Photoperiod and temperature constraints on the relationship between the photochemical reflectance index and the light use efficiency of photosynthesis in Pinus strobus.

Science.gov (United States)

Fréchette, Emmanuelle; Chang, Christine Yao-Yun; Ensminger, Ingo

2016-03-01

The photochemical reflectance index (PRI) is a proxy for the activity of the photoprotective xanthophyll cycle and photosynthetic light use efficiency (LUE) in plants. Evergreen conifers downregulate photosynthesis in autumn in response to low temperature and shorter photoperiod, and the dynamic xanthophyll cycle-mediated non-photochemical quenching (NPQ) is replaced by sustained NPQ. We hypothesized that this shift in xanthophyll cycle-dependent energy partitioning during the autumn is the cause for variations in the PRI-LUE relationship. In order to test our hypothesis, we characterized energy partitioning and pigment composition during a simulated summer-autumn transition in a conifer and assessed the effects of temperature and photoperiod on the PRI-LUE relationship. We measured gas exchange, chlorophyll fluorescence and leaf reflectance during the photosynthetic downregulation in Pinus strobus L. seedlings exposed to low temperature/short photoperiod or elevated temperature/short photoperiod conditions. Shifts in energy partitioning during simulated autumn were observed when the pools of chlorophylls decreased and pools of photoprotective carotenoids increased. On a seasonal timescale, PRI was controlled by carotenoid pool sizes rather than xanthophyll cycle dynamics. Photochemical reflectance index variation under cold autumn conditions mainly reflected long-term pigment pool adjustments associated with sustained NPQ, which impaired the PRI-LUE relationship. Exposure to warm autumn conditions prevented the induction of sustained NPQ but still impaired the PRI-LUE relationship. We therefore conclude that alternative zeaxanthin-independent NPQ mechanisms, which remain undetected by the PRI, are present under both cold and warm autumn conditions, contributing to the discrepancy in the PRI-LUE relationship during autumn. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

A micellar model system for the role of zeaxanthin in the non-photochemical quenching process of photosynthesis--chlorophyll fluorescence quenching by the xanthophylls.

Science.gov (United States)

Avital, Shlomo; Brumfeld, Vlad; Malkin, Shmuel

2006-07-01

To get an insight to the mechanism of the zeaxanthin-dependent non-photochemical quenching in photosystem II of photosynthesis, we probed the interaction of some xanthophylls with excited chlorophyll-a by trapping both pigments in micelles of triton X-100. Optimal distribution of pigments among micelles was obtained by proper control of the micelle concentration, using formamide in the reaction mixture, which varies the micellar aggregation number over three orders of magnitude. The optimal reaction mixture was obtained around 40% (v/v) formamide in 0.2-0.4% (v/v) triton X-100 in water. Zeaxanthin in the micellar solution exhibited initially absorption and circular dichroism spectral features corresponding to a J-type aggregate. The spectrum was transformed over time (half-time values vary-an average characteristic figure is roughly 20 min) to give features representing an H-type aggregate. The isosbestic point in the series of spectral curves favors the supposition of a rather simple reaction between two pure J and H-types dimeric species. Violaxanthin exhibited immediately stable spectral features corresponding to a mixture of J-type and more predominately H-type dimers. Lutein, neoxanthin and beta-carotene did not show any aggregated spectral forms in micelles. The spectral features in micelles were compared to spectra in aqueous acetone, where the assignment to various aggregated types was established previously. The specific tendency of zeaxanthin to form the J-type dimer (or aggregate) could be important for its function in photosynthesis. The abilities of five carotenoids (zeaxanthin, violaxanthin, lutein, neoxanthin and beta-carotene) to quench chlorophyll-a fluorescence were compared. Zeaxanthin, in its two micellar dimeric forms, and beta-carotene were comparable good quenchers of chlorophyll-a fluorescence. Violaxanthin was a much weaker quencher, if at all. Lutein and neoxanthin rather enhanced the fluorescence. The implications to non-photochemical

Revisiting the Role of Xanthophylls in Nonphotochemical Quenching

NARCIS (Netherlands)

van Oort, Bart; Roy, Laura M; Xu, Pengqi; Lu, Yinghong; Karcher, Daniel; Bock, Ralph; Croce, Roberta

2018-01-01

Photoprotective nonphotochemical quenching (NPQ) of absorbed solar energy is vital for survival of photosynthetic organisms, and NPQ modifications significantly improve plant productivity. However, the exact NPQ quenching mechanism is obscured by discrepancies between reported mechanisms, involving

PsbS-specific zeaxanthin-independent changes in fluorescence emission spectrum as a signature of energy-dependent non-photochemical quenching in higher plants.

Science.gov (United States)

Zulfugarov, Ismayil S; Tovuu, Altanzaya; Dogsom, Bolormaa; Lee, Chung Yeol; Lee, Choon-Hwan

2010-05-01

The PsbS protein of photosystem II is necessary for the development of energy-dependent quenching of chlorophyll (Chl) fluorescence (qE), and PsbS-deficient Arabidopsis plant leaves failed to show qE-specific changes in the steady-state 77 K fluorescence emission spectra observed in wild-type leaves. The difference spectrum between the quenched and un-quenched states showed a negative peak at 682 nm. Although the level of qE development in the zeaxanthin-less npq1-2 mutant plants, which lacked violaxanthin de-epoxidase enzyme, was only half that of wild type, there were no noticeable changes in this qE-dependent difference spectrum. This zeaxanthin-independent DeltaF682 signal was not dependent on state transition, and the signal was not due to photobleaching of pigments either. These results suggest that DeltaF682 signal is formed due to PsbS-specific conformational changes in the quenching site of qE and is a new signature of qE generation in higher plants.

Detection of radioactively labeled proteins is quenched by silver staining methods: quenching is minimal for 14C and partially reversible for 3H with a photochemical stain

International Nuclear Information System (INIS)

Van Keuren, M.L.; Goldman, D.; Merril, C.R.

1981-01-01

Silver staining methods for protein detection in polyacrylamide gels have a quenching effect on autoradiography and fluorography. This effect was quantitated for proteins in two-dimensional gels by microdensitometry using a computer equipped with an image processor and by scintillation counting of proteins solubilized from the gels. The original histologically derived silver stain had a quenching effect that was severe and irreversible for 3 H detection and moderate for 14 C detection. A silver stain based on photochemical methods had minimal quenching of 14 C detection and less of a quenching effect than the histological stain for 3 H detection. The 3 H quenching effect was partially reversible for the photochemical stain

Quenching of excited uranyl ion during its photochemical reduction by triphenylphosphine: Part III

International Nuclear Information System (INIS)

Sidhu, M.S.; Chahal, P.; Singh, R.J.

1993-01-01

Relative rates of bimolecular quenching of excited uranyl ion by some mono and di-substituted benzene derivatives have been measured during its photochemical reduction with triphenylphosphine. For the related compounds in a series it has been found that substituent groups enriching the aromatic π-electron cloud due to resonance stabilization, show an enhanced photophysical quenching action. The substituents decreasing the π-electron cloud and delocalization of positive charger over the benzene ring decrease the quenching action. (author). 16 refs., 2 figs., 1 tab

Intraspecific variation in Pinus pinaster PSII photochemical efficiency in response to winter stress and freezing temperatures.

Directory of Open Access Journals (Sweden)

Leyre Corcuera

Full Text Available As part of a program to select maritime pine (Pinus pinaster Ait. genotypes for resistance to low winter temperatures, we examined variation in photosystem II activity by chlorophyll fluorescence. Populations and families within populations from contrasting climates were tested during two consecutive winters through two progeny trials, one located at a continental and xeric site and one at a mesic site with Atlantic influence. We also obtained the LT₅₀, or the temperature that causes 50% damage, by controlled freezing and the subsequent analysis of chlorophyll fluorescence in needles and stems that were collected from populations at the continental trial site.P. pinaster showed sensitivity to winter stress at the continental site, during the colder winter. The combination of low temperatures, high solar irradiation and low precipitation caused sustained decreases in maximal photochemical efficiency (F(v/F(m, quantum yield of non-cyclic electron transport (Φ(PSII and photochemical quenching (qP. The variation in photochemical parameters was larger among families than among populations, and population differences appeared only under the harshest conditions at the continental site. As expected, the environmental effects (winter and site on the photochemical parameters were much larger than the genotypic effects (population or family. LT₅₀ was closely related to the minimum winter temperatures of the population's range. The dark-adapted F(v/F(m ratio discriminated clearly between interior and coastal populations.In conclusion, variations in F(v/F(m, Φ(PSII, qP and non-photochemical quenching (NPQ in response to winter stress were primarily due to the differences between the winter conditions and the sites and secondarily due to the differences among families and their interactions with the environment. Populations from continental climates showed higher frost tolerance (LT₅₀ than coastal populations that typically experience mild

Intraspecific variation in Pinus pinaster PSII photochemical efficiency in response to winter stress and freezing temperatures.

Science.gov (United States)

Corcuera, Leyre; Gil-Pelegrin, Eustaquio; Notivol, Eduardo

2011-01-01

As part of a program to select maritime pine (Pinus pinaster Ait.) genotypes for resistance to low winter temperatures, we examined variation in photosystem II activity by chlorophyll fluorescence. Populations and families within populations from contrasting climates were tested during two consecutive winters through two progeny trials, one located at a continental and xeric site and one at a mesic site with Atlantic influence. We also obtained the LT₅₀, or the temperature that causes 50% damage, by controlled freezing and the subsequent analysis of chlorophyll fluorescence in needles and stems that were collected from populations at the continental trial site.P. pinaster showed sensitivity to winter stress at the continental site, during the colder winter. The combination of low temperatures, high solar irradiation and low precipitation caused sustained decreases in maximal photochemical efficiency (F(v)/F(m)), quantum yield of non-cyclic electron transport (Φ(PSII)) and photochemical quenching (qP). The variation in photochemical parameters was larger among families than among populations, and population differences appeared only under the harshest conditions at the continental site. As expected, the environmental effects (winter and site) on the photochemical parameters were much larger than the genotypic effects (population or family). LT₅₀ was closely related to the minimum winter temperatures of the population's range. The dark-adapted F(v)/F(m) ratio discriminated clearly between interior and coastal populations.In conclusion, variations in F(v)/F(m), Φ(PSII), qP and non-photochemical quenching (NPQ) in response to winter stress were primarily due to the differences between the winter conditions and the sites and secondarily due to the differences among families and their interactions with the environment. Populations from continental climates showed higher frost tolerance (LT₅₀) than coastal populations that typically experience mild winters

Distortions of the Xanthophylls Caused by Interactions with Neighboring Pigments and the LHCII Protein Are Crucial for Studying Energy Transfer Pathways within the Complex.

Science.gov (United States)

Fox, K F; Bricker, William P; Lo, Cynthia; Duffy, C D P

2015-12-24

It has been proposed that photoprotective non-photochemical quenching (NPQ) in higher plants arises from a conformational change in the antenna which alters pigment-pigment interactions. This brings about the formation of energy quenching "traps" that capture and dissipate excitation energy as heat. We have used the semiempirical AM1-CAS-CI method combined with the transition density cube (TDC) approach to model chlorophyll (Chl) to xanthophyll (Xanth) resonant Coulomb couplings in the crystal structure of LHCII. Due to its proposed role as the NPQ quenching site we have focused on lutein interactions and have explored how distortions to lutein conformation, as well as interpigment distances and relative orientations, affect this coupling. Our calculations indicate that distortions as well as Chl-lutein angle have a significant effect on coupling, whereas interpigment distances have a relatively minor effect. We therefore conclude that particular attention to the distortions of the Xanths should be given for calculation of energy transfer pathways and study of the NPQ mechanism.

Photosynthetic Properties and Potentials for Improvement of Photosynthesis in Pale Green Leaf Rice under High Light Conditions

Directory of Open Access Journals (Sweden)

Junfei Gu

2017-06-01

Full Text Available Light is the driving force of plant growth, providing the energy required for photosynthesis. However, photosynthesis is also vulnerable to light-induced damage caused by the production of reactive oxygen species (ROS. Plants have therefore evolved various protective mechanisms such as non-photochemical quenching (NPQ to dissipate excessively absorbed solar energy as heat; however, photoinhibition and NPQ represent a significant loss in solar energy and photosynthetic efficiency, which lowers the yield potential in crops. To estimate light capture and light energy conversion in rice, a genotype with pale green leaves (pgl and a normally pigmented control (Z802 were subjected to high (HL and low light (LL. Chlorophyll content, light absorption, chloroplast micrographs, abundance of light-harvesting complex (LHC binding proteins, electron transport rates (ETR, photochemical and non-photochemical quenching, and generation of ROS were subsequently examined. Pgl had a smaller size of light-harvesting chlorophyll antenna and absorbed less photons than Z802. NPQ and the generation of ROS were also low, while photosystem II efficiency and ETR were high, resulting in improved photosynthesis and less photoinhibition in pgl than Z802. Chlorophyll synthesis and solar conversion efficiency were higher in pgl under HL compared to LL treatment, while Z802 showed an opposite trend due to the high level of photoinhibition under HL. In Z802, excessive absorption of solar energy not only increased the generation of ROS and NPQ, but also exacerbated the effects of increases in temperature, causing midday depression in photosynthesis. These results suggest that photosynthesis and yield potential in rice could be enhanced by truncated light-harvesting chlorophyll antenna size.

Photosynthetic Properties and Potentials for Improvement of Photosynthesis in Pale Green Leaf Rice under High Light Conditions

Science.gov (United States)

Gu, Junfei; Zhou, Zhenxiang; Li, Zhikang; Chen, Ying; Wang, Zhiqin; Zhang, Hao; Yang, Jianchang

2017-01-01

Light is the driving force of plant growth, providing the energy required for photosynthesis. However, photosynthesis is also vulnerable to light-induced damage caused by the production of reactive oxygen species (ROS). Plants have therefore evolved various protective mechanisms such as non-photochemical quenching (NPQ) to dissipate excessively absorbed solar energy as heat; however, photoinhibition and NPQ represent a significant loss in solar energy and photosynthetic efficiency, which lowers the yield potential in crops. To estimate light capture and light energy conversion in rice, a genotype with pale green leaves (pgl) and a normally pigmented control (Z802) were subjected to high (HL) and low light (LL). Chlorophyll content, light absorption, chloroplast micrographs, abundance of light-harvesting complex (LHC) binding proteins, electron transport rates (ETR), photochemical and non-photochemical quenching, and generation of ROS were subsequently examined. Pgl had a smaller size of light-harvesting chlorophyll antenna and absorbed less photons than Z802. NPQ and the generation of ROS were also low, while photosystem II efficiency and ETR were high, resulting in improved photosynthesis and less photoinhibition in pgl than Z802. Chlorophyll synthesis and solar conversion efficiency were higher in pgl under HL compared to LL treatment, while Z802 showed an opposite trend due to the high level of photoinhibition under HL. In Z802, excessive absorption of solar energy not only increased the generation of ROS and NPQ, but also exacerbated the effects of increases in temperature, causing midday depression in photosynthesis. These results suggest that photosynthesis and yield potential in rice could be enhanced by truncated light-harvesting chlorophyll antenna size. PMID:28676818

[PS II photochemical efficiency in flag leaf of wheat varieties and its adaptation to strong sun- light intensity on farmland of Xiangride in Qinghai Province, Northwest China].

Science.gov (United States)

Shi, Sheng-Bo; Chen, Wen-Jie; Shi, Rui; Li, Miao; Zhang, Huai-Gang; Sun, Ya-Nan

2014-09-01

Taking four wheat varieties developed by Northwest Institute of Plateau Biology, Chinese Academy of Sciences, as test materials, with the measurement of content of photosynthetic pigments, leaf area, fresh and dry mass of flag leaf, the PS II photochemistry efficiency of abaxial and adaxial surface of flag leaf and its adaptation to strong solar radiation during the period of heading stage in Xiangride region were investigated with the pulse-modulated in-vivo chlorophyll fluorescence technique. The results indicated that flag leaf angle mainly grew in horizontal state in Gaoyuan 314, Gaoyuan 363 and Gaoyuan 584, and mainly in vertical state in Gaoyuan 913 because of its smaller leaf area and larger width. Photosynthetic pigments were different among the 4 varieties, and positively correlated with intrinsic PS II photochemistry efficiencies (Fv/Fm). In clear days, especially at noon, the photosynthetic photoinhibition was more serious in abaxial surface of flag leaf due to directly facing the solar radiation, but it could recover after reduction of sunlight intensity in the afternoon, which meant that no inactive damage happened in PS II reaction centers. There were significant differences of PS II actual and maximum photochemical efficiencies at the actinic light intensity (ΦPS II and Fv'/Fm') between abaxial and adaxial surface, and their relative variation trends were on the contrary. The photochemical and non-photochemical quenching coefficients (qP and NPQ) had a similar tendency in both abaxial and adaxial surfaces. Although ΦPS II and qP were lower in adaxial surface of flag leaf, the Fv'/Fm' was significantly higher, which indicated that the potential PS II capture efficiency of excited energy was higher. The results demonstrated that process of photochemical and non-photochemical quenching could effectively dissipate excited energy caused by strong solar radiation, and there were higher adaptation capacities in wheat varieties natively cultivated in

Genetic manipulation of carotenoid biosynthesis and photoprotection.

Science.gov (United States)

Pogson, B J; Rissler, H M

2000-10-29

There are multiple complementary and redundant mechanisms to provide protection against photo-oxidative damage, including non-photochemical quenching (NPQ). NPQ dissipates excess excitation energy as heat by using xanthophylls in combination with changes to the light-harvesting complex (LHC) antenna. The xanthophylls are oxygenated carotenoids that in addition to contributing to NPQ can quench singlet or triplet chlorophyll and are necessary for the assembly and stability of the antenna. We have genetically manipulated the expression of the epsilon-cyclase and beta-carotene hydroxylase carotenoid biosynthetic enzymes in Arabidopsis thaliana. The epsilon-cyclase overexpression confirmed that lut2 (lutein deficient) is a mutation in the epsilon-cyclase gene and demonstrated that lutein content can be altered at the level of mRNA abundance with levels ranging from 0 to 180% of wild-type. Also, it is clear that lutein affects the induction and extent of NPQ. The deleterious effects of lutein deficiency on NPQ in Arabidopsis and Chlamydomonas are additive, no matter what the genetic background, whether npq1 (zeaxanthin deficient), aba1 or antisense beta-hydroxylase (xanthophyll cycle pool decreased). Additionally, increasing lutein content causes a marginal, but significant, increase in the rate of induction of NPQ despite a reduction in the xanthophyll cycle pool size.

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

NARCIS (Netherlands)

Dinc, E.; Tian, L.; Roy, L.M.; Roth, R.; Goodenough, U.; Croce, R.

2016-01-01

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

Arbuscular mycorrhizal symbiosis ameliorates the optimum quantum yield of photosystem II and reduces non-photochemical quenching in rice plants subjected to salt stress.

Science.gov (United States)

Porcel, Rosa; Redondo-Gómez, Susana; Mateos-Naranjo, Enrique; Aroca, Ricardo; Garcia, Rosalva; Ruiz-Lozano, Juan Manuel

2015-08-01

Rice is the most important food crop in the world and is a primary source of food for more than half of the world population. However, salinity is considered the most common abiotic stress reducing its productivity. Soil salinity inhibits photosynthetic processes, which can induce an over-reduction of the reaction centres in photosystem II (PSII), damaging the photosynthetic machinery. The arbuscular mycorrhizal (AM) symbiosis may improve host plant tolerance to salinity, but it is not clear how the AM symbiosis affects the plant photosynthetic capacity, particularly the efficiency of PSII. This study aimed at determining the influence of the AM symbiosis on the performance of PSII in rice plants subjected to salinity. Photosynthetic activity, plant gas-exchange parameters, accumulation of photosynthetic pigments and rubisco activity and gene expression were also measured in order to analyse comprehensively the response of the photosynthetic processes to AM symbiosis and salinity. Results showed that the AM symbiosis enhanced the actual quantum yield of PSII photochemistry and reduced the quantum yield of non-photochemical quenching in rice plants subjected to salinity. AM rice plants maintained higher net photosynthetic rate, stomatal conductance and transpiration rate than nonAM plants. Thus, we propose that AM rice plants had a higher photochemical efficiency for CO2 fixation and solar energy utilization and this increases plant salt tolerance by preventing the injury to the photosystems reaction centres and by allowing a better utilization of light energy in photochemical processes. All these processes translated into higher photosynthetic and rubisco activities in AM rice plants and improved plant biomass production under salinity. Copyright © 2015 Elsevier GmbH. All rights reserved.

Quenching of excited uranyl ion during its photochemical reduction with triphenyl-phosphine : Part IV - effect of heterocyclic molecules

International Nuclear Information System (INIS)

Sidhu, M.S.; Bhatia, P.V.K.

1994-01-01

The presence of heterocyclic compounds triggers off a competition between photophysical and photochemical annihilation of excited uranyl ion during its photochemical reduction with triphenylphosphine. This competition is used to measure Stern-Volmer constant using UV visible spectrophotometer for quenching the uranyl ion luminescence with a number of heterocyclic molecules viz., pyridine, thiophene bipyridyl, tetrahydrofuran and piperidine. (author). 7 refs., 2 figs., 1 tab

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

Energy Technology Data Exchange (ETDEWEB)

Berman, Gennady P. [Theoretical Division, T-4, Los Alamos National Laboratory, and the New Mexico Consortium, Los Alamos, NM 87544 (United States); Nesterov, Alexander I., E-mail: nesterov@cencar.udg.mx [Departamento de Física, CUCEI, Universidad de Guadalajara, Av. Revolución 1500, Guadalajara, CP 44420, Jalisco (Mexico); Sayre, Richard T. [Biological Division, B-11, Los Alamos National Laboratory, and the New Mexico Consortium, Los Alamos, NM 87544 (United States); Still, Susanne [Department of Information and Computer Sciences, and Department of Physics and Astronomy, University of Hawaii at Mānoa, 1860 East–West Road, Honolulu, HI 96822 (United States)

2016-03-22

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. - Highlights: • Improvement of the efficiency of the charge-transfer nonphotochemical quenching in CP29. • Strategy for restoring the NPQ efficiency when the environment changes. • By changing of energy transfer rates to the sinks, one can significantly improve the performance of the NPQ.

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

Science.gov (United States)

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

2016-07-05

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.

[Effects of groundwater level on chlorophyll fluorescence characteristics of Tamarix hispida in lower reaches of Tarim River].

Science.gov (United States)

Zhu, Cheng-gang; Li, Wei-hong; Ma, Jian-xin; Ma, Xiao-dong

2010-07-01

Based on the monitoring data of groundwater level at the typical sections in lower reaches of Tarim River, three survey plots nearby the ecological monitoring wells with groundwater depths > 6 m were selected to investigate the chlorophyll fluorescence characteristics of Tamarix hispida and its photosynthetic activity of PSII under effects of different groundwater depths. With increasing groundwater depth, the chlorophyll fluorescence parameters such as actual photochemical efficiency of PSII in the light (phi(PSII)), electron transport rate (ETR), and photochemistry quenching (q(p)) of T. hispida decreased, while the non-photochemistry quenching (q(N), NPQ) and the yield for dissipation by down-regulation (Y(NPQ)) increased remarkably, and the maximal photochemical efficiency of PSII (Fv/Fm) maintained an optimum value. All the results suggested that the PSII photosynthetic activity of T. hispida under drought stress declined with increasing groundwater depth, and the greater excess energy could result in more risk of photo-inhibition. However, the good adaptability and drought tolerance of T. hispida could make its PSII not seriously damaged, though the drought stress actually existed.

Photosystem II functionality in barley responds dynamically to changes in leaf manganese status

DEFF Research Database (Denmark)

Schmidt, Sidsel Birkelund; Powikrowska, Marta; Krogholm, Ken Suszkiewicz

2016-01-01

functionality. We have here used parameters derived from measurements of fluorescence induction kinetics (OJIP transients), non-photochemical quenching (NPQ) and PSII subunit composition to investigate how latent Mn deficiency changes the photochemistry in two barley genotypes differing in Mn efficiency. Mn...... the plants incapable of dissipating excess energy in a controlled way. Thus, the Mn deficient plants became severely affected in their ability to recover from high light-induced photoinhibition, especially under strong Mn deficiency. Interestingly, the Mn-efficient genotype was able to maintain a higher NPQ...... decrease in the abundance of the OEC protein subunits, PsbP and PsbQ in response to Mn deficiency for both genotypes. We conclude that regulation of photosynthetic performance by means of maintaining and inducing NPQ mechanisms contribute to genotypic differences in the Mn efficiency of barley genotypes...

Reduced calcification decreases photoprotective capability in the coccolithophorid Emiliania huxleyi.

Science.gov (United States)

Xu, Kai; Gao, Kunshan

2012-07-01

Intracellular calcification of coccolithophores generates CO₂ and consumes additional energy for acquisition of calcium and bicarbonate ions; therefore, it may correlate with photoprotective processes by influencing the energetics. To address this hypothesis, a calcifying Emiliania huxleyi strain (CS-369) was grown semi-continuously at reduced (0.1 mM, LCa) and ambient Ca²⁺ concentrations (10 mM, HCa) for 150 d (>200 generations). The HCa-grown cells had higher photosynthetic and calcification rates and higher contents of Chl a and carotenoids compared with the naked (bearing no coccoliths) LCa-grown cells. When exposed to stressfull levels of photosynthetically active radiation (PAR), LCa-grown cells displayed lower photochemical yield and less efficient non-photochemical quenching (NPQ). When the LCa- or HCa-grown cells were inversely shifted to their counterpart medium, LCa to HCa transfer increased photosynthetic carbon fixation (P), calcification rate (C), the C/P ratio, NPQ and pigment contents, whereas those shifted from HCa to LCa exhibited the opposite effects. Increased NPQ, carotenoids and quantum yield were clearly linked with increased or sustained calcification in E. huxleyi. The calcification must have played a role in dissipating excessive energy or as an additional drainage of electrons absorbed by the photosynthetic antennae. This phenomenon was further supported by testing two non-calcifying strains, which showed insignificant changes in photosynthetic carbon fixation and NPQ when transferred to LCa conditions.

Evaluation of barley (hordeum vulgare l.) germplasm for high forage production under salt stress

International Nuclear Information System (INIS)

Saleem, A.; Qurainy, F.A.; Akram, N.A.

2014-01-01

To explore high biomass producing salt tolerant cultivars of a potential forage crop barley (Hordeum vulgare L.), 30-day old plants of 105 different accessions from different origin were subjected to saline and non-saline (control) conditions for 45 days. Salinity stress (150 mM NaCl) markedly suppressed plant growth (shoot and/or root fresh and dry weights), chlorophyll pigments (a and b), internal CO/sub 2/ concentration, stomatal conductance, rate of transpiration and photosynthesis, while a considerable salt-induced increase was observed in all fluorescence related attributes including efficiency of photosystem-II (Fv/Fm), co-efficient of non-photochemical quenching (QN), photochemical quenching (QP), and non-photochemical quenching (NPQ) in all 105 accessions of barley. The response of all 105 barley accessions to salt stress varied significantly for all the morpho-physiological attributes determined in the present study. Overall, on the basis of shoot and root dry weights, accessions, 4050, 4053, 4056, 4163, 4228, 4229, 4244, 4245, 4290, 4414, 4415, 4427, 4452, Mahali, Jesto, 4165, 4229, 4249, 4405, 4409, 4426, 4456, and Giza 123 were found superior while accessions, 4245, 4158, 4166, 4246, 4406, 4423, 4441, 4442 4447, 4453 and 4458 inferior under saline conditions. (author)

Zeaxanthin-independent energy quenching and alternative electron sinks cause a decoupling of the relationship between the photochemical reflectance index (PRI) and photosynthesis in an evergreen conifer during spring.

Science.gov (United States)

Fréchette, Emmanuelle; Wong, Christopher Y S; Junker, Laura Verena; Chang, Christine Yao-Yun; Ensminger, Ingo

2015-12-01

In evergreen conifers, the winter down-regulation of photosynthesis and its recovery during spring are the result of a reorganization of the chloroplast and adjustments of energy-quenching mechanisms. These phenological changes may remain undetected by remote sensing, as conifers retain green foliage during periods of photosynthetic down-regulation. The aim was to assess if the timing of the spring recovery of photosynthesis and energy-quenching characteristics are accurately monitored by the photochemical reflectance index (PRI) in the evergreen conifer Pinus strobus. The recovery of photosynthesis was studied using chlorophyll fluorescence, leaf gas exchange, leaf spectral reflectance, and photosynthetic pigment measurements. To assess if climate change might affect the recovery of photosynthesis, seedlings were exposed to cold spring conditions or warm spring conditions with elevated temperature. An early spring decoupling of the relationship between photosynthesis and PRI in both treatments was observed. This was caused by differences between the timing of the recovery of photosynthesis and the timing of carotenoid and chlorophyll pool size adjustments which are the main factors controlling PRI during spring. It was also demonstrated that zeaxanthin-independent NPQ mechanisms undetected by PRI further contributed to the early spring decoupling of the PRI-LUE relationship. An important mechanism undetected by PRI seems to involve increased electron transport around photosystem I, which was a significant energy sink during the entire spring transition, particularly in needles exposed to a combination of high light and cold temperatures. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Significance of the lipid phase in the dynamics and functions of the xanthophyll cycle as revealed by PsbS overexpression in tobacco and in-vitro de-epoxidation in monogalactosyldiacylglycerol micelles.

Science.gov (United States)

Hieber, A David; Kawabata, Osamu; Yamamoto, Harry Y

2004-01-01

The dynamics of the xanthophyll cycle relative to non-photochemical quenching (NPQ) were examined in tobacco plants overexpressing violaxanthin de-epoxidase (VDE), PsbS and PsbS+VDE for effects on NPQ and violaxanthin (V) de-epoxidation over a range of light intensities. Induction of de-epoxidation and NPQ increased in overexpressed VDE and PsbS plants, respectively. Surprisingly, under low light, overexpressing PsbS enhanced de-epoxidation in addition to NPQ. The effect was hypothesized as due to PsbS binding zeaxanthin (Z) or inducing the binding of Z within the quenching complex, thus shifting the equilibrium toward higher de-epoxidation states. Studies in model systems show that Z can stereospecifically inhibit VDE activity against violaxanthin. This effect, observed under conditions of limiting lipid concentration, was interpreted as product feedback inhibition. These results support the hypothesis that the capacity of the thylakoid lipid phase for xanthophylls is limited and modulates xanthophyll-cycle activity, in conjunction with the release of V and binding of Z by pigment-binding proteins. These modulating factors are incorporated into a lipid-matrix model that has elements of a signal transduction system wherein the light-generated protons are the signal, VDE the signal receptor, Z the secondary messenger, the lipid phase the transduction network, and Z-binding proteins the targets.

Photosystem II functionality in barley responds dynamically to changes in leaf manganese status

Directory of Open Access Journals (Sweden)

Sidsel Birkelund Schmidt

2016-11-01

Full Text Available A catalytic manganese (Mn cluster is required for the oxidation of water in the oxygen-evolving complex (OEC of photosystem II (PSII in plants. Despite this essential role of Mn in generating the electrons driving photosynthesis, limited information is available on how Mn deficiency affects PSII functionality. We have here used parameters derived from measurements of fluorescence induction kinetics (OJIP transients, non-photochemical quenching and PSII subunit composition to investigate how latent Mn deficiency changes the photochemistry in two barley genotypes differing in Mn efficiency. Mn deficiency caused dramatic reductions in the quantum yield of PSII and led to the appearance of two new inflection points, the K step and the D dip, in the OJIP fluorescence transients, indicating severe damage to the OEC. In addition, Mn deficiency decreased the ability to induce non-photochemical quenching (NPQ in the light, rendering the plants incapable of dissipating excess energy in a controlled way. Thus, the Mn deficient plants became severely affected in their ability to recover from high light-induced photoinhibition, especially under strong Mn deficiency. Interestingly, the Mn-efficient genotype was able to maintain a higher non-photochemical quenching than the Mn-inefficient genotype when exposed to mild Mn deficiency. However, during severe Mn deficiency, there were no differences between the two genotypes, suggesting a general loss of the ability to disassemble and repair PSII. The pronounced defects of PSII activity were supported by a dramatic decrease in the abundance of the OEC protein subunits, PsbP and PsbQ in response to Mn deficiency for both genotypes. We conclude that regulation of photosynthetic performance by means of maintaining and inducing NPQ mechanisms contribute to genotypic differences in the Mn efficiency of barley genotypes growing under conditions with mild Mn deficiency.

A temperature-sensitive winter wheat chlorophyll mutant derived from space mutagenesis

International Nuclear Information System (INIS)

Zhao Hongbin; Guo Huijun; Zhao Linshu; Gu Jiayu; Zhao Shirong; Li Junhui; Liu Luxiang

2010-01-01

A temperature-sensitive winter wheat (Triticum aestivum L.) chlorophyll mutant Mt18, induced by spaceflight mutagenesis, was studied on agronomic traits, ultrastructure of chloroplast and photosynthesis characteristics. The leaf color of the mutant Mt18 showed changes from green to albino and back to green during the whole growth period. Plant height, productive tillers, spike length, grains and grain weight per plant, and 1000-grain weight of the mutant were lower than those of the wild type. The ultrastructural observation showed that no significant difference was found between the mutant and the wild type during prior albino stage, however, at the albino stage the number of granum-thylakoids and grana lamellae became fewer or completely disappeared, but the strom-thylakoid was obviously visible. After turning green,the structure of most chloroplasts recovered to normal, but number of chloroplast was still lower than that of the wild type. When exposed to photosynthetic active radiation (PAR) of 110 μmol·m -2 ·s -1 , the non-photochemical quenching (NPQ) of mutant was significantly lower than that of the wild type, and the non-regulated energy dissipation (Y NO ) was significantly higher than that of the wild type, while the change of the maximum photosystem II quantum yield (F v /F m ), potential activity of photosystem II (F v /F o ), photochemical quenching (q P ), effective quantum yield (Y PSI I) and regulated non-photochemical energy dissipation (Y NPQ ) were different at various stages. In addition, the differences of the electron transport rate (ETR), photochemical quenching (q P ), and effective quantum yield (Y PSI I) between mutant and wild type varied under different PAR conditions. It was concluded that with the change of chloroplast ultrastructure, the leaf color and photosynthesis of the wheat mutant Mt18 change correspondingly. The chloroplast ultrastructure was obviously different from that of wild type, and the photosynthetic efficiency

Chlorophyll Fluorescence in Partially Defoliated Grape Plants (Vitis vinifera L. cv. Chardonnay / Fluorescencia de la Clorofila en Plantas de Uva (Vitis vinifera L. cv. Chardonnay Defoliadas Parcialmente

Directory of Open Access Journals (Sweden)

Peña Olmos Jaime Ernesto

2013-08-01

Full Text Available The chlorophyll content and fluorescence weredetermined in five-year-old grape plants (Vitis vinifera L. cv.Chardonnay that were subjected to early partial defoliation,in Villa de Leyva, Colombia. The experimental design wascompletely randomized, consisting of two treatments (50%defoliation and control, each with four replications of 35 plants. Every two weeks, one of every two recently-emerged leaves was removed from the non-control plants. The determination of total chlorophyll content was carried out on six leaves per plant using a CCM-200 Plus chlorophyll meter, while chlorophyll fluorescence measurements were taken with one darkadapted leaf per plant using a Junior-PAM fluorometer. Initial fluorescence (Fo, maximum fluorescence (Fm, terminal fluorescence (Ft, variable fluorescence (Fv, electron transport rate (ETR, maximum photochemical quantum yield of PSII (Fv/ Fm, effective photochemical quantum yield of photosystem II (Y(II, photochemical fluorescence quenching coefficient (qP, two non-photochemical quenching coefficients (qN and NPQ,quantum yield of light-induced non-photochemical fluorescence quenching (Y(NPQ, and quantum yield of non-light-induced non-photochemical quenching (Y(NO were measured. The chlorophyll concentration index showed higher values in the defoliated plants. There were no significant differences for the values of Fm, Ft and Fv. Fo was higher in the defoliated plants, while ETR, Fv/Fm and Y(II showed higher values in the control plants. It is evident that a reduction in leaf area modifies thepartitioning of excitation energy destined for photochemicaland non-photochemical processes, thus directly influencing the photosynthetic process of the plants evaluated. / Utilizando un diseño completamente aleatorizado,con dos tratamientos (defoliación al 50% y control y cuatrorepeticiones de 35 plantas cada una, se determinó el contenido y la fluorescencia de la clorofila en plantas de uva, sometidas a defoliación parcial

Spectral radiation dependent photoprotective mechanism in the diatom Pseudo-nitzschia multistriata.

