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Sample records for nonphotochemical excitation quenching

  1. Alteration of photosystem II properties with non-photochemical excitation quenching.

    PubMed Central

    Laisk, A; Oja, V

    2000-01-01

    Oxygen yield from single turnover flashes and multiple turnover pulses was measured in sunflower leaves differently pre-illuminated to induce either 'energy-dependent type' non-photochemical excitation quenching (qE) or reversible, inhibitory type non-photochemical quenching (qI). A zirconium O2 analyser, combined with a flexible gas system, was used for these measurements. Oxygen yield from saturating single turnover flashes was the equivalent of 1.3-2.0 micromole(-) m(-2) in leaves pre-adapted to low light. It did not decrease when qE quenching was induced by a 1 min exposure to saturating light, but it decreased when pre-illumination was extended to 30-60 min. Oxygen evolution from saturating multiple turnover pulses behaved similarly: it did not decrease with the rapidly induced qE but decreased considerably when exposure to saturating light was extended or O2 concentration was decreased to 0.4%. Parallel recording of chlorophyll fluorescence and O2 evolution during multiple turnover pulses, interpreted with the help of a mathematical model of photosystem II (PS II) electron transport, revealed PS II donor and acceptor side resistances. These experiments showed that PS II properties depend on the type of non-photochemical quenching present. The rapidly induced and rapidly reversible qE type (photoprotective) quenching does not induce changes in the number of active PS II or in the PS II maximum turnover rate, thus confirming the antenna mechanism of qE. The more slowly induced but still reversible qE type quenching (photoinactivation) induced a decrease in the number of active PS II and in the maximum PS II turnover rate. Modelling showed that, mainly, the acceptor side resistance of PS II increased in parallel with the reversible qI. PMID:11127995

  2. Mechanism of nonphotochemical quenching in green plants: energies of the lowest excited singlet states of violaxanthin and zeaxanthin.

    PubMed

    Frank, H A; Bautista, J A; Josue, J S; Young, A J

    2000-03-21

    The xanthophyll cycle is an enzymatic, reversible process through which the carotenoids violaxanthin, antheraxanthin, and zeaxanthin are interconverted in response to the need to balance light absorption with the capacity to use the energy to drive the reactions of photosynthesis. The cycle is thought to be one of the main avenues for safely dissipating excitation energy absorbed by plants in excess of that needed for photosynthesis. One of the key factors needed to elucidate the molecular mechanism by which the potentially damaging excess energy is dissipated is the energy of the lowest excited singlet (S(1)) state of the xanthophyll pigments. Absorption from the ground state (S(0)) to S(1) is forbidden by symmetry, making a determination of the S(1) state energies of these molecules by absorption spectroscopy very difficult. Fluorescence spectroscopy is potentially the most direct method for obtaining the S(1) state energies. However, because of problems with sample purity, low emission quantum yields, and detection sensitivity, fluorescence spectra from these molecules, until now, have never been reported. In this work these technical obstacles have been overcome, and S(1) --> S(0) fluorescence spectra of violaxanthin and zeaxanthin are presented. The energies of the S(1) states deduced from the fluorescence spectra are 14 880 +/- 90 cm(-)(1) for violaxanthin and 14 550 +/- 90 cm(-)(1) for zeaxanthin. The results provide important insights into the mechanism of nonphotochemical dissipation of excess energy in plants. PMID:10715102

  3. Higher Plant Photosystem II Light-Harvesting Antenna, Not the Reaction Center, Determines the Excited-State Lifetime—Both the Maximum and the Nonphotochemically Quenched

    PubMed Central

    Belgio, Erica; Johnson, Matthew P.; Jurić, Snježana; Ruban, Alexander V.

    2012-01-01

    The maximum chlorophyll fluorescence lifetime in isolated photosystem II (PSII) light-harvesting complex (LHCII) antenna is 4 ns; however, it is quenched to 2 ns in intact thylakoid membranes when PSII reaction centers (RCIIs) are closed (Fm). It has been proposed that the closed state of RCIIs is responsible for the quenching. We investigated this proposal using a new, to our knowledge, model system in which the concentration of RCIIs was highly reduced within the thylakoid membrane. The system was developed in Arabidopsis thaliana plants under long-term treatment with lincomycin, a chloroplast protein synthesis inhibitor. The treatment led to 1), a decreased concentration of RCIIs to 10% of the control level and, interestingly, an increased antenna component; 2), an average reduction in the yield of photochemistry to 0.2; and 3), an increased nonphotochemical chlorophyll fluorescence quenching (NPQ). Despite these changes, the average fluorescence lifetimes measured in Fm and Fm′ (with NPQ) states were nearly identical to those obtained from the control. A 77 K fluorescence spectrum analysis of treated PSII membranes showed the typical features of preaggregation of LHCII, indicating that the state of LHCII antenna in the dark-adapted photosynthetic membrane is sufficient to determine the 2 ns Fm lifetime. Therefore, we conclude that the closed RCs do not cause quenching of excitation in the PSII antenna, and play no role in the formation of NPQ. PMID:22735526

  4. A kinetic model of rapidly reversible nonphotochemical quenching

    PubMed Central

    Zaks, Julia; Amarnath, Kapil; Kramer, David M.; Niyogi, Krishna K.; Fleming, Graham R.

    2012-01-01

    Oxygen-evolving photosynthetic organisms possess nonphotochemical quenching (NPQ) pathways that protect against photo-induced damage. The majority of NPQ in plants is regulated on a rapid timescale by changes in the pH of the thylakoid lumen. In order to quantify the rapidly reversible component of NPQ, called qE, we developed a mathematical model of pH-dependent quenching of chlorophyll excitations in Photosystem II. Our expression for qE depends on the protonation of PsbS and the deepoxidation of violaxanthin by violaxanthin deepoxidase. The model is able to simulate the kinetics of qE at low and high light intensities. The simulations suggest that the pH of the lumen, which activates qE, is not itself affected by qE. Our model provides a framework for testing hypothesized qE mechanisms and for assessing the role of qE in improving plant fitness in variable light intensity. PMID:22891305

  5. Nonphotochemical quenching of chlorophyll fluorescence in Chlamydomonas reinhardtii.

    PubMed

    Finazzi, Giovanni; Johnson, Giles N; Dall'Osto, Luca; Zito, Francesca; Bonente, Giulia; Bassi, Roberto; Wollman, Francis-André

    2006-02-01

    Unlike plants, Chlamydomonas reinhardtii shows a restricted ability to develop nonphotochemical quenching upon illumination. Most of this limited quenching is due to state transitions instead of DeltapH-driven high-energy state quenching, qE. The latter could only be observed when the ability of the cells to perform photosynthesis was impaired, either by lowering temperature to approximately 0 degrees C or in mutants lacking RubisCO activity. Two main features were identified that account for the low level of qE in Chlamydomonas. On one hand, the electrochemical proton gradient generated upon illumination is apparently not sufficient to promote fluorescence quenching. On the other hand, the capacity to transduce the presence of a DeltapH into a quenching response is also intrinsically decreased in this alga, when compared to plants. The possible mechanism leading to these differences is discussed. PMID:16445291

  6. Superradiance Transition and Nonphotochemical Quenching in Photosynthetic Complexes

    SciTech Connect

    Berman, Gennady Petrovich; Nesterov, Alexander; Lopez, Gustavo; Sayre, Richard Thomas

    2015-04-23

    Photosynthetic organisms have evolved protective strategies to allow them to survive in cases of intense sunlight fluctuation with the development of nonphotochemical quenching (NPQ). This process allows light harvesting complexes to transfer the excess sunlight energy to non-damaging quenching channels. This report compares the NPQ process with the superradiance transition (ST). We demonstrated that the maximum of the NPQ efficiency is caused by the ST to the sink associated with the CTS. However, experimental verifications are required in order to determine whether or not the NPQ regime is associated with the ST transition for real photosynthetic complexes. Indeed, it can happen that, in the photosynthetic apparatus, the NPQ regime occurs in the “non-optimal” region of parameters, and it could be independent of the ST.

  7. Non-photochemical Fluorescence Quenching in Photosystem II Antenna Complexes by the Reaction Center Cation Radical.

    PubMed

    Paschenko, V Z; Gorokhov, V V; Grishanova, N P; Korvatovskii, B N; Ivanov, M V; Maksimov, E G; Mamedov, M D

    2016-06-01

    In direct experiments, rate constants of photochemical (kP) and non-photochemical (kP(+)) fluorescence quenching were determined in membrane fragments of photosystem II (PSII), in oxygen-evolving PSII core particles, as well as in core particles deprived of the oxygen-evolving complex. For this purpose, a new approach to the pulse fluorometry method was implemented. In the "dark" reaction center (RC) state, antenna fluorescence decay kinetics were measured under low-intensity excitation (532 nm, pulse repetition rate 1 Hz), and the emission was registered by a streak camera. To create a "closed" [P680(+)QA(-)] RC state, a high-intensity pre-excitation pulse (pump pulse, 532 nm) of the sample was used. The time advance of the pump pulse against the measuring pulse was 8 ns. In this experimental configuration, under the pump pulse, the [P680(+)QA(-)] state was formed in RC, whereupon antenna fluorescence kinetics was measured using a weak testing picosecond pulsed excitation light applied to the sample 8 ns after the pump pulse. The data were fitted by a two-exponential approximation. Efficiency of antenna fluorescence quenching by the photoactive RC pigment in its oxidized (P680(+)) state was found to be ~1.5 times higher than that of the neutral (P680) RC state. To verify the data obtained with a streak camera, control measurements of PSII complex fluorescence decay kinetics by the single-photon counting technique were carried out. The results support the conclusions drawn from the measurements registered with the streak camera. In this case, the fitting of fluorescence kinetics was performed in three-exponential approximation, using the value of τ1 obtained by analyzing data registered by the streak camera. An additional third component obtained by modeling the data of single photon counting describes the P680(+)Pheo(-) charge recombination. Thus, for the first time the ratio of kP(+)/kP = 1.5 was determined in a direct experiment. The mechanisms of higher

  8. Light-induced dissociation of an antenna hetero-oligomer is needed for non-photochemical quenching induction.

    PubMed

    Betterle, Nico; Ballottari, Matteo; Zorzan, Simone; de Bianchi, Silvia; Cazzaniga, Stefano; Dall'osto, Luca; Morosinotto, Tomas; Bassi, Roberto

    2009-05-29

    PsbS plays a major role in activating the photoprotection mechanism known as "non-photochemical quenching," which dissipates chlorophyll excited states exceeding the capacity for photosynthetic electron transport. PsbS activity is known to be triggered by low lumenal pH. However, the molecular mechanism by which this subunit regulates light harvesting efficiency is still unknown. Here we show that PsbS controls the association/dissociation of a five-subunit membrane complex, composed of two monomeric Lhcb proteins (CP29 and CP24) and the trimeric LHCII-M. Dissociation of this supercomplex is indispensable for the onset of non-photochemical fluorescence quenching in high light, strongly suggesting that protein subunits catalyzing the reaction of heat dissipation are buried into the complex and thus not available for interaction with PsbS. Consistently, we showed that knock-out mutants on two subunits participating to the B4C complex were strongly affected in heat dissipation. Direct observation by electron microscopy and image analysis showed that B4C dissociation leads to the redistribution of PSII within grana membranes. We interpreted these results to mean that the dissociation of B4C makes quenching sites, possibly CP29 and CP24, available for the switch to an energy-quenching conformation. These changes are reversible and do not require protein synthesis/degradation, thus allowing for changes in PSII antenna size and adaptation to rapidly changing environmental conditions. PMID:19307183

  9. A zeaxanthin-independent nonphotochemical quenching mechanism localized in the photosystem II core complex.

    PubMed

    Finazzi, Giovanni; Johnson, Giles N; Dall'Osto, Luca; Dallosto, Luca; Joliot, Pierre; Wollman, Francis-André; Bassi, Roberto

    2004-08-17

    Illumination of dark-adapted barley plants with low light transiently induced a large nonphotochemical quenching of chlorophyll fluorescence. This reaction was identified as a form of high-energy-state quenching. Its appearance was not accompanied by zeaxanthin synthesis but was associated with a reversible inactivation of a fraction of photosystem II (PSII) centers. Both the fluorescence quenching and PSII inactivation relaxed in parallel with the activation of the Calvin cycle. We interpret the induction of this phenomenon as due to the generation of a quenched state in the PSII core complex. This reaction is probably caused by the transient overacidification of the thylakoid lumen, whereas its dissipation results from the relaxation of both the pH gradient across the thylakoid membrane and redox pressure upon activation of carbon fixation. At saturating light intensities, inactivation of PSII was still observed at the onset of illumination, although its recovery did not result in dissipation of high-energy quenching, which presents typical characteristics of an antenna-associated quenching at steady state. Reaction-center quenching seems therefore to be a common transient feature during illumination, being replaced by other phenomena (photochemical or antenna quenching and photoinhibition), depending on the balance between light and carbon fixation fluxes. PMID:15304641

  10. Kinetic and Spectral Resolution of Multiple Nonphotochemical Quenching Components in Arabidopsis Leaves1[C

    PubMed Central

    Lambrev, Petar H.; Nilkens, Manuela; Miloslavina, Yuliya; Jahns, Peter; Holzwarth, Alfred R.

    2010-01-01

    Using novel specially designed instrumentation, fluorescence emission spectra were recorded from Arabidopsis (Arabidopsis thaliana) leaves during the induction period of dark to high-light adaptation in order to follow the spectral changes associated with the formation of nonphotochemical quenching. In addition to an overall decrease of photosystem II fluorescence (quenching) across the entire spectrum, high light induced two specific relative changes in the spectra: (1) a decrease of the main emission band at 682 nm relative to the far-red (750–760 nm) part of the spectrum (Δ F682); and (2) an increase at 720 to 730 nm (Δ F720) relative to 750 to 760 nm. The kinetics of the two relative spectral changes and their dependence on various mutants revealed that they do not originate from the same process but rather from at least two independent processes. The Δ F720 change is specifically associated with the rapidly reversible energy-dependent quenching. Comparison of the wild-type Arabidopsis with mutants unable to produce or overexpressing the PsbS subunit of photosystem II showed that PsbS was a necessary component for Δ F720. The spectral change Δ F682 is induced both by energy-dependent quenching and by PsbS-independent mechanism(s). A third novel quenching process, independent from both PsbS and zeaxanthin, is activated by a high turnover rate of photosystem II. Its induction and relaxation occur on a time scale of a few minutes. Analysis of the spectral inhomogeneity of nonphotochemical quenching allows extraction of mechanistically valuable information from the fluorescence induction kinetics when registered in a spectrally resolved fashion. PMID:20032080

  11. Light-induced Dissociation of an Antenna Hetero-oligomer Is Needed for Non-photochemical Quenching InductionS⃞

    PubMed Central

    Betterle, Nico; Ballottari, Matteo; Zorzan, Simone; de Bianchi, Silvia; Cazzaniga, Stefano; Dall'Osto, Luca; Morosinotto, Tomas; Bassi, Roberto

    2009-01-01

    PsbS plays a major role in activating the photoprotection mechanism known as “non-photochemical quenching,” which dissipates chlorophyll excited states exceeding the capacity for photosynthetic electron transport. PsbS activity is known to be triggered by low lumenal pH. However, the molecular mechanism by which this subunit regulates light harvesting efficiency is still unknown. Here we show that PsbS controls the association/dissociation of a five-subunit membrane complex, composed of two monomeric Lhcb proteins (CP29 and CP24) and the trimeric LHCII-M. Dissociation of this supercomplex is indispensable for the onset of non-photochemical fluorescence quenching in high light, strongly suggesting that protein subunits catalyzing the reaction of heat dissipation are buried into the complex and thus not available for interaction with PsbS. Consistently, we showed that knock-out mutants on two subunits participating to the B4C complex were strongly affected in heat dissipation. Direct observation by electron microscopy and image analysis showed that B4C dissociation leads to the redistribution of PSII within grana membranes. We interpreted these results to mean that the dissociation of B4C makes quenching sites, possibly CP29 and CP24, available for the switch to an energy-quenching conformation. These changes are reversible and do not require protein synthesis/degradation, thus allowing for changes in PSII antenna size and adaptation to rapidly changing environmental conditions. PMID:19307183

  12. On improving the performance of nonphotochemical quenching in CP29 light-harvesting antenna complex

    NASA Astrophysics Data System (ADS)

    Berman, Gennady P.; Nesterov, Alexander I.; Sayre, Richard T.; Still, Susanne

    2016-03-01

    We model and simulate the performance of charge-transfer in nonphotochemical quenching (NPQ) in the CP29 light-harvesting antenna-complex associated with photosystem II (PSII). The model consists of five discrete excitonic energy states and two sinks, responsible for the potentially damaging processes and charge-transfer channels, respectively. We demonstrate that by varying (i) the parameters of the chlorophyll-based dimer, (ii) the resonant properties of the protein-solvent environment interaction, and (iii) the energy transfer rates to the sinks, one can significantly improve the performance of the NPQ. Our analysis suggests strategies for improving the performance of the NPQ in response to environmental changes, and may stimulate experimental verification.

  13. Increased biomass productivity in green algae by tuning non-photochemical quenching.

    PubMed

    Berteotti, Silvia; Ballottari, Matteo; Bassi, Roberto

    2016-01-01

    Photosynthetic microalgae have a high potential for the production of biofuels and highly valued metabolites. However, their current industrial exploitation is limited by a productivity in photobioreactors that is low compared to potential productivity. The high cell density and pigment content of the surface layers of photosynthetic microalgae result in absorption of excess photons and energy dissipation through non-photochemical quenching (NPQ). NPQ prevents photoinhibition, but its activation reduces the efficiency of photosynthetic energy conversion. In Chlamydomonas reinhardtii, NPQ is catalyzed by protein subunits encoded by three lhcsr (light harvesting complex stress related) genes. Here, we show that heat dissipation and biomass productivity depends on LHCSR protein accumulation. Indeed, algal strains lacking two lhcsr genes can grow in a wide range of light growth conditions without suffering from photoinhibition and are more productive than wild-type. Thus, the down-regulation of NPQ appears to be a suitable strategy for improving light use efficiency for biomass and biofuel production in microalgae. PMID:26888481

  14. Increased biomass productivity in green algae by tuning non-photochemical quenching

    PubMed Central

    Berteotti, Silvia; Ballottari, Matteo; Bassi, Roberto

    2016-01-01

    Photosynthetic microalgae have a high potential for the production of biofuels and highly valued metabolites. However, their current industrial exploitation is limited by a productivity in photobioreactors that is low compared to potential productivity. The high cell density and pigment content of the surface layers of photosynthetic microalgae result in absorption of excess photons and energy dissipation through non-photochemical quenching (NPQ). NPQ prevents photoinhibition, but its activation reduces the efficiency of photosynthetic energy conversion. In Chlamydomonas reinhardtii, NPQ is catalyzed by protein subunits encoded by three lhcsr (light harvesting complex stress related) genes. Here, we show that heat dissipation and biomass productivity depends on LHCSR protein accumulation. Indeed, algal strains lacking two lhcsr genes can grow in a wide range of light growth conditions without suffering from photoinhibition and are more productive than wild-type. Thus, the down-regulation of NPQ appears to be a suitable strategy for improving light use efficiency for biomass and biofuel production in microalgae. PMID:26888481

  15. Non-Photochemical Quenching Capacity in Arabidopsis thaliana Affects Herbivore Behaviour

    PubMed Central

    Johansson Jänkänpää, Hanna; Frenkel, Martin; Zulfugarov, Ismayil; Reichelt, Michael; Krieger-Liszkay, Anja; Mishra, Yogesh; Gershenzon, Jonathan; Moen, Jon; Lee, Choon-Hwan; Jansson, Stefan

    2013-01-01

    Under natural conditions, plants have to cope with numerous stresses, including light-stress and herbivory. This raises intriguing questions regarding possible trade-offs between stress defences and growth. As part of a program designed to address these questions we have compared herbivory defences and damage in wild type Arabidopsis thaliana and two “photoprotection genotypes”, npq4 and oePsbS, which respectively lack and overexpress PsbS (a protein that plays a key role in qE-type non-photochemical quenching). In dual-choice feeding experiments both a specialist (Plutella xylostella) and a generalist (Spodoptera littoralis) insect herbivore preferred plants that expressed PsbS most strongly. In contrast, although both herbivores survived equally well on each of the genotypes, for oviposition female P. xylostella adults preferred plants that expressed PsbS least strongly. However, there were no significant differences between the genotypes in levels of the 10 most prominent glucosinolates; key substances in the Arabidopsis anti-herbivore chemical defence arsenal. After transfer from a growth chamber to the field we detected significant differences in the genotypes’ metabolomic profiles at all tested time points, using GC-MS, but no consistent “metabolic signature” for the lack of PsbS. These findings suggest that the observed differences in herbivore preferences were due to differences in the primary metabolism of the plants rather than their contents of typical “defence compounds”. A potentially significant factor is that superoxide accumulated most rapidly and to the highest levels under high light conditions in npq4 mutants. This could trigger changes in planta that are sensed by herbivores either directly or indirectly, following its dismutation to H2O2. PMID:23301046

  16. Possible role of interference, protein noise, and sink effects in nonphotochemical quenching in photosynthetic complexes

    DOE PAGESBeta

    Berman, Gennady P.; Nesterov, Alexander I.; Gurvitz, Shmuel; Sayre, Richard T.

    2016-04-30

    Here, we analyze theoretically a simple and consistent quantum mechanical model that reveals the possible role of quantum interference, protein noise, and sink effects in the nonphotochemical quenching (NPQ) in light-harvesting complexes (LHCs). The model consists of a network of five interconnected sites (excitonic states of light-sensitive molecules) responsible for the NPQ mechanism. The model also includes the “damaging” and the dissipative channels. The damaging channel is responsible for production of singlet oxygen and other destructive outcomes. In this model, both damaging and “dissipative” charge transfer channels are described by discrete electron energy levels attached to their sinks, that mimicmore » the continuum part of electron energy spectrum. All five excitonic sites interact with the protein environment that is modeled using a stochastic process. Our approach allowed us to derive the exact and closed system of linear ordinary differential equations for the reduced density matrix and its first momentums. Moreover, these equations are solved numerically including for strong interactions between the light-sensitive molecules and protein environment. As an example, we apply our model to demonstrate possible contributions of quantum interference, protein noise, and sink effects in the NPQ mechanism in the CP29 minor LHC. The numerical simulations show that using proper combination of quantum interference effects, properties of noise, and sinks, one can significantly suppress the damaging channel. Finally, our findings demonstrate the possible role of interference, protein noise, and sink effects for modeling, engineering, and optimizing the performance of the NPQ processes in both natural and artificial light-harvesting complexes.« less

  17. Mechanisms of photoprotection and nonphotochemical quenching in pea light-harvesting complex at 2.5 A resolution.

    PubMed

    Standfuss, Jörg; Terwisscha van Scheltinga, Anke C; Lamborghini, Matteo; Kühlbrandt, Werner

    2005-03-01

    The plant light-harvesting complex of photosystem II (LHC-II) collects and transmits solar energy for photosynthesis in chloroplast membranes and has essential roles in regulation of photosynthesis and in photoprotection. The 2.5 A structure of pea LHC-II determined by X-ray crystallography of stacked two-dimensional crystals shows how membranes interact to form chloroplast grana, and reveals the mutual arrangement of 42 chlorophylls a and b, 12 carotenoids and six lipids in the LHC-II trimer. Spectral assignment of individual chlorophylls indicates the flow of energy in the complex and the mechanism of photoprotection in two close chlorophyll a-lutein pairs. We propose a simple mechanism for the xanthophyll-related, slow component of nonphotochemical quenching in LHC-II, by which excess energy is transferred to a zeaxanthin replacing violaxanthin in its binding site, and dissipated as heat. Our structure shows the complex in a quenched state, which may be relevant for the rapid, pH-induced component of nonphotochemical quenching. PMID:15719016

  18. Mechanisms of photoprotection and nonphotochemical quenching in pea light-harvesting complex at 2.5 Å resolution

    PubMed Central

    Standfuss, Jörg; Terwisscha van Scheltinga, Anke C; Lamborghini, Matteo; Kühlbrandt, Werner

    2005-01-01

    The plant light-harvesting complex of photosystem II (LHC-II) collects and transmits solar energy for photosynthesis in chloroplast membranes and has essential roles in regulation of photosynthesis and in photoprotection. The 2.5 Å structure of pea LHC-II determined by X-ray crystallography of stacked two-dimensional crystals shows how membranes interact to form chloroplast grana, and reveals the mutual arrangement of 42 chlorophylls a and b, 12 carotenoids and six lipids in the LHC-II trimer. Spectral assignment of individual chlorophylls indicates the flow of energy in the complex and the mechanism of photoprotection in two close chlorophyll a–lutein pairs. We propose a simple mechanism for the xanthophyll-related, slow component of nonphotochemical quenching in LHC-II, by which excess energy is transferred to a zeaxanthin replacing violaxanthin in its binding site, and dissipated as heat. Our structure shows the complex in a quenched state, which may be relevant for the rapid, pH-induced component of nonphotochemical quenching. PMID:15719016

  19. An 'all pigment' model of excitation quenching in LHCII.

    PubMed

    Chmeliov, Jevgenij; Bricker, William P; Lo, Cynthia; Jouin, Elodie; Valkunas, Leonas; Ruban, Alexander V; Duffy, Christopher D P

    2015-06-28

    The rapid, photoprotective down-regulation of plant light-harvesting in bright light proceeds via the non-photochemical quenching of chlorophyll excitation energy in the major photosystem II light-harvesting complex LHCII. However, there is currently no consensus regarding the precise mechanism by which excess energy is quenched. Current X-ray structures of this complex correspond to a dissipative conformation and therefore correct microscopic theoretical modelling should capture this property. Despite their accuracy in explaining the steady state spectroscopy of this complex, chlorophyll-only models (those that neglect the energetic role of carotenoids) do not explain the observed fluorescence quenching. To address this gap, we have used a combination of the semi-empirical MNDO-CAS-CI and the Transition Density Cube method to model all chlorophyll-carotenoid energy transfer pathways in the highly quenched LHCII X-ray structure. Our simulations reveal that the inclusion of carotenoids in this microscopic model results in profound excitation quenching, reducing the predicted excitation lifetime of the complex from 4 ns (chlorophyll-only) to 67 ps. The model indicates that energy dissipation proceeds via slow excitation transfer (>20 ps) from chlorophyll to the forbidden S1 excited state of the centrally bound lutein molecules followed by the rapid (∼10 ps) radiationless decay to the ground state, with the latter being assumed from experimental measurements of carotenoid excited state lifetimes. Violaxanthin and neoxanthin do not contribute to this quenching. This work presents the first all-pigment microscopic model of LHCII and the first attempt to capture the dissipative character of the known structure. PMID:26017055

  20. Zeaxanthin Binds to Light-Harvesting Complex Stress-Related Protein to Enhance Nonphotochemical Quenching in Physcomitrella patens[W

    PubMed Central

    Pinnola, Alberta; Dall’Osto, Luca; Gerotto, Caterina; Morosinotto, Tomas; Bassi, Roberto; Alboresi, Alessandro

    2013-01-01

    Nonphotochemical quenching (NPQ) dissipates excess energy to protect the photosynthetic apparatus from excess light. The moss Physcomitrella patens exhibits strong NPQ by both algal-type light-harvesting complex stress-related (LHCSR)–dependent and plant-type S subunit of Photosystem II (PSBS)-dependent mechanisms. In this work, we studied the dependence of NPQ reactions on zeaxanthin, which is synthesized under light stress by violaxanthin deepoxidase (VDE) from preexisting violaxanthin. We produced vde knockout (KO) plants and showed they underwent a dramatic reduction in thermal dissipation ability and enhanced photoinhibition in excess light conditions. Multiple mutants (vde lhcsr KO and vde psbs KO) showed that zeaxanthin had a major influence on LHCSR-dependent NPQ, in contrast with previous reports in Chlamydomonas reinhardtii. The PSBS-dependent component of quenching was less dependent on zeaxanthin, despite the near-complete violaxanthin to zeaxanthin exchange in LHC proteins. Consistent with this, we provide biochemical evidence that native LHCSR protein binds zeaxanthin upon excess light stress. These findings suggest that zeaxanthin played an important role in the adaptation of modern plants to the enhanced levels of oxygen and excess light intensity of land environments. PMID:24014548

  1. Zeaxanthin binds to light-harvesting complex stress-related protein to enhance nonphotochemical quenching in Physcomitrella patens.

    PubMed

    Pinnola, Alberta; Dall'Osto, Luca; Gerotto, Caterina; Morosinotto, Tomas; Bassi, Roberto; Alboresi, Alessandro

    2013-09-01

    Nonphotochemical quenching (NPQ) dissipates excess energy to protect the photosynthetic apparatus from excess light. The moss Physcomitrella patens exhibits strong NPQ by both algal-type light-harvesting complex stress-related (LHCSR)-dependent and plant-type S subunit of Photosystem II (PSBS)-dependent mechanisms. In this work, we studied the dependence of NPQ reactions on zeaxanthin, which is synthesized under light stress by violaxanthin deepoxidase (VDE) from preexisting violaxanthin. We produced vde knockout (KO) plants and showed they underwent a dramatic reduction in thermal dissipation ability and enhanced photoinhibition in excess light conditions. Multiple mutants (vde lhcsr KO and vde psbs KO) showed that zeaxanthin had a major influence on LHCSR-dependent NPQ, in contrast with previous reports in Chlamydomonas reinhardtii. The PSBS-dependent component of quenching was less dependent on zeaxanthin, despite the near-complete violaxanthin to zeaxanthin exchange in LHC proteins. Consistent with this, we provide biochemical evidence that native LHCSR protein binds zeaxanthin upon excess light stress. These findings suggest that zeaxanthin played an important role in the adaptation of modern plants to the enhanced levels of oxygen and excess light intensity of land environments. PMID:24014548

  2. The chloroplast NADPH thioredoxin reductase C, NTRC, controls non-photochemical quenching of light energy and photosynthetic electron transport in Arabidopsis.

    PubMed

    Naranjo, Belén; Mignée, Clara; Krieger-Liszkay, Anja; Hornero-Méndez, Dámaso; Gallardo-Guerrero, Lourdes; Cejudo, Francisco Javier; Lindahl, Marika

    2016-04-01

    High irradiances may lead to photooxidative stress in plants, and non-photochemical quenching (NPQ) contributes to protection against excess excitation. One of the NPQ mechanisms, qE, involves thermal dissipation of the light energy captured. Importantly, plants need to tune down qE under light-limiting conditions for efficient utilization of the available quanta. Considering the possible redox control of responses to excess light implying enzymes, such as thioredoxins, we have studied the role of the NADPH thioredoxin reductase C (NTRC). Whereas Arabidopsis thaliana plants lacking NTRC tolerate high light intensities, these plants display drastically elevated qE, have larger trans-thylakoid ΔpH and have 10-fold higher zeaxanthin levels under low and medium light intensities, leading to extremely low linear electron transport rates. To test the impact of the high qE on plant growth, we generated an ntrc-psbs double-knockout mutant, which is devoid of qE. This double mutant grows faster than the ntrc mutant and has a higher chlorophyll content. The photosystem II activity is partially restored in the ntrc-psbs mutant, and linear electron transport rates under low and medium light intensities are twice as high as compared with plants lacking ntrc alone. These data uncover a new role for NTRC in the control of photosynthetic yield. PMID:26476233

  3. THE IMPACT OF NONPHOTOCHEMICAL QUENCHING OF FLUORESCENCE ON THE PHOTON BALANCE IN DIATOMS UNDER DYNAMIC LIGHT CONDITIONS(1).

    PubMed

    Su, Wanwen; Jakob, Torsten; Wilhelm, Christian

    2012-04-01

    The nonphotochemical quenching (NPQ) of fluorescence is an important photoprotective mechanism in particular under dynamic light conditions. Its photoprotective potential was suggested to be a functional trait of algal diversity. In the present study, the influence of the photoprotective capacity on the growth balance was investigated in two diatoms, which possess different NPQ characteristics. It was hypothesized that under fluctuating light conditions Cyclotella meneghiniana Kütz. would benefit from its large and flexible NPQ potential, whereas the comparably small NPQ capacity in Skeletonema costatum (Grev.) Cleve should exert an unfavorable impact on growth. The results of the study clearly falsify this hypothesis. Although C. meneghiniana possesses a fast NPQ component, this diatom was not able to recover its full NPQ capacity under fluctuating light. On the other hand, the induction of NPQ at relatively low irradiance in S. costatum resulted in rather small differences in the fraction of energy dissipation by the NPQ mechanism in the comparison of both diatoms. Larger differences were found in the metabolic characteristics. Both diatoms differed in their biomass composition, with a higher content of lipids in C. meneghiniana but higher amounts of carbohydrates in S. costatum. Finally, the lower degree of reduction in the biomass compensated for the higher respiration rates in S. costatum and resulted in a higher quantum efficiency of biomass production. An indirect correlation between the photoprotective and the metabolic capacity is discussed. PMID:27009723

  4. Ethylene Regulates Energy-Dependent Non-Photochemical Quenching in Arabidopsis through Repression of the Xanthophyll Cycle

    PubMed Central

    Chen, Zhong; Gallie, Daniel R.

    2015-01-01

    Energy-dependent (qE) non-photochemical quenching (NPQ) thermally dissipates excess absorbed light energy as a protective mechanism to prevent the over reduction of photosystem II and the generation of reactive oxygen species (ROS). The xanthophyll cycle, induced when the level of absorbed light energy exceeds the capacity of photochemistry, contributes to qE. In this work, we show that ethylene regulates the xanthophyll cycle in Arabidopsis. Analysis of eto1-1, exhibiting increased ethylene production, and ctr1-3, exhibiting constitutive ethylene response, revealed defects in NPQ resulting from impaired de-epoxidation of violaxanthin by violaxanthin de-epoxidase (VDE) encoded by NPQ1. Elevated ethylene signaling reduced the level of active VDE through decreased NPQ1 promoter activity and impaired VDE activation resulting from a lower transthylakoid membrane pH gradient. Increasing the concentration of CO2 partially corrected the ethylene-mediated defects in NPQ and photosynthesis, indicating that changes in ethylene signaling affect stromal CO2 solubility. Increasing VDE expression in eto1-1 and ctr1-3 restored light-activated de-epoxidation and qE, reduced superoxide production and reduced photoinhibition. Restoring VDE activity significantly reversed the small growth phenotype of eto1-1 and ctr1-3 without altering ethylene production or ethylene responses. Our results demonstrate that ethylene increases ROS production and photosensitivity in response to high light and the associated reduced plant stature is partially reversed by increasing VDE activity. PMID:26630486

  5. Lutein Accumulation in the Absence of Zeaxanthin Restores Nonphotochemical Quenching in the Arabidopsis thaliana npq1 Mutant[W][OA

    PubMed Central

    Li, Zhirong; Ahn, Tae Kyu; Avenson, Thomas J.; Ballottari, Matteo; Cruz, Jeffrey A.; Kramer, David M.; Bassi, Roberto; Fleming, Graham R.; Keasling, Jay D.; Niyogi, Krishna K.

    2009-01-01

    Plants protect themselves from excess absorbed light energy through thermal dissipation, which is measured as nonphotochemical quenching of chlorophyll fluorescence (NPQ). The major component of NPQ, qE, is induced by high transthylakoid ΔpH in excess light and depends on the xanthophyll cycle, in which violaxanthin and antheraxanthin are deepoxidized to form zeaxanthin. To investigate the xanthophyll dependence of qE, we identified suppressor of zeaxanthin-less1 (szl1) as a suppressor of the Arabidopsis thaliana npq1 mutant, which lacks zeaxanthin. szl1 npq1 plants have a partially restored qE but lack zeaxanthin and have low levels of violaxanthin, antheraxanthin, and neoxanthin. However, they accumulate more lutein and α-carotene than the wild type. szl1 contains a point mutation in the lycopene β-cyclase (LCYB) gene. Based on the pigment analysis, LCYB appears to be the major lycopene β-cyclase and is not involved in neoxanthin synthesis. The Lhcb4 (CP29) and Lhcb5 (CP26) protein levels are reduced by 50% in szl1 npq1 relative to the wild type, whereas other Lhcb proteins are present at wild-type levels. Analysis of carotenoid radical cation formation and leaf absorbance changes strongly suggest that the higher amount of lutein substitutes for zeaxanthin in qE, implying a direct role in qE, as well as a mechanism that is weakly sensitive to carotenoid structural properties. PMID:19549928

  6. Characterizing non-photochemical quenching in leaves through fluorescence lifetime snapshots.

    PubMed

    Sylak-Glassman, Emily J; Zaks, Julia; Amarnath, Kapil; Leuenberger, Michelle; Fleming, Graham R

    2016-01-01

    We describe a technique to measure the fluorescence decay profiles of intact leaves during adaptation to high light and subsequent relaxation to dark conditions. We show how to ensure that photosystem II reaction centers are closed and compare data for wild type Arabidopsis thaliana with conventional pulse-amplitude modulated (PAM) fluorescence measurements. Unlike PAM measurements, the lifetime measurements are not sensitive to photobleaching or chloroplast shielding, and the form of the fluorescence decay provides additional information to test quantitative models of excitation dynamics in intact leaves. PMID:25762378

  7. Enhancement of non-photochemical quenching in the Bryophyte Physcomitrella patens during acclimation to salt and osmotic stress.

