time, under the inlet volume flow rate of 0.5cm3/s, the optimal gas lenth of gas-assisted extrusion forming is about 10mm.

  1. Gravity-Assist Mechanical Simulator for Outreach

    NASA Technical Reports Server (NTRS)

    Doody, David F.; White, Victor E.; Schaff, Mitch D.

    2012-01-01

    There is no convenient way to demonstrate mechanically, as an outreach (or inreach) topic, the angular momentum trade-offs and the conservation of angular momentum associated with gravityassist interplanetary trajectories. The mechanical concepts that underlie gravity assist are often misunderstood or confused, possibly because there is no mechanical analog to it in everyday experience. The Gravity Assist Mech - anical Simulator is a hands-on solution to this longstanding technical communications challenge. Users intuitively grasp the concepts, meeting specific educational objectives. A manually spun wheel with high angular mass and low-friction bearings supplies momentum to an attached spherical neodymium magnet that represents a planet orbiting the Sun. A steel bearing ball following a trajectory across a glass plate above the wheel and magnet undergoes an elastic collision with the revolving magnet, illustrating the gravitational elastic collision between spacecraft and planet on a gravity-assist interplanetary trajectory. Manually supplying the angular momentum for the elastic collision, rather than observing an animation, intuitively conveys the concepts, meeting nine specific educational objectives. Many NASA and JPL interplanetary missions are enabled by the gravity-assist technique.

  2. Spatially Assisted Schwinger Mechanism and Magnetic Catalysis

    NASA Astrophysics Data System (ADS)

    Copinger, Patrick; Fukushima, Kenji

    2016-08-01

    Using the worldline formalism we compute an effective action for fermions under a temporally modulated electric field and a spatially modulated magnetic field. It is known that the former leads to an enhanced Schwinger mechanism, while we find that the latter can also result in enhanced particle production and even cause a reorganization of the vacuum to acquire a larger dynamical mass in equilibrium which spatially assists the magnetic catalysis.

  3. Gentle protein ionization assisted by high-velocity gas flow.

    PubMed

    Yang, Pengxiang; Cooks, R Graham; Ouyang, Zheng; Hawkridge, Adam M; Muddiman, David C

    2005-10-01

    Gentle protein electrospray ionization is achieved using the high-velocity gas flow of an air amplifier to improve desolvation in conventional ESI and generate intact folded protein ions in the gas phase. Comparisons are made between the ESI spectra of a number of model proteins, including ubiquitin, cytochrome c, lysozyme, and myoglobin, over a range of pH values under optimized conditions, with and without using an air amplifier to achieve high-velocity gas flow. Previously reported increased ion signals are confirmed. In addition, the peaks recorded using the air amplifier are shown to be narrower, corresponding to more complete desolvation. Significant changes in the charge-state distribution also are observed, with a shift to lower charge state at high-velocity flow. The relationship between the observed charge-state distribution and protein conformation was explored by comparing the charge-state shifts and the distributions of charge states for proteins that are or are not stable in their native conformations in low pH solutions. The data suggest retention of native or nativelike protein conformations using the air amplifier in all cases examined. This is explained by a mechanism in which the air amplifier rapidly creates small droplets from the original large ESI droplets and these microdroplets then desolvate without a significant decrease in pH, resulting in retention of the folded protein conformations. Furthermore, the holoform of ionized myoglobin is visible at pH 3.5, a much lower value than the minimum needed to see this form in conventional ESI. These results provide evidence for the importance of the conditions used in the desolvation process for the preservation of the protein conformation and suggest that the conditions achieved when using high-velocity gas flows to assist droplet evaporation and ion desolvation are much gentler than those in conventional ESI experiments.

  4. Mechanisms of inert gas narcosis

    NASA Technical Reports Server (NTRS)

    1973-01-01

    Experiments describing the mechanism of inert gas narcosis are reported. A strain of mice, genetically altered to increase susceptibility to botulin poisoning (synaptic response) appears to increase metabolic rates while breathing argon; this infers a genetically altered synaptic response to both botulin toxin and narcotic gases. Studies of metabolic depression in human subjects breathing either air or a 30% mixture of nitrous oxide indicate that nitrous oxide narcosis does not produce pronounced metabolic depression. Tests on mice for relative susceptibilities to narcosis and oxygen poisoning as a function of fatty membrane composition show that alteration of the fatty acid composition of phospholipids increases resistance to metabolically depressant effects of argon but bas no effect on nitrous oxide narcosis. Another study suggests that acclimatization to low tension prior to high pressure oxygen treatment enhances susceptibility of mice to convulsions and death; developing biochemical lesions cause CNS metabolite reductions and pulmonary damage.

  5. Mechanically assisted laser forming of thin beams

    NASA Astrophysics Data System (ADS)

    Mucha, Zygmunt; Widłaszewski, Jacek; Kurp, Piotr; Mulczyk, Krystian

    2016-12-01

    Laser-assisted forming techniques have been developed in recent years to aid plastic working of materials, which are difficult in processing at normal temperatures due to a high brittleness, effects of high work-hardening or a high spring-back phenomenon. This paper reports initial experimental investigations and numerical simulations of a mechanically-assisted laser forming process. The research is aimed at facilitating plastic shaping of thin-walled parts made of high temperature resistant alloys. Stainless steel plate, 1 mm thick, 20 mm wide, was mounted in the cantilever arrangement and a gravitational load was applied to its free end. A CO2 laser beam with rectangular cross-section traversed along the plate, towards the fixed edge. Laser spot covered the whole width of the plate. Experiments and simulations using the finite element method were performed for different values of mechanical load and with constant laser processing parameters. Experimentally validated numerical model allowed analysis of plastic deformation mechanism under the hybrid thermo-mechanical processing. The revealed mechanism of deformation consists in intense material plastic flow near the laser heated surface. This behavior results mainly from the tension state close to the heated surface and the decrease of material yield stress at elevated temperature. Stress state near the side edges of the processed plate favored more intense plastic deformation and the involved residual stress in this region.

  6. Improved gas chromatography-negative ion chemical ionization tandem mass spectrometric method for determination of 11-nor-Δ9-tetrahydrocannabinol-9-carboxylic acid in hair using mechanical pulverization and bead-assisted liquid-liquid extraction.

    PubMed

    Kim, Jin Young; Cheong, Jae Chul; Lee, Jae Il; In, Moon Kyo

    2011-03-20

    A gas chromatography-negative ion chemical ionization tandem mass spectrometric (GC-NCI-MS/MS) method was developed and validated for the determination of 11-nor-Δ(9)-tetrahydrocannabinol-9-carboxylic acid (THC-COOH) in human hair. After decontamination, hair samples were weighed (25mg), mechanically pulverized with a bead mill, and incubated in 0.7 mL of 1.0M sodium hydroxide at 95 °C for 30 min. Bead-assisted liquid-liquid extraction was performed with n-hexane:ethyl acetate (9:1, v/v), a method developed in our laboratory. The extract was evaporated to dryness, derivatized with pentafluoropropanol and pentafluoropropionic anhydride, and analyzed by GC-MS/MS in the negative ion chemical ionization mode using methane as the reagent gas. The linear ranges were 0.05-10.0 pg/mg for THC-COOH with the coefficient of determination (r(2) = 0.9976). The intra-day and inter-day precisions were within 1.7 and 13.8%, respectively. The intra-day and inter-day accuracies were -4.8 to 10.0% and -3.9 to 3.8%, respectively. The limit of detection and quantification were 0.015 and 0.05 pg/mg, respectively. The recoveries were in the range of 79.4-87.1%. The results indicate that the proposed method is simple, rapid, accurate, and precise for determination of THC-COOH in hair. The method identified THC-COOH in hair specimens from suspected marijuana abusers.

  7. [Mechanical cardiac assist systems in intensive care].

    PubMed

    Figulla, H R; Scholz, K H

    1994-01-01

    The indications for the use of mechanical cardiac assist-devices are sudden death, cardiogenic shock, severe coronary ischemia and high-risk PTCA. Among the cardiac assist-devices, currently available for cardiologists and cardiac surgeons, are the Intraaortal Balloon Pump (IABP), the implantable turbine-pump, the percutaneous cardiopulmonary support (PCPS), centrifugal pumps which are connected via a thoracotomy and intra- and extrathoracic total artificial hearts. It is easy to position the IABP, which can be continuously used over the course of several days. In the case of cardiogenic shock, the pump should be implanted as soon as possible, in order to facilitate revascularisation procedure in a patient with ischemic heart disease. By this procedures the survival rate of ischemic cardiogenic shock has been raised from 20% to 60%. However, the IABP does not prove supportive in the case of an MI without shock or in high-risk PTCA. The implantable turbine pump (Hemopump TM) is available in 3 configurations, ranging in external size from 14 F to 26 F. Of these, only the 14 F pumps can be implanted percutaneously by a Seldinger technique, whereas the bigger pumps require arteriotomy or thoracotomy for placement. The pump-rates of these systems reach from 2.0 l/min to 4.5 l/min. These pumps are used in high-risk PTCA as well as CABG-surgery without cardiopulmonary support, but are still currently in a test phase. However, at this point, it is still too early to finally evaluate the clinical importance of these systems. The percutaneous cardiopulmonary support (PCPS) has a major advantage over all other assist device systems, as it completely replaces the circulation. Therefore, PCPS is especially indicated in cardiac arrest, because it can be inserted very quickly, even without having to interrupt resuscitation. A second indication is high-risk PTCA, where it can be used also as a stand-by system. A study with 801 patients, investigating the use of this system in high

  8. Microengineered cold gas thruster system for a co-orbiting satellite assistant (COSA)

    NASA Astrophysics Data System (ADS)

    Huang, Adam; Hansen, William W.; Janson, Siegfried W.; Helvajian, Henry

    2001-10-01

    Miniaturization technologies such as Micro-Electro-Mechanical Systems (MEMS) have been used to fabricate a prototype 100-gm class cold gas propulsion system suitable for use on a Co-Orbiting Satellite Assistant (COSA). The propulsion system is fabricated from bonded layers of photostructurable glass (Foturan glass; the design is based on fabricating integrated modular parts. Thus, the propulsion system is mass producible, expandable, expendable (low unit cost), and highly integrated.

  9. Study of Formation Mechanisms of Gas Hydrate

    NASA Astrophysics Data System (ADS)

    Yang, Jia-Sheng; Wu, Cheng-Yueh; Hsieh, Bieng-Zih

    2015-04-01

    Gas hydrates, which had been found in subsurface geological environments of deep-sea sediments and permafrost regions, are solid crystalline compounds of gas molecules and water. The estimated energy resources of hydrates are at least twice of that of the conventional fossil fuel in the world. Gas hydrates have a great opportunity to become a dominating future energy. In the past years, many laboratory experiments had been conducted to study chemical and thermodynamic characteristics of gas hydrates in order to investigate the formation and dissociation mechanisms of hydrates. However, it is difficult to observe the formation and dissociation of hydrates in a porous media from a physical experiment directly. The purpose of this study was to model the dynamic formation mechanisms of gas hydrate in porous media by reservoir simulation. Two models were designed for this study: 1) a closed-system static model with separated gas and water zones; this model was a hydrate equilibrium model to investigate the behavior of the formation of hydrates near the initial gas-water contact; and 2) an open-system dynamic model with a continuous bottom-up gas flow; this model simulated the behavior of gas migration and studied the formation of hydrates from flowed gas and static formation water in porous media. A phase behavior module was developed in this study for reservoir simulator to model the pressure-volume-temperature (PVT) behavior of hydrates. The thermodynamic equilibriums and chemical reactions were coupled with the phase behavior module to have functions modelling the formation and dissociation of hydrates from/to water and gas. The simulation models used in this study were validated from the code-comparison project proposed by the NETL. According to the modelling results of the closed-system static model, we found that predominated location for the formation of hydrates was below the gas-water contact (or at the top of water zone). The maximum hydrate saturation

  10. Mechanism of plasma-assisted ignition for H2 and C1-C5 hydrocarbons

    NASA Astrophysics Data System (ADS)

    Starikovskiy, Andrey; Aleksandrov, Nikolay

    2016-09-01

    Nonequilibrium plasma demonstrates ability to control ultra-lean, ultra-fast, low-temperature flames and appears to be an extremely promising technology for a wide range of applications, including aviation GTEs, piston engines, ramjets, scramjets and detonation initiation for pulsed detonation engines. To use nonequilibrium plasma for ignition and combustion in real energetic systems, one must understand the mechanisms of plasma-assisted ignition and combustion and be able to numerically simulate the discharge and combustion processes under various conditions. A new, validated mechanism for high-temperature hydrocarbon plasma assisted combustion was built and allows to qualitatively describe plasma-assisted combustion close and above the self-ignition threshold. The principal mechanisms of plasma-assisted ignition and combustion have been established and validated for a wide range of plasma and gas parameters. These results provide a basis for improving various energy-conversion combustion systems, from automobile to aircraft engines, using nonequilibrium plasma methods.

  11. Effect of the working gas of the ion-assisted source on the optical and mechanical properties of SiO2 films deposited by dual ion beam sputtering with Si and SiO2 as the starting materials.

    PubMed

    Wu, Jean-Yee; Lee, Cheng-Chung

    2006-05-20

    Silicon and fused-silica targets are used as the starting materials for depositing silicon oxide (SiO2) films. The SiO2 films are prepared by a dual ion beam sputtering deposition system with a main ion source and an ion-assisted source with different working gases. The films deposited are then examined and compared by using a visible spectrophotometer, a Fourier-transform IR spectrophotometer, an atomic force microscope, and contact angle instruments. A Twyman-Green interferometer is employed to study the film stress by phase-shift interferometry. All the SiO2 films show excellent optical properties with extra-low extinction coefficients (below 2x10(-5)) and have no water absorption. When the working gas is O2 for the ion-assisted source, the deposited SiO2 films show good properties in terms of stress and roughness and with a good molecular bonding structure order for both targets. However, SiO2 films deposited from the fused-silica target had a larger contact angle, while those deposited from the silicon target had 2.5 times the deposition rate.

  12. Development and Optimization of Gas-Assisted Gravity Drainage (GAGD) Process for Improved Light Oil Recovery

    SciTech Connect

    Dandina N. Rao; Subhash C. Ayirala; Madhav M. Kulkarni; Wagirin Ruiz Paidin; Thaer N. N. Mahmoud; Daryl S. Sequeira; Amit P. Sharma

    2006-09-30

    This is the final report describing the evolution of the project ''Development and Optimization of Gas-Assisted Gravity Drainage (GAGD) Process for Improved Light Oil Recovery'' from its conceptual stage in 2002 to the field implementation of the developed technology in 2006. This comprehensive report includes all the experimental research, models developments, analyses of results, salient conclusions and the technology transfer efforts. As planned in the original proposal, the project has been conducted in three separate and concurrent tasks: Task 1 involved a physical model study of the new GAGD process, Task 2 was aimed at further developing the vanishing interfacial tension (VIT) technique for gas-oil miscibility determination, and Task 3 was directed at determining multiphase gas-oil drainage and displacement characteristics in reservoir rocks at realistic pressures and temperatures. The project started with the task of recruiting well-qualified graduate research assistants. After collecting and reviewing the literature on different aspects of the project such gas injection EOR, gravity drainage, miscibility characterization, and gas-oil displacement characteristics in porous media, research plans were developed for the experimental work to be conducted under each of the three tasks. Based on the literature review and dimensional analysis, preliminary criteria were developed for the design of the partially-scaled physical model. Additionally, the need for a separate transparent model for visual observation and verification of the displacement and drainage behavior under gas-assisted gravity drainage was identified. Various materials and methods (ceramic porous material, Stucco, Portland cement, sintered glass beads) were attempted in order to fabricate a satisfactory visual model. In addition to proving the effectiveness of the GAGD process (through measured oil recoveries in the range of 65 to 87% IOIP), the visual models demonstrated three possible

  13. Fundamental mechanisms in flue gas conditioning

    SciTech Connect

    Bush, P.V.; Snyder, T.R.

    1992-01-09

    The overall goal of this research project is to formulate a mathematical model of flue gas conditioning. This model will be based on an understanding of why ask properties, such as cohesivity and resistivity, are changed by conditioning. Such a model could serve as a component of the performance models of particulate control devices where flue gas conditioning is used. There are two specific objectives of this research project, which divide the planned research into two main parts. One part of the project is designed to determine how ash particles are modified by interactions with sorbent injection processes and to describe the mechanisms by which these interactions affect fine particle collection. The objective of the other part of the project is to identify the mechanisms by which conditioning agents, including chemically active compounds, modify the key properties of fine fly ash particles.

  14. Fundamental mechanisms in flue-gas conditioning

    SciTech Connect

    Dahlin, R.S.; Vann Bush, P.; Snyder, T.R.

    1992-01-09

    The overall goal of this research project is to formulate a mathematical model of flue gas conditioning. This model will be based on an understanding of why ash properties, such as cohesivity and resistivity, are changed by conditioning. Such a model could serve as a component of the performance models of particulate control devices where flue gas conditioning is used. There are two specific objectives of this research project, which divide the planned research into two main parts. One part of the project is designed to determine how ash particles are modified by interactions with sorbent injection processes and to describe the mechanisms by which these interactions affect fine particle collection. The objective of the other part of the project is to identify the mechanisms by which conditioning agents, including chemically active compounds, modify the key properties of fine fly ash particles.

  15. Gas-Assisted Capture of the Irregular Satellites of Jupiter

    NASA Astrophysics Data System (ADS)

    Cuk, M.; Burns, J. A.

    2001-11-01

    Recent discoveries of ``irregular'' satellites about the giant planets have dramatically increased their number such that systematic studies of their origin can begin. Since irregulars move along large, inclined and eccentric orbits, capture from circumsolar orbit is usually suspected (Franklin and Colombo 1971, Heppenheimer and Porco 1977). Because permanent capture is not possible in a strictly gravitational three-body problem, a dissipative mechanism is needed. Many assume that gas drag by protojovian nebula led to their capture (cf. Pollack et al. 1979). We numerically simulate the gas-aided capture of a planetesimal by Jupiter. The distribution and velocity of gas come from hydrocode simulations (Lubow et al. 1999). In our simple replication of their model, gas is assumed to follow gravitational trajectories, except at the shockwave fronts (taken from Lubow et al.) which the gas is forbidden to cross. The planetesimal's motion is integrated using a mixture of modern and traditional techniques. We employ a symplectic integration algorithm (Malhotra 1994) within the circumsolar and circumjovian disks. In the transitional region we used a fourth-order Runge-Kutta integrator expressed in rotating coordinates. The method's timesteps are independent of the presence of the gas. Subsequent orbital evolution is handled in a symplectic way, thus avoiding ``fake captures'' due to energy leakage owing to integration errors. By incorporating more sophisticated models of protoJupiter's environs, we hope to refine the nebular models and/or to elucidate the capture process. Preliminary results indicate that the parent body of the prograde cluster of Jovian irregulars (Himalia's group) may have originated from the Hilda region, at around 4 AU from the Sun. This is consistent with the taxonomical types of the cluster members (Sykes et al. 2000) being similar to those of Hildas that are close in size to Himalia (Dahlgren and Lagerkvist 1995).

  16. Chaos and Gas-Assisted Capture of Kozai Resonators

    NASA Astrophysics Data System (ADS)

    Carruba, V.; Nesvorny, D.; Cuk, M.; Burns, J. A.; Rand, R.

    2003-05-01

    Carruba et al. (2003) previously studied a layer of chaos for satellites in Kozai resonance, i.e., satellites whose argument of pericenter, instead of circulating from 0 to 360 degrees, librates around +/- 90 degrees. By performing numerical simulations with test particles covering the orbital space surrounding S/2000S5, a satellite of Saturn currently in this resonance, and by applying the Frequency Analysis Method of Laskar (Laskar, 1993, 1999), we identified a layer of chaos at the transition between circulation and libration. We now further investigate this chaotic boundary and try to determine its cause(s). Our simulations suggest that, for the case of S5, perturbations from Jupiter are needed to create the chaotic boundary. In order to understand if secular or short-period terms in the disturbing potential of Jupiter are actually responsible for the appearance of the layer of chaos we are performing simulations where test particles are subjected to perturbations from a Jupiter on a fictitious orbit whose parameters are determined using the Bretagnon model (Bretagnon and Francou 1992). By perfoming simulations with Jovian orbits that only include either secular or secular and short-period terms, we are confident we shall be able to identify the source of chaos. Another problem posed by the existence of the chaotic boundary is its possible relevance for capture mechanisms. In this work we have modified the SWIFT-WHM integrator to account for gas-drag, according to the model of Cuk and Burns (2003). Preliminary results of our simulations suggest that, for typical values of gas density at the mid-point of the disk (6*10-9 g/cm3), the chaotic layer does not affect the capture of satellites into Kozai resonance. The chaotic layer might, however, still play a role in the very last phases of capture, when the gas-disk is dissipating. We are currently investigating different sets of gas-densities and disk parameters. As Cuk et al. (2002) found, preliminary results of

  17. Fundamental mechanisms in flue gas conditioning

    SciTech Connect

    Snyder, T.R.; Robinson, M.S.; Bush, P.V.

    1992-04-27

    This project is divided into four tasks. The Management Plan was developed in task 1. Task 2, Evaluation of Mechanisms in FGD Sorbent and Ash Interactions, focuses on the characteristics of binary mixtures of these distinct powders. Task 3, Evaluation of Mechanisms in Conditioning Agents and Ash, is designed to examine the effects of various conditioning agents on fine ash particles to determine the mechanisms by which these agents alter the physical properties of the ash. Tasks 2 and 3 began with an extensive literature search and the assembly of existing theories. This phase of the project is now complete. During the past quarter, initial preparations of laboratory equipment for laboratory testing have been made. A plan for initial laboratory tests has been submitted to the Project Manager for review. Laboratory testing will commence once these laboratory plans have been formally approved. The results of the work performed under task 2 and 3 will be included in a Flue Gas Conditioning Model that will be issued under task 4. The Final Report for the project will also be prepared under task 4.

  18. Laser-assisted focused He+ ion beam induced etching with and without XeF2 gas assist

    DOE PAGES

    Stanford, Michael G.; Mahady, Kyle; Lewis, Brett B.; ...

    2016-10-04

    Focused helium ion (He+) milling has been demonstrated as a high-resolution nanopatterning technique; however, it can be limited by its low sputter yield as well as the introduction of undesired subsurface damage. Here, we introduce pulsed laser- and gas-assisted processes to enhance the material removal rate and patterning fidelity. A pulsed laser-assisted He+ milling process is shown to enable high-resolution milling of titanium while reducing subsurface damage in situ. Gas-assisted focused ion beam induced etching (FIBIE) of Ti is also demonstrated in which the XeF2 precursor provides a chemical assist for enhanced material removal rate. In conclusion, a pulsed laser-assistedmore » and gas-assisted FIBIE process is shown to increase the etch yield by ~9× relative to the pure He+ sputtering process. These He+ induced nanopatterning techniques improve material removal rate, in comparison to standard He+ sputtering, while simultaneously decreasing subsurface damage, thus extending the applicability of the He+ probe as a nanopattering tool.« less

  19. Gas assisted thin-film evaporation from confined spaces

    NASA Astrophysics Data System (ADS)

    Narayanan, Shankar

    A novel cooling mechanism based on evaporation of thin liquid films is presented for thermal management of confined heat sources, such as microprocessor hotspots, high power light emitting diodes and RF packages with a high operational frequency. A thin nanoporous membrane (˜1--5microm) is utilized to maintain microscopically thin liquid films (˜1--5microm) by capillary action, while providing a pathway for the vapor generated due to evaporation at the liquid-vapor interface. The vapor generated by evaporation is continuously removed by using a dry sweeping gas, keeping the membrane outlet dry. This thesis presents a detailed theoretical, computational and experimental investigation of the heat and mass transfer mechanisms that result in cooling the confined heat sources. Performance analysis of this cooling mechanism demonstrates heat fluxes over 600W/cm2 for sufficiently thin membrane and film thicknesses (˜1--5microm) and by using air jet impingement for advection of vapor from the membrane surface. Based on the results from this performance analysis, a monolithic micro-fluidic device is designed and fabricated incorporating micro and nanoscale features. This MEMS/NEMS device serves multiple functionalities of hotspot simulation, temperature sensing, and evaporative cooling. Subsequent experimental investigations using this microfluidic device demonstrate heat fluxes in excess of 600W/cm2 at 90 °C using water as the evaporating coolant. In order to further enhance the device performance, a comprehensive theoretical and computational analysis of heat and mass transfer at micro and nanoscales is carried out. Since the coolant is confined using a nanoporous membrane, a detailed study of evaporation inside a nanoscale cylindrical pore is performed. The continuum analysis of water confined within a cylindrical nanopore determines the effect of electrostatic interaction and Van der Waals forces in addition to capillarity on the interfacial transport

  20. Numerical simulations of CO2 -assisted gas production from hydrate reservoirs

    NASA Astrophysics Data System (ADS)

    Sridhara, P.; Anderson, B. J.; Myshakin, E. M.

    2015-12-01

    A series of experimental studies over the last decade have reviewed the feasibility of using CO2 or CO2+N2 gas mixtures to recover CH4 gas from hydrates deposits. That technique would serve the dual purpose of CO2 sequestration and production of CH4 while maintaining the geo-mechanical stability of the reservoir. In order to analyze CH4 production process by means of CO2 or CO2+N2 injection into gas hydrate reservoirs, a new simulation tool, Mix3HydrateResSim (Mix3HRS)[1], was previously developed to account for the complex thermodynamics of multi-component hydrate phase and to predict the process of CH4 substitution by CO2 (and N2) in the hydrate lattice. In this work, Mix3HRS is used to simulate the CO2 injection into a Class 2 hydrate accumulation characterized by a mobile aqueous phase underneath a hydrate bearing sediment. That type of hydrate reservoir is broadly confirmed in permafrost and along seashore. The production technique implies a two-stage approach using a two-well design, one for an injector and one for a producer. First, the CO2 is injected into the mobile aqueous phase to convert it into immobile CO2 hydrate and to initiate CH4 release from gas hydrate across the hydrate-water boundary (generally designating the onset of a hydrate stability zone). Second, CH4 hydrate decomposition is induced by the depressurization method at a producer to estimate gas production potential over 30 years. The conversion of the free water phase into the CO2 hydrate significantly reduces competitive water production in the second stage, thereby improving the methane gas production. A base case using only the depressurization stage is conducted to compare with enhanced gas production predicted by the CO2-assisted technique. The approach also offers a possibility to permanently store carbon dioxide in the underground formation to greater extent comparing to a direct injection of CO2 into gas hydrate sediment. Numerical models are based on the hydrate formations at the

  1. Environmentally Assisted Cracking of Drill Pipes in Deep Drilling Oil and Natural Gas Wells

    NASA Astrophysics Data System (ADS)

    Ziomek-Moroz, M.

    2012-06-01

    Corrosion fatigue (CF), hydrogen induced cracking (HIC) and sulfide stress cracking (SSC), or environmentally assisted cracking (EAC) have been identified as the most challenging causes of catastrophic brittle fracture of drill pipes during drilling operations of deep oil and natural gas wells. Although corrosion rates can be low and tensile stresses during service can be below the material yield stress, a simultaneous action between the stress and corrosive environment can cause a sudden brittle failure of a drill component. Overall, EAC failure consists of two stages: incubation and propagation. Defects, such as pits, second-phase inclusions, etc., serve as preferential sites for the EAC failure during the incubation stage. Deep oil and gas well environments are rich in chlorides and dissolved hydrogen sulfide, which are extremely detrimental to steels used in drilling operations. This article discusses catastrophic brittle fracture mechanisms due to EAC of drill pipe materials, and the corrosion challenges that need to be overcome for drilling ultra-deep oil and natural gas wells.

  2. SDS-assisted hydrothermal synthesis of NiO flake-flower architectures with enhanced gas-sensing properties

    NASA Astrophysics Data System (ADS)

    Miao, Ruiyang; Zeng, Wen; Gao, Qi

    2016-10-01

    A facile hydrothermal route was developed for the preparation of well-aligned hierarchical flower-like NiO nanostructure with the assistance of SDS that served as a structure-directing agent as well as a capping agent in the process of aggregation and assembly. Notably, the NiO sensors exhibit enhanced gas-sensing performance towards ethanol, which could be explained in association with the ultrathin nanosheets that are close to Debye length (LD) scale and thus get the majority carriers fully depleted due to the ionization of adsorbed oxygen, abundant effective gas diffusion paths as well as high surface-to-volume ratio to promote sufficient contact and reaction between the NiO sample and ethanol molecules, and numerous miniature reaction rooms assembled with nanosheets to make the test gas molecules stay long enough for completed gas-sensing reactions. Besides, a novel growth mechanism with the passage of reaction time was also proposed in detail.

  3. Vibrationally Assisted Electron Transfer Mechanism of Olfaction: Myth or Reality?

    PubMed Central

    Solov’yov, Ilia A.; Chang, Po-Yao; Schulten, Klaus

    2012-01-01

    Smell is a vital sense for animals. The mainstream explanation of smell is based on recognition of the odorant molecules through characteristics of their surface, e.g., shape, but certain experiments suggest that such recognition is complemented by recognition of vibrational modes. According to this suggestion an olfactory receptor is activated by electron transfer assisted through odorant vibrational excitation. The hundreds to thousands of different olfactory receptors in an animal recognize odorants over a discriminant landscape with surface properties and vibrational frequencies as the two major dimensions. In the present paper we introduce the vibrationally assisted mechanism of olfaction and demonstrate for several odorants that, indeed, a strong enhancement of an electron tunneling rate due to odorant vibrations can arise. We discuss in this regard the influence of odorant deuteration and explain, thereby, recent experiments performed on Drosophila melanogaster. Our demonstration is based on known physical properties of biological electron transfer and on ab initio calculations on odorants carried out for the purpose of the present study. We identify a range of physical characteristics which olfactory receptors and odorants must obey for the vibrationally assisted electron transfer mechanism to function. We argue that the stated characteristics are feasible for realistic olfactory receptors, noting, though, that the receptor structure presently is still unknown, but can be studied through homology modeling. PMID:22899100

  4. [Importance of mechanical assist devices in acute circulatory arrest].

    PubMed

    Ferrari, Markus Wolfgang

    2016-03-01

    Mechanical assist devices are indicated for hemodynamic stabilization in acute circulatory arrest if conventional means of cardiopulmonary resuscitation are unable to re-establish adequate organ perfusion. Their temporary use facilitates further diagnostic and therapeutic options in selected patients, e.g. coronary angiography followed by revascularization.External thorax compression devices allow sufficient cardiac massage in case of preclinical or in-hospital circulatory arrest, especially under complex transfer conditions. These devices perform standardized thorax compressions at a rate of 80-100 per minute. Invasive mechanical support devices are used in the catheter laboratory or in the intensive care unit. Axial turbine pumps, e.g. the Impella, continuously pump blood from the left ventricle into the aortic root. The Impella can also provide right ventricle support by pumping blood from the vena cava into the pulmonary artery. So-called emergency systems or ECMO devices consist of a centrifugal pump and a membrane oxygenator allowing complete takeover of cardiac and pulmonary functions. Withdrawing blood from the right atrium and vena cava, oxygenated blood is returned to the abdominal aorta. Isolated centrifugal pumps provide left heart support without an oxygenator after transseptal insertion of a venous cannula into the left atrium.Mechanical assist devices are indicated for acute organ protection and hemodynamic stabilization for diagnostic and therapeutic measures as well as bridge to myocardial recovery. Future technical developments and better insights into the pathophysiology of mechanical circulatory support will broaden the spectrum of indications of such devices in acute circulatory arrest.

  5. Mechanisms in environmentally assisted one-photon phase control

    NASA Astrophysics Data System (ADS)

    Pachón, Leonardo A.; Brumer, Paul

    2013-10-01

    The ability of an environment to assist in one-photon phase control relies upon entanglement between the system and bath and on the breaking of the time reversal symmetry. Here, one-photon phase control is examined analytically and numerically in a model system, allowing an analysis of the relative strength of these contributions. Further, the significant role of non-Markovian dynamics and of moderate system-bath coupling in enhancing one-photon phase control is demonstrated, and an explicit role for quantum mechanics is noted in the existence of initial non-zero stationary coherences. Finally, desirable conditions are shown to be required to observe such environmentally assisted control, since the system will naturally equilibrate with its environment at longer times, ultimately resulting in the loss of phase control.

  6. Growth mechanism of carbon nanotubes grown by microwave plasma-assisted chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Muneyoshi, T.; Okai, M.; Yaguchi, T.; Sasaki, S.

    2001-10-01

    To investigate the most suitable deposition conditions and growth mechanism, we grew carbon nanotubes (CNTs) by microwave plasma-assisted chemical vapor deposition under various conditions. The experimental parameters we varied were (a) the mixture ratio of methane in hydrogen, (b) the total gas pressure, and (c) the bias electric current. We found that the bias electric current was the most influential parameter in determining the shape of CNTs. We believe that the growth process of CNTs can be explained by using the solid solubility curves of metal-carbon phase diagrams. Selective growth and low-temperature growth of CNTs can also be understood from these phase diagrams.

  7. Kinetics in Gas Mixtures for Problem of Plasma Assisted Combustion

    DTIC Science & Technology

    2010-05-01

    exothermal chemical hydrocarbon oxidation process, and (iii) subsequent thermal ignition. The role of gas temperature increase in the experiments on...the nonequilibrium plasma, (ii) chemical reactions of hydrocarbon oxidation with participa- tion of O atoms and gas heating due to net exothermal ...autoignition) the ignition delay de- pends upon the rate of the dissociation reaction which is endothermic . Generally the induction delay time is greatly

  8. Mechanisms of gas permeation through polymer membranes

    SciTech Connect

    Stern, S.A.

    1992-01-01

    Progress is reported in two areas: (1) Concentration-temperature superposition principle (CTSP). CTSP is a theoretical model for describing the gas solubility in glassy polymers swollen by the penetrant gas. It has been extended to describe the dependence of gas diffusivity and permeability on penetrant pressure. Further extension to diffusion of gas mixtures is being studied. (2)Solubility of gases in poly(alkyl methacrylates). Solubility of methane in poly(ethyl methacrylate) and poly(n-butyl methacrylate) was measured; the Langmuir capacity constant was found to not reflect a lower excess free volume; an equation is given for relating the constant to the glass transition temperature. Solubility of ethane in the latter polymer is affected by plasticization.

  9. Fundamental mechanisms in flue gas conditioning

    SciTech Connect

    Snyder, T.R.; Vann Bush, P.

    1995-11-01

    The overall goal of this research project has been to formulate a model describing effects of flue gas conditioning on particulate properties. By flue gas conditioning we mean any process by which solids, gases, or liquids are added to the combustor and/or the exhaust stream to the extent that flue gas and particulate properties may be altered. Our modeling efforts, which are included in our Final Report, are based on an understanding of how ash properties, such as cohesivity and resistivity, are changed by conditioning. Flue gas conditioning involves the modification of one or more of the parameters that determine the magnitude of forces acting on the fly ash particles, and can take place through many different methods. Modification of particulate properties can alter ash resistivity or ash cohesivity and result in improved or degraded control device performance. Changes to the flue gas, addition or particulate matter such as flue gas desulfurization (FGD) sorbents, or the addition of reactive gases or liquids can modify these properties. If we can better understand how conditioning agents react with fly ash particles, application of appropriate conditioning agents or processes may result in significantly improved fine particle collection at low capital and operating costs.

  10. Analysis of the dynamic characteristics of gas flow inside a laser cut kerf under high cut-assist gas pressure

    NASA Astrophysics Data System (ADS)

    Man, H. C.; Duan, J.; Yue, T. M.

    1999-07-01

    The behaviour of the cut-assist gas jet inside a simulating laser cut kerf for a supersonic and a conical nozzle tip were studied by a shadowgraphic technique under conditions of inlet stagnation pressure from 3 to 7 bar. The effects of the stand-off distance, kerf width, material thickness and the inlet stagnation pressure upon the dynamic characteristics and momentum thrust of the gas flow inside the cut kerf were investigated. It was found that under a gas pressure of 7 bar, the gas jet from a conical nozzle tip expands radially and the jet momentum deteriorates rapidly inside the kerf. The behaviour of the jet is strongly influenced by the stand-off distance and thickness of the workpiece. On the other hand, the gas jet from a supersonic nozzle inside the cut kerf has tidy boundary and uniform distribution of pressure and thrust. The sensitivity to the stand-off distance and the workpiece thickness of the supersonic nozzle are much less as compared with the conical nozzle. With the supersonic nozzle, a dross free clean cut on 5 mm stainless steel can be achieved at an inert cut-assist gas pressure as low as 5 bar instead of the normal operating range of 10 bar or above for the conical nozzle.

  11. Environment assisted degradation mechanisms in aluminum-lithium alloys

    NASA Technical Reports Server (NTRS)

    Gangloff, Richard P.; Stoner, Glenn E.; Swanson, Robert E.

    1988-01-01

    Section 1 of this report records the progress achieved on NASA-LaRC Grant NAG-1-745 (Environment Assisted Degradation Mechanisms in Al-Li Alloys), and is based on research conducted during the period April 1 to November 30, 1987. A discussion of work proposed for the project's second year is included. Section 2 provides an overview of the need for research on the mechanisms of environmental-mechanical degradation of advanced aerospace alloys based on aluminum and lithium. This research is to provide NASA with the basis necessary to permit metallurgical optimization of alloy performance and engineering design with respect to damage tolerance, long term durability and reliability. Section 3 reports on damage localization mechanisms in aqueous chloride corrosion fatigue of aluminum-lithium alloys. Section 4 reports on progress made on measurements and mechanisms of localized aqueous corrosion in aluminum-lithium alloys. Section 5 provides a detailed technical proposal for research on environmental degradation of Al-Li alloys, and the effect of hydrogen in this.

  12. Mechanics of gas-vapor bubbles

    NASA Astrophysics Data System (ADS)

    Hao, Yue; Zhang, Yuhang; Prosperetti, Andrea

    2017-03-01

    Most bubbles contain a mixture of vapor and incondensible gases. While the limit cases of pure vapor and pure gas bubbles are well studied, much less is known about the more realistic case of a mixture. The bubble contents continuously change due to the combined effects of evaporation and condensation and of gas diffusion in the liquid and in the bubble. This paper presents a model for this situation and illustrates by means of examples several physical processes that can occur: a bubble undergoing a temporary pressure reduction, which makes the liquid temporarily superheated; a bubble subjected to a burst of sound; and a bubble continuously growing by rectified diffusion of heat in the presence of an incondensible gas.

  13. Solar assisted gas-fired absorption heat pump

    NASA Astrophysics Data System (ADS)

    Murphy, K. P.; Burke, J. C.; Phillips, B. A.

    1982-08-01

    An evaluation of the technical and economic feasibility of coupling an absorption heat pump and an active solar system for residential applications is discussed. The absorption heat pump is based on a new absorption working pair developed by Allied. Three basic modes of coupling were considered, a series arrangement, a parallel arrangement, and a solar drive arrangement. Little overall difference in performance was found for these three modes but the solar drive was chosen for detailed study. A preliminary design of a dual mode absorption generator was developed capable of using simultaneously heat from gas and solar. The performance of such a system was examined in three cities.

  14. Mechanism on microwave-assisted acidic solvolysis of black-liquor lignin.

    PubMed

    Dong, Chengjian; Feng, Chunguang; Liu, Qian; Shen, Dekui; Xiao, Rui

    2014-06-01

    Microwave-assisted degradation of black-liquor lignin with formic acid was studied, concerning the product yield and distribution of phenolic compounds against reaction temperature (110-180°C) and reaction time (5-90 min). The liquid product consisting of bio-oil 1 and bio-oil 2, achieved the maxima yield of 64.08% at 160°C and 30 min (bio-oil 1: 9.69% and bio-oil 2: 54.39%). The chemical information of bio-oil 1 and bio-oil 2 were respectively identified by means of Gas Chromatography-Mass Spectrometer (GC-MS) and Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), while the solid residue was analyzed by Gel Permeation Chromatography (GPC) and Fourier Transform Infrared Spectroscopy (FTIR). A possible mechanism was proposed for the microwave-assisted acidic solvolysis of lignin, specifying the kinetic relationship among the primary cracking of lignin, repolymerization of the oligomers and formation of solid residue.

  15. On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection

    NASA Astrophysics Data System (ADS)

    Nardon, E.; Fil, A.; Chauveau, P.; Tamain, P.; Guirlet, R.; Koslowski, H. R.; Lehnen, M.; Reux, C.; Saint-Laurent, F.; Contributors, JET

    2017-01-01

    A new 1D radial fluid code, IMAGINE, is used to simulate the penetration of gas into a tokamak plasma during a massive gas injection (MGI). The main result is that the gas is in general strongly braked as it reaches the plasma, due to mechanisms related to charge exchange and (to a smaller extent) recombination. As a result, only a fraction of the gas penetrates into the plasma. Also, a shock wave is created in the gas which propagates away from the plasma, braking and compressing the incoming gas. Simulation results are quantitatively consistent, at least in terms of orders of magnitude, with experimental data for a D 2 MGI into a JET Ohmic plasma. Simulations of MGI into the background plasma surrounding a runaway electron beam show that if the background electron density is too high, the gas may not penetrate, suggesting a possible explanation for the recent results of Reux et al in JET (2015 Nucl. Fusion 55 093013).

  16. A mechanically assisted heat pipe using micro-pumps

    SciTech Connect

    Wong, J.L.; Campbell, G.; Hassapis, C.; Chang, W.S.

    1996-12-31

    A new mechanically assisted heat pipe has been developed and tested by the authors that combines the high performance of a pumped fluid loop with the reliability of passive heat pipes. The new unit employs micro-pumps inside a passive heat pipe to enhance the return of working fluid from the condenser to the evaporator, and thereby increases the capability of the system. This hybrid device is lighter, smaller and handles higher heat flux compared with a passive heat pipe of similar weight and dimensions. Best of all, if the mechanical pump fails, the heat transport will be impaired, but not totally paralyzed, allowing some form of lower level operation. This micro-pump design installs fins at critical locations inside the heat pipe. These fins can be parallel (flag) or perpendicular (flap) to the flow direction. By vibrating these fins in a motion similar to dolphin kicks for the flaps, and in a motion similar to a fishtail for the flags, these fins were found capable of pumping the working fluid effectively. The size and geometry of these fins were tested extensively. Several actuation approaches were examined. The results of these tests are presented in this paper.

  17. Mechanisms for leaf control of gas exchange

    SciTech Connect

    Mansfield, T.A.; Davies, W.J.

    1985-03-01

    Several mechanisms enable leaf stomata to optimize water loss with respect to carbon gain. Stomatal responses to environmental variation constitute a plant's first and second lines of defense against damaging water deficits. Changes in the concentrations of endogenous growth regulations and their influence on stomata may well be important to both defense strategies.

  18. Fundamental mechanisms in flue gas conditioning

    SciTech Connect

    Snyder, T.R.; Vann Bush, P.

    1992-10-27

    This project is divided into four tasks. We developed our management plan in Task 1. Task 2, evaluation of mechanisms in FGD sorbent and ash interactions, focuses on characteristics of binary mixtures of these distinct powders. Task 3, evaluation of mechanisms in conditioning agents and ash, is designed to examine effects of various conditioning agents on fine ash particles to determine mechanisms by which these agents alter physical properties of ash. We began Tasks 2 and 3 with an extensive literature search and assembly of existing theories. We completed this phase of the project with publication of two special Topical Reports. Our laboratory analyses during the past quarter covered a variety of topics. We quantified increases in surface area, changes in particle morphology, and increases in cohesivity that result when sorbents are mixed with ashes. Measurements of water content illustrated the increased tendency of the mixtures to adsorb and absorb water. Our analyses of leached and unleached dust cake ashes provided some interesting insights into effects that compounds adsorbed on surfaces of ash particles can have on bulk ash behavior. We also observed the effects that pozzolanic reactions can have on ash resistivity. Initial examinations of outputs of the SRI-EPA resistivity prediction model showed that the model could not accurately predict the resistivities we measured for leached and unleached dust cake ashes.

  19. Effect of impeller design and spacing on gas exchange in a percutaneous respiratory assist catheter.

    PubMed

    Jeffries, R Garrett; Frankowski, Brian J; Burgreen, Greg W; Federspiel, William J

    2014-12-01

    Providing partial respiratory assistance by removing carbon dioxide (CO2 ) can improve clinical outcomes in patients suffering from acute exacerbations of chronic obstructive pulmonary disease and acute respiratory distress syndrome. An intravenous respiratory assist device with a small (25 Fr) insertion diameter eliminates the complexity and potential complications associated with external blood circuitry and can be inserted by nonspecialized surgeons. The impeller percutaneous respiratory assist catheter (IPRAC) is a highly efficient CO2 removal device for percutaneous insertion to the vena cava via the right jugular or right femoral vein that utilizes an array of impellers rotating within a hollow-fiber membrane bundle to enhance gas exchange. The objective of this study was to evaluate the effects of new impeller designs and impeller spacing on gas exchange in the IPRAC using computational fluid dynamics (CFD) and in vitro deionized water gas exchange testing. A CFD gas exchange and flow model was developed to guide a progressive impeller design process. Six impeller blade geometries were designed and tested in vitro in an IPRAC device with 2- or 10-mm axial spacing and varying numbers of blades (2-5). The maximum CO2 removal efficiency (exchange per unit surface area) achieved was 573 ± 8 mL/min/m(2) (40.1 mL/min absolute). The gas exchange rate was found to be largely independent of blade design and number of blades for the impellers tested but increased significantly (5-10%) with reduced axial spacing allowing for additional shaft impellers (23 vs. 14). CFD gas exchange predictions were within 2-13% of experimental values and accurately predicted the relative improvement with impellers at 2- versus 10-mm axial spacing. The ability of CFD simulation to accurately forecast the effects of influential design parameters suggests it can be used to identify impeller traits that profoundly affect facilitated gas exchange.

  20. 3D Numerical study on the hollow profile polymer extrusion forming based on the gas-assisted technique

    NASA Astrophysics Data System (ADS)

    Ren, Z.; Huang, X. Y.; Liu, H. S.

    2016-07-01

    In this study, gas-assisted extrusion method was introduced into the extrusion of the hollow profiles. To validate the feasibility of the new extrusion method, 3D numerical simulation of the hollow profiles based on gas-assisted technique was carried out by using the finite element method. The Phan-Thien-Tanner (PTT) mode was selected as the construction equation. In the simulations, the physical field distributions of four different extrusion modes were obtained and analyzed. Results showed that the extrudate effect of traditional no gas- assisted mode was poor because the extrudate swell phenomenon is obvious and the physical field values are larger. For the gas-assisted of the inner wall, the extrudate swell of the melt was more obvious than that of the traditional no gas-assisted mode on account of the no-slip boundary condition on the outer wall. For the gas-assisted of the outer wall, the dimple effect of the inner wall is more obvious owing to the no-slip boundary condition on the inner wall. However, the extrusion effect of the double walls gas-assisted mode is very good because of the full-slip effect on the both walls.

  1. Fundamental Mechanisms, Predictive Modeling, and Novel Aerospace Applications of Plasma Assisted Combustion

    DTIC Science & Technology

    2011-11-01

    Fundamental Mechanisms, Predictive Modeling, and Novel Aerospace Applications of Plasma Assisted Combustion Yiguang Ju AFOSR MURI Review Meeting...SUBTITLE Fundamental Mechanisms, Predictive Modeling, and Novel Aerospace Applications of Plasma Assisted Combustion 5a. CONTRACT NUMBER 5b. GRANT...stabilization • Combustion completion F135 engine: (F35, 2011) Mach 6-8 Ignition instability Plasma assisted combustion Plasma Ions/electrons Excited species

  2. METHANE EMISSIONS FROM THE NATURAL GAS INDUSTRY VOLUME 15: GAS-ASSISTED GLYCOL PUMPS

    EPA Science Inventory

    The 15-volume report summarizes the results of a comprehensive program to quantify methane (CH4) emissions from the U.S. natural gas industry for the base year. The objective was to determine CH4 emissions from the wellhead and ending downstream at the customer's meter. The accur...

  3. Sensing Mechanisms for Carbon Nanotube Based NH3 Gas Detection

    SciTech Connect

    Peng, Ning; Zhang, Qing; Chow, Chee L.; Tan, Ooi K.; Marzari, Nicola N.

    2009-03-31

    There has been an argument on carbon nanotube (CNT) based gas detectors with a field-effect transistor (FET) geometry: do the response signals result from charge transfer between adsorbed gas molecules and the CNT channel and/or from the gas species induced Schottky barrier modulation at the CNT/metal contacts? To differentiate the sensing mechanisms, we employed three CNTFET structures, i.e., (1) the entire CNT channel and CNT/electrode contacts are accessible to NH3 gas; (2) the CNT/electrode contacts are passivated with a Si3N4 thin film, leaving the CNT channel open to the gas and, in contrast, (3) the CNT channel is covered with the film, while the contacts are open to the gas. We suggest that the Schottky barrier modulation at the contacts is the dominant mechanism from room temperature to 150°C. At higher temperatures, the charge transfer process contributes to the response signals. There is a clear evidence that the adsorption of NH3 on the CNT channel is facilitated by environmental oxygen.

  4. Sensing mechanisms for carbon nanotube based NH3 gas detection.

    PubMed

    Peng, Ning; Zhang, Qing; Chow, Chee Lap; Tan, Ooi Kiang; Marzari, Nicola

    2009-04-01

    There has been an argument on carbon nanotube (CNT) based gas detectors with a field-effect transistor (FET) geometry: do the response signals result from charge transfer between adsorbed gas molecules and the CNT channel and/or from the gas species induced Schottky barrier modulation at the CNT/metal contacts? To differentiate the sensing mechanisms, we employed three CNTFET structures, i.e., (1) the entire CNT channel and CNT/electrode contacts are accessible to NH(3) gas; (2) the CNT/electrode contacts are passivated with a Si(3)N(4) thin film, leaving the CNT channel open to the gas and, in contrast, (3) the CNT channel is covered with the film, while the contacts are open to the gas. We suggest that the Schottky barrier modulation at the contacts is the dominant mechanism from room temperature to 150 degrees C. At higher temperatures, the charge transfer process contributes to the response signals. There is a clear evidence that the adsorption of NH(3) on the CNT channel is facilitated by environmental oxygen.

  5. DEVELOPMENT AND OPTIMIZATION OF GAS-ASSISTED GRAVITY DRAINAGE (GAGD) PROCESS FOR IMPROVED LIGHT OIL RECOVERY

    SciTech Connect

    Dandina N. Rao; Subhash C. Ayirala; Madhav M. Kulkarni; Thaer N.N. Mahmoud; Wagirin Ruiz Paidin

    2006-01-01

    This report describes the progress of the project ''Development And Optimization of Gas-Assisted Gravity Drainage (GAGD) Process for Improved Light Oil Recovery'' for the duration of the thirteenth project quarter (Oct 1, 2005 to Dec 30, 2005). There are three main tasks in this research project. Task 1 is a scaled physical model study of the GAGD process. Task 2 is further development of a vanishing interfacial tension (VIT) technique for miscibility determination. Task 3 is determination of multiphase displacement characteristics in reservoir rocks. Section I reports experimental work designed to investigate wettability effects of porous medium, on secondary and tertiary mode GAGD performance. The experiments showed a significant improvement of oil recovery in the oil-wet experiments versus the water-wet runs, both in secondary as well as tertiary mode. When comparing experiments conducted in secondary mode to those run in tertiary mode an improvement in oil recovery was also evident. Additionally, this section summarizes progress made with regard to the scaled physical model construction and experimentation. The purpose of building a scaled physical model, which attempts to include various multiphase mechanics and fluid dynamic parameters operational in the field scale, was to incorporate visual verification of the gas front for viscous instabilities, capillary fingering, and stable displacement. Preliminary experimentation suggested that construction of the 2-D model from sintered glass beads was a feasible alternative. During this reporting quarter, several sintered glass mini-models were prepared and some preliminary experiments designed to visualize gas bubble development were completed. In Section II, the gas-oil interfacial tensions measured in decane-CO{sub 2} system at 100 F and live decane consisting of 25 mole% methane, 30 mole% n-butane and 45 mole% n-decane against CO{sub 2} gas at 160 F have been modeled using the Parachor and newly proposed

  6. On mechanisms of choked gas flows in microchannels

    NASA Astrophysics Data System (ADS)

    Shan, Xiaodong; Wang, Moran

    2015-10-01

    Choked gas flows in microchannels have been reported before based solely on experimental measurements, but the underlining physical mechanism has yet to be clarified. In this work, we are to explore the process via numerical modeling of choked gas flows through a straight microchannel that connects two gas reservoirs. The major theoretical consideration lies in that, since the gas in microchannels may not be necessarily rarefied even at a high Knudsen number, a generalized Monte Carlo method based on the Enskog theory, GEMC, was thus used instead of direct simulation Monte Carlo (DSMC). Our results indicate that the choked gas flows in microchannels can be divided into two types: sonic choking and subsonic choking, because the sonic point does not always exist even though the gas flows appear choked, depending on the inlet-outlet pressure ratio and the length-height ratio of the channel. Even if the gas flow does not reach a sonic point at the outlet region, the effective pressure ratio (pi /po) acting on the channel becomes asymptotically changeless when the pressure ratio on the buffer regions (pi‧ / po‧) is higher than a certain value. The subsonic choking may caused by the expansion wave or the strong non-equilibrium effect at the outlet.

  7. Combustion Instability Mechanisms in a Pressure-coupled Gas-gas Coaxial Rocket Injector

    DTIC Science & Technology

    2013-06-01

    Coaxial Rocket Injector 5a. CONTRACT NUMBER In-House 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Harvazinski, M. , Huang, C...Combustion Instability Mechanisms in a Pressure-coupled Gas-gas Coaxial Rocket Injector Matthew E. Harvazinski∗, Air Force Research Laboratory...downstream and the vortex partially decayed before impingement, the timing of this event was not well correlated with the acoustic mode.11 For the third

  8. Gas-evaporation in low-gravity field (cogelation mechanism of metal vapors) (M-14)

    NASA Technical Reports Server (NTRS)

    Wada, N.

    1993-01-01

    When metal and alloy compounds are heated and vaporized in a rare gas such as helium, argon, or xenon, the vaporized substances diffused in the rare gas are supersaturated resulting in a smoke of fine particles of the material congealing as snow or fog. The gas vaporizing method is a fine particle generation method. Though the method has a variety of applications, the material vapor flow is disturbed by gravitational convection on Earth. The inability to elucidate the fine particle generation mechanism results in an obstruction to improving the method to mass production levels. As no convection occurs in microgravity in space, the fine particle generation mechanism influenced only by diffusion can be investigated. Investigators expect that excellent particles with homogeneous diameter distribution can be obtained. Experiment data and facts will assist in improving efficiency, quality, and scale or production processes including element processes such as vaporization, diffusion, and condensation. The objective of this experiment is to obtain important information related to the mechanism of particle formation in the gas atmosphere (smoke particles) and the production of submicron powders of extremely uniform size.

  9. Robot assisted treadmill training: mechanisms and training strategies.

    PubMed

    Hussain, Shahid; Xie, Sheng Quan; Liu, Guangyu

    2011-06-01

    The rehabilitation engineering community is working towards the development of robotic devices that can assist during gait training of patients suffering from neurologic injuries such as stroke and spinal cord injuries (SCI). The field of robot assisted treadmill training has rapidly evolved during the last decade. The robotic devices can provide repetitive, systematic and prolonged gait training sessions. This paper presents a review of the treadmill based robotic gait training devices. An overview of design configurations and actuation methods used for these devices is provided. Training strategies designed to actively involve the patient in robot assisted treadmill training are studied. These training strategies assist the patient according to the level of disability and type of neurologic injury. Although the efficacy of these training strategies is not clinically proven, adaptive strategies may result in substantial improvements. We end our review with a discussion covering major advancements made at device design and training strategies level and potential challenges to the field.

  10. Gas-assisted gravity drainage (GAGD) process for improved oil recovery

    SciTech Connect

    Rao, Dandina N

    2012-07-10

    A rapid and inexpensive process for increasing the amount of hydrocarbons (e.g., oil) produced and the rate of production from subterranean hydrocarbon-bearing reservoirs by displacing oil downwards within the oil reservoir and into an oil recovery apparatus is disclosed. The process is referred to as "gas-assisted gravity drainage" and comprises the steps of placing one or more horizontal producer wells near the bottom of a payzone (i.e., rock in which oil and gas are found in exploitable quantities) of a subterranean hydrocarbon-bearing reservoir and injecting a fluid displacer (e.g., CO.sub.2) through one or more vertical wells or horizontal wells. Pre-existing vertical wells may be used to inject the fluid displacer into the reservoir. As the fluid displacer is injected into the top portion of the reservoir, it forms a gas zone, which displaces oil and water downward towards the horizontal producer well(s).

  11. Gas-assisted annular microsprayer for sample preparation for time-resolved cryo-electron microscopy

    NASA Astrophysics Data System (ADS)

    Lu, Zonghuan; Barnard, David; Shaikh, Tanvir R.; Meng, Xing; Mannella, Carmen A.; Yassin, Aymen S.; Agrawal, Rajendra K.; Wagenknecht, Terence; Lu, Toh-Ming

    2014-11-01

    Time-resolved cryo-electron microscopy (TRCEM) has emerged as a powerful technique for transient structural characterization of isolated biomacromolecular complexes in their native state within the time scale of seconds to milliseconds. For TRCEM sample preparation, a microfluidic device has been demonstrated to be a promising approach to facilitate TRCEM biological sample preparation. It is capable of achieving rapidly aqueous sample mixing, controlled reaction incubation, and sample deposition on electron microscopy (EM) grids for rapid freezing. One of the critical challenges is to transfer samples to cryo-EM grids from the microfluidic device. By using a microspraying method, the generated droplet size needs to be controlled to facilitate thin ice film formation on the grid surface for efficient data collection, whilst not being so thin that it dries out before freezing, i.e. an optimized mean droplet size needs to be achieved. In this work, we developed a novel monolithic three dimensional (3D) annular gas-assisted microfluidic sprayer using 3D MEMS (MicroElectroMechanical System) fabrication techniques. The microsprayer demonstrated dense and consistent microsprays with average droplet size between 6 and 9 μm, which fulfilled the droplet size requirement for TRCEM sample preparation. With droplet density of around 12-18 per grid window (window size 58  ×  58 μm), and a data collectible thin ice region of >50% total wetted area, we collected ~800-1000 high quality CCD micrographs in a 6-8 h period of continuous effort. This level of output is comparable to what were routinely achieving using cryo-grids prepared by conventional blotting and manual data collection. In this case, weeks of data collection with the previous device has been shortened to a day or two. And hundreds of microliters of valuable sample consumption can be reduced to only a small fraction.

  12. Gas-Assisted Annular Microsprayer for Sample Preparation for Time-Resolved Cryo-Electron Microscopy

    PubMed Central

    Lu, Zonghuan; Barnard, David; Shaikh, Tanvir R.; Meng, Xing; Mannella, Carmen A.; Yassin, Aymen; Agrawal, Rajendra; Wagenknecht, Terence; Lu, Toh-Ming

    2014-01-01

    Time-resolved cryo electron microscopy (TRCEM) has emerged as a powerful technique for transient structural characterization of isolated biomacromolecular complexes in their native state within the time scale of seconds to milliseconds. For TRCEM sample preparation, microfluidic device [9] has been demonstrated to be a promising approach to facilitate TRCEM biological sample preparation. It is capable of achieving rapidly aqueous sample mixing, controlled reaction incubation, and sample deposition on electron microscopy (EM) grids for rapid freezing. One of the critical challenges is to transfer samples to cryo-EM grids from the microfluidic device. By using microspraying method, the generated droplet size needs to be controlled to facilitate the thin ice film formation on the grid surface for efficient data collection, while not too thin to be dried out before freezing, i.e., optimized mean droplet size needs to be achieved. In this work, we developed a novel monolithic three dimensional (3D) annular gas-assisted microfluidic sprayer using 3D MEMS (MicroElectroMechanical System) fabrication techniques. The microsprayer demonstrated dense and consistent microsprays with average droplet size between 6-9 μm, which fulfilled the above droplet size requirement for TRCEM sample preparation. With droplet density of around 12-18 per grid window (window size is 58×58 μm), and the data collectible thin ice region of >50% total wetted area, we collected ~800-1000 high quality CCD micrographs in a 6-8 hour period of continuous effort. This level of output is comparable to what were routinely achieved using cryo-grids prepared by conventional blotting and manual data collection. In this case, weeks of data collection process with the previous device [9] has shortened to a day or two. And hundreds of microliter of valuable sample consumption can be reduced to only a small fraction. PMID:25530679

  13. Microscale mechanisms of gas exchange in fruit tissue.

    PubMed

    Ho, Q T; Verboven, P; Mebatsion, H K; Verlinden, B E; Vandewalle, S; Nicolaï, B M

    2009-01-01

    * Gas-filled intercellular spaces are considered the predominant pathways for gas transport through bulky plant organs such as fruit. Here, we introduce a methodology that combines a geometrical model of the tissue microstructure with mathematical equations to describe gas exchange mechanisms involved in fruit respiration. * Pear (Pyrus communis) was chosen as a model system. The two-dimensional microstructure of cortex tissue was modelled based on light microscopy images. The transport of O(2) and CO(2) in the intercellular space, cell wall network and cytoplasm was modelled using diffusion laws, irreversible thermodynamics and enzyme kinetics. * In silico analysis showed that O(2) transport mainly occurred through intercellular spaces and less through the intracellular liquid, while CO(2) was transported at equal rates in both phases. Simulations indicated that biological variation of the apparent diffusivity appears to be caused by the random distribution of cells and intercellular spaces in tissue. Temperature does not affect modelled gas exchange properties; it rather acts on the respiration metabolism. * This modelling approach provides, for the first time, detailed information about gas exchange mechanisms at the microscopic scale in bulky plant organs, such as fruit, and can be used to study conditions of anoxia.

  14. DEVELOPMENT AND OPTIMIZATION OF GAS-ASSISTED GRAVITY DRAINAGE (GAGD) PROCESS FOR IMPROVED LIGHT OIL RECOVERY

    SciTech Connect

    Dandina N. Rao; Subhash C. Ayirala; Madhav M. Kulkarni; Amit P. Sharma

    2004-10-01

    This report describes the progress of the project ''Development and Optimization of Gas-Assisted Gravity Drainage (GAGD) Process for Improved Light Oil Recovery'' for the duration of the second project year (October 1, 2003--September 30, 2004). There are three main tasks in this research project. Task 1 is scaled physical model study of GAGD process. Task 2 is further development of vanishing interfacial tension (VIT) technique for miscibility determination. Task 3 is determination of multiphase displacement characteristics in reservoir rocks. In Section I, preliminary design of the scaled physical model using the dimensional similarity approach has been presented. Scaled experiments on the current physical model have been designed to investigate the effect of Bond and capillary numbers on GAGD oil recovery. Experimental plan to study the effect of spreading coefficient and reservoir heterogeneity has been presented. Results from the GAGD experiments to study the effect of operating mode, Bond number and capillary number on GAGD oil recovery have been reported. These experiments suggest that the type of the gas does not affect the performance of GAGD in immiscible mode. The cumulative oil recovery has been observed to vary exponentially with Bond and capillary numbers, for the experiments presented in this report. A predictive model using the bundle of capillary tube approach has been developed to predict the performance of free gravity drainage process. In Section II, a mechanistic Parachor model has been proposed for improved prediction of IFT as well as to characterize the mass transfer effects for miscibility development in reservoir crude oil-solvent systems. Sensitivity studies on model results indicate that provision of a single IFT measurement in the proposed model is sufficient for reasonable IFT predictions. An attempt has been made to correlate the exponent (n) in the mechanistic model with normalized solute compositions present in both fluid phases

  15. Fundamental mechanisms in flue gas conditioning. Final report

    SciTech Connect

    Snyder, T.R.; Bush, P.V.; Dahlin, R.S.

    1996-03-20

    The US Department of Energy`s Pittsburgh Energy Technology Center (DOE/PETC) initiated this project as part of a program to study the control of fine particles from coal combustion. Our project focus was flue gas conditioning. Various conditioning processes have lowered operating costs and increased collection efficiency at utility particulate control devices. By improving fine particle collection, flue gas conditioning also helps to control the emission of toxic metals, which are concentrated in the fine particle fraction. By combining a review of pertinent literature, laboratory characterization of a variety of fine powders and ashes, pilot-scale studies of conditioning mechanisms, and field experiences, Southern Research Institute has been able to describe many of the key processes that account for the effects that conditioning can have on fine-particle collection. The overall goal of this research project was to explain the mechanisms by which various flue gas conditioning processes alter the performance of particulate control devices. Conditioning involves the modification of one or more of the parameters that determine the magnitude of the forces acting on the fly ash particles. Resistivity, chemistry, cohesivity, size distribution, and particle morphology are among the basic properties of fly ash that significantly influence fine particle collection. Modifications of particulate properties can result in improved or degraded control device performance. These modifications can be caused by (1) changes to the process design or operation that affect properties of the flue gas, (2) addition of particulate matter such as flue-gas desulfurization sorbents to the process effluent stream, (3) injection of reactive gases or liquids into the flue gas. We recommend that humidification be seriously considered as a flue gas conditioning option. 80 refs., 69 figs., 23 tabs.

  16. Mechanical ventilation and thoracic artificial lung assistance during mechanical circulatory support with PUCA pump: in silico study.

    PubMed

    De Lazzari, Claudio; Genuini, Igino; Quatember, Bernhard; Fedele, Francesco

    2014-02-01

    Patients assisted with left ventricular assist device (LVAD) may require prolonged mechanical ventilatory assistance secondary to postoperative respiratory failure. The goal of this work is the study of the interdependent effects LVAD like pulsatile catheter (PUCA) pump and mechanical ventilatory support or thoracic artificial lung (TAL), by the hemodynamic point of view, using a numerical simulator of the human cardiovascular system. In the simulator, different circulatory sections are described using lumped parameter models. Lumped parameter models have been designed to describe the hydrodynamic behavior of both PUCA pump and thoracic artificial lung. Ventricular behavior atrial and septum functions were reproduced using variable elastance model. Starting from simulated pathological conditions we studied the effects produced on some hemodynamic variables by simultaneous PUCA pump, thoracic artificial lung or mechanical ventilation assistance. Thoracic artificial lung was applied in parallel or in hybrid mode. The effects of mechanical ventilation have been simulated by changing mean intrathoracic pressure value from -4 mmHg to +5 mmHg. The hemodynamic variables observed during the simulations, in different assisted conditions, were: left and right ventricular end systolic (diastolic) volume, systolic/diastolic aortic pressure, mean pulmonary arterial pressure, left and right mean atrial pressure, mean systemic venous pressure and the total blood flow. Results show that the application of PUCA (without mechanical ventilatory assistance) increases the total blood flow, reduces the left ventricular end systolic volume and increases the diastolic aortic pressure. Parallel TAL assistance increases the right ventricular end diastolic (systolic) volume reduction both when PUCA is switched "ON" and both when PUCA is switched "OFF". By switching "OFF" the PUCA pump, it seems that parallel thoracic artificial lung assistance produces a greater cardiac output (respect to

  17. [Neurally adjusted ventilatory assist: a revolution of mechanical ventilation?].

    PubMed

    Piquilloud, Lise; Jolliet, Philippe; Tassaux, Didier

    2010-12-15

    Neurally adjusted ventilatory assist or NAVA is a new assisted ventilatory mode which, in comparison with pressure support, leads to improved patient-ventilator synchrony and a more variable ventilatory pattern. It also improves arterial oxygenation. With NAVA, the electrical activity of the diaphragm is recorded through a nasogastric tube equipped with electrodes. This electrical activity is then used to pilot the ventilator. With NAVA, the patient's respiratory pattern controls the ventilator's timing of triggering and cycling as well as the magnitude of pressurization, which is proportional to inspiratory demand. The effect of NAVA on patient outcome remains to be determined through well-designed prospective studies.

  18. The mechanism of galvanic/metal-assisted etching of silicon

    NASA Astrophysics Data System (ADS)

    Kolasinski, Kurt W.

    2014-08-01

    Metal-assisted etching is initiated by hole injection from an oxidant catalyzed by a metal nanoparticle or film on a Si surface. It is shown that the electronic structure of the metal/Si interface, i.e., band bending, is not conducive to diffusion of the injected hole away from the metal in the case of Ag or away from the metal/Si interface in the cases of Au, Pd, and Pt. Since holes do not diffuse away from the metals, the electric field resulting from charging of the metal after hole injection must instead be the cause of metal-assisted etching.

  19. The mechanism of galvanic/metal-assisted etching of silicon.

    PubMed

    Kolasinski, Kurt W

    2014-01-01

    Metal-assisted etching is initiated by hole injection from an oxidant catalyzed by a metal nanoparticle or film on a Si surface. It is shown that the electronic structure of the metal/Si interface, i.e., band bending, is not conducive to diffusion of the injected hole away from the metal in the case of Ag or away from the metal/Si interface in the cases of Au, Pd, and Pt. Since holes do not diffuse away from the metals, the electric field resulting from charging of the metal after hole injection must instead be the cause of metal-assisted etching.

  20. Laser-assisted focused He+ ion beam induced etching with and without XeF2 gas assist

    SciTech Connect

    Stanford, Michael G.; Mahady, Kyle; Lewis, Brett B.; Fowlkes, Jason D.; Tan, Shida; Livengood, Richard; Magel, Gregory A.; Moore, Thomas M.; Rack, Philip D.

    2016-10-04

    Focused helium ion (He+) milling has been demonstrated as a high-resolution nanopatterning technique; however, it can be limited by its low sputter yield as well as the introduction of undesired subsurface damage. Here, we introduce pulsed laser- and gas-assisted processes to enhance the material removal rate and patterning fidelity. A pulsed laser-assisted He+ milling process is shown to enable high-resolution milling of titanium while reducing subsurface damage in situ. Gas-assisted focused ion beam induced etching (FIBIE) of Ti is also demonstrated in which the XeF2 precursor provides a chemical assist for enhanced material removal rate. In conclusion, a pulsed laser-assisted and gas-assisted FIBIE process is shown to increase the etch yield by ~9× relative to the pure He+ sputtering process. These He+ induced nanopatterning techniques improve material removal rate, in comparison to standard He+ sputtering, while simultaneously decreasing subsurface damage, thus extending the applicability of the He+ probe as a nanopattering tool.

  1. Spectrum of temperature pulsations of the melt in gas-assisted cutting with fiber laser

    NASA Astrophysics Data System (ADS)

    Dubrov, Alexander V.; Zavalov, Yury N.; Dubrov, Vladimir D.; Grezev, Anatoly N.; Grezev, Nikolay V.; Makarova, Elena S.; Dubrovin, Nickolay G.

    2012-09-01

    Measurements of the temperature behavior in the zone of action of the laser-radiation on the molten metal have been performed using multichannel pyrometer. Measurements were carried out for test cutting of a 3-mm mild-steel plate with several values of cutting speed and pressure of assist gas (oxygen), using an 1800-watt Ytterbium fiber laser. It is shown that fluctuations of temperature are related to local melt's surface deformations due to unequal radiation absorption; thus the noise spectrum of temperature fluctuations reflects turbulent surface deformation caused by gas jet and capillary waves. The maximum density of turbulent energy dissipation ε depends on cutting conditions: its value rises with increasing cutting velocity and oxygen pressure in a described range of parameters. The maximum of ε is localized near depth of (1.2…1.5) mm along the cutting front. We can distinguish the specific radiation pulsation spectrum of laser cutting from other processes of radiation affection to the sample, including unwanted degrading of the quality of technological operations. The spectrum of capillary waves on the melt's surface is formed under the effect of assisted gas jet and has a function of ω-3, ω is cycle frequency. The results of this investigation can be useful for the development of monitoring and quality-control systems for the laser-cutting process.

  2. Solar-assisted gas-energy water-heating feasibility for apartments

    NASA Technical Reports Server (NTRS)

    Davis, E. S.

    1975-01-01

    Studies of residential energy use, solar-energy technology for buildings, and the requirements for implementing technology in the housing industry led to a project to develop a solar water heater for apartments. A design study for a specific apartment was used to establish a solar water-heater cost model which is based on plumbing contractor bids and manufacturer estimates. The cost model was used to size the system to minimize the annualized cost of hot water. The annualized cost of solar-assisted gas-energy water heating is found to be less expensive than electric water heating but more expensive than gas water heating. The feasibility of a natural gas utility supplying the auxiliary fuel is evaluated. It is estimated that gas-utilizing companies will find it profitable to offer solar water heating as part of a total energy service option or on a lease basis when the price of new base-load supplies of natural gas reaches $2.50-$3.00 per million Btu.

  3. Gravitational assist in celestial mechanics-a tutorial

    NASA Astrophysics Data System (ADS)

    van Allen, James A.

    2003-05-01

    In planning certain types of trajectories of spacecraft within the solar system, engineers rely on a technique called gravitational assist, or gravity assist. This technique underlies the feasibility of effecting a net change in both the speed and direction of motion of a spacecraft by passage through the gravitational field of a planet or a planetary satellite. The resulting increase, or decrease, in the kinetic energy of the spacecraft appears to contradict the casual expectation that in such an encounter the kinetic energy of the spacecraft after the encounter would be the same as that before the encounter. This paper describes the December 1973 encounter of the Pioneer 10 spacecraft with the planet Jupiter as a real-life example of gravitational assist. It then discusses the physical principles involved in understanding the dynamics of the encounter and concludes with remarks on the important role of gravitational assist in space exploration with artificial spacecraft and in understanding the motion of comets within the solar system.

