Science.gov

Sample records for controlling spontaneous emission

  1. Controlling spontaneous emission in bioreplica photonic crystals

    NASA Astrophysics Data System (ADS)

    Jorgensen, Matthew R.; Butler, Elizabeth S.; Bartl, Michael H.

    2012-04-01

    Sophisticated methods have been created by nature to produce structure-based colors as a way to address the need of a wide variety of organisms. This pallet of available structures presents a unique opportunity for the investigation of new photonic crystal designs. Low-temperature sol-gel biotemplating methods were used to transform a single biotemplate into a variety of inorganic oxide structures. The density of optical states was calculated for a diamond-based natural photonic crystal, as well as several structures templated from it. Calculations were experimentally probed by spontaneous emission studies using time correlated single photon counting measurements.

  2. Active magneto-optical control of spontaneous emission in graphene

    DOE PAGESBeta

    Kort-Kamp, W. J. M.; Amorim, B.; Bastos, G.; Pinheiro, F. A.; Rosa, F. S. S.; Peres, N. M. R.; Farina, C.

    2015-11-13

    In this study, we investigate the spontaneous emission rate of a two-level quantum emitter near a graphene-coated substrate under the influence of an external magnetic field or strain induced pseudomagnetic field. We demonstrate that the application of the magnetic field can substantially increase or decrease the decay rate. We show that a suppression as large as 99% in the Purcell factor is achieved even for moderate magnetic fields. The emitter's lifetime is a discontinuous function of |B|, which is a direct consequence of the occurrence of discrete Landau levels in graphene. We demonstrate that, in the near-field regime, the magneticmore » field enables an unprecedented control of the decay pathways into which the photon/polariton can be emitted. Our findings strongly suggest that a magnetic field could act as an efficient agent for on-demand, active control of light-matter interactions in graphene at the quantum level.« less

  3. Active magneto-optical control of spontaneous emission in graphene

    SciTech Connect

    Kort-Kamp, W. J. M.; Amorim, B.; Bastos, G.; Pinheiro, F. A.; Rosa, F. S. S.; Peres, N. M. R.; Farina, C.

    2015-11-13

    In this study, we investigate the spontaneous emission rate of a two-level quantum emitter near a graphene-coated substrate under the influence of an external magnetic field or strain induced pseudomagnetic field. We demonstrate that the application of the magnetic field can substantially increase or decrease the decay rate. We show that a suppression as large as 99% in the Purcell factor is achieved even for moderate magnetic fields. The emitter's lifetime is a discontinuous function of |B|, which is a direct consequence of the occurrence of discrete Landau levels in graphene. We demonstrate that, in the near-field regime, the magnetic field enables an unprecedented control of the decay pathways into which the photon/polariton can be emitted. Our findings strongly suggest that a magnetic field could act as an efficient agent for on-demand, active control of light-matter interactions in graphene at the quantum level.

  4. Controlling the directionality of spontaneous emission by evanescent wave coupling

    SciTech Connect

    Wang, Xue-Lun E-mail: gdhao2@hotmail.com; Hao, Guo-Dong E-mail: gdhao2@hotmail.com; Toda, Naoya

    2015-09-28

    We report an approach toward controlling the directionality of spontaneous emissions by employing the evanescent wave coupling effect in a subwavelength-sized ridge or truncated cone structure. An InGaAs/GaAs light-emitting diode in which a stripe-shaped InGaAs/GaAs quantum well with a stripe width of about 100 nm is embedded at the center of a subwavelength-sized GaAs ridge (of width ∼520 nm) is fabricated by micro processing and epitaxial regrowth techniques. Strong directionalities characterized by a half-intensity angle of 43° are observed in planes perpendicular to the ridge axis. The directionality is found to be almost independent of operating conditions.

  5. Plasmonic phase-gradient metasurface for spontaneous emission control

    NASA Astrophysics Data System (ADS)

    Langguth, L.; Schokker, A. H.; Guo, K.; Koenderink, A. F.

    2015-11-01

    We combine the concept of phase-gradient metasurfaces with fluorescence directionality control of an ensemble of incoherent emitters. We design a periodic metasurface to control the scattering amplitude of the lattice in momentum space. The lattice is embedded in a waveguiding layer doped with organic fluorophores. In contrast to the usual symmetric directionality that plasmonic lattices impart on emission, we find that the phase gradient translates into asymmetric directional emission into the far field, determined by scattering on a subset of the reciprocal lattice vectors. The measured asymmetry is well explained by analytical modeling.

  6. Quantum dot spontaneous emission control in a ridge waveguide

    SciTech Connect

    Stepanov, Petr; Delga, Adrien; Bleuse, Joël; Dupuy, Emmanuel; Peinke, Emanuel; Gérard, Jean-Michel; Claudon, Julien; Zang, Xiaorun; Lalanne, Philippe

    2015-01-26

    We investigate the spontaneous emission (SE) of self-assembled InAs quantum dots (QDs) embedded in GaAs ridge waveguides that lay on a low index substrate. In thin enough waveguides, the coupling to the fundamental guided mode is vanishingly small. A pronounced anisotropy in the coupling to non-guided modes is then directly evidenced by normal-incidence photoluminescence polarization measurements. In this regime, a measurement of the QD decay rate reveals a SE inhibition by a factor up to 4. In larger wires, which ensure an optimal transverse confinement of the fundamental guided mode, the decay rate approaches the bulk value. Building on the good agreement with theoretical predictions, we infer from calculations the fraction β of SE coupled to the fundamental guided mode for some important QD excitonic complexes. For a charged exciton (isotropic in plane optical dipole), β reaches 0.61 at maximum for an on-axis QD. In the case of a purely transverse linear optical dipole, β increases up to 0.91. This optimal configuration is achievable through the selective excitation of one of the bright neutral excitons.

  7. Controlling the spontaneous emission rate of monolayer MoS2 in a photonic crystal nanocavity

    NASA Astrophysics Data System (ADS)

    Gan, Xuetao; Gao, Yuanda; Fai Mak, Kin; Yao, Xinwen; Shiue, Ren-Jye; van der Zande, Arend; Trusheim, Matthew E.; Hatami, Fariba; Heinz, Tony F.; Hone, James; Englund, Dirk

    2013-10-01

    We report on controlling the spontaneous emission (SE) rate of a molybdenum disulfide (MoS2) monolayer coupled with a planar photonic crystal (PPC) nanocavity. Spatially resolved photoluminescence (PL) mapping shows strong variations of emission when the MoS2 monolayer is on the PPC cavity, on the PPC lattice, on the air gap, and on the unpatterned gallium phosphide substrate. Polarization dependences of the cavity-coupled MoS2 emission show a more than 5 times stronger extracted PL intensity than the un-coupled emission, which indicates an underlying cavity mode Purcell enhancement of the MoS2 SE rate exceeding a factor of 70.

  8. Controlling spontaneous emission rates of quantum dots with plasmonic nanopatch antennas

    NASA Astrophysics Data System (ADS)

    Hoang, Thang; Akselrod, Gleb; Argyropoulos, Christos; Huang, Jiani; Smith, David; Mikkelsen, Maiken

    2015-03-01

    The radiative processes associated with quantum emitters can be strongly enhanced due to intense electromagnetic fields created by plasmonic nanostructures. Here, we experimentally demonstrate large enhancements of the spontaneous emission rate of colloidal quantum dots coupled to single plasmonic nanopatch antennas. The antennas consist of silver nanocubes (75 nm) coupled to a gold film separated by a thin polyelectrolyte spacer layer (~1 nm) and core-shell CdSe/ZnS quantum dots (~6 nm). By optimizing the size of the nanopatch antenna, the plasmonic mode is tuned to be on resonance with the quantum dot emission. We show an increase in the spontaneous emission rate by a factor of 880 (Purcell factor) and a 2300-fold enhancement in the total fluorescence while maintaining a high radiative quantum efficiency of ~50 %. The nanopatch antenna, as demonstrated here, offers highly directional and broadband radiation that can be tailored for emitters from the visible to the near infrared, providing a promising approach for the spontaneous emission control of single quantum emitters.

  9. Controlling the spontaneous emission rate of monolayer MoS2 in a photonic crystal nanocavity

    PubMed Central

    Gan, Xuetao; Gao, Yuanda; Fai Mak, Kin; Yao, Xinwen; Shiue, Ren-Jye; van der Zande, Arend; Trusheim, Matthew E.; Hatami, Fariba; Heinz, Tony F.; Hone, James; Englund, Dirk

    2013-01-01

    We report on controlling the spontaneous emission (SE) rate of a molybdenum disulfide (MoS2) monolayer coupled with a planar photonic crystal (PPC) nanocavity. Spatially resolved photoluminescence (PL) mapping shows strong variations of emission when the MoS2 monolayer is on the PPC cavity, on the PPC lattice, on the air gap, and on the unpatterned gallium phosphide substrate. Polarization dependences of the cavity-coupled MoS2 emission show a more than 5 times stronger extracted PL intensity than the un-coupled emission, which indicates an underlying cavity mode Purcell enhancement of the MoS2 SE rate exceeding a factor of 70. PMID:24273329

  10. Control of the entanglement between triple quantum dot molecule and its spontaneous emission fields via quantum entropy

    NASA Astrophysics Data System (ADS)

    Sahrai, M.; Arzhang, B.; Taherkhani, D.; Boroojerdi, V. Tahmoorian Askari

    2015-03-01

    The time evolution of the quantum entropy in a coherently driven triple quantum dot molecule is investigated. The entanglement of the quantum dot molecule and its spontaneous emission field is coherently controlled by the gate voltage and the rate of an incoherent pump field. The degree of entanglement between a triple quantum dot molecule and its spontaneous emission fields is decreased by increasing the tunneling parameter.

  11. Spontaneous emission control of quantum dots embedded in photonic crystals: Effects of external fields and dimension

    NASA Astrophysics Data System (ADS)

    Vaseghi, B.; Hashemi, H.

    2016-06-01

    In this paper simultaneous effects of external electric and magnetic fields and quantum confinement on the radiation properties of spherical quantum dot embedded in a photonic crystal are investigated. Under the influence of photonic band-gap, effects of external static fields and dot dimension on the amplitude and spectrum of different radiation fields emitted by the quantum dot are studied. Our results show the considerable effects of external fields and quantum confinement on the spontaneous emission of the system.

  12. On coherence in spontaneous emission

    NASA Astrophysics Data System (ADS)

    Cummings, F. W.; Dorri, Ali

    1983-05-01

    The case of a single excited two-level atom emitting spontaneously in the presence of N unexcited atoms is solved exactly for emission into a single electromagnetic mode. The two-level atoms are in inequivalent mode positions.

  13. Optical antenna enhanced spontaneous emission.

    PubMed

    Eggleston, Michael S; Messer, Kevin; Zhang, Liming; Yablonovitch, Eli; Wu, Ming C

    2015-02-10

    Atoms and molecules are too small to act as efficient antennas for their own emission wavelengths. By providing an external optical antenna, the balance can be shifted; spontaneous emission could become faster than stimulated emission, which is handicapped by practically achievable pump intensities. In our experiments, InGaAsP nanorods emitting at ∼ 200 THz optical frequency show a spontaneous emission intensity enhancement of 35 × corresponding to a spontaneous emission rate speedup ∼ 115 ×, for antenna gap spacing, d = 40 nm. Classical antenna theory predicts ∼ 2,500 × spontaneous emission speedup at d ∼ 10 nm, proportional to 1/d(2). Unfortunately, at d < 10 nm, antenna efficiency drops below 50%, owing to optical spreading resistance, exacerbated by the anomalous skin effect (electron surface collisions). Quantum dipole oscillations in the emitter excited state produce an optical ac equivalent circuit current, I(o) = qω|x(o)|/d, feeding the antenna-enhanced spontaneous emission, where q|x(o)| is the dipole matrix element. Despite the quantum-mechanical origin of the drive current, antenna theory makes no reference to the Purcell effect nor to local density of states models. Moreover, plasmonic effects are minor at 200 THz, producing only a small shift of antenna resonance frequency. PMID:25624503

  14. Optical antenna enhanced spontaneous emission

    PubMed Central

    Eggleston, Michael S.; Messer, Kevin; Zhang, Liming; Yablonovitch, Eli; Wu, Ming C.

    2015-01-01

    Atoms and molecules are too small to act as efficient antennas for their own emission wavelengths. By providing an external optical antenna, the balance can be shifted; spontaneous emission could become faster than stimulated emission, which is handicapped by practically achievable pump intensities. In our experiments, InGaAsP nanorods emitting at ∼200 THz optical frequency show a spontaneous emission intensity enhancement of 35× corresponding to a spontaneous emission rate speedup ∼115×, for antenna gap spacing, d = 40 nm. Classical antenna theory predicts ∼2,500× spontaneous emission speedup at d ∼ 10 nm, proportional to 1/d2. Unfortunately, at d < 10 nm, antenna efficiency drops below 50%, owing to optical spreading resistance, exacerbated by the anomalous skin effect (electron surface collisions). Quantum dipole oscillations in the emitter excited state produce an optical ac equivalent circuit current, Io = qω|xo|/d, feeding the antenna-enhanced spontaneous emission, where q|xo| is the dipole matrix element. Despite the quantum-mechanical origin of the drive current, antenna theory makes no reference to the Purcell effect nor to local density of states models. Moreover, plasmonic effects are minor at 200 THz, producing only a small shift of antenna resonance frequency. PMID:25624503

  15. Controlling the 1 μm spontaneous emission in Er/Yb co-doped fiber amplifiers.

    PubMed

    Sobon, Grzegorz; Kaczmarek, Pawel; Antonczak, Arkadiusz; Sotor, Jaroslaw; Abramski, Krzysztof M

    2011-09-26

    In this paper we present our experimental studies on controlling the amplified spontaneous emission (ASE) from Yb(3+) ions in Er/Yb co-doped fiber amplifiers. We propose a new method of controlling the Yb-ASE by stimulating a laser emission at 1064 nm in the amplifier, by providing a positive 1 μm signal feedback loop. The results are discussed and compared to a conventional amplifier setup without 1 μm ASE control and to an amplifier with auxiliary 1064 nm seeding. We have shown, that applying a 1064 nm signal loop in an Er/Yb amplifier can increase the output power at 1550 nm and provide stable operation without parasitic lasing at 1 μm. PMID:21996851

  16. Spontaneous-emission control by local density of states of photonic crystal cavity

    NASA Astrophysics Data System (ADS)

    Jiang, Bin; Zhang, Ye-Jin; Zhou, Wen-Jun; Chen, Wei; Liu, An-Jin; Zheng, Wan-Hua

    2011-02-01

    The local density of states (LDOS) of two-dimensional square lattice photonic crystal (PhC) defect cavity is studied. The results show that the LDOS in the centre is greatly reduced, while the LDOS at the point off the centre (for example, at the point (0.3a, 0.4a), where a is the lattice constant) is extremely enhanced. Further, the disordered radii are introduced to imitate the real devices fabricated in our experiment, and then we study the LDOS of PhC cavity with configurations of different disordered radii. The results show that in the disordered cavity, the LDOS in the centre is still greatly reduced, while the LDOS at the point (0.3a, 0.4a) is still extremely enhanced. It shows that the LDOS analysis is useful. When a laser is designed on the basis of the square lattice PhC rod cavity, in order to enhance the spontaneous emission, the active materials should not be inserted in the centre of the cavity, but located at positions off the centre. So LDOS method gives a guide to design the positions of the active materials (quantum dots) in the lasers.

  17. Control of spontaneous emission from a microwave-field-coupled three-level{Lambda}-type atom in photonic crystals

    SciTech Connect

    Jiang, X. Q.; Zhang, B.; Sun, X. D.; Lu, Z. W.

    2011-05-15

    The spontaneous emission spectrum of a three-level {Lambda}-type atom driven by a microwave field was studied. For the two transitions coupled to the same modified reservoir, we discussed the influence of photonic band gap and Rabi frequency of the microwave field on the emission spectrum. The emission spectrum is given for different locations of the upper band-edge frequency. With the transition frequencies moving from outside the band gap to inside, the number of peaks decreases in the emission spectrum and the multipeak structure of spectral line is finally replaced by a strong non-Lorentzian shape. With increase of the Rabi frequency of the microwave field, we find the spectral line changes from a multipeak structure to a two-peak structure, originating from the inhibition of spontaneous emission for the corresponding decay channel.

  18. Mapping quantum state dynamics in spontaneous emission.

    PubMed

    Naghiloo, M; Foroozani, N; Tan, D; Jadbabaie, A; Murch, K W

    2016-01-01

    The evolution of a quantum state undergoing radiative decay depends on how its emission is detected. If the emission is detected in the form of energy quanta, the evolution is characterized by a quantum jump to a lower energy state. In contrast, detection of the wave nature of the emitted radiation leads to different dynamics. Here, we investigate the diffusive dynamics of a superconducting artificial atom under continuous homodyne detection of its spontaneous emission. Using quantum state tomography, we characterize the correlation between the detected homodyne signal and the emitter's state, and map out the conditional back-action of homodyne measurement. By tracking the diffusive quantum trajectories of the state as it decays, we characterize selective stochastic excitation induced by the choice of measurement basis. Our results demonstrate dramatic differences from the quantum jump evolution associated with photodetection and highlight how continuous field detection can be harnessed to control quantum evolution. PMID:27167893

  19. Mapping quantum state dynamics in spontaneous emission

    NASA Astrophysics Data System (ADS)

    Naghiloo, M.; Foroozani, N.; Tan, D.; Jadbabaie, A.; Murch, K. W.

    2016-05-01

    The evolution of a quantum state undergoing radiative decay depends on how its emission is detected. If the emission is detected in the form of energy quanta, the evolution is characterized by a quantum jump to a lower energy state. In contrast, detection of the wave nature of the emitted radiation leads to different dynamics. Here, we investigate the diffusive dynamics of a superconducting artificial atom under continuous homodyne detection of its spontaneous emission. Using quantum state tomography, we characterize the correlation between the detected homodyne signal and the emitter's state, and map out the conditional back-action of homodyne measurement. By tracking the diffusive quantum trajectories of the state as it decays, we characterize selective stochastic excitation induced by the choice of measurement basis. Our results demonstrate dramatic differences from the quantum jump evolution associated with photodetection and highlight how continuous field detection can be harnessed to control quantum evolution.

  20. Mapping quantum state dynamics in spontaneous emission

    PubMed Central

    Naghiloo, M.; Foroozani, N.; Tan, D.; Jadbabaie, A.; Murch, K. W.

    2016-01-01

    The evolution of a quantum state undergoing radiative decay depends on how its emission is detected. If the emission is detected in the form of energy quanta, the evolution is characterized by a quantum jump to a lower energy state. In contrast, detection of the wave nature of the emitted radiation leads to different dynamics. Here, we investigate the diffusive dynamics of a superconducting artificial atom under continuous homodyne detection of its spontaneous emission. Using quantum state tomography, we characterize the correlation between the detected homodyne signal and the emitter's state, and map out the conditional back-action of homodyne measurement. By tracking the diffusive quantum trajectories of the state as it decays, we characterize selective stochastic excitation induced by the choice of measurement basis. Our results demonstrate dramatic differences from the quantum jump evolution associated with photodetection and highlight how continuous field detection can be harnessed to control quantum evolution. PMID:27167893

  1. Using Spontaneous Emission of a Qubit as a Resource for Feedback Control

    NASA Astrophysics Data System (ADS)

    Campagne-Ibarcq, P.; Jezouin, S.; Cottet, N.; Six, P.; Bretheau, L.; Mallet, F.; Sarlette, A.; Rouchon, P.; Huard, B.

    2016-08-01

    Persistent control of a transmon qubit is performed by a feedback protocol based on continuous heterodyne measurement of its fluorescence. By driving the qubit and cavity with microwave signals whose amplitudes depend linearly on the instantaneous values of the quadratures of the measured fluorescence field, we show that it is possible to stabilize permanently the qubit in any targeted state. Using a Josephson mixer as a phase-preserving amplifier, it was possible to reach a total measurement efficiency η =35 %, leading to a maximum of 59% of excitation and 44% of coherence for the stabilized states. The experiment demonstrates multiple-input multiple-output analog Markovian feedback in the quantum regime.

  2. Plasmon-induced modifications in spontaneous emission of fluorophores in controlled nanoscale geometries

    NASA Astrophysics Data System (ADS)

    Lal, Surbhi; Goodrich, Glenn P.; Brinson, Bruce E.; Halas, N. J.

    2004-03-01

    It is well known that a variety of fundamental photophysical processes, such as absorption, fluorescence, and Raman scattering, are greatly substantially modified in the vicinity of metal surfaces or structures such as gratings, island films or colloids. [1] The collective electromagnetic resonances, or plasmon resonances, supported by metallic structures, as well as modifications in the local electromagnetic mode density near these structures, are responsible for influencing the radiating dipole of vicinal fluorophores. Nanoshells are dielectric core-metal shell nanoparticles whose plasmon resonance can be controllably tuned by varying the relative dimensions of its core and shell layers [2]. Nanoshells provide a practical substrate for the systematic investigation of the role of the plasmon-induced near field in fluorescence enhancement and quenching. We have fabricated two systems for the study of lanthanide ions and molecular fluorophores, respectively, at controlled distances above a nanoshell surface. Initial results examining the fluorophore-metal distance dependence and dependence on plasmon resonance detuning with respect to excitations in the fluorophore will be discussed. [1] Moskovits, M., Rev. Mod. Phys. 57, 783 (1985) [2] S. Oldenburg, R. D. Averitt, S. Westcott, and N. J. Halas, Chem. Phys. Lett. 288, 243 (1998); E. Prodan, C. Radloff, N. J. Halas and P. J. Nordlander, Science 301, 419 (2003).

  3. Spontaneous emission in stimulated Raman adiabatic passage

    SciTech Connect

    Ivanov, P. A.; Vitanov, N. V.; Bergmann, K.

    2005-11-15

    This work explores the effect of spontaneous emission on the population transfer efficiency in stimulated Raman adiabatic passage (STIRAP). The approach uses adiabatic elimination of weakly coupled density matrix elements in the Liouville equation, from which a very accurate analytic approximation is derived. The loss of population transfer efficiency is found to decrease exponentially with the factor {omega}{sub 0}{sup 2}/{gamma}, where {gamma} is the spontaneous emission rate and {omega}{sub 0} is the peak Rabi frequency. The transfer efficiency increases with the pulse delay and reaches a steady value. For large pulse delay and large spontaneous emission rate STIRAP degenerates into optical pumping.

  4. Using Spontaneous Emission of a Qubit as a Resource for Feedback Control.

    PubMed

    Campagne-Ibarcq, P; Jezouin, S; Cottet, N; Six, P; Bretheau, L; Mallet, F; Sarlette, A; Rouchon, P; Huard, B

    2016-08-01

    Persistent control of a transmon qubit is performed by a feedback protocol based on continuous heterodyne measurement of its fluorescence. By driving the qubit and cavity with microwave signals whose amplitudes depend linearly on the instantaneous values of the quadratures of the measured fluorescence field, we show that it is possible to stabilize permanently the qubit in any targeted state. Using a Josephson mixer as a phase-preserving amplifier, it was possible to reach a total measurement efficiency η=35%, leading to a maximum of 59% of excitation and 44% of coherence for the stabilized states. The experiment demonstrates multiple-input multiple-output analog Markovian feedback in the quantum regime. PMID:27541448

  5. Dynamics of spontaneous otoacoustic emissions

    NASA Astrophysics Data System (ADS)

    Bergevin, Christopher; Salerno, Anthony

    2015-12-01

    Spontaneous otoacoustic emissions (SOAEs) have become a hallmark feature in modern theories of an `active' inner ear, given their numerous correlations to auditory function (e.g., threshold microstructure, neurophysiological tuning curves), near universality across tetrapod classes, and physiological correlates at the single hair cell level. However, while several different classes of nonlinear models exist that describe the mechanisms underlying SOAE generation (e.g., coupled limit-cycle oscillators, global standing waves), there is still disagreement as to precisely which biophysical concepts are at work. Such is further compounded by the idiosyncratic nature of SOAEs: Not all ears emit, and when present, SOAE activity can occur at seemingly arbitrary frequencies (though always within the most sensitive range of the audiogram) and in several forms (e.g., peaks, broad `baseline' plateaus). The goal of the present study was to develop new signal processing and stimulation techniques that would allow for novel features of SOAE activity to be revealed. To this end, we analyzed data from a variety of different species: human, lizard, and owl. First, we explored several strategies for examining SOAE waveforms in the absence of external stimuli to further ascertain what constitutes `self-sustained sinusoids' versus `filtered noise'. We found that seemingly similar peaks in the spectral domain could exhibit key differences in the time domain, which we interpret as providing critical information about the underlying oscillators and their coupling. Second, we introduced dynamic stimuli (swept-tones, tone bursts) at a range of levels, whose interaction with SOAEs could be visualized in the time-frequency domain. Aside from offering a readily accessible way to visualize many previously reported effects (e.g., entrainment, facilitation), we observed several new features such as subharmonic distortion generation and competing pulling/pushing effects when multiple tones were

  6. Control of the spontaneous emission from a single quantum dash using a slow-light mode in a two-dimensional photonic crystal on a Bragg reflector

    SciTech Connect

    Chauvin, N.; Fiore, A.; Nedel, P.; Seassal, C.; Ben Bakir, B.; Letartre, X.; Gendry, M.; Viktorovitch, P.

    2009-07-15

    We demonstrate the coupling of a single InAs/InP quantum, emitting around 1.55 {mu}m, to a slow-light mode in a two-dimensional photonic crystal on Bragg reflector. These surface addressable 2.5D photonic crystal band-edge modes present the advantages of a vertical emission and the mode area and localization may be controlled, leading to a less critical spatial alignment with the emitter. An increase in the spontaneous emission rate by a factor of 1.5-2 is measured at low temperature and is compared to the Purcell factor predicted by three-dimensional time-domain electromagnetic simulations.

  7. Ultrafast spontaneous emission source using plasmonic nanoantennas

    NASA Astrophysics Data System (ADS)

    Hoang, Thang B.; Akselrod, Gleb M.; Argyropoulos, Christos; Huang, Jiani; Smith, David R.; Mikkelsen, Maiken H.

    2015-07-01

    Typical emitters such as molecules, quantum dots and semiconductor quantum wells have slow spontaneous emission with lifetimes of 1-10 ns, creating a mismatch with high-speed nanoscale optoelectronic devices such as light-emitting diodes, single-photon sources and lasers. Here we experimentally demonstrate an ultrafast (<11 ps) yet efficient source of spontaneous emission, corresponding to an emission rate exceeding 90 GHz, using a hybrid structure of single plasmonic nanopatch antennas coupled to colloidal quantum dots. The antennas consist of silver nanocubes coupled to a gold film separated by a thin polymer spacer layer and colloidal core-shell quantum dots, a stable and technologically relevant emitter. We show an increase in the spontaneous emission rate of a factor of 880 and simultaneously a 2,300-fold enhancement in the total fluorescence intensity, which indicates a high radiative quantum efficiency of ~50%. The nanopatch antenna geometry can be tuned from the visible to the near infrared, providing a promising approach for nanophotonics based on ultrafast spontaneous emission.

  8. Ultrafast spontaneous emission source using plasmonic nanoantennas

    PubMed Central

    Hoang, Thang B.; Akselrod, Gleb M.; Argyropoulos, Christos; Huang, Jiani; Smith, David R.; Mikkelsen, Maiken H.

    2015-01-01

    Typical emitters such as molecules, quantum dots and semiconductor quantum wells have slow spontaneous emission with lifetimes of 1–10 ns, creating a mismatch with high-speed nanoscale optoelectronic devices such as light-emitting diodes, single-photon sources and lasers. Here we experimentally demonstrate an ultrafast (<11 ps) yet efficient source of spontaneous emission, corresponding to an emission rate exceeding 90 GHz, using a hybrid structure of single plasmonic nanopatch antennas coupled to colloidal quantum dots. The antennas consist of silver nanocubes coupled to a gold film separated by a thin polymer spacer layer and colloidal core–shell quantum dots, a stable and technologically relevant emitter. We show an increase in the spontaneous emission rate of a factor of 880 and simultaneously a 2,300-fold enhancement in the total fluorescence intensity, which indicates a high radiative quantum efficiency of ∼50%. The nanopatch antenna geometry can be tuned from the visible to the near infrared, providing a promising approach for nanophotonics based on ultrafast spontaneous emission. PMID:26212857

  9. Spontaneous emission and oscillation in a planar microcavity dye laser

    NASA Astrophysics Data System (ADS)

    Osuge, Michihiro; Ujihara, Kikuo

    1994-09-01

    Characteristics of a planar microcavity laser using rhodamine 6G with pulsed excitation is studied. Theoretical aspects of controlled spontaneous emission and oscillation in a planar microcavity laser are discussed. The measured spectrum and the angular divergence of spontaneous emission below threshold are in good agreement with theory. The angular divergence yields the radius of the cavity quasimode. The spontaneous emission coupling ratio obtained from the measured input-output characteristics is in reasonable agreement with the theoretical value. The expression for the coupling ratio derived for a Fabry-Perot-type microcavity is shown to be essentially equal to that of a closed cavity or guided mode cavity derived by Yamamoto, Machida, and Bjoerk (1991). The observed spectral behavior near the threshold approximately follows the Schawlow-Townes formula, but for a limited range of output power. The observed spectrum and divergence above threshold indicate incoherence much worse than the Schawlow-Townes limit.

  10. Photonic Crystals-Inhibited Spontaneous Emission: Optical Antennas-Enhanced Spontaneous Emission

    NASA Astrophysics Data System (ADS)

    Yablonovitch, Eli

    Photonic crystals are also part of everyday technological life in opto-electronic telecommunication devices that provide us with internet, cloud storage, and email. But photonic crystals have also been identified in nature, in the coloration of peacocks, parrots, chameleons, butterflies and many other species.In spite of its broad applicability, the original motivation of photonic crystals was to create a ``bandgap'' in which the spontaneous emission of light would be inhibited. Conversely, the opposite is now possible. The ``optical antenna'' can accelerate spontaneous emission. Over 100 years after the radio antenna, we finally have tiny ``optical antennas'' which can act on molecules and quantum dots. Employing optical antennas, spontaneous light emission can become faster than stimulated emission.

  11. Competition between coherent emission and broadband spontaneous emission in the quantum free electron laser

    SciTech Connect

    Robb, G. R. M.; Bonifacio, R.

    2013-03-15

    We extend previous analyses of spontaneous emission in a quantum free electron laser (QFEL) and competition between spontaneous and coherent QFEL emission to include a broad distribution of photon frequencies and momenta appropriate for spontaneous undulator radiation. We show that although the predictions of monochromatic and broadband models predict different electron momentum distributions for the quantum regime due to spontaneous emission alone after many photon emissions, the inclusion of broadband spontaneous emission has a negligible effect on the competition between spontaneous and coherent emission in the QFEL. Numerical results from both models are well described by the same condition for the threshold/critical value of spontaneous emission rate.

  12. Transformation quantum optics: designing spontaneous emission using coordinate transformations

    NASA Astrophysics Data System (ADS)

    Zhang, Jingjing; Wubs, Martijn; Ginzburg, Pavel; Wurtz, Gregory; Zayats, Anatoly V.

    2016-04-01

    Spontaneous decay is a fundamental quantum property of emitters that can be controlled in a material environment via modification of the local density of optical states (LDOS). Here we use transformation optics methods in order to design required density of states and thus spontaneous emission (SE) rate. Specifically, we show that the SE rate can be either enhanced or suppressed using invisibility cloaks or gradient index lenses. Furthermore, the anisotropic material profile of the cloak enables the directional control of SE. We also discuss how the practical issues, such as dispersion and losses, affect the LDOS in complex materials. Tailoring SE properties using transformation optics approach provides an innovative way for designing emission properties in a complex material environment needed for the development of active nanophotonic devices.

  13. Spontaneous emission from a fractal vacuum

    NASA Astrophysics Data System (ADS)

    Akkermans, Eric; Gurevich, Evgeni

    2013-08-01

    Spontaneous emission of a quantum emitter coupled to a QED vacuum with a deterministic fractal structure of its spectrum is considered. We show that the decay probability does not follow a Wigner-Weisskopf exponential decrease but rather an overall power law behavior with a rich oscillatory structure, both depending on the local fractal properties of the vacuum spectrum. These results are obtained by giving first a general perturbative derivation for short times. Then we propose a simplified model which retains the main features of a fractal spectrum to establish analytic expressions valid for all time scales. Finally, we discuss the case of a Fibonacci cavity and its experimental relevance to observe these results.

  14. Modified spontaneous emissions of europium complex in weak PMMA opals.

    PubMed

    Wang, Wei; Song, Hongwei; Bai, Xue; Liu, Qiong; Zhu, Yongsheng

    2011-10-28

    Engineering spontaneous emission by means of photonic crystals (PHC) is under extensive study. However PHC modification of line emissions of rare earth (RE) ions has not been thoroughly understood, especially in cases of weak opal PHCs and while emitters are well dispersed into dielectric media. In this study, poly-methyl methacrylate (PMMA) opal PHCs containing uniformly dispersed europium chelate were fabricated with finely controlled photonic stop band (PSB) positions. Measurements of luminescent dynamics and angle resolved/integrated emission spectra as well as numerical calculations of total densities of states (DOS) were performed. We determined that in weak opals, the total spontaneous emission rate (SER) of Σ(5)D(0)-(7)F(J) for Eu(3+) was independent of PSB positions but was higher than that of the disordered powder sample, which was attributed to higher effective refractive indices in the PHC rather than PSB effect. Branch SER of (5)D(0)-(7)F(2) for Eu(3+) in the PHCs, on the other hand, was spatially redistributed, suppressed or enhanced in directions of elevated or reduced optical modes, keeping the angle-integrated total unchanged. All the results are in agreement with total DOS approximation. Our paper addressed two unstudied issues regarding modified narrow line emission in weak opal PHCs: firstly whether PSB could change the SER of emitters and whether there exist, apart from PSB, other reasons to change SERs; secondly, while directional enhancement and suppression by PSB has been confirmed, whether the angle-integrated overall effect is enhancing or suppressing. PMID:21938288

  15. Modification and control of coherence effects in the spontaneous emission spectrum of a three-level atom at weak field regime

    NASA Astrophysics Data System (ADS)

    Dutta, Bibhas Kumar; Panchadhyayee, Pradipta

    2016-09-01

    It has been shown that coherence effects have a marked influence in the spontaneous emission spectrum of a three-level Λ -type atom driven by weak coherent and incoherent fields. Phase dependent evolution of interference effects leading to spectral narrowing, generation of spectral hole and dark line are exhibited in the present scheme when the atom does not interact with the incoherent fields. The basic mechanism underlying this scheme seems to be appropriate for a phaseonium. Apart from phase-coherence introduced in the system the phenomenon of line narrowing, in the presence of weak incoherent pumping, can be achieved in a different way as a consequence of two competitive resonant effects: sharp non-Lorentzian and symmetric Fano-like-resonance contributions to the line shape. In both the situations, the evolution of narrow structures in the line shape can be achieved even when the emission is influenced by the dephasing of Raman coherence.

  16. Quantitative analysis of directional spontaneous emission spectra from light sources in photonic crystals

    SciTech Connect

    Nikolaev, Ivan S.; Lodahl, Peter; Vos, Willem L.

    2005-05-15

    We have performed angle-resolved measurements of spontaneous-emission spectra from laser dyes and quantum dots in opal and inverse opal photonic crystals. Pronounced directional dependencies of the emission spectra are observed: angular ranges of strongly reduced emission adjoin with angular ranges of enhanced emission. It appears that emission from embedded light sources is affected both by the periodicity and by the structural imperfections of the crystals: the photons are Bragg diffracted by lattice planes and scattered by unavoidable structural disorder. Using a model comprising diffuse light transport and photonic band structure, we quantitatively explain the directional emission spectra. This work provides detailed understanding of the transport of spontaneously emitted light in real photonic crystals, which is essential in the interpretation of quantum optics in photonic-band-gap crystals and for applications wherein directional emission and total emission power are controlled.

  17. Spontaneous emission enhancement in micropatterned GaN

    NASA Astrophysics Data System (ADS)

    Niehus, M.; Sanguino, P.; Monteiro, T.; Soares, M. J.; Schwarz, R.

    2004-10-01

    With two interfering pulses from the fourth harmonic of a Nd-YAG laser we burnt a periodic lattice structure into the surface of GaN thin films. The lattice period of this permanent grating could be controlled between less than one and several tens of microns. Above the decomposition threshold, nitrogen evades from the sample surface, and the residual metallic gallium accumulates in the form of tiny droplets at the surfaces. The patterned structure shows structural similarities with microcavities. The question arises if the residual metallic gallium may act as a partially reflecting mirror. To test this hypothesis, we studied the steady-state and transient photoluminescence through the modulation of light emerging from the ubiquitous broad "yellow" photoluminescence band. The microlattice is evidenced by energy-equidistant spontaneous emission enhancement peaks in the steady-state photoluminescence spectra. We suggest that the partial reflection due to the residual metallic gallium leads to the observed enhancement effect.

  18. Tunable Casimir-Polder Forces and Spontaneous Emission Rates

    NASA Astrophysics Data System (ADS)

    Rosa, Felipe; Kort-Kamp, Wilton; Pinheiro, Felipe; Cysne, Tarik; Oliver, Diego; Farina, Carlos

    2015-03-01

    We investigate the dispersive Casimir-Polder interaction between a Rubidium atom and a graphene sheet subjected to an external magnetic field B. We demonstrate that this concrete physical system allows for a high degree of control of dispersive interactions at micro and nanoscales. Indeed, we show that the application of an external magnetic field can induce a 80 % reduction of the Casimir-Polder energy relative to its value without the field. We also show that sharp discontinuities emerge in the Casimir-Polder interaction energy for certain values of the applied magnetic field at low temperatures. In addition, we also show that atomic spontaneous emission rates can be greatly modified by the action of the magnetic field, with an order of magnitude enhancement or suppression depending on the dipole's moment orientation.

  19. Reversible Modulation of Spontaneous Emission by Strain in Silicon Nanowires

    PubMed Central

    Shiri, Daryoush; Verma, Amit; Selvakumar, C. R.; Anantram, M. P.

    2012-01-01

    We computationally study the effect of uniaxial strain in modulating the spontaneous emission of photons in silicon nanowires. Our main finding is that a one to two orders of magnitude change in spontaneous emission time occurs due to two distinct mechanisms: (A) Change in wave function symmetry, where within the direct bandgap regime, strain changes the symmetry of wave functions, which in turn leads to a large change of optical dipole matrix element. (B) Direct to indirect bandgap transition which makes the spontaneous photon emission to be of a slow second order process mediated by phonons. This feature uniquely occurs in silicon nanowires while in bulk silicon there is no change of optical properties under any reasonable amount of strain. These results promise new applications of silicon nanowires as optoelectronic devices including a mechanism for lasing. Our results are verifiable using existing experimental techniques of applying strain to nanowires. PMID:22708056

  20. Large spontaneous emission rate enhancement in grating coupled hyperbolic metamaterials

    PubMed Central

    Sreekanth, Kandammathe Valiyaveedu; Krishna, Koduru Hari; De Luca, Antonio; Strangi, Giuseppe

    2014-01-01

    Hyperbolic metamaterial (HMM), a sub-wavelength periodic artificial structure with hyperbolic dispersion, can enhance the spontaneous emission of quantum emitters. Here, we demonstrate the large spontaneous emission rate enhancement of an organic dye placed in a grating coupled hyperbolic metamaterial (GCHMM). A two-dimensional (2D) silver diffraction grating coupled with an Ag/Al2O3 HMM shows 18-fold spontaneous emission decay rate enhancement of dye molecules with respect to the same HMM without grating. The experimental results are compared with analytical models and numerical simulations, which confirm that the observed enhancement of GCHMM is due to the outcoupling of non-radiative plasmonic modes as well as strong plasmon-exciton coupling in HMM via diffracting grating. PMID:25209102

  1. Picosecond time of spontaneous emission in plasmonic patch nanoantennas

    NASA Astrophysics Data System (ADS)

    Eliseev, S. P.; Vitukhnovsky, A. G.; Chubich, D. A.; Kurochkin, N. S.; Sychev, V. V.; Marchenko, A. A.

    2016-01-01

    A significant (to 12 ps) decrease in the lifetime of excited states of quantum emitters in the form of three-layer colloidal quantum dots (CdSe/CdS/ZnS) placed in an aluminum-triangular silver nanoprism cavity (patch nanoantenna) has been experimentally demonstrated. The decrease in the time of spontaneous emission of quantum dots has been explained by the Purcell effect. The Purcell coefficient for an emitter in the resonator has been found to be 625. Such a significant increase in the rate of spontaneous emission in the patch nanoantenna is due to an increase in the local density of photon states in the plasmonic cavity.

  2. Photoluminescence and spontaneous emission enhancement in metamaterial nanostructures

    NASA Astrophysics Data System (ADS)

    Singh, M. R.; Cox, J. D.; Brzozowski, M.

    2014-02-01

    We present a theory for the photoluminescence (PL) and spontaneous emission of semiconductor nanoparticles (quantum dots—QDS) doped in a metamaterial heterostructure. The heterostructure is formed by fabricating a split-ring resonator and metallic rod metamaterial on a dielectric substrate. QDs are doped near the interface in the heterostructure. Our results indicate that the PL and spontaneous emission of the QDs are enhanced in the presence of the metamaterial when the exciton and surface plasmon frequencies are resonant. These findings are consistent with recent experimental studies. The present study can be used to make new types of nanoscale optical devices for sensing, switching and imaging applications based on metamaterials.

  3. QED (quantum-electrodynamical) theory of excess spontaneous emission noise

    SciTech Connect

    Milonni, P.W.

    1990-01-01

    The results of a quantum-electrodynamical theory of excess spontaneous emission noise in lossy resonators will be presented. The Petermann K factor'' does not enter into the spontaneous emission rate of a single atom in the cavity. The QED theory allows different interpretations of the K factor, and we use this fact to justify semiclassical analyses and to provide in one example a simple derivation of K in terms of the amplification of the quantum vacuum field entering the resonator through its mirrors. 17 refs.

  4. Spontaneous Radio Frequency Emissions from Natural Aurora. Chapter 4

    NASA Technical Reports Server (NTRS)

    LaBelle, J.

    2009-01-01

    At high latitudes, suitably sensitive radio experiments tuned below 5 MHz detect up to three types of spontaneous radio emissions from the Earth s ionosphere. In recent years, ground-based and rocket-borne experiments have provided strong evidence for theoretical explanations of the generation mechanism of some of these emissions, but others remain unexplained. Achieving a thorough understanding of these ionospheric emissions, accessible to ground-based experiments, will not only bring a deeper understanding of Earth s radio environment and the interactions between waves and particles in the ionosphere but also shed light on similar spontaneous emissions occurring elsewhere in Earth s environment as well as other planetary and stellar atmospheres.

  5. Amplified spontaneous emission in solar-pumped iodine laser

    NASA Technical Reports Server (NTRS)

    Cho, Yong S.; Hwang, In H.; Han, Kwang S.; Lee, Ja H.

    1992-01-01

    The amplified spontaneous emission (ASE) from a long pulse, solar-simulating radiation pumped iodine laser amplifier is studied. The ASE threshold pump intensity is almost proportional to the inverse of the laser gain length when the gas pressure is constant in the laser tube.

  6. Spontaneous emission effects in optically pumped x-ray FEL

    SciTech Connect

    Smetanin, I.V.; Grigor`ev, S.V.

    1995-12-31

    An effect of spontaneous emission in both quantum and classical regimes of the optically pumped X-ray free electron laser (FEL) in investigated. The quantum properties of an FEL are determined by the ratio of the separation {h_bar} between the absorption and emission lines (i.e. the quanta emitted) and their effective width {Delta}{epsilon} {eta}={h_bar}/{Delta}{epsilon}. In the conventional classical regime {eta} {much_lt} 1 an electron emits and absorbes a great number of shortwavelength photons over the interaction region, the gain in FEL being the result of these competitive processes. In the quantum limit {eta} {much_gt} 1 the emission and absorption lines are completely separated and thus the FEL becomes a two-level quantum oscillator with a completely inverted active medium. Spontaneous emission causes the electron to leave the range of energies where resonant interaction with the laser field occurs, thus effectively reducing the number of particles that take part in generating the induced X-ray signal. This effect is found to be crucial for lasing in optically pumped X-ray FEL. The characteristic relaxation times are calculated for both classical and quantum FEL regimes. It is shown that spontaneous emission results in FEL electron beam threshold current, which is of rather high value. An optimal range of pumping laser intensities is determined.

  7. Spontaneous emission of the non-Wiener type

    SciTech Connect

    Basharov, A. M.

    2011-09-15

    The spontaneous emission of a quantum particle and superradiation of an ensemble of identical quantum particles in a vacuum electromagnetic field with zero photon density are examined under the conditions of significant Stark particle and field interaction. New fundamental effects are established: suppression of spontaneous emission by the Stark interaction, an additional 'decay' shift in energy of the decaying level as a consequence of Stark interaction unrelated to the Lamb and Stark level shifts, excitation conservation phenomena in a sufficiently dense ensemble of identical particles and suppression of superradiaton in the decay of an ensemble of excited quantum particles of a certain density. The main equations describing the emission processes under conditions of significant Stark interaction are obtained in the effective Hamiltonian representation of quantum stochastic differential equations. It is proved that the Stark interaction between a single quantum particle and a broadband electromagnetic field is represented as a quantum Poisson process and the stochastic differential equations are of the non-Wiener (generalized Langevin) type. From the examined case of spontaneous emission of a quantum particle, the main rules are formulated for studying open systems in the effective Hamiltonian representation.

  8. Spontaneous emission of the non-Wiener type

    NASA Astrophysics Data System (ADS)

    Basharov, A. M.

    2011-09-01

    The spontaneous emission of a quantum particle and superradiation of an ensemble of identical quantum particles in a vacuum electromagnetic field with zero photon density are examined under the conditions of significant Stark particle and field interaction. New fundamental effects are established: suppression of spontaneous emission by the Stark interaction, an additional "decay" shift in energy of the decaying level as a consequence of Stark interaction unrelated to the Lamb and Stark level shifts, excitation conservation phenomena in a sufficiently dense ensemble of identical particles and suppression of superradiaton in the decay of an ensemble of excited quantum particles of a certain density. The main equations describing the emission processes under conditions of significant Stark interaction are obtained in the effective Hamiltonian representation of quantum stochastic differential equations. It is proved that the Stark interaction between a single quantum particle and a broadband electromagnetic field is represented as a quantum Poisson process and the stochastic differential equations are of the non-Wiener (generalized Langevin) type. From the examined case of spontaneous emission of a quantum particle, the main rules are formulated for studying open systems in the effective Hamiltonian representation.

  9. A hybrid nanoantenna for highly enhanced directional spontaneous emission

    SciTech Connect

    Chou, R. Yuanying; Lu, Guowei Shen, Hongming; He, Yingbo; Cheng, Yuqing; Perriat, Pascal; Martini, Matteo; Tillement, Olivier; Gong, Qihuang

    2014-06-28

    Spontaneous emission modulated by a hybrid plasmonic nanoantenna has been investigated by employing finite-difference time-domain method. The hybrid nanoantenna configurations constituted by a gap hot-spot and of a plasmonic corrugated grating and a metal reflector sandwiching a SiO{sub 2} thin layer which appears promising for high spontaneous emission enhancement devices. Simulation assays show that the coupling between the gap-antenna and plasmonic corrugations reaches an ultra-high near-field enhancement factor in the excitation process. Moreover, concerning the emission process, the corrugations concentrate the far-field radiated power within a tiny angular volume, offering unprecedented collection efficiency. In the past decades, many kinds of optical antennas have been proposed and optimized to enhance single molecule detection. However, the excitation enhancement effect for single individual or dimmer plasmonic nanostructure is limited due to intrinsic nonradiative decay of the nanoparticle plasmon and quantum tunneling effect. The proposed hybrid configuration overwhelms the enhancement limit of single individual plasmonic structure. The findings provide an insight into spontaneous emission high enhancement through integrating the functions of different metallic nanostructures.

  10. Electrically induced spontaneous emission in open electronic system

    NASA Astrophysics Data System (ADS)

    Wang, Rulin; Zhang, Yu; Yam, Chiyung; Computation Algorithms Division (CSRC) Team; Theoretical; Computational Chemistry (HKU) Collaboration

    A quantum mechanical approach is formulated for simulation of electroluminescence process in open electronic system. Based on nonequilibrium Green's function quantum transport equations and combining with photon-electron interaction, this method is used to describe electrically induced spontaneous emission caused by electron-hole recombination. The accuracy and reliability of simulation depends critically on correct description of the electronic band structure and the electron occupancy in the system. In this work, instead of considering electron-hole recombination in discrete states in the previous work, we take continuous states into account to simulate the spontaneous emission in open electronic system, and discover that the polarization of emitted photon is closely related to its propagation direction. Numerical studies have been performed to silicon nanowire-based P-N junction with different bias voltage.

  11. Are Einstein's transition probabilities for spontaneous emission constant in plasmas?

    NASA Technical Reports Server (NTRS)

    Griem, H. R.; Huang, Y. W.; Wang, J.-S.; Moreno, J. C.

    1991-01-01

    An investigation is conducted with a ruby laser to experimentally confirm the quenching of spontaneous emission coefficients and propose a mechanism for the phenomenon. Results of previous experiments are examined to determine the consistency and validity of interpretations of the spontaneous emissions. For the C IV 3s-3p and 2s-3p transitions, the line-intensity ratios are found to be dependent on the separation of the laser from the target. Density gradients and Stark broadening are proposed to interpret the results in a way that does not invalidate the Einstein A values. The interpretation is extended to C III and N V, both of which demonstrate similar changes in A values in previous experiments. The apparent quenching of Ar II by photon collisions is explained by Rabi oscillations and power broadening in the argon-ion laser cavity. It is concluded that the changes in A values cannot result from dense plasma effects.

  12. Demonstration of photon-echo rephasing of spontaneous emission.

    PubMed

    Beavan, Sarah E; Hedges, Morgan P; Sellars, Matthew J

    2012-08-31

    In this paper we report the first demonstration of "rephased amplified spontaneous emission" (RASE) with photon-counting detection. This protocol provides an all-in-one photon-pair source and quantum-memory that has applications as a quantum repeater node. The RASE protocol is temporally multimode, and in this demonstration the photon echo was generated in a way that is spatially multimode and includes intermediate storage between two potentially long-lived spin states. A correlation between spontaneous emission and its photon echo was observed, using an ensemble of Pr(3+) ions doped into a Y2SiO5 crystal. Alterations that would allow for the measurement of nonclassical correlations are identified. These should generally apply for future experiments in rare-earth ion crystals, which are promising systems for implementing highly-multiplexed quantum repeater operations. PMID:23002833

  13. Comprehensive, nonintercepting electron-beam diagnostics using spontaneous emission

    SciTech Connect

    Lumpkin, A.H.

    1989-01-01

    Characterization and optimization of electron-beam parameters are important aspects of optimizing free-electron laser (FEL) performance. The visible spontaneous emission ({lambda}{approximately}650 nm) from the 5-meter long undulator of the Boeing FEL experiment can be characterized in sufficient detail with a streak/spectrometer to deduce time-resolved electron-beam spatial position and profile, micropulse duration, and energy. 7 refs., 13 figs., 2 tabs.

  14. ``Excess'' polarization of the spontaneous emission in laser heterostructures

    NASA Astrophysics Data System (ADS)

    Ptashchenko, A. A.; Ptashchenko, F. A.

    1996-10-01

    "Excess" polarization of the spontaneous emission (EPSE) of diode lasers at low injection levels, being more pronounced in degraded specimens, has been observed. A model of EPSE is proposed, involving tunnel radiative recombination of electrons and light holes at inhomogeneities of the p- n junction. Separating EPSE from the polarization effect caused by elastic deformation enables the strain in the active region of laser heterostructures to be determined.

  15. Engineering Filters for Reducing Spontaneous Emission in cQED

    NASA Astrophysics Data System (ADS)

    Bronn, Nicholas; Masluk, Nicholas; Srinivasan, Srikanth; Chow, Jerry; Abraham, David; Rothwell, Mary; Keefe, George; Gambetta, Jay; Steffen, Matthias; Lirakis, Chris

    2014-03-01

    Inserting a notch filter between a qubit and the external environment at the qubit frequency can significantly suppress spontaneous emission mediated by the cavity (``Purcell effect''). In order to realize this filtering in multi-qubit architectures, where space comes at a premium, we will present a filter with minimal space requirements. We acknowledge support from IARPA under contract W911NF-10-1-0324.

  16. 2-.mu.m fiber amplified spontaneous emission (ASE) source

    NASA Technical Reports Server (NTRS)

    Jiang, Shibin (Inventor); Wu, Jianfeng (Inventor); Geng, Jihong (Inventor)

    2007-01-01

    A 2-.mu.m fiber Amplified Spontaneous Emission (ASE) source provides a wide emission bandwidth and improved spectral stability/purity for a given output power. The fiber ASE source is formed from a heavy metal oxide multicomponent glass selected from germanate, tellurite and bismuth oxides and doped with high concentrations, 0.5-15 wt. %, thulium oxides (Tm.sub.2O.sub.3) or 0.1-5 wt% holmium oxides (Ho.sub.2O.sub.3) or mixtures thereof. The high concentration of thulium dopants provide highly efficient pump absorption and high quantum efficiency. Co-doping of Tm and Ho can broaden the ASE spectrum.

  17. Spontaneous pion emission as a new natural radioactivity

    NASA Astrophysics Data System (ADS)

    Ion, D. B.; Ivascu, M.; Ion-Mihai, R.

    1986-10-01

    In this paper the pionic nuclear radioactivity or spontaneous poin emission by a nucleus from its ground state is investigated. The Qπ-values as well as the statistical factors are calculated using the experimental masses tabulated by Wapstra and Audi. Then it was shown that the pionic radioactivity of the nuclear ground state is energetically possible via three-body channels for all nuclides with Z > 80. This new type of natural radioactivity is statistically favored especially for Z = 92 - 106 for which F π/F SF = 40 - 200 [ MeV] 2. Experimental detection of the neutral pion and also some possible emission mechanisms are discussed.

  18. Highly enhanced spontaneous emission with nanoshell-based metallodielectric hybrid antennas

    NASA Astrophysics Data System (ADS)

    Cheng, Yuqing; Lu, Guowei; shen, Hongming; Wang, Yuwei; He, Yingbo; Chou, R. Yuanying; Gong, Qihuang

    2015-09-01

    The metallodielectric hybrid nanoantenna integrating plasmonic nanostructures with dielectric planar substrate can improve the spontaneous emission greatly. We demonstrated that the performances of the hybrid antenna can be substantially optimized with specific plasmonic nanostructures by employing finite-difference time-domain method. The hybrid antenna with core-shell nanostructure can enhance spontaneous emission greatly rather than the individual spherical nanoparticle. Moreover, the performances of the hybrid antenna can be boosted further through using asymmetrical nanoshell. The mechanism of the high enhancement effect is due to the hybrid structure being able to couple efficiently with the electric field by a larger dipolar moment. And the emission directivity of the hybrid antenna is able to be modified by adjusting the geometry of the plasmonic nanostructures. The results should be beneficial for various fundamental and applied research fields, including single molecule fluorescence and surface enhance Raman spectroscopy, etc. The enhancement of spontaneous emission is in demand in fundamental interests and various applied research fields. However, the electromagnetic enhancement of single plasmonic nanostructure is limited due to intrinsic loss of metal materials and quantum tunneling effect which also limits the ability of enhancement of spontaneous emission. Interestingly, it was found that hybrid structures can provide higher enhancement effect. This study is about a kind new type of optical antenna to control spontaneous emission of single emitter, i.e. a metallodielectric hybrid nanoantenna integrating plasmonic nanostructures with dielectric planar substrate which can improve the spontaneous emission greatly. We demonstrated that the performances of the hybrid antenna can be substantially optimized with specific plasmonic nanostructures by employing finite-difference time-domain method. The hybrid antenna with core-shell nanostructure can enhance

  19. Insect spontaneous ultraweak photon emission as an indicator of insecticidal compounds.

    PubMed

    Tian, Yongqing; Yang, Chuping; Xu, Hanhong

    2014-11-01

    The influence of beta-cypermethrin, a commercial insecticide, and Cicuta virosa L. var. latisecta Celak (Umbelliferae:Cicutal), an insecticidal plant, on the spontaneous ultraweak photon emissions from larvae of Spodoptera litura Fabricius and Zophobas morio Fabricius were studied. The increased percentages of spontaneous photon emission intensities from S. litura treated with 0.1 and 1 μg/ml beta-cypermethrin were both lower than those of the control in the 24 post-treatment hours, remarkable difference could also be observed during the same period from Z. morio treated with beta-cypermethrin at 0.156, 0.313 and 0.625 μg/ml. The increased percentages of spontaneous photon emission intensities from the two mentioned insects treated with 10,100 and 1000 μg/ml petroleum ether fraction of C. virosa L. var. latisecta, which displayed little activity against whole insects, could also be changed noticeably. The present study indicated that change in the intensity of spontaneous ultraweak photon emission from insect could be used as a novel method for screening insecticidal compounds with very low content in plant. PMID:25108203

  20. Plasmonic nanogaps for broadband and large spontaneous emission rate enhancement

    SciTech Connect

    Edwards, Anthony P.; Adawi, Ali M.

    2014-02-07

    We present the optical properties of a plasmonic nanogap formed between a silver metallic nanoparticle and an extended silver film that shows a strong enhancement in the spontaneous emission rate over the whole visible range. In particular, we use three-dimensional finite difference time domain calculations to study the spontaneous emission rate and the quantum efficiency of an emitting material placed within the gap region as a function of the geometrical parameters of the plasmonic nanogap. Our calculations reveal that the enhancements in the total decay rate can be divided into two regions as a function of wavelength; region I spans the wavelength range from 350 nm to 500 nm and peaks at approximately at 400 nm. Region II covers the spectral range between 500 nm and 1000 nm. The enhancements in total decay rate in region I are mainly dominated by Ohmic losses by the metal, while the enhancements in total decay rate in region II are mainly dominated by radiative decay rate enhancements. Furthermore, our calculations show over 100 times enhancement in the spontaneous emission rate in region II. We combine this with quantum efficiency enhancements of almost 30 times from materials with low intrinsic quantum efficiencies and only a small reduction in efficiency from those with high intrinsic quantum efficiencies. All results appear easily achievable using realistic geometrical parameters and simple synthesis techniques. These results are attributed to the strong field confinements in the nanogap region. The structures are of high interest for both the fundamental understanding of light mater interactions under extreme electromagnetic field confinements and also potential applications in quantum optics and Raman spectroscopy.

  1. Amplified spontaneous emission in the spiropyran-biopolymer based system

    NASA Astrophysics Data System (ADS)

    Mysliwiec, Jaroslaw; Sznitko, Lech; Bartkiewicz, Stanislaw; Miniewicz, Andrzej; Essaidi, Zacaria; Kajzar, Francois; Sahraoui, Bouchta

    2009-06-01

    Amplified spontaneous emission (ASE) phenomenon in the 6-nitro-1',3',3'-trimethylspiro[2H-1-benzopyran-2,2'-indolin] organic dye dispersed in a solid matrix has been observed. The biopolymer system deoxyribonucleic acid blended with cationic surfactant molecule cetyltrimethyl-ammonium chloride served as a matrix. ASE appeared under sample excitation by UV light pulses (λ =355 nm) coming from nanosecond or picosecond neodymium doped yttrium aluminum garnet lasers and has been reinforced with green (λ =532 nm) light excitation followed UV light pulse. The ASE characteristics in function of different excitation pulse energies as well as signal gain were measured.

  2. Spontaneous pion emission as a new natural radioactivity

    SciTech Connect

    Ion, D.B.; Ivascu, M.; Ion-Mihai, R.

    1986-10-15

    In this paper the pionic nuclear radioactivity or spontaneous pion emission by a nucleus from its ground state is investigated. The Q/sub ..pi../-values as well as the statistical factors are calculated using the experimental masses tabulated by Wapstra and Audi. Then it was shown that the pionic radioactivity of the nuclear ground state is energetically possible via three-body channels for all nuclides with Z>80. This new type of natural radioactivity is statistically favored especially for Z = 92-106 for which F/sub ..pi..//F/sub S//sub F/ = 40-200 (MeV)/sup 2/. Experimental detection of the neutral pion and also some possible emission mechanisms are discussed.

  3. Amplified Spontaneous Emission Properties of Semiconducting Organic Materials

    PubMed Central

    Calzado, Eva M.; Boj, Pedro G.; Díaz-García, María A.

    2010-01-01

    This paper aims to review the recent advances achieved in the field of organic solid-state lasers with respect to the usage of semiconducting organic molecules and oligomers in the form of thin films as active laser media. We mainly focus on the work performed in the last few years by our research group. The amplified spontaneous emission (ASE) properties, by optical pump, of various types of molecules doped into polystyrene films in waveguide configuration, are described. The various systems investigated include N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD), several perilenediimide derivatives (PDIs), as well as two oligo-phenylenevinylene derivatives. The ASE characteristics, i.e., threshold, emission wavelength, linewidth, and photostability are compared with that of other molecular materials investigated in the literature. PMID:20640167

  4. Spontaneous Radiation Emission from Short, High Field Strength Insertion Devices

    SciTech Connect

    Geoffrey Krafft

    2005-09-15

    Since the earliest papers on undulaters were published, it has been known how to calculate the spontaneous emission spectrum from ''short'' undulaters when the magnetic field strength parameter is small compared to unity, or in ''single'' frequency sinusoidal undulaters where the magnetic field strength parameter is comparable to or larger than unity, but where the magnetic field amplitude is constant throughout the undulater. Fewer general results have been obtained in the case where the insertion device is both short, i.e., the magnetic field strength parameter changes appreciably throughout the insertion device, and the magnetic field strength is high enough that ponderomotive effects, radiation retardation, and harmonic generation are important physical phenomena. In this paper a general method is presented for calculating the radiation spectrum for short, high-field insertion devices. It is used to calculate the emission from some insertion device designs of recent interest.

  5. TRASER - Total Reflection Amplification of Spontaneous Emission of Radiation

    PubMed Central

    Zachary, Christopher B.; Gustavsson, Morgan

    2012-01-01

    Background and Objective Light and lasers in medical therapy have made dramatic strides since their invention five decades ago. However, the manufacture of lasers can be complex and expensive which often makes treatments limited and costly. Further, no single laser will provide the correct parameters to treat all things. Hence, laser specialists often need multiple devices to practice their specialty. A new concept is described herein that has the potential to replace many lasers and light sources with a single ‘tunable’ device. Study Design/Material and Methods This device amplifies spontaneous emission of radiation by capturing and retaining photons through total internal reflection, hence the acronym Total Reflection Amplification of Spontaneous Emission of Radiation, or TRASER. Results Specific peaks of light can be produced in a reproducible manner with high peak powers of variable pulse durations, a large spot size, and high repetition rate. Conclusion Considering the characteristics and parameters of Traser technology, it is possible that this one device would likely be able to replace the pulsed dye laser and many other light based systems. PMID:22558261

  6. Spontaneous emission enhancement of colloidal CdSe nanoplatelets

    NASA Astrophysics Data System (ADS)

    Yang, Zhili; Pelton, Matthew; Waks, Edo

    Colloidal CdS /CdSe/CdS nanoplatelets synthesized recently are high efficient nano-emitters and gain media for nanoscale lasers and other nonlinear optical devices. They are characterized as quantum well structure due to energy gap difference between core CdSe and shell CdS, of which the luminescent wavelength could be tuned precisely by their thickness of growth. However, the influence of environment on the material's optical properties and further enhancement of the emission to implement nanoscale systems remains to be investigated. Here we demonstrate spontaneous emission rate enhancement of these CdSe nanoplatelets coupled to a photonic crystal cavity. We show clearly the photoluminescent spectrum modification of the nanoplatelets emission and an averaged Purcell enhancement factor of 3.1 is achieved when they are coupled to carefully-designed nanobeam photonic crystal cavities compared to the ones on unpatterned surface in our experiment of lifetime measurement. Also the phenomenon of cavity quality factor increasing is observed when increasing intensity of pumping, which attributes to saturable absorption of the nanoplatelets. Our success in enhancement of emission from these nanoplatelets here paves the road to realize actual nanoscale integrated systems such as ultra-low threshold micro-cavity lasers.

  7. The amplified spontaneous emission in EDF with small pulse pump

    NASA Astrophysics Data System (ADS)

    Wang, Fu; Wu, Chongqing; Liu, Lanlan; Wang, Zhi; Sun, Zhenchao; Mao, Yaya

    2012-11-01

    The amplified Spontaneous Emission (ASE) is the important noise source for EDFA, affecting the EDFA based fiber laser seriously. The theory and practice have shown that the ASE is closely related with pump methods, so the study on the ASE of EDF under the condition of the pulse pumping has important academic significations. What's more, the mode-locked laser based on EDFA fiber ring could be pumping by the pulse to realized mode-lock, and the ASE will impact its characteristics. In this paper, the effects of pump pulse with different width and amplitude on the ASE were investigated by the theoretical and experiment methods. Beginning with the carrier density rate equation, we can get each level of the distribution of the number of particles carriers along with the change of time based on the relationship between the average number of photons of the spontaneous radiation and the number of particles carriers distribution. An approximate analytic solution of output ASE noise average is derived when pump signal is small.Building an experimental system, the results show that the output amplitude of ASE is proportional to the input width of pump pulse when the pump pulse is small. It's also shows that the output amplitude of ASE is proportional to the input amplitude of pump pulse. The new phenomena can be used for the all-optical measurement of a pulse width.