    PubMed

    Azzabi, Ghazi; Pinnola, Alberta; Betterle, Nico; Bassi, Roberto; Alboresi, Alessandro

    2012-10-01

    Drought and salt stress are major abiotic constraints affecting plant growth worldwide. Under these conditions, the production of reactive oxygen species (ROS) is a common phenomenon taking place mainly in chloroplasts, peroxisomes, mitochondria and apoplasts, especially when associated with high light stress. ROS are harmful because of their high reactivity to cell components, thereby leading to cytotoxicity and cell death. During the Ordovician and early Devonian period, photosynthetic organisms colonized terrestrial habitats, and the acquisition of desiccation tolerance has been a major component of their evolution. We have studied the capacity for acclimation to drought and salt stress of the moss Physcomitrella patens, a representative of the early land colonization stage. Exposure to high concentrations of NaCl and sorbitol strongly affects chloroplast development, the Chl content and the thylakoid protein composition in this moss. Under sublethal conditions (0.2 M NaCl and 0.4 M sorbitol), the photosynthetic apparatus of P. patens responds to oxidative stress by increasing non-photochemical quenching (NPQ). Surprisingly, the accumulation of PSBS and LHCSR, the two polypeptides essential for NPQ in P. patens, was not up-regulated in these conditions. Rather, an increased NPQ amplitude correlated with the overaccumulation of zeaxanthin and the presence of the enzyme violaxanthin de-epoxidase. These results suggest that the regulation of excess energy dissipation through control of PSBS and LHCSR is mainly driven by light conditions, while osmotic and salt stress act through acclimative regulation of the xanthophyll cycle. We conclude that regulation of the xanthophyll cycle is an important anticipatory strategy against photoinhibition by high light. PMID:22952250

  8. Temperature-induced greening of Chlorella vulgaris. The role of the cellular energy balance and zeaxanthin-dependent nonphotochemical quenching.

    PubMed

    Wilson, Kenneth E; Król, Marianna; Huner, Norman P A

    2003-08-01

    When cells of the green alga Chlorella vulgaris Beij. are transferred from growth at 5 degrees C and an irradiance of 150 micromol photons m(-2) s(-1) to 27 degrees C and the same irradiance, they undergo what is normally considered a high-light to low-light phenotypic change. This involves a 3-fold increase in cellular chlorophyll content with a concomitant increase in light-harvesting complex polypeptide levels. This process appears to occur in response to the cellular capacity to utilize the products of photosynthesis, with the redox state of the plastoquinone pool sensing the cellular energy balance. The phenotypic adjustment can be enhanced or blocked using chemical inhibitors that modulate the redox state of the plastoquinone pool. The functional changes in the photosynthetic apparatus that occurred during the high-light to low-light acclimation were examined with special consideration paid to the paradox that 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU)-treated cells, with non-functional photosystem II (PSII), accumulate light-harvesting polypeptides. At the structural and basic functional levels, the light-harvesting complex of the cells treated with DCMU was indistinguishable from that of the untreated, control cells. To examine how PSII was protected in the DCMU-treated cells, we measured the content of xanthophyll-cycle pigments. It appeared that a zeaxanthin-dependent nonphotochemical quenching process was involved in PSII protection during greening in the presence of DCMU. Metabolic inhibitors of mitochondrial respiration were used to examine how the change in cellular energy balance regulates the greening process. Apparently, the mitochondrion acts to supply energy to the chloroplast during greening, and inhibition of mitochondrial respiration diminishes chlorophyll accumulation apparently through an increase in the redox state of the plastoquinone pool. PMID:12905022

  9. Kinetic Studies on the Xanthophyll Cycle in Barley Leaves (Influence of Antenna Size and Relations to Nonphotochemical Chlorophyll Fluorescence Quenching).

    PubMed Central

    Hartel, H.; Lokstein, H.; Grimm, B.; Rank, B.

    1996-01-01

    Xanthophyll-cycle kinetics as well as the relationship between the xanthophyll de-epoxidation state and Stern-Volmer type nonphotochemical chlorophyll (Chl) fluorescence quenching (qN) were investigated in barley (Hordeum vulgare L.) leaves comprising a stepwise reduced antenna system. For this purpose plants of the wild type (WT) and the Chl b-less mutant chlorina 3613 were cultivated under either continuous (CL) or intermittent light (IML). Violaxanthin (V) availability varied from about 70% in the WT up to 97 to 98% in the mutant and IML-grown plants. In CL-grown mutant leaves, de-epoxidation rates were strongly accelerated compared to the WT. This is ascribed to a different accessibility of V to the de-epoxidase due to the existence of two V pools: one bound to light-harvesting Chl a/b-binding complexes (LHC) and the other one not bound. Epoxidation rates (k) were decreased with reduction in LHC protein contents: kWT > kmutant >> kIML plants. This supports the idea that the epoxidase activity resides on certain LHC proteins. Irrespective of huge zeaxanthin and antheraxanthin accumulation, the capacity to develop qN was reduced stepwise with antenna size. The qN level obtained in dithiothreitol-treated CL- and IML-grown plants was almost identical with that in untreated IML-grown plants. The findings provide evidence that structural changes within the LHC proteins, mediated by xanthophyll-cycle operation, render the basis for the development of a major proportion of qN. PMID:12226199

  10. The time course of non-photochemical quenching in phycobilisomes of Synechocystis sp. PCC6803 as revealed by picosecond time-resolved fluorimetry.

    PubMed

    Maksimov, E G; Schmitt, F-J; Shirshin, E A; Svirin, M D; Elanskaya, I V; Friedrich, T; Fadeev, V V; Paschenko, V Z; Rubin, A B

    2014-09-01

    As high-intensity solar radiation can lead to extensive damage of the photosynthetic apparatus, cyanobacteria have developed various protection mechanisms to reduce the effective excitation energy transfer (EET) from the antenna complexes to the reaction center. One of them is non-photochemical quenching (NPQ) of the phycobilisome (PB) fluorescence. In Synechocystis sp. PCC6803 this role is carried by the orange carotenoid protein (OCP), which reacts to high-intensity light by a series of conformational changes, enabling the binding of OCP to the PBs reducing the flow of energy into the photosystems. In this paper the mechanisms of energy migration in two mutant PB complexes of Synechocystis sp. were investigated and compared. The mutant CK is lacking phycocyanin in the PBs while the mutant ΔPSI/PSII does not contain both photosystems. Fluorescence decay spectra with picosecond time resolution were registered using a single photon counting technique. The studies were performed in a wide range of temperatures - from 4 to 300 K. The time course of NPQ and fluorescence recovery in darkness was studied at room temperature using both steady-state and time-resolved fluorescence measurements. The OCP induced NPQ has been shown to be due to EET from PB cores to the red form of OCP under photon flux densities up to 1000 μmolphotonsm⁻²s⁻¹. The gradual changes of the energy transfer rate from allophycocyanin to OCP were observed during the irradiation of the sample with blue light and consequent adaptation to darkness. This fact was interpreted as the revelation of intermolecular interaction between OCP and PB binding site. At low temperatures a significantly enhanced EET from allophycocyanin to terminal emitters has been shown, due to the decreased back transfer from terminal emitter to APC. The activation of OCP not only leads to fluorescence quenching, but also affects the rate constants of energy transfer as shown by model based analysis of the decay associated

  11. Carotenoid-induced non-photochemical quenching in the cyanobacterial chlorophyll synthase-HliC/D complex.

    PubMed

    Niedzwiedzki, Dariusz M; Tronina, Tomasz; Liu, Haijun; Staleva, Hristina; Komenda, Josef; Sobotka, Roman; Blankenship, Robert E; Polívka, Tomáš

    2016-09-01

    Chl synthase (ChlG) is an important enzyme of the Chl biosynthetic pathway catalyzing attachment of phytol/geranylgeraniol tail to the chlorophyllide molecule. Here we have investigated the Flag-tagged ChlG (f.ChlG) in a complex with two different high-light inducible proteins (Hlips) HliD and HliC. The f.ChlG-Hlips complex binds a Chl a and three different carotenoids, β-carotene, zeaxanthin and myxoxanthophyll. Application of ultrafast time-resolved absorption spectroscopy performed at room and cryogenic temperatures revealed excited-state dynamics of complex-bound pigments. After excitation of Chl a in the complex, excited Chl a is efficiently quenched by a nearby carotenoid molecule via energy transfer from the Chl a Qy state to the carotenoid S1 state. The kinetic analysis of the spectroscopic data revealed that quenching occurs with a time constant of ~2ps and its efficiency is temperature independent. Even though due to its long conjugation myxoxanthophyll appears to be energetically best suited for role of Chl a quencher, based on comparative analysis and spectroscopic data we propose that β-carotene bound to Hlips acts as the quencher rather than myxoxanthophyll and zeaxanthin, which are bound at the f.ChlG and Hlips interface. The S1 state lifetime of the quencher has been determined to be 13ps at room temperature and 21ps at 77K. These results demonstrate that Hlips act as a conserved functional module that prevents photodamage of protein complexes during photosystem assembly or Chl biosynthesis. PMID:27133505

  12. Three-dimensional model of zeaxanthin binding PsbS protein associated with nonphotochemical quenching of excess quanta of light energy absorbed by the photosynthetic apparatus.

    PubMed

    Haripal, Prafulla K; Raval, Hemant K; Raval, Mukesh K; Rawal, Rakesh M; Biswal, Basanti; Biswal, Udaya C

    2006-09-01

    A three-dimensional model of the PsbS protein was built with the help of homology-modeling methods. This protein is also known as CP22 and is associated with the protection of photosystem II of thylakoid from excess quanta of light energy absorbed by the photosynthetic apparatus. PsbS is reported to bind two molecules of zeaxanthin at low pH (<5.0) and is believed to be essential for rapid nonphotochemical quenching (qE) of chlorophyll a fluorescence in photosystem II. An attempt was made to explain the pH modulation of the conformation of protein through salt-bridges Glu(-)(122)-Lys(+)(113) and Glu(-)(226)-Lys(+)(217). Binding of two molecules of zeaxanthin in the three-dimensional model of PsbS is postulated. The molecular mechanism of photoprotection by PsbS is explained through the model. PMID:16538483

  13. Multi-Level, Multi Time-Scale Fluorescence Intermittency of Photosynthetic LH2 Complexes: A Precursor of Non-Photochemical Quenching?

    PubMed

    Schörner, Mario; Beyer, Sebastian Reinhardt; Southall, June; Cogdell, Richard J; Köhler, Jürgen

    2015-11-01

    The light harvesting complex LH2 is a chromoprotein that is an ideal system for studying protein dynamics via the spectral fluctuations of the emission of its intrinsic chromophores. We have immobilized these complexes in a polymer film and studied the fluctuations of the fluorescence intensity from individual complexes over 9 orders of magnitude in time. Combining time-tagged detection of single photons with a change-point analysis has allowed the unambigeous identification of the various intensity levels due to the huge statistical basis of the data set. We propose that the observed intensity level fluctuations reflect conformational changes of the protein backbone that might be a precursor of the mechanism from which nonphotochemical quenching of higher plants has evolved. PMID:26419118

  14. Temperature and Light modulate the trans-delta3-hexadecenoic acid content of phosphatidylglycerol: light-harvesting complex II organization and non-photochemical quenching.

    PubMed

    Gray, Gordon R; Ivanov, Alexander G; Król, Marianna; Williams, John P; Kahn, Mobashoher U; Myscich, Elizabeth G; Huner, Norman P A

    2005-08-01

    The interaction of light and temperature in the modulation of the trans-delta3-hexadecenoic acid (trans-16:1) content of phosphatidylglycerol (PG) in winter rye (Secale cereale L.) was assessed and related to the organization of light-harvesting complex II (LHCII). Increasing the growth irradiance from 50 to 800 micromol m(-2) s(-1) at 20 degrees C resulted in a 1.8-fold increase in the trans-16:1 content in PG which favoured a greater preponderance of oligomeric LHCII, measured in vitro as the ratio of oligomer : monomer. Similar irradiance-dependent increases were observed during growth at 5 degrees C; however, 1.4-fold lower trans-16:1 contents and lower LHCII oligomer : monomer ratios were observed compared with growth at 20 degrees C and the same irradiance. These trends were also observed under natural field conditions. Thus, the accumulation of trans-16:1, as well as the organization of LHCII are modulated by both growth irradiance and growth temperature in an independent but additive manner. We also examined how changes in the supramolecular organization of LHCII affected the capacity for non-photochemical quenching (q(N)) and photoprotection via antenna quenching (q(O)). While q(O) was positively correlated with q(N), there was no correlation with either LHCII organization or xanthophyll cycle activity under the steady-state growth conditions examined. PMID:15946983

  15. Collisional quenching of highly rotationally excited HF

    NASA Astrophysics Data System (ADS)

    Yang, B.; Walker, K. M.; Forrey, R. C.; Stancil, P. C.; Balakrishnan, N.

    2015-06-01

    Context. Collisional excitation rate coefficients play an important role in the dynamics of energy transfer in the interstellar medium. In particular, accurate rotational excitation rates are needed to interpret microwave and infrared observations of the interstellar gas for nonlocal thermodynamic equilibrium line formation. Aims: Theoretical cross sections and rate coefficients for collisional deexcitation of rotationally excited HF in the vibrational ground state are reported. Methods: The quantum-mechanical close-coupling approach implemented in the nonreactive scattering code MOLSCAT was applied in the cross section and rate coefficient calculations on an accurate 2D HF-He potential energy surface. Estimates of rate coefficients for H and H2 colliders were obtained from the HF-He collisional data with a reduced-potential scaling approach. Results: The calculation of state-to-state rotational quenching cross sections for HF due to He with initial rotational levels up to j = 20 were performed for kinetic energies from 10-5 to 15 000 cm-1. State-to-state rate coefficients for temperatures between 0.1 and 3000 K are also presented. The comparison of the present results with previous work for lowly-excited rotational levels reveals significant differences. In estimating HF-H2 rate coefficients, the reduced-potential method is found to be more reliable than the standard reduced-mass approach. Conclusions: The current state-to-state rate coefficient calculations are the most comprehensive to date for HF-He collisions. We attribute the differences between previously reported data and our results to differences in the adopted interaction potential energy surfaces. The new He rate coefficients can be used in a variety of applications. The estimated H2 and H collision rates can also augment the smaller datasets previously developed for H2 and electrons. Rate coefficient tables are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130

  16. Identification of pH-sensing Sites in the Light Harvesting Complex Stress-related 3 Protein Essential for Triggering Non-photochemical Quenching in Chlamydomonas reinhardtii*

    PubMed Central

    Ballottari, Matteo; Truong, Thuy B.; De Re, Eleonora; Erickson, Erika; Stella, Giulio R.; Fleming, Graham R.; Bassi, Roberto; Niyogi, Krishna K.

    2016-01-01

    Light harvesting complex stress-related 3 (LHCSR3) is the protein essential for photoprotective excess energy dissipation (non-photochemical quenching, NPQ) in the model green alga Chlamydomonas reinhardtii. Activation of NPQ requires low pH in the thylakoid lumen, which is induced in excess light conditions and sensed by lumen-exposed acidic residues. In this work we have used site-specific mutagenesis in vivo and in vitro for identification of the residues in LHCSR3 that are responsible for sensing lumen pH. Lumen-exposed protonatable residues, aspartate and glutamate, were mutated to asparagine and glutamine, respectively. By expression in a mutant lacking all LHCSR isoforms, residues Asp117, Glu221, and Glu224 were shown to be essential for LHCSR3-dependent NPQ induction in C. reinhardtii. Analysis of recombinant proteins carrying the same mutations refolded in vitro with pigments showed that the capacity of responding to low pH by decreasing the fluorescence lifetime, present in the wild-type protein, was lost. Consistent with a role in pH sensing, the mutations led to a substantial reduction in binding the NPQ inhibitor dicyclohexylcarbodiimide. PMID:26817847

  17. Impact of chlororespiration on non-photochemical quenching of chlorophyll fluorescence and on the regulation of the diadinoxanthin cycle in the diatom Thalassiosira pseudonana

    PubMed Central

    Goss, Reimund; Wilhelm, Christian; Leegood, Richard; Horton, Peter; Jakob, Torsten

    2011-01-01

    In diatoms, metabolic activity during long dark periods leads to a chlororespiratory electron flow, which is accompanied by the build-up of a proton gradient strong enough to activate the diadinoxanthin (Ddx) de-epoxidation reaction of the Ddx cycle. In the present study, the impact of chlororespiration on non-photochemical quenching (NPQ) of chlorophyll fluorescence and the regulation of the Ddx cycle in the diatom Thalassiosira pseudonana was investigated by manipulation of the redox state of the photosynthetic electron transport chain during darkness. The response of a transfer of T. pseudonana cells from growth light conditions to 60 min darkness was found to depend on oxygen: in its presence there was no significant reduction of the PQ pool and no de-epoxidation of Ddx to diatoxanthin (Dtx). Under anaerobic conditions a high reduction state of the electron transport chain and a slow but steady de-epoxidation of Ddx was observed, which resulted in a significant accumulation of Dtx after 60 min of anaerobiosis. Unexpectedly, this high concentration of Dtx did not induce a correspondingly high NPQ as it would have been observed with Dtx formed under high light conditions. However, the sensitivity of NPQ to Dtx in cells kept under dark anaerobic conditions increased during reoxygenation and far-red (FR) light illumination. The results are discussed with respect to the activation of the de-epoxidation reaction and the formation of NPQ and their dependence on the extent of the proton gradient across the thylakoid membrane. PMID:20876335

  18. High Light-Dependent Phosphorylation of Photosystem II Inner Antenna CP29 in Monocots Is STN7 Independent and Enhances Nonphotochemical Quenching1

    PubMed Central

    Betterle, Nico; Ballottari, Matteo; Baginsky, Sacha; Bassi, Roberto

    2015-01-01

    Phosphorylation of the photosystem II antenna protein CP29 has been reported to be induced by excess light and further enhanced by low temperature, increasing resistance to these stressing factors. Moreover, high light-induced CP29 phosphorylation was specifically found in monocots, both C3 and C4, which include the large majority of food crops. Recently, knockout collections have become available in rice (Oryza sativa), a model organism for monocots. In this work, we have used reverse genetics coupled to biochemical and physiological analysis to elucidate the molecular basis of high light-induced phosphorylation of CP29 and the mechanisms by which it exerts a photoprotective effect. We found that kinases and phosphatases involved in CP29 phosphorylation are distinct from those reported to act in State 1-State 2 transitions. In addition, we elucidated the photoprotective role of CP29 phosphorylation in reducing singlet oxygen production and enhancing excess energy dissipation. We thus established, in monocots, a mechanistic connection between phosphorylation of CP29 and nonphotochemical quenching, two processes so far considered independent from one another. PMID:25501945

  19. Identification of pH-sensing Sites in the Light Harvesting Complex Stress-related 3 Protein Essential for Triggering Non-photochemical Quenching in Chlamydomonas reinhardtii.

    PubMed

    Ballottari, Matteo; Truong, Thuy B; De Re, Eleonora; Erickson, Erika; Stella, Giulio R; Fleming, Graham R; Bassi, Roberto; Niyogi, Krishna K

    2016-04-01

    Light harvesting complex stress-related 3 (LHCSR3) is the protein essential for photoprotective excess energy dissipation (non-photochemical quenching, NPQ) in the model green algaChlamydomonas reinhardtii Activation of NPQ requires low pH in the thylakoid lumen, which is induced in excess light conditions and sensed by lumen-exposed acidic residues. In this work we have used site-specific mutagenesisin vivoandin vitrofor identification of the residues in LHCSR3 that are responsible for sensing lumen pH. Lumen-exposed protonatable residues, aspartate and glutamate, were mutated to asparagine and glutamine, respectively. By expression in a mutant lacking all LHCSR isoforms, residues Asp(117), Glu(221), and Glu(224)were shown to be essential for LHCSR3-dependent NPQ induction inC. reinhardtii Analysis of recombinant proteins carrying the same mutations refoldedin vitrowith pigments showed that the capacity of responding to low pH by decreasing the fluorescence lifetime, present in the wild-type protein, was lost. Consistent with a role in pH sensing, the mutations led to a substantial reduction in binding the NPQ inhibitor dicyclohexylcarbodiimide. PMID:26817847

  20. Excitation energy after a smooth quench in a Luttinger liquid

    SciTech Connect

    Dziarmaga, Jacek; Tylutki, Marek

    2011-12-01

    Low-energy physics of quasi-one-dimensional ultracold atomic gases is often described by a gapless Luttinger liquid (LL). It is nowadays routine to manipulate these systems by changing their parameters in time but, no matter how slow the manipulation is, it must excite a gapless system. We study a smooth change of parameters of the LL (a smooth ''quench'') with a variable quench time and find that the excitation energy decays with an inverse power of the quench time. This universal exponent is -2 at zero temperature and -1 for slow enough quenches at finite temperature. The smooth quench does not excite beyond the range of validity of the low-energy LL description.

  1. Silencing of the Violaxanthin De-Epoxidase Gene in the Diatom Phaeodactylum tricornutum Reduces Diatoxanthin Synthesis and Non-Photochemical Quenching

    PubMed Central

    Vugrinec, Sascha; Kroth, Peter G.

    2012-01-01

    Diatoms are a major group of primary producers ubiquitous in all aquatic ecosystems. To protect themselves from photooxidative damage in a fluctuating light climate potentially punctuated with regular excess light exposures, diatoms have developed several photoprotective mechanisms. The xanthophyll cycle (XC) dependent non-photochemical chlorophyll fluorescence quenching (NPQ) is one of the most important photoprotective processes that rapidly regulate photosynthesis in diatoms. NPQ depends on the conversion of diadinoxanthin (DD) into diatoxanthin (DT) by the violaxanthin de-epoxidase (VDE), also called DD de-epoxidase (DDE). To study the role of DDE in controlling NPQ, we generated transformants of P. tricornutum in which the gene (Vde/Dde) encoding for DDE was silenced. RNA interference was induced by genetic transformation of the cells with plasmids containing either short (198 bp) or long (523 bp) antisense (AS) fragments or, alternatively, with a plasmid mediating the expression of a self-complementary hairpin-like construct (inverted repeat, IR). The silencing approaches generated diatom transformants with a phenotype clearly distinguishable from wildtype (WT) cells, i.e. a lower degree as well as slower kinetics of both DD de-epoxidation and NPQ induction. Real-time PCR based quantification of Dde transcripts revealed differences in transcript levels between AS transformants and WT cells but also between AS and IR transformants, suggesting the possible presence of two different gene silencing mediating mechanisms. This was confirmed by the differential effect of the light intensity on the respective silencing efficiency of both types of transformants. The characterization of the transformants strengthened some of the specific features of the XC and NPQ and confirmed the most recent mechanistic model of the DT/NPQ relationship in diatoms. PMID:22629333

  2. Proton Gradient Regulation5-Like1-Mediated Cyclic Electron Flow Is Crucial for Acclimation to Anoxia and Complementary to Nonphotochemical Quenching in Stress Adaptation1[W

    PubMed Central

    Kukuczka, Bernadeta; Magneschi, Leonardo; Petroutsos, Dimitris; Steinbeck, Janina; Bald, Till; Powikrowska, Marta; Fufezan, Christian; Finazzi, Giovanni; Hippler, Michael

    2014-01-01

    To investigate the functional importance of Proton Gradient Regulation5-Like1 (PGRL1) for photosynthetic performances in the moss Physcomitrella patens, we generated a pgrl1 knockout mutant. Functional analysis revealed diminished nonphotochemical quenching (NPQ) as well as decreased capacity for cyclic electron flow (CEF) in pgrl1. Under anoxia, where CEF is induced, quantitative proteomics evidenced severe down-regulation of photosystems but up-regulation of the chloroplast NADH dehydrogenase complex, plastocyanin, and Ca2+ sensors in the mutant, indicating that the absence of PGRL1 triggered a mechanism compensatory for diminished CEF. On the other hand, proteins required for NPQ, such as light-harvesting complex stress-related protein1 (LHCSR1), violaxanthin de-epoxidase, and PSII subunit S, remained stable. To further investigate the interrelation between CEF and NPQ, we generated a pgrl1 npq4 double mutant in the green alga Chlamydomonas reinhardtii lacking both PGRL1 and LHCSR3 expression. Phenotypic comparative analyses of this double mutant, together with the single knockout strains and with the P. patens pgrl1, demonstrated that PGRL1 is crucial for acclimation to high light and anoxia in both organisms. Moreover, the data generated for the C. reinhardtii double mutant clearly showed a complementary role of PGRL1 and LHCSR3 in managing high light stress response. We conclude that both proteins are needed for photoprotection and for survival under low oxygen, underpinning a tight link between CEF and NPQ in oxygenic photosynthesis. Given the complementarity of the energy-dependent component of NPQ (qE) and PGRL1-mediated CEF, we suggest that PGRL1 is a capacitor linked to the evolution of the PSII subunit S-dependent qE in terrestrial plants. PMID:24948831

  3. Lutein from Deepoxidation of Lutein Epoxide Replaces Zeaxanthin to Sustain an Enhanced Capacity for Nonphotochemical Chlorophyll Fluorescence Quenching in Avocado Shade Leaves in the Dark1

    PubMed Central

    Förster, Britta; Pogson, Barry James; Osmond, Charles Barry

    2011-01-01

    Leaves of avocado (Persea americana) that develop and persist in deep shade canopies have very low rates of photosynthesis but contain high concentrations of lutein epoxide (Lx) that are partially deepoxidized to lutein (L) after 1 h of exposure to 120 to 350 μmol photons m−2 s−1, increasing the total L pool by 5% to 10% (ΔL). Deepoxidation of Lx to L was near stoichiometric and similar in kinetics to deepoxidation of violaxanthin (V) to antheraxanthin (A) and zeaxanthin (Z). Although the V pool was restored by epoxidation of A and Z overnight, the Lx pool was not. Depending on leaf age and pretreatment, the pool of ΔL persisted for up to 72 h in the dark. Metabolism of ΔL did not involve epoxidation to Lx. These contrasting kinetics enabled us to differentiate three states of the capacity for nonphotochemical chlorophyll fluorescence quenching (NPQ) in attached and detached leaves: ΔpH dependent (NPQΔpH) before deepoxidation; after deepoxidation in the presence of ΔL, A, and Z (NPQΔLAZ); and after epoxidation of A+Z but with residual ΔL (NPQΔL). The capacity of both NPQΔLAZ and NPQΔL was similar and 45% larger than NPQΔpH, but dark relaxation of NPQΔLAZ was slower. The enhanced capacity for NPQ was lost after metabolism of ΔL. The near equivalence of NPQΔLAZ and NPQΔL provides compelling evidence that the small dynamic pool ΔL replaces A+Z in avocado to “lock in” enhanced NPQ. The results are discussed in relation to data obtained with other Lx-rich species and in mutants of Arabidopsis (Arabidopsis thaliana) with increased L pools. PMID:21427278

  4. Quenching of excited triplet states by dissolved natural organic matter.

    PubMed

    Wenk, Jannis; Eustis, Soren N; McNeill, Kristopher; Canonica, Silvio

    2013-11-19

    Excited triplet states of aromatic ketones and quinones are used as proxies to assess the reactivity of excited triplet states of the dissolved organic matter ((3)DOM*) in natural waters. (3)DOM* are crucial transients in environmental photochemistry responsible for contaminant transformation, production of reactive oxygen species, and potentially photobleaching of DOM. In recent photochemical studies aimed at clarifying the role of DOM as an inhibitor of triplet-induced oxidations of organic contaminants, aromatic ketones have been used in the presence of DOM, and the question of a possible interaction between their excited triplet states and DOM has emerged. To clarify this issue, time-resolved laser spectroscopy was applied to measure the excited triplet state quenching of four different model triplet photosensitizers induced by a suite of DOM from various aquatic and terrestrial sources. While no quenching for the anionic triplet sensitizers 4-carboxybenzophenone (CBBP) and 9,10-anthraquinone-2,6-disulfonic acid (2,6-AQDS) was detected, second-order quenching rate constants with DOM for the triplets of 2-acetonaphthone (2AN) and 3-methoxyacetophenone (3MAP) in the range of 1.30-3.85 × 10(7) L mol(C)(-1) s(-1) were determined. On the basis of the average molecular weight of DOM molecules, the quenching for these uncharged excited triplet molecules is nearly diffusion-controlled, but significant quenching (>10%) in aerated water is not expected to occur below DOM concentrations of 22-72 mg(C) L(-1). PMID:24083647

  5. Quenching of Excited Na due to He Collisions

    NASA Technical Reports Server (NTRS)

    Lin, C. Y.; Stancil, P. C.; Liebermann, H. P.; Funke, P.; Buenker, R. J.

    2006-01-01

    The quenching and elastic scattering of excited Sodium by collisions with Helium have been investigated for energies between 10(exp -13) eV and 10 eV. With the ab initio adiabatic potentials and nonadiabatic radial and rotational couplings obtained from multireference single- and double-excitation configuration interaction approach, we carried out scattering calculations by the quantum-mechanical molecular-orbital close-coupling method. Cross sections for quenching reactions and elastic collisions are presented. Quenching and elastic collisional rate coefficients as a function of temperature between 1 micro-K and 10,000 K are also obtained. The results are relevant to modeling non-LTE effects on Na D absorption lines in extrasolar planets and brown dwarfs.

  6. Collisional energy transfer and quenching of electronic excitation

    PubMed Central

    Lin, S. H.; Eyring, H.

    1975-01-01

    The purpose of this paper has been to explore in a preliminary way the nature and mechanism of collisional energy transfer and quenching of electronic excitation. For this purpose, the Born approximation has been used, and the triplet-triplet and singlet-singlet transfer, and the triplet-triplet and singlet-singlet quenching have been studied. It has been shown theoretically that (i) the singlet-singlet transfer constants (or cross sections) are always larger than the triplet-triplet transfer constants (or cross sections) for the same system of donor and acceptor; (ii) for the singlet-singlet transfer, the observed cross section varies linearly with respect to the spectral overlap between the donor emission and the acceptor absorption; (iii) the reason that the quenching constants (or cross sections) are always smaller than the energy transfer constants (or cross sections) is due to the fact that for the quenching the vibration of the acceptor hardly participates in accepting the electronic excitation and for the energy transfer only part of the excited electron energy of the donor is converted into the energy of nuclear motion; and (iv) the polar acceptor molecules are better quenchers than nonpolar acceptor molecules. PMID:16592281

  7. Quenching rate constants of excited halogen atoms in quartet states

    NASA Astrophysics Data System (ADS)

    Mizuta, K.; Kuramasu, T.; Ishikawa, Y.; Arai, S.

    1994-04-01

    Excited halogen atoms in quartet spin states F*(2p43s, 4P5/2), Cl*(3p44s, 4P5/2), and Br*(4p45s, 4P5/2) were produced from helium sensitized radiation chemical decomposition of SF6, CF3Cl, CF3Br, and CF2Br2. Quenching rate constants of these excited halogen atoms by simple gas molecules such as O2, N2, H2, CO, CO2, NO, NO2, N2O, CH4, C2H6, and Xe including parent molecules were determined from absorption decay curves at 685.8 nm for F*, 837.5 nm for Cl*, and 827.4 nm for Br*. The optical densities were assumed to be proportional to (number of excited atoms per one cubic centimeter)0.9. The quenching rate constants obtained here were compared to those reported of metastable rare-gas atoms and an excited oxygen atom O*(2p33s, 5S2), and further discussed in terms of several theoretical kinetic models.

  8. Excited atomic bromine energy transfer and quenching mechanisms

    NASA Astrophysics Data System (ADS)

    Johnson, Ray O.

    1993-08-01

    Pulsed and steady-state photolysis experiments have been conducted to determine the rate coefficients for collisional deactivation of the spin-orbit excited state of atomic bromine, Br((sup 2)P(sub 1/2)). Pulsed lifetime studies for quenching by Br2 and CO2 established absolute rate coefficients at room temperature of k(sub Br2) = 1.2 +/- 0.1 x 10(exp-12) and k(sub CO2) = 1.5 +/0.2 x 10(exp-11) cu cm/molecule-s. Steady-state photolysis methods were used to determine the quenching rates for the rare gases, N2, 02, H2, D2, NO, NO2, N2O, SF6, CF4, CH4, CO, CO2, COS, SO2, H2S, HBr, HC1, and HI relative to that for Br2. Quenching rate temperature dependence was examined for Br2, CO2, N2O, HCl, COS, NO, and NO2 for temperatures from 300 to 420 K. Diffusion and three body effects were examined in order to determine the slowest relative quenching rate measurable by this experimental technique.

  9. Effects of habitat light conditions on the excitation quenching pathways in desiccating Haberlea rhodopensis leaves: an Intelligent FluoroSensor study.

    PubMed

    Solti, Ádám; Lenk, Sándor; Mihailova, Gergana; Mayer, Péter; Barócsi, Attila; Georgieva, Katya

    2014-01-01

    Resurrection plants can survive dehydration to air-dry state, thus they are excellent models of understanding drought and dehydration tolerance mechanisms. Haberlea rhodopensis, a chlorophyll-retaining resurrection plant, can survive desiccation to relative water content below 10%. Leaves, detached from plants of sun and shade habitats, were moderately (∼50%) dehydrated in darkness. During desiccation, chlorophyll a fluorescence was detected by the recently innovated wireless Intelligent FluoroSensor (IFS) chlorophyll fluorometer, working with three different detectors: a pulse-amplitude-modulated (PAM) broadband channel and two channels to measure non-modulated red and far-red fluorescence. No change in area-based chlorophyll content of leaves was observed. The maximal quantum efficiency of photosystem II decreased gradually in both shade and sun leaves. Shade leaves could not increase antennae-based quenching, thus inactivated photosystem II took part in quenching of excess irradiation. Sun leaves seemed to be pre-adapted to quench excess light as they established an intensive increase in antennae-based non-photochemical quenching parallel to desiccation. The higher far-red to red antennae-based quenching may sign light-harvesting complex reorganization. Thus, compared to PAM, IFS chlorophyll fluorometer has additional benefits including (i) parallel estimation of changes in the Chl content and (ii) prediction of underlying processes of excitation energy quenching. PMID:24345600

  10. Chlamydomonas Xanthophyll Cycle Mutants Identified by Video Imaging of Chlorophyll Fluorescence Quenching.

    PubMed Central

    Niyogi, K. K.; Bjorkman, O.; Grossman, A. R.

    1997-01-01

    The photosynthetic apparatus in plants is protected against oxidative damage by processes that dissipate excess absorbed light energy as heat within the light-harvesting complexes. This dissipation of excitation energy is measured as nonphotochemical quenching of chlorophyll fluorescence. Nonphotochemical quenching depends primarily on the [delta]pH that is generated by photosynthetic electron transport, and it is also correlated with the amounts of zeaxanthin and antheraxanthin that are formed from violaxanthin by the operation of the xanthophyll cycle. To perform a genetic dissection of nonphotochemical quenching, we have isolated npq mutants of Chlamydomonas by using a digital video-imaging system. In excessive light, the npq1 mutant is unable to convert violaxanthin to antheraxanthin and zeaxanthin; this reaction is catalyzed by violaxanthin de-epoxidase. The npq2 mutant appears to be defective in zeaxanthin epoxidase activity, because it accumulates zeaxanthin and completely lacks antheraxanthin and violaxanthin under all light conditions. Characterization of these mutants demonstrates that a component of nonphotochemical quenching that develops in vivo in Chlamydomonas depends on the accumulation of zeaxanthin and antheraxanthin via the xanthophyll cycle. However, observation of substantial, rapid, [delta]pH-dependent nonphotochemical quenching in the npq1 mutant demonstrates that the formation of zeaxanthin and antheraxanthin via violaxanthin de-epoxidase activity is not required for all [delta]pH-dependent nonphotochemical quenching in this alga. Furthermore, the xanthophyll cycle is not required for survival of Chlamydomonas in excessive light. PMID:12237386

  11. Excitation energy partitioning and quenching during cold acclimation in Scots pine.

    PubMed

    Sveshnikov, Dmitry; Ensminger, Ingo; Ivanov, Alexander G; Campbell, Douglas; Lloyd, Jon; Funk, Christiane; Hüner, Norman P A; Oquist, Gunnar

    2006-03-01

    We studied the influence of two irradiances on cold acclimation and recovery of photosynthesis in Scots pine (Pinus sylvestris L.) seedlings to assess mechanisms for quenching the excess energy captured by the photosynthetic apparatus. A shift in temperature from 20 to 5 degrees C caused a greater decrease in photosynthetic activity, measured by chlorophyll fluorescence and oxygen evolution, in plants exposed to moderate light (350 micromol m(-2) s(-1)) than in shaded plants (50 micromol m(-2) s(-1)). In response to the temperature shift, maximal photochemical efficiency of photosystem II (PSII), measured as the ratio of variable to maximal chlorophyll fluorescence (Fv/Fm) of dark-adapted samples, decreased to 70% in exposed seedlings, whereas shaded seedlings maintained Fv/Fm close to initial values. After a further temperature decrease to -5 degrees C, only 8% of initial Fv/Fm remained in exposed plants, whereas shaded plants retained 40% of initial Fv/Fm. Seven days after transfer from -5 to 20 degrees C, recovery of photochemical efficiency was more complete in the shaded plants than in the exposed plants (87 and 65% of the initial Fv/Fm value, respectively). In response to cold stress, the estimated functional absorption cross section per remaining PSII reaction center increased at both irradiances, but the increase was more pronounced in exposed seedlings. Estimates of energy partitioning in the needles showed a much higher dissipative component in the exposed seedlings at low temperatures, pointing to stronger development of non-photochemical quenching at moderate irradiances. The de-epoxidation state of the xanthophyll cycle pigments increased in exposed seedlings at 5 degrees C, contributing to the quenching capacity, whereas significant de-epoxidation in the shaded plants was observed only when temperatures decreased to -5 degrees C. Thermoluminescence (TL) measurements of PSII revealed that charge recombinations between the second oxidation state of Mn

  12. Heterologous expression of moss light-harvesting complex stress-related 1 (LHCSR1), the chlorophyll a-xanthophyll pigment-protein complex catalyzing non-photochemical quenching, in Nicotiana sp.