  4. Mechanisms of hydrogen-assisted fracture in austenitic stainless steel welds.

    SciTech Connect

    Balch, Dorian K.; Sofronis, Petros; Somerday, Brian P.; Novak, Paul

    2005-03-01

    The objective of this study was to quantify the hydrogen-assisted fracture susceptibility of gas-tungsten arc (GTA) welds in the nitrogen-strengthened, austenitic stainless steels 21Cr-6Ni-9Mn (21-6-9) and 22Cr-13Ni-5Mn (22-13-5). In addition, mechanisms of hydrogen-assisted fracture in the welds were identified using electron microscopy and finite-element modeling. Elastic-plastic fracture mechanics experiments were conducted on hydrogen-charged GTA welds at 25 C. Results showed that hydrogen dramatically lowered the fracture toughness from 412 kJ/m{sup 2} to 57 kJ/m{sup 2} in 21-6-9 welds and from 91 kJ/m{sup 2} to 26 kJ/m{sup 2} in 22-13-5 welds. Microscopy results suggested that hydrogen served two roles in the fracture of welds: it promoted the nucleation of microcracks along the dendritic structure and accelerated the link-up of microcracks by facilitating localized deformation. A continuum finite-element model was formulated to test the notion that hydrogen could facilitate localized deformation in the ligament between microcracks. On the assumption that hydrogen decreased local flow stress in accordance with the hydrogen-enhanced dislocation mobility argument, the finite-element results showed that deformation was localized in a narrow band between two parallel, overlapping microcracks. In contrast, in the absence of hydrogen, the finite-element results showed that deformation between microcracks was more uniformly distributed.

  5. Conformation of Macromolecules in the Gas Phase: Use of Matrix-Assisted Laser Desorption Methods in Ion Chromatography

    NASA Astrophysics Data System (ADS)

    von Helden, Gert; Wyttenbach, Thomas; Bowers, Michael T.

    1995-03-01

    Conformational data for macromolecules in the gas phase have been obtained by the coupling of a matrix-assisted laser desorption ion source to an ion chromatograph. A series of polyethylene glycol (PEG) polymers "cationized" (converted to a cation) by sodium ions (Na^+PEG9 to Na^+PEG19) and a protonated neurotransmitter protein, bradykinin, were studied. Mobilities of Na^+PEG9 to Na^+PEG19 are reported. Detailed modeling of Na^+PEG9 with molecular mechanics methods indicates that the lowest energy structure has the Na^+ ion "solvated" by the polymer chain with seven oxygen atoms as nearest neighbors. The agreement between the model and experiment is within 1 percent for Na^+PEG9, Na^+PEG13, and Na^+PEG17, giving strong support to both the method and the deduced structures. Similar agreement was obtained in initial studies that modeled experimental data for arginine-protonated bradykinin.

  6. The Growing Role of Trade as A Development Assistance Mechanism.

    DTIC Science & Technology

    1981-08-11

    Malaysia, Thailand, the Philippines, and Indonesia are coun- tries in which (1) the industrial world has an important stake in stable economic development...developed countries, to assist in their economic growth. In recent years, developed-country imports from (non- oil) developing countries as a share of...questionnaires to 677 American importers who do business in Malaysia, Thailand, the Philippines, Indonesia , and South Korea. We sent our questionnaire to obtain

  7. Relevance of trapping mechanisms in certain Michigan formation stray sandstone gas reservoirs to gas storage operations

    SciTech Connect

    Nowaczewski, S.F. )

    1994-08-01

    The Stray sandstones of the Michigan Formation were early exploration targets in the Michigan basin. Subsequent to primary production, some of these reservoirs were converted to gas storage. Many of the Stray fields were discovered in an underpressured state, whereas peak storage pressures often exceed native brine gradients. It can be demonstrated that the Stray sandstones exist in sheets and lenses throughout the central basin area, and that gas/water contacts exist in the gas reservoirs but behave volumetrically. Various indirect and direct evidence indicates that gas is trapped structurally by the antiformal geometry of the sandstone bodies, by probable fracture-controlled porosity, stratigraphically by the isolation of parts of the sand bodies due to depositional and diagenetic influences, and by structurally controlled stratigraphic relationships. The understanding of the trapping mechanisms allows successful high pressure-gradient gas storage and leads to understanding reservoir behavior, which should result in efficient storage development and operation. Additional direct and secondary benefits of understanding Stray sandstone structure and stratigraphy are demonstrated for gas storage operation nuisances such as water production, and for use of the Stray as a window to or a type for deeper formations.

  8. Pre-breakdown evaluation of gas discharge mechanisms in microgaps

    SciTech Connect

    Semnani, Abbas; Peroulis, Dimitrios; Venkattraman, Ayyaswamy; Alexeenko, Alina A.

    2013-04-29

    The individual contributions of various gas discharge mechanisms to total pre-breakdown current in microgaps are quantified numerically. The variation of contributions of field emission and secondary electron emission with increasing electric field shows contrasting behavior even for a given gap size. The total current near breakdown decreases rapidly with gap size indicating that microscale discharges operate in a high-current, low-voltage regime. This study provides the first such analysis of breakdown mechanisms and aids in the formulation of physics-based theories for microscale breakdown.

  9. Microwave-assisted synthesis of SnO₂ nanorods for oxygen gas sensing at room temperature.

    PubMed

    Azam, Ameer; Habib, Sami S; Salah, Numan A; Ahmed, Faheem

    2013-01-01

    High-quality single-crystalline SnO₂ nanorods were synthesized using a microwave-assisted solution method. The nanorods were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), ultraviolet-visible and Raman spectroscopy, Brunauer-Emmett-Teller (BET), and electrical resistance measurements. The XRD pattern indicated the formation of single-phase SnO₂ nanorods with rutile structure. FE-SEM and TEM images revealed tetragonal nanorods of about 450-500 nm in length and 60-80 nm in diameter. The nanorods showed a higher BET surface area of 288 m²/g, much higher than that of previously reported work. The Raman scattering spectra indicated a typical rutile phase of the SnO₂. The absorption spectrum showed an absorption peak centered at 340 nm, and the band-gap value was found to be 3.64 eV. The gas-sensing properties of the SnO₂ nanorods for oxygen gas with different concentrations were measured at room temperature. It was found that the value of resistance increased with the increase in oxygen gas concentration in the test chamber. The SnO₂ nanorods exhibited high sensitivity and rapid response-recovery characteristics to oxygen gas, and could detect oxygen concentration as low as 1, 3, 5, and 10 ppm.

  10. Unconventional mechanisms control cyclic respiratory gas release in flying Drosophila.

    PubMed

    Lehmann, Fritz-Olaf; Heymann, Nicole

    2005-10-01

    The high power output of flight muscles places special demands on the respiratory gas exchange system in insects. In small insects, respiration relies on diffusion, and for elevated locomotor performance such as flight, instantaneous gas exchange rates typically co-vary with the animal's metabolic activity. By contrast, under certain conditions, instantaneous release rate of carbon dioxide from the fruit fly Drosophila flying in a virtual-reality flight arena may oscillate distinctly at low frequency (0.37+/-0.055 Hz), even though flight muscle mechanical power output requires constant metabolic activity. Cross-correlation analysis suggests that this uncoupling between respiratory and metabolic rate is not driven by conventional types of convective flow reinforcement such as abdominal pumping, but might result from two unusual mechanisms for tracheal breathing. Simplified analytical modeling of diffusive tracheal gas exchange suggests that cyclic release patterns in the insect occur as a consequence of the stochastically synchronized control of spiracle opening area by the four large thoracic spiracles. Alternatively, in-flight motion analysis of the abdomen and proboscis using infra-red video imaging suggests utilization of the proboscis extension reflex (PER) for tracheal convection. Although the respiratory benefit of synchronized spiracle opening activity in the fruit fly is unclear, proboscis-induced tracheal convection might potentially help to balance the local oxygen supply between different body compartments of the flying animal.

  11. The application of an assisting gas plasma generator for low- temperature magnetron sputtering of Ti-C-Mo-S antifriction coatings on titanium alloys

    NASA Astrophysics Data System (ADS)

    Potekaev, A. I.; Savostikov, V. M.; Tabachenko, A. N.; Dudarev, E. F.; Melnikova, E. A.; Shulepov, I. A.

    2015-11-01

    The positive effect of assisting influence of high-density gas plasma formed by an independent plasma generator PINK on mechanical and tribological characteristics of Ti-C- Mo-S magnetron coating on titanium alloys at lowered to 350°C temperature of coating regardless of alloy structural condition was revealed by methods of calotest, nanorecognition, scratch testing and frictional material tests. The coating formed by means of a combined magnetron plasma method reduces titanium alloys friction coefficient in multiple times and increases wear resistance by two orders of magnitude. At the same time the mechanical properties of ultra-fine-grained titanium alloys obtained by nanostructuring do not deteriorate.

  12. Analysis and Methane Gas Separations Studies for City of Marsing, Idaho An Idaho National Laboratory Technical Assistance Program Study

    SciTech Connect

    Christopher Orme

    2012-08-01

    Introduction and Background Large amounts of methane in well water is a wide spread problem in North America. Methane gas from decaying biomass and oil and gas deposits escape into water wells typically through cracks or faults in otherwise non-porous rock strata producing saturated water systems. This methane saturated water can pose several problems in the delivery of drinking water. The problems range from pumps vapor locking (cavitating), to pump houses exploding. The City of Marsing requested Idaho National Laboratory (INL) to assist with some water analyses as well as to provide some engineering approaches to methane capture through the INL Technical Assistance Program (TAP). There are several engineering approaches to the removal of methane and natural gas from water sources that include gas stripping followed by compression and/or dehydration; membrane gas separators coupled with dehydration processes, membrane water contactors with dehydration processes.

  13. Brillouin microspectroscopy of nanostructured biomaterials: photonics assisted tailoring mechanical properties

    NASA Astrophysics Data System (ADS)

    Meng, Zhaokai; Jaiswal, Manish K.; Chitrakar, Chandani; Thakur, Teena; Gaharwar, Akhilesh K.; Yakovlev, Vladislav V.

    2016-03-01

    Developing new biomaterials is essential for the next-generation of materials for bioenergy, bioelectronics, basic biology, medical diagnostics, cancer research, and regenerative medicine. Specifically, recent progress in nanotechnology has stimulated the development of multifunctional biomaterials for tissue engineering applications. The physical properties of nanocomposite biomaterials, including elasticity and viscosity, play key roles in controlling cell fate, which underlines therapeutic success. Conventional mechanical tests, including uniaxial compression and tension, dynamic mechanical analysis and shear rheology, require mechanical forces to be directly exerted onto the sample and therefore may not be suitable for in situ measurements or continuous monitoring of mechanical stiffness. In this study, we employ spontaneous Brillouin spectroscopy as a viscoelasticity-specific probing technique. We utilized a Brillouin spectrometer to characterize biomaterial's microscopic elasticity and correlated those with conventional mechanical tests (e.g., rheology).

  14. [Mechanical circulatory assist using a miniaturized Archimedes screw].

    PubMed

    von Segesser, L K; Bisang, B; Leskosek, B; Turina, M

    1991-01-01

    An axial flow blood pump (Archimedes screw) for intraarterial left ventricular assist was evaluated in comparison to standard roller pump left heart bypass (LHBP) in 13 bovine experiments (bodyweight 74 +/- 15 kg). Full systemic heparinization (ACT greater than 500 s) was used for LHBP in comparison to limited systemic heparinization (ACT greater than 180 s) for axial. A standard battery of blood samples was taken before and at regular intervals throughout perfusion: (table; see text) Transarterial access and relatively limited blood trauma appear to be the main advantages of the evaluated axial flow blood pump. However, the impossibility to assess the pump flow may be a major problem for the management of the failing left ventricle.

  15. Inert Gas Enhanced Laser-Assisted Purification of Platinum Electron-Beam-Induced Deposits.

    PubMed

    Stanford, Michael G; Lewis, Brett B; Noh, Joo Hyon; Fowlkes, Jason D; Rack, Philip D

    2015-09-09

    Electron-beam-induced deposition patterns, with composition of PtC5, were purified using a pulsed laser-induced purification reaction to erode the amorphous carbon matrix and form pure platinum deposits. Enhanced mobility of residual H2O molecules via a localized injection of inert Ar-H2 (4%) is attributed to be the reactive gas species for purification of the deposits. Surface purification of deposits was realized at laser exposure times as low as 0.1 s. The ex situ purification reaction in the deposit interior was shown to be rate-limited by reactive gas diffusion into the deposit, and deposit contraction associated with the purification process caused some loss of shape retention. To circumvent the intrinsic flaws of the ex situ anneal process, in situ deposition and purification techniques were explored that resemble a direct write atomic layer deposition (ALD) process. First, we explored a laser-assisted electron-beam-induced deposition (LAEBID) process augmented with reactive gas that resulted in a 75% carbon reduction compared to standard EBID. A sequential deposition plus purification process was also developed and resulted in deposition of pure platinum deposits with high fidelity and shape retention.

  16. Inert gas enhanced laser-assisted purification of platinum electron-beam-induced deposits

    SciTech Connect

    Stanford, Michael G.; Lewis, Brett B.; Noh, Joo Hyon; Fowlkes, Jason Davidson; Rack, Philip D.

    2015-06-30

    Electron-beam-induced deposition patterns, with composition of PtC5, were purified using a pulsed laser-induced purification reaction to erode the amorphous carbon matrix and form pure platinum deposits. Enhanced mobility of residual H2O molecules via a localized injection of inert Ar–H2 (4%) is attributed to be the reactive gas species for purification of the deposits. Surface purification of deposits was realized at laser exposure times as low as 0.1 s. The ex situ purification reaction in the deposit interior was shown to be rate-limited by reactive gas diffusion into the deposit, and deposit contraction associated with the purification process caused some loss of shape retention. To circumvent the intrinsic flaws of the ex situ anneal process, in situ deposition and purification techniques were explored that resemble a direct write atomic layer deposition (ALD) process. First, we explored a laser-assisted electron-beam-induced deposition (LAEBID) process augmented with reactive gas that resulted in a 75% carbon reduction compared to standard EBID. Lastly, a sequential deposition plus purification process was also developed and resulted in deposition of pure platinum deposits with high fidelity and shape retention.

  17. Inert gas enhanced laser-assisted purification of platinum electron-beam-induced deposits

    DOE PAGES

    Stanford, Michael G.; Lewis, Brett B.; Noh, Joo Hyon; ...

    2015-06-30

    Electron-beam-induced deposition patterns, with composition of PtC5, were purified using a pulsed laser-induced purification reaction to erode the amorphous carbon matrix and form pure platinum deposits. Enhanced mobility of residual H2O molecules via a localized injection of inert Ar–H2 (4%) is attributed to be the reactive gas species for purification of the deposits. Surface purification of deposits was realized at laser exposure times as low as 0.1 s. The ex situ purification reaction in the deposit interior was shown to be rate-limited by reactive gas diffusion into the deposit, and deposit contraction associated with the purification process caused some lossmore » of shape retention. To circumvent the intrinsic flaws of the ex situ anneal process, in situ deposition and purification techniques were explored that resemble a direct write atomic layer deposition (ALD) process. First, we explored a laser-assisted electron-beam-induced deposition (LAEBID) process augmented with reactive gas that resulted in a 75% carbon reduction compared to standard EBID. Lastly, a sequential deposition plus purification process was also developed and resulted in deposition of pure platinum deposits with high fidelity and shape retention.« less

  18. Reaction mechanism and tautomeric equilibrium of 2-mercaptopyrimidine in the gas phase and in aqueous solution: a combined Monte Carlo and quantum mechanics study.

    PubMed

    Lima, Maria Carolina P; Coutinho, Kaline; Canuto, Sylvio; Rocha, Willian R

    2006-06-08

    A combined Monte Carlo and quantum mechanical study was carried out to analyze the tautomeric equilibrium of 2-mercaptopyrimidine in the gas phase and in aqueous solution. Second- and fourth-order Møller-Plesset perturbation theory calculations indicate that in the gas phase thiol (Pym-SH) is more stable than the thione (Pym-NH) by ca. 8 kcal/mol. In aqueous solution, thermodynamic perturbation theory implemented on a Monte Carlo NpT simulation indicates that both the differential enthalpy and Gibbs free energy favor the thione form. The calculated differential enthalpy is DeltaH(SH)(-->)(NH)(solv) = -1.7 kcal/mol and the differential Gibbs free energy is DeltaG(SH)(-->)(NH)(solv) = -1.9 kcal/mol. Analysis is made of the contribution of the solute-solvent hydrogen bonds and it is noted that the SH group in the thiol and NH group in the thione tautomers act exclusively as a hydrogen bond donor in aqueous solution. The proton transfer reaction between the tautomeric forms was also investigated in the gas phase and in aqueous solution. Two distinct mechanisms were considered: a direct intramolecular transfer and a water-assisted mechanism. In the gas phase, the intramolecular transfer leads to a large energy barrier of 34.4 kcal/mol, passing through a three-center transition state. The proton transfer with the assistance of one water molecule decreases the energy barrier to 17.2 kcal/mol. In solution, these calculated activation barriers are, respectively, 32.0 and 14.8 kcal/mol. The solvent effect is found to be sizable but it is considerably more important as a participant in the water-assisted mechanism than the solvent field of the solute-solvent interaction. Finally, the calculated total Gibbs free energy is used to estimate the equilibrium constant.

  19. Environment assisted degradation mechanisms in advanced light metals

    NASA Technical Reports Server (NTRS)

    Gangloff, R. P.; Stoner, G. E.; Swanson, R. E.

    1989-01-01

    A multifaceted research program on the performance of advanced light metallic alloys in aggressive aerospace environments, and associated environmental failure mechanisms was initiated. The general goal is to characterize alloy behavior quantitatively and to develop predictive mechanisms for environmental failure modes. Successes in this regard will provide the basis for metallurgical optimization of alloy performance, for chemical control of aggressive environments, and for engineering life prediction with damage tolerance and long term reliability.

  20. Highly selective NH3 gas sensor based on Au loaded ZnO nanostructures prepared using microwave-assisted method.

    PubMed

    Shingange, K; Tshabalala, Z P; Ntwaeaborwa, O M; Motaung, D E; Mhlongo, G H

    2016-10-01

    ZnO nanorods synthesized using microwave-assisted approach were functionalized with gold (Au) nanoparticles. The Au coverage on the surface of the functionalized ZnO was controlled by adjusting the concentration of the Au precursor. According to X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) results, it was confirmed that Au form nanoparticles loaded on the surface of ZnO. The small Au loading level of 0.5wt% showed the highest response of 1600-100ppm of NH3 gas at room temperature (RT) whereas further increase of Au loading level resulted in poor detection of NH3. All Au loaded ZnO (Au/ZnO) based sensors exhibited very short recovery and response times compared to unloaded ZnO sensing materials. The responses of ZnO and Au/ZnO based sensors (0.5-2.5wt%) to other flammable gases, including H2, CO and CH4, were considerably less, demonstrating that Au/ZnO based sensors were highly selective to NH3 gas at room temperature. Spill over mechanism which is the main reason for the observed enhanced NH3 response with 0.5 Au loading level is explained in detail.

  1. Effect of Gas Tungsten Arc Welding Parameters on Hydrogen-Assisted Cracking of Type 321 Stainless Steel

    NASA Astrophysics Data System (ADS)

    Rozenak, Paul; Unigovski, Yaakov; Shneck, Roni

    2016-05-01

    The susceptibility of AISI type 321 stainless steel welded by the gas tungsten arc welding (GTAW) process to hydrogen-assisted cracking (HAC) was studied in a tensile test combined with in situ cathodic charging. Specimen charging causes a decrease in ductility of both the as-received and welded specimens. The mechanical properties of welds depend on welding parameters. For example, the ultimate tensile strength and ductility increase with growing shielding gas (argon) rate. More severe decrease in the ductility was obtained after post-weld heat treatment (PWHT). In welded steels, in addition to discontinuous grain boundary carbides (M23C6) and dense distribution of metal carbides MC ((Ti, Nb)C) precipitated in the matrix, the appearance of delta-ferrite phase was observed. The fracture of sensitized specimens was predominantly intergranular, whereas the as-welded specimens exhibited mainly transgranular regions. High-dislocation density regions and stacking faults were found in delta-ferrite formed after welding. Besides, thin stacking fault plates and epsilon-martensite were found in the austenitic matrix after the cathodic charging.

  2. Review of coaxial flow gas core nuclear rocket fluid mechanics

    NASA Technical Reports Server (NTRS)

    Weinstein, H.

    1976-01-01

    Almost all of the fluid mechanics research associated with the coaxial flow gas core reactor ended abruptly with the interruption of NASA's space nuclear program because of policy and budgetary considerations in 1973. An overview of program accomplishments is presented through a review of the experiments conducted and the analyses performed. Areas are indicated where additional research is required for a fuller understanding of cavity flow and of the factors which influence cold and hot flow containment. A bibliography is included with graphic material.

  3. Photon assisted hopping conduction mechanism in Tl2SSe crystals

    NASA Astrophysics Data System (ADS)

    Qasrawi, A. F.; Ziqan, Abdelhalim M.; Jazzar, Suha Kh.; Gasanly, N. M.

    2015-02-01

    In this article, the powder X-ray diffraction data and the dark and the photo-excited electrical conduction parameters of Tl2SSe crystal are reported. The dark and photon excited electrical conduction in the tetragonal crystal are found to be dominated by thermionic emission assisted variable range hopping conduction (VRH). The dark Mott's VRH parameters representing by the degree of disorder (To), the density of localized states near the Fermi level (N (EF)), the average hopping range (R) and average hopping energy (W) exhibited wide tunability via incremental photon intensity. Particularly, while the dark values of T0 , W and R significantly decreased from 2.32 ×108 to 1.52 ×105 K, 114 to 18.25 meV and from 66.15 to 10.58 A°, respectively, the values of N (EF) increased from 7.23 ×1018 to 1.10 ×1022cm-3 /eV when the crystal was photo-excited with a 53.6 mW/cm2 light intensity. These variations in the hopping parameters via photon excitations are promisig for using the crystal in the fabrication of well controlled, widely tunable, low energy consuming and highly efficient electronic devices.

  4. Patient-ventilator dyssynchrony during assisted invasive mechanical ventilation.

    PubMed

    Murias, G; Villagra, A; Blanch, L

    2013-04-01

    Patient-ventilator dyssynchrony is common during mechanical ventilation. Dyssynchrony decreases comfort, prolongs mechanical ventilation and intensive care unit stays, and might lead to worse outcome. Dyssynchrony can occur during the triggering of the ventilator, the inspiration period after triggering, the transition from inspiration to expiration, and the expiratory phase. The most common dyssynchronies are delayed triggering, autotriggering, ineffective inspiratory efforts (which can occur at any point in the respiratory cycle), mismatch between the patient's and ventilator's inspiratory times, and double triggering. At present, the detection of dyssynchronies usually depends on healthcare staff observing ventilator waveforms; however, performance is suboptimal and many events go undetected. To date, technological complexity has made it impossible to evaluate patient-ventilator synchrony throughout the course of mechanical ventilation. Studies have shown that a high index of dyssynchrony may increase the duration of mechanical ventilation. Better training, better ventilatory modes, and/or computerized systems that permit better synchronization of patients' demands and ventilator outputs are necessary to improve patient-ventilator synchrony.

  5. Environment assisted degradation mechanisms in advanced light metals

    NASA Technical Reports Server (NTRS)

    Gangloff, Richard P.; Stoner, Glenn E.; Swanson, Robert E.

    1988-01-01

    The general goals of the research program are to characterize alloy behavior quantitatively and to develop predictive mechanisms for environmental failure modes. Successes in this regard will provide the basis for metallurgical optimization of alloy performance, for chemical control of aggressive environments, and for engineering life prediction with damage tolerance and long term reliability.

  6. Mechanism of gas sensing in carbon nanotube field effect transistors

    NASA Astrophysics Data System (ADS)

    Dube, Isha

    Gas sensors based on carbon nanotubes in the field effect transistor configuration have exhibited impressive sensitivities compared to the existing technologies. However, the lack of an understanding of the gas sensing mechanism in these carbon nanotube field effect transistors (CNTFETs) has impeded setting-up a calibration standard and customization of these nano-sensors for specified gas sensing application. Calibration requires identifying fundamental transistor parameters and establishing how they vary in the presence of a gas and influence the overall sensing behavior. This work focuses on modeling the sensing behavior of a CNTFET in the presence of oxidizing (NO 2) and reducing (NH3) gases and determining how each of the transistor parameters, namely: the Schottky barrier height, Schottky barrier width and doping level of the nanotube are affected by the presence of these gases. Earlier experiments have shown that the carbon nanotube-metal interface is responsible for the observed change in the CNTFET response. The interface consists of the metal contact and the depletion region in the carbon nanotube. A change in the metal work function will change the Schottky barrier height, whereas doping of the depletion region will affect the Schottky barrier width and the doping level of the carbon nanotube. A theoretical model containing these parameters was systematically fitted to the experimental transfer characteristics for different concentrations of NO2 and NH3. A direct correlation between the measured changes in the CNTFET saturated conductance and the Schottky barrier height was found. These changes are directly related to the changes in the metal work function of the electrodes that I determined experimentally, independently, with a Kelvin probe system. The overall change in the CNTFET characteristics were explained and quantified by also including changes due to doping from molecules adsorbed at the carbon nanotube-metal interface through the parameters

  7. Surface Defects Control for ZnO Nanorods Synthesized Through a Gas-Assisted Hydrothermal Process

    NASA Astrophysics Data System (ADS)

    Zhao, Limin; Shu, Changhua; Jia, Zhengfeng; Wang, Changzheng

    2017-01-01

    Oxygen vacancies in crystal have an important impact on the electronic properties of zinc oxide (ZnO). In this paper, ZnO nanorods with rich oxygen vacancies were prepared through a novel gas-assisted hydrothermal growth process. X-ray diffraction data showed that single-phase ZnO with the wurtzite crystal structure was obtained and the crystallite size decreased as the reaction atmosphere pressure increased. The oxygen vacancies of ZnO were confirmed using x-ray photoelectron spectroscopy and photoluminescence spectroscopy. The results showed that the concentration of oxygen vacancies could be regulated by both the atmosphere pressure and the atmosphere properties. The oxygen vacancies in ZnO samples were reduced when the pressure increase in the hydrogen reaction environment (reducing atmosphere) and the oxygen vacancies in ZnO samples were increased when the pressure increased in the oxygen reaction environment (oxidizing atmosphere).

  8. Microwave-assisted derivatization: application to steroid profiling by gas chromatography/mass spectrometry.

    PubMed

    Casals, Gregori; Marcos, Josep; Pozo, Oscar J; Alcaraz, José; Martínez de Osaba, María Jesús; Jiménez, Wladimiro

    2014-06-01

    Gas chromatography-mass spectrometry (GC-MS) remains as the gold-standard technique for the study of the steroid metabolome. A main limitation is the need of performing a derivatization step since incubation with strong silylations agents for long periods of time (usually 16 h) is required for the derivatization of hindered hydroxyls present in some steroids of interest. In the present work, a rapid, simple and reproducible microwave-assisted derivatization method was developed. In the method, 36 steroids already treated with methoxyamine (2% in pyridine) were silylated with 50 μl of N-trimethylsilylimidazole by using microwave irradiation, and the formed methyloxime-trimethylsilyl derivatives were analyzed by GC-MS. Microwave power and derivatization time silylation conditions were optimized being the optimum conditions 600 W and 3 min respectively. In order to evaluate the usefulness of this technique, the urine steroid profiles for 20 healthy individuals were analyzed. The results of a comparison of microwave irradiation with the classical heating protocol showed similar derivatization yields, thus suggesting that microwave-assisted silylation is a valid tool for the rapid steroid metabolome study.

  9. Buffer gas-assisted four-wave mixing resonances in alkali vapor excited by a single cw laser

    NASA Astrophysics Data System (ADS)

    Shmavonyan, Svetlana; Khanbekyan, Aleksandr; Khanbekyan, Alen; Mariotti, Emilio; Papoyan, Aram V.

    2016-12-01

    We report the observation of a fluorescence peak appearing in dilute alkali (Rb, Cs) vapor in the presence of a buffer gas when the cw laser radiation frequency is tuned between the Doppler-broadened hyperfine transition groups of an atomic D2 line. Based on steep laser radiation intensity dependence above the threshold and spectral composition of the observed features corresponding to atomic resonance transitions, we have attributed these features to the buffer gas-assisted four-wave mixing process.

  10. Fluid Assisted Fault Weakening: Mechanical vs. Chemical Processes

    NASA Astrophysics Data System (ADS)

    Collettini, C.

    2011-12-01

    The influx of fluids into fault zones can trigger two main types of weakening process that operate over different timescales, facilitate fault movement and influence fault slip behaviour. During the seismic cycle fluids can be trapped by low permeability fault zones or stratigraphic barriers favoring fluid overpressure (mechanical weakening) and earthquake nucleation. In the entire fault history fluids can react with fault rocks to produce weak mineral phases (chemical weakening) that alter the mechanical properties of the fault zones. Here I will present two examples of mechanical and chemical fault-weakening from the Apennines of Italy. Seismic profiles and deep borehole data show that the strongest earthquakes of the Apennines nucleate within overpressured Evaporites consisting of dolostones and anhydrites. Field and experimental studies on exhumed faults within the same lithology depict a cataclastic inner fault that can generate frictional instabilities with localization and increasing sliding velocity. The outer fault core presents barrier-like portions associated with foliated anhydrites, 10-21 ≤ permeability ≤10-19 m2. The combination of field observations and rock deformation measurements suggests a fault zone structure capable of developing fluid overpressures during the seismic cycle: fluid overpressures can potentially promote earthquake nucleation and aftershock triggering. Field studies from an exhumed regional low-angle normal fault show that in the long term fluids reacted (diffusion-mass transfer processes) with fine-grained cataclasites in the fault core to produce a phyllosilicates-rich and foliated fault rock. Within the foliated microstructure, that is rich in talc, smectite and chlorite, deformation occurs by frictional sliding along 50-200-nm-thick lamellae. Rock deformation experiments show that the foliated fault rock is weak, 0.2 < friction< 0.35, it is characterized by a stable sliding slip-behaviour with no strength recovery with

  11. Ruptured subcapsular liver haematoma following mechanically-assisted cardiopulmonary resuscitation.

    PubMed

    Joseph, John R; Freundlich, Robert Edward; Abir, Mahshid

    2016-02-02

    A 64-year-old man with a history of ascending aortic surgery and pulmonary embolus presented with shortness of breath. He rapidly decompensated, prompting intubation, after which he lost pulses. Manual resuscitation was initiated immediately, with subsequent use of a LUCAS-2 mechanical compression device. The patient was given bolus thrombolytic therapy and regained pulses after 7 min of CPR. Compressions were reinitiated with the LUCAS-2 twice more during resuscitation over the subsequent hour for brief episodes of PEA. After confirmation of massive pulmonary embolism on CT, the patient underwent interventional radiology-guided ultrasonic catheter placement with local thrombolytic therapy and experienced immediate improvement in oxygenation. He later developed abdominal compartment syndrome, despite cessation of thrombolytic and anticoagulation therapy. Bedside exploratory abdominal laparotomy revealed a ruptured subcapsular haematoma of the liver. The patient's haemodynamics improved following surgery and he was extubated 11 days postarrest with intact neurological function.

  12. Cavopulmonary assist for the failing Fontan circulation: Impact of ventricular function on mechanical support strategy

    PubMed Central

    Giridharan, Guruprasad A; Ising, Mickey; Sobieski, Michael A.; Koenig, Steven C; Chen, Jun; Frankel, Steven; Rodefeld, Mark D

    2015-01-01

    Mechanical circulatory support - either ventricular assist device (VAD, left-sided systemic support) or cavopulmonary assist device (CPAD, right-sided support) - has been suggested as treatment for Fontan failure. The selection of left- vs. right-sided support for failing Fontan has not been previously defined. Computer simulation and mock circulation models of pediatric Fontan patients (15–25 kg) with diastolic, systolic, and combined systolic and diastolic dysfunction were developed. The global circulatory response to assisted Fontan flow using VAD (HeartWare HVAD, FL) support, CPAD (Viscous Impeller Pump, IN) support, and combined VAD and CPAD support were evaluated. Cavopulmonary assist improves failing Fontan circulation during diastolic dysfunction but preserved systolic function. In the presence of systolic dysfunction and elevated ventricular end-diastolic pressure (VEDP), VAD support augments cardiac output and diminishes VEDP, while increased preload with cavopulmonary assist may worsen circulatory status. Fontan circulation can be stabilized to biventricular values with modest cavopulmonary assist during diastolic dysfunction. Systemic VAD support may be preferable to maintain systemic output during systolic dysfunction. Both systemic and cavopulmonary support may provide best outcome during combined systolic and diastolic dysfunction. These findings may be useful to guide clinical cavopulmonary assist strategies in failing Fontan circulations. PMID:25158887

  13. Effects of Interaction Between Ventricular Assist Device Assistance and Autoregulated Mock Circulation Including Frank-Starling Mechanism and Baroreflex.

    PubMed

    Jansen-Park, So-Hyun; Mahmood, Mohammad Nauzef; Müller, Indra; Turnhoff, Lisa Kathrin; Schmitz-Rode, Thomas; Steinseifer, Ulrich; Sonntag, Simon Johannes

    2016-10-01

    A mock heart circulation loop (MHCL) is a hydraulic model simulating the human circulatory system. It allows in vitro investigations of the interaction between cardiac assist devices and the human circulatory system. In this study, a preload sensitive MHCL, the MHCLAUTO , was developed to investigate the interaction between the left ventricle and left ventricular assist devices (LVADs). The Frank-Starling mechanism was modeled by regulating the stroke volume (SV) based on the measured mean diastolic left atrial pressure (MLAPdiast ). The baroreflex autoregulation mechanism was implemented to maintain a constant mean aortic pressure (MAP) by varying ventricular contractility (Emax ), heart rate (HR), afterload/systemic vascular resistance (SVR) and unstressed venous volume (UVV). The DP3 blood pump (Medos Medizintechnik GmbH) was used to simulate the LVAD. Characteristic parameters were measured in pathological conditions both with and without LVAD to assess the hemodynamic effect of LVAD on the MHCLAUTO . The results obtained from the MHCLAUTO show a high correlation to literature data. The study demonstrates the possibility of using the MHCLAUTO as a research tool to better understand the physiological interactions between cardiac implants and human circulation.

  14. The mechanism of coal gas desulfurization by iron oxide sorbents.

    PubMed

    Lin, Yi-Hsing; Chen, Yen-Chiao; Chu, Hsin

    2015-02-01

    This study aims to understand the roles of hydrogen and carbon monoxide during the desulfurization process in a coal gasification system that H2S of the syngas was removed by Fe2O3/SiO2 sorbents. The Fe2O3/SiO2 sorbents were prepared by incipient wetness impregnation. Through the breakthrough experiments and Fourier transform infrared spectroscopy analyses, the overall desulfurization mechanism of the Fe2O3/SiO2 sorbents was proposed in this study. The results show that the major reaction route is that Fe2O3 reacts with H2S to form FeS, and the existence of CO and H2 in the simulated gas significantly affects equilibrium concentrations of H2S and COS. The formation of COS occurs when the feeding gas is blended with CO and H2S, or CO2 and H2S. The pathways in the formation of products from the desulfurization process by the reaction of Fe2O3 with H2S have been successfully established.

  15. Mechanism of gas pipeline failures on Balboa Boulevard during the 1994 Northridge earthquake

    SciTech Connect

    Nishio, Nobuaki

    1995-12-31

    A possible mechanism of gas pipeline failures on Balboa Boulevard during the 1994 Northridge earthquake is proposed. This mechanism is the one that has been adopted by the Japan Gas Association in the Recommended Practice for the Earthquake-Resistant Design of Gas Pipelines. The possible mode of ground displacement that might have caused the above pipeline failures is also discussed.

  16. Mechanical behavior of thermal barrier coatings for gas turbine blades

    NASA Technical Reports Server (NTRS)

    Berndt, C. C.; Phucharoen, W.; Chang, G. C.

    1984-01-01

    Plasma-sprayed thermal barrier coatings (TBCs) will enable turbine components to operate at higher temperatures and lower cooling gas flow rates; thereby improving their efficiency. Future developments are limited by precise knowledge of the material properties and failure mechanisms of the coating system. Details of this nature are needed for realistic modeling of the coating system which will, in turn, promote advancements in coating technology. Complementary experiments and analytical modeling which were undertaken in order to define and measure the important failure processes for plasma-sprayed coatings are presented. The experimental portion includes two different tests which were developed to measure coating properties. These are termed tensile adhesion and acoustic emission tests. The analytical modeling section details a finite element method which was used to calculate the stress distribution in the coating system. Some preliminary results are presented.

  17. THE FORMATION MECHANISM OF GAS GIANTS ON WIDE ORBITS

    SciTech Connect

    Dodson-Robinson, Sarah E.; Veras, Dimitri; Ford, Eric B.; Beichman, C. A.

    2009-12-10

    The recent discoveries of massive planets on ultra-wide orbits of HR 8799 and Fomalhaut present a new challenge for planet formation theorists. Our goal is to figure out which of three giant planet formation mechanisms-core accretion (with or without migration), scattering from the inner disk, or gravitational instability-could be responsible for Fomalhaut b, HR 8799 b, c and d, and similar planets discovered in the future. This paper presents the results of numerical experiments comparing the long-period planet formation efficiency of each possible mechanism in model A star, G star, and M star disks. First, a simple core accretion simulation shows that planet cores forming beyond 35 AU cannot reach critical mass, even under the most favorable conditions one can construct. Second, a set of N-body simulations demonstrates that planet-planet scattering does not create stable, wide-orbit systems such as HR 8799. Finally, a linear stability analysis verifies previous work showing that global spiral instabilities naturally arise in high-mass disks. We conclude that massive gas giants on stable orbits with semimajor axes a approx> 35 AU form by gravitational instability in the disk. We recommend that observers examine the planet detection rate as a function of stellar age, controlling for the planets' dimming with time. Any age trend would indicate that planets on wide orbits are transient relics of scattering from the inner disk. If planet detection rate is found to be independent of stellar age, it would confirm our prediction that gravitational instability is the dominant mode of producing detectable planets on wide orbits. We also predict that the occurrence ratio of long-period to short-period gas giants should be highest for M dwarfs due to the inefficiency of core accretion and the expected small fragment mass (approx10 M {sub Jup}) in their disks.

  18. Flow and heat transfer characteristics of assisting gas impingining onto an alumina coated hole in relation to laser drilling

    NASA Astrophysics Data System (ADS)

    Shuja, S. Z.; Yilbas, B. S.

    2014-07-01

    Flow and heat transfer characteristics of the assisting gas impinging onto the coated holes are investigated in relation to the laser drilling process. The alumina coating with thickness of 250 μm is considered at the surface of the carbon steel substrate. Three cases are considered by incorporating different locations of the coating on the carbon steel. These cases include coating at the top of the workpiece, coating at the bottom of the workpiece, and coating both at the top and at the bottom of the workpiece. A no-coating situation of the hole is also presented for the comparison reason. To resemble the laser drilling process, the wall temperature of the coating and the carbon steel substrate is kept at the melting temperatures during the simulations. A numerical scheme incorporating the control volume approach is introduced and the Reynolds stress turbulence model is used to account for the turbulence effect of the impinging assisting gas. An experiment is carried out in line with the simulation conditions to examine the morphological changes at the coating-carbon steel interface. It is found that the assisting gas temperature exceeds the melting temperature of the steel substrate along the coating thickness and as the assisting gas progresses further into the hole, heat transfer from the assisting gas to the hole wall takes place. This, in turn, increases thermal erosion at the hole wall in the vicinity of the coating-steel substrate interface. The Nusselt number and the skin friction attain large values along the coating thickness in the hole.

  19. Magnetic-Assisted Noncontact Triboelectric Nanogenerator Converting Mechanical Energy into Electricity and Light Emissions.

    PubMed

    Huang, Long-Biao; Bai, Gongxun; Wong, Man-Chung; Yang, Zhibin; Xu, Wei; Hao, Jianhua

    2016-04-13

    A magnetic-assisted noncontact triboelectric nanogenerator (TENG) is developed by combining a magnetic responsive layer with a TENG. The novel TENG device is applied to harvest mechanical energy which can be converted into electricity and light emissions. This work has potential for energy harvesting, magnetic sensors, self-powered electronics and optoelectronics applications.

  20. The ionization mechanisms in direct and dopant-assisted atmospheric pressure photoionization and atmospheric pressure laser ionization.

    PubMed

    Kauppila, Tiina J; Kersten, Hendrik; Benter, Thorsten

    2014-11-01

    A novel, gas-tight API interface for gas chromatography-mass spectrometry was used to study the ionization mechanism in direct and dopant-assisted atmospheric pressure photoionization (APPI) and atmospheric pressure laser ionization (APLI). Eight analytes (ethylbenzene, bromobenzene, naphthalene, anthracene, benzaldehyde, pyridine, quinolone, and acridine) with varying ionization energies (IEs) and proton affinities (PAs), and four common APPI dopants (toluene, acetone, anisole, and chlorobenzene) were chosen. All the studied compounds were ionized by direct APPI, forming mainly molecular ions. Addition of dopants suppressed the signal of the analytes with IEs above the IE of the dopant. For compounds with suitable IEs or Pas, the dopants increased the ionization efficiency as the analytes could be ionized through dopant-mediated gas-phase reactions, such as charge exchange, proton transfer, and other rather unexpected reactions, such as formation of [M + 77](+) in the presence of chlorobenzene. Experiments with deuterated toluene as the dopant verified that in case of proton transfer, the proton originated from the dopant instead of proton-bound solvent clusters, as in conventional open or non-tight APPI sources. In direct APLI using a 266 nm laser, a narrower range of compounds was ionized than in direct APPI, because of exceedingly high IEs or unfavorable two-photon absorption cross-sections. Introduction of dopants in the APLI system changed the ionization mechanism to similar dopant-mediated gas-phase reactions with the dopant as in APPI, which produced mainly ions of the same form as in APPI, and ionized a wider range of analytes than direct APLI.

  1. Modeling of Gas Production from Shale Reservoirs Considering Multiple Transport Mechanisms.

    PubMed

    Guo, Chaohua; Wei, Mingzhen; Liu, Hong

    2015-01-01

    Gas transport in unconventional shale strata is a multi-mechanism-coupling process that is different from the process observed in conventional reservoirs. In micro fractures which are inborn or induced by hydraulic stimulation, viscous flow dominates. And gas surface diffusion and gas desorption should be further considered in organic nano pores. Also, the Klinkenberg effect should be considered when dealing with the gas transport problem. In addition, following two factors can play significant roles under certain circumstances but have not received enough attention in previous models. During pressure depletion, gas viscosity will change with Knudsen number; and pore radius will increase when the adsorption gas desorbs from the pore wall. In this paper, a comprehensive mathematical model that incorporates all known mechanisms for simulating gas flow in shale strata is presented. The objective of this study was to provide a more accurate reservoir model for simulation based on the flow mechanisms in the pore scale and formation geometry. Complex mechanisms, including viscous flow, Knudsen diffusion, slip flow, and desorption, are optionally integrated into different continua in the model. Sensitivity analysis was conducted to evaluate the effect of different mechanisms on the gas production. The results showed that adsorption and gas viscosity change will have a great impact on gas production. Ignoring one of following scenarios, such as adsorption, gas permeability change, gas viscosity change, or pore radius change, will underestimate gas production.

  2. Modeling of Gas Production from Shale Reservoirs Considering Multiple Transport Mechanisms

    PubMed Central

    Guo, Chaohua; Wei, Mingzhen; Liu, Hong

    2015-01-01

    Gas transport in unconventional shale strata is a multi-mechanism-coupling process that is different from the process observed in conventional reservoirs. In micro fractures which are inborn or induced by hydraulic stimulation, viscous flow dominates. And gas surface diffusion and gas desorption should be further considered in organic nano pores. Also, the Klinkenberg effect should be considered when dealing with the gas transport problem. In addition, following two factors can play significant roles under certain circumstances but have not received enough attention in previous models. During pressure depletion, gas viscosity will change with Knudsen number; and pore radius will increase when the adsorption gas desorbs from the pore wall. In this paper, a comprehensive mathematical model that incorporates all known mechanisms for simulating gas flow in shale strata is presented. The objective of this study was to provide a more accurate reservoir model for simulation based on the flow mechanisms in the pore scale and formation geometry. Complex mechanisms, including viscous flow, Knudsen diffusion, slip flow, and desorption, are optionally integrated into different continua in the model. Sensitivity analysis was conducted to evaluate the effect of different mechanisms on the gas production. The results showed that adsorption and gas viscosity change will have a great impact on gas production. Ignoring one of following scenarios, such as adsorption, gas permeability change, gas viscosity change, or pore radius change, will underestimate gas production. PMID:26657698

  3. Accretion and Orbital Inspiral in Gas-assisted Supermassive Black Hole Binary Mergers

    NASA Astrophysics Data System (ADS)

    Rafikov, Roman R.

    2016-08-01

    Many galaxies are expected to harbor binary supermassive black holes (SMBHs) in their centers. Their interaction with the surrounding gas results in the accretion and exchange of angular momentum via tidal torques, facilitating binary inspiral. Here, we explore the non-trivial coupling between these two processes and analyze how the global properties of externally supplied circumbinary disks depend on the binary accretion rate. By formulating our results in terms of the angular momentum flux driven by internal stresses, we come up with a very simple classification of the possible global disk structures, which differ from the standard constant \\dot{M} accretion disk solution. The suppression of accretion by the binary tides, leading to a significant mass accumulation in the inner disk, accelerates binary inspiral. We show that once the disk region strongly perturbed by the viscously transmitted tidal torque exceeds the binary semimajor axis, the binary can merge in less than its mass-doubling time due to accretion. Thus, unlike the inspirals driven by stellar scattering, the gas-assisted merger can occur even if the binary is embedded in a relatively low-mass disk (lower than its own mass). This is important for resolving the “last parsec” problem for SMBH binaries and understanding powerful gravitational wave sources in the universe. We argue that the enhancement of accretion by the binary found in some recent simulations cannot persist for a long time and should not affect the long-term orbital inspiral. We also review existing simulations of SMBH binary-disk coupling and propose a numerical setup which is particularly well suited to verifying our theoretical predictions.

  4. A novel method for furfural recovery via gas stripping assisted vapor permeation by a polydimethylsiloxane membrane

    PubMed Central

    Hu, Song; Guan, Yu; Cai, Di; Li, Shufeng; Qin, Peiyong; Karim, M. Nazmul; Tan, Tianwei

    2015-01-01

    Furfural is an important platform chemical with a wide range of applications. However, due to the low concentration of furfural in the hydrolysate, the conventional methods for furfural recovery are energy-intensive and environmentally unfriendly. Considering the disadvantages of pervaporation (PV) and distillation in furfural separation, a novel energy-efficient ‘green technique’, gas stripping assisted vapor permeation (GSVP), was introduced in this work. In this process, the polydimethylsiloxane (PDMS) membrane was prepared by employing water as solvent. Coking in pipe and membrane fouling was virtually non-existent in this new process. In addition, GSVP was found to achieve the highest pervaporation separation index of 216200 (permeate concentration of 71.1 wt% and furfural flux of 4.09 kgm−2h−1) so far, which was approximately 2.5 times higher than that found in pervaporation at 95°C for recovering 6.0 wt% furfural from water. Moreover, the evaporation energy required for GSVP decreased by 35% to 44% relative to that of PV process. Finally, GSVP also displayed more promising potential in industrial application than PV, especially when coupled with the hydrolysis process or fermentation in biorefinery industry. PMID:25819091

  5. A novel method for furfural recovery via gas stripping assisted vapor permeation by a polydimethylsiloxane membrane.

    PubMed

    Hu, Song; Guan, Yu; Cai, Di; Li, Shufeng; Qin, Peiyong; Karim, M Nazmul; Tan, Tianwei

    2015-03-30

    Furfural is an important platform chemical with a wide range of applications. However, due to the low concentration of furfural in the hydrolysate, the conventional methods for furfural recovery are energy-intensive and environmentally unfriendly. Considering the disadvantages of pervaporation (PV) and distillation in furfural separation, a novel energy-efficient 'green technique', gas stripping assisted vapor permeation (GSVP), was introduced in this work. In this process, the polydimethylsiloxane (PDMS) membrane was prepared by employing water as solvent. Coking in pipe and membrane fouling was virtually non-existent in this new process. In addition, GSVP was found to achieve the highest pervaporation separation index of 216200 (permeate concentration of 71.1 wt% and furfural flux of 4.09 kg m(-2) h(-1)) so far, which was approximately 2.5 times higher than that found in pervaporation at 95°C for recovering 6.0 wt% furfural from water. Moreover, the evaporation energy required for GSVP decreased by 35% to 44% relative to that of PV process. Finally, GSVP also displayed more promising potential in industrial application than PV, especially when coupled with the hydrolysis process or fermentation in biorefinery industry.

  6. A novel method for furfural recovery via gas stripping assisted vapor permeation by a polydimethylsiloxane membrane

    NASA Astrophysics Data System (ADS)

    Hu, Song; Guan, Yu; Cai, Di; Li, Shufeng; Qin, Peiyong; Karim, M. Nazmul; Tan, Tianwei

    2015-03-01

    Furfural is an important platform chemical with a wide range of applications. However, due to the low concentration of furfural in the hydrolysate, the conventional methods for furfural recovery are energy-intensive and environmentally unfriendly. Considering the disadvantages of pervaporation (PV) and distillation in furfural separation, a novel energy-efficient `green technique', gas stripping assisted vapor permeation (GSVP), was introduced in this work. In this process, the polydimethylsiloxane (PDMS) membrane was prepared by employing water as solvent. Coking in pipe and membrane fouling was virtually non-existent in this new process. In addition, GSVP was found to achieve the highest pervaporation separation index of 216200 (permeate concentration of 71.1 wt% and furfural flux of 4.09 kgm-2h-1) so far, which was approximately 2.5 times higher than that found in pervaporation at 95°C for recovering 6.0 wt% furfural from water. Moreover, the evaporation energy required for GSVP decreased by 35% to 44% relative to that of PV process. Finally, GSVP also displayed more promising potential in industrial application than PV, especially when coupled with the hydrolysis process or fermentation in biorefinery industry.

  7. Gas assisted method synthesis nitrogen-doped carbon quantum dots and Hg (II) sensing.

    PubMed

    Li, Yamei; Wang, Nan; He, Zhanhang

    2016-11-29

    Nitrogen-doped fluorescent carbon quantum dots (CQDs) was prepared by gas-assisted method using cellulose as precursors under ammonia atmosphere, which not only exhibited excellent photoluminescent properties, but also showed highly selective and sensitive detection of mercury ion. The nitrogen-doped CQDs displayed excitation wavelength dependent fluorescent behavior with outstanding dispersibility. Moreover, they exhibited high tolerance to various external conditions, such as storage time, pH value, and ionic strength. The rapid detection of Hg (II) by one-step operation within 1 min and the good linear correlation between I0/I and Hg (II) concentration in the range of 10-100 nM made the nitrogen-doped CQDs a promising nanoprobe for Hg (II) detection. The detection limit of the nitrogen-doped CQDs is about 7.7 nM. Such a nanoprobe has been successfully applied for the analysis of Hg (II) in natural water samples, demonstrating excellent practical feasibility.

  8. Acquisition of Mechanically Assisted Spark Plasma Sintering System for Advanced Research and Education on Functionally Graded Hybrid Materials

    DTIC Science & Technology

    2012-03-14

    March 14, 2012 Final Progress Report September 15, 2010 - December 14, 2011 ACQUISITION OF MECHANICALLY ASSISTED SPARK PLASMA SINTERING SYSTEM FOR...Instrumentation Program (DURIP) Project titled, “Acquisition of Mechanically Assisted Spark Plasma Sintering System for Advanced Research and Education...at developing facilities for pressure-assisted fabrication of hybrid materials by spark plasma sintering (SPS) of metallic and ceramic powders to

  9. Surfactant assisted solid-state synthesis and gas sensor application of a SWCNT/SnO2 nanocomposite material.

    PubMed

    Lu, Jun; Ma, Anson; Yang, Shihe; Ng, Ka Ming

    2007-01-01

    Although tin oxide has been the most widely investigated metal oxide material for gas detection, it suffers from the large resistance and high operating temperature. This could be overcome by hybridization with nanostructured carbon. In this work, tin oxide nanoparticles with ultrasmall sizes of 1-3 nm have been uniformly coated onto bundles of single-walled carbon nanotubes by a surfactant assisted solid state synthesis approach for the first time. Gas sensor properties of the as-synthesized nanocomposite material toward NO2 (from 5 to 60 ppm) are measured at 150 degrees C. Compared to the pure carbon tubes gas sensors, the nanocomposite gas sensor responds to NO2 in low concentrations with good linearity, high sensitivity, and fast recovery, while working at a relatively low temperature.

  10. Metal-Assisted Laser-Induced Gas Plasma for the Direct Analysis of Powder Using Pulse CO2 Laser

    NASA Astrophysics Data System (ADS)

    Khumaeni, A.; Lie, Z. S.; Kurniawan, K. H.; Kagawa, K.

    2017-01-01

    Analysis of powder samples available in small quantities has been carried out using metal-assisted gas plasma by utilizing a transversely excited atmospheric (TEA) CO2 laser. The powder was homogeneously mixed with Si grease, and the mixed powder was painted on a metal subtarget. When a TEA CO2 laser was directly focused on the metal subtarget at atmospheric pressure of He gas, a high-temperature He gas plasma was induced. It is assumed that the powder particles were vaporized to be effectively atomized and excited in the gas plasma region. This method has been employed in the rapid analyses of elements in organic and inorganic powder samples present in small quantities. Detection of trace elements of Cr and Pb has been successfully made by using the supplement powder and loam soil, respectively. The detection limits of Pb in loam soil were approximately 20 mg/kg.

  11. Green house gas emissions from composting and mechanical biological treatment.

    PubMed

    Amlinger, Florian; Peyr, Stefan; Cuhls, Carsten

    2008-02-01

    In order to carry out life-cycle assessments as a basis for far-reaching decisions about environmentally sustainable waste treatment, it is important that the input data be reliable and sound. A comparison of the potential greenhouse gas (GHG) emissions associated with each solid waste treatment option is essential. This paper addresses GHG emissions from controlled composting processes. Some important methodological prerequisites for proper measurement and data interpretation are described, and a common scale and dimension of emission data are proposed so that data from different studies can be compared. A range of emission factors associated with home composting, open windrow composting, encapsulated composting systems with waste air treatment and mechanical biological waste treatment (MBT) are presented from our own investigations as well as from the literature. The composition of source materials along with process management issues such as aeration, mechanical agitation, moisture control and temperature regime are the most important factors controlling methane (CH4), nitrous oxide (N2O) and ammoniac (NH3) emissions. If ammoniac is not stripped during the initial rotting phase or eliminated by acid scrubber systems, biofiltration of waste air provides only limited GHG mitigation, since additional N2O may be synthesized during the oxidation of NH3, and only a small amount of CH4 degradation occurs in the biofilter. It is estimated that composting contributes very little to national GHG inventories generating only 0.01-0.06% of global emissions. This analysis does not include emissions from preceding or post-treatment activities (such as collection, transport, energy consumption during processing and land spreading), so that for a full emissions account, emissions from these activities would need to be added to an analysis.

  12. Formation mechanism of gas bubble superlattice in UMo metal fuels: Phase-field modeling investigation

    NASA Astrophysics Data System (ADS)

    Hu, Shenyang; Burkes, Douglas E.; Lavender, Curt A.; Senor, David J.; Setyawan, Wahyu; Xu, Zhijie

    2016-10-01

    Nano-gas bubble superlattices are often observed in irradiated UMo nuclear fuels. However, the formation mechanism of gas bubble superlattices is not well understood. A number of physical processes may affect the gas bubble nucleation and growth; hence, the morphology of gas bubble microstructures including size and spatial distributions. In this work, a phase-field model integrating a first-passage Monte Carlo method to investigate the formation mechanism of gas bubble superlattices was developed. Six physical processes are taken into account in the model: 1) heterogeneous generation of gas atoms, vacancies, and interstitials informed from atomistic simulations; 2) one-dimensional (1-D) migration of interstitials; 3) irradiation-induced dissolution of gas atoms; 4) recombination between vacancies and interstitials; 5) elastic interaction; and 6) heterogeneous nucleation of gas bubbles. We found that the elastic interaction doesn't cause the gas bubble alignment, and fast 1-D migration of interstitials along <110> directions in the body-centered cubic U matrix causes the gas bubble alignment along <110> directions. It implies that 1-D interstitial migration along [110] direction should be the primary mechanism of a fcc gas bubble superlattice which is observed in bcc UMo alloys. Simulations also show that fission rates, saturated gas concentration, and elastic interaction all affect the morphology of gas bubble microstructures.

  13. Formation mechanism of gas bubble superlattice in UMo metal fuels: Phase-field modeling investigation

    SciTech Connect

    Hu, Shenyang; Burkes, Douglas E.; Lavender, Curt A.; Senor, David J.; Setyawan, Wahyu; Xu, Zhijie

    2016-07-08

    Nano-gas bubble superlattices are often observed in irradiated UMo nuclear fuels. However, the for- mation mechanism of gas bubble superlattices is not well understood. A number of physical processes may affect the gas bubble nucleation and growth; hence, the morphology of gas bubble microstructures including size and spatial distributions. In this work, a phase-field model integrating a first-passage Monte Carlo method to investigate the formation mechanism of gas bubble superlattices was devel- oped. Six physical processes are taken into account in the model: 1) heterogeneous generation of gas atoms, vacancies, and interstitials informed from atomistic simulations; 2) one-dimensional (1-D) migration of interstitials; 3) irradiation-induced dissolution of gas atoms; 4) recombination between vacancies and interstitials; 5) elastic interaction; and 6) heterogeneous nucleation of gas bubbles. We found that the elastic interaction doesn’t cause the gas bubble alignment, and fast 1-D migration of interstitials along $\\langle$110$\\rangle$ directions in the body-centered cubic U matrix causes the gas bubble alignment along $\\langle$110$\\rangle$ directions. It implies that 1-D interstitial migration along [110] direction should be the primary mechanism of a fcc gas bubble superlattice which is observed in bcc UMo alloys. Simulations also show that fission rates, saturated gas concentration, and elastic interaction all affect the morphology of gas bubble microstructures.

  14. UV-assisted room temperature gas sensing of GaN-core/ZnO-shell nanowires

    NASA Astrophysics Data System (ADS)

    Park, Sunghoon; Ko, Hyunsung; Kim, Soohyun; Lee, Chongmu

    2014-11-01

    GaN is highly sensitive to low concentrations of H2 in ambient air and is almost insensitive to most other common gases. However, enhancing the sensing performance and the detection limit of GaN is a challenge. This study examined the H2-gas-sensing properties of GaN nanowires encapsulated with ZnO. GaN-core/ZnO-shell nanowires were fabricated by using a two-step process comprising the thermal evaporation of GaN powders and the atomic layer deposition of ZnO. The core-shell nanowires ranged from 80 to 120 nm in diameter and from a few tens to a few hundreds of micrometers in length, with a mean shell layer thickness of ~8 nm. Multiple-networked pristine GaN nanowire and ZnO-encapsulated GaN (or GaN-core/ZnO-shell) nanowire sensors showed responses of 120-147% and 179-389%, respectively, to 500-2,500 ppm of H2 at room temperature under UV (254 nm) illumination. The underlying mechanism of the enhanced response of the GaN nanowire to H2 gas when using ZnO encapsulation and UV irradiation is discussed.

  15. Acoustically assisted removal of nitrogen oxide from high temperature flue gas.

    PubMed

    Komarov, Sergey V; Nemeth, Szabolcs; Hirasawa, Masahiro

    2005-02-01

    The present study focuses on a possibility for improving NO removal efficiency from flue gas by application of powerful sound waves. The sound waves (frequency 6.9-17.2kHz, intensity 144-160dB) are propagated from Hartmann sound generators to a preheated graphite disk inside a vertical reaction tube (height 1.8m, I.D. 105mm). An Ar-NO synthetic mixture (NO 911-934ppm) is blown onto the disk surface to perform reactions in the system C-NO. It is found that the NO reduction rate can be significantly enhanced by the sound waves but the enhancement effect is dependent on the sound frequency, intensity and temperature of disk surface. The better effects are obtained at a temperature of 973K and sound frequencies between 9.6 and 12.4kHz. Under these conditions, the sound application results in 3-5-fold enhancement of NO reduction rate. The obtained effects are explained in terms of gas-phase mass transfer controlling mechanism and of near surface turbulent diffusivity.

  16. Response surface methodology for the modeling and optimization of oil-in-water emulsion separation using gas sparging assisted microfiltration.

    PubMed

    Fouladitajar, Amir; Zokaee Ashtiani, Farzin; Dabir, Bahram; Rezaei, Hamid; Valizadeh, Bardiya

    2015-02-01

    Response surface methodology (RSM) and central composite design (CCD) were used to develop models for optimization and modeling of a gas sparging assisted microfiltration of oil-in-water (o/w) emulsion. The effect of gas flow rate (Q G ), oil concentration (C oil ), transmembrane pressure (TMP), and liquid flow rate (Q L ) on the permeate flux and oil rejection were studied by RSM. Two sets of experiments were designed to investigate the effects of different gas-liquid two-phase flow regimes; low and high gas flow rates. Two separate RSM models were developed for each experimental set. The oil concentration and TMP were found to be the most significant factors influencing both permeate flux and rejection. Also, the interaction between these parameters was the most significant one. At low Q G , the more the gas flow rate, the higher the permeate flux; however, in the high gas flow rate region, higher Q G did not necessarily improve the permeate flux. In the case of rejection, gas and liquid flow rates were found to be insignificant. The optimum process conditions were found to be the following: Q G  = 1.0 (L/min), C oil  = 1,290 (mg/L), TMP = 1.58 (bar), and Q L  = 3.0 (L/min). Under these optimal conditions, maximum permeate flux and rejection (%) were 115.9 (L/m(2)h) and 81.1 %, respectively.

  17. Application of Hydrogen Assisted Lean Operation to Natural Gas-Fueled Reciprocating Engines (HALO)

    SciTech Connect

    Chad Smutzer

    2006-01-01

    Two key challenges facing Natural Gas Engines used for cogeneration purposes are spark plug life and high NOx emissions. Using Hydrogen Assisted Lean Operation (HALO), these two keys issues are simultaneously addressed. HALO operation, as demonstrated in this project, allows stable engine operation to be achieved at ultra-lean (relative air/fuel ratios of 2) conditions, which virtually eliminates NOx production. NOx values of 10 ppm (0.07 g/bhp-hr NO) for 8% (LHV H2/LHV CH4) supplementation at an exhaust O2 level of 10% were demonstrated, which is a 98% NOx emissions reduction compared to the leanest unsupplemented operating condition. Spark ignition energy reduction (which will increase ignition system life) was carried out at an oxygen level of 9%, leading to a NOx emission level of 28 ppm (0.13 g/bhp-hr NO). The spark ignition energy reduction testing found that spark energy could be reduced 22% (from 151 mJ supplied to the coil) with 13% (LHV H2/LHV CH4) hydrogen supplementation, and even further reduced 27% with 17% hydrogen supplementation, with no reportable effect on NOx emissions for these conditions and with stable engine torque output. Another important result is that the combustion duration was shown to be only a function of hydrogen supplementation, not a function of ignition energy (until the ignitability limit was reached). The next logical step leading from these promising results is to see how much the spark energy reduction translates into increase in spark plug life, which may be accomplished by durability testing.

  18. Muscle-tendon mechanics explain unexpected effects of exoskeleton assistance on metabolic rate during walking.

    PubMed

    Jackson, Rachel W; Dembia, Christopher L; Delp, Scott L; Collins, Steven H

    2017-03-24

    The goal of this study was to gain insight into how ankle exoskeletons affect the behavior of the plantarflexor muscles during walking. Using data from previous experiments, we performed electromyography-driven simulations of musculoskeletal dynamics to explore how changes in exoskeleton assistance affected plantarflexor muscle-tendon mechanics, particularly for the soleus. We used a model of muscle energy consumption to estimate individual muscle metabolic rate. As average exoskeleton torque was increased, while no net exoskeleton work was provided, a reduction in tendon recoil led to an increase in positive mechanical work performed by the soleus muscle fibers. As net exoskeleton work was increased, both soleus muscle fiber force and positive mechanical work decreased. Trends in the sum of the metabolic rates of the simulated muscles correlated well with trends in experimentally-observed whole-body metabolic rate (R(2) = 0.9), providing confidence in our model estimates. Our simulation results suggest that different exoskeleton behaviors can alter the functioning of the muscles and tendons acting at the assisted joint. Furthermore, our results support the idea that the series tendon helps reduce positive work done by the muscle fibers by storing and returning energy elastically. We expect the results from this study to promote the use of electromyography-driven simulations to gain insight into the operation of muscle-tendon units and to guide the design and control of assistive devices.

  19. Development of an assistive motorized hip orthosis: kinematics analysis and mechanical design.

    PubMed

    Olivier, Jeremy; Bouri, Mohamed; Ortlieb, Amalric; Bleuler, Hannes; Clavel, Reymond

    2013-06-01

    With the increase of life expectancy, a higher number of elderly need assistance to maintain their mobility and their independance. The hip joint is crucial for walking and is problematic for a large number of aged people. In this paper we present a novel design of a motorized hip orthosis to assist elderly people while walking, stair climbing and during the sit-to-stand transistions. The kinematics was developed based on biomechanics considerations. To be able to achieve a large assistance rate, velocity and torques of the hip joint were studied from the literature. In order to fit with these requirements, an amplification mechanism inspired by excavators was developed and implemented. Comfort considerations were also taken into account and a custom interface was designed with the collaboration of a professional orthopaedic technician. First tests with the prototype showed that the workspace is sufficient for walking, for stair climbing as well as for sit-to-stand transitions. The assistance rate can go up to 30% for a 70 kg subject during walking at a cadence of 100 steps/min. The comfort is guaranteed despite the important weight (4.3 kg) of this first prototype.

  20. Reducing Mechanical Formation Damage by Minimizing Interfacial Tension and Capillary Pressure in Tight Gas

    NASA Astrophysics Data System (ADS)

    Ahmed, Arshad; Talib Shuker, Muhannad; Rehman, Khalil; Bahrami, Hassan; Memon, Muhammad Khan

    2013-12-01

    Tight gas reservoirs incur problems and significant damage caused by low permeability during drilling, completion, stimulation and production. They require advanced improvement techniques to achieve flow gas at optimum rates. Water blocking damage (phase Trapping/retention of fluids) is a form of mechanical formation damage mechanism, which is caused by filtrate invasion in drilling operations mostly in fracturing. Water blocking has a noticeable impact on formation damage in gas reservoirs which tends to decrease relative permeability near the wellbore. Proper evaluation of damage and the factors which influence its severity is essential to optimize well productivity. Reliable data regarding interfacial tension between gas and water is required in order to minimize mechanical formation damage potential and to optimize gas production. This study was based on the laboratory experiments of interfacial tension by rising drop method between gas-brine, gas-condensate and gas-brine. The results showed gas condensate has low interfacial tension value 6 - 11 dynes/cm when compared to gas-brine and gas- diesel which were 44 - 58 dynes/cm and 14 - 19 dynes/cm respectively. In this way, the capillary pressure of brine-gas system was estimated as 0.488 psi, therefore diesel-gas system was noticed about 0.164 psi and 0.098 psi for condensate-gas system. A forecast model was used by using IFT values to predict the phase trapping which shows less severe phase trapping damage in case of condensate than diesel and brine. A reservoir simulation study was also carried out in order to better understand the effect of hysteresis on well productivity and flow efficiency affected due to water blocking damage in tight gas reservoirs.

  1. Binocular indirect ophthalmo microscope-assistant gas-perfused pars plana vitrectomy

    PubMed Central

    Zhang, Luyi; Yang, Xiaoli; Zheng, Qingqing; Wu, Miaoqin

    2016-01-01

    Abstract The vitreous sample has been used for the diagnosis of uveitis and intraocular malignancy for decades. The sample volume is usually limited to 1 mL with current techniques. In the present study, a novel technique for higher amount of vitreous sample acquisition, that is, Binocular Indirect Ophthalmo Microscope-assistant gas-perfused pars plana vitrectomy (BAG-PPV) was invented. For diagnostic purpose, BAG-PPV with 23-ga vitrectomy system was performed on a 54-year-old Chinese male with the symptom of bilateral atypical uveitis. More than 3 mL of vitreous sample per eye was collected without any significant complications. Cytopathology was confirmed on the basis of cell surface markers and released cytokines by flow cytometry analysis and cytokine assays respectively. A monoclonal B-cell population with the pattern of CD5−, CD10−, cyKi67+, CD71+, FMC7+, CD23−, and kappa light chain single expression for the right eye and a monoclonal B-cell pattern with CD5−, CD10−, cyKi67+, and kappa light chain restriction for the left eye were identified. The cytokine assay revealed high levels of interleukin (IL)-10 (90,838.30 and 41,098.0 pg/mL for the right and left eyes, respectively) and IL10/IL6 ratios for both eyes (with 90.78 and 63.26 for the IL10/IL6 ratios of the right and left eyes, respectively), while those for the cerebrospinal fluid were low (4.77 pg/mL for the IL10 level and 0.65 for the IL10/IL6 ratio). Based on the results, the patient was diagnosed with primary intraocular lymphoma for bilateral eyes. Our results demonstrated that diagnostic vitrectomy with BAG-PPV using the 23-ga vitrectomy system was safe, efficient, and able to provide useful diagnostic information for suspicious intraocular malignancy and other atypical uveitis. PMID:27930538

  2. Gas block mechanism for water removal in fuel cells

    DOEpatents

    Issacci, Farrokh; Rehg, Timothy J.

    2004-02-03

    The present invention is directed to apparatus and method for cathode-side disposal of water in an electrochemical fuel cell. There is a cathode plate. Within a surface of the plate is a flow field comprised of interdigitated channels. During operation of the fuel cell, cathode gas flows by convection through a gas diffusion layer above the flow field. Positioned at points adjacent to the flow field are one or more porous gas block mediums that have pores sized such that water is sipped off to the outside of the flow field by capillary flow and cathode gas is blocked from flowing through the medium. On the other surface of the plate is a channel in fluid communication with each porous gas block mediums. The method for water disposal in a fuel cell comprises installing the cathode plate assemblies at the cathode sides of the stack of fuel cells and manifolding the single water channel of each of the cathode plate assemblies to the coolant flow that feeds coolant plates in the stack.

  3. Beyond the VAD: Human Factors Engineering for Mechanically Assisted Circulation in the 21st Century.

    PubMed

    Throckmorton, Amy L; Patel-Raman, Sonna M; Fox, Carson S; Bass, Ellen J

    2016-06-01

    Thousands of ventricular assist devices (VADs) currently provide circulatory support to patients worldwide, and dozens of heart pump designs for adults and pediatric patients are under various stages of development in preparation for translation to clinical use. The successful bench-to-bedside development of a VAD involves a structured evaluation of possible system states, including human interaction with the device and auxiliary component usage in the hospital or home environment. In this study, we review the literature and present the current landscape of preclinical design and assessment, decision support tools and procedures, and patient-centered therapy. Gaps of knowledge are identified. The study findings support the need for more attention to user-centered design approaches for medical devices, such as mechanical circulatory assist systems, that specifically involve detailed qualitative and quantitative assessments of human-device interaction to mitigate risk and failure.

  4. Incidence and Outcomes of Anterior Chamber Gas Bubble during Femtosecond Flap Creation for Laser-Assisted In Situ Keratomileusis.

    PubMed

    Rush, Sloan W; Cofoid, Philip; Rush, Ryan B

    2015-01-01

    Purpose. To report the incidence and outcomes of anterior chamber gas bubble formation during femtosecond laser flap creation for laser-assisted in situ keratomileusis (LASIK). Methods. The charts of 2,886 consecutive eyes that underwent femtosecond LASIK from May 2011 through August 2014 were retrospectively reviewed. The incidence, preoperative characteristics, intraoperative details, and postoperative outcomes were analyzed in subjects developing anterior chamber gas bubble formation during the procedure. Results. A total of 4 cases (0.14%) developed anterior chamber gas bubble formation during femtosecond laser flap creation. In all four cases, the excimer laser was unable to successfully track the pupil immediately following the anterior chamber bubble formation, temporarily postponing the completion of the procedure. There was an ethnicity predilection of anterior chamber gas formation toward Asians (p = 0.0055). An uncorrected visual acuity of 20/20 was ultimately achieved in all four cases without further complications. Conclusions. Anterior chamber gas bubble formation during femtosecond laser flap creation for LASIK is an uncommon event that typically results in a delay in treatment completion; nevertheless, it does influence final positive visual outcome.

  5. Improvement of mechanical properties by additive assisted laser sintering of PEEK

    SciTech Connect

    Kroh, M. Bonten, C.; Eyerer, P.