  8. Effects of salicylates and aminoglycosides on spontaneous otoacoustic emissions in the Tokay gecko.

    PubMed

    Stewart, C E; Hudspeth, A J

    2000-01-01

    The high sensitivity and sharp frequency discrimination of hearing depend on mechanical amplification in the cochlea. To explore the basis of this active process, we examined the pharmacological sensitivity of spontaneous otoacoustic emissions (SOAEs) in a lizard, the Tokay gecko. In a quiet environment, each ear produced a complex but stable pattern of emissions. These SOAEs were reversibly modulated by drugs that affect mammalian otoacoustic emissions, the salicylates and the aminoglycoside antibiotics. The effect of a single i.p. injection of sodium salicylate depended on the initial power of the emissions: ears with strong control SOAEs displayed suppression at all frequencies, whereas those with weak control emissions showed enhancement. Repeated oral administration of acetylsalicylic acid reduced all emissions. Single i.p. doses of gentamicin or kanamycin suppressed SOAEs below 2.6 kHz, while modulating those above 2.6 kHz in either of two ways. For ears whose emission power at 2.6-5.2 kHz encompassed more than half of the total, individual emissions displayed facilitation as great as 35-fold. For the remaining ears, emissions dropped to as little as one-sixth of their initial values. The similarity of the responses of reptilian and mammalian cochleas to pharmacological intervention provides further evidence for a common mechanism of cochlear amplification. PMID:10618439

  9. Long-term stability of spontaneous otoacoustic emissions

    PubMed Central

    Burns, Edward M.

    2009-01-01

    Spontaneous otoacoustic emissions (SOAEs) were measured longitudinally for durations up to 19.5 years. Initial ages of the subjects ranged from 6 to 41 years. The most compelling finding was a decrease in frequency of all emissions in all subjects, which was approximately linear in %∕year and averaged 0.25%∕year. SOAE levels also tended to decrease with age, a trend that was significant, but not consistent across emissions, either within or across subjects. Levels of individual SOAEs might decrease, increase, or remain relatively constant with age. Several types of frequency∕level instabilities were noted in which some SOAEs within an ear interacted such that their levels were negatively correlated. These instabilities often persisted for many years. SOAEs were also measured in two females over the course of their pregnancies. No changes in SOAE levels or frequencies were seen, that were larger than have been reported in females over a menstrual cycle, suggesting that levels of female gonadal hormones do not have a significant direct effect on SOAE frequencies or levels. PMID:19425659

  10. Temperature quenching of spontaneous emission in tunnel-injection nanostructures

    SciTech Connect

    Talalaev, V. G. Novikov, B. V.; Cirlin, G. E.; Leipner, H. S.

    2015-11-15

    The spontaneous-emission spectra in the near-IR range (0.8–1.3 μm) from inverted tunnel-injection nanostructures are measured. These structures contain an InAs quantum-dot layer and an InGaAs quantum-well layer, separated by GaAs barrier spacer whose thickness varies in the range 3–9 nm. The temperature dependence of this emission in the range 5–295 K is investigated, both for optical excitation (photoluminescence) and for current injection in p–n junction (electroluminescence). At room temperature, current pumping proves more effective for inverted tunnel-injection nanostructures with a thin barrier (<6 nm), when the apexes of the quantum dots connect with the quantum well by narrow InGaAs straps (nanobridges). In that case, the quenching of the electroluminescence by heating from 5 to 295 K is slight. The quenching factor S{sub T} of the integrated intensity I is S{sub T} = I{sub 5}/I{sub 295} ≈ 3. The temperature stability of the emission from inverted tunnel-injection nanostructures is discussed on the basis of extended Arrhenius analysis.

  11. Sex and Ear Differences in Spontaneous and Click-Evoked Otoacoustic Emissions in Young Adults

    ERIC Educational Resources Information Center

    Snihur, Adrian W. K.; Hampson, Elizabeth

    2011-01-01

    Effects of sex and handedness on the production of spontaneous and click-evoked otoacoustic emissions (OAEs) were explored in a non-hearing impaired population (ages 17-25 years). A sex difference in OAEs, either produced spontaneously (spontaneous OAEs or SOAEs) or in response to auditory stimuli (click-evoked OAEs or CEOAEs) has been reported in…

  12. High spectral density transmission emulation using amplified spontaneous emission noise.

    PubMed

    Elson, Daniel J; Galdino, Lidia; Maher, Robert; Killey, Robert I; Thomsen, Benn C; Bayvel, Polina

    2016-01-01

    We demonstrate the use of spectrally shaped amplified spontaneous emission (SS-ASE) noise for wideband channel loading in the investigation of nonlinear transmission limits in wavelength-division multiplexing transmission experiments using Nyquist-spaced channels. The validity of this approach is explored through statistical analysis and experimental transmission of Nyquist-spaced 10 GBaud polarization-division multiplexing (PDM) quadrature phase-shift keying and PDM-16-ary quadrature amplitude modulation (QAM) channels, co-propagated with SS-ASE over single mode fiber. It is shown that this technique, which is simpler to implement than a fully modulated comb of channels, is valid for distances exceeding 240 km for PDM-16QAM with dispersion of 16 ps/nm/km, yields a good agreement with theory, and provides a conservative measure of system performance. PMID:26696160

  13. WDM optical steganography based on amplified spontaneous emission noise.

    PubMed

    Wu, Ben; Tait, Alexander N; Chang, Matthew P; Prucnal, Paul R

    2014-10-15

    We propose and experimentally demonstrate a wavelength-division multiplexed (WDM) optical stealth transmission system carried by amplified spontaneous emission (ASE) noise. The stealth signal is hidden in both time and frequency domains by using ASE noise as the signal carrier. Each WDM channel uses part of the ASE spectrum, which provides more flexibility to apply stealth transmission in a public network and adds another layer of security to the stealth channel. Multi-channel transmission also increases the overall channel capacity, which is the major limitation of the single stealth channel transmission based on ASE noise. The relations between spectral bandwidth and coherence length of ASE carrier have been theoretically analyzed and experimentally investigated. PMID:25361121

  14. Optical steganography based on amplified spontaneous emission noise.

    PubMed

    Wu, Ben; Wang, Zhenxing; Tian, Yue; Fok, Mable P; Shastri, Bhavin J; Kanoff, Daniel R; Prucnal, Paul R

    2013-01-28

    We propose and experimentally demonstrate an optical steganography method in which a data signal is transmitted using amplified spontaneous emission (ASE) noise as a carrier. The ASE serving as a carrier for the private signal has an identical frequency spectrum to the existing noise generated by the Erbium doped fiber amplifiers (EDFAs) in the transmission system. The system also carries a conventional data channel that is not private. The so-called "stealth" or private channel is well-hidden within the noise of the system. Phase modulation is used for both the stealth channel and the public channel. Using homodyne detection, the short coherence length of the ASE ensures that the stealth signal can only be recovered if the receiver closely matches the delay-length difference, which is deliberately changed in a dynamic fashion that is only known to the transmitter and its intended receiver. PMID:23389187

  15. Frequency Clustering in Spontaneous Otoacoustic Emissions from a Lizard's Ear

    PubMed Central

    Vilfan, Andrej; Duke, Thomas

    2008-01-01

    Spontaneous otoacoustic emissions (SOAEs) are indicators of an active process in the inner ear that enhances the sensitivity and frequency selectivity of hearing. They are particularly regular and robust in certain lizards, so these animals are good model organisms for studying how SOAEs are generated. We show that the published properties of SOAEs in the bobtail lizard are wholly consistent with a mathematical model in which active oscillators, with exponentially varying characteristic frequencies, are coupled together in a chain by visco-elastic elements. Physically, each oscillator corresponds to a small group of hair cells, covered by a tectorial sallet, so our theoretical analysis directly links SOAEs to the micromechanics of active hair bundles. PMID:18689448

  16. Two-atom spontaneous emission in a planar microcavity

    SciTech Connect

    Ujihara, Kikuo; Dung, Ho Trung

    2002-11-01

    Spontaneous emission in a planar microcavity by two identical and spatially separated two-level atoms, both of them initially excited, is considered under fourth-order perturbation approximation in atom-field coupling constants. A delay-differential equation with proper retardation times for the probability of both atoms in the upper state is derived and expressions for the emitted-light intensity and spectrum are given. It is numerically shown that, while two-atom cooperation is enhanced for small interatomic distances, the two-atom vacuum Rabi oscillation is somewhat suppressed compared to the single-atom oscillation level when the interatomic separation is close to the cavity transverse coherence length.

  17. Amplified spontaneous emission of pyranyliden derivatives in PVK matrix

    NASA Astrophysics Data System (ADS)

    Vembris, Aivars; Zarinsh, Elmars; Kokars, Valdis

    2016-04-01

    One of the well-known red light emitting laser dyes is 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4Hpyran (DCM). Amplified spontaneous emission (ASE) has been widely investigated of DCM molecules or its derivatives in polymer or low molecular weight matrix. The main issue for these molecules is aggregation which limits doping concentration in matrix. Lowest ASE threshold values within concentration range of 2 and 4 wt% were obtained. In this work ASE properties of two original DCM derivatives in poly(N-vinylcarbazole) (PVK) at various concentrations will be discussed. One of the derivatives is the same DCM dye with replaced butyl groups at electron donor part with bulky trytiloxyethyl groups (DWK-1). These groups do not influence electron transitions in the dye but prevent aggregation of the molecules. Second derivative (DWK-2) consists of two equal donor groups with the attached trytiloxyethyl groups. All results were compared with DCM:PVK system. Photoluminescence quantum yield (PLQY) is almost three times larger for DWK-1 concentration up to 20wt% with respect to DCM systems. PLQY was saturated on 0.06 at higher DWK-1 concentrations. Bulky trytiloxyethyl groups prevent aggregation of the molecules thus decreasing interaction between dyes and numbers of non-radiative decays. Red shift of photoluminescence and amplified spontaneous emission at higher concentrations were observed due to the solid state solvation effect. Increases of dye density in matrix with smaller lose in PLQY resulted in low ASE threshold energy. The lowest threshold value was obtained around 29 μJ/cm2 in DWK-1:PVK films.

  18. Spontaneous emission and the operation of invisibility cloaks

    NASA Astrophysics Data System (ADS)

    Morshed Behbahani, Mina; Amooghorban, Ehsan; Mahdifar, Ali

    2016-07-01

    As a probe to explore the ability of invisibility cloaks to conceal objects in the quantum mechanics domain, we study the spontaneous emission rate of an excited two-level atom in the vicinity of an ideal invisibility cloaking. On this base, first, a canonical quantization scheme is presented for the electromagnetic field interacting with atomic systems in an anisotropic, inhomogeneous, and absorbing magnetodielectric medium which can suitably be used for studying the influence of arbitrary invisibility cloak on the atomic radiative properties. The time dependence of the atomic subsystem is obtained in the Schrodinger picture. By introducing a modified set of the spherical wave-vector functions, the Green tensor of the system is calculated via exact and discrete methods. In this formalism, the decay rate and as well the emission pattern of the aforementioned atom are computed analytically for both weak and strong coupling interaction, and then numerically calculations are done to demonstrate the performances of cloaking in the quantum mechanics domain. Special attention is paid to different possible orientations and locations of the atomic system near the spherical invisibility cloaking. Results in the presence and the absence of the invisibility cloak are compared. We find that the cloak works very well far from its resonance frequency to conceal a macroscopic object, whereas at near the resonance frequency the object is more visible than the situation where the object is not covered by the cloak.

  19. Spontaneous emission noise in long-range surface plasmon polariton waveguide based optical gyroscope

    PubMed Central

    Wang, Yang-Yang; Zhang, Tong

    2014-01-01

    Spontaneous emission noise is an important limit to the performance of active plasmonic devices. Here, we investigate the spontaneous emission noise in the long-range surface plasmon-polariton waveguide based optical gyroscope. A theoretical model of the sensitivity is established to study the incoherent multi-beam interference of spontaneous emission in the gyroscope. Numerical results show that spontaneous emission produces a drift in the transmittance spectra and lowers the signal-to-noise-ratio of the gyroscope. It also strengthens the shot noise to be the main limit to the sensitivity of the gyroscope for high propagation loss. To reduce the negative effects of the spontaneous emission noise on the gyroscope, an external feedback loop is suggested to estimate the drift in the transmittance spectra and therefor enhance the sensitivity. Our work lays a foundation for the improvement of long-range surface plasmon-polariton gyroscope and paves the way to its practical application. PMID:25234712

  20. Dynamics of Relaxation Processes of Spontaneous Otoacoustic Emissions

    NASA Astrophysics Data System (ADS)

    Murphy, William James

    The dynamical response of spontaneous otoacoustic emissions (SOAEs) to suppression by ipsilateral pulsed external tones of different frequencies and levels is investigated in nine female subjects under normal conditions and in four female subjects during periods when aspirin is being administered. A simple Van der Pol limit-cycle oscillator driven by an external tone is used as an interpretive model. Typical results for both the onset of, and recovery from suppression yield 1/r_1 (where -r_1 is the negative linear component of the damping function) in the range of 2-25 msec. In accordance with the predictions of the model: (a) the relaxation time for the onset of suppression increases with the amount of suppression induced by the external tone, (b) the values of r _1 and the amplitudes of the unsuppressed emissions exhibit an inverse correlation, (c) the values inferred for r_1 are not significantly dependent on the frequency of the pulsed suppressor tone and (d) the inferred r_1 values are not significantly dependent upon the amount of suppression. In investigations involving subjects under aspirin administration, the changes in the relaxation time constants indicate that the main effect of aspirin administration is to reduce the negative damping parameter r_1. The salicylate is apparently not metabolized in some subjects whose emissions are negligibly affected by aspirin administration. A modification of the single-oscillator model is used to describe pulsed suppression data obtained from a primary SOAE (2545 Hz) which is suppressed by a neighboring secondary emission (2895 Hz). The response of the SOAE amplitude during pulsed suppression is modeled by a pair of Van der Pol limit-cycle oscillators with the primary oscillator linearly coupled to the displacement of the secondary higher-frequency one. The relaxation time constants for the onset of, and recovery from, suppression are 4.5 and 4.8 msec, respectively, for the primary SOAE and 7.5 and 10.5 msec for the

  1. Prompt Neutron Emission in 252CF Spontaneous Fission

    NASA Astrophysics Data System (ADS)

    Hambsch, F.-J.; Oberstedt, S.; Zeynalov, Sh.

    2011-10-01

    The prompt neutron emission in spontaneous fission of 252Cf has been investigated applying digital signal electronics. The goal was to compare the results from digital data acquisition and digital signal processing analysis with results of the pioneering work of Budtz-Jørgensen and Knitter. Using a twin Frisch-grid ionization chamber for fission fragment (FF) detection and a NE213-equivalent neutron detector in total about 107 fission fragment-neutron coincidences have been registered. Fission fragment kinetic energy, mass and angular distribution, neutron time-of-flight and pulse shape have been investigated using a 12 bit waveform digitizer. The signal waveforms have been analyzed using digital signal processing algorithms. The results are in very good agreement with literature. For the first time the dependence of the number of emitted neutrons as a function of total kinetic energy (TKE) of the fragments is in very good agreement with theoretical calculations in the range of TKE from 140-220 MeV.

  2. Vacuum field energy and spontaneous emission in anomalously dispersive cavities

    SciTech Connect

    Bradshaw, Douglas H.; Di Rosa, Michael D.

    2011-05-15

    Anomalously dispersive cavities, particularly white-light cavities, may have larger bandwidth to finesse ratios than their normally dispersive counterparts. Partly for this reason, they have been proposed for use in laser interferometer gravitational-wave observatory (LIGO)-like gravity-wave detectors and in ring-laser gyroscopes. In this paper we analyze the quantum noise associated with anomalously dispersive cavity modes. The vacuum field energy associated with a particular cavity mode is proportional to the cavity-averaged group velocity of that mode. For anomalously dispersive cavities with group index values between 1 and 0, this means that the total vacuum field energy associated with a particular cavity mode must exceed ({h_bar}/2{pi}){omega}/2. For white-light cavities in particular, the group index approaches zero and the vacuum field energy of a particular spatial mode may be significantly enhanced. We predict enhanced spontaneous emission rates into anomalously dispersive cavity modes and broadened laser linewidths when the linewidth of intracavity emitters is broader than the cavity linewidth.

  3. Amplified spontaneous emission and lasing in colloidal nanoplatelets.

    PubMed

    Guzelturk, Burak; Kelestemur, Yusuf; Olutas, Murat; Delikanli, Savas; Demir, Hilmi Volkan

    2014-07-22

    Colloidal nanoplatelets (NPLs) have recently emerged as favorable light-emitting materials, which also show great potential as optical gain media due to their remarkable optical properties. In this work, we systematically investigate the optical gain performance of CdSe core and CdSe/CdS core/crown NPLs having different CdS crown size with one- and two-photon absorption pumping. The core/crown NPLs exhibit enhanced gain performance as compared to the core-only NPLs due to increased absorption cross section and the efficient interexciton funneling, which is from the CdS crown to the CdSe core. One- and two-photon absorption pumped amplified spontaneous emission thresholds are found as low as 41 μJ/cm(2) and 4.48 mJ/cm(2), respectively. These thresholds surpass the best reported optical gain performance of the state-of-the-art colloidal nanocrystals (i.e., quantum dots, nanorods, etc.) emitting in the same spectral range as the NPLs. Moreover, gain coefficient of the NPLs is measured as high as 650 cm(-1), which is 4-fold larger than the best reported gain coefficient of the colloidal quantum dots. Finally, we demonstrate a two-photon absorption pumped vertical cavity surface emitting laser of the NPLs with a lasing threshold as low as 2.49 mJ/cm(2). These excellent results are attributed to the superior properties of the NPLs as optical gain media. PMID:24882737

  4. Efficient computation of spontaneous emission dynamics in arbitrary photonic structures

    NASA Astrophysics Data System (ADS)

    Teimourpour, M. H.; El-Ganainy, R.

    2015-12-01

    Defining a quantum mechanical wavefunction for photons is one of the remaining open problems in quantum physics. Thus quantum states of light are usually treated within the realm of second quantization. Consequently, spontaneous emission (SE) in arbitrary photonic media is often described by Fock space Hamiltonians. Here, we present a real space formulation of the SE process that can capture the physics of the problem accurately under different coupling conditions. Starting from first principles, we map the unitary evolution of a dressed two-level quantum emitter onto the problem of electromagnetic radiation from a self-interacting complex harmonic oscillator. Our formalism naturally leads to an efficient computational scheme of SE dynamics using finite difference time domain method without the need for calculating the photonic eigenmodes of the surrounding environment. In contrast to earlier investigations, our computational framework provides a unified numerical treatment for both weak and strong coupling regimes alike. We illustrate the versatility of our scheme by considering several different examples.

  5. A coupling model for amplified spontaneous emission in laser resonators

    NASA Astrophysics Data System (ADS)

    Su, Hua; Wang, Xiaojun; Shang, Jianli; Yu, Yi; Tang, Chun

    2015-10-01

    The competition between amplified spontaneous emission (ASE) and main laser in solid-state laser resonators is investigated both theoretically and experimentally. A coupled model using the spatial volume integral instead of the Monte Carlo type raytrace technique is proposed to depict ASE in the laser resonators. This model is able to evaluate all possible reflections at both the polishing surface and the diffusive side, to calculate ASE for an inhomogeneous gain distribution, and to include the spectral correction. An experiment is carefully designed to verify the theoretical model and to investigate the distinct physical properties caused by the coupling between ASE and the laser oscillations. The experimental data exhibit an excellent agreement with the theoretical predictions. According to that model, we confirm that ASE in thin-disk lasers can be characterized approximately by the product of the threshold gain of the resonator and the diameter of the disks, as laser modes are highly overlapped with the pumping beam. Theoretical evaluation shows that the scattering characteristic of the disk side impacts on ASE significantly. Furthermore, we point out that ASE decreases output laser power by affecting threshold pumping power, while slope efficiency is not changed by ASE. This observation provides us with a simple way to estimate the decrease of the optical efficiency by ASE.

  6. Self-amplified spontaneous emission free electron laser devices and nonideal electron beam transport

    NASA Astrophysics Data System (ADS)

    Lazzarino, L. L.; Di Palma, E.; Anania, M. P.; Artioli, M.; Bacci, A.; Bellaveglia, M.; Chiadroni, E.; Cianchi, A.; Ciocci, F.; Dattoli, G.; Di Giovenale, D.; Di Pirro, G.; Ferrario, M.; Gatti, G.; Giannessi, L.; Mostacci, A.; Musumeci, P.; Petralia, A.; Petrillo, V.; Pompili, R.; Rau, J. V.; Rossi, A. R.; Sabia, E.; Vaccarezza, C.; Villa, F.

    2014-11-01

    We have developed, at the SPARC test facility, a procedure for a real time self-amplified spontaneous emission free electron laser (FEL) device performance control. We describe an actual FEL, including electron and optical beam transport, through a set of analytical formulas, allowing a fast and reliable on-line "simulation" of the experiment. The system is designed in such a way that the characteristics of the transport elements and the laser intensity are measured and adjusted, via a real time computation, during the experimental run, to obtain an on-line feedback of the laser performances. The detail of the procedure and the relevant experimental results are discussed.

  7. Automotive Emission Control.

    ERIC Educational Resources Information Center

    Lee, Billy D.; And Others

    This publication contains instructional materials for both teachers and students for a course in automotive emission control. Instructional materials in this publication are written in terms of student performance using measurable objectives. The course includes 16 units. Each instructional unit includes some or all of the basic components of a…

  8. Automotive Emission Control.

    ERIC Educational Resources Information Center

    Lee, Billy D.; Ragazzi, Ronald

    This guide designed to assist teachers in improving instruction in the area of automotive emission control curriculum includes four areas. Each area consists of one or more units of instruction, with each instructional unit including some or all of the following basic components: Performance objectives, suggested activities for teacher and…

  9. Spectral modulation of higher harmonic spontaneous emission from an optical klystron.

    PubMed

    Sei, Norihiro; Ogawa, Hiroshi; Yamada, Kawakatsu; Koike, Masaki; Ohgaki, Hideaki

    2014-07-01

    Higher harmonics of spontaneous emission from an optical klystron have been observed. The modulation factor of the spontaneous emission spectrum for the higher harmonics can be described by considering the observation system. When the dispersive gap of the optical klystron was fixed, the microstructure interval of the spontaneous emission spectrum at a certain resonant wavelength became narrower as the order of the higher harmonic became larger. Some unique characteristics of the higher harmonics have been clarified, and these studies are likely to contribute to the development of free-electron lasers using higher harmonics of an optical klystron in the shorter-wavelengths region. PMID:24971958

  10. Extracting photon periodic orbits from spontaneous emission spectra in laterally confined vertically emitted cavities.

    PubMed

    Chen, Yung-Fu; Yu, Yan-Ting; Huang, Yu-Jen; Chiang, Po-Yi; Su, Kuan-Wei; Huang, Kai-Feng

    2010-08-15

    We report our observation of the signature of photon periodic orbits in the spontaneous emission spectra of large-aperture vertical-cavity surface-emitting lasers (VCSELs). The high-resolution measurement clearly demonstrates that over a thousand cavity modes with a narrow linewidth can be perfectly exhibited in the spontaneous emission spectrum just below the lasing threshold. The Fourier-transformed spectrum is analyzed to confirm that the spontaneous emission spectra of large-aperture VCSELs can be exploited to analogously investigate the energy spectra of the 2D quantum billiards. PMID:20717436

  11. A semi-analytical approach for evaluating effects of amplified spontaneous emission on characteristics of Q-switched lasers

    SciTech Connect

    Razzaghi, D; Hajiesmaeilbaigi, F; Ruzbehani, M

    2012-08-31

    Possible effects of amplified spontaneous emission on output pulse characteristics of a Q-switched laser are discussed within the framework of a semi-analytical approach. It is shown that output energy decreases almost exponentially with average path length of the spontaneously emitted photons which in turn depends on geometrical specification and active medium properties as well as on optical finishing of the surfaces (for solid-state lasers). Optimal coupling dependence on the average path length is also investigated and shown to increase with average path length increment. (control of laser radiation parameters)

  12. Visible-infrared self-amplified spontaneous emission amplifier free electron laser undulator

    NASA Astrophysics Data System (ADS)

    Carr, Roger; Cornacchia, Max; Emma, Paul; Nuhn, Heinz-Dieter; Poling, Ben; Ruland, Robert; Johnson, Erik; Rakowsky, George; Skaritka, John; Lidia, Steve; Duffy, Pat; Libkind, Marcus; Frigola, Pedro; Murokh, Alex; Pellegrini, Claudio; Rosenzweig, James; Tremaine, Aaron

    2001-12-01

    The visible-infrared self-amplified spontaneous emission amplifier (VISA) free electron laser (FEL) is an experimental device designed to show self-amplified spontaneous emission (SASE) to saturation in the near infrared to visible light energy range. It generates a resonant wavelength output from 800-600 nm, so that silicon detectors may be used to characterize the optical properties of the FEL radiation. VISA is designed to show how SASE FEL theory corresponds with experiment in this wavelength range, using an electron beam with emittance close to that planned for the future Linear Coherent Light Source at SLAC. VISA comprises a 4 m pure permanent magnet undulator with four 99 cm segments, each of 55 periods, 18 mm long. The undulator has distributed focusing built into it, to reduce the average beta function of the 70-85 MeV electron beam to about 30 cm. There are four FODO cells per segment. The permanent magnet focusing lattice consists of blocks mounted on either side of the electron beam, in the undulator gap. The most important undulator error parameter for a free electron laser is the trajectory walk-off, or lack of overlap of the photon and electron beams. Using pulsed wire magnet measurements and magnet shimming, we were able to control trajectory walk-off to less than +/-50 μm per field gain length.

  13. Controlled positions and kinetic analysis of spontaneous tin whisker growth

    NASA Astrophysics Data System (ADS)

    Su, Chien-Hao; Chen, Hao; Lee, Hsin-Yi; Wu, Albert T.

    2011-09-01

    This study achieved controlling the positions of spontaneous growth of tin whiskers. We surmounted the unpredictable growing nature of such whiskers and performed accurately quantitative analyses of the growth kinetics and yielded precise measurement of the growth rate. Furthermore, using synchrotron radiation x-ray, this study determined the stress variations in conjunction with whisker growth that fitted appropriately to the model. Accordingly, the results could address the debate held for decades and prove that forming a surface oxide layer is one of the required and necessary conditions for controlling the positions of spontaneous growth of tin whiskers.

  14. Controlling boiler emissions

    SciTech Connect

    Katzel, J.

    1992-10-22

    This paper reports that if you are confused about how to interpret the Clean Air Act Amendments of 1990, you are not alone. The massive document runs several hundred pages and consists of 11 titles, each addressing a different aspect of air quality. In some cases, specific emissions levels are established; in others, they are left to the discretion of state and local governments. In many ways, the impact of the CAAA right now is no impact. But now is not the time for plant engineers to play any waiting games. The annual cost of complying with the comprehensive environmental legislation is estimated at $4 to $7 billion. Despite the ambiguity and uncertainty, one conclusion appears clear: control of emissions, especially nitrogen oxides, from all types of boilers and process units can be expected to become more stringent. More and more equipment and industries will fall under the regulations as they are implemented by the Environmental Protection Agency (EPA). An newly available and improved strategies and technologies will make it more and more difficult to circumvent the law. As the general concepts of the legislation are molded into specifics, plant engineers are well advised to take an active role in shaping the attainment and control programs being formed by their state sand in understanding and applying available control technologies.

  15. Spontaneous emission of electromagnetic radiation in turbulent plasmas

    SciTech Connect

    Ziebell, L. F.; Yoon, P. H.; Simões, F. J. R.; Pavan, J.; Gaelzer, R.

    2014-01-15

    Known radiation emission mechanisms in plasmas include bremmstrahlung (or free-free emission), gyro- and synchrotron radiation, cyclotron maser, and plasma emission. For unmagnetized plasmas, only bremmstrahlung and plasma emissions are viable. Of these, bremmstrahlung becomes inoperative in the absence of collisions, and the plasma emission requires the presence of electron beam, followed by various scattering and conversion processes. The present Letter proposes a new type of radiation emission process for plasmas in a state of thermodynamic quasi-equilibrium between particles and enhanced Langmuir turbulence. The radiation emission mechanism proposed in the present Letter is not predicted by the linear theory of thermal plasmas, but it relies on nonlinear wave-particle resonance processes. The electromagnetic particle-in-cell numerical simulation supports the new mechanism.

  16. Spontaneous emission lifetimes in the ground electronic states of HD/+/ and H2/+/a

    NASA Technical Reports Server (NTRS)

    Peek, J. M.; Hashemi-Attar, A.-R.; Beckel, C. L.

    1979-01-01

    Because of their simplicity, H2(+) and its isotopic species are of particular interest to molecular theorists and experimentalists. If these ions are formed in excited vibrational states under conditions of highly improbable electron-ion recombination or other reactions, spontaneous emission will occur. The present note calculates the (vibrational quantum number, J prime = 0) state lifetimes under spontaneous emission for all 22 excited vibrations of HD(+) and all 19 excited vibrations of H2(+) in their ground electron states. The lifetimes presented in Tables I and III justify the assumption that spontaneous radiative processes are unimportant under certain realizable conditions. When spontaneous radiation plays a role, however, minimum lifetime at intermediate vibrational quantum number could lead to unusual vibrational distribution functions.

  17. Progress in emission control technologies

    SciTech Connect

    1994-12-31

    Partial contents of this book include: Ozone precursor emissions from alternatively fueled vehicles; Cycle resolved measurements of diesel particulate by optical techniques; A lubricant formulation for lower unburnt hydrocarbon emissions; Chassis test cycles for assessing emissions from heavy duty trucks; A non-intrusive method of measuring PCV blowby constituents; Some problems in the improvement of measurement of transient emissions; and Oxidation catalyst systems for emission control of LPG-powered forklift trucks.

  18. Protecting remote atomic entanglement against spontaneous emission by separated photonic pulses

    NASA Astrophysics Data System (ADS)

    Zong, Xiao-Lan; Du, Chao-Qun; Yang, Ming; Zhang, Gang; Yang, Qing; Cao, Zhuo-Liang

    2015-07-01

    We study the entanglement dynamics between two spatially separated atoms trapped in two separate optical cavities. Based on cavity-assisted interactions between the atoms and separated photonic pulses, we propose a scheme for the implemention of a controlled-phase-flip gate (CPF gate) between each of the atoms and the photonic pulse to protect the remote atomic quantum entanglement against the decaying caused by spontaneous emission. What we need to do is to shoot the horizontally polarized photons onto the cavity mirror successively, plus a train of Hadamard operations on the atoms, and no measurement is needed here. It is shown that the quantum entanglement of the two remote atoms can be protected effectively in this way. We also extend our scheme to the case of weak coupling and low Q cavity cases. The simplicity of the current scheme may warrant its experimental realization.

  19. Control of Emissions

    NASA Technical Reports Server (NTRS)

    Parrish, Clyde F. (Inventor); Chung, Landy (Inventor)

    2013-01-01

    Methods and apparatus utilizing chlorine dioxide and hydrogen peroxide are useful to reduce NOx emissions, as well as SOx and mercury (or other heavy metal) emissions, from combustion flue gas streams.

  20. Exponential Gain and Saturation of a Self-Amplified Spontaneous Emission Free-Electron Laser

    NASA Astrophysics Data System (ADS)

    Milton, S. V.; Gluskin, E.; Arnold, N. D.; Benson, C.; Berg, W.; Biedron, S. G.; Borland, M.; Chae, Y.-C.; Dejus, R. J.; Den Hartog, P. K.; Deriy, B.; Erdmann, M.; Eidelman, Y. I.; Hahne, M. W.; Huang, Z.; Kim, K.-J.; Lewellen, J. W.; Li, Y.; Lumpkin, A. H.; Makarov, O.; Moog, E. R.; Nassiri, A.; Sajaev, V.; Soliday, R.; Tieman, B. J.; Trakhtenberg, E. M.; Travish, G.; Vasserman, I. B.; Vinokurov, N. A.; Wang, X. J.; Wiemerslage, G.; Yang, B. X.

    2001-06-01

    Self-amplified spontaneous emission in a free-electron laser has been proposed for the generation of very high brightness coherent x-rays. This process involves passing a high-energy, high-charge, short-pulse, low-energy-spread, and low-emittance electron beam through the periodic magnetic field of a long series of high-quality undulator magnets. The radiation produced grows exponentially in intensity until it reaches a saturation point. We report on the demonstration of self-amplified spontaneous emission gain, exponential growth, and saturation at visible (530 nanometers) and ultraviolet (385 nanometers) wavelengths. Good agreement between theory and simulation indicates that scaling to much shorter wavelengths may be possible. These results confirm the physics behind the self-amplified spontaneous emission process and forward the development of an operational x-ray free-electron laser.

  1. Spontaneous emission measurements from a low voltage pre-bunched electron beam

    SciTech Connect

    Dearden, G.; Mayhew, S.E.; Lucas, J.

    1995-12-31

    Recently we have carried out measurements on the spontaneous microwave (8.2 GHz) emission which results when a low-voltage (55kV) pre-punched electron beam is passed through a waveguide in a wiggler magnetic field. The variation of the spontaneous emission output power level with the average electron beam current and energy are reported and compared with the theory presented by Doria et al. The effect of the degree of bunching of the electron beam has also been observed and compared with theory.

  2. Spontaneous synchrotron emission from a plasma with an energetic runaway electron tail

    NASA Technical Reports Server (NTRS)

    Freund, H. P.; Dillenburg, D.; Wu, C. S.; Lee, L. C.

    1978-01-01

    The emissivity of spontaneous synchrotron radiation is computed for a plasma consisting of a background thermal plasma in addition to an energetic runaway electron component. The analysis is performed for both the ordinary and extraordinary modes, for frequencies in the vicinity of the electron plasma frequency and the higher harmonics of the electron gyrofrequency, and for the case when the electron plasma frequency is approximately the same as or smaller than the cyclotron frequency. The relativistic gyroresonance with the runaway electrons is found to result in a level of spontaneous emission which, for frequencies in the neighborhood of the electron plasma frequency, is significantly enhanced over the thermal radiation.

  3. Increased Spontaneous Otoacoustic Emissions in Mice with a Detached Tectorial Membrane.

    PubMed

    Cheatham, Mary Ann; Ahmad, Aisha; Zhou, Yingjie; Goodyear, Richard J; Dallos, Peter; Richardson, Guy P

    2016-04-01

    Mutations in genes encoding tectorial membrane (TM) proteins are a significant cause of human hereditary hearing loss (Hildebrand et al. 2011), and several mouse models have been developed to study the functional significance of this accessory structure in the mammalian cochlea. In this study, we use otoacoustic emissions (OAE), signals obtained from the ear canal that provide a measure of cochlear function, to characterize a mouse in which the TM is detached from the spiral limbus due to an absence of otoancorin (Otoa, Lukashkin et al. 2012). Our results demonstrate that spontaneous emissions (SOAE), sounds produced in the cochlea without stimulation, increase dramatically in mice with detached TMs even though their hearing sensitivity is reduced. This behavior is unusual because wild-type (WT) controls are rarely spontaneous emitters. SOAEs in mice lacking Otoa predominate around 7 kHz, which is much lower than in either WT animals when they generate SOAEs or in mutant mice in which the TM protein Ceacam16 is absent (Cheatham et al. 2014). Although both mutants lack Hensen's stripe, loss of this TM feature is only observed in regions coding frequencies greater than ~15 kHz in WT mice so its loss cannot explain the low-frequency, de novo SOAEs observed in mice lacking Otoa. The fact that ~80 % of mice lacking Otoa produce SOAEs even when they generate smaller distortion product OAEs suggests that the active process is still functioning in these mutants but the system(s) involved have become less stable due to alterations in TM structure. PMID:26691158

  4. Subradiant spontaneous undulator emission through collective suppression of shot noise

    NASA Astrophysics Data System (ADS)

    Ratner, D.; Hemsing, E.; Gover, A.; Marinelli, A.; Nause, A.

    2015-05-01

    The phenomenon of Dicke's subradiance, in which the collective properties of a system suppress radiation, has received broad interest in atomic physics. Recent theoretical papers in the field of relativistic electron beams have proposed schemes to achieve subradiance through suppression of shot noise current fluctuations. The resulting "quiet" beam generates less spontaneous radiation than emitted even by a shot noise beam when oscillating in an undulator. Quiet beams could have diverse accelerator applications, including lowering power requirements for seeded free-electron lasers and improving efficiency of hadron cooling. In this paper we present experimental observation of a strong reduction in undulator radiation, demonstrating the feasibility of noise suppression as a practical tool in accelerator physics.

  5. Electrically controllable spontaneous magnetism in nanoscale mixed phase multiferroics.

    PubMed

    He, Q; Chu, Y-H; Heron, J T; Yang, S Y; Liang, W I; Kuo, C Y; Lin, H J; Yu, P; Liang, C W; Zeches, R J; Kuo, W C; Juang, J Y; Chen, C T; Arenholz, E; Scholl, A; Ramesh, R

    2011-01-01

    Magnetoelectrics and multiferroics present exciting opportunities for electric-field control of magnetism. However, there are few room-temperature ferromagnetic-ferroelectrics. Among the various types of multiferroics the bismuth ferrite system has received much attention primarily because both the ferroelectric and the antiferromagnetic orders are quite robust at room temperature. Here we demonstrate the emergence of an enhanced spontaneous magnetization in a strain-driven rhombohedral and super-tetragonal mixed phase of BiFeO₃. Using X-ray magnetic circular dichroism-based photoemission electron microscopy coupled with macroscopic magnetic measurements, we find that the spontaneous magnetization of the rhombohedral phase is significantly enhanced above the canted antiferromagnetic moment in the bulk phase, as a consequence of a piezomagnetic coupling to the adjacent tetragonal-like phase and the epitaxial constraint. Reversible electric-field control and manipulation of this magnetic moment at room temperature is also shown. PMID:21407191

  6. Highly elevated emission of mercury vapor due to the spontaneous combustion of refuse in a landfill

    NASA Astrophysics Data System (ADS)

    Zhu, Wei; Sommar, Jonas; Li, Zhonggen; Feng, Xinbin; Lin, Che-Jen; Li, Guanghui

    2013-11-01

    Refuse disposal (e.g., landfilling and incineration) have been recognized as a significant anthropogenic source of mercury (Hg) emission globally. However, in-situ measurements of Hg emission from landfill or refuse dumping sites where fugitive spontaneous combustion occurs have not been reported. Gaseous elemental mercury (Hg0) concentration and emission flux were observed near spontaneous combustions of refuse at a landfill site in southwestern China. Ambient Hg0 concentrations above the refuse surface ranged from 42.7 ± 20.0 to 396.4 ± 114.2 ng m-3, up to 10 times enhancement due to the spontaneous burning. Using a box model with Hg0 data obtained from 2004 to 2013, we estimated that the Hg0 emission from refuse was amplified by 8-40 times due to spontaneous combustion. A micrometeorological flux measurement system based on relaxed eddy accumulation was configured downwind of the combustion sites to quantify the Hg0 emission. Extremely large turbulent deposition fluxes (up to -128.6 μg m-2 h-1, 20 min average) were detected during periods of high Hg0 concentration events over the measurement footprint. The effect of temperature, moisture and light on the air-surface exchange of Hg0 exchange was found to be masked by the overwhelming deposition of Hg0 from the enriched air from the refuse combustion plumes. This research reveals that mercury emission from the landfill refuse can be boosted by fugitive spontaneous combustion of refuse. The emission represents an anthropogenic source that has been overlooked in Hg inventory estimates.

  7. Interactions between Hair Cells Shape Spontaneous Otoacoustic Emissions in a Model of the Tokay Gecko's Cochlea

    PubMed Central

    Gelfand, Michael; Piro, Oreste; Magnasco, Marcelo O.; Hudspeth, A. J.

    2010-01-01

    Background The hearing of tetrapods including humans is enhanced by an active process that amplifies the mechanical inputs associated with sound, sharpens frequency selectivity, and compresses the range of responsiveness. The most striking manifestation of the active process is spontaneous otoacoustic emission, the unprovoked emergence of sound from an ear. Hair cells, the sensory receptors of the inner ear, are known to provide the energy for such emissions; it is unclear, though, how ensembles of such cells collude to power observable emissions. Methodology and Principal Findings We have measured and modeled spontaneous otoacoustic emissions from the ear of the tokay gecko, a convenient experimental subject that produces robust emissions. Using a van der Pol formulation to represent each cluster of hair cells within a tonotopic array, we have examined the factors that influence the cooperative interaction between oscillators. Conclusions and Significance A model that includes viscous interactions between adjacent hair cells fails to produce emissions similar to those observed experimentally. In contrast, elastic coupling yields realistic results, especially if the oscillators near the ends of the array are weakened so as to minimize boundary effects. Introducing stochastic irregularity in the strength of oscillators stabilizes peaks in the spectrum of modeled emissions, further increasing the similarity to the responses of actual ears. Finally, and again in agreement with experimental findings, the inclusion of a pure-tone external stimulus repels the spectral peaks of spontaneous emissions. Our results suggest that elastic coupling between oscillators of slightly differing strength explains several properties of the spontaneous otoacoustic emissions in the gecko. PMID:20559557

  8. ADVANCED EMISSIONS CONTROL DEVELOPMENT PROGRAM

    SciTech Connect

    G.A. Farthing

    2001-02-06

    The primary objective of the Advanced Emissions Control Development Program (AECDP) is to develop practical, cost-effective strategies for reducing the emissions of hazardous air pollutants (HAPs, or air toxics) from coal-fired boilers. The project goal is to effectively control air toxic emissions through the use of conventional flue gas cleanup equipment such as electrostatic precipitators (ESPs), fabric filters (baghouses), and wet flue gas desulfurization (WFGD) systems. Development work initially concentrated on the capture of trace metals, fine particulate, hydrogen chloride, and hydrogen fluoride. Recent work has focused almost exclusively on the control of mercury emissions.

  9. Advanced Emissions Control Development Program

    SciTech Connect

    G. A. Farthing; G. T. Amrhein; G. A. Kudlac; D. A. Yurchison; D. K. McDonald; M. G. Milobowski

    2001-03-31

    The primary objective of the Advanced Emissions Control Development Program (AECDP) is to develop practical, cost-effective strategies for reducing the emissions of hazardous air pollutants (HAPs, or air toxics) from coal-fired boilers. This objective is being met by identifying ways to effectively control air toxic emissions through the use of conventional flue gas cleanup equipment such as electrostatic precipitators (ESPs), fabric filters (fabric filters), and wet flue gas desulfurization (wet FGD) systems. Development work initially concentrated on the capture of trace metals, hydrogen chloride, and hydrogen fluoride. Recent work has focused almost exclusively on the control of mercury emissions.

  10. Effect of surface-plasmon polaritons on spontaneous emission and intermolecular energy-transfer rates in multilayered geometries

    SciTech Connect

    Marocico, C. A.; Knoester, J.

    2011-11-15

    We use a Green's tensor method to investigate the spontaneous emission rate of a molecule and the energy-transfer rate between molecules placed in two types of layered geometries: a slab geometry and a planar waveguide. We focus especially on the role played by surface-plasmon polaritons in modifying the spontaneous emission and energy-transfer rates as compared to free space. In the presence of more than one interface, the surface-plasmon polariton modes split into several branches, and each branch can contribute significantly to modifying the electromagnetic properties of atoms and molecules. Enhancements of several orders of magnitude both in the spontaneous emission rate of a molecule and the energy-transfer rate between molecules are obtained and, by tuning the parameters of the geometry, one has the ability to control the range and magnitude of these enhancements. For the energy-transfer rate interference effects between contributions of different plasmon-polariton branches are observed as oscillations in the distance dependence of this rate.

  11. Nonlocal effects: relevance for the spontaneous emission rates of quantum emitters coupled to plasmonic structures.

    PubMed

    Filter, Robert; Bösel, Christoph; Toscano, Giuseppe; Lederer, Falk; Rockstuhl, Carsten

    2014-11-01

    The spontaneous emission rate of dipole emitters close to plasmonic dimers are theoretically studied within a nonlocal hydrodynamic model. A nonlocal model has to be used since quantum emitters in the immediate environment of a metallic nanoparticle probe its electronic structure. Compared to local calculations, the emission rate is significantly reduced. The influence is mostly pronounced if the emitter is located close to sharp edges. We suggest to use quantum emitters to test nonlocal effects in experimentally feasible configurations. PMID:25361293

  12. Optical instabilities and spontaneous light emission in moving media

    NASA Astrophysics Data System (ADS)

    Silveirinha, Mario

    2015-03-01

    We show that when an uncharged plasmonic material is set in relative motion with respect to another uncharged polarizable body the system may be electromagnetically unstable. Particularly, when the relative velocity of the two bodies is enforced to remain constant the system may support natural oscillations that grow exponentially with time, even in presence of realistic material loss and dispersion. It is proven that a friction-type force acts on the moving bodies to oppose their relative motion. Hence, the optical instabilities result from the conversion of kinetic energy into electromagnetic energy. This new purely classical phenomenon is analogous to the Cherenkov and Smith-Purcell effects but for uncharged polarizable matter. We link the optical instabilities to a spontaneous parity-time symmetry breaking of the system, and demonstrate the possibility of optical amplification of a light pulse in the broken parity-time symmetry regime. This work is supported in part by Fundação para a Ciência e a Tecnologia Grant Number PTDC/EEI-TEL/2764/2012.

  13. Low threshold amplified spontaneous emission and ambipolar charge transport in non-volatile liquid fluorene derivatives.

    PubMed

    Ribierre, Jean-Charles; Zhao, Li; Inoue, Munetomo; Schwartz, Pierre-Olivier; Kim, Ju-Hyung; Yoshida, Kou; Sandanayaka, Atula S D; Nakanotani, Hajime; Mager, Loic; Méry, Stéphane; Adachi, Chihaya

    2016-02-21

    Highly fluorescent non-volatile fluidic fluorene derivatives functionalized with siloxane chains were synthesized and used in monolithic solvent-free liquid organic semiconductor distributed feedback lasers. The photoluminescence quantum yield values, the amplified spontaneous emission thresholds and the ambipolar charge carrier mobilities demonstrate that this class of materials is extremely promising for organic fluidic light-emitting and lasing devices. PMID:26734693

  14. Comparison of amplified spontaneous emission pulse cleaners for use in chirped pulse amplification front end lasers

    SciTech Connect

    Dawson, J; Siders, C; Phan, H; Kanz, V; Barty, C

    2007-07-02

    We compare various schemes for removing amplified spontaneous emission from seed laser pulses. We focus on compact schemes that are compatible with fiber laser front end systems with pulse energies in the 10nJ-1{micro}J range and pulse widths in the 100fs-10ps range. Pre-pulse contrast ratios greater than 10{sup 9} have been measured.

  15. Exact solution for spontaneous emission in the presence of N atoms

    NASA Astrophysics Data System (ADS)

    Cummings, F. W.; Dorri, Ali

    1983-10-01

    N two-level "atoms" are considered in interaction with a single-mode resonant electromagnetic field. The exact solution is given nonrelativistically for all times for the case of spontaneous emission, when only one atom is initially excited. The solution is given for the general case of the N atoms in inequivalent mode positions.

  16. Large spontaneous-emission enhancements in metallic nanostructures: towards LEDs faster than lasers.

    PubMed

    Tsakmakidis, Kosmas L; Boyd, Robert W; Yablonovitch, Eli; Zhang, Xiang

    2016-08-01

    Recent progress in the design and realization of optical antennas enclosing fluorescent materials has demonstrated large spontaneous-emission enhancements and, simultaneously, high radiation efficiencies. We discuss here that an important objective of such work is to increase spontaneous-emission rates to such a degree that light-emitting diodes (LEDs) can possess modulation speeds exceeding those of typical semiconductor lasers, which are usually in the range ~20-50 GHz. We outline the underlying physics that enable large spontaneous-emission enhancements in metallic nanostructures, and we then discuss recent theoretical and experimentally promising results, where enhancements larger than a factor of ~300 have been reported, with radiation efficiencies exceeding 50%. We provide key comparative advantages of these structures in comparison to conventional dielectric microcavity designs, namely the fact that the enhancement of spontaneous emission can be relatively nonresonant (i.e., broadband) and that the antenna nanostructures can be spectrally and structurally compatible for integration with a wide class of emitters, including organic dyes, diamond nanocrystals and colloidal quantum dots. Finally, we point out that physical insight into the underlying effects can be gained by analyzing these metallic nanostructures in their equivalent-circuit (or nano-antenna) model, showing that all main effects (including the Purcell factor) can adequately be described in that approach. PMID:27505759

  17. Plasmonic engineering of spontaneous emission from silicon nanocrystals

    PubMed Central

    Goffard, Julie; Gérard, Davy; Miska, Patrice; Baudrion, Anne-Laure; Deturche, Régis; Plain, Jérôme

    2013-01-01

    Silicon nanocrystals offer huge advantages compared to other semi-conductor quantum dots as they are made from an abundant, non-toxic material and are compatible with silicon devices. Besides, among a wealth of extraordinary properties ranging from catalysis to nanomedicine, metal nanoparticles are known to increase the radiative emission rate of semiconductor quantum dots. Here, we use gold nanoparticles to accelerate the emission of silicon nanocrystals. The resulting integrated hybrid emitter is 5-fold brighter than bare silicon nanocrystals. We also propose an in-depth analysis highlighting the role of the different physical parameters in the photoluminescence enhancement phenomenon. This result has important implications for the practical use of silicon nanocrystals in optoelectronic devices, for instance for the design of efficient down-shifting devices that could be integrated within future silicon solar cells. PMID:24037020

  18. Electrically Controllable Spontaneous Magnetism in Nanoscale Mixed Phase Multiferroics

    SciTech Connect

    He, Q.; Chu, Y. H.; Heron, J. T.; Yang, S. Y.; Wang, C. H.; Kuo, C. Y.; Lin, H. J.; Yu, P.; Liang, C. W.; Zeches, R. J.; Chen, C. T.; Arenholz, E.; Scholl, A.; Ramesh, R.

    2010-08-02

    The emergence of enhanced spontaneous magnetic moments in self-assembled, epitaxial nanostructures of tetragonal (T-phase) and rhombohedral phases (R-phase) of the multiferroic BiFeO{sub 3} system is demonstrated. X-ray magnetic circular dichroism based photoemission electron microscopy (PEEM) was applied to investigate the local nature of this magnetism. We find that the spontaneous magnetization of the R-phase is significantly enhanced above the canted antiferromagnetic moment in the bulk phase, as a consequence of a piezomagnetic coupling to the adjacent T-phase and the epitaxial constraint. Reversible electric field control and manipulation of this magnetic moment at room temperature is shown using a combination of piezoresponse force microscopy and PEEM studies.

  19. Spontaneous emission intensity and anisotropy of quantum dot films in proximity to nanoscale photonic–plasmonic templates

    NASA Astrophysics Data System (ADS)

    Indukuri, Chaitanya; Basu, J. K.

    2016-07-01

    We discuss results on spontaneous emission intensity and lifetime anisotropy of cadmium selenide quantum dot monolayer films placed in close proximity to a porous block copolymer based photonic–plasmonic two dimensional array. The porous block copolymer cylinders can be filled with metal nanoparticles and the concentration of these nanoparticles is varied to control both the photoluminescence intensity and lifetime of a layer of quantum dots placed above the template. Significant emission enhancement is achieved even for the quantum dot layer whose core lies about 1 nm above the template surface. Interestingly, polarised decay lifetime analysis indicates considerable emission anisotropy, as well for these quantum dots. Our results thus demonstrates how such hybrid optical materials can be created with controlled optical properties and suggests extension of this method to other novel two dimensional materials in combination with the photonic–plasmonic template.

  20. Fast and bright spontaneous emission of Er3+ ions in metallic nanocavity

    PubMed Central

    Song, Jung-Hwan; Kim, Jisu; Jang, Hoon; Yong Kim, In; Karnadi, Indra; Shin, Jonghwa; Shin, Jung H.; Lee, Yong-Hee

    2015-01-01

    By confining light in a small cavity, the spontaneous emission rate of an emitter can be controlled via the Purcell effect. However, while Purcell factors as large as ∼10,000 have been predicted, actual reported values were in the range of about 10–30 only, leaving a huge gap between theory and experiment. Here we report on enhanced 1.54-μm emission from Er3+ ions placed in a very small metallic cavity. Using a cavity designed to enhance the overall Purcell effect instead of a particular component, and by systematically investigating its photonic properties, we demonstrate an unambiguous Purcell factor that is as high as 170 at room temperature. We also observe >90 times increase in the far-field radiant flux, indicating that as much as 55% of electromagnetic energy that was initially supplied to Er3+ ions in the cavity escape safely into the free space in just one to two optical cycles. PMID:25940839

  1. Emission control system

    NASA Technical Reports Server (NTRS)

    Parrish, Clyde F. (Inventor); Chung, J. Landy (Inventor)

    2009-01-01

    Methods and apparatus utilizing hydrogen peroxide are useful to reduce SOx and mercury (or other heavy metal) emissions from combustion flue gas streams. The methods and apparatus may further be modified to reduce NOx emissions. Continuous concentration of hydrogen peroxide to levels approaching or exceeding propellant-grade hydrogen peroxide facilitates increased system efficiency. In this manner, combustion flue gas streams can be treated for the removal of SOx and heavy metals, while isolating useful by-products streams of sulfuric acid as well as solids for the recovery of the heavy metals. Where removal of NOx emissions is included, nitric acid may also be isolated for use in fertilizer or other industrial applications.

  2. Spontaneous ultraweak photon emission imaging of oxidative metabolic processes in human skin: effect of molecular oxygen and antioxidant defense system

    NASA Astrophysics Data System (ADS)

    Rastogi, Anshu; Pospíšil, Pavel

    2011-09-01

    All living organisms emit spontaneous ultraweak photon emission as a result of cellular metabolic processes. In this study, the involvement of reactive oxygen species (ROS) formed as the byproduct of oxidative metabolic processes in spontaneous ultraweak photon emission was studied in human hand skin. The effect of molecular oxygen and ROS scavengers on spontaneous ultraweak photon emission from human skin was monitored using a highly sensitive photomultiplier tube and charged coupled device camera. When spontaneous ultraweak photon emission was measured under anaerobic conditions, the photon emission was decreased, whereas under hyperaerobic condition the enhancement in photon emission was observed. Spontaneous ultraweak photon emission measured after topical application of glutathione, α-tocopherol, ascorbate, and coenzyme Q10 was observed to be decreased. These results reveal that ROS formed during the cellular metabolic processes in the epidermal cells play a significant role in the spontaneous ultraweak photon emission. It is proposed that spontaneous ultraweak photon emission can be used as a noninvasive tool for the temporal and spatial monitoring of the oxidative metabolic processes and intrinsic antioxidant system in human skin.

  3. Enhancing spontaneous emission rates of molecules using nanopatterned multilayer hyperbolic metamaterials.

    PubMed

    Lu, Dylan; Kan, Jimmy J; Fullerton, Eric E; Liu, Zhaowei

    2014-01-01

    Plasmonic nanostructures have been extensively used to manipulate the spontaneous light emission rate of molecules and their radiative efficiency. Because molecules near a metallic surface experience a different environment than in free space, their spontaneous radiative emission rate is generally enhanced. Such enhancement, measured by means of the Purcell factor, arises as a consequence of the overlap between the surface plasmon mode frequency and the emission spectrum of the molecule. However, such overlap is available only for a few narrow bands of frequency due to the limited plasmonic materials existing in nature. Although this limitation can be overcome by using hyperbolic metamaterials (HMMs)—a type of nanoscale artificial material with hyperbolic dispersion relations—the Purcell factor and the radiative power have remained relatively low. Here, we show that by nanopatterning a hyperbolic metamaterial made of Ag and Si multilayers, the spontaneous emission rate of rhodamine dye molecules is enhanced 76-fold at tunable frequencies and the emission intensity of the dye increases by ~80-fold compared with the same hyperbolic metamaterial without nanostructuring. We explain these results using a dynamic Lorentzian model in the time domain. PMID:24390565

  4. Enhancing spontaneous emission rates of molecules using nanopatterned multilayer hyperbolic metamaterials

    NASA Astrophysics Data System (ADS)

    Lu, Dylan; Kan, Jimmy J.; Fullerton, Eric E.; Liu, Zhaowei

    2014-01-01

    Plasmonic nanostructures have been extensively used to manipulate the spontaneous light emission rate of molecules and their radiative efficiency. Because molecules near a metallic surface experience a different environment than in free space, their spontaneous radiative emission rate is generally enhanced. Such enhancement, measured by means of the Purcell factor, arises as a consequence of the overlap between the surface plasmon mode frequency and the emission spectrum of the molecule. However, such overlap is available only for a few narrow bands of frequency due to the limited plasmonic materials existing in nature. Although this limitation can be overcome by using hyperbolic metamaterials (HMMs)--a type of nanoscale artificial material with hyperbolic dispersion relations--the Purcell factor and the radiative power have remained relatively low. Here, we show that by nanopatterning a hyperbolic metamaterial made of Ag and Si multilayers, the spontaneous emission rate of rhodamine dye molecules is enhanced 76-fold at tunable frequencies and the emission intensity of the dye increases by ~80-fold compared with the same hyperbolic metamaterial without nanostructuring. We explain these results using a dynamic Lorentzian model in the time domain.

  5. Spontaneous emission in the presence of a realistically sized cylindrical waveguide

    NASA Astrophysics Data System (ADS)

    Dung, Ho Trung

    2016-02-01

    Various quantities characterizing the spontaneous emission process of a dipole emitter including the emission rate and the emission pattern can be expressed in terms of the Green tensor of the surrounding environment. By expanding the Green tensor around some analytically known background one as a Born series, and truncating it under appropriate conditions, complicated boundaries can be tackled with ease. However, when the emitter is embedded in the medium, even the calculation of the first-order term in the Born series is problematic because of the presence of a singularity. We show how to eliminate this singularity for a medium of arbitrary size and shape by expanding around the bulk medium rather than vacuum. In the highly symmetric configuration of an emitter located on the axis of a realistically sized cylinder, it is shown that the singularity can be removed by changing the integral variables and then the order of integration. Using both methods, we investigate the spontaneous emission rate of an initially excited two-level dipole emitter, embedded in a realistically sized cylinder, which can be a common optical fiber in the long-length limit and a disk in the short-length limit. The spatial distribution of the emitted light is calculated using the Born-expansion approach, and local-field corrections to the spontaneous emission rate are briefly discussed.

  6. The interplay between spontaneous and controlled processing in creative cognition

    PubMed Central

    Mok, Leh Woon

    2014-01-01

    Neural studies of creativity have yielded relatively little consistent results. For example, in functional neuroanatomical studies, the prefrontal cortex (PFC) has often been implicated as a critical neural substrate. However, results in electrophysiological (EEG) studies have been inconsistent as to the role of the PFC. EEG results have more often implicated widespread alpha synchronization, particularly in posterior regions, in creative cognition. Recent fMRI evidence has indicated that the PFC may be activated as a part of and together with other components of a deliberate control brain network. Controlled processing is neurologically dissociated from, but may co-occur with, spontaneous cognition mediated by a subset of the default-mode network (e.g., the angular gyrus [BA 39] in the posterior parietal cortex, which has been increasingly implicated in creative cognition). When the demand for controlled processing is substantially increased, default-mode processing may be suppressed. There is now preliminary evidence to suggest an association between alpha synchronization and default-mode processing. Creative cognition likely emerges from an optimal balance between spontaneous processing and controlled processing. PMID:25221497

  7. Spontaneous emission with a cascaded driving field in the same transition channel

    NASA Astrophysics Data System (ADS)

    Liu, Ronggang; Liu, Tong

    2015-11-01

    We study the spontaneous emission spectrum of a driven four-level atom in both Markovian reservoir and non-Markovian reservoir, in which the two driving fields are applied to the same transition channel. It is very interesting that the increase of the Rabi frequency of the first driving field leads to the emission spectrum enhancement in Markovian reservoir, but the increase of the second one can suppress the emission spectrum significantly. The phenomenon originates from the dressed states variation induced by the first driving field. For non-Markovian reservoir case, the rich spectrum behavior is due to a strong coupling between driving fields and modified reservoir.

  8. Fabrication and characterization of plasmonic nanocone antennas for strong spontaneous emission enhancement.

    PubMed

    Hoffmann, Björn; Vassant, Simon; Chen, Xue-Wen; Götzinger, Stephan; Sandoghdar, Vahid; Christiansen, Silke

    2015-10-01

    Plasmonic antennas are attractive nanostructures for a large variety of studies ranging from fundamental aspects of light-matter interactions at the nanoscale to industry-relevant applications such as ultrasensitive sensing, enhanced absorption in solar cells or solar fuel generation. A particularly interesting feature of these antennas is that they can enhance the fluorescence properties of emitters. Theoretical calculations have shown that nanocone antennas provide ideal results, but a high degree of manufacturing precision and control is needed to reach optimal performance. In this study, we report on the fabrication of nanocones with base diameters and heights in the range of 100 nm with variable aspect ratios using focused ion beam milling of sputtered nano-crystalline gold layers. The controlled fabrication process allows us to obtain cones with tailored plasmon resonances. The measured plasmon spectra show very good agreement with finite-difference time-domain calculations. Theoretical investigations predict that these nanocones can enhance the spontaneous emission rate of a quantum emitter by several hundred times while keeping its quantum efficiency above 60%. PMID:26376922

  9. Fabrication and characterization of plasmonic nanocone antennas for strong spontaneous emission enhancement

    NASA Astrophysics Data System (ADS)

    Hoffmann, Björn; Vassant, Simon; Chen, Xue-Wen; Götzinger, Stephan; Sandoghdar, Vahid; Christiansen, Silke

    2015-10-01

    Plasmonic antennas are attractive nanostructures for a large variety of studies ranging from fundamental aspects of light-matter interactions at the nanoscale to industry-relevant applications such as ultrasensitive sensing, enhanced absorption in solar cells or solar fuel generation. A particularly interesting feature of these antennas is that they can enhance the fluorescence properties of emitters. Theoretical calculations have shown that nanocone antennas provide ideal results, but a high degree of manufacturing precision and control is needed to reach optimal performance. In this study, we report on the fabrication of nanocones with base diameters and heights in the range of 100 nm with variable aspect ratios using focused ion beam milling of sputtered nano-crystalline gold layers. The controlled fabrication process allows us to obtain cones with tailored plasmon resonances. The measured plasmon spectra show very good agreement with finite-difference time-domain calculations. Theoretical investigations predict that these nanocones can enhance the spontaneous emission rate of a quantum emitter by several hundred times while keeping its quantum efficiency above 60%.

  10. Characteristics of Spontaneous Emission of Polarized Atoms in Metal Dielectric Multiple Layer Structures

    NASA Astrophysics Data System (ADS)

    Zhao, Li-Ming; Gu, Ben-Yuan; Zhou, Yun-Song

    2007-11-01

    The spontaneous emission (SE) progress of polarized atoms in a stratified structure of air-dielectric(D0)-metal(M)-dielectric(D1)-air can be controlled effectively by changing the thickness of the D1 layer and rotating the polarized direction of atoms. It is found that the normalized SE rate of atoms located inside the D0 layer crucially depends on the atomic position and the thickness of the D1 layer. When the atom is located near the D0-M interface, the normalized atomic SE rate as a function of the atomic position is abruptly onset for the thin D1 layer. However, with the increasing thickness of the D1 layer, the corresponding curve profile exhibits plateau and stays nearly unchanged. The substantial change of the SE rate stems from the excitation of the surface plasmon polaritons in metal-dielectric interface, and the feature crucially depends on the thickness of D1 layer. If atoms are positioned near the D0-air interface, the substantial variation of the normalized SE rate appears when rotating the polarized direction of atoms. These findings manifest that the atomic SE processes can be flexibly controlled by altering the thickness of the dielectric layer D1 or rotating the orientation of the polarization of atoms.

  11. Emission control system

    NASA Technical Reports Server (NTRS)

    Parrish, Clyde F. (Inventor)

    2008-01-01

    Methods and apparatus utilizing hydrogen peroxide are useful to reduce NOx, SOx and mercury (or other heavy metal) emissions from combustion flue gas streams. Continuous concentration of hydrogen peroxide to levels approaching or exceeding propellant-grade hydrogen peroxide facilitates increased system efficiency. In this manner, combustion flue gas streams can be treated for the removal of NOx, SOx and heavy metals, while isolating useful by-products streams of sulfuric acid and nitric acid as well as solids for the recovery of the heavy metals.

  12. Spontaneous otoacoustic emissions in the European edible frog (Rana esculenta): spectral details and temperature dependence.