    PubMed

    Pinnola, Alberta; Ghin, Leonardo; Gecchele, Elisa; Merlin, Matilde; Alboresi, Alessandro; Avesani, Linda; Pezzotti, Mario; Capaldi, Stefano; Cazzaniga, Stefano; Bassi, Roberto

    2015-10-01

    Oxygenic photosynthetic organisms evolved mechanisms for thermal dissipation of energy absorbed in excess to prevent formation of reactive oxygen species. The major and fastest component, called non-photochemical quenching, occurs within the photosystem II antenna system by the action of two essential light-harvesting complex (LHC)-like proteins, photosystem II subunit S (PSBS) in plants and light-harvesting complex stress-related (LHCSR) in green algae and diatoms. In the evolutionary intermediate Physcomitrella patens, a moss, both gene products are active. These proteins, which are present in low amounts, are difficult to purify, preventing structural and functional analysis. Here, we report on the overexpression of the LHCSR1 protein from P. patens in the heterologous systems Nicotiana benthamiana and Nicotiana tabacum using transient and stable nuclear transformation. We show that the protein accumulated in both heterologous systems is in its mature form, localizes in the chloroplast thylakoid membranes, and is correctly folded with chlorophyll a and xanthophylls but without chlorophyll b, an essential chromophore for plants and algal LHC proteins. Finally, we show that recombinant LHCSR1 is active in quenching in vivo, implying that the recombinant protein obtained is a good material for future structural and functional studies. PMID:26260788

  13. Quenching of highly rotationally excited HCl in collisions with He

    SciTech Connect

    Yang, Benhui; Stancil, P. C. E-mail: stancil@physast.uga.edu

    2014-03-10

    We report rotational quenching cross sections and rate coefficients of HCl due to collisions with He. The close-coupling method and the coupled-states approximation are applied in quantum-mechanical scattering calculations of state-to-state cross sections for HCl with initial rotational levels up to j = 20 for kinetic energies from 10{sup –5} to 15,000 cm{sup –1}. State-to-state rate coefficients for temperatures between 0.1 and 3000 K are also presented. Comparison of the present rate coefficients with previous results reported in the literature for lowly excited rotational levels shows reasonable agreement. Small differences are attributed to the differences in the interaction potential energy surfaces. The uncertainty in the computed cross sections and rate coefficients is estimated by varying the potential well depth. Applications of current results to astrophysical systems are also briefly discussed.

  14. Integrating transient heterogeneity of non-photochemical quenching in shade-grown heterobaric leaves of avocado (Persea americana L.): responses to CO2 concentration, stomatal occlusion, dehydration and relative humidity.

    PubMed

    Takayama, Kotaro; King, Diana; Robinson, Sharon A; Osmond, Barry

    2013-11-01

    Long-lived shade leaves of avocado had extremely low rates of photosynthesis. Gas exchange measurements of photosynthesis were of limited use, so we resorted to Chl fluorescence imaging (CFI) and spot measurements to evaluate photosynthetic electron transport rates (ETRs) and non-photochemical quenching (NPQ). Imaging revealed a remarkable transient heterogeneity of NPQ during photosynthetic induction in these hypostomatous, heterobaric leaves, but was adequately integrated by spot measurements, despite long-lasting artifacts from repeated saturating flashes during assays. Major veins (mid-vein, first- and second-order veins) defined areas of more static large-scale heterogeneous NPQ, with more dynamic small-scale heterogeneity most strongly expressed in mesophyll cells between third- and fourth-order veins. Both responded to external CO2 concentration ([CO2]), occlusion of stomata with Vaseline™, leaf dehydration and relative humidity (RH). We interpreted these responses in terms of independent behavior of stomata in adjacent areoles that was largely expressed through CO2-limited photosynthesis. Heterogeneity was most pronounced and prolonged in the absence of net CO2 fixation in 100 p.p.m. [CO2] when respiratory and photorespiratory CO2 cycling constrained the inferred ETR to ~75% of values in 400 or 700 p.p.m. [CO2]. Likewise, sustained higher NPQ under Vaseline™, after dehydration or at low RH, also restricted ETR to ~75% of control values. Low NPQ in chloroplast-containing cells adjacent to major veins but remote from stomata suggested internal sources of high [CO2] in these tissues. PMID:24078766

  15. On the O2(a1Δ) quenching by vibrationally excited ozone

    NASA Astrophysics Data System (ADS)

    Azyazov, V. N.; Mikheyev, P. A.; Heaven, M. C.

    2010-09-01

    The development of a discharge oxygen iodine laser (DOIL) requires efficient production of singlet delta oxygen (O2(a)) in electric discharge. It is important to understand the mechanisms by which O2(a) is quenched in these devices. To gain understanding of this mechanisms quenching of O2(a) in O(3P)/O2/O3/CO2/He/Ar mixtures has been investigated. Oxygen atoms and singlet oxygen molecules were produced by the 248 nm laser photolysis of ozone. The kinetics of O2(a) quenching were followed by observing the 1268 nm fluorescence of the O2 a --> X transition. Fast quenching of O2(a) in the presence of oxygen atoms and molecules was observed. The mechanism of the process has been examined using kinetic models, which indicate that quenching by vibrationally excited ozone is the dominant reaction.

  16. Nonlinear quenching of densely excited states in wide-gap solids

    NASA Astrophysics Data System (ADS)

    Grim, Joel Q.; Ucer, K. B.; Burger, A.; Bhattacharya, P.; Tupitsyn, E.; Rowe, E.; Buliga, V. M.; Trefilova, L.; Gektin, A.; Bizarri, G. A.; Moses, W. W.; Williams, R. T.

    2013-03-01

    Dense interband electronic excitations on the order of 0.2 electron-hole pairs per nm3 are encountered in a number of circumstances of fundamental and practical significance. We report measurements of the kinetic order and rate constants of nonlinear quenching in pure and doped materials with band gaps in the range from 6 eV down to 1.4 eV. The principal method used can be described as interband Z-scan luminescence yield with subpicosecond pulse excitations. A clear delineation of second-order and third-order quenching kinetics is found between oxide and iodide insulating crystals. This delineation suggests that the hot-electron thermalization rate mediated by LO phonon frequencies governs whether free carriers can pair as excitons within the time period of nonlinear quenching.

  17. Semiclassical study of the quenching of excited-state fluorine atom by hydrogen molecule - Comparison between reactive and nonreactive processes

    NASA Technical Reports Server (NTRS)

    Yuan, J.-M.; Skuse, B. M.; Jaffe, R. L.; Komornicki, A.; Morokuma, K.; George, T. F.

    1980-01-01

    Semiclassical calculations are carried out for the quenching of excited-state fluorine atom by collinear collisions with hydrogen molecule. The overall quenching probability is the sum of two contributions: the reactive quenching probability associated with the formation of hydrogen fluoride and the nonreactive quenching probability leading to ground-state fluorine atom and hydrogen molecule. The reactive probability is greater in the threshold region of the collision energy, whereas the nonreactive probability dominates for energies above the threshold region.

  18. Dissociative excitation of the N(+)(5S) state by electron impact on N2 - Excitation function and quenching

    NASA Technical Reports Server (NTRS)

    Erdman, P. W.; Zipf, E. C.

    1986-01-01

    Metastable N(+)(5S) ions were produced in the laboratory by dissociative excitation of N2 with energetic electrons. The resulting radiative decay of the N(+)(5S) state was observed with sufficient resolution to completely resolve the doublet from the nearby N2 molecular radiation. The excitation function was measured from threshold to 500 eV. The cross section peaks at a high electron energy and also exhibits a high threshold energy both of which are typical of dissociative excitation-ionization processes. This finding complicates the explanation of electron impact on N2 as the mechanism for the source of the 2145 A 'auroral mystery feature' by further increasing the required peak cross section. It is suggested that the apparent N(+)(5S) quenching in auroras may be an artifact due to the softening of the electron energy spectrum in the auroral E region.

  19. Intermolecular chiral recognition probed by enantiodifferential excited-state quenching kinetics.

    PubMed

    Stockman, T G; Klevickis, C A; Grisham, C M; Richardson, F S

    1996-01-01

    Time-resolved chiroptical luminescence (TR-CL) measurements are used to study the kinetics of chirality-dependent excited-state quenching processes in aqueous solution. Experiments are carried out on samples that contain a racemic mixture of chiral luminophore molecules (L) in solution with a small, optically active concentration of chiral quencher molecules (Q). The luminophores are excited with a pulse of unpolarized light to create an initially racemic excited-state population of lambda L* and delta L* enantiomers, and TR-CL measurements are then used to monitor the differential decay kinetics of the lambda L* and delta L* subpopulations. Observed differences between the lambda L* and delta L* decay kinetics reflect differential rate processes and efficiencies for lambda L*-Q versus delta L*-Q quenching actions, and they are diagnostic of chiral discriminatory interactions between the luminophore and quencher molecules. In this study, the luminophores are either Eu(dpa)3(3-) or Tb(dpa)3(3-) coordination complexes (where dpa denotes a dipicolinate dianion ligand), and the quenchers are diastereomeric structures of Cr(H2O)4(ATP), Rh(H2O)4(ATP) and Rh(H2O)3(ATP) (where ATP identical to adenosine triphosphate). The Ln(dpa)3(3-) (Ln identical to En3+ or Tb3+) complexes have three-bladed propeller-like structures of D3 symmetry, and in aqueous solution they exist as a racemic mixture of left-handed (lambda) and right-handed (delta) configurational isomers (enantiomers). The results show that the chiral quencher molecules can distinguish between the lambda and delta enantiomeric structures of the luminophores in their excited-state quenching actions. The degree and sense of enantiomeric preference in these quenching actions are governed by the electronic and stereochemical properties of the quencher molecules. Twenty-one different luminophore-quencher systems are examined in this study, and they exhibit interestingly diverse enantiodifferential quenching kinetics. The

  20. Positive-parity excited states of the nucleon in quenched lattice QCD

    SciTech Connect

    Mahbub, M. S.; Cais, Alan O.; Kamleh, Waseem; Leinweber, Derek B.; Williams, Anthony G.

    2010-11-01

    Positive-parity spin-(1/2) excitations of the nucleon are explored in lattice QCD. The variational method is used in this investigation and several correlation matrices are employed. As our focus is on the utility and methodology of the variational approach, we work in the quenched approximation to QCD. Various sweeps of Gaussian fermion-field smearing are applied at the source and at the sink of {chi}{sub 1{chi}1} and {chi}{sub 1{chi}2} correlation functions to obtain a large basis of operators. Using several different approaches for constructing basis interpolators, we demonstrate how improving the basis can split what otherwise might be interpreted as a single state into multiple eigenstates. Consistency of the extracted excited energy states are explored over various dimensions of the correlation matrices. The use of large correlation matrices is emphasized for the reliable extraction of the excited eigenstates of QCD.

  1. Onset of quenching of the giant dipole resonance at high excitation energies

    NASA Astrophysics Data System (ADS)

    Santonocito, D.; Blumenfeld, Y.; Agodi, C.; Alba, R.; Bellia, G.; Coniglione, R.; Delaunay, F.; Del Zoppo, A.; Finocchiaro, P.; Hongmei, F.; Lima, V.; Maiolino, C.; Migneco, E.; Piattelli, P.; Sapienza, P.; Scarpaci, J. A.; Wieland, O.

    2014-11-01

    The evolution of the giant dipole resonance (GDR) properties in nuclei of mass A =120 to 132 has been investigated in an excitation energy range between 150 and 270 MeV through the study of complete and nearly complete fusion reactions using 116Sn beams at 17 A and 23 A MeV from the cyclotron of the Laboratorio Nazionale del Sud impinging on 12C and 24Mg targets. γ rays and light charged particles were detected using the multi-element detector array MEDEA in coincidence with evaporation residues detected by using mass and charge identification spectrometry with telescope (MACISTE). Light-charged-particle energy spectra were analyzed within the framework of a multiple-source-emission scenario by using a fitting procedure to determine the amount of pre-equilibrium emission and deduce the excitation energies reached in the compound nuclei. A detailed analysis of the γ -ray spectra and their comparison with statistical model calculations is presented. Evidence of a quenching of the GDR gamma yield was found at 270 MeV excitation energy. The quenching effect becomes progressively more important with increasing excitation energy, as observed when the comparison is extended to data from the reaction 36Ar+96Mo at 37 A MeV where hot nuclei were populated up to 430 MeV excitation energy. A coherent scenario emerges indicating the existence of a limiting excitation energy for the collective motion of about E*/A =2.1 MeV for systems of mass A =105 to 111 while a slightly lower value was observed for nuclei of mass A ˜132 . The existence of a possible link between GDR disappearance and the liquid-gas phase transition is discussed.

  2. Elimination of photon quenching by a transition layer to fabricate a quenching-shield sandwich structure for 800 nm excited upconversion luminescence of Nd3+-sensitized nanoparticles.

    PubMed

    Zhong, Yeteng; Tian, Gan; Gu, Zhanjun; Yang, Yijun; Gu, Lin; Zhao, Yuliang; Ma, Ying; Yao, Jiannian

    2014-05-01

    Nd3+-sensitized quenching-shield sandwich-structured upconversion nanoparticles are reported, which exhibit highly efficient upconversion photoluminescence under excitation by an 800 nm continuous-wave laser. The transition-layer structure is essential to bridge energy transfer from the sensitizer to the activator and simultaneously block energy back-transfer from the activator to the sensitizer. These 800 nm-excited upconversion nanoparticles are a key step toward the development of upconversion nanophosphors for biological applications. PMID:24338994

  3. Adiabatic quenches and characterization of amplitude excitations in a continuous quantum phase transition.

    PubMed

    Hoang, Thai M; Bharath, Hebbe M; Boguslawski, Matthew J; Anquez, Martin; Robbins, Bryce A; Chapman, Michael S

    2016-08-23

    Spontaneous symmetry breaking occurs in a physical system whenever the ground state does not share the symmetry of the underlying theory, e.g., the Hamiltonian. This mechanism gives rise to massless Nambu-Goldstone modes and massive Anderson-Higgs modes. These modes provide a fundamental understanding of matter in the Universe and appear as collective phase or amplitude excitations of an order parameter in a many-body system. The amplitude excitation plays a crucial role in determining the critical exponents governing universal nonequilibrium dynamics in the Kibble-Zurek mechanism (KZM). Here, we characterize the amplitude excitations in a spin-1 condensate and measure the energy gap for different phases of the quantum phase transition. At the quantum critical point of the transition, finite-size effects lead to a nonzero gap. Our measurements are consistent with this prediction, and furthermore, we demonstrate an adiabatic quench through the phase transition, which is forbidden at the mean field level. This work paves the way toward generating entanglement through an adiabatic phase transition. PMID:27503886

  4. Adiabatic quenches and characterization of amplitude excitations in a continuous quantum phase transition

    PubMed Central

    Hoang, Thai M.; Bharath, Hebbe M.; Boguslawski, Matthew J.; Anquez, Martin; Robbins, Bryce A.; Chapman, Michael S.

    2016-01-01

    Spontaneous symmetry breaking occurs in a physical system whenever the ground state does not share the symmetry of the underlying theory, e.g., the Hamiltonian. This mechanism gives rise to massless Nambu–Goldstone modes and massive Anderson–Higgs modes. These modes provide a fundamental understanding of matter in the Universe and appear as collective phase or amplitude excitations of an order parameter in a many-body system. The amplitude excitation plays a crucial role in determining the critical exponents governing universal nonequilibrium dynamics in the Kibble–Zurek mechanism (KZM). Here, we characterize the amplitude excitations in a spin-1 condensate and measure the energy gap for different phases of the quantum phase transition. At the quantum critical point of the transition, finite-size effects lead to a nonzero gap. Our measurements are consistent with this prediction, and furthermore, we demonstrate an adiabatic quench through the phase transition, which is forbidden at the mean field level. This work paves the way toward generating entanglement through an adiabatic phase transition. PMID:27503886

  5. Quenching excited triplet C{sub 60} fullerene by tetracyanoethylene in benzonitrile

    SciTech Connect

    Nadtochenko, V.A.; Denisov, N.N.; Rubtsov, I.V.; Lobach, A.S.; Moravsky, A.P.

    1994-01-01

    The main photophysical properties of C{sub 60} fullerene: The absorption spectra of excited singlet C{sub 60}, the inter-combinational conversion time, the quantum yield of triplet C{sub 60}, the triplet-triplet absorption spectra, and the channels and rate constants of the deactivation of triplet C{sub 60} have been established. The photochemical properties of C{sub 60} fullerene have been investigated to a lesser degree. C{sub 60} is known to be readily reduced (E{sub 1/2} = {minus}0.4 in relation to Ag/Ag{sup +}), in particular, photochemically. For example, photoexcitation of charge-transfer complexes of C{sub 60} with amines gives the radical anion C{sup {minus}}{sub 60} which is also formed in reactions of photoexcited C{sub 60} fullerene. The formation of the radical cation C{sup +}{sub 60} under the action of light has been detected in the reaction with colloidal TiO{sub 2}. The radical ion C{sup +}{sub 60} has been obtained in a homogeneous photochemical process: the reaction of unexcited C{sub 60} with excited singlet N-methylacridinium hexafluorophosphate or with the biphenyl radical cation generated in the reaction with excited singlet N-methylacridinium hexafluorophosphate. The formation of C{sup +}{sub 60} with an electron acceptor in a homogeneous process has not so far been observed. The purpose of this work has been to study the quenching of triplet {sup 3}C{sub 60} with an electron acceptor, tetracyanoethylene (TCNE), which is known to oxidize unsaturated or aromatic hydrocarbons in photochemical reactions.

  6. ROTATIONAL QUENCHING OF ROTATIONALLY EXCITED H{sub 2}O IN COLLISIONS WITH He

    SciTech Connect

    Yang Benhui; Stancil, P. C.; Nagao, M.; Satomi, W.; Kimura, M. E-mail: stancil@physast.uga.edu

    2013-03-10

    Theoretical rotational quenching cross sections and rate coefficients of ortho- and para-H{sub 2}O due to collisions with He atoms are presented. The complete angular momentum close-coupling approach as well as the coupled-states approximation for the angular momentum decoupling was applied to solve the scattering problem for a large range of rotationally excited states of water. Results are obtained for quenching from initial levels 1{sub 1,0}, 2{sub 1,2}, 2{sub 2,1}, 3{sub 0,3}, 3{sub 1,2}, 3{sub 2,1}, 4{sub 1,4}, 3{sub 3,0}, and 4{sub 2,3} of ortho-H{sub 2}O and from initial levels 1{sub 1,1}, 2{sub 0,2}, 2{sub 1,1}, 2{sub 2,0}, 3{sub 1,3}, 3{sub 2,2}, 4{sub 0,4}, 4{sub 1,3}, and 3{sub 3,1} of para-H{sub 2}O for kinetic energies from 10{sup -5} to 10{sup 4} cm{sup -1}. State-to-state and total deexcitation cross sections and rate coefficients for temperatures between 0.1 and 3000 K are reported. The present state-to-state rate coefficients are found to be in good agreement with previous results obtained by Green and coworkers at high temperatures, but significant discrepancies are obtained at lower temperatures likely due to differences in the adopted potential energy surfaces. Astrophysical applications of the current rate coefficients are briefly discussed.

  7. Effect of gold nanoparticles on the fluorescence excitation spectrum of α-fetoprotein: Local environment dependent fluorescence quenching

    NASA Astrophysics Data System (ADS)

    Li, Jian-jun; Chen, Yu; Wang, A.-qing; Zhu, Jian; Zhao, Jun-wu

    2011-01-01

    The effect of colloid gold nanoparticles (AuNPs) on the fluorescence excitation spectrum of α-fetoprotein (AFP) has been investigated experimentally. The excitation spectral peaks of AFP with low concentration from 0.01 ng ml -1 to 12 ng ml -1 increase monotonically with increasing of AFP concentration. When some gold colloids were added to the AFP solution, the excitation peak at 285 nm decreases distinctly. By comparing the excitation peak intensity of AFP solution with gold colloids and without gold colloids at different AFP concentrations, the quenching effect from gold nanoparticle was more effective at lower AFP concentration. So the range of concentration from 0.01 ng ml -1 to 0.09 ng ml -1 will be the potential range of applications because of the higher sensitivity. The physical origin based on local field effect was investigated to illuminate this local environment dependent fluorescence quenching. The changing extent of quenching with different AFP concentrations can be attributed to the nonlinear decreasing of the local field factor of gold nanoparticles as a function of environmental dielectric constant.

  8. Collision quenching effects in nitrogen and helium excited by a 30-keV electron beam

    NASA Technical Reports Server (NTRS)

    Lillicrap, D. C.

    1973-01-01

    The quenching cross section for the 0-0 first negative band of nitrogen is determined for temperatures between 78 K and 300 K. As the temperature increases above 78 K, the quenching reaches a maximum at approximately 140 K and then decreases as 300 K is approached. At temperatures on the order of 5000 K, quenching is reported to increase with temperature and must therefore reach a minimum at some intermediate temperature between 300 K and 5000 K. By comparison, quenching of the 5016 A helium line increases continuously over the temperature range 78 K to 300 K.

  9. Optical excitation and quenching of photocurrent in single-crystal diamond

    NASA Astrophysics Data System (ADS)

    Chen, Jeson; Lourette, Sean; Rezai, Kristine; Kehayias, Pauli; Lake, Michael; Jarmola, Andrey; Nesladek, Milos; Bouchard, Louis; Hemmer, Philip; Budker, Dmitry

    2016-05-01

    Diamond has found important applications in optoelectronics including electron emitters, windows for high power devices, and x-ray photon detectors, thanks to its unique properties, such as a wide bandgap, high thermal conductance and broadband optical transmittance. It is thus of paramount importance to investigate the photoelectric properties of diamond in greater details. Here we report the observation of optical quenching of photocurrent in diamond using simultaneous illumination of pulsed and continuous wave lasers at the same wavelength and different wavelengths. The quenched photocurrent shows a recovery related to the external bias voltage, pulsed optical power and wavelength. The recovery of the quenched photocurrent provides information on the nature of the electron trap states in diamond. Current: Academia Sinica, Taiwan.

  10. HANDBOOK ON ADVANCED NONPHOTOCHEMICAL OXIDATION PROCESSES

    EPA Science Inventory

    The purpose of this handbook is to summarize commercial-scale system performance and cost data for advanced nonphotochemical oxidation (ANPO) treatment of contaminated water, air, and soil. Similar information from pilot-and bench-scale evaluations of ANPO processes is also inclu...

  11. Geometrical information on core-excited states obtained from interference quenching of vibrational states in resonant x-ray photoemission

    SciTech Connect

    Baev, A.; Gel'mukhanov, F.; Aagren, H.; Feifel, R.; Baessler, M.; Miron, C.; Bjoerneholm, O.; Karlsson, L.; Svensson, S.; Piancastelli, M.N.; Sorensen, S.L.; Naves de Brito, A.

    2003-02-01

    An interference quenching of the m=1 final state vibrational line in the resonant Auger decay of N 1s{yields}{pi}{sup *} core-excited N{sub 2} is observed and analyzed. The intensity ratio between the m=1 and m=0 vibrational levels of the X {sup 2}{sigma}{sub g}{sup +} final state shows a surprising nonmonotonic variation as a function of frequency detuning, going through a minimum with a complete suppression of m=1. We have developed a simple model which indicates a linear relation between the value of the detuning frequency for this minimum and the equilibrium bond distance of the core-excited state. This implies the possibility of determining the equilibrium bond distances for core-excited states to a high degree of accuracy. Simultaneously with the simple model we present a strict theory of the studied effect. This strict theory allows us to explore the accuracy of determining the bond length of the core-excited state from resonant Auger spectra. We obtain a weak influence of the core-hole lifetime on the determined bond length, whereas the number of intermediate vibrational states accounted for in the numerical simulations seems to be quite important.

  12. Preparation of stable excited states in an optical lattice via sudden quantum quench

    SciTech Connect

    Wang, Li; Chen, Shu; Hao, Yajiang

    2010-06-15

    We study how stable excited many-body states of the Bose-Hubbard model, including both the gaslike state for strongly attractive bosons and bound cluster state for repulsive bosons, can be produced with cold bosonic atoms in an one-dimensional optical lattice. Starting from the initial ground states of strongly interacting bosonic systems, we can achieve stable excited states of the systems with opposite interaction strength by suddenly switching the interaction to the opposite limit. By exactly solving dynamics of the Bose-Hubbard model, we demonstrate that the produced excited state can be a very stable dynamic state. This allows the experimental study of excited state properties of ultracold atoms system in optical lattices.

  13. Excitation induced spectroscopic study and quenching effect in cerium samarium codoped lithium aluminoborate glasses

    NASA Astrophysics Data System (ADS)

    Kaur, Parvinder; Kaur, Simranpreet; Singh, Gurinder Pal; Arora, Deepawali; Kumar, Sunil; Singh, D. P.

    2016-08-01

    Lithium aluminium borate host has been codoped with cerium and samarium to prepare glass by conventional melt quench technique. Their structural and spectroscopic investigation has been carried out using XRD, FTIR and density measurements. The UV-Vis absorption spectra and fluorescence spectra (λexc.=380 nm and 400 nm) have been studied for spectroscopic analysis. The amorphous nature of the prepared samples is shown by XRD. The density is increasing with addition of cerium at the expense of aluminium, keeping other components constant. FTIR study also shows the presence of compact and stable tetrahedral BO4 units thus supporting the density results. The UV- Vis absorption spectra show a shift of optical absorption edge towards longer wavelength along with an increase in intensity of peaks with rising samarium concentration. The fluorescence spectra show a blue shift and subsequent suppression of cerium peaks with addition of samarium.

  14. Quenching of the 2pnd Po1 doubly excited states of helium by a dc electric field

    NASA Astrophysics Data System (ADS)

    Bučar, K.; Žitnik, M.; Mihelič, A.; Penent, F.; Lablanquie, P.; Palaudoux, J.; Andrić, L.; Braune, M.; Püttner, R.

    2014-07-01

    The fluorescence yield quenching of low-lying doubly excited 2pnd Po1 states is observed to depend strongly on a dc electric field strength and its orientation with respect to the polarization of the incoming photon beam. The reduction of the yield accompanied by the lifetime shortening is attributed to the Stark mixing with the neighboring 2sns Se1 states, which redirects the 2pnd Po1 decay to the prompt autoionization channel. For n ≥4, the lifetimes decrease from several hundred picoseconds down to several tens of picoseconds when an electric field in the kV/cm range is applied parallel to the photon probe polarization. Practically no lifetime change is observed for polarization perpendicular to the electric field direction. The results of the complex-scaling calculations are in a good agreement with the experimental data.

  15. The study of excited oxygen molecule gas species production and quenching on thermal protection system materials

    NASA Technical Reports Server (NTRS)

    Nordine, Paul C.; Fujimoto, Gordon T.; Greene, Frank T.

    1987-01-01

    The detection of excited oxygen and ozone molecules formed by surface catalyzed oxygen atom recombination and reaction was investigated by laser induced fluorescence (LIF), molecular beam mass spectrometric (MBMS), and field ionization (FI) techniques. The experiment used partially dissociated oxygen flows from a microwave discharge at pressures in the range from 60 to 400 Pa or from an inductively coupled RF discharge at atmospheric pressure. The catalyst materials investigated were nickel and the reaction cured glass coating used for Space Shuttle reusable surface insulation tiles. Nonradiative loss processes for the laser excited states makes LIF detection of O2 difficult such that formation of excited oxygen molecules could not be detected in the flow from the microwave discharge or in the gaseous products of atom loss on nickel. MBMS experiments showed that ozone was a product of heterogeneous O atom loss on nickel and tile surfaces at low temperatures and that ozone is lost on these materials at elevated temperatures. FI was separately investigated as a method by which excited oxygen molecules may be conveniently detected. Partial O2 dissociation decreases the current produced by FI of the gas.

  16. Excited state kinetics in crystalline solids: self-quenching in nanocrystals of 4,4'-disubstituted benzophenone triplets occurs by a reductive quenching mechanism.

    PubMed

    Kuzmanich, Gregory; Simoncelli, Sabrina; Gard, Matthew N; Spänig, Fabian; Henderson, Bryana L; Guldi, Dirk M; Garcia-Garibay, Miguel A

    2011-11-01

    We report an efficient triplet state self-quenching mechanism in crystals of eight benzophenones, which included the parent structure (1), six 4,4'-disubstituted compounds with NH(2) (2), NMe(2) (3), OH (4), OMe (5), COOH (6), and COOMe (7), and benzophenone-3,3',4,4'-tetracarboxylic dianhydride (8). Self-quenching effects were determined by measuring their triplet-triplet lifetimes and spectra using femtosecond and nanosecond transient absorption measurements with nanocrystalline suspensions. When possible, triplet lifetimes were confirmed by measuring the phosphorescence lifetimes and with the help of diffusion-limited quenching with iodide ions. We were surprised to discover that the triplet lifetimes of substituted benzophenones in crystals vary over 9 orders of magnitude from ca. 62 ps to 1 ms. In contrast to nanocrystalline suspensions, the lifetimes in solution only vary over 3 orders of magnitude (1-1000 μs). Analysis of the rate constants of quenching show that the more electron-rich benzophenones are the most efficiently deactivated such that there is an excellent correlation, ρ = -2.85, between the triplet quenching rate constants and the Hammet σ(+) values for the 4,4' substituents. Several crystal structures indicate the existence of near-neighbor arrangements that deviate from the proposed ideal for "n-type" quenching, suggesting that charge transfer quenching is mediated by a relatively loose arrangement. PMID:21936539

  17. Quenching of highly vibrationally excited pyrimidine by collisions with CO{sub 2}

    SciTech Connect

    Johnson, Jeremy A.; Duffin, Andrew M.; Hom, Brian J.; Jackson, Karl E.; Sevy, Eric T.

    2008-02-07

    Relaxation of highly vibrationally excited pyrimidine (C{sub 4}N{sub 2}H{sub 4}) by collisions with carbon dioxide has been investigated using diode laser transient absorption spectroscopy. Vibrationally hot pyrimidine (E{sup '}=40 635 cm{sup -1}) was prepared by 248-nm excimer laser excitation, followed by rapid radiationless relaxation to the ground electronic state. The nascent rotational population distribution (J=58-80) of the 00{sup 0}0 ground state of CO{sub 2} resulting from collisions with hot pyrimidine was probed at short times following the excimer laser pulse. Doppler spectroscopy was used to measure the CO{sub 2} recoil velocity distribution for J=58-80 of the 00{sup 0}0 state. Rate constants and probabilities for collisions populating these CO{sub 2} rotational states were determined. The measured energy transfer probabilities, indexed by final bath state, were resorted as a function of {delta}E to create the energy transfer distribution function, P(E,E{sup '}), from E{sup '}-E{approx}1300-7000 cm{sup -1}. P(E,E{sup '}) is fitted to a single exponential and a biexponential function to determine the average energy transferred in a single collision between pyrimidine and CO{sub 2} and parameters that can be compared to previously studied systems using this technique, pyrazine/CO{sub 2}, C{sub 6}F{sub 6}/CO{sub 2}, and methylpyrazine/CO{sub 2}. P(E,E{sup '}) parameters for these four systems are also compared to various molecular properties of the donor molecules. Finally, P(E,E{sup '}) is analyzed in the context of two models, one which suggests that the shape of P(E,E{sup '}) is primarily determined by the low-frequency out-of-plane donor vibrational modes and one which suggests that the shape of P(E,E{sup '}) can be determined by how the donor molecule final density of states changes with {delta}E.

  18. Luminescence quenching of conductive Si nanocrystals via “Linkage emission”: Hopping-like propagation of infrared-excited Auger electrons

    SciTech Connect

    Ishii, Masashi; Crowe, Iain F.; Halsall, Matthew P.; Hamilton, Bruce; Knights, Andrew P.; Gwilliam, Russell M.

    2014-08-14

    Phosphorus (P) is an n-type dopant for conductive silicon nanocrystals (Si-nc's), the electrical activation of which may be monitored through a non-radiative Auger recombination process that quenches the Si-nc luminescence. We investigated this quenching mechanism through electrical measurements of Si-nc's. Infrared-excited Auger electron emission as the non-radiative process was directly probed and the dynamics of the process are determined from a frequency response analysis. To explain the dynamics, we propose a model in which Auger electrons with a low kinetic energy establish a local inter-nanocrystal conductance and the repetition of this local conductance results in a constant photocurrent (“linkage emission”). This emission becomes significant by electron filling in the Si-nc's owing to the electrical activation of P, which is consistent with observed luminescence quenching behavior. We found that the IR photo-excited emission is distinct from the thermally induced hopping conduction and show that confined, rather than trapped, charges are the source of the Auger electrons. Thus, the process consumes both confined charges and the recombination energy for Auger emission, which explains the luminescence quenching mechanism of Si-nc:P.

  19. Quench in the 1D Bose-Hubbard model: Topological defects and excitations from the Kosterlitz-Thouless phase transition dynamics

    PubMed Central

    Dziarmaga, Jacek; Zurek, Wojciech H.

    2014-01-01

    Kibble-Zurek mechanism (KZM) uses critical scaling to predict density of topological defects and other excitations created in second order phase transitions. We point out that simply inserting asymptotic critical exponents deduced from the immediate vicinity of the critical point to obtain predictions can lead to results that are inconsistent with a more careful KZM analysis based on causality – on the comparison of the relaxation time of the order parameter with the “time distance” from the critical point. As a result, scaling of quench-generated excitations with quench rates can exhibit behavior that is locally (i.e., in the neighborhood of any given quench rate) well approximated by the power law, but with exponents that depend on that rate, and that are quite different from the naive prediction based on the critical exponents relevant for asymptotically long quench times. Kosterlitz-Thouless scaling (that governs e.g. Mott insulator to superfluid transition in the Bose-Hubbard model in one dimension) is investigated as an example of this phenomenon. PMID:25091996

  20. Quenched Magnon excitations by oxygen sublattice reconstruction in (SrCuO2)n/(SrTiO3)2 superlattices.

    PubMed

    Dantz, M; Pelliciari, J; Samal, D; Bisogni, V; Huang, Y; Olalde-Velasco, P; Strocov, V N; Koster, G; Schmitt, T

    2016-01-01

    The recently discovered structural reconstruction in the cuprate superlattice (SrCuO2)n/(SrTiO3)2 has been investigated across the critical value of n = 5 using resonant inelastic x-ray scattering (RIXS). We find that at the critical value of n, the cuprate layer remains largely in the bulk-like two-dimensional structure with a minority of Cu plaquettes being reconstructed. The partial reconstruction leads to quenching of the magnons starting at the Γ-point due to the minority plaquettes acting as scattering points. Although comparable in relative abundance, the doped charge impurities in electron-doped cuprate superconductors do not show this quenching of magnetic excitations. PMID:27616448

  1. The OI/1S/ state - Its quenching by O2 and formation by the dissociative recombination of vibrationally excited O2/+/ ions

    NASA Technical Reports Server (NTRS)

    Zipf, E. C.

    1979-01-01

    The rate coefficient for the quenching of metastable O(1S) atoms by O2 was measured as a function of temperature from 250 to 550 K. The resulting Arrhenius expression correlates well with previous laboratory work. It is suggested that the much larger value of the rate coefficient inferred from an analysis of artificial auroral experiment, Precede, may be explained by overestimation of the contribution of O(1S) production from O2(+) dissociative recombination. The possibility that O(1S) atoms are produced only by the dissociative recombination of vibrationally excited O2(+) ions is examined; such excited ions would not exist in the Precede experiment because of the rapid cooling of the ions by resonant charge transfer processes.

  2. "Super-quenching" state protects Symbiodinium from thermal stress - Implications for coral bleaching.

    PubMed

    Slavov, Chavdar; Schrameyer, Verena; Reus, Michael; Ralph, Peter J; Hill, Ross; Büchel, Claudia; Larkum, Anthony W D; Holzwarth, Alfred R

    2016-06-01

    The global rise in sea surface temperatures causes regular exposure of corals to high temperature and high light stress, leading to worldwide disastrous coral bleaching events (loss of symbiotic dinoflagellates (Symbiodinium) from reef-building corals). Our picosecond chlorophyll fluorescence experiments on cultured Symbiodinium clade C cells exposed to coral bleaching conditions uncovered the transformations of the alga's photosynthetic apparatus (PSA) that activate an extremely efficient non-photochemical "super-quenching" mechanism. The mechanism is associated with a transition from an initially heterogeneous photosystem II (PSII) pool to a homogeneous "spillover" pool, where nearly all excitation energy is transferred to photosystem I (PSI). There, the inherently higher stability of PSI and high quenching efficiency of P(700)(+) allow dumping of PSII excess excitation energy into heat, resulting in almost complete cessation of photosynthetic electron transport (PET). This potentially reversible "super-quenching" mechanism protects the PSA against destruction at the cost of a loss of photosynthetic activity. We suggest that the inhibition of PET and the consequent inhibition of organic carbon production (e.g. sugars) in the symbiotic Symbiodinium provide a trigger for the symbiont expulsion, i.e. bleaching. PMID:26869375

  3. Excitation of C 60, solubilized in water by triton X-100 and γ-cyclodextrin, and subsequent charge separation via reductive quenching

    NASA Astrophysics Data System (ADS)

    Guldi, Dirk M.; Huie, Robert E.; Neta, Pedatsur; Hungerbühler, Hartmut; Asmus, Klaus-Dieter

    1994-07-01

    The excitation of C 60 incorporated in triton X-100 micelles has been studied by laser flash photolysis. Reductive quenching of triplet-excited 3C 60 by diazabicyclooctane (DABCO) has been established in the micellar assembly, in aqueous solution of the fullerene embedded in γ-cyclodextrin, in alcohols and non-polar toluene. In aqueous media potassium hexacyanoferrate(II) and potassium iodide have been employed in the reductive quenching process as well. The C 60- radical anion in all investigations has been characterized by its IR absorption. The formation and the half-life of C 60- have been shown to be strongly dependent on the polarity of the environment. By utilizing DABCO as a quencher a half-life of 440 μs has been observed in the micellar assembly, while the respective values in propan-2-ol and butan-1-ol are 110 and 98 μs, respectively. In aqueous solution the radical anion γ-CD/C 60- decays with a half-life of 59 μs and, in contrast, in the non-polar toluene no formation of any C 60-. could be detected. The results are consistent with a charge-separated 3C 60-quencher contact pair.