    2014-05-15

    The additive assisted laser sintering was recently developed at IKT: A carbon black (CB) additive is used to adjust the polymer's laser absorption behavior with the aim to improve the interconnection of sintered powder layers. In this paper a parameter study, Polyetheretherketone (PEEK) samples were prepared with different contents of carbon black and were laser sintered with varying thermal treatment. The samples were mechanically tested and investigated by optical light and transmission electron microscopy. An influence on the morphology at the border areas of particles and intersections of laser sintered layers was found. Depending on the viscosity of the raw material and CB content, different shapes of lamellae were observed. These (trans-) crystalline or polymorph structures, respectively, influence the thermal and mechanical behavior of the virgin PEEK. Moreover, the thermal treatment during the sintering process caused an improvement of mechanical properties like tensile strength and elongation at break.

  6. Non-mechanical traumatic gas gangrene: forgotten but not gone.

    PubMed

    Senthilkumaran, Subramanian; Menezes, Ritesh G; Pant, Sadip; Khartode, Chhagan P; Balamurugan, Namasivayam; Thirumalaikolundusubramanian, Ponniah

    2012-04-01

    We report a case of gas gangrene (GG) in a non-diabetic HIV seronegative man who died within 60 hours following an intramuscular injection in rural India. The occurrence of GG after intramuscular injection is rare and only a few cases have been reported in the published literature.

  7. Robot-assisted total knee arthroplasty accurately restores the joint line and mechanical axis. A prospective randomised study.

    PubMed

    Liow, Ming Han Lincoln; Xia, Zhan; Wong, Merng Koon; Tay, Keng Jin; Yeo, Seng Jin; Chin, Pak Lin

    2014-12-01

    Robot-assisted Total Knee Arthroplasty (TKA) improves the accuracy and precision of component implantation and mechanical axis (MA) alignment. Joint-line restoration in robot-assisted TKA is not widely described and joint-line deviation of>5mm results in mid-flexion instability and poor outcomes. We prospectively randomised 60 patients into two groups: 31 patients (robot-assisted), 29 patients (conventional). No MA outliers (>±3° from neutral) or notching was noted in the robot-assisted group as compared with 19.4% (P=0.049) and 10.3% (P=0.238) respectively in the conventional group. The robot-assisted group had 3.23% joint-line outliers (>5mm) as compared to 20.6% in the conventional group (P=0.049). Robot-assisted TKA produces similar short-term clinical outcomes when compared to conventional methods with reduction of MA alignment and joint-line deviation outliers.

  8. Using Noble Gas Geochemistry to Determine the Source and Mechanism of Natural Gas Leakage into Shallow Aquifers Near Unconventional Drilling

    NASA Astrophysics Data System (ADS)

    Darrah, T.; Whyte, C. J.

    2015-12-01

    Horizontal drilling and hydraulic fracturing have enhanced energy production but raised concerns about drinking-water contamination and other environmental impacts associated with unconventional energy development. The occurrence of fugitive gas contamination in drinking-water wells near unconventional natural gas development has been central to the debate about the environmental impacts of hydraulic fracturing, but still has a controversial origin that has variably been attributed to natural geogenic occurrences, poor well bore integrity, and crustal-scale migration of natural gas along natural deformation features. Differentiating amongst these possibilities is critical to ongoing efforts to understand the environmental implications for the presence of elevated methane and aliphatic hydrocarbons (ethane, propane, etc.) in drinking-water and a necessary step toward the development of implementable solutions that limit the occurrence of future fugitive gas events. Here we will expand upon our recent work in the Marcellus and Barnett gas fields (Jackson et al., 2013; Darrah et al., 2014; 2015) that developed noble gas techniques for distinguishing natural and anthropogenic mechanisms of natural gas migration by integrating the molecular and isotopic composition of non-hydrocarbon molecules (N2, H2S, CO2) in addition to compound specific isotopes of hydrocarbons (d2H of CH4 and d2H-C2H6 and d13C of CH4, C2H6, and C3H8) and non-hydrocarbon compounds (d15N-N2). The expanded data sets validate our initial study and support the hypothesis that a subset of drinking-water wells experience natural gas contamination following faulty well construction or poor well integrity amid a background of naturally occurring gas and salt-rich groundwater.

  9. Percutaneous mechanical assist for severe cardiogenic shock due to acute right ventricular failure.

    PubMed

    Kipp, Ryan; Raval, Amish N

    2015-05-01

    Acute right ventricular failure can lead to severe cardiogenic shock and death. Recovery may be achieved with early supportive measures. In many patients, intravenous fluid and inotropic resuscitation is inadequate to improve cardiac output. In these cases, percutaneous mechanical assist may provide a non-surgical bridge to recovery. Herein, we describe a case series of patients with severe, refractory cardiogenic shock due to acute right ventricular failure who received a continuous flow percutaneous ventricular device primarily utilizing the right internal jugular vein for out flow cannula placement.

  10. The combined influence of chemical, metallurgical and mechanical factors on environment assisted cracking

    NASA Technical Reports Server (NTRS)

    Williams, D. P., III; Pao, P. S.; Wei, R. P.

    1979-01-01

    The principal aim of the paper is to re-emphasize and focus on both the multidisciplinary nature of the environment assisted cracking or embrittlement phenomenon. The multiplicity of factors involved in the embrittlement process is indicated, the mutual dependence of these factors and the influences of mechanical and environmental conditions are considered, and the interactions of various factors in determining the overall embrittlement response are discussed. The need for an interdisciplinary approach for resolving the major differences and for understanding embrittlement is outlined.

  11. Mechanical Modulation of Phonon-Assisted Field Emission in a Silicon Nanomembrane Detector for Time-of-Flight Mass Spectrometry

    PubMed Central

    Park, Jonghoo; Blick, Robert H.

    2016-01-01

    We demonstrate mechanical modulation of phonon-assisted field emission in a free-standing silicon nanomembrane detector for time-of-flight mass spectrometry of proteins. The impacts of ion bombardment on the silicon nanomembrane have been explored in both mechanical and electrical points of view. Locally elevated lattice temperature in the silicon nanomembrane, resulting from the transduction of ion kinetic energy into thermal energy through the ion bombardment, induces not only phonon-assisted field emission but also a mechanical vibration in the silicon nanomembrane. The coupling of these mechanical and electrical phenomenon leads to mechanical modulation of phonon-assisted field emission. The thermal energy relaxation through mechanical vibration in addition to the lateral heat conduction and field emission in the silicon nanomembrane offers effective cooling of the nanomembrane, thereby allowing high resolution mass analysis. PMID:26861329

  12. Microwave plasma assisted supersonic gas jet deposition of thin film materials

    DOEpatents

    Schmitt, III, Jerome J.; Halpern, Bret L.

    1993-01-01

    An apparatus for fabricating thin film materials utilizing high speed gas dynamics relies on supersonic free jets of carrier gas to transport depositing vapor species generated in a microwave discharge to the surface of a prepared substrate where the vapor deposits to form a thin film. The present invention generates high rates of deposition and thin films of unforeseen high quality at low temperatures.

  13. Coupling of highly explicit gas and aqueous chemistry mechanisms for use in 3-D

    NASA Astrophysics Data System (ADS)

    Ginnebaugh, Diana L.; Jacobson, Mark Z.

    2012-12-01

    This study discusses the coupling of a near-explicit gas-phase chemical mechanism with an extensive aqueous-phase mechanism in an accurate chemical solver designed for use in 3-D models. The gas and aqueous mechanisms and the solver used are the Master Chemical Mechanism (MCM 3.1), the Chemical Aqueous Phase Radical Mechanism (CAPRAM 3.0i), and the SMVGEAR II ordinary differential solver, respectively. The MCM has over 13,500 reactions and 4600 species, whereas CAPRAM treats aqueous chemistry among 390 species and 829 reactions (including 51 gas-to-aqueous phase reactions). SMVGEAR II is a sparse-matrix Gear solver that reduces the computation time significantly while maintaining any specified accuracy. MCM has been used previously with SMVGEAR II in 3-D, and computer timings here indicate that coupling MCM with CAPRAM in SMVGEAR II is also practical. Gas- and aqueous-phase species are coupled through time-dependent dissolutional growth and dissociation equations. This method is validated with a smaller mechanism against results from a previous model intercomparison. When the smaller mechanism is compared with the full MCM-CAPRAM mechanism, some concentrations are still similar but others differ due to the greater detail in chemistry. We also expand the mechanism to include gas-aqueous transfer of two acids, glycolic acid and glyoxylic acid, and modify the glyoxal Henry's law constant from recent measurements. The average glyoxal partitioning in the cloud changed from 67% aqueous-phase to 87% aqueous-phase with the modifications. The addition of gas-aqueous transfer reactions increased the average gas-phase percentage of glycolic acid to 19% and of glyoxylic acid to 16%. This full gas-phase and aqueous-phase chemistry module is a potentially useful tool for studying air pollution in a cloud or a fog.

  14. Modelling of powder consolidation using electro heating assisted by mechanical loading

    NASA Astrophysics Data System (ADS)

    Knyazeva, A.; Sorokova, S.

    2017-01-01

    The model of the process of reactive sintering assisted by mechanical loading is suggested. The conjugate heat exchange of powder mixture is taken into account. The powder mixture motion is described as viscous liquid with effective viscosity. Mechanical sub problem is one dimensional because friction near the wall is assumed negligible small. Conjugate thermal conductivity problem includes thermal conduction equations for various materials (reactive mixture and walls of the camber. Heat release is possible due to external electrical heating, viscous dissipation and chemical reactions. Kinetical equations correspond to detailed reaction scheme. The problem is solved numerically with special algorithm. As a result the composition of the mixture is obtained for different time moments. The final composition is not uniform.

  15. Prototype of a mechanical assistance device for the wrists' flexion-extension movement

    NASA Astrophysics Data System (ADS)

    Politti, Julio C.; Puglisi, Lisandro J.; Farfán, Fernando D.

    2007-11-01

    Using CMU actuators, a Prototype of Mechanical Assistance Device for the Wrist's Flexion Movement (PMA) was developed and probed in a mechanical model, in order to be implemented in a future as a dynamic powered orthosis or as a rehabilitation assistant instrument. Two Mayor Actuators conformed by three CMU actuators arranged in a series configuration, allows to an artificial hand to be placed in four predefined positions: 0°, 20°, 40° and 60°. The synchronism and control of the actuators is achieved with the Programmable Control Module (PCM). It is capable to drive up to six CMU actuators, and possess two different modes of execution: a Manual mode and an Exercise mode. In the Manual Mode, the position of the hand responds directly to the commands of the keyboard of the front panel, and in the Exercise mode, the hand realizes a repetitive and programmed movement. The prototype was tested in 100 positions in the Manual Mode and for 225 works cycles in the Exercise Mode. The relative repetition error was less than 5% for both test. This prototype only consumes 4,15W, which makes it possible to be powered by small rechargeable batteries, allowing its use as a portable device.

  16. [Mechanical cardiac-assist devices in ST segment elevation myocardial infarction].

    PubMed

    Spaulding, C

    2015-12-01

    A 49-year-old woman was admitted for an anterior ST segment elevation myocardial infarction (STEMI). At hospital arrival, she presented with cardiogenic shock. An immediate coronary angiogram showed an occluded ostial left anterior descending artery. During percutaneous coronary intervention (PCI), ventricular fibrillation occurred requiring multiple electrical counter-shocks. The coronary artery was opened during cardiopulmonary resuscitation and two drug-eluting stents were implanted. At the end of the procedure, an Impella CP® mechanical cardiac-assist device was inserted. Rapid and marked improvement in the hemodynamic status was noted in the following days. The Impella CP® was withdrawn after five days and the patient was discharged two weeks later. Despite limited data, mechanical cardiac assistance is recommended in cardiogenic shock. Several devices are currently available; the choice of the system is based on the clinical presentation and the experience of each center. The Impella CP® is a microaxial pump which is inserted percutaneously and delivers up to 3.5L/min of continuous flow. In cardiogenic shock due to STEMI, this device allows temporary support while awaiting left ventricular recovery after primary PCI.

  17. Methods and mechanisms for contact feedback in a robot-assisted minimally invasive environment.

    PubMed

    Tavakoli, M; Aziminejad, A; Patel, R V; Moallem, M

    2006-10-01

    Providing a surgeon with information regarding contacts made between instruments and tissue during robot-assisted interventions can improve task efficiency and reliability. In this report, different methods for feedback of such information to the surgeon are discussed. It is hypothesized that various methods of contact feedback have the potential to enhance performance in a robot-assisted minimally invasive environment. To verify the hypothesis, novel mechanisms needed for incorporating contact feedback were designed, including a surgeon-robot interface with full force feedback capabilities and a surgical end-effector with full force sensing capabilities, that are suitable for minimally invasive applications. These two mechanisms were used to form a robotic "master-slave" test bed for studying the effect of contact feedback on the system and user performance. Using the master-slave system, experiments for surgical tasks involving soft tissue palpation were conducted. The performance of the master-slave system was validated in terms of criteria that assess the accurate transmission of task-related information to the surgeon, which is critical in the context of soft tissue surgical applications. Moreover, using a set of experiments involving human subjects, the performance of several users in carrying out the task was compared among different methods of contact feedback.

  18. Degradation Mechanisms of SOFC Anodes in Coal Gas Containing Phosphorus

    SciTech Connect

    Marina, Olga A.; Coyle, Christopher A.; Thomsen, Edwin C.; Edwards, Danny J.; Coffey, Greg W.; Pederson, Larry R.

    2010-01-22

    The interaction of phosphorus in synthetic coal gas with the nickel-based anode of solid oxide fuel cells has been investigated. Tests with both anode-supported and electrolyte-supported button cells were performed at 700 to 800oC in synthetic coal gas containing 0.5 to 10 ppm phosphorus, introduced as phosphine. Two primary modes of degradation were observed. The most obvious was the formation of a series of bulk nickel phosphide phases, of which Ni3P, Ni5P2, Ni12P5 and Ni2P were identified. Phosphorus was essentially completely captured by the anode, forming a sharp boundary between converted and unconverted anode portions. These products partially coalesced into large grains, which eventually affected electronic percolation through the anode support. Thermodynamic calculations predict that formation of the first binary nickel phosphide phase is possible at sub-parts per billion concentrations in coal gas at temperatures relevant to fuel cell operation. A second mode of degradation is attributed to surface diffusion of phosphorus to the active anode/electrolyte interface to form an adsorption layer. Direct evidence for the presence of such an adsorption layer on nickel was obtained by surface spectroscopies on fracture surfaces. Further, cell performance losses were observed well before the entire anode was converted to bulk nickel phosphide. Impedance spectroscopy revealed that these losses were primarily due to growth in electrodic resistance, whereas large ohmic increases were visible when the entire anode was converted to nickel phosphide phases. The rate of resistance growth for anode-supported cells showed a very low dependence on phosphorus concentration, attributed to phosphorus activity control within the anode by bulk nickel phosphide products.

  19. Mechanical response of noble gas films to an oscillating substrate

    NASA Astrophysics Data System (ADS)

    Kobayashi, Hajime; Taniguchi, Junko; Suzuki, Masaru; Miura, Kouji; Arakawa, Ichiro

    2012-12-01

    We carried out quartz-crystal microbalance (QCM) experiments for Xe films adsorbed on an exfoliated single-crystalline graphite substrate (Xe/Gr) and Kr 1ms adsorbed on a synthetic mica substrate (Kr/mica) around LN2 temperature. For Xe/Gr, it was found that the resonance frequency decreases greatly around the first layer completion, while it does not decrease at low coverages. The observed behavior is similar to that of Kr films on a graphite substrate (Kr/Gr). This demonstrates that the layer completion strongly affects the sliding motion of noble gas films on graphite.

  20. Mechanisms of combustion limits in premixed gas flames at microgravity

    NASA Technical Reports Server (NTRS)

    Ronney, Paul D.

    1991-01-01

    A three-year experimental and theoretical research program on the mechanisms of combustion limits of premixed gasflames at microgravity was conducted. Progress during this program is identified and avenues for future studies are discussed.

  1. Microwave plasma assisted supersonic gas jet deposition of thin film materials

    DOEpatents

    Schmitt, J.J. III; Halpern, B.L.

    1993-10-26

    An apparatus for fabricating thin film materials utilizing high speed gas dynamics relies on supersonic free jets of carrier gas to transport depositing vapor species generated in a microwave discharge to the surface of a prepared substrate where the vapor deposits to form a thin film. The present invention generates high rates of deposition and thin films of unforeseen high quality at low temperatures. 5 figures.

  2. Method for microwave plasma assisted supersonic gas jet deposition of thin films

    DOEpatents

    Schmitt, J.J. III; Halpern, B.L.

    1994-10-18

    A thin film is formed on a substrate positioned in a vacuum chamber by use of a gas jet apparatus affixed to a vacuum chamber port and having an outer nozzle with an interior cavity into which carrier gas is fed, an inner nozzle located within the outer nozzle interior cavity into which reactant gas is introduced, a tip of the inner nozzle being recessed from the vacuum chamber port within the outer nozzle interior cavity, and a microwave discharge device configured about the apparatus for generating a discharge in the carrier gas and reactant gas only in a portion of the outer nozzle interior cavity extending from approximately the inner nozzle tip towards the vacuum chamber. A supersonic free jet of carrier gas transports vapor species generated in the microwave discharge to the surface of the substrate to form a thin film on the substrate. The substrate can be translated from the supersonic jet to a second supersonic jet in less time than needed to complete film formation so that the film is chemically composed of chemical reaction products of vapor species in the jets. 5 figs.

  3. Method for microwave plasma assisted supersonic gas jet deposition of thin films

    DOEpatents

    Schmitt, III, Jerome J.; Halpern, Bret L.

    1994-01-01

    A thin film is formed on a substrate positioned in a vacuum chamber by use of a gas jet apparatus affixed to a vacuum chamber port and having an outer nozzle with an interior cavity into which carrier gas is fed, an inner nozzle located within the outer nozzle interior cavity into which reactant gas is introduced, a tip of the inner nozzle being recessed from the vacuum chamber port within the outer nozzle interior cavity, and a microwave discharge device configured about the apparatus for generating a discharge in the carrier gas and reactant gas only in a portion of the outer nozzle interior cavity extending from approximately the inner nozzle tip towards the vacuum chamber. A supersonic free jet of carrier gas transports vapor species generated in the microwave discharge to the surface of the substrate to form a thin film on the substrate. The substrate can be translated from the supersonic jet to a second supersonic jet in less time than needed to complete film formation so that the film is chemically composed of chemical reaction products of vapor species in the jets.

  4. Effect of drive mode of left ventricular assist device on the left ventricular mechanics.

    PubMed

    Nakamura, T; Hayashi, K; Seki, J; Nakatani, T; Noda, H; Takano, H; Akutsu, T

    1988-02-01

    Pneumatically driven left ventricular assist devices (LVADs) were acutely implanted between the left atria and the descending aortas of dogs, and were driven in five pumping modes: electrocardiogram synchronous modes with the duty factors of 1:1, 2:1, and 4:1, and asynchronous modes with the pulse rates of 60 and 80 beats/min (bpm). The ventricular diameter and myocardial segment length were measured by an ultrasonic displacement meter and implantable miniature sensors. Bulk mechanical work of the left ventricle and regional mechanical work of the myocardium were calculated from these dimensions and the left ventricular pressure. LVAD reduced the bulk mechanical work of the left ventricle by 30-50% and the regional work by 30-60%. The mean aortic pressure and the total flow (= aortic flow + pump bypass flow) were highest in the 1:1 synchronous pumping mode, which indicates that this mode is most effective to maintain the systemic circulation and coronary blood flow. Asynchronous pumping and synchronous pumping with 2:1 duty factor were most useful to reduce the mechanical work of the left ventricle.

  5. Estimation of mechanical dispersion and dispersivity in a soil-gas system by column experiments and the dusty gas model.

    PubMed

    Hibi, Yoshihiko; Kanou, Yuki; Ohira, Yuki

    2012-04-01

    In a previous study, column experiments were carried out with Toyoura sand (permeability 2.05×10(-11)m(2)) and Toyoura sand mixed with bentonite (permeability 9.96×10(-13)m(2)) to obtain the molecular diffusion coefficient, the Knudsen diffusion coefficient, the tortuosity for the molecular diffusion coefficient, and the mechanical dispersion coefficient of soil-gas systems. In this study, we conducted column experiments with field soil (permeability 2.0×10(-13)m(2)) and showed that the above parameters can be obtained for both less-permeable and more-permeable soils by using the proposed method for obtaining the parameters and performing column experiments. We then estimated dispersivity from the mechanical dispersion coefficients obtained by the column experiments. We found that the dispersivity depended on the mole fraction of the tracer gas and could be represented by a quadratic equation.

  6. Mechanisms and Kinetics of Environmentally Assisted Cracking: Current Status, Issues, and Suggestions for Further Work

    NASA Astrophysics Data System (ADS)

    Lynch, S. P.

    2013-03-01

    Mechanisms and kinetics of metal-induced embrittlement, hydrogen-embrittlement, and stress-corrosion cracking are discussed, and long-standing controversies are addressed by reviewing critical observations. Recommendations are also made regarding further work (including repetition of previous work using more advanced measurement and characterisation techniques) that should be carried out in order to resolve some of the contentious issues. The evidence to date suggests that adsorption-based mechanisms, involving weakening of substrate interatomic bonds so that dislocation emission or decohesion is facilitated, accounts for embrittlement in many systems. Embrittling adsorbed species include some metal atoms, hydrogen, and complex ions produced by de-alloying. Other viable mechanisms of embrittlement include those based on (1) dissolution of anodic grain-boundary regions, and (2) decohesion at grain boundaries owing to segregated hydrogen and impurities. The hydrogen-enhanced localised-plasticity mechanism, based on solute hydrogen facilitating dislocation activity in the plastic zone ahead of cracks, makes a contribution in some cases, but is relatively unimportant compared with these other mechanisms for most fracture modes. The film-induced cleavage mechanism, proposed especially for stress-corrosion cracking in systems involving de-alloying at crack tips, is questionable on numerous grounds, and is probably not viable. Rate-controlling processes for environmentally assisted cracking are not well established, except for solid-metal induced embrittlement where surface self-diffusion of embrittling atoms to crack tips controls cracking kinetics. In some systems, adsorption kinetics are probably rate-controlling for liquid-metal embrittlement, hydrogen-environment embrittlement, and stress-corrosion cracking. In other cases, rate-controlling processes could include the rate of anodic or cathodic reactions at and behind crack tips (responsible for producing embrittling

  7. Gas cluster ion beam assisted NiPt germano-silicide formation on SiGe

    NASA Astrophysics Data System (ADS)

    Ozcan, Ahmet S.; Lavoie, Christian; Alptekin, Emre; Jordan-Sweet, Jean; Zhu, Frank; Leith, Allen; Pfeifer, Brian D.; LaRose, J. D.; Russell, N. M.

    2016-04-01

    We report the formation of very uniform and smooth Ni(Pt)Si on epitaxially grown SiGe using Si gas cluster ion beam treatment after metal-rich silicide formation. The gas cluster ion implantation process was optimized to infuse Si into the metal-rich silicide layer and lowered the NiSi nucleation temperature significantly according to in situ X-ray diffraction measurements. This novel method which leads to more uniform films can also be used to control silicide depth in ultra-shallow junctions, especially for high Ge containing devices, where silicidation is problematic as it leads to much rougher interfaces.

  8. Surface reaction mechanisms during ozone and oxygen plasma assisted atomic layer deposition of aluminum oxide.

    PubMed

    Rai, Vikrant R; Vandalon, Vincent; Agarwal, Sumit

    2010-09-07

    We have elucidated the reaction mechanism and the role of the reactive intermediates in the atomic layer deposition (ALD) of aluminum oxide from trimethyl aluminum in conjunction with O(3) and an O(2) plasma. In situ attenuated total reflection Fourier transform infrared spectroscopy data show that both -OH groups and carbonates are formed on the surface during the oxidation cycle. These carbonates, once formed on the surface, are stable to prolonged O(3) exposure in the same cycle. However, in the case of plasma-assisted ALD, the carbonates decompose upon prolonged O(2) plasma exposure via a series reaction kinetics of the type, A (CH(3)) --> B (carbonates) --> C (Al(2)O(3)). The ratio of -OH groups to carbonates on the surface strongly depends on the oxidizing agent, and also the duration of the oxidation cycle in plasma-assisted ALD. However, in both O(3) and O(2) plasma cycles, carbonates are a small fraction of the total number of reactive sites compared to the hydroxyl groups.

  9. 157. ARAIII Reactor building (ARA608) Main gas loop mechanical flow ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    157. ARA-III Reactor building (ARA-608) Main gas loop mechanical flow sheet. This drawing was selected as a typical example of mechanical arrangements within reactor building. Aerojet-general 880-area/GCRE-0608-50-013-102634. - Idaho National Engineering Laboratory, Army Reactors Experimental Area, Scoville, Butte County, ID

  10. Mechanical properties of monolayer GaS and GaSe crystals

    NASA Astrophysics Data System (ADS)

    Yagmurcukardes, M.; Senger, R. T.; Peeters, F. M.; Sahin, H.

    2016-12-01

    The mechanical properties of monolayer GaS and GaSe crystals are investigated in terms of their elastic constants: in-plane stiffness (C), Poisson ratio (ν ), and ultimate strength (σU) by means of first-principles calculations. The calculated elastic constants are compared with those of graphene and monolayer MoS2. Our results indicate that monolayer GaS is a stiffer material than monolayer GaSe crystals due to the more ionic character of the Ga-S bonds than the Ga-Se bonds. Although their Poisson ratio values are very close to each other, 0.26 and 0.25 for GaS and GaSe, respectively, monolayer GaS is a stronger material than monolayer GaSe due to its slightly higher σU value. However, GaS and GaSe crystals are found to be more ductile and flexible materials than graphene and MoS2. We have also analyzed the band-gap response of GaS and GaSe monolayers to biaxial tensile strain and predicted a semiconductor-metal crossover after 17 % and 14 % applied strain, respectively, for monolayer GaS and GaSe. In addition, we investigated how the mechanical properties are affected by charging. We found that the flexibility of single layer GaS and GaSe displays a sharp increase under 0.1 e /cell charging due to the repulsive interactions between extra charges located on chalcogen atoms. These charging-controllable mechanical properties of single layers of GaS and GaSe can be of potential use for electromechanical applications.

  11. Hydraulic and Mechanical Effects from Gas Hydrate Conversion and Secondary Gas Hydrate Formation during Injection of CO2 into CH4-Hydrate-Bearing Sediments

    NASA Astrophysics Data System (ADS)

    Bigalke, N.; Deusner, C.; Kossel, E.; Schicks, J. M.; Spangenberg, E.; Priegnitz, M.; Heeschen, K. U.; Abendroth, S.; Thaler, J.; Haeckel, M.

    2014-12-01

    The injection of CO2 into CH4-hydrate-bearing sediments has the potential to drive natural gas production and simultaneously sequester CO2 by hydrate conversion. The process aims at maintaining the in situ hydrate saturation and structure and causing limited impact on soil hydraulic properties and geomechanical stability. However, to increase hydrate conversion yields and rates it must potentially be assisted by thermal stimulation or depressurization. Further, secondary formation of CO2-rich hydrates from pore water and injected CO2 enhances hydrate conversion and CH4 production yields [1]. Technical stimulation and secondary hydrate formation add significant complexity to the bulk conversion process resulting in spatial and temporal effects on hydraulic and geomechanical properties that cannot be predicted by current reservoir simulation codes. In a combined experimental and numerical approach, it is our objective to elucidate both hydraulic and mechanical effects of CO2 injection and CH4-CO2-hydrate conversion in CH4-hydrate bearing soils. For the experimental approach we used various high-pressure flow-through systems equipped with different online and in situ monitoring tools (e.g. Raman microscopy, MRI and ERT). One particular focus was the design of triaxial cell experimental systems, which enable us to study sample behavior even during large deformations and particle flow. We present results from various flow-through high-pressure experimental studies on different scales, which indicate that hydraulic and geomechanical properties of hydrate-bearing sediments are drastically altered during and after injection of CO2. We discuss the results in light of the competing processes of hydrate dissociation, hydrate conversion and secondary hydrate formation. Our results will also contribute to the understanding of effects of temperature and pressure changes leading to dissociation of gas hydrates in ocean and permafrost systems. [1] Deusner C, Bigalke N, Kossel E

  12. Mechanisms for Orientation in Low Energy Ion Beam Assisted TiAlN Thin Film Growth

    NASA Astrophysics Data System (ADS)

    Aliotta, Paul V.

    The effects of off-normal ionized vapor bombardment on the orientation and structure of off-normal sputter deposited TiAlN thin films has been investigated with the goal of better understanding the mechanistic pathways in ion beam assisted thin film growth for better control of film properties during deposition. The effects of incident angle for ion bombardment has been investigated as a potential variable during deposition and a comprehensive comparison to current theories of thin film orientation development has been made. It is shown that for low levels of ion energies and rates, films develop (220) orientation with a near amorphous zone 1 (Z1) morphology for low ion incident angles. As the rates and energies of ions increases, (111) orientation and fibrous transition zone (ZT) morphology develops. It is also seen that as the angle of ion bombardment increases the threshold level for rates and energies of ions to cause (111) orientation and ZT morphologies is reduced. This change in orientation and morphology has been shown to change in-situ according to the level of ion bombardment making this transition a potential tool for developing microstructures within thin films. Commonly accepted theories of thin film orientation have been investigated with respect to the development of (111) orientation for low energy ion beam assisted deposition including surface energy reduction, thermal influences, strain energy reduction, ion channeling, and ion damage anisotropy though such mechanisms were not successful in describing the development of (111) orientation. Atomic subplantation, generally regarded as a mechanism for bond formation in diamond-like carbon films, has also been investigated as a potential mechanism for orientation development. By treating the interaction of ions with the depositing film as a collision between ion and surface atom, the transition from (220) to (111) orientation is found to occur when the average energy transferred per atom normal to the

  13. Gas dependent sensing mechanism in ZnO nanobelt sensor

    NASA Astrophysics Data System (ADS)

    Kaur, Manmeet; Kailasaganapathi, S.; Ramgir, Niranjan; Datta, Niyanta; Kumar, Sushil; Debnath, A. K.; Aswal, D. K.; Gupta, S. K.

    2017-02-01

    Gas sensing properties of ZnO nanobelts synthesized using carbothermal reduction method has been investigated. At room temperature (28 °C), the sensor films exhibit an appreciable response towards H2S and NO and response of these two gases were studied as a function of concentration. For NO the sensor films exhibit a complete reversible curve for the concentration range between 1 and 60 ppm. However, for H2S a complete recovery was obtained for concentration <5 ppm and for higher concentration a partial recovery of the baseline resistance was observed. The reason for the incomplete recovery was investigated using X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) studies of the sample before and after the H2S exposure. After exposure, appearance of an additional peak at 26.6° corresponding to the formation of ZnS was observed in XRD. Formation of additional phase was further corroborated using the results of XPS. H2S exposure causes decrease in the intensity of O 1s peak and appearance of sulphide peaks at binding energies of 162.8 and 161.8 eV corresponding to S-2p peaks - 2p3/2 and 2p1/2, confirms the formation of ZnS upon exposure.

  14. Upper extremity muscle tone and response of tidal volume during manually assisted breathing for patients requiring prolonged mechanical ventilation

    PubMed Central

    Morino, Akira; Shida, Masahiro; Tanaka, Masashi; Sato, Kimihiro; Seko, Toshiaki; Ito, Shunsuke; Ogawa, Shunichi; Yokoi, Yuka; Takahashi, Naoaki

    2015-01-01

    [Purpose] The aim of the present study was to examine, in patients requiring prolonged mechanical ventilation, if the response of tidal volume during manually assisted breathing is dependent upon both upper extremity muscle tone and the pressure intensity of manually assisted breathing. [Subjects] We recruited 13 patients on prolonged mechanical ventilation, and assessed their upper extremity muscle tone using the modified Ashworth scale (MAS). The subjects were assigned to either the low MAS group (MAS≤2, n=7) or the high MAS group (MAS≥3, n=6). [Methods] The manually assisted breathing technique was applied at a pressure of 2 kgf and 4 kgf. A split-plot ANOVA was performed to compare the tidal volume of each pressure during manually assisted breathing between the low and the high MAS groups. [Results] Statistical analysis showed there were main effects of the upper extremity muscle tone and the pressure intensity of the manually assisted breathing technique. There was no interaction between these factors. [Conclusion] Our findings reveal that the tidal volume during the manually assisted breathing technique for patients with prolonged mechanical ventilation depends upon the patient’s upper extremity muscle tone and the pressure intensity. PMID:26357431

  15. Mechanisms of heat transport across a nano-scale gap in heat assisted magnetic recording

    NASA Astrophysics Data System (ADS)

    Budaev, Bair V.; Bogy, David B.

    2012-06-01

    This paper compares different mechanisms of heat transport across nano-scale gaps and discusses the role of electromagnetic phenomena in heat transport in general nano-scale layered structures. The results of the analysis suggest that heat transfer across sub-5 nm gaps like that appearing in prototypes of heat assisted magnetic recording (HAMR) systems is dominated by direct intermolecular interactions between the separated bodies and is little affected by electromagnetic radiation. The analysis further suggests that local heating for HAMR with sub-5 nm spacing can be more efficiently achieved by a Joule heater that is simpler to fabricate than laser-based optical systems and is less destructive for the nano-scale transducers than laser radiation, which may lead to their structural damage and short duration life of nanoscale transducers.

  16. Preparing high-density polymer brushes by mechanically assisted polymer assembly (MAPA)

    NASA Astrophysics Data System (ADS)

    Wu, Tao; Efimenko, Kirill; Genzer, Jan

    2001-03-01

    We introduce a novel method of modifying the surface properties of materials. This technique, called MAPA (="mechanically assisted polymer assembly"), is based on: 1) chemically attaching polymerization initiators to the surface of an elastomeric network that has been previously stretched by a certain length, Δx, and 2) growing end-anchored macromolecules using surface initiated ("grafting from") atom transfer living radical polymerization. After the polymerization, the strain is removed from the substrate, which returns to its original size causing the grafted macromolecules to stretch away from the substrate and form a dense polymer brush. We demonstrate the feasibility of the MAPA method by preparing high-density polymer brushes of poly(acryl amide), PAAm. We show that, as expected, the grafting density of the PAAm brushes can be increased by increasing Δx. We demonstrate that polymer brushes with extremely high grafting densities can be successfully prepared by MAPA.

  17. Beta-MnO2 3D nanostructures: mineralizer-assisted synthesis, characterization, and growth mechanism.

    PubMed

    Zhou, Fu; Zhao, Xuemei; Yuan, Cunguang; Xu, Hai

    2007-09-01

    The beta-MnO2 three-dimensional (3D) nanostructures were synthesized in large area by a mineralizer-assisted hydrothermal route. KNO3 was introduced as inorganic mineralizer to direct the growth of beta-MnO2 3D nanostructures from Mn(NO3)2 solutions. The samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). Possible growth mechanism of beta-MnO2 3D nanostructures was proposed based on comparative experiments, indicating that KNO3 mineralizer and the concentration of Mn(NO3)2 solution were the two decisive factors in the fabrication of beta-MnO2 3D nanostructures.

  18. The mechanism of lipids extraction from wet microalgae Scenedesmus sp. by ionic liquid assisted subcritical water

    NASA Astrophysics Data System (ADS)

    Yu, Zhuanni; Chen, Xiaolin; Xia, Shuwei

    2016-06-01

    In this paper, the total sugar concentration, protein concentration, lipid yield and morphology characteristics of the algae residue were determined to explain the mechanism of lipids extraction from wet microalgae Scenedesmus sp. by ionic liquid assisted subcritical water. The results showed similar variation for the sugar, protein and lipid. However, the total sugar was more similar to lipids yield, so the results showed that the reaction between ionic liquid and cellulose and hemicellulose in cell wall was the most important step which determined the lipids extration directly. And the total sugar variation may be representing the lipids yield. For later lipids extraction, we can determine the total sugar concentration to predict the extraction end product.

  19. A microfluidic respiratory assist device with high gas permeance for artificial lung applications.

    PubMed

    Kniazeva, Tatiana; Hsiao, James C; Charest, Joseph L; Borenstein, Jeffrey T

    2011-04-01

    One of the principal challenges in artificial lung technology has been the ability to provide levels of oxygen and carbon dioxide exchange that rival those of the natural human lung, while mitigating the deleterious interaction between blood and the surface of the synthetic gas exchange membrane. This interaction is exacerbated by the large oxygenator surface area required to achieve sufficient levels of gas transfer. In an effort to address this challenge, microfluidics-based artificial lung technologies comprising stacked microchannel networks have been explored by several groups. Here we report the design, fabrication and initial testing of a parallel plate multilayered silicone-based microfluidic construct containing ultrathin gas exchange membranes, aimed at maximizing gas transfer efficiency while minimizing membrane-blood contact area. The device comprises a branched microvascular network that provides controlled wall shear stress and uniform blood flow, and is designed to minimize blood damage, thrombosis and inflammatory responses seen in current oxygenators. Initial testing indicates that flow distribution through the multilayer structure is uniform and that the thin membrane can withstand pressures equivalent to those expected during operation. Oxygen transfer using phosphate buffered saline as the carrier fluid has also been assessed, demonstrating a sharp increase in oxygen transfer as membrane thickness is reduced, consistent with the expected values of oxygen permeance for thin silicone membranes.

  20. Investigation of Sterilization Mechanism for Geobacillus stearothermophilus Spores with Plasma-Excited Neutral Gas

    NASA Astrophysics Data System (ADS)

    Matsui, Kei; Ikenaga, Noriaki; Sakudo, Noriyuki

    2015-09-01

    We investigate the mechanism of the sterilization with plasma-excited neutral gas that uniformly sterilizes both the space and inner wall of the reactor chamber at atmospheric pressure. Only reactive neutral species such as plasma-excited gas molecules and radicals are separated from the plasma and sent to the reactor chamber for chemical sterilization. The plasma source gas uses humidified mixture of nitrogen and oxygen. Geobacillus stearothermophilus spores and tyrosine which is amino acid are treated by the plasma-excited neutral gas. Shape change of the treated spore is observed by SEM, and chemical modification of the treated tyrosine is analyzed by HPLC. As a result, the surface of the treated spore shows depression. Hydroxylation and nitration of tyrosine are shown after the treatment. For these reasons, we believe that the sterilization with plasma-excited neutral gas results from the deformation of spore structure due to the chemical modification of amino acid.

  1. Assessment of solar-assisted gas-fired heat pump systems

    NASA Technical Reports Server (NTRS)

    Lansing, F. L.

    1981-01-01

    As a possible application for the Goldstone Energy Project, the performance of a 10 ton heat pump unit using a hybrid solar gas energy source was evaluated in an effort to optimize the solar collector size. The heat pump system is designed to provide all the cooling and/or heating requirements of a selected office building. The system performance is to be augmented in the heating mode by utilizing the waste heat from the power cycle. A simplified system analysis is described to assess and compute interrrelationships of the engine, heat pump, and solar and building performance parameters, and to optimize the solar concentrator/building area ratio for a minimum total system cost. In addition, four alternative heating cooling systems, commonly used for building comfort, are described; their costs are compared, and are found to be less competitive with the gas solar heat pump system at the projected solar equipment costs.

  2. Assessment of solar-assisted gas-fired heat pump systems

    NASA Astrophysics Data System (ADS)

    Lansing, F. L.

    1981-06-01

    As a possible application for the Goldstone Energy Project, the performance of a 10 ton heat pump unit using a hybrid solar gas energy source was evaluated in an effort to optimize the solar collector size. The heat pump system is designed to provide all the cooling and/or heating requirements of a selected office building. The system performance is to be augmented in the heating mode by utilizing the waste heat from the power cycle. A simplified system analysis is described to assess and compute interrrelationships of the engine, heat pump, and solar and building performance parameters, and to optimize the solar concentrator/building area ratio for a minimum total system cost. In addition, four alternative heating cooling systems, commonly used for building comfort, are described; their costs are compared, and are found to be less competitive with the gas solar heat pump system at the projected solar equipment costs.

  3. Structural and composition investigations at delayered locations of low k integrated circuit device by gas-assisted focused ion beam

    SciTech Connect

    Wang, Dandan Kee Tan, Pik; Yamin Huang, Maggie; Lam, Jeffrey; Mai, Zhihong

    2014-05-15

    The authors report a new delayering technique – gas-assisted focused ion beam (FIB) method and its effects on the top layer materials of integrated circuit (IC) device. It demonstrates a highly efficient failure analysis with investigations on the precise location. After removing the dielectric layers under the bombardment of an ion beam, the chemical composition of the top layer was altered with the reduced oxygen content. Further energy-dispersive x-ray spectroscopy and Fourier transform infrared analysis revealed that the oxygen reduction lead to appreciable silicon suboxide formation. Our findings with structural and composition alteration of dielectric layer after FIB delayering open up a new insight avenue for the failure analysis in IC devices.

  4. Sterilization mechanism of nitrogen gas plasma: induction of secondary structural change in protein.

    PubMed

    Sakudo, Akikazu; Higa, Masato; Maeda, Kojiro; Shimizu, Naohiro; Imanishi, Yuichiro; Shintani, Hideharu

    2013-07-01

    The mechanism of action on biomolecules of N₂ gas plasma, a novel sterilization technique, remains unclear. Here, the effect of N₂ gas plasma on protein structure was investigated. BSA, which was used as the model protein, was exposed to N₂ gas plasma generated by short-time high voltage pulses from a static induction thyristor power supply. N₂ gas plasma-treated BSA at 1.5 kilo pulses per second showed evidence of degradation and modification when assessed by Coomassie brilliant blue staining and ultraviolet spectroscopy at 280 nm. Fourier transform infrared spectroscopy analysis was used to determine the protein's secondary structure. When the amide I region was analyzed in the infrared spectra according to curve fitting and Fourier self-deconvolution, N₂ gas plasma-treated BSA showed increased α-helix and decreased β-turn content. Because heating decreased α-helix and increased β-sheet content, the structural changes induced by N₂ gas plasma-treatment of BSA were not caused by high temperatures. Thus, the present results suggest that conformational changes induced by N₂ gas plasma are mediated by mechanisms distinct from heat denaturation.

  5. Strategies and methodologies to develop techniques for computer-assisted analysis of gas phase formation during altitude decompression

    NASA Technical Reports Server (NTRS)

    Powell, Michael R.; Hall, W. A.

    1993-01-01

    It would be of operational significance if one possessed a device that would indicate the presence of gas phase formation in the body during hypobaric decompression. Automated analysis of Doppler gas bubble signals has been attempted for 2 decades but with generally unfavorable results, except with surgically implanted transducers. Recently, efforts have intensified with the introduction of low-cost computer programs. Current NASA work is directed towards the development of a computer-assisted method specifically targeted to EVA, and we are most interested in Spencer Grade 4. We note that Spencer Doppler Grades 1 to 3 have increased in the FFT sonogram and spectrogram in the amplitude domain, and the frequency domain is sometimes increased over that created by the normal blood flow envelope. The amplitude perturbations are of very short duration, in both systole and diastole and at random temporal positions. Grade 4 is characteristic in the amplitude domain but with modest increases in the FFT sonogram and spectral frequency power from 2K to 4K over all of the cardiac cycle. Heart valve motion appears to characteristic display signals: (1) the demodulated Doppler signal amplitude is considerably above the Doppler-shifted blow flow signal (even Grade 4); and (2) demodulated Doppler frequency shifts are considerably greater (often several kHz) than the upper edge of the blood flow envelope. Knowledge of these facts will aid in the construction of a real-time, computer-assisted discriminator to eliminate cardiac motion artifacts. There could also exist perturbations in the following: (1) modifications of the pattern of blood flow in accordance with Poiseuille's Law, (2) flow changes with a change in the Reynolds number, (3) an increase in the pulsatility index, and/or (4) diminished diastolic flow or 'runoff.' Doppler ultrasound devices have been constructed with a three-transducer array and a pulsed frequency generator.

  6. Redeposition in plasma-assisted atomic layer deposition: Silicon nitride film quality ruled by the gas residence time

    SciTech Connect

    Knoops, Harm C. M. E-mail: w.m.m.kessels@tue.nl; Peuter, K. de; Kessels, W. M. M. E-mail: w.m.m.kessels@tue.nl

    2015-07-06

    The requirements on the material properties and growth control of silicon nitride (SiN{sub x}) spacer films in transistors are becoming ever more stringent as scaling of transistor structures continues. One method to deposit high-quality films with excellent control is atomic layer deposition (ALD). However, depositing SiN{sub x} by ALD has turned out to be very challenging. In this work, it is shown that the plasma gas residence time τ is a key parameter for the deposition of SiN{sub x} by plasma-assisted ALD and that this parameter can be linked to a so-called “redeposition effect”. This previously ignored effect, which takes place during the plasma step, is the dissociation of reaction products in the plasma and the subsequent redeposition of reaction-product fragments on the surface. For SiN{sub x} ALD using SiH{sub 2}(NH{sup t}Bu){sub 2} as precursor and N{sub 2} plasma as reactant, the gas residence time τ was found to determine both SiN{sub x} film quality and the resulting growth per cycle. It is shown that redeposition can be minimized by using a short residence time resulting in high-quality films with a high wet-etch resistance (i.e., a wet-etch rate of 0.5 nm/min in buffered HF solution). Due to the fundamental nature of the redeposition effect, it is expected to play a role in many more plasma-assisted ALD processes.

  7. Substrate-assisted cysteine deprotonation in the mechanism of dimethylargininase (DDAH) from Pseudomonas aeruginosa.

    PubMed

    Stone, Everett M; Costello, Alison L; Tierney, David L; Fast, Walter

    2006-05-02

    The enzyme dimethylargininase (also known as dimethylarginine dimethylaminohydrolase or DDAH; EC 3.5.3.18) catalyzes the hydrolysis of endogenous nitric oxide synthase inhibitors, N(omega)-methyl-l-arginine and N(omega),N(omega)-dimethyl-l-arginine. Understanding the mechanism and regulation of DDAH activity is important for developing ways to control nitric oxide production during angiogenesis and in many cases of vascular endothelial pathobiology. Several possible physiological regulation mechanisms of DDAH depend upon the presence of an active-site cysteine residue, Cys249 in Pseudomonas aeruginosa (Pa) DDAH, which is proposed to serve as a nucleophile in the catalytic mechanism. Through the use of pH-dependent ultraviolet and visible (UV-vis) difference spectroscopy and inactivation kinetics, the pK(a) of the active-site Cys249 in the resting enzyme was found to be unperturbed from pK(a) values of typical noncatalytic cysteine residues. In contrast, the pH dependence of k(cat) values indicates a much lower apparent pK(a) value. UV-vis difference spectroscopy between wild-type and C249S DDAH shows absorbance changes consistent with Cys249 deprotonation to the anionic thiolate upon binding positively charged ligands. The proton from Cys249 is lost either to the solvent or to an unidentified general base. A mutation of the active-site histidine residue, H162G, does not eliminate cysteine nucleophilicity, further arguing against a pre-formed ion pair with Cys249. Finally, UV-vis and X-ray absorption spectroscopy revealed that inhibitory metal ions can bind at these two active-site residues, Cys249 and His162, and also stabilize the anionic form of Cys249. These results support a proposed substrate-assisted mechanism for Pa DDAH in which ligand binding modulates the reactivity of the active-site cysteine.

  8. Assessment of Initial Test Conditions for Experiments to Assess Irradiation Assisted Stress Corrosion Cracking Mechanisms

    SciTech Connect

    Busby, Jeremy T; Gussev, Maxim N

    2011-04-01

    Irradiation-assisted stress corrosion cracking is a key materials degradation issue in today s nuclear power reactor fleet and affects critical structural components within the reactor core. The effects of increased exposure to irradiation, stress, and/or coolant can substantially increase susceptibility to stress-corrosion cracking of austenitic steels in high-temperature water environments. . Despite 30 years of experience, the underlying mechanisms of IASCC are unknown. Extended service conditions will increase the exposure to irradiation, stress, and corrosive environment for all core internal components. The objective of this effort within the Light Water Reactor Sustainability program is to evaluate the response and mechanisms of IASCC in austenitic stainless steels with single variable experiments. A series of high-value irradiated specimens has been acquired from the past international research programs, providing a valuable opportunity to examine the mechanisms of IASCC. This batch of irradiated specimens has been received and inventoried. In addition, visual examination and sample cleaning has been completed. Microhardness testing has been performed on these specimens. All samples show evidence of hardening, as expected, although the degree of hardening has saturated and no trend with dose is observed. Further, the change in hardening can be converted to changes in mechanical properties. The calculated yield stress is consistent with previous data from light water reactor conditions. In addition, some evidence of changes in deformation mode was identified via examination of the microhardness indents. This analysis may provide further insights into the deformation mode under larger scale tests. Finally, swelling analysis was performed using immersion density methods. Most alloys showed some evidence of swelling, consistent with the expected trends for this class of alloy. The Hf-doped alloy showed densification rather than swelling. This observation may be

  9. Mechanical Characteristics of Submerged Arc Weldment in API Gas Pipeline Steel of Grade X65

    NASA Astrophysics Data System (ADS)

    Hashemi, S. H.; Mohammadyani, D.

    2011-01-01

    The mechanical properties of submerged arc weldment (SAW) in gas transportation pipeline steel of grade API X65 (65 ksi yield strength) were investigated. This steel is produced by thermo mechanical control rolled (TMC), and is largely used in Iran gas piping systems and networks. The results from laboratory study on three different regions; i.e. base metal (BM), fusion zone (FZ) and heat affected zone (HAZ) were used to compare weldment mechanical characteristics with those specified by API 5L (revision 2004) standard code. Different laboratory experiments were conducted on test specimens taken from 48 inch outside diameter and 14.3 mm wall thickness gas pipeline. The test results showed a gradient of microstructure and Vickers hardness data from the centerline of FZ towards the unaffected MB. Similarly, lower Charpy absorbed energy (compared to BM) was observed in the FZ impact specimens. Despite this, the API specifications were fulfilled in three tested zones, ensuring pipeline structural integrity under working conditions.

  10. The coercivity mechanism of Pr-Fe-B nanoflakes prepared by surfactant-assisted ball milling

    NASA Astrophysics Data System (ADS)

    Zuo, Wen-Liang; Zhang, Ming; Niu, E.; Shao, Xiao-Ping; Hu, Feng-Xia; Sun, Ji-Rong; Shen, Bao-Gen

    2015-09-01

    The strong (00l) textured Pr12+xFe82-xB6 (x=0, 1, 2, 3, 4) nanoflakes with high coercivity were prepared by surfactant-assisted ball milling (SABM). The thickness and length of the flakes are mainly in the range of 50-200 nm and 0.5-2 μm, respectively. A coercivity of 4.16 kOe for Pr15Fe79B6 nanoflakes was obtained, which is the maximum coercivity of R2Fe14B (R=Pr, Nd) nanoflakes or nanoparticles reported up to now. The results of XRD and SEM for the aligned Pr15Fe79B6 nanoflakes indicate that a strong (00l) texture is obtained and the easy magnetization direction is parallel to the surface of the flakes. The angular dependence of coercivity for aligned sample indicates that the coercivity mechanism of the as-milled nanoflakes is mainly dominated by domain wall pinning. Meanwhile, the field dependence of coercivity, isothermal (IRM) and dc demagnetizing (DCD) remanence curves also indicate that the coercivity is mainly determined by domain wall pinning, and nucleation also has an important effect. In addition, the mainly interaction of flakes is dipolar coupling. The research of coercivity mechanism for Pr15Fe79B6 nanoflakes is important for guidance the further increase its value, and is useful for the future development of the high performance nanocomposite magnets and soft/hard exchange spring magnets.

  11. Safety mechanism assisted by the repressor of tetracycline (SMART) vaccinia virus vectors for vaccines and therapeutics.

    PubMed

    Grigg, Patricia; Titong, Allison; Jones, Leslie A; Yilma, Tilahun D; Verardi, Paulo H

    2013-09-17

    Replication-competent viruses, such as Vaccinia virus (VACV), are powerful tools for the development of oncolytic viral therapies and elicit superior immune responses when used as vaccine and immunotherapeutic vectors. However, severe complications from uncontrolled viral replication can occur, particularly in immunocompromised individuals or in those with other predisposing conditions. VACVs constitutively expressing interferon-γ (IFN-γ) replicate in cell culture indistinguishably from control viruses; however, they replicate in vivo to low or undetectable levels, and are rapidly cleared even in immunodeficient animals. In an effort to develop safe and highly effective replication-competent VACV vectors, we established a system to inducibly express IFN-γ. Our SMART (safety mechanism assisted by the repressor of tetracycline) vectors are designed to express the tetracycline repressor under a constitutive VACV promoter and IFN-γ under engineered tetracycline-inducible promoters. Immunodeficient SCID mice inoculated with VACVs not expressing IFN-γ demonstrated severe weight loss, whereas those given VACVs expressing IFN-γ under constitutive VACV promoters showed no signs of infection. Most importantly, mice inoculated with a VACV expressing the IFN-γ gene under an inducible promoter remained healthy in the presence of doxycycline, but exhibited severe weight loss in the absence of doxycycline. In this study, we developed a safety mechanism for VACV based on the conditional expression of IFN-γ under a tightly controlled tetracycline-inducible VACV promoter for use in vaccines and oncolytic cancer therapies.

  12. Mechanical analysis of lunar gravity assist in the Earth-Moon system

    NASA Astrophysics Data System (ADS)

    Qi, Yi; Xu, Shijie

    2015-12-01

    In this paper, the lunar gravity assist (LGA) is investigated under the planar circular restricted three-body problem (PCRTBP) and two-body model. In the PCRTBP, the approximate expression of energy of the LGA in a small region of the Moon is derived. The expression uncovers the mechanism and mechanical process of the LGA in the framework of the PCRTBP. Based on the expression, the change of energy during the LGA is obtained and analyzed. To solve the limitation of the expressions and complete the research range of the LGA, a numerical methodology based on the patched-conic model is presented to analyze the LGA in a large region near the Moon. This numerical methodology cannot only obtain the change of energy but also may classify the trajectories before and after the LGA. As an application, we present a method to design a special kind of double LGA orbit. The design method synthesizes the preliminary results in the patched-conic model and the optimization in the PCRTBP. We can quickly obtain abundant double LGA orbits for the Earth-Moon transfer and interplanetary spaceflight.

  13. Electrochemically assisted deposition of transparent, mechanically robust TiO2 films for advanced applications

    NASA Astrophysics Data System (ADS)

    Maino, Giulia; Meroni, Daniela; Pifferi, Valentina; Falciola, Luigi; Soliveri, Guido; Cappelletti, Giuseppe; Ardizzone, Silvia

    2013-11-01

    In recent years, titanium dioxide has received ever growing interest, thanks to its promising applications in numerous fields such as environmental remediation, H2 generation and photovoltaics. Here, transparent and mechanically robust TiO2 films are deposited by a simple and inexpensive electrochemically assisted procedure on various kinds of substrates, both conductive and nonconductive (e.g., glass slides or different metal laminas with variable surface roughness). The obtained films are uniform, crack-free and exhibit excellent chemical, mechanical, and electrochemical robustness. The obtained layers are compared to films prepared by a routine preparation technique, such as dip coating, showing much better morphological, optical, and conductive properties. The photo-activity of TiO2 can be exploited to obtain transparent spectroelectrochemical systems and to control the wetting features of the surface. Applications concerning the modulation of the wettability are presented with respect to both the antifogging and antistain properties. The photoelectrochemical properties of TiO2 films are exploited to activate a photoelectrochemical polymerization of polypyrrole onto an unconductive support. These materials are promising for numerous applications such as smart windows, antifogging mirrors, solar cells, and optically transparent electrodes.

  14. Mechanistic studies of protein arginine deiminase 2: evidence for a substrate-assisted mechanism.

    PubMed

    Dreyton, Christina J; Knuckley, Bryan; Jones, Justin E; Lewallen, Daniel M; Thompson, Paul R

    2014-07-15

    Citrullination, which is catalyzed by protein arginine deiminases (PADs 1-4 and 6), is a post-translational modification (PTM) that effectively neutralizes the positive charge of a guanidinium group by its replacement with a neutral urea. Given the sequence similarity of PAD2 across mammalian species and the genomic organization of the PAD2 gene, PAD2 is predicted to be the ancestral homologue of the PADs. Although PAD2 has long been known to play a role in myelination, it has only recently been linked to other cellular processes, including gene transcription and macrophage extracellular trap formation. For example, PAD2 deiminates histone H3 at R26, and this PTM leads to the increased transcription of more than 200 genes under the control of the estrogen receptor. Given that our understanding of PAD2 biology remains incomplete, we initiated mechanistic studies on this enzyme to aid the development of PAD2-specific inhibitors. Herein, we report that the substrate specificity and calcium dependence of PAD2 are similar to those of PADs 1, 3, and 4. However, unlike those isozymes, PAD2 appears to use a substrate-assisted mechanism of catalysis in which the positively charged substrate guanidinium depresses the pKa of the nucleophilic cysteine. By contrast, PADs 1, 3, and 4 use a reverse-protonation mechanism. These mechanistic differences will aid the development of isozyme-specific inhibitors.

  15. The strained sesquiterpene β-caryophyllene as a probe for the solvent-assisted epoxidation mechanism.

    PubMed

    Steenackers, Bart; Neirinckx, Alexander; De Cooman, Luc; Hermans, Ive; De Vos, Dirk

    2014-04-04

    In our attempt to synthesize β-caryophyllene oxide in food-compatible conditions, we observed the uncatalyzed and highly selective epoxidation of β-caryophyllene, a strained bicyclic sesquiterpene, in ethanol with aqueous H2 O2 under radical-suppressing conditions without the addition of a catalyst. The unusual reactivity of β-caryophyllene allowed us to use it as a probe for the mechanism of the solvent-assisted epoxidation in a wide range of organic solvents. A kinetic study was performed to investigate the epoxidation mechanism; an excellent correlation was found between the observed epoxidation rates in different solvents and the Abraham's hydrogen bond formation parameters of these solvents. By means of computational analysis, it was found that the main role of the solvent consists of the stabilization of the elongated OO bond of H2 O2 in the transition state through hydrogen-bond donation to the leaving OH moiety of H2 O2 . α-Humulene was found to possess similar reactivity as β-caryophyllene whereas isocaryophyllene-the unstrained isomer of β-caryophyllene-was unreactive.

  16. Coupled simulation of CFD-flight-mechanics with a two-species-gas-model for the hot rocket staging

    NASA Astrophysics Data System (ADS)

    Li, Yi; Reimann, Bodo; Eggers, Thino

    2016-11-01

    The hot rocket staging is to separate the lowest stage by directly ignite the continuing-stage-motor. During the hot staging, the rocket stages move in a harsh dynamic environment. In this work, the hot staging dynamics of a multistage rocket is studied using the coupled simulation of Computational Fluid Dynamics and Flight Mechanics. Plume modeling is crucial for a coupled simulation with high fidelity. A 2-species-gas model is proposed to simulate the flow system of the rocket during the staging: the free-stream is modeled as "cold air" and the exhausted plume from the continuing-stage-motor is modeled with an equivalent calorically-perfect-gas that approximates the properties of the plume at the nozzle exit. This gas model can well comprise between the computation accuracy and efficiency. In the coupled simulations, the Navier-Stokes equations are time-accurately solved in moving system, with which the Flight Mechanics equations can be fully coupled. The Chimera mesh technique is utilized to deal with the relative motions of the separated stages. A few representative staging cases with different initial flight conditions of the rocket are studied with the coupled simulation. The torque led by the plume-induced-flow-separation at the aft-wall of the continuing-stage is captured during the staging, which can assist the design of the controller of the rocket. With the increasing of the initial angle-of-attack of the rocket, the staging quality becomes evidently poorer, but the separated stages are generally stable when the initial angle-of-attack of the rocket is small.

  17. CO2 Binding Organic Liquids Gas Capture with Polarity Swing Assisted Regeneration

    SciTech Connect

    Heldebrant, David

    2014-05-31

    This report outlines the comprehensive bench-scale testing of the CO2-binding organic liquids (CO2BOLs) solvent platform and its unique Polarity Swing Assisted Regeneration (PSAR). This study outlines all efforts on a candidate CO2BOL solvent molecule, including solvent synthesis, material characterization, preliminary toxicology studies, and measurement of all physical, thermodynamic and kinetic data, including bench-scale testing. Equilibrium and kinetic models and analysis were made using Aspen Plus™. Preliminary process configurations, a technoeconomic assessment and solvent performance projections for separating CO2 from a subcritical coal-fired power plant are compared to the U.S. Department of Energy's Case 10 monoethanolamine baseline.

  18. Photon-Assisted Tunneling in a Biased Strongly Correlated Bose Gas

    SciTech Connect

    Ma Ruichao; Tai, M. Eric; Preiss, Philipp M.; Bakr, Waseem S.; Simon, Jonathan; Greiner, Markus

    2011-08-26

    We study the impact of coherently generated lattice photons on an atomic Mott insulator subjected to a uniform force. Analogous to an array of tunnel-coupled and biased quantum dots, we observe sharp, interaction-shifted photon-assisted tunneling resonances corresponding to tunneling one and two lattice sites either with or against the force and resolve multiorbital shifts of these resonances. By driving a Landau-Zener sweep across such a resonance, we realize a quantum phase transition between a paramagnet and an antiferromagnet and observe quench dynamics when the system is tuned to the critical point. Direct extensions will produce gauge fields and site-resolved spin flips, for topological physics and quantum computing.

  19. Plasma-assisted cleanup of flue gas. Technical report, March 1, 1994--May 31, 1994

    SciTech Connect

    Dhali, S.K.

    1994-09-01

    The experimental data reported in the last quarterly report were verified by repeating the experiments. It was consistently determined that there is nearly 80% removal of SO{sub 2} in a flue gas containing 775 ppm (parts per million) of SO{sub 2} and 99% for SO{sub 2} in concentrations of 300 ppm. The reduction increases with increasing electrode length. Also during this period, the removal studies for higher concentrations of SO{sub 2} (1400 ppm) were studied. For this a variable frequency power supply was used. It was found that the removal efficiency increased with frequency (in the range 60-400 Hz).

  20. Fully automated system for the gas chromatographic characterization of polar biopolymers based on thermally assisted hydrolysis and methylation.

    PubMed

    Kaal, Erwin; de Koning, Sjaak; Brudin, Stella; Janssen, Hans-Gerd

    2008-08-08

    Pyrolysis-gas chromatography (Py-GC) is a powerful tool for the detailed compositional analysis of polymers. A major problem of Py-GC is that polar (bio)polymers yield polar pyrolyzates which are not easily accessible to further GC characterization. In the present work, a newly developed fully automated procedure for thermally assisted hydrolysis and methylation (THM) of biopolymers is described. Drying of the sample, addition of the reagent, incubation and pyrolysis are performed inside the liner of a programmable temperature vaporizer injector. The new system not only allows efficient analysis of large series of samples, but also allows automated optimization of the experimental parameters based on an experimental design approach. The performance of the automated THM-procedure was evaluated by performing THM-GC of a poly(acrylic acid)-poly(maleic anhydride) copolymer (PAA/PMAH) and several polysaccharides. The optimized THM-procedure was applied for the structural characterization and differentiation of several lignins and hydroxypropylmethyl-celluloses. It was also applied to proteins. Here myoglobin and cytochrome c were used as the model compounds. Both conventional GC-mass spectrometry (MS) and comprehensive two-dimensional gas chromatography (GCxGC)-time-of-flight (TOF) MS were used for separation and identification of the species formed. The information obtained can aid in structure elucidation of polar biopolymers as well as in providing detailed compositional information which can be used to differentiate structurally similar biopolymers.

  1. The Detonation Mechanism of the Pulsationally Assisted Gravitationally Confined Detonation Model of Type Ia Supernovae

    NASA Astrophysics Data System (ADS)

    Jordan, G. C., IV; Graziani, C.; Fisher, R. T.; Townsley, D. M.; Meakin, C.; Weide, K.; Reid, L. B.; Norris, J.; Hudson, R.; Lamb, D. Q.

    2012-11-01

    We describe the detonation mechanism composing the "pulsationally assisted" gravitationally confined detonation (GCD) model of Type Ia supernovae. This model is analogous to the previous GCD model reported in Jordan et al.; however, the chosen initial conditions produce a substantively different detonation mechanism, resulting from a larger energy release during the deflagration phase. The resulting final kinetic energy and 56Ni yields conform better to observational values than is the case for the "classical" GCD models. In the present class of models, the ignition of a deflagration phase leads to a rising, burning plume of ash. The ash breaks out of the surface of the white dwarf, flows laterally around the star, and converges on the collision region at the antipodal point from where it broke out. The amount of energy released during the deflagration phase is enough to cause the star to rapidly expand, so that when the ash reaches the antipodal point, the surface density is too low to initiate a detonation. Instead, as the ash flows into the collision region (while mixing with surface fuel), the star reaches its maximally expanded state and then contracts. The stellar contraction acts to increase the density of the star, including the density in the collision region. This both raises the temperature and density of the fuel-ash mixture in the collision region and ultimately leads to thermodynamic conditions that are necessary for the Zel'dovich gradient mechanism to produce a detonation. We demonstrate feasibility of this scenario with three three-dimensional (3D), full star simulations of this model using the FLASH code. We characterized the simulations by the energy released during the deflagration phase, which ranged from 38% to 78% of the white dwarf's binding energy. We show that the necessary conditions for detonation are achieved in all three of the models.

  2. Hybrid test bench for evaluation of any device related to mechanical cardiac assistance.

    PubMed

    Colacino, F M; Arabia, M; Danieli, G A; Moscato, F; Nicosia, S; Piedimonte, F; Valigi, P; Pagnottelli, S

    2005-08-01

    Hydraulic mock circulatory systems have low flexibility to allow tests of different cardiovascular devices and low precision when a reference model must be reproduced. In this paper a new bench is described. It combines the computer model of the environment in which the device will operate and the electro-hydraulic interfaces by which device and computer are connected. A models library provided with basic functions allows implementing many layouts of the bench, which in turn depend both on the device properties and the desired experiment. In case of an apical LVAD evaluation, the bench can reproduce right and left ventricles, pulmonary and systemic circulations, inlet and outlet LVAD cannulas. An interface forces the instantaneous calculated flow at the VAD input and feeds back the measured pressure to the computer; another interface works in a similar -but complementary- way at the VAD output. The paper focuses on the operating principle of the electro hydraulic interfaces which represent a relevant component of the bench, on the RT-Linux-based software architecture, on the models of the basic elements of the bench. A patent is under preparation. At the moment, only a portion of the bench has been developed. It consists of a piston-cylinder mechanism, which mimics the elastance-based mechanism of a natural ventricle, and a hydraulic circuit representing the arterial load according to a modified windkessel model and the venous return according to the Guyton's model. The pump is driven by a real-time simulation of the cardiovascular system. This preliminary layout allowed testing the piston-cylinder mechanism, its control, and the software. This electro-hydraulic interface has been used to reproduce a pulsatile pump working in different modes. The hybrid model approach can support the development of new cardiac assist devices from their computer model to their manufacture.

  3. Hematite (alpha-Fe2O3) with various morphologies: ionic liquid-assisted synthesis, formation mechanism, and properties.

    PubMed

    Lian, Jiabiao; Duan, Xiaochuan; Ma, Jianmin; Peng, Peng; Kim, Tongil; Zheng, Wenjun

    2009-11-24

    The alpha-Fe(2)O(3) with various morphologies has been successfully synthesized via an ionic liquid-assisted hydrothermal synthetic method. The samples are characterized by X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscope (FE-SEM), transmission electron microscopy, and high-resolution transmission electron microscopy. The results indicate that the as-prepared samples are alpha-Fe(2)O(3) nanoparticles, mesoporous hollow microspheres, microcubes, and porous nanorods. The effects of the ionic liquid 1-n-butyl-3-methylimidazolium chloride ([bmim][Cl]) on the formation of the alpha-Fe(2)O(3) with various morphologies have been investigated systematically. The proposed formation mechanisms have also been investigated on the basis of a series of FE-SEM studies of the products obtained at different durations. Because of the unique porous structure, the potential application in water treatment of the alpha-Fe(2)O(3) porous nanorods was investigated. The UV-vis measurements suggest that the as-synthesized pure alpha-Fe(2)O(3) with various morphologies possess different optical properties depending on the shape and size of the samples. The magnetic hysteresis measurements indicate the interesting magnetic property evolution in the as-prepared alpha-Fe(2)O(3) samples, which is attributed to the superstructure or the shape anisotropy of the samples. This method is expected to be a useful technique for controlling the diverse shapes of crystalline inorganic materials for a variety of applications, such as sensors, gas and heavy metal ion adsorbents, catalytic fields, hydrogen and Li ion storage, and controlled drug delivery, etc.

  4. Effect of laser parameters and assist gas on spectral response of silicon fibrous nanostructure

    SciTech Connect

    Mahmood, Abdul Salam; Venkatakrishnan, Krishnan; Alubiady, M.; Tan, Bo

    2010-11-15

    This article report, for the first time, the influence of laser parameters on the spectral response of weblike silicon fibrous nanostructures. These nanostructures are formed by femtosecond laser irradiation at megahertz pulse frequency under atmosphere and nitrogen ambient. The observed decreasing in reflectance is correlated with the density of fibrous nanostructures and the size of the agglomerated nanoparticles. Compared to bulk silicon, Raman spectra of fibrous nanostructures shows a downward shift and asymmetric broadening at the first order phonon peak. The shift and broadening are attributed to phonon confinement of fibrous nanostructure. Polarization and nitrogen gas modify the morphology of generated nanomaterials but does not have effect on light absorptance. Pulsewidth and pulse frequency do not have significant effect on light absorptance.

  5. Fundamental mechanisms that influence the estimate of heat transfer to gas turbine blades

    NASA Technical Reports Server (NTRS)

    Graham, R. W.

    1979-01-01

    Estimates of the heat transfer from the gas to stationary (vanes) or rotating blades poses a major uncertainty due to the complexity of the heat transfer processes. The gas flow through these blade rows is three dimensional with complex secondary viscous flow patterns that interact with the endwalls and blade surfaces. In addition, upstream disturbances, stagnation flow, curvature effects, and flow acceleration complicate the thermal transport mechanisms in the boundary layers. Some of these fundamental heat transfer effects are discussed. The chief purpose of the discussion is to acquaint those in the heat transfer community, not directly involved in gas turbines, of the seriousness of the problem and to recommend some basic research that would improve the capability for predicting gas-side heat transfer on turbine blades and vanes.

  6. Neutralization of solvated protons and formation of noble-gas hydride molecules: Matrix-isolation indications of tunneling mechanisms?

    SciTech Connect

    Khriachtchev, Leonid; Lignell, Antti; Raesaenen, Markku

    2005-08-08

    The (NgHNg){sup +} cations (Ng=Ar and Kr) produced via the photolysis of HF/Ar, HF/Kr, and HBr/Kr solid mixtures are studied, with emphasis on their decay mechanisms. The present experiments provide a large variety of parameters connected to this decay phenomenon, which allows us to reconsider various models for the decay of the (NgHNg){sup +} cations in noble-gas matrices. As a result, we propose that this phenomenon could be explained by the neutralization of the solvated protons by electrons. The mechanism of this neutralization reaction probably involves tunneling of an electron from an electronegative fragment or another trap to the (NgHNg){sup +} cation. The proposed electron-tunneling mechanism should be considered as a possible alternative to the literature models based on tunneling-assisted or radiation-induced diffusion of protons in noble-gas solids. As a novel experimental observation of this work, the efficient formation of HArF molecules occurs at 8 K in a photolyzed HF/Ar matrix. It is probable that the low-temperature formation of HArF involves local tunneling of the H atom to the Ar-F center, which in turn supports the locality of HF photolysis in solid Ar. In this model, the decay of (ArHAr){sup +} ions and the formation of HArF molecules observed at low temperatures are generally unconnected processes; however, the decaying (ArHAr){sup +} ions may contribute to some extent to the formation of HArF molecules.

  7. Matrix-assisted laser desorption mass spectrometry of gas-phase peptide-metal complexes

    NASA Astrophysics Data System (ADS)

    Hortal, Ana R.; Hurtado, Paola; Martínez-Haya, Bruno

    2008-12-01

    Cation attachment to a model peptide has been investigated in matrix-assisted laser desorption experiments. Angiotensin I (Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-His-Leu) is chosen as a system for study, and Cu2+ and K+ salts are used as cationizing agents. Three fundamentally different types of samples are investigated: (1) a crystalline sample of Ang I, metal salt and MALDI matrix, prepared with the conventional dried droplet method; (2) a solvent-free fine powder mixture of the same three compounds, and (3) a solution of the angiotensin and the metal salt in an ionic liquid matrix (a molten organic salt that acts as a MALDI active solvent). Effective protonation and cationization of the peptide are achieved with the three methods. The transition metal systematically provides more efficient cationization than the alkali metal. At sufficiently high concentration of the salt, the attachment of up to four copper cations to the angiotensin is observed in the MALDI spectrum. In contrast, only one K+ cation is efficiently bound to the peptide. For a given salt concentration, the highest degree of cationization is obtained in the laser desorption from the ionic liquid matrix. This is attributed to the efficient transfer of free metal cations to the desorption plume, where the complexation takes place.

  8. Mechanisms of direct detonation initiation via thermal explosion of radiatively heated gas-particles layer

    NASA Astrophysics Data System (ADS)

    Efremov, V. P.; Ivanov, M. F.; Kiverin, A. D.; Yakovenko, I. S.