Directory of Open Access Journals (Sweden)

Christophe Brunet

Full Text Available Phytoplankton, such as diatoms, experience great variations of photon flux density (PFD and light spectrum along the marine water column. Diatoms have developed some rapidly-regulated photoprotective mechanisms, such as the xanthophyll cycle activation (XC and the non-photochemical chlorophyll fluorescence quenching (NPQ, to protect themselves from photooxidative damages caused by excess PFD. In this study, we investigate the role of blue fluence rate in combination with red radiation in shaping photoacclimative and protective responses in the coastal diatom Pseudo-nitzschia multistriata. This diatom was acclimated to four spectral light conditions (blue, red, blue-red, blue-red-green, each of them provided with low and high PFD. Our results reveal that the increase in the XC pool size and the amplitude of NPQ is determined by the blue fluence rate experienced by cells, while cells require sensing red radiation to allow the development of these processes. Variations in the light spectrum and in the blue versus red radiation modulate either the photoprotective capacity, such as the activation of the diadinoxanthin-diatoxanthin xanthophyll cycle, the diadinoxanthin de-epoxidation rate and the capacity of non-photochemical quenching, or the pigment composition of this diatom. We propose that spectral composition of light has a key role on the ability of diatoms to finely balance light harvesting and photoprotective capacity.

Biophysical modeling of in vitro and in vivo processes underlying regulated photoprotective mechanism in cyanobacteria.

Science.gov (United States)

Shirshin, Evgeny A; Nikonova, Elena E; Kuzminov, Fedor I; Sluchanko, Nikolai N; Elanskaya, Irina V; Gorbunov, Maxim Y; Fadeev, Victor V; Friedrich, Thomas; Maksimov, Eugene G

2017-09-01

Non-photochemical quenching (NPQ) is a mechanism responsible for high light tolerance in photosynthetic organisms. In cyanobacteria, NPQ is realized by the interplay between light-harvesting complexes, phycobilisomes (PBs), a light sensor and effector of NPQ, the photoactive orange carotenoid protein (OCP), and the fluorescence recovery protein (FRP). Here, we introduced a biophysical model, which takes into account the whole spectrum of interactions between PBs, OCP, and FRP and describes the experimental PBs fluorescence kinetics, unraveling interaction rate constants between the components involved and their relative concentrations in the cell. We took benefit from the possibility to reconstruct the photoprotection mechanism and its parts in vitro, where most of the parameters could be varied, to develop the model and then applied it to describe the NPQ kinetics in the Synechocystis sp. PCC 6803 mutant lacking photosystems. Our analyses revealed  that while an excess of the OCP over PBs is required to obtain substantial PBs fluorescence quenching in vitro, in vivo the OCP/PBs ratio is less than unity, due to higher local concentration of PBs, which was estimated as ~10 -5 M, compared to in vitro experiments. The analysis of PBs fluorescence recovery on the basis of the generalized model of enzymatic catalysis resulted in determination of the FRP concentration in vivo close to 10% of the OCP concentration. Finally, the possible role of the FRP oligomeric state alteration in the kinetics of PBs fluorescence was shown. This paper provides the most comprehensive model of the OCP-induced PBs fluorescence quenching to date and the results are important for better understanding of the regulatory molecular mechanisms underlying NPQ in cyanobacteria.

Decreased Photochemical Efficiency of Photosystem II following Sunlight Exposure of Shade-Grown Leaves of Avocado: Because of, or in Spite of, Two Kinetically Distinct Xanthophyll Cycles?1[W

Science.gov (United States)

Jia, Husen; Förster, Britta; Chow, Wah Soon; Pogson, Barry James; Osmond, C. Barry

2013-01-01

This study resolved correlations between changes in xanthophyll pigments and photosynthetic properties in attached and detached shade-grown avocado (Persea americana) leaves upon sun exposure. Lutein epoxide (Lx) was deepoxidized to lutein (L), increasing the total pool by ΔL over 5 h, whereas violaxanthin (V) conversion to antheraxanthin (A) and zeaxanthin (Z) ceased after 1 h. During subsequent dark or shade recovery, de novo synthesis of L and Z continued, followed by epoxidation of A and Z but not of L. Light-saturated nonphotochemical quenching (NPQ) was strongly and linearly correlated with decreasing [Lx] and increasing [∆L] but showed a biphasic correlation with declining [V] and increasing [A+Z] separated when V deepoxidation ceased. When considering [ΔL+∆Z], the monophasic linear correlation was restored. Photochemical efficiency of photosystem II (PSII) and photosystem (PSI; deduced from the delivery of electrons to PSI in saturating single-turnover flashes) showed a strong correlation in their continuous decline in sunlight and an increase in NPQ capacity. This decrease was also reflected in the initial reduction of the slope of photosynthetic electron transport versus photon flux density. Generally longer, stronger sun exposures enhanced declines in both slope and maximum photosynthetic electron transport rates as well as photochemical efficiency of PSII and PSII/PSI more severely and prevented full recovery. Interestingly, increased NPQ capacity was accompanied by slower relaxation. This was more prominent in detached leaves with closed stomata, indicating that photorespiratory recycling of CO2 provided little photoprotection to avocado shade leaves. Sun exposure of these shade leaves initiates a continuum of photoprotection, beyond full engagement of the Lx and V cycle in the antenna, but ultimately photoinactivated PSII reaction centers. PMID:23213134

Occurrence of the PsbS and LhcSR products in the green alga Ulva linza and their correlation with excitation pressure.

Science.gov (United States)

Zhang, Xiaowen; Ye, Naihao; Mou, Shanli; Xu, Dong; Fan, Xiao

2013-09-01

To avoid photoinhibition, plants have developed diverse photoprotection mechanisms. One of the short-term high light protection mechanisms in plants is non-photochemical quenching (NPQ), which dissipates the absorbed light energy as thermal energy. In the green alga, Ulva linza, the kinetics of NPQ starts with an initial, quick rise followed by a decline, and then a second and higher rise at longer time periods. During the whole phase, NPQ is triggered and controlled by ΔpH, then strengthened and modulated by zeaxanthin. Light-harvesting complex (LHC) family members are known to play crucial roles in this mechanism. The PSBS protein, a member of the LHC family that was thought to be present exclusively in higher plants, has been identified for the first time in U. linza. The expression of both PSBS and LHCSR was up-regulated during high light conditions, and LHCSR increased more than PSBS. Both LHCSR and PSBS-dependent NPQ may be important strategies for adapting to the environment, and they have undoubtedly played a role in their evolution. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

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.*

Science.gov (United States)

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

2015-01-01

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

Brevetoxin, the Dinoflagellate Neurotoxin, Localizes to Thylakoid Membranes and Interacts with the Light-Harvesting Complex II (LHCII) of Photosystem II.

Science.gov (United States)

Cassell, Ryan T; Chen, Wei; Thomas, Serge; Liu, Li; Rein, Kathleen S

2015-05-04

The brevetoxins are neurotoxins that are produced by the "Florida red tide" dinoflagellate Karenia brevis. They bind to and activate the voltage-gated sodium channels in higher organisms, specifically the Nav 1.4 and Nav 1.5 channel subtypes. However, the native physiological function that the brevetoxins perform for K. brevis is unknown. By using fluorescent and photoactivatable derivatives, brevetoxin was shown to localize to the chloroplast of K. brevis where it binds to the light-harvesting complex II (LHCII) and thioredoxin. The LHCII is essential to non-photochemical quenching (NPQ), whereas thioredoxins are critical to the maintenance of redox homeostasis within the chloroplast and contribute to the scavenging of reactive oxygen. A culture of K. brevis producing low levels of toxin was shown to be deficient in NPQ and produced reactive oxygen species at twice the rate of the toxic culture, implicating a role in NPQ for the brevetoxins. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photophysical, Photochemical, and BQ Quenching Properties of Zinc Phthalocyanines with Fused or Interrupted Extended Conjugation

Directory of Open Access Journals (Sweden)

Gülşah Gümrükçü

2014-01-01

Full Text Available The effects of substituents and solvents on the photophysical and photochemical parameters of zinc(II phthalocyanines containing four Schiff’s base substituents attached directly and through phenyleneoxy-bridges on peripheral positions are reported. The group effects on peripheral position and the continual and intermittent conjugation of the phthalocyanine molecules on the photophysical and photochemical properties are also investigated. General trends are described for photodegradation, singlet oxygen, and fluorescence quantum yields of these compounds in dimethylsulfoxide (DMSO, dimethylformamide (DMF, and tetrahydrofurane (THF. Among the different substituents, phthalocyanines with cinnamaldimine moieties (1c and 2c have the highest singlet oxygen quantum yields (ΦΔ and those with nitro groups (1a and 2a have the highest fluorescence quantum yields in all the solvents used. The fluorescence of the substituted zinc(II phthalocyanine complexes is effectively quenched by 1,4-benzoquinone (BQ in these solvents.

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

Science.gov (United States)

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.

Ecophysiological Responses of Three Tree Species to a High-Altitude Environment in the Southeastern Tibetan Plateau

Directory of Open Access Journals (Sweden)

Jirui Gong

2018-01-01

Full Text Available This paper measured the ecophysiological responses of Populus cathayana Rehd., Salix longistamina C. Wang et P. Y. Fu., and Ulmus pumila L. to high altitude in the Tibetan Plateau based on changes in water relations, gas exchange, and chlorophyll fluorescence. P. cathayana and U. pumila have higher survival rates than S. longistamina, but the latter has highest biomass. S. longistamina has higher water-use efficiency (WUE, lower transpiration rates (E, higher water potential (Ψ, highest light saturation point (LSP and higher photosystem II (PSII photochemistry efficiency (Fv’/Fm’ and non-photochemistry quenching (NPQ than the other species, and is thus adapted to its habitat for afforestation. U. pumila has lower E, light compensation point (LCP, dark respiration (Rd, Fv’/Fm’ and electron transport rate (ETR, with higher Ψ, apparent quantum yield (AQY, net photosynthetic rate (Pn and non-photochemical quenching (NPQ, which helps it maintain water balance and utilize weak light to survive at high altitude. Relative low WUE, Ψ, Rd, NPQ, with high E, Pn, Fv’/Fm’ and biomass, imply that P. cathayana is more suitable for shelterbelt forests than for a semi-arid habitat. These three species can adapt to high-altitude conditions by different physiological mechanisms and morphological characteristics, which can provide a theoretical basis for afforestation and forest management in the Qinghai Tibetan Plateau.

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

Science.gov (United States)

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.

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

Science.gov (United States)

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

Using optical remote sensing techniques to track the development of ozone-induced stress

Energy Technology Data Exchange (ETDEWEB)

Meroni, Michele, E-mail: michele.meroni@unimib.i [Remote Sensing of Environmental Dynamics Laboratory, DISAT, University of Milan-Bicocca, Piazza della Scienza, 1, 20126 Milan (Italy); Panigada, Cinzia; Rossini, Micol [Remote Sensing of Environmental Dynamics Laboratory, DISAT, University of Milan-Bicocca, Piazza della Scienza, 1, 20126 Milan (Italy); Picchi, Valentina [CNR, Plant Virology Institute, Milan Unit, Milan (Italy); Department of Tree Science, Entomology and Plant Pathology ' G. Scaramuzzi' , University of Pisa, Pisa (Italy); Cogliati, Sergio; Colombo, Roberto [Remote Sensing of Environmental Dynamics Laboratory, DISAT, University of Milan-Bicocca, Piazza della Scienza, 1, 20126 Milan (Italy)

2009-05-15

In this paper, a literature review about optical remote sensing (RS) of O{sub 3} stress is presented. Studies on O{sub 3}-induced effects on vegetation reflectance have been conducted since late '70s based on the analysis of optical RS data. Literature review reveals that traditional RS techniques were able to detect changes in leaf and canopy reflectance related to O{sub 3}-induced stress when visible symptoms already occurred. Only recently, advanced RS techniques using hyperspectral sensors, demonstrated the feasibility of detecting the stress in its early phase by monitoring excess energy dissipation pathways such as chlorophyll fluorescence and non-photochemical quenching (NPQ). Steady-state fluorescence (Fs), measured by exploiting the Fraunhofer line depth principle and NPQ related xanthophyll-cycle, estimated through the photochemical reflectance index (PRI) responded to O{sub 3} fumigation before visible symptoms occurred. This opens up new possibilities for the early detection of vegetation O{sub 3} stress by means of hyperspectral RS. - Possibilities for the early detection of vegetation O{sub 3} stress by means of optical remote sensing are discussed.

Using optical remote sensing techniques to track the development of ozone-induced stress

International Nuclear Information System (INIS)

Meroni, Michele; Panigada, Cinzia; Rossini, Micol; Picchi, Valentina; Cogliati, Sergio; Colombo, Roberto

2009-01-01

In this paper, a literature review about optical remote sensing (RS) of O 3 stress is presented. Studies on O 3 -induced effects on vegetation reflectance have been conducted since late '70s based on the analysis of optical RS data. Literature review reveals that traditional RS techniques were able to detect changes in leaf and canopy reflectance related to O 3 -induced stress when visible symptoms already occurred. Only recently, advanced RS techniques using hyperspectral sensors, demonstrated the feasibility of detecting the stress in its early phase by monitoring excess energy dissipation pathways such as chlorophyll fluorescence and non-photochemical quenching (NPQ). Steady-state fluorescence (Fs), measured by exploiting the Fraunhofer line depth principle and NPQ related xanthophyll-cycle, estimated through the photochemical reflectance index (PRI) responded to O 3 fumigation before visible symptoms occurred. This opens up new possibilities for the early detection of vegetation O 3 stress by means of hyperspectral RS. - Possibilities for the early detection of vegetation O 3 stress by means of optical remote sensing are discussed.

LHCSR Expression under HSP70/RBCS2 Promoter as a Strategy to Increase Productivity in Microalgae

Directory of Open Access Journals (Sweden)

Federico Perozeni

2018-01-01

Full Text Available Microalgae are unicellular photosynthetic organisms considered as potential alternative sources for biomass, biofuels or high value products. However, limited biomass productivity is commonly experienced in their cultivating system despite their high potential. One of the reasons for this limitation is the high thermal dissipation of the light absorbed by the outer layers of the cultures exposed to high light caused by the activation of a photoprotective mechanism called non-photochemical quenching (NPQ. In the model organism for green algae Chlamydomonas reinhardtii, NPQ is triggered by pigment binding proteins called light-harvesting-complexes-stress-related (LHCSRs, which are over-accumulated in high light. It was recently reported that biomass productivity can be increased both in microalgae and higher plants by properly tuning NPQ induction. In this work increased light use efficiency is reported by introducing in C. reinhardtii a LHCSR3 gene under the control of Heat Shock Protein 70/RUBISCO small chain 2 promoter in a npq4 lhcsr1 background, a mutant strain knockout for all LHCSR genes. This complementation strategy leads to a low expression of LHCSR3, causing a strong reduction of NPQ induction but is still capable of protecting from photodamage at high irradiance, resulting in an improved photosynthetic efficiency and higher biomass accumulation.

LHCSR Expression under HSP70/RBCS2 Promoter as a Strategy to Increase Productivity in Microalgae.

Science.gov (United States)

Perozeni, Federico; Stella, Giulio Rocco; Ballottari, Matteo

2018-01-05

Microalgae are unicellular photosynthetic organisms considered as potential alternative sources for biomass, biofuels or high value products. However, limited biomass productivity is commonly experienced in their cultivating system despite their high potential. One of the reasons for this limitation is the high thermal dissipation of the light absorbed by the outer layers of the cultures exposed to high light caused by the activation of a photoprotective mechanism called non-photochemical quenching (NPQ). In the model organism for green algae Chlamydomonas reinhardtii , NPQ is triggered by pigment binding proteins called light-harvesting-complexes-stress-related (LHCSRs), which are over-accumulated in high light. It was recently reported that biomass productivity can be increased both in microalgae and higher plants by properly tuning NPQ induction. In this work increased light use efficiency is reported by introducing in C. reinhardtii a LHCSR3 gene under the control of Heat Shock Protein 70 / RUBISCO small chain 2 promoter in a npq4 lhcsr1 background, a mutant strain knockout for all LHCSR genes. This complementation strategy leads to a low expression of LHCSR3 , causing a strong reduction of NPQ induction but is still capable of protecting from photodamage at high irradiance, resulting in an improved photosynthetic efficiency and higher biomass accumulation.

Effects of water stress and light intensity on chlorophyll fluorescence parameters and pigments of Aloe vera L.

Science.gov (United States)

Hazrati, Saeid; Tahmasebi-Sarvestani, Zeinolabedin; Modarres-Sanavy, Seyed Ali Mohammad; Mokhtassi-Bidgoli, Ali; Nicola, Silvana

2016-09-01

Aloe vera L. is one of the most important medicinal plants in the world. In order to determine the effects of light intensity and water deficit stress on chlorophyll (Chl) fluorescence and pigments of A. vera, a split-plot in time experiment was laid out in a randomized complete block design with four replications in a research greenhouse. The factorial combination of three light intensities (50, 75 and 100% of sunlight) and four irrigation regimes (irrigation after depleting 20, 40, 60 and 80% of soil water content) were considered as main factors. Sampling time was considered as sub factor. The first, second and third samplings were performed 90, 180 and 270 days after imposing the treatments, respectively. The results demonstrated that the highest light intensity and the severe water stress decreased maximum fluorescence (Fm), variable fluorescence (Fv)/Fm, quantum yield of PSII photochemistry (ФPSII), Chl and photochemical quenching (qP) but increased non-photochemical quenching (NPQ), minimum fluorescence (F0) and Anthocyanin (Anth). Additionally, the highest Fm, Fv/Fm, ФPSII and qP and the lowest NPQ and F0 were observed when 50% of sunlight was blocked and irrigation was done after 40% soil water depletion. Irradiance of full sunlight and water deficit stress let to the photoinhibition of photosynthesis, as indicated by a reduced quantum yield of PSII, ФPSII, and qP, as well as higher NPQ. Thus, chlorophyll florescence measurements provide valuable physiological data. Close to half of total solar radiation and irrigation after depleting 40% of soil water content were selected as the most efficient treatments. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Roles of xanthophylls and exogenous ABA in protection against NaCl-induced photodamage in rice (Oryza sativa L) and cabbage (Brassica campestris).

Science.gov (United States)

Zhu, Su-Qin; Chen, Ming-Wei; Ji, Ben-Hua; Jiao, De-Mao; Liang, Jian-Sheng

2011-08-01

Changes in actual efficiency of PS II photochemistry, non-photochemical quenching (NPQ), content of xanthophylls and kinetics of de-epoxidation were studied in ABA-fed and non-ABA-fed leaves of rice and cabbage under NaCl stress. Salt stress induced more progressive decrease in actual efficiency of PS II photochemistry (ФPS II), higher reduction state of PS II, and a small significant increase in NPQ in NaCl-sensitive rice plants as compared with NaCl-tolerant cabbage plants, whereas exogenously supplied ABA alleviated the decrease in actual efficiency of PS II photochemistry (ФPS II), induced a lower reduction state of PS II, and caused higher capacity of NPQ in ABA-fed plants than in non-ABA-fed plants. As a result, there were higher activities of photosynthetic electron transport, higher capacity of energy dissipation, and lower cumulation of excess light in cabbage than in rice plants, and in ABA-fed leaves than in non-ABA-fed leaves. The effect of ABA was more efficient in cabbage than in rice plants. Addition of exogenous ABA resulted in enhancement of the size of the xanthophyll cycle pool, promotion of de-epoxidation of the xanthophyll cycle components, and a rise in the level of NPQ by altering the kinetics of de-epoxidation of the xanthophyll cycle. Protection from photodamage appears to be achieved by coordinated contributions by exogenous ABA and xanthophyll cycle-mediated NPQ. This variety of photoprotective mechanisms may be essential for conferring photodamage tolerance under NaCl stress. © The Author [2011]. Published by Oxford University Press [on behalf of the Society for Experimental Biology]. All rights reserved.

Acute exposure to UV-B sensitizes cucumber, tomato, and Arabidopsis plants to photooxidative stress by inhibiting thermal energy dissipation and antioxidant defense

International Nuclear Information System (INIS)

Moon, Yu-Ran; Lee, Min-Hee; Chung, Byung-Yeoup; Kim, Jin-Hong; Tovuu, Altanzaya; Lee, Choon-Hwan; Park, Youn-Il

2011-01-01

The purpose of this study was to characterize a change in Non-photochemical quenching (NPQ) upon exposure to ultraviolet-B (UV-B), the xanthophyll cycle-dependent and -independent NPQs were compared in Cucumis sativus, Lycopersicum esculentum, and Arabidopsis thaliana leaves. The xanthophyll cycle-dependent NPQ was dramatically but reversibly suppressed by UV-B radiation. This suppression was correlated more strongly with a marked decrease in photosynthetic electron transport rather than changes in xanthophyll cycle enzymes such as violaxanthin de-epoxidase and zeaxanthin epoxidase. Accordingly, the UV-B-induced suppression of NPQ cannot be attributed to changes in expressions of violaxanthin de-epoxidase (VDE) and zeaxanthin epoxidase (ZEP). However, suppression of the xanthophyll cycle-dependent NPQ could only account for the 77 K fluorescence emission spectra of thylakoid membranes and the increased level of 1 O 2 production, but not for the decreased levels of hydroxyl radical O 2 - production and H 2 O 2 scavenging. These results suggest that a gradual reduction of H 2 O 2 scavenging activity as well as a transient and reversible suppression of thermal energy dissipation may contribute differentially to increased photooxidative damages in cucumber, tomato, and Arabidopsis plants after acute exposure to UV-B radiation. (author)

Foliar K application delays leaf senescence of winter rape-seed (Brassica napus L.) under waterlogging

Institute of Scientific and Technical Information of China (English)

Lin Wan; Chao Hu; Chang Chen; Liyan Zhang; Ni Ma; Chunlei Zhang

2017-01-01

To better understand waterlogging effect on leaf senescence in winter rapseed (Brassica napus L.) during flowering stage, experiments were designed to explore foliar K application influences on adverse effects of waterlogging stress. Winter rapeseed was sprayed with K after waterlogging at initial flowering stage. Results indicated that waterlog-ging significantly decreased leaf net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular CO2 concentration (Ci) and transpiration rate (Tr). It also declined maximum quantum yield of PS II (Fv/Fm), quantum yield of electron transport (ΦPS II) and pho-tochemical quenching (qP), but increased leaf non-photochemical quenching (NPQ) and minimal fluorescence (Fo). Interestingly, exogenous application of K significantly alleviated waterlogging-induced photosynthesis inhibition. Foliar K application increased RuBisCO activation, chlorophyll and soluble protein contents, while significantly decreased MDA con-tent under waterlogging stress. Moreover, K supplementation improved accumulation of K+, Ca2+, Mg2+, N, Zn2+, Mn2+, Fe2+ in leaves. In general, foliar K application is effective in alleviating deleterious effects of waterlogging stress and delays leaf senescence of winter rapeseed.

Manipulation of the Xanthophyll Cycle Increases Plant Susceptibility to Sclerotinia sclerotiorum.

Directory of Open Access Journals (Sweden)

Jun Zhou

2015-05-01

Full Text Available The xanthophyll cycle is involved in dissipating excess light energy to protect the photosynthetic apparatus in a process commonly assessed from non-photochemical quenching (NPQ of chlorophyll fluorescence. Here, it is shown that the xanthophyll cycle is modulated by the necrotrophic pathogen Sclerotinia sclerotiorum at the early stage of infection. Incubation of Sclerotinia led to a localized increase in NPQ even at low light intensity. Further studies showed that this abnormal change in NPQ was closely correlated with a decreased pH caused by Sclerotinia-secreted oxalate, which might decrease the ATP synthase activity and lead to a deepening of thylakoid lumen acidification under continuous illumination. Furthermore, suppression (with dithiothreitol or a defect (in the npq1-2 mutant of violaxanthin de-epoxidase (VDE abolished the Sclerotinia-induced NPQ increase. HPLC analysis showed that the Sclerotinia-inoculated tissue accumulated substantial quantities of zeaxanthin at the expense of violaxanthin, with a corresponding decrease in neoxanthin content. Immunoassays revealed that the decrease in these xanthophyll precursors reduced de novo abscisic acid (ABA biosynthesis and apparently weakened tissue defense responses, including ROS induction and callose deposition, resulting in enhanced plant susceptibility to Sclerotinia. We thus propose that Sclerotinia antagonizes ABA biosynthesis to suppress host defense by manipulating the xanthophyll cycle in early pathogenesis. These findings provide a model of how photoprotective metabolites integrate into the defense responses, and expand the current knowledge of early plant-Sclerotinia interactions at infection sites.

Seasonal changes in photosynthesis and photoprotection in a Quercus ilex subsp. ballota woodland located in its upper altitudinal extreme in the Iberian Peninsula.

Science.gov (United States)

Corcuera, L; Morales, F; Abadía, A; Gil-Pelegrín, E

2005-05-01

Quercus ilex L. subsp. ballota (Desf.) Samp., a Mediterranean evergreen species growing in a continental Mediterranean climate, did not experience water stress and showed greater sensitivity to winter stress than to summer stress over a 12-month period. Net CO2 assimilation rates and photosystem II (PSII) efficiency decreased markedly during the cold months and recovered completely in spring. Lutein, neoxanthin and beta-carotene to chlorophyll (Chl) molar ratios all showed the same trend throughout the year, increasing from September to March. This increase was a result of increases in carotenoid concentrations, because Chl concentration per unit leaf area remained stable, and was higher at the end than at the beginning of the first growing season. Lutein-epoxide was a minor component of the total lutein pool. Thermal energy dissipation and non-photochemical quenching (NPQ) were associated with the de-epoxidated forms of the xanthophyll cycle pigments in the warm months. Photosynthetic rates decreased slightly at midday in summer. These changes were accompanied by decreases in maximum potential PSII efficiency (which recovered during the night), actual and intrinsic PSII efficiencies, photochemical quenching and increases in NPQ. Overall, our data indicate down-regulation of photosynthesis during the summer. The diurnal de-epoxidation of violaxanthin to antheraxanthin and zeaxanthin occurred throughout the year, except in January. Antioxidant enzymatic activity increased in the winter months, especially during the coldest months, highlighting its key role in photoprotection against photo-oxidation. Structural and functional modifications protected PSII from permanent damage and allowed 1-year-old leaves to photosynthesize at high rates when temperatures increased in spring.

Utility of Photochemical Traits as Diagnostics of Thermal Tolerance amongst Great Barrier Reef Corals

Directory of Open Access Journals (Sweden)

Matthew R. Nitschke

2018-02-01

Full Text Available Light availability is considered a key factor regulating the thermal sensitivity of reef building corals, where excessive excitation of photosystem II (PSII further exacerbates pressure on photochemical pathways already compromised by heat stress. Coral symbionts acclimate to changes in light availability (photoacclimation by continually fine-tuning the photochemical operating efficiency of PSII. However, how this process adjusts throughout the warmest months in naturally heat-tolerant or sensitive species is unknown, and whether this influences the capacity to tolerate transient heat stress is untested. We therefore examined the PSII photophysiology of 10 coral species (with known thermal tolerances from shallow reef environments at Heron Island (Great Barrier Reef, Australia, in spring (October-November, 2015 vs. summer (February-March, 2016. Corals were maintained in flow-through aquaria and rapid light curve (RLC protocols using pulse amplitude modulated (PAM fluorometry captured changes in the PSII photoacclimation strategy, characterized as the minimum saturating irradiance (Ek, and the extent of photochemical ([1 – C], operating efficiency vs. non-photochemical ([1 – Q] energy dissipation. Values of Ek across species were >2-fold higher in all coral species in spring, consistent with a climate of higher overall light exposure (i.e., higher PAR from lower cloud cover, rainfall and wind speed compared with summer. Summer decreases in Ek were combined with a shift toward preferential photochemical quenching in all species. All coral species were subsequently subjected to thermal stress assays. An equivalent temperature-ramping profile of 1°C increase per day and then maintenance at 32°C was applied in each season. Despite the significant seasonal photoacclimation, the species hierarchy of thermal tolerance [maximum quantum yields of PSII (Fv/Fm, monitored at dawn and dusk] did not shift between seasons, except for Pocillopora

Influence of arbuscular mycorrhizae on photosynthesis and water status of maize plants under salt stress.

Science.gov (United States)

Sheng, Min; Tang, Ming; Chen, Hui; Yang, Baowei; Zhang, Fengfeng; Huang, Yanhui

2008-09-01

The influence of arbuscular mycorrhizal (AM) fungus Glomus mosseae on characteristics of the growth, water status, chlorophyll concentration, gas exchange, and chlorophyll fluorescence of maize plants under salt stress was studied in the greenhouse. Maize plants were grown in sand and soil mixture with five NaCl levels (0, 0.5, 1.0, 1.5, and 2.0 g/kg dry substrate) for 55 days, following 15 days of non-saline pretreatment. Under salt stress, mycorrhizal maize plants had higher dry weight of shoot and root, higher relative chlorophyll content, better water status (decreased water saturation deficit, increased water use efficiency, and relative water content), higher gas exchange capacity (increased photosynthetic rate, stomatal conductance and transpiration rate, and decreased intercellular CO(2) concentration), higher non-photochemistry efficiency [increased non-photochemical quenching values (NPQ)], and higher photochemistry efficiency [increased the maximum quantum yield in the dark-adapted state (Fv/Fm), the maximum quantum yield in the light-adapted sate (Fv'/Fm'), the actual quantum yield in the light-adapted steady state (phiPSII) and the photochemical quenching values (qP)], compared with non-mycorrhizal maize plants. In addition, AM symbiosis could trigger the regulation of the energy biturcation between photochemical and non-photochemical events reflected in the deexcitation rate constants (kN, kN', kP, and kP'). All the results show that G. mosseae alleviates the deleterious effect of salt stress on plant growth, through improving plant water status, chlorophyll concentration, and photosynthetic capacity, while the influence of AM symbiosis on photosynthetic capacity of maize plants can be indirectly affected by soil salinity and mycorrhizae-mediated enhancement of water status, but not by the mycorrhizae-mediated enhancement of chlorophyll concentration and plant biomass.

Method for resolution and quantification of components of the non-photochemical quenching (qN)

Czech Academy of Sciences Publication Activity Database

Roháček, Karel

2010-01-01

Roč. 105, č. 2 (2010), s. 101-113 ISSN 0166-8595 R&D Projects: GA AV ČR IAA600960716 Institutional research plan: CEZ:AV0Z50510513 Keywords : Dark relaxation * Fluorescence quenching * Multi-exponential regression Subject RIV: BO - Biophysics Impact factor: 2.410, year: 2010

Non-self-averaging nucleation rate due to quenched disorder

International Nuclear Information System (INIS)

Sear, Richard P

2012-01-01

We study the nucleation of a new thermodynamic phase in the presence of quenched disorder. The quenched disorder is a generic model of both impurities and disordered porous media; both are known to have large effects on nucleation. We find that the nucleation rate is non-self-averaging. This is in a simple Ising model with clusters of quenched spins. We also show that non-self-averaging behaviour is straightforward to detect in experiments, and may be rather common. (fast track communication)

Photochemical efficiency of PSII and photoprotective pigments in seedlings and adults of two Proteaceae with different shade tolerance from the Chilean temperate rain forest Eficiencia fotoquímica del PSII y pigmentos fotoprotectores en plántulas y adultos de dos Proteáceas con diferente tolerancia a la sombra del bosque lluvioso templado chileno

Directory of Open Access Journals (Sweden)

MIREN ALBERDI

2009-01-01

Full Text Available The seasonal variation in energy quenching parameters of photosystem II and photoprotective pigments were studied in seedlings and adults of two Proteaceae: a shade-intolerant species (Embotrium coccineum J.R. et G. Forster and a shade-tolerant species (Lomatia ferruginea (Cav. R. Br.. We postúlate that the shade intolerant species favors photochemical energy driven processes (mainly C0(2 assimilation while the shade tolerant species exhibits higher non-photochemical energy dissipation under unfavorable conditions. Moreover, the shade tolerant species presents lower seasonal variations in these parameters that the shade intolerant species. Differences in energy dissipation should be more evident in seedlings than adults because of their contrasting light environments and temperatures are more evident at this stage. Their maximal photochemical efficiency (Fv/Fm was in the range 0.70-0.83. The effective photochemical efficiency (PSII, photochemical quenching (qP, and electrón transport rate (ETR were higher in seedlings of E. coccineum than in seedlings of L. ferruginea. Adults showed higher photochemical energy quenching parameters than seedlings. Non-photochemical quenching (NPQ was frequently similar between daily periods, seasons, species, and developmental stages, with the exception of the lowest non-photochemical quenching in seedlings of E. coccineum in summer. Seedlings and adults showed a larger xanthophyll cycle pool contení at midday in summer than in winter, while the pool of antheraxanthin + zeaxanthin was always higher at midday. Lutein increased the most during summer. Thus, E. coccineum seedlings and adults maintained high photosynthesis, a higher fraction of open reaction centres, and higher ETR than the shade tolerant species. These differences are consistent with the ecological functions of both species: a pioneer character, higher growth rate, and wide altitudinal and latitudinal distribution of E. coccineum compared to L

Electron transfer between carotenoid and chlorophyll contributes to quenching in the LHCSR1 protein from Physcomitrella patens

Czech Academy of Sciences Publication Activity Database

Pinnola, A.; Staleva-Musto, H.; Capaldi, S.; Ballottari, M.; Bassini, R.; Polívka, Tomáš

2016-01-01

Roč. 1857, č. 12 (2016), s. 1870-1878 ISSN 0005-2728 R&D Projects: GA ČR GBP501/12/G055 Institutional support: RVO:60077344 Keywords : Carotenoids * Femtosecond spectroscopy * LHCSR * Non-photochemical quenching Subject RIV: BO - Biophysics Impact factor: 4.932, year: 2016

Correlation between Strawberry (Fragaria ananassa Duch. Productivity and Photosynthesis-related Parameters under Various Growth Conditions

Directory of Open Access Journals (Sweden)

Hyo Gil Choi

2016-10-01

Full Text Available In the present study, we investigated changes in chlorophyll fluorescence, photosynthetic parameters and fruit yields, as well as fruit phytochemical accumulation of strawberry (Fragaria ananassa Duch. that had been cultivated in a greenhouse under different combinations of light intensity and temperature. In plants grown with low light (LL photosystem II chlorophyll fluorescence was found to increase as compared with those grown under high light (HL. When strawberry plants were grown with temperature higher than 5◦C in addition to LL, they showed decrease in non-photochemical quenching (NPQ, photochemical quenching (qP, as well as chlorophyll fluorescence decrease ratio (RFd when compared with other combinations of light and temperature. Moreover, fruit yield of strawberry was closely correlated with chlorophyll fluorescence-related parameters such as NPQ, qP, and RFd, but not with the maximum efficiency of PS II (Fv/Fm. Although plant groups grown under different combinations of light and temperature showed almost comparable levels of photosynthesis rates (Pr when irradiated with low-intensity light, they displayed clear differences when measured with higher irradiances. Plants grown under HL with temperature above 10◦C showed the highest Pr, in contrast to the plants grown under LL with temperature above 5◦C. When the stomatal conductance and the transpiration rate were measured, plants of each treatment showed clear differences even when analyzed with lower irradiances. We also found that fruit production during winter season was more strongly influenced by growth temperature than light intensity. We suggest that fruit productivity of strawberry is closely associated with chlorophyll fluorescence and photosynthesis-related parameters during cultivation under different regimes of temperature and light.