  4. LHCSR1 induces a fast and reversible pH-dependent fluorescence quenching in LHCII in Chlamydomonas reinhardtii cells.

    PubMed

    Dinc, Emine; Tian, Lijin; Roy, Laura M; Roth, Robyn; Goodenough, Ursula; Croce, Roberta

    2016-07-01

    To avoid photodamage, photosynthetic organisms are able to thermally dissipate the energy absorbed in excess in a process known as nonphotochemical quenching (NPQ). Although NPQ has been studied extensively, the major players and the mechanism of quenching remain debated. This is a result of the difficulty in extracting molecular information from in vivo experiments and the absence of a validation system for in vitro experiments. Here, we have created a minimal cell of the green alga Chlamydomonas reinhardtii that is able to undergo NPQ. We show that LHCII, the main light harvesting complex of algae, cannot switch to a quenched conformation in response to pH changes by itself. Instead, a small amount of the protein LHCSR1 (light-harvesting complex stress related 1) is able to induce a large, fast, and reversible pH-dependent quenching in an LHCII-containing membrane. These results strongly suggest that LHCSR1 acts as pH sensor and that it modulates the excited state lifetimes of a large array of LHCII, also explaining the NPQ observed in the LHCSR3-less mutant. The possible quenching mechanisms are discussed. PMID:27335457

  5. Laser excitation of O 2(b 1Σ g+, ν' = 0, 1, 2) - rates and channels of energy transfer and quenching

    NASA Astrophysics Data System (ADS)

    Wildt, J.; Bednarek, G.; Fink, E. H.; Wayne, R. P.

    1988-06-01

    Molecular oxygen was selectively excited to vibrational levels ν' =0, 1 and 2 of the b 1Σ g+ state by pulsed dye laser absorption in the (0,0), (1,0) and (2,0) bands of the b 1Σ g+ ← X 3Σ g- system in the near-infrared region. Time-resolved fluorescence was observed in the Δν=0 and -1 sequences of the b→X system near λ = 760 and 860 nm and in the (0,0) band of the a→X system at λ = 1270 nm. Lower limits have been deduced for the rate constants of vibrational relaxation in the b 1Σ g+ state and for electronic-to-electronic energy exchange of the b 1Σ g+ state energy between 16O 2 and 18O 2 isotopes. Rate constants for quenching of O 2 (b 1Σ g+, ν'=0) were remeasured for H 2, D 2, N 2, CO 2, and CH 4. From studies of the a→X emission intensity as a function of added gas pressure it was concluded that, with most gases, the b 1Σ g+ state is quenched to the a 1Δ g state with yields of ⩾ 90%. Measurements of the decay of the a→X band as a function of time at different O 2 pressures yielded a rate constant for self-quenching of the a 1Δ g state by O 2 of (1.5 ± 0.2) × 10 -18 cm 3 s -1.

  6. A novel Gaussian Binning (1GB) analysis of vibrational state distributions in highly excited H2O from reactive quenching of OH* by H2

    NASA Astrophysics Data System (ADS)

    Conte, Riccardo; Fu, Bina; Kamarchik, Eugene; Bowman, Joel M.

    2013-07-01

    As shown in experiments by Lester and co-workers [J. Chem. Phys. 110, 11117 (1999)], 10.1063/1.479053, the reactive quenching of OH* by H_2 produces highly excited H_2O. Previous limited analysis of quasiclassical trajectory calculations using standard Histogram Binning (HB) was reported [B. Fu, E. Kamarchik, and J. M. Bowman, J. Chem. Phys. 133, 164306 (2010)], 10.1063/1.3488167. Here, we examine the quantized internal state distributions of H_2O in more detail, using two versions of Gaussian Binning (denoted 1GB). In addition to the standard version of 1GB, which relies on the harmonic energies of the states (1GB-H), we propose a new and more accurate technique based on exact quantum vibrational energies (1GB-EQ). Data from about 42 000 trajectories from previous calculations that give excited water molecules are used in the two versions of 1GB as well as HB. For the vibrationally hot molecules considered in this study, the classical internal energy distribution serves as a benchmark to estimate the accuracy of the different binning methods analyzed. The 1GB discretization methods, especially the one using exact quantum energies, reconstruct the classical distribution much more accurately than HB and also the original, more elaborate Gaussian Binning method. Detailed quantum state distributions are presented for pure overtone excitations as well as several antisymmetric stretch distributions. The latter are focused on because the antisymmetric stretch has the largest emission oscillator strength of the three water modes.

  7. Excitation migration in fluctuating light-harvesting antenna systems.

    PubMed

    Chmeliov, Jevgenij; Trinkunas, Gediminas; van Amerongen, Herbert; Valkunas, Leonas

    2016-01-01

    Complex multi-exponential fluorescence decay kinetics observed in various photosynthetic systems like photosystem II (PSII) have often been explained by the reversible quenching mechanism of the charge separation taking place in the reaction center (RC) of PSII. However, this description does not account for the intrinsic dynamic disorder of the light-harvesting proteins as well as their fluctuating dislocations within the antenna, which also facilitate the repair of RCs, state transitions, and the process of non-photochemical quenching. Since dynamic fluctuations result in varying connectivity between pigment-protein complexes, they can also lead to non-exponential excitation decay kinetics. Based on this presumption, we have recently proposed a simple conceptual model describing excitation diffusion in a continuous medium and accounting for possible variations of the excitation transfer pathways. In the current work, this model is further developed and then applied to describe fluorescence kinetics originating from very diverse antenna systems, ranging from PSII of various sizes to LHCII aggregates and even the entire thylakoid membrane. In all cases, complex multi-exponential fluorescence kinetics are perfectly reproduced on the entire relevant time scale without assuming any radical pair equilibration at the side of the excitation quencher, but using just a few parameters reflecting the mean excitation energy transfer rate as well as the overall average organization of the photosynthetic antenna. PMID:25605669

  8. Photochemical Hydrogen Generation Initiated by Oxidative Quenching of the Excited Ru(bpy)3 (2+) * by a Bio-Inspired [2Fe2S] Complex.

    PubMed

    Na, Yong; Wei, Peicheng; Zhou, Li

    2016-07-18

    A diiron dithiolate complex 1 containing 1,8-naphthalic anhydride bridge was prepared, which possessed the lowest reduction potential for the synthetic diiron complexes modeled on the active site of [FeFe] hydrogenase reported so far. For the first time, oxidative quenching of the excited Ru(bpy)3 (2+) * through electron transfer to a bio-inspired [2Fe2S] complex was corroborated. Hydrogen evolution, driven by visible light, was successfully observed for a three-component system, consisting of Ru(bpy)3 (2+) , complex 1, and EDTA as electron donor in aqueous/organic media. These results provide a basis and also opportunity to develop a photo water splitting system employing Fe-based catalysts without sacrificial electron donors. PMID:26879325

  9. Quenching of the 1.0 and 2.3 µm excited electronic states of PuF6 at room temperature by selected rare gases and small polyatomic molecules

    NASA Astrophysics Data System (ADS)

    Barefield, J. E., II; Rice, W. W.; Dye, B. A.

    1985-07-01

    The quenching rate constants kq for the following rare gases and small molecules (He, Ar, Xe, H2, D2, N2, O2, F2, Cl2, HF, CO, CO2, CH4, CHF3, CF4, NO2F, SOF4, SF6, and UF6) are reported in units of cm3 molecule-1 s-1 for both the 1.0 and 2.3 μm excited electronic states of PuF6 (see Table I). The self-quenching rate constants for PuF6 at room temperture are kq(1.0 μm) =1.12±0.01×10-12 and kq(2.3 μm)=5.01±0.11×10-15 cm3 molecule-1 s-1. The magnitude of the quenching rate constants for most all of the gases considered above suggest that the dominant process in the collisional deexcitation of excited state PuF*6 (1.0 or 2.3 μm) molecules at room temperature is physical quenching (i.e., E-T or electronic-to-translational collisional energy transfer). Our data also indicate that E-V (electronic-to-vibrational) energy transfer is responsible for the efficient quenching of electronically excited PuF6 by H2, HF, CH4, and CHF3. There is also evidence from our data that the efficient quenching of the excited states of PuF6 by ground state PuF6 molecules proceeds via resonant energy transfer.

  10. Identification and quantification of carbamate pesticides in dried lime tree flowers by means of excitation-emission molecular fluorescence and parallel factor analysis when quenching effect exists.

    PubMed

    Rubio, L; Ortiz, M C; Sarabia, L A

    2014-04-11

    A non-separative, fast and inexpensive spectrofluorimetric method based on the second order calibration of excitation-emission fluorescence matrices (EEMs) was proposed for the determination of carbaryl, carbendazim and 1-naphthol in dried lime tree flowers. The trilinearity property of three-way data was used to handle the intrinsic fluorescence of lime flowers and the difference in the fluorescence intensity of each analyte. It also made possible to identify unequivocally each analyte. Trilinearity of the data tensor guarantees the uniqueness of the solution obtained through parallel factor analysis (PARAFAC), so the factors of the decomposition match up with the analytes. In addition, an experimental procedure was proposed to identify, with three-way data, the quenching effect produced by the fluorophores of the lime flowers. This procedure also enabled the selection of the adequate dilution of the lime flowers extract to minimize the quenching effect so the three analytes can be quantified. Finally, the analytes were determined using the standard addition method for a calibration whose standards were chosen with a D-optimal design. The three analytes were unequivocally identified by the correlation between the pure spectra and the PARAFAC excitation and emission spectral loadings. The trueness was established by the accuracy line "calculated concentration versus added concentration" in all cases. Better decision limit values (CCα), in x0=0 with the probability of false positive fixed at 0.05, were obtained for the calibration performed in pure solvent: 2.97 μg L(-1) for 1-naphthol, 3.74 μg L(-1) for carbaryl and 23.25 μg L(-1) for carbendazim. The CCα values for the second calibration carried out in matrix were 1.61, 4.34 and 51.75 μg L(-1) respectively; while the values obtained considering only the pure samples as calibration set were: 2.65, 8.61 and 28.7 μg L(-1), respectively. PMID:24745733

  11. Photoprotective capacity of non-photochemical quenching in plants acclimated to different light intensities.

    PubMed

    Ware, Maxwell A; Belgio, Erica; Ruban, Alexander V

    2015-12-01

    Arabidopsis plants grown at low light were exposed to a gradually increasing actinic light routine. This method allows for the discerning of the photoprotective component of NPQ, pNPQ and photoinhibition. They exhibited lower values of Photosystem II (PSII) yield in comparison to high-light grown plants, and higher calculated dark fluorescence level (F'o calc.) than the measured one (F'o act.). As a result, in low-light grown plants, the values of qP measured in the dark appeared higher than 1. Normally, F'o act. and F'o calc. match well at moderate light intensities but F'o act. becomes higher at increasing intensities due to reaction centre (RCII) damage; this indicates the onset of photoinhibition. To explain the unusual increase of qP in the dark in low-light grown plants, we have undertaken an analysis of PSII antenna size using biochemical and spectroscopic approaches. Sucrose gradient separation of thylakoid membrane complexes and fast fluorescence induction experiments illustrated that the relative PSII cross section does not increase appreciably with the rise in PSII antenna size in the low-light grown plants. This suggests that part of the increased LHCII antenna is less efficiently coupled to the RCII. A model based upon the existence of an uncoupled population LHCII is proposed to explain the discrepancies in calculated and measured values of F'o. PMID:25702085

  12. Chlorophyll fluorescence quenching during ozone exposure of leaves of Phaseolus vulgaris (pinto)

    SciTech Connect

    Guralnick, L.J. ); Miller, R.; Heath, R.L. )

    1990-05-01

    During ozone exposure, observations have noted an initial decrease in CO{sub 2} uptake followed by a decrease in stomatal conductance. We examined this response utilizing the technique of fluorescence quenching. Fourteen day old plants were exposed to 0.3 ul/l ozone for 1 hour. Fluorescence quenching was monitored using the Hanstech modulated fluorescence system. This enabled us to measure changes in photochemical quenching (qQ) and non-photochemical quenching (qE) in control and ozone treated plants. Results have indicated no differences in qQ and qE between ozone treated and control plants. We are initiating further studies utilizing different ozone levels.

  13. Photosystem II reaction centre quenching: mechanisms and physiological role.

    PubMed

    Ivanov, Alexander G; Sane, Prafullachandra V; Hurry, Vaughan; Oquist, Gunnar; Huner, Norman P A

    2008-01-01

    Dissipation of excess absorbed light energy in eukaryotic photoautotrophs through zeaxanthin- and DeltapH-dependent photosystem II antenna quenching is considered the major mechanism for non-photochemical quenching and photoprotection. However, there is mounting evidence of a zeaxanthin-independent pathway for dissipation of excess light energy based within the PSII reaction centre that may also play a significant role in photoprotection. We summarize recent reports which indicate that this enigma can be explained, in part, by the fact that PSII reaction centres can be reversibly interconverted from photochemical energy transducers that convert light into ATP and NADPH to efficient, non-photochemical energy quenchers that protect the photosynthetic apparatus from photodamage. In our opinion, reaction centre quenching complements photoprotection through antenna quenching, and dynamic regulation of photosystem II reaction centre represents a general response to any environmental condition that predisposes the accumulation of reduced Q(A) in the photosystem II reaction centres of prokaryotic and eukaryotic photoautotrophs. Since the evolution of reaction centres preceded the evolution of light harvesting systems, reaction centre quenching may represent the oldest photoprotective mechanism. PMID:18821028

  14. Nonphotochemical base-catalyzed hydroxylation of 2,6-dichloroquinone by H2O2 occurs by a radical mechanism.

    PubMed

    Franzen, Stefan; Sasan, Koroush; Sturgeon, Bradley E; Lyon, Blake J; Battenburg, Benjamin J; Gracz, Hanna; Dumariah, Rania; Ghiladi, Reza

    2012-02-01

    Kinetic and structural studies have shown that peroxidases are capable of the oxidation of 2,4,6-trichlorophenol (2,4,6-TCP) to 2,6-dichloro-1,4-benzoquinone (2,6-DCQ). Further reactions of 2,6-DCQ in the presence of H(2)O(2) and OH(-) yield 2,6-dichloro-3-hydroxy-1,4-benzoquinone (2,6-DCQOH). The reactions of 2,6-DCQ have been monitored spectroscopically [UV-visible and electron spin resonance (ESR)] and chromatographically. The hydroxylation product, 2,6-DCQOH, has been observed by UV-visible and characterized structurally by (1)H and (13)C NMR spectroscopy. The results are consistent with a nonphotochemical base-catalyzed oxidation of 2,6-DCQ at pH > 7. Because H(2)O(2) is present in peroxidase reaction mixtures, there is also a potential role for the hydrogen peroxide anion (HOO(-)). However, in agreement with previous work, we observe that the nonphotochemical epoxidation by H(2)O(2) at pH < 7 is immeasurably slow. Both room-temperature ESR and rapid-freeze-quench ESR methods were used to establish that the dominant nonphotochemical mechanism involves formation of a semiquinone radical (base -catalyzed pathway), rather than epoxidation (direct attack by H(2)O(2) at low pH). Analysis of the kinetics using an Arrhenius model permits determination of the activation energy of hydroxylation (E(a) = 36 kJ/mol), which is significantly lower than the activation energy of the peroxidase-catalyzed oxidation of 2,4,6-TCP (E(a) = 56 kJ/mol). However, the reaction is second order in both 2,6-DCQ and OH(-) so that its rate becomes significant above 25 °C due to the increased rate of formation of 2,6-DCQ that feeds the second-order process. The peroxidase used in this study is the dehaloperoxidase-hemoglobin (DHP A) from Amphitrite ornata , which is used to study the effect of a catalyst on the reactions. The control experiments and precedents in studies of other peroxidases lead to the conclusion that hydroxylation will be observed following any process that leads to the

  15. Photochemical and Nonphotochemical Transformations of Cysteine with Dissolved Organic Matter.

    PubMed

    Chu, Chiheng; Erickson, Paul R; Lundeen, Rachel A; Stamatelatos, Dimitrios; Alaimo, Peter J; Latch, Douglas E; McNeill, Kristopher

    2016-06-21

    Cysteine (Cys) plays numerous key roles in the biogeochemistry of natural waters. Despite its importance, a full assessment of Cys abiotic transformation kinetics, products and pathways under environmental conditions has not been conducted. This study is a mechanistic evaluation of the photochemical and nonphotochemical (dark) transformations of Cys in solutions containing chromophoric dissolved organic matter (CDOM). The results show that Cys underwent abiotic transformations under both dark and irradiated conditions. Under dark conditions, the transformation rates of Cys were moderate and were highly pH- and temperature-dependent. Under UVA or natural sunlight irradiations, Cys transformation rates were enhanced by up to two orders of magnitude compared to rates under dark conditions. Product analysis indicated cystine and cysteine sulfinic acid were the major photooxidation products. In addition, this study provides an assessment of the contributions of singlet oxygen, hydroxyl radical, hydrogen peroxide, and triplet dissolved organic matter to the CDOM-sensitized photochemical oxidation of Cys. The results suggest that another unknown pathway was dominant in the CDOM-sensitized photodegradation of Cys, which will require further study to identify. PMID:27172378

  16. Nonphotochemical hole burning and dispersive kinetics in amorphous solids

    SciTech Connect

    Kenney, M.J.

    1990-09-21

    Results covering burn intensities in the nW to {mu}W/cm{sup 2} range, of dispersive hole growth kinetics are reported for Oxazine 720 in glycerol glasses and polyvinyl alcohol polymer films and their deuterated analogues. A theoretical model which employs a distribution function for the hole burning rate constant based upon a Gaussian distribution for the tunnel parameter is shown to accurately describe the kinetic data. This model incorporates the linear electron-phonon coupling. A method for calculating the nonphotochemical quantum yield is presented which utilizes the Gaussian distribution of tunnel parameters. The quantum yield calculation can be extended to determine a quantum yield as a function of hole depth. The effect of spontaneous hole filling is shown to be insignificant over the burn intensity range studied. Average relaxation rates for hole burning are {approximately}8 orders of magnitude greater than for hole filling. The dispersive kinetics of hole burning are observed to be independent over the temperature range of these experiments, 1.6 to 7.0 K. 6 refs., 20 figs., 1 tab.

  17. Nonphotochemical hole burning of the reaction center of Rhodopseudomonas viridis

    SciTech Connect

    Reddy, N.R.S.; Kolaczkowski, S.V.; Small, G.J. )

    1993-07-01

    Reddy et al. (Science, accepted) have reported persistent, nonphotochemical hole-burned (NPHB) spectra for the Q[sub y] states of the reaction center of Rhodopseudomonas viridis. The photoinduced structural transformation was shown to be highly localized on the special pair. This transformation leads to a red shift of the special pair's lowest-energy absorption band, P960, of 150 cm[sup [minus]1] and a comparable blue shift for a state at 850 nm, which, as a consequence, could be assigned as being most closely associated with the upper dimer component. Additional experimental results are presented here together with a theoretical analysis of the extent to which the NPHB spectra provide information on the contribution from the bacteriochlorophyll monomers of the special pair to the Q[sub y] states that absorb higher in energy than P960. Structured photochemical hole-burned (PHB) spectra of P960 are also presented that underscore the importance of strong electron-phonon coupling from a broad distribution of modes with a mean frequency of 30 cm[sup [minus]1] for an understanding of the P960 absorption profile. These spectra also identify the zero-phonon hole of the strongly damped special pair marker mode (145 cm[sup [minus]1]) and its associated phonon sideband structure. Calculated spectra are presented which are in good agreement with the experimental PHB spectra. 30 refs., 6 figs., 4 tabs.

  18. LHC magnet quench protection system

    NASA Astrophysics Data System (ADS)

    Coull, L.; Hagedorn, D.; Remondino, V.; Rodriguez-Mateos, F.

    1994-07-01

    The quench protection system for the superconducting magnets of the CERN Large Hadron Collider (LHC) is described. The system is based on the so called 'cold diode' concept. In a group of series connected magnets if one magnet quenches then the magnetic energy of all the magnets will be dissipated in the quenched magnet so destroying it. This is avoided by by-passing the quenched magnet and then rapidly de-exciting the unquenched magnets. For the LHC machine it is foreseen to use silicon diodes situated inside the cryostat as by-pass elements - so called 'cold diodes'. The diodes are exposed to some 50 kGray of radiation during a 10 year operation life-time. The high energy density of the LHC magnets (500 kJ/m) coupled with the relatively slow propagation speed of a 'natural' quench (10 to 20 m/s) can lead to excessive heating of the zone where the quench started and to high internal voltages. It is therefore necessary to detect quickly the incipient quench and fire strip heaters which spread the quench out more quickly over a large volume of the magnet. After a quench the magnet chain must be de-excited rapidly to avoid spreading the quench to other magnets and over-heating the by-pass diode. This is done by switching high-power energy-dump resistors in series with the magnets. The LHC main ring magnet will be divided into 16 electrically separated units which has important advantages.

  19. Spectral analysis on origination of the bands at 437 nm and 475.5 nm of chlorophyll fluorescence excitation spectrum in Arabidopsis chloroplasts.

    PubMed

    Zeng, Lizhang; Wang, Yongqiang; Zhou, Jun

    2016-05-01

    Chlorophyll fluorescence has been often used as an intrinsic optical molecular probe to study photosynthesis. In this study, the origin of bands at 437 and 475.5 nm in the chlorophyll fluorescence excitation spectrum for emission at 685 nm in Arabidopsis chloroplasts was investigated using various optical analysis methods. The results revealed that this fluorescence excitation spectrum was related to the absorption characteristics of pigment molecules in PSII complexes. Moreover, the excitation band centred at 475.5 nm had a blue shift, but the excitation band at 437 nm changed relatively less due to induction of non-photochemical quenching (NPQ). Furthermore, fluorescence emission spectra showed that this blue shift occurred when excitation energy transfer from both chlorophyll b (Chl b) and carotenoids (Cars) to chlorophyll a (Chl a) was blocked. These results demonstrate that the excitation band at 437 nm was mainly contributed by Chl a, while the excitation band at 475.5 nm was mainly contributed by Chl b and Cars. The chlorophyll fluorescence excitation spectrum, therefore, could serve as a useful tool to describe specific characteristics of light absorption and energy transfer between light-harvesting pigments. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26358732

  20. Translational and rotational excitation of the CO{sub 2}(00{sup 0}0) vibrationless state in the collisional quenching of highly vibrationally excited 2-methylpyrazine: Kinetics and dynamics of large energy transfers

    SciTech Connect

    Sevy, Eric T.; Rubin, Seth M.; Lin, Zhen; Flynn, George W.

    2000-09-22

    The relaxation of highly vibrationally excited methylpyrazine (C{sub 5}N{sub 2}H{sub 6}) by collisions with CO{sub 2} molecules has been investigated over the temperature range 243-364 K using diode laser transient absorption spectroscopy. Particular focus is placed on understanding both the dynamical features and the kinetics of collisions which are accompanied by large energy transfers into the CO{sub 2} rotational and translational degrees of freedom. Vibrationally hot methylpyrazine (E{sup '}=40 987 cm{sup -1}) was prepared by 248 nm excimer laser pumping, followed by rapid radiationless transitions to the ground electronic state. The nascent rotational population distributions (J=58-80) of the 00{sup 0}0 ground state of CO{sub 2} resulting from collisions with hot methylpyrazine were probed at short times following the excimer laser pulse. Doppler spectroscopy was used to measure the distributions of CO{sub 2} recoil velocities for individual rotational levels of the 00{sup 0}0 state. In addition, the temperature dependence of the state resolved, absolute rate constants for collisions populating high J states of CO{sub 2} was determined. The rotational population distributions, distributions of recoil velocities, and quenching rates for production of CO{sub 2} high J states (J=58-80) exhibit a very weak temperature dependence. The slight temperature dependence indicates that CO{sub 2} molecules which scatter into high J states of the ground vibrationless level originate from rotational levels near the mean of the precollision thermal rotational distribution. A gap law model is used to estimate the average initial rotational state and velocity of the CO{sub 2} bath, which allows for the calculation of the energy transfer magnitudes, {delta}E. The measured energy transfer probabilities which are indexed by final bath state are resorted as a function of {delta}E to create the energy transfer distribution function, P(E,E{sup '}) from E{sup '}-E{approx}1500-6000 cm

  1. Enantioselective excited-state quenching of racemic Tb (III) and Eu (III) Tris (pyridine-2,6-dicarboxylate) by vitamin B 12 derivatives

    NASA Astrophysics Data System (ADS)

    Meskers, Stefan C. J.; Dekkers, Harry P. J. M.

    1999-08-01

    Enantioselectivity in the dynamic quenching of the luminescence of the Δ and Λ enantiomers of racemic Tb(III)(pyridine-2,6-dicarboxylate=DPA) 33- and Eu(DPA) 33- by a series of corrinoids is demonstrated by time resolved luminescence and circular-polarization-of-luminescence (CPL) spectroscopy. Studied are cyanocobalamin (vitamin B 12), aquacobalamin (B 12a) and its conjugated base hydroxocobalamin (HOCbl), dicyanocobinamide ((CN) 2Cbi) and the heptamethyl ester of dicyanocobyrinic acid ((CN) 2Cby(OMe) 7). For this set of quenchers (Q), the diastereomeric quenching rate constants ( kqΔ and kqΛ) are reported together with the degree of enantioselectivity Eq=( kqΔ- kqΛ)/( kqΔ+ kqΛ). In the systems with Tb, values of the average rate constant kqavg(=( kqΔ+ kqΛ)/2) are 1.0, 2.9 and 0.53 10 8 M -1 s -1 for CNCbl, (CN) 2Cbi, (CN) 2Cby(OMe) 7 with Eq=-0.24, -0.20, +0.01 (standard error of Eq is 0.01). The quenching by B 12a is strongly dependent on pH and ionic strength ( I); when I=12 mM we find kqavg=5.3, Eq=-0.23 at pH 6.7 and kqavg=1.3, Eq=-0.27 at pH 8.9. Corresponding rates for Eu are 0.41, 27, 3.4 10 7 M -1 s -1 and for B 12a, 7.3 and 1.2 10 7 M -1 s -1, corresponding values for Eq -0.27, -0.29, +0.02, -0.21 and -0.29. The quenching reaction is modeled as a pre-equilibrium involving the formation of an encounter complex (association constant K) followed by the actual electronic energy transfer step (rate ket). By relating the quenching data with molecular structure it is argued that the binding in the encounter complex involves two hydrogen bonds between the uncoordinated carboxylate oxygen atom of two DPA ligands of Ln(DPA) 33- and two amide groups of the corrinoid, presumably involving the a and g, the a and b, or the b and g side chains. For some corrinoid/Ln(DPA) 33- complexes the association constants and enantioselectivities in the ground state are known (Spectrochimica Acta 55A (1999) 1837-1855), which allows for an estimate of the average rate of

  2. Molecular insights into Zeaxanthin-dependent quenching in higher plants

    PubMed Central

    Xu, Pengqi; Tian, Lijin; Kloz, Miroslav; Croce, Roberta

    2015-01-01

    Photosynthetic organisms protect themselves from high-light stress by dissipating excess absorbed energy as heat in a process called non-photochemical quenching (NPQ). Zeaxanthin is essential for the full development of NPQ, but its role remains debated. The main discussion revolves around two points: where does zeaxanthin bind and does it quench? To answer these questions we have followed the zeaxanthin-dependent quenching from leaves to individual complexes, including supercomplexes. We show that small amounts of zeaxanthin are associated with the complexes, but in contrast to what is generally believed, zeaxanthin binding per se does not cause conformational changes in the complexes and does not induce quenching, not even at low pH. We show that in NPQ conditions zeaxanthin does not exchange for violaxanthin in the internal binding sites of the antennas but is located at the periphery of the complexes. These results together with the observation that the zeaxanthin-dependent quenching is active in isolated membranes, but not in functional supercomplexes, suggests that zeaxanthin is acting in between the complexes, helping to create/participating in a variety of quenching sites. This can explain why none of the antennas appears to be essential for NPQ and the multiple quenching mechanisms that have been observed in plants. PMID:26323786

  3. Transient Loschmidt echo in quenched Ising chains

    NASA Astrophysics Data System (ADS)

    Lupo, Carla; Schiró, Marco

    2016-07-01

    We study the response to sudden local perturbations of highly excited quantum Ising spin chains. The key quantity encoding this response is the overlap between time-dependent wave functions, which we write as a transient Loschmidt Echo. Its asymptotics at long time differences contain crucial information about the structure of the highly excited nonequilibrium environment induced by the quench. We compute the echo perturbatively for a weak local quench but for arbitrarily large global quench, using a cumulant expansion. Our perturbative results suggest that the echo decays exponentially, rather than power law as in the low-energy orthogonality catastrophe, a further example of quench-induced decoherence already found in the case of quenched Luttinger liquids. The emerging decoherence scale is set by the strength of the local potential and the bulk excitation energy.

  4. Analysis of LhcSR3, a protein essential for feedback de-excitation in the green alga Chlamydomonas reinhardtii.

    PubMed

    Bonente, Giulia; Ballottari, Matteo; Truong, Thuy B; Morosinotto, Tomas; Ahn, Tae K; Fleming, Graham R; Niyogi, Krishna K; Bassi, Roberto

    2011-01-01

    In photosynthetic organisms, feedback dissipation of excess absorbed light energy balances harvesting of light with metabolic energy consumption. This mechanism prevents photodamage caused by reactive oxygen species produced by the reaction of chlorophyll (Chl) triplet states with O₂. Plants have been found to perform the heat dissipation in specific proteins, binding Chls and carotenoids (Cars), that belong to the Lhc family, while triggering of the process is performed by the PsbS subunit, needed for lumenal pH detection. PsbS is not found in algae, suggesting important differences in energy-dependent quenching (qE) machinery. Consistent with this suggestion, a different Lhc-like gene product, called LhcSR3 (formerly known as LI818) has been found to be essential for qE in Chlamydomonas reinhardtii. In this work, we report the production of two recombinant LhcSR isoforms from C. reinhardtii and their biochemical and spectroscopic characterization. We found the following: (i) LhcSR isoforms are Chl a/b- and xanthophyll-binding proteins, contrary to higher plant PsbS; (ii) the LhcSR3 isoform, accumulating in high light, is a strong quencher of Chl excited states, exhibiting a very fast fluorescence decay, with lifetimes below 100 ps, capable of dissipating excitation energy from neighbor antenna proteins; (iii) the LhcSR3 isoform is highly active in the transient formation of Car radical cation, a species proposed to act as a quencher in the heat dissipation process. Remarkably, the radical cation signal is detected at wavelengths corresponding to the Car lutein, rather than to zeaxanthin, implying that the latter, predominant in plants, is not essential; (iv) LhcSR3 is responsive to low pH, the trigger of non-photochemical quenching, since it binds the non-photochemical quenching inhibitor dicyclohexylcarbodiimide, and increases its energy dissipation properties upon acidification. This is the first report of an isolated Lhc protein constitutively active in

  5. An alternative method for correcting fluorescence quenching

    NASA Astrophysics Data System (ADS)

    Biermann, L.; Guinet, C.; Bester, M.; Brierley, A.; Boehme, L.

    2015-01-01

    Under high light intensity, phytoplankton protect their photosystems from bleaching through non-photochemical quenching processes. The consequence of this is suppression of fluorescence emission, which must be corrected when measuring in situ yield with fluorometers. We present data from the Southern Ocean, collected over five austral summers by 19 southern elephant seals tagged with fluorometers. Conventionally, fluorescence data collected during the day (quenched) were corrected using the limit of the mixed layer, assuming that phytoplankton are uniformly mixed from the surface to this depth. However, distinct deep fluorescence maxima were measured in approximately 30% of the night (unquenched) data. To account for the evidence that chlorophyll is not uniformly mixed in the upper layer, we propose correcting from the limit of the euphotic zone, defined as the depth at which photosynthetically available radiation is ~ 1% of the surface value. Mixed layer depth exceeded euphotic depth over 80% of the time. Under these conditions, quenching was corrected from the depth of the remotely derived euphotic zone Zeu, and compared with fluorescence corrected from the depth of the density-derived mixed layer. Deep fluorescence maxima were evident in only 10% of the day data when correcting from mixed layer depth. This was doubled to 21% when correcting from Zeu, more closely matching the unquenched (night) data. Furthermore, correcting from Zeu served to conserve non-uniform chlorophyll features found between the 1% light level and mixed layer depth.

  6. Modeling of fluorescence quenching by lutein in the plant light-harvesting complex LHCII.

    PubMed

    Duffy, C D P; Chmeliov, J; Macernis, M; Sulskus, J; Valkunas, L; Ruban, A V

    2013-09-26

    Photoprotective non-photochemical quenching (NPQ) in higher plants is the result of the formation of energy quenching traps in the light-harvesting antenna of photosystem II (PSII). It has been proposed that this quenching trap is a lutein molecule closely associated with the chlorophyll terminal emitter of the major light-harvesting complex LHCII. We have used a combination of time-dependent density functional theory (TD-DFT) and the semiempirical MNDO-CAS-CI method to model the chlorophyll-lutein energy transfer dynamics of the highly quenched crystal structure of LHCII. Our calculations reveal that the incoherent "hopping" of energy from Chla612 to the short-lived, dipole forbidden 2(1)A(g)(-) state of lutein620 accounts for the strong fluorescence quenching observed in these crystals. This adds weight to the argument that the same dissipative pathway is responsible for in vivo NPQ. PMID:23234311

  7. Assessment of the impact of photosystem I chlorophyll fluorescence on the pulse-amplitude modulated quenching analysis in leaves of Arabidopsis thaliana.

    PubMed

    Giovagnetti, Vasco; Ware, Maxwell A; Ruban, Alexander V

    2015-08-01

    In their natural environment, plants are exposed to varying light conditions, which can lead to a build-up of excitation energy in photosystem (PS) II. Non-photochemical quenching (NPQ) is the primary defence mechanism employed to dissipate this excess energy. Recently, we developed a fluorescence-quenching analysis procedure that enables the protective effectiveness of NPQ in intact Arabidopsis leaves to be determined. However, pulse-amplitude modulation measurements do not currently allow distinguishing between PSII and PSI fluorescence levels. Failure to account for PSI contribution is suggested to lead to inaccurate measurements of NPQ and, particularly, maximum PSII yield (F v/F m). Recently, Pfündel et al. (Photosynth Res 114:189-206, 2013) proposed a method that takes into account PSI contribution in the measurements of F o fluorescence level. However, when PSI contribution was assumed to be constant throughout the induction of NPQ, we observed lower values of the measured minimum fluorescence level ([Formula: see text]) than those calculated according to the formula of Oxborough and Baker (Photosynth Res 54:135-142 1997) ([Formula: see text]), regardless of the light intensity. Therefore, in this work, we propose a refined model to correct for the presence of PSI fluorescence, which takes into account the previously observed NPQ in PSI. This method efficiently resolves the discrepancies between measured and calculated F o' produced by assuming a constant PSI fluorescence contribution, whilst allowing for the correction of the maximum PSII yield. PMID:25613087

  8. Luminescence Decay Times and Bimolecular Quenching: An Ultrafast Kinetics Experiment

    ERIC Educational Resources Information Center

    Demas, J. N.

    1976-01-01

    Describes the theory, apparatus, and procedure for an experiment that measures the bimolecular quenching constant for the deactivation of an excited ruthenium ion complex using dissolved oxygen. (MLH)

  9. Atrazine resistance entails a limited xanthophyll cycle activity, a lower PSII efficiency and an altered pattern of excess excitation dissipation.

    PubMed

    Váradi, Gyula; Polyánka, Hilda; Darkó, Eva; Lehoczki, Endre

    2003-05-01

    Atrazine-resistant (AR) weeds have a modified D1 protein structure, with a Ser264-->Gly mutation on the D1 protein, near the plastoquinone binding niche. The photosynthetic performance, the light response of the xanthophyll cycle and chlorophyll fluorescence quenching-related parameters were compared in attached leaves of susceptible (S) and AR biotypes of the C3 dicot Chenopodium album L., Epilobium adenocaulon Hausskn., Erigeron canadensis L., Senecio vulgaris L. and Solanum nigrum L. and the C4 dicot Amaranthus retroflexus L. grown under natural high-light conditions. No significant difference in CO2 assimilation rate per leaf area unit was found between the S and AR biotypes of the investigated C3 plants, whereas the AR biotype of A. retroflexus exhibited a relatively poor photosynthetic performance. The D1 protein mutant plants expressed a reduced activity of light-stimulated zeaxanthin formation. Neither the lower violaxanthin de-epoxidase activity nor the depletion of ascorbate seems to be the cause of the lower in vivo zeaxanthin formation in the AR plants. All the D1 mutant weeds had limited light-induced non-photochemical (NPQ) and photochemical (qP) quenching capacities, and displayed a higher photosensitivity, as characterized by the ratio (1-qP)/NPQ and a higher susceptibility to photoinhibition. Analysis of the chlorophyll fluorescence parameters showed that a lower proportion of excitation energy was allocated to PSII photochemistry, while a higher excess of excitation remained in the AR weeds relative to the S plants. PMID:12702013

  10. An optimised method for correcting quenched fluorescence yield

    NASA Astrophysics Data System (ADS)

    Biermann, L.; Guinet, C.; Bester, M.; Brierley, A.; Boehme, L.

    2014-05-01

    Under high light intensity, phytoplankton protect their photosystems from bleaching through non-photochemical quenching processes. The consequence of this is suppression of fluorescence emission, which must be corrected when measuring in situ yield with fluorometers. Previously, this has been done using the limit of the mixed layer, assuming that phytoplankton are uniformly mixed from the surface to this depth. However, the assumption of homogeneity is not robust in oceanic regimes that support deep chlorophyll maxima. To account for these features, we correct from the limit of the euphotic zone, defined as the depth at which light is at ~1% of the surface value. This method was applied to fluorescence data collected by eleven animal-borne fluorometers deployed in the Southern Ocean over four austral summers. Six tags returned data showing evidence of deep chlorophyll features. Using the depth of the euphotic layer, quenching was corrected without masking subsurface fluorescence signals.