    PubMed

    van Dijk, P; Wit, H P; Segenhout, J M

    1989-11-01

    Spontaneous otoacoustic emissions were recorded in 41 ears of 29 European edible frogs (Rana esculenta). Emission frequencies ranged from 450 to 1350 Hz. The distribution of frequencies shows two distinct populations: one above and one below 1 kHz. With one exception, a maximum number of two emissions were recorded per ear, each in a different population. An amplitude distribution of a frog emission was sampled, from which it was concluded that the emission is generated by an active oscillator. The spectral width of an emission ranged from 1 to 200 Hz (average 38 Hz). There was negative correlation between sound pressure level of an emission and spectral width. In 4 frogs the dependence of emission power and frequency on temperature was investigated. An emission could be 'switched on and off' within a few degrees centigrade. At temperatures below the switching interval no emission was recorded; for higher temperatures emission power showed no dependence on temperature. Frequency increased with temperature (Q10 = 1.1 to 1.3). This yields a mismatch with temperature dependence of best frequencies of auditory fibers. The consequences of this mismatch are discussed. PMID:2691473

  13. Spontaneous Fluctuations in the Flexible Control of Covert Attention

    PubMed Central

    Courtney, Susan M.; Yantis, Steven

    2016-01-01

    Spontaneous fluctuations in cognitive flexibility are characterized by moment-to-moment changes in the efficacy of control over attentional shifts. We used fMRI to investigate the neural correlates in humans of spontaneous fluctuations in readiness to covertly shift attention between two peripheral rapid serial visual presentation streams. Target detection response time (RT) after a shift or hold of covert spatial attention served as a behavioral index of fluctuations in attentional flexibility. In particular, the cost associated with shifting attention compared with holding attention varied as a function of pretrial brain activity in key regions of the default mode network (DMN), but not the dorsal attention network. High pretrial activity within the DMN was associated with a greater increase in shift trial RT relative to hold trial RT, revealing that these areas are associated with a state of attentional stability. Conversely, high pretrial activity within bilateral anterior insula and the presupplementary motor area/supplementary motor area was associated with a greater decrease in shift trial RT relative to hold trial RT, reflecting increased flexibility. Our results importantly clarify the roles of the precuneus, medial prefrontal cortex, and lateral parietal cortex, indicating that reduced activity may not simply indicate greater task engagement, but also, specifically, a readiness to update the focus of attention. Investigation of the neural correlates of spontaneous changes in attentional flexibility may contribute to our understanding of disorders of cognitive control as well as healthy variability in the control of spatial attention. SIGNIFICANCE STATEMENT Individuals regularly experience fluctuations in preparatory cognitive control that affect performance in everyday life. For example, individuals are able to more quickly initiate a spatial shift of attention at some moments than at others. The current study revealed that pretrial brain activity in

  14. Experimental demonstration of enhanced self-amplified spontaneous emission by an optical klystron.

    PubMed

    Penco, G; Allaria, E; De Ninno, G; Ferrari, E; Giannessi, L

    2015-01-01

    We report the first experimental evidence of enhancement of self-amplified spontaneous emission, due to the use of an optical klystron. In this free-electron laser scheme, a relativistic electron beam passes through two undulators, separated by a dispersive section. The latter converts the electron-beam energy modulation produced in the first undulator in density modulation, thus enhancing the free-electron laser gain. The experiment has been carried out at the FERMI facility in Trieste. Powerful radiation has been produced in the extreme ultraviolet range, with an intensity a few orders of magnitude larger than in pure self-amplified spontaneous emission mode. Data have been benchmarked with an existing theoretical model. PMID:25615469

  15. Experimental Demonstration of Enhanced Self-Amplified Spontaneous Emission by an Optical Klystron

    NASA Astrophysics Data System (ADS)

    Penco, G.; Allaria, E.; De Ninno, G.; Ferrari, E.; Giannessi, L.

    2015-01-01

    We report the first experimental evidence of enhancement of self-amplified spontaneous emission, due to the use of an optical klystron. In this free-electron laser scheme, a relativistic electron beam passes through two undulators, separated by a dispersive section. The latter converts the electron-beam energy modulation produced in the first undulator in density modulation, thus enhancing the free-electron laser gain. The experiment has been carried out at the FERMI facility in Trieste. Powerful radiation has been produced in the extreme ultraviolet range, with an intensity a few orders of magnitude larger than in pure self-amplified spontaneous emission mode. Data have been benchmarked with an existing theoretical model.

  16. Directional spontaneous emission and lateral Casimir-Polder force on an atom close to a nanofiber

    NASA Astrophysics Data System (ADS)

    Scheel, Stefan; Buhmann, Stefan Yoshi; Clausen, Christoph; Schneeweiss, Philipp

    2015-10-01

    We study the spontaneous emission of an excited atom close to an optical nanofiber and the resulting scattering forces. For a suitably chosen orientation of the atomic dipole, the spontaneous emission pattern becomes asymmetric and a resonant Casimir-Polder force parallel to the fiber axis arises. For a simple model case, we show that such a lateral force is due to the interaction of the circularly oscillating atomic dipole moment with its image inside the material. With the Casimir-Polder energy being constant in the lateral direction, the predicted lateral force does not derive from a potential in the usual way. Our results have implications for optical force measurements on a substrate as well as for laser cooling of atoms in nanophotonic traps.

  17. Cavity-enhanced spontaneous emission rates for rhodamine 6-G in levitated microdroplets

    SciTech Connect

    Barnes, M.D.; Whitten, W.B.; Ramsey, J.M. ); Arnold, S. )

    1992-01-01

    Fluorescence decay kinetics of Rhodamine 6-G molecules in levitated glycerol microdroplets (4--20 microns in diameter) have been investigated to determine the effects of spherical cavity resonances on spontaneous emission rates. For droplet diameters greater than 10 microns, the fluorescence lifetime is essentially the same as in bulk glycerol. As the droplet diameter is decreased below 10 microns, bi-exponential decay behavior is observed with a slow component whose rate is similar to bulk glycerol, and a fast component whose rate is as much as a factor of 10 larger than the bulk decay rate. This fast component is attributed to cavity enhancement of the spontaneous emission rate and, within the weak coupling approximation, a value for the homogeneous linewidth at room temperature can be estimated from the fluorescence lifetime data.

  18. Cavity-enhanced spontaneous emission rates for rhodamine 6-G in levitated microdroplets

    SciTech Connect

    Barnes, M.D.; Whitten, W.B.; Ramsey, J.M.; Arnold, S.

    1992-11-01

    Fluorescence decay kinetics of Rhodamine 6-G molecules in levitated glycerol microdroplets (4--20 microns in diameter) have been investigated to determine the effects of spherical cavity resonances on spontaneous emission rates. For droplet diameters greater than 10 microns, the fluorescence lifetime is essentially the same as in bulk glycerol. As the droplet diameter is decreased below 10 microns, bi-exponential decay behavior is observed with a slow component whose rate is similar to bulk glycerol, and a fast component whose rate is as much as a factor of 10 larger than the bulk decay rate. This fast component is attributed to cavity enhancement of the spontaneous emission rate and, within the weak coupling approximation, a value for the homogeneous linewidth at room temperature can be estimated from the fluorescence lifetime data.

  19. Simulations of the spontaneous emission of a quantum dot near a gap plasmon waveguide

    SciTech Connect

    Perera, Chamanei S. Vernon, Kristy C.; Mcleod, Angus

    2014-02-07

    In this paper, we modeled a quantum dot at near proximity to a gap plasmon waveguide to study the quantum dot-plasmon interactions. Assuming that the waveguide is single mode, this paper is concerned about the dependence of spontaneous emission rate of the quantum dot on waveguide dimensions such as width and height. We compare coupling efficiency of a gap waveguide with symmetric configuration and asymmetric configuration illustrating that symmetric waveguide has a better coupling efficiency to the quantum dot. We also demonstrate that optimally placed quantum dot near a symmetric waveguide with 50 nm × 50 nm cross section can capture 80% of the spontaneous emission into a guided plasmon mode.

  20. All-optical cooling of Fermi gases via Pauli inhibition of spontaneous emission

    NASA Astrophysics Data System (ADS)

    Onofrio, Roberto

    2016-03-01

    A technique is proposed to cool Fermi gases to the regime of quantum degeneracy based on the expected inhibition of spontaneous emission due to the Pauli principle. The reduction of the linewidth for spontaneous emission originates a corresponding reduction of the Doppler temperature, which under specific conditions may give rise to a runaway process through which fermions are progressively cooled. The approach requires a combination of a magneto-optical trap as a cooling system and an optical dipole trap to enhance quantum degeneracy. This results in expected Fermi degeneracy factors T /TF comparable to the lowest values recently achieved, with potential for a direct implementation in optical lattices. The experimental demonstration of this technique should also indirectly provide a macroscopic manifestation of the Pauli exclusion principle at the atomic physics level.

  1. Effect of amplified spontaneous emission on selectivity of laser photoionisation of the 177Lu radioisotope

    NASA Astrophysics Data System (ADS)

    D'yachkov, A. B.; Gorkunov, A. A.; Labozin, A. V.; Mironov, S. M.; Panchenko, V. Ya; Firsov, V. A.; Tsvetkov, G. O.

    2016-06-01

    A significant deselecting effect of amplified spontaneous emission has been observed in the experiments on selective laser photoionisation of the 177Lu radioisotope according to the scheme 5d6s2 2D3/2 → 5d6s6p 4Fo5/2 (18505 cm-1) → 5d6s7s 4D3/2(37194 cm-1) → autoionisation state (53375 cm-1). The effect is conditioned by involvement of non-target isotopes from the lower metastable level 5d6s2 2D5/2(1994 cm-1) into the ionisation process. Spectral filtering of spontaneous emission has allowed us to significantly increase the selectivity of the photoionisation process of the radioisotope and to attain a selectivity value of 105 when using saturating light intensities.

  2. Optical microcavities based on F2 color centers in lithium fluoride films: modification of spontaneous emission

    NASA Astrophysics Data System (ADS)

    Bonfigli, Francesca; Jacquier, Bernard; Montereali, Rosamaria; Moretti, Paul; Nichelatti, Enrico; Piccinini, M.; Rigneault, Herve; Somma, F.

    2003-04-01

    Lithium fluoride (LiF) films irradiated by low energy electrons were employed as active spacers in all-solid, dielectric optical microcavities emitting in the visible spectral range. We present the results of optical characterization of the spontaneous emission from F2 color centers embedded in a LiF layer confined inside a planar microcavity. These structures seem promising for the realization of novel kinds of solid-state miniaturized emitting devices.

  3. Scalarized photon analysis of spontaneous emission in the uniform magnetic field free-electron laser

    NASA Astrophysics Data System (ADS)

    Soln, Josip

    1990-04-01

    The recently developed concept of scalarized photons (formally photons of any polarization) is used to analyze the spontaneous emission in the uniform magnetic field free-electron laser in the microwave spectral region. With the electron beam energy of up to 10 MeV and the uniform magnetic field of up to 4 Tesla, the radiation (occurring with the fundamental and higher harmonic frequencies) can easily cover a 10- to 10,000 GHz spectral region.

  4. Ultrafast spontaneous emission of copper-doped silicon enhanced by an optical nanocavity

    PubMed Central

    SUMIKURA, HISASHI; KURAMOCHI, EIICHI; TANIYAMA, HIDEAKI; NOTOMI, MASAYA

    2014-01-01

    Dopants in silicon (Si) have attracted attention in the fields of photonics and quantum optics. However, the optical characteristics are limited by the small spontaneous emission rate of dopants in Si. This study demonstrates a large increase in the spontaneous emission rate of copper isoelectronic centres (Cu-IECs) doped into Si photonic crystal nanocavities. In a cavity with a quality factor (Q) of ~16,000, the photoluminescence (PL) lifetime of the Cu-IECs is 1.1 ns, which is 30 times shorter than the lifetime of a sample without a cavity. The PL decay rate is increased in proportion to Q/Vc (Vc is the cavity mode volume), which indicates the Purcell effect. This is the first demonstration of a cavity-enhanced ultrafast spontaneous emission from dopants in Si, and it may lead to the development of fast and efficient Si light emitters and Si quantum optical devices based on dopants with efficient optical access. PMID:24853336

  5. Advanced Emissions Control Development Program

    SciTech Connect

    A.P.Evans; K.E. Redinger; M.J. Holmes

    1998-04-01

    The objective of the Advanced Emissions Control Development Program (AECDP) is to develop practical, cost-effective strategies for reducing the emissions of air toxics from coal-fired boilers. Ideally, the project aim is to effectively control air toxic emissions through the use of conventional flue gas cleanup equipment such as electrostatic precipitators (ESPS), fabric filters (baghouse), and wet flue gas desulfurization. Development work to date has concentrated on the capture of mercury, other trace metals, fine particulate and hydrogen chloride. Following the construction and evaluation of a representative air toxics test facility in Phase I, Phase II focused on the evaluation of mercury and several other air toxics emissions. The AECDP is jointly funded by the United States Department of Energy's Federal Energy Technology Center (DOE), the Ohio Coal Development Office within the Ohio Department of Development (oCDO), and Babcock& Wilcox-a McDermott company (B&W).

  6. Calculation of the spontaneous cyclotron emissivity using the complete relativistic resonance condition

    NASA Technical Reports Server (NTRS)

    Freund, H. P.; Wu, C. S.; Gaffey, J. D., Jr.

    1984-01-01

    An expression for the spectral emissivity of spontaneous synchrotron radiation for a plasma which consists of both thermal and suprathermal electron components is derived using the complete relativistic cyclotron resonance condition. The expression is valid over all angles of propagation. The result is applied to the study of the emission of radiation from an energetic population of electrons with a loss-cone distribution in a relatively low-density plasma (i.e., the electron plasma frequency is less than the cyclotron frequency).

  7. Amplified spontaneous emission in an organic semiconductor multilayer waveguide structure including a highly conductive transparent electrode

    NASA Astrophysics Data System (ADS)

    Reufer, M.; Feldmann, J.; Rudati, P.; Ruhl, A.; Müller, D.; Meerholz, K.; Karnutsch, C.; Gerken, M.; Lemmer, U.

    2005-05-01

    We demonstrate that the amplified spontaneous emission (ASE) threshold in multilayer waveguide structures suitable for the use in future organic injection lasers can be drastically reduced by inserting a crosslinked hole transport layer (HTL) between a highly conductive indium tin oxide (ITO) electrode and the polymer emission layer. While no ASE is observed when the active layer material is directly spincoated onto the ITO electrode, it can be completely restored upon insertion of a 300-nm-thick HTL. This observation is attributed to reduced attenuation of the waveguided mode enabling the ASE process and is theoretically confirmed by calculations of the mode intensity fraction propagating in the absorptive ITO electrode.

  8. Ultrafast spontaneous emission modulation of graphene quantum dots interacting with Ag nanoparticles in solution

    NASA Astrophysics Data System (ADS)

    Zhao, Jianwei; Lu, Jian; Wang, Liang; Tian, Linfan; Deng, Xingxia; Tian, Lijun; Pan, Dengyu; Wang, Zhongyang

    2016-07-01

    We investigated the strong interaction between graphene quantum dots and silver nanoparticles in solution using time-resolved photoluminescence techniques. In solution, the silver nanoparticles are surrounded by graphene quantum dots and interacted with graphene quantum dots through exciton-plasmon coupling. An ultrafast spontaneous emission process (lifetime 27 ps) was observed in such a mixed solution. This ultrafast lifetime corresponds to the emission rate exceeding 35 GHz, with the purcell enhancement by a factor of ˜12. These experiment results pave the way for the realization of future high speed light sources applications.

  9. Spontaneous otoacoustic emissions in an active nonlinear cochlear model in the time domain

    NASA Astrophysics Data System (ADS)

    Fruth, Florian; Jülicher, Frank; Lindner, Benjamin

    2015-12-01

    A large fraction of human cochleas emits sounds even in the absence of external stimulation. These so-called spontaneous otoacoustic emissions (SOAEs) are a hallmark of the active nonlinear amplification process taking place in the cochlea. Here, we extend a previously proposed frequency domain model and put forward an active nonlinear one-dimensional model of the cochlea in the time domain describing human SOAEs [5]. In our model, oscillatory elements are close to an instability (Hopf bifurcation), they are subject to dynamical noise and coupled by hydrodynamic, elastic and dissipative interactions. Furthermore, oscillators are subject to a weak spatial irregularity in their activity (normally distributed and exponentially correlated in space) that gives rise to the individuality of each simulated cochlea. Our model captures main statistical features of the distribution of emission frequencies, the distribution of the numbers of emissions per cochlea, and the distribution of the distances between neighboring emissions as were previously measured in experiment [14].

  10. Greenhouse gas emissions from Australian open-cut coal mines: contribution from spontaneous combustion and low-temperature oxidation.

    PubMed

    Day, Stuart J; Carras, John N; Fry, Robyn; Williams, David J

    2010-07-01

    Spontaneous combustion and low-temperature oxidation of waste coal and other carbonaceous material at open-cut coal mines are potentially significant sources of greenhouse gas emissions. However, the magnitude of these emissions is largely unknown. In this study, emissions from spontaneous combustion and low-temperature oxidation were estimated for six Australian open-cut coal mines with annual coal production ranging from 1.7 to more than 16 Mt. Greenhouse emissions from all other sources at these mines were also estimated and compared to those from spontaneous combustion and low-temperature oxidation. In all cases, fugitive emission of methane was the largest source of greenhouse gas; however, in some mines, spontaneous combustion accounted for almost a third of all emissions. For one mine, it was estimated that emissions from spontaneous combustion were around 250,000 t CO(2)-e per annum. The contribution from low-temperature oxidation was generally less than about 1% of the total for all six mines. Estimating areas of spoil affected by spontaneous combustion by ground-based surveys was prone to under-report the area. Airborne infrared imaging appears to be a more reliable method. PMID:19572109

  11. Advanced Emission Control Development Program.

    SciTech Connect

    Evans, A.P.

    1997-12-31

    Babcock & Wilcox (B&W) is conducting a five-year project aimed at the development of practical, cost-effective strategies for reducing the emissions of hazardous air pollutants (commonly called air toxics) from coal-fired electric utility plants. The need for air toxic emissions controls may arise as the U. S. Environmental Protection Agency proceeds with implementation of Title III of the Clean Air Act Amendment (CAAA) of 1990. Data generated during the program will provide utilities with the technical and economic information necessary to reliably evaluate various air toxics emissions compliance options such as fuel switching, coal cleaning, and flue gas treatment. The development work is being carried out using B&W`s new Clean Environment Development Facility (CEDF) wherein air toxics emissions control strategies can be developed under controlled conditions, and with proven predictability to commercial systems. Tests conducted in the CEDF provide high quality, repeatable, comparable data over a wide range of coal properties, operating conditions, and emissions control systems. Development work to date has concentrated on the capture of mercury, other trace metals, fine particulate, and the inorganic species hydrogen chloride and hydrogen fluoride.

  12. Advanced Emissions Control Development Program

    SciTech Connect

    Evans, A P

    1998-12-03

    Babcock & Wilcox (B&W) is conducting a five-year project aimed at the development of practical, cost-effective strategies for reducing the emissions of hazardous air pollutants (commonly called air toxics) from coal-fired electric utility plants. The need for air toxic emissions controls may arise as the U. S. Environmental Protection Agency proceeds with implementation of Title III of the Clean Air Act Amendment (CAAA) of 1990. Data generated during the program will provide utilities with the technical and economic information necessary to reliably evaluate various air toxics emissions compliance options such as fuel switching, coal cleaning, and flue gas treatment. The development work is being carried out using B&W's new Clean Environment Development Facility (CEDF) wherein air toxics emissions control strategies can be developed under controlled conditions, and with proven predictability to commercial systems. Tests conducted in the CEDF provide high quality, repeatable, comparable data over a wide range of coal properties, operating conditions, and emissions control systems. Development work to date has concentrated on the capture of mercury, other trace metals, fine particulate, and the inorganic species hydrogen chloride and hydrogen fluoride.

  13. Advanced Emissions Control Development Program

    SciTech Connect

    M. J. Holmes

    1998-12-03

    McDermott Technology, Inc. (MTI) is conducting a five-year project aimed at the development of practical, cost-effective strategies for reducing the emissions of hazardous air pollutants (commonly called air toxics) from coal-fired electric utility plants. The need for air toxic emissions controls may arise as the U. S. Environmental Protection Agency proceeds with implementation of Title III of the Clean Air Act Amendment (CAAA) of 1990. Data generated during the program will provide utilities with the technical and economic information necessary to reliably evaluate various air toxics emissions compliance options such as fuel switching, coal cleaning, and flue gas treatment. The development work is being carried out using the Clean Environment Development Facility (CEDF) wherein air toxics emissions control strategies can be developed under controlled conditions, and with proven predictability to commercial systems. Tests conducted in the CEDF provide high quality, repeatable, comparable data over a wide range of coal properties, operating conditions, and emissions control systems. Development work to date has concentrated on the capture of mercury, other trace metals, fine particulate, and hydrogen chloride and hydrogen fluoride.

  14. Advanced Emissions Control Development Program

    SciTech Connect

    A. P. Evans

    1998-12-03

    McDermott Technology, Inc. (MTI) is conducting a five-year project aimed at the development of practical, cost-effective strategies for reducing the emissions of hazardous air pollutants (commonly called air toxics) from coal-fired electric utility plants. The need for air toxic emissions controls may arise as the U. S. Environmental Protection Agency proceeds with implementation of Title III of the Clean Air Act Amendment (CAAA) of 1990. Data generated during the program will provide utilities with the technical and economic information necessary to reliably evaluate various air toxics emissions compliance options such as fuel switching, coal cleaning, and flue gas treatment. The development work is being carried out using the Clean Environment Development Facility (CEDF) wherein air toxics emissions control strategies can be developed under controlled conditions, and with proven predictability to commercial systems. Tests conducted in the CEDF provide high quality, repeatable, comparable data over a wide range of coal properties, operating conditions, and emissions control systems. Development work to date has concentrated on the capture of mercury, other trace metals, fine particulate, and the inorganic species, hydrogen chloride and hydrogen fluoride.

  15. Using spontaneous photon emission to image lipid oxidation patterns in plant tissues.

    PubMed

    Birtic, Simona; Ksas, Brigitte; Genty, Bernard; Mueller, Martin J; Triantaphylidès, Christian; Havaux, Michel

    2011-09-01

    Plants, like almost all living organisms, spontaneously emit photons of visible light. We used a highly sensitive, low-noise cooled charge coupled device camera to image spontaneous photon emission (autoluminescence) of plants. Oxidative stress and wounding induced a long-lasting enhancement of plant autoluminescence, the origin of which is investigated here. This long-lived phenomenon can be distinguished from the short-lived chlorophyll luminescence resulting from charge recombinations within the photosystems by pre-adapting the plant to darkness for about 2 h. Lipids in solvent were found to emit a persistent luminescence after oxidation in vitro, which exhibited the same time and temperature dependence as plant autoluminescence. Other biological molecules, such as DNA or proteins, either did not produce measurable light upon oxidation or they did produce a chemiluminescence that decayed rapidly, which excludes their significant contribution to the in vivo light emission signal. Selective manipulation of the lipid oxidation levels in Arabidopsis mutants affected in lipid hydroperoxide metabolism revealed a causal link between leaf autoluminescence and lipid oxidation. Addition of chlorophyll to oxidized lipids enhanced light emission. Both oxidized lipids and plants predominantly emit light at wavelengths higher than 600 nm; the emission spectrum of plant autoluminescence was shifted towards even higher wavelengths, a phenomenon ascribable to chlorophyll molecules acting as luminescence enhancers in vivo. Taken together, the presented results show that spontaneous photon emission imaged in plants mainly emanates from oxidized lipids. Imaging of this signal thus provides a simple and sensitive non-invasive method to selectively visualize and map patterns of lipid oxidation in plants. PMID:21595761

  16. Exhaust emission control apparatus

    SciTech Connect

    Eng, J.W.

    1991-09-24

    This patent describes an exhaust control apparatus for muffling noise and treating odors and pollutants, including solid particulate and gases in the exhaust of an internal combustion engine. It comprises an exhaust inlet tube for receiving the exhaust generated by an internal combustion engine; a cyclone barrier concentrically surrounding the exhaust inlet tube, a ring cavity between the cyclone tube and exhaust inlet tube defining a cyclone chamber in which the exhaust is treated; means for directing the exhaust from the exhaust inlet tube into the cyclone chamber; electrode means having small openings through which the exhaust passes to enter the cyclone chamber, the electrode means generating electrostatic forces which charge the solid particulate in the exhaust, ionize air and generate ozone in the cyclone chamber near the electrode; means for injecting air into the cyclone chamber causing centrifugal flow of the air and the exhausted within the cyclone chamber and increasing a dwell time of the exhaust within the cyclone chamber.

  17. Controlled release mechanisms of spontaneously forming unilamellar vesicles.

    PubMed

    Nieh, Mu-Ping; Katsaras, John; Qi, Xiaoyang

    2008-06-01

    Spontaneously forming small unilamellar vesicles (SULVs) are easy to prepare and show great promise for use in delivering therapeutic payloads. We report of SULVs made up of the ternary phospholipid mixture, dimyristoyl-phosphatidylcholine (DMPC), dihexanoyl-phosphatidylcholine (DHPC) and dimyristoyl-phosphatidylglycerol (DMPG), which have been characterized by small angle neutron scattering (SANS). These low-polydispersity (0.14-0.19) SULVs range in size (i.e., radius) from 110 to 215 A and are capable of entrapping, and subsequently releasing, hydrophilic molecules (e.g., fluorescent dyes and quenchers) in a controlled fashion over two different temperature ranges. The low-temperature release mechanism involves the SULVs transforming into discoidal micelles, with an onset temperature (T(o)) of ~32 degrees C, while the high-temperature release mechanism is more gradual, presumably the result of defects formed through the continuous dissolution of DHPC into solution. Both of these mechanisms differ from other, previously reported thermosensitive liposomes. PMID:18394425

  18. Broadband Enhancement of Spontaneous Emission in Two-Dimensional Semiconductors Using Photonic Hypercrystals.

    PubMed

    Galfsky, Tal; Sun, Zheng; Considine, Christopher R; Chou, Cheng-Tse; Ko, Wei-Chun; Lee, Yi-Hsien; Narimanov, Evgenii E; Menon, Vinod M

    2016-08-10

    The low quantum yield observed in two-dimensional semiconductors of transition metal dichalcogenides (TMDs) has motivated the quest for approaches that can enhance the light emission from these systems. Here, we demonstrate broadband enhancement of spontaneous emission and increase in Raman signature from archetype two-dimensional semiconductors: molybdenum disulfide (MoS2) and tungsten disulfide (WS2) by placing the monolayers in the near field of a photonic hypercrystal having hyperbolic dispersion. Hypercrystals are characterized by a large broadband photonic density of states due to hyperbolic dispersion while having enhanced light in/out coupling by a subwavelength photonic crystal lattice. This dual advantage is exploited here to enhance the light emission from the 2D TMDs and can be utilized for developing light emitters and solar cells using two-dimensional semiconductors. PMID:27420735

  19. Laser-assisted ultracold lithium-hydride molecule formation: stimulated versus spontaneous emission

    NASA Astrophysics Data System (ADS)

    Juarros, Elizabeth; Kirby, Kate; Côté, Robin

    2006-10-01

    We investigate the feasibility of forming ultracold LiH from a mixture of the ultracold atomic gases, by using B1Π as an intermediate state in the photoassociation process. Using accurate molecular potential energy curves and dipole transition moments, we calculate and compare two possible schemes to populate vibrational levels of the ground electronic state, X1Σ+: (1) two-photon stimulated radiative association and (2) excitation to bound levels of the B1Π state, followed by spontaneous emission to the X1Σ+ state. With laser intensities and atomic densities that are easily attainable experimentally, we find that significant quantities of molecules can be formed in various v, J levels of the electronic ground state. We examine the spontaneous emission cascade which takes place from the upper vibrational levels on a time scale of milliseconds. We discuss the issue of back-stimulation for the two-photon process and ways to mitigate it. Because photon emission in the cascade process does not contribute to trap loss, a sizable population of molecules in v = 0 can be achieved.

  20. Molecular hot electroluminescence due to strongly enhanced spontaneous emission rates in a plasmonic nanocavity.

    PubMed

    Chen, Gong; Li, Xiao-Guang; Zhang, Zhen-Yu; Dong, Zhen-Chao

    2015-02-14

    We have recently demonstrated anomalous relaxationless hot electroluminescence from molecules in the tunnel junction of a scanning tunneling microscope [Dong et al., Nat. Photonics, 2010, 4, 50]. In the present paper, based on physically realistic parameters, we aim to unravel the underlying physical mechanism using a multiscale modeling approach that combines classical generalized Mie theory with the quantum master equation. We find that the nanocavity-plasmon-tuned spontaneous emission rate plays a crucial role in shaping the spectral profile. In particular, on resonance, the radiative decay rate can be enhanced by three-to-five orders of magnitude, which enables the radiative process to occur on the lifetime scale of picoseconds and become competitive to the vibrational relaxation. Such a large Purcell effect opens up new emission channels to generate the hot luminescence that arises directly from higher vibronic levels of the molecular excited state. We also stress that the critical role of resonant plasmonic nanocavities in tunneling electron induced molecular luminescence is to enhance the spontaneous radiative decay through plasmon enhanced vacuum fluctuations rather than to generate an efficient plasmon stimulated emission process. This improved understanding has been partly overlooked in previous studies but is believed to be very important for further developments of molecular plasmonics and optoelectronics. PMID:25565003

  1. An active oscillator model describes the statistics of spontaneous otoacoustic emissions.

    PubMed

    Fruth, Florian; Jülicher, Frank; Lindner, Benjamin

    2014-08-19

    Even in the absence of external stimulation, the cochleas of most humans emit very faint sounds below the threshold of hearing, sounds that are known as spontaneous otoacoustic emissions. They are a signature of the active amplification mechanism in the cochlea. Emissions occur at frequencies that are unique for an individual and change little over time. The statistics of a population of ears exhibit characteristic features such as a preferred relative frequency distance between emissions (interemission intervals). We propose a simplified cochlea model comprising an array of active nonlinear oscillators coupled both hydrodynamically and viscoelastically. The oscillators are subject to a weak spatial disorder that lends individuality to the simulated cochlea. Our model captures basic statistical features of the emissions: distributions of 1), emission frequencies; 2), number of emissions per ear; and 3), interemission intervals. In addition, the model reproduces systematic changes of the interemission intervals with frequency. We show that the mechanism for the preferred interemission interval in our model is the occurrence of synchronized clusters of oscillators. PMID:25140416

  2. An Active Oscillator Model Describes the Statistics of Spontaneous Otoacoustic Emissions

    PubMed Central

    Fruth, Florian; Jülicher, Frank; Lindner, Benjamin

    2014-01-01

    Even in the absence of external stimulation, the cochleas of most humans emit very faint sounds below the threshold of hearing, sounds that are known as spontaneous otoacoustic emissions. They are a signature of the active amplification mechanism in the cochlea. Emissions occur at frequencies that are unique for an individual and change little over time. The statistics of a population of ears exhibit characteristic features such as a preferred relative frequency distance between emissions (interemission intervals). We propose a simplified cochlea model comprising an array of active nonlinear oscillators coupled both hydrodynamically and viscoelastically. The oscillators are subject to a weak spatial disorder that lends individuality to the simulated cochlea. Our model captures basic statistical features of the emissions: distributions of 1), emission frequencies; 2), number of emissions per ear; and 3), interemission intervals. In addition, the model reproduces systematic changes of the interemission intervals with frequency. We show that the mechanism for the preferred interemission interval in our model is the occurrence of synchronized clusters of oscillators. PMID:25140416

  3. Modified spontaneous emission of organic molecules in-filled in inverse opals.

    PubMed

    Deng, Lier; Wang, Yongsheng; He, Dawei

    2011-11-01

    Inverse opals were prepared by replication of colloidal crystal templates made from silica spheres 298 nm in diameter. The air between the silica spheres was filled with the mixture of the monomer poly(methyl methacrylate) (PMMA) and the organic molecule Alq3 that can be subsequently polymerized. After removing the silica sphere templates, the photonic bandgap effect on the spontaneous emission of Alq3 were investigated. The dip in the fluorescence spectrum was interpreted in terms of redistribution of the photon density of states in the photonic crystal. PMID:22413286

  4. Calculated half-lives and kinetic energies for spontaneous emission of heavy ions from nuclei

    SciTech Connect

    Poenaru, D.N.; Greiner, W.; Depta, K.; Ivascu, M.; Mazilu, D.; Sandulescu, A.

    1986-05-01

    The most probable decays by spontaneous emission of heavy ions are listed for nuclides with Z = 47--106 and total half-lives>1 ..mu..sec. Partial half-lives, branching ratios relative to ..cap alpha.. decay, kinetic energies, and Q values are estimated by using the analytical superasymmetric fission model, a semiempirical formula for those ..cap alpha..-decay lifetimes which have not been measured, and the new Wapstra--Audi mass tables. Numerous ''stable'' nuclides with Z>40 are found to be metastable with respect to the new decay modes. The current experimental status is briefly reviewed.

  5. Observation of Self-Amplified Spontaneous Emission and Exponential Growth at 530 nm

    NASA Astrophysics Data System (ADS)

    Milton, S. V.; Gluskin, E.; Biedron, S. G.; Dejus, R. J.; den Hartog, P. K.; Galayda, J. N.; Kim, K.-J.; Lewellen, J. W.; Moog, E. R.; Sajaev, V.; Sereno, N. S.; Travish, G.; Vinokurov, N. A.; Arnold, N. D.; Benson, C.; Berg, W.; Biggs, J. A.; Borland, M.; Carwardine, J. A.; Chae, Y.-C.; Decker, G.; Deriy, B. N.; Erdmann, M. J.; Friedsam, H.; Gold, C.; Grelick, A. E.; Hahne, M. W.; Harkay, K. C.; Huang, Z.; Lessner, E. S.; Lill, R. M.; Lumpkin, A. H.; Makarov, O. A.; Markovich, G. M.; Meyer, D.; Nassiri, A.; Noonan, J. R.; Pasky, S. J.; Pile, G.; Smith, T. L.; Soliday, R.; Tieman, B. J.; Trakhtenberg, E. M.; Trento, G. F.; Vasserman, I. B.; Walters, D. R.; Wang, X. J.; Wiemerslage, G.; Xu, S.; Yang, B.-X.

    2000-07-01

    Experimental evidence for self-amplified spontaneous emission (SASE) at 530 nm is reported. The measurements were made at the low-energy undulator test line facility at the Advanced Photon Source, Argonne National Laboratory. The experimental setup and details of the experimental results are presented, as well as preliminary analysis. This experiment extends to shorter wavelengths the operational knowledge of a linac-based SASE free-electron laser and explicitly shows the predicted exponential growth in intensity of the optical pulse as a function of length along the undulator.

  6. Broadband filters for abatement of spontaneous emission in circuit quantum electrodynamics

    SciTech Connect

    Bronn, Nicholas T. Hertzberg, Jared B.; Córcoles, Antonio D.; Gambetta, Jay M.; Chow, Jerry M.; Liu, Yanbing; Houck, Andrew A.

    2015-10-26

    The ability to perform fast, high-fidelity readout of quantum bits (qubits) is essential to the goal of building a quantum computer. However, coupling a fast measurement channel to a superconducting qubit typically also speeds up its relaxation via spontaneous emission. Here, we use impedance engineering to design a filter by which photons may easily leave the resonator at the cavity frequency but not at the qubit frequency. We implement this broadband filter in both an on-chip and off-chip configuration.

  7. Trace element emissions from spontaneous combustion of gob piles in coal mines, Shanxi, China

    USGS Publications Warehouse

    Zhao, Y.; Zhang, Jiahua; Chou, C.-L.; Li, Y.; Wang, Z.; Ge, Y.; Zheng, C.

    2008-01-01

    The emissions of potentially hazardous trace elements from spontaneous combustion of gob piles from coal mining in Shanxi Province, China, have been studied. More than ninety samples of solid waste from gob piles in Shanxi were collected and the contents of twenty potentially hazardous trace elements (Be, F, V, Cr, Mn, Co, Ni, Cu, Zn, As, Se, Mo, Cd, Sn, Sb, Hg, Tl, Pb, Th, and U) in these samples were determined. Trace element contents in solid waste samples showed wide ranges. As compared with the upper continental crust, the solid waste samples are significantly enriched in Se (20x) and Tl (12x) and are moderately enriched in F, As, Mo, Sn, Sb, Hg, Th, and U (2-5x). The solid waste samples are depleted in V, Cr, Mn, Co, Ni, Cu, and Zn. The solid waste samples are enriched in F, V, Mn, Cr, Co, Ni, Cu, Zn, Sb, Th, and U as compared with the Shanxi coals. Most trace elements are higher in the clinker than in the unburnt solid waste except F, Sn, and Hg. Trace element abundances are related to the ash content and composition of the samples. The content of F is negatively correlated with the ash content, while Pb is positively correlated with the ash. The concentrations of As, Mn, Zn, and Cd are highly positively correlated with Fe2O3 in the solid waste. The As content increases with increasing sulfur content in the solid waste. The trace element emissions are calculated for mass balance. The emission factors of trace elements during the spontaneous combustion of the gobs are determined and the trace element concentrations in the flue gas from the spontaneous combustion of solid waste are calculated. More than a half of F, Se, Hg and Pb are released to the atmosphere during spontaneous combustion. Some trace element concentrations in flue gas are higher than the national emission standards. Thus, gob piles from coal mining pose a serious environmental problem. ?? 2007 Elsevier B.V. All rights reserved.

  8. Spontaneous emission from an excited atom in the presence of N atoms and M modes

    NASA Astrophysics Data System (ADS)

    Cummings, F. W.

    1985-05-01

    The spontaneous emission of an excited two-level atom into a system of N nonexcited atoms of the same type (with N much greater than 1) in the presence of M electromagnetic-field modes is investigated analytically, applying the Hamiltonian formulation of Dicke (1954) studied by Jaynes and Cummings (1963), Tavis and Cummings (1968), and Buley and Cummings (1964). It is shown that the trapping of radiation in the system seen when one EM mode is present does not persist as M approaches N. The feasibility of an experimental verification of these phenomena is discussed.

  9. Amplified spontaneous emission from the exciplex state of a conjugated polymer "PFO" in oleic acid

    NASA Astrophysics Data System (ADS)

    Idriss, Hajo; Taha, Kamal K.; Aldaghri, O.; Alhathlool, R.; AlSalhi, M. S.; Ibnaouf, K. H.

    2016-09-01

    The amplified spontaneous emission (ASE) characteristics of a conjugated polymer poly (9, 9-dioctylfluorenyl-2, 7-diyl) (PFO) in oleic acid have been studied under different concentrations and temperatures. Here, the ASE spectra of PFO in oleic acid have been obtained using a transverse cavity configuration where the conjugated PFO was pumped by laser pulses from the third harmonic of Nd: YAG laser (355 nm). The PFO in oleic acid produces ASE from an exciplex state - a new molecular species. The obtained results were compared with the PFO in benzene. Such ASE spectra from the exciplex state have not been observed for the PFO in benzene.

  10. Transverse amplified spontaneous emission: The limiting factor for output energy of ultra-high power lasers

    NASA Astrophysics Data System (ADS)

    Chvykov, Vladimir; Nees, John; Krushelnick, Karl

    2014-02-01

    For the new generation of the ultra-high power lasers with tens of PW of output power, kJ-level energies have to be reached. Our modeling, applied to Ti:sapphire amplifiers, demonstrates for the first time, according our knowledge, that Transverse Amplified Spontaneous Emission (TASE) places an additional restriction on storing and extracting energy in larger gain apertures, even stronger than transverse parasitic generation (TPG). Nevertheless, we demonstrate that extracting during pumping (EDP) can significantly reduce parasitic losses due to both TASE and TPG.

  11. Spontaneous-emission rates in finite photonic crystals of plane scatterers.

    PubMed

    Wubs, Martijn; Suttorp, L G; Lagendijk, A

    2004-01-01

    The concept of a plane scatterer that was developed earlier for scalar waves is generalized so that polarization of light is included. Starting from a Lippmann-Schwinger formalism for vector waves, we show that the Green function has to be regularized before T matrices can be defined in a consistent way. After the regularization, optical modes and Green functions are determined exactly for finite structures built up of an arbitrary number of parallel planes, at arbitrary positions, and where each plane can have different optical properties. The model is applied to the special case of finite crystals consisting of regularly spaced identical planes, where analytical methods can be taken further and only light numerical tasks remain. The formalism is used to calculate position- and orientation-dependent spontaneous-emission rates inside and near the finite photonic crystals. The results show that emission rates and reflection properties can differ strongly for scalar and for vector waves. The finite size of the crystal influences the emission rates. For parallel dipoles close to a plane, emission into guided modes gives rise to a peak in the frequency-dependent emission rate. PMID:14995745

  12. Plasma effects on the spontaneous emission of synchrotron radiation from weakly relativistic electrons

    NASA Technical Reports Server (NTRS)

    Freund, H. P.; Wu, C. S.

    1977-01-01

    A method for computing the spectral emissivity of spontaneous synchrotron radiation is discussed. The Klimontovich (1967) formalism in plasma kinetic theory is adopted in which an ensemble average of the microscopically emitted power is considered. The present method clarifies the meaning of the random phase approximation which is imposed in several existing theories of synchrotron radiation. Both the effects of dielectric polarization and two-particle correlations are included in the present discussion. The theory is applied to the case of a plasma in thermal equilibrium, for which it is shown that the effect of pair correlations on the emissivity vanishes. On the other hand, the effect of dielectric polarization is studied numerically for a wide range of parameters.

  13. Monte Carlo simulation of the atomic master equation for spontaneous emission

    NASA Astrophysics Data System (ADS)

    Dum, R.; Zoller, P.; Ritsch, H.

    1992-04-01

    A Monte Carlo simulation of the atomic master equation for spontaneous emission in terms of atomic wave functions is developed. Realizations of the time evolution of atomic wave functions are constructed that correspond to an ensemble of atoms driven by laser light undergoing a sequence of spontaneous emissions. The atomic decay times are drawn according to the photon count distribution of the driven atom. Each quantum jump of the atomic electron projects the atomic wave function to the ground state of the atom. Our theory is based on a stochastic interpretation and generalization of Mollow's pure-state analysis of resonant light scattering, and the Srinivas-Davies theory of continuous measurements in photodetection. An extension of the theory to include mechanical light effects and a generalization to atomic systems with Zeeman substructure are given. We illustrate the method by simulating the solutions of the optical Bloch equations for two-level systems, and laser cooling of a two-level atom in an ion trap where the center-of-mass motion of the atom is described quantum mechanically.

  14. The generation of amplified spontaneous emission in high‐power CPA laser systems

    PubMed Central

    Sävert, Alexander; Körner, Jörg; Hornung, Marco; Liebetrau, Hartmut; Hein, Joachim; Kaluza, Malte Christoph

    2015-01-01

    Abstract An analytical model is presented describing the temporal intensity contrast determined by amplified spontaneous emission in high‐intensity laser systems which are based on the principle of chirped pulse amplification. The model describes both the generation and the amplification of the amplified spontaneous emission for each type of laser amplifier. This model is applied to different solid state laser materials which can support the amplification of pulse durations ≤350 fs . The results are compared to intensity and fluence thresholds, e.g. determined by damage thresholds of a certain target material to be used in high‐intensity applications. This allows determining if additional means for contrast improvement, e.g. plasma mirrors, are required for a certain type of laser system and application. Using this model, the requirements for an optimized high‐contrast front‐end design are derived regarding the necessary contrast improvement and the amplified “clean” output energy for a desired focussed peak intensity. Finally, the model is compared to measurements at three different high‐intensity laser systems based on Ti:Sapphire and Yb:glass. These measurements show an excellent agreement with the model. PMID:27134684

  15. Spontaneous emission of electromagnetic and electrostatic fluctuations in magnetized plasmas: Quasi-parallel modes

    NASA Astrophysics Data System (ADS)

    Kim, Sunjung; Yoon, Peter H.; Choe, G. S.

    2016-02-01

    The present paper is devoted to the theoretical and numerical analysis of the spontaneously emitted electromagnetic fluctuations characterized by quasi-parallel wave vectors relative to the ambient magnetic field. The formulation is based upon the Klimontovich plasma kinetic theory. The comparative study is carried out between the spontaneously emitted field fluctuation spectrum constructed on the basis of a single Maxellian velocity distribution function (VDF) and the spectrum that arises from multi-component electron VDFs similar to those found in the solar wind. Typical solar wind electron VDF is composed of a Gaussian core and kappa distributions of halo and super-halo components. Of these, the halo and super-halo populations represent tenuous but energetic components. It is found that the energetic electrons make important contributions to the total emission spectrum. It is also found that the halo electrons are largely responsible for the emission spectrum in the whistler frequency range, whereas the more energetic super-halo electrons emit quasi-longitudinal fluctuations in the Langmuir frequency range, thus validating the recent quasi-steady state model of the solar wind electrons put forth by the present authors [Kim et al., Astrophys. J. 806, 32 (2015); Yoon et al., Astrophys. J. 812, 169 (2015)].

  16. On the spontaneous emission of electromagnetic radiation in the CSL model

    NASA Astrophysics Data System (ADS)

    Donadi, Sandro; Deckert, Dirk-André; Bassi, Angelo

    2014-01-01

    Spontaneous photon emission in the Continuous Spontaneous Localization (CSL) model is studied one more time. In the CSL model each particle interacts with a noise field that induces the collapse of its wave function. As a consequence of this interaction, when the particle is electrically charged, it radiates. As discussed in Adler (2013) the formula for the emission rate, to first perturbative order, contains two terms: one is proportional to the Fourier component of the noise field at the same frequency as that of the emitted photon and one is proportional to the zero Fourier component of the noise field. As discussed in previous works, this second term seems unphysical. In Adler (2013) it was shown that the unphysical term disappears when the noise is confined to a bounded region and the final particle's state is a wave packet. Here we investigate the origin of this unphysical term and why it vanishes according to the previous prescription. We will see that perturbation theory is formally not valid in the large time limit since the effect of the noise accumulates continuously in time. Therefore either one performs an exact calculation (or at least in some way includes higher order terms) as we do here, or one finds a way to make a perturbative calculation meaningful, e.g., by confining the system as in Adler (2013).

  17. Performance of a quantum teleportation protocol based on collective spontaneous emission

    SciTech Connect

    Wagner, Richard Jr.; Clemens, James P.

    2009-03-15

    Recently a conditional quantum teleportation protocol has been proposed by Chen et al. [New J. Phys. 7, 172 (2005)], which is based on the collective spontaneous emission of a photon from a pair of quantum dots. We formulate a similar protocol for collective emission from a pair of atoms, one of which is entangled with a single mode of an optical cavity. We focus on the performance of the protocol as characterized by the fidelity of the teleported state and the overall success probability. We consider a strategy employing spatially resolved photodetection of the emitted photon in order to distinguish superradiant from subradiant emission on the basis of a single detected photon. We find that fidelity approaches unity as the spacing of the atoms becomes much smaller than the emission wavelength with a success probability of 0.25. The fidelity remains above the classical limit of 2/3 for arbitrary atomic separations with the ultimate limit of performance coming from the spatial resolution of the detectors.

  18. Epitaxy, phase separation and band-edge emission of spontaneously formed InGaN nanorods

    NASA Astrophysics Data System (ADS)

    De, Arpan; Shivaprasad, S. M.

    2016-09-01

    An In-flux dependent study of the nature of epitaxy, compositional phase separation and band-edge emission of spontaneously formed c-oriented InGaN nanorods on c-sapphire is performed. At higher In flux-rates, m-faceted thick nanorods (≈700 nm) form with two in-plane epitaxial orientations, and display compositional phases with In composition varying from 14 to 63%. In these rods, photo-luminescent (PL) emission is seen to originate only from the localized high-In phase (63%) that is embedded in the low-In (14%) InGaN matrix. As the In flux-rate is reduced, nanorods of smaller diameter (≈60 nm) and a coalesced nanorod network are formed, with In incorporation of 15% and 9%, respectively. These faceted, c-aligned thinner nanorods are of a single compositional phase and epitaxy and display room-temperature PL emission. Optical absorption and emission properties of these nanostructures follow Vegard’s law of band-gaps, and the observed bowing parameter and Stokes shifts correlate to the observed compositional inhomogeneity and carrier localization.

  19. Frequency selectivity of the human cochlea: Suppression tuning of spontaneous otoacoustic emissions.

    PubMed

    Manley, Geoffrey A; van Dijk, Pim

    2016-06-01

    Frequency selectivity is a key functional property of the inner ear and since hearing research began, the frequency resolution of the human ear has been a central question. In contrast to animal studies, which permit invasive recording of neural activity, human studies must rely on indirect methods to determine hearing selectivity. Psychophysical studies, which used masking of a tone by other sounds, indicate a modest frequency selectivity in humans. By contrast, estimates using the phase delays of stimulus-frequency otoacoustic emissions (SFOAE) predict a remarkably high selectivity, unique among mammals. An alternative measure of cochlear frequency selectivity are suppression tuning curves of spontaneous otoacoustic emissions (SOAE). Several animal studies show that these measures are in excellent agreement with neural frequency selectivity. Here we contribute a large data set from normal-hearing young humans on suppression tuning curves (STC) of spontaneous otoacoustic emissions (SOAE). The frequency selectivities of human STC measured near threshold levels agree with the earlier, much lower, psychophysical estimates. They differ, however, from the typical patterns seen in animal auditory nerve data in that the selectivity is remarkably independent of frequency. In addition, SOAE are suppressed by higher-level tones in narrow frequency bands clearly above the main suppression frequencies. These narrow suppression bands suggest interactions between the suppressor tone and a cochlear standing wave corresponding to the SOAE frequency being suppressed. The data show that the relationship between pre-neural mechanical processing in the cochlea and neural coding at the hair-cell/auditory nerve synapse needs to be reconsidered. PMID:27139323

  20. Final LDRD report : enhanced spontaneous emission rate in visible III-nitride LEDs using 3D photonic crystal cavities.

    SciTech Connect

    Fischer, Arthur Joseph; Subramania, Ganapathi S.; Coley, Anthony J.; Lee, Yun-Ju; Li, Qiming; Wang, George T.; Luk, Ting Shan; Koleske, Daniel David; Fullmer, Kristine Wanta

    2009-09-01

    The fundamental spontaneous emission rate for a photon source can be modified by placing the emitter inside a periodic dielectric structure allowing the emission to be dramatically enhanced or suppressed depending on the intended application. We have investigated the relatively unexplored realm of interaction between semiconductor emitters and three dimensional photonic crystals in the visible spectrum. Although this interaction has been investigated at longer wavelengths, very little work has been done in the visible spectrum. During the course of this LDRD, we have fabricated TiO{sub 2} logpile photonic crystal structures with the shortest wavelength band gap ever demonstrated. A variety of different emitters with emission between 365 nm and 700 nm were incorporated into photonic crystal structures. Time-integrated and time-resolved photoluminescence measurements were performed to measure changes to the spontaneous emission rate. Both enhanced and suppressed emission were demonstrated and attributed to changes to the photonic density of states.

  1. Exhaust emission control and diagnostics

    DOEpatents

    Mazur, Christopher John; Upadhyay, Devesh

    2006-11-14

    A diesel engine emission control system uses an upstream oxidation catalyst and a downstream SCR catalyst to reduce NOx in a lean exhaust gas environment. The engine and upstream oxidation catalyst are configured to provide approximately a 1:1 ratio of NO to NO2 entering the downstream catalyst. In this way, the downstream catalyst is insensitive to sulfur contamination, and also has improved overall catalyst NOx conversion efficiency. Degradation of the system is determined when the ratio provided is no longer near the desired 1:1 ratio. This condition is detected using measurements of engine operating conditions such as from a NOx sensor located downstream of the catalysts. Finally, control action to adjust an injected amount of reductant in the exhaust gas based on the actual NO to NO2 ratio upstream of the SCR catalyst and downstream of the oxidation catalyst.

  2. Observation of novel radioactive decay by spontaneous emission of complex nuclei

    SciTech Connect

    Barwick, S.W.

    1986-01-01

    Two years of experimental investigation on the subject of spontaneous emission of intermediate-mass fragments is described in this manuscript. A short introduction on this subject and a historical review are presented in chapter 1. In chapter 2, the author describe the experimental methods which led to the observation of /sup 14/C emission in polycarbonate etched-track detectors from the isotopes /sup 222/Ra, /sup 223/Ra, /sup 224/Ra and /sup 226/Ra at the branching ratios with respect to ..cap alpha..-decay of (3.7 +/- 0.6) x 10/sup -10/, (6.1 +/- 1.0) x 10/sup -10/, (4.3 +/- 1.2) x 10/sup -10/ and (2.9 +/- 1.0) x 10/sup -11/ respectively. Branching ratio limits for heavy-ion emission from /sup 221/Fr, /sup 221/Ra and /sup 225/Ac were determined to be at < 5.0 x 10/sup -14/, < 1.2 x 10/sup -13/ and < 4.0 x 10/sup -13/ respectively for the 90% C.L. The emission of /sup 24/Ne from /sup 232/U at a branching ratio of (2.0 +/- 0.5) x 10/sup -12/ has been discovered using polyethylene terephthalate etched-track plastics. A confirmation of /sup 24/Ne and/or /sup 25/Ne emission from /sup 233/U at a branching ratio of (5.3 +/- 2.3) x 10/sup -13/ is also reported. In chapter 3, three models of intermediate-mass decay are discussed-the analytic superasymmetric fission model, the model by Shi and Swiatecki, and a model based on a square-well + Coulomb potential.

  3. Enhanced amplified spontaneous emission in a quantum dot-doped polymer-dispersed liquid crystal.

    PubMed

    Cao, Mingxuan; Zhang, Yating; Song, Xiaoxian; Che, Yongli; Zhang, Haiting; Yan, Chao; Dai, Haitao; Liu, Guang; Zhang, Guizhong; Yao, Jianquan

    2016-07-01

    Quantum dot-doped polymer-dispersed liquid crystals (QD-PDLCs) were prepared by photoinitiated polymerization and sealed in capillary tubes. The concentration of QDs in the PDLC was 1 wt%. Amplified spontaneous emission (ASE) of the quantum dot-doped polymer-dispersed liquid crystals was observed with 532 nm wavelength laser excitation. The threshold for ASE was 6 mJ cm(-2), which is much lower than that for homogeneous quantum dot-doped polymer (25 mJ cm(-2)). The threshold for ASE was dramatically enhanced when the working temperature exceeded the clearing point of the liquid crystal; this result demonstrates that multi-scattering caused by the liquid crystals effectively improved the path length or dwell time of light in the gain region, which played a key role in decreasing the threshold for ASE. PMID:27196786

  4. Enhanced amplified spontaneous emission using layer-by-layer assembled cowpea mosaic virus

    NASA Astrophysics Data System (ADS)

    Li, Na; Deng, Zhaoqi; Lin, Yuan; Zhang, Xiaojie; Geng, Yanhou; Ma, Dongge; Su, Zhaohui

    2009-01-01

    Layer-by-layer assembly technique was used to construct ultrathin film of cowpea mosaic virus (CPMV) by electrostatic interactions, and the film was employed as a precursor on which an OF8T2 film was deposited by spin coating. Amplified spontaneous emission (ASE) was observed and improved for the OF8T2 film. Compared with OF8T2 film on quartz, the introduction of CPMV nanoparticles reduced the threshold and loss, and remarkably increased the net gain. The threshold, loss, and gain reached 0.05 mJ/pulse, 6.9 cm-1, and 82 cm-1, respectively. CPMV nanoparticles may enormously scatter light, resulting in a positive feedback, thus the ASE is easily obtained and improved.

  5. Low threshold amplified spontaneous emission from dye-doped DNA biopolymer

    NASA Astrophysics Data System (ADS)

    Hung, Yu-Chueh; Su, Che-Hsuan; Huang, Hsien-Wen

    2012-06-01

    In this study, we investigate the amplified spontaneous emission (ASE) properties and conduct a comparative study for two kinds of dye-doped deoxyribonucleic acid (DNA) biopolymers. The system consists of optical films made of DNA modified by two types of surfactants and doped with a common laser dye rhodamine 6G (Rh6G). The ASE properties of the optical films were characterized by a pulsed Nd:YAG laser. The results show that low threshold of DNA biopolymer can be achieved by the employment of suitable surfactant in the system, resulting from an efficient energy transfer process. Coupled with the fluorescence enhancement exhibited in DNA, this effect can further advance biopolymers toward highly efficient media for lasing applications and organic solid-state lasers.

  6. Spontaneous emission of the Super-ACO fel optical klystron domino

    NASA Astrophysics Data System (ADS)

    Couprie, M. E.; Bazin, C.; Billardon, M.; Velghe, M.

    1989-12-01

    New free electron laser experiments are planned on the Orsay storage ring Super-ACO, which has been commisioned in 1987 at LURE (Laboratoire d'Utilisation du Rayonnement Electromagnétique). For this purpose, a new insertion device, DOMINO, was set up on Super-ACO in January 1988; it consists of a permanent magnet optical klystron composed of two undulators separated by a dispersive section; the magnetic gaps can be changed independently. Here, the parameters of the optical klystron are specified, and the main steps of the optimization are described. Then, the effect of the insertion device on the stored beam is discussed. The spontaneous emission of the optical klystron has been observed and analysed. Consequently, with the ring parameters measurements, the free electron laser gain versus the current can be evaluated.

  7. Amplified spontaneous emission from a new 4-triarylamine substituted 1,8-naphthalimide semiconductor oligomer

    NASA Astrophysics Data System (ADS)

    Lu, Wu; Tu, Guoli; Zhong, Bo; Ma, Dongge; Wang, Lixiang; Jing, Xiabin; Wang, Fosong

    2005-06-01

    Amplified spontaneous emission has been observed in a new semiconductor oligomer of 2-decyl-6-{[4'-(naphthalene-1-yl-phenyl-amino)-biphenyl-4-yl]-[4-(naphthalene-1-yl-phenyl-amino)-phenyl]-amino}-benzo[ de]isoquinoline-1,3-dione (4-triarylamine substituted 1,8-naphthalimide TAANPI) doped polymer films pumped by the second harmonic of a Nd:YAG laser. The dependence of the threshold and gain on the oligomer concentration in polymer was studied in detail. It was found that the semiconductor oligomer shows low threshold, high gain and low loss even though the doped oligomer concentration is up to 60%, indicating a low concentration quenching effect. This demonstrates that the oligomer could be a promising candidate as gain medium for organic diode lasers.

  8. Temporal phase mask encrypted optical steganography carried by amplified spontaneous emission noise.

    PubMed

    Wu, Ben; Wang, Zhenxing; Shastri, Bhavin J; Chang, Matthew P; Frost, Nicholas A; Prucnal, Paul R

    2014-01-13

    A temporal phase mask encryption method is proposed and experimentally demonstrated to improve the security of the stealth channel in an optical steganography system. The stealth channel is protected in two levels. In the first level, the data is carried by amplified spontaneous emission (ASE) noise, which cannot be detected in either the time domain or spectral domain. In the second level, even if the eavesdropper suspects the existence of the stealth channel, each data bit is covered by a fast changing phase mask. The phase mask code is always combined with the wide band noise from ASE. Without knowing the right phase mask code to recover the stealth data, the eavesdropper can only receive the noise like signal with randomized phase. PMID:24515055

  9. Spontaneous Hot-Electron Light Emission from Electron-Fed Optical Antennas.

    PubMed

    Buret, Mickael; Uskov, Alexander V; Dellinger, Jean; Cazier, Nicolas; Mennemanteuil, Marie-Maxime; Berthelot, Johann; Smetanin, Igor V; Protsenko, Igor E; Colas-des-Francs, Gérard; Bouhelier, Alexandre

    2015-09-01

    Nanoscale electronics and photonics are among the most promising research areas providing functional nanocomponents for data transfer and signal processing. By adopting metal-based optical antennas as a disruptive technological vehicle, we demonstrate that these two device-generating technologies can be interfaced to create an electronically driven self-emitting unit. This nanoscale plasmonic transmitter operates by injecting electrons in a contacted tunneling antenna feedgap. Under certain operating conditions, we show that the antenna enters a highly nonlinear regime in which the energy of the emitted photons exceeds the quantum limit imposed by the applied bias. We propose a model based upon the spontaneous emission of hot electrons that correctly reproduces the experimental findings. The electron-fed optical antennas described here are critical devices for interfacing electrons and photons, enabling thus the development of optical transceivers for on-chip wireless broadcasting of information at the nanoscale. PMID:26214575

  10. Enhanced amplified spontaneous emission in a quantum dot-doped polymer-dispersed liquid crystal

    NASA Astrophysics Data System (ADS)

    Cao, Mingxuan; Zhang, Yating; Song, Xiaoxian; Che, Yongli; Zhang, Haiting; Yan, Chao; Dai, Haitao; Liu, Guang; Zhang, Guizhong; Yao, Jianquan

    2016-07-01

    Quantum dot-doped polymer-dispersed liquid crystals (QD-PDLCs) were prepared by photoinitiated polymerization and sealed in capillary tubes. The concentration of QDs in the PDLC was 1 wt%. Amplified spontaneous emission (ASE) of the quantum dot-doped polymer-dispersed liquid crystals was observed with 532 nm wavelength laser excitation. The threshold for ASE was 6 mJ cm‑2, which is much lower than that for homogeneous quantum dot-doped polymer (25 mJ cm‑2). The threshold for ASE was dramatically enhanced when the working temperature exceeded the clearing point of the liquid crystal; this result demonstrates that multi-scattering caused by the liquid crystals effectively improved the path length or dwell time of light in the gain region, which played a key role in decreasing the threshold for ASE.

  11. Nematicon-driven injection of amplified spontaneous emission into an optical fiber.

    PubMed

    Bolis, Serena; Virgili, Tersilla; Rajendran, Sai Kiran; Beeckman, Jeroen; Kockaert, Pascal

    2016-05-15

    We investigate experimentally the interaction between amplified spontaneous emission (ASE) and a soliton, which are both generated in a dye-doped nematic liquid crystal (LC) cell. A light beam is injected through an optical fiber slid into the cell to form a soliton beam. ASE is then automatically collected by this self-induced waveguide and efficiently coupled into the same optical fiber, in the backward direction. We demonstrate that the presence of the soliton improves the ASE collection by one order of magnitude. We also show that the ASE is highly polarized in the plane of the LC cell and that the ASE spectrum depends on the pump stripe orientation with respect to the LC director. The origin of the spectral anisotropy of the gain curves is determined with the help of femtosecond pump-probe spectroscopy. PMID:27176973

  12. Spontaneous emission of radiation by relativistic electrons in a gyro-klystron

    NASA Astrophysics Data System (ADS)

    Mishra, G.; Prakash, Bramha; Sharma, Geetanjali

    2016-03-01

    In this paper, we study spontaneous emission of radiation by relativistic electrons in a gyro-klystron. The scheme consists of two solenoid sections separated by a dispersive section. In the dispersive section the electrons are made non resonant with the radiation. The dispersive section transforms a small change of the velocity into changes of the phases of the electrons.This leads to enhanced radiation as compared to a conventional gyrotron type device driven by cyclotron maser interaction. It is shown that the klystron modulated spectrum depends on the dispersive field strength, finite perpendicular velocity component and length of the solenoids but do not depend on the axial magnetic field strength. The analysis is further extended to include the combined effects of the undulator aided gyrotron klystron radiation.

  13. Enhancing mammalian hearing by a balancing between spontaneous otoacoustic emissions and spatial coupling

    NASA Astrophysics Data System (ADS)

    Liu, Zonghua; Li, Baowen; Lai, Ying-Cheng

    2012-04-01

    Nonlinear dynamics has provided significant insights into the origin of frequency discrimination and signal amplification underlying mammalian hearing. Existing signal amplification models, however, tend to ignore two basic known aspects of the hearing: spontaneous otoacoustic emissions (SOAEs) and intrinsic dynamical coupling in the cochlea. We construct and study a class of coupled-oscillator models to remedy this deficiency. Our analysis and computations reveal that the interplay and balance between the two aspects can naturally explain the phenomena of frequency discrimination and signal amplification and, more strikingly, the origin of hearing loss, all at a quantitative level. In the presence of SOAEs, there exists a critical coupling threshold below which hearing loss can occur, suggesting enhancement of coupling as a potentially effective therapeutic strategy to restore or even significantly enhance hearing.

  14. Gravity Wave Emission by Spontaneous Imbalance of Baroclinic Waves in the Continuously Stratified Rotating Annulus

    NASA Astrophysics Data System (ADS)

    Borchert, Sebastian; Achatz, Ulrich; Rieper, Felix; Fruman, Mark

    2013-04-01

    We use a numerical model of the classic differentially heated rotating annulus experiment to study the spontaneous emission of gravity waves (GWs) from jet stream imbalances, which is a major source of these waves in the atmosphere for which no satisfactory parameterization exists. Atmospheric observations are the main tool for the testing and verification of theoretical concepts but have their limitations. Given their specific potential for yielding reproducible data and for studying process dependence on external system parameters, laboratory experiments are an invaluable complementary tool. Experiments with a rotating annulus exhibiting a jet modulated by large-scale waves due to baroclinic instability have already been used to study GWs: Williams et al (2008) observed spontaneously emitted interfacial GWs in a two-layer flow, and Jacoby et al (2011) detected GWs emitted from boundary-layer instabilities in a differentially heated rotating annulus. Employing a finite-volume code for the numerical simulation of a continuously stratified liquid in a differentially heated rotating annulus, we here investigate the GWs in a wide and shallow annulus with relatively large temperature difference between inner and outer cylinder walls. In this atmosphere-like regime where the Brunt-Vaisala frequency is larger than the inertial frequency, various analyses suggest a distinct gravity wave activity. To identify regions of GW emission we decompose the flow into the geostrophic and ageostrophic part through the inversion of the quasi-geostrophic potential vorticity (e.g. Verkley, 2009). The analysis of the geostrophic sources of the ageostrophic flow indicates that, in addition to boundary layer instabilities, spontaneous imbalance in the jet region acts as an important source mechanism. Jacoby, T. N. L., Read, P. L., Williams, P. D. and Young, R. M. B., 2011: Generation of inertia-gravity waves in the rotating thermal annulus by a localised boundary layer instability. Geophys

  15. PARTICULATE EMISSION MEASUREMENTS FROM CONTROLLED CONSTRUCTION ACTIVITIES

    EPA Science Inventory

    The report summarized the results of field testing of the effectiveness of control measures for sources of fugitive particulate emissions found at construction sites. The effectiveness of watering temporary, unpaved travel surfaces on emissions of particulate matter with aerodyna...