    Conceptual approach of detonation wave direct initiation by external radiative heating of microparticles locally suspended in flammable gaseous mixture is proposed. Combustion waves and detonation initiation mechanisms in the congestion regions of microparticles heated by radiation are studied numerically. Necessary criteria on geometrical scales of gas-particles layer and spatial uniformity of particles distribution for successful detonation initiation are formulated.

  9. Recent advances in computational methodology for simulation of mechanical circulatory assist devices

    PubMed Central

    Marsden, Alison L.; Bazilevs, Yuri; Long, Christopher C.; Behr, Marek

    2014-01-01

    Ventricular assist devices (VADs) provide mechanical circulatory support to offload the work of one or both ventricles during heart failure. They are used in the clinical setting as destination therapy, as bridge to transplant, or more recently as bridge to recovery to allow for myocardial remodeling. Recent developments in computational simulation allow for detailed assessment of VAD hemodynamics for device design and optimization for both children and adults. Here, we provide a focused review of the recent literature on finite element methods and optimization for VAD simulations. As VAD designs typically fall into two categories, pulsatile and continuous flow devices, we separately address computational challenges of both types of designs, and the interaction with the circulatory system with three representative case studies. In particular, we focus on recent advancements in finite element methodology that has increased the fidelity of VAD simulations. We outline key challenges, which extend to the incorporation of biological response such as thrombosis and hemolysis, as well as shape optimization methods and challenges in computational methodology. PMID:24449607

  10. A study on dynamic heat assisted magnetization reversal mechanisms under insufficient reversal field conditions

    SciTech Connect

    Chen, Y. J.; Yang, H. Z.; Leong, S. H.; Yu Ko, Hnin Yu; Wu, B. L.; Ng, V.; Asbahi, M.; Yang, J. K. W.

    2014-10-20

    We report an experimental study on the dynamic thermomagnetic (TM) reversal mechanisms at around Curie temperature (Tc) for isolated 60 nm pitch single-domain [Co/Pd] islands heated by a 1.5 μm spot size laser pulse under an applied magnetic reversal field (Hr). Magnetic force microscopy (MFM) observations with high resolution MFM tips clearly showed randomly trapped non-switched islands within the laser irradiated spot after dynamic TM reversal process with insufficient Hr strength. This observation provides direct experimental evidence by MFM of a large magnetization switching variation due to increased thermal fluctuation/agitation over magnetization energy at the elevated temperature of around Tc. The average percentage of non-switched islands/magnetization was further found to be inversely proportional to the applied reversal field Hr for incomplete magnetization reversal when Hr is less than 13% of the island coercivity (Hc), showing an increased switching field distribution (SFD) at elevated temperature of around Tc (where main contributions to SFD broadening are from Tc distribution and stronger thermal fluctuations). Our experimental study and results provide better understanding and insight on practical heat assisted magnetic recording (HAMR) process and recording performance, including HAMR writing magnetization dynamics induced SFD as well as associated DC saturation noise that limits areal density, as were previously observed and investigated by theoretical simulations.

  11. Surfactant-assisted dispersion of carbon nanotubes: mechanism of stabilization and biocompatibility of the surfactant

    NASA Astrophysics Data System (ADS)

    Singh, Raman Preet; Jain, Sanyog; Ramarao, Poduri

    2013-10-01

    Nanoparticles (NPs) are thermodynamically unstable system and tend to aggregate to reduce free energy. The aggregation property of NPs results in inhomogeneous exposure of cells to NPs resulting in variable cellular responses. Several types of surfactants are used to stabilize NP dispersions and obtain homogenous dispersions. However, the effects of these surfactants, per se, on cellular responses are not completely known. The present study investigated the application of Pluronic F68 (PF68) for obtaining stable dispersion of NPs using carbon nanotubes as model NPs. PF68-stabilized NP suspensions are stable for long durations and do not show signs of aggregation or settling during storage or after autoclaving. The polyethylene oxide blocks in PF68 provide steric hindrance between adjacent NPs leading to stable NP dispersions. Further, PF68 is biocompatible in nature and does not affect integrity of mitochondria, lysosomes, DNA, and nuclei. Also, PF68 neither induce free radical or cytokine production nor does it interfere with cellular uptake mechanisms. The results of the present study suggest that PF68-assisted dispersion of NPs produced suspensions, which are stable after autoclaving. Further, PF68 does not interfere with normal physiological functions suggesting its application in nanomedicine and nanotoxicity evaluation.

  12. Strong magnetic field-assisted growth of carbon nanofibers and its microstructural transformation mechanism

    NASA Astrophysics Data System (ADS)

    Luo, Chengzhi; Fu, Qiang; Pan, Chunxu

    2015-03-01

    It is well-known that electric and magnetic fields can control the growth direction, morphology and microstructure of one-dimensional carbon nanomaterials (1-DCNMs), which plays a key role for its potential applications in micro-nano-electrics and devices. In this paper, we introduce a novel process for controlling growth of carbon nanofibers (CNFs) with assistance of a strong magnetic field (up to 0.5 T in the center) in a chemical vapor deposition (CVD) system. The results reveal that: 1) The CNFs get bundled when grown in the presence of a strong magnetic field and slightly get aligned parallel to the direction of the magnetic field; 2) The CNFs diameter become narrowed and homogenized with increase of the magnetic field; 3) With the increase of the magnetic field, the microstructure of CNFs is gradually changed, i.e., the strong magnetic field makes the disordered ``solid-cored'' CNFs transform into a kind of bamboo-liked carbon nanotubes; 4) We propose a mechanism that the reason for these variations and transformation is due to diamagnetic property of carbon atoms, so that it has direction selectivity in the precipitation process.

  13. Mechanism of irradiation assisted stress corrosion crack initiation in thermally sensitized 304 stainless steel

    NASA Astrophysics Data System (ADS)

    Onchi, T.; Dohi, K.; Soneda, N.; Navas, Marta; Castaño, M. L.

    2005-04-01

    Thermally sensitized 304 stainless steels, irradiated up to 1.2 × 1021 n/cm2 (E > 1 MeV), were slow-strain-rate-tensile tested in 290 °C water containing 0.2 ppm dissolved oxygen (DO), followed by scanning and transmission electron microscopic examinations, to study mechanism of irradiation-assisted-stress-corrosion-crack (IASCC) initiation. Intergranular (IG) cracking behaviors changed at a border fluence (around 1 × 1020 n/cm2), above which deformation twinning were predominant and deformation localization occurred earlier with increasing fluence. The crack initiation sites tended to link to the deformation bands, indicating that the crack initiation may be brought about by the deformation bands interacted with grain boundaries. Thus the border fluence is equivalent to the IASCC threshold fluence for the sensitized material, although the terminology of IASCC is originally given to the non-sensitized materials without microstructural definition. The IASCC threshold fluence was found to change with irradiation conditions. Changes in IASCC susceptibility and IASCC threshold fluence with fluence and DO were further discussed.

  14. Mechanical circulatory assist device development at the Texas Heart Institute: a personal perspective.

    PubMed

    Frazier, O H

    2014-06-01

    In December 2013, we performed our 1000th ventricular assist device implantation at the Texas Heart Institute. In my professional career, I have been fortunate to see the development of numerous mechanical circulatory support devices for the treatment of patients with advanced heart failure. In fact, most of the cardiac pumps in wide use today were developed in the Texas Heart Institute research laboratories in cooperation with the National Heart, Lung and Blood Institute or device innovators and manufacturers and implanted clinically at our partner St. Luke's Episcopal Hospital. My early involvement in this field was guided by my mentors, Dr Michael E. DeBakey and, especially, Dr Denton A. Cooley. Also, many of the advances are directly attributable to my ongoing clinical experience. What I learned daily in my surgical practice allowed me to bring insights to the development of this technology that a laboratory researcher alone might not have had. Young academic surgeons interested in this field might be well served to be active not only in laboratory research but also in clinical practice.

  15. Mechanisms and clinical applications of the vacuum-assisted closure (VAC) Device: a review.

    PubMed

    Venturi, Mark L; Attinger, Christopher E; Mesbahi, Ali N; Hess, Christopher L; Graw, Katherine S

    2005-01-01

    The use of sub-atmospheric pressure dressings, available commercially as the vacuum-assisted closure (VAC) device, has been shown to be an effective way to accelerate healing of various wounds. The optimal sub-atmospheric pressure for wound healing appears to be approximately 125 mm Hg utilizing an alternating pressure cycle of 5 minutes of suction followed by 2 minutes off suction. Animal studies have demonstrated that this technique optimizes blood flow, decreases local tissue edema, and removes excessive fluid from the wound bed. These physiologic changes facilitate the removal of bacteria from the wound. Additionally, the cyclical application of sub-atmospheric pressure alters the cytoskeleton of the cells in the wound bed, triggering a cascade of intracellular signals that increases the rate of cell division and subsequent formation of granulation tissue. The combination of these mechanisms makes the VAC device an extremely versatile tool in the armamentarium of wound healing. This is evident in the VAC device's wide range of clinical applications, including treatment of infected surgical wounds, traumatic wounds, pressure ulcers, wounds with exposed bone and hardware, diabetic foot ulcers, and venous stasis ulcers. VAC has also proven useful in reconstruction of wounds by allowing elective planning of the definitive reconstructive surgery without jeopardizing the wound or outcome. Furthermore, VAC has significantly increased the skin graft success rate when used as a bolster over the freshly skin-grafted wound. VAC is generally well tolerated and, with few contraindications or complications, is fast becoming a mainstay of current wound care.

  16. Strong magnetic field-assisted growth of carbon nanofibers and its microstructural transformation mechanism

    PubMed Central

    Luo, Chengzhi; Fu, Qiang; Pan, Chunxu

    2015-01-01

    It is well-known that electric and magnetic fields can control the growth direction, morphology and microstructure of one-dimensional carbon nanomaterials (1-DCNMs), which plays a key role for its potential applications in micro-nano-electrics and devices. In this paper, we introduce a novel process for controlling growth of carbon nanofibers (CNFs) with assistance of a strong magnetic field (up to 0.5 T in the center) in a chemical vapor deposition (CVD) system. The results reveal that: 1) The CNFs get bundled when grown in the presence of a strong magnetic field and slightly get aligned parallel to the direction of the magnetic field; 2) The CNFs diameter become narrowed and homogenized with increase of the magnetic field; 3) With the increase of the magnetic field, the microstructure of CNFs is gradually changed, i.e., the strong magnetic field makes the disordered “solid-cored” CNFs transform into a kind of bamboo-liked carbon nanotubes; 4) We propose a mechanism that the reason for these variations and transformation is due to diamagnetic property of carbon atoms, so that it has direction selectivity in the precipitation process. PMID:25761381

  17. Design of Mechanism for Assisting Standing Movement Using Planar Linkage and Gear Train

    NASA Astrophysics Data System (ADS)

    Nango, Jun; Yoshizawa, Hisato; Liu, Jiajun

    The number of people who are in need of nursing care due to difficulties they experience with performing various activities of daily living is increasing. In particular, the action of standing up is performed frequently in daily life, and this action starts to induce pain in joints as people age. In this research, we develop a device whose seat plate follows the movement of the thigh in the action of standing up for the purpose of relieving the burden from the joints and reducing the effort associated with nursing care. The device is designed by using a planar five-link mechanism and a gear train, and only a single input is needed to drive the device. The respective lengths of the links are determined by comparing the movement of the seat plate of the device with the movement of the human thigh in the action of standing up. In addition, this device is expected to be useful for assisting users in standing up in a natural manner, including in the case when the body remains supported by the seat plate, as well as for guiding the individual movements of users in the action of standing up.

  18. Chromophore-assisted laser inactivation (CALI) to elucidate cellular mechanisms of cancer.

    PubMed

    Jay, D G; Sakurai, T

    1999-10-29

    Chromophore-assisted laser inactivation (CALI) is a new technology for acute protein inactivation in living cells. It targets laser energy to specific proteins via non-function-blocking antibodies that are labeled with the dye malachite green. Excitation of the dye generates short-lived free radicals that damage the bound protein without affecting other cellular components. The wavelength of laser light used (620 nm) is not readily absorbed by cells such that non-specific light damage does not occur. CALI provides an alternative to other inactivation strategies and has the advantages of high spatial and temporal resolution. The ultimate value of this technology for cancer research will be assessed by how effective CALI is in ascribing in situ function during cancer-relevant processes and in identifying and validating protein targets for drug discovery. Recent work using CALI on ezrin and pp60-c-src, two proteins that may be involved in cancer, suggests its potential. Further application of CALI will likely be of utility for understanding cellular mechanisms of cancer and developing cancer therapeutics.

  19. Mechanisms of defect complex formation and environmental-assisted fracture behavior of iron aluminides

    SciTech Connect

    Cooper, B.R.; Muratov, L.S.; Kang, B.S.J.; Li, K.Z.

    1997-12-01

    Iron aluminide has excellent corrosion resistance in high-temperature oxidizing-sulfidizing environments; however, there are problems at room and medium temperature with hydrogen embrittlement as related to exposure to moisture. In this research, a coordinated computational modeling/experimental study of mechanisms related to environmental-assisted fracture behavior of selected iron aluminides is being undertaken. The modeling and the experimental work will connect at the level of coordinated understanding of the mechanisms for hydrogen penetration and for loss of strength and susceptibility to fracture. The focus of the modeling component at this point is on the challenging question of accurately predicting the iron vacancy formation energy in Fe{sub 3}A{ell} and the subsequent tendency, if present, for vacancy clustering. The authors have successfully performed, on an ab initio basis, the first calculation of the vacancy formation energy in Fe{sub 3}A{ell}. These calculations include lattice relaxation effects which are quite large. This has significant implications for vacancy clustering effects with consequences to be explored for hydrogen diffusion. The experimental work at this stage has focused on the relationship of the choice and concentration of additives to the improvement of resistance to hydrogen embrittlement and hence to the fracture behavior. For this reason, comparative crack growth tests of FA-186, FA-187, and FA-189 iron aluminides (all with basic composition of Fe-28A{ell}-5Cr, at % with micro-alloying additives of Zr, C or B) under, air, oxygen, or water environment have been performed. These tests showed that the alloys are susceptible to room temperature hydrogen embrittlement in both B2 and DO{sub 3} conditions. Test results indicated that FA-187, and FA-189 are intrinsically more brittle than FA-186.

  20. Impact of Gas-Phase Mechanisms on Weather Research Forecasting Model with Chemistry (WRF/Chem) Predictions: Mechanism Implementation and Comparative Evaluation

    EPA Science Inventory

    Gas-phase mechanisms provide important oxidant and gaseous precursors for secondary aerosol formation. Different gas-phase mechanisms may lead to different predictions of gases, aerosols, and aerosol direct and indirect effects. In this study, WRF/Chem-MADRID simulations are cond...

  1. Plasma-assisted cleanup of flue gas. Technical report, 1 December 1993--28 February 1994

    SciTech Connect

    Dhali, S.K.

    1994-06-01

    The authors have conclusively demonstrated that plasma chemistry alone is sufficient to convert SO{sub 2} to H{sub 2}SO{sub 4}, the plasma being produced by a dielectric-barrier discharge. They get nearly 80% removal of SO{sub 2} in a flue gas containing 775 ppm (parts per million) of SO{sub 2} and 99% for SO{sub 2} in concentrations of 300 ppm. A significant achievement during this period is the progress the authors have made with the wetting of the glass by the acid. They are using a simple and cheap method of coating the glass with Teflon (PTFE 30) to provide a hydrophobic surface. These films show chemical inertness to nearly all chemical and solvents and have low friction and antistick surfaces. The following important conclusions can be drawn from the results: (1) The percentage removal does not show saturation with the applied voltage. (2) The removal efficiency at an inlet temperature of 300 C is almost similar to 25 C at high voltages. (3) With longer electrodes the efficiency of removal increases. These results suggest that removal efficiency can be improved further by increasing the voltage and electrode length. The authors are yet to exploit the full range of parameters available. Therefore, it is likely that they will get much improved performance from the system.

  2. Surfactant assisted growth of nanostructured tin oxide films for gas sensing applications

    NASA Astrophysics Data System (ADS)

    Khun, Kamalpreet Khun; Mahajan, Aman; Bedi, R. K.

    2011-12-01

    Porous nanostructured SnO2 films have been prepared using an ultrasonic spray pyrolysis technique in conjunction with cationic, anionic and non ionic surfactants namely CTAB (Cetyl trimethyl ammonium bromide), SDS (sodium dodecyl sulphate) and PEG (polyethylene glycol) respectively. The effect of surfactants on the structural, electrical, optical and gas sensing properties of SnO2 films were investigated by using different techniques such as X-ray diffraction (XRD), Field emission scanning electroscope microscopy (FESEM), two probe technique and Photoluminiscence (PL) studies. The results reveal that the addition of surfactants in the precursor solutions leads to reduction in crystallite size with significant changes in porosity of SnO2 films. PL studies of the films show emissions in the visible region which exhibit changes in the intensities upon variation of surfactants in the precursor solutions. The prepared films were tested for their sensing behaviour towards chlorine and the results reveal that the films prepared in conjunction with cationic surfactant CTAB exhibits a sensing response of 53.5% towards 20 ppm chlorine at a low operating temperature of 150°C.

  3. Controls and measurements of KU engine test cells for biodiesel, SynGas, and assisted biodiesel combustion

    NASA Astrophysics Data System (ADS)

    Cecrle, Eric Daniel

    This thesis is comprised of three unique data acquisition and controls (CDAQ) projects. Each of these projects differs from each other; however, they all include the concept of testing renewable or future fuel sources. The projects were the following: University of Kansas's Feedstock-to-Tailpipe Initiative's Synthesis Gas Reforming rig, Feedstock-to-Tailpipe Initiative's Biodiesel Single Cylinder Test Stand, and a unique Reformate Assisted Biodiesel Combustion architecture. The main responsibility of the author was to implement, develop and test CDAQ systems for the projects. For the Synthesis Gas Reforming rig, this thesis includes a report that summarizes the analysis and solution of building a controls and data acquisition system for this setup. It describes the purpose of the sensors selected along with their placement throughout the system. Moreover, it includes an explanation of the planned data collection system, along with two models describing the reforming process useful for system control. For the Biodiesel Single Cylinder Test Stand, the responsibility was to implement the CDAQ system for data collection. This project comprised a variety of different sensors that are being used collect the combustion characteristics of different biodiesel formulations. This project is currently being used by other graduates in order to complete their projects for subsequent publication. For the Reformate Assisted Biodiesel Combustion architecture, the author developed a reformate injection system to test different hydrogen and carbon monoxide mixtures as combustion augmentation. Hydrogen combustion has certain limiting factors, such as pre-ignition in spark ignition engines and inability to work as a singular fuel in compression ignition engines. To offset these issues, a dual-fuel methodology is utilized by injecting a hydrogen/carbon monoxide mixture into the intake stream of a diesel engine operating on biodiesel. While carbon monoxide does degrade some of the

  4. Experimental study on mechanical properties of gas hydrate-bearing sediments using kaolin clay

    NASA Astrophysics Data System (ADS)

    Li, Yang-Hui; Song, Yong-Chen; Yu, Feng; Liu, Wei-Guo; Zhao, Jia-Fei

    2011-03-01

    A triaxial system is designed with a temperature range from -20 °C to 25 °C and a pressure range from 0 MPa to 30 MPa in order to improve the understanding of the mechanical properties of gas hydrate-bearing sediments. The mechanical properties of synthetic gas hydrate-bearing sediments (gas hydrate-kaolin clay mixture) were measured by using current experimental apparatus. The results indicate that: (1) the failure strength of gas hydrate-bearing sediments strongly depends on the temperature. The sediment's strength increases with the decreases of temperature. (2) The maximum deviator stress increases linearly with the confining pressure at a low-pressure stage. However, it fluctuates at a high-pressure stage. (3) Maximum deviator stress increases with increasing strain rate, whereas the strain-stress curve has no tremendous change until the axial strain reaches approximately 0.5%. (4) The internal friction angles of gas hydrate-bearing sediments are not sensitive to kaolin volume ratio. The cohesion shows a high kaolin volume ratio dependency.

  5. Conventional gas ventilation, liquid-assisted high-frequency oscillatory ventilation, and tidal liquid ventilation in surfactant-treated preterm lambs.

    PubMed

    Degraeuwe, P L; Thunnissen, F B; Jansen, N J; Dormaar, J T; Dohmen, L R; Blanco, C E

    2000-11-01

    This study was designed to compare the efficacy and potential protective or injurious effects of tidal liquid ventilation (TLV), liquid-assisted high-frequency oscillatory ventilation (LA-HFOV), and high PEEP conventional mechanical ventilation (CMV) in neonatal respiratory distress syndrome. Preterm lambs (124-126 days gestation), prophylactically treated with natural surfactant, were allocated to one of the treatment modalities or to an untreated fetal control group (F), euthanised after tracheal ligation. LA-HFOV animals received an intratracheal loading dose of 5 mL x kg(-1) followed by a continuous intrapulmonary instillation of 12 mL x kg(-1);h(-1) FC-75 perfluorocarbon liquid. The ventilation strategies aimed at keeping clinically appropriate arterial blood gases for a study period of 5 hours. A histological lung injury score was calculated and semiquantitative morphometry was performed on lung tissue fixed by vascular perfusion. The alveolar-arterial pressure difference for O2 was significantly lower throughout the study in TLV compared to CMV lambs; at 1, 2, and 5 hours, oxygenation was better in TLV when compared to LA-HFOV. Total lung injury scores in TLV lambs were significantly lower than in either CMV or LA-HFOV animals, but higher when compared to F. CMV and LA-HFOV induced an excess of collapsed and overdistended alveoli, whereas in TLV alveolar expansion was normally distributed around predominantly normal alveoli. CMV and LA-HFOV, but not TLV, were associated with an excess of dilated airways. Thus, in the ovine neonatal RDS model, TLV compared favourably to either gas ventilation strategy by its more uniform ventilation, reduced lung injury, and improved gas exchange.

  6. DEVELOPMENT AND OPTIMIZATION OF GAS-ASSISTED GRAVITY DRAINAGE (GAGD) PROCESS FOR IMPROVED LIGHT OIL RECOVERY

    SciTech Connect

    Dandina N. Rao

    2003-10-01

    This is the first Annual Technical Progress Report being submitted to the U. S. Department of Energy on the work performed under the Cooperative Agreement DE-FC26-02NT15323. This report follows two other progress reports submitted to U.S. DOE during the first year of the project: The first in April 2003 for the project period from October 1, 2002 to March 31, 2003, and the second in July 2003 for the period April 1, 2003 to June 30, 2003. Although the present Annual Report covers the first year of the project from October 1, 2002 to September 30, 2003, its contents reflect mainly the work performed in the last quarter (July-September, 2003) since the work performed during the first three quarters has been reported in detail in the two earlier reports. The main objective of the project is to develop a new gas-injection enhanced oil recovery process to recover the oil trapped in reservoirs subsequent to primary and/or secondary recovery operations. The project is divided into three main tasks. Task 1 involves the design and development of a scaled physical model. Task 2 consists of further development of the vanishing interfacial tension (VIT) technique for miscibility determination. Task 3 involves the determination of multiphase displacement characteristics in reservoir rocks. Each technical progress report, including this one, reports on the progress made in each of these tasks during the reporting period. Section I covers the scaled physical model study. A survey of literature in related areas has been conducted. Test apparatus has been under construction throughout the reporting period. A bead-pack visual model, liquid injection system, and an image analysis system have been completed and used for preliminary experiments. Experimental runs with decane and paraffin oil have been conducted in the bead pack model. The results indicate the need for modifications in the apparatus, which are currently underway. A bundle of capillary tube model has been considered and

  7. Improved conventional and microwave-assisted silylation protocols for simultaneous gas chromatographic determination of tocopherols and sterols: Method development and multi-response optimization.

    PubMed

    Poojary, Mahesha M; Passamonti, Paolo

    2016-12-09

    This paper reports on improved conventional thermal silylation (CTS) and microwave-assisted silylation (MAS) methods for simultaneous determination of tocopherols and sterols by gas chromatography. Reaction parameters in each of the methods developed were systematically optimized using a full factorial design followed by a central composite design. Initially, experimental conditions for CTS were optimized using a block heater. Further, a rapid MAS was developed and optimized. To understand microwave heating mechanisms, MAS was optimized by two distinct modes of microwave heating: temperature-controlled MAS and power-controlled MAS, using dedicated instruments where reaction temperature and microwave power level were controlled and monitored online. Developed methods: were compared with routine overnight derivatization. On a comprehensive level, while both CTS and MAS were found to be efficient derivatization techniques, MAS significantly reduced the reaction time. The optimal derivatization temperature and time for CTS found to be 55°C and 54min, while it was 87°C and 1.2min for temperature-controlled MAS. Further, a microwave power of 300W and a derivatization time 0.5min found to be optimal for power-controlled MAS. The use of an appropriate derivatization solvent, such as pyridine, was found to be critical for the successful determination. Catalysts, like potassium acetate and 4-dimethylaminopyridine, enhanced the efficiency slightly. The developed methods showed excellent analytical performance in terms of linearity, accuracy and precision.

  8. Fast low-pressure microwave assisted extraction and gas chromatographic determination of polychlorinated biphenyls in soil samples.

    PubMed

    Bruzzoniti, M C; Maina, R; Tumiatti, V; Sarzanini, C; Rivoira, L; De Carlo, R M

    2012-11-23

    A new technology equipment for low-pressure microwave assisted extraction (usually employed for organic chemistry reactions), recently launched in the market, is used for the first time in environmental analysis for the extraction of commercial technical Aroclor mixtures from soil. Certified reference materials of Aroclor 1260, Aroclor 1254 and Aroclor 1242 in transformer oils were used to contaminate the soil samples and to optimize the extraction method as well as the subsequent gas chromatographic electron capture detection (GC-ECD) analytical method. The study was performed optimizing the extraction, the purification and the gas chromatographic separation conditions to enhance the resolution of difficult pairs of congeners (C28/31 and C141/179). After optimization, the recovery yields were included within the range 79-84%. The detection limits, evaluated for two different commercial polychlorinated biphenyl (PCB) mixtures (Aroclor 1260 and Aroclor 1242) were 0.056 ± 0.001 mg/kg and 0.290 ± 0.006 mg/kg, respectively. The method, validated with certified soil samples, was used to analyze a soil sample after an event of failure of a pole-mounted transformer which caused the dumping of PCB contaminated oil in soil. Moreover, the method provides simple sample handling, fast extraction with reduced amount of sample and solvents than usually required, and simple purification step involving the use of solvent (cyclohexane) volumes as low as 5 mL. Reliability and reproducibility of extraction conditions are ensured by direct and continuous monitoring of temperature and pressure conditions.

  9. Molecular mechanism of adsorption/desorption hysteresis: dynamics of shale gas in nanopores

    NASA Astrophysics Data System (ADS)

    Chen, Jie; Wang, FengChao; Liu, He; Wu, HengAn

    2017-01-01

    Understanding the adsorption and desorption behavior of methane has received considerable attention since it is one of the crucial aspects of the exploitation of shale gas. Unexpectedly, obvious hysteresis is observed from the ideally reversible physical sorption of methane in some experiments. However, the underlying mechanism still remains an open problem. In this study, Monte Carlo (MC) and molecular dynamics (MD) simulations are carried out to explore the molecular mechanisms of adsorption/desorption hysteresis. First, a detailed analysis about the capillary condensation of methane in micropores is presented. The influence of pore width, surface strength, and temperature on the hysteresis loop is further investigated. It is found that a disappearance of hysteresis occurs above a temperature threshold. Combined with the phase diagram of methane, we explicitly point out that capillary condensation is inapplicable for the hysteresis of shale gas under normal temperature conditions. Second, a new mechanism, variation of pore throat size, is proposed and studied. For methane to pass through the throat, a certain energy is required due to the repulsive interaction. The required energy increases with shrinkage of the throat, such that the originally adsorbed methane cannot escape through the narrowed throat. These trapped methane molecules account for the hysteresis. Furthermore, the hysteresis loop is found to increase with the increasing pressure and decreasing temperature. We suggest that the variation of pore throat size can explain the adsorption/desorption hysteresis of shale gas. Our conclusions and findings are of great significance for guiding the efficient exploitation of shale gas.

  10. Reduced and Validated Kinetic Mechanisms for Hydrogen-CO-sir Combustion in Gas Turbines

    SciTech Connect

    Yiguang Ju; Frederick Dryer

    2009-02-07

    Rigorous experimental, theoretical, and numerical investigation of various issues relevant to the development of reduced, validated kinetic mechanisms for synthetic gas combustion in gas turbines was carried out - including the construction of new radiation models for combusting flows, improvement of flame speed measurement techniques, measurements and chemical kinetic analysis of H{sub 2}/CO/CO{sub 2}/O{sub 2}/diluent mixtures, revision of the H{sub 2}/O{sub 2} kinetic model to improve flame speed prediction capabilities, and development of a multi-time scale algorithm to improve computational efficiency in reacting flow simulations.

  11. Comparison of different gas-phase mechanisms and aerosol modules for simulating particulate matter formation.

    PubMed

    Kim, Youngseob; Couvidat, Florian; Sartelet, Karine; Seigneur, Christian

    2011-11-01

    The effects of two gas-phase chemical kinetic mechanisms, Regional Atmospheric Chemistry Mechanism version 2 (RACM2) and Carbon-Bond 05 (CB05), and two secondary organic aerosol (SOA) modules, the Secondary Organic Aerosoi Model (SORGAM) and AER/EPRI/Caltech model (AEC), on fine (aerodynamic diameter < or =2.5 microm) particulate matter (PM2.5) formation is studied. The major sources of uncertainty in the chemistry of SOA formation are investigated. The use of all major SOA precursors and the treatment of SOA oligomerization are found to be the most important factors for SOA formation, leading to 66% and 60% more SOA, respectively. The explicit representation of high-NO, and low-NOx gas-phase chemical regimes is also important with increases in SOA of 30-120% depending on the approach used to implement the distinct SOA yields within the gas-phase chemical kinetic mechanism; further work is needed to develop gas-phase mechanisms that are fully compatible with SOA formation algorithms. The treatment of isoprene SOA as hydrophobic or hydrophilic leads to a significant difference, with more SOA being formed in the latter case. The activity coefficients may also be a major source of uncertainty, as they may differ significantly between atmospheric particles, which contain a myriad of SOA, primary organic aerosol (POA), and inorganic aerosol species, and particles formed in a smog chamber from a single precursor under dry conditions. Significant interactions exist between the uncertainties of the gas-phase chemistry and those of the SOA module.

  12. Neural Response During a Mechanically Assisted Spinal Manipulation in an Animal Model: A Pilot Study

    PubMed Central

    Reed, William R.; Liebschner, Michael A.K.; Sozio, Randall S.; Pickar, Joel G.; Gudavalli, Maruti R.

    2015-01-01

    Introduction Mechanoreceptor stimulation is theorized to contribute to the therapeutic efficacy of spinal manipulation. Use of mechanically-assisted spinal manipulation (MA-SM) devices is increasing among manual therapy clinicians worldwide. The purpose of this pilot study is to determine the feasibility of recording in vivo muscle spindle responses during a MA-SM in an intervertebral fixated animal model. Methods Intervertebral fixation was created by inserting facet screws through the left L5-6 and L6-7 facet joints of a cat spine. Three L6muscle spindle afferents with receptive fields in back muscles were isolated. Recordings were made during MA-SM thrusts delivered to the L7 spinous process using an instrumented Activator IV clinical device. Results Nine MA-SM thrusts were delivered with peak forces ranging from 68-122N and with thrust durations of less than 5ms. High frequency muscle spindle discharge occurred during MA-SM. Following the MA-SM, muscle spindle responses included returning to pre-manipulation levels, slightly decreasing for a short window of time, and greatly decreasing for more than 40s. Conclusion This study demonstrates that recording in vivo muscle spindle response using clinical MA-SM devices in an animal model is feasible. Extremely short duration MA-SM thrusts (<5ms) can have an immediate and/or a prolonged (> 40s) effect on muscle spindle discharge. Greater peak forces during MA-SM thrusts may not necessarily yield greater muscle spindle responses. Determining peripheral response during and following spinal manipulation may be an important step in optimizing its’ clinical efficacy. Future studies may investigate the effect of thrust dosage and magnitude. PMID:26618202

  13. Characterization and growth mechanisms of boron nitride films synthesized by ion-beam-assisted deposition

    NASA Astrophysics Data System (ADS)

    Burat, O.; Bouchier, D.; Stambouli, V.; Gautherin, G.

    1990-09-01

    We have studied boron nitride films deposited at room temperature by ion-beam-assisted deposition in an ultrahigh vacuum apparatus, with ion accelerating voltages ranging between 0.25 and 2 kV. By using complementarily in situ Auger electron spectrometry and ex situ nuclear analyses to determine the respective surface and bulk N concentrations in the deposited films, we were able to identify the different phases of the mechanism leading to the nitridation of evaporated boron by nitrogen ions. For low nitrogen/boron flux ratios, the incorporation of nitrogen seems to be only governed by ion implantation, and, with respect to the depth of the deposit, the surface is found largely depleted in nitrogen, while the N-incorporation yield remains close to one whatever the ion energy. Such a behavior is well verified as long as a critical bulk nitrogen concentration close to 5.5×1022 cm-3 has not been achieved. For concentrations greater than this, superstoichiometric material is obtained up to a saturation which corresponds to a bulk N incorporation ranging from 6 to 7×1022 cm-3. Further increase of the N/B flux ratio induces a strong diffusion process from N-rich bulk to N-depleted surface, which results in the nitridation of surface boron atoms and a loss of nitrogen by sputtering or desorption. The density measurements seem to indicate that the synthesized phase is close to h-BN. However, the density of B-rich layers ([N]/[B]≊0.2-0.3) is found to be very close to that calculated for a mixture of pure boron and c-BN. The transparency and microhardness of the synthesized BN have satisfying values for its application as a wear-resistant optical coating, but it is not c-BN.

  14. Method of long-term corrosion-mechanical tests of metal of gas industry pipes

    SciTech Connect

    Gutman, E.M.; Zainullin, R.S.

    1987-10-01

    The resistance of the metal of gas industry pipes to hydrogen-sulfide (sulfide) cracking is usually evaluated on the basis of the results of long-term corrosion-mechanical tests on cylindrical specimens (diameter 6 mm) in the conditions of uniaxial tensile loading generated by the force constant with time. Because of the comparatively large dimensions of devices for producing the stress state in these specimens, it is difficult to carry out large-scale corrosion-mechanical tests. The authors assume that it is more advantageous to evaluate the hydrogen-sulfide cracking resistance of gas industry pipes on the basis of the results of corrosion-mechanical tests on semicircular specimens compressed or tensile-loaded at the ends. The method proposed was used in long-term corrosion-mechanical tests on the metal of seamless pipes made of low-alloy (08G2SFT) and low-carbon (St20) steels. The steel with the lower ratio of the yield stress to ultimate strength k/sub TB/ is characterized by a higher limit of the long-term corrosion strength expressed in the fractions of the yield stress of the metal. This indicates that it is useful to take into account the k/sub TB/ ratio in determining the safety factor of the strength of the gas industry pipes.

  15. Growth dynamics and gas transport mechanism of nanobubbles in graphene liquid cells.

    PubMed

    Shin, Dongha; Park, Jong Bo; Kim, Yong-Jin; Kim, Sang Jin; Kang, Jin Hyoun; Lee, Bora; Cho, Sung-Pyo; Hong, Byung Hee; Novoselov, Konstantin S

    2015-02-02

    Formation, evolution and vanishing of bubbles are common phenomena in nature, which can be easily observed in boiling or falling water, carbonated drinks, gas-forming electrochemical reactions and so on. However, the morphology and the growth dynamics of the bubbles at nanoscale have not been fully investigated owing to the lack of proper imaging tools that can visualize nanoscale objects in the liquid phase. Here, we demonstrate for the first time that the nanobubbles in water encapsulated by graphene membrane can be visualized by in-situ ultra-high vacuum transmission electron microscopy. Our microscopic results indicate two distinct growth mechanisms of merging nanobubbles and the existence of a critical radius of nanobubbles that determines the unusually long stability of nanobubbles. Interestingly, the gas transport through ultrathin water membranes at nanobubble interface is free from dissolution, which is clearly different from conventional gas transport that includes condensation, transmission and evaporation.

  16. Growth dynamics and gas transport mechanism of nanobubbles in graphene liquid cells

    NASA Astrophysics Data System (ADS)

    Shin, Dongha; Park, Jong Bo; Kim, Yong-Jin; Kim, Sang Jin; Kang, Jin Hyoun; Lee, Bora; Cho, Sung-Pyo; Hong, Byung Hee; Novoselov, Konstantin S.

    2015-02-01

    Formation, evolution and vanishing of bubbles are common phenomena in nature, which can be easily observed in boiling or falling water, carbonated drinks, gas-forming electrochemical reactions and so on. However, the morphology and the growth dynamics of the bubbles at nanoscale have not been fully investigated owing to the lack of proper imaging tools that can visualize nanoscale objects in the liquid phase. Here, we demonstrate for the first time that the nanobubbles in water encapsulated by graphene membrane can be visualized by in-situ ultra-high vacuum transmission electron microscopy. Our microscopic results indicate two distinct growth mechanisms of merging nanobubbles and the existence of a critical radius of nanobubbles that determines the unusually long stability of nanobubbles. Interestingly, the gas transport through ultrathin water membranes at nanobubble interface is free from dissolution, which is clearly different from conventional gas transport that includes condensation, transmission and evaporation.

  17. Fundamental Mechanisms, Predictive Modeling, and Novel Aerospace Applications of Plasma Assisted Combustion

    DTIC Science & Technology

    2009-11-04

    intrusive diagnostics • Task 2: Laminar Flow Reactor and Nanoparticle Studies at Low to Intermediate Temperatures (Radar REMPI and Filtered Rayleigh...using counterflow flames Thrust 2. Intermediate Species Measurements at Elevated Pressures by Using a Plasma Assisted Jet Stirred Reactor with...Molecular Beam Sampling – Task 1: Development of plasma assisted a jet stirred reactor Task 2: Measurements of intermediate species of fuel oxidation

  18. Mechanisms of gas exchange response to lung volume reduction surgery in severe emphysema.

    PubMed

    Cremona, George; Barberà, Joan A; Barbara, Joan A; Melgosa, Teresa; Appendini, Lorenzo; Roca, Josep; Casadio, Caterina; Donner, Claudio F; Rodriguez-Roisin, Roberto; Wagner, Peter D

    2011-04-01

    Lung volume reduction surgery (LVRS) improves lung function, respiratory symptoms, and exercise tolerance in selected patients with chronic obstructive pulmonary disease, who have heterogeneous emphysema. However, the reported effects of LVRS on gas exchange are variable, even when lung function is improved. To clarify how LVRS affects gas exchange in chronic obstructive pulmonary disease, 23 patients were studied before LVRS, 14 of whom were again studied afterwards. We performed measurements of lung mechanics, pulmonary hemodynamics, and ventilation-perfusion (Va/Q) inequality using the multiple inert-gas elimination technique. LVRS improved arterial Po₂ (Pa(O₂)) by a mean of 6 Torr (P = 0.04), with no significant effect on arterial Pco₂ (Pa(CO₂)), but with great variability in both. Lung mechanical properties improved considerably more than did gas exchange. Post-LVRS Pa(O₂) depended mostly on its pre-LVRS value, whereas improvement in Pa(O(2)) was explained mostly by improved Va/Q inequality, with lesser contributions from both increased ventilation and higher mixed venous Po(2). However, no index of lung mechanical properties correlated with Pa(O₂). Conversely, post-LVRS Pa(CO₂) bore no relationship to its pre-LVRS value, whereas changes in Pa(CO₂) were tightly related (r² = 0.96) to variables, reflecting decrease in static lung hyperinflation (intrinsic positive end-expiratory pressure and residual volume/total lung capacity) and increase in airflow potential (tidal volume and maximal inspiratory pressure), but not to Va/Q distribution changes. Individual gas exchange responses to LVRS vary greatly, but can be explained by changes in combinations of determining variables that are different for oxygen and carbon dioxide.

  19. A Mechanism for Stimulating AGN Feedback by Lifting Gas in Massive Galaxies

    NASA Astrophysics Data System (ADS)

    McNamara, B. R.; Russell, H. R.; Nulsen, P. E. J.; Hogan, M. T.; Fabian, A. C.; Pulido, F.; Edge, A. C.

    2016-10-01

    Observation shows that nebular emission, molecular gas, and young stars in giant galaxies are associated with rising X-ray bubbles inflated by radio jets launched from nuclear black holes. We propose a model where molecular clouds condense from low-entropy gas caught in the updraft of rising X-ray bubbles. The low-entropy gas becomes thermally unstable when it is lifted to an altitude where its cooling time is shorter than the time required to fall to its equilibrium location in the galaxy, i.e., {t}{{c}}/{t}{{I}}≲ 1. The infall speed of a cloud is bounded by the lesser of its free-fall and terminal speeds, so that the infall time here can exceed the free-fall time by a significant factor. This mechanism is motivated by Atacama Large Millimeter Array observations revealing molecular clouds lying in the wakes of rising X-ray bubbles with velocities well below their free-fall speeds. Our mechanism would provide cold gas needed to fuel a feedback loop while stabilizing the atmosphere on larger scales. The observed cooling time threshold of ∼ 5× {10}8 {yr}—the clear-cut signature of thermal instability and the onset of nebular emission and star formation—may result from the limited ability of radio bubbles to lift low-entropy gas to altitudes where thermal instabilities can ensue. Outflowing molecular clouds are unlikely to escape, but instead return to the central galaxy in a circulating flow. We contrast our mechanism to precipitation models where the minimum value of {t}{{c}}/{t}{{ff}}≲ 10 triggers thermal instability, which we find to be inconsistent with observation.

  20. Simultaneous analysis of polychlorinated biphenyls and organochlorine pesticides in seawater samples by membrane-assisted solvent extraction combined with gas chromatography-electron capture detector and gas chromatography-tandem mass spectrometry.

    PubMed

    Shi, Xizhi; Tang, Zigang; Sun, Aili; Zhou, Lei; Zhao, Jian; Li, Dexiang; Chen, Jiong; Pan, Daodong

    2014-12-01

    A highly efficient and environment-friendly membrane-assisted solvent extraction system combined with gas chromatography-electron capture detector was applied in the simultaneous determination of 17 polychlorinated biphenyls and organochlorine pesticides in seawater samples. Variables affecting extraction efficiency, including extraction solvent used, stirring rate, extraction time, and temperature, were optimized extensively. Under optimal extraction conditions, recoveries between 76.9% and 104.6% in seawater samples were achieved, and relative standard deviation values below 10% were obtained. The limit of detection (signal-to-noise ratio=3) and limit of quantification (signal-to-noise ratio=10) of 17 polychlorinated biphenyls and organochlorine pesticides in seawater ranged from 0.14ngL(-1) to 0.36ngL(-1) and 0.46ngL(-1) to 1.19ngL(-1), respectively. Matrix effects on extraction efficiency were evaluated by comparing with the results obtained using tap water. The extraction effect of developed membrane-assisted solvent extraction method was further demonstrated by gas chromatography-tandem mass spectrometry which can provide structural information of the analytes for more accurate identification, and results identical to those produced by gas chromatography-electron capture detector were obtained. These findings demonstrate the applicability of the developed membrane-assisted solvent extraction determination method for coupling to gas chromatography-electron capture detector or tandem mass spectrometry for determining polychlorinated biphenyls and organochlorine pesticides in seawater samples.

  1. Mechanisms Leading to Co-Existence of Gas Hydrate in Ocean Sediments [Part 1 of 2

    SciTech Connect

    Bryant, Steven; Juanes, Ruben

    2011-12-31

    In this project we have sought to explain the co-existence of gas and hydrate phases in sediments within the gas hydrate stability zone. We have focused on the gas/brine interface at the scale of individual grains in the sediment. The capillary forces associated with a gas/brine interface play a dominant role in many processes that occur in the pores of sediments and sedimentary rocks. The mechanical forces associated with the same interface can lead to fracture initiation and propagation in hydrate-bearing sediments. Thus the unifying theme of the research reported here is that pore scale phenomena are key to understanding large scale phenomena in hydrate-bearing sediments whenever a free gas phase is present. Our analysis of pore-scale phenomena in this project has delineated three regimes that govern processes in which the gas phase pressure is increasing: fracturing, capillary fingering and viscous fingering. These regimes are characterized by different morphology of the region invaded by the gas. On the other hand when the gas phase pressure is decreasing, the corresponding regimes are capillary fingering and compaction. In this project, we studied all these regimes except compaction. Many processes of interest in hydrate-bearing sediments can be better understood when placed in the context of the appropriate regime. For example, hydrate formation in sub-permafrost sediments falls in the capillary fingering regime, whereas gas invasion into ocean sediments is likely to fall into the fracturing regime. Our research provides insight into the mechanisms by which gas reservoirs are converted to hydrate as the base of the gas hydrate stability zone descends through the reservoir. If the reservoir was no longer being charged, then variation in grain size distribution within the reservoir explain hydrate saturation profiles such as that at Mt. Elbert, where sand-rich intervals containing little hydrate are interspersed between intervals containing large hydrate

  2. Mechanisms Leading to Co-Existence of Gas Hydrate in Ocean Sediments [Part 2 of 2

    SciTech Connect

    Bryant, Steven; Juanes, Ruben

    2011-12-31

    In this project we have sought to explain the co-existence of gas and hydrate phases in sediments within the gas hydrate stability zone. We have focused on the gas/brine interface at the scale of individual grains in the sediment. The capillary forces associated with a gas/brine interface play a dominant role in many processes that occur in the pores of sediments and sedimentary rocks. The mechanical forces associated with the same interface can lead to fracture initiation and propagation in hydrate-bearing sediments. Thus the unifying theme of the research reported here is that pore scale phenomena are key to understanding large scale phenomena in hydrate-bearing sediments whenever a free gas phase is present. Our analysis of pore-scale phenomena in this project has delineated three regimes that govern processes in which the gas phase pressure is increasing: fracturing, capillary fingering and viscous fingering. These regimes are characterized by different morphology of the region invaded by the gas. On the other hand when the gas phase pressure is decreasing, the corresponding regimes are capillary fingering and compaction. In this project, we studied all these regimes except compaction. Many processes of interest in hydrate-bearing sediments can be better understood when placed in the context of the appropriate regime. For example, hydrate formation in sub-permafrost sediments falls in the capillary fingering regime, whereas gas invasion into ocean sediments is likely to fall into the fracturing regime. Our research provides insight into the mechanisms by which gas reservoirs are converted to hydrate as the base of the gas hydrate stability zone descends through the reservoir. If the reservoir was no longer being charged, then variation in grain size distribution within the reservoir explain hydrate saturation profiles such as that at Mt. Elbert, where sand-rich intervals containing little hydrate are interspersed between intervals containing large hydrate

  3. Atomistic modeling of structure II gas hydrate mechanics: Compressibility and equations of state

    NASA Astrophysics Data System (ADS)

    Vlasic, Thomas M.; Servio, Phillip; Rey, Alejandro D.

    2016-08-01

    This work uses density functional theory (DFT) to investigate the poorly characterized structure II gas hydrates, for various guests (empty, propane, butane, ethane-methane, propane-methane), at the atomistic scale to determine key structure and mechanical properties such as equilibrium lattice volume and bulk modulus. Several equations of state (EOS) for solids (Murnaghan, Birch-Murnaghan, Vinet, Liu) were fitted to energy-volume curves resulting from structure optimization simulations. These EOS, which can be used to characterize the compressional behaviour of gas hydrates, were evaluated in terms of their robustness. The three-parameter Vinet EOS was found to perform just as well if not better than the four-parameter Liu EOS, over the pressure range in this study. As expected, the Murnaghan EOS proved to be the least robust. Furthermore, the equilibrium lattice volumes were found to increase with guest size, with double-guest hydrates showing a larger increase than single-guest hydrates, which has significant implications for the widely used van der Waals and Platteeuw thermodynamic model for gas hydrates. Also, hydrogen bonds prove to be the most likely factor contributing to the resistance of gas hydrates to compression; bulk modulus was found to increase linearly with hydrogen bond density, resulting in a relationship that could be used predictively to determine the bulk modulus of various structure II gas hydrates. Taken together, these results fill a long existing gap in the material chemical physics of these important clathrates.

  4. An investigation of cutting mechanics in 2 dimensional ultrasonic vibration assisted milling toward chip thickness and chip formation

    NASA Astrophysics Data System (ADS)

    Rasidi, I. I.; Rafai, N. H.; Rahim, E. A.; Kamaruddin, S. A.; Ding, H.; Cheng, K.

    2015-12-01

    The purpose of this paper is to investigate the effects of 2 dimensional Ultrasonic Vibration Assisted Milling (UVAM) cutting mechanics, considering tool path trajectory and the effect on the chip thickness. The theoretical modelling of cutting mechanics is focused by considering the trajectory of the tool locus into the workpiece during the machining. The studies found the major advantages of VAM are come from the intermittent tool tip interaction phenomena between cutting tool and workpiece. The reduction of thinning chip thickness formations can be identifying advantages from vibration assisted milling in 2 dimensional. The finding will be discussing the comparison between conventional machining the potential of the advantages toward the chip thickness and chip formation in conclusion.

  5. Novel view on the mechanism of water-assisted proton transfer in the DNA bases: bulk water hydration.

    PubMed

    Furmanchuk, Al'ona; Isayev, Olexandr; Gorb, Leonid; Shishkin, Oleg V; Hovorun, Dmytro M; Leszczynski, Jerzy

    2011-03-14

    In the present work, the conventional static ab initio picture of a water-assisted mechanism of the tautomerization of Nucleic Acid Bases (NABs) in an aqueous environment is enhanced by the classical and Car-Parrinello molecular dynamics simulations. The inclusion of the dynamical contribution is vital because the formation and longevity of the NAB-water bridge complexes represent decisive factors for further tautomerization. The results of both molecular dynamic techniques indicate that the longest time when such complexes exist is significantly shorter than the time required for proton transfer suggested by the static ab initio level of theory. New rate constants of tautomerization corrected for the dynamic effect of environment are proposed based on the first principles molecular dynamics data. Those values are used for the evaluation of a water-assisted mechanism that is feasible in such biological systems as E. coli cell.

  6. Mechanical and microstructural/chemical degradation of coating and substrate in gas turbine blade

    SciTech Connect

    Sugita, Y.; Ito, M.; Sakurai, S.; Gold, C.R.; Bloomer, T.E.; Kameda, J.

    1995-12-31

    The mechanical property degradation (295--1223 K) and microstructural/chemical evolution of CoNiCrAlY coatings and superalloy (Rene 80) substrates in gas turbine blades operated in- service have been studied using a small punch (SP) testing technique and scanning Auger microprobe. In SP tests, coating cracks continuously and discretely propagated at 295 K and higher temperatures, respectively. The ductile-brittle transition temperature of the coatings was increased during long time exposure of gas turbine blades to oxidizing environments while that of the substrate did not change. The low cycle fatigue life of the coatings at 295 K was also reduced in-service. Oxidation and sulfur segregation near the coating surface were found to be major causes of the mechanical degradation of the coatings.

  7. Functionalized low defect graphene nanoribbons and polyurethane composite film for improved gas barrier and mechanical performances.

    PubMed

    Xiang, Changsheng; Cox, Paris J; Kukovecz, Akos; Genorio, Bostjan; Hashim, Daniel P; Yan, Zheng; Peng, Zhiwei; Hwang, Chih-Chau; Ruan, Gedeng; Samuel, Errol L G; Sudeep, Parambath M; Konya, Zoltan; Vajtai, Robert; Ajayan, Pulickel M; Tour, James M

    2013-11-26

    A thermoplastic polyurethane (TPU) composite film containing hexadecyl-functionalized low-defect graphene nanoribbons (HD-GNRs) was produced by solution casting. The HD-GNRs were well distributed within the polyurethane matrix, leading to phase separation of the TPU. Nitrogen gas effective diffusivity of TPU was decreased by 3 orders of magnitude with only 0.5 wt % HD-GNRs. The incorporation of HD-GNRs also improved the mechanical properties of the composite films, as predicted by the phase separation and indicated by tensile tests and dynamic mechanical analyses. The improved properties of the composite film could lead to potential applications in food packaging and lightweight mobile gas storage containers.

  8. Acetone gas sensing mechanism on zinc oxide surfaces: A first principles calculation

    NASA Astrophysics Data System (ADS)

    Sadeghian Lemraski, M.; Nadimi, E.

    2017-03-01

    Semiconducting metal oxide gas sensors have attracted growing interest as a result of their outstanding performance in the bio and industrial applications. Nevertheless, the sensing mechanism is yet not totally understood. In this study, we extensively investigate the adsorption mechanism of acetone molecule on ZnO-based thin film sensors by performing ab initio density functional theory calculations and employing quantum molecular dynamic simulations. Since the sensitivity of a metal oxide sensor is exceedingly depends on molecular oxygen exposure and operating temperature, we explore the competitive adsorption of acetone and oxygen molecule on the most stable orientation of ZnO surface (10 1 ̅ 0) at different temperatures. Results indicate that at elevated temperatures acetone gains required thermal energy to remove preadsorbed oxygen molecule from the surface in a competitive process. We will show that this competition is responsible for the resistive switching behavior in the ZnO-based gas sensors.

  9. Surface Forces and Interaction Mechanisms of Emulsion Drops and Gas Bubbles in Complex Fluids.

    PubMed

    Xie, Lei; Shi, Chen; Cui, Xin; Zeng, Hongbo

    2017-02-22

    The interactions of emulsion drops and gas bubbles in complex fluids play important roles in a wide range of biological and technological applications, such as programmable drug and gene delivery, emulsion and foam formation, and froth flotation of mineral particles. In this feature article, we have reviewed our recent progress on the quantification of surface forces and interaction mechanisms of gas bubbles and emulsion drops in different material systems by using several complementary techniques, including the drop/bubble probe atomic force microscope (AFM), surface forces apparatus (SFA), and four-roll mill fluidic device. These material systems include the bubble-self-assembled monolayer (SAM), bubble-polymer, bubble-superhydrophobic surface, bubble-mineral, water-in-oil and oil-in-water emulsions with interface-active components in oil production, and oil/water wetting on polyelectrolyte surfaces. The bubble probe AFM combined with reflection interference contrast microscopy (RICM) was applied for the first time to simultaneously quantify the interaction forces and spatiotemporal evolution of a confined thin liquid film between gas bubbles and solid surfaces with varying hydrophobicity. The nanomechanical results have provided useful insights into the fundamental interaction mechanisms (e.g., hydrophobic interaction in aqueous media) at gas/water/solid interfaces, the stabilization/destabilization mechanisms of emulsion drops, and oil/water wetting mechanisms on solid surfaces. A long-range hydrophilic attraction was found between water and polyelectrolyte surfaces in oil, with the strongest attraction for polyzwitterions, contributing to their superior water wettability in oil and self-cleaning capability of oil contamination. Some remaining challenges and future research directions are discussed and provided.

  10. Section 6—Mechanical Bioeffects in the Presence of Gas-Carrier Ultrasound Contrast Agents

    PubMed Central

    2007-01-01

    This review addresses the issue of mechanical ultrasound-induced bioeffects in the presence of gas carrier contrast agents (GCAs). Here, the term “contrast agent” refers to those agents that provide ultrasound contrast by being composed of microbubbles, encapsulated or not, containing one or more gases. Provided in this section are summaries on how contrast agents work, some of their current uses, and the potential for bio-effects associated with their presence in an ultrasonic field. PMID:10680618

  11. Delayed-onset cerebral arterial gas embolism in a commercial airline mechanic.

    PubMed

    Hickey, Matthew J; Zanetti, Claude L

    2003-09-01

    A commercial airline mechanic was evaluated for right-sided hemianesthesia. Thorough diagnostic testing failed to identify a definitive etiology, and the mechanic was assessed as having symptoms of a left internal capsule lesion, likely from an ischemic event. On day 12 after symptom onset, he consulted a diving medicine specialist for clearance to continue recreational scuba diving. A thorough history revealed that the patient worked regularly in a compressed air environment of commercial aircraft and had experienced a rapid decompression approximately 48 h prior to onset of the hemianesthesia. The specialist considered pulmonary barotrauma-induced cerebral arterial gas embolism as a possible diagnosis. On day 13 he was treated with hyperbaric oxygen using Treatment Table VI, which produced immediate relief. Following three additional hyperbaric oxygen treatments in the next 11 d, he reported nearly total resolution of his symptoms. This occurrence is believed to be the second report of a cerebral arterial gas embolism in an aircraft mechanic or maintenance crewman and suggests that the latency between time of depressurization and the development of symptoms from a pulmonary barotrauma-induced cerebral arterial gas embolism may extend longer than previously believed.

  12. Evaluation of a detailed gas-phase atmospheric reaction mechanism using environmental chamber data

    NASA Astrophysics Data System (ADS)

    Carter, William P. L.; Lurmann, Fredrick W.

    This paper describes an evaluation of the performance of a detailed gas-phase reaction mechanism in simulating the results of 561 experiments carried out in four different environmental chambers. The experiments included background air, NO x-air, CONO x-air and aldehyde-air irradiations used for chamber characterization, NO x-air irradiations of single organics as well as simple and complex organic mixtures, and irradiations of auto exhaust. The methods used to represent the major chamber effects and the lighting characteristics in the model simulations of the experiments are described and their associated uncertainties are discussed. Statistical measures of the performance of the mechanism in simulating results of the various types of experiments are summarized and discussed. The mechanism was able to predict maximum ozone yields and rates of NO oxidation to within ±30% for 63% of the experiments modeled, and to within ±50% for 85% of the runs. There is a slight bias (˜15%) towards overprediction of ozone in mixture runs. Although there are cases where the simulations suggest possible problems with the gas-phase mechanism, much of the variability in the goodness of the fits could be attributed to uncertainties in chamber effects. It is concluded that better characterization of chamber conditions are needed if more comprehensive tests of atmospheric photochemical mechanisms are desired.

  13. Is Submarine Groundwater Discharge a Gas Hydrate Formation Mechanism on the Circum-Arctic Shelf?

    NASA Astrophysics Data System (ADS)

    Frederick, J. M.; Buffett, B. A.

    2015-12-01

    Methane hydrate is an ice-like solid that can sequester large quantities of methane gas in marine sediments along most continental margins where thermodynamic conditions permit its formation. Along the circum-Arctic shelf, relict permafrost-associated methane hydrate deposits formed when non-glaciated portions of the shelf experienced subaerial exposure during ocean transgressions. Gas hydrate stability and the permeability of circum-Arctic shelf sediments to gas migration is closely linked with relict submarine permafrost. Heat flow observations on the Alaskan North Slope and Canadian Beaufort Shelf suggest the movement of groundwater offshore, but direct observations of groundwater flow do not exist. Submarine discharge, an offshore flow of fresh, terrestrial groundwater, can affect the temperature and salinity field in shelf sediments, and may be an important factor in submarine permafrost and gas hydrate evolution on the Arctic continental shelf. Submarine groundwater discharge may also enhance the transport of organic matter for methanogenesis within marine sediments. Because it is buoyancy-driven, the velocity field contains regions with a vertical (upward) component as groundwater flows offshore. This combination of factors makes submarine groundwater discharge a potential mechanism controlling permafrost-associated gas hydrate evolution on the Arctic continental shelf. In this study, we quantitatively investigate the feasibility of submarine groundwater discharge as a control on permafrost-associated gas hydrate formation on the Arctic continental shelf, using the Canadian Beaufort Shelf as an example. We have developed a shelf-scale, two-dimensional numerical model based on the finite volume method for two-phase flow of pore fluid and methane gas within Arctic shelf sediments. The model tracks the evolution of the pressure, temperature, salinity, methane gas, methane hydrate, and permafrost fields given imposed boundary conditions, with latent heat of

  14. Mechanical load-assisted dissolution of metallic implant surfaces: influence of contact loads and surface stress state.

    PubMed

    Mitchell, Andrew; Shrotriya, Pranav

    2008-03-01

    Mechanical load-assisted dissolution is identified as one of the key mechanisms governing material removal in fretting and crevice corrosion of biomedical implants. In the current study, material removal on a stressed surface of cobalt-chromium-molybdenum (CoCrMo) subjected to single asperity contact is investigated in order to identify the influence of contact loads and in-plane stress state on surface damage mechanisms. The tip of an atomic force microscope is used as a well-characterized "asperity" to apply controlled contact forces and mechanically stimulate the loaded specimen surface in different aqueous environments from passivating to corroding. The volume of the material removed is measured to determine the influence of contact loads, in-plane stresses and the environment on the material dissolution rate. Experimental results indicate that surface damage is initiated at all the contact loads studied and as expected in a wear situation, removal rate increases with increase in contact loads. Removal rates display a complex dependence on residual stresses and the environment. In a passivating environment, the material removal rate is linearly dependent on the stress state such that surface damage is accelerated under compressive stresses and suppressed under tensile stresses. In a corrosive environment, the dissolution rate demonstrates a quadratic dependence on stress, with both compressive and tensile stresses accelerating material dissolution. A surface damage mechanism based on stress-assisted dissolution is proposed to elucidate the experimental observations.

  15. Mechanism of aneurysm formation after 830-nm diode-laser-assisted microarterial anastomosis

    NASA Astrophysics Data System (ADS)

    Tang, Jing; Godlewski, Guilhem; Rouy, Simone

    1998-01-01

    A series of 830 nm diode laser assisted longitudinal aortorrhophy with a condition of 400 to 500 J/mm2 for one cm length of anastomosis versus conventional manual anastomoses were performed in 90 Wistar rats. With comparing with normal media process, a histologic examination of aneurysm formation was conducted. The results show that there are two important factors to cause aneurysm formation after laser assisted anastomosis: (1) vessel wall is damaged by laser heating; (2) proliferation of collagen fiber at adventitia is absent when media reconstruction.

  16. Noble gases solubility models of hydrocarbon charge mechanism in the Sleipner Vest gas field

    NASA Astrophysics Data System (ADS)

    Barry, P. H.; Lawson, M.; Meurer, W. P.; Warr, O.; Mabry, J. C.; Byrne, D. J.; Ballentine, C. J.

    2016-12-01

    Noble gases are chemically inert and variably soluble in crustal fluids. They are primarily introduced into hydrocarbon reservoirs through exchange with formation waters, and can be used to assess migration pathways and mechanisms, as well as reservoir storage conditions. Of particular interest is the role groundwater plays in hydrocarbon transport, which is reflected in hydrocarbon-water volume ratios. Here, we present compositional, stable isotope and noble gas isotope and abundance data from the Sleipner Vest field, in the Norwegian North Sea. Sleipner Vest gases are generated from primary cracking of kerogen and the thermal cracking of oil. Gas was emplaced into the Sleipner Vest from the south and subsequently migrated to the east, filling and spilling into the Sleipner Ost fields. Gases principally consist of hydrocarbons (83-93%), CO2 (5.4-15.3%) and N2 (0.6-0.9%), as well as trace concentrations of noble gases. Helium isotopes (3He/4He) are predominantly radiogenic and range from 0.065 to 0.116 RA; reported relative to air (RA = 1.4 × 10-6; Clarke et al., 1976; Sano et al., 1988), showing predominantly (>98%) crustal contributions, consistent with Ne (20Ne/22Ne from 9.70 to 9.91; 21Ne/22Ne from 0.0290 to 0.0344) and Ar isotopes (40Ar/36Ar from 315 to 489). Air-derived noble gas isotopes (20Ne, 36Ar, 84Kr, 132Xe) are introduced into the hydrocarbon system by direct exchange with air-saturated water (ASW). The distribution of air-derived noble gas species are controlled by phase partitioning processes; in that they preferentially partition into the gas (i.e., methane) phase, due to their low solubilities in fluids. Therefore, the extent of exchange between hydrocarbon phases and formation waters - that have previously equilibrated with the atmosphere - can be determined by investigating air-derived noble gas species. We utilize both elemental ratios to address process (i.e., open vs. closed system) and concentrations to quantify the extent of hydrocarbon

  17. Gas-bubble growth mechanisms in the analysis of metal fuel swelling

    SciTech Connect

    Gruber, E.E.; Kramer, J.M.

    1986-06-01

    During steady-state irradiation, swelling rates associated with growth of fission-gas bubbles in metallic fast reactor fuels may be expected to remain small. As a consequence, bubble-growth mechanisms are not a major consideration in modeling the steady-state fuel behavior, and it is usually adequate to consider the gas pressure to be in equilibrium with the external pressure and surface tension restraint. On transient time scales, however, various bubble-growth mechanisms become important components of the swelling rate. These mechanisms include growth by diffusion, for bubbles within grains and on grain boundaries; dislocation nucleation at the bubble surface, or ''punchout''; and bubble growth by creep. Analyses of these mechanisms are presented and applied to provide information on the conditions and the relative time scales for which the various processes should dominate fuel swelling. The results are compared to a series of experiments in which the swelling of irradiated metal fuel was determined after annealing at various temperatures and pressures. The diffusive growth of bubbles on grain boundaries is concluded to be dominant in these experiments.

  18. Mechanisms to enhance the effectiveness of allied health and social care assistants in community-based rehabilitation services: a qualitative study.

    PubMed

    Moran, Anna; Nancarrow, Susan A; Enderby, Pamela

    2015-07-01

    This research aims to describe the factors associated with successful employment of allied health and social care assistants in community-based rehabilitation services (CBRS) in England. The research involved the thematic analysis of interviews and focus groups with 153 professionally qualified and assistant staff from 11 older people's interdisciplinary community rehabilitation teams. Data were collected between November 2006 and December 2008. Assistants were perceived as a focal point for care delivery and conduits for enabling a service to achieve goals within interdisciplinary team structures. Nine mechanisms were identified that promoted the successful employment of assistants: (i) Multidisciplinary team input into assistant training and support; (ii) Ensuring the timely assessment of clients by qualified staff; (iii) Establishing clear communication structures between qualified and assistant staff; (iv) Co-location of teams to promote communication and skill sharing; (v) Removing barriers that prevent staff working to their full scope of practice; (vi) Facilitating role flexibility of assistants, while upholding the principles of reablement; (vii) Allowing sufficient time for client-staff interaction; (viii) Ensuring an appropriate ratio of assistant to qualified staff to enable sufficient training and supervision of assistants; and (ix) Appropriately, resourcing the role for training and reimbursement to reflect responsibility. We conclude that upholding these mechanisms may help to optimise the efficiency and productivity of assistant and professionally qualified staff in CBRS.

  19. [Anesthesia during video-assisted thoracoscopic lobectomy using laryngeal ductwork and auxiliary mechanical ventilation].

    PubMed

    Porkhanov, V A; Polyakov, I S; Danilov, V V; Kononenko, V B; Zhikharev, V A

    2016-01-01

    The article presents the experience of video-assisted thoracoscopic lobectomies in patients without endotracheal intubation and sparing of spontaneous breathing. The results of intraoperative monitoring and laboratory data of all perioperative period are described. In view of these data it was concluded that such approach can decline the severity of stress-response against surgical aggression in this group of patients.

  20. Thermo-mechanical modelling of cyclic gas storage applications in salt caverns

    NASA Astrophysics Data System (ADS)

    Böttcher, Norbert; Watanabe, Norihiro; Görke, Uwe-Jens; Kolditz, Olaf; Nagel, Thomas

    2016-04-01

    Due to the growing importance of renewable energy sources it becomes more and more necessary to investigate energy storage potentials. One major way to store energy is the power-to-gas concept. Excessive electrical energy can be used either to produce hydrogen or methane by electrolysis or methanation or to compress air, respectively. Those produced gases can then be stored in artificial salt caverns, which are constructed in large salt formations by solution mining. In combination with renewable energy sources, the power-to-gas concept is subjected to fluctuations. Compression and expansion of the storage gases lead to temperature differences within the salt rock. The variations can advance several metres into the host rock, influencing its material behaviour, inducing thermal stresses and altering the creep response. To investigate the temperature influence on the cavern capacity, we have developed a numerical model to simulate the thermo-mechanical behaviour of salt caverns during cyclic gas storage. The model considers the thermodynamic behaviour of the stored gases as well as the heat transport and the temperature dependent material properties of the host rock. Therefore, we utilized well-known constitutive thermo-visco-plastic material models, implemented into the open source-scientific software OpenGeoSys. Both thermal and mechanical processes are solved using a finite element approach, connected via a staggered coupling scheme. The model allows the assessment of the structural safety as well as the convergence of the salt caverns.

  1. Gas-phase Ion Isomer Analysis Reveals the Mechanism of Peptide Sequence Scrambling

    PubMed Central

    Jia, Chenxi; Wu, Zhe; Lietz, Christopher B.; Liang, Zhidan; Cui, Qiang; Li, Lingjun

    2014-01-01

    Peptide sequence scrambling during mass spectrometry-based gas-phase fragmentation analysis causes misidentification of peptides and proteins. Thus, there is a need to develop an efficient approach to probing the gas-phase fragment ion isomers related to sequence scrambling and the underlying fragmentation mechanism, which will facilitate the development of bioinformatics algorithm for proteomics research. Herein, we report on the first use of electron transfer dissociation (ETD)-produced diagnostic fragment ions to probe the components of gas-phase peptide fragment ion isomers. In combination with ion mobility spectrometry (IMS) and formaldehyde labeling, this novel strategy enables qualitative and quantitative analysis of b-type fragment ion isomers. ETD fragmentation produced diagnostic fragment ions indicative of the precursor ion isomer components, and subsequent IMS analysis of b ion isomers provided their quantitative and structural information. The isomer components of three representative b ions (b9, b10, and b33 from three different peptides) were accurately profiled by this method. IMS analysis of the b9 ion isomers exhibited dynamic conversion among these structures. Furthermore, molecular dynamics simulation predicted theoretical drift time values which were in good agreement with experimentally measured values. Our results strongly support the mechanism of peptide sequence scrambling via b ion cyclization, and provide the first experimental evidence to support that the conversion from molecular precursor ion to cyclic b ion (M→cb) pathway is less energetically (or kinetically) favored. PMID:24313304

  2. Gas-phase ion isomer analysis reveals the mechanism of peptide sequence scrambling.

    PubMed

    Jia, Chenxi; Wu, Zhe; Lietz, Christopher B; Liang, Zhidan; Cui, Qiang; Li, Lingjun

    2014-03-18

    Peptide sequence scrambling during mass spectrometry-based gas-phase fragmentation analysis causes misidentification of peptides and proteins. Thus, there is a need to develop an efficient approach to probing the gas-phase fragment ion isomers related to sequence scrambling and the underlying fragmentation mechanism, which will facilitate the development of bioinformatics algorithm for proteomics research. Herein, we report on the first use of electron transfer dissociation (ETD)-produced diagnostic fragment ions to probe the components of gas-phase peptide fragment ion isomers. In combination with ion mobility spectrometry (IMS) and formaldehyde labeling, this novel strategy enables qualitative and quantitative analysis of b-type fragment ion isomers. ETD fragmentation produced diagnostic fragment ions indicative of the precursor ion isomer components, and subsequent IMS analysis of b ion isomers provided their quantitative and structural information. The isomer components of three representative b ions (b9, b10, and b33 from three different peptides) were accurately profiled by this method. IMS analysis of the b9 ion isomers exhibited dynamic conversion among these structures. Furthermore, molecular dynamics simulation predicted theoretical drift time values, which were in good agreement with experimentally measured values. Our results strongly support the mechanism of peptide sequence scrambling via b ion cyclization, and provide the first experimental evidence to support that the conversion from molecular precursor ion to cyclic b ion (M → (c)b) pathway is less energetically (or kinetically) favored.

  3. Electrophilic assistance to the cleavage of an RNA model phopshodiester via specific and general base-catalyzed mechanisms.

    PubMed

    Corona-Martínez, David Octavio; Gomez-Tagle, Paola; Yatsimirsky, Anatoly K

    2012-10-19

    Kinetics of transesterification of the RNA model substrate 2-hydroxypropyl 4-nitrophenyl phosphate promoted by Mg(2+) and Ca(2+), the most common biological metals acting as cofactors for nuclease enzymes and ribozymes, as well as by Co(NH(3))(6)(3+), Co(en)(3)(3+), Li(+), and Na(+) cations, often employed as mechanistic probes, was studied in 80% v/v (50 mol %) aqueous DMSO, a medium that allows one to discriminate easily specific base (OH(-)-catalyzed) and general base (buffer-catalyzed) reaction paths. All cations assist the specific base reaction, but only Mg(2+) and Na(+) assist the general base reaction. For Mg(2+)-assisted reactions, the solvent deuterium isotope effects are 1.23 and 0.25 for general base and specific base mechanisms, respectively. Rate constants for Mg(2+)-assisted general base reactions measured with different bases fit the Brønsted correlation with a slope of 0.38, significantly lower than the slope for the unassisted general base reaction (0.77). Transition state binding constants for catalysts in the specific base reaction (K(‡)(OH)) both in aqueous DMSO and pure water correlate with their binding constants to 4-nitrophenyl phosphate dianion (K(NPP)) used as a minimalist transition state model. It was found that K(‡)(OH) ≈ K(NPP) for "protic" catalysts (Co(NH(3))(6)(3+), Co(en)(3)(3+), guanidinium), but K(‡)(OH) ≫ K(NPP) for Mg(2+) and Ca(2+) acting as Lewis acids. It appears from results of this study that Mg(2+) is unique in its ability to assist efficiently the general base-catalyzed transesterification often occurring in active sites of nuclease enzymes and ribozymes.