  11. Relationship between efficiency of photosynthetic energy conversion and chlorophyll fluorescence quenching in upland cotton (Gossypium hirsutum L.).

    PubMed

    Schäfer, C; Björkman, O

    1989-06-01

    The relationship between components of non-photochemical quenching of chlorophyll fluorescence yield (qNP) and dissipation of excessive excitation energy was determined in cotton leaves using concurrent measurements of fluorescence and gas-exchange at 2% and 20% O2 under a range of photon flux densities and CO2 pressures. A nearly stoichiometric relationship was obtained between dissipation of energy not used in photosynthetic CO2 fixation or photorespiration and qNP provided that a component, probably associated with state transitions, was not included in qNP. Although two distinct components of qNP were resolved on the basis of their relaxation kinetics, both components appear effective in energy dissipation. The photon yield of "open" photosystem-II reaction centers decreased linearly with increases in qNP, indicating that much of the energy dissipation occurs in the pigment bed. However, increases in qNP appear dependent on the redox state of these centers. The results are discussed in relation to current hypotheses of the molecular basis of non-radiative energy dissipation. It is concluded that determinations of qNP can provide a quantitative measure of the dissipation of excessive excitation energy if precautions are taken to ensure that the maximum fluorescence yield is measured under conditions that provide complete closure of the photosystem-II reaction centers. It is also concluded that such dissipation can prevent photoinhibitory damage in cotton leaves even under extreme conditions where as much as 80% of the excitation energy is excessive. PMID:24212903

  12. Relationship Between Photochemical Quenching and Non-Photochemical Quenching in Six Species of Cyanobacteria Reveals Species Difference in Redox State and Species Commonality in Energy Dissipation

    PubMed Central

    Misumi, Masahiro; Katoh, Hiroshi; Tomo, Tatsuya; Sonoike, Kintake

    2016-01-01

    Although the photosynthetic reaction center is well conserved among different cyanobacterial species, the modes of metabolism, e.g. respiratory, nitrogen and carbon metabolism and their mutual interaction, are quite diverse. To explore such uniformity and diversity among cyanobacteria, here we compare the influence of the light environment on the condition of photosynthetic electron transport through Chl fluorescence measurement of six cyanobacterial species grown under the same photon flux densities and at the same temperature. In the dark or under weak light, up to growth light, a large difference in the plastoquinone (PQ) redox condition was observed among different cyanobacterial species. The observed difference indicates that the degree of interaction between respiratory electron transfer and photosynthetic electron transfer differs among different cyanobacterial species. The variation could not be ascribed to the phylogenetic differences but possibly to the light environment of the original habitat. On the other hand, changes in the redox condition of PQ were essentially identical among different species at photon flux densities higher than the growth light. We further analyzed the response to high light by using a typical energy allocation model and found that ‘non-regulated’ thermal dissipation was increased under high-light conditions in all cyanobacterial species tested. We assume that such ‘non-regulated’ thermal dissipation may be an important ‘regulatory’ mechanism in the acclimation of cyanobacterial cells to high-light conditions. PMID:26712847

  13. Fluidized bed quenching technology

    SciTech Connect

    Reynoldson, R.

    1996-12-31

    The use of fluidized beds for quenching ferrous materials is outlined and compared with the more traditional techniques commonly used in the heat treatment industry. The use of fluidized bed quenching to control distortion of metal parts is also discussed. A case study is provided to illustrate a practical application of fluidized bed quenching.

  14. High Photosynthetic Capacity in a Shade-Tolerant Crassulacean Acid Metabolism Plant (Implications for Sunfleck Use, Nonphotochemical Energy Dissipation, and Susceptibility to Photoinhibition).

    PubMed Central

    Skillman, J. B.; Winter, K.

    1997-01-01

    Aechmea magdalenae Andre ex Baker, a constitutive Crassulacean acid metabolism (CAM) plant from the shaded Panamanian rain forest understory, has a maximum photosynthesis rate 2 to 3 times that of co-occurring C3 species and a limited potential for photosynthetic acclimation to high light. Chlorophyll fluorescence measurements indicated that (a) compared with co-occurring C3 species, photosynthetic electron transport in A. magdalenae responded more rapidly to light flecks of moderate intensity, attained a higher steady-state rate, and maintained a lower reduction state of plastoquinone during light flecks; (b) these characteristics were associated with phase III CO2 fixation of CAM; (c) when grown in full sun, A. magdalenae was chronically photoinhibited despite a remarkably high nonphotochemical quenching capacity, indicating a large potential for photoprotection; and (d) the degree of photoinhibition was inversely proportional to the length of phase III. Results from the light fleck studies suggest that understory A. magdalenae plants can make more efficient use of sun flecks for leaf carbon gain over most of the day than co-occurring C3 species. The association between the duration of phase III and the degree of photoinhibition for A. magdalenae in high light is discussed in relation to the limited photosynthetic plasticity in this species. PMID:12223618

  15. High Photosynthetic Capacity in a Shade-Tolerant Crassulacean Acid Metabolism Plant (Implications for Sunfleck Use, Nonphotochemical Energy Dissipation, and Susceptibility to Photoinhibition).

    PubMed

    Skillman, J. B.; Winter, K.

    1997-02-01

    Aechmea magdalenae Andre ex Baker, a constitutive Crassulacean acid metabolism (CAM) plant from the shaded Panamanian rain forest understory, has a maximum photosynthesis rate 2 to 3 times that of co-occurring C3 species and a limited potential for photosynthetic acclimation to high light. Chlorophyll fluorescence measurements indicated that (a) compared with co-occurring C3 species, photosynthetic electron transport in A. magdalenae responded more rapidly to light flecks of moderate intensity, attained a higher steady-state rate, and maintained a lower reduction state of plastoquinone during light flecks; (b) these characteristics were associated with phase III CO2 fixation of CAM; (c) when grown in full sun, A. magdalenae was chronically photoinhibited despite a remarkably high nonphotochemical quenching capacity, indicating a large potential for photoprotection; and (d) the degree of photoinhibition was inversely proportional to the length of phase III. Results from the light fleck studies suggest that understory A. magdalenae plants can make more efficient use of sun flecks for leaf carbon gain over most of the day than co-occurring C3 species. The association between the duration of phase III and the degree of photoinhibition for A. magdalenae in high light is discussed in relation to the limited photosynthetic plasticity in this species. PMID:12223618

  16. Nonphotochemical Reduction of the Plastoquinone Pool in Sunflower Leaves Originates from Chlororespiration1

    PubMed Central

    Feild, Taylor S.; Nedbal, Ladislav; Ort, Donald R.

    1998-01-01

    We investigated the relationship between nonphotochemical plastoquinone reduction and chlororespiration in leaves of growth-chamber-grown sunflower (Helianthus annuus L.). Following a short induction period, leaves of previously illuminated sunflower showed a substantially increased level of minimal fluorescence following a light-to-dark transition. This increase in minimal fluorescence was reversed by far-red illumination, inhibited by rotenone or photooxidative methyl viologen treatment, and stimulated by fumigation with CO. Using flash-induced electrochromic absorption-change measurements, we observed that the capacity of sunflower to reduce plastoquinone in the dark influenced the activation state of the chloroplast ATP synthase, although chlororespiratory transmembrane electrochemical potential formation alone does not fully explain our observations. We have added several important new observations to the work of others, forming, to our knowledge, the first strong experimental evidence that chlororespiratory, nonphotochemical plastoquinone reduction and plastoquinol oxidation occur in the chloroplasts of higher plants. We have introduced procedures for monitoring and manipulating chlorores-piratory activity in leaves that will be important in subsequent work aimed at defining the pathway and function of this dark electron flux in higher plant chloroplasts. PMID:9536037

  17. Edge mode dynamics of quenched topological wires

    NASA Astrophysics Data System (ADS)

    Sacramento, P. D.

    2016-06-01

    The fermionic and Majorana edge mode dynamics of various topological systems are compared, after a sudden global quench of the Hamiltonian parameters takes place. Attention is focused on the regimes where the survival probability of an edge state has oscillations either due to critical or off-critical quenches. The nature of the wave functions and the overlaps between the eigenstates of different points in parameter space determine the various types of behaviors, and the distinction due to the Majorana nature of the excitations plays a lesser role. Performing a sequence of quenches, it is shown that the edge states, including Majorana modes, may be switched off and on. Also, the generation of Majoranas due to quenching from a trivial phase is discussed.

  18. The Type II NADPH Dehydrogenase Facilitates Cyclic Electron Flow, Energy-Dependent Quenching, and Chlororespiratory Metabolism during Acclimation of Chlamydomonas reinhardtii to Nitrogen Deprivation.

    PubMed

    Saroussi, Shai I; Wittkopp, Tyler M; Grossman, Arthur R

    2016-04-01

    When photosynthetic organisms are deprived of nitrogen (N), the capacity to grow and assimilate carbon becomes limited, causing a decrease in the productive use of absorbed light energy and likely a rise in the cellular reduction state. Although there is a scarcity of N in many terrestrial and aquatic environments, a mechanistic understanding of how photosynthesis adjusts to low-N conditions and the enzymes/activities integral to these adjustments have not been described. In this work, we use biochemical and biophysical analyses of photoautotrophically grown wild-type and mutant strains of Chlamydomonas reinhardtii to determine the integration of electron transport pathways critical for maintaining active photosynthetic complexes even after exposure of cells to N deprivation for 3 d. Key to acclimation is the type II NADPH dehydrogenase, NDA2, which drives cyclic electron flow (CEF), chlororespiration, and the generation of an H(+) gradient across the thylakoid membranes. N deprivation elicited a doubling of the rate of NDA2-dependent CEF, with little contribution from PGR5/PGRL1-dependent CEF The H(+) gradient generated by CEF is essential to sustain nonphotochemical quenching, while an increase in the level of reduced plastoquinone would promote a state transition; both are necessary to down-regulate photosystem II activity. Moreover, stimulation of NDA2-dependent chlororespiration affords additional relief from the elevated reduction state associated with N deprivation through plastid terminal oxidase-dependent water synthesis. Overall, rerouting electrons through the NDA2 catalytic hub in response to photoautotrophic N deprivation sustains cell viability while promoting the dissipation of excess excitation energy through quenching and chlororespiratory processes. PMID:26858365

  19. The Type II NADPH Dehydrogenase Facilitates Cyclic Electron Flow, Energy-Dependent Quenching, and Chlororespiratory Metabolism during Acclimation of Chlamydomonas reinhardtii to Nitrogen Deprivation1[OPEN

    PubMed Central

    Grossman, Arthur R.

    2016-01-01

    When photosynthetic organisms are deprived of nitrogen (N), the capacity to grow and assimilate carbon becomes limited, causing a decrease in the productive use of absorbed light energy and likely a rise in the cellular reduction state. Although there is a scarcity of N in many terrestrial and aquatic environments, a mechanistic understanding of how photosynthesis adjusts to low-N conditions and the enzymes/activities integral to these adjustments have not been described. In this work, we use biochemical and biophysical analyses of photoautotrophically grown wild-type and mutant strains of Chlamydomonas reinhardtii to determine the integration of electron transport pathways critical for maintaining active photosynthetic complexes even after exposure of cells to N deprivation for 3 d. Key to acclimation is the type II NADPH dehydrogenase, NDA2, which drives cyclic electron flow (CEF), chlororespiration, and the generation of an H+ gradient across the thylakoid membranes. N deprivation elicited a doubling of the rate of NDA2-dependent CEF, with little contribution from PGR5/PGRL1-dependent CEF. The H+ gradient generated by CEF is essential to sustain nonphotochemical quenching, while an increase in the level of reduced plastoquinone would promote a state transition; both are necessary to down-regulate photosystem II activity. Moreover, stimulation of NDA2-dependent chlororespiration affords additional relief from the elevated reduction state associated with N deprivation through plastid terminal oxidase-dependent water synthesis. Overall, rerouting electrons through the NDA2 catalytic hub in response to photoautotrophic N deprivation sustains cell viability while promoting the dissipation of excess excitation energy through quenching and chlororespiratory processes. PMID:26858365

  20. Fluorescence changes accompanying short-term light adaptations in photosystem I and photosystem II of the cyanobacterium Synechocystis sp. PCC 6803 and phycobiliprotein-impaired mutants: State 1/State 2 transitions and carotenoid-induced quenching of phycobilisomes.

    PubMed

    Stadnichuk, Igor N; Lukashev, Evgeny P; Elanskaya, Irina V

    2009-03-01

    The features of the two types of short-term light-adaptations of photosynthetic apparatus, State 1/State 2 transitions, and non-photochemical fluorescence quenching of phycobilisomes (PBS) by orange carotene-protein (OCP) were compared in the cyanobacterium Synechocystis sp. PCC 6803 wild type, CK pigment mutant lacking phycocyanin, and PAL mutant totally devoid of phycobiliproteins. The permanent presence of PBS-specific peaks in the in situ action spectra of photosystem I (PSI) and photosystem II (PSII), as well as in the 77 K fluorescence excitation spectra for chlorophyll emission at 690 nm (PSII) and 725 nm (PSI) showed that PBS are constitutive antenna complexes of both photosystems. The mutant strains compensated the lack of phycobiliproteins by higher PSII content and by intensification of photosynthetic linear electron transfer. The detectable changes of energy migration from PBS to the PSI and PSII in the Synechocystis wild type and the CK mutant in State 1 and State 2 according to the fluorescence excitation spectra measurements were not registered. The constant level of fluorescence emission of PSI during State 1/State 2 transitions and simultaneous increase of chlorophyll fluorescence emission of PSII in State 1 in Synechocystis PAL mutant allowed to propose that spillover is an unlikely mechanism of state transitions. Blue-green light absorbed by OCP diminished the rout of energy from PBS to PSI while energy migration from PBS to PSII was less influenced. Therefore, the main role of OCP-induced quenching of PBS is the limitation of PSI activity and cyclic electron transport under relatively high light conditions. PMID:19169839

  1. Identification of two quenching sites active in the regulation of photosynthetic light-harvesting studied by time-resolved fluorescence

    NASA Astrophysics Data System (ADS)

    Holzwarth, Alfred R.; Miloslavina, Yuliya; Nilkens, Manuela; Jahns, Peter

    2009-12-01

    The regulation of light-harvesting (called non-photochemical quenching, NPQ) is an essential photoprotective mechanism active in plants. Total NPQ is dependent on PsbS, a pH-sensing protein, and on the action of the xanthophyll carotenoid zeaxanthin (Zx). Using ultrafast fluorescence on intact leaves we demonstrate two independent NPQ quenching sites in vivo which depend differently on the actions of PsbS and Zx. The first site is formed in the functionally detached major light-harvesting complex of PS II and depends strictly on PsbS. The second site is in the minor antennae of photosystem (PS) II and quenching depends on the presence of Zx.

  2. Quenching fundamentals: Heat transfer

    SciTech Connect

    MacKenzie, D.S.; Totten, G.E.; Webster, G.M.

    1996-12-31

    Quenching is essentially a heat transfer problem. It is necessary to quench parts fast enough that adequate mechanical and corrosion properties are achieved, but not so fast that detrimental distortion and residual stresses are formed. In addition, non-uniform heat transfer across the surface of a part will produce thermal gradients which will also create distortion or residual stresses. In this paper, the role of agitation will be discussed in terms of the heat transfer coefficient. A brief review of the published heat transfer literature will be discussed in terms of the fluid flow on heat transfer coefficient, with implications on quenching.

  3. Theory of light quenching: effects of fluorescence polarization, intensity, and anisotropy decays.

    PubMed Central

    Kuśba, J; Bogdanov, V; Gryczynski, I; Lakowicz, J R

    1994-01-01

    Experimental studies have recently demonstrated that fluorescence emission can be quenched by laser light pulses from modern high repetition rate lasers, a phenomenon we call "light quenching." We now describe the theory of light quenching and some of its effects on the steady-state and time-resolved intensity and anisotropy decays of fluorophores. Light quenching can decrease or increase the steady-state or time-zero anisotropy. Remarkably, the light quenching can break the usual z axis symmetry of the excited-state population, and the emission polarization can range from -1 to +1 under selected conditions. The measured anisotropy (or polarization) depends upon whether the observation axis is parallel or perpendicular to the propagation direction of the light quenching beam. The effects of light quenching are different for a single pulse, which results in both excitation and quenching, as compared with a time-delayed quenching pulse. Time-delayed light quenching pulses can result in step-like changes in the time-dependent intensity or anisotropy and are predicted to cause oscillations in the frequency-domain intensity and anisotropy decays. The increasing availability of pulsed laser sources offers the opportunity for a new class of two-pulse or multiple-pulse experiments where the sample is prepared by an excitation pulse, the excited state population is modified by the quenching pulse(s), followed by time- or frequency-domain measurements of the resulting emission. PMID:7858140

  4. Rare earth luminescence: A way to overcome concentration quenching

    NASA Astrophysics Data System (ADS)

    Benz, Felix; Strunk, Horst P.

    2012-12-01

    A model is developed to simulate the rare earth luminescence intensity in dependence of both the excitation rate and the dopant concentration. For low excitation rates, as in the case of photoluminescence investigations, concentration quenching is expected. In contrast for high excitation rates (as generally realized in cathodoluminescence experiments) concentration quenching can be suppressed and thus luminescence intensity increases with increasing dopant concentration. These results reconcile the recent photo- and cathodoluminescence results on GaN:Er presented by Chen et al. (APL 96, 181901, 2010), 10.1063/1.3421535. Further experimental results indicate that the physical basis of the model is adequate.

  5. Cool Flame Quenching

    NASA Technical Reports Server (NTRS)

    Pearlman, Howard; Chapek, Richard

    2001-01-01

    Cool flame quenching distances are generally presumed to be larger than those associated with hot flames, because the quenching distance scales with the inverse of the flame propagation speed, and cool flame propagation speeds are often times slower than those associated with hot flames. To date, this presumption has never been put to a rigorous test, because unstirred, non-isothermal cool flame studies on Earth are complicated by natural convection. Moreover, the critical Peclet number (Pe) for quenching of cool flames has never been established and may not be the same as that associated with wall quenching due to conduction heat loss in hot flames, Pe approx. = 40-60. The objectives of this ground-based study are to: (1) better understand the role of conduction heat loss and species diffusion on cool flame quenching (i.e., Lewis number effects), (2) determine cool flame quenching distances (i.e, critical Peclet number, Pe) for different experimental parameters and vessel surface pretreatments, and (3) understand the mechanisms that govern the quenching distances in premixtures that support cool flames as well as hot flames induced by spark-ignition. Objective (3) poses a unique fire safety hazard if conditions exist where cool flame quenching distances are smaller than those associated with hot flames. For example, a significant, yet unexplored risk, can occur if a multi-stage ignition (a cool flame that transitions to a hot flame) occurs in a vessel size that is smaller than that associated with the hot quenching distance. To accomplish the above objectives, a variety of hydrocarbon-air mixtures will be tested in a static reactor at elevated temperature in the laboratory (1g). In addition, reactions with chemical induction times that are sufficiently short will be tested aboard NASA's KC-135 microgravity (mu-g) aircraft. The mu-g results will be compared to a numerical model that includes species diffusion, heat conduction, and a skeletal kinetic mechanism

  6. Nonphotochemical Hole-Burning Studies of Energy Transfer Dynamics in Antenna Complexes of Photosynthetic Bacteria

    SciTech Connect

    Satoshi Matsuzaki

    2002-08-01

    This thesis contains the candidate's original work on excitonic structure and energy transfer dynamics of two bacterial antenna complexes as studied using spectral hole-burning spectroscopy. The general introduction is divided into two chapters (1 and 2). Chapter 1 provides background material on photosynthesis and bacterial antenna complexes with emphasis on the two bacterial antenna systems related to the thesis research. Chapter 2 reviews the underlying principles and mechanism of persistent nonphotochemical hole-burning (NPHB) spectroscopy. Relevant energy transfer theories are also discussed. Chapters 3 and 4 are papers by the candidate that have been published. Chapter 3 describes the application of NPHB spectroscopy to the Fenna-Matthews-Olson (FMO) complex from the green sulfur bacterium Prosthecochloris aestuarii; emphasis is on determination of the low energy vibrational structure that is important for understanding the energy transfer process associated within three lowest energy Qy-states of the complex. The results are compared with those obtained earlier on the FMO complex from Chlorobium tepidum. In Chapter 4, the energy transfer dynamics of the B800 molecules of intact LH2 and B800-deficient LH2 complexes of the purple bacterium Rhodopseudomonas acidophila are compared. New insights on the additional decay channel of the B800 ring of bacteriochlorophyll a (BChl a) molecules are provided. General conclusions are given in Chapter 5.

  7. The Quench Action

    NASA Astrophysics Data System (ADS)

    Caux, Jean-Sébastien

    2016-06-01

    We give a pedagogical introduction to the methodology of the Quench Action, which is an effective representation for the calculation of time-dependent expectation values of physical operators following a generic out-of-equilibrium state preparation protocol (for example a quantum quench). The representation, originally introduced in Caux and Essler (2013 Phys. Rev. Lett. 110 257203), is founded on a mixture of exact data for overlaps together with variational reasonings. It is argued to be quite generally valid and thermodynamically exact for arbitrary times after the quench (from short times all the way up to the steady state), and applicable to a wide class of physically relevant observables. Here, we introduce the method and its language, give an overview of some recent results, suggest a roadmap and offer some perspectives on possible future research directions.

  8. 3. EXTERIOR VIEW, LOOKING EAST, SHOWING QUENCH TOWER, WITH QUENCH ...

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

    3. EXTERIOR VIEW, LOOKING EAST, SHOWING QUENCH TOWER, WITH QUENCH IN PROGRESS, WILPUTTE BATTERY, COAL PRE-HEATING UNIT, INCLINE CONVEYOR AND BATHHOUSE. - Alabama By-Products Company, Coke Plant, Highway 79 (Pinson Valley Parkway), Tarrant City, Jefferson County, AL

  9. Dye induced quenching of firefly luciferase-luciferin bioluminescence

    NASA Astrophysics Data System (ADS)

    KrishnaMurthy, N. V.; Sudhaharan, T.; Ram Reddy, A.

    2007-11-01

    The quenching of firefly bioluminescence (BL) in presence of xanthene dyes and tetratolylporphyrin was investigated. The BL intensity was quenched with an altered decay pattern in presence of xanthene dyes and tetratolylporphyrin. The electronic absorption spectra indicate that there is no significant interaction occurring between the dyes and the BL components in the ground state. The BL quenching decay rate and fluorescence quenching studies of luciferin by the dyes suggest an energy transfer through an exciplex, involving oxyluciferin, in the excited state and the dyes, in the ground state. The bimolecular quenching rate constant ( Kq) values obtained from fluorescence studies varied between 7.7 × 10 12 and 19.8 × 10 12 M -1 s -1. The magnitude of the bimolecular quenching rate constants confirmed the complex formation between dye and excited oxyluciferin. The exciplex subsequently undergoes a non-radiative decay to the ground state via a combination of heavy atom induced and Förster-type energy transfer. The decay rate constants in presence and in absence of dyes vary between 7.47 × 10 -4 and 7.6 × 10 -2 s -1. In the presence of dyes the effective decay rate constants ( keff) increased while the lifetime of light emitting species decreased. The kinetic studies in presence of singlet oxygen scavengers, like β-carotene and NaN 3, prove that there is no significant quenching of the firefly BL due to the formation of singlet oxygen.

  10. Excitation mechanism and thermal emission quenching of Tb ions in silicon rich silicon oxide thin films grown by plasma-enhanced chemical vapour deposition—Do we need silicon nanoclusters?

    SciTech Connect

    Podhorodecki, A. Golacki, L. W.; Zatryb, G.; Misiewicz, J.; Wang, J.; Jadwisienczak, W.; Fedus, K.

    2014-04-14

    In this work, we will discuss the excitation and emission properties of Tb ions in a Silicon Rich Silicon Oxide (SRSO) matrix obtained at different technological conditions. By means of electron cyclotron resonance plasma-enhanced chemical vapour deposition, undoped and doped SRSO films have been obtained with different Si content (33, 35, 39, 50 at. %) and were annealed at different temperatures (600, 900, 1100 °C). The samples were characterized optically and structurally using photoluminescence (PL), PL excitation, time resolved PL, absorption, cathodoluminescence, temperature dependent PL, Rutherford backscattering spectrometry, Fourier transform infrared spectroscopy and positron annihilation lifetime spectroscopy. Based on the obtained results, we discuss how the matrix modifications influence excitation and emission properties of Tb ions.

  11. Excitation mechanism and thermal emission quenching of Tb ions in silicon rich silicon oxide thin films grown by plasma-enhanced chemical vapour deposition—Do we need silicon nanoclusters?

    NASA Astrophysics Data System (ADS)

    Podhorodecki, A.; Golacki, L. W.; Zatryb, G.; Misiewicz, J.; Wang, J.; Jadwisienczak, W.; Fedus, K.; Wojcik, J.; Wilson, P. R. J.; Mascher, P.

    2014-04-01

    In this work, we will discuss the excitation and emission properties of Tb ions in a Silicon Rich Silicon Oxide (SRSO) matrix obtained at different technological conditions. By means of electron cyclotron resonance plasma-enhanced chemical vapour deposition, undoped and doped SRSO films have been obtained with different Si content (33, 35, 39, 50 at. %) and were annealed at different temperatures (600, 900, 1100 °C). The samples were characterized optically and structurally using photoluminescence (PL), PL excitation, time resolved PL, absorption, cathodoluminescence, temperature dependent PL, Rutherford backscattering spectrometry, Fourier transform infrared spectroscopy and positron annihilation lifetime spectroscopy. Based on the obtained results, we discuss how the matrix modifications influence excitation and emission properties of Tb ions.

  12. Spontaneous and nonphotochemical laser-induced nucleation in levitated supersaturated microdroplets

    NASA Astrophysics Data System (ADS)

    Fang, Ke

    Research of nucleation in levitated supersaturated microdroplets was conducted in this dissertation. An unconventional crystallization system, levitated microdroplets, was utilized in this research. The microdroplet was levitated by an electrodynamic balance (EDB) constructed inside a vacuum chamber. EDB has the advantage of creating a containerless environment for the crystallization system. Spontaneous nucleation in levitated microdroplets was investigated. Spontaneous nucleation of aqueous microdroplets was caused by reducing the ambient relative humidity (RH) surrounding the solution droplets. Different polymorphs of glutaric acid and malonic acid are nucleated in levitated microdroplets when injected into a chamber maintained at different initial RH values. Effect of surfactant as additive is also investigated. A site-dependent evaporation-driven crystallization theory is established to explain the spontaneous nucleation phenomena in levitated aqueous microdroplets. Levitated microdroplets containing a solute and an organic solvent were also investigated. The crystallization behavior of glutaric acid methanol solutions and ethanol solutions was observed. ROY, a deca-polymorphic compound, was also studied from its DMSO solution microdroplets. Non-photochemical laser induced nucleation (NPLIN) was observed in levitated microdroplets of supersaturated potassium chloride (KCl) aqueous solution. A focused green (532 nm) pulsed laser with 1 ns pulse width was used to induce nucleation. Nucleation of levitated KCl microdroplet with high supersaturation was observed upon laser irradiation. A laser-induced charge loss phenomenon was also observed. A hypothesis of laser-induced electrostriction and corona discharge is discussed. Analysis with classical nucleation theory suggests that the NPLIN results in levitated microdroplets are consistent with previously published data on bulk samples.

  13. Nonphotochemical Hole-Burning Studies of Energy Transfer Dynamics in Antenna Complexes of Photosynthetic Bacteria

    SciTech Connect

    Satoshi Matsuzaki

    2002-06-27

    This thesis contains the candidate's original work on excitonic structure and energy transfer dynamics of two bacterial antenna complexes as studied using spectral hole-burning spectroscopy. The general introduction is divided into two chapters (1 and 2). Chapter 1 provides background material on photosynthesis and bacterial antenna complexes with emphasis on the two bacterial antenna systems related to the thesis research. Chapter 2 reviews the underlying principles and mechanism of persistent nonphotochemical hole-burning (NPHB) spectroscopy. Relevant energy transfer theories are also discussed. Chapters 3 and 4 are papers by the candidate that have been published. Chapter 3 describes the application of NPHB spectroscopy to the Fenna-Matthews-Olson (FMO) complex from the green sulfur bacterium Prosthecochloris aestuarii; emphasis is on determination of the low energy vibrational structure that is important for understanding the energy transfer process associated within three lowest energy Q{sub y}-states of the complex. The results are compared with those obtained earlier on the FMO complex from Chlorobium tepidum. In Chapter 4, the energy transfer dynamics of the B800 molecules of intact LH2 and B800-deficient LH2 complexes of the purple bacterium Rhodopseudomonas acidophila are compared. New insights on the additional decay channel of the B800 ring of bacteriochlorophyll{sub a} (BChl{sub a}) molecules are provided. General conclusions are given in Chapter 5. A version of the hole spectrum simulation program written by the candidate for the FMO complex study (Chapter 3) is included as an appendix. The references for each chapter are given at the end of each chapter.

  14. Fluorescence-quenching mechanism of tryptophan. Remarkably efficient internal proton-induced quenching and charge-transfer quenching

    SciTech Connect

    Shizuka, H.; Serizawa, M.; Shimo, T.; Saito, I.; Matsuura, T.

    1988-03-16

    The fluorescence quenching of tyrptophan (Trp) in the absence and presence of 18-crown-6 in CH/sub 3/OH-H/sub 2/ (9:1), vv) mixtures has been studied by means of nanosecond time-resolved single-photon counting, fluorimetry, and photochemical H-D isotope exchange. The fluorescence intensity increases markedly with increasing concentration of 18-crown-6. The quenching can be estimated from the equation k/sub q/ = tau/sub 1//sup 1 -/ - (tau /sub 2//sup max/)/sup -1/, where tau/sub 1/ and tau/sub 1//sup max/ denote the fluorescence lifetimes for free Trp and the 1:1 Trp-18-crown-6 complex, respectively. The internal quenching originates from the electrophilic protonation of the /sup +/NH/sub 3/ group of Trp at the C-4 position of the excited indole ring plus the charge-transfer interaction between the excited indole ring and the ammonium group. The stabilization constant K/sub g/ for the 1:1 complex of Trp with 18-crown-6 has been determined by means of fluorimetry.

  15. Quench studies of ILC cavities

    SciTech Connect

    Eremeev, Grigory; Geng, Rongli; Palczewski, Ari; Dai, Jin

    2011-07-01

    Quench limits accelerating gradient in SRF cavities to a gradient lower than theoretically expected for superconducting niobium. Identification of the quenching site with thermometry and OST, optical inspection, and replica of the culprit is an ongoing effort at Jefferson Lab aimed at better understanding of this limiting phenomenon. In this contribution we present our finding with several SRF cavities that were limited by quench.

  16. Characterizing Water Quenching Systems with a Quench Probe

    NASA Astrophysics Data System (ADS)

    Ferguson, B. Lynn; Li, Zhichao; Freborg, Andrew M.

    2014-12-01

    Quench probes have been used effectively to characterize the quality of quenchants for many years. For this purpose, a variety of commercial probes, as well as the necessary data acquisition system for determining the time-temperature data for a set of standardized test conditions, are available for purchase. The type of information obtained from such probes provides a good basis for comparing media, characterizing general cooling capabilities, and checking media condition over time. However, these data do not adequately characterize the actual production quenching process in terms of heat transfer behavior in many cases, especially when high temperature gradients are present. Faced with the need to characterize water quenching practices, including conventional and intensive practices, a quench probe was developed. This paper describes that probe, the data collection system, the data gathered for both intensive quenching and conventional water quenching, and the heat transfer coefficients determined for these processes. Process sensitivities are investigated and highlight some intricacies of quenching.

  17. Quorum quenching enzymes.

    PubMed

    Fetzner, Susanne

    2015-05-10

    Bacteria use cell-to-cell communication systems based on chemical signal molecules to coordinate their behavior within the population. These quorum sensing systems are potential targets for antivirulence therapies, because many bacterial pathogens control the expression of virulence factors via quorum sensing networks. Since biofilm maturation is also usually influenced by quorum sensing, quenching these systems may contribute to combat biofouling. One possibility to interfere with quorum sensing is signal inactivation by enzymatic degradation or modification. Such quorum quenching enzymes are wide-spread in the bacterial world and have also been found in eukaryotes. Lactonases and acylases that hydrolyze N-acyl homoserine lactone (AHL) signaling molecules have been investigated most intensively, however, different oxidoreductases active toward AHLs or 2-alkyl-4(1H)-quinolone signals as well as other signal-converting enzymes have been described. Several approaches have been assessed which aim at alleviating virulence, or biofilm formation, by reducing the signal concentration in the bacterial environment. These involve the application or stimulation of signal-degrading bacteria as biocontrol agents in the protection of crop plants against soft-rot disease, the use of signal-degrading bacteria as probiotics in aquaculture, and the immobilization or entrapment of quorum quenching enzymes or bacteria to control biofouling in membrane bioreactors. While most approaches to use quorum quenching as antivirulence strategy are still in the research phase, the growing number of organisms and enzymes known to interfere with quorum sensing opens up new perspectives for the development of innovative antibacterial strategies. PMID:25220028

  18. A new quenching alternative

    SciTech Connect

    Brennan, R.J.; Faulkner, C.H.

    1996-12-31

    The quenching of ferrous alloys implies the controlled extraction of heat from a part at a rate sufficient to harden the part and still control the desired dimensional limitations. Quenchants in common use today are: molten metals, molten salts, petroleum oils, polymer solutions, water, and salt/water solutions. Each type of quenchant has its benefits and limitations. With current waste legislation and the trends toward environmentally friendlier industrial working fluids, many of these quenching products are coming under close scrutiny by the users and legislators. The most widely used quenchant is petroleum oil due to its favorable heat extraction characteristics. The dependence upon imports, price vulnerability, and contamination potential have caused suppliers and users to look into alternative products. Research into renewable resource, non-petroleum, vegetable oils has been going on globally for several years. The drawbacks encountered with many vegetable oils were widely known and only years of research enabled them to be overcome. The presently formulated product not only performs as well as petroleum oil but shows some characteristics better than those of the petroleum products, especially in the biodegradability and ecological aspects of the products. Stability and reproducible quenching properties have been proven with over two and one half years of field testing.

  19. Quench from Mott Insulator to Superfluid

    SciTech Connect

    Zurek, Wojciech H.; Dziarmaga, Jacek; Tylutki, Marek

    2012-06-01

    We study a linear ramp of the nearest-neighbor tunneling rate in the Bose-Hubbard model driving the system from the Mott insulator state into the superfluid phase. We employ the truncated Wigner approximation to simulate linear quenches of a uniform system in 1...3 dimensions, and in a harmonic trap in 3 dimensions. In all these setups the excitation energy decays like one over third root of the quench time. The -1/3 scaling is explained by an impulse-adiabatic approximation - a variant of the Kibble-Zurek mechanism - describing a crossover from non-adiabatic to adiabatic evolution when the system begins to keep pace with the increasing tunneling rate.

  20. The lack of LHCII proteins modulates excitation energy partitioning and PSII charge recombination in Chlorina F2 mutant of barley.

    PubMed

    Ivanov, A G; Krol, M; Zeinalov, Y; Huner, N P A; Sane, P V

    2008-07-01

    Analysis of the partitioning of absorbed light energy within PSII into fractions utilized by PSII photochemistry (ØPSII), thermally dissipated via ΔpH-and zeaxanthin-dependent energy quenching (ØNPQ) and constitutive non-photochemical energy losses (ØNO) was performed in wild type and F2 mutant of barley. The estimated energy partitioning of absorbed light to various pathways indicated that the fraction of ØPSII was slightly higher, while the proportion of thermally dissipated energy through ØNPQ was 38% lower in F2 mutant than in WT. In contrast, ØNO, i.e. the fraction of absorbed light energy dissipated by additional quenching mechanism(s) was 34% higher in F2 mutant. The increased proportion of ØNO correlated with narrowing the temperature gap (ΔT M) between S2/3QB- and S2QA- charge recombinations in F2 mutant as revealed by thermoluminescence measurements. We suggest that this would result in increased probability for an alternative non-radiative P680+QA- radical pair recombination pathway for energy dissipation within the reaction centre of PSII (reaction center quenching) and that this additional quenching mechanism might play an important role in photoprotection when the capacity for the primary, zeaxanthin-dependent non-photochemical quenching (ØNPQ) and state transitions pathways are restricted in the absence of LHCII polypeptides in F2 mutant. PMID:23572888

  1. Study of intermediates from transition metal excited-state electron- transfer reactions

    SciTech Connect

    Hoffman, M.Z.

    1993-03-31

    Progress on 6 projects is reported: excited state absorption spectrum of Ru(bpy)[sub 3][sup 2+], solvent cage model for electron transfer quenching, reductive quenching of [sup *]Cr(III) complexes, solution medium effects in oxidative quenching of [sup *]Ru(II) complexes, photosensitized oxidation of phenol in aqueous solution, and quenching of Ru(II) complexes by oxygen.

  2. Light Response of CO(2) Assimilation, Dissipation of Excess Excitation Energy, and Zeaxanthin Content of Sun and Shade Leaves.

    PubMed

    Demmig-Adams, B; Winter, K; Krüger, A; Czygan, F C

    1989-07-01

    Intact attached sun leaves of Helianthus annuus and shade leaves of Monstera deliciosa and Hedera helix were used to obtain light response curves of CO(2) uptake, the content of the carotenoid zeaxanthin (formed by violaxanthin de-epoxidation), as well as nonphotochemical quenching (q(NP)), and the rate constant of radiationless energy dissipation (k(D)). The latter two parameters were calculated from the decrease of chlorophyll a fluorescence at closed photosystem II traps in saturating pulses in the light. Among the three species, the light-saturated capacity of CO(2) uptake differed widely and light saturation of CO(2) uptake occurred at very different photon flux densities. Fluorescence quenching and zeaxanthin content exhibited features which were common to all three species: below light-saturation of CO(2) uptake nonphotochemical quenching occurred in the absence of zeaxanthin and was not accompanied by a decrease in the yield of instantaneous fluorescence. Nonphotochemical quenching, q(NP), increased up to values which ranged between 0.35 and 0.5 when based on a control value of the yield of variable fluorescence determined after 12 hours of darkness. As light saturation of CO(2) uptake was approached, q(NP) showed a secondary increase and the zeaxanthin content of the leaves began to rise. This was also the point from which the yield of instantaneous fluorescence began to decrease. The increase in zeaxanthin was paralleled by an increase in the rate constant for radiationless energy dissipation k(D), which opens the possibility that zeaxanthin is related to the rapidly relaxing "high-energy-state quenching" in leaves. PMID:16666892

  3. Excitation dynamics and structural implication of the stress-related complex LHCSR3 from the green alga Chlamydomonas reinhardtii.

    PubMed

    Liguori, Nicoletta; Novoderezhkin, Vladimir; Roy, Laura M; van Grondelle, Rienk; Croce, Roberta

    2016-09-01

    LHCSR3 is a member of the Light-Harvesting Complexes (LHC) family, which is mainly composed of pigment-protein complexes responsible for collecting photons during the first steps of photosynthesis. Unlike related LHCs, LHCSR3 is expressed in stress conditions and has been shown to be essential for the fast component of photoprotection, non-photochemical quenching (NPQ), in the green alga Chlamydomonas reinhardtii. In plants, which do not possess LHCSR homologs, NPQ is triggered by the PSBS protein. Both PSBS and LHCSR3 possess the ability to sense pH changes but, unlike PSBS, LHCSR3 binds multiple pigments. In this work we have analyzed the properties of the pigments bound to LHCSR3 and their excited state dynamics. The data show efficient excitation energy transfer between pigments with rates similar to those observed for the other LHCs. Application of an exciton model based on a template of LHCII, the most abundant LHC, satisfactorily explains the collected steady state and time-resolved spectroscopic data, indicating that LHCSR3 has a LHC-like molecular architecture, although it probably binds less pigments. The model suggests that most of the chlorophylls have similar energy and interactions as in LHCII. The most striking difference is the localization of the lowest energy state, which is not on the Chlorophyll a (Chl a) 610-611-612 triplet as in all the LHCB antennas, but on Chl a613, which is located close to the lumen and to the pH-sensing region of the protein. PMID:27150505

  4. Fast quench reactor method

    SciTech Connect

    Detering, Brent A.; Donaldson, Alan D.; Fincke, James R.; Kong, Peter C.; Berry, Ray A.

    1999-01-01

    A fast quench reaction includes a reactor chamber having a high temperature heating means such as a plasma torch at its inlet and a means of rapidly expanding a reactant stream, such as a restrictive convergent-divergent nozzle at its outlet end. Metal halide reactants are injected into the reactor chamber. Reducing gas is added at different stages in the process to form a desired end product and prevent back reactions. The resulting heated gaseous stream is then rapidly cooled by expansion of the gaseous stream.

  5. Fast quench reactor method

    DOEpatents

    Detering, B.A.; Donaldson, A.D.; Fincke, J.R.; Kong, P.C.; Berry, R.A.

    1999-08-10

    A fast quench reaction includes a reactor chamber having a high temperature heating means such as a plasma torch at its inlet and a means of rapidly expanding a reactant stream, such as a restrictive convergent-divergent nozzle at its outlet end. Metal halide reactants are injected into the reactor chamber. Reducing gas is added at different stages in the process to form a desired end product and prevent back reactions. The resulting heated gaseous stream is then rapidly cooled by expansion of the gaseous stream. 8 figs.

  6. Coal liquefaction quenching process

    DOEpatents

    Thorogood, Robert M.; Yeh, Chung-Liang; Donath, Ernest E.

    1983-01-01

    There is described an improved coal liquefaction quenching process which prevents the formation of coke with a minimum reduction of thermal efficiency of the coal liquefaction process. In the process, the rapid cooling of the liquid/solid products of the coal liquefaction reaction is performed without the cooling of the associated vapor stream to thereby prevent formation of coke and the occurrence of retrograde reactions. The rapid cooling is achieved by recycling a subcooled portion of the liquid/solid mixture to the lower section of a phase separator that separates the vapor from the liquid/solid products leaving the coal reactor.

  7. Tryptophan and ATTO 590: Mutual Fluorescence Quenching and Exciplex Formation

    SciTech Connect

    Bhattacharjee, Ujjal; Beck, Christie; Winter, Arthur; Wells, Carson; Petrich, Jacob W

    2014-07-24

    Investigation of fluorescence quenching of probes, such as ATTO dyes, is becoming an increasingly important topic owing to the use of these dyes in super-resolution microscopies and in single-molecule studies. Photoinduced electron transfer is their most important nonradiative pathway. Because of the increasing frequency of the use of ATTO and related dyes to investigate biological systems, studies are presented for inter- and intramolecular quenching of ATTO 590 with tryptophan. In order to examine intramolecular quenching, an ATTO 590–tryptophan conjugate was synthesized. It was determined that tryptophan is efficiently quenching ATTO 590 fluorescence by excited-state charge transfer and two charge transfer complexes are forming. In addition, it was discovered that an exciplex (whose lifetime is 5.6 ns) can be formed between tryptophan and ATTO 590, and it is suggested that the possibility of such exciplex formation should be taken into account when protein fluorescence is monitored in a system tagged with ATTO dyes.

  8. Dynamical Outcomes of Quenching: Reflections on a Conical Intersection

    NASA Astrophysics Data System (ADS)

    Lehman, Julia H.; Lester, Marsha I.

    2014-04-01

    This review focuses on experimental studies of the dynamical outcomes following collisional quenching of electronically excited OH A2Σ+ radicals by molecular partners. The experimental observables include the branching between reactive and nonreactive decay channels, kinetic energy release, and quantum state distributions of the products. Complementary theoretical investigations reveal regions of strong nonadiabatic coupling, known as conical intersections, which facilitate the quenching process. The dynamical outcomes observed experimentally are connected to the local forces and geometric properties of the nuclei in the conical intersection region. Dynamical calculations for the benchmark OH-H2 system are in good accord with experimental observations, demonstrating that the outcomes reflect the strong coupling in the conical intersection region as the system evolves from the excited electronic state to quenched products.

  9. Changes in the Xanthophyll Cycle and Fluorescence Quenching Indicate Light-Dependent Early Events in the Action of Paraquat and the Mechanism of Resistance to Paraquat in Erigeron canadensis (L.) Cronq1

    PubMed Central

    Váradi, Gyula; Darkó, Éva; Lehoczki, Endre

    2000-01-01

    Violaxanthin de-epoxidation, chlorophyll fluorescence quenching, and photosynthetic O2 evolution in the presence of paraquat (Pq) were studied in intact attached leaves of Pq-susceptible, and Pq-resistant (PqR) biotypes of Erigeron canadensis under different light conditions. Initially, similar changes were induced in the two biotypes, but the effects relaxed only in the PqR plants, indicating a Pq elimination process. The penetration of Pq into the chloroplasts of PqR plants proved to be somewhat restricted and highly light-dependent, as revealed by both the light response curves of violaxanthin de-epoxidation and fluorescence quenching and the short-term high-light pre-illumination experiments. An irregular down-regulation of the non-photochemical fluorescence quenching processes was observed, reflected by lower steady-state zeaxanthin and non-photochemical fluorescence quenching levels as compared with the corresponding non-treated high-light controls. It is concluded that light is essential not only for the initiation of the mechanism of resistance to Pq, but also for the penetration of Pq into the chloroplasts in the PqR E. canadensis. Also, the Pq elimination process may cause a modification to the regulation of the non-radiative energy dissipation in PqR plants in the presence of Pq. PMID:10938362

  10. Quench dynamics near a quantum critical point: Application to the sine-Gordon model

    NASA Astrophysics Data System (ADS)

    de Grandi, C.; Gritsev, V.; Polkovnikov, A.

    2010-06-01

    We discuss the quench dynamics near a quantum critical point focusing on the sine-Gordon model as a primary example. We suggest a unified approach to sudden and slow quenches, where the tuning parameter λ(t) changes in time as λ(t)˜υtr , based on the adiabatic expansion of the excitation probability in powers of υ . We show that the universal scaling of the excitation probability can be understood through the singularity of the generalized adiabatic susceptibility χ2r+2(λ) , which for sudden quenches (r=0) reduces to the fidelity susceptibility. In turn this class of susceptibilities is expressed through the moments of the connected correlation function of the quench operator. We analyze the excitations created after a sudden quench of the cosine potential using a combined approach of form-factors expansion and conformal perturbation theory for the low-energy and high-energy sector, respectively. We find the general scaling laws for the probability of exciting the system, the density of excited quasiparticles, the entropy and the heat generated after the quench. In the two limits where the sine-Gordon model maps to hard-core bosons and free massive fermions we provide the exact solutions for the quench dynamics and discuss the finite temperature generalizations.

  11. Fluid mechanics of quenching

    NASA Astrophysics Data System (ADS)

    Drew, D. A.; Brent, R.; Melly, S.; Schroeder, W.; Wells, S.

    1985-02-01

    An array of heated rods is lowered vertically in a cold water bath at a constant speed V in order to quench them to obtain desired mechanical properties. Relative to the rods, the water flows in a subchannel, is heated, and boils, while cooling the rods. A model is proposed and studied which considers a one dimensional flow in a subchannel. It is argued that the heat release occurs in a thin region, where water is heated to boiling conditions and boils completely to steam. Above this boiling layer, steam flows rapidly against the friction of the rod bundle. Below the boiling layer, the water flow is approximately hydrostatic. This results in the boiling layer moving at a constant speed proportional to V. The effect of cross flow (leaking into or out of the channel) is also investigated, and the results discussed.

  12. Quench Crucibles Reinforced with Metal

    NASA Technical Reports Server (NTRS)

    Holmes, Richard R.; Carrasquillo, Edgar; O'Dell, J. Scott; McKehnie, N.

    2008-01-01

    Improved crucibles consisting mainly of metal-reinforced ceramic ampules have been developed for use in experiments in which material specimens are heated in the crucibles to various high temperatures, then quenched by, for example, plunging the crucibles into water at room temperature. In a traditional quench crucible, the gap between the ampule and the metal cartridge impedes the transfer of heat to such a degree that the quench rate (the rate of cooling of the specimen) can be too low to produce the desired effect in the specimen. One can increase the quench rate by eliminating the metal cartridge to enable direct quenching of the ampule, but then the thermal shock of direct quenching causes cracking of the ampule. In a quench crucible of the present improved type, there is no gap and no metal cartridge in the traditional sense. Instead, there is an overlay of metal in direct contact with the ampule, as shown on the right side of the figure. Because there is no gap between the metal overlay and the ampule, the heat-transfer rate can be much greater than it is in a traditional quench crucible. The metal overlay also reinforces the ampule against cracking.

  13. Light Response of CO2 Assimilation, Dissipation of Excess Excitation Energy, and Zeaxanthin Content of Sun and Shade Leaves 1

    PubMed Central

    Demmig-Adams, Barbara; Winter, Klaus; Krüger, Almuth; Czygan, Franz-Christian

    1989-01-01

    Intact attached sun leaves of Helianthus annuus and shade leaves of Monstera deliciosa and Hedera helix were used to obtain light response curves of CO2 uptake, the content of the carotenoid zeaxanthin (formed by violaxanthin de-epoxidation), as well as nonphotochemical quenching (qNP), and the rate constant of radiationless energy dissipation (kD). The latter two parameters were calculated from the decrease of chlorophyll a fluorescence at closed photosystem II traps in saturating pulses in the light. Among the three species, the light-saturated capacity of CO2 uptake differed widely and light saturation of CO2 uptake occurred at very different photon flux densities. Fluorescence quenching and zeaxanthin content exhibited features which were common to all three species: below light-saturation of CO2 uptake nonphotochemical quenching occurred in the absence of zeaxanthin and was not accompanied by a decrease in the yield of instantaneous fluorescence. Nonphotochemical quenching, qNP, increased up to values which ranged between 0.35 and 0.5 when based on a control value of the yield of variable fluorescence determined after 12 hours of darkness. As light saturation of CO2 uptake was approached, qNP showed a secondary increase and the zeaxanthin content of the leaves began to rise. This was also the point from which the yield of instantaneous fluorescence began to decrease. The increase in zeaxanthin was paralleled by an increase in the rate constant for radiationless energy dissipation kD, which opens the possibility that zeaxanthin is related to the rapidly relaxing “high-energy-state quenching” in leaves. PMID:16666892

  14. Zeaxanthin and the Induction and Relaxation Kinetics of the Dissipation of Excess Excitation Energy in Leaves in 2% O2, 0% CO21

    PubMed Central

    Demmig-Adams, Barbara; Winter, Klaus; Krüger, Almuth; Czygan, Franz-Christian

    1989-01-01

    The relationship between the carotenoid zeaxanthin, formed by violaxanthin de-epoxidation, and nonphotochemical fluorescence quenching (qNP) in the light was investigated in leaves of Glycine max during a transient from dark to light in 2% O2, 0% CO2 at 100 to 200 micromoles of photons per square meter per second. (a) Up to a qNP (which can vary between 0 and 1) of about 0.7, the zeaxanthin content of leaves was linearly correlated with qNP as well as with the rate constant for radiationless energy dissipation in the antenna chlorophyll (kD). Beyond this point, at very high degrees of fluorescence quenching, only kD was directly proportional to the zeaxanthin content. (b) The relationship between zeaxanthin and kD was quantitatively similar for the rapidly relaxing quenching induced in 2% O2, 0% CO2 at 200 micromoles of photons per square meter per second and for the sustained quenching induced by long-term exposure of Nerium oleander to drought in high light (B Demmig, K Winter, A Krüger, F-C Czygan [1988] Plant Physiol 87: 17-24). These findings suggest that the same dissipation process may be induced by very different treatments and that this particular dissipation process can have widely different relaxation kinetics. (c) A rapid induction of strong nonphotochemical fluorescence quenching within about 1 minute was observed exclusively in leaves which already contained a background level of zeaxanthin. PMID:16666893

  15. Positronium quenching via collisions with triplet states of photomagnetic molecules

    SciTech Connect

    Eom, C.I.; Naidu, S.V.; Sharma, S.C.; Kowalski, J.M. )

    1991-04-01

    We have studied positronium quenching resulting from collisions with the triplet states of benzaldehyde, oxygen, benzophenone, and bromonaphthalene. Positronium pick-off decay rates are presented as functions of triplet populations via uv irradiation of benzaldehyde-ethane, benzaldehyde-helium, and oxgyen-ethane gaseous mixtures and of benzophenone and bromonaphthalene adsorbed porous silicas. Our results show that the cross sections for positronium quenching in collisions with excited triplet states are not as high as reported previously. The oxygen data suggest reactions between hot'' (nonthermal) positronium and oxygen molecules.

  16. Study of intermediates from transition metal excited-state electron- transfer reactions. Progress report, January 1, 1992--March 31, 1993

    SciTech Connect

    Hoffman, M.Z.

    1993-03-31

    Progress on 6 projects is reported: excited state absorption spectrum of Ru(bpy){sub 3}{sup 2+}, solvent cage model for electron transfer quenching, reductive quenching of {sup *}Cr(III) complexes, solution medium effects in oxidative quenching of {sup *}Ru(II) complexes, photosensitized oxidation of phenol in aqueous solution, and quenching of Ru(II) complexes by oxygen.

  17. Universal transport dynamics in a quenched tunnel-coupled Luttinger liquid

    NASA Astrophysics Data System (ADS)

    Gambetta, F. M.; Cavaliere, F.; Citro, R.; Sassetti, M.

    2016-07-01

    The transport dynamics of a quenched Luttinger liquid tunnel-coupled to a fermionic reservoir is investigated. In the transient dynamics, we show that for a sudden quench of the electron interaction universal power-law decay in time of the tunneling current occurs, ascribed to the presence of entangled compound excitations created by the quench. In sharp contrast to the usual nonuniversal power-law behavior of a zero-temperature nonquenched Luttinger liquid, the steady-state tunneling current is Ohmic and can be explained in terms of an effective quench-activated heating of the system. Our study unveils an unconventional dynamics for a quenched Luttinger liquid that could be identified in quenched cold Fermi gases.

  18. Quench ring for a gasifier

    SciTech Connect

    Denbleyker, A.L.

    1989-01-31

    This patent describes a gasifier for the high temperature combustion of a carbonaceous fuel to produce a usable gas, which gasifier includes an insulated shell having a combustion chamber in which the fuel is burned at an elevated temperature and pressure, a quench chamber in the shell holding a liquid bath for cooling products of combustion, a constricted throat communicating the respective combustion chamber and quench chamber, and an elongated dip tube having an inner wall which defines a flow guide path between the combustion chamber and the quench chamber, and having opposed upper and lower edges.

  19. Holographic Jet Quenching

    NASA Astrophysics Data System (ADS)

    Ficnar, Andrej

    In this dissertation we study the phenomenon of jet quenching in quark-gluon plasma using the AdS/CFT correspondence. We start with a weakly coupled, perturbative QCD approach to energy loss, and present a Monte Carlo code for computation of the DGLV radiative energy loss of quarks and gluons at an arbitrary order in opacity. We use the code to compute the radiated gluon distribution up to n=9 order in opacity, and compare it to the thin plasma (n=1) and the multiple soft scattering (n=infinity) approximations. We furthermore show that the gluon distribution at finite opacity depends in detail on the screening mass mu and the mean free path lambda. In the next part, we turn to the studies of how heavy quarks, represented as "trailing strings" in AdS/CFT, lose energy in a strongly coupled plasma. We study how the heavy quark energy loss gets modified in a "bottom-up" non-conformal holographic model, constructed to reproduce some properties of QCD at finite temperature and constrained by fitting the lattice gauge theory results. The energy loss of heavy quarks is found to be strongly sensitive to the medium properties. We use this model to compute the nuclear modification factor RAA of charm and bottom quarks in an expanding plasma with Glauber initial conditions, and comment on the range of validity of the model. The central part of this thesis is the energy loss of light quarks in a strongly coupled plasma. Using the standard model of "falling strings", we present an analytic derivation of the stopping distance of light quarks, previously available only through numerical simulations, and also apply it to the case of Gauss-Bonnet higher derivative gravity. We then present a general formula for computing the instantaneous energy loss in non-stationary string configurations. Application of this formula to the case of falling strings reveals interesting phenomenology, including a modified Bragg-like peak at late times and an approximately linear path dependence. Based

  20. Flavodiiron protein Flv2/Flv4-related photoprotective mechanism dissipates excitation pressure of PSII in cooperation with phycobilisomes in Cyanobacteria.

    PubMed

    Bersanini, Luca; Battchikova, Natalia; Jokel, Martina; Rehman, Ateeq; Vass, Imre; Allahverdiyeva, Yagut; Aro, Eva-Mari

    2014-02-01

    Oxygenic photosynthesis evolved with cyanobacteria, the ancestors of plant chloroplasts. The highly oxidizing chemistry of water splitting required concomitant evolution of efficient photoprotection mechanisms to safeguard the photosynthetic machinery. The role of flavodiiron proteins (FDPs), originally called A-type flavoproteins or Flvs, in this context has only recently been appreciated. Cyanobacterial FDPs constitute a specific protein group that evolved to protect oxygenic photosynthesis. There are four FDPs in Synechocystis sp. PCC 6803 (Flv1 to Flv4). Two of them, Flv2 and Flv4, are encoded by an operon together with a Sll0218 protein. Their expression, tightly regulated by CO2 levels, is also influenced by changes in light intensity. Here we describe the overexpression of the flv4-2 operon in Synechocystis sp. PCC 6803 and demonstrate that it results in improved photochemistry of PSII. The flv4-2/OE mutant is more resistant to photoinhibition of PSII and exhibits a more oxidized state of the plastoquinone pool and reduced production of singlet oxygen compared with control strains. Results of biophysical measurements indicate that the flv4-2 operon functions in an alternative electron transfer pathway from PSII, and thus alleviates PSII excitation pressure by channeling up to 30% of PSII-originated electrons. Furthermore, intact phycobilisomes are required for stable expression of the flv4-2 operon genes and for the Flv2/Flv4 heterodimer-mediated electron transfer mechanism. The latter operates in photoprotection in a complementary way with the orange carotenoid protein-related nonphotochemical quenching. Expression of the flv4-2 operon and exchange of the D1 forms in PSII centers upon light stress, on the contrary, are mutually exclusive photoprotection strategies among cyanobacteria. PMID:24367022

  1. Selective quenching of 2-naphtholate fluorescence by imidazolium ionic liquids.

    PubMed

    Kumar, Vinod; Pandey, Siddharth

    2012-10-01

    The effect of addition of water-miscible ionic liquids (ILs), 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF(4)]), 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([bmim][OTf]), and 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate ([bmpyrr][OTf]), on photophysical properties of 2-naphthol in water at various pHs is reported. Electronic absorbance behavior of 2-naphthol dissolved in aqueous mixtures of ILs is observed to be similar to that found in water at different pHs. The excited-state properties, however, are changed dramatically as the IL is added to the milieu. The presence of imidazolium IL results in significant quenching of the fluorescence emission from 2-naphtholate. On the contrary, pyrrolidinium IL does not quench the fluorescence from the anionic species. The quenching of 2-naphtholate fluorescence by aromatic imidazolium cations in aqueous IL mixtures is found to follow simple Stern-Volmer behavior. The aromatic imidazolium cation acts as an electron/charge acceptor during the quenching process where formation of a weakly fluorescent complex between the imidazolium cation and the excited 2-naphtholate anion possibly involving the acidic C2 proton of imidazolium is proposed. Because of the absence of such an acidic proton, the nonaromatic pyrrolidinium cation is not able to form a complex with the excited 2-naphtholate and cannot act as an electron/charge acceptor. Excited-state emission intensity decay data further corroborate this hypothesis as the intensity decay fits well to a single-exponential decay with no change in recovered lifetimes as [bmpyrr][OTf] is added; a double-exponential decay is required to satisfactorily fit the decay data in the presence of [bmim][BF(4)], hinting at the presence of a weakly fluorescent complex. The uniqueness of ILs in affecting excited-state properties of the 2-naphthol system is demonstrated through comparison with NaBF(4), NaCl, and polyethylene glycol with an average molecular weight of

  2. Holographic quenches with a gap

    NASA Astrophysics Data System (ADS)

    da Silva, Emilia; Lopez, Esperanza; Mas, Javier; Serantes, Alexandre

    2016-06-01

    In order to holographically model quenches with a gapped final hamiltonian, we consider a gravity-scalar theory in anti-de Sitter space with an infrared hard wall. We allow a time dependent profile for the scalar field at the wall. This induces an energy exchange between bulk and wall and generates an oscillating scalar pulse. We argue that such backgrounds are the counterpart of quantum revivals in the dual field theory. We perform a qualitative comparison with the quench dynamics of the massive Schwinger model, which has been recently analyzed using tensor network techniques. Agreement is found provided the width of the oscillating scalar pulse is inversely linked to the energy density communicated by the quench. We propose this to be a general feature of holographic quenches.

  3. Single vs multi-level quenching of the hydroxyl airglow

    NASA Astrophysics Data System (ADS)

    Franzen, Christoph; Espy, Patrick J.; Hibbins, Robert; Djupvik, Anlaug Amanda

    2016-04-01

    The reaction in the upper mesosphere between atomic hydrogen and ozone results in hydroxyl (OH) that is produced in excited vibrational levels 6 through 9. The vibrationally excited OH radiates in a thin (~8 km thick) layer near 87 km, giving rise to the strong near infrared airglow emission that has been used for remote sensing of the mesopause region. The interpretation of the emission relies on accurate knowledge of the population and quenching of the upper states, and open questions remain as to whether the quenching takes place through single- or multi-quantum deactivation. Here we will demonstrate how high quality spectral observations of OH (9,7) and (8,6) airglow emissions are available as background measurements during standard K-band astronomical observations from the Nordic Optical Telescope (18°W, 29°N). These emissions have been analysed to ascertain the quenching of the upper vibrational populations. Together with a steady-state model of these emissions, an estimate of the ratio of single to multi-quantum quenching efficiency and the impact on the populations of the lower vibrational levels will be presented.

  4. Study of fluorescence quenching of Barley α-amylase

    NASA Astrophysics Data System (ADS)

    Bakkialakshmi, S.; Shanthi, B.; Bhuvanapriya, T.

    2012-05-01

    The fluorescence quenching of Barley α-amylase by acrylamide and succinimide has been studied in water using steady-state and time-resolved fluorescence techniques. The steady-state fluorescence quenching technique has been performed in three different pHs (i.e., 6, 7 and 8) of water. Ground state and excited state binding constants (Kg &Ke) have been calculated. From the calculated binding constants (Kg &Ke) the free energy changes for the ground (ΔGg) and excited (ΔGe) states have been calculated and are presented in tables. UV and FTIR spectra have also been recorded to prove the binding of Barley α-amylase with acrylamide and succinimide.

  5. Electronic excitation and quenching of atoms at insulator surfaces

    NASA Technical Reports Server (NTRS)

    Swaminathan, P. K.; Garrett, Bruce C.; Murthy, C. S.

    1988-01-01

    A trajectory-based semiclassical method is used to study electronically inelastic collisions of gas atoms with insulator surfaces. The method provides for quantum-mechanical treatment of the internal electronic dynamics of a localized region involving the gas/surface collision, and a classical treatment of all the nuclear degrees of freedom (self-consistently and in terms of stochastic trajectories), and includes accurate simulation of the bath-temperature effects. The method is easy to implement and has a generality that holds promise for many practical applications. The problem of electronically inelastic dynamics is solved by computing a set of stochastic trajectories that on thermal averaging directly provide electronic transition probabilities at a given temperature. The theory is illustrated by a simple model of a two-state gas/surface interaction.

  6. Continuum limit of quenched theories

    SciTech Connect

    Holdom, B.

    1989-02-27

    We study chiral-symmetry breaking in quenched gauge theories with ultraviolet cutoff ..lambda.., to all orders in the gauge coupling. For large ..lambda../kappa, where kappa is the chiral-symmetry-breaking scale, we derive ..lambda../kappaproportionalexp(const/ ..sqrt..(..cap alpha..-..cap alpha../sub c/) as ..cap alpha --> cap alpha../sub c/+. This is a gauge-invariant, universal consequence of quenched theories. But we argue that this relation does not define a ..beta.. function. We also obtain an explicit expression for the self-energy ..sigma..(p) which applies over most of the range kappa

  7. ENVIRONMENTAL ASSESSMENT OF DRY COKE QUENCHING VS. CONTINUOUS WET QUENCHING

    EPA Science Inventory

    The report gives results of an assessment of the multimedia environmental impacts of continuous wet and dry quenching at National Steel's Weirton, West Virginia, Brown's Island coke plant. The report, based primarily on design data, test data from related processes, and engineeri...

  8. Quench anaylsis of MICE spectrometer superconducting solenoid

    SciTech Connect

    Kashikhin, Vladimir; Bross, Alan; Prestemon, Soren; / /LBL, Berkeley

    2011-09-01

    MICE superconducting spectrometer solenoids fabrication and tests are in progress now. First tests of the Spectrometer Solenoid discovered some issues which could be related to the chosen passive quench protection system. Both solenoids do not have heaters and quench propagation relied on the 'quench back' effect, cold diodes, and shunt resistors. The solenoids have very large inductances and stored energy which is 100% dissipated in the cold mass during a quench. This makes their protection a challenging task. The paper presents the quench analysis of these solenoids based on 3D FEA solution of coupled transient electromagnetic and thermal problems. The simulations used the Vector Fields QUENCH code. It is shown that in some quench scenarios, the quench propagation is relatively slow and some areas can be overheated. They describe ways of improving the solenoids quench protection in order to reduce the risk of possible failure.

  9. A study of polymer quenching on gears

    SciTech Connect

    Zhao, H.; Yi, T.

    1996-12-31

    The quenching oil was widely used as a quenchant for the carburized gear direct hardening. With the progress of the quenching technology, however, the oil quenching of gears has been successfully replaced by the polymer quenching in the production. This paper will investigate the principle and application of gear quenching to replace oil, with aqueous polymer quenchants. During the direct quenching of carburized gear and precision forging gear, cracking and distortion reduction, and maximum and uniformity hardness can be achieved. From the quenching process and economic, advantages and limitations of polymer quenching of gears will be discussed. The data of production indicate that it is suitable for gear hardening to use polymer quenchant. The characteristics of polymer quenching are the improved performance, reduced fire hazards and environmental safety, processing flexibility and lower process costs.

  10. Fluorescence quenching induced by conformational fluctuations in unsolvated polypeptides.

    PubMed

    Shi, Xiangguo; Duft, Denis; Parks, Joel H

    2008-10-01

    Time-resolved measurements were conducted to relate the fluorescence lifetimes of dye-derivatized polypeptides to local conformational dynamics in trapped, unsolvated peptide ions. This research was performed to better understand the intramolecular interactions leading to the observed increase of fluorescence quenching with temperature and, in particular, how this quenching is related to conformational fluctuations. Dye-derivatized polyproline ions, Dye-[Pro] n -Arg (+)-Trp, are formed by electrospray ionization and trapped in a variable-temperature quadrupole ion trap where they are exposed to a pulsed laser which excites fluorescence. Lifetime data exhibit fluorescence quenching as a result of an interaction between the dye and tryptophan (Trp) side chain. This result is consistent with solution measurements performed for comparison. The lifetime temperature dependence is closely fit over the range 150-463 K by an Arrhenius model of the ensemble averaged quenching rate, k q. Model fits of the measured lifetimes yield a frequency prefactor of approximately 10 (11) s (-1) for k q characteristic of collective motions of the side chains identified in molecular dynamics (MD) simulations. The data fits also yield activation barriers of approximately 0.3 eV, which are comparable to intramolecular electrostatic interactions calculated between the unshielded charge on the Arg residue and the dye. As a result, the quenching rate appears to be determined by the rate of conformational fluctuations and not by the rate of a specific quenching mechanism. The peptide sequence of Dye-Trp-[Pro] n -Arg (+) was also studied and identified a dependence of the quenching rate on the electrostatic field in the vicinity of the dye, Trp pair. Molecular dynamics simulations were performed over the range of experimental measurements to study trajectories relevant to the quenching interaction. The MD simulations indicate that as the temperature is increased, conformational fluctuations in

  11. Atomizer with liquid spray quenching

    DOEpatents

    Anderson, Iver E.; Osborne, Matthew G.; Terpstra, Robert L.

    1998-04-14

    Method and apparatus for making metallic powder particles wherein a metallic melt is atomized by a rotating disk or other atomizer at an atomizing location in a manner to form molten droplets moving in a direction away from said atomizing location. The atomized droplets pass through a series of thin liquid quenching sheets disposed in succession about the atomizing location with each successive quenching sheet being at an increasing distance from the atomizing location. The atomized droplets are incrementally cooled and optionally passivated as they pass through the series of liquid quenching sheets without distorting the atomized droplets from their generally spherical shape. The atomized, cooled droplets can be received in a chamber having a collection wall disposed outwardly of the series of liquid quenching sheets. A liquid quenchant can be flowed proximate the chamber wall to carry the cooled atomized droplets to a collection chamber where atomized powder particles and the liquid quenchant are separated such that the liquid quenchant can be recycled.

  12. Atomizer with liquid spray quenching

    DOEpatents

    Anderson, I.E.; Osborne, M.G.; Terpstra, R.L.

    1998-04-14

    Method and apparatus are disclosed for making metallic powder particles wherein a metallic melt is atomized by a rotating disk or other atomizer at an atomizing location in a manner to form molten droplets moving in a direction away from said atomizing location. The atomized droplets pass through a series of thin liquid quenching sheets disposed in succession about the atomizing location with each successive quenching sheet being at an increasing distance from the atomizing location. The atomized droplets are incrementally cooled and optionally passivated as they pass through the series of liquid quenching sheets without distorting the atomized droplets from their generally spherical shape. The atomized, cooled droplets can be received in a chamber having a collection wall disposed outwardly of the series of liquid quenching sheets. A liquid quenchant can be flowed proximate the chamber wall to carry the cooled atomized droplets to a collection chamber where atomized powder particles and the liquid quenchant are separated such that the liquid quenchant can be recycled. 6 figs.

  13. Chiral logarithms in quenched QCD

    SciTech Connect

    Y. Chen; S. J. Dong; T. Draper; I. Horvath; F. X. Lee; K. F. Liu; N. Mathur; and J. B. Zhang

    2004-08-01

    The quenched chiral logarithms are examined on a 163x28 lattice with Iwasaki gauge action and overlap fermions. The pion decay constant fpi is used to set the lattice spacing, a = 0.200(3) fm. With pion mass as low as {approx}180 MeV, we see the quenched chiral logarithms clearly in mpi2/m and fP, the pseudoscalar decay constant. The authors analyze the data to determine how low the pion mass needs to be in order for the quenched one-loop chiral perturbation theory (chiPT) to apply. With the constrained curve-fitting method, they are able to extract the quenched chiral logarithmic parameter delta together with other low-energy parameters. Only for mpi<=300 MeV do we obtain a consistent and stable fit with a constant delta which they determine to be 0.24(3)(4) (at the chiral scale Lambdachi = 0.8 GeV). By comparing to the 123x28 lattice, they estimate the finite volume effect to be about 2.7% for the smallest pion mass. They also fitted the pion mass to the form for the re-summed cactus diagrams and found that its applicable region is extended farther than the range for the one-loop formula, perhaps up to mpi {approx}500-600 MeV. The scale independent delta is determined to be 0.20(3) in this case. The authors study the quenched non-analytic terms in the nucleon mass and find that the coefficient C1/2 in the nucleon mass is consistent with the prediction of one-loop chiPT. They also obtain the low energy constant L5 from fpi. They conclude from this study that it is imperative to cover only the range of data with the pion mass less than {approx}300 MeV in order to examine the chiral behavior of the hadron masses and decay constants in quenched QCD and match them with quenched one-loop chiPT.

  14. Effects of cyclosis on chloroplast-cytoplasm interactions revealed with localized lighting in Characean cells at rest and after electrical excitation.

    PubMed

    Bulychev, Alexander A; Dodonova, Svetlana O

    2011-09-01

    Cytoplasmic streaming in Characean internodes enables rapid intracellular transport and facilitates interactions between spatially remote cell regions. Cyclosis-mediated distant interactions might be particularly noticeable under nonuniform illumination, in the vicinity of light-shade borders where metabolites are transported between functionally distinct cell regions. In support of this notion, chlorophyll fluorescence parameters assessed on a microscopic area of Chara corallina internodal cells (area of inspection, AOI) responded to illumination of nearby regions in asymmetric manner depending on the vector of cytoplasmic streaming. When a beam of white light was applied through a 400-μm optic fiber upstream of AOI with regard to the direction of cytoplasmic streaming, non-photochemical quenching (NPQ) developed after a lag period in AOI exposed to moderate intensity light. Conversely, no NPQ was induced in the same cell area when the beam position was shifted to an equal distance downstream of AOI. Light-response curves for the efficiency of photosystem II electron transport in chloroplasts differed markedly depending on the illumination pattern (whole-cell versus small area illumination) but these differences were eliminated after the inhibition of cytoplasmic streaming with cytochalasin B. Localized illumination promoted chloroplast fluorescence responses to electrical plasmalemma excitation at high light intensities, which contrasts to the requirement of low to moderate irradiances for observation of the stimulus-response coupling under whole-cell illumination. The results indicate that different photosynthetic capacities of chloroplasts under general and localized illumination are related to lateral transport of nonevenly distributed cytoplasmic components between the cell parts with dominant photosynthetic and respiratory metabolism. PMID:21708122

  15. Nonphotochemical hole burning of organic dyes and rare earth ions in polymers and glasses: a probe of the amorphous state

    SciTech Connect

    Fearey, B.L.

    1986-01-01

    New and in depth studies of amorphous materials (e.g., glasses and polymers) probed via the low temperature optical technique of nonphotochemical hole burning (NPHB) are presented. An extensive review of the phenomena itself, along with selected topics involving the use of persistent hole burning techniques, is given. In addition, a semi-complete tabulation of essentially all hole burning systems to date is included. The deuteration dependence in an amorphous host is examined for the system of tetracene in an ethanol/methanol mixture. The results illustrate the importance of hydrogen bonding in the hole burning process. The discovery of a highly efficient (or facile) class of hole burning systems, i.e., ionic dyes in hydroxylated polymers (i.e., poly(vinyl alcohol) (PVOH) and poly(acrylic acid) (PAA)), is presented and discussed. Ultrafast relaxation processes (i.e., dephasing) are studied for the system of cresyl violet perchlorate (CV) in PVOH. Further, for the first time, NPHB of rare earth ions, specifically Pr/sup +3/ and Nd/sup +3/, in a soft organic glass (i.e., PVOH) is discussed briefly. Detailed experimental results of two related phenomena, spontaneous hole filling (SPHF) and laser induced hole filling (LIHF), are presented and discussed for several systems: rhodamine 560 perchlorate (R560), rhodamine 640 perchlorate (R640), CV, Pr/sup +3/ and Nd..mu../sup 3/ in either PVOH or PAA. A theoretical model is developed for SPHF. The model invokes a correlated feedback mechanism from the anti-hole, which is able to account for the fact that no line broadening is observed. A tentative model is also presented for the phenomenon of LIHF.

  16. Rapid-quench axially staged combustor

    DOEpatents

    Feitelberg, Alan S.; Schmidt, Mark Christopher; Goebel, Steven George

    1999-01-01

    A combustor cooperating with a compressor in driving a gas turbine includes a cylindrical outer combustor casing. A combustion liner, having an upstream rich section, a quench section and a downstream lean section, is disposed within the outer combustor casing defining a combustion chamber having at least a core quench region and an outer quench region. A first plurality of quench holes are disposed within the liner at the quench section having a first diameter to provide cooling jet penetration to the core region of the quench section of the combustion chamber. A second plurality of quench holes are disposed within the liner at the quench section having a second diameter to provide cooling jet penetration to the outer region of the quench section of the combustion chamber. In an alternative embodiment, the combustion chamber quench section further includes at least one middle region and at least a third plurality of quench holes disposed within the liner at the quench section having a third diameter to provide cooling jet penetration to at least one middle region of the quench section of the combustion chamber.