  16. Inhibition and enhancement of the spontaneous emission of quantum dots in micropillar cavities with radial-distributed Bragg reflectors.

    PubMed

    Jakubczyk, Tomasz; Franke, Helena; Smoleński, Tomasz; Sciesiek, Maciej; Pacuski, Wojciech; Golnik, Andrzej; Schmidt-Grund, Rüdiger; Grundmann, Marius; Kruse, Carsten; Hommel, Detlef; Kossacki, Piotr

    2014-10-28

    We present a micropillar cavity where nondesired radial emission is inhibited. The photonic confinement in such a structure is improved by implementation of an additional concentric radial-distributed Bragg reflector. Such a reflector increases the reflectivity in all directions perpendicular to the micropillar axis from a typical value of 15-31% to above 98%. An inhibition of the spontaneous emission of off-resonant excitonic states of quantum dots embedded in the microcavity is revealed by time-resolved experiments. It proves a decreased density of photonic states related to unwanted radial leakage of photons out of the micropillar. For on-resonance conditions, we find that the dot emission rate is increased, evidencing the Purcell enhancement of spontaneous emission. The proposed design can increase the efficiency of single-photon sources and bring to micropillar cavities the functionalities based on lengthened decay times. PMID:25181393

  17. Observation and analysis of self-amplified spontaneous emission at the APS low-energy undulator test line

    NASA Astrophysics Data System (ADS)

    Arnold, N. D.; Attig, J.; Banks, G.; Bechtold, R.; Beczek, K.; Benson, C.; Berg, S.; Berg, W.; Biedron, S. G.; Biggs, J. A.; Borland, M.; Boerste, K.; Bosek, M.; Brzowski, W. R.; Budz, J.; Carwardine, J. A.; Castro, P.; Chae, Y.-C.; Christensen, S.; Clark, C.; Conde, M.; Crosbie, E. A.; Decker, G. A.; Dejus, R. J.; DeLeon, H.; Den Hartog, P. K.; Deriy, B. N.; Dohan, D.; Dombrowski, P.; Donkers, D.; Doose, C. L.; Dortwegt, R. J.; Edwards, G. A.; Eidelman, Y.; Erdmann, M. J.; Error, J.; Ferry, R.; Flood, R.; Forrestal, J.; Freund, H.; Friedsam, H.; Gagliano, J.; Gai, W.; Galayda, J. N.; Gerig, R.; Gilmore, R. L.; Gluskin, E.; Goeppner, G. A.; Goetzen, J.; Gold, C.; Gorski, A. J.; Grelick, A. E.; Hahne, M. W.; Hanuska, S.; Harkay, K. C.; Harris, G.; Hillman, A. L.; Hogrefe, R.; Hoyt, J.; Huang, Z.; Jagger, J. M.; Jansma, W. G.; Jaski, M.; Jones, S. J.; Keane, R. T.; Kelly, A. L.; Keyser, C.; Kim, K.-J.; Kim, S. H.; Kirshenbaum, M.; Klick, J. H.; Knoerzer, K.; Koldenhoven, R. J.; Knott, M.; Labuda, S.; Laird, R.; Lang, J.; Lenkszus, F.; Lessner, E. S.; Lewellen, J. W.; Li, Y.; Lill, R. M.; Lumpkin, A. H.; Makarov, O. A.; Markovich, G. M.; McDowell, M.; McDowell, W. P.; McNamara, P. E.; Meier, T.; Meyer, D.; Michalek, W.; Milton, S. V.; Moe, H.; Moog, E. R.; Morrison, L.; Nassiri, A.; Noonan, J. R.; Otto, R.; Pace, J.; Pasky, S. J.; Penicka, J. M.; Pietryla, A. F.; Pile, G.; Pitts, C.; Power, J.; Powers, T.; Putnam, C. C.; Puttkammer, A. J.; Reigle, D.; Reigle, L.; Ronzhin, D.; Rotela, E. R.; Russell, E. F.; Sajaev, V.; Sarkar, S.; Scapino, J. C.; Schroeder, K.; Seglem, R. A.; Sereno, N. S.; Sharma, S. K.; Sidarous, J. F.; Singh, O.; Smith, T. L.; Soliday, R.; Sprau, G. A.; Stein, S. J.; Stejskal, B.; Svirtun, V.; Teng, L. C.; Theres, E.; Thompson, K.; Tieman, B. J.; Torres, J. A.; Trakhtenberg, E. M.; Travish, G.; Trento, G. F.; Vacca, J.; Vasserman, I. B.; Vinokurov, N. A.; Walters, D. R.; Wang, J.; Wang, X. J.; Warren, J.; Wesling, S.; Weyer, D. L.; Wiemerslage, G.; Wilhelmi, K.; Wright, R.; Wyncott, D.; Xu, S.; Yang, B.-X.; Yoder, W.; Zabel, R. B.

    2001-12-01

    Exponential growth of self-amplified spontaneous emission at 530 nm was first experimentally observed at the Advanced Photon Source low-energy undulator test line in December 1999. Since then, further detailed measurements and analysis of the results have been made. Here, we present the measurements and compare these with calculations based on measured electron beam properties and theoretical expectations.

  18. EFFECTS OF INSTILLED EMISSION PARTICULATE MATTER ON ELECTROCARDIOGRAPHIC INDICES AND HEART RATE VARIABILITY (HRV) IN SPONTANEOUSLY HYPERTENSIVE RATS

    EPA Science Inventory

    EFFECTS OF INSTILLED EMISSION PARTICULATE MATTER (EPM) ON ELECTROCARDIOGRAPHIC INDICES AND HEART RATE VARIABILITY (HRV) IN SPONTANEOUSLY HYPERTENSIVE (SH) RATS. L.B. Wichers1, J.P. Nolan2, W.H. Rowan2, M.J. Campen3, T.P. Jenkins4, D.L. Costa2, and W.P. Watkinson2. 1UNC SPH, Chap...

  19. Prolonged spontaneous emission and dephasing of localized excitons in air-bridged carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Sarpkaya, Ibrahim; Zhang, Zhengyi; Walden-Newman, William; Wang, Xuesi; Hone, James; Wong, Chee W.; Strauf, Stefan

    2013-07-01

    The bright exciton emission of carbon nanotubes is appealing for optoelectronic devices and fundamental studies of light-matter interaction in one-dimensional nanostructures. However, to date, the photophysics of excitons in carbon nanotubes is largely affected by extrinsic effects. Here we perform time-resolved photoluminescence measurements over 14 orders of magnitude for ultra-clean carbon nanotubes bridging an air gap over pillar posts. Our measurements demonstrate a new regime of intrinsic exciton photophysics with prolonged spontaneous emission times up to T1=18 ns, about two orders of magnitude better than prior measurements and in agreement with values hypothesized by theorists about a decade ago. Furthermore, we establish for the first time exciton decoherence times of individual nanotubes in the time domain and find fourfold prolonged values up to T2=2.1 ps compared with ensemble measurements. These first observations motivate new discussions about the magnitude of the intrinsic dephasing mechanism while the prolonged exciton dynamics is promising for applications.

  20. Amplified spontaneous emission from a microtube cavity with whispering gallery modes

    NASA Astrophysics Data System (ADS)

    Rakovich, Y. P.; Balakrishnan, S.; Gun'ko, Y.; Perova, T. S.; Moore, A.; Donegan, J. F.

    2007-05-01

    We present a detailed study of the photonic modes in microtube cavity of ~ 7-8 μm outer diameter that can act as micron-scale optical cylindrical resonator. We demonstrate a new route to the fabrication of individual microtubes with the maximum length of 200 μm, using a vacuum assisted wetting and filtration through a microchannel glass matrix. The microtubes were studied using micro-photoluminescence spectroscopy and luminescence lifetime imaging confocal microscopy. In the emission spectra of the microresonators we find periodic very narrow peaks corresponding to the whispering gallery modes of two orthogonal polarizations with quality factors upto 3200 at room temperature. In order to identify the peaks in the observed mode structure, we have adopted the boundary-value solution to the problem of scattering of electromagnetic waves by a dielectric micro-cylinder. A strong enhancement in photoluminescence decay rates at high excitation power suggest the occurrence of amplified spontaneous emission from a single microtube. The evanescent field in these photonic structures extends a couple of micrometers into the surroundings providing the possibility for efficient coupling to an external photonic device.

  1. Spectroscopic properties and amplified spontaneous emission of fluorescein laser dye in ionic liquids as green media

    NASA Astrophysics Data System (ADS)

    AL-Aqmar, Dalal M.; Abdelkader, H. I.; Abou Kana, Maram T. H.

    2015-09-01

    The use of ionic liquids (ILs) as milieu materials for laser dyes is a promising field and quite competitive with volatile organic solvents and solid state-dye laser systems. This paper investigates some photo-physical parameters of fluorescein dye incorporated into ionic liquids; 1-Butyl-3-methylimidazolium chloride (BMIM Cl), 1-Butyl-3-methylimidazolium tetrachloroaluminate (BMIM AlCl4) and 1-Butyl-3-methylimidazolium tetrafluoroborate (BMIM BF4) as promising host matrix in addition to ethanol as reference. These parameters are: absorption and emission cross-sections, fluorescence lifetime and quantum yield, in addition to the transition dipole moment, the attenuation length and oscillator strength were also investigated. Lasing characteristics such as amplified spontaneous emission (ASE), the gain, and the photostability of fluorescein laser dye dissolved in different host materials were assessed. The composition and properties of the matrix of ILs were found that it has great interest in optimizing the laser performance and photostability of the investigated laser dye. Under transverse pumping of fluorescein dye by blue laser diode (450 nm) of (400 mW), the initial ASE for dye dissolved in BMIM AlCl4 and ethanol were decreased to 39% and 36% respectively as time progressed 132 min. Relatively high efficiency and high fluorescence quantum yield (11.8% and 0.82% respectively) were obtained with good photostability in case of fluorescein in BMIM BF4 that was decreased to ∼56% of the initial ASE after continuously pumping with 400 mW for 132 min.

  2. Impact of photodepletion to amplified spontaneous emission of proton-transfer dyes in polymeric matrices

    NASA Astrophysics Data System (ADS)

    Täuber, U.; Carvalho, C. E. M.; Dos Santos, R. F.; Carvalhaes, C. G.; Fellows, C. E.

    2007-05-01

    A six level rate equation system was used to investigate the impact of photodepletion to amplified spontaneous emission (ASE) of intramolecular proton-transfer (IPT) dyes incorporated into polymeric hosts. The model includes the most important transitions for the normal and tautomer form of the molecule as well as intersystem crossing and triplet-triplet transitions. The experimentally observed pulse shape as well as photodepletion phenomena, i.e. a first order exponential decay of the ASE intensity and a shortening in ASE pulse width, have been simulated successfully. Additionally, the model was used to propose an explanation of the unexpected high photodepletion of proton-transfer dyes in solids. The results show that the emission cross section and reabsorption cross section of the tautomer form of the molecule are the most important parameter not only for efficiency but also for photodepletion. The model was tested by comparison with experimental results of 2-(2’-hydroxyphenyl)benzimidazole in polymethylmethacrylate (PMMA), polystyrene (PS) and a 1:1 alternating copolymer matrix PS-co-PMMA.

  3. Gravity Wave Emission by Spontaneous Imbalance of Baroclinic Waves in the Continuously Stratified Rotating Annulus

    NASA Astrophysics Data System (ADS)

    Borchert, S.; Achatz, U.; Rieper, F.; Fruman, M. D.

    2012-04-01

    We use a numerical model of the classic differentially heated rotating annulus experiment to study the spontaneous emission of gravity waves (GWs) from jet stream imbalances, which is a major source of these waves in the atmosphere for which no satisfactory parameterization exists. Atmospheric observations are the main tool for the testing and verification of theoretical concepts but have their limitations. Given their specific potential for yielding reproducible data and for studying process dependence on external system parameters, laboratory experiments are an invaluable complementary tool. Experiments with a rotating annulus exhibiting a jet modulated by large-scale waves due to baroclinic instability have already been used to study GWs: Williams et al (2008) observed spontaneously emitted interfacial GWs in a two-layer flow, and Jacoby et al (2011) detected GWs emitted from boundary-layer instabilities in a differentially heated rotating annulus. Employing a new finite-volume code for the numerical simulation of a continuously stratified liquid in a differentially heated rotating annulus, we here investigate whether such an experiment might be useful for studies of spontaneous imbalance. A major problem was the identification of experimental parameters yielding an atmosphere-like regime where the Brunt-Vaisala frequency is larger than the inertial frequency, so that energy transport by the lowest-frequency waves is predominantly horizontal while high-frequency GWs transport energy vertically. We show that this is indeed the case for a wide and shallow annulus with relatively large temperature difference between the inner and outer cylinder walls. We also show that this set-up yields a conspicuous signal in the horizontal divergence field close to the meandering jet. Various analyses support the notion that this signal is predominantly due to GWs superposed on a geostrophic flow. Jacoby, T. N. L., Read, P. L., Williams, P. D. and Young, R. M. B., 2011

  4. Coke pushing emission control system

    SciTech Connect

    Kwasnoski, D.; Symons, C.

    1980-07-08

    A method is described for controlling coke oven emissions comprising the steps of: (A) aligning a one-spot, open-top coke quenching car with the coke oven, (B) providing a coke guide from the coke oven to the car, (C) positioning a fume hood over the car, with the fume hood having a length about equal to the length of the car, (D) pushing hot coke from the coke oven through the coke guide and into the car, (E) withdrawing gases from the fume hood during step (D) and passing said gases to gas cleaning equipment at a gas flowrate of between about 1000 and about 3500 scfmd per ton of coke pushed under step (D), and (F) substantially upon completion of step (E) moving the car from under the fume hood to a quenching station with the hot coke in the car exposed to the atmosphere and without further withdrawal of gases from the hot coke to the gas cleaning equipment.

  5. Loss of the Tectorial Membrane Protein CEACAM16 Enhances Spontaneous, Stimulus-Frequency, and Transiently Evoked Otoacoustic Emissions

    PubMed Central

    Goodyear, Richard J.; Homma, Kazuaki; Legan, P. Kevin; Korchagina, Julia; Naskar, Souvik; Siegel, Jonathan H.; Dallos, Peter; Zheng, Jing

    2014-01-01

    α-Tectorin (TECTA), β-tectorin (TECTB), and carcinoembryonic antigen-related cell adhesion molecule 16 (CEACAM) are secreted glycoproteins that are present in the tectorial membrane (TM), an extracellular structure overlying the hearing organ of the inner ear, the organ of Corti. Previous studies have shown that TECTA and TECTB are both required for formation of the striated-sheet matrix within which collagen fibrils of the TM are imbedded and that CEACAM16 interacts with TECTA. To learn more about the structural and functional significance of CEACAM16, we created a Ceacam16-null mutant mouse. In the absence of CEACAM16, TECTB levels are reduced, a clearly defined striated-sheet matrix does not develop, and Hensen's stripe, a prominent feature in the basal two-thirds of the TM in WT mice, is absent. CEACAM16 is also shown to interact with TECTB, indicating that it may stabilize interactions between TECTA and TECTB. Although brain-stem evoked responses and distortion product otoacoustic emissions are, for most frequencies, normal in young mice lacking CEACAM16, stimulus-frequency and transiently evoked emissions are larger. We also observed spontaneous otoacoustic emissions (SOAEs) in 70% of the homozygous mice. This incidence is remarkable considering that <3% of WT controls have SOAEs. The predominance of SOAEs >15 kHz correlates with the loss of Hensen's stripe. Results from mice lacking CEACAM16 are consistent with the idea that the organ of Corti evolved to maximize the gain of the cochlear amplifier while preventing large oscillations. Changes in TM structure appear to influence the balance between energy generation and dissipation such that the system becomes unstable. PMID:25080593

  6. Realization of dynamic thermal emission control.

    PubMed

    Inoue, Takuya; De Zoysa, Menaka; Asano, Takashi; Noda, Susumu

    2014-10-01

    Thermal emission in the infrared range is important in various fields of research, including chemistry, medicine and atmospheric science. Recently, the possibility of controlling thermal emission based on wavelength-scale optical structures has been intensively investigated with a view towards a new generation of thermal emission devices. However, all demonstrations so far have involved the 'static' control of thermal emission; high-speed modulation of thermal emission has proved difficult to achieve because the intensity of thermal emission from an object is usually determined by its temperature, and the frequency of temperature modulation is limited to 10-100 Hz even when the thermal mass of the object is small. Here, we experimentally demonstrate the dynamic control of thermal emission via the control of emissivity (absorptivity), at a speed four orders of magnitude faster than is possible using the conventional temperature-modulation method. Our approach is based on the dynamic control of intersubband absorption in n-type quantum wells, which is enhanced by an optical resonant mode in a photonic crystal slab. The extraction of electrical carriers from the quantum wells leads to an immediate change in emissivity from 0.74 to 0.24 at the resonant wavelength while maintaining much lower emissivity at all other wavelengths. PMID:25064232

  7. Mono- to few-layered graphene oxide embedded randomness assisted microcavity amplified spontaneous emission source.

    PubMed

    Das, Pratyusha; Maiti, Rishi; Barman, Prahalad K; Ray, Samit K; Shivakiran, Bhaktha B N

    2016-02-01

    The realization of optoelectronic devices using two-dimensional materials such as graphene and its intermediate product graphene oxide (GO) is extremely challenging owing to the zero band gap of the former. Here, a novel amplified spontaneous emission (ASE) system based on a GO-embedded all-dielectric one-dimensional photonic crystal (1DPhC) micro-resonator is presented. The mono- to few-layered GO sheet is inserted within a microcavity formed by two 5-bilayered SiO2/SnO2 Bragg reflectors. Significantly enhanced photoluminescence (PL) emission of GO embedded in 1DPhC is explicated by studying the electric field confined within the micro-resonator using the transfer matrix method. The inherent randomness, due to fabrication limitations, in the on-average periodic 1DPhC is exploited to further enhance the PL of the optically active micro-resonator. The 1DPhC and randomness assisted field confinement reduces the ASE threshold of the mono- to few-layered weak emitter making the realization of an ASE source feasible. Consequently, ASE at the microcavity resonance and at the low-frequency band-edge of photonic stop-band is demonstrated. Variation of the detection angle from 5° to 30°, with respect to the sample surface normal allows reallocation of the defect mode ASE peak over a spectral range of 558-542 nm, making the GO-incorporated 1DPhC a novel and attractive system for integrated optic applications. PMID:26670725

  8. Mono- to few-layered graphene oxide embedded randomness assisted microcavity amplified spontaneous emission source

    NASA Astrophysics Data System (ADS)

    Das, Pratyusha; Maiti, Rishi; Barman, Prahalad K.; Ray, Samit K.; Shivakiran, Bhaktha B. N.

    2016-02-01

    The realization of optoelectronic devices using two-dimensional materials such as graphene and its intermediate product graphene oxide (GO) is extremely challenging owing to the zero band gap of the former. Here, a novel amplified spontaneous emission (ASE) system based on a GO-embedded all-dielectric one-dimensional photonic crystal (1DPhC) micro-resonator is presented. The mono- to few-layered GO sheet is inserted within a microcavity formed by two 5-bilayered SiO2/SnO2 Bragg reflectors. Significantly enhanced photoluminescence (PL) emission of GO embedded in 1DPhC is explicated by studying the electric field confined within the micro-resonator using the transfer matrix method. The inherent randomness, due to fabrication limitations, in the on-average periodic 1DPhC is exploited to further enhance the PL of the optically active micro-resonator. The 1DPhC and randomness assisted field confinement reduces the ASE threshold of the mono- to few-layered weak emitter making the realization of an ASE source feasible. Consequently, ASE at the microcavity resonance and at the low-frequency band-edge of photonic stop-band is demonstrated. Variation of the detection angle from 5° to 30°, with respect to the sample surface normal allows reallocation of the defect mode ASE peak over a spectral range of 558-542 nm, making the GO-incorporated 1DPhC a novel and attractive system for integrated optic applications.

  9. Amplified Spontaneous Emission and Gain from Optically Pumped Films of Dye-Doped Polymers

    NASA Astrophysics Data System (ADS)

    Lu, Wu; Zhong, Bo; Ma, Dongge

    2004-09-01

    The amplified spontaneous emission and gain characteristics of various fluorescent dyes, 2-(1,1-dimethylethyl)-6(2-(2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H,5H-benzo[ij] quinolizin-9-1)ethenyl)-4H-pyran-4-ylidene) propanedinitrile (DCJTB) and 4-dicyanomethylene-2-methyl-6-(p-dimethyl-aminostyryl)-4H-pyran (DCM), doped in polystyrene (PS) matrices were studied and compared. It was found that DCJTB has a larger net gain, 40.72 cm^-1, a lower loss, 2.49 cm^-1, and a lower threshold, 0.16 (mJ/pulse)/cm^2, than DCM, which has a net gain of 11.95 cm^-1, a loss of 9.25 cm^-1, and a threshold of 4(mJ/pulse)/cm^2. The improvement of performance in DCJTB PS films is attributed to the larger free volume of DCJTB caused by the introduction of steric spacer groups into the DCJTB molecule.

  10. Amplified spontaneous emission from DCJTB encapsulated in mesostructured composite silica SBA-15.

    PubMed

    Zhang, Dingke; Duan, Zhuojun; Wang, Yu; Zhang, Peng; Chen, Shijian

    2016-06-10

    Amplified spontaneous emission (ASE) characteristics of a red dye 4-(Dicyanomethylene)-2-t-butyl-6-(1,1,7,7- etramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) encapsulated in a highly ordered mesoporous SBA-15 were studied. The mesoporous composite silica film loaded with organic dye has been successfully synthesized by a solgel reaction process and a simple postgrafting method at room temperature. The spectrum narrowing phenomena has been observed when the composite film is pumped at λp=532  nm by a Nd:YAG ed laser. There is a substantial reduction in the full width at half-maximum of the emitting light, which is one of the signatures of the presence of ASE. The ASE threshold and net gain, respectively, reached 0.03  mJ pulse-1 and 34.7  cm-1 for the DCJTB encapsulated in mesoporous SBA-15 film. The optimized ASE properties owe much to the effects of the better spatial confinement of the molecules in the ordered mesoporous structure of the host SBA-15. PMID:27409033

  11. Endogenous spontaneous ultraweak photon emission in the formation of eye-specific retinogeniculate projections before birth.

    PubMed

    Bókkon, István; Scholkmann, Felix; Salari, Vahid; Császár, Noémi; Kapócs, Gábor

    2016-06-01

    In 1963, it was suggested [Sperry, R.W. (1963). Chemoaffinity in the orderly growth of nerve fiber patterns and connections. Proc. Natl. Acad. Sci. USA 50, 703-710.] that molecular cues can direct the development of orderly connections between the eye and the brain (the "chemoaffinity hypothesis"). In the same year, the amazing degree of functional accuracy of the visual pathway in the absence of any external light/photon perception prior to birth [Wiesel, T.N and Hubel, D.H. (1963). Single-cell responses in striate cortex of kittens deprived of vision in one eye. J. Neurophysiol. 26, 1003-1017.] was discovered. These recognitions revealed that the wiring of the visual system relies on innate cues. However, how the eye-specific retinogeniculate pathway can be developed before birth without any visual experience is still an unresolved issue. In the present paper, we suggest that Müller cells (functioning as optical fibers), Müller cell cone (i.e. the inner half of the foveola that is created of an inverted cone-shaped zone of Müller cells), discrete retinal noise of rods, and intrinsically photosensitive retinal ganglion cells might have key functions by means of retinal spontaneous ultraweak photon emission in the development of eye-specific retinogeniculate pathways prior to birth. PMID:26656799

  12. Red, Yellow, Green, and Blue Amplified Spontaneous Emission and Lasing Using Colloidal CdSe Nanoplatelets.

    PubMed

    She, Chunxing; Fedin, Igor; Dolzhnikov, Dmitriy S; Dahlberg, Peter D; Engel, Gregory S; Schaller, Richard D; Talapin, Dmitri V

    2015-10-27

    There have been multiple demonstrations of amplified spontaneous emission (ASE) and lasing using colloidal semiconductor nanocrystals. However, it has been proven difficult to achieve low thresholds suitable for practical use of nanocrystals as gain media. Low-threshold blue ASE and lasing from nanocrystals is an even more challenging task. Here, we show that colloidal nanoplatelets (NPLs) with electronic structure of quantum wells can produce ASE in the red, yellow, green, and blue regions of the visible spectrum with low thresholds and high gains. In particular, for blue-emitting NPLs, the ASE threshold is 50 μJ/cm(2), lower than any reported value for nanocrystals. We then demonstrate red, yellow, green, and blue lasing using NPLs with different thicknesses. We find that the lateral size of NPLs does not show any strong effect on the Auger recombination rates and, correspondingly, on the ASE threshold or gain saturation. This observation highlights the qualitative difference of multiexciton dynamics in CdSe NPLs and other quantum-confined CdSe materials, such as quantum dots and rods. Our measurements of the gain bandwidth and gain lifetime further support the prospects of colloidal NPLs as solution-processed optical gain materials. PMID:26302368

  13. Measuring the energy of amplified spontaneous emission (ASE) in a short pulse laser amplifier

    NASA Astrophysics Data System (ADS)

    Iliev, Marin; Adams, Daniel; Greco, Michael; Meier, Amanda; Squier, Jeff; Durfee, Charles

    2010-10-01

    In high-gain pulsed laser amplifiers, amplified spontaneous emission (ASE) tends to limit the gain in single stage fiber amplifiers. Even if ASE is not strong enough to deplete the gain of the amplifier, it still contributes strongly to a low-intensity background output in the amplified signal. The intensity contrast between the amplified short pulse and this background ASE pedestal can be measured with third-order autocorrelation, but this method cannot be used to completely specify the ASE's energy, which is distributed over many nanoseconds. We have developed a novel method that allows us to determine the energy and the spectrum of the ASE. We use a cross polarized wave (XPW) generating crystal such as BaF2 to ``clean up'' the ASE from the short pulse(SP). The input pulse (SP and ASE) and the cross-polarized signal are passed through a birefringent crystal such as sapphire. The relative group velocity difference along each crystal axis results in a delay between both channels. After passing through a polarizer, an interferogram is obtained in a spectrometer. This interferogram results from interference of the XPW pulse with the short-pulse content of the amplifier output, with a background of the ASE spectrum. Fourier analysis yields both the ASE energy and its spectrum.

  14. Low-threshold amplified spontaneous emission and lasing from colloidal nanocrystals of caesium lead halide perovskites

    PubMed Central

    Yakunin, Sergii; Protesescu, Loredana; Krieg, Franziska; Bodnarchuk, Maryna I.; Nedelcu, Georgian; Humer, Markus; De Luca, Gabriele; Fiebig, Manfred; Heiss, Wolfgang; Kovalenko, Maksym V.

    2015-01-01

    Metal halide semiconductors with perovskite crystal structures have recently emerged as highly promising optoelectronic materials. Despite the recent surge of reports on microcrystalline, thin-film and bulk single-crystalline metal halides, very little is known about the photophysics of metal halides in the form of uniform, size-tunable nanocrystals. Here we report low-threshold amplified spontaneous emission and lasing from ∼10 nm monodisperse colloidal nanocrystals of caesium lead halide perovskites CsPbX3 (X=Cl, Br or I, or mixed Cl/Br and Br/I systems). We find that room-temperature optical amplification can be obtained in the entire visible spectral range (440–700 nm) with low pump thresholds down to 5±1 μJ cm−2 and high values of modal net gain of at least 450±30 cm−1. Two kinds of lasing modes are successfully observed: whispering-gallery-mode lasing using silica microspheres as high-finesse resonators, conformally coated with CsPbX3 nanocrystals and random lasing in films of CsPbX3 nanocrystals. PMID:26290056

  15. Low-threshold amplified spontaneous emission and lasing from colloidal nanocrystals of caesium lead halide perovskites

    NASA Astrophysics Data System (ADS)

    Yakunin, Sergii; Protesescu, Loredana; Krieg, Franziska; Bodnarchuk, Maryna I.; Nedelcu, Georgian; Humer, Markus; de Luca, Gabriele; Fiebig, Manfred; Heiss, Wolfgang; Kovalenko, Maksym V.

    2015-08-01

    Metal halide semiconductors with perovskite crystal structures have recently emerged as highly promising optoelectronic materials. Despite the recent surge of reports on microcrystalline, thin-film and bulk single-crystalline metal halides, very little is known about the photophysics of metal halides in the form of uniform, size-tunable nanocrystals. Here we report low-threshold amplified spontaneous emission and lasing from ~10 nm monodisperse colloidal nanocrystals of caesium lead halide perovskites CsPbX3 (X=Cl, Br or I, or mixed Cl/Br and Br/I systems). We find that room-temperature optical amplification can be obtained in the entire visible spectral range (440-700 nm) with low pump thresholds down to 5+/-1 μJ cm-2 and high values of modal net gain of at least 450+/-30 cm-1. Two kinds of lasing modes are successfully observed: whispering-gallery-mode lasing using silica microspheres as high-finesse resonators, conformally coated with CsPbX3 nanocrystals and random lasing in films of CsPbX3 nanocrystals.

  16. Enhanced Amplified Spontaneous Emission in Perovskites Using a Flexible Cholesteric Liquid Crystal Reflector.

    PubMed

    Stranks, Samuel D; Wood, Simon M; Wojciechowski, Konrad; Deschler, Felix; Saliba, Michael; Khandelwal, Hitesh; Patel, Jay B; Elston, Steve J; Herz, Laura M; Johnston, Michael B; Schenning, Albertus P H J; Debije, Michael G; Riede, Moritz K; Morris, Stephen M; Snaith, Henry J

    2015-08-12

    Organic-inorganic perovskites are highly promising solar cell materials with laboratory-based power conversion efficiencies already matching those of established thin film technologies. Their exceptional photovoltaic performance is in part attributed to the presence of efficient radiative recombination pathways, thereby opening up the possibility of efficient light-emitting devices. Here, we demonstrate optically pumped amplified spontaneous emission (ASE) at 780 nm from a 50 nm-thick film of CH3NH3PbI3 perovskite that is sandwiched within a cavity composed of a thin-film (∼7 μm) cholesteric liquid crystal (CLC) reflector and a metal back-reflector. The threshold fluence for ASE in the perovskite film is reduced by at least two orders of magnitude in the presence of the CLC reflector, which results in a factor of two reduction in threshold fluence compared to previous reports. We consider this to be due to improved coupling of the oblique and out-of-plane modes that are reflected into the bulk in addition to any contributions from cavity modes. Furthermore, we also demonstrate enhanced ASE on flexible reflectors and discuss how improvements in the quality factor and reflectivity of the CLC layers could lead to single-mode lasing using CLC reflectors. Our work opens up the possibility of fabricating widely wavelength-tunable "mirror-less" single-mode lasers on flexible substrates, which could find use in applications such as flexible displays and friend or foe identification. PMID:25989354

  17. Spontaneous emission dynamics in an omnidirectional waveguide made of photonic crystals

    NASA Astrophysics Data System (ADS)

    Huang, Chih-Hsien; Cheng, Szu-Cheng; Wu, Jing-Nuo; Hsieh, Wen-Feng

    2011-06-01

    The spontaneous emission dynamics of atoms embedded in an omnidirectional waveguide (ODWG), a novel optical waveguide, is studied on the basis of the complete reflection of one-dimensional photonic crystals. With the dispersion curve of the single waveguide mode within the photonic band gap and various extents of background dissipation, we characterize the photon-atom interaction in the ODWG. The photon emitter of the system is a two-level atom embedded in the low-index medium of the multilayer-film ODWG or the atom-ODWG system. Fractional calculus, an innovative mathematical method in optical systems, is applied to solve the equation of motion for this atom-ODWG system. Two kinds of states with different group velocities exhibit totally distinctive dynamical behavior. The high frequency waveguide mode with a fast group velocity shows fast exponential decay in propagation while the band-edge mode with a slow group velocity displays non-Markovian dynamics with non-exponential oscillating time evolution. We therefore suggest different functions of this atom-ODWG system for these two kinds of states. The richness of the physical content of the system is also revealed through investigating the dynamical behavior of the band-edge mode. These results aid in further application and fundamental understanding of the atom-ODWG system.

  18. Spontaneous emission of a photon: Wave-packet structures and atom-photon entanglement

    SciTech Connect

    Fedorov, M.V.; Efremov, M.A.; Kazakov, A.E.; Chan, K.W.; Eberly, J.H.; Law, C.K.

    2005-09-15

    Spontaneous emission of a photon by an atom is described theoretically in three dimensions with the initial wave function of a finite-mass atom taken in the form of a finite-size wave packet. Recoil and wave-packet spreading are taken into account. The total atom-photon wave function is found in the momentum and coordinate representations as the solution of an initial-value problem. The atom-photon entanglement arising in such a process is shown to be closely related to the structure of atom and photon wave packets which can be measured in the coincidence and single-particle schemes of measurements. Two predicted effects, arising under the conditions of high entanglement, are anomalous narrowing of the coincidence wave packets and, under different conditions, anomalous broadening of the single-particle wave packets. Fundamental symmetry relations between the photon and atom single-particle and coincidence wave-packet widths are established. The relationship with the famous scenario of Einstein-Podolsky-Rosen is discussed.

  19. Cold test, spontaneous emission and gain in a rectangular Cerenkov amplifier

    SciTech Connect

    Scharer, J.E.; Joe, J.; Booske, J.H.; Basten, M.; Kirolous, H.

    1994-12-31

    The authors present experimental results for the rectangular Cerenkov grating amplifier. This research is being carried out to develop a Ka-band (35 GHz), low voltage (10 kV), moderate power (10 kW) source. They have constructed a Ku-band grating structure to study a scaled version of this source. The tapered grating consists of two tapered Ku-band smooth wave guide sections and two 3.5-inch sections of five-step-tapered gratings. Both tapered and untapered grating structures have been cold tested utilizing the network analyzer measurements. They find that their taper design reduced the reflection coefficient from {minus}5 dB to less than {minus}20 dB over a 12--15 GHz bandwidth. Spontaneous emission results resulting from passing the circular electron beam from a Litton thermionic gun over the grating structure will be presented. They have theoretically investigated the sheet beam interaction with hybrid modes in a deep groove rectangular grating waveguide. A complex dispersion relation, which includes a finite axial energy spread of the beam, describing the interaction has been solved. The authors find that the instability is always convective in the forward wave mode regime.

  20. Statistical quantification of 24-hour and monthly variabilities of spontaneous otoacoustic emission frequency in humans.

    PubMed

    Haggerty, H S; Lusted, H S; Morton, S C

    1993-10-01

    Previous evidence has suggested a relationship between spontaneous otoacoustic emissions (SOAEs) and established, biological cycles, although detailed statistical quantifications of the suggested relationships do not exist in the literature. In an attempt to statistically quantify the purported circadian and monthly influences on this phenomenon, two experiments were undertaken. The first experiment was conducted over eight weeks, investigating 31 SOAEs recorded from eight women and two men. Time series statistical analysis examined whether daily, weekly, and/or monthly cycles characterized SOAE frequency variability. Results yielded a significant monthly cycle for the majority of SOAEs recorded from the women but for none of the SOAEs recorded from the men. These results suggest the possibility that SOAE frequency fluctuation in women may be entrained to the monthly menstrual cycle. In the second experiment, hourly SOAE frequency stability was examined over a 24-h period to ascertain the nature of the daily frequency variation as precisely as possible. Four SOAEs from two subjects were examined, and time series analysis of these data included (1) modelling the autocorrelation structure of the measurements, (2) resolving each 24-h series of measurements into cyclical components of various periodicities, and (3) testing the statistical significance of given cycles within the spectrum of each series. Findings included a significant 24-h variability of frequency for each SOAE, suggesting the possibility of a circadian influence on frequency fluctuation. Results from the two experiments provide quantitative evidence supporting a hypothetical relationship between SOAEs and established, biological cycles. PMID:8276731

  1. Nonequilibrium quantum fluctuations of a dispersive medium: Spontaneous emission, photon statistics, entropy generation, and stochastic motion

    NASA Astrophysics Data System (ADS)

    Maghrebi, Mohammad F.; Jaffe, Robert L.; Kardar, Mehran

    2014-07-01

    We study the implications of quantum fluctuations of a dispersive medium, under steady rotation, either in or out of thermal equilibrium with its environment. A rotating object exhibits a quantum instability by dissipating its mechanical motion via spontaneous emission of photons, as well as internal heat generation. Universal relations are derived for the radiated energy and angular momentum as trace formulas involving the object's scattering matrix. We also compute the quantum noise by deriving the full statistics of the radiated photons out of thermal and/or dynamic equilibrium. The (entanglement) entropy generation is quantified and the total entropy is shown to be always increasing. Furthermore, we derive a Fokker-Planck equation governing the stochastic angular motion resulting from the fluctuating backreaction frictional torque. As a result, we find a quantum limit on the uncertainty of the object's angular velocity in steady rotation. Finally, we show in some detail that a rotating object drags nearby objects, making them spin parallel to its axis of rotation. A scalar toy model is introduced to simplify the technicalities and ease the conceptual complexities and then a detailed discussion of quantum electrodynamics is presented.

  2. Bleederless ventilation systems as a spontaneous combustion control measure in US coal mines. Information circular/1994

    SciTech Connect

    Smith, A.C.; Diamond, W.P.; Mucho, T.P.; Organiscak, J.A.

    1994-01-01

    The U.S. Bureau of Mines conducted a worldwide literature review of bleederless ventilation practices to evaluate their use as a spontaneous combustion control measure in U.S. coal mines. Factors that must be taken into account in the design and use of these systems include seal construction, the use of ventilation control devices, the use of methane-drainage systems in gassy mines, and the ground control plan. Monitoring for the detection of spontaneous combustion and the control of methane when methane-drainage techniques are employed is critical to the successful use of a bleederless ventilation system. The report describes the types of ventilation systems used throughout the world and the spontaneous combustion risks associated with these systems.

  3. Ecological controls over monoterpene emissions from confiers

    SciTech Connect

    Lerdau, M.T.

    1994-01-01

    Ecological controls over monoterpene emissions from two species of conifers, Ponderosa pine and Douglas fir are studied. Monoterpenes are hydrocarbons that serve as part of these plant's chemical defense system. They are highly volatile and make up approximately 40% of the reduced carbon budget of the lower atmosphere playing a major role in tropospheric photochemistry. Previous research has emphasized the controls over emissions from any one plant at any one time. This paper considers some of the controls over the baseline emission rates from different plants. In field studies on Ponderosa pine and greenhouse experiments with Douglas fir in which photosynthesis, tissue chemistry, and monoterpene emissions were measured, there is a strong correlation between the concentration of particular monoterpenes within foliage and emissions from that foliage. Changes in pine photosynthesis were not correlated with changes in monoterpene emissions. In Douglas fir a strong relationship existed among nitrogen availability, phenology (seasonal plant growth), and monoterpene concentration and emission. When foliage is not expanding, there is a direct relationship among nitrogen availability and monoterpene concentrations and emissions. However, during that time of the year when needles are expanding, there is a negative relationship among nitrogen availability and monoterpene concentrations and emissions. From these results I have parameterized a model of monoterpene emissions from vegetation that runs as a subroutine of an ecosystem gas exchange model. The model includes the physiochemical controls on instantaneous flux found in previous work and biological controls on baseline emission rates. Results from initial simulations suggest that low temperatures can decouple monoterpene concentrations from monoterpene emissions. These results also indicate that herbivory could be a major factor controlling monoterpene emissions from forests.

  4. Controlling air emissions from incinerators

    SciTech Connect

    Foisy, M.B.; Li, R.; Chattapadhyay, A.

    1994-04-01

    Last year, EPA published final rules establishing technical standards for the use and disposal of wastewater biosolids (40 CFR, Part 503). Subpart E specifically regulates the operations of and emissions from municipal wastewater biosolids incinerators.

  5. Examination of bleederless ventilation practices for spontaneous combustion control in US coal mines

    SciTech Connect

    Organiscak, J.A.; Smith, A.C.; Diamond, W.P.; Mucho, T.P.

    1995-12-31

    The U.S. Bureau of Mines examined bleederless ventilation practices to evaluate their use as a spontaneous combustion control measure in U.S. coal mines. Results indicate that restricting airflow into mined-out areas (bleederless ventilation) is recognized worldwide as a spontaneous combustion control measure. However, ventilation practices commonly used to limit airflow to mined-out areas are not easily applicable to United States mining conditions, systems, experience and regulations. The types of bleederless ventilation systems used throughout the world and the spontaneous combustion risks associated with these systems are discussed. Primary design considerations for bleederless ventilation consist of the interaction of ventilation practices, methane drainage, ground control, seal construction and mine monitoring. Technological improvements needed for U.S. application of bleederless ventilation are also discussed.

  6. Calculation of spontaneous emission from a V-type three-level atom in photonic crystals using fractional calculus

    SciTech Connect

    Huang, Chih-Hsien; Hsieh, Wen-Feng; Wu, Jing-Nuo; Cheng, Szu-Cheng; Li, Yen-Yin

    2011-07-15

    Fractional time derivative, an abstract mathematical operator of fractional calculus, is used to describe the real optical system of a V-type three-level atom embedded in a photonic crystal. A fractional kinetic equation governing the dynamics of the spontaneous emission from this optical system is obtained as a fractional Langevin equation. Solving this fractional kinetic equation by fractional calculus leads to the analytical solutions expressed in terms of fractional exponential functions. The accuracy of the obtained solutions is verified through reducing the system into the special cases whose results are consistent with the experimental observation. With accurate physical results and avoiding the complex integration for solving this optical system, we propose fractional calculus with fractional time derivative as a better mathematical method to study spontaneous emission dynamics from the optical system with non-Markovian dynamics.

  7. Analysis and simulation of nonlinearity and effects of spontaneous emission in Schottky-junction-based plasmonic amplifiers.

    PubMed

    Livani, Abdolber Mallah; Kaatuzian, Hassan

    2015-07-01

    An amplifier that operates on surface plasmon polaritons has been analyzed and simulated. Nonlinearity behavior and the spontaneous emission effects of the plasmonic amplifier are investigated in this paper. A rate equations approach has been used in which parameters are derived from simulation results of the plasmonic amplifier (Silvaco/ATLAS). Details on the method of this derivation are included, which were not previously reported. Rate equations are solved numerically by MATLAB codes. These codes verify the Silvaco results. The plasmonic amplifier operates on surface plasmons with a free-space wavelength of 1550 nm. Results show that, even without the effect of spontaneous emission, gain of the plasmonic amplifier saturates in high input levels. Saturation power, which can be used for comparing nonlinearity of different amplifiers, is 2.1 dBm for this amplifier. Amplified spontaneous emission reduces the gain of the amplifiers, which is long. There is an optimum value for the length of the amplifier. For the amplifier of this work, the optimum length for the small signal condition is 265 μm. PMID:26193159

  8. Detailed Study of the Angular Correlations in the Prompt Neutron Emission in Spontaneous Fission of 252Cf

    NASA Astrophysics Data System (ADS)

    Kopatch, Yu.; Chietera, A.; Stuttgé, L.; Gönnenwein, F.; Mutterer, M.; Gagarski, A.; Guseva, I.; Chernysheva, E.; Dorvaux, O.; Hambsch, F.-J.; Hanappe, F.; Mezentseva, Z.; Telezhnikov, S.

    An experiment has been performed at IPHC Strasbourg, aimed at the detailed investigation of angular correlations in the neutron emission from spontaneous fission of 252Cf. Fission fragments were measured by the angle-sensitive double ionization chamber CODIS while neutrons were detected by a set of 60 DEMON scintillator counters. The main aim of the experiment is the observation of the correlation between the fragment spins and neutron emission anisotropy. Preliminary results, based on the Monte-Carlo simulations, as well as the preliminary analysis of the experimental data are shown.

  9. Spontaneous centralization of control in a network of company ownerships.

    PubMed

    Krause, Sebastian M; Peixoto, Tiago P; Bornholdt, Stefan

    2013-01-01

    We introduce a model for the adaptive evolution of a network of company ownerships. In a recent work it has been shown that the empirical global network of corporate control is marked by a central, tightly connected "core" made of a small number of large companies which control a significant part of the global economy. Here we show how a simple, adaptive "rich get richer" dynamics can account for this characteristic, which incorporates the increased buying power of more influential companies, and in turn results in even higher control. We conclude that this kind of centralized structure can emerge without it being an explicit goal of these companies, or as a result of a well-organized strategy. PMID:24324594

  10. Spontaneous Centralization of Control in a Network of Company Ownerships

    PubMed Central

    Krause, Sebastian M.; Peixoto, Tiago P.; Bornholdt, Stefan

    2013-01-01

    We introduce a model for the adaptive evolution of a network of company ownerships. In a recent work it has been shown that the empirical global network of corporate control is marked by a central, tightly connected “core” made of a small number of large companies which control a significant part of the global economy. Here we show how a simple, adaptive “rich get richer” dynamics can account for this characteristic, which incorporates the increased buying power of more influential companies, and in turn results in even higher control. We conclude that this kind of centralized structure can emerge without it being an explicit goal of these companies, or as a result of a well-organized strategy. PMID:24324594

  11. Variable emissivity laser thermal control system

    DOEpatents

    Milner, Joseph R.

    1994-01-01

    A laser thermal control system for a metal vapor laser maintains the wall mperature of the laser at a desired level by changing the effective emissivity of the water cooling jacket. This capability increases the overall efficiency of the laser.

  12. Comment on “Competition between coherent emission and broadband spontaneous emission in the quantum free electron laser” [Phys. Plasmas 20, 033106 (2013)

    SciTech Connect

    Petrillo, V.; Rossi, A. R.; Serafini, L.

    2013-12-15

    We point out that in the equation for the electron distribution evolution during Thomson/Compton or undulator radiation used in the paper: “Competition between coherent emission and broadband spontaneous emission in the quantum free electron laser” by G. R. M. Robb and R. Bonifacio [Phys. Plasmas 20, 033106 (2013)], the weight function should be the distribution of the number of emitted photons and not the photon energy distribution. Nevertheless, the considerations expressed in this comment do not alter the conclusions drawn in the paper in object.

  13. Ongoing Spontaneous Activity Controls Access to Consciousness: A Neuronal Model for Inattentional Blindness

    PubMed Central

    2005-01-01

    Even in the absence of sensory inputs, cortical and thalamic neurons can show structured patterns of ongoing spontaneous activity, whose origins and functional significance are not well understood. We use computer simulations to explore the conditions under which spontaneous activity emerges from a simplified model of multiple interconnected thalamocortical columns linked by long-range, top-down excitatory axons, and to examine its interactions with stimulus-induced activation. Simulations help characterize two main states of activity. First, spontaneous gamma-band oscillations emerge at a precise threshold controlled by ascending neuromodulator systems. Second, within a spontaneously active network, we observe the sudden “ignition” of one out of many possible coherent states of high-level activity amidst cortical neurons with long-distance projections. During such an ignited state, spontaneous activity can block external sensory processing. We relate those properties to experimental observations on the neural bases of endogenous states of consciousness, and particularly the blocking of access to consciousness that occurs in the psychophysical phenomenon of “inattentional blindness,” in which normal subjects intensely engaged in mental activity fail to notice salient but irrelevant sensory stimuli. Although highly simplified, the generic properties of a minimal network may help clarify some of the basic cerebral phenomena underlying the autonomy of consciousness. PMID:15819609

  14. Io control of Jovian radio emission

    NASA Technical Reports Server (NTRS)

    Desch, M. D.

    1980-01-01

    The possibility of Io controlling Jovian decametric radio emission, particularly in the region below 22 MHz, is discussed. Results of a two-year survey at 26.3 at 26.3 MHz are presented which demonstrate the control of Io over a high-intensity storm component of the radio emission and the independence of a weak radio component from the phase of Io, as was observed at lower frequencies. It is thus hypothesized that Io control is a flux-dependent rather than a frequency-dependent phenomenon, and results of analyses at 18 and 10 MHz which support this hypothesis are presented. The apparent correlation between frequency and Io control is thus shown to result from a selection effect due to the increase of non-Io emission with decreasing frequency and relative antenna detection threshold. This result implies a contiguous Io-controlled source region extending out several Jovian radii along the Io flux tube.

  15. Control of Jovian Radio Emission by Callisto

    NASA Technical Reports Server (NTRS)

    Menietti, J. D.; Gurnett, D. A.; Christopher, I.

    2001-01-01

    Galileo has been in orbit around Jupiter since December 1995 and a large database has been collected. We present the results of a survey of the plasma wave data for the frequency range 2.0 MHz to 5.6 MHz, the low frequency decametric (DAM) emissions. While the control of a portion of the radio emission by the moon lo is well known, and Ganymede control has been more recently indicated, we report that a small but significant portion of DAM emission is seen to be correlated with the orbital phase of Callisto. While the occurrence rate of emission controlled by Ganymede and Callisto is considerably less than for lo, the power levels can be nearly the same. We estimate the power of the Callisto-dependent emission to be approx. 70% of the Io-dependent radio emission and about the same as the Ganymede-dependent radio emission. This result indicates an Alfven current system associated with Callisto, and thus a significant interaction of the magnetosphere of Callisto with that of Jupiter as is believed to exist for both lo and Ganymede.

  16. Effect of Zn-Cd interdiffusion on the band structure and spontaneous emission of ZnO/Zn1-xCdxO/ZnO quantum wells

    NASA Astrophysics Data System (ADS)

    Shtepliuk, I.; Khranovskyy, V.; Yakimova, R.

    2015-09-01

    Needs in more-efficient visible light sources based on quantum wells (QWs) requires the diversification of traditional optoelectronics' materials as well as development of the cost-effective approaches for reliable quantum confinement engineering. Interdiffusion approach has a great potential to become a simple method for controlling the optical properties of QWs and diminishing the quantum confined Stark effect (QCSE). In this work we theoretically study the effect of Zn-Cd interdiffusion in ZnCdO/ZnO QWs on their band structure, optical matrix elements and spontaneous emission properties. The QW intermixing leads to improving both the transverse electric (TE) and transverse magnetic (TM) optical matrix elements due to enhancement of the overlap integral between electron and hole wave functions and modification of the confinement potential from triangle-shaped to parabolic-like. The optimized diffusion length 4 Å provided by the annealing at 700 K during 60 s was determined for 2 nm-thick Zn0.85Cd0.15O QW, which offers higher spontaneous emission rate in comparison to conventional QW. The reasonable interpretation of the interdiffusion effect on the optical properties of QWs is proposed in terms of low diffusion length and high diffusion length regimes. Thus, suitable combination of annealing duration and annealing temperature with the geometrical/compositional parameters of QWs can be the efficient way for improving the optical performance of ZnO-based QWs.

  17. CONTROL OF AIR EMISSIONS FROM SUPERFUND SITES

    EPA Science Inventory

    This handbook is an easy-to-use tool for decision makers to evaluate emission control devices for use with Superfund remediation actions. t will assist in the selection of cost-effective control options. t is intended for use by engineers and scientists involved in preparing reme...

  18. CO2 emission of coal spontaneous combustion and its relation with coal microstructure, China.

    PubMed

    Wang, Haiyan; Chen Chen; Huang, Tao; Gao, Wei

    2015-07-01

    Coal spontaneous combustion is widely distributed all over the world. CO2 is the main greenhouse gas emitted by coal spontaneous combustion. In the present study characters of CO2 emitted by 10 typical Chinese coal spontaneous combustion and the influence of raw coal functional group on CO2 was studied. CO2 already exists under normal temperature as coal exposed in atmosphere. Under low temperature, the quality of CO2 released by coal spontaneous combustion is relatively small, but tends to increase. And corresponding with it, the oxygen consumption amount is also small. At medium temperature, the oxygen consumption increases rapidly and CO2 mass release rate begins to increase rapidly. Then, CO2 release rate increase rapidly under relatively high temperature (higher than 673 K). Over 873K, concentration of O2 is 6% and release rate of CO2 tends to be steady. It also concluded that mass ratio of CO to CO2 (CO/CO2) during coal spontaneous combustion was lowerthan 0.10 at low temperature. And then, it increased rapidly at medium temperature and reached to top at about 673 K. At 673-873 K, the ratio decreased again, and did not decrease evidently at about 873K. At temperature higher than 873K, the ratio was about 0.13. During the whole testing temperature range, CO/CO2 was not be higher than 0.26, lower than 0.2. This means that release rate of CO2 was much higher than CO during the whole process of coal spontaneous combustion. Moreover, the gas release quantity of CO2 is positively related with carbony content in raw coal. Carbonyl and carboxyl were both material basis of CO2. PMID:26364484

  19. Control of Jovian Radio Emission by Ganymede

    NASA Technical Reports Server (NTRS)

    Menietti, J. D.; Gurnett, D. A.; Kurth, W. S.; Groene, J. B.

    1998-01-01

    Galileo has been in orbit around Jupiter since December 1995. We present the results of a survey of the data for the frequency range 3.2 MHz to 5.6 MHz, the low-frequency decametric (DAM) emissions. While the control of a portion of the radio emission by the moon Io is well-known, we report that a small but significant portion of low-frequency DAM emission is seen to be correlated with the orbital phase of Ganymede. This result is in agreement with other recent results indicating a significant interaction of the magnetosphere of Ganymede with that of Jupiter.

  20. Multi-level quantum electrodynamic calculation of spontaneous emission and small signal gain in high voltage free electron lasers

    NASA Astrophysics Data System (ADS)

    Chang, C. S.; Fluhler, H. U.

    1991-12-01

    Using the Weisskopf-Wigner technique, a self consistent quantum electrodynamic (SCQED) theory of spontaneous emission of radiation and single photon small signal gain is developed for high voltage free electron lasers (FEL). Excellent agreement is obtained simultaneously to our knowledge for the first time between the predictions and the experimental observations for lineshift, linewidth and gain. The SCQED theory predicts lineshift and broadening due to quantum mechanical effects for linear, helical and tapered undulator FELs which are not predicted by the classical/conventional FEL theories, but which have been observed 4,5,18,22,23,45,46. Excellent agreement is obtained between the SCQED theory predicted spontaneous emission spectra and the 1980?81 ACO FEL4,18, ACO Optical Klystron FEL45,46, Stanford 10.6 ?m FEL22 and Stanford 3.4 ?m FEL23 experimental spectra. This agreement is much better than the prediction from the classical/conventional FEL theory which gives errors of many tens of percent. We show that the spontaneous emission spectrum obtained from classical/conventional FEL theories is valid only in the limit of a short undulator containing a small number of periods. The small signal gain derived from the SCQED theory is shown to reduce to Colson's gain formula12,34 in the classical limit. However, the SCQED theory predicts significant reductions in the small signal gain which agree well with the ACO gain data5, and are not predicted well by Colson's formula. Due to the non-neglible finite electron state lifetime, it is discovered that a fundamental physical gain limit exists which is universal to all types of FELs within the limits of the single photon transition scheme considered (i.e. if multiphoton effects are ignored). Finally, the implications of the theoretically obtained results are discussed for practical conditions of experimental interest. It is shown that under practical experimental conditions quantum effects can be quite important in the

  1. Controlling light scattering and emission at subwavelength scale with plasmonic nanopatch antennas (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Wu, Zilong; Zheng, Yuebing

    2015-09-01

    Controlling light scattering and emission at subwavelength scale has significant implications for solar energy conversion, sensing, and nanophotonic devices. Plasmonic nanopatch antennas (PNAs), which consist of plasmonic nanoparticle coupled with metallic films, have shown directionality of radiation and large emission rate enhancement due to the strong plasmonic waveguide modes within the spacer layer. Herein, we comparatively study the light scattering and emission behaviors of a series of plasmonic nanopatch antennas (PNAs) with different plasmonic nanoparticles (i.e., nanosquare, nanotriangle, nanorod, and nanodisk) to develop the design rules of the PNAs. Using finite-difference time-domain (FDTD) simulations, we show that the shape and size of plasmonic nanoparticles can be tuned to control the resonance peak, intensity, directionality, and spatial distribution of the scattering light as well as the directionality, spatial distribution, spontaneous emission rate, quantum efficiency, and radiation enhancement factor of light emission. For example, high radiative quantum efficiency (0.74) and radiation enhancement factor (>20) can be achieved by disk PNA, while triangle PNA shows remarkable spontaneous emission rate enhancement of over 2,500. The effects of locations of emitters relative to the PNAs on the emission properties are also examined. Our results pave the way towards the rational design of PNAs for the optimal light scattering and emission as required by targeted applications.

  2. High-precision three-dimensional atom localization via spontaneous emission in a four-level atomic system

    NASA Astrophysics Data System (ADS)

    Wang, Zhiping; Yu, Benli

    2016-06-01

    We investigate the three-dimensional atom localization via spontaneous emission in a four-level atomic system. It is found that the detecting probability and precision of atom localization can be significantly improved due to the interference effects induced by the vacuum radiation field and the two laser fields. More importantly, the almost 100% probability of finding an atom within a certain range can be reached when corresponding conditions are satisfied. As a result, our scheme may be helpful in a spatially selective single-qubit phase gate, entangling gates, and quantum error correction for quantum information processing.

  3. Self-Amplified Spontaneous Emission Free-Electron Laser with an Energy-Chirped Electron Beam and Undulator Tapering

    SciTech Connect

    Giannessi, L.; Ciocci, F.; Dattoli, G.; Del Franco, M.; Petralia, A.; Quattromini, M.; Ronsivalle, C.; Sabia, E.; Spassovsky, I.; Surrenti, V.; Bacci, A.; Rossi, A. R.; Bellaveglia, M.; Castellano, M.; Chiadroni, E.; Cultrera, L.; Filippetto, D.; Di Pirro, G.; Ferrario, M.; Ficcadenti, L.

    2011-04-08

    We report the first experimental implementation of a method based on simultaneous use of an energy chirp in the electron beam and a tapered undulator, for the generation of ultrashort pulses in a self-amplified spontaneous emission mode free-electron laser (SASE FEL). The experiment, performed at the SPARC FEL test facility, demonstrates the possibility of compensating the nominally detrimental effect of the chirp by a proper taper of the undulator gaps. An increase of more than 1 order of magnitude in the pulse energy is observed in comparison to the untapered case, accompanied by FEL spectra where the typical SASE spiking is suppressed.

  4. Experimental Characterization of Nonlinear Harmonic Radiation from a Visible Self-Amplified Spontaneous Emission Free-Electron Laser at Saturation

    NASA Astrophysics Data System (ADS)

    Tremaine, A.; Wang, X. J.; Babzien, M.; Ben-Zvi, I.; Cornacchia, M.; Nuhn, H.-D.; Malone, R.; Murokh, A.; Pellegrini, C.; Reiche, S.; Rosenzweig, J.; Yakimenko, V.

    2002-05-01

    Nonlinear harmonic radiation was observed using the VISA self-amplified, spontaneous emission (SASE) free-electron laser (FEL) at saturation. The gain lengths, spectra, and energies of the three lowest SASE FEL modes were experimentally characterized. The measured nonlinear harmonic gain lengths and center spectral wavelengths decrease with harmonic number, n, which is consistent with nonlinear harmonic theory. Both the second and third nonlinear harmonics energies are about 1% of the fundamental energy. These experimental results demonstrate for the first time the feasibility of using nonlinear harmonic SASE FEL radiation to produce coherent, femtosecond x rays.

  5. EFFECT OF LASER LIGHT ON MATTER. LASER PLASMAS: Distributed extraction of amplified spontaneous emission from a randomly inhomogeneous active medium

    NASA Astrophysics Data System (ADS)

    Starikov, F. A.

    1993-05-01

    This paper investigates the dynamics of amplified spontaneous x-ray emission escaping from a randomly inhomogeneous plasma active medium through its ends and lateral surface. It is shown that the scattering of radiation by fluctuations in the dielectric permittivity, ɛ˜, can be utilized to extract energy through the lateral surface of the active medium. The radiant intensity is maximal in an off-axis direction in this case. When both regular refraction and scattering by ɛ˜ are operating, the distributed extraction of the light is determined by that effect which has the smaller characteristic length (i.e., the scattering length or the refraction length).

  6. Enhanced spontaneous emission rate from single InAs quantum dots in a photonic crystal nanocavity at telecom wavelengths

    NASA Astrophysics Data System (ADS)

    Balet, L.; Francardi, M.; Gerardino, A.; Chauvin, N.; Alloing, B.; Zinoni, C.; Monat, C.; Li, L. H.; Le Thomas, N.; Houdré, R.; Fiore, A.

    2007-09-01

    The authors demonstrate coupling at 1.3μm between single InAs quantum dots (QDs) and a mode of a two dimensional photonic crystal (PhC) defect cavity with a quality factor of 15 000. By spectrally tuning the cavity mode, they induce coupling with excitonic lines. They perform a time integrated and time-resolved photoluminescence and measure an eightfold increase in the spontaneous emission rate inducing a coupling efficiency of 96%. These measurements indicate the potential of single QDs in PhC cavities as efficient single-photon emitters for fiber-based quantum information processing applications.

  7. Advanced CIDI Emission Control System Development

    SciTech Connect

    Lambert, Christine

    2006-05-31

    Ford Motor Company, with ExxonMobil and FEV, participated in the Department of Energy's (DOE) Ultra-Clean Transportation Fuels Program with the goal to develop an innovative emission control system for light-duty diesel vehicles. The focus on diesel engine emissions was a direct result of the improved volumetric fuel economy (up to 50%) and lower CO2 emissions (up to 25%) over comparable gasoline engines shown in Europe. Selective Catalytic Reduction (SCR) with aqueous urea as the NOx reductant and a Catalyzed Diesel Particulate Filter (CDPF) were chosen as the primary emission control system components. The program expected to demonstrate more than 90% durable reduction in particulate matter (PM) and NOx emissions on a light-duty truck application, based on the FTP-75 drive cycle. Very low sulfur diesel fuel (<15 ppm-wt) enabled lower PM emissions, reduced fuel economy penalty due to the emission control system and improved long-term system durability. Significant progress was made toward a durable system to meet Tier 2 Bin 5 emission standards on a 6000 lbs light-duty truck. A 40% reduction in engine-out NOx emissions was achieved with a mid-size prototype diesel engine through engine recalibration and increased exhaust gas recirculation. Use of a rapid warm-up strategy and urea SCR provided over 90% further NOx reduction while the CDPF reduced tailpipe PM to gasoline vehicle levels. Development work was conducted to separately improve urea SCR and CDPF system durability, as well as improved oxidation catalyst function. Exhaust gas NOx and ammonia sensors were also developed further. While the final emission control system did not meet Tier 2 Bin 5 NOx after 120k mi of aging on the dynamometer, it did meet the standards for HC, NMOG, and PM, and an improved SCR catalyst was shown to have potential to meet the NOx standard, assuming the DOC durability could be improved further. Models of DOC and SCR function were developed to guide the study of several key design

  8. Estimate of sulfur, arsenic, mercury, fluorine emissions due to spontaneous combustion of coal gangue: An important part of Chinese emission inventories.

    PubMed

    Wang, Shaobin; Luo, Kunli; Wang, Xing; Sun, Yuzhuang

    2016-02-01

    A rough estimate of the annual amount of sulfur, arsenic, mercury and fluoride emission from spontaneous combustion of coal gangue in China was determined. The weighted mean concentrations of S, As, Hg, and F in coal gangue are 1.01%, 7.98, 0.18, and 365.54 mg/kg, respectively. Amounts of S, As, Hg, and F emissions from coal gangue spontaneous combustion show approximately 1.13 Mt, and 246, 45, and 63,298 tons in 2013, respectively. The atmospheric release amount of sulfur from coal gangue is more than one tenth of this from coal combustion, and the amounts of As, Hg, and F are close to or even exceed those from coal combustion. China's coal gangue production growth from 1992 to 2013 show an obvious growth since 2002. It may indicate that Chinese coal gangue has become a potential source of air pollution, which should be included in emission inventories. PMID:26650082

  9. Low Threshold Two-Photon-Pumped Amplified Spontaneous Emission in CH3NH3PbBr3 Microdisks.

    PubMed

    Yang, Bin; Mao, Xin; Yang, Songqiu; Li, Yajuan; Wang, Yanqiu; Wang, Meishan; Deng, Weiqiao; Han, Keli

    2016-08-01

    Two-photon-pumped amplified spontaneous emission (ASE) of CH3NH3PbBr3 microdisks (MDs) were investigated by using femtosecond laser system. Low threshold at 2.2 mJ cm(-2) was obtained. Also, emission spectral tunability from 500 to 570 nm was demonstrated by synthesis the mixed halide perovskite MDs. The spatial effect of photoluminescence (PL) properties under one-photon and two-photon excitation were also studied by means of two-photon laser scanning microscope (TPLSM) and time-resolved PL spectroscopy. It was found that the band to band emission of near-surface regions and photocarriers' diffusion from near-surface regions to interior regions is significant for one-photon excitation. By contrast, reabsorption of emission under two-photon excitation plays a major role in the emission properties of the MDs. These results will give a more comprehensive understanding of the nonlinear effect of CH3NH3PbBr3 single crystals. PMID:27391527

  10. Systematics of spontaneous emission of intermediate mass fragments from heavy nuclei

    SciTech Connect

    Barwick, S.W.; Price, P.B.; Ravn, H.L.; Hourani, E.; Hussonnois, M.