Proton Gradient Regulation5-Like1-Mediated Cyclic Electron Flow Is Crucial for Acclimation to Anoxia and Complementary to Nonphotochemical Quenching in Stress Adaptation

DEFF Research Database (Denmark)

Kukuczka, Bernadeta; Magneschi, Leonardo; Petroutsos, Dimitris

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...

Chlorophyll fluorescence lifetime imaging provides new insight into the chlorosis induced by plant virus infection.

Science.gov (United States)

Lei, Rong; Jiang, Hongshan; Hu, Fan; Yan, Jin; Zhu, Shuifang

2017-02-01

Leaf chlorosis induced by plant virus infection has a short fluorescence lifetime, which reflects damaged photosynthetic complexes and degraded chloroplasts. Plant viruses often induce chlorosis and necrosis, which are intimately related to photosynthetic functions. Chlorophyll fluorescence lifetime measurement is a valuable noninvasive tool for analyzing photosynthetic processes and is a sensitive indicator of the environment surrounding the fluorescent molecules. In this study, our central goal was to explore the effect of viral infection on photosynthesis by employing chlorophyll fluorescence lifetime imaging (FLIM), steady-state fluorescence, non-photochemical quenching (NPQ), transmission electron microscopy (TEM), and pigment analysis. The data indicated that the chlorophyll fluorescence lifetime of chlorotic leaves was significantly shorter than that of healthy control leaves, and the fitted short lifetime component of chlorophyll fluorescence of chlorotic leaves was dominant. This dominant short lifetime component may result from damage to the structure of thylakoid, which was confirmed by TEM. The NPQ value of chlorotic leaves was slightly higher than that of healthy green leaves, which can be explained by increased neoxanthin, lutein and violaxanthin content relative to chlorophyll a. The difference in NPQ is slight, but FLIM can provide simple and direct characterization of PSII structure and photosynthetic function. Therefore, this technique shows great potential as a simple and rapid method for studying mechanisms of plant virus infection.

Distinct roles of the photosystem II protein PsbS and zeaxanthin in the regulation of light harvesting in plants revealed by fluorescence lifetime snapshots.

Science.gov (United States)

Sylak-Glassman, Emily J; Malnoë, Alizée; De Re, Eleonora; Brooks, Matthew D; Fischer, Alexandra Lee; Niyogi, Krishna K; Fleming, Graham R

2014-12-09

The photosystem II (PSII) protein PsbS and the enzyme violaxanthin deepoxidase (VDE) are known to influence the dynamics of energy-dependent quenching (qE), the component of nonphotochemical quenching (NPQ) that allows plants to respond to fast fluctuations in light intensity. Although the absence of PsbS and VDE has been shown to change the amount of quenching, there have not been any measurements that can detect whether the presence of these proteins alters the type of quenching that occurs. The chlorophyll fluorescence lifetime probes the excited-state chlorophyll relaxation dynamics and can be used to determine the amount of quenching as well as whether two different genotypes with the same amount of NPQ have similar dynamics of excited-state chlorophyll relaxation. We measured the fluorescence lifetimes on whole leaves of Arabidopsis thaliana throughout the induction and relaxation of NPQ for wild type and the qE mutants, npq4, which lacks PsbS; npq1, which lacks VDE and cannot convert violaxanthin to zeaxanthin; and npq1 npq4, which lacks both VDE and PsbS. These measurements show that although PsbS changes the amount of quenching and the rate at which quenching turns on, it does not affect the relaxation dynamics of excited chlorophyll during quenching. In addition, the data suggest that PsbS responds not only to ΔpH but also to the Δψ across the thylakoid membrane. In contrast, the presence of VDE, which is necessary for the accumulation of zeaxanthin, affects the excited-state chlorophyll relaxation dynamics.

Photo-protection in the centric diatom Coscinodiscus granii is not controlled by chloroplast high-light avoidance movement.

Directory of Open Access Journals (Sweden)

Johannes Wilhelm Goessling

2016-01-01

Full Text Available Diatoms are important phototrophs in the worlds’ oceans contributing approximately 40% of the global primary photosynthetic production. This is partially explained by their capacity to exploit environments with variable light conditions, but there is limited knowledge on how diatoms cope with changes in the spectral composition and intensity of light. In this study, the influence of light quality and high irradiance on photosynthesis in the centric diatom Coscinodiscus granii was investigated with microscopic imaging and variable chlorophyll fluorescence techniques. Determination of the wavelength-dependent functional absorption cross-section of photosystem (PS II revealed that absorption of blue light (BL and red light (RL was 2.3-fold and 0.8-fold that of white light (WL, respectively. Hence, BL was more efficiently converted into photo-chemical energy. Excessive energy from BL was dissipated via non-photochemical quenching (NPQ mechanisms, while RL apparently induced only negligible NPQ even at high irradiance. A dose dependent increase of cells exhibiting an altered chloroplast distribution was observed after exposure to high levels of BL and WL, but not RL. However, no effective quantum yield of PSII was measured in the majority of cells with an altered chloroplast distribution, and positive Sytox green® death staining confirmed that most of these cells were dead. We conclude that although Coscinodiscus granii can sustain high irradiance it does not perform chloroplast high-light avoidance movements for photo-protection.

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

Science.gov (United States)

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

2017-01-01

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 our model, both damaging and "dissipative" charge transfer channels are described by discrete electron energy levels attached to their sinks, that mimic 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. 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. 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.

The impacts of phosphorus deficiency on the photosynthetic electron transport chain

DEFF Research Database (Denmark)

Carstensen, Andreas; Herdean, Andrei; Schmidt, Sidsel Birkelund

2018-01-01

light conditions. Under P deficiency, the enhanced electron flow through PSI increases the levels of NADPH, whereas ATP production remains restricted and hence reduces CO2 fixation. In parallel, lumen acidification activates the qE component of the non-photochemical quenching (NPQ) mechanism......Phosphorus (P) is an essential macronutrient, and P deficiency limits plant productivity. Recent work showed that P deficiency affects electron transport to photosystem I (PSI), but the underlying mechanisms are unknown. Here, we present a comprehensive biological model describing how P deficiency...... accumulate in the thylakoids and cause lumen acidification, which inhibits linear electron flow. Limited plastoquinol (PQH2) oxidation retards electron transport to the cytochrome (Cyt) b6f complex, yet the electron transfer rate of PSI is increased under steady-state growth light and is limited under high...

Ecophysiological, anatomical and ultrastructural characteristics of Vitex polygama Cham. (Verbenaceae submitted to different concentrations of fluoride

Directory of Open Access Journals (Sweden)

Zélia Terezinha Teixeira Rossi

2016-12-01

Full Text Available Fluorides released during the manufacture of aluminum, fertilizers, glass and ceramics are considered to be highly toxic to plants, causing damages in relatively small concentrations. This study aimed to evaluate fluoride (F accumulation and its effects on Vitex polygama Cham. (Verbenaceae exposed to simulated rain containing potassium fluoride in concentrations of 5, 10, 15 and 20 mg L-1. Vitex polygama presented no visual symptoms of foliar injury and accumulated a relatively small amount of F-, significant only for the treatments with higher concentrations of the pollutant.  F- promoted an increase in non-photochemical quenching (qN and in the coefficient due to non-photochemical extinction (NPQ, which indicates higher dissipation of radiant energy in the heat form. Damages in the chloroplast structure, in cellular membranes and in epicuticular waxes, besides cytoplasm granulation and irregularities in the epidermal cell walls were also detected in plants exposed to the pollutant. The results show a considerable resistance of Vitex polygama to F and reinforce the prognostic value of physiological, anatomical and ultrastructural analysis in the detection of damages caused by the pollutant in the leaf structure of this species.

The velocity of light intensity increase modulates the photoprotective response in coastal diatoms.

Directory of Open Access Journals (Sweden)

Vasco Giovagnetti

Full Text Available In aquatic ecosystems, the superimposition of mixing events to the light diel cycle exposes phytoplankton to changes in the velocity of light intensity increase, from diurnal variations to faster mixing-related ones. This is particularly true in coastal waters, where diatoms are dominant. This study aims to investigate if coastal diatoms differently activate the photoprotective responses, xanthophyll cycle (XC and non-photochemical fluorescence quenching (NPQ, to cope with predictable light diel cycle and unpredictable mixing-related light variations. We compared the effect of two fast light intensity increases (simulating mixing events with that of a slower increase (corresponding to the light diel cycle on the modulation of XC and NPQ in the planktonic coastal diatom Pseudo-nitzschia multistriata. During each light treatment, the photon flux density (PFD progressively increased from darkness to five peaks, ranging from 100 to 650 µmol photons m-2 s-1. Our results show that the diel cycle-related PFD increase strongly activates XC through the enhancement of the carotenoid biosynthesis and induces a moderate and gradual NPQ formation over the light gradient. In contrast, during mixing-related PFD increases, XC is less activated, while higher NPQ rapidly develops at moderate PFD. We observe that together with the light intensity and its increase velocity, the saturation light for photosynthesis (Ek is a key parameter in modulating photoprotection. We propose that the capacity to adequately regulate and actuate alternative photoprotective 'safety valves' in response to changing velocity of light intensity increase further enhances the photophysiological flexibility of diatoms. This might be an evolutionary outcome of diatom adaptation to turbulent marine ecosystems characterized by unpredictable mixing-related light changes over the light diel cycle.

[Effects of soil progressive drought during the flowering and boll-forming stage on gas exchange parameters and chlorophyll fluorescence characteristics of the subtending leaf to cotton boll].

Science.gov (United States)

Liu, Zhao-wei; Zhang, Pan; Wang, Rui; Kuai, Jie; Li, Lei; Wang, You-hua; Zhou, Zhi-guo

2014-12-01

To investigate the dynamic changes and response mechanisms of gas exchange parameters and fluorescence indices of the subtending leaf to cotton boll under soil progressive drought stress, pot experiments of the hybrid cotton No. 3 were conducted with soil relative water content (SRWC) (75 +/- 5)% as control group, SRWC (60 +/- 5)% and SRWC (45 +/- 5)% as experimental groups dealt with progressive drought for 50 days. Results showed that, the net photosynthetic rate (Pn), stomatal conductance (g(s)) and leaf intercellular CO2 concentration (Ci) decreased while Ls increased under SRWC (60 +/- 5)% for 0-21 days. Furthermore, there was no significant change in chlorophyll fluorescence indices. This indicated that stomatal limitation was the main reason for the reduction of photosynthesis of cotton. In addition, when drought for 21-49 days under SRWC (60 +/- 5)%, Pn kept decreasing, while Ci began to increase and Ls began to decrease. Potential photochemical efficiency (Fv/Fm), quantum yield of photo system II (phi(PSI)) and photochemical quenching coefficient (q(P)) reduced significantly, but non-photochemical quenching coefficient (NPQ) first rose then decreased. Thus, nonstomatal limitation was the main reason why the photosynthesis of cotton reduced. Photosynthetic organization and photosynthetic enzyme system were destroyed, boll setting intensity reduced and the number of boll and yield reduced significantly. Drought for 0-14 days under SRWC (45 +/- 5)% treatment led to sharp decrease in Pn, g(s) and Ci, whereas Ls obviously increased. There was no significant change in Fv/Fm, phi(PSII), q(P), indicating stomatal limitation was the main reason why the photosynthesis of cotton reduced. Pn decreased slowly, while Ci began to rise and Ls began to decline under SRWC (45 +/- 5)% treatment for 14-49 days. Fv/Fm, phi(PSII), q(P) decreased while NPQ rose first then declined, which indicated that nonstomatal limitation worked to reduce the cotton photosynthetic performance

Photoprotection vs. Photoinhibition of Photosystem II in Transplastomic Lettuce (Lactuca sativa) Dominantly Accumulating Astaxanthin.

Science.gov (United States)

Fujii, Ritsuko; Yamano, Nami; Hashimoto, Hideki; Misawa, Norihiko; Ifuku, Kentaro

2016-07-01

Transplastomic (chloroplast genome-modified; CGM) lettuce that dominantly accumulates astaxanthin grows similarly to a non-transgenic control with almost no accumulation of naturally occurring photosynthetic carotenoids. In this study, we evaluated the activity and assembly of PSII in CGM lettuce. The maximum quantum yield of PSII in CGM lettuce was <0.6; however, the quantum yield of PSII was comparable with that in control leaves under higher light intensity. CGM lettuce showed a lower ability to induce non-photochemical quenching (NPQ) than the control under various light intensities. The fraction of slowly recovering NPQ in CGM lettuce, which is considered to be photoinhibitory quenching (qI), was less than half that of the control. In fact, 1 O 2 generation was lower in CGM than in control leaves under high light intensity. CGM lettuce contained less PSII, accumulated mostly as a monomer in thylakoid membranes. The PSII monomers purified from the CGM thylakoids bound echinenone and canthaxanthin in addition to β-carotene, suggesting that a shortage of β-carotene and/or the binding of carbonyl carotenoids would interfere with the photophysical function as well as normal assembly of PSII. In contrast, high accumulation of astaxanthin and other carbonyl carotenoids was found within the thylakoid membranes. This finding would be associated with the suppression of photo-oxidative stress in the thylakoid membranes. Our observation suggests the importance of a specific balance between photoprotection and photoinhibition that can support normal photosynthesis in CGM lettuce producing astaxanthin. © The Author 2015. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Plasmon mediated non-photochemical nucleation of nanoparticles by circularly polarized light

OpenAIRE

Karpov, Victor G.; Grigorchuk, Nicholas I.

2014-01-01

We predict nucleation of pancake shaped metallic nanoparticles having plasmonic frequencies in resonance with a non-absorbed circularly polarized electromagnetic field. We show that the same field can induce nucleation of randomly oriented needle shaped particles. The probabilities of these shapes are estimated vs. field frequency and strength, material parameters, and temperature. This constitutes a quantitative model of non-photochemical laser induced nucleation (NPLIN) consistent with the ...

Photophysical and photochemical properties of novel metallophthalocyanines bearing 7-oxy-3-(m-methoxyphenyl)coumarin groups

International Nuclear Information System (INIS)

Taştemel, Ayşegül; Karaca, Birsen Yılmaz; Durmuş, Mahmut; Bulut, Mustafa

2015-01-01

Tetra-peripherally and non-peripherally 7-oxy-3-(m-methoxyphenyl)coumarin-substituted zinc(II) (4a and 5a), indium(III)acetate (4b and 5b) and magnesium(II) (4c and 5c) phthalocyanines were synthesized for the first time. These phthalocyanines were characterized by elemental analysis, FT-IR, 1 H NMR, UV–vis spectroscopy and mass spectra. The novel phthalocyanines showed excellent solubility in general organic solvents, such as dichloromethane, chloroform, tetrahydrofuran (THF), N,N-dimethylformamide (DMF) and dimethylsulfoxide (DMSO). The photophysical and photochemical properties of these phthalocyanines were investigated in DMF. The effects of the central metal ions (Zn 2+ , Mg 2+ , In +3 ) and the position (peripheral or non-peripheral) of the substituents on the photophysical and photochemical parameters were reported for comparison. The singlet oxygen quantum yield values of novel phthalocyanines ranged from 0.29 to 0.82 in DMF. In this study, the fluorescence quenching behavior of the studied zinc(II) and magnesium(II) phthalocyanine complexes was also described by the addition of 1,4-benzoquinone. - Highlights: • 7-oxy-3-(m-methoxyphenyl)coumarin-substituted Zn, In(III)OAc and Mg phthalocyanines. • Investigation of their photophysical and photochemical properties in DMF. • The effects of metal types and position of the substituents on these properties.

Photochemical reduction of uranyl ion by acetonitrile and propionitrile

International Nuclear Information System (INIS)

Brar, A.S.; Chander, R.; Sandhu, S.S.

1979-01-01

The photochemical reduction of uranyl ion by acetonitrile, propionitrile, benzonitrile, phenylacetonitrile, cyanoacetic acid and malononitrile in aqueous or aq. acetone medium using radiations >= 400 nm from a medium pressure mercury vapour lamp has been investigated. Except acetonitrile and propionitrile all other nitriles fail to bring about the reduction of uranyl ion. The reduction with aceto- and propionitriles has been found to obey pseudo-first order kinetics. The magnitude of rate of reduction with propionitrile is higher than that with acetonitrile. The pseudo-first order rate constants and quenching constant have been calculated from the kinetic data. It has been found that physical and chemical quenching compete with each other. The plot of reciprocal of quantum yield versus reciprocal (nitrile) is linear with a small intercept on the ordinate axis. Absorption spectra of uranyl ion in pure water, in the presence of acid and in the presence of acid+nitrile reveal that there is no ground state interaction between uranyl ion and the nitrile. A mechanism of photochemical reduction of uranyl ion based on α-hydrogen abstraction from the nitrile has been proposed. (auth.)

Assembly of the Major Light-Harvesting Complex II in Lipid Nanodiscs.

NARCIS (Netherlands)

Pandit, A.; Shirzad-Wasei, N.; Wlodarczyk, L.M.; Roon, H. van; Boekema, E.J.; Dekker, J.P.; Grip, W.J. de

2011-01-01

Self-aggregation of isolated plant light-harvesting complexes (LHCs) upon detergent extraction is associated with fluorescence quenching and is used as an in vitro model to study the photophysical processes of nonphotochemical quenching (NPQ). In the NPQ state, in vivo induced under excess solar

Assembly of the Major Light-Harvesting Complex II in Lipid Nanodiscs

NARCIS (Netherlands)

Pandit, Anjali; Shirzad-Wasei, Nazhat; Wlodarczyk, Lucyna M.; van Roon, Henny; Boekema, Egbert J.; Dekker, Jan P.; de Grip, Willem J.; Brown, Leonid S.

2011-01-01

Self-aggregation of isolated plant light-harvesting complexes (LHCs) upon detergent extraction is associated with fluorescence quenching and is used as an in vitro model to study the photophysical processes of nonphotochemical quenching (NPQ). In the NPQ state, in vivo induced under excess solar

Plant experiments with light-emitting diode module in Svet space greenhouse

Science.gov (United States)

Ilieva, Iliyana; Ivanova, Tania; Naydenov, Yordan; Dandolov, Ivan; Stefanov, Detelin

Light is necessary for photosynthesis and shoot orientation in the space plant growth facilities. Light modules (LM) must provide sufficient photosynthetic photon flux for optimal efficiency of photosynthetic processes and also meet the constraints for power, volume and mass. A new LM for SVET Space Greenhouse using Cree R XLamp R 7090 XR light-emitting diodes (LEDs) is developed. Three types of monochromic LEDs emitting in the red, green, and blue region of the spectrum are used. The new LM contains 36 LED spots - 30 LED spots with one red, green and blue LED and 6 LED spots with three red LEDs. DMX programming device controls the LED spots and can set 231 levels of light intensity thus achieving Photosynthetic Photon Flux Density (PPFD) in the range 0-400 µmol.m-2 .s-1 and different percentages of the red, green and blue light, depending on the experimental objectives. Two one-month experiments with "salad-type" plants - lettuce and chicory were carried at 400 µmol.m-2 .s-1 PPFD (high light - HL) and 220 µmol.m-2 .s-1 PPFD (low light - LL) and composition 70% red, 20% green and 10% blue light. In vivo modulated chlorophyll fluorescence was measured by a PAM fluorometer on leaf discs and the following parameters: effective quantum yield of Photosystem II (ΦP SII ) and non-photochemical quenching (NPQ) were calculated. Both lettuce and chicory plants grown at LL express higher photochemical activity of Photosystem II (PSII) than HL grown plants, evaluated by the actual PSII quantum yield, ΦP SII . The calculated steady state NPQ values did not differ significantly in lettuce and chicory. The rapid phase of the NPQ increase was accelerated in all studied LL leaves. In conclusion low light conditions ensured more effective functioning of PSII than HL when lettuce and chicory plants were grown at 70% red, 20% green and 10% blue light composition.

Use of Open Source Hardware and Software Platforms to Quantify Spectrally Dependent Differences in Photochemical Efficiency and Functional Absorption Cross Section within the Dinoflagellate Symbiodinium spp.

Directory of Open Access Journals (Sweden)

Kenneth D. Hoadley

2017-11-01

Full Text Available Active chlorophyll a fluorescence is an essential tool for understanding photosynthetic activity within cnidarian/dinoflagellate symbioses. Fluorescence measurement is typically achieved by utilizing a blue or red monochromatic excitation light source. However, algal photosynthetic pigments can differ in their absorption spectra, potentially leading to excitation wavelength dependent measurements of maximal and light acclimated PSII photosynthetic quantum yield (Fv/Fm or Fq′/Fm′ and functional absorption cross section (σPSII or σPSII′. Here we utilized an open source hardware development platform to construct a multispectral excitation fluorometer to assess spectrally dependent differences in photochemistry within four different Symbiodinium species (two of each ITS2-type A4 and B1. Multivariate analysis of light acclimated photochemical signatures showed separation between most alga types. These spectrally dependent differences in light acclimated PSII efficiency and PSII functional absorption cross section likely reflect changes in light harvesting compounds, their connectivity to the PSII reaction centers and the balance between photochemical and non-photochemical fluorescence quenching. Additionally, acclimation to low (20 μmol photons m−2 s−1 and high (200 μmol photons m−2 s−1 light conditions was examined in two of these symbionts types (ITS-2 type A4 and B1 As expected, chlorophyll a cell−1 decreased under high light acclimation in both symbionts. However, only A4 saw a subsequent reduction in absorbance whereas cellular volume decreased in the B1 (S. minutum symbiont. In response to high light acclimation, Fv/Fm was significantly lower at all excitation wavelengths for the B1 symbiont where as efficiencies remained the same for A4. However, high-light acclimated Fq′/Fm′ levels decreased in both symbionts, but only when measured using the 615 or 625 nm excitation wavelengths. Non-photochemical quenching within the

Non-kinematic Flux-transport Dynamos Including the Effects of Diffusivity Quenching

Energy Technology Data Exchange (ETDEWEB)

Ichimura, Chiaki; Yokoyama, Takaaki [Department of Earth and Planetary Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

2017-04-10

Turbulent magnetic diffusivity is quenched when strong magnetic fields suppress turbulent motion in a phenomenon known as diffusivity quenching. Diffusivity quenching can provide a mechanism for amplifying magnetic field and influencing global velocity fields through Lorentz force feedback. To investigate this effect, we conducted mean field flux-transport dynamo simulations that included the effects of diffusivity quenching in a non-kinematic regime. We found that toroidal magnetic field strength is amplified by up to approximately 1.5 times in the convection zone as a result of diffusivity quenching. This amplification is much weaker than that in kinematic cases as a result of Lorentz force feedback on the system’s differential rotation. While amplified toroidal fields lead to the suppression of equatorward meridional flow locally near the base of the convection zone, large-scale equatorward transport of magnetic flux via meridional flow, which is the essential process of the flux-transport dynamo, is sustainable in our calculations.

Photophysical and photochemical properties of novel metallophthalocyanines bearing 7-oxy-3-(m-methoxyphenyl)coumarin groups

Energy Technology Data Exchange (ETDEWEB)

Taştemel, Ayşegül; Karaca, Birsen Yılmaz [Marmara University, Faculty of Art and Science, Department of Chemistry, 34722 Kadıkoy-Istanbul (Turkey); Durmuş, Mahmut [Gebze Technical University, Department of Chemistry, P.O. Box 141, Gebze 41400, Kocaeli (Turkey); Bulut, Mustafa, E-mail: mbulut@marmara.edu.tr [Marmara University, Faculty of Art and Science, Department of Chemistry, 34722 Kadıkoy-Istanbul (Turkey)

2015-12-15

Tetra-peripherally and non-peripherally 7-oxy-3-(m-methoxyphenyl)coumarin-substituted zinc(II) (4a and 5a), indium(III)acetate (4b and 5b) and magnesium(II) (4c and 5c) phthalocyanines were synthesized for the first time. These phthalocyanines were characterized by elemental analysis, FT-IR, {sup 1}H NMR, UV–vis spectroscopy and mass spectra. The novel phthalocyanines showed excellent solubility in general organic solvents, such as dichloromethane, chloroform, tetrahydrofuran (THF), N,N-dimethylformamide (DMF) and dimethylsulfoxide (DMSO). The photophysical and photochemical properties of these phthalocyanines were investigated in DMF. The effects of the central metal ions (Zn{sup 2+}, Mg{sup 2+}, In{sup +3}) and the position (peripheral or non-peripheral) of the substituents on the photophysical and photochemical parameters were reported for comparison. The singlet oxygen quantum yield values of novel phthalocyanines ranged from 0.29 to 0.82 in DMF. In this study, the fluorescence quenching behavior of the studied zinc(II) and magnesium(II) phthalocyanine complexes was also described by the addition of 1,4-benzoquinone. - Highlights: • 7-oxy-3-(m-methoxyphenyl)coumarin-substituted Zn, In(III)OAc and Mg phthalocyanines. • Investigation of their photophysical and photochemical properties in DMF. • The effects of metal types and position of the substituents on these properties.

Chlamydomonas reinhardtii responding to high light: a role for 2-propenal (acrolein).

Science.gov (United States)

Roach, Thomas; Baur, Theresa; Stöggl, Wolfgang; Krieger-Liszkay, Anja

2017-09-01

High light causes photosystem II to generate singlet oxygen ( 1 O 2 ), a reactive oxygen species (ROS) that can react with membrane lipids, releasing reactive electrophile species (RES), such as acrolein. To investigate how RES may contribute to light stress responses, Chlamydomonas reinhardtii was high light-treated in photoautotrophic and mixotrophic conditions and also in an oxygen-enriched atmosphere to elevate ROS production. The responses were compared to exogenous acrolein. Non-photochemical quenching (NPQ) was higher in photoautotrophic cells, as a consequence of a more de-epoxidized state of the xanthophyll cycle pool and more LHCSR3 protein, showing that photosynthesis was under more pressure than in mixotrophic cells. Photoautotrophic cells had lowered α-tocopherol and β-carotene contents and a higher level of protein carbonylation, indicators of elevated 1 O 2 production. Levels of glutathione, glutathione peroxidase (GPX5) and glutathione-S-transferase (GST1), important antioxidants against RES, were also increased in photoautotrophic cells. In parallel to the wild-type, the LHCSR3-deficient npq4 mutant was high light-treated, which in photoautotrophic conditions exhibited particular sensitivity under elevated oxygen, the treatment that induced the highest RES levels, including acrolein. The npq4 mutant had more GPX5 and GST1 alongside higher levels of carbonylated protein and a more oxidized glutathione redox state. In wild-type cells glutathione contents doubled after 4 h treatment, either with high light under elevated oxygen or with a non-critical dose (600 ppm) of acrolein. Exogenous acrolein also increased GST1 levels, but not GPX5. Overall, RES-associated oxidative damage and glutathione metabolism are prominently associated with light stress and potentially in signaling responses of C. reinhardtii. © 2017 Scandinavian Plant Physiology Society.

1.8K conditioning (non-quench training) of a model SSC dipole

International Nuclear Information System (INIS)

Gilbert, W.S.; Hassenzahl, W.V.

1986-09-01

The accepted hypothesis is that training quenches are caused by heat generation when conductors move under Lorentz force. Afterwards no conductor motion will occur until a higher field and greater Lorentz force acts. If superior heat transfer and/or greater temperature margin is provided by operating at lower bath temperature, one might expect that the heat generated by conductor motion will not cause a runaway temperature increase, or quench. To test this hypothesis, the central dipole field in SSC model magnets was ramped at 1.8 K to 7.1 tesla without the magnets' quenching. The bath was then raised to 4.4 K and the magnets quenched at their short sample limits of 6.6 tesla or higher. Comparison with similar magnets trained in He I at 4.4 K is made and the significance of the non-quench training on system operation is discussed

1. 8K conditioning (non-quench training) of a model SSC dipole

Energy Technology Data Exchange (ETDEWEB)

Gilbert, W.S.; Hassenzahl, W.V.

1986-09-01

The accepted hypothesis is that training quenches are caused by heat generation when conductors move under Lorentz force. Afterwards no conductor motion will occur until a higher field and greater Lorentz force acts. If superior heat transfer and/or greater temperature margin is provided by operating at lower bath temperature, one might expect that the heat generated by conductor motion will not cause a runaway temperature increase, or quench. To test this hypothesis, the central dipole field in SSC model magnets was ramped at 1.8 K to 7.1 tesla without the magnets' quenching. The bath was then raised to 4.4 K and the magnets quenched at their short sample limits of 6.6 tesla or higher. Comparison with similar magnets trained in He I at 4.4 K is made and the significance of the non-quench training on system operation is discussed.

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

Science.gov (United States)

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. Copyright © 2016. Published by Elsevier B.V.

Xanthophylls as modulators of membrane protein function.

Science.gov (United States)

Ruban, Alexander V; Johnson, Matthew P

2010-12-01

This review discusses the structural aspect of the role of photosynthetic antenna xanthophylls. It argues that xanthophyll hydrophobicity/polarity could explain the reason for xanthophyll variety and help to understand their recently emerging function--control of membrane organization and the work of membrane proteins. The structure of a xanthophyll molecule is discussed in relation to other amphiphilic compounds like lipids, detergents, etc. Xanthophyll composition of membrane proteins, the role of their variety in protein function are discussed using as an example for the major light harvesting antenna complex of photosystem II, LHCII, from higher plants. A new empirical parameter, hydrophobicity parameter (H-parameter), has been introduced as an effective measure of the hydrophobicity of the xanthophyll complement of LHCII from different xanthophyll biosynthesis mutants of Arabidopsis. Photosystem II quantum efficiency was found to correlate well with the H-parameter of LHCII xanthophylls. PSII down-regulation by non-photochemical chlorophyll fluorescence quenching, NPQ, had optimum corresponding to the wild-type xanthophyll composition, where lutein occupies intrinsic sites, L1 and L2. Xanthophyll polarity/hydrophobicity alteration by the activity of the xanthophyll cycle explains the allosteric character of NPQ regulation, memory of illumination history and the hysteretic nature of the relationship between the triggering factor, ΔpH, and the energy dissipation process. Copyright © 2010 Elsevier Inc. All rights reserved.

Mathematical Modeling of Acclimation Processes of the Photosynthetic Chain

Directory of Open Access Journals (Sweden)

S Heidari

2016-10-01

Full Text Available Introduction Photosynthetic energy conversion efficiency is characteristic of a system which is determined by interactions between various components of the system. The complex process of photosynthesis has been studied as a whole system which enables in silico examination of a large number of candidate genes for genetic engineering for a higher photosynthetic energy conversion efficiency. One of the most important environmental factors which influence the photosynthesis efficiency is light regime which can cause producing ROS components. To acclimate to such fluctuations, plants have evolved adaptive mechanisms to minimize damage of the photosynthetic apparatus excess light. A fast compatibility response to high light stresses is non-photochemical quenching process (NPQ, dissipating excessive energy to heat. Light harvested state switches into a quenched state by a conformational change of light harvesting complex (LHCII that regulated by xanthophylls and the PsbS protein within seconds. Low lumen pH activates xanthophyll synthesis via a xanthophyll cycle which consists of the de-epoxidation of violaxanthin to zeaxanthin by violaxanthin de-epoxidase in high light and inversely by zeaxanthin epoxidase in low light which occurs more slowly. Materials and Methods Thale cress (Arabidopsis thaliana (Chlombia-0 were grown on soil at 25/22 °C day/night temperature, with a 16/8 h photoperiod, and 40-70% (depend of plant species relative humidity. The light intensity was 150–200 µE m-2s-1 white light. Intensity of chlorophyll fluorescence was measured with PAM-2000 fluorometer (Heinz Walz, Germany and the manufacturer’s software (PamWin v.2. Results and Discussion In the present study, a dynamic kinetics amplified mathematical model was developed based on differential equations in order to predict short-term changes in NPQ in the process of adaptation to different light conditions. We investigated the stationary and dynamic behavior of the model

The roles of specific xanthophylls in light utilization.

Science.gov (United States)

Kalituho, Ljudmila; Rech, Jennifer; Jahns, Peter

2007-01-01

To evaluate the role of specific xanthophylls in light utilization, wild-type and xanthophyll mutant plants (npq1, npq2, lut2, lut2npq1 and lut2npq2) from Arabidopsis thaliana were grown under three different light regimes: 30 (low light, LL), 150 (medium light, ML) and 450 (high light, HL) mumol photons m(-2) s(-1). We studied the pigment content, growth rate, xanthophyll cycle activity, chlorophyll fluorescence parameters and the response to photoinhibition. All genotypes differed strongly in the growth rates and the resistance against photoinhibition. In particular, replacement of lutein (Lut) by violaxanthin (Vx) in the lut2npq1 mutant did not affect the growth at non-saturating light intensities (LL and ML), but led to a pronounced reduction of growth under HL conditions, indicating an important photoprotective role of Lut. This was further supported by a much higher sensitivity of all Lut-deficient plants to photoinhibition in comparison with the wild type. In contrast, replacement of Lut by zeaxanthin (Zx) in lut2npq2 led to a pronounced reduction of growth under all light regimes, most likely related to the permanent non-photochemical dissipation of excitation energy by Zx at Vx-binding sites and the destabilization of antenna proteins by binding of Zx to Lut-binding sites. The high susceptibility of lut2npq2 to photoinhibition in comparison with npq2 further indicated that the photoprotective function of Zx is abolished in the absence of Lut. Thus, it can be concluded from our work that neither Vx nor Zx is able to fulfil the essential photoprotective function at Lut-binding sites under in vivo conditions.

Effect of Mahanarva fimbriolata (Hemiptera: Cercopidae) Attack on Photosynthetic Parameters of Sugarcane Genotypes of Contrasting Susceptibility.