  17. Charmonium excited state spectrum in lattice QCD

    SciTech Connect

    Jozef Dudek; Robert Edwards; Nilmani Mathur; David Richards

    2008-02-01

    Working with a large basis of covariant derivative-based meson interpolating fields we demonstrate the feasibility of reliably extracting multiple excited states using a variational method. The study is performed on quenched anisotropic lattices with clover quarks at the charm mass. We demonstrate how a knowledge of the continuum limit of a lattice interpolating field can give additional spin-assignment information, even at a single lattice spacing, via the overlap factors of interpolating field and state. Excited state masses are systematically high with respect to quark potential model predictions and, where they exist, experimental states. We conclude that this is most likely a result of the quenched approximation.

  18. Quenching in Arabidopsis thaliana mutants lacking monomeric antenna proteins of photosystem II.

    PubMed

    Miloslavina, Yuliya; de Bianchi, Silvia; Dall'Osto, Luca; Bassi, Roberto; Holzwarth, Alfred R

    2011-10-21

    The minor light-harvesting complexes CP24, CP26, and CP29 have been proposed to play a key role in the zeaxanthin (Zx)-dependent high light-induced regulation (NPQ) of excitation energy in higher plants. To characterize the detailed roles of these minor complexes in NPQ and to determine their specific quenching effects we have studied the ultrafast fluorescence kinetics in knockout (ko) mutants koCP26, koCP29, and the double mutant koCP24/CP26. The data provide detailed insight into the quenching processes and the reorganization of the Photosystem (PS) II supercomplex under quenching conditions. All genotypes showed two NPQ quenching sites. Quenching site Q1 is formed by a light-induced functional detachment of parts of the PSII supercomplex and a pronounced quenching of the detached antenna parts. The antenna remaining bound to the PSII core was also quenched substantially in all genotypes under NPQ conditions (quenching site Q2) as compared with the dark-adapted state. The latter quenching was about equally strong in koCP26 and the koCP24/CP26 mutants as in the WT. Q2 quenching was substantially reduced, however, in koCP29 mutants suggesting a key role for CP29 in the total NPQ. The observed quenching effects in the knockout mutants are complicated by the fact that other minor antenna complexes do compensate in part for the lack of the CP24 and/or CP29 complexes. Their lack also causes some LHCII dissociation already in the dark. PMID:21844190

  19. Quenching in Arabidopsis thaliana Mutants Lacking Monomeric Antenna Proteins of Photosystem II*

    PubMed Central

    Miloslavina, Yuliya; de Bianchi, Silvia; Dall'Osto, Luca; Bassi, Roberto; Holzwarth, Alfred R.

    2011-01-01

    The minor light-harvesting complexes CP24, CP26, and CP29 have been proposed to play a key role in the zeaxanthin (Zx)-dependent high light-induced regulation (NPQ) of excitation energy in higher plants. To characterize the detailed roles of these minor complexes in NPQ and to determine their specific quenching effects we have studied the ultrafast fluorescence kinetics in knockout (ko) mutants koCP26, koCP29, and the double mutant koCP24/CP26. The data provide detailed insight into the quenching processes and the reorganization of the Photosystem (PS) II supercomplex under quenching conditions. All genotypes showed two NPQ quenching sites. Quenching site Q1 is formed by a light-induced functional detachment of parts of the PSII supercomplex and a pronounced quenching of the detached antenna parts. The antenna remaining bound to the PSII core was also quenched substantially in all genotypes under NPQ conditions (quenching site Q2) as compared with the dark-adapted state. The latter quenching was about equally strong in koCP26 and the koCP24/CP26 mutants as in the WT. Q2 quenching was substantially reduced, however, in koCP29 mutants suggesting a key role for CP29 in the total NPQ. The observed quenching effects in the knockout mutants are complicated by the fact that other minor antenna complexes do compensate in part for the lack of the CP24 and/or CP29 complexes. Their lack also causes some LHCII dissociation already in the dark. PMID:21844190

  20. Cryogenic exciter

    SciTech Connect

    Bray, James William; Garces, Luis Jose

    2012-03-13

    The disclosed technology is a cryogenic static exciter. The cryogenic static exciter is connected to a synchronous electric machine that has a field winding. The synchronous electric machine is cooled via a refrigerator or cryogen like liquid nitrogen. The static exciter is in communication with the field winding and is operating at ambient temperature. The static exciter receives cooling from a refrigerator or cryogen source, which may also service the synchronous machine, to selected areas of the static exciter and the cooling selectively reduces the operating temperature of the selected areas of the static exciter.

  1. Fast quench reactor and method

    SciTech Connect

    Detering, Brent A.; Donaldson, Alan D.; Fincke, James R.; Kong, Peter C.

    2002-01-01

    A fast quench reaction includes a reactor chamber having a high temperature heating means such as a plasma torch at its inlet and a restrictive convergent-divergent nozzle at its outlet end. Reactants are injected into the reactor chamber. The resulting heated gaseous stream is then rapidly cooled by passage through the nozzle. This "freezes" the desired end product(s) in the heated equilibrium reaction stage.

  2. Fast quench reactor and method

    SciTech Connect

    Detering, Brent A.; Donaldson, Alan D.; Fincke, James R.; Kong, Peter C.

    1998-01-01

    A fast quench reaction includes a reactor chamber having a high temperature heating means such as a plasma torch at its inlet and a restrictive convergent-divergent nozzle at its outlet end. Reactants are injected into the reactor chamber. The resulting heated gaseous stream is then rapidly cooled by passage through the nozzle. This "freezes" the desired end product(s) in the heated equilibrium reaction stage.

  3. Fast quench reactor and method

    SciTech Connect

    Detering, Brent A.; Donaldson, Alan D.; Fincke, James R.; Kong, Peter C.

    2002-09-24

    A fast quench reaction includes a reactor chamber having a high temperature heating means such as a plasma torch at its inlet and a restrictive convergent-divergent nozzle at its outlet end. Reactants are injected into the reactor chamber. The resulting heated gaseous stream is then rapidly cooled by passage through the nozzle. This "freezes" the desired end product(s) in the heated equilibrium reaction stage.

  4. Fast quench reactor and method

    DOEpatents

    Detering, B.A.; Donaldson, A.D.; Fincke, J.R.; Kong, P.C.

    1998-05-12

    A fast quench reactor includes a reactor chamber having a high temperature heating means such as a plasma torch at its inlet and a restrictive convergent-divergent nozzle at its outlet end. Reactants are injected into the reactor chamber. The resulting heated gaseous stream is then rapidly cooled by passage through the nozzle. This ``freezes`` the desired end product(s) in the heated equilibrium reaction stage. 7 figs.

  5. TASK 2: QUENCH ZONE SIMULATION

    SciTech Connect

    Fusselman, Steve

    2015-09-30

    Aerojet Rocketdyne (AR) has developed an innovative gasifier concept incorporating advanced technologies in ultra-dense phase dry feed system, rapid mix injector, and advanced component cooling to significantly improve gasifier performance, life, and cost compared to commercially available state-of-the-art systems. A key feature of the AR gasifier design is the transition from the gasifier outlet into the quench zone, where the raw syngas is cooled to ~ 400°C by injection and vaporization of atomized water. Earlier pilot plant testing revealed a propensity for the original gasifier outlet design to accumulate slag in the outlet, leading to erratic syngas flow from the outlet. Subsequent design modifications successfully resolved this issue in the pilot plant gasifier. In order to gain greater insight into the physical phenomena occurring within this zone, AR developed a cold flow simulation apparatus with Coanda Research & Development with a high degree of similitude to hot fire conditions with the pilot scale gasifier design, and capable of accommodating a scaled-down quench zone for a demonstration-scale gasifier. The objective of this task was to validate similitude of the cold flow simulation model by comparison of pilot-scale outlet design performance, and to assess demonstration scale gasifier design feasibility from testing of a scaled-down outlet design. Test results did exhibit a strong correspondence with the two pilot scale outlet designs, indicating credible similitude for the cold flow simulation device. Testing of the scaled-down outlet revealed important considerations in the design and operation of the demonstration scale gasifier, in particular pertaining to the relative momentum between the downcoming raw syngas and the sprayed quench water and associated impacts on flow patterns within the quench zone. This report describes key findings from the test program, including assessment of pilot plant configuration simulations relative to actual

  6. Quenching of chlorophyll fluorescence induced by silver nanoparticles.

    PubMed

    Queiroz, A M; Mezacasa, A V; Graciano, D E; Falco, W F; M'Peko, J-C; Guimarães, F E G; Lawson, T; Colbeck, I; Oliveira, S L; Caires, A R L

    2016-11-01

    The interaction between chlorophyll (Chl) and silver nanoparticles (AgNPs) was evaluated by analyzing the optical behavior of Chl molecules surrounded by different concentrations of AgNPs (10, 60, and 100nm of diameter). UV-Vis absorption, steady state and time-resolved fluorescence measurements were performed for Chl in the presence and absence of these nanoparticles. AgNPs strongly suppressed the Chl fluorescence intensity at 678nm. The Stern-Volmer constant (KSV) showed that fluorescence suppression is driven by the dynamic quenching process. In particular, KSV was nanoparticle size-dependent with an exponential decrease as a function of the nanoparticle diameter. Finally, changes in the Chl fluorescence lifetime in the presence of nanoparticles demonstrated that the fluorescence quenching may be induced by the excited electron transfer from the Chl molecules to the metal nanoparticles. PMID:27280858

  7. Nonphotochemical Hole-Burning Imaging Studies of in vitro Carcinoma and Normal Cells Utilizing a Mitochondrial Specific Dye

    SciTech Connect

    Richard Joseph Walsh

    2002-06-27

    Low temperature Nonphotochemical Hole Burning (NPHB) Spectroscopy of the dye rhodamine 800 (MF680) was applied for the purpose of discerning differences between cultured normal and carcinoma ovarian surface epithelial (OSE) cells. Both the cell lines were developed and characterized at the Mayo Clinic (Rochester, MN), with the normal cell line having been transfected with a strain of temperature sensitive Simian Virus 40 Large T Antigen (SV40) for the purpose of extending the life of the cell culture without inducing permanent changes in the characteristics of the cell line. The cationic lipophilic fluorophore rhodamine 800 preferentially locates in in situ mitochondria due to the high lipid composition of mitochondria and the generation of a large negative membrane potential (relative to the cellular cytoplasm) for oxidative phosphorylation. Results presented for NPHB of MF680 located in the cells show significant differences between the two cell lines. The results are interpreted on the basis of the NPHB mechanism and characteristic interactions between the host (cellular mitochondrial) and the guest (MF680) in the burning of spectral holes, thus providing an image of the cellular ultrastructure. Hole growth kinetics (HGK) were found to differ markedly between the two cell lines, with the carcinoma cell line burning at a faster average rate for the same exposure fluence. Theoretical fits to the data suggest a lower degree of structural heterogeneity in the carcinoma cell line relative to the normal cell line. Measurement of changes in the permanent dipole moment (f{Delta}{mu}) were accomplished by measurement of changes in hole width in response to the application of an external electric field (the Stark effect), and found that {Delta}{mu} values for the carcinoma line were 1.5x greater than those of the SV40 antigen-free normal analogs. These findings are interpreted in terms of effects from the mitochondrial membrane potential. Results for HGK on the scale of

  8. Nonphotochemical Hole-Burning Imaging Studies of In Vitro Carcinoma and Normal Cells Utilizing a Mitochondrial Specific Dye

    SciTech Connect

    Richard Joseph Walsh

    2002-08-01

    Low temperature Nonphotochemical Hole Burning (NPHB) Spectroscopy of the dye rhodamine 800 (MF680) was applied for the purpose of discerning differences between cultured normal and carcinoma ovarian surface epithelial (OSE) cells. Both the cell lines were developed and characterized at the Mayo Clinic (Rochester, MN), with the normal cell line having been transfected with a strain of temperature sensitive Simian Virus 40 Large T Antigen (SV40) for the purpose of extending the life of the cell culture without inducing permanent changes in the characteristics of the cell line. The cationic lipophilic fluorophore rhodamine 800 preferentially locates in in situ mitochondria due to the high lipid composition of mitochondria and the generation of a large negative membrane potential (relative to the cellular cytoplasm) for oxidative phosphorylation. Results presented for NPHB of MF680 located in the cells show significant differences between the two cell lines. The results are interpreted on the basis of the NPHB mechanism and characteristic interactions between the host (cellular mitochondrial) and the guest (MF680) in the burning of spectral holes, thus providing an image of the cellular ultrastructure. Hole growth kinetics (HGK) were found to differ markedly between the two cell lines, with the carcinoma cell line burning at a faster average rate for the same exposure fluence. Theoretical fits to the data suggest a lower degree of structural heterogeneity in the carcinoma cell line relative to the normal cell line. Measurement of changes in the permanent dipole moment (f{Delta}{mu})were accomplished by measurement of changes in hole width in response to the application of an external electric field (the Stark effect), and found that {Delta}{mu} values for the carcinoma line were 1.5x greater than those of the SV40 antigen-free normal analogs. These findings are interpreted in terms of effects from the mitochondrial membrane potential. Results for HGK on the scale of

  9. Europium doped lanthanum zirconate nanoparticles with high concentration quenching

    SciTech Connect

    Alaparthi, Suresh B.; Lu, Long; Tian, Yue; Mao, Yuanbing

    2014-01-01

    Graphical abstract: - Highlights: • Eu:La{sub 2}Zr{sub 2}O{sub 7} nanoparticles were prepared facilely by a kinetically modified molten salt method. • High color purity and concentration quenching were achieved in these La{sub 2}Zr{sub 2}O{sub 7}:Eu nanoparticles. • Concentration quenching mechanism was discussed for Eu{sup 3+} in these Eu:La{sub 2}Zr{sub 2}O{sub 7} nanoparticles. - Abstract: A series of Eu{sup 3+} doped lanthanum zirconate (La{sub 2}Zr{sub 2}O{sub 7}) nanoparticles (NPs, 20 ± 5 nm in diameter) with cubic fluorite structure were facilely synthesized by a kinetically modified molten salt synthetic (MSS) process and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and photoluminescence spectra (PL). Under the excitation of 405 nm, intense red emission with high color purity can be observed in the Eu{sup 3+} doped La{sub 2}Zr{sub 2}O{sub 7} NPs. Moreover, the as-prepared Eu:La{sub 2}Zr{sub 2}O{sub 7} NPs possess high concentration quenching, which is as high as ∼32.5 mol% of europium dopants in the La{sub 2}Zr{sub 2}O{sub 7} host. The corresponding concentration quenching mechanism was discussed as well. Our results confirm that the kinetically modified MSS process is a promising approach for preparing rare earth (RE) ions doped A{sub 2}B{sub 2}O{sub 7} nanoparticles with uniform RE doping and high concentration quenching.

  10. Fluorescence lifetime imaging microscopy reveals quenching of fluorescein within corneal epithelium.

    PubMed

    Glasgow, Ben J

    2016-06-01

    Topical application of fluorescein results in background fluorescence of normal corneal epithelial cells. The fluorescence appears relatively weak and is often ignored clinically. The concentrations of fluorescein applied clinically exceed the threshold for self quenching. The possibility that exuberant topical concentrations of fluorescein result in quenching of fluorescence in tears and normal corneal epithelium is explored. Fluorescence lifetime measurements are sensitive to quenching and are less vulnerable to inner filter effect than steady state measurements. The types of fluorescence lifetime quenching often report informative molecular interactions. Therefore, fluorescence lifetime confocal imaging was performed in solutions, tears and corneal epithelium removed by membrane cytology following applied fluorescein. Amplitude averaged fluorescence lifetimes (τamp) were measured with time resolved single photon counting using a pulsed diode laser for excitation of fluorescein. Lifetime decays were fit to multi-exponential models with least squares analysis. Stern-Volmer plots for both intensity (I) and (τamp) were determined. Stern-Volmer plots demonstrated both dynamic and static quenching components (R(2) = 0.98 exponential fit, I0/I). Plots of τamp versus concentration of fluorescein revealed a linear relationship. Immediately after fluorescein application, quenching was evident in tears (τamp < 1 ns) versus tears sampled after 5 min (τamp = 3.7 ns). Corneal epithelium showed quenching (τamp ≤ 2 ns) from 1 to 16 min post fluorescein instillation. Clinical concentrations of fluorescein show self-quenching but rapidly dilute as tears turnover. Intracellular quenching occurs in normal corneal epithelium. Lifetime decay curves suggest complex mechanisms are involved. Quenching is a plausible explanation for the low fluorescence background observed clinically. PMID:27106141

  11. The impact of nanoperforation on persistent photoconductivity and optical quenching effects in suspended GaN nanomembranes

    NASA Astrophysics Data System (ADS)

    Volciuc, Olesea; Braniste, Tudor; Tiginyanu, Ion; Stevens-Kalceff, Marion A.; Ebeling, Jakob; Aschenbrenner, Timo; Hommel, Detlef; Ursaki, Veaceslav; Gutowski, Jürgen

    2013-12-01

    We report on fabrication of suspended ˜15 nm thick GaN membranes nanoperforated in an ordered fashion using direct writing of negative charges by focused ion beam and subsequent photoelectrochemical etching of GaN epilayers. Both continuous and nanoperforated membranes exhibit persistent photoconductivity (PPC), which can be optically quenched under excitation by 546 nm radiation. Optical quenching of PPC occurs also under relatively intense intrinsic excitation of nanoperforated membranes by 355 nm radiation at T < 100 K. The proposed explanation is based on strong surface localization of charge carriers in nanoperforated membranes and UV-induced reactions occurring at surface states under intense intrinsic excitation.

  12. Quenching star formation in cluster galaxies

    NASA Astrophysics Data System (ADS)

    Taranu, Dan S.; Hudson, Michael J.; Balogh, Michael L.; Smith, Russell J.; Power, Chris; Oman, Kyle A.; Krane, Brad

    2014-05-01

    In order to understand the processes that quench star formation in cluster galaxies, we construct a library of subhalo orbits drawn from Λ cold dark matter cosmological N-body simulations of four rich clusters. We combine these orbits with models of star formation followed by environmental quenching, comparing model predictions with observed bulge and disc colours and stellar absorption line-strength indices of luminous cluster galaxies. Models in which the bulge stellar populations depend only on the galaxy subhalo mass while the disc is quenched upon infall are acceptable fits to the data. An exponential disc quenching time-scale of 3-3.5 Gyr is preferred. Quenching in lower mass groups prior to infall (`pre-processing') provides better fits, with similar quenching time-scales. Models with short (≲1 Gyr) quenching time-scales yield excessively steep cluster-centric gradients in disc colours and Balmer line indices, even if quenching is delayed for several Gyr. The data slightly prefer models where quenching occurs only for galaxies falling within ˜0.5r200. These results imply that the environments of rich clusters must impact star formation rates of infalling galaxies on relatively long time-scales, indicative of gentler quenching mechanisms such as slow `strangulation' over more rapid ram-pressure stripping.

  13. Quenching methods for background reduction in luminescence-based probe-target binding assays

    DOEpatents

    Cai, Hong; Goodwin, Peter M; Keller, Richard A.; Nolan, Rhiannon L.

    2007-04-10

    Background luminescence is reduced from a solution containing unbound luminescent probes, each having a first molecule that attaches to a target molecule and having an attached luminescent moiety, and luminescent probe/target adducts. Quenching capture reagent molecules are formed that are capable of forming an adduct with the unbound luminescent probes and having an attached quencher material effective to quench luminescence of the luminescent moiety. The quencher material of the capture reagent molecules is added to a solution of the luminescent probe/target adducts and binds in a proximity to the luminescent moiety of the unbound luminescent probes to quench luminescence from the luminescent moiety when the luminescent moiety is exposed to exciting illumination. The quencher capture reagent does not bind to probe molecules that are bound to target molecules and the probe/target adduct emission is not quenched.

  14. Thioamide Quenching of Fluorescent Probes Through Photoinduced Electron Transfer: Mechanistic Studies and Applications

    PubMed Central

    Goldberg, Jacob M.; Batjargal, Solongo; Chen, Benson S.; Petersson, E. James

    2014-01-01

    Previously we have shown that thioamides can be incorporated into proteins as minimally perturbing fluorescence- quenching probes to study protein dynamics, folding, and aggregation. Here, we show that the spontaneity of photoinduced electron transfer between a thioamide and an excited fluorophore is governed by the redox potentials of each moiety according to a Rehm-Weller-type model. We have used this model to predict thioamide quenching of various common fluorophores, and we rigorously tested more than a dozen examples. In each case, we found excellent agreement between our theoretical predictions and experimental observations. In this way, we have been able to expand the scope of fluorophores quenched by thioamides to include dyes suitable for microscopy and single molecule studies, including fluorescein, Alexa Fluor 488, BODIPY FL, and rhodamine 6G. We describe the photochemistry of these systems and explore applications that demonstrate the utility of thioamide quenching of fluorescein to studying protein folding and proteolysis. PMID:24266520

  15. Momentum-Space Entanglement and Loschmidt Echo in Luttinger Liquids after a Quantum Quench

    NASA Astrophysics Data System (ADS)

    Dóra, Balázs; Lundgren, Rex; Selover, Mark; Pollmann, Frank

    2016-07-01

    Luttinger liquids (LLs) arise by coupling left- and right-moving particles through interactions in one dimension. This most natural partitioning of LLs is investigated by the momentum-space entanglement after a quantum quench using analytical and numerical methods. We show that the momentum-space entanglement spectrum of a LL possesses many universal features both in equilibrium and after a quantum quench. The largest entanglement eigenvalue is identical to the Loschmidt echo, i.e., the overlap of the disentangled and final wave functions of the system. The second largest eigenvalue is the overlap of the first excited state of the disentangled system with zero total momentum and the final wave function. The entanglement gap is universal both in equilibrium and after a quantum quench. The momentum-space entanglement entropy is always extensive and saturates fast to a time independent value after the quench, in sharp contrast to a spatial bipartitioning.

  16. Thioamide quenching of fluorescent probes through photoinduced electron transfer: mechanistic studies and applications.

    PubMed

    Goldberg, Jacob M; Batjargal, Solongo; Chen, Benson S; Petersson, E James

    2013-12-11

    Previously we have shown that thioamides can be incorporated into proteins as minimally perturbing fluorescence-quenching probes to study protein dynamics, folding, and aggregation. Here, we show that the spontaneity of photoinduced electron transfer between a thioamide and an excited fluorophore is governed by the redox potentials of each moiety according to a Rehm-Weller-type model. We have used this model to predict thioamide quenching of various common fluorophores, and we rigorously tested more than a dozen examples. In each case, we found excellent agreement between our theoretical predictions and experimental observations. In this way, we have been able to expand the scope of fluorophores quenched by thioamides to include dyes suitable for microscopy and single-molecule studies, including fluorescein, Alexa Fluor 488, BODIPY FL, and rhodamine 6G. We describe the photochemistry of these systems and explore applications that demonstrate the utility of thioamide quenching of fluorescein to studying protein folding and proteolysis. PMID:24266520

  17. Light Harvesting in Microscale Metal-Organic Frameworks by Energy Migration and Interfacial Electron Transfer Quenching

    SciTech Connect

    Kent, Caleb A.; Liu, Demin; Ma, Liqing; Papanikolas, John M.; Meyer, Thomas J.; Lin, Wenbin

    2011-08-24

    Microscale metal–organic frameworks (MOFs) were synthesized from photoactive Ru(II)-bpy building blocks with strong visible light absorption and long-lived triplet metal-to-ligand charge transfer (³MLCT) excited states. These MOFs underwent efficient luminescence quenching in the presence of either oxidative or reductive quenchers. Up to 98% emission quenching was achieved with either an oxidative quencher (1,4-benzoquinone) or a reductive quencher (N,N,N',N'-tetramethylbenzidine), as a result of rapid energy migration over several hundred nanometers followed by efficient electron transfer quenching at the MOF/solution interface. The photoactive MOFs act as an excellent light-harvesting system by combining intraframework energy migration and interfacial electron transfer quenching.

  18. Momentum-Space Entanglement and Loschmidt Echo in Luttinger Liquids after a Quantum Quench.

    PubMed

    Dóra, Balázs; Lundgren, Rex; Selover, Mark; Pollmann, Frank

    2016-07-01

    Luttinger liquids (LLs) arise by coupling left- and right-moving particles through interactions in one dimension. This most natural partitioning of LLs is investigated by the momentum-space entanglement after a quantum quench using analytical and numerical methods. We show that the momentum-space entanglement spectrum of a LL possesses many universal features both in equilibrium and after a quantum quench. The largest entanglement eigenvalue is identical to the Loschmidt echo, i.e., the overlap of the disentangled and final wave functions of the system. The second largest eigenvalue is the overlap of the first excited state of the disentangled system with zero total momentum and the final wave function. The entanglement gap is universal both in equilibrium and after a quantum quench. The momentum-space entanglement entropy is always extensive and saturates fast to a time independent value after the quench, in sharp contrast to a spatial bipartitioning. PMID:27419554

  19. Photoprotection in the lichen Parmelia sulcata: the origins of desiccation-induced fluorescence quenching.

    PubMed

    Veerman, John; Vasil'ev, Sergej; Paton, Gavin D; Ramanauskas, Justin; Bruce, Doug

    2007-11-01

    Lichens, a symbiotic relationship between a fungus (mycobiont) and a photosynthetic green algae or cyanobacteria (photobiont), belong to an elite group of survivalist organisms termed resurrection species. When lichens are desiccated, they are photosynthetically inactive, but upon rehydration they can perform photosynthesis within seconds. Desiccation is correlated with both a loss of variable chlorophyll a fluorescence and a decrease in overall fluorescence yield. The fluorescence quenching likely reflects photoprotection mechanisms that may be based on desiccation-induced changes in lichen structure that limit light exposure to the photobiont (sunshade effect) and/or active quenching of excitation energy absorbed by the photosynthetic apparatus. To separate and quantify these possible mechanisms, we have investigated the origins of fluorescence quenching in desiccated lichens with steady-state, low temperature, and time-resolved chlorophyll fluorescence spectroscopy. We found the most dramatic target of quenching to be photosystem II (PSII), which produces negligible levels of fluorescence in desiccated lichens. We show that fluorescence decay in desiccated lichens was dominated by a short lifetime, long-wavelength component energetically coupled to PSII. Remaining fluorescence was primarily from PSI and although diminished in amplitude, PSI decay kinetics were unaffected by desiccation. The long-wavelength-quenching species was responsible for most (about 80%) of the fluorescence quenching observed in desiccated lichens; the rest of the quenching was attributed to the sunshade effect induced by structural changes in the lichen thallus. PMID:17827268

  20. Photoprotection in the Lichen Parmelia sulcata: The Origins of Desiccation-Induced Fluorescence Quenching1

    PubMed Central

    Veerman, John; Vasil'ev, Sergej; Paton, Gavin D.; Ramanauskas, Justin; Bruce, Doug

    2007-01-01

    Lichens, a symbiotic relationship between a fungus (mycobiont) and a photosynthetic green algae or cyanobacteria (photobiont), belong to an elite group of survivalist organisms termed resurrection species. When lichens are desiccated, they are photosynthetically inactive, but upon rehydration they can perform photosynthesis within seconds. Desiccation is correlated with both a loss of variable chlorophyll a fluorescence and a decrease in overall fluorescence yield. The fluorescence quenching likely reflects photoprotection mechanisms that may be based on desiccation-induced changes in lichen structure that limit light exposure to the photobiont (sunshade effect) and/or active quenching of excitation energy absorbed by the photosynthetic apparatus. To separate and quantify these possible mechanisms, we have investigated the origins of fluorescence quenching in desiccated lichens with steady-state, low temperature, and time-resolved chlorophyll fluorescence spectroscopy. We found the most dramatic target of quenching to be photosystem II (PSII), which produces negligible levels of fluorescence in desiccated lichens. We show that fluorescence decay in desiccated lichens was dominated by a short lifetime, long-wavelength component energetically coupled to PSII. Remaining fluorescence was primarily from PSI and although diminished in amplitude, PSI decay kinetics were unaffected by desiccation. The long-wavelength-quenching species was responsible for most (about 80%) of the fluorescence quenching observed in desiccated lichens; the rest of the quenching was attributed to the sunshade effect induced by structural changes in the lichen thallus. PMID:17827268

  1. Xanthophyll cycle-dependent quenching of photosystem II chlorophyll a fluorescence: Formation of a quenching complex with a short fluorescence lifetime

    SciTech Connect

    Gilmore, A.M.; Hazlett, T.L.; Govindjee

    1995-03-14

    Excess light triggers protective nonradiative dissipation of excitation energy in photosystem II through the formation of a trans-thylakoid pH gradient that in turn stimulates formation of zeaxanthin and antheraxanthin. These xanthophylls when combined with protonation of antenna pigment-protein complexes may increase nonradiative dissipation and, thus, quench chlorophyll a fluorescence. Here we measured, in parallel, the chlorophyll a fluorescence lifetime and intensity to understand the mechanism of this process. Increasing the xanthophyll concentration in the presence of a pH gradient (quenched conditions) decreases the fractional intensity of a fluorescence lifetime component centered at {approx}2 ns and increases a component at {approx}0.4 ns. Uncoupling the pH gradient (unquenched conditions) eliminates the 0.4-ns component. Changes in the xanthophyll concentration do not significantly affect the fluorescence lifetimes in either the quenched or unquenched sample conditions. However, there are differences in fluorescence lifetimes between the quenched and unquenched states that are due to pH-related, but nonxanthophyll-related, processes. Quenching of the maximal fluorescence intensity correlates with both the xanthophyll concentration and the fractional intensity of the 0.4-ns component. The unchanged fluorescence lifetimes and the proportional quenching of the maximal and dark-level fluorescence intensities indicate that the xanthophyllact on antenna, not reaction center processes. Further, the fluorescence quenching is interpreted as the combined effect of the pH gradient and xanthophyll concentration, resulting in the formation of a quenching complex with a short ({approx}0.4 ns) fluorescence lifetime. 33 refs., 6 figs., 2 tabs.

  2. Quench antennas for RHIC quadrupole magnets

    SciTech Connect

    Ogitsu, T.; Terashima, A.; Tsuchiya, K.; Ganetis, G.; Muratore, J.; Wanderer, P.

    1995-05-01

    Quench antennas for RHIC quadrupole magnets are being developed jointly by KEK and BNL. A quench antenna is a device to localize a quench origin using arrays of pick-up coils lined up along the magnet bore. Each array contains four pick-up coils: sensitive to normal sextupole, skew sextupole, normal octupole, and skew octupole field. This array configuration allows an azimuthal localization of a quench front while a series of arrays gives an axial localization and a quench propagation velocity. Several antennas have been developed for RHIC magnets and they are now routinely used for quench tests of production magnets. The paper discusses the description of the method and introduces a measured example using an antenna designed for quadrupole magnets.

  3. Rapid Quench in an Electrostatic Levitator

    NASA Technical Reports Server (NTRS)

    SanSoucie, Michael P.; Rogers, Jan R.; Matson, Michael M.

    2016-01-01

    The Electrostatic Levitation (ESL) Laboratory at the NASA Marshall Space Flight Center (MSFC) is a unique facility for investigators studying high-temperature materials. The ESL laboratory’s main chamber has been upgraded with the addition of a rapid quench system. This system allows samples to be dropped into a quench vessel that can be filled with a low melting point material, such as a gallium or indium alloy, as a quench medium. Thereby allowing rapid quenching of undercooled liquid metals. Up to eight quench vessels can be loaded into a wheel inside the chamber that is indexed with control software. The system has been tested successfully with samples of zirconium, iron-cobalt alloys, iron-chromium-nickel, titanium-zirconium-nickel alloys, and a silicon-cobalt alloy. This new rapid quench system will allow materials science studies of undercooled materials and new materials development. The system is described and some initial results are presented.

  4. Rapid Quench in an Electrostatic Levitator

    NASA Technical Reports Server (NTRS)

    SanSoucie, Michael P.; Rogers, Jan R.; Matson, Douglas M.

    2016-01-01

    The Electrostatic Levitation (ESL) Laboratory at the NASA Marshall Space Flight Center (MSFC) is a unique facility for investigators studying high-temperature materials. The ESL laboratory's main chamber has been upgraded with the addition of a rapid quench system. This system allows samples to be dropped into a quench vessel that can be filled with a low melting point material, such as a gallium or indium alloy, as a quench medium. Thereby allowing rapid quenching of undercooled liquid metals. Up to eight quench vessels can be loaded into a wheel inside the chamber that is indexed with control software. The system has been tested successfully with samples of zirconium, iron-cobalt alloys, titanium-zirconium-nickel alloys, and a silicon-cobalt alloy. This new rapid quench system will allow materials science studies of undercooled materials and new materials development. In this presentation, the system is described and some initial results are presented.

  5. Reduced pressure quenching oil and distortion

    SciTech Connect

    Asada, S.; Ogino, M.

    1996-12-31

    Cooling process observed in a quenching oil`s cooling curve determination by JIS silver probe method, has been divided into three stages, vapor blanket stage, boiling stage and convection stage. Under reduced pressure vaporization is accelerated and extend the vapor blanket stage which shift the position of boiling stage the fastest of cooling speed among the cooling process toward low temperature side. Taking advantage of this behavior in quenching under reduced pressure, it is possible to improve quench hardenability by controlling reduced pressure. Vapor pressure of quenching oil increases under very high vacuum and accelerates vapor blanket formation and covers the material with more vapor blanket, resulting in reduction of cooling speed. Excessive vapor blanket covering the material will lead to partially uneven quenching of the treated material caused by uneven conditions by partial decomposition. Making vapor blanket distribution more even and to optimize uniform coating condition enables to prevent heat treatment distortion caused by uneven quenching conditions.

  6. Quench propagation velocity for highly stabilized conductors

    SciTech Connect

    Mints, R.G. |; Ogitsu, T. |; Devred, A.

    1995-05-01

    Quench propagation velocity in conductors having a large amount of stabilizer outside the multifilamentary area is considered. It is shown that the current redistribution process between the multifilamentary area and the stabilizer can strongly effect the quench propagation. A criterion is derived determining the conditions under which the current redistribution process becomes significant, and a model of effective stabilizer area is suggested to describe its influence on the quench propagation velocity. As an illustration, the model is applied to calculate the adiabatic quench propagation velocity for a conductor geometry with a multifilamentary area embedded inside the stabilizer.

  7. Coat forming quenching oil and distortion

    SciTech Connect

    Asada, S.

    1996-12-31

    Coat forming quenching oil which provides lubricous black coating on the treated surface of materials simultaneously with quenching is known to improve effectively surface characteristics of parts/materials treated. However, Zn-DTP added to this oil will be consumed some what at each quenching and gradual deterioration of the oil is inevitable and affecting greatly to cooling performance of the oil. To maintain long period oil stability by minimizing consumption of additive and suppressing cooling performance degradation, a new coat forming quenching oil containing petroleum type sulfonate has been developed. This is finally to contribute keeping low distortion level of treated materials in long term.

  8. Equilibrating dynamics in quenched Bose gases: Characterizing multiple time regimes

    NASA Astrophysics Data System (ADS)

    Rançon, A.; Levin, K.

    2014-08-01

    We address the physics of equilibration in ultracold atomic gases following a quench of the interaction parameter. Our work is based on a bath model which generates damping of the bosonic excitations. We illustrate this dissipative behavior through the momentum distribution of the excitations nk, observing that larger k modes have shorter relaxation times τ (k); they will equilibrate faster, as has been claimed in recent experimental work. We identify three time regimes. At short times nk exhibits oscillations; these are damped out at intermediate times where the system appears to be in a false or slowly converging equilibrium. Finally, at longer times, full equilibration occurs. This false equilibrium is, importantly, associated with the k dependence in τ (k) and has implications for experiment.

  9. Collisional quenching of CH(A), OH(A), and NO(A) in low pressure hydrocarbon flames

    SciTech Connect

    Tamura, Masayuki; Berg, P.A.; Harrington, J.E.; Lique, J.; Jeffries, J.B.; Smith, G.P.; Crosley, D.R.

    1998-08-01

    Excited state lifetimes have been measured for the A-states of CH, OH, and NO in a number of low-pressure, premixed, laminar flow methane flames. From these lifetimes, collisional quenching rates were determined as a function of height above the burner and thus as a function of flame temperature and composition. The results were compared with values calculated using a model of the flame chemistry to predict collider mole fractions, together with parameterizations of quenching rate coefficients and modeled flame composition data. This indicates that collisional quenching corrections for laser-induced fluorescence measurements can be calculated from knowledge of major species mole fractions and gas temperature. Predicted quenching rates for CH range from agreement with measured values to 27% higher than measured values. This discrepancies suggest insufficient knowledge of high temperature quenching by H{sub 2}O and N{sub 2}.

  10. Luminescence Spectroscopy and Bimolecular Quenching

    ERIC Educational Resources Information Center

    Demas, J. N.

    1975-01-01

    Describes an undergraduate physical chemistry experiment in which a low cost spectrofluorimeter is used to carry out elementary emission measurements on a transition metal complex. The students measure uncorrected emission and excitation spectra, and determine the rate constant for an exceedingly fast bimolecular reaction, the deactivation of an…

  11. COKE QUENCH TOWER EMISSION TESTING PROGRAM

    EPA Science Inventory

    The report gives results of a field study to further define quench tower organic emissions, the character and magnitude of which are virtually unknown. (Limited testing in 1976 indicated that a large quantity of organic material was emitted from quench towers, but these data were...