  4. Hybrid field-assisted solid-liquid-solid dispersive extraction for the determination of organochlorine pesticides in tobacco with gas chromatography.

    PubMed

    Zhou, Ting; Xiao, Xiaohua; Li, Gongke

    2012-01-03

    A novel one-step sample preparation technique termed hybrid field-assisted solid-liquid-solid dispersive extraction (HF-SLSDE) was developed in this study. A simple glass system equipped with a condenser was designed as an extraction vessel. The HF-SLSDE technique was a three-phase dispersive extraction approach. Target analytes were extracted from the sample into the extraction solvent enhanced by the hybrid field. Meanwhile, the interfering components were adsorbed by dispersing sorbent. No cleanup step preceded chromatographic analysis. The efficiency of the HF-SLSDE approach was demonstrated in the determination of organochlorine pesticide (OCP) residues in tobacco with a gas chromatography-electron capture detector (GC-ECD). Various operation conditions were studied systematically. Low detection limits (0.3-1.6 μg/kg) and low quantification limits (1.0-4.5 μg/kg) were achieved under the optimized conditions. The recoveries of OCPs ranged from 70.2% to 118.2%, with relative standard deviations of <9.6%, except for the lowest fortification level. Because of the effect of the hybrid field, HF-SLSDE showed significant predominance compared with other extraction techniques. The dispersing sorbent with good cleanup ability used in this study was also found to be a microwave absorption medium, which could heat the nonpolar extraction solvent under microwave irradiation. Different microstructures of tobacco samples before and after extractions demonstrated the mechanism of HF-SLSDE was based on an explosion at the cell level. According to the results, HF-SLSDE was proved to be a simple and effective sample preparation method for the analysis of pesticide residues in solid samples and could potentially be extended to other nonpolar target analytes in a complex matrix.

  5. Synergistic catalytic removal NOX and the mechanism of plasma and hydrocarbon gas

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Sha, Xiang-ling; Zhang, Lei; He, Hui-bin; Ma, Zhen-hua; Wang, Long-wei; Wang, Yu-xin; She, Li-xia

    2016-07-01

    This paper using a method of catalytic adsorption combined with dielectric barrier discharge plasma which added to hydrocarbon gases. The different background gases, different dielectric properties and different pore sizes of the hydrolysis coke on the denitrification performance was studied. The effect of the coaction of plasma and the different properties of the removal of NO in flue gas was investigated, and the catalytic mechanism of the synergistic effect of plasma and hydrocarbon gas was discussed. The results shown that: The denitrification rate was significantly affected by plasma power and the initial concentration of NO; the reaction was restrained by the presence of oxygen and greatly promoted by the hydrocarbon gases. The permittivity of the catalyst has a great influence on the activity and the porous structure of the catalyst can obviously promote the reaction when the low temperature plasma combined with hydrocarbon gases.

  6. Solid-gas reactions driven by mechanical alloying of niobium and tantalum in nitrogen

    SciTech Connect

    Liu, L.; Lu, L.; Chen, L.; Qin, Y.; Zhang, L.D.

    1999-04-01

    Solid-gas reactions of niobium and tantalum with molecular nitrogen driven by mechanical alloying (MA) have been investigated by X-ray diffraction, transmission electron microscopy, and differential thermal analysis. It was found that the phase transition followed a sequence of Nb{sub 2}N {r_arrow} Nb{sub 3}N{sub 4} {r_arrow} NbN when Nb was milled with N{sub 2}. The chemosorption of nitrogen onto the clean metal surfaces created by ball milling is believed to be the fundamental process governing solid-gas reactions, and the defects generated during MA can promote the diffusion of adsorbed nitrogen, and consequently the formation of metal nitrides. The difference in phase transition between the two systems is discussed.

  7. Statistical mechanical model of gas adsorption in porous crystals with dynamic moieties.

    PubMed

    Simon, Cory M; Braun, Efrem; Carraro, Carlo; Smit, Berend

    2017-01-17

    Some nanoporous, crystalline materials possess dynamic constituents, for example, rotatable moieties. These moieties can undergo a conformation change in response to the adsorption of guest molecules, which qualitatively impacts adsorption behavior. We pose and solve a statistical mechanical model of gas adsorption in a porous crystal whose cages share a common ligand that can adopt two distinct rotational conformations. Guest molecules incentivize the ligands to adopt a different rotational configuration than maintained in the empty host. Our model captures inflections, steps, and hysteresis that can arise in the adsorption isotherm as a signature of the rotating ligands. The insights disclosed by our simple model contribute a more intimate understanding of the response and consequence of rotating ligands integrated into porous materials to harness them for gas storage and separations, chemical sensing, drug delivery, catalysis, and nanoscale devices. Particularly, our model reveals design strategies to exploit these moving constituents and engineer improved adsorbents with intrinsic thermal management for pressure-swing adsorption processes.

  8. Strong-Sludge Gas Retention and Release Mechanisms in Clay Simulants

    SciTech Connect

    Gauglitz, Phillip A.; Buchmiller, William C.; Probert, Samuel G.; Owen, Antionette T.; Brockman, Fred J.

    2012-02-24

    The Hanford Site has 28 double-shell tanks (DSTs) and 149 single-shell tanks (SSTs) containing radioactive wastes that are complex mixes of radioactive and chemical products. The mission of the Department of Energy's River Protection Project is to retrieve and treat the Hanford tank waste for disposal and close the tank farms. A key aspect of the mission is to retrieve and transfer waste from the SSTs, which are at greater risk for leaking, into DSTs for interim storage until the waste is transferred to and treated in the Waste Treatment and Immobilization Plant. There is, however, limited space in the existing DSTs to accept waste transfers from the SSTs, and approaches to overcoming the limited DST space will benefit the overall mission. The purpose of this study is to summarize and analyze the key previous experiment that forms the basis for the relaxed controls and to summarize progress and results on new experiments focused on understanding the conditions that result in low gas retention. The previous large-scale test used about 50 m3 of sediment, which would be unwieldy for doing multiple parametric experiments. Accordingly, experiments began with smaller-scale tests to determine whether the desired mechanisms can be studied without the difficulty of conducting very large experiments. The most significant results from the current experiments are that progressively lower gas retention occurs in tests with progressively deeper sediment layers and that the method of gas generation also affects the maximum retention. Based on the results of this study, it is plausible that relatively low gas retention could occur in sufficiently deep tank waste in DSTs. The current studies and previous work, however, have not explored how gas retention and release will behave when two or more layers with different properties are present.

  9. Seismic Source Mechanism of Gas-Piston Activity at Kilauea Inferred from Inversion of Broadband Waveforms

    NASA Astrophysics Data System (ADS)

    Chouet, B. A.; Dawson, P. B.

    2015-12-01

    Among the broad range of magmatic processes observed in the Overlook pit crater in Kilauea Caldera are recurring episodes of gas-piston activity. This activity is accompanied by repetitive seismic signals recorded by a broadband network deployed in the summit caldera. We use the seismic data to model the source mechanism of representative gas-piston events in a sequence that occurred on 20-25 August 2011 during a gentle inflation of the Kilauea summit. We apply a new waveform inversion method that accounts for the contributions from both translation and tilt in horizontal seismograms through the use of Green's functions representing the seismometer response to translation and tilt ground motions. This method enables a robust description of the source mechanism over the period range of 1 - 10,000 s. Most of the seismic wave field produced by gas-pistoning originates in a source region ~1 km below the eastern perimeter of Halema'uma'u pit crater. The observed waveforms are well explained by a simple volumetric source with geometry composed of two intersecting cracks featuring an east-striking crack (dike) dipping 80° to the north, intersecting a north-striking crack (inclined sheet) dipping 65° to the east. Each gas-piston event is characterized by a rapid inflation lasting a few minutes trailed by a slower deflation ramp extending up to 15 minutes, attributed to the efficient coupling at the source centroid location of the pressure and momentum changes accompanying the growth and collapse of a layer of foam at the top of the magma column. Assuming a simple lumped parameter representation of the shallow magmatic system, the observed pressure and volume variations can be modeled with the following attributes: foam thickness (10 - 50 m), foam cell diameter (0.04 - 0.10 m), and gas-injection velocity (0.01 - 0.06 m s-1). Based on the change in the period of very-long-period oscillations accompanying the onset of the gas-piston signal and tilt evidence, the height of

  10. Partial discharge and breakdown mechanisms in ultra-dilute SF6 and PFC gases mixed with N2 gas

    NASA Astrophysics Data System (ADS)

    Okubo, H.; Yamada, T.; Hatta, K.; Hayakawa, N.; Yuasa, S.; Okabe, S.

    2002-11-01

    Because of the high global warming potential of SF6 gas, research on alternative gases for electrical insulation with a lower environmental impact is essential. Gas mixtures composed of electronegative gases and N2 gas have the advantage of the reduction of the amount of SF6 gas and of utilizing the synergistic effect in electrical insulation performance. We investigated the partial discharge (PD) and breakdown (BD) characteristics of SF6/N2 and PFC (C3F8/N2 and C2F6/N2) gas mixtures under non-uniform electric field conditions, by changing the dilute content of electronegative gases. As a result, the synergistic effect in SF6/N2 gas mixtures was verified to be higher than that in PFC/N2 gas mixtures. The physical mechanism from PD inception to BD was discussed with consideration of the difference in electronegativity of SF6 and PFC gases. Furthermore, we found that PD inception and PD-to-BD mechanisms changed at a content of 10 ppm for SF6 due to the electron attachment activity of SF6 gas. The change in the PD and BD mechanisms in C3F8/N2 and C2F6/N2 gas mixtures appeared at 0.1% content for C3F8 and at 1% content for C2F6.

  11. Study on the micro-heater geometry in In,2O3 micro electro mechanical systems gas sensor platforms and effects on NO2 gas detecting performances.

    PubMed

    Choi, Woo-Seok; Kim, Bum-Joon; Lee, Hoi-Jung; Choi, Jung-Woon; Kim, Si-Dong; Min, Nam-Ki

    2012-02-01

    Micro electro mechanical systems (MEMS) platforms for gas sensing devices with the co-planar type micro-heaters were designed, fabricated and its effects on the In2O3 gas sensors were investigated. Micro-heaters in MEMS gas sensor platforms were designed in the four-type heater patterns with different geometries. Electro-thermal characterizations showed that the designed platforms had highly thermal efficiency because the micro hot-plate structures were formed in the diaphragm and the thermal efficiencies were analyzed for all of 16 models and compared with each other, respectively. The designed micro-platforms were fabricated by MEMS process, and Indium oxide (In2O3) nanoparticles were synthesized by sol-gel process and dropped on the MEMS platforms for detecting the noxious oxide gas (NO2) Fabricated micro-platforms had a very low power consumption in the fabricated 16-type models, especially, the minimum power consumption was 41 mW at the operating temperature of 250 degrees C. After experiments on gas sensing characteristics to NO2 gases, fabricated In2O3 gas sensors had almost the same gas sensitivity (Rs) at the operation temperature of 250 degrees C. It is concluded that the micro-heater geometries, pattern shapes and sizes, can be influential on the power consumption of the devices and its gas sensing characteristics.

  12. Fundamental mechanisms in flue gas conditioning. Quarterly technical progress report, April 1995--June 1995

    SciTech Connect

    Snyder, T.R.; Bush, P.V.

    1995-07-11

    This project is divided into four tasks. We developed our Management Plan in Task 1. Task 2, Evaluation of Mechanisms in FGD Sorbent and Ash Interactions, focused on characteristics of binary mixtures of these distinct powders. Task 3, Evaluation of Mechanisms in Conditioning Agents and Ash, was designed to examine effects of various conditioning agents on fine ash particles to determine mechanisms by which these agents alter physical properties of ash. We began Tasks 2 and 3 with an extensive literature search and assembly of existing theories. We completed this phase of the project with publication of two special Topical Reports. In our literature reviews reported in Topical Reports 1 and 2, we emphasized the roles adsorbed water can have in controlling bulk properties of powders. During the next phase of the project we analyzed a variety of fly ashes and fine powders in the laboratory. The experiments we performed were primarily designed to define the extent to which water affects key properties of ashes, powders, and mixtures of sorbents and ashes. We have recently completed a series of pilot-scale tests designed to determine the effects that adsorbed water has on fabric filtration and electrostatic precipitation of entrained fly ash particles in actual flue gas environments. Under Task 4 we will issue our Final Report that will summarize the results of our laboratory and pilot-scale work and will also include a model of flue gas conditioning. Our efforts during this reporting quarter have been directed toward production of the Draft Final Report and the Flue Gas Conditioning Model. In addition to these efforts, we have prepared a paper for presentation at the Eleventh Annual Coal Preparation, Utilization, and Environmental Control Contractor`s Conference to be held in Pittsburgh in July, 1995.

  13. Gas-phase Mechanisms of Sulfur Isotope Mass-independent Fractionation

    NASA Astrophysics Data System (ADS)

    Lyons, J. R.

    2006-12-01

    Mass-independent fractionation (MIF) in sulfur isotopes in ancient sulfur-bearing rocks (Farquhar et al. 2000a) is interpreted as evidence for gas-phase MIF processes in the early Earth atmosphere. This interpretation is made by analogy with oxygen isotope MIF in the modern atmosphere (produced during ozone formation), and by laboratory photolysis experiments on SO2 (Farquhar et al. 2001; Wing et al. 2004) that yield both elemental sulfur and sulfate with S MIF signatures at wavelengths above and below the SO2 dissociation limit. What is lacking is a quantitative understanding of the mechanisms of gas-phase S MIF. Quantification is essential in order to extract the full implications of sulfur MIF throughout Earth history, including for bacterial sulfate reduction processes which largely conserve D33S and D36S. Several sulfur MIF mechanisms are possible. The most obvious is the gas-phase thiozone reaction, which is isovalent to the ozone formation reaction. Ozone formation produces a well-known MIF signature in oxygen isotopes (Thiemens and Heidenreich 1983), and a symmetry-dependent non-RRKM mechanism has been proposed as the origin of O MIF (Gao and Marcus 2001). It is possible and perhaps likely that S3 formation also proceeds by a non-RRKM process. Data are lacking on isotopic (an even non-isotopic) rates of S3 formation, so it is not possible to make definitive statements about MIF in S3 at this time. However modeling results suggest that the vapor pressure of S2 is too low for gas-phase S3 formation to be significant. Two additional species that may exhibit a non-RRKM MIF signature are S2O2 and S4. Again, there is a lack of isotopomer-specific kinetic data for these reactions, and gas-phase formation of S4 is likely inconsequential. Perhaps the most obvious mechanism is simply the primary act of SO2 photolysis. The SO2 absorption spectrum is highly structured, with strong vibronic bands above and below the dissociation limit. In contrast H2S, with its mostly

  14. UNDERSTANDING THE MECHANISMS CONTROLLING ENVIRONMENTALLY-ASSISTED INTERGRANULAR CRACKING OF NICKEL-BASE ALLOYS

    SciTech Connect

    Gary S. Was

    2004-02-13

    Creep and IG cracking of nickel-base alloys depend principally on two factors--the deformation behavior and the effect of the environment. We have shown that both contribute to the observed degradation in primary water. The understanding of cracking does not lie wholly within the environmental effects arena, nor can it be explained only by intrinsic mechanical behavior. Rather, both processes contribute to the observed behavior in primary water. In this project, we had three objectives: (1) to verify that grain boundaries control deformation in Ni-16Cr-9Fe at 360 C, (2) to identify the environmental effect on IGSCC, and (3) to combine CSLBs and GBCs to maximize IGSCC resistance in Ni-Cr-Fe in 360 C primary water. Experiments performed in hydrogen gas at 360 C confirm an increase in the primary creep rate in Ni-16Cr-9Fe at 360 C due to hydrogen. The creep strain transients caused by hydrogen are proposed to be due to the collapse of dislocation pile-ups, as confirmed by observations in HVEM. The observations only partially support the hydrogen-enhanced plasticity model, but also suggest a potential role of vacancies in the accelerate creep behavior in primary water. In high temperature oxidation experiments designed to examine the potential for selective internal oxidation in the IGSCC process, cracking is greatest in the more oxidizing environments compared to the low oxygen potential environments where nickel metal is stable. In Ni-Cr-Fe alloys, chromium oxides form preferentially along the grain boundaries, even at low oxygen potential, supporting a potential role in grain boundary embrittlement due to preferential oxidation. Experiments designed to determine the role of grain boundary deformation on intergranular cracking have established, for the first time, a cause-and-effect relationship between grain boundary deformation and IGSCC. That is, grain boundary deformation in Ni-16Cr-9Fe in 360 C primary water leads to IGSCC of the deformed boundaries. As well

  15. Synthesis of ZnO Nanocrystal-Graphene Composite by Mechanical Milling and Sonication-Assisted Exfoliation

    NASA Astrophysics Data System (ADS)

    Arora, Sweety; Srivastava, Chandan

    2017-02-01

    A ZnO nanocrystal-graphene composite was synthesized by a two-step method involving mechanical milling and sonication-assisted exfoliation. Zn metal powder was first ball-milled with graphite powder for 30 h in water medium. This ball-milled mixture was then subjected to exfoliation by sonication in the presence of sodium lauryl sulfate surfactant to produce graphene decorated with spherical agglomerates of ultrafine nanocrystalline ZnO. The presence of a few layers of graphene was confirmed by Raman spectroscopy and atomic force microscopy measurements. The size, phase identity and composition of the ZnO nanocrystals was determined by transmission electron microscopy measurements.

  16. Sorption Mechanisms for Mercury Capture in Warm Post-Gasification Gas Clean-Up Systems

    SciTech Connect

    Jost Wendt; Sung Jun Lee; Paul Blowers

    2008-09-30

    The research was directed towards a sorbent injection/particle removal process where a sorbent may be injected upstream of the warm gas cleanup system to scavenge Hg and other trace metals, and removed (with the metals) within the warm gas cleanup process. The specific objectives of this project were to understand and quantify, through fundamentally based models, mechanisms of interaction between mercury vapor compounds and novel paper waste derived (kaolinite + calcium based) sorbents (currently marketed under the trade name MinPlus). The portion of the research described first is the experimental portion, in which sorbent effectiveness to scavenge metallic mercury (Hg{sup 0}) at high temperatures (>600 C) is determined as a function of temperature, sorbent loading, gas composition, and other important parameters. Levels of Hg{sup 0} investigated were in an industrially relevant range ({approx} 25 {micro}g/m{sup 3}) although contaminants were contained in synthetic gases and not in actual flue gases. A later section of this report contains the results of the complementary computational results.

  17. Noble gases identify the mechanisms of fugitive gas contamination in drinking-water wells overlying the Marcellus and Barnett Shales.

    PubMed

    Darrah, Thomas H; Vengosh, Avner; Jackson, Robert B; Warner, Nathaniel R; Poreda, Robert J

    2014-09-30

    Horizontal drilling and hydraulic fracturing have enhanced energy production but raised concerns about drinking-water contamination and other environmental impacts. Identifying the sources and mechanisms of contamination can help improve the environmental and economic sustainability of shale-gas extraction. We analyzed 113 and 20 samples from drinking-water wells overlying the Marcellus and Barnett Shales, respectively, examining hydrocarbon abundance and isotopic compositions (e.g., C2H6/CH4, δ(13)C-CH4) and providing, to our knowledge, the first comprehensive analyses of noble gases and their isotopes (e.g., (4)He, (20)Ne, (36)Ar) in groundwater near shale-gas wells. We addressed two questions. (i) Are elevated levels of hydrocarbon gases in drinking-water aquifers near gas wells natural or anthropogenic? (ii) If fugitive gas contamination exists, what mechanisms cause it? Against a backdrop of naturally occurring salt- and gas-rich groundwater, we identified eight discrete clusters of fugitive gas contamination, seven in Pennsylvania and one in Texas that showed increased contamination through time. Where fugitive gas contamination occurred, the relative proportions of thermogenic hydrocarbon gas (e.g., CH4, (4)He) were significantly higher (P < 0.01) and the proportions of atmospheric gases (air-saturated water; e.g., N2, (36)Ar) were significantly lower (P < 0.01) relative to background groundwater. Noble gas isotope and hydrocarbon data link four contamination clusters to gas leakage from intermediate-depth strata through failures of annulus cement, three to target production gases that seem to implicate faulty production casings, and one to an underground gas well failure. Noble gas data appear to rule out gas contamination by upward migration from depth through overlying geological strata triggered by horizontal drilling or hydraulic fracturing.

  18. Noble gases identify the mechanisms of fugitive gas contamination in drinking-water wells overlying the Marcellus and Barnett Shales

    PubMed Central

    Darrah, Thomas H.; Vengosh, Avner; Jackson, Robert B.; Warner, Nathaniel R.; Poreda, Robert J.

    2014-01-01

    Horizontal drilling and hydraulic fracturing have enhanced energy production but raised concerns about drinking-water contamination and other environmental impacts. Identifying the sources and mechanisms of contamination can help improve the environmental and economic sustainability of shale-gas extraction. We analyzed 113 and 20 samples from drinking-water wells overlying the Marcellus and Barnett Shales, respectively, examining hydrocarbon abundance and isotopic compositions (e.g., C2H6/CH4, δ13C-CH4) and providing, to our knowledge, the first comprehensive analyses of noble gases and their isotopes (e.g., 4He, 20Ne, 36Ar) in groundwater near shale-gas wells. We addressed two questions. (i) Are elevated levels of hydrocarbon gases in drinking-water aquifers near gas wells natural or anthropogenic? (ii) If fugitive gas contamination exists, what mechanisms cause it? Against a backdrop of naturally occurring salt- and gas-rich groundwater, we identified eight discrete clusters of fugitive gas contamination, seven in Pennsylvania and one in Texas that showed increased contamination through time. Where fugitive gas contamination occurred, the relative proportions of thermogenic hydrocarbon gas (e.g., CH4, 4He) were significantly higher (P < 0.01) and the proportions of atmospheric gases (air-saturated water; e.g., N2, 36Ar) were significantly lower (P < 0.01) relative to background groundwater. Noble gas isotope and hydrocarbon data link four contamination clusters to gas leakage from intermediate-depth strata through failures of annulus cement, three to target production gases that seem to implicate faulty production casings, and one to an underground gas well failure. Noble gas data appear to rule out gas contamination by upward migration from depth through overlying geological strata triggered by horizontal drilling or hydraulic fracturing. PMID:25225410

  19. Arapahoe low-sulfur-coal fabric filter pilot plant: Volume 3, Characterization of sonic-assisted reverse-gas cleaning, May 1982--May 1984: Final report

    SciTech Connect

    Cushing, K.M.; Bustard, C.J.; Pontius, D.H.; Pyle, B.E.; Smith, W.B.

    1989-02-01

    During 1981 intense interest developed in the utility industry regarding the use of horns as a supplement to reverse-gas bag cleaning. To characterize and assess sonic-enhanced, reverse-gas cleaning, horns were installed at EPRI's 10-MW Fabric Filter Pilot Plant (FFPP) at its Arapahoe Test Facility located at Public Service Company of Colorado's Arapahoe Steam Plant in Denver, Colorado. In addition to the FFPP tests, laboratory studies of sonic cleaning were conducted to supplement the pilot plant data. To verify the applicability of the pilot plant and laboratory work to full-scale baghouses, field data from utility baghouses in which horns had been installed were collected. The purpose of the testing was to determine the range of horn frequencies and total output power most effective in removing residual dustcakes from bags in reverse-gas-cleaned baghouses and, hence, most effective in reducing baghouse pressure drop. No attempt was made to identify a specific horn or horns most appropriate for baghouse application. The report presents the results of this testing from May 1982 through May 1984. Results showed that horns can dislodge a significant fraction of residual dustcake, thereby reducing pressure drop by as much as 60% without any noticeable reduction in bag life. Although outlet particulate emissions are higher with sonic assistance, they are generally <0.01 lb/10/sup 6/ Btu---below the 1979 New Source Performance Standards of 0.03 lb/MBtu. The overall results of this sonic horn investigation indicate that reverse-gas cleaning with sonic assistance definitely promotes more effective bag filter cleaning and lower pressure drop, and it should be considered as a supplement for most reverse-gas cleaned baghouse applications. 10 refs., 37 figs., 7 tabs.

  20. Anisotropic mechanical behaviour of sedimentary basins inferred by advanced radar interferometry above gas storage fields

    NASA Astrophysics Data System (ADS)

    Teatini, P.; Gambolati, G.; Ferretti, A.

    2010-12-01

    Natural gas is commonly stored underground in depleted oil and gas fields to provide safe storage capacity and deliverability to market areas where production is limited, or to take advantage of seasonal price swings. In response to summer gas injection and winter gas withdrawal the reservoir expands and contracts with the overlying land that moves accordingly. Depending on the field burial depth, a few kilometres of the upper lithosphere are subject to local three-dimensional deformations with the related cyclic motion of the ground surface being both vertical and horizontal. Advanced Persistent Scatterer Interferometry (PSI) data, obtained by combining ascending and descending RADARSAT-1 images acquired from 2003 to 2008 above gas storage fields located in the sedimentary basin of the Po river plain, Italy, provide reliable measurement of these seasonal vertical ups and downs as well as horizontal displacements to and from the injection/withdrawal wells. Combination of the land surface movements together with an accurate reconstruction of the subsurface geology made available by three-dimensional seismic surveys and long-time records of fluid pore pressure within the 1000-1500 m deep reservoirs has allowed for the development of an accurate 3D poro-mechanical finite-element model of the gas injection/removal occurrence. Model calibration based on the observed cyclic motions, which are on the range of 10-15 mm and 5-10 mm in the vertical and horizontal west-east directions, respectively, helps characterize the nonlinear hysteretic geomechanical properties of the basin. First, using a basin-scale relationship between the oedometric rock compressibility cM in virgin loading conditions versus the effective intergranular stress derived from previous experimental studies, the modeling results show that the ratio s between loading and unloading-reloading cM is about 4, consistent with in-situ expansions measured by the radioactive marker technique in similar reservoirs

  1. Study of detecting mechanism of carbon nanotubes gas sensor based on multi-stable stochastic resonance model.

    PubMed

    Jingyi, Zhu

    2015-01-01

    The detecting mechanism of carbon nanotubes gas sensor based on multi-stable stochastic resonance (MSR) model was studied in this paper. A numerically stimulating model based on MSR was established. And gas-ionizing experiment by adding electronic white noise to induce 1.65 MHz periodic component in the carbon nanotubes gas sensor was performed. It was found that the signal-to-noise ratio (SNR) spectrum displayed 2 maximal values, which accorded to the change of the broken-line potential function. The experimental results of gas-ionizing experiment demonstrated that periodic component of 1.65 MHz had multiple MSR phenomena, which was in accordance with the numerical stimulation results. In this way, the numerical stimulation method provides an innovative method for the detecting mechanism research of carbon nanotubes gas sensor.

  2. Investigation of Gas Phase Transport Mechanisms in Unsaturated Zones Under Natural Conditions

    NASA Astrophysics Data System (ADS)

    You, K.; Zhan, H.

    2012-12-01

    Diffusive flux is traditionally treated as the dominant mechanism for gas transport in unsaturated zones without active disturbance. However, some researchers have found that the pressure-driven and density-driven advective flux may also be important under certain conditions. This article conducts a comprehensive study of the diffusive, pressure-driven and density-driven advective fluxes of the gas phase volatile organic compounds (VOCs) in the unsaturated zone under various hydrogeological conditions. The presence of a less or more permeable layer at ground surface in a heterogeneous unsaturated zone is investigated for their influence on the time-averaged advective and diffusive fluxes. Our developed numerical solution is applied to interpret a field study of the trichloroethylene contamination in the unsaturated zone at Picatinny Arsenal in Morris County, New Jersey. Results show that under most of the field conditions the time-averaged advective flux is one to three orders of magnitude smaller than the diffusive flux, and the influence of the density-driven flux on the advective flux is undetectable. The time-averaged advective flux is comparable in magnitude with the diffusive flux only in a deep unsaturated zone (thickness greater than 15 m), or when the gas-filled porosity is less than 0.05, or the magnitude of the water table fluctuation is greater than 0.2 m for the default parameters used in this study. A less permeable layer at ground surface increases the total flux of VOCs under it, while a permeable layer at ground surface increases the total flux in it. The error induced by fixing the water table position but allowing the fluctuation of water table moving velocity is negligible for predicting the gas phase VOCs transport in an unsaturated zone at non-coastal sites.

  3. Robustness of Modeling of Out-of-Service Gas Mechanical Face Seal

    NASA Technical Reports Server (NTRS)

    Green, Itzhak

    2007-01-01

    Gas lubricated mechanical face seal are ubiquitous in many high performance applications such as compressors and gas turbines. The literature contains various analyses of seals having orderly face patterns (radial taper, waves, spiral grooves, etc.). These are useful for design purposes and for performance predictions. However, seals returning from service (or from testing) inevitably contain wear tracks and warped faces that depart from the aforementioned orderly patterns. Questions then arise as to the heat generated at the interface, leakage rates, axial displacement and tilts, minimum film thickness, contact forces, etc. This work describes an analysis of seals that may inherit any (i.e., random) face pattern. A comprehensive computer code is developed, based upon the Newton- Raphson method, which solves for the equilibrium of the axial force and tilting moments that are generated by asperity contact and fluid film effects. A contact mechanics model is incorporated along with a finite volume method that solves the compressible Reynolds equation. Results are presented for a production seal that has sustained a testing cycle.

  4. Electronic transport mechanism in polydiacetylene crystals — variable range hopping or phonon-assisted tunnelling

    NASA Astrophysics Data System (ADS)

    Pipinys, Povilas; Kiveris, Antanas

    2007-03-01

    Experimental results on the current-voltage characteristics of polydiacetylene (PDA) single crystals reported by Aleshin et al [Phys. Rev. Vol. B 69, (2004) art. 214203] are reinterpreted in terms of the phonon-assisted electron tunnelling model. It is shown that the experimental results, measured in the temperature range from 1.8 K to 300 K are consistent with the tunnelling rate dependence on field strength, computed for the same range of temperatures. An advantage of this model over that of Aleshin et al, using the variable range hopping (VRH) model, is the possibility of describing the behaviour of I — V data measured at both high and low temperatures with the same set of parameters characterizing this material. This assertion is confirmed by comparison of the temperature-dependent current-voltage data extracted from Aleshin et al’s work with tunnelling rate dependence on temperature, computed using two different expressions of the phonon-assisted tunnelling theory. The temperature dependence of the conductivity of an ion implanted PDA crystals [B. S. Elman et al, Appl. Phys. Lett., Vol. 46, (1985) p. 100] and polypyrrole [P. Dutta et al, Synth. Met., Vol. 139 (2003) p. 201] are also explained on the basis of this model.

  5. Electronic transport mechanism in polydiacetylene crystals — variable range hopping or phonon-assisted tunnelling

    NASA Astrophysics Data System (ADS)

    Pipinys, Povilas; Kiveris, Antanas

    2007-03-01

    Experimental results on the current-voltage characteristics of polydiacetylene (PDA) single crystals reported by Aleshin et al [Phys. Rev. Vol. B 69, (2004) art. 214203] are reinterpreted in terms of the phonon-assisted electron tunnelling model. It is shown that the experimental results, measured in the temperature range from 1.8 K to 300 K are consistent with the tunnelling rate dependence on field strength, computed for the same range of temperatures. An advantage of this model over that of Aleshin et al, using the variable range hopping (VRH) model, is the possibility of describing the behaviour of I — V data measured at both high and low temperatures with the same set of parameters characterizing this material. This assertion is confirmed by comparison of the temperature-dependent current-voltage data extracted from Aleshin et al's work with tunnelling rate dependence on temperature, computed using two different expressions of the phonon-assisted tunnelling theory. The temperature dependence of the conductivity of an ion implanted PDA crystals [B. S. Elman et al, Appl. Phys. Lett., Vol. 46, (1985) p. 100] and polypyrrole [P. Dutta et al, Synth. Met., Vol. 139 (2003) p. 201] are also explained on the basis of this model.

  6. Wellbore Stability in Oil and Gas Drilling with Chemical-Mechanical Coupling

    PubMed Central

    Deng, Jingen

    2013-01-01

    Wellbore instability in oil and gas drilling is resulted from both mechanical and chemical factors. Hydration is produced in shale formation owing to the influence of the chemical property of drilling fluid. A new experimental method to measure diffusion coefficient of shale hydration is given, and the calculation method of experimental results is introduced. The diffusion coefficient of shale hydration is measured with the downhole temperature and pressure condition, then the penetration migrate law of drilling fluid filtrate around the wellbore is calculated. Furthermore, the changing rules of shale mechanical properties affected by hydration and water absorption are studied through experiments. The relationships between shale mechanical parameters and the water content are established. The wellbore stability model chemical-mechanical coupling is obtained based on the experimental results. Under the action of drilling fluid, hydration makes the shale formation softened and produced the swelling strain after drilling. This will lead to the collapse pressure increases after drilling. The study results provide a reference for studying hydration collapse period of shale. PMID:23935430

  7. Wellbore stability in oil and gas drilling with chemical-mechanical coupling.

    PubMed

    Yan, Chuanliang; Deng, Jingen; Yu, Baohua

    2013-01-01

    Wellbore instability in oil and gas drilling is resulted from both mechanical and chemical factors. Hydration is produced in shale formation owing to the influence of the chemical property of drilling fluid. A new experimental method to measure diffusion coefficient of shale hydration is given, and the calculation method of experimental results is introduced. The diffusion coefficient of shale hydration is measured with the downhole temperature and pressure condition, then the penetration migrate law of drilling fluid filtrate around the wellbore is calculated. Furthermore, the changing rules of shale mechanical properties affected by hydration and water absorption are studied through experiments. The relationships between shale mechanical parameters and the water content are established. The wellbore stability model chemical-mechanical coupling is obtained based on the experimental results. Under the action of drilling fluid, hydration makes the shale formation softened and produced the swelling strain after drilling. This will lead to the collapse pressure increases after drilling. The study results provide a reference for studying hydration collapse period of shale.

  8. Determination of chlorobenzenes in textiles by pressurized hot water extraction followed by vortex-assisted liquid-liquid microextraction and gas chromatography-mass spectrometry.

    PubMed

    Lu, Yang; Zhu, Yan

    2013-12-06

    A method for quantitative determination of chlorobenzenes in textiles is developed, using pressurized hot water extraction (PHWE), vortex-assisted liquid-liquid microextraction (VALLME) and gas chromatography-mass spectrometry (GC-MS). VALLME serves as a trapping step after PHWE. The extraction conditions are investigated, as well as the quantitative features such as linearity, limits of detection (LODs), limits of quantification (LOQs), repeatabilities and reproducibilities between days. LOQs of 0.018-0.032mg/kg were achieved. The present method provides good repeatabilities (RSD<6.9%) and demonstrates that PHWE-VALLME-GC-MS is a simple, rapid and environmentally friendly method for determination of chlorobenzenes in textiles.

  9. Volcanic tremors and magma wagging: gas flux interactions and forcing mechanism

    NASA Astrophysics Data System (ADS)

    Bercovici, David; Jellinek, A. Mark; Michaut, Chloé; Roman, Diana C.; Morse, Robert

    2013-11-01

    Volcanic tremor is an important precursor to explosive eruptions and is ubiquitous across most silicic volcanic systems. Oscillations can persist for days and occur in a remarkably narrow frequency band (i.e. 0.5-7 Hz). The recently proposed magma-wagging model of Jellinek & Bercovici provides a basic explanation for the emergence and frequency evolution of tremor that is consistent with observations of many active silicic and andesitic volcanic systems. This model builds on work suggesting that the magma column rising in the volcanic conduit is surrounded by a permeable vesicular annulus of sheared bubbles. The magma-wagging model stipulates that the magma column rattles within the spring like foam of the annulus, and predicts oscillations at the range of observed tremor frequencies for a wide variety of volcanic environments. However, the viscous resistance of the magma column attenuates the oscillations and thus a forcing mechanism is required. Here we provide further development of the magma-wagging model and demonstrate that it implicitly has the requisite forcing to excite wagging behaviour. In particular, the extended model allows for gas flux through the annulus, which interacts with the wagging displacements and induces a Bernoulli effect that amplifies the oscillations. This effect leads to an instability involving growing oscillations at the lower end of the tremor frequency spectrum, and that drives the system against viscous damping of the wagging magma column. The fully non-linear model displays tremor oscillations associated with pulses in gas flux, analogous to observations of audible `chugging'. These oscillations also occur in clusters or envelopes that are consistent with observations of sporadic tremor envelopes. The wagging model further accurately predicts that seismic signals on opposite sides of a volcano are out of phase by approximately half a wagging or tremor period. Finally, peaks in gas flux occur at the end of the growing instability

  10. Nucleation mechanism of gallium-assisted molecular beam epitaxy growth of gallium arsenide nanowires

    SciTech Connect

    Fontcuberta i Morral, A.; Colombo, C.; Abstreiter, G.; Arbiol, J.; Morante, J. R.

    2008-02-11

    Molecular beam epitaxy Ga-assisted synthesis of GaAs nanowires is demonstrated. The nucleation and growth are seen to be related to the presence of a SiO{sub 2} layer previously deposited on the GaAs wafer. The interaction of the reactive gallium with the SiO{sub 2} pinholes induces the formation of nanocraters, found to be the key for the nucleation of the nanowires. With SiO{sub 2} thicknesses up to 30 nm, nanocraters reach the underlying substrate, resulting into a preferential growth orientation of the nanowires. Possibly related to the formation of nanocraters, we observe an incubation period of 258 s before the nanowires growth is initiated.

  11. SnO2 highly sensitive CO gas sensor based on quasi-molecular-imprinting mechanism design.

    PubMed

    Li, Chenjia; Lv, Meng; Zuo, Jialin; Huang, Xintang

    2015-02-05

    Response of highly sensitive SnO2 semiconductor carbon monoxide (CO) gas sensors based on target gas CO quasi-molecular-imprinting mechanism design is investigated with gas concentrations varied from 50 to 3000 ppm. SnO2 nanoparticles prepared via hydrothermal method and gas sensor film devices SC (exposed to the target gas CO for 12 h after the suspension coating of SnO2 film to be fully dried, design of quasi-molecular-imprinting mechanism, the experiment group) and SA (exposed to air after the suspension coating of SnO2 film to be fully dried, the comparison group) made from SnO2 nanoparticles are all characterized by XRD, SEM and BET surface area techniques, respectively. The gas response experimental results reveal that the sensor SC demonstrates quicker response and higher sensitivity than the sensor SA does. The results suggest that in addition to the transformation of gas sensor materials, surface area, and porous membrane devices, the Molecular Imprinting Theory is proved to be another way to promote the performance of gas sensors.

  12. SnO2 Highly Sensitive CO Gas Sensor Based on Quasi-Molecular-Imprinting Mechanism Design

    PubMed Central

    Li, Chenjia; Lv, Meng; Zuo, Jialin; Huang, Xintang

    2015-01-01

    Response of highly sensitive SnO2 semiconductor carbon monoxide (CO) gas sensors based on target gas CO quasi-molecular-imprinting mechanism design is investigated with gas concentrations varied from 50 to 3000 ppm. SnO2 nanoparticles prepared via hydrothermal method and gas sensor film devices SC (exposed to the target gas CO for 12 h after the suspension coating of SnO2 film to be fully dried, design of quasi-molecular-imprinting mechanism, the experiment group) and SA (exposed to air after the suspension coating of SnO2 film to be fully dried, the comparison group) made from SnO2 nanoparticles are all characterized by XRD, SEM and BET surface area techniques, respectively. The gas response experimental results reveal that the sensor SC demonstrates quicker response and higher sensitivity than the sensor SA does. The results suggest that in addition to the transformation of gas sensor materials, surface area, and porous membrane devices, the Molecular Imprinting Theory is proved to be another way to promote the performance of gas sensors. PMID:25664435

  13. The Resonating Arm Exerciser: design and pilot testing of a mechanically passive rehabilitation device that mimics robotic active assistance

    PubMed Central

    2013-01-01

    Background Robotic arm therapy devices that incorporate actuated assistance can enhance arm recovery, motivate patients to practice, and allow therapists to deliver semi-autonomous training. However, because such devices are often complex and actively apply forces, they have not achieved widespread use in rehabilitation clinics or at home. This paper describes the design and pilot testing of a simple, mechanically passive device that provides robot-like assistance for active arm training using the principle of mechanical resonance. Methods The Resonating Arm Exerciser (RAE) consists of a lever that attaches to the push rim of a wheelchair, a forearm support, and an elastic band that stores energy. Patients push and pull on the lever to roll the wheelchair back and forth by about 20 cm around a neutral position. We performed two separate pilot studies of the device. In the first, we tested whether the predicted resonant properties of RAE amplified a user’s arm mobility by comparing his or her active range of motion (AROM) in the device achieved during a single, sustained push and pull to the AROM achieved during rocking. In a second pilot study designed to test the therapeutic potential of the device, eight participants with chronic stroke (35 ± 24 months since injury) and a mean, stable, initial upper extremity Fugl-Meyer (FM) score of 17 ± 8 / 66 exercised with RAE for eight 45 minute sessions over three weeks. The primary outcome measure was the average AROM measured with a tilt sensor during a one minute test, and the secondary outcome measures were the FM score and the visual analog scale for arm pain. Results In the first pilot study, we found people with a severe motor impairment after stroke intuitively found the resonant frequency of the chair, and the mechanical resonance of RAE amplified their arm AROM by a factor of about 2. In the second pilot study, AROM increased by 66% ± 20% (p = 0.003). The mean FM score increase was 8.5 ± 4 pts (p = 0

  14. Dopant-assisted negative photoionization Ion mobility spectrometry coupled with on-line cooling inlet for real-time monitoring H2S concentration in sewer gas.

    PubMed

    Peng, Liying; Jiang, Dandan; Wang, Zhenxin; Hua, Lei; Li, Haiyang

    2016-06-01

    Malodorous hydrogen sulfide (H2S) gas often exists in the sewer system and associates with the problems of releasing the dangerous odor to the atmosphere and causing sewer pipe to be corroded. A simple method is in demand for real-time measuring H2S level in the sewer gas. In this paper, an innovated method based on dopant-assisted negative photoionization ion mobility spectrometry (DANP-IMS) with on-line semiconductor cooling inlet was put forward and successfully applied for the real-time measurement of H2S in sewer gas. The influence of moisture was effectively reduced via an on-line cooling method and a non-equilibrium dilution with drift gas. The limits of quantitation for the H2S in ≥60% relative humidity air could be obtained at ≤79.0ng L(-1) with linear ranges of 129-2064ng L(-1). The H2S concentration in a sewer manhole was successfully determined while its product ions were identified by an ion-mobility time-of-fight mass spectrometry. Finally, the correlation between sewer H2S concentration and the daily routines and habits of residents was investigated through hourly or real-time monitoring the variation of sewer H2S in manholes, indicating the power of this DANP-IMS method in assessing the H2S concentration in sewer system.

  15. On the Mechanism of Low-Temperature Water Gas Shift Reaction on Copper

    SciTech Connect

    Gokhale, Amit A.; Dumesic, James A.; Mavrikakis, Manos

    2008-01-30

    The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. Periodic, self-consistent density functional theory (DFT-GGA) calculations are used to investigate the water gas shift reaction (WGSR) mechanism on Cu(111). The thermochemistry and activation energy barriers for all the elementary steps of the commonly accepted redox mechanism, involving complete water activation to atomic oxygen, are presented. Through our calculations, we identify carboxyl, a new reactive intermediate, which plays a central role in WGSR on Cu(111). The thermochemistry and activation energy barriers of the elementary steps of a new reaction path, involving carboxyl, are studied. A detailed DFTbased microkinetic model of experimental reaction rates, accounting for both the previous and the new WGSR mechanism show that, under relevant experimental conditions, (1) the carboxyl-mediated route is the dominant path, and (2) the initial hydrogen abstraction from water is the rate-limiting step. Formate is a stable “spectator” species, formed predominantly through CO₂ hydrogenation. In addition, the microkinetic model allows for predictions of (i) surface coverage of intermediates, (ii) WGSR apparent activation energy, and (iii) reaction orders with respect to CO, H₂O, CO₂, and H₂.

  16. Fundamental mechanisms in flue gas conditioning. Quarterly report, January 1992--March 1992

    SciTech Connect

    Snyder, T.R.; Robinson, M.S.; Bush, P.V.

    1992-04-27

    This project is divided into four tasks. The Management Plan was developed in task 1. Task 2, Evaluation of Mechanisms in FGD Sorbent and Ash Interactions, focuses on the characteristics of binary mixtures of these distinct powders. Task 3, Evaluation of Mechanisms in Conditioning Agents and Ash, is designed to examine the effects of various conditioning agents on fine ash particles to determine the mechanisms by which these agents alter the physical properties of the ash. Tasks 2 and 3 began with an extensive literature search and the assembly of existing theories. This phase of the project is now complete. During the past quarter, initial preparations of laboratory equipment for laboratory testing have been made. A plan for initial laboratory tests has been submitted to the Project Manager for review. Laboratory testing will commence once these laboratory plans have been formally approved. The results of the work performed under task 2 and 3 will be included in a Flue Gas Conditioning Model that will be issued under task 4. The Final Report for the project will also be prepared under task 4.

  17. Microstructure, Texture, and Mechanical Property Analysis of Gas Metal Arc Welded AISI 304 Austenitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Saha, Saptarshi; Mukherjee, Manidipto; Pal, Tapan Kumar

    2015-03-01

    The present study elaborately explains the effect of welding parameters on the microstructure, texture, and mechanical properties of gas metal arc welded AISI 304 austenitic stainless steel sheet (as received) of 4 mm thickness. The welded joints were prepared by varying welding speed (WS) and current simultaneously at a fixed heat input level using a 1.2-mm-diameter austenitic filler metal (AISI 316L). The overall purpose of this study is to investigate the effect of the variation of welding conditions on: (i) Microstructural constituents using optical microscope and transmission electron microscope; (ii) Micro-texture evolution, misorientation distributions, and grain boundaries at welded regions by measuring the orientation data from electron back scattered diffraction; and (iii) Mechanical properties such as hardness and tensile strength, and their correlation with the microstructure and texture. It has been observed that the higher WS along with the higher welding current (weld metal W1) can enhance weld metal mechanical properties through alternation in microstructure and texture of the weld metal. Higher δ-ferrite formation and high-angle boundaries along with the <101> + <001> grain growth direction of the weld metal W1 were responsible for dislocation pile-ups, SFs, deformation twinning, and the induced martensite with consequent strain hardening during tensile deformation. Also, fusion boundary being the weakest link in the welded structure, failure took place mainly at this region.

  18. A System for Delivering Mechanical Stimulation and Robot-Assisted Therapy to the Rat Whisker Pad during Facial Nerve Regeneration

    PubMed Central

    Heaton, James T.; Knox, Christopher; Malo, Juan; Kobler, James B.; Hadlock, Tessa A.

    2013-01-01

    Functional recovery is typically poor after facial nerve transection and surgical repair. In rats, whisking amplitude remains greatly diminished after facial nerve regeneration, but can recover more completely if the whiskers are periodically mechanically stimulated during recovery. Here we present a robotic “whisk assist” system for mechanically driving whisker movement after facial nerve injury. Movement patterns were either pre-programmed to reflect natural amplitudes and frequencies, or movements of the contralateral (healthy) side of the face were detected and used to control real-time mirror-like motion on the denervated side. In a pilot study, twenty rats were divided into nine groups and administered one of eight different whisk assist driving patterns (or control) for 5–20 minutes, five days per week, across eight weeks of recovery after unilateral facial nerve cut and suture repair. All rats tolerated the mechanical stimulation well. Seven of the eight treatment groups recovered average whisking amplitudes that exceeded controls, although small group sizes precluded statistical confirmation of group differences. The potential to substantially improve facial nerve recovery through mechanical stimulation has important clinical implications, and we have developed a system to control the pattern and dose of stimulation in the rat facial nerve model. PMID:23475376

  19. Respiratory mechanics and plasma levels of tumor necrosis factor alpha and interleukin 6 are affected by gas humidification during mechanical ventilation in dogs.

    PubMed

    Hernández-Jiménez, Claudia; García-Torrentera, Rogelio; Olmos-Zúñiga, J Raúl; Jasso-Victoria, Rogelio; Gaxiola-Gaxiola, Miguel O; Baltazares-Lipp, Matilde; Gutiérrez-González, Luis H

    2014-01-01

    The use of dry gases during mechanical ventilation has been associated with the risk of serious airway complications. The goal of the present study was to quantify the plasma levels of TNF-alpha and IL-6 and to determine the radiological, hemodynamic, gasometric, and microscopic changes in lung mechanics in dogs subjected to short-term mechanical ventilation with and without humidification of the inhaled gas. The experiment was conducted for 24 hours in 10 dogs divided into two groups: Group I (n = 5), mechanical ventilation with dry oxygen dispensation, and Group II (n = 5), mechanical ventilation with oxygen dispensation using a moisture chamber. Variance analysis was used. No changes in physiological, hemodynamic, or gasometric, and radiographic constants were observed. Plasma TNF-alpha levels increased in group I, reaching a maximum 24 hours after mechanical ventilation was initiated (ANOVA p = 0.77). This increase was correlated to changes in mechanical ventilation. Plasma IL-6 levels decreased at 12 hours and increased again towards the end of the study (ANOVA p>0.05). Both groups exhibited a decrease in lung compliance and functional residual capacity values, but this was more pronounced in group I. Pplat increased in group I (ANOVA p = 0.02). Inhalation of dry gas caused histological lesions in the entire respiratory tract, including pulmonary parenchyma, to a greater extent than humidified gas. Humidification of inspired gases can attenuate damage associated with mechanical ventilation.

  20. Respiratory Mechanics and Plasma Levels of Tumor Necrosis Factor Alpha and Interleukin 6 Are Affected by Gas Humidification during Mechanical Ventilation in Dogs

    PubMed Central

    Hernández-Jiménez, Claudia; García-Torrentera, Rogelio; Olmos-Zúñiga, J. Raúl; Jasso-Victoria, Rogelio; Gaxiola-Gaxiola, Miguel O.; Baltazares-Lipp, Matilde; Gutiérrez-González, Luis H.

    2014-01-01

    The use of dry gases during mechanical ventilation has been associated with the risk of serious airway complications. The goal of the present study was to quantify the plasma levels of TNF-alpha and IL-6 and to determine the radiological, hemodynamic, gasometric, and microscopic changes in lung mechanics in dogs subjected to short-term mechanical ventilation with and without humidification of the inhaled gas. The experiment was conducted for 24 hours in 10 dogs divided into two groups: Group I (n = 5), mechanical ventilation with dry oxygen dispensation, and Group II (n = 5), mechanical ventilation with oxygen dispensation using a moisture chamber. Variance analysis was used. No changes in physiological, hemodynamic, or gasometric, and radiographic constants were observed. Plasma TNF-alpha levels increased in group I, reaching a maximum 24 hours after mechanical ventilation was initiated (ANOVA p = 0.77). This increase was correlated to changes in mechanical ventilation. Plasma IL-6 levels decreased at 12 hours and increased again towards the end of the study (ANOVA p>0.05). Both groups exhibited a decrease in lung compliance and functional residual capacity values, but this was more pronounced in group I. Pplat increased in group I (ANOVA p = 0.02). Inhalation of dry gas caused histological lesions in the entire respiratory tract, including pulmonary parenchyma, to a greater extent than humidified gas. Humidification of inspired gases can attenuate damage associated with mechanical ventilation. PMID:25036811

  1. DNA sequence-dependent mechanics and protein-assisted bending in repressor-mediated loop formation

    NASA Astrophysics Data System (ADS)

    Boedicker, James Q.; Garcia, Hernan G.; Johnson, Stephanie; Phillips, Rob

    2013-12-01

    As the chief informational molecule of life, DNA is subject to extensive physical manipulations. The energy required to deform double-helical DNA depends on sequence, and this mechanical code of DNA influences gene regulation, such as through nucleosome positioning. Here we examine the sequence-dependent flexibility of DNA in bacterial transcription factor-mediated looping, a context for which the role of sequence remains poorly understood. Using a suite of synthetic constructs repressed by the Lac repressor and two well-known sequences that show large flexibility differences in vitro, we make precise statistical mechanical predictions as to how DNA sequence influences loop formation and test these predictions using in vivo transcription and in vitro single-molecule assays. Surprisingly, sequence-dependent flexibility does not affect in vivo gene regulation. By theoretically and experimentally quantifying the relative contributions of sequence and the DNA-bending protein HU to DNA mechanical properties, we reveal that bending by HU dominates DNA mechanics and masks intrinsic sequence-dependent flexibility. Such a quantitative understanding of how mechanical regulatory information is encoded in the genome will be a key step towards a predictive understanding of gene regulation at single-base pair resolution.

  2. A novel mechanical lung model of pulmonary diseases to assist with teaching and training

    PubMed Central

    Chase, J Geoffrey; Yuta, Toshinori; Mulligan, Kerry J; Shaw, Geoffrey M; Horn, Beverley

    2006-01-01

    Background A design concept of low-cost, simple, fully mechanical model of a mechanically ventilated, passively breathing lung is developed. An example model is built to simulate a patient under mechanical ventilation with accurate volumes and compliances, while connected directly to a ventilator. Methods The lung is modelled with multiple units, represented by rubber bellows, with adjustable weights placed on bellows to simulate compartments of different superimposed pressure and compliance, as well as different levels of lung disease, such as Acute Respiratory Distress Syndrome (ARDS). The model was directly connected to a ventilator and the resulting pressure volume curves recorded. Results The model effectively captures the fundamental lung dynamics for a variety of conditions, and showed the effects of different ventilator settings. It was particularly effective at showing the impact of Positive End Expiratory Pressure (PEEP) therapy on lung recruitment to improve oxygenation, a particulary difficult dynamic to capture. Conclusion Application of PEEP therapy is difficult to teach and demonstrate clearly. Therefore, the model provide opportunity to train, teach, and aid further understanding of lung mechanics and the treatment of lung diseases in critical care, such as ARDS and asthma. Finally, the model's pure mechanical nature and accurate lung volumes mean that all results are both clearly visible and thus intuitively simple to grasp. PMID:16919173

  3. Arraying single microbeads in microchannels using dielectrophoresis-assisted mechanical traps

    NASA Astrophysics Data System (ADS)

    Tirapu-Azpiroz, Jaione; Temiz, Yuksel; Delamarche, Emmanuel

    2015-11-01

    Manipulating and immobilizing single microbeads in flowing fluids is relevant for biological assays and chemical tests but typically requires expensive laboratory equipment and trapping mechanisms that are not reversible. In this paper, we present a highly efficient and reversible mechanism for trapping microbeads by combining dielectrophoresis (DEP) with mechanical traps. The integration of planar electrodes and mechanical traps in a microchannel enables versatile manipulation of microbeads via DEP for their docking in recessed structures of mechanical traps. By simulating the combined effects of the hydrodynamic drag and DEP forces on microbeads, we explore a configuration of periodic traps where the beads are guided by the electrodes and immobilized in recess areas of the traps. The design of the electrode layout and operating configuration are optimized for the efficient trapping of single microbeads. We demonstrated the predicted guiding and trapping effectiveness of the design as well as the reversibility of the system on 10 μm polystyrene beads. Experimental verification used an array of 96 traps in an area of 420 × 420 μm2, reaching a trapping efficiency of 63% when 7 Vpp is applied to the electrodes under 80 nl min-1 flow rate conditions, and 98% of bead release when the voltage is turned off.

  4. Statistical mechanical model of gas adsorption in porous crystals with dynamic moieties

    PubMed Central

    Braun, Efrem; Carraro, Carlo; Smit, Berend

    2017-01-01

    Some nanoporous, crystalline materials possess dynamic constituents, for example, rotatable moieties. These moieties can undergo a conformation change in response to the adsorption of guest molecules, which qualitatively impacts adsorption behavior. We pose and solve a statistical mechanical model of gas adsorption in a porous crystal whose cages share a common ligand that can adopt two distinct rotational conformations. Guest molecules incentivize the ligands to adopt a different rotational configuration than maintained in the empty host. Our model captures inflections, steps, and hysteresis that can arise in the adsorption isotherm as a signature of the rotating ligands. The insights disclosed by our simple model contribute a more intimate understanding of the response and consequence of rotating ligands integrated into porous materials to harness them for gas storage and separations, chemical sensing, drug delivery, catalysis, and nanoscale devices. Particularly, our model reveals design strategies to exploit these moving constituents and engineer improved adsorbents with intrinsic thermal management for pressure-swing adsorption processes. PMID:28049851

  5. Studies Related to Chemical Mechanisms of Gas Formation in Hanford High-Level Nuclear Wastes

    SciTech Connect

    E. Kent Barefield; Charles L. Liotta; Henry M. Neumann

    2002-04-08

    The objective of this work is to develop a more detailed mechanistic understanding of the thermal reactions that lead to gas production in certain high-level waste storage tanks at the Hanford, Washington site. Prediction of the combustion hazard for these wastes and engineering parameters for waste processing depend upon both a knowledge of the composition of stored wastes and the changes that they undergo as a result of thermal and radiolytic decomposition. Since 1980 when Delagard first demonstrated that gas production (H2and N2O initially, later N2 and NH3)in the affected tanks was related to oxidative degradation of metal complexants present in the waste, periodic attempts have been made to develop detailed mechanisms by which the gases were formed. These studies have resulted in the postulation of a series of reactions that account for many of the observed products, but which involve several reactions for which there is limited, or no, precedent. For example, Al(OH)4 has been postulated to function as a Lewis acid to catalyze the reaction of nitrite ion with the metal complexants, NO is proposed as an intermediate, and the ratios of gaseous products may be a result of the partitioning of NO between two or more reactions. These reactions and intermediates have been the focus of this project since its inception in 1996.

  6. Microstructural characterization and some mechanical properties of gas-borided Inconel 600-alloy

    NASA Astrophysics Data System (ADS)

    Makuch, N.; Kulka, M.

    2014-09-01

    The excellent resistance of Ni-based alloys to corrosion and oxidation is well-known. Boriding can be applied to these alloys in order to obtain suitable wear protection. In this paper, two-stage gas boronizing in N2-H2-BCl3 atmosphere is proposed for the producing the boride layer on Inconel®600-alloy. This process consists in two stages alternately repeated: saturation by boron and diffusion annealing. Such a gas boriding is applied in order to accelerate the saturation by boron and its diffusion. It turns out to be more effective because of eliminating the excess of boron, diffusing into the substrate, during the second stage. Microstructure and some mechanical properties of the produced layer are presented. Microstructural characterization is studied with using an optical microscope, scanning electron microscope, energy-dispersive x-ray microanalysis and x-ray diffraction. The diffusion zone consists of the mixture of nickel and chromium borides, occurring in the compact boride zone and in the area located beneath, at grain boundaries. The improved hardness and wear resistance characterize the layer. The formed boride layer is significantly thicker than those-obtained by the pack-boronizing or paste process at comparable temperature and time. Simultaneously, the measured depth of layer is slightly smaller than that-reported for electrolytic boriding.

  7. EFFECTS OF TRITIUM GAS EXPOSURE ON THE DYNAMIC MECHANICAL PROPERTIES OF EPDM ELASTOMER

    SciTech Connect

    Clark, E; Gregory Staack, G

    2007-08-13

    Samples of ethylene propylene diene monomer (EPDM) elastomer were exposed to tritium gas in closed containers initially at 101 kPa (1 atmosphere) pressure and ambient temperature for about one week. Tritium exposure effects on the samples were characterized by dynamic mechanical analysis (DMA) and radiolysis products were characterized by measuring the total final pressure and composition in the exposure containers at the end of exposure period. There was no effect of one week tritium exposure on the glass transition temperature, Tg, of the samples tested. Impurity gases produced in the closed containers included HT and lesser amounts of H{sub 2}, DTO, and CT{sub 4}. The total pressure remained the same during exposure.

  8. Effects of tritium gas exposure on the dynamic mechanical properties of EPDM elastomer

    SciTech Connect

    Clark, E. A.; Staack, G. C.

    2008-07-15

    Samples of ethylene propylene diene monomer (EPDM) elastomer were exposed to tritium gas in closed containers at 101 kPa (1 atmosphere) pressure and ambient temperature for about one week. Tritium exposure effects on the samples were characterized by dynamic mechanical analysis (DMA) and radiolysis products were characterized by measuring the total final pressure and composition in the exposure containers at the end of exposure period. There was no effect of one week tritium exposure on the glass transition temperature, Tg, of the samples tested. Impurity gases produced in the closed containers included HT and lesser amounts of H{sub 2}, DTO, and CT{sub 4}. The total pressure remained the same during exposure. (authors)

  9. Catalytic formation of ammonia: a lattice gas non-thermal Langmuir Hinshelwood mechanism

    NASA Astrophysics Data System (ADS)

    Khan, K. M.; Ahmad, N.; Albano, E. V.

    2001-11-01

    The catalytic formation of ammonia synthesis through dimers N 2 and H 2 has been studied through Monte-Carlo simulation via a model based on lattice gas non-thermal Langmuir-Hinshelwood mechanism, which involves the precursor motion of H 2 molecule. The most interesting feature of this model is it yields a steady reactive window, which is separated by continuous and discontinuous irreversible phase transitions. The phase diagram is qualitatively similar to well-known ZGB model. The width of the window depends upon the mobility of precursors. The continuous transition disappears when mobility of precursors is extended to third nearest neighbourhood. The dependence of production rate on partial pressure of hydrogen is predicted by simple mathematical equations in our model. Some more interesting results are observed when reaction between precursors and chemisorbed hydrogen atoms is considered.

  10. Compressibility effects on the dynamic characteristics of gas lubricated mechanical components

    NASA Astrophysics Data System (ADS)

    Arghir, Mihai; Matta, Pierre

    2009-11-01

    The present Note deals with the effects of compressibility on the linearized dynamic characteristics of gas lubricated mechanical components (journal and thrust bearings). Although the effect of compressibility on the static characteristics is well known, its influence on the dynamic characteristics is still not clearly understood. The present Note uses Lubrication's simplest model problems (the 1D slider) to qualitatively describe this effect. An analytic solution obtained for the parallel 1D slider depicts the variation of stiffness and damping with the excitation frequency and shows that this nonlinearity must be taken into account for squeeze number larger than 1. A convenient way of handling this nonlinearity in a dynamic system is described for an aerodynamic thrust bearing. To cite this article: M. Arghir, P. Matta, C. R. Mecanique 337 (2009).

  11. Mechanisms of gas generation from simulated SY tank farm wastes: FY 1995 progress report

    SciTech Connect

    Barefield, E.K.; Boatright, D.; Deshpande, A.; Doctorovich, F.; Liotta, C.L.; Neumann, H.M.; Seymore, S.

    1996-07-01

    The objective of this work is to develop a better understanding of the mechanism of formation of flammable gases in the thermal decomposition of metal complexants such as HEDTA and sodium glycolate in simulated SY tank farm waste mixtures. This report summarizes the results of work done at the Georgia Institute of Technology in fiscal year 1995. Topics discussed are (1) long-term studies of the decomposition of HEDTA in simulated waste mixtures under an argon atmosphere at 90 and 120{degrees}C, including time profiles for disappearance of HEDTA and appearance of products and the quantitative analysis of the kinetic behavior; (2) considerations of hydroxylamine as an intermediate in the production of nitrogen containing gases by HEDTA decomposition; (3) some thoughts on the revision of the global mechanism for thermal decomposition of HEDTA under argon; (4) preliminary long-term studies of the decomposition of HEDTA in simulated waste under an oxygen atmosphere at 120{degrees}C; (5) estimation of the amount of NH{sub 3} in the gas phase above HEDTA reaction mixtures; and (6) further, examination of the interaction of aluminum with nitrite ion using {sup 27}Al NMR spectroscopy. Section 2 of this report describes the work conducted over the last three years at GIT. Section 3 contains a discussion of the kinetic behavior of HEDTA under argon; Section 4 discusses the role of hydroxylamine. Thermal decomposition of HEDTA to ED3A is the subject of Section 5, and decomposition of HEDTA in simulated waste mixtures under oxygen is covered in Section 6. In Section 7 we estimate ammonia in the gas phase; the role of aluminum is discussed in Section 8.

  12. Mechanical behavior of ceramic composite hot-gas filters after exposure to severe environments

    SciTech Connect

    Pysher, D.J.; Weaver, B.L.; Smith, R.G.

    1995-08-01

    A novel type of hot-gas filter based on a ceramic fiber reinforced ceramic matrix has been developed, as reported at previous Fossil Energy Materials Conferences, through research activities at Oak Ridge National Laboratory (ORNL) and at the 3M Company. Simulated testing has been done at the Westinghouse Science and Technology Center. This filter technology has been extended to full size, 60 mm OD by 1.5 meter long candle filters and a commercially viable process for producing the filters has been developed filters are undergoing testing and demonstration use throughout the world for applications in pressurized fluidized-bed combustion (PFBC) and integrated gasification combined cycle (IGCC) plants. Demonstration tests of this ceramic composite filter along with other filters are in progress at the Tidd PFBC plant Mechanical tests were performed on the 3 M brand Ceramic Composite Candle Filter after exposure to various corrosive environments in order to assess its ability to function as a hot gas filter in coal-fired applications. Due to the different construction of ceramic composite filters and the thin composite wall versus the typical thick-walled monolithic filter, standard mechanical property tests had to be refined or modified to accurately determine the filters properties. These tests and filter property results will be described Longitudinal tensile and diametral O-ring compression tests were performed on as-produced candle filters as well as on filters which had been exposed to various environments. The exposures were for 1000 hrs at 850{degrees}C in wet air, in wet air containing Na{sub 2}CO{sub 3}, and in wet air containing NaCl. In addition, a filter which bad been coated with ash (Old Grimethorpe) was exposed to wet air at 850{degrees}C for 1000 hours.

  13. Mechanical Circulatory Support for the Failing Heart: Continuous-Flow Left Ventricular Assist Devices

    PubMed Central

    Englert, Joseph A. R.; Davis, Jennifer A.; Krim, Selim R.

    2016-01-01

    Background: Heart transplantation remains the definitive therapy for patients with advanced heart failure; however, owing to limited donor organ availability and long wait times, continuous-flow left ventricular assist devices (LVADs) have become standard therapy. Methods: This review summarizes the history, progression, function, and basic management of LVADs. Additionally, we provide some clinical pearls and important caveats for managing this unique patient population. Results: Currently, the most common LVADs being implanted in the United States are second- and third-generation devices, the HeartMate II (Thoratec Corp., St. Jude Medical) and the HeartWare HVAD (HeartWare International, Inc.). A newer third-generation pump, the HeartMate III (Thoratec Corp., St. Jude Medical), is designed to create an artificial pulse and is currently under investigation in the United States. Conclusion: LVAD use is promising, will continue to grow, and has become standard therapy for advanced heart failure as a bridge to recovery, as destination therapy, and as a bridge to transplantation. PMID:27660575

  14. Determination of mercury species in fish reference materials by gas chromatography-atomic fluorescence detection after closed-vessel microwave-assisted extraction.

    PubMed

    Nevado, Juan José Berzas; Martín-Doimeadios, Rosa Carmen Rodríguez; Bernardo, Francisco Javier Guzmán; Moreno, María Jiménez

    2005-11-04

    A simple and rapid method has been developed for speciation analysis of inorganic mercury and monomethylmercury (MMHg) in biological tissues. The procedure is based on the quantitative closed-vessel microwave-assisted leaching of mercury from biological samples with an alkaline extractant. The extracted mercury species are ethylated and analysed by capillary gas chromatography coupled to an atomic fluorescence detector via pyrolysis (CGC-pyro-AFS). The coupling between capillary gas chromatography and atomic fluorescence detector was optimized with the aim of minimizing the detection limits and time necessary for the species-selective determination of mercury compounds. The use of closed-vessel microwave-assisted extraction along with no clean-up steps before the ethylation leads to a significant total analysis time decrease with respect to similar procedures. The detection limit was 2 pg for MMHg (as Hg) and 1 pg for inorganic mercury. The method was validated by the analysis of DORM-2 (dogfish muscle) and DOLT-3 (dogfish liver) certified reference materials. The inorganic mercury and methylmercury concentrations found were in good agreement with the certified values. Recovery studies of fish muscle tissue spiked with inorganic mercury and MMHg were done to check the reliability of the method. In all cases satisfactory recoveries (92-105%) were obtained.

  15. Dynamical mechanism in aero-engine gas path system using minimum spanning tree and detrended cross-correlation analysis

    NASA Astrophysics Data System (ADS)

    Dong, Keqiang; Zhang, Hong; Gao, You

    2017-01-01

    Identifying the mutual interaction in aero-engine gas path system is a crucial problem that facilitates the understanding of emerging structures in complex system. By employing the multiscale multifractal detrended cross-correlation analysis method to aero-engine gas path system, the cross-correlation characteristics between gas path system parameters are established. Further, we apply multiscale multifractal detrended cross-correlation distance matrix and minimum spanning tree to investigate the mutual interactions of gas path variables. The results can infer that the low-spool rotor speed (N1) and engine pressure ratio (EPR) are main gas path parameters. The application of proposed method contributes to promote our understanding of the internal mechanisms and structures of aero-engine dynamics.

  16. Study of the Stereochemistry and Oxidation Mechanism of Plant Polyphenols, Assisted by Computational Chemistry.

    PubMed

    Matsuo, Yosuke

    2017-01-01

     In recent years, plant polyphenols have attracted great attention due to their wide range of biological activities. Certain kinds of polyphenols have complex structures; therefore, it is difficult to elucidate their total structure, including stereochemistry. In this study, we reinvestigated the stereostructures of two major C-glycosidic ellagitannins contained in Quercus plants, vescalagin and castalagin, and revised their stereostructures based on theoretical calculations of spectroscopic data. We also determined the structures of quercusnins A and B, isolated from the sapwood of Quercus crispula, based on theoretical calculations of NMR data. The oxidation mechanism of polyphenols has not been entirely elucidated. Therefore, we have also studied the oxidation mechanism of tea catechins during black tea production. Our investigation of the oxidation mechanism of black tea pigment theaflavins revealed that the difference in the position of the galloyl ester affords different oxidation products of theaflavins. In addition, oxidation products of pyrogallol-type catechins could be classified into three types-dehydrotheasinensins, theacitrins, and proepitheaflagallins; their detailed production and degradation mechanisms were also examined.

  17. Multivariate analysis of the volatile components in tobacco based on infrared-assisted extraction coupled to headspace solid-phase microextraction and gas chromatography-mass spectrometry.

    PubMed

    Yang, Yanqin; Pan, Yuanjiang; Zhou, Guojun; Chu, Guohai; Jiang, Jian; Yuan, Kailong; Xia, Qian; Cheng, Changhe

    2016-11-01

    A novel infrared-assisted extraction coupled to headspace solid-phase microextraction followed by gas chromatography with mass spectrometry method has been developed for the rapid determination of the volatile components in tobacco. The optimal extraction conditions for maximizing the extraction efficiency were as follows: 65 μm polydimethylsiloxane-divinylbenzene fiber, extraction time of 20 min, infrared power of 175 W, and distance between the infrared lamp and the headspace vial of 2 cm. Under the optimum conditions, 50 components were found to exist in all ten tobacco samples from different geographical origins. Compared with conventional water-bath heating and nonheating extraction methods, the extraction efficiency of infrared-assisted extraction was greatly improved. Furthermore, multivariate analysis including principal component analysis, hierarchical cluster analysis, and similarity analysis were performed to evaluate the chemical information of these samples and divided them into three classifications, including rich, moderate, and fresh flavors. The above-mentioned classification results were consistent with the sensory evaluation, which was pivotal and meaningful for tobacco discrimination. As a simple, fast, cost-effective, and highly efficient method, the infrared-assisted extraction coupled to headspace solid-phase microextraction technique is powerful and promising for distinguishing the geographical origins of the tobacco samples coupled to suitable chemometrics.

  18. Walnut-like In2S3 microspheres: ionic liquid-assisted solvothermal synthesis, characterization and formation mechanism

    NASA Astrophysics Data System (ADS)

    Chai, Bo; Zeng, Peng; Zhang, Xiaohu; Mao, Jin; Zan, Ling; Peng, Tianyou

    2012-03-01

    Walnut-like In2S3 microspheres were synthesized through an ionic liquid-assisted solvothermal method for the first time. The crystal structure and morphology of the as-synthesized products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectra (DRS) and nitrogen adsorption-desorption measurement. It was found that the additional amount of ionic liquid, solvothermal temperature and time played crucial roles in controlling the structure and morphology of the In2S3 microspheres. A possible formation mechanism of the walnut-like In2S3 microsphere was proposed on the basis of the experimental results.

  19. Walnut-like In2S3 microspheres: ionic liquid-assisted solvothermal synthesis, characterization and formation mechanism.

    PubMed

    Chai, Bo; Zeng, Peng; Zhang, Xiaohu; Mao, Jin; Zan, Ling; Peng, Tianyou

    2012-04-07

    Walnut-like In(2)S(3) microspheres were synthesized through an ionic liquid-assisted solvothermal method for the first time. The crystal structure and morphology of the as-synthesized products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectra (DRS) and nitrogen adsorption-desorption measurement. It was found that the additional amount of ionic liquid, solvothermal temperature and time played crucial roles in controlling the structure and morphology of the In(2)S(3) microspheres. A possible formation mechanism of the walnut-like In(2)S(3) microsphere was proposed on the basis of the experimental results.