    1986-07-01

    We have used polycarbonate track-recording films to confirm the rare decay mode of /sup 226/Ra by /sup 14/C emission and to set stringent upper limits on /sup 14/C-emission rates of /sup 221/Fr, /sup 221/Ra, and /sup 225/Ac. The /sup 14/C-emission rate exhibits a pronounced odd-even effect. For Ra isotopes the hindrance factor for odd-even parents relative to even-even parents is at least 10 times higher for /sup 14/C emission than for ..cap alpha.. emission.

  11. Amplified spontaneous emission from 2,7-bis(4-pyridyl)fluorene-doped DNA-cetyltrimethyl ammonium complex films

    NASA Astrophysics Data System (ADS)

    Zhao, Xiuhua; Li, Xing; Zhao, Yayun; Zhang, Jie; Pan, Jianguo; Zhou, Jun

    2013-10-01

    The 2,7-bis(4-pyridyl)fluorene (BPF) was synthesized via a Suzuki coupling reaction. The optical spectra properties of BPF and BPF-deoxyribonucleic acid (DNA)-cetyltrimethyl ammonium (CTMA) thin films composed of BPF, DNA, and CTMA were characterized by the measurements of UV/Vis absorption spectra and fluorescence spectra. The amplified spontaneous emission (ASE) of the BPF-DNA-CTMA films was researched experimentally by pumping of a pulse laser with a wavelength of 355 nm. The results show that the absorption peak and the fluorescence peak of BPF are located at 327 and 380 nm, respectively. The emission peak of BPF corresponds to the vibronic transitions from an excited state of S1 level to the ground state of S0 level. The ASE peak of the BPF-DNA-CTMA film is located at 384 nm, and the threshold of ASE excited energy density is 3.12 mJ.cm-2.

  12. Controllable optical bistability and multistability in asymmetric double quantum wells via spontaneously generated coherence

    SciTech Connect

    Chen, Yuan; Deng, Li; Chen, Aixi

    2015-02-15

    We investigate the nonlinear optical phenomena of the optical bistability and multistability via spontaneously generated coherence in an asymmetric double quantum well structure coupled by a weak probe field and a controlling field. It is shown that the threshold and hysteresis cycle of the optical bistability can be conveniently controlled only by adjusting the intensity of the SGC or the controlling field. Moreover, switching between optical bistability and multistability can be achieved. These studies may have practical significance for the preparation of optical bistable switching device.

  13. On what controls the spacing of spontaneous adiabatic shear bands in collapsing thick-walled cylinders

    NASA Astrophysics Data System (ADS)

    Lovinger, Zev; Rosenberg, Zvi; Rittel, Daniel

    2015-09-01

    Shear bands formation in collapsing thick walled cylinders occurs in a spontaneous manner. The advantage of examining spontaneous, as opposed to forced shear localization, is that it highlights the inherent susceptibility of the material to adiabatic shear banding without prescribed geometrical constraints. The Thick-Walled Cylinder technique (TWC) provides a controllable and repeatable technique to create and study multiple adiabatic shear bands. The technique, reported in the literature uses an explosive cylinder to create the driving force, collapsing the cylindrical sample. Recently, we developed an electro-magnetic set-up using a pulsed current generator to provide the collapsing force, replacing the use of explosives. Using this platform we examined the shear band evolution at different stages of formation in 7 metallic alloys, spanning a wide range of strength and failure properties. We examined the number of shear bands and spacing between them for the different materials to try and figure out what controls these parameters. The examination of the different materials enabled us to better comprehend the mechanisms which control the spatial distribution of multiple shear bands in this geometry. The results of these tests are discussed and compared to explosively driven collapsing TWC results in the literature and to existing analytical models for spontaneous adiabatic shear localization.

  14. Voltage-Mediated Control of Spontaneous Bundle Oscillations in Saccular Hair Cells.

    PubMed

    Meenderink, Sebastiaan W F; Quiñones, Patricia M; Bozovic, Dolores

    2015-10-28

    Hair cells of the vertebrate vestibular and auditory systems convert mechanical inputs into electrical signals that are relayed to the brain. This transduction involves mechanically gated ion channels that open following the deflection of mechanoreceptive hair bundles that reside on top of these cells. The mechano-electrical transduction includes one or more active feedback mechanisms to keep the mechanically gated ion channels in their most sensitive operating range. Coupling between the gating of the mechanosensitive ion channels and this adaptation mechanism leads to the occurrence of spontaneous limit-cycle oscillations, which indeed have been observed in vitro in hair cells from the frog sacculus and the turtle basilar papilla. We obtained simultaneous optical and electrophysiological recordings from bullfrog saccular hair cells with such spontaneously oscillating hair bundles. The spontaneous bundle oscillations allowed us to characterize several properties of mechano-electrical transduction without artificial loading the hair bundle with a mechanical stimulus probe. We show that the membrane potential of the hair cell can modulate or fully suppress innate oscillations, thus controlling the dynamic state of the bundle. We further demonstrate that this control is exerted by affecting the internal calcium concentration, which sets the resting open probability of the mechanosensitive channels. The auditory and vestibular systems could use the membrane potential of hair cells, possibly controlled via efferent innervation, to tune the dynamic states of the cells. PMID:26511238

  15. Theory of phonon-modified spontaneous emission and photoluminescence intensity from quantum dots coupled to structured photonic reservoirs

    NASA Astrophysics Data System (ADS)

    Roy Choudhury, Kaushik; Hughes, S.

    2015-08-01

    We present a general theory for calculating the spontaneous emission (SE) rate and the photoluminescence intensity of a quantum dot (QD) exciton coupled to an arbitrary structured photonic reservoir and a bath of acoustic phonons. We describe a polaron master equation (ME) approach which includes phonon interaction nonperturbatively and assume a weak coupling with the photon reservoir which is valid in the Purcell coupling regime. As examples of structured photonic reservoirs, we choose the cases of a Lorentzian cavity and a slow-light coupled-cavity waveguide. In analogy with a simple atom, the SE rate of a QD is expected to be proportional to the local density of photon states (LDOS) of the structured reservoir at the resonant frequency of a QD exciton. However, using a polaron ME theory, we show how the phonon-dressed SE rate of a QD is determined by a broad bandwidth of the photonic LDOS, in violation of the well known Fermi's golden rule. This broadband frequency dependence results in rich spontaneous emission enhancement and suppression, manifesting in significant changes in the Purcell factor and photoluminescence intensity as a function of frequency.

  16. Variable emissivity laser thermal control system

    DOEpatents

    Milner, J.R.

    1994-10-25

    A laser thermal control system for a metal vapor laser maintains the wall temperature of the laser at a desired level by changing the effective emissivity of the water cooling jacket. This capability increases the overall efficiency of the laser. 8 figs.

  17. FIRED HEATERS: NITROGEN OXIDES EMISSIONS AND CONTROLS

    EPA Science Inventory

    The report gives results of a study of nitrogen oxide (NOx) emissions from, and controls for, fired heaters. The petroleum refining and chemical manufacturing industries account for most of fired-heater energy use with an estimated 4600 fired heaters in operation, in these two in...

  18. CONTROLLING ODOROUS EMISSIONS FROM IRON FOUNDRIES

    EPA Science Inventory

    The report discusses the control of odorous emissions from iron foundries. he main process sources of odors in iron foundries are mold and core making, casting, and sand shakeout. he odors are usually caused by chemicals, which may be present as binders and other additives to the...

  19. CONTROLLING EMISSIONS FROM FUEL AND WASTE COMBUSTION

    EPA Science Inventory

    Control of emissions from combustion of fuels and wastes has been a traditional focus of air pollution regulations. Significant technology developments of the '50s and '60s have been refined into reliable chemical and physical process unit operations. In the U.S., acid rain legis...

  20. Photoelectric charging of dust particles: Effect of spontaneous and light induced field emission of electrons

    SciTech Connect

    Sodha, M. S.; Dixit, A.

    2009-09-07

    The authors have analyzed the charging of dust particles in a plasma, taking into account the electron/ion currents to the particles, electron/ion generation and recombination, electric field emission, photoelectric emission and photoelectric field emission of electrons under the influence of light irradiation; the irradiance has been assumed to be at a level, which lets the particles retain the negative sign of the charge. Numerical results and discussion conclude the papers.

  1. Voltage-Mediated Control of Spontaneous Bundle Oscillations in Saccular Hair Cells

    PubMed Central

    Meenderink, Sebastiaan W. F.; Quiñones, Patricia M.

    2015-01-01

    Hair cells of the vertebrate vestibular and auditory systems convert mechanical inputs into electrical signals that are relayed to the brain. This transduction involves mechanically gated ion channels that open following the deflection of mechanoreceptive hair bundles that reside on top of these cells. The mechano-electrical transduction includes one or more active feedback mechanisms to keep the mechanically gated ion channels in their most sensitive operating range. Coupling between the gating of the mechanosensitive ion channels and this adaptation mechanism leads to the occurrence of spontaneous limit-cycle oscillations, which indeed have been observed in vitro in hair cells from the frog sacculus and the turtle basilar papilla. We obtained simultaneous optical and electrophysiological recordings from bullfrog saccular hair cells with such spontaneously oscillating hair bundles. The spontaneous bundle oscillations allowed us to characterize several properties of mechano-electrical transduction without artificial loading the hair bundle with a mechanical stimulus probe. We show that the membrane potential of the hair cell can modulate or fully suppress innate oscillations, thus controlling the dynamic state of the bundle. We further demonstrate that this control is exerted by affecting the internal calcium concentration, which sets the resting open probability of the mechanosensitive channels. The auditory and vestibular systems could use the membrane potential of hair cells, possibly controlled via efferent innervation, to tune the dynamic states of the cells. SIGNIFICANCE STATEMENT The sensation of sound and balance starts by converting minute mechanical motions into electrical signals. This is accomplished by sensory hair cells, in which the opening and closing of mechanosensitive channels follows the motion of their hair bundles. These hair bundles can exhibit motility without an external drive. Underlying these spontaneous bundle oscillations are two

  2. Controllable cavity linewidth narrowing via spontaneously generated coherence in a four level atomic system

    NASA Astrophysics Data System (ADS)

    Tian, Si-Cong; Wan, Ren-Gang; Shan, Xiao-Nan; Tong, Cun-Zhu; Qin, Li; Ning, Yong-Qiang

    2015-12-01

    A scheme for cavity linewidth narrowing in a four-level atomic system with spontaneously generated coherence is proposed. The atomic system consists of three closely spaced excited levels, which decay to one common ground level. In such a system, spontaneously generated coherence can result in the appearance of two narrow transparency windows accomplished by steep normal dispersion. When the medium is embedded in a ring cavity, two ultranarrow transmission peaks locating close to the position of the transparency windows can be obtained simultaneously. The cavity linewidth narrowing is owing to the quantum interference between the three decay channels and can be controlled by the frequency splitting of the excited levels, requiring no coupling lasers.

  3. Photogeneration of charge carrier correlated with amplified spontaneous emission in single crystals of a thiophene/phenylene co-oligomer.

    PubMed

    Saeki, Akinori; Seki, Shu; Shimizu, Yasuhiro; Yamao, Takeshi; Hotta, Shu

    2010-04-01

    Thiophene/phenylene co-oligomers have substantial promise for the use of not only organic electronics but also organic optical devices. However, considerably less is known about the correlation between their optical and optoelectronic properties. We have investigated the charge carrier generation in 1,4-bis(5-phenylthiophen-2-yl)benzene (AC5) single crystals by flash-photolysis time-resolved microwave conductivity (TRMC) and transient absorption spectroscopy (TAS). It was found that the dependence of photocarrier generation efficiency on excitation photon density differed from that of emission efficiency once amplified spontaneous emission (ASE) and resultant spectrally narrowed emission occur upon exposure to 355 nm. In contrast, the dependences of emission and photocarrier generation efficiencies were identical when ASE was not involved at a different excitation wavelength (193 nm). An approximated analytical solution of rate equation considering ASE or singlet-singlet annihilation was applied to the experiments, exhibiting good agreement. On the basis of TRMC, TAS, and extinction coefficient of radical cation assessed by pulse radiolysis, the minimum charge carrier mobility was estimated, without electrodes, to be 0.12 cm(2) V(-1) s(-1). The dynamics of charge carrier and triplet excited state is discussed, accompanying with examination by time-dependent density functional theory. The present work would open the way to a deeper understanding of the fate of excited state in optically robust organic semiconducting crystals. PMID:20387943

  4. Homogeneous linewidths of Rhodamine 6G at room temperature from cavity-enhanced spontaneous emission rates

    SciTech Connect

    Barnes, M.D.; Whitten, W.B.; Arnold, S.; Ramsey, J.M. )

    1992-11-15

    Fluorescence lifetimes of Rhodamine 6G in levitated micron-sized droplets have been measured using a time-correlated photon counting technique. The coupling of emission into spherical cavity modes of the droplet results in significant emission rate enhancements which allow estimation of the homogeneous linewidth at room temperature.

  5. Neutron emission as a function of fragment energy in the spontaneous fission of /sup 260/Md

    SciTech Connect

    Wild, J.F.; van Aarle, J.; Westmeiser, W.; Lougheed, R.W.; Hulet, E.K.; Moody, K.J.; Dougan, R.J.; Brandt, R.; Patzelt, P.

    1989-04-19

    We have made the first measurement of the number of neutrons emitted in the spontaneous fission of a nuclide in which very high fragment energies dominate the fission process. In bombardments of /sup 254/Es, we produced 28-d /sup 260/Md, which was neutron-counted in a 1-m-diam spherical tank containing a Gd-doped scintillator solution. The average number of neutrons emitted per fission is only 2.58 +- 0.11, substantially less than for other actinides. A direct correlation of neutron multiplicity with fragment excitation energy is clearly demonstrated. 3 refs., 5 figs.

  6. Prompt neutron emission from the spontaneous fission of sup 260 Md

    SciTech Connect

    Wild, J.F.; van Aarle, J.; Westmeier, W.; Lougheed, R.W.; Hulet, E.K.; Moody, K.J.; Dougan, R.J.; Koop, E.; Glaser, R.E.; Brandt, R.; Patzelt, P. Philipps University, D-3550, Marburg an der Lahn, )

    1990-02-01

    We have made the first measurement of the number of neutrons emitted from the spontaneous fission of a nuclide in which very high fragment energies dominate the fission process. In bombardments of {sup 254}Es, we produced a large sample of 28-d {sup 260}Md, which was neutron counted in a 1-m-diameter spherical tank containing a Gd-doped scintillator solution. The average number of neutrons emitted per fission is only 2.58{plus minus}0.11, substantially less than for other actinides. A linear dependence of neutron multiplicity on fragment-excitation energy is observed to the highest values of total kinetic energy.

  7. Spontaneous epileptiform activity in rat neocortex after controlled cortical impact injury.

    PubMed

    Yang, Lie; Afroz, Sonia; Michelson, Hillary B; Goodman, Jeffrey H; Valsamis, Helen A; Ling, Douglas S F

    2010-08-01

    A hallmark of severe traumatic brain injury (TBI) is the development of post-traumatic epilepsy (PTE). However, the mechanisms underlying PTE remain poorly understood. In this study, we used a controlled cortical impact (CCI) model in rats to examine post-traumatic changes in neocortical excitability. Neocortical slices were prepared from rats at 7-9 days (week 1) and 14-16 days (week 2) after CCI injury. By week 2, we observed a substantial gray matter lesion with a cavity that extended to the hippocampal structure. Fluoro-Jade B staining of slices revealed active neuronal degeneration during weeks 1 and 2. Intracellular and extracellular recordings obtained from layer V revealed evoked and spontaneous epileptiform discharges in neocortices of CCI-injured rats. At week 1, intracellular recordings from pyramidal cells revealed evoked epileptiform firing that was synchronized with population events recorded extracellularly, suggestive of increased excitability. This activity was characterized by bursts of action potentials that were followed by recurrent, repetitive after-discharges. At week 2, both spontaneous and evoked epileptiform firing were recorded in slices from injured rats. The evoked discharges resembled those observed at week 1, but with longer burst durations. Spontaneous activity included prolonged, ictal-like discharges lasting up to 8-10 sec, and briefer interictal-like burst events (<1 sec). These results indicate that during the first 2 weeks following severe CCI injury, there is a progressive development of neocortical hyperexcitability that ultimately leads to spontaneous epileptiform firing, suggesting a rapid epileptogenic process. PMID:20504156

  8. Terahertz-range spontaneous emission under the optical excitation of donors in uniaxially stressed bulk silicon and SiGe/Si heterostructures

    SciTech Connect

    Zhukavin, R. Kh. Kovalevsky, K. A.; Orlov, M. L.; Tsyplenkov, V. V.; Bekin, N. A.; Yablonskiy, A. N.; Yunin, P. A.; Pavlov, S. G.; Abrosimov, N. V.; Hübers, H.-W.; Radamson, H. H.; Shastin, V. N.

    2015-01-15

    The results of measurements of the total terahertz-range photoluminescence of Group-V donors (phosphorus, antimony, bismuth, arsenic) in bulk silicon and SiGe/Si heterostructures depending on the excitation intensity are presented. The signal of bulk silicon was also measured as a function of uniaxial stress. The results of measurement of the dependence of the spontaneous emission intensity on the uniaxial stress is in rather good agreement with theoretical calculations of the relaxation times of excited states of donors in bulk silicon. Comparative measurements of the spontaneous emission from various strained heterostructures showed that the photoluminescence signal is caused by donor-doped silicon regions.

  9. Advanced Emissions Control Development Program: Phase III

    SciTech Connect

    G.T. Amrhein; R.T. Bailey; W. Downs; M.J. Holmes; G.A. Kudlac; D.A. Madden

    1999-07-01

    The primary objective of the Advanced Emissions Control Development Program (AECDP) is to develop practical, cost-effective strategies for reducing the emissions of air toxics from coal-fired boilers. The project goal is to effectively control air toxic emissions through the use of conventional flue gas clean-up equipment such as electrostatic precipitators (ESPs), fabric filters (baghouses - BH), and wet flue gas desulfurization systems (WFGD). Development work concentrated on the capture of trace metals, fine particulate, hydrogen chloride and hydrogen fluoride, with an emphasis on the control of mercury. The AECDP project is jointly funded by the US Department of Energy's Federal Energy Technology Center (DOE), the Ohio Coal Development Office within the Ohio Department of Development (OCDO), and Babcock and Wilcox, a McDermott company (B and W). This report discusses results of all three phases of the AECDP project with an emphasis on Phase III activities. Following the construction and evaluation of a representative air toxics test facility in Phase I, Phase II focused on characterization of the emissions of mercury and other air toxics and the control of these emissions for typical operating conditions of conventional flue gas clean-up equipment. Some general comments that can be made about the control of air toxics while burning a high-sulfur bituminous coal are as follows: (1) particulate control devices such as ESP's and baghouses do a good job of removing non-volatile trace metals, (2) particulate control devices (ESPs and baghouses) effectively remove the particulate-phase mercury, but the particulate-phase mercury was only a small fraction of the total for the coals tested, (3) wet scrubbing can effectively remove hydrogen chloride and hydrogen fluoride, and (4) wet scrubbers show good potential for the removal of mercury when operated under certain conditions, however, for certain applications, system enhancements can be required to achieve high

  10. Immune responses during spontaneous control of HIV and AIDS: what is the hope for a cure?

    PubMed Central

    Saez-Cirion, A.; Jacquelin, B.; Barré-Sinoussi, F.; Müller-Trutwin, M.

    2014-01-01

    HIV research has made rapid progress and led to remarkable achievements in recent decades, the most important of which are combination antiretroviral therapies (cART). However, in the absence of a vaccine, the pandemic continues, and additional strategies are needed. The ‘towards an HIV cure’ initiative aims to eradicate HIV or at least bring about a lasting remission of infection during which the host can control viral replication in the absence of cART. Cases of spontaneous and treatment-induced control of infection offer substantial hope. Here, we describe the scientific knowledge that is lacking, and the priorities that have been established for research into a cure. We discuss in detail the immunological lessons that can be learned by studying natural human and animal models of protection and spontaneous control of viraemia or of disease progression. In particular, we describe the insights we have gained into the immune mechanisms of virus control, the impact of early virus–host interactions and why chronic inflammation, a hallmark of HIV infection, is an obstacle to a cure. Finally, we enumerate current interventions aimed towards improving the host immune response. PMID:24821922

  11. Experimental study on CO and CO2 emissions from spontaneous heating of coals at varying temperatures and O2 concentrations

    PubMed Central

    Yuan, Liming; Smith, Alex C.

    2015-01-01

    Laboratory experiments were conducted to investigate carbon monoxide (CO) and carbon dioxide (CO2) emissions from spontaneous heating of three U.S. coal samples in an isothermal oven at temperatures between 50 and 110 °C. The oxygen (O2) concentration of an oxygen/nitrogen (N2) mixture flowing through the coal sample was 3, 5, 10, 15, and 21%, respectively. The temperature at the center of the coal sample was continuously monitored, while the CO, CO2, and O2 concentrations of the exit gas were continuously measured. The results indicate that the CO and CO2 concentrations and the CO/CO2 ratio increased when the initial temperature was increased. As the inlet O2 concentration increased, the CO and CO2 concentrations increased, while the CO/CO2 ratios tended to converge to the same value. The ratio of CO/CO2 was found to be independent of coal properties, approaching a constant value of 0.2. The maximum CO production rate correlated well with the maximum coal temperature rise. The apparent order of reaction for coal oxidation was estimated to be between 0.52 and 0.72. The experimental results in this study could be used for early detection and evaluation of a spontaneous heating in underground coal mines. PMID:26203211

  12. Criterion of transverse coherence of self-amplified spontaneous emission in high gain free electron laser amplifiers

    SciTech Connect

    Xie, M.; Kim, K.J.

    1995-12-31

    In a high gain free electron laser amplifier based on Self-Amplified Spontaneous Emission (SASE) the spontaneous radiation generated by an electron beam near the undulator entrance is amplified many orders of magnitude along the undulator. The transverse coherence properties of the amplified radiation depends on both the amplification process and the coherence of the seed radiation (the undulator radiation generated in the first gain length or so). The evolution of the transverse coherence in the amplification process is studied based on the solution of the coupled Maxwell-Vlasov equations including higher order transverse modes. The coherence of the seed radiation is determined by the number of coherent modes in the phase space area of the undulator radiation. We discuss the criterion of transverse coherence and identify governing parameters over a broad range of parameters. In particular we re-examine the well known emittance criterion for the undulator radiation, which states that full transverse coherence is guaranteed if the rms emittance is smaller than the wavelength divided by 4{pi}. It is found that this criterion is modified for SASE because of the different optimization conditions required for the electron beam. Our analysis is a generalization of the previous study by Yu and Krinsky for the case of vanishing emittance with parallel electron beam. Understanding the transverse coherence of SASE is important for the X-ray free electron laser projects now under consideration at SLAC and DESY.

  13. Two-Dimensional Organic Single Crystals with Scale Regulated, Phase-Switchable, Polymorphism-Dependent, and Amplified Spontaneous Emission Properties.

    PubMed

    Zhang, Zhenyu; Song, Xiaoxian; Wang, Shipan; Li, Feng; Zhang, Hongyu; Ye, Kaiqi; Wang, Yue

    2016-05-01

    The successful preparation of two-dimensional (2D) single crystals can promote the development of organic optoelectronic devices with excellent performance. A Schiff base compound salicylidene(4-dimethylamino)aniline with aggregation induced emission (AIE) property was employed as the building block to fabricate 2D thin single crystal plates with scales from around 50 μm to 1.5 cm. Yellow and red emissive polymorphs were concomitantly obtained during crystallization. The single-crystal-to-single-crystal (SC-to-SC) transformation from yellow polymorph to red one was demonstrated. Furthermore, both polymorphs exhibited amplified spontaneous emission (ASE) properties. Interestingly, the red polymorph displayed size-dependent ASE characteristics. The larger red polymorph showed near-infrared ASE with maximum at 706 nm, whereas the smaller one presented red ASE with maximum at 610 nm. These results suggest that the different scale single crystalline thin films with perfect optoelectronic properties may be fabricated by using the organic molecules with 2D assembly feature. PMID:27096197

  14. Controlling NOx emission from industrial sources

    SciTech Connect

    Srivastava, R.K.; Nueffer, W.; Grano, D.; Khan, S.; Staudt, J.E.; Jozewicz, W.

    2005-07-01

    A number of regulatory actions focused on reducing NOx emissions from stationary combustion sources have been taken in the United States in the last decade. These actions include the Acid Rain NOx regulations, the Ozone Transport Commission's NOx Budget Program, and the NOx SIP Call rulemakings. In addition to these regulations, the recent Interstate Air Quality Rulemaking proposal and other bills in the Congress are focusing on additional reductions of NOx. Industrial combustion sources accounted for about 18016 of NOx emissions in the United States in 2000 and constituted the second largest emitting source category within stationary sources, only behind electric utility sources. Based on these data, reduction of NOx emissions from industrial combustion sources is an important consideration in efforts undertaken to address the environmental concerns associated with NOx. This paper discusses primary and secondary NOx control technologies applicable to various major categories of industrial sources. The sources considered in this paper include large boilers, furnaces and fired heaters, combustion turbines, large IC engines, and cement kilns. For each source category considered in this paper, primary NOx controls are discussed first, followed by a discussion of secondary NOx controls.

  15. Spontaneous emission from a two-level atom in anisotropic one-band photonic crystals: A fractional calculus approach

    SciTech Connect

    Wu, J.-N.; Huang, C.-H.; Cheng, S.-C.; Hsieh, W.-F.

    2010-02-15

    Spontaneous emission (SE) from a two-level atom in an anisotropic photonic crystal (PC) is investigated by the fractional calculus. Physical phenomena of the SE are studied analytically by solving the fractional kinetic equations of the SE. There is a dynamical discrepancy between the SE of anisotropic and isotropic PCs. We find that, contrary to the SE phenomenon of the isotropic PC, the SE near the band edge of an anisotropic PC shows no photon-atom bound state. It is consistent with the experimental results of Barth, Schuster, Gruber, and Cichos [Phys. Rev. Lett. 96, 243902 (2006)] that the anisotropic property of the system enhances the SE. We also study effects of dispersion curvatures on the changes of the photonic density of states and the appearance of the diffusion fields in the SE.

  16. Biopolymer based system doped with nonlinear optical dye as a medium for amplified spontaneous emission and lasing

    NASA Astrophysics Data System (ADS)

    Sznitko, Lech; Mysliwiec, Jaroslaw; Karpinski, Pawel; Palewska, Krystyna; Parafiniuk, Kacper; Bartkiewicz, Stanislaw; Rau, Ileana; Kajzar, Francois; Miniewicz, Andrzej

    2011-07-01

    In this paper, we present results of detailed studies on amplified spontaneous emission (ASE) and lasing achieved in a double-layer system consisted of a biopolymer based matrix loaded with 3-(1,1-dicyanoethenyl1)-1phenyl-4,5dihydro-1H-pyrazole organic nonlinear optical dye and photochromic polymer. The laser action was achieved via distributed feedback configuration with third order of Bragg scattering on surface relief grating generated in photochromic polymer. To excite the luminescence, we have used 6 ns pulses of Nd:YAG laser at 532 nm. The ASE and lasing thresholds were estimated to be 17 mJ/cm2 and 11 mJ/cm2, respectively.

  17. Spontaneous emission and spectral properties of radiation by relativistic electrons in a gyro-klystron and optical-klystron undulator.

    PubMed

    Prakash, Bramha; Mishra, Ganeswar; Khullar, Roma

    2016-03-01

    In this paper spontaneous emission of radiation by relativistic electrons in a gyro-klystron is studied. The scheme consists of two solenoid sections separated by a dispersive section. In the dispersive section the electrons are made non-resonant with the radiation. The dispersive section transforms a small change of the velocity into changes of the phases of the electrons. This leads to enhanced radiation due to klystron-type modulation as compared with a conventional gyrotron-type device driven by cyclotron maser interaction. It is shown that the klystron-modulated spectrum depends on the dispersive field strength, finite perpendicular velocity component and length of the solenoids but is independent of the axial magnetic field strength. A simple scheme to design a gyro-klystron is discussed. PMID:26917129

  18. Amplified spontaneous emission measurement of a line-narrowed, tunable, Ti:Al2O3 amplifier using rubidium absorption

    NASA Technical Reports Server (NTRS)

    Barnes, James C.; Barnes, Norman P.; Lockard, George E.; Cross, Patricia L.

    1989-01-01

    Amplified spontaneous emission, ASE, generated by a Ti:Al2O3 laser amplifier has been measured as a function of pump energy, and thus gain, using the atomic absorption of rubidium, Rb, gas at 0.780 micron. By tuning the Ti:Al2O3 laser, the Rb cell could selectively absorb the narrow spectral bandwidth laser radiation while transmitting the wide spectral bandwidth ASE. Transmission of laser amplifier pulses through a Rb absorption cell, measured at various temperatures, thus allows the measurement of the weak ASE in the vicinity of the strong laser pulse. A model for the transmission of Rb as a function of temperature and wavelength has been developed. The measured transmissions are in good agreement with the transmission model predictions.

  19. Spontaneous emission interference enhancement with a {mu}-negative metamaterial slab

    SciTech Connect

    Zeng Xiaodong; Xu Jingping; Yang Yaping

    2011-09-15

    The spontaneous decay and quantum interference of a V-type Zeeman atom placed near a {mu}-negative metamaterial (MNG) slab are investigated. Based on the fact that MNG slab supports only TE-polarized surface-plasmon polariton (SPP) modes, the decay rate of the dipole component parallel to the interface would be much larger than that normal to the interface, because one can couple while another decouple to TE modes. Consequently, high-level anisotropic environment is created and the two dipoles can interfere with each other strongly by sharing such SPP modes even if they are orthogonal. In our work, we analyze the influence of the parameters of the MNG slab as well as the atomic location on the interference intensity in detail. In addition, the dissipation of the slab is considered, and the quantum interference is still excellent even with large absorption.

  20. Spectral broadening effects of spontaneous emission and density of state on plasmonic enhancement in cermet waveguides.

    PubMed

    Chen, Keyong; Feng, Xue; Zhang, Chao; Cui, Kaiyu; Huang, Yidong

    2013-01-14

    Based on the full integration formula of Purcell factor (PF) deduced from Fermi's Golden Rule, the plasmonic enhancement in Au(1-α)S3N4(α) cermet waveguides is evaluated with the joint impact of finite emission linewidth and the broadening of PF spectrum. The calculation results indicate that the PF would be significantly degraded by the two broadening effects though the SPP resonance frequency can be tuned with different volume fractions (α) of Si3N4. It is also found that the critical emission linewidth is approximately linear to the PF spectrum linewidth. Thus in order to achieve strong plasmonic enhancement, both the emission and PF spectrum linewidths should be dramatically reduced. PMID:23388935

  1. Spectral discrimination between healthy people and cold patients using spontaneous photon emission

    PubMed Central

    Yang, Meina; Pang, Jiangxiang; Liu, Junyan; Liu, Yanli; Fan, Hua; Han, Jinxiang

    2015-01-01

    In this paper, ultra-weak photon emission (UPE) was used to distinguish cold patients from healthy subjects. The UPE intensity of fingertips of two hands from healthy subjects and cold patients was measured using a two-hand UPE detecting system and a group of cut-off filters. We found a significant difference in the maximum spectral peak and photon emission ratio between the filter of 550nm and 495nm, which can be used in distinguish cold patients from healthy people. Methods and results in this work could be useful for developing a new optical diagnostic tool for early disease diagnosis in the future. PMID:25909016

  2. Factors controlling dimethylsulfide emission from salt marshes

    NASA Technical Reports Server (NTRS)

    Dacey, John W. H.; Wakeham, S. G.; Howes, B. L.

    1985-01-01

    The factors that control the emission of methylated gases from salt marshes are being studied. Research focusses on dimethylsulfide (DMS) formation and the mechanism of DMS and CH4 emission to the atmosphere. The approach is to consider the plants as valves regulating the emission of methylated gases to the atmosphere with the goal of developing appropriate methods for emission measurement. In the case of CH4, the sediment is the source and transport to the atmosphere occurs primarily through the internal gas spaces in the plants. The source of DMS appears to be dimethyl sulfoniopropionate (DMSP) which may play a role in osmoregulation in plant tissues. Concentrations of DMSP in leaves are typically several-fold higher than in roots and rhizomes. Even so, the large below ground biomass of this plant means that 2/3 of the DMSP in the ecosystem is below ground on the aerial basis. Upon introduction to sediment water, DMSP rapidly decomposes to DMS and acrylic acid. The solubility of a gas (its equilibrium vapor pressure) is a fundamental aspect of gas exchange kinetics. The first comprehensive study was conducted of DMS solubility in freshwater and seawater. Data suggest that the Setchenow relation holds for H at intermediate salinities collected. These data support the concept that the concentration of DMS in the atmosphere is far from equilibrium with seawater.

  3. Model Identification for Optimal Diesel Emissions Control

    SciTech Connect

    Stevens, Andrew J.; Sun, Yannan; Song, Xiaobo; Parker, Gordon

    2013-06-20

    In this paper we develop a model based con- troller for diesel emission reduction using system identification methods. Specifically, our method minimizes the downstream readings from a production NOx sensor while injecting a minimal amount of urea upstream. Based on the linear quadratic estimator we derive the closed form solution to a cost function that accounts for the case some of the system inputs are not controllable. Our cost function can also be tuned to trade-off between input usage and output optimization. Our approach performs better than a production controller in simulation. Our NOx conversion efficiency was 92.7% while the production controller achieved 92.4%. For NH3 conversion, our efficiency was 98.7% compared to 88.5% for the production controller.

  4. Brief Report: Pilot Randomized Controlled Trial of Reciprocal Imitation Training for Teaching Elicited and Spontaneous Imitation to Children with Autism

    PubMed Central

    Ingersoll, Brooke

    2013-01-01

    Children with autism exhibit significant deficits in imitation skills. Reciprocal Imitation Training (RIT), a naturalistic imitation intervention, was developed to teach young children with autism to imitate during play. This study used a randomized controlled trial to evaluate the efficacy of RIT on elicited and spontaneous imitation skills in 21 young children with autism. Results found that children in the treatment group made significantly more gains in elicited and spontaneous imitation, replicating previous single-subject design studies. Number of spontaneous play acts at pre-treatment was related to improvements in imitation during the intervention, suggesting that children with a greater play repertoire make greater gains during RIT. PMID:20155309

  5. CONTROLLING MULTIPLE EMISSIONS FROM COAL-FIRED POWER PLANTS

    EPA Science Inventory

    The paper presents and analyzes nine existing and novel control technologies designed to achieve multipollutant emissions reductions. It provides an evaluation of multipollutant emission control technologies that are potentially available for coal-fired power plants of 25 MW capa...

  6. Hot stuff controls for VOC emissions

    SciTech Connect

    Yewshenko, P.

    1995-12-01

    For close to three decades, American industry has paved the way and led the world in controlling volatile organic compound (VOC) emissions. As more and more systems have been installed, the history of operation for the various types of systems has broadened dramatically, spurring significant technological advances, the traditional technologies and those on the cutting edge of VOC control. With the number of technologies available, the environmental professional may have a difficult task choosing the most strategic environmental solution. The conventional, traditional or proven methodology for VOC control has been incineration. Other technologies have been used for very specific applications. In deciding the specific type of incineration system to select, the environmental professional will look at a broad spectrum of evaluation factors. These include initial system cost, operational cost, maintenance requirements, reliability factors and most importantly, the projected success of achieving 99% VOC destruction efficiency. This article provides an overview of the basic differences among incineration technologies.

  7. The research and implementation of coalfield spontaneous combustion of carbon emission WebGIS based on Silverlight and ArcGIS server

    NASA Astrophysics Data System (ADS)

    Zhu, Z.; Bi, J.; Wang, X.; Zhu, W.

    2014-02-01

    As an important sub-topic of the natural process of carbon emission data public information platform construction, coalfield spontaneous combustion of carbon emission WebGIS system has become an important study object. In connection with data features of coalfield spontaneous combustion carbon emissions (i.e. a wide range of data, which is rich and complex) and the geospatial characteristics, data is divided into attribute data and spatial data. Based on full analysis of the data, completed the detailed design of the Oracle database and stored on the Oracle database. Through Silverlight rich client technology and the expansion of WCF services, achieved the attribute data of web dynamic query, retrieval, statistical, analysis and other functions. For spatial data, we take advantage of ArcGIS Server and Silverlight-based API to invoke GIS server background published map services, GP services, Image services and other services, implemented coalfield spontaneous combustion of remote sensing image data and web map data display, data analysis, thematic map production. The study found that the Silverlight technology, based on rich client and object-oriented framework for WCF service, can efficiently constructed a WebGIS system. And then, combined with ArcGIS Silverlight API to achieve interactive query attribute data and spatial data of coalfield spontaneous emmission, can greatly improve the performance of WebGIS system. At the same time, it provided a strong guarantee for the construction of public information on China's carbon emission data.

  8. The Effect of Ear Canal Pressure on Spontaneous Otoacoustic Emissions:. Comparison Between Human and Lizard Ears

    NASA Astrophysics Data System (ADS)

    van Dijk, P.; Manley, G. A.

    2009-02-01

    The center frequency, height and width of peaks in SOAE spectra depend on ear canal pressure. The width is interpreted as a measure of the inner ear source-signal-to-(e.g. thermal)-noise ratio. In humans, width increases with decreasing height. Apparently, ear canal pressure modifies the amplitude of the inner ear emission source signal. In lizards, the relation between peak width and height is not consistent. Here, middle ear transmission changes may account for many the observed amplitude effects.

  9. Coherent optical transition radiation and self-amplified spontaneous emission generated by chicane-compressed electron beams

    SciTech Connect

    Lumpkin, A.H.; Dejus, R.J.; Sereno, N.S.; /Argonne

    2009-02-01

    Observations of strongly enhanced optical transition radiation (OTR) following significant bunch compression of photoinjector beams by a chicane have been reported during the commissioning of the Linac Coherent Light Source (LCLS) accelerator and recently at the Advanced Photon Source (APS) linac. These localized transverse spatial features involve signal enhancements of nearly a factor of 10 and 100 in the APS case at the 150-MeV and 375-MeV OTR stations, respectively. They are consistent with a coherent process seeded by noise and may be evidence of a longitudinal space charge (LSC) microbunching instability which leads to coherent OTR (COTR) emissions. Additionally, we suggest that localized transverse structure in the previous self-amplified spontaneous emission (SASE) free-electron laser (FEL) data at APS in the visible-UV regime as reported at FEL02 may be attributed to such beam structure entering the FEL undulators and inducing the SASE startup at those structures. Separate beam structures 120 microns apart in x and 2.9 nm apart in wavelength were reported. The details of these observations and operational parameters will be presented.

  10. Emission control apparatus for diesel engines

    SciTech Connect

    Strachan, J. B.

    1980-02-26

    Apparatus for controlling the emission of exhaust gases from a diesel engine used in mining operations consists of a purifier chamber within a water jacketed adaptor and having an inlet for connection to the outlet from the exhaust manifold of the engine. The purifier chamber contains a catalytic purifier for the reduction of carbon monoxide passing from the inlet of the purifier chamber to its outlet, which is connected to a water scrubber for the reduction of the temperature of exhaust gases, the removal of some of the products of combustion, and for quenching exhaust flames.

  11. Continuous particulate monitoring for emission control

    SciTech Connect

    Bock, A.H. )

    1993-08-01

    An optical continuous particle monitoring system has been developed to overcome common problems associated with emissions monitoring equipment. Opacity monitors generally use a single- or double-pass system to analyze the presence of dust particles in the flue gas stream. The particles scatter and absorb light as it passes through the stack. As the particle content in the gas stream increases due to bag failure or some other problem, the amount of light that is blocked also increases. The opacity monitor compares the amount of lost light energy to the total energy of the light available and translates the signal to percentage of opacity. Opacity monitors are typically installed to meet the requirements set forth by pollution control agencies. Most opacity monitors are designed to meet all of the requirements of the Environmental Protection Agency (EPA) 40 CFR, Part 60, Appendix B, Performance Specification. The new continuous particle monitor (CPM) increases the accuracy of emission monitoring and overcomes typical problems found in conventional emission monitoring devices. The CPM is an optically based, calibratible, continuous dust monitor that uses a microprocessor, transmitter head, and receiver head. When calibrated with an isokinetic sample, a continuous readout of particulate concentration (in mg/m[sup 3]) in the exhaust gas is provided. The system can be used as a filter bag failure system or a long-term emission trend analyzer. Formal testing was conducted to evaluate the effectiveness of the optically based CPM. The monitor was calibrated using particles of a range of compositions, size distributions, and concentrations. The feasibility of using the instrument to measure particle concentration as low as 10 mg/m[sup 3] was examined.

  12. Characterization of the spontaneous light emission of the PMTs used in the Double Chooz experiment

    NASA Astrophysics Data System (ADS)

    Abe, Y.; Abrahão, T.; Alt, C.; Appel, S.; Bekman, I.; Bergevin, M.; Bezerra, T. J. C.; Bezrukov, L.; Blucher, E.; Brugière, T.; Buck, C.; Busenitz, J.; Cabrera, A.; Calvo, E.; Camilleri, L.; Carr, R.; Cerrada, M.; Chauveau, E.; Chimenti, P.; Collin, A. P.; Conover, E.; Conrad, J. M.; Crespo-Anadón, J. I.; Crum, K.; Cucoanes, A. S.; Damon, E.; Dawson, J. V.; de Kerret, H.; Dhooghe, J.; Dietrich, D.; Djurcic, Z.; dos Anjos, J. C.; Dracos, M.; Etenko, A.; Fallot, M.; Felde, J.; Fernandes, S. M.; Fischer, V.; Franco, D.; Franke, M.; Furuta, H.; Gil-Botella, I.; Giot, L.; Göger-Neff, M.; Gomez, H.; Gonzalez, L. F. G.; Goodenough, L.; Goodman, M. C.; Haag, N.; Hara, T.; Haser, J.; Hellwig, D.; Hofmann, M.; Horton-Smith, G. A.; Hourlier, A.; Ishitsuka, M.; Jiménez, S.; Jochum, J.; Jollet, C.; Kaether, F.; Kalousis, L. N.; Kamyshkov, Y.; Kaneda, M.; Kaplan, D. M.; Kawasaki, T.; Kemp, E.; Kryn, D.; Kuze, M.; Lachenmaier, T.; Lane, C. E.; Lasserre, T.; Letourneau, A.; Lhuillier, D.; Lima, H. P., Jr.; Lindner, M.; López-Castaño, J. M.; LoSecco, J. M.; Lubsandorzhiev, B.; Lucht, S.; Maeda, J.; Mariani, C.; Maricic, J.; Martino, J.; Matsubara, T.; Mention, G.; Meregaglia, A.; Miletic, T.; Minotti, A.; Nagasaka, Y.; Navas-Nicolás, D.; Novella, P.; Nunokawa, H.; Obolensky, M.; Onillon, A.; Osborn, A.; Palomares, C.; Pepe, I. M.; Perasso, S.; Porta, A.; Pronost, G.; Reichenbacher, J.; Reinhold, B.; Röhling, M.; Roncin, R.; Rybolt, B.; Sakamoto, Y.; Santorelli, R.; Schilithz, A. C.; Schönert, S.; Schoppmann, S.; Shaevitz, M. H.; Sharankova, R.; Shrestha, D.; Sibille, V.; Sinev, V.; Skorokhvatov, M.; Smith, E.; Soiron, M.; Spitz, J.; Stahl, A.; Stancu, I.; Stokes, L. F. F.; Strait, M.; Suekane, F.; Sukhotin, S.; Sumiyoshi, T.; Sun, Y.; Svoboda, R.; Terao, K.; Tonazzo, A.; Trinh Thi, H. H.; Valdiviesso, G.; Vassilopoulos, N.; Verdugo, A.; Veyssiere, C.; Vivier, M.; von Feilitzsch, F.; Wagner, S.; Walsh, N.; Watanabe, H.; Wiebusch, C.; Wurm, M.; Yang, G.; Yermia, F.; Zimmer, V.

    2016-08-01

    During the commissioning of the first of the two detectors of the Double Chooz experiment, an unexpected and dominant background caused by the emission of light inside the optical volume has been observed. A specific study of the ensemble of phenomena called Light Noise has been carried out in-situ, and in an external laboratory, in order to characterize the signals and to identify the possible processes underlying the effect. Some mechanisms of instrumental noise originating from the PMTs were identified and it has been found that the leading one arises from the light emission localized on the photomultiplier base and produced by the combined effect of heat and high voltage across the transparent epoxy resin covering the electric components. The correlation of the rate and the amplitude of the signal with the temperature has been observed. For the first detector in operation the induced background has been mitigated using online and offline analysis selections based on timing and light pattern of the signals, while a modification of the photomultiplier assembly has been implemented for the second detector in order to blacken the PMT bases.

  13. Sediment and Planform Controls on the Spontaneous Formation and Self Maintenance of Pool-Riffle Sequences

    NASA Astrophysics Data System (ADS)

    De Almeida, G. M.; Rodriguez, J. F.

    2011-12-01

    Continuous numerical simulations coupling unsteady-flow, fractional sediment transport, morphodynamics and grain sorting have been carried out to investigate the complex mechanisms and interactions driving the formation of the irregular morphology and sediment sorting patterns found in streams with pool-riffle sequences. We performed a series of experiments based on field data in which we explore the spontaneous formation of pool-riffle sequences from an initially flat bed topography and the resilience of the bedforms to a series of flood events. Firstly, a one-year long unsteady flow simulation remarkably captured the spontaneous formation of both bed profile and longitudinal sediment sorting observed in the reach. Results show a strong correlation between the stream width and the location and height of pools and riffles. We also performed simulations on existing pool-riffle sequences and analysed feedback mechanisms that enhance the bedforms self maintenance including riffle control, armouring and selective transport. The detailed information provided by these simulations has paved the way for a novel hypothesis explaining the dynamics in pool-riffle sequences, which is strongly linked to the disparity in the time scales of sorting and morphodynamic processes, as well as to the variability of the flow regime. Finally, a series of long term steady flow runs were carried out to study the bed and grain sorting evolution both during the formation and degradation of pool-rifle sequences, demonstrating that steady flows cannot maintain or generate the sediment sorting observed in natural streams.

  14. Electrostatic control of acid mist emissions

    SciTech Connect

    Dahlin, R S; Brown, T D

    1991-01-01

    This paper describes a two-phased study of the control of acid mist emissions using a compact, wet electrostatic precipitator (WESP). The goal of the study was to determine the degree of acid mist control that could be achieved when a compact WESP is used to replace or augment the mist eliminators in a flue gas desulfurization (FGD) system. Phase I of the study examined the electrical operation of a lab-scale WESP collecting an acid mist from a coal combustion pilot plant equipped with a spray chamber. The results of this study were used to develop and validate a computer model of the WESP. In Phase II, measurements were made at two utility scrubber installations to determine the loadings of acid mist, fly ash, and scrubber carryover. These measurements were used as input to the model to project the performance of a retrofitted WESP.

  15. IDENTIFICATION, ASSESSMENT, AND CONTROL OF FUGITIVE PARTICULATE EMISSIONS

    EPA Science Inventory

    The technical manual, designed to assist national, state, and local control agency personnel and industry personnel in evaluating fugitive emission control plans and in developing cost-effective control strategies, describes the identification, assessment, and control of fugitive...

  16. Amplified spontaneous emission from PicoGreen dye intercalated in deoxyribonucleic acid lipid complex

    NASA Astrophysics Data System (ADS)

    Pradeep, C.; Vallabhan, C. P. G.; Radhakrishnan, P.; Nampoori, V. P. N.

    2015-12-01

    DNA as a genetic biomolecule is more commonly referred to in life sciences, genetics, and microbiology. With the development of ‘DNA photonics’, it has shown tremendous applicability as an optical and photonic material. In this letter, we introduce a novel dye PicoGreen as a lasing medium in which DNA not only acts as a host matrix but also functions as a fluorescence enhancer. A dramatic increase in the fluorescence led us to the observation of optical amplification in dye doped DNA thin films. We also indicate the possible tunability of the output emission in the green-yellow region. With the obtained results, we have enough reasons to lead to the development of DNA-based bio-lasers.

  17. Naphthyl-functionalized oligophenyls: Photophysical properties, film morphology, and amplified spontaneous emission

    NASA Astrophysics Data System (ADS)

    Ma, Lin; Wu, Zhaoxin; Lei, Ting; Yu, Yue; Yuan, Fang; Jiao, Bo; Hou, Xun

    2016-04-01

    Herein, we reported a series of deep-blue-emitting naphthyl-functionalized oligophenyls as new organic laser active materials with tunable wavelength from 385 to 410 nm in solid state. Introduction of peripheral naphthyl into the oligophenyls enabled the great sterical dimensions due to the prominent steric hindrance but not destroyed the molecular conjugation. We assumed that it would suppress the π-π stacking efficiently, driving by intermolecular interaction, to hinder crystallization in solid films. Finally, the neat films of naphthyl-functionalized oligophenyls demonstrated amorphous state compared to the polycrystalline state of oligophenyls. Thus, naphthyl-functionalized oligophenyls displayed high emission quantum yield (22-35%) in solid state neat films. In addition, these molecules possessed large oscillator strength and radiative decay rate, as predicted by the theoretical analysis. The outstanding photophysical properties and amorphous films render naphthyl-functionalized oligophenyls a new class of optical gain media in solid state.

  18. Peritonitis - spontaneous

    MedlinePlus

    ... a catheter used in peritoneal dialysis. Antibiotics may control infection in cases of spontaneous peritonitis with liver or kidney disease. Intravenous therapy can treat dehydration . You may need to stay in the hospital so health care providers can rule out conditions ...

  19. Control emissions from marine vessel loading

    SciTech Connect

    Lawrence, G.N.; Cross, S.R.

    1994-03-01

    Regulations set by the US Coast Guard require safety measures during the loading of marine vessels connected to vapor collection systems. These regulations (which were promulgated in July 1990) immediately impacted all companies involved with the loading of benzene, due to previously enacted US Environmental Protection Agency regulations governing benzene transfer. In addition, regulations issued by the states of California, New Jersey, and Louisiana impose additional marine emission control requirements. These regulations effectively work together--the federal or state environmental rule first requires the collection of the vapors generate from vessel loading, and then the Coast Guard regulation governs the safety features that must be applied to the system. Depending on the vapor pressure of the chemical, a 10,000-barrel barge may emit over one ton of chemical to the atmosphere. Such large volumes make marine loading a prime target for the push to further reduce atmospheric pollution, and its is a good be that many more companies will be asked to look at the recovery of vapors during the loading of marine vessels. This article will aid the engineer who may be asked to evaluate the various methods of controlling emissions from vessel loading. It provides some guidance on the requirements of the Coast Guard regulations and briefly outlines some of the technologies that have been used to process the collected vapors. Some important design considerations unique to marine systems are discussed to help engineers avoid some of the potential pitfalls. Finally, some estimated costs are provided for two common types of marine vapor control systems.

  20. 40 CFR 89.110 - Emission control information label.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 20 2011-07-01 2011-07-01 false Emission control information label. 89.110 Section 89.110 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) CONTROL OF EMISSIONS FROM NEW AND IN-USE NONROAD COMPRESSION-IGNITION ENGINES Emission Standards and Certification Provisions §...

  1. 40 CFR 89.110 - Emission control information label.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Emission control information label. 89.110 Section 89.110 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) CONTROL OF EMISSIONS FROM NEW AND IN-USE NONROAD COMPRESSION-IGNITION ENGINES Emission Standards and Certification Provisions §...

  2. 40 CFR 89.110 - Emission control information label.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 21 2012-07-01 2012-07-01 false Emission control information label. 89.110 Section 89.110 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) CONTROL OF EMISSIONS FROM NEW AND IN-USE NONROAD COMPRESSION-IGNITION ENGINES Emission Standards and Certification Provisions §...

  3. Spontaneous emission from a single two-level atom in the presence of N initially unexcited identical atoms

    NASA Astrophysics Data System (ADS)

    Cummings, F. W.

    1986-03-01

    The quantum-electrodynamical problem of N identical two-level atoms interacting with M field modes is considered, and an exact solution for the case of spontaneous emission from a single atom is obtained. The behavior of this system is shown to be quite different from the exponential decay of a single excited atom radiating into free space. A 'ringing' behavior at the enigmatic frequency of approximately the square root of N, which occurs when only one mode is accessible to the field, persists when many modes are present. When a continuum of modes is accessible, the long-time limit shows that the energy of the originally excited atom is equally likely to be shared by the N-1 originally unexcited atoms and the electromagnetic field when M/N approaches 1. 'Radiation suppression' occurs whenever N is much greater than 1 and M is much less than N, when the originally excited atom does not emit its energy. When M = N much greater than 1, the single atom decays monotonically to zero (and approximately exponentially), but with a decay rate that is the square root of N times the Rabi frequency. Such unexpected affects are presently within experimental range.

  4. Amplified and directional spontaneous emission from arbitrary composite bodies: A self-consistent treatment of Purcell effect below threshold

    NASA Astrophysics Data System (ADS)

    Jin, Weiliang; Khandekar, Chinmay; Pick, Adi; Polimeridis, Athanasios G.; Rodriguez, Alejandro W.

    2016-03-01

    We study amplified spontaneous emission (ASE) from wavelength-scale composite bodies—complicated arrangements of active and passive media—demonstrating highly directional and tunable radiation patterns, depending strongly on pump conditions, materials, and object shapes. For instance, we show that under large enough gain, PT symmetric dielectric spheres radiate mostly along either active or passive regions, depending on the gain distribution. Our predictions are based on a recently proposed fluctuating-volume-current formulation of electromagnetic radiation that can handle inhomogeneities in the dielectric and fluctuation statistics of active media, e.g., arising from the presence of nonuniform pump or material properties, which we exploit to demonstrate an approach to modeling ASE in regimes where Purcell effect (PE) has a significant impact on the gain, leading to spatial dispersion and/or changes in power requirements. The nonlinear feedback of PE on the active medium, captured by the Maxwell-Bloch equations but often ignored in linear formulations of ASE, is introduced into our linear framework by a self-consistent renormalization of the (dressed) gain parameters, requiring the solution of a large system of nonlinear equations involving many linear scattering calculations.

  5. CONTROL OF HYDROCARBON EMISSIONS FROM GASOLINE LOADING BY REFRIGERATION SYSTEMS

    EPA Science Inventory

    The report gives results of a study of the capabilities of refrigeration systems, operated at three temperatures, to control volatile organic compound (VOC) emissions from truck loading at bulk gasoline terminals. Achievable VOC emission rates were calculated for refrigeration sy...

  6. Implications of diesel emissions control failures to emission factors and road transport NOx evolution

    NASA Astrophysics Data System (ADS)

    Ntziachristos, Leonidas; Papadimitriou, Giannis; Ligterink, Norbert; Hausberger, Stefan

    2016-09-01

    Diesel NOx emissions have been at the forefront of research and regulation scrutiny as a result of failures of late vehicle technologies to deliver on-road emissions reductions. The current study aims at identifying the actual emissions levels of late light duty vehicle technologies, including Euro 5 and Euro 6 ones. Mean NOx emission factor levels used in the most popular EU vehicle emission models (COPERT, HBEFA and VERSIT+) are compared with latest emission information collected in the laboratory over real-world driving cycles and on the road using portable emissions measurement systems (PEMS). The comparison shows that Euro 5 passenger car (PC) emission factors well reflect on road levels and that recently revealed emissions control failures do not call for any significant corrections. However Euro 5 light commercial vehicles (LCVs) and Euro 6 PCs in the 2014-2016 period exhibit on road emission levels twice as high as used in current models. Moreover, measured levels vary a lot for Euro 6 vehicles. Scenarios for future evolution of Euro 6 emission factors, reflecting different degree of effectiveness of emissions control regulations, show that total NOx emissions from diesel Euro 6 PC and LCV may correspond from 49% up to 83% of total road transport emissions in 2050. Unless upcoming and long term regulations make sure that light duty diesel NOx emissions are effectively addressed, this will have significant implications in meeting future air quality and national emissions ceilings targets.

  7. Organic Crystals with Near-Infrared Amplified Spontaneous Emissions Based on 2'-Hydroxychalcone Derivatives: Subtle Structure Modification but Great Property Change.

    PubMed

    Cheng, Xiao; Wang, Kai; Huang, Shuo; Zhang, Houyu; Zhang, Hongyu; Wang, Yue

    2015-07-13

    A series of highly efficient deep red to near-infrared (NIR) emissive organic crystals 1-3 based on the structurally simple 2'-hydroxychalcone derivatives were synthesized through a simple one-step condensation reaction. Crystal 1 displays the highest quantum yield (Φf) of 0.32 among the reported organic single crystals with an emission maximum (λem) over 710 nm. Comparison between the bright emissive crystals 1-3 and the nearly nonluminous compounds 4-7 clearly gives evidence that a subtle structure modification can arouse great property changes, which is instructive in designing new high-efficiency organic luminescent materials. Notably, crystals 1-3 exhibit amplified spontaneous emissions (ASE) with extremely low thresholds. Thus, organic deep red to NIR emissive crystals with very high Φf have been obtained and are found to display the first example of NIR fluorescent crystal ASE. PMID:26036645

  8. Change in spontaneous baroreflex control of pulse interval during heat stress in humans.

    PubMed

    Lee, Kichang; Jackson, Dwayne N; Cordero, Douglas L; Nishiyasu, Takeshi; Peters, Jochen K; Mack, Gary W

    2003-11-01

    Spontaneous baroreflex control of pulse interval (PI) was assessed in healthy volunteers under thermoneutral and heat stress conditions. Subjects rested in the supine position with their lower legs in a water bath at 34 degrees C. Heat stress was imposed by increasing the bath temperature to 44 degrees C. Arterial blood pressure (Finapres), PI (ECG), esophageal and skin temperature, and stroke volume were continuously collected during each 5-min experimental stage. Spontaneous baroreflex function was evaluated by multiple techniques, including 1) the mean slope of the linear relationship between PI and systolic blood pressure (SBP) with three or more simultaneous increasing or decreasing sequences, 2) the linear relationship between changes in PI and SBP (deltaPI/DeltaSBP) derived by using the first differential equation, 3) the linear relationship between changes in PI and SBP with simultaneously increasing or decreasing sequences (+deltaPI/+deltaSBP or -deltaPI/-deltaSBP), and 4) transfer function analysis. Heat stress increased esophageal temperature by 0.6 +/- 0.1 degrees C, decreased PI from 1,007 +/- 43 to 776 +/- 37 ms and stroke volume by 16 +/- 5 ml/beat. Heat stress reduced baroreflex sensitivity but increased the incidence of baroreflex slopes from 5.2 +/- 0.8 to 8.6 +/- 0.9 sequences per 100 heartbeats. Baroreflex sensitivity was significantly correlated with PI or vagal power (r2 = 0.45, r2 = 0.71, respectively; P < 0.05). However, the attenuation in baroreflex sensitivity during heat stress appeared related to a shift in autonomic balance (shift in resting PI) rather than heat stress per se. PMID:12882987

  9. A quantum dot single-photon source with on-the-fly all-optical polarization control and timed emission

    NASA Astrophysics Data System (ADS)

    Heinze, Dirk; Breddermann, Dominik; Zrenner, Artur; Schumacher, Stefan

    2015-10-01

    Sources of single photons are key elements for applications in quantum information science. Among the different sources available, semiconductor quantum dots excel with their integrability in semiconductor on-chip solutions and the potential that photon emission can be triggered on demand. Usually, the photon is emitted from a single-exciton ground state. Polarization of the photon and time of emission are either probabilistic or pre-determined by electronic properties of the system. Here, we study the direct two-photon emission from the biexciton. The two-photon emission is enabled by a laser pulse driving the system into a virtual state inside the band gap. From this intermediate state, the single photon of interest is then spontaneously emitted. We show that emission through this higher-order transition provides a versatile approach to generate a single photon. Through the driving laser pulse, polarization state, frequency and emission time of the photon can be controlled on-the-fly.

  10. Brief Report: Pilot Randomized Controlled Trial of Reciprocal Imitation Training for Teaching Elicited and Spontaneous Imitation to Children with Autism

    ERIC Educational Resources Information Center

    Ingersoll, Brooke

    2010-01-01

    Children with autism exhibit significant deficits in imitation skills. Reciprocal Imitation Training (RIT), a naturalistic imitation intervention, was developed to teach young children with autism to imitate during play. This study used a randomized controlled trial to evaluate the efficacy of RIT on elicited and spontaneous imitation skills in 21…

  11. COMPUTER-CONTROLLED, REAL-TIME AUTOMOBILE EMISSIONS MONITORING SYSTEM

    EPA Science Inventory

    A minicomputer controlled automotive emissions sampling and analysis system (the Real-Time System) was developed to determine vehicular modal emissions over various test cycles. This data acquisition system can sample real-time emissions at a rate of 10 samples/s. A buffer utiliz...

  12. Emissions control for ground power gas turbines

    NASA Technical Reports Server (NTRS)

    Rudney, R. A.; Priem, R. J.; Juhasz, A. J.; Anderson, D. N.; Mroz, T. S.; Mularz, E. J.

    1977-01-01

    The similarities and differences of emissions reduction technology for aircraft and ground power gas turbines is described. The capability of this technology to reduce ground power emissions to meet existing and proposed emissions standards is presented and discussed. Those areas where the developing aircraft gas turbine technology may have direct application to ground power and those areas where the needed technology may be unique to the ground power mission are pointed out. Emissions reduction technology varying from simple combustor modifications to the use of advanced combustor concepts, such as catalysis, is described and discussed.

  13. Percolating plasmonic networks for light emission control.

    PubMed

    Gaio, Michele; Castro-Lopez, Marta; Renger, Jan; van Hulst, Niek; Sapienza, Riccardo

    2015-01-01

    Optical nanoantennas have revolutionised the way we manipulate single photons emitted by individual light sources in a nanostructured photonic environment. Complex plasmonic architectures allow for multiscale light control by shortening or stretching the light wavelength for a fixed operating frequency, meeting the size of the emitter and that of propagating modes. Here, we study self-assembled semi-continuous gold films and lithographic gold networks characterised by large local density of optical state (LDOS) fluctuations around the electrical percolation threshold, a regime where the surface is characterised by large metal clusters with fractal topology. We study the formation of plasmonic networks and their effect on light emission from embedded fluorescent probes in these systems. Through fluorescence dynamics experiments we discuss the role of global long-range interactions linked to the degree of percolation and to the network fractality, as well as the local near-field contributions coming from the local electro-magnetic fields and the topology. Our experiments indicate that local properties dominate the fluorescence modification. PMID:25711923

  14. Dynamic behavioural changes in the Spontaneously Hyperactive Rat: 3. Control by reinforcer rate changes and predictability.

    PubMed

    Williams, Jonathan; Sagvolden, Geir; Taylor, Eric; Sagvolden, Terje

    2009-03-17

    Variable intervals are widely believed to produce steady rates of responding. However, based on the calming effect of unpredictability in attention deficit hyperactivity disorder (ADHD) we hypothesised that an animal model of this disorder, the Spontaneously Hyperactive (or Hypertensive) Rat, would become less active following particularly variable sequences of interval-lengths in a variable interval schedule. From a large dataset of holepokes and tray-reports by rats in a variable interval reinforcement schedule, we extracted numerous short sequences of intervals on the basis of the first, second, and third derivatives of reinforcement timing (i.e. rate, acceleration, and jerk) in recent intervals. Sets of selected intervals were compared with one another to elucidate the effect of these different derivatives on behaviour in the current interval. Results show that SHR are more active after richer recent reinforcement; after decelerating reinforcers; and after predictable reinforcers. The hypothesis is supported. In conclusion, SHR behaviour largely complies with the Extended Temporal Difference model which in turn has been previously validated against published data in ADHD. The Extended TD model therefore is able to account for two species' behaviour in a wide range of experimental paradigms. SHR are similar in several respects to group averages of children with ADHD, except that SHR have reduced variability and perform actions faster than controls. Hyperactivity in the SHR is very dependent on momentary environmentally determined states, which is an important area for future investigation of ADHD. PMID:18824035

  15. Autonomic control of heart rate and blood pressure in spontaneously hypertensive rats during aversive classical conditioning.

    PubMed

    Hatton, D C; Buchholz, R A; Fitzgerald, R D

    1981-12-01

    An examination was made of the heart rate (HR) and blood pressure (BP) responses of 7-9-wk-old spontaneously hypertensive rats (SHR) and genetical control Wistar/Kyoto (WKY) rats during aversive classical conditioning. Subsequent to the development of conditioned responding (CRs), assessments were made of the effects of selective autonomic blockade by methyl atropine (10 mg/kg), phentolamine (2 mg/kg), and propranolol (2 mg/kg). The CR complex in the two strains consisted of pressor BP CRs in conjunction with vagally mediated decelerative HR CRs in the SHR strain and sympathetically mediated accelerative HR CRs in the WKY strain. The decelerative SHR HR CR did not appear to be secondary to baroreceptor reflex activity, although such activity did appear to be involved in the pressor BP and decelerative HR orienting response (OR) and unconditioned response (UR) complex of the SHRs on the initial application of the CS and the US, respectively. Augmented pressor BP ORs, CRs, and URs in the SHRs relative to the WKYs and differential drug effects on BP and HR baselines of the two strains suggested the presence of enhanced sympathetic activity in the SHRs that was not reflected in the SHR decelerative HR CR. Phentolamine unmasked evidence of reflex beta 2-vasodilation deficiency in the SHRs that could have contributed to the enhancement of their BP OR and CR. PMID:7320284

  16. Numerical investigation of spontaneous flame propagation under Reactivity Controlled Compression Ignition (RCCI) conditions

    NASA Astrophysics Data System (ADS)

    Bhagatwala, Ankit; Sankaran, Ramanan; Kokjohn, Sage; Chen, Jacqueline

    2014-11-01

    Results from one and two-dimensional direct numerical simulations under dual-fuel Reactivity Controlled Compression Ignition (RCCI) conditions will be presented. These simulations employ an improved model of compression heating through mass source/sink terms developed in a previous work, which incorporates feedback from the flow to follow a predetermined experimental pressure trace. One-dimensional simulations explored the effect of temperature and fuel concentration gradients on the combustion mode. Two-dimensional simulations explored parametric variation in temperature stratification, pressure profiles and n-heptane concentration. Statistics derived from analysis of local diffusion/reaction balances were used to elucidate combustion characteristics for the different cases. Both deflagration and spontaneous ignition modes were observed to co-exist. Higher n-heptane concentration and higher level of thermal stratification resulted in a greater degree of flame propagation, whereas lower n-heptane concentration (higher fraction of iso-octane) and higher pressure resulted in more prevalent autoignition. Starting with a uniform initial temperature and a stratified n-heptane concentration also resulted in a large fraction of combustion occurring through flame propagation.

  17. 40 CFR 52.987 - Control of hydrocarbon emissions.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 3 2012-07-01 2012-07-01 false Control of hydrocarbon emissions. 52... (CONTINUED) APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS Louisiana § 52.987 Control of hydrocarbon... compliance date of January 1, 1980. This shall result in an estimated hydrocarbon emission reduction of...

  18. 40 CFR 52.987 - Control of hydrocarbon emissions.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 3 2011-07-01 2011-07-01 false Control of hydrocarbon emissions. 52... (CONTINUED) APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS Louisiana § 52.987 Control of hydrocarbon... compliance date of January 1, 1980. This shall result in an estimated hydrocarbon emission reduction of...

  19. 40 CFR 52.987 - Control of hydrocarbon emissions.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 3 2010-07-01 2010-07-01 false Control of hydrocarbon emissions. 52... (CONTINUED) APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS Louisiana § 52.987 Control of hydrocarbon... compliance date of January 1, 1980. This shall result in an estimated hydrocarbon emission reduction of...

  20. 40 CFR 52.987 - Control of hydrocarbon emissions.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 3 2014-07-01 2014-07-01 false Control of hydrocarbon emissions. 52... (CONTINUED) APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS Louisiana § 52.987 Control of hydrocarbon... compliance date of January 1, 1980. This shall result in an estimated hydrocarbon emission reduction of...

  1. 40 CFR 52.987 - Control of hydrocarbon emissions.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 3 2013-07-01 2013-07-01 false Control of hydrocarbon emissions. 52... (CONTINUED) APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS Louisiana § 52.987 Control of hydrocarbon... compliance date of January 1, 1980. This shall result in an estimated hydrocarbon emission reduction of...

  2. 40 CFR 52.1384 - Emission control regulations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 4 2010-07-01 2010-07-01 false Emission control regulations. 52.1384 Section 52.1384 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS (CONTINUED) Montana § 52.1384 Emission control regulations. (a) Administrative Rules...

  3. 40 CFR 52.1384 - Emission control regulations.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 4 2013-07-01 2013-07-01 false Emission control regulations. 52.1384 Section 52.1384 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS (CONTINUED) Montana § 52.1384 Emission control regulations. (a) Administrative Rules...

  4. Design and control of a demand flow system assuring spontaneous breathing of a patient connected to an HFO ventilator.

    PubMed

    Roubík, Karel; Ráfl, Jakub; van Heerde, Marc; Markhorst, Dick G

    2011-11-01

    Lung protective ventilation is intended to minimize the risk of ventilator induced lung injury and currently aimed at preservation of spontaneous breathing during mechanical ventilation. High-frequency oscillatory ventilation (HFOV) is a lung protective ventilation strategy. Commonly used high-frequency oscillatory (HFO) ventilators, SensorMedics 3100, were not designed to tolerate spontaneous breathing. Respiratory efforts in large pediatric and adult patients impose a high workload to the patient and may cause pressure swings that impede ventilator function. A Demand Flow System (DFS) was designed to facilitate spontaneous breathing during HFOV. Using a linear quadratic Gaussian state feedback controller, the DFS alters the inflow of gas into the ventilator circuit, so that it instantaneously compensates for the changes in mean airway pressure (MAP) in the ventilator circuit caused by spontaneous breathing. The undesired swings in MAP are thus eliminated. The DFS significantly reduces the imposed work of breathing and improves ventilator function. In a bench test the performance of the DFS was evaluated using a simulator ASL 5000. With the gas inflow controlled, MAP was returned to its preset value within 115 ms after the beginning of inspiration. The DFS might help to spread the use of HFOV in clinical practice. PMID:21859597

  5. Gaseous emissions from plants in controlled environments

    NASA Technical Reports Server (NTRS)

    Dubay, Denis T.

    1988-01-01

    Plant growth in a controlled ecological life support system may entail the build-up over extended time periods of phytotoxic concentrations of volatile organic compounds produced by the plants themselves. Ethylene is a prominent gaseous emission of plants, and is the focus of this report. The objective was to determine the rate of ethylene release by spring wheat, white potato, and lettuce during early, middle, and late growth stages, and during both the light and dark segments of the diurnal cycle. Plants grown hydroponically using the nutrient film technique were covered with plexiglass containers for 4 to 6 h. At intervals after enclosure, gas samples were withdrawn with a syringe and analyzed for ethylene with a gas chromatograph. Lettuce produced 10 to 100 times more ethylene than wheat or potato, with production rates ranging from 141 to 158 ng g-dry/wt/h. Wheat produced from 1.7 to 14.3 ng g-dry/wt/h, with senescent wheat producing the least amount and flowering wheat the most. Potatoes produced the least amount of ethylene, with values never exceeding 5 ng g-dry/wt/h. Lettuce and potatoes each produced ethylene at similar rates whether in dark period or light period. Ethylene sequestering of 33 to 43 percent by the plexiglass enclosures indicated that these production estimates may be low by one-third to one-half. These results suggest that concern for ethylene build-up in a contained atmosphere should be greatest when growing lettuce, and less when growing wheat or potato.

  6. Detection and control of spontaneous heating in coal mine pillars -- A case study

    SciTech Connect

    Timko, R.J.; Derick, R.L.

    1995-12-31

    This US Bureau of Mines study examined spontaneous heating episodes in coal mine pillars in an active underground coal mine. The information obtained from these incidents was then analyzed to learn which sampling methods provided the earliest indication of pillar heating. The objective of this study was to discover if the location of future events of pillar spontaneous heating could be inferred from the available information. The spontaneous heating-prone area in this evaluation involved pillars located just in by the mine portals. Several detection methods were used to determine gas levels outside as well as inside the affected pillars. It was hoped that, by incorporating external and internal sampling methods into an organized program, locations undergoing spontaneous heat could be determined more readily. This study found that by drilling small-diameter boreholes into the pillars, then obtaining gas samples from the affected pillars, the ability to locate early spontaneous heating episodes was improved. However, the ability to accurately predict future spontaneous heat events remains in question.

  7. Controlled and Spontaneous Magnetic Field Generation in a Gun-Driven Spheromak

    SciTech Connect

    Woodruff, S; Cohen, B I; Hooper, E B; McLean, H S; Stallard, B W; Hill, D N; Holcomb, C T; Romero-Talamas, C; Wood, R D; Cone, G; Sovinec, C R

    2004-10-01

    In the Sustained Spheromak Physics Experiment, SSPX, progress has been made in understanding the mechanisms that generate fields by helicity injection. SSPX injects helicity (linked magnetic flux) from 1-m diameter magnetized coaxial electrodes into a flux-conserving confinement region. Control of magnetic fluctuations ({delta}B/B{approx}1% on the midplane edge) yields T{sub e} profiles peaked at > 200eV. Trends indicate a limiting beta ({beta}{sub e} {approx} 4-6%), and so we have been motivated to increase T{sub e} by operating with stronger magnetic field. Two new operating modes are observed to increase the magnetic field: (A) Operation with constant current and spontaneous gun voltage fluctuations. In this case, the gun is operated continuously at the threshold for ejection of plasma from the gun: stored magnetic energy of the spheromak increases gradually with {delta}B/B {approx}2% and large voltage fluctuations ({delta}V {approx} 1kV), giving a 50% increase in current amplification, I{sub tor}/I{sub gun}. (B) Operation with controlled current pulses. In this case, spheromak magnetic energy increases in a stepwise fashion by pulsing the gun, giving the highest magnetic fields observed for SSPX ({approx}0.7T along the geometric axis). By increasing the time between pulses, a quasi-steady sustainment is produced (with periodic good confinement), comparing well with resistive MHD simulations. In each case, the processes that transport the helicity into the spheromak are inductive and exhibit a scaling of field with current that exceeds those previously obtained. We use our newly found scaling to suggest how to achieve higher temperatures with a series of pulses.

  8. Temperature Dependence of Factors Controlling Isoprene Emissions

    NASA Technical Reports Server (NTRS)

    Duncan, Bryan N.; Yoshida, Yasuko; Damon, Megan R.; Douglass, Anne R.; Witte, Jacquelyn C.

    2009-01-01

    We investigated the relationship of variability in the formaldehyde (HCHO) columns measured by the Aura Ozone Monitoring Instrument (OMI) to isoprene emissions in the southeastern United States for 2005-2007. The data show that the inferred, regional-average isoprene emissions varied by about 22% during summer and are well correlated with temperature, which is known to influence emissions. Part of the correlation with temperature is likely associated with other causal factors that are temperature-dependent. We show that the variations in HCHO are convolved with the temperature dependence of surface ozone, which influences isoprene emissions, and the dependence of the HCHO column to mixed layer height as OMI's sensitivity to HCHO increases with altitude. Furthermore, we show that while there is an association of drought with the variation in HCHO, drought in the southeastern U.S. is convolved with temperature.

  9. Gas turbine combustion and emission control

    NASA Astrophysics Data System (ADS)

    Schetter, B.

    The fundamentals of combustion are discussed in the context of gaseous and liquid fuels and gas turbine fuels. Methods for reducing the emission of pollutants in gas turbines are considered. These emissions are carbon monoxide, unburnt hydrocarbons, smoke/soot, nitrogen oxides, sulphur oxides, and carbon dioxide. The focus is on nitrogen oxides. The general principles of combustor and burner design are considered: aero/can type combustors, silo combustors, and annular combustors. Premix and diffusion flames are discussed.

  10. Active control of excessive sound emission on a mobile device.

    PubMed

    Jeon, Se-Woon; Youn, Dae Hee; Park, Young-cheol; Lee, Gun-Woo

    2015-04-01

    During a phone conversation, loud vocal emission from the far-end to the near-end space can disturb nearby people. In this paper, the possibility of actively controlling such unwanted sound emission using a control source placed on the mobile device is investigated. Two different approaches are tested: Global control, minimizing the potential energy measured along a volumetric space surface, and local control, minimizing the squared sound pressure at a discrete point on the phone. From the test results, both approaches can reduce the unwanted sound emission by more than 6 dB in the frequency range up to 2 kHz. PMID:25920885

  11. Self-amplified spontaneous emission saturation at the Advanced Photon Source free-electron laser (abstract) (invited)

    NASA Astrophysics Data System (ADS)

    Moog, E. R.; Milton, S. V.; Arnold, N. D.; Benson, C.; Berg, W.; Biedron, S. G.; Borland, M.; Chae, Y.-C.; Dejus, R. J.; Den Hartog, P. K.; Deriy, B.; Erdmann, M.; Gluskin, E.; Huang, Z.; Kim, K.-J.; Lewellen, J. W.; Li, Y.; Lumpkin, A. H.; Makarov, O.; Nassiri, A.; Sajaev, V.; Soliday, R.; Tieman, B. J.; Trakhtenberg, E. M.; Travish, G.; Vasserman, I. B.; Vinokurov, N. A.; Wiemerslage, G.; Yang, B. X.

    2002-03-01

    Today, many bright photon beams in the ultraviolet and x-ray wavelength range are produced by insertion devices installed in specially designed third-generation storage rings. There is the possibility of producing photon beams that are orders of magnitude brighter than presently achieved at synchrotron sources, by using self-amplified spontaneous emission (SASE). At the Advanced Photon Source (APS), the low-energy undulator test line (LEUTL) free-electron laser (FEL) project was built to explore the SASE process in the visible through vacuum ultraviolet wavelength range. While the understanding gained in these experiments will guide future work to extend SASE FELs to shorter wavelengths, the APS FEL itself will become a continuously tunable, bright light source. Measurements of the SASE process to saturation have been made at 530 and 385 nm. A number of quantities were measured to confirm our understanding of the SASE process and to verify that saturation was reached. The intensity of the FEL light was measured versus distance along the FEL, and was found to flatten out at saturation. The statistical variation of the light intensity was found to be wide in the exponential gain region where the intensity is expected to be noisy, and narrower once saturation was reached. Absolute power measurements compare well with GINGER simulations. The FEL light spectrum at different distances along the undulator line was measured with a high-resolution spectrometer, and the many sharp spectral spikes at the beginning of the SASE process coalesce into a single peak at saturation. The energy spread in the electron beam widens markedly after saturation due to the number of electrons that transfer a significant amount of energy to the photon beam. Coherent transition radiation measurements of the electron beam as it strikes a foil provide additional confirmation of the microbunching of the electron beam. The quantities measured confirm that saturation was indeed reached. Details are

  12. Structure of the spontaneous emission spectra of high-{gamma} free electron lasers as measured at the Darmstadt (S-Dalinac) FEL

    SciTech Connect

    Renz, G.; Spindler, G.; Schlott, V.

    1995-12-31

    Recent spontaneous emission measurements at the Darmstadt infrared FEL indicate a relatively broad (down-shifted) spectrum with several intensity maxima. The typical features of the measured spectrum can be well reproduced by a numerical simulation comprising the 3-d electron dynamics in a realizable planar wiggler field, the spontaneous radiation according to the well-known Jackson formula, as well as the detection of the radiation with a finite aperture detector. An analytical consideration attributes the observed down-shift to the reduced Doppler up-shift of the radiation as observed under a finite angle with respect to the axis. The intensity peaks appear as a consequence of a modulation of the transverse velocity amplitudes of the electrons due to the betatron oscillation. The spectral spacing of these {open_quote}sidebands{close_quote} are roughly given by the Doppler up-shifted betatron frequency. Consequences for very high energy FELs will be discussed.

  13. Dynamic control of light emission faster than the lifetime limit using VO2 phase-change

    NASA Astrophysics Data System (ADS)

    Cueff, Sébastien; Li, Dongfang; Zhou, You; Wong, Franklin J.; Kurvits, Jonathan A.; Ramanathan, Shriram; Zia, Rashid

    2015-10-01

    Modulation is a cornerstone of optical communication, and as such, governs the overall speed of data transmission. Currently, the two main strategies for modulating light are direct modulation of the excited emitter population (for example, using semiconductor lasers) and external optical modulation (for example, using Mach-Zehnder interferometers or ring resonators). However, recent advances in nanophotonics offer an alternative approach to control spontaneous emission through modifications to the local density of optical states. Here, by leveraging the phase-change of a vanadium dioxide nanolayer, we demonstrate broadband all-optical direct modulation of 1.5 μm emission from trivalent erbium ions more than three orders of magnitude faster than their excited state lifetime. This proof-of-concept demonstration shows how integration with phase-change materials can transform widespread phosphorescent materials into high-speed optical sources that can be integrated in monolithic nanoscale devices for both free-space and on-chip communication.

  14. Dynamic control of light emission faster than the lifetime limit using VO2 phase-change.

    PubMed

    Cueff, Sébastien; Li, Dongfang; Zhou, You; Wong, Franklin J; Kurvits, Jonathan A; Ramanathan, Shriram; Zia, Rashid

    2015-01-01

    Modulation is a cornerstone of optical communication, and as such, governs the overall speed of data transmission. Currently, the two main strategies for modulating light are direct modulation of the excited emitter population (for example, using semiconductor lasers) and external optical modulation (for example, using Mach-Zehnder interferometers or ring resonators). However, recent advances in nanophotonics offer an alternative approach to control spontaneous emission through modifications to the local density of optical states. Here, by leveraging the phase-change of a vanadium dioxide nanolayer, we demonstrate broadband all-optical direct modulation of 1.5 μm emission from trivalent erbium ions more than three orders of magnitude faster than their excited state lifetime. This proof-of-concept demonstration shows how integration with phase-change materials can transform widespread phosphorescent materials into high-speed optical sources that can be integrated in monolithic nanoscale devices for both free-space and on-chip communication. PMID:26489436

  15. X-RAY NONLINEAR OPTICAL PROCESSES IN ATOMS USING A SELF-AMPLIFIED SPONTANEOUS EMISSION FREE-ELECTRON LASER

    SciTech Connect

    Rohringer, N

    2008-08-08

    X-ray free electron lasers (xFEL) will open new avenues to the virtually unexplored territory of non-linear interactions of x rays with matter. Initially xFELs will be based on the principle of self-amplified spontaneous emission (SASE). Each SASE pulse consists of a number of coherent intensity spikes of random amplitude, i.e. the process is chaotic and pulses are irreproducible. The coherence time of SASE xFELs will be a few femtoseconds for a photon energy near 1 keV. The importance of coherence properties of light in non-linear optical processes was theoretically discovered in the early 1960s. In this contribution we will illustrate the impact of field chaoticity on x-ray non-linear optical processes on neon for photon energies around 1 keV and intensities up to 10{sup 18} W/cm{sup 2}. Resonant and non-resonant processes are discussed. The first process to be addressed is the formation of a double-core hole in neon by photoionization with x rays above 1.25 keV energy. In contrast to the long-wavelength regime, non-linear optical processes in the x-ray regime are characterized in general by sequential single-photon single-electron interactions. Despite this fact, the sequential absorption of multiple x-ray photons depends on the statistical properties of the radiation field. Treating the x rays generated by a SASE FEL as fully chaotic, a quantum-mechanical analysis of inner-shell two-photon absorption is performed. By solving a system of time-dependent rate equations, we demonstrate that double-core hole formation in neon via x-ray two-photon absorption is enhanced by chaotic photon statistics. At an intensity of 10{sup 16} W/cm{sup 2}, the statistical enhancement is about 30%, much smaller than typical values in the optical regime. The second part of this presentation discusses the resonant Auger effect of atomic neon at the 1s-3p transition (at 867.1 eV). For low X-ray intensity, the excitation process 1s {yields} 3p in Neon can be treated perturbatively. The

  16. Controlling laser emission by selecting crystal orientation

    NASA Astrophysics Data System (ADS)

    Chen, Lijuan; Han, Shujuan; Wang, Zhengping; Wang, Jiyang; Zhang, Huanjin; Yu, Haohai; Han, Shuo; Xu, Xinguang

    2013-01-01

    Based on the anisotropy of laser crystal, we demonstrate a method of adjusting laser emission by selecting crystal orientation. When the light propagating direction varies from a to c axis of Nd:LiGd(MoO4)2 crystal, emission wavelength exhibits a sensitive change of 1061 nm → 1061/1062 + 1068 nm → 1068 nm. The experimental discipline is well explained by a theoretical study of simulating on the spatial distribution of stimulated emission cross-section. This letter manifests that the laser property along non-principal-axis direction is also valuable for research and application, which breaks through the traditional custom of using laser materials processed along principal-axis.

  17. Controls over hydrocarbon emissions from boreal forest conifers

    SciTech Connect

    Lerdau, M.; Litvak, M.; Monson, R. |

    1995-06-01

    The emissions of monoterpenes and isoprene were measured from two species of conifers native to the boreal forest of Canada, jack pine, Pinus rigida, and black spruce, Picea Mariana. We examined the effects of phenology and needle age on the emissions of these compounds, and the variations in tissue concentrations of monoterpenes. We measured photosynthetic carbon uptake and hydrocarbon emissions at two sites in northern Saskatchewan under controlled light, temperatures, and CO{sub 2} concentrations, and analyzed carbon uptake rates using an infra-red gas analyzer and hydrocarbon emissions using a solid sorbent/thermal desorption system coupled to a gas chromatograph with a mass spectrometer. Our data indicate a strong effect of temperature and seasonality on emissions but only small effects of site conditions. These results suggest that regional models of hydrocarbon emissions from boreal forests should focus on temperature and phenology as the most important controlling variables.

  18. CONTROLLING NOX EMISSION FROM INDUSTRIAL SOURCES

    EPA Science Inventory

    A number of regulatory actions focused on reducing NOx emissions from stationary combustion sources have been taken in the United States in the last decade. These actions include the Acid Rain NOx regulations, the Ozone Transport Commission's NOx ...

  19. Sulfur oxide adsorbents and emissions control

    DOEpatents

    Li, Liyu; King, David L.

    2006-12-26

    High capacity sulfur oxide absorbents utilizing manganese-based octahedral molecular sieve (Mn--OMS) materials are disclosed. An emissions reduction system for a combustion exhaust includes a scrubber 24 containing these high capacity sulfur oxide absorbents located upstream from a NOX filter 26 or particulate trap.

  20. Emission control devices, fuel additive, and fuel composition changes.

    PubMed Central

    Piver, W T

    1977-01-01

    Emission control devices are installed to meet the exhaust standards of the Clean Air Act for carbon monoxide and hydrocarbons, and it is necessary to know, from a public health point of view, how exhaust emissions may be affected by changes in fuel additives and fuel composition. Since these topics are concerned with developing technologies, the available literature on exhaust emission characteristics and the limited information on health effects, is reviewed. PMID:71235

  1. Emission control devices, fuel additive, and fuel composition changes.

    PubMed

    Piver, W T

    1977-08-01

    Emission control devices are installed to meet the exhaust standards of the Clean Air Act for carbon monoxide and hydrocarbons, and it is necessary to know, from a public health point of view, how exhaust emissions may be affected by changes in fuel additives and fuel composition. Since these topics are concerned with developing technologies, the available literature on exhaust emission characteristics and the limited information on health effects, is reviewed. PMID:71235

  2. Alternative control technology document for bakery oven emissions. Final report

    SciTech Connect

    Sanford, C.W.

    1992-12-01

    The document was produced in response to a request by the baking industry for Federal guidance to assist in providing a more uniform information base for State decision-making with regard to control of bakery oven emissions. The information in the document pertains to bakeries that produce yeast-leavened bread, rolls, buns, and similar products but not crackers, sweet goods, or baked foodstuffs that are not yeast leavened. Information on the baking processes, equipment, operating parameters, potential emissions from baking, and potential emission control options are presented. Catalytic and regenerative oxidation are identified as the most appropriate existing control technologies applicable to VOC emissions from bakery ovens. Cost analyses for catalytic and regenerative oxidation are included. A predictive formula for use in estimating oven emissions has been derived from source tests done in junction with the development of the document. Its use and applicability are described.

  3. Achieving Acceptable Air Quality: Some Reflections on Controlling Vehicle Emissions

    NASA Astrophysics Data System (ADS)

    Calvert, J. G.; Heywood, J. B.; Sawyer, R. F.; Seinfeld, J. H.

    1993-07-01

    Motor vehicle emissions have been and are being controlled in an effort to abate urban air pollution. This article addresses the question: Will the vehicle exhaust emission control and fuel requirements in the 1990 Clean Air Act Amendments and the California Air Resources Board regulations on vehicles and fuels have a significant impact? The effective control of in-use vehicle emissions is the key to a solution to the motor vehicle part of the urban air pollution problem for the next decade or so. It is not necessary, except perhaps in Southern California, to implement extremely low new car emission standards before the end of the 20th century. Some of the proposed gasoline volatility and composition changes in reformulated gasoline will produce significant reductions in vehicle emissions (for example, reduced vapor pressure, sulfur, and light olefin and improved high end volatility), whereas others (such as substantial oxygenate addition and aromatics reduction) will not.

  4. Integrated emissions control system for residential CWS furnace

    SciTech Connect

    Balsavich, J.C. Jr.

    1991-11-01

    To meet the emission goals set by the Pittsburgh Energy Technology Center (PETC), Tecogen Inc. is developing a novel, integrated emission control system to control NO{sub x}, SO{sub 2}, and particulate emissions. At the heart of this system is a unique emissions control reactor for the control of SO{sub 2}. This reactor provides high sorbent particle residence time within the reactor while doing so in a very compact geometry. In addition to controlling SO{sub 2} emissions, the reactor provides a means of extracting a substantial amount of the particulates present in the combustion gases. Final cleanup of any fine particulates exiting the reactor, including respirable-sized particulates, is completed with the use of high efficiency bag filters. With SO{sub 2} and particulate emissions being dealt with by an emissions control reactor and bag filters, the control of NO{sub x} emissions needs to be addressed. Under a previous contract with PETC (contract No. AC22-87PC79650), Tecogen developed a residential-scale Coal Water Slurry (CWS) combustor. This combustor makes use of centrifugal forces, set up by a predominantly tangential flow field, to separate and confine larger unburned coal particles in the furnace upper chamber. Various partitions are used to retard the axial, downward flow of these particles, and thus maximize their residence time in the hottest section of the combustor. By operating this combustor under staged conditions, the local stoichiometry in the primary zone can be controlled in such a manner as to minimize NO{sub x} emissions.

  5. Angular distribution of polarized spontaneous emissions and its effect on light extraction behavior in InGaN-based light emitting diodes

    SciTech Connect

    Yuan, Gangcheng; Chen, Xinjuan; Yu, Tongjun Lu, Huimin; Chen, Zhizhong; Kang, Xiangning; Wu, Jiejun; Zhang, Guoyi

    2014-03-07

    Angular intensity distributions of differently polarized light sources in multiple quantum wells (MQWs) and their effects on extraction behavior of spontaneous emission from light emitting diode (LED) chips have been studied. Theoretical calculation based on k·p approximation, ray tracing simulation and angular electroluminescence measurement were applied in this work. It is found that the electron-hole recombination in the InGaN MQWs produces a spherical distribution of an s-polarized source and a dumbbell-shaped p-polarized source. Light rays from different polarized sources experience different extraction processes, determining the polarization degree of electro-luminescence and extraction efficiency of LEDs.

  6. Measure of the transverse coherence of a self amplified spontaneous emission of a free electron laser with the heterodyne speckles method

    NASA Astrophysics Data System (ADS)

    Siano, M.; Paroli, B.; Manfredda, M.; Alaimo, M.; Potenza, M. A. C.

    2015-05-01

    We describe the method of Heterodyne Near Field Speckles (HNFS) for the characterization of spatial and temporal coherence of radiation. The method relies on the statistical properties of the speckle field produced by spherical particles randomly distributed and suspended in a fluid. We report preliminary results obtained with broadband light sources. We discuss the results obtained with the Self-Amplified Spontaneous Emission free electron laser SPARC LAB. This method will enable to calibrate and realize a diagnostics for the X-ray, broadband betatron radiation emitted in laser-plasma accelerators.

  7. Wavefront Analysis of Nonlinear Self-Amplified Spontaneous-Emission Free-Electron Laser Harmonics in the Single-Shot Regime

    SciTech Connect

    Bachelard, R.; Chubar, O.; Mercere, P.; Idir, M.; Couprie, M.E.; Lambert, G.; Zeitoun, Ph.; Kimura, H.; Ohashi, H.; Higashiya, A.; Yabashi, M.; Nagasono, M.; Hara, T. and Ishikawa, T.

    2011-06-08

    The single-shot spatial characteristics of the vacuum ultraviolet self-amplified spontaneous emission of a free electron laser (FEL) is measured at different stages of amplification up to saturation with a Hartmann wavefront sensor. We show that the fundamental radiation at 61.5 nm tends towards a single-mode behavior as getting closer to saturation. The measurements are found in good agreement with simulations and theory. A near diffraction limited wavefront was measured. The analysis of Fresnel diffraction through the Hartmann wavefront sensor hole array also provides some further insight for the evaluation of the FEL transverse coherence, of high importance for various applications.

  8. High amplified spontaneous emission contrast of 1011 in a Nd:glass laser based on a hybrid double chirped pulse amplification scheme

    NASA Astrophysics Data System (ADS)

    Lu, X. M.; Leng, Y. X.; Sui, Z.; Li, Y. Y.; Zhang, Z. X.; Xu, Y.; Guo, X. Y.; Liu, Y. Q.

    2014-10-01

    By using a Ti:sapphire-Nd:glass hybrid double chirped pulse amplification scheme and a pulse cleaner based on optical parametric amplification and second harmonic generation, we demonstrate high amplified spontaneous emission (ASE) contrast at 1053 nm. The optimized ASE temporal contrast of the output pulse is about 1011 at about 160 ps before the main peak with an output of 140 mJ/500 fs. And the potential of 10 J level output with high ASE contrast is demonstrated in a laser system with attenuated injection.

  9. Wideband thulium-holmium-doped fiber source with combined forward and backward amplified spontaneous emission at 1600-2300  nm spectral band.

    PubMed

    Honzatko, Pavel; Baravets, Yauhen; Kasik, Ivan; Podrazky, Ondrej

    2014-06-15

    We have experimentally demonstrated two extremely wideband amplified spontaneous emission (ASE) sources. High bandwidth is achieved by combining the backward and forward ASEs generated in thulium-holmium-doped fiber using appropriate wideband couplers. The ASE source optimized for flat spectral power density covers a spectral range from 1527 to 2171 nm at a -10  dB level. The ASE source optimized for spectroscopy features an enhancement with respect to single-mode fiber (SMF) coupled halogen lamps within the spectral range from 1540 nm to more than 2340 nm covering the 800 nm bandwidth. PMID:24978559

  10. CONTROL OF MOTOR VEHICLE EMISSIONS - THE U.S. EXPERIENCE

    EPA Science Inventory

    An historical overview of the U.S. experience with controlling emissions from highway motor vehicles is presented. he evolution of new motor vehicle emissions certification practice, end-of-assembly-line inspection, in-use surveillance and recall, inspection and maintenance, and ...

  11. IRON AND STEEL PLANT OPEN SOURCE FUGITIVE EMISSION CONTROL EVALUATION

    EPA Science Inventory

    The report gives results of measurements of the control efficiency of various techniques used to mitigate emissions from open dust sources in the iron and steel industry. Of estimated emissions of 88,800 tons/year suspended particulate in 1978 (based on a 10-plant survey), 70, 13...

  12. PERFORMANCE OF EMISSIONS CONTROL SYSTEMS ON MUNICIPAL WASTE COMBUSTORS

    EPA Science Inventory

    The paper reports results of several EPA-supported field evaluations of data on gaseous pollutant emissions from modern municipal waste combustors/incinerators and emissions control by flue gas cleaning systems. The results are presented in terms of acid gas (HCl and SO2), trace ...

  13. EVALUATION OF MAINTENANCE FOR FUGITIVE VOC EMISSIONS CONTROL

    EPA Science Inventory

    The U.S. EPA Office of Air Quality Planning and Standards (OAQPS) has the responsibility for formulating regulations for the control of fugitive emissions of volatile organic compounds (VOC). 'Fugitive emissions' generally refers to the diffuse release of vaporized hydrocarbon or...

  14. Advanced Combustion and Emission Control Technical Team Roadmap

    SciTech Connect

    2013-06-01

    The Advanced Combustion and Emission Control (ACEC) Technical Team is focused on removing technical barriers to the commercialization of advanced, high-efficiency, emission-compliant internal combustion (IC) engines for light-duty vehicle powertrains (i.e., passenger car, minivan, SUV, and pickup trucks).

  15. Controls on methane emissions from Alnus glutinosa saplings.

    PubMed

    Pangala, Sunitha R; Gowing, David J; Hornibrook, Edward R C; Gauci, Vincent

    2014-02-01

    Recent studies have confirmed significant tree-mediated methane emissions in wetlands; however, conditions and processes controlling such emissions are unclear. Here we identify factors that control the emission of methane from Alnus glutinosa. Methane fluxes from the soil surface, tree stem surfaces, leaf surfaces and whole mesocosms, pore water methane concentrations and physiological factors (assimilation rate, stomatal conductance and transpiration) were measured from 4-yr old A. glutinosa trees grown under two artificially controlled water-table positions. Up to 64% of methane emitted from the high water-table mesocosms was transported to the atmosphere through A. glutinosa. Stem emissions from 2 to 22 cm above the soil surface accounted for up to 42% of total tree-mediated methane emissions. Methane emissions were not detected from leaves and no relationship existed between leaf surface area and rates of tree-mediated methane emissions. Tree stem methane flux strength was controlled by the amount of methane dissolved in pore water and the density of stem lenticels. Our data show that stem surfaces dominate methane egress from A. glutinosa, suggesting that leaf area index is not a suitable approach for scaling tree-mediated methane emissions from all types of forested wetland. PMID:24219654

  16. Genetic Control of Spontaneous Arthritis in a Four-Way Advanced Intercross Line

    PubMed Central

    Ranea, Laura Mellado; de Castro Marques, Andreia; Möller, Steffen; Gupta, Yask; Ibrahim, Saleh M.

    2013-01-01

    Identifying the genetic basis of complex diseases, such as rheumatoid arthritis, remains a challenge that requires experimental models to reduce the genetic and environmental variability. Numerous loci for arthritis have been identified in induced animal models; however, few spontaneous models have been genetically studied. Therefore, we generated a four-way advanced intercross line (AIL) from four inbred strains, including BXD2/TyJ which spontaneously develops autoimmune arthritis. A genome-wide scan for spontaneous arthritis was performed in a cohort of 366 mice of the fourth generation (G4) of this cross. Five loci contributing to clinical phenotypes were identified in chromosomes 3, 7, 13, 18, and X. Three of the loci found in this study, confirm previously identified loci; whereas two of them are novel loci. Interesting candidate genes for the loci are highlighted. This study provides a genetic overview of spontaneous arthritis in mice and aids to solve the genetic etiology of rheumatoid arthritis and to gain a better understanding of the disease. PMID:24146764

  17. Using Transfer of Stimulus Control Technology to Promote Generalization and Spontaneity of Language

    ERIC Educational Resources Information Center

    Spencer, Trina D.; Higbee, Thomas S.

    2012-01-01

    Children with autism often use newly acquired language in restricted contexts and with limited variability. Instructional tactics that embed generalization technology have shown promise for increasing spontaneity, response variation, and the generalized use of language across settings, people, and materials. In this study, we explored the…

  18. Energetic ion emission for active spacecraft control

    NASA Astrophysics Data System (ADS)

    Schmidt, R.; Arends, H.; Riedler, W.; Torkar, K.; Ruedenauer, F.; Fehringer, M.; Maehlum, B.; Narheim, B.

    1992-12-01

    First results from vacuum chamber tests are presented, and the emission behavior and characteristics of emitters producing In(+) and N2(+) beams with an energy of not less than 5 keV are described. The liquid metal ion source (LMIS) is a 'solid-needle' type liquid metal ion source using indium as a charge metal. The typical operating characteristics of the LMIS for space applications require a high voltage of 5 to 8 kV applied across the extraction electrode and the needle/reservoir combination. The nitrogen ion source (NIS) is a type of cold cathode source based on prolonged electron oscillatory paths around an electric field saddle point. Both LMIS and NIS are designed for a mean operational lifetime of 5000 hr in orbit at a typical ion emission current of 10 micro-A.

  19. Self-organized global control of carbon emissions

    NASA Astrophysics Data System (ADS)

    Zhao, Zhenyuan; Fenn, Daniel J.; Hui, Pak Ming; Johnson, Neil F.

    2010-09-01

    There is much disagreement concerning how best to control global carbon emissions. We explore quantitatively how different control schemes affect the collective emission dynamics of a population of emitting entities. We uncover a complex trade-off which arises between average emissions (affecting the global climate), peak pollution levels (affecting citizens’ everyday health), industrial efficiency (affecting the nation’s economy), frequency of institutional intervention (affecting governmental costs), common information (affecting trading behavior) and market volatility (affecting financial stability). Our findings predict that a self-organized free-market approach at the level of a sector, state, country or continent can provide better control than a top-down regulated scheme in terms of market volatility and monthly pollution peaks. The control of volatility also has important implications for any future derivative carbon emissions market.

  20. VOC from Vehicular Evaporation Emissions: Status and Control Strategy.

    PubMed

    Liu, Huan; Man, Hanyang; Tschantz, Michael; Wu, Ye; He, Kebin; Hao, Jiming

    2015-12-15

    Vehicular evaporative emissions is an important source of volatile organic carbon (VOC), however, accurate estimation of emission amounts and scientific evaluation of control strategy for these emissions have been neglected outside of the United States. This study provides four kinds of basic emission factors: diurnal, hot soak, permeation, and refueling. Evaporative emissions from the Euro 4 vehicles (1.6 kg/year/car) are about four times those of U.S. vehicles (0.4 kg/year/car). Closing this emissions gap would have a larger impact than the progression from Euro 3 to Euro 6 tailpipe HC emission controls. Even in the first 24 h of parking, China's current reliance upon the European 24 h diurnal standard results in 508 g/vehicle/year emissions, higher than 32 g/vehicle/year from Tier 2 vehicles. The U.S. driving cycle matches Beijing real-world conditions much better on both typical trip length and average speed than current European driving cycles. At least two requirements should be added to the Chinese emissions standards: an onboard refueling vapor recovery to force the canister to be sized sufficiently large, and a 48-h evaporation test requirement to ensure that adequate purging occurs over a shorter drive sequence. PMID:26599318

  1. Emission control cost-effectiveness of alternative-fuel vehicles

    SciTech Connect

    Wang, Q.; Sperling, D.; Olmstead, J.

    1993-06-14

    Although various legislation and regulations have been adopted to promote the use of alternative-fuel vehicles for curbing urban air pollution problems, there is a lack of systematic comparisons of emission control cost-effectiveness among various alternative-fuel vehicle types. In this paper, life-cycle emission reductions and life-cycle costs were estimated for passenger cars fueled with methanol, ethanol, liquefied petroleum gas, compressed natural gas, and electricity. Vehicle emission estimates included both exhaust and evaporative emissions for air pollutants of hydrocarbon, carbon monoxide, nitrogen oxides, and air-toxic pollutants of benzene, formaldehyde, 1,3-butadiene, and acetaldehyde. Vehicle life-cycle cost estimates accounted for vehicle purchase prices, vehicle life, fuel costs, and vehicle maintenance costs. Emission control cost-effectiveness presented in dollars per ton of emission reduction was calculated for each alternative-fuel vehicle types from the estimated vehicle life-cycle emission reductions and costs. Among various alternative-fuel vehicle types, compressed natural gas vehicles are the most cost-effective vehicle type in controlling vehicle emissions. Dedicated methanol vehicles are the next most cost-effective vehicle type. The cost-effectiveness of electric vehicles depends on improvements in electric vehicle battery technology. With low-cost, high-performance batteries, electric vehicles are more cost-effective than methanol, ethanol, and liquified petroleum gas vehicles.

  2. Emission current control system for multiple hollow cathode devices

    NASA Technical Reports Server (NTRS)

    Beattie, John R. (Inventor); Hancock, Donald J. (Inventor)

    1988-01-01

    An emission current control system for balancing the individual emission currents from an array of hollow cathodes has current sensors for determining the current drawn by each cathode from a power supply. Each current sensor has an output signal which has a magnitude proportional to the current. The current sensor output signals are averaged, the average value so obtained being applied to a respective controller for controlling the flow of an ion source material through each cathode. Also applied to each controller are the respective sensor output signals for each cathode and a common reference signal. The flow of source material through each hollow cathode is thereby made proportional to the current drawn by that cathode, the average current drawn by all of the cathodes, and the reference signal. Thus, the emission current of each cathode is controlled such that each is made substantially equal to the emission current of each of the other cathodes. When utilized as a component of a multiple hollow cathode ion propulsion motor, the emission current control system of the invention provides for balancing the thrust of the motor about the thrust axis and also for preventing premature failure of a hollow cathode source due to operation above a maximum rated emission current.

  3. On Io's control of Jovian decametric radio emissions

    NASA Technical Reports Server (NTRS)

    Winglee, R. M.

    1986-01-01

    Io's control of Jovian decametric radio emission (DAM) has been attributed to Io distorting the electron distribution in the inner Jovian magnetosphere. Observations of Faraday rotation in DAM are used to determine the properties of the electron distribution before and after its interaction with Io. It is shown that there is an enhancement in the density of the energetic component in the Io plasma torus correlated with certain Jovian longitude. Io's interaction with this energetic component can produce heating of this component. The Io-controlled emission is attributed to enhanced emission from the heated electrons moving down the field lines to Jupiter.

  4. Spectroscopic studies, fluorescence quenching by molecular oxygen and amplified spontaneous emission of 1,4-bis [2-(2-pyridyl) vinyl] benzene (P2VB) diolefinic laser dye

    NASA Astrophysics Data System (ADS)

    El-Daly, Samy A.; Ebeid, E. M.

    2014-04-01

    The UV-visible electronic absorption spectra, molar absorptivity, fluorescence spectra, fluorescence quantum yield and excited state lifetime of 1,4-bis [2-(2-pyridyl) vinyl] benzene P2VB were measured in different solvents. The fluorescence quenching of P2VB by molecular oxygen was also studied using lifetime measurements. A 2 × 10-4 mol dm-3 solution of P2VB in dimethyl formamide (DMF) gave amplified spontaneous emission (ASE) in blue spectral region with emission maximum at 420 nm upon pumping by 337.1 nitrogen laser pulse. The photochemical quantum yields (ϕc) of trans-cis photoisomerization of P2VB were calculated in different organic solvents. The photoreactivity of P2VB are also studied PMMA matrix.

  5. Spontaneous ultra-weak light emissions from wheat seedlings are rhythmic and synchronized with the time profile of the local gravimetric tide

    NASA Astrophysics Data System (ADS)

    Moraes, Thiago A.; Barlow, Peter W.; Klingelé, Emile; Gallep, Cristiano M.

    2012-06-01

    Semi-circadian rhythms of spontaneous photon emission from wheat seedlings germinated and grown in a constant environment (darkened chamber) were found to be synchronized with the rhythm of the local gravimetric (lunisolar) tidal acceleration. Time courses of the photon-count curves were also found to match the growth velocity profile of the seedlings. Pair-wise analyses of the data—growth, photon count, and tidal—by local tracking correlation always revealed significant coefficients ( P > 0.7) for more than 80% of any of the time periods considered. Using fast Fourier transform, the photon-count data revealed periodic components similar to those of the gravimetric tide. Time courses of biophoton emissions would appear to be an additional, useful, and innovative tool in both chronobiological and biophysical studies.

  6. Infrared amplified spontaneous emission from the 0 ((3)P0) and 0 ((1)D2) ion-pair states of molecular bromine.

    PubMed

    Hoshino, Shoma; Araki, Mitsunori; Ishiwata, Takashi; Tsukiyama, Koichi

    2016-07-28

    We report the observation of amplified spontaneous emission for the first time from the 0 ((3)P0) and 0 ((1)D2) ion-pair states of Br2 by using an optical-optical double resonance technique through the B (3)Π(0) valence state as the intermediate state. The strong infrared emission propagating along the incident laser radiation is assigned to the parallel ASE transitions from the 0 ion-pair states down to the nearby 0 ion-pair states. The subsequent UV fluorescence from the 0 states to the high vibrational levels of the ground state is also observed. By the Franck-Condon simulation of the cascade UV fluorescence, we determine the vibrational distributions in the 0 states populated by ASE, which are consistent with the intensity distribution in the dispersed infrared ASE spectrum. The lifetimes of the relevant ion-pair states are evaluated by analyzing the temporal profiles of the UV fluorescence. PMID:27410159

  7. Neurophysiology of spontaneous facial expressions: I. Motor control of the upper and lower face is behaviorally independent in adults.

    PubMed

    Ross, Elliott D; Gupta, Smita S; Adnan, Asif M; Holden, Thomas L; Havlicek, Joseph; Radhakrishnan, Sridhar

    2016-03-01

    Facial expressions are described traditionally as monolithic entities. However, humans have the capacity to produce facial blends, in which the upper and lower face simultaneously display different emotional expressions. This, in turn, has led to the Component Theory of facial expressions. Recent neuroanatomical studies in monkeys have demonstrated that there are separate cortical motor areas for controlling the upper and lower face that, presumably, also occur in humans. The lower face is represented on the posterior ventrolateral surface of the frontal lobes in the primary motor and premotor cortices and the upper face is represented on the medial surface of the posterior frontal lobes in the supplementary motor and anterior cingulate cortices. Our laboratory has been engaged in a series of studies exploring the perception and production of facial blends. Using high-speed videography, we began measuring the temporal aspects of facial expressions to develop a more complete understanding of the neurophysiology underlying facial expressions and facial blends. The goal of the research presented here was to determine if spontaneous facial expressions in adults are predominantly monolithic or exhibit independent motor control of the upper and lower face. We found that spontaneous facial expressions are very complex and that the motor control of the upper and lower face is overwhelmingly independent, thus robustly supporting the Component Theory of facial expressions. Seemingly monolithic expressions, be they full facial or facial blends, are most likely the result of a timing coincident rather than a synchronous coordination between the ventrolateral and medial cortical motor areas responsible for controlling the lower and upper face, respectively. In addition, we found evidence that the right and left face may also exhibit independent motor control, thus supporting the concept that spontaneous facial expressions are organized predominantly across the horizontal facial

  8. Self-consistent quantum-electrodynamic calculation of spontaneous emission and small-signal gain in high-voltage free-electron lasers

    NASA Astrophysics Data System (ADS)

    Chang, C. S.; Fluhler, H. U.

    1990-10-01

    A self-consistent QED (SCQED) theory of spontaneous emission of radiation and single-photon small-signal gain (SSG) is developed for FELs using the Weisskopf-Wigner method. The results agree with existing experimental data on both the line broadening and the line shift and to a reasonable extent with the measured gain. It is shown that the spontaneous-emission spectrum obtained from classical or conventional FEL theories is valid only in the limit of a short undulator that contains a small number of periods. The SSG derived from the SCQED theory is shown to reduce to Colson's (1977) gain formula in the classical limit. However, the SCQED theory predicts significant reductions in the SSG that agree well with the ACO gain data and are not predicted well by Colson's formula. It is discovered that a fundamental physical gain limit exists that is universal to all types of FELs within the limits of the single-photon transition scheme considered.

  9. Programmable smart electron emission controller for hot filament

    NASA Astrophysics Data System (ADS)

    Flaxer, Eli

    2011-02-01

    In electron ionization source, electrons are produced through thermionic emission by heating a wire filament, accelerating the electrons by high voltage, and ionizing the analyzed molecules. In such a system, one important parameter is the filament emission current that determines the ionization rate; therefore, one needs to regulate this current. On the one hand, fast responses control is needed to keep the emission current constant, but on the other hand, we need to protect the filament from damage that occurs by large filaments current transients and overheating. To control our filament current and emission current, we developed a digital circuit based on a digital signal processing controller that has several modes of operation. We used a smart algorithm that has a fast response to a small signal and a slow response to a large signal. In addition, we have several protective measures that prevent the current from reaching unsafe values.

  10. Electric-utility emissions: control strategies and costs

    SciTech Connect

    Van Horn, A.; Arpi, D.; Bowen, C.; Chapman, R.; Cooper, R.; Greenfield, S.; Moffett, M.; Wells, M.

    1981-04-01

    The Utility Simulation Model has been used to project the emissions, costs, and operating decisions of the electric utilities for each year between 1980 and 2000. For each steam generating unit in the United States, the model simulates the compliance decision, including choice of fuels and pollution controls, as well as emissions and pollution control costs. Results are aggregated to state, regional, and national levels. The results presented here, summarized by strategy for selected years, include SO/sub 2/ and NO/sub x/ emissions, annual revenue requirements, the average price of electricity, dollars per ton of SO/sub 2/ reduced, coal capacity with FGD, utility fuel consumption, and regional production of coal for utility consumption. Because the strategies analyzed were aimed at SO/sub 2/ reduction, the results focus on the emissions and costs of controlling SO/sub 2/. This report is not intended to provide complete analysis and interpretation of the numerical results given in Section 3.

  11. Inhibitory control and l2 proficiency modulate bilingual language production: evidence from spontaneous monologue and dialogue speech.

    PubMed

    Pivneva, Irina; Palmer, Caroline; Titone, Debra

    2012-01-01

    Bilingual language production requires that speakers recruit inhibitory control (IC) to optimally balance the activation of more than one linguistic system when they produce speech. Moreover, the amount of IC necessary to maintain an optimal balance is likely to vary across individuals as a function of second language (L2) proficiency and inhibitory capacity, as well as the demands of a particular communicative situation. Here, we investigate how these factors relate to bilingual language production across monologue and dialogue spontaneous speech. In these tasks, 42 English-French and French-English bilinguals produced spontaneous speech in their first language (L1) and their L2, with and without a conversational partner. Participants also completed a separate battery that assessed L2 proficiency and inhibitory capacity. The results showed that L2 vs. L1 production was generally more effortful, as was dialogue vs. monologue speech production although the clarity of what was produced was higher for dialogues vs. monologues. As well, language production effort significantly varied as a function of individual differences in L2 proficiency and inhibitory capacity. Taken together, the overall pattern of findings suggests that both increased L2 proficiency and inhibitory capacity relate to efficient language production during spontaneous monologue and dialogue speech. PMID:22438846

  12. Inhibitory Control and L2 Proficiency Modulate Bilingual Language Production: Evidence from Spontaneous Monologue and Dialogue Speech

    PubMed Central

    Pivneva, Irina; Palmer, Caroline; Titone, Debra

    2012-01-01

    Bilingual language production requires that speakers recruit inhibitory control (IC) to optimally balance the activation of more than one linguistic system when they produce speech. Moreover, the amount of IC necessary to maintain an optimal balance is likely to vary across individuals as a function of second language (L2) proficiency and inhibitory capacity, as well as the demands of a particular communicative situation. Here, we investigate how these factors relate to bilingual language production across monologue and dialogue spontaneous speech. In these tasks, 42 English–French and French–English bilinguals produced spontaneous speech in their first language (L1) and their L2, with and without a conversational partner. Participants also completed a separate battery that assessed L2 proficiency and inhibitory capacity. The results showed that L2 vs. L1 production was generally more effortful, as was dialogue vs. monologue speech production although the clarity of what was produced was higher for dialogues vs. monologues. As well, language production effort significantly varied as a function of individual differences in L2 proficiency and inhibitory capacity. Taken together, the overall pattern of findings suggests that both increased L2 proficiency and inhibitory capacity relate to efficient language production during spontaneous monologue and dialogue speech. PMID:22438846

  13. Application of Foam-gel Technique to Control CO Exposure Generated During Spontaneous Combustion of Coal in Coal Mines.

    PubMed

    Ren, Xing W; Wang, Feng Z; Guo, Qing; Zuo, Zhao B; Fang, Qi S

    2015-01-01

    In China, 47.3% of state-owned coal mines are located in coal seams that are prone to spontaneous combustion. The spontaneous combustion of coal is the main cause of the generation of a large amount of carbon monoxide, which can cause serious health issues to miners. A new technique using foam-gel formation was developed to effectively control the spontaneous combustion of coal. The gel can capture more than 90% of the water in the grout and at the same time the foam can cover dangerous areas in the goaf by stacking and cooling of foam in all directions. In this study, a mechanism of foam-gel formation was introduced and the optimal proportions of additives were defined based on experiments of different foaming properties, gelling time and water loss rate as the main index parameters. The results of a field application in a coal mine promise that this new technique would effectively prevent coal oxidation in the goaf and reduce the generation of carbon monoxide. PMID:26259722

  14. Historical evaluation of vehicle emission control in Guangzhou based on a multi-year emission inventory

    NASA Astrophysics Data System (ADS)

    Zhang, Shaojun; Wu, Ye; Liu, Huan; Wu, Xiaomeng; Zhou, Yu; Yao, Zhiliang; Fu, Lixin; He, Kebin; Hao, Jiming

    2013-09-01

    The Guangzhou government adopted many vehicle emission control policies and strategies during the five-year preparation (2005-2009) to host the 2010 Asian Games. This study established a multi-year emission inventory for vehicles in Guangzhou during 2005-2009 and estimated the uncertainty in total vehicle emissions by taking the assumed uncertainties in fleet-average emission factors and annual mileage into account. In 2009, the estimated total vehicle emissions in Guangzhou were 313 000 (242 000-387 000) tons of CO, 60 900 (54 000-70 200) tons of THC, 65 600 (56 800-74 100) tons of NOx and 2740 (2100-3400) tons of PM10. Vehicle emissions within the urban area of Guangzhou were estimated to be responsible for ˜40% of total gaseous pollutants and ˜25% of total PM10 in the entire city. Although vehicle use intensity increased rapidly in Guangzhou during 2005-2009, vehicle emissions were estimated to have been reduced by 12% for CO, 21% for THC and 20% for PM10 relative to those in 2005. NOx emissions were estimated to have remained almost constant during this period. Compared to the "without control" scenario, 19% (15%-23%) of CO, 20% (18%-23%) of THC, 9% (8%-10%) of NOx and 16% (12%-20%) of PM10 were estimated to have been mitigated from a combination of the implementation of Euro III standards for light-duty vehicles (LDVs) and heavy-duty diesel vehicles and improvement of fuel quality. This study also evaluated several enhanced vehicle emission control actions taken recently. For example, the enhanced I/M program for LDVs was estimated to reduce 11% (9%-14%) of CO, 9% (8%-10%) of THC and 2% (2%-3%) of NOx relative to total vehicle emissions in 2009. Total emission reductions by temporary traffic controls for the Asian Games were estimated equivalent to 9% (7%-11%) of CO, 9% (8%-10%) of THC, 5% (5%-6%) of NOx and 10% (8%-13%) of PM10 estimated total vehicle emissions in 2009. Those controls are essential to further vehicle emission mitigation in Guangzhou

  15. Method and apparatus for emission control

    SciTech Connect

    Kempf, T.W.; Corcoran, R.F.; Sikora, D.

    1992-01-01

    The invention includes process and apparatus for removing pollutants from a gas including fluidizing a bed of particles in a container, introducing a gas containing pollutant into the bed, removing the pollutant through deposition on the particles, controlling temperatures in the container by injecting coolant fluid through a coolant nozzle, and reducing clogging or fouling on the coolant nozzle. The process and apparatus includes controlling temperatures in the container within narrowly specified ranges of temperatures and providing a constant pressure of coolant fluid and constant pressure of purge gas to the coolant nozzle such that interchangeable selection made between the coolant fluid and purge gas in a time period sufficiently short provides accurate temperature control and reduces clogging or fouling on the coolant nozzle.

  16. CONTROL OF SULFUR EMISSIONS FROM OIL SHALE RETORTS

    EPA Science Inventory

    The objectives of this study were to determine the best available control technology (BACT) for control of sulfur emissions from oil shale processing facilities and then to develop a design for a mobile slipstream pilot plant that could be used to test and demonstrate that techno...

  17. SUMMARY REPORT CONTROL OF NOX EMISSIONS BY REBURNING

    EPA Science Inventory

    This report covers NOx control employing reburning technology: A new, effective method of controlling NOx emissions from a wide range of stationary combustion sources including large, coal-fired, utility boilers. Although reburning potentially is applicable ...

  18. Insertion/deletion polymorphism in intron 16 of ACE gene in idiopathic recurrent spontaneous abortion: case-control study, systematic review and meta-analysis.

    PubMed

    Pereza, Nina; Ostojić, Saša; Zdravčević, Matea; Volk, Marija; Kapović, Miljenko; Peterlin, Borut

    2016-02-01

    The insertion/deletion (I/D) polymorphism in intron 16 of the angiotensin I-converting enzyme gene (ACE) has been extensively studied as a predisposing factor for idiopathic recurrent spontaneous abortion (IRSA). A case-control study including 149 women with ≥3 spontaneous abortions and 149 controls was performed to test the association of ACE I/D polymorphism with IRSA. A systematic review was conducted of previous case-control studies, with strict selection criteria for meta-analyses. We also aimed to evaluate the potential differences in summary estimates between studies defining IRSA as ≥2 and ≥3 spontaneous abortions. Genotyping was performed by PCR, and systematic review conducted using PubMed and Scopus. There was no association of the polymorphism with IRSA in Slovenian women. Sixteen case-control studies, showing substantial differences regarding IRSA definition and selection criteria for women were identified. Meta-analysis was performed and included four studies defining IRSA as ≥2 spontaneous abortions and the current study, which defined IRSA as ≥3 spontaneous abortions. Based on random effects model, meta-analysis conducted on 1192 patients and 736 controls showed no association with IRSA under dominant(DD+IDvsII) and recessive(DDvsID+II) genetic models. Well-designed studies are needed to evaluate the role of ACE I/D polymorphism in IRSA defined as ≥3 spontaneous abortions. PMID:26673102

  19. Systems and methods for controlling diesel engine emissions

    DOEpatents

    Webb, Cynthia Chaffin; Weber, Phillip Anthony; Khair, Magdi K.

    2004-06-01

    Systems and methods for controlling diesel engine emissions, including, for example, oxides of nitrogen emissions, particulate matter emissions, and the like. The emission control system according to this invention is provided in the exhaust passageway of a diesel engine and includes a catalyst-based particulate filter; and first and second lean NO.sub.x trap systems coupled to the catalyst-based particulate filter. The first and second lean NO.sub.x trap systems are arranged in a parallel flow configuration with each other. Each of the first and second lean NO.sub.x trap systems include a carbon monoxide generating catalyst device, a sulfur trap device, a lean NO.sub.x device, a supplemental fuel injector device, and a plurality of flow diverter devices.

  20. Coal-fueled diesel emissions control technology development

    SciTech Connect

    Cook, C.; Gal, E.; Mengel, M.; Van Kleunen, W.

    1993-03-01

    The objective of this project is to develop an emissions control system for a GE locomotive powered by a Coal Water Slurry (CWS) fuel diesel engine. The development effort is directed toward reducing particulate matter, SO{sub 2} and NO{sub x} emissions from the engine exhaust gas at 700--800F and 1-2 psig. The commercial system should be economically attractive while subject to limited space constraints. After testing various alternatives, a system composed of a barrier filter with sorbent injection ups was selected for controlling particulates, SO{sub 2} and NO{sub x} emissions. In bench scale and 500 acfm slip s tests, removal efficiencies greater than 90% for SO{sub 2} and 85% for NO{sub x} were achieved. Particulate emissions from the barrier filter are within NSPS limits.

  1. Coal-fueled diesel emissions control technology development

    SciTech Connect

    Cook, C.; Gal, E.; Mengel, M.; Van Kleunen, W.

    1993-01-01

    The objective of this project is to develop an emissions control system for a GE locomotive powered by a Coal Water Slurry (CWS) fuel diesel engine. The development effort is directed toward reducing particulate matter, SO[sub 2] and NO[sub x] emissions from the engine exhaust gas at 700--800F and 1-2 psig. The commercial system should be economically attractive while subject to limited space constraints. After testing various alternatives, a system composed of a barrier filter with sorbent injection ups was selected for controlling particulates, SO[sub 2] and NO[sub x] emissions. In bench scale and 500 acfm slip s tests, removal efficiencies greater than 90% for SO[sub 2] and 85% for NO[sub x] were achieved. Particulate emissions from the barrier filter are within NSPS limits.

  2. Glutamatergic system controls synchronization of spontaneous neuronal activity in the murine neonatal entorhinal cortex.

    PubMed

    Unichenko, Petr; Yang, Jeng-Wei; Luhmann, Heiko J; Kirischuk, Sergei

    2015-07-01

    Synchronized spontaneous neuronal activity is a characteristic feature of the developing brain. Rhythmic network discharges in the neonatal medial entorhinal cortex (mEC) in vitro depend on activation of ionotropic glutamate receptors, but spontaneously active neurons are required for their initiation. Field potential recordings revealed synchronized neuronal activity in the mEC in vivo developmentally earlier than in vitro. We suggested that not only ionotropic receptors, but also other components of the glutamatergic system modulate neuronal activity in the mEC. Ca(2+) imaging was used to record neuronal activity in neonatal murine brain slices. Two types of spontaneous events were distinguished: global synchronous discharges (synchronous activity) and asynchronously (not synchronized with global discharges) active cells (asynchronous activity). AMPA receptor blockade strongly reduced the frequency of synchronous discharges, while NMDA receptor inhibition was less effective. AMPA and NMDA receptor blockade or activation of group 2/3 metabotropic glutamate receptors (mGluR2/3) completely suppressed synchronous discharges and increased the number of active cells. Blockade of glutamate transporters with DL-TBOA led to NMDA receptor-mediated hyper-synchronization of neuronal activity. Inhibition of NMDA receptors in the presence of DL-TBOA failed to restore synchronous discharges. The latter were partially reestablished only after blockade of mGluR2/3. We conclude that the glutamatergic system can influence neuronal activity via different receptors/mechanisms. As both NMDA and mGluR2/3 receptors have a high affinity for glutamate, changes in extracellular glutamate levels resulting for instance from glutamate transporter malfunction can balance neuronal activity in the mEC, affecting in turn synapse and network formation. PMID:25163767

  3. Positional control of plasmonic fields and electron emission

    SciTech Connect

    Word, R. C.; Fitzgerald, J. P. S.; Könenkamp, R.

    2014-09-15

    We report the positional control of plasmonic fields and electron emission in a continuous gap antenna structure of sub-micron size. We show experimentally that a nanoscale area of plasmon-enhanced electron emission can be motioned by changing the polarization of an exciting optical beam of 800 nm wavelength. Finite-difference calculations are presented to support the experiments and to show that the plasmon-enhanced electric field distribution of the antenna can be motioned precisely and predictively.

  4. Primary production control of methane emission from wetlands

    NASA Technical Reports Server (NTRS)

    Whiting, G. J.; Chanton, J. P.

    1993-01-01

    Based on simultaneous measurements of CO2 and CH4 exchange in wetlands extending from subarctic peatlands to subtropical marshes, a positive correlation between CH4 emission and net ecosystem production is reported. It is suggested that net ecosystem production is a master variable integrating many factors which control CH4 emission in vegetated wetlands. It is found that about 3 percent of the daily net ecosystem production is emitted back to the atmosphere as CH4. With projected stimulation of primary production and soil microbial activity in wetlands associated with elevated atmospheric CO2 concentration, the potential for increasing CH4 emission from inundated wetlands, further enhancing the greenhouse effect, is examined.

  5. Environmental controls over methyl halide emissions from rice paddies

    NASA Astrophysics Data System (ADS)

    Redeker, K. R.; Cicerone, R. J.

    2004-03-01

    This paper examines primary controlling factors that affect methyl halide emissions from rice paddy ecosystems. Observations of four cultivars under multiple growth conditions during studies in commercial fields and the University of California, Irvine, greenhouse lead to the conclusion that daily emissions of methyl halides are primarily determined by the growth stage of the rice plant, with the exception that methyl chloride emissions show no clear seasonal pattern. Methyl chloride emissions appear to be more from the paddy water and/or soil as opposed to the plants; however, in soils with high chloride content, these emissions appear to peak during the reproductive phase. Strong secondary influences include air temperature, soil halide concentration, and soil pore water saturation. The cultivars studied had statistically separate seasonally integrated emissions. Irradiant light and aboveground biomass appear to have little effect on emissions. Emissions of methyl chloride, methyl bromide, and methyl iodide are estimated to be 3.5, 2.3, and 48 mg/m2/yr, or 5.3, 3.5, and 72 Gg/yr, from rice paddies globally.

  6. Surgery for Patients With Spontaneous Deep Supratentorial Intracerebral Hemorrhage: A Retrospective Case-Control Study Using Propensity Score Matching.

    PubMed

    Zheng, Jun; Li, Hao; Zhao, He-Xiang; Guo, Rui; Lin, Sen; Dong, Wei; Ma, Lu; Fang, Yuan; Tian, Meng; Liu, Ming; You, Chao

    2016-03-01

    Spontaneous intracerebral hemorrhage (sICH) is one of the most dangerous cerebrovascular diseases, especially when in deep brain. The treatment of spontaneous deep supratentorial intracerebral hemorrhage is still controversial. We conducted a retrospective case-control study using propensity score matching to compare the efficacy of surgery and conservative treatment for patients with deep surpatentorial hemorrhage. We observed the outcomes of consecutive patients with spontaneous deep supratentorial hemorrhage retrospectively from December 2008 to July 2013. Clinical outcomes of surgery and conservative treatments were compared in patients with deep sICH using propensity score matching method. The primary outcome was neurological function status at 6 months post ictus. The second outcomes included mortality at 30 days and 6 months, and the incidence of complications. Subgroup analyses of 6-month outcome were conducted. Sixty-three (22.66%) of the 278 patients who received surgery had a favorable neurological function status at 6 months, whereas in the conservative group, 66 of 278 (23.74%) had the same result (P = 0.763). The 30-day mortality in the surgical group was 19.06%, whereas 30.58% in the conservative group (P = 0.002). There was significant difference in the mortality at 6 months after ictus as well (23.38% vs 36.33%, P = 0.001). The subgroup analyses showed significantly better outcomes for the surgical group when hematoma was >40 mL (13.33% vs 0%, P = 0.005) or complicated with intraventricular hemorrhage (16.67% vs 7.27%, P = 0.034). For complications, the risk of pulmonary infection, gastrointestinal hemorrhage, urinary infection, pulmonary embolus, and need for tracheostomy/long term ventilation in the surgical group was higher than the conservative group (31.29% vs 15.47%, P < 0.001; 6.83% vs 3.96%, P = 0.133; 2.88% vs 1.80%, P = 0.400; 1.80% vs 1.08%, P = 0.476; 32.73% vs 23.38%, P = 0.014). Surgery could

  7. The use of intake condition modifications to control diesel emissions

    SciTech Connect

    Bowen, C.E.; Reader, G.T.; Potter, I.J.; Gustafson, R.W.

    1995-12-31

    Diesel engines have the inherent capability of producing emissions, such as NOx, particulates, unburned hydrocarbons, and noise which at certain levels and concentrations are considered to be environmentally unfriendly. To control these emissions, techniques have been developed which are aimed at reducing the amount of pollutants formed in the combustion process or preventing them from reaching the atmosphere (after treatment). The initial condition of the in-cylinder reactants and diluents affects how the combustion process proceeds and hence influences the formation and rate of formation of the pollutants. Thus, one approach to emission control is to modify the intake oxidant conditions, i.e., the composition and thermodynamic state of the working fluid. This modification can be accomplished by the use of exhaust gas recirculation (EGR). EGR has been extensively developed for use with SI engine emission control systems and for specialized diesel engine operations where synthetic atmospheres are used (underwater) or where operations take place in contaminated environments (underground). More recently EGR has been considered as a technique for helping reduce NOx emissions from conventional diesel engine systems. Usually, experimental investigations involving EGR have dealt with the global effects on emissions and performance but in the research reported in this paper efforts have been made to identify the specific effects of altering intake conditions, e.g., oxygen concentration, on the operation of an Indirect-Injection (IDI) diesel engine.

  8. Controlling formaldehyde emissions with boiler ash.

    PubMed

    Cowan, Jennifer; Abu-Daabes, Malyuba; Banerjee, Sujit

    2005-07-01

    Fluidized wood ash reduces formaldehyde in air from about 20 to <1 ppmv. Methanol is removed to a much lower extent. The efficiency of formaldehyde reduction increases with increasing moisture content of the ash. Sorption of formaldehyde to ash can be substantially accounted for by partitioning to the water contained in the ash followed by rate-controlling binding to the ash solids. Adsorption occurs at temperatures of up to 165 degrees C; oxidation predominates thereafter. It is proposed that formaldehyde could be stripped from an air stream in a fluidized bed containing ash, which could then be returned to a boiler to incinerate the formaldehyde. PMID:16053116

  9. New emission controls for Missouri batch-type charcoal kilns

    SciTech Connect

    Yronwode, P.; Graf, W.J.

    1999-07-01

    Charcoal kilns have been exempted from air emission regulation in the state of Missouri. Today, 80% of US charcoal production takes place in Missouri. As a result of a petition filed by people in the area around an installation in southern Missouri, the US Environmental Protection Agency (EPA) set up air monitors and measured ambient air levels at that charcoal manufacturing installation. These monitors yielded the highest particulate matter less than 10 micron (PM{sub 10}) levels ever recorded in the state. Earlier stack testing at another charcoal manufacturing installation indicated that toxics and carcinogens are present in charcoal kiln air emissions. A Charcoal Kiln Workgroup was formed to determine the Best Available Control Technology (BACT) for charcoal kilns and to draft a charcoal kiln rule that requires BACT. The BACT report determined that afterburners were suitable for controlling emissions from batch-type charcoal kilns. In addition, the charcoal industry supported incorporating the BACT limits and requirements into an enforceable state rule and submitting this rule to the EPA for federal approval. A consent agreement between the EPA and three major charcoal companies was signed with provisions to install, operate, and maintain emission control devices on charcoal kilns. This agreement was to settle complaints alleging that the three major charcoal producers had failed to report toxic air emissions to federal and state regulators. The agreement provided that industry would install control devices on a set schedule with some charcoal kilns being shut down.

  10. Acoustic emission feedback control for control of boiling in a microwave oven

    DOEpatents

    White, Terry L.

    1991-01-01

    An acoustic emission based feedback system for controlling the boiling level of a liquid medium in a microwave oven is provided. The acoustic emissions from the medium correlated with surface boiling is used to generate a feedback control signal proportional to the level of boiling of the medium. This signal is applied to a power controller to automatically and continuoulsly vary the power applied to the oven to control the boiling at a selected level.

  11. Mercury emissions control technologies for mixed waste thermal treatment

    SciTech Connect

    Chambers, A.; Knecht, M.; Soelberg, N.; Eaton, D.; Roberts, D.; Broderick, T.

    1997-12-31

    EPA has identified wet scrubbing at low mercury feedrates, as well as carbon adsorption via carbon injection into the offgas or via flow through fixed carbon beds, as control technologies that can be used to meet the proposed Maximum Achievable Control Technology (MACT) rule limit for mercury emissions from hazardous waste incinerators. DOE is currently funding demonstrations of gold amalgamation that may also control mercury to the desired levels. Performance data from a variety of sources was reviewed to determine ranges of achievable mercury control. Preliminary costs were estimated for using these technologies to control mercury emissions from mixed waste incineration. Mercury emissions control for mixed waste incineration may need to be more efficient than for incineration of other hazardous wastes because of higher mercury concentrations in some mixed waste streams. However, mercury control performance data for wet scrubbing and carbon adsorption is highly variable. More information is needed to demonstrate control efficiencies that are achievable under various design and operating conditions for wet scrubbing, carbon adsorption, and gold amalgamation technologies. Given certain assumptions made in this study, capital costs, operating costs, and lifecycle costs for carbon injection, carbon beds, and gold amalgamation generally vary for different assumed mercury feedrates and for different offgas flowrates. Assuming that these technologies can in fact provide the necessary mercury control performance, each of these technologies may be less costly than the others for certain mercury feedrates and the offgas flowrates.

  12. External control of planetary radio emission

    NASA Technical Reports Server (NTRS)

    Rucker, H. O.; Desch, M. D.

    1983-01-01

    Recent studies using data from Voyagers 1 and 2 to correlate variations in the Saturn kilometric radiation (SKR) with changes in solar-wind properties are summarized and illustrated with graphs. Best SKR correlations have been obtained with the solar-wind ram pressure and the related kinetic energy flux. It is pointed out that the related phenomenon on earth, the auroral kilometric radiation, occurs mainly in the nightside auroral region (as opposed to the dayside cleft region for SKR) and is best correlated with solar-wind velocity and inverted-V electron-precipitation events, implying a different stimulation process. The evidence for solar-wind control of the non-Io-related decametric radiation of Jupiter is also reviewed.

  13. Coal-fueled diesel technology development emissions control

    NASA Astrophysics Data System (ADS)

    Vankleunen, W.; Kaldor, S.; Gal, E.; Mengel, M.; Arnold, M.

    1994-01-01

    General Electric Environmental Services, Inc. (GEESI), Emissions Control program activity ranged from control concept testing of 10 CFM slipstream from a coal-water-slurry (CWS) fuel single cylinder research diesel engine to the design, installation, and operation of a full-size emissions control system for a full-size CWS fuel diesel engine designed for locomotive operation. Early 10 CFM slipstream testing program activity was performed to determine emissions characteristics and to evaluate emissions control concepts such a barrier filtration, granular bed filtration, and cyclone particulate collection for reduction of particulate and gaseous emissions. Use of sorbent injection into the engine exhaust gas upstream of the barrier filter or use of sorbent media in the granular bed filter were found to provide reduction of exhaust gas SO2 and NO(x) in addition to collection of ash particulate. Emergence of the use of barrier filtration as a most practical emissions control concept disclosed a need to improve cleanability of the filter media in order to avoid reduction of turbocharger performance by excessive barrier filter pressure drop. The next progression of program activity, after the slipstream feasibility state, was 500 CFM cold flow testing of control system concepts. The successful completion of 500 CFM cold flow testing of the envelope filter led to a subsequent progression to a similar configuration envelope filter designed to operate at 500 CFM hot gas flow from the CWS fuel research diesel engine in the GETS engine test laboratory. This envelope filter included the design aspect proven by cold flow testing as well as optimization of the selection of the installed filter media.

  14. Coal-fueled diesel technology development Emissions Control

    SciTech Connect

    Van Kleunen, W.; Kaldor, S.; Gal, E.; Mengel, M.; Arnold, M.

    1994-01-01

    GEESI Emissions Control program activity ranged from control concept testing of 10 CFM slipstream from a CWS fuel single cylinder research diesel engine to the design, installation, and operation of a full-size Emissions Control system for a full-size CWS fuel diesel engine designed for locomotive operation.Early 10 CFM slipstream testing program activity was performed to determine Emissions Characteristics and to evaluate Emissions Control concepts such a Barrier filtration, Granular bed filtration, and Cyclone particulate collection for reduction of particulate and gaseous emissions. Use of sorbent injection into the engine exhaust gas upstream of the barrier filter or use of sorbent media in the granular bed filter were found to provide reduction of exhaust gas SO{sub 2} and NO{sub x} in addition to collection of ash particulate. Emergence of the use of barrier filtration as a most practical Emissions Control concept disclosed a need to improve cleanability of the filter media in order to avoid reduction of turbocharger performance by excessive barrier filter pressure drop. The next progression of program activity, after the slipstream feasibility state, was 500 CFM cold flow testing of control system concepts. The successful completion of 500 CFM cold flow testing of the Envelope Filter led to a subsequent progression to a similar configuration Envelope Filter designed to operate at 500 CFM hot gas flow from the CWS fuel research diesel engine in the GETS engine test laboratory. This Envelope Filter included the design aspect proven by cold flow testing as well as optimization of the selection of the installed filter media.

  15. Properties of the ultrashort gain length, self-amplified spontaneous emission free-electron laser in the linear regime and saturation

    NASA Astrophysics Data System (ADS)

    Murokh, A.; Agustsson, R.; Babzien, M.; Ben-Zvi, I.; Bertolini, L.; van Bibber, K.; Carr, R.; Cornacchia, M.; Frigola, P.; Hill, J.; Johnson, E.; Klaisner, L.; Le Sage, G.; Libkind, M.; Malone, R.; Nuhn, H.-D.; Pellegrini, C.; Reiche, S.; Rakowsky, G.; Rosenzweig, J.; Ruland, R.; Skaritka, J.; Toor, A.; Tremaine, A.; Wang, X.; Yakimenko, V.

    2003-06-01

    VISA (Visible to Infrared SASE Amplifier) is a high-gain self-amplified spontaneous emission (SASE) free-electron laser (FEL), which achieved saturation at 840 nm within a single-pass 4-m undulator. The experiment was performed at the Accelerator Test Facility at BNL, using a high brightness 70-MeV electron beam. A gain length shorter than 18 cm has been obtained, yielding a total gain of 2×108 at saturation. The FEL performance, including the spectral, angular, and statistical properties of SASE radiation, has been characterized for different electron beam conditions. Results are compared to the three-dimensional SASE FEL theory and start-to-end numerical simulations of the entire injector, transport, and FEL systems. An agreement between simulations and experimental results has been obtained at an unprecedented level of detail.

  16. Reduction of amplified spontaneous emission from a transmitted soliton signal using a nonlinear amplifying loop mirror and a nonlinear optical loop mirror

    NASA Astrophysics Data System (ADS)

    Yamada, Eiichi; Nakazawa, Masataka

    1994-08-01

    The amplified spontaneous emission (ASE) from concatenated erbium-doped fiber amplifiers (EDFA's) in a 10 Gb / s 500 km soliton transmission system has been successfully reduced through the use of a nonlinear amplifying-loop mirror (NALM). By using the NALM the ratio of the signal peak to ASE was improved from 17.4:1 to 24.9:1. A similar result was obtained for a nonlinear optical-loop mirror (NOLM) with a 6:4 directional coupler. It is noted that pulse transmission through the NALM or the NOLM gives rise to frequency chirp, which means that these fiber devices are not appropriate for use at the midpoint of a long-distance soliton transmission. The chirp characteristics caused by the NALM were also described and the optimum condition for nonlinear switching was obtained.

  17. Environmental controls on Pan-Arctic wetland methane emissions

    NASA Astrophysics Data System (ADS)

    Chen, Xiaodong; Bohn, Theodore; Lettenmaier, Dennis

    2015-04-01

    Environmental conditions such as soil temperature and moisture, incident solar radiation, and atmospheric carbon dioxide concentration are important environmental controls on methane emissions from northern wetlands. We investigated the spatio-temporal distributions of influence of these factors over northern wetland methane emissions via the Variable Infiltration Capacity (VIC) model. We simulated methane emissions from wetlands across the Pan-Arctic domain over the period 1948-2006, with annual average emissions of 35.1±6.7 TgCH4/year. From control simulations that each held one environmental factor constant, we characterized sensitivities to air temperature, precipitation, incident long- and short-wave radiation, and atmospheric [CO2] as a function of average summer air temperature and precipitation. Trade-offs between air temperature and precipitation caused maximal emissions to occur along a line in precipitation-temperature space with a slope of approximately 13 mm month-1 / K, leading to separation of wetlands into various combinations of water-limited and temperature-limited regimes. Emissions from relatively warm and dry wetlands in the southern (permafrost-free) portion of the domain tended to be positively correlated with precipitation and negatively correlated with air temperature, while emissions from wetter and colder wetlands further north (permafrost) tended to be positively correlated with air temperature. Over the period 1960-2006, emissions increased by 20%, over 90% of which can be attributed to climate change, with summer air temperatures explaining the majority of the variance. We estimated future emissions in response to CMIP5 model projections under the RCP4.5 scenario via two methods: (1) the VIC model and (2) the temperature- and precipitation-dependent sensitivities computed from the historical simulation. The two methods yielded similar projections of emissions, with end-of-century emissions at 142% of present-day levels, accompanied by

  18. The controls of methane emission from an Indian mangrove

    NASA Astrophysics Data System (ADS)

    Purvaja, R.; Ramesh, R.; Frenzel, P.

    2003-04-01

    Mangroves have been rated for a long time as a minor methane source, but recent reports have shown that polluted mangroves may emit substantial amounts of methane. In an Indian mangrove dominated by Avicennia marina we measured annual methane emission rates of 10 g methane/year, comparable to those from Northern wetlands. Methane emission from a freshwater-influenced area was higher, but lower from a stunted mangrove growing on a hypersaline soil, respectively. Methane emission was mediated by the pneumatophores of Avicennia. This was consistent with the methane concentration in the aerenchyma that decreased on average from 350 ppmv in the cable roots to 10 ppmv in the emergent part of the pneumatophores. The number of pneumatophores varied seasonally. During the monsoon floods less pneumatophores emerged from the water, reducing methane fluxes largely. Hence, CH4 emission was controlled via the pneumatophores by the water level.

  19. Survey of medical waste incinerators and emissions control. Final report

    SciTech Connect

    Barton, R.G.; Hansell, D.W.; Furlong, D.; Hassell, G.R.; Lanier, W.S.

    1992-01-01

    The report contains two volumes. Volume I of the report assesses the state-of-the-art of medical waste thermal treatment. The program involved a survey of existing information on medical waste treatment. This information was combined with data from municipal and hazardous waste combustion to identify potential mechanisms responsible for toxic emissions. Manufacturers of combustion and flue gas cleaning equipment were contacted. Information on current design practice was obtained. Volume II was prepared to assist local air pollution management districts implement Section 93104, Title 17, of the California Code of Regulations. Section 93104 places restrictions on polychlorodibenzo-p-dioxins (PCDD) and polychlorodibenzofurans (PCDF) emission levels and medical waste incinerator operating parameters which may affect PCDD/PCDF emissions. Part I of Volume II provides direct guidance for implementing the regulations. Part II provides background information on the operation and capabilities of flue gas cleaning systems used to control particulate, acid gas, metals, and PCDD/PCDF emissions.

  20. NOx Sensor for Direct Injection Emission Control

    SciTech Connect

    Betteridge, William J

    2006-02-28

    The Electricore/Delphi team continues to leverage the electrochemical planar sensor technology that has produced stoichiometric planar and wide range oxygen sensors as the basis for development of a NOx sensor. Zirconia cell technology with an integrated heater will provide the foundation for the sensor structure. Proven materials and packaging technology will help to ensure a cost-effective approach to the manufacture of this sensor. The electronics technique and interface is considered to be an area where new strategies need to be employed to produce higher S/N ratios of the NOx signal with emphasis on signal stability over time for robustness and durability Both continuous mode and pulse mode control techniques are being evaluated. Packaging the electronics requires careful design and circuit partitioning so that only the necessary signal conditioning electronics are coupled directly in the wiring harness, while the remainder is situated within the ECM for durability and costs reasons. This task continues to be on hold due to the limitation that the definition of the interface electronics was unavailable until very late in the project. The sense element is based on the amperometric method utilizing integrated alumina and zirconia ceramics. Precious metal electrodes are used to form the integrated heater, the cell electrodes and leads. Inside the actual sense cell structure, it is first necessary to separate NOx from the remaining oxygen constituents of the exhaust, without reducing the NOx. Once separated, the NOx will be measured using a measurement cell. Development or test coupons have been used to facilitate material selection and refinement, cell, diffusion barrier, and chamber development. The sense element currently requires elaborate interconnections. To facilitate a robust durable connection, mechanical and metallurgical connections are under investigation. Materials and process refinements continue to play an important role in the development of the

  1. Carrier-mediated transport controls hydroxyproline catabolism in heart mitochondria from spontaneously hypertensive rat.

    PubMed

    Atlante, A; Seccia, T M; Marra, E; Minervini, G M; Vulpis, V; Pirrelli, A; Passarella, S

    1996-11-01

    In this study we have investigated hydroxyproline transport in rat heart mitochondria and, in particular, in heart left ventricle mitochondria isolated from both spontaneously hypertensive and Wistar-Kyoto rats. Hydroxyproline uptake by mitochondria, where its catabolism takes place, occurs via a carrier-mediated process as demonstrated by the occurrence of both saturation kinetics and the inhibition shown by phenylsuccinate and the thiol reagent mersalyl. In any case, hydroxyproline transport was found to limit the rate of mitochondrial hydroxyproline catabolism. A significant change in Vmax and Km values was found in mitochondria from hypertensive/hypertrophied rats in which the Km value decreases and the Vmax value increases with respect to normotensive rats, thus accounting for the increase of hydroxyproline metabolism due to its increased concentration in a hypertrophic/hypertensive state. PMID:8915003

  2. Pulsed amplified spontaneous Raman emission at 2.2 μm in silica-based fiber

    NASA Astrophysics Data System (ADS)

    Jiang, Huawei; Zhang, Lei; Yang, Xuezong; Yu, Ting; Feng, Yan

    2016-04-01

    All-fiber source at 2.2 μm is investigated with amplified spontaneous Raman scattering process in highly Ge-doped silica fiber. By optimizing the gain fiber length, the second-order Raman Stokes light at 2.43 μm is suppressed and 3 W first-order Raman Stokes light at 2.2 μm is obtained with a homemade 2-μm Q-switched Tm3+-doped fiber laser as pump source. The conversion efficiency is 35.9 % from 2.0 to 2.2 μm, and the peak power of the 2.2-μm laser is about 400 W.

  3. Modeling the benefits of power plant emission controls in Massachusetts.

    PubMed

    Levy, Jonathan I; Spengler, John D

    2002-01-01

    Older fossil-fueled power plants provide a significant portion of emissions of criteria air pollutants in the United States, in part because these facilities are not required to meet the same emission standards as new sources under the Clean Air Act. Pending regulations for older power plants need information about any potential public health benefits of emission reductions, which can be estimated by combining emissions information, dispersion modeling, and epidemiologic evidence. In this article, we develop an analytical modeling framework that can evaluate health benefits of emission controls, and we apply our model to two power plants in Massachusetts. Using the CALPUFF atmospheric dispersion model, we estimate that use of Best Available Control Technology (BACT) for NOx and SO2 would lead to maximum annual average secondary particulate matter (PM) concentration reductions of 0.2 microg/m3. When we combine concentration reductions with current health evidence, our central estimate is that the secondary PM reductions from these two power plants would avert 70 deaths per year in a population of 33 million individuals. Although benefit estimates could differ substantially with different interpretations of the health literature, parametric perturbations within CALPUFF and other simple model changes have relatively small impacts from an aggregate risk perspective. While further analysis would be required to reduce uncertainties and expand on our analytical model, our framework can help decision-makers evaluate the magnitude and distribution of benefits under different control scenarios. PMID:15152660

  4. Amplified spontaneous emission of phonons as a likely mechanism for density-dependent velocity saturation in GaN transistors

    NASA Astrophysics Data System (ADS)

    Khurgin, Jacob B.; Bajaj, Sanyam; Rajan, Siddharth

    2016-09-01

    We show that density-dependent velocity saturation in a GaN high electron mobility transistor (HEMT) can be related to the stimulated emission of longitudinal optical (LO) phonons. As the drift velocity of electrons increases, the drift of the Fermi distribution in reciprocal space results in population inversion and gain for the LO phonons. Once this gain reaches a threshold value, the avalanche-like increase in LO phonon emission causes a rapid loss of electron energy and momentum and leads to drift velocity saturation. Our simple model correctly predicts both the general trend of decreasing saturation velocity with increasing electron density, and the measured experimental values of saturation.

  5. Enhanced control of mercury emissions through modified speciation

    SciTech Connect

    Livengood, C.D.; Mendelsohn, M.H.

    1997-07-01

    In anticipation of possible regulations regarding mercury emissions, research efforts sponsored by DOE, EPRI, and others are investigating the risks posed by mercury emissions, improved techniques for measuring those emissions, and possible control measures. The focus in the control research is on techniques that can be used in conjunction with existing flue-gas-cleanup (FGC) systems in order to minimize additional capital costs and operational complexity. Argonne National Laboratory has supported the DOE Fossil Energy Program for over 15 years with research on advanced environmental control technologies. The emphasis in Argonne`s work has been on integrated systems that combine control of several pollutants. Specific topics have included spray drying for sulfur dioxide and particulate-matter control with high-sulfur coal, combined sulfur dioxide and nitrogen oxides control technologies, and techniques to enhance mercury control in existing FGC systems. The latter area has focused on low-cost dry sorbents for use with fabric filters or electrostatic precipitators and techniques for improving the capture of mercury in wet flue-gas desulfurization (FGD) systems. This paper presents results from recent work that has studied the effects of several oxidizing agents in combination with typical flue-gas species (e.g., nitrogen oxides and sulfur dioxide) on the oxidation of Hg{sup 0}.

  6. Switching regulator emission control circuit for ion sources

    NASA Technical Reports Server (NTRS)

    Clay, F. P., Jr.; Brock, F. J.; Melfi, L. T., Jr.

    1975-01-01

    An electron emission control circuit of the switching regulator type operating at 100 kHz has been developed which maintains a constant emission current within 0.1% for a cathode power demand variation of approximately 100%. The power output stage has an efficiency of 67%, and the overall efficiency is 45% when driving a thoria-coated iridium cathode having a nominal resistance at operating temperature of 2.5 ohms. Under optimum conditions, the bus power demand is 1.75 W. The circuit is useful in controlling the electron emission current of ion sources in applications which involve a substantial variation of the cathode work function, such as oxygen partial pressure measurements over a large dynamic range.

  7. Controlling sulfur emissions with BSRP and Selectox technologies

    SciTech Connect

    Hass, R.H.; Ward, J.W.; Bertram, R.V.; Robinson, P.R.

    1986-01-01

    Two processes have been developed for controlling sulfur emissions from gas streams. They are the Beavon Sulfur Recovery Process (BSRP) which recovers sulfur from Claus tail gas, and the Selectox process which oxidizes gaseous H/sub 2/S to sulfur using air. Recent developments and commercial experience for both processes are reviewed.

  8. SPRAY CHARGING AND TRAPPING SCRUBBER FOR FUGITIVE PARTICLE EMISSION CONTROL

    EPA Science Inventory

    The report gives results of a theoretical and experimental evaluation of the control of fugitive particle emissions (FPE) with a Spray Charging and Trapping (SCAT) Scrubber that uses an air curtain and/or jets to contain, convey, and divert the FPE into a charged spray scrubber. ...

  9. ASSESSMENT OF THE USE OF FUGITIVE EMISSION CONTROL DEVICES

    EPA Science Inventory

    The report compares the efficiencies and utility consumptions expected from three fugitive emission control techniques--building evacuation, charged fog sprays, and water sprays with additives--if they were applied in primary lead and copper smelters. Estimates are provided of th...

  10. PHYSICAL COAL CLEANING FOR UTILITY BOILER SO2 EMISSION CONTROL

    EPA Science Inventory

    The report examines physical coal cleaning as a control technique for sulfur oxides emissions. It includes an analysis of the availability of low-sulfur coal and of coal cleanable to compliance levels for alternate New Source Performance Standards (NSPS). Various alternatives to ...

  11. Tillage and field scale controls on greenhouse gas emissions.

    PubMed

    Lee, Juhwan; Six, Johan; King, Amy P; van Kessel, Chris; Rolston, Dennis E

    2006-01-01

    There is a lack of understanding of how associations among soil properties and management-induced changes control the variability of greenhouse gas (GHG) emissions from soil. We performed a laboratory investigation to quantify relationships between GHG emissions and soil indicators in an irrigated agricultural field under standard tillage (ST) and a field recently converted (2 yr) to no-tillage (NT). Soil cores (15-cm depth) were incubated at 25 degrees C at field moisture content and 75% water holding capacity. Principal component analysis (PCA) identified that most of the variation of the measured soil properties was related to differences in soil C and N and soil water conditions under ST, but soil texture and bulk density under NT. This trend became more apparent after irrigation. However, principal component regression (PCR) suggested that soil physical properties or total C and N were less important in controlling GHG emissions across tillage systems. The CO2 flux was more strongly determined by microbial biomass under ST and inorganic N content under NT than soil physical properties. Similarly, N2O and CH4 fluxes were predominantly controlled by NO3- content and labile C and N availability in both ST and NT soils at field moisture content, and NH4+ content after irrigation. Our study indicates that the field-scale variability of GHG emissions is controlled primarily by biochemical parameters rather than physical parameters. Differences in the availability and type of C and N sources for microbial activity as affected by tillage and irrigation develop different levels and combinations of field-scale controls on GHG emissions. PMID:16585613

  12. Particulate Emissions from a Pre-Emissions Control Era Spark-Ignition Vehicle: A Historical Benchmark

    SciTech Connect

    John M.E. Storey; C. Scott Sluder; Douglas A. Blom; Erin Higinbotham

    2000-06-19

    This study examined the particulate emissions from a pre-emissions control era vehicle operated on both leaded and unleaded fuels for the purpose of establishing a historical benchmark. A pre-control vehicle was located that had been rebuilt with factory original parts to approximate an as-new vehicle prior to 1968. The vehicle had less than 20,000 miles on the rebuilt engine and exhaust. The vehicle underwent repeated FTP-75 tests to determine its regulated emissions, including particulate mass. Additionally, measurements of the particulate size distribution were made, as well as particulate lead concentration. These tests were conducted first with UTG96 certification fuel, followed by UTG96 doped with tetraethyl lead to approximate 1968 levels. Results of these tests, including transmission electron micrographs of individual particles from both the leaded and unleaded case are presented. The FTP composite PM emissions from this vehicle averaged 40.5 mg/mile using unleaded fuel. The results from the leaded fuel tests showed that the FTP composite PM emissions increased to an average of 139.5 mg/mile. Analysis of the particulate size distribution for both cases demonstrated that the mass-based size distribution of particles for this vehicle is heavily skewed towards the nano-particle range. The leaded-fuel tests showed a significant increase in mass concentration at the <0.1 micron size compared with the unleaded-fuel test case. The leaded-fuel tests produced lead emissions of nearly 0.04 g/mi, more than a 4-order-of-magnitude difference compared with unleaded-fuel results. Analysis of the size-fractionated PM samples showed that the lead PM emissions tended to be distributed in the 0.25 micron and smaller size range.

  13. Effects of inspiratory muscle training on exercise capacity and spontaneous physical activity in elderly subjects: a randomized controlled pilot trial.

    PubMed

    Aznar-Lain, S; Webster, A L; Cañete, S; San Juan, A F; López Mojares, L M; Pérez, M; Lucia, A; Chicharro, J L

    2007-12-01

    Inspiratory muscle training (IMT) has been shown to improve exercise capacity in diseased populations. We chose to examine the effects of eight weeks of IMT on exercise capacity and spontaneous physical activity in elderly individuals. Eighteen moderately active elderly subjects (68.1 +/- 6.8 years [mean +/- SD]; range 58 - 78 years) were randomly assigned to either an experimental group (n = 9) or a control group (n = 9) in a double-blind manner. All subjects underwent inspiratory muscle testing, treadmill exercise testing and a four-day measurement period of spontaneous physical activity (using accelerometry) both pre- and post-intervention. The experimental group underwent eight weeks of incremental IMT using a pressure threshold device, while the control group underwent sham training using identical devices. After IMT training, inspiratory muscle strength (mean + 21.5 cm H (2)O; 95 % CI: 9.3, 33.7; p = 0.002), V.O (2peak) (+ 2.8 ml x min (-1) x kg (-1); 95 % CI: 0.5, 5.2; p = 0.022), time to exhaustion during a fixed workload treadmill test (+ 7.1 min; 95 % CI: 1.8, 2.4; p = 0.013) and time engaged in moderate-to-vigorous physical activity (+ 59 min; 95 % CI: 15, 78; p = 0.008) improved. Except for a decline in moderate-to-vigorous physical activity, no significant changes were seen in the control group. Therefore, IMT may be a useful technique for positively influencing exercise capacity and physical activity in elderly individuals. PMID:17534784

  14. Control of diesel engine emissions by dilute oxidizer injection

    SciTech Connect

    Duva, A.W.; Ibrahim, O.; Zhang, Z.

    1996-12-31

    The current diesel engine power systems have progressed to the point where significant reduction in emissions or fuel consumption are at the limit of the state of the art with the present fuels. It is proposed that overall system weight, power or efficiency must be traded to achieve reduced exhaust emission levels. Emission control through the injection of dilute oxidizers are explored to minimize the formation of noxious gases, emission of unburned hydrocarbons and soot in internal combustion diesel cycle engines. Relevant literature detailing the attempts to control exhaust emissions by altering the intake charge are reviewed and utilized as the foundation for the current study. Steady flow type combustion simulations utilizing low concentration hydrogen peroxide with available air in varying ratios are presented for trend comparison to experimental data developed during this investigation. The empirical portion of the study focused on the adaptation of proposed dilute hydrogen peroxide injection to a standard four cylinder marine diesel engine. The main thrust evaluated the impact of oxidizer injection on an aging engine without significant modifications to the existing auxiliary equipment. A simple spray apparatus delivered the dilute hydrogen peroxide to the air intake stream to minimize the alterations to the existing system. Water injection was performed as an experimental control for comparison to reference literature and to normalize the results obtained from the injection of the 5% and 10% concentration hydrogen peroxide. The injection of both concentrations of hydrogen peroxide showed an improvement relative to water injection for unburned hydrocarbon and oxides of nitrogen emissions. The improvements relative to water was greater with the higher concentration of hydrogen peroxide.

  15. Spontaneous oscillations in a model for active control of microvessel diameters

    PubMed Central

    Arciero, J. C.; Secomb, T. W.

    2012-01-01

    A new theory is presented for the origin of spontaneous oscillations in blood vessel diameters that are observed experimentally in the microcirculation. These oscillations, known as vasomotion, involve time-varying contractions of the vascular smooth muscle in the walls of arterioles. It is shown that such oscillations can arise as a result of interactions between the mechanics of the vessel wall and the dynamics of the active contraction of smooth muscle cells in response to circumferential tension in the wall. A theoretical model is developed in which the diameter and the degree of activation in a vessel are dynamic variables. The model includes effects of wall shear stress and oxygen-dependent metabolic signals on smooth muscle activation and is applied to a single vessel and to simplified network structures. The model equations predict limit cycle oscillations for certain ranges of parameters such as wall shear stress, arterial pressure and oxygen consumption rate. Predicted characteristics of the oscillations, including their sensitivity to arterial pressure, are consistent with experimental observations. PMID:21525236

  16. On the understanding and control of the spontaneous heating of dried tannery wastewater sludge.

    PubMed

    Biasin, A; Della Zassa, M; Zerlottin, M; Refosco, D; Bertani, R; Canu, P

    2014-04-01

    We studied the spontaneous heating of dried sludge produced by treating wastewater mainly originating from tanneries. Heating up to burning has been observed in the presence of air and moisture, starting at ambient temperature. To understand and prevent the process we combined chemical and morphological analyses (ESEM) with thermal activity monitoring in insulated vessels. Selective additions of chemicals, either to amplify or depress the reactivity, have been used to investigate and identify both the chemical mechanism causing the sludge self-heating, and a prevention or a mitigation strategy. FeS additions accelerate the onset of reactivity, while S sustains it over time. On the contrary, Ca(OH)2, Na2CO3, NaHCO3, FeCl2, EDTA, NaClO can limit, up to completely preventing, the exothermic activity. All the experimental evidences show that the reactions supporting the dried sludge self-heating involve the Fe/S/O system. The total suppression of the reactivity requires amounts of additives that are industrially incompatible with waste reduction and economics. The best prevention requires reduction or removal of S and Fe from the dried solid matrix. PMID:24484766

  17. Effects of opioid peptides on neural control of renal function in spontaneously hypertensive rats.

    PubMed

    Kapusta, D R; Jones, S Y; DiBona, G F

    1990-06-01

    The aims of the present study were to examine the effects of opioid receptor agonists and antagonists on the renal vascular (renal blood flow) and tubular (urinary sodium excretion) responses to renal nerve stimulation and norepinephrine in anesthetized spontaneously hypertensive rats (SHR). Graded frequency renal nerve stimulation (0.5-4.0 Hz) and doses of norepinephrine (10-80 ng/kg) produced frequency and dose-dependent decreases in renal blood flow. The renal vasoconstrictor responses were not altered by intravenous infusion of the opioid receptor agonists methionine enkephalin (mu and delta, 75 micrograms/kg/min) or U-50488H (kappa, 20 micrograms/kg/min) or administration of the opioid receptor antagonist naloxone (1 mg/kg i.v.). The antinatriuretic response to low frequency (less than 1.0 Hz) electrical renal nerve stimulation was prevented by naloxone but not affected by methionine enkephalin administration without changes in glomerular filtration rate or effective renal plasma flow. These studies suggest that endogenous opioid receptor mechanisms are involved in the increased renal tubular sodium reabsorption response to low frequency renal nerve stimulation but not in the renal vasoconstrictor response to either renal nerve stimulation or norepinephrine. This might occur by facilitation of the renal nerve terminal release, the direct renal tubular action, or both, of norepinephrine to influence renal tubular sodium reabsorption. PMID:2351429

  18. Modeling study of natural emissions, source apportionment, and emission control of atmospheric mercury

    NASA Astrophysics Data System (ADS)

    Shetty, Suraj K.

    ) and CAMNet (Canadian Atmospheric Mercury Measurement Network). The model estimated a total deposition of 474 Mg yr-1 to the CONUS (Contiguous United States) domain, with two-thirds being dry deposited. Reactive gaseous mercury contributed the most to 60% of deposition. Emission speciation distribution is a key factor for local deposition as contribution from large point sources can be as high as 75% near (< 100 km) the emission sources, indicating that emission reduction may result in direct deposition decrease near the source locations. Among the sources, BC contributes to about 68% to 91% of total deposition. Excluding the BC's contribution, EGU contributes to nearly 50% of deposition caused by CONUS emissions in the Northeast, Southeast and East Central regions, while emissions from natural processes are more important in the Pacific and West Central regions (contributing up to 40% of deposition). The modeling results implies that implementation of the new emission standards proposed by USEPA (United States Environmental Protection Agency) would significantly benefit regions that have larger contributions from EGU sources. Control of mercury emissions from coal combustion processes has attracted great attention due to its toxicity and the emission-control regulations and has lead to advancement in state-of-the-art control technologies that alleviate the impact of mercury on ecosystem and human health. This part of the work applies a sorption model to simulate adsorption of mercury in flue gases, onto a confined-bed of activated carbon. The model's performances were studied at various flue gas flow rates, inlet mercury concentrations and adsorption bed temperatures. The process simulated a flue gas, with inlet mercury concentration of 300 ppb, entering at a velocity of 0.3 m s-1 from the bottom into a fixed bed (inside bed diameter of 1 m and 3 m bed height; bed temperature of 25 °C) of activated carbon (particle size of 0.004 m with density of 0.5 g cm-3 and

  19. Spontaneous organisation of ZnS nanoparticles into monocrystalline nanorods with highly enhanced dopant-related emission

    NASA Astrophysics Data System (ADS)

    Manzoor, K.; Aditya, V.; Vadera, S. R.; Kumar, N.; Kutty, T. R. N.

    2005-07-01

    A natural self-assembly process of semiconductor nanoparticles leading to the formation of doped, monocrystalline nanorods with highly enhanced dopant-related luminescence properties is reported. ˜4 nm sized, polycrystalline ZnS nanoparticles of zinc-blende (cubic) structure, doped with Cu+-Al3+ or Mn2+ have been aggregated in the aqueous solution and grown into nanorods of length ˜400 nm and aspect ratio ˜12. Transmission electron microscopic (TEM) images indicate crystal growth mechanisms involving both Ostwald-ripening and particle-to-particle oriented-attachment. Sulphur sulphur catenation is proposed for the covalent-linkage between the attached particles. The nanorods exhibit self-assembly mediated quenching of the lattice defect-related emission accompanied by multifold enhancement in the dopant-related emission. This study demonstrates that the collective behavior of an ensemble of bare nanoparticles, under natural conditions, can lead to the formation of functionalized (doped) nanorods with enhanced luminescence properties.

  20. Solar wind control of Jupiter's hectometric radio emission

    NASA Technical Reports Server (NTRS)

    Barrow, C. H.; Desch, M. D.

    1989-01-01

    Radio, plasma, and magnetic field data obtained by Voyager 1 and Voyager 2 were used to examine the manner in which the Jovian hectometric radio emission (HOM) is controlled by the solar wind. Using the method of superposed epochs, it was found that the higher energy HOM is correlated with the IMF as well as with the solar wind density and pressure. However, unlike the Io-independent decametric radio emission (Non-Io DAM), the HOM displayed no correlation with the solar wind velocity, although this radio component appear to be also influenced by the IMF. The results suggest separate HOM amd Non-Io DAM sources.

  1. Standardized Emission Quantification and Control of Costs for Environmental Measures

    NASA Astrophysics Data System (ADS)

    Walter, J.; Hustedt, M.; Wesling, V.; Barcikowski, S.

    Laser welding and soldering are important industrial joining processes. As is known, LGACs (Laser Generated Air Contaminants) cause costs for environmental measures during production of complex metallic components (steel, aluminium, magnesium, alloys). The hazardous potential of such processes has been assessed by analyzing the specific emissions with respect to relevant threshold limit values (TLVs). Avoiding and controlling emissions caused by laser processing of metals or metal composites is an important task. Using the experimental results, the planning of appropriate exhaust systems for laser processing is facilitated significantly. The costs quantified for environmental measures account for significant percentages of the total manufacturing costs.

  2. Control of Trace Metal Emissions During Coal Combustion

    SciTech Connect

    Thomas C. Ho

    1996-10-01

    Emissions of toxic trace metals in the form of metal fumes or submicron particulate from a coal-fired combustion source have received greater environmental and regulatory concern over the past years. Current practice of controlling these emissions is to collect them at the cold-end of the process by air-pollution control devices (APCDS) such as electrostatic precipitators and baghouses. However, trace metal fumes may not always be effectively collected by these devices because the formed fumes are extremely small. The proposed research is to explore the opportunities for improved control of toxic trace metal emissions, alternatively, at the hot-end of the coal combustion process, i.e., in the combustion chamber. The technology proposed is to prevent the metal fumes from forming during the process, which would effectively eliminate the metal emission problems. Specifically, the technology is to employ suitable sorbents to (1) reduce the amount of metal volatilization during combustion and (2) capture volatilized metal vapors. The objectives of the project are to demonstrate the technology and to characterize the metal capture process during coal combustion in a fluidized bed combustor.

  3. Air emission control equipment - the new challenge for equpiment suppliers

    SciTech Connect

    Lobb, F.H.

    1997-12-31

    The combination of Title V, the CAM Rule and the Credible Evidence Rule demand industrial sites view the selection and operation of emission control devices in a whole new light. No longer can users see these devices as detached end of pipe pieces of equipment essentially purchased off lowest bid. These regulatory changes force plants to fully integrate the operation of these devices into their process control systems and instrumentation. And this is specifically EPA`s stated intent. EPA believes that by forcing sites to exercise the same knowledge and attention to air emissions that they do to operate their production processes, emissions will undergo a natural reduction across the country. Process and operational data that historically has been the sole province of sites becomes public. And compliance with state defined requirements must be demonstrated essentially continuously. This paper explores the new approach to compliance and provides insight through specific field examples/installations of emission control equipment. The author seeks to promote understanding through discussion of these significant regulatory changes.

  4. Control of Trace Metal Emissions During Coal Combustion

    SciTech Connect

    Thomas C. Ho

    1997-10-01

    Emissions of toxic trace metals in the form of metal fumes or submicron particulates from a coal-fired combustion source have received greater environmental and regulatory concern over the past years. Current practice of controlling these emissions is to collect them at the cold-end of the process by air-pollution control devices (APCDs) such as electrostatic precipitators and baghouses. However, trace metal fumes may not always be effectively collected by these devices because the formed fumes are extremely small. The proposed research is to explore the opportunities for improved control of toxic trace metal emissions, alternatively, at the hot-end of the coal combustion process, i.e., in the combustion chamber. The technology proposed is to prevent the metal fumes from forming during the process, which would effectively eliminate the metal emission problems. Specifically, the technology is to employ suitable sorbents to (1) reduce the amount of metal volatilization during combustion and (2) capture volatilized metal vapors. The objectives of the project are to demonstrate the technology and to characterize the metal capture process during coal combustion in a fluidized bed combustor. The project was started on July 1, 1994 and this is the thirteenth quarterly technical progress report. Specifically, the following progress has been made during this performance period from July 1, 1997 through September 30, 1997.

  5. Control of Trace Metal Emissions During Coal Combustion

    SciTech Connect

    Thomas C. Ho

    1997-01-01

    Emissions of toxic trace metals in the form of metal fumes or submicron particulates from a coal-fired combustion source have received greater environmental and regulatory concern over the past years. Current practice of controlling these emissions is to collect them at the cold-end of the process by air-pollution control devices (APCDs) such as electrostatic precipitators and baghouses. However, trace metal fumes may not always be effectively collected by these devices because the formed fumes are extremely small. The proposed research is to explore the opportunities for improved control of toxic trace metal emissions, alternatively, at the hot-end of the coal combustion process, i.e., in the combustion chamber. The technology proposed is to prevent the metal fumes from forming during the process, which would effectively eliminate the metal emission problems. Specifically, the technology is to employ suitable sorbents to (1) reduce the amount of metal volatilization during combustion and (2) capture volatilized metal vapors. The objectives of the project are to demonstrate the technology and to characterize the metal capture process during coal combustion in a fluidized bed combustor.

  6. Control of Trace Metal Emissions During Coal Combustion

    SciTech Connect

    Thomas C. Ho

    1997-07-01

    Emissions of toxic trace metals in the form of metal fumes or submicron particulates from a coal-fired combustion source have received greater environmental and regulatory concern over the past years. Current practice of controlling these emissions is to collect them at the cold-end of the process by air-pollution control devices (APCDs) such as electrostatic precipitators and baghouses. However, trace metal fumes may not always be effectively collected by these devices because the formed fumes are extremely small. The proposed research is to explore the opportunities for improved control of toxic trace metal emissions, alternatively, at the hot-end of the coal combustion process, i.e., in the combustion chamber. The technology proposed is to prevent the metal fumes from forming during the process, which would effectively eliminate the metal emission problems. Specifically, the technology is to employ suitable sorbents to (1) reduce the amount of metal volatilization during combustion and (2) capture volatilized metal vapors. The objectives of the project are to demonstrate the technology and to characterize the metal capture process during coal combustion in a fluidized bed combustor.

  7. Control of Trace Metal Emissions During Coal Combustion

    SciTech Connect

    Thomas C. Ho

    1997-04-01

    Emissions of toxic trace metals in the form of metal fumes or submicron particulates from a coal-fired combustion source have received greater environmental and regulatory concern over the past years. Current practice of controlling these emissions is to collect them at the cold-end of the process by air-pollution control devices (APCDs) such as electrostatic precipitators and baghouses. However, trace metal fumes may not always be effectively collected by these devices because the formed fumes are extremely small. The proposed research is to explore the opportunities for improved control of toxic trace metal emissions, alternatively, at the hot-end of the coal combustion process, i.e., in the combustion chamber. The technology proposed is to prevent the metal fumes from forming during the process, which would effectively eliminate the metal emission problems. Specifically, the technology is to employ suitable sorbents to (1) reduce the amount of metal volatilization during combustion and (2) capture volatilized metal vapors. The objectives of the project are to demonstrate the technology and to characterize the metal capture process during coal combustion in a fluidized bed combustor.

  8. Control of mercury emissions from coal-fired boilers

    SciTech Connect

    Huang, H.S.; Livengood, C.D.

    1992-01-01

    This project at Argonne is designed to investigate new concepts leading to advanced control technologies for fossil-energy systems. The objective of this new task on air toxics control is to develop new or improved, cost-effective control technology for the abatement of emissions of hazardous air pollutants (HAPs) from fossil-fuel combustion plants and to evaluate the possible effects of any captured species on waste disposal. The HAPs to be investigated initially in this task include mercury and arsenic compounds.

  9. Control of mercury emissions from coal-fired boilers

    SciTech Connect

    Huang, H.S.; Livengood, C.D.

    1992-09-01

    This project at Argonne is designed to investigate new concepts leading to advanced control technologies for fossil-energy systems. The objective of this new task on air toxics control is to develop new or improved, cost-effective control technology for the abatement of emissions of hazardous air pollutants (HAPs) from fossil-fuel combustion plants and to evaluate the possible effects of any captured species on waste disposal. The HAPs to be investigated initially in this task include mercury and arsenic compounds.

  10. Controlled synthesis and tunable properties of ultrathin silica nanotubes through spontaneous polycondensation on polyamine fibrils

    PubMed Central

    Yuan, Jian-Jun; Zhu, Pei-Xin; Noda, Daisuke

    2013-01-01

    Summary This paper describes a facile approach to a biomimetic rapid fabrication of ultrathin silica nanotubes with a highly uniform diameter of 10 nm and inner hollow of around 3 nm. The synthesis is carried out through a spontaneous polycondensation of alkoxysilane on polyamine crystalline fibrils that were conveniently produced from the neutralization of a solution of protonated linear polyethyleneimine (LPEI–H+) by alkali compounds. A simple mixing the fibrils with alkoxysilane in aqueous solution allowed for the rapid formation of silica to produce LPEI@silica hybrid nanotubes. These 10-nm nanotubes were hierarchically organized in a mat-like morphology with a typical size of 1–2 micrometers. The subsequent removal of organic LPEI via calcination resulted in silica nanotubes that keep this morphology. The morphology, the structure, the pore properties and the formation mechanism of the silica nanotubes were carefully investigated with scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller measurements (BET), and X-ray diffraction (XRD). Detailed studies demonstrated that the formation of the nanotubes depends on the molar ratio of [OH]/[CH2CH2NH] during the neutralization as well as on the basicity of the alkali compound and on the concentration of the silica source. The synthesis of silica nanotubes established here could be easily applied to a fabrication on the kilogram scale. Silica nanotubes that were obtained from the calcination of hybrid nanotubes of LPEI@silica in an N2 atmosphere showed a distinct photoluminescence centered at 540 nm with a maximum excitation wavelength of 320 nm. Furthermore, LPEI@silica hybrid nanotubes were applied to create silica–carbon composite nanotubes by alternative adsorption of ionic polymers and subsequent carbonization. PMID:24367748

  11. 78 FR 36776 - Proposed Information Collection Request; Comment Request; Emission Control System Performance...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-19

    ... AGENCY Proposed Information Collection Request; Comment Request; Emission Control System Performance... an information collection request (ICR), ``Emission Control System Performance Warranty Regulations and Voluntary Aftermarket Part Certification Program (Renewal)'' (EPA ICR No. 0116.10, OMB Control...

  12. Emissions from premixed charge compression ignition (PCCI) combustion and affect on emission control devices

    SciTech Connect

    Parks, II, James E; Kass, Michael D; Huff, Shean P; Barone, Teresa L; Lewis Sr, Samuel Arthur; Prikhodko, Vitaly Y; Storey, John Morse

    2010-01-01

    A light-duty diesel engine has been operated in advanced combustion modes known generally as premixed charge compression ignition (PCCI). The emissions have been characterized for several load and speed combinations. Fewer NO{sub x} and particulate matter (PM) emissions are produced by PCCI, but higher CO and hydrocarbon (HC) emissions result. In addition, the nature of the PM differs from conventional combustion; the PM is smaller and has a much higher soluble organic fraction (SOF) content (68% vs. 30% for conventional combustion). Three catalyst technologies were studied to determine the affects of HECC on catalyst performance; the technologies were a lean NO{sub x} trap (LNT), diesel oxidation catalyst (DOC), and diesel particulate filter (DPF). The LNT benefited greatly from the reduced NO{sub x} emissions associated with PCCI. NO{sub x} capacity requirements are reduced as well as overall tailpipe NO{sub x} levels particularly at low load and temperature conditions where regeneration of the LNT is difficult. The DOC performance requirements for PCCI are more stringent due to the higher CO and HC emissions; however, the DOC was effective at controlling the higher CO and HC emissions at conditions above the light-off temperature. Below light-off, CO and HC emissions are problematic. The study of DPF technology focused on the fuel penalties associated with DPF regeneration or 'desoot' due to the different PM loading rates from PCCI vs. conventional combustion. Less frequent desoot events were required from the lower PM from PCCI and, when used in conjunction with an LNT, the lower PM from less frequent LNT regeneration. The lower desoot frequency leads a {approx}3% fuel penalty for a mixture of PCCI and conventional loads vs. {approx}4% for conventional only combustion.

  13. Control of Several Emissions during Olive Pomace Thermal Degradation

    PubMed Central

    Miranda, Teresa; Nogales, Sergio; Román, Silvia; Montero, Irene; Arranz, José Ignacio; Sepúlveda, Francisco José

    2014-01-01

    Biomass plays an important role as an energy source, being an interesting alternative to fossil fuels due to its environment-friendly and sustainable characteristics. However, due to the exposure of customers to emissions during biomass heating, evolved pollutants should be taken into account and controlled. Changing raw materials or mixing them with another less pollutant biomass could be a suitable step to reduce pollution. This work studied the thermal behaviour of olive pomace, pyrenean oak and their blends under combustion using thermogravimetric analysis. It was possible to monitor the emissions released during the process by coupling mass spectrometry analysis. The experiments were carried out under non-isothermal conditions at the temperature range 25–750 °C and a heating rate of 20 °C·min−1. The following species were analysed: aromatic compounds (benzene and toluene), sulphur emissions (sulphur dioxide), 1,4-dioxin, hydrochloric acid, carbon dioxide and nitrogen oxides. The results indicated that pollutants were mainly evolved in two different stages, which are related to the thermal degradation steps. Thus, depending on the pollutant and raw material composition, different emission profiles were observed. Furthermore, intensity of the emission profiles was related, in some cases, to the composition of the precursor. PMID:25314298

  14. Ozone trends in Atlanta, Georgia - Have emission controls been effective?

    NASA Technical Reports Server (NTRS)

    Lindsay, Ronald W.; Richardson, Jennifer L.; Chameldes, William L.

    1989-01-01

    Nine years of summertime ozone data from the Atlanta metropolitan area are analyzed and compared to local emissions of volatile organic carbon and nitrogen oxides. Trends from 1979 to 1987 were studied for the number of days per year ozone exceeded the NAAQS standard, the second-highest ozone level observed per year, and the first quartile summertime average ozone observed, as well as the mean difference between the ozone level observed downwind and upwind of the city. Because this last parameter is sensitive to chemical factors but relatively insensitive to the number of days each year with meteorological conditions conducive to ozone formation, its trend may be best suited for determining how effective emission controls have been in reducing O3 in the Atlanta area. In spite of the fact that sizeable reductions have been claimed for volatile organic carbon emissions over the past several years, the data give no indication that ozone levels have decreased and in fact, imply that summertime ozone production may have increased. The results imply that either emissions have not decreased as much as has been claimed or that ozone is not sensitive to anthropogenic volatile organic carbon emissions.

  15. Control of several emissions during olive pomace thermal degradation.

    PubMed

    Miranda, Teresa; Nogales, Sergio; Román, Silvia; Montero, Irene; Arranz, José Ignacio; Sepúlveda, Francisco José

    2014-01-01

    Biomass plays an important role as an energy source, being an interesting alternative to fossil fuels due to its environment-friendly and sustainable characteristics. However, due to the exposure of customers to emissions during biomass heating, evolved pollutants should be taken into account and controlled. Changing raw materials or mixing them with another less pollutant biomass could be a suitable step to reduce pollution. This work studied the thermal behaviour of olive pomace, pyrenean oak and their blends under combustion using thermogravimetric analysis. It was possible to monitor the emissions released during the process by coupling mass spectrometry analysis. The experiments were carried out under non-isothermal conditions at the temperature range 25-750 °C and a heating rate of 20 °C·min⁻¹. The following species were analysed: aromatic compounds (benzene and toluene), sulphur emissions (sulphur dioxide), 1,4-dioxin, hydrochloric acid, carbon dioxide and nitrogen oxides. The results indicated that pollutants were mainly evolved in two different stages, which are related to the thermal degradation steps. Thus, depending on the pollutant and raw material composition, different emission profiles were observed. Furthermore, intensity of the emission profiles was related, in some cases, to the composition of the precursor. PMID:25314298

  16. Venturi/vortex technology for controlling chromium electroplating emissions

    SciTech Connect

    Hay, K.J.; Northrup, J.; Heck, S.R.

    1997-12-31

    A new technology has been developed to control air emissions from hexavalent chromium electroplating tanks. The venturi/vortex scrubber uses a patented drain assembly to pull plating solution, air with toxic particulates above the solution, and unpopped bubbles of generated gases down with a gravity generated vortex effect. The recirculated plating solution acts as the scrubbing liquid and air agitation is eliminated. Separated gases are passed through a condenser/filter to remove any remaining fumes. The device is almost entirely constructed of CPVC. This device offers several advantages over conventional end-of-pipe systems including significantly lower cost, no wastewater, no extensive ventilation system, and emissions are recycled. The system can be is easily retrofitted to existing tanks, however, a loose fitting tank lid is recommended. A pilot demonstration has been performed at Benet Laboratory, Watervliet, NY (US Army) with a 1,500 gallon chromic acid electroplating tank and 1,500 Amps of applied current. Overall chromium emissions results were 0.00002 mg/Amp-hr, surpassing the stringent California State requirement of 0.006 mg/Amp-hr. Emission prevention by capturing unpopped bubbles is the method in which this system reduces the most emissions. The system met current ambient worker safety standards. Two major improvements are recommended: an increase in gas flow rate through the system and a solution to the system`s sensitivity to the plating solution level.

  17. LANDFILL OPERATION FOR CARBON SEQUESTRATION AND MAXIMUM METHANE EMISSION CONTROL

    SciTech Connect

    Don Augenstein

    1999-01-11

    ''Conventional'' waste landfills emit methane, a potent greenhouse gas, in quantities such that landfill methane is a major factor in global climate change. Controlled landfilling is a novel approach to manage landfills for rapid completion of total gas generation, maximizing gas capture and minimizing emissions of methane to the atmosphere. With controlled landfilling, methane generation is accelerated and brought to much earlier completion by improving conditions for biological processes (principally moisture levels) in the landfill. Gas recovery efficiency approaches 100% through use of surface membrane cover over porous gas recovery layers operated at slight vacuum. A field demonstration project's results at the Yolo County Central Landfill near Davis, California are, to date, highly encouraging. Two major controlled landfilling benefits would be the reduction of landfill methane emissions to minuscule levels, and the recovery of greater amounts of landfill methane energy in much shorter times than with conventional landfill practice. With the large amount of US landfill methane generated, and greenhouse potency of methane, better landfill methane control can play a substantial role in reduction of US greenhouse gas emissions.

  18. Spontaneous Fission

    DOE R&D Accomplishments Database

    Segre, Emilio

    1950-11-22

    The first attempt to discover spontaneous fission in uranium was made by [Willard] Libby, who, however, failed to detect it on account of the smallness of effect. In 1940, [K. A.] Petrzhak and [G. N.] Flerov, using more sensitive methods, discovered spontaneous fission in uranium and gave some rough estimates of the spontaneous fission decay constant of this substance. Subsequently, extensive experimental work on the subject has been performed by several investigators and will be quoted in the various sections. [N.] Bohr and [A.] Wheeler have given a theory of the effect based on the usual ideas of penetration of potential barriers. On this project spontaneous fission has been studied for the past several years in an effort to obtain a complete picture of the phenomenon. For this purpose the spontaneous fission decay constants {lambda} have been measured for separated isotopes of the heavy elements wherever possible. Moreover, the number {nu} of neutrons emitted per fission has been measured wherever feasible, and other characteristics of the spontaneous fission process have been studied. This report summarizes the spontaneous fission work done at Los Alamos up to January 1, 1945. A chronological record of the work is contained in the Los Alamos monthly reports.

  19. Health and climate policy impacts on sulfur emission control

    NASA Astrophysics Data System (ADS)

    Ming, Yi; Russell, Lynn M.; Bradford, David F.

    2005-12-01

    Sulfate aerosol from burning fossil fuels not only has strong cooling effects on the Earth's climate but also imposes substantial costs on human health. To assess the impact of addressing air pollution on climate policy, we incorporate both the climate and health effects of sulfate aerosol into an integrated-assessment model of fossil fuel emission control. Our simulations show that a policy that adjusts fossil fuel and sulfur emissions to address both warming and health simultaneously will support more stringent fossil fuel and sulfur controls. The combination of both climate and health objectives leads to an acceleration of global warming in the 21st century as a result of the short-term climate response to the decreased cooling from the immediate removal of short-lived sulfate aerosol. In the long term (more than 100 years), reducing sulfate aerosol emissions requires that we decrease fossil fuel combustion in general, thereby removing some of the coemitted carbon emissions and leading to a reduction in global warming.

  20. The effects of energy paths and emission controls and standards on future trends in China's emissions of primary air pollutants

    NASA Astrophysics Data System (ADS)

    Zhao, Y.; Zhang, J.; Nielsen, C. P.

    2014-03-01

    To examine the efficacy of China's actions to control atmospheric pollution, three levels of growth of energy consumption and three levels of implementation of emission controls are estimated, generating a total of nine combined activity-emission control scenarios that are then used to estimate trends of national emissions of primary air pollutants through 2030. The emission control strategies are expected to have more effects than the energy paths on the future emission trends for all the concerned pollutants. As recently promulgated national action plans of air pollution prevention and control (NAPAPPC) are implemented, China's anthropogenic pollutant emissions should decline. For example, the emissions of SO2, NOx, total primary particulate matter (PM), PM10, and PM2.5 are estimated to decline 7%, 20%, 41%, 34%, and 31% from 2010 to 2030, respectively, in the "best guess" scenario that includes national commitment of energy saving policy and partial implementation of NAPAPPC. Should the issued/proposed emission standards be fully achieved, a less likely scenario, annual emissions would be further reduced, ranging from 17% (for primary PM2.5) to 29% (for NOx) declines in 2015, and the analogue numbers would be 12% and 24% in 2030. The uncertainties of emission projections result mainly from the uncertain operational conditions of swiftly proliferating air pollutant control devices and lack of detailed information about emission control plans by region. The predicted emission trends by sector and chemical species raise concerns about current pollution control strategies: the potential for emissions abatement in key sectors may be declining due to the near saturation of emission control devices use; risks of ecosystem acidification could rise because emissions of alkaline base cations may be declining faster than those of SO2; and radiative forcing could rise because emissions of positive-forcing carbonaceous aerosols may decline more slowly than those of SO2

  1. The effects of energy paths and emission controls and standards on future trends in China's emissions of primary air pollutants

    NASA Astrophysics Data System (ADS)

    Zhao, Y.; Zhang, J.; Nielsen, C. P.

    2014-09-01

    To examine the efficacy of China's actions to control atmospheric pollution, three levels of growth of energy consumption and three levels of implementation of emission controls are estimated, generating a total of nine combined activity-emission control scenarios that are then used to estimate trends of national emissions of primary air pollutants through 2030. The emission control strategies are expected to have more effects than the energy paths on the future emission trends for all the concerned pollutants. As recently promulgated national action plans of air pollution prevention and control (NAPAPPC) are implemented, China's anthropogenic pollutant emissions should decline. For example, the emissions of SO2, NOx, total suspended particles (TSP), PM10, and PM2.5 are estimated to decline 7, 20, 41, 34, and 31% from 2010 to 2030, respectively, in the "best guess" scenario that includes national commitment of energy saving policy and implementation of NAPAPPC. Should the issued/proposed emission standards be fully achieved, a less likely scenario, annual emissions would be further reduced, ranging from 17 (for primary PM2.5) to 29% (for NOx) declines in 2015, and the analogue numbers would be 12 and 24% in 2030. The uncertainties of emission projections result mainly from the uncertain operational conditions of swiftly proliferating air pollutant control devices and lack of detailed information about emission control plans by region. The predicted emission trends by sector and chemical species raise concerns about current pollution control strategies: the potential for emissions abatement in key sectors may be declining due to the near saturation of emission control devices use; risks of ecosystem acidification could rise because emissions of alkaline base cations may be declining faster than those of SO2; and radiative forcing could rise because emissions of positive-forcing carbonaceous aerosols may decline more slowly than those of SO2 emissions and thereby

  2. Dynamic control of light emission faster than the lifetime limit using VO2 phase-change

    PubMed Central

    Cueff, Sébastien; Li, Dongfang; Zhou, You; Wong, Franklin J.; Kurvits, Jonathan A.; Ramanathan, Shriram; Zia, Rashid

    2015-01-01

    Modulation is a cornerstone of optical communication, and as such, governs the overall speed of data transmission. Currently, the two main strategies for modulating light are direct modulation of the excited emitter population (for example, using semiconductor lasers) and external optical modulation (for example, using Mach–Zehnder interferometers or ring resonators). However, recent advances in nanophotonics offer an alternative approach to control spontaneous emission through modifications to the local density of optical states. Here, by leveraging the phase-change of a vanadium dioxide nanolayer, we demonstrate broadband all-optical direct modulation of 1.5 μm emission from trivalent erbium ions more than three orders of magnitude faster than their excited state lifetime. This proof-of-concept demonstration shows how integration with phase-change materials can transform widespread phosphorescent materials into high-speed optical sources that can be integrated in monolithic nanoscale devices for both free-space and on-chip communication. PMID:26489436

  3. Detection and control of spontaneous heating in coal mine pillars: A case study. Report of investigations/1995

    SciTech Connect

    Timko, R.J.; Derick, R.L.

    1995-08-01

    The U.S. Bureau of Mines study examined spontaneous heating episodes in coal mine pillars in an active underground coal mine. The information obtained from these incidents was then analyzed to learn which sampling methods provided the earliest indications of pillar heating. The objective of the study was to discover if the location of future pillar spontaneous heating events could be inferred from the available information. The study found that by drilling small-diameter boreholes into the pillars, then obtaining gas samples from the affected pillars, the ability to locate early spontaneous heating episodes was improved. However, the ability to accurately predict future spontaneous heating events remains in question.

  4. Method and means for diesel exhaust particulate emission control

    SciTech Connect

    Ludecke, O.A.

    1983-04-19

    A method and means for controlling diesel particulate emissions involves providing an exhaust trap filter to collect exhaust particulates at a point near the engine exhaust ports and providing means to periodically vent burning combustion chamber gases to the exhaust filter to initiate combustion and incineration of the collected particulates. Various means for conducting burning mixture to ignite the particulates in the filter are disclosed.

  5. Controlling automotive exhaust emissions: successes and underlying science.

    PubMed

    Twigg, Martyn V

    2005-04-15

    Photochemical reactions of vehicle exhaust pollutants were responsible for photochemical smog in many cities during the 1960s and 1970s. Engine improvements helped, but additional measures were needed to achieve legislated emissions levels. First oxidation catalysts lowered hydrocarbon and carbon monoxide, and later nitrogen oxides were reduced to nitrogen in a two-stage process. By the 1980s, exhaust gas could be kept stoichiometric and hydrocarbons, carbon monoxide and nitrogen oxides were simultaneously converted over a single 'three-way catalyst'. Today, advanced three-way catalyst systems emissions are exceptionally low. NOx control from lean-burn engines demands an additional approach because NO cannot be dissociated under lean conditions. Current lean-burn gasoline engine NOx control involves forming a nitrate phase and periodically enriching the exhaust to reduce it to nitrogen, and this is being modified for use on diesel engines. Selective catalytic reduction with ammonia is an alternative that can be very efficient, but it requires ammonia or a compound from which it can be obtained. Diesel engines produce particulate matter, and, because of health concerns, filtration processes are being introduced to control these emissions. On heavy duty diesel engines the exhaust gas temperature is high enough for NO in the exhaust to be oxidised over a catalyst to NO2 that smoothly oxidises particulate material (PM) in the filter. Passenger cars operate at lower temperatures, and it is necessary to periodically burn the PM in air at high temperatures. PMID:15901550

  6. Solid state carbon nanotube device for controllable trion electroluminescence emission

    NASA Astrophysics Data System (ADS)

    Liang, Shuang; Ma, Ze; Wei, Nan; Liu, Huaping; Wang, Sheng; Peng, Lian-Mao

    2016-03-01

    Semiconducting carbon nanotubes (CNTs) have a direct chirality-dependent bandgap and reduced dimensionality-related quantum confinement effects, which are closely related to the performance of optoelectronic devices. Here, taking advantage of the large energy separations between neutral singlet excitons and charged excitons, i.e. trions in CNTs, we have achieved for the first time all trion electroluminescence (EL) emission from chirality-sorted (8,3) and (8,4) CNT-based solid state devices. We showed that strong trion emission can be obtained as a result of localized impact excitation and electrically injected holes, with an estimated efficiency of ~5 × 10-4 photons per injected hole. The importance of contact-controlled carrier injection (including symmetric and asymmetric contact configurations) and EL spectral stability for gradually increasing bias were also investigated. The realization of electrically induced pure trion emission opens up a new opportunity for CNT film-based optoelectronic devices, providing a new degree of freedom in controlling the devices to extend potential applications in spin or magnetic optoelectronics fields.Semiconducting carbon nanotubes (CNTs) have a direct chirality-dependent bandgap and reduced dimensionality-related quantum confinement effects, which are closely related to the performance of optoelectronic devices. Here, taking advantage of the large energy separations between neutral singlet excitons and charged excitons, i.e. trions in CNTs, we have achieved for the first time all trion electroluminescence (EL) emission from chirality-sorted (8,3) and (8,4) CNT-based solid state devices. We showed that strong trion emission can be obtained as a result of localized impact excitation and electrically injected holes, with an estimated efficiency of ~5 × 10-4 photons per injected hole. The importance of contact-controlled carrier injection (including symmetric and asymmetric contact configurations) and EL spectral stability for

  7. THE IMPACT OF PARTICULATE EMISSIONS CONTROL ON THE CONTROL OF OTHER MWC AIR EMISSIONS

    EPA Science Inventory

    On December 20, 1989, the Environmental Protection Agency (EPA) proposed revised new source performance standards for new municipal waste combustion (MWC) units and guidelines for existing sources. The proposed national regulations require tighter particulate matter control and a...

  8. Failing to Forget: Prospective Memory Commission Errors Can Result from Spontaneous Retrieval and Impaired Executive Control

    ERIC Educational Resources Information Center

    Scullin, Michael K.; Bugg, Julie M.

    2013-01-01

    Prospective memory (PM) research typically examines the ability to remember to execute delayed intentions but often ignores the ability to forget finished intentions. We had participants perform (or not perform; control group) a PM task and then instructed them that the PM task was finished. We later (re)presented the PM cue. Approximately 25% of…

  9. Spontaneous and electric field–controlled front–rear polarization of human keratinocytes

    PubMed Central

    Saltukoglu, Deniz; Grünewald, Julian; Strohmeyer, Nico; Bensch, Robert; Ulbrich, Maximilian H.; Ronneberger, Olaf; Simons, Matias

    2015-01-01

    It has long been known that electrical fields (EFs) are able to influence the direction of migrating cells, a process commonly referred to as electrotaxis or galvanotaxis. Most studies have focused on migrating cells equipped with an existing polarity before EF application, making it difficult to delineate EF-specific pathways. Here we study the initial events in front–rear organization of spreading keratinocytes to dissect the molecular requirements for random and EF-controlled polarization. We find that Arp2/3-dependent protrusive forces and Rac1/Cdc42 activity were generally required for both forms of polarization but were dispensable for controlling the direction of EF-controlled polarization. By contrast, we found a crucial role for extracellular pH as well as G protein coupled–receptor (GPCR) or purinergic signaling in the control of directionality. The normal direction of polarization toward the cathode was reverted by lowering extracellular pH. Polarization toward the anode was also seen at neutral pH when GPCR or purinergic signaling was inhibited. However, the stepwise increase of extracellular pH in this scenario led to restoration of cathodal polarization. Overall our work puts forward a model in which the EF uses distinct polarization pathways. The cathodal pathway involves GPCR/purinergic signaling and is dominant over the anodal pathway at neutral pH. PMID:26424799

  10. Enhancement in the excitonic spontaneous emission rates for Si nanocrystal multi-layers covered with thin films of Au, Ag, and Al.

    PubMed

    Estrin, Y; Rich, D H; Rozenfeld, N; Arad-Vosk, N; Ron, A; Sa'ar, A

    2015-10-30

    The enhancement in the spontaneous emission rate (SER) for Ag, Au, and Al films on multilayer Si nanocrystals (SiNCs) was probed with time-resolved cathodoluminescence (CL). The SiNCs were grown on Si(100) using plasma enhanced chemical vapor deposition. Electron-hole pairs were generated in the metal-covered SiNCs by injecting a pulsed high-energy electron beam through the thin metal films, which is found to be an ideal method of excitation for plasmonic quantum heterostructures and nanostructures that are opaque to laser or light excitation. Spatially, spectrally, and temporally resolved CL was used to measure the excitonic lifetime of the SiNCs in metal-covered and bare regions of the same samples. The observed enhancement in the SER for the metal-covered SiNCs, relative to the SER for the bare sample, is attributed to a coupling of the SiNC excitons with surface plasmon polaritons (SPPs) of the thin metal films. A maximum SER enhancement of ∼2.0, 1.4 and 1.2 was observed for the Ag, Au, and Al films, respectively, at a temperature of 55 K. The three chosen plasmonic metals of Ag, Au, and Al facilitate an interesting comparison of the exciton-SPP coupling for metal films that exhibit varying differences between the surface plasmon energy, ω(sp), and the SiNC excitonic emission energy. A modeling of the temperature dependence of the Purcell enhancement factor, Fp, was performed and included the temperature dependence of the dielectric properties of the metals. PMID:26436289

  11. Emission control of gas effluents from geothermal power plants.

    PubMed

    Axtmann, R C

    1975-01-01

    Geothermal steam at the world's five largest power plants contains from 0.15 to 30% noncondensable gases including CO(2), H(2)S, H(2), CH(4), N(2), H(3)BO(3), and NH(3). At four of the plants the gases are first separated from the steam and then discharged to the environment; at the fifth, the noncondensables exhaust directly to the atmosphere along with spent steam. Some CO(2) and sulfur emission rates rival those from fossil-fueled plants on a per megawatt-day basis. The ammonia and boron effluents can interfere with animal and plant life. The effects of sulfur (which emerges as H(2)S but may oxidize to SO(2)) on either ambient air quality or longterm human health are largely unknown. Most geothermal turbines are equipped with direct contact condensers which complicate emission control because they provide two or more pathways for the effluents to reach the environment. Use of direct contact condensers could permit efficient emission control if coupled to processes that produce saleable quantities of purified carbon dioxide and elemental sulfur. PMID:1132388

  12. Solid state carbon nanotube device for controllable trion electroluminescence emission.

    PubMed

    Liang, Shuang; Ma, Ze; Wei, Nan; Liu, Huaping; Wang, Sheng; Peng, Lian-Mao

    2016-03-28

    Semiconducting carbon nanotubes (CNTs) have a direct chirality-dependent bandgap and reduced dimensionality-related quantum confinement effects, which are closely related to the performance of optoelectronic devices. Here, taking advantage of the large energy separations between neutral singlet excitons and charged excitons, i.e. trions in CNTs, we have achieved for the first time all trion electroluminescence (EL) emission from chirality-sorted (8,3) and (8,4) CNT-based solid state devices. We showed that strong trion emission can be obtained as a result of localized impact excitation and electrically injected holes, with an estimated efficiency of ∼5 × 10(-4) photons per injected hole. The importance of contact-controlled carrier injection (including symmetric and asymmetric contact configurations) and EL spectral stability for gradually increasing bias were also investigated. The realization of electrically induced pure trion emission opens up a new opportunity for CNT film-based optoelectronic devices, providing a new degree of freedom in controlling the devices to extend potential applications in spin or magnetic optoelectronics fields. PMID:26953676

  13. Technology for CO{sub 2} emission monitoring and control

    SciTech Connect

    Joyce, E.L. Jr.; Unkefer, P.J.; Pendergrass, J.H.; Parkinson, W.J.; Loose, V.W.; Brainard, J.R.

    1998-12-31

    The authors examined three specific areas relative to CO{sub 2} emissions and controls: (1) the effect of deregulation of the utility industry on emissions, (2) the role of advanced power systems in reducing emissions, and (3) developing CO{sub 2} mitigation technologies. In this work the Energy Technologies program office at Los Alamos attempted to initiate an integrated approach that includes a range of tasks involving both point and distributed CO{sub 2} control. The authors have examined evolving mitigation (separation and sequestration) technologies for CO{sub 2} disposal. The separation of hydrogen gas from high-temperature CO{sub 2}-containing streams is a critical component of carbon dioxide mitigation technology, and cost-effective point sequestration will require separation of CO{sub 2} from H{sub 2}. They investigated four types of separation techniques: two high-temperature membrane technologies, an intermediate-temperature membrane technology, and a separation technology based on the formation of CO{sub 2} hydrate compounds through reaction of CO{sub 2} with water at near freezing conditions. At Los Alamos, sequestration technologies are being developed along three principal areas: mineral sequestration of CO{sub 2}, the enhancement of natural sinks using biotechnology methods, and the conversion of CO{sub 2} to methanol using high-temperature photolysis.

  14. Self-assembly, highly modified spontaneous emission and energy transfer properties of LaPO4:Ce3+, Tb3+ inverse opals.

    PubMed

    Zhu, Yongsheng; Sun, Zhipeng; Yin, Ze; Song, Hongwei; Xu, Wen; Wang, Yunfeng; Zhang, Ligong; Zhang, Hanzhuang

    2013-06-14

    The modification of photonic crystals (PCs) on photoluminescence of rare earth (RE) ions has attracted considerable interest, however, the modification of PCs on energy transfer (ET) processes of two separate RE centers has not been investigated yet. In this paper, three-dimensional Ce(3+), Tb(3+)-codoped LaPO4 inverse opal PCs (IOPCs) were fabricated by the PMMA colloidal template method. The modification of the photonic stop band (PSB) on emission spectra and the dynamics of the 5d-4f transition of Ce(3+) and the 4f-4f transition of Tb(3+) ions were systematically studied. It is interesting to observe that the spontaneous decay rates (SDR) of (5)D4-(7)F5 in the IOPCs were suppressed as highly as 173% in contrast to the reference ground powder samples (REF) due to the modification of the effective refractive index (n(eff)). The energy transfer (ET) rate of Ce(3+) to Tb(3+) did not change in the IOPCs, however, the energy migration rate among Tb(3+) ions was largely restrained. It is also significant to observe that, in the IOPCs, the temperature quenching and radiation trapping of photoluminescence were greatly suppressed due to the periodic empty cavity structure of IOPCs, which is significant for high-power light sources and laser devices. PMID:23571776

  15. Real-time monitoring and fault locating using amplified spontaneous emission noise reflection for tree-structured Ethernet passive optical networks

    NASA Astrophysics Data System (ADS)

    Naim, Nani Fadzlina; Ab-Rahman, Mohammad Syuhaimi; Kamaruddin, Nur Hasiba; Bakar, Ahmad Ashrif A.

    2013-09-01

    Nowadays, optical networks are becoming dense while detecting faulty branches in the tree-structured networks has become problematic. Conventional methods are inconvenient as they require an engineer to visit the failure site to check the optical fiber using an optical time-domain reflectometer. An innovative monitoring technique for tree-structured network topology in Ethernet passive optical networks (EPONs) by using the erbium-doped fiber amplifier to amplify the traffic signal is demonstrated, and in the meantime, a residual amplified spontaneous emission spectrum is used as the input signal to monitor the optical cable from the central office. Fiber Bragg gratings with distinct center wavelengths are employed to reflect the monitoring signals. Faulty branches of the tree-structured EPONs can be identified using a simple and low-cost receiver. We will show that this technique is capable of providing monitoring range up to 32 optical network units using a power meter with a sensitivity of -65 dBm while maintaining the bit error rate of 10-13.

  16. Air-Stable Surface-Passivated Perovskite Quantum Dots for Ultra-Robust, Single- and Two-Photon-Induced Amplified Spontaneous Emission.

    PubMed

    Pan, Jun; Sarmah, Smritakshi P; Murali, Banavoth; Dursun, Ibrahim; Peng, Wei; Parida, Manas R; Liu, Jiakai; Sinatra, Lutfan; Alyami, Noktan; Zhao, Chao; Alarousu, Erkki; Ng, Tien Khee; Ooi, Boon S; Bakr, Osman M; Mohammed, Omar F

    2015-12-17

    We demonstrate ultra-air- and photostable CsPbBr3 quantum dots (QDs) by using an inorganic-organic hybrid ion pair as the capping ligand. This passivation approach to perovskite QDs yields high photoluminescence quantum yield with unprecedented operational stability in ambient conditions (60 ± 5% lab humidity) and high pump fluences, thus overcoming one of the greatest challenges impeding the development of perovskite-based applications. Due to the robustness of passivated perovskite QDs, we were able to induce ultrastable amplified spontaneous emission (ASE) in solution processed QD films not only through one photon but also through two-photon absorption processes. The latter has not been observed before in the family of perovskite materials. More importantly, passivated perovskite QD films showed remarkable photostability under continuous pulsed laser excitation in ambient conditions for at least 34 h (corresponds to 1.2 × 10(8) laser shots), substantially exceeding the stability of other colloidal QD systems in which ASE has been observed. PMID:26624490

  17. Role of amplified spontaneous emission in optical free-space communication links with optical amplification: impact on isolation and data transmission and utilization for pointing, acquisition, and

    NASA Astrophysics Data System (ADS)

    Winzer, Peter J.; Kalmar, Andras; Leeb, Walter R.

    1999-04-01

    We investigate the role of amplified spontaneous emission (ASE) produced by an optical booster amplifier at the transmitter of free-space optical communication links. In a communication terminal with a single telescope for both transmission and reception, this ASE power has to be taken into account in connection with transmit-to-receive channel isolation, especially since it partly occupies the same state of polarization and the same frequency band as the receive signal. We show that the booster ASE intercepted by the receiver can represent a non-negligible source of background radiation: In a typical optical intersatellite link scenario, the ASE power spectral density generated by the booster amplifier at the transmitter and coupled to the receiver will be on the order of 10-20 W/Hz, which equals the background radiation of the sun. Exploiting these findings for pointing, acquisition, and tracking (PAT) purposes, we describe a patent-pending PAT system doing without beacon lasers and without the need for diverting a part of the data signal for PAT. Utilizing the transmit booster ASE over a bandwidth of e.g. 20 nm at the receiver, a total power of about -46 dBm is available for PAT purposes without extra power consumption at the transmitter and without the need for beacon lAser alignment.

  18. Propagation of a strong x-ray pulse: Pulse compression, stimulated Raman scattering, amplified spontaneous emission, lasing without inversion, and four-wave mixing

    SciTech Connect

    Sun Yuping; Wang Chuankui; Liu Jicai; Gel'mukhanov, Faris

    2010-01-15

    We study the compression of strong x-ray pulses from x-ray free-electron lasers (XFELs) propagating through the resonant medium of atomic argon. The simulations are based on the three-level model with the frequency of the incident x-ray pulse tuned in the 2p{sub 3/2}-4s resonance. The pulse propagation is accompanied by the self-seeded stimulated resonant Raman scattering (SRRS). The SRRS starts from two channels of amplified spontaneous emission (ASE), 4s-2p{sub 3/2} and 3s-2p{sub 3/2}, which form the extensive ringing pattern and widen the power spectrum. The produced seed field triggers the Stokes ASE channel 3s-2p{sub 3/2}. The population inversion is quenched for longer propagation distances where the ASE is followed by the lasing without inversion (LWI), which amplifies the Stokes component. Both ASE and LWI reshape the input pulse: The compressed front part of the pulse (up to 100 as) is followed by the long tail of the ringing and beating between the pump and Stokes frequencies. The pump pulse also generates weaker Stokes and anti-Stokes fields caused by four-wave mixing. These four spectral bands have fine structures caused by the dynamical Stark effect. A slowdown of the XFEL pulse up to 78% of the speed of light in vacuum is found because of a large nonlinear refractive index.

  19. A Highly Crystalline and Wide-Bandgap Polydiarylfluorene with β-Phase Conformation toward Stable Electroluminescence and Dual Amplified Spontaneous Emission.

    PubMed

    Liu, Bin; Lin, Jinyi; Liu, Feng; Yu, Mengna; Zhang, Xinwen; Xia, Ruidong; Yang, Tao; Fang, Yueting; Xie, Linghai; Huang, Wei

    2016-08-24

    Bulky conjugated polymers with high crystallinity is the prerequisite for the overall improvement of performance in wide-bandgap semiconductors, including charge transport, photoluminescence quantum yield, processing reliability, and stability. Herein, we report a stable β-phase film of bulky polydiarylfluorene (PODPF) preparing by thermal annealing at ∼220 °C. The β-phase conformation and regular molecular packing are confirmed by UV-vis, photoluminescence (PL), Raman spectra, and grazing incidence X-ray diffraction (GIXD), respectively. Polymer light-emitting diodes (PLEDs) with crystalline and β-phase film serving as the active layer exhibit higher current efficiency of 1.8 cd/A (6.0 V) and more stable electroluminescence over the amorphous one. Surprisingly, mixed conformations in PODPF film produce dually tunable amplified spontaneous emission (ASE) at 463 and 482 nm. Polydiarylfluorenes with quasi-planar conformation will be a promising candidate for the next-generation gain medium toward a broadly tunable lasing and dual-wavelength laser. PMID:27480142

  20. Active Control of Combustor Instability Shown to Help Lower Emissions

    NASA Technical Reports Server (NTRS)

    DeLaat, John C.; Chang, Clarence T.

    2002-01-01

    In a quest to reduce the environmental impact of aerospace propulsion systems, extensive research is being done in the development of lean-burning (low fuel-to-air ratio) combustors that can reduce emissions throughout the mission cycle. However, these lean-burning combustors have an increased susceptibility to thermoacoustic instabilities, or high-pressure oscillations much like sound waves, that can cause severe high-frequency vibrations in the combustor. These pressure waves can fatigue the combustor components and even the downstream turbine blades. This can significantly decrease the safe operating life of the combustor and turbine. Thus, suppression of the thermoacoustic combustor instabilities is an enabling technology for lean, low-emissions combustors. Under the Aerospace Propulsion and Power Base Research and Technology Program, the NASA Glenn Research Center, in partnership with Pratt & Whitney and United Technologies Research Center, is developing technologies for the active control of combustion instabilities. With active combustion control, the fuel is pulsed to put pressure oscillations into the system. This cancels out the pressure oscillations being produced by the instabilities. Thus, the engine can have lower pollutant emissions and long life.The use of active combustion instability control to reduce thermo-acoustic-driven combustor pressure oscillations was demonstrated on a single-nozzle combustor rig at United Technologies. This rig has many of the complexities of a real engine combustor (i.e., an actual fuel nozzle and swirler, dilution cooling, etc.). Control was demonstrated through modeling, developing, and testing a fuel-delivery system able to the 280-Hz instability frequency. The preceding figure shows the capability of this system to provide high-frequency fuel modulations. Because of the high-shear contrarotating airflow in the fuel injector, there was some concern that the fuel pulses would be attenuated to the point where they would

  1. CONTROL OF AIR EMISSIONS FROM MOLYBDENUM ROASTING. VOLUME 1. EMISSIONS CHARACTERIZATION AND PARTICULATE CONTROL

    EPA Science Inventory

    The primary objective of this project was to evaluate a baghouse employing Teflon coated fabric bags for particulate recovery and control. This system was of great interest because of the corrosion resistance of Teflon coated fabric filters and this unique application in the nonf...

  2. Proposed rule highlights need for effective emissions monitoring, control

    SciTech Connect

    Not Available

    1994-03-01

    While the regulated community for the last year or so has found comfort in reports that EPA has failed to meet its mandated schedule for issuing new CAA regulations and setting compliance deadlines, the Agency has not been idle. The Agency in October proposed a major rule that would, in effect, abandon traditional methods of monitoring and enforcing compliance with CAA's air pollution control regulations. Instead of relying on plant inspections or citizens' complaints to uncover regulatory infractions, the proposed regulations would require most emissions sources to demonstrate--not during a single test or inspection, but continuously--compliance with emissions regulations. This proposed continuous, or enhanced,'' monitoring rule would be tied to CAA's Title 5 operating permit program.

  3. Emission control of four-stroke motorcycle engine

    SciTech Connect

    Wu, C.Y.Y.; Peng, Y.Y.; Gau, T.H.

    1995-12-31

    Experimental studies of the intake-generated charge motion (swirl and tumble) and engine combustion were conducted in a 125 cc four-stroke motorcycle engine. In this work, a Variable Inlet Port (VIP) was designed to generate various levels of charge motion in different operation conditions. The static flow test and the engine experiments were performed to study the effects of inlet charge motion on the engine combustion, cycle variation, fuel consumption and exhaust emissions. The results show that the cycle variation decreased, the lean limit extended, and the burning rate and the fuel economy increased when the charge motion increased. With this new design of flow control system, the motorcycle can be run with lean mixture and drastically reduce the exhaust emissions and fuel consumption while still maintaining high specific power output.

  4. DEGRADATION OF EMISSIONS CONTROL PERFORMANCE OF WOODSTOVES IN CRESTED BUTTE, CO

    EPA Science Inventory

    The report discusses the degradation of emissions control performance of woodstoves in Crested Butte, Colorado. Four seasons of field monitoring of EPA-certified woodstoves in and around Crested Butte has demonstrated some significant failures in emissions control performance. In...

  5. Greenhouse gas emission from covered windrow composting with controlled ventilation.

    PubMed

    Ermolaev, Evgheni; Pell, Mikael; Smårs, Sven; Sundberg, Cecilia; Jönsson, Håkan

    2012-02-01

    Data on greenhouse gas (GHG) emissions from full-scale composting of municipal solid waste, investigating the effects of process temperature and aeration combinations, is scarce. Oxygen availability affects the composition of gases emitted during composting. In the present study, two experiments with three covered windrows were set up, treating a mixture of source separated biodegradable municipal solid waste (MSW) fractions from Uppsala, Sweden, and structural amendment (woodchips, garden waste and re-used compost) in the volume proportion 1:2. The effects of different aeration and temperature settings on the emission of methane (CH(4)), nitrous oxide (N(2)O) and carbon dioxide (CO(2)) during windrow composting with forced aeration following three different control schemes were studied. For one windrow, the controller was set to keep the temperature below 40 °C until the pH increased, another windrow had minimal aeration at the beginning of the process and the third one had constant aeration. In the first experiment, CH(4) concentrations (CH(4):CO(2) ratio) increased, from around 0.1% initially to between 1 and 2% in all windrows. In the second experiment, the initial concentrations of CH(4) displayed similar patterns of increase between windrows until day 12, when concentration peaked at 3 and 6%, respectively, in two of the windrows. In general, the N(2)O fluxes remained low (0.46 ± 0.02 ppm) in the experiments and were two to three times the ambient concentrations. In conclusion, the emissions of CH(4) and N(2)O were low regardless of the amount of ventilation. The data indicates a need to perform longer experiments in order to observe further emission dynamics. PMID:21994145

  6. 40 CFR 63.325 - Determination of equivalent emission control technology.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... control technology. 63.325 Section 63.325 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Determination of equivalent emission control technology. (a) Any person requesting that the use of certain... equivalent emission reductions: (1) Diagrams, as appropriate, illustrating the emission control...

  7. 40 CFR 63.325 - Determination of equivalent emission control technology.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... control technology. 63.325 Section 63.325 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Determination of equivalent emission control technology. (a) Any person requesting that the use of certain... equivalent emission reductions: (1) Diagrams, as appropriate, illustrating the emission control...

  8. 40 CFR 63.325 - Determination of equivalent emission control technology.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... control technology. 63.325 Section 63.325 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Determination of equivalent emission control technology. (a) Any person requesting that the use of certain... equivalent emission reductions: (1) Diagrams, as appropriate, illustrating the emission control...

  9. 40 CFR 63.325 - Determination of equivalent emission control technology.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... control technology. 63.325 Section 63.325 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Determination of equivalent emission control technology. (a) Any person requesting that the use of certain... equivalent emission reductions: (1) Diagrams, as appropriate, illustrating the emission control...

  10. Optimizing the mix of strategies for control of vehicular emissions

    SciTech Connect

    Lejano, R.P.; Ayala, P.M.; Gonzales, E.A.

    1997-01-01

    A number of strategies for the control of vehicular emissions are being considered by the Philippine government to address Metropolitan Manila`s air quality problem. An analytical tool is needed for optimizing criteria pollutant reductions given the budgetary constraints. The simplest approach is to take costs and pollutant removals to be linear with each strategy`s scale of activity, and this is readily solved as a linear programming problem. Another approach is to use a dynamic system of weights which shift with progressive improvements in pollutant emissions. The two approaches yield somewhat different results, suggesting the sensitivity of the solution to the assumed weights. The study also illustrates the importance of a sound methodology for evaluating priorities given to different air quality goals. One such methodology may involve a polling of expert panels and the public to gain insight into the relative importance given to competing emissions reduction goals. An informal polling of resource agency staff was conducted and discussed in this paper. The authors take the position that proper planning involves tracing intermediate steps to the final outcome and not just focusing on the latter. 17 refs., 1 fig., 8 tabs.

  11. Jovian longitudinal control of Io-related radio emissions

    NASA Technical Reports Server (NTRS)

    Dessler, A. J.; Hill, T. W.

    1979-01-01

    A theoretical model is proposed to explain the control of Io-related radio emissions by Jupiter's rotational phase. The model is based on the hypothesis that the radio emissions are generated by Birkeland currents flowing between Io and the Jovian ionosphere. Specifically, it is suggested that the precipitation of radiation-belt electrons within a certain range of Jovian longitudes produces a restricted region of enhanced ionization and correspondingly enhanced conductivity in Jupiter's ionosphere and that the Io-Jupiter Birkeland current and the associated radio emissions are dramatically increased when Io's flux tube encounters this sector of enhanced ionization in Jupiter's ionosphere. The magnitude of the current is found to be about 100,000 A at most Jovian longitudes because of ionospheric resistance. It is estimated that within the favored longitudinal sector electron precipitation produces an enhancement of this current by one to three orders of magnitude. The model predictions are compared with observations made during the Pioneer 10 and 11 flybys, and satisfactory agreement is obtained.

  12. Survey of Emissions Associated with Enclosed Combustor Emission Control Devices in the Denver-Julesburg Basin

    NASA Astrophysics Data System (ADS)

    Knighton, W. B.; Floerchinger, C. R.; Wormhoult, J.; Massoli, P.; Fortner, E.; Brooks, B.; Roscioli, J. R.; Bon, D.; Herndon, S. C.

    2014-12-01

    Volatile organic compounds (VOCs) play an important role in local and regional air quality. A large source of VOCs comes from the oil and gas industry and the Denver-Julesburg Basin (D-J Basin) has seen a sharp increase in production in recent years primarily due to advances in horizontal drilling techniques. To help curb emissions with extraction and production of natural gas and its associated oil, emission control devices are required for facilities emitting over 6 tons of hydrocarbons per year. Within the ozone non-attainment area, which encompasses Denver and much of the front range, enclosed combustion devices (enclosed flares) are required to reduce hydrocarbon emissions by at least 95%. While certification tests indicate that these enclosed combustor devices provide high destruction removal efficiencies, there is considerable interest in knowing how well they perform in the field. As part of Front Range Air Pollution and Photochemistry Experiment (FRAPPE) project conducted during the Summer of 2014, the Aerodyne Mobile Laboratory (AML) surveyed oil and gas operations within the Wattenberg gas field and the surrounding D-J Basin. The AML deployed a full suite of gas and particle phase instrumentation providing a comprehensive set of on-line, real-time measurements for the major natural gas components (methane and ethane) and their combustion products (CO2, CO, NOx) using a variety of spectroscopic techniques. Additional gas phase organic gas emissions were made using a proton transfer reaction mass spectrometer (PTR-MS). Particle number and composition were determined using a condensation particle counter and an Aerodyne Aerosol Mass Spectrometer (AMS). A summary of the number of enclosed combustor devices measured and their observed combustion efficiencies will be presented.

  13. CONTROL OF TRACE METAL EMISSIONS DURING COAL COMBUSTION

    SciTech Connect

    THOMAS C. HO

    1998-02-18

    Emissions of toxic trace metals in the form of metal fumes or submicron particulates from a coal-fired combustion source have received greater environmental and regulatory concern over the past years. Current practice of controlling these emissions is to collect them at the cold-end of the process by air-pollution control devices (APCDs) such as electrostatic precipitators and baghouses. However, trace metal fumes may not always be effectively collected by these devices because the formed fumes are extremely small. The proposed research is to explore the opportunities for improved control of toxic trace metal emissions, alternatively, at the hot-end of the coal combustion process, i.e., in the combustion chamber. The technology proposed is to prevent the metal fumes from forming during the process, which would effectively eliminate the metal emission problems. Specifically, the technology is to employ suitable sorbents to (1) reduce the amount of metal volatilization during combustion and (2) capture volatilized metal vapors. The objectives of the project are to demonstrate the technology and to characterize the metal capture process during coal combustion in a fluidized bed combustor. This final technical report details the work performed, the conclusions obtained, and the accomplishments achieved over the project performance period from July 1, 1994 through December 31, 1997. Specifically, this report consists of the following five chapters: Chapter 1. Executive Summary; Chapter 2. Metal Capture by Various Sorbents; Chapter 3. Simultaneous Metal and Sulfur Capture; Chapter 4. Sorption and Desorption of Mercury on Sorbents; and Chapter 5. Project Conclusions. In summary, the metals involved in the project were arsenic, cadmium, chromium, lead, mercury and selenium and the sorbents tested included bauxite, zeolite and calcined limestone. The three sorbents have been found to have various degree of metal capture capability on arsenic, cadmium, chromium and lead

  14. Integrated low emissions cleanup system for multi-contaminant control

    SciTech Connect

    Alvin, M.A.; Bachovchin, D.M.; Smeltzer, E.E.

    1993-06-01

    The Westinghouse Electric Corporation, Science & Technology Center (W-STC) is developing an Integrated Low Emissions Cleanup (ILEC) concept for high-temperature gas cleaning to meet environmental standards, as well as to provide economical gas turbine life. The ILEC concept can simultaneously control particulate, sulfur, alkali, and other contaminants in high-pressure fuel gases, or combustion gases, at temperatures up to about 1700{degrees}F in advanced, coal-fired, power generation systems. The objective of this program is to demonstrate, at a bench scale, the conceptual, technical feasibility of the ILEC concept for multi-contaminant control, and to provide test data applicable to the design of subsequent field tests.

  15. Control of acid mist emissions from FGD systems

    SciTech Connect

    Dahlin, R S; Brown, T D

    1991-01-01

    Improved control of acid mist emissions can be achieved by replacing or augmenting the conventional mist eliminators with a wet electrostatic precipitator (WESP). This paper describes a two-phased study performed to determine the degree of control that can be achieved with this approach. Phase I was a study of the electrical operation of a lab-scale WESP collecting an acid mist from a coal combustion pilot plant equipped with a spray chamber. The results of this study were used to develop and validate a computer model of the WESP. In Phase II, measurements were made at two utility scrubber installations to determine the loadings of acid mist, fly ash, and scrubber carryover. These measurements were used as input to the model to project the performance of a retrofitted WESP.

  16. Controlling mercury emissions from coal-fired power plants

    SciTech Connect

    Chang, R.

    2009-07-15

    Increasingly stringent US federal and state limits on mercury emissions form coal-fired power plants demand optimal mercury control technologies. This article summarises the successful removal of mercury emissions achieved with activated carbon injection and boiler bromide addition, technologies nearing commercial readiness, as well as several novel control concepts currently under development. It also discusses some of the issues standing in the way of confident performance and cost predictions. In testing conducted on western coal-fired units with fabric filters or TOXECON to date, ACI has generally achieved mercury removal rates > 90%. At units with ESPs, similar performance requires brominated ACI. Alternatively, units firing western coals can use boiler bromide addition to increase flue gas mercury oxidation and downstream capture in a wet scrubber, or to enhance mercury removal by ACI. At eastern bituminous fired units with ESPs, ACI is not as effective, largely due to SO{sub 3} resulting from the high sulfur content of the coal or the use of SO{sub 3} flue gas conditioning to improve ESP performance. 7 refs., 3 figs.

  17. "APEC Blue": Secondary Aerosol Reductions from Emission Controls in Beijing.

    PubMed

    Sun, Yele; Wang, Zifa; Wild, Oliver; Xu, Weiqi; Chen, Chen; Fu, Pingqing; Du, Wei; Zhou, Libo; Zhang, Qi; Han, Tingting; Wang, Qingqing; Pan, Xiaole; Zheng, Haitao; Li, Jie; Guo, Xiaofeng; Liu, Jianguo; Worsnop, Douglas R

    2016-01-01

    China implemented strict emission control measures in Beijing and surrounding regions to ensure good air quality during the 2014 Asia-Pacific Economic Cooperation (APEC) summit. We conducted synchronous aerosol particle measurements with two aerosol mass spectrometers at different heights on a meteorological tower in urban Beijing to investigate the variations in particulate composition, sources and size distributions in response to emission controls. Our results show consistently large reductions in secondary inorganic aerosol (SIA) of 61-67% and 51-57%, and in secondary organic aerosol (SOA) of 55% and 37%, at 260 m and ground level, respectively, during the APEC summit. These changes were mainly caused by large reductions in accumulation mode particles and by suppression of the growth of SIA and SOA by a factor of 2-3, which led to blue sky days during APEC commonly referred to as "APEC Blue". We propose a conceptual framework for the evolution of primary and secondary species and highlight the importance of regional atmospheric transport in the formation of severe pollution episodes in Beijing. Our results indicate that reducing the precursors of secondary aerosol over regional scales is crucial and effective in suppressing the formation of secondary particulates and mitigating PM pollution. PMID:26891104

  18. Automated Boiler Combustion Controls for Emission Reduction and Efficiency Improvement

    SciTech Connect

    1998-12-02

    In the late 1980s, then President Bush visited Krakow, Poland. The terrible air quality theremotivated him to initiate a USAID-funded program, managed by DOE, entitled �Krakow Clean Fossil Fuels and Energy Efficiency Program.� The primary objective of this program was to encourage the formation of commercial ventures between U.S. and Polish firms to provide equipment and/or services to reduce pollution from low-emission sources in Krakow, Poland. This program led to the award of a number of cooperative agreements, including one to Control Techtronics International. The technical objective of CTI�s cooperative agreement is to apply combustion controls to existing boiler plants in Krakow and transfer knowledge and technology through a joint U.S. and Polish commercial venture. CTI installed automatic combustion controls on five coal boilers for the district heating system in Krakow. Three of these were for domestic hot-water boilers, and two were for steam for industrial boilers. The following results have occurred due to the addition of CTI�s combustion controls on these five existing boilers: ! 25% energy savings ! 85% reduction in particulate emissions The joint venture company CTI-Polska was then established. Eleven additional technical and costing proposals were initiated to upgrade other coal boilers in Krakow. To date, no co-financing has been made available on the Polish side. CTI-Polska continues in operation, serving customers in Russia and Ukraine. Should the market in Poland materialize, the joint venture company is established there to provide equipment and service.

  19. CO₂ laser emission modes to control enamel erosion.

    PubMed

    Scatolin, Renata Siqueira; Alonso-Filho, Fernando Luiz; Galo, Rodrigo; Rios, Daniela; Borsatto, Maria Cristina; Corona, Silmara Aparecida Milori

    2015-08-01

    Considering the importance and prevalence of dental erosion, the aim of this in vitro study was to evaluate the influence of different modes of pulse emission of CO2 laser associated or not to acidulated phosphate fluoride (APF) 1.23% gel, in controlling enamel erosion by profilometry. Ninety-six fragments of bovine enamel were flattened and polished, and the specimens were subjected to initial erosive challenge with hydrochloric acid (pH = 2). Specimens were randomly assigned according to surface treatment: APF 1.23% gel and gel without fluoride (control), and subdivided according to the modes of pulse CO2 laser irradiation: no irradiation (control), continuous, ultrapulse, and repeated pulse (n = 12). After surface treatment, further erosive challenges were performed for 5 days, 4 × 2 min/day. Enamel structure loss was quantitatively determined by a profilometer, after surface treatment and after 5 days of erosive challenges. Two-away ANOVA revealed a significant difference between the pulse emission mode of the CO2 laser and the presence of fluoride (P ≤ 0.05). The Duncan's test showed that CO2 laser irradiation in continuous mode and the specimens only received fluoride, promoted lower enamel loss than that other treatments. A lower dissolution of the enamel prisms was observed when it was irradiated with CO2 laser in continuous mode compared other groups. It can be concluded that CO2 laser irradiation in continuous mode was the most effective to control the enamel structure loss submitted to erosive challenges with hydrochloric acid. PMID:25988247

  20. LANDFILL OPERATION FOR CARBON SEQUESTRATION AND MAXIMUM METHANE EMISSION CONTROL

    SciTech Connect

    Don Augenstein; Ramin Yazdani; Rick Moore; Michelle Byars; Jeff Kieffer; Professor Morton Barlaz; Rinav Mehta

    2000-02-26

    Controlled landfilling is an approach to manage solid waste landfills, so as to rapidly complete methane generation, while maximizing gas capture and minimizing the usual emissions of methane to the atmosphere. With controlled landfilling, methane generation is accelerated to more rapid and earlier completion to full potential by improving conditions (principally moisture, but also temperature) to optimize biological processes occurring within the landfill. Gas is contained through use of surface membrane cover. Gas is captured via porous layers, under the cover, operated at slight vacuum. A field demonstration project has been ongoing under NETL sponsorship for the past several years near Davis, CA. Results have been extremely encouraging. Two major benefits of the technology are reduction of landfill methane emissions to minuscule levels, and the recovery of greater amounts of landfill methane energy in much shorter times, more predictably, than with conventional landfill practice. With the large amount of US landfill methane generated, and greenhouse potency of methane, better landfill methane control can play a substantial role both in reduction of US greenhouse gas emissions and in US renewable energy. The work described in this report, to demonstrate and advance this technology, has used two demonstration-scale cells of size (8000 metric tons [tonnes]), sufficient to replicate many heat and compaction characteristics of larger ''full-scale'' landfills. An enhanced demonstration cell has received moisture supplementation to field capacity. This is the maximum moisture waste can hold while still limiting liquid drainage rate to minimal and safely manageable levels. The enhanced landfill module was compared to a parallel control landfill module receiving no moisture additions. Gas recovery has continued for a period of over 4 years. It is quite encouraging that the enhanced cell methane recovery has been close to 10-fold that experienced with conventional

  1. Experimental and analytical study of a high gain self amplified spontaneous emission free electron laser operating in a large spectral bandwidth regime

    NASA Astrophysics Data System (ADS)

    Andonian, Gerard Cosmos

    The drive to create and measure ultra-short pulses in the x-ray regime advances the ongoing development of free electron lasers (FEL). Several proposed schemes, to shorten the pulse length of the radiation, involve driving the FEL with a chirped (linear longitudinal phase space correlation) electron beam in the self amplified spontaneous emission (SASE) mode. This dissertation examines the experiments conducted under such conditions, canvassing analytical and numerical studies of beam dynamics and radiation properties, experimental observations, and descriptions of the development of novel diagnostics. The VISA (Visible-Infrared SASE Amplifier) program has achieved saturation at 840 nm within a 4 m long undulator. A novel bunch compression mechanism during transport was discovered and ultimately responsible for the high peak current required to drive the FEL. Start-to-end simulations, detailing the dynamics from electron beam inception at the photocathode to the FEL radiation properties at the undulator, were successfully benchmarked to observable data. The VISA II experiment is an extension of this SASE FEL operating under different experimental conditions. Driving the SASE FEL with a chirped electron beam requires maintaining the chirp throughout transport by the use of sextupole magnets to correct for second-order compression effects. The emitted radiation is frequency chirped, diagnosed via a modified frequency resolved optical gating (FROG) technique. Specific numerical simulations and diagnostic developments are presented. A set of measurements, without sextupole corrections, displays anomalous features, namely large spectral bandwidth of the radiation at stable and sustained high gain lasing. The bandwidth has an rms value of 21 nm (12% full width), previously unobserved in a FEL. In addition, the far-field angular distribution yields a hollow mode structure, similar to earlier results yet more pronounced in angle. Start-to-end simulations reproduced the

  2. Implementing Strategies for Drying and Pressing Wood Without Emissions Controls

    SciTech Connect

    Sujit Banerjee; Terrance Conners

    2007-09-07

    Drying and pressing wood for the manufacture of lumber, particleboard, oriented strand board (OSB), veneer and medium density fiberboard (MDF) release volatile organic compounds (VOCs) into the atmosphere. These emissions require control equipment that are capital-intensive and consume significant quantities of natural gas and electricity. The objective of our work was to understand the mechanisms through which volatile organic compounds are generated and released and to develop simple control strategies. Of the several strategies developed, two have been implemented for OSB manufacture over the course of this study. First, it was found that increasing final wood moisture by about 2-4 percentage points reduced the dryer emissions of hazardous air pollutants by over 70%. As wood dries, the escaping water evaporatively cools the wood. This cooling tapers off wood when the wood is nearly dry and the wood temperature rises. Thermal breakdown of the wood tissue occurs and VOCs are released. Raising the final wood moisture by only a few percentage points minimizes the temperature rise and reduces emissions. Evaporative cooling also impacts has implications for VOC release from wood fines. Flaking wood for OSB manufacture inevitable generates fines. Fines dry out rapidly because of their high surface area and evaporative cooling is lost more rapidly than for flakes. As a result, fines emit a disproportionate quantity of VOCs. Fines can be reduced in two ways: through screening of the green furnish and through reducing their generation during flaking. The second approach is preferable because it also increased wood yield. A procedure to do this by matching the sharpness angle of the flaker knife to the ambient temperature was also developed. Other findings of practical interests are as follows: Dielectric heating of wood under low-headspace conditions removes terpenes and other extractives from softwood; The monoterpene content in trees depend upon temperature and seasonal

  3. N2O and NO2 Emissions from Heavy-Duty Diesel Trucks with Advanced Emission Controls

    NASA Astrophysics Data System (ADS)

    Preble, C.; Harley, R.; Kirchstetter, T.

    2014-12-01

    Diesel engines are the largest source of nitrogen oxides (NOx) emissions nationally, and also a major contributor to the black carbon (BC) fraction of fine particulate matter (PM). Recently, diesel particle filter (DPF) and selective catalytic reduction (SCR) emission control systems that target exhaust PM and NOx have become standard equipment on new heavy-duty diesel trucks. However, the deliberate catalytic oxidation of engine-out nitric oxide (NO) to nitrogen dioxide (NO2) in continuously regenerating DPFs leads to increased tailpipe emission of NO2. This is of potential concern due to the toxicity of NO2 and the resulting increases in atmospheric formation of other air pollutants such as ozone, nitric acid, and fine PM. While use of SCR reduces emissions of both NO and NO2, it may lead to increased emissions of nitrous oxide (N2O), a potent greenhouse gas. Here we report results from on-road measurements of heavy-duty diesel truck emissions conducted at the Port of Oakland and the Caldecott Tunnel in the San Francisco Bay Area. Emission factors (g pollutant per kg of diesel) were linked via recorded license plates to individual truck attributes, including engine model year and installed emission control equipment. Between 2009 and 2013, the fraction of DPF-equipped trucks at the Port of Oakland increased from 2 to 99%, and median engine age decreased from 11 to 6 years. Over the same period, fleet-average emission factors for black carbon and NOx decreased by 76 ± 22% and 53 ± 8%, respectively. However, direct emissions of NO2 increased, and consequently the NO2/NOx emission ratio increased from 0.03 ± 0.02 to 0.18 ± 0.03. Older trucks retrofitted with DPFs emitted approximately 3.5 times more NO2 than newer trucks equipped with both DPF and SCR. Preliminary data from summer 2014 measurements at the Caldecott Tunnel suggest that some older trucks have negative emission factors for N2O, and that for newer trucks, N2O emission factors have changed sign and

  4. 40 CFR 1060.103 - What permeation emission control requirements apply for fuel tanks?

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... requirements specified in 40 CFR 1051.110 or in this section. (4) Small SI fuel tanks must meet the permeation... AGENCY (CONTINUED) AIR POLLUTION CONTROLS CONTROL OF EVAPORATIVE EMISSIONS FROM NEW AND IN-USE NONROAD... tanks to a family emission limit for calculating evaporative emission credits as described in subpart...

  5. 40 CFR 1060.103 - What permeation emission control requirements apply for fuel tanks?

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... requirements specified in 40 CFR 1051.110 or in this section. (4) Small SI fuel tanks must meet the permeation... AGENCY (CONTINUED) AIR POLLUTION CONTROLS CONTROL OF EVAPORATIVE EMISSIONS FROM NEW AND IN-USE NONROAD... tanks to a family emission limit for calculating evaporative emission credits as described in subpart...

  6. 40 CFR 1060.103 - What permeation emission control requirements apply for fuel tanks?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... requirements specified in 40 CFR 1051.110 or in this section. (4) Small SI fuel tanks must meet the permeation... AGENCY (CONTINUED) AIR POLLUTION CONTROLS CONTROL OF EVAPORATIVE EMISSIONS FROM NEW AND IN-USE NONROAD... tanks to a family emission limit for calculating evaporative emission credits as described in subpart...

  7. Advanced Petroleum-Based Fuels -- Diesel Emissions Control Project (APBF-DEC)

    SciTech Connect

    Not Available

    2003-03-01

    Annual progress report of the Advanced Petroleum-based fuels-Diesel Emissions Control Project. Contains information on 5 test projects to determine the best combinations of low-sulfur diesel fuels, lubricants, diesel engines, and emission control systems to meet projected emissions standards.

  8. Increased Spontaneous Central Bleeding and Cognition Impairment in APP/PS1 Mice with Poorly Controlled Diabetes Mellitus.

    PubMed

    Ramos-Rodriguez, Juan José; Infante-Garcia, Carmen; Galindo-Gonzalez, Lucia; Garcia-Molina, Yaiza; Lechuga-Sancho, Alfonso; Garcia-Alloza, Mónica

    2016-05-01

    Alzheimer's disease (AD) and vascular dementia (VaD) are the most common causes of dementia, and borderlines are blurred in many cases. Aging remains the main risk factor to suffer dementia; however, epidemiological studies reveal that diabetes may also predispose to suffer AD. In order to further study this relationship, we have induced hypoinsulinemic diabetes to APPswe/PS1dE9 (APP/PS1) mice, a classical model of AD. APP/PS1 mice received streptozotocin (STZ) ip at 18 weeks of age, when AD pathology is not yet established in this animal model. Cognition was evaluated at 26 weeks of age in the Morris water maze and the new object discrimination tests. We observed that STZ-induced episodic and working memory impairment was significantly worsened in APP/PS1 mice. Postmortem assessment included brain atrophy, amyloid-beta and tau pathology, spontaneous bleeding, and increased central inflammation. Interestingly, in APP/PS1-STZ diabetic mice, we detected a shift in Aβ soluble/insoluble levels, towards more toxic soluble species. Phospho-tau levels were also increased in APP/PS1-STZ mice, accompanied by an exacerbated inflammatory process, both in the close proximity to senile plaque (SP) and in SP-free areas. The presence of hemorrhages was significantly higher in APP/PS1-STZ mice, and although pericytes and endothelium were only partially affected, it remains possible that blood-brain barrier alterations underlie observed pathological features. Our data support the implication of the diabetic process in AD and VaD, and it is feasible that improving metabolic control could delay observed central pathology. PMID:26156287

  9. The effect of spontaneously generated coherence on the Goos-Hänchen shifts behavior

    NASA Astrophysics Data System (ADS)

    Rezaei, Mojtaba; Sahrai, Mostafa

    2014-12-01

    The behavior of the Goos-Hänchen (GH) shifts of a probe beam reflected from or transmitted through a cavity with a fixed geometrical configuration is theoretically investigated. It is shown that in the absence of coherent control fields and just by quantum interference of spontaneous emission, the behavior of GH shift can be controlled.

  10. Three years operation demonstrates exhaust emission control system

    SciTech Connect

    1995-10-01

    The first field installation of a patented NO{sub x} emissions system completed its third year of operation as a demonstration site last August. The cogeneration site is powered by three Caterpillar 350 kW G398 natural gas-fueled engines. The Hybrid Low NO{sub x} system has achieved NO{sub x} and CO levels below 10 ppm consistently. Although this system initially appears complicated and somewhat sophisticated, it has been relatively maintenance free and easy to operate, according to university officials. Petrocon Technologies, of Beaumont, Texas, acquired the license to use the technology in 1994. The first step in the Hybrid Low NO{sub x} system`s process is an afterburner fired at substoichiometric conditions to increase the temperature while also increasing the CO content of the engine exhaust. The added fuel consumption of the burner limits the economy of the system to sites that have use for the additional thermal energy. Cogeneration plants are good candidates. Downstream from the burner, the high-temperature, CO-enriched exhaust passes through a heat recovery steam generator where the gas temperature is reduced to about 538{degree}C. Exhaust then passes over an Allied Signal-supplied reduction catalyst, where NO{sub x} is reduced to below 10 ppm. Controlled levels of CO in contact with the proprietary catalyst is the primary factor in achieving such extraordinarily low NO{sub x} emission levels.

  11. Solar control of the earth's emission of energetic O(+)

    NASA Technical Reports Server (NTRS)

    Lennartsson, W.

    1991-01-01

    Energetic (0.1-16 keV/e) O(+) data obtained in the earth's plasma sheet (between 10 and 23 RE) by an ion mass spectrometer on the ISEE-1 spacecraft are compared statistically with published data on the concurrent solar wind and IMF. The most strongly variable parameter of the plasma sheet O(+) is its density, which is found to be well correlated with certain solar wind parameters, especially with the solar wind flow speed and the IMF component perpendicular to the flow vector. When those two solar wind parameters are combined to form an electric field (-v x B), both the number density and the energy density of the O(+) are found to vary in proportion to the square of that electric field, on average, suggesting that the emission of energetic O(+) ions from the earth may be powered by that same field. Based on this and on the previously published correlation with solar activity, it is argued that the emission of O(+) is controlled by a combination of HF (ionizing) and quasi-static (accelerating) solar electromagnetic fields.

  12. Methane emissions from process equipment at natural gas production sites in the United States: pneumatic controllers.

    PubMed

    Allen, David T; Pacsi, Adam P; Sullivan, David W; Zavala-Araiza, Daniel; Harrison, Matthew; Keen, Kindal; Fraser, Matthew P; Daniel Hill, A; Sawyer, Robert F; Seinfeld, John H

    2015-01-01

    Emissions from 377 gas actuated (pneumatic) controllers were measured at natural gas production sites and a small number of oil production sites, throughout the United States. A small subset of the devices (19%), with whole gas emission rates in excess of 6 standard cubic feet per hour (scf/h), accounted for 95% of emissions. More than half of the controllers recorded emissions of 0.001 scf/h or less during 15 min of measurement. Pneumatic controllers in level control applications on separators and in compressor applications had higher emission rates than controllers in other types of applications. Regional differences in emissions were observed, with the lowest emissions measured in the Rocky Mountains and the highest emissions in the Gulf Coast. Average methane emissions per controller reported in this work are 17% higher than the average emissions per controller in the 2012 EPA greenhouse gas national emission inventory (2012 GHG NEI, released in 2014); the average of 2.7 controllers per well observed in this work is higher than the 1.0 controllers per well reported in the 2012 GHG NEI. PMID:25488196

  13. Application of microturbines to control emissions from associated gas

    DOEpatents

    Schmidt, Darren D.

    2013-04-16

    A system for controlling the emission of associated gas produced from a reservoir. In an embodiment, the system comprises a gas compressor including a gas inlet in fluid communication with an associated gas source and a gas outlet. The gas compressor adjusts the pressure of the associated gas to produce a pressure-regulated associated gas. In addition, the system comprises a gas cleaner including a gas inlet in fluid communication with the outlet of the gas compressor, a fuel gas outlet, and a waste product outlet. The gas cleaner separates at least a portion of the sulfur and the water from the associated gas to produce a fuel gas. Further, the system comprises a gas turbine including a fuel gas inlet in fluid communication with the fuel gas outlet of the gas cleaner and an air inlet. Still further, the system comprises a choke in fluid communication with the air inlet.

  14. Landfill aeration for emission control before and during landfill mining.

    PubMed

    Raga, Roberto; Cossu, Raffaello; Heerenklage, Joern; Pivato, Alberto; Ritzkowski, Marco

    2015-12-01

    The landfill of Modena, in northern Italy, is now crossed by the new high velocity railway line connecting Milan and Bologna. Waste was completely removed from a part of the landfill and a trench for the train line was built. With the aim of facilitating excavation and further disposal of the material extracted, suitable measures were defined. In order to prevent undesired emissions into the excavation area, the aerobic in situ stabilisation by means of the Airflow technology took place before and during the Landfill Mining. Specific project features involved the pneumatic leachate extraction from the aeration wells (to keep the leachate table low inside the landfill and increase the volume of waste available for air migration) and the controlled moisture addition into a limited zone, for a preliminary evaluation of the effects on process enhancement. Waste and leachate were periodically sampled in the landfill during the aeration before the excavation, for quality assessment over time; the evolution of biogas composition in the landfill body and in the extraction system for different plant set-ups during the project was monitored, with specific focus on uncontrolled migration into the excavation area. Waste biological stability significantly increased during the aeration (waste respiration index dropped to 33% of the initial value after six months). Leachate head decreased from 4 to 1.5m; leachate recirculation tests proved the beneficial effects of moisture addition on temperature control, without hampering waste aerobization. Proper management of the aeration plant enabled the minimization of uncontrolled biogas emissions into the excavation area. PMID:26445364

  15. Controlling satellite communication system unwanted emissions in congested RF spectrum

    NASA Astrophysics Data System (ADS)

    Olsen, Donald; Heymann, Roger

    2007-09-01

    The International Telecommunication Union (ITU), a United Nations (UN) agency, is the agency that, under an international treaty, sets radio spectrum usage regulations among member nations. Within the United States of America (USA), the organization that sets regulations, coordinates an application for use, and provides authorization for federal government/agency use of the radio frequency (RF) spectrum is the National Telecommunications and Information Administration (NTIA). In this regard, the NTIA defines which RF spectrum is available for federal government use in the USA, and how it is to be used. The NTIA is a component of the United States (U.S.) Department of Commerce of the federal government. The significance of ITU regulations is that ITU approval is required for U.S. federal government/agency permission to use the RF spectrum outside of U.S. boundaries. All member nations have signed a treaty to do so. U.S. federal regulations for federal use of the RF spectrum are found in the Manual of Regulations and Procedures for Federal Radio Frequency Management, and extracts of the manual are found in what is known as the Table of Frequency Allocations. Nonfederal government and private sector use of the RF spectrum within the U.S. is regulated by the Federal Communications Commission (FCC). There is a need to control "unwanted emissions" (defined to include out-of-band emissions, which are those immediately adjacent to the necessary and allocated bandwidth, plus spurious emissions) to preclude interference to all other authorized users. This paper discusses the causes, effects, and mitigation of unwanted RF emissions to systems in adjacent spectra. Digital modulations are widely used in today's satellite communications. Commercial communications sector standards are covered for the most part worldwide by Digital Video Broadcast - Satellite (DVB-S) and digital satellite news gathering (DSNG) evolutions and the second generation of DVB-S (DVB-S2) standard

  16. Dynamics of non-Controlled Emission of Biogas From Landfills

    NASA Astrophysics Data System (ADS)

    Lima, R.; Salazar, J.; Hernandez, P.; Perez, N.

    2001-12-01

    Landfills are important sources of CH4 and CO2 as well as other toxic gas components to the atmosphere. A significant amount of gases could be released to the surrounding environment as a "non-controlled" emission in a diffuse form. To understand the dynamics of non-controlled emission of biogas from landfills several soil gas and CO2 efflux surveys were performed at Arico's landfill (Tenerife, Canary Islands). Estimated diffuse CO2 emission for Arico's landfill (0.33 Km2) were 507 td-1 (1998) and 131 td-1 (2000), showing different spatial CO2 efflux patterns that can be explained in terms of new waste disposal and covering materials as well as the action of the biogas extraction system. Secular variations of diffuse CO2 efflux and meteorological and soil variables were measured hourly at one site in the center of the landfill for 11 months. Diffuse CO2 efflux ranged from 9.9 to 433.3 gm-2d^{-1} with a median value of 242.7 \\pm 73.3 gm^{-2}d-1. Diffuse CO2 efflux showed a temporal behavior that could be divided in two different periods: (a) a quasi-stationary period with minor fluctuations due to the influence of meteorological and soil variables, and (b) a non-stationary period with changing CO2 efflux level and major variations related to the preliminary tests on the biogas extraction system for Arico's landfill. Air and ground temperatures exhibit significant positive correlation with the observed CO2 efflux. Peaks of maximum inverse correlation between barometric pressure and CO2 efflux are found at semi-diurnal and diurnal frequencies. Wind speed and wind direction are cross-correlated with CO2 efflux by 12 hours. These results suggest that (i) minor fluctuations in the CO2 efflux could be driven by meteorological variations (solar radiation cycles and local wind patterns), and (ii) sudden and major fluctuations in the CO2 efflux cannot be explained sufficiently in terms of the observed meteorological and soil variables' fluctuations.

  17. A bi-hemispheric neuronal network model of the cerebellum with spontaneous climbing fiber firing produces asymmetrical motor learning during robot control.

    PubMed

    Pinzon-Morales, Ruben-Dario; Hirata, Yutaka

    2014-01-01

    To acquire and maintain precise movement controls over a lifespan, changes in the physical and physiological characteristics of muscles must be compensated for adaptively. The cerebellum plays a crucial role in such adaptation. Changes in muscle characteristics are not always symmetrical. For example, it is unlikely that muscles that bend and straighten a joint will change to the same degree. Thus, different (i.e., asymmetrical) adaptation is required for bending and straightening motions. To date, little is known about the role of the cerebellum in asymmetrical adaptation. Here, we investigate the cerebellar mechanisms required for asymmetrical adaptation using a bi-hemispheric cerebellar neuronal network model (biCNN). The bi-hemispheric structure is inspired by the observation that lesioning one hemisphere reduces motor performance asymmetrically. The biCNN model was constructed to run in real-time and used to control an unstable two-wheeled balancing robot. The load of the robot and its environment were modified to create asymmetrical perturbations. Plasticity at parallel fiber-Purkinje cell synapses in the biCNN model was driven by error signal in the climbing fiber (cf) input. This cf input was configured to increase and decrease its firing rate from its spontaneous firing rate (approximately 1 Hz) with sensory errors in the preferred and non-preferred direction of each hemisphere, as demonstrated in the monkey cerebellum. Our results showed that asymmetrical conditions were successfully handled by the biCNN model, in contrast to a single hemisphere model or a classical non-adaptive proportional and derivative controller. Further, the spontaneous activity of the cf, while relatively small, was critical for balancing the contribution of each cerebellar hemisphere to the overall motor command sent to the robot. Eliminating the spontaneous activity compromised the asymmetrical learning capabilities of the biCNN model. Thus, we conclude that a bi

  18. A bi-hemispheric neuronal network model of the cerebellum with spontaneous climbing fiber firing produces asymmetrical motor learning during robot control

    PubMed Central

    Pinzon-Morales, Ruben-Dario; Hirata, Yutaka

    2014-01-01

    To acquire and maintain precise movement controls over a lifespan, changes in the physical and physiological characteristics of muscles must be compensated for adaptively. The cerebellum plays a crucial role in such adaptation. Changes in muscle characteristics are not always symmetrical. For example, it is unlikely that muscles that bend and straighten a joint will change to the same degree. Thus, different (i.e., asymmetrical) adaptation is required for bending and straightening motions. To date, little is known about the role of the cerebellum in asymmetrical adaptation. Here, we investigate the cerebellar mechanisms required for asymmetrical adaptation using a bi-hemispheric cerebellar neuronal network model (biCNN). The bi-hemispheric structure is inspired by the observation that lesioning one hemisphere reduces motor performance asymmetrically. The biCNN model was constructed to run in real-time and used to control an unstable two-wheeled balancing robot. The load of the robot and its environment were modified to create asymmetrical perturbations. Plasticity at parallel fiber-Purkinje cell synapses in the biCNN model was driven by error signal in the climbing fiber (cf) input. This cf input was configured to increase and decrease its firing rate from its spontaneous firing rate (approximately 1 Hz) with sensory errors in the preferred and non-preferred direction of each hemisphere, as demonstrated in the monkey cerebellum. Our results showed that asymmetrical conditions were successfully handled by the biCNN model, in contrast to a single hemisphere model or a classical non-adaptive proportional and derivative controller. Further, the spontaneous activity of the cf, while relatively small, was critical for balancing the contribution of each cerebellar hemisphere to the overall motor command sent to the robot. Eliminating the spontaneous activity compromised the asymmetrical learning capabilities of the biCNN model. Thus, we conclude that a bi

  19. The next decade and emission controls for electric utilities

    SciTech Connect

    Herrin, W.D.

    1997-12-31

    The historical efforts to achieve attainment with the ozone and particulate related standards span over 25 years and involve billions of dollars with only minimal success related to ozone and unknown success related to certain fine particulates. The 1990 Clean Air Act Amendments mandated significant new efforts, including Title IV - Acid Rain, to achieve reductions in ozone and fine particulate precursors and attainment with the standards. Initial reduction efforts have only recently been implemented and yet another hot summer continues to portray our futile efforts to gain much ground towards attainment with existing and revised or new standards. In order to review the issues more fully and to investigate the issue of regional transport. EPA has given the states a reprieve on ozone attainment plans until mid-1997 and set up the Clean Air Act Advisory Committee (CAAAC) structure to review implementation issues with new or revised standards. The states and other stockholders are involved in these EPA processes through the Ozone Transport Assessment Group (OTAG) and the CAAAC along with numerous working groups to get new answers arid help towards innovative solutions. A major target in these efforts is emissions from fossil-fuel fired utility boilers. The OTAG process has developed regional control strategy targets for utility NO{sub x} sources at three levels. These levels include consideration of costs, timing and availability of controls, and the anticipated reductions in NO{sub x}. The CAAAC is also considering regional controls and the associated implementation issues for both ozone and fine particulates. EPA is also considering a Clean Air Power Initiative (CAPI) to wrap all the utility control issues in a single consensus package. The next 10 years will be a crucial time for electric utilities in juggling environmental and competitive issues.

  20. Experimental characterization of the saturating, near infrared, self-amplified spontaneous emission free electron laser: Analysis of radiation properties and electron beam dynamics

    NASA Astrophysics Data System (ADS)

    Murokh, Alex

    2002-01-01

    In this work, the main results of the VISA experiment (Visible to Infrared SASE Amplifier) are presented and analyzed. The purpose of the experiment was to build a state-of-the-art single pass self-amplified spontaneous emission (SASE) free electron laser (FEL) based on a high brightness electron beam, and characterize its operation, including saturation, in the near infrared spectral region. This experiment was hosted by Accelerator Test Facility (ATF) at Brookhaven National Laboratory, which is a users facility that provides high brightness relativistic electron beams generated with the photoinjector. During the experiment, SASE FEL performance was studied in two regimes: a long bunch, lower gain operation; and a short bunch high gain regime. The transition between the two conditions was possible due to a novel bunch compression mechanism, which was discovered in the course of the experiment. This compression allowed the variation of peak current in the electron beam before it was launched into the 4-m VISA undulator. In the long bunch regime, a SASE FEL power gain length of 29 cm was obtained, and the generated radiation spectral and statistical properties were characterized. In the short bunch regime, a power gain length of under 18 cm was achieved at 842 nm, which is at least a factor of two shorter than ever previously achieved in this spectral range. Further, FEL saturation was obtained before the undulator exit. The FEL system's performance was measured along the length of the VISA undulator, and in the final state. Statistical, spectral and angular properties of the short bunch SASE radiation have been measured in the exponential gain regime, and at saturation. One of the most important aspects of the data analysis presented in this thesis was the development and use of start-to-end numerical simulations of the experiment. The dynamics of the ATF electron beam was modeled starting from the photocathode, through acceleration, transport, and inside the VISA