Science.gov

Sample records for air gap formation

  1. Dynamics of air gap formation around roots with changing soil water content.

    NASA Astrophysics Data System (ADS)

    Vetterlein, D.; Carminati, A.; Weller, U.; Oswald, S.; Vogel, H.-J.

    2009-04-01

    Most models regarding uptake of water and nutrients from soil assume intimate contact between roots and soil. However, it is known for a long time that roots may shrink under drought conditions. Due to the opaque nature of soil this process could not be observed in situ until recently. Combining tomography of the entire sample (field of view of 16 x 16 cm, pixel side 0.32 mm) with local tomography of the soil region around roots (field of view of 5 x 5 cm, pixel side 0.09 mm), the high spatial resolution required to image root shrinkage and formation of air-filled gaps around roots could be achieved. Applying this technique and combining it with microtensiometer measurements, measurements of plant gas exchange and microscopic assessment of root anatomy, a more detailed study was conducted to elucidate at which soil matric potential roots start to shrink in a sandy soil and which are the consequences for plant water relations. For Lupinus albus grown in a sandy soil tomography of the entire root system and of the interface between taproot and soil was conducted from day 11 to day 31 covering two drying cycles. Soil matric potential decreased from -36 hPa at day 11 after planting to -72, -251, -429 hPa, on day 17, 19, 20 after planting. On day 20 an air gap started to occur around the tap root and extended further on day 21 with matric potential below -429 hPa (equivalent to 5 v/v % soil moisture). From day 11 to day 21 stomatal conductivity decreased from 467 to 84 mmol m-2 s-1, likewise transpiration rate decreased and plants showed strong wilting symptoms on day 21. Plants were watered by capillary rise on day 21 and recovered completely within a day with stomatal conductivity increasing to 647 mmol m-2 s-1. During a second drying cycle, which was shorter as plants continuously increased in size, air gap formed again at the same matric potential. Plant stomatal conductance and transpiration decreased in a similar fashion with decreasing matric potential and

  2. 30 CFR 56.6603 - Air gap.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Air gap. 56.6603 Section 56.6603 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Explosives Extraneous...

  3. 30 CFR 57.6603 - Air gap.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Air gap. 57.6603 Section 57.6603 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Explosives Extraneous...

  4. 30 CFR 57.6603 - Air gap.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Air gap. 57.6603 Section 57.6603 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Explosives Extraneous...

  5. 30 CFR 57.6603 - Air gap.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Air gap. 57.6603 Section 57.6603 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Explosives Extraneous...

  6. 30 CFR 56.6603 - Air gap.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Air gap. 56.6603 Section 56.6603 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Explosives Extraneous...

  7. 30 CFR 56.6603 - Air gap.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Air gap. 56.6603 Section 56.6603 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Explosives Extraneous...

  8. 30 CFR 56.6603 - Air gap.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Air gap. 56.6603 Section 56.6603 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Explosives Extraneous...

  9. 30 CFR 56.6603 - Air gap.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Air gap. 56.6603 Section 56.6603 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Explosives Extraneous...

  10. 30 CFR 57.6603 - Air gap.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Air gap. 57.6603 Section 57.6603 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Explosives Extraneous...

  11. 30 CFR 57.6603 - Air gap.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Air gap. 57.6603 Section 57.6603 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Explosives Extraneous...

  12. Temperature Tunable Air-Gap Etalon Filter

    NASA Technical Reports Server (NTRS)

    Krainak, Michael A.; Stephen, Mark A.; Lunt, David L.

    1998-01-01

    We report on experimental measurements of a temperature tuned air-gap etalon filter. The filter exhibits temperature dependent wavelength tuning of 54 pm/C. It has a nominal center wavelength of 532 nm. The etalon filter has a 27 pm optical bandpass and 600 pm free spectral range (finesse approximately 22). The experimental results are in close agreement with etalon theory.

  13. Acoustic Band Gap Formation in Metamaterials

    NASA Astrophysics Data System (ADS)

    Elford, D. P.; Chalmers, L.; Kusmartsev, F.; Swallowe, G. M.

    We present several new classes of metamaterials and/or locally resonant sonic crystal that are comprised of complex resonators. The proposed systems consist of multiple resonating inclusion that correspond to different excitation frequencies. This causes the formation of multiple overlapped resonance band gaps. We demonstrate theoretically and experimentally that the individual band gaps achieved, span a far greater range (≈ 2kHz) than previously reported cases. The position and width of the band gap is independent of the crystal's lattice constant and forms in the low frequency regime significantly below the conventional Bragg band gap. The broad envelope of individual resonance band gaps is attractive for sound proofing applications and furthermore the devices can be tailored to attenuate lower or higher frequency ranges, i.e., from seismic to ultrasonic.

  14. Acoustic Band Gap Formation in Metamaterials

    NASA Astrophysics Data System (ADS)

    Elford, D. P.; Chalmers, L.; Kusmartsev, F.; Swallowe, G. M.

    2011-03-01

    We present several new classes of metamaterials and/or locally resonant sonic crystal that are comprised of complex resonators. The proposed systems consist of multiple resonating inclusion that correspond to different excitation frequencies. This causes the formation of multiple overlapped resonance band gaps. We demonstrate theoretically and experimentally that the individual band gaps achieved, span a far greater range (≈ 2kHz) than previously reported cases. The position and width of the band gap is independent of the crystal's lattice constant and forms in the low frequency regime significantly below the conventional Bragg band gap. The broad envelope of individual resonance band gaps is attractive for sound proofing applications and furthermore the devices can be tailored to attenuate lower or higher frequency ranges, i.e., from seismic to ultrasonic.

  15. Vertical hydraulic generators experience with dynamic air gap monitoring

    SciTech Connect

    Pollock, G.B.; Lyles, J.F )

    1992-12-01

    Until recently, dynamic monitoring of the rotor to stator air gap of hydraulic generators was not practical. Cost effective and reliable dyamic air gap monitoring equipment has been developed in recent years. Dynamic air gap monitoring was originally justified because of the desire of the owner to minimize the effects of catastrophic air gap failure. However, monitoring air gaps on a time basis has been shown to be beneficial by assisting in the assessment of hydraulic generator condition. The air gap monitor provides useful information on rotor and stator condition and generator vibration. The data generated by air gap monitors will assist managers in the decision process with respect to the timing and extent of required maintenance for a particular generating unit.

  16. Air Gap Effects in LX-17

    SciTech Connect

    Souers, P C; Ault, S; Avara, R; Bahl, K L; Boat, R; Cunningham, B; Gidding, D; Janzen, J; Kuklo, D; Lee, R; Lauderbach, L; Weingart, W C; Wu, B; Winer, K

    2005-09-26

    Three experiments done over twenty years on gaps in LX-17 are reported. For the detonation front moving parallel to the gaps, jets of gas products were seen coming from the gaps at velocities greater than the detonation velocity. A case can be made that the jet velocity increased with gap thickness but the data is scattered. For the detonation front moving transverse to the gap, time delays were seen. The delays roughly increase with gap width, going from 0-70 ns at 'zero gap' to around 300 ns at 0.5-1 mm gap. Larger gaps of up to 6 mm width almost certainly stopped the detonation, but this was not proved. Real-time resolution of the parallel jets and determination of the actual re-detonation or failure in the transverse case needs to be done in future experiments.

  17. An air gap moderates the performance of nanowire array transistors

    NASA Astrophysics Data System (ADS)

    Yang, Tong; Mehta, Jeremy S.; Mativetsky, Jeffrey M.

    2017-03-01

    Solution-processed nanowires are promising for low-cost and flexible electronics. When depositing nanowires from solution, due to stacking of the nanowires, an air gap exists between the substrate and much of the active material. Here, using confocal Raman spectroscopy, we quantify the thickness of the air gap in transistors comprising organic semiconductor nanowires. The average air gap thickness is found to be unexpectedly large, being at least three times larger than the nanowire diameter, leading to a significant impact on transistor performance. The air gap acts as an additional dielectric layer that reduces the accumulation of charge carriers due to a gate voltage. Conventional determination of the charge carrier mobility ignores the presence of an air gap, resulting in an overestimate of charge carrier accumulation and an underestimate of charge carrier mobility. It is shown that the larger the air gap, the larger the mobility correction (which can be greater than an order of magnitude) and the larger the degradation in on–off current ratio. These results demonstrate the importance of minimizing the air gap and of taking the air gap into consideration when analyzing the electrical performance of transistors consisting of stacked nanowires. This finding is applicable to all types of stacked one-dimensional materials including organic and inorganic nanowires, and carbon nanotubes.

  18. An air gap moderates the performance of nanowire array transistors.

    PubMed

    Yang, Tong; Mehta, Jeremy S; Mativetsky, Jeffrey M

    2017-03-24

    Solution-processed nanowires are promising for low-cost and flexible electronics. When depositing nanowires from solution, due to stacking of the nanowires, an air gap exists between the substrate and much of the active material. Here, using confocal Raman spectroscopy, we quantify the thickness of the air gap in transistors comprising organic semiconductor nanowires. The average air gap thickness is found to be unexpectedly large, being at least three times larger than the nanowire diameter, leading to a significant impact on transistor performance. The air gap acts as an additional dielectric layer that reduces the accumulation of charge carriers due to a gate voltage. Conventional determination of the charge carrier mobility ignores the presence of an air gap, resulting in an overestimate of charge carrier accumulation and an underestimate of charge carrier mobility. It is shown that the larger the air gap, the larger the mobility correction (which can be greater than an order of magnitude) and the larger the degradation in on-off current ratio. These results demonstrate the importance of minimizing the air gap and of taking the air gap into consideration when analyzing the electrical performance of transistors consisting of stacked nanowires. This finding is applicable to all types of stacked one-dimensional materials including organic and inorganic nanowires, and carbon nanotubes.

  19. Air gap sparkover and gap factors: Analysis of published data. Final report

    SciTech Connect

    Gela, G.

    1994-12-01

    This report is an account of a literature search on air gap sparkover which was conducted as part of the Live Working 2000 project. The objective of this literature search was to locate and analyze published data on sparkover of air gaps which are relevant to live working. The sparkover data form the basis for determination of gap factors for live working situations. Data dating back to 1930`s were located in published papers and reports, extracted and analyzed for a variety of air gaps, including: rod-to-plane, rod-to-rod, sphere-to-plane, bundle-to-plane, hoop-to-plane, bundle-to-tower window, bundle-to-tower outside phase, and worker-to-tower air gap. The rod-to-plane air gap has been analyzed extensively in the literature, and several accurate empirical formulae have been developed to calculate the 50% sparkover voltage of the gap when subjected to transient overvoltages with the critical wave shape. The terms, such as gap factor, transient overvoltage (TOV), critical wave shape, and other relevant terms, are defined in this report for completeness. The CRIEPI formula is used as the reference in this report, since this formula has been adopted by several technical organizations (IEC, IEEE). Comparisons are also made with the second popular formula, the Gallet formula. All sparkover data obtained from the literature are presented in tables and graphs. In addition, where applicable and available, data for the critical wave shape are identified and placed in separate tables for ready reference. The calculated gap factors are based on the CRIEPI formula. Detailed comparisons of the CRIEPI and the Gallet formulae allow easy determination of the gap factors based on the Gallet formula, should one desire to compute these numbers. The calculated gap factors are summarized in tables and compared with the gap factor values tentatively suggested for use by IEC TC 78 WG 10.

  20. In vitro formation of gap junction vesicles.

    PubMed

    Goodenough, D A

    1976-02-01

    A method is described that uses trypsin digestion combined with collagenase-hyaluronidase which produces a population of gap junction vesicles. The hexagonal lattice of subunits ("connexons") comprising the gapjunctions appears unaltered by various structural criteria and by buoyant density measurements. The gap junction vesciles are closed by either a single or a double profile of nonjunctional "membrane," which presents a smooth, particle-free fracture face. Horseradish peroxidase and cytochrome c studies have revealed that about 20% of the gap junction vesicles are impermeable to proteins 12,000 daltons or larger. The increased purity of the trypsinized junction preparation suggests that one of the disulfide reduction products of the gap-junction principal protein may be a nonjunctional contaminating peptide. The gap junction appears to be composed of a single 18,000-dalton protein, connexin, which may be reduced to a single 9,000-dalton peak. The number of peptides in this reduced peak are still unknown.

  1. Permanent-magnet-less machine having an enclosed air gap

    SciTech Connect

    Hsu, John S.

    2013-03-05

    A permanent magnet-less, brushless synchronous system includes a stator that generates a magnetic rotating field when sourced by an alternating current. An uncluttered rotor disposed within the magnetic rotating field is spaced apart from the stator to form an air gap relative to an axis of rotation. A stationary excitation core spaced apart from the uncluttered rotor by an axial air gap and a radial air gap substantially encloses the stationary excitation core. Some permanent magnet-less, brushless synchronous systems include stator core gaps to reduce axial flux flow. Some permanent magnet-less, brushless synchronous systems include an uncluttered rotor coupled to outer laminations. The quadrature-axis inductance may be increased in some synchronous systems. Some synchronous systems convert energy such as mechanical energy into electrical energy (e.g., a generator); other synchronous systems may convert any form of energy into mechanical energy (e.g., a motor).

  2. Permanent-magnet-less machine having an enclosed air gap

    SciTech Connect

    Hsu, John S

    2012-02-07

    A permanent magnet-less, brushless synchronous system includes a stator that generates a magnetic rotating field when sourced by an alternating current. An uncluttered rotor disposed within the magnetic rotating field is spaced apart from the stator to form an air gap relative to an axis of rotation. A stationary excitation core spaced apart from the uncluttered rotor by an axial air gap and a radial air gap substantially encloses the stationary excitation core. Some permanent magnet-less, brushless synchronous systems include stator core gaps to reduce axial flux flow. Some permanent magnet-less, brushless synchronous systems include an uncluttered rotor coupled to outer laminations. The quadrature-axis inductance may be increased in some synchronous systems. Some synchronous systems convert energy such as mechanical energy into electrical energy (e.g., a generator); other synchronous systems may convert any form of energy into mechanical energy (e.g., a motor).

  3. Novel Approach for Modeling of Nonuniform Slag Layers and Air Gap in Continuous Casting Mold

    NASA Astrophysics Data System (ADS)

    Wang, Xudong; Kong, Lingwei; Yao, Man; Zhang, Xiaobing

    2017-02-01

    Various kinds of surface defects on the continuous casting slab usually originate from nonuniform heat transfer and mechanical behavior, especially during the initial solidification inside the mold. In this article, a model-coupled inverse heat transfer problem incorporating the effect of slag layers and air gap is developed to study the nonuniform distribution of liquid slag, solid slag, and air gap layers. The model considers not only the formation and evolution of slag layers and air gap but also the temperatures in the mold copper as measured by thermocouples. The simulation results from the model and the measured temperatures from experiments are shown to be in good agreement with each other. At the casting speed of 0.65 m/min, the liquid slag film disappears and transforms into solid slag entirely at about 400 mm away from meniscus, and an air gap begins to form. Until the mold exit, the maximum thickness of the solid slag layer and air gap gradually increases to 1.34 and 0.056 mm, respectively. The results illustrate that the magnitude and nonuniform distribution of the slag layers and air gap along the cross direction, correlating with heat flux between the shell and mold, eventually determine the temperature profiles of the mold hot face and slab surface. The proposed model may provide a convenient approach for analyzing nonuniform heat transfer and mechanical behaviors between the mold and slab in the real casting process.

  4. Gap formation following climatic events in spatially structured plant communities

    PubMed Central

    Liao, Jinbao; De Boeck, Hans J.; Li, Zhenqing; Nijs, Ivan

    2015-01-01

    Gaps play a crucial role in maintaining species diversity, yet how community structure and composition influence gap formation is still poorly understood. We apply a spatially structured community model to predict how species diversity and intraspecific aggregation shape gap patterns emerging after climatic events, based on species-specific mortality responses. In multispecies communities, average gap size and gap-size diversity increased rapidly with increasing mean mortality once a mortality threshold was exceeded, greatly promoting gap recolonization opportunity. This result was observed at all levels of species richness. Increasing interspecific difference likewise enhanced these metrics, which may promote not only diversity maintenance but also community invasibility, since more diverse niches for both local and exotic species are provided. The richness effects on gap size and gap-size diversity were positive, but only expressed when species were sufficiently different. Surprisingly, while intraspecific clumping strongly promoted gap-size diversity, it hardly influenced average gap size. Species evenness generally reduced gap metrics induced by climatic events, so the typical assumption of maximum evenness in many experiments and models may underestimate community diversity and invasibility. Overall, understanding the factors driving gap formation in spatially structured assemblages can help predict community secondary succession after climatic events. PMID:26114803

  5. Tuning Ferritin's Band Gap through Mixed Metal Oxide Nanoparticle Formation.

    PubMed

    Olsen, Cameron; Embley, Jacob; Hansen, Kameron; Henrichsen, Andrew; Peterson, J; Colton, John S; Watt, Richard

    2017-03-23

    This study uses the formation of a mixed metal oxide inside ferritin to tune the band gap energy of the ferritin mineral. The mixed metal oxide is composed of both Co and Mn, and is formed by reacting aqueous Co2+ with MnO4- in the presence of apoferritin. Altering the ratio between the two reactants allowed for controlled tuning of the band gap energies. All minerals formed were indirect band gap materials, with indirect band gap energies ranging from 0.52 to 1.30 eV. The direct transitions were also measured, with energy values ranging from 2.71 to 3.11 eV. Tuning the band gap energies of these samples changes the wavelengths absorbed by each mineral, increasing ferritin's potential in solar-energy harvesting. Additionally, the success of using MnO4- in ferritin mineral formation opens the possibility for new mixed metal oxide cores inside ferritin.

  6. Excitonic gap formation and condensation in the bilayer graphene structure

    NASA Astrophysics Data System (ADS)

    Apinyan, V.; Kopeć, T. K.

    2016-09-01

    We have studied the excitonic gap formation in the Bernal Stacked, bilayer graphene (BLG) structures at half-filling. Considering the local Coulomb interaction between the layers, we calculate the excitonic gap parameter and we discuss the role of the interlayer and intralayer Coulomb interactions and the interlayer hopping on the excitonic pair formation in the BLG. Particularly, we predict the origin of excitonic gap formation and condensation, in relation to the furthermost interband optical transition spectrum. The general diagram of excitonic phase transition is given, explaining different interlayer correlation regimes. The temperature dependence of the excitonic gap parameter is shown and the role of the chemical potential, in the BLG, is discussed in details.

  7. An ultrasonic air pump using an acoustic traveling wave along a small air gap.

    PubMed

    Koyama, Daisuke; Wada, Yuji; Nakamura, Kentaro; Nishikawa, Masato; Nakagawa, Tatsuyuki; Kihara, Hitoshi

    2010-01-01

    An ultrasonic air pump that uses a traveling wave along a small air gap between a bending vibrator and a reflector is discussed. The authors investigate ultrasonic air pumps that make use of bending vibrators and reflectors and confirm that air can be induced to flow by generating an asymmetric acoustic standing wave along an air gap. In this paper, we proposed a novel ultrasonic air pump in which a traveling wave along an air gap induces acoustic streaming and achieves one-way airflow. Two new reflector configurations, stepped and tapered, were designed and used to generate traveling waves. To predict airflow generation, sound pressure distribution in the air gap was calculated by means of finite element analysis (FEA). As a preliminary step, 2 FEA models were compared: one piezoelectric-structure-acoustic model and one piezoelectric- structure-fluid model, which included the viscosity effect of the fluid. The sound pressure distribution in the air gap, including fluid viscosity, was calculated by the FEA because it is expected to be dominant and thus have a strong effect on the sound pressure field in such a thin fluid layer. Based on the FEA results of the stepped and the tapered reflectors, it was determined that acoustic traveling waves could propagate along the gaps. Experiments were carried out with the designed bending vibrator and the reflectors. The acoustic fields in the air gap were measured via a fiber optic probe, and it was determined that the sound pressure and the phase distribution tendencies corresponded well with the results computed by FEA. Through our experiments, one-way airflow generation, in the same direction of the traveling wave and with the maximum flow velocity of 5.6 cm/s, was achieved.

  8. Acoustic Band Gap Formation in Two-Dimensional Locally Resonant Sonic Crystals Comprised of Helmholtz Resonators

    NASA Astrophysics Data System (ADS)

    Chalmers, L.; Elford, D. P.; Kusmartsev, F. V.; Swallowe, G. M.

    2010-12-01

    We present a new type of sonic crystal technology offering a novel method of achieving broad acoustic band gaps. The proposed design of a locally resonating sonic crystal (LRSC) is constructed from "C"-shaped Helmholtz resonators as opposed to traditional solid scattering units. This unique construction enables a two band gap system to be generated in which the first -- a Bragg type band gap, arises due to the periodic nature of the crystal, whilst the second gap results from resonance of the air column within the resonators. The position of this secondary band gap is found to be dependent upon the dimensions of the resonating cavity. The band gap formation is investigated theoretically using finite element methods, and confirmed through experimental testing. It is noted that the resonance band gaps detected cover a much broader frequency range (in the order of kHz) than has been achieved to date. In addition the possibility of overlapping such a wide band gap with the characteristic Bragg gap generated by the structure itself could yield gaps of even greater range. A design of sonic crystal is proposed, that comprises of several resonators with differing cavity sizes. Such a structure generates multiple resonance gaps corresponding to the various resonator sizes, which may be overlapped to form yet larger band gaps. This multiple resonance gap system can occur in two configurations. Firstly a simple mixed array can be created by alternating resonator sizes in the array and secondly using a System coined the Matryoshka (Russian doll) array in which the resonators are distributed inside one another. The proposed designs of LRSC's offer a real potential for acoustic shielding using sonic crystals, as both the size and position of the band gaps generated can be controlled. This is an application which has been suggested and investigated for several years with little progress. Furthermore the frequency region attenuated by resonance is unrelated to the crystals lattice

  9. Acoustic Band Gap Formation in Two-Dimensional Locally Resonant Sonic Crystals Comprised of Helmholtz Resonators

    NASA Astrophysics Data System (ADS)

    Chalmers, L.; Elford, D. P.; Kusmartsev, F. V.; Swallowe, G. M.

    We present a new type of sonic crystal technology offering a novel method of achieving broad acoustic band gaps. The proposed design of a locally resonating sonic crystal (LRSC) is constructed from "C"-shaped Helmholtz resonators as opposed to traditional solid scattering units. This unique construction enables a two band gap system to be generated in which the first — a Bragg type band gap, arises due to the periodic nature of the crystal, whilst the second gap results from resonance of the air column within the resonators. The position of this secondary band gap is found to be dependent upon the dimensions of the resonating cavity. The band gap formation is investigated theoretically using finite element methods, and confirmed through experimental testing. It is noted that the resonance band gaps detected cover a much broader frequency range (in the order of kHz) than has been achieved to date. In addition the possibility of overlapping such a wide band gap with the characteristic Bragg gap generated by the structure itself could yield gaps of even greater range. A design of sonic crystal is proposed, that comprises of several resonators with differing cavity sizes. Such a structure generates multiple resonance gaps corresponding to the various resonator sizes, which may be overlapped to form yet larger band gaps. This multiple resonance gap system can occur in two configurations. Firstly a simple mixed array can be created by alternating resonator sizes in the array and secondly using a system coined the Matryoshka (Russian doll) array in which the resonators are distributed inside one another. The proposed designs of LRSC's offer a real potential for acoustic shielding using sonic crystals, as both the size and position of the band gaps generated can be controlled. This is an application which has been suggested and investigated for several years with little progress. Furthermore the frequency region attenuated by resonance is unrelated to the crystals

  10. Direct control of air gap flux in permanent magnet machines

    DOEpatents

    Hsu, John S.

    2000-01-01

    A method and apparatus for field weakening in PM machines uses field weakening coils (35, 44, 45, 71, 72) to produce flux in one or more stators (34, 49, 63, 64), including a flux which counters flux normally produced in air gaps between the stator(s) (34, 49, 63, 64) and the rotor (20, 21, 41, 61) which carries the PM poles. Several modes of operation are introduced depending on the magnitude and polarity of current in the field weakening coils (35, 44, 45, 71, 72). The invention is particularly useful for, but not limited to, the electric vehicle drives and PM generators.

  11. Supersonic flow and shock formation in turbine tip gaps

    NASA Technical Reports Server (NTRS)

    Moore, John

    1993-01-01

    Shock formation due to overexpansion of supersonic flow at the inlet to the tip clearance gap of a turbomachine has been studied. As the flow enters the tip gap, it accelerates around the blade pressure-side corner creating a region of minimum static pressure. The 'free streamline' separates from the wall at the corner; and, for Mach numbers greater than about 1.3, it curves back to intersect the blade tip. At this point, the freestream flow is abruptly turned parallel to the surface, giving rise to an oblique shock. The results are consistent with compressible sharp-edged orifice flow calculations found in the literature and with the theory of oblique shock wave formation in supersonic flow over a wedge. For freestream Mach numbers of 1.4 to 1.8, wave angles are 43 to 54 deg, and turning angles are 9 to 20 deg; as the Mach number increases, the angle of turn also increases. It appears that in a turbine, after separating from the inlet corner, the flow reattaches on the blade tip and an oblique shock is formed at 0.4-1.4 tip gap heights into the clearance gap. The resulting shock-boundary layer interaction may contribute to further enhancement of already high heat transfer to the blade tip in this region. This in turn could lead to higher blade temperatures and adversely affect blade life and turbine efficiency.

  12. Gap soliton formation in a nonlinear anti-directional coupler

    SciTech Connect

    Ryzhov, M S; Maimistov, Andrei I

    2012-11-30

    We consider propagation of electromagnetic solitary waves in two tunnel-coupled waveguides. It is assumed that one of the waveguides is made of a positive-index dielectric, having a Kerr nonlinearity. The other waveguide is made of a linear optical metamaterial characterised by the so-called negative refraction. The gap soliton formation in such a system, which, as shown, has a threshold character, is studied numerically. (solitons)

  13. Investigation of a single barrier discharge in submillimeter air gaps. Nonuniform field

    NASA Astrophysics Data System (ADS)

    Bondarenko, P. N.; Emel'yanov, O. A.; Shemet, M. V.

    2014-08-01

    Pulse characteristics of single barrier discharges as well as parameters of charges accumulated on the surface of a dielectric under the atmospheric pressure in the "needle-(0.1-2.0)-mm air gap-polymer barrier-plane" system are investigated. It is found experimentally that for the positive polarity of the needle, the voltage for the discharge initiation is higher than in the case of the negative polarity by ˜25-35%. The reversal of the needle polarity from negative to positive increases the amplitude of the discharge current and the accumulated surface charge by ˜1.5-3 times. For the positive polarity of the needle, the discharge is governed by a streamer mechanism, while for the negative polarity, the discharge is initiated by the formation of a single Trichel pulse. The single pulse regime is observed for the discharge current up to a certain electrode gap d CR. For the positive needle and for air gap width d air > d CR ≈ 1.5 mm, a multipulse burst corona is formed, while for the negative needle and d air > d CR ≈ 0.9 mm, a damped sequence of Trichel pulses evolves in the system.

  14. Modeling Plasma Formation in a Micro-gap at Microwave Frequency

    NASA Astrophysics Data System (ADS)

    Bowman, Arthur; Remillard, Stephen

    2013-03-01

    In the presence of a strong electric field, gas molecules become ionized, forming a plasma. The study of this dielectric breakdown at microwave frequency has important applications in improving the operation of radio frequency (RF) devices, where the high electric fields present in small gaps can easily ionize gases like air. A cone and tuner resonant structure was used to induce breakdown of diatomic Nitrogen in adjustable micro-gaps ranging from 13 to 1,156 μm. The electric field for plasma formation exhibited strong pressure dependence in the larger gap sizes, as predicted by previous theoretical and experimental work. Pressure is proportional to the frequency of collision between electrons and molecules, which increases with pressure when the gap is large, but levels off in the micro-gap region. A separate model of the breakdown electric field based on the characteristic diffusion length of the plasma also fit the data poorly for these smaller gap sizes. This may be explained by a hypothesis that dielectric breakdown at and below the 100 μm gap size occurs outside the gap, an argument that is supported by the observation of very high breakdown threshold electric fields in this region. Optical emissions revealed that vibrational and rotational molecular transitions of the first positive electronic system are suppressed in micro-gaps, indicating that transitions into the molecular ground state do not occur in micro-gap plasmas. Acknowledgements: National Science Foundation under NSF-REU Grant No. PHY/DMR-1004811, the Provost's Office of Hope College, and the Hope College Division of Natural and Applied Sciences.

  15. Influence of composite insertion technique on gap formation

    PubMed Central

    Kapoor, Neha; Bahuguna, Nikhil; Anand, Surbhi

    2016-01-01

    Aim: To compare newer bulk-fill composites with an incrementally filled composite for adaptability and subsequent gap formation at the pulpal floor. Materials and Methods: Class I cavities were prepared in 60 intact molars, with a shallow depression in the center of the pulpal floor. The samples were divided into four groups (n = 15), according to the material used; smart dentine replacement (SDR), SonicFill, Ever X Flow and Z350 XT, restored to a depth of 4 mm. Following thermocycling, samples were sectioned buccolingually and examined under a stereomicroscope. Seven samples from each group were coated with nail varnish except for approximately 1 mm around the tooth restoration junction. These samples were examined under stereomicroscope after staining with 2% buffered methylene blue dye. The remaining samples were examined under a scanning electron microscope for gap formation. The data were statistically analyzed using one-way ANOVA and post-hoc Bonferroni test. Results: SDR showed the significantly best adaptability as compared to both SonicFill and Ever X Flow (comparable). However, significantly least adaptive capacity was seen in the incrementally filled group (Z350 XT). Conclusion: Bulk-fill composites performed better than incremental composites, demonstrating better adaptability and less gap formation at the pulpal floor. PMID:26957799

  16. Sparkover performance and gap factors of air gaps below 1 meter: Analysis of published data. Final report

    SciTech Connect

    Gela, G.

    1998-03-01

    This report is an account of a literature search on sparkover performance of various air gaps shorter than 1 meter. The report is a part of the Live Working 2000 project. The objective of the literature search was to locate and analyze published data on sparkover performance of air gaps below 1 meter, with special emphasis on live working. Published data dating back to 1930`s are analyzed for a variety of air gaps: rod-to-plane; rod-to-rod; sphere-to-plane; bundle-to-plane; hoop-to-plane, conductor-to-rod; and worker-to-tower. Data for all voltage types, and both polarities (where applicable) are analyzed: power frequency alternating current; direct current; lightning; fast front impulse; and switching impulse. As is the case for longer air gaps and higher voltages, several accurate empirical formulae for calculation of the sparkover voltage have been developed, and are analyzed. Also, the rod-to-plane air gap is used in this report as the reference gap for calculation of gap factors.

  17. Plasma formation in a double-gap vircator

    SciTech Connect

    Queller, T.; Shlapakovski, A.; Krasik, Ya. E.

    2010-11-15

    Time-resolved light emission imaging was used to observe the plasma formation within the cavity of the double-gap vircator powered by a sub-microsecond generator ({approx}500 kV, {approx}10 kA, {approx}500 ns). The vircator generated well reproducible S-band microwave pulses of {approx}200 MW peak power and up to 200 ns full duration. The plasma light emission was observed {approx}30 ns prior to the ending of the generated microwave pulses at the surface of the aluminum foil separating the vircator cavity gaps, in the gap where the virtual cathode is formed. Estimations showed that the energy deposition into the foil by the high-current electron beam is sufficient for the surface plasma formation. The plasma ions accelerated toward the virtual cathode neutralize its electron space charge. The latter was confirmed by the increase in the electron current transmitted through the vircator cavity. In addition, the time of the plasma appearance was determined by comparing the measured transmitted current with that following from the one-dimensional model of a stationary un-neutralized two-stream electron flow. This time agrees with the maximum of the microwave power observed in the experiments, thus showing that the plasma ions cause the termination of the microwave generation.

  18. Electric field step in air gap streamer discharges

    SciTech Connect

    Zeng Rong; Zhuang Chijie; Yu Zhanqing; Li Zhizhao; Geng Yinan

    2011-11-28

    Electric field (E-field) in air gap streamer discharges under positive lightning impulse was measured by specifically developed integrated electro-optic sensors. An E-field step phenomenon was observed. The E-field firstly agreed with the Laplace field, then suddenly increased with a rise time of {mu}s. The occurrence probability of this phenomenon increased as the applied voltage increased. The discharge current waveforms and photos taken by a fast camera prove the E-field step was caused by the space net charge. From the E-step rise time and the corona area range, the average electron drift speed under the experiment situation was estimated about 0.2 x 10{sup 6} - 0.6x 10{sup 6} m/s.

  19. Field assessment of induction motor efficiency through air-gap torque

    SciTech Connect

    Hsu, J.S.; Sorenson, P.L.

    1995-11-01

    Induction motors are the most popular motors used in industry. This paper further suggests the use of air-gap torque method to evaluate their efficiency and load changes. The fundamental difference between Method E and the air-gap torque method is discussed. Efficiency assessments conducted on induction motors under various conditions show the accuracy and potential of the air-gap torque method.

  20. Development of a highly efficient brushless dc motor utilizing both radial and axial air gaps

    NASA Astrophysics Data System (ADS)

    Kang, K. J.; Jang, G. H.; Sung, S. J.; Chang, J. H.

    2012-04-01

    This research proposes an effective structure for a brushless dc motor utilizing both radial and axial air gaps. The proposed motor generates torque in both the radial and axial air gaps, while the conventional motor generates torque only in the radial air gap. The proposed motor was optimized to minimize the electromagnetic loss of the motor to increase the effective air gap length and fill-factor of the coil while decreasing the saturation of the core at the same time. The electromagnetic loss was reduced by 35% in comparison with a conventional motor.

  1. Distribution Characteristics of Air-Bone Gaps – Evidence of Bias in Manual Audiometry

    PubMed Central

    Margolis, Robert H.; Wilson, Richard H.; Popelka, Gerald R.; Eikelboom, Robert H.; Swanepoel, De Wet; Saly, George L.

    2015-01-01

    Objective Five databases were mined to examine distributions of air-bone gaps obtained by automated and manual audiometry. Differences in distribution characteristics were examined for evidence of influences unrelated to the audibility of test signals. Design The databases provided air- and bone-conduction thresholds that permitted examination of air-bone gap distributions that were free of ceiling and floor effects. Cases with conductive hearing loss were eliminated based on air-bone gaps, tympanometry, and otoscopy, when available. The analysis is based on 2,378,921 threshold determinations from 721,831 subjects from five databases. Results Automated audiometry produced air-bone gaps that were normally distributed suggesting that air- and bone-conduction thresholds are normally distributed. Manual audiometry produced air-bone gaps that were not normally distributed and show evidence of biasing effects of assumptions of expected results. In one database, the form of the distributions showed evidence of inclusion of conductive hearing losses. Conclusions Thresholds obtained by manual audiometry show tester bias effects from assumptions of the patient’s hearing loss characteristics. Tester bias artificially reduces the variance of bone-conduction thresholds and the resulting air-bone gaps. Because the automated method is free of bias from assumptions of expected results, these distributions are hypothesized to reflect the true variability of air- and bone-conduction thresholds and the resulting air-bone gaps. PMID:26627469

  2. Thickness and air gap measurement of assembled IR objectives

    NASA Astrophysics Data System (ADS)

    Lueerss, B.; Langehanenberg, P.

    2015-05-01

    A growing number of applications like surveillance, thermography, or automotive demand for infrared imaging systems. Their imaging performance is significantly influenced by the alignment of the individual lens elements. Besides the lateral orientation of lenses, the air spacing between the lenses is a crucial parameter. Because of restricted mechanical accessibility within an assembled objective, a non-contact technique is required for the testing of these parameters. So far commercial measurement systems were not available for testing of IR objectives since many materials used for infrared imaging are non-transparent at wavelengths below 2 μm. We herewith present a time-domain low coherent interferometer capable of measuring any kind of infrared material (e.g., Ge, Si, etc.) as well as VIS materials. The fiber-optic set-up is based on a Michelson-Interferometer in which the light from a broadband super-luminescent diode is split into a reference arm with a variable optical delay and a measurement arm where the sample is placed. On a photo detector, the reflected signals from both arms are superimposed and recorded as a function of the variable optical path. Whenever the group delay difference is zero, a coherence peak occurs and the relative lens' surface distances are derived from the optical delay. In order to penetrate IR materials, the instrument operates at 2.2 μm. The set-up allows the contactless determination of thicknesses and air gaps inside of assembled infrared objective lenses with accuracy in the micron range. It therefore is a tool for the precise manufacturing or quality control.

  3. Wh-filler-gap dependency formation guides reflexive antecedent search

    PubMed Central

    Frazier, Michael; Ackerman, Lauren; Baumann, Peter; Potter, David; Yoshida, Masaya

    2015-01-01

    Prior studies on online sentence processing have shown that the parser can resolve non-local dependencies rapidly and accurately. This study investigates the interaction between the processing of two such non-local dependencies: wh-filler-gap dependencies (WhFGD) and reflexive-antecedent dependencies. We show that reflexive-antecedent dependency resolution is sensitive to the presence of a WhFGD, and argue that the filler-gap dependency established by WhFGD resolution is selected online as the antecedent of a reflexive dependency. We investigate the processing of constructions like (1), where two NPs might be possible antecedents for the reflexive, namely which cowgirl and Mary. Even though Mary is linearly closer to the reflexive, the only grammatically licit antecedent for the reflexive is the more distant wh-NP, which cowgirl. (1). Which cowgirl did Mary expect to have injured herself due to negligence? Four eye-tracking text-reading experiments were conducted on examples like (1), differing in whether the embedded clause was non-finite (1 and 3) or finite (2 and 4), and in whether the tail of the wh-dependency intervened between the reflexive and its closest overt antecedent (1 and 2) or the wh-dependency was associated with a position earlier in the sentence (3 and 4). The results of Experiments 1 and 2 indicate the parser accesses the result of WhFGD formation during reflexive antecedent search. The resolution of a wh-dependency alters the representation that reflexive antecedent search operates over, allowing the grammatical but linearly distant antecedent to be accessed rapidly. In the absence of a long-distance WhFGD (Experiments 3 and 4), wh-NPs were not found to impact reading times of the reflexive, indicating that the parser's ability to select distant wh-NPs as reflexive antecedents crucially involves syntactic structure. PMID:26500579

  4. Air bearing center cross gap of neutron stress spectrometer sample table support system

    NASA Astrophysics Data System (ADS)

    Li, Yang; Wu, Yunxin; Gong, Hai; Feng, Xiaolei

    2016-12-01

    A support system is the main load-bearing component of sample table for neutron stress spectrometer, and air bearing is an important element of a support system. The neutron stress spectrometer sample table was introduced, and the scheme for air bearing combination was selected. To study the performance of air bearing center cross gap, finite element models (FEMs) were established based on air motion and Reynolds equations, effects of air supply pressure, and gap parameters on the overturning moment and bearing capacity of air bearing center cross gap were analyzed. Results indicate that the width, depth, and height differences of the marble floor gap played important roles in the performance of the air bearing. When gap width is lesser than 1 mm and gap depth is lower than 0.4 mm, bearing capacity and overturning moment would vary rapidly with the variation of the width and depth. A gap height difference results in the bearing capacity dropping rapidly. The FEM results agree well with experimental results. Further, findings of the study could guide the design of the support system and marble floor.

  5. Tunable mode-locked laser with micro-air gap cavity

    NASA Astrophysics Data System (ADS)

    Ahmad, H.; Aidit, S. N.; Hassan, N. A.; Ooi, S. I.; Tiu, Z. C.

    2017-02-01

    A tunable mode-locked laser with a micro-air gap cavity acting as a high resolution tuning is proposed and demonstrated. The laser utilizes the nonlinear polarization technique in the cavity to obtain a reliable and stable mode locking over the whole tuning range at a resolution of 1 nm. The micro-air gap is constructed by aligning two fiber facets coaxially, and the variation of micro-air gap introduces a tuning mechanism where it changes the gain saturation compensation in the gain medium and thus induces wavelength shifting on the generated solitons.

  6. Mapping forest canopy gaps using air-photo interpretation and ground surveys

    USGS Publications Warehouse

    Fox, T.J.; Knutson, M.G.; Hines, R.K.

    2000-01-01

    Canopy gaps are important structural components of forested habitats for many wildlife species. Recent improvements in the spatial accuracy of geographic information system tools facilitate accurate mapping of small canopy features such as gaps. We compared canopy-gap maps generated using ground survey methods with those derived from air-photo interpretation. We found that maps created from high-resolution air photos were more accurate than those created from ground surveys. Errors of omission were 25.6% for the ground-survey method and 4.7% for the air-photo method. One variable of inter est in songbird research is the distance from nests to gap edges. Distances from real and simulated nests to gap edges were longer using the ground-survey maps versus the air-photo maps, indicating that gap omission could potentially bias the assessment of spatial relationships. If research or management goals require location and size of canopy gaps and specific information about vegetation structure, we recommend a 2-fold approach. First, canopy gaps can be located and the perimeters defined using 1:15,000-scale or larger aerial photographs and the methods we describe. Mapped gaps can then be field-surveyed to obtain detailed vegetation data.

  7. Test Format and the Variation of Gender Achievement Gaps within the United States

    ERIC Educational Resources Information Center

    Reardon, Sean; Fahle, Erin; Kalogrides, Demetra; Podolsky, Anne; Zarate, Rosalia

    2016-01-01

    Prior research demonstrates the existence of gender achievement gaps and the variation in the magnitude of these gaps across states. This paper characterizes the extent to which the variation of gender achievement gaps on standardized tests across the United States can be explained by differing state accountability test formats. A comprehensive…

  8. Aging and the 4-kHz Air-Bone Gap

    ERIC Educational Resources Information Center

    Nondahl, David M.; Tweed, Ted S.; Cruickshanks, Karen J.; Wiley, Terry L.; Dalton, Dayna S.

    2012-01-01

    Purpose: In this study, the authors assessed age- and sex-related patterns in the prevalence and 10-year incidence of 4-kHz air-bone gaps and associated factors. Method: Data were obtained as part of the longitudinal, population-based Epidemiology of Hearing Loss Study ( Cruickshanks et al., 1998). An air-bone gap at 4 kHz was defined as an…

  9. Characterization of Air-Gap Sealing with Organic Dielectric Using Spin-Coating Film Transfer and Hot-Pressing Technology

    NASA Astrophysics Data System (ADS)

    Sato, Norio; Machida, Katsuyuki; Ishii, Hiromu; Ishimura, Yoji; Saito, Hidenori; Asakuma, Sumitoshi; Kawagoe, Masafumi; Adachi, Hideki

    2007-12-01

    This paper describes a dielectric material and its application to sealing air gaps using spin-coating film transfer and hot-pressing (STP) technology. STP technology is a new film-formation process that consists of spin coating a dielectric material on a base film, hot pressing the dielectric film on a wafer with gaps in a vacuum chamber, and peeling the base film off the dielectric adhered to the wafer. In order to seal the gaps with thin dielectric films, it is necessary to prevent the dielectric from breaking during the peel-off step. Thus, a dielectric of poly(benzoxazole) (PBO) with additives for reducing the adhesion strength between the dielectric and the base film is proposed. The experimental results show that 0.3-μm-wide gaps can be sealed with dielectric films as thin as 0.25 μm without film breaking. The mechanism by which adhesion strength decreases in the peel-off step is discussed in terms of its dependence on the proportion of additives. The synergy of the STP process and the type of dielectric material used paves the way for the development of future interconnect schemes using air gaps.

  10. Effect of air gap variation on the performance of single stator single rotor axial flux permanent magnet generator

    NASA Astrophysics Data System (ADS)

    Kasim, Muhammad; Irasari, Pudji; Hikmawan, M. Fathul; Widiyanto, Puji; Wirtayasa, Ketut

    2017-02-01

    The axial flux permanent magnet generator (AFPMG) has been widely used especially for electricity generation. The effect of the air gap variation on the characteristic and performances of single rotor - single stator AFPMG has been described in this paper. Effect of air gap length on the magnetic flux distribution, starting torque and MMF has been investigated. The two dimensional finite element magnetic method has been deployed to model and simulated the characteristics of the machine which is based on the Maxwell equation. The analysis has been done for two different air gap lengths which were 2 mm and 4 mm using 2D FEMM 4.2 software at no load condition. The increasing of air gap length reduces the air-gap flux density. For air gap 2 mm, the maximum value of the flux density was 1.04 T while 0.73 T occured for air gap 4 mm.. Based on the experiment result, the increasing air gap also reduced the starting torque of the machine with 39.2 Nm for air gap 2 mm and this value decreased into 34.2 Nm when the air gap increased to 4 mm. Meanwhile, the MMF that was generated by AFPMG decreased around 22% at 50 Hz due to the reduction of magnetic flux induced on stator windings. Overall, the research result showed that the variation of air gap has significant effect on the machine characteristics.

  11. Air Pollution and Health: Bridging the Gap from Health Outcomes: Conference Summary

    EPA Science Inventory

    Air Pollution and Health: Bridging the Gap from Sources to Health Outcomes,” an international specialty conference sponsored by the American Association for Aerosol Research, was held to address key uncertainties in our understanding of adverse health effects related to air po...

  12. 30 CFR 285.659 - What requirements must I include in my SAP, COP, or GAP regarding air quality?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 2 2010-07-01 2010-07-01 false What requirements must I include in my SAP, COP, or GAP regarding air quality? 285.659 Section 285.659 Mineral Resources MINERALS MANAGEMENT SERVICE... must I include in my SAP, COP, or GAP regarding air quality? (a) You must comply with the Clean Air...

  13. Influence of the air gap between protective clothing and skin on clothing performance during flash fire exposure

    NASA Astrophysics Data System (ADS)

    Ghazy, Ahmed; Bergstrom, Donald J.

    2011-10-01

    A finite volume model was developed to simulate transient heat transfer in protective clothing during flash fire exposure. The model accounts for the combined conduction-radiation heat transfer in the air gap between the fabric and skin. The variation in the fabric and air gap properties with temperature and the thermochemical reactions in the fabric are also considered. This study investigates the influence of the air gap in protective clothing on the energy transfer through the clothing and hence on its performance. Different parameters that affect the conduction-radiation heat transfer through the air gap such as the air gap absorption coefficient and the air gap width were studied. Finally, the paper demonstrates that an innovative and potentially significant way to improve protective clothing performance is to reduce the emissivity on the backside of the fabric.

  14. Air gap resonant tunneling bandpass filter and polarizer.

    PubMed

    Melnyk, A; Bitarafan, M H; Allen, T W; DeCorby, R G

    2016-04-15

    We describe a bandpass filter based on resonant tunneling through an air layer in the frustrated total internal reflection regime, and show that the concept of induced transmission can be applied to the design of thin film matching stacks. Experimental results are reported for Si/SiO2-based devices exhibiting a polarization-dependent passband, with bandwidth on the order of 10 nm in the 1550 nm wavelength range, peak transmittance on the order of 80%, and optical density greater than 5 over most of the near infrared region.

  15. Study on the wide-angle Michelson interferometer with large air gap.

    PubMed

    Gao, Haiyang; Tang, Yuanhe; Hua, Dengxin; Liu, Hanchen

    2011-10-10

    A wide-angle Michelson interferometer with large air gap is proposed to effectively reduce the size of the glass arms and constraint on material. It provides a novel and practical instrument for ground based wind measurement of the upper atmosphere. The field widening conditions for the large air gap are calculated in theory. For the five spectral lines of 557.7 nm, 630.0 nm, 732.0 nm, 834.6 nm, and 865.7 nm, the optimal results under ideal condition are obtained with air gaps of 1.0 cm, 1.5 cm, and 2.0 cm, respectively. With the fixed optical path difference (OPD) of 7.495 cm, three pairs of glass arms are optimized. The pair with length of 1.5 cm for air gap, 5.765 cm for H-ZF12, and 2.956 cm for H-ZLaF54, has better effect of field widening than the other two pairs and its OPD variation is only within 0.30 wavelengths at incident angle of 3°. For developing a more practical wide-angle Michelson interferometer, the H-K9L glass with size of 4.445 cm is employed as the arm material of solid interferometer. The experiment for field of view of 3° is designed and the data processing and analysis for 60 images show the agreement between experimental results and theoretical simulation. The OPD variations are only within 0.27 wavelengths for image edge. The feasibility and practicality of the wide-angle Michelson interferometer with large air gap is proved by means of theory and experiment.

  16. The effect of body postures on the distribution of air gap thickness and contact area.

    PubMed

    Mert, Emel; Psikuta, Agnes; Bueno, Marie-Ange; Rossi, René M

    2017-02-01

    The heat and mass transfer in clothing is predominantly dependent on the thickness of air layer and the magnitude of contact area between the body and the garment. The air gap thickness and magnitude of the contact area can be affected by the posture of the human body. Therefore, in this study, the distribution of the air gap and the contact area were investigated for different body postures of a flexible manikin. In addition, the effect of the garment fit (regular and loose) and style (t-shirts, sweatpants, jacket and trousers) were analysed for the interaction between the body postures and the garment properties. A flexible manikin was scanned using a three-dimensional (3D) body scanning technique, and the scans were post-processed in dedicated software. The body posture had a strong effect on the air gap thickness and the contact area for regions where the garment had a certain distance from the body. Furthermore, a mathematical model was proposed to estimate the possible heat transfer coefficient for the observed air layers and their change with posture. The outcome of this study can be used to improve the design of the protective and functional garments and predict their effect on the human body.

  17. The effect of body postures on the distribution of air gap thickness and contact area

    NASA Astrophysics Data System (ADS)

    Mert, Emel; Psikuta, Agnes; Bueno, Marie-Ange; Rossi, René M.

    2017-02-01

    The heat and mass transfer in clothing is predominantly dependent on the thickness of air layer and the magnitude of contact area between the body and the garment. The air gap thickness and magnitude of the contact area can be affected by the posture of the human body. Therefore, in this study, the distribution of the air gap and the contact area were investigated for different body postures of a flexible manikin. In addition, the effect of the garment fit (regular and loose) and style (t-shirts, sweatpants, jacket and trousers) were analysed for the interaction between the body postures and the garment properties. A flexible manikin was scanned using a three-dimensional (3D) body scanning technique, and the scans were post-processed in dedicated software. The body posture had a strong effect on the air gap thickness and the contact area for regions where the garment had a certain distance from the body. Furthermore, a mathematical model was proposed to estimate the possible heat transfer coefficient for the observed air layers and their change with posture. The outcome of this study can be used to improve the design of the protective and functional garments and predict their effect on the human body.

  18. Preprophase band formation and cortical division zone establishment: RanGAP behaves differently from microtubules during their band formation

    PubMed Central

    Yabuuchi, Takatoshi; Nakai, Tomonori; Sonobe, Seiji; Yamauchi, Daisuke; Mineyuki, Yoshinobu

    2015-01-01

    Correct positioning of the division plane is a prerequisite for plant morphogenesis. The preprophase band (PPB) is a key intracellular structure of division site determination. PPB forms in G2 phase as a broad band of microtubules (MTs) that narrows in prophase and specializes few-micrometer-wide cortical belt region, named the cortical division zone (CDZ), in late prophase. The PPB comprises several molecules, some of which act as MT band organization and others remain in the CDZ marking the correct insertion of the cell plate in telophase. Ran GTPase-activating protein (RanGAP) is accumulated in the CDZ and forms a RanGAP band in prophase. However, little is known about when and how RanGAPs gather in the CDZ, and especially with regard to their relationships to MT band formation. Here, we examined the spatial and temporal distribution of RanGAPs and MTs in the preprophase of onion root tip cells using confocal laser scanning microscopy and showed that the RanGAP band appeared in mid-prophase as the width of MT band was reduced to nearly 7 µm. Treatments with cytoskeletal inhibitors for 15 min caused thinning or broadening of the MT band but had little effects on RanGAP band in mid-prophase and most of late prophase cells. Detailed image analyses of the spatial distribution of RanGAP band and MT band showed that the RanGAP band positioned slightly beneath the MT band in mid-prophase. These results raise a possibility that RanGAP behaves differently from MTs during their band formation. PMID:26237087

  19. 30 CFR 585.659 - What requirements must I include in my SAP, COP, or GAP regarding air quality?

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 2 2012-07-01 2012-07-01 false What requirements must I include in my SAP, COP, or GAP regarding air quality? 585.659 Section 585.659 Mineral Resources BUREAU OF OCEAN ENERGY... What requirements must I include in my SAP, COP, or GAP regarding air quality? (a) You must comply...

  20. 30 CFR 585.659 - What requirements must I include in my SAP, COP, or GAP regarding air quality?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 2 2013-07-01 2013-07-01 false What requirements must I include in my SAP, COP, or GAP regarding air quality? 585.659 Section 585.659 Mineral Resources BUREAU OF OCEAN ENERGY... What requirements must I include in my SAP, COP, or GAP regarding air quality? (a) You must comply...

  1. 30 CFR 285.659 - What requirements must I include in my SAP, COP, or GAP regarding air quality?

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 2 2011-07-01 2011-07-01 false What requirements must I include in my SAP, COP, or GAP regarding air quality? 285.659 Section 285.659 Mineral Resources BUREAU OF OCEAN ENERGY... Pipeline Deviations § 285.659 What requirements must I include in my SAP, COP, or GAP regarding air...

  2. 30 CFR 585.659 - What requirements must I include in my SAP, COP, or GAP regarding air quality?

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 2 2014-07-01 2014-07-01 false What requirements must I include in my SAP, COP, or GAP regarding air quality? 585.659 Section 585.659 Mineral Resources BUREAU OF OCEAN ENERGY... What requirements must I include in my SAP, COP, or GAP regarding air quality? (a) You must comply...

  3. Influence of elasticity on gap formation in a lining technique with flowable composite.

    PubMed

    Cho, Eitetsu; Chikawa, Hirokazu; Kishikawa, Ryuzo; Inai, Norimichi; Otsuki, Masayuki; Foxton, Richard M; Tagami, Junji

    2006-09-01

    The purpose of this study was to investigate the effect of flowable composites as liners for direct composite restorations, with key focus on the elastic moduli of flowable and condensable composites. After treating the composite mold cavity surface with an adhesive system, one of the flowable composites was placed as a 1 mm-thick layer on the cavity floor and irradiated for 20 seconds. The rest of cavity was subsequently filled with a condensable composite and irradiated for 40 seconds. Gap formation at both interfaces--between the cavity floor and flowable composite, and between the flowable and condensable composites--was examined. No gaps were detected at the interface between the cavity floor and flowable composite. Gap percentage at the interface between the flowable and condensable composites was dependent on the difference in elastic modulus. It was concluded that flowable composite with high elastic modulus could inhibit gap formation between flowable and condensable composites.

  4. Nonlinear sub-cyclotron resonance as a formation mechanism for gaps in banded chorus

    DOE PAGES

    Fu, Xiangrong; Guo, Zehua; Dong, Chuanfei; ...

    2015-05-14

    An interesting characteristic of magnetospheric chorus is the presence of a frequency gap at ω ≃ 0.5Ωe, where Ωe is the electron cyclotron angular frequency. Recent chorus observations sometimes show additional gaps near 0.3Ωe and 0.6Ωe. Here we present a novel nonlinear mechanism for the formation of these gaps using Hamiltonian theory and test particle simulations in a homogeneous, magnetized, collisionless plasma. We find that an oblique whistler wave with frequency at a fraction of the electron cyclotron frequency can resonate with electrons, leading to effective energy exchange between the wave and particles.

  5. A micro-gap, air-filled ionisation chamber as a detector for criticality accident dosimetry.

    PubMed

    Murawski, Ł; Zielczyński, M; Golnik, N; Gryziński, M A

    2014-10-01

    A micro-gap air-filled ionisation chamber was designed for criticality dosimetry. The special feature of the chamber is its very small gap between electrodes of only 0.3 mm. This prevents ion recombination at high dose rates and minimises the influence of gas on secondary particles spectrum. The electrodes are made of polypropylene because of higher content of hydrogen in this material, when compared with soft tissue. The difference between neutron and gamma sensitivity in such chamber becomes practically negligible. The chamber's envelope contains two specially connected capacitors, one for polarising the electrodes and the other for collecting the ionisation charge.

  6. Hybrid plasmonic microcavity with an air-filled gap for sensing applications

    NASA Astrophysics Data System (ADS)

    Zhang, Meng; Liu, Binbin; Wu, Genzhu; Chen, Daru

    2016-12-01

    In this paper, a novel hybrid plasmonic microcavity with air-filled regions in the low-permittivity dielectric gap is proposed for sensing applications. Compared with the conventional structure with homogeneous gap, the introduced air-filled regions could improve the key modal characteristics of the hybrid mode. Simulation results reveal that this kind of hybrid microcavity maintains low loss with high quality factor ∼3062, and high field confinement with small mode volume 0.891 μm3. Moreover, in the sensing applications, this hybrid microcavity features simultaneously large refractive index sensitivity of 100 nm/RIU (refractive index unit) and relatively high quality factor of 3062. Hence, it shows that the hybrid plasmonic microcavity has potential applications in ultra-compact refractive index sensor.

  7. Observations of the Valley of Mexico Basin Ventilation Through the Tenango del Aire- Amecameca Geographical Gap

    NASA Astrophysics Data System (ADS)

    Ruiz-Suarez, G.; Torres-Jarón, R.; Steinbrecher, R.; Junkermann, W.; Torres-Jaramillo, A.; Garcia, A. R.; Mar-Morales, B.

    2007-05-01

    Past air quality modeling exercises have suggested the existence of basin drainage flows which may transport Mexico City Metropolitan Area's air pollution plume outside the Valley of Mexico Basin. The MCMA-2006 field campaign offered the opportunity to study the basin ventilation through a geographical gap in the southeast mountains of the basin. A mobile monitoring lab was placed at the Tenango del Aire town, a unique site located in this gap for measuring the pass of air masses from (and towards) the MCMA to (and from) the Cuautla Valley. O3, CO, NOx, NOy, CH2O global and UV radiation and MLH were measured continuously during MILAGRO from March 2 until April 6, together with other chemical species. Complementary backward and forward trajectories were constructed for the site using MCCM in prognostic mode during MILAGRO. An exploratory analysis of the air pollution roses measured at Tenango showed a sharp dominance of two flow patterns: one from the north well associated with relatively higher levels of primary pollutants and ozone levels; and another one from the south typically associated with lower levels primary pollutants but not so low of secondary ones as ozone. On the other hand, measured CO data at Tenango were compared with CO data measured at one local monitoring station in the town of Ocuituco in the State of Morelos. Ocuituco is located to the south of Tenango towards the Cuautla Valley. The preliminary results suggest that the back and forth pass of air masses through the Tenango del Aire - Amecameca area can be an important process in the regional transport of air pollution between two valleys and their metropolitan areas within the Central Mexico region.

  8. Local droplet etching – Nanoholes, quantum dots, and air-gap heterostructures

    SciTech Connect

    Heyn, Ch.; Sonnenberg, D.; Graf, A.; Kerbst, J.; Stemmann, A.; Hansen, W.

    2014-05-15

    Local droplet etching (LDE) allows the self-organized generation of nanoholes in semiconductor surfaces and is fully compatible with molecular beam epitaxy (MBE). The influence of the process parameters as well as of droplet and substrate materials on the LDE nanohole morphology is discussed. Furthermore, recent applications of LDE, the fabrication of quantum dots by hole filling and the creation of air-gap heterostructures are addressed.

  9. Air Gaps, Size Effect, and Corner-Turning in Ambient LX-17

    SciTech Connect

    Souers, P C; Hernandez, A; Cabacungan, C; Fried, L; Garza, R; Glaesemann, K; Lauderbach, L; Liao, S; Vitello, P

    2008-02-05

    Various ambient measurements are presented for LX-17. The size (diameter) effect has been measured with copper and Lucite confinement, where the failure radii are 4.0 and 6.5 mm, respectively. The air well corner-turn has been measured with an LX-07 booster, and the dead-zone results are comparable to the previous TATB-boosted work. Four double cylinders have been fired, and dead zones appear in all cases. The steel-backed samples are faster than the Lucite-backed samples by 0.6 {micro}s. Bare LX-07 and LX-17 of 12.7 mm-radius were fired with air gaps. Long acceptor regions were used to truly determine if detonation occurred or not. The LX-07 crossed at 10 mm with a slight time delay. Steady state LX-17 crossed at 3.5 mm gap but failed to cross at 4.0 mm. LX-17 with a 12.7 mm run after the booster crossed a 1.5 mm gap but failed to cross 2.5 mm. Timing delays were measured where the detonation crossed the gaps. The Tarantula model is introduced as embedded in 0 reactive flow JWL++ and Linked Cheetah V4, mostly at 4 zones/mm. Tarantula has four pressure regions: off, initiation, failure and detonation. The physical basis of the input parameters is considered.

  10. Force versus current and air gap calibration of a double acting magnetic thrust bearing

    SciTech Connect

    Baun, D.O.; Fittro, R.L.; Maslen, E.H.

    1995-12-31

    Force versus current and air gap measurements were obtained for a double acting thrust bearing. Static force measurements were made for various air gap settings and bearing current combinations. The resulting data was reduced and an optimized expression representing the force versus current and air gap relationship of the bearing was found. In addition, a theoretical force model was developed using simple magnetic circuit theory and magnetic properties obtained from standard magnetic material tests. The theoretical and the experimentally derived force models were compared. Hysteresis tests were conducted with the thrust disk in the centered position for various current perturbation amplitudes about the design bias current. Hysteresis effects were shown to cause a difference between the measured force as the current was increasing as compared to when the current was decreasing. A second order polynomial expression was developed to express the coercive force as a function of the perturbation current amplitude. The bearing frequency response was examined by injecting sinusoidal currents of varying frequencies into the bearing. A maximum actuator bandwidth of approximately 700 Hz was determined. Above 700 Hz the bearing frequency response could not be distinguished from the test fixture frequency response.

  11. Dynamic analysis of a BLDC motor with mechanical and electromagnetic interaction due to air gap variation

    NASA Astrophysics Data System (ADS)

    Im, Hyungbin; Yoo, Hong Hee; Chung, Jintai

    2011-04-01

    In this study, the dynamic behaviors of a BLDC motor are analyzed, when the motor undergoes mechanical and electromagnetic interaction due to an air gap variation between the stator and rotor. When considering the air gap variation caused by the translational motion of the rotor relative to the stator, the kinetic and potential energies, Rayleigh dissipation function, and the magnetic coenergy are expressed in terms of the rotor displacements and stator currents. With these energies and function, new equations of motion are derived using Lagrange's equation. The equations for the proposed model are nonlinear equations in which the displacements and currents are coupled. The time responses for the displacements and currents are computed for the proposed and previous models. Furthermore, the effects of rotor eccentricity are also investigated. It is found that, when the air gap varies with time, the time responses for the proposed and previous models have small differences in the stator currents, electromagnetic torques, and rotating speeds. However, the time responses have large differences in the rotor displacements. Therefore, this paper claims that the proposed model describes the dynamic behaviors of the motor more accurately than the previous model. It is also shown that rotor eccentricity increases the stator current period and the electromagnetic torque, while it decreases the rotating speed of the rotor.

  12. Effect of heterogenous and homogenous air gaps on dry heat loss through the garment.

    PubMed

    Mert, Emel; Psikuta, Agnes; Bueno, Marie-Ange; Rossi, René M

    2015-11-01

    In real life conditions, the trapped air between the human body and the garment has uneven shape and vary over the body parts as a consequence of the complex geometry of the human body. However, the existing clothing models assume uniform air layer between the human body and the garment or its full contact, which may cause large error in the output of simulations. Therefore, the aim of this study was to investigate the effect of a heterogeneous vertical air gap with different configuration of folds (size and frequency) on dry heat loss using a heated cylinder (Torso). It was found that the presence of folds in the garment led to an increased heat loss from the body in comparison to a homogeneous air gap of comparable size. Interestingly, the size of folds did not have an influence on the dry heat loss. Additionally, the effect of the contact area on dry heat loss became important when exceeding a threshold of about 42%. The results from this study are useful for modelling of a realistic dry heat loss through the clothing and contribute to the improvement of design of protective and active sport garments.

  13. Effect of heterogenous and homogenous air gaps on dry heat loss through the garment

    NASA Astrophysics Data System (ADS)

    Mert, Emel; Psikuta, Agnes; Bueno, Marie-Ange; Rossi, René M.

    2015-11-01

    In real life conditions, the trapped air between the human body and the garment has uneven shape and vary over the body parts as a consequence of the complex geometry of the human body. However, the existing clothing models assume uniform air layer between the human body and the garment or its full contact, which may cause large error in the output of simulations. Therefore, the aim of this study was to investigate the effect of a heterogeneous vertical air gap with different configuration of folds (size and frequency) on dry heat loss using a heated cylinder (Torso). It was found that the presence of folds in the garment led to an increased heat loss from the body in comparison to a homogeneous air gap of comparable size. Interestingly, the size of folds did not have an influence on the dry heat loss. Additionally, the effect of the contact area on dry heat loss became important when exceeding a threshold of about 42 %. The results from this study are useful for modelling of a realistic dry heat loss through the clothing and contribute to the improvement of design of protective and active sport garments.

  14. Materials, processes, and characterization of extended air-gaps for the intra-level interconnection of integrated circuits

    NASA Astrophysics Data System (ADS)

    Park, Seongho

    The integration of an air-gap as an ultra low dielectric constant material in an infra-metal dielectric region of interconnect structure in integrated circuits was investigated in terms of material properties of a thermally decomposable sacrificial polymer, fabrication processes and electrical performance. Extension of the air-gap into the inter-layer dielectric region reduces the interconnect capacitance. In order to enhance the hardness of a polymer for the better process reliabilities, a conventional norbornene-based sacrificial polymer was electron-beam irradiated. Although the hardness of the polymer increased, the thermal properties degraded. A new high modulus tetracyclododecene-based sacrificial polymer was characterized and compared to the norbornene-based polymer in terms of hardness, process reliability and thermal properties. The tetracyclododecene-based polymer was harder and showed better process reliability than the norbomene-based sacrificial polymer. Using the tetracyclododecene-based sacrificial polymer, a single layer Cu/air-gap and extended Culair-gap structures were fabricated. The effective dielectric constant of the air-gap and extended air-gap structures were 2.42 and 2.17, respectively. This meets the requirements for the 32 nm node. Moisture uptake of the extended Cu/air-gap structure increased the effective dielectric constant. The exposure of the structure to hexamethyldisilazane vapor removed the absorbed moisture and changed the structure hydrophobic, improving the integration reliability. The integration processes of the air-gap and the extended air-gap into a dual damascene Cu metallization process has been proposed and compared to state-of-the-art integration approaches.

  15. The extracellular matrix component laminin promotes gap junction formation in the rat anterior pituitary gland.

    PubMed

    Horiguchi, Kotaro; Kouki, Tom; Fujiwara, Ken; Kikuchi, Motoshi; Yashiro, Takashi

    2011-03-01

    Folliculo-stellate (FS) cells in the anterior pituitary gland are believed to have multifunctional properties. FS cells connect to each other not only by mechanical means, but also by gap junctional cell-to-cell communication. Using transgenic rats that express green fluorescent protein (GFP) specifically in FS cells in the anterior pituitary gland (S100b-GFP rats), we recently revealed that FS cells in primary culture markedly change their shape, and form numerous interconnections with neighboring FS cells in the presence of laminin, an extracellular matrix (ECM) component of the basement membrane. Morphological and functional changes in cells are believed to be partly modified by matricrine signaling, by which ECM components function as cellular signals. In the present study, we examined whether gap junction formation between FS cells is affected by matricrine cues. A cell sorter was used to isolate FS cells from male S100b-GFP rat anterior pituitary for primary culture. We observed that mRNA and protein levels of connexin 43 in gap junction channels were clearly higher in the presence of laminin. In addition, we confirmed the formation of gap junctions between FS cells in primary culture by electron microscopy. Interestingly, we also observed that FS cells in the presence of laminin displayed well-developed rough endoplasmic reticulum and Golgi apparatus. Our findings suggest that, in anterior pituitary gland, FS cells may facilitate functional roles such as gap junctional cell-to-cell communication by matricrine signaling.

  16. Surface dose measurements from air gaps under a bolus by using a MOSFET dosimeter in clinical oblique photon beams

    NASA Astrophysics Data System (ADS)

    Chung, Jin-Beom; Kim, Jae-Sung; Kim, In-Ah; Lee, Jeong-Woo

    2012-10-01

    This study is intended to investigate the effects of surface dose from air gaps under the bolus in clinically used oblique photon beams by using a Markus parallel-plate chamber and a metal-oxide semiconductor field-effect transistor (MOSFET) dosimeter. To evaluate the performances of the two detectors, the percentage surface doses of the MOSFET dosimeters in without an air gap under the bolus material were measured and compared with those of the Markus parallel-plate chamber. MOSFET dosimeters at the surface provided results mostly in good agreement with the parallelplate chamber. The MOSFET dosimeters seemed suitable for surface dose measurements having excellent accuracy for clinical used photon beams. The relative surface doses were measured with air gaps (2, 5, 10 mm) and without an air gap under 3 different bolus setups: (1) unbolused (no bolus), (2) 5-mm bolus, and (3) 10-mm bolus. The reductions in the surface dose substantially increased with small field size, thick bolus, and large air gap. The absolute difference in the reductions of the surface dose between the MOSFET dosimeter and the Markus parallel-plate chamber was less than 1.1%. Results at oblique angles of incidence showed larger reductions in surface dose with increasing angle of incidence. The largest reduction in surface dose was recorded for a 6 × 6 cm2 field at a 60° angle of incidence with an 10-mm air gap under a 10-mm bolus. When a 10-mm bolus was used, a reduction in the surface dose with an air gap of up to 10.5% could be achieved by varying the field size and the incident angle. Therefore, air gaps under the bolus should be avoided in radiotherapy treatment, especially for photon beam with highly oblique angles of incidence.

  17. Laser-guided energetic discharges over large air gaps by electric-field enhanced plasma filaments

    PubMed Central

    Théberge, Francis; Daigle, Jean-François; Kieffer, Jean-Claude; Vidal, François; Châteauneuf , Marc

    2017-01-01

    Recent works on plasma channels produced during the propagation of ultrashort and intense laser pulses in air demonstrated the guiding of electric discharges along the laser path. However, the short plasma lifetime limits the length of the laser-guided discharge. In this paper, the conductivity and lifetime of long plasma channels produced by ultrashort laser pulses is enhanced efficiently over many orders of magnitude by the electric field of a hybrid AC-DC high-voltage source. The AC electric pulse from a Tesla coil allowed to stimulate and maintain the highly conductive channel during few milliseconds in order to guide a subsequent 500 times more energetic discharge from a 30-kV DC source. This DC discharge was laser-guided over an air gap length of two metres, which is more than two orders of magnitude longer than the expected natural discharge length. Long plasma channel induced by laser pulses and stimulated by an external high-voltage source opens the way for wireless and efficient transportation of energetic current pulses over long air gaps and potentially for guiding lightning. PMID:28053312

  18. Laser-guided energetic discharges over large air gaps by electric-field enhanced plasma filaments

    NASA Astrophysics Data System (ADS)

    Théberge, Francis; Daigle, Jean-François; Kieffer, Jean-Claude; Vidal, François; Châteauneuf, Marc

    2017-01-01

    Recent works on plasma channels produced during the propagation of ultrashort and intense laser pulses in air demonstrated the guiding of electric discharges along the laser path. However, the short plasma lifetime limits the length of the laser-guided discharge. In this paper, the conductivity and lifetime of long plasma channels produced by ultrashort laser pulses is enhanced efficiently over many orders of magnitude by the electric field of a hybrid AC-DC high-voltage source. The AC electric pulse from a Tesla coil allowed to stimulate and maintain the highly conductive channel during few milliseconds in order to guide a subsequent 500 times more energetic discharge from a 30-kV DC source. This DC discharge was laser-guided over an air gap length of two metres, which is more than two orders of magnitude longer than the expected natural discharge length. Long plasma channel induced by laser pulses and stimulated by an external high-voltage source opens the way for wireless and efficient transportation of energetic current pulses over long air gaps and potentially for guiding lightning.

  19. Nonlinear sub-cyclotron resonance as a formation mechanism for gaps in banded chorus

    SciTech Connect

    Fu, Xiangrong; Guo, Zehua; Dong, Chuanfei; Gary, S. Peter

    2015-05-14

    An interesting characteristic of magnetospheric chorus is the presence of a frequency gap at ω ≃ 0.5Ωe, where Ωe is the electron cyclotron angular frequency. Recent chorus observations sometimes show additional gaps near 0.3Ωe and 0.6Ωe. Here we present a novel nonlinear mechanism for the formation of these gaps using Hamiltonian theory and test particle simulations in a homogeneous, magnetized, collisionless plasma. We find that an oblique whistler wave with frequency at a fraction of the electron cyclotron frequency can resonate with electrons, leading to effective energy exchange between the wave and particles.