  20. Increasing reliability of gas-air systems of piston and combined internal combustion engines by improving thermal and mechanic flow characteristics

    NASA Astrophysics Data System (ADS)

    Brodov, Yu. M.; Grigor'ev, N. I.; Zhilkin, B. P.; Plotnikov, L. V.; Shestakov, D. S.

    2015-12-01

    Results of experimental study of thermal and mechanical characteristics of gas exchange flow in piston and combined engines are presented. Ways for improving intake and exhaust processes to increase reliability of gas-air engine systems are proposed.

  1. Mechanisms for the formation of secondary organic aerosol components from the gas-phase ozonolysis of alpha-pinene.

    PubMed

    Ma, Yan; Russell, Andrew T; Marston, George

    2008-08-07

    Gas-phase ozonolysis of alpha-pinene was studied in static chamber experiments under 'OH-free' conditions. A range of multifunctional products-in particular low-volatility carboxylic acids-were identified in the condensed phase using gas chromatography coupled to mass spectrometry after derivatisation. The dependence of product yields on reaction conditions (humidity, choice of OH radical scavengers, added Criegee intermediate scavengers, NO(2)etc.) was investigated to probe the mechanisms of formation of these products; additional information was obtained by studying the ozonolysis of an enal and an enone derived from alpha-pinene. On the basis of experimental findings, previously suggested mechanisms were evaluated and detailed gas-phase mechanisms were developed to explain the observed product formation. Atmospheric implications of this work are discussed.

  2. Mechanical Activation-Assisted Reductive Leaching of Cadmium from Zinc Neutral Leaching Residue Using Sulfur Dioxide

    NASA Astrophysics Data System (ADS)

    Zhang, Chun; Min, Xiaobo; Chai, Liyuan; Zhang, Jianqiang; Wang, Mi

    2015-12-01

    In this work, zinc neutral leaching residue was mechanically activated by ball-milling. The subsequent leaching behavior and kinetics of cadmium extraction in a mixed SO2-H2SO4 system were studied. Changes in the crystalline phase, lattice distortion, particle size and morphology, which were induced by mechanical activation, were also investigated. The activated samples showed different physicochemical characteristics, and cadmium extraction was found to be easier than for the un-activated samples. Under the same conditions, mechanical activation contributed to higher cadmium leaching. The cadmium extraction kinetics at 75-95°C was found to fit the shrinking core model. The raw neutral leaching residue, and the samples activated for 60 min and 120 min had a calculated activation energy of 65.02 kJ/mol, 59.45 kJ/mol and 53.46 kJ/mol, respectively. The leaching residue was characterized by ICP, XRD and SEM analysis. According to XRD analysis, the main phases in the residue were lead sulfate (PbSO4), zinc sulfide (ZnS) and cadmium sulfide (CdS).

  3. Development of a novel technique to assess the vulnerability of micro-mechanical system components to environmentally assisted cracking.

    SciTech Connect

    Enos, David George; Goods, Steven Howard

    2006-11-01

    Microelectromechanical systems (MEMS) will play an important functional role in future DOE weapon and Homeland Security applications. If these emerging technologies are to be applied successfully, it is imperative that the long-term degradation of the materials of construction be understood. Unlike electrical devices, MEMS devices have a mechanical aspect to their function. Some components (e.g., springs) will be subjected to stresses beyond whatever residual stresses exist from fabrication. These stresses, combined with possible abnormal exposure environments (e.g., humidity, contamination), introduce a vulnerability to environmentally assisted cracking (EAC). EAC is manifested as the nucleation and propagation of a stable crack at mechanical loads/stresses far below what would be expected based solely upon the materials mechanical properties. If not addressed, EAC can lead to sudden, catastrophic failure. Considering the materials of construction and the very small feature size, EAC represents a high-risk environmentally induced degradation mode for MEMS devices. Currently, the lack of applicable characterization techniques is preventing the needed vulnerability assessment. The objective of this work is to address this deficiency by developing techniques to detect and quantify EAC in MEMS materials and structures. Such techniques will allow real-time detection of crack initiation and propagation. The information gained will establish the appropriate combinations of environment (defining packaging requirements), local stress levels, and metallurgical factors (composition, grain size and orientation) that must be achieved to prevent EAC.

  4. Microstructure and Mechanical Properties of Ultrafine-Grained Copper Produced Using Intermittent Ultrasonic-Assisted Equal-Channel Angular Pressing

    NASA Astrophysics Data System (ADS)

    Lu, Jianxun; Wu, Xiaoyu; Liu, Zhiyuan; Chen, Xiaoqiang; Xu, Bin; Wu, Zhaozhi; Ruan, Shuangchen

    2016-09-01

    We proposed intermittent ultrasonic-assisted equal-channel angular pressing (IU-ECAP) and used it to produce ultrafine-grained copper. The main aim of this work was to investigate the microstructure and mechanical properties of copper processed by IU-ECAP. We performed experiments with two groups of specimens: group 1 used conventional ECAP, and group 2 combined ECAP with intermittent ultrasonic vibration. The extrusion forces, microstructure, mechanical properties, and thermal stability of the two groups were compared. It was revealed that more homogeneous microstructure with smaller grains could be obtained by IU-ECAP compared with copper obtained using the traditional ECAP method. Mechanical testing showed that IU-ECAP significantly reduced the extrusion force and increased both the hardness and ultimate tensile stress owing to the higher dislocation density and smaller grains. IU-ECAP promotes conversion from low-angle grain boundaries to high-angle grain boundaries, and it increases the fractions of subgrains and dynamic recrystallized grains. Group 2 statically recrystallized at a higher temperature or longer duration than group 1, showing that group 2 had better thermal stability.

  5. Does benign paroxysmal positional vertigo explain age and gender variation in patients with vertigo by mechanical assistance maneuvers?

    PubMed

    Wang, Jing; Chi, Fang-Lu; Jia, Xian-Hao; Tian, Liang; Richard-Vitton, Th

    2014-11-01

    Benign paroxysmal positional vertigo (BPPV) is one of the most common peripheral vestibular diseases. The aim of this study was to explore the prevalence of BPPV in vertigo patients and the characteristics of BPPV in diagnosis and repositioning using mechanical assistance maneuvers and to analyze and summarize the reasons showing these characteristics. Seven hundred and twenty-six patients with vertigo were enrolled in this study. All patients were inspected by TRV armchair (SYNAPSYS, model TRV, France). BPPV patients were identified by the examination results. The characteristics and results using TRV armchair in diagnosis and treatment of BPPV were compared and analyzed. Of 726 vertigo patients, 209 BPPV patients were diagnosed, including 58 men and 151 women, aged from 16 to 87 (mean 52.90 ± 11.93) years. There were significant differences in the proportion of BPPV in male and female vertigo patients (P = 0.0233), but no differences among all age groups (P = 0.3201). Of 209 BPPV patients, 208 cases were repositioned by TRV armchair and no one appeared to have otolithic debris relocated into another canal in the repositioning procedures. 202 cases (97.12 %) were successful and six cases (2.87 %) were effective. None of them failed. This study suggests that BPPV is one of the most common diseases in the young vertigo patients, just like that in the old ones. Female of the species has predilection for BPPV and the site of predilection is the right posterior semicircular canals (PC-BPPV). The results of repositioning are perfect using mechanical assistance maneuvers.

  6. Effect of Alternate Supply of Shielding Gases of Tungsten Inert Gas Welding on Mechanical Properties of Austenitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Shinde, Neelam Vilas; Telsang, Martand Tamanacharya

    2016-07-01

    In the present study, an attempt is made to study the effect of alternate supply of the shielding gas in comparison with the conventional method of TIG welding with pure argon gas. The two sets of combination are used as 10-10 and 40-20 s for alternate supply of the Argon and Helium shielding gas respectively. The effect of alternate supply of shielding gas is studied on the mechanical properties like bend test, tensile test and impact test. The full factorial experimental design is applied for three set of combinations. The ANOVA is used to find significant parameters for the process and regression analysis used to develop the mathematical model. The result shows that the alternate supply of the shielding gas for 10-10 s provides better result for the bend, tensile and impact test as compared with the conventional argon gas and the alternate supply of 40-20 s argon and helium gas respectively. Welding speed can be increased for alternate supply of the shielding gas that can reduce the total welding cost.

  7. Geo-mechanical Model Testing for Stability of Underground Gas Storage in Halite During the Operational Period

    NASA Astrophysics Data System (ADS)

    Chen, Xuguang; Zhang, Qiangyong; Li, Shucai; Liu, Dejun

    2016-07-01

    A 3D geo-mechanical model test is conducted to study the stability of underground gas storage in halite, modeled after the Jintan gas storage constructed in bedded salt rock in China. A testing apparatus is developed to generate long-term stable trapezoid geostresses onto the model cavity, corresponding to the actual gas storage cavern. The time-depending character of the material is simulated using a rheological material, which was tested using a self-developed apparatus. The model cavern is built using an ellipsoid wooden mold divided into small blocks which are assembled and placed into the designed position during the model construction. They are then pulled out one by one to form the cavern. The ellipsoid cavern wall is then lined within a latex balloon. Gas is injected into the cavity and extracted to simulate the operational process of gas injection and recovery. Optical sensors embedded into the model to measure the displacement around the cavity showed that the largest deformation occurs in the middle section of the cavity. The deformation rate increases with increasing gas pressure. At 11 MPa the cavity is in equilibrium with the geostress. The pressure is highest during the gas recovery stages, indicating that gas recovery can threaten the cavern's operational stability, while high gas injection causes rock mass compression and deformation outward from the cavern. The deformation is the combination of cavern convergence and gas-induced rebound which leads to tensile and compression during gas injection and recovery. Hence, the fatigue properties of salt rock should be studied further.

  8. Mechanism of gas saturated oil viscosity anomaly near to phase transition point

    NASA Astrophysics Data System (ADS)

    Suleimanov, Baghir A.; Abbasov, Elkhan M.; Sisenbayeva, Marziya R.

    2017-01-01

    The article presents experimental studies of the phase behavior by the flash liberation test and of the viscosity of the live oil at different pressures. Unlike the typical studies at the pressure near the saturation pressure, the measurements were conducted at a relatively small pressure increment of 0.08-0.25 MPa. The viscosity anomaly was discovered experimentally near to the phase transition point in the range of the pressure levels P/Pb = 1-1.14 (Pb—bubble point pressure) and shows that it decreases about 70 times in comparison to the viscosity at the reservoir pressure. It was found that the bubble point pressure decreases significantly (up to 36%) with surfactant addition. Furthermore, the viscosity of the live oil at the surfactant concentration of 5 wt. % decreases almost 37 times in comparison to the viscosity at the reservoir pressure. The mechanism of observed effects was suggested based on the formation of the stable subcritical gas nuclei and associated slippage effect. The mechanism for the stabilization of the subcritical nuclei by the combined action of the surface and electrical forces, as well as the morphology of the formed nanobubbles, was considered. The model for determining the oil viscosity taking into account the slippage effect was suggested.

  9. Modifications in Structural, Electrical, Electronic and Mechanical Properties of Titanium Thin Films under different Gas Plasmas

    NASA Astrophysics Data System (ADS)

    Singh, Omveer; Dahiya, Raj P.; Malik, Hitendra K.

    2015-09-01

    In the recent past, Titanium thin films can be grown over different substrates such as silicon, glass and quartz by using versatile deposition techniques DC, RF sputtering, electronic beam and thermal evaporation etc. The grown films are then exposed in different gas environments for individual application. It has been found that Titanium nitride exhibits good chemical stability, mechanical and electrical properties. To investigate these properties in titanium nitride thin films, we have developed a new approach hot cathode arc discharge plasma system. By using this technique, we can measure plasma and nitriding parameters independently. In the present work, we have investigated gases mixture (Nitrogen, Argon and Hydrogen) effect on the structural, mechanical, electrical and electronic properties in plasma system. We have used 100% N2, 50% N2 + 50% Ar and 50% N2 + 50% H2 gases ratio for plasma nitriding. Structural and electronic structure properties are measured from X-ray diffractions (XRD) and X-ray photoelectron spectroscopy (XPS) respectively. The surface morphology of these films were measured using Atomic Force Microscopy (AFM) and the nano-indentation mode is used to find out the hardness of the samples. Government of India.

  10. Thermal-Mechanical Studies for Gas-Cooled Space Reactor Designs

    SciTech Connect

    Kapernick, Richard J.; Creamer, William C.

    2006-01-20

    Los Alamos National Laboratory has been involved in the development of reactor concepts to be used as a power source for nuclear electric propulsion and/or for surface power sources. As part of this effort, a high fidelity thermal-mechanical analysis method has been developed for rapid performance assessments of these designs. This method has been used to study several concept alternatives, including both annular and multi-hole monolithic block designs. This paper presents the analysis method developed and results of analyses performed for a gas-cooled reactor. Key results are 1) the annular block design is lower mass than the multi-hole block design, 2) fuel temperatures are effectively controlled by adjusting the number of fuel pins in the core, 3) large thermal-hydraulic performance enhancements are produced by increasing coolant pressure and/or helium mole fraction, and 4) manufacturing and assembly parameters have relatively small effects on thermal-hydraulic performance and care should be taken to balance mechanical design complexity and reliability issues with thermal-hydraulic performance.

  11. Processing, Microstructure and Mechanical Behavior of Ultrasonic Assisted Cast Magnesium 1wt% Silicon Carbide Nano-Composites

    NASA Astrophysics Data System (ADS)

    Erman, Ari

    The goal of this dissertation is to establish an understanding of processing -- microstructure -- mechanical behavior relationship in Mg-1wt% SiC metal matrix nano-composites fabricated via an ultrasonic assisted casting process, with the emphasis on the effect of the distribution of nanoparticles on this relationship. Ultrasonic assisted casting has been proved as an effective technique to distribute nanoparticles in Mg metal matrix nano-composites (MMNCs). Mg MMNCs reinforced with 1 wt% SiC nanoparticles, were cast by ultrasonic cavitation-based dispersion methods. Microstructural analyses of as cast specimens were conducted to characterize the grain size, shape and distribution, SiC nanoparticle size and distribution, and nanoparticle-matrix interface. Average grain size for the ultrasonic assisted cast composite specimens was 72 mum compared to 181 mum for pure Mg samples prepared by the same method. The average measured SiC nanoparticle size was 66 nm. TEM studies showed good local dispersion of SiC nanoparticles, with only a few small, widely spaced clusters. HRTEM showed a clean interface between SiC nanoparticles and the Mg matrix, with no evidence of secondary phases. The yield strength of Mg-1 wt% SiC nanocomposites was 67 MPa, which showed improvement from 47 MPa for the pure Mg samples. This extra strengthening is due to Orowan and Hall-Petch effects. Fatigue experiments were conducted to characterize the cyclic stress-strain response of pure Mg and Mg-1wt% SiC samples at 0.2%, 0.4% and 0.6% plastic strain amplitudes. The analyses of the cyclic stress response curves and hysteresis loops, combined with post failure TEM analyses provided an understanding of the role of twinning, and twin-particle interactions on the cyclic deformation behavior of Mg MMNCs. Tensile twinning and basal slip are the main forms of deformation mechanisms under compression, followed by detwinning and basal slip in subsequent tension. Fatigue lives of Mg MMNCs are comparable to

  12. Parametric Study On The CW Nd: YAG Laser Cutting Quality Of 1.25 mm Ultra Low Carbon Steel Sheets Using O2 Assist Gas

    NASA Astrophysics Data System (ADS)

    Salem, Hanadi G.; Abbas, Wafaa A.; Mansour, Mohy S.; Badr, Yehia A.

    2007-02-01

    There are many non-linear interaction factors responsible for the performance of the laser cutting process. Identification of the dominant factors that significantly affect the cut quality is important. In the current research, the gas pressure, laser power and scanning speed were selected as the cutting parameters. Effect of the cutting parameters on the cut quality was investigated, by monitoring the variation in hardness, oxide layer width and microstructural changes within the heat affected zone (HAZ). Results revealed that good quality cuts can be produced in ultra low carbon steel thin sheets, using CW Nd:YAG laser at a window of scanning speed ranging from 1100-1500 mm/min at a minimum heat input of 337watts under an assisting O2 gas pressure of 5 bar. Higher laser power resulted in either strengthening or softening in the HAZ surrounding the cut kerf. The oxide layer width is not affected by the energy density input but rather affected by the O2 gas pressure due to exothermal reaction.

  13. Evidence for a novel affinity mechanism of motor-assisted transport along microtubules.

    PubMed

    Wada, Y; Hamasaki, T; Satir, P

    2000-01-01

    In microtubule (MT) translocation assays, using colloidal gold particles coupled to monoclonal tubulin antibodies to mark positions along MTs, we found that relative motion is possible between the gold particle and an MT, gliding on dynein or kinesin. Such motion evidently occurred by an affinity release and rebinding mechanism that did not require motor activity on the particle. As the MTs moved, particles drifted to the trailing edge of the MT and then were released. Sometimes the particles transferred from one MT to another, moving orthogonally. Although motion of the particles was uniformly rearward, movement was toward the (-) or (+) end of the MT, depending on whether dynein or kinesin, respectively, was used in the assay. These results open possibilities for physiological mechanisms of organelle and other movement that, although dependent on motor-driven microtubule transport, do not require direct motor attachment between the organelle and the microtubule. Our observations on the direction of particle drift and time of release may also provide confirmation in a dynamic system for the conclusion that beta tubulin is exposed at the (+) end of the MT.

  14. Some considerations about the possible mechanisms of lead assisted stress corrosion cracking of steam generator tubing

    SciTech Connect

    Helie, M.; Lambert, I.; Santarini, G.

    1995-12-31

    A number of experimental studies have been performed since the examination of tubes pulled from nuclear power plants revealed the presence of lead associated with secondary side mixed Inter/Trans-Granular Stress Corrosion Cracking (IG/TG SCC). Various testing methods were employed on Alloys 600, 690, and 800, and the available studies involve Constant Elongation Rate Tests (CERTs), constant deformation tests in caustic, neutral, or acidic solutions, as well as electrochemical tests and surface layer analyses. Complementary tests are presented on the influence of the solution temperature, and of the elongation rate in CERTS. An analysis of the various results obtained is interpreted in the framework of a mechanism involving both anodic dissolution and fracture events. This analysis indicates that such a mechanism can account for the influence of lead by considering a lowering of the global activation energy of the repassivation processes without changes in the apparent activation energy of the crack growth rate. Comparison to in-service cracking also indicates that the influence of lead seems more predominant in neutral pH solutions than in caustic or acidic ones.

  15. Generating Singlet Oxygen Bubbles: A New Mechanism for Gas-Liquid Oxidations in Water

    PubMed Central

    Bartusik, Dorota; Aebisher, David; Ghafari, BiBi

    2012-01-01

    Laser-coupled microphotoreactors were developed to bubble singlet oxygen [1O2 (1Δg)] into an aqueous solution containing an oxidizable compound. The reactors consisted of custom-modified SMA fiber-optic receptacles loaded with 150-μm silicon phthalocyanine glass sensitizer particles, where the particles were isolated from direct contact with water by a membrane adhesively bonded to the bottom of each device. A tube fed O2 gas to the reactor chambers. In the presence of O2, singlet oxygen was generated by illuminating the sensitizer particles with 669-nm light from an optical fiber coupled to the top of the reactor. The generated 1O2 was transported through the membrane by the O2 stream and formed bubbles in solution. In solution, singlet oxygen reacted with probe compounds (either 9,10-anthracene dipropionate dianion, trans-2-methyl-2-pentanoate anion, N-benzoyl-D,L-methionine, and N-acetyl-D,L-methionine) to give oxidized products in two stages. The early stage was rapid and showed that 1O2 transfer occurred via bubbles mainly in the bulk water solution. The later stage was slow, it arose only from 1O2-probe molecule contact at the gas/liquid interface. A mechanism is proposed that involves 1O2 mass transfer and solvation, where smaller bubbles provide better penetration of 1O2 into the flowing stream due to higher surface-to-volume contact between the probe molecules and 1O2. PMID:22260325

  16. Greenhouse gas emissions from mechanical and biological waste treatment of municipal waste.

    PubMed

    Clemens, J; Cuhls, C

    2003-06-01

    The mechanical and biological waste treatment (MBT) is an increasingly important technology for the treatment of municipal solid waste (MSW) before landfilling. This process includes composting of the material with intensive aeration in order to minimize the organic fraction that may induce methane and leachate emissions after landfilling. The exhaust air is treated by biofilters to remove odorous and volatile organic compounds. The emission of direct and indirect greenhouse gases, namely methane (CH4), carbon dioxide (CO2), ammonia (NH3), nitric (NO) and nitrous oxide (N2O) was studied in four existing treatment plants. All gases except NO were emitted from the composting material. The emission factors were 12 to 185 kg ton(-1) substrate for CO2, 6-12 x 10(3) g ton(-1) substrate for CH4, 1.44 to 378 g ton(-1) substrate for N2O and 18-1150 g ton(-1) for NH3. In general, emission factors increased with increasing treatment time. The biofilters had no net effect on CH4, but removed 13-89% of the NH3. For CO2 the biofilters were a small, for N2O a major and for NO the exclusive source. Approximately 26% of the NH3-N that was removed in the biofilter was transformed into N2O when NH3 was the exclusive nitrogen source. Assuming that all municipal waste was treated by MBT, the emissions would account for 0.3 to 5% of the N2O and for 0.1 to 3% of the CH4 emissions in Germany, respectively. Optimising aeration and removing NH3 before the exhaust gas enters the biofilter could lead to reduced greenhouse gas emissions.

  17. Simulation of Mechanical Processes in Gas Storage Caverns for Short-Term Energy Storage

    NASA Astrophysics Data System (ADS)

    Böttcher, Norbert; Nagel, Thomas; Kolditz, Olaf

    2015-04-01

    In recent years, Germany's energy management has started to be transferred from fossil fuels to renewable and sustainable energy carriers. Renewable energy sources such as solar and wind power are subjected by fluctuations, thus the development and extension of energy storage capacities is a priority in German R&D programs. This work is a part of the ANGUS+ Project, funded by the federal ministry of education and research, which investigates the influence of subsurface energy storage on the underground. The utilization of subsurface salt caverns as a long-term storage reservoir for fossil fuels is a common method, since the construction of caverns in salt rock is inexpensive in comparison to solid rock formations due to solution mining. Another advantage of evaporate as host material is the self-healing behaviour of salt rock, thus the cavity can be assumed to be impermeable. In the framework of short-term energy storage (hours to days), caverns can be used as gas storage reservoirs for natural or artificial fuel gases, such as hydrogen, methane, or compressed air, where the operation pressures inside the caverns will fluctuate more frequently. This work investigates the influence of changing operation pressures at high frequencies on the stability of the host rock of gas storage caverns utilizing numerical models. Therefore, we developed a coupled Thermo-Hydro-Mechanical (THM) model based on the finite element method utilizing the open-source software platform OpenGeoSys. The salt behaviour is described by well-known constitutive material models which are capable of predicting creep, self-healing, and dilatancy processes. Our simulations include the thermodynamic behaviour of gas storage process, temperature development and distribution on the cavern boundary, the deformation of the cavern geometry, and the prediction of the dilatancy zone. Based on the numerical results, optimal operation modes can be found for individual caverns, so the risk of host rock damage

  18. On the Importance of the Associative Carboxyl Mechanism for the Water-Gas Shift Reaction at Pt/CeO2 Interface Sites

    SciTech Connect

    Aranifard, Sara; Ammal, Salai Cheettu; Heyden, Andreas

    2014-03-06

    Periodic density functional theory calculations and microkinetic modeling are used to investigate the associative carboxyl pathways of the water-gas shift (WGS) reaction at the Pt/CeO2 (111) interface. Analysis of a microkinetic model based on parameters obtained from first principles suggests that the turnover frequencies for the CO-assisted associative carboxyl mechanism are comparable to experimental results. However, this microkinetic model containing various associative carboxyl pathways at interface sites cannot explain the experimentally observed activation barriers and reaction orders of Pt/CeO2 catalysts. Considering furthermore that a model of an associative carboxyl mechanism with redox regeneration, also derived from first principles and recently published by us, accurately predicts all kinetic parameters while displaying a 2 orders of magnitude higher turnover frequency, we conclude that at Pt/CeO2 interface sites, the WGS reaction follows a bifunctional Mars-van Krevelen mechanism in which support oxygen vacancies facilitate water dissociation.

  19. Formic acid catalyzed hydrolysis of SO3 in the gas phase: a barrierless mechanism for sulfuric acid production of potential atmospheric importance.

    PubMed

    Hazra, Montu K; Sinha, Amitabha

    2011-11-02

    Computational studies at the B3LYP/6-311++G(3df,3pd) and MP2/6-311++G(3df,3pd) levels are performed to explore the changes in reaction barrier height for the gas phase hydrolysis of SO(3) to form H(2)SO(4) in the presence of a single formic acid (FA) molecule. For comparison, we have also performed calculations for the reference reaction involving water assisted hydrolysis of SO(3) at the same level. Our results show that the FA assisted hydrolysis of SO(3) to form H(2)SO(4) is effectively a barrierless process. The barrier heights for the isomerization of the SO(3)···H(2)O···FA prereactive collision complex, which is the rate limiting step in the FA assisted hydrolysis, are found to be respectively 0.59 and 0.08 kcal/mol at the B3LYP/6-311++G(3df,3pd) and MP2/6-311++G(3df,3pd) levels. This is substantially lower than the ~7 kcal/mol barrier for the corresponding step in the hydrolysis of SO(3) by two water molecules--which is currently the accepted mechanism for atmospheric sulfuric acid production. Simple kinetic analysis of the relative rates suggests that the reduction in barrier height facilitated by FA, combined with the greater stability of the prereactive SO(3)···H(2)O···FA collision complex compared to SO(3)···H(2)O···H(2)O and the rather plentiful atmospheric abundance of FA, makes the formic acid mediated hydrolysis reaction a potentially important pathway for atmospheric sulfuric acid production.

  20. Spectacular reproduction: Ron's Angels and mechanical reproduction in the age of ART (assisted reproductive technology).

    PubMed

    Hafstein, Valdimar Tr

    2007-03-01

    Ron Harris captured the popular imagination in October 1999 with a website where he auctioned off the ova of fashion models to the highest bidder. This article treats the controversy surrounding Harris' site within a dual frame of critical theory's approach to reproduction and a folkloristic approach to discourse. The website fuses traditional narrative motifs and structures with the logic of advertising, seventies television, family-values rhetoric, and the fertility industry. I argue that the great attraction of ronsangels.com is that it put into relief the intervention of mechanical reproduction in human fertility together with the state of genetics at the turn of the 21st century. The result is not only a disconcerting aestheticization and commodification of biological reproduction, but also the biological reproduction of a particular aesthetic and moral code--a generation of reality by model.

  1. The fluid mechanics of a sac-type ventricular assist device.

    PubMed

    Clark, C; Jin, W; Glaser, A

    1990-12-01

    Flow visualisation and velocity measurement studies have been carried out on the liquid side of a sac-type VAD. The objectives have been to identify both good (e.g. short residence times) and bad (e.g. high turbulence levels) flow characteristics. The flow was visualised using polystyrene micro-spheres illuminated with white light on selected transverse planes across the pumping chamber and its inlet and outlet connections. These results then served as a guide for velocity measurements using laser-Doppler anemometry. Flow tests were run using water or a water/glycerol mixture. Operating conditions were determined from the appropriate fluid mechanics modelling laws to ensure dynamical similarity. Initially, steady flow behaviour was investigated including the effects of removal and insertion of the tilting-disc inlet and outlet valves. In subsequent full pumping tests, using a pneumatic driver, regions of high shear, separation, and high turbulence intensity have been identified.

  2. Atom-assisted quadrature squeezing of a mechanical oscillator inside a dispersive cavity

    NASA Astrophysics Data System (ADS)

    Chauhan, Anil Kumar; Biswas, Asoka

    2016-08-01

    We present a hybrid optomechanical scheme to achieve dynamical squeezing of position quadrature of a mesoscopic mechanical oscillator, that can be externally controlled by classical fields. A membrane-in-the-middle setup is employed, in which an atom in Λ configuration is considered to be trapped on either side of the membrane inside the cavity. We show that a considerable amount of squeezing (beyond the 3-dB limit) can be achieved and maintained at a transient time scale that is not affected by the spontaneous emission of the atom. Squeezing depends upon the initial preparation of atomic states. Further, a strong effective coupling (larger than the relevant decay rates) between the atom and the oscillator can be attained by using large control fields that pump the atom and the cavity. The effects of cavity decay and the phononic bath on squeezing are studied. The results are supported by the detailed analytical calculations.

  3. Analysis of vapor-liquid-solid mechanism in Au-assisted GaAs nanowire growth

    NASA Astrophysics Data System (ADS)

    Harmand, J. C.; Patriarche, G.; Péré-Laperne, N.; Mérat-Combes, M.-N.; Travers, L.; Glas, F.

    2005-11-01

    GaAs nanowires were grown by molecular-beam epitaxy on (111)B oriented surfaces, after the deposition of Au nanoparticles. Different growth durations and different growth terminations were tested. After the growth of the nanowires, the structure and the composition of the metallic particles were analyzed by transmission electron microscopy and energy dispersive x-ray spectroscopy. We identified three different metallic compounds: the hexagonal β'Au7Ga2 structure, the orthorhombic AuGa structure, and an almost pure Au face centered cubic structure. We explain how these different solid phases are related to the growth history of the samples. It is concluded that during the wire growth, the metallic particles are liquid, in agreement with the generally accepted vapor-liquid-solid mechanism. In addition, the analysis of the wire morphology indicates that Ga adatoms migrate along the wire sidewalls with a mean length of about 3μm.

  4. Mechanism of silver(I)-assisted growth of gold nanorods and bipyramids.

    PubMed

    Liu, Mingzhao; Guyot-Sionnest, Philippe

    2005-12-01

    The seed-mediated growth of gold nanostructures is shown to be strongly dependent on the gold seed nanocrystal structure. The gold seed solutions can be prepared such that the seeds are either single crystalline or multiply twinned. With added silver(I) in the cetyltrimethylammonium bromide (CTAB) aqueous growth solutions, the two types of seeds yield either nanorods or elongated bipyramidal nanoparticles, in good yields. The gold nanorods are single crystalline, with a structure similar to those synthesized electrochemically (Yu, Y. Y. et al. J. Phys. Chem. B 1997, 101, 6661). In contrast, the gold bipyramids are pentatwinned. These bipyramids are strikingly monodisperse in shape. This leads to the sharpest ensemble longitudinal plasmon resonance reported so far for metal colloid solutions, with an inhomogeneous width as narrow as 0.13 eV for a resonance at approximately 1.5 eV. Ag(I) plays an essential role in the growth mechanism. Ag(I) slows down the growth of the gold nanostructures. Ag(I) also leads to high-energy side facets that are {110} for the single crystalline gold nanorods and unusually highly stepped {11n} (n approximately 7) for the bipyramid. To rationalize these observations, it is proposed that it is the underpotential deposition of Ag(I) that leads to the dominance of the facets with the more open surface structures. This forms the basis for the one-dimensional growth mechanism of single crystal nanorods, while it affects the shape of the nanostructures growing along a single twinning axis.

  5. Operative Mechanism of Hole-Assisted Negative Charge Motion in Ground States of Radical-Anion Molecular Wires.

    PubMed

    Franco, Carlos; Burrezo, Paula Mayorga; Lloveras, Vega; Caballero, Rubén; Alcón, Isaac; Bromley, Stefan T; Mas-Torrent, Marta; Langa, Fernando; López Navarrete, Juan T; Rovira, Concepciò; Casado, Juan; Veciana, Jaume

    2017-01-18

    Charge transfer/transport in molecular wires over varying distances is a subject of great interest. The feasible transport mechanisms have been generally accounted for on the basis of tunneling or superexchange charge transfer operating over small distances which progressively gives way to hopping transport over larger distances. The underlying molecular sequential steps that likely take place during hopping and the operative mechanism occurring at intermediate distances have received much less attention given the difficulty in assessing detailed molecular-level information. We describe here the operating mechanisms for unimolecular electron transfer/transport in the ground state of radical-anion mixed-valence derivatives occurring between their terminal perchlorotriphenylmethyl/ide groups through thiophene-vinylene oligomers that act as conjugated wires of increasing length up to 53 Å. The unique finding here is that the net transport of the electron in the larger molecular wires is initiated by an electron-hole dissociation intermediated by hole delocalization (conformationally assisted and thermally dependent) forming transient mobile polaronic states in the bridge that terminate by an electron-hole recombination at the other wire extreme. On the contrary, for the shorter radical-anions our results suggest that a flickering resonance mechanism which is intermediate between hopping and superexchange is the operative one. We support these mechanistic interpretations by applying the pertinent biased kinetic models of the charge/spin exchange rates determined by electron paramagnetic resonance and by molecular structural level information obtained from UV-vis and Raman spectroscopies and by quantum chemical modeling.

  6. A Substrate-Assisted Mechanism of Nucleophile Activation in a Ser-His-Asp Containing C-C Bond Hydrolase

    SciTech Connect

    Ruzzini, Antonio C.; Bhowmik, Shiva; Ghosh, Subhangi; Yam, Katherine C.; Bolin, Jeffrey T.; Eltis, Lindsay D.

    2013-11-12

    The meta-cleavage product (MCP) hydrolases utilize a Ser–His–Asp triad to hydrolyze a carbon–carbon bond. Hydrolysis of the MCP substrate has been proposed to proceed via an enol-to-keto tautomerization followed by a nucleophilic mechanism of catalysis. Ketonization involves an intermediate, ESred, which possesses a remarkable bathochromically shifted absorption spectrum. We investigated the catalytic mechanism of the MCP hydrolases using DxnB2 from Sphingomonas wittichii RW1. Pre-steady-state kinetic and LC ESI/MS evaluation of the DxnB2-mediated hydrolysis of 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoic acid to 2-hydroxy-2,4-pentadienoic acid and benzoate support a nucleophilic mechanism catalysis. In DxnB2, the rate of ESred decay and product formation showed a solvent kinetic isotope effect of 2.5, indicating that a proton transfer reaction, assigned here to substrate ketonization, limits the rate of acylation. For a series of substituted MCPs, this rate was linearly dependent on MCP pKa2nuc ~ 1). Structural characterization of DxnB2 S105A:MCP complexes revealed that the catalytic histidine is displaced upon substrate-binding. The results provide evidence for enzyme-catalyzed ketonization in which the catalytic His–Asp pair does not play an essential role. The data further suggest that ESred represents a dianionic intermediate that acts as a general base to activate the serine nucleophile. This substrate-assisted mechanism of nucleophilic catalysis distinguishes MCP hydrolases from other serine hydrolases.

  7. Plasma Discharges in Gas Bubbles in Liquid Water: Breakdown Mechanisms and Resultant Chemistry

    NASA Astrophysics Data System (ADS)

    Gucker, Sarah M. N.

    is created either through flowing gas around the high voltage electrode in the discharge tube or self-generated by the plasma as in the steam discharge. This second method allows for large scale processing of contaminated water and for bulk chemical and optical analysis. Breakdown mechanisms of attached and unattached gas bubbles in liquid water were investigated using the first device. The breakdown scaling relation between breakdown voltage, pressure and dimensions of the discharge was studied. A Paschen-like voltage dependence for air bubbles in liquid water was discovered. The results of high-speed photography suggest the physical charging of the bubble due to a high voltage pulse; this charging can be significant enough to produce rapid kinetic motion of the bubble about the electrode region as the applied electric field changes over a voltage pulse. Physical deformation of the bubble is observed. This charging can also prevent breakdown from occurring, necessitating higher applied voltages to overcome the phenomenon. This dissertation also examines the resulting chemistry from plasma interacting with the bubble-liquid system. Through the use of optical emission spectroscopy, plasma parameters such as electron density, gas temperature, and molecular species production and intensity are found to have a time-dependence over the ac voltage cycle. This dependence is also source gas type dependent. These dependencies afford effective control over plasma-driven decomposition. The effect of plasma-produced radicals on various wastewater simulants is studied. Various organic dyes, halogenated compounds, and algae water are decomposed and assessed. Toxicology studies with melanoma cells exposed to plasma-treated dye solutions are completed, demonstrating the non-cytotoxic quality of the decomposition process. Thirdly, this dissertation examines the steam plasma system, developed through this research to circumvent the acidification associated with gas-feed discharges

  8. Durability Prediction of Solid Oxide Fuel Cell Anode Material under Thermo-Mechanical and Fuel Gas Contaminants Effects

    SciTech Connect

    Iqbal, Gulfam; Guo, Hua; Kang , Bruce S.; Marina, Olga A.

    2011-01-10

    Solid Oxide Fuel Cells (SOFCs) operate under harsh environments, which cause deterioration of anode material properties and service life. In addition to electrochemical performance, structural integrity of the SOFC anode is essential for successful long-term operation. The SOFC anode is subjected to stresses at high temperature, thermal/redox cycles, and fuel gas contaminants effects during long-term operation. These mechanisms can alter the anode microstructure and affect its electrochemical and structural properties. In this research, anode material degradation mechanisms are briefly reviewed and an anode material durability model is developed and implemented in finite element analysis. The model takes into account thermo-mechanical and fuel gas contaminants degradation mechanisms for prediction of long-term structural integrity of the SOFC anode. The proposed model is validated experimentally using a NexTech ProbostatTM SOFC button cell test apparatus integrated with a Sagnac optical setup for simultaneously measuring electrochemical performance and in-situ anode surface deformation.

  9. Investigations in physical mechanism of the oxidative desulfurization process assisted simultaneously by phase transfer agent and ultrasound.

    PubMed

    Bhasarkar, Jaykumar B; Chakma, Sankar; Moholkar, Vijayanand S

    2015-05-01

    This paper attempts to discern the physical mechanism of the oxidative desulfurization process simultaneously assisted by ultrasound and phase transfer agent (PTA). With different experimental protocols, an attempt is made to deduce individual beneficial effects of PTA and ultrasound on the oxidative desulfurization system, and also the synergy between the effects of PTA and ultrasound. Effect of PTA is more marked for mechanically stirred system due to mass transfer limitations, while intense emulsification due to ultrasound helps overcome the mass transfer limitations and reduces the extent of enhancement of oxidation by PTA. Despite application of PTA and ultrasound, the intrinsic factors and properties of the reactants such as polarity (and hence partition coefficient) and diffusivity have a crucial effect on the extent of oxidation. The intrinsic reactivity of the oxidant also plays a vital role, as seen from the extent of oxidation achieved with performic acid and peracetic acid. The interfacial transport of oxidant in the form of oxidant-PTA complex reduces the undesired consumption of oxidant by the reducing species formed during transient cavitation in organic medium, which helps effective utilization of oxidant towards desulfurization.

  10. Therapeutic effectiveness of instrument-assisted soft tissue mobilization for soft tissue injury: mechanisms and practical application

    PubMed Central

    Kim, Jooyoung; Sung, Dong Jun; Lee, Joohyung

    2017-01-01

    This article reviews the mechanism and effects of instrument-assisted soft tissue mobilization (IASTM), along with guidelines for its practical application. IASTM refers to a technique that uses instruments to remove scar tissues from injured soft tissues and facilitate healing process through formation of new extracellular matrix proteins such as collagen. Recently, frequent use of this instrument has increased in the fields of sports rehabilitation and athlete training. Some experimental studies and case reports have reported that IASTM can significantly improve soft tissue function and range of motion following sports injury, while also reducing pain. Based on the previous studies, it is thought that IASTM can help shorten the rehabilitation period and time to return to sports among athletes and ordinary people who have suffered sports injuries. However, few experimental studies of the mechanisms and effects of IASTM have examined, while case reports have accounted for the majority of articles. In the future, the scientific basis of IASTM and its reliability should be provided through well-designed experimental studies on humans. Moreover, IASTM studies that have mostly focused on tendons need to broaden their scope toward other soft tissues such as muscles and ligaments. PMID:28349028

  11. A Novel Pinhole-Assisted Mechanical Scanning 28-kHz Ultrasonic Device to Open the Blood-Brain Barrier

    NASA Astrophysics Data System (ADS)

    Liu, Hao-Li; Chen, Pin-Yuan; Wei, Kuo-Chen

    2011-09-01

    Disruption of the blood-brain barrier (BBB) may be transiently achieved via high-frequency focused ultrasound in the presence of microbubbles. In the present study, we sought to confirm that BBB opening can be induced with low-frequency (20-30 kHz) unfocused ultrasonic waves. We developed a novel method using a pinhole-assisted mechanical-scanning configuration that allows the regulation of the exposure patterns. A tight regulation of the ultrasound patterns can be achieved using a mechanical scanning device equipped with a pinhole. Rat and pig experiments were conducted to show the feasibility of our technique. Histological examination of the sonicated brains was performed to analyze the minimum pressure threshold and the safety of the method, and contrast-enhanced MRI was also used to investigate the BBB-opening patterns. The inherent advantages of our BBB opening method include improved portability, the possibility to obtain fairly wide areas of BBB opening and a low incidence of hemorrhagic complications. In addition, our system has the potential to reduce the need for image guidance for brain drug delivery for superficial brain lesions.

  12. Effect of process parameters on the mechanical properties of carbon nitride thin films synthesized by plasma assisted pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Tabbal, M.; Mérel, P.; Chaker, M.

    We present an investigation of the effect of the process parameters, namely deposition pressure and laser intensity, on the growth and mechanical properties of carbon nitride (CNx) thin films synthesized by plasma assisted pulsed laser deposition. Deposition at high remote plasma pressure (200 mTorr) enhances both growth rate and nitrogen incorporation (up to 40 at.%), but nano-indentation measurements indicate that these films are very soft and have poor mechanical properties. At low remote plasma pressure (0.5 mTorr), the nitrogen content varies from 24 to 16 at.% with increasing laser intensity as the films become much harder and more elastic, with hardness and Young's modulus values reaching 24 GPa and 230 GPa, respectively. These effects are explained in terms of a thermalization of the laser plasma at 200 mTorr and indicate that plasma activation of nitrogen does not provide any particular benefit to the film properties when deposition is performed at high pressure. However, at low pressure, the benefit of plasma activation is evidenced through enhanced nitrogen incorporation in the films while preserving the highly energetic species in the ablation plume. Such conditions lead to the synthesis, at room temperature, of hard and elastic films having properties close to those of fullerene-like CNx.

  13. Degradation kinetics and mechanism of aniline by heat-assisted persulfate oxidation.

    PubMed

    Xie, Xiaofang; Zhang, Yongqing; Huang, Weilin; Huang, Shaobing

    2012-01-01

    Oxidation of aniline by persulfate in aqueous solutions was investigated and the reaction kinetic rates under different temperature, persulfate concentration and pH conditions were examined in batch experiments. The results showed that, the aniline degradation followed pseudo first-order reaction model. Aniline degradation rate increased with increasing temperature or persulfate concentration. In the pH range of 3 to 11, a low aniline degradation rate was obtained at strong acid system (pH 3), while a high degradation rate was achieved at strong alkalinity (pH 11). Maximum aniline degradation occurred at pH 7 when the solution was in a weak level of acid and alkalinity (pH 5, 7 and 9). Produced intermediates during the oxidation process were identified using liquid chromatography-mass spectrometry technology. And nitrobenzene, 4-4'-diaminodiphenyl and 1-hydroxy-1,2-diphenylhydrazine have been identified as the major intermediates of aniline oxidation by persulfate and the degradation mechanism of aniline was also tentatively proposed.

  14. New sedimentary structures in seismites from SW Tanzania: Evaluating gas- vs. water-escape mechanisms of soft-sediment deformation

    NASA Astrophysics Data System (ADS)

    Hilbert-Wolf, Hannah L.; Roberts, Eric M.; Simpson, Edward L.

    2016-10-01

    Seismite horizons are abundant in Cretaceous sandstones of the Rukwa Rift Basin, southwestern Tanzania. Diverse morphologies of soft-sediment deformation are preserved, including two new, unusual sedimentary structures, herein referred to as 1) balloon-shaped inflation structures and 2) surface fractures with linked sandstone splays. This original description of new sedimentary structures contributes to the growing catalogue of seismically induced deformation features. Their unusual morphologies bring to the forefront an important, though seldom touched upon, question of how to differentiate between gas- and water-escape in soft-sediment deformation features. The recognition of the spectrum of soft-sediment deformation structures contained in strata and their deformational mechanisms is important because it permits the differentiation between triggering mechanisms, particularly seismic activity, and can constrain such events spatially and temporally. We interpret the surface fractures and linked sandstone splays to reflect a high gas effusion rate, formed by the release of high-pressure gas followed by a limited expulsion of water. The balloon-shaped inflation structures reflect lower gas effusion rates due to expulsion of lower pressure gas that did not breach the Cretaceous surface seal. When these gas pulses did breach the paleosurface, they formed gas-discharge pits. These seismogenic structures are consistent with deposition of Cretaceous strata in the Rukwa Rift during periods of active carbonatite volcanism, seismicity, and possibly hot spring activity. This documentation serves as an important data point for the re-examination of the classification scheme of soft-sediment deformation structures as primarily water-escape structures to accommodate for the genesis of some secondary sedimentary features by gas-escape.

  15. Gas bubble retention and its effect on waste properties: Retention mechanisms, viscosity, and tensile and shear strengths

    SciTech Connect

    Gauglitz, P.A.; Rassat, S.D.; Powell, M.R.

    1995-08-01

    Several of the underground nuclear storage tanks at Hanford have been placed on a flammable gas watch list, because the waste is either known or suspected to generate, store, and episodically release flammable gases. Because retention and episodic release of flammable gases from these tanks containing radioactive waste slurries are critical safety concerns, Pacific Northwest Laboratory (PNL) is studying physical mechanisms and waste properties that contribute to the episodic gas release from these storage tanks. This study is being conducted for Westinghouse Hanford Company as part of the PNL Flammable Gas project. Previous investigations have concluded that gas bubbles are retained by the slurry or sludge that has settled at the bottom of the tanks; however, the mechanisms responsible for the retention of these bubbles are not well understood. Understanding the rheological behavior of the waste, particularly of the settled sludge, is critical to characterizing the tendency of the waste to retain gas bubbles and the dynamics of how these bubbles are released from the waste. The presence of gas bubbles is expected to affect the rheology of the sludge, specifically its viscosity and tensile and shear strengths, but essentially no literature data are available to assess the effect of bubbles. The objectives of this study were to conduct experiments and develop theories to understand better how bubbles are retained by slurries and sludges, to measure the effect of gas bubbles on the viscosity of simulated slurries, and to measure the effect of gas bubbles on the tensile and shear strengths of simulated slurries and sludges. In addition to accomplishing these objectives, this study developed correlations, based on the new experimental data, that can be used in large-scale computations of waste tank physical phenomena.

  16. Assistance in Determining BACT for Simple-Cycle Natural Gas Turbine Peaker Project Proposed by Standard Energy Ventures

    EPA Pesticide Factsheets

    This document may be of assistance in applying the New Source Review (NSR) air permitting regulations including the Prevention of Significant Deterioration (PSD) requirements. This document is part of the NSR Policy and Guidance Database. Some documents in the database are a scanned or retyped version of a paper photocopy of the original. Although we have taken considerable effort to quality assure the documents, some may contain typographical errors. Contact the office that issued the document if you need a copy of the original.

  17. Mechanism of cholesterol-assisted oligomeric channel formation by a short Alzheimer β-amyloid peptide.

    PubMed

    Di Scala, Coralie; Troadec, Jean-Denis; Lelièvre, Clément; Garmy, Nicolas; Fantini, Jacques; Chahinian, Henri

    2014-01-01

    Alzheimer β-amyloid (Aβ) peptides can self-organize into oligomeric ion channels with high neurotoxicity potential. Cholesterol is believed to play a key role in this process, but the molecular mechanisms linking cholesterol and amyloid channel formation have so far remained elusive. Here, we show that the short Aβ22-35 peptide, which encompasses the cholesterol-binding domain of Aβ, induces a specific increase of Ca(2+) levels in neural cells. This effect is neither observed in calcium-free medium nor in cholesterol-depleted cells, and is inhibited by zinc, a blocker of amyloid channel activity. Double mutations V24G/K28G and N27R/K28R in Aβ22-35 modify cholesterol binding and abrogate channel formation. Molecular dynamic simulations suggest that cholesterol induces a tilted α-helical topology of Aβ22-35. This facilitates the establishment of an inter-peptide hydrogen bond network involving Asn-27 and Lys-28, a key step in the octamerization of Aβ22-35 which proceeds gradually until the formation of a perfect annular channel in a phosphatidylcholine membrane. Overall, these data give mechanistic insights into the role of cholesterol in amyloid channel formation, opening up new therapeutic options for Alzheimer's disease. Aβ22-35 peptide, which encompasses the cholesterol binding domain of Aβ, induces a specific increase of Ca(2+) level in neural cells. Double mutations V24G/K28G and N27R/K28R modify cholesterol binding and abrogate channels formation. Molecular dynamic simulations suggest that cholesterol induces a tilted α-helical peptide topology facilitating the formation of annular octameric channels, as schematically shown in the graphic (with a hydrogen bond shown in green for two vicinal peptides). Overall, the data give insights into the role of cholesterol in amyloid channel formation and open up new therapeutic options for Alzheimer's disease.

  18. Laryngeal response patterns influence the efficacy of mechanical assisted cough in amyotrophic lateral sclerosis

    PubMed Central

    Andersen, Tiina; Sandnes, Astrid; Brekka, Anne Kristine; Hilland, Magnus; Clemm, Hege; Fondenes, Ove; Tysnes, Ole-Bjørn; Heimdal, John-Helge; Halvorsen, Thomas; Vollsæter, Maria; Røksund, Ola Drange

    2017-01-01

    Background Most patients with amyotrophic lateral sclerosis (ALS) are treated with mechanical insufflation–exsufflation (MI-E) in order to improve cough. This method often fails in ALS with bulbar involvement, allegedly due to upper-airway malfunction. We have studied this phenomenon in detail with laryngoscopy to unravel information that could lead to better treatment. Methods We conducted a cross-sectional study of 20 patients with ALS and 20 healthy age-matched and sex-matched volunteers. We used video-recorded flexible transnasal fibre-optic laryngoscopy during MI-E undertaken according to a standardised protocol, applying pressures of ±20 to ±50 cm H2O. Laryngeal movements were assessed from video files. ALS type and characteristics of upper and lower motor neuron symptoms were determined. Results At the supraglottic level, all patients with ALS and bulbar symptoms (n=14) adducted their laryngeal structures during insufflation. At the glottic level, initial abduction followed by subsequent adduction was observed in all patients with ALS during insufflation and exsufflation. Hypopharyngeal constriction during exsufflation was observed in all subjects, most prominently in patients with ALS and bulbar symptoms. Healthy subjects and patients with ALS and no bulbar symptoms (n=6) coordinated their cough well during MI-E. Conclusions Laryngoscopy during ongoing MI-E in patients with ALS and bulbar symptoms revealed laryngeal adduction especially during insufflation but also during exsufflation, thereby severely compromising the size of the laryngeal inlet in some patients. Individually customised settings can prevent this and thereby improve and extend the use of non-invasive MI-E. PMID:27174631

  19. Hydrazine detection in the gas state and aqueous solution based on the Gabriel mechanism and its imaging in living cells.

    PubMed

    Cui, Lei; Peng, Zhixing; Ji, Chunfei; Huang, Junhai; Huang, Dongting; Ma, Jie; Zhang, Shuping; Qian, Xuhong; Xu, Yufang

    2014-02-11

    A new probe based on the Gabriel mechanism was designed and first used for hydrazine detection with high selectivity against other amines in aqueous solution. Importantly, the probe could be used for gas-state discrimination of hydrazine with different concentrations. Additionally, probe could also be applied for the imaging of hydrazine in living cells.

  20. Assisted Ventilation.

    PubMed

    Dries, David J

    2016-01-01

    Controlled Mechanical Ventilation may be essential in the setting of severe respiratory failure but consequences to the patient including increased use of sedation and neuromuscular blockade may contribute to delirium, atelectasis, and diaphragm dysfunction. Assisted ventilation allows spontaneous breathing activity to restore physiological displacement of the diaphragm and recruit better perfused lung regions. Pressure Support Ventilation is the most frequently used mode of assisted mechanical ventilation. However, this mode continues to provide a monotonous pattern of support for respiration which is normally a dynamic process. Noisy Pressure Support Ventilation where tidal volume is varied randomly by the ventilator may improve ventilation and perfusion matching but the degree of support is still determined by the ventilator. Two more recent modes of ventilation, Proportional Assist Ventilation and Neurally Adjusted Ventilatory Assist (NAVA), allow patient determination of the pattern and depth of ventilation. Proposed advantages of Proportional Assist Ventilation and NAVA include decrease in patient ventilator asynchrony and improved adaptation of ventilator support to changing patient demand. Work of breathing can be normalized with these modes as well. To date, however, a clear pattern of clinical benefit has not been demonstrated. Existing challenges for both of the newer assist modes include monitoring patients with dynamic hyperinflation (auto-positive end expiratory pressure), obstructive lung disease, and air leaks in the ventilator system. NAVA is dependent on consistent transduction of diaphragm activity by an electrode system placed in the esophagus. Longevity of effective support with this technique is unclear.

  1. Comparative study of matrix-assisted laser desorption/ionization and gas chromatography for quantitative determination of cocoa butter and cocoa butter equivalent triacylglycerol composition.

    PubMed

    Guyon, F; Absalon, Ch; Eloy, A; Salagoity, M H; Esclapez, M; Medina, B

    2003-01-01

    The triacylglycerol (TAG) composition study of cocoa butter (CB) and cocoa butter equivalents (CBEs) has been performed by gas chromatography (GC) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). These two techniques provided comparable results. The advantage of the MALDI technique was the detection of each compound comprising the triacylglycerol classes (Cn). Moreover, comparison of the data obtained by these two techniques indicated that TAG relative percentages could be obtained quantitatively with the MALDI technique. These techniques have been applied for the composition determination of CB + CBE mixtures. Encouraging results showed that it is possible to quantify an admixture containing as little as 4% of CBE.

  2. Automated fast extraction of nitrated polycyclic aromatic hydrocarbons from soil by focused microwave-assisted Soxhlet extraction prior to gas chromatography--electron-capture detection.

    PubMed

    Priego-Capote, F; Luque-García, J L; Luque de Castro, M D

    2003-04-25

    An approach for the automated fast extraction of nitrated polycyclic aromatic hydrocarbons (nitroPAHs) from soil, using a focused microwave-assisted Soxhlet extractor, is proposed. The main factors affecting the extraction efficiency (namely: irradiation power, irradiation time, number of cycles and extractant volume) were optimised by using experimental design methodology. The reduction of the nitro-PAHs to amino-PAHs and the derivatisation of the reduced analytes with heptafluorobutyric anhydride was mandatory prior to the separation-determination step by gas chromatography--electron-capture detection. The proposed approach has allowed the extraction of these pollutants from spiked and "real" contaminated soils with extraction efficiencies similar to those provided by the US Environmental Protection Agency methods 3540-8091, but with a drastic reduction in both the extraction time and sample handling, and using less organic solvent, as 75-85% of it was recycled.

  3. Ultrasonic nebulization extraction assisted dispersive liquid-liquid microextraction followed by gas chromatography for the simultaneous determination of six parabens in cosmetic products.

    PubMed

    Wei, Hongmin; Yang, Jinjuan; Zhang, Hanqi; Shi, Yuhua

    2014-09-01

    A simple, rapid, and efficient method of ultrasonic nebulization extraction assisted dispersive liquid-liquid microextraction was developed for the simultaneous determination of six parabens in cosmetic products. The analysis was carried out by gas chromatography. Water was used as the dispersive solvent instead of traditional organic disperser. The experimental factors affecting the extraction yield, such as the extraction solvent and volume, extraction time, dispersive solvent and volume, ionic strength, and centrifuging condition were studied and optimized in detail. The limit of detections for the target analytes were in the range of 2.0-9.5 μg/g. Good linear ranges were obtained with the coefficients ranging from 0.9934 to 0.9969. The proposed method was successfully applied to the analysis of six parabens in 16 cosmetic products. The recoveries of the target analytes in real samples ranged from 81.9 to 108.7%, and the relative standard deviations were <5.3%.

  4. Biosynthesis of Gold Nanoparticles and Identification of Capping Agent Using Gas Chromatography-Mass Spectrometry and Matrix Assisted Laser Desorption Ionization-Mass Spectrometry.

    PubMed

    Karthick, V; Kumar, V Ganesh; Dhas, T Stalin; Govindaraju, K; Sinha, Sweta; Singaravelu, G

    2015-06-01

    In the present study, gold nanoparticles (AuNPs) were synthesized using leaf extract of Syzygium jambolanum and capping agent has been explored. The synthesized AuNPs have been characterized using UV-visible spectroscopy (UV-vis), Fourier transform infrared spectroscopy (FTIR), high resolution transmission electron microscopy (HRTEM) and atomic force microscopic (AFM) analysis. The AuNPs show intense surface plasmon resonance (SPR) band at 528 nm and were found to be spherical and hexagonal in shape with particle size ranging from 20-30 nm. Transmission electron microscopy and atomic force microscopy were used to analyze the surface morphology of synthesized AuNPs. The capping ligand has been evaluated using matrix assisted laser desorption ionization-mass spectrometry (MALDI-MS) and gas chromatography-mass spectrometry (GC-MS) analysis.

  5. Determination of volatile components of green, black, oolong and white tea by optimized ultrasound-assisted extraction-dispersive liquid-liquid microextraction coupled with gas chromatography.

    PubMed

    Sereshti, Hassan; Samadi, Soheila; Jalali-Heravi, Mehdi

    2013-03-08

    Ultrasound assisted extraction (UAE) followed by dispersive liquid-liquid microextraction (DLLME) was used for extraction and preconcentration of volatile constituents of six tea plants. The preconcentrated compounds were analyzed by gas chromatography-mass spectrometry (GC-MS). Totally, 42 compounds were identified and caffeine was quantitatively determined. The main parameters (factors) of the extraction process were optimized by using a central composite design (CCD). Methanol and chloroform were selected as the extraction solvent and preconcentration solvent, respectively .The optimal conditions were obtained as 21 in for sonication time; 32°C for temperature; 27 L for volume of extraction solvent and 7.4% for salt concentration (NaCl/H(2)O). The determination coefficient (R(2)) was 0.9988. The relative standard deviation (RSD %) was 4.8 (n=5), and the enhancement factors (EFs) were 4.0-42.6.

  6. Determination of nonylphenol and octylphenol in paper by microwave-assisted extraction coupled to headspace solid-phase microextraction and gas chromatography-mass spectrometry.

    PubMed

    Latorre, A; Lacorte, S; Barceló, D; Montury, M

    2005-02-18

    A novel and simple method for the determination of active endocrine disrupter compounds (octylphenol OP, and nonylphenol NP) in paper using microwave-assisted extraction (MAE) and headspace solid-phase microextraction, coupled with gas chromatography-mass spectrometry has been developed. Parameters affecting the efficiency in the MAE process such as exposure time and extraction solvent were studied in order to determine operating conditions. The optimised method was linear over the range studied (1.25-125 microg kg(-1) for OP and 9.50-950 microg kg(-1) for NP) and showed good level of precision, with a RSD lower than 10% and detection limits at 0.10 and 4.56 microg kg(-1) for OP and NP, respectively. The results obtained from six different types of paper revealed the presence of the target compounds in all samples analysed, at levels ranging between 3 and 211 microg kg(-1).

  7. Stopped flow studies of the mechanisms of ozone-alkene reactions in the gas phase: tetramethylethylene

    SciTech Connect

    Martinez, R.I.; Herron, J.T.

    1987-02-12

    The reaction of ozone with tetramethylethylene (TME) has been studied in the gas phase at 294 K and 539 Pa (4 Torr) with a stopped-flow reactor coupled to a photoionization mass spectrometer. The concentrations of reactants and products were determined as a function of reaction time. The major products were (CH/sub 3/)/sub 2/CO, H/sub 2/CO, CH/sub 3/C(O)CH/sub 2/OH (hydroxyacetone), and CH/sub 3/C(O)C(O)H (methylglyoxal). Computer simulation of the experimentally observed temporal profiles supports the mechanism shown in Scheme I. The hot ester channel (R,R''COO ..-->.. R'C(O)OR''* ..-->.. products) available to the H/sub 2/COO formed by ozonolysis of terminal olefins R'R''C double bonded CH/sub 2/ is not available for alkyl-substituted R'R''COO. Thus the secondary chemistry for R'R''COO is substantially different from that for H/sub 2/COO.

  8. Preliminary Study of Strong-Sludge Gas Retention and Release Mechanisms in Clay Simulants

    SciTech Connect

    Gauglitz, Phillip A.; Buchmiller, William C.; Probert, Samuel G.; Owen, Antionette T.

    2010-10-12

    The Hanford Site has 28 double-shell tanks (DSTs) and 149 single-shell tanks (SSTs) containing radioactive wastes that are complex mixes of radioactive and chemical products. The mission of the Department of Energy’s River Protection Project is to retrieve and treat the Hanford tank waste for disposal and close the tank farms. A key aspect of the mission is to retrieve and transfer waste from the SSTs, which are at greater risk for leaking, into DSTs for interim storage until the waste is transferred to and treated in the Waste Treatment and Immobilization Plant. There is, however, limited space in the existing DSTs to accept waste transfers from the SSTs, and approaches to overcoming the limited DST space will benefit the overall mission. The purpose of this study is to summarize and analyze the key previous experiment that forms the basis for the relaxed controls and to summarize initial progress and results on new experiments focused on understanding the conditions that result in low gas retention. The work is ongoing; this report provides a summary of the initial findings. The previous large-scale test used about 50 m3 of sediment, which would be unwieldy for doing multiple parametric experiments. Accordingly, experiments will begin with smaller-scale tests to determine whether the desired mechanisms can be studied without the difficulty of conducting very large experiments.

  9. Formation Mechanism of Fe Nanocubes by Magnetron Sputtering Inert Gas Condensation.

    PubMed

    Zhao, Junlei; Baibuz, Ekaterina; Vernieres, Jerome; Grammatikopoulos, Panagiotis; Jansson, Ville; Nagel, Morten; Steinhauer, Stephan; Sowwan, Mukhles; Kuronen, Antti; Nordlund, Kai; Djurabekova, Flyura

    2016-04-26

    In this work, we study the formation mechanisms of iron nanoparticles (Fe NPs) grown by magnetron sputtering inert gas condensation and emphasize the decisive kinetics effects that give rise specifically to cubic morphologies. Our experimental results, as well as computer simulations carried out by two different methods, indicate that the cubic shape of Fe NPs is explained by basic differences in the kinetic growth modes of {100} and {110} surfaces rather than surface formation energetics. Both our experimental and theoretical investigations show that the final shape is defined by the combination of the condensation temperature and the rate of atomic deposition onto the growing nanocluster. We, thus, construct a comprehensive deposition rate-temperature diagram of Fe NP shapes and develop an analytical model that predicts the temporal evolution of these properties. Combining the shape diagram and the analytical model, morphological control of Fe NPs during formation is feasible; as such, our method proposes a roadmap for experimentalists to engineer NPs of desired shapes for targeted applications.

  10. Gas breakdown mechanism in pulse-modulated asymmetric ratio frequency dielectric barrier discharges

    NASA Astrophysics Data System (ADS)

    Wang, Qi; Sun, Jizhong; Nozaki, Tomohiro; Ding, Zhenfeng; Ding, Hongbin; Wang, Zhanhui; Wang, Dezhen

    2014-08-01

    The gas breakdown mechanisms, especially the roles of metastable species in atmospheric pressure pulse-modulated ratio frequency barrier discharges with co-axial cylindrical electrodes, were studied numerically using a one dimensional self-consistent fluid model. Simulation results showed that in low duty cycle cases, the electrons generated from the channels associated with metastable species played a more important role in initializing next breakdown than the direct ionization of helium atoms of electronic grounded states by electron-impact. In order to quantitatively evaluate the contribution to the discharge by the metastables, we defined a "characteristic time" and examined how the value varied with the gap distance and the electrode asymmetry. The results indicated that the lifetime of the metastable species (including He*and He2*) was much longer than that of the pulse-on period and as effective sources of producing electrons they lasted over a period up to millisecond. When the ratio of the outer radius to the inner radius of the cylindrical electrodes was far bigger than one, it was found that the metastables distributed mainly in a cylindrical region around the inner electrode. When the ratio decreased as the inner electrode moved outward, the density of metastables in the discharge region near the outer electrode became gradually noticeable. As the discharging gap continued to decrease, the two hill-shaped distributions gradually merged to one big hill. When the discharge spacing was fixed, asymmetric electrodes facilitated the discharge.

  11. Growth mechanisms of GaAs nanowires by gas source molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Plante, M. C.; LaPierre, R. R.

    2006-01-01

    GaAs nanowires were grown on GaAs (1 1 1)B substrates in a gas source molecular beam epitaxy system, using self-assembled Au particles with diameters between 20 and 800 nm as catalytic agents. The growth kinetics of the wires was investigated for substrate temperatures between 500 and 600 °C, and V/III flux ratios of 1.5 and 2.3. The broad distribution of Au particles enabled the first observation of two distinct growth regimes related to the size of the catalyst. The origins of this transition are discussed in terms of the various mass transport mechanisms that drive the wire growth. Diffusion of the growth species on the 2-D surface and up the wire sidewalls dominates for catalyst diameters smaller than ˜130 nm on average, while direct impingement on the catalyst followed by bulk diffusion through the Au particle appears to sustain the wire growth for larger catalyst diameters. A change in wire sidewall facets, indicating a probable transition in the crystal structure, is found to be primarily dependent on the V/III flux ratio.

  12. Microwave-assisted extraction: a simpler and faster method for the determination of ethyl glucuronide in hair by gas chromatography-mass spectrometry.

    PubMed

    Alvarez, Iván; Bermejo, Ana María; Tabernero, María Jesús; Fernández, Purificación; Cabarcos, Pamela; López, Patricia

    2009-02-01

    Alcohol is the most frequently abused "addictive substance" that causes serious social problems throughout the world; thus, alcoholism is of particular interest in clinical and forensic medicine. Alcohol biomarkers are physiological indicators of alcohol exposure or ingestion and may reflect the presence of an alcohol use disorder. The glucuronide conjugation is a minor pathway of ethanol metabolism. Ethyl glucuronide (EtG) is a marker of recent alcohol consumption that detects alcohol use reliably over a definite time period. The present paper describes a new method for the determination of EtG in hair. It is based both in the microwave-assisted extraction (MAE), to extract the analyte from hair samples, and gas chromatography-mass spectrometry (GC-MS), to identify and quantify the EtG in selected ion monitoring (SIM) mode. The method was applied to 15 hair samples from occasional alcohol users, obtaining positive results in all cases. It was fully validated, including a linear range (0.3-10 ng/mg) and the main precision parameters. In summary, the use of microwave-assisted extraction turned out to be a substantially simpler, faster, and a more sensitive procedure than any other conventional sample preparations.

  13. Microwave-assisted one-step extraction-derivatization for rapid analysis of fatty acids profile in herbal medicine by gas chromatography-mass spectrometry.

    PubMed

    Liu, Rui-Lin; Zhang, Jing; Mou, Zhao-Li; Hao, Shuang-Li; Zhang, Zhi-Qi

    2012-11-07

    A rapid and practical microwave-assisted one-step extraction-derivatization (MAED) method was developed for gas chromatography-mass spectrometry analysis of fatty acids profile in herbal medicine. Several critical experimental parameters for MAED, including reaction temperature, microwave power and the amount of derivatization reagent (methanol), were optimized with response surface methodology. The results showed that the chromatographic peak areas of total fatty acids and total unsaturated fatty acids content obtained with MAED were markedly higher than those obtained by the conventional Soxhlet or microwave extraction and then derivatization method. The investigation of kinetics and thermodynamics of the derivatization reaction revealed that microwave assistance could reduce activation energy and increase the Arrhenius pre-exponential factor. The MAED method simplified the sample preparation procedure, shortened the reaction time, but improved the extraction and derivatization efficiency of lipids and reduced ingredient losses, especially for the oxidization and isomerization of unsaturated fatty acids. The simplicity, speed and practicality of this method indicates great potential for high throughput analysis of fatty acids in natural medicinal samples.

  14. Polytetrafluoroethylene physisorption-assisted emulsification microextraction as a cleanup and preconcentration step in the gas chromatography determination of aliphatic hydrocarbons in marine sediment samples.

    PubMed

    Molaei, Saeideh; Saleh, Abolfazl; Ghoulipour, Vanik; Seidi, Shahram

    2017-02-01

    For the first time, the application of polytetrafluoroethylene powder as an extractant phase collector or holder in liquid-phase microextraction has been developed. For this purpose, the analytical performances of two different ways of applying polytetrafluoroethylene powder in microextraction methods including polytetrafluoroethylene physisorption-assisted emulsification microextraction and dispersive liquid-phase microextraction via polytetrafluoroethylene extractant phase holders have been compared for analysis of aliphatic hydrocarbons in aqueous phases. Under the same conditions, the former showed better extraction efficiencies over the latter and as a result, it was applied as preconcentration and cleanup step in the analysis of aliphatic hydrocarbons in sediment samples followed by gas chromatography analysis. The linearity of the polytetrafluoroethylene physisorption-assisted emulsification microextraction method was obtained over a range of 3.7 and 2000 ng/g (R(2) > 0.993). The relative standard deviations were less than 6.5% (n = 3). The limits of detection and quantification obtained by this method were 1.1-9.0 and 3.7-30 ng/g, respectively, indicating that satisfactory results were achieved by the procedure.

  15. Microwave-assisted extraction and large-volume injection gas chromatography tandem mass spectrometry determination of multiresidue pesticides in edible seaweed.

    PubMed

    García-Rodríguez, D; Carro, A M; Cela, R; Lorenzo, R A

    2010-09-01

    A microwave-assisted extraction method followed by clean-up with solid-phase extraction (SPE) combined with large-volume injection gas chromatography-tandem mass spectrometry (LVI-GC-MS/MS) for the analysis of 17 pesticides in wild and aquaculture edible seaweeds has been developed. An experimental central composite design was employed to evaluate the effects of the main variables potentially affecting the extraction (temperature, time, and solvent volume) and to optimize the process. The most effective microwave extraction conditions were achieved at 125 °C and 12 min with 24 mL of hexane/ethyl acetate (80:20). SPE clean-up of the extracts with graphitized carbon and Florisil, optimized by means of the experimental design, proved to be efficient in the removal of matrix interferences. The analytical recoveries were close to 100% for all the analytes, with relative standard deviations lower than 13%. The limits of detection ranged from 0.3 to 23.1 pg g(-1) and the limits of quantification were between 2.3 and 76.9 pg g(-1), far below the maximum residue levels established by the European Union for pesticides in seaweed. The results obtained prove the suitability of the microwave-assisted extraction for the routine analysis of pesticides in aquaculture and wild seaweed samples.

  16. Suppression of the quantum-mechanical collapse by repulsive interactions in a quantum gas

    SciTech Connect

    Sakaguchi, Hidetsugu; Malomed, Boris A.

    2011-01-15

    The quantum-mechanical collapse (alias fall onto the center of particles attracted by potential -r{sup -2}) is a well-known issue in quantum theory. It is closely related to the quantum anomaly, i.e., breaking of the scaling invariance of the respective Hamiltonian by quantization. We demonstrate that the mean-field repulsive nonlinearity prevents the collapse and thus puts forward a solution to the quantum-anomaly problem that differs from that previously developed in the framework of the linear quantum-field theory. This solution may be realized in the 3D or 2D gas of dipolar bosons attracted by a central charge and in the 2D gas of magnetic dipoles attracted by a current filament. In the 3D setting, the dipole-dipole interactions are also taken into regard, in the mean-field approximation, resulting in a redefinition of the scattering length which accounts for the contact repulsion between the bosons. In lieu of the collapse, the cubic nonlinearity creates a 3D ground state (GS), which does not exist in the respective linear Schroedinger equation. The addition of the harmonic trap gives rise to a tristability, in the case when the Schroedinger equation still does not lead to the collapse. In the 2D setting, the cubic nonlinearity is not strong enough to prevent the collapse; however, the quintic term does it, creating the GS, as well as its counterparts carrying the angular momentum (vorticity). Counterintuitively, such self-trapped 2D modes exist even in the case of a weakly repulsive potential r{sup -2}. The 2D vortical modes avoid the phase singularity at the pivot (r=0) by having the amplitude diverging at r{yields}0 instead of the usual situation with the amplitude of the vortical mode vanishing at r{yields}0 (the norm of the mode converges despite of the singularity of the amplitude at r{yields}0). In the presence of the harmonic trap, the 2D quintic model with a weakly repulsive central potential r{sup -2} gives rise to three confined modes, the middle

  17. Reprint of: A numerical modelling of gas exchange mechanisms between air and turbulent water with an aquarium chemical reaction

    NASA Astrophysics Data System (ADS)

    Nagaosa, Ryuichi S.