  12. MSFC Electrostatic Levitator (ESL) Rapid Quench System

    NASA Technical Reports Server (NTRS)

    SanSoucie, Michael P.; Craven, Paul D.; Rogers, Jan R.

    2014-01-01

    The NASA Marshall Space Flight Center (MSFC) Electrostatic Levitator (ESL) Laboratory is a unique facility for investigators studying high-temperature materials. The laboratory boasts two levitators in which samples can be levitated, heated, melted, undercooled, and resolidified, all without the interference of a container or data-gathering instrument. The ESL main chamber has been upgraded with the addition of a rapid quench system. This system allows samples to be dropped into a quench vessel that can be filled with a low melting point material, such as a gallium or indium alloy. Thereby allowing rapid quenching of undercooled liquid metals. Up to 8 quench vessels can be loaded into the quench wheel, which is indexed with LabVIEW control software. This allows up to 8 samples to be rapidly quenched before having to open the chamber. The system has been tested successfully on several zirconium samples. Future work will be done with other materials using different quench mediums. Microstructural analysis will also be done on successfully quench samples.

  13. On the scaling properties of quenched QED

    SciTech Connect

    Bardeen, William A.; Love, Sherwin T.; Miransky, Vladimir A.

    1990-06-17

    Critical scaling laws are studied in quenched quantum electrodynamics with induced four-fermion interactions that drive the theory to criticality. The critical exponents are calculated in the quenched, planar model and the physical picture extracted is consistent with recent results from lattice simulations. Near criticality, a composite scalar state plays an essential role in the effective dynamics.

  14. A thermal equation for flame quenching

    NASA Technical Reports Server (NTRS)

    Potter, A E , Jr; Berlad, A I

    1956-01-01

    An approximate thermal equation was derived for quenching distance based on a previously proposed diffusional treatment. The quenching distance was expressed in terms of the thermal conductivity, the fuel mole fraction, the heat capacity, the rate of the rate-controlling chemical reaction, a constant that depends on the geometry of the quenching surface, and one empirical constant. The effect of pressure on quenching distance was shown to be inversely proportional to the pressure dependence of the flame reaction, with small correction necessitated by the effect of pressure on flame temperature. The equation was used with the Semenov equation for burning velocity to show that the quenching distance was inversely proportional to burning velocity and pressure at any given initial temperature and equivalence ratio.

  15. QUENCH STUDIES AND PREHEATING ANALYSIS OF SEAMLESS

    SciTech Connect

    Palczewski, Ari; Geng, Rongli; Eremeev, Grigory

    2013-09-01

    One of the alternative manufacturing technologies for SRF cavities is hydroforming from seamless tubes. Although this technology has produced cavities with gradient and Q-values comparable to standard EBW/EP cavities, a few questions remain. One of these questions is whether the quench mechanism in hydroformed cavities is the same as in standard electron beam welded cavities. Towards this effort Jefferson Lab performed quench studies on 2 9 cell seamless hydroformed cavities. These cavities include DESY's - Z163 and Z164 nine-cell cavities hydroformed at DESY. Initial Rf test results Z163 were published in SRF2011. In this report we will present post JLAB surface re-treatment quench studies for each cavity. The data will include OST and T-mapping quench localization as well as quench location preheating analysis comparing them to the observations in standard electron beam welded cavities.

  16. Concentration quenching in Nd-doped glasses

    SciTech Connect

    Stokowski, S.E.; Cook, L.; Mueller, H.; Weber, M.J.

    1984-08-28

    Fluorescence from trivalent Nd in solids is unfortunately quenched by interactions between Nd ions. Thus, laser materials with high Nd concentrations have reduced efficiencies because of this self-quenching, also known as concentration quenching. Nd self-quenching in different crystals and glasses varies considerably. We are therefore investigating this effect in a large number of materials in an effort to: (1) find those materials with long Nd fluorescent lifetimes at high Nd concentrations; and (2) elucidate the basic mechanisms of quenching and how the material structure controls its magnitude. We have concentrated on Nd-doped glasses because they provide a rich variety of structures, albeit complicated by Nd site inhomogeneities, and are easily and quickly made.

  17. Quenching using air-water mixtures

    SciTech Connect

    Wallis, R.A.; Garwood, R.; Ward, J.; Xia, Q.

    1996-12-31

    With the current trend toward reduced manufacturing cycle time there is considerable interest in minimizing heat treatment related distortion and the residual stresses that are present in components. There is therefore a need to optimize the quenching process for a particular part such that the desired cooling rate, and hence mechanical properties, are obtained while minimizing distortion. This paper describes work aimed at developing a system to provide heat transfer rates between those obtained for oil quenching and fan cooling. Tests are described in which quenching was carried out by spraying water into the stream of air exiting a fan cooling system. Data are also presented for air mist quenching using atomizing nozzles. Comparison of computer predicted cooling rates and residual stress levels in components are presented for oil quenching, fan cooling, fan plus water injection cooling and air-mist cooling.

  18. Doubly heavy baryons and quark-diquark symmetry in quenched and partially quenched chiral perturbation theory

    SciTech Connect

    Thomas Mehen; Brian C. Tiburzi

    2006-07-17

    We extend the chiral Lagrangian with heavy quark-diquark symmetry to quenched and partially quenched theories. These theories are used to derive formulae for the chiral extrapolation of masses and hyperfine splittings of doubly heavy baryons in lattice QCD simulations. A quark-diquark symmetry prediction for the hyperfine splittings of heavy mesons and doubly heavy baryons is rather insensitive to chiral corrections in both quenched and partially quenched QCD. Extrapolation formulae for the doubly heavy baryon electromagnetic transition moments are also determined for the partially quenched theory.

  19. Quenching and anisotropy of hydromagnetic turbulent transport

    SciTech Connect

    Karak, Bidya Binay; Brandenburg, Axel; Rheinhardt, Matthias; Käpylä, Petri J.; Käpylä, Maarit J.

    2014-11-01

    Hydromagnetic turbulence affects the evolution of large-scale magnetic fields through mean-field effects like turbulent diffusion and the α effect. For stronger fields, these effects are usually suppressed or quenched, and additional anisotropies are introduced. Using different variants of the test-field method, we determine the quenching of the turbulent transport coefficients for the forced Roberts flow, isotropically forced non-helical turbulence, and rotating thermal convection. We see significant quenching only when the mean magnetic field is larger than the equipartition value of the turbulence. Expressing the magnetic field in terms of the equipartition value of the quenched flows, we obtain for the quenching exponents of the turbulent magnetic diffusivity about 1.3, 1.1, and 1.3 for Roberts flow, forced turbulence, and convection, respectively. However, when the magnetic field is expressed in terms of the equipartition value of the unquenched flows, these quenching exponents become about 4, 1.5, and 2.3, respectively. For the α effect, the exponent is about 1.3 for the Roberts flow and 2 for convection in the first case, but 4 and 3, respectively, in the second. In convection, the quenching of turbulent pumping follows the same power law as turbulent diffusion, while for the coefficient describing the Ω×J effect nearly the same quenching exponent is obtained as for α. For forced turbulence, turbulent diffusion proportional to the second derivative along the mean magnetic field is quenched much less, especially for larger values of the magnetic Reynolds number. However, we find that in corresponding axisymmetric mean-field dynamos with dominant toroidal field the quenched diffusion coefficients are the same for the poloidal and toroidal field constituents.

  20. Quenching and Anisotropy of Hydromagnetic Turbulent Transport

    NASA Astrophysics Data System (ADS)

    Karak, Bidya Binay; Rheinhardt, Matthias; Brandenburg, Axel; Käpylä, Petri J.; Käpylä, Maarit J.

    2014-11-01

    Hydromagnetic turbulence affects the evolution of large-scale magnetic fields through mean-field effects like turbulent diffusion and the α effect. For stronger fields, these effects are usually suppressed or quenched, and additional anisotropies are introduced. Using different variants of the test-field method, we determine the quenching of the turbulent transport coefficients for the forced Roberts flow, isotropically forced non-helical turbulence, and rotating thermal convection. We see significant quenching only when the mean magnetic field is larger than the equipartition value of the turbulence. Expressing the magnetic field in terms of the equipartition value of the quenched flows, we obtain for the quenching exponents of the turbulent magnetic diffusivity about 1.3, 1.1, and 1.3 for Roberts flow, forced turbulence, and convection, respectively. However, when the magnetic field is expressed in terms of the equipartition value of the unquenched flows, these quenching exponents become about 4, 1.5, and 2.3, respectively. For the α effect, the exponent is about 1.3 for the Roberts flow and 2 for convection in the first case, but 4 and 3, respectively, in the second. In convection, the quenching of turbulent pumping follows the same power law as turbulent diffusion, while for the coefficient describing the {\\boldsymbolΩ} × \\boldsymbol {{J}} effect nearly the same quenching exponent is obtained as for α. For forced turbulence, turbulent diffusion proportional to the second derivative along the mean magnetic field is quenched much less, especially for larger values of the magnetic Reynolds number. However, we find that in corresponding axisymmetric mean-field dynamos with dominant toroidal field the quenched diffusion coefficients are the same for the poloidal and toroidal field constituents.

  1. Simulations of fluorescence quenching using theoretical models of energy and electron transfer in random arrays

    NASA Astrophysics Data System (ADS)

    Boulu, Laurent G.; Kozak, John J.

    A master equation is solved numerically for investigating energy transfer and trapping in two-dimensional disordered systems of chlorophylls and quinones. Quenching of the excitation occurs both by electron transfer from a chlorophyll to a neighbouring quinone and by energy transfer to self-quenching traps consisting of statistical pairs of chlorophyll molecules closer than a critical distance. The quinone concentration dependence of the average lifetime of the calculated fluorescence decay is determined for different values of the Förster transfer radius 0 and A, the microscopic electron transfer rate at 'zero distance'. Quasi-Stern-Volmer behaviour is obtained. The half-quenching concentration and the quenching rate kQ depend strongly on A; they increase little with faster energy transfer because of competing self-quenching and slow electron transfer. Our results are compared to recent fluorescence quenching data that Chauvet and Patterson obtained from real-time measurements in monolayers of chlorophyll a and vitamin K1 diluted in dioleylphosphatidylcholine (DOL). Our convoluted decays fit the experimental data if A = 50-100 ns-1 and tMPH0193_images = 60-70 Å. Accordingly, kQ = 3-5 × 10-5 cm2/molecules·s. These values are in close agreement with those reported in the literature.

  2. Fluorescence quenching effects of antibiotics on the main components of dissolved organic matter.

    PubMed

    Yan, Peng-Fei; Hu, Zhen-Hu; Yu, Han-Qing; Li, Wei-Hua; Liu, Li

    2016-03-01

    Dissolved organic matter (DOM) in wastewater can be characterized using fluorescence excitation-emission matrix and parallel factor (EEM-PARAFAC) analysis. Wastewater from animal farms or pharmaceutical plants usually contains high concentration of antibiotics. In this study, the quenching effect of antibiotics on the typical components of DOM was explored using fluorescence EEM-PARAFAC analysis. Four antibiotics (roxarsone, sulfaquinoxaline sodium, oxytetracycline, and erythromycin) at the concentration of 0.5∼4.0 mg/L and three typical components of DOM (tyrosine, tryptophan, and humic acid) were selected. Fluorescence quenching effects were observed with the addition of antibiotics. Among these four antibiotics, roxarsone (2.9∼20.2 %), sulfaquinoxaline sodium (0∼32.0 %), and oxytetracycline (0∼41.8 %) led to a stronger quenching effect than erythromycin (0∼8.0 %). From the side of DOM, tyrosine and tryptophan (0.5∼41.8 %) exhibited a similar quenching effect, but they were higher than humic acids (0∼20.2 %) at the same concentration of antibiotics. For humic acid, a significant quenching effect was observed only with the addition of roxarsone. This might be the first report about the fluorescence quenching effect caused by antibiotics. The results from this study confirmed the interference of antibiotics on the fluorescence intensity of the main components of DOM and highlighted the importance of correcting fluorescence data in the wastewater containing antibiotics. PMID:26578380

  3. Collisional Quenching of OH A{^2Σ^+} by H_2 and N_2: Dynamical Outcomes

    NASA Astrophysics Data System (ADS)

    Dempsey, Logan P.; Sechler, Timothy D.; Murray, Craig; Lester, Marsha I.; Matsika, Spiridoula

    2009-06-01

    The nascent OH X{^2Π} product state distributions arising from collisional quenching of electronically excited OH A{^2Σ^+} by H_2 and N_2 have been determined using a pump-probe technique. For both collision partners, the majority of OH X{^2Π} products are observed in their lowest vibrational level, {v^''=0}, with significantly less population in {v^''=1}. The OH ({v^''=0}) products are generated with a substantial degree of rotational excitation, peaking around {N^''=15} with H_2 as the collision partner and {N^''=18} with N_2. Complementary measurements of the branching fraction into OH X{^2Π} product states demonstrate that reaction is the dominant decay pathway for quenching of OH A{^2Σ^+} by H_2, while nonreactive quenching is the dominant pathway for N_2. These observations are discussed in the context of theoretical calculations that examine the topography of the conical intersections which couple the electronically excited and ground state potential energy surfaces. The experimental observables are interpreted as dynamical signatures of nonadiabatic passage through the conical intersection regions responsible for quenching in both systems.

  4. Method for the substantial reduction of quenching effects in luminescence spectrometry

    DOEpatents

    Demas, James N.; Jones, Wesley M.; Keller, Richard A.

    1989-01-01

    Method for reducing quenching effects in analytical luminescence measurements. Two embodiments of the present invention are described which relate to a form of time resolution based on the amplitudes and phase shifts of modulated emission signals. In the first embodiment, the measured modulated emission signal is substantially independent of sample quenching at sufficiently high frequenices. In the second embodiment, the modulated amplitude and the phase shift between the emission signal and the excitation source are simultaneously measured. Using either method, the observed modulated amplitude may reduced to tis unquenched value.

  5. Method for the substantial reduction of quenching effects in luminescence spectrometry

    DOEpatents

    Demas, J.N.; Jones, W.M.; Keller, R.A.

    1987-06-26

    Method for reducing quenching effects in analytical luminescence measurements. Two embodiments of the present invention are described which relate to a form of time resolution based on the amplitudes and phase shifts of modulated emission signals. In the first embodiment, the measured modulated emission signal is substantially independent of sample quenching at sufficiently high frequencies. In the second embodiment, the modulated amplitude and the phase shift between the emission signal and the excitation source are simultaneously measured. Using either method, the observed modulated amplitude may be reduced to its unquenched value. 3 figs.

  6. Alleviation of catastrophic quenching in solar dynamo model with nonlocal alpha-effect

    NASA Astrophysics Data System (ADS)

    Kitchatinov, L. L.; Olemskoy, S. V.

    2011-06-01

    The nonlocal alpha-effect of Babcock-Leighton type is not prone to the catastrophic quenching due to conservation of magnetic helicity. This is shown with a dynamo model, which jointly applies the nonlocal alpha-effect, the diamagnetic pumping, and dynamical equation for the magnetic alpha-effect. The same model shows catastrophic quenching when the alpha-effect is changed to its local formulation. The nonlocal model shows a preferred excitation of magnetic fields of dipolar symmetry, which oscillate with a period of about ten years and have a toroidal-to-polar fields ratio of about a thousand.

  7. Transfer and quenching rate constants for XeF(B) and XeF(C) state in low vibrational levels

    NASA Astrophysics Data System (ADS)

    Brashears, H. C., Jr.; Setser, D. W.

    1982-05-01

    The relative XeF(B-X) and XeF(C-A) emission intensities from the steady-state vacuum ultraviolet photolysis of XeF2 have been used to measure the B-C transfer and quenching rate constants of XeF molecules in low vibrational levels. The rare gases N2, CF4, SF6, F2, NF3, CF3H, CF3Cl, HF, CO2, and XeF2 were investigated as buffer gases at room temperature. The transfer rate constants are much larger than the quenching rate constants for He, Ne, Ar, Kr, N2, CF4, and SF6. For Xe, NF3, CHF3, and CClF3 transfer is only 2-4 times faster than quenching and for F2, HF, and CO2 quenching is faster than B-C state transfer. Quenching for XeF(D) was studied for rare gases and for N2. No convincing evidence was found for three-body quenching by the rare gases and their quenching of the XeF(B, C) and XeF(D) states are reported as two-body processes for pressures below ˜5 atm. The XeF(D) quenching rate constants are of the same magnitude as the B-C state transfer rate constants. The photochemical and collisional (metastable rare gas atom) dissociative excitation of XeF2 and KrF2 are summarized in the Appendix.

  8. Jet quenching from QCD evolution

    NASA Astrophysics Data System (ADS)

    Chien, Yang-Ting; Emerman, Alexander; Kang, Zhong-Bo; Ovanesyan, Grigory; Vitev, Ivan

    2016-04-01

    Recent advances in soft-collinear effective theory with Glauber gluons have led to the development of a new method that gives a unified description of inclusive hadron production in reactions with nucleons and heavy nuclei. We show how this approach, based on the generalization of the DGLAP evolution equations to include final-state medium-induced parton shower corrections for large Q2 processes, can be combined with initial-state effects for applications to jet quenching phenomenology. We demonstrate that the traditional parton energy loss calculations can be regarded as a special soft-gluon emission limit of the general QCD evolution framework. We present phenomenological comparison of the SCETG -based results on the suppression of inclusive charged hadron and neutral pion production in √{sNN }=2.76 TeV lead-lead collisions at the Large Hadron Collider to experimental data. We also show theoretical predictions for the upcoming √{sNN }≃5.1 TeV Pb +Pb run at the LHC.

  9. Domain wall fermion quenched spectroscopy

    NASA Astrophysics Data System (ADS)

    Malureanu, Catalin Ionut

    We measure y and the hadron spectrum on quenched ensembles using the domain wall fermion formulation. For the first time a 1/mf behavior of y for small valence masses has been observed. Our measurements of y on two different volumes of 83 x 32 and 163 x 32 at β = 5.85 suggest the behavior goes away on large enough volumes. Extensive spectrum calculations were done on 8 3 x 32 lattices at β = 5.7 and 5.85 corresponding roughly to a box size of 1.6 fm and 1.0 fm respectively. We have investigated five values of the extent of the fifth dimension Ls = 10, 16, 24, 32 and 48 with valence masses in the range 0.02 to 0.2 for the β = 5.7 ensemble and two values of Ls = 10 and 16 with valence masses in the range 0.02 to 0.08 for the β = 5.85 ensemble. Our pion remains massive in the infinite Ls extrapolation. This may be a finite volume effect. The nucleon to rho mass ratio stays constant at 1.4(1). Scaling violations for domain wall fermions are smaller roughly by a factor of four compared to the scaling violations in similar calculations done with staggered fermions.

  10. A quench detection/logging system for the SSCL Magnet Test Laboratory

    SciTech Connect

    Kim, K.; Coles, M.; Dryer, J.; Lambert, D.

    1993-05-01

    The quench in a magnet describes a process which occurs while the superconductivity state goes to the normal resistive state. The consequence of a quench is the conversion of the stored electromagnetic energy into heat. During this process the initiating point will reach a high temperature, which will char the insulation or melt the conductor and thereby destroy the magnet. To prevent the magnet from being lost, it is standard practice to observe several resistance and/or inductance voltages across the magnet as quench signatures -- detection. When a quench symptom is detected, protection operations are initiated: proper shutdown of the magnet excitation systems and treatment to dilute the heat energy at a spot -- protection. The temperature rise is diluted by firing heaters along the length of the magnet to insure that the dissipated energy is spread. To develop a reliable quench detection system, two distinct approaches have been tried in the past: (i) Understanding of the Noise Mechanism and Sub-system Optimization, and (ii) Escaping from the Known Electromagnetic Noises by Observing Optical Waves or Acoustic Waves. The MTL of SSCL confronts a mass-measurement of about 10,000 production magnets. To meet the testing schedule, the false quench detection rate needs to be further optimized while the true quench detection rate remains secure for the magnet measurement safety. To meet these requirements, we followed an iterative top-down approach. First we defined the signal and noise characteristics of the quench phenomena by using existing software tools to build a rapid prototype system incorporating all proven functionality of the existing system. Then we further optimize the system through iterative upgrading based on our signal and noise character findings.

  11. Quenching of the perylene fluorophore by stable nitroxide radical-containing macromolecules.

    PubMed

    Hughes, Barbara K; Braunecker, Wade A; Ferguson, Andrew J; Kemper, Travis W; Larsen, Ross E; Gennett, Thomas

    2014-10-30

    Stable nitroxide radical bearing organic polymer materials are attracting much attention for their application as next generation energy storage materials. A greater understanding of the inherent charge transfer mechanisms in such systems will ultimately be paramount to further advancements in the understanding of both intrafilm and interfacial ion- and electron-transfer reactions. This work is focused on advancing the fundamental understanding of these dynamic charge transfer properties by exploiting the fact that these species are efficient fluorescence quenchers. We systematically incorporated fluorescent perylene dyes into solutions containing the 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) radical and controlled their interaction by binding the TEMPO moiety into macromolecules with varying morphologies (e.g., chain length, density of radical pendant groups). In the case of the model compound, 4-oxo-TEMPO, quenching of the perylene excited state was found to be dominated by a dynamic (collisional) process, with a contribution from an apparent static process that is described by an ∼2 nm quenching sphere of action. When we incorporated the TEMPO unit into a macromolecule, the quenching behavior was altered significantly. The results can be described by using two models: (A) a collisional quenching process that becomes less efficient, presumably due to a reduction in the diffusion constant of the quenching entity, with a quenching sphere of action similar to 4-oxo-TEMPO or (B) a collisional quenching process that becomes more efficient as the radius of interaction grows larger with increasing oligomer length. This is the first study that definitively illustrates that fluorophore quenching by a polymer system cannot be explained using merely a classical Stern-Volmer approach but rather necessitates a more complex model. PMID:25329883

  12. Gluonic excitation of nonexotic hybrid charmonium from lattice QCD

    SciTech Connect

    Luo Xiangqian; Liu Yan

    2006-08-01

    The ground and first excited states of the hybrid charmonium ccg, with nonexotic quantum numbers J{sup PC}=0{sup -+}, 1{sup --}, and 1{sup ++} are investigated using quenched lattice QCD. The excited states are completely ignored in the literature. However, we observe strong gluonic radial excitations in the first excited states; We find their masses are completely different from the first excited states of the corresponding conventional charmonium. Their relevance to the recent discovery of the Y(4260) state and future experimental search for other states are also discussed.

  13. Accelerating slow excited state proton transfer.

    PubMed

    Stewart, David J; Concepcion, Javier J; Brennaman, M Kyle; Binstead, Robert A; Meyer, Thomas J

    2013-01-15

    Visible light excitation of the ligand-bridged assembly [(bpy)(2)Ru(a)(II)(L)Ru(b)(II)(bpy)(OH(2))(4+)] (bpy is 2,2'-bipyridine; L is the bridging ligand, 4-phen-tpy) results in emission from the lowest energy, bridge-based metal-to-ligand charge transfer excited state (L(-•))Ru(b)(III)-OH(2) with an excited-state lifetime of 13 ± 1 ns. Near-diffusion-controlled quenching of the emission occurs with added HPO(4)(2-) and partial quenching by added acetate anion (OAc(-)) in buffered solutions with pH control. A Stern-Volmer analysis of quenching by OAc(-) gave a quenching rate constant of k(q) = 4.1 × 10(8) M(-1) • s(-1) and an estimated pK(a)* value of ~5 ± 1 for the [(bpy)(2)Ru(a)(II)(L(•-))Ru(b)(III)(bpy)(OH(2))(4+)]* excited state. Following proton loss and rapid excited-state decay to give [(bpy)(2)Ru(a)(II)(L)Ru(b)(II)(bpy)(OH)(3+)] in a H(2)PO(4)(-)/HPO(4)(2-) buffer, back proton transfer occurs from H(2)PO(4)(-) to give [(bpy)(2)Ru(a)(II)(L)Ru(b)(bpy)(OH(2))(4+)] with k(PT,2) = 4.4 × 10(8) M(-1) • s(-1). From the intercept of a plot of k(obs) vs. [H(2)PO(4)(-)], k = 2.1 × 10(6) s(-1) for reprotonation by water providing a dramatic illustration of kinetically limiting, slow proton transfer for acids and bases with pK(a) values intermediate between pK(a)(H(3)O(+)) = -1.74 and pK(a)(H(2)O) = 15.7. PMID:23277551

  14. Photosystem II Subunit PsbS Is Involved in the Induction of LHCSR Protein-dependent Energy Dissipation in Chlamydomonas reinhardtii.

    PubMed

    Correa-Galvis, Viviana; Redekop, Petra; Guan, Katharine; Griess, Annika; Truong, Thuy B; Wakao, Setsuko; Niyogi, Krishna K; Jahns, Peter

    2016-08-12

    Non-photochemical quenching of excess excitation energy is an important photoprotective mechanism in photosynthetic organisms. In Arabidopsis thaliana, a high quenching capacity is constitutively present and depends on the PsbS protein. In the green alga Chlamydomonas reinhardtii, non-photochemical quenching becomes activated upon high light acclimation and requires the accumulation of light harvesting complex stress-related (LHCSR) proteins. Expression of the PsbS protein in C. reinhardtii has not been reported yet. Here, we show that PsbS is a light-induced protein in C. reinhardtii, whose accumulation under high light is further controlled by CO2 availability. PsbS accumulated after several hours of high light illumination at low CO2 At high CO2, however, PsbS was only transiently expressed under high light and was degraded after 1 h of high light exposure. PsbS accumulation correlated with an enhanced non-photochemical quenching capacity in high light-acclimated cells grown at low CO2 However, PsbS could not compensate for the function of LHCSR in an LHCSR-deficient mutant. Knockdown of PsbS accumulation led to reduction of both non-photochemical quenching capacity and LHCSR3 accumulation. Our data suggest that PsbS is essential for the activation of non-photochemical quenching in C. reinhardtii, possibly by promoting conformational changes required for activation of LHCSR3-dependent quenching in the antenna of photosystem II. PMID:27358399

  15. The dominance of quenching through cosmic times

    NASA Astrophysics Data System (ADS)

    Renzini, Alvio

    2016-04-01

    The evolution with cosmic time of the star formation rate density (SFRD) and of the Main Sequence star formation rate-stellar mass relations are two well established observational facts. In this paper the implications of these two relations combined are analytically explored, showing that quenching of star formation must start already at very early cosmic times and the quenched fraction then dominates ever since over the star forming one. Thus, a simple picture of the cosmic evolution of the global SFRD is derived, in terms of the interplay between star formation and its quenching.

  16. The dominance of quenching through cosmic times

    NASA Astrophysics Data System (ADS)

    Renzini, Alvio

    2016-07-01

    The evolution with cosmic time of the star formation rate density (SFRD) and of the main-sequence star formation rate-stellar mass relations are two well-established observational facts. In this Letter, the implications of these two relations combined are analytically explored, showing that quenching of star formation must start already at very early cosmic times and the quenched fraction then dominates ever since over the star-forming one. Thus, a simple picture of the cosmic evolution of the global SFRD is derived, in terms of the interplay between star formation and its quenching.

  17. Quenching phenomena in natural circulation loop

    SciTech Connect

    Umekawa, Hisashi; Ozawa, Mamoru; Ishida, Naoki

    1995-09-01

    Quenching phenomena has been investigated experimentally using circulation loop of liquid nitrogen. During the quenching under natural circulation, the heat transfer mode changes from film boiling to nucleate boiling, and at the same time flux changes with time depending on the vapor generation rate and related two-phase flow characteristics. Moreover, density wave oscillations occur under a certain operating condition, which is closely related to the dynamic behavior of the cooling curve. The experimental results indicates that the occurrence of the density wave oscillation induces the deterioration of effective cooling of the heat surface in the film and the transition boiling regions, which results in the decrease in the quenching velocity.

  18. Rapid quenching effects in PVC films

    NASA Technical Reports Server (NTRS)

    Lee, H. D.; Mandell, J. F.; Mcgarry, F. J.

    1981-01-01

    Using a specially constructed microbalance for hydrostatic weighing, density changes in PVC thin films (with no additives, 30-100 micrometers thick), due to rapid quenching (approximately 300 C/sec) through the glass transition temperature, have been observed. The more severe the quench, the greater is the free volume content. Isobaric volume recovery of PVC has also been studied by volume dilatometry. Both show aging of relaxing molecular rearrangements takes place as a linear function of logarithmic aging time at room temperature. Distribution of retardation times and Primak's distributed activation energy spectra have been applied to the volume recovery data. The concomitant changes in mechanical properties of PVC after quenching have been monitored by tensile creep and stress-strain to failure. All reflect the presence of excess free volume content, due to rapid quenching.

  19. The Rate Constant for Fluorescence Quenching

    ERIC Educational Resources Information Center

    Legenza, Michael W.; Marzzacco, Charles J.

    1977-01-01

    Describes an experiment that utilizes fluorescence intensity measurements from a Spectronic 20 to determine the rate constant for the fluorescence quenching of various aromatic hydrocarbons by carbon tetrachloride in an ethanol solvent. (MLH)

  20. Torus CLAS12-Superconducting Magnet Quench Analysis

    SciTech Connect

    Kashikhin, V. S.; Elouadhiri, L.; Ghoshal, P. K.; Kashy, D.; Makarov, A.; Pastor, O.; Quettier, L.; Velev, G.; Wiseman, M.

    2014-01-01

    The JLAB Torus magnet system consists of six superconducting trapezoidal racetrack-type coils assembled in a toroidal configuration. These coils are wound with SSC-36 Nb-Ti superconductor and have the peak magnetic field of 3.6 T. The first coil manufacturing based on the JLAB design began at FNAL. The large magnet system dimensions (8 m diameter and 14 MJ of stored energy) dictate the need for quench protection. Each coil is placed in an aluminum case mounted inside a cryostat and cooled by 4.6 K supercritical helium gas flowing through a copper tube attached to the coil ID. The large coil dimensions and small cryostat thickness drove the design to challenging technical solutions, suggesting that Lorentz forces due to transport currents and eddy currents during quench and various failure scenarios are analyzed. The paper covers the magnet system quench analysis using the OPERA3d Quench code.

  1. Quenching gas for detectors of charged particles

    DOEpatents

    Atac, M.

    1974-01-22

    Operation of detectors of charged particles such as wire counters and Geiger-Muller tubes is improved by filling the counters with a quenching-gas mixture of argon, isobutane and methylchloroform. (Official Gazette)

  2. Torus CLAS12-Superconducting Magnet Quench Analysis

    SciTech Connect

    Kashikhin, V S; Elouadhiri, L; Ghoshal, P K; Kashy, D; Makarov, A; Pastor, O; Quettier, L; Velev, G; Wiseman, M

    2014-06-01

    The JLAB Torus magnet system consists of six superconducting trapezoidal racetrack-type coils assembled in a toroidal configuration. These coils are wound with SSC-36 Nb-Ti superconductor and have the peak magnetic field of 3.6 T. The first coil manufacturing based on the JLAB design began at FNAL. The large magnet system dimensions (8 m diameter and 14 MJ of stored energy) dictate the need for quench protection. Each coil is placed in an aluminum case mounted inside a cryostat and cooled by 4.6 K supercritical helium gas flowing through a copper tube attached to the coil ID. The large coil dimensions and small cryostat thickness drove the design to challenging technical solutions, suggesting that Lorentz forces due to transport currents and eddy currents during quench and various failure scenarios are analyzed. The paper covers the magnet system quench analysis using the OPERA3d Quench code.

  3. Rapid quenching effects in glassy polymers

    NASA Technical Reports Server (NTRS)

    Mcgarry, F. J.

    1982-01-01

    Using a specially constructed microbalance for hydrostatic weighing, density changes in PVC thin film due to rapid quenching through the glass transition temperature were observed. The more severe the quench, the greater the free volume content. Isobaric volume recovery of PVC was also studied by volume dilatometry. Both show aging of relaxing molecular rearrangements taking place as a linear function of logarithmic aging time at room temperature. Distribution of retardation times and Primak's distributed activation energy spectra were applied to the volume recovery data. The concomitant changes in mechanical properties of PVC after quenching were monitored by tensile creep stress-stran to failure rates. All reflect the presence of excess free volume content due to rapid quenching.

  4. Collisional quenching of OH radio emission from comet Hale-Bopp

    NASA Technical Reports Server (NTRS)

    Schloerb, F. P.; Devries, C. H.; Lovell, A. J.; Irvine, W. M.; Senay, M.; Wootten, H. A.; Ferris, J. P. (Principal Investigator)

    1997-01-01

    Observations of comets in the 18-cm OH transitions offer a means to probe gas production, kinematics, and OH excitation in comets. We present initial results of OH observations of comet Hale-Bopp obtained with the NRAO 43 m antenna located in Greenbank, WV. Maps of the emission provide strong constraints on the amount of quenching of the inversion of the OH ground state A-doublet in the coma. Analysis of the total radio OH flux and maps of its radial brightness distribution indicate a quenched region on the order of approximately 500,000 km during March and April 1997. This large value is generally consistent with previous observations of radio OH quenching in lower production rate comets when the high production rate of comet Hale-Bopp is considered.

  5. Exact work statistics of quantum quenches in the anisotropic XY model.

    PubMed

    Bayocboc, Francis A; Paraan, Francis N C

    2015-09-01

    We derive exact analytic expressions for the average work done and work fluctuations in instantaneous quenches of the ground and thermal states of a one-dimensional anisotropic XY model. The average work and a quantum fluctuation relation is used to determine the amount of irreversible entropy produced during the quench, eventually revealing how the closing of the excitation gap leads to increased dissipated work. The work fluctuation is calculated and shown to exhibit nonanalytic behavior as the prequench anisotropy parameter and transverse field are tuned across quantum critical points. Exact compact formulas for the average work and work fluctuation in ground state quenches of the transverse field Ising model allow us to calculate the first singular field derivative at the critical field values. PMID:26465461

  6. Collisional quenching of OH radio emission from comet Hale-Bopp.

    PubMed

    Schloerb, F P; Devries, C H; Lovell, A J; Irvine, W M; Senay, M; Wootten, H A

    1997-01-01

    Observations of comets in the 18-cm OH transitions offer a means to probe gas production, kinematics, and OH excitation in comets. We present initial results of OH observations of comet Hale-Bopp obtained with the NRAO 43 m antenna located in Greenbank, WV. Maps of the emission provide strong constraints on the amount of quenching of the inversion of the OH ground state A-doublet in the coma. Analysis of the total radio OH flux and maps of its radial brightness distribution indicate a quenched region on the order of approximately 500,000 km during March and April 1997. This large value is generally consistent with previous observations of radio OH quenching in lower production rate comets when the high production rate of comet Hale-Bopp is considered. PMID:11543323

  7. Solvent refined coal reactor quench system

    DOEpatents

    Thorogood, Robert M.

    1983-01-01

    There is described an improved SRC reactor quench system using a condensed product which is recycled to the reactor and provides cooling by evaporation. In the process, the second and subsequent reactors of a series of reactors are cooled by the addition of a light oil fraction which provides cooling by evaporation in the reactor. The vaporized quench liquid is recondensed from the reactor outlet vapor stream.

  8. Solvent refined coal reactor quench system

    DOEpatents

    Thorogood, R.M.

    1983-11-08

    There is described an improved SRC reactor quench system using a condensed product which is recycled to the reactor and provides cooling by evaporation. In the process, the second and subsequent reactors of a series of reactors are cooled by the addition of a light oil fraction which provides cooling by evaporation in the reactor. The vaporized quench liquid is recondensed from the reactor outlet vapor stream. 1 fig.

  9. Photosynthetic Light Utilization Efficiency, Photosystem II Heterogeneity, and Fluorescence Quenching in Chlamydomonas reinhardtii during the Induction of the CO2-Concentrating Mechanism 1

    PubMed Central

    Falk, Stefan; Palmqvist, Kristin

    1992-01-01

    The photosynthetic light-response curve, the relative amounts of the different photosystem II (PSII) units, and fluorescence quenching were altered in an adaptive manner when CO2-enriched wild-type Chlamydomonas reinhardtii cells were transferred to low levels of CO2. This treatment is known to result in the induction of an energy-dependent CO2-concentrating mechanism (CCM) that increases the internal inorganic carbon concentration and thus the photosynthetic CO2 utilization efficiency. After 3 to 6 h of low inorganic carbon treatment, several changes in the photosynthetic energy-transducing reactions appeared and proceeded for about 12 h. After this time, the fluorescence parameter variable/maximal fluorescence yield and the amounts of both PSIIα and PSIIβ (secondary quinone electron acceptor of PSII-reducing) centers had decreased, whereas the amount of PSIIβ (secondary quinone electron acceptor of PSII-nonreducing) centers had increased. The yield of noncyclic electron transport also decreased during the induction of the CCM, whereas both photochemical and nonphotochemical quenching of PSII fluorescence increased. Concurrent with these changes, the photosynthetic light-utilization efficiency also decreased significantly, largely attributed to a decline in the curvature parameter θ, the convexity of the photosynthetic light-response curve. Thus, it is concluded that the increased CO2 utilization efficiency in algal cells possessing the CCM is maintained at the cost of a reduced light utilization efficiency, most probably due to the reduced energy flow through PSII. PMID:16653047

  10. Quench antenna studies of mechanical and quench performance in Fermilab interaction region quadrupoles for LHC

    SciTech Connect

    Tartaglia, M.A.; Feher, S.; Hocker, A.; Lamm, M.; Schlabach, P.; Sylvester, C.; Tompkins, J.C.; /Fermilab

    2005-09-01

    As part of the US-LHC collaboration, Fermilab has built and tested seventeen high gradient quadrupole magnets, assembled into nine cryostats, for installation at the Large Hadron Collider Interaction Regions. Most of these magnets have only quarter coil voltage taps for quench characterization, but the magnetic measurement warm bore is instrumented with a quench antenna for localization and characterization. We report on studies using the quench antenna for pre-production prototype (with extensive voltage taps) and 17 production magnets. These include a summary of quench localization and development characteristics, as well as general features of flux changes observed during training ramps.