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. Surfactant-Assisted Voltage-Driven Silver Nanoparticle Chain Formation across Microelectrode Gaps in Air.

    PubMed

    Shah, Nidhi; Zamborini, Francis P

    2015-10-27

    Here we describe the electrodeposition of Ag in the presence of cetyltrimethylammonium bromide (CTAB) onto 5 μm gap Au interdigitated array (IDA) electrodes that are bare, thiol-functionalized, or thiol-functionalized and seeded with 4 nm diameter Au nanoparticles (NPs). After deposition, applying a voltage between 5 and 10 V in air for 0 to 1000 s resulted in one-dimensional (1D) Ag NP chains spanning across the IDA gap. The Ag NP chains form on IDAs functionalized with thiols and Au NP-seeded at about 5 V and at 10 V for the other nonseeded surfaces. Ag NP chains do not form at all up to 10 V when IDAs are treated with ozone or water soaking to remove possible CTA(+) ions from the surface, when Ag deposition takes place in the absence of CTAB, or when the voltage is applied under dry N2 (low humidity). Chain formation occurs by Ag moving from the positive to negative electrode. Coating the devices with a negatively charged surfactant, sodium dodecyl sulfate, also results in Ag NP chains by Ag moving from the positive to the negative electrodes, which confirms that the chains form by electrochemical oxidation at the positive electrode and deposition at the negative electrode. The surfactant ions and thin layer of water present in the humid environment facilitate this electrochemical process. PMID:26344389

  3. 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... § 56.6603 Air gap. At least a 15-foot air gap shall be provided between the blasting circuit and...

  4. Engine piston having an insulating air gap

    DOEpatents

    Jarrett, Mark Wayne; Hunold,Brent Michael

    2010-02-02

    A piston for an internal combustion engine has an upper crown with a top and a bottom surface, and a lower crown with a top and a bottom surface. The upper crown and the lower crown are fixedly attached to each other using welds, with the bottom surface of the upper crown and the top surface of the lower crown forming a mating surface. The piston also has at least one centrally located air gap formed on the mating surface. The air gap is sealed to prevent substantial airflow into or out of the air gap.

  5. 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.

  6. 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...

  7. 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...

  8. 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...

  9. 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...

  10. 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...

  11. 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...

  12. 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...

  13. 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...

  14. 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...

  15. Tunable optofluidic dye laser with integrated air-gap etalon

    NASA Astrophysics Data System (ADS)

    Song, Wuzhou; Vasdekis, Andreas E.; Psaltis, Demetri

    2010-11-01

    In this work we demonstrate an integrated air-gap etalon that enables single wavelength operation and tuning ability for optofluidic dye laser. The integrated elastomeric air-gap etalon is controlled by air pressure. The chip was fabricated with polydimethylsiloxane (PDMS) via replica molding. It comprises a liquid waveguide and micro-scale air-gap mirrors providing the feedback. The lasing wavelength is chosen by the interference between two parallel PDMS-air interfaces inside the internal tunable air-gap etalon, of which pneumatic tuning can be realized by inflating the air-gap etalon with compressed air. This dye laser exhibits a pumping threshold of 1.6 μJ/pulse, a lasing linewidth of 3 nm and a tuning range of 14 nm.

  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. The mechanics of endothelial gap formation

    NASA Astrophysics Data System (ADS)

    Chattoraj, Joyjit; Del Gado, Emanuela; Hardin, C. Corey; Krishnan, Ramaswamy

    The vascular endothelium is a layer of specialized cells, referred to as endothelial cells (EC) that line the internal surfaces of blood vessels and are largely responsible for regulating the transit of fluids, solutes and immune system cells from the circulation, across the vessel wall, and into the tissues. We investigate the physics of the mechanical events that may proceed and eventually lead to dramatic increase of its permeability, leading to serious illness. In combination with experiments measuring local stresses and gap formation in EC in different conditions, we devise a minimal model based on an amorphous assembly of adhesive particles, subjected to an imposed tension. Numerical simulations of the model show that, as a function of the rate at which the tension is imposed, the system goes from an elastic regime in which small gaps increase in number to a ``plastic'' one, where pre-existing gaps increase in size, and internal stresses display large hetereogeneities and long range correlations. This second regime bears intriguing similarities with the experimental finding in EC monolayers.

  18. Transmission properties of frequency selective structures with air gaps

    NASA Astrophysics Data System (ADS)

    Meng, Zhi-Jun; Wang, Li-Feng; Lü, Ming-Yun; Wu, Zhe

    2010-12-01

    The transmission properties of compound frequency selective structures with dielectric slab and air gaps were investigated by computation and experimentation. Mechanism analyses were also carried out. Results show that the air gaps have a distinct influence on the transmission properties. Resonant frequency of the structure would increase rapidly when the air gap appears. After the gap gets larger to a specific value, generally 1/5 wavelength corresponding to the resonant frequency, the transmission properties would change periodically with the gap thickness. The change of transmission properties in one period has a close relationship with the dielectric thickness. These results provide a new method for designing a bandpass radome of large incidence angle and low loss with the concept of stealth shield radome.

  19. Influence of film thickness and air exposure on the transport gap of manganese phthalocyanine

    SciTech Connect

    Haidu, F.; Fechner, A.; Salvan, G.; Gordan, O. D.; Fronk, M.; Zahn, D. R. T.; Lehmann, D.; Mahns, B.; Knupfer, M.

    2013-06-15

    The interface formation between manganese phthalocyanine (MnPc) and cobalt was investigated combining ultraviolet photoelectron spectroscopy and inverse photoelectron spectroscopy. The transport band gap of the MnPc increases with the film thickness up to a value of (1.2 {+-} 0.3) eV while the optical band gap as determined from spectroscopic ellipsometry amounts to 0.5 eV. The gap values are smaller compared to other phthalocyanines due to metallic Mn 3d states close to the Fermi level. The transport band gap was found to open upon air exposure as a result of the disappearance of the occupied 3d electronic states.

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

    DOEpatents

    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).

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

    DOEpatents

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

    PubMed

    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

  3. Zooplankton patch dynamics: daily gap formation over abrupt topography

    NASA Astrophysics Data System (ADS)

    Genin, Amatzia; Greene, Charles; Haury, Loren; Wiebe, Peter; Gal, Gideon; Kaartvedt, Stein; Meir, Eli; Fey, Connie; Dawson, Jim

    1994-05-01

    Net tow and acoustic surveys of zooplankton distributions were made over and around Sixtymile Bank (110 km southwest of San Diego, California). Gaps devoid of vertically migrating zooplankton were formed every evening above the summit of the bank. Interactions between the migrating animals, their predators, physical advection and the local topography appear to determine the gap formation and dynamics. Gaps were transported downstream during the night and appeared to disintegrate slowly through vertical swimming behavior, current shear and mixing processes. Patch dynamics following gap formation, mediated by both ocean currents and animal behavior, should augment the spatial heterogeneity of zooplankton and affect marine food webs in areas where abrupt topography features are common.

  4. The Air Gap Phenomenon in Children's Landscape Drawings.

    ERIC Educational Resources Information Center

    Hargreaves, David J.; And Others

    1981-01-01

    These studies confirm the view that the "air gap" phenomenon, which refers to the area that remains when ground and sky lines are constructed at the bottom and top of a drawing, is commonly found in the free drawings of middle and later childhood, but that it is readily abandoned when task demands are modified accordingly. (Author/DB)

  5. 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.

  6. Simulation of air gap vibration on aerostatic bearing under flow/structure coupled conditions

    NASA Astrophysics Data System (ADS)

    Wang, Qian; Wu, Jianjin; Li, Dongsheng

    2008-10-01

    The vibration of aerostatic bearing air gap is one of the main factors, which restricts the precision of nano-processing and nano-measurement. Finite volume method was employed to obtain the air gap steady flow of different air gap thicknesses for the demonstration of vibrations under flow/structure coupled conditions. The unsteady flow of air gap was analyzed numerically by using the air gap flow & boundary movement control equations to get the pressure distribution on the slide surface and the amplitude of air gap for further study on the self-excited vibration of aerostatic bearings. Numerical analyses show that the highest aerostatic bearing amplitude is relative to the difference between load capacity and gravity at the initial moment as air gap rises, and the final air gap thickness has nothing to do with the initial air gap thickness. The results presented a new analytic demonstration for the research on the reduction of aerostatic bearing vibration.

  7. Gas Giant Planet Formation in the Photoevaporating Disk. I. Gap Formation

    NASA Astrophysics Data System (ADS)

    Xiao, Lin; Jin, Liping; Liu, Chengzhi; Fan, Cunbo

    2016-08-01

    Planet formation and photoevaporation have both been considered as gap opening mechanisms in protoplanetary disks. We have studied giant planet formation in a photoevaporating disk with long-term evolution. Our calculations suggest that the core accretion rate of a protoplanet declines and the trigger of the runaway gas accretion for a giant planet is delayed under the action of photoevaporation. We find that the final mass of a giant planet characterized by the “gap-limiting” case is not influenced by photoevaporation but the final mass of a giant planet characterized by the “diffusion-limiting” case is greatly influenced by photoevaporation. Considering the formation process of giant planets, we suggest that the locations of the gaps opened by giant planets are within 30–40 au and the gap width in the “gap-limiting” case is wider than that in the “diffusion-limiting” case. We also find that gaps in photoevaporating disks are wider than those in non-photoevaporating disks. Our calculations suggest that the origins of multiple gaps in a disk can be diverse depending on their formation locations. In the formation region of giant planets, gaps are opened by giant planets. The outer gap beyond the giant planet formation region may be opened under the action of photoevaporation. A gap may also be opened at 1–3 au under the actions of photoevaporating dissipation and gas accretion of the outer giant planets.

  8. 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.

  9. Model of Layered Weld Formation Under Narrow Gap Pulse Welding

    NASA Astrophysics Data System (ADS)

    Krampit, A. G.

    2016-04-01

    The model parameters of narrow gap pulse welding can be divided into input, internal and output ones. The breadth of gap, that is, clearance breadth between upright edges is one of key parameters securing high quality of a weld joint. The paper presents theoretical outcomes for the model of layered weld formation under narrow gap pulse welding. Based on these studies is developed model of processes, which occur in the weld pool under pulse grove welding. It comprises the scheme of liquid metal motion in the weld pool, scheme of fusion with the side edge and in the bottom part, and the scheme of welding current impulse effect on the structure of a weld joint.

  10. 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)

  11. 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

  12. Bremsstrahlung of fast electrons in long air gaps

    SciTech Connect

    Oreshkin, E. V.; Barengolts, S. A.; Chaikovsky, S. A.; Oginov, A. V.; Shpakov, K. V.; Bogachenkov, V. A.

    2012-01-15

    The results of an experiment on discharges in long atmospheric pressure air gaps at a pulsed voltage of amplitude up to 800 kV and risetime 150-200 ns have been analyzed. In the experiment, a radiation pulse of photon energy >5 keV and duration 10-20 ns was observed. In analyzing the experimental data it was supposed that a streamer is a plasma protrusion whose surface is equipotential to the cathode surface. It has been shown that the x-ray pulse results from the switch of electrons into the mode of ''runaway'' from the head of anode-directed streamers. For the electrons injected in the electrode gap from the streamer head, conditions for their switching into the mode of continuous acceleration are realized due to the enhanced electric field at the head. The predicted maximum of the spectrum of the bremsstrahlung generated by the runaway electron beam is around 15 keV. The presence of a maximum in the bremsstrahlung spectrum is due to that the photons emitted by electrons are absorbed by atoms of the gas in which the discharge operate.

  13. Plasma formation in a double-gap vircator

    NASA Astrophysics Data System (ADS)

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

    2010-11-01

    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 (˜500 kV, ˜10 kA, ˜500 ns). The vircator generated well reproducible S-band microwave pulses of ˜200 MW peak power and up to 200 ns full duration. The plasma light emission was observed ˜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.

  14. 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.

  15. 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.

  16. 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.

  17. Traction force dynamics predict gap formation in activated endothelium.

    PubMed

    Valent, Erik T; van Nieuw Amerongen, Geerten P; van Hinsbergh, Victor W M; Hordijk, Peter L

    2016-09-10

    In many pathological conditions the endothelium becomes activated and dysfunctional, resulting in hyperpermeability and plasma leakage. No specific therapies are available yet to control endothelial barrier function, which is regulated by inter-endothelial junctions and the generation of acto-myosin-based contractile forces in the context of cell-cell and cell-matrix interactions. However, the spatiotemporal distribution and stimulus-induced reorganization of these integral forces remain largely unknown. Traction force microscopy of human endothelial monolayers was used to visualize contractile forces in resting cells and during thrombin-induced hyperpermeability. Simultaneously, information about endothelial monolayer integrity, adherens junctions and cytoskeletal proteins (F-actin) were captured. This revealed a heterogeneous distribution of traction forces, with nuclear areas showing lower and cell-cell junctions higher traction forces than the whole-monolayer average. Moreover, junctional forces were asymmetrically distributed among neighboring cells. Force vector orientation analysis showed a good correlation with the alignment of F-actin and revealed contractile forces in newly formed filopodia and lamellipodia-like protrusions within the monolayer. Finally, unstable areas, showing high force fluctuations within the monolayer were prone to form inter-endothelial gaps upon stimulation with thrombin. To conclude, contractile traction forces are heterogeneously distributed within endothelial monolayers and force instability, rather than force magnitude, predicts the stimulus-induced formation of intercellular gaps. PMID:27498166

  18. 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

  19. Hot air balloons fill gap in atmospheric and sensing platforms

    NASA Astrophysics Data System (ADS)

    Watson, Steven M.; Price, Russ

    Eric Edgerton was having a problem he could not solve: how to noninvasively collect in situ incinerator plume data. So he called in the Air Force and learned about its Atmospheric and Sensor Test Platform program; its platform is a manned hot air balloon. Many investigators are discovering the advantages of hot air balloons as stable, inexpensive platforms for performing in situ atmospheric measurements. Some are also using remote sensing capabilities on the balloon platforms.

  20. Relative dose efficiencies of antiscatter grids and air gaps in pediatric radiography

    SciTech Connect

    McDaniel, D.L.; Cohen, G.; Wagner, L.K.; Robinson, L.H.

    1984-07-01

    The relative dose efficiencies (RDE) of various antiscatter grids and air gaps were determined for conditions simulating those found in pediatric radiography, using phantoms representing a newborn child, a 5-yr-old and a 10-yr-old child. Our data indicate than an air gap is best for the newborn, due to the low levels of scatter. The 8:1 fiber grid or 15.2-cm air gap without a grid can improve dose efficiency (DE) for the 5-yr-old child by 20%--25% relative to the 3.3-cm air gap and no-grid technique, while for the 10-yr-old child, DE can be improved by 40% with an 8:1 fiber grid.

  1. 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…

  2. 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…

  3. Self-pulsation in two-section laser with an air gap

    NASA Astrophysics Data System (ADS)

    Lin, Chien-Chung; Lin, Chih-Wei; Chien, Chen-Yu; Kuo, Hao-Chung

    2012-02-01

    This study explores the optical field distribution of 1.55μm InGaAsP distributed feedback Laser with an air gap in the middle section. The optical field distribution was analyzed by different depth and width of an air gap. From the calculation, we could observe how the gap affect the coupling of the optical field into the other cavity. The percentage of the coupling is a crucial factor to the injection-locking operation. Both effective index model and commercial software were used to predict this coupling.

  4. Numerical Simulation of Two-phase Flow in a Microchannel with Air Gap

    NASA Astrophysics Data System (ADS)

    Liu, Xiaojun; Meinhart, Carl D.

    2001-11-01

    Fluid transport in nano- and micro-scale devices becomes more and more important. The potential advantages of micro-channel with air gap are studied. A simple one-dimensional model of air-water two-phase flow is investigated theoretically. The flow of water is driven by pressure drop. The air in the gap is driven by surface tension and friction forces that exist at the interface between the water and air. With the limitation that air flow rate is zero, the theoretical results are obtained based on continuity and Navier-Stokes equations. Because the viscosity of air is much less than that of water, under same pressure drop, the flow rate of water can be increased to as 4.76 times as that of normal channel without air gap. The theoretical results are tested by numerical simulation with three different software package (CFD2000, FEMLab and CFDRC) using a two-dimensional model. The interface shape, interface velocity, water flow rate and optimum height ratio are studied. Thenumerical results for different package match each other very well. The numerical results show that increasing water flow rate by adding air gap in the micro channel is practicable.

  5. 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...

  6. The effects of air gap reflections during air-coupled leaky Lamb wave inspection of thin plates.

    PubMed

    Fan, Zichuan; Jiang, Wentao; Cai, Maolin; Wright, William M D

    2016-02-01

    Air-coupled ultrasonic inspection using leaky Lamb waves offers attractive possibilities for non-contact testing of plate materials and structures. A common method uses an air-coupled pitch-catch configuration, which comprises a transmitter and a receiver positioned at oblique angles to a thin plate. It is well known that the angle of incidence of the ultrasonic bulk wave in the air can be used to preferentially generate specific Lamb wave modes in the plate in a non-contact manner, depending on the plate dimensions and material properties. Multiple reflections of the ultrasonic waves in the air gap between the transmitter and the plate can produce additional delayed waves entering the plate at angles of incidence that are different to those of the original bulk wave source. Similarly, multiple reflections of the leaky Lamb waves in the air gap between the plate and an inclined receiver may then have different angles of incidence and propagation delays when arriving at the receiver and hence the signal analysis may become complex, potentially leading to confusion in the identification of the wave modes. To obtain a better understanding of the generation, propagation and detection of leaky Lamb waves and the effects of reflected waves within the air gaps, a multiphysics model using finite element methods was established. This model facilitated the visualisation of the propagation of the reflected waves between the transducers and the plate, the subsequent generation of additional Lamb wave signals within the plate itself, their leakage into the adjacent air, and the reflections of the leaky waves in the air gap between the plate and receiver. Multiple simulations were performed to evaluate the propagation and reflection of signals produced at different transducer incidence angles. Experimental measurements in air were in good agreement with simulation, which verified that the multiphysics model can provide a convenient and accurate way to interpret the signals in

  7. Technical Note: Spatial resolution of proton tomography: Impact of air gap between patient and detector

    SciTech Connect

    Schneider, Uwe; Besserer, Juergen; Hartmann, Matthias

    2012-02-15

    Purpose: Proton radiography and tomography were investigated since the early 1970s because of its low radiation dose, high density resolution, and ability to image directly proton stopping power. However, spatial resolution is still a limiting factor. In this note, preliminary results of the impact of an air gap between detector system and patient on spatial resolution are presented. Methods: Spatial resolution of proton radiography and tomography is governed by multiple Coulomb scattering (MCS) of the protons in the patient. In this note, the authors employ Monte Carlo simulations of protons traversing a 20 cm thick water box. Entrance and exit proton coordinate measurements were simulated for improved spatial resolution. The simulations were performed with and without a 5 cm air gap in front of and behind the patient. Loss of spatial resolution due to the air gap was studied for protons with different initial angular confusion. Results: It was found that spatial resolution is significantly deteriorated when a 5 cm air gap between the position sensitive detector and the patient is included. For a perfect parallel beam spatial resolution worsens by about 40%. Spatial resolution is getting worse with increasing angular confusion and can reach 80%. Conclusions: When proton radiographies are produced by measuring the entrance and exit coordinates of the protons in front of and behind the patient the air gap between the detector and the patient can significantly deteriorate the spatial resolution of the system by up to 80%. An alternative would be to measure in addition to the coordinates also the exit and entrance angles of each proton. In principle, using the air gap size and proton angle, images can be reconstructed with the same spatial resolution than without air gap.

  8. Dominant regulation of interendothelial cell gap formation by calcium-inhibited type 6 adenylyl cyclase

    PubMed Central

    Cioffi, Donna L.; Moore, Timothy M.; Schaack, Jerry; Creighton, Judy R.; Cooper, Dermot M.F.; Stevens, Troy

    2002-01-01

    Acute transitions in cytosolic calcium ([Ca2+]i) through store-operated calcium entry channels catalyze interendothelial cell gap formation that increases permeability. However, the rise in [Ca2+]i only disrupts barrier function in the absence of a rise in cAMP. Discovery that type 6 adenylyl cyclase (AC6; EC 4.6.6.1) is inhibited by calcium entry through store-operated calcium entry pathways provided a plausible explanation for how inflammatory [Ca2+]i mediators may decrease cAMP necessary for endothelial cell gap formation. [Ca2+]i mediators only modestly decrease global cAMP concentrations and thus, to date, the physiological role of AC6 is unresolved. Present studies used an adenoviral construct that expresses the calcium-stimulated AC8 to convert normal calcium inhibition into stimulation of cAMP, within physiologically relevant concentration ranges. Thrombin stimulated a dose-dependent [Ca2+]i rise in both pulmonary artery (PAECs) and microvascular (PMVEC) endothelial cells, and promoted intercellular gap formation in both cell types. In PAECs, gap formation was progressive over 2 h, whereas in PMVECs, gap formation was rapid (within 10 min) and gaps resealed within 2 h. Expression of AC8 resulted in a modest calcium stimulation of cAMP, which virtually abolished thrombin-induced gap formation in PMVECs. Findings provide the first direct evidence that calcium inhibition of AC6 is essential for endothelial gap formation. PMID:12082084

  9. Dual channel formation in a laser-triggered spark gap

    NASA Astrophysics Data System (ADS)

    Kushner, M. J.; Kimura, W. D.; Ford, D. H.; Byron, S. R.

    1985-12-01

    During self-break in spark-gap switches, multiple streamers can form in close proximity to one another. The rate of expansion of these streamers is sufficiently fast that they can interact during the current pulse. To help understand how these closely spaced, expanding spark columns interact, a laser-triggered spark gap has been studied in which two parallel columns (separation 1.3 mm) are simultaneously preionized, resulting in a pair of nearly identical, axisymmetric spark columns. The spark gap (electrode separation 1.2 cm) switches a 100 ns, 40-60 kV, 12-20 kA, 1.5 Ω waterline. Interferograms of the expanding arc channels are obtained with a laser interferometer having a time and spatial resolution of 5 ns and 10 μm, respectively. Voltage and current were measured with an internal capacitive-voltage divider and a current viewing resistor. The interferograms show that for initially identical axisymmetric columns, the individual channels do not merge into a single larger axisymmetric spark column. Instead, regions of high gas density remain inside the combined column long into the recovery period. The columns also do not remain axisymmetric as they grow, indicating a long-range interaction between the channels. The voltage drop and resistance of the dual channel spark gaps changes by less than 15% from that of a single spark channel. A scaling model is presented to explain the resistance measurements and to predict the change in resistance for multichannel spark gaps.

  10. Molecular mechanisms regulating formation, trafficking and processing of annular gap junctions.

    PubMed

    Falk, Matthias M; Bell, Cheryl L; Kells Andrews, Rachael M; Murray, Sandra A

    2016-01-01

    Internalization of gap junction plaques results in the formation of annular gap junction vesicles. The factors that regulate the coordinated internalization of the gap junction plaques to form annular gap junction vesicles, and the subsequent events involved in annular gap junction processing have only relatively recently been investigated in detail. However it is becoming clear that while annular gap junction vesicles have been demonstrated to be degraded by autophagosomal and endo-lysosomal pathways, they undergo a number of additional processing events. Here, we characterize the morphology of the annular gap junction vesicle and review the current knowledge of the processes involved in their formation, fission, fusion, and degradation. In addition, we address the possibility for connexin protein recycling back to the plasma membrane to contribute to gap junction formation and intercellular communication. Information on gap junction plaque removal from the plasma membrane and the subsequent processing of annular gap junction vesicles is critical to our understanding of cell-cell communication as it relates to events regulating development, cell homeostasis, unstable proliferation of cancer cells, wound healing, changes in the ischemic heart, and many other physiological and pathological cellular phenomena. PMID:27230503

  11. Thickness and air gap measurement of assembled IR objectives

    NASA Astrophysics Data System (ADS)

    Lueerss, B.; Langehanenberg, P.

    2015-10-01

    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 lenses. 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 most 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 set-up is based on a Michelson interferometer in which the light from a broadband superluminescent diode is split into a reference arm with a variable optical delay and a measurement arm where the sample is placed. On a 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 distances of the lens surfaces are derived from the optical delay. In order to penetrate IR materials, the instrument operates at 2.2 μm. Together with an LWIR autocollimator, this technique allows for the determination of centering errors, lens thicknesses and air spacings of assembled IR objective lenses with a micron accuracy. It is therefore a tool for precision manufacturing and quality control.

  12. Electromagnetic forces in the air gap of a permanent magnet linear generator at no load

    NASA Astrophysics Data System (ADS)

    Nilsson, K.; Danielsson, O.; Leijon, M.

    2006-02-01

    The basis for the work is the slow speed energy conversion of ocean wave energy into electricity using a direct-drive three-phase permanent magnetized linear generator. One of several important issues is the normal forces in the air gap, which is critical when designing the support structure of the generator. The electromagnetic forces in the air gap have been analyzed using Maxwell stress tensor method implemented in a two- dimensional finite element code. Simplified analytic calculations are made in order to validate the results from the extensive computer calculations. The normal electromagnetic forces in the air gap, Fδ, are analyzed for a two-sided linear generator at no load. An unstable condition of the global force on the piston occurs due to the fast increasing normal force as the air gap width decreases. A horizontal displacement of the piston from a neutral position with 3 mm air gap on both sides produces a resulting horizontal force on the piston, increasing with the displacement. A displacement of 1 mm gives a resulting horizontal force on the piston of 5.5 kN per pole and meter of core length, which is increased to 9 kN per pole and meter of core length for a displacement of 1.5 mm. Furthermore, the normal force varies due to cogging as the piston moves vertically. At a constant air gap width of 3 mm the normal forces per pole are varying between 9.9 and 11.3 kN/m of core length as the piston is moving from one pole to the next.

  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. Measuring air gap width of permanent magnet linear generators using search coil sensor

    NASA Astrophysics Data System (ADS)

    Waters, R.; Danielsson, O.; Leijon, M.

    2007-01-01

    A concept for a wave power plant is being developed at the Centre for Renewable Electric Energy Conversion at the Ångström Laboratory at Uppsala University. The concept is based on a permanent magnet linear generator placed on the seabed, directly driven by a surface following buoy. Critical for the survival of the generator is that the air gap between the moving and static parts of the generator is constantly fixed at the designed width to prevent the moving and static parts from connecting during operation. This paper shows the design and evaluation of an inductive sensor for measuring the air gap width during generator operation. In order to survive during years on the seafloor inside the wave power plants, the sensor has deliberately been chosen to be a passive component, as well as robust and compact. A coil etched on a printed circuit board, i.e., a search coil, was the chosen basis for the sensor. The sensor has been tested on an existing test rig of a wave power plant and the results have been compared with finite element simulations.The results show that a search coil magnetic sensor etched on a printed circuit board is a suitable concept for measuring the air gap width. Experimentally measured and theoretically calculated sensor signals show very good agreement. The setup has a sensitivity of ±0.4mm in the range of 4-9.5mm air gap. The potential for future improvements of the sensitivity is considerable.

  15. Measuring air gap width of permanent magnet linear generators using search coil sensor

    SciTech Connect

    Waters, R.; Danielsson, O.; Leijon, M.

    2007-01-15

    A concept for a wave power plant is being developed at the Centre for Renewable Electric Energy Conversion at the Angstroem Laboratory at Uppsala University. The concept is based on a permanent magnet linear generator placed on the seabed, directly driven by a surface following buoy. Critical for the survival of the generator is that the air gap between the moving and static parts of the generator is constantly fixed at the designed width to prevent the moving and static parts from connecting during operation. This paper shows the design and evaluation of an inductive sensor for measuring the air gap width during generator operation. In order to survive during years on the seafloor inside the wave power plants, the sensor has deliberately been chosen to be a passive component, as well as robust and compact. A coil etched on a printed circuit board, i.e., a search coil, was the chosen basis for the sensor. The sensor has been tested on an existing test rig of a wave power plant and the results have been compared with finite element simulations.The results show that a search coil magnetic sensor etched on a printed circuit board is a suitable concept for measuring the air gap width. Experimentally measured and theoretically calculated sensor signals show very good agreement. The setup has a sensitivity of {+-}0.4 mm in the range of 4-9.5 mm air gap. The potential for future improvements of the sensitivity is considerable.

  16. 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

    ..., DEPARTMENT OF THE INTERIOR OFFSHORE RENEWABLE ENERGY ALTERNATE USES OF EXISTING FACILITIES ON THE OUTER... must I include in my SAP, COP, or GAP regarding air quality? (a) You must comply with the Clean Air...

  17. CHARACTERIZING DETONATING LX-17 CHARGES CROSSING A TRANSVERSE AIR GAP WITH EXPERIMENTS AND MODELING

    SciTech Connect

    Lauderbach, L M; Souers, P C; Garcia, F; Vitello, P; Vandersall, K S

    2009-06-26

    Experiments were performed using detonating LX-17 (92.5% TATB, 7.5% Kel-F by weight) charges with various width transverse air gaps with manganin peizoresistive in-situ gauges present. The experiments, performed with 25 mm diameter by 25 mm long LX-17 pellets with the transverse air gap in between, showed that transverse gaps up to about 3 mm could be present without causing the detonation wave to fail to continue as a detonation. The Tarantula/JWL{sup ++} code was utilized to model the results and compare with the in-situ gauge records with some agreement to the experimental data with additional work needed for a better match to the data. This work will present the experimental details as well as comparison to the model results.

  18. Seed Regeneration Potential of Canopy Gaps at Early Formation Stage in Temperate Secondary Forests, Northeast China

    PubMed Central

    Yan, Qiao-Ling; Zhu, Jiao-Jun; Yu, Li-Zhong

    2012-01-01

    Promoting the seed regeneration potential of secondary forests undergoing gap disturbances is an important approach for achieving forest restoration and sustainable management. Seedling recruitment from seed banks strongly determines the seed regeneration potential, but the process is poorly understood in the gaps of secondary forests. The objectives of the present study were to evaluate the effects of gap size, seed availability, and environmental conditions on the seed regeneration potential in temperate secondary forests. It was found that gap formation could favor the invasion of more varieties of species in seed banks, but it also could speed up the turnover rate of seed banks leading to lower seed densities. Seeds of the dominant species, Fraxinus rhynchophylla, were transient in soil and there was a minor and discontinuous contribution of the seed bank to its seedling emergence. For Quercus mongolica, emerging seedling number was positively correlated with seed density in gaps (R = 0.32, P<0.01), especially in medium and small gaps (<500 m2). Furthermore, under canopies, there was a positive correlation between seedling number and seed density of Acer mono (R = 0.43, P<0.01). Gap formation could promote seedling emergence of two gap-dependent species (i.e., Q. mongolica and A. mono), but the contribution of seed banks to seedlings was below 10% after gap creation. Soil moisture and temperature were the restrictive factors controlling the seedling emergence from seeds in gaps and under canopies, respectively. Thus, the regeneration potential from seed banks is limited after gap formation. PMID:22745771

  19. Experimental investigations into capability of terahertz surface plasmons to bridge macroscopic air gaps.

    PubMed

    Gerasimov, V V; Knyazev, B A; Nikitin, A K; Zhizhin, G N

    2015-12-28

    Results of experimental and theoretical studies of the capability of terahertz surface plasmons (SPs) to cross macroscopic air gaps in a substrate (or between substrates) with admissible losses are presented. SPs were launched with quasi-cw free-electron laser radiation with 130 μm wavelength (λ). We managed to detect SPs passing across gaps as wide as 100 mm (or about 10(3)⋅λ), which is very promising for development of terahertz SP circuitry. The phenomenon was harnessed for splitting an SP beam into two new ones, guided by their own individual plane-surface substrates. PMID:26832009

  20. A barometric pressure sensor based on the air-gap scale effect in a cantilever

    NASA Astrophysics Data System (ADS)

    Minh-Dung, Nguyen; Takahashi, Hidetoshi; Uchiyama, Takeshi; Matsumoto, Kiyoshi; Shimoyama, Isao

    2013-09-01

    The most common structure for a conventional barometric pressure sensor consists of a vacuum-sealed cavity and a diaphragm. However, we hypothesize that a simple structure with an unsealed cavity and an ultra-thin cantilever can provide more sensitive measurements. We produced a 300-nm-thick cantilever with a small spring constant, which made the cantilever sensitive to low pressures. We demonstrated that miniaturizing the air-gap of the cantilever enables the sensor to measure barometric pressure changes at a low pressure change rate with a high resolution, which was 1 Pa at 0.05 Hz, and for a gap size of 1.7 μm.

  1. 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. PMID:24324250

  2. Band gap of two-dimensional fiber-air photonic crystals

    NASA Astrophysics Data System (ADS)

    Yang, Shu; Li, Masha

    2016-04-01

    A two-dimensional photonic crystal (PC) composed of textile fiber and air is initially discussed in this paper. Textile materials are so called soft materials, which are different from the previous PCs composed of rigid materials. The plain wave expansion method is used to calculate band structure of different PCs by altering component properties or structural parameters. Results show that the dielectric constant of textile fibers, fiber filling ratio and lattice arrangement are effective factors which influence PCs' band gap. Yet lattice constant and fiber diameter make inconspicuous influence on the band gap feature.

  3. 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

  4. Induced membrane formation in a case of infected gap nonunion of radius: Case report

    PubMed Central

    Ahmad, Shameem; Kalra, Mukesh; Selvamari, Mariappan

    2013-01-01

    Infected gap nonunion in long bone fractures is a common problem seen in our setup after compound injuries. Treatment options are limited such as Ilizarov ring fixation with bone transport, vascularised bone graft etc. These techniques require expertise and are associated with their own morbidity and complications. A novel technique called as induced membrane formation, is used to bridge a gap nonunion of more than 5 cm using bone cement as a spacer in first stage and autologous cancellous bone graft to fill the gap once infection is healed along with a bridging plate in second stage. PMID:26403556

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

    DOE PAGESBeta

    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.

  6. The measurement of water vapour transfer rate through clothing system with air gap between layers

    NASA Astrophysics Data System (ADS)

    Oh, Ae-Gyeong

    2008-02-01

    The experiments described in this paper are designed to test the water vapour transfer rates through outdoor clothing system with air gap between layers under conditions more closely actual wear. It was adopted distance of 5 mm to ensure no disturbance of the air gap thickness between layers throughout the measurement period with all fabrics. The results have indicated that the water vapour transfer rates of clothing system decrease very slightly with time, it is shown that they approached nearly equilibrium state throughout the experiment. It is revealed that the water vapour transfer rates of the clothing system were ordered into groups determined by the type of waterproof breathable fabric as a shell layer being ordered.

  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. Gap formation and its consequence in the evolution of SMBHs binaries in galaxy mergers

    NASA Astrophysics Data System (ADS)

    del Valle, L.; Escala, A.

    2015-11-01

    Motivated by the theoretical and observational evidence that after a major merger of gas-rich galaxies a massive gaseous disk with a SMBH binary will be formed in the nuclear region of the remnant, we study the interaction between an unequal mass binary and an isothermal circumbinary disk. We focus our study in the transport of angular momentum from the binary to the disk and how this transport can result on the formation of a cavity or gap in the gaseous disk. We propose that, for comparable mass binaries, this exchange of angular momentum is driven by the gravitational interaction of the binary and a strong non-axisymmetric density perturbation that is formed in the disk as response to the presence of the gravitational field of the binary. We compare the efficiency of this gravitational torque on extract angular momentum from the binary with the efficiency of redistribution of the extracted angular momentum in the disk to derive a gap-opening criterion. We run a set of SPH simulations of binaries embedded in isothermal gaseous disks to test our gap-opening criterion. We find that our gap-opening criterion successfully predicts in which simulations a gap will form on the disk. We also run simulations of merging galaxies and we apply our criterion to the more real SMBHB-Disk systems that are formed in situ in these simulations. We find that, in the conditions of our galaxy mergers simulations, the formation of a circumbinary gap is unlikely.

  11. 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.

  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. PMID:25796204

  13. 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.

  14. Communicating air quality information: experimental evaluation of alternative formats.

    PubMed

    Johnson, Branden B

    2003-02-01

    A long-running effort in environmental communication is daily publication of a report on local air pollution in many American newspapers based on the Pollutant Standards Index (PSI). A 1998 proposal by the U.S. Environmental Protection Agency (U.S. EPA) to change the PSI prompted a survey experiment with 1,100 adults in Philadelphia, evaluating the proposed change's ability to better inform the populace. The effects of exposure to the old and new versions of the PSI, as well as health cautions and information about groups sensitive to air pollution, were compared with evaluation criteria suggested by Weinstein and Sandman (1993). Sample respondents had strong baseline concerns about air pollution. Descriptors of air quality (e.g., "good; " "unhealthy") were difficult to discriminate, particularly in the New format. Concern rose as hypothetical air pollution levels rose, but the New format (as well as PSI versions without health cautions or sensitive-group information) evoked a sharp discontinuity in concern between below- and above-standard pollution levels. Both Old and New formats reduced concern relative to no provision of PSI information at all, but the New format reduced concern significantly more than the Old version. No PSI format did particularly well at increasing knowledge of air pollution or decreasing intentions to be active outdoors during high pollution, contrary to the agency's aim. Although U.S. EPA has since adopted the new proposal as a national "Air Quality Index" requirement, the experiment's results illuminate the strengths and limitations of the new PSI as a means of informing citizens and motivating them to protect themselves. PMID:12635725

  15. Air Plasma Formation in MHD Slipstream Accelerator for Mercury Lightcraft

    SciTech Connect

    Myrabo, L.N.; Raizer, Y.P.; Surzhikov, S.

    2004-03-30

    This paper investigates the physics of air plasma formation at the entrance of the MHD slipstream accelerator for the 'tractor-beam' Mercury Lightcraft. Two scenarios are analyzed. The first addresses the needs of the minimum power airspike assuming that all the power required for air plasma formation must come from the remote laser beam. The second case considers the constant-focus airspike and assumes that the breakdown criteria is satisfied by an on-board auxiliary source (e.g., electric discharge, RF source, microwave source, or E-beam)

  16. Air Plasma Formation in MHD Slipstream Accelerator for Mercury Lightcraft

    NASA Astrophysics Data System (ADS)

    Myrabo, L. N.; Raizer, Y. P.; Surzhikov, S.

    2004-03-01

    This paper investigates the physics of air plasma formation at the entrance of the MHD slipstream accelerator for the `tractor-beam' Mercury Lightcraft. Two scenarios are analyzed. The first addresses the needs of the minimum power airspike assuming that all the power required for air plasma formation must come from the remote laser beam. The second case considers the constant-focus airspike and assumes that the breakdown criteria is satisfied by an on-board auxiliary source (e.g., electric discharge, RF source, microwave source, or E-beam).

  17. 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.

  18. 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

    ..., or GAP regarding air quality? 285.659 Section 285.659 Mineral Resources BUREAU OF OCEAN ENERGY MANAGEMENT, REGULATION, AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE RENEWABLE ENERGY ALTERNATE USES...? (a) You must comply with the Clean Air Act (42 U.S.C. 7409) and its implementing...

  19. 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

    ... implementing regulations as promulgated by the EPA under 40 CFR part 55. (b) For air quality modeling that you..., or GAP regarding air quality? 585.659 Section 585.659 Mineral Resources BUREAU OF OCEAN ENERGY MANAGEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE RENEWABLE ENERGY AND ALTERNATE USES OF EXISTING FACILITIES...

  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

    ... implementing regulations as promulgated by the EPA under 40 CFR part 55. (b) For air quality modeling that you..., or GAP regarding air quality? 585.659 Section 585.659 Mineral Resources BUREAU OF OCEAN ENERGY MANAGEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE RENEWABLE ENERGY AND ALTERNATE USES OF EXISTING FACILITIES...

  1. 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

    ... implementing regulations as promulgated by the EPA under 40 CFR part 55. (b) For air quality modeling that you..., or GAP regarding air quality? 585.659 Section 585.659 Mineral Resources BUREAU OF OCEAN ENERGY MANAGEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE RENEWABLE ENERGY AND ALTERNATE USES OF EXISTING FACILITIES...

  2. Wave propagation in single column woodpile phononic crystals: Formation of tunable band gaps

    NASA Astrophysics Data System (ADS)

    Kim, Eunho; Yang, Jinkyu

    2014-11-01

    We study the formation of frequency band gaps in single column woodpile phononic crystals composed of orthogonally stacked slender cylinders. We focus on investigating the effect of the cylinders' local vibrations on the dispersion of elastic waves along the stacking direction of the woodpile phononic crystals. We experimentally verify that their frequency band structures depend significantly on the bending resonant behavior of unit cells. We propose a simple theoretical model based on a discrete element method to associate the behavior of locally resonant cylindrical rods with the band gap formation mechanism in woodpile phononic crystals. The findings in this work imply that we can achieve versatile control of frequency band structures in phononic crystals by using woodpile architectures. The woodpile phononic crystals can form a new type of vibration filtering devices that offer an enhanced degree of freedom in manipulating stress wave propagation.

  3. 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

  4. Mist Formation in Heat Exchanger of Air-Conditioners

    NASA Astrophysics Data System (ADS)

    Ishihara, Isao; Matsumoto, Ryosuke; Shibata, Yutaka

    The mist formation is found occasionally at the outlet of the air-conditioner, especially in the high temperature and high humidity environment. When the condensation takes place, a certain degree of the super-saturation is needed. Some researchers introduced the critical saturation model1-3) into the condensation process concerning with the super-saturation. However, under the ordinary environmental conditions where air-conditioners are installed, there are many nuclei for the phase change such as dusts in the humid air. They may offer the trigger to condense; that is to form the mist. In this research, with taking into account the super-saturation depending on the diameter of foreign nucleus, the mist formation is numerically predicted by solving boundary layer equations for the cold parallel plate channel simulating the heat exchanger of air-conditioner with the slit fins. The effects of the humidity and channel dimension on the mist formation rate and on heat and mass transfer are investigated. In addition, the numerical results are compared with those for the plate channel reported previously.

  5. Air-gap gating of MgZnO/ZnO heterostructures

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    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.

  6. 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.

  7. High performance of InGaN light-emitting diodes by air-gap/GaN distributed Bragg reflectors.

    PubMed

    Ryu, Jae Hyoung; Kim, Hee Yun; Kim, Hyun Kyu; Katharria, Yashpal Singh; Han, Nam; Kang, Ji Hye; Park, Young Jae; Han, Min; Ryu, Beo Deul; Ko, Kang Bok; Suh, Eun-Kyoung; Hong, Chang-Hee

    2012-04-23

    The effect of air-gap/GaN DBR structure, fabricated by selective lateral wet-etching, on InGaN light-emitting diodes (LEDs) is investigated. The air-gap/GaN DBR structures in LED acts as a light reflector, and thereby improve the light output power due to the redirection of light into escape cones on both front and back sides of the LED. At an injection current of 20 mA, the enhancement in the radiometric power as high as 1.91 times as compared to a conventional LED having no DBR structure and a far-field angle as low as 128.2° are realized with air-gap/GaN DBR structures. PMID:22535092

  8. Spontaneous formation of stringlike clusters and smectic sheets for colloidal rods confined in thin wedgelike gaps.

    PubMed

    Maeda, Hideatsu; Maeda, Yoshiko

    2013-08-20

    Monodispersed colloidal rods of β-FeOOH with sizes ranging from 270 to 580 nm in length and 50 to 80 nm in width were synthesized. Narrow wedgelike gaps (0 to 700 nm in height) were formed around the inner bottom edge of the suspension glass cells. Optical microscopic observations revealed the formation of stringlike clusters of the rods and smectic sheets (by spontaneous side-by-side clustering of the strings) in the isotropic phase of the rod suspensions confined in narrow gaps; the electrolyte (HCl) concentrations of the suspensions are 5-40 mM, at which inter-rod interactions are attractive. The strings exhibit different colors that were used to investigate the structures of the strings with the help of interference color theory for thin films. The results are as follows. (1) The rods, lying flat on the gap bottom, are connected side-by-side and stacked upward to form stringlike clusters with different thicknesses depending on the gap height. (2) The stacking numbers (N(sr)) of the rods are estimated to be 1-5. With N(sr) increasing from 2 to 5, the volume fractions (ϕ) of the rods in the strings increased typically from 0.25-0.3 to 0.35-0.42 to reach limiting values (close to the ϕ values of the rods in the bulk smectic phase). (3) Unexpected low-ϕ strings are found in regions with an intermediate height in the gaps. These behaviors of ϕ may be caused by thermal fluctuations of the strings. PMID:23876087

  9. Tunable complete photonic band gap in anisotropic photonic crystal slabs with non-circular air holes using liquid crystals

    NASA Astrophysics Data System (ADS)

    Fathollahi Khalkhali, T.; Bananej, A.

    2016-06-01

    In this study, we analyze the tunability of complete photonic band gap of square and triangular photonic crystal slabs composed of square and hexagonal air holes in anisotropic tellurium background with SiO2 as cladding material. The non-circular holes are infiltrated with liquid crystal. Using the supercell method based on plane wave expansion, we study the variation of complete band gap by changing the optical axis orientation of liquid crystal. Our numerical results show that noticeable tunability of complete photonic band gap can be obtained in both square and triangular structures with non-circular holes.

  10. Long-wave infrared 1 × 2 MMI based on air-gap beneath silicon rib waveguides.

    PubMed

    Wei, Yuxin; Li, Guoyi; Hao, Yinlei; Li, Yubo; Yang, Jianyi; Wang, Minghua; Jiang, Xiaoqing

    2011-08-15

    The undercut long-wave infrared (LWIR) waveguide components with air-gap beneath are analyzed and fabricated on the Si-wafer with simple manufacturing process. A 1 × 2 multimode interference (MMI) splitter based on this structure is presented and measured under the 10.6 μm wavelength experimental setup. The uniformity of the MMI fabricated is 0.76 dB. The relationship among the output power, slab thickness and air-gap width is also fully discussed. Furthermore, undercut straight waveguides based on SOI platform are fabricated for propagation loss evaluation. Ways to reduce the loss are discussed either. PMID:21934942

  11. Fabrication and optical properties of non-polar III-nitride air-gap distributed Bragg reflector microcavities

    SciTech Connect

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

    2013-11-11

    Using the thermal decomposition technique, non-polar III-nitride air-gap distributed Bragg reflector (DBR) microcavities (MCs) with a single quantum well have been fabricated. Atomic force microscopy reveals a locally smooth DBR surface, and room-temperature micro-photoluminescence measurements show cavity modes. There are two modes per cavity due to optical birefringence in the non-polar MCs, and a systematic cavity mode shift with cavity thickness was also observed. Although the structures consist of only 3 periods (top) and 4 periods (bottom), a quality factor of 1600 (very close to the theoretical value of 2100) reveals the high quality of the air-gap DBR MCs.

  12. 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.

  13. GLOBAL CALCULATIONS OF DENSITY WAVES AND GAP FORMATION IN PROTOPLANETARY DISKS USING A MOVING MESH

    SciTech Connect

    Duffell, Paul C.; MacFadyen, Andrew I. E-mail: macfadyen@nyu.edu

    2012-08-10

    We calculate the global quasi-steady state of a thin disk perturbed by a low-mass protoplanet orbiting at a fixed radius using extremely high resolution numerical integrations of Euler's equations in two dimensions. The calculations are carried out using a moving computational domain, which greatly reduces advection errors and allows for much longer time steps than a fixed grid. We calculate the angular momentum flux and the torque density as a function of radius and compare them with analytical predictions. We discuss the quasi-steady state after 100 orbits and the prospects for gap formation by low-mass planets.

  14. The reversed description-experience gap: Disentangling sources of presentation format effects in risky choice.

    PubMed

    Glöckner, Andreas; Hilbig, Benjamin E; Henninger, Felix; Fiedler, Susann

    2016-04-01

    Previous literature has suggested that risky choice patterns in general--and probability weighting in particular--are strikingly different in experience-based as compared with description-based formats. In 2 reanalyses and 3 new experiments, we investigate differences between experience-based and description-based decisions using a parametric approach based on cumulative prospect theory (CPT). Once controlling for sampling biases, we consistently find a reversal of the typical description-experience gap, that is, a reduced sensitivity to probabilities and increased overweighting of small probabilities in decisions from experience as compared with decisions from descriptions. This finding supports the hypothesis that regression to the mean effects in probability estimation are a crucial source of differences between both presentation formats. Further analyses identified task specific information asymmetry prevalent in gambles involving certainty as a third source of differences. We present a novel conceptualization of multiple independent sources of bias that contribute to the description-experience gap, namely sampling biases and task specific information asymmetry on the one hand, and regression to the mean effects in probability estimation on the other hand. PMID:26974209

  15. A class of supported membranes: formation of fluid phospholipid bilayers on photonic band gap colloidal crystals.

    PubMed

    Brozell, Adrian M; Muha, Michelle A; Sanii, Babak; Parikh, Atul N

    2006-01-11

    We report the formation of a new class of supported membranes consisting of a fluid phospholipid bilayer coupled directly to a broadly tunable colloidal crystal with a well-defined photonic band gap. For nanoscale colloidal crystals exhibiting a band gap at the optical frequencies, substrate-induced vesicle fusion gives rise to a surface bilayer riding onto the crystal surface. The bilayer is two-dimensionally continuous, spanning multiple beads with lateral mobilities which reflect the coupling between the bilayer topography and the curvature of the supporting colloidal surface. In contrast, the spreading of vesicles on micrometer scale colloidal crystals results in the formation of bilayers wrapping individual colloidal beads. We show that simple UV photolithography of colloidal crystals produces binary patterns of crystal wettabilities, photonic stopbands, and corresponding patterns of lipid mono- and bilayer morphologies. We envisage that these approaches will be exploitable for the development of optical transduction assays and microarrays for many membrane-mediated processes, including transport and receptor-ligand interactions. PMID:16390122

  16. 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.

  17. Indoor air chemistry: Formation of organic acids and aldehydes

    SciTech Connect

    Zhang, J.; Lioy, P.J. ||; Wilson, W.E.

    1994-12-31

    Laying emphasis on the formation of aldehydes and organic acids, the study has examined the gas-phase reactions of ozone with unsaturated VOCs. The formation of formaldehyde and formic acid was observed for all the three selected unsaturated VOCs: styrene, limonene, and 4-vinylcyclohexene. In addition, benzaldehyde was detected in the styrene-ozone-air reaction system, and acetic acid was also found in limonene-ozone-air system. The study has also examined the gas-phase reactions among formaldehyde, ozone, and nitrogen dioxide and found the formation of formic acid. The nitrate radical was suggested to play an important role in converting formaldehyde into formic acid. Experiments for all the reactions were conducted by using a 4.3 m{sup 3} Teflon chamber. Since the conditions for the reactions were similar to those for indoor environments, the results from the study can be implicated to real indoor situations and can be employed to support the findings and suggestions from the previous studies: certain aldehydes and organic acids could be generated by indoor chemistry.

  18. 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).

  19. Edge-state-dependent tunneling of dipole-exchange spin waves in submicrometer magnetic strips with an air gap

    NASA Astrophysics Data System (ADS)

    Xing, X. J.; Zhang, D.; Li, S. W.

    2012-12-01

    We have investigated the tunneling of dipole-exchange spin waves across an air gap in submicrometer-sized permalloy magnetic strips by means of micromagnetic simulations. The magnetizations beside the gap could form three distinct end-domain states with various strengths of dipolar coupling. Spin-wave tunneling through the gap at individual end-domain states is studied. It is found that the tunneling behavior is strongly dependent on these domain states. Nonmonotonic decay of transmission of spin waves with the increase of the gap width is observed. The underlying mechanism for these behaviors is proposed. The tunneling characteristics of the dipole-exchange spin waves differ essentially from those of the magnetostatic ones reported previously.

  20. 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.

  1. Hereditary mucoepithelial dysplasia: a disease apparently of desmosome and gap junction formation.

    PubMed Central

    Witkop, C J; White, J G; King, R A; Dahl, M V; Young, W G; Sauk, J J

    1979-01-01

    A previously unrecognized autosomal dominant syndrome affecting oral, nasal, vaginal, urethral, anal, bladder, and conjunctival mucosa with cataracts, follicular keratosis, nonscarring alopecia, and terminal lung disease is described in a four-generation kindred of German extraction. Severe photophobia, tearing, and nystagmus in infancy heralds the development of keratitis, corneal vascularization, and lens cataracts. Repeated corneal transplants have failed. Red, periorificial mucosal lesions involving the above structures are noted by 1 year of age and may persist throughout life. Chronic rhinorrhea and repeated upper respiratory infections frequently progress to bilateral pneumonia accompanied by loss of hair, diarrhea, occasional melena, enuresis, pyuria, and hematuria. Spontaneous pneumothorax is frequent, terminating in fibrocystic-type lung disease and cor pulmonale. Women have had repeated abnormal vaginal PAP smears. Histologically the mucosal epithelium shows dyshesion, thinning of the epithelial layer, and dyskeratosis. Mucosal PAP smears show lack of epithelial maturation, cytoplasmic vacuoles and inclusions, and individual cell dyskeratosis. Histochemically there is a lack of cornification and keratinization. Ultrastructural studies show lack of keratohyalin granules, a paucity of desmosomes, intercellular accumulations, cytoplasmic vacuolization, and formation of bands and aggregates of filamentous fibers and structures in the cytoplasm resembling desmosomes and gap junctions. The condition is probably a panepithelial cell defect of desmosomal and gap junction structure most prominently affecting mucosal epithelia associated with an increased susceptibility to a variety of adventitious organisms. Images Fig. 2-5 Fig. 6 Fig. 7 Fig. 8 Fig. 9 Fig. 10 PMID:484550

  2. 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.

  3. 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.

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

    PubMed

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

    2016-07-29

    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. PMID:27517772

  5. Gap formation in a self-gravitating disk and the associated migration of the embedded giant planet

    NASA Astrophysics Data System (ADS)

    Zhang, Hui; Liu, Hui-Gen; Zhou, Ji-Lin; Wittenmyer, Robert A.

    2014-04-01

    We present the results of our recent study on the interactions between a giant planet and a self-gravitating gas disk. We investigate how the disk's self-gravity affects the gap formation process and the migration of the giant planet. Two series of 1-D and 2-D hydrodynamic simulations are performed. We select several surface densities and focus on the gravitationally stable region. To obtain more reliable gravity torques exerted on the planet, a refined treatment of the disk's gravity is adopted in the vicinity of the planet. Our results indicate that the net effect of the disk's self-gravity on the gap formation process depends on the surface density of the disk. We notice that there are two critical values, ΣI and ΣII. When the surface density of the disk is lower than the first one, Σ0 < ΣI, the effect of self-gravity suppresses the formation of a gap. When Σ0 > ΣI, the self-gravity of the gas tends to benefit the gap formation process and enlarges the width/depth of the gap. According to our 1-D and 2-D simulations, we estimate the first critical surface density to be ΣI ≈ 0.8 MMSN. This effect increases until the surface density reaches the second critical value ΣII. When Σ0 > ΣII, the gravitational turbulence in the disk becomes dominant and the gap formation process is suppressed again. Our 2-D simulations show that this critical surface density is around 3.5 MMSN. We also study the associated orbital evolution of a giant planet. Under the effect of the disk's self-gravity, the migration rate of the giant planet increases when the disk is dominated by gravitational turbulence. We show that the migration timescale correlates with the effective viscosity and can be up to 104 yr.

  6. Gap-dependent arrangements of dielectric barrier discharges in open air

    SciTech Connect

    Chu, Hong-Yu; Liou, Bang-Tsui

    2014-08-15

    Investigations of the structural arrangement of the atmospheric filamentary discharges were carried out. By observing the initial discharge events, we find that the surface charge plays a significant role of seeding electrons. The filamentary discharges show ordered and disordered patterns in parallel plates with different gap distances. A critical gap distance for an ordered pattern is found at about 700 μm. The transition of the order-disorder discharge pattern is also confirmed in a wedged-plates setup with a continuous change of gap distance. The bond-orientational function of the structure of the pattern is related to the mutual Coulomb interaction between discharges.

  7. Characteristics of a laser triggered spark gap using air, Ar, CH4, H2, He, N2, SF6, and Xe

    NASA Astrophysics Data System (ADS)

    Kimura, W. D.; Kushner, M. J.; Seamans, J. F.

    1988-03-01

    A KrF discharge laser (248 nm) has been used to laser trigger, by volume preionization, a spark gap switch (38-65 kV, >10 kA, 100 ns pulse duration) filled with 20 different gas mixtures using various combinations of air, Ar, CH4, H2, He, N2 SF6, and Xe. A pulsed laser interferometer is used to probe the spark column. Characteristics studied include the internal structure of the column, the arc expansion rate, and evidence of any photoionization precursor effect. Our results show that the rate of arc expansion varies depending on the average molecular weight of the mixtures. In this experiment, pure H2 has the highest rate (≊9.5×105 cm/s) and air has one of the lowest (≊7×105 cm/s) for the same hold-off voltage. A computer model of the spark column formation is able to predict most of the structure observed in the arcs, including the effect of mixing gases with widely different molecular weights. The work suggests that, under proper circumstances, the spark gap switch performance may be improved by using gases lighter than conventional switch gases such as SF6.

  8. Experimental Study on Branch and Diffuse Type of Streamers in Leader Restrike of Long Air Gap Discharge

    NASA Astrophysics Data System (ADS)

    Chen, She; Zeng, Rong; Zhuang, Chijie; Zhou, Xuan; Ding, Yujian

    2016-03-01

    One of the main problems in the Ultra High Voltage (UHV) transmission project is to choose the external insulation distance, which requires a deep understanding of the long air gap discharge mechanism. The leader-streamer propagation is one of most important stages in long air gap discharge. In the conductor-tower lattice configuration, we have measured the voltage, the current on the high voltage side and the electric field in the gap. While the streamer in the leader-streamer system presented a conical or hyperboloid diffuse shape, the clear branch structure streamer in front of the leader was firstly observed by a high speed camera in the experiment. Besides, it is found that the leader velocity, width and injected charge for the branch type streamer are greater than those of a diffuse type. We propose that the phenomenon results from the high humidity, which was 15.5-16.5 g/m3 in our experiment. supported by the Fund of the National Priority Basic Research of China (2011CB209403) and National Natural Science Foundation of China (Nos. 51325703, 51377094, 51577098)

  9. The influence of the sand-dust environment on air-gap breakdown discharge characteristics of the plate-to-plate electrode

    NASA Astrophysics Data System (ADS)

    He, Bo; Zhang, Gang; Chen, Bangfa; Gao, Naikui; Li, Yaozhong; Peng, Zongren; Jin, Haiyun

    2010-03-01

    The experiments of plane-plane gap discharge was carried out in an environment of artificial sandstorm. By comparing and analyzing the differences in gap breakdown voltage between the sand & dust environment and clean air, some problems were investigated, such as effects of wind speed and particle concentration on the breakdown voltage, differences of gap discharge characteristics between the dust & sand medium and the clean air medium. The results showed that compared with the clean air environment, the dust & sand environment had a decreased gap breakdown voltage. The longer the gap distance, the greater the voltage drop; the breakdown voltage decreased with the increase of particle concentration in flow. With the increase of wind speed, the breakdown voltage decreased at the beginning and rose afterwards. The results of the paper may helpful for further research regarding the unidentified flashover and external insulation characteristics of the HV power grid in the dust & sand environment.

  10. 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 [...

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Rab3Gap1 mediates exocytosis of Claudin-1 and tight junction formation during epidermal barrier acquisition

    PubMed Central

    Youssef, G.; Gerner, L.; Naeem, A.S.; Ralph, O.; Ono, M.; O’Neill, C.A.; O’Shaughnessy, R.F.L.

    2013-01-01

    Epidermal barrier acquisition during late murine gestation is accompanied by an increase in Akt kinase activity and cJun dephosphorlyation. The latter is directed by the Ppp2r2a regulatory subunit of the Pp2a phosphatase. This was accompanied by a change of Claudin-1 localisation to the cell surface and interaction between Occludin and Claudin-1 which are thought to be required for tight junction formation. The aim of this study was to determine the nature of the barrier defect caused by the loss of AKT/Ppp2r2a function. There was a paracellular barrier defect in rat epidermal keratinocytes expressing a Ppp2r2a siRNA. In Ppp2r2a knockdown cells, Claudin-1 was located to the cytoplasm and its expression was increased. Inhibiting cJun phosphorylation restored barrier function and plasma membrane localisation of Claudin-1. Expression of the Rab3 GTPase activating protein, Rab3Gap1, was restored in Ppp2r2a siRNA cells when cJun phosphorylation was inhibited. During normal mouse epidermal development, Claudin-1 plasma membrane localisation and Rab3Gap1 cell surface expression were co-incident with Akt activation in mouse epidermis, strongly suggesting a role of Rab3Gap1 in epidermal barrier acquisition. Supporting this hypothesis, siRNA knockdown of Rab3Gap1 prevented plasma membrane Claudin-1 expression and the formation of a barrier competent epithelium. Replacing Rab3Gap1 in Ppp2r2a knockdown cells was sufficient to rescue Claudin-1 transport to the cell surface. Therefore these data suggest Rab3Gap1 mediated exocytosis of Claudin-1 is an important component of epidermal barrier acquisition during epidermal development. PMID:23685254

  17. Qualitative SEM/EDS analysis of microleakage and apical gap formation of adhesive root-filling materials

    PubMed Central

    SOUZA, Soraia de Fátima Carvalho; FRANCCI, Carlos; BOMBANA, Antonio C.; KENSHIMA, Silvia; BARROSO, Lúcia P.; D'AGOSTINO, Liz Z.; LOGUERCIO, Alessandro D.

    2012-01-01

    Objective The aim of this study was to compare the correspondence between gap formation and apical microleakage in root canals filled with epoxy resin-based (AH Plus) combined or not with resinous primer or with a dimethacrylate-based root canal sealer (Epiphany). Material and Methods Thirty-nine lower single-rooted human premolars were filled by the lateral condensation technique (LC) and immersed in a 50-wt% aqueous silver nitrate solution at 37ºC (24 h). After longitudinal sectioning, epoxy resin replicas were made from the tooth specimens. Both the replicas and the specimens were prepared for scanning electron microscopy (SEM). The gaps were observed in the replicas. Apical microleakage was detected in the specimens by SEM/energy dispersive spectroscopy (SEM/EDS). The data were analyzed statistically using an Ordinal Logistic Regression model and Analysis of Correspondence (α=0.05). Results Epiphany presented more regions containing gaps between dentin and sealer (p<0.05). There was correspondence between the presence of gaps and microleakage (p<0.05). Microleakage was similar among the root-filling materials (p>0.05). Conclusions The resinous primer did not improve the sealing ability of AH Plus sealer and the presence of gaps had an effect on apical microleakage for all materials. PMID:22858699

  18. Threshold for formation of atom-photon bound states in a coherent photonic band-gap reservoir

    NASA Astrophysics Data System (ADS)

    Wu, Yunan; Wang, Jing; Zhang, Hanzhuang

    2016-05-01

    We study the threshold for the formation of atom-photon bound (APB) states from a two-level atom embedded in a coherent photonic band-gap (PBG) reservoir. It is shown that the embedded position of the atom plays an important role in the threshold. By varying the atomic embedded position, a part of formation range of APB states can be moved from inside to outside the band gap. The direct link between the steady-state entanglement and APB states is also investigated. We show that the values of entanglement between reservoir modes reflect the amount of bounded energy caused by APB states. The feasible experimental systems for verifying the above phenomena are discussed. Our results provide a clear clue on how to form and control APB states in PBG materials.

  19. Band gap shift in the indium-tin-oxide films on polyethylene napthalate after thermal annealing in air

    NASA Astrophysics Data System (ADS)

    Han, H.; Mayer, J. W.; Alford, T. L.

    2006-10-01

    Indium-tin-oxide (ITO) thin films on polyethylene napthalate (PEN) with high carrier concentration (˜1021/cm3) have been grown by electron-beam deposition without the introduction of oxygen into the chamber. The electrical properties of the ITO films (such as, carrier concentration, electrical mobility, and resistivity) abruptly changed after annealing in the air atmospheres. In addition, optical transmittance and optical band gap values significantly changed after heat treatment. The optical band gap narrowing behavior is observed in the as-deposited sample because of impurity band and heavy carrier concentration. The influence of annealing in air on the electrical and optical properties of ITO/PEN samples can be explained by the change in the free electron concentration, which is evaluated in terms of the oxygen content. Rutherford backscattering spectrometry and x-ray photoelectron spectroscopy analyses are used to determine the oxygen content in the film. Hall effect measurements are used to determine the dependence of electrical properties on oxygen content.

  20. 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.

  1. Novel method for Ag colloidal cluster formation by laser ablation at the air-liquid interface

    NASA Astrophysics Data System (ADS)

    Nishi, Teppei; Akimoto, Yusuke; Takahashi, Naoko; Kitazumi, Kosuke; Kajiya, Shuji; Watanabe, Yoshihide

    2015-09-01

    We report a novel method for formation of sub-nanoclusters by laser ablation at the air-liquid interface. The density of plasma induced by laser ablation at the air-liquid interface should be lower than that produced by laser ablation in liquid. In the lower density plasma, the produced clusters rarely grow or aggregate into larger clusters because the collision probability is low, resulting in the formation of small clusters. Ag sub-nanoclusters were observed by electrospray ionization mass spectrometry (ESI-MS) and X-ray photoelectron spectroscopy (XPS). These results show that low-density plasma can be applied to small-cluster formation and that laser ablation at the air-liquid interface produces a good reactive field for the formation of sub-nanoclusters. Our results highlight the importance of low-density plasma induced at the air-liquid interface for sub-nanocluster formation.

  2. Gap Formations in Simulations of Shpb Tests on Elastic Materials Soft in Shear

    NASA Astrophysics Data System (ADS)

    Raftenberg, M. N.; Scheidler, M. J.

    2009-12-01

    The LS-DYNA code was applied to split Hopkinson pressure bar tests on a material at least two orders of magnitude stiffer in dilatation than in shear. Two constitutive models were applied, linear elasticity and a compressible form of Mooney-Rivlin elasticity. The latter was fitted to data from ballistic gelatin. The incident and transmission bars were aluminum. The nominal strain rate was 2500/s. Gaps appeared at the interfaces between the specimen and both bars. Unloading of the specimen and bars accompanied these gaps. The input-velocity rise time was varied to observe pulse shaping effects. Mesh sensitivity and contact-parameter sensitivity studies were performed.

  3. Circumjovian Disk Clearing After Gap-Opening and the Formation of a Partially Differentiated Callisto

    NASA Technical Reports Server (NTRS)

    Mosqueira, I.; Estrada, P. R.; Cuzzi, J.; Squyres, S. W.

    2001-01-01

    We look into the possibility that Callisto's accretional history straddled the time during which Jupiter opened a gap in the solar nebula and occurred over an extended period from a very extended very low density disk. Additional information is contained in the original extended abstract.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. Estimation of Minimal Breakdown Point in a GaP Plasma Structure and Discharge Features in Air and Argon Media

    NASA Astrophysics Data System (ADS)

    Kurt, H. Hilal; Tanrıverdi, Evrim

    2016-08-01

    We present gas discharge phenomena in argon and air media using a gallium phosphide (GaP) semiconductor and metal electrodes. The system has a large-diameter ( D) semiconductor and a microscaled adjustable interelectrode gap ( d). Both theoretical and experimental findings are discussed for a direct-current (dc) electric field ( E) applied to this structure with parallel-plate geometry. As one of the main parameters, the pressure p takes an adjustable value from 0.26 kPa to 101 kPa. After collection of experimental data, a new theoretical formula is developed to estimate the minimal breakdown point of the system as a function of p and d. It is proven that the minimal breakdown point in the semiconductor and metal electrode system differs dramatically from that in metal and metal electrode systems. In addition, the surface charge density σ and spatial electron distribution n e are calculated theoretically. Current-voltage characteristics (CVCs) demonstrate that there exist certain negative differential resistance (NDR) regions for small interelectrode separations (i.e., d = 50 μm) and low and moderate pressures between 3.7 kPa and 13 kPa in Ar medium. From the difference of currents in CVCs, the bifurcation of the discharge current is clarified for an applied voltage U. Since the current differences in NDRs have various values from 1 μA to 7.24 μA for different pressures, the GaP semiconductor plasma structure can be used in microwave diode systems due to its clear NDR region.

  10. Single micro-channel formation in a gap between probe electrodes by freezing an aqueous electrolyte.

    PubMed

    Arai, Yuta; Harada, Makoto; Okada, Tetsuo

    2014-01-01

    A size-tunable micro-channel is fabricated in a gap between two probe electrodes by freezing aqueous KCl. The channel has been characterized by resistance measurements and channel blocking by resistive particles. The channel size can be varied by the temperature even after the preparation of the channel. The channel is potentially useful not only for size-selective particle counting but also for the size-selective separation or filtration of particles and macromolecules. PMID:25382037

  11. Influence of Interface Structure on Chemical Etching Process for Air Gap of Microelectromechanical System Based on Surface Micromachining

    NASA Astrophysics Data System (ADS)

    Yoon, Young; Kim, Joon; Polla, Dennis.; Shin, Young

    1998-12-01

    This paper analyses the problems posed by the interface structure during chemical etching by Hydro-fluoric (HF) acid for creating air gaps in microelectromechnical system (MEMS) devices using PZT(53/47) films and surface micromachining techniques. In order to investigate the influence of interface structure on the HF chemical etching process, Pt/PZT/Pt/Ti/TiO2/polysilicon/Si3N4/PSG/Si (Samples A and C) and Pt/PZT/RuO2/Ru/Si3N4/PSG/Si (Sample B) structures were fabricated. These structures are selected for a microcantilever beam and/or an uncooled IR detectors fabricated with PZT piezoelectric/pyroelectric films based on the surface micromachining technique. Both need etching for the removal of phosphor silicate glass (PSG) to create an air gap. If the devices had a poor interface structure, they would fail during the HF chemical etching process because the poor interface structure would act as a kind of penetration path for etching acid leading to unwanted etching. Therefore, it is very important to investigate the interface structure to fabricate efficient MEMS devices. In this study two different solutions have been suggested to improve the interface structure. The first is post thermal annealing at 900°C for 30 min. after deposition of polycrystalline silicon for sample A. Secondly, a RuO2/Ru hybrid electrode was deposited on Si3N4 directly instead of on the Pt/Ti/TiO2/Polysilicon electrode, which has Pt/PZT/RuO2/Ru/Si3N4/PSG/Si as the device structure. These two solutions suggest that a dense interface structure increases enhances of success of the chemical etching process of MEMS devices fabricated using PZT films and surface micromachining techniques.

  12. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    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/cm2 (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 (LP12,1), 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.

  14. 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.

  15. 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..

  16. Similarity laws for cathode-directed streamers in gaps with an inhomogeneous field at elevated air pressures

    SciTech Connect

    Bolotov, O. V.; Golota, V. I.; Kadolin, B. B.; Karas', V. I.; Ostroushko, V. N.; Zavada, L. M.; Shulika, A. Yu.

    2010-11-15

    Results are presented from experimental studies of cathode-directed streamers in the gap closure regime without a transition into spark breakdown. Spatiotemporal, electrodynamic, and spectroscopic characteristics of streamer discharges in air at different pressures were studied. Similarity laws for streamer discharges were formulated. These laws allow one to compare the discharge current characteristics and streamer propagation dynamics at different pressures. Substantial influence of gas photoionization on the deviations from the similarity laws was revealed. The existence of a pressure range in which the discharges develop in a similar way was demonstrated experimentally. In particular, for fixed values of the product pd and discharge voltage U, the average streamer velocity is also fixed. It is found that, although the similarity laws are violated in the interstreamer pause of the discharge, the average discharge current and the product of the pressure and the streamer repetition period remain the same at different pressures. The radiation spectra of the second positive system of nitrogen (the C{sup 3{Pi}}{sub u}-B{sup 3{Pi}}{sub g} transitions) in a wavelength range of 300-400 nm at air pressures of 1-3 atm were recorded. It is shown that, in the entire pressure range under study, the profiles of the observed radiation bands practically remain unchanged and the relative intensities of the spectral lines corresponding to the {sup 3{Pi}}{sub u}-B{sup 3{Pi}}{sub g} transitions are preserved.

  17. Formation of accurate 1-nm gaps using the electromigration method during metal deposition

    NASA Astrophysics Data System (ADS)

    Naitoh, Yasuhisa; Wei, Qingshuo; Mukaida, Masakazu; Ishida, Takao

    2016-03-01

    We investigate the origin of fabricated nanogap width variations using the electromigration method during metal deposition. This method also facilitates improved control over the nanogap width. A large suppression in the variation is achieved by sample annealing at 373 K during the application of bias voltages for electromigration, which indicates that the variation is caused by structural changes. This electromigration method during metal deposition for the fabrication of an accurate 1-nm gap electrode is useful for single-molecule-sized electronics. Furthermore, it opens the door for future research on integrated sub-1-nm-sized nanogap devices.

  18. Sequential formation of multiple lattice gap solitons in defocusing photovoltaic-photorefractive crystals

    NASA Astrophysics Data System (ADS)

    Hui, Juanli; Lu, Keqing; Zhao, Chong; Gao, Lixu; Chen, Weijun

    2016-05-01

    We show that an odd- or even-numbered sequence of multiple gap solitons (MGSs) supported by optical lattices imprinted in defocusing photovoltaic-photorefractive (PP) crystals is possible. The side lobes of MGSs are the small intensity, which can be controlled by changing the propagation constant. The lobes of MGSs are the same intensity except for the side lobes. The existence domain of MGSs decreases with decreasing the lattice depth and vanishes when the lattice depth decreases to below a certain threshold. The stability of MGSs has been investigated numerically and it has been found that they are stable.

  19. Gap junctions composed of connexins 41.8 and 39.4 are essential for colour pattern formation in zebrafish

    PubMed Central

    Irion, Uwe; Frohnhöfer, Hans Georg; Krauss, Jana; Çolak Champollion, Tuǧba; Maischein, Hans-Martin; Geiger-Rudolph, Silke; Weiler, Christian; Nüsslein-Volhard, Christiane

    2014-01-01

    Interactions between all three pigment cell types are required to form the stripe pattern of adult zebrafish (Danio rerio), but their molecular nature is poorly understood. Mutations in leopard (leo), encoding Connexin 41.8 (Cx41.8), a gap junction subunit, cause a phenotypic series of spotted patterns. A new dominant allele, leotK3, leads to a complete loss of the pattern, suggesting a dominant negative impact on another component of gap junctions. In a genetic screen, we identified this component as Cx39.4 (luchs). Loss-of-function alleles demonstrate that luchs is required for stripe formation in zebrafish; however, the fins are almost not affected. Double mutants and chimeras, which show that leo and luchs are only required in xanthophores and melanophores, but not in iridophores, suggest that both connexins form heteromeric gap junctions. The phenotypes indicate that these promote homotypic interactions between melanophores and xanthophores, respectively, and those cells instruct the patterning of the iridophores. DOI: http://dx.doi.org/10.7554/eLife.05125.001 PMID:25535837

  20. 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.

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

    DOE PAGESBeta

    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

  2. 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.

  3. 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.

  4. The role of deep centers in formation of dosimetric properties of wide-gap materials

    NASA Astrophysics Data System (ADS)

    Nikiforov, S. V.; Kortov, V. S.

    2014-11-01

    The direct and indirect methods of experimental detection of deep traps in wide-gap insulators are described. The experimentally observed effects of influence of deep traps with different nature on luminescent and dosimetric properties of materials are analyzed. It is established that the most wide-spread and well-studied effects are the sensitization and superlinearity of dose response. They are interpreted in terms of the kinetic model of competitive electron traps. Taking into account the temperature dependence of capture probability by deep traps in this model allows one to explain some new effects associated with luminescence thermal quenching. The luminescence model of Al2O3:C single crystal is described. In this model the temperature dependence of competitive interaction between the main and deep traps is caused by thermal ionization of excited states of F-centers.

  5. Field experiments yield new insights into gas exchange and excess air formation in natural porous media

    NASA Astrophysics Data System (ADS)

    Klump, Stephan; Tomonaga, Yama; Kienzler, Peter; Kinzelbach, Wolfgang; Baumann, Thomas; Imboden, Dieter M.; Kipfer, Rolf

    2007-03-01

    Gas exchange between seepage water and soil air within the unsaturated and quasi-saturated zones is fundamentally different from gas exchange between water and gas across a free boundary layer, e.g., in lakes or rivers. In addition to the atmospheric equilibrium fraction, most groundwater samples contain an excess of dissolved atmospheric gases which is called "excess air". Excess air in groundwater is not only of crucial importance for the interpretation of gaseous environmental tracer data, but also for other aspects of groundwater hydrology, e.g., for oxygen availability in bio-remediation and in connection with changes in transport dynamics caused by the presence of entrapped air bubbles. Whereas atmospheric solubility equilibrium is controlled mainly by local soil temperature, the excess air component is characterized by the (hydrostatic) pressure acting on entrapped air bubbles within the quasi-saturated zone. Here we present the results of preliminary field experiments in which we investigated gas exchange and excess air formation in natural porous media. The experimental data suggest that the formation of excess air depends significantly on soil properties and on infiltration mechanisms. Excess air was produced by the partial dissolution of entrapped air bubbles during a sprinkling experiment in fine-grained sediments, whereas similar experiments conducted in coarse sand and gravel did not lead to the formation of excess air in the infiltrating water. Furthermore, the experiments revealed that the noble gas temperatures determined from noble gases dissolved in seepage water at different depths are identical to the corresponding in situ soil temperatures. This finding is important for all applications of noble gases as a paleotemperature indicator in groundwater since these applications are always based on the assumption that the noble gas temperature is identical to the (past) soil temperature.

  6. 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

  7. 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

    2016-01-01

    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

  8. 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.

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

    NASA Astrophysics Data System (ADS)

    Hwang, Don-Ha; Han, Sang-Bo; Woo, Byung-Chul; Sun, Jong-Ho; Kang, Dong-Sik; 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 1.3T. On the other hand, the eccentric air-gap condition displays about 1.1T at 60° and 1.6T at 240°. A difference of flux density is 0.5T in the abnormal condition, whereas no difference is detected in the normal motor. In the broken rotor bar conditions, the flux densities at 65° and 155° are about 0.4 T and 0.8T, 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.

  10. 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

  11. Subnanometer poly-silicon gap structure formation: Comparison study between size expansion and size reduction

    NASA Astrophysics Data System (ADS)

    Hashim, U.; Nazwa, T.; Dhahi, Th. S.

    2012-06-01

    This study describes the comparison among the three fabrication methods of an array of poly-silicon nanogap structures. The three different methods are size expansion technique (SET), size reduction technique (SRT) and e-beam lithography (EBL) technique. Generally, SRT involves the breaking of the primarily pattern with no gap structure into nanogap scale. Conversely, SET engages in the process of enhancing the initially microgap pattern into nanogap scale. EBL refers to a lithographic process that uses a focused beam of electrons to form the circuit patterns needed for material deposition on or removal from the wafer. Using conventional photolithography, a procedure to fabricate poly-silicon nanogap structure on the wafer scale is designed. The nanogap (NG) fabrication procedure is based on the standard CMOS technology follows by employing both methods respectively. The lateral nanogap is introduced in the fabrication process using poly-silicon as an anode electrode. The similarity and distinction will be highlighted for each particular process involved in the fabrication of nanogap structures. The simple least-cost method does not require complicated nanolithography method of fabrication but it is still possible to measure the electrical properties of a single molecule. On top of that, these techniques can be applied extensively to different designs of nanogap structure down to several nanometer levels of dimensions. The innovative method reported here can easily produce a nanogap electrode in a reproducible manner.

  12. 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.

  13. Experimental observation of phonons as spectators in FeSi electronic gap formation

    NASA Astrophysics Data System (ADS)

    Parshin, P. P.; Chumakov, A. I.; Alekseev, P. A.; Nemkovski, K. S.; Perßon, J.; Dubrovinsky, L.; Kantor, A.; Rüffer, R.

    2016-02-01

    The evolution of a phonon spectrum in a narrow-gap semiconductor FeSi was investigated in a wide range of temperatures (46 K ≤T ≤ 297 K, P =0.1 MPa) and pressures (0.1 MPa ≤P ≤ 43 GPa, T =297 K) using nuclear inelastic scattering of synchrotron radiation with the energy resolution 0.53 meV. Decreasing temperature as well as increasing pressure causes a strong reorganization of the phonon spectrum manifested in splitting and shifts of the phonon peaks. The phonon spectra measured under the temperature and pressure conditions corresponding to the same unit cell volume reveal nearly complete matching. On the contrary, the spectra measured under the conditions of the equal mean-square atomic displacements differ drastically. These observations suggest that the transformation of the electronic spectrum of FeSi is controlled predominantly by the change of the unit cell volume. The corresponding changes of the interatomic forces and the resulting modification of the phonon spectrum appear as the direct consequence of this transformation.

  14. 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.

  15. 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

  16. 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.

  17. 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).

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

    PubMed

    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

  19. 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

  20. The role of magnetism in the formation of the two-phase miscibility gap in β Cu-Al-Mn

    NASA Astrophysics Data System (ADS)

    Lanzini, Fernando; Alés, Alejandro

    2015-12-01

    A theoretical study of the ground state properties of alloys with compositions along the pseudobinary line Cu3Al-Cu2AlMn is presented. Cohesive energies, lattice parameters and magnetic moments of the two limiting compounds and three intermediate compositions are calculated by means of density functional theory. In order to evaluate the role of magnetism, both the spin-polarized (SP) and the non spin-polarized (NSP) cases have been considered. It is shown that magnetism plays a central role on the stabilization of the L21 crystal structure in Cu2AlMn, and in the formation of the miscibility gap in Cu3Al-Cu2AlMn. The considerable lattice mismatch between the end compounds can be attributed also to magnetic effects.

  1. Evidence for Air-Seeding: Watching the Formation of Embolism in Conifer Xylem

    PubMed Central

    Mayr, S.; Kartusch, B.; Kikuta, S.

    2016-01-01

    Water transport in plants is based on a metastable system as the xylem “works” at negative water potentials (ψ). At critically low ψ, water columns can break and cause embolism. According to the air-seeding hypothesis, this occurs by air entry via the pits. We studied the formation of embolism in dehydrating xylem sections of Juniperus virginiana (Cupressaceae), which were monitored microscopically and via ultrasonic emission analyses. After replacement of water by air in outer tracheid layers, a complex movement of air-water menisci into tracheids was found. With decreasing ψ, pits started to aspirate and the speed of menisci movements increased. In one experiment, an airseeding event could be detected at a pit. The onset of ultrasonic activity was observed when pits started to close, and ultrasonic emission ceased at intense dehydration. Experiments clearly indicated that predictions of the air-seeding hypothesis are correct: At low ψ, pit mechanisms to prevent air entry failed and air spread into tracheids. ψ fluctuations caused complex movements of air-water menisci and pits, and at low ψ, air-seeding caused ultrasonic emissions. Main insights are presented in a video.

  2. 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.

  3. 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.

  4. Determinants of Change in Air-Bone Gap and Bone Conduction in Patients Operated on for Chronic Otitis Media

    PubMed Central

    Wiatr, Maciej; Wiatr, Agnieszka; Składzień, Jacek; Stręk, Paweł

    2015-01-01

    Background Middle ear surgery aims to eliminate pathology from the middle ear, improve drainage and ventilation of the postoperative cavity, and reconstruct the tympanic membrane and ossicles. The aim of this work is to define the factors that affect ABG (air-bone gap) and bone conduction in the patients operated on due to chronic otitis media. Material/Methods A prospective analysis of patients operated on due to diseases of the middle ear during 2009–2012 was carried out. The cases of patients operated on for the first time due to chronic otitis media were analyzed. The analysis encompassed patients who had undergone middle ear surgery. The patients were divided into several groups taking into account the abnormalities of the middle ear mucous and damage of the ossicular chain observed during otosurgery. Results A significant hearing improvement was observed in patients with type 2 tympanoplasty in the course of chronic cholesteatoma otitis media and in patients with simple chronic inflammatory process in whom a PORP was used in the reconstruction. Granulation tissue was an unfavorable factor of hearing improvement following tympanoplasty. A significant improvement of bone conduction was observed in the patients with dry perforation without other lesions in the middle ear. The elimination of granulation lesions was a positive factor for the future improvement of the function of the inner ear. Conclusions The presence of granuloma-related lesions in the middle ear spaces is likely to impede hearing improvement. Damage to the ossicular chain rules out the possibility of bone conduction improvement after surgery. The prognosis on tube-related simple chronic otitis media after myringoplasty, with the preserved continuity of the ossicular chain, consists of closing the ABG and leads to significant improvement of bone conduction. PMID:26259623

  5. PIC (PRODUCTS OF INCOMPLETE COMBUSTION) FORMATION UNDER PYROLYTIC AND STARVED AIR CONDITIONS

    EPA Science Inventory

    A comprehensive program of laboratory studies based on the non-flame mode of thermal decomposition produced much data on PIC (Products of Incomplete Combustion) formation, primarily under pyrolytic and starved air conditions. Most significantly, laboratory results from non-flame ...

  6. 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 ...

  7. The gap gene giant of Rhodnius prolixus is maternally expressed and required for proper head and abdomen formation.

    PubMed

    Lavore, Andrés; Pagola, Lucía; Esponda-Behrens, Natalia; Rivera-Pomar, Rolando

    2012-01-01

    The segmentation process in insects depends on a hierarchical cascade of gene activity. The first effectors downstream of the maternal activation are the gap genes, which divide the embryo in broad fields. We discovered a sequence corresponding to the leucine-zipper domain of the orthologue of the gene giant (Rp-gt) in traces from the genome of Rhodnius prolixus, a hemipteran with intermediate germ-band development. We cloned the Rp-gt gene from a normalized cDNA library and characterized its expression and function. Bioinformatic analysis of 12.5 kbp of genomic sequence containing the Rp-gt transcriptional unit shows a cluster of bona fide regulatory binding sites, which is similar in location and structure to the predicted posterior expression domain of the Drosophila orthologue. Rp-gt is expressed in ovaries and maternally supplied in the early embryo. The maternal contribution forms a gradient of scattered patches of mRNA in the preblastoderm embryo. Zygotic Rp-gt is expressed in two domains that after germ band extension are restricted to the head and the posterior growth zone. Parental RNAi shows that Rp-gt is required for proper head and abdomen formation. The head lacks mandibulary and maxillary appendages and shows reduced clypeus-labrum, while the abdomen lacks anterior segments. We conclude that Rp-gt is a gap gene on the head and abdomen and, in addition, has a function in patterning the anterior head capsule suggesting that the function of gt in hemipterans is more similar to dipterans than expected. PMID:21763688

  8. 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. PMID:26382942

  9. Formation of mesostructured thin films at the air-liquid interface.

    PubMed

    Edler, Karen J; Yang, Bin

    2013-05-01

    The growth of free-standing surfactant-templated films of inorganic oxides at the air-solution interface is an attractive route to manufacture unsupported mesostructured membranes for a range of potential applications. So far this synthesis method has been relatively neglected due to the fragility of the initial films. More recent work to understand the mechanism of formation has led to development of thicker, more robust films, as well as providing new information on the general formation mechanisms of mesoporous materials whether in film or particulate form. This review describes the properties of silica and other inorganic oxide films templated by surfactants and grown at the air-solution interface, their formation mechanisms and implications for further development of these materials. PMID:23090013

  10. Identification of processes affecting excess air formation during natural bank filtration and managed aquifer recharge

    NASA Astrophysics Data System (ADS)

    Massmann, Gudrun; Sültenfuß, Jürgen

    2008-09-01

    SummaryManaged aquifer recharge is gaining importance as a practice to bank and treat surface water for drinking water production. Neon (Ne) concentrations were analysed at four different recharge sites in and near Berlin, where groundwater is recharged directly from surface water courses, either by near-natural bank filtration, induced bank filtration or engineered basin recharge. Neon concentrations in excess of saturation (ΔNe) were used to identify excess air in the infiltrates. Excess air concentrations were around saturation at the near-natural bank filtration site, where river water infiltrates through a permeable river bed into a confined aquifer under completely saturated conditions. At two induced unconfined bank filtration sites, samples generally contained excess air (up to 60% ΔNe). Highest excess air concentrations (up to 81% ΔNe) were encountered at the engineered basin recharge site. The degree of water table fluctuations, the water saturation of the sediments in the infiltration zone and the presence of a confining layer affect the formation of excess air. Excess air can only be used to trace bank filtrate or artificially recharged water in a setting where the ambient groundwater in the near vicinity of production wells is not affected by large water-table fluctuations. Nevertheless, excess air concentrations provide valuable additional information on the type of recharge (saturated or unsaturated, degree of water table fluctuations).

  11. 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

  12. Pulsed IR laser ablation of organic polymers in air: shielding effects and plasma pipe formation

    NASA Astrophysics Data System (ADS)

    Panchenko, A. N.; Shulepov, M. A.; Tel'minov, A. E.; Zakharov, L. A.; Paletsky, A. A.; Bulgakova, N. M.

    2011-09-01

    We report the effect of 'plasma pipe' formation on pulsed laser ablation of organic polymers in air under normal conditions. Ablation of polymers (PMMA, polyimide) is carried out in a wide range of CO2 laser fluences with special attention to plasma formation in the ablation products. Evolution of laser ablation plumes in air under different pressures is investigated with simultaneous registration of radiation spectra of the ablation products. An analysis based on thermo-chemical modelling is performed to elucidate the effects of laser light attenuation upon ablation, including plasma and chemical processes in a near-target space. The analysis has shown that the experimental observations of plume development in air can be explained by a combination of processes including formation of a pre-ionized channel along the laser beam propagation, laser-supported detonation wave and effective combustion of the polymer ablation products. A scenario of a streamer-like polymer plasma flow within an air plasma pipe created via laser-induced breakdown is proposed.

  13. High-resolution solid air gapped etalon in the 9500-nm region: application for nadir remote sounding of tropospheric ozone

    NASA Astrophysics Data System (ADS)

    Kumer, John B.; Rairden, Richard L.; Roche, Aidan E.; Mergenthaler, John L.; Naes, Lawrence G., Jr.; Jamieson, Thomas H.; Stephen, Thomas

    2003-03-01

    We present test data for a solid ZnSe air gapped etalon with free spectral range 3 cm-1 and finesse >70 (i.e., spectral resolution <0.043 cm-1). We present an instrument concept, the Tropopsheric Ozone Sounding (TOS) Dual Etalon Cross Tilt Order Sorting Spectrometer (DECTOSS), that would use an etalon like this to acquire nadir data at resolution <0.06 cm-1 and signal to noise the order 1000 on a range from 1036 to 1071 cm-1 in footprints with crosstrack dimension selectable (e.g., the order tens to hundreds of km), and with along track dimension the order 17 km. Instrument accommodation is the order 25 kg, 110 W and 1 mbps. We present linear error analysis for retrieval of tropospheric ozone from the data acquired by the TOS-DECTOSS. Indication is that more than 2.5 vertical layers of information on tropospheric information are retrievable. An example of the deployment of the TOS-DECTOSS would be as an instrument of opportunity (IOO) add on to the US National Polar-orbiting Operational Environmental Satellite System (NPOESS). The huge advantage of the TOS-DECTOSS as compared with UV techniques for tropospheric ozone measurement is that it the can be used both day and night, the latter is not possible in the UV. The considerable advantage in signal to noise compared with a Fourier Transform Spectrometer (FTS) for tropospheric ozone measurement, on considering that for a given footprint the DECTOSS and FTS integration times are comparable, is that the DECTOSS noise per spectral sample is dominated by statistical fluctuations of signal photons that are passed through its narrow 0.06 cm-1 bandpass, while for a similar FTS spectral sample the noise is due to fluctuations of the signal photons through the FTS bandpass of tens of cm-1. The TOS-DECTOSS signal to noise advantage on the FTS is also enhanced in that the spectral sample density of the TOS-DECTOSS data is more than one hundred times larger than for the FTS.

  14. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    We studied the electrical, thermal, and thermoelectric properties of the polycrystalline compound of SmNiC2. The electrical resistivity and magnetization measurement show the interplay between the charge density wave at TCDW=150 K and the ferromagnetic ordering of Tc=18 K. Below the ferromagnetic transition temperature, we observed the magnon gap formation of Δ≃4.3-4.4 meV by ρ(T) and Cp(T) measurements. The charge density wave is attributed to the increase of the Seebeck coefficient resulting in the increase of the power factor S2σ. The thermal conductivity anomalously increases with increasing temperature along the whole measured temperature range, which implies the weak attribution of Umklapp phonon scattering. The thermoelectric figure of merit ZT significantly increases due to the increase of the power factor at TCDW=150 K. Here we argue that the competing interaction between electron-phonon and electron-magnon couplings exhibits the unconventional behavior of electrical and thermal properties.

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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

    2016-01-01

    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. 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. PMID:27572095

  1. Formation of small polarons in Li2O2 and implications for Li-air batteries

    NASA Astrophysics Data System (ADS)

    Kang, Joongoo; Jung, Yoon-Seok; Wei, Su-Huai; Dillon, Anne

    2012-02-01

    Lithium-air batteries (LABs) have recently been revitalized as a promising electrical energy storage system due to their exceptionally high theoretical energy density. However, its usage is limited by poor rate capability and large polarization in the cell voltage due primarily to the formation of Li2O2 in the air cathode. Here, using hybrid density functional theory, we found that the formation of small polarons in Li2O2 is the origin that limits the electron transport in Li2O2. Consequently, the low electron mobility contributes to the hysteresis in cell voltage and limits the power density of the LABs. We suggest that similar behavior should exist in other peroxides, and p-type doping in Li2O2 could significantly improve the performance of LABs at high current densities.

  2. 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

  3. 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. PMID:26324919

  4. Effects of Air-Fuel Spray and Flame Formation in a Compression-Ignition Engine

    NASA Technical Reports Server (NTRS)

    Rothrock, A M; Waldron, C D

    1937-01-01

    High-speed motion pictures were taken at the rate of 2,500 frames per second of the fuel spray and flame formation in the combustion chamber of the NACA combustion apparatus. The compression ratio was 13.2 and the speed 1,500 revolutions per minute. An optical indicator was used to record the time-pressure relationship in the combustion chamber. The air-fuel ratio was varied from 10.4 to 365. The results showed that as the air-fuel ratio was increased definite stratification of the charge occurred in the combustion chamber even though moderate air flow existed. The results also showed the rate of vapor diffusion to be relatively slow.

  5. Interactions of fire emissions and urban pollution over California: Ozone formation and air quality simulations

    NASA Astrophysics Data System (ADS)

    Singh, H. B.; Cai, C.; Kaduwela, A.; Weinheimer, A.; Wisthaler, A.

    2012-09-01

    An instrumented DC-8 aircraft was employed to perform airborne observations in rural and urban environs of California during the summer 2008 NASA ARCTAS-CARB campaign. The fortuitous occurrence of large wildfire episodes in Northern California allowed for studies of fire emissions, their composition, and their interactions with rural and urban air. Relative to CO, emissions of HCN were shown to vary non-linearly with fire characteristics while those of CH3CN were nearly unchanged, making the latter a superior quantitative tracer of biomass combustion. Although some fire plumes over California contained little NOx and virtually no O3 enhancement, others contained ample VOCs and sufficient NOx, largely from urban influences, to result in significant ozone formation. The highest observed O3 mixing ratios (170 ppb) were also in fire-influenced urban air masses. Attempts to simulate these interactions using CMAQ, a high-resolution state of the art air quality model, were only minimally successful and indicated several shortcomings in simulating fire emission influences on urban smog formation. A variety of secondary oxidation products (e.g. O3, PAN, HCHO) were substantially underestimated in fire-influenced air masses. Available data involving fire plumes and anthropogenic pollution interactions are presently quite sparse and additional observational and mechanistic studies are needed.

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

    NASA Astrophysics Data System (ADS)

    Palm, B. B.; Campuzano-Jost, P.; Ortega, A. M.; Day, D. A.; Kaser, L.; Jud, W.; Karl, T.; Hansel, A.; Hunter, J. F.; Cross, E. S.; Kroll, J. H.; Peng, Z.; Brune, W. H.; Jimenez, J. L.

    2015-11-01

    Ambient air was oxidized by OH radicals in an oxidation flow reactor (OFR) located in a montane pine forest during the BEACHON-RoMBAS campaign to study biogenic secondary organic aerosol (SOA) formation and aging. High OH concentrations and short residence times allowed for semi-continuous 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 time scales 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 4 μg m-3 when LVOC fate corrected) compared to daytime (average 1 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 LT. 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), 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 compounds, and net production at lower ages followed by net consumption of terpenoid oxidation products as photochemical age increased. New particle formation was observed in the reactor after oxidation, especially during times when precursor gas concentrations and SOA formation were largest. Approximately 6 times more SOA was formed in the reactor from OH oxidation than

  7. 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

  8. 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 ...

  9. Field emission in air and space-charge-limited currents from iridium-iridium oxide tips with gaps below 100 nm

    NASA Astrophysics Data System (ADS)

    Brimley, Scott; Miller, Mark S.; Hagmann, Mark J.

    2011-05-01

    Field emission diodes made with Ir/IrO2 tips separated by gaps below 100 nm and operating in air gave currents of up to 1 μA just above 10 V and largely survived potentials up to 200 V. The current-voltage characteristics included signatures of Fowler-Nordheim emission and both coherent and incoherent space-charge limited emission, where both behaviors implied molecular-scale effective emission areas. The significant, nanoampere currents that flowed at biases below the expected bulk work functions corroborate the 0.1 eV work functions from Fowler-Nordheim analysis, and are attributed to molecular scale oxide structures and adsorbates shifting the surface Fermi level. Electron transit time analysis indicates that on average only one electron crossed the gap at a time, implying that the space-charge effects are due to self-interactions.

  10. Air pollution control and decreasing new particle formation lead to strong climate warming

    NASA Astrophysics Data System (ADS)

    Makkonen, R.; Asmi, A.; Kerminen, V.-M.; Boy, M.; Arneth, A.; Hari, P.; Kulmala, M.

    2011-09-01

    The number of cloud droplets determines several climatically relevant cloud properties. A major cause for the high uncertainty in the indirect aerosol forcing is the availability of cloud condensation nuclei (CCN), which in turn is highly sensitive to atmospheric new particle formation. Here we present the effect of new particle formation on anthropogenic aerosol forcing in present-day (year 2000) and future (year 2100) conditions. The total aerosol forcing (-1.61 W m-2 in year 2000) is simulated to be greatly reduced in the future, to -0.23 W m-2, mainly due to decrease in SO2 emissions and resulting decrease in new particle formation. With the total aerosol forcing decreasing in response to air pollution control measures taking effect, warming from increased greenhouse gas concentrations can potentially increase at a very rapid rate.

  11. Special Issue of Inhalation Toxicology for Air Pollution and Health: Bridging the Gap from Sources-to-Health Outcomes

    EPA Science Inventory

    Pollution and Health: Bridging the Gap from Sources to Health Outcomes”, an international specialty conference by the American Association for Aerosol Research (AAAR) (http://aaar.2010specialty.org/), provided one such opportunity for these interactions. The Conference was organi...

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

    The combustion of Zr and (Zr+ZrO2) 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 Y2O3 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+ZrO2) samples with the Y2O3 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.

  13. 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.

  14. 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.

  15. 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

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

    DOE PAGESBeta

    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.; et al

    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 small

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

    DOE PAGESBeta

    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.; et al

    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

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

    SciTech Connect

    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.

    2016-01-01

    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

  19. Formation of functional gap junctions in amniotic fluid-derived stem cells induced by transmembrane co-culture with neonatal rat cardiomyocytes

    PubMed Central

    Connell, Jennifer Petsche; Augustini, Emily; Moise, Kenneth J; Johnson, Anthony; Jacot, Jeffrey G

    2013-01-01

    Amniotic fluid-derived stem cells (AFSC) have been reported to differentiate into cardiomyocyte-like cells and form gap junctions when directly mixed and cultured with neonatal rat ventricular myocytes (NRVM). This study investigated whether or not culture of AFSC on the opposite side of a Transwell membrane from NRVM, allowing for contact and communication without confounding factors such as cell fusion, could direct cardiac differentiation and enhance gap junction formation. Results were compared to shared media (Transwell), conditioned media and monoculture media controls. After a 2-week culture period, AFSC did not express cardiac myosin heavy chain or troponin T in any co-culture group. Protein expression of cardiac calsequestrin 2 was up-regulated in direct transmembrane co-cultures and media control cultures compared to the other experimental groups, but all groups were up-regulated compared with undifferentiated AFSC cultures. Gap junction communication, assessed with a scrape-loading dye transfer assay, was significantly increased in direct transmembrane co-cultures compared to all other conditions. Gap junction communication corresponded with increased connexin 43 gene expression and decreased phosphorylation of connexin 43. Our results suggest that direct transmembrane co-culture does not induce cardiomyocyte differentiation of AFSC, though calsequestrin expression is increased. However, direct transmembrane co-culture does enhance connexin-43-mediated gap junction communication between AFSC. PMID:23634988

  20. Band gap formation in La0.7Sr0.3MnO3 (LSMO) thin films measured by reflectivity/absorption and ultrafast spectroscopy

    NASA Astrophysics Data System (ADS)

    Cabrera, Guerau; Trappen, Robbyn; Chu, Ying-Hao; Holcomb, Mikel

    Thin film La0.7Sr0.3MnO3 (LSMO) is a prime candidate for highly spin-polarized magnetic-tunnel-junction memories. Due to its magnetic properties, it is also a good candidate for applications utilizing electrical control of magnetism when grown adjacent to a ferroelectric layer such as Pb(Zr/Ti)O3 (PZT). Recently, Wu and others have seen the emergence of a band gap (about 1eV) in LSMO thin films, when grown adjacent to PZT. Currently, it is understood that LSMO is a half-metal, with a pseudo-gap due to a low desity of states (DOS) near the Fermi level. The transition from pseudo-gap to band gap is not yet fully understood. It is therefore our aim to investigate the formation of this band gap through optical reflectivity/absorption and ultrafast carrier dynamics for a variety of thicknesses ranging from a few nanometers to thicker films (about 100 nm).

  1. Effect of electron divergence in air gaps on the measurement of the energy of cascades in emulsion chambers

    NASA Technical Reports Server (NTRS)

    Apanasenko, A. V.; Baradzey, L. T.; Kanevskaya, Y. A.; Smorodin, Y. A.

    1975-01-01

    The effect of an increase in electron density in the vicinity of the cascade axis caused by an avalanche passing through the gap between lead filters of the emulsion chamber was investigated experimentally. Optical densities were measured in three X-ray films spaced at 400, 800 and 1200 micrometer from the filter surface having a thickness of 6 cascade units. The optical densities of blackening spots caused by electron photon cascades of 1 to 2, 2 to 7 and greater than 7 BeV energies were measured. The results prove the presence of a gap between the filter and the nuclear emulsion which results in the underestimation of energy by several tenths of a percent.

  2. 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)

  3. 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.

  4. 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.

  5. 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.

  6. Theoretical aspects of fluoride air contaminant formation in aluminium smelter potrooms.

    PubMed

    L'vov, Boris V; Polzik, Leonid K; Weinbruch, Stephan; Ellingsen, Dag G; Thomassen, Yngvar

    2005-05-01

    The amount of particulate fluorides evolved from aluminium electrolysis cells is not entirely accounted for by the fluorides entrained in the anode gas. The largest additional source of particulate fluoride formation is by direct evaporation of fluorides into the anode gas stream and subsequent condensation on the drops of electrolyte generated in the process of bubble burst. A theoretical model was used for the calculation of the main physical parameters responsible for the formation of particle nuclei when the hot anode-gas is mixed with ambient air. The results of these calculations are in agreement with experimental observations reported in the literature. In particular, the size distribution, composition and morphology of the nano-particles support the theory of a vapour condensation mechanism under conditions of extreme supersaturation, but further studies are necessary. PMID:15877162

  7. 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.

  8. 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. PMID:27451229

  9. 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.

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

    DOE PAGESBeta

    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 ≥0.5more » 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

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

    PubMed Central

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

    2014-01-01

    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. PMID:25407432

  12. 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.

  13. 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.

  14. Air-Liquid Interface Biofilms of Bacillus cereus: Formation, Sporulation, and Dispersion▿

    PubMed Central

    Wijman, Janneke G. E.; de Leeuw, Patrick P. L. A.; Moezelaar, Roy; Zwietering, Marcel H.; Abee, Tjakko

    2007-01-01

    Biofilm formation by Bacillus cereus was assessed using 56 strains of B. cereus, including the two sequenced strains, ATCC 14579 and ATCC 10987. Biofilm production in microtiter plates was found to be strongly dependent on incubation time, temperature, and medium, as well as the strain used, with some strains showing biofilm formation within 24 h and subsequent dispersion within the next 24 h. A selection of strains was used for quantitative analysis of biofilm formation on stainless steel coupons. Thick biofilms of B. cereus developed at the air-liquid interface, while the amount of biofilm formed was much lower in submerged systems. This suggests that B. cereus biofilms may develop particularly in industrial storage and piping systems that are partly filled during operation or where residual liquid has remained after a production cycle. Moreover, depending on the strain and culture conditions, spores constituted up to 90% of the total biofilm counts. This indicates that B. cereus biofilms can act as a nidus for spore formation and subsequently can release their spores into food production environments. PMID:17209076

  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.

    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.

  16. Nanoparticle formation by laser ablation in air and by spark discharges at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Itina, T. E.; Voloshko, A.

    2013-12-01

    Recent promising methods of nanoparticle fabrication include laser ablation and spark discharge. Despite different experimental conditions, a striking similarity is often observed in the sizes of the obtained particles. To explain this result, we elucidate physical mechanisms involved in the formation of metallic nanoparticles. In particular, we compare supersaturation degree and sizes of critical nucleus obtained under laser ablation conditions with that obtained for spark discharge in air. For this, the dynamics of the expansion of either ablated or eroded products is described by using a three-dimensional blast wave model. Firstly, we consider nanosecond laser ablation in air. In the presence of a background gas, the plume expansion is limited by the gas pressure. Nanoparticles are mostly formed by nucleation and condensation taking place in the supersaturated vapor. Secondly, we investigate nanoparticles formation by spark discharge at atmospheric pressure. After efficient photoionization and streamer expansion, the cathode material suffers erosion and NPs appear. The calculation results allow us to examine the sizes of critical nuclei as function of the experimental parameters and to reveal the conditions favorable for the size reduction and for the increase in the nanoparticle yield.

  17. 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.

  18. 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).

  19. Formation, disruption and mechanical properties of a rigid hydrophobin film at an air-water interface

    NASA Astrophysics Data System (ADS)

    Walker, Lynn; Kirby, Stephanie; Anna, Shelley; CMU Team

    Hydrophobins are small, globular proteins with distinct hydrophilic and hydrophobic regions that make them extremely surface active. The behavior of hydrophobins at surfaces has raised interest in their potential industrial applications, including use in surface coatings, food foams and emulsions, and as dispersants. Practical use of hydrophobins requires an improved understanding of the interfacial behavior of these proteins, both individually and in the presence of surfactants. Cerato-ulmin (CU) is a hydrophobin that has been shown to strongly stabilize air bubbles and oil droplets through the formation of a persistent protein film at the interface. In this work, we characterize the adsorption behavior of CU at air/water interfaces by measuring the surface tension and interfacial rheology as a function of adsorption time. CU is found to strongly, irreversibly adsorb at air/water interfaces; the magnitude of the dilatational modulus increases with adsorption time and surface pressure, until the CU eventually forms a rigid film. The persistence of this film is tested through the addition of SDS, a strong surfactant, to the bulk. SDS is found to co-adsorb to interfaces pre-coated with a CU film. At high concentrations, the addition of SDS significantly decreases the dilatational modulus, indicating disruption and displacement of CU. These results lend insight into the complex interfacial interactions between hydrophobins and surfactants. Funding from GoMRI.

  20. 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,…

  1. End field formation in planar hybrid undulators to ensure gap independence of the first and second field integrals

    NASA Astrophysics Data System (ADS)

    Papadichev, V. A.; Rybalchenko, G. V.

    2004-10-01

    Magnetic field amplitude in pure permanent magnet (PPM) or hybrid undulators is varied by changing the gap. It is necessary to ensure that for all gaps the deviation of the first and second field integrals from ideal be sufficiently small, especially in the XFEL project where dozens of undulator sections, each about 5-m long, are to be used. Since a high field is required, a hybrid undulator should be used. In this paper, field calculations for such an undulator were carried out using the "Radia" code. Unlike a PPM undulator scheme, hybrid ones require more sophisticated schemes of minimizing field integrals because of complicated redistribution of magnetic flux at the undulator ends with changing gap. Saturation of iron poles makes solution of the problem more difficult. Both effects were studied and several compensating methods were found. Parameters of the permanent magnets and iron poles of the first and last end-field-forming undulator periods were varied in order to change the form and mean value of the first and second integrals versus undulator gap.

  2. 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.

  3. 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. PMID:24690169

  4. Traffic-related air pollution and obesity formation in children: a longitudinal, multilevel analysis

    PubMed Central

    2014-01-01

    Background Biologically plausible mechanisms link traffic-related air pollution to metabolic disorders and potentially to obesity. Here we sought to determine whether traffic density and traffic-related air pollution were positively associated with growth in body mass index (BMI = kg/m2) in children aged 5–11 years. Methods Participants were drawn from a prospective cohort of children who lived in 13 communities across Southern California (N = 4550). Children were enrolled while attending kindergarten and first grade and followed for 4 years, with height and weight measured annually. Dispersion models were used to estimate exposure to traffic-related air pollution. Multilevel models were used to estimate and test traffic density and traffic pollution related to BMI growth. Data were collected between 2002–2010 and analyzed in 2011–12. Results Traffic pollution was positively associated with growth in BMI and was robust to adjustment for many confounders. The effect size in the adjusted model indicated about a 13.6% increase in annual BMI growth when comparing the lowest to the highest tenth percentile of air pollution exposure, which resulted in an increase of nearly 0.4 BMI units on attained BMI at age 10. Traffic density also had a positive association with BMI growth, but this effect was less robust in multivariate models. Conclusions Traffic pollution was positively associated with growth in BMI in children aged 5–11 years. Traffic pollution may be controlled via emission restrictions; changes in land use that promote jobs-housing balance and use of public transit and hence reduce vehicle miles traveled; promotion of zero emissions vehicles; transit and car-sharing programs; or by limiting high pollution traffic, such as diesel trucks, from residential areas or places where children play outdoors, such as schools and parks. These measures may have beneficial effects in terms of reduced obesity formation in children. PMID:24913018

  5. Experimental investigations on decay heat removal in advanced nuclear reactors using single heater rod test facility: Air alone in the annular gap

    SciTech Connect

    Bopche, Santosh B.; Sridharan, Arunkumar

    2010-11-15

    During a loss of coolant accident in nuclear reactors, radiation heat transfer accounts for a significant amount of the total heat transfer in the fuel bundle. In case of heavy water moderator nuclear reactors, the decay heat of a fuel bundle enclosed in the pressure tube and outer concentric calandria tube can be transferred to the moderator. Radiation heat transfer plays a significant role in removal of decay heat from the fuel rods to the moderator, which is available outside the calandria tube. A single heater rod test facility is designed and fabricated as a part of preliminary investigations. The objective is to anticipate the capability of moderator to remove decay heat, from the reactor core, generated after shut down. The present paper focuses mainly on the role of moderator in removal of decay heat, for situation with air alone in the annular gap of pressure tube and calandria tube. It is seen that the naturally aspirated air is capable of removing the heat generated in the system compared to the standstill air or stagnant water situations. It is also seen that the flowing moderator is capable of removing a greater fraction of heat generated by the heater rod compared to a stagnant pool of boiling moderator. (author)

  6. Percolation Cooling of the Three Mile Island Unit 2 Lower Head by Way of Thermal Cracking and Gap Formation

    SciTech Connect

    Thomsen, K.L.

    2002-01-15

    Two partial models have been developed to elucidate the Three Mile Island Unit 2 lower head coolability by water percolation from above into the thermally cracking debris bed and into a gap between the debris and the wall. The bulk permeability of the cracked top crust is estimated based on simple fracture mechanics and application of Poiseuille's law to the fractures. The gap is considered as an abstraction representing an initially rugged interface, which probably expanded by thermal deformation and cracking in connection with the water ingress. The coupled flow and heat conduction problem for the top crust is solved in slab geometry based on the two-phase Darcy equations together with quasi-steady mass and energy conservation equations. The resulting water penetration depth is in good agreement with the depth of the so-called loose debris bed. The lower-head and bottom-crust problem is treated analogously by a two-dimensional axisymmetric model. The notion of a gap is maintained as a useful concept in the flow analysis. Simulations show that a central hot spot with a peak wall temperature of 1075 to 1100 deg. C can be obtained, but the quenching rates are not satisfactory. It is concluded that a three-dimensional model with an additional mechanism to explain the sudden water ingress to the hot spot center would be more appropriate.

  7. 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.

  8. 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.

  9. 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. PMID:25989935

  10. Influence of the Saharan Air Layer on Atlantic tropical cyclone formation during the period 1-12 September 2003

    NASA Astrophysics Data System (ADS)

    Pan, Weiyu; Wu, Liguang; Shie, Chung-Lin

    2011-01-01

    Atmospheric Infrared Sounder (AIRS) data show that the Saharan air layer (SAL) is a dry, warm, and well-mixed layer between 950 and 500 hPa over the tropical Atlantic, extending westward from the African coast to the Caribbean Sea. The formations of both Hurricane Isabel and Tropical Depression 14 (TD14) were accompanied with outbreaks of SAL air during the period 1-12 September 2003, although TD14 failed to develop into a named tropical cyclone. The influence of the SAL on their formations is investigated by examining data from satellite observations and numerical simulations, in which AIRS data are incorporated into the MM5 model through the nudging technique. Analyses of the AIRS and simulation data suggest that the SAL may have played two roles in the formation of tropical cyclones during the period 1-12 September 2003. First, the outbreaks of SAL air on 3 and 8 September enhanced the transverse-vertical circulation with the rising motion along the southern edge of the SAL and the sinking motion inside the SAL, triggering the development of two tropical disturbances associated with Hurricane Isabel and TD14. Second, in addition to the reduced environmental humidity and enhanced static stability in the lower troposphere, the SAL dry air intruded into the inner region of these tropical disturbances as their cyclonic flows became strong. This effect may have slowed down the formation of Isabel and inhibited TD14 becoming a named tropical cyclone, while the enhanced vertical shear contributed little to tropical cyclone formation during this period. The 48-h trajectory calculations confirm that the parcels from the SAL can be transported into the inner region of an incipient tropical cyclone.

  11. Air pollution control and decreasing new particle formation lead to strong climate warming

    NASA Astrophysics Data System (ADS)

    Makkonen, R.; Asmi, A.; Kerminen, V.-M.; Boy, M.; Arneth, A.; Hari, P.; Kulmala, M.

    2012-02-01

    The number concentration of cloud droplets determines several climatically relevant cloud properties. A major cause for the high uncertainty in the indirect aerosol forcing is the availability of cloud condensation nuclei (CCN), which in turn is highly sensitive to atmospheric new particle formation. Here we present the effect of new particle formation on anthropogenic aerosol forcing in present-day (year 2000) and future (year 2100) conditions. The present-day total aerosol forcing is increased from -1.0 W m-2 to -1.6 W m-2 when nucleation is introduced into the model. Nucleation doubles the change in aerosol forcing between years 2000 and 2100, from +0.6 W m-2 to +1.4 W m-2. Two climate feedbacks are studied, resulting in additional negative forcings of -0.1 W m-2 (+10% DMS emissions in year 2100) and -0.5 W m-2 (+50% BVOC emissions in year 2100). With the total aerosol forcing diminishing in response to air pollution control measures taking effect, warming from increased greenhouse gas concentrations can potentially increase at a very rapid rate.

  12. [Temporal-spatial distribution characteristics of microclimate in tropical secondary forest canopy gap in Xishuangbanna].

    PubMed

    Zhang, Yiping; Dou, Junxia; Ma, Youxin; Liu, Yuhong; Guo, Ping

    2003-12-01

    Based on the data obtained from vertical gradient measurements of microclimatic elements of canopy gap in tropical secondary forest of Xishuangbanna in fog-cool and dry-hot season, the daytime characteristics of temporal-spatial distribution and variation of trunk surface temperature, air temperature, water vapor pressure and relative humidity in canopy gap were discussed. The data showed that gap edge had not only a remarkable thermal effect, but also a significant water vapor effect. These effects resulted in environmental heterogeneity in canopy gap. The results provided a basis for further studying heat and water vapor transport, microclimatic formation, biodiversity, and forest succession in canopy gap. PMID:15031901

  13. 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.

  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. Kinetic studies of NO formation in pulsed air-like low-pressure dc plasmas

    NASA Astrophysics Data System (ADS)

    Hübner, M.; Gortschakow, S.; Guaitella, O.; Marinov, D.; Rousseau, A.; Röpcke, J.; Loffhagen, D.

    2016-06-01

    The kinetics of the formation of NO in pulsed air-like dc plasmas at a pressure of 1.33 mbar and mean currents between 50 and 150 mA of discharge pulses with 5 ms duration has been investigated both experimentally and by self-consistent numerical modelling. Using time-resolved quantum cascade laser absorption spectroscopy, the densities of NO, NO2 and N2O have been measured in synthetic air as well as in air with 0.8% of NO2 and N2O, respectively. The temporal evolution of the NO density shows four distinct phases during the plasma pulse and the early afterglow in the three gas mixtures that were used. In particular, a steep density increase during the ignition phase and after termination of the discharge current pulse has been detected. The NO concentration has been found to reach a constant value of 0.57× {{10}14}~\\text{molecules}~\\text{c}{{\\text{m}}-3} , 1.05× {{10}14}~\\text{molecules}~\\text{c}{{\\text{m}}-3} , and 1.3× {{10}14}~\\text{molecules}~\\text{c}{{\\text{m}}-3} for mean plasma currents of 50 mA, 100 mA and 150 mA, respectively, in the afterglow. The measured densities of NO2 and N2O in the respective mixture decrease exponentially during the plasma pulse and remain almost constant in the afterglow, especially where the admixture of NO2 has a remarkable impact on the NO production during the ignition. The numerical results of the coupled solution of a set of rate equations for the various heavy particles and the time-dependent Boltzmann equation of the electrons agree quite well with the experimental findings for the different air-like plasmas. The main reaction processes have been analysed on the basis of the model calculations and the remaining differences between the experiment and modelling especially during the afterglow are discussed.

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

    PubMed

    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

  17. 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

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

    NASA Astrophysics Data System (ADS)

    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.

  19. Aqueous photooxidation of ambient Po Valley Italy air samples: Insights into secondary organic aerosol formation

    NASA Astrophysics Data System (ADS)

    Kirkland, J. R.; Lim, Y. B.; Sullivan, A. P.; Decesari, S.; Facchini, C.; Collett, J. L.; Keutsch, F. N.; Turpin, B. J.

    2012-12-01

    In this work, we conducted aqueous photooxidation experiments with ambient samples in order to develop insights concerning the formation of secondary organic aerosol through gas followed by aqueous chemistry (SOAaq). Water-soluble organics (e.g., glyoxal, methylglyoxal, glycolaldehyde, acetic acid, acetone) are formed through gas phase oxidation of alkene and aromatic emissions of anthropogenic and biogenic origin. Their further oxidation in clouds, fogs and wet aerosols can form lower volatility products (e.g., oligomers, organic acids) that remain in the particle phase after water evaporation, thus producing SOA. The aqueous OH radical oxidation of several individual potentially important precursors has been studied in the laboratory. In this work, we used a mist-chamber apparatus to collect atmospheric mixtures of water-soluble gases from the ambient air at San Pietro Capofiume, Italy during the PEGASOS field campaign. We measured the concentration dynamics after addition of OH radicals, in order to develop new insights regarding formation of SOA through aqueous chemistry. Specifically, batch aqueous reactions were conducted with 33 ml mist-chamber samples (TOC ~ 50-100μM) and OH radicals (~10-12M) in a new low-volume aqueous reaction vessel. OH radicals were formed in-situ, continuously by H2O2 photolysis. Products were analyzed by ion chromatography (IC), electrospray ionization mass spectrometry (ESI-MS +/-), and ESI-MS with IC pre-separation (IC/ESI-MS-). Reproducible formation of pyruvate and oxalate were observed both by IC and ESI-MS. These compounds are known to form from aldehyde oxidation in the aqueous phase. New insights regarding the aqueous chemistry of these "more atmospherically-realistic" experiments will be discussed.

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

    PubMed

    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

  1. 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.

  2. 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

  3. 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.

  4. Kinetics of NO formation and decay in nanosecond pulse discharges in Air, H2-Air, and C2H4-Air mixtures

    NASA Astrophysics Data System (ADS)

    Burnette, David; Shkurenkov, Ivan; Adamovich, Igor V.; Lempert, Walter R.

    2016-04-01

    Time-resolved, absolute NO and N atom number densities are measured by NO Laser Induced Fluorescence (LIF) and N Two-Photon Absorption LIF in a diffuse plasma filament, nanosecond pulse discharge in dry air, hydrogen-air, and ethylene-air mixtures at 40 Torr, over a wide range of equivalence ratios. The results are compared with kinetic modeling calculations incorporating pulsed discharge dynamics, kinetics of vibrationally and electronically excited states of nitrogen, plasma chemical reactions, and radial transport. The results show that in air afterglow, NO decay occurs primarily by the reaction with N atoms, NO  +  N  →  N2  +  O. In the presence of hydrogen, this reaction is mitigated by reaction of N atoms with OH, N  +  OH  →  NO  +  H, resulting in significant reduction of N atom number density in the afterglow, additional NO production, and considerably higher NO number densities. In fuel-lean ethylene-air mixtures, a similar trend (i.e. N atom concentration reduction and NO number density increase) is observed, although [NO] increase on ms time scale is not as pronounced as in H2-air mixtures. In near-stoichiometric and fuel-lean ethylene-air mixtures, when N atom number density was below detection limit, NO concentration was measured to be lower than in air plasma. These results suggest that NO kinetics in hydrocarbon-air plasmas is more complex compared to air and hydrogen-air plasmas, additional NO reaction pathways may well be possible, and their analysis requires further kinetic modeling calculations.

  5. 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.

  6. 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.

  7. 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

  8. Formation of plasma channels in air under filamentation of focused ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Ionin, A. A.; Seleznev, L. V.; Sunchugasheva, E. S.

    2015-03-01

    The formation of plasma channels in air under filamentation of focused ultrashort laser pulses was experimentally and theoretically studied together with theoreticians of the Moscow State University and the Institute of Atmospheric Optics. The influence of various characteristics of ultrashort laser pulses on these plasma channels is discussed. Plasma channels formed under filamentation of focused laser beams with a wavefront distorted by spherical aberration (introduced by adaptive optics) and by astigmatism, with cross-section spatially formed by various diaphragms and with different UV and IR wavelengths, were experimentally and numerically studied. The influence of plasma channels created by a filament of a focused UV or IR femtosecond laser pulse (λ = 248 nm or 740 nm) on characteristics of other plasma channels formed by a femtosecond pulse at the same wavelength following the first one with varied nanosecond time delay was also experimentally studied. An application of plasma channels formed due to the filamentation of focused UV ultrashort laser pulses including a train of such pulses and a combination of ultrashort and long (~100 ns) laser pulses for triggering and guiding long (~1 m) electric discharges is discussed.

  9. 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.

  10. Soot formation and temperature field structure in laminar propane-air diffusion flames at elevated pressures

    SciTech Connect

    Bento, Decio S.; Guelder, OEmer L.; Thomson, Kevin A.

    2006-06-15

    The effect of pressure on soot formation and the structure of the temperature field was studied in coflow propane-air laminar diffusion flames over the pressure range of 0.1 to 0.73 MPa in a high-pressure combustion chamber. The fuel flow rate was selected so that the soot was completely oxidized within the visible flame and the flame was stable at all pressures. Spectral soot emission was used to measure radially resolved soot volume fraction and soot temperature as a function of pressure. Additional soot volume fraction measurements were made at selected heights using line-of-sight light attenuation. Soot concentration values from these two techniques agreed to within 30% and both methods exhibited similar trends in the spatial distribution of soot concentration. Maximum line-of-sight soot concentration along the flame centerline scaled with pressure; the pressure exponent was about 1.4 for pressures between 0.2 and 0.73 MPa. Peak carbon conversion to soot, defined as the percentage of fuel carbon content converted to soot, also followed a power-law dependence on pressure, where the pressure exponent was near to unity for pressures between 0.2 and 0.73 MPa. Soot temperature measurements indicated that the overall temperatures decreased with increasing pressure; however, the temperature gradients increased with increasing pressure. (author)

  11. 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)

  12. The NEMO-AROME WMED high-resolution air-sea coupled system: impact on dense water formation

    NASA Astrophysics Data System (ADS)

    Léger, Fabien; Lebeaupin Brossier, Cindy; Giordani, Hervé; Arsouze, Thomas; Beuvier, Jonathan; Bouin, Marie-Noëlle; Ducrocq, Véronique; Fourrié, Nadia

    2016-04-01

    The North-Western Mediterranean Sea is a key location where intense air-sea exchanges occur, especially during winter when the succession of strong northerly and north-westerly wind boosts the dense water formation. The second Special Observation Period (SOP2) of the HyMeX program, which took place between 1st February and 15th March 2013, was dedicated to the observation of the dense water formation and ocean deep convection processes. During this period, several platforms sampled the area, providing a unique dataset to better identify the coupled processes leading to dense water formation. This study investigates the impacts of the fine scale ocean-atmosphere coupled processes on dense water formation during winter 2012-2013. We developed the coupling between the NEMO-WMED36 ocean model (1/36° resolution) and the AROME-WMED numerical weather prediction model (2.5 km resolution) and ran the high-resolution air-sea coupled system over SOP2. The coupled simulation is compared to an ocean-only simulation forced by AROME-WMED operational forecasts and to air-sea observations collected during the HyMeX SOP2. The results show small differences in term of surface fluxes. Dense water formation is slightly changed in the coupled simulation, whereas fine-scale ocean processes are significantly modified.

  13. 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.

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

    PubMed

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

    2015-05-01

    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

  16. 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. PMID:25966888

  17. 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. PMID:21114115

  18. 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.

  19. 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.

  20. Bacterial lipopolysaccharide induces actin reorganization, intercellular gap formation, and endothelial barrier dysfunction in pulmonary vascular endothelial cells: concurrent F-actin depolymerization and new actin synthesis.

    PubMed

    Goldblum, S E; Ding, X; Brann, T W; Campbell-Washington, J

    1993-10-01

    Bacterial lipopolysaccharide (LPS) influences pulmonary vascular endothelial barrier function in vitro. We studied whether LPS regulates endothelial barrier function through actin reorganization. Postconfluent bovine pulmonary artery endothelial cell monolayers were exposed to Escherichia coli 0111:B4 LPS 10 ng/ml or media for up to 6 h and evaluated for: 1) transendothelial 14C-albumin flux, 2) F-actin organization with fluorescence microscopy, 3) F-actin quantitation by spectrofluorometry, and 4) monomeric G-actin levels by the DNAse 1 inhibition assay. LPS induced increments in 14C-albumin flux (P < 0.001) and intercellular gap formation at > or = 2-6 h. During this same time period the endothelial F-actin pool was not significantly changed compared to simultaneous media controls. Mean (+/- SE) G-actin (micrograms/mg total protein) was significantly (P < 0.002) increased compared to simultaneous media controls at 2, 4, and 6 h but not at 0.5 or 1 h. Prior F-actin stabilization with phallicidin protected against the LPS-induced increments in G-actin (P = 0.040) as well as changes in barrier function (P < 0.0001). Prior protein synthesis inhibition unmasked an LPS-induced decrement in F-actin (P = 0.0044), blunted the G-actin increment (P = 0.010), and increased LPS-induced changes in endothelial barrier function (P < 0.0001). Therefore, LPS induces pulmonary vascular endothelial F-actin depolymerization, intercellular gap formation, and barrier dysfunction. Over the same time period, LPS increased total actin (P < 0.0001) and new actin synthesis (P = 0.0063) which may be a compensatory endothelial cell response to LPS-induced F-actin depolymerization. PMID:8408232

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. Supercell-size convergence of formation energies and gap levels of vacancy complexes in crystalline silicon in density functional theory calculations

    NASA Astrophysics Data System (ADS)

    Dabrowski, J.; Kissinger, G.

    2015-10-01

    Results for supercell-size convergence of formation energies and charge transition levels of vacancy complexes Vn(1 ≤n ≤11 ) in crystalline Si are reported for the ab initio density functional theory (DFT) with generalized gradient approximation (GGA) pseudopotentials. When extrapolated to the dilute limit, the formation energy of an uncharged vacancy becomes 3.74 ±0.1 eV , and the binding energy of an uncharged divacancy becomes 1.9 ±0.2 eV . Stable Vn clusters are built on the basis of sixfold rings (n ≤6 ) and of octahedral voids (n ≥7 ) . If the well-known underestimate of the band gap by the DFT and the accuracy of extrapolations are taken into account, the extrapolated levels are in good agreement with experiment. We discuss the implications for simulation of vacancy clustering during thermal quenching, for interpretation of deep-level spectroscopy and electron paramagnetic resonance in irradiated Si, and for cell and Brillouin-zone sampling choice when DFT-related methods beyond local-density approximation or GGA are used.

  6. Regional Changes of AQP0-dependent Square Array Junction and Gap Junction Associated with Cortical Cataract Formation in the Emory Mutant Mouse

    PubMed Central

    Biswas, Sondip K.; Brako, Lawrence; Gu, Sumin; Jiang, Jean X.; Lo, Woo-Kuen

    2014-01-01

    The Emory mutant mouse has been widely used as an animal model for human senile cataract since it develops late-onset hereditary cataract. Here, we focus on the regional changes of aquaporin-0 (AQP0) and connexins that are associated with the cortical cataract formation in the Emory mutant mice. Emory mutant and CFW wild-type mice at age 1 to 16 months were used in this study. By using an established photography system with dissecting microscopy, the opacities were first detected at the anterior or posterior lens center surface in Emory mice at age 7 months, and gradually extended toward the equator during the 16 months examined. Scanning EM verified that disorganized and fragmented fiber cells were associated with the areas of opacities within approximately 200 µm from the lens surface, indicating that Emory mouse cataracts belong to the cortical cataracts. Freeze-fracture TEM further confirmed that cortical cataracts exhibited extensive wavy square array junctions, small gap junctions and globules. Immunofluorescence analysis showed that in contrast to the high labeling intensity of AQP0-loop antibody, the labeling of AQP0 C-terminus antibody was decreased considerably in superficial fibers in Emory cataracts. Similarly, a significant decrease in the labeling of the antibody against Cx50 C-terminus, but not Cx46 C-terminus, occurred in superficial and outer cortical fibers in Emory cataracts. Western blotting further revealed that the C-termini of both AQP0 and Cx50 in Emory cataracts were decreased to over 50% to that of the wild-type. Thus, this systematic study concludes that the Emory mouse cataract belongs to the cortical cataract which is due to regional breakdown of superficial fibers associated with formation of AQP0-dependent wavy square array junctions, small gap junctions and globules. The marked decreases of the C-termini of both AQP0 and Cx50 in the superficial fibers may disturb the needed interaction between these two proteins during fiber cell

  7. Measurement of non-methane hydrocarbons in Taipei city and their impact on ozone formation in relation to air quality.

    PubMed

    Wu, Ben-Zen; Chang, Chih-Chung; Sree, Usha; Chiu, Konghwa; Lo, Jiunn-Guang

    2006-08-18

    Air pollutants data from semi-continuous measurements at multiple sampling sites in Taipei metropolitan area of Taiwan was obtained by collecting air samples in canisters. The hydrocarbon composition was determined by using GC/MS and GC/FID. The air samples were pre-concentrated onto glass beads prior to separation by PLOT and DB-1 columns of GC. The method showed detection limit of <1 ppb and relative standard deviation in the range of 5-30% for different compounds. Aromatic hydrocarbons (toluene, benzene, etc.) and aliphatic hydrocarbons (ethylene, acetylene, propane, etc.) were correlated primarily to determine the source of emission. The estimated hydrocarbons were ranked according to their abundance and photochemical reactivity. The criteria pollutants, ozone and NO2 were measured by UV-differential optical absorption spectroscopy (UV-DOAS), and were utilized to determine the relative importance of non-methane hydrocarbons (NMHC) and significant contribution of NO2 in limiting ozone formation. The obtained results suggest that ozone formation in Taipei city is probably limited by the supply of non-methane hydrocarbons. The concentration profile of targeted pollutants was compared to other metropolitan areas to determine air quality and the pollutant sources. PMID:17723619

  8. 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

  9. 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. PMID:25907963

  10. Formation of Carbon-Rich Grains in Air by Meteoritic Showers of Tke Nio and Chelyabinsk

    NASA Astrophysics Data System (ADS)

    Miura, Y.

    2015-07-01

    Carbon separation and concentration process can be formed at explosions of meteorite shower in air of the Nio (Japan) and Chelyabinsk (Russia) meteorites. Carbon concentration process by meteoritic explosions is an impact above terrestrial surface.

  11. 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.

  12. 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

  13. 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

    ...EPA is revising the format of its regulations for materials submitted by the State of Indiana that have been incorporated by reference (IBR) into its State Implementation Plan (SIP). The regulations and other materials affected by this format change have all been previously submitted by Indiana and approved by EPA as SIP...

  14. 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.

  15. Numerical study on the influence of hydrogen addition on soot formation in a laminar ethylene-air diffusion flame

    SciTech Connect

    Guo, Hongsheng; Liu, Fengshan; Smallwood, Gregory J.; Guelder, OEmer L.

    2006-04-15

    The influence of hydrogen addition to the fuel of an atmosphere pressure coflow laminar ethylene-air diffusion flame on soot formation was studied by numerical simulation. A detailed gas-phase reaction mechanism, which includes aromatic chemistry up to four rings, and complex thermal and transport properties were used. The fully coupled elliptic governing equations were solved. The interactions between soot and gas-phase chemistry were taken into account. Radiation heat transfer from CO{sub 2}, CO, H{sub 2}O, and soot was calculated using the discrete-ordinates method coupled to a statistical narrow-band-correlated K-based wide-band model. The predicted results were compared with the available experimental data and analyzed. It is indicated that the addition of hydrogen to the fuel in an ethylene-air diffusion flame suppresses soot formation through the effects of dilution and chemistry. This result is in agreement with available experiments. The simulations further suggest that the chemically inhibiting effect of hydrogen addition on soot formation is due to the decrease of hydrogen atom concentration in soot surface growth regions and higher concentration of molecular hydrogen in the lower flame region. (author)

  16. 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)

  17. 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.

  18. Photosensitized Formation of Secondary Organic Aerosols above the Air/Water Interface.

    PubMed

    Bernard, F; Ciuraru, R; Boréave, A; George, C

    2016-08-16

    In this study, we evaluated photosensitized chemistry at the air-sea interface as a source of secondary organic aerosols (SOA). Our results show that, in addition to biogenic emissions, abiotic processes could also be important in the marine boundary layer. Photosensitized production of marine secondary organic aerosol was studied in a custom-built multiphase atmospheric simulation chamber. The experimental chamber contained water, humic acid (1-10 mg L(-1)) as a proxy for dissolved organic matter, and nonanoic acid (0.1-10 mM), a fatty acid proxy which formed an organic film at the air-water interface. Dark secondary reaction with ozone after illumination resulted in SOA particle concentrations in excess of 1000 cm(-3), illustrating the production of unsaturated compounds by chemical reactions at the air-water interface. SOA numbers via photosensitization alone and in the absence of ozone did not exceed background levels. From these results, we derived a dependence of SOA numbers on nonanoic acid surface coverage and dissolved organic matter concentration. We present a discussion on the potential role of the air-sea interface in the production of atmospheric organic aerosol from photosensitized origins. PMID:27434860

  19. 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...

  20. 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.

  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. 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

  3. 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

  4. 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. PMID:26611985

  5. 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.

  6. In-situ formation of multiphase air plasma sprayed barrier coatings for turbine components

    DOEpatents

    Subramanian, Ramesh

    2001-01-01

    A turbine component (10), such as a turbine blade, is provided which is made of a metal alloy (22) and a base, planar-grained thermal barrier layer (28) applied by air plasma spraying on the alloy surface, where a heat resistant ceramic oxide overlay material (32') covers the bottom thermal barrier coating (28), and the overlay material is the reaction product of the precursor ceramic oxide overlay material (32) and the base thermal barrier coating material (28).

  7. Focused excimer laser initiated and radio frequency sustained plasma formation in high pressure air

    NASA Astrophysics Data System (ADS)

    Giar, Ryan

    A doctoral thesis project was performed to experimentally investigate the feasibility of focused excimer laser initiation of air plasmas for radio frequency sustainment. A 193 nm, 15 MW, 300 mJ laser was focused with a 18 cm focal length lens to form a small, high density (ne ~ 10 14 cm--3) seed plasma. These laser plasmas were produced inside a borosilicate glass tube around which was wrapped a 5 turn helical antenna. This antenna was powered with 5 kW of 13.56 MHz of radiation for 1.5 s. This was accomplished at a pressure of 22 Torr, resulting in a large volume (300 cm3) air plasma. Diagnostic measurements of this air plasma determined an electron density of 5E10 cm-3 and an electron temperature 1.3 eV with a neutral temperature of 3500 K. The collision frequency was measured to be 9E10 Hz which resulted in a plasma-loaded antenna resistance of 6 O with a voltage reflection coefficient of 0.7.

  8. 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.

  9. Implications of the Formation of Small Polarons in Li2O2 for Li-Air Batteries

    SciTech Connect

    Kang, J.; Jung, Y. S.; Wei, S. H.; Dillon, A. C.

    2012-01-15

    Lithium-air batteries (LABs) are an intriguing next-generation technology due to their high theoretical energy density of {approx}11 kWh/kg. However, LABs are hindered by both poor rate capability and significant polarization in cell voltage, primarily due to the formation of Li{sub 2}O{sub 2} in the air cathode. Here, by employing hybrid density functional theory, we show that the formation of small polarons in Li{sub 2}O{sub 2} limits electron transport. Consequently, the low electron mobility {mu} = 10{sup -10}-10{sup -9} cm{sup 2}/V s contributes to both the poor rate capability and the polarization that limit the LAB power and energy densities. The self-trapping of electrons in the small polarons arises from the molecular nature of the conduction band states of Li{sub 2}O{sub 2} and the strong spin polarization of the O 2p state. Our understanding of the polaronic electron transport in Li{sub 2}O{sub 2} suggests that designing alternative carrier conduction paths for the cathode reaction could significantly improve the performance of LABs at high current densities.

  10. Implications of the formation of small polarons in Li2O2 for Li-air batteries

    NASA Astrophysics Data System (ADS)

    Kang, Joongoo; Jung, Yoon Seok; Wei, Su-Huai; Dillon, Anne C.

    2012-01-01

    Lithium-air batteries (LABs) are an intriguing next-generation technology due to their high theoretical energy density of ˜11 kWh/kg. However, LABs are hindered by both poor rate capability and significant polarization in cell voltage, primarily due to the formation of Li2O2 in the air cathode. Here, by employing hybrid density functional theory, we show that the formation of small polarons in Li2O2 limits electron transport. Consequently, the low electron mobility μ = 10-10-10-9 cm2/V s contributes to both the poor rate capability and the polarization that limit the LAB power and energy densities. The self-trapping of electrons in the small polarons arises from the molecular nature of the conduction band states of Li2O2 and the strong spin polarization of the O 2p state. Our understanding of the polaronic electron transport in Li2O2 suggests that designing alternative carrier conduction paths for the cathode reaction could significantly improve the performance of LABs at high current densities.

  11. 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.

  12. Formation of a Rigid Hydrophobin Film and Disruption by an Anionic Surfactant at an Air/Water Interface.

    PubMed

    Kirby, Stephanie M; Zhang, Xujun; Russo, Paul S; Anna, Shelley L; Walker, Lynn M

    2016-06-01

    Hydrophobins are amphiphilic proteins produced by fungi. Cerato-ulmin (CU) is a hydrophobin that has been associated with Dutch elm disease. Like other hydrophobins, CU stabilizes air bubbles and oil droplets through the formation of a persistent protein film at the interface. The behavior of hydrophobins at surfaces has raised interest in their potential applications, including use in surface coatings, food foams, and emulsions and as dispersants. The practical use of hydrophobins requires an improved understanding of the interfacial behavior of these proteins, alone and in the presence of added surfactants. In this study, the adsorption behavior of CU at air/water interfaces is characterized by measuring the surface tension and interfacial rheology as a function of adsorption time. CU is found to adsorb irreversibly at air/water interfaces. The magnitude of the dilatational modulus increases with adsorption time and surface pressure until CU eventually forms a rigid film. The persistence of this film is tested through the sequential addition of strong surfactant sodium dodecyl sulfate (SDS) to the bulk liquid adjacent to the interface. SDS is found to coadsorb to interfaces precoated with a CU film. At high concentrations, the addition of SDS significantly decreases the dilatational modulus, indicating disruption and displacement of CU by SDS. Sequential adsorption results in mixed layers with properties not observed in interfaces generated from complexes formed in the bulk. These results lend insight to the complex interfacial interactions between hydrophobins and surfactants. PMID:27164189

  13. 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

  14. 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.

  15. Gap Resolution

    SciTech Connect

    2009-06-16

    With the continued improvements of next generation DNA sequencing technologies and their advantages over traditional Sanger sequencing, the Joint Genome Institute (JGI) has modified its sequencing pipeline to take advantage of the benefits of such technologies. Currently, standard 454 Titanium, paired end 454 Titanium, and Illumina GAll data are generated for all microbial projects and then assembled using draft assemblies at a much greater throughput than before. However, it also presents us with new challenges. In addition to the increased throughput, we also have to deal with a larger number of gaps in the Newbler genome assemblies. Gaps in these assemblies are usually caused by repeats (Newbler collapses repeat copies into individual contigs, thus creating gaps), strong secondary structures, and artifacts of the PCR process (specific to 454 paired end libraries). Some gaps in draft assemblies can be resolved merely by adding back the collapsed data from repeats. To expedite gap closure and assembly improvement on large numbers of these assemblies, we developed software to address this issue.

  16. Gap Resolution

    2009-06-16

    With the continued improvements of next generation DNA sequencing technologies and their advantages over traditional Sanger sequencing, the Joint Genome Institute (JGI) has modified its sequencing pipeline to take advantage of the benefits of such technologies. Currently, standard 454 Titanium, paired end 454 Titanium, and Illumina GAll data are generated for all microbial projects and then assembled using draft assemblies at a much greater throughput than before. However, it also presents us with new challenges.more » In addition to the increased throughput, we also have to deal with a larger number of gaps in the Newbler genome assemblies. Gaps in these assemblies are usually caused by repeats (Newbler collapses repeat copies into individual contigs, thus creating gaps), strong secondary structures, and artifacts of the PCR process (specific to 454 paired end libraries). Some gaps in draft assemblies can be resolved merely by adding back the collapsed data from repeats. To expedite gap closure and assembly improvement on large numbers of these assemblies, we developed software to address this issue.« less

  17. Air pollution and acid rain in Chongqing City: The source and formation

    SciTech Connect

    Yu Xu

    1996-12-31

    Chongqing, the biggest city of Southwestern China, is suffered from air pollution and acid rain for a long time. Studies have shown that coal-burning results in pollution of sulfur dioxide and causes acid rain on a wide range in the area. Emission of sulfur dioxide has met by 0.8 million tons in Chongqing a year. Concentrations of sulfur dioxide in ambient air are above 0.20 mg/m{sup 3} during the recent thirty years. Results of precipitation monitoring show annual precipitation-weighted mean pH ranged from 3.91 to 4.70 and sulfate concentrations ranged from 8.71 mg/1 to 26.29 mg/1 in Chongqing for the past decades. The equivalent ratio of SO{sup 2-}{sub 4} / NO{sup -}{sub 3} in Chongqing (also in China) is higher than those in other countries. It is found that fog water is also acidified in Chongqing City and the concentrations of pollutants in fog water are much higher than those in rain.

  18. 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.

  19. 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.

  20. 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

  1. Qandilite (Mg2TiO4) in Vesuvius skarn lithics: Conditions of formation and miscibility gap in the ternary spinel - qandilite - magnesioferrite

    NASA Astrophysics Data System (ADS)

    Pascal, Marie-Lola; Boudouma, Omar; Fonteilles, Michel; Principe, Claudia

    2010-05-01

    The carbonate host-rocks of the Vesuvius magma chamber(s) are involved in fluid-rock interactions during magma storage, whose consequences on the pre-eruptive conditions are the aim of a continuing study (Principe et al. 2003, Pascal et al. 2009) focussed to the reconstruction of the pre-eruptive conditions in the 1631 magma chamber. Such interactions are recorded by skarn tephra, in which we have found a variety of coexisting minerals of the spinel group with compositions close to the ternary system spinel - qandilite - magnesioferrite (with a small amount of Fe2+), some of which correspond to qandilite much richer in Al than any composition already reported. The large compositional range displayed by these minerals in the Vesuvius occurrences outlines the miscibility gap in the spinel - qandilite - magnesioferrite ternary (with a small amount of Fe2+), at present solely determined on the spinel-qandilite binary at T > 1000°C (Boden & Glasser 1973). The analyzed spinel-qandilite and spinel-magnesioferrite pairs are consistent with the solvus and tie-lines (except for a temperature offset) derived from the thermochemical model of spinel solid solutions of Sack & Ghiorso (1991). Formation temperatures in the range 650 - 700°C are inferred from the petrological study of the involved skarn-forming processes, that typically include two types of metasomatic reactions, i.e., formation of spinel-forsterite-calcite endoskarns by desilication of magmatic bodies at the contact of dolostone wallrocks, and reaction of such preexisting endoskarns with new magma+/-fluid influxes. Calculated phase relations yield logfCO2 = 2.2-2.3, logfO2 = NNO+4, and show that qandilite with moderate magnesioferrite contents, compared to perovskite and geikielite, is the high-temperature Ti-mineral stable in magnesian and extremely silica-deficient surroundings under such oxidized conditions. Boden, P., Glasser, F.P. (1973) Phase relations in the system MgO-Al2O3-TiO2. Transactions and Journal

  2. 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

  3. 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.

  4. 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

  5. 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

  6. Gas-Surface Interactions of Importance to Particle Formation and Growth in Air

    NASA Astrophysics Data System (ADS)

    Finlayson-Pitts, B. J.; Fairhurst, M. C.; Waring-Kidd, C.; Arquero, K. D.; Ezell, M. J.; Perraud, V. M.

    2014-12-01

    Interactions of gases with the condensed phase of airborne particles in the troposphere play an important role in air quality, climate, visibility and deleterious health impacts. However, for most of these interactions, a fundamental mechanistic understanding of the chemistry is lacking. Without this, the development of models that have sufficiently accurate predictive capability on scales from local to regional to global is severely hampered. Studies of the interactions of gas phase organics with bulk condensed phases that are proxies for secondary organic aerosol (SOA) and for "urban grime" on boundary layer surfaces will be presented. These use a combination of techniques, including attenuated total reflectance-Fourier transform infrared spectrometry (ATR-FTIR) and a flow system coupled to a mass spectrometer. The results of studies of the interactions of gas phase organics with clusters of methanesulfonic acid, amines and water using a flow system combined with measurements of the time dependence of particle size distributions and mass spectrometry will also be described. The outcome of these studies is an improved understanding of how SOA is formed and grows, as well as the heterogeneous chemistry of organics on urban surfaces.

  7. Reliable Formation of Single Molecule Junctions with Air-Stable Diphenylphosphine Linkers

    SciTech Connect

    Parameswaran, R.; Hybertsen, M.; Widawsky, J.R.; Vázquez H.; Park, Y.S.; Boardman, B.M.; Nuckolls, C.; Steigerwald, M.L.; Venkataraman, L.

    2010-07-15

    We measure the conductance of single Au-molecule-Au junctions with a series of air-stable diphenylphosphine-terminated molecules using the scanning tunneling microscope-based break junction technique. Thousands of conductance versus displacement traces collected for each molecule are used to statistically analyze junction conductance and evolution upon elongation. Measured conductances for a series of alkane-based molecules exhibit an exponential decrease with increasing length, as expected for saturated molecules, with a tunneling decay constant of 0.98 {+-} 0.04. Measurements of junction elongation indicate strong metal-molecule binding, with a length that increases with the number of methylene groups in the backbone. Measured conductance histograms for four molecules with short, unsaturated backbones (e.g., benzene) are much broader with less well-defined peaks. These measurements are supported by density function theory calculations. The phosphine binds selectively to under-coordinated gold atoms through a donor-acceptor bond with a binding energy of about 1 eV. The calculated tunnel coupling correlates very well with experiment.

  8. Ultrafast formation of air-processable and high-quality polymer films on an aqueous substrate.

    PubMed

    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

  9. 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.

  10. 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.

  11. Mechanistic Evaluation of LixOy Formation on δ-MnO2 in Nonaqueous Li-Air Batteries.

    PubMed

    Liu, Zhixiao; De Jesus, Luis R; Banerjee, Sarbajit; Mukherjee, Partha P

    2016-09-01

    Transition metal oxides are usually used as catalysts in the air cathode of lithium-air (Li-air) batteries. This study elucidates the mechanistic origin of the oxygen reduction reaction catalyzed by δ-MnO2 monolayers and maps the conditions for Li2O2 growth using a combination of first-principles calculations and mesoscale modeling. The MnO2 monolayer, in the absence of an applied potential, preferentially reacts with a Li atom instead of an O2 molecule to initiate the formation of LiO2. The oxygen reduction products (LiO2, Li2O2, and Li2O molecules) strongly interact with the MnO2 monolayer via the stabilization of Li-O chemical bonds with lattice oxygen atoms. As compared to the disproportionation reaction, direct lithiation reactions are the primary contributors to the stabilization of Li2O2 on the MnO2 monolayer. The energy profiles of (Li2O2)2 and (Li2O)2 nucleation on δ-MnO2 monolayer during the discharge process demonstrate that Li2O2 is the predominant discharge product and that further reduction to Li2O is inhibited by the high overpotential of 1.21 V. Interface structures have been examined to study the interaction between the Li2O2 and MnO2 layers. This study demonstrates that a Li2O2 film can be homogeneously deposited onto δ-MnO2 and that the Li2O2/MnO2 interface acts as an electrical conductor. A mesoscale model, developed based on findings from the first-principles calculations, further shows that Li2O2 is the primary product of electrochemical reactions when the applied potential is smaller than 2.4 V. PMID:27532334

  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. Application of laser microetching in formation of air-bearing surface for magnetic head sliders

    SciTech Connect

    Lu, Y.F.; Ye, K.D.

    1996-12-31

    Laser-induced etching of polycrystalline Al{sub 2}O{sub 3}TiC material by a tightly-focused CW Ar ion laser has been investigated in a KOH solution with different concentrations. It is found that the KOH concentration can strongly affect the etching quality where low KOH concentration can result in rough and irregular patterns. The etching effect is also related to laser power and scanning speed. Laser-induced etching of polycrystalline Al{sub 2}O{sub 3}TiC in a KOH solution is found to be a photothermal reaction in which a threshold laser power exists. With an appropriate set of etching parameters, well defined grooves can be obtained with clean side walls and with an etching rate up to several hundred micrometers per second. It is also found that the grains in the polycrystalline Al{sub 2}O{sub 3}TiC material play an important role in the etching dynamics and etching quality. This etching process is believed to be applicable to the formation of a slider surface of magnetic heads in the future.

  14. Number size distribution of aerosols at Mt. Huang and Nanjing in the Yangtze River Delta, China: Effects of air masses and characteristics of new particle formation

    NASA Astrophysics Data System (ADS)

    Wang, Honglei; Zhu, Bin; Shen, Lijuan; An, Junlin; Yin, Yan; Kang, Hanqing

    2014-12-01

    Aerosol number spectra in the range of 10 nm-10 μm were observed at Mt. Huang (Aug. 15-Sep. 15) and Nanjing (Oct. 13-Nov. 15) by a wide-range particle spectrometer (WPS) in 2011. Based on the backward trajectories obtained using the HYSPLIT model, the transport pathways of observed air masses during the study periods were classified into the following four groups: maritime air mass, continental air mass, marine-continental mixed air mass and local air mass. The variations in the aerosol number spectrum and the new particle formation (NPF) events for various types of air masses were discussed, along with meteorological data. The results showed that the average number concentration was 12,540 cm- 3 at Nanjing and only 2791 cm- 3 at Mt. Huang. The aerosol number concentration in Nanjing was 3-7 times higher than that in Mt. Huang; the large discrepancy was in the range of 10-100 nm. Different types of air masses had different effects on number concentration distribution. The number concentration of aerosols was higher in marine air masses, continental air masses and continental-marine mixed air masses at 10-50 nm, 100-500 nm and 50-200 nm, respectively. Under the four types of air masses, the aerosol size spectra had bimodal distributions in Nanjing and unimodal distributions in Mt. Huang (except under continental air masses: HT1). The effects of the diverse air masses on aerosol size segments of the concentration peak in Mt. Huang were stronger than those in Nanjing. The local air masses were dominant at these two sites and accounted for 44% of the total air masses. However, the aerosol number concentration was the lowest in Mt. Huang and the highest in Nanjing when local air masses were present. The number concentrations for foreign air masses increased at Mt. Huang and decreased at Nanjing. Different types of air masses had greater effects on the aerosol spectrum distribution at Mt. Huang than at Nanjing. During the NPF events, the particle growth rates at Mt

  15. 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. PMID:26894568

  16. Instabilities and soot formation in high-pressure, rich, iso-octane-air explosion flames. 1. Dynamical structure

    SciTech Connect

    Lockett, R.D.; Woolley, R.

    2007-12-15

    Simultaneous OH planar laser-induced fluorescence (PLIF) and Rayleigh scattering measurements have been performed on 2-bar rich iso-octane-air explosion flames obtained in the optically accessible Leeds combustion bomb. Separate shadowgraph high-speed video images have been obtained from explosion flames under similar mixture conditions. Shadowgraph images, quantitative Rayleigh images, and normalized OH concentration images have been presented for a selection of these explosion flames. Normalized experimental equilibrium OH concentrations behind the flame fronts have been compared with normalized computed equilibrium OH concentrations as a function of equivalence ratio. The ratio of superequilibrium OH concentration in the flame front to equilibrium OH concentration behind the flame front reveals the response of the flame to the thermal-diffusive instability and the resistance of the flame front to rich quenching. Burned gas temperatures have been determined from the Rayleigh scattering images in the range 1.4{<=}{phi}{<=}1.9 and are found to be in good agreement with the corresponding predicted adiabatic flame temperatures. Soot formation was observed to occur behind deep cusps associated with large-wavelength cracks occurring in the flame front for equivalence ratio {phi}{>=}1.8 (C/O{>=}0.576). The reaction time-scale for iso-octane pyrolysis to soot formation has been estimated to be approximately 7.5-10 ms. (author)

  17. 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

  18. IMAGING OF A TRANSITIONAL DISK GAP IN REFLECTED LIGHT: INDICATIONS OF PLANET FORMATION AROUND THE YOUNG SOLAR ANALOG LkCa 15

    SciTech Connect

    Thalmann, C.; Goto, M.; Henning, T.; Carson, J.; Brandner, W.; Feldt, M.; Grady, C. A.; Wisniewski, J. P.; Janson, M.; Fukagawa, M.; Honda, M.; Mulders, G. D.; Min, M.; Moro-MartIn, A.; Hodapp, K. W.; Abe, L.; Egner, S.; Golota, T.; Fukue, T.

    2010-08-01

    We present H- and K{sub 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 {approx}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{sub Jup} on companions at separations outside of 0.''1 and of 13 M{sub Jup} outside of 0.''2. Thus, we find that a planetary system around LkCa 15 is the most likely explanation for the disk architecture.

  19. Significant reduction in NiO band gap upon formation of Lix Ni1-x O alloys: applications to solar energy conversion.

    PubMed

    Alidoust, Nima; Toroker, Maytal Caspary; Keith, John A; Carter, Emily A

    2014-01-01

    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. We show that Lix Ni1-x O 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. PMID:24265209

  20. Gas phase formation of extremely oxidized pinene reaction products in chamber and ambient air

    NASA Astrophysics Data System (ADS)

    Ehn, M.; Kleist, E.; Junninen, H.; Petäjä, T.; Lönn, G.; Schobesberger, S.; Dal Maso, M.; Trimborn, A.; Kulmala, M.; Worsnop, D. R.; Wahner, A.; Wildt, J.; Mentel, Th. F.

    2012-06-01

    High molecular weight (300-650 Da) naturally charged negative ions have previously been observed at a boreal forest site in Hyytiälä, Finland. The long-term measurements conducted in this work showed that these ions are observed practically every night between spring and autumn in Hyytiälä. The ambient mass spectral patterns could be reproduced in striking detail during additional measurements of α-pinene (C10H16) oxidation at low-OH conditions in the Jülich Plant Atmosphere Chamber (JPAC). The ions were identified as clusters of the nitrate ion (NO3-) and α-pinene oxidation products reaching oxygen to carbon ratios of 0.7-1.3, while retaining most of the initial ten carbon atoms. Attributing the ions to clusters instead of single molecules was based on additional observations of the same extremely oxidized organics in clusters with HSO4- (Hyytiälä) and C3F5O2- (JPAC). The most abundant products in the ion spectra were identified as C10H14O7, C10H14O9, C10H16O9, and C10H14O11. The mechanism responsible for forming these molecules is still not clear, but the initial reaction is most likely ozone attack at the double bond, as the ions are mainly observed under dark conditions. β-pinene also formed highly oxidized products under the same conditions, but less efficiently, and mainly C9 compounds which were not observed in Hyytiälä, where β-pinene on average is 4-5 times less abundant than α-pinene. Further, to explain the high O/C together with the relatively high H/C, we propose that geminal diols and/or hydroperoxide groups may be important. We estimate that the night-time concentration of the sum of the neutral extremely oxidized products is on the order of 0.1-1 ppt (~106-107 molec cm-3). This is in a similar range as the amount of gaseous H2SO4 in Hyytiälä during day-time. As these highly oxidized organics are roughly 3 times heavier, likely with extremely low vapor pressures, their role in the initial steps of new aerosol particle formation and

  1. Gas phase formation of extremely oxidized pinene reaction products in chamber and ambient air

    NASA Astrophysics Data System (ADS)

    Ehn, M.; Kleist, E.; Junninen, H.; Petäjä, T.; Lönn, G.; Schobesberger, S.; Dal Maso, M.; Trimborn, A.; Kulmala, M.; Worsnop, D. R.; Wahner, A.; Wildt, J.; Mentel, Th. F.

    2012-02-01

    High molecular weight (300-650 Da) naturally charged negative ions have previously been observed at a boreal forest site in Hyytiälä, Finland. The long-term measurements conducted in this work showed that these ions are observed practically every night during spring and summer in Hyytiälä. The ambient mass spectral patterns could be reproduced in striking detail during additional measurements of α-pinene (C10H16) oxidation at low-OH conditions in the Jülich Plant Atmosphere Chamber (JPAC). The ions were identified as clusters of the nitrate ion (NO3-) and α-pinene oxidation products reaching oxygen to carbon ratios of 0.7-1.3, while retaining most of the initial ten carbon atoms. Attributing the ions to clusters instead of single molecules was based on additional observations of the same extremely oxidized organics in clusters with HSO4- (Hyytiälä) and C3F5O2- (JPAC). The most abundant products in the ion spectra were identified as C105H14O7, C10H14O9, C10H16O9, and C10H14O11. The mechanism responsible for forming these molecules is still not clear, but the initial reaction is most likely ozone attack at the double bond, as the ions are mainly observed under dark conditions. β-pinene also formed highly oxidized products under the same conditions, but less efficiently, and mainly C9 compounds which were not observed in Hyytiälä, where β-pinene on average is 4-5 times less abundant than α-pinene. Further, to explain the high O/C together with the relatively high H/C, we propose that geminal diols and/or hydroperoxide groups may be important. We estimate that the night-time concentration of the sum of the neutral extremely oxidized products is on the order of 0.1-1 ppt (~106-107 molec cm-3). This is in a similar range as the amount of gaseous H2SO4 in Hyytiälä during day-time. As these highly oxidized organics are roughly 3 times heavier, likely with extremely low vapor pressures, their role in the initial steps of new aerosol particle formation and

  2. Preliminary formation analysis for compressed air energy storage in depleted natural gas reservoirs : a study for the DOE Energy Storage Systems Program.

    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

  3. 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.

  4. The reasons for the epilepsy treatment gap in Kilifi, Kenya: Using formative research to identify interventions to improve adherence to antiepileptic drugs

    PubMed Central

    Carter, Julie A.; Molyneux, Catherine S.; Mbuba, Caroline K.; Jenkins, Jo; Newton, Charles R.J.C.; Hartley, Sally D.

    2012-01-01

    Many people with epilepsy (PWE) in resource‐poor countries do not receive appropriate treatment, a phenomenon referred to as the epilepsy treatment gap (ETG). We conducted a qualitative study to explore the reasons for this gap and to identify possible interventions in Kilifi, Kenya. Focus group discussions (FGDs) were carried out of PWE and their caregivers. Individual interviews were conducted of PWE, their caregivers, traditional healers, community health workers and leaders, nurses and doctors. In addition, a series of workshops was conducted, and four factors contributing to the ETG were identified: 1) lack of knowledge about the causes, treatment and prognosis of epilepsy; 2) inaccessibility to antiepileptic drugs; 3) misconceptions about epilepsy derived from superstitions about its origin; 4) and dissatisfaction with the communication skills of health providers. These data indicated possible interventions: 1) education and support for PWE and their caregivers; 2) communication skills training for health providers; 3) and improved drug provision. PMID:23160097

  5. 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

    2016-01-01

    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

  6. 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

  7. Oxygen miscibility gap and spin glass formation in the pyrochlore Lu{sub 2}Mo{sub 2}O{sub 7}

    SciTech Connect

    Clark, L.; Ritter, C.; Harrison, A.; Attfield, J.P.

    2013-07-15

    Rare earth (R) molybdate pyrochlores, R{sub 2}Mo{sub 2}O{sub 7}, are of interest as frustrated magnets. Polycrystalline samples of Lu{sub 2}Mo{sub 2}O{sub 7−x} prepared at 1600 °C display a coexistence of cubic pyrochlore phases. Rietveld fits to powder neutron diffraction data and chemical analyses show that the miscibility gap is between a stoichiometric x=0 and an oxygen-deficient x≈0.4 phase. Lu{sub 2}Mo{sub 2}O{sub 7} behaves as a spin glass material, with a divergence of field cooled and zero field cooled DC magnetic susceptibilities at a spin freezing temperature T{sub f}=16 K, that varies with frequency in AC measurements following a Vogel–Fulcher law. Lu{sub 2}Mo{sub 2}O{sub 6.6} is more highly frustrated spin glass and has T{sub f}=20 K. - Graphical abstract: The cubic Lu{sub 2}Mo{sub 2}O{sub 7−x} system exhibits a miscibility gap between coexisting pyrochlore phases at 1600 °C. Neutron powder diffraction refinement and chemical analysis shows that the gap separates stoichiometric x=0 and oxygen-deficient x≈0.4 phases. Lu{sub 2}Mo{sub 2}O{sub 7−x} has a frustrated spin glass ground state that is sensitive to the oxygen content. - Highlights: • The cubic Lu{sub 2}Mo{sub 2}O{sub 7−x} system has a miscibility gap between coexisting pyrochlore phases at 1600 °C. • Neutron powder diffraction shows that the gap separates x=0 and oxygen-deficient x≈0.4 phases. • Lu{sub 2}Mo{sub 2}O{sub 7−x} has a frustrated spin glass ground state that is sensitive to the oxygen content.

  8. 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).

  9. 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).

  10. 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.

  11. 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.

  12. 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.

  13. 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. PMID:14968859

  14. 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.

  15. Numerical studies of nitric oxide formation in nanosecond-pulsed discharge-stabilized flames of premixed methane/air.

    PubMed

    Bak, Moon Soo; Cappelli, Mark A

    2015-08-13

    A simulation is developed to investigate the kinetics of nitric oxide (NO) formation in premixed methane/air combustion stabilized by nanosecond-pulsed discharges. The simulation consists of two connected parts. The first part calculates the kinetics within the discharge while considering both plasma/combustion reactions and species diffusion, advection and thermal conduction to the surrounding flow. The second part calculates the kinetics of the overall flow after mixing the discharge flow with the surrounding flow to account for the effect that the discharge has on the overall kinetics. The simulation reveals that the discharge produces a significant amount of atomic oxygen (O) as a result of the high discharge temperature and dissociative quenching of excited state nitrogen by molecular oxygen. This atomic oxygen subsequently produces hydroxyl (OH) radicals. The fractions of these O and OH then undergo Zel'dovich reactions and are found to contribute to as much as 73% of the total NO that is produced. The post-discharge simulation shows that the NO survives within the flow once produced. PMID:26170428

  16. Humidity effects on photochemical aerosol formation in the SO 2-NO-C 3H 6-air system

    NASA Astrophysics Data System (ADS)

    Izumi, Katsuyuki; Mizuochi, Motoyuki; Murano, Kentaro; Fukuyama, Tsutomu

    In order to investigate the effects of humidity on the gas-phase oxidation of SO 2 in polluted air and on the subsequent aerosol formation process, photoirradiation experiments were carried out by means of a 4-m 3 chamber, in which mixtures containing SO 2, NO and C 3H 6 with concentrations in the ppm range were exposed to simulated solar radiation in different relative humidity (r.h.) conditions. The total amount of oxidized SO 2 was quantified from the SO 42- yield determined by the chemical analysis of the aerosol product, and a part due to the oxidation by the OH radical was evaluated by estimating the OH concentration from the decay rate of C 3H 6. The remaining part was assigned to the oxidation by the Criegee intermediate, as it had a good correlation with the progress of the O 3 + C 3H 6 reaction. The contributions of the two oxidizing species to the total conversion and the oxidation rate of SO 2 were measured as functions of r.h. As a result, experimental evidence was obtained for the prediction of Calvert and Stockwell's (1983, Envir. Sci. Technol. 17, 428A-443A) simulation that the oxidation due to the Criegee intermediate was retarded by the increase in humidity. The OH contribution, on the other hand, was almost independent of r.h. It was observed consequently that the total oxidized amount of SO 2 considerably decreased as r.h. was higher. The humidity effect on the aerosol formation process was found to be more complicated than the effect on the gas-phase chemistry. The maximum rate of increase in the particle number concentration rose linearly with increasing r.h., but the number concentration itself measured at its maximum or at the end of the irradiation reached a ceiling value around r.h. = 30% and went down for higher r.h. The average panicle size in the final stage of the reaction showed a minimum around the same r.h. at which the number concentration was maximum. The H 2SO 4 concentration in the mist particles, however, decreased

  17. Atmospheric air diffuse array-needles dielectric barrier discharge excited by positive, negative, and bipolar nanosecond pulses in large electrode gap

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Yang, De-zheng; Wang, Wen-chun; Liu, Zhi-jie; Wang, Sen; Jiang, Peng-chao; Zhang, Shuai

    2014-09-01

    In this paper, positive, negative, and bipolar nanosecond pulses are employed to generate stable and diffuse discharge plasma using array needles-plate electrode configuration at atmospheric pressure. A comparison study of discharge images, electrical characteristics, optical emission spectra, and plasma vibrational temperature and rotational temperatures in three pulsed polarity discharges is carried on under different discharge conditions. It is found that bipolar pulse is beneficial to the excitation of diffuse dielectric barrier discharge, which can generate a room temperature plasma with more homogeneous and higher discharge intensity compared with unipolar discharges. Under the condition of 6 mm electrode gap distance, 26 kV pulse peak voltage, and 150 Hz pulse repetition rate, the emission intensity of N2 (C3Πu → B3Πg) of the bipolar pulsed discharge is 4 times higher than the unipolar discharge (both positive and negative), while the plasma gas temperature is kept at 300 K, which is about 10-20 K lower than the unipolar discharge plasma.

  18. 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.

  19. Air filtering device

    SciTech Connect

    Backus, A.L.

    1992-07-28

    This patent describes a room air cleaning device. It comprises: a box housing having an air inlet and an air outlet provided therein; a vertical baffle coupled to the box housing opposite the air outlet and spaced form the box housing such that an air egress outlet is formed between the vertical baffle and the box housing; air cleansing means substantially disposed within the box housing and cleansing air passing into the inlet and out of the air egress outlet; a fan disposed within the box housing, the fan providing air movement through the air inlet and the air egress outlet; wherein air exits the room air cleaning device through the air egress outlet as a vertical plane of moving air; and wherein formation of the vertical plane of moving air contributes to the formation of a low pressure area drawing impure air toward the air inlet.

  20. Hydrogen supplemented air inhalation reduces changes of prooxidant enzyme and gap junction protein levels after transient global cerebral ischemia in the rat hippocampus.

    PubMed

    Hugyecz, Marietta; Mracskó, Eva; Hertelendy, Péter; Farkas, Eszter; Domoki, Ferenc; Bari, Ferenc

    2011-08-01

    Transient global cerebral ischemia (TGCI) occurs during acute severe hypotension depriving the brain of oxygen and glucose for a short period of time. During reperfusion, several mechanisms can induce secondary neuronal damage, including the increased production of reactive oxygen species (ROS). Hydrogen gas-enriched air inhalation is a neuroprotective approach with proven antioxidant potential, which has not yet been examined in TGCI. Accordingly, we set out to describe the effect of inhalation of 2.1% hydrogen supplemented room air (H(2)-RA) in comparison with a well studied neuroprotective agent, rosiglitazone (RSG) in a TGCI rat model. Male Wistar rats were exposed to TGCI (n=26) or sham operation (n=26), while a third group served as intact control (naive, n=5). The operated groups were further divided into non-treated, H(2)-RA, RSG (6 mg/kg i.v.) and vehicle treated animals. Tissue samples from the hippocampus and frontal cortex were taken 3 days following surgery. Western blot analysis was applied to determine the expressions of cyclooxygenase-2 (COX-2), neuronal and endothelial nitric oxide synthase (nNOS and eNOS, respectively), manganese superoxide dismutase (MnSOD) and glial connexin proteins: connexin 30 and connexin 43. The expressions of COX-2, and connexin proteins were upregulated, while nNOS was downregulated 3 days after TGCI. Both RSG and H(2)-RA prevented the changes of enzyme and connexin levels. Considering the lack of harmful side effects, inhalation of H(2)-RA can be a promising approach to reduce neuronal damage after TGCI. PMID:21718970

  1. Connexin43 gap junctions in normal, regenerating, and cultured mouse bone marrow and in human leukemias: their possible involvement in blood formation.

    PubMed Central

    Krenacs, T.; Rosendaal, M.

    1998-01-01

    Communicating channels called gap junctions are thought to play a ubiquitous part in cell growth and development. Based on earlier work, we have recently found functional evidence of their presence in human and mouse bone marrow. In this study we studied the cell-type association of the gap junction channel-forming protein, connexin, in mouse and human bone marrow under different physiological and pathological conditions and tested the pathway of communication in bone marrow cultures. For high-resolution antigen demonstration we took advantage of semi-thin resin sections, antigen retrieval methods, immunofluorescence, and confocal laser scanning microscopy. Connexin43 (Cx43) and its mRNA were consistently expressed in human and rodent marrow. Cx37 was found only in the arteriolar endothelium, but neither Cx32 nor -26 were expressed. In tissue sections, the immunostained junctions appeared as dots, which were digitally measured and counted. Their average size was 0.40 mm in human and 0.49 mm in mice marrow. There were at least twice as many gap junctions in the femoral midshaft of 6-week-old mice (1.75 x 10(5)/mm3) as in those older than 12 weeks (0.89 x 10(5)/mm3). Most Cx43 was associated with collagen III+ endosteal and adventitial stromal cells and with megakaryocytes. Elsewhere, they were few and randomly distributed between all kinds of hematopoietic cells. In the femoral epiphysis of juvenile mice, stromal cell processes full of Cx43 enmeshed three to six layers of hematopoietic cells near the endosteum. The same pattern was seen in the midshaft of regenerating mouse marrow 3 to 5 days after cytotoxic treatment with 5-fluorouracil. Functional tests in cultures showed the transfer of small fluorescent dyes, Lucifer Yellow and 2',7'-bis-(2-carboxyethyl)-5, 6-carboxyfluorescein, between stromal cells and in rare cases between stromal and hematopoietic cells too. The stromal cells were densely packed with Cx43 and we found aggregates of connexon particles in

  2. 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%).

  3. 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.

  4. A computational study of radiation and gravity effect on temperature and soot formation in a methane air co-flow diffusion flame

    NASA Astrophysics Data System (ADS)

    Bhowal, Arup Jyoti; Mandal, Bijan Kumar

    2016-07-01

    An effort has been made for a quantitative assessment of the soot formed under steady state in a methane air co flow diffusion flame by a numerical simulation at normal gravity and at lower gravity levels of 0.5 G, 0.1 G and 0.0001 G (microgravity). The peak temperature at microgravity is reduced by about 50 K than that at normal gravity level. There is an augmentation of soot formation at lower gravity levels. Peak value at microgravity multiplies by a factor of ˜7 of that at normal gravity. However, if radiation is not considered, soot formation is found to be much more.

  5. 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 ...

  6. 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...

  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. 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.

  9. Investigation of the impact of imposed air inlet velocity oscillations on the formation and oxidation of soot using simultaneous 2-Colour-TIRE-LII

    NASA Astrophysics Data System (ADS)

    Aleksandrov, A.; Suntz, R.; Bockhorn, H.

    2015-05-01

    The response of non-premixed swirling flames to acoustic perturbations at various frequencies (0-350 Hz) and the impact of imposed air inlet velocity oscillations on the formation and oxidation of soot are investigated. The results obtained from these flames are of special interest for "rich-quenched-lean" (RQL) combustion concepts applied in modern gas turbines. In RQL combustion, the fuel is initially oxidized by air under fuel-rich conditions in a first stage followed by a fuel-lean combustion step in a second stage. To mimic soot formation and oxidation in RQL combustion, soot particle measurements in highly turbulent, non-premixed swirling natural gas/ethylene-confined flames at imposed air inlet velocity oscillations are performed using simultaneous 2-Colour-Time-Resolved-Laser-Induced Incandescence (simultaneous 2-Colour-TIRE-LII). The latter technique is combined with line-of-sight averaged OH*-chemiluminescence imaging, measurements of the velocity field by high-speed particle imaging velocimetry under reactive combustion conditions and measurements of the mean temperature field obtained by a thermocouple. A natural gas/ethylene mixture (Φ = 1.56, 42 % C2H4, 58 % natural gas, P th = 17.6 kW at atmospheric pressure) is used as a fuel, which is oxidized by air under fuel-rich conditions in the first combustion chamber.

  10. 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.

  11. Filling the launch gap

    NASA Astrophysics Data System (ADS)

    Hoeser, S.

    1986-05-01

    Vehicles proposed to fill the gap in the U.S. space program's space transport needs for the next decade resulting from the January Challenger disaster, are discussed. Prior to the accident, the Air Force planned to purchase a Complementary Expendable Launch Vehicle system consisting of 10 single-use Titan-34D7 rockets. Another heavy lift booster now considered is the Phoenix H. Commercial launch vehicle systems projected to be available in the necessary time frame include the 215,000-pound thrust 4000-pound LEO payload capacity NASA Delta, the 11,300-pound LEO payload capacity Atlas Centaur the first ICBM, and the all-solid propellant expendable 2000-pound LEO payload Conestoga rocket. Also considered is the man-rated fully reusable Phoenix vertical take-off and vertical-landing launch vehicle.

  12. 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, A. M.; Hayes, P. L.; Peng, Z.; Palm, B. B.; Hu, W.; Day, D. A.; Li, R.; Cubison, M. J.; Brune, W. H.; Graus, M.; Warneke, C.; Gilman, J. B.; Kuster, W. C.; de Gouw, J. A.; Jimenez, J. L.

    2015-08-01

    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 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, achieving equivalent atmospheric aging from hours up to several weeks in 3 min of processing. OH radical concentration was continuously stepped, obtaining measurements of real-time SOA formation and oxidation at multiple equivalent ages from 0.8 days-6.4 weeks. Enhancement of 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 VOC correlation, indicates the importance of relatively reactive (τOH ∼ 0.3 day) SOA precursors in the LA-Basin. 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 higher ages where OA loss dominates. The mass added at low

  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. PMID:24290796

  14. A Numerical Study of the Impacts of Dry Air on Tropical Cyclone Formation: A Development Case and a Non-development Case

    NASA Astrophysics Data System (ADS)

    Fritz, C.; Wang, Z.

    2012-12-01

    The impacts of dry air on tropical cyclone formation are examined in the numerical model simulations of ex-Gaston (2010) and pre-Fay (2008). The former, a remnant low downgraded from a short-lived tropical cyclone, can be regarded as a non-developing system as it failed to redevelop, and the latter developed into a tropical cyclone despite lateral dry air entrainment and a transient upper-level dry air intrusion. Water vapor budget analysis suggests that the mean vertical moisture transport plays the dominant role in moistening the free atmosphere. Backward trajectory analysis and water budget analysis show that vertical transport of dry air from the middle and upper troposphere, where a well-defined wave pouch is absent, contributes to the mid-level drying near the pouch center in ex-Gaston. The mid-level drying suppresses deep convection, reduces moisture supply from the boundary layer, and contributes to the non-development of ex-Gaston. Three-dimensional trajectory analysis based on the numerical model simulation of Fay suggests that dry air entrained at the pouch periphery tends to stay off the pouch center due to the weak mid-level inflow or gets moistened along its path even if being wrapped into the wave pouch. Lateral entrainment in the middle troposphere thus does not suppress convection near the pouch center or prevent the development of Tropical Storm Fay. This study suggests that the upper troposphere is a weak spot of the wave pouch at the early formation stage and that the vertical transport is likely a more direct pathway for dry air to influence moist convection near the pouch center. Fig. 1 (a) 3 km relative humidity and storm relative streamlines for Gaston (2010) at 0800 UTC 05 September 2010 with a group of ensemble forward parcel trajectories (gray); (b) vertical cross section of RH along 17.5°N (contour intervals are set to 15%) and backward trajectories (gray) projected on the longitude-height plane. The box in (a) highlights a pocket of

  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. Formation of Nano-Bacteria-Like Flow Textures Formed at Oxygen-Rich Air Condition of Shock Wave Reaction

    NASA Astrophysics Data System (ADS)

    Miura, Y.; Tanosaki, T.

    2011-03-01

    Nano-flow textures with irregular shapes are obtained by shock impact on carbon-fibers with oxygen-rich air condition (not at vacuum condition), which are different with nano-bacteria texture of the martian meteorite with regular nano-flow textures.

  17. Airborne Measurements of Ammonia and Implications for Ammonium Nitrate Formation in the Central Valley and the South Coast Air Basin of California

    NASA Astrophysics Data System (ADS)

    Nowak, J. B.; Neuman, J.; Bahreini, R.; Middlebrook, A. M.; Brock, C. A.; Frost, G. J.; Holloway, J. S.; McKeen, S. A.; Peischl, J.; Pollack, I. B.; Roberts, J. M.; Ryerson, T. B.; Trainer, M.; Parrish, D. D.

    2010-12-01

    Ammonia (NH3) is the dominant gas-phase base in the troposphere. As a consequence, NH3 abundance influences aerosol formation and composition. Ammonium nitrate aerosol is formed from the reaction of gas phase NH3 and nitric acid (HNO3). Anthropogenic emissions of NH3 and NOx (NO + NO2), which in sunlight can be oxidized to form HNO3, can react to form ammonium nitrate aerosol. Agricultural activity (i.e., dairy farms), and urban centers (i.e., Fresno, Los Angeles) are sources of ammonium nitrate gas-phase precursors in both the Central Valley and the South Coast Air Basin. Airborne measurements of NH3, HNO3, particle composition, and particle size distribution were made aboard the NOAA WP-3D research aircraft during May and June 2010 in the Central Valley and the South Coast Air Basin of California, as part of CalNex 2010 (California Research at the Nexus of Air Quality and Climate Change). The highest mixing ratios of NH3, well over 100 parts-per-billion by volume (ppbv), were measured downwind of dairy farms. The high NH3 mixing ratios were highly anti-correlated with HNO3 mixing ratios on fast time scales (~1 s) that correspond to short flight distances (~100 m). During these periods particulate nitrate (NO3-) concentrations increased, indicating ammonium nitrate formation. The meteorological and chemical environments during these periods will be studied to determine the factors driving or limiting ammonium nitrate formation and the resulting regional differences. Finally, the relationship between the NH3 observations and NH3 sources will be examined to assess the emissions and their contribution to ammonium nitrate abundance.

  18. Exploring morphological variations of a laser-induced water jet in temporal evolution: formation of an air bubble enclosing a water drop

    NASA Astrophysics Data System (ADS)

    Chen, Ross C. C.; Yu, Y. T.; Su, K. W.; Chen, Y. F.

    2013-11-01

    We explore the spatio-temporal dynamics of a water jet that is generated by laser-induced water breakdown beneath a flat free surface. We find that morphological variations in the temporal evolution can be divided into three categories depending on the depth parameter γ, which is the ratio of the water-breakdown depth to the maximum bubble radius. For a depth parameter in the range 0.8 ≤ γ ≤ 1.03, we observe an intriguing pattern formation in which an air bubble perfectly encloses a water drop through the process of the Plateau-Rayleigh instability.

  19. Effects of cloudy/clear air mixing and droplet pH on sulfate aerosol formation in a coupled chemistry/climate global model

    SciTech Connect

    Molenkamp, C.R.; Atherton, C.A.; Penner, J.E.; Walton, J.J.

    1996-10-01

    In this paper we will briefly describe our coupled ECHAM/GRANTOUR model, provide a detailed description of our atmospheric chemistry parameterizations, and discuss a couple of numerical experiments in which we explore the influence of assumed pH and rate of mixing between cloudy and clear air on aqueous sulfate formation and concentration. We have used our tropospheric chemistry and transport model, GRANTOUR, to estimate the life cycle and global distributions of many trace species. Recently, we have coupled GRANTOUR with the ECHAM global climate model, which provides several enhanced capabilities in the representation of aerosol interactions.

  20. 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.

  1. Formation of elevated refractive layers in the oceanic boundary layer by modification of land air flowing offshore

    NASA Astrophysics Data System (ADS)

    Gossard, Earl E.

    1982-03-01

    The usual picture of the development of temperature and humidity boundary layers in a land air mass that moves offshore is shown to be very wrong under one type of Foehn condition in southern California, and it is probable that similar conditions can prevail in widespread areas around the globe, notably the Mediterranean Sea and the monsoonal regions of the Near East and Southeast Asia. A formalism is developed for analyzing the modification that seems to represent the observations satisfactorily, and graphical solutions for radio and optical ducting are given. It is shown that offshore modification can lead to elevated layers rather than to surface based layers, and the height of the layer base is theoretically predicted. Values of evaporation and heat flux into such an air mass are calculated, and the distance offshore at which dew point depression becomes zero is predicted. A method for measuring the downward heat flux in elevated inversion layers is described and results are given.

  2. Formation of photochemical air pollution in central California 1. Development of a revised motor vehicle emission inventory

    NASA Astrophysics Data System (ADS)

    Marr, Linsey C.; Black, Douglas R.; Harley, Robert A.

    2002-03-01

    Photochemical air pollution problems have proved difficult to understand and control in central California. A major source of uncertainty is the rate of precursor volatile organic compounds and NOx emissions, especially from motor vehicles. We develop alternative emissions estimates for on-road motor vehicles in 1990, using fuel sales data, emission factors measured in on-road studies, and ambient pollutant ratios, for a region that includes the San Francisco Bay and San Joaquin Valley air basins and Sacramento County. Fuel-based emissions estimates are compared with predictions of California's most recent motor vehicle emission factor model (EMFAC) and with an inventory that has been used in previous regional-scale photochemical modeling studies. The fuel-based inventory contains 10-50% less CO, 40-100% more nonmethane organic compounds, and 10-20% less NOx than estimated both by EMFAC and the photochemical modeling inventory. We also describe new temporal distributions of vehicle emissions by hour and day of week. Diesel trucks, a major source of NOx, have a broad midday peak in emissions on weekdays, in contrast to passenger vehicles, which show morning and afternoon commuter peaks. While passenger vehicle travel is similar on weekdays and weekends, diesel truck activity and emissions decrease by 70-80% on weekends. Vehicle emission rates and their temporal patterns are linked to a regional photochemical air pollution episode that spans a weekend in August 1990.

  3. 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

  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 PAGESBeta

    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; et al

    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 particulate sulfate and nitrate over the Pearl River Delta in the fall: Diagnostic analysis using the Community Multiscale Air Quality model

    NASA Astrophysics Data System (ADS)

    Qin, Momei; Wang, Xuesong; Hu, Yongtao; Huang, Xiaofeng; He, Lingyan; Zhong, Liuju; Song, Yu; Hu, Min; Zhang, Yuanhang

    2015-07-01

    In recent years, fine particulate matter (PM) pollution and visibility degradation have become severe air quality issues in China. In this study, PM2.5 pollution over the Pearl River Delta (PRD) region during January, April, August, and November 2009 was simulated using the Community Multiscale Air Quality (CMAQ) model. An in-depth diagnostic analysis, focused on November 2009, was also conducted to reveal the patterns of sulfate and nitrate distribution, and to identify the main factors that influence the formation of sulfate and nitrate under typical meteorological conditions. The CMAQ model reasonably reproduced the observed concentrations, but showed better performance for January and November than it did for April and August, for which there was light-moderate underestimation of SO2, NOx, O3, PM10, and PM2.5 concentrations, and slight overestimation of daily 8-h maximum concentrations of O3. Utilizing a sulfate tracking technique, it was found that on nearly 20 days in November 2009, characterized by northeasterly winds, cross-boundary transport contributed to >75% of the total sulfate budget, while local gas phase oxidation and primary emissions averaged 10% and 8%, respectively. Aqueous sulfate typically contributed less than 1% of the total sulfate budget, except when the winds were directed from the sea and high humidity favored aqueous oxidation, and the percentage contribution reached up to 46%. NH3 was generally sufficient to fully neutralize H2SO4; however, the formation of nitrate over the PRD was limited by the availability of NH3.

  7. 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.

  8. The Foulness multiton air blast simulator. Part 3: Blast wave formation and methods used to drive the simulator

    NASA Astrophysics Data System (ADS)

    Clare, P. M.

    1980-03-01

    The mechanisms by which blast waves are generated by a helical charge of detonating fuse in a 4.9 m diameter nuclear air blast simulator were studied in order to achieve control over the waveform produced. The problem of producing low pressure blast waves with long duration was overcome by immersing the charge in an aqueous foam in the firing chamber. A comparison is made with pressure-time profiles of a 1 kton nuclear shot, concluding that an accurate simulation involves a combination of techniques rather than the simple firing of an axially placed charge.

  9. 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

  10. 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.

  11. Formation of reactive oxygen and nitrogen species by repetitive negatively pulsed helium atmospheric pressure plasma jets propagating into humid air

    NASA Astrophysics Data System (ADS)

    Norberg, Seth A.; Johnsen, Eric; Kushner, Mark J.

    2015-06-01

    Atmospheric pressure plasma jets have many beneficial effects in their use in surface treatment and, in particular, plasma medicine. One of these benefits is the controlled production of reactive oxygen and nitrogen species (RONS) in the active discharge through the molecular gases added to the primary noble gas in the input mixture, and through the interaction of reactive species in the plasma effluent with the ambient air. In this computational investigation, a parametric study was performed on the production of RONS in a multiply pulsed atmospheric pressure plasma jet sustained in a He/O2 mixture and flowing into ambient humid air. The consequences of flow rate, O2 fraction, voltage, and repetition rate on reactant densities after a single discharge pulse, after 30 pulses, and after the same total elapsed time were investigated. At the end of the first discharge pulse, voltage has the greatest influence on RONS production. However, the systematic trends for production of RONS depend on repetition rate and flow rate in large part due to the residence time of RONS in the plasma zone. Short residence times result in reactive species produced by the previous pulse still being in the discharge tube or in the path of the ionization wave at the next pulse. The RONS therefore accumulate in the tube and in the near effluent on a pulse-to-pulse basis. This accumulation enables species requiring multiple reactions among the primary RONS species to be produced in greater numbers.

  12. Thin plate gap bridging study for Nd:YAG pulsed laser lap welds.

    SciTech Connect

    Roach, Robert Allen; Fuerschbach, Phillip William; Bernal, John E.; Norris, Jerome T.

    2006-01-01

    In an on going study of gap bridging for thin plate Nd:YAG laser lap welds, empirical data, high speed imaging, and computer modeling were utilized to better understand surface physics attributed to the formation and solidification of a weld pool. Experimental data indicates better gap bridging can be achieved through optimized laser parameters such as pulse length, duration, and energy. Long pulse durations at low energies generating low peak powers were found to create the highest percent of gap bridging ability. At constant peak power, gap-bridging ability was further improved by using a smaller spot diameter resulting in higher irradiances. Hence, welding in focus is preferable for bridging gaps. Gas shielding was also found to greatly impact gap-bridging ability. Gapped lap welds that could not be bridged with UHP Argon gas shielding, were easily bridged when left unshielded and exposed to only air. Incident weld angle and joint offset were also investigated for their ability to improve gap bridging. Optical filters and brightlight surface illumination enabled high-speed imaging to capture the fluid dynamics of a forming and solidifying weld pool. The effects of various laser parameters and the weld pool's interaction with the laser beam could also be observed utilizing the high-speed imaging. The work described is used to develop and validate a computer model with improved weld pool physics. Finite element models have been used to derive insight into the physics of gap bridging. The dynamics of the fluid motion within the weld pool in conjunction with the free surface physics have been the primary focus of the modeling efforts. Surface tension has been found to be a more significant factor in determining final weld pool shape than expected.

  13. NATIONAL GAP ANALYSIS PROGRAM

    EPA Science Inventory

    GAP Analysis is a rapid conservation evaluation method for assessing the current status of biodiversity at large spatial scales. GAP Analysis provides a systematic approach for evaluating the protection afforded biodiversity in given areas. It uses Geographic Information System (...

  14. Practice Gaps in Pruritus.

    PubMed

    Silverberg, Jonathan I

    2016-07-01

    There are several practice gaps in the evaluation and management of itch. These gaps include a dearth of objective measures of itch, infrequent use of validated patient-reported outcomes for itch, non-evidence-based treatment, and lack of consensus about the ideal workup for generalized itch. The present article reviews these gaps and presents potential solutions. PMID:27363881

  15. 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.…

  16. Funding Gap Study.

    ERIC Educational Resources Information Center

    Newmyer, Joe; McIntyre, Chuck

    The "funding gap" in public higher education in California represents the difference between state appropriations and the amount needed to fully support each segment's educational mission. This report identifies and defines the funding gap for the California Community Colleges (CCC); measures the consequences of this gap on program quality and…

  17. Role of the reaction of stabilized Criegee intermediates with peroxy radicals in particle formation and growth in air.

    PubMed

    Zhao, Yue; Wingen, Lisa M; Perraud, Véronique; Greaves, John; Finlayson-Pitts, Barbara J

    2015-05-21

    Ozonolysis of alkenes is an important source of secondary organic aerosol (SOA) in the atmosphere. However, the mechanisms by which stabilized Criegee intermediates (SCI) react to form and grow the particles, and in particular the contributions from oligomers, are not well understood. In this study, ozonolysis of trans-3-hexene (C6H12), as a proxy for small alkenes, was investigated with an emphasis on the mechanisms of particle formation and growth. Ozonolysis experiments were carried out both in static Teflon chambers (18-20 min reaction times) and in a glass flow reactor (24 s reaction time) in the absence and presence of OH or SCI scavengers, and under different relative humidity (RH) conditions. The chemical composition of polydisperse and size-selected SOA particles was probed using different mass spectrometric techniques and infrared spectroscopy. Oligomers having SCI as the chain unit are found to be the dominant components of such SOA particles. The formation mechanism for these oligomers suggested by our results follows the sequential addition of SCI to organic peroxy (RO2) radicals, in agreement with previous studies by Moortgat and coworkers. Smaller particles are shown to have a relatively greater contribution from longer oligomers. Higher O/C ratios are observed in smaller particles and are similar to those of oligomers resulting from RO2 + nSCI, supporting a significant role for longer oligomers in particle nucleation and early growth. Under atmospherically relevant RH of 30-80%, water vapor suppresses oligomer formation through scavenging SCI, but also enhances particle nucleation. Under humid conditions, or in the presence of formic or hydrochloric acid as SCI scavengers, peroxyhemiacetals are formed by the acid-catalyzed particle phase reaction between oligomers from RO2 + nSCI and a trans-3-hexene derived carbonyl product. In contrast to the ozonolysis of trans-3-hexene, oligomerization involving RO2 + nSCI does not appear to be prevalent in the

  18. 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

    2012-07-01

    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. PMID:22658137

  19. Formation of amorphous silicon passivation films with high stability against postannealing, air exposure, and light soaking using liquid silicon

    NASA Astrophysics Data System (ADS)

    Guo, Cheng; Ohdaira, Keisuke; Takagishi, Hideyuki; Masuda, Takashi; Shen, Zhongrong; Shimoda, Tatsuya

    2016-04-01

    We applied liquid-source vapor deposition (LVD), thermal CVD from the vapor of cyclopentasilane (CPS), to form amorphous silicon (a-Si) passivation films on crystalline Si (c-Si) wafers, and investigated the thermal stability of the films against postannealing. LVD a-Si passivation films showed a high initial effective minority carrier lifetime (τeff) of >300 µs and a higher thermal stability than a reference plasma-enhanced chemical-vapor-deposited (PECVD) sample. The high thermal stability of LVD a-Si passivation films may be attributed to the considerably high deposition temperature of the films at 360 °C or more. LVD a-Si passivation films were sufficiently stable also against air exposure and 1-sun light soaking. We also confirmed that the epitaxial growth of Si films does not occur on c-Si even at such high deposition temperatures, and LVD could realize the simultaneous deposition of a-Si films on both sides of a c-Si wafer.

  20. Interannual variability of the air-sea heat exchange in the western Mediterranean in relation to the deep-water formation processes

    NASA Astrophysics Data System (ADS)

    Soto, J.; Criado Aldeanueva, F.; García Lafuente, J.; Sanchez Román, A.; Carracedo, L.

    2009-04-01

    A 60-year long time series of heat fluxes (long and short wave radiation, sensible and latent contributions) from NCEP reanalysis dataset and a 22-year long time series of Sea Surface Temperature (SST) from JPL AVHRR Oceans Pathfinder dataset have been combined to study the seasonal and interannual variability of air-sea heat exchanges over the Mediterranean Sea and correlate them with the characteristics of the Mediterranean outflow through the Strait of Gibraltar collected in the frame of the INGRES projects in the last years. Special attention has been devoted to the historically reported deep-water formation basin of the Western Mediterranean (Gulf of Lions) during the pre-conditioning (November and December) and winter seasons. Until around 1970, no clear trend is found in the net heat flux winter series since positive and negative anomalies are observed alternatively. From then onwards, negative anomalies are frequently observed until the 2003-2006 positive events. A net heat loss of about 150 W/m2 is observed in 2005, the highest value since 1956, especially due to evaporation losses towards the atmosphere. The anomalously cold air and sea surface temperature in the area help to increase this contribution that reflects in a higher fraction of Western Mediterranean Deep Water (WMDW) in the outflow through the Strait.

  1. 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.

  2. The gap gene network

    PubMed Central

    2010-01-01

    Gap genes are involved in segment determination during the early development of the fruit fly Drosophila melanogaster as well as in other insects. This review attempts to synthesize the current knowledge of the gap gene network through a comprehensive survey of the experimental literature. I focus on genetic and molecular evidence, which provides us with an almost-complete picture of the regulatory interactions responsible for trunk gap gene expression. I discuss the regulatory mechanisms involved, and highlight the remaining ambiguities and gaps in the evidence. This is followed by a brief discussion of molecular regulatory mechanisms for transcriptional regulation, as well as precision and size-regulation provided by the system. Finally, I discuss evidence on the evolution of gap gene expression from species other than Drosophila. My survey concludes that studies of the gap gene system continue to reveal interesting and important new insights into the role of gene regulatory networks in development and evolution. PMID:20927566

  3. 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. PMID:23305985

  4. Atlantic tropical cyclone formation: Pre-genesis evolution of tropical easterly waves and impacts of the middle to upper tropospheric dry air

    NASA Astrophysics Data System (ADS)

    Hankes, Isaac E.

    This study first provides an overview of the dynamic and thermodynamic evolution of tropical easterly waves (TEWs) for 164 named tropical storms over the Atlantic during 1989-2010 July-October. The evolution of precipitation and the low-level convergence suggests that convection begins to organize near the center of the wave critical layer about one day prior to genesis, along with the rapid intensification of vorticity. The composites derived from the ERA-Interim reanalysis reveal higher specific humidity and equivalent potential temperature near the center of the wave critical layer, especially in the middle troposphere within one day prior to genesis. The study then focuses on the formation of the Cape Verde storms over the East Atlantic. There are two groups of easterly waves over West Africa, one to the south and the other to the north of the African Easterly Jet (AEJ), which sometimes merge near the coast of West Africa. Three groups of waves are identified in order to determine the role of wave merger in tropical cyclogenesis over the East Atlantic: non-merger developers, merger developers, and merger non-developers. Relative to non-mergers, it is found that merger developers have a weaker circulation near the surface at the early stages but the merger of a southern wave with a northern wave leads to a stronger and deeper wave pouch, which is more conducive to tropical cyclogenesis. It is also found that dry air intrusion west of the wave trough in the middle and upper troposphere inhibits deep convection and leads to the nondevelopment of some mergers, but that boundary layer dry air in the northern waves moistens quickly over the ocean and does not impede development. The interannual variability of the middle and upper tropospheric dry air and its impacts on tropical cyclone activity over the Atlantic are further examined using the EOF analysis and composite analysis. It is found that the interannual variability of the upper-tropospheric (300-500 hPa) dry

  5. 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.

  6. 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. PMID:23638086

  7. 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.

  8. 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.

  9. Ionizing radiation and genetic risks. XVII. Formation mechanisms underlying naturally occurring DNA deletions in the human genome and their potential relevance for bridging the gap between induced DNA double-strand breaks and deletions in irradiated germ cells.

    PubMed

    Sankaranarayanan, Krishnaswami; Taleei, Reza; Rahmanian, Shirin; Nikjoo, Hooshang

    2013-01-01

    While much is known about radiation-induced DNA double-strand breaks (DSBs) and their repair, the question of how deletions of different sizes arise as a result of the processing of DSBs by the cell's repair systems has not been fully answered. In order to bridge this gap between DSBs and deletions, we critically reviewed published data on mechanisms pertaining to: (a) repair of DNA DSBs (from basic studies in this area); (b) formation of naturally occurring structural variation (SV) - especially of deletions - in the human genome (from genomic studies) and (c) radiation-induced mutations and structural chromosomal aberrations in mammalian somatic cells (from radiation mutagenesis and radiation cytogenetic studies). The specific aim was to assess the relative importance of the postulated mechanisms in generating deletions in the human genome and examine whether empirical data on radiation-induced deletions in mouse germ cells are consistent with predictions of these mechanisms. The mechanisms include (a) NHEJ, a DSB repair process that does not require any homology and which functions in all stages of the cell cycle (and is of particular relevance in G0/G1); (b) MMEJ, also a DSB repair process but which requires microhomology and which presumably functions in all cell cycle stages; (c) NAHR, a recombination-based DSB repair mechanism which operates in prophase I of meiosis in germ cells; (d) MMBIR, a microhomology-mediated, replication-based mechanism which operates in the S phase of the cell cycle, and (e) strand slippage during replication (involved in the origin of small insertions and deletions (INDELs). Our analysis permits the inference that, between them, these five mechanisms can explain nearly all naturally occurring deletions of different sizes identified in the human genome, NAHR and MMBIR being potentially more versatile in this regard. With respect to radiation-induced deletions, the basic studies suggest that those arising as a result of the operation

  10. 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

  11. 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…

  12. 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…

  13. 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…

  14. 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…

  15. 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…

  16. 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

  17. 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.

  18. Monolayers of the lipid derivatives of isoniazid at the air/water interface and the formation of self-assembled nanostructures in water.

    PubMed

    Jin, Yiguang; Chen, Shufeng; Xin, Rui; Zhou, Yisheng

    2008-07-15

    Isoniazid (INH, isonicotinic acid hydrazide) is one of the most commonly used anti-tubercular drugs. However, resistance of Mycobacterium tuberculosis strains to anti-mycobacterial agents including INH is an increasing problem worldwide. Development of new anti-mycobacterial agents thus has attracted attention. Five lipid derivatives of INH were prepared in this study. They formed monolayers at the air/water interface, and some nanostructures with different morphologies were obtained through molecular self-assembly in water. The derivatives included one fatty acyl derivative containing a 12-C hydrocarbon-long chain (1), three fatty alcohol derivatives with a succinyl as spacer and an 8, 12 or 16-C hydrocarbon-long chain (2, 3 and 4), and one tetrahydro-2H-1,3,5-thiadiazine-2-thione (THTT) derivative containing a 12-C hydrocarbon-long chain (5). The surface pressure-area isotherms depended on the volume and configuration of heads and the length of tails of derivatives. Compound 2 had a relatively large head and a short tail, easily standing uprightly at the interface. Under a certain surface pressure, the linear polar head groups of 3 could be partly squeezed out and insert into subphase because the length of heads were comparable to the one of tails. The very long tails of 4 always maintained above the interface and led to a high collapse pressure. Compound 5 possessed an extended and large head consisting of the THTT and INH groups so that the relatively short tails tilted at the interface and difficultly contact with each other. The THTT rings might be partly squeezed out and enter into air under a certain surface pressure. The self-assembly behaviours of derivatives in water depended on the molecular configuration and agreed with the corresponding monolayer behaviours. The flexible and medium-long tails (1 and 3) led to the derivatives to form nanoscale vesicles, though the short or very long tails did not (2 and 4). Interestingly, intermolecular hydrogen

  19. 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.

  20. 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.

  1. Photonic band gap materials

    SciTech Connect

    Soukoulis, C.M. |

    1993-12-31

    An overview of the theoretical and experimental efforts in obtaining a photonic band gap, a frequency band in three-dimensional dielectric structures in which electromagnetic waves are forbidden, is presented.

  2. 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.

  3. Gaps in Oncology

    Cancer.gov

    The first plenary of the EPEC-O (Education in Palliative and End-of-Life Care for Oncology) Self-Study Original Version provides background for the curriculum and identifies gaps in current and desired comprehensive cancer care.

  4. Robotic Tube-Gap Inspector

    NASA Technical Reports Server (NTRS)

    Gilbert, Jeffrey L.; Gutow, David A.; Maslakowski, John E.

    1993-01-01

    Robotic vision system measures small gaps between nearly parallel tubes. Robot-held video camera examines closely spaced tubes while computer determines gaps between tubes. Video monitor simultaneously displays data on gaps.

  5. 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

  6. 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

  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.; 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.

  8. Gap Cycling for SWIFT

    PubMed Central

    Corum, Curtis A.; Idiyatullin, Djaudat; Snyder, Carl J.; Garwood, Michael

    2014-01-01

    Purpose SWIFT (SWeep Imaging with Fourier Transformation) is a non-Cartesian MRI method with unique features and capabilities. In SWIFT, radiofrequency (RF) excitation and reception are performed nearly simultaneously, by rapidly switching between transmit and receive during a frequency-swept RF pulse. Because both the transmitted pulse and data acquisition are simultaneously amplitude-modulated in SWIFT (in contrast to continuous RF excitation and uninterrupted data acquisition in more familiar MRI sequences), crosstalk between different frequency bands occurs in the data. This crosstalk leads to a “bulls-eye” artifact in SWIFT images. We present a method to cancel this inter-band crosstalk by cycling the pulse and receive gap positions relative to the un-gapped pulse shape. We call this strategy “gap cycling.” Methods We carry out theoretical analysis, simulation and experiments to characterize the signal chain, resulting artifacts, and their elimination for SWIFT. Results Theoretical analysis reveals the mechanism for gap-cycling’s effectiveness in canceling inter-band crosstalk in the received data. We show phantom and in-vivo results demonstrating bulls-eye artifact free images. Conclusion Gap cycling is an effective method to remove bulls-eye artifact resulting from inter-band crosstalk in SWIFT data. PMID:24604286

  9. THE DYNAMICALLY DISRUPTED GAP IN HD 142527

    SciTech Connect

    Casassus, S.; Perez M, S.; Menard, F.; Jordan, A.; 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 {approx}10 to {approx}140 AU, and a massive outer disk extending out to {approx}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 0.''17 {+-} 0.''02 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{sub 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.

  10. [Effects of forest gap size and within-gap position on the microclimate in Pinus koraiensis-dominated broadleaved mixed forest].

    PubMed

    Feng, Jing; Duan, Wen-Biao; Chen, Li-Xin

    2012-07-01

    HOBO automatic weather stations were installed in the central parts and at the south, north, east, and west edges of large, medium, and small gaps in a Pinus koraiensis-dominated broadleaved mixed forest in Xiaoxing' anling Mountains to measure the air temperature, relative humidity, and photosynthetic photon flux density (PPFD) in these locations and the total radiation and precipitation in the gap centres from June to September 2010, taking the closed forest stand and open field as the controls. The differences in the microclimate between various size forest gaps and between the gap centers and their edges as well as the variations of the microclimatic factors over time were analyzed, and the effects of sunny and overcast days on the diurnal variations of the microclimatic factors within forest gaps were compared, aimed to offer basic data and practice reference for gap regeneration and sustainable management of Pinus koraiensis-dominated broadleaved mixed forest. The PPFD was decreased in the order of large gap, medium gap, and small gap. For the same gaps, the PPFD in gap centre was greater than that in gap edge. The mean monthly air temperature and total radiation in gap centres were declined in the sequence of July, June, August, and September, and the amplitudes of the two climatic factors were decreased in the order of open field, large gap, medium gap, small gap, and closed forest stand. The mean monthly relative humidity in gap centres dropped in the order of August, July, September, and June, and the amplitude of this climatic factor was decreased in the sequence of closed forest stand, small gap, medium gap, large gap, and open field. The total and monthly precipitations for the three different size gaps and open field during measurement period generally decreased in the order of open field, large gap, medium gap, small gap, and closed forest stand. In sunny days, the variations of PPFD, air temperature, and relative humidity were greater in large gap

  11. 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.

  12. Numerical simulation of supersonic gap flow.

    PubMed

    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

  13. 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

  14. 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.

  15. 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.

  16. Bridging NCL research gaps.

    PubMed

    Stehr, Frank; van der Putten, Herman

    2015-10-01

    The neuronal ceroid lipofuscinoses, collectively called NCLs, are rare and fatal lysosomal storage diseases that mainly affect children. Due to the fact that NCLs are both rare and heterogeneous (mutations in thirteen different genes) significant gaps exist in both preclinical and clinical research. Altogether, these gaps are major hurdles to bring therapies to patients while the need for new therapies is urgent to help them and their families. To define gaps and discuss solutions, a round table discussion involving teams and different stake holders took place during the 14th International Conference on Neuronal Ceroid Lipofuscinoses (Batten Disease) in Cordóba, Argentina. Topics covered by the teams and their leaders (in parentheses) included basic and translational research gaps with regard to large animal models (I. Tammen, D.N. Palmer), human NCL pathology and access to human tissue (J.D. Cooper, H.H. Goebel), rare NCLs (S. Hofman, I. Noher), links of NCLs to other diseases (F.M. Platt), gaps between clinic and clinical trials (H. Adams, A. Schulz), international collaborative efforts working towards a cure (S.E. Mole, H. Band) perspectives on palliative care from patient organizations (M. Frazier, A. West), and issues NCL researchers face when progressing to independent career in academia (M. Bond). Thoughts presented by the team leaders include previously unpublished opinions and information on the lack of understanding of disease pathomechanisms, gene function, assays for drug discovery and target validation, natural history of disease, and biomarkers for monitoring disease progression and treatment effects. This article is not intended to review the NCL literature. It includes personal opinions of the authors and it provides the reader with a summary of gaps discussed and solutions proposed by the teams. This article is part of a Special Issue entitled: Current Research on the Neuronal Ceroid Lipofuscinoses (Batten Disease). PMID:26056946

  17. 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. PMID:26641519

  18. Spark gap electrode erosion

    NASA Astrophysics Data System (ADS)

    Krompholz, H.; Kristiansen, M.

    1984-12-01

    The results of a one-year contract on electrode erosion phenomena are summarized. The arc voltage drop in a spark gap was measured for various electrode, gas, and pressure combinations. A previously developed model of self breakdown voltage distribution was extended. A jet model for electrode erosion was proposed and an experimental arrangement for testing the model was constructed. The effects of inhomogeneities and impurities in the electrodes were investigated. Some of the work described here is scheduled for completion in 1985 under a current grant (AFOSR 84-0032). The areas of investigation described here include: (1) Self breakdown voltage distributions; (2) Electrode erosion; (3) Spark gap voltage recovery.

  19. Sculpting the band gap: a computational approach.

    PubMed

    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

  20. 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

  1. 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)

  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. 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.

  4. 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…

  5. Bridge the Gap.

    ERIC Educational Resources Information Center

    Klein, Mel; Cufaude, Jeffrey B.

    1989-01-01

    This document consists of two paired articles: the first, "Preparing Faculty Out of Class Experiences," by Mel Klein, and the second, "Help Advisers Be More Than Ghost Signatures," by Jeffrey B. Calfaude. Each article shares insights on how faculty advisers "bridge the gap" between students and faculty. When faculty members are asked to advise…

  6. 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…

  7. Gaining on the Gap

    ERIC Educational Resources Information Center

    Smith, Robert G.

    2010-01-01

    About three-quarters of the 2009 graduates of the highly diverse Arlington, Virginia, Public Schools completed one or more Advanced Placement or International Baccalaureate courses during their high school careers. That figure serves as one indicator of a decade-long initiative to eliminate achievement gaps while raising achievement for all…

  8. Air Pollution

    PubMed Central

    Clifton, Marjorie

    1964-01-01

    Dr Marjorie Clifton describes the classification of gaseous and nongaseous constituents of air pollution and then outlines the methods of measuring these. The National Survey embraced 150 towns of all sizes throughout England and Wales and provided data on smoke and sulphur dioxide in relation to climate, topography, industrialization, population density, fuel utilization and urban development. Dr W C Turner discusses the relationship between air pollution and mortality from respiratory conditions, and particularly the incidence of chronic bronchitis. He postulates a theory that such respiratory conditions arise as an allergy to the spores of certain moulds, spore formation being encouraged by the air humidity in Greatv Britain and overcrowded and damp living conditions. He describes the results of a twenty-week study undertaken in 1962-3, showing associations between respiratory disease and levels of air pollution. Dr Stuart Carne undertook a survey in general practice to plot the patterns of respiratory illness in London during the winter of 1962-3. There were two peaks of respiratory illnesses coinciding with the fog at the beginning of December and the freeze-up from the end of December until the beginning of March. PMID:14178955

  9. 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

  10. Oxidative Stress, Lens Gap Junctions, and Cataracts

    PubMed Central

    Beyer, Eric C.

    2009-01-01

    Abstract The eye lens is constantly subjected to oxidative stress from radiation and other sources. The lens has several mechanisms to protect its components from oxidative stress and to maintain its redox state, including enzymatic pathways and high concentrations of ascorbate and reduced glutathione. With aging, accumulation of oxidized lens components and decreased efficiency of repair mechanisms can contribute to the development of lens opacities or cataracts. Maintenance of transparency and homeostasis of the avascular lens depend on an extensive network of gap junctions. Communication through gap junction channels allows intercellular passage of molecules (up to 1 kDa) including antioxidants. Lens gap junctions and their constituent proteins, connexins (Cx43, Cx46, and Cx50), are also subject to the effects of oxidative stress. These observations suggest that oxidative stress-induced damage to connexins (and consequent altered intercellular communication) may contribute to cataract formation. Antioxid. Redox Signal. 11, 339–353. PMID:18831679

  11. Alternate pathways involving Sgs1/Top3, Mus81/ Mms4, and Srs2 prevent formation of toxic recombination intermediates from single-stranded gaps created by DNA replication

    PubMed Central

    Fabre, Francis; Chan, Allan; Heyer, Wolf-Dietrich; Gangloff, Serge

    2002-01-01

    Toxic recombination events are detected in vegetative Saccharomyces cerevisiae cells through negative growth interactions between certain combinations of mutations. For example, mutations affecting both the Srs2 and Sgs1 helicases result in extremely poor growth, a phenotype suppressed by mutations in genes that govern early stages of recombination. Here, we identify a similar interaction involving double mutations affecting Sgs1 or Top3 and Mus81 or Mms4. We also find that the primary DNA structures that initiate these toxic recombination events cannot be double-strand breaks and thus are likely to be single-stranded DNA. We interpret our results in the context of the idea that replication stalling leaves single-stranded DNA, which can then be processed by two competing mechanisms: recombination and nonrecombination gap-filling. Functions involved in preventing toxic recombination would either avoid replicative defects or act on recombination intermediates. Our results suggest that Srs2 channels recombination intermediates back into the gap-filling route, whereas Sgs1/Top3 and Mus81/Mms4 are involved in recombination and/or in replication to allow replication restart. PMID:12475932

  12. Deterministic multidimensional nonuniform gap sampling

    NASA Astrophysics Data System (ADS)

    Worley, Bradley; Powers, Robert

    2015-12-01

    Born from empirical observations in nonuniformly sampled multidimensional NMR data relating to gaps between sampled points, the Poisson-gap sampling method has enjoyed widespread use in biomolecular NMR. While the majority of nonuniform sampling schemes are fully randomly drawn from probability densities that vary over a Nyquist grid, the Poisson-gap scheme employs constrained random deviates to minimize the gaps between sampled grid points. We describe a deterministic gap sampling method, based on the average behavior of Poisson-gap sampling, which performs comparably to its random counterpart with the additional benefit of completely deterministic behavior. We also introduce a general algorithm for multidimensional nonuniform sampling based on a gap equation, and apply it to yield a deterministic sampling scheme that combines burst-mode sampling features with those of Poisson-gap schemes. Finally, we derive a relationship between stochastic gap equations and the expectation value of their sampling probability densities.

  13. 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.

  14. The formation of surface multilayers at the air-water interface from sodium polyethylene glycol monoalkyl ether sulfate/AlCl(3) solutions: the role of the size of the polyethylene oxide group.

    PubMed

    Xu, Hui; Penfold, Jeff; Thomas, Robert K; Petkov, Jordan T; Tucker, Ian; Webster, John P R

    2013-09-17

    Neutron reflectivity, NR, and surface tension, ST, have been used to study the surface adsorption properties at the air-water interface of the anionic surfactant sodium polyethylene glycol monododecyl ether sulfate (sodium lauryl ether sulfate, SLES) in the presence of Al(3+) multivalent counterions, by the addition of AlCl3. In the absence of AlCl3 and at low AlCl3 concentrations monolayer adsorption is observed. With increasing AlCl3 concentration, surface multilayer formation is observed, driven by SLES/Al(3+) complex formation. The onset of multilayer formation occurs initially as a single bilayer or a multilayer structure with a limited number of bilayers, N, ≤3, and ultimately at higher AlCl3 concentrations N is large, >20. The evolution in the surface structure is determined by the surfactant and AlCl3 concentrations, and the size of the polyethylene oxide group in the different SLES surfactants studied. From the NR data, approximate surface phase diagrams are constructed, and the evolution of the surface structure with surfactant and electrolyte concentration is shown to be dependent on the size of the polyethylene oxide group. As the polyethylene oxide group increases in size the multilayer formation requires increasingly higher surfactant and AlCl3 concentrations to promote the formation. This is attributed to the increased steric hindrance of the polyethylene oxide group disrupting SLES/Al(3+) complex formation. PMID:23968161

  15. 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…

  16. GapBlaster—A Graphical Gap Filler for Prokaryote Genomes

    PubMed Central

    Veras, Adonney; de Melo, Diego Magalhães; Soares, Siomar; Pinheiro, Kenny; Guimarães, Luis; Azevedo, Vasco; Silva, Artur; Ramos, Rommel T. J.

    2016-01-01

    The advent of NGS (Next Generation Sequencing) technologies has resulted in an exponential increase in the number of complete genomes available in biological databases. This advance has allowed the development of several computational tools enabling analyses of large amounts of data in each of the various steps, from processing and quality filtering to gap filling and manual curation. The tools developed for gap closure are very useful as they result in more complete genomes, which will influence downstream analyses of genomic plasticity and comparative genomics. However, the gap filling step remains a challenge for genome assembly, often requiring manual intervention. Here, we present GapBlaster, a graphical application to evaluate and close gaps. GapBlaster was developed via Java programming language. The software uses contigs obtained in the assembly of the genome to perform an alignment against a draft of the genome/scaffold, using BLAST or Mummer to close gaps. Then, all identified alignments of contigs that extend through the gaps in the draft sequence are presented to the user for further evaluation via the GapBlaster graphical interface. GapBlaster presents significant results compared to other similar software and has the advantage of offering a graphical interface for manual curation of the gaps. GapBlaster program, the user guide and the test datasets are freely available at https://sourceforge.net/projects/gapblaster2015/. It requires Sun JDK 8 and Blast or Mummer. PMID:27171416

  17. GapBlaster-A Graphical Gap Filler for Prokaryote Genomes.

    PubMed

    de Sá, Pablo H C G; Miranda, Fábio; Veras, Adonney; de Melo, Diego Magalhães; Soares, Siomar; Pinheiro, Kenny; Guimarães, Luis; Azevedo, Vasco; Silva, Artur; Ramos, Rommel T J

    2016-01-01

    The advent of NGS (Next Generation Sequencing) technologies has resulted in an exponential increase in the number of complete genomes available in biological databases. This advance has allowed the development of several computational tools enabling analyses of large amounts of data in each of the various steps, from processing and quality filtering to gap filling and manual curation. The tools developed for gap closure are very useful as they result in more complete genomes, which will influence downstream analyses of genomic plasticity and comparative genomics. However, the gap filling step remains a challenge for genome assembly, often requiring manual intervention. Here, we present GapBlaster, a graphical application to evaluate and close gaps. GapBlaster was developed via Java programming language. The software uses contigs obtained in the assembly of the genome to perform an alignment against a draft of the genome/scaffold, using BLAST or Mummer to close gaps. Then, all identified alignments of contigs that extend through the gaps in the draft sequence are presented to the user for further evaluation via the GapBlaster graphical interface. GapBlaster presents significant results compared to other similar software and has the advantage of offering a graphical interface for manual curation of the gaps. GapBlaster program, the user guide and the test datasets are freely available at https://sourceforge.net/projects/gapblaster2015/. It requires Sun JDK 8 and Blast or Mummer. PMID:27171416

  18. Hybrid Air-Electrode for Li/Air Batteries

    SciTech Connect

    Xiao, Jie; Xu, Wu; Wang, Deyu; Zhang, Jiguang

    2010-01-20

    A novel hybrid air-electrode is designed to improve the power density of Li/air batteries operating in an ambient environment. Three lithium insertion materials, MnO2, V2O5, and CFx (x = 1.0 to 1.15), are mixed with activated carbon to prepare different hybrid air-electrodes used in Li/air batteries. When compared with pure carbon-based Li/air batteries, the batteries using hybrid air-electrodes demonstrate significantly improved power capacities, especially for the CFx-based hybrid Li/air batteries. Because it is hydrophobic, CFx also facilitates the formation of air-flow channels in the carbon matrix, and alleviates air-electrode blocking problem during the discharge process. These hybrid air-electrodes provide a promising approach to improve the power density of Li/air batteries.

  19. 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…

  20. 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...

  1. Air Pollution

    MedlinePlus

    Air pollution is a mixture of solid particles and gases in the air. Car emissions, chemicals from factories, dust, ... a gas, is a major part of air pollution in cities. When ozone forms air pollution, it's ...

  2. 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 ...

  3. Studies on the cell biology of interendothelial cell gaps

    PubMed Central

    Ochoa, Cristhiaan D.

    2012-01-01

    Pain, redness, heat, and swelling are hallmarks of inflammation that were recognized as early as the first century AD. Despite these early observations, the mechanisms responsible for swelling, in particular, remained an enigma for nearly two millennia. Only in the past century have scientists and physicians gained an appreciation for the role that vascular endothelium plays in controlling the exudation that is responsible for swelling. One of these mechanisms is the formation of transient gaps between adjacent endothelial cell borders. Inflammatory mediators act on endothelium to reorganize the cytoskeleton, decrease the strength of proteins that connect cells together, and induce transient gaps between endothelial cells. These gaps form a paracellular route responsible for exudation. The discovery that interendothelial cell gaps are causally linked to exudation began in the 1960s and was accompanied by significant controversy. Today, the role of gap formation in tissue edema is accepted by many, and significant scientific effort is dedicated toward developing therapeutic strategies that will prevent or reverse the endothelial cell gaps that are present during the course of inflammatory illness. Given the importance of this field in endothelial cell biology and inflammatory disease, this focused review catalogs key historical advances that contributed to our modern-day understanding of the cell biology of interendothelial gap formation. PMID:21964402

  4. Three-dimensionally ordered array of air bubbles in a polymer film

    NASA Technical Reports Server (NTRS)

    Srinivasarao, M.; Collings, D.; Philips, A.; Patel, S.; Brown, C. S. (Principal Investigator)

    2001-01-01

    We report the formation of a three-dimensionally ordered array of air bubbles of monodisperse pore size in a polymer film through a templating mechanism based on thermocapillary convection. Dilute solutions of a simple, coil-like polymer in a volatile solvent are cast on a glass slide in the presence of moist air flowing across the surface. Evaporative cooling and the generation of an ordered array of breath figures leads to the formation of multilayers of hexagonally packed water droplets that are preserved in the final, solid polymer film as spherical air bubbles. The dimensions of these bubbles can be controlled simply by changing the velocity of the airflow across the surface. When these three-dimensionally ordered macroporous materials have pore dimensions comparable to the wavelength of visible light, they are of interest as photonic band gaps and optical stop-bands.

  5. Electroburning of few-layer graphene flakes, epitaxial graphene, and turbostratic graphene discs in air and under vacuum

    PubMed Central

    Richter, Nils; Convertino, Domenica; Coletti, Camilla; Balestro, Franck; Wernsdorfer, Wolfgang; Kläui, Mathias; Affronte, Marco

    2015-01-01

    Summary Graphene-based electrodes are very promising for molecular electronics and spintronics. Here we report a systematic characterization of the electroburning (EB) process, leading to the formation of nanometer-spaced gaps, on different types of few-layer graphene (namely mechanically exfoliated graphene on SiO2, graphene epitaxially grown on the C-face of SiC and turbostratic graphene discs deposited on SiO2) under air and vacuum conditions. The EB process is found to depend on both the graphene type and on the ambient conditions. For the mechanically exfoliated graphene, performing EB under vacuum leads to a higher yield of nanometer-gap formation than working in air. Conversely, for graphene on SiC the EB process is not successful under vacuum. Finally, the EB is possible with turbostratic graphene discs only after the creation of a constriction in the sample using lithographic patterning. PMID:25821711

  6. 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. PMID:23283173

  7. Study of Discharging Characteristics of Hollow Cathode Surge Protective Gap

    NASA Astrophysics Data System (ADS)

    Yao, Xueling; Chen, Jingliang; Xu, Xiaowei; Liu, Yong; Zhao, Yong

    2010-02-01

    A hollow cathode surge protective gap (HCSPG) was designed, and the discharge characteristics was investigated in an air and nitrogen gas environment. For both the gap spacing D and the hole diameter varphi of HCSPG of 3 mm, the voltage protective value Up of HCSPG is about 3.5 kV and its converting time tc exceeds 100 ns at an air pressure from 10 Pa to 100 Pa. The maximum converting time tc from glow to arc discharging reaches 1600 ns at an air pressure of 100 Pa, while the minimum converting time tc is 120 ns at 10 Pa. For a triggered HCSPG, Up is reduced to about 1.6 kV while the converting time is 120 ns with a semiconductor trigger device and 50 ns with a dielectric porcelain trigger device under an air pressure of 100 Pa.

  8. Turbine blade tip gap reduction system

    DOEpatents

    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.

  9. A photonic thermalization gap in disordered lattices

    NASA Astrophysics Data System (ADS)

    Kondakci, H. Esat; Abouraddy, Ayman F.; Saleh, Bahaa E. A.

    2015-11-01

    The formation of gaps--forbidden ranges in the values of a physical parameter--is common to a variety of physical systems: from energy bandgaps of electrons in periodic lattices and their analogues in photonic, phononic and plasmonic systems to pseudo-energy gaps in aperiodic quasicrystals. Here, we predict a thermalization gap for light propagating in finite disordered structures characterized by disorder-immune chiral symmetry--the appearance of the eigenvalues and eigenvectors in skew-symmetric pairs. In these systems, the span of sub-thermal photon statistics is inaccessible to input coherent light, which--once the steady state is reached--always emerges with super-thermal statistics no matter how small the disorder level. We formulate an independent constraint of the input field for the chiral symmetry to be activated and the gap to be observed. This unique feature enables a new form of photon-statistics interferometry: the deterministic tuning of photon statistics via controlled excitation symmetry breaking realized by sculpting the amplitude or phase of the input coherent field.

  10. 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.

  11. 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.

  12. RhoGAPs and Rho GTPases in platelets.

    PubMed

    Elvers, Margitta

    2016-08-01

    Platelet cytoskeletal reorganization is essential for platelet adhesion and thrombus formation in hemostasis and thrombosis. The Rho GTPases RhoA, Rac1 and Cdc42 are the main players in cytoskeletal dynamics of platelets responsible for the formation of filopodia and lamellipodia to strongly increase the platelet surface upon activation. They are involved in platelet activation and aggregate formation including platelet secretion, integrin activation and arterial thrombus formation. The activity of Rho GTPases is tightly controlled by different proteins such as GTPase-activating proteins (GAPs). GAPs stimulate GTP hydrolysis to terminate Rho signaling. The role and impact of GAPs in platelets is not well-defined and many of the RhoGAPs identified are not known to be present in platelets or to have any function in platelets. The recently identified RhoGAPs Oligophrenin1 (OPHN1) and Nadrin regulate the activity of RhoA, Rac1 and Cdc42 and subsequent platelet cytoskeletal reorganization, platelet activation and thrombus formation. In the last years, the analysis of genetically modified mice helped to gain the understanding of Rho GTPases and their regulators in cytoskeletal rearrangements and other Rho mediated cellular processes in platelets. PMID:25639730

  13. 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…

  14. 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. PMID:26659181

  15. 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.

  16. 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.

  17. 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 (...

  18. Evaluating the Role of the Air-Solution Interface on the Mechanism of Subvisible Particle Formation Caused by Mechanical Agitation for an IgG1 mAb.

    PubMed

    Ghazvini, Saba; Kalonia, Cavan; Volkin, David B; Dhar, Prajnaparamita

    2016-05-01

    Mechanical agitation of monoclonal antibody (mAb) solutions often leads to protein particle formation. In this study, various formulations of an immunoglobulin G (IgG) 1 mAb were subjected to different controlled interfacial stresses using a Langmuir trough, and protein particles formed at the interface and measured in bulk solution were characterized using atomic force microscopy and flow digital imaging. Results were compared to mAb solutions agitated in glass vials and unstressed controls. At lower pH, mAb solutions exhibited larger hysteresis in their surface pressure versus area isotherms and increased number of particles in bulk solution, when subjected to interfacial stresses. mAb samples subjected to 750-1000 interfacial compression-expansion cycles in 6 h contained high particle numbers in bulk solution, and displayed similar particulation trends when agitated in vials. At compression rates of 50 cycles in 6 h, however, particle levels in mAb solutions were comparable to unstressed controls, despite protein aggregates being present at the air-solution interface. These results suggest that while the air-solution interface serves as a nucleation site for initiating protein aggregation, the number of protein particles measured in bulk mAb solutions depends on the total number of compression cycles that proteins at the air-solution interface are subjected to within a fixed time. PMID:27025981

  19. A new inclination shallowing correction of the Mauch Chunk Formation of Pennsylvania, based on high field-AIR results: Implications for the Carboniferous North American APW path and Pangea reconstructions

    NASA Astrophysics Data System (ADS)

    Bilardello, D.; Kodama, K. P.

    2010-12-01

    A new rock-magnetic study was performed on samples of the Lower Carboniferous Mauch Chunk Formation of Pennsylvania. These red beds had been sampled for an inclination shallowing study by Tan and Kodama (2002). High anisotropy values lead Kodama (2009) to suspect that the Formation had been affected by strain. However, more detailed rock-magnetic measurements also show that both magnetite and hematite contribute to the remanence, leading to the application of a high field anisotropy of isothermal remanence magnetization (hf-AIR) technique specifically designed to isolate the anisotropy of the hematite, the characteristic remanence carrier. The newly measured fabric has a smaller anisotropy than Kodama (2009) observed (~9-17% as opposed to ~25-40%) and shows a pronounced ENE-WSW magnetic lineation that is sub-parallel to the trend of the Appalachians and interpretable as a hematite intersection lineation that occurred during local NNW-directed shortening. Results also yield a much different AIR/ anisotropy of magnetic susceptibility (AMS) relationship than previously reported. We attribute the differences in the AIR/AMS relationship to varying concentrations of magnetite. Because the AIR/AMS relationship has been used to constrain the individual particle anisotropy we suggest this approach to determine grain anisotropy is invalid, at least until the AIR/AMS relationship for single domain hematite only is measured. The measured magnetic fabric yields a new inclination correction with a corrected paleopole that is in better agreement with recently corrected Carboniferous paleopoles than the previously corrected Mauch Chunk paleopole, defining a more consistent APW path. The corrected paleopoles allow calculation of new mean Early (~325 Ma) and Late (~312 Ma) Carboniferous inclination-corrected paleopoles for North America, which can be compared to coeval, but uncorrected, paleopoles from Gondwana. Results suggest a Pangea B assemblage unless Gondwanan sedimentary

  20. 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.

  1. [Gap junction and diabetic foot].

    PubMed

    Zou, Xiao-rong; Tao, Jian; Wang, Yun-kai

    2015-11-01

    Gap junctions play a critical role in electrical synchronization and exchange of small molecules between neighboring cells; connexins are a family of structurally related transmembrane proteins that assemble to form vertebrate gap junctions. Hyperglycemia changes the structure gap junction proteins and their expression, resulting in obstruction of neural regeneration, vascular function and wound healing, and also promoting vascular atherosclerosis. These pathogenic factors would cause diabetic foot ulcers. This article reviews the involvement of connexins in pathogenesis of diabetic foot. PMID:26822053

  2. Seed arrival in tropical forest tree fall gaps.

    PubMed

    Puerta-Pińero, Carolina; Muller-Landau, Helene C; Calderón, Osvaldo; Wright, S Joseph

    2013-07-01

    Tree deaths open gaps in closed-canopy forests, which allow light to reach the forest floor and promote seed germination and seedling establishment. Gap dependence of regeneration is an important axis of life history variation among forest plant species, and many studies have evaluated how plant species differ in seedling and sapling performance in gaps. However, relatively little is known about how seed arrival in gaps compares with seed arrival in the understory, even though seed dispersal by wind and animals is expected to be altered in gaps. We documented seed arrival for the first seven years after gap formation in the moist tropical forests of Barro Colorado Island (BCI), Panama, and evaluated how the amount and functional composition of arriving seeds compared with understory sites. On average, in the first three years after gap formation, 72% fewer seeds arrived in gaps than in the understory (207 vs. 740 seeds x m(-2) x yr(-1)). The reduction in number of arriving seeds fell disproportionately on animal-dispersed species, which suffered an 86% reduction in total seed number, while wind-dispersed species experienced only a 47% reduction, and explosively dispersed species showed increased seed numbers arriving. The increase in explosively dispersed seeds consisted entirely of the seeds of several shrub species, a result consistent with greater in situ seed production by explosively dispersed shrubs that survived gap formation or recruited immediately thereafter. Lianas did relatively better in seed arrival into gaps than did trees, suffering less of a reduction in seed arrival compared with understory sites. This result could in large part be explained by the greater predominance of wind dispersal among lianas: there were no significant differences between lianas and trees when controlling for dispersal syndromes. Our results show that seed arrival in gaps is very different from seed arrival in the understory in both total seeds arriving and functional

  3. Undecidability of the spectral gap

    NASA Astrophysics Data System (ADS)

    Cubitt, Toby S.; Perez-Garcia, David; Wolf, Michael M.

    2015-12-01

    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.

  4. 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.

  5. Gap and stripline combined monitor

    DOEpatents

    Yin, Yan

    1986-01-01

    A combined gap and stripline monitor device (10) for measuring the intensity and position of a charged particle beam bunch in a beam pipe of a synchotron radiation facility. The monitor has first and second beam pipe portions (11a, 11b) with an axial gap (12) therebetween. An outer pipe (14) cooperates with the first beam pipe portion (11a) to form a gap enclosure, while inner strips (23a-d) cooperate with the first beam pipe portion (11a) to form a stripline monitor, with the stripline length being the same as the gap enclosure length.

  6. Air Abrasion

    MedlinePlus

    ... delivered directly to your desktop! more... What Is Air Abrasion? Article Chapters What Is Air Abrasion? What Happens? The Pros and Cons Will I Feel Anything? Is Air Abrasion for Everyone? print full article print this ...

  7. Enhancement of diffuse reflectance using air tunnel structure.

    PubMed

    Jang, Jae Eun; Lee, Gae Hwang; Song, Byoung Gwon; Cha, Seung Nam; Jung, Jae Eun

    2013-02-01

    Submicrometer air gap structure has formed on diffuse reflection structure to improve light reflectance. Covering polymer or liquid on a diffuse reflector to make optical components induces the severe decrease of the total reflectance, since the diffuse reflected angle of some light rays is larger than the critical angle and the rays travel to the medium until meeting a proper small incident angle. The reflectance drops to 68% of the original value with just a polymer coating on the diffuse reflector. The formation of an air tunnel structure between the polymer layer and the diffuse reflector makes a symmetrical reflective index matching state and recovers 95% of the original reflectance. Due to the simple fabrication process and the chemical stability, the structure can be applied to various optical components and reflective display devices. PMID:23381414

  8. Bioinorganic Chemistry Special Feature: Gapped DNA is anisotropically bent

    NASA Astrophysics Data System (ADS)

    Guo, Hong; Tullius, Thomas D.

    2003-04-01

    Ionizing radiation damages DNA in several ways, including through formation of a single-nucleoside gap in one DNA strand. We have developed a two-dimensional gel electrophoresis method to investigate the effect of a strand gap on DNA structure. We generate a library of gapped DNA molecules by treating a DNA restriction fragment with the hydroxyl radical, generated by the reaction of Fe(II) EDTA with hydrogen peroxide. The DNA molecule studied contains a fixed bend produced by a set of phased adenine tracts. The A-tract bend serves as a reference bend for investigating the conformational nature of a strand gap. In the first electrophoretic dimension, a bent DNA molecule that has been treated with the hydroxyl radical is electrophoresed on a native gel. Smearing of the band on the native gel indicates that the library of gapped DNA molecules contains a variety of DNA conformations. In the second electrophoretic dimension, gapped DNA molecules having different native gel mobilities are electrophoresed on separate lanes of a denaturing gel to reveal how each strand gap affects the native gel mobility (and thus shape) of the DNA. Our results demonstrate that a single-nucleoside gap in a DNA duplex leads to an anisotropic, directional bend in the DNA helix axis. The implications of our findings for recognition of this lesion by DNA repair proteins are discussed.

  9. Molecular assemblies of 4-(hexadecyloxy)-n-(pyridinylmethylene)anilines at the air-water interface and Cu(II)-promoted vesicle formation via metal coordination.

    PubMed

    Wang, Haibo; Miao, Wangen; Liu, Huijin; Zhang, Xianfeng; Du, Xuezhong

    2010-09-01

    The molecular assemblies of 4-(hexadecyloxy)-N-(pyridinylmethylene)anilines (HPA) at the air-water interface on pure water and aqueous Cu(II) subphases have been investigated using in situ infrared reflection absorption spectroscopy (IRRAS). The Schiff base units were oriented with their long axes almost perpendicular to the water surface, and both imine and pyridinyl nitrogen atoms of the Schiff base units were coordinated to Cu(II) ions together with their geometrical conversions. The alkyl chains in the monolayers were quantitatively determined on the assumption that the HPA monolayers at the air-water interface were composed of sublayers of alkyl chains and Schiff base units, and the chain orientation angle on pure water was 30 +/- 2 degrees and increased to 37 +/- 2 degrees on the aqueous Cu(II) subphase. The HPA amphiphiles could not be dispersed in pure water but could self-organize into vesicles with metal-coordinated headgroups and interdigitated-packed alkyl chains in the presence of Cu(II) ions in aqueous solution. Transmission electron microscopy (TEM), differential scanning calorimetry (DSC), UV-vis spectroscopy, and small-angle X-ray diffraction (XRD) were used to investigate the aggregate structures and specific properties of the coordinated vesicles. PMID:20698514

  10. 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.

  11. 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

  12. 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

  13. 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.

  14. Formation of densely populated SiOx microtree-like structures on the Si (100) surface using excimer laser irradiation in air

    NASA Astrophysics Data System (ADS)

    Yang, De-Quan; Sacher, Edward; Meunier, Michel

    2004-10-01

    SiOx microforest-like structures have been produced on Si (100) surfaces by pulsed excimer laser irradiation in air. Scanning electron microscopic observations have indicated these structures, which are composed of aggregated nanoparticles, to be 1-5 μm in diameter and 10-20 μm high, and to have the appearance of trees. XPS analysis has shown them to be composed of a-SiOx (1

  15. [Growth and polysaccharide formation in Sinorhizobium meliloti strains in an air-lift-type fermentor. Effect on nodulation velocity in alfalfa plants].

    PubMed

    Lorda, G S; Castaño, R C; Pordomingo, A B; Pastor, M D; Balatti, A P

    2003-01-01

    In this paper the influence of the exopolysaccharides produced by Sinorhizobium meliloti strains on the nodulation rates in alfalfa plants has been considered. The experiments were performed in a rotary shaker and in an air-lift type fermentor. Different Sinorhizobium meliloti strains were used. Bacterial growth rates were determined by viable cell counts. Exopolysaccharide concentration was determined by precipitation with ethanol. It was observed that maximum cell concentration was in the order of 1 x 10(10) cell/ml and exopolysaccharide content was approximately 11 g/l. The experiments performed with alfalfa plants in a controlled environment chamber showed that, when inoculation was carried out with diluted suspensions (1/10), nodulation time was reduced from 10 to 4 days, while the strains retained their symbiotic properties. PMID:12920984

  16. 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.

  17. GAP Analysis Bulletin Number 15

    USGS Publications Warehouse

    Maxwell, Jill, (Edited By); 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

  18. 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.

  19. Quantum chemical clarification of the alkyl chain length threshold of nonionic surfactants for monolayer formation at the air/water interface.

    PubMed

    Vysotsky, Yu B; Kartashynska, E S; Belyaeva, E A; Vollhardt, D; Fainerman, V B; Miller, R

    2016-03-21

    A theoretical basis is provided for the experimental fact that for various surfactant classes the alkyl chain length threshold varies for the formation of condensed monolayers. The existence of the alkyl chain length threshold for a surfactant enabling the formation of monolayers is determined by the entropy increment to the Gibbs' energy, assessed by using the quantum chemical semiempiric method PM3. The value of the clusterization threshold is not stipulated by the surfactant solubility in water, rather by the electron-donor and electron-seeking properties of the head groups. These properties in turn impact the value of the solubility threshold for surfactants. The value of the clusterization threshold depends quadratically on the substituent constants, i.e. it is independent of whether the functional group is a donor or an acceptor of electrons. Rather it depends only on the donor or the acceptor 'force' of the substituent. The square-law dependence of the surface clusterization threshold of the amphiphile on the solubility threshold is evidenced. PMID:26957020

  20. AIRE-Linux

    NASA Astrophysics Data System (ADS)

    Zhou, Jianfeng; Xu, Benda; Peng, Chuan; Yang, Yang; Huo, Zhuoxi

    2015-08-01

    AIRE-Linux is a dedicated Linux system for astronomers. Modern astronomy faces two big challenges: massive observed raw data which covers the whole electromagnetic spectrum, and overmuch professional data processing skill which exceeds personal or even a small team's abilities. AIRE-Linux, which is a specially designed Linux and will be distributed to users by Virtual Machine (VM) images in Open Virtualization Format (OVF), is to help astronomers confront the challenges. Most astronomical software packages, such as IRAF, MIDAS, CASA, Heasoft etc., will be integrated into AIRE-Linux. It is easy for astronomers to configure and customize the system and use what they just need. When incorporated into cloud computing platforms, AIRE-Linux will be able to handle data intensive and computing consuming tasks for astronomers. Currently, a Beta version of AIRE-Linux is ready for download and testing.

  1. 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

  2. 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

  3. 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.

  4. 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.

  5. Ion Engine Grid Gap Measurements

    NASA Technical Reports Server (NTRS)

    Soulas, Gerge C.; Frandina, Michael M.

    2004-01-01

    A simple technique for measuring the grid gap of an ion engine s ion optics during startup and steady-state operation was demonstrated with beam extraction. The grid gap at the center of the ion optics assembly was measured with a long distance microscope that was focused onto an alumina pin that protruded through the center accelerator grid aperture and was mechanically attached to the screen grid. This measurement technique was successfully applied to a 30 cm titanium ion optics assembly mounted onto an NSTAR engineering model ion engine. The grid gap and each grid s movement during startup from room temperature to both full and low power were measured. The grid gaps with and without beam extraction were found to be significantly different. The grid gaps at the ion optics center were both significantly smaller than the cold grid gap and different at the two power levels examined. To avoid issues associated with a small grid gap during thruster startup with titanium ion optics, a simple method was to operate the thruster initially without beam extraction to heat the ion optics. Another possible method is to apply high voltage to the grids prior to igniting the discharge because power deposition to the grids from the plasma is lower with beam extraction than without. Further testing would be required to confirm this approach.

  6. Synthesis and characterization of poly(divinylbenzene)-coated magnetic iron oxide nanoparticles as precursor for the formation of air-stable carbon-coated iron crystalline nanoparticles.

    PubMed

    Boguslavsky, Yonit; Margel, Shlomo

    2008-01-01

    Maghemite (gamma-Fe2O3) nanoparticles of 15 +/- 3 nm diameter were prepared by nucleation of gelatin/iron oxide followed by growth of gamma-Fe2O3 films onto these nuclei. The gamma-Fe2O3 nanoparticles were coated with polydivinylbenzene (PDVB) by emulsion polymerization of divinylbenzene (DVB) in an aqueous continuous phase containing the gamma-Fe2O3 nanoparticles. The PDVB-coated gamma-Fe2O3 nanoparticles, dispersed in water, were separated from homo-PDVB nanoparticles using the high gradient magnetic field (HGMF) technique. The influence of DVB concentration on the amount of PDVB coating, on the size and size distribution of the coated gamma-Fe2O3 nanoparticles and on their magnetic properties, has been investigated. Air-stable carbon-coated iron (alpha-Fe/C) crystalline nanoparticles of 41 +/- 12 nm diameter have been prepared by annealing the PDVB-coated gamma-Fe2O3 nanoparticles at 1050 degrees C in an inert atmosphere. These nanoparticles exhibit high saturation magnetization value (83 emu g(-1)) and excellent resistance to oxidation. Characterization of the PDVB-coated gamma-Fe2O3 and of the alpha-Fe/C nanoparticles has been accomplished by TEM, HRTEM, DLS, FTIR, XRD, thermal analysis, zeta-potential, and magnetic measurements. PMID:17927999

  7. Use of a versatile high efficiency multiparallel denuder for the sampling of PAHs in ambient air: gas and particle phase concentrations, particle size distribution and artifact formation.

    PubMed

    Delgado-Saborit, Juana Maria; Stark, Christopher; Harrison, Roy M

    2014-01-01

    The design and performance of a multiparallel plate denuder able to operate at low and high-flow (3-30 L/min) for the collection of polycyclic aromatic hydrocarbon (PAH) vapor is described. The denuder, in combination with a micro orifice uniform deposit impactor (MOUDI) was used to assess processes of artifact formation in MOUDIs used with and without an upstream denuder. Duplicate sampling trains with an upstream denuder showed good repeatability of the measured gas and particle-phase concentrations and low breakthrough in the denuder (3.5-15%). The PAH size distributions within undenuded and denuded MOUDIs were studied. Use of the denuder altered the measured size distribution of PAHs toward smaller sizes, but both denuded and undenuded systems are subject to sampling artifacts. PMID:24279283

  8. 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.

  9. ALMA images of discs: are all gaps carved by planets?

    NASA Astrophysics Data System (ADS)

    Gonzalez, J.-F.; Laibe, G.; Maddison, S. T.; Pinte, C.; Ménard, F.

    2015-11-01

    Protoplanetary discs are now routinely observed and exoplanets, after the numerous indirect discoveries, are starting to be directly imaged. To better understand the planet formation process, the next step is the detection of forming planets or of signposts of young planets still in their disc, such as gaps. A spectacular example is the Atacama Large Millimeter/submillimeter Array (ALMA) science verification image of HL Tau showing numerous gaps and rings in its disc. To study the observability of planet gaps, we ran 3D hydrodynamical simulations of a gas and dust disc containing a 5 MJ gap-opening planet and characterized the spatial distribution of migrating, growing and fragmenting dust grains. We then computed the corresponding synthetic images for ALMA. For a value of the dust fragmentation threshold of 15 m s-1 for the collisional velocity, we identify for the first time a self-induced dust pile-up in simulations taking fragmentation into account. This feature, in addition to the easily detected planet gap, causes a second apparent gap that could be mistaken for the signature of a second planet. It is therefore essential to be cautious in the interpretation of gap detections.

  10. Implications of mercury interactions with band-gap semiconductor oxides

    SciTech Connect

    Granite, E.J.; King, W.P.; Stanko, D.C.; Pennline, H.W.

    2008-09-01

    Titanium dioxide is a well-known photooxidation catalyst. It will oxidize mercury in the presence of ultraviolet light from the sun and oxygen and/or moisture to form mercuric oxide. Several companies manufacture self-cleaning windows. These windows have a transparent coating of titanium dioxide. The titanium dioxide is capable of destroying organic contaminants in air in the presence of ultraviolet light from the sun, thereby keeping the windows clean. The commercially available self-cleaning windows were used to sequester mercury from oxygen–nitrogen mixtures. Samples of the self-cleaning glass were placed into specially designed photo-reactors in order to study the removal of elemental mercury from oxygen–nitrogen mixtures resembling air. The possibility of removing mercury from ambient air with a self-cleaning glass apparatus is examined. The intensity of 365-nm ultraviolet light was similar to the natural intensity from sunlight in the Pittsburgh region. Passive removal of mercury from the air may represent an option in lieu of, or in addition to, point source clean-up at combustion facilities. There are several common band-gap semiconductor oxide photocatalysts. Sunlight (both the ultraviolet and visible light components) and band-gap semiconductor particles may have a small impact on the global cycle of mercury in the environment. The potential environmental consequences of mercury interactions with band-gap semiconductor oxides are discussed. Heterogeneous photooxidation might impact the global transport of elemental mercury emanating from flue gases.

  11. 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.

  12. 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.

  13. Formation process of the widespread extreme haze pollution over northern China in January 2013: Implications for regional air quality and climate

    NASA Astrophysics Data System (ADS)

    Tao, Minghui; Chen, Liangfu; Xiong, Xiaozhen; Zhang, Meigen; Ma, Pengfei; Tao, Jinhua; Wang, Zifeng

    2014-12-01

    In this study, we present a regional insight into characteristics and formation process of the widespread extreme haze pollution in northern China during January of 2013 using integrated satellite observations and ground measurements. Different from common regional pollution, dense haze clouds during the most polluted period not only wandered over northern China for more than one week, but also exhibited large spatial variations with some abrupt peak values in Beijing. High UV Aerosol Index (UVAI) values >2.5 indicate prevalent absorbing aerosols in upper part of the haze clouds. CALIPSO vertical detection shows that the haze layers were more than 3 km thick, with strong extinction within 1 km near surface and elevated dust layers above. Top of the more than 2 km thick dust plumes can reach 5 km, having a substantial contribution to the haze clouds. Movement of high aerosol loading regions with aerosol optical depth (AOD) exceeding 2.0 shows a notable superposition of different pollution processes within boundary layer, which largely enhanced the haze pollution. Peak value of PM10 in industrial cities of Hebei was around 1000 μg/m3, almost twice of that in usual pollution. Subsequent peak values of PM10 from south to north confirm the intense regional transport, which could be the main cause of sudden record-breaking particle concentration in Beijing. Anomalous weather conditions facilitated the unusual heavy pollution became extremely severe. Our results indicate close connections between variation of atmospheric circulation and the regional heavy pollution over northern China.

  14. 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.

  15. Outdoor air pollution and asthma

    PubMed Central

    Guarnieri, Michael; Balmes, John R.

    2015-01-01

    Traffic and power generation are the main sources of urban air pollution. The idea that outdoor air pollution can cause exacerbations of pre-existing asthma is supported by an evidence base that has been accumulating for several decades, with several studies suggesting a contribution to new-onset asthma as well. In this Series paper, we discuss the effects of particulate matter (PM), gaseous pollutants (ozone, nitrogen dioxide, and sulphur dioxide), and mixed traffic-related air pollution. We focus on clinical studies, both epidemiological and experimental, published in the previous 5 years. From a mechanistic perspective, air pollutants probably cause oxidative injury to the airways, leading to inflammation, remodelling, and increased risk of sensitisation. Although several pollutants have been linked to new-onset asthma, the strength of the evidence is variable. We also discuss clinical implications, policy issues, and research gaps relevant to air pollution and asthma. PMID:24792855

  16. Tuning of full band gap in anisotropic photonic crystal slabs using a liquid crystal

    NASA Astrophysics Data System (ADS)

    Khalkhali, T. Fathollahi; Rezaei, B.; Ramezani, A. H.

    2012-11-01

    We analyze the tunability of full band gap in photonic crystal slabs created by square and triangular lattices of air holes in anisotropic tellurium background, considering that the regions above and below the slab are occupied by SiO2 and the holes are infiltrated with liquid crystals. Using the supercell method based on plane wave expansion, we study the variation of full band gap by changing the optical axis orientation of liquid crystal. Our results demonstrate the existence and remarkable tunability of full band gap in both square and triangular lattices, largest band gap and tunability being obtained for the triangular lattice.

  17. Air Pollution and Control Legislation in India

    NASA Astrophysics Data System (ADS)

    P Bhave, Prashant; Kulkarni, Nikhil

    2015-09-01

    Air pollution in urban areas arises from multiple sources, which may vary with location and developmental activities. Anthropogenic activities as rampant industrialization, exploitation and over consumption of natural resources, ever growing population size are major contributors of air pollution. The presented review is an effort to discuss various aspects of air pollution and control legislation in India emphasizing on the history, present scenario, international treaties, gaps and drawbacks. The review also presents legislative controls with judicial response to certain landmark judgments related to air pollution. The down sides related to enforcement mechanism for the effective implementation of environmental laws for air pollution control have been highlighted.

  18. Air resources

    SciTech Connect

    1995-10-01

    This section describes the ambient (surrounding) air quality of the TVA region, discusses TVA emission contributions to ambient air quality, and identifies air quality impacts to human health and welfare. Volume 2 Technical Document 2, Environmental Consequences, describes how changes in TVA emissions could affect regional air quality, human health, environmental resources, and materials. The primary region of the affected environment is broadly defined as the state of Tennessee, as well as southern Kentucky, western Virginia, southern West Virginia, western North Carolina, and northern Georgia, Alabama, and Mississippi. This area represents the watershed of the Tennessee River and the 201 counties of the greater TVA service area. Emissions from outside the Tennessee Valley region contribute to air quality in the Valley. Also, TVA emissions are transported outside the Valley and have some impact on air quality beyond the primary study area. Although the study area experiences a number of air quality problems, overall air quality is good.

  19. Air Pollution.

    ERIC Educational Resources Information Center

    Gilpin, Alan

    A summary of one of our most pressing environmental problems, air pollution, is offered in this book by the Director of Air Pollution Control for the Queensland (Australia) State Government. Discussion of the subject is not restricted to Queensland or Australian problems and policies, however, but includes analysis of air pollution the world over.…

  20. Air Pollution Control, Part I.

    ERIC Educational Resources Information Center

    Strauss, Werner, Ed.

    Authoritative reviews in seven areas of current importance in air pollution control are supplied in this volume, the first of a two-part set. Titles contained in this book are: "Dispersion of Pollutants Emitted into the Atmosphere,""The Formation and Control of Oxides of Nitrogen in Air Pollution,""The Control of Sulfur Emissions from Combustion…