    2014-08-01

    This paper proposes a new numerical modelling to examine environmental chemodynamics of a gaseous material exchanged between the air and turbulent water phases across a gas-liquid interface, followed by an aquarium chemical reaction. This study uses an extended concept of a two-compartment model, and assumes two physicochemical substeps to approximate the gas exchange processes. The first substep is the gas-liquid equilibrium between the air and water phases, A(g)⇌A(aq), with Henry's law constant H. The second is a first-order irreversible chemical reaction in turbulent water, A(aq)+H2O→B(aq)+H+ with a chemical reaction rate κA. A direct numerical simulation (DNS) technique has been employed to obtain details of the gas exchange mechanisms and the chemical reaction in the water compartment, while zero velocity and uniform concentration of A is considered in the air compartment. The study uses the different Schmidt numbers between 1 and 8, and six nondimensional chemical reaction rates between 10(≈0) to 101 at a fixed Reynolds number. It focuses on the effects of the Schmidt number and the chemical reaction rate on fundamental mechanisms of the gas exchange processes across the interface.

  18. A numerical modelling of gas exchange mechanisms between air and turbulent water with an aquarium chemical reaction

    NASA Astrophysics Data System (ADS)

    Nagaosa, Ryuichi S.

    2014-01-01

    This paper proposes a new numerical modelling to examine environmental chemodynamics of a gaseous material exchanged between the air and turbulent water phases across a gas-liquid interface, followed by an aquarium chemical reaction. This study uses an extended concept of a two-compartment model, and assumes two physicochemical substeps to approximate the gas exchange processes. The first substep is the gas-liquid equilibrium between the air and water phases, A(g)⇌A(aq), with Henry's law constant H. The second is a first-order irreversible chemical reaction in turbulent water, A(aq)+H2O→B(aq)+H+ with a chemical reaction rate κA. A direct numerical simulation (DNS) technique has been employed to obtain details of the gas exchange mechanisms and the chemical reaction in the water compartment, while zero velocity and uniform concentration of A is considered in the air compartment. The study uses the different Schmidt numbers between 1 and 8, and six nondimensional chemical reaction rates between 10(≈0) to 101 at a fixed Reynolds number. It focuses on the effects of the Schmidt number and the chemical reaction rate on fundamental mechanisms of the gas exchange processes across the interface.

  19. Insights into secondary organic aerosol formation mechanisms from measured gas/particle partitioning of specific organic tracer compounds.

    PubMed

    Zhao, Yunliang; Kreisberg, Nathan M; Worton, David R; Isaacman, Gabriel; Weber, Robin J; Liu, Shang; Day, Douglas A; Russell, Lynn M; Markovic, Milos Z; VandenBoer, Trevor C; Murphy, Jennifer G; Hering, Susanne V; Goldstein, Allen H

    2013-04-16

    In situ measurements of organic compounds in both gas and particle phases were made with a thermal desorption aerosol gas chromatography (TAG) instrument. The gas/particle partitioning of phthalic acid, pinonaldehyde, and 6,10,14-trimethyl-2-pentadecanone is discussed in detail to explore secondary organic aerosol (SOA) formation mechanisms. Measured fractions in the particle phase (f(part)) of 6,10,14-trimethyl-2-pentadecanone were similar to those expected from the absorptive gas/particle partitioning theory, suggesting that its partitioning is dominated by absorption processes. However, f(part) of phthalic acid and pinonaldehyde were substantially higher than predicted. The formation of low-volatility products from reactions of phthalic acid with ammonia is proposed as one possible mechanism to explain the high f(part) of phthalic acid. The observations of particle-phase pinonaldehyde when inorganic acids were fully neutralized indicate that inorganic acids are not required for the occurrence of reactive uptake of pinonaldehyde on particles. The observed relationship between f(part) of pinonaldehyde and relative humidity suggests that the aerosol water plays a significant role in the formation of particle-phase pinonaldehyde. Our results clearly show it is necessary to include multiple gas/particle partitioning pathways in models to predict SOA and multiple SOA tracers in source apportionment models to reconstruct SOA.

  20. Pressure-assisted synthesis of HKUST-1 thin film on polymer hollow fiber at room temperature toward gas separation.

    PubMed

    Mao, Yiyin; Li, Junwei; Cao, Wei; Ying, Yulong; Sun, Luwei; Peng, Xinsheng

    2014-03-26

    The scalable fabrication of continuous and defect-free metal-organic framework (MOF) films on the surface of polymeric hollow fibers, departing from ceramic supported or dense composite membranes, is a huge challenge. The critical way is to reduce the growth temperature of MOFs in aqueous or ethanol solvents. In the present work, a pressure-assisted room temperature growth strategy was carried out to fabricate continuous and well-intergrown HKUST-1 films on a polymer hollow fiber by using solid copper hydroxide nanostrands as the copper source within 40 min. These HKUST-1 films/polyvinylidenefluoride (PVDF) hollow fiber composite membranes exhibit good separation performance for binary gases with selectivity 116% higher than Knudsen values via both inside-out and outside-in modes. This provides a new way to enable for scale-up preparation of HKUST-1/polymer hollow fiber membranes, due to its superior economic and ecological advantages.

  1. Alveolar recruiting maneuver in dogs under general anesthesia: effects on alveolar ventilation, gas exchange, and respiratory mechanics.

    PubMed

    Staffieri, F; De Monte, V; De Marzo, C; Scrascia, F; Crovace, A

    2010-06-01

    The aim of this study was to evaluate the effects of a recruiting maneuver (RM) on lung aeration, gas exchange, and respiratory mechanics during general anesthesia in mechanically ventilated dogs. A thoracic computed tomography (CT) scan, an arterial blood sample, and measurement of respiratory mechanics were performed 10 min before (baseline) and both 5 and 30 min after a vital capacity RM in 10 dogs under general anesthesia. The RM was performed by inflating the lung at 40 cm H(2)O for 20 s. Lung aeration was estimated by analyzing the radiographic attenuation of the CT images. Lung aeration and gas exchange improved significantly 5 min after the RM compared to baseline and returned to values similar to baseline by 30 min. Static lung compliance was not significantly affected by the RM. An RM induces a temporary improvement in lung function in healthy dogs under general anesthesia.

  2. Preferential Mode of gas invasion in sediments: Grain-scale mechanistic model of coupled multiphase fluid flow and sediment mechanics

    NASA Astrophysics Data System (ADS)

    Jain, A. K.; Juanes, R.

    2009-08-01

    We present a discrete element model for simulating, at the grain scale, gas migration in brine-saturated deformable media. We rigorously account for the presence of two fluids in the pore space by incorporating forces on grains due to pore fluid pressures and surface tension between fluids. This model, which couples multiphase fluid flow with sediment mechanics, permits investigation of the upward migration of gas through a brine-filled sediment column. We elucidate the ways in which gas migration may take place: (1) by capillary invasion in a rigid-like medium and (2) by initiation and propagation of a fracture. We find that grain size is the main factor controlling the mode of gas transport in the sediment, and we show that coarse-grain sediments favor capillary invasion, whereas fracturing dominates in fine-grain media. The results have important implications for understanding vent sites and pockmarks in the ocean floor, deep subseabed storage of carbon dioxide, and gas hydrate accumulations in ocean sediments and permafrost regions. Our results predict that in fine sediments, hydrate will likely form in veins following a fracture network pattern, and the hydrate concentration will likely be quite low. In coarse sediments, the buoyant methane gas is likely to invade the pore space more uniformly, in a process akin to invasion percolation, and the overall pore occupancy is likely to be much higher than for a fracture-dominated regime. These implications are consistent with laboratory experiments and field observations of methane hydrates in natural systems.

  3. Determination of triazine and chloroacetanilide herbicides in soils by microwave-assisted extraction (MAE) coupled to gas chromatographic analysis with either GC-NPD or GC-MS.

    PubMed

    Vryzas, Zisis; Papadopoulou-Mourkidou, Euphemia

    2002-08-28

    A simple and rapid method based on microwave-assisted extraction (MAE) coupled to gas chromatographic analysis was developed for the analysis of triazine (atrazine, cyanazine, metribuzine, simazine and deethylatrazine, and deisopropylatrazine) and chloroacetanilide (acetochlor, alachlor, and metolachlor) herbicide residues in soils. Soil samples are processed by MAE for 5 min at 80 degrees C in the presence of acetonitrile (20 mL/sample). Mean recovery values of most solutes are >80% in the 10 to 500 microg/kg fortification range with respective RSDs (relative standard deviations) < 20%. The limits of quantification (LOQ) and limits of detection (LOD) are 10 and 1 to 5 microg/kg, respectively. The method was validated with two types of soils containing 1.5 and 3.0% organic matter content, respectively; no statistically significant differences were found between solute recovery values from the two types of soils. The solute mean recovery values from freshly spiked (24 h aging) and spiked samples stored refrigerated for one week before processed were also not statistically different. Residue levels determined in field weathered soils were higher when soils were processed by MAE than with a comparison method based on flask-shaking of soil suspensions overnight. Extracts were analyzed by a gas chromatographic system equipped either with a thermionic (GC-NPD) or a mass spectrometric detector (GC-MS).

  4. Purge-assisted headspace solid-phase microextraction combined with gas chromatography-mass spectrometry for determination of chlorophenols in aqueous samples.

    PubMed

    Ho, Hsin-Pin; Lee, Ren-Jye; Lee, Maw-Rong

    2008-12-12

    A simple, economical and very effective method is demonstrated for simultaneous determination of 2,4-dichlorophenol, 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol and pentachlorophenol, in aqueous samples, by using purge-assisted headspace solid-phase microextraction (PA/HS-SPME) coupled to gas chromatography-mass spectrometry (GC-MS). In the new method, purging the sample enhances the removal of the trace chlorophenols without derivatization from the matrices to the headspace. Extraction parameters including extraction temperature, purge gas flow rate and extraction time were systematically investigated. Under optimal conditions, the relative standard deviations (RSDs) were 4-11% at 50 pg/mL and 5-14% at 5 pg/mL, respectively. The recoveries were in the range of 83-114%. Detection limits were determined at the fg level. These results indicate that PA/HS-SPME provides a significant contribution to highly efficient extraction of semi-volatile CPs, especially for pentachlorophenol, which has the smallest Henry's constant and large octanol-water partitioning coefficient. In addition, the proposed method was successfully applied to the analysis of chlorophenols in landfill leachate. New perspectives are opened for headspace extraction of relatively low vapor pressure compounds in complex matrices.

  5. Influence of chemical structure on hydration and gas transport mechanisms of sulfonated poly(aryl ether ketone) membranes.

    PubMed

    Simon, Sandra; Espuche, Eliane; Gouanvé, Fabrice; Chauveau, Edouard; Marestin, Catherine; Mercier, Régis

    2012-10-25

    This work reports the influence of the chemical structure of two sulfonated poly(aryl ether ketone)s (SPAEK) on the hydration and gas transport mechanism of thin membranes made thereupon. For this purpose, two sulfonated poly(aryl ether ketone)s having the same ionic exchange capacity (IEC) but bearing a different repartition of the sulfonic acid groups along the polymer backbone were prepared. These polymers were synthesized by direct copolymerization of two specific sulfonated precursors, bisphenol AF and 4,4'-difluorobenzophenone. The morphology of the membranes was studied by transmission electron microscopy, and the thermal properties of the ionomers were determined from differential scanning calorimetry and thermogravimetric analyses. A detailed analysis of the water sorption isotherms and kinetics was performed. The gas transport properties were also determined for He, H(2), and CO(2) in the full range of water activity. From the detailed analysis of the water sorption isotherm and of the relative contributions of the Fickian diffusion and relaxation phenomena, a water sorption mechanism was proposed in relation with the SPAEK architectures and polymers' chain mobility. This mechanism allowed explaining the different evolution of the gas transport properties observed as a function of the gas nature and hydration rate.

  6. CHARACTERIZATION OF CONDITIONS OF NATURAL GAS STORAGE RESERVOIRS AND DESIGN AND DEMONSTRATION OF REMEDIAL TECHNIQUES FOR DAMAGE MECHANISMS FOUND THEREIN

    SciTech Connect

    J.H. Frantz; K.E. Brown

    2003-02-01

    There are four primary goals of contract DE-FG26-99FT40703: (1) We seek to better understand how and why two damage mechanisms--(1) inorganic precipitants, and (2) hydrocarbons and organic residues, occur at the reservoir/wellbore interface in gas storage wells. (2) We plan on testing potential prevention and remediation strategies related to these two damage mechanisms in the laboratory. (3) We expect to demonstrate in the field, cost-effective prevention and remediation strategies that laboratory testing deems viable. (4) We will investigate new technology for the gas storage industry that will provide operators with a cost effective method to reduce non-darcy turbulent flow effects on flow rate. For the above damage mechanisms, our research efforts will demonstrate the diagnostic technique for determining the damage mechanisms associated with lost deliverability as well as demonstrate and evaluate the remedial techniques in the laboratory setting and in actual gas storage reservoirs. We plan on accomplishing the above goals by performing extensive lab analyses of rotary sidewall cores taken from at least two wells, testing potential remediation strategies in the lab, and demonstrating in the field the applicability of the proposed remediation treatments. The benefits from this work will be quantified from this study and extrapolated to the entire storage industry. The technology and project results will be transferred to the industry through DOE dissemination and through the industry service companies that work on gas storage wells. Achieving these goals will enable the underground gas storage industry to more cost-effectively mitigate declining deliverability in their storage fields. Work completed to date includes the following: (1) Solicited potential participants from the gas storage industry; (2) Selected one participant experiencing damage from inorganic precipitates; (3) Developed laboratory testing procedures; (4) Collected cores from National Fuel Gas

  7. Perspectives from Mechanical Circulatory Support Coordinators on the Pre-Implantation Decision Process for Destination Therapy Left Ventricular Assist Devices

    PubMed Central

    McIlvennan, Colleen K.; Matlock, Daniel D.; Narayan, Madhav P.; Nowels, Carolyn; Thompson, Jocelyn S.; Cannon, Anne; Bradley, William J.; Allen, Larry A.

    2015-01-01

    Objective To understand mechanical circulatory support (MCS) coordinators’ perspectives related to destination therapy left ventricular assist devices (DT LVAD) decision making Background MCS coordinators are central to the team that interacts with patients considering DT LVAD, and are well positioned to comment upon the pre-implantation process. Methods From August 2012–January 2013, MCS coordinators were recruited to participate in semi-structured, in-depth interviews. Established qualitative approaches were used to analyze and interpret data. Results Eighteen MCS coordinators from 18 programs were interviewed. We found diversity in coordinators’ roles and high programmatic variability in how DT LVAD decisions are approached. Despite these differences, three themes were consistently recommended: 1) DT LVAD is a major patient-centered decision: “you’re your best advocate…this may not be the best choice for you”; 2) this decision benefits from an iterative, multidisciplinary process: “It is not a one-time conversation”; and 3) this process involves a tension between conveying enough detail about the process yet not overwhelming patients: “It’s sometimes hard to walk that line to not scare them but not paint a rainbow and butterflies picture.” Conclusions MCS coordinators endorsed a shared decision-making process that starts early, uses non-biased educational materials, and involves a multidisciplinary team sensitive to the tension between conveying enough detail about the therapy yet not overwhelming patients. PMID:25724116

  8. Tailored Height Gradients in Vertical Nanowire Arrays via Mechanical and Electronic Modulation of Metal-Assisted Chemical Etching.

    PubMed

    Otte, M A; Solis-Tinoco, V; Prieto, P; Borrisé, X; Lechuga, L M; González, M U; Sepulveda, B

    2015-09-02

    In current top-down nanofabrication methodologies the design freedom is generally constrained to the two lateral dimensions, and is only limited by the resolution of the employed nanolithographic technique. However, nanostructure height, which relies on certain mask-dependent material deposition or etching techniques, is usually uniform, and on-chip variation of this parameter is difficult and generally limited to very simple patterns. Herein, a novel nanofabrication methodology is presented, which enables the generation of high aspect-ratio nanostructure arrays with height gradients in arbitrary directions by a single and fast etching process. Based on metal-assisted chemical etching using a catalytic gold layer perforated with nanoholes, it is demonstrated how nanostructure arrays with directional height gradients can be accurately tailored by: (i) the control of the mass transport through the nanohole array, (ii) the mechanical properties of the perforated metal layer, and (iii) the conductive coupling to the surrounding gold film to accelerate the local electrochemical etching process. The proposed technique, enabling 20-fold on-chip variation of nanostructure height in a spatial range of a few micrometers, offers a new tool for the creation of novel types of nano-assemblies and metamaterials with interesting technological applications in fields such as nanophotonics, nanophononics, microfluidics or biomechanics.

  9. Synthesis of nanoparticles from malleable and ductile metals using powder-free, reactant-assisted mechanical attrition.

    PubMed

    McMahon, Brandon W; Perez, Jesus Paulo L; Yu, Jiang; Boatz, Jerry A; Anderson, Scott L

    2014-11-26

    A reactant-assisted mechanochemical method was used to produce copious nanoparticles from malleable/ductile metals, demonstrated here for aluminum, iron, and copper. The milling media is intentionally degraded via a reactant-accelerated wear process, where the reactant aids particle production by binding to the metal surfaces, enhancing particle production, and reducing the tendency toward mechanochemical (cold) welding. The mechanism is explored by comparing the effects of different types of solvents and solvent mixtures on the amount and type of particles produced. Particles were functionalized with oleic acid to aid in particle size separation, enhance dispersion in hydrocarbon solvents, and protect the particles from oxidation. For aluminum and iron, the result is air-stable particles, but for copper, the suspended particles are found to dissolve when exposed to air. Characterization was performed using electron microscopy, dynamic light scattering, Fourier transform infrared spectroscopy, solid state nuclear magnetic resonance, and X-ray photoelectron spectroscopy. Density functional theory was used to examine the nature of carboxylic acid binding to the aluminum surface, confirming the dominance of bridging bidentate binding.

  10. Hemolysate-mediated platelet aggregation: an additional risk mechanism contributing to thrombosis of continuous flow ventricular assist devices.

    PubMed

    Tran, Phat L; Pietropaolo, Maria-Grazia; Valerio, Lorenzo; Brengle, William; Wong, Raymond K; Kazui, Toshinobu; Khalpey, Zain I; Redaelli, Alberto; Sheriff, Jawaad; Bluestein, Danny; Slepian, Marvin J

    2016-07-01

    Despite the clinical success and growth in the utilization of continuous flow ventricular assist devices (cfVADs) for the treatment of advanced heart failure, hemolysis and thrombosis remain major limitations. Inadequate and/or ineffective anticoagulation regimens, combined with high pump speed and non-physiological flow patterns, can result in hemolysis which often is accompanied by pump thrombosis. An unexpected increase in cfVADs thrombosis was reported by multiple major VAD implanting centers in 2014, highlighting the association of hemolysis and a rise in lactate dehydrogenase (LDH) presaging thrombotic events. It is well established that thrombotic complications arise from the abnormal shear stresses generated by cfVADs. What remains unknown is the link between cfVAD-associated hemolysis and pump thrombosis. Can hemolysis of red blood cells (RBCs) contribute to platelet aggregation, thereby, facilitating prothrombotic complications in cfVADs? Herein, we examine the effect of RBC-hemolysate and selected major constituents, i.e., lactate dehydrogenase (LDH) and plasma free hemoglobin (pHb) on platelet aggregation, utilizing electrical resistance aggregometry. Our hypothesis is that elements of RBCs, released as a result of shear-mediated hemolysis, will contribute to platelet aggregation. We show that RBC hemolysate and pHb, but not LDH, are direct contributors to platelet aggregation, posing an additional risk mechanism for cfVAD thrombosis.

  11. Temperature assisted radiative and non-radiative recombination mechanisms in sillimanite (Al2SiO5) mineral

    NASA Astrophysics Data System (ADS)

    Kalita, J. M.; Wary, G.

    2017-03-01

    Temperature assisted luminescence in sillimanite (Al2SiO5) mineral was studied using thermoluminescence (TL). TL characteristics were studied in un-annealed and different annealed samples. Analysis showed that in the un-annealed sample, there was four electron trapping sites at depths 0.56, 0.87, 1.08, 1.32 eV and a hole trapping site at depth 3.63 eV from the conduction band acting as a recombination center. Further analysis on the annealed samples showed that the 0.56 eV trapping site was a pressure induced surface trap and it disappeared after annealing. However, the other trapping and recombination sites were found to be stable under thermal treatment. Due to this trap distribution, three partially overlapping glow peaks were observed. The glow peaks were found to be affected by thermal quenching. The thermal quenching parameters were evaluated from the composite glow curves by using Computerized Resolved Peak (CRP) technique. The activation energies for thermal quenching (W) estimated from the three peaks were found to be 0.69 ± 0.05, 0.92 ± 0.06 and 1.15 ± 0.03 eV respectively and the pre-exponential factors (C) were 1.12 × 108, 2.65 × 1010 and 9.23 × 1011 respectively. Based on the analysis, a band model was proposed and the whole radiative and non-radiative recombination mechanisms were discussed.

  12. Chronic effects of a cardiac assist device on the bulk and regional mechanics of the failed left ventricle in goats.

    PubMed

    Nakamura, T; Hayashi, K; Seki, J; Fukuda, S; Noda, H; Nakatani, T; Takano, H; Akutsu, T

    1993-05-01

    Pneumatically driven, diaphragm-type left ventricular assist devices (LVADs) were implanted into 8 goats with profound induced infarction to the left ventricle by using multiple ligations of the left anterior descending (LAD) coronary artery as well as small arteries in the LAD distribution area. Left ventricular diameters, regional myocardial segment lengths, and wall thicknesses were measured by sono-micrometers. After left ventricular function seemed to be recovered, the goats were weaned off the LVADs after a gradual decrease of pump bypass flow over several days. Thereafter, hemodynamic and cardiac parameters were observed for about 1 month more. Three animals recovered successfully owing to the LVAD pumping. Before starting pump-weaning procedures, the bulk mechanical work (BMW) done by the left ventricle during LVAD pumping and under temporary pump-off conditions was 0.08 +/- 0.01 (mean +/- SE) and 0.22 +/- 0.01 W/100 g left ventricular weight (LVW), respectively, while the regional mechanical work done by the normal myocardium (RMWn) was 1.5 +/- 0.4 and 4.3 +/- 0.9 mW/cm3 during pumping and under temporary pump-off conditions, respectively. BMW and RMWn values obtained under pump-on conditions both increased gradually during the weaning process. Even after pump removal, they continued to increase and reached constant values of about 0.3 W/100 g LVW and 10 mW/cm3, respectively, around 2 weeks after pump removal. Although the myocardium in the infarction area did no work for the first several days after surgery, it recovered to do some external work with the aid of LVAD pumping. However, recovery of left ventricular function owed more to compensatory increases in pumping ability of the remaining normal myocardium than to recovery of the damaged myocardium. The LVAD could salvage severely damaged hearts unless the infarction area exceeded 50% of the left ventricular wall.

  13. The mechanism of improved aeration due to gas films on leaves of submerged rice.

    PubMed

    Verboven, Pieter; Pedersen, Ole; Ho, Quang Tri; Nicolai, Bart M; Colmer, Timothy D

    2014-10-01

    Some terrestrial wetland plants, such as rice, have super-hydrophobic leaf surfaces which retain a gas film when submerged. O2 movement through the diffusive boundary layer (DBL) of floodwater, gas film and stomata into leaf mesophyll was explored by means of a reaction-diffusion model that was solved in a three-dimensional leaf anatomy model. The anatomy and dark respiration of leaves of rice (Oryza sativa L.) were measured and used to compute O2 fluxes and partial pressure of O2 (pO2 ) in the DBL, gas film and leaf when submerged. The effects of floodwater pO2 , DBL thickness, cuticle permeability, presence of gas film and stomatal opening were explored. Under O2 -limiting conditions of the bulk water (pO2  < 10 kPa), the gas film significantly increases the O2 flux into submerged leaves regardless of whether stomata are fully or partly open. With a gas film, tissue pO2 substantially increases, even for the slightest stomatal opening, but not when stomata are completely closed. The effect of gas films increases with decreasing cuticle permeability. O2 flux and tissue pO2 decrease with increasing DBL thickness. The present modelling analysis provides a mechanistic understanding of how leaf gas films facilitate O2 entry into submerged plants.

  14. Self-Activated Transparent All-Graphene Gas Sensor with Endurance to Humidity and Mechanical Bending.

    PubMed

    Kim, Yeon Hoo; Kim, Sang Jin; Kim, Yong-Jin; Shim, Yeong-Seok; Kim, Soo Young; Hong, Byung Hee; Jang, Ho Won

    2015-10-27

    Graphene is considered as one of leading candidates for gas sensor applications in the Internet of Things owing to its unique properties such as high sensitivity to gas adsorption, transparency, and flexibility. We present self-activated operation of all graphene gas sensors with high transparency and flexibility. The all-graphene gas sensors which consist of graphene for both sensor electrodes and active sensing area exhibit highly sensitive, selective, and reversible responses to NO2 without external heating. The sensors show reliable operation under high humidity conditions and bending strain. In addition to these remarkable device performances, the significantly facile fabrication process enlarges the potential of the all-graphene gas sensors for use in the Internet of Things and wearable electronics.

  15. Ghost peaks observed after AP-MALDI experiment may disclose new ionization mechanism of matrix assisted hypersonic velocity impact ionization

    PubMed Central

    Moskovets, Eugene

    2015-01-01

    RATIONALE Understanding the mechanisms of MALDI promises improvements in the sensitivity and specificity of many established applications in the field of mass spectrometry. This paper reports a serendipitous observation of a significant ion yield in a post-ionization experiment conducted after the sample has been removed from a standard atmospheric pressure (AP)-MALDI source. This post-ionization is interpreted in terms of collisions of microparticles moving with a hypersonic velocity into a solid surface. Calculations show that the thermal energy released during such collisions is close to that absorbed by the top matrix layer in traditional MALDI. The microparticles, containing both the matrix and analytes, could be detached from a film produced inside the inlet capillary during the sample ablation and accelerated by the flow rushing through the capillary. These observations contribute some new perspective to ion formation in both laser and laserless matrix-assisted ionization. METHODS An AP-MALDI ion source hyphenated with a three-stage high-pressure ion funnel system was utilized for peptide mass analysis. After the laser was turned off and MALDI sample was removed, ions were detected during a gradual reduction of the background pressure in the first funnel. The constant-rate pressure reduction led to the reproducible appearance of different singly- and doubly-charged peptide peaks in mass spectra taken a few seconds after the end of the MALDI analysis of a dried-droplet spot. RESULTS The ion yield as well as the mass range of ions observed with a significant delay after a completion of the primary MALDI analysis depended primarily on the background pressure inside the first funnel. The production of ions in this post-ionization step was exclusively observed during the pressure drop. A lower matrix background and significant increase in relative yield of double-protonated ions are reported. CONCLUSIONS The observations were partially consistent with a model of

  16. Experimental Investigation on the Mechanism of Chelation-Assisted, Copper(II) Acetate-Accelerated Azide-Alkyne Cycloaddition

    PubMed Central

    Kuang, Gui-Chao; Guha, Pampa M.; Brotherton, Wendy S.; Simmons, J. Tyler; Stankee, Lisa A.; Nguyen, Brian T.; Clark, Ronald J.; Zhu, Lei

    2011-01-01

    A mechanistic model is formulated to account for the high reactivity of chelating azides (organic azides capable of chelation-assisted metal coordination at the alkylated azido nitrogen position) and copper(II) acetate (Cu(OAc)2) in copper(II)-mediated azide-alkyne cycloaddition (AAC) reactions. Fluorescence and 1H NMR assays are developed for monitoring the reaction progress in two different solvents – methanol and acetonitrile. Solvent kinetic isotopic effect and pre-mixing experiments give credence to the proposed different induction reactions for converting copper(II) to catalytic copper(I) species in methanol (methanol oxidation) and acetonitrile (alkyne oxidative homocoupling), respectively. The kinetic orders of individual components in a chelation-assisted, copper(II)-accelerated AAC reaction are determined in both methanol and acetonitrile. Key conclusions resulting from the kinetic studies include (1) the interaction between copper ion (either in +1 or +2 oxidation state) and a chelating azide occurs in a fast, pre-equilibrium step prior to the formation of the in-cycle copper(I)-acetylide, (2) alkyne deprotonation is involved in several kinetically significant steps, and (3) consistent with prior experimental and computational results by other groups, two copper centers are involved in the catalysis. The X-ray crystal structures of chelating azides with Cu(OAc)2 suggest a mechanistic synergy between alkyne oxidative homocoupling and copper(II)-accelerated AAC reactions, in which both a bimetallic catalytic pathway and a base are involved. The different roles of the two copper centers (a Lewis acid to enhance the electrophilicity of the azido group and a two-electron reducing agent in oxidative metallacycle formation, respectively) in the proposed catalytic cycle suggest that a mixed valency (+2 and +1) dinuclear copper species be a highly efficient catalyst. This proposition is supported by the higher activity of the partially reduced Cu(OAc)2 in

  17. Native and enzymatically modified wheat (Triticum aestivum L.) endogenous lipids in bread making: a focus on gas cell stabilization mechanisms.

    PubMed

    Gerits, Lien R; Pareyt, Bram; Masure, Hanne G; Delcour, Jan A

    2015-04-01

    Lipopan F and Lecitase Ultra lipases were used in straight dough bread making to study how wheat lipids affect bread loaf volume (LV) and crumb structure setting. Lipase effects on LV were dose and dough piece weight dependent. The bread quality improving mechanisms exerted by endogenous lipids were studied in terms of gluten network strengthening, which indirectly stabilizes gas cells, and in terms of direct interfacial gas cell stabilization. Unlike diacetyl tartaric esters of mono- and diacylglycerols (DATEM, used as control), lipase use did not impact dough extensibility. The effect on dough extensibility was therefore related to its lipid composition at the start of mixing. Both lipases and DATEM strongly increase the levels of polar lipids in dough liquor and their availability for and potential accumulation at gas cell interfaces. Lipases form lysolipids that emulsify other lipids. We speculate that DATEM competes with (endogenous) polar lipids for interacting with gluten proteins.

  18. Non-mechanical optical path switching and its application to dual beam spectroscopy including gas filter correlation radiometry

    NASA Technical Reports Server (NTRS)

    Sachse, Glen W. (Inventor); Wang, Liang-Guo (Inventor)

    1992-01-01

    A non-mechanical optical switch is developed for alternately switching a monochromatic or quasi-monochromatic light beam along two optical paths. A polarizer polarizes light into a single, e.g., vertical component which is then rapidly modulated into vertical and horizontal components by a polarization modulator. A polarization beam splitter then reflects one of these components along one path and transmits the other along the second path. In the specific application of gas filter correlation radiometry, one path is directed through a vacuum cell and one path is directed through a gas correlation cell containing a desired gas. Reflecting mirrors cause these two paths to intersect at a second polarization beam splitter which reflects one component and transmits the other to recombine them into a polarization modulated beam which can be detected by an appropriate single sensor.

  19. Gas chromatographic-mass spectrometric study of the oil fractions produced by microwave-assisted pyrolysis of different sewage sludges.

    PubMed

    Domínguez, A; Menéndez, J A; Inguanzo, M; Bernad, P L; Pis, J J

    2003-09-19

    The pyrolysis of sewage sludge was studied in a microwave oven using graphite as microwave absorber. The pyrolysis temperature ranged from 800 to 1000 degrees C depending on the type of sewage sludge. A conventional electrical furnace was also employed in order to compare the results obtained with both methods. The pyrolysis oils were trapped in a series of condensers and their characteristics such as elemental analysis and calorific value were determined and compared with those of the initial sludge. The oil composition was analyzed by GC-MS. The oils from the microwave oven had n-alkanes and 1-alkenes, aromatic compounds, ranging from benzene derivatives to polycyclic aromatic hydrocarbons (PAHs), nitrogenated compounds, long chain aliphatic carboxylic acids, ketones and esters and also monoterpenes and steroids. The oil from the electric oven was composed basically of PAHs such as naphthalene, acenapthylene, phenanthrene, fluoranthene, benzo[a]anthracene, benzofluoranthenes, benzopyrenes, indenepyrene, benzo[ghi]perylene, and anthanthrene. In contrast, these compounds were not produced in the case of microwave-assisted pyrolysis.

  20. Inactivation Kinetics and Mechanism of a Human Norovirus Surrogate on Stainless Steel Coupons via Chlorine Dioxide Gas

    PubMed Central

    Yeap, Jia Wei; Kaur, Simran; Lou, Fangfei; DiCaprio, Erin; Morgan, Mark; Linton, Richard

    2015-01-01

    Acute gastroenteritis caused by human norovirus is a significant public health issue. Fresh produce and seafood are examples of high-risk foods associated with norovirus outbreaks. Food contact surfaces also have the potential to harbor noroviruses if exposed to fecal contamination, aerosolized vomitus, or infected food handlers. Currently, there is no effective measure to decontaminate norovirus on food contact surfaces. Chlorine dioxide (ClO2) gas is a strong oxidizer and is used as a decontaminating agent in food processing plants. The objective of this study was to determine the kinetics and mechanism of ClO2 gas inactivation of a norovirus surrogate, murine norovirus 1 (MNV-1), on stainless steel (SS) coupons. MNV-1 was inoculated on SS coupons at the concentration of 107 PFU/coupon. The samples were treated with ClO2 gas at 1, 1.5, 2, 2.5, and 4 mg/liter for up to 5 min at 25°C and a relative humidity of 85%, and virus survival was determined by plaque assay. Treatment of the SS coupons with ClO2 gas at 2 mg/liter for 5 min and 2.5 mg/liter for 2 min resulted in at least a 3-log reduction in MNV-1, while no infectious virus was recovered at a concentration of 4 mg/liter even within 1 min of treatment. Furthermore, it was found that the mechanism of ClO2 gas inactivation included degradation of viral protein, disruption of viral structure, and degradation of viral genomic RNA. In conclusion, treatment with ClO2 gas can serve as an effective method to inactivate a human norovirus surrogate on SS contact surfaces. PMID:26475110

  1. Inactivation Kinetics and Mechanism of a Human Norovirus Surrogate on Stainless Steel Coupons via Chlorine Dioxide Gas.

    PubMed

    Yeap, Jia Wei; Kaur, Simran; Lou, Fangfei; DiCaprio, Erin; Morgan, Mark; Linton, Richard; Li, Jianrong

    2015-10-16

    Acute gastroenteritis caused by human norovirus is a significant public health issue. Fresh produce and seafood are examples of high-risk foods associated with norovirus outbreaks. Food contact surfaces also have the potential to harbor noroviruses if exposed to fecal contamination, aerosolized vomitus, or infected food handlers. Currently, there is no effective measure to decontaminate norovirus on food contact surfaces. Chlorine dioxide (ClO2) gas is a strong oxidizer and is used as a decontaminating agent in food processing plants. The objective of this study was to determine the kinetics and mechanism of ClO2 gas inactivation of a norovirus surrogate, murine norovirus 1 (MNV-1), on stainless steel (SS) coupons. MNV-1 was inoculated on SS coupons at the concentration of 10(7) PFU/coupon. The samples were treated with ClO2 gas at 1, 1.5, 2, 2.5, and 4 mg/liter for up to 5 min at 25°C and a relative humidity of 85%, and virus survival was determined by plaque assay. Treatment of the SS coupons with ClO2 gas at 2 mg/liter for 5 min and 2.5 mg/liter for 2 min resulted in at least a 3-log reduction in MNV-1, while no infectious virus was recovered at a concentration of 4 mg/liter even within 1 min of treatment. Furthermore, it was found that the mechanism of ClO2 gas inactivation included degradation of viral protein, disruption of viral structure, and degradation of viral genomic RNA. In conclusion, treatment with ClO2 gas can serve as an effective method to inactivate a human norovirus surrogate on SS contact surfaces.

  2. Teaching assistants' performance at identifying common introductory student difficulties in mechanics revealed by the Force Concept Inventory

    NASA Astrophysics Data System (ADS)

    Maries, Alexandru; Singh, Chandralekha

    2016-06-01

    The Force Concept Inventory (FCI) has been widely used to assess student understanding of introductory mechanics concepts by a variety of educators and physics education researchers. One reason for this extensive use is that many of the items on the FCI have strong distractor choices which correspond to students' alternate conceptions in mechanics. Instruction is unlikely to be effective if instructors do not know the common alternate conceptions of introductory physics students and explicitly take into account students' initial knowledge states in their instructional design. Here, we discuss research involving the FCI to evaluate one aspect of the pedagogical content knowledge of teaching assistants (TAs): knowledge of introductory student alternate conceptions in mechanics as revealed by the FCI. For each item on the FCI, the TAs were asked to identify the most common incorrect answer choice of introductory physics students. This exercise was followed by a class discussion with the TAs related to this task, including the importance of knowing student difficulties in teaching and learning. Then, we used FCI pretest and post-test data from a large population (˜900 ) of introductory physics students to assess the extent to which TAs were able to identify alternate conceptions of introductory students related to force and motion. In addition, we carried out think-aloud interviews with graduate students who had more than two semesters of teaching experience in recitations to examine how they reason about the task. We find that while the TAs, on average, performed better than random guessing at identifying introductory students' difficulties with FCI content, they did not identify many common difficulties that introductory physics students have after traditional instruction. We discuss specific alternate conceptions, the extent to which TAs are able to identify them, and results from the think-aloud interviews that provided valuable information about why TAs sometimes

  3. Influence of mechanical-biological waste pre-treatment methods on the gas formation in landfills

    SciTech Connect

    Bockreis, A. . E-mail: a.bockreis@iwar.tu-darmstadt.de; Steinberg, I.

    2005-07-01

    In order to minimise emissions and environmental impacts, only pre-treated waste should be disposed of. For the last six years, a series of continuous experiments has been conducted at the Institute WAR, TU Darmstadt, in order to determine the emissions from pre-treated waste. Different kinds of pre-treated waste were incubated in several reactors and various data, including production and composition of the gas and the leachate, were collected. In this paper, the interim results of gas production and the gas composition from different types of waste after a running time of six years are presented and discussed.

  4. Source Mechanism, Stress Triggering, and Hazard Analysis of Induced Seismicity in Oil/Gas Fields in Oman and Kuwait

    NASA Astrophysics Data System (ADS)

    Gu, C.; Toksoz, M. N.; Ding, M.; Al-Enezi, A.; Al-Jeri, F.; Meng, C.

    2015-12-01

    Induced seismicity has drawn new attentions in both academia and industry in recent years as the increasing seismic activity in the regions of oil/gas fields due to fluid injection/extraction and hydraulic fracturing. Source mechanism and triggering stress of these induced earthquakes are of great importance for understanding their causes and the physics of the seismic processes in reservoirs. Previous research on the analysis of induced seismic events in conventional oil/gas fields assumed a double couple (DC) source mechanism. The induced seismic data in this study are from both Oman and Kuwait. For the Oman data, the induced seismicity is monitored by both surface network (0gas field. The data used in the study consist of 800 events located by the surface network and 2000 events from the downhole network. For the Kuwait data a surface network is used to collect the local seismic data (0mechanisms and triggering stress. We determine the full moment tensor of the induced seismicity data, based on a full-waveform inversion method (Song and Toksöz, 2011). With the full moment tensor inversion results, Coulomb stress is calculated to investigate the triggering features of the induced seismicity data. Our results show a detailed evolution of 3D triggering stress in oil/gas fields from year 1999 to 2007 for Oman, and from year 2006 to 2015 for Kuwait. In addition, the local hazard corresponding to the induced seismicity in these oil/gas fields is assessed and compared to ground motion prediction due to large (M>5.0) regional tectonic earthquakes.

  5. Effect and mechanism of coking residual ammonia water treating by flue gas.

    PubMed

    Cheng, Z J; Yin, G J; Yang, L Q; Wang, W; Cheng, D D

    2001-04-01

    The treatment of coking residual ammonia water has been a big difficult problem at home and abroad, and there is no breakthrough research achievement in the past. The invention patent "The method of treating all coking wastewater or treating coking residual ammonia water by flue gas" has been successfully used in Huaian Steel Works for high concentration and organic industry wastewater treatment. Not only can it realize the wastewater zero discharge, but also the wastewater treatment has an effect of de-sulfur and de-nitrogen for flue gas. So that the flue gas exhaust can meet the requirement of emission standard. The mass transfer and heat transfer, fly ash absorption and coagulation, acid and alkali neutralization reaction, catalysis oxidation and reduction reaction in flue gas would be the major factors.

  6. ENVIRONMENTAL ANALYSIS BY AB INITIO QUANTUM MECHANICAL COMPUTATION AND GAS CHROMATOGRAPHY/FOURIER TRANSFORM INFRARED SPECTROMETRY.

    EPA Science Inventory

    Computational chemistry, in conjunction with gas chromatography/mass spectrometry/Fourier transform infrared spectrometry (GC/MS/FT-IR), was used to tentatively identify seven tetrachlorobutadiene (TCBD) isomers detected in an environmental sample. Computation of the TCBD infrare...

  7. Mechanisms of gas permeation through polymer membranes. Summary technical report, September 1991--August 1992

    SciTech Connect

    Stern, S.A.

    1992-12-31

    Progress is reported in two areas: (1) Concentration-temperature superposition principle (CTSP). CTSP is a theoretical model for describing the gas solubility in glassy polymers swollen by the penetrant gas. It has been extended to describe the dependence of gas diffusivity and permeability on penetrant pressure. Further extension to diffusion of gas mixtures is being studied. (2)Solubility of gases in poly(alkyl methacrylates). Solubility of methane in poly(ethyl methacrylate) and poly(n-butyl methacrylate) was measured; the Langmuir capacity constant was found to not reflect a lower excess free volume; an equation is given for relating the constant to the glass transition temperature. Solubility of ethane in the latter polymer is affected by plasticization.

  8. Surftherm: A program to analyze thermochemical and kinetic data in gas-phase and surface chemical reaction mechanisms

    SciTech Connect

    Coltrin, M.E.; Moffat, H.K.

    1994-06-01

    This report documents the Surftherm program that analyzes transport coefficient, thermochemical- and kinetic rate information in complex gas-phase and surface chemical reaction mechanisms. The program is designed for use with the Chemkin (gas-phase chemistry) and Surface Chemkin (heterogeneous chemistry) programs. It was developed as a ``chemist`s companion`` in using the Chemkin packages with complex chemical reaction mechanisms. It presents in tabular form detailed information about the temperature and pressure dependence of chemical reaction rate constants and their reverse rate constants, reaction equilibrium constants, reaction thermochemistry, chemical species thermochemistry and transport properties. This report serves as a user`s manual for use of the program, explaining the required input and the output.

  9. Soil radium, soil gas radon and indoor radon empirical relationships to assist in post-closure impact assessment related to near-surface radioactive waste disposal.

    PubMed

    Appleton, J D; Cave, M R; Miles, J C H; Sumerling, T J

    2011-03-01

    Least squares (LS), Theil's (TS) and weighted total least squares (WTLS) regression analysis methods are used to develop empirical relationships between radium in the ground, radon in soil and radon in dwellings to assist in the post-closure assessment of indoor radon related to near-surface radioactive waste disposal at the Low Level Waste Repository in England. The data sets used are (i) estimated ²²⁶Ra in the < 2 mm fraction of topsoils (eRa226) derived from equivalent uranium (eU) from airborne gamma spectrometry data, (ii) eRa226 derived from measurements of uranium in soil geochemical samples, (iii) soil gas radon and (iv) indoor radon data. For models comparing indoor radon and (i) eRa226 derived from airborne eU data and (ii) soil gas radon data, some of the geological groupings have significant slopes. For these groupings there is reasonable agreement in slope and intercept between the three regression analysis methods (LS, TS and WTLS). Relationships between radon in dwellings and radium in the ground or radon in soil differ depending on the characteristics of the underlying geological units, with more permeable units having steeper slopes and higher indoor radon concentrations for a given radium or soil gas radon concentration in the ground. The regression models comparing indoor radon with soil gas radon have intercepts close to 5 Bq m⁻³ whilst the intercepts for those comparing indoor radon with eRa226 from airborne eU vary from about 20 Bq m⁻³ for a moderately permeable geological unit to about 40 Bq m⁻³ for highly permeable limestone, implying unrealistically high contributions to indoor radon from sources other than the ground. An intercept value of 5 Bq m⁻³ is assumed as an appropriate mean value for the UK for sources of indoor radon other than radon from the ground, based on examination of UK data. Comparison with published data used to derive an average indoor radon: soil ²²⁶Ra ratio shows that whereas the published data are

  10. An atmospheric pressure flow reactor: Gas phase kinetics and mechanism in tropospheric conditions without wall effects

    NASA Technical Reports Server (NTRS)

    Koontz, Steven L.; Davis, Dennis D.; Hansen, Merrill

    1988-01-01

    A new type of gas phase flow reactor, designed to permit the study of gas phase reactions near 1 atm of pressure, is described. A general solution to the flow/diffusion/reaction equations describing reactor performance under pseudo-first-order kinetic conditions is presented along with a discussion of critical reactor parameters and reactor limitations. The results of numerical simulations of the reactions of ozone with monomethylhydrazine and hydrazine are discussed, and performance data from a prototype flow reactor are presented.

  11. Reaction mechanism of oxidation, hydroxylation, and epoxidation by hypofluorous acid: a theoretical study of unusual H-bond-assisted catalysis.

    PubMed

    Srnec, Martin; Oncak, Milan; Zahradník, Rudolf

    2008-04-24

    The oxidation of organic molecules by hypofluorous acid (HOF) was studied extensively and systematically by Rozen et al. Therefore, it seems appropriate to refer to the process as Rozen oxidation. An entire set of model molecules was selected for quantum chemical investigation of the oxidation mechanism: a C=C double bond in ethylene, sulfur and selenium in dimethyl derivatives, nitrogen and phosphorus in trimethyl derivatives, as well as methyl azides. In the gas phase, van der Waals complexes between HOF and the previously mentioned species easily are formed, but these complexes are reluctant to undergo oxidation. The addition of another HOF molecule connected with the formation of a cyclic complex (i.e., substrate and two molecules of HOF) seems to be decisive for the oxidation process. The attempt to substitute the second HOF molecule with H2O demonstrated the superiority of HOF. Complexes of this kind decompose along the reaction path smoothly (i.e., with a low activation energy) to the respective oxidation product. A potential role of the hydroxyl cation (HO+) in the oxidation step is mentioned. Besides an oxidation product, one HOF molecule is released (an essential feature of catalysis), and furthermore, hydrogen fluoride is formed. It was suggested by Sertchook et al. (J. Phys. Chem. A 2006, 110, 8275) that the interaction between the substrate to be oxidized and HOF is catalytically influenced by the HF molecule. The mechanism suggested here is more feasible and, particularly at the early stages of the oxidation process, decisive. Also, the role of acetonitrile, used as a solvent by Rozen et al., is discussed in terms of a continuum model. Moreover, passing from potential energies to Gibbs energies is considered.

  12. Determination of the solubility of low volatility liquid organic compounds in water using volatile-tracer assisted headspace gas chromatography.

    PubMed

    Zhang, Shu-Xin; Chai, Xin-Sheng; Barnes, Donald G

    2016-02-26

    This study reports a new headspace gas chromatographic method (HS-GC) for the determination of water solubility of low volatility liquid organic compounds (LVLOs). The HS-GC analysis was performed on a set of aqueous solutions containing a range of concentrations of toluene-spiked (as a tracer) LVLOs, from under-saturation to over-saturation. A plot of the toluene tracer GC signal vs. the concentration of the LVLO results in two lines of different slopes that intersect at the concentration corresponding to the compound's solubility in water. The results showed that the HS-GC method has good precision (RSD <6.3%) and good accuracy, in which the relative deference between the data measured by the HS-GC method and the reference method were within 6.0%. The HS-GC method is simple and particularly suitable for measuring the solubility of LVLOs at elevated temperatures. This approach should be of special interest to those concerned about the impact of the presence of low-volatility organic liquids in waters of environmental and biological systems.

  13. Plasma-assisted cleanup of flue gas. Final technical report, 1 September, 1992--31 August, 1993

    SciTech Connect

    Dhali, S.K.

    1993-12-31

    The objective of the proposed research is to design and implement a novel scheme for the combined removal of SO{sub 2} and NO{sub x} using a dielectric-barrier discharge in conjunction with UV irradiation. This investigation requires the design of a dielectric-barrier reactor and testing the proposed scheme under different conditions that exist in a flue gas. A reactor has been designed and electrical tests have been performed. The voltage characteristics of the plasma reactor has been studied. The authors have found that a discharge can be sustained at atmospheric pressures with a large inner electrode in the coaxial configuration. The testing of the uniformity of the discharge with UV irradiation has been very successful. The details are provided in this report and have been submitted to the Applied Physics Letter. Also both experimental and simulation work were carried out on the removal of SO{sub 2} and NO{sub x}. With the improved reactor, they have achieved a conversions of SO{sub 2} up to 85%. The simulation studies indicate that complete removal of NO{sub x} is possible at reduced electric fields (E/N) of above 100 Td.

  14. Ballistic-Failure Mechanisms in Gas Metal Arc Welds of MIL A46100 Armor-Grade Steel: A Computational Investigation

    DTIC Science & Technology

    2014-06-12

    distribution is unlimited. Ballistic-Failure Mechanisms in Gas Metal Arc Welds of Mil A46100 Armor- Grade Steel : A Computational Investigation The views...Welds of Mil A46100 Armor- Grade Steel : A Computational Investigation Report Title In our recent work, a multi-physics computational model for the...utility of the upgraded GMAW process model, it is next applied to the case of butt-welding of a prototypical high-hardness armor- grade martensitic steel

  15. [Simultaneous determination of six organophosphorous flame retardants in textiles by gas chromatography-tandem mass spectrometry combined with microwave assisted extraction].

    PubMed

    Wang, Chengyun; Li, Lixia; Xie, Tangtang; Zhang, Weiya; Liu, Caiming; Zhu, Naiqing

    2011-08-01

    An effective method was established for the simultaneous determination of six banned organophosphorous flame retardants in textiles by gas chromatography-tandem mass spectrometry (GC-MS/MS) combined with microwave assisted extraction (MAE). By investigating the extraction efficiency of 12 different extraction solvents for the target analytes, the optimal conditions were that the sample was extracted by microwave assisted extraction using acetone as the solvent at 76 degrees C for 30 min. Then the extract was analyzed by GC-MS/MS in multiple reaction monitoring (MRM) mode, and the concentration of each analyte was calibrated by external standard method. The linear ranges of tris-(1-aziridinyl) phosphine oxide (TEPA), tris-(2-chloroethyl) phosphate (TCEP), tris-(1,3-dichloropropyl) phosphate (TDCP), bis-(2,3-dibromopropyl) phosphate (DDBPP), tri-o-cresyl phosphate (TOCP) and tris-(2,3-dibromopropyl) phosphate (TRIS) were 9.17 - 366.80, 0.95 - 75.98, 1.04 - 83.20, 41.60 - 832.00, 3.80 - 75.90, and 40.48 - 809.60 microg/L, respectively, the correlation coefficients were not less than 0.997 5, while the limits of quantification (LOQ) (S/N = 10) were 3.0, 0.2, 0.3, 25.0, 2.5 and 29.0 microg/kg, respectively. The spiked recoveries varied from 82.62% to 96.88% with the relative standard deviations of 3.80% to 8.79%. The proposed method was successfully applied to the determination of organophosphorous flame retardants in eight commercial textiles. The experimental results demonstrated that the method developed is simple, rapid, sensitive and accurate, which could satisfy the demand of the analysis of banned organophosphorous flame retardants in textiles.

  16. Microwave-assisted on-spot derivatization for gas chromatography-mass spectrometry based determination of polar low molecular weight compounds in dried blood spots.

    PubMed

    Sadones, Nele; Van Bever, Elien; Archer, John R H; Wood, David M; Dargan, Paul I; Van Bortel, Luc; Lambert, Willy E; Stove, Christophe P

    2016-09-23

    Dried blood spot (DBS) sampling and analysis is increasingly being applied in bioanalysis. Although the use of DBS has many advantages, it is also associated with some challenges. E.g. given the limited amount of available material, highly sensitive detection techniques are often required to attain sufficient sensitivity. In gas chromatography coupled to mass spectrometry (GC-MS), derivatization can be helpful to achieve adequate sensitivity. Because this additional sample preparation step is considered as time-consuming, we introduce a new derivatization procedure, i.e. "microwave-assisted on-spot derivatization", to minimize sample preparation of DBS. In this approach the derivatization reagents are directly applied onto the DBS and derivatization takes place in a microwave instead of via conventional heating. In this manuscript we evaluated the applicability of this new concept of derivatization for the determination of two polar low molecular weight molecules, gamma-hydroxybutyric acid (GHB) and gabapentin, in DBS using a standard GC-MS configuration. The method was successfully validated for both compounds, with imprecision and bias values within acceptance criteria (<20% at LLOQ, <15% at 3 other QC levels). Calibration lines were linear over the 10-100μg/mL and 1-30μg/mL range for GHB and gabapentin, respectively. Stability studies revealed no significant decrease of gabapentin and GHB in DBS upon storage at room temperature for at least 84 days. Furthermore, DBS-specific parameters, including hematocrit and volume spotted, were evaluated. As demonstrated by the analysis of GHB and gabapentin positive samples, "microwave-assisted on-spot derivatization" proved to be reliable, fast and applicable in routine toxicology. Moreover, other polar low molecular weight compounds of interest in clinical and/or forensic toxicology, including vigabatrin, beta-hydroxybutyric acid, propylene glycol, diethylene glycol, 1,4-butanediol and 1,2-butanediol, can also be

  17. Ultrasound-assisted extraction and derivatization of sterols and fatty alcohols from olive leaves and drupes prior to determination by gas chromatography-tandem mass spectrometry.

    PubMed

    Orozco-Solano, M; Ruiz-Jiménez, J; Luque de Castro, M D

    2010-02-19

    A method for simultaneous determination of sterols and fatty alcohols in olive leaves and drupes based on ultrasound-assisted extraction and derivatization prior to individual identification-quantitation by chromatographic separation and mass spectrometry detection (single ion monitoring mode) is reported here. The sample preparation procedure involves the following steps: (i) leaching of the raw material accelerated by ultrasound; (ii) saponification of the leachate, also accelerated by ultrasound, and separation of the unsaponifiable matter; (iii) cleaning of the extract by solid-phase extraction; (iv) silylation of the target analytes-also assisted by ultrasound; (v) injection into the gas chromatograph for identification-simultaneous quantitation of the two families of compounds. Individual separation-determination of the fatty alcohols and sterols provide limits of detection (LOD) in the range 9.8 x 10(-2) to 2 microg/l and 5.0-6.0 microg/l, respectively. The LOQs range from 0.3 to 0.9 microg/l and 17.0 to 21.0 microg/l, and the linear dynamic ranges are between LOQ and 25.0 microg/ml. The between-day precision, expressed as relative standard deviation (RSD), ranges between 3.6 and 6.1% and the within-laboratory reproducibility, also expressed as RSD, between 6.4 and 9.2%. Within the study of the metabolomic profile of the unsaponifiable fraction in olive tree, the method has been applied to the determination of the target analytes in different varieties of olive trees cultivated in the same zone, so that differences in this unsaponifiable fraction can be attributed to characteristics of the target varieties. As compared with its European Union counterpart, the method is endowed with similar analytical characteristics and drastic shortening of the operational time.

  18. Novel methods and self-reinforced composite materials for assessment and prevention of mechanically assisted corrosion in modular implants

    NASA Astrophysics Data System (ADS)

    Ouellette, Eric S.

    Novel methods for assessing the electrochemical and micromechanical performance of modular tapers were evaluated, and self-reinforced composite materials were developed for their potential to prevent the onset of mechanically assisted corrosion in modular taper devices. A study of the seating and taper locking mechanics of modular taper samples was conducted, and the effect on taper engagement strength of seating load, loading rate, taper moisture, and taper design/material combination was studied. The load-displacement behavior was captured during seating, and the subsequent pull off load was correlated to seating displacement, seating energy, and seating load. The primary factor affecting taper engagement strength was seating load, and loading rate and design/material factors did not have a significant impact on the quality of the taper engagement. Next, the effect of variation of 7 different design, material, and surgical factors on the fretting corrosion and micromechanical behavior during incremental cyclic fretting corrosion testing was examined using a design of experiments matrix. Seating load and head offset length were the most influential factors affecting fretting corrosion, with low seating loads and high head offsets giving rise to increased currents during sequentially incremented cyclic loads. Poly(ether ether ketone) (PEEK) fibers were produced, and the effects of varying draw down ratio, molecular weight, and post-spinning treatment on the structural and mechanical properties of the fibers were studied. Highly drawn fibers showed the highest increase in molecular orientation and mechanical properties. PEEK fibers were then utilized in the design and fabrication of self-reinforced composite PEEK (SRC-PEEK) thin film composites, and self-reinforced composite ultra-high molecular weight polyethylene (SRC-PE) produced from Spectra fiber was also introduced. Pin on disk studies were employed to understand the potential of both of these SRC materials to

  19. Metallographic structure, mechanical properties, and process parameter optimization of 5A06 joints formed by ultrasonic-assisted refill friction stir spot welding

    NASA Astrophysics Data System (ADS)

    Liu, Xin-bo; Qiao, Feng-bin; Guo, Li-jie; Qiu, Xiong-er

    2017-02-01

    Novel hybrid refill friction stir spot welding (RFSSW) assisted with ultrasonic oscillation was introduced to 5A06 aluminum alloy joints. The metallographic structure and mechanical properties of 5A06 aluminum alloy RFSSW joints formed without ultrasonic assistance and with lateral and longitudinal ultrasonic assistance were compared, and the ultrasonic-assisted RFSSW process parameters were optimized. The results show that compared with lateral ultrasonic oscillation, longitudinal ultrasonic oscillation strengthens the horizontal bonding ligament in the joint and has a stronger effect on the joint's shear strength. By contrast, lateral ultrasonic oscillation strengthens the vertical bonding ligament and is more effective in increasing the joint's tensile strength. The maximum shear strength of ultrasonic-assisted RFSSW 5A06 aluminum alloy joints is as high as 8761 N, and the maximum tensile strength is 3679 N when the joints are formed at a tool rotating speed of 2000 r/min, a welding time of 3.5 s, a penetration depth of 0.2 mm, and an axial pressure of 11 kN.

  20. Theoretical study on the gas-phase reaction mechanism between palladium monoxide and methane.

    PubMed

    Yang, Hua-Qing; Hu, Chang-Wei; Gao, Chao; Yang, Meng-Yao; Li, Fang-Ming; Li, Cai-Qin; Li, Xiang-Yuan

    2011-12-01

    The gas-phase reaction mechanism between palladium monoxide and methane has been theoretically investigated on the singlet and triplet state potential energy surfaces (PESs) at the CCSD(T)/AVTZ//B3LYP/6-311+G(2d, 2p), SDD level. The major reaction channel leads to the products PdCH(2) + H(2)O, whereas the minor channel results in the products Pd + CH(3)OH, CH(2)OPd + H(2), and PdOH + CH(3). The minimum energy reaction pathway for the formation of main products (PdCH(2) + H(2)O), involving one spin inversion, prefers to start at the triplet state PES and afterward proceed along the singlet state PES, where both CH(3)PdOH and CH(3)Pd(O)H are the critical intermediates. Furthermore, the rate-determining step is RS-CH(3) PdOH → RS-2-TS1cb → RS-CH(2)Pd(H)OH with the rate constant of k = 1.48 × 10(12) exp(-93,930/RT). For the first C-H bond cleavage, both the activation strain ΔE(≠)(strain) and the stabilizing interaction ΔE(≠)(int) affect the activation energy ΔE(≠), with ΔE(≠)(int) in favor of the direct oxidative insertion. On the other hand, in the PdCH(2) + H(2) O reaction, the main products are Pd + CH(3)OH, and CH(3)PdOH is the energetically preferred intermediate. In the CH(2)OPd + H(2) reaction, the main products are Pd + CH(3)OH with the energetically preferred intermediate H(2)PdOCH(2). In the Pd + CH(3)OH reaction, the main products are CH(2)OPd + H(2), and H(2)PdOCH(2) is the energetically predominant intermediate. The intermediates, PdCH(2), H(2) PdCO, and t-HPdCHO are energetically preferred in the PdC + H(2), PdCO + H(2), and H(2)Pd + CO reactions, respectively. Besides, PdO toward methane activation exhibits higher reaction efficiency than the atom Pd and its first-row congener NiO.

  1. Mechanisms of NOx removal from flue gas by zero valent iron

    SciTech Connect

    Shiao-Shing Chen; Chih-Yu Cheng; Jung-Chun Chang; Chih-Hui Tang

    2006-06-15

    Chemical reaction between nitric oxide (NO) and zero valent iron (ZVI) was studied in a packed-bed column process with high temperatures based on ZVI strong reducing abilities. For six controlled temperatures of 523- 773 K and 400 ppm of NO (typical flue gas temperature and concentration), under short empty bed contact time, NO was completely removed for temperature of 573-773 K but not for 523 K. Breakthrough curves were conducted for the five working temperatures, and the results indicated that NO reductions by ZVI were varied from 2 to 26.7 mg NO/g ZVI. Higher temperature and longer EBCT achieved better NO removal efficiency. X-ray diffraction (XRD) and electron spectroscopy for chemical analysis (ESCA) were conducted to analyze the crystal structure and oxidation state of the reacted ZVI. Three layers of iron species were detected by XRD: ZVI, Fe{sub 3}O{sub 4}, and Fe{sub 2}O{sub 3}. ZVI was the most prevalent species, and Fe{sub 3}O{sub 4} and Fe{sub 2}O{sub 3} were less from the XRD analysis. By ESCA, the oxidation state on the reacted ZVI surface was determined, and the species was identified as Fe{sub 2}O{sub 3}, which is the most oxidizing species for iron. Therefore, three layers from the ZVI core to the ZVI surface can be identified: ZVI, Fe{sub 3}O{sub 4}, and Fe{sub 2}O{sub 3}. Combining the results from XRD and ESCA, the mechanisms for ZVI and NO can be proposed as two consecutive reactions from lower oxidation state (ZVI) in the core to higher oxidation state on the iron surface (Fe{sub 2}O{sub 3}). Because there was only {lt}5% ZVI used to remove NO comparing to theoretical ZVI used based on the proposed stoichiometry, it can be concluded that the heterogeneous reaction only occurred on the ZVI surface instead of on bulk of the ZVI. 11 refs., 8 figs., 3 tabs.

  2. Evaluation of Mechanical Properties and Structural Changes of Ceramic Filter Materials for Hot Gas Cleaning under Simulated Process Conditions

    SciTech Connect

    Westerheide, R.; von der Wehd, C.; Adler, J.; Rehak, P.

    2002-09-19

    The objective of this study is to evaluate changes in structure and mechanical properties of ceramic filter materials under simulated corrosive process conditions. Due to an analysis of the mechanisms of degradation firstly an optimization of materials shall be enabled and secondly a material selection for specific applications shall be relieved. This publication describes the investigations made on many ceramic support materials based on oxides and carbides. Both commercially available and newly developed support materials have been evaluated for specific applications in hot gas cleaning.

  3. Tactics for mechanized reasoning: a commentary on Milner (1984) ‘The use of machines to assist in rigorous proof’

    PubMed Central

    Gordon, M. J. C.

    2015-01-01

    Robin Milner's paper, ‘The use of machines to assist in rigorous proof’, introduces methods for automating mathematical reasoning that are a milestone in the development of computer-assisted theorem proving. His ideas, particularly his theory of tactics, revolutionized the architecture of proof assistants. His methodology for automating rigorous proof soundly, particularly his theory of type polymorphism in programing, led to major contributions to the theory and design of programing languages. His citation for the 1991 ACM A.M. Turing award, the most prestigious award in computer science, credits him with, among other achievements, ‘probably the first theoretically based yet practical tool for machine assisted proof construction’. This commentary was written to celebrate the 350th anniversary of the journal Philosophical Transactions of the Royal Society. PMID:25750147

  4. Ultrasound assisted synthesis of PANI/ZnMoO4 nanocomposite for simultaneous improvement in anticorrosion, physico-chemical properties and its application in gas sensing.

    PubMed

    Bhanvase, B A; Darda, N S; Veerkar, N C; Shende, A S; Satpute, S R; Sonawane, S H

    2015-05-01

    Ultrasound assisted in-situ semi-batch emulsion polymerization has been used for the preparation of polyaniline (PANI) and PANI/ZnMoO4 nanocomposite with different loading of ZnMoO4 (ZM) nanoparticles. ZM nanoparticles were functionalized using Myristic acid (MA) for better compatibility with PANI. The cavitational effects induced due to ultrasonic irradiations have been shown significant enhancement in the dispersion of functionalized ZM nanoparticles into the PANI during ultrasound assisted in-situ emulsion polymerization process. TEM images of PANI/ZM nanocomposite particles give the direct evidence of fine dispersion and encapsulation of MA treated ZM nanoparticles in PANI matrix. The presence of ZM nanoparticles in PANI/ZM nanocomposite shows significant improvement in the mechanical (cross-cut adhesion), thermal, anticorrosion and sensing properties of PANI/ZM nanocomposite/alkyd coatings over PANI/alkyd and neat alkyd resin coating. Fine and uniform dispersion of ZM nanoparticles in PANI matrix using this novel synthesis method (PANI (p-type)/ZM (n-type) hetero-junction) improves LPG sensing ability and minimizes response time to sense LPG significantly compared with neat PANI.

  5. Determination of ultraviolet filters in water samples by vortex-assisted dispersive liquid-liquid microextraction followed by gas chromatography-mass spectrometry.

    PubMed

    Zhang, Yufeng; Lee, Hian Kee

    2012-08-03

    For the first time, a simple solvent microextraction method termed vortex-assisted liquid-liquid microextraction (VADLLME) coupled with gas chromatography-mass spectrometry (GC-MS) has been developed and used for the analysis of six benzophenone ultraviolet (UV) filters (i.e. benzhydrol, 2,4-dihydroxybenzophenone, benzophenone, 2-hydroxy-4-methoxybenzophenone, ethylhexyl salicylate and homosalate) in water samples. The most favorable extraction variables in the VADLLME process were determined. In the extraction procedure, 40 μL of tetrachloroethene as extraction solvent were directly injected into a 15-mL centrifuge tube containing 10 mL of aqueous sample, adjusted to pH 4 for VADLLME. After VADLLME, the extract was evaporated under a gentle nitrogen gas stream and then reconstituted with N,O-bis-(trimethylsilyl)trifluoroacetamide (BSTFA), thus allowing the target analytes to be converted into their trimethylsilyl derivatives to optimize the GC-MS analysis. No centrifugation and disperser solvent were required in this microextraction procedure. Significantly, short extraction time and high extraction efficiency were achieved. This method opens up a potentially new horizon for on-site dispersive liquid-liquid microextraction. Under the optimum conditions, the proposed method provided good enrichment factors up to 310, with relative standard deviations ranging from 6.1 to 12.9%. The limits of quantification were in the range of 20-100 ng/L, depending on the analytes. The linearities were between 0.05 and 10 μg/L and 0.1 and 10 μg/L for different UV filters. Finally, the proposed method was successfully applied to the determination of UV filters from spiked genuine water samples and acceptable recoveries over the range of 71.0-120.0% were obtained.

  6. Pore-scale mechanisms of gas flow in tight sand reservoirs

    SciTech Connect

    Silin, D.; Kneafsey, T.J.; Ajo-Franklin, J.B.; Nico, P.

    2010-11-30

    Tight gas sands are unconventional hydrocarbon energy resource storing large volume of natural gas. Microscopy and 3D imaging of reservoir samples at different scales and resolutions provide insights into the coaredo not significantly smaller in size than conventional sandstones, the extremely dense grain packing makes the pore space tortuous, and the porosity is small. In some cases the inter-granular void space is presented by micron-scale slits, whose geometry requires imaging at submicron resolutions. Maximal Inscribed Spheres computations simulate different scenarios of capillary-equilibrium two-phase fluid displacement. For tight sands, the simulations predict an unusually low wetting fluid saturation threshold, at which the non-wetting phase becomes disconnected. Flow simulations in combination with Maximal Inscribed Spheres computations evaluate relative permeability curves. The computations show that at the threshold saturation, when the nonwetting fluid becomes disconnected, the flow of both fluids is practically blocked. The nonwetting phase is immobile due to the disconnectedness, while the permeability to the wetting phase remains essentially equal to zero due to the pore space geometry. This observation explains the Permeability Jail, which was defined earlier by others. The gas is trapped by capillarity, and the brine is immobile due to the dynamic effects. At the same time, in drainage, simulations predict that the mobility of at least one of the fluids is greater than zero at all saturations. A pore-scale model of gas condensate dropout predicts the rate to be proportional to the scalar product of the fluid velocity and pressure gradient. The narrowest constriction in the flow path is subject to the highest rate of condensation. The pore-scale model naturally upscales to the Panfilov's Darcy-scale model, which implies that the condensate dropout rate is proportional to the pressure gradient squared. Pressure gradient is the greatest near the matrix

  7. Instantaneous insulation in a micro-slab: A mechanism for flow generation in a rarefied gas

    NASA Astrophysics Data System (ADS)

    Manela, A.; Pogorelyuk, L.

    2016-12-01

    We analyze the response of a gas in a micro-slab, set at an initial pure-conduction state, to instantaneous thermal insulation of its boundaries. In line with ongoing efforts in generating gas flows at the microscale, thermal insulation is suggested as a means for flow excitation with no moving parts. The problem is analyzed in the entire range of gas rarefaction rates and for arbitrary initial temperature differences between the walls. Analytical solutions are obtained in the linearized limit of small temperature differences for large (collisionless) and small (continuum) Knudsen numbers. These solutions are supported by direct simulation Monte Carlo calculations, which are then used to investigate the nonlinear problem with large initial temperature differences. Followed by the system's initial state, boundary insulation results in a series of time-decaying waves, propagating across the slab, and transferring the system between its conductive and adiabatic equilibrium states. While larger initial temperature differences result in higher flow rates, it is found that nonlinear effects reduce the efficiency of flow excitation through boundaries insulation. At high Knudsen numbers, this is rationalized through the system's initial state, in which the gas uniform temperature is lower than the arithmetic mean of walls temperatures. At low Knudsen numbers, the dominant effect of molecular collisions causes thermal dissipation, which in turn results in kinetic energy losses. The analysis may be readily applied to calculate the gas response to arbitrary time variations of the boundary-imposed heat flux.

  8. Electrochemical studies of hydrogen chloride gas in several room temperature ionic liquids: mechanism and sensing.

    PubMed

    Murugappan, Krishnan; Silvester, Debbie S

    2016-01-28

    The electrochemical behaviour of highly toxic hydrogen chloride (HCl) gas has been investigated in six room temperature ionic liquids (RTILs) containing imidazolium/pyrrolidinium cations and range of anions on a Pt microelectrode using cyclic voltammetry (CV). HCl gas exists in a dissociated form of H(+) and [HCl2](-) in RTILs. A peak corresponding to the oxidation of [HCl2](-) was observed, resulting in the formation of Cl2 and H(+). These species were reversibly reduced to H2 and Cl(-), respectively, on the cathodic CV scan. The H(+) reduction peak is also present initially when scanned only in the cathodic direction. In the RTILs with a tetrafluoroborate or hexafluorophosphate anion, CVs indicated a reaction of the RTIL with the analyte/electrogenerated products, suggesting that these RTILs might not be suitable solvents for the detection of HCl gas. This was supported by NMR spectroscopy experiments, which showed that the hexafluorophosphate ionic liquid underwent structural changes after HCl gas electrochemical experiments. The analytical utility was then studied in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C2mim][NTf2]) by utilising both peaks (oxidation of [HCl2](-) and reduction of protons) and linear calibration graphs for current vs. concentration for the two processes were obtained. The reactive behaviour of some ionic liquids clearly shows that the choice of the ionic liquid is very important if employing RTILs as solvents for HCl gas detection.

  9. A predictive mechanism for mercury oxidation on selective catalytic reduction catalysts under coal-derived flue gas

    SciTech Connect

    Stephen Niksa; Naoki Fujiwara

    2005-12-15

    This paper introduces a predictive mechanism for elemental mercury (Hg{sup 0}) oxidation on selective catalytic reduction (SCR) catalysts in coal-fired utility gas cleaning systems, given the ammonia (NH{sub 3})/nitric oxide (NO) ratio and concentrations of Hg{sup 0} and HCl at the monolith inlet, the monolith pitch and channel shape, and the SCR temperature and space velocity. A simple premise connects the established mechanism for catalytic NO reduction to the Hg{sup 0} oxidation behavior on SCRs: that hydrochloric acid (HCl) competes for surface sites with NH{sub 3} and that Hg{sup 0} contacts these chlorinated sites either from the gas phase or as a weakly adsorbed species. This mechanism explicitly accounts for the inhibition of Hg{sup 0} oxidation by NH{sub 3}, so that the monolith sustains two chemically distinct regions. In the inlet region, strong NH{sub 3} adsorption minimizes the coverage of chlorinated surface sites, so NO reduction inhibits Hg{sup 0} oxidation. But once NH{sub 3} has been consumed, the Hg{sup 0} oxidation rate rapidly accelerates, even while the HCl concentration in the gas phase is uniform. Factors that shorten the length of the NO reduction region factors that enhance surface chlorination, promote Hg{sup 0} oxidation. This mechanism accurately interprets the reported tendencies for greater extents of Hg{sup 0} oxidation on honeycomb monoliths with smaller channel pitches and hotter temperatures and the tendency for lower extents of Hg{sup 0} oxidation for hotter temperatures on plate monoliths. The mechanism reproduces the reported extents of Hg{sup 0} oxidation on a single catalyst for four coals that generated HCl concentrations from 8 to 241 ppm, which covers the entire range encountered in the U.S. utility industry. Similar performance is also demonstrated for full-scale SCRs with diverse coal types and operating conditions. 28 refs., 5 figs., 3 tabs.

  10. One-step microwave-assisted headspace solid-phase microextraction for the rapid determination of synthetic polycyclic musks in oyster by gas chromatography-mass spectrometry.

    PubMed

    Wu, Shin-Fang; Liu, Li-Lian; Ding, Wang-Hsien

    2012-07-15

    A rapid, simple and solvent-free procedure was developed for the determination of synthetic polycyclic musks in oyster samples by using one-step microwave-assisted headspace solid-phase microextraction (MA-HS-SPME) and gas chromatography-mass spectrometry (GC-MS). Two commonly used synthetic polycyclic musks, galaxolide (HHCB) and tonalide (AHTN), were selected in the method development and validation. The parameters (microwave irradiation power, extraction time, amount of water added, pH value and addition of NaCl) affecting the extraction efficiency of analytes from oyster slurry were systematically investigated and optimised. The best extraction conditions were achieved when the oyster tissue mixed with 10-mL deionised water (containing 3g of NaCl in a 40-mL sample-vial) was microwave irradiated at 80 W for 5 min. The limit of quantification (LOQ) was 0.1 ng/g in 5-g of wet tissue. The good precision and accuracy of one-step MA-HS-SPME coupled with GC-MS for the determination of trace level of AHTN in oyster samples was also demonstrated.

  11. Rapid method for the determination of 16 organochlorine pesticides in sesame seeds by microwave-assisted extraction and analysis of extracts by gas chromatography-mass spectrometry.

    PubMed

    Papadakis, Emmanouil N; Vryzas, Zisis; Papadopoulou-Mourkidou, Euphemia

    2006-09-15

    A method for the multiresidue analysis of 16 organochlorine insecticides in sesame seeds has been developed. The method is based on the microwave-assisted extraction (MAE) of the sesame seeds by the use of a water-acetonitrile mixture followed by Florisil clean-up of the extracts and subsequent analysis by gas chromatography-mass spectrometry (GC/MS) in the selected ion monitoring (SIM) mode. MAE operational parameters (extraction solvent, temperature and time, extractant volume) were optimized with respect to extraction efficiency of the target compounds from sesame seeds with 46% oil content. Recoveries >80% with relative standard deviations (RSD) <12% were obtained for all compounds under the selected parameters. The Florisil clean-up step proved sufficient for the removal of co-extracted substances so that no adverse effect on the chromatographic system was observed. Limit of quantification (LOQ) values were in the range of 5-10 microg/kg. The proposed method was applied in the analysis of sesame seed samples imported to Greece.

  12. Membrane-assisted liquid-liquid extraction coupled with gas chromatography-mass spectrometry for determination of selected polycyclic musk compounds and drugs in water samples.

    PubMed

    Einsle, T; Paschke, H; Bruns, K; Schrader, S; Popp, P; Moeder, M

    2006-08-18

    Selected polycyclic musk compounds and drugs were extracted from water samples by membrane-assisted micro liquid-liquid extraction. The two-phase extraction system consisted of polyethylene membrane bags filled with an organic solvent. Chloroform proved to be most suited as acceptor phase to extract caffeine, Galaxolide, Tonalide, phenazone and carbamazepine from aqueous samples. The compounds were enriched from 50 mL sample into a volume of 500 microL of chloroform. Gas chromatography-mass spectrometry (GC-MS) was applied for analysis. The extraction procedure was optimised in regard to membrane material, extraction time and temperature. The evaluation of the entire analysis protocol found limits of detection that ranged from 20 to 200 ng/L. The linear range of calibration covered one magnitude with standard deviations between 4 and 12%. Method comparison with standard analysis techniques such as solid-phase extraction (SPE) combined with GC-MS as well as LC-MS-MS confirmed this method as an easy and reliable protocol, even for the monitoring of matrix-loaded wastewater. The analysis of real samples established the feasibility of the technique.

  13. A novel ultrasound-assisted back extraction reverse micelles method coupled with gas chromatography-flame ionization detection for determination of aldehydes in heated edibles oils.

    PubMed

    Ramezani, Zahra; Mirzajani, Roya; Kardani, Fatemeh

    2015-12-01

    A novel ultrasound-assisted back extraction reverse micelles coupled with gas chromatography-flame ionization detection has been developed for the extraction and determination of some short chain aldehydes in different heated edible oil samples. After the homogenization of the oil samples with Triton X-100, 200 μL of methanol was added to facilitate the phase separation. The aqueous micelle phase has been separated by centrifugation, then it was treated with a mixture of H2O: CHCl3 and ultrasonic vibration, were used to effectively back-extraction of the analytes into the chloroform phase. The sedimented organic phase was obtained after centrifugation, withdrawn into the microsyringe and directly injected into the GC-FID system. The calibration graphs were linear in the range 0.05-20 mg L(-1). The limits of detection were in the range of 0.02-0.15 mg L(-1). This procedure was successfully applied for determination of propanal, butanal, hexanal and heptanal in real heated oil samples.

  14. Optimized ultrasonic assisted extraction-dispersive liquid-liquid microextraction coupled with gas chromatography for determination of essential oil of Oliveria decumbens Vent.

    PubMed

    Sereshti, Hassan; Izadmanesh, Yahya; Samadi, Soheila

    2011-07-22

    Ultrasonic assisted extraction-dispersive liquid-liquid microextraction (UAE-DLLME) coupled with gas chromatography (GC) was applied for extraction and determination of essential oil constituents of the plant Oliveria decumbens Vent. Scanning electron microscopy (SEM) was used to see the effect of ultrasonic radiation on the extraction efficiency. By comparison with hydrodistillation, UAE-DLLME is fast, low cost, simple, efficient and consuming small amount of plant materials (∼1.0 g). The effects of various parameters such as temperature, ultrasonication time, volume of disperser and extraction solvents were investigated by a full factorial design to identify significant variables and their interactions. The results demonstrated that temperature and ultrasonication time had no considerable effect on the results. In the next step, a central composite design (CCD) was performed to obtain the optimum levels of significant parameters. The obtained optimal conditions were: 0.45 mL for disperser solvent (acetonitrile) and 94.84 μL for extraction solvent (chlorobenzene). The limits of detection (LODs), linear dynamic range and determination coefficients (R(2)) were 0.2-29 ng mL(-1), 1-2100 ng mL(-1) and 0.995-0.998, respectively. The main components of the essential oil were: thymol (47.06%), carvacrol (23.31%), gamma-terpinene (18.94%), p-cymene (8.71%), limonene (0.76%) and myristicin (0.63%).

  15. Vortex-assisted matrix solid-liquid dispersive microextraction for the analysis of triazole fungicides in cotton seed and honeysuckle by gas chromatography.

    PubMed

    Xue, Jiaying; Li, Huichen; Liu, Fengmao; Jiang, Wenqing; Hou, Fan

    2016-04-01

    A one-step analytical method termed vortex-assisted matrix solid-liquid dispersive microextraction (VA-MSLDME) was developed for the determination of seven triazole fungicides from cotton seed and honeysuckle prior to gas chromatography with electron capture detection. The VA-MSLDME was performed by mixing the matrix, primary secondary amine, acetonitrile, toluene, and water in one single system. The target fungicides in the sample were extracted, cleaned up and preconcentrated simultaneously in the matrix/acetonitrile/water/toluene system. Meanwhile, the interferences were adsorbed by the cleanup adsorbent. The extraction recoveries of the fungicides from the samples varied from 82.9% to 97.8% with relative standard deviations of 4.4-8.5%. The enrichment factors of the analytes ranged from 22 to 47, and the limits of detection were in the range of 0.05-20 μg/kg. The results demonstrated the significant predominance of VA-MSLDME in the analysis of pesticide residues in cotton seed and honeysuckle samples.

  16. Rapid determination of polycyclic aromatic hydrocarbons in grilled meat using microwave-assisted extraction and dispersive liquid-liquid microextraction coupled to gas chromatography-mass spectrometry.

    PubMed

    Kamankesh, Marzieh; Mohammadi, Abdorreza; Hosseini, Hedayat; Modarres Tehrani, Zohreh

    2015-05-01

    A simple and rapid analytical tech nique for the simultaneous determination of 16 polycyclic aromatic hydrocarbons (PAHs) in grilled meat was developed using microwave-assisted extraction and dispersive liquid-liquid microextraction (MAE-DLLME) followed by gas chromatography-mass spectrometry (GC-MS). The effective parameters in DLLME process were optimized. Good linear relationships were obtained for 16 PAHs in a range of 1-200 ng g(-1), with a correlation coefficient (R(2)) higher than 0.98. Limits of detection and limits of quantification were 0.15-0.3 ng g(-1) and 0.47-1 ng g(-1), respectively. The relative standard deviations (RSD%) for seven analyses were less than 9%. The recoveries of those compounds in grilled meat were obtained from 85% to 104%. Low consumption of the solvent, high recovery, short extraction time, no matrix interference and good merit figures compared to other methods are advantages of the proposed method. The performance of the present method was evaluated for the determination of PAHs in various types of real grilled meat samples, and satisfactory results were obtained.

  17. Rapid screening of haloacetamides in water using salt-assisted liquid-liquid extraction coupled injection-port silylation gas chromatography-mass spectrometry.

    PubMed

    Chen, Tzu-Ling; Tzing, Shin-Hwa; Ding, Wang-Hsien

    2015-11-27

    The rapid screening of trace amounts of the nitrogenous disinfection by-products, haloacetamides (HAcAms), in drinking and swimming pool water was performed by a simple and reliable procedure based on salt-assisted liquid-liquid extraction (SALLE) combined with injection-port silylation gas chromatography-mass spectrometry (IPS-GC-MS) method. The optimal SALLE conditions involved the injection of 4-mL of ethyl acetate into a 10-mL water sample (pH 7) containing 3-g of sodium sulfate. After vortex extraction for 1min and centrifugation, 10μL of the extract (mixed with 1μL of MTBSTFA) was directly determined by IPS-GC-MS. The limits of quantitation (LOQs) were determined to be 0.03-0.3μg/L. Precision, as indicated by relative standard deviations (RSDs), was less than 10% for both intra- and inter-day analysis. Accuracy, expressed as the mean extraction recovery, was between 76% and 94%. The SALLE plus IPS-GC-MS was successfully applied to quantitatively determine HAcAms from drinking and swimming pool water samples, and the total concentrations of the compounds ranged from 0.43 to 4.03μg/L.

  18. Rapid analysis of Fructus forsythiae essential oil by ionic liquids-assisted microwave distillation coupled with headspace single-drop microextraction followed by gas chromatography-mass spectrometry.

    PubMed

    Jiao, Jiao; Ma, Dan-Hui; Gai, Qing-Yan; Wang, Wei; Luo, Meng; Fu, Yu-Jie; Ma, Wei

    2013-12-04

    A rapid, green and effective miniaturized sample preparation and analytical technique, i.e. ionic liquids-assisted microwave distillation coupled with headspace single-drop microextraction (ILAMD-HS-SDME) followed by gas chromatography-mass spectrometry (GC-MS) was developed for the analysis of essential oil (EO) in Fructus forsythiae. In this work, ionic liquids (ILs) were not only used as the absorption medium of microwave irradiation but also as the destruction agent of plant cell walls. 1-Ethyl-3-methylimidazolium acetate ([C2mim]OAc) was chosen as the optimal ILs. Moreover, n-heptadecane (2.0 μL) was selected as the appropriate suspended solvent for the extraction and concentration of EO. Extraction conditions of the proposed method were optimized using the relative peak area of EO constituents as the index, and the optimal operational parameters were obtained as follows: irradiation power (300 W), sample mass (0.7 g), mass ratio of ILs to sample (2.4), temperature (78°C) and time (3.4 min). In comparison to previous reports, the proposed method was faster and required smaller sample amount but could equally monitor all EO constituents with no significant differences.

  19. Rapid analysis of pyrethroid insecticides in aquaculture seawater samples via membrane-assisted solvent extraction coupled with gas chromatography-electron capture detection.

    PubMed

    Shi, X Z; Song, S Q; Sun, A L; Liu, J H; Li, D X; Chen, J

    2012-01-21

    A simple, efficient, and environmentally friendly membrane-assisted solvent extraction (MASE) method for the extraction and preconcentration of six pyrethroid insecticides from aquaculture seawater samples followed by gas chromatography-electron capture detection (GC-ECD) was successfully proposed. The operating conditions for MASE, such as the extraction solvent, solvent volume, NaCl concentration, stirring rate, extraction time, and temperature, were optimized. Compared to conventional Florisil-solid phase extraction (SPE), higher extraction recoveries (85.9% to 105.9%) of three spiked levels of the six pyrethroid pesticides in aquaculture seawater were obtained using MASE, and the RSD values were lower than 7.9%. The limits of detection (LOD, signal-to-noise ratio (S/N)=3) and quantification (LOQ, S/N = 10) were in the range of 0.037-0.166 and 0.12-0.55 μg L(-1), respectively. The results demonstrate the excellent applicability of the MASE method in analyzing the six pyrethroid pesticides in aqueous samples. The proposed method exhibited a high potential for routine monitoring analysis of pyrethroid insecticides in seawater samples.

  20. Ultrasound-assisted extraction and solid-phase extraction for the simultaneous determination of five amide herbicides in fish samples by gas chromatography with electron capture detection.

    PubMed

    Qu, Zhipeng; Bai, Xiuzhi; Zhang, Ting; Yang, Zhaoguang

    2017-03-01

    An efficient sample extraction and clean-up method was developed for simultaneous determination of five amide herbicides (alachlor, acetochlor, propisochlor, metazachlor, and butachlor) in fish samples. The protocol consisted of ultrasound-assisted solvent extraction and solid-phase extraction clean-up. In detail, aliquots of homogenized fish flesh were thoroughly mixed with 20 mL of n-hexane and then extracted with ultrasonication for 40 min. Each sample was centrifuged and the supernatant was collected for the subsequent clean-up. For the sample preparation, the above supernatant was processed with a C18 column with 3 mL of dichloromethane/n-hexane (1:1, v/v) as the eluant. Then the samples were analyzed by gas chromatography with electron capture detection. The correlation coefficients of the five calibration curves were 0.9976-0.9998 (n = 3). The limits of detection (S/N = 3, n = 11) and limits of quantification (S/N = 10, n = 11) were 0.19-0.42 and 0.63-1.39 μg/kg, respectively. The recoveries of this method were 71.2-92.6% with good precision (<4.7% relative standard deviations, n = 6). The developed method was successfully applied to monitor the five amide herbicides in fish samples collected from different cities.

  1. Solvent-enhanced microwave-assisted derivatization following solid-phase extraction combined with gas chromatography-mass spectrometry for determination of amphetamines in urine.

    PubMed

    Chung, Li-Wen; Liu, Geng-Jhih; Li, Zu-Guang; Chang, Yan-Zin; Lee, Maw-Rong

    2008-10-15

    An approach using microwave-assisted derivatization (MAD) following solid-phase extraction (SPE) combined with gas chromatography-mass spectrometry (GC-MS) was developed to determine amphetamines in urine samples. The parameters affecting the derivatization efficiency - including microwave power and irradiation time - were investigated. Besides, solvent is thought critically important to MAD. Derivatization performance was studied using various solvents and compared with the performance obtained without solvent. Derivatization efficiency was clearly found to be enhanced by the presence of solvent. The highest derivatization efficiencies were obtained in ethyl acetate (EA) under microwave power of 250W for 1min. Calibration curves for all amphetamines were linear over a range from 1 to 1000ng/mL, with correlation coefficients above 0.9992. The intra-day and inter-day precision were less than 15%. The applicability of the method was tested by analyzing amphetamine-abusing subjects urine samples. Accordingly, the solvent-enhanced MAD-GC-MS method appears to be adequate for determining amphetamines in urine.

  2. Validation of thermally assisted hydrolysis and methylation-gas chromatography for rapid and direct compositional analysis of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) in whole bacterial cells.

    PubMed

    Baidurah, Siti; Murugan, Paramasivam; Joyyi, Lee; Fukuda, Junya; Yamada, Masaya; Sudesh, Kumar; Ishida, Yasuyuki

    2016-11-04

    Thermally assisted hydrolysis and methylation-gas chromatography (THM-GC) in the presence of an organic alkali was validated for the compositional analysis of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [P(3HB-co-3HHx)] accumulated in whole bacterial cells. Recombinant Cupriavidus necator Re2058/pCB113 was grown in a batch fermentation with different concentration of palm oil and fructose in order to control the molar fraction of 3HHx in P(3HB-co-3HHx) produced in the cells. Trace amounts (30μg) of freeze-dried cells were directly subjected to THM-GC in the presence of tetramethylammonium hydroxide (TMAH) at 400°C. The obtained chromatograms clearly showed nine characteristic peaks, attributed to the THM products from 3HB and 3HHx units in the polymer chains, without any appreciable interference by the bacterial matrix components. Based on these peak intensities, the copolymer compositions were determined rapidly without using any cumbersome and lengthy sample pretreatment as in conventional GC method. Moreover, the compositions thus obtained were strongly correlated with those by NMR and conventional GC involving solvent extraction.

  3. Ultrasound-assisted dispersive liquid-liquid microextraction for the determination of seven recreational drugs in human whole blood using gas chromatography-mass spectrometry.

    PubMed

    Lin, Zebin; Li, Jiaolun; Zhang, Xinyu; Qiu, Meihong; Huang, Zhibin; Rao, Yulan

    2017-03-01

    Recreational drugs have large impact on public health and security, and to monitor them is of urgent demand. In the present study, ultrasound-assisted dispersive liquid-liquid microextraction combined with the detection of gas chromatography-mass spectrometry was applied to the determination of seven common recreational drugs, including amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine, 3,4-methylenedioxymethamphetamine, meperidine, methadone and ketamine in 200μL of human whole blood. A series of factors which would affect the extraction efficiency were systematically investigated, including the nature and the volume of extraction and dispersing solvents, ultrasonication time, salting-out effect and pH value. The method consumed small amount of sample. The limits of detection and limits of quantification for each analyte were 10 and 40ng/mL, respectively, and the linearity was in the range of 0.04-25μg/mL (R(2) higher than 0.99). Good specificity, precision (1.5-8.2% for the intra-day study and 2.6-12.8% for the inter-day study), satisfactory accuracy (85.0-117.1%) and extraction recovery (77.0-92.4%) were obtained, which makes it a high performance method for the determination of recreational drugs in human whole blood samples.

  4. Determination of volatile components of saffron by optimised ultrasound-assisted extraction in tandem with dispersive liquid-liquid microextraction followed by gas chromatography-mass spectrometry.

    PubMed

    Sereshti, Hassan; Heidari, Reza; Samadi, Soheila

    2014-01-15

    In the present research, a combined extraction method of ultrasound-assisted extraction (UAE) in conjunction with dispersive liquid-liquid microextraction (DLLME) was applied to isolation and enrichment of saffron volatiles. The extracted components of the saffron were separated and determined by gas chromatography-mass spectrometry (GC-MS) technique. The mixture of methanol/acetonitrile was chosen for the extraction of the compounds and chloroform was used at the preconcentration stage. The important parameters, such as composition of extraction solvent, volume of preconcentration solvent, ultrasonic applying time, and salt concentration were optimised by using a half-fraction factorial central composite design (CCD). Under the optimal conditions, the linear dynamic ranges (LDRs) were 10-10,000mgL(-)(1). The determination coefficients (R(2)) were from 0.9990 to 0.9997. The limits of detection (LODs) and limits of quantification (LOQs) for the extracted compounds were 6-123mgL(-)(1) and 20-406mgL(-)(1), respectively. The relative standard deviations (RSDs) were 2.48-9.82% (n=3). The enhancement factors (EFs) were 3.6-41.3.

  5. Determination of cyclic and linear siloxanes in wastewater samples by ultrasound-assisted dispersive liquid-liquid microextraction followed by gas chromatography-mass spectrometry.

    PubMed

    Cortada, Carol; dos Reis, Luciana Costa; Vidal, Lorena; Llorca, Julio; Canals, Antonio

    2014-03-01

    A fast, simple and environmentally friendly ultrasound-assisted dispersive liquid-liquid microextraction (USA-DLLME) procedure has been developed to preconcentrate eight cyclic and linear siloxanes from wastewater samples prior to quantification by gas chromatography-mass spectrometry (GC-MS). A two-stage multivariate optimization approach has been developed employing a Plackett-Burman design for screening and selecting the significant factors involved in the USA-DLLME procedure, which was later optimized by means of a circumscribed central composite design. The optimum conditions were: extractant solvent volume, 13 µL; solvent type, chlorobenzene; sample volume, 13 mL; centrifugation speed, 2300 rpm; centrifugation time, 5 min; and sonication time, 2 min. Under the optimized experimental conditions the method gave levels of repeatability with coefficients of variation between 10 and 24% (n=7). Limits of detection were between 0.002 and 1.4 µg L(-1). Calculated calibration curves gave high levels of linearity with correlation coefficient values between 0.991 and 0.9997. Finally, the proposed method was applied for the analysis of wastewater samples. Relative recovery values ranged between 71 and 116% showing that the matrix had a negligible effect upon extraction. To our knowledge, this is the first time that combines LLME and GC-MS for the analysis of methylsiloxanes in wastewater samples.

  6. Up-and-down-shaker-assisted dispersive liquid-liquid microextraction coupled with gas chromatography-mass spectrometry for the determination of fungicides in wine.

    PubMed

    Chu, Shang-Ping; Tseng, Wan-Chi; Kong, Po-Hsin; Huang, Chun-Kai; Chen, Jung-Hsuan; Chen, Pai-Shan; Huang, Shang-Da

    2015-10-15

    An up-and-down-shaker-assisted dispersive liquid-liquid microextraction (UDSA-DLLME) method coupled with gas chromatography-mass spectrometry was developed for the determination of fungicides (cyprodinil, procymidone, fludioxonil, flusilazole, benalaxyl, and tebuconazole) in wine. The developed method requires 11 μL of 1-octanol without the need for dispersive solvents. The total extraction time was approximately 3 min. Under optimum conditions, the linear range of the method was 0.05-100 μg L(-1) for all fungicides and the limit of detection was 0.007-0.025 μg L(-1). The absolute and relative recoveries were 31-83% and 83-107% for white wine, respectively, and 32-85% and 83-108% for red wine, respectively. The intra-day and inter-day precision were 0.5-7.5% and 0.7-6.1%, respectively. Our developed method had good sensitivity and high extraction efficiency. UDSA-DLLME is a desirable method in terms of performance and speed.

  7. Plasma-Assisted Combustion Studies at AFRL

    DTIC Science & Technology

    2009-11-04

    important for lean, gas-turbine ( powerplant ) operation Might one also mitigate/influence acoustic fluctuations? Potential for uniform performance with...Thermometry with pulsed -W Source No -W Pulsed -W Direct coupled plasma torch: flame OH vs. - wave power: Plasma-assisted Ignition Cathey, Gundersen, Wang...Determine physical mechanism, primarily for transient plasma ignition  What is role of humidity: XH2O affects detonation wave speed in PDE but not

  8. Gradation of mechanical properties in gas-diffusion electrode. Part 2: Heterogeneous carbon fiber and damage evolution in cell layers

    NASA Astrophysics Data System (ADS)

    Poornesh, K. K.; Cho, C. D.; Lee, G. B.; Tak, Y. S.

    In PEM fuel cell, gas-diffusion electrode (GDE) plays very significant role in force transmission from bipolar plate to the membrane. This paper investigates the effects of geometrical heterogeneities of gas-diffusion electrode layer (gas-diffusion layer (GDL) and catalyst layer (CL)) on mechanical damage evolution and propagation. We present a structural integrity principle of membrane electrode assembly (MEA) based on the interlayer stress transfer capacity and corresponding cell layer material response. Commonly observable damages such as rupture of hydrophobic coating and breakage of carbon fiber in gas-diffusion layer are attributed to the ductile to brittle phase transition within a single carbon fiber. Effect of material inhomogeneity on change in modulus, hardness, contact stiffness, and electrical contact resistance is also discussed. Fracture statistics of carbon fiber and variations in flexural strength of GDL are studied. The damage propagation in CL is perceived to be influenced by the type of gradation and the vicinity from which crack originates. Cohesive zone model has been proposed based on the traction-separation law to investigate the damage propagation throughout the two interfaces (carbon fiber/CL and CL/membrane).

  9. On the mechanism of the runaway of electrons in a gas: the universal escape curves for He, Xe, N2

    NASA Astrophysics Data System (ADS)

    Yakovlenko, Sergey I.; Tkachev, A. N.

    2004-05-01

    Basing on the simple form of the energy conservation law and taking into account a multiplication of electrons, we show that the Townsend mechanism of electron multiplication in a gas is valid at sufficiently large interelectrode distance even at so large values of an electric field strength, when it is possible to neglect ionization friction. Correspondingly, the runaway electron producing in a gas is determined not by the local criteria accepted presently, but by the ratio of interelectrode distance and the characteristic electron multiplication length. Basing on numerical simulations for nitrogen gas we show that the critical discharge voltage Ucr(pd), at which the runaway electrons begin prevail, is a function of the product of the interelectrode distance by the gas pressure pd. This function (escape curve of Ucr-pd dependence) separates the area of an effective multiplication of electrons and the area, in which electrons escape discharge gap not having time to be multiplied. The curve Ucr(pd) has the upper and lower branches. Using Ucr(pd) we obtain the analog of well-known Paschen curve, which describes additionally the absence of a self-sustained discharge at a high voltages sufficiently rapidly supplied across the electrodes. Escape curves for helium, xenon and nitrogen are presented.

  10. Investigation Into Gas-Sensing Mechanism of Nanostructured Magnesium Aluminate as a Function of Temperature.

    PubMed

    Nithyavathy, N; Arunmetha, S; Dhineshbabu, N R; Rajendran, V

    2015-07-01

    In this study, we used a new simple chemical method to synthesise nanostructured magnesium aluminate (NMA) powder. Sol-gel technique followed by sonication was used to develop different sensor samples namely NMA573, NMA873, and NMA1 073 by calcination at temperatures of 573, 873, and 1073 K respectively. Average crystallite size of 18-27 nm and specific surface area of 68.09 to 61.84 m2 g(-1) was obtained for the sensor samples. The existence of functional groups at 800 and 550 cm-1 corresponding respectively to AIO6 group and the lattice vibration of MgO4 stretching were confirmed through FTIR studies; SEM/EDX confirm the spherical morphology with elemental composition Mg, Al and O at different calcination temperatures. UV-Vis absorption spectra show band gap energy as 3.50, 3.48, and 3.44 eV for the sensor samples NMA573, NMA873, and NMA1 073 respectively. The effect of polyethylene glycol on the gas-sensing behaviour was studied in all the sensor samples. In particular, NMA1073 was found to have better resistance and sensor response for CO gas than NMA573 and NMA873. The effect of increase in calcination temperature of the sensor samples on the structural, morphological, optical, and gas response properties were carried out extensively to explore its gas sensing applications.

  11. Severe Local Hypothermia from Laparoscopic Gas Evaporative Jet Cooling: A Mechanism To Explain Clinical Observations

    PubMed Central

    Gray, Robert I.; Henderson, A. Courtney; Cochran, Steve A.; Roth, Elizabeth A.

    1999-01-01

    Background and Objectives: Explanations for laparoscopic-induced hypothermia fail to explain clinical observations. It is possible that water evaporation occurs from the jet stream of gas inflation resulting in tissue surface super-cooling leading to tissue damage and drying. Methods: Theoretical calculations based on thermal conductivity, mass transfer effects and heat flux considerations correlated closely with synthetic and tissue experiments. Thermocouple measurements at a rate of 15 data points per second were performed. Results: Cooling rates of 10 to 25 degrees centigrade per second for high flow rates were found based on gas flow rate and effective size of gas delivery site. These rapid temperature drops extended beyond a 2 cm2 diameter. Conclusions: Evaporative cooling accounts for significant hypothermia. The cooling is dependent on the lack of water vapor in the gases currently used during laparoscopy. Cooling rates are independent of height from tissue and geometry of delivery port. Heating and hydrating the gas to a physiologic condition eliminates hypothermia and tissue dessication. PMID:10527326

  12. Physical mechanisms of self-organization and formation of current patterns in gas discharges of the Townsend and glow types

    SciTech Connect

    Raizer, Yu. P.; Mokrov, M. S.

    2013-10-15

    The paper discusses current filamentation and formation of current structures (in particular, hexagonal current patterns) in discharges of the Townsend and glow types. The aim of the paper, which is in part a review, is to reveal basic reasons for formation of current patterns in different cases, namely, in dielectric barrier discharge, discharge with semiconductor cathode, and micro-discharge between metallic electrodes. Pursuing this goal, we give a very brief review of observations and discuss only those theoretical, computational, and experimental papers that shed light on the physical mechanisms involved. The mechanisms are under weak currents—the thermal expansion of the gas as a result of Joule heating; under enhanced currents—the electric field and ionization rate redistribution induced by space charge. Both mechanisms lead to instability of the homogeneous discharges. In addition, we present new results of numerical simulations of observed short-living current filaments which are chaotic in space and time.

  13. Synthesis of TiN and (Ti, Al)N powders by mechanical alloying in nitrogen gas

    SciTech Connect

    Ogino, Y.; Yamasaki, T.; Miki, M.; Atsumi, N.; Yoshioka, K. )

    1993-04-15

    Mechanical alloying (MA) is a nonequilibrium alloying process with which various unstable or metastable materials, such as highly supersaturated solid solutions, amorphous alloys and intermetallic compounds, can be prepared. Although MA has been applied most extensively to alloying between solid elements, it is also an effective means for allying gaseous elements by solid-gas reactions. In particular, nitrogen can be alloyed up to very high concentrations with nitride-forming transition metals and their alloys by ball milling their powders in nitrogen gas. In the present study, the authors applied this new nitriding technique to the preparation of TiN and a solid solution nitride (Ti, Al)N, and examined the nitriding kinetics and thermal stabilities of the nitrides.

  14. Gas-phase and solution-phase polymerization of epoxides by Cr(salen) complexes: evidence for a dinuclear cationic mechanism.

    PubMed

    Schön, Eva; Zhang, Xiangyang; Zhou, Zhiping; Chisholm, Malcolm H; Chen, Peter

    2004-11-15

    The gas-phase reactions of a series of mass-selected mononuclear and dinuclear Cr(salen) complexes with propylene oxide suggest that the enhanced reactivity of the dinuclear complexes in gas-phase and in solution may derive from a dicationic mechanism in which the alkoxide chain is mu(2)-coordinated to two Lewis acidic metal centers. The double coordination is proposed to suppress backbiting, and hence chain-transfer in the gas-phase homopolymerization of epoxides.

  15. Effects of void size and gas content on electrical breakdown in lightweight, mechanically compliant, void-filled dielectrics

    NASA Astrophysics Data System (ADS)

    Anderson, R. A.; Lagasse, R. R.; Russick, E. M.; Schroeder, J. L.

    2002-03-01

    Dielectric potting materials (encapsulants) are used to prevent air breakdown in high-voltage electrical devices. We report breakdown strengths in void-filled encapsulants, stressed with unipolar voltage pulses of the order of 10 μs duration. High strengths, on the order of 100 kV mm-1, are measured under these test conditions. The materials studied include low-density open celled gel-derived foams with cell sizes of 4 μm or less, closed celled CO2-blown polystyrene and urethane foams, and epoxies containing 48 vol % of hollow glass microballoon (GMB) fillers. These last specimens varied the void gas (N2 or SO2) and also the void diameters (tens to hundreds of μm). Our measurements are thought to be directly sensitive to the rate of field-induced ionization events in the void gas; however, the breakdown strengths of the materials tested appeared to vary in direct proportion with the conventional Paschen-law gas-discharge inception threshold, the electric stress at which gas-ionization avalanches become possible. The GMB-epoxy specimens displayed this type of dependence of breakdown strength on the void-gas density and void size, but the measurements were an order of magnitude above the conventional predictions. Small-celled foams also showed increased breakdown strengths with decreased cell size, although their irregular void geometry prevented a direct comparison with the more uniformly structured microballoon-filled encapsulants. The experimental observations are consistent with a breakdown mechanism in which the discharge of a few voids can launch a full breakdown in the composite material.

  16. Fast self-diffusion of ions in CH 3 NH 3 PbI 3 : the interstiticaly mechanism versus vacancy-assisted mechanism

    SciTech Connect

    Yang, Ji-Hui; Yin, Wan-Jian; Park, Ji-Sang; Wei, Su-Huai

    2016-01-01

    The stability of organic-inorganic halide perovskites is a major challenge for their applications and has been extensively studied. Among the possible underlying reasons, ion self-diffusion has been inferred to play important roles. While theoretical studies congruously support that iodine is more mobile, experimental studies only observe the direct diffusion of the MA ion and possible diffusion of iodine. The discrepancy may result from the incomplete understanding of ion diffusion mechanisms. With the help of first-principles calculations, we studied ion diffusion in CH3NH3PbI3 (MAPbI3) through not only the vacancy-assisted mechanisms presumed in previous theoretical studies, but also the neglected interstiticaly mechanisms. We found that compared to the diffusion through the vacancy-assisted mechanism, MA ion diffusion through the interstiticaly mechanism has a much smaller barrier which could explain experimental observations. For iodine diffusion, both mechanisms can yield relatively small barriers. Depending on the growth conditions, defect densities of vacancies and interstitials can vary and so do the diffusion species as well as diffusion mechanisms. Our work thus supports that both MA and iodine ion diffusion could contribute to the performance instability of MAPbI3. While being congruous with experimental results, our work fills the research gap by providing a full understanding of ion diffusion in halide perovskites.

  17. Mechanism of wiggling enhancement due to HBr gas addition during amorphous carbon etching

    NASA Astrophysics Data System (ADS)

    Kofuji, Naoyuki; Ishimura, Hiroaki; Kobayashi, Hitoshi; Une, Satoshi

    2015-06-01

    The effect of gas chemistry during etching of an amorphous carbon layer (ACL) on wiggling has been investigated, focusing especially on the changes in residual stress. Although the HBr gas addition reduces critical dimension loss, it enhances the surface stress and therefore increases wiggling. Attenuated total reflectance Fourier transform infrared spectroscopy revealed that the increase in surface stress was caused by hydrogenation of the ACL surface with hydrogen radicals. Three-dimensional (3D) nonlinear finite element method analysis confirmed that the increase in surface stress is large enough to cause the wiggling. These results also suggest that etching with hydrogen compound gases using an ACL mask has high potential to cause the wiggling.

  18. Mechanical degradation of API X65 pipeline steel by exposure to hydrogen gas

    NASA Astrophysics Data System (ADS)

    Lee, Yun-Hee; Lee, Hae Moo; Kim, Yong-il; Nahm, Seung-Hoon

    2011-06-01

    Hydrogen-induced degradations have generally been investigated through the ex situ testing of cathodically hydrogen-charged specimens. However, the cathodic charging cannot realize damage accumulation by gaseous hydrogen in transportation pipelines. Thus, we designed an ampule specimen which enables an in situ tensile test containing gaseous hydrogen. Ampule specimens made of API (American Petroleum Institute) X65 pipeline steel showed significant reductions of 3.4 % and 4.1 %, respectively, in their ultimate tensile strength and fracture strain after exposure to 20 MPa of hydrogen gas. The resulting fracture surface showed quasi-cleavage perpendicular to the loading direction and a fracture thickness close to the initial wall thickness, significantly different from the complex dimples and highly reduced fracture thickness by shear deformations in nitrogen gas and air environments.

  19. The quantum mechanics of ion-enhanced field emission and how it influences microscale gas breakdown

    SciTech Connect

    Li, Yingjie; Go, David B.

    2014-09-14

    The presence of a positive gas ion can enhance cold electron field emission by deforming the potential barrier and increasing the tunneling probability of electrons—a process known as ion-enhanced field emission. In microscale gas discharges, ion-enhanced field emission produces additional emission from the cathode and effectively reduces the voltage required to breakdown a gaseous medium at the microscale (<10 μm). In this work, we enhance classic field emission theory by determining the impact of a gaseous ion on electron tunneling and compute the effect of ion-enhanced field emission on the breakdown voltage. We reveal that the current density for ion-enhanced field emission retains the same scaling as vacuum cold field emission and that this leads to deviations from traditional breakdown theory at microscale dimensions.

  20. Architectural and Biochemical Expressions of Mustard Gas Keratopathy: Preclinical Indicators and Pathogenic Mechanisms

    DTIC Science & Technology

    2012-08-10

    Nanoscale topography of the basement membrane underlying the corneal epithelium of the rhesus macaque. Cell Tissue Res 299: 39–46. 28. Pal-Ghosh S...with associated secondary pathologies, collectively referred to as mustard gas keratopathy (MGK). MGK involves a progressive corneal degeneration...resulting in chronic ocular discomfort and impaired vision for which clinical interventions have typically had poor outcomes. Using a rabbit corneal vapor

  1. Mechanisms of disruptions caused by noble gas injection into tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Morozov, D. Kh.; Yurchenko, E. I.; Lukash, V. E.; Baronova, E. O.; Pozdnyakov, Yu. I.; Rozhansky, V. A.; Senichenkov, I. Yu.; Veselova, I. Yu.; Schneider, R.

    2005-08-01

    Noble gas injection for disruption mitigation in DIII-D is simulated. The simulation of the first two stages of the disruption is performed: the first one is the neutral gas jet penetration through the background plasmas, and the second one is the instability growth. In order to simulate the first stage, the MHD pellet code LLP with improved radiation model for noble gas is used. Plasma cooling at this stage is provided by the energy exchange with the jet. The opacity effects in radiation losses are found to be important in the energy balance calculations. The magnetic surfaces in contact with the jet are cooled significantly; however, the temperature as well as the electric conductivity, remains high. The cooling front propagates towards the plasma centre. It has been shown that the cooling front is accompanied by strongly localized 'shark fin-like' perturbation in toroidal current density profile. The simplified cylindrical model shows that the cooling front is able to produce the internal kink-like mode with growth rate significantly higher than the tearing mode. The unstable kink perturbation obtained is non-resonant for any magnetic surface, both inside the plasma column, and in the vacuum space outside the separatrix. The mode disturbs mainly the core region. The growth time of the 'shark fin-like' mode is higher than the Alfven time by a factor of 10-100 for DIII-D parameters.

  2. Assessing the Relative Contributions of Active Ankle and Knee Assistance to the Walking Mechanics of Transfemoral Amputees Using a Powered Prosthesis

    PubMed Central

    Simon, Ann M.; Hargrove, Levi J.

    2016-01-01

    Powered knee-ankle prostheses are capable of providing net-positive mechanical energy to amputees. Yet, there are limitless ways to deliver this energy throughout the gait cycle. It remains largely unknown how different combinations of active knee and ankle assistance affect the walking mechanics of transfemoral amputees. This study assessed the relative contributions of stance phase knee swing initiation, increasing ankle stiffness and powered plantarflexion as three unilateral transfemoral amputees walked overground at their self-selected walking speed. Five combinations of knee and ankle conditions were evaluated regarding the kinematics and kinetics of the amputated and intact legs using repeated measures analyses of variance. We found eliminating active knee swing initiation or powered plantarflexion was linked to increased compensations of the ipsilateral hip joint during the subsequent swing phase. The elimination of knee swing initiation or powered plantarflexion also led to reduced braking ground reaction forces of the amputated and intact legs, and influenced both sagittal and frontal plane loading of the intact knee joint. Gradually increasing prosthetic ankle stiffness influenced the shape of the prosthetic ankle plantarflexion moment, more closely mirroring the intact ankle moment. Increasing ankle stiffness also corresponded to increased prosthetic ankle power generation (despite a similar maximum stiffness value across conditions) and increased braking ground reaction forces of the amputated leg. These findings further our understanding of how to deliver assistance with powered knee-ankle prostheses and the compensations that occur when specific aspects of assistance are added/removed. PMID:26807889

  3. Sprayed zinc oxide films: Ultra-violet light-induced reversible surface wettability and platinum-sensitization-assisted improved liquefied petroleum gas response.

    PubMed

    Nakate, Umesh T; Patil, Pramila; Bulakhe, R N; Lokhande, C D; Kale, Sangeeta N; Naushad, Mu; Mane, Rajaram S

    2016-10-15

    We report the rapid (superhydrophobic to superhydrophilic) transition property and improvement in the liquefied petroleum gas (LPG) sensing response of zinc oxide (ZnO) nanorods (NRs) on UV-irradiation and platinum (Pt) surface sensitization, respectively. The morphological evolution of ZnO NRs is evidenced from the field emission scanning electron microscope and atomic force microscope digital images and for the structural elucidation X-ray diffraction pattern is used. Elemental survey mapping is obtained from energy dispersive X-ray analysis spectrum. The optical properties have been studied by UV-Visible and photoluminescence spectroscopy measurements. The rapid (120sec) conversion of superhydrophobic (154°) ZnO NRs film to superhydrophilic (7°) is obtained under UV light illumination and the superhydrophobicity is regained by storing sample in dark. The mechanism for switching wettability behavior of ZnO NRs has thoroughly been discussed. In second phase, Pt-sensitized ZnO NRs film has demonstrated considerable gas sensitivity at 260ppm concentration of LPG. At 623K operating temperature, the maximum LPG response of 58% and the response time of 49sec for 1040ppm LPG concentration of Pt- sensitized ZnO NRs film are obtained. This higher LPG response of Pt-sensitized ZnO NRs film over pristine is primarily due to electronic effect and catalytic effect (spill-over effect) caused by an additional of Pt on ZnO NRs film surface.

  4. Biomolecule-assisted synthesis and gas-sensing properties of porous nanosheet-based corundum In{sub 2}O{sub 3} microflowers

    SciTech Connect

    Zhang Wenhui; Zhang Weide

    2012-02-15

    Porous nanosheet-based corundum In{sub 2}O{sub 3} microflowers were fabricated by one-pot hydrothermal treatment of D-fructose and In(NO{sub 3}){sub 3} mixture using urea as a precipitating agent followed by calcination. The products were characterized by X-ray diffraction, scanning and transmission electron microscopy. The effects of D-fructose and urea on the fabrication of nanosheet-based corundum In{sub 2}O{sub 3} microflowers were investigated and a possible mechanism is proposed to explain the formation of the hierarchical nanostructures. The gas sensor based on the In{sub 2}O{sub 3} microflowers exhibits excellent sensing properties for the detection of formaldehyde. - Graphical abstract: Nanosheets-based corundum In{sub 2}O{sub 3} microflowers were fabricated by one-pot hydrothermal treatment of D-fructose/In(NO{sub 3}){sub 3} mixture followed by calcination, which show high performance for formaldehyde sensing. Highlights: Black-Right-Pointing-Pointer Preparation of porous nanosheet-based corundum In{sub 2}O{sub 3} microflowers. Black-Right-Pointing-Pointer Morphology and phase control of In{sub 2}O{sub 3}. Black-Right-Pointing-Pointer Gas sensor based on the In{sub 2}O{sub 3} microflowers exhibits excellent sensing properties for the detection of formaldehyde.

  5. Microstructure and Mechanical Properties of Gas-Tungsten-Arc-Welded Ti-15-3 Beta Titanium Alloy

    NASA Astrophysics Data System (ADS)

    Balachandar, K.; Subramanya Sarma, V.; Pant, Bhanu; Phanikumar, G.

    2009-11-01

    Microstructure and mechanical properties of gas-tungsten-arc (GTA)-welded Ti-15V-3Cr-3Sn-3Al alloy in direct current electrode negative mode are characterized. The thermal profile was measured during welding with continuous current (CC) and pulsed current (PC) at different frequencies. A single-step postweld aging of the welded samples at subtransus temperature was attempted to study precipitation of alpha phase. Two different morphologies of alpha phase are observed along with a partitioning of alloying elements into the two phases. Processing conditions for higher strength are identified and correlated with the thermal profile. Microstructure changes due to postweld heat treatment were characterized.

  6. CO2-Binding Organic Liquids Gas Capture with Polarity-Swing-Assisted Regeneration Full Technology Feasibility Study B1 - Solvent-based Systems

    SciTech Connect

    Heldebrant, David J

    2014-08-31

    PNNL, Fluor Corporation and Queens University (Kingston, ON) successfully completed a three year comprehensive study of the CO2BOL water-lean solvent platform with Polarity Swing Assisted Regeneration (PSAR). This study encompassed solvent synthesis, characterization, environmental toxicology, physical, thermodynamic and kinetic property measurements, Aspen Plus™ modeling and bench-scale testing of a candidate CO2BOL solvent molecule. Key Program Findings The key program findings are summarized as follows: • PSAR favorably reduced stripper duties and reboiler temperatures with little/no impact to absorption column • >90% CO2 capture was achievable at reasonable liquid-gas ratios in the absorber • High rich solvent viscosities (up to 600 cP) were successfully demonstrated in the bench-scale system. However, the projected impacts of high viscosity to capital cost and operational limits compromised the other levelized cost of electricity benefits. • Low thermal conductivity of organics significantly increased the required cross exchanger surface area, and potentially other heat exchange surfaces. • CO2BOL had low evaporative losses during bench-scale testing • There was no evidence of foaming during bench scale testing • Current CO2BOL formulation costs project to be $35/kg • Ecotoxicity (Water Daphnia) was comparable between CO2BOL and MEA (169.47 versus 103.63 mg/L) • Full dehydration of the flue gas was determined to not be economically feasible. However, modest refrigeration (13 MW for the 550 MW reference system) was determined to be potentially economically feasible, and still produce a water-lean condition for the CO2BOLs (5 wt% steady-state water loading). • CO2BOLs testing with 5 wt% water loading did not compromise anhydrous performance behavior, and showed actual enhancement of CO2 capture performance. • Mass transfer of CO2BOLs was not greatly impeded by viscosity • Facile separation of antisolvent from lean CO2BOL was

  7. Ultrasonic-assisted water extraction and solvent bar microextraction followed by gas chromatography-ion trap mass spectrometry for determination of chlorobenzenes in soil samples.

    PubMed

    Wang, Li; Wang, Linling; Chen, Jing; Du, Wenjun; Fan, Guoliang; Lu, Xiaohua

    2012-09-21

    A novel and simple analytical method for the determination of chlorobenzenes (CBs) in soil samples was developed using ultrasonic-assisted water extraction (UAWE) coupled with solvent bar microextraction (SBME). Four chlorobenzenes, 1,2,3-trichlorobenzene (1,2,3-TCB), 1,2,3,4-tetrachlorobenzene (1,2,3,4-TeCB), hexachlorobenzene (HCB), and 1-chloro-4-nitrobenzene (1-C-4-NB), were used as model compounds to investigate the extraction performance. Parameters affecting the extraction efficiency were investigated in detail. UAWE was used for the extraction of CBs from 1.0 g of sediment using 10 mL of ultrapure water at 100 W for 30 min at 30-35 °C. The extract was subsequently subjected to a single step SBME cleanup and enrichment procedure. Both ends of the solvent bar with about 4 μL of 1-octanol were sealed by a sealing machine, and it was placed in the soil slurry for extraction. After extraction, analysis was carried out by gas chromatography-ion trap mass spectrometry (GC-ITMS) detection. The relative recoveries from the spiked soil sample varied between 93 and 105% for CBs, and exceeded levels achieved for conventional Soxhlet extraction. The method linearities were 10-150, 40-600, and 100-1500 ng g(-1) for different CBs. The limits of detection (LODs) and the limits of quantification (LOQs) were in the range of 0.7-27.3 ng g(-1) and 2.2-90.9 ng g(-1), respectively. Good reproducibilities were obtained with relative standard deviation (RSD) values below 6.8%. The analytical potential of the method was demonstrated by applying the method to spiked soil sample.

  8. A new method for quantifying prenatal exposure to ethanol by microwave-assisted extraction (MAE) of meconium followed by gas chromatography-mass spectrometry (GC-MS).

    PubMed

    Cabarcos, Pamela; Tabernero, María Jesús; Alvarez, Iván; Miguez, Martha; Fernández, Purificación; Bermejo, Ana María

    2012-07-01

    Ethanol is a legal and widely available substance. There are health and social consequences associated with its abuse. One of the most important problems is related to alcohol consumption during pregnancy. In fact, prenatal ethanol exposure can be associated with fetal alcohol spectrum disorder (FASD), a term used to describe a wide range of potentially lifelong effects that include physical, mental, behavioral, and learning disabilities. Fatty acid ethyl esters (FAEEs), which are non-oxidative metabolites of ethanol, are currently used as biomarkers of direct ethanol consumption in different matrices, including hair, blood, skin surface, and meconium. Analysis of these compounds in meconium reveals exposure to alcohol during the second and third trimesters of pregnancy. An important finding for evaluation of gestational ethanol exposure is the fact that FAEEs do not cross the placenta. Because they accumulate in the fetal gut from approximately the 20th week of gestation until birth, this provides a wide window of detection of chronic exposure to alcohol. The sum of the concentrations of all the FAEEs, with a cutoff of 2 nmol g(-1) or 600 ng g(-1) meconium, has been recommended as evidence of maternal alcohol use. We introduce a novel technique to quantify ethyl myristate, ethyl palmitate, ethyl stearate, and their deuterated analogues (as internal standards, IS) in meconium using microwave-assisted extraction (MAE) coupled with gas chromatography-mass spectrometry (GC-MS). Limits of detection and quantification were 50 and 100 ng g(-1) for all analytes except ethyl stearate (LOD 100 ng g(-1) and LOQ 500 ng g(-1)). Calibration curves were linear from the LOQ to 5000 ng g(-1). The validated method was applied to the analysis of 81 meconium samples.

  9. Application of microwave-assisted desorption/headspace solid-phase microextraction as pretreatment step in the gas chromatographic determination of 1-naphthylamine in silica gel adsorbent.

    PubMed

    Yan, Cheing-Tong; Jen, Jen-Fon; Shih, Tung-Sheng

    2007-03-30

    Pretreatment of silica gel sample containing 1-naphthylamine by microwave-assisted desorption (MAD) coupled to in situ headspace solid phase microextraction (HS-SPME) has been investigated as a possible alternative to conventional methods prior to gas chromatographic (GC) analysis. The 1-naphthylamine desorbs from silica gel to headspace under microwave irradiation, and directly absorbs onto a SPME fiber located in a controlled-temperature headspace area. After being collected on the SPME fiber, and desorbed in the GC injection port, 1-naphthylamine is analyzed by GC-FID. Parameters that influence the extraction efficiency of the MAD/HS-SPME, such as the extraction media and its pH, the microwave irradiation power and irradiation time as well as desorption conditions of the GC injector, have been investigated. Experimental results indicate that the extraction of a 150mg silica gel sample by using 0.8ml of 1.0M NaOH solution and a PDMS/DVB fiber under high-powered irradiation (477W) for 5min maximizes the extraction efficiency. Desorption of 1-naphthylamine from the SPME fiber in GC injector is optimal at 250 degrees C held for 3min. The detection limit of method is 8.30ng. The detected quantity of 1-naphthylamine obtained by the proposed method is 33.3 times of that obtained by the conventional solvent extraction method for the silica gel sample containing 100ng of 1-naphthylamine. It provides a simple, fast, sensitive and organic-solvent-free pretreatment procedure prior to the analysis of 1-naphthylamine collected on a silica gel adsorbent.

  10. Analyses of polychlorinated biphenyls in waters and wastewaters using vortex-assisted liquid-liquid microextraction and gas chromatography-mass spectrometry.

    PubMed

    Ozcan, Senar

    2011-03-01

    A method was developed for viable and rapid determination of seven polychlorinated biphenyls (PCBs) in water samples with vortex-assisted liquid-liquid microextraction (VALLME) using gas chromatography-mass spectrometry (GC-MS). At first, the most suitable extraction solvent and extraction solvent volume were determined. Later, the parameters affecting the extraction efficiency such as vortex extraction time, rotational speed of the vortex, and ionic strength of the sample were optimized by using a 2(3) factorial experimental design. The optimized extraction conditions for 5 mL water sample were as follows: extractant solvent 200 μL of chloroform; vortex extraction time of 2 min at 3000 rpm; centrifugation 5 min at 4000 rpm, and no ionic strength. Under the optimum condition, limits of detection (LOD) ranged from 0.36 to 0.73 ng/L. Mean recoveries of PCBs from fortified water samples are 96% for three different fortification levels and RSDs of the recoveries are below 5%. The developed procedure was successfully applied to the determination of PCBs in real water and wastewater samples such as tap, well, surface, bottled waters, and municipal, treated municipal, and industrial wastewaters. The performance of the proposed method was compared with traditional liquid-liquid extraction (LLE) of real water samples and the results show that efficiency of proposed method is comparable to the LLE. However, the proposed method offers several advantages, i.e. reducing sample requirement for measurement of target compounds, less solvent consumption, and reducing the costs associated with solvent purchase and waste disposal. It is also viable, rapid, and easy to use for the analyses of PCBs in water samples by using GC-MS.

  11. Ultrasound-assisted dispersive liquid-liquid microextraction for the determination of synthetic musk fragrances in aqueous matrices by gas chromatography-mass spectrometry.

    PubMed

    Homem, Vera; Alves, Alice; Alves, Arminda; Santos, Lúcia

    2016-01-01

    A rapid and simple method for the simultaneous determination of twelve synthetic musks in water samples, using ultrasound-assisted dispersive liquid-liquid microextraction (UA-DLLME) coupled with gas chromatography-mass spectrometry (GC-MS) was successfully developed. The influence of seven factors (volume of the extraction solvent and disperser solvent, sample volume, extraction time, ionic strength, type of extraction and disperser solvent) affecting the UA-DLLME extraction efficiency was investigated using a screening design. The significant factors were selected and optimised employing a central composite design: 80 μL of chloroform, 880 μL of acetonitrile, 6 mL of sample volume, 3.5% (wt) of NaCl and 2 min of extraction time. Under the optimised conditions, this methodology was successfully validated for the analysis of 12 synthetic musk compounds in different aqueous samples (tap, sea and river water, effluent and influent wastewater). The proposed method showed enrichment factors between 101 and 115 depending on the analyte, limits of detection in the range of 0.004-54 ng L(-1) and good repeatability (most relative standard deviation values below 10%). No significant matrix effects were found, since recoveries ranged between 71% and 118%. Finally, the method was satisfactorily applied to the analysis of five different aqueous samples. Results demonstrated the existence of a larger amount of synthetic musks in wastewaters than in other water samples (average concentrations of 2800 ng L(-1) in influent and 850 ng L(-1) in effluent). Galaxolide, tonalide and exaltolide were the compounds most detected.

  12. Determination of nitroaromatic explosives in water samples by direct ultrasound-assisted dispersive liquid-liquid microextraction followed by gas chromatography-mass spectrometry.

    PubMed

    Cortada, Carol; Vidal, Lorena; Canals, Antonio

    2011-10-15

    A fast, simple, inexpensive, sensitive, efficient and environmental friendly direct ultrasound-assisted dispersive liquid-liquid microextraction (DUSA-DLLME) procedure has been developed to concentrate five nitroaromatic explosives from water samples prior to quantification by gas chromatography-mass spectrometry (GC-MS). An efficient ultrasonic probe has been used to radiate directly the samples producing very fine emulsions from immiscible liquids. A D-optimal design was used for optimizing the factors and to evaluate their influential upon extraction. The optimum experimental conditions were: sample volume, 10 mL; extraction time, 60s; cycles, 0.6s(s(-1)); power of ultrasound energy, 40% (70 W); and, extractant solvent (chlorobenzene) volume, 20 μL. Under the optimized experimental conditions the method presents good level of repeatability with coefficients of variation under 6% (n=8; spiking level 10 μg L(-1)). Calculated calibration curves gave high level of linearity with correlation coefficient values between 0.9949 and 0.9992. Limits of detection were ranged between 0.03 and 0.91 μg L(-1). Finally, the proposed method was applied to the analysis of two types of water samples, reservoir and effluent wastewater. The samples were previously analysed and confirmed free of target analytes. At 5 μg L(-1) spiking level recovery values ranged between 75 and 96% for reservoir water sample showing that the matrix had a negligible effect upon extraction. However, a noticeable matrix effect (around 50% recovery) was observed for effluent wastewater sample. In order to alleviate this matrix effect, the standard addition calibration method was used for quantitative determination. This calibration method supplied recovery values ranged between 71 and 79%. The same conclusions have been obtained from an uncertainty budget evaluation study.

  13. Determination of geosmin and 2-methylisoborneol in water and wine samples by ultrasound-assisted dispersive liquid-liquid microextraction coupled to gas chromatography-mass spectrometry.

    PubMed

    Cortada, Carol; Vidal, Lorena; Canals, Antonio

    2011-01-07

    A fast, simple and environmentally friendly ultrasound-assisted dispersive liquid-liquid microextraction (USADLLME) procedure has been developed to preconcentrate geosmin and 2-methylisoborneol (MIB) from water and wine samples prior to quantification by gas chromatography-mass spectrometry (GC-MS). A two-stage multivariate optimization approach was developed by means of a Plackett-Burman design for screening and selecting the significant variables involved in the USADLLME procedure, which was later optimized by means of a circumscribed central composite design. The optimum conditions were: solvent volume, 8μL; solvent type: tetrachloroethylene; sample volume, 12 mL; centrifugation speed, 2300 rpm; extraction temperature 20 °C; extraction time, 3 min; and centrifugation time, 3 min. Under the optimized experimental conditions the method gave good levels of repeatability with coefficient of variation under 11% (n=10). Limits of detection were 2 and 9 ng L⁻¹ for geosmin and MIB, respectively. Calculated calibration curves gave high levels of linearity with correlation coefficient values of 0.9988 and 0.9994 for geosmin and MIB, respectively. Finally, the proposed method was applied to the analysis of two water (reservoir and tap) samples and three wine (red, rose and white) samples. The samples were previously analyzed and confirmed free of target analytes. Recovery values ranged between 70 and 113% at two spiking levels (0.25 μg L⁻¹ and 30 ng L⁻¹) showing that the matrix had a negligible effect upon extraction. Only red wine showed a noticeable matrix effect (70-72% recovery). Similar conclusions have been obtained from an uncertainty budget evaluation study.

  14. Determination of polycyclic aromatic hydrocarbons in aqueous samples by microwave assisted headspace solid-phase microextraction and gas chromatography/flame ionization detection.

    PubMed

    Wei, Ming-Chi; Jen, Jen-Fon

    2007-06-15

    The novel pretreatment technique, microwave-assisted heating coupled to headspace solid-phase microextraction (MA-HS-SPME) has been studied for one-step in situ sample preparation for polycyclic aromatic hydrocarbons (PAHs) in aqueous samples before gas chromatography/flame ionization detection (GC/FID). The PAHs evaporated into headspace with the water by microwave irradiation, and absorbed directly on a SPME fiber in the headspace. After being desorbed from the SPME fiber in the GC injection port, PAHs were analyzed by GC/FID. Parameters affecting extraction efficiency, such as SPME fiber coating, adsorption temperature, microwave power and irradiation time, and desorption conditions were investigated. Experimental results indicated that extraction of 20mL aqueous sample containing PAHs at optional pH, by microwave irradiation with effective power 145W for 30min (the same as the extraction time), and collection with a 65mum PDMS/DVB fiber at 20 degrees C circular cooling water to control sampling temperature, resulted in the best extraction efficiency. Optimum desorption of PAHs from the SPME fiber in the GC hot injection port was achieved at 290 degrees C for 5min. The method was developed using spiked water sample such as field water with a range of 0.1-200mug/L PAHs. Detection limits varied from 0.03 to 1.0mug/L for different PAHs based on S/N=3 and the relative standard deviations for repeatability were <13%. A real sample was collected from the scrubber water of an incineration system. PAHs of two to three rings were measured with concentrations varied from 0.35 to 7.53mug/L. Recovery was more than 88% and R.S.D. was less than 17%. The proposed method is a simple, rapid, and organic solvent-free procedure for determination of PAHs in wastewater.

  15. Salt-assisted dispersive liquid-liquid microextraction coupled with programmed temperature vaporization gas chromatography-mass spectrometry for the determination of haloacetonitriles in drinking water.

    PubMed

    Ma, Huilian; Li, Yun; Zhang, Haijun; Shah, Syed Mazhar; Chen, Jiping

    2014-09-05

    We report here a new analytical method for the simultaneous determination of seven haloacetonitriles (HANs) in drinking water by coupling salt-assisted dispersive liquid-liquid microextraction (SADLLME) with programmed temperature vaporizer-gas chromatography-mass spectrometry (PTV-GC-MS). The newly developed method involves the dispersion of the extractant in aqueous sample by addition of a few grams of salt and no dispersion liquid was required as compared to the traditional DLLME methods. The extractant (CH2Cl2, 50μL) and the salt (Na2SO4, 2.4g) were successively added to water (8mL) in a conical centrifuge tube that was shaken for 1min and centrifuged (3500rpm, 3min). The aliquot of sedimented phase (4μL) was then directly injected into the PTV-GC-MS system. The limits of detection and quantification for the HANs were 0.4-13.2ngL(-1) and 1.2-43.9ngL(-1), respectively. The calibration curves showed good linearity (r(2)≥0.9904) over 3 orders of magnitude. The repeatability of the method was investigated by evaluating the intra- and inter-day precisions. The relative standard deviations (RSDs) obtained were lower than 10.2% and 7.8% at low and high concentration levels. The relative recoveries ranged from 79.3% to 105.1%. The developed methodology was applied for the analysis of seven HANs in several drinking water samples in coastal and inland cities of China. It was demonstrated to be a simple, sensible, reproducible and environment friendly method for the determination of trace HANs in drinking water samples.

  16. Chemometric-based determination of polycyclic aromatic hydrocarbons in aqueous samples using ultrasound-assisted emulsification microextraction combined to gas chromatography-mass spectrometry.

    PubMed

    Ahmadvand, Mohammad; Sereshti, Hassan; Parastar, Hadi

    2015-09-25

    In the present research, ultrasonic-assisted emulsification-microextraction (USAEME) coupled with gas chromatography-mass spectrometry (GC-MS) has been proposed for analysis of thirteen environmental protection agency (EPA) polycyclic aromatic hydrocarbons (PAHs) in aqueous samples. Tetrachloroethylene was selected as extraction solvent. The main parameters of USAEME affecting the efficiency of the method were modeled and optimized using a central composite design (CCD). Under the optimum conditions (9μL for extraction solvent, 1.15% (w/v) NaCl (salt concentration) and 10min for ultrasonication time), preconcentration factor (PF) of the PAHs was in the range of 500-950. In order to have a comprehensive analysis, multivariate curve resolution-alternating least squares (MCR-ALS) as a second-order calibration algorithm was used for resolution, identification and quantification of the target PAHs in the presence of uncalibrated interferences. The regression coefficients and relative errors (REs, %) of calibration curves of the PAHs were in the satisfactory range of 0.9971-0.9999 and 1.17-6.59%, respectively. Furthermore, analytical figures of merit (AFOM) for univariate and second-order calibrations were obtained and compared. As an instance, the limit of detections (LODs) of target PAHs were in the range of 1.87-18.9 and 0.89-6.49ngmL(-1) for univariate and second-order calibration, respectively. Finally, the proposed strategy was used for determination of target PAHs in real water samples (tap and hookah waters). The relative recoveries (RR) and the relative standard deviations (RSDs) were 68.4-109.80% and 2.15-6.93%, respectively. It was concluded that combination of multivariate chemometric methods with USAEME-GC-MS can be considered as a new insight for the analysis of target analytes in complex sample matrices.

  17. Purge-assisted headspace solid-phase microextraction combined with gas chromatography/mass spectrometry for the determination of trace nitrated polycyclic aromatic hydrocarbons in aqueous samples.

    PubMed

    Hung, Cheng-Han; Ho, Hsin-Pin; Lin, Mei-Tzu; Chen, Chung-Yu; Shu, Youn-Yuen; Lee, Maw-Rong

    2012-11-23

    This study describes a new procedure, namely, purge-assisted headspace solid phase microextraction combined with gas chromatography/negative ion chemical ionization mass spectrometry (PA/HS-SPME-GC/NICI-MS), which is used to determine seven nitrated polycyclic aromatic hydrocarbons (NPAHs) in aqueous samples. High extraction efficiency was obtained with PA/HS-SPME with polydimethylsiloxane (PDMS) fiber coating. A programmable temperature vaporizing (PTV) inlet was used in the desorption process. Selected ion monitoring (SIM) was used for quantitative and qualitative purposes. The linear range of detection of the proposed method was 5-5000 pg/mL with coefficients of determination between 0.995 and 0.999. Limits of detection (LODs) for seven NPAHs were 0.01-0.06 pg/mL. The relative standard deviation was below 12.7% at a concentration of 50 pg/mL. Compared with headspace-solid phase microextraction (HS-SPME), the purge procedure enhanced the extraction efficiency for high boiling point analytes, such as 7-nitrobenz[a]anthracene (7-NBA) and 6-nitrochrysene (6-NC). The proposed method provides a sensitive method for NPAH analysis at the pg/mL level. The application of the proposed method for the determination of trace NPAHs in real samples was investigated by analyzing aqueous samples from rivers. The concentrations of NPAHs detected from the samples ranged from 5.2 to 7.5 pg/mL. This method was applied successfully in the analysis of trace NPAHs in river samples.

  18. Extraction of Mg(OH)2 from Mg silicate minerals with NaOH assisted with H2O: implications for CO2 capture from exhaust flue gas.

    PubMed

    Madeddu, Silvia; Priestnall, Michael; Godoy, Erik; Kumar, R Vasant; Raymahasay, Sugat; Evans, Michael; Wang, Ruofan; Manenye, Seabelo; Kinoshita, Hajime

    2015-01-01

    The utilisation of Mg(OH)2 to capture exhaust CO2 has been hindered by the limited availability of brucite, the Mg(OH)2 mineral in natural deposits. Our previous study demonstrated that Mg(OH)2 can be obtained from dunite, an ultramafic rock composed of Mg silicate minerals, in highly concentrated NaOH aqueous systems. However, the large quantity of NaOH consumed was considered an obstacle for the implementation of the technology. In the present study, Mg(OH)2 was extracted from dunite reacted in solid systems with NaOH assisted with H2O. The consumption of NaOH was reduced by 97% with respect to the NaOH aqueous systems, maintaining a comparable yield of Mg(OH)2 extraction, i.e. 64.8-66%. The capture of CO2 from a CO2-N2 gas mixture was tested at ambient conditions using a Mg(OH)2 aqueous slurry. Mg(OH)2 almost fully dissolved and reacted with dissolved CO2 by forming Mg(HCO3)2 which remained in equilibrium storing the CO2 in the aqueous solution. The CO2 balance of the process was assessed from the emissions derived from the power consumption for NaOH production and Mg(OH)2 extraction together with the CO2 captured by Mg(OH)2 derived from dunite. The process resulted as carbon neutral when dunite is reacted at 250 °C for durations of 1 and 3 hours and CO2 is captured as Mg(HCO3)2.

  19. Exploring the Gas Phase Synthesis of the Elusive Class of Boronyls and the Mechanism of Boronyl Radical Reactions under Single Collision Conditions.

    PubMed

    Kaiser, Ralf I; Balucani, Nadia

    2016-12-19

    Until recently, the chemistry of boronyl (BO), a diatomic radical isolectronic with the cyano (CN) species, has remained unknown. The boronyl group is characterized by a boron-oxygen multiple bond, and because of the inherent electron deficiency of the boron atom, boronyls (RBO) are highly reactive and typically only exist in their cyclotrimeric form (RBO)3. Due to their invaluable role as reactants, the isolation of the monomers in gas phase experiments has been extensively sought after by the organic synthesis and physical organic chemistry communities but never achieved. Besides the interests from a physical organic and synthetic point of view, boronyls also play a role as reaction intermediates in boron-assisted rocket propulsion systems. In this Account, we review recent experimental work in which gas phase organo boronyl monomers (RBO) are formed via bimolecular reactions of the boronyl radical (BO) with C2-C6 unsaturated hydrocarbons. The investigated hydrocarbons are widely exploited as fuels, and their reactions with boronyl radicals under single collision conditions lead to the formation of organo boronyls. Our studies also elucidate the mechanisms of their formation reactions thus furnishing a comprehension at the molecular level of this reaction class. The variety of the employed hydrocarbon substrates has allowed us to systematically classify the chemical behavior of the boronyl radicals. With the exception of the case of the dimethylacetylene reaction, the boron monoxide radical versus atomic hydrogen exchange mechanisms were always open leading to the formation of highly unsaturated organo boronyl monomers (RBO), which could be easily identified because they cannot trimerize under single collision conditions. Besides the hydrogen displacement pathway, methylacetylene, dimethylacetylene, and propylene, carrying one or two methyl groups, were also found to eliminate a methyl group. In all systems, the reactions were barrierless, indirect, and initiated

  20. Modeling of tRNA-assisted mechanism of Arg activation based on a structure of Arg-tRNA synthetase, tRNA, and an ATP analog (ANP).

    PubMed

    Konno, Michiko; Sumida, Tomomi; Uchikawa, Emiko; Mori, Yukie; Yanagisawa, Tatsuo; Sekine, Shun-ichi; Yokoyama, Shigeyuki; Yokoyama, Shigeuki

    2009-09-01

    The ATP-pyrophosphate exchange reaction catalyzed by Arg-tRNA, Gln-tRNA and Glu-tRNA synthetases requires the assistance of the cognate tRNA. tRNA also assists Arg-tRNA synthetase in catalyzing the pyrophosphorolysis of synthetic Arg-AMP at low pH. The mechanism by which the 3'-end A76, and in particular its hydroxyl group, of the cognate tRNA is involved with the exchange reaction catalyzed by those enzymes has yet to be established. We determined a crystal structure of a complex of Arg-tRNA synthetase from Pyrococcus horikoshii, tRNA(Arg)(CCU) and an ATP analog with Rfactor = 0.213 (Rfree = 0.253) at 2.0 A resolution. On the basis of newly obtained structural information about the position of ATP bound on the enzyme, we constructed a structural model for a mechanism in which the formation of a hydrogen bond between the 2'-OH group of A76 of tRNA and the carboxyl group of Arg induces both formation of Arg-AMP (Arg + ATP --> Arg-AMP + pyrophosphate) and pyrophosphorolysis of Arg-AMP (Arg-AMP + pyrophosphate --> Arg + ATP) at low pH. Furthermore, we obtained a structural model of the molecular mechanism for the Arg-tRNA synthetase-catalyzed deacylation of Arg-tRNA (Arg-tRNA + AMP --> Arg-AMP + tRNA at high pH), in which the deacylation of aminoacyl-tRNA bound on Arg-tRNA synthetase and Glu-tRNA synthetase is catalyzed by a quite similar mechanism, whereby the proton-donating group (-NH-C+(NH2)2 or -COOH) of Arg and Glu assists the aminoacyl transfer from the 2'-OH group of tRNA to the phosphate group of AMP at high pH.

  1. Gas sensitivity and sensing mechanism studies on Au-doped TiO₂ nanotube arrays for detecting SF₆ decomposed components.

    PubMed

    Zhang, Xiaoxing; Yu, Lei; Tie, Jing; Dong, Xingchen

    2014-10-17

    The analysis to SF6 decomposed component gases is an efficient diagnostic approach to detect the partial discharge in gas-insulated switchgear (GIS) for the purpose of accessing the operating state of power equipment. This paper applied the Au-doped TiO2 nanotube array sensor (Au-TiO2 NTAs) to detect SF6 decomposed components. The electrochemical constant potential method was adopted in the Au-TiO2 NTAs' fabrication, and a series of experiments were conducted to test the characteristic SF6 decomposed gases for a thorough investigation of sensing performances. The sensing characteristic curves of intrinsic and Au-doped TiO2 NTAs were compared to study the mechanism of the gas sensing response. The results indicated that the doped Au could change the TiO2 nanotube arrays' performances of gas sensing selectivity in SF6 decomposed components, as well as reducing the working temperature of TiO2 NTAs.

  2. A study of the feasibility of directly applying gas generator systems to space shuttle mechanical functions

    NASA Technical Reports Server (NTRS)

    Lake, E. R.

    1974-01-01

    This study examined the current status and potential application of pyrotechnic gas generators and energy convertors for the space shuttle program. While most pyrotechnic devices utilize some form of linear actuation, only limited use of rotary actuators has been observed. This latter form of energy conversion, using a vane-type actuator as optimum, offers considerable potential in the area of servo, as well as non-servo systems, and capitalizes on a means of providing prolonged operating times. Pyrotechnic devices can often be shown to provide the optimum means of attaining a truly redundant back-up to a primary, non-pyrotechnic system.

  3. Designing economic and legal mechanism of land management in oil and gas companies

    NASA Astrophysics Data System (ADS)

    Tsibulnikova, M. R.; Pogharnitskaya, O. V.; Strelnikova, A. B.

    2015-02-01

    The article deals with the problem of economic and legal relationship in the sphere of land management provided by Russian government. The gas pipeline construction serves as an example to analyze the problems connected with leasing of both federal and privately owned lands. Comparative analysis of costs made by Gazprom to lease the lands at the stage of construction has been conducted. It has been concluded that the government should regulate relationships within the land sector to harmonize the interests of the Federation and private landowners.

  4. Gas flow and fluidization in a thick dynamic regolith: A new mechanism for the formation of chondritic meteorites

    NASA Technical Reports Server (NTRS)

    Huang, Shaoxiong; Sears, Derek W. G.

    1995-01-01

    We have previously shown that size and density sorting in a regolith which has been 'fluidized' by the passage or gases from the interior or the body can quantitatively explain metal-silicate fractionation, an important property of ordinary chondrites. Here we discuss whether the flow