  20. Air Gaps, Size Effect, and Corner-Turning in Ambient LX-17

    SciTech Connect

    Souers, P C; Hernandez, A; Cabacungen, C; Fried, L; Garza, R; Glaesemann, K; Lauderbach, L; Liao, S; Vitello, P

    2007-05-30

    Various ambient measurements are presented for LX-17. The size (diameter) effect has been measured with copper and Lucite confinement, where the failure radii are 4.0 and 6.5 mm, respectively. The air well corner-turn has been measured with an LX-07 booster, and the dead-zone results are comparable to the previous TATB-boosted work. Four double cylinders have been fired, and dead zones appear in all cases. The steel-backed samples are faster than the Lucite-backed samples by 0.6 {micro}s. Bare LX-07 and LX-17 of 12.7 mm-radius were fired with air gaps. Long acceptor regions were used to truly determine if detonation occurred or not. The LX-07 crossed at 10 mm with a slight time delay. Steady state LX-17 crossed at 3.5 mm gap but failed to cross at 4.0 mm. LX-17 with a 12.7 mm run after the booster crossed a 1.5 mm gap but failed to cross 2.5 mm. Timing delays were measured where the detonation crossed the gaps. The Tarantula model is introduced as embedded in the Linked Cheetah V4.0 reactive flow code at 4 zones/mm. Tarantula has four pressure regions: off, initiation, failure and detonation. A report card of 25 tests run with the same settings on LX-17 is shown, possibly the most extensive simultaneous calibration yet tried with an explosive. The physical basis of some of the input parameters is considered.

  1. Vertical cavity surface emitting laser based on gallium arsenide/air-gap distributed Bragg reflectors: From concept to working devices

    NASA Astrophysics Data System (ADS)

    Mo, Qingwei

    Vertical-cavity surface-emitting lasers (VCSELs) have created new opportunities in optoelectronics. However, VCSELs have so far been commercialized mainly for operation at 0.85 mum, despite their potential importance at other wavelengths, such as 1.3 mum and 1.55 mum. The limitations at these longer wavelengths come from material characteristics, such as a low contrast ratio in mirror materials, lower mirror reflectivity, and smaller optical gain for longer wavelength materials versus AlGaAs/GaAs quantum wells. A similar situation, insufficient gain relative to the cavity loss, existed in the past for shorter wavelength VCSELs before high quality epitaxial mirrors were developed. Semiconductor/air-gap Distributed Bragg Reflectors (DBRs) are attractive due to their high index contrast, which leads to a high reflectivity, wide stop band and low optical loss mirror with a small number of pairs. This concept is ready to be integrated into material systems other than AlGaAs/GaAs, which is studied in this work. Therefore, the impact of these DBRs can be extended into both visible and longer infrared wavelengths as a solution to the trade-off between DBR and active region materials. Air-gap DBRs can also be used as basic building blocks of micro-opto-electro-mechanical systems (MOEMS). The high Q microcavity formed by the air-gap DBRs also provide a good platform for microcavity physics study. Air-gap DBRs are modeled using the transmission matrix formulae of the Maxwell equations. A comparison to existing DBR technology shows the great advantage and potential that the air-gap DBR possesses. Two types of air-gap are proposed and developed. The first one includes multiple GaAs/air pairs while the second one combines a single air-gap with metal and dielectric mirrors. New device structures and processing designs, especially an all-epitaxial lateral current and optical confinement technique, are carried out to incorporate air-gap DBRs into VCSEL structures. The first VCSEL

  2. Control of deformable mirrors including a nonlinear modal model for air gap damping

    NASA Astrophysics Data System (ADS)

    Böhm, Michael; Sawodny, Oliver

    2016-09-01

    In this paper, we present nonlinear pressure dynamics as an extension to a linear distributed parameters model of a deformable mirror. The original, undamped model is recalled and measurement results are shown supporting the need for a damping model which includes the pressure dynamics of the air gap behind the mirror membrane. We will derive the damping coefficients to match our measurement results. Based on the mew model, we will derive a modal feedforward and feedback control law for 88 actuators based on only 3 position sensors and show simulation results to support the algorithm's effectiveness.

  3. Pattern formation in the flow between two horizontal coaxial cylinders with a partially filled gap

    NASA Astrophysics Data System (ADS)

    Mutabazi, Innocent; Hegseth, John J.; Andereck, C. David; Wesfreid, Jose E.

    1988-11-01

    Flow between two horizontal coaxial cylinders with a partially filled gap is subject to several types of centrifugal instabilities which lead to the formation of a variety of spatial patterns. An experimental investigation has shown that there are five distinct branches of primary instabilities occurring in the system and that four codimension-2 points are easily reached. Theoretical predictions are in qualitative agreement with the observations.

  4. Interfingering of the Frontier Formation and Aspen Shale, Cumberland Gap, Wyoming.

    USGS Publications Warehouse

    M'gonigle, J.

    1982-01-01

    The basal part, or the Chalk Creek Member, of the non-marine lower Frontier Formation (Upper Cretaceous) includes a thin coal bed that grades S into a carbonaceous shale. The latter plus associated sandstones and shales pinch out S of Cumberland Gap and lie stratigraphically below the top of the Aspen Shale. The beds in the upper part of the Aspen, in turn, pinch out within the Frontier Formation. The coal bed and equivalent carbonaceous shale represent in-place accumulation of peat. The interfingering suggests that in SW Wyoming the Lower/Upper Cretaceous boundary is within the Chalk Creek Member. -from Author

  5. Toward a global network for persistent organic pollutants in air: results from the GAPS study.

    PubMed

    Pozo, Karla; Harner, Tom; Wania, Frank; Muir, Derek C G; Jones, Kevin C; Barrie, Leonard A

    2006-08-15

    The Global Atmospheric Passive Sampling (GAPS) study aims to demonstrate the feasibility of using passive samplers to assess the spatial distribution of persistent organic pollutants on a worldwide basis. The GAPS network includes more than 40 sites on 7 continents, mainly in background locations, with some representation of urban and agricultural areas. Here we present concentrations of organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs) in polyurethane foam disk samplers, deployed from December 2004 to March 2005. Legacy OCPs such as alpha-HCH (hexachlorocyclohexane), Chlordanes (trans- and cis-Chlordane and trans-Nonachlor), Dieldrin, and dichlorodiphenyltrichloroethane isomers were detected at most sites with some high values that may be related to possible continued use and/or re-emissions related to historic use. Geometric mean (GM) air concentrations (pg/m3) were: 8.5 for sigmaHCH (sum of alpha- and gamma-isomers), 2.6 for sigmaChlordanes, 0.8 for Dieldrin, and 0.8 for p,p'-DDE. Current-use pesticides such as gamma-HCH (lindane) and especially Endosulfan I exhibited more variable and higher concentrations with GMs of 5 and 58, respectively. PCBs and PBDEs were elevated at urban/suburban sites consistent with their historical use pattern. GM concentrations (pg/m3) were 17 for PCBs and 4 for PBDEs. Sampling under GAPS will continue and will eventually allow seasonality effects and longer-term temporal and spatial trends to be evaluated.

  6. Root-soil air gap and resistance to water flow at the soil-root interface of Robinia pseudoacacia.

    PubMed

    Liu, X P; Zhang, W J; Wang, X Y; Cai, Y J; Chang, J G

    2015-12-01

    During periods of water deficit, growing roots may shrink, retaining only partial contact with the soil. In this study, known mathematical models were used to calculate the root-soil air gap and water flow resistance at the soil-root interface, respectively, of Robinia pseudoacacia L. under different water conditions. Using a digital camera, the root-soil air gap of R. pseudoacacia was investigated in a root growth chamber; this root-soil air gap and the model-inferred water flow resistance at the soil-root interface were compared with predictions based on a separate outdoor experiment. The results indicated progressively greater root shrinkage and loss of root-soil contact with decreasing soil water potential. The average widths of the root-soil air gap for R. pseudoacacia in open fields and in the root growth chamber were 0.24 and 0.39 mm, respectively. The resistance to water flow at the soil-root interface in both environments increased with decreasing soil water potential. Stepwise regression analysis demonstrated that soil water potential and soil temperature were the best predictors of variation in the root-soil air gap. A combination of soil water potential, soil temperature, root-air water potential difference and soil-root water potential difference best predicted the resistance to water flow at the soil-root interface.

  7. Numerical modeling of the thermoelectric cooler with a complementary equation for heat circulation in air gaps

    NASA Astrophysics Data System (ADS)

    Fang, En; Wu, Xiaojie; Yu, Yuesen; Xiu, Junrui

    2017-01-01

    In this paper, a numerical model is developed by combining thermodynamics with heat transfer theory. Taking inner and external multi-irreversibility into account, it is with a complementary equation for heat circulation in air gaps of a steady cooling system with commercial thermoelectric modules operating in refrigeration mode. With two modes concerned, the equation presents the heat flowing through air gaps which forms heat circulations between both sides of thermoelectric coolers (TECs). In numerical modelling, a TEC is separated as two temperature controlled constant heat flux reservoirs in a thermal resistance network. In order to obtain the parameter values, an experimental apparatus with a commercial thermoelectric cooler was built to characterize the performance of a TEC with heat source and sink assembly. At constant power dissipation, steady temperatures of heat source and both sides of the thermoelectric cooler were compared with those in a standard numerical model. The method displayed that the relationship between Φf and the ratio Φ_{c}'/Φ_{c} was linear as expected. Then, for verifying the accuracy of proposed numerical model, the data in another system were recorded. It is evident that the experimental results are in good agreement with simulation(proposed model) data at different heat transfer rates. The error is small and mainly results from the instabilities of thermal resistances with temperature change and heat flux, heat loss of the device vertical surfaces and measurements.

  8. Sensitivity analysis of air gap motion with respect to wind load and mooring system for semi-submersible platform design

    NASA Astrophysics Data System (ADS)

    Huo, Fa-li; Nie, Yan; Yang, De-qing; Dong, Gang; Cui, Jin

    2016-07-01

    A design of semi-submersible platform is mainly based on the extreme response analysis due to the forces experienced by the components during lifetime. The external loads can induce the extreme air gap response and potential deck impact to the semi-submersible platform. It is important to predict air gap response of platforms accurately in order to check the strength of local structures which withstand the wave slamming due to negative air gap. The wind load cannot be simulated easily by model test in towing tank whereas it can be simulated accurately in wind tunnel test. Furthermore, full scale simulation of the mooring system in model test is still a tuff work especially the stiffness of the mooring system. Owing to the above mentioned problem, the model test results are not accurate enough for air gap evaluation. The aim of this paper is to present sensitivity analysis results of air gap motion with respect to the mooring system and wind load for the design of semi-submersible platform. Though the model test results are not suitable for the direct evaluation of air gap, they can be used as a good basis for tuning the radiation damping and viscous drag in numerical simulation. In the presented design example, a numerical model is tuned and validated by ANSYS AQWA based on the model test results with a simple 4 line symmetrical horizontal soft mooring system. According to the tuned numerical model, sensitivity analysis studies of air gap motion with respect to the mooring system and wind load are performed in time domain. Three mooring systems and five simulation cases about the presented platform are simulated based on the results of wind tunnel tests and sea-keeping tests. The sensitivity analysis results are valuable for the floating platform design.

  9. Soot Formation in Hydrocarbon/Air Laminar Jet Diffusion Flames

    NASA Technical Reports Server (NTRS)

    Sunderland, P. B.; Faeth, G. M.

    1994-01-01

    Soot processes within hydrocarbon/air diffusion flames are important because they affect the durability and performance of propulsion systems, the hazards of unwanted fires, the pollutant and particulate emissions from combustion processes, and the potential for developing computational combustion. Motivated by these observations, this investigation involved an experimental study of the structure and soot properties of round laminar jet diffusion flames, seeking an improved understanding of soot formation (growth and nucleation) within diffusion flames. The present study extends earlier work in this laboratory concerning laminar smoke points (l) and soot formation in acetylene/air laminar jet diffusion flames (2), emphasizing soot formation in hydrocarbon/air laminar jet diffusion flames for fuels other than acetylene. In the flame system, acetylene is the dominant gas species in the soot formation region and both nucleation and growth were successfully attributed to first-order reactions of acetylene, with nucleation exhibiting an activation energy of 32 kcal/gmol while growth involved negligible activation energy and a collision efficiency of O.53%. In addition, soot growth in the acetylene diffusion flames was comparable to new soot in premixed flame (which also has been attributed to first-order acetylene reactions). In view of this status, a major issue is the nature of soot formation processes in diffusion flame involving hydrocarbon fuels other than acetylene. In particular, information is needed about th dominant gas species in the soot formation region and the impact of gas species other than acetylene on soot nucleation and growth.

  10. Measurement of the air gap width between double-deck metal layers based on surface plasmon resonance

    NASA Astrophysics Data System (ADS)

    Wu, Pao-Tung; Wu, Meng-Chyi; Wu, Chien-Ming

    2010-04-01

    In this article, we verify that the traditional Kretschmann-Raether configuration of surface plasmon resonance (SPR) could be used to measure the air gap width between a gold-plated prism and another gold-plated glass slide. Due to the presence of double-deck metal layers, the Fabry-Perot resonance and surface plasmon tunnel-coupled effects could occur, which would cause the SPR angle to begin to shift at a larger air gap width of about 700 nm as compared to the case of single metal layer with an air gap width of about 350 nm. The simulated results reveal that the SPR angle begins monotonically to shift initially from 44.5° to 46° when the air gap width between double-deck metal layers decreases from 700 to 500 nm. The smallest air gap width is measured to be 539 nm, in which the SPR angle is 45.5°, by fitting the simulated curves to the experimental results.

  11. Photonic band-gap formation by optical-phase-mask lithography.

    PubMed

    Chan, Timothy Y M; Toader, Ovidiu; John, Sajeev

    2006-04-01

    We demonstrate an approach for fabricating photonic crystals with large three-dimensional photonic band gaps (PBG's) using single-exposure, single-beam, optical interference lithography based on diffraction of light through an optical phase mask. The optical phase mask (OPM) consists of two orthogonally oriented binary gratings joined by a thin, solid layer of homogeneous material. Illuminating the phase mask with a normally incident beam produces a five-beam diffraction pattern which can be used to expose a suitable photoresist and produce a photonic crystal template. Optical-phase-mask Lithography (OPML) is a major simplification from the previously considered multibeam holographic lithography of photonic crystals. The diffracted five-beam intensity pattern exhibits isointensity surfaces corresponding to a diamondlike (face-centered-cubic) structure, with high intensity contrast. When the isointensity surfaces in the interference patterns define a silicon-air boundary in the resulting photonic crystal, with dielectric contrast 11.9 to 1, the optimized PBG is approximately 24% of the gap center frequency. The ideal index contrast for the OPM is in the range of 1.7-2.3. Below this range, the intensity contrast of the diffraction pattern becomes too weak. Above this range, the diffraction pattern may become too sensitive to structural imperfections of the OPM. When combined with recently demonstrated polymer-to-silicon replication methods, OPML provides a highly efficient approach, of unprecedented simplicity, for the mass production of large-scale three-dimensional photonic band-gap materials.

  12. Gap formation processes in a high-density plasma opening switch

    NASA Astrophysics Data System (ADS)

    Grossmann, J. M.; Swanekamp, S. B.; Ottinger, P. F.; Commisso, R. J.; Hinshelwood, D. D.; Weber, B. V.

    1995-01-01

    A gap opening process in plasma opening switches (POS) is examined with the aid of numerical simulations. In these simulations, a high density (ne=1014-5×1015 cm-3) uniform plasma initially bridges a small section of the coaxial transmission line of an inductive energy storage generator. A short section of vacuum transmission line connects the POS to a short circuit load. The results presented here extend previous simulations in the ne=1012-1013 cm-3 density regime. The simulations show that a two-dimensional (2-D) sheath forms in the plasma near a cathode. This sheath is positively charged, and electrostatic sheath potentials that are large compared to the anode-cathode voltage develop. Initially, the 2-D sheath is located at the generator edge of the plasma. As ions are accelerated out of the sheath, it retains its original 2-D structure, but migrates axially toward the load creating a magnetically insulated gap in its wake. When the sheath reaches the load edge of the POS, the POS stops conducting current and the load current increases rapidly. At the end of the conduction phase a gap exists in the POS whose size is determined by the radial dimensions of the 2-D sheath. Simulations at various plasma densities and current levels show that the radial size of the gap scales roughly as B/ne, where B is the magnetic field. The results of this work are discussed in the context of long-conduction-time POS physics, but exhibit the same physical gap formation mechanisms as earlier lower density simulations more relevant to short-conduction-time POS.

  13. RacGAP1-driven focal adhesion formation promotes melanoma transendothelial migration through mediating adherens junction disassembly.

    PubMed

    Zhang, Pu; Bai, Huiyuan; Fu, Changliang; Chen, Feng; Zeng, Panying; Wu, Chengxiang; Ye, Qichao; Dong, Cheng; Song, Yang; Song, Erqun

    2015-03-27

    Melanoma cell migration across vascular endothelial cells is an essential step of tumor metastasis. Here, we provide evidence that RacGAP1, a cytokinesis-related Rho GTPase-activating protein, contributed to this process. Depletion of RacGAP1 with RacGAP1-targeting siRNA or overexpression of RacGAP1 mutant (T249A) attenuated melanoma cell transendothelial migration and concomitant changes of adherens junctions. In addition, RacGAP1 promoted the activations of RhoA, FAK, paxillin and triggered focal adhesion formation and cytoskeletal rearrangement. By overexpressing FAK-related non-kinase (FRNK) in endothelium, we showed that RacGAP1 mediated endothelial barrier function loss and melanoma transmigration in a focal adhesion-dependent manner. These results suggest that endothelial RacGAP1 may play critical roles in pathogenic processes of cancer by regulating endothelial permeability.

  14. VAN3 ARF-GAP-mediated vesicle transport is involved in leaf vascular network formation.

    PubMed

    Koizumi, Koji; Naramoto, Satoshi; Sawa, Shinichiro; Yahara, Natsuko; Ueda, Takashi; Nakano, Akihiko; Sugiyama, Munetaka; Fukuda, Hiroo

    2005-04-01

    Within the leaf of an angiosperm, the vascular system is constructed in a complex network pattern called venation. The formation of this vein pattern has been widely studied as a paradigm of tissue pattern formation in plants. To elucidate the molecular mechanism controlling the vein patterning process, we previously isolated Arabidopsis mutants van1 to van7, which show a discontinuous vein pattern. Here we report the phenotypic analysis of the van3 mutant in relation to auxin signaling and polar transport, and the molecular characterization of the VAN3 gene and protein. Double mutant analyses with pin1, emb30-7/gn and mp, and physiological analyses using the auxin-inducible marker DR5::GUS and an auxin transport inhibitor indicated that VAN3 may be involved in auxin signal transduction, but not in polar auxin transport. Positional cloning identified VAN3 as a gene that encodes an adenosine diphosphate (ADP)-ribosylation factor-guanosine triphosphatase (GTPase) activating protein (ARF-GAP). It resembles animal ACAPs and contains four domains: a BAR (BIN/amphiphysin/RVS) domain, a pleckstrin homology (PH) domain, an ARF-GAP domain and an ankyrin (ANK)-repeat domain. Recombinant VAN3 protein showed GTPase-activating activity and a specific affinity for phosphatidylinositols. This protein can self-associate through the N-terminal BAR domain in the yeast two-hybrid system. Subcellular localization analysis by double staining for Venus-tagged VAN3 and several green-fluorescent-protein-tagged intracellular markers indicated that VAN3 is located in a subpopulation of the trans-Golgi network (TGN). Our results indicate that the expression of this gene is induced by auxin and positively regulated by VAN3 itself, and that a specific ACAP type of ARF-GAP functions in vein pattern formation by regulating auxin signaling via a TGN-mediated vesicle transport system.

  15. Water desalination by air-gap membrane distillation using meltblown polypropylene nanofiber membrane

    NASA Astrophysics Data System (ADS)

    Rosalam, S.; Chiam, C. K.; Widyaparamitha, S.; Chang, Y. W.; Lee, C. A.

    2016-06-01

    This paper presents a study of air gap membrane distillation (AGMD) using meltblown polypropylene (PP) nanofiber membrane to produce fresh water via desalination process. PP nanofiber membranes with the effective area 0.17 m2 are tested with NaCl solutions (0.5 - 4.0 wt.%) and seawater as the feed solutions (9400 - 64800 μS/cm) in a tubular membrane module. Results show that the flux decreases with increasing the membrane thickness from 547 to 784 μm. The flux increases with the feed flow rate and temperature difference across the membrane. The feed concentration affects the flux insignificantly. The AGMD system can reject the salts at least 96%. Water vapor permeation rate is relatively higher than solute permeation rate resulting in the conductivity value of permeate decreases when the corresponding flux increases. The AGMD system produces the fresh water (200 - 1520 μS/cm) that is suitable for drinking, fisheries or irrigation.

  16. A fiber inclinometer using a fiber microtaper with an air-gap microcavity fiber interferometer

    NASA Astrophysics Data System (ADS)

    Feng, Zhongyao; Gang, Tingting; Hu, Manli; Qiao, Xueguang; Liu, Nan; Rong, Qiangzhou

    2016-04-01

    A micro-inclinometer is proposed and demonstrated experimentally; the device consists of a micro-fiber taper followed by an air-gap microcavity. A part of the core mode can couple to cladding modes via the taper. These cladding modes and residual core modes transmitted to downstream of the Fabry-Perot (FP) interferometer. A fraction of these modes are reflected back to the SMF by two surfaces of the FP cavity and eventually recoupled to the leading-in SMF, resulting in a well-defined interference spectrum. The fringe contrast of the interferometer is highly sensitive to fiber bending with direction-independence and thus is capable of measuring tilt angles in high resolution. In addition, the interference wavelength always remains unchanged during the fiber bending.

  17. Experimental investigation on flame pattern formations of DME-air mixtures in a radial microchannel

    SciTech Connect

    Fan, Aiwu; Maruta, Kaoru; Nakamura, Hisashi; Kumar, Sudarshan; Liu, Wei

    2010-09-15

    Flame pattern formations of premixed DME-air mixture in a heated radial channel with a gap distance of 2.5 mm were experimentally investigated. The DME-air mixture was introduced into the radial channel through a delivery tube which connected with the center of the top disk. With an image-intensified high-speed video camera, rich flame pattern formations were identified in this configuration. Regime diagram of all these flame patterns was drawn based on the experimental findings in the equivalence ratio range of 0.6-2.0 and inlet velocity range of 1.0-5.0 m/s. Compared with our previous study on premixed methane-air flames, there are several distinct characteristics for the present study. First, Pelton-wheel-like rotary flames and traveling flames with kink-like structures were observed for the first time. Second, in most cases, flames can be stabilized near the inlet port of the channel, exhibiting a conical or cup-like shape, while the conventional circular flame was only observed under limited conditions. Thirdly, an oscillating flame phenomenon occurred under certain conditions. During the oscillation process, a target appearance was seen at some instance. These pattern formation characteristics are considered to be associated with the low-temperature oxidation of DME. (author)

  18. Experimental verification of the capillary plasma triggered long spark gap under the extremely low working coefficient in air

    SciTech Connect

    Huang, D.; Yang, L. J. Ma, J. B.; Liu, S.; Wang, W.; Ding, W. D.; Huo, P.; Li, G.; Yao, S. L.

    2016-01-15

    The paper has proposed a new triggering method for long spark gap based on capillary plasma ejection and conducted the experimental verification under the extremely low working coefficient, which represents that the ratio of the spark gap charging voltage to the breakdown voltage is particularly low. The quasi-neutral plasma is ejected from the capillary and develops through the axial direction of the spark gap. The electric field in the spark gap is thus changed and its breakdown is incurred. It is proved by the experiments that the capillary plasma ejection is effective in triggering the long spark gap under the extremely low working coefficient in air. The study also indicates that the breakdown probabilities, the breakdown delay, and the delay dispersion are all mainly determined by the characteristics of the ejected plasma, including the length of the plasma flow, the speed of the plasma ejection, and the ionization degree of the plasma. Moreover, the breakdown delay and the delay dispersion increase with the length of the long spark gap, and the polarity effect exists in the triggering process. Lastly, compared with the working patterns of the triggering device installed in the single electrode, the working pattern of the devices installed in both the two electrodes, though with the same breakdown process, achieves the ignition under longer gap distance. To be specific, at the gap length of 14 cm and the working coefficient of less than 2%, the spark gap is still ignited accurately.

  19. Tuneable polaritonics at room temperature with strongly coupled Tamm plasmon polaritons in metal/air-gap microcavities

    NASA Astrophysics Data System (ADS)

    Grossmann, C.; Coulson, C.; Christmann, G.; Farrer, I.; Beere, H. E.; Ritchie, D. A.; Baumberg, J. J.

    2011-06-01

    We report strong coupling between Tamm plasmons and excitons in III-V quantum wells at room temperature in ultracompact sample designs. A high refractive index contrast air-gap mirror together with optical Tamm states at a metal/semiconductor interface tightly confines the intracavity field leading to substantial local field enhancements. Angular-resolved reflectivity spectra give clear evidence for anticrossing in the dispersion relation. Room temperature Rabi splittings of 10 meV are found in excellent agreement with simulations. Electrical control of the polariton modes is realized without need for doped mirror layers. Such air-gap microcavities open innovative possibilites for electrically tunable microcavities and polaritonic microelectromechanics.

  20. Erythrocyte migration and gap formation in rabbit blood clots in vitro.

    PubMed

    Ueki, T; Yazama, F; Horiuchi, T; Yamada, M

    2008-04-01

    Thrombolytic agents must be carried by the blood circulation to thrombi to exert their functions. Structural gaps exist between blood vessels and thrombi or in the area surrounding thrombi. Therefore, information about fundamental gap formation at thrombotic areas is critically important for thrombolytic therapy. We previously reported that t-PA accelerates the activities of bovine erythrocytes and hemoglobin (Hb) towards bovine plasminogen activation. Here, we examined gap generation by observing morphological changes during thrombolytic processes in rabbit blood clots deformation of erythrocytes from blood clots and Hb transfer from erythrocytes to serum in vitro. Rabbit venous blood samples (1 ml) were stored under sterile conditions in glass tubes at 37 degrees C for 2, 24, 48 h, 1, and 2 weeks. We examined clot diameter, erythrocyte diameter and number as well as Hb volume in the serum, as well as histological changes in the clots. The diameter of blood clots did not change until 2 weeks after sampling. Erythrocyte diameter decreased within 48 h and at 2 weeks after sampling at the clot surface (p < 0.001) and interior (p < 0.001). The number of erythrocytes in the serum started to increase starting from 24 h after sampling (p < 0.01). Serum Hb volume also gradually increased from 24 h until 2 weeks after sampling (p < 0.01). The erythrocyte envelope became disrupted and cytoplasm started to flow through pores into the serum at 24 h. The results indicated that blood clots are reduced due to clot retraction, erythrocyte dissociation and cytoplasm leakage without a distinct fibrinolytic reaction. These results indicated that gaps start to form between 2 and 24 h after blood clotting.

  1. Effect of silver incorporation in phase formation and band gap tuning of tungsten oxide thin films

    SciTech Connect

    Jolly Bose, R.; Kumar, R. Vinod; Sudheer, S. K.; Mahadevan Pillai, V. P.; Reddy, V. R.; Ganesan, V.

    2012-12-01

    Silver incorporated tungsten oxide thin films are prepared by RF magnetron sputtering technique. The effect of silver incorporation in micro structure evolution, phase enhancement, band gap tuning and other optical properties are investigated using techniques such as x-ray diffraction, micro-Raman spectroscopy, atomic force microscopy, scanning electron microscopy, energy dispersive x-ray spectroscopy, and UV-Visible spectroscopy. Effect of silver addition in phase formation and band gap tuning of tungsten oxide thin films are investigated. It is found that the texturing and phase formation improves with enhancement in silver content. It is also found that as the silver incorporation enhances the thickness of the films increases at the same time the strain in the film decreases. Even without annealing the desired phase can be achieved by doping with silver. A broad band centered at the wavelength 437 nm is observed in the absorption spectra of tungsten oxide films of higher silver incorporation and this can be attributed to surface plasmon resonance of silver atoms present in the tungsten oxide matrix. The transmittance of the films is decreased with increase in silver content which can be due to increase in film thickness, enhancement of scattering, and absorption of light caused by the increase of grain size, surface roughness and porosity of films and enhanced absorption due to surface plasmon resonance of silver. It is found that silver can act as the seed for the growth of tungsten oxide grains and found that the grain size increases with silver content which in turn decreases the band gap of tungsten oxide from 3.14 eV to 2.70 eV.

  2. Study of Various Slanted Air-Gap Structures of Interior Permanent Magnet Synchronous Motor with Brushless Field Excitation

    SciTech Connect

    Tolbert, Leon M; Lee, Seong T

    2010-01-01

    This paper shows how to maximize the effect of the slanted air-gap structure of an interior permanent magnet synchronous motor with brushless field excitation (BFE) for application in a hybrid electric vehicle. The BFE structure offers high torque density at low speed and weakened flux at high speed. The unique slanted air-gap is intended to increase the output torque of the machine as well as to maximize the ratio of the back-emf of a machine that is controllable by BFE. This irregularly shaped air-gap makes a flux barrier along the d-axis flux path and decreases the d-axis inductance; as a result, the reluctance torque of the machine is much higher than a uniform air-gap machine, and so is the output torque. Also, the machine achieves a higher ratio of the magnitude of controllable back-emf. The determination of the slanted shape was performed by using magnetic equivalent circuit analysis and finite element analysis (FEA).

  3. Parasitic effects of air-gap through-silicon vias in high-speed three-dimensional integrated circuits

    NASA Astrophysics Data System (ADS)

    Liu, Xiaoxian; Zhu, Zhangming; Yang, Yintang; Ding, Ruixue; Li, Yuejin

    2016-11-01

    In this paper, ground-signal-ground type through-silicon vias (TSVs) exploiting air gaps as insulation layers are designed, analyzed and simulated for applications in millimeter wave. The compact wideband equivalent-circuit model and passive elements (RLGC) parameters based on the physical parameters are presented with the frequency up to 100 GHz. The parasitic capacitance of TSVs can be approximated as the dielectric capacitance of air gaps when the thickness of air gaps is greater than 0.75 μm. Therefore, the applied voltage of TSVs only needs to achieve the flatband voltage, and there is no need to indicate the threshold voltage. This is due to the small permittivity of air gaps. The proposed model shows good agreement with the simulation results of ADS and Ansoft’s HFSS over a wide frequency range. Project supported by the National Basic Research Program of China (Grant No. 2014CB339900) and the National Natural Science Foundation of China (Grant Nos. 61376039, 61334003, 61574104, and 61474088).

  4. GAPS IN THE HD 169142 PROTOPLANETARY DISK REVEALED BY POLARIMETRIC IMAGING: SIGNS OF ONGOING PLANET FORMATION?

    SciTech Connect

    Quanz, Sascha P.; Avenhaus, Henning; Garufi, Antonio; Schmid, Hans Martin; Buenzli, Esther; Wolf, Sebastian

    2013-03-20

    We present H-band Very Large Telescope/NACO polarized light images of the Herbig Ae/Be star HD 169142 probing its protoplanetary disk as close as {approx}0.''1 to the star. Our images trace the face-on disk out to {approx}1.''7 ({approx}250 AU) and reveal distinct substructures for the first time: (1) the inner disk ({approx}<20 AU) appears to be depleted in scattering dust grains; (2) an unresolved disk rim is imaged at {approx}25 AU; (3) an annular gap extends from {approx}40 to 70 AU; (4) local brightness asymmetries are found on opposite sides of the annular gap. We discuss different explanations for the observed morphology among which ongoing planet formation is a tempting, but yet to be proven, one. Outside of {approx}85 AU the surface brightness drops off roughly {proportional_to}r {sup -3.3}, but describing the disk regions between 85-120 AU and 120-250 AU separately with power laws {proportional_to}r {sup -2.6} and {proportional_to}r {sup -3.9} provides a better fit hinting toward another discontinuity in the disk surface. The flux ratio between the disk-integrated polarized light and the central star is {approx}4.1 Multiplication-Sign 10{sup -3}. Finally, combining our results with those from the literature, {approx}40% of the scattered light in the H band appears to be polarized. Our results emphasize that HD 169142 is an interesting system for future planet formation or disk evolution studies.

  5. Plasma treatment of polyethersulfone membrane for benzene removal from water by air gap membrane distillation.

    PubMed

    Pedram, Sara; Mortaheb, Hamid Reza; Arefi-Khonsari, Farzaneh

    2017-03-13

    In order to obtain a durable cost-effective membrane for membrane distillation (MD) process, flat sheet polyethersulfone (PES) membranes were modified by an atmospheric pressure nonequilibrium plasma generated using a dielectric barrier discharge in a mixture of argon and hexamethyldisiloxane as the organosilicon precursor. The surface properties of the plasma-modified membranes were characterized by water contact angle (CA), liquid entry pressure, X-ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy. The water CA of the membrane was increased from 64° to 104° by depositing a Si(CH3)-rich thin layer. While the pristine PES membrane was not applicable in the MD process, the modified PES membrane could be applied for the first time in an air gap membrane distillation setup for the removal of benzene as a volatile organic compound from water. The experimental design using central composite design and response surface methodology was applied to study the effects of feed temperature, concentration, and flow rate as well as their binary interactions on the overall permeate flux and separation factor. The separation factor and permeation flux of the modified PES membrane at optimum conditions were comparable with those of commercial polytetrafluoroethylene membrane.

  6. Design and performance of an axial air-gap solution pump motor

    NASA Astrophysics Data System (ADS)

    Hawsey, R. A.; Sohns, C. W.; Daniel, D. S.; Bailey, J. M.

    1990-05-01

    An axial air gap, permanent magnet, brushless dc motor was designed and was evaluated on a dynamometer to measure operating characteristics. The motor must deliver 0.167 hp (approx. 120 W) to the pump rotor at 1800 rpm. Initial performance data with a half-bridge, Hall-probe synchronized drive system and a dry motor bearing did not achieve the desired motor performance. Subsequently, a commercial full-bridge, speed regulated sensorless drive system was used to test the motor. The motor delivered the required 90 oz-in. of torque at 1800 rpm. These data revealed the need for rewinding the stator core to improve motor efficiency. A second stator core, with deeper slots and additional turns of wire, was subsequently fabricated and tested. At 1800 rpm, the drive system could produce only 60 oz-in. of torque due to an unexpectedly high generated voltage. Motor efficiency was 60 to 70 pct. at this torque level when the data were corrected for bearing and coupling drag.

  7. Role of Short-Range Order and Hyperuniformity in the Formation of Band Gaps in Disordered Photonic Materials

    NASA Astrophysics Data System (ADS)

    Froufe-Pérez, Luis S.; Engel, Michael; Damasceno, Pablo F.; Muller, Nicolas; Haberko, Jakub; Glotzer, Sharon C.; Scheffold, Frank

    2016-07-01

    We study photonic band gap formation in two-dimensional high-refractive-index disordered materials where the dielectric structure is derived from packing disks in real and reciprocal space. Numerical calculations of the photonic density of states demonstrate the presence of a band gap for all polarizations in both cases. We find that the band gap width is controlled by the increase in positional correlation inducing short-range order and hyperuniformity concurrently. Our findings suggest that the optimization of short-range order, in particular the tailoring of Bragg scattering at the isotropic Brillouin zone, are of key importance for designing disordered PBG materials.

  8. The role of foehn in the formation of heavy air pollution events in Urumqi, China

    NASA Astrophysics Data System (ADS)

    Li, X.; Xia, X.; Wang, L.; Cai, R.; Zhao, L.; Feng, Z.; Ren, Q.; Zhao, K.

    2015-06-01

    The impact of sandwich foehn on air pollution in Urumqi, a gap town located on the northern lee side of the Tianshan Mountains of China, is analyzed. The results show that during days with high pollution, the boundary layer over the city and the down-valley area can be divided into a three-layer structure, with the southeasterly foehn sandwiched between the northwesterly winds on top and the cold air surface pool beneath. The southeasterly foehn at heights between 480 and 2100 m results in a very stable boundary layer structure. In combination with the decoupling between the foehn flow and cold air pool, such boundary layer structure prevents vertical mixing of atmospheric pollutants. In the up-valley area from the northern lee side flank to the southern urban area, the ground-based foehn confronts the thermally driven valley breeze and forms a "minifront," which moves northward in the morning and retreats southward in the afternoon. Although the minifront disappears in the early evening, the wind shear of the mountain breeze between the southern suburb and downtown areas is still remarkable, which is favorable for a convergence line to persist around the city all day long. In this case, air pollutants emitted from the up-valley and down-valley areas are transported toward the urban area. Therefore, the air pollutants accumulate daily, leading to the frequent occurrence of heavy pollution events in Urumqi. This indicates that the sandwich foehn plays a critical role in the formation of heavy air pollution events in Urumqi.

  9. On-site formation of emulsions by controlled air plugs.

    PubMed

    Huang, Xiaowen; Hui, Wenli; Hao, Chonglei; Yue, Wanqing; Yang, Mengsu; Cui, Yali; Wang, Zuankai

    2014-02-26

    Air plugs are usually undesirable in microfluidic systems because of their detrimental effect on the system's stability and integrity. By controlling the wetting properties as well as the topographical geometry of the microchannel, it is reported herein that air plugs can be generated in pre-defined locations to function as a unique valve, allowing for the on-site formation of various emulsions including single-component droplets, composite droplets with droplet-to-droplet concentration gradient, blood droplets, paired droplets, as well as bubble arrays without the need for precious flow control, a difficult task with conventional droplet microfluidics. Moreover, the self-generated air valve can be readily deactivated (turned off) by the introduction of an oil phase, allowing for the on-demand release of as-formed droplets for downstream applications. It is proposed that the simple, yet versatile nature of this technique can act as an important method for droplet microfluidics and, in particular, is ideal for the development of affordable lab-on-a-chip systems without suffering from scalability and manufacturing challenges that typically confound the conventional droplet microfluidics.

  10. High efficient OLED displays prepared with the air-gapped bridges on quantum dot patterns for optical recycling.

    PubMed

    Kim, Hyo-Jun; Shin, Min-Ho; Kim, Joo-Suc; Kim, Se-Eun; Kim, Young-Joo

    2017-02-17

    An optically efficient structure was proposed and fabricated to realize high brightness organic light emitting diode (OLED) displays based on a white OLED prepared with the air-gapped bridges on the quantum dot (QD) patterns. Compared with a conventional white OLED display, in our experiments, the optical intensity of the proposed OLED display shows the enhancement of 58.2% in the red color and 16.8% in the green color after applying the air-gapped bridge structure on QD patterns of 20 wt% concentration. This enhancement comes from the two facts that the QD patterns downconvert unnecessary blue or blue/green light to the required green or red light and the air-gapped bridges increase the color conversion efficiency of QDs by optical recycling using total internal reflection (TIR) at the interface. In addition, the color gamut of the proposed OLED display increases from 65.5 to 75.9% (NTSC x, y ratio) due to the narrow emission spectra of QDs.

  11. High efficient OLED displays prepared with the air-gapped bridges on quantum dot patterns for optical recycling

    PubMed Central

    Kim, Hyo-Jun; Shin, Min-Ho; Kim, Joo-Suc; Kim, Se-Eun; Kim, Young-Joo

    2017-01-01

    An optically efficient structure was proposed and fabricated to realize high brightness organic light emitting diode (OLED) displays based on a white OLED prepared with the air-gapped bridges on the quantum dot (QD) patterns. Compared with a conventional white OLED display, in our experiments, the optical intensity of the proposed OLED display shows the enhancement of 58.2% in the red color and 16.8% in the green color after applying the air-gapped bridge structure on QD patterns of 20 wt% concentration. This enhancement comes from the two facts that the QD patterns downconvert unnecessary blue or blue/green light to the required green or red light and the air-gapped bridges increase the color conversion efficiency of QDs by optical recycling using total internal reflection (TIR) at the interface. In addition, the color gamut of the proposed OLED display increases from 65.5 to 75.9% (NTSC x, y ratio) due to the narrow emission spectra of QDs. PMID:28211516

  12. High efficient OLED displays prepared with the air-gapped bridges on quantum dot patterns for optical recycling

    NASA Astrophysics Data System (ADS)

    Kim, Hyo-Jun; Shin, Min-Ho; Kim, Joo-Suc; Kim, Se-Eun; Kim, Young-Joo

    2017-02-01

    An optically efficient structure was proposed and fabricated to realize high brightness organic light emitting diode (OLED) displays based on a white OLED prepared with the air-gapped bridges on the quantum dot (QD) patterns. Compared with a conventional white OLED display, in our experiments, the optical intensity of the proposed OLED display shows the enhancement of 58.2% in the red color and 16.8% in the green color after applying the air-gapped bridge structure on QD patterns of 20 wt% concentration. This enhancement comes from the two facts that the QD patterns downconvert unnecessary blue or blue/green light to the required green or red light and the air-gapped bridges increase the color conversion efficiency of QDs by optical recycling using total internal reflection (TIR) at the interface. In addition, the color gamut of the proposed OLED display increases from 65.5 to 75.9% (NTSC x, y ratio) due to the narrow emission spectra of QDs.

  13. Nanodiamond formation via thermal radiation from an air shock

    NASA Astrophysics Data System (ADS)

    de Carli, Paul

    2013-06-01

    Nanodiamonds have recently been found in sediments of Younger Dryas age, about 12,900 years ago. Carbon isotope ratios imply that the source of carbon was terrestrial organic matter and rule out the possibility that the diamond was of cosmic origin, e.g., from an influx of meteorites. The nanodiamonds are associated with mineral spherules (and other shapes) that have compositions and textures consistent with the rapid melting and solidification of local soil. The inferred temperatures are much too high for natural events such as forest fires. Similar deposits of nanodiamond have been found in the 65 million year old K-Pg layer associated with the ca. 200 km diameter Chicxulub impact crater. Nanodiamond have also been reported in the vicinity of the Tunguska event, presumed to be the result of an air shock produced by the interaction of a rapidly moving cosmic body with the Earth's atmosphere. We infer that the nanodiamonds were formed when the thermal radiation from the air shock pyrolyzed surface organic matter. Rapid reaction locally depleted the atmosphere of oxygen and the remaining carbon could condense as nanodiamond. A similar mechanism can be invoked to account for the formation of nanodiamond as a froduct of the detonation of ozygen-deficient high explosives.

  14. Improved Antishock Air-Gap Control Algorithm with Acceleration Feedforward Control for High-Numerical Aperture Near-Field Storage System Using Solid Immersion Lens

    NASA Astrophysics Data System (ADS)

    Kim, Jung-Gon; Shin, Won-Ho; Hwang, Hyun-Woo; Jeong, Jun; Park, Kyoung-Su; Park, No-Cheol; Yang, Hyunseok; Park, Young-Pil; Moo Park, Jin; Son, Do Hyeon; Kyo Seo, Jeong; Choi, In Ho

    2010-08-01

    A near-field storage system using a solid immersion lens (SIL) has been studied as a high-density optical disc drive system. The major goal of this research is to improve the robustness of the air-gap controller for a SIL-based near-field recording (NFR) system against dynamic disturbances, such as external shocks. The servo system is essential in near-field (NF) technology because the nanogap distance between the SIL and the disc is 50 nm or less. Also, the air-gap distance must be maintained without collision between the SIL and the disc to detect a stable gap error and read-out signals when an external shock is applied. Therefore, we propose an improved air-gap control algorithm using only an acceleration feedforward controller (AFC) to maintain the air-gap distance without contact for a 4.48 G at 10 ms shock. Thus, the antishock control performance for the SIL-based NF storage system in the presence of external shocks is markedly improved. Furthermore, to enhance the performance of the antishock air-gap control, we use the AFC with a double disturbance observer and a dead-zone nonlinear controller. As a result, the air-gap distance is maintained without contact for a 6.56 G@10 ms shock.

  15. Gap Junction in the Teleost Fish Lineage: Duplicated Connexins May Contribute to Skin Pattern Formation and Body Shape Determination

    PubMed Central

    Watanabe, Masakatsu

    2017-01-01

    Gap junctions are intercellular channels that allow passage of ions and small molecules between adjacent cells. Gap junctions in vertebrates are composed of connexons, which are an assembly of six proteins, connexins. Docking of two connexons on the opposite cell surfaces forms a gap junction between the cytoplasm of two neighboring cells. Connexins compose a family of structurally related four-pass transmembrane proteins. In mammals, there are ~20 connexins, each of which contributes to unique permeability of gap junctions, and mutations of some connexin-encoding genes are associated with human diseases. Zebrafish has been predicted to contain 39 connexin-encoding genes; the high number can be attributed to gene duplication during fish evolution, which resulted in diversified functions of gap junctions in teleosts. The determination of body shapes and skin patterns in animal species is an intriguing question. Mathematical models suggest principle mechanisms explaining the diversification of animal morphology. Recent studies have revealed the involvement of gap junctions in fish morphological diversity, including skin pattern formation and body shape determination. This review focuses on connexins in teleosts, which are integrated in the mathematical models explaining morphological diversity of animal skin patterns and body shapes. PMID:28271062

  16. Coherent Synchrotron-Based Micro-Imaging Employed for Studies of Micro-Gap Formation in Dental Implants

    SciTech Connect

    Rack, T.; Stiller, M.; Nelson, K.; Zabler, S.; Rack, A.; Riesemeier, H.; Cecilia, A.

    2011-09-09

    Biocompatible materials such as titanium are regularly applied in oral surgery. Titanium-based implants for the replacement of missing teeth demand a high mechanical precision in order to minimize micro-bacterial leakage, especially when two-piece concepts are used. Synchrotron-based hard x-ray radiography, unlike conventional laboratory radiography, allows high spatial resolution in combination with high contrast even when micro-sized features in such highly attenuating objects are visualized. Therefore, micro-gap formation at interfaces in two-piece dental implants with the sample under different mechanical loads can be studied. We show the existence of micro-gaps in implants with conical connections and study the mechanical behavior of the mating zone of conical implants during loading. The micro-gap is a potential source of implant failure, i.e., bacterial leakage, which can be a stimulus for an inflammatory process.

  17. Coherent Synchrotron-Based Micro-Imaging Employed for Studies of Micro-Gap Formation in Dental Implants

    NASA Astrophysics Data System (ADS)

    Rack, T.; Zabler, S.; Rack, A.; Stiller, M.; Riesemeier, H.; Cecilia, A.; Nelson, K.

    2011-09-01

    Biocompatible materials such as titanium are regularly applied in oral surgery. Titanium-based implants for the replacement of missing teeth demand a high mechanical precision in order to minimize micro-bacterial leakage, especially when two-piece concepts are used. Synchrotron-based hard x-ray radiography, unlike conventional laboratory radiography, allows high spatial resolution in combination with high contrast even when micro-sized features in such highly attenuating objects are visualized. Therefore, micro-gap formation at interfaces in two-piece dental implants with the sample under different mechanical loads can be studied. We show the existence of micro-gaps in implants with conical connections and study the mechanical behavior of the mating zone of conical implants during loading. The micro-gap is a potential source of implant failure, i.e., bacterial leakage, which can be a stimulus for an inflammatory process.

  18. Amyloid fibril formation at a uniformly sheared air/water interface

    NASA Astrophysics Data System (ADS)

    Posada, David; Hirsa, Amir

    2013-11-01

    Amyloid fibril formation is a process by which protein molecules in solution form nuclei and aggregate into fibrils. Amyloid fibrils have long been associated with several common diseases such as Parkinson's disease and Alzheimer's. More recently, fibril protein deposition has been implicated in uncommon disorders leading to the failure of various organs including the kidneys, heart, and liver. Fibrillization can also play a detrimental role in biotherapeutic production. Results from previous studies show that a hydrophobic interface, such air/water, can accelerate fibrillization. Studies also show that agitation accelerates fibrillization. When attempting to elucidate fundamental mechanisms of fibrillization and distinguish the effects of interfaces and flow, it can be helpful to experiment with uniformly sheared interfaces. A new Taylor-Couette device is introduced for in situ, real-time high resolution microscopy. With a sub-millimeter annular gap, surface tension acts as the channel floor, permitting a stable meniscus to be placed arbitrarily close to a microscope to study amyloid fibril formation over long periods.

  19. Air Pollution and Health: Bridging the Gap from Sources to Health Outcomes

    EPA Science Inventory

    The U.S. Environmental Protection Agency (EPA) has established National Ambient Air Quality Standards (NAAQS) for six principal air pollutants (“criteria” pollutants): carbon monoxide (CO), lead (Pb), nitrogen dioxide (NO2), particulate matter (PM) in two size ranges [...

  20. Closing the Irregular Warfare Air Capability Gap. The Missing Puzzle Piece: Rugged Utility Aircraft and Personnel

    DTIC Science & Technology

    2010-01-01

    Army Air Forces initially found itself unprepared. In the Pacific theater, the First Air Commando Group performed a daring glider operation in...hatch with a trainable gun and hanging standoff weap- ons under the wings (or both) convert it into a gunship. The Pilatus has almost limit- less

  1. The role of disk self-gravity on gap formation of the HL Tau proto-planetary disk

    SciTech Connect

    Li, Shengtai; Li, Hui

    2016-05-31

    Here, we use extensive global hydrodynamic disk gas+dust simulations with embedded planets to model the dust ring and gap structures in the HL Tau protoplanetary disk observed with the Atacama Large Millimeter/Submillimeter Array (ALMA). Since the HL Tau is a relatively massive disk, we find the disk self-gravity (DSG) plays an important role in the gap formation induced by the planets. Our simulation results demonstrate that DSG is necessary in explaining of the dust ring and gap in HL Tau disk. The comparison of simulation results shows that the dust rings and gap structures are more evident when the fully 2D DSG (non-axisymmetric components are included) is used than if 1D axisymmetric DSG (only the axisymetric component is included) is used, or the disk self-gravity is not considered. We also find that the couple dust+gas+planet simulations are required because the gap and ring structure is different between dust and gas surface density.

  2. The role of disk self-gravity on gap formation of the HL Tau proto-planetary disk

    DOE PAGES

    Li, Shengtai; Li, Hui

    2016-05-31

    Here, we use extensive global hydrodynamic disk gas+dust simulations with embedded planets to model the dust ring and gap structures in the HL Tau protoplanetary disk observed with the Atacama Large Millimeter/Submillimeter Array (ALMA). Since the HL Tau is a relatively massive disk, we find the disk self-gravity (DSG) plays an important role in the gap formation induced by the planets. Our simulation results demonstrate that DSG is necessary in explaining of the dust ring and gap in HL Tau disk. The comparison of simulation results shows that the dust rings and gap structures are more evident when the fullymore » 2D DSG (non-axisymmetric components are included) is used than if 1D axisymmetric DSG (only the axisymetric component is included) is used, or the disk self-gravity is not considered. We also find that the couple dust+gas+planet simulations are required because the gap and ring structure is different between dust and gas surface density.« less

  3. Analysis and experimental study on formation conditions of large-scale barrier-free diffuse atmospheric pressure air plasmas in repetitive pulse mode

    NASA Astrophysics Data System (ADS)

    Li, Lee; Liu, Lun; Liu, Yun-Long; Bin, Yu; Ge, Ya-Feng; Lin, Fo-Chang

    2014-01-01

    Atmospheric air diffuse plasmas have enormous application potential in various fields of science and technology. Without dielectric barrier, generating large-scale air diffuse plasmas is always a challenging issue. This paper discusses and analyses the formation mechanism of cold homogenous plasma. It is proposed that generating stable diffuse atmospheric plasmas in open air should meet the three conditions: high transient power with low average power, excitation in low average E-field with locally high E-field region, and multiple overlapping electron avalanches. Accordingly, an experimental configuration of generating large-scale barrier-free diffuse air plasmas is designed. Based on runaway electron theory, a low duty-ratio, high voltage repetitive nanosecond pulse generator is chosen as a discharge excitation source. Using the wire-electrodes with small curvature radius, the gaps with highly non-uniform E-field are structured. Experimental results show that the volume-scaleable, barrier-free, homogeneous air non-thermal plasmas have been obtained between the gap spacing with the copper-wire electrodes. The area of air cold plasmas has been up to hundreds of square centimeters. The proposed formation conditions of large-scale barrier-free diffuse air plasmas are proved to be reasonable and feasible.

  4. Analysis and experimental study on formation conditions of large-scale barrier-free diffuse atmospheric pressure air plasmas in repetitive pulse mode

    SciTech Connect

    Li, Lee Liu, Lun; Liu, Yun-Long; Bin, Yu; Ge, Ya-Feng; Lin, Fo-Chang

    2014-01-14

    Atmospheric air diffuse plasmas have enormous application potential in various fields of science and technology. Without dielectric barrier, generating large-scale air diffuse plasmas is always a challenging issue. This paper discusses and analyses the formation mechanism of cold homogenous plasma. It is proposed that generating stable diffuse atmospheric plasmas in open air should meet the three conditions: high transient power with low average power, excitation in low average E-field with locally high E-field region, and multiple overlapping electron avalanches. Accordingly, an experimental configuration of generating large-scale barrier-free diffuse air plasmas is designed. Based on runaway electron theory, a low duty-ratio, high voltage repetitive nanosecond pulse generator is chosen as a discharge excitation source. Using the wire-electrodes with small curvature radius, the gaps with highly non-uniform E-field are structured. Experimental results show that the volume-scaleable, barrier-free, homogeneous air non-thermal plasmas have been obtained between the gap spacing with the copper-wire electrodes. The area of air cold plasmas has been up to hundreds of square centimeters. The proposed formation conditions of large-scale barrier-free diffuse air plasmas are proved to be reasonable and feasible.

  5. Calcofluor white and Congo red inhibit chitin microfibril assembly of Poterioochromonas: evidence for a gap between polymerization and microfibril formation

    PubMed Central

    1980-01-01

    The influence of the light microscopical stains, Calcofluor white and Congo red, on the process of chitin microfibril formation of the chrysoflagellate alga Poterioochromonas stipitata was studied with light and electron microscopy. There is a concentration-dependent inhibition of lorica formation with both dyes. In the presence of the inhibitors malformed loricae are made, which do not show the usual ultrastructure and arrangement of the chitin microfibrils. Instead of long, laterally associated microfibrils, short rods or irregular networks of subelementary (15-25 A) fibrils are found. Microfibril assembly obviously takes place on the accessible outside of the plasma membrane. There must be a gap between the polymerization and microfibril formation reactions, allowing the stains to bind to the polymerized subunits. Thus, later association of these units to form microfibrils is disturbed. The microfibril-orienting mechanism also depends on normal microfibril formation. A model summarizing these hypotheses is suggested. PMID:7430250

  6. Air-Gapped Structures as Magnetic Elements for Use in Power Processing Systems. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Ohri, A. K.

    1977-01-01

    Methodical approaches to the design of inductors for use in LC filters and dc-to-dc converters using air gapped magnetic structures are presented. Methods for the analysis and design of full wave rectifier LC filter circuits operating with the inductor current in both the continuous conduction and the discontinuous conduction modes are also described. In the continuous conduction mode, linear circuit analysis techniques are employed, while in the case of the discontinuous mode, the method of analysis requires computer solutions of the piecewise linear differential equations which describe the filter in the time domain. Procedures for designing filter inductors using air gapped cores are presented. The first procedure requires digital computation to yield a design which is optimized in the sense of minimum core volume and minimum number of turns. The second procedure does not yield an optimized design as defined above, but the design can be obtained by hand calculations or with a small calculator. The third procedure is based on the use of specially prepared magnetic core data and provides an easy way to quickly reach a workable design.

  7. Gap Formations Along Specimen-Bar Interfaces in Numerical Simulations of SHPB Tests on Elastic Materials Soft in Shear

    NASA Astrophysics Data System (ADS)

    Raftenberg, Martin N.; Scheidler, Mike

    2009-06-01

    Simulations of split Hopkinson pressure bar (SHPB) tests on elastic materials were performed using LS-DYNA. The specimens were much stiffer in dilatation than in shear. A compressible form of Mooney-Rivlin elasticity was applied with parameters evaluated from ballistic gelatin data. The bars were aluminum. The velocity prescribed on the incident bar increased over a rise time until attaining a steady-state value corresponding to a nominal strain rate of 2500/s. The rise time was varied to observe effects of pulse shaping. All calculations were 2D axisymmetric. A penalty-based contact algorithm was applied at the specimen-bar interfaces. This algorithm introduced a stiffness and a viscosity parameter. In sensitivity studies we varied the radius of the bars, the specimen's mesh, and the two contact parameters. In all calculations with the Mooney-Rivlin model, gaps formed at both specimen-bar interfaces over a wide range of strains. This gap phenomenon appears not to have been previously reported in the SHPB literature. We replaced the Mooney-Rivlin model with linear elasticity in order to explore whether the gaps were associated with material nonlinearity. We fixed Young's modulus at a value much smaller than that of aluminum. For sufficiently large Poisson ratios, we again observed gap formations at both specimen-bar interfaces.

  8. Design of single-winding energy-storage reactors for dc-to-dc converters using air-gapped magnetic-core structures

    NASA Technical Reports Server (NTRS)

    Ohri, A. K.; Wilson, T. G.; Owen, H. A., Jr.

    1977-01-01

    A procedure is presented for designing air-gapped energy-storage reactors for nine different dc-to-dc converters resulting from combinations of three single-winding power stages for voltage stepup, current stepup and voltage stepup/current stepup and three controllers with control laws that impose constant-frequency, constant transistor on-time and constant transistor off-time operation. The analysis, based on the energy-transfer requirement of the reactor, leads to a simple relationship for the required minimum volume of the air gap. Determination of this minimum air gap volume then permits the selection of either an air gap or a cross-sectional core area. Having picked one parameter, the minimum value of the other immediately leads to selection of the physical magnetic structure. Other analytically derived equations are used to obtain values for the required turns, the inductance, and the maximum rms winding current. The design procedure is applicable to a wide range of magnetic material characteristics and physical configurations for the air-gapped magnetic structure.

  9. Air-liquid biofilm formation is dependent on ammonium depletion in a Saccharomyces cerevisiae flor strain.

    PubMed

    Zara, Giacomo; Budroni, Marilena; Mannazzu, Ilaria; Zara, Severino

    2011-12-01

    Air-liquid biofilm formation appears to be an adaptive mechanism that promotes foraging of Saccharomyces cerevisiae flor strains in response to nutrient starvation. The FLO11 gene plays a central role in this phenotype as its expression allows yeast cells to rise to the liquid surface. Here, we investigated the role of ammonium depletion in air-liquid biofilm formation and FLO11 expression in a S. cerevisiae flor strain. The data obtained show that increasing ammonium concentrations from 0 to 450 m m reduce air-liquid biofilm in terms of biomass and velum formation and correlate with a reduction of FLO11 expression. Rapamycin inhibition of the TOR pathway and deletion of RAS2 gene significantly reduced biofilm formation and FLO11 expression. Taken together, these data suggest that ammonium depletion is a key factor in the induction of air-liquid biofilm formation and FLO11 expression in S. cerevisiae flor strains.

  10. Dual rotor single- stator axial air gap PMSM motor/generator drive for high torque vehicles applications

    NASA Astrophysics Data System (ADS)

    Tutelea, L. N.; Deaconu, S. I.; Boldea, I.; Popa, G. N.

    2014-03-01

    The actual e - continuously variable transmission (e-CVT) solution for the parallel Hybrid Electric Vehicle (HEV) requires two electric machines, two inverters, and a planetary gear. A distinct electric generator and a propulsion electric motor, both with full power converters, are typical for a series HEV. In an effort to simplify the planetary-geared e-CVT for the parallel HEV or the series HEV we hereby propose to replace the basically two electric machines and their two power converters by a single, axial-air-gap, electric machine central stator, fed from a single PWM converter with dual frequency voltage output and two independent PM rotors, destined for hybrid electric vehicles (HEV) and military vehicles applications. The proposed topologies and the magneto-motive force analysis are the core of the paper.

  11. Ultra sub-wavelength surface plasmon confinement using air-gap, sub-wavelength ring resonator arrays

    PubMed Central

    Lee, Jaehak; Sung, Sangkeun; Choi, Jun-Hyuk; Eom, Seok Chan; Mortensen, N. Asger; Shin, Jung H.

    2016-01-01

    Arrays of sub-wavelength, sub-10 nm air-gap plasmonic ring resonators are fabricated using nanoimprinting. In near infra-red (NIR) range, the resonator supports a single dipole mode which is excited and identified via simple normal illumination and explored through transmission measurements. By controlling both lateral and vertical confinement via a metal edge, the mode volume is successfully reduced down to 1.3 × 10−5 λ03. The advantage of such mode confinement is demonstrated by applying the resonators biosensing. Using bovine serum albumin (BSA) molecules, a dramatic enhancement of surface sensitivity up to 69 nm/nm is achieved as the modal height approaches the thickness of the adsorbed molecule layers. PMID:26923610

  12. Ultra sub-wavelength surface plasmon confinement using air-gap, sub-wavelength ring resonator arrays

    NASA Astrophysics Data System (ADS)

    Lee, Jaehak; Sung, Sangkeun; Choi, Jun-Hyuk; Eom, Seok Chan; Mortensen, N. Asger; Shin, Jung H.

    2016-02-01

    Arrays of sub-wavelength, sub-10 nm air-gap plasmonic ring resonators are fabricated using nanoimprinting. In near infra-red (NIR) range, the resonator supports a single dipole mode which is excited and identified via simple normal illumination and explored through transmission measurements. By controlling both lateral and vertical confinement via a metal edge, the mode volume is successfully reduced down to 1.3 × 10-5 λ03. The advantage of such mode confinement is demonstrated by applying the resonators biosensing. Using bovine serum albumin (BSA) molecules, a dramatic enhancement of surface sensitivity up to 69 nm/nm is achieved as the modal height approaches the thickness of the adsorbed molecule layers.

  13. Prediction of DC Corona Onset Voltage for Rod-Plane Air Gaps by a Support Vector Machine

    NASA Astrophysics Data System (ADS)

    Jin, Shuo; Ruan, Jiangjun; Du, Zhiye; Zhu, Lin; Shu, Shengwen

    2016-10-01

    This paper proposes a new method to predict the corona onset voltage for a rod-plane air gap, based on the support vector machine (SVM). Because the SVM is not limited by the size, dimension and nonlinearity of the samples, this method can realize accurate prediction with few training data. Only electric field features are chosen as the input; no geometric parameter is included. Therefore, the experiment data of one kind of electrode can be used to predict the corona onset voltages of other electrodes with different sizes. With the experimental data obtained by ozone detection technology, and experimental data provided by the reference, the efficiency of the proposed method is validated. Accurate predicted results with an average relative less than 3% are obtained with only 6 experimental data. supported by National Natural Science Foundation of China (No. 51477120)

  14. Analysis and Design Considerations of a High-Power Density, Dual Air Gap, Axial-Field Brushless, Permanent Magnet Motor.

    NASA Astrophysics Data System (ADS)

    Cho, Chahee Peter

    1995-01-01

    Until recently, brush dc motors have been the dominant drive system because they provide easily controlled motor speed over a wide range, rapid acceleration and deceleration, convenient control of position, and lower product cost. Despite these capabilities, the brush dc motor configuration does not satisfy the design requirements for the U.S. Navy's underwater propulsion applications. Technical advances in rare-earth permanent magnet materials, in high-power semiconductor transistor technology, and in various rotor position-sensing devices have made using brushless permanent magnet motors a viable alternative. This research investigates brushless permanent magnet motor technology, studying the merits of dual-air gap, axial -field, brushless, permanent magnet motor configuration in terms of power density, efficiency, and noise/vibration levels. Because the design objectives for underwater motor applications include high-power density, high-performance, and low-noise/vibration, the traditional, simplified equivalent circuit analysis methods to assist in meeting these goals were inadequate. This study presents the development and verification of detailed finite element analysis (FEA) models and lumped parameter circuit models that can calculate back electromotive force waveforms, inductance, cogging torque, energized torque, and eddy current power losses. It is the first thorough quantification of dual air-gap, axial -field, brushless, permanent magnet motor parameters and performance characteristics. The new methodology introduced in this research not only facilitates the design process of an axial field, brushless, permanent magnet motor but reinforces the idea that the high-power density, high-efficiency, and low-noise/vibration motor is attainable.

  15. Nonpolar III-nitride vertical-cavity surface-emitting laser with a photoelectrochemically etched air-gap aperture

    SciTech Connect

    Leonard, J. T. Yonkee, B. P.; Cohen, D. A.; Megalini, L.; Speck, J. S.; Lee, S.; DenBaars, S. P.; Nakamura, S.

    2016-01-18

    We demonstrate a III-nitride nonpolar vertical-cavity surface-emitting laser (VCSEL) with a photoelectrochemically (PEC) etched aperture. The PEC lateral undercut etch is used to selectively remove the multi-quantum well (MQW) region outside the aperture area, defined by an opaque metal mask. This PEC aperture (PECA) creates an air-gap in the passive area of the device, allowing one to achieve efficient electrical confinement within the aperture, while simultaneously achieving a large index contrast between core of the device (the MQW within the aperture) and the lateral cladding of the device (the air-gap formed by the PEC etch), leading to strong lateral confinement. Scanning electron microscopy and focused ion-beam analysis is used to investigate the precision of the PEC etch technique in defining the aperture. The fabricated single mode PECA VCSEL shows a threshold current density of ∼22 kA/cm{sup 2} (25 mA), with a peak output power of ∼180 μW, at an emission wavelength of 417 nm. The near-field emission profile shows a clearly defined single linearly polarized (LP) mode profile (LP{sub 12,1}), which is in contrast to the filamentary lasing that is often observed in III-nitride VCSELs. 2D mode profile simulations, carried out using COMSOL, give insight into the different mode profiles that one would expect to be displayed in such a device. The experimentally observed single mode operation is proposed to be predominantly a result of poor current spreading in the device. This non-uniform current spreading results in a higher injected current at the periphery of the aperture, which favors LP modes with high intensities near the edge of the aperture.

  16. Gap formation and phase transition of the anisotropic Kondo necklace model: Density matrix renormalization group analysis

    NASA Astrophysics Data System (ADS)

    Mendoza-Arenas, J. J.; Franco, R.; Silva-Valencia, J.

    2010-01-01

    We analyze the one-dimensional Kondo necklace model, at zero temperature, with an anisotropy parameter η in the interaction of the conduction chain, by means of the density matrix renormalization group. We calculate the energy gap and estimate the quantum critical points that separate a Kondo singlet state from an antiferromagnetic state, assuming a Kosterlitz-Thouless tendency. We also observe the correlation functions and the structure factors that support our critical points. The resulting phase diagram is presented and compared to that reported previously using Lanczos calculations. It is shown that the quantum critical points vary very slowly with η , but when η approaches zero, they drop abruptly.

  17. Sedimentology of the Mesaverde Formation at Rifle Gap, Colorado and implications for gas-bearing intervals in the subsurface

    SciTech Connect

    Lorenz, J.C.

    1982-03-01

    The exposures of the Mesaverde Formation at Rifle Gap, Colorado, are of a regressive series of marine to fluvial deposits about 1650 m (5000 ft) thick. Grading up out of the marine Mancos Shale, the blanket shoreline sandstones of the Corcoran, Cozzette, and Rollins Sandstones record substages of the regression as delta lobes were activated and abandoned in northwestern Colorado during Late Cretaceous time. The overlying coals, sandstones, and carbonaceous mudstones were deposited on the paludal lower delta plain behind the shoreline. Meandering fluvial systems prograded over the paludal deposits. These systems deposited point-bar sandstones and overbank mudstones and siltstones in composite meander-belt trends, some of which are now gas-bearing, low-permeability reservoirs. Reorientation of the paleogeography during the Laramide orogeny (contemporaneous with fluvial deposition) probably changed the orientation of the meander belt trends. The uppermost sandstones at Rifle Gap, including the Ohio Creek conglomerate, are interpreted as shoreline deposits of a transgression that has been previously unrecognized in the area. Most of the record of this transgression has been destroyed by pre-Eocene erosion. The outcrops at Rifle Gap provide a basis for interpreting subsurface deposis in the Department of Energy's Western Gas Sands Project Multi-Well Experiment, 12 miles away.

  18. Foam and cluster structure formation by latex particles at the air/water interface

    NASA Astrophysics Data System (ADS)

    Ruiz-Garcia, Jaime; Gámez-Corrales, Rogelio; Ivlev, Boris I.

    1997-02-01

    We report the formation of two-dimensional foam and cluster structures by spherical polystyrene particles trapped at the air/water interface. The colloidal foam is a transient structure that evolves to the formation of clusters, but clusters can also be formed after deposition of the sample. We also observed the formation of small aggregates, whose formation along with the cluster stabilization can be explained in terms of a balance between electrostatic repulsive and van der Waals attractive interactions.

  19. VAP-B binds to Rab3GAP1 at the ER: its implication in nuclear envelope formation through the ER-Golgi intermediate compartment.

    PubMed

    Hantan, Degejirihu; Yamamoto, Yasunori; Sakisaka, Toshiaki

    2014-10-01

    The vesicle-associated membrane protein-associated protein B (VAP-B) is a tail-anchored protein in the endoplasmic reticulum (ER). VAP-B functions as an adaptor protein to recruit target proteins to the ER and execute various cellular functions, lipid transport, membrane traffic, ER stress etc. Recently, VAP-B has been shown to regulate the nuclear envelope protein transport through the ER-Golgi intermediate compartment (ERGIC). We showed here that VAP-B directly binds to Rab3 GTPase activating protein 1 (Rab3GAP1), the catalytic subunit of Rab3GAP, through the two phenylalanines (FF) in an acidic tract (FFAT)-like motif of Rab3GAP1. Rab3GAP consists of two subunits, the catalytic subunit Rab3GAP1 and the non-catalytic subunit Rab3GAP2. VAP-B binds to Rab3GAP1 even in the Rab3GAP1/2 heterodimer complex. A single amino acid substitution of the FFAT-like motif reduces the binding activity of Rab3GAP1 to VAP-B. On the other hand, the FFAT-like motif mutation increases the binding activity of Rab3GAP1 to ERGIC-53, the ERGIC marker protein. Overexpression of Rab3GAP1 affects nuclear envelope formation more potently than that of Rab3GAP1 FFAT-like motif mutant. These results suggest that the binding of VAP-B to Rab3GAP1 is implicated in the regulation of nuclear envelope formation through ERGIC.

  20. Gap formation in the semimetal U 2Ru 2Sn: evidence from 119Sn NMR investigations

    NASA Astrophysics Data System (ADS)

    Baenitz, M.; Rabis, A.; Paschen, S.; Senthilkumaran, N.; Steglich, F.; Tran, V. H.; de V. du Plessis, P.; Strydom, A. M.

    2003-05-01

    We report measurements of the 119Sn nuclear spin-lattice relaxation rate 1/ T1 and the Knight shift K for polycrystalline U 2Ru 2Sn powder samples as a function of temperature. The T dependence of 1/ T1 is very similar to that of CeNiSn with the only difference that the temperature scale is increased roughly by a factor of 10. Therefore a first estimate gives a (pseudo-) gap value of Δ/k B≈140 K ( ≈14 K for CeNiSn). At low temperatures similar to CeNiSn a T1T=constant behaviour is observed which indicates the presence of a residual density of states at the Fermi level N( EF) in the pseudo-gap. Knight shift measurements on oriented polycrystalline powder samples show nearly no magnetic anisotropy, whereas the temperature dependence roughly follows the behaviour of the magnetic susceptibility. First investigations on the non-magnetic reference compound Th 2Ru 2Sn are also discussed.

  1. Formation of Bragg band gaps in anisotropic phononic crystals analyzed with the empty lattice model

    SciTech Connect

    Wang, Yan -Feng; Maznev, Alexei; Laude, Vincent

    2016-05-11

    Bragg band gaps of phononic crystals generally, but not always, open at Brillouin zone boundaries. The commonly accepted explanation stems from the empty lattice model: assuming a small material contrast between the constituents of the unit cell, avoided crossings in the phononic band structure appear at frequencies and wavenumbers corresponding to band intersections; for scalar waves the lowest intersections coincide with boundaries of the first Brillouin zone. However, if a phononic crystal contains elastically anisotropic materials, its overall symmetry is not dictated solely by the lattice symmetry. We construct an empty lattice model for phononic crystals made of isotropic and anisotropic materials, based on their slowness curves. We find that, in the anisotropic case, avoided crossings generally do not appear at the boundaries of traditionally defined Brillouin zones. Furthermore, the Bragg "planes" which give rise to phononic band gaps, are generally not flat planes but curved surfaces. Lastly, the same is found to be the case for avoided crossings between shear (transverse) and longitudinal bands in the isotropic case.

  2. Formation of Bragg band gaps in anisotropic phononic crystals analyzed with the empty lattice model

    DOE PAGES

    Wang, Yan -Feng; Maznev, Alexei; Laude, Vincent

    2016-05-11

    Bragg band gaps of phononic crystals generally, but not always, open at Brillouin zone boundaries. The commonly accepted explanation stems from the empty lattice model: assuming a small material contrast between the constituents of the unit cell, avoided crossings in the phononic band structure appear at frequencies and wavenumbers corresponding to band intersections; for scalar waves the lowest intersections coincide with boundaries of the first Brillouin zone. However, if a phononic crystal contains elastically anisotropic materials, its overall symmetry is not dictated solely by the lattice symmetry. We construct an empty lattice model for phononic crystals made of isotropic andmore » anisotropic materials, based on their slowness curves. We find that, in the anisotropic case, avoided crossings generally do not appear at the boundaries of traditionally defined Brillouin zones. Furthermore, the Bragg "planes" which give rise to phononic band gaps, are generally not flat planes but curved surfaces. Lastly, the same is found to be the case for avoided crossings between shear (transverse) and longitudinal bands in the isotropic case.« less

  3. SU-E-T-454: Impact of Air Gap On PDDs of 6 MV Photon Beam for Various Field Sizes in Inhomogeneous Phantoms

    SciTech Connect

    Oyewale, S; Pokharel; Singh, H; Islam, M; Rana, S

    2015-06-15

    Purpose: To investigate how the shape of air gap and its size will impact the percent depth doses (PDDs) of a 6MV photon beam for various field sizes. Methods: Two in-house phantoms were manufactured containing rectangular (phantom A) and circular (phantom B) air gaps. Both phantoms A and B were composed of same top layer (solid-water; 30×30cm{sup 2},5cm thickness) and bottom layer (solid-water; 30×30cm {sup 2},8cm thickness), but middle layer was varied to observe air gap effects and scatter contribution to the measurement point. In phantom A, a rectangular shaped air gap (30×30cm{sup 2},7cm thickness) was created by placing Styrofoam blocks between top and bottom layers of the phantom. In phantom B, middle layer was replaced by “inhomogenous block”, composed of acrylic plate (30×30cm{sup 2}, 4cm thickness) followed by PVC(30×30cm{sup 2},3cm thickness). Additionally, circular air gap was created by drilling a hole (diameter=2.8cm, length=7cm) at the center of “inhomogenous block”. In both phantoms, measurement readings were obtained at 13cm depth (i.e., 1cm after air gap) and depth of maximum dose(6MV energy; 100 MUs; field sizes ranged from 3×3cm{sup 2} to 10×10cm{sup 2}). The PDDs at 13cm depth were compared in both phantoms. Results: The measurements in both phantoms A and B showed an almost linear increase in PDDs with increasing field size, especially for smaller field sizes (from 3×3 to 7×7cm{sup 2}). For each field size, the PDD in phantom A was smaller compared to the one in phantom B. The difference in PDDs between two phantoms decreased with an increase in field size as the PDD difference decreased from 9.0% to 6.4%. Conclusion: The shape and size of air gap affect the PDD measurements in secondary build-up region as 6 MV primary beam traverses through the center of air gap. The scatter contribution due to increase in field size was more noticeable for field sizes ≤7×7cm{sup 2}.

  4. Bridging the Gap from Galactic to Extragalactic: Star Formation and Giant Molecular Clouds within the Nearby Spiral Galaxy NGC 300

    NASA Astrophysics Data System (ADS)

    Faesi, Christopher

    2017-01-01

    The questions surrounding the origins of stars are of key importance in astrophysics across a huge range in physical scales. However, until recently, investigations have been restricted to either detailed studies targeting a few nearby regions in the Milky Way, or kpc- or larger-scale studies of entire galaxies. Between these two scales lies a crucial gap in understanding. In this thesis work, I have taken steps in bridging this gap between Galactic and extragalactic star formation. I will present the results of a campaign of observations and modeling targeting the nearby spiral galaxy NGC 300. Using an extensive suite of multi-wavelength data I have characterized the star formation activity and molecular gas in a large sample of star-forming regions within this galaxy. Additionally, I have assembled an extensive (300 clouds) and high resolution (10 pc) catalog of Giant Molecular Clouds (GMCs) based on ALMA CO observations. This unprecedented look at the population of GMCs in a nearby spiral galaxy reveals an astonishing range of morphologies and properties in the Molecular Gas as well as providing a key testbed for comparison with GMCs in the Milky Way and other nearby galaxies. The GMCs in NGC 300 appear to have similar global properties and show scaling relations consistent with those seen in the Milky Way. Furthermore, the star formation rate appears to correlate with the mass of molecular gas with approximately 250 Gyr depletion time, extending the relation discovered in the Milky Way linearly to larger scales. These results suggest a level of universality in the star formation process within spiral galaxy disks like our own Milky Way.

  5. Influence of different light sources on microtensile bond strength and gap formation of resin cement under porcelain inlay restorations.

    PubMed

    Ozturk, A N; Usumez, A

    2004-09-01

    Clinical success with ceramic inlays/onlays has been assisted by the ability to develop a reliable bond of composite resin to dental tissues. The purpose of this study was to test the efficiency of two different light sources on microtensile bond strength and the gap formation of resin cement under class II porcelain inlay restorations. Standardized mesio-occlusal cavities were prepared in 30 freshly extracted, intact human premolar teeth. Then impressions were made and ceramic inlays were fabricated. In the cementation process, the resin cement/inlay combinations were exposed to two different photopolymerization units. The polymerizations through 15 specimens were performed with a conventional halogen light source for 60 s, and the other specimens were cured by a plasma arc light for 9 s. After the cementation process, two 1.2 x 1.2 mm wide 'I' shape sections per tooth were produced with a sectioning machine and sections were subjected to microtensile testing after 24 h or 1 week. Gap formation of specimens cured by different photopolymerization units were evaluated with scanning electron microscopy (SEM). Statistically significant differences were found between the microtensile bond strength of inlays exposed to conventional light and plasma arc curing unit (P < 0.001). Plasma arc curing units make it possible to polymerize composite in much shorter times than conventional curing unit. However, the samples polymerized with conventional halogen light produced better microtensile bond strength than the plasma arc unit.

  6. Air-gap gating of MgZnO/ZnO heterostructures

    SciTech Connect

    Tambo, T.; Falson, J. Kozuka, Y.; Maryenko, D.; Tsukazaki, A.; Kawasaki, M.

    2014-08-28

    The adaptation of “air-gap” dielectric based field-effect transistor technology to controlling the MgZnO/ZnO heterointerface confined two-dimensional electron system (2DES) is reported. We find it possible to tune the charge density of the 2DES via a gate electrode spatially separated from the heterostructure surface by a distance of 5 μm. Under static gating, the observation of the quantum Hall effect suggests that the charge carrier density remains homogeneous, with the 2DES in the 3 mm square sample the sole conductor. The availability of this technology enables the exploration of the charge carrier density degree of freedom in the pristine sample limit.

  7. Mass Gap for Black-Hole Formation in Higher-Derivative and Ghost-Free Gravity.

    PubMed

    Frolov, Valeri P

    2015-07-31

    We study a spherical gravitational collapse of a small mass in higher-derivative and ghost-free theories of gravity. By boosting a solution of linearized equations for a static point mass in such theories we obtain in the Penrose limit the gravitational field of an ultrarelativistic particle. Taking a superposition of such solutions we construct a metric of a collapsing null shell in the linearized higher-derivative and ghost-free gravity. The latter allows one to find the gravitational field of a thick null shell. By analyzing these solutions we demonstrate that in a wide class of the higher dimensional theories of gravity as well as for the ghost-free gravity there exists a mass gap for mini-black-hole production. We also found conditions when the curvature invariants remain finite at r=0 for the collapse of the thick null shell.

  8. Mass Gap for Black-Hole Formation in Higher-Derivative and Ghost-Free Gravity

    NASA Astrophysics Data System (ADS)

    Frolov, Valeri P.

    2015-07-01

    We study a spherical gravitational collapse of a small mass in higher-derivative and ghost-free theories of gravity. By boosting a solution of linearized equations for a static point mass in such theories we obtain in the Penrose limit the gravitational field of an ultrarelativistic particle. Taking a superposition of such solutions we construct a metric of a collapsing null shell in the linearized higher-derivative and ghost-free gravity. The latter allows one to find the gravitational field of a thick null shell. By analyzing these solutions we demonstrate that in a wide class of the higher dimensional theories of gravity as well as for the ghost-free gravity there exists a mass gap for mini-black-hole production. We also found conditions when the curvature invariants remain finite at r =0 for the collapse of the thick null shell.

  9. Resistance modulation in VO2 nanowires induced by an electric field via air-gap gates

    NASA Astrophysics Data System (ADS)

    Kanki, Teruo; Chikanari, Masashi; Wei, Tingting; Tanaka, Hidekazu; The Institute of Scientific; Industrial Research Team

    Vanadium dioxide (VO2) shows huge resistance change with metal-insulator transition (MIT) at around room temperature. Controlling of the MIT by applying an electric field is a topical ongoing research toward the realization of Mott transistor. In this study, we have successfully switched channel resistance of VO2 nano-wire channels by a pure electrostatic field effect using a side-gate-type field-effect transistor (SG-FET) viaair gap and found that single crystalline VO2 nanowires and the channels with narrower width enhance transport modulation rate. The rate of change in resistance ((R0-R)/R, where R0 and R is the resistance of VO2 channel with off state and on state gate voltage (VG) , respectively) was 0.42 % at VG = 30 V in in-plane poly-crystalline VO2 channels on Al2O3(0001) substrates, while the rate in single crystalline channels on TiO2 (001) substrates was 3.84 %, which was 9 times higher than that using the poly-crystalline channels. With reducing wire width from 3000 nm to 400 nm of VO2 on TiO2 (001) substrate, furthermore, resistance modulation ratio enhanced from 0.67 % to 3.84 %. This change can not be explained by a simple free-electron model. In this presentation, we will compare the electronic properties between in-plane polycrystalline VO2 on Al2O3 (0001) and single crystalline VO2 on TiO2 (001) substrates, and show experimental data in detail..

  10. Bridging the gap: disk formation in the Class 0 phase with ambipolar diffusion and Ohmic dissipation

    NASA Astrophysics Data System (ADS)

    Dapp, Wolf B.; Basu, Shantanu; Kunz, Matthew W.

    2012-05-01

    Context. Ideal magnetohydrodynamical (MHD) simulations have revealed catastrophic magnetic braking in the protostellar phase, which prevents the formation of a centrifugal disk around a nascent protostar. Aims: We determine if non-ideal MHD, including the effects of ambipolar diffusion and Ohmic dissipation determined from a detailed chemical network model, will allow for disk formation at the earliest stages of star formation. Methods: We employ the axisymmetric thin-disk approximation in order to resolve a dynamic range of 9 orders of magnitude in length and 16 orders of magnitude in density, while also calculating partial ionization using up to 19 species in a detailed chemical equilibrium model. Magnetic braking is applied to the rotation using a steady-state approximation, and a barotropic relation is used to capture the thermal evolution. Results: We resolve the formation of the first and second cores, with expansion waves at the periphery of each, a magnetic diffusion shock, and prestellar infall profiles at larger radii. Power-law profiles in each region can be understood analytically. After the formation of the second core, the centrifugal support rises rapidly and a low-mass disk of radius ≈ 10 R⊙ is formed at the earliest stage of star formation, when the second core has mass ~10-3 M⊙. The mass-to-flux ratio is ~104 times the critical value in the central region. Conclusions: A small centrifugal disk can form in the earliest stage of star formation, due to a shut-off of magnetic braking caused by magnetic field dissipation in the first core region. There is enough angular momentum loss to allow the second collapse to occur directly, and a low-mass stellar core to form with a surrounding disk. The disk mass and size will depend upon how the angular momentum transport mechanisms within the disk can keep up with mass infall onto the disk. Accounting only for direct infall, we estimate that the disk will remain ≲10 AU, undetectable even by ALMA, for

  11. Bomber: The Formation and Early Years of Strategic Air Command

    DTIC Science & Technology

    2012-11-01

    engine Model 299 had its maiden flight on 28 July 1935. The all-metal plane had wing flaps for better performance at slow airspeeds, electric trim tabs...fighting had been on- going for over two years. Airmen, like soldiers and sailors, struggled to catch up . Technology, which lay at the root of air...immediately, however, fundamental issues regarding intelli- gence of the new Soviet adversary, an intelligence bound up with technology to gather and

  12. Robust carrier formation process in low-band gap organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Yonezawa, Kouhei; Kamioka, Hayato; Yasuda, Takeshi; Han, Liyuan; Moritomo, Yutaka

    2013-10-01

    By means of femto-second time-resolved spectroscopy, we investigated the carrier formation process against film morphology and temperature (T) in highly-efficient organic photovoltaic, poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b '] dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b] thiophenediyl

  13. Formation of antiwaves in gap-junction-coupled chains of neurons

    NASA Astrophysics Data System (ADS)

    Urban, Alexander; Ermentrout, Bard

    2012-07-01

    Using network models consisting of gap-junction-coupled Wang-Buszaki neurons, we demonstrate that it is possible to obtain not only synchronous activity between neurons but also a variety of constant phase shifts between 0 and π. We call these phase shifts intermediate stable phase-locked states. These phase shifts can produce a large variety of wavelike activity patterns in one-dimensional chains and two-dimensional arrays of neurons, which can be studied by reducing the system of equations to a phase model. The 2π periodic coupling functions of these models are characterized by prominent higher order terms in their Fourier expansion, which can be varied by changing model parameters. We study how the relative contribution of the odd and even terms affects what solutions are possible, the basin of attraction of those solutions, and their stability. These models may be applicable to the spinal central pattern generators of the dogfish and also to the developing neocortex of the neonatal rat.

  14. Measurements of electron avalanche formation time in W-band microwave air breakdown

    SciTech Connect

    Cook, Alan M.; Hummelt, Jason S.; Shapiro, Michael A.; Temkin, Richard J.

    2011-08-15

    We present measurements of formation times of electron avalanche ionization discharges induced by a focused 110 GHz millimeter-wave beam in atmospheric air. Discharges take place in a free volume of gas, with no nearby surfaces or objects. When the incident field amplitude is near the breakdown threshold for pulsed conditions, measured formation times are {approx}0.1-2 {mu}s over the pressure range 5-700 Torr. Combined with electric field breakdown threshold measurements, the formation time data shows the agreement of 110 GHz air breakdown with the similarity laws of gas discharges.

  15. Measurements of electron avalanche formation time in W-band microwave air breakdown

    NASA Astrophysics Data System (ADS)

    Cook, Alan M.; Hummelt, Jason S.; Shapiro, Michael A.; Temkin, Richard J.

    2011-08-01

    We present measurements of formation times of electron avalanche ionization discharges induced by a focused 110 GHz millimeter-wave beam in atmospheric air. Discharges take place in a free volume of gas, with no nearby surfaces or objects. When the incident field amplitude is near the breakdown threshold for pulsed conditions, measured formation times are ˜0.1-2 μs over the pressure range 5-700 Torr. Combined with electric field breakdown threshold measurements, the formation time data shows the agreement of 110 GHz air breakdown with the similarity laws of gas discharges.

  16. Detection of air-gap eccentricity and broken-rotor bar conditions in a squirrel-cage induction motor using the radial flux sensor

    SciTech Connect

    Hwang, Don-Ha; Woo, Byung-Chul; Sun, Jong-Ho; Kang, Dong-Sik; Han, Sang-Bo; Kim, Byung-Kuk; Cho, Youn-Hyun

    2008-04-01

    A new method for detecting eccentricity and broken rotor bar conditions in a squirrel-cage induction motor is proposed. Air-gap flux variation analysis is done using search coils, which are inserted at stator slots. Using this method, the leakage flux in radial direction can be directly detected. Using finite element method, the air-gap flux variation is accurately modeled and analyzed. From the results of the simulation, a motor under normal condition shows maximum magnetic flux density of 1.3 T. On the other hand, the eccentric air-gap condition displays about 1.1 T at 60 deg. and 1.6 T at 240 deg. A difference of flux density is 0.5 T in the abnormal condition, whereas no difference is detected in the normal motor. In the broken rotor bar conditions, the flux densities at 65 deg. and 155 deg. are about 0.4 T and 0.8 T, respectively. These simulation results are coincided with those of experiment. Consequently, the measurement of the magnetic flux at air gap is one of effective ways to discriminate the faulted conditions of the eccentricity and broken rotor bars.

  17. Error Analysis of Clay-Rock Water Content Estimation with Broadband High-Frequency Electromagnetic Sensors—Air Gap Effect

    PubMed Central

    Bore, Thierry; Wagner, Norman; Delepine Lesoille, Sylvie; Taillade, Frederic; Six, Gonzague; Daout, Franck; Placko, Dominique

    2016-01-01

    Broadband electromagnetic frequency or time domain sensor techniques present high potential for quantitative water content monitoring in porous media. Prior to in situ application, the impact of the relationship between the broadband electromagnetic properties of the porous material (clay-rock) and the water content on the frequency or time domain sensor response is required. For this purpose, dielectric properties of intact clay rock samples experimental determined in the frequency range from 1 MHz to 10 GHz were used as input data in 3-D numerical frequency domain finite element field calculations to model the one port broadband frequency or time domain transfer function for a three rods based sensor embedded in the clay-rock. The sensor response in terms of the reflection factor was analyzed in time domain with classical travel time analysis in combination with an empirical model according to Topp equation, as well as the theoretical Lichtenecker and Rother model (LRM) to estimate the volumetric water content. The mixture equation considering the appropriate porosity of the investigated material provide a practical and efficient approach for water content estimation based on classical travel time analysis with the onset-method. The inflection method is not recommended for water content estimation in electrical dispersive and absorptive material. Moreover, the results clearly indicate that effects due to coupling of the sensor to the material cannot be neglected. Coupling problems caused by an air gap lead to dramatic effects on water content estimation, even for submillimeter gaps. Thus, the quantitative determination of the in situ water content requires careful sensor installation in order to reach a perfect probe clay rock coupling. PMID:27096865

  18. Error Analysis of Clay-Rock Water Content Estimation with Broadband High-Frequency Electromagnetic Sensors--Air Gap Effect.

    PubMed

    Bore, Thierry; Wagner, Norman; Lesoille, Sylvie Delepine; Taillade, Frederic; Six, Gonzague; Daout, Franck; Placko, Dominique

    2016-04-18

    Broadband electromagnetic frequency or time domain sensor techniques present high potential for quantitative water content monitoring in porous media. Prior to in situ application, the impact of the relationship between the broadband electromagnetic properties of the porous material (clay-rock) and the water content on the frequency or time domain sensor response is required. For this purpose, dielectric properties of intact clay rock samples experimental determined in the frequency range from 1 MHz to 10 GHz were used as input data in 3-D numerical frequency domain finite element field calculations to model the one port broadband frequency or time domain transfer function for a three rods based sensor embedded in the clay-rock. The sensor response in terms of the reflection factor was analyzed in time domain with classical travel time analysis in combination with an empirical model according to Topp equation, as well as the theoretical Lichtenecker and Rother model (LRM) to estimate the volumetric water content. The mixture equation considering the appropriate porosity of the investigated material provide a practical and efficient approach for water content estimation based on classical travel time analysis with the onset-method. The inflection method is not recommended for water content estimation in electrical dispersive and absorptive material. Moreover, the results clearly indicate that effects due to coupling of the sensor to the material cannot be neglected. Coupling problems caused by an air gap lead to dramatic effects on water content estimation, even for submillimeter gaps. Thus, the quantitative determination of the in situ water content requires careful sensor installation in order to reach a perfect probe clay rock coupling.

  19. Gap-fill type HSQ/ZEP520A bilayer resist process-(II): HSQ island and spacer formation

    NASA Astrophysics Data System (ADS)

    Chen, Wei-Su; Gu, Pei-Yi; Kao, Ming-Jer; Tsai, Ming-Jinn

    2008-03-01

    Hydrogen silsesquioxane (HSQ) bilayer resist (BLR) processes are attractive to obtain nano-sized features with high aspect ratio by dry-transferring thin e-beam pattern to thick underlayer to strengthen the etch resistance. However, there are drawbacks of high e-beam dosage for HSQ patterning and difficulty in controlling the underlayer resist profile by O2 plasma with anisotropic etching. In this study gap-fill type HSQ/ZEP520A BLR processes were studied to overcome these problems. The advantage of gap-fill type BLR processes is that the dosage for patterning on thick ZEP520A e-beam positive resist is not as high as that for HSQ and the resist profile can be tuned by exposure and development processes without depending on O2 plasma. By gap-filling of HSQ in ZEP520A trench patterns and then stripping ZEP520A by O2 plasma the tone is conversed from trench to line. The gap filling quality attributes include (1) the void size and number of HSQ lines and (2) spacer adhesion on HSQ line edge. Only the non-diluted HSQ solution could completely fill the trench and the HSQ line formed after stripping of ZEP520A. The spacer formed by diluted HSQ is found to be composed of oxide without any ZEP520A-related elements by FTIR analysis. The ZEP520A trench CD monotonically increases with decrease of W/L ratio. The HSQ line CD also follows the same trend. The extension of HSQ in ZEP520A, i.e. HSQ line CD minus ZEP520A trench CD, basically follows the reverse trend. It is therefore concluded that extension of HSQ lines in ZEP520A and HSQ spacers are formed from the diffused HSQ in trench sidewall without any reaction with ZEP520A. Voids were generally observed at the bottom of the HSQ line. Size and quantity of voids are larger for lower W/L ratios, indicating that the voids were formed due to insufficient HSQ volume for gap-filling. Increasing e-beam dose, baking or reflow temperature, and reflow of ZEP520A before HSQ coating could reduce the void formation. Multiple gap

  20. Jumping the gap: the formation conditions and mass function of `pebble-pile' planetesimals

    NASA Astrophysics Data System (ADS)

    Hopkins, Philip F.

    2016-03-01

    In a turbulent proto-planetary disc, dust grains undergo large-density fluctuations and under the right circumstances, grain overdensities can collapse under self-gravity (forming a `pebble-pile' planetesimal). Using a simple model for fluctuations predicted in simulations, we estimate the rate of formation and mass function of self-gravitating planetesimal-mass bodies formed by this mechanism. This depends sensitively on the grain size, disc surface density, and turbulent Mach numbers. However, when it occurs, the resulting planetesimal mass function is broad and quasi-universal, with a slope dN/dM ∝ M-(1-2), spanning size/mass range ˜10-104 km (˜10-9-5 M⊕). Collapse to planetesimal through super-Earth masses is possible. The key condition is that grain density fluctuations reach large amplitudes on large scales, where gravitational instability proceeds most easily (collapse of small grains is suppressed by turbulence). This leads to a new criterion for `pebble-pile' formation: τs ≳ 0.05 ln (Q1/2/Zd)/ln (1 + 10 α1/4) ˜ 0.3 ψ(Q, Z, α) where τs = ts Ω is the dimensionless particle stopping time. In a minimum-mass solar nebula, this requires grains larger than a = (50, 1, 0.1) cm at r=(1, 30, 100) au}. This may easily occur beyond the ice line, but at small radii would depend on the existence of large boulders. Because density fluctuations depend strongly on τs (inversely proportional to disc surface density), lower density discs are more unstable. Conditions for pebble-pile formation also become more favourable around lower mass, cooler stars.

  1. The formation of Ti-O tetrahedra and band gap reduction in SiO2 via pulsed ion implantation

    NASA Astrophysics Data System (ADS)

    Green, R. J.; Zatsepin, D. A.; Hunt, A.; Kurmaev, E. Z.; Gavrilov, N. V.; Moewes, A.

    2013-03-01

    Titanium ions are implanted into amorphous SiO2 at two different fluences using pulsed ion implantation, and the resulting samples are annealed. Bulk sensitive soft X-ray absorption spectroscopy of the Ti L2,3 edge reveal strikingly different spectra for the two fluences. Spectral simulations using multiplet crystal field theory show clearly that for low fluence the Ti ions have a local octahedral coordination, while at higher fluence the formation of Ti4+-O tetrahedra dominates. Using O K-edge X-ray absorption and emission, the effect of the Ti states on the valence and conduction bands of the host SiO2 is revealed. With the introduction of Ti tetrahedra, the band gap reduces from about 8 eV to just over 4 eV, due entirely to the Ti 3d conduction band states. These results demonstrate the possibility to obtain Ti-O tetrahedra in silica by Ti ion implantation and a suitable thermal treatment, clarify the mechanism of band gap reduction with Ti doping in SiO2, and demonstrate the sensitivity of L-edge X-ray absorption with a multiplet crystal field theory analysis to the Ti coordination of novel materials.

  2. The role of school performance in narrowing gender gaps in the formation of STEM aspirations: a cross-national study

    PubMed Central

    Mann, Allison; Legewie, Joscha; DiPrete, Thomas A.

    2015-01-01

    This study uses cross-national evidence to estimate the effect of school peer performance on the size of the gender gap in the formation of STEM career aspirations. We argue that STEM aspirations are influenced not only by gender stereotyping in the national culture but also by the performance of peers in the local school environment. Our analyses are based on the Program for International Student Assessment (PISA). They investigate whether 15-year-old students from 55 different countries expect to have STEM jobs at the age of 30. We find considerable gender differences in the plans to pursue careers in STEM occupations in all countries. Using PISA test scores in math and science aggregated at the school level as a measure of school performance, we find that stronger performance environments have a negative impact on student career aspirations in STEM. Although girls are less likely than boys to aspire to STEM occupations, even when they have comparable abilities, boys respond more than girls to competitive school performance environments. As a consequence, the aspirations gender gap narrows for high-performing students in stronger performance environments. We show that those effects are larger in countries that do not sort students into different educational tracks. PMID:25762961

  3. Chemical potential shift and gap-state formation in SrTiO3-δ revealed by photoemission spectroscopy

    NASA Astrophysics Data System (ADS)

    Pal, Prabir; Kumar, Pramod; Aswin, V.; Dogra, Anjana; Joshi, Amish G.

    2014-08-01

    In this study, we report on investigations of the electronic structure of SrTiO3 annealed at temperature ranging between 550 and 840 °C in an ultrahigh vacuum. Annealing induced oxygen vacancies (Ovac) impart considerable changes in the electronic structure of SrTiO3. Using core-level photoemission spectroscopy, we have studied the chemical potential shift (Δμ) as a function of annealing temperature. The result shows that the chemical potential monotonously increases with electron doping in SrTiO3-δ. The monotonous increase of the chemical potential rules out the existence of electronic phase separation in the sample. Using valence band photoemission, we have demonstrated the formation of a low density of states at the near Fermi level electronic spectrum of SrTiO3-δ. The gap-states were observed by spectral weight transfer over a large energy scale of the stoichiometric band gap of SrTiO3 system leading finally to an insulator-metal transition. We have interpreted our results from the point of structural distortions induced by oxygen vacancies.

  4. A comparative study on the effects of air gap wind and walking motion on the thermal properties of Arabian Thawbs and Chinese Cheongsams.

    PubMed

    Cui, Zhiying; Fan, Jintu; Wu, Yuenshing

    2016-08-01

    This paper reports on an experimental investigation on the effects of air gap, wind and walking motion on the thermal properties of traditional Arabian thawbs and Chinese cheongsams. Total thermal resistance (It) and vapour resistance (Re) were measured using the sweating fabric manikin - 'Walter', and the air gap volumes of the garments were determined by a 3D body scanner. The results showed the relative changes of It and Re of thawbs due to wind and walking motion are greater than those of cheongsams, which provided an explanation of why thawbs are preferred in extremely hot climate. It is further shown that thermal insulation and vapour resistance of thawbs increase with the air gap volume up to about 71,000 cm(3) and then decrease gradually. Thawbs with higher air permeability have significantly lower evaporative resistance particularly under windy conditions demonstrating the advantage of air permeable fabrics in body cooling in hot environments. Practitioner Summary: This paper aims to better understand the thermal insulation and vapour resistance of traditional Arabian thawbs and Chinese cheongsams, and the relationship between the thermal properties and their fit and design. The results of this study provide a scientific basis for designing ethnic clothing used in hot environments.

  5. Strong coupling in non-polar GaN/AlGaN microcavities with air-gap/III-nitride distributed Bragg reflectors

    NASA Astrophysics Data System (ADS)

    Tao, Renchun; Arita, Munetaka; Kako, Satoshi; Kamide, Kenji; Arakawa, Yasuhiko

    2015-09-01

    Strong coupling between excitons and photons is experimentally demonstrated in m-plane GaN/AlGaN microcavities (MCs) with air/AlGaN distributed Bragg reflectors (DBRs) at room temperature. Strong coupling is confirmed by momentum space spectroscopy, and a Rabi splitting (Ω) of 84 meV is estimated. A Rabi splitting of 84 meV is the largest value reported in a III-nitride DBR MC to date and is mainly attributed to the shortened effective cavity length resulting from the high index contrast in the air-gap DBRs used here. These results show that III-nitride air-gap DBR MCs have a high potential for realizing high Ω / κ systems (where κ is the cavity loss).

  6. Geochemical factors promoting die-back gap formation in colonizing patches of Spartina densiflora in an irregularly flooded marsh

    NASA Astrophysics Data System (ADS)

    Mirlean, Nicolai; Costa, Cesar S. B.

    2017-04-01

    Circular (RP) and ring-shape (RP) patches of vegetation in intertidal flats have been associated with the radial expansion of tussock growth forms and die-back gap in older central stands, respectively. RP formation has not yet been sufficiently explained. We accomplished a comparative geochemical study of CP and RP structures of Spartina densiflora within a single saltmarsh in a microtidal estuary (<0.5 m). The pore water under these structures demonstrated distinctive physical-chemical properties by marked seasonal changing in water level and salinity. During high-water period dissolved H2S was frequently low in pore waters of S. densiflora structures due to reactive-Fe, which scavenge the sulfide from solution and form solid sulfides. During less flooded-brackish water period, pore water pH goes down below 4 inside the vegetated bordering areas of RP. In these locations the concentration of soluble sulfides dramatically increases up to 140 μM L-1. The high concentration of protons in pore water is the result of solid sulfides atmospheric oxidation to sulfuric acid. High dissolution of H2S, along with the low pH, creates a toxic environment for S. densiflora and die-back central gap formation in RP. CP structure was 5 cm higher in the intertidal than RP but shows frequent presence of a water layer, less severe oxidation of sulfides and limited building-up of toxic condition to plants. Development of S. densiflora RP probably indicates the uplift of sediment by this bioengineer grass and/or periodic lowering of the water surface below a certain critical level.

  7. The Effect of the Saharan Air Layer on the Formation of Hurricane Isabel (2003) Simulated with AIRS Data

    NASA Technical Reports Server (NTRS)

    Wu, iguang; Braun, Scott A.; Qu, John J.

    2006-01-01

    The crucial physics of how the atmosphere really accomplishes the tropical cyclogenesis process is still poorly understood. The presence of the Saharan Air Layer (SAL), an elevated mixed layer of warm and dry air that extends from Africa to the tropical Atlantic and contains a substantial amount of mineral dust, adds more complexity to the tropical cyclogenesis process in the Atlantic basin. The impact of the SAL on tropical cyclogenesis is still uncertain. Karyampudi and Carlson (1988) conclude that a strong SAL can potentially aid tropical cyclone development while Dunion and Velden (2004) argue that the SAL generally inhibits tropical cyclogenesis and intensification. Advancing our understanding of the physical mechanisms of tropical cyclogenesis and the associated roles of the SAL strongly depends on the improvement in the observations over the data-sparse ocean areas. After the Atmospheric Infrared Sounder (AIRS), the Advanced Microwave Sounding Unit (AMSU), and the microwave Humidity Sounder of Brazil (HSB) were launched with the NASA Aqua satellite in 2002, new data products retrieved from the AIRS suite became available for studying the effect of the warm, dry air mass associated with the SAL (referred to as the thermodynamic effect). The vertical profiles of the AIRS retrieved temperature and humidity provide an unprecedented opportunity to examine the thermodynamic effect of the SAL. The observational data can be analyzed and assimilated into numerical models, in which the model thermodynamic state is allowed to relax to the observed state from AIRS data. The objective of this study is to numerically demonstrate that the thermodynamic effect of the SAL on the formation of Hurricane Isabel (2003) can be largely simulated through nudging of the AIRS data.

  8. The health impacts of exposure to indoor air pollution from solid fuels in developing countries: knowledge, gaps, and data needs.

    PubMed Central

    Ezzati, Majid; Kammen, Daniel M

    2002-01-01

    Globally, almost 3 billion people rely on biomass (wood, charcoal, crop residues, and dung) and coal as their primary source of domestic energy. Exposure to indoor air pollution (IAP) from the combustion of solid fuels is an important cause of morbidity and mortality in developing countries. In this paper, we review the current knowledge on the relationship between IAP exposure and disease and on interventions for reducing exposure and disease. We take an environmental health perspective and consider the details of both exposure and health effects that are needed for successful intervention strategies. We also identify knowledge gaps and detailed research questions that are essential in successful design and dissemination of preventive measures and policies. In addition to specific research recommendations, we conclude that given the interaction of housing, household energy, and day-to-day household activities in determining exposure to indoor smoke, research and development of effective interventions can benefit tremendously from integration of methods and analysis tools from a range of disciplines in the physical, social, and health sciences. PMID:12417475

  9. Temperature dependence of beat-length and confinement loss in an air-core photonic band-gap fiber

    NASA Astrophysics Data System (ADS)

    Xu, Zhenlong; Li, Xuyou; Hong, Yong; Liu, Pan; Yang, Hanrui; Ling, Weiwei

    2016-05-01

    The temperature dependence of polarization-maintaining (PM) property and loss in a highly-birefringent air-core photonic band-gap fiber (PBF) is investigated. The effects of temperature variation on the effective index, beat-length and confinement loss are studied numerically by using the full-vector finite element method (FEM). It is found that, the PM property of this PBF is insensitive to the temperature, and the temperature-dependent beat-length coefficient can be as low as 2.86×10-8 m/°C, which is typically 200 times less than those of conventional panda fibers, the PBF has a stable confinement loss of 0.01 dB/m over the temperature range of -30 to 20 °C for the slow axis at the wavelength of 1.55 μm. The PBF with ultra-low temperature-dependent PM property and low loss can reduce the thermally induced polarization instability apparently in interferometric applications such as resonant fiber optic gyroscope (RFOG), optical fiber sensors, and so on.

  10. Indium phosphide all air-gap Fabry-Pérot filters for near-infrared spectroscopic applications

    NASA Astrophysics Data System (ADS)

    Ullah, A.; Butt, M. A.; Fomchenkov, S. A.; Khonina, S. N.

    2016-08-01

    Food quality can be characterized by noninvasive techniques such as spectroscopy in the Near Infrared wavelength range. For example, 930 -1450 nm wavelength range can be used to detect diseases and differentiate between meat samples. Miniaturization of such NIR spectrometers is useful for quick and mobile characterization of food samples. Spectrometers can be miniaturized, without compromising the spectral resolution, using Fabry-Pérot (FP) filters consisting of two highly reflecting mirrors with a central cavity in between. The most commonly used mirrors in the design of FP filters are Distributed Bragg Reflections (DBRs) consisting of alternating high and low refractive index material pairs, due to their high reflectivity compared to metal mirrors. However, DBRs have high reflectivity for a selected range of wavelengths known as the stopband of the DBR. This range is usually much smaller than the sensitivity range of the spectrometer detector. Therefore, a bandpass filter is usually required to restrict wavelengths outside the stopband of the FP DBRs. Such bandpass filters are difficult to design and implement. Alternatively, high index contrast materials must be can be used to broaden the stopband width of the FP DBRs. In this work, Indium phosphide all air-gap filters are proposed in conjunction with InGaAs based detectors. The designed filter has a wide stopband covering the entire InGaAs detector sensitivity range. The filter can be tuned in the 950-1450 nm with single mode operation. The designed filter can hence be used for noninvasive meat quality control.

  11. Effect of pressure on structure and NO sub X formation in CO-air diffusion flames

    NASA Technical Reports Server (NTRS)

    Maahs, H. G.; Miller, I. M.

    1979-01-01

    A study was made of nitric oxide formation in a laminar CO-air diffusion flame over a pressure range from 1 to 50 atm. The carbon monoxide (CO) issued from a 3.06 mm diameter port coaxially into a coflowing stream of air confined within a 20.5 mm diameter chimney. Nitric oxide concentrations from the flame were measured at two carbon monoxide (fuel) flow rates: 73 standard cubic/min and 146 sccm. Comparison of the present data with data in the literature for a methane-air diffusion flame shows that for flames of comparable flame height (8 to 10 mm) and pseudoequivalence ratio (0.162), the molar emission index of a CO-air flame is significantly greater than that of a methane-air flame.

  12. General anesthesia improves contact force and reduces gap formation in pulmonary vein isolation: a comparison with conscious sedation.

    PubMed

    Chikata, Akio; Kato, Takeshi; Yaegashi, Takanori; Sakagami, Satoru; Kato, Chieko; Saeki, Takahiro; Kawai, Keiichi; Takashima, Shin-Ichiro; Murai, Hisayoshi; Usui, Soichiro; Furusho, Hiroshi; Kaneko, Shuichi; Takamura, Masayuki

    2017-03-04

    Compared to conscious sedation (CS), the use of general anesthesia (GA) in pulmonary vein isolation (PVI) is associated with a lower recurrence rate of atrial fibrillation (AF). GA may improve catheter stability and mapping system accuracy compared to CS, but its influence on contact force (CF) parameters during ipsilateral PVI has not previously been investigated. The study population comprised 176 consecutive patients (107 in GA group and 69 in CS group) with AF who underwent their first PVI procedure. We retrospectively assessed CF parameters, force-time integral (FTI), FTI/wall thickness during anatomical ipsilateral PVI and long-term outcome after ablation. Complete PVI with single continuous circular lesions around the ipsilateral PVs was achieved in 54 patients (50.5%) in the GA group but only 24 patients (34.8%) in the CS group (P = 0.04). The distribution of gaps did not differ between the groups. All CF parameters were significantly higher in the GA group than in the CS group (average CF: 19.4 ± 8.7 vs. 16.7 ± 7.7 g, P < 0.0001; FTI: 399.0 ± 262.5 vs. 293.9 ± 193.4 gs, P < 0.0001; FTI/wall thickness: 155.5 ± 106.1 vs. 115.7 ± 85.5 gs, P < 0.0001). GA was associated with lower AF recurrence rate in patients with paroxysmal AF but not with persistent AF. Compared with CS, GA improves CF parameters, FTI and FTI/wall thickness, and reduced gap formation after ipsilateral PVI.

  13. The importance of corona generation and leader formation during laser filament guided discharges in air

    NASA Astrophysics Data System (ADS)

    Schmitt-Sody, Andreas; French, David; White, William; Lucero, Adrian; Roach, William P.; Hasson, Victor

    2015-03-01

    Images taken with an intensified CCD camera show the dynamics during filament guided discharge events. The images reveal that filament initiated corona plays a role in the presented results. Furthermore, the images show the formation of leaders, propagating and eventually bridging the gap between the high voltage (HV) electrodes. Analysis of the images and comparison to oscilloscope traces of voltage and current dynamics reveal the origin of the delay between the filament and HV discharge and allows for a probability of discharge analysis.

  14. Preliminary formation analysis for compressed air energy storage in depleted natural gas reservoirs :

    SciTech Connect

    Gardner, William Payton

    2013-06-01

    The purpose of this study is to develop an engineering and operational understanding of CAES performance for a depleted natural gas reservoir by evaluation of relative permeability effects of air, water and natural gas in depleted natural gas reservoirs as a reservoir is initially depleted, an air bubble is created, and as air is initially cycled. The composition of produced gases will be evaluated as the three phase flow of methane, nitrogen and brine are modeled. The effects of a methane gas phase on the relative permeability of air in a formation are investigated and the composition of the produced fluid, which consists primarily of the amount of natural gas in the produced air are determined. Simulations of compressed air energy storage (CAES) in depleted natural gas reservoirs were carried out to assess the effect of formation permeability on the design of a simple CAES system. The injection of N2 (as a proxy to air), and the extraction of the resulting gas mixture in a depleted natural gas reservoir were modeled using the TOUGH2 reservoir simulator with the EOS7c equation of state. The optimal borehole spacing was determined as a function of the formation scale intrinsic permeability. Natural gas reservoir results are similar to those for an aquifer. Borehole spacing is dependent upon the intrinsic permeability of the formation. Higher permeability allows increased injection and extraction rates which is equivalent to more power per borehole for a given screen length. The number of boreholes per 100 MW for a given intrinsic permeability in a depleted natural gas reservoir is essentially identical to that determined for a simple aquifer of identical properties. During bubble formation methane is displaced and a sharp N2methane boundary is formed with an almost pure N2 gas phase in the bubble near the borehole. During cycling mixing of methane and air occurs along the boundary as the air bubble boundary moves. The extracted gas mixture changes as a

  15. Foam formation and acute air emboli with the maquet paediatric Quadrox I: a word of caution.

    PubMed

    Fouilloux, Virginie; Davey, Lisa; Van Arsdell, Glen S; Honjo, Osami

    2014-07-01

    We report 3 cases of significant foam formation in the venous reservoir with the Maquet Quadrox-I oxygenator and VHK 31 000 reservoir system. All the 3 patients required maximal suction return during procedures, causing pressurization of reservoir and foam formation. Two patients experienced systemic air emboli, which were dealt with by means of retrograde cerebral perfusion and hypothermia with no neurological sequela. These events emphasize the importance of device selection in high-risk patients as well as crisis management.

  16. Traffic-Related Air Pollution and Childhood Asthma: Recent Advances and Remaining Gaps in the Exposure Assessment Methods.

    PubMed

    Khreis, Haneen; Nieuwenhuijsen, Mark J

    2017-03-17

    Background: Current levels of traffic-related air pollution (TRAP) are associated with the development of childhood asthma, although some inconsistencies and heterogeneity remain. An important part of the uncertainty in studies of TRAP-associated asthma originates from uncertainties in the TRAP exposure assessment and assignment methods. In this work, we aim to systematically review the exposure assessment methods used in the epidemiology of TRAP and childhood asthma, highlight recent advances, remaining research gaps and make suggestions for further research. Methods: We systematically reviewed epidemiological studies published up until 8 September 2016 and available in Embase, Ovid MEDLINE (R), and "Transport database". We included studies which examined the association between children's exposure to TRAP metrics and their risk of "asthma" incidence or lifetime prevalence, from birth to the age of 18 years old. Results: We found 42 studies which examined the associations between TRAP and subsequent childhood asthma incidence or lifetime prevalence, published since 1999. Land-use regression modelling was the most commonly used method and nitrogen dioxide (NO₂) was the most commonly used pollutant in the exposure assessments. Most studies estimated TRAP exposure at the residential address and only a few considered the participants' mobility. TRAP exposure was mostly assessed at the birth year and only a few studies considered different and/or multiple exposure time windows. We recommend that further work is needed including e.g., the use of new exposure metrics such as the composition of particulate matter, oxidative potential and ultra-fine particles, improved modelling e.g., by combining different exposure assessment models, including mobility of the participants, and systematically investigating different exposure time windows. Conclusions: Although our previous meta-analysis found statistically significant associations for various TRAP exposures and

  17. Traffic-Related Air Pollution and Childhood Asthma: Recent Advances and Remaining Gaps in the Exposure Assessment Methods

    PubMed Central

    Khreis, Haneen; Nieuwenhuijsen, Mark J.

    2017-01-01

    Background: Current levels of traffic-related air pollution (TRAP) are associated with the development of childhood asthma, although some inconsistencies and heterogeneity remain. An important part of the uncertainty in studies of TRAP-associated asthma originates from uncertainties in the TRAP exposure assessment and assignment methods. In this work, we aim to systematically review the exposure assessment methods used in the epidemiology of TRAP and childhood asthma, highlight recent advances, remaining research gaps and make suggestions for further research. Methods: We systematically reviewed epidemiological studies published up until 8 September 2016 and available in Embase, Ovid MEDLINE (R), and “Transport database”. We included studies which examined the association between children’s exposure to TRAP metrics and their risk of “asthma” incidence or lifetime prevalence, from birth to the age of 18 years old. Results: We found 42 studies which examined the associations between TRAP and subsequent childhood asthma incidence or lifetime prevalence, published since 1999. Land-use regression modelling was the most commonly used method and nitrogen dioxide (NO2) was the most commonly used pollutant in the exposure assessments. Most studies estimated TRAP exposure at the residential address and only a few considered the participants’ mobility. TRAP exposure was mostly assessed at the birth year and only a few studies considered different and/or multiple exposure time windows. We recommend that further work is needed including e.g., the use of new exposure metrics such as the composition of particulate matter, oxidative potential and ultra-fine particles, improved modelling e.g., by combining different exposure assessment models, including mobility of the participants, and systematically investigating different exposure time windows. Conclusions: Although our previous meta-analysis found statistically significant associations for various TRAP exposures and

  18. Experimental method to reveal the effect of rotor magnet size and air gap on artificial heart driving motor torque and efficiency.

    PubMed

    Qian, K X; Yuan, H Y; Ru, W M; Zeng, P

    2002-01-01

    To investigate experimentally the effect of rotor magnet design on artificial heart driving motor performance, seven rotors with different magnet lengths or thicknesses, as well as different peripheral angles, were manufactured and tested in the same motor stator with different rotating speeds. The input power (voltage and current) and output torque were measured and the motor efficiency was computed. The results demonstrated that the reduction of rotor magnet size and the enlargement of the air gap between the rotor magnets and the stator coil core have no significant effect on motor efficiency, but will reduce the torque value on which the motor achieves the highest efficiency; it could be remedied however by increasing the rotating speed, because the torque at the high efficiency point will increase along with the rotating speed. These results may provide a basis for developing small rotor magnets, large air gap and high efficiency motors for driving an artificial heart pump.

  19. Static air-gap eccentricity fault diagnosis using rotor slot harmonics in line neutral voltage of three-phase squirrel cage induction motor

    NASA Astrophysics Data System (ADS)

    Oumaamar, Mohamed El Kamel; Maouche, Yassine; Boucherma, Mohamed; Khezzar, Abdelmalek

    2017-02-01

    The mixed eccentricity fault detection in a squirrel cage induction motor has been thoroughly investigated. However, a few papers have been related to pure static eccentricity fault and the authors focused on the RSH harmonics presented in stator current. The main objective of this paper is to present an alternative method based on the analysis of line neutral voltage taking place between the supply and the stator neutrals in order to detect air-gap static eccentricity, and to highlight the classification of all RSH harmonics in line neutral voltage. The model of squirrel cage induction machine relies on the rotor geometry and winding layout. Such developed model is used to analyze the impact of the pure static air-gap eccentricity by predicting the related frequencies in the line neutral voltage spectrum. The results show that the line neutral voltage spectrum are more sensitive to the air-gap static eccentricity fault compared to stator current one. The theoretical analysis and simulated results are confirmed by experiments.

  20. A Novel 96well-formatted Micro-gap Plate Enabling Drug Response Profiling on Primary Tumour Samples

    NASA Astrophysics Data System (ADS)

    Ma, Wei-Yuan; Hsiung, Lo-Chang; Wang, Chen-Ho; Chiang, Chi-Ling; Lin, Ching-Hung; Huang, Chiun-Sheng; Wo, Andrew M.

    2015-04-01

    Drug-based treatments are the most widely used interventions for cancer management. Personalized drug response profiling remains inherently challenging with low cell count harvested from tumour sample. We present a 96well-formatted microfluidic plate with built-in micro-gap that preserves up to 99.2% of cells during multiple assay/wash operation and only 9,000 cells needed for a single reagent test (i.e. 1,000 cells per test spot x 3 selected concentration x triplication), enabling drug screening and compatibility with conventional automated workstations. Results with MCF7 and MDA-MB-231 cell lines showed that no statistical significance was found in dose-response between the device and conventional 96-well plate control. Primary tumour samples from breast cancer patients tested in the device also showed good IC50 prediction. With drug screening of primary cancer cells must consider a wide range of scenarios, e.g. suspended/attached cell types and rare/abundant cell availability, the device enables high throughput screening even for suspended cells with low cell count since the signature microfluidic cell-trapping feature ensures cell preservation in a multiple solution exchange protocol.

  1. Magnon gap formation and charge density wave effect on thermoelectric properties in SmNiC2 compound

    NASA Astrophysics Data System (ADS)

    Kim, Jin-Hee; Rhyee, Jong-Soo; Kwon, Yong Seung

    2013-03-01

    We studied the magnetic, electrical, and thermal properties of polycrystalline compound of SmNiC2. The electrical resistivity and magnetization measurement show the interplay between the charge density wave at TCDW = 157 K and the ferromagnetic ordering of Tc = 18 K. Below the ferromagnetic transition temperature, we observed the magnon gap formation of 4.3 ~ 4.4 meV by ρ(T) and Cp(T) measurements. The charge density wave is attributed to the increase of Seebeck coefficient resulting in the increase of power factor S2 σ . The thermoelectric figure-of-merit ZT significantly increases due to the increase of power factor at TCDW = 157 K. Here we argue that the competing interaction between electron-phonon and electron-magnon couplings exhibits the unconventional behavior of electrical and thermal properties. This research was supported by Basic Science Research Program (2011-0021335), Nano-Material Technology Development Program (2011-0030147), and Mid-career Research Program (Strategy) (No. 2012R1A2A1A03005174) through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology.

  2. Hydrophilic strips for preventing air bubble formation in a microfluidic chamber.

    PubMed

    Choi, Munseok; Na, Yang; Kim, Sung-Jin

    2015-12-01

    In a microfluidic chamber, unwanted formation of air bubbles is a critical problem. Here, we present a hydrophilic strip array that prevents air bubble formation in a microfluidic chamber. The array is located on the top surface of the chamber, which has a large variation in width, and consists of a repeated arrangement of super- and moderately hydrophilic strips. This repeated arrangement allows a flat meniscus (i.e. liquid front) to form when various solutions consisting of a single stream or two parallel streams with different hydrophilicities move through the chamber. The flat meniscus produced by the array completely prevents the formation of bubbles. Without the array in the chamber, the meniscus shape is highly convex, and bubbles frequently form in the chamber. This hydrophilic strip array will facilitate the use of a microfluidic chamber with a large variation in width for various microfluidic applications.

  3. A High-Latitude Winter Continental Low Cloud Feedback Suppresses Arctic Air Formation in Warmer Climates

    NASA Astrophysics Data System (ADS)

    Cronin, T.; Tziperman, E.; Li, H.

    2015-12-01

    High latitude continents have warmed much more rapidly in recent decades than the rest of the globe, especially in winter, and the maintenance of warm, frost-free conditions in continental interiors in winter has been a long-standing problem of past equable climates. It has also been found that the high-latitude lapse rate feedback plays an important role in Arctic amplification of climate change in climate model simulations, but we have little understanding of why lapse rates at high latitudes change so strongly with warming. To better understand these problems, we study Arctic air formation - the process by which a high-latitude maritime air mass is advected over a continent during polar night, cooled at the surface by radiation, and transformed into a much colder continental polar air mass - and its sensitivity to climate warming. We use a single-column version of the WRF model to conduct two-week simulations of the cooling process across a wide range of initial temperature profiles and microphysics schemes, and find that a low cloud feedback suppresses Arctic air formation in warmer climates. This cloud feedback consists of an increase in low cloud amount with warming, which shields the surface from radiative cooling, and increases the continental surface air temperature by roughly two degrees for each degree increase of the initial maritime surface air temperature. The time it takes for the surface air temperature to drop below freezing increases nonlinearly to ~10 days for initial maritime surface air temperatures of 20 oC. Given that this is about the time it takes an air mass starting over the Pacific to traverse the north American continent, this suggests that optically thick stratus cloud decks could help to maintain frost-free winter continental interiors in equable climates. We find that CMIP5 climate model runs show large increases in cloud water path and surface cloud longwave forcing in warmer climates, consistent with the proposed low-cloud feedback

  4. Air

    MedlinePlus

    ... do to protect yourself from dirty air . Indoor air pollution and outdoor air pollution Air can be polluted indoors and it can ... this chart to see what things cause indoor air pollution and what things cause outdoor air pollution! Indoor ...

  5. Format and basic geometry of a perspective display of air traffic for the cockpit

    NASA Technical Reports Server (NTRS)

    Mcgreevy, Michael Wallace; Ellis, Stephen R.

    1991-01-01

    The design and implementation of a perspective display of air traffic for the cockpit is discussed. Parameters of the perspective are variable and interactive so that the appearance of the projected image can be widely varied. This approach makes allowances for exploration of perspective parameters and their interactions. The display was initially used to study the cases of horizontal maneuver biases found in experiments involving a plan view air traffic display format. Experiments to determine the effect of perspective geometry on spatial judgements have evolved from the display program. Several scaling techniques and other adjustments to the perspective are used to tailor the geometry for effective presentation of 3-D traffic situations.

  6. Formation of oxygen vacancies and Ti3+ state in TiO2 thin film and enhanced optical properties by air plasma treatment

    PubMed Central

    Bharti, Bandna; Kumar, Santosh; Lee, Heung-No; Kumar, Rajesh

    2016-01-01

    This is the first time we report that simply air plasma treatment can also enhances the optical absorbance and absorption region of titanium oxide (TiO2) films, while keeping them transparent. TiO2 thin films having moderate doping of Fe and Co exhibit significant enhancement in the aforementioned optical properties upon air plasma treatment. The moderate doping could facilitate the formation of charge trap centers or avoid the formation of charge recombination centers. Variation in surface species viz. Ti3+, Ti4+, O2−, oxygen vacancies, OH group and optical properties was studied using X-ray photon spectroscopy (XPS) and UV-Vis spectroscopy. The air plasma treatment caused enhanced optical absorbance and optical absorption region as revealed by the formation of Ti3+ and oxygen vacancies in the band gap of TiO2 films. The samples were treated in plasma with varying treatment time from 0 to 60 seconds. With the increasing treatment time, Ti3+ and oxygen vacancies increased in the Fe and Co doped TiO2 films leading to increased absorbance; however, the increase in optical absorption region/red shift (from 3.22 to 3.00 eV) was observed in Fe doped TiO2 films, on the contrary Co doped TiO2 films exhibited blue shift (from 3.36 to 3.62 eV) due to Burstein Moss shift. PMID:27572095

  7. Formation of oxygen vacancies and Ti(3+) state in TiO2 thin film and enhanced optical properties by air plasma treatment.

    PubMed

    Bharti, Bandna; Kumar, Santosh; Lee, Heung-No; Kumar, Rajesh

    2016-08-30

    This is the first time we report that simply air plasma treatment can also enhances the optical absorbance and absorption region of titanium oxide (TiO2) films, while keeping them transparent. TiO2 thin films having moderate doping of Fe and Co exhibit significant enhancement in the aforementioned optical properties upon air plasma treatment. The moderate doping could facilitate the formation of charge trap centers or avoid the formation of charge recombination centers. Variation in surface species viz. Ti(3+), Ti(4+), O(2-), oxygen vacancies, OH group and optical properties was studied using X-ray photon spectroscopy (XPS) and UV-Vis spectroscopy. The air plasma treatment caused enhanced optical absorbance and optical absorption region as revealed by the formation of Ti(3+) and oxygen vacancies in the band gap of TiO2 films. The samples were treated in plasma with varying treatment time from 0 to 60 seconds. With the increasing treatment time, Ti(3+) and oxygen vacancies increased in the Fe and Co doped TiO2 films leading to increased absorbance; however, the increase in optical absorption region/red shift (from 3.22 to 3.00 eV) was observed in Fe doped TiO2 films, on the contrary Co doped TiO2 films exhibited blue shift (from 3.36 to 3.62 eV) due to Burstein Moss shift.

  8. Formation of oxygen vacancies and Ti3+ state in TiO2 thin film and enhanced optical properties by air plasma treatment

    NASA Astrophysics Data System (ADS)

    Bharti, Bandna; Kumar, Santosh; Lee, Heung-No; Kumar, Rajesh

    2016-08-01

    This is the first time we report that simply air plasma treatment can also enhances the optical absorbance and absorption region of titanium oxide (TiO2) films, while keeping them transparent. TiO2 thin films having moderate doping of Fe and Co exhibit significant enhancement in the aforementioned optical properties upon air plasma treatment. The moderate doping could facilitate the formation of charge trap centers or avoid the formation of charge recombination centers. Variation in surface species viz. Ti3+, Ti4+, O2‑, oxygen vacancies, OH group and optical properties was studied using X-ray photon spectroscopy (XPS) and UV-Vis spectroscopy. The air plasma treatment caused enhanced optical absorbance and optical absorption region as revealed by the formation of Ti3+ and oxygen vacancies in the band gap of TiO2 films. The samples were treated in plasma with varying treatment time from 0 to 60 seconds. With the increasing treatment time, Ti3+ and oxygen vacancies increased in the Fe and Co doped TiO2 films leading to increased absorbance; however, the increase in optical absorption region/red shift (from 3.22 to 3.00 eV) was observed in Fe doped TiO2 films, on the contrary Co doped TiO2 films exhibited blue shift (from 3.36 to 3.62 eV) due to Burstein Moss shift.

  9. Fuel Spray and Flame Formation in a Compression-Ignition Engine Employing Air Flow

    NASA Technical Reports Server (NTRS)

    Rothrock, A M; Waldron, C D

    1937-01-01

    The effects of air flow on fuel spray and flame formation in a high-speed compression-ignition engine have been investigated by means of the NACA combustion apparatus. The process was studied by examining high-speed motion pictures taken at the rate of 2,200 frames a second. The combustion chamber was of the flat-disk type used in previous experiments with this apparatus. The air flow was produced by a rectangular displacer mounted on top of the engine piston. Three fuel-injection nozzles were tested: a 0.020-inch single-orifice nozzle, a 6-orifice nozzle, and a slit nozzle. The air velocity within the combustion chamber was estimated to reach a value of 425 feet a second. The results show that in no case was the form of the fuel spray completely destroyed by the air jet although in some cases the direction of the spray was changed and the spray envelope was carried away by the moving air. The distribution of the fuel in the combustion chamber of a compression-ignition engine can be regulated to some extent by the design of the combustion chamber, by the design of the fuel-injection nozzle, and by the use of air flow.

  10. Secondary organic aerosol formation from photo-oxidation of toluene with NOx and SO2: Chamber simulation with purified air versus urban ambient air as matrix

    NASA Astrophysics Data System (ADS)

    Deng, Wei; Liu, Tengyu; Zhang, Yanli; Situ, Shuping; Hu, Qihou; He, Quanfu; Zhang, Zhou; Lü, Sujun; Bi, Xinhui; Wang, Xuemei; Boreave, Antoinette; George, Christian; Ding, Xiang; Wang, Xinming

    2017-02-01

    Chamber studies on the formation of secondary aerosols are mostly performed with purified air as matrix, it is of wide concern in what extent they might be different from the situations in ambient air, where a variety of gaseous and particulate components preexist. Here we compared the photo-oxidation of "toluene + NOx + SO2" combinations in a smog chamber in real urban ambient air matrix with that in purified air matrix. The secondary organic aerosols (SOA) mass concentrations and yields from toluene in the ambient air matrix, after subtracted ambient air background primary and secondary organic aerosols, were 9.0-34.0 and 5.6-12.9 times, respectively, greater than those in purified air matrix. Both homogeneous and heterogeneous oxidation of SO2 were enhanced in ambient air matrix experiments with observed 2.0-7.5 times higher SO2 degradation rates and 2.6-6.8 times faster sulfate formation than that in purified air matrix, resulting in higher in-situ particle acidity and consequently promoting acid-catalyzed SOA formation. In the ambient air experiments although averaged OH radical levels were elevated probably due to heterogeneous formation of OH on particle surface and/or ozonolysis of alkenes, non-OH oxidation pathways of SO2 became even more dominating. Under the same organic aerosol mass concentration, the SOA yields of toluene in purified air matrix experiments matched very well with the two-product model curve by Ng et al. (2007), yet the yields in ambient air on average was over two times larger. The results however were much near the best fit curve by Hildebrandt et al. (2009) with the volatility basis set (VBS) approach.

  11. Low clouds suppress Arctic air formation and amplify high-latitude continental winter warming

    PubMed Central

    Cronin, Timothy W.; Tziperman, Eli

    2015-01-01

    High-latitude continents have warmed much more rapidly in recent decades than the rest of the globe, especially in winter, and the maintenance of warm, frost-free conditions in continental interiors in winter has been a long-standing problem of past equable climates. We use an idealized single-column atmospheric model across a range of conditions to study the polar night process of air mass transformation from high-latitude maritime air, with a prescribed initial temperature profile, to much colder high-latitude continental air. We find that a low-cloud feedback—consisting of a robust increase in the duration of optically thick liquid clouds with warming of the initial state—slows radiative cooling of the surface and amplifies continental warming. This low-cloud feedback increases the continental surface air temperature by roughly two degrees for each degree increase of the initial maritime surface air temperature, effectively suppressing Arctic air formation. The time it takes for the surface air temperature to drop below freezing increases nonlinearly to ∼10 d for initial maritime surface air temperatures of 20 °C. These results, supplemented by an analysis of Coupled Model Intercomparison Project phase 5 climate model runs that shows large increases in cloud water path and surface cloud longwave forcing in warmer climates, suggest that the “lapse rate feedback” in simulations of anthropogenic climate change may be related to the influence of low clouds on the stratification of the lower troposphere. The results also indicate that optically thick stratus cloud decks could help to maintain frost-free winter continental interiors in equable climates. PMID:26324919

  12. Low clouds suppress Arctic air formation and amplify high-latitude continental winter warming.

    PubMed

    Cronin, Timothy W; Tziperman, Eli

    2015-09-15

    High-latitude continents have warmed much more rapidly in recent decades than the rest of the globe, especially in winter, and the maintenance of warm, frost-free conditions in continental interiors in winter has been a long-standing problem of past equable climates. We use an idealized single-column atmospheric model across a range of conditions to study the polar night process of air mass transformation from high-latitude maritime air, with a prescribed initial temperature profile, to much colder high-latitude continental air. We find that a low-cloud feedback--consisting of a robust increase in the duration of optically thick liquid clouds with warming of the initial state--slows radiative cooling of the surface and amplifies continental warming. This low-cloud feedback increases the continental surface air temperature by roughly two degrees for each degree increase of the initial maritime surface air temperature, effectively suppressing Arctic air formation. The time it takes for the surface air temperature to drop below freezing increases nonlinearly to ∼ 10 d for initial maritime surface air temperatures of 20 °C. These results, supplemented by an analysis of Coupled Model Intercomparison Project phase 5 climate model runs that shows large increases in cloud water path and surface cloud longwave forcing in warmer climates, suggest that the "lapse rate feedback" in simulations of anthropogenic climate change may be related to the influence of low clouds on the stratification of the lower troposphere. The results also indicate that optically thick stratus cloud decks could help to maintain frost-free winter continental interiors in equable climates.

  13. The X-linked intellectual disability protein IL1RAPL1 regulates excitatory synapse formation by binding PTPδ and RhoGAP2.

    PubMed

    Valnegri, Pamela; Montrasio, Chiara; Brambilla, Dario; Ko, Jaewon; Passafaro, Maria; Sala, Carlo

    2011-12-15

    Mutations of the Interleukin-1-receptor accessory protein like 1 (IL1RAPL1) gene are associated with cognitive impairment ranging from non-syndromic X-linked mental retardation to autism. IL1RAPL1 belongs to a novel family of IL1/Toll receptors, which is localized at excitatory synapses and interacts with PSD-95. We previously showed that IL1RAPL1 regulates the synaptic localization of PSD-95 by controlling c-Jun N-terminal kinase activity and PSD-95 phosphorylation. Here, we show that the IgG-like extracellular domains of IL1RAPL1 induce excitatory pre-synapse formation by interacting with protein tyrosine phosphatase delta (PTPδ). We also found that IL1RAPL1 TIR domains interact with RhoGAP2, which is localized at the excitatory post-synaptic density. More interestingly, the IL1RAPL1/PTPδ complex recruits RhoGAP2 at excitatory synapses to induce dendritic spine formation. We also found that the IL1RAPL1 paralog, IL1RAPL2, interacts with PTPδ and induces excitatory synapse and dendritic spine formation. The interaction of the IL1RAPL1 family of proteins with PTPδ and RhoGAP2 reveals a pathophysiological mechanism of cognitive impairment associated with a novel type of trans-synaptic signaling that regulates excitatory synapse and dendritic spine formation.

  14. Secondary organic aerosol formation initiated by α-terpineol ozonolysis in indoor air.

    PubMed

    Yang, Y; Waring, M S

    2016-12-01

    Secondary organic aerosol (SOA) owing to reactive organic gas (ROG) ozonolysis can be an important indoor particle source. However, SOA formation owing to ozonolysis of α-terpineol, which is emitted by consumer product usage and reacts strongly with ozone, has not been systematically quantified. Therefore, we conducted 21 experiments to investigate the SOA formation initiated by α-terpineol ozonolysis for high (0.84 h(-1) ), moderate (0.61 h(-1) ), and low (0.36 h(-1) ) air exchange rates (AER), which is the frequency with which indoor is replaced by outdoor air. α-Terpineol concentrations of 6.39 to 226 ppb were combined with high ozone (~25 ppm) to ensure rapid and complete ozonolysis. No reactants were replenished, so SOA peaked quickly and then decreased due to AER and surface losses, and peak SOA ranged from 2.03 to 281 μg/m(3) at unit density. SOA mass formation was parameterized with the aerosol mass fraction (AMF), a.k.a. the SOA yield, and AMFs ranged from 0.056 to 0.24. The AMFs strongly and positively correlated with reacted α-terpineol, whereas they weakly and negatively correlated with higher AERs. One-product, two-product, and volatility basis set (VBS) models were fit to the AMF data. Predictive modeling demonstrated that α-terpineol ozonolysis could meaningfully form SOA in indoor air.

  15. SU-E-T-777: Use of Tennis Racket and Air Gap Between the Body and Carbon Fiber Couch for Skin Sparing in Radiation Therapy of Prone Breast

    SciTech Connect

    Lief, E

    2015-06-15

    Purpose: To reduce the skin dose from the carbon fiber couch scatter in radiation treatment of breast cancer in the prone position. If this issue is not addressed, the prone breast touching the solid carbon fiber couch can absorb significant dose to the skin and cause the skin reaction. Methods: 1. Use of “tennis racket” instead of the solid couch. To check this hypothesis, we measured the dose at the depth of 5 mm in solid water phantom placed on the couch, using a Farmer chamber. A plan for a patient with 6MV beams, gantry angles of 113 and 286 degrees Varian scale was used. It was found that treatment with “tennis racket” instead of the solid carbon fiber couch reduces the surface dose by 5–7%, depending on the beam direction. 2. Use of the air gap between the couch and the body was analyzed using radiochromic film on the surface of the solid water phantom 10 cm thick. Initially the phantom was placed on the couch with the film sandwiched in between. Two fields at the angles of 135 and 315 degrees were used. The measurements were repeated for the air gap of 2 and 5 cm and 6 and 15 MV beams. Results: It was found that a 2-cm gap decreased the surface dose by 3% for a 6 MV beam and by 5.5% for a 15 MV beam. A 5-cm gap reduced the dose by 9% for 6 MV and 13.5% for 15 MV. Conclusion: Use of both methods (combined if possible) can significantly reduce the surface dose in radiation therapy of the prone breast and possible skin reaction. We plan to explore dependence of the dose reduction upon the angle of incidence.

  16. Wintertime Air Quality Impacts from Oil and Natural Gas Drilling Operations in the Bakken Formation Region

    NASA Astrophysics Data System (ADS)

    Evanoski-Cole, Ashley; Sive, Barkley; Zhou, Yong; Prenni, Anthony; Schurman, Misha; Day, Derek; Sullivan, Amy; Li, Yi; Hand, Jenny; Gebhart, Kristi; Schichtel, Bret; Collett, Jeffrey

    2016-04-01

    Oil and natural gas extraction has dramatically increased in the last decade in the United States due to the increased use of unconventional drilling techniques which include horizontal drilling and hydraulic fracturing. The impact of these drilling activities on local and regional air quality in oil and gas basins across the country are still relatively unknown, especially in recently developed basins such as the Bakken shale formation. This study is the first to conduct a comprehensive characterization of the regional air quality in the Bakken region. The Bakken shale formation, part of the Williston basin, is located in North Dakota and Montana in the United States and Saskatchewan and Manitoba in Canada. Oil and gas drilling operations can impact air quality in a variety of ways, including the generation of atmospheric particulate matter (PM), hazardous air pollutants, ozone, and greenhouse gas emissions. During the winter especially, PM formation can be enhanced and meteorological conditions can favor increased concentrations of PM and other pollutants. In this study, ground-based measurements throughout the Bakken region in North Dakota and Montana were collected over two consecutive winters to gain regional trends of air quality impacts from the oil and gas drilling activities. Additionally, one field site had a comprehensive suite of instrumentation operating at high time resolution to gain detailed characterization of the atmospheric composition. Measurements included organic carbon and black carbon concentrations in PM, the characterization of inorganic PM, inorganic gases, volatile organic compounds (VOCs), precipitation and meteorology. These elevated PM episodes were further investigated using the local meteorological conditions and regional transport patterns. Episodes of elevated concentrations of nitrogen oxides and sulfur dioxide were also detected. The VOC concentrations were analyzed and specific VOCs that are known oil and gas tracers were used

  17. Introduction: Special Issue of Air Quality, Atmosphere and Health for Air Pollution and Health: Bridging the Gap from Source-to-Health Outcomes

    EPA Science Inventory

    The U.S. Environmental Protection Agency has established the National Ambient Air Quality Standards for six principal air pollutants (criteria pollutants): carbon monoxide (CO), lead (Pb), nitrogen dioxide, particulate matter in two size ranges [less than 2.5 μm (PM2.5) and less ...

  18. Formation of quantum spin Hall state on Si surface and energy gap scaling with strength of spin orbit coupling

    DOE PAGES

    Zhou, Miao; Ming, Wenmei; Liu, Zheng; ...

    2014-11-19

    For potential applications in spintronics and quantum computing, it is desirable to place a quantum spin Hall insulator [i.e., a 2D topological insulator (TI)] on a substrate while maintaining a large energy gap. Here, we demonstrate a unique approach to create the large-gap 2D TI state on a semiconductor surface, based on first-principles calculations and effective Hamiltonian analysis. We show that when heavy elements with strong spin orbit coupling (SOC) such as Bi and Pb atoms are deposited on a patterned H-Si(111) surface into a hexagonal lattice, they exhibit a 2D TI state with a large energy gap of ≥0.5more » eV. The TI state arises from an intriguing substrate orbital filtering effect that selects a suitable orbital composition around the Fermi level, so that the system can be matched onto a four-band effective model Hamiltonian. Furthermore, it is found that within this model, the SOC gap does not increase monotonically with the increasing strength of SOC. These interesting results may shed new light in future design and fabrication of large-gap topological quantum states.« less

  19. Formation of quantum spin Hall state on Si surface and energy gap scaling with strength of spin orbit coupling

    SciTech Connect

    Zhou, Miao; Ming, Wenmei; Liu, Zheng; Wang, Zhengfei; Yao, Yugui; Liu, Feng

    2014-11-19

    For potential applications in spintronics and quantum computing, it is desirable to place a quantum spin Hall insulator [i.e., a 2D topological insulator (TI)] on a substrate while maintaining a large energy gap. Here, we demonstrate a unique approach to create the large-gap 2D TI state on a semiconductor surface, based on first-principles calculations and effective Hamiltonian analysis. We show that when heavy elements with strong spin orbit coupling (SOC) such as Bi and Pb atoms are deposited on a patterned H-Si(111) surface into a hexagonal lattice, they exhibit a 2D TI state with a large energy gap of ≥0.5 eV. The TI state arises from an intriguing substrate orbital filtering effect that selects a suitable orbital composition around the Fermi level, so that the system can be matched onto a four-band effective model Hamiltonian. Furthermore, it is found that within this model, the SOC gap does not increase monotonically with the increasing strength of SOC. These interesting results may shed new light in future design and fabrication of large-gap topological quantum states.

  20. Effect of inlet-air humidity on the formation of oxides of nitrogen in a gas-turbine combustor

    NASA Technical Reports Server (NTRS)

    Marchionna, N. R.

    1973-01-01

    Tests were conducted to determine the effect of inlet-air humidity on the formation of oxides of nitrogen from a gas-turbine combustor. Combustor inlet-air temperature ranged from 450 F to 1050 F. The tests were run at a constant pressure of 6 atmospheres and reference Mach number of 0.065. The NO sub x emission index was found to decrease with increasing inlet-air humidity at a constant exponential rate of 19 percent per mass percent water vapor in the air. This decrease of NO sub x emission index with increasing humidity was found to be independent of inlet-air temperature.

  1. In situ observation of peptide bond formation at the water-air interface.

    PubMed

    Griffith, Elizabeth C; Vaida, Veronica

    2012-09-25

    We report unambiguous spectroscopic evidence of peptide bond formation at the air-water interface, yielding a possible mechanism providing insight into the formation of modern ribosomal peptide bonds, and a means for the emergence of peptides on early Earth. Protein synthesis in aqueous environments, facilitated by sequential amino acid condensation forming peptides, is a ubiquitous process in modern biology, and a fundamental reaction necessary in prebiotic chemistry. Such reactions, however, are condensation reactions, requiring the elimination of a water molecule for every peptide bond formed, and are thus unfavorable in aqueous environments both from a thermodynamic and kinetic point of view. We use the hydrophobic environment of the air-water interface as a favorable venue for peptide bond synthesis, and demonstrate the occurrence of this chemistry with in situ techniques using Langmuir-trough methods and infrared reflection absorption spectroscopy. Leucine ethyl ester (a small amino acid ester) first partitions to the water surface, then coordinates with Cu(2+) ions at the interface, and subsequently undergoes a condensation reaction selectively forming peptide bonds at the air-water interface.

  2. Formation and growth of indoor air aerosol particles as a result of D-limonene oxidation

    NASA Astrophysics Data System (ADS)

    Vartiainen, E.; Kulmala, M.; Ruuskanen, T. M.; Taipale, R.; Rinne, J.; Vehkamäki, H.

    Oxidation of D-limonene, which is a common monoterpene, can lead to new aerosol particle formation in indoor environments. Thus, products containing D-limonene, such as citrus fruits, air refresheners, household cleaning agents, and waxes, can act as indoor air aerosol particle sources. We released D-limonene into the room air by peeling oranges and measured the concentration of aerosol particles of three different size ranges. In addition, we measured the concentration of D-limonene, the oxidant, and the concentration of ozone, the oxidizing gas. Based on the measurements we calculated the growth rate of the small aerosol particles, which were 3-10 nm in diameter, to be about 6300nmh-1, and the losses of the aerosol particles that were due to the coagulation and condensation processes. From these, we further approximated the concentration of the condensable vapour and its source rate and then calculated the formation rate of the small aerosol particles. For the final result, we calculated the nucleation rate and the maximum number of molecules in a critical cluster. The nucleation rate was in the order of 105cm-3s-1 and the number of molecules in a critical-sized cluster became 1.2. The results were in agreement with the activation theory.

  3. Quantum many-body intermetallics: Phase stability of Fe3Al and small-gap formation in Fe2VAl

    NASA Astrophysics Data System (ADS)

    Kristanovski, Oleg; Richter, Raphael; Krivenko, Igor; Lichtenstein, Alexander I.; Lechermann, Frank

    2017-01-01

    Various intermetallic compounds harbor subtle electronic correlation effects. To elucidate this fact for the Fe-Al system, we perform a realistic many-body investigation based on a combination of density functional theory with dynamical mean-field theory in a charge self-consistent manner. A better characterization and understanding of the phase stability of bcc-based D 03-Fe3Al through an improved description of the correlated charge density and the magnetic energy is achieved. Upon replacement of one Fe sublattice with V, the Heusler compound Fe2VAl is realized, known to display bad-metal behavior and increased specific heat. Here we document a charge-gap opening at low temperatures in line with previous experimental work. The gap structure does not match conventional band theory and is reminiscent of (pseudo)gap characteristics in correlated oxides.

  4. Electronic Characterization of Defects in Narrow Gap Semiconductors-Comparison of Electronic Energy Levels and Formation Energies in Mercury Cadmium Telluride, Mercury Zinc Telluride, and Mercury Zinc Selenide

    NASA Technical Reports Server (NTRS)

    Patterson, James D.

    1996-01-01

    We have used a Green's function technique to calculate the energy levels and formation energy of deep defects in the narrow gap semiconductors mercury cadmium telluride (MCT), mercury zinc telluride (MZT) and mercury zinc selenide (MZS). The formation energy is calculated from the difference between the total energy with an impurity cluster and the total energy for the perfect crystal. Substitutional (including antisite), interstitial (self and foreign), and vacancy deep defects are considered. Relaxation effects are calculated (with molecular dynamics). By use of a pseudopotential, we generalize the ideal vacancy model so as to be able to consider relaxation for vacancies. Different charge states are considered and the charged state energy shift (as computed by a modified Haldane-Anderson model) can be twice that due to relaxation. Different charged states for vacancies were not calculated to have much effect on the formation energy. For all cases we find deep defects in the energy gap only for cation site s-like orbitals or anion site p-like orbitals, and for the substitutional case only the latter are appreciably effected by relaxation. For most cases for MCT, MZT, MZS, we consider x (the concentration of Cd or Zn) in the range appropriate for a band gap of 0.1 eV. For defect energy levels, the absolute accuracy of our results is limited, but the precision is good, and hence chemical trends are accurately predicted. For the same reason, defect formation energies are more accurately predicted than energy level position. We attempt, in Appendix B, to calculate vacancy formation energies using relatively simple chemical bonding ideas due to Harrison. However, these results are only marginally accurate for estimating vacancy binding energies. Appendix C lists all written reports and publications produced for the grant. We include abstracts and a complete paper that summarizes our work which is not yet available.

  5. Effects of flow on insulin fibril formation at an air/water interface

    NASA Astrophysics Data System (ADS)

    Posada, David; Heldt, Caryn; Sorci, Mirco; Belfort, Georges; Hirsa, Amir

    2009-11-01

    The amyloid fibril formation process, which is implicated in several diseases such as Alzheimer's and Huntington's, is characterized by the conversion of monomers to oligomers and then to fibrils. Besides well-studied factors such as pH, temperature and concentration, the kinetics of this process are significantly influenced by the presence of solid or fluid interfaces and by flow. By studying the nucleation and growth of a model system (insulin fibrils) in a well-defined flow field with an air/water interface, we can identify the flow conditions that impact protein aggregation kinetics both in the bulk solution and at the air/water interface. The present flow system (deep-channel surface viscometer) consists of an annular region bounded by stationary inner and outer cylinders, an air/water interface, and a floor driven at constant rotation. We show the effects of Reynolds number on the kinetics of the fibrillation process both in the bulk solution and at the air/water interface, as well as on the structure of the resultant amyloid aggregates.

  6. Guided Discharge Path by Weak Ionized Region between Two Plasmas Produced by YAG Laser in Atmospheric Air Gap with Non-Uniform DC Electric Field

    NASA Astrophysics Data System (ADS)

    Okano, Daisuke

    1998-11-01

    Guided Discharge Path by Weak Ionized Region between Two Plasmas Produced by YAG Laser in Atmospheric Air Gap with Non-Uniform DC Electric Field*, Daisuke Okano, Kyushu Tokai University, 9-1-1 Toroku, Kumamoto, Japan. -----We have studied on guiding discharge path by weak ionized region between plasmas produced by a visible laser, that is, a YAG laser with wavelength 532nm, in an atmospheric air gap with DC non-uniform electric field using a rod-to-plate electrode. We succeeded in capturing the framing images in the temporal evolution on guiding discharge along the YAG laser light path. From the results of experiments, the region between two plasmas produced by a YAG laser can guide a discharge path, and the region between two plasmas on the laser light path is considered as well as a weak ionized one [1] produced by an excimer laser. [1]J.Sasaki, S.Kubodera, R.Ozaki and T.Uchiyama, J. Appl. Phys., 60 (1986) 3845. *This work was supported by Grant-in-Aid for Scientific Research (C)-no.10650295 of The Ministry of education, Science Sports and Culture in japan.

  7. X-ray and runaway electron generation in repetitive pulsed discharges in atmospheric pressure air with a point-to-plane gap

    SciTech Connect

    Shao Tao; Yan Ping; Tarasenko, Victor F.; Shut'ko, Yuliya V.; Zhang Cheng

    2011-05-15

    In this paper, using two repetitive nanosecond generators, x-rays were detected in atmospheric air with a highly inhomogeneous electric field by a point-to- plane gap. The rise times of the generators were about 15 and 1 ns. The x-rays were directly measured by various dosimeters and a NaI scintillator with a photomultiplier tube. X-rays were detected in the continuous mode at pulse repetition frequency up to 1 kHz and a voltage pulse rise time of {approx}15 ns. It is shown that the maximum x-ray intensity is attainable at different pulse repetition frequencies depending on the voltage pulse parameters and cathode design. In atmospheric pressure air the x-ray intensity is found to increase with increasing the pulse repetition frequency up to 1 kHz. It is confirmed that the maximum x-ray intensity is attained in a diffuse discharge in a point-to-plane gap.

  8. In situ secondary organic aerosol formation from ambient pine forest air using an oxidation flow reactor

    NASA Astrophysics Data System (ADS)

    Palm, Brett B.; Campuzano-Jost, Pedro; Ortega, Amber M.; Day, Douglas A.; Kaser, Lisa; Jud, Werner; Karl, Thomas; Hansel, Armin; Hunter, James F.; Cross, Eben S.; Kroll, Jesse H.; Peng, Zhe; Brune, William H.; Jimenez, Jose L.

    2016-03-01

    An oxidation flow reactor (OFR) is a vessel inside which the concentration of a chosen oxidant can be increased for the purpose of studying SOA formation and aging by that oxidant. During the BEACHON-RoMBAS (Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics & Nitrogen-Rocky Mountain Biogenic Aerosol Study) field campaign, ambient pine forest air was oxidized by OH radicals in an OFR to measure the amount of SOA that could be formed from the real mix of ambient SOA precursor gases, and how that amount changed with time as precursors changed. High OH concentrations and short residence times allowed for semicontinuous cycling through a large range of OH exposures ranging from hours to weeks of equivalent (eq.) atmospheric aging. A simple model is derived and used to account for the relative timescales of condensation of low-volatility organic compounds (LVOCs) onto particles; condensational loss to the walls; and further reaction to produce volatile, non-condensing fragmentation products. More SOA production was observed in the OFR at nighttime (average 3 µg m-3 when LVOC fate corrected) compared to daytime (average 0.9 µg m-3 when LVOC fate corrected), with maximum formation observed at 0.4-1.5 eq. days of photochemical aging. SOA formation followed a similar diurnal pattern to monoterpenes, sesquiterpenes, and toluene+p-cymene concentrations, including a substantial increase just after sunrise at 07:00 local time. Higher photochemical aging (> 10 eq. days) led to a decrease in new SOA formation and a loss of preexisting OA due to heterogeneous oxidation followed by fragmentation and volatilization. When comparing two different commonly used methods of OH production in OFRs (OFR185 and OFR254-70), similar amounts of SOA formation were observed. We recommend the OFR185 mode for future forest studies. Concurrent gas-phase measurements of air after OH oxidation illustrate the decay of primary VOCs, production of small oxidized organic

  9. In situ secondary organic aerosol formation from ambient pine forest air using an oxidation flow reactor

    DOE PAGES

    Palm, Brett B.; Campuzano-Jost, Pedro; Ortega, Amber M.; ...

    2016-03-08

    An oxidation flow reactor (OFR) is a vessel inside which the concentration of a chosen oxidant can be increased for the purpose of studying SOA formation and aging by that oxidant. During the BEACHON-RoMBAS (Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics & Nitrogen–Rocky Mountain Biogenic Aerosol Study) field campaign, ambient pine forest air was oxidized by OH radicals in an OFR to measure the amount of SOA that could be formed from the real mix of ambient SOA precursor gases, and how that amount changed with time as precursors changed. High OH concentrations and short residence times allowed formore » semicontinuous cycling through a large range of OH exposures ranging from hours to weeks of equivalent (eq.) atmospheric aging. A simple model is derived and used to account for the relative timescales of condensation of low-volatility organic compounds (LVOCs) onto particles; condensational loss to the walls; and further reaction to produce volatile, non-condensing fragmentation products. More SOA production was observed in the OFR at nighttime (average 3 µg m−3 when LVOC fate corrected) compared to daytime (average 0.9 µg m−3 when LVOC fate corrected), with maximum formation observed at 0.4–1.5 eq. days of photochemical aging. SOA formation followed a similar diurnal pattern to monoterpenes, sesquiterpenes, and toluene+p-cymene concentrations, including a substantial increase just after sunrise at 07:00 local time. Higher photochemical aging (> 10 eq. days) led to a decrease in new SOA formation and a loss of preexisting OA due to heterogeneous oxidation followed by fragmentation and volatilization. When comparing two different commonly used methods of OH production in OFRs (OFR185 and OFR254-70), similar amounts of SOA formation were observed. We recommend the OFR185 mode for future forest studies. Concurrent gas-phase measurements of air after OH oxidation illustrate the decay of primary VOCs, production of

  10. Shock Separation and Dead-Zone Formation from Detonations in an Internal Air-Well Geometry

    NASA Astrophysics Data System (ADS)

    Molitoris, John; Andreski, Henry; Garza, Raul; Batteux, Jan; Vitello, Peter; Souers, Clark

    2007-06-01

    Here we report on measurements of dead-zone formation due to shock separation from detonations attempting to corner-turn in an internal air-well geometry. This geometry is also known as a ``hockey-puck'' configuration. These measurements were performed on detonations in LX-17 and PBX9502 using time sequence radiography to image the event with surface contact timing pins as an additional diagnostic. In addition to an open corner in the high-explosive component we also examined the effects of steel defining the corner. In these experiments we find a long lived dead-zone consisting of shocked explosive that persists to very late times. Data and numerical modeling will be presented in addition to a comparison with previous work using an external air well. This work was performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.

  11. On the mechanism of zirconium nitride formation by zirconium, zirconia and yttria burning in air

    SciTech Connect

    Malikova, Ekaterina; Pautova, Julia; Gromov, Alexander; Monogarov, Konstantin; Larionov, Kirill; Teipel, Ulrich

    2015-10-15

    The combustion of Zr and (Zr+ZrO{sub 2}) powdery mixtures in air was accompanied by major ZrN stabilization. The synthesis of cheap ZrN with the high yield in air was facile and utile. The influence of Y{sub 2}O{sub 3} additive on the content of ZrN the solid combustion products (SCP) was investigated. The reagents and SCP were analyzed by BET, DTA–TGA, XRD, SEM and EDS. Burning temperature was measured by thermal imager. The yield of ZrN in the SCP has been varied by the time regulation of the combustion process. The burning samples were quenched at a certain time to avoid the re-oxidation of the obtained ZrN by oxygen. The quenching of the burned (Zr+ZrO{sub 2}) samples with the Y{sub 2}O{sub 3} additive was allowed increasing the ZrN yield in SCP up to 66 wt%. The chemical mechanism of ZrN formation in air was discussed and the probable source of ZrN massive formation is suggested. - Highlights: • Combustion of Zr, (Zr+ZrO{sub 2}) and (Zr+ZrO{sub 2}+Y{sub 2}O{sub 3}) powdery mixtures in air was studied. • The new combustion phenomenon has been found: metal (Zr) chemically reacts with its oxide (ZrO{sub 2}) in the burning wave. • The effective influence of Y{sub 2}O{sub 3} additive (2–3 wt%) on ZrN yield in combustion products is shown. • The yield of ZrN in the combustion products can be varied by the burning time regulation (quenching)

  12. The School Age Gender Gap in Reading Achievement: Examining the Influences of Item Format and Intrinsic Reading Motivation

    ERIC Educational Resources Information Center

    Schwabe, Franziska; McElvany, Nele; Trendtel, Matthias

    2015-01-01

    The importance of reading competence for both individuals and society underlines the strong need to understand the gender gap in reading achievement. Beyond mean differences in reading comprehension, research has indicated that girls possess specific advantages on constructed-response items compared with boys of the same reading ability. Moreover,…

  13. Biofilm formation at the solid-liquid and air-liquid interfaces by Acinetobacter species

    PubMed Central

    2011-01-01

    Background The members of the genus Acinetobacter are Gram-negative cocobacilli that are frequently found in the environment but also in the hospital setting where they have been associated with outbreaks of nosocomial infections. Among them, Acinetobacter baumannii has emerged as the most common pathogenic species involved in hospital-acquired infections. One reason for this emergence may be its persistence in the hospital wards, in particular in the intensive care unit; this persistence could be partially explained by the capacity of these microorganisms to form biofilm. Therefore, our main objective was to study the prevalence of the two main types of biofilm formed by the most relevant Acinetobacter species, comparing biofilm formation between the different species. Findings Biofilm formation at the air-liquid and solid-liquid interfaces was investigated in different Acinetobacter spp. and it appeared to be generally more important at 25°C than at 37°C. The biofilm formation at the solid-liquid interface by the members of the ACB-complex was at least 3 times higher than the other species (80-91% versus 5-24%). In addition, only the isolates belonging to this complex were able to form biofilm at the air-liquid interface; between 9% and 36% of the tested isolates formed this type of pellicle. Finally, within the ACB-complex, the biofilm formed at the air-liquid interface was almost 4 times higher for A. baumannii and Acinetobacter G13TU than for Acinetobacter G3 (36%, 27% & 9% respectively). Conclusions Overall, this study has shown the capacity of the Acinetobacter spp to form two different types of biofilm: solid-liquid and air-liquid interfaces. This ability was generally higher at 25°C which might contribute to their persistence in the inanimate hospital environment. Our work has also demonstrated for the first time the ability of the members of the ACB-complex to form biofilm at the air-liquid interface, a feature that was not observed in other

  14. Involvement of the adrenal glands and testis in gap junction formation via testosterone within the male rat anterior pituitary gland.

    PubMed

    Sakuma, Eisuke; Wada, Ikuo; Otsuka, Takanobu; Wakabayashi, Kenjiro; Ito, Kinya; Soji, Tsuyoshi; Herbert, Damon C

    2012-12-01

    We investigated the influence of testicular and adrenal androgens on the presence of gap junctions between folliculo-stellate cells in the anterior pituitary glands of 60-day-old Wistar-Imamichi strain male rats. The animals were separated into six groups: Group A served as the controls and had free access to a normal diet and water, Group B was given a normal diet and 0.9% NaCl for their drinking water as the controls of adrenalectomized groups, Group C was castrated, Group D was adrenalectomized, Group E was both castrated and adrenalectomized, and Group F was also both castrated and adrenalectomized. In addition, the animals of Group F were administered a dose of testosterone that is known to produce high physiological levels of the hormones in plasma. Five rats from each group were sacrificed 1, 2, 3, 4, 5, 6, and 7 days after their respective operation, and the anterior pituitary glands were removed and prepared for observation by transmission electron microscopy. We quantified the number of follicles and gap junctions and calculated the rate of occurrence as the ratio of the number of gap junctions existing between folliculo-stellate cells per intersected follicle profile. Simultaneous removal of adrenal glands with castration resulted in a significantly decrease in the number of gap junctions, whereas the administration of testosterone to these rats compensated for this change. These observations indicate that the preservation of gap junctions between folliculo-stellate cells is mainly dependent on androgens from both the testes and adrenal glands in adult male rats.

  15. Indirect effects of emerald ash borer-induced ash mortality and canopy gap formation on epigaeic beetles.

    PubMed

    Gandhi, Kamal J K; Smith, Annemarie; Hartzler, Diane M; Herms, Daniel A

    2014-06-01

    Exotic herbivorous insects have drastically and irreversibly altered forest structure and composition of North American forests. For example, emerald ash borer (Agrilus planipennis Fairmaire) from Asia has caused wide-scale mortality of ash trees (Fraxinus spp.) in eastern United States and Canada. We studied the effects of forest changes resulting from emerald ash borer invasion on epigaeic or ground beetles (Coleoptera: Carabidae) along a gradient of ash dieback and gap sizes in southeastern Michigan. Ground beetles were sampled in hydric, mesic, and xeric habitats in which black (Fraxinus nigra Marshall), green (Fraxinus pennsylvanica Marshall), and white (Fraxinus americana L.) ash were the most common species, respectively. During 2006-2007, we trapped 2,545 adult ground beetles comprising 52 species. There was a negative correlation between percent ash tree mortality in 2006 and catches of all beetles. Catches of Agonum melanarium Dejean (in 2006) and Pterostichus mutus (Say) (in 2006-2007) were negatively correlated with tree mortality and gap size, respectively. However, catches of Pterostichus corvinus Dejean were positively correlated with gap size in 2006. As ash mortality and average gap size increased from 2006 to 2007, catches of all beetles as well as P. mutus and Pterostichus stygicus (Say) increased (1.3-3.9 times), while species diversity decreased, especially in mesic and xeric stands. Cluster analysis revealed that beetle assemblages in hydric and mesic stand diverged (25 and 40%, respectively) in their composition from 2006 to 2007, and that hydric stands had the most unique beetle assemblages. Overall, epigaeic beetle assemblages were altered in ash stands impacted by emerald ash borer; however, these impacts may dissipate as canopy gaps close.

  16. Soot Formation in Laminar Acetylene/Air Diffusion Flames at Atmospheric Pressure. Appendix H

    NASA Technical Reports Server (NTRS)

    Xu, F.; Faeth, G. M.; Yuan, Z.-G. (Technical Monitor); Urban, D. L. (Technical Monitor); Yuan, Z.-G. (Technical Monitor)

    2001-01-01

    The flame structure and soot-formation (soot nucleation and growth) properties of axisymmetric laminar coflowing jet diffusion flames were studied experimentally. Test conditions involved acetylene-nitrogen jets burning in coflowing air at atmospheric pressure. Measurements were limited to the axes of the flames and included soot concentrations, soot temperatures, soot structure, major gas species concentrations, radical species (H, OH, and O) concentrations, and gas velocities. The results show that as distance increases along the axes of the flames, detectable soot formation begins when significant H concentrations are present, and ends when acetylene concentrations become small. Species potentially associated with soot oxidation-O2, CO2, H2O, O, and OH-are present throughout the soot-formation region so that soot formation and oxidation proceed at the same time. Strong rates of soot growth compared to soot nucleation early in the soot-formation process, combined with increased rates of soot nucleation and oxidation as soot formation proceeds, causes primary soot particle diameters to reach a maximum relatively early in the soot-formation process. Aggregation of primary soot particles proceeds, however, until the final stages of soot oxidation. Present measurements of soot growth (corrected for soot oxidation) in laminar diffusion flames were consistent with earlier measurements of soot growth in laminar premixed flames and exhibited encouraging agreement with existing hydrogen-abstraction/carbon-addition (HACA) soot growth mechanisms in the literature that were developed based on measurements within laminar premixed flames. Measured primary soot particle nucleation rates in the present laminar diffusion flames also were consistent with corresponding rates measured in laminar premixed flames and yielded a crude correlation in terms of acetylene and H concentrations and the temperature.

  17. Soot Formation in Laminar Acetylene/Air Diffusion Flames at Atmospheric Pressure. Appendix J

    NASA Technical Reports Server (NTRS)

    Xu, F.; Faeth, G. M.; Urban, D. L. (Technical Monitor); Yuan, Z.-G. (Technical Monitor)

    2001-01-01

    The flame structure and soot-formation (soot nucleation and growth) properties of axisymmetric laminar coflowing jet diffusion flames were studied experimentally. Test conditions involved acetylene-nitrogen jets burning in coflowing air at atmospheric pressure. Measurements were limited to the axes of the flames and included soot concentrations, soot temperatures, soot structure, major gas species concentrations, radical species (H, OH, and O) concentrations, and gas velocities. The results show that as distance increases along the axes of the flames, detectable soot formation begins when significant H concentrations are present, and ends when acetylene concentrations become small. Species potentially associated with soot oxidation--O2, CO2, H2O, O, and OH-are present throughout the soot-formation region so that soot formation and oxidation proceed at the same time. Strong rates of soot growth compared to soot nucleation early in the soot-formation process, combined with increased rates of soot nucleation and oxidation as soot formation proceeds, causes primary soot particle diameters to reach a maximum relatively early in the soot-formation process. Aggregation of primary soot particles proceeds, however, until the final stages of soot oxidation. Present measurements of soot growth (corrected for soot oxidation) in laminar diffusion flames were consistent with earlier measurements of soot growth in laminar premixed flames and exhibited encouraging agreement with existing hydrogen-abstraction/carbon-addition (HACA) soot growth mechanisms in the literature that were developed based on measurements within laminar premixed flames. Measured primary soot particle nucleation rates in the present laminar diffusion flames also were consistent with corresponding rates measured in laminar premixed flames and yielded a crude correlation in terms of acetylene and H concentrations and the temperature.

  18. Soot Formation in Laminar Acetylene/Air Diffusion Flames at Atmospheric Pressure. Appendix C

    NASA Technical Reports Server (NTRS)

    Xu, F.; Faeth, G. M.; Urban, D. L. (Technical Monitor); Yuan, Z.-G. (Technical Monitor)

    2000-01-01

    The flame structure and soot-formation (soot nucleation and growth) properties of axisymmetric laminar coflowing jet diffusion flames were studied experimentally. Test conditions involved acetylene-nitrogen jets burning in coflowing air at atmospheric pressure. Measurements were limited to the axes of the flames and included soot concentrations, soot temperatures, soot structure, major gas species concentrations, radical species (H, OH, and O) concentrations, and gas velocities. The results show that as distance increases along the axes of the flames, detectable soot formation begins when significant H concentrations are present, and ends when acetylene concentrations become small. Species potentially associated with soot oxidation-O2, CO2, H2O, O, and OH-are present throughout the soot-formation region so that soot formation and oxidation proceed at the same time. Strong rates of soot growth compared to soot nucleation early in the soot-formation process, combined with increased rates of soot nucleation and oxidation as soot formation proceeds, causes primary soot particle diameters to reach a maximum relatively early in the soot-formation process. Aggregation of primary soot particles proceeds, however, until the final stages of soot oxidation. Present measurements of soot growth (corrected for soot oxidation) in laminar diffusion flames were consistent with earlier measurements of soot growth in laminar premixed flames and exhibited encouraging agreement with existing hydrogen-abstraction/carbon-addition (HACA) soot growth mechanisms in the literature that were developed based on measurements within laminar premixed flames. Measured primary soot particle nucleation rates in the present laminar diffusion flames also were consistent with corresponding rates measured in laminar premixed flames and yielded a crude correlation in terms of acetylene and H concentrations and the temperature.

  19. Formation of calcium in the products of iron oxide-aluminum thermite combustion in air

    NASA Astrophysics Data System (ADS)

    Gromov, A. A.; Gromov, A. M.; Popenko, E. M.; Sergienko, A. V.; Sabinskaya, O. G.; Raab, B.; Teipel, U.

    2016-10-01

    The composition of condensed products resulting from the combustion of thermite mixtures (Al + Fe2O3) in air is studied by precise methods. It is shown that during combustion, calcium is formed and stabilized in amounts of maximal 0.55 wt %, while is missing from reactants of 99.7 wt % purity. To explain this, it is hypothesized that a low-energy nuclear reaction takes place alongside the reactions of aluminum oxidation and nitridation, resulting in the formation of calcium (Kervran-Bolotov reaction).

  20. Advection fog formation and aerosols produced by combustion-originated air pollution

    NASA Technical Reports Server (NTRS)

    Hung, R. J.; Liaw, G. S.; Vaughan, O. H., Jr.

    1980-01-01

    The way in which pollutants produced by the photochemical reaction of NO(X) and SO(X) affect the quality of the human environment through such phenomena as the formation of advection fog is considered. These pollutants provide the major source of condensation nuclei for the formation of fog in highways, airports and seaports. Results based on the monodisperse, multicomponent aerosol model show that: (1) condensation nuclei can grow and form a dense fog without the air having attained supersaturation; (2) the mass concentration range for NO(X) is one-third that of SO(X); and (3) the greater the mass concentration, the particle concentration, and the radius of condensation nuclei, the denser the fog that is formed.

  1. Relation between crust development and heterocyclic aromatic amine formation when air-roasting a meat cylinder.

    PubMed

    Kondjoyan, Alain; Chevolleau, Sylvie; Portanguen, Stéphane; Molina, Jérôme; Ikonic, Predrag; Clerjon, Sylvie; Debrauwer, Laurent

    2016-12-15

    The meat crust that develops during cooking is desired by consumers for its organoleptic properties, but it is also where heterocyclic aromatic amines (HAs) are formed. Here we measured HAs formation during the development of a colored crust on the surface of a beef meat piece. HAs formation was lower in the crust than previously measured in meat slices subjected to the same air jet conditions. This difference is explained by a lower average temperature in the colored crust than in the meat slices. Temperature effects can also explain why colored crust failed to reproduce the plateauing and decrease in HAs content observed in meat slices. We observed a decrease in creatine content from the center of the meat piece to the crust area. In terms of the implications for practice, specific heating conditions can be found to maintain a roast beef meat aspect while dramatically reducing HAs content.

  2. The influence of gravity levels on soot formation for the combustion of ethylene-air mixture

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Liu, D.; Li, S.; Li, Y.; Lou, C.

    2014-12-01

    The reduced mechanism coupled with 2D flame code using CHEMKIN II to investigate the effect of gravity on flame structure and soot formation in diffusion flames. The results show that the gravity has a rather significant effect on flame structure and soot formation. The visible flame height and peak soot volume fraction in general increases with the gravity from 1 g decreased to 0 g. The peak flame temperature decreases with decreasing gravity level. Comparing the calculated results from 1 g to 0 g, the flame shape becomes wider, the high temperature zone becomes shorter, the mixture velocity has a sharp decrease, the soot volume fraction has a sharp increase and CO and unprovided species distribution becomes wider along radial direction. At normal and half gravity, the flame is buoyancy controlled and the axial velocity is largely independent of the coflow air velocity. At microgravity (0 g), the flame is momentum controlled.

  3. The role of heparan sulfate deficiency in autistic phenotype: potential involvement of Slit/Robo/srGAPs-mediated dendritic spine formation.

    PubMed

    Pérez, Christine; Sawmiller, Darrell; Tan, Jun

    2016-04-18

    Autism Spectrum Disorders (ASD) are the second most common developmental cause of disability in the United States. ASDs are accompanied with substantial economic and emotional cost. The brains of ASD patients have marked structural abnormalities, in the form of increased dendritic spines and decreased long distance connections. These structural differences may be due to deficiencies in Heparin Sulfate (HS), a proteoglycan involved in a variety of neurodevelopmental processes. Of particular interest is its role in the Slit/Robo pathway. The Slit/Robo pathway is known to be involved in the regulation of axonal guidance and dendritic spine formation. HS mediates the Slit/Robo interaction; without its presence Slit's repulsive activity is abrogated. Slit/Robo regulates dendritic spine formation through its interaction with srGAPs (slit-robo GTPase Activating Proteins), which leads to downstream signaling, actin cytoskeleton depolymerization and dendritic spine collapse. Through interference with this pathway, HS deficiency can lead to excess spine formation.

  4. Clinical, histologic, cytologic, and ultrastructural characteristics of the oral lesions from hereditary mucoepithelial dysplasia. A disease of gap junction and desmosome formation.

    PubMed

    Witkop, C J; White, J G; Sauk, J J; King, R A

    1978-11-01

    Hereditary mucoepithelial dysplasia is an autosomal, dominantly inherited disorder affecting all of the orificial mucosa with cataracts, follicular keratosis of skin, nonscarring alopecia, bouts of pneumonia, spontaneous pneumothorax, and terminal cor pulmonale. The oral lesion is a fiery red, flat or micropapillary-appearing mucosa most frequently involving the gingiva and hard palate. All oral and pharyngeal mucosa may be involved, however. Red scrotal mucosa of the tongue is common. Histologically, the oral mucosa shows a lack of cornified and keratinized cells, a decrease in the thickness of the epithelial cell layer, dyshesion, and dyskeratosis. Papanicolaou smears show lack of epithelial cell maturation, poikilocytosis, anisocytosis, large paranuclear cytoplasmic vacuoles, and cytoplasmic strand-shaped inclusions. Ultrastructural features include a paucity of desmosomes, intercellular accumulations of amorphous material, cytoplasmic vacuoles, and paranuclear lesions with strands of material resembling gap junctions and desmosomes. The condition most likely represents a basic defect in gap junction and desmosome formation.

  5. A Feasibility Study on Operating Large Scale Compressed Air Energy Storage in Porous Formations

    NASA Astrophysics Data System (ADS)

    Wang, B.; Pfeiffer, W. T.; Li, D.; Bauer, S.

    2015-12-01

    Compressed air energy storage (CAES) in porous formations has been considered as one promising option of large scale energy storage for decades. This study, hereby, aims at analyzing the feasibility of operating large scale CAES in porous formations and evaluating the performance of underground porous gas reservoirs. To address these issues quantitatively, a hypothetic CAES scenario with a typical anticline structure in northern Germany was numerically simulated. Because of the rapid growth in photovoltaics, the period of extraction in a daily cycle was set to the early morning and the late afternoon in order to bypass the massive solar energy production around noon. The gas turbine scenario was defined referring to the specifications of the Huntorf CAES power plant. The numerical simulations involved two stages, i.e. initial fill and cyclic operation, and both were carried out using the Eclipse E300 simulator (Schlumberger). Pressure loss in the gas wells was post analyzed using an analytical solution. The exergy concept was applied to evaluate the potential energy amount stored in the specific porous formation. The simulation results show that porous formations prove to be a feasible solution of large scale CAES. The initial fill with shut-in periods determines the spatial distribution of the gas phase and helps to achieve higher gas saturation around the wells, and thus higher deliverability. The performance evaluation shows that the overall exergy flow of stored compressed air is also determined by the permeability, which directly affects the deliverability of the gas reservoir and thus the number of wells required.

  6. Air Force Officer Accession Planning: Addressing Key Gaps in Meeting Career Field Academic Degree Requirements for Nonrated Officers

    DTIC Science & Technology

    2016-06-09

    Integration and AF/A1P Force Management Policy and conducted within the Manpower, Personnel, and Training Program of RAND Project AIR FORCE as part...website: http://www.rand.org/paf/ iv Table of Contents Preface...Nonrated Line OR Production ................................................................................. 56 7.10. History, Foreign Language

  7. Ammonia sources in the California South Coast Air Basin and their impact on ammonium nitrate formation

    NASA Astrophysics Data System (ADS)

    Nowak, J. B.; Neuman, J. A.; Bahreini, R.; Middlebrook, A. M.; Holloway, J. S.; McKeen, S. A.; Parrish, D. D.; Ryerson, T. B.; Trainer, M.

    2012-04-01

    Observations from the NOAA WP-3D aircraft during CalNex in May and June 2010 are used to quantify ammonia (NH3) emissions from automobiles and dairy facilities in the California South Coast Air Basin (SoCAB) and assess their impact on particulate ammonium nitrate (NH4NO3) formation. These airborne measurements in the SoCAB are used to estimate automobile NH3 emissions, 62 ± 24 metric tons day-1, and dairy facility NH3 emissions, 33 ± 16 to 176 ± 88 metric tons day-1. Emission inventories agree with the observed automobile NH3:CO emission ratio, but substantially underpredict dairy facility NH3 emissions. Conditions observed downwind of the dairy facilities were always thermodynamically favorable for NH4NO3 formation due to high NH3 mixing ratios from the concentrated sources. Although automobile emissions generated lower NH3 mixing ratios, they also can thermodynamically favor NH4NO3 formation. As an aerosol control strategy, addressing the dairy NH3 source would have the larger impact on reducing SoCAB NH4NO3 formation.

  8. Towards a regional passive air sampling network and strategy for new POPs in the GRULAC region: Perspectives from the GAPS Network and first results for organophosphorus flame retardants.

    PubMed

    Rauert, Cassandra; Harner, Tom; Schuster, Jasmin K; Quinto, Karen; Fillmann, Gilberto; Castillo, Luisa Eugenia; Fentanes, Oscar; Ibarra, Martín Villa; Miglioranza, Karina S B; Rivadeneira, Isabel Moreno; Pozo, Karla; Puerta, Andrea Padilla; Zuluaga, Beatriz Helena Aristizábal

    2016-12-15

    A discussion is presented on the limitations for air monitoring studies around the Group of Latin American and Caribbean Countries (GRULAC), highlighting key issues requiring further attention, and reports on how a special initiative is addressing these limitations. Preliminary results are presented for the first reported data on organophosphorus flame retardant (OPFR) concentrations in outdoor air from the GRULAC region. At the majority of sites the concentrations and the profile of the OPFRs detected were similar with tris (chloroisopropyl) phosphate (TCPP) dominating (air levels. This preliminary study of only 7 sites highlights how extensive regional passive sampling networks (such as GAPS) can provide important new information to support risk assessment of these and similar chemicals. Finally, the various challenges with implementing a regional monitoring program are discussed, including harmonizing data from various monitoring programs for reporting to the GMP.

  9. Biofilm Formation Derived from Ambient Air and the Characteristics of Apparatus

    NASA Astrophysics Data System (ADS)

    Kanematsu, H.; Kougo, H.; Kuroda, D.; Itho, H.; Ogino, Y.; Yamamoto, Y.

    2013-04-01

    Biofilm is a kind of thin film on solidified matters, being derived from bacteria. Generally, planktonic bacteria float in aqueous environments, soil or air, most of which can be regarded as oligotrophic environments. Since they have to survive by instinct, they seek for nutrients that would exist on materials surfaces as organic matters. Therefore, bacteria attach materials surfaces reversibly. The attachment and detachment repeat for a while and finally, they attach on them irreversibly and the number of bacteria on them increases. At a threshold number, bacteria produce polymeric matters at the same time by quorum sensing mechanism and the biofilm produces on material surfaces. The biofilm produced in that way generally contains water (more than 80%), EPS (Exopolymeric Substance) and bacteria themselves. And they might bring about many industrial problems, fouling, corrosion etc. Therefore, it is very important for us to control and prevent the biofilm formation properly. However, it is generally very hard to produce biofilm experimentally and constantly in ambient atmosphere on labo scale. The authors invented an apparatus where biofilm could form on specimen's surfaces from house germs in the ambient air. In this experiment, we investigated the basic characteristics of the apparatus, reproducibility, the change of biofilm with experimental time, the quality change of water for biofilm formation and their significance for biofilm research.

  10. The relationship between ozone formation and air temperature in the atmospheric surface layer

    NASA Astrophysics Data System (ADS)

    Belan, Boris D.; Savkin, Denis; Tolmachev, Gennadii

    2016-04-01

    Studying the formation and dynamics of ozone in the atmosphere is important due to several reasons. First, the contribution of tropospheric ozone to the global greenhouse effect is only slightly less than that of water vapor, carbon dioxide, and methane. Second, tropospheric ozone acts as a strong poison that has negative effects on human health, animals, and vegetation. Third, being a potent oxidizer, ozone destroys almost all materials, including platinum group metals and compounds. Fourthly, ozone is formed in situ from precursors as a result of photochemical processes, but not emitted into the atmosphere by any industrial enterprises directly. In this work, we present some results of the study aimed at the revealing relationship between ozone formation rate and surface air temperature in the background atmosphere. It has been found that this relationship is nonlinear. Analysis of the possible reasons showed that the nonlinear character of this relationship may be due to a nonlinear increase in the reaction constants versus air temperature and a quadratic increase in the concentration of hydrocarbons with increasing temperature. This work was supported by the Ministry of Education and Science contract no.14.613.21.0013 (ID: RFMEFI61314X0013).

  11. Effect of nitric oxide on photochemical ozone formation in mixtures of air with molecular chlorine and with trichlorofluoromethane

    NASA Technical Reports Server (NTRS)

    Bittker, D. A.; Wong, E. L.

    1978-01-01

    Ozone formation in a reaction chamber at room temperature and atmospheric pressure were studied for the photolysis of mixtures of NO with either Cl2 or CFCl3 in air. Both Cl2 + NO and CFCl3 + NO in air strongly inhibited O3 formation during the entire 3 to 4 hour reaction. A chemical mechanism that explains the results was presented. An important part of this mechanism was the formation and destruction of chlorine nitrate. Computations were performed with this same mechanism for CFCl3-NO-air mixtures at stratospheric temperatures, pressures, and concentrations. Results showed large reductions in steady-state O3 concentrations in these mixtures as compared with pure air.

  12. In vitro apatite formation on nano-crystalline titania layer aligned parallel to Ti6Al4V alloy substrates with sub-millimeter gap.

    PubMed

    Hayakawa, Satoshi; Matsumoto, Yuko; Uetsuki, Keita; Shirosaki, Yuki; Osaka, Akiyoshi

    2015-06-01

    Pure titanium substrates were chemically oxidized with H2O2 and subsequent thermally oxidized at 400 °C in air to form anatase-type titania layer on their surface. The chemically and thermally oxidized titanium substrate (CHT) was aligned parallel to the counter specimen such as commercially pure titanium (cpTi), titanium alloy (Ti6Al4V) popularly used as implant materials or Al substrate with 0.3-mm gap. Then, they were soaked in Kokubo's simulated body fluid (SBF, pH 7.4, 36.5 °C) for 7 days. XRD and SEM analysis showed that the in vitro apatite-forming ability of the contact surface of the CHT specimen decreased in the order: cpTi > Ti6Al4V > Al. EDX and XPS surface analysis showed that aluminum species were present on the contact surface of the CHT specimen aligned parallel to the counter specimen such as Ti6Al4V and Al. This result indicated that Ti6Al4V or Al specimens released the aluminum species into the SBF under the spatial gap. The released aluminum species might be positively or negatively charged in the SBF and thus can interact with calcium or phosphate species as well as titania layer, causing the suppression of the primary heterogeneous nucleation and growth of apatite on the contact surface of the CHT specimen under the spatial gap. The diffusion and adsorption of aluminum species derived from the half-sized counter specimen under the spatial gap resulted in two dimensionally area-selective deposition of apatite particles on the contact surfaces of the CHT specimen.

  13. In depth analysis of the role of the mountain gap south of the Valley of Mexico on the air quality in Mexico City.

    NASA Astrophysics Data System (ADS)

    Gerardo Ruiz Suarez, Luis

    2010-05-01

    38 days of air quality observations in Tenango del Aire (TENAI), south of Mexico City during MILAGRO were analyzed. That site was managed by FQA-CCA-UNAM's team with a mobile laboratory equipped with standard air quality monitors: O3, NOx, NOy, CO, SO2 and surface meteorological parameters. Hosted additional instruments were: CH2O, column NO2 (DOAS), backscatter (Lidar) and pilot balloons. Also, an ultra light plane from IMK-IFU, equipped with O3, PM10, CN, Dew Point monitors flew around the Popocatepetl and Iztaccihuatl volcanoes and above of TENAI some days during MILAGRO. Atop of TENAI, the ultra light descended in spiral until near ground and ascended to resume its path. In addition to these measurements, UNAM team ran air quality numerical simulations using the Mesoscale Climate and Chemistry Model (MCCM) and an online coupled Wind Erosion Processor to MCCM we call WEPS-MCCM. The combined observations on the ground, the ultra light plane and the models results enabled us to carry out an in depth analysis of air quality in such important region south of Mexico City. Comparison were made with the episodes classification proposed by De Foy; Ozone North and South, Convection North and South, Cold Surge and South Venting to characterize dynamics in the Valley of Mexico. The aim was to define how well connected is TENAI with the air quality network in the MCMA. The influence of the mountain gap on ozone and PM10 levels in Mexico City is analyzed by episode type. Also, the impact of the mega city of Mexico on the nearby region to the south can be understood by observations in TENAI. More polluted episode types in TENAI are those called: Cold Surge, Ozone South and South Venting due to a wind shift occurring in early afternoon that brings back polluted air that was drained south during the morning and returns back to TENAI rich in aged air parcels. March 17 was chosen to show the integrated analysis of all variables observed and modeled (MCCM) in TENAI. In that day

  14. Electronic characterization of defects in narrow gap semiconductors: Comparison of electronic energy levels and formation energies in mercury cadmium telluride, mercury zinc telluride, and mercury zinc selenide

    NASA Astrophysics Data System (ADS)

    Patterson, James D.; Li, Wei-Gang

    1995-03-01

    The project has evolved to that of using Green's functions to predict properties of deep defects in narrow gap materials. Deep defects are now defined as originating from short range potentials and are often located near the middle of the energy gap. They are important because they affect the lifetime of charge carriers and hence the switching time of transistors. We are now moving into the arena of predicting formation energies of deep defects. This will also allow us to make predictions about the relative concentrations of the defects that could be expected at a given temperature. The narrow gap materials mercury cadmium telluride (MCT), mercury zinc telluride (MZT), and mercury zinc selenide (MZS) are of interest to NASA because they have commercial value for infrared detecting materials, and because there is a good possibility that they can be grown better in a microgravity environment. The uniform growth of these crystals on earth is difficult because of convection (caused by solute depletion just ahead of the growing interface, and also due to thermal gradients). In general it is very difficult to grow crystals with both radial and axial homogeneity.

  15. Electronic characterization of defects in narrow gap semiconductors: Comparison of electronic energy levels and formation energies in mercury cadmium telluride, mercury zinc telluride, and mercury zinc selenide

    NASA Technical Reports Server (NTRS)

    Patterson, James D.; Li, Wei-Gang

    1995-01-01

    The project has evolved to that of using Green's functions to predict properties of deep defects in narrow gap materials. Deep defects are now defined as originating from short range potentials and are often located near the middle of the energy gap. They are important because they affect the lifetime of charge carriers and hence the switching time of transistors. We are now moving into the arena of predicting formation energies of deep defects. This will also allow us to make predictions about the relative concentrations of the defects that could be expected at a given temperature. The narrow gap materials mercury cadmium telluride (MCT), mercury zinc telluride (MZT), and mercury zinc selenide (MZS) are of interest to NASA because they have commercial value for infrared detecting materials, and because there is a good possibility that they can be grown better in a microgravity environment. The uniform growth of these crystals on earth is difficult because of convection (caused by solute depletion just ahead of the growing interface, and also due to thermal gradients). In general it is very difficult to grow crystals with both radial and axial homogeneity.

  16. Characterization of the NOx-Ox relationship in a mountain gap rural area of interchange of air masses southeast of the Metropolitan Area of Mexico City

    NASA Astrophysics Data System (ADS)

    Ruiz Suarez, L.; Garcia-Yee, J.; Torres-JArdon, R.; Barrera Huertas, H.; Torres-Jaramillo, A.; Ortinez, A.

    2013-05-01

    Varying levels of oxidants (Ox = O3 + NO2) with respect to NOx were registered at three sites in a mountain southeast of the Mexico City Metropolitan Area (MCMA) in February and March 2011. The Ox-NOx ratio was used to gain a better understanding of the photochemical and transport processes happening over this mountain pass. Relatively high concentrations of O3 (moving average concentrations of 8 hours) exceeded maximum levels of the World Health Organization, and the European Union. The cumulative exceedances above background level of O3 in the one month-long campaign also exceeded the three months accumulative UN-ECE AOT40 critical level for crop protection. It was observed that the level of Ox in the mountain gap sites consisted of two contributions: One, independent of NOx emissions, extremely dominant and considered equivalent to the regional background O3 concentration; the second and much smaller was dependent of NOx local concentrations. Evidence was found that the oxidation of NO provided the major contribution of NO2 to Ox, rather than direct NO2 emissions. The contribution of regional Ox dominated from midmorning to noon when the boundary layer height began to increase due to sunlight heating of the surface leading to the mixing of higher concentrations of O3 above the nighttime thermal inversion. After noon, when the ozone vertical distribution was uniform, the Ox and O3 concentrations reached their maximum; they were very similar with very low levels of NO2. The analysis of wind data collected at the monitoring sites showed that from mid-morning to early afternoon, a northerly weak flow was common. Afterwards stronger southerly winds became dominant bringing in O3 rich air parcels into the atmospheric basin where MCMA is located. The high regional ozone concentrations add evidence for the need of coordinated air quality management policies for the complete central part of Mexico. Keywords: mountain gap, oxidant, ground level ozone, Central Mexico

  17. Gas heating effects on the formation and propagation of a microwave streamer in air

    NASA Astrophysics Data System (ADS)

    Kourtzanidis, Konstantinos; Rogier, François; Boeuf, Jean-Pierre

    2015-09-01

    The development of microwave plasma streamers at 110 GHz in atmospheric pressure air is numerically investigated taking into account the intense gas heating and its effects on the plasma formation and dynamics. The simulations are based on an implicit finite difference time domain formulation of Maxwell's equations coupled with a simple plasma fluid model and a real gas Euler equation solver. The numerical results show how the formation of a shock wave due to the large microwave power absorbed by the plasma and converted into gas heating strongly modifies the streamer elongation and dynamics. A microwave streamer filament stretches along its axis because of ionization-diffusion mechanisms in the enhanced electric field at the streamer tips. The change in the gas density distribution associated with the formation of shock wave due to gas heating strongly modifies the ionization and diffusion mechanisms and tends to limit the on-axis microwave streamer elongation by enhancing resonance effects. The simulations suggest that gas heating effects also play an important role in the observed bending or branching of microwave streamers after they have reached a critical length.

  18. Unconventional Magnetism and Band Gap Formation in LiFePO4: Consequence of Polyanion Induced Non-planarity.

    PubMed

    Jena, Ajit; Nanda, B R K

    2016-01-21

    Oxygen plays a critical role in strongly correlated transition metal oxides as crystal field effect is one of the key factors that determine the degree of localization of the valence d/f states. Based on the localization, a set of conventional mechanisms such as Mott-Hubbard, Charge-transfer and Slater were formulated to explain the antiferromagnetic and insulating (AFI) phenomena in many of these correlated systems. From the case study on LiFePO4, through density-functional calculations, we demonstrate that none of these mechanisms are strictly applicable to explain the AFI behavior when the transition metal oxides have polyanions such as (PO4)(3-). The symmetry-lowering of the metal-oxygen complex, to stabilize the polyanion, creates an asymmetric crystal field for d/f states. In LiFePO4 this field creates completely non-degenerate Fe-d states which, with negligible p-d and d-d covalent interactions, become atomically localized to ensure a gap at the Fermi level. Due to large exchange splitting, high spin state is favored and an antiferromagnetic configuration is stabilized. For the prototype LiFePO4, independent electron approximation is good enough to obtain the AFI ground state. Inclusion of additional correlation measures like Hubbard U simply amplifies the gap and therefore LiFePO4 can be preferably called as weakly coupled Mott insulator.

  19. Unconventional Magnetism and Band Gap Formation in LiFePO4: Consequence of Polyanion Induced Non-planarity

    PubMed Central

    Jena, Ajit; Nanda, B. R. K.

    2016-01-01

    Oxygen plays a critical role in strongly correlated transition metal oxides as crystal field effect is one of the key factors that determine the degree of localization of the valence d/f states. Based on the localization, a set of conventional mechanisms such as Mott-Hubbard, Charge-transfer and Slater were formulated to explain the antiferromagnetic and insulating (AFI) phenomena in many of these correlated systems. From the case study on LiFePO4, through density-functional calculations, we demonstrate that none of these mechanisms are strictly applicable to explain the AFI behavior when the transition metal oxides have polyanions such as (PO4)3−. The symmetry-lowering of the metal-oxygen complex, to stabilize the polyanion, creates an asymmetric crystal field for d/f states. In LiFePO4 this field creates completely non-degenerate Fe-d states which, with negligible p-d and d-d covalent interactions, become atomically localized to ensure a gap at the Fermi level. Due to large exchange splitting, high spin state is favored and an antiferromagnetic configuration is stabilized. For the prototype LiFePO4, independent electron approximation is good enough to obtain the AFI ground state. Inclusion of additional correlation measures like Hubbard U simply amplifies the gap and therefore LiFePO4 can be preferably called as weakly coupled Mott insulator. PMID:26791249

  20. FLO11 expression and lipid biosynthesis are required for air-liquid biofilm formation in a Saccharomyces cerevisiae flor strain.

    PubMed

    Zara, Giacomo; Goffrini, Paola; Lodi, Tiziana; Zara, Severino; Mannazzu, Ilaria; Budroni, Marilena

    2012-11-01

    Air-liquid biofilm formation is largely dependent on Flo11p and seems related to cell lipid content and composition. Here, it is shown that in the presence of cerulenin, a known inhibitor of the fatty acid synthase complex, biofilm formation is inhibited together with FLO11 transcription in a flor strain of Saccharomyces cerevisiae, while the administration of saturated fatty acids to cerulenin-containing medium restores biofilm formation and FLO11 transcription. It is also shown that, in biofilm cells, the FLO11 transcription is accompanied by the transcription of ACC1, ACS1 and INO1 key genes in lipid biosynthesis and that biofilm formation is affected by the lack of inositol in flor medium. These results are compatible with the hypothesis that the air-liquid biofilm formation depends on FLO11 transcription levels as well as on fatty acids biosynthesis.

  1. Axial gap rotating electrical machine

    DOEpatents

    None

    2016-02-23

    Direct drive rotating electrical machines with axial air gaps are disclosed. In these machines, a rotor ring and stator ring define an axial air gap between them. Sets of gap-maintaining rolling supports bear between the rotor ring and the stator ring at their peripheries to maintain the axial air gap. Also disclosed are wind turbines using these generators, and structures and methods for mounting direct drive rotating electrical generators to the hubs of wind turbines. In particular, the rotor ring of the generator may be carried directly by the hub of a wind turbine to rotate relative to a shaft without being mounted directly to the shaft.

  2. The lasting effect of limonene-induced particle formation on air quality in a genuine indoor environment.

    PubMed

    Rösch, Carolin; Wissenbach, Dirk K; von Bergen, Martin; Franck, Ulrich; Wendisch, Manfred; Schlink, Uwe

    2015-09-01

    Atmospheric ozone-terpene reactions, which form secondary organic aerosol (SOA) particles, can affect indoor air quality when outdoor air mixes with indoor air during ventilation. This study, conducted in Leipzig, Germany, focused on limonene-induced particle formation in a genuine indoor environment (24 m(3)). Particle number, limonene and ozone concentrations were monitored during the whole experimental period. After manual ventilation for 30 min, during which indoor ozone levels reached up to 22.7 ppb, limonene was introduced into the room at concentrations of approximately 180 to 250 μg m(-3). We observed strong particle formation and growth within a diameter range of 9 to 50 nm under real-room conditions. Larger particles with diameters above 100 nm were less affected by limonene introduction. The total particle number concentrations (TPNCs) after limonene introduction clearly exceed outdoor values by a factor of 4.5 to 41 reaching maximum concentrations of up to 267,000 particles cm(-3). The formation strength was influenced by background particles, which attenuated the formation of new SOA with increasing concentration, and by ozone levels, an increase of which by 10 ppb will result in a six times higher TPNC. This study emphasizes indoor environments to be preferred locations for particle formation and growth after ventilation events. As a consequence, SOA formation can produce significantly higher amounts of particles than transported by ventilation into the indoor air.

  3. Enhanced soot formation in flickering CH{sub 4}/air diffusion flames

    SciTech Connect

    Shaddix, C.R.; Harrington, J.E.; Smyth, K.C.

    1994-12-31

    Optical methods are used to examine soot production in a co-flowing, axisymmetric CH{sub 4}/air diffusion flame in which the fuel flow rate is acoustically forced to create a time-varying flowfield. For a particular forcing condition in which tip clipping occurs (0.75 V loudspeaker excitation), elastic scattering of vertically polarized light from the soot particles increases by nearly an order of magnitude with respect to that observed for a steady flame with the same mean fuel flow rate. Peak soot volume fractions, as measured by time-resolved laser extinction/tomography at 632.8 and 454.5 run and calibrated laser-induced incandescence (LII), show a factor of 4-5 enhancement in this flickering flame. A Mie analysis suggests that most of the enhanced soot production results from the formation of larger particles in the time-varying flowfield.

  4. Spray formation of biodiesel-water in air-assisted atomizer using Schlieren photography

    NASA Astrophysics Data System (ADS)

    Amirnordin, S. H.; Khalid, A.; Sapit, A.; Salleh, H.; Razali, A.; Fawzi, M.

    2016-11-01

    Biodiesels are attractive renewable energy sources, particularly for industrial boiler and burner operators. However, biodiesels produce higher nitrogen oxide (NOx) emissions compared with diesel. Although water-emulsified fuels can lower NOx emissions by reducing flame temperature, its influence on atomization needs to be investigated further. This study investigates the effects of water on spray formation in air-assisted atomizers. The Schlieren method was used to capture the spray images in terms of tip penetration, spray angle, and spray area. The experiment used palm oil biodiesel at different blending ratios (B5, B10, and B15) and water contents (0vol%-15vol%). Results show that water content in the fuel increases the spray penetration and area but reduces the spray angle because of the changes in fuel properties. Therefore, biodiesel-water application is applicable to burner systems.

  5. Nanograting formation on metals in air with interfering femtosecond laser pulses

    SciTech Connect

    Miyazaki, Kenzo E-mail: kmiyazaki@wind.ocn.ne.jp; Miyaji, Godai; Inoue, Toshishige

    2015-08-17

    It is demonstrated that a homogeneous nanograting having the groove period much smaller than the laser wavelength (∼800 nm) can be fabricated on metals in air through ablation induced by interfering femtosecond laser pulses (100 fs at a repetition rate of 10 Hz). Morphological changes on stainless steel and Ti surfaces, observed with an increase in superimposed shots of the laser pulses at a low fluence, have shown that the nanograting is developed through bonding structure change at the interference fringes, plasmonic near-field ablation to create parallel grooves on the fringe, and subsequent excitation of surface plasmon polaritons to regulate the groove intervals at 1/3 or 1/4 of the fringe period over the whole irradiated area. Calculation for a model target having a thin oxide layer on the metal substrate reproduces well the observed groove periods and explains the mechanism for the nanograting formation.

  6. Understanding the origin of band gap formation in graphene on metals: graphene on Cu/Ir(111)

    NASA Astrophysics Data System (ADS)

    Vita, H.; Böttcher, S.; Horn, K.; Voloshina, E. N.; Ovcharenko, R. E.; Kampen, Th.; Thissen, A.; Dedkov, Yu. S.

    2014-07-01

    Understanding the nature of the interaction at the graphene/metal interfaces is the basis for graphene-based electron- and spin-transport devices. Here we investigate the hybridization between graphene- and metal-derived electronic states by studying the changes induced through intercalation of a pseudomorphic monolayer of Cu in between graphene and Ir(111), using scanning tunnelling microscopy and photoelectron spectroscopy in combination with density functional theory calculations. We observe the modifications in the band structure by the intercalation process and its concomitant changes in the charge distribution at the interface. Through a state-selective analysis of band hybridization, we are able to determine their contributions to the valence band of graphene giving rise to the gap opening. Our methodology reveals the mechanisms that are responsible for the modification of the electronic structure of graphene at the Dirac point, and permits to predict the electronic structure of other graphene-metal interfaces.

  7. Formation of 3-mercaptopropionic acid-ZnxCd1-xSe quantum dots with tunable band gap

    NASA Astrophysics Data System (ADS)

    Geng, Yue; Chen, Qian; Zhou, Chunyan; Song, Jiahui; Wang, Rongfang; Zhou, Liya

    2015-08-01

    Alloyed ZnxCd1-xSe quantum dots (QDs) covering the UV-visible spectral region are successfully synthesized using 3-mercaptopropionic acid (MPA) as a capping agent. The optical properties of the alloyed QDs are determined on the basis of different ligands, reaction times, pH, Se/Zn molar ratios, and Zn/Cd molar ratios. The band gaps of the as-prepared QDs can be tuned by adjusting the compositions of the dots, and the quantum yield of ZnxCd1-xSe QDs is 33%. All results indicate that ZnxCd1-xSe QDs can be potentially applied in photochemical devices.

  8. Physics of band-gap formation and its evolution in the pillar-based phononic crystal structures

    SciTech Connect

    Pourabolghasem, Reza; Mohammadi, Saeed; Eftekhar, Ali Asghar; Adibi, Ali; Khelif, Abdelkrim

    2014-07-07

    In this paper, the interplay of Bragg scattering and local resonance is theoretically studied in a phononic crystal (PnC) structure composed of a silicon membrane with periodic tungsten pillars. The comparison of phononic band gaps (PnBGs) in three different lattice types (i.e., square, triangular, and honeycomb) with different pillar geometries shows that different PnBGs have varying degrees of dependency on the lattice symmetry based on the interplay of the local resonances and the Bragg effect. The details of this interplay is discussed. The significance of locally resonating pillars, specially in the case of tall pillars, on PnBGs is discussed and verified by examining the PnBG position and width in perturbed lattices via Monte Carlo simulations. It is shown that the PnBGs caused by the local resonance of the pillars are more resilient to the lattice perturbations than those caused by Bragg scattering.

  9. Formation of high conductive nano-crystalline silicon embedded in amorphous silicon-carbide films with large optical band gap

    NASA Astrophysics Data System (ADS)

    Ji, Yang; Shan, Dan; Qian, Mingqing; Xu, Jun; Li, Wei; Chen, Kunji

    2016-10-01

    High conductive phosphorus-doped nano-crystalline Si embedded in Silicon-Carbide (SiC) host matrix (nc-Si:SiC) films were obtained by thermally annealing doped amorphous Si-rich SiC materials. It was found that the room conductivity is increased significantly accompanying with the increase of doping concentrations as well as the enhanced crystallizations. The conductivity can be as high as 630 S/cm for samples with the optical band gap around 2.7 eV, while the carrier mobility is about 17.9 cm2/ V.s. Temperature-dependent conductivity and mobility measurements were performed which suggested that the carrier transport process is strongly affected by both the grain boundaries and the doping concentrations.

  10. Understanding the origin of band gap formation in graphene on metals: graphene on Cu/Ir(111)

    PubMed Central

    Vita, H.; Böttcher, S.; Horn, K.; Voloshina, E. N.; Ovcharenko, R. E.; Kampen, Th.; Thissen, A.; Dedkov, Yu. S.

    2014-01-01

    Understanding the nature of the interaction at the graphene/metal interfaces is the basis for graphene-based electron- and spin-transport devices. Here we investigate the hybridization between graphene- and metal-derived electronic states by studying the changes induced through intercalation of a pseudomorphic monolayer of Cu in between graphene and Ir(111), using scanning tunnelling microscopy and photoelectron spectroscopy in combination with density functional theory calculations. We observe the modifications in the band structure by the intercalation process and its concomitant changes in the charge distribution at the interface. Through a state-selective analysis of band hybridization, we are able to determine their contributions to the valence band of graphene giving rise to the gap opening. Our methodology reveals the mechanisms that are responsible for the modification of the electronic structure of graphene at the Dirac point, and permits to predict the electronic structure of other graphene-metal interfaces. PMID:25027748

  11. Geothermal Evaluation of The Hosston Formation Lackland Air Force Base, San Antonio, Texas Phase II Report

    SciTech Connect

    Zeisloft, Jon; Foley, Duncan

    1984-05-30

    This report summarizes the results of a phased program to test the geothermal characteristics of the Hosston Formation at Lackland Air Force Base, San Antonio, Texas. The geothermal resource evaluation was made possible through drilling and preliminary testing of a large diameter well, Lackland AFB No.1, at the south portion of the base. Phase I of the program had 3 major components: (1) compilation and interpretation of surface and subsurface geologic data to site the well; (2) design of the well; and (3) permitting the well. Phase II consisted of well drilling and preliminary development. The goal of the program was to identify water temperature, water quality, and productivity characteristics of the Hosston aquifer, which preliminary studies suggested might be favorable for direct applications on the base. Results reported herein suggest that heat pumps or other engineering alternatives might be needed for such applications. Results of the well drilling give data on water productivity, quality and temperature. Air-lift testing shows that, although the well does not flow to surface, good artesian pressure exists. Water quality appears acceptable, with about 2200 parts per million total dissolved solids. Equilibrated reservoir temperatures appear to be slightly less than 108 F (42 C).

  12. Plagioclase zonation styles in hornblende gabbro inclusions from Little Glass Mountain, Medicine Lake volcano, California: Implications for fractionation mechanisms and the formation of composition gaps

    USGS Publications Warehouse

    Brophy, J.G.; Dorais, M.J.; Donnelly-Nolan, J.; Singer, B.S.

    1997-01-01

    The rhyolite of Little Glass Mountain (73-74% SiO2) is a single eruptive unit that contains inclusions of quenched andesite liquid (54-61% SiO2) and partially crystalline cumulate hornblende gabbro (53-55% SiO2). Based on previous studies, the quenched andesite inclusions and host rhyolite lava are related to one another through fractional crystallization and represent an example of a fractionation-generated composition gap. The hornblende gabbros represent the cumulate residue associated with the rhyolite-producing and composition gap-forming fractionation event. This study combines textural (Nomarski Differential Interference Contrast, NDIC, imaging), major element (An content) and trace element (Mg, Fe, Sr, K, Ti, Ba) data on the style of zonation of plagioclase crystals from representative andesite and gabbro inclusions, to assess the physical environment in which the fractionation event and composition gap formation took place. The andesite inclusions (54-61% SiO2) are sparsely phyric with phenocrysts of plagioclase, augite and Fe-oxide??olivine, +/-orthopyroxene, +/-hornblende set within a glassy to crystalline matrix. The gabbro cumulates (53-55% SiO2) consist of an interconnected framework of plagioclase, augite, olivine, orthopyroxene, hornblende and Fe-oxide along with highly vesicular interstitial glass (70-74% SiO2). The gabbros record a two-stage crystallization history of plagioclase + olivine + augite (Stage I) followed by plagioclase+orthopyroxene + hornblende + Fe-oxide (Stage II). Texturally, the plagioclase crystals in the andesite inclusions are characterized by complex, fine-scale oscillatory zonation and abundant dissolution surfaces. Compositionally (An content) the crystals are essentially unzoned from core-to-rim. These features indicate growth within a dynamic (convecting?), reservoir of andesite magma. In contrast, the plagioclase crystals in the gabbros are texturally smooth and featureless with strong normal zonation from An74 at the

  13. Mutagenicity and DNA adduct formation by the urban air pollutant 2-nitrobenzanthrone.

    PubMed

    Arlt, Volker M; Glatt, Hansruedi; Gamboa da Costa, Gonçalo; Reynisson, Jóhannes; Takamura-Enya, Takeji; Phillips, David H

    2007-08-01

    2-Nitrobenzanthrone (2-NBA) has recently been detected in ambient air particulate matter. Its isomer 3-nitrobenzanthrone (3-NBA) is a potent mutagen and suspected human carcinogen identified in diesel exhaust. The highest mutagenic activity of 2-NBA tested in Salmonella typhimurium was exhibited in strain TA1538-hSULT1A1 expressing human sulfotransferase (SULT) 1A1. 2-NBA also induced mutations in Chinese hamster lung V79 cells expressing human N-acetyltransferase 2 or SULT1A1, but no mutagenicity was observed in the parental cell line. DNA adduct formation in vitro was examined in different human cell lines by thin-layer chromatography (32)P-postlabeling. Whereas 3-NBA formed characteristic DNA adducts in lung A549, liver HepG2, colon HCT116, and breast MCF-7 cells, 2-NBA-derived DNA adducts were only observed in A549 and HepG2 cells, indicating differences in the bioactivation of each isomer. The pattern of 2-NBA-derived DNA adducts in both cell lines consisted of a cluster of up to five adducts. In HepG2 cells DNA binding by 2-NBA was up to 14-fold lower than by 3-NBA. DNA adduct formation of 2-NBA was also investigated in vivo in Wistar rats treated with a single dose of 2, 10, or 100 mg/kg body weight (bw). No DNA adduct formation was detected at doses of up to 10 mg/kg bw 2-NBA, even though 3-NBA induced DNA adducts at a dose of 2 mg/kg bw. Only after administration of one high dose of 100 mg/kg bw 2-NBA was a low level of DNA adduct formation detected, and then only in lung tissue. Density functional theory calculations for both NBAs revealed that the nitrenium ion of the 3-isomer is considerably more stable ( approximately 10 kcal/mol) than that of the 2-isomer, providing a possible explanation for the large differences in DNA adduct formation and mutagenicity between 2- and 3-NBA.

  14. FGFR1 signaling in hypertrophic chondrocytes is attenuated by the Ras-GAP neurofibromin during endochondral bone formation

    PubMed Central

    Karolak, Matthew R.; Yang, Xiangli; Elefteriou, Florent

    2015-01-01

    Aberrant fibroblast growth factor receptor 3 (FGFR3) signaling disrupts chondrocyte proliferation and growth plate size and architecture, leading to various chondrodysplasias or bone overgrowth. These observations suggest that the duration, intensity and cellular context of FGFR signaling during growth plate chondrocyte maturation require tight, regulated control for proper bone elongation. However, the machinery fine-tuning FGFR signaling in chondrocytes is incompletely defined. We report here that neurofibromin, a Ras-GAP encoded by Nf1, has an overlapping expression pattern with FGFR1 and FGFR3 in prehypertrophic chondrocytes, and with FGFR1 in hypertrophic chondrocytes during endochondral ossification. Based on previous evidence that neurofibromin inhibits Ras-ERK signaling in chondrocytes and phenotypic analogies between mice with constitutive FGFR1 activation and Nf1 deficiency in Col2a1-positive chondrocytes, we asked whether neurofibromin is required to control FGFR1-Ras-ERK signaling in maturing chondrocytes in vivo. Genetic Nf1 ablation in Fgfr1-deficient chondrocytes reactivated Ras-ERK1/2 signaling in hypertrophic chondrocytes and reversed the expansion of the hypertrophic zone observed in mice lacking Fgfr1 in Col2a1-positive chondrocytes. Histomorphometric and gene expression analyses suggested that neurofibromin, by inhibiting Rankl expression, attenuates pro-osteoclastogenic FGFR1 signaling in hypertrophic chondrocytes. We also provide evidence suggesting that neurofibromin in prehypertrophic chondrocytes, downstream of FGFRs and via an indirect mechanism, is required for normal extension and organization of proliferative columns. Collectively, this study indicates that FGFR signaling provides an important input into the Ras-Raf-MEK-ERK1/2 signaling axis in chondrocytes, and that this input is differentially regulated during chondrocyte maturation by a complex intracellular machinery, of which neurofibromin is a critical component. PMID:25616962

  15. Mechanisms for secondary eyewall formation, and cold-air damming: Tropical cyclone interactions

    NASA Astrophysics Data System (ADS)

    Garcia-Rivera, Jose Manuel

    This dissertation consists of two topics, the mechanisms leading to secondary eyewall formation in tropical cyclones, and effects of tropical cyclone---cold-air interactions on heavy precipitation. The first research topic involves a proposed coupled mechanism for secondary eyewall formation (SEF; initiation of an eyewall replacement cycle), using a WRF-ARW simulation of Hurricane Katrina (2005). The storm underwent a series of structural changes that were deemed necessary for the cycle to begin. These included a significant increase of rainband activity in the SEF region and the eventual vertical coupling of azimuthal-mean updrafts that led to cycle initiation. Increased rainband activity outside the primary eyewall in the hours before was mostly related to an intensifying main feeder band. Close to initiation, an updraft (explained by a pre-existing hypothesis) emerged outside the primary eyewall near the top of the boundary layer (BL). This updraft then intensified and extended both upward and outward, while the storm intensified and approached SEF. Eventually, the updraft coupled with the upward motion associated with rainband-related convection near the SEF radius. Once the alignment occurred, the deep updraft quickly organized to support deep convection that led to SEF within hours of initiation. The coupling of updrafts emanating from the BL with the environmental upward motion associated with the pre-existing rainband activity is proposed to be the key for SEF initiation in this case. The second topic investigates the interactions between an Appalachian cold-air damming event and the near-passage of Tropical Storm Kyle (2002) along the coastal Carolinas, as assessed by using a numerical weather prediction model. While the storm moved along the coastline, it began extra-tropical transition, bringing heavy rains to both the coastal region and inland towards the Piedmont of North Carolina. Our goal is to quantify the effects of both interacting weather systems

  16. Chemical potential shift and gap-state formation in SrTiO{sub 3−δ} revealed by photoemission spectroscopy

    SciTech Connect

    Pal, Prabir Kumar, Pramod; Aswin, V.; Dogra, Anjana; Joshi, Amish G.

    2014-08-07

    In this study, we report on investigations of the electronic structure of SrTiO{sub 3} annealed at temperature ranging between 550 and 840 °C in an ultrahigh vacuum. Annealing induced oxygen vacancies (O{sub vac}) impart considerable changes in the electronic structure of SrTiO{sub 3}. Using core-level photoemission spectroscopy, we have studied the chemical potential shift (Δμ) as a function of annealing temperature. The result shows that the chemical potential monotonously increases with electron doping in SrTiO{sub 3−δ}. The monotonous increase of the chemical potential rules out the existence of electronic phase separation in the sample. Using valence band photoemission, we have demonstrated the formation of a low density of states at the near Fermi level electronic spectrum of SrTiO{sub 3−δ}. The gap-states were observed by spectral weight transfer over a large energy scale of the stoichiometric band gap of SrTiO{sub 3} system leading finally to an insulator-metal transition. We have interpreted our results from the point of structural distortions induced by oxygen vacancies.

  17. Propagation or failure of detonation across an air gap in an LX-17 column: continuous time-dependent detonation or shock speed using the Embedded Fiber Optic (EFO) technique

    SciTech Connect

    Hare, D E; Chandler, J B; Compton, S M; Garza, R G; Grimsley, D A; Hernandez, A; Villafana, R J; Wade, J T; Weber, S R; Wong, B M; Souers, P C

    2008-01-16

    The detailed history of the shock/detonation wave propagation after crossing a room-temperature-room-pressure (RTP) air gap between a 25.4 mm diameter LX-17 donor column and a 25.4 mm diameter by 25.4 mm long LX-17 acceptor pellet is investigated for three different gap widths (3.07, 2.08, and 0.00 mm) using the Embedded Fiber Optic (EFO) technique. The 2.08 mm gap propagated and the 3.07 mm gap failed and this can be seen clearly and unambiguously in the EFO data even though the 25.4 mm-long acceptor pellet would be considered quite short for a determination by more traditional means such as pins.

  18. Ammonia sources and ammonium nitrate formation in the California South Coast Air Basin

    NASA Astrophysics Data System (ADS)

    Nowak, J. B.; Neuman, J.; Bahreini, R.; Middlebrook, A. M.; Holloway, J. S.; Cai, C.; Kaduwela, A.; McKeen, S. A.; Parrish, D. D.; Ryerson, T. B.; Trainer, M.

    2011-12-01

    The South Coast Air Basin (SoCAB) of California is designated by the US Environmental Protection Agency (EPA) as being in non-attainment of the National Ambient Air Quality Standards (NAAQS) for both PM2.5 and PM10. Formation of fine aerosol nitrates (e.g., ammonium nitrate (NH4NO3)) from gas-phase ammonia (NH3) and nitric acid (HNO3) accounts for a significant fraction of the PM2.5 mass. Quantifying the sources of NH3 in the SoCAB is important for developing aerosol control strategies. Fast-time resolution observations of NH3, particulate ammonium (NH4+), and carbon monoxide (CO) made aboard the NOAA WP-3D aircraft during the CalNex 2010 campaign are used to quantify and compare the major NH3 sources to the SoCAB atmosphere: automobiles and dairy farms. From the automobile NH3:CO emission ratio inferred from the WP-3D observations and CO inventory data the NH3 automobile emissions in the SoCAB are estimated at 38 ± 15 metric tons day-1. Atmospheric mass fluxes are calculated for observed NH3 plumes from dairy farms to estimate the NH3 dairy farm emissions at 27 ± 14 to 120 ± 60 metric tons day-1. Comparison with two emission inventories show good agreement for the automobile NH3:CO emission ratio, however, both inventories under predict NH3 emissions from the dairy farms. The observations suggest that automobiles and dairy farms contributed similar amounts of NH3 to the SoCAB in May 2010. However, observed particle mass was greater downwind from dairy farms, where high NH3 mixing ratios from more concentrated sources shift the NH4NO3 equilibrium toward favorable thermodynamic conditions for the condensation of NH4NO3 onto particles.

  19. Experimental and Modeling Investigation of the Effect of Air Preheat on the Formation of NOx in an RQL Combustor

    NASA Technical Reports Server (NTRS)

    Samuelsen, G. S.; Brouwer, J.; Vardakas, M. A.; Holderman, J. D.

    2012-01-01

    The Rich-burn/Quick-mix/Lean-burn (RQL) combustor concept has been proposed to minimize the formation of oxides of nitrogen (NOx) in gas turbine systems. The success of this low-NOx combustor strategy is dependent upon the links between the formation of NOx, inlet air preheat temperature, and the mixing of the jet air and fuel-rich streams. Chemical equilibrium and kinetics modeling calculations and experiments were performed to further understand NOx emissions in an RQL combustor. The results indicate that as the temperature at the inlet to the mixing zone increases (due to preheating and/or operating conditions) the fuel-rich zone equivalence ratio must be increased to achieve minimum NOx formation in the primary zone of the combustor. The chemical kinetics model illustrates that there is sufficient residence time to produce NOx at concentrations that agree well with the NOx measurements. Air preheat was found to have very little effect on mixing, but preheating the air did increase NOx emissions significantly. By understanding the mechanisms governing NOx formation and the temperature dependence of key reactions in the RQL combustor, a strategy can be devised to further reduce NOx emissions using the RQL concept.

  20. Potential of Aerosol Liquid Water to Facilitate Organic Aerosol Formation: Assessing Knowledge Gaps about Precursors and Partitioning.

    PubMed

    Sareen, Neha; Waxman, Eleanor M; Turpin, Barbara J; Volkamer, Rainer; Carlton, Annmarie G

    2017-03-06

    Isoprene epoxydiol (IEPOX), glyoxal, and methylglyoxal are ubiquitous water-soluble organic gases (WSOGs) that partition to aerosol liquid water (ALW) and clouds to form aqueous secondary organic aerosol (aqSOA). Recent laboratory-derived Setschenow (or salting) coefficients suggest glyoxal's potential to form aqSOA is enhanced by high aerosol salt molality, or "salting-in". In the southeastern U.S., aqSOA is responsible for a significant fraction of ambient organic aerosol, and correlates with sulfate mass. However, the mechanistic explanation for this correlation remains elusive, and an assessment of the importance of different WSOGs to aqSOA is currently missing. We employ EPA's CMAQ model to the continental U.S. during the Southern Oxidant and Aerosol Study (SOAS) to compare the potential of glyoxal, methylglyoxal, and IEPOX to partition to ALW, as the initial step toward aqSOA formation. Among these three studied compounds, IEPOX is a dominant contributor, ∼72% on average in the continental U.S., to potential aqSOA mass due to Henry's Law constants and molecular weights. Glyoxal contributes significantly, and application of the Setschenow coefficient leads to a greater than 3-fold model domain average increase in glyoxal's aqSOA mass potential. Methylglyoxal is predicted to be a minor contributor. Acid or ammonium - catalyzed ring-opening IEPOX chemistry as well as sulfate-driven ALW and the associated molality may explain positive correlations between SOA and sulfate during SOAS and illustrate ways in which anthropogenic sulfate could regulate biogenic aqSOA formation, ways not presently included in atmospheric models but relevant to development of effective control strategies.

  1. Fabrication of macromolecular gradients in aligned fiber scaffolds using a combination of in-line blending and air-gap electrospinning.

    PubMed

    Kishan, Alysha P; Robbins, Andrew B; Mohiuddin, Sahar F; Jiang, Mingliang; Moreno, Michael R; Cosgriff-Hernandez, Elizabeth M

    2016-12-22

    Although a variety of fabrication methods have been developed to generate electrospun meshes with gradient properties, no platform has yet to achieve fiber alignment in the direction of the gradient that mimics the native tendon-bone interface. In this study, we present a method combining in-line blending and air-gap electrospinning to address this limitation in the field. A custom collector with synced rotation permitted fiber collection with uniform mesh thickness and periodic copper wires were used to induce fiber alignment. Two poly(ester urethane ureas) with different hard segment contents (BPUR 50, BPUR 10) were used to generate compositional gradient meshes with and without fiber alignment. The compositional gradient across the length of the mesh was characterized using a fluorescent dye and the results indicated a continuous transition from the BPUR 50 to the BPUR 10. As expected, the fiber alignment of the gradient meshes induced a corresponding alignment of adherent cells in static culture. Tensile testing of the sectioned meshes confirmed a graded transition in mechanical properties and an increase in anisotropy with fiber alignment. Finite element modeling was utilized to illustrate the gradient mechanical properties across the full length of the mesh and lay the foundation for future computational development work. Overall, these results indicate that this electrospinning method permits the fabrication of macromolecular gradients in the direction of fiber alignment and demonstrate its potential for use in interfacial tissue engineering.

  2. Performance and emission characteristics of a low heat rejection engine with different air gap thicknesses with Jatropha oil based bio-diesel.

    PubMed

    Murali Krishna, M V S; Sarita, G; Seshagiri Rao, V V R; Chowdary, R P; Ramana Reddy, Ch V

    2010-04-01

    The research work on alternate fuels has been the topic of wider interest in the context of depletion of fossil fuels and increasing of pollution levels of the engines with conventional fossil fuels. Alcohols and vegetable oils are considered to replace diesel fuels as they are renewable in nature. However, use of alcohols in internal combustion engines is limited in India, as these fuels are diverted to PetroChemical industries and hence much emphasis is given to the non-edible vegetable oils as alternate fuels in internal combustion engines. However, the drawbacks of low volatility and high viscosity associated with non-edible vegetable oils call for hot combustion chamber, provided by low heat rejection (LHR) diesel engine. Investigations are carried out on a LHR diesel engine with varied air gap thicknesses and injection pressures with jatropha oil based bio-diesel at normal temperature. Performance is improved with high degree of insulation with LHR engine with vegetable oil in comparison with conventional engine (CE) with pure diesel operation.

  3. Simulation-based conceptual design of an acoustic metamaterial with full band gap using an air-based 1-3 piezoelectric composite for ultrasonic noise control

    NASA Astrophysics Data System (ADS)

    Rezaei, Shahrokh; Eskandari-Ghadi, Morteza; Rahimian, Mohammad

    2017-02-01

    This paper aims at proposing a novel type of acoustic metamaterials with complete band gap composed of piezoelectric rods with square array as inclusions embedded in an air background (matrix). A modified plane wave expansion method accompanied with the principles of the Bloch-Floquet method with electromechanical coupling effect and also impedance spectra are used to get a band frequency and to investigate the passband for the selected cut of piezoelectric rods. We investigate both the electromechanical coupling coefficient and mechanical quality factor and their dependency to passband and bandwidth, which depends on both the density and the wave impedance of the matrix and the inclusions (rods). The ratio of the volume of inclusion to the matrix is used to define the fill factor or the so-called inclusion ratio, to introduce the bandwidth as a function of that. Furthermore, the fabrication method is presented in this paper. The results make a suitable foundation for design purposes and may develop an inherently passive ultrasonic noise control. In addition, the results provide the required guidance for a simulation-based design of elastic wave filters or wave guide that might be useful in high-precision mechanical systems operated in certain frequency ranges and switches made of piezoelectric materials; they also propose a novel type of elastic metamaterials, which is independent of the wave direction and has an equal sensitivity in all directions in which it reacts omnidirectionally and mitigates the occupational noise exposure.

  4. The interaction between soot and NO formation in a laminar axisymmetric coflow ethylene/air diffusion flame

    SciTech Connect

    Guo, Hongsheng; Smallwood, Gregory J.

    2007-04-15

    The interaction between soot and NO formation in a laminar axisymmetric coflow ethylene/air diffusion flame was investigated by numerical simulation. A detailed gas-phase reaction scheme and a simplified soot model were employed. The results show that the formation of NO has little effect on that of soot. However, the formation of soot in the flame significantly suppresses the formation of NO. The peak NO concentration and NO emission index are reduced by 28 and 46%, respectively, due to the formation of soot. The influence of soot on NO formation is caused by not only the radiation-induced thermal effect, but also the reaction-induced chemical effect. Relatively the thermal effect is more significant, causing 25 and 38% reduction, respectively, in peak NO concentration and NO emission index. The chemical effect is caused by the competition for acetylene (C{sub 2}H{sub 2}) between soot and NO formation. The formation of soot consumes acetylene in the flame and thus lowers the formation rate of radical CH. This reduces the reaction rate of CH + N{sub 2} = HCN + N, which is the rate-limiting step of the prompt NO formation route, the dominant route in the studied flame. (author)

  5. Sensitivity analysis of ozone formation and transport for a Central California air pollution episode

    SciTech Connect

    Jin, Ling; Tonse, Shaheen; Cohan, Daniel S.; Mao, Xiaoling; Harley, Robert A.; Brown, Nancy J.

    2009-05-15

    CMAQ-HDDM is used to determine spatial and temporal variations in ozone limiting reagents and local vs upwind source contributions for an air pollution episode in Central California. We developed a first- and second- order sensitivity analysis approach with the Decoupled Direct Method to examine spatial and temporal variations of ozone-limiting reagents and the importance of local vs upwind emission sources in the San Joaquin Valley of central California for a five-day ozone episode (29th July-3rd Aug, 2000). Despite considerable spatial variations, nitrogen oxides (NO{sub x}) emission reductions are overall more effective than volatile organic compound (VOC) control for attaining the 8-hr ozone standard in this region for this episode, in contrast to the VOC control that works better for attaining the prior 1-hr ozone standard. Inter-basin source contributions of NO{sub x} emissions are limited to the northern part of the SJV, while anthropogenic VOC (AVOC) emissions, especially those emitted at night, influence ozone formation in the SJV further downwind. Among model input parameters studied here, uncertainties in emissions of NO{sub x} and AVOC, and the rate coefficient of the OH + NO{sub 2} termination reaction, have the greatest effect on first-order ozone responses to changes in NO{sub x} emissions. Uncertainties in biogenic VOC emissions only have a modest effect because they are generally not collocated with anthropogenic sources in this region.

  6. Non-isothermal analysis of die corner gap formation for materials deformed by multi-pass ECAP

    NASA Astrophysics Data System (ADS)

    Medeiros, N.; Moreira, L. P.

    2014-08-01

    In this paper, the upper-bound solutions proposed by Eivani and Karimi Taheri [Comp. Mater. Sci. 42 (2008) 14] to calculate processing force and evaluate die corner angle Ψ formation in terms of tribology and die configurations during cold single pass equal channels angular pressed metals with constant flow stress were extended to work-hardening metals processed by two passes according to route A by using the Swift model combined to von Mises isotropic plasticity criterion. Also, adiabatic heat equation was coupled to solutions to express the final temperature of the workpiece. For that, thermomechanical properties of a hot-dip galvanized interstitial-free (IF) were considered and its behavior under pressing was evaluated to non-hardening and work-hardening conditions in all performed analyses. By including work-hardening in the models and for the critical friction factor of 0.4, theoretical predictions after single pass showed a decreasing of die corner angle and pressing force predictions and increasing of effective plastic strain and end temperature for all friction conditions and tooling geometries evaluated. In addition, after second pass, these responses showed higher values. Finally, with the proposed upper-bound models it was possible to analyze the dependency of angle Ψ, effective plastic strain, pressing load and sample temperature with the instantaneous workpiece height at the entry surface of deformation zone.

  7. Modeling of wind gap formation and development of sedimentary basins during fold growth: application to the Zagros Fold Belt, Iran.

    NASA Astrophysics Data System (ADS)

    Collignon, Marine; Yamato, Philippe; Castelltort, Sébastien; Kaus, Boris

    2016-04-01

    Mountain building and landscape evolution are controlled by the interactions between river dynamics and tectonic forces. Such interactions have been largely studied but a quantitative evaluation of tectonic/geomorphic feedbacks remains required for understanding sediments routing within orogens and fold-and-thrust belts. Here, we employ numerical simulations to assess the conditions of uplift and river incision necessary to deflect an antecedent drainage network during the growth of one or several folds. We propose that a partitioning of the river network into internal (endorheic) and longitudinal drainage arises as a result of lithological differences within the deforming crustal sedimentary cover. We show with examples from the Zagros Fold Belt (ZFB) that drainage patterns can be linked to the incision ratio R between successive lithological layers, corresponding to the ratio between their relative erodibilities or incision coefficients. Transverse drainage networks develop for uplift rates smaller than 0.8 mm.yr-1 and -10 < R < 10. Intermediate drainage network are obtained for uplift rates up to 2 mm.yr-1 and incision ratios of 20. Parallel drainage networks and formation of sedimentary basins occur for large values of incision ratio (R >20) and uplift rates between 1 and 2 mm.yr-1. These results have implications for predicting the distribution of sediment depocenters in fold-and-thrust belts, which can be of direct economic interest for hydrocarbon exploration.

  8. Effect of air-staging on anthracite combustion and NOx formation

    SciTech Connect

    Weidong Fan; Zhengchun Lin; Youyi Li; Jinguo Kuang; Mingchuan Zhang

    2009-01-15

    Experiments were carried out in a multipath air inlet one-dimensional furnace to assess NOx emission characteristics of the staged combustion of anthracite coal. These experiments allowed us to study the impact of pulverized coal fineness and burnout air position on emission under both deep and shallow air-staged combustion conditions. We also studied the impact of char-nitrogen release on both the burning-out process of the pulverized coal and the corresponding carbon content in fly ash. We found that air-staged combustion affects a pronounced reduction in NOx emissions from the combustion of anthracite coal. The more the air is staged, the more NOx emission is reduced. In shallow air-staged combustion (f{sub M} = 0.85), the fineness of the pulverized coal strongly influences emissions, and finer coals result in lower emissions. Meanwhile, the burnout air position has only a weak effect. In the deep air-staged combustion (f{sub M} = 0.6), the effect of coal fineness is smaller, and the burnout air position has a stronger effect. When the primary combustion air is stable, NOx emissions increase with increasing burnout air. This proves that, in the burnout zone, coal char is responsible for the discharge of fuel-nitrogen that is oxidized to NOx. The measurement of secondary air staging in a burnout zone can help inhibit the oxidization of NO caused by nitrogen release. Air-staged combustion has little effect on the burnout of anthracite coal, which proves to be suitable for air-staged combustion. 31 refs., 11 figs., 1 tab.

  9. An experimental and numerical study of nitrogen oxide formation mechanisms in ammonia-hydrogen-air flames

    NASA Astrophysics Data System (ADS)

    Kumar, Praveen

    quantitatively. The NOx predictions by all the three chemical mechanisms are observed to be in fairly good agreement with the measured NOx, qualitatively, however predictions are found to be 3 to 4 times higher than the measurements for both lean and rich H 2/NH3 premixed flames. For laminar H2/NH3 diffusion flames, detailed 2-D comparisons of in-situ NO measurements with the 2-D simulated NO using the Tian, GRI-Mech3.0 and modified GRI-Mech chemical mechanisms are performed and found to differ from the measured NO by approximately an order of magnitude. For NH3 seeded H2/air diffusion flames, GRI-Mech3.0 seemed to overpredict NO by more than an order of magnitude and failed to capture the fundamental flame characteristics, such as the flame length variation with increasing NH3 in the fuel mixture. On the other hand, the predicted NO profiles by the Tian mechanism were not only found to be in better agreement with the measured NO, but they also captured the in-flame NO distribution as well, both qualitatively and quantitatively. Overall, the Tian mechanism is found to be the superior chemical mechanism to capture the NOx formation chemistry in NH3 seeded flames.

  10. The Role of Gap Junctions and Mechanical Loading on Mineral Formation in a Collagen-I Scaffold Seeded with Osteoprogenitor Cells

    PubMed Central

    Damaraju, Swathi; Matyas, John R.; Rancourt, Derrick E.

    2015-01-01

    Fracture nonunions represent one of many large bone defects where current treatment strategies fall short in restoring both form and function of the injured tissue. In this case, the use of a tissue-engineered scaffold for promoting bone healing offers an accessible and easy-to-manipulate environment for studying bone formation processes in vitro. We have previously shown that mechanical prestimulation using confined compression of differentiating osteoblasts results in an increase in mineralization formed in a 3D collagen-I scaffold. This study builds on this knowledge by evaluating the short and long-term effects of blocking gap junction-mediated intercellular communication among osteogenic cells on their effectiveness to mineralize collagen-I scaffolds in vitro, and in the presence and absence of mechanical stimulation. In this study, confined compression was applied in conjunction with octanol (a general communication blocker) or 18-α-glycerrhetinic acid (AGA, a specific gap junction blocker) using a modified FlexCell plate to collagen-I scaffolds seeded with murine embryonic stem cells stimulated toward osteoblast differentiation using beta-glycerol phosphate. The activity, presence, and expression of osteoblast cadherin, connexin-43, as well as various pluripotent and osteogenic markers were examined at 5–30 days of differentiation. Fluorescence recovery after photobleaching, immunofluorescence, viability, histology assessments, and reverse-transcriptase polymerase chain reaction assessments revealed that inhibiting communication in this scaffold altered the lineage and function of differentiating osteoblasts. In particular, treatment with communication inhibitors caused reduced mineralization in the matrix, and dissociation between connexin-43 and integrin α5β1. This dissociation was not restored even after long-term recovery. Thus, in order for this scaffold to be considered as an alternative strategy for the repair of large bone defects, cell

  11. Site specific comparison of H2, CH4 and compressed air energy storage in porous formations

    NASA Astrophysics Data System (ADS)

    Tilmann Pfeiffer, Wolf; Wang, Bo; Bauer, Sebastian

    2016-04-01

    The supply of energy from renewable sources like wind or solar power is subject to fluctuations determined by the climatic and weather conditions, and shortage periods can be expected on the order of days to weeks. Energy storage is thus required if renewable energy dominates the total energy production and has to compensate the shortages. Porous formations in the subsurface could provide large storage capacities for various energy carriers, such as hydrogen (H2), synthetic methane (CH4) or compressed air (CAES). All three energy storage options have similar requirements regarding the storage site characteristics and consequently compete for suitable subsurface structures. The aim of this work is to compare the individual storage methods for an individual storage site regarding the storage capacity as well as the achievable delivery rates. This objective is pursued using numerical simulation of the individual storage operations. In a first step, a synthetic anticline with a radius of 4 km, a drop of 900 m and a formation thickness of 20 m is used to compare the individual storage methods. The storage operations are carried out using -depending on the energy carrier- 5 to 13 wells placed in the top of the structure. A homogeneous parameter distribution is assumed with permeability, porosity and residual water saturation being 500 mD, 0.35 and 0.2, respectively. N2 is used as a cushion gas in the H2 storage simulations. In case of compressed air energy storage, a high discharge rate of 400 kg/s equating to 28.8 mio. m³/d at surface conditions is required to produce 320 MW of power. Using 13 wells the storage is capable of supplying the specified gas flow rate for a period of 31 hours. Two cases using 5 and 9 wells were simulated for both the H2 and the CH4 storage operation. The target withdrawal rates of 1 mio. sm³/d are maintained for the whole extraction period of one week in all simulations. However, the power output differs with the 5 well scenario producing

  12. Soot Formation in Laminar Premixed Ethylene/Air Flames at Atmospheric Pressure. Appendix G

    NASA Technical Reports Server (NTRS)

    Xu, F.; Sunderland, P. B.; Faeth, G. M.; Urban, D. L. (Technical Monitor)

    2001-01-01

    Soot formation was studied within laminar premixed ethylene/air flames (C/O ratios of 0.78-0.98) stabilized on a flat-flame burner operating at atmospheric pressure. Measurements included soot volume fractions by both laser extinction and gravimetric methods, temperatures by multiline emission, soot structure by thermophoretic sampling and transmission electron microscopy, major gas species concentrations by sampling and gas chromatography, concentrations of condensable hydrocarbons by gravimetric sampling. and velocities by laser velocimetry. These data were used to find soot surface growth rates and primary soot particle nucleation rates along the axes of the flames. Present measurements of soot surface growth rates were correlated successfully by predictions based on typical hydrogen-abstraction/carbon-addition (HACA) mechanisms of Frenklach and co-workers and Colket and Hall. These results suavest that reduced soot surface growth rates with increasing residence time seen in the present and other similar flames were mainly caused by reduced rates of surface activation due to reduced H atom concentrations as temperatures decrease as a result of radiative heat losses. Primary soot particle nucleation rates exhibited variations with temperature and acetylene concentrations that were similar to recent observations for diffusion flames; however, nucleation rates in the premixed flames were significantly lower than in, the diffusion flames for reasons that still must be explained. Finally, predictions of yields of major gas species based on mechanisms from both Frenklach and co-workers and Leung and Lindstedt were in good agreement with present measurements and suggest that H atom concentrations (relevant to HACA mechanisms) approximate estimates based on local thermodynamic equilibrium in the present flames.

  13. Measurement of the c-axis optical reflectance of AFe2As2 (A=Ba, Sr) single crystals: evidence of different mechanisms for the formation of two energy gaps.

    PubMed

    Chen, Z G; Dong, T; Ruan, R H; Hu, B F; Cheng, B; Hu, W Z; Zheng, P; Fang, Z; Dai, X; Wang, N L

    2010-08-27

    We present the c-axis optical reflectance measurement on single crystals of BaFe2As2 and SrFe2As2, the parent compounds of FeAs based superconductors. Different from the ab-plane optical response where two distinct energy gaps were observed in the spin-density-wave (SDW) state, only the smaller energy gap could be seen clearly for E∥c axis. The very pronounced energy gap structure seen at a higher energy scale for E∥ab plane is almost invisible. We propose a novel picture for the band structure evolution across the SDW transition and suggest different driving mechanisms for the formation of the two energy gaps.

  14. Study of the formation of 3-D titania nanofibrous structure by MHz femtosecond laser in ambient air

    SciTech Connect

    Tavangar, Amirhossein; Venkatakrishnan, K.; Tan Bo

    2013-01-14

    In this study, we describe the formation mechanism of web-like three-dimensional (3-D) titania nanofibrous structures during femtosecond laser ablation of titanium (Ti) targets in the presence of background air. First, we demonstrate the mechanism of ablation of Ti targets by multiple femtosecond laser pulses at ambient air in an explicit analytical form. The formulas for evaporation rates and the number of ablated particles, which is analogous to the deposition rate of the synthesized nanofibers, for the ablation by a single pulse and multiple pulses as a function of laser parameters, background gas, and material properties are predicted and compared to experimental results. Afterwards, the formation of nanofibrous structures is demonstrated by applying an existing simplified kinetic model to Ti targets and ambient conditions. The predicted theory provides nanofiber diameter dependency with the combination of laser parameters, target properties, and ambient gas characteristics. Experimental studies are then performed on titania nanofibrous structures synthesized by laser ablation of Ti targets using MHz repletion-rate femtosecond laser at ambient air. The models' predictions are then compared with the experimental results, where nanostructures with different morphologies are manufactured by altering laser parameters. Our results indicate that femtosecond laser ablation of Ti targets at air background yields crystalline titania nanostructures. The formation of crystalline titania nanostructures is preceded by thermal mechanism of nucleation and growth. The results point out that laser pulse repetition and dwell time can control the density, size, and pore size of the engineered nanofibrous structure. As the deposition rate of nanostructures is analogous to the ablation rate of the target, higher density of nanofibrous structure is seen at greater laser fluences. The predicted theory can be applied to predict ablation mechanism and nanofiber formation of different

  15. AIR VEHICLE INTEGRATION AND TECHNOLOGY RESEARCH (AVIATR) Task Order 0015: Predictive Capability for Hypersonic Structural Response and Life Prediction: Phase 1-Identification of Knowledge Gaps, Volume 1: Nonproprietary Version

    DTIC Science & Technology

    2010-09-01

    AFRL-RB-WP-TR-2010-3068,V1 AIR VEHICLE INTEGRATION AND TECHNOLOGY RESEARCH (AVIATR) Task Order 0015: Predictive Capability for Hypersonic ...Order 0015: Predictive Capability for Hypersonic Structural Response and Life Prediction: Phase 1-Identification of Knowledge Gaps, Volume 1...AND ADDRESS(ES) 8. PERFORMING ORGANIZATION The Boeing Company M/C 110-SK56 2600 Westminster Avenue Seal Beach , CA 90740 REPORT NUMBER 9

  16. Global hydromagnetic simulations of a planet embedded in a dead zone: Gap opening, gas accretion, and formation of a protoplanetary jet

    SciTech Connect

    Gressel, O.; Nelson, R. P.; Turner, N. J.; Ziegler, U. E-mail: r.p.nelson@qmul.ac.uk E-mail: uziegler@aip.de

    2013-12-10

    We present global hydrodynamic (HD) and magnetohydrodynamic (MHD) simulations with mesh refinement of accreting planets embedded in protoplanetary disks (PPDs). The magnetized disk includes Ohmic resistivity that depends on the overlying mass column, leading to turbulent surface layers and a dead zone near the midplane. The main results are: (1) the accretion flow in the Hill sphere is intrinsically three-dimensional for HD and MHD models. Net inflow toward the planet is dominated by high-latitude flows. A circumplanetary disk (CPD) forms. Its midplane flows outward in a pattern whose details differ between models. (2) The opening of a gap magnetically couples and ignites the dead zone near the planet, leading to stochastic accretion, a quasi-turbulent flow in the Hill sphere, and a CPD whose structure displays high levels of variability. (3) Advection of magnetized gas onto the rotating CPD generates helical fields that launch magnetocentrifugally driven outflows. During one specific epoch, a highly collimated, one-sided jet is observed. (4) The CPD's surface density is ∼30 g cm{sup −2}, small enough for significant ionization and turbulence to develop. (5) The accretion rate onto the planet in the MHD simulation reaches a steady value 8 × 10{sup –3} M {sub ⊕} yr{sup –1} and is similar in the viscous HD runs. Our results suggest that gas accretion onto a forming giant planet within a magnetized PPD with a dead zone allows rapid growth from Saturnian to Jovian masses. As well as being relevant for giant planet formation, these results have important implications for the formation of regular satellites around gas giant planets.

  17. Gap junctions.

    PubMed

    Goodenough, Daniel A; Paul, David L

    2009-07-01

    Gap junctions are aggregates of intercellular channels that permit direct cell-cell transfer of ions and small molecules. Initially described as low-resistance ion pathways joining excitable cells (nerve and muscle), gap junctions are found joining virtually all cells in solid tissues. Their long evolutionary history has permitted adaptation of gap-junctional intercellular communication to a variety of functions, with multiple regulatory mechanisms. Gap-junctional channels are composed of hexamers of medium-sized families of integral proteins: connexins in chordates and innexins in precordates. The functions of gap junctions have been explored by studying mutations in flies, worms, and humans, and targeted gene disruption in mice. These studies have revealed a wide diversity of function in tissue and organ biology.

  18. Gap Junctions

    PubMed Central

    Goodenough, Daniel A.; Paul, David L.

    2009-01-01

    Gap junctions are aggregates of intercellular channels that permit direct cell–cell transfer of ions and small molecules. Initially described as low-resistance ion pathways joining excitable cells (nerve and muscle), gap junctions are found joining virtually all cells in solid tissues. Their long evolutionary history has permitted adaptation of gap-junctional intercellular communication to a variety of functions, with multiple regulatory mechanisms. Gap-junctional channels are composed of hexamers of medium-sized families of integral proteins: connexins in chordates and innexins in precordates. The functions of gap junctions have been explored by studying mutations in flies, worms, and humans, and targeted gene disruption in mice. These studies have revealed a wide diversity of function in tissue and organ biology. PMID:20066080

  19. Studies on the tempo of bubble formation in recently cavitated vessels: a model to predict the pressure of air bubbles.

    PubMed

    Wang, Yujie; Pan, Ruihua; Tyree, Melvin T

    2015-06-01

    A cavitation event in a vessel replaces water with a mixture of water vapor and air. A quantitative theory is presented to argue that the tempo of filling of vessels with air has two phases: a fast process that extracts air from stem tissue adjacent to the cavitated vessels (less than 10 s) and a slow phase that extracts air from the atmosphere outside the stem (more than 10 h). A model was designed to estimate how water tension (T) near recently cavitated vessels causes bubbles in embolized vessels to expand or contract as T increases or decreases, respectively. The model also predicts that the hydraulic conductivity of a stem will increase as bubbles collapse. The pressure of air bubbles trapped in vessels of a stem can be predicted from the model based on fitting curves of hydraulic conductivity versus T. The model was validated using data from six stem segments each of Acer mono and the clonal hybrid Populus 84 K (Populus alba × Populus glandulosa). The model was fitted to results with root mean square error less than 3%. The model provided new insight into the study of embolism formation in stem tissue and helped quantify the bubble pressure immediately after the fast process referred to above.

  20. The effect of sidewall forest canopies on the formation of cold-air pools: A numerical study

    NASA Astrophysics Data System (ADS)

    Kiefer, M. T.; Zhong, S.

    2013-06-01

    While the evolution and dynamics of cold-air pools in basins and valleys continue to be an active area of research, the influence of vegetation cover on cold-air pools remains largely unexamined. Recently, the Advanced Regional Prediction System (ARPS) atmospheric model has been modified to allow simulation of flow through a multilayer canopy (ARPS-CANOPY). In this study, two-dimensional numerical simulations are performed with ARPS-CANOPY to examine the impact of sidewall forest cover on diurnal cold-air pool formation inside an idealized valley. A cold-air pool develops regardless of the presence or absence of sidewall vegetation. However, the strength of the temperature inversion and the overall cooling appear to be substantially modified by sidewall vegetation. The coldest overall valley temperature occurs with no sidewall vegetation cover while the warmest occurs when the valley sidewalls are fully covered with vegetation. In simulations with partial forest cover, the nocturnal cooling in approximately the upper two thirds (lower one third) of the valley atmosphere is shown to be most sensitive to forest cover along the upper half (lower half) of the sidewall. The sidewall forest cover also affects downslope flows through a combination of weaker surface cooling beneath the forest canopy and increased drag on air flowing down the sidewalls. Finally, the strength of downslope flow is shown to be highly sensitive to the presence or absence of trees farther up the slope.

  1. Gap Junctions

    PubMed Central

    Nielsen, Morten Schak; Axelsen, Lene Nygaard; Sorgen, Paul L.; Verma, Vandana; Delmar, Mario; Holstein-Rathlou, Niels-Henrik

    2013-01-01

    Gap junctions are essential to the function of multicellular animals, which require a high degree of coordination between cells. In vertebrates, gap junctions comprise connexins and currently 21 connexins are known in humans. The functions of gap junctions are highly diverse and include exchange of metabolites and electrical signals between cells, as well as functions, which are apparently unrelated to intercellular communication. Given the diversity of gap junction physiology, regulation of gap junction activity is complex. The structure of the various connexins is known to some extent; and structural rearrangements and intramolecular interactions are important for regulation of channel function. Intercellular coupling is further regulated by the number and activity of channels present in gap junctional plaques. The number of connexins in cell-cell channels is regulated by controlling transcription, translation, trafficking, and degradation; and all of these processes are under strict control. Once in the membrane, channel activity is determined by the conductive properties of the connexin involved, which can be regulated by voltage and chemical gating, as well as a large number of posttranslational modifications. The aim of the present article is to review our current knowledge on the structure, regulation, function, and pharmacology of gap junctions. This will be supported by examples of how different connexins and their regulation act in concert to achieve appropriate physiological control, and how disturbances of connexin function can lead to disease. © 2012 American Physiological Society. Compr Physiol 2:1981-2035, 2012. PMID:23723031

  2. 75 FR 58305 - Approval and Promulgation of Air Quality Implementation Plans; Indiana; Revised Format for...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-24

    ... in 40 CFR Part 52 Environmental protection, Air pollution control, Carbon monoxide, Hydrocarbons, Incorporation by reference, Intergovernmental relations, Lead, Nitrogen dioxide, Ozone, Particulate matter... 14383. Particulate Matter Contingency Measures. Article 7. Sulfur Dioxide Rules 7-1.1 Sulfur...

  3. Secondary Organic Aerosol Formation from Ambient Air in an Oxidation Flow Reactor at GoAmazon2014/5

    NASA Astrophysics Data System (ADS)

    Palm, Brett B.; de Sa, Suzane S.; Campuzano-Jost, Pedro; Day, Douglas A.; Hu, Weiwei; Seco, Roger; Park, Jeong-Hoo; Guenther, Alex; Kim, Saewung; Brito, Joel; Wurm, Florian; Artaxo, Paulo; Yee, Lindsay; Isaacman-VanWertz, Gabrial; Goldstein, Allen; Newburn, Matt K.; Lizabeth Alexander, M.; Martin, Scot T.; Brune, William H.; Jimenez, Jose L.

    2016-04-01

    During GoAmazon2014/5, ambient air was exposed to controlled concentrations of OH or O3 in situ using an oxidation flow reactor (OFR). Oxidation ranged from hours-several weeks of aging. Oxidized air was sampled by several instruments (e.g., HR-AMS, ACSM, PTR-TOF-MS, SMPS, CCN) at both the T3 site (IOP1: Feb 1-Mar 31, 2014, and IOP2: Aug 15-Oct 15, 2014) and T2 site (between IOPs and into 2nd IOP). The oxidation of ambient air in the OFR led to substantial and variable secondary organic aerosol (SOA) formation from any SOA-precursor gases, known and unknown, that entered the OFR. In general, more SOA was produced during the nighttime than daytime, suggesting that SOA-precursor gases were found in relatively higher concentrations at night. Similarly, more SOA was formed in the dry season (IOP2) than wet season (IOP1). The maximum amount of SOA produced during nighttime from OH oxidation ranged from less than 1 μg/m3 on some nights to greater than 10 μg/m3 on other nights. O3 oxidation of ambient air also led to SOA formation, although several times less than from OH oxidation. The amount of SOA formation sometimes, but not always, correlated with measured gas-phase biogenic and/or anthropogenic SOA precursors (e.g., SV-TAG sesquiterpenes, PTR-TOFMS aromatics, isoprene, and monoterpenes). The SOA mass formed in the OFR from OH oxidation was up to an order of magnitude larger than could be explained from aerosol yields of measured primary VOCs. This along with measurements from previous campaigns suggests that most SOA was formed from intermediate S/IVOC sources (e.g., VOC oxidation products, evaporated POA, or direct emissions). To verify the SOA yields of VOCs under OFR experimental conditions, atmospherically-relevant concentrations of several VOCs were added individually into ambient air in the OFR and oxidized by OH or O3. SOA yields in the OFR were similar to published chamber yields. Preliminary PMF factor analysis showed production of secondary factors in

  4. Effects of operational conditions on sludge degradation and organic acids formation in low-critical wet air oxidation.

    PubMed

    Chung, Jinwook; Lee, Mikyung; Ahn, Jaehwan; Bae, Wookeun; Lee, Yong-Woo; Shim, Hojae

    2009-02-15

    Wet air oxidation processes are to treat highly concentrated organic compounds including refractory materials, sludge, and night soil, and usually operated at supercritical water conditions of high temperature and pressure. In this study, the effects of operational conditions including temperature, pressure, and oxidant dose on sludge degradation and conversion into subsequent intermediates such as organic acids were investigated at low critical wet oxidation conditions. The reaction time and temperature in the wet air oxidation process was shown an important factor affecting the liquefaction of volatile solids, with more significant effect on the thermal hydrolysis reaction rather than the oxidation reaction. The degradation efficiency of sludge and the formation of organic acids were improved with longer reaction time and higher reaction temperature. For the sludge reduction and the organic acids formation under the wet air oxidation, the optimal conditions for reaction temperature, time, pressure, and oxidant dose were shown approximately 240 degrees C, 30min, 60atm, and 2.0L/min, respectively.

  5. Magnetic susceptibility and cyclostratigraphy of upper Jurassic marly formations (ANDRA, underground research laboratory, Bure, Eastern Paris Basin): Record of Milankovitch cycles, sedimentary gaps, and implications for regional correlation

    NASA Astrophysics Data System (ADS)

    Emilia, H.; Bruno, G.; Pierre-Yves, C.; Slah, B.; Pascal, E.; Linda, H.; Christian, R.

    2006-05-01

    This study integrates research conducted by ANDRA at the Underground Research Laboratory of Bure (Meuse, France) to investigate the feasibility of a deep geological waste repository in clay for high-level and long-lived intermediate-level radioactive waste. The aim of this study is to detect possible sedimentary gaps in the upper Callovian-lower Oxfordian homogeneous marly formation where the laboratory is located, and to estimate the duration of stages and biostratigraphic zonation by comparison with a basin sequence from the southeast of France that is presumed to have accumulated continuously. The search for hiatuses was made using a high resolution cyclostratigraphic approach based on the study of magnetic susceptibility (MS) fluctuations. Four ANDRA boreholes (EST 342, EST 322, EST 103 and EST 312) oriented on a SW-NE transect (40 kilometers) were analyzed. Magnetic susceptibility measurements were made on core samples with a Bartington Instruments MS2E1 sensor every 4 centimeters. Sedimentological data suggest that variations of the clay content influence the long term evolution of MS. The high frequency variations in MS were subjected to spectral analysis. Composite cycles of 0.5, 1 and 2.5 m thickness were recognized on the basis of frequency ratio and correspond to the frequency ratio of orbital Milankovitch cycles. The duration of the Mariae ammonite zone in the Paris Basin was estimated by counting the cycles, to be between 2.4 and 2.6 My ± 0.3 ky (borehole EST 322 & EST 103). The amplitude spectrum shows (1) sedimentation rate variations in particular in the lower Oxfordian and (2) interruptions in cycle evolution correlated to sequential limits. We interpret these zones as short condensed levels. The same methods were applied to sections from the southeast of France (Aspres-sur-Buëch, Thuoux), and the Mariae ammonite zone estimated to be between 2.3 and 2.8 My of age. By comparison of this biostratigraphic zone between the two studied regions

  6. On the effect of carbon monoxide addition on soot formation in a laminar ethylene/air coflow diffusion flame

    SciTech Connect

    Guo, Hongsheng; Thomson, Kevin A.; Smallwood, Gregory J.

    2009-06-15

    The effect of carbon monoxide addition on soot formation in an ethylene/air diffusion flame is investigated by experiment and detailed numerical simulation. The paper focuses on the chemical effect of carbon monoxide addition by comparing the results of carbon monoxide and nitrogen diluted flames. Both experiment and simulation show that although overall the addition of carbon monoxide monotonically reduces the formation of soot, the chemical effect promotes the formation of soot in an ethylene/air diffusion flame. The further analysis of the details of the numerical result suggests that the chemical effect of carbon monoxide addition may be caused by the modifications to the flame temperature, soot surface growth and oxidation reactions. Flame temperature increases relative to a nitrogen diluted flame, which results in a higher surface growth rate, when carbon monoxide is added. Furthermore, the addition of carbon monoxide increases the concentration of H radical owing to the intensified forward rate of the reaction CO + OH = CO{sub 2} + H and therefore increases the surface growth reaction rates. The addition of carbon monoxide also slows the oxidation rate of soot because the same reaction CO + OH = CO{sub 2} + H results in a lower concentration of OH. (author)

  7. Formation and Evaluation of Protective Layer over Magnesium Melt Under CO2/Air Mixtures

    NASA Astrophysics Data System (ADS)

    Emami, Samar; Sohn, Hong Yong

    2015-02-01

    Molten magnesium oxidizes rapidly when exposed to air causing melt loss and handling difficulties. The use of certain additive gases to form a protective MgO layer over a magnesium melt has been proposed. The oxidation behavior of molten magnesium in air that contains various concentrations of CO2 was investigated, including the kinetics of the oxide layer growth. Experiments were performed using a thermogravimetric analysis unit in the temperature range of 943 K to 1043 K (670 °C to 770 °C). Results showed that a thin, coherent, and protective MgO-C layer was formed under the test conditions. The thicknesses of this layer formed under CO2/air ranged from 500 nm to 12 μm. Rate parameters were calculated and a model for the process was developed. The morphology and composition of the surface films were studied using SEM and EDS.

  8. Laser prepulse induced plasma channel formation in air and relativistic self focusing of an intense short pulse

    SciTech Connect

    Kumar, Ashok; Dahiya, Deepak; Sharma, A. K.

    2011-02-15

    An analytical formalism is developed and particle-in-cell simulations are carried out to study plasma channel formation in air by a two pulse technique and subsequent relativistic self focusing of the third intense laser through it. The first prepulse causes tunnel ionization of air. The second pulse heats the plasma electrons and establishes a prolonged channel. The third pulse focuses under the combined effect of density nonuniformity of the channel and relativistic mass nonlinearity. A channel with 20% density variation over the spot size of the third pulse is seen to strongly influence relativistic self focusing at normalized laser amplitude {approx}0.4-1. In deeper plasma channels, self focusing is less sensitive to laser amplitude variation. These results are reproduced in particle-in-cell simulations. The present treatment is valid for millimeter range plasma channels.

  9. Electric field and dewetting induced hierarchical structure formation in polymer/polymer/air trilayers.

    PubMed

    Leach, K Amanda; Gupta, Suresh; Dickey, Michael D; Willson, C Grant; Russell, Thomas P

    2005-12-01

    Electrohydrodynamics were studied in a trilayer thin film system consisting of two different polymeric layers and air. A polymer with a higher dielectric constant, poly(methyl methacrylate), was sandwiched between air and a lower dielectric constant polymer, polystyrene. An electric field was applied normal to the interfaces. Along with electrostatic forces, dewetting forces were significant at two of the interfaces, namely, the polystyrene/silicon wafer and the polystyrene/poly(methyl methacrylate) interfaces. These two combined forces produce novel closed-cell structures that are difficult to produce by other existing techniques.

  10. Solar driven nitrous acid formation on building material surfaces containing titanium dioxide: A concern for air quality in urban areas?

    NASA Astrophysics Data System (ADS)

    Langridge, Justin M.; Gustafsson, R. Joel; Griffiths, Paul T.; Cox, R. Anthony; Lambert, Richard M.; Jones, Roderic L.

    The photoenhanced uptake of nitrogen dioxide (NO 2) to the surface of commercially available self-cleaning window glass has been studied under controlled laboratory conditions. This material is one of an array of modern building products which incorporate titanium dioxide (TiO 2) nanoparticles and are finding increasing use in populated urban areas. Amongst the principal drivers for the use of these materials is that they are thought to facilitate the irreversible removal of pollutants such as NO 2 and organic molecules from the atmosphere and thus act to remediate air quality. While it appears that TiO 2 materials do indeed remove organic molecules from built environments, in this study we show that the photoenhanced uptake of NO 2 to one example material, self-cleaning window glass, is in fact accompanied by the substantial formation (50-70%) of gaseous nitrous acid (HONO). This finding has direct and serious implications for the use of these materials in urban areas. Not only is HONO a harmful respiratory irritant, it is also readily photolysed by solar radiation leading to the formation of hydroxyl radicals (OH) together with the re-release of NO x as NO. The net effect of subsequent OH initiated chemistry can then be the further degradation of air quality through the formation of secondary pollutants such as ozone and VOC oxidation products. In summary, we suggest that a scientifically conceived technical strategy for air quality remediation based on this technology, while widely perceived as universally beneficial, could in fact have effects precisely opposite to those intended.

  11. Three air quality studies: Great Lakes ozone formation and nitrogen dry deposition; and Tucson aerosol chemical characterization

    NASA Astrophysics Data System (ADS)

    Foley, Theresa

    The Clean Air Act of 1970 was promulgated after thousands of lives were lost in four catastrophic air pollution events. It authorized the establishment of National Ambient Air Quality Standards or (NAAQS) for six pollutants that are harmful to human health and welfare: carbon monoxide, lead, nitrogen dioxide, particulate matter, ozone and sulfur dioxide. The Clean Air Act also led to the establishment of the United Stated Environmental Protection Agency (US EPA) to set and enforce regulations. The first paper in this dissertation studies ozone in the Lake Michigan region (Foley, T., Betterton, E.A., Jacko, R., Hillery, J., 2011. Lake Michigan air quality: The 1994-2003 LADCO Aircraft Project (LAP). Atmospheric Environment 45, 3192-3202.) The Chicago-Milwaukee-Gary metropolitan area has been unable to meet the ozone NAAQS since the Clean Air Act was implemented. The Lake Michigan Air Directors' Consortium (LADCO) hypothesized that land breezes transport ozone precursor compounds over the lake, where a large air/water temperature difference creates a shallow conduction layer, which is an efficient reaction chamber for ozone formation. In the afternoon, lake breezes and prevailing synoptic winds then transport ozone back over the land. To further evaluate this hypothesis, LADCO sponsored the 1994-2003 LADCO Aircraft Project (LAP) to measure the air quality over Lake Michigan and the surrounding areas. This study has found that the LAP data supports this hypothesis of ozone formation, which has strong implications for ozone control strategies in the Lake Michigan region. The second paper is this dissertation (Foley, T., Betterton, E.A., Wolf, A.M.A., 2012. Ambient PM10 and metal concentrations measured in the Sunnyside Unified School District, Tucson, Arizona. Journal of the Arizona-Nevada Academy of Science, 43, 67-76) evaluated the airborne concentrations of PM10 (particulate matter with an aerodynamic diameter of 10 microns or less) and eight metalloids and metals

  12. FORMATION OF POLYKETONES IN IRRADIATED TOLUENE/PROPYLENE/NOX/AIR MIXTURES

    EPA Science Inventory

    A laboratory study was carried out to investigate the formation of polyketones in secondary organic aerosol from photooxidation of the aromatic hydrocarbon toluene, a major constituent of automobile exhaust. The laboratory experiments consisted of irradiating toluene/propylene...

  13. Evaluation of thermal formation and air ventilation inside footwear during gait: The role of gait and fitting.

    PubMed

    Shimazaki, Yasuhiro; Matsutani, Toshiki; Satsumoto, Yayoi

    2016-07-01

    Comfort is an important concept in footwear design. The microclimate inside footwear contributes to the perception of thermal comfort. To investigate the effect of ventilation on microclimate formation inside footwear, experiments with subjects were conducted at four gait speeds with three different footwear sizes. Skin temperature, metabolism, and body mass were measured at approximately 25 °C and 50% relative humidity, with no solar radiation and a calm wind. The footwear occupancy and ventilation rate were also estimated, with the latter determined using the tracer gas method. The experimental results revealed that foot movement, metabolism, evaporation, radiation, convection, and ventilation were the main factors influencing the energy balance for temperature formation on the surface of the foot. The cooling effect of ventilation on the arch temperature was observed during gait. The significance of the amount of air space and ventilation on the improvement in the thermal comfort of footwear was clarified.

  14. AlFx affects the formation of focal complexes by stabilizing the Arf-GAP ASAP1 in a complex with Arf1.

    PubMed

    Klein, Stéphanie; Franco, Michel; Chardin, Pierre; Luton, Frédéric

    2005-10-24

    Aluminum fluoride (AlFx) is known to activate directly the alpha subunit of G-proteins but not the homologous small GTP-binding proteins. However, AlFx can stabilize complexes formed between Ras, RhoA or Cdc42 and their corresponding GTPase-activating proteins (GAPs). Here, we demonstrate that Arf1GDP can be converted into an active conformation by AlFx to form a complex with the Arf-GAP ASAP1 in vitro and in vivo. Within this complex ASAP1, which GAP activity is inoperative, can still alter the recruitment of paxillin to the focal complexes, thus indicating that ASAP1 interferes with focal complexes independently of its GAP activity.

  15. Design and characterization of a novel coaxial VHF plasma source for air plasma formation

    NASA Astrophysics Data System (ADS)

    Byrns, Brandon; Wooten, Daniel; Shannon, Steven

    2011-10-01

    A key challenge in the expansion of atmospheric plasma applicators into new markets is the effective surface area that these systems can efficiently treat. To this end, a large area atmospheric air glow discharge, with approximately 9.5 cm2 cross sectional area, is obtained using a simple coaxial structure. The room air plasma is driven by a 162MHz generator at powers ranging from 300W-1000W. The VHF drive appears to produce a steady state glow void of streamers or arcs typically found in atmospheric air systems. Electrical measurements coupled with a global plasma model and transmission line theory allow for the calculation of electron density. Densities calculated for 400W are approximately 1011 cm-3. Spectroscopy data shows dominant emissions consist of OH, N2, and N2+,along with a continuum indicating neutral bremsstrahlung radiation; this is used for electron density calculations and model validation. In this presentation, source design, plasma characterization, and preliminary surface treatments of HDPE will be presented. A key challenge in the expansion of atmospheric plasma applicators into new markets is the effective surface area that these systems can efficiently treat. To this end, a large area atmospheric air glow discharge, with approximately 9.5 cm2 cross sectional area, is obtained using a simple coaxial structure. The room air plasma is driven by a 162MHz generator at powers ranging from 300W-1000W. The VHF drive appears to produce a steady state glow void of streamers or arcs typically found in atmospheric air systems. Electrical measurements coupled with a global plasma model and transmission line theory allow for the calculation of electron density. Densities calculated for 400W are approximately 1011 cm-3. Spectroscopy data shows dominant emissions consist of OH, N2, and N2+,along with a continuum indicating neutral bremsstrahlung radiation; this is used for electron density calculations and model validation. In this presentation, source design

  16. Biostratigraphy and biochronology of the Monte Hermoso Formation (early Pliocene) at its type locality, Buenos Aires Province, Argentina

    NASA Astrophysics Data System (ADS)

    Tomassini, Rodrigo L.; Montalvo, Claudia I.; Deschamps, Cecilia M.; Manera, Teresa

    2013-12-01

    The Monte Hermoso Formation, cropping out at its type locality of Farola Monte Hermoso (Buenos Aires Province), is a classical fossiliferous unit of the South American Neogene, highlighted by the abundance and diversity of its vertebrate remains. However, its biostratigraphy and age have been largely debated, and numerous discrepancies and controversies have been stated. In this regard, the result of the analysis of new materials recovered from the different levels of this formation, following a strict control of stratigraphic provenance, is here reported. As well, the provenance of specimens of previous collections has been evaluated. The studied assemblage consists of Osteichthyes, Amphibia, Reptilia, Aves and Mammalia. These latter are the most numerous and belong to the Didelphimorphia, Polydolopimorphia, Rodentia, Notoungulata, Litopterna and Xenarthra. The recorded taxa suggest no important faunistic variations among the different levels of the Monte Hermoso Formation that would imply significant chronological differences, and hence, justify the recognition of two biostratigraphic units. The analysis of the first and last records as well as the taxa considered as exclusive, does not support the validity of the biozones of Trigodon gaudryi and Neocavia depressidens previously proposed. On this basis, a new scheme for the Monte Hermoso Formation at its type locality is proposed, including a new single biostratigraphic unit. This unit is the Eumysops laeviplicatus Range Zone, which represents the biostratigraphic base for the Montehermosan Stage/Age of the early Pliocene.

  17. Hydrochloric acid aerosol formation by the interaction of hydrogen chloride with humid air

    NASA Technical Reports Server (NTRS)

    Rhein, R. A.

    1973-01-01

    The conditions in which hydrochloric acid aerosol is predicted by the interaction of hydrogen chloride gas with the water vapor in humid air are analyzed. The liquid gas phase equilibrium for the HCL-H2O system is expressed in terms of relative humidity and hydrogen chloride concentration as parts per million, units commonly used in pollution studies. Presented are the concentration (wt %) of HC1 in the aerosol and the concentration of aerosol (ppm) predicted.

  18. Formation of thermal flow fields and chemical transport in air and water by atmospheric plasma

    NASA Astrophysics Data System (ADS)

    Shimizu, Tetsuji; Iwafuchi, Yutaka; Morfill, Gregor E.; Sato, Takehiko

    2011-05-01

    Cold atmospheric plasma is a potential tool for medical purposes, e.g. disinfection/sterilization. In order for it to be effective and functional, it is crucial to understand the transport mechanism of chemically reactive species in air as well as in liquid. An atmospheric plasma discharge was produced between a platinum pin electrode and the surface of water. The thermal flow field of a cold atmospheric plasma as well as its chemical components was measured. A gas flow with a velocity of around 15 m s-1 to the water's surface was shown to be induced by the discharge. This air flow induced a circulating flow in the water from the discharge point at the water's surface because of friction. It was also demonstrated that the chemical components generated in air dissolved in water and the properties of the water changed. The reactive species were believed to be distributed mainly by convective transport in water, because the variation in the pH profile indicated by a methyl red solution resembled the induced flow pattern.

  19. Contributions of vehicular emissions and secondary formation to nitrous acid concentrations in ambient urban air in Tokyo in the winter.

    PubMed

    Nakashima, Yoshihiro; Sadanaga, Yasuhiro; Saito, Shinji; Hoshi, Junya; Ueno, Hiroyuki

    2017-03-15

    Nitrous acid (HONO) plays an important role in the formation of OH radicals, which are involved in photochemical oxidation. HONO concentrations in ambient air at urban sites have previously been measured, but very few studies have been performed in central Tokyo. In this study, HONO concentrations in ambient air in southeast central Tokyo (near Tokyo Bay) in winter were determined by incoherent cavity enhanced absorption spectroscopy. The O3, NO, NO2, and SO2 concentrations were simultaneously determined. The NO concentrations were used to classify the parts of the study period into types I (high pollution), II (medium pollution), and III (low pollution). The maximum HONO concentrations in the type I, II, and III periods were 7.1, 4.5, and 3.0ppbv, respectively. These concentrations were comparable to concentrations previously found in other Asian megacities. The mean HONO concentration varied diurnally, and HONO was depleted between 00:00 and 03:00 each day. The sampling site is surrounded by roads with high traffic loads, but vehicular emissions were estimated to contribute <10% of the HONO concentrations. Two positive and negative relative humidity dependences of the HONO to NO2 ratio were confirmed, implying the existence of the two different secondary formation process of HONO. The NO2 to HONO conversion rates at night in the type I, II, and III periods were 6.3×10(-3), 7.6×10(-3), and 4.2×10(-3)h(-1), respectively.

  20. Real-Time Secondary Aerosol Formation Measurements using a Photooxidation Reactor (PAM) and AMS in Urban Air and Biomass Smoke

    NASA Astrophysics Data System (ADS)

    Ortega, A. M.; Cubison, M.; Hayes, P. L.; Brune, W. H.; Hu, W.; Flynn, J. H.; Grossberg, N.; Lefer, B. L.; Alvarez, S. L.; Rappenglueck, B.; Bon, D.; Graus, M.; Warneke, C.; Gilman, J. B.; Kuster, W. C.; De Gouw, J. A.; Sullivan, A. P.; Jimenez, J. L.

    2011-12-01

    Recent field studies reveal large formation of secondary organic aerosol (SOA) under urban polluted ambient conditions, while SOA formation in biomass burning smoke appears to be variable but sometimes substantial. To study this formation in real-time, a Potential Aerosol Mass (PAM) photooxidation reactor was deployed with submicron aerosol size and chemical composition measurements during two studies: FLAME-3, a biomass-burning study at USDA Fire Sciences Laboratory in Missoula in 2009, MT and CalNex-LA in Pasadena, CA in 2010. A high-resolution aerosol mass spectrometer (HR-AMS) and a scanning mobility particle sizer (SMPS) alternated sampling unprocessed and PAM-processed aerosol. The PAM reactor produces OH concentrations up to 4 orders of magnitude higher than in ambient air, achieving equivalent aging of ~2 weeks in 5 minutes of processing. The OH intensity was also scanned every 20 min. in both field studies. Results show the value of PAM-AMS as a tool for in-situ evaluation of changes in OA concentration and composition due to SOA formation and POA oxidation. In FLAME-3, net SOA formation was variable among smokes from different biomasses; however, OA oxidation was always observed. The average SOA enhancement factor was 1.7 +/- 0.5 of the initial POA. Reactive VOCs such as toluene, monoterpenes, and acetaldehyde, as measured from a PIT-MS, decreased with increased PAM processing; however, formic acid, acetone, and some unidentified OVOCs increased after significant exposure to high oxidant levels suggesting multigenerational chemistry. Results from CalNex-LA show enhancement of SOA and inorganic aerosol from gas-phase precursors. This enhanced OA mass increase from PAM processing is maximum at night and correlates with trimethylbenzene concentrations, which indicates the dominance of short-lived SOA precursors in the LA Basin. A traditional SOA model with mostly aromatic precursors underpredicts the amount of SOA formed by about an order-of-magnitude, which

  1. Effect of the Graded-Gap Layer Composition on the Formation of n + -n - -p Structures in Boron-Implanted Heteroepitaxial Cd x Hg1- x Te Layers

    NASA Astrophysics Data System (ADS)

    Talipov, N. Kh.; Voitsekhovskii, А. V.; Grigor'ev, D. V.

    2014-07-01

    Processes of formation of n + -n--p-structures in boron-implanted heteroepitaxial (HEL) CdxHg1-xTe (CMT) layers of p-type grown by molecular beam epitaxy (HEL CMT MBE) with different compositions of the upper graded-gap layer are studied. It is shown that the surface composition (xs) of HEL CMT MBE significantly affects both the electrical parameters of the implanted layer and the spatial distribution of radiation defects of donor type. For HEL CMT MBE with the small surface composition xs = 0.22-0.33, it is found that the layer electron concentration (Ns) is decreased after saturation with accumulation of radiation defects, as the dose of B+ ions is increased in the range of D = 1ṡ1011-3ṡ1015 сm-2. An increase of the surface composition up to xs = 0.49-0.56 results in a significant decrease in Ns and a disappearance of the saturation of concentration in the whole dose range. The value of Ns monotonically increases with the energy (E) of boron ions and composition xs. It is found that for B+-ion energies E = 20-100 keV, the depth of the surface n + -layer increases with increasing energy and exceeds the total projected path of boron ions. However, in the energy range E = 100-150 keV, the depth of n+-layer stops increasing with the increase of the surface composition. The depth (dn) of a lightly doped n--layer monotonically decreases with increasing energy of boron ions in the entire range of E = 20-150 keV. With increasing dose (D) of B+ ions in the interval D = 1ṡ1014-1ṡ1015сm-2, deep n--layers with dn = 4-5 μm are formed only in the HEL CMT MBE with xs = 0.22-0.33. For the samples with xs = 0.49-0.56, the depth changes in the interval dn = 1.5-2.5 μm. At D ≤ 3ṡ1013сm-2, n + -n--p-structure is not formed for all surface compositions, if implantation is performed at room temperature. However, implantation at T = 130°C leads to the formation of a deep n--layer. Planar photodiodes with the n-p-junction area of A = 35×35 μm2 made on the basis of

  2. Fuel Efficient Strategies for Reducing Contrail Formations in United States Air Space

    NASA Technical Reports Server (NTRS)

    Sridhar, Banavar; Chen, Neil Y.; Ng, Hok K.

    2010-01-01

    This paper describes a class of strategies for reducing persistent contrail formation in the United States airspace. The primary objective is to minimize potential contrail formation regions by altering the aircraft's cruising altitude in a fuel-efficient way. The results show that the contrail formations can be reduced significantly without extra fuel consumption and without adversely affecting congestion in the airspace. The contrail formations can be further reduced by using extra fuel. For the day tested, the maximal reduction strategy has a 53% contrail reduction rate. The most fuel-efficient strategy has an 8% reduction rate with 2.86% less fuel-burnt compared to the maximal reduction strategy. Using a cost function which penalizes extra fuel consumed while maximizing the amount of contrail reduction provides a flexible way to trade off between contrail reduction and fuel consumption. It can achieve a 35% contrail reduction rate with only 0.23% extra fuel consumption. The proposed fuel-efficient contrail reduction strategy provides a solution to reduce aviation-induced environmental impact on a daily basis.

  3. Formation of H-type liquid crystal dimer at air-water interface

    SciTech Connect

    Karthik, C. Gupta, Adbhut Joshi, Aditya Manjuladevi, V. Gupta, Raj Kumar; Varia, Mahesh C.; Kumar, Sandeep

    2014-04-24

    We have formed the Langmuir monolayer of H-shaped Azo linked liquid crystal dimer molecule at the air-water interface. Isocycles of the molecule showed hysteresis suggesting the ir-reversible nature of the monolayer formed. The thin film deposited on the silicon wafer was characterized using Atomic Force Microscopy (AFM) and Field Emission Scanning Electron Microscopy (FESEM). The images showed uniform domains of the dimer molecule. We propose that these molecules tend to take book shelf configuration in the liquid phase.

  4. Ozone formation potentials of organic compounds from different emission sources in the South Coast Air Basin of California

    NASA Astrophysics Data System (ADS)

    Chen, Jianjun; Luo, Dongmin

    2012-08-01

    Different organic compounds exhibit different propensities for ozone formation. Two approaches were used to study the ozone formation potentials or source reactivities of different anthropogenic organic compounds emission categories in California's South Coast Air Basin (SoCAB). The first approach was based on the combination of total organic gases (TOG) emission speciation profiles and the maximum incremental reactivity (MIR) scale of organic species. The second approach quantified ozone impacts from different emission sources by performing 3-dimensional air quality model sensitivity analysis involving increased TOG emissions from particular sources. The source reactivities derived from these two approaches agree reasonably well for 58 anthropogenic organic compounds emission categories in the SoCAB. Both approaches identify TOG emissions from mobile sources as having the highest reactivity. Source reactivities from both approaches were also combined with TOG emissions from each source category to produce a 2005 reactivity-based anthropogenic TOG emission inventory for the SoCAB. The top five reactivity-based anthropogenic TOG emission sources in the SoCAB during 2005 were: light-duty passenger cars, off-road equipment, consumer products, light-duty trucks category 2 (i.e., 3751-5750 lb), and recreational boats. This is in contrast to the mass-based TOG emission inventory, which indicates that livestock waste and composting emission categories were two of the five largest mass-based anthropogenic TOG emission sources. The reactivity-based TOG emission inventory is an important addition to the mass-based TOG emission inventory because it represents the ozone formation potentials from emission sources and can be used to assist in determining targeted sources for developing organic compounds reduction policies.

  5. Ozone Formation Potentials from Different Anthropogenic Emission Sources of Volatile Organic Compounds in California's South Coast Air Basin

    NASA Astrophysics Data System (ADS)

    Chen, J.; Luo, D.; Croes, B.

    2010-12-01

    Different volatile organic compounds (VOC) exhibit different propensities for ozone formation. Two approaches were used to study the relative ozone formation potentials (source reactivities) of different anthropogenic VOC emission source categories in California’s South Coast Air Basin (SoCAB). The first approach combined emission speciation profiles for total organic gases (TOG) with maximum incremental reactivity (MIR) scales for VOC species. The second approach quantified ozone impacts from different sources by performing 3-dimensional air quality model sensitivity analyses involving increased TOG emissions from particular sources. The source reactivities for 58 VOC emission categories in SoCAB derived from these two approaches agree reasonably well (R2 = ~0.9). Both approaches revealed the two emissions source types with the highest TOG reactivity were mobile sources and managed forest burning. Also, a reactivity-based TOG emission inventory for SoCAB in 2005 was produced by combining the source reactivities from both approaches with TOG emissions from anthropogenic source categories. The top five reactivity-based source categories are: light-duty passenger cars, off-road equipments, consumer products, light-duty trucks, and recreational boats. This is in contrast to the mass-based TOG emission inventory, which indicates that farming operations (mainly from animal waste) was one of the five largest mass-based anthropogenic TOG emission sources. Compared to the mass-based TOG emission inventory, the reactivity-based TOG emission inventory more appropriately represents the ozone formation potentials from emission sources, and highlights those sources that should be targeted for future regulations.

  6. Air-sea fluxes and satellite-based estimation of water masses formation

    NASA Astrophysics Data System (ADS)

    Sabia, Roberto; Klockmann, Marlene; Fernandez-Prieto, Diego; Donlon, Craig

    2015-04-01

    Recent work linking satellite-based measurements of sea surface salinity (SSS) and sea surface temperature (SST) with traditional physical oceanography has demonstrated the capability of generating routinely satellite-derived surface T-S diagrams [1] and analyze the distribution/dynamics of SSS and its relative surface density with respect to in-situ measurements. Even more recently [2,3], this framework has been extended by exploiting these T-S diagrams as a diagnostic tool to derive water masses formation rates and areas. A water mass describes a water body with physical properties distinct from the surrounding water, formed at the ocean surface under specific conditions which determine its temperature and salinity. The SST and SSS (and thus also density) at the ocean surface are largely determined by fluxes of heat and freshwater. The surface density flux is a function of the latter two and describes the change of the density of seawater at the surface. To obtain observations of water mass formation is of great interest, since they serve as indirect observations of the thermo-haline circulation. The SSS data which has become available through the SMOS [4] and Aquarius [5] satellite missions will provide the possibility of studying also the effect of temporally-varying SSS fields on water mass formation. In the present study, the formation of water masses as a function of SST and SSS is derived from the surface density flux by integrating the latter over a specific area and time period in bins of SST and SSS and then taking the derivative of the total density flux with respect to density. This study presents a test case using SMOS SSS, OSTIA SST, as well as Argo ISAS SST and SSS for comparison, heat fluxes from the NOCS Surface Flux Data Set v2.0, OAFlux evaporation and CMORPH precipitation. The study area, initially referred to the North Atlantic, is extended over two additional ocean basins and the study period covers the 2011-2012 timeframe. Yearly, seasonal

  7. Air oxidation method employed for the disulfide bond formation of natural and synthetic peptides.

    PubMed

    Calce, Enrica; Vitale, Rosa Maria; Scaloni, Andrea; Amodeo, Pietro; De Luca, Stefania

    2015-08-01

    Among the available protocols, chemically driven approaches to oxidize cysteine may not be required for molecules that, under the native-like conditions, naturally fold in conformations ensuring an effective pairing of the right disulfide bridge pattern. In this contest, we successfully prepared the distinctin, a natural heterodimeric peptide, and some synthetic cyclic peptides that are inhibitors of the CXCR4 receptor. In the first case, the air oxidation reaction allowed to connect two peptide chains via disulfide bridge, while in the second case allowed the cyclization of rationally designed peptides by an intramolecular disulfide bridge. Computational approaches helped to either drive de-novo design or suggest structural modifications and optimal oxidization protocols for disulfide-containing molecules. They are able to both predict and to rationalize the propensity of molecules to spontaneously fold in suitable conformations to achieve the right disulfide bridges.

  8. Enhanced formation of secondary air pollutants and aggravation of urban smog due to crop residue burning emissions in North India

    NASA Astrophysics Data System (ADS)

    Sarkar, Chinmoy; Kumar, Vinod; Sinha, Vinayak

    2013-04-01

    implications for the oxidizing capacity of the atmosphere increased from an average value of 14 /s (N.F.E.) to 40 /s (F.E.) just due to CO, NOx and the measured aromatics. The observed increase in ozone was 10ppbV higher after sunrise on the day after the fire plume was sampled and driven by the sudden NOx availability at a site that normally falls in a NOx limited ozone production regime. The strong pollutant enhancements in carcinogenic aromatic hydrocarbons that are also highly reactive and fuel ozone and secondary organic aerosol formation when accompanied by the high NOx and CO levels resulting from crop residue burning in N. India, clearly highlight the need to address the practice of crop residue burning which strongly alters the composition and chemistry of the atmosphere with adverse effects on both air quality and health. This study is the first from within India to combine fast in-situ PTR-MS VOC emission tracer measurements with online measurements of primary pollutants and MODIS satellite data. Further targeted studies employing a comprehensive measurement suite of both aerosol and gas species are needed to assess the full impact of crop residue burning on atmospheric chemistry and regional air quality. Acknowledgement: We thank the IISER Mohali Atmospheric Chemistry Facility for data and the Ministry of Human Resource Development (MHRD),India and IISER Mohali for funding the facility. Vinod Kumar acknowledges the DST INSPIRE Fellowship programme. Chinmoy Sarkar thanks the Max Planck-DST India Partner Group on Tropospheric OH reactivity and VOCs for funding support.

  9. Influence of aerosol spectrum and air pollutants on fog formation in urban environment of megacity Delhi, India.

    PubMed

    Mohan, Manju; Payra, Swagata

    2009-04-01

    Urban areas are facing increasing fog frequencies that may result due to increased air pollution emanating from variety of sources. The increased pollution levels may lead to the atmospheric reactions resulting into the formation of secondary pollutants that may also lead to increased aerosol number concentrations (ANC) in the atmosphere. This could cause enhanced water aerosols in the presence of favourable meteorological conditions and high relative humidity. This study deals with the atmospheric pollution and visibility during winter season of megacity Delhi in order to assess the relationship between the two specifically during fog episodes. Thus, this study analyses the levels of air pollutants, aerosol spectrum and meteorological conditions during one week each in the winter season of the years 2004 and 2006 in order to have an improved understanding of their role in fog formation in mega-city Delhi. More than 300 h of measurements which included episodes of dense, thick and moderate fogs of about 25 h, were studied. The measurements cover most of the accumulation mode and greater size spectrum of aerosols. Thus, the analysis is performed for the entire period, specifically, before the fog sets up, during and afterwards. In general, the relatively small variations in number concentration show larger variations in visibility prior and post dense fog formation than during dense fog episodes. Preliminary analysis of monthly averaged RSPM (Respirable Suspended particulate Matter or PM(10)) concentration values for four winter months for a period of 6 years (1996-2001) and visibility did not show a good correlation with total occurrences of fog. However, daily averaged RSPM concentration showed a good correlation with the occurrences of thick fog. Diurnal variation of Sulfur-dioxide and Nitrogen dioxide were found to have inverse relationship with visibility during fog which may be due to formation of secondary pollutants such as sulfate and to a lesser extent

  10. The formation of ignition centers before the front of spherical flame in hydrogen-air mixtures under intense initiation

    NASA Astrophysics Data System (ADS)

    Petukhov, V. A.; Bublik, N. P.; Gusev, P. A.; Gutkin, L. D.; Solntsev, O. I.

    2016-11-01

    Studied is the influence of volume of hydrogen-air mixture, its composition and energy of its initiation on the formation of ignition centers before the front of spherical flame. During the experiments the mixture was placed into thin rubber envelopes of spherical shape having the initial volume of 7 and 40 m3. The mixture was initiated in the center of the reaction volume by the energy which was several times less than the critical energy of direct initiation of detonation. With increasing the initial volume of the mixture with the identical composition, registered is a decrease of the initiation energy at which the ignition centers before the front of spherical flame are formed.

  11. Ammonia conversion and NOx formation in laminar coflowing nonpremixed methane-air flames

    SciTech Connect

    Sullivan, Neal; Jensen, Anker; Glarborg, Peter; Day, Marcus S.; Grcar, Joseph F.; Bell, John B.; Pope, Christopher J.; Kee, Robert J.

    2002-01-07

    This paper reports on a combined experimental and modeling investigation of NOx formation in nitrogen-diluted laminar methane diffusion flames seeded with ammonia. The methane-ammonia mixture is a surrogate for biomass fuels which contain significant fuel-bound nitrogen. The experiments use flue-gas sampling to measure the concentration of stable species in the exhaust gas, including NO, O2, CO, and CO2. The computations evolve a two-dimensional low Mach number model using a solution-adaptive projection algorithm to capture fine-scale features of the flame. The model includes detailed thermodynamics and chemical kinetics, differential diffusion, buoyancy, and radiative losses. The model shows good agreement with the measurements over the full range of experimental NH3 seeding amounts. As more NH3 is added, a greater percentage is converted to N2 rather than to NO. The simulation results are further analyzed to trace the changes in NO formation mechanisms with increasing amounts of ammonia in the fuel.

  12. Properties of the seawater-air interface. 2. Rates of surface film formation under steady state conditions

    SciTech Connect

    Dragcevic, D.; Pravdic, V.

    1981-05-01

    The laboratory techniques of dynamic surface tension and of surface electrical potential measurements were used to determine rates of formation and of reorientation of organic surface films at the seawater-air interface. Relaxation times of surface films were determined for three characteristic samples obtained by screen and bottle sampling in the coastal waters of the northern Adriatic area. These data were compared with those for model samples produced by spreading oleic acid and crude oil on or dissolving polyethyleneglycol and sodium dodecyl sulfate in artificial seawater. Relaxation times were in the range of 0.1-1 s for most of the samples. A good representative value for field samples is 0.2 s. The temperature-dependence (the energies of activation) for the surface film relaxation indicates that several processes control material transport toward the seawater-air interface. The findings are interpreted as showing that an almost ever-present organic surface film influences the mechanism and the rate of material transport across the sea-atmosphere boundary.

  13. Ultrafast formation of air-processable and high-quality polymer films on an aqueous substrate

    NASA Astrophysics Data System (ADS)

    Noh, Jonghyeon; Jeong, Seonju; Lee, Jung-Yong

    2016-08-01

    Polymer solar cells are attracting attention as next-generation energy sources. Scalable deposition techniques of high-quality organic films should be guaranteed to realize highly efficient polymer solar cells in large areas for commercial viability. Herein, we introduce an ultrafast, scalable, and versatile process for forming high-quality organic films on an aqueous substrate by utilizing the spontaneous spreading phenomenon. This approach provides easy control over the thickness of the films by tuning the spreading conditions, and the films can be transferred to a variety of secondary substrates. Moreover, the controlled Marangoni flow and ultrafast removal of solvent during the process cause the films to have a uniform, high-quality nanomorphology with finely separated phase domains. Polymer solar cells were fabricated from a mixture of polymer and fullerene derivatives on an aqueous substrate by using the proposed technique, and the device exhibited an excellent power conversion efficiency of 8.44 %. Furthermore, a roll-to-roll production system was proposed as an air-processable and scalable commercial process for fabricating organic devices.

  14. Ultrafast formation of air-processable and high-quality polymer films on an aqueous substrate

    PubMed Central

    Noh, Jonghyeon; Jeong, Seonju; Lee, Jung-Yong

    2016-01-01

    Polymer solar cells are attracting attention as next-generation energy sources. Scalable deposition techniques of high-quality organic films should be guaranteed to realize highly efficient polymer solar cells in large areas for commercial viability. Herein, we introduce an ultrafast, scalable, and versatile process for forming high-quality organic films on an aqueous substrate by utilizing the spontaneous spreading phenomenon. This approach provides easy control over the thickness of the films by tuning the spreading conditions, and the films can be transferred to a variety of secondary substrates. Moreover, the controlled Marangoni flow and ultrafast removal of solvent during the process cause the films to have a uniform, high-quality nanomorphology with finely separated phase domains. Polymer solar cells were fabricated from a mixture of polymer and fullerene derivatives on an aqueous substrate by using the proposed technique, and the device exhibited an excellent power conversion efficiency of 8.44 %. Furthermore, a roll-to-roll production system was proposed as an air-processable and scalable commercial process for fabricating organic devices. PMID:27507624

  15. Relevance of PCDD/PCDF formation for the evaluation of POPs destruction technologies--review on current status and assessment gaps.

    PubMed

    Weber, Roland

    2007-04-01

    One important criterion for assessment of a POPs destruction technology is the potential formation of new POPs and other toxic by-products, in particular whether the highly toxic PCDDs/PCDFs are formed and under which operation conditions their formation is relevant. For incineration processes the formation mechanisms of PCDDs/PCDFs have been investigated thoroughly and strategies and technologies were developed to minimize their formation and emission. A detailed assessment of non-combustion technologies with respect to PCDD/PCDF formation is, however, lacking to date. A comparison of reaction conditions for PCDD/PCDF formation from precursor formation studies and actual applied conditions of a broad range of POPs destruction technologies in the present paper indicates that the operation conditions for a number of destruction technologies have the potential to generate high concentrations of PCDDs/PCDFs if dioxin precursors are present and that also PCDD/PCDF de novo formation can take place. Therefore a strategy and regulations for a more profound assessment and monitoring of the fate of PCDD/PCDF formation and emission is essential for the evaluation of POP destruction technologies and for a sound risk management of POPs. The present paper aims to provide a critical impulse in this respect, discusses the relevant formation pathways with respect to POPs destruction technologies and proposes a basic framework on how evaluations may be performed.

  16. Three dimensional simulations of pattern formation during high-pressure, freely localized microwave breakdown in air

    SciTech Connect

    Kourtzanidis, K. Boeuf, J. P.; Rogier, F.

    2014-12-15

    Recent experiments have demonstrated that a freely localized 100 GHz microwave discharge can propagate towards the microwave source with high speed, forming a complex pattern of self-organized filaments. We present three-dimensional simulations of the formation and propagation of such patterns that reveal more information on their nature and interaction with the electromagnetic waves. The developed three-dimensional Maxwell-plasma solver permits the study of different forms of incident field polarization. Results for linear and circular polarization of the wave are presented and comparisons with recent experiments show a good overall agreement. The three dimensional simulations provide a quantitative analysis of the parameters controlling the time and length scales of the strongly non-linear plasma dynamics and could be useful for potential microwave plasma applications such as aerodynamic flow and combustion control.

  17. Imaging of a Transitional Disk Gap in Reflected Light: Indications of Planet Formation Around the Young Solar Analog LkCa 15

    NASA Astrophysics Data System (ADS)

    Thalmann, C.; Grady, C. A.; Goto, M.; Wisniewski, J. P.; Janson, M.; Henning, T.; Fukagawa, M.; Honda, M.; Mulders, G. D.; Min, M.; Moro-Martín, A.; McElwain, M. W.; Hodapp, K. W.; Carson, J.; Abe, L.; Brandner, W.; Egner, S.; Feldt, M.; Fukue, T.; Golota, T.; Guyon, O.; Hashimoto, J.; Hayano, Y.; Hayashi, M.; Hayashi, S.; Ishii, M.; Kandori, R.; Knapp, G. R.; Kudo, T.; Kusakabe, N.; Kuzuhara, M.; Matsuo, T.; Miyama, S.; Morino, J.-I.; Nishimura, T.; Pyo, T.-S.; Serabyn, E.; Shibai, H.; Suto, H.; Suzuki, R.; Takami, M.; Takato, N.; Terada, H.; Tomono, D.; Turner, E. L.; Watanabe, M.; Yamada, T.; Takami, H.; Usuda, T.; Tamura, M.

    2010-08-01

    We present H- and K s-band imaging data resolving the gap in the transitional disk around LkCa 15, revealing the surrounding nebulosity. We detect sharp elliptical contours delimiting the nebulosity on the inside as well as the outside, consistent with the shape, size, ellipticity, and orientation of starlight reflected from the far-side disk wall, whereas the near-side wall is shielded from view by the disk's optically thick bulk. We note that forward scattering of starlight on the near-side disk surface could provide an alternate interpretation of the nebulosity. In either case, this discovery provides confirmation of the disk geometry that has been proposed to explain the spectral energy distributions of such systems, comprising an optically thick disk with an inner truncation radius of ~46 AU enclosing a largely evacuated gap. Our data show an offset of the nebulosity contours along the major axis, likely corresponding to a physical pericenter offset of the disk gap. This reinforces the leading theory that dynamical clearing by at least one orbiting body is the cause of the gap. Based on evolutionary models, our high-contrast imagery imposes an upper limit of 21 M Jup on companions at separations outside of 0farcs1 and of 13 M Jup outside of 0farcs2. Thus, we find that a planetary system around LkCa 15 is the most likely explanation for the disk architecture. Based on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan, and on data obtained from the ESO Science Archive Facility under program ID 280.C-5033(A).

  18. A Computational Study of Soot Formation in Methane Air Co-Flow Diffusion Flame Under Microgravity Conditions

    NASA Astrophysics Data System (ADS)

    Bhowal, Arup Jyoti; Mandal, Bijan Kumar

    2016-08-01

    An in-house developed code has been used to predict soot formation in a methane air co flow diffusion flame at normal gravity and at lower gravity levels of 0.5 G, and 0.0001 G (microgravity). There is an augmentation of soot formation at lower gravity levels because of lower buoyancy induced acceleration leading to an increased residence time. The peak temperature at microgravity is reduced by about 50 K than that at normal gravity level. The axial velocity under normal gravity and reduced gravity show negative values (relatively small in magnitude) near the wall at axial height beyond 15 cm; but axial velocity is never negative in microgravity condition. Peak value of soot volume fraction at 0.5 G and microgravity multiplies by a factor of ˜3 and ˜7, respectively of that at normal gravity. The zone of peak soot volume fraction shifts away from the axis towards the wings, as gravity level is lowered. In comparison to soot volume fraction, the factors of amplification of soot number density at reduced gravity and at microgravity are comparatively lower at 1.2 and 1.5 of that at normal gravity respectively. On the other hand, mean soot particle sizes at reduced gravity and microgravity increase to 1.5 and 2 times of that at normal gravity respectively.

  19. Combustion characteristics and air pollutant formation during oxy-fuel co-combustion of microalgae and lignite.

    PubMed

    Gao, Yuan; Tahmasebi, Arash; Dou, Jinxiao; Yu, Jianglong

    2016-05-01

    Oxy-fuel combustion of solid fuels is seen as one of the key technologies for carbon capture to reduce greenhouse gas emissions. The combustion characteristics of lignite coal, Chlorella vulgaris microalgae, and their blends under O2/N2 and O2/CO2 conditions were studied using a Thermogravimetric Analyzer-Mass Spectroscopy (TG-MS). During co-combustion of blends, three distinct peaks were observed and were attributed to C. vulgaris volatiles combustion, combustion of lignite, and combustion of microalgae char. Activation energy during combustion was calculated using iso-conventional method. Increasing the microalgae content in the blend resulted in an increase in activation energy for the blends combustion. The emissions of S- and N-species during blend fuel combustion were also investigated. The addition of microalgae to lignite during air combustion resulted in lower CO2, CO, and NO2 yields but enhanced NO, COS, and SO2 formation. During oxy-fuel co-combustion, the addition of microalgae to lignite enhanced the formation of gaseous species.

  20. Comparison of inclined plate sedimentation and dissolved air flotation for the minimisation of subsequent nitrogenous disinfection by-product formation.

    PubMed

    Chu, Wen-Hai; Gao, Nai-Yun; Templeton, Michael R; Yin, Da-Qiang

    2011-04-01

    The formation of disinfection by-products (DBPs), including both nitrogenous disinfection by-products (N-DBPs) and carbonaceous disinfection by-products (C-DBPs), was investigated upon chlorination of water samples following two treatment processes: (i) coagulation-inclined plate sedimentation (IPS)-filtration and (ii) coagulation-dissolved air flotation (DAF)-filtration. The removal of algae, dissolved organic nitrogen (DON), dissolved organic carbon (DOC) and UV(254) by coagulation-DAF-filtration was superior to coagulation-IPS-filtration. On average, 53%, 53% and 31% of DOC, DON and UV(254) were removed by coagulation-DAF-filtration process, which were higher than 47%, 31% and 27% of that by coagulation-IPS-filtration process. Additionally, coagulation-IPS-filtration performed less well at removing the low molecular weight organics than coagulation-DAF-filtration process. The concentrations of chloroform, dichloroacetamide (DCAcAm) and dichloroacetonitrile (DCAN) formed during chlorination after coagulation-DAF-filtration reached their maximum values of 13, 1.5 and 4.7μgL(-1), respectively, and were lower than those after coagulation-IPS-filtration with the maximum detected levels of 17, 2.9 and 6.3μgL(-1). However, the trichloronitromethane (TCNM) concentration after the two processes was similar, suggesting that DON may have less of a contribution to TCNM formation than DCAcAm and DCAN.

  1. Characterizing the Amount and Chemistry of Biogenic SOA Formation from Pine Forest Air Using a Flow Reactor

    NASA Astrophysics Data System (ADS)

    Palm, B. B.; Ortega, A. M.; Campuzano Jost, P.; Day, D. A.; Fry, J.; Zarzana, K. J.; Draper, D. C.; Brown, S. S.; Kaser, L.; Karl, T.; Jud, W.; Hansel, A.; Hodzic, A.; Dube, W. P.; Wagner, N. L.; Brune, W. H.; Jimenez, J. L.

    2013-12-01

    The amount and chemistry of biogenic secondary organic aerosol (SOA) formation was characterized as a function of oxidant exposure using a Potential Aerosol Mass (PAM) oxidative flow reactor, sampling air in a terpene- and MBO-dominated pine forest during the 2011 BEACHON-RoMBAS field campaign at the U.S. Forest Service Manitou Forest Experimental Observatory in the Colorado Rocky Mountains. In the reactor, a chosen oxidant (OH, O3, or NO3) was generated and stepped over a range of values up to 10,000 times ambient levels, accelerating the gas-phase and heterogeneous oxidative aging of volatile organic compounds (VOCs), inorganic gases, and preexisting aerosol. The resulting SOA formation was measured using an Aerodyne HR-ToF-AMS, a TSI SMPS and a PTR-TOF-MS. Oxidative processing in the flow reactor was equivalent to a few hours up to ~20 days of atmospheric aging during the ~4-min reactor residence time. During BEACHON-RoMBAS, OH oxidation led to a net production of up to several μg/m3 of SOA at intermediate exposures (1-10 equivalent days) but resulted in net loss of OA mass (up to ~30%) at higher OH exposures (10-20 equivalent days), demonstrating the competing effects of functionalization/condensation vs. fragmentation/evaporation reactions as OH exposure increased. O3 and NO3 oxidation led to smaller (up to 0.5 μg/m3) SOA production, and loss of SOA mass due to fragmentation reactions was not observed. OH oxidation resulted in f44 vs. f43 and Van Krevelen diagram (H:C vs. O:C) slopes similar to ambient oxidation, suggesting the flow reactor oxidation pathways are similar to those in ambient air. Organic nitrate SOA production was observed from NO3 radical oxidation only. New particle formation was observed from OH oxidation, but not O3 or NO3 oxidation under our experimental conditions. An enhancement of SOA production under the influence of anthropogenic pollution (Denver) was also observed. High-resolution AMS measurements showed that the O:C and H

  2. Modelling of cloud formation due to air-sea interactions in an energy-active zone

    NASA Astrophysics Data System (ADS)

    Kondratyev, K. Ya.; Khvorostyanov, V. I.

    1989-02-01

    A mesoscale 3D numerical model is described, with which detailed calculations have been made of turbulence and wind characteristics in the atmospheric boundary layer (ABL), as well as cloud particle size distribution, longwave and solar radiation fluxes and flux divergences, and atmosphere-ocean heat exchange. Based on numerical experiments simulating winter conditions of the Newfoundland energy-active zone of the ocean (EAZO), atmosphere-ocean energy exchange is investigated. It is shown that the basic mechanisms for the EAZO formation involve the following processes: (i) at the hydrological front between cold and warm ocean currents, the fluxes of sensible and latent heat grow significantly; (ii) at this front, in a particular synoptic situation, overcast low-level cloudiness forms, screening solar radiation so that in winter, the radiation budget at the front is reduced, and the radiative flux into the ocean is less than the energy release to the atmosphere; (iii) frequent occurrence of such synoptic situations with cloudiness decreases the oceanic enthalpy and creates negative SST anomalies. The transport of these anomalies by currents to the western coasts of the continents causes anomalies of weather and climate.

  3. The Possibilities and Limitations of Assessment for Learning: Exploring the Theory of Formative Assessment and the Notion of "Closing the Learning Gap"

    ERIC Educational Resources Information Center

    Ninomiya, Shuichi

    2016-01-01

    Black and Wiliam (1998a, 1998b) demonstrate that formative assessment is one of the most effective strategies for promoting student learning. Since the publication of their reviews, formative assessment has gained increasing international prominence in both policy and practice. However, despite this early innovation, the theory and practice of…

  4. Band gaps in bubble phononic crystals

    NASA Astrophysics Data System (ADS)

    Leroy, V.; Bretagne, A.; Lanoy, M.; Tourin, A.

    2016-12-01

    We investigate the interaction between Bragg and hybridization effects on the band gap properties of bubble phononic crystals. These latter consist of air cavities periodically arranged in an elastomer matrix and are fabricated using soft-lithography techniques. Their transmission properties are affected by Bragg effects due to the periodicity of the structure as well as hybridization between the propagating mode of the embedding medium and bubble resonance. The hybridization gap survives disorder while the Bragg gap requires a periodic distribution of bubbles. The distance between two bubble layers can be tuned to make the two gaps overlap or to create a transmission peak in the hybridization gap.

  5. Formation of Dirac point and the topological surface states inside the strained gap for mixed 3D Hg1-xCdx Te

    NASA Astrophysics Data System (ADS)

    Marchewka, Michał

    2016-10-01

    In this paper the results of the numerical calculation obtained for the three-dimensional (3D) strained Hg1-xCdx Te layers for the x-Cd composition from 0.1 to 0.155 and a different mismatch of the lattice constant are presented. For the investigated region of the Cd composition (x value) the negative energy gap (Eg =Γ8 -Γ6) in the Hg1-xCdx Te is smaller than in the case of pure HgTe which, as it turns out, has a significant influence on the topological surface states (TSS) and the position of the Dirac point. The numerical calculation based on the finite difference method applied for the 8×8 kp model with the in-plane tensile strain for (001) growth oriented structure shows that the Dirac cone inside the induced insulating band gap for non zero of the Cd composition and a bigger strain caused by the bigger lattice mismatch (than for the 3D HgTe TI) can be obtained. It was also shown how different x-Cd compounds move the Dirac cone from the valence band into the band gap. The presented results show that 75 nm wide 3D Hg1-xCdx Te structures with x ≈ 0.155 and 1.6% lattice mismatch make the system a true topological insulator with the dispersion of the topological surface states similar to those ones obtained for the strained CdTe/HgTe QW.

  6. Suppression of Arctic Air Formation by Cloud Radiative Effects in a Two-Dimensional Cloud Resolving Model

    NASA Astrophysics Data System (ADS)

    Cronin, T.; Li, H.

    2015-12-01

    To better understand equable paleoclimates, Arctic amplification of winter warming, and the high-latitude lapse-rate feedback, we investigate the process of Arctic air formation, wherein a high latitude maritime air mass is advected over land during polar night and strongly cooled from the surface up. We extend previous work done using a single-column model (Cronin and Tziperman, PNAS, in press) by performing two-dimensional idealized cloud-resolving simulations with the Weather Research and Forecasting (WRF) model. Quantitatively consistent with previous results, we find that as the initial atmospheric state is warmed, increases in low cloud amount reduce the average surface cooling over a 14-day period by roughly a degree for each degree of warming of the initial atmospheric state, with the feedback strength increasing with warming. This is primarily attributed to a monotonic increase in surface cloud radiative forcing of approximately 2 W m-2 for each degree that the initial atmospheric sounding is warmed. The use of a two-dimensional model as opposed to a single-column model shows that the lower-tropospheric cloud layer becomes more turbulent and dominated by cumulus clouds as the climate is warmed, yet the cloud fraction remains high owing to the continued prevalence of stratus and fog layers. These results are robust across a variety of cloud microphysics schemes and are not sensitive to the horizontal or vertical resolution of the model. We also explore the vertical structure and horizontal variability of the bulk horizontal flow, the sensitivity of the results to subsidence and atmospheric carbon dioxide concentration, and the contrasting roles of top-of-atmosphere and surface cloud radiative effects.

  7. Surface pressure affects B-hordein network formation at the air-water interface in relation to gastric digestibility.

    PubMed

    Yang, Jingqi; Huang, Jun; Zeng, Hongbo; Chen, Lingyun

    2015-11-01

    Protein interfacial network formation under mechanical pressure and its influence on degradation was investigated at molecular level using Langmuir-Blodgett B-hordein monolayer as a 2D model. Surface properties, such as surface pressure, dilatational and shear rheology and the surface pressure--area (π-A) isotherm, of B-hordein at air-water interface were analyzed by tensiometer, rheometer and a Langmuir-Blodgett trough respectively. B-Hordein conformation and orientation under different surface pressures were determined by polarization modulation-infrared reflection absorption spectroscopy (PM-IRRAS). The interfacial network morphology was observed by atomic force microscopy (AFM). B-Hordein could reduce the air-water surface tension rapidly to ∼ 45 mN/m and form a solid-like network with high rheological elasticity and compressibility at interface, which could be a result of interactions developed by intermolecular β-sheets. The results also revealed that B-hordein interfacial network switched from an expanded liquid phase to a solid-like film with increasing compression pressure. The orientation of B-hordein was parallel to the surface when in expended liquid phase, whereas upon compression, the hydrophobic repetitive region tilted away from water phase. When compressed to 30 mN/m, a strong elastic network was formed at the interface, and it was resistant to a harsh gastric-like environment of low pH and pepsin. This work generated fundamental knowledge, which suggested the potential to design B-hordein stabilized emulsions and encapsulations with controllable digestibility for small intestine targeted delivery of bioactive compounds.

  8. Evaluation of the Community Multiscale Air Quality Model for Simulating Winter Ozone Formation in the Uinta Basin with Intensive Oil and Gas Production

    NASA Astrophysics Data System (ADS)

    Matichuk, R.; Tonnesen, G.; Luecken, D.; Roselle, S. J.; Napelenok, S. L.; Baker, K. R.; Gilliam, R. C.; Misenis, C.; Murphy, B.; Schwede, D. B.

    2015-12-01

    The western United States is an important source of domestic energy resources. One of the primary environmental impacts associated with oil and natural gas production is related to air emission releases of a number of air pollutants. Some of these pollutants are important precursors to the formation of ground-level ozone. To better understand ozone impacts and other air quality issues, photochemical air quality models are used to simulate the changes in pollutant concentrations in the atmosphere on local, regional, and national spatial scales. These models are important for air quality management because they assist in identifying source contributions to air quality problems and designing effective strategies to reduce harmful air pollutants. The success of predicting oil and natural gas air quality impacts depends on the accuracy of the input information, including emissions inventories, meteorological information, and boundary conditions. The treatment of chemical and physical processes within these models is equally important. However, given the limited amount of data collected for oil and natural gas production emissions in the past and the complex terrain and meteorological conditions in western states, the ability of these models to accurately predict pollution concentrations from these sources is uncertain. Therefore, this presentation will focus on understanding the Community Multiscale Air Quality (CMAQ) model's ability to predict air quality impacts associated with oil and natural gas production and its sensitivity to input uncertainties. The results will focus on winter ozone issues in the Uinta Basin, Utah and identify the factors contributing to model performance issues. The results of this study will help support future air quality model development, policy and regulatory decisions for the oil and gas sector.

  9. Developmental transcriptome analysis and identification of genes involved in formation of intestinal air-breathing function of Dojo loach, Misgurnus anguillicaudatus.

    PubMed

    Luo, Weiwei; Cao, Xiaojuan; Xu, Xiuwen; Huang, Songqian; Liu, Chuanshu; Tomljanovic, Tea

    2016-08-22

    Dojo loach, Misgurnus anguillicaudatus is a freshwater fish species of the loach family Cobitidae, using its posterior intestine as an accessory air-breathing organ. Little is known about the molecular regulatory mechanisms in the formation of intestinal air-breathing function of M. anguillicaudatus. Here high-throughput sequencing of mRNAs was performed from six developmental stages of posterior intestine of M. anguillicaudatus: 4-Dph (days post hatch) group, 8-Dph group, 12-Dph group, 20-Dph group, 40-Dph group and Oyd (one-year-old) group. These six libraries were assembled into 81300 unigenes. Totally 40757 unigenes were annotated. Subsequently, 35291 differentially expressed genes (DEGs) were scanned among different developmental stages and clustered into 20 gene expression profiles. Finally, 15 key pathways and 25 key genes were mined, providing potential targets for candidate gene selection involved in formation of intestinal air-breathing function in M. anguillicaudatus. This is the first report of developmental transcriptome of posterior intestine in M. anguillicaudatus, offering a substantial contribution to the sequence resources for this species and providing a deep insight into the formation mechanism of its intestinal air-breathing function. This report demonstrates that M. anguillicaudatus is a good model for studies to identify and characterize the molecular basis of accessory air-breathing organ development in fish.

  10. Developmental transcriptome analysis and identification of genes involved in formation of intestinal air-breathing function of Dojo loach, Misgurnus anguillicaudatus

    PubMed Central

    Luo, Weiwei; Cao, Xiaojuan; Xu, Xiuwen; Huang, Songqian; Liu, Chuanshu; Tomljanovic, Tea

    2016-01-01

    Dojo loach, Misgurnus anguillicaudatus is a freshwater fish species of the loach family Cobitidae, using its posterior intestine as an accessory air-breathing organ. Little is known about the molecular regulatory mechanisms in the formation of intestinal air-breathing function of M. anguillicaudatus. Here high-throughput sequencing of mRNAs was performed from six developmental stages of posterior intestine of M. anguillicaudatus: 4-Dph (days post hatch) group, 8-Dph group, 12-Dph group, 20-Dph group, 40-Dph group and Oyd (one-year-old) group. These six libraries were assembled into 81300 unigenes. Totally 40757 unigenes were annotated. Subsequently, 35291 differentially expressed genes (DEGs) were scanned among different developmental stages and clustered into 20 gene expression profiles. Finally, 15 key pathways and 25 key genes were mined, providing potential targets for candidate gene selection involved in formation of intestinal air-breathing function in M. anguillicaudatus. This is the first report of developmental transcriptome of posterior intestine in M. anguillicaudatus, offering a substantial contribution to the sequence resources for this species and providing a deep insight into the formation mechanism of its intestinal air-breathing function. This report demonstrates that M. anguillicaudatus is a good model for studies to identify and characterize the molecular basis of accessory air-breathing organ development in fish. PMID:27545457

  11. Photonic band gap in isotropic hyperuniform disordered solids with low dielectric contrast.

    PubMed

    Man, Weining; Florescu, Marian; Matsuyama, Kazue; Yadak, Polin; Nahal, Geev; Hashemizad, Seyed; Williamson, Eric; Steinhardt, Paul; Torquato, Salvatore; Chaikin, Paul

    2013-08-26

    We report the first experimental demonstration of a TE-polarization photonic band gap (PBG) in a 2D isotropic hyperuniform disordered solid (HUDS) made of dielectric media with a dielectric index contrast of 1.6:1, very low for PBG formation. The solid is composed of a connected network of dielectric walls enclosing air-filled cells. Direct comparison with photonic crystals and quasicrystals permitted us to investigate band-gap properties as a function of increasing rotational isotropy. We present results from numerical simulations proving that the PBG observed experimentally for HUDS at low index contrast has zero density of states. The PBG is associated with the energy difference between complementary resonant modes above and below the gap, with the field predominantly concentrated in the air or in the dielectric. The intrinsic isotropy of HUDS may offer unprecedented flexibilities and freedom in applications (i. e. defect architecture design) not limited by crystalline symmetries.

  12. [METHODOLOGY FOR THE ASSESSMENT OF THE IMPACT OF THE ATMOSPHERIC AIR POLLUTION ON THE FORMATION OF THE LEVELS OF OVERALL MORBIDITY RATE OF BRONCHIAL ASTHMA].

    PubMed

    Veremchuk, L V; Cherpack, N A; Gvozdenko, T A; Volkova, M V

    2015-01-01

    In large cities with strong air pollution the formation of the levels of morbidity rate of bronchial asthma has a complex causation that requires the search for informative methods for identification of causes and consequences of this dependence. Method for the assessment of the dependence of overall levels of morbidity rate of bronchial asthma on the degree of air pollution allows you to select a "useful information" of the direct impact of air pollution on a background of random processes and latent relationship between human and environment. The use of the method of the information entropy analysis allowed us to estimate the total and the individual contribution of the separate components of air pollution on the formation of levels of total morbidity rate of bronchial asthma in the population of the city of Vladivostok. Levels of total incidence of this pathology were established to differ in various age groups. The adult population is more adapted to air pollution, but retains a high sensitivity to the impact of nitrogen dioxide. Levels of overall l morbidity rate of bronchial asthma in children and adolescents depend on the total air pollution with some dominance of the influence of suspended matter and carbon monoxide.

  13. AIR VEHICLES INTEGRATION AND TECHNOLOGY RESEARCH (AVIATR) Task Order 0015: Predictive Capability for Hypersonic Structural Response and Life Prediction Phase 1 - Identification of Knowledge Gaps

    DTIC Science & Technology

    2010-08-01

    rudder, all-moving horizontal tails, and body flap were “beefed up ” based on preliminary flutter assessment. The all-moving tail/ wing carry-through...external surface temperatures on the fuselage and wings of up to 640°F, and the acreage surface and structural temperatures in the engine nacelle area...edge to rotate up into the air-stream inducing a heating amplification on the panel edge as well as on the adjacent panels. In the X-33 program the

  14. The effect of fission products on the rate of U3O8 formation in SIMFUEL oxidized in air at 250°C

    NASA Astrophysics Data System (ADS)

    Choi, Jong-Won; McEachern, Rod J.; Taylor, Peter; Wood, Donald D.

    1996-06-01

    The effect of fission products on the rate of U3O8 formation was investigated by oxidizing UO2-based SIMFUEL (simulated high burnup nuclear fuel) and unirradiated UO2 fuel specimens in air at 250°C for different times (1-317 days). The progress of oxidation was monitored by X-ray diffraction, revealing that the rate of U3O8 formation declines with increasing burnup. An expression was derived to describe quantitatively the time for U3O8 powder formation as a function of simulated burnup. These findings were supported by additional isochronal oxidation experiments conducted between 200 and 300°C.

  15. Radiation effects in moist-air systems and the influence of radiolytic product formation on nuclear waste glass corrosion

    SciTech Connect

    Wronkiewicz, D.J.; Bates, J.K.; Buck, E.C.; Hoh, J.C.; Emery, J.W.; Wang, L.M.

    1997-07-01

    Ionizing radiation may affect the performance of glass in an unsaturated repository site by interacting with air, water vapor, or liquid water to produce a variety of radiolytic products. Tests were conducted to examine the effects of radiolysis under high gas/liquid ratios. Results indicate that nitrate is the predominant radiolytic product produced following both gamma and alpha radiation exposure, with lesser amounts of nitrite and carboxylic acids. The formation of nitrogen acids during exposure to long-lived, alpha-particle-emitting transuranic elements indicates that these acids may play a role in influencing nuclear waste form reactions in a long-term unsaturated disposal scenario. Experiments were also conducted with samples that simulate the composition of Savannah River Plant nuclear waste glasses. Radiolytic product formation in batch tests (340 m{sup {minus}1}, 90 C) resulted in a small increase in the release rates of many glass components, such as alkali and alkaline earth elements, although silicon and uranium release rates were slightly reduced indicating an overall beneficial effect of radiation on waste form stability. The radiolytic acids increased the rate of ion exchange between the glass and the thin film of condensate, resulting in accelerated corrosion rates for the glass. The paragenetic sequence of alteration phases formed on both the irradiated and nonirradiated glass samples reacted in the vapor hydration tests matches closely with those developed during volcanic glass alteration in naturally occurring saline-alkaline lake systems. This correspondence suggests that the high temperatures used in these tests have not changed the underlying glass reaction mechanism relate to that which controls glass reactions under ambient surficial conditions.

  16. The footprints of Saharan air layer and lightning on the formation of tropical depressions over the eastern Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Centeno Delgado, Diana C.; Chiao, Sen

    2014-09-01

    The roles of the Saharan Air Layer (SAL) and lightning during genesis of Tropical Depression (TD) 8 (2006) and TD 12 (2010) were investigated in relation to the interaction of the dust outbreaks with each system and their surrounding environment. This study applied data collected from the 2006 NASA African Monsoon Multidisciplinary Analysis and 2010 Genesis and Rapid Intensification Processes projects. Satellite observations from METEOSAT and Moderate Resolution Imaging Spectroradiometer (MODIS)—Aerosol Optical Depth (AOD) were also employed for the study of the dust content. Lightning activity data from the Met Office Arrival Time Difference (ATD) system were used as another parameter to correlate moist convective overturning and a sign of cyclone formation. The AOD and lightning analysis for TD 8 demonstrated the time-lag connection through their positive contribution to TC-genesis. TD 12 developed without strong dust outbreak, but with lower wind shear (2 m s-1) and an organized Mesoscale Convective System (MCS). Overall, the results from the combination of various data analyses in this study support the fact that both systems developed under either strong or weak dust conditions. From these two cases, the location (i.e., the target area) of strong versus weak dust outbreaks, in association with lightning, were essential interactions that impacted TC-genesis. While our dust footprints hypothesis applied under strong dust conditions (i.e., TD 8), other factors (e.g., vertical wind shear, pre-existing vortex and trough location, thermodynamics) need to be evaluated as well. The results from this study suggest that the SAL is not a determining factor that affects the formation of tropical cyclones (i.e., TD 8 and TD 12).

  17. The footprints of Saharan air layer and lightning on the formation of tropical depressions over the eastern Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Centeno Delgado, Diana C.; Chiao, Sen

    2015-02-01

    The roles of the Saharan Air Layer (SAL) and lightning during genesis of Tropical Depression (TD) 8 (2006) and TD 12 (2010) were investigated in relation to the interaction of the dust outbreaks with each system and their surrounding environment. This study applied data collected from the 2006 NASA African Monsoon Multidisciplinary Analysis and 2010 Genesis and Rapid Intensification Processes projects. Satellite observations from METEOSAT and Moderate Resolution Imaging Spectroradiometer (MODIS)—Aerosol Optical Depth (AOD) were also employed for the study of the dust content. Lightning activity data from the Met Office Arrival Time Difference (ATD) system were used as another parameter to correlate moist convective overturning and a sign of cyclone formation. The AOD and lightning analysis for TD 8 demonstrated the time-lag connection through their positive contribution to TC-genesis. TD 12 developed without strong dust outbreak, but with lower wind shear (2 m s-1) and an organized Mesoscale Convective System (MCS). Overall, the results from the combination of various data analyses in this study support the fact that both systems developed under either strong or weak dust conditions. From these two cases, the location (i.e., the target area) of strong versus weak dust outbreaks, in association with lightning, were essential interactions that impacted TC-genesis. While our dust footprints hypothesis applied under strong dust conditions (i.e., TD 8), other factors (e.g., vertical wind shear, pre-existing vortex and trough location, thermodynamics) need to be evaluated as well. The results from this study suggest that the SAL is not a determining factor that affects the formation of tropical cyclones (i.e., TD 8 and TD 12).

  18. An examination of boundary layer structure under the influence of the gap winds in Urumqi, China, during air pollution episode in winter.

    PubMed

    Li, Xia; Xia, Xiangao; Xin, Yu; Ma, Yufen; Yang, Jing; Li, Jinglin; Yang, Xinghua

    2012-01-01

    Tethered-sonde measurements of atmospheric profiles were performed at Urumuqi, capital of the Xinjiang Uyghur Autonomous Region of China, from 29 December 2008 to 14 January 2009. The data were used to examine the boundary layer structure during this severe air pollution period. Diurnal evolution of local wind flow near Urumqi was simulated using the fifth-generation Pennsylvania State University-National Center for Atmospheric Research (NCAR) Mesoscale Model (MM5). Measurements from operational radiosonde data showed that a southeasterly elevated low-level jet often intruded upon Urumqi through the middle Tianshan Mountain pass to the south of the city. The tethered-sonde measurements showed that calm and northwesterly winds prevailed near the surface in Urumqi, whereas the southeasterly winds of relatively higher speed were dominant above approximately 400 m. Both temperature inversion and humidity inversion frequently occured during day and nighttime. Temperature inversion intensity could sharply rise as the stronger elevated southeasterly gale (ESEG) happened. Model simulations showed that the winds near the surface around Urumqi remained calm during nighttime and developed toward the mountains during daytime. As cool airflow in the basin confronted the southeasterly winds from the pass in the lower layer, they formed a convergence line around Urumqi city, which was not favor for dilution of air pollutants.

  19. Analysis of photonic band gaps in two-dimensional photonic crystals with rods covered by a thin interfacial layer

    SciTech Connect

    Trifonov, T.; Marsal, L.F.; Pallares, J.; Rodriguez, A.; Alcubilla, R.

    2004-11-15

    We investigate different aspects of the absolute photonic band gap (PBG) formation in two-dimensional photonic structures consisting of rods covered with a thin dielectric film. Specifically, triangular and honeycomb lattices in both complementary arrangements, i.e., air rods drilled in silicon matrix and silicon rods in air, are studied. We consider that the rods are formed of a dielectric core (silicon or air) surrounded by a cladding layer of silicon dioxide (SiO{sub 2}), silicon nitride (Si{sub 3}N{sub 4}), or germanium (Ge). Such photonic lattices present absolute photonic band gaps, and we study the evolution of these gaps as functions of the cladding material and thickness. Our results show that in the case of air rods in dielectric media the existence of dielectric cladding reduces the absolute gap width and may cause complete closure of the gap if thick layers are considered. For the case of dielectric rods in air, however, the existence of a cladding layer can be advantageous and larger absolute PBG's can be achieved.

  20. Effect of inlet-air humidity, temperature, pressure, and reference Mach number on the formation of oxides of nitrogen in a gas turbine combustor

    NASA Technical Reports Server (NTRS)

    Marchionna, N. R.; Diehl, L. A.; Trout, A. M.

    1973-01-01

    Tests were conducted to determine the effect of inlet air humidity on the formation of oxides of nitrogen (NOx) from a gas turbine combustor. Combustor inlet air temperature ranged from 506 K (450 F) to 838 K (1050 F). The tests were primarily run at a constant pressure of 6 atmospheres and reference Mach number of 0.065. The NOx emission index was found to decrease with increasing inlet air humidity at a constant exponential rate: NOx = NOx0e-19H (where H is the humidity and the subscript 0 denotes the value at zero humidity). the emission index increased exponentially with increasing normalized inlet air temperature to the 1.14 power. Additional tests made to determine the effect of pressure and reference Mach number on NOx showed that the NOx emission index varies directly with pressure to the 0.5 power and inversely with reference Mach number.

  1. A numerical study on the effect of hydrogen/reformate gas addition on flame temperature and NO formation in strained methane/air diffusion flames

    SciTech Connect

    Guo, Hongsheng; Neill, W. Stuart

    2009-02-15

    This paper investigates the effects of hydrogen/reformate gas addition on flame temperature and NO formation in strained methane/air diffusion flames by numerical simulation. The results reveal that flame temperature changes due to the combined effects of adiabatic temperature, fuel Lewis number and radiation heat loss, when hydrogen/reformate gas is added to the fuel of a methane/air diffusion flame. The effect of Lewis number causes the flame temperature to increase much faster than the corresponding adiabatic equilibrium temperature when hydrogen is added, and results in a qualitatively different variation from the adiabatic equilibrium temperature as reformate gas is added. At some conditions, the addition of hydrogen results in a super-adiabatic flame temperature. The addition of hydrogen/reformate gas causes NO formation to change because of the variations in flame temperature, structure and NO formation mechanism, and the effect becomes more significant with increasing strain rate. The addition of a small amount of hydrogen or reformate gas has little effect on NO formation at low strain rates, and results in an increase in NO formation at moderate or high strain rates. However, the addition of a large amount of hydrogen increases NO formation at all strain rates, except near pure hydrogen condition. Conversely, the addition of a large amount of reformate gas results in a reduction in NO formation. (author)

  2. The footprints of Saharan Air Layer and lightning on the formation of tropical depressions over the eastern Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Centeno Delgado, Diana C.

    In this study, the results of an observational analysis and a numerical analysis on the role of the Saharan Air Layer during tropical cyclogenesis (TC-genesis) are described. The observational analysis investigates the interaction of dust particles and lightning during the genesis stage of two developed cases (Hurricanes Helene 2006 and Julia 2010). The Weather Research and Forecasting (WRF) and WRF-Chemistry models were used to include and monitor the aerosols and chemical processes that affect TC-genesis. The numerical modeling involved two developed cases (Hurricanes Helene 2006 and Julia 2010) and two non-developed cases (Non-Developed 2011 and Non-Developed 2012). The Aerosol Optical Depth (AOD) and lightning analysis for Hurricane Helene 2006 demonstrated the time-lag connection through their positive contribution to TC-genesis. The observational analyses supported the fact that both systems developed under either strong or weak dust conditions. From the two cases, the location of strong versus weak dust outbreaks in association with lightning was essential interactions that impacted TC-genesis. Furthermore, including dust particles, chemical processes, and aerosol feedback in the simulations with WRF-CHEM provides results closer to observations than regular WRF. The model advantageously shows the location of the dust particles inside of the tropical system. Overall, the results from this study suggest that the SAL is not a determining factor that affects the formation of tropical cyclones.

  3. Modeling the oxidative capacity of the atmosphere of the south coast air basin of California. 1. Ozone formation metrics.

    PubMed

    Griffin, Robert J; Revelle, Meghan K; Dabdub, Donald

    2004-02-01

    Metrics associated with ozone (O3) formation are investigated using the California Institute of Technology (CIT) three-dimensional air-quality model. Variables investigated include the O3 production rate (P(O3)), O3 production efficiency (OPE), and total reactivity (the sum of the reactivity of carbon monoxide (CO) and all organic gases that react with the hydroxyl radical). Calculations are spatially and temporally resolved; surface-level and vertically averaged results are shown for September 9, 1993 for three Southern California locations: Central Los Angeles, Azusa, and Riverside. Predictions indicate increasing surface-level O3 concentrations with distance downwind, in line with observations. Surface-level and vertically averaged P(O3) values peak during midday and are highest downwind; surface P(O3) values are greater than vertically averaged values. Surface OPEs generally are highest downwind and peak during midday in downwind locations. In contrast, peaks occur in early morning and late afternoon in the vertically averaged case. Vertically averaged OPEs tend to be greater than those for the surface. Total reactivities are highest in upwind surface locations and peak during rush hours; vertically averaged reactivities are smaller and tend to be more uniform temporally and spatially. Total reactivity has large contributions from CO, alkanes, alkenes, aldehydes, unsubstituted monoaromatics, and secondary organics. Calculations using estimated emissions for 2010 result in decreases in P(O3) values and reactivities but increases in OPEs.

  4. New particle formation under the influence of the long-range transport of air pollutants in East Asia

    NASA Astrophysics Data System (ADS)

    Chandra, Indra; Kim, Seyoung; Seto, Takafumi; Otani, Yoshio; Takami, Akinori; Yoshino, Ayako; Irei, Satoshi; Park, Kihong; Takamura, Tamio; Kaneyasu, Naoki; Hatakeyama, Shiro

    2016-09-01

    Field observations to investigate the correlation between New Particle Formation (NPF) and the long-range transport of air pollutants in the East Asia region were carried out on a rural Island of Japan in the East-China Sea (Fukue Island, 32.8°N, 128.7°E) over three periods (February 23 to March 7, 2013; November 7 to 20, 2013; and November 2 to 24, 2014). Frequent NPF events were identified (16 events in 50 days), typically in association with sudden increases in particle number concentrations and the successive growth of particles to mobility diameters of several tens of nanometers. The NPF events were classified into two types (A and B) according to the initially detected particle sizes (onset diameters). Type-A consisted of strong NPF events with onset diameters as small as 5 nm. Type-B consisted of NPF events whose onset (<10 nm) was not clearly identifiable. The correlations of SO2 concentrations, solar radiation, PM2.5 concentrations, and chemical composition were analyzed based on the types of NPF events.

  5. Effect of different sulphur precursors on morphology and band-gap on the formation of Cu2ZnSnS4 (CZTS) particles with microwave irradiation

    NASA Astrophysics Data System (ADS)

    Patro, Bharati; Vijaylakshmi, S.; Sharma, Pratibha

    2016-05-01

    Cu2ZnSnS4 (CZTS) is a promising semiconductor material for ecological cost effective thin film Photovoltaic (PV) devices. As it contains earth abundant and non-toxic elements, it has the advantages over commercially available CIGS and CdTe thin film PV devices. In the present work, the pure phase Cu2ZnSnS4 particles were successfully synthesised with microwave irradiation. The morphology and phase study was carried out for the samples prepared with two different sulphur precursors viz. thiourea and thioacetamide (TAA). CZTS particles with thiourea as sulphur precursor are more crystalline than CZTS particles with TAA. The band gap of 1.654eV and 1.713eV were calculated for the samples prepared with thiourea and TAA respectively.

  6. Elemental composition and radical formation potency of PM10 at an urban background station in Germany in relation to origin of air masses

    NASA Astrophysics Data System (ADS)

    Hellack, Bryan; Quass, Ulrich; Beuck, Henning; Wick, Gabriele; Kuttler, Wilhelm; Schins, Roel P. F.; Kuhlbusch, Thomas A. J.

    2015-03-01

    At an urban background station in Mülheim-Styrum, North Rhine Westphalia, Germany, a set of 75 PM10 samples was collected over a one year period, followed by analyses for mass, chemical composition and hydroxyl radical (OHrad) formation potency. Additionally, the origin of air masses for the sampling days was calculated by 48-h backward trajectories, subdivided into the four cardinal sectors. Significant lower PM10 mass concentrations were observed for summertime air masses from the west compared to the other seasons and cardinal sectors. For the OHrad formation potency higher values were detected if air masses originate from east and south, thus predominantly being of continental origin. From the elevated OHrad formation potencies in fall and winter a seasonal trend with low potencies in summers is assumed. Furthermore, source apportionment was performed by a positive matrix factor analysis, separating seven plausible factors which could be attributed to mineral dust, secondary nitrate, industry, non-exhaust traffic, fossil fuel combustion, marine aerosol and secondary aerosol factors. The intrinsic OHrad formation potency was found to be associated mainly with the fossil fuel combustion factor (45%) and industry factor (22%).

  7. Interfacial chemical reaction and multiple gap state formation on three layer cathode in organic light-emitting diode: Ca/BaF{sub 2}/Alq{sub 3}

    SciTech Connect

    Kim, Tae Gun; Kim, Jeong Won; Lee, Hyunbok; Yi, Yeonjin; Lee, Seung Mi

    2015-07-14

    A three layer cathode is a promising stack structure for long lifetime and high efficiency in organic light-emitting diodes. The interfacial chemical reactions and their effects on electronic structures for alkaline-earth metal (Ca, Ba)/Alq{sub 3} [tris(8-hydroxyquinolinato)aluminum] and Ca/BaF{sub 2}/Alq{sub 3} are investigated using in-situ X-ray and ultraviolet photoelectron spectroscopy, as well as molecular model calculation. The BaF{sub 2} interlayer initially prevents direct contact between Alq{sub 3} and the reactive Ca metal, but it is dissociated into Ba and CaF{sub 2} by the addition of Ca. As the Ca thickness increases, the Ca penetrates the interlayer to directly participate in the reaction with the underlying Alq{sub 3}. This series of chemical reactions takes place irrespective of the BaF{sub 2} buffer layer thickness as long as the Ca overlayer thickness is sufficient. The interface reaction between the alkaline-earth metal and Alq{sub 3} generates two energetically separated gap states in a sequential manner. This phenomenon is explained by step-by-step charge transfer from the alkaline-earth metal to the lowest unoccupied molecular orbital states of Alq{sub 3}, forming new occupied states below the Fermi level.

  8. Final Report for Department of Energy Grant DE-FG02-97ER45666 ?Interface Diffusion and Deep Level Formation of SiC and Other Wide Gap Materials?

    SciTech Connect

    Leonard J. Brillson

    2006-03-24

    This final report describes the research effort focusing on the nature of charge transfer and localized electronic structure at semiconductor interfaces, one of the most fundamental issues in the solid state. The basic charge exchange between two materials in general is directly connected with the systematic atomic bonding changes and redistribution that occurs at the nanoscale interface. Our programhas extended our understanding of the atomic-scale nature of electrostatic barrier formation, heterojunction band offsets, and the optical and electronic features of impurity confinement in a set of model materials systems, including nanometer-scale wide band gap semiconductor and insulator structures. This fundamentally new class of materials investigation utilizes a powerful and unique combination of techniques that are revealing the atomic-scale movement, chemical bonding, and resultant charge transfer across well-defined model interfaces.

  9. The Effect of Air Preheat at Atmospheric Pressure on the Formation of NO(x) in the Quick-Mix Sections of an Axially Staged Combustor

    NASA Technical Reports Server (NTRS)

    Vardakas, M. A.; Leong, M. Y.; Brouwer, J.; Samuelsen, G. S.; Holdeman, J. D.

    1999-01-01

    The Rich-burn/Quick-mix/Lean-burn (RQL) combustor concept has been proposed to minimize the formation of nitrogen oxides (NO(x)) in gas turbine systems. The success of this combustor strategy is dependent upon the efficiency of the mixing section bridging the fuel-rich and fuel-lean stages. Note that although these results were obtained from an experiment designed to study an RQL mixer, the link between mixing and NOx signatures is considerably broader than this application, in that the need to understand this link exists in most advanced combustors. The experiment reported herein was designed to study the effects of inlet air temperature on NO(x) formation in a mixing section. The results indicate that NO(x) emission is increased for all preheated cases compared to non-preheated cases. When comparing the various mixing modules, the affect of jet penetration is important, as this determines where NO(x) concentrations peak, and affects overall NO(x) production. Although jet air comprises 70 percent of the total airflow, the impact that jet air preheat has on overall NO(x) emissions is small compared to preheating both main and jet air flow.

  10. IN VIVO EVIDENCE OF FREE RADICAL FORMATION IN THE RAT LUNG AFTER EXPOSURE TO AN EMISSION SOURCE AIR POLLUTION PARTICLE

    EPA Science Inventory

    Exposure to air pollution particles can be associated with increased human morbidity and mortality. The mechanism(s) of lung injury remains unknown. We tested the hypothesis that lung exposure to oil fly ash (an emission source air pollution particle) causes in vivo free radical ...

  11. Evaluation of the Community Multiscale Air Quality Model for Simulating Winter Ozone Formation in the Uinta Basin

    EPA Science Inventory

    Areas with close proximity to oil and natural gas operations in rural Utah have experienced winter ozone levels that exceed EPA’s National Ambient Air Quality Standards (NAAQS). Through a collaborative effort, EPA Region 8 – Air Program, ORD, and OAQPS used the Commun...

  12. Studies on the Tempo of Bubble Formation in Recently Cavitated Vessels: A Model to Predict the Pressure of Air Bubbles1

    PubMed Central

    Wang, Yujie; Pan, Ruihua; Tyree, Melvin T.

    2015-01-01

    A cavitation event in a vessel replaces water with a mixture of water vapor and air. A quantitative theory is presented to argue that the tempo of filling of vessels with air has two phases: a fast process that extracts air from stem tissue adjacent to the cavitated vessels (less than 10 s) and a slow phase that extracts air from the atmosphere outside the stem (more than 10 h). A model was designed to estimate how water tension (T) near recently cavitated vessels causes bubbles in embolized vessels to expand or contract as T increases or decreases, respectively. The model also predicts that the hydraulic conductivity of a stem will increase as bubbles collapse. The pressure of air bubbles trapped in vessels of a stem can be predicted from the model based on fitting curves of hydraulic conductivity versus T. The model was validated using data from six stem segments each of Acer mono and the clonal hybrid Populus 84K (Populus alba × Populus glandulosa). The model was fitted to results with root mean square error less than 3%. The model provided new insight into the study of embolism formation in stem tissue and helped quantify the bubble pressure immediately after the fast process referred to above. PMID:25907963

  13. Formative research on the primo vascular system and acceptance by the korean scientific community: the gap between creative basic science and practical convergence technology.

    PubMed

    Kim, Hoon Gi

    2013-12-01

    The purpose of this study was to trace the formative process of primo vascular system (PVS) research over the past decade and to describe the characteristics of the Korean scientific community. By publishing approximately 30 papers in journals ranking in the Science Citation Index (Expanded), the PVS research team actively convinced domestic and international scientists of the anatomical existence of the PVS and its possible application to Korean and Western medicine. In addition, by sharing the PVS observation technique, the team promoted the dissemination and further pursuit of the research. In 2012, however, PVS researchers performed smaller scale research without advancing to a higher level as compared to the early days. The main reasons were found to be the Korean Research and Development policy of supporting creative, small-scale basic research and applied research of Western scientific fields that promised potentially greater success on an extensive scale; the indifference concerning, and the disbelief in, the existence of a new circulatory system were shown by the Western medical community. In addition, the Oriental medical community was apathetic about working with the PVS team. Professors Kwang-Sup Soh and Byung-Cheon Lee were the prime movers of PVS research under difficult conditions. Spurred by their belief in the existence and significance of the PVS, they continued with their research despite insufficient experimental data. The Korean scientific community is not ready to promote the Korea-oriented creative field of the PVS team.

  14. Characterizing the chemical evolution of air masses via multi-platform measurements of volatile organic compounds (VOCs) during CalNEX: Composition, OH reactivity, and potential SOA formation

    NASA Astrophysics Data System (ADS)

    Gilman, J. B.; Kuster, W. C.; Bon, D.; Warneke, C.; Lerner, B. M.; Williams, E. J.; Holloway, J. S.; Pollack, I. B.; Ryerson, T. B.; Atlas, E. L.; Blake, D. R.; Herndon, S. C.; Zahniser, M. S.; Vlasenko, A. L.; Li, S.; Alvarez, S. L.; Rappenglueck, B.; Flynn, J. H.; Grossberg, N.; Lefer, B. L.; De Gouw, J. A.

    2011-12-01

    Volatile organic compounds (VOCs) are critical components in the photochemical production of ozone (O3) and secondary organic aerosol (SOA). During the CalNex 2010 field campaign, an extensive set of VOCs were measured at the Pasadena ground site, and aboard the NOAA WP-3D aircraft and the WHOI Research Vessel Atlantis. The measurements from each platform provide a unique perspective into the emissions, transport, and atmospheric processing of VOCs within the South Coast Air Basin (SoCAB). The observed enhancement ratios of the hydrocarbons measured on all three platforms are in good agreement and are generally well correlated with carbon monoxide (CO), indicating the prevalence of on-road VOC emission sources throughout the SoCAB. Offshore measurements aboard the ship and aircraft are used to characterize the air mass composition as a function of the land/sea-breeze effect. VOC ratios and other trace gases are used to identify air masses containing relatively fresh emissions that were often associated with offshore flow and re-circulated continental air associated with onshore flow conditions. With the prevailing southwesterly airflow pattern in the LAB throughout the daytime, the Pasadena ground site effectively functions as a receptor site and is used to characterize primary VOC emissions from downtown Los Angeles and to identify the corresponding secondary oxidation products. The chemical evolution of air masses as a function of the time of day is investigated in order to determine the relative impacts of primary emissions vs. secondary VOC products on OH reactivity and potential SOA formation. The reactivity of VOCs with the hydroxyl radical (OH) at the Pasadena site was dominated by the light hydrocarbons, isoprene, and oxygenated VOCs including aldehydes (secondary products) and alcohols (primary anthropogenic emissions). Toluene and benzaldehyde, both of which are associated with primary anthropogenic emissions, are the predominant VOC precursors to the

  15. Indoor transient SOA formation from ozone + α-pinene reactions: Impacts of air exchange and initial product concentrations, and comparison to limonene ozonolysis

    NASA Astrophysics Data System (ADS)

    Youssefi, Somayeh; Waring, Michael S.

    2015-07-01

    The ozonolysis of reactive organic gases (ROG), e.g. terpenes, generates secondary organic aerosol (SOA) indoors. The SOA formation strength of such reactions is parameterized by the aerosol mass fraction (AMF), a.k.a. SOA yield, which is the mass ratio of generated SOA to oxidized ROG. AMFs vary in magnitude both among and for individual ROGs. Here, we quantified dynamic SOA formation from the ozonolysis of α-pinene with 'transient AMFs,' which describe SOA formation due to pulse emission of a ROG in an indoor space with air exchange, as is common when consumer products are intermittently used in ventilated buildings. We performed 19 experiments at low, moderate, and high (0.30, 0.52, and 0.94 h-1, respectively) air exchange rates (AER) at varying concentrations of initial reactants. Transient AMFs as a function of peak SOA concentrations ranged from 0.071 to 0.25, and they tended to increase as the AER and product of the initial reactant concentrations increased. Compared to our similar research on limonene ozonolysis (Youssefi and Waring, 2014), for which formation strength was driven by secondary ozone reactions, the AER impact for α-pinene was opposite in direction and weaker, while the initial reactant product impact was in the same direction but stronger for α-pinene than for limonene. Linear fits of AMFs for α-pinene ozonolysis as a function of the AER and initial reactant concentrations are provided so that future indoor models can predict SOA formation strength.

  16. Spinodal instability and pattern formation in thin liquid films confined between two plates.

    PubMed

    Verma, Ruhi; Sharma, Ashutosh; Banerjee, Indrani; Kargupta, Kajari

    2006-04-01

    The instability, morphology and pattern formation engendered by the van der Waals force in a thin liquid film of thickness h confined between two closely placed solid surfaces (at distance d > h) are investigated based on nonlinear 3D simulations. The initial and the final stages of dewetting and pattern formation are found to be crucially dependent on the volumetric (thickness) ratio of air and liquid and its deviation from the location of the maximum of the spinodal parameter versus volumetric ratio curve. On a low energy surface, relatively thinner films and wider air gaps favor initial dewetting of the lower plate by the formation of holes, whereas thicker films with thinner air gaps initially evolve by the formation of columns/bridges that join the upper plate. In the later stage of evolution, the initial holes in thinner films evolve into columns/drops, while a rapid coalescence of columns in the thicker films eventually causes formation of holes. Thus, a phase inversion, either from liquid-in-air to air-in-liquid dispersion or vice versa, occurs during the final stages of evolution. A thin film confined between two high-energy solid surfaces forms columns (bridges) only when its mean thickness, h0, is greater than a critical thickness (hc) or the air gap is smaller than a critical distance. The patterns can be aligned by using a topographically patterned confining surface. Conditions on pattern periodicity, amplitude, and the volumetric ratio of air and liquid in the gap are explored for the formation of various types of ordered patterns including annular rings of columns, concentric ripples, parallel channels and a rectangular array of complex features. The results are of significance in soft lithographies such as LISA, soft stamping and capillary force lithography.

  17. Freezing Fog Formation in a Supercooled Boundary Layer: Solving the Winter Fog Forecasting Challenge for Elmendorf Air Force Base, Alaska

    DTIC Science & Technology

    2007-03-01

    vicinity of the base are a wide variety of streams, small lakes and tundra , with large trees along some streams in the valley. The largest stream in the...and dry cA air mass move in from 15 the northwest associated with a Siberian High, while a much warmer and moister mP air mass would move in from...a Siberian High and a Gulf of Alaska Low at the start of the fog event. The low pressure center was nearly 400NM southeast of the base with an

  18. Sea-air CO2 flux in the North Atlantic subtropical gyre: Role and influence of Sub-Tropical Mode Water formation

    NASA Astrophysics Data System (ADS)

    Andersson, Andreas J.; Krug, Lilian A.; Bates, Nicholas R.; Doney, Scott C.

    2013-07-01

    The uptake of atmospheric carbon dioxide (CO2) into the mid-latitudes of the North Atlantic Ocean through the production of wintertime Sub-Tropical Mode Water (STMW) also known as Eighteen Degree Water (EDW) is poorly quantified and constrained. Nonetheless, it has been proposed that the EDW could serve as an important short-term sink of anthropogenic CO2. The objective of the present investigation was to determine sea-air CO2 gas exchange rates and seawater CO2 dynamics during wintertime formation of EDW in the North Atlantic Ocean. During 2006 and 2007, several research cruises were undertaken as part of the CLIMODE project across the northwest Atlantic Ocean with the intent to study the pre-conditioning, formation, and the evolution of EDW. Sea-air CO2 exchange rates were calculated based on measurements of atmospheric pCO2, surface seawater pCO2 and wind speed with positive values denoting a net flux from the surface ocean to the atmosphere. Average sea-air CO2 flux calculated along cruise tracks in the formation region equaled -18±6 mmol CO2 m-2 d-1 and -14±9 mmol CO2 m-2 d-1 in January of 2006 and March of 2007, respectively. Average sea-air CO2 flux in newly formed outcropping EDW in February and March of 2007 equaled -28±10 mmol CO2 m-2 d-1. These estimates exceeded previous flux estimates in this region by 40-185%. The magnitude of CO2 flux was mainly controlled by the observed variability in wind speed and ΔpCO2 with smaller changes owing to variability in sea surface temperature. Small but statistically significant difference (4.1±2.6 μmol kg-1) in dissolved inorganic carbon (DIC) was observed in two occurrences of newly formed EDW in February and March of 2007. This difference was explained either by differences in the relative contribution from different water masses involved in the initial formation process of EDW or temporal changes owing to sea-air CO2 exchange (˜25%) and vertical and/or lateral mixing (˜75%) with water masses high in DIC

  19. On the Loss of Protective Scale Formation in Creep-Resistant, Alumina-Forming Austenitic Stainless Steels at 900?aC in Air

    SciTech Connect

    Brady, Michael P; Yamamoto, Yukinori; Pint, Bruce A; Santella, Michael L; Maziasz, Philip J; Walker, Larry R

    2008-01-01

    A family of creep-resistant, Al2O3-forming austenitic (AFA) stainless steels was recently developed. The alloys exhibit excellent oxidation resistance up to 800 aC, but are susceptible to internal attack of Al at higher temperatures. In the present work, higher levels of Ni, Cr, Al, and Nb additions were found to correlate with improved oxidation behavior at 900 aC in air. The alloys generally appeared to be initially capable of external Al2O3 scale formation, with a subsequent transition to internal attack of Al (internal oxidation and internal nitridation) that is dependent on alloy composition. Compositional profiles at the alloy/scale interface suggest that the transition to internal oxidation is preceded by subsurface depletion of Al. Alloy design directions to increase the upper-temperature limit of protective Al2O3 scale formation in these alloys are discussed

  20. Behind the Pay Gap

    ERIC Educational Resources Information Center

    Dey, Judy Goldberg; Hill, Catherine

    2007-01-01

    Women have made remarkable gains in education during the past three decades, yet these achievements have resulted in only modest improvements in pay equity. The gender pay gap has become a fixture of the U.S. workplace and is so ubiquitous that many simply view it as normal. "Behind the Pay Gap" examines the gender pay gap for college graduates.…

  1. Characterization of key aerosol, trace gas and meteorological properties and particle formation and growth processes dependent on air mass origins in coastal Southern Spain

    NASA Astrophysics Data System (ADS)

    Diesch, J.; Drewnick, F.; Sinha, V.; Williams, J.; Borrmann, S.

    2011-12-01

    The chemical composition and concentration of aerosols at a certain site can vary depending on season, the air mass source region and distance from sources. Regardless of the environment, new particle formation (NPF) events are one of the major sources for ultrafine particles which are potentially hazardous to human health. Grown particles are optically active and efficient CCN resulting in important implications for visibility and climate (Zhang et al., 2004). The study presented here is intended to provide information about various aspects of continental, urban and marine air masses reflected by wind patterns of the air arriving at the measurement site. Additionally we will be focusing on NPF events associated with different types of air masses affecting their emergence and temporal evolution. Measurements of the ambient aerosol, various trace gases and meteorological parameters were performed within the framework of the DOMINO (Diel Oxidant Mechanisms In relation to Nitrogen Oxides) project. The field campaign took place from mid-November to mid-December 2008 at the atmospheric research station "El Arenosillo" located at the interface between a natural park, industrial cities (Huelva, Seville) and the Atlantic Ocean. Number and mass as well as PAH and black carbon concentrations were measured in PM1 and size distribution instruments covered the size range 6 nm up to 32 μm. The chemical composition of the non-refractory submicron aerosol was measured by means of an Aerosol Mass Spectrometer (AMS). In order to evaluate the characteristics of different air masses linking local and regional sources as well as NPF processes, characteristic air mass types were classified dependent on backwards trajectory pathways and local meteorology. Large nuclei mode concentrations in the number size distribution were found within continental and urban influenced air mass types due to frequently occurring NPF events. Exploring individual production and sink variables, sulfuric

  2. Nitric oxide formation in a lean, premixed-prevaporized jet A/air flame tube: An experimental and analytical study

    NASA Technical Reports Server (NTRS)

    Lee, Chi-Ming; Bianco, Jean; Deur, John M.; Ghorashi, Bahman

    1992-01-01

    An experimental and analytical study was performed on a lean, premixed-prevaporized Jet A/air flame tube. The NO(x) emissions were measured in a flame tube apparatus at inlet temperatures ranging from 755 to 866 K (900 to 1100 F), pressures from 10 to 15 atm, and equivalence ratios from 0.37 to 0.62. The data were then used in regressing an equation to predict the NO(x) production levels in combustors of similar design. Through an evaluation of parameters it was found that NO(x) is dependent on adiabatic flame temperature and combustion residence time, yet independent of pressure and inlet air temperature for the range of conditions studied. This equation was then applied to experimental data that were obtained from the literature, and a good correlation was achieved.

  3. Real-time measurements of secondary organic aerosol formation and aging from ambient air in an oxidation flow reactor in the Los Angeles area

    SciTech Connect

    Ortega, Amber M.; Hayes, Patrick L.; Peng, Zhe; Palm, Brett B.; Hu, Weiwei; Day, Douglas A.; Li, Rui; Cubison, Michael J.; Brune, William H.; Graus, Martin; Warneke, Carsten; Gilman, Jessica B.; Kuster, William C.; de Gouw, Joost; Gutierrez-Montes, Candido; Jimenez, Jose L.

    2016-06-15

    Field studies in polluted areas over the last decade have observed large formation of secondary organic aerosol (SOA) that is often poorly captured by models. The study of SOA formation using ambient data is often confounded by the effects of advection, vertical mixing, emissions, and variable degrees of photochemical aging. An oxidation flow reactor (OFR) was deployed to study SOA formation in real-time during the California Research at the Nexus of Air Quality and Climate Change (CalNex) campaign in Pasadena, CA, in 2010. A high-resolution aerosol mass spectrometer (AMS) and a scanning mobility particle sizer (SMPS) alternated sampling ambient and reactor-aged air. The reactor produced OH concentrations up to 4 orders of magnitude higher than in ambient air. OH radical concentration was continuously stepped, achieving equivalent atmospheric aging of 0.8 days–6.4 weeks in 3 min of processing every 2 h. Enhancement of organic aerosol (OA) from aging showed a maximum net SOA production between 0.8–6 days of aging with net OA mass loss beyond 2 weeks. Reactor SOA mass peaked at night, in the absence of ambient photochemistry and correlated with trimethylbenzene concentrations. Reactor SOA formation was inversely correlated with ambient SOA and Ox, which along with the short-lived volatile organic compound correlation, indicates the importance of very reactive (τOH ~ 0.3 day) SOA precursors (most likely semivolatile and intermediate volatility species, S/IVOCs) in the Greater Los Angeles Area. Evolution of the elemental composition in the reactor was similar to trends observed in the atmosphere (O : C vs. H : C slope ~ –0.65). Oxidation state of carbon (OSc) in reactor SOA increased steeply with age and remained elevated (OSC ~ 2) at the highest photochemical ages probed. The ratio of OA in the reactor output to excess CO (ΔCO, ambient CO above regional background) vs. photochemical age is similar to

  4. Real-time measurements of secondary organic aerosol formation and aging from ambient air in an oxidation flow reactor in the Los Angeles area

    DOE PAGES

    Ortega, Amber M.; Hayes, Patrick L.; Peng, Zhe; ...

    2016-06-15

    Field studies in polluted areas over the last decade have observed large formation of secondary organic aerosol (SOA) that is often poorly captured by models. The study of SOA formation using ambient data is often confounded by the effects of advection, vertical mixing, emissions, and variable degrees of photochemical aging. An oxidation flow reactor (OFR) was deployed to study SOA formation in real-time during the California Research at the Nexus of Air Quality and Climate Change (CalNex) campaign in Pasadena, CA, in 2010. A high-resolution aerosol mass spectrometer (AMS) and a scanning mobility particle sizer (SMPS) alternated sampling ambient andmore » reactor-aged air. The reactor produced OH concentrations up to 4 orders of magnitude higher than in ambient air. OH radical concentration was continuously stepped, achieving equivalent atmospheric aging of 0.8 days–6.4 weeks in 3 min of processing every 2 h. Enhancement of organic aerosol (OA) from aging showed a maximum net SOA production between 0.8–6 days of aging with net OA mass loss beyond 2 weeks. Reactor SOA mass peaked at night, in the absence of ambient photochemistry and correlated with trimethylbenzene concentrations. Reactor SOA formation was inversely correlated with ambient SOA and Ox, which along with the short-lived volatile organic compound correlation, indicates the importance of very reactive (τOH ~ 0.3 day) SOA precursors (most likely semivolatile and intermediate volatility species, S/IVOCs) in the Greater Los Angeles Area. Evolution of the elemental composition in the reactor was similar to trends observed in the atmosphere (O : C vs. H : C slope ~ –0.65). Oxidation state of carbon (OSc) in reactor SOA increased steeply with age and remained elevated (OSC ~ 2) at the highest photochemical ages probed. The ratio of OA in the reactor output to excess CO (ΔCO, ambient CO above regional background) vs. photochemical age is similar to previous studies at low to moderate ages and

  5. Real-time measurements of secondary organic aerosol formation and aging from ambient air in an oxidation flow reactor in the Los Angeles area

    NASA Astrophysics Data System (ADS)

    Ortega, Amber M.; Hayes, Patrick L.; Peng, Zhe; Palm, Brett B.; Hu, Weiwei; Day, Douglas A.; Li, Rui; Cubison, Michael J.; Brune, William H.; Graus, Martin; Warneke, Carsten; Gilman, Jessica B.; Kuster, William C.; de Gouw, Joost; Gutiérrez-Montes, Cándido; Jimenez, Jose L.

    2016-06-01

    Field studies in polluted areas over the last decade have observed large formation of secondary organic aerosol (SOA) that is often poorly captured by models. The study of SOA formation using ambient data is often confounded by the effects of advection, vertical mixing, emissions, and variable degrees of photochemical aging. An oxidation flow reactor (OFR) was deployed to study SOA formation in real-time during the California Research at the Nexus of Air Quality and Climate Change (CalNex) campaign in Pasadena, CA, in 2010. A high-resolution aerosol mass spectrometer (AMS) and a scanning mobility particle sizer (SMPS) alternated sampling ambient and reactor-aged air. The reactor produced OH concentrations up to 4 orders of magnitude higher than in ambient air. OH radical concentration was continuously stepped, achieving equivalent atmospheric aging of 0.8 days-6.4 weeks in 3 min of processing every 2 h. Enhancement of organic aerosol (OA) from aging showed a maximum net SOA production between 0.8-6 days of aging with net OA mass loss beyond 2 weeks. Reactor SOA mass peaked at night, in the absence of ambient photochemistry and correlated with trimethylbenzene concentrations. Reactor SOA formation was inversely correlated with ambient SOA and Ox, which along with the short-lived volatile organic compound correlation, indicates the importance of very reactive (τOH ˜ 0.3 day) SOA precursors (most likely semivolatile and intermediate volatility species, S/IVOCs) in the Greater Los Angeles Area. Evolution of the elemental composition in the reactor was similar to trends observed in the atmosphere (O : C vs. H : C slope ˜ -0.65). Oxidation state of carbon (OSc) in reactor SOA increased steeply with age and remained elevated (OSC ˜ 2) at the highest photochemical ages probed. The ratio of OA in the reactor output to excess CO (ΔCO, ambient CO above regional background) vs. photochemical age is similar to previous studies at low to moderate ages and also extends to

  6. Formation of Langmuir Monolayers of Titanium Dioxide Nanoparticles at Air/Aqueous Interfaces by the Addition of Ions to the Subphase: Effect of Ion Concentration and Type.

    PubMed

    Iwafuji, Yuya; McNamee, Cathy E

    2015-09-17

    A Langmuir monolayer of bare, hydrophilic TiO2 nanoparticles (diameter = 75 nm) was formed at an air/pH 5.8 aqueous interface by adding salt to the subphase. The effect of the concentration and type of salt in the subphase on the surface pressure-area per particle isotherms was determined. Increasing the concentration of NaCl from 0 to 3.8 M increased the maximum surface pressure (Πmax) and shifted the isotherms to a larger area per particle. The ion type also affected the area at which the close packing commenced and the value of Πmax. The presence of salt in the subphase also stabilized SiO2 nanoparticles, suggesting that the ions in the subphase interacted with the dioxide groups on the particles. The combination of structure making or borderline ions with structure breaking ions (LiCl, MgCl2, NaCl, and CaCl2) appeared to stabilize the particulate monolayers more than the combination of structure breaking ions (KBr and KCl). These results suggested that the particles were stabilized by a hydrogen bond network between the particles or the formation of a salt bridge between the particles. Attractions between particles at the air/aqueous interface caused the particles to aggregate, resulting in the particles becoming more stable at the air/aqueous interface.

  7. A novel approach to regulate cell membrane permeability for ATP and NADH formation in Saccharomyces cerevisiae induced by air cold plasma

    NASA Astrophysics Data System (ADS)

    Xiaoyu, DONG; Tingting, LIU; Yuqin, XIONG

    2017-02-01

    Air cold plasma has been used as a novel method for enhancing microbial fermentation. The aim of this work was to explore the effect of plasma on membrane permeability and the formation of ATP and NADH in Saccharomyces cerevisiae, so as to provide valuable information for large-scale application of plasma in the fermentation industry. Suspensions of S. cerevisiae cells were exposed to air cold plasma for 0, 1, 2, 3, 4 and 5 min, and then subjected to various analyses prior to fermentation (0 h) and at the 9 and 21 h stages of fermentation. Compared with non-exposed cells, cells exposed to plasma for 1 min exhibited a marked increase in cytoplasmic free Ca2+ concentration as a result of the significant increase in membrane potential prior to fermentation. At the same time, the ATP level in the cell suspension decreased by about 40%, resulting in a reduction of about 60% in NADH prior to culturing. However, the levels of ATP and NADH in the culture at the 9 and 21 h fermentation stages were different from the level at 0 h. Taken together, the results indicated that exposure of S. cerevisiae to air cold plasma could increase its cytoplasmic free Ca2+ concentration by improving the cell membrane potential, consequently leading to changes in ATP and NADH levels. Supported by National Natural Science Foundation of China (Nos. 21246012, 21306015 and 21476032).

  8. The Impact of Post Harvest Agricultural Crop Residue Fires on Volatile Organic Compounds and Formation of Secondary Air Pollutants in the N.W. Indo-Gangetic Plain

    NASA Astrophysics Data System (ADS)

    Sinha, V.; Chandra, P.; Kumar, V.; Sarkar, C.

    2015-12-01

    The N.W. Indo-Gangetic Plain (IGP) is an agriculturally and demographically important region of the world. Every year during the post harvest months of April-May and October-November, large scale open burning of wheat straw and paddy straw occurs in the region impairing the regional air quality and resulting in air pollution episodes. Here, using online in-situ measurements from the IISER Mohali Atmospheric Chemistry Facility (Sinha et al., Atmos Chem Phys, 2014), which is located at a regionally representative suburban site in the agricultural state of Punjab, India, we investigated the effects of this activity on gas phase chemistry. The online data pertaining to the pre harvest and post harvest paddy residue fires in 2012, 2013 and 2014 were analyzed to understand the effect of this anthropogenic activity on atmospheric chemistry and regional air quality with respect to health relevant VOCs such as benzenoids and isocyanic acid and trace gases such as ozone and carbon monoxide. These compounds showed marked increases (factor of 2-3 times higher) in their concentrations which correlated with the biomass combustion tracers such as acetonitrile. Emissions from the paddy residue fires did not result in significant enhancement of ambient ozone in 2012 but instead sustained hourly daytime ozone concentrations at ~ 50 ppb during the late post monsoon season, despite decreases in solar radiation and temperature. Results of such massive perturbations to ambient chemical composition, reactivity and formation of secondary pollutants and its implications for human health will be presented in this paper.

  9. Detection of Free Tropospheric Air Masses With High So2 and Aerosol Concentrations: Evidence For New Aerosol Particle Formation By H2so4/h2o Nucleation

    NASA Astrophysics Data System (ADS)

    Katragkou, E.; Wilhelm, S.; Kiendler, A.; Arnold, F.; Minikin, A.; Schlager, H.; van Velthoven, P.

    Sulfur dioxide and aerosol measurements were performed in the free troposphere (FT) and the Planetary Boundary Layer (PBL) above continental Europe. The measure- ments took place on board of the German research aircraft "Falcon" in 18 April 2001 as a part of the SCAVEX campaign. A novel aircraft based CIMS (Chemical Ion- ization Mass Spectrometry) instrument equipped with an ion trap mass spectrometer (ITMS) with a low detection limit (50pptv) and a high time resolution (1.3s) operated by MPI-K was used to perform the SO2 measurements. For the aerosol measurements DLR-IPA operated a Condensation Particle Size Analyzer, detecting particles with diameters d > 4, 7, 9 and 20nm and a PCASP-100X aerosol spectrometer probe (d > 100nm). In the measurements made mostly around 5000m altitude SO2 rich air masses were occasionally observed with SO2 VMR of up to 2900pptv. The strong SO2 pollu- tion was due to fast vertical transport of polluted continental PBL air and small-scale deep convection, as indicated by the 5-day backward 3D trajectories. These observa- tions of strong SO2 pollution have interesting implications for aerosol processes, in- cluding efficient formation of gaseous sulfuric acid (GSA) and new aerosol particles. They also imply fast growth of freshly nucleated aerosol particles, which increases the chance for new particles to grow to the size of a CCN. Our analysis indicates the occurrence of new particle formation by H2SO4/H2O nucleation and fast new particle growth by H2SO4/H2O condensation and self-coagulation in the different air masses encountered during the flight.

  10. Prediction of hydrodynamics and chemistry of confined turbulent methane-air flames with attention to formation of oxides of nitrogen

    NASA Technical Reports Server (NTRS)

    Elghobashi, S.; Spalding, D. B.; Srivatsa, S. K.

    1977-01-01

    A formulation of the governing partial differential equations for fluid flow and reacting chemical species in a tubular combustor is presented. A numerical procedure for the solution of the governing differential equations is described, and models for chemical equilibrium and chemical kinetics calculations are presented. The chemical equilibrium model is used to characterize the hydrocarbon reactions. The chemical kinetics model is used to predict the concentrations of the oxides of nitrogen. The combustor consists of a cylindrical duct of varying cross sections with concentric streams of gaseous fuel and air entering the duct at one end. Four sample cases with specified inlet and boundary conditions are considered, and the results are discussed

  11. Impacts of the Denver Cyclone on regional air quality and aerosol formation in the Colorado Front Range during FRAPPÉ 2014

    NASA Astrophysics Data System (ADS)

    Vu, Kennedy T.; Dingle, Justin H.; Bahreini, Roya; Reddy, Patrick J.; Apel, Eric C.; Campos, Teresa L.; DiGangi, Joshua P.; Diskin, Glenn S.; Fried, Alan; Herndon, Scott C.; Hills, Alan J.; Hornbrook, Rebecca S.; Huey, Greg; Kaser, Lisa; Montzka, Denise D.; Nowak, John B.; Pusede, Sally E.; Richter, Dirk; Roscioli, Joseph R.; Sachse, Glen W.; Shertz, Stephen; Stell, Meghan; Tanner, David; Tyndall, Geoffrey S.; Walega, James; Weibring, Peter; Weinheimer, Andrew J.; Pfister, Gabriele; Flocke, Frank

    2016-09-01

    We present airborne measurements made during the 2014 Front Range Air Pollution and Photochemistry Experiment (FRAPPÉ) project to investigate the impacts of the Denver Cyclone on regional air quality in the greater Denver area. Data on trace gases, non-refractory submicron aerosol chemical constituents, and aerosol optical extinction (βext) at λ = 632 nm were evaluated in the presence and absence of the surface mesoscale circulation in three distinct study regions of the Front Range: In-Flow, Northern Front Range, and the Denver metropolitan area. Pronounced increases in mass concentrations of organics, nitrate, and sulfate in the Northern Front Range and the Denver metropolitan area were observed during the cyclone episodes (27-28 July) compared to the non-cyclonic days (26 July, 2-3 August). Organic aerosols dominated the mass concentrations on all evaluated days, with a 45 % increase in organics on cyclone days across all three regions, while the increase during the cyclone episode was up to ˜ 80 % over the Denver metropolitan area. In the most aged air masses (NOx / NOy < 0.5), background organic aerosols over the Denver metropolitan area increased by a factor of ˜ 2.5 due to transport from Northern Front Range. Furthermore, enhanced partitioning of nitric acid to the aerosol phase was observed during the cyclone episodes, mainly due to increased abundance of gas phase ammonia. During the non-cyclone events, βext displayed strong correlations (r = 0.71) with organic and nitrate in the Northern Front Range and only with organics (r = 0.70) in the Denver metropolitan area, while correlation of βext during the cyclone was strongest (r = 0.86) with nitrate over Denver. Mass extinction efficiency (MEE) values in the Denver metropolitan area were similar on cyclone and non-cyclone days despite the dominant influence of different aerosol species on βext. Our analysis showed that the meteorological patterns associated with the Denver Cyclone increased aerosol

  12. Impacts of the Denver Cyclone on Regional Air Quality and Aerosol Formation in the Colorado Front Range during the Front Range Air Pollution and Photochemistry Éxperiment (FRAPPÉ) 2014

    NASA Astrophysics Data System (ADS)

    Vu, K. K. T.; Dingle, J. H.; Bahreini, R.; Apel, E. C.; Campos, T. L.; Cantrell, C. A.; Flocke, F. M.; Fried, A.; Herndon, S. C.; Hills, A. J.; Hornbrook, R. S.; Huey, L. G.; Kaser, L.; Mauldin, L.; Montzka, D. D.; Nowak, J. B.; Richter, D.; Roscioli, J. R.; Shertz, S.; Stell, M. H.; Tanner, D.; Tyndall, G. S.; Walega, J.; Weibring, P.; Weinheimer, A. J.

    2015-12-01

    The northern Colorado Front Range continues to face challenges related to air quality, specifically ozone, and has been classified as a marginal non-attainment area by the U.S EPA. The highly complex topography and meteorology in the Colorado Front Range provide flow patterns that are driven by mountain-valley circulation, resulting in formation of the Denver Cyclone, strongly influencing concentrations of ozone and aerosol particles. However, the impact of the Denver Cyclone on aerosol formation has not been previously explored. In this study, airborne measurements were made during July 16 - August 18, 2014 aboard the NSF C-130 aircraft during the 2014 Front Range Air Pollution and Photochemistry Éxperiment (FRAPPÉ) project. We carried out fast time resolved measurements of ambient aerosol chemical constituents (organics, sulfate, nitrate, ammonium, and chloride) of non-refractory sub-micrometer particles using an Aerodyne compact time-of-flight aerosol mass spectrometer (mAMS). Pronounced increased mass concentrations of organics, nitrate, and sulfate in two distinct regions in the Front Range were observed during the cyclone episodes, in contrast to the non-cyclonic days. Organics dominated the mass concentrations on all days evaluated. The average mass concentration of organics during a cyclone event was 5.79 ± 1.48 μg·m-3 and were lower during the two non-cyclonic measurement days, 3.09 ± 1.18 μg·m-3. Average sulfate mass concentrations were 1.25 ± 0.41 μg·m-3 vs. 0.58 ± 0.20 μg·m-3 followed by nitrate with an average of 1.66 ± 0.92 μg·m-3 vs. 0.32 ± 0.41 μg·m-3 on cyclone vs. non-cyclonic days, respectively. Correlations between trace gas markers (carbon monoxide, nitrogen oxides, ozone, ammonia, and ethane), meteorological variables (relative humidity, temperature), and the extent of aerosol aging are evaluated and used to assess the Front Range aerosol formation and air quality impacts in the region during these events.

  13. Influences of flame-vortex interactions on formation of oxides of nitrogen in curved methane-air diffusion flamelets

    SciTech Connect

    Card, J.M.; Ryden, R.; Williams, F.A.

    1996-05-01

    Previous work has identified a parabolic flamelet in a uniform flow as a useful model for studying flame-vortex interactions and has presented an asymptotic analysis of this flamelet structure for two-step reduced chemistry of the methane-air system. The present paper addresses production rates of oxides of nitrogen in this flamelet by one-step reduced-chemistry descriptions of both thermal and prompt mechanisms, for both two-step and three-step methane-air reduced chemistry, and also reports some results of calculations of production rates with a full-chemistry description of planar counterflow flames, for purposes of comparison. The comparisons suggest that the asymptotic approximations significantly overestimate production rates and fail as extinction is approached but give qualitatively correct trends away from extinction. These trends show that increasing the tip curvature of the flamelet increases the prompt contribution while decreasing the thermal contribution. It is concluded that more research is needed on both elementary rates and asymptotic descriptions, especially for the prompt mechanism.

  14. Large gap control in electromagnetic levitation.

    PubMed

    Banerjee, Subrata; Prasad, Dinkar; Pal, Jayanta

    2006-04-01

    This paper describes design and implementation of a single axis dc attraction type electromagnetic suspension system where an electromagnet of 2.6 kg mass is levitated over a large gap under a fixed ferromagnetic guide-way. The electromagnet exhibits nonlinear force-current-distance characteristics, and if controllers are to be designed by using linear analysis, the air-gap is restricted to a small region around the chosen nominal operating point. In this work, an attempt has been made to increase the operating range of an electromagnetic suspension system by using the concept of piecewise linear control where the nonlinear force-current-airgap relationships of the magnetic suspension system have been successively linearized at several operating points with a suitable controller designed for each operating point. A novel analog switching scheme has been designed and implemented to automatically switch to the relevant controller depending on the actual air-gap.

  15. Method and radial gap machine for high strength undiffused brushless operation

    DOEpatents

    Hsu, John S.

    2006-10-31

    A radial gap brushless electric machine (30) having a stator (31) and a rotor (32) and a main air gap (34) also has at least one stationary excitation coil (35a, 36a) separated from the rotor (32) by a secondary air gap (35e, 35f, 36e, 36f) so as to induce a secondary flux in the rotor (32) which controls a resultant flux in the main air gap (34). Permanent magnetic (PM) material (38) is disposed in spaces between the rotor pole portions (39) to inhibit the second flux from leaking from the pole portions (39) prior to reaching the main air gap (34). By selecting the direction of current in the stationary excitation coil (35a, 36a) both flux enhancement and flux weakening are provided for the main air gap (34). A method of non-diffused flux enhancement and flux weakening for a radial gap machine is also disclosed.

  16. Kinetics of the formation of ozone and nitrogen oxides due to a pulsed microwave discharge in air

    NASA Astrophysics Data System (ADS)

    Larin, V. F.; Rumiantsev, S. A.

    1989-03-01

    The paper presents results of a numerical simulation of the kinetics of plasma-chemical processes induced by a single microwave pulse in the stratosphere. It is shown that the gas temperature is one of the main factors influencing the concentration ratio of ozone and nitrogen oxides formed under the effect of a microwave pulse. Long pulses, producing considerable gas heating, favor the formation of nitrogen oxides.

  17. PEM fuel cell cathode carbon corrosion due to the formation of air/fuel boundary at the anode

    NASA Astrophysics Data System (ADS)

    Tang, Hao; Qi, Zhigang; Ramani, Manikandan; Elter, John F.

    The impacts of unprotected start up and shut down on fuel cell performance degradation was investigated using both single cell and dual cell configurations. It was found that the air/fuel boundary developed at the anode side after a fuel cell shut down or during its restart caused extremely quick degradation of the cathode. The thickness, the electrochemical active surface area, and the performance of the cathode catalyst layer were significantly reduced. By using a dual cell configuration, cathode potential as high as two times of open circuit voltage was measured, and the corrosion current flowing externally between the two cells was detected and quantified. Carbon catalyst-support corrosion/oxidation at such a high potential was largely responsible for the accelerated fuel cell performance degradation.

  18. Closing the Pay Gap

    DTIC Science & Technology

    2000-10-01

    the pay gap has been narrowed, hut only to just under 10 percent. And current military compensation legislation does not close the gap until 2026. There...will continue to be a pay gap until 2026 unless the next administration and the next Congress provide more for pay above the 1999 legislated ramp- up...of .5 percent (one half of one percent) per year to attain pay equality . That means that soldiers, sailors, airmen, marines and Coast Guardsmen

  19. A first principles analysis of the effect of hydrogen concentration in hydrogenated amorphous silicon on the formation of strained Si-Si bonds and the optical and mobility gaps

    SciTech Connect

    Legesse, Merid; Nolan, Michael Fagas, Giorgos

    2014-05-28

    In this paper, we use a model of hydrogenated amorphous silicon generated from molecular dynamics with density functional theory calculations to examine how the atomic geometry and the optical and mobility gaps are influenced by mild hydrogen oversaturation. The optical and mobility gaps show a volcano curve as the hydrogen content varies from undersaturation to mild oversaturation, with largest gaps obtained at the saturation hydrogen concentration. At the same time, mid-gap states associated with dangling bonds and strained Si-Si bonds disappear at saturation but reappear at mild oversaturation, which is consistent with the evolution of optical gap. The distribution of Si-Si bond distances provides the key to the change in electronic properties. In the undersaturation regime, the new electronic states in the gap arise from the presence of dangling bonds and strained Si-Si bonds, which are longer than the equilibrium Si-Si distance. Increasing hydrogen concentration up to saturation reduces the strained bonds and removes dangling bonds. In the case of mild oversaturation, the mid-gap states arise exclusively from an increase in the density of strained Si-Si bonds. Analysis of our structure shows that the extra hydrogen atoms form a bridge between neighbouring silicon atoms, thus increasing the Si-Si distance and increasing disorder in the sample.

  20. Minimisation of artefact formation of dimethyl disulphide during sampling and analysis of methanethiol in air using solid sorbent materials.

    PubMed

    Andersen, Kristin Barkve; Hansen, Michael Jørgen; Feilberg, Anders

    2012-07-06

    Methanethiol (MT) is a potent odorant that can be difficult to measure due to its high volatility and reactivity; it easily reacts to form dimethyl disulphide (DMDS) during sampling and/or analysis. This paper focuses on finding an optimal method for sampling and measuring MT with minimum artefact formation using sorbent materials and a thermal desorption-gas chromatography-mass spectrometry method (TD-GC-MS). Experiments were conducted to identify suitable sorbent materials and tubes for analysis. Breakthrough, desorption rate, the effects of storage and desorption temperatures were investigated and different drying methods were established with respect to quantitative sampling and formation of DMDS. Proton-transfer-reaction mass spectrometry (PTR-MS) was used in the development of the method and was an especially useful tool for determination of breakthrough. The results show that glass tubes packed with silica gel for pre-concentration of MT before analysis with TD-GC-MS give the best results. In addition, a combination of Tenax TA and carbonised molecular sieve or Tenax TA cooled to ≤0°C gives acceptable results. 80°C was found to be the optimal desorption temperature. For all the sampling methods tested, storage conditions were observed to be very critical for transformation of MT. Room temperature storage should be limited to few minutes and, in general, tubes should be kept at 0°C or lower during storage.

  1. Conditions for electron runaway under leader breakdown of long gaps

    SciTech Connect

    Ul'yanov, K. N.

    2008-04-15

    An original hydrodynamic model in which inelastic collisions in the equations of motion and energy balance play a decisive role is developed and applied to simulate electron avalanches in strong electric fields. The mean energy and drift velocity of electrons, as well as the ionization coefficient and electric field in a wide range of mean electron energies, are determined for helium and xenon. A criterion is derived for the runaway of the average electron in discharges with ionization multiplication. It is shown that runaway can take place at any value of E/p, provided that the momentum mean free path exceeds the gap length. The voltage corresponding to electron runaway is found for helium, xenon, and air as a function of the electric field, the electron mean energy, and the parameter pd. Conditions for the formation of a precursor in electronegative gases are analyzed. It is shown that the presence of a precursor with a high electric conductance is necessary for the formation of a new leader step. The voltage and time ranges corresponding to efficient electron runaway and X-ray generation during leader breakdown in air are determined.

  2. Senseless Extravagance, Shocking Gaps

    ERIC Educational Resources Information Center

    Weissbourd, Richard; Dodge, Trevor

    2012-01-01

    Although most people in the United States believe, at least theoretically, in educational equality, fewer and fewer appear to care about the resource gaps between affluent and poor schools, says Weissbourd. He illustrates these gaps with vivid descriptions of what he calls an "opulence arms race" among affluent independent schools, but…

  3. Information Gap Activities.

    ERIC Educational Resources Information Center

    Cicekdag, Mehmet Ali

    1995-01-01

    Focuses on a real world technique used to teach language proficiency in the classroom. This method involves creating deliberate information and opinion gaps by administering pop quizzes and other communicative games and filling those gaps through cooperative action. Use of this technique generated heated discussion among students. (nine…

  4. Bridging a Cultural Gap

    ERIC Educational Resources Information Center

    Leviatan, Talma

    2008-01-01

    There has been a broad wave of change in tertiary calculus courses in the past decade. However, the much-needed change in tertiary pre-calculus programmes--aimed at bridging the gap between high-school mathematics and tertiary mathematics--is happening at a far slower pace. Following a discussion on the nature of the gap and the objectives of a…

  5. Narrowing Participation Gaps

    ERIC Educational Resources Information Center

    Hand, Victoria; Kirtley, Karmen; Matassa, Michael

    2015-01-01

    Shrinking the achievement gap in mathematics is a tall order. One way to approach this challenge is to think about how the achievement gap manifests itself in the classroom and take concrete action. For example, opportunities to participate in activities that involve mathematical reasoning and argumentation in a safe and supportive manner are…

  6. Confronting the Achievement Gap

    ERIC Educational Resources Information Center

    Gardner, David

    2007-01-01

    This article talks about the large achievement gap between children of color and their white peers. The reasons for the achievement gap are varied. First, many urban minorities come from a background of poverty. One of the detrimental effects of growing up in poverty is receiving inadequate nourishment at a time when bodies and brains are rapidly…

  7. The National "Expertise Gap"

    ERIC Educational Resources Information Center

    Hamilton, Kendra

    2005-01-01

    This article discusses the Woodrow Wilson National Fellowship Foundation's report, "Diversity and the Ph.D.," released in May, which documents in troubling detail the exact dimensions of what the foundation's president, Dr. Robert Weisbuch, is calling the national "expertise gap." Weisbuch states that the expertise gap extends beyond the…

  8. The Parenting Gap

    ERIC Educational Resources Information Center

    Reeves, Richard V.; Howard, Kimberly

    2013-01-01

    The parenting gap is a big factor in the opportunity gap. The chances of upward social mobility are lower for children with parents struggling to do a good job--in terms of creating a supportive and stimulating home environment. Children lucky enough to have strong parents are more likely to succeed at all the critical life stages, which means…

  9. Which Achievement Gap?

    ERIC Educational Resources Information Center

    Anderson, Sharon; Medrich, Elliott; Fowler, Donna

    2007-01-01

    From the halls of Congress to the local elementary school, conversations on education reform have tossed around the term "achievement gap" as though people all know precisely what that means. As it's commonly used, "achievement gap" refers to the differences in scores on state or national achievement tests between various…

  10. States Address Achievement Gaps.

    ERIC Educational Resources Information Center

    Christie, Kathy

    2002-01-01

    Summarizes 2 state initiatives to address the achievement gap: North Carolina's report by the Advisory Commission on Raising Achievement and Closing Gaps, containing an 11-point strategy, and Kentucky's legislation putting in place 10 specific processes. The North Carolina report is available at www.dpi.state.nc.us.closingthegap; Kentucky's…

  11. Particle monolayer formation with arrayed structure by PMMA-grafted polystyrene Latex at the air-water interface.

    PubMed

    Mouri, Emiko; Terada, Motokazu; Koga, Ryosuke; Karakawa, Hiroyuki; Yoshinaga, Kohji

    2010-09-01

    The structure of the particle monolayer formed by the polymer-grafted latex particle at the air-water interface was estimated mainly by pi--A isotherm measurement and SEM observation to examine the effect of core particle characteristics and to generalize the key factors in determining the polymer-grafted particle monolayer structure. Methyl methacrylate (MMA) was polymerized from the polystyrene latex (PSL) surface by atom transfer radical polymerization to give a PMMA-grafted PSL (PSL-PMMA) with a relatively high graft density of about 0.2 nm-2. We obtained PSL-PMMA with PMMA of different molecular weights but almost the same graft density. The onset area of increasing surface pressure in pi-A isotherm was in agreement with the value of effective radius of PSL-PMMA with quite extended PMMA chains. The particle monolayer structure deposited on the substrate was strongly dependent on the molecular weight of the grafted PMMA. The aggregation size was reduced with increasing molecular weight and a lattice-like structure was observed for PSL-PMMA monolayer with a high molecular weight PMMA. The interparticle distance was decreased and structure becomes ordered with increasing surface pressure. The monolayer structure obtained here was consistent with that of the PMMA-grafted silica particle system. We also synthesized polystyrene (PS)-grafted PMMA latex (PML-PS) and compared the two systems. We confirmed that the lattice-like structure depended on the nature of the grafted PMMA chain, not the core particle characteristics.

  12. Body fat does not affect venous bubble formation after air dives of moderate severity: theory and experiment.

    PubMed

    Schellart, Nico A M; van Rees Vellinga, Tjeerd P; van Hulst, Rob A

    2013-03-01

    For over a century, studies on body fat (BF) in decompression sickness and venous gas embolism of divers have been inconsistent. A major problem is that age, BF, and maximal oxygen consumption (Vo2max) show high multicollinearity. Using the Bühlmann model with eight parallel compartments, preceded by a blood compartment in series, nitrogen tensions and loads were calculated with a 40 min/3.1 bar (absolute) profile. Compared with Haldanian models, the new model showed a substantial delay in N2 uptake and (especially) release. One hour after surfacing, an increase of 14-28% in BF resulted in a whole body increase of the N2 load of 51%, but in only 15% in the blood compartment. This would result in an increase in the bubble grade of only 0.01 Kisman-Masurel (KM) units at the scale near KM = I-. This outcome was tested indirectly by a dry dive simulation (air breathing) with 53 male divers with a small range in age and Vo2max to suppress multicollinearity. BF was determined with the four-skinfold method. Precordial Doppler bubble grades determined at 40, 80, 120, and 160 min after surfacing were used to calculate the Kisman Integrated Severity Score and were also transformed to the logarithm of the number of bubbles/cm(2) (logB). The highest of the four scores yielded logB = -1.78, equivalent to KM = I-. All statistical outcomes of partial correlations with BF were nonsignificant. These results support the model outcomes. Although this and our previous study suggest that BF does not influence venous gas embolism (Schellart NAM, van Rees Vellinga TP, van Dijk FH, Sterk W. Aviat Space Environ Med 83: 951-957, 2012), more studies with different profiles under various conditions are needed to establish whether BF remains (together with age and Vo2max) a basic physical characteristic or will become less important for the medical examination and for risk assessment.

  13. Influences of flame-vortex interactions on formation of oxides of nitrogen in curved methane-air diffusion flamelets

    SciTech Connect

    Card, J.M.; Ryden, R.; Williams, F.A.

    1994-01-01

    To improve knowledge of production rates of nitrogen oxides in turbulent diffusion flames in reaction-sheet regimes, an analytical investigation is made of the structure of a parabolic flamelet. The mixture-fraction field, scalar dissipation rate and gas velocity relative to the flamelet in the vortex are related to flame curvature at the parabolic tip. Flame structure for major species and temperature is described by rate-ratio asymptotics based on two-step and three-step reduced chemical-kinetic mechanisms. Production rates by prompt, thermal and nitrous-oxide mechanisms are obtained from one-step reduced-chemistry approximations that employ steady states for all reaction intermediaries. For sufficiently large streamwise separation distances between isoscalar surfaces, it is found that equilibrium conditions are closely approached near the flame tip, and the thermal mechanism dominates there, but the prompt mechanism always dominates in the wings, away from the tip, where the highest rates of scalar dissipation occur. Increasing the tip curvature increases the Peclet number and the prompt contribution while decreasing the thermal contribution. At 1 atm and ambient temperatures of 300 K, the prompt mechanism always dominates the total production rate in the parabolic flamelet, and, perhaps surprisingly, the rate of the nitrous-oxide mechanism is faster than that of the thermal mechanism and varies with the tip curvature and with scalar dissipation in the same manner as that of the prompt mechanism, different from that of the thermal mechanism. Conclusion reached is that Zel`dovich NO is relatively insignificant in hydrocarbon-air mixtures in reaction-sheet regimes.

  14. Formation and Collapse of Single-Monomer-Thick Monolayers of Poly(n-Butyl Acrylate) at the Air-Water Interface

    NASA Astrophysics Data System (ADS)

    Won, You-Yeon; Witte, Kevin; Sun, Wei; Kewalramani, Sumit; Fukuto, Masafumi; Kuzmenko, Ivan

    2010-03-01

    The behavior of poly(n-butyl acrylate) (PnBA) spread at the air-water interface has been studied for a full range of surface coverages. Beginning in the concentrated regime, and through the full coverage regime, x-ray reflectivity measurements show the formation of a continuous water-free one-monomer-thick film of the polymer. At surface concentrations above the transition point to the full coverage regime, Brewster angle microscopy shows that the excess polymer material does not distribute uniformly in the polymer film layer but instead leads to formation of micrometer-scale isolated globular domains. Further, the number of such domains increases as the surface polymer concentration is increased, whereas the size of the domains is unaffected by the concentration variation. X-ray grazing incidence diffraction indicates that these domains are regions of bulk-like polymer. We speculate that the globular domains are formed as a result of the interplay between the tendency of PnBA to adsorb to the water surface and the entropic resistance to this adsorption. A simple theoretical model based on this picture is shown to capture the main features of the experimental data.

  15. Formation of Stylet Sheaths in āere (in air) from eight species of phytophagous hemipterans from six families (Suborders: Auchenorrhyncha and Sternorrhyncha).

    PubMed

    Morgan, J Kent; Luzio, Gary A; Ammar, El-Desouky; Hunter, Wayne B; Hall, David G; Shatters, Robert G

    2013-01-01

    Stylet sheath formation is a common feature among phytophagous hemipterans. These sheaths are considered essential to promote a successful feeding event. Stylet sheath compositions are largely unknown and their mode of solidification remains to be elucidated. This report demonstrates the formation and solidification of in āere (in air) produced stylet sheaths by six hemipteran families: Diaphorina citri (Psyllidae, Asian citrus psyllid), Aphis nerii (Aphididae, oleander/milkweed aphid), Toxoptera citricida (Aphididae, brown citrus aphid), Aphis gossypii (Aphididae, cotton melon aphid), Bemisia tabaci biotype B (Aleyrodidae, whitefly), Homalodisca vitripennis (Cicadellidae, glassy-winged sharpshooter), Ferrisia virgata (Pseudococcidae, striped mealybug), and Protopulvinaria pyriformis (Coccidae, pyriform scale). Examination of in āere produced stylet sheaths by confocal and scanning electron microscopy shows a common morphology of an initial flange laid down on the surface of the membrane followed by continuous hollow core structures with sequentially stacked hardened bulbous droplets. Single and multi-branched sheaths were common, whereas mealybug and scale insects typically produced multi-branched sheaths. Micrographs of the in āere formed flanges indicate flange sealing upon stylet bundle extraction in D. citri and the aphids, while the B. tabaci whitefly and H. vitripennis glassy-winged sharpshooter flanges remain unsealed. Structural similarity of in āere sheaths are apparent in stylet sheaths formed in planta, in artificial diets, or in water. The use of 'Solvy', a dissolvable membrane, for intact stylet sheath isolation is reported. These observations illustrate for the first time this mode of stylet sheath synthesis adding to the understanding of stylet sheath formation in phytophagous hemipterans and providing tools for future use in structural and compositional analysis.

  16. Formation of Stylet Sheaths in āere (in air) from Eight Species of Phytophagous Hemipterans from Six Families (Suborders: Auchenorrhyncha and Sternorrhyncha)

    PubMed Central

    Morgan, J. Kent; Luzio, Gary A.; Ammar, El-Desouky; Hunter, Wayne B.; Hall, David G.; Shatters Jr, Robert G.

    2013-01-01

    Stylet sheath formation is a common feature among phytophagous hemipterans. These sheaths are considered essential to promote a successful feeding event. Stylet sheath compositions are largely unknown and their mode of solidification remains to be elucidated. This report demonstrates the formation and solidification of in āere (in air) produced stylet sheaths by six hemipteran families: Diaphorina citri (Psyllidae, Asian citrus psyllid), Aphis nerii (Aphididae, oleander/milkweed aphid), Toxoptera citricida (Aphididae, brown citrus aphid), Aphis gossypii (Aphididae, cotton melon aphid), Bemisia tabaci biotype B (Aleyrodidae, whitefly), Homalodisca vitripennis (Cicadellidae, glassy-winged sharpshooter), Ferrisia virgata (Pseudococcidae, striped mealybug), and Protopulvinaria pyriformis (Coccidae, pyriform scale). Examination of in āere produced stylet sheaths by confocal and scanning electron microscopy shows a common morphology of an initial flange laid down on the surface of the membrane followed by continuous hollow core structures with sequentially stacked hardened bulbous droplets. Single and multi-branched sheaths were common, whereas mealybug and scale insects typically produced multi-branched sheaths. Micrographs of the in āere formed flanges indicate flange sealing upon stylet bundle extraction in D. citri and the aphids, while the B. tabaci whitefly and H. vitripennis glassy-winged sharpshooter flanges remain unsealed. Structural similarity of in āere sheaths are apparent in stylet sheaths formed in planta, in artificial diets, or in water. The use of ‘Solvy’, a dissolvable membrane, for intact stylet sheath isolation is reported. These observations illustrate for the first time this mode of stylet sheath synthesis adding to the understanding of stylet sheath formation in phytophagous hemipterans and providing tools for future use in structural and compositional analysis. PMID:23638086

  17. Geotechnical Feasibility Analysis of Compressed Air Energy Storage (CAES) in Bedded Salt Formations: a Case Study in Huai'an City, China

    NASA Astrophysics Data System (ADS)

    Zhang, Guimin; Li, Yinping; Daemen, Jaak J. K.; Yang, Chunhe; Wu, Yu; Zhang, Kai; Chen, Yanlong

    2015-09-01

    The lower reaches of the Yangtze River is one of the most developed regions in China. It is desirable to build compressed air energy storage (CAES) power plants in this area to ensure the safety, stability, and economic operation of the power network. Geotechnical feasibility analysis was carried out for CAES in impure bedded salt formations in Huai'an City, China, located in this region. First, geological investigation revealed that the salt groups in the Zhangxing Block meet the basic geological conditions for CAES storage, even though the possible unfavorable characteristics of the salt formations include bedding and different percentages of impurities. Second, mechanical tests were carried out to determine the mechanical characteristics of the bedded salt formations. It is encouraging that the samples did not fail even when they had undergone large creep deformation. Finally, numerical simulation was performed to evaluate the stability and volume shrinkage of the CAES under the following conditions: the shape of a single cavern is that of a pear; the width of the pillar is adopted as two times the largest diameter; three regular operating patterns were adopted for two operating caverns (internal pressure 9-10.5 MPa, 10-11.5 MPa, and 11-12.5 MPa), while the other two were kept at high pressure (internal pressure 10.5, 11.5, and 12.5 MPa) as backups; an emergency operating pattern in which two operating caverns were kept at atmospheric pressure (0.1 MPa) for emergency while the backups were under operation (9-10.5 MPa), simulated for 12 months at the beginning of the 5th year. The results of the analysis for the plastic zone, displacement, and volume shrinkage support the feasibility of the construction of an underground CAES power station.

  18. SPARK GAP SWITCH

    DOEpatents

    Neal, R.B.

    1957-12-17

    An improved triggered spark gap switch is described, capable of precisely controllable firing time while switching very large amounts of power. The invention in general comprises three electrodes adjustably spaced and adapted to have a large potential impressed between the outer electrodes. The central electrode includes two separate elements electrically connected togetaer and spaced apart to define a pair of spark gaps between the end electrodes. Means are provided to cause the gas flow in the switch to pass towards the central electrode, through a passage in each separate element, and out an exit disposed between the two separate central electrode elements in order to withdraw ions from the spark gap.

  19. Aerodynamic and Acoustic Effects of Ventricular Gap

    PubMed Central

    Alipour, Fariborz; Karnell, Michael

    2013-01-01

    Purpose Supraglottic compression is frequently observed in individuals with dysphonia. It is commonly interpreted as an indication of excessive circumlaryngeal muscular tension and ventricular medialization. The purpose of this study was to describe the aerodynamic and acoustic impact of varying ventricular medialization in a canine model. Methods Subglottal air pressure, glottal airflow, electroglottograph, acoustic signals and high-speed video images were recorded in seven excised canine larynges mounted in vitro for laryngeal vibratory experimentation. The degree of gap between the ventricular folds was adjusted and measured using sutures and weights. Data was recorded during phonation when the ventricular gap was narrow, neutral, and large. Glottal resistance was estimated by measures of subglottal pressure and glottal flow. Results Glottal resistance increased systematically as ventricular gap became smaller. Wide ventricular gaps were associated with increases in fundamental frequency and decreases in glottal resistance. Sound pressure level did not appear to be impacted by the adjustments in ventricular gap used in this research. Conclusions Increases in supraglottic compression and associated reduced ventricular width may be observed in a variety of disorders that affect voice quality. Ventricular compression may interact with true vocal fold posture and vibration resulting in predictable changes in aerodynamic, physiologic, acoustic, and perceptual measures of phonation. The data from this report supports the theory that narrow ventricular gaps may be associated with disordered phonation. In vitro and in vivo human data are needed to further test this association. PMID:24321590

  20. Investigating the pathway for the photochemical formation of VOCs in presence of an organic monolayer at the air/water interface.

    NASA Astrophysics Data System (ADS)

    Tinel, Liselotte; Rossignol, Stéphanie; Ciuraru, Raluca; George, Christian

    2015-04-01

    Investigating the pathway for the photochemical formation of VOCs in presence of an organic monolayer at the air/water interface. Liselotte Tinel, Stéphanie Rossignol, Raluca Ciuraru and Christian George Université de Lyon, Université Lyon 1, CNRS, UMR5256, IRCELYON, Institut de recherches sur la catalyse et l'environnement de Lyon, Villeurbanne, F-69626, France Recently the surface microlayer (SML) has received growing attention for its role in the deposition and emission of trace gases. This SML is presumably a highly efficient environment for photochemical reactions thanks to its physical and chemical properties, showing enrichment in chromophores [1]. Still, little is known about the possible photochemical processes that could influence the emission and deposition of volatile organic compounds (VOCs) in the SML. A recent study underlines the particularity of the presence of an organic microlayer, showing enhanced formation of peptide bonds at the air-water interface, although this reaction is thermodynamically disfavoured in bulk water [2]. Also, emissions of small gas phase carbonyl compounds formed photochemically by dissolved organic matter have been measured above natural water and glyoxal, for example, measured above the open ocean is thought to be photochemically produced [3, 4]. This study presents the results of a set of laboratory studies set up in order to better understand the role of the SML in the photochemical production of VOCs. Recently, our group has shown the formation of VOCs by light driven reactions in a small quartz reactor (14mL) containing aqueous solutions of humic acids (HA) in the presence of an organic (artificial or natural) microlayer [5]. The main VOCs produced were oxidized species, such as aldehydes, ketones and alcohols, as classically can be expected by the oxidation of the organics present at the interface initiated by triplet excited chromophores present in the HA. But also alkenes, dienes, including isoprene and

  1. Characteristics and formation mechanism of a heavy air pollution episode caused by biomass burning in Chengdu, Southwest China.

    PubMed

    Chen, Yuan; Xie, Shao-Dong

    2014-03-01

    To track the chemical characteristics and formation mechanism of biomass burning pollution, the hourly variations of meteorological factors and pollutant concentrations during a heavy pollution on 18-21 May, 2012 in Chengdu are presented in this study. The episode was the heaviest and most long-lasting pollution event in the historical record of Chengdu caused by a combination of stagnant dispersion conditions and enhanced PM2.5 emission from intensive biomass burning, with peak values surpassing 500 μg m(-3). The event was characterized by three nighttime peaks, relating to the burning practice and decreased boundary layer height at night. The prevailing northeasterly wind during nighttime preferentially brought more pollutants to the urban regions from northern suburbs of Chengdu, where dense fire spots were observed. Due to the obstruction of hilly topography and weak wind speed, minor regional features were reflected from the PM10 variations in nearby cities, whereas the long-distance transport of the plume impacted extensive regions in northern and eastern China. Carbon monoxide (CO) concentrations increased by more than 200%, while exceptionally high PM2.5 levels of 190.1 and 268.4 μg m(-3) on 17 May and 18 May, were observed and showed high correlation with CO (r=0.75). The relative contribution of biomass burning smoke to organic carbon was estimated from OC/EC ratios (organic carbon/elemental carbon) and elevated to 81.3% during the episode, indicating a significant impact on urban aerosol levels. The occurrence of high PM2.5/PM10 ratios (>0.80) and K(+)/EC ratios (>1.0), along with the increased carbonaceous concentrations and their fraction in PM2.5 (>40%) and high OC/EC ratios (about 8), could be used as immediate indicators for biomass burning pollution in cities. In addition, the heavy pollution involved a mixture of anthropogenic sources, reflected from the high SOR and NOR values and increases in the EFs (enrichment factors) of Mo, Zn, Cd, and Pb.

  2. Long-term aerosol and trace gas measurements in Eastern Lapland, Finland: the impact of Kola air pollution to new particle formation and potential CCN

    NASA Astrophysics Data System (ADS)

    Kyrö, Ella-Maria; Väänänen, Riikka; Kerminen, Veli-Matti; Virkkula, Aki; Asmi, Ari; Nieminen, Tuomo; Dal Maso, Miikka; Petäjä, Tuukka; Keronen, Petri; Aalto, Pasi; Riipinen, Ilona; Lehtipalo, Katrianne; Hari, Pertti; Kulmala, Markku

    2014-05-01

    Sulphur and primary emissions have been decreasing largely all over Europe, resulting in improved air quality and decreased direct radiation forcing by aerosols. The smelter industry in Kola Peninsula is one of largest sources of anthropogenic SO2 within the Arctic domain and since late 1990s the sulphur emissions have been decreasing rapidly (Paatero et al., 2008; Prank et al., 2010). New particle formation (NPF) is tightly linked with the oxidizing product of SO2, namely sulphuric acid (H2SO4), since it is known to be the key component in atmospheric nucleation (Sipilä et al., 2010). Thus, decreasing sulphur pollution may lead to less NPF. However, low values of condensation sink (CS), which is determined by the amount of pre-existing particles, favours NPF. We used 14 years (1998-2011) of aerosol number size distribution and trace gas data from SMEAR I station in Eastern Lapland, Finland, to investigate these relationships between SO2, NPF and CS. The station is a clean background station with occasional sulphur pollution episodes when the air masses arrive over Kola Peninsula. We found that while SO2 decreased by 11.3 % / year, the number of clear NPF event days was also decreasing by 9.9 % / year. At the same time, CS was decreasing also (-8.0 % / year) leading to formation of more particles per single NPF event (J3 increased by 29.7 % / year in 2006-2011) but the low vapour concentrations of H2SO4 (proxy decreased by 6.2 % / year) did not allow them to grow into climatically relevant sizes. Over the time, concentrations of potential CCN (cloud condensing nuclei) were also decreasing with more moderate pace, -4.0 % / year. The events started on average earlier after sunrise when the SO2 concentration during the start of the event was higher and NPF occurred more frequently in air masses which were travelling over Kola. Despite the total decrease in sulphur pollution originating from Kola there is currently no evidence of cleaning of the emissions, rather the

  3. Fiber optic gap gauge

    DOEpatents

    Wood, Billy E.; Groves, Scott E.; Larsen, Greg J.; Sanchez, Roberto J.

    2006-11-14

    A lightweight, small size, high sensitivity gauge for indirectly measuring displacement or absolute gap width by measuring axial strain in an orthogonal direction to the displacement/gap width. The gap gauge includes a preferably titanium base having a central tension bar with springs connecting opposite ends of the tension bar to a pair of end connector bars, and an elongated bow spring connected to the end connector bars with a middle section bowed away from the base to define a gap. The bow spring is capable of producing an axial strain in the base proportional to a displacement of the middle section in a direction orthogonal to the base. And a strain sensor, such as a Fabry-Perot interferometer strain sensor, is connected to measure the axial strain in the base, so that the displacement of the middle section may be indirectly determined from the measurement of the axial strain in the base.

  4. Spatial distribution and size of small canopy gaps created by Japanese black bears: estimating gap size using dropped branch measurements

    PubMed Central

    2013-01-01

    Background Japanese black bears, a large-bodied omnivore, frequently create small gaps in the tree crown during fruit foraging. However, there are no previous reports of black bear-created canopy gaps. To characterize physical canopy disturbance by black bears, we examined a number of parameters, including the species of trees in which canopy gaps were created, gap size, the horizontal and vertical distribution of gaps, and the size of branches broken to create gaps. The size of black bear-created canopy gaps was estimated using data from branches that had been broken and dropped on the ground. Results The disturbance regime was characterized by a highly biased distribution of small canopy gaps on ridges, a large total overall gap area, a wide range in gap height relative to canopy height, and diversity in gap size. Surprisingly, the annual rate of bear-created canopy gap formation reached 141.3 m2 ha–1 yr–1 on ridges, which were hot spots in terms of black bear activity. This rate was approximately 6.6 times that of tree-fall gap formation on ridges at this study site. Furthermore, this rate was approximately two to three times that of common tree-fall gap formation in Japanese forests, as reported in other studies. Conclusions Our findings suggest that the ecological interaction between black bears and fruit-bearing trees may create a unique light regime, distinct from that created by tree falls, which increases the availability of light resources to plants below the canopy. PMID:23758683

  5. Significant Reduction in NiO Band Gap Upon Formation of LixNi1-xO alloys: Applications To Solar Energy Conversion

    SciTech Connect

    Alidoust, Nima; Toroker, Maytal Caspary; Keith, John A.; Carter, Emily A.

    2013-11-21

    Long-term sustainable solar energy conversion relies on identifying economical and versatile semiconductor materials with appropriate band structures for photovoltaic and photocatalytic applications (e.g., band gaps of ~1.5–2.0 eV). Nickel oxide (NiO) is an inexpensive yet highly promising candidate. Its charge-transfer character may lead to longer carrier lifetimes needed for higher efficiencies, and its conduction band edge is suitable for driving hydrogen evolution via water-splitting. However, NiO’s large band gap (~4 eV) severely limits its use in practical applications. Our first-principles quantum mechanics calculations show band gaps dramatically decrease to ~2.0 eV when NiO is alloyed with Li2O. In this paper, we show that LixNi1-xO alloys (with x=0.125 and 0.25) are p-type semiconductors, contain states with no impurity levels in the gap and maintain NiO’s desirable charge-transfer character. Lastly, we show that the alloys have potential for photoelectrochemical applications, with band edges well-placed for photocatalytic hydrogen production and CO2 reduction, as well as in tandem dye-sensitized solar cells as a photocathode.

  6. Supramolecular assembly at interfaces: formation of an extended two-dimensional coordinate covalent square grid network at the air-water interface.

    PubMed

    Culp, Jeffrey T; Park, Ju-Hyun; Stratakis, Diktys; Meisel, Mark W; Talham, Daniel R

    2002-08-28

    Reaction of a Langmuir monolayer of an amphiphilic pentacyanoferrate(3+) complex with Ni(2+) ions from the subphase results in the formation of a two-dimensional iron-nickel cyanide-bridged network at the air-water interface. The network can be transferred to various supports to form monolayer or multilayer lamellar films by the Langmuir-Blodgett (LB) technique. The same network does not form from homogeneous reaction conditions. Therefore, the results demonstrate the potential utility of an interface as a structure director in the assembly of low dimensional coordinate covalent network solids. Characterization of the LB film extended networks by X-ray photoelectron spectroscopy (XPS), FT-IR spectroscopy, SQUID magnetometry, X-ray absorption fine structure (XAFS), and grazing incidence synchrotron X-ray diffraction (GIXD) revealed a face-centered square grid structure with an average domain size of 3600 A(2). Magnetic measurements indicated that the network undergoes a transition to a ferromagnetic state below a T(c) of 8 K.

  7. Formation of gas-phase carbonyls from heterogeneous oxidation of polyunsaturated fatty acids at the air-water interface and of the sea surface microlayer

    NASA Astrophysics Data System (ADS)

    Zhou, S.; Gonzalez, L.; Leithead, A.; Finewax, Z.; Thalman, R.; Vlasenko, A.; Vagle, S.; Miller, L. A.; Li, S.-M.; Bureekul, S.; Furutani, H.; Uematsu, M.; Volkamer, R.; Abbatt, J.

    2014-02-01

    Motivated by the potential for reactive heterogeneous chemistry occurring at the ocean surface, gas-phase products were observed when a reactive sea surface microlayer (SML) component, i.e. the polyunsaturated fatty acids (PUFA) linoleic acid (LA), was exposed to gas-phase ozone at the air-seawater interface. Similar oxidation experiments were conducted with SML samples collected from two different oceanic locations, in the eastern equatorial Pacific Ocean and from the west coast of Canada. Online proton-transfer-reaction mass spectrometry (PTR-MS) University of Colorado light-emitting diode cavity-enhanced differential optical absorption spectroscopy (LED-CE-DOAS) were used to detect oxygenated gas-phase products from the ozonolysis reactions. The LA studies indicate that oxidation of a PUFA monolayer on seawater gives rise to prompt and efficient formation of gas-phase aldehydes. The products are formed via the decomposition of primary ozonides which form upon the initial reaction of ozone with the carbon-carbon double bonds in the PUFA molecules. In addition, two highly reactive dicarbonyls, malondialdehyde (MDA) and glyoxal, were also generated, likely as secondary products. Specific yields relative to reactant loss were 78%, 29%, 4% and < 1% for n-hexanal, 3-nonenal, MDA and glyoxal, respectively, where the yields for MDA and glyoxal are likely lower limits. Heterogeneous oxidation of SML samples confirm for the first time that similar carbonyl products are formed via ozonolysis of environmental samples.

  8. Influence of surface emission processes on a fast-pulsed dielectric barrier discharge in air at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Pechereau, François; Bonaventura, Zdeněk; Bourdon, Anne

    2016-08-01

    This paper presents simulations of an atmospheric pressure air discharge in a point-to-plane geometry with a dielectric layer parallel to the cathode plane. Experimentally, a discharge reignition in the air gap below the dielectrics has been observed. With a 2D fluid model, it is shown that due to the fast rise of the high voltage applied and the sharp point used, a first positive spherical discharge forms around the point. Then this discharge propagates axially and impacts the dielectrics. As the first discharge starts spreading on the upper dielectric surface, in the second air gap with a low preionization density of {{10}4}~\\text{c}{{\\text{m}}-3} , the 2D fluid model predicts a rapid reignition of a positive discharge. As in experiments, the discharge reignition is much slower, a discussion on physical processes to be considered in the model to increase the reignition delay is presented. The limit case with no initial seed charges in the second air gap has been studied. First, we have calculated the time to release an electron from the cathode surface by thermionic and field emission processes for a work function φ \\in ≤ft[3,4\\right] eV and an amplification factor β \\in ≤ft[100,220\\right] . Then a 3D Monte Carlo model has been used to follow the dynamics of formation of an avalanche starting from a single electron emitted at the cathode. Due to the high electric field in the second air gap, we have shown that in a few nanoseconds, a Gaussian cloud of seed charges is formed at a small distance from the cathode plane. This Gaussian cloud has been used as the initial condition of the 2D fluid model in the second air gap. In this case, the propagation of a double headed discharge in the second air gap has been observed and the reignition delay is in rather good agreement with experiments.

  9. Flows of gas through a protoplanetary gap

    NASA Astrophysics Data System (ADS)

    Casassus, Simon; van der Plas, Gerrit; M, Sebastian Perez; Dent, William R. F.; Fomalont, Ed; Hagelberg, Janis; Hales, Antonio; Jordán, Andrés; Mawet, Dimitri; Ménard, Francois; Wootten, Al; Wilner, David; Hughes, A. Meredith; Schreiber, Matthias R.; Girard, Julien H.; Ercolano, Barbara; Canovas, Hector; Román, Pablo E.; Salinas, Vachail

    2013-01-01

    The formation of gaseous giant planets is thought to occur in the first few million years after stellar birth. Models predict that the process produces a deep gap in the dust component (shallower in the gas). Infrared observations of the disk around the young star HD 142527 (at a distance of about 140 parsecs from Earth) found an inner disk about 10 astronomical units (AU) in radius (1 AU is the Earth-Sun distance), surrounded by a particularly large gap and a disrupted outer disk beyond 140 AU. This disruption is indicative of a perturbing planetary-mass body at about 90 AU. Radio observations indicate that the bulk mass is molecular and lies in the outer disk, whose continuum emission has a horseshoe morphology. The high stellar accretion rate would deplete the inner disk in less than one year, and to sustain the observed accretion matter must therefore flow from the outer disk and cross the gap. In dynamical models, the putative protoplanets channel outer-disk material into gap-crossing bridges that feed stellar accretion through the inner disk. Here we report observations of diffuse CO gas inside the gap, with denser HCO+ gas along gap-crossing filaments. The estimated flow rate of the gas is in the range of 7 × 10-9 to 2 × 10-7 solar masses per year, which is sufficient to maintain accretion onto the star at the present rate.

  10. Flows of gas through a protoplanetary gap.

    PubMed

    Casassus, Simon; van der Plas, Gerrit; Sebastian Perez, M; Dent, William R F; Fomalont, Ed; Hagelberg, Janis; Hales, Antonio; Jordán, Andrés; Mawet, Dimitri; Ménard, Francois; Wootten, Al; Wilner, David; Hughes, A Meredith; Schreiber, Matthias R; Girard, Julien H; Ercolano, Barbara; Canovas, Hector; Román, Pablo E; Salinas, Vachail

    2013-01-10

    The formation of gaseous giant planets is thought to occur in the first few million years after stellar birth. Models predict that the process produces a deep gap in the dust component (shallower in the gas). Infrared observations of the disk around the young star HD 142527 (at a distance of about 140 parsecs from Earth) found an inner disk about 10 astronomical units (AU) in radius (1 AU is the Earth-Sun distance), surrounded by a particularly large gap and a disrupted outer disk beyond 140 AU. This disruption is indicative of a perturbing planetary-mass body at about 90 AU. Radio observations indicate that the bulk mass is molecular and lies in the outer disk, whose continuum emission has a horseshoe morphology. The high stellar accretion rate would deplete the inner disk in less than one year, and to sustain the observed accretion matter must therefore flow from the outer disk and cross the gap. In dynamical models, the putative protoplanets channel outer-disk material into gap-crossing bridges that feed stellar accretion through the inner disk. Here we report observations of diffuse CO gas inside the gap, with denser HCO(+) gas along gap-crossing filaments. The estimated flow rate of the gas is in the range of 7 × 10(-9) to 2 × 10(-7) solar masses per year, which is sufficient to maintain accretion onto the star at the present rate.

  11. Numerical Simulation of Supersonic Gap Flow

    PubMed Central

    Jing, Xu; Haiming, Huang; Guo, Huang; Song, Mo

    2015-01-01

    Various gaps in the surface of the supersonic aircraft have a significant effect on airflows. In order to predict the effects of attack angle, Mach number and width-to-depth ratio of gap on the local aerodynamic heating environment of supersonic flow, two-dimensional compressible Navier-Stokes equations are solved by the finite volume method, where convective flux of space term adopts the Roe format, and discretization of time term is achieved by 5-step Runge-Kutta algorithm. The numerical results reveal that the heat flux ratio is U-shaped distribution on the gap wall and maximum at the windward corner of the gap. The heat flux ratio decreases as the gap depth and Mach number increase, however, it increases as the attack angle increases. In addition, it is important to find that chamfer in the windward corner can effectively reduce gap effect coefficient. The study will be helpful for the design of the thermal protection system in reentry vehicles. PMID:25635395

  12. Gap-flow Mediated Transport of Pollution to a Remote Coastal Site: Effects upon Aerosol Composition

    NASA Astrophysics Data System (ADS)

    Cornwell, G.; Martin, A.; Petters, M.; Prather, K. A.; Taylor, H.; Rothfuss, N.; DeMott, P. J.; Kreidenweis, S. M.

    2015-12-01

    During the CalWater 2015 field campaign, observations of aerosol size, concentration, chemical composition, and cloud activity were made at Bodega Bay, CA on the remote California coast. Strong anthropogenic influence on air quality, aerosol physicochemical properties and cloud activity was observed at Bodega Bay during periods of special meteorological conditions, known as Petaluma Gap Flow, in which air from California's interior is transported to the coast. This study utilizes single particle mass spectrometry, along with aerosol physical and chemical measurements and meteorological measurements to show that the dramatic change in aerosol properties is strongly related to regional meteorology and anthropogenically-influenced chemical processes in California's Central Valley. The change in airmass properties from those typical of a remote marine environment to properties of a continental regime has impacts on atmospheric radiative balance and cloud formation that must be accounted for in regional climate simulation.

  13. Precision gap particle separator

    DOEpatents

    Benett, William J.; Miles, Robin; Jones, II., Leslie M.; Stockton, Cheryl

    2004-06-08

    A system for separating particles entrained in a fluid includes a base with a first channel and a second channel. A precision gap connects the first channel and the second channel. The precision gap is of a size that allows small particles to pass from the first channel into the second channel and prevents large particles from the first channel into the second channel. A cover is positioned over the base unit, the first channel, the precision gap, and the second channel. An port directs the fluid containing the entrained particles into the first channel. An output port directs the large particles out of the first channel. A port connected to the second channel directs the small particles out of the second channel.

  14. MULTIPLE SPARK GAP SWITCH

    DOEpatents

    Schofield, A.E.

    1958-07-22

    A multiple spark gap switch of unique construction is described which will permit controlled, simultaneous discharge of several capacitors into a load. The switch construction includes a disc electrode with a plurality of protuberances of generally convex shape on one surface. A firing electrode is insulatingly supponted In each of the electrode protuberances and extends substantially to the apex thereof. Individual electrodes are disposed on an insulating plate parallel with the disc electrode to form a number of spark gaps with the protuberances. These electrodes are each connected to a separate charged capacitor and when a voltage ls applied simultaneously between the trigger electrodes and the dlsc electrode, each spark gap fires to connect its capacitor to the disc electrode and a subsequent load.

  15. Sculpting the band gap: a computational approach

    PubMed Central

    Prasai, Kiran; Biswas, Parthapratim; Drabold, D. A.

    2015-01-01

    Materials with optimized band gap are needed in many specialized applications. In this work, we demonstrate that Hellmann-Feynman forces associated with the gap states can be used to find atomic coordinates that yield desired electronic density of states. Using tight-binding models, we show that this approach may be used to arrive at electronically designed models of amorphous silicon and carbon. We provide a simple recipe to include a priori electronic information in the formation of computer models of materials, and prove that this information may have profound structural consequences. The models are validated with plane-wave density functional calculations. PMID:26490203

  16. Sculpting the band gap: a computational approach

    NASA Astrophysics Data System (ADS)

    Prasai, Kiran; Biswas, Parthapratim; Drabold, D. A.

    2015-10-01

    Materials with optimized band gap are needed in many specialized applications. In this work, we demonstrate that Hellmann-Feynman forces associated with the gap states can be used to find atomic coordinates that yield desired electronic density of states. Using tight-binding models, we show that this approach may be used to arrive at electronically designed models of amorphous silicon and carbon. We provide a simple recipe to include a priori electronic information in the formation of computer models of materials, and prove that this information may have profound structural consequences. The models are validated with plane-wave density functional calculations.

  17. Influence of ozone concentration and temperature on ultra-fine particle and gaseous volatile organic compound formations generated during the ozone-initiated reactions with emitted terpenes from a car air freshener.

    PubMed

    Lamorena, Rheo B; Lee, Woojin

    2008-10-30

    Experiments were conducted to identify the emissions from the car air freshener and to identify the formation of ultra-fine particles and secondary gaseous compounds during the ozone-initiated oxidations with emitted volatile organic compounds (VOCs). The identified primary constituents emitted from the car air freshener in this study were alpha-pinene, beta-pinene, p-cymene, and limonene. Formation of ultra-fine particles (4.4-160 nm) was observed when ozone was injected into the chamber containing emitted monoterpenes from the air freshener. Particle number concentrations, particle mass concentrations, and surface concentrations were measured in time dependent experiments to describe the particle formation and growth within the chamber. The irritating secondary gaseous products formed during the ozone-initiated reactions include formaldehyde, acetaldehyde, acrolein, acetone, and propionaldehyde. Ozone concentration (50 and 100 ppb) and temperature (30 and 40 degrees C) significantly affect the formation of particles and gaseous products during the ozone-initiated reactions. The results obtained in this study provided an insight on the potential exposure of particles and irritating secondary products formed during the ozone-initiated reaction to passengers in confined spaces.

  18. Rho GAPs and GEFs

    PubMed Central

    van Buul, Jaap D; Geerts, Dirk; Huveneers, Stephan

    2014-01-01

    Within blood vessels, endothelial cell–cell and cell–matrix adhesions are crucial to preserve barrier function, and these adhesions are tightly controlled during vascular development, angiogenesis, and transendothelial migration of inflammatory cells. Endothelial cellular signaling that occurs via the family of Rho GTPases coordinates these cell adhesion structures through cytoskeletal remodelling. In turn, Rho GTPases are regulated by GTPase-activating proteins (GAPs) and guanine nucleotide exchange factors (GEFs). To understand how endothelial cells initiate changes in the activity of Rho GTPases, and thereby regulate cell adhesion, we will discuss the role of Rho GAPs and GEFs in vascular biology. Many potentially important Rho regulators have not been studied in detail in endothelial cells. We therefore will first overview which GAPs and GEFs are highly expressed in endothelium, based on comparative gene expression analysis of human endothelial cells compared with other tissue cell types. Subsequently, we discuss the relevance of Rho GAPs and GEFs for endothelial cell adhesion in vascular homeostasis and disease. PMID:24622613

  19. Closing the Performance Gap.

    ERIC Educational Resources Information Center

    Riggins, Cheryl G.

    2002-01-01

    Describes how the principal of a K-2, 400-student suburban elementary school near Flint, Michigan, worked with her staff and superintendent to develop and implement a strategic plan to close the student achievement gap. Reports significant improvement in reading and math scores after 1 year. (PKP)

  20. STEMMING the Gap

    ERIC Educational Resources Information Center

    Kahler, Jim; Valentine, Nancy

    2011-01-01

    America has a gap when it comes to youth pursuing science and technology careers. In an effort to improve the knowledge and application of science, technology, engineering, and math (STEM), after-school programs can work in conjunction with formal in-school curriculum to improve science education. One organization that actively addresses this…

  1. Confronting the Autonomy Gap

    ERIC Educational Resources Information Center

    Adamowski, Steven; Petrilli, Michael J.

    2007-01-01

    "The Autonomy Gap," a recent study by the American Institute for Research and the Thomas B. Fordham Institute, found that many public elementary school principals feel constrained by a bureaucracy that impedes their ability to raise student achievement. Unfortunately, those principals are still held accountable for their school's results--even…

  2. The Academic Generation Gap

    ERIC Educational Resources Information Center

    Dronzek, Anna

    2008-01-01

    The current generation gap in academia is different--fundamentally shaped by the structural problems of academic employment. The job market has especially exacerbated tensions between senior and junior faculty by ratcheting up expectations and requirements at every stage of the academic career. The disparities have been mentioned often enough to…

  3. Structuring the Information Gap.

    ERIC Educational Resources Information Center

    Edge, Julian

    1984-01-01

    Describes an information gap procedure to teach a new structure which requires students to look for and exchange information in order to complete a task in an English as a second language class. Illustrates the method with a set of materials and suggests ways for teachers to produce similar materials. (SED)

  4. Multiple gap photovoltaic device

    DOEpatents

    Dalal, Vikram L.

    1981-01-01

    A multiple gap photovoltaic device having a transparent electrical contact adjacent a first cell which in turn is adjacent a second cell on an opaque electrical contact, includes utilizing an amorphous semiconductor as the first cell and a crystalline semiconductor as the second cell.

  5. Estimating Gender Wage Gaps

    ERIC Educational Resources Information Center

    McDonald, Judith A.; Thornton, Robert J.

    2011-01-01

    Course research projects that use easy-to-access real-world data and that generate findings with which undergraduate students can readily identify are hard to find. The authors describe a project that requires students to estimate the current female-male earnings gap for new college graduates. The project also enables students to see to what…

  6. California: Emigrant Gap

    Atmospheric Science Data Center

    2014-05-15

    ... Imaging SpectroRadiometer (MISR) images of the Central Valley and the Sierra Nevada Mountains show several smoke plumes from wildfires ... from the Emigrant Gap Fire, located about 40 kilometers west of Lake Tahoe. The animated panorama uses different MISR cameras to enable ...

  7. Bridging a Communication Gap

    ERIC Educational Resources Information Center

    Kahn, Ethel

    1972-01-01

    Description of a community program in cooperation with a regional extension service. The goals were to explore the generation gap, and conflict in life values, understand family role, increase self awareness, improve adult-youth communication, and understand the individual and his relationship to basic social principles. (Author/JB)

  8. Bridging the Development Gap.

    DTIC Science & Technology

    1999-11-01

    Bridging the Development Gap is contractual cooperative agreement between Mercury Computer Systems, Inc. and DARPA. This program was developed...processing, interfacing with I/O devices, memory constraints, as well as real-time throughput and latency challenges. Mercury has bridged the indicated

  9. Superposition-additive approach in the description of thermodynamic parameters of formation and clusterization of substituted alkanes at the air/water interface.

    PubMed

    Vysotsky, Yu B; Belyaeva, E A; Fomina, E S; Vasylyev, A O; Vollhardt, D; Fainerman, V B; Aksenenko, E V; Miller, R

    2012-12-01

    The superposition-additive approach developed previously was shown to be applicable for the calculations of the thermodynamic parameters of formation and atomization of conjugate systems, their dipole polarizability, molecular diamagnetic susceptibility, π-electronic ring currents, etc. In the present work, the applicability of this approach for the calculation of the thermodynamic parameters of formation and clusterization at the water/air interface of alkanes, fatty alcohols, thioalcohols, amines, nitriles, fatty acids (C(n)H(2n+1)X, X is the functional group) and cis-unsaturated carboxylic acids (C(n)H(2n-1)COOH) is studied. Using the proposed approach the thermodynamic quantities determined agree well with the available data, either calculated using the semiempirical (PM3) quantum chemical method, or obtained in experiments. In particular, for enthalpy and Gibbs' energy of the formation of substituted alkane monomers from the elementary substances, and their absolute entropy, the standard deviations of the values calculated according to the superposition-additive scheme with the mutual superimposition domain C(n-2)H(2n-4) (n is the number of carbon atoms in the alkyl chain) from the results of PM3 calculations for alkanes, alcohols, thioalcohols, amines, fatty acids, nitriles and cis-unsaturated carboxylic acids are respectively: 0.05, 0.004, 2.87, 0.02, 0.01, 0.77, and 0.01 kJ/mol for enthalpy; 2.32, 5.26, 4.49, 0.53, 1.22, 1.02, 5.30 J/(molK) for absolute entropy; 0.69, 1.56, 3.82, 0.15, 0.37, 0.69, 1.58 kJ/mol for Gibbs' energy, whereas the deviations from the experimental data are: 0.52, 5.75, 1.40, 1.00, 4.86 kJ/mol; 0.52, 0.63, 1.40, 6.11, 2.21 J/(molK); 2.52, 5.76, 1.58, 1.78, 4.86 kJ/mol, respectively (for nitriles and cis-unsaturated carboxylic acids experimental data are not available). The proposed approach provides also quite accurate estimates of enthalpy, entropy and Gibbs' energy of boiling and melting, critical temperatures and standard heat

  10. Formation of gas-phase carbonyls from heterogeneous oxidation of polyunsaturated fatty acids at the air-water interface and of the sea surface microlayer

    NASA Astrophysics Data System (ADS)

    Zhou, S.; Gonzalez, L.; Leithead, A.; Finewax, Z.; Thalman, R.; Vlasenko, A.; Vagle, S.; Miller, L.; Li, S.-M.; Bureekul, S.; Furutani, H.; Uematsu, M.; Volkamer, R.; Abbatt, J.

    2013-07-01

    Motivated by the potential for reactive heterogeneous chemistry occurring at the ocean surface, gas-phase products were observed when a reactive sea surface microlayer (SML) component, i.e. the polyunsaturated fatty acid (PUFA) linoleic acid (LA), was exposed to gas-phase ozone at the air-seawater interface. Similar oxidation experiments were conducted with SML samples collected from two different oceanic locations, in the eastern equatorial Pacific Ocean and from the west coast of Canada. Online proton-transfer-reaction mass spectrometry (PTR-MS) and light-emitting diode cavity enhanced differential optical absorption spectroscopy (LED-CE-DOAS) were used to detect oxygenated gas-phase products from the ozonolysis reactions. The LA studies indicate that oxidation of a PUFA monolayer on seawater gives rise to prompt and efficient formation of gas phase aldehydes. The products are formed via the decomposition of primary ozonides which form upon the initial reaction of ozone with the carbon-carbon double bonds in the PUFA molecules. In addition, two highly reactive di-carbonyls, malondialdehyde (MDA) and glyoxal, were also generated, likely as secondary products. Specific yields relative to reactant loss were 78%, 29%, 4% and <1% for n-hexanal, 3-nonenal, MDA and glyoxal, respectively, where the yields for MDA and glyoxal are likely lower limits. Heterogeneous oxidation of SML samples confirm for the first time that similar carbonyl products are formed via ozonolysis of environmental samples. The potential impact of such chemistry on the atmosphere of the marine boundary layer is discussed.

  11. WRF-Chem Simulation of Air Quality in China: Sensitivity Analyses of PM Concentrations to Emissions, Atmospheric Transport, and Secondary Organic Aerosol Formation

    NASA Astrophysics Data System (ADS)

    Zhong, M.; Saikawa, E.; Naik, V.; Horowitz, L. W.; Takigawa, M.; Zhao, Y.

    2014-12-01

    We investigate air quality in China in April 2007, using the Weather Research and Forecasting model coupled with Chemistry version 3.5 (WRF-Chem) at a spatial resolution of 20km × 20km with 31 vertical levels. The model domain covers the entire East Asian region with 399 × 299 grid cells. The initial and lateral chemical boundary conditions are taken from a present-day simulation of the NOAA Geophysical Fluid Dynamics Laboratory (GFDL) global chemistry-climate model AM3. The Regional Acid Deposition version 2 (RADM2) atmospheric chemical mechanism is used for gas-phase chemistry and the Model Aerosol Dynamics for Europe with the Secondary Organic Aerosol Model (MADE/SORGAM) and aqueous chemistry is used for aerosol chemistry. The emissions of gaseous pollutants (CO, NOx, NH3, VOCs, and SO2) and particulate matter (BC, OC, PM2.5, and PM10) are taken from the Regional Emission Inventory in Asia (REAS) version 2. Dust and sea salt emissions are simulated online, where dust parameters are optimized using observed particular matter (PM10) concentrations in 73 cities in China. We add gravitational settlement for dust and sea salt in vertical levels. The preliminary results show that the model predicts PM10 reasonably well compared to the ground measurement data. The bias in modeled PM10 concentrations in South and Northwest­­­­­­­ China is less than 10%. We will present results of sensitivity analyses that assess the impact of emissions, atmospheric transport, and secondary organic aerosol formation on PM concentrations.

  12. Health risk assessment of migrant workers' exposure to polychlorinated biphenyls in air and dust in an e-waste recycling area in China: Indication for a new wealth gap in environmental rights.

    PubMed

    Wang, Yalin; Hu, Jinxing; Lin, Wei; Wang, Ning; Li, Cheng; Luo, Peng; Hashmi, Muhammad Zaffar; Wang, Wenbo; Su, Xiaomei; Chen, Chen; Liu, Yindong; Huang, Ronglang; Shen, Chaofeng

    2016-02-01

    Migrant workers who work and live in polluted environment are a special vulnerable group in the accelerating pace of urbanization and industrialization in China. In the electronic waste (e-waste) recycling area, for example, migrant workers' exposure to pollutants, such as PCBs (polychlorinated biphenyls), is the result of an informal e-waste recycling process. A village in an electronic waste recycling area where migrant workers gather was surveyed. The migrant workers' daily routines were simulated according to the three-space transition: work place-on the road-home. Indoor air and dust in the migrant workers' houses and workplaces and the ambient air on the roads were sampled. The PCB levels of the air and dust in the places corresponding to the migrant workers are higher than those for local residents. The migrant workers have health risks from PCBs that are 3.8 times greater than those of local residents. This is not only caused by the exposure at work but also by their activity patterns and the environmental conditions of their dwellings. These results revealed the reason for the health risk difference between the migrant workers and local residents, and it also indicated that lifestyle and economic status are important factors that are often ignored compared to occupational exposure.

  13. Optimum Design for Noncontact Ultrasonic Motor with Flexurally Vibrating Disk Using an Equivalent Circuit Considering Viscosity of Air

    NASA Astrophysics Data System (ADS)

    Yamayoshi, Yasuhiro; Tamura, Hideki; Hirose, Seiji

    2009-07-01

    The optimum design for a noncontact ultrasonic motor with a flexurally vibrating disk has been investigated by analyzing the sound pressure in the air gap using an equivalent circuit considering the viscosity of air. The calculated results indicate that the sound pressure is affected by the viscosity and mass effect in the air gap, which are changed by the gap distance. The experimental results of revolution speed measured at various gap distances agree qualitatively with the sound pressure calculated using the equivalent circuit. In the case of wider gaps, a design satisfying the resonant condition of the air gap is necessary for optimizing the motor because the air gap resonates by the mass effect. However, in motors with an air gap narrower than about 50 µm, a higher speed rotation can be obtained for a wide range of rotor diameters and for a wide frequency range without consideration of the air gap resonance because the air viscosity effect becomes dominant.

  14. Heat and moisture transfer in gaps between sweating imitation skin and nonwoven cloth: effect of gap space and alignment of skin and clothing on the moisture transfer

    NASA Astrophysics Data System (ADS)

    Morozumi, Yoshio; Akaki, Kenichi; Tanabe, Naomasa

    2012-07-01

    This study investigates heat and moisture transfer between a sweating film and a nonwoven sheet both experimentally and numerically. A mathematical model based on heat conduction and moisture diffusion in both the air gap and cloth is presented. The evaporation rate and surface temperature of the sweating film are well predicted under various conditions such as air gap height, heating conditions, and sweating film orientation by evaluating the effective thermal conductivity and diffusion coefficient from the empirical equations of the Nusselt number for a fluid layer, even though the air gap height is sufficiently large to cause natural convections.

  15. Plasmonic band gap cavities on biharmonic gratings

    NASA Astrophysics Data System (ADS)

    Kocabas, Askin; Seckin Senlik, S.; Aydinli, Atilla

    2008-05-01

    In this paper, we have experimentally demonstrated the formation of plasmonic band gap cavities in infrared and visible wavelength range. The cavity structure is based on a biharmonic metallic grating with selective high dielectric loading. A uniform metallic grating structure enables strong surface plasmon polariton (SPP) excitation and a superimposed second harmonic component forms a band gap for the propagating SPPs. We show that a high dielectric superstructure can dramatically perturb the optical properties of SPPs and enables the control of the plasmonic band gap structure. Selective patterning of the high index superstructure results in an index contrast in and outside the patterned region that forms a cavity. This allows us to excite the SPPs that localize inside the cavity at specific wavelengths, satisfying the cavity resonance condition. Experimentally, we observe the formation of a localized state in the band gap and measure the dispersion diagram. Quality factors as high as 37 have been observed in the infrared wavelength. The simplicity of the fabrication and the method of testing make this approach attractive for applications requiring localization of propagating SPPs.

  16. Minding the Gap

    SciTech Connect

    Firestone, Millicent Anne

    2015-02-23

    Neutron & X-ray scattering provides nano- to meso-scale details of complex fluid structure; 1D electronic density maps dervied from SAXS yield molecular level insights; Neutron reflectivity provides substructure details of substrate supported complex fluids; Complex fluids composition can be optimized to support a wide variety of both soluble and membrane proteins; The water gap dimensions can be finely tuned through polymer component.

  17. Variable Gap Conjugated Polymers

    DTIC Science & Technology

    2005-12-01

    conducting gold interfacial layer interjected between the ITO glass electrode and the PEDOT/PSS hole transport layer . A family of low band gap, and near IR...which can be used as both electrochromics and as the hole transport layers in light emitting diodes. Hybrid electrochromic and electroluminescent (EC...MEH-PPV, P3HT, etc.) in order to blanket the solar spectrum. Initial device results on these multi-component blends are promising. In addition, we

  18. Formative Assessment in Context

    ERIC Educational Resources Information Center

    Oxenford-O'Brian, Julie

    2013-01-01

    This dissertation responds to critical gaps in current research on formative assessment practice which could limit successful implementation of this practice within the K-12 classroom context. The study applies a socio cultural perspective of learning to interpret a cross-case analysis of formative assessment practice occurring during one…

  19. Electron energy-loss spectroscopy of branched gap plasmon resonators

    PubMed Central

    Raza, Søren; Esfandyarpour, Majid; Koh, Ai Leen; Mortensen, N. Asger; Brongersma, Mark L.; Bozhevolnyi, Sergey I.

    2016-01-01

    The miniaturization of integrated optical circuits below the diffraction limit for high-speed manipulation of information is one of the cornerstones in plasmonics research. By coupling to surface plasmons supported on nanostructured metallic surfaces, light can be confined to the nanoscale, enabling the potential interface to electronic circuits. In particular, gap surface plasmons propagating in an air gap sandwiched between metal layers have shown extraordinary mode confinement with significant propagation length. In this work, we unveil the optical properties of gap surface plasmons in silver nanoslot structures with widths of only 25 nm. We fabricate linear, branched and cross-shaped nanoslot waveguide components, which all support resonances due to interference of counter-propagating gap plasmons. By exploiting the superior spatial resolution of a scanning transmission electron microscope combined with electron energy-loss spectroscopy, we experimentally show the propagation, bending and splitting of slot gap plasmons. PMID:27982030

  20. Electron energy-loss spectroscopy of branched gap plasmon resonators

    NASA Astrophysics Data System (ADS)

    Raza, Søren; Esfandyarpour, Majid; Koh, Ai Leen; Mortensen, N. Asger; Brongersma, Mark L.; Bozhevolnyi, Sergey I.

    2016-12-01

    The miniaturization of integrated optical circuits below the diffraction limit for high-speed manipulation of information is one of the cornerstones in plasmonics research. By coupling to surface plasmons supported on nanostructured metallic surfaces, light can be confined to the nanoscale, enabling the potential interface to electronic circuits. In particular, gap surface plasmons propagating in an air gap sandwiched between metal layers have shown extraordinary mode confinement with significant propagation length. In this work, we unveil the optical properties of gap surface plasmons in silver nanoslot structures with widths of only 25 nm. We fabricate linear, branched and cross-shaped nanoslot waveguide components, which all support resonances due to interference of counter-propagating gap plasmons. By exploiting the superior spatial resolution of a scanning transmission electron microscope combined with electron energy-loss spectroscopy, we experimentally show the propagation, bending and splitting of slot gap plasmons.

  1. DNA adduct formation and oxidative stress from the carcinogenic urban air pollutant 3-nitrobenzanthrone and its isomer 2-nitrobenzanthrone, in vitro and in vivo.

    PubMed

    Nagy, Eszter; Adachi, Shuichi; Takamura-Enya, Takeji; Zeisig, Magnus; Möller, Lennart

    2007-03-01

    The carcinogenic vehicle emission product 3-nitrobenzanthrone (3-NBA) is known to rearrange in the atmosphere to the isomer 2-nitrobenzanthrone (2-NBA), which exists in 70-fold higher concentration in ambient air. The genotoxicity of 2-NBA and 3-NBA was studied both in vitro (human cell lines A549 and HepG2) and in vivo (F344 female rats intra-tracheally administered 5 mg/kg body weight of 3-NBA) models, using the (32)P-HPLC and the single-cell gel electrophoresis (Comet assay) methods. In vitro, also the parent compound benzanthrone (BA) and the metabolite 3-aminobenzanthrone (3-ABA) were evaluated. 3-NBA gave highest levels of DNA adducts in the two cell lines, but significantly higher in HepG2 (relative adduct level approximately 500 adducts/10(8) normal nucleotides), whereas 2-NBA formed about one-third and one-twentieth of the DNA adduct amount in A549 and HepG2 cells, respectively. 3-ABA formed only minute amounts of DNA adducts and only in the A549 cells, whereas BA did not give rise to any detectable levels. The DNA adduct patterns from 3-NBA were similar between the two model systems, but differed somewhat for 2-NBA. The oxidative stress induced by BA was almost as high as what was observed for 3-NBA and 3-ABA in both cell lines, and 2-NBA induced lowest level of oxidative stress. The oxidative stress and DNA adduct level, in whole blood, was significantly increased by 3-NBA but not by 2-NBA. However, 2-NBA showed similar toxicity to 3-NBA, with respect to DNA adduct formation in vivo, hence it is important to further study 2-NBA as a potential contributor to health risk. While DNA adduct level in the 3-NBA-exposed animals reached a peak around 1 and 2 days after instillation, 2-NBA-treated animals showed a tendency towards a continuing increase at the end of the study.

  2. Modeling ozone and aerosol formation and transport in the pacific northwest with the community Multi-Scale Air Quality (CMAQ) modeling system.

    PubMed

    O'Neill, Susan M; Lamb, Brian K; Chen, Jack; Claiborn, Candis; Finn, Dennis; Otterson, Sally; Figueroa, Cristiana; Bowman, Clint; Boyer, Mike; Wilson, Rob; Arnold, Jeff; Aalbers, Steven; Stocum, Jeffrey; Swab, Christopher; Stoll, Matt; Dubois, Mike; Anderson, Mary

    2006-02-15

    The Community Multi-Scale Air Quality (CMAQ) modeling system was used to investigate ozone and aerosol concentrations in the Pacific Northwest (PNW) during hot summertime conditions during July 1-15, 1996. Two emission inventories (El) were developed: emissions for the first El were based upon the National Emission Trend 1996 (NET96) database and the BEIS2 biogenic emission model, and emissions for the second El were developed through a "bottom up" approach that included biogenic emissions obtained from the GLOBEIS model. The two simulations showed that elevated PM2.5 concentrations occurred near and downwind of the Interstate-5 corridor along the foothills of the Cascade Mountains and in forested areas of central Idaho. The relative contributions of organic and inorganic aerosols varied by region, but generally organic aerosols constituted the largest fraction of PM2.5. In wilderness areas near the 1-5 corridor, organic carbon from anthropogenic sources contributed approximately 50% of the total organic carbon with the remainder from biogenic precursors, while in wilderness areas in Idaho, biogenic organic carbon accounted for 80% of the total organic aerosol. Regional analysis of the secondary organic aerosol formation in the Columbia River Gorge, Central Idaho, and the Olympics/Puget Sound showed that the production rate of secondary organic carbon depends on local terpene concentrations and the local oxidizing capacity of the atmosphere, which was strongly influenced by anthropogenic emissions. Comparison with observations from 12 IMPROVE sites and 21 ozone monitoring sites showed that results from the two El simulations generally bracketed the average observed PM parameters and that errors calculated for the model results were within acceptable bounds. Analysis across all statistical parameters indicated that the NW-AIRQUEST El solution performed better at predicting PM2.5, PM1, and beta(ext) even though organic carbon PM was over-predicted, and the NET96 El

  3. What is the Mass of a Gap-opening Planet?

    NASA Astrophysics Data System (ADS)

    Dong, Ruobing; Fung, Jeffrey

    2017-02-01

    High-contrast imaging instruments such as GPI and SPHERE are discovering gap structures in protoplanetary disks at an ever faster pace. Some of these gaps may be opened by planets forming in the disks. In order to constrain planet formation models using disk observations, it is crucial to find a robust way to quantitatively back out the properties of the gap-opening planets, in particular their masses, from the observed gap properties, such as their depths and widths. Combining 2D and 3D hydrodynamics simulations with 3D radiative transfer simulations, we investigate the morphology of planet-opened gaps in near-infrared scattered-light images. Quantitatively, we obtain correlations that directly link intrinsic gap depths and widths in the gas surface density to observed depths and widths in images of disks at modest inclinations under finite angular resolution. Subsequently, the properties of the surface density gaps enable us to derive the disk scale height at the location of the gap h, and to constrain the quantity Mp2/α, where Mp is the mass of the gap-opening planet and α characterizes the viscosity in the gap. As examples, we examine the gaps recently imaged by VLT/SPHERE, Gemini/GPI, and Subaru/HiCIAO in HD 97048, TW Hya, HD 169142, LkCa 15, and RX J1615.3-3255. Scale heights of the disks and possible masses of the gap-opening planets are derived assuming each gap is opened by a single planet. Assuming α = 10‑3, the derived planet masses in all cases are roughly between 0.1 and 1 MJ.

  4. SOUTHWEST REGIONAL GAP LAND COVER

    EPA Science Inventory

    The Gap Analysis Program is a national inter-agency program that maps the distribution

    of plant communities and selected animal species and compares these distributions with land

    stewardship to identify gaps in biodiversity protection. GAP uses remote satellite imag...

  5. Skills Gaps in Australian Firms

    ERIC Educational Resources Information Center

    Lindorff, Margaret

    2011-01-01

    This paper reports the results of a survey of more than 2000 managers examining perceptions of skills gaps in a range of Australian firms. It finds that three quarters report a skills gap, and almost one third report skills gaps across the whole organisation. Firm size and industry differences exist in perceptions of the effect of the skills gap…

  6. Air Research

    EPA Pesticide Factsheets

    EPA's air research provides the critical science to develop and implement outdoor air regulations under the Clean Air Act and puts new tools and information in the hands of air quality managers and regulators to protect the air we breathe.

  7. The global drug gap.

    PubMed

    Reich, M R

    2000-03-17

    Global inequities in access to pharmaceutical products exist between rich and poor countries because of market and government failures as well as huge income differences. Multiple policies are required to address this global drug gap for three categories of pharmaceutical products: essential drugs, new drugs, and yet-to-be-developed drugs. Policies should combine "push" approaches of subsidies to support targeted drug development, "pull" approaches of financial incentives such as market guarantees, and "process" approaches aimed at improved institutional capacity. Constructive solutions are needed that can both protect the incentives for research and development and reduce the inequities of access.

  8. Mind the gap.

    SciTech Connect

    Bhagwat, M. S.; Krassnigg, A.; Maris, P.; Roberts, C. D.; Physics; Univ. Graz; Univ. of Pittsburgh

    2007-03-01

    In this summary of the application of Dyson-Schwinger equations to the theory and phenomenology of hadrons, some deductions following from a nonperturbative, symmetry-preserving truncation are highlighted, notable amongst which are results for pseudoscalar mesons. We also describe inferences from the gap equation relating to the radius of convergence of a chiral expansion, applications to heavy-light and heavy-heavy mesons, and quantitative estimates of the contribution of quark orbital angular momentum in pseudoscalar mesons; and recapitulate upon studies of nucleon electromagnetic form factors.

  9. Turbine blade tip gap reduction system

    SciTech Connect

    Diakunchak, Ihor S.

    2012-09-11

    A turbine blade sealing system for reducing a gap between a tip of a turbine blade and a stationary shroud of a turbine engine. The sealing system includes a plurality of flexible seal strips extending from a pressure side of a turbine blade generally orthogonal to the turbine blade. During operation of the turbine engine, the flexible seal strips flex radially outward extending towards the stationary shroud of the turbine engine, thereby reducing the leakage of air past the turbine blades and increasing the efficiency of the turbine engine.

  10. Superconductivity of the Sr2Ca12Cu24O41 spin-ladder system: are the superconducting pairing and the spin-gap formation of the same origin?

    PubMed

    Fujiwara, Naoki; Môri, Nobuo; Uwatoko, Yoshiya; Matsumoto, Takehiko; Motoyama, Naoki; Uchida, Shinichi

    2003-04-04

    Pressure-induced superconductivity in a spin-ladder cuprate Sr2Ca12Cu24O41 has not been studied on a microscopic level thus far although the superconductivity was already discovered in 1996. We have improved the high-pressure technique using a large high-quality crystal, and succeeded in studying the superconductivity using 63Cu nuclear magnetic resonance. We found that the anomalous metallic state reflecting the spin-ladder structure is realized and the superconductivity possesses an s-wave-like character in the meaning that a finite gap exists in the quasiparticle excitation: At a pressure of 3.5 GPa, we observed two excitation modes in the normal state from the relaxation rate T-11. One gives rise to an activation-type component in T-11, and the other T-linear component linking directly with the superconductivity. This gapless mode likely arises from free motion of holon-spinon bound states appearing by hole doping, and the pairing of them likely causes the superconductivity.

  11. Gap analysis: Concepts, methods, and recent results

    USGS Publications Warehouse

    Jennings, M.D.

    2000-01-01

    Rapid progress is being made in the conceptual, technical, and organizational requirements for generating synoptic multi-scale views of the earth's surface and its biological content. Using the spatially comprehensive data that are now available, researchers, land managers, and land-use planners can, for the first time, quantitatively place landscape units - from general categories such as 'Forests' or 'Cold-Deciduous Shrubland Formation' to more categories such as 'Picea glauca-Abies balsamea-Populus spp. Forest Alliance' - in their large-area contexts. The National Gap Analysis Program (GAP) has developed the technical and organizational capabilities necessary for the regular production and analysis of such information. This paper provides a brief overview of concepts and methods as well as some recent results from the GAP projects. Clearly, new frameworks for biogeographic information and organizational cooperation are needed if we are to have any hope of documenting the full range of species occurrences and ecological processes in ways meaningful to their management. The GAP experience provides one model for achieving these new frameworks.

  12. Small Multiples with Gaps.

    PubMed

    Meulemans, Wouter; Dykes, Jason; Slingsby, Aidan; Turkay, Cagatay; Wood, Jo

    2017-01-01

    Small multiples enable comparison by providing different views of a single data set in a dense and aligned manner. A common frame defines each view, which varies based upon values of a conditioning variable. An increasingly popular use of this technique is to project two-dimensional locations into a gridded space (e.g. grid maps), using the underlying distribution both as the conditioning variable and to determine the grid layout. Using whitespace in this layout has the potential to carry information, especially in a geographic context. Yet, the effects of doing so on the spatial properties of the original units are not understood. We explore the design space offered by such small multiples with gaps. We do so by constructing a comprehensive suite of metrics that capture properties of the layout used to arrange the small multiples for comparison (e.g. compactness and alignment) and the preservation of the original data (e.g. distance, topology and shape). We study these metrics in geographic data sets with varying properties and numbers of gaps. We use simulated annealing to optimize for each metric and measure the effects on the others. To explore these effects systematically, we take a new approach, developing a system to visualize this design space using a set of interactive matrices. We find that adding small amounts of whitespace to small multiple arrays improves some of the characteristics of 2D layouts, such as shape, distance and direction. This comes at the cost of other metrics, such as the retention of topology. Effects vary according to the input maps, with degree of variation in size of input regions found to be a factor. Optima exist for particular metrics in many cases, but at different amounts of whitespace for different maps. We suggest multiple metrics be used in optimized layouts, finding topology to be a primary factor in existing manually-crafted solutions, followed by a trade-off between shape and displacement. But the rich range of possible

  13. Gap Opening in 3D: Single-planet Gaps

    NASA Astrophysics Data System (ADS)

    Fung, Jeffrey; Chiang, Eugene

    2016-12-01

    Giant planets can clear deep gaps when embedded in 2D (razor-thin) viscous circumstellar disks. We show by direct simulation that giant planets are just as capable of carving out gaps in 3D. Surface density maps are similar between 2D and 3D, even in detail. In particular, the scaling {{{Σ }}}{gap}\\propto {q}-2 of gap surface density with planet mass, derived from a global “zero-dimensional” balance of Lindblad and viscous torques, applies equally well to results obtained at higher dimensions. Our 3D simulations reveal extensive, near-sonic, meridional flows both inside and outside the gaps; these large-scale circulations might bear on disk compositional gradients, in dust or other chemical species. At high planet mass, gap edges are mildly Rayleigh unstable and intermittently shed streams of material into the gap—less so in 3D than in 2D.

  14. Edge configurational effect on band gaps in graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Deepika, Kumar, T. J. Dhilip; Shukla, Alok; Kumar, Rakesh

    2015-03-01

    In this article, we put forward a resolution to the prolonged ambiguity in energy band gaps between theory and experiments of fabricated graphene nanoribbons (GNRs). Band structure calculations using density functional theory are performed on oxygen-passivated GNR supercells of customized edge configurations without disturbing the inherent s p2 hybridization of carbon atoms. Direct band gaps are observed for both zigzag and armchair GNRs, consistent with the experimental reports. In addition, we provide an explanation of the experimentally observed scattered band gap values of GNRs as a function of width in a crystallographic orientation on the basis of edge configurations. We conclude that edge configurations of GNRs significantly contribute to band gap formation in addition to its width for a given crystallographic orientation and will play a crucial role in band gap engineering of GNRs for future research on fabrication of nanoelectronic devices.

  15. The Gap-Tpc

    NASA Astrophysics Data System (ADS)

    Rossi, B.; Anastasio, A.; Boiano, A.; Catalanotti, S.; Cocco, A. G.; Covone, G.; Di Meo, P.; Longo, G.; Vanzanella, A.; Walker, S.; Wang, H.; Wang, Y.; Fiorillo, G.

    2016-02-01

    Several experiments have been conducted worldwide, with the goal of observing low-energy nuclear recoils induced by WIMPs scattering off target nuclei in ultra-sensitive, low-background detectors. In the last few decades noble liquid detectors designed to search for dark matter in the form of WIMPs have been extremely successful in improving their sensitivities and setting the best limits. One of the crucial problems to be faced for the development of large size (multi ton-scale) liquid argon experiments is the lack of reliable and low background cryogenic PMTs: their intrinsic radioactivity, cost, and borderline performance at 87 K rule them out as a possible candidate for photosensors. We propose a brand new concept of liquid argon-based detector for direct dark matter search: the Geiger-mode Avalanche Photodiode Time Projection Chamber (GAP-TPC) optimized in terms of residual radioactivity of the photosensors, energy and spatial resolution, light and charge collection efficiency.

  16. Undecidability of the spectral gap.

    PubMed

    Cubitt, Toby S; Perez-Garcia, David; Wolf, Michael M

    2015-12-10

    The spectral gap--the energy difference between the ground state and first excited state of a system--is central to quantum many-body physics. Many challenging open problems, such as the Haldane conjecture, the question of the existence of gapped topological spin liquid phases, and the Yang-Mills gap conjecture, concern spectral gaps. These and other problems are particular cases of the general spectral gap problem: given the Hamiltonian of a quantum many-body system, is it gapped or gapless? Here we prove that this is an undecidable problem. Specifically, we construct families of quantum spin systems on a two-dimensional lattice with translationally invariant, nearest-neighbour interactions, for which the spectral gap problem is undecidable. This result extends to undecidability of other low-energy properties, such as the existence of algebraically decaying ground-state correlations. The proof combines Hamiltonian complexity techniques with aperiodic tilings, to construct a Hamiltonian whose ground state encodes the evolution of a quantum phase-estimation algorithm followed by a universal Turing machine. The spectral gap depends on the outcome of the corresponding 'halting problem'. Our result implies that there exists no algorithm to determine whether an arbitrary model is gapped or gapless, and that there exist models for which the presence or absence of a spectral gap is independent of the axioms of mathematics.

  17. Annealing-induced structural rearrangement and optical band gap change in Mg–Ni–H thin films

    NASA Astrophysics Data System (ADS)

    Rašković-Lovre, Ž.; Mongstad, T. T.; Karazhanov, S.; You, C. C.; Lindberg, S.; Lelis, M.; Milcius, D.; Deledda, S.

    2017-01-01

    It is well known that optical properties of Mg–Ni–H films can be tuned by hydrogen uptake from Mg–Ni–H and upload into Mg–Ni systems. In this work we show that modulation of optical properties of Mg–Ni–H can take place as a result of thermal processing in air as well. When reactively sputter deposited semiconducting Mg–Ni–H films are annealed at temperatures of 200 °C–300 °C in air, gradual band gap change from 1.6 to 2.04 eV occurs followed by change in optical appearance, from brown, to orange and, subsequently, to yellow. We investigate this phenomenon using optical and structural characterization tools, and link the changes to an atomic rearrangement and a structure reordering of the [NiH4]4‑complex. The films are x-ray amorphous up to 280 °C, where above this temperature an increase in crystallite size and establishing of long-range order lead to a formation of the cubic crystalline phase of Mg2NiH4. Also, the results suggest that even though annealing was conducted in air, no oxidation or other changes in chemical composition of the bulk of the film occurred. Therefore, the band gap of this semiconductor can be tuned permanently by heat treatment, in the range from 1.6 to 2 eV.

  18. Formative Assessment: Simply, No Additives

    ERIC Educational Resources Information Center

    Roskos, Kathleen; Neuman, Susan B.

    2012-01-01

    Among the types of assessment the closest to daily reading instruction is formative assessment. In contrast to summative assessment, which occurs after instruction, formative assessment involves forming judgments frequently in the flow of instruction. Key features of formative assessment include identifying gaps between where students are and…

  19. Hydrogeologic Model for the Gable Gap Area, Hanford Site

    SciTech Connect

    Bjornstad, Bruce N.; Thorne, Paul D.; Williams, Bruce A.; Last, George V.; Thomas, Gregory S.; Thompson, Michael D.; Ludwig, Jami L.; Lanigan, David C.

    2010-09-30

    Gable Gap is a structural and topographic depression between Gable Mountain and Gable Butte within the central Hanford Site. It has a long and complex geologic history, which includes tectonic uplift synchronous with erosional downcutting associated with the ancestral Columbia River during both Ringold and Cold Creek periods, and by the later Ice Age (mostly glacial Lake Missoula) floods. The gap was subsequently buried and partially backfilled by mostly coarse-grained, Ice Age flood deposits (Hanford formation). Erosional remnants of both the Ringold Formation and Cold Creek unit locally underlie the high-energy flood deposits. A large window exists in the gap where confined basalt aquifers are in contact with the unconfined suprabasalt aquifer. Several paleochannels, of both Hanford and Ringold Formation age, were eroded into the basalt bedrock across Gable Gap. Groundwater from the Central Plateau presently moves through Gable Gap via one or more of these shallow paleochannels. As groundwater levels continue to decline in the region, groundwater flow may eventually be cut off through Gable Gap.

  20. Terminology gap in hydrological cycle

    NASA Astrophysics Data System (ADS)

    Zhuo, Lu; Han, Dawei

    2016-04-01

    Water is central to life on Earth. People have been trying to understand how water moves in the hydrosphere throughout the human history. In the 9th century BC, the famous Greek poet Homer described the hydrological cycle in Iliad as "okeanos whose stream bends back in a circle" with a belief that rivers are ocean-fed from subterranean seas. Later, Aristotle (4th century BC) claimed that most of the water came from underground caverns in which air was transformed into water. It was only until 1674, French scientist Perrault developed the correct concept of the water cycle. In modern times, scientists are interested in understanding the individual processes of the hydrological cycle with a keen focus on runoff which supplies water to rivers, lakes, and oceans. Currently, the prevailing concepts on runoff processes include 'infiltration excess runoff' and 'saturation excess runoff'. However, there is no term to describe another major runoff due to the excess beyond the soil water holding capacity (i.e., the field capacity). We argue that a new term should be introduced to fill this gap, and it could be called 'holding excess runoff' which is compatible with the convention. This new term is significant in correcting a half-century misnomer where 'holding excess runoff' has been incorrectly named as 'saturation excess runoff', which was introduced by the Xinanjiang model in China in 1960s. Similar concept has been adopted in many well-known hydrological models such as PDM and HBV in which the saturation refers to the field capacity. The term 'holding excess runoff' resolves such a common confusion in the hydrological community.

  1. Ion-gap sensing for engine control

    SciTech Connect

    1995-09-01

    This article reports that in addition to detecting misfire to conform with California onboard diagnostic (OBD II) regulations, Delco Electronics and Mecel AB engineers are looking at ion-gap sensing to control knock, A/F ratio, and other possible engine control parameters. The combustion of fuel in an engine cylinder produces ions. Detection of those ions by the spark plug (ion-gap sensing), and use of the resulting ion currents, has been employed in engine management systems since 1988. Saab introduced the first application, for cam-phase sensing. The main driving force for ion-gap sensing is OBD II requirements for 100% misfire detection at all speeds and loads. The technique has been expanded in subsequent applications to include misfire, knock, and pre-ignition detection and control, and more recently in combustion-ion detection using a capacitance-type, ion-current measurement method. Use of the ion current`s wave shape to control knock allows elimination of the separate piezoelectric type (PZT) sensor. Future applications could provide additional engine-control features including air/fuel ratio measurement and control.

  2. Spark Gap Electrode Erosion

    DTIC Science & Technology

    1984-12-01

    between shots, leading to thermal expansion and contraction of the surface . Calculations of the temperature differen- tial between the heating and cooling...and (b) copper-tungsten iK-33) anode surfaces in nitrogen 127 36 IEEE TRANSACTIONS ON PLASMA SCIENCE. VOL. PS-I 2, NO. 1. MARCH 1984 S Air : 2t Lr o...describe the self breakdown voltage distribution ""[ * as a function of the relevant parameters (such as elec- trode surface conditions, gas type and

  3. [Effects of forest gap size and uprooted microsite on the microclimate in Pinus koraiensis-dominated broad-leaved mixed forest].

    PubMed

    Duan, Wen-biao; Du, Shan; Chen, Li-xin; Wang, Li-xia; Wei, Quan-shuai; Zhao, Jian-hui

    2013-08-01

    Three representative forest gaps with pit-mound microsites formed by uprooted trees were selected within the 2.55 hm2 plot in a Pinus koraiensis-dominated broad-leaved mixed forest in Xiao Xing'an Mountains of Northeast China. The cleared land and closed stand were set up as the controls, and the PAR, air temperature and relative humidity in the centers of different size gaps and in mound top as well as the total radiation and precipitation in the gap centers were measured between July and September, 2011 by using multichannel automatic meteorological stations. The differences of the microclimate between the gap centers and mound top in different months were compared, and the monthly and diurnal variations of the microclimatic factors in the gap centers and in the mound top under typical weather conditions were analyzed. The results showed that the mean monthly PAR and air temperature in the three gaps of different sizes were in the order of large gap > medium gap > small gap, and the mean monthly relative humidity was in the order of small gap > medium gap > large gap. For the same size gap, the mean monthly PAR and air temperature were higher in the mound top than in the gap center, whereas the mean monthly relative humidity was higher in the gap center than in the mound top. Both the mean monthly total radiation and the mean monthly air temperature in the forest gaps and in the controls were in the order of July > August > September and of cleared land > large gap > medium gap > small gap > closed stand, while the mean monthly relative humidity was in the order of closed stand > small gap > medium gap > large gap > cleared land. The differences in the mean monthly relative humidity between closed stand and various gaps and between closed stand and cleared land reached significant level. The monthly precipitation from July to September decreased in the order of cleared land > large gap > medium gap > small gap > closed stand. Whether in sunny days or in overcast

  4. Air Pollution

    MedlinePlus

    Air pollution is a mixture of solid particles and gases in the air. Car emissions, chemicals from factories, ... Ozone, a gas, is a major part of air pollution in cities. When ozone forms air pollution, it's ...

  5. Gap and stripline combined monitor

    DOEpatents

    Yin, Y.

    1984-02-16

    A combined gap and stripline monitor device for measuring the intensity and position of a charged particle beam bunch in a beam pipe of a synchrotron radiation facility. The monitor has first and second beam pipe portions with an axial gap therebetween. An outer pipe cooperates with the first beam pipe portion to form a gap enclosure, while inner strips cooperate with the first beam pipe portion to form a stripline monitor, with the stripline length being the same as the gap enclosure length.

  6. Gap and stripline combined monitor

    DOEpatents

    Yin, Y.

    1986-08-19

    A combined gap and stripline monitor device for measuring the intensity and position of a charged particle beam bunch in a beam pipe of a synchrotron radiation facility is disclosed. The monitor has first and second beam pipe portions with an axial gap therebetween. An outer pipe cooperates with the first beam pipe portion to form a gap enclosure, while inner strips cooperate with the first beam pipe portion to form a stripline monitor, with the stripline length being the same as the gap enclosure length. 4 figs.

  7. p120 GAP requirement in normal and malignant human hematopoiesis

    PubMed Central

    1993-01-01

    There is evidence to suggest that the p120 GAP (GAP), originally described as an inhibitor of p21ras, may also serve as a downstream effector of ras-regulated signal transduction. To determine whether GAP expression is required for the growth of human normal and leukemic hematopoietic cells, we used GAP antisense oligodeoxynucleotides to inhibit it and analyzed the effects of this inhibition on the colony- forming ability of nonadherent, T lymphocyte-depleted mononuclear cells and of highly purified progenitors (CD34+ MNC) obtained from the bone marrow and peripheral blood of healthy volunteers or chronic myeloid leukemia (CML, bcr-abl-positive) patients. The acute myelogenous leukemia cell line MO7, the Philadelphia BV173 cell line, and the acute promyelocytic leukemia NB4 and HL-60 cell lines were similarly examined. GAP antisense treatment inhibited colony formation from normal myelo-, erythro-, and megakaryopoietic progenitor cells as well as from CML progenitor cells. Proliferation of MO7 (growth factor- dependent) and BV173 (bcr-abl-dependent) cells, but not that of NB4 and HL-60 (growth factor-independent) cells, was also inhibited, even though a specific downregulation of GAP was observed in each cell line, as analyzed by either or both mRNA and protein expression. Stimulation of MO7 cells with hematopoietic growth factors increased the expression of GAP as well as the levels of active GTP-bound p21ras. Stimulation of GAP expression was inhibited upon GAP antisense treatment. These data indicate that p120 GAP is involved in human normal and leukemic hemopoiesis and strongly suggest that GAP is not only a p21ras inhibitor (signal terminator), but also a positive signal transducer. PMID:8245773

  8. Gap Assessment (FY 13 Update)

    DOE Data Explorer

    Getman, Dan

    2013-09-30

    each data category. The first file contains the grid and is in the SHP file format (shape file.) Each populated grid cell represents a 10k area within which data is known to exist. The second file is a CSV (comma separated value) file that contains all of the individual layers that intersected with the grid. This CSV can be joined with the map to retrieve a list of datasets that are available at any given site. The attributes in the CSV include: 1. grid_id : The id of the grid cell that the data intersects with 2. title: This represents the name of the WFS service that intersected with this grid cell 3. abstract: This represents the description of the WFS service that intersected with this grid cell 4. gap_type: This represents the category of data availability that these data fall within. As the current processing is pulling data from NGDS, this category universally represents data that are available in the NGDS and are ready for acquisition for analytic purposes. 5. proprietary_type: Whether the data are considered proprietary 6. service_type: The type of service 7. base_url: The service URL

  9. A novel multi-level interconnect scheme with air as low K inter-metal dielectric for ultradeep submicron application

    NASA Astrophysics Data System (ADS)

    Chen, Chung-Hui; Fang, Yean-Kuen; Lin, Chun-Sheng; Yang, Chih-Wei; Hsieh, Jang-Cheng

    2001-01-01

    In this letter, a novel multi-level interconnect scheme with air as the low K inter-metal dielectric for ultra large scale integrated circuit (ULSI) application in ultradeep submicron (UDSM) range is proposed. The detailed process integration with copper dual damascene processing is described. The feasibility of the scheme is examined by trimethylaluminum Raphael simulation for the effective dielectric constant and the cutoff frequency in a standard divide by three counter. The simulation results are also compared with these reported air gap formation technologies. The results show the developed multi-level interconnect system is suitable for UDSM application.

  10. Recruitment of Class I Hydrophobins to the Air:Water Interface Initiates a Multi-step Process of Functional Amyloid Formation*

    PubMed Central

    Morris, Vanessa K.; Ren, Qin; Macindoe, Ingrid; Kwan, Ann H.; Byrne, Nolene; Sunde, Margaret

    2011-01-01

    Class I fungal hydrophobins form amphipathic monolayers composed of amyloid rodlets. This is a remarkable case of functional amyloid formation in that a hydrophobic:hydrophilic interface is required to trigger the self-assembly of the proteins. The mechanism of rodlet formation and the role of the interface in this process have not been well understood. Here, we have studied the effect of a range of additives, including ionic liquids, alcohols, and detergents, on rodlet formation by two class I hydrophobins, EAS and DewA. Although the conformation of the hydrophobins in these different solutions is not altered, we observe that the rate of rodlet formation is slowed as the surface tension of the solution is decreased, regardless of the nature of the additive. These results suggest that interface properties are of critical importance for the recruitment, alignment, and structural rearrangement of the amphipathic hydrophobin monomers. This work gives insight into the forces that drive macromolecular assembly of this unique family of proteins and allows us to propose a three-stage model for the interface-driven formation of rodlets. PMID:21454575

  11. Measuring the Gap

    PubMed Central

    She, Xinshu; Zhao, Deqing; Scholnick, Jenna

    2016-01-01

    China is a large country where rapid development is accompanied by growing inequalities. How economic inequalities translate to health inequalities is unknown. Baseline health assessment is lacking among rural Chinese children. We aimed at assessing baseline student health of rural Chinese children and comparing them with those of urban children of similar ages. A cross-sectional study was conducted using the 2003 Global School-Based Student Health Survey among 100 students Grade 4 to 6 from rural Guizhou, China. Results were summarized and compared with public data from urban Beijing using multivariate logistic regression models. Rural children are more likely to not wash their hands before a meal (odds ratio [OR] = 5.71, P < .01) and after using the toilet (OR = 5.41, P < .01). They are more likely to feel sick or to get into trouble after drinking (OR = 7.28, P < .01). They are more likely to have used drugs (OR = 8.54, P < .01) and to have no close friends (OR = 8.23, P < .01). An alarming percentage of rural (8.22%) and urban (14.22%) children have had suicidal ideation in the past year (OR = 0.68, P > .05). Rural parents are more likely to not know their children’s whereabouts (OR = 1.81, P < .05). Rural children are more than 4 times likely to have serious injuries (OR = 4.64, P < .01) and to be bullied (OR = 4.01, P < .01). In conclusion, school-age rural Chinese children exhibit more health risk behaviors and fewer protective factors at baseline compared to their urban counterparts. Any intervention aimed at improving child health should take this distributive gap into consideration. PMID:27335999

  12. GAP Analysis Bulletin Number 15

    USGS Publications Warehouse

    Maxwell, Jill; Gergely, Kevin; Aycrigg, Jocelyn; Canonico, Gabrielle; Davidson, Anne; Coffey, Nicole

    2008-01-01

    The Mission of the Gap Analysis Program (GAP) is to promote conservation by providing broad geographic information on biological diversity to resource managers, planners, and policy makers who can use the information to make informed decisions. As part of the National Biological Information Infrastructure (NBII) ?a collaborative program to provide increased access to data and information on the nation?s biological resources--GAP data and analytical tools have been used in hundreds of applications: from basic research to comprehensive state wildlife plans; from educational projects in schools to ecoregional assessments of biodiversity. The challenge: keeping common species common means protecting them BEFORE they become threatened. To do this on a state or regional basis requires key information such as land cover descriptions, predicted distribution maps for native animals, and an assessment of the level of protection currently given to those plants and animals. GAP works cooperatively with Federal, state, and local natural resource professionals and academics to provide this kind of information. GAP activities focus on the creation of state and regional databases and maps that depict patterns of land management, land cover, and biodiversity. These data can be used to identify ?gaps? in conservation--instances where an animal or plant community is not adequately represented on the existing network of conservation lands. GAP is administered through the U.S. Geological Survey. Through building partnerships among disparate groups, GAP hopes to foster the kind of collaboration that is needed to address conservation issues on a broad scale. For more information, contact: John Mosesso National GAP Director 703-648-4079 Kevin Gergely National GAP Operations Manager 208-885-3565

  13. A Comparative Study of O3 Formation in the Houston Urban and Industrial Plumes During the 2000 Texas Air Quality Study

    SciTech Connect

    Daum, Peter H.; Kleinman, Lawrence I.; Springston, Stephen R.; Nunnermacker, L. J.; Lee, Y.- N.; Weinstein-Lloyd, Judy; Zheng, J.; Berkowitz, Carl M.

    2003-12-02

    Photochemical box model calculations constrained by observations of NOx, VOCs, O3 and other stable species indicate that the instantaneous ozone formation rate was much lower over downtown Houston than it was over the Ship Channel. The much faster O3 formation rates and higher concentrations observed over the Ship Channel are attributed to the much higher hydrocarbon reactivity, the majority of which was contributed by low molecular weight alkenes. These high hydrocarbon reactivities also caused O3 over the ship Channel to be produced with much higher efficiency than over urban Houston.

  14. Formation of Giant Planets

    NASA Technical Reports Server (NTRS)

    Lin, Douglas

    1999-01-01

    Under the support of NASA Origins grant, we studied the formation of gaps in protoplanetary disks due the tidal interaction between a fully grown protoplanet and protostellar disk. The result of this study is published in the Astrophysical Journal, (vol 514, 344-367, 1999) and in several conference proceedings. The main focus of this work is to analyze planet-disk interaction during the final stages of protoplanetary formation.

  15. Gene Circuit Analysis of the Terminal Gap Gene huckebein

    PubMed Central

    Ashyraliyev, Maksat; Siggens, Ken; Janssens, Hilde; Blom, Joke; Akam, Michael; Jaeger, Johannes

    2009-01-01

    The early embryo of Drosophila melanogaster provides a powerful model system to study the role of genes in pattern formation. The gap gene network constitutes the first zygotic regulatory tier in the hierarchy of the segmentation genes involved in specifying the position of body segments. Here, we use an integrative, systems-level approach to investigate the regulatory effect of the terminal gap gene huckebein (hkb) on gap gene expression. We present quantitative expression data for the Hkb protein, which enable us to include hkb in gap gene circuit models. Gap gene circuits are mathematical models of gene networks used as computational tools to extract regulatory information from spatial expression data. This is achieved by fitting the model to gap gene expression patterns, in order to obtain estimates for regulatory parameters which predict a specific network topology. We show how considering variability in the data combined with analysis of parameter determinability significantly improves the biological relevance and consistency of the approach. Our models are in agreement with earlier results, which they extend in two important respects: First, we show that Hkb is involved in the regulation of the posterior hunchback (hb) domain, but does not have any other essential function. Specifically, Hkb is required for the anterior shift in the posterior border of this domain, which is now reproduced correctly in our models. Second, gap gene circuits presented here are able to reproduce mutants of terminal gap genes, while previously published models were unable to reproduce any null mutants correctly. As a consequence, our models now capture the expression dynamics of all posterior gap genes and some variational properties of the system correctly. This is an important step towards a better, quantitative understanding of the developmental and evolutionary dynamics of the gap gene network. PMID:19876378

  16. Formation of stylet sheaths in aere (in air) from eight species of phytophagous hemipterans from six families (suborders: Auchenorrhyncha and Sternorrhyncha)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Stylet sheath formation is a common feature among phytophagous hemipterans. These sheaths are considered essential to promote a successful feeding event of these piercing-sucking insects. The stylet sheath composition is unknown, and it is suggested that it forms through interactions with external (...

  17. The quantum-chemical approach to calculations of thermodynamic and structural parameters of formation of fatty acid monolayers with hexagonal packing at the air/water interface.

    PubMed

    Vysotsky, Yu B; Belyaeva, E A; Fomina, E S; Vollhardt, D; Fainerman, V B; Miller, R

    2014-02-21

    The structural parameters of fatty acid (with formula CnH2n+1COOH, n = 7-16) monolayers at the air/water interface were modeled within quantum-chemical semiempirical program complex Mopac 2012 (PM3 method). On the basis of quantum-chemical calculations it was shown that molecules in the highly ordered monolayer can be oriented at the angle ∼16° (tilted monolayer), or at the angle ∼0° to the normal to the air/water interface (untilted monolayer). The structural parameters of both tilted and untilted monolayers correspond well to the experimental data. The parameters of the unit cell of the modelled tilted monolayer are: a = 8.0-8.2 Å and b = 4.2-4.5 Å (with the corresponding experimental data 8.4-8.7 Å and 4.9-5.0 Å). For the modelled untilted monolayer these parameters are: a = 7.7-8.0 Å; b = 4.6 Å (with the corresponding experimental data 8.4 Å and 4.8-4.9 Å). Enthalpy, entropy and Gibbs' energy of clusterization were calculated for both structures. The correlation dependencies of the calculated parameters on the number of pair intermolecular CHHC interactions in the clusters and the pair interactions between functional groups were obtained. It was shown that the spontaneous clusterization of the fatty carboxylic acids at the air/water interface under standard conditions is energetically preferable for molecules which have 13 or more carbon atoms in the alkyl chain and this result also agrees with the corresponding experimental parameters.

  18. The Dynamically Disrupted Gap in HD 142527

    NASA Astrophysics Data System (ADS)

    Casassus, S.; Perez M., S.; Jordán, A.; Ménard, F.; Cuadra, J.; Schreiber, M. R.; Hales, A. S.; Ercolano, B.

    2012-08-01

    The vestiges of planet formation have been observed in debris disks harboring young and massive gaseous giants. The process of giant planet formation is terminated by the dissipation of gas in the protoplanetary disk. The gas-rich disk around HD 142527 features a small inner disk, a large gap from ~10 to ~140 AU, and a massive outer disk extending out to ~300 AU. The gap could have been carved out by a giant planet. We have imaged the outer regions of this gap using the adaptive optics camera NICI on Gemini South. Our images reveal that the disk is dynamically perturbed. The outer boundary of the roughly elliptical gap appears to be composed of several segments of spiral arms. The stellar position is offset by 0farcs17 ± 0farcs02 from the centroid of the cavity, consistent with earlier imaging at coarser resolutions. These transient morphological features are expected in the context of disk evolution in the presence of a perturbing body located inside the cavity. We perform hydrodynamical simulations of the dynamical clearing of a gap in a disk. A 10 M jup body in a circular orbit at r = 90 AU perturbs the whole disks, even after thousands of orbits. By then the model disk has an eccentric and irregular cavity, flanked by tightly wound spiral arms, but it is still evolving far from steady state. A particular transient configuration that is a qualitative match to HD 142527 is seen at 1.7 Myr. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência e Tecnologia (Brazil), and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina). The Gemini run ID is

  19. Pneumatic gap sensor and method

    DOEpatents

    Bagdal, Karl T.; King, Edward L.; Follstaedt, Donald W.

    1992-01-01

    An apparatus and method for monitoring and maintaining a predetermined width in the gap between a casting nozzle and a casting wheel, wherein the gap is monitored by means of at least one pneumatic gap sensor. The pneumatic gap sensor is mounted on the casting nozzle in proximity to the casting surface and is connected by means of a tube to a regulator and a transducer. The regulator provides a flow of gas through a restictor to the pneumatic gap sensor, and the transducer translates the changes in the gas pressure caused by the proximity of the casting wheel to the pneumatic gap sensor outlet into a signal intelligible to a control device. The relative positions of the casting nozzle and casting wheel can thereby be selectively adjusted to continually maintain a predetermined distance between their adjacent surfaces. The apparatus and method enables accurate monitoring of the actual casting gap in a simple and reliable manner resistant to the extreme temperatures and otherwise hostile casting environment.

  20. Pneumatic gap sensor and method

    DOEpatents

    Bagdal, K.T.; King, E.L.; Follstaedt, D.W.

    1992-03-03

    An apparatus and method for monitoring and maintaining a predetermined width in the gap between a casting nozzle and a casting wheel, wherein the gap is monitored by means of at least one pneumatic gap sensor. The pneumatic gap sensor is mounted on the casting nozzle in proximity to the casting surface and is connected by means of a tube to a regulator and a transducer. The regulator provides a flow of gas through a restictor to the pneumatic gap sensor, and the transducer translates the changes in the gas pressure caused by the proximity of the casting wheel to the pneumatic gap sensor outlet into a signal intelligible to a control device. The relative positions of the casting nozzle and casting wheel can thereby be selectively adjusted to continually maintain a predetermined distance between their adjacent surfaces. The apparatus and method enables accurate monitoring of the actual casting gap in a simple and reliable manner resistant to the extreme temperatures and otherwise hostile casting environment. 6 figs.

  1. ArfGAPs: key regulators for receptor sorting

    PubMed Central

    Shiba, Yoko; Randazzo, Paul A.

    2015-01-01

    Mammalian cells have many membranous organelles that require proper composition of proteins and lipids. Cargo sorting is a process required for transporting specific proteins and lipids to appropriate organelles, and if this process is disrupted, organelle function as well as cell function is disrupted. ArfGAP family proteins have been found to be critical for receptor sorting. In this review, we summarize our recent knowledge about the mechanism of cargo sorting that require function of ArfGAPs in promoting the formation of transport vesicles, and discuss the involvement of specific ArfGAPs for the sorting of a variety of receptors, such as MPR, EGFR, TfR, Glut4, TRAIL-R1/DR4, M5-muscarinic receptor, c-KIT, rhodopsin and β1-integrin. Given the importance of many of these receptors to human disease, the studies of ArfGAPs may provide novel therapeutic strategies in addition to providing mechanistic insight of receptor sorting. PMID:26046097

  2. Electronic properties of Janus silicene: new direct band gap semiconductors

    NASA Astrophysics Data System (ADS)

    Sun, Minglei; Ren, Qingqiang; Wang, Sake; Yu, Jin; Tang, Wencheng

    2016-11-01

    Using first-principles calculations, we propose a new class of materials, Janus silicene, which is silicene asymmetrically functionalized with hydrogen and halogen atoms. Formation energies and phonon dispersion indicated that all the Janus silicene systems exhibit good kinetic stability. As compared to silicane, all Janus silicene systems are direct band gap semiconductors. The band gap of Janus silicene can take any value between 1.91 and 2.66 eV by carefully tuning the chemical composition of the adatoms. In addition, biaxial elastic strain can further reduce the band gap to 1.11 eV (under a biaxial tensile strain up to 10%). According to moderate direct band gap, these materials demonstrate potential applications in optoelectronics, exhibiting a very wide spectral range, and they are expected to be highly stable under ambient conditions.

  3. Effect of impurity doping in gapped bilayer graphene

    SciTech Connect

    Han, Qi; Yan, Baoming; Jia, Zhenzhao; Niu, Jingjing; Yu, Dapeng; Wu, Xiaosong

    2015-10-19

    Impurity doping plays a pivotal role in semiconductor electronics. We study the doping effect in a two-dimensional semiconductor, gapped bilayer graphene. By employing in situ deposition of calcium on the bilayer graphene, dopants are controllably introduced. Low temperature transport results show a variable range hopping conduction near the charge neutrality point persisting up to 50 K, providing evidence for the impurity levels inside the gap. Our experiment confirms a predicted peculiar effect in the gapped bilayer graphene, i.e., formation of in-gap states even if the bare impurity level lies in the conduction band. The result provides perspective on the effect of doping and impurity levels in semiconducting bilayer graphene.

  4. Immunotoxicity of air pollutants

    SciTech Connect

    Graham, J.A.; Gardner, D.E.

    1984-01-01

    The most common ubiquitous air pollutants, as well as some point source (e.g. metals) air pollutants, decrease the function of pulmonary host defense mechanisms against infection. Most of this knowledge is based on animal studies and involves cellular antibacterial defenses such as alveolar macrophages and mucociliary clearance. Information on viral infectivity is more sparse. Since there is no routine treatment for viral infections which have a relatively high rate of occurrence, this gap in knowledge is of concern. Given the major gaps in knowledge, resaonably accurate assessment of the immunotoxicity of air pollutants is not possible. When the limited data base is reviewed relative to ambient levels of the common pollutants, it appears that acute exposures to O3 and H2SO4 and chronic exposures to NO2 are the major exposures of concern for immunotoxic effects. It is critical to point out, however, that until information is available for chronic exposures to low levels of metals and for exposures to common organic vapors, the immunotoxicity of air pollutants cannot be assessed adequately.

  5. Method and apparatus for wind turbine air gap control

    DOEpatents

    Grant, James Jonathan; Bagepalli, Bharat Sampathkumaran; Jansen, Patrick Lee; DiMascio, Paul Stephen; Gadre, Aniruddha Dattatraya; Qu, Ronghai

    2007-02-20

    Methods and apparatus for assembling a wind turbine generator are provided. The wind turbine generator includes a core and a plurality of stator windings circumferentially spaced about a generator longitudinal axis, a rotor rotatable about the generator longitudinal axis wherein the rotor includes a plurality of magnetic elements coupled to a radially outer periphery of the rotor such that an airgap is defined between the stator windings and the magnetic elements and the plurality of magnetic elements including a radially inner periphery having a first diameter. The wind turbine generator also includes a bearing including a first member in rotatable engagement with a radially inner second member, the first member including a radially outer periphery, a diameter of the radially outer periphery of the first member being substantially equal to the first diameter, the rotor coupled to the stator through the bearing such that a substantially uniform airgap is maintained.

  6. Micronucleus formation, DNA damage and repair in premenopausal women chronically exposed to high level of indoor air pollution from biomass fuel use in rural India.

    PubMed

    Mondal, Nandan Kumar; Mukherjee, Bidisha; Das, Debangshu; Ray, Manas Ranjan

    2010-03-29

    Genotoxicity of indoor air pollution from biomass fuel use has been examined in 132 biomass users (median age 34 years) and 85 age-matched control women from eastern India who used the cleaner fuel liquefied petroleum gas (LPG) to cook. Micronucleus (MN) frequency was evaluated in buccal (BEC) and airway epithelial cells (AEC); DNA damage was examined by comet assay in peripheral blood lymphocytes (PBL); and expressions of gamma-H2AX, Mre11 and Ku70 proteins were localized in AEC and PBL by immunocytochemistry. Reactive oxygen species (ROS) generation in leukocytes was measured by flow cytometry, and the levels of superoxide dismutase (SOD) and total antioxidant status (TAS) in blood were measured by spectrophotometry. Real-time aerosol monitor was used to measure particulate pollutants in indoor air. Compared with controls, biomass users had increased frequencies of micronucleated cells in BEC (3.5 vs. 1.7, p<0.001) and AEC (4.54 vs. 1.86, p<0.001), and greater comet tail % DNA (18.6 vs. 11.7%, p<0.01), tail length (45.5 vs. 31.4mum, p<0.01) and olive tail moment (4.0 vs. 1.4, p<0.01) in PBL. Moreover, biomass users had more gamma-H2AX-positive nuclei in PBL (49.5 vs. 8.5%, p<0.01) and AEC (11.3 vs. 2.9%, p<0.01) along with higher expression of DNA repair proteins Mre11 and Ku70 in these cells, suggesting stimulation of DNA repair mechanism. Biomass users showed rise in ROS generation and depletion of SOD and TAS. Biomass-using households had 2-4 times more particulate matter with diameter less than 10 and 2.5mum in indoor air, and MN frequency and comet tail % DNA were positively associated with these pollutants after controlling potential confounders. Thus, chronic exposure to biomass smoke causes chromosomal and DNA damage and upregulation of DNA repair mechanism.

  7. Nitric Oxide Studies in Low Temperature Plasmas Generated with a Nanosecond Pulse Sphere Gap Electrical Discharge

    NASA Astrophysics Data System (ADS)

    Burnette, David Dean

    This dissertation presents studies of NO kinetics in a plasma afterglow using various nanosecond pulse discharges across a sphere gap. The discharge platform is developed to produce a diffuse plasma volume large enough to allow for laser diagnostics in a plasma that is rich in vibrationally-excited molecules. This plasma is characterized by current and voltage traces as well as ICCD and NO PLIF images that are used to monitor the plasma dimensions and uniformity. Temperature and vibrational loading measurements are performed via coherent anti-Stokes Raman spectroscopy (CARS). Absolute NO concentrations are obtained by laser-induce fluorescence (LIF) measurements, and N and O densities are found using two photon absorption laser-induced fluorescence (TALIF). For all dry air conditions studied, the NO behavior is characterized by a rapid rate of formation consistent with an enhanced Zeldovich process involving electronically-excited nitrogen species that are generated within the plasma. After several microseconds, the NO evolution is entirely controlled by the reverse Zeldovich process. These results show that under the chosen range of conditions and even in extreme instances of vibrational loading, there is no formation channel beyond ~2 musec. Both the NO formation and consumption mechanisms are strongly affected by the addition of fuel species, producing much greater NO concentrations in the afterglow.

  8. Measurement of reflection phase using thick-gap Fabry-Perot etalon.

    PubMed

    Yung, Tsz Kit; Gao, Wensheng; Leung, Ho Ming; Zhao, Qiuling; Wang, Xia; Tam, Wing Yim

    2016-09-10

    We report measurement of the reflection phase of a dielectric (glass)/titanium (Ti) surface in the visible wavelength using a thick-gap Fabry-Perot (FP) interferometry technique. Using a two-beam interference model for the reflection peaks and troughs of the FP etalon, we obtain the air-gap spacing of the etalon and, more importantly, the reflection phase of the etalon substrate. We find systematic dependence of the as-measured reflection phase on the air-gap spacing due to the numerical aperture effect of the measuring objective. However, the relative reflection phase of Ti with respect to glass is independent of the air-gap spacing. As a demonstration of our approach in the optical characterization of small metamaterial samples, we also measure the reflection phase of a micron-sized 2D Au sawtooth nanoarray. The experiment is in good agreement with the model simulation.

  9. Aqueous-phase chemistry and bactericidal effects from an air discharge plasma in contact with water: evidence for the formation of peroxynitrite through a pseudo-second-order post-discharge reaction of H2O2 and HNO2

    NASA Astrophysics Data System (ADS)

    Lukes, P.; Dolezalova, E.; Sisrova, I.; Clupek, M.

    2014-02-01

    The formation of transient species (OH·, NO2·, NO radicals) and long-lived chemical products (O3, H2O2, NO_{3}^{-} , NO_{2}^{-} ) produced by a gas discharge plasma at the gas-liquid interface and directly in the liquid was measured in dependence on the gas atmosphere (20% oxygen mixtures with nitrogen or with argon) and pH of plasma-treated water (controlled by buffers at pH 3.3, 6.9 or 10.1). The aqueous-phase chemistry and specific contributions of these species to the chemical and biocidal effects of air discharge plasma in water were evaluated using phenol as a chemical probe and bacteria Escherichia coli. The nitrated and nitrosylated products of phenol (4-nitrophenol, 2-nitrophenol, 4-nitrocatechol, 4-nitrosophenol) in addition to the hydroxylated products (catechol, hydroquinone, 1,4-benzoquinone, hydroxy-1,4-benzoquinone) evidenced formation of NO2·, NO· and OH· radicals and NO+ ions directly by the air plasma at the gas-liquid interface and through post-discharge processes in plasma-activated water (PAW) mediated by peroxynitrite (ONOOH). Kinetic study of post-discharge evolution of H2O2 and NO_{2}^{-} in PAW has demonstrated excellent fit with the pseudo-second-order reaction between H2O2 and NO_{2}^{-} . The third-order rate constant k = 1.1 × 103 M-2 s-1 for the reaction NO_{2}^{-} +H_{2}O_{2}+H^{+}\\to ONOOH+H_{2}O was determined in PAW at pH 3.3 with the rate of ONOOH formation in the range 10-8-10-9 M s-1. Peroxynitrite chemistry was shown to significantly participate in the antibacterial properties of PAW. Ozone presence in PAW was proved indirectly by pH-dependent degradation of phenol and detection of cis,cis-muconic acid, but contribution of ozone to the inactivation of bacteria by the air plasma was negligible.

  10. GAP Analysis. Bulletin Number 11

    DTIC Science & Technology

    2002-01-01

    Lucas jack pine that is the habitat but rather (say) jack pine in which tree dynamics, and the test of accuracy was done at a time of high popu... testing are elaborated by Krohn [1996]). stresses) killed the birds that would have occupied them, in which Commission error (predicting the presence...thereby destroying the dove-arable correlation that would which GAP has historically been based should lead it to accept any have underlain a GAP assessment

  11. Eight electrode optical readout gap

    DOEpatents

    Boettcher, Gordon E.; Crain, Robert W.

    1985-01-01

    A protective device for a plurality of electrical circuits includes a pluity of isolated electrodes forming a gap with a common electrode. An output signal, electrically isolated from the circuits being monitored, is obtained by a photosensor viewing the discharge gap through an optical window. Radioactive stabilization of discharge characteristics is provided for slowly changing voltages and carbon tipped dynamic starters provide desirable discharge characteristics for rapidly varying voltages. A hydrogen permeation barrier is provided on external surfaces of the device.

  12. BINARY-DISK INTERACTION: GAP-OPENING CRITERIA

    SciTech Connect

    Valle, Luciano del; Escala, Andres

    2012-12-10

    We study the interaction of an equal mass binary with an isothermal circumbinary disk motivated by the evidence of the formation of massive black hole binaries surrounded by gas, after a major merger of gas-rich galaxies. We focus on the torques that the binary produces on the disk and how the exchange of angular momentum can drive the gap formation on it. We propose that the angular momentum exchange between the binary and the disk is through the gravitational interaction of the binary and a (tidally formed) global non-axisymmetric perturbation in the disk. Using this interaction, we derive an analytic criterion for the gap formation in the disk that can be expressed either via the characteristic velocities of the binary-disk system or in terms of the structural parameters h/a and M(< r)/M{sub bin}. Using numerical simulations we show that the simulations where the binary opens a gap in the disk and the simulations where the disk does not have a gap are distributed into two well separated regions. Our analytic criterion predicts a shape of the threshold between these two regions that is consistent with our simulations and the other ones in the literature. We propose an analogy between the regime without (with) a gap in the disk and the Type I (Type II) migration that is observed in simulations of planet-disk interaction (extreme mass ratio binary), emphasizing that the interaction that drives the formation of a gap on the disk is different in the regime that we analyze (comparable mass binary).

  13. Wintertime CO2 fluxes in an Arctic polynya using eddy covariance: Evidence for enhanced air-sea gas transfer during ice formation

    NASA Astrophysics Data System (ADS)

    Else, B. G. T.; Papakyriakou, T. N.; Galley, R. J.; Drennan, W. M.; Miller, L. A.; Thomas, H.

    2011-09-01

    Between Nov. 1 2007 and Jan. 31 2008, we calculated the air-sea flux of CO2, sensible heat, and water vapor in an Arctic polynya system (Amundsen Gulf, Canada) using eddy covariance equipment deployed on the research icebreaker CCGS Amundsen. During this time period, Amundsen Gulf was a dynamic sea ice environment composed primarily of first year ice with open water coverage varying between 1-14%. In all cases where measurements were influenced by open water we measured CO2 fluxes that were 1-2 orders of magnitude higher than those expected under similar conditions in the open ocean. Fluxes were typically directed toward the water surface with a mean flux of -4.88 μmol m-2 s-1 and a maximum of -27.95 μmol m-2 s-1. One case of rapid outgassing (mean value +2.10 μmol m-2 s-1) was also observed. The consistent patten of enhanced gas exchange over open water allows us to hypothesize that high water-side turbulence is the main cause of these events. Modification of the physical and chemical properties of the surface seawater by cooling and brine rejection may also play a role. A rough calculation using an estimate of open water coverage suggests that the contribution of these events to the annual regional air-sea CO2 exchange budget may make the winter months as important as the open water months. Although high, the uptake of CO2 fits within mixed layer dissolved inorganic carbon budgets derived for the region by other investigators.

  14. Air pollution from aircraft

    NASA Technical Reports Server (NTRS)

    Heywood, J. B.; Fay, J. A.; Chigier, N. A.

    1979-01-01

    A series of fundamental problems related to jet engine air pollution and combustion were examined. These include soot formation and oxidation, nitric oxide and carbon monoxide emissions mechanisms, pollutant dispension, flow and combustion characteristics of the NASA swirl can combustor, fuel atomization and fuel-air mixing processes, fuel spray drop velocity and size measurement, ignition and blowout. A summary of this work, and a bibliography of 41 theses and publications which describe this work, with abstracts, is included.

  15. Simulation of a runaway electron avalanche developing in an atmospheric pressure air discharge

    SciTech Connect

    Oreshkin, E. V.; Barengolts, S. A.; Chaikovsky, S. A.; Oreshkin, V. I.

    2015-12-15

    To gain a better understanding of the operation of atmospheric pressure air discharges, the formation of a runaway electron beam at an individual emission site on the cathode has been numerically simulated. The model provides a description of the dynamics of the fast electrons emitted into an air gap from the surface of the emission zone by solving numerically two-dimensional equations for the electrons. It is supposed that the electric field at the surface of the emission zone is enhanced, providing conditions for continuous acceleration of the emitted electrons. It is shown that the formation of a runaway electron beam in a highly overvolted discharge is largely associated with avalanche-type processes and that the number of electrons in the avalanche reaches 50% of the total number of runaway electrons.

  16. Simulation of a runaway electron avalanche developing in an atmospheric pressure air discharge

    NASA Astrophysics Data System (ADS)

    Oreshkin, E. V.; Barengolts, S. A.; Chaikovsky, S. A.; Oreshkin, V. I.

    2015-12-01

    To gain a better understanding of the operation of atmospheric pressure air discharges, the formation of a runaway electron beam at an individual emission site on the cathode has been numerically simulated. The model provides a description of the dynamics of the fast electrons emitted into an air gap from the surface of the emission zone by solving numerically two-dimensional equations for the electrons. It is supposed that the electric field at the surface of the emission zone is enhanced, providing conditions for continuous acceleration of the emitted electrons. It is shown that the formation of a runaway electron beam in a highly overvolted discharge is largely associated with avalanche-type processes and that the number of electrons in the avalanche reaches 50% of the total number of runaway electrons.

  17. Src Family Tyrosine Kinase Signaling Regulates FilGAP through Association with RBM10

    PubMed Central

    Yamada, Hazuki; Tsutsumi, Koji; Nakazawa, Yuki; Shibagaki, Yoshio; Hattori, Seisuke; Ohta, Yasutaka

    2016-01-01

    FilGAP is a Rac-specific GTPase-activating protein (GAP) that suppresses lamellae formation. In this study, we have identified RBM10 (RNA Binding Motif domain protein 10) as a FilGAP-interacting protein. Although RBM10 is mostly localized in the nuclei in human melanoma A7 cells, forced expression of Src family tyrosine kinase Fyn induced translocation of RBM10 from nucleus into cell peripheries where RBM10 and FilGAP are co-localized. The translocation of RBM10 from nucleus appears to require catalytic activity of Fyn since kinase-negative Fyn mutant failed to induce translocation of RBM10 in A7 cells. When human breast carcinoma MDA-MB-231 cells are spreading on collagen-coated coverslips, endogenous FilGAP and RBM10 were localized at the cell periphery with tyrosine-phosphorylated proteins. RBM10 appears to be responsible for targeting FilGAP at the cell periphery because depletion of RBM10 by siRNA abrogated peripheral localization of FilGAP during cell spreading. Association of RBM10 with FilGAP may stimulate RacGAP activity of FilGAP. First, forced expression of RBM10 suppressed FilGAP-mediated cell spreading on collagen. Conversely, depletion of endogenous RBM10 by siRNA abolished FilGAP-mediated suppression of cell spreading on collagen. Second, FilGAP suppressed formation of membrane ruffles induced by Fyn and instead produced spiky cell protrusions at the cell periphery. This protrusive structure was also induced by depletion of Rac, suggesting that the formation of protrusions may be due to suppression of Rac by FilGAP. We found that depletion of RBM10 markedly reduced the formation of protrusions in cells transfected with Fyn and FilGAP. Finally, depletion of RBM10 blocked FilGAP-mediated suppression of ruffle formation induced by EGF. Taken together, these results suggest that Src family tyrosine kinase signaling may regulate FilGAP through association with RBM10. PMID:26751795

  18. Stabilizers for GAP and GAP-based Propellants Interim Report

    DTIC Science & Technology

    2008-10-09

    the m j o r deconposit inn pathways of GAP and U P prope l lan ts i n o r d e r to i n p r o w long term storage stabi l i ty. Model c- s inw...la t i ng t h e ut ido-bear ing frmctional units of GAP ( a z i d e adjacent t o po lye ther k k b o n e , az ide sd jacent t o terminal...binder i n prope l lan t -ag ing studies has varied accord2~g t o the to t of GAP used. This v a r i a b i l i t y my k linked to residual i n p

  19. Bubble dynamics in a variable gap Hele-Shaw cell

    NASA Astrophysics Data System (ADS)

    Piedra, Saul; Domiguez, Roberto; Ramos, Eduardo

    2015-11-01

    We present observations of the dynamics of individual air bubbles ascending in a Hele-Shaw cell filled with water. Cells with gaps of 1 mm, 1.5 and 2.5 mm are used and the volume of the bubbles is such that we observe bubbles with apparent diameter from 2 mm to 7.3 mm. Given that we work with air and water in all experiments, the Morton number is constant and equal to 2 . 5 ×10-11 . The results are given in terms of the Eotvos, Archimedes and Reynolds numbers, and the trajectories and wakes of the bubbles are described as functions of the gap. In all cases we observe a linear relationship between the Reynolds and Archimedes numbers, but the proportionality constant varies with the gap. Also, although the wake is composed of alternating vortices similar to the von Karman vortex street, the size and location of the vortices vary with the gap. The analysis of some features of the observations and the description of the shape of the bubbles and dominant forces are made with a two dimensional numerical solution of the conservation equations using a front tracking strategy.

  20. Semicontinuous measurements of organic carbon and acidity during the Pittsburgh air quality study: implications for acid-catalyzed organic aerosol formation

    SciTech Connect

    S. Takahama; C.I. Davidson; S.N. Pandis

    2006-04-01

    Laboratory evidence suggests that inorganic acid seed particles may increase secondary organic aerosol yields secondary organic aerosol (SOA) through heterogeneous chemistry. Additional laboratory studies, however, report that organic acidity generated in the same photochemical process by which SOA is formed may be sufficient to catalyze these heterogeneous reactions. Understanding the interaction between inorganic acidity and SOA mass is important when evaluating emission controls to meet PM2.5 regulations. Semicontinuous measurements of organic carbon (OC), elemental carbon (EC), and inorganic species from the Pittsburgh Air Quality Study were examined to determine if coupling in the variations of inorganic acidity and OC could be detected. Significant enhancements of SOA production could not be detected due to inorganic acidity in Western Pennsylvania most of the time, but its signal might have been lost in the noise. If a causal relationship between inorganic acidity and OC is assumed, reductions in OC for Western Pennsylvania that might result from drastic reductions in inorganic acidity were estimated to be 2 {+-} 4% by a regression technique, and an upper bound for this geographic area was estimated to be 5 {+-} 8% based on calculations from laboratory measurements. 48 refs., 7 figs., 3 tabs.