Science.gov (United States)

Soares, Bruno Oliveira; Chaves, Vinicius de Vicente; Tomaz, Adriano Cirino; Kuki, Kacilda Naomi; Peternelli, Luiz Alexandre; Barbosa, Márcio Henrique Pereira

2017-12-05

The aim of this study was to compare the effect of spittlebug Mahanarva fimbriolata Stål (Hemiptera: Cercopidae) on photosynthetic parameters of both a susceptible (SP81-3250) and a resistant (H.Kawandang) sugarcane genotype. In the first assay, the susceptibility level of genotypes to spittlebug was confirmed by comparing damage score and chlorophyll content of the plants. In the second assay, the effect of spittlebug nymphs on photosynthetic characteristics was assessed using the following parameters: Net photosynthetic rate (A), carboxylation efficiency (A/Ci), stomata conductance (gS), transpiration (E), electron transport rate (ETR), maximum quantum yield of Photosystem 2 (PSII) (FV/FM), effective quantum yield (Y(II)), photochemical quenching (Y(NPQ)), and nonphotochemical quenching (Y(NO)). Spittlebug nymphs affected the photosynthetic process of the susceptible genotype SP81-3250 by decreasing the Chl content, ETR, FV/FM, and Y(II). However, this genotype was able to maintain A probably due to its ability to maintain stomata aperture, increase the carboxylation efficiency of Rubisco, and dissipate excess energy through the xanthophyll cycle, as Y(NPQ) increased under the spittlebug attack. On the other hand, the spittlebug did not affect Chl content and FV/FM of the H.Kawandang genotype. Furthermore, H.Kawandang increased A to compensate for the sink demand by the spittlebug by increasing stomatal aperture and carboxylation efficiency and increasing efficiency of the photochemical apparatus in converting light energy into chemical products. We can conclude that the feeding habits of spittlebug nymphs have different impacts on photosynthesis of susceptible and resistant sugarcane genotypes. © The Author(s) 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Growth inhibition and effect on photosystem by three imidazolium chloride ionic liquids in rice seedlings

Energy Technology Data Exchange (ETDEWEB)

Liu, Huijun, E-mail: lhj@mail.zjgsu.edu.cn [School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou 310018, Zhejiang Province (China); Zhang, Shuxian [School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou 310018, Zhejiang Province (China); Jiaxing University, Jiaxing 314001, Zhejiang Province (China); Zhang, Xiaoqiang; Chen, Caidong [School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou 310018, Zhejiang Province (China)

2015-04-09

Highlights: • The three ILs have phytotoxic on rice growth. • The antioxidant enzyme activities increased first and then declined with ILs concentration increased. • The Hill reaction activity decreased and the PS II of leaves was damaged by ILs. • The toxicity of ILs increased as the alkyl chain length increased as the order: [OMIM]Cl < [DMIM]Cl < [C{sub 12}MIM]Cl. - Abstract: The effects of three imidazolium chloride ionic liquids (ILs) including 1-octyl-3-methylimidazolium chloride ionic liquid ([OMIM]Cl), 1-decyl-3-methylimidazolium chloride ionic liquid ([DMIM]Cl) and 1-dodecyl-3-methylimidazolium chloride ionic liquid ([C{sub 12}MIM]Cl) were studied in hydroponically grown rice seedlings. The growth inhibition rate increased and the Hill reaction activity of isolated rice chloroplasts decreased with increasing ILs concentrations. The IC{sub 50,5d} for stem length was 0.70 mg/L of [OMIM]Cl, 0.15 mg/L of [DMIM]Cl, and 0.055 mg/L of [C{sub 12}MIM]Cl, respectively. The SOD, POD and CAT activities of chloroplast exhibited initial increases followed by decreases in activity with increasing ILs concentrations. Chlorophyll fluorescence parameters such as the maximum effective quantum yield of PSII(F{sub v}/F{sub m}), the potential activity of PSII(F{sub v}/F{sub 0}), the yield of photochemical quantum [Y(II)], the photochemical quenching coefficient (qP), the non-photochemical quenching coefficient (NPQ) and the relative electron transport ratio (rETR) were affected, showing that ILs will damage the PSII. The results demonstrated that imidazolium chloride ILs are phytotoxic to rice growth and their photosystem, the toxicity increased as the alkyl chain length increased with the following order: [OMIM]Cl < [DMIM]Cl < [C{sub 12}MIM]Cl. The results will help to better understand the possible role of the defense mechanism in rice caused by ILs exposure.

Behavioral and physiological photoresponses to light intensity by intertidal microphytobenthos

Science.gov (United States)

Du, Guoying; Yan, Hongmei; Liu, Chunrong; Mao, Yunxiang

2017-03-01

Behavioral and physiological responses to light are the two major mechanisms by which natural microphytobenthic assemblages adapt to the intertidal environment and protect themselves from light stress. The present study investigated these photoresponses with different light intensities over 8 h of illumination, and used a specific inhibitor (Latrunculin A, Lat A) for migration to compare migratory and non-migratory microphytobenthos (MPB). Photosynthetic activity was detected using rapid light curves and induction curves by chlorophyll fluorescence. It showed distinct variation in migratory responses to different light intensities; high light induced downward migration to avoid photoinhibition, and low and medium light (50-250 μmol/(m2·s)) promoted upward migration followed by downward migration after certain period of light exposure. No significant difference in non-photochemical quenching (NPQ) or PSII maximal quantum yield (Fv/Fm) was detected between low and medium light irradiance, possibly indicating that only high light influences the photosynthetic capability of MPB. Decreased photosynthetic activity, indicated by three parameters, the maximum relative electron transport rate (rETRmax), minimum saturating irradiance (E k) and light utilization coefficient (α), was observed in MPB after exposure to prolonged illumination under low and medium light. Lat A effectively inhibited the migration of MPB in all light treatments and induced lower Fv/Fmunder high light (500 and 100 μmol/(m2·s)) and prolonged illumination at 250 μmol/(m2·s), but did not significantly influence Fv/Fmunder low light (0-100 μmol/(m2·s)) or NPQ. The increase of NPQ in Lat A treatments with time implied that the MPB assemblages can recover their physiological photoprotection capacity to adapt to light stress. Non-migratory MPB exhibited lower light use efficiency (lower α) and lower maximum photosynthetic capacity (lower rETRmax) than migratory MPB under light intensities above

Comparative Study on the Effect of Water Stress and Rootstock on Photosynthetic Function in Pistachio (Pistacia vera L. Trees

Directory of Open Access Journals (Sweden)

Abolfazl Ranjbar

2017-12-01

Full Text Available The aim of this study is to evaluate the  effects of water deficit stress on chlorophyll fluorescence (CF characteristics of photosystem II (PSII and pigment contents in two rootstock seedlings (Pistacia atlantica L. and P. khinjuk L.. Three levels of soil water potential (Ψs was used, including WWD (-0.05 MPa, MWD (-0.7 MPa and SWD (-1.5 MPa. It was found that water stress increased the minimal fluorescence (F0, quantum yield baseline (F0/Fm and decreased the maximal fluorescence (Fm and maximum quantum yield of PSII photochemistry (Fv/Fm parameters in dark adapted leaves. In light adapted leaves, a significant increase in non-photochemical quenching (NPQ and thermal dissipation of light energy to heat (D and a decrease in electron transport rate (ETR and photochemical efficiency of photosystem II (ΦPSII occurred. The results demonstrated a decline in photosynthetic pigments (Chla, (Chlb and carotenoids (Car content with increasing water stress, whereas there was no significant effect on Chl (a/b and Car/(a+b ratios. Our data revealed there was no different in terms of performance between the two rootstocks in the alteration rate of pigment contents and photosynthetic features against soil water deficit conditions.

Enhanced salt-induced antioxidative responses involve a contribution of polyamine biosynthesis in grapevine plants.

Science.gov (United States)

Ikbal, Fatima Ezzohra; Hernández, José Antonio; Barba-Espín, Gregorio; Koussa, Tayeb; Aziz, Aziz; Faize, Mohamed; Diaz-Vivancos, Pedro

2014-06-15

The possible involvement of polyamines in the salt stress adaptation was investigated in grapevine (Vitis vinifera L.) plantlets focusing on photosynthesis and oxidative metabolism. Salt stress resulted in the deterioration of plant growth and photosynthesis, and treatment of plantlets with methylglyoxal-bis(guanylhydrazone) (MGBG), a S-adenosylmethionine decarboxylase (SAMDC) inhibitor, enhanced the salt stress effect. A decrease in PSII quantum yield (Fv/Fm), effective PSII quantum yield (Y(II)) and coefficient of photochemical quenching (qP) as well as increases in non-photochemical quenching (NPQ) and its coefficient (qN) was observed by these treatments. Salt and/or MGBG treatments also triggered an increase in lipid peroxidation and reactive oxygen species (ROS) accumulation as well as an increase of superoxide dismutase (SOD) and peroxidase (POX) activities, but not ascorbate peroxidase (APX) activity. Salt stress also resulted in an accumulation of oxidized ascorbate (DHA) and a decrease in reduced glutathione. MGBG alone or in combination with salt stress increased monodehydroascorbate reductase (MDHAR), SOD and POX activities and surprisingly no accumulation of DHA was noticed following treatment with MGBG. These salt-induced responses correlated with the maintaining of high level of free and conjugated spermidine and spermine, whereas a reduction of agmatine and putrescine levels was observed, which seemed to be amplified by the MGBG treatment. These results suggest that maintaining polyamine biosynthesis through the enhanced SAMDC activity in grapevine leaf tissues under salt stress conditions could contribute to the enhanced ROS scavenging activity and a protection of photosynthetic apparatus from oxidative damages. Copyright © 2014 Elsevier GmbH. All rights reserved.

Rate Constants of PSII Photoinhibition and its Repair, and PSII Fluorescence Parameters in Field Plants in Relation to their Growth Light Environments.

Science.gov (United States)

Miyata, Kazunori; Ikeda, Hiroshi; Nakaji, Masayoshi; Kanel, Dhana Raj; Terashima, Ichiro

2015-09-01

The extent of photoinhibition of PSII is determined by a balance between the rate of photodamage to PSII and that of repair of the damaged PSII. It has already been indicated that the rate constants of photodamage (kpi) and repair (krec) of the leaves differ depending on their growth light environment. However, there are no studies using plants in the field. We examined these rate constants and fluorescence parameters of several field-grown plants to determine inter-relationships between these values and the growth environment. The kpi values were strongly related to the excess energy, EY, of the puddle model and non-regulated energy dissipation, Y(NO), of the lake model, both multiplied by the photosynthetically active photon flux density (PPFD) level during the photoinhibitory treatment. In contrast, the krec values corrected against in situ air temperature were very strongly related to the daily PPFD level. The plants from the fields showed higher NPQ than the chamber-grown plants, probably because these field plants acclimated to stronger lightflecks than the averaged growth PPFD. Comparing chamber-grown plants and the field plants, we showed that kpi is determined by the incident light level and the photosynthetic capacities such as in situ rate of PSII electron transport and non-photochemical quenching (NPQ) [e.g. Y(NO)×PPFD] and that krec is mostly determined by the growth light and temperature levels. © The Author 2015. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Thoughts on non-perturbative thermalization and jet quenching in heavy ion collisions

International Nuclear Information System (INIS)

Kovchegov, Yuri V.

2006-01-01

We start by presenting physical arguments for the impossibility of perturbative thermalization leading to (non-viscous) Bjorken hydrodynamic description of heavy ion collisions. These arguments are complimentary to our more formal argument presented in [Yu.V. Kovchegov, hep-ph/0503038]. We argue that the success of hydrodynamic models in describing the quark-gluon system produced in heavy ion collisions could only be due to non-perturbative strong coupling effects. We continue by studying non-perturbative effects in heavy ion collisions at high energies. We model non-perturbative phenomena by an instanton ensemble. We show that non-perturbative instanton vacuum fields may significantly contribute to jet quenching in nuclear collisions. At the same time, the instanton ensemble contribution to thermalization is likely to be rather weak, leading to non-perturbative thermalization time comparable to the time of hadronization. This example illustrates that jet quenching is not necessarily a signal of a thermalized medium. Indeed, since the instanton models do not capture all the effects of QCD vacuum (e.g., they do not account for confinement), there may be other non-perturbative effects facilitating thermalization of the system

Enhancing photophysical and photochemical properties of zinc(II) phthalocyanine dyes by substitution of triptycene moieties

Energy Technology Data Exchange (ETDEWEB)

Al-Sohaimi, Bander Roshadan [Department of Chemistry, Faculty of Science, Taibah University, P.O. Box 344, Al-Madinah Al Munawwrah (Saudi Arabia); Pişkin, Mehmet [Çanakkale Onsekiz Mart University, Vocational School of Technical Sciences, Department of Food Technology, Çanakkale 17100 (Turkey); Aljuhani, Ateyatallah; Al-Raqa, Shaya Y. [Department of Chemistry, Faculty of Science, Taibah University, P.O. Box 344, Al-Madinah Al Munawwrah (Saudi Arabia); Durmuş, Mahmut, E-mail: durmus@gtu.edu.tr [Gebze Technical University, Department of Chemistry, P.O. Box 141, Gebze 41400, Kocaeli (Turkey)

2016-05-15

The symmetrical zinc(II) phthalocyanines conjugated with 9,10-dioctyl-6,7-dimethoxy-2,3-dioxytriptycene or 9,10-diundecyl-6,7-dimethoxy-2,3-dioxytriptycene moieties were synthesized in this study. These novel phthalocyanines were characterized by standard characterization techniques such as {sup 1}H-NMR, FT-IR, UV–vis, Mass and Elemental Analysis. All these phthalocyanines showed highly solubility and formed non-aggregated monomeric species in most of the organic solvents. Their photochemical properties such as singlet oxygen, and photodegradation quantum yields, and photophysical properties including fluorescence quantum yields and lifetimes were investigated in toluene. The fluorescence quenching behavior of the studied zinc(II) phthalocyanines by the addition of 1,4-benzoquinone were also described in toluene.

Enhancing photophysical and photochemical properties of zinc(II) phthalocyanine dyes by substitution of triptycene moieties

International Nuclear Information System (INIS)

Al-Sohaimi, Bander Roshadan; Pişkin, Mehmet; Aljuhani, Ateyatallah; Al-Raqa, Shaya Y.; Durmuş, Mahmut

2016-01-01

The symmetrical zinc(II) phthalocyanines conjugated with 9,10-dioctyl-6,7-dimethoxy-2,3-dioxytriptycene or 9,10-diundecyl-6,7-dimethoxy-2,3-dioxytriptycene moieties were synthesized in this study. These novel phthalocyanines were characterized by standard characterization techniques such as 1 H-NMR, FT-IR, UV–vis, Mass and Elemental Analysis. All these phthalocyanines showed highly solubility and formed non-aggregated monomeric species in most of the organic solvents. Their photochemical properties such as singlet oxygen, and photodegradation quantum yields, and photophysical properties including fluorescence quantum yields and lifetimes were investigated in toluene. The fluorescence quenching behavior of the studied zinc(II) phthalocyanines by the addition of 1,4-benzoquinone were also described in toluene.

Regulation of energy partitioning and alternative electron transport pathways during cold acclimation of lodgepole pine is oxygen dependent.

Science.gov (United States)

Savitch, Leonid V; Ivanov, Alexander G; Krol, Marianna; Sprott, David P; Oquist, Gunnar; Huner, Norman P A

2010-09-01

Second year needles of Lodgepole pine (Pinus contorta L.) were exposed for 6 weeks to either simulated control summer ['summer'; 25 °C/250 photon flux denisty (PFD)], autumn ('autumn'; 15°C/250 PFD) or winter conditions ('winter'; 5 °C/250 PFD). We report that the proportion of linear electron transport utilized in carbon assimilation (ETR(CO2)) was 40% lower in both 'autumn' and 'winter' pine when compared with the 'summer' pine. In contrast, the proportion of excess photosynthetic linear electron transport (ETR(excess)) not used for carbon assimilation within the total ETR(Jf) increased by 30% in both 'autumn' and 'winter' pine. In 'autumn' pine acclimated to 15°C, the increased amounts of 'excess' electrons were directed equally to 21  kPa O2-dependent and 2  kPa O2-dependent alternative electron transport pathways and the fractions of excitation light energy utilized by PSII photochemistry (Φ(PSII)), thermally dissipated through Φ(NPQ) and dissipated by additional quenching mechanism(s) (Φ(f,D)) were similar to those in 'summer' pine. In contrast, in 'winter' needles acclimated to 5 °C, 60% of photosynthetically generated 'excess' electrons were utilized through the 2  kPa O2-dependent electron sink and only 15% by the photorespiratory (21  kPa O2) electron pathway. Needles exposed to 'winter' conditions led to a 3-fold lower Φ(PSII), only a marginal increase in Φ(NPQ) and a 2-fold higher Φ(f,D), which was O2 dependent compared with the 'summer' and 'autumn' pine. Our results demonstrate that the employment of a variety of alternative pathways for utilization of photosynthetically generated electrons by Lodgepole pine depends on the acclimation temperature. Furthermore, dissipation of excess light energy through constitutive non-photochemical quenching mechanisms is O2 dependent.

Integration of physio-biochemical processes at different phenological stages of wheat (triticum aestivum l.) plants in response to heat stress

International Nuclear Information System (INIS)

Javed, N.

2014-01-01

A study was conducted to assess the influence of heat stress imposed at different growth stages of wheat (Triticum aestivum L.) plants. Four wheat cultivars namely S-24, Saher-2006, Lasani and AARI-10 were subjected to high temperature (HT) stress at tillering and booting phenological phases. Under stress conditions, root and shoot fresh weights, membrane thermostability (MTS) and non-photochemical quenching (NPQ) were significantly perturbed in all four wheat cultivars at both developmental stages. However, HT stress did not influence all the other attributes significantly including shoot fresh weight, chlorophyll a and b pigments, photosynthetic rate (A), leaf water (w), internal CO/sub 2/ (Ci), osmotic (s) and turgor (p) potentials, transpiration rate (E), water-use-efficiency (A/E), stomatal conductance (gs) as well as Fv/Fm ratio. Among all wheat cultivars, cv. Lasani performed better in shoot and root fresh weight, and chlorophyll a contents at the tillering stage, while in MTS at the booting phase, cv. S-24 in shoot fresh weight, E, and gs at the boot stage and highest MTS and WUE at the tillering stage. However, cv. AARI-10 performed well in root fresh weight, w, s, p,,WUE and NPQ when stress was applied at the boot stage, while E and Fv/Fm in this cultivar on exposure to stress at the tillering stage. Cultivar Saher-2006 performed better in gs, leaf s and p at the tillering stage, while Fv/Fm was recorded better at the boot stage and A in the same cultivar at all growth stages. Overall, HT stress applied at different growth stages was only effective in altering root fresh weight, MTS and NPQ in all four wheat cultivars. Of all wheat cultivars, cv. AARI-10 performed better in growth and physiological attributes examined in the present study under HT stress applied at different phenological stages. (author)

Estimating Chlorophyll Fluorescence Parameters Using the Joint Fraunhofer Line Depth and Laser-Induced Saturation Pulse (FLD-LISP Method in Different Plant Species

Directory of Open Access Journals (Sweden)

Parinaz Rahimzadeh-Bajgiran

2017-06-01

Full Text Available A comprehensive evaluation of the recently developed Fraunhofer line depth (FLD and laser-induced saturation pulse (FLD-LISP method was conducted to measure chlorophyll fluorescence (ChlF parameters of the quantum yield of photosystem II (ΦPSII, non-photochemical quenching (NPQ, and the photosystem II-based electron transport rate (ETR in three plant species including paprika (C3 plant, maize (C4 plant, and pachira (C3 plant. First, the relationships between photosynthetic photon flux density (PPFD and ChlF parameters retrieved using FLD-LISP and the pulse amplitude-modulated (PAM methods were analyzed for all three species. Then the relationships between ChlF parameters measured using FLD-LISP and PAM were evaluated for the plants in different growth stages of leaves from mature to aging conditions. The relationships of ChlF parameters/PPFD were similar in both FLD-LISP and PAM methods in all plant species. ΦPSII showed a linear relationship with PPFD in all three species whereas NPQ was found to be linearly related to PPFD in paprika and maize, but not for pachira. The ETR/PPFD relationship was nonlinear with increasing values observed for PPFDs lower than about 800 μmol m−2 s−1 for paprika, lower than about 1200 μmol m−2 s−1 for maize, and lower than about 800 μmol m−2 s−1 for pachira. The ΦPSII, NPQ, and ETR of both the FLD-LISP and PAM methods were very well correlated (R2 = 0.89, RMSE = 0.05, (R2 = 0.86, RMSE = 0.44, and (R2 = 0.88, RMSE = 24.69, respectively, for all plants. Therefore, the FLD-LISP method can be recommended as a robust technique for the estimation of ChlF parameters.

WATER DEFICIT ENSURES THE PHOTOCHEMICAL EFFICIENCY OF Copaifera langsdorffii Desf1

Directory of Open Access Journals (Sweden)

Angélica Lino Rodrigues

2017-02-01

Full Text Available ABSTRACT The intensity and frequency of drought periods has increased according to climate change predictions. The fast overcome and recovery are important adaptive features for plant species found in regions presenting water shortage periods. Copaifera langsdorffii is a neotropical species that has developed leaves presenting physiological mechanisms and morphological adaptations that allow its survival under seasonal water stress. We aimed in this work to observe substantial physiological responses for water saving and damage representative to the photochemical reaction after exposed plants to water stress and to subsequent recovery. We found in plants mechanisms to control water loss through the lower stomatal conductance, even after rehydration. It goes against the rapid recovery of leaves, indicated by the relative water content values restored to previously unstressed plants. Stomatal conductance was the only variable presenting high plasticity index. In photochemical activity, the species presented higher photochemical quenching, electron transport rate and effective quantum yield of photosystem II when they were subjected to rehydration after water stress period. Our results suggest that C. langsdorffii presented rapid rehydration and higher photochemical efficiency even after water restriction. These data demonstrate that this species can be used as a model for physiological studies due to the adjustment developed in response to different environmental schemes.

Linking FRRF Derived Photophysiology with Carbon-based Primary Productivity: Insights from Concepts of Cellular Energy Allocation

Science.gov (United States)

Schuback, N.; Schallenberg, C.; Duckham, C.; Flecken, M.; Maldonado, M. T.; Tortell, P. D.

2016-02-01

Active chlorophyll a fluorescence approaches, including fast repetition rate fluorometry (FRRF), have the potential to provide estimates of phytoplankton primary productivity at unprecedented spatial and temporal resolution. FRRF-derived productivity rates are based on estimates of charge separation in photosystem II (ETRRCII), which must be converted into ecologically relevant units of carbon fixation. Understanding sources of variability in the coupling of ETRRCII and carbon fixation provides important physiological insight into phytoplankton photosynthesis, and is critical for the application of FRRF as a primary productivity measurement tool. We present data from a series of experiments during which we simultaneously measured phytoplankton carbon fixation and ETRRCII in the iron-limited NE subarctic Pacific. Our results show significant variability of the derived conversion factor (Ve:C/nPSII), with highest values observed under conditions of excess excitation pressure at the level of photosystem II, caused by high light and/or low iron. Our results will be discussed in the context of metabolic plasticity, which evolved in phytoplankton to simultaneously maximize growth and provide photoprotection under fluctuating light and limiting nutrient availabilities. Because the derived conversion factor is associated with conditions of excess light, it correlates with the expression of non-photochemical quenching (NPQ) in the pigment antenna, also derived from FRRF measurements. Our results demonstrate a significant correlation between NPQ and the conversion factor Ve:C/nPSII, and the potential of this relationship to improve FRRF-based estimates of phytoplankton carbon fixation rates is discussed.

Alterations in Gas Exchange and Oxidative Metabolism in Rice Leaves Infected by Pyricularia oryzae are Attenuated by Silicon.

Science.gov (United States)

Domiciano, Gisele Pereira; Cacique, Isaías Severino; Chagas Freitas, Cecília; Filippi, Marta Cristina Corsi; DaMatta, Fábio Murilo; do Vale, Francisco Xavier Ribeiro; Rodrigues, Fabrício Ávila

2015-06-01

Rice blast, caused by Pyricularia oryzae, is the most important disease in rice worldwide. This study investigated the effects of silicon (Si) on the photosynthetic gas exchange parameters (net CO2 assimilation rate [A], stomatal conductance to water vapor [gs], internal-to-ambient CO2 concentration ratio [Ci/Ca], and transpiration rate [E]); chlorophyll fluorescence a (Chla) parameters (maximum photochemical efficiency of photosystem II [Fv/Fm], photochemical [qP] and nonphotochemical [NPQ] quenching coefficients, and electron transport rate [ETR]); concentrations of pigments, malondialdehyde (MDA), and hydrogen peroxide (H2O2); and activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR), and lypoxigenase (LOX) in rice leaves. Rice plants were grown in a nutrient solution containing 0 or 2 mM Si (-Si or +Si, respectively) with and without P. oryzae inoculation. Blast severity decreased with higher foliar Si concentration. The values of A, gs and E were generally higher for the +Si plants in comparison with the -Si plants upon P. oryzae infection. The Fv/Fm, qp, NPQ, and ETR were greater for the +Si plants relative to the -Si plants at 108 and 132 h after inoculation (hai). The values for qp and ETR were significantly higher for the -Si plants in comparison with the +Si plants at 36 hai, and the NPQ was significantly higher for the -Si plants in comparison with the +Si plants at 0 and 36 hai. The concentrations of Chla, Chlb, Chla+b, and carotenoids were significantly greater in the +Si plants relative to the -Si plants. For the -Si plants, the MDA and H2O2 concentrations were significantly higher than those in the +Si plants. The LOX activity was significantly higher in the +Si plants than in the -Si plants. The SOD and GR activities were significantly higher for the -Si plants than in the +Si plants. The CAT and APX activities were significantly higher in the +Si plants than in the -Si plants. The supply of

Gas exchange and chlorophyll fluorescence of pea (Pisum sativum L.) plants in response to ambient ozone at a rural site in Egypt

International Nuclear Information System (INIS)

Ismail, I.M.; Basahi, J.M.; Hassan, I.A.

2014-01-01

Egyptian pea cultivars (Pisum sativum L. cultivars Little Marvel, Perfection and Victory) grown in open-top chambers were exposed to either charcoal-filtered (FA) or non-filtered air (NF) for five consecutive years (2009–2013) at a rural site in northern Egypt. Net photosynthetic rates (P N ), stomatal conductance (g s ), intercellular CO 2 (C i ) and chlorophyll fluorescence were measured. Ozone (O 3 ) was found to be the most prevalent pollutant common at the rural site and is suspected to be involved in the alteration of the physiological parameters measured in the present investigation. P N of different cultivars were found to respond similarly; decreases of 23, 29 and 39% were observed in the cultivars Perfection, Little Marvel and Victory, respectively (averaged over the five years) due to ambient O 3 . The maximum impairment in P N was recorded in the cultivar Victory (46%) in 2013 when the highest O 3 levels were recorded (90 nL L −1 ). The average stomatal conductance decreased by 20 and 18% in the cultivars Little Marvel and Perfection, respectively, while the average stomatal conductance increased on average by 27% in the cultivar Victory. A significant correlation was found between P N and C i , indicating the importance of non-stomatal limitations of photosynthesis, especially in the cultivar Victory. The P N vs. Ci curves were fitted to a non-rectangular hyperbolic model. The actual quantum yield (Φ PSII ) and photochemical quenching coefficient (qP) were significantly decreased in the leaves of plants exposed to NF air. Non-photochemical quenching (NPQ) was increased in all cultivars. Exposure to NF air caused reductions in chlorophyll (Chl a) of 19, 16 and 30% in the Little Marvel, Perfection and Victory cultivars, respectively. - Highlights: • Ozone (O 3 ) concentrations recorded were within the ranges of phytotoxicity. • O 3 has a clear influence on the physiological parameters. • O 3 decreased Photosynthetic rates, chlorophyll

Biomonitoring chromium III or VI soluble pollution by moss chlorophyll fluorescence.

Science.gov (United States)

Chen, Yang-Er; Mao, Hao-Tian; Ma, Jie; Wu, Nan; Zhang, Chao-Ming; Su, Yan-Qiu; Zhang, Zhong-Wei; Yuan, Ming; Zhang, Huai-Yu; Zeng, Xian-Yin; Yuan, Shu

2018-03-01

We systematically compared the impacts of four Cr salts (chromic chloride, chromic nitrate, potassium chromate and potassium bichromate) on physiological parameters and chlorophyll fluorescence in indigenous moss Taxiphyllum taxirameum. Among the four Cr salts, K 2 Cr 2 O 7 treatment resulted in the most significant decrease in photosynthetic efficiency and antioxidant enzymes, increase in reactive oxygen species (ROS), and obvious cell death. Different form the higher plants, although hexavalent Cr(VI) salt treatments resulted in higher accumulation levels of Cr and were more toxic than Cr(III) salts, Cr(III) also induced significant changes in moss physiological parameters and chlorophyll fluorescence. Our results showed that Cr(III) and Cr(VI) could be monitored distinguishably according to the non-photochemical quenching (NPQ) fluorescence of sporadic purple and sporadic lavender images respectively. Then, the valence states and concentrations of Cr contaminations could be evaluated according to the image of maximum efficiency of PSII photochemistry (Fv/Fm) and the quantum yield of PSII electron transport (ΦPSII). Therefore, this study provides new ideas of moss's sensibility to Cr(III) and a new method to monitor Chromium contaminations rapidly and non-invasively in water. Copyright © 2017 Elsevier Ltd. All rights reserved.

Photochemical reduction of water-soluble C60 derivatives (EPR study)

International Nuclear Information System (INIS)

Brezova, V.; Stasko, A.; Dvoranova, D.; Asmus, K.D.; Guldi, D.M.

1999-01-01

The photochemical reduction of three bis-functionalized C 60 derivatives resulted in the formation of a single radical product, characterized by relatively narrow EPR line (g M = 2.0007, pp < 0.02 mT). In the irradiated aqueous solutions containing L-ascorbic acid, in the addition to the EPR line related to bis-adduct mono-anion, also 6-line EPR spectrum of ascorbyl radical was observed. Consequently, the photoinduced formation of ascorbyl radical was attributed to the intermolecular quenching of fullerenes excited states. (authors)

Chlorophyll fluorescence, photochemical reflective index and normalized difference vegetative index during plant senescence.

Science.gov (United States)

Cordon, Gabriela; Lagorio, M Gabriela; Paruelo, José M

2016-07-20

The relationship between the Photochemical Reflectance Index (PRI), Normalized Difference Vegetation Index (NDVI) and chlorophyll fluorescence along senescence was investigated in this work. Reflectance and radiance measurements were performed at canopy level in grass species presenting different photosynthetic metabolism: Avena sativa (C3) and Setaria italica (C4), at different stages of the natural senescence process. Sun induced-chlorophyll fluorescence at 760nm (SIF 760 ) and the apparent fluorescence yield (SIF 760 /a, with a=irradiance at time of measurement) were extracted from the radiance spectra of canopies using the Fraunhofer Line Discrimination-method. The photosynthetic parameters derived from Kautsky kinetics and pigment content were also calculated at leaf level. Whilst stand level NDVI patterns were related to changes in the structure of canopies and not in pigment content, stand level PRI patterns suggested changes both in terms of canopy and of pigment content in leaves. Both SIF 760 /a and Φ PSII decreased progressively along senescence in both species. A strong increment in NPQ was evident in A. sativa while in S. italica NPQ values were lower. Our most important finding was that two chlorophyll fluorescence signals, Φ PSII and SIF 760 /a, correlated with the canopy PRI values in the two grasses assessed, even when tissues at different ontogenic stages were present. Even though significant changes occurred in the Total Chlr/Car ratio along senescence in both studied species, significant correlations between PRI and chlorophyll fluorescence signals might indicate the usefulness of this reflectance index as a proxy of photosynthetic RUE, at least under the conditions of this study. The relationships between stand level PRI and the fluorescence estimators (Φ PSII and SIF 760 /a) were positive in both cases. Therefore, an increase in PRI values as in the fluorescence parameters would indicate higher RUE. Copyright © 2016 Elsevier GmbH. All

Potentials of satellite derived SIF products to constrain GPP simulated by the new ORCHIDEE-FluOR terrestrial model at the global scale

Science.gov (United States)

Bacour, C.; Maignan, F.; Porcar-Castell, A.; MacBean, N.; Goulas, Y.; Flexas, J.; Guanter, L.; Joiner, J.; Peylin, P.

2016-12-01

A new era for improving our knowledge of the terrestrial carbon cycle at the global scale has begun with recent studies on the relationships between remotely sensed Sun Induce Fluorescence (SIF) and plant photosynthetic activity (GPP), and the availability of such satellite-derived products now "routinely" produced from GOSAT, GOME-2, or OCO-2 observations. Assimilating SIF data into terrestrial ecosystem models (TEMs) represents a novel opportunity to reduce the uncertainty of their prediction with respect to carbon-climate feedbacks, in particular the uncertainties resulting from inaccurate parameter values. A prerequisite is a correct representation in TEMs of the several drivers of plant fluorescence from the leaf to the canopy scale, and in particular the competing processes of photochemistry and non photochemical quenching (NPQ).In this study, we present the first results of a global scale assimilation of GOME-2 SIF products within a new version of the ORCHIDEE land surface model including a physical module of plant fluorescence. At the leaf level, the regulation of fluorescence yield is simulated both by the photosynthesis module of ORCHIDEE to calculate the photochemical yield and by a parametric model to estimate NPQ. The latter has been calibrated on leaf fluorescence measurements performed for boreal coniferous and Mediterranean vegetation species. A parametric representation of the SCOPE radiative transfer model is used to model the plant fluorescence fluxes for PSI and PSII and the scaling up to the canopy level. The ORCHIDEE-FluOR model is firstly evaluated with respect to in situ measurements of plant fluorescence flux and photochemical yield for scots pine and wheat. The potentials of SIF data to constrain the modelled GPP are evaluated by assimilating one year of GOME-2-SIF products within ORCHIDEE-FluOR. We investigate in particular the changes in the spatial patterns of GPP following the optimization of the photosynthesis and phenology parameters

Fluorescence Quenching of Alpha-Fetoprotein by Gold Nanoparticles: Effect of Dielectric Shell on Non-Radiative Decay

Science.gov (United States)

Zhu, Jian; Li, Jian-Jun; Wang, A.-Qing; Chen, Yu; Zhao, Jun-Wu

2010-09-01

Fluorescence quenching spectrometry was applied to study the interactions between gold colloidal nanoparticles and alpha-fetoprotein (AFP). Experimental results show that the gold nanoparticles can quench the fluorescence emission of adsorbed AFP effectively. Furthermore, the intensity of fluorescence emission peak decreases monotonously with the increasing gold nanoparticles content. A mechanism based on surface plasmon resonance-induced non-radiative decay was investigated to illuminate the effect of a dielectric shell on the fluorescence quenching ability of gold nanoparticles. The calculation results show that the increasing dielectric shell thickness may improve the monochromaticity of fluorescence quenching. However, high energy transfer efficiency can be obtained within a wide wavelength band by coating a thinner dielectric shell.

Quantum Quench Dynamics in the Transverse Field Ising Model at Non-zero Temperatures

Science.gov (United States)

Abeling, Nils; Kehrein, Stefan

The recently discovered Dynamical Phase Transition denotes non-analytic behavior in the real time evolution of quantum systems in the thermodynamic limit and has been shown to occur in different systems at zero temperature [Heyl et al., Phys. Rev. Lett. 110, 135704 (2013)]. In this talk we present the extension of the analysis to non-zero temperature by studying a generalized form of the Loschmidt echo, the work distribution function, of a quantum quench in the transverse field Ising model. Although the quantitative behavior at non-zero temperatures still displays features derived from the zero temperature non-analyticities, it is shown that in this model dynamical phase transitions do not exist if T > 0 . This is a consequence of the system being initialized in a thermal state. Moreover, we elucidate how the Tasaki-Crooks-Jarzynski relation can be exploited as a symmetry relation for a global quench or to obtain the change of the equilibrium free energy density. This work was supported through CRC SFB 1073 (Project B03) of the Deutsche Forschungsgemeinschaft (DFG).

Ecophysiology of two tropical species in an abandoned eucalypt plantation: effect of plant litter removal and seasonality

Directory of Open Access Journals (Sweden)

Frederico Lage-Pinto

2015-05-01

Full Text Available The effect of the removal of plant litter on photosynthetic variables (gas exchanges, chlorophyll a fluorescence, and content of photosynthetic pigments of the tropical species Xylopia sericea A. St.-Hil. and Siparuna guianensis Aubl. was evaluated in an abandoned plantation of eucalypt (Corymbia citriodora (Hook. K.D. Hill & L.A.S. Johnson (Myrtaceae. The study was conducted at the União Biological Reserve, Rio de Janeiro State, Brazil during the rainy and dry periods, after five years of litter removal. The removal of plant litter did not influence the ecophysiological responses of the species. There was however significant seasonal variation. During the dry period, intercellular CO2 concentration (Ci, transpiration (E, and stomatal conductance (gs were decreased, while intrinsic efficiency of water use (IWUE, non-photochemical quenching (NPQ, and carotenoid values increased, suggesting a protective strategy against stress. Nevertheless, the values for Fv/Fm (maximum quantum efficiency and Fm/Fo (ratio of fluorescence yields for open and closed states indicated that even during the dry period there was no reduction in photochemical activity in these species. Only S. guianensis exhibited a reduced net photosynthetic rate (A during the dry period. The data indicated that X. sericea was photosynthetically more efficient under conditions of low water availability and that a 5-year period of plant litter removal failed to produce differences in ecophysiological processes in the species analyzed.

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

Science.gov (United States)

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

2015-11-05

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.

Diurnal variation in the coupling of photosynthetic electron transport and carbon fixation in iron-limited phytoplankton in the NE subarctic Pacific

Science.gov (United States)

Schuback, Nina; Flecken, Mirkko; Maldonado, Maria T.; Tortell, Philippe D.

2016-02-01

Active chlorophyll a fluorescence approaches, including fast repetition rate fluorometry (FRRF), have the potential to provide estimates of phytoplankton primary productivity at an unprecedented spatial and temporal resolution. FRRF-derived productivity rates are based on estimates of charge separation in reaction center II (ETRRCII), which must be converted into ecologically relevant units of carbon fixation. Understanding sources of variability in the coupling of ETRRCII and carbon fixation provides physiological insight into phytoplankton photosynthesis and is critical for the application of FRRF as a primary productivity measurement tool. In the present study, we simultaneously measured phytoplankton carbon fixation and ETRRCII in the iron-limited NE subarctic Pacific over the course of a diurnal cycle. We show that rates of ETRRCII are closely tied to the diurnal cycle in light availability, whereas rates of carbon fixation appear to be influenced by endogenous changes in metabolic energy allocation under iron-limited conditions. Unsynchronized diurnal oscillations of the two rates led to 3.5-fold changes in the conversion factor between ETRRCII and carbon fixation (Kc / nPSII). Consequently, diurnal variability in phytoplankton carbon fixation cannot be adequately captured with FRRF approaches if a constant conversion factor is applied. Utilizing several auxiliary photophysiological measurements, we observed that a high conversion factor is associated with conditions of excess light and correlates with the increased expression of non-photochemical quenching (NPQ) in the pigment antenna, as derived from FRRF measurements. The observed correlation between NPQ and Kc / nPSII requires further validation but has the potential to improve estimates of phytoplankton carbon fixation rates from FRRF measurements alone.

Trace organic removal by photochemical oxidation

International Nuclear Information System (INIS)

Gupta, S.K. Sen; Peori, R.G.; Wickware, S.L.

1995-02-01

Photochemical oxidation methods can be used for the destruction of dissolved organic contaminants in most process effluent streams, including those originating from the nuclear power sector. Evaporators can be used to separate organic contaminants from the aqueous phase if they are non volatile, but a large volume of secondary waste (concentrate) is produced, and the technology is capital-intensive. This paper describes two different types of photochemical oxidation technologies used to destroy trace organics in wastewater containing oil and grease. (author). 9 refs., 4 figs

The quenched limit of lattice QCD at non-zero baryon number

International Nuclear Information System (INIS)

Engels, J.; Kaczmarek, O.; Karsch, F.; Laermann, E.

1999-01-01

We discuss the thermodynamics of gluons in the background of static quark sources. In order to do so we formulate the quenched limit of QCD at non-zero baryon number. A first numerical analysis of this system shows that it undergoes a smooth deconfining transition. We find evidence for a region of coexisting phases that becomes broader with increasing baryon number density. Although the action is in our formulation explicitly Z(3) symmetric the Polyakov loop expectation value becomes non-zero already in the low temperature phase. It indicates that the heavy quark potential stays finite at large distances, i.e. the string between static quarks breaks at non-zero baryon number density already in the hadronic phase

Non-animal photosafety assessment approaches for cosmetics based on the photochemical and photobiochemical properties.

Science.gov (United States)

Onoue, Satomi; Suzuki, Gen; Kato, Masashi; Hirota, Morihiko; Nishida, Hayato; Kitagaki, Masato; Kouzuki, Hirokazu; Yamada, Shizuo

2013-12-01

The main purpose of the present study was to establish a non-animal photosafety assessment approach for cosmetics using in vitro photochemical and photobiochemical screening systems. Fifty-one cosmetics, pharmaceutics and other chemicals were selected as model chemicals on the basis of animal and/or clinical photosafety information. The model chemicals were assessed in terms of photochemical properties by UV/VIS spectral analysis, reactive oxygen species (ROS) assay and 3T3 neutral red uptake phototoxicity testing (3T3 NRU PT). Most phototoxins exhibited potent UV/VIS absorption with molar extinction coefficients of over 1000M(-1)cm(-1), although false-negative prediction occurred for 2 cosmetic phototoxins owing to weak UV/VIS absorption. Among all the cosmetic ingredients, ca. 42% of tested chemicals were non-testable in the ROS assay because of low water solubility; thereby, micellar ROS (mROS) assay using a solubilizing surfactant was employed for follow-up screening. Upon combination use of ROS and mROS assays, the individual specificity was 88.2%, and the positive and negative predictivities were estimated to be 94.4% and 100%, respectively. In the 3T3 NRU PT, 3 cosmetics and 4 drugs were incorrectly predicted not to be phototoxic, although some of them were typical photoallergens. Thus, these in vitro screening systems individually provide false predictions; however, a systematic tiered approach using these assays could provide reliable photosafety assessment without any false-negatives. The combined use of in vitro assays might enable simple and fast non-animal photosafety evaluation of cosmetic ingredients. Copyright © 2013 Elsevier Ltd. All rights reserved.

Toxicity and deficiency of copper in Elsholtzia splendens affect photosynthesis biophysics, pigments and metal accumulation.

Science.gov (United States)

Peng, Hongyun; Kroneck, Peter M H; Küpper, Hendrik

2013-06-18

Elsholtzia splendens is a copper-tolerant plant species growing on copper deposits in China. Spatially and spectrally resolved kinetics of in vivo absorbance and chlorophyll fluorescence in mesophyll of E. splendens were used to investigate the copper-induced stress from deficiency and toxicity as well as the acclimation to excess copper stress. The plants were cultivated in nutrient solutions containing either Fe(III)-EDTA or Fe(III)-EDDHA. Copper toxicity affected light-acclimated electron flow much stronger than nonphotochemical quenching (NPQ) or dark-acclimated photochemical efficiency of PSIIRC (Fv/Fm). It also changed spectrally resolved Chl fluorescence kinetics, in particular by strengthening the short-wavelength (<700 nm) part of NPQ altering light harvesting complex II (LHCII) aggregation. Copper toxicity reduced iron accumulation, decreased Chls and carotenoids in leaves. During acclimation to copper toxicity, leaf copper decreased but leaf iron increased, with photosynthetic activity and pigments recovering to normal levels. Copper tolerance in E. splendens was inducible; acclimation seems be related to homeostasis of copper and iron in E. splendens. Copper deficiency appeared at 10 mg copper per kg leaf DW, leading to reduced growth and decreased photosynthetic parameters (F0, Fv/Fm, ΦPSII). The importance of these results for evaluating responses of phytoremediation plants to stress in their environment is discussed.

Carotenoids quench evolution of excited species in epidermis exposed to UV-B (290-320 nm) light

International Nuclear Information System (INIS)

Mathews-Roth, M.M.

1986-01-01

Reactions involving singlet oxygen and other free radicals have been identified in epidermis containing either exogenous or endogenous photosensitizers, soaked in a singlet oxygen/free radical trap, and then exposed to visible or UV-A (320-400 nm) light. Such reactions can be quenched by the presence of the carotenoid pigments β-carotene and canthaxanthin which accumulate in epidermis after oral administration. It is reported that the carotenoid pigments β-carotene, canthaxanthin and phytoene accumulating in epidermis can also quench to some degree those photochemical reactions involving singlet oxygen and free radicals that occur when epidermis is exposed to the sunburn spectrum of light (UV-B, 290-320 nm). (author)

Photochemical reduction of uranyl ion with amides

International Nuclear Information System (INIS)

Brar, A.S.; Chander, R.; Sandhu, S.S.

1981-01-01

The photochemical reduction of uranyl ion by formamide, acetamide, propionamide, butyramide, iso butyramids, n-methylformamide, N, N-dimethylformamide and N, N-diethylformamide in aqueous medium using radiation >= 380 nm from a medium pressure mercury vapour lamp has been investigated. The reduction with the said amides has been found to obey pseudo first order kinetics. The magnitude of the rate of reduction for the simple amides has been found to follow the following order formamide > isobutyramide approx. butyramide > propionamide > acetamide while the rate order for N-alkylformamides compared with that of the formamide has been found to be formamide > N-methylformamide > N,N-diethylformamide approx. N,N-dimethylformamide. The pseudo first order rate constants and quenching constants have been found from the kinetic data. It has been found that physical and chemical quenching compete with each other. Plots of reciprocal of quantum yields versus reciprocal [amide] have been found to be linear with intercepts on the ordinate axis. Absorption spectra of uranyl ion in doubly distilled water, in the presence of acid and in the presence of acid and amide reveal that there is no ground state interaction between uranyl ion and the amide. A mechanism of photoreduction of uranyl ion with amides has been proposed. (author)

Non-animal photosafety screening for complex cosmetic ingredients with photochemical and photobiochemical assessment tools.

Science.gov (United States)

Nishida, Hayato; Hirota, Morihiko; Seto, Yoshiki; Suzuki, Gen; Kato, Masashi; Kitagaki, Masato; Sugiyama, Mariko; Kouzuki, Hirokazu; Onoue, Satomi

2015-08-01

Previously, a non-animal screening approach was proposed for evaluating photosafety of cosmetic ingredients by means of in vitro photochemical and photobiochemical assays; however, complex cosmetic ingredients, such as plant extracts and polymers, could not be evaluated because their molecular weight is often poorly defined and so their molar concentration cannot be calculated. The aim of the present investigation was to establish a photosafety screen for complex cosmetic ingredients by using appropriately modified in vitro photosafety assays. Twenty plant extracts were selected as model materials on the basis of photosafety information, and their phototoxic potentials were assessed by means of ultraviolet (UV)/visible light (VIS) spectral analysis, reactive oxygen species (ROS)/micellar ROS (mROS) assays, and 3T3 neutral red uptake phototoxicity testing (3T3 NRU PT). The maximum UV/VIS absorption value was employed as a judgment factor for evaluating photoexcitability of samples, and the value of 1.0 was adopted as a tentative criterion for photosafety identification. The ROS/mROS assays were conducted at 50 μg/mL, and no false negative prediction was obtained. Furthermore, the ROS/mROS assays at 50 μg/mL had a similar predictive capacity to the ROS/mROS assays in the previous study. A systematic tiered approach for simple and rapid non-animal photosafety evaluation of complex cosmetic ingredients can be constructed using these modified in vitro photochemical assays. Copyright © 2015 Elsevier Inc. All rights reserved.

Photochemical air pollution

International Nuclear Information System (INIS)

Te Winkel, B.H.

1992-01-01

During periods of severe photochemical air pollution (smog) the industry in the Netherlands is recommended by the Dutch government to strongly reduce the emissions of air pollutants. For the electric power generating companies it is important to investigate the adequacy of this policy. The purpose of this investigation is to determine the contribution of electric power plants to photochemical air pollution and to assess the efficacy of emission reducing measures. A literature survey on the development of photochemical air pollution was carried out and modelled calculations concerning the share of the electric power plants to the photochemical air pollution were executed

Effects of garlic and diallyl trisulfide on the growth, photosynthesis, and alkaline phosphatase activity of the toxic cyanobacterium Microcystis aeruginosa.

Science.gov (United States)

Wang, Shoubing; Wang, Yuanan; Ma, Xiaoxue; Xu, Ziran

2016-03-01

To identify a botanical algicide and elucidate the response of cyanobacteria to the extract from higher plants, the effects of garlic and garlic-derived diallyl trisulfide on Microcystis aeruginosa were studied. Effects were evaluated by changes in cell density, chlorophyll a, maximum effective quantum yield (Fv/Fm), effective quantum yield (YII), non-photochemical quenching (NPQ), and rapid light curves of M. aeruginosa. In addition, alkaline phosphatase activity (APA) was measured when M. aeruginosa was incubated with diallyl trisulfide. Results indicated that the inhibition by garlic and diallyl trisulfide was significant. The 120-h 50 % effective concentrations of garlic and diallyl trisulfide (EC50) were 0.75 g L(-1) and 2.84 mg L(-1), respectively. Moreover, the inhibitory rate increased with increasing concentration and the growth of M. aeruginosa was inhibited by 90.0 % at the highest concentrations. We also show that the response of M. aeruginosa to stress could involve both impairment of the photosynthetic center PSII and alteration of APA. For example, at high garlic concentration (2.0 g L(-1)), Fv/Fm significantly decreased from 0.501 to 0.084 (p garlic as an environmentally friendly algicide.

Non-equilibrium transport in the quantum dot: quench dynamics and non-equilibrium steady state

Science.gov (United States)

Culver, Adrian; Andrei, Natan

We present an exact method of calculating the non-equilibrium current driven by a voltage drop across a quantum dot. The system is described by the two lead Anderson model at zero temperature with on-site Coulomb repulsion and non-interacting, linearized leads. We prepare the system in an initial state consisting of a free Fermi sea in each lead with the voltage drop given as the difference between the two Fermi levels. We quench the system by coupling the dot to the leads at t = 0 and following the time evolution of the wavefunction. In the long time limit a new type of Bethe Ansatz wavefunction emerges, which satisfies the Lippmann-Schwinger equation with the two Fermi seas serving as the boundary conditions. This exact, non-perturbative solution describes the non-equilibrium steady state of the system. We describe how to use this solution to compute the infinite time limit of the expectation value of the current operator at a given voltage, which would yield the I-V characteristic of the dot. Research supported by NSF Grant DMR 1410583.

Gas exchange and chlorophyll fluorescence of pea (Pisum sativum L.) plants in response to ambient ozone at a rural site in Egypt

Energy Technology Data Exchange (ETDEWEB)

Ismail, I.M.; Basahi, J.M. [Air Pollution Laboratory (APL), Centre of Excellence in Environmental Studies (CEES), King Abdulaziz University, P. O. Box 80216, Jeddah 21589 (Saudi Arabia); Hassan, I.A., E-mail: ihassan_eg@yahoo.com [Air Pollution Laboratory (APL), Centre of Excellence in Environmental Studies (CEES), King Abdulaziz University, P. O. Box 80216, Jeddah 21589 (Saudi Arabia); Department of Botany, Faculty of Science, Alexandria University, 21526 El Shatby, Alexandria (Egypt)

2014-11-01

Egyptian pea cultivars (Pisum sativum L. cultivars Little Marvel, Perfection and Victory) grown in open-top chambers were exposed to either charcoal-filtered (FA) or non-filtered air (NF) for five consecutive years (2009–2013) at a rural site in northern Egypt. Net photosynthetic rates (P{sub N}), stomatal conductance (g{sub s}), intercellular CO{sub 2} (C{sub i}) and chlorophyll fluorescence were measured. Ozone (O{sub 3}) was found to be the most prevalent pollutant common at the rural site and is suspected to be involved in the alteration of the physiological parameters measured in the present investigation. P{sub N} of different cultivars were found to respond similarly; decreases of 23, 29 and 39% were observed in the cultivars Perfection, Little Marvel and Victory, respectively (averaged over the five years) due to ambient O{sub 3}. The maximum impairment in P{sub N} was recorded in the cultivar Victory (46%) in 2013 when the highest O{sub 3} levels were recorded (90 nL L{sup −1}). The average stomatal conductance decreased by 20 and 18% in the cultivars Little Marvel and Perfection, respectively, while the average stomatal conductance increased on average by 27% in the cultivar Victory. A significant correlation was found between P{sub N} and C{sub i}, indicating the importance of non-stomatal limitations of photosynthesis, especially in the cultivar Victory. The P{sub N} vs. Ci curves were fitted to a non-rectangular hyperbolic model. The actual quantum yield (Φ{sub PSII}) and photochemical quenching coefficient (qP) were significantly decreased in the leaves of plants exposed to NF air. Non-photochemical quenching (NPQ) was increased in all cultivars. Exposure to NF air caused reductions in chlorophyll (Chl a) of 19, 16 and 30% in the Little Marvel, Perfection and Victory cultivars, respectively. - Highlights: • Ozone (O{sub 3}) concentrations recorded were within the ranges of phytotoxicity. • O{sub 3} has a clear influence on the physiological

Protein-protein interactions within photosystem II under photoprotection: the synergy between CP29 minor antenna, subunit S (PsbS) and zeaxanthin at all-atom resolution.

Science.gov (United States)

Daskalakis, Vangelis

2018-05-07

The assembly and disassembly of protein complexes within cells are crucial life-sustaining processes. In photosystem II (PSII) of higher plants, there is a delicate yet obscure balance between light harvesting and photo-protection under fluctuating light conditions, that involves protein-protein complexes. Recent breakthroughs in molecular dynamics (MD) simulations are combined with new approaches herein to provide structural and energetic insight into such a complex between the CP29 minor antenna and the PSII subunit S (PsbS). The microscopic model involves extensive sampling of bound and dissociated states at atomic resolution in the presence of photo-protective zeaxanthin (Zea), and reveals well defined protein-protein cross-sections. The complex is placed within PSII, and macroscopic connections are emerging (PsbS-CP29-CP24-CP47) along the energy transfer pathways from the antenna to the PSII core. These connections explain macroscopic observations in the literature, while the previously obscured atomic scale details are now revealed. The implications of these findings are discussed in the context of the Non-Photochemical Quenching (NPQ) of chlorophyll fluorescence, the down-regulatory mechanism of photosynthesis, that enables the protection of PSII against excess excitation load. Zea is found at the PsbS-CP29 cross-section and a pH-dependent equilibrium between PsbS dimer/monomers and the PsbS-CP29 dissociation/association is identified as the target for engineering tolerant plants with increased crop and biomass yields. Finally, the new MD based approaches can be used to probe protein-protein interactions in general, and the PSII structure provided can initiate large scale molecular simulations of the photosynthetic apparatus, under NPQ conditions.

Water relation, leaf gas exchange and chlorophyll a fluorescence imaging of soybean leaves infected with Colletotrichum truncatum.

Science.gov (United States)

Dias, Carla Silva; Araujo, Leonardo; Alves Chaves, Joicy Aparecida; DaMatta, Fábio M; Rodrigues, Fabrício A

2018-06-01

Considering the potential of anthracnose to decrease soybean yield and the need to gain more information regarding its effect on soybean physiology, the present study performed an in-depth analysis of the photosynthetic performance of soybean leaflets challenged with Colletotrichum truncatum by combining chlorophyll a fluorescence images with gas-exchange measurements and photosynthetic pigment pools. There were no significant differences between non-inoculated and inoculated plants in leaf water potential, apparent hydraulic conductance, net CO 2 assimilation rate, stomatal conductance to water vapor and transpiration rate. For internal CO 2 concentration, significant difference between non-inoculated and inoculated plants occurred only at 36 h after inoculation. Reductions in the values of the chlorophyll a fluorescence parameters [initial fluorescence (F 0 ), maximal fluorescence (F m ), maximal photosystem II quantum yield (F v /F m ), quantum yield of regulated energy dissipation (Y(NPQ))] and increases in effective PS II quantum yield (Y(II)), quantum yield of non-regulated energy dissipation Y(NO) and photochemical quenching coefficient (q P ) were noticed on the necrotic vein tissue in contrast to the surrounding leaf tissue. It appears that the impact of the infection by C. truncatum on the photosynthetic performance of the leaflets was minimal considering the preference of the fungus to colonize the veins. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

Mimicking the Role of the Antenna in Photosynthetic Photoprotection

Energy Technology Data Exchange (ETDEWEB)

Terazono, Yuichi; Kodis, Gerdenis; Bhushan, Kul; Zaks, Julia; Madden, Christopher; Moore, Ana L.; Moore, Thomas A.; Fleming, Graham R.; Gust, Devens

2011-03-09

One mechanism used by plants to protect against damage from excess sunlight is called nonphotochemical quenching (NPQ). Triggered by low pH in the thylakoid lumen, NPQ leads to conversion of excess excitation energy in the antenna system to heat before it can initiate production of harmful chemical species by photosynthetic reaction centers. Here we report a synthetic hexad molecule that functionally mimics the role of the antenna in NPQ. When the hexad is dissolved in an organic solvent, five zinc porphyrin antenna moieties absorb light, exchange excitation energy, and ultimately decay by normal photophysical processes. Their excited-state lifetimes are long enough to permit harvesting of the excitation energy for photoinduced charge separation or other work. However, when acid is added, a pH-sensitive dye moiety is converted to a form that rapidly quenches the first excited singlet states of all five porphyrins, converting the excitation energy to heat and rendering the porphyrins kinetically incompetent to readily perform useful photochemistry.

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

Science.gov (United States)

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

Relationships between ozone and other photochemical products at Ll. Valby, Denmark

DEFF Research Database (Denmark)

Skov, H.; Egeløv, A.H.; Granby, K.

1997-01-01

literature results it is estimated that the non-photochemical background mixing ratio of O-3 in the Northern Hemisphere is 24+/-6 ppbv. The correlation of HCOOH and CH3COOH with Ox indicates that these acids are of photochemical origin. A high correlation of HNO3 with Ox is also found. The anti-correlation...

Connecting active to passive fluorescence with photosynthesis: a method for evaluating remote sensing measurements of Chl fluorescence.

Science.gov (United States)

Magney, Troy S; Frankenberg, Christian; Fisher, Joshua B; Sun, Ying; North, Gretchen B; Davis, Thomas S; Kornfeld, Ari; Siebke, Katharina

2017-09-01

Recent advances in the retrieval of Chl fluorescence from space using passive methods (solar-induced Chl fluorescence, SIF) promise improved mapping of plant photosynthesis globally. However, unresolved issues related to the spatial, spectral, and temporal dynamics of vegetation fluorescence complicate our ability to interpret SIF measurements. We developed an instrument to measure leaf-level gas exchange simultaneously with pulse-amplitude modulation (PAM) and spectrally resolved fluorescence over the same field of view - allowing us to investigate the relationships between active and passive fluorescence with photosynthesis. Strongly correlated, slope-dependent relationships were observed between measured spectra across all wavelengths (F λ , 670-850 nm) and PAM fluorescence parameters under a range of actinic light intensities (steady-state fluorescence yields, F t ) and saturation pulses (maximal fluorescence yields, F m ). Our results suggest that this method can accurately reproduce the full Chl emission spectra - capturing the spectral dynamics associated with changes in the yields of fluorescence, photochemical (ΦPSII), and nonphotochemical quenching (NPQ). We discuss how this method may establish a link between photosynthetic capacity and the mechanistic drivers of wavelength-specific fluorescence emission during changes in environmental conditions (light, temperature, humidity). Our emphasis is on future research directions linking spectral fluorescence to photosynthesis, ΦPSII, and NPQ. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

Splitting and non splitting are pollution models photochemical reactions in the urban areas of greater Tehran area

International Nuclear Information System (INIS)

Heidarinasab, A.; Dabir, B.; Sahimi, M.; Badii, Kh.

2003-01-01

During the past years, one of the most important problems has been air pollution in urban areas. In this regards, ozone, as one of the major products of photochemical reactions, has great importance. The term 'photochemical' is applied to a number of secondary pollutants that appear as a result of sun-related reactions, ozone being the most important one. So far various models have been suggested to predict these pollutants. In this paper, we developed the model that has been introduced by Dabir, et al. [4]. In this model more than 48 chemical species and 114 chemical reactions are involved. The result of this development, showed good to excellent agreement across the region for compounds such as O 3 , NO, NO 2 , CO, and SO 2 with regard to VOC and NMHC. The results of the simulation were compared with previous work [4] and the effects of increasing the number of components and reactions were evaluated. The results of the operator splitting method were compared with non splitting solving method. The result showed that splitting method with one-tenth time step collapsed with non splitting method (Crank-Nicolson, under-relaxation iteration method without splitting of the equation terms). Then we developed one dimensional model to 3-D and were compared with experimental data

Effects of artificial sweeteners on metal bioconcentration and toxicity on a green algae Scenedesmus obliquus.

Science.gov (United States)

Hu, Hongwei; Deng, Yuanyuan; Fan, Yunfei; Zhang, Pengfei; Sun, Hongwen; Gan, Zhiwei; Zhu, Hongkai; Yao, Yiming

2016-05-01

The ecotoxicity of heavy metals depends much on their speciation, which is influenced by other co-existing substances having chelating capacity. In the present study, the toxic effects of Cd(2+) and Cu(2+) on a green algae Scenedesmus obliquus were examined in the presence of two artificial sweeteners (ASs), acesulfame (ACE) and sucralose (SUC) by comparing the cell specific growth rate μ and pulse-amplitude-modulated (PAM) parameters (maximal photosystem II photochemical efficiency Fv/Fm, actual photochemical efficiency Yield, and non-photochemical quenching NPQ) of the algae over a 96-h period. Simultaneously, the bioconcentration of the metals by the algal cells in the presence of the ASs was measured. The presence of ACE enhanced the growth of S. obliquus and promoted the bioconcentration of Cd(2+) in S. obliquus, while the impacts of SUC were not significant. Meanwhile, EC50 values of Cd(2+) on the growth of S. obliquus increased from 0.42 mg/L to 0.54 mg/L and 0.48 mg/L with the addition of 1.0 mg/L ACE and SUC, respectively. As for Cu(2+), EC50 values increased from 0.13 mg/L to 0.17 mg/L and 0.15 mg/L with the addition of 1.0 mg/L ACE and SUC, respectively. In summary, the two ASs reduced the toxicity of the metals on the algae, with ACE showing greater effect than SUC. Although not as sensitive as the cell specific growth rate, PAM parameters could disclose the mechanisms involved in metal toxicity at subcellular levels. This study provides the first evidence for the possible impact of ASs on the ecotoxicity of heavy metals. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effect of ionic liquids with different cations and anions on photosystem and cell structure of Scenedesmus obliquus.

Science.gov (United States)

Xia, Yilu; Liu, Dingdong; Dong, Ying; Chen, Jiazheng; Liu, Huijun

2018-03-01

The rapid increase in the production and practical application of ionic liquids (ILs) could pose potential threats to aquatic systems. In this study, we investigated the effects of four ILs with different cations and anions, including 1-hexyl-3-methylimidazolium nitrate ([HMIM]NO 3 ), 1-hexyl-3-methylimidazolium chloride ([HMIM]Cl), N-hexyl-3-metylpyridinium chloride ([HMPy]Cl), and N-hexyl-3-metylpyridinium bromide ([HMPy]Br), on photosystem and cellular structure of Scenedesmus obliquus. The results indicated that ILs are phytotoxic to S. obliquus. The contents of chlorophyll a, chlorophyll b and total chlorophyll decreased with increasing ILs concentrations. The chlorophyll fluorescence parameters of photosynthetic system II (PSII), including minimal fluorescence yield (F 0 ), potential efficiency of PSII (F v /F o ), maximum quantum efficiency of PSII photochemistry (F v /F m ), yield of photochemical quantum [Y(II)], and non-photochemical quenching coefficient without measuring F 0 ' (NPQ), were all affected. This indicates that ILs could damage PSII, inhibit the primary reaction of photosynthesis, interdict the process of electron-transfer and lead to loss of heat-dissipating ability. ILs also increased cell membrane permeability of S. obliquus, influenced the cellular ultrastructure, changed the morphology of algae cells and destroyed the cell wall, cell membrane and organelles. The results indicated that imidazolium ILs had greater effect than pyridinium ILs, NO 3 - -IL and Br - -IL had greater effect than Cl - -IL. To minimize threats to the environment, the structure of ILs should be taken into consideration. Copyright © 2017 Elsevier Ltd. All rights reserved.

Non-perturbative renormalization of static-light four-fermion operators in quenched lattice QCD

Energy Technology Data Exchange (ETDEWEB)

Palombi, F. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Papinutto, M.; Pena, C. [CERN, Geneva (Switzerland). Physics Dept., Theory Div.; Wittig, H. [Mainz Univ. (Germany). Inst. fuer Kernphysik

2007-06-15

We perform a non-perturbative study of the scale-dependent renormalization factors of a multiplicatively renormalizable basis of {delta}B=2 parity-odd four-fermion operators in quenched lattice QCD. Heavy quarks are treated in the static approximation with various lattice discretizations of the static action. Light quarks are described by nonperturbatively O(a) improved Wilson-type fermions. The renormalization group running is computed for a family of Schroedinger functional (SF) schemes through finite volume techniques in the continuum limit. We compute non-perturbatively the relation between the renormalization group invariant operators and their counterparts renormalized in the SF at a low energy scale. Furthermore, we provide non-perturbative estimates for the matching between the lattice regularized theory and all the SF schemes considered. (orig.)

Quench of non-Markovian coherence in the deep sub-Ohmic spin–boson model: A unitary equilibration scheme

International Nuclear Information System (INIS)

Yao, Yao

2015-01-01

The deep sub-Ohmic spin–boson model shows a longstanding non-Markovian coherence at low temperature. Motivating to quench this robust coherence, the thermal effect is unitarily incorporated into the time evolution of the model, which is calculated by the adaptive time-dependent density matrix renormalization group algorithm combined with the orthogonal polynomials theory. Via introducing a unitary heating operator to the bosonic bath, the bath is heated up so that a majority portion of the bosonic excited states is occupied. It is found in this situation the coherence of the spin is quickly quenched even in the coherent regime, in which the non-Markovian feature dominates. With this finding we come up with a novel way to implement the unitary equilibration, the essential term of the eigenstate-thermalization hypothesis, through a short-time evolution of the model

Classical vs. evolved quenching parameters and procedures in scintillation measurements: The importance of ionization quenching

International Nuclear Information System (INIS)

Bagan, H.; Tarancon, A.; Rauret, G.; Garcia, J.F.

2008-01-01

The quenching parameters used to model detection efficiency variations in scintillation measurements have not evolved since the decade of 1970s. Meanwhile, computer capabilities have increased enormously and ionization quenching has appeared in practical measurements using plastic scintillation. This study compares the results obtained in activity quantification by plastic scintillation of 14 C samples that contain colour and ionization quenchers, using classical (SIS, SCR-limited, SCR-non-limited, SIS(ext), SQP(E)) and evolved (MWA-SCR and WDW) parameters and following three calibration approaches: single step, which does not take into account the quenching mechanism; two steps, which takes into account the quenching phenomena; and multivariate calibration. Two-step calibration (ionization followed by colour) yielded the lowest relative errors, which means that each quenching phenomenon must be specifically modelled. In addition, the sample activity was quantified more accurately when the evolved parameters were used. Multivariate calibration-PLS also yielded better results than those obtained using classical parameters, which confirms that the quenching phenomena must be taken into account. The detection limits for each calibration method and each parameter were close to those obtained theoretically using the Currie approach

Effects of quenching and partial quenching on penguin matrix elements

NARCIS (Netherlands)

Golterman, Maarten; Pallante, Elisabetta

2001-01-01

In the calculation of non-leptonic weak decay rates, a "mismatch" arises when the QCD evolution of the relevant weak hamiltonian down to hadronic scales is performed in unquenched QCD, but the hadronic matrix elements are then computed in (partially) quenched lattice QCD. This mismatch arises

Use of the ICU Nurse-Physician Questionnaire (ICU N-P-Q): testing reliability and validity in neonatal intensive care units in Japan.

Science.gov (United States)

Sasaki, Hatoko; Yonemoto, Naohiro; Mori, Rintaro; Nishida, Toshihiko; Kusuda, Satoshi; Nakayama, Takeo

2016-05-09

Although communication among health providers has become a critical part of improving quality of care, few studies on this topic have been conducted in Japan. This study aimed to examine the reliability and validity of the Intensive Care Unit Nurse-Physician Questionnaire (ICU N-P-Q) for use among nurses and physicians in neonatal ICUs (NICUs) in Japan. A Japanese translation of the ICU N-P-Q was administered to physicians and nurses working at 40 NICUs across Japan, which were participating in the Improvement of NICU Practice and Team Approach Cluster randomized controlled trial (INTACT). We used the principal components analysis to evaluate the factor structure of the instruments. Convergent validity was assessed by examining correlations between the subscales of Communication and Conflict Management of the ICU N-P-Q and the subscales and total score of the Nurse-Physician Collaboration Scale (NPCS). Correlations between the subscales of Communication and Conflict Management by correlation with scales that refer to performance, including Job Satisfaction and Unit Effectiveness, were calculated to test the criterion validity. In total, 2006 questionnaires were completed by 316 physicians and 1690 nurses. The exploratory factor analysis revealed 15 factors in the physicians' questionnaire and 12 in the nurses' questionnaire. Convergent validity was confirmed, except for 'Between-group Accuracy' and 'Cooperativeness' in the physicians' scale, and for 'Between-group Accuracy' and 'Sharing of Patient Information' in the nurses' scale. Correlations between the subscales of communication and outcomes were confirmed in the nurses' questionnaire but were not fully supported in the physicians' questionnaire. Although the psychometric property behaved somewhat differently by occupation, the present findings provide preliminary support for the utility of the common item structure with the original scale, to measure the degree and quality of communication and collaboration

Far-red light is needed for efficient photochemistry and photosynthesis.

Science.gov (United States)

Zhen, Shuyang; van Iersel, Marc W

2017-02-01

The efficiency of monochromatic light to drive photosynthesis drops rapidly at wavelengths longer than 685nm. The photosynthetic efficiency of these longer wavelengths can be improved by adding shorter wavelength light, a phenomenon known as the Emerson enhancement effect. The reverse effect, the enhancement of photosynthesis under shorter wavelength light by longer wavelengths, however, has not been well studied and is often thought to be insignificant. We quantified the effect of adding far-red light (peak at 735nm) to red/blue or warm-white light on the photosynthetic efficiency of lettuce (Lactuca sativa). Adding far-red light immediately increased quantum yield of photosystem II (Φ PSII ) of lettuce by an average of 6.5 and 3.6% under red/blue and warm-white light, respectively. Similar or greater increases in Φ PSII were observed after 20min of exposure to far-red light. This longer-term effect of far-red light on Φ PSII was accompanied by a reduction in non-photochemical quenching of fluorescence (NPQ), indicating that far-red light reduced the dissipation of absorbed light as heat. The increase in Φ PSII and complementary decrease in NPQ is presumably due to preferential excitation of photosystem I (PSI) by far-red light, which leads to faster re-oxidization of the plastoquinone pool. This facilitates reopening of PSII reaction centers, enabling them to use absorbed photons more efficiently. The increase in Φ PSII by far-red light was associated with an increase in net photosynthesis (P n ). The stimulatory effect of far-red light increased asymptotically with increasing amounts of far-red. Overall, our results show that far-red light can increase the photosynthetic efficiency of shorter wavelength light that over-excites PSII. Copyright © 2016 Elsevier GmbH. All rights reserved.

Positive feedback regulation of a Lycium chinense-derived VDE gene by drought-induced endogenous ABA, and over-expression of this VDE gene improve drought-induced photo-damage in Arabidopsis.

Science.gov (United States)

Guan, Chunfeng; Ji, Jing; Zhang, Xuqiang; Li, Xiaozhou; Jin, Chao; Guan, Wenzhu; Wang, Gang

2015-03-01

Violaxanthin de-epoxidase (VDE) plays an important role in protecting the photosynthetic apparatus from photo-damage by dissipating excessively absorbed light energy as heat, via the conversion of violaxanthin (V) to intermediate product antheraxanthin (A) and final product zeaxanthin (Z) under light stress. We have cloned a VDE gene (LcVDE) from Lycium chinense, a deciduous woody perennial halophyte, which can grow in a large variety of soil types. The amino acid sequence of LcVDE has high homology with VDEs in other plants. Under drought stress, relative expression of LcVDE and the de-epoxidation ratio (Z+0.5A)/(V+A+Z) increased rapidly, and non-photochemical quenching (NPQ) also rose. Interestingly, these elevations induced by drought stress were reduced by the topical administration of abamine SG, a potent ABA inhibitor via inhibition of NCED in the ABA synthesis pathway. Until now, little has been done to explore the relationship between endogenous ABA and the expression of VDE genes. Since V serves as a common precursor for ABA, these data support the possible involvement of endogenous ABA in the positive feedback regulation of LcVDE gene expression in L. chinense under drought stress. Moreover, the LcVDE may be involved in modulating the level of photosynthesis damage caused by drought stress. Furthermore, the ratio of (Z+0.5A)/(V+A+Z) and NPQ increased more in transgenic Arabidopsis over-expressing LcVDE gene than the wild types under drought stress. The maximum quantum yield of primary photochemistry of PSII (Fv/Fm) in transgenic Arabidopsis decreased more slowly during the stressed period than that in wild types under the same conditions. Furthermore, transgenic Arabidopsis over-expressing LcVDE showed increased tolerance to drought stress. Copyright © 2014 Elsevier GmbH. All rights reserved.

Feeding sustains photosynthetic quantum yield of a scleractinian coral during thermal stress.

Science.gov (United States)

Borell, Esther M; Bischof, Kai

2008-10-01

Thermal resistance of the coral-zooxanthellae symbiosis has been associated with chronic photoinhibition, increased antioxidant activity and protein repair involving high demands of nitrogen and energy. While the relative importance of heterotrophy as a source of nutrients and energy for cnidarian hosts, and as a means of nitrogen acquisition for their zooxanthellae, is well documented, the effect of feeding on the thermal sensitivity of the symbiotic association has been so far overlooked. Here we examine the effect of zooplankton feeding versus starvation on the bleaching susceptibility and photosynthetic activity of photosystem II (PSII) of zooxanthellae in the scleractinian coral Stylophora pistillata in response to thermal stress (daily temperature rises of 2-3 degrees C) over 10 days, employing pulse-amplitude-modulated chlorophyll fluorometry. Fed and starved corals displayed a decrease in daily maximum potential quantum yield (F (v)/F (m)) of PSII, effective quantum yield (F/F (m)') and relative electron transport rates over the course of 10 days. However after 10 days of exposure to elevated temperature, F (v)/F (m) of fed corals was still 50-70% higher than F (v)/F (m) of starved corals. Starved corals showed strong signs of chronic photoinhibition, which was reflected in a significant decline in nocturnal recovery rates of PSII relative to fed corals. This was paralleled by the progressive inability to dissipate excess excitation energy via non-photochemical quenching (NPQ). After 10 days, NPQ of starved corals had decreased by about 80% relative to fed corals. Feeding treatment had no significant effect on chlorophyll a and c (2) concentrations and zooxanthellae densities, but the mitotic indices were significantly lower in starved than in fed corals. Collectively the results indicate that exogenous food may reduce the photophysiological damage of zooxanthellae that typically leads to bleaching and could therefore play an important role in mediating the

The role of coccoliths in protecting Emiliania huxleyi against stressful light and UV radiation

Science.gov (United States)

Xu, Juntian; Bach, Lennart T.; Schulz, Kai G.; Zhao, Wenyan; Gao, Kunshan; Riebesell, Ulf

2016-08-01

Coccolithophores are a group of phytoplankton species which cover themselves with small scales (coccoliths) made of calcium carbonate (CaCO3). The reason why coccolithophores form these calcite platelets has been a matter of debate for decades but has remained elusive so far. One hypothesis is that they play a role in light or UV protection, especially in surface dwelling species like Emiliania huxleyi, which can tolerate exceptionally high levels of solar radiation. In this study, we tested this hypothesis by culturing a calcified and a naked strain under different light conditions with and without UV radiation. The coccoliths of E. huxleyi reduced the transmission of visible radiation (400-700 nm) by 7.5 %, that of UV-A (315-400 nm) by 14.1 % and that of UV-B (280-315 nm) by 18.4 %. Growth rates of the calcified strain (PML B92/11) were about 2 times higher than those of the naked strain (CCMP 2090) under indoor constant light levels in the absence of UV radiation. When exposed to outdoor conditions (fluctuating sunlight with UV radiation), growth rates of calcified cells were almost 3.5 times higher compared to naked cells. Furthermore, the relative electron transport rate was 114 % higher and non-photochemical quenching (NPQ) was 281 % higher in the calcified compared to the naked strain, implying higher energy transfer associated with higher NPQ in the presence of calcification. When exposed to natural solar radiation including UV radiation, the maximal quantum yield of photosystem II was only slightly reduced in the calcified strain but strongly reduced in the naked strain. Our results reveal an important role of coccoliths in mitigating light and UV stress in E. huxleyi.

Quenching of p-Cyanophenylalanine Fluorescence by Various Anions.

Science.gov (United States)

Pazos, Ileana M; Roesch, Rachel M; Gai, Feng

2013-03-20

To expand the spectroscopic utility of the non-natural amino acid p -cyanophenylalanine (Phe CN ), we examine the quenching efficiencies of a series of commonly encountered anions toward its fluorescence. We find that iodide exhibits an unusually large Stern-Volmer quenching constant, making it a convenient choice in Phe CN fluorescence quenching studies. Indeed, using the villin headpiece subdomain as a testbed we demonstrate that iodide quenching of Phe CN fluorescence offers a convenient means to reveal protein conformational heterogeneity. Furthermore, we show that the amino group of Phe CN strongly quenches its fluorescence, suggesting that Phe CN could be used as a local pH sensor.

Indications for chlororespiration in relation to light regime in the marine diatom Thalassiosira weissflogii.

Science.gov (United States)

Dijkman, Nicole A; Kroon, Bernd M A

2002-04-01

The marine diatom Thalassiosira weissflogii was cultured under a light regime simulating the daily rise and fall of the sun. The light regime caused a daily cycle in non-photochemical quenching. Remarkable were the changes in fluorescence directly after a light-to-dark transition that occurred in addition to the changes induced by non-photochemical quenching. A transient non-photochemical reduction of PQ and of Q(A) was indicated by a transient increase in apparent F(o) and by changes in the shape of the fluorescence induction curve. The observed changes developed approximately the first 100-120 s after a light-to-dark transition and could be reversed by the application of far-red illumination. Chlororespiration is thought to cause the reduction of PQ and, as the PQ-pool is in equilibrium with Q(A), also a reduction of Q(A). The function and ecological relevance of chlororespiration are discussed.

International conference on the photochemical conversion and storage of solar energy

Energy Technology Data Exchange (ETDEWEB)

Hofman, M.Z.

1977-01-31

Abstracts are given for the eight formal lectures and the contributed papers from delegates which were presented in the form of posters. There were seven sessions divided by subject as follows: (1) photochemistry, (2) electron transfer mechanisms in photochemical energy conversion processes, (3) photoelectrolysis, (4) photogalvanics, (5) photochemical production of fuels in homogeneous solutions, (6) membranes for photosynthesis reactions, and (7) non-biological systems for organic molecular energy storage. (WHK)

A Study on Photosynthetic Physiological Characteristics of Six Rare and Endangered Species

Institute of Scientific and Technical Information of China (English)

Tailin ZHONG; Guangwu ZHAO; Jiamiao CHU; Xiaomin GUO; Genyou LI

2014-01-01

The parameters of gas exchange and chlorophyl fluorescence in leaves of six rare and endangered species Neolitsea sericea, Cinnamomum japonicum var. cheni , Sinojackia microcarpa, Discocleidion glabrum var. trichocarpum, Parrotia sub-aequalis, Cercidiphyl um japonicum were measured in fields. The results showed that there were significant differences in photosynthetic capacity, intrinsic water use effi-ciency (WUEi ), the efficiency of primary conversion of light energy of PSⅡ and its potential activity, the quantum yield of PSⅡ electron transport, and the potential ca-pacity of heat dissipation among the six species. However, there was no significant difference in WUE. The highest values of net photosynthetic rate (Pn), transpiration rate (Tr) and stomatal conductance (gs) occurred in D. glabrum var. trichocarpum and the lowest in S. microcarpa. On the contrary, D. glabrum var. trichocarpum had the lowest WUE, intrinsic water use efficiency (WUEi ) and S. microcarpa had the highest. The results indicated that D. glabrum var. trichocarpum had higher photo-synthetic capacity and poorer WUE, while S. microcarpa had lower photosynthetic capacity and greater WUE. Furthermore, the mean values of maximal fluorescence (Fm), potential efficiency of primary conversion of light energy of PSⅡ (Fv/Fm),ΦPSⅡ, actual efficiency of primary conversion of light energy of PSⅡ (F′v/F′m) and non-photochemical quenching coefficient (NPQ) were the highest in S. micro-carpa, indicating that its PSⅡ had higher capacity of heat dissipation and could prevent photosynthetic apparatus from damage by excessive light energy. Correlation analysis showed that there were significant correlations among photosynthetic physi-ological parameters. However, the initial fluorescence (Fo) was not significantly cor-related with any other parameters. This study also revealed the extremely significant positive correlations between Pn and Tr, gs, apparent quantum yield (AQY), be-tween Tr and

Growth and physiological characteristics of the weed false johnsongrass ( Sorghum arundinaceum (Desv. Stapf

Directory of Open Access Journals (Sweden)

Deborah Amorim Martins

2016-02-01

Full Text Available ABSTRACT Sorghum arundinaceum (Desv. Stapf is a weed that belongs to the Poaceae family and is widespread throughout Brazil. Despite the frequent occurrence, infesting cultivated areas, there is little research concerning the biology and physiology of this species. The objective of this research was to evaluate the growth, carbon partitioning and physiological characteristics of the weed Sorghum arundinaceum in greenhouse. Plants were collected at regular intervals of seven days, from 22 to 113 days after transplanting (DAT. In each sample, we determined plant height, root volume, leaf area and dry matter, and subsequently we perfomed the growth analysis, we have determined the dry matter partitioning among organs, the accumulation of dry matter, the specific leaf area, the relative growth rate and leaf weight ratio. At 36, 78 and 113 DAT, the photosynthetic and transpiration rates, stomatal conductance, CO2 concentration and chlorophyll fluorescence were evaluated. The Sorghum arundinaceum reached 1.91 in height, with slow initial growth and allocated much of the biomass in the roots. The photosynthetic rate and the maximum quantum yield of FSII are similar throughout the growth cycle. At maturity the Sorghum arundinaceum presents higher values of transpiration rate, stomatal conductance and non-photochemical quenching coefficient (NPQ.

PHYTOALEXIN DEFICIENT 4 affects reactive oxygen species metabolism, cell wall and wood properties in hybrid aspen (Populus tremula L. × tremuloides).

Science.gov (United States)

Ślesak, Ireneusz; Szechyńska-Hebda, Magdalena; Fedak, Halina; Sidoruk, Natalia; Dąbrowska-Bronk, Joanna; Witoń, Damian; Rusaczonek, Anna; Antczak, Andrzej; Drożdżek, Michał; Karpińska, Barbara; Karpiński, Stanisław

2015-07-01

The phytoalexin deficient 4 (PAD4) gene in Arabidopsis thaliana (AtPAD4) is involved in the regulation of plant--pathogen interactions. The role of PAD4 in woody plants is not known; therefore, we characterized its function in hybrid aspen and its role in reactive oxygen species (ROS)-dependent signalling and wood development. Three independent transgenic lines with different suppression levels of poplar PAD expression were generated. All these lines displayed deregulated ROS metabolism, which was manifested by an increased H2O2 level in the leaves and shoots, and higher activities of manganese superoxide dismutase (MnSOD) and catalase (CAT) in the leaves in comparison to the wild-type plants. However, no changes in non-photochemical quenching (NPQ) between the transgenic lines and wild type were observed in the leaves. Moreover, changes in the ROS metabolism in the pad4 transgenic lines positively correlated with wood formation. A higher rate of cell division, decreased tracheid average size and numbers, and increased cell wall thickness were observed. The results presented here suggest that the Populus tremula × tremuloides PAD gene might be involved in the regulation of cellular ROS homeostasis and in the cell division--cell death balance that is associated with wood development. © 2014 John Wiley & Sons Ltd.

Loss of Functional Photosystem II Reaction Centres in Zooxanthellae of Corals Exposed to Bleaching Conditions: Using Fluorescence Rise Kinetics.

Science.gov (United States)

Hill, R; Larkum, A W D; Frankart, C; Kühl, M; Ralph, P J

2004-01-01

Mass coral bleaching is linked to elevated sea surface temperatures, 1-2 degrees C above average, during periods of intense light. These conditions induce the expulsion of zooxanthellae from the coral host in response to photosynthetic damage in the algal symbionts. The mechanism that triggers this release has not been clearly established and to further our knowledge of this process, fluorescence rise kinetics have been studied for the first time. Corals that were exposed to elevated temperature (33 degrees C) and light (280 mumol photons m(-2) s(-1)), showed distinct changes in the fast polyphasic induction of chlorophyll-a fluorescence, indicating biophysical changes in the photochemical processes. The fluorescence rise over the first 2000ms was monitored in three species of corals for up to 8 h, with a PEA fluorometer and an imaging-PAM. Pocillopora damicornis showed the least impact on photosynthetic apparatus, while Acropora nobilis was the most sensitive, with Cyphastrea serailia intermediate between the other two species. A. nobilis showed a remarkable capacity for recovery from bleaching conditions. For all three species, a steady decline in the slope of the initial rise and the height of the J-transient was observed, indicating the loss of functional Photosystem II (PS II) centres under elevated-temperature conditions. A significant loss of PS II centres was confirmed by a decline in photochemical quenching when exposed to bleaching stress. Non-photochemical quenching was identified as a significant mechanism for dissipating excess energy as heat under the bleaching conditions. Photophosphorylation could explain this decline in PS II activity. State transitions, a component of non-photochemical quenching, was a probable cause of the high non-photochemical quenching during bleaching and this mechanism is associated with the phosphorylation-induced dissociation of the light harvesting complexes from the PS II reaction centres. This reversible process may

Environmental Quenching of Low-Mass Field Galaxies

Science.gov (United States)

Fillingham, Sean P.; Cooper, Michael C.; Boylan-Kolchin, Michael; Bullock, James S.; Garrison-Kimmel, Shea; Wheeler, Coral

2018-04-01

In the local Universe, there is a strong division in the star-forming properties of low-mass galaxies, with star formation largely ubiquitous amongst the field population while satellite systems are predominantly quenched. This dichotomy implies that environmental processes play the dominant role in suppressing star formation within this low-mass regime (M⋆ ˜ 105.5 - 8 M⊙). As shown by observations of the Local Volume, however, there is a non-negligible population of passive systems in the field, which challenges our understanding of quenching at low masses. By applying the satellite quenching models of Fillingham et al. (2015) to subhalo populations in the Exploring the Local Volume In Simulations (ELVIS) suite, we investigate the role of environmental processes in quenching star formation within the nearby field. Using model parameters that reproduce the satellite quenched fraction in the Local Group, we predict a quenched fraction - due solely to environmental effects - of ˜0.52 ± 0.26 within 1 systems observed at these distances are quenched via environmental mechanisms. Beyond 2 Rvir, however, dwarf galaxy quenching becomes difficult to explain through an interaction with either the Milky Way or M31, such that more isolated, field dwarfs may be self-quenched as a result of star-formation feedback.

Quench studies of YBCO insulated and non-insulated pancake coils

OpenAIRE

Glowa Natalia; Wesche Rainer; Bruzzone Pierluigi

2014-01-01

As a result of extremely high upper critical fields Bc2 high temperature superconductors (HTSs) have the potential to be used as high field insert coils in magnet systems where the background field is provided by low temperature superconductors (LTS). However due to low quench propagation velocity in HTS as compared to LTS the issue of developing a fast and reliable quench detection and protection scheme for such magnet systems remains a serious challenge. In order to provide a stable operati...

Physiological characteristics and metabolomics of transgenic wheat containing the maize C4 phosphoenolpyruvate carboxylase (PEPC) gene under high temperature stress.

Science.gov (United States)

Qi, Xueli; Xu, Weigang; Zhang, Jianzhou; Guo, Rui; Zhao, Mingzhong; Hu, Lin; Wang, Huiwei; Dong, Haibin; Li, Yan

2017-03-01

In this paper, two transgenic wheat lines, PC27 and PC51, containing the maize PEPC gene and its wild-type (WT) were used as experimental material to study the effects of high temperature on their photosynthetic physiological characteristics and metabolome. The results showed that transgenic wheat lines had higher photosynthetic rate (P n ) than WT under non-stress treatment (NT) and high temperature stress treatment (HT), and more significantly under HT. The change trends of F v /F m , Ф PSII , and q P were similar to P n , whereas that of non-photochemical quenching (NPQ) was the opposite. Compared with WT, no differences in chlorophyll content between the transgenic wheat and WT were observed under NT, but two transgenic lines had relatively higher contents than WT under HT. The change trends of Chlorophyll a/b radio, the decreased values of F m , W k , and V j , and the activity of the antioxidant enzyme were consistent with the chlorophyll content. Compared with WT, transgenic wheat lines exhibited lower rate of superoxide anion production, H 2 O 2 and malondialdehyde content under HT, and no significant differences were observed under NT. The expression pattern of the ZmPEPC gene and wheat endogenous photosynthesis-related genes were in agreement with that of P n . Compared with WT, about 13 different metabolites including one organic acid, six amino acids, four sugars, and two polyols were identified under NT; 25 different metabolites including six organic acids, 12 amino acids, four sugars, and three polyols were identified under HT. Collectively, our results indicate that ZmPEPC gene can enhance photochemical and antioxidant enzyme activity, upregulate the expression of photosynthesis-related genes, delay degradation of chlorophyll, change contents of proline and other metabolites in wheat, and ultimately improves its heat tolerance.

Quenched chiral logarithms

International Nuclear Information System (INIS)

Sharpe, S.R.

1992-04-01

I develop a diagrammatic method for calculating chiral logarithms in the quenched approximation. While not rigorous, the method is based on physically reasonable assumptions, which can be tested by numerical simulations. The main results are that, at leading order in the chiral expansion, (a) there are no chiral logarithms in quenched f π m u = m d ; (b) the chiral logarithms in B K and related kaon B-parameters are, for m d = m s the same in the quenched approximation as in the full theory (c) for m π and the condensate, there are extra chiral logarithms due to loops containing the η', which lead to a peculiar non-analytic dependence of these quantities on the bare quark mass. Following the work of Gasser and Leutwyler, I discuss how there is a predictable finite volume dependence associated with each chiral logarithm. I compare the resulting predictions with numerical results: for most quantities the expected volume dependence is smaller than the errors. but for B V and B A there is an observed dependence which is consistent with the predictions

Photochemical effects of sunlight.

Science.gov (United States)

Daniels, F

1972-07-01

The importance of sunlight in bringing about not only photosynthesis in plants, but also other photochemical effects, is reviewed. More effort should be devoted to photochemical storage of the sun's energy without the living plant. There is no theoretical reason to believe that such reactions are impossible. Ground rules for searching for suitable solar photochemical reactions are given, and a few attempts are described, but nothing successful has yet been found. Future possibilities are suggested. Photogalvanic cells which convert sunlight into electricity deserve further research. Eugene Rabinowitch has been an active pioneer in these fields.

Analysis of Photosystem I Donor and Acceptor Sides with a New Type of Online-Deconvoluting Kinetic LED-Array Spectrophotometer.

Science.gov (United States)

Schreiber, Ulrich; Klughammer, Christof

2016-07-01

The newly developed Dual/KLAS-NIR spectrophotometer, technical details of which were reported very recently, is used in measuring redox changes of P700, plastocyanin (PC) and ferredoxin (Fd) in intact leaves of Hedera helix, Taxus baccata and Brassica napus An overview of various light-/dark-induced changes of deconvoluted P700 + , PC + and Fd - signals is presented demonstrating the wealth of novel information and the consistency of the obtained results. Fd - changes are particularly large after dark adaptation. PC oxidation precedes P700 oxidation during dark-light induction and in steady-state light response curves. Fd reoxidation during induction correlates with the secondary decline of simultaneously measured fluorescence yield, both of which are eliminated by removal of O 2 By determination of 100% redox changes, relative contents of PC/P700 and Fd/P700 can be assessed, which show considerable variations between different leaves, with a trend to higher values in sun leaves. Based on deconvoluted P700 + signals, the complementary quantum yields of PSI, Y(I) (photochemical energy use), Y(ND) (non-photochemical loss due to oxidized primary donor) and Y(NA) (non-photochemical loss due to reduced acceptor) are determined as a function of light intensity and compared with the corresponding complementary quantum yields of PSII, Y(II) (photochemical energy use), Y(NPQ) (regulated non-photochemical loss) and Y(NO) (non-regulated non-photochemical loss). The ratio Y(I)/Y(II) increases with increasing intensities. In the low intensity range, a two-step increase of PC + is indicative of heterogeneous PC pools. © The Author 2016. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Effects of space environment on chlorophyll fluorescence and photosynthesis characteristics of wheat

International Nuclear Information System (INIS)

Lu Li; Lv Jinyin; Gong Qingzhu; Gao Junfeng

2006-01-01

The effects of the space environment on the chlorophyll fluorescence parameters and photosynthesis characteristics of wheat cultivars, Xinong 1043 M1 and Shaan253 M 1 , were studied. The results showed that the decrement of contents of PS II primary photochemical efficiency (F v /F m ), potential activity (F v /F 0 ), photochemical quenching coefficient (qP) and photosynthesis rate (Pn) were less than that of control, increment of non-photochemical quenching coefficient (qN) were more than that of control. The results suggested that photosynthetic apparatus were damaged, photosynthetic electron transport, photosynthetic primary reaction were inhibited, rate of photosynthesis decreased and growth of M 1 plant were retarded, which leading to thousand kernel weights decreased. (authors)

Characterizing Water Quenching Systems with a Quench Probe

Science.gov (United States)

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.

Rapid hydrogen hydrate growth from non-stoichiometric tuning mixtures during liquid nitrogen quenching.

Science.gov (United States)

Grim, R Gary; Kerkar, Prasad B; Sloan, E Dendy; Koh, Carolyn A; Sum, Amadeu K

2012-06-21

In this study the rapid growth of sII H(2) hydrate within 20 min of post formation quenching towards liquid nitrogen (LN(2)) temperature is presented. Initially at 72 MPa and 258 K, hydrate samples would cool to the conditions of ~60 MPa and ~90 K after quenching. Although within the stability region for H(2) hydrate, new hydrate growth only occurred under LN(2) quenching of the samples when preformed hydrate "seeds" of THF + H(2) were in the presence of unconverted ice. The characterization of hydrate seeds and the post-quenched samples was performed with confocal Raman spectroscopy. These results suggest that quenching to LN(2) temperature, a common preservation technique for ex situ hydrate analysis, can lead to rapid unintended hydrate growth. Specifically, guest such as H(2) that may otherwise need sufficiently long induction periods to nucleate, may still experience rapid growth through an increased kinetic effect from a preformed hydrate template.

Two-level quenching of photoluminescence in hexagonal boron nitride micropowder

Energy Technology Data Exchange (ETDEWEB)

Henaish, A. M. A. [Ural Federal University, NANOTECH Center, Mira Street, 19, Yekaterinburg, Russia, 620002 (Russian Federation); Tanta University, Physics Department, Tanta, Egypt, 31527 (Egypt); Vokhmintsev, A. S.; Weinstein, I. A., E-mail: i.a.weinstein@urfu.ru [Ural Federal University, NANOTECH Center, Mira Street, 19, Yekaterinburg, Russia, 620002 (Russian Federation)

2016-03-29

The processes of photoluminescence thermal quenching in the range RT – 800 K of h-BN micropowder in the 3.56 eV band were studied. It was found that two non-radiative channels of excitations relaxation with activation energies of 0.27 and 0.81 eV control the quenching for emission observed. It was assumed that emptying the shallow traps based on O{sub N}-centers characterized external quenching in RT – 530 K range and non-radiative mechanism of donor-acceptor recombination began to dominate at T > 530 K.

Two-level quenching of photoluminescence in hexagonal boron nitride micropowder

International Nuclear Information System (INIS)

Henaish, A. M. A.; Vokhmintsev, A. S.; Weinstein, I. A.

2016-01-01

The processes of photoluminescence thermal quenching in the range RT – 800 K of h-BN micropowder in the 3.56 eV band were studied. It was found that two non-radiative channels of excitations relaxation with activation energies of 0.27 and 0.81 eV control the quenching for emission observed. It was assumed that emptying the shallow traps based on O N -centers characterized external quenching in RT – 530 K range and non-radiative mechanism of donor-acceptor recombination began to dominate at T > 530 K.

Quench origins

International Nuclear Information System (INIS)

Devred, A.

1990-03-01

Quenches can be divided into two categories; conductor-limited and energy-deposited quenches. A conductor-limited quench occurs when the current in the magnet exceeds the capacity of the superconductor; it is characterized by a strong correlation with temperature. An energy-deposited quench occurs when a disturbance releases enough energy to trigger a quench; the main disturbances during magnet energization are frictional movements of the conductor due to increasing Lorentz forces. The current level of the conductor-limited quenches defines the limit of the magnet performance, and can only be surpassed by lowering the operating temperature; the occurrence of a constant current at quench during the magnetic testing is called a plateau. Usually it takes a few energy-deposited quenches of increasing currents to reach the plateau; these first few steps are called the magnet's training. The goal in designing a magnet is to be able to energize it and to reliably operate it at the design current without training. This can be achieved by optimizing the magnet's operating margin, that is, by designing and building the magnet in such a way that the sizes of the mechanical disturbances needed to trigger a quench are much larger than the achievable mechanical tolerances. (N.K.) 112 refs

Strain-based quench detection for a solenoid superconducting magnet

International Nuclear Information System (INIS)

Wang Xingzhe; Guan Mingzhi; Ma Lizhen

2012-01-01

In this paper, we present a non-electric quench detection method based on the strain gauge measurement of a superconducting solenoid magnet at cryogenic temperature under an intense magnetic field. Unlike the traditional voltage measurement of quench detection, the strain-based detection method utilizes low-temperature strain gauges, which evidently reduce electromagnetic noise and breakdown, to measure the magneto/thermo-mechanical behavior of the superconducting magnet during excitation. The magnet excitation, quench tests and trainings were performed on a prototype 5 T superconducting solenoid magnet. The transient strains and their abrupt changes were compared with the current, magnetic field and temperature signals collected during excitation and quench tests to indicate that the strain gauge measurements can detect the quench feature of the superconducting magnet. The proposed method is expected to be able to detect the quench of a superconducting coil independently or utilized together with other electrical methods. In addition, the axial quench propagation velocity of the solenoid is evaluated by the quench time lags among different localized strains. The propagation velocity is enhanced after repeated quench trainings. (paper)

Quantum quenches with integrable pre-quench dynamics

OpenAIRE

Delfino, Gesualdo

2014-01-01

We consider the unitary time evolution of a one-dimensional quantum system which is in a stationary state for negative times and then undergoes a sudden change (quench) of a parameter of its Hamiltonian at t=0. For systems possessing a continuum limit described by a massive quantum field theory we investigate in general perturbative quenches for the case in which the theory is integrable before the quench.

Quantum quenches with integrable pre-quench dynamics

International Nuclear Information System (INIS)

Delfino, Gesualdo

2014-01-01

We consider the unitary time evolution of a one-dimensional quantum system which is in a stationary state for negative times and then undergoes a sudden change (quench) of a parameter of its Hamiltonian at t = 0. For systems possessing a continuum limit described by a massive quantum field theory we investigate in general perturbative quenches for the case in which the theory is integrable before the quench. (fast track communication)

Calculating Quench Propagation with ANSYS(regsign)

International Nuclear Information System (INIS)

Caspi, S.; Chiesa, L.; Ferracin, P.; Gourlay, S.A.; Hafalia, R.; Hinkins, R.; Lietzke, A.F.; Prestemon, S.

2002-01-01

A commercial Finite-Element-Analysis program, ANSYS(reg s ign), is widely used in structural and thermal analysis. With the program's ability to include non-linear material properties and import complex CAD files, one can generate coil geometries and simulate quench propagation in superconducting magnets. A 'proof-of-principle' finite element model was developed assuming a resistivity that increases linearly from zero to its normal value at a temperature consistent with the assumed B magnetic field. More sophisticated models could easily include finer-grained coil, cable, structural, and circuit details. A quench is provoked by raising the temperature of an arbitrary superconducting element above its T c . The time response to this perturbation is calculated using small time-steps to allow convergence between steps. Snapshots of the temperature and voltage distributions allow examination of longitudinal and turn-to-turn quench propagation, quench-front annihilation, and cryo-stability. Modeling details are discussed, and a computed voltage history was compared with measurements from a recent magnet test.

Quorum Quenching Revisited—From Signal Decays to Signalling Confusion

Directory of Open Access Journals (Sweden)

Kok-Gan Chan

2012-04-01

Full Text Available In a polymicrobial community, while some bacteria are communicating with neighboring cells (quorum sensing, others are interrupting the communication (quorum quenching, thus creating a constant arms race between intercellular communication. In the past decade, numerous quorum quenching enzymes have been found and initially thought to inactivate the signalling molecules. Though this is widely accepted, the actual roles of these quorum quenching enzymes are now being uncovered. Recent evidence extends the role of quorum quenching to detoxification or metabolism of signalling molecules as food and energy source; this includes “signalling confusion”, a term coined in this paper to refer to the phenomenon of non-destructive modification of signalling molecules. While quorum quenching has been explored as a novel anti-infective therapy targeting, quorum sensing evidence begins to show the development of resistance against quorum quenching.

HQET at order 1/m. Pt. 1. Non-perturbative parameters in the quenched approximation

International Nuclear Information System (INIS)

Blossier, Benoit; Della Morte, Michele; Garron, Nicolas; Edinburgh Univ.; Sommer, Rainer

2010-01-01

We determine non-perturbatively the parameters of the lattice HQET Lagrangian and those of heavy-light axial-vector and vector currents in the quenched approximation. The HQET expansion includes terms of order 1/m b . Our results allow to compute, for example, the heavy-light spectrum and B-meson decay constants in the static approximation and to order 1/m b in HQET. The determination of the parameters is separated into universal and non-universal parts. The universal results can be used to determine the parameters for various discretizations. The computation reported in this paper uses the plaquette gauge action and the ''HYP1/2'' action for the b-quark described by HQET. The parameters of the currents also depend on the light-quark action, for which we choose non-perturbatively O(a)-improved Wilson fermions. (orig.)

HQET at order 1/m. Pt. 1. Non-perturbative parameters in the quenched approximation

Energy Technology Data Exchange (ETDEWEB)

Blossier, Benoit [Paris XI Univ., 91 - Orsay (France). Lab. de Physique Theorique; Della Morte, Michele [Mainz Univ. (Germany). Inst. fuer Kernphysik; Garron, Nicolas [Universidad Autonoma de Madrid (Spain). Dept. Fisica Teorica y Inst. de Fisica Teorica UAM/CSIC; Edinburgh Univ. (United Kingdom). School of Physics and Astronomy - SUPA; Sommer, Rainer [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC

2010-01-15

We determine non-perturbatively the parameters of the lattice HQET Lagrangian and those of heavy-light axial-vector and vector currents in the quenched approximation. The HQET expansion includes terms of order 1/m{sub b}. Our results allow to compute, for example, the heavy-light spectrum and B-meson decay constants in the static approximation and to order 1/m{sub b} in HQET. The determination of the parameters is separated into universal and non-universal parts. The universal results can be used to determine the parameters for various discretizations. The computation reported in this paper uses the plaquette gauge action and the ''HYP1/2'' action for the b-quark described by HQET. The parameters of the currents also depend on the light-quark action, for which we choose non-perturbatively O(a)-improved Wilson fermions. (orig.)

Quench limits

International Nuclear Information System (INIS)

Sapinski, M.

2012-01-01

With thirteen beam induced quenches and numerous Machine Development tests, the current knowledge of LHC magnets quench limits still contains a lot of unknowns. Various approaches to determine the quench limits are reviewed and results of the tests are presented. Attempt to reconstruct a coherent picture emerging from these results is taken. The available methods of computation of the quench levels are presented together with dedicated particle shower simulations which are necessary to understand the tests. The future experiments, needed to reach better understanding of quench limits as well as limits for the machine operation are investigated. The possible strategies to set BLM (Beam Loss Monitor) thresholds are discussed. (author)

Two mechanisms for dissipation of excess light in monomeric and trimeric light-harvesting complexes

Energy Technology Data Exchange (ETDEWEB)

Dall' Osto, Luca [Univ. di Verona, Verona (Italy). Dipartimento di Biotecnologie; Cazzaniga, Stefano [Univ. di Verona, Verona (Italy). Dipartimento di Biotecnologie; Bressan, Mauro [Univ. di Verona, Verona (Italy). Dipartimento di Biotecnologie; Paleček, David [Lund Univ. (Sweden). Dept. of Chemical Physics; Židek, Karel [Lund Univ. (Sweden). Dept. of Chemical Physics; Niyogi, Krishna K. [Univ. of California, Berkeley, CA (United States). Howard Hughes Medical Inst., Dept. of Plant and Microbial Biology; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Molecular Biophysics and Integrated Bioimaging Division; Fleming, Graham R. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Molecular Biophysics and Integrated Bioimaging Division; Univ. of California, Berkeley, CA (United States). Dept. of Chemistry, Graduate Group in Applied Science and Technology; Zigmantas, Donatas [Lund Univ. (Sweden). Dept. of Chemical Physics; Bassi, Roberto [Univ. di Verona, Verona (Italy). Dipartimento di Biotecnologie; Consiglio Nazionale delle Ricerche (CNR), Firenze (Italy). Istituto per la Protezione delle Piante (IPP)

2017-04-10

Oxygenic photoautotrophs require mechanisms for rapidly matching the level of chlorophyll excited states from light harvesting with the rate of electron transport from water to carbon dioxide. These photoprotective reactions prevent formation of reactive excited states and photoinhibition. The fastest response to excess illumination is the so-called non-photochemical quenching which, in higher plants, requires the luminal pH sensor PsbS and other yet unidentified components of the photosystem II antenna. Both trimeric light-harvesting complex II (LHCII) and monomeric LHC proteins have been indicated as site(s) of the heat-dissipative reactions. Different mechanisms have been proposed: Energy transfer to a lutein quencher in trimers, formation of a zeaxanthin radical cation in monomers. Here, we report on the construction of a mutant lacking all monomeric LHC proteins but retaining LHCII trimers. Its non-photochemical quenching induction rate was substantially slower with respect to the wild type. A carotenoid radical cation signal was detected in the wild type, although it was lost in the mutant. Here, we conclude that non-photochemical quenching is catalysed by two independent mechanisms, with the fastest activated response catalysed within monomeric LHC proteins depending on both zeaxanthin and lutein and on the formation of a radical cation. Trimeric LHCII was responsible for the slowly activated quenching component whereas inclusion in supercomplexes was not required. Finally, this latter activity does not depend on lutein nor on charge transfer events, whereas zeaxanthin was essential.

Investigating and comparing uranium and gamma radiation induced effects on photosynthetic parameters for Arabidopsis thaliana

Energy Technology Data Exchange (ETDEWEB)

Vanhoudt, Nathalie; Horemans, Nele; Saenen, Eline; Biermans, Geert; Nauts, Robin; Wannijn, Jean; Van Hees, May; Vandenhove, Hildegarde [Belgian Nuclear Research Centre (SCK.CEN), Biosphere Impact Studies, 2400, Mol (Belgium)

2014-07-01

As the environment is inevitably exposed to radionuclides and ionizing radiation from natural and anthropogenic sources, it is important to study the effects induced by these stressors on plants. In addition, it is already known that photosynthesis can be affected under various metal exposure situations. The objective of this research is to compare uranium induced effects with gamma radiation induced effects on photosynthetic parameters in Arabidopsis thaliana. First, 18-day-old seedlings were exposed to 50 μM uranium during 4 days. Second, 14-day-old seedlings were exposed to gamma radiation for 7 days to a total dose of 6.7 Gy. By using chlorophyll fluorescence measurements, the photosynthetic performance was assessed. Based on the data obtained during the measurement of induction curves, parameters providing information on the photosynthetic efficiency and heat dissipation can be calculated. For uranium exposed leaves, it was observed that the potential photosynthetic efficiency (measured as Fv/Fm) remained maximal while the effective efficiency of photosystem II (φPSII), which is a measure for the proportion of light absorbed by PSII used in photochemistry, even increased. The increase of φPSII could be related to a decrease in non-photochemical quenching (NPQ), which reflects the protective mechanism against excess light intensity by converting energy into heat, but no alterations in non-regulated energy dissipation (NO). A high NO value would indicate the inefficiency of photochemistry and heat conversion and the plant's inability to regulate the radiation energy. In plants exposed to uranium, NO levels were similar to the control. Under gamma irradiation, the capacity of PSII remained intact and plants started optimizing their photosynthetic process by increasing φPSII and decreasing NPQ. When comparing the NPQ kinetic responses of gamma radiation and uranium exposure, a remarkable difference can be highlighted. While gamma radiation exposure

Changes in photosynthetic performance and antioxidative strategies during maturation of Norway maple (Acer platanoides L.) leaves.

Science.gov (United States)

Lepeduš, Hrvoje; Gaća, Vlatka; Viljevac, Marija; Kovač, Spomenka; Fulgosi, Hrvoje; Simić, Domagoj; Jurković, Vlatka; Cesar, Vera

2011-04-01

Different structural and functional changes take place during leaf development. Since some of them are highly connected to oxidative metabolism, regulation of reactive oxygen species (ROS) abundance is required. Most of the reactive oxygen species ROS in plant cells are produced in chloroplasts as a result of highly energetic reactions of photosynthesis. The aim of our study was to examine the changes in concentration of oxidative stress parameters (TBARS - thiobarbituric acid-reacting substances and protein carbonyls) as well as antioxidative strategies during development of maple (Acer platanoides L.) leaves in the light of their enhanced photosynthetic performance. We reveal that biogenesis of the photosynthetic apparatus during maple leaf maturation corresponded with oxidative damage of lipids, but not proteins. In addition, antioxidative responses in young leaves differed from that in older leaves. Young leaves had high values of non-photochemical quenching (NPQ) and catalase (CAT, EC 1.11.1.6) activity which declined during the maturation process. Developing leaves were characterized by an increase in TBARS level, the content of non-enzymatic antioxidants as well as ascorbate peroxidase activity (APX, EC 1.11.1.11), while the content of protein carbonyls decreased with leaf maturation. Fully developed leaves had the highest lipid peroxidation level accompanied by a maximum in ascorbic acid content and superoxide dismutase activity (SOD, EC1.15.1.1). These observations imply completely different antioxidative strategies during leaf maturation enabling them to perform their basic function. Copyright © 2011 Elsevier Masson SAS. All rights reserved.

The quench detection system of Wendelstein 7-X

International Nuclear Information System (INIS)

Birus, Dietrich; Schneider, Matthias; Rummel, Thomas; Fricke, Marko

2011-01-01

The Quench Detection System of Wendelstein W7-X has been developed, pretested and manufactured during the last four years. This safety subsystem of the superconducting magnet power supply will guarantee the safe operating of the whole magnet system. The main targets of the Quench Detection System are the complete data acquisition of all the voltages along the superconducting components, i.e. non planar and planar coils, and bus bars, the evaluation of this data and the control of the magnet system safety discharges. The Quench Detection System is generating control commands for the magnet power supply control system and the electrical status of the superconducting components of W7-X. The Quench Detection System consists of nearly 580 Quench Detection Units (QDU) located in 10 QD-subsystems, 8 racks in each, one host system and two special interfaces for evaluation of the quench control commands and the failure signals. The operating software suite of the QD System allows the configuration, the operation and the maintenance of the whole system.

Quench origins

International Nuclear Information System (INIS)

Devred, A.

1990-03-01

In this paper, I shall discuss the quench origins. I shall first establish a method of classification and introduce the notions of conductor-limited and energy-deposited quenches. Next the paper will be devoted to the study of conductor-limited quenches, and I shall introduce the notions of plateau and of fraction of short sample. Also the paper will be devoted to the study of energy-deposited quenches, and I shall introduce the notions of training and of minimum energy deposit; I shall then review the possible causes of energy release. Lastly, I shall introduce the notion of operating margin, and I shall indicate how to optimize the operating margin in order to limit the risk of premature quenching. 112 refs., 14 figs

Porous debris behavior modeling of QUENCH-02, QUENCH-03 and QUENCH-09 experiments

International Nuclear Information System (INIS)

Kisselev, A.E.; Kobelev, G.V.; Strizhov, V.F.; Vasiliev, A.D.

2006-01-01

The heat-up, melting, relocation, hydrogen generation phenomena, relevant for high-temperature stages both in a reactor case and small-scale integral tests like QUENCH, are governed in particular by heat and mass transfer in porous debris and molten pools which are formed in the core region. Porous debris formation and behavior in QUENCH experiments (QUENCH-02, QUENCH-03, QUENCH-09) plays a considerable role and its adequate modeling is important for thermal analysis. In particular, the analysis of QUENCH experiments shows that the major hydrogen release takes place in debris and melt regions formed in the upper part of the fuel assembly. The porous debris model was implemented in the Russian best estimate numerical code RATEG/SVECHA/HEFEST developed for modelling thermal hydraulics and severe accident phenomena in a reactor. The original approach for debris evolution is developed in the model from classical principles using a set of parameters including debris porosity; average particle diameter; temperatures and mass fractions of solid, liquid and gas phases; specific interface areas between different phases; effective thermal conductivity of each phase, including radiative heat conductivity; mass and energy fluxes through the interfaces. The debris model is based on the system of continuity, momentum and energy conservation equations, which consider the dynamics of volume-averaged velocities and temperatures of fluid, solid and gaseous phases of porous debris. The model is used for calculation of QUENCH experiments. The results obtained by the model are compared to experimental data concerning different aspects of thermal behavior: thermal hydraulics of porous debris, radiative heat transfer in a porous medium, the generalized melting and refreezing behavior of materials, hydrogen production. (author)

Non-perturbative renormalization of left-left four-fermion operators in quenched lattice QCD

CERN Document Server

Guagnelli, M; Peña, C; Sint, S; Vladikas, A

2006-01-01

We define a family of Schroedinger Functional renormalization schemes for the four-quark multiplicatively renormalizable operators of the $\\Delta F = 1$ and $\\Delta F = 2$ effective weak Hamiltonians. Using the lattice regularization with quenched Wilson quarks, we compute non-perturbatively the renormalization group running of these operators in the continuum limit in a large range of renormalization scales. Continuum limit extrapolations are well controlled thanks to the implementation of two fermionic actions (Wilson and Clover). The ratio of the renormalization group invariant operator to its renormalized counterpart at a low energy scale, as well as the renormalization constant at this scale, is obtained for all schemes.

Passive quench arrest by a chimney induced deluge at every quench front

International Nuclear Information System (INIS)

Sydoriak, S.G.

1984-01-01

This chapter describes a magnet in which a growing quench stops itself spontaneously within a fraction of one winding turn because vapor in quench-heated channels generates a progressively increasing downflow of liquid in advance of each of the quench fronts. The downflow eventually becomes a deluge as the quench grows. The design of the multiple arrested quench magnet is discussed. It is shown how to construct a magnet so that if an arrested quench arises when it is at its highest operating current, peak nucleate boiling will exist in all quenching channels

Exciplex formation accompanied with excitation quenching.

Science.gov (United States)

Fedorenko, Stanislav G; Burshtein, Anatoly I

2010-04-08

The competence of the reversible exciplex formation and parallel quenching of excitation (by electron or energy transfer) was considered using a non-Markovian pi-forms approach, identical to integral encounter theory (IET). General equations accounting for the reversible quenching and exciplex formation are derived in the contact approximation. Their general solution was obtained and adopted to the most common case when the ground state particles are in great excess. Particular cases of only photoionization or just exciplex formation separately studied earlier by means of IET are reproduced. In the case of the irreversible excitation quenching, the theory allows specifying the yields of the fluorescence and exciplex luminescence, as well as the long time kinetics of excitation and exciplex decays, in the absence of quenching. The theory distinguishes between the alternative regimes of (a) fast equilibration between excitations and exciplexes followed by their decay with a common average rate and (b) the fastest and deep excitation decay followed by the weaker and slower delayed fluorescence, backed by exciplex dissociation.

High light acclimation of Chromera velia points to photoprotective NPQ

Czech Academy of Sciences Publication Activity Database

Belgio, Erica; Trsková, Eliška; Kotabová, Eva; Ewe, Daniela; Prášil, Ondřej; Kaňa, Radek

2018-01-01

Roč. 135, 1-3 SI (2018), s. 263-274 ISSN 0166-8595 R&D Projects: GA MŠk(CZ) LO1416; GA ČR(CZ) GA16-10088S; GA ČR(CZ) GJ17-02363Y Institutional support: RVO:61388971 Keywords : Nonphotochemical quenching * Photoinhibition * Chromera velia alga Subject RIV: EE - Microbiology, Virology OBOR OECD: Microbiology Impact factor: 3.864, year: 2016

Interactions between the photosystem II subunit PsbS and xanthophylls studied in vivo and in vitro.

Science.gov (United States)

Bonente, Giulia; Howes, Barry D; Caffarri, Stefano; Smulevich, Giulietta; Bassi, Roberto

2008-03-28

The photosystem II subunit PsbS is essential for excess energy dissipation (qE); however, both lutein and zeaxanthin are needed for its full activation. Based on previous work, two models can be proposed in which PsbS is either 1) the gene product where the quenching activity is located or 2) a proton-sensing trigger that activates the quencher molecules. The first hypothesis requires xanthophyll binding to two PsbS-binding sites, each activated by the protonation of a dicyclohexylcarbodiimide-binding lumen-exposed glutamic acid residue. To assess the existence and properties of these xanthophyll-binding sites, PsbS point mutants on each of the two Glu residues PsbS E122Q and PsbS E226Q were crossed with the npq1/npq4 and lut2/npq4 mutants lacking zeaxanthin and lutein, respectively. Double mutants E122Q/npq1 and E226Q/npq1 had no qE, whereas E122Q/lut2 and E226Q/lut2 showed a strong qE reduction with respect to both lut2 and single glutamate mutants. These findings exclude a specific interaction between lutein or zeaxanthin and a dicyclohexylcarbodiimide-binding site and suggest that the dependence of nonphotochemical quenching on xanthophyll composition is not due to pigment binding to PsbS. To verify, in vitro, the capacity of xanthophylls to bind PsbS, we have produced recombinant PsbS refolded with purified pigments and shown that Raman signals, previously attributed to PsbS-zeaxanthin interactions, are in fact due to xanthophyll aggregation. We conclude that the xanthophyll dependence of qE is not due to PsbS but to other pigment-binding proteins, probably of the Lhcb type.

Interactions between the Photosystem II Subunit PsbS and Xanthophylls Studied in Vivo and in Vitro*

Science.gov (United States)

Bonente, Giulia; Howes, Barry D.; Caffarri, Stefano; Smulevich, Giulietta; Bassi, Roberto

2008-01-01

The photosystem II subunit PsbS is essential for excess energy dissipation (qE); however, both lutein and zeaxanthin are needed for its full activation. Based on previous work, two models can be proposed in which PsbS is either 1) the gene product where the quenching activity is located or 2) a proton-sensing trigger that activates the quencher molecules. The first hypothesis requires xanthophyll binding to two PsbS-binding sites, each activated by the protonation of a dicyclohexylcarbodiimide-binding lumen-exposed glutamic acid residue. To assess the existence and properties of these xanthophyll-binding sites, PsbS point mutants on each of the two Glu residues PsbS E122Q and PsbS E226Q were crossed with the npq1/npq4 and lut2/npq4 mutants lacking zeaxanthin and lutein, respectively. Double mutants E122Q/npq1 and E226Q/npq1 had no qE, whereas E122Q/lut2 and E226Q/lut2 showed a strong qE reduction with respect to both lut2 and single glutamate mutants. These findings exclude a specific interaction between lutein or zeaxanthin and a dicyclohexylcarbodiimide-binding site and suggest that the dependence of nonphotochemical quenching on xanthophyll composition is not due to pigment binding to PsbS. To verify, in vitro, the capacity of xanthophylls to bind PsbS, we have produced recombinant PsbS refolded with purified pigments and shown that Raman signals, previously attributed to PsbS-zeaxanthin interactions, are in fact due to xanthophyll aggregation. We conclude that the xanthophyll dependence of qE is not due to PsbS but to other pigment-binding proteins, probably of the Lhcb type. PMID:18070876

Photochemical hydrogen production system

International Nuclear Information System (INIS)

Copeland, R.J.

1990-01-01

Both technical and economic factors affect the cost of producing hydrogen by photochemical processes. Technical factors include the efficiency and the capital and operating costs of the renewable hydrogen conversion system; economic factors include discount rates, economic life, credit for co-product oxygen, and the value of the energy produced. This paper presents technical and economic data for a system that generates on-peak electric power form photochemically produced hydrogen

Photochemical decomposition of catecholamines

International Nuclear Information System (INIS)

Mol, N.J. de; Henegouwen, G.M.J.B. van; Gerritsma, K.W.

1979-01-01

During photochemical decomposition (lambda=254 nm) adrenaline, isoprenaline and noradrenaline in aqueous solution were converted to the corresponding aminochrome for 65, 56 and 35% respectively. In determining this conversion, photochemical instability of the aminochromes was taken into account. Irradiations were performed in such dilute solutions that the neglect of the inner filter effect is permissible. Furthermore, quantum yields for the decomposition of the aminochromes in aqueous solution are given. (Author)

Differential expression of carotenogenic genes, associated changes on astaxanthin production and photosynthesis features induced by JA in H. pluvialis.

Directory of Open Access Journals (Sweden)

Zhengquan Gao

Full Text Available Haematococcus pluvialis is an organism that under certain conditions can produce astaxanthin, an economically important carotenoid. In this study, the transcriptional expression patterns of eight carotenogenic genes of H. pluvialis in response to jasmonic acid (JA were evaluated using real-time PCR. Astaxanthin accumulation action and photosynthesis flourescence were monitored at the same time. The results showed all eight genes exhibited higher transcriptional expression significantly under JA treatments. JA25 (25 mg/L induction had greater effect (>10-fold up-regulation on the transcriptional expression of pds, crtR-B and lyc than on ipi-1, ipi-2, psy, bkt2, and crtO. JA50 (50 mg/L treatment had greater impact on the transcriptional expression of ipi-1, ipi-2, psy, crtR-B and crtO than on pds, lyc and bkt2. Astaxanthin biosynthesis in the presence of JA appeared to be up-regulated mainly by psy, pds, crtR-B, lyc, bkt2 and crtO at the transcriptional level and ipi-1, ipi-2 at both transcriptional and post-transcriptional levels. Under JA induction, the photosynthetic efficiency [Y (II] and the maximum quantum efficiency of PS II (Fv/Fm decreased significantly, but the non-photochemical quenching of chlorophyll fluorescence (NPQ increased drastically with the accumulation of astaxanthin.

Agrobacterium rhizogenes rolB gene affects photosynthesis and chlorophyll content in transgenic tomato (Solanum lycopersicum L.) plants.

Science.gov (United States)

Bettini, Priscilla P; Marvasi, Massimiliano; Fani, Fabiola; Lazzara, Luigi; Cosi, Elena; Melani, Lorenzo; Mauro, Maria Luisa

2016-10-01

Insertion of Agrobacterium rhizogenes rolB gene into plant genome affects plant development, hormone balance and defence. However, beside the current research, the overall transcriptional response and gene expression of rolB as a modulator in plant is unknown. Transformed rolB tomato plant (Solanum lycopersicum L.) cultivar Tondino has been used to investigate the differential expression profile. Tomato is a well-known model organism both at the genetic and molecular level, and one of the most important commercial food crops in the world. Through the construction and characterization of a cDNA subtracted library, we have investigated the differential gene expression between transgenic clones of rolB and control tomato and have evaluated genes specifically transcribed in transgenic rolB plants. Among the selected genes, five genes encoding for chlorophyll a/b binding protein, carbonic anhydrase, cytochrome b 6 /f complex Fe-S subunit, potassium efflux antiporter 3, and chloroplast small heat-shock protein, all involved in chloroplast function, were identified. Measurement of photosynthesis efficiency by the level of three different photosynthetic parameters (F v /F m , rETR, NPQ) showed rolB significant increase in non-photochemical quenching and a, b chlorophyll content. Our results point to highlight the role of rolB on plant fitness by improving photosynthesis. Copyright © 2016 Elsevier GmbH. All rights reserved.

Elevated CO2 causes changes in the photosynthetic apparatus of a toxic cyanobacterium, Cylindrospermopsis raciborskii.

Science.gov (United States)

Pierangelini, Mattia; Stojkovic, Slobodanka; Orr, Philip T; Beardall, John

2014-07-15

We studied the physiological acclimation of growth, photosynthesis and CO2-concentrating mechanism (CCM) in Cylindrospermopsis raciborskii exposed to low (present day; L-CO2) and high (1300ppm; H-CO2) pCO2. Results showed that under H-CO2 the cell specific division rate (μc) was higher and the CO2- and light-saturated photosynthetic rates (Vmax and Pmax) doubled. The cells' photosynthetic affinity for CO2 (K0.5CO2) was halved compared to L-CO2 cultures. However, no significant differences were found in dark respiration rates (Rd), pigment composition and light harvesting efficiency (α). In H-CO2 cells, non-photochemical quenching (NPQ), associated with state transitions of the electron transport chain (ETC), was negligible. Simultaneously, a reorganisation of PSII features including antenna connectivity (JconPSIIα), heterogeneity (PSIIα/β) and effective absorption cross sectional area (σPSIIα/β) was observed. In relation to different activities of the CCM, our findings suggest that for cells grown under H-CO2: (1) there is down-regulation of CCM activity; (2) the ability of cells to use the harvested light energy is altered; (3) the occurrence of state transitions is likely to be associated with changes of electron flow (cyclic vs linear) through the ETC; (4) changes in PSII characteristics are important in regulating state transitions. Copyright © 2014 Elsevier GmbH. All rights reserved.

Photosynthesis and metabolite responses of Isatis indigotica Fortune to elevated [CO2

Institute of Scientific and Technical Information of China (English)

Ping Li; Hongying Li; Yuzheng Zong; Frank Yonghong Li; Yuanhuai Han; Xingyu Hao

2017-01-01

Climate change is affecting global crop productivity, food quality, and security. However, few studies have addressed the mechanism by which elevated CO2 may affect the growth of medicinal plants. Isatis indigotica Fortune is a widely used Chinese medicinal herb with multiple pharmacological properties. To investigate the physiological mechanism of I. indigotica response to elevated [CO2], plants were grown at either ambient [CO2] (385μmol mol?1) or elevated [CO2] (590μmol mol?1) in an open-top chamber (OTC) experimental facility in North China. A significant reduction in transpiration rate (Tr) and stomatal conductance (gs) and a large increase in water-use efficiency contributed to an increase in net photosynthetic rate (Pn) under elevated [CO2] 76 days after sowing. Leaf non-photochemical quenching (NPQ) was decreased, so that more energy was used in effective quantum yield of PSII photochemistry (ΦPSI ) under elevated [CO2]. High ΦPSI , meaning high electron transfer efficiency, also increased Pn. The [CO2]-induced increase in photosynthesis significantly increased biomass by 36.8%. Amounts of metabolic compounds involved in sucrose metabolism, pyrimidine metabolism, flavonoid biosynthesis, and other processes in leaves were reduced under elevated [CO2]. These results showed that the fertilization effect of elevated [CO2] is conducive to increasing dry weight but not secondary metabolism in I. indigotica.

Comparative Effects of Salt Stress and Extreme pH Stress Combined on Glycinebetaine Accumulation, Photosynthetic Abilities and Growth Characters of Two Rice Genotypes

Directory of Open Access Journals (Sweden)

Suriyan CHA-UM

2009-12-01

Full Text Available Glycinebetaine (Glybet accumulation, photosynthetic efficiency and growth performance in indica rice cultivated under salt stress and extreme pH stress were investigated. Betaine aldehyde dehydrogenase (BADH activity and Glybet accumulation in the seedlings of salt-tolerant and salt-sensitive rice varieties grown under saline and acidic conditions peaked after treatment for 72 h and 96 h, respectively, and were higher than those grown under neutral pH and alkaline salt stress. A positive correlation was found between BADH activity and Glybet content in both salt-tolerant (r2 = 0.71 and salt-sensitive (r2 = 0.86 genotypes. The chlorophyll a, chlorophyll b, total chlorophyll and total carotenoids contents in the stressed seedlings significantly decreased under both acidic and alkaline stresses, especially in the salt-sensitive genotype. Similarly, the maximum quantum yield of PSII (Fv/Fm, photon yield of PSII (ΦPSII, non-photochemical quenching (NPQ and net photosynthetic rate (Pn in the stressed seedlings were inhibited, leading to overall growth reduction. The positive correlations between chlorophyll a content and Fv/Fm, total chlorophyll content and ΦPSII, ΦPSII and Pn as well as Pn and leaf area in both salt-tolerant and salt-sensitive genotypes were found. Saline acidic and saline alkaline soils may play a key role affecting vegetative growth prior to the reproductive stage in rice plants.

Molecular cloning and characterization of violaxanthin de-epoxidase (CsVDE in cucumber.

Directory of Open Access Journals (Sweden)

Xin Li

Full Text Available Violaxanthin de-epoxidase (VDE plays an important role in protecting the photosynthetic apparatus from photo-damage by dissipating excessively absorbed light energy as heat, via the conversion of violaxanthin (V to intermediate product antheraxanthin (A and final product zeaxanthin (Z under high light stress. We have cloned a violaxanthin de-epoxidase gene (CsVDE from cucumber. The amino acid sequence of CsVDE has high homology with VDEs in other plants. RT-PCR analysis and histochemical staining show that CsVDE is expressed in all green tissues in cucumber and Arabidopsis. Using GFP fusion protein and immunogold labeling methods, we show that CsVDE is mainly localized in chloroplasts in cucumber. Under high light stress, relative expression of CsVDE and the de-epoxidation ratio (A+Z/(V+A+Z is increased rapidly, and abundance of the gold particles was also increased. Furthermore, CsVDE is quickly induced by cold and drought stress, reaching maximum levels at the 2(nd hour and the 9(th day, respectively. The ratio of (A+Z/(V+A+Z and non-photochemical quenching (NPQ is reduced in transgenic Arabidopsis down-regulated by the antisense fragment of CsVDE, compared to wild type (WT Arabidopsis under high light stress. This indicates decreased functionality of the xanthophyll cycle and increased sensitivity to photoinhibition of photosystem II (PSII in transgenic Arabidopsis under high light stress.

Quenching of liquid scintillator fluorescence by chloroalkanes and chloroalkenes

International Nuclear Information System (INIS)

Hariharan, Chithra; Mishra, A.K.

2000-01-01

The fluorescence quenching of 2,5-diphenyloxazole (PPO) by a series of chloroalkanes and chloroalkenes including carbon tetrachloride, chloroform, dichloroethane, tetrachloroethane, dichloroethylene, trichloroethylene and tetrachloroethylene was studied in toluene as solvent at room temperature. CCl 4 was found to be the most efficient quencher in the series. The quenching was found to be appreciable and a positive deviation from linearity was observed in the Stern-Volmer (SV) plots for all the quenchers in the concentration range studied. From the studies of effect of temperature, solvent viscosity and excitation wavelength dependence for the PPO-CCl 4 system, it was inferred that non-linearity is due to the presence of a minor static quenching component in an overall dynamic quenching. The static (K S ) and the dynamic (K D ) quenching constants were calculated from the modified SV equation using quadratic least square fits. Fluorescence quenching experiments with CCl 4 were done for four other scintillators (POPOP, α-NPO, BBO and PBBO). The mechanism of quenching was established to be via charge-transfer, with the direction of transfer being from the scintillators to the chloroalkanes and chloroalkenes

Photoprotection in Plants Involves a Change in Lutein 1 Binding Domain in the Major Light-harvesting Complex of Photosystem II

NARCIS (Netherlands)

Ilioaia, C.; Johnson, M.P.; Liao, P.N.; Pascal, A.A.; van Grondelle, R.; Walla, P.J.; Ruban, A.V.; Robert, B.

2011-01-01

Nonphotochemical quenching (NPQ) is the fundamental process by which plants exposed to high light intensities dissipate the potentially harmful excess energy as heat. Recently, it has been shown that efficient energy dissipation can be induced in the major light-harvesting complexes of photosystem

Quench observation using quench antennas on RHIC IR quadrupole magnets

International Nuclear Information System (INIS)

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

1995-01-01

Quench observation using quench antennas is now being performed routinely on RHIC dipole and quadrupole magnets. Recently, a quench antenna was used on a RHIC IR magnet which is heavily instrumented with voltage taps. It was confirmed that the signals detected in the antenna coils do not contradict the voltage tap signals. The antenna also detects a sign of mechanical disturbance which could be related to a training quench. This paper summarizes signals detected in the antenna and discusses possible causes of these signals

Quench observation using quench antennas on RHIC IR quadrupole magnets

International Nuclear Information System (INIS)

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

1996-01-01

Quench observation using quench antennas is now being performed routinely on RHIC dipole and quadrupole magnets. Recently, a quench antenna was used on a RHIC IR magnet which is heavily instrumented with voltage taps. It was confirmed that the signals detected in the antenna coils do not contradict the voltage tap signals. The antenna also detects a sign of mechanical disturbance which could be related to a training quench. This paper summarizes signals detected in the antenna and discusses possible causes of these signals

An experimental study on quenching of a radially stratified heated porous bed

International Nuclear Information System (INIS)

Nayak, Arun K.; Sehgal, Bal Raj; Stepanyan, Armen V.

2006-01-01

The quenching characteristics of a volumetrically-heated particulate bed composed of radially stratified sand layers were investigated experimentally in the POMECO facility. The sand bed simulates the corium particulate debris bed which is formed when the molten corium released from the vessel fragments in water and deposits on the cavity floor during a postulated severe accident in a light water reactor (LWR). The electrically-heated bed was quenched by water from a water column established over top of it, and later also with water coming from its bottom, which was circulating from the water overlayer through downcomers. A series of experiments were conducted to reveal the effects of the size of downcomers, and their locations in the bed, on the quenching characteristics of the radially stratified debris beds. The downcomers were found to significantly increase the bed quenching rate. To simulate the non-condensable gases generated during the MCCI, air and argon were injected from the bottom of the bed at different flow rates. The effects of gas flow rate and its properties on the quenching behaviour were observed. The results indicate that the non-condensable gas flows reduce the quenching rate significantly. The gas properties also affect the quenching characteristics

Quenches after LS1

International Nuclear Information System (INIS)

Verweij, A.P.

2012-01-01

In this paper I will give an overview of the different types of quenches that occur in the LHC, followed by an estimate of the number of quenches that we can expect after LS1. Beam-induced quenches and false triggering of the QPS will be the main cause of those quenches that cause a beam dump. Possibly in total up to 10-20 per year. After consolidation of the 13 kA joints, the approach for the BLM settings can be less conservative than in 2010-2012 in order to maximize beam time. This will cause some quenches but, anyhow, a beam.induced quench is not more risky than a quench provoked by false triggering. It is not easy to predict the number of BLM triggered beam dumps, needed to avoid magnet quenches, because it is not sure how to scale beam losses and UFO's from 3.5 TeV to 6.5 TeV, and it is not sure if the thresholds at 3.5 TeV are correct. Quench events will be much more massive (ex: RB quench at 6 kA → 2 MJ, RB quench at 11 kA → 6-20 MJ), and as a result cryo recuperation much longer. There will also be more ramp induced quenches after a FPA in other circuits due to higher ramp rates and smaller temperature margins (mutual coupling)

Modelling of pressure tube Quench using PDETWO

International Nuclear Information System (INIS)

Parlatan, Y.; Lei, Q.M.; Kwee, M.

2004-01-01

Transient two-dimensional heat conduction calculations have been carried out to determine the time-dependent temperature distribution in an overheated pressure tube during quenching with water. The purpose of the calculations is to provide input for evaluation of thermal (secondary) stresses in the pressure tube due to quench. The quench phenomenon in pressure tubes could occur in several hypothetical accident scenarios, including incidents involving intermittent buoyancy-induced flow during outages. In these scenarios, there will be two (radial and axial) or three dimensional temperature gradients, resulting in thermal stresses in the pressure tube, as the water front reaches and starts to cool down the hot pressure tube. The transient, two-dimensional heat conduction equation in the pressure tube during quench is solved using a FORTRAN package called PDETWO, available in the open literature for solving time-dependent coupled systems of non-linear partial differential equations over a two-dimensional rectangular region. This routine is based on finite difference solution of coupled, non-linear partial differential equations. Temperature gradient in the circumferential gradient is neglected for conservatism and convenience. The advancing water front is not modelled explicitly, and assumed to be at a uniform temperature and moving at a constant velocity inferred from experimental data. For outer surface and both ends of the pressure tube in the axial direction, a zero-heat flux boundary condition is assumed, while for the inner surface a moving water-quench front is assumed by appropriately varying the fluid temperature and the heat transfer coefficient. The pressure tube is assumed to be at a uniform temperature of 400 o C initially, to represent conditions expected during an intermittent buoyancy-influenced flow scenario. The results confirm the expectations that axial temperature gradients and associated heat fluxes are small in comparison with those in the

Research opportunities in photochemical sciences

Energy Technology Data Exchange (ETDEWEB)

NONE

1996-07-01

The workshop entitled {open_quotes}Research Opportunities in Photochemical Sciences{close_quotes} was initiated by the U.S. Department of Energy (DOE), Office of Energy Research (ER), Office of Basic Energy Sciences (BES), Division of Chemical Sciences. The National Renewable Energy Laboratory (NREL) in Golden, Colorado was requested by ER to host the workshop. It was held February 5-8, 1996 at the Estes Park Conference Center, Estes Park, CO, and attended by about 115 leading scientists and engineers from the U.S., Japan, and Europe; program managers for the DOE ER and Energy Efficiency and Renewable Energy (EERE) programs also attended. The purpose of the workshop was to bridge the communication gap between the practioneers and supporters of basic research in photochemical science and the practioneers and supporters of applied research and development in technologies related to photochemical science. For the purposes of the workshop the definition of the term {open_quotes}photochemical science{close_quotes} was broadened to include homogeneous photochemistry, heterogeneous photochemistry, photoelectrochemistry, photocatalysis, photobiology (for example, the light-driven processes of biological photosynthesis and proton pumping), artificial photosynthesis, solid state photochemistry, and solar photochemistry. The technologies under development through DOE support that are most closely related to photochemical science, as defined above, are the renewable energy technologies of photovoltaics, biofuels, hydrogen energy, carbon dioxide reduction and utilization, and photocatalysis for environmental cleanup of water and air. Individual papers were processed separately for the United states Department of Energy databases.

Exogenous Calcium Alleviates Photoinhibition of PSII by Improving the Xanthophyll Cycle in Peanut (Arachis Hypogaea) Leaves during Heat Stress under High Irradiance

Science.gov (United States)

Yang, Sha; Wang, Fang; Guo, Feng; Meng, Jing-Jing; Li, Xin-Guo; Dong, Shu-Ting; Wan, Shu-Bo

2013-01-01

Peanut is one of the calciphilous plants. Calcium (Ca) serves as a ubiquitous central hub in a large number of signaling pathways. The effect of exogenous calcium nitrate [Ca(NO3)2] (6 mM) on the dissipation of excess excitation energy in the photosystem II (PSII) antenna, especially on the level of D1 protein and the xanthophyll cycle in peanut plants under heat (40°C) and high irradiance (HI) (1 200 µmol m−2 s−1) stress were investigated. Compared with the control plants [cultivated in 0 mM Ca(NO3)2 medium], the maximal photochemical efficiency of PSII (Fv/Fm) in Ca2+-treated plants showed a slighter decrease after 5 h of stress, accompanied by higher non-photochemical quenching (NPQ), higher expression of antioxidative genes and less reactive oxygen species (ROS) accumulation. Meanwhile, higher content of D1 protein and higher ratio of (A+Z)/(V+A+Z) were also detected in Ca2+-treated plants under such stress. These results showed that Ca2+ could help protect the peanut photosynthetic system from severe photoinhibition under heat and HI stress by accelerating the repair of D1 protein and improving the de-epoxidation ratio of the xanthophyll cycle. Furthermore, EGTA (a chelant of Ca ion), LaCl3 (a blocker of Ca2+ channel in cytoplasmic membrane), and CPZ [a calmodulin (CaM) antagonist] were used to analyze the effects of Ca2+/CaM on the variation of (A+Z)/(V+A+Z) (%) and the expression of violaxanthin de-epoxidase (VDE). The results indicated that CaM, an important component of the Ca2+ signal transduction pathway, mediated the expression of the VDE gene in the presence of Ca to improve the xanthophyll cycle. PMID:23940721

Exogenous calcium alleviates photoinhibition of PSII by improving the xanthophyll cycle in peanut (Arachis hypogaea leaves during heat stress under high irradiance.

Directory of Open Access Journals (Sweden)

Sha Yang

Full Text Available Peanut is one of the calciphilous plants. Calcium (Ca serves as a ubiquitous central hub in a large number of signaling pathways. The effect of exogenous calcium nitrate [Ca(NO32] (6 mM on the dissipation of excess excitation energy in the photosystem II (PSII antenna, especially on the level of D1 protein and the xanthophyll cycle in peanut plants under heat (40°C and high irradiance (HI (1 200 µmol m(-2 s(-1 stress were investigated. Compared with the control plants [cultivated in 0 mM Ca(NO32 medium], the maximal photochemical efficiency of PSII (Fv/Fm in Ca(2+-treated plants showed a slighter decrease after 5 h of stress, accompanied by higher non-photochemical quenching (NPQ, higher expression of antioxidative genes and less reactive oxygen species (ROS accumulation. Meanwhile, higher content of D1 protein and higher ratio of (A+Z/(V+A+Z were also detected in Ca(2+-treated plants under such stress. These results showed that Ca(2+ could help protect the peanut photosynthetic system from severe photoinhibition under heat and HI stress by accelerating the repair of D1 protein and improving the de-epoxidation ratio of the xanthophyll cycle. Furthermore, EGTA (a chelant of Ca ion, LaCl3 (a blocker of Ca(2+ channel in cytoplasmic membrane, and CPZ [a calmodulin (CaM antagonist] were used to analyze the effects of Ca(2+/CaM on the variation of (A+Z/(V+A+Z (% and the expression of violaxanthin de-epoxidase (VDE. The results indicated that CaM, an important component of the Ca(2+ signal transduction pathway, mediated the expression of the VDE gene in the presence of Ca to improve the xanthophyll cycle.

Atmospheric carbon dioxide changes photochemical activity, soluble sugars and volatile levels in broccoli (Brassica oleracea var. italica).

Science.gov (United States)

Krumbein, Angelika; Kläring, Hans-Peter; Schonhof, Ilona; Schreiner, Monika

2010-03-24

Atmospheric carbon dioxide (CO(2)) concentration is an environmental factor currently undergoing dramatic changes. The objective of the present study was to determine the effect of doubling the ambient CO(2) concentration on plant photochemistry as measured by photochemical quenching coefficient (qP), soluble sugars and volatiles in broccoli. Elevated CO(2) concentration increased qP values in leaves by up to 100% and 89% in heads, while glucose and sucrose in leaves increased by about 60%. Furthermore, in broccoli heads elevated CO(2) concentration induced approximately a 2-fold increase in concentrations of three fatty acid-derived C(7) aldehydes ((E)-2-heptenal, (E,Z)-2,4-heptadienal, (E,E)-2,4-heptadienal), two fatty acid-derived C(5) alcohols (1-penten-3-ol, (Z)-2-pentenol), and two amino acid-derived nitriles (phenyl propanenitrile, 3-methyl butanenitrile). In contrast, concentrations of the sulfur-containing compound 2-ethylthiophene and C(6) alcohol (E)-2-hexenol decreased. Finally, elevated CO(2) concentration increased soluble sugar concentrations due to enhanced photochemical activity in leaves and heads, which may account for the increased synthesis of volatiles.

Study on the mechanism of allelopathic influence on cyanobacteria and chlorophytes by submerged macrophyte (Myriophyllum spicatum) and its secretion

International Nuclear Information System (INIS)

Zhu Junying; Liu Biyun; Wang Jing; Gao Yunni; Wu Zhenbin

2010-01-01

For revealing the mechanism of allelopathic influence on phytoplankton by aquatic macrophytes, the growth and photosynthetic activities of cyanobacteria Microcystis aeruginosa and the chlorophyte Selenastrum capricornutum were investigated when they coexisted with submerged macrophyte Myriophyllum spicatum and were exposed to allelopathic polyphenols: pyrogallic acid (PA), gallic acid (GA), ellagic acid (EA) and (+)-catechin (CA). According to the results of coexistence assays, the non-photochemical quenching (NPQ) and effective quantum efficiency (YII) of M. aeruginosa were affected earlier and more rapidly than the cell density. However, the influence of M. spicatum on S. capricornutum was not found. When the Toxicity Index (TI) was applied to evaluate the combined effects of binary and multiple mixtures of polyphenols, it was found that the four tested polyphenols with the proportion identified in the M. spicatum-cultured solution were observed to present synergistic effect (0.36-0.49) according to the cell density, NPQ and YII of M. aeruginosa. With the combined effects of polyphenols on S. capricornutum, only additive action (0.52-1.62) was found. On the other hand, PA (2.97 mg L -1 ), GA (2.65 mg L -1 ) caused significant reductions of photosystem II (PSII) and whole electron transport chain activities of M. aeruginosa by 71.43 and 18.37%, 70.95 and 40.77% (P < 0.05), respectively, after 24-h exposure, but no inhibition effect was found in S. capricornutum. The dark respiration and photosystem I (PSI) activities of M. aeruginosa were significantly increased by exposure to PA and GA (P < 0.05). Nevertheless, EA and CA had no influence on the electron transport activities of the tested organisms. These results indicate that the reduction in photosynthetic activity of M. aeruginosa and the synergistic effect of allelochemicals may be two important causes for the inhibition of undesired phytoplankton by submersed macrophytes in natural aquatic ecosystems, and

Study on the mechanism of allelopathic influence on cyanobacteria and chlorophytes by submerged macrophyte (Myriophyllum spicatum) and its secretion

Energy Technology Data Exchange (ETDEWEB)

Zhu Junying [State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei 430072 (China); Graduate School of Chinese Academy of Sciences, Beijing 100039 (China); Liu Biyun [State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei 430072 (China); Wang Jing; Gao Yunni [State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei 430072 (China); Graduate School of Chinese Academy of Sciences, Beijing 100039 (China); Wu Zhenbin, E-mail: wuzb@ihb.ac.cn [State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei 430072 (China)

2010-06-10

For revealing the mechanism of allelopathic influence on phytoplankton by aquatic macrophytes, the growth and photosynthetic activities of cyanobacteria Microcystis aeruginosa and the chlorophyte Selenastrum capricornutum were investigated when they coexisted with submerged macrophyte Myriophyllum spicatum and were exposed to allelopathic polyphenols: pyrogallic acid (PA), gallic acid (GA), ellagic acid (EA) and (+)-catechin (CA). According to the results of coexistence assays, the non-photochemical quenching (NPQ) and effective quantum efficiency (YII) of M. aeruginosa were affected earlier and more rapidly than the cell density. However, the influence of M. spicatum on S. capricornutum was not found. When the Toxicity Index (TI) was applied to evaluate the combined effects of binary and multiple mixtures of polyphenols, it was found that the four tested polyphenols with the proportion identified in the M. spicatum-cultured solution were observed to present synergistic effect (0.36-0.49) according to the cell density, NPQ and YII of M. aeruginosa. With the combined effects of polyphenols on S. capricornutum, only additive action (0.52-1.62) was found. On the other hand, PA (2.97 mg L{sup -1}), GA (2.65 mg L{sup -1}) caused significant reductions of photosystem II (PSII) and whole electron transport chain activities of M. aeruginosa by 71.43 and 18.37%, 70.95 and 40.77% (P < 0.05), respectively, after 24-h exposure, but no inhibition effect was found in S. capricornutum. The dark respiration and photosystem I (PSI) activities of M. aeruginosa were significantly increased by exposure to PA and GA (P < 0.05). Nevertheless, EA and CA had no influence on the electron transport activities of the tested organisms. These results indicate that the reduction in photosynthetic activity of M. aeruginosa and the synergistic effect of allelochemicals may be two important causes for the inhibition of undesired phytoplankton by submersed macrophytes in natural aquatic ecosystems

Photoacclimation in a tropical population of Cladophora glomerata (L.) Kützing 1843 (Chlorophyta) from southeastern Brazil.

Science.gov (United States)

Bautista, A I N; Necchi-Júnior, O

2008-02-01

Photoacclimation of photosynthesis was investigated in a tropical population of C. glomerata (São Paulo State, southeastern Brazil, 20 degrees 48' 24" S and 49 degrees 22' 24" W) by chlorophyll fluorescence parameters and chlorophyll a content. Plants were acclimated to two levels of irradiance: low (65 +/- 5 micromol.m(-2).s(-1)) and high (300 +/- 10 micromol.m(-2).s(-1)) and exposed short-term (4 days) and long-term (28 days) under a light-dark cycle of 12:12 hours. Photosynthesis-irradiance (PI) curves revealed distinct strategies of photoacclimation. In long-term exposure, plants acclimated by altering the photosynthetic units (PSU) number and keeping fixed the PSU size, revealed by increased rates of maximum photosynthesis (Pmax), lower photosynthetic efficiency (alpha) and higher values of the saturation parameter (Ik) under high irradiance. The short-term acclimation strategy consisted of changing the PSU size, with a fixed number of PSUs, as revealed by similar Pmax but higher alpha and lower Ik under low irradiance. Chlorophyll a contents followed the general pattern reported in green algae of higher concentrations under lower irradiance. Dark/light induction curves revealed consistently higher values of potential quantum yield under low irradiance. Initial and final values showed a higher recovery capacity in the short (84.4-90.6%) term exposure than in the long-term case (81.4-81.5%). ETR (electron transport rate) and NPQ (non-photochemical quenching) values were consistently higher under low irradiance. ETR showed a continuous and steady increase along the light exposure period in the short and long-term experiments, whereas NPQ values revealed a rapid increase after 15 seconds of light exposure, kept a slightly increasing trend and stabilized in most treatments. Lower photosynthetic performance (ETR) and recovery capacity of potential quantum yield were observed, particularly in long-term exposure, suggesting that this population is constrained by the

Effects of nanomolar copper on water plants—Comparison of biochemical and biophysical mechanisms of deficiency and sublethal toxicity under environmentally relevant conditions

Energy Technology Data Exchange (ETDEWEB)

Thomas, George, E-mail: george.thomas@uni.kn [Universität Konstanz, Mathematisch-Naturwissenschaftliche Sektion, Fachbereich Biologie, D-78457 Konstanz (Germany); Stärk, Hans-Joachim, E-mail: ha-jo.staerk@ufz.de [UFZ – Helmholtz Centre for Environmental Research, Department of Analytical Chemistry, Permoserstr. 15, D-04318 Leipzig (Germany); Wellenreuther, Gerd, E-mail: Gerd.wellenreuther@desy.de [HASYLAB at DESY, Notkestr. 85, 22603 Hamburg (Germany); Dickinson, Bryan C., E-mail: bryan.dickinson@gmail.com [Harvard University, Department of Chemistry and Chemical Biology, 12 Oxford Street, Cambridge, MA 02138 (United States); Küpper, Hendrik, E-mail: hendrik.kuepper@uni-konstanz.de [Universität Konstanz, Mathematisch-Naturwissenschaftliche Sektion, Fachbereich Biologie, D-78457 Konstanz (Germany); University of South Bohemia, Faculty of Biological Sciences and Institute of Physical Biology, Branišovská 31, CZ-370 05 České Budejovice (Czech Republic)

2013-09-15

Highlights: •We found different optimal Cu requirement for different physiological mechanisms. •Kinetics and concentration thresholds of damage mechanisms were established. •Cu toxicity caused internal Cu re-distribution and inhibition of Zn uptake. •Cu deficient plants released Cu, indicating lack of high-affinity Cu transporters. •Cu deficiency caused re-distribution of zinc in the plant. -- Abstract: Toxicity and deficiency of essential trace elements like Cu are major global problems. Here, environmentally relevant sub-micromolar concentrations of Cu (supplied as CuSO{sub 4}) and simulations of natural light- and temperature cycles were applied to the aquatic macrophyte Ceratophyllum demersum. Growth was optimal at 10 nM Cu, while PSII activity (F{sub v}/F{sub m}) was maximal around 2 nM Cu. Damage to the PSII reaction centre was the first target of Cu toxicity, followed by disturbed regulation of heat dissipation (NPQ). Only after that, electron transport through PSII (Φ{sub PSII}) was inhibited, and finally chlorophylls decreased. Copper accumulation in the plants was stable until 10 nM Cu in solution, but strongly increased at higher concentrations. The vein was the main storage site for Cu up to physiological concentrations (10 nM). At toxic levels it was also sequestered to the epidermis and mesophyll until export from the vein became inhibited, accompanied by inhibition of Zn uptake. Copper deficiency led to a complete stop of growth at “0” nM Cu after 6 weeks. This was accompanied by high starch accumulation although electron flow through PSII (Φ{sub PSII}) decreased from 2 weeks, followed by decrease in pigments and increase of non photochemical quenching (NPQ). Release of Cu from the plants below 10 nM Cu supply in the nutrient solution indicated lack of high-affinity Cu transporters, and on the tissue level copper deficiency led to a re-distribution of zinc.

Photochemical smog and plants

Energy Technology Data Exchange (ETDEWEB)

Sawada, T.

1974-07-01

Surveys of plant damage due to photochemical smog are summarized. The components of smog which appear to be responsible for plant damage include ozone and peroxyacyl nitrates. Their phytotoxic effects are much greater than those due to sulfur oxides. Damage surveys since 1970 reveal the following symptoms appearing on herbaceous plants (morning glory, cocks comb, dahlia, knotweed, petunia, chickweed, Welsh onion, spinach, Chinese cabbage, chard, taro): yellowish-white leaf discoloration, white and brown spots on matured leaves, and silvering of the lower surfaces of young leaves. Symptoms which appear on arboraceous plants such as zelkova, poplar, ginkgo, planetree, rose mallow, magnolia, pine tree, and rhododendron include early yellowing and reddening, white or brown spots, and untimely leaf-fall. The above plants are now utilized as indicator plants of photochemical smog. Surveys covering a broad area of Tokyo and three other prefectures indicate that plant damage due to photochemical smog extends to relatively unpolluted areas.

Quark contributions to baryon magnetic moments in full, quenched, and partially quenched QCD

International Nuclear Information System (INIS)

Leinweber, Derek B.

2004-01-01

The chiral nonanalytic behavior of quark-flavor contributions to the magnetic moments of octet baryons is determined in full, quenched and partially quenched QCD, using an intuitive and efficient diagrammatic formulation of quenched and partially quenched chiral perturbation theory. The technique provides a separation of quark-sector magnetic-moment contributions into direct sea-quark loop, valence-quark, indirect sea-quark loop and quenched valence contributions, the latter being the conventional view of the quenched approximation. Both meson and baryon mass violations of SU(3)-flavor symmetry are accounted for. Following a comprehensive examination of the individual quark-sector contributions to octet baryon magnetic moments, numerous opportunities to observe and test the underlying structure of baryons and the nature of chiral nonanalytic behavior in QCD and its quenched variants are discussed. In particular, the valence u-quark contribution to the proton magnetic moment provides the optimal opportunity to directly view nonanalytic behavior associated with the meson cloud of full QCD and the quenched meson cloud of quenched QCD. The u quark in Σ + provides the best opportunity to display the artifacts of the quenched approximation

Holographic quenches towards a Lifshitz point

Energy Technology Data Exchange (ETDEWEB)

Camilo, Giancarlo [Instituto de Física, Universidade de São Paulo,C.P. 66318, CEP: 05315-970, São Paulo (Brazil); Cuadros-Melgar, Bertha [Escola de Engenharia de Lorena, Universidade de São Paulo,Estrada Municipal do Campinho S/N, CEP: 12602-810, Lorena (Brazil); Abdalla, Elcio [Instituto de Física, Universidade de São Paulo,C.P. 66318, CEP: 05315-970, São Paulo (Brazil)

2016-02-01

We use the holographic duality to study quantum quenches of a strongly coupled CFT that drive the theory towards a non-relativistic fixed point with Lifshitz scaling. We consider the case of a Lifshitz dynamical exponent z close to unity, where the non-relativistic field theory can be understood as a specific deformation of the corresponding CFT and, hence, the standard holographic dictionary can be applied. On the gravity side this amounts to finding a dynamical bulk solution which interpolates between AdS and Lishitz spacetimes as time evolves. We show that an asymptotically Lifshitz black hole is always formed in the final state. This indicates that it is impossible to reach the vacuum state of the Lifshitz theory from the CFT vacuum as a result of the proposed quenching mechanism. The nonequilibrium dynamics following the breaking of the relativistic scaling symmetry is also probed using both local and non-local observables. In particular, we conclude that the equilibration process happens in a top-down manner, i.e., the symmetry is broken faster for UV modes.

Spectral analysis of colour-quenched and chemically quenched C 14 samples

International Nuclear Information System (INIS)

Grau Malonda, A.; Scott Guillearrd, P.E.

1987-01-01

Pairs of pulse height distribution curves, of C-14 samples, colour quenched and chemically quenched were obtained. The possibility to choose a counting window in order to obtain the counting efficiency curves, for both type of quenching was studied. (author). 7 figs., 7 refs

Spectral analysis of colour-quenched and chemically quenched C-14 samples

International Nuclear Information System (INIS)

Scott, P. E.; Grau, A.

1987-01-01

In this paper pairs of pulse height distribution curves, of C-14 samples, colour-quenched and chemically quenched was obtained. The possibility to choose a counting window in order to obtain the counting efficiency curves, for both type of quenching was studied. (Author) 7 refs

Remote monitoring of dynamic canopy photosynthesis with high time resolution light-induced fluorescence transients

Czech Academy of Sciences Publication Activity Database

Wyber, R.; Osmond, B.; Ashcroft, M. B.; Malenovský, Zbyněk; Robinson, S. A.

(2017) ISSN 0829-318X Institutional support: RVO:86652079 Keywords : constitutive heat dissipation * electron transport rate * LIFT * non-photochemical quenching * PAM * photosynthetically active radiation * sunfleck Subject RIV: EH - Ecology, Behaviour Impact factor: 3.653, year: 2016

A quenched study of the Schroedinger functional with chirally rotated boundary conditions. Non-preturbative tuning

Energy Technology Data Exchange (ETDEWEB)

Lopez, J. Gonzalez [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik; Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Jansen, K. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Renner, D.B. [Jefferson Lab, Newport News, VA (United States); Shindler, A. [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik

2012-08-23

The use of chirally rotated boundary conditions provides a formulation of the Schroedinger functional that is compatible with automatic O(a) improvement of Wilson fermions up to O(a) boundary contributions. The elimination of bulk O(a) effects requires the non-perturbative tuning of the critical mass and one additional boundary counterterm. We present the results of such a tuning in a quenched setup for several values of the renormalized gauge coupling, from perturbative to nonperturbative regimes, and for a range of lattice spacings. We also check that the correct boundary conditions and symmetries are restored in the continuum limit. (orig.)

A quenched study of the Schroedinger functional with chirally rotated boundary conditions. Non-preturbative tuning

International Nuclear Information System (INIS)

Lopez, J. Gonzalez; Jansen, K.; Renner, D.B.; Shindler, A.

2012-01-01

The use of chirally rotated boundary conditions provides a formulation of the Schroedinger functional that is compatible with automatic O(a) improvement of Wilson fermions up to O(a) boundary contributions. The elimination of bulk O(a) effects requires the non-perturbative tuning of the critical mass and one additional boundary counterterm. We present the results of such a tuning in a quenched setup for several values of the renormalized gauge coupling, from perturbative to nonperturbative regimes, and for a range of lattice spacings. We also check that the correct boundary conditions and symmetries are restored in the continuum limit. (orig.)

A fluorescence quenching test for the detection of flavonoid transformation.

Science.gov (United States)

Schoefer, L; Braune, A; Blaut, M

2001-11-13

A novel fluorescence quenching test for the detection of flavonoid degradation by microorganisms was developed. The test is based on the ability of the flavonoids to quench the fluorescence of 1,6-diphenyl-1,3,5-hexatriene (DPH). Several members of the anthocyanidins, flavones, isoflavones, flavonols, flavanones, dihydroflavanones, chalcones, dihydrochalcones and catechins were tested with regard to their quenching properties. The anthocyanidins were the most potent quenchers of DPH fluorescence, while the flavanones, dihydroflavanones and dihydrochalcones, quenched the fluorescence only weakly. The catechins had no visible impact on DPH fluorescence. The developed test allows a quick and easy differentiation between flavonoid-degrading and flavonoid-non-degrading bacteria. The investigation of individual reactions of flavonoid transformation with the developed test system is also possible.

Comparison of the quench experiments CORA-12, CORA-13, CORA-17

International Nuclear Information System (INIS)

Hagen, S.; Hofmann, P.; Noack, V.; Sepold, L.; Schanz, G.; Schumacher, G.

1996-08-01

The CORA quench experiments 12, 13 (PWR) und 17 (BWR) are in agreement with the inpile tests LOFT LP-FP-2 and PBF SFD-ST and the TMI accident: Flooding of hot Zircaloy clad fuel rods does not result in an immediate cooldown of the bundle, but produces a remarkable temporary temperature increase connected to a strong peak in hydrogen production. For the preparation of new quench bundle tests, necessary for the understanding of the mechanisms governing the quench process and support for validation of future quench models in SFD codes the three tests are compared to each other and to the relevant non-quench tests CORA-29 (PWR) and CORA-16 (BWR). The PWR tests CORA-12 and CORA-13 are of the same geometrical arrangement and test conduct. An exception is the shorter time between power shutdown and quench initiation for CORA 13, resulting in a higher temperature of the bundle at start of quenching. The BWR test CORA-17 used B 4 C absorber and Zircaloy channel box walls, but was in respect to the delay time between power shutdown and start of quenching similar to test CORA-12. (orig./GL) [de

Thermo-cleavable polymers: Materials with enhanced photochemical stability

DEFF Research Database (Denmark)

Manceau, Matthieu; Petersen, Martin Helgesen; Krebs, Frederik C

2010-01-01

Photochemical stability of three thermo-cleavable polymers was investigated as thin films under atmospheric conditions. A significant increase in lifetime was observed once the side-chain was cleaved emphasizing the detrimental effect of solubilizing groups on the photochemical stability of conju......Photochemical stability of three thermo-cleavable polymers was investigated as thin films under atmospheric conditions. A significant increase in lifetime was observed once the side-chain was cleaved emphasizing the detrimental effect of solubilizing groups on the photochemical stability...... of conjugated polymers. In addition to their ease of processing, thermo-cleavable polymers thus also offer a greater intrinsic stability under illumination....

Hamiltonian truncation approach to quenches in the Ising field theory

Directory of Open Access Journals (Sweden)

T. Rakovszky

2016-10-01

Full Text Available In contrast to lattice systems where powerful numerical techniques such as matrix product state based methods are available to study the non-equilibrium dynamics, the non-equilibrium behaviour of continuum systems is much harder to simulate. We demonstrate here that Hamiltonian truncation methods can be efficiently applied to this problem, by studying the quantum quench dynamics of the 1+1 dimensional Ising field theory using a truncated free fermionic space approach. After benchmarking the method with integrable quenches corresponding to changing the mass in a free Majorana fermion field theory, we study the effect of an integrability breaking perturbation by the longitudinal magnetic field. In both the ferromagnetic and paramagnetic phases of the model we find persistent oscillations with frequencies set by the low-lying particle excitations not only for small, but even for moderate size quenches. In the ferromagnetic phase these particles are the various non-perturbative confined bound states of the domain wall excitations, while in the paramagnetic phase the single magnon excitation governs the dynamics, allowing us to capture the time evolution of the magnetisation using a combination of known results from perturbation theory and form factor based methods. We point out that the dominance of low lying excitations allows for the numerical or experimental determination of the mass spectra through the study of the quench dynamics.

Participation of intracellular and extracellular pH changes in photosynthetic response development induced by variation potential in pumpkin seedlings.

Science.gov (United States)

Sherstneva, O N; Vodeneev, V A; Katicheva, L A; Surova, L M; Sukhov, V S

2015-06-01

Electrical signals presented in plants by action potential and by variation potential (VP) can induce a reversible inactivation of photosynthesis. Changes in the intracellular and extracellular pH during VP generation are a potential mechanism of photosynthetic response induction; however, this hypothesis requires additional experimental investigation. The purpose of the present work was to analyze the influence of pH changes on induction of the photosynthetic response in pumpkin. It was shown that a burning of the cotyledon induced VP propagation into true leaves of pumpkin seedlings inducing a decrease in the photosynthetic CO2 assimilation and an increase in non-photochemical quenching of fluorescence, whereas respiration was activated insignificantly. The photosynthetic response magnitude depended linearly on the VP amplitude. The intracellular and extracellular concentrations of protons were analyzed using pH-sensitive fluorescent probes, and the VP generation was shown to be accompanied by apoplast alkalization (0.4 pH unit) and cytoplasm acidification (0.3 pH unit). The influence of changes in the incubation medium pH on the non-photochemical quenching of fluorescence of isolated chloroplasts was also investigated. It was found that acidification of the medium stimulated the non-photochemical quenching, and the magnitude of this increase depended on the decrease in pH. Our results confirm the contribution of changes in intracellular and extracellular pH to induction of the photosynthetic response caused by VP. Possible mechanisms of the influence of pH changes on photosynthesis are discussed.

The fate of a gray soliton in a quenched Bose-Einstein condensate

Science.gov (United States)

Gamayun, Oleksandr; Bezvershenko, Yulia; Cheianov, Vadim

2015-03-01

We investigate the destiny of a gray soliton in a repulsive one-dimensional Bose-Einstein condensate undergoing a sudden quench of the non-linearity parameter. The outcome of the quench is found to depend dramatically on the ratio η of the final and initial values of the speed of sound. For integer η the soliton splits into exactly 2 η - 1 solitons. For non-integer η the soliton decays into multiple solitons and Bogoliubov modes. The case of integer η is analyzed in detail. The parameters of solitons in the out-state are found explicitly. Our approach exploits the inverse scattering method and can be easily used for the similar quenches in any classical integrable system.

Quench detection system of the EURATOM coil for the Large Coil Task

International Nuclear Information System (INIS)

Noether, G.; Gauss, S.; Maurer, W.; Siewerdt, L.; Ulbricht, A.; Wuechner, F.

1989-01-01

A special quench detection system has been developed for the EURATOM Large Coil Task (LCT) coil. The system is based on a bridge circuit which uses a special 'two in hand' winding technique for the pancakes of the EURATOM LCT coil. The electronic circuit was designed in a fail safe way to prevent failure of the quench detector due to failure of one of its components. A method for quick balancing of the quench detection system in a large toroidal magnet system was applied. The quench detection system worked very reliably during the experimental phase of the LCT and was within the quench detection level setting of 50 mV, i.e. the system was not sensitive to poloidal field transients at or below this level. Non-electrical methods for quench detection were also investigated. (author)

Development of rapidly quenched nickel-based non-boron filler metals for brazing corrosion resistant steels

Science.gov (United States)

Ivannikov, A.; Kalin, B.; Suchkov, A.; Penyaz, M.; Yurlova, M.

2016-04-01

Corrosion-resistant steels are stably applied in modern rocket and nuclear technology. Creating of permanent joints of these steels is a difficult task that can be solved by means of welding or brazing. Recently, the use rapidly quenched boron-containing filler metals is perspective. However, the use of such alloys leads to the formation of brittle borides in brazing zone, which degrades the corrosion resistance and mechanical properties of the compounds. Therefore, the development of non-boron alloys for brazing stainless steels is important task. The study of binary systems Ni-Be and Ni-Si revealed the perspective of replacing boron in Ni-based filler metals by beryllium, so there was the objective of studying of phase equilibrium in the system Ni-Be-Si. The alloys of the Ni-Si-Be with different contents of Si and Be are considered in this paper. The presence of two low-melting components is revealed during of their studying by methods of metallography analysis and DTA. Microhardness is measured and X-ray diffraction analysis is conducted for a number of alloys of Ni-Si-Be. The compositions are developed on the basis of these data. Rapidly quenched brazing alloys can be prepared from these compositions, and they are suitable for high temperature brazing of steels.

Non-perturbative renormalization of the static vector current and its O(a)-improvement in quenched QCD

Energy Technology Data Exchange (ETDEWEB)

Palombi, F.

2007-06-15

We carry out the renormalization and the Symanzik O(a)-improvement programme for the static vector current in quenched lattice QCD. The scale independent ratio of the renormalization constants of the static vector and axial currents is obtained non-perturbatively from an axial Ward identity with Wilson-type light quarks and various lattice discretizations of the static action. The improvement coefficients c{sub V}{sup stat} and b{sub V}{sup stat} are obtained up to O(g{sub 4}{sup 0})-terms by enforcing improvement conditions respectively on the axial Ward identity and a three-point correlator of the static vector current. A comparison between the non-perturbative estimates and the corresponding one-loop results shows a non-negligible effect of the O(g{sub 4}{sup 0})-terms on the improvement coefficients but a good accuracy of the perturbative description of the ratio of the renormalization constants. (orig.)

Quench detection of superconducting magnets using ultrasonic wave

International Nuclear Information System (INIS)

Ninomiya, A.; Sakaniwa, K.; Kado, H.; Ishigohka, T.; Higo, Y.

1989-01-01

A method to detect a quench of a superconducting magnet using ultrasonic technique is presented. This method is a kind of non-destructive one which monitors a change of acoustic transfer function of a superconducting magnet induced by a local temperature rise or an epoxy crack etc.. Some experiments are carried out on a small epoxy impregnated magnet. The experimental results show that a local temperature rise of about 2-3K can be detected by this method. And, some leading symptoms before quench were detected

Laser induced photochemical and photophysical processes in fuel reprocessing: present scenario and future prospects

International Nuclear Information System (INIS)

Bhowmick, G.K.; Sarkar, S.K.; Ramanujam, A.

2001-01-01

State-of-art lasers can meet the very stringent requirements of nuclear technology and hence find application in varied areas of nuclear fuel cycle. Here, we discuss two specific applications in nuclear fuel reprocessing namely (a) add-on photochemical modifications of PUREX process where photochemical reactors replace the chemical reactors, and (b) fast, matrix independent sensitive laser analytical techniques. The photochemical modifications based on laser induced valency adjustment offers efficient separation, easy maintenance and over all reduction in the volume of radioactive waste. The analytical technique of time resolved laser induced fluorescence (TRLIF) has several attractive features like excellent sensitivity, element selective, and capability of on line remote process monitoring. For optically opaque solutions, optical excitation is detected by its conversion into thermal energy by non-radiative relaxation processes using the photo-thermal spectroscopic techniques. (author)

Zinc Oxide Nano crystals Synthesized by Quenching Technique

International Nuclear Information System (INIS)

Norhayati Abu Bakar; Akrajas Ali Umar; Muhamad Mat Salleh; Muhammad Yahya

2011-01-01

This paper reports an attempt to synthesize non toxic zinc oxide (ZnO) nano crystals using a simple quenching technique. The hot zinc oxide powder was quenched in hexane solution to obtain ZnO nano crystals. As the result, diameter size of the synthesized ZnO is 200 nm. It was also exhibited a good crystalline with wurtzite phase. The nano crystals properties of ZnO were revealed from good absorbance and green luminescence under UV exposure. This may be related with oxygen vacancy ionization during the annealing process. (author)

Doubler system quench detection threshold

International Nuclear Information System (INIS)

Kuepke, K.; Kuchnir, M.; Martin, P.

1983-01-01

The experimental study leading to the determination of the sensitivity needed for protecting the Fermilab Doubler from damage during quenches is presented. The quench voltage thresholds involved were obtained from measurements made on Doubler cable of resistance x temperature and voltage x time during quenches under several currents and from data collected during operation of the Doubler Quench Protection System as implemented in the B-12 string of 20 magnets. At 4kA, a quench voltage threshold in excess of 5.OV will limit the peak Doubler cable temperature to 452K for quenches originating in the magnet coils whereas a threshold of 0.5V is required for quenches originating outside of coils

Zeaxanthin Has Enhanced Antioxidant Capacity with Respect to All Other Xanthophylls in Arabidopsis Leaves and Functions Independent of Binding to PSII Antennae1[C][W

Science.gov (United States)

Havaux, Michel; Dall'Osto, Luca; Bassi, Roberto

2007-01-01

The ch1 mutant of Arabidopsis (Arabidopsis thaliana) lacks chlorophyll (Chl) b. Leaves of this mutant are devoid of photosystem II (PSII) Chl-protein antenna complexes and have a very low capacity of nonphotochemical quenching (NPQ) of Chl fluorescence. Lhcb5 was the only PSII antenna protein that accumulated to a significant level in ch1 mutant leaves, but the apoprotein did not assemble in vivo with Chls to form a functional antenna. The abundance of Lhca proteins was also reduced to approximately 20% of the wild-type level. ch1 was crossed with various xanthophyll mutants to analyze the antioxidant activity of carotenoids unbound to PSII antenna. Suppression of zeaxanthin by crossing ch1 with npq1 resulted in oxidative stress in high light, while removing other xanthophylls or the PSII protein PsbS had no such effect. The tocopherol-deficient ch1 vte1 double mutant was as sensitive to high light as ch1 npq1, and the triple mutant ch1 npq1 vte1 exhibited an extreme sensitivity to photooxidative stress, indicating that zeaxanthin and tocopherols have cumulative effects. Conversely, constitutive accumulation of zeaxanthin in the ch1 npq2 double mutant led to an increased phototolerance relative to ch1. Comparison of ch1 npq2 with another zeaxanthin-accumulating mutant (ch1 lut2) that lacks lutein suggests that protection of polyunsaturated lipids by zeaxanthin is enhanced when lutein is also present. During photooxidative stress, α-tocopherol noticeably decreased in ch1 npq1 and increased in ch1 npq2 relative to ch1, suggesting protection of vitamin E by high zeaxanthin levels. Our results indicate that the antioxidant activity of zeaxanthin, distinct from NPQ, can occur in the absence of PSII light-harvesting complexes. The capacity of zeaxanthin to protect thylakoid membrane lipids is comparable to that of vitamin E but noticeably higher than that of all other xanthophylls of Arabidopsis leaves. PMID:17932304

Zeaxanthin has enhanced antioxidant capacity with respect to all other xanthophylls in Arabidopsis leaves and functions independent of binding to PSII antennae.

Science.gov (United States)

Havaux, Michel; Dall'osto, Luca; Bassi, Roberto

2007-12-01

The ch1 mutant of Arabidopsis (Arabidopsis thaliana) lacks chlorophyll (Chl) b. Leaves of this mutant are devoid of photosystem II (PSII) Chl-protein antenna complexes and have a very low capacity of nonphotochemical quenching (NPQ) of Chl fluorescence. Lhcb5 was the only PSII antenna protein that accumulated to a significant level in ch1 mutant leaves, but the apoprotein did not assemble in vivo with Chls to form a functional antenna. The abundance of Lhca proteins was also reduced to approximately 20% of the wild-type level. ch1 was crossed with various xanthophyll mutants to analyze the antioxidant activity of carotenoids unbound to PSII antenna. Suppression of zeaxanthin by crossing ch1 with npq1 resulted in oxidative stress in high light, while removing other xanthophylls or the PSII protein PsbS had no such effect. The tocopherol-deficient ch1 vte1 double mutant was as sensitive to high light as ch1 npq1, and the triple mutant ch1 npq1 vte1 exhibited an extreme sensitivity to photooxidative stress, indicating that zeaxanthin and tocopherols have cumulative effects. Conversely, constitutive accumulation of zeaxanthin in the ch1 npq2 double mutant led to an increased phototolerance relative to ch1. Comparison of ch1 npq2 with another zeaxanthin-accumulating mutant (ch1 lut2) that lacks lutein suggests that protection of polyunsaturated lipids by zeaxanthin is enhanced when lutein is also present. During photooxidative stress, alpha-tocopherol noticeably decreased in ch1 npq1 and increased in ch1 npq2 relative to ch1, suggesting protection of vitamin E by high zeaxanthin levels. Our results indicate that the antioxidant activity of zeaxanthin, distinct from NPQ, can occur in the absence of PSII light-harvesting complexes. The capacity of zeaxanthin to protect thylakoid membrane lipids is comparable to that of vitamin E but noticeably higher than that of all other xanthophylls of Arabidopsis leaves.

Photochemical dynamics of surface oriented molecules

International Nuclear Information System (INIS)

Ho, W.

1992-01-01

The period 8/01/91-7/31/92 is the first year of a new project titled ''Photochemical Dynamics of Surface Oriented Molecules'', initiated with DOE Support. The main objective of this project is to understand the dynamics of elementary chemical reactions by studying photochemical dynamics of surface-oriented molecules. In addition, the mechanisms of photon-surface interactions need to be elucidated. The strategy is to carry out experiments to measure the translational energy distribution, as a function of the angle from the surface normal, of the photoproducts by time-of-flight (TOF) technique by varying the photon wavelength, intensity, polarization, and pulse duration. By choosing adsorbates with different bonding configuration, the effects of adsorbate orientation on surface photochemical dynamics can be studied

Investigation of an overheated PWR-type fuel rod simulator bundle cooled down by steam. Pt. 1: experimental and calculational results of the QUENCH-04 test. Pt. 2: application of the SVECHA/QUENCH code to the analysis of the QUENCH-01 and QUENCH-04 bundle tests

International Nuclear Information System (INIS)

Sepold, L.; Hofmann, P.; Homann, C.

2002-04-01

The QUENCH experiments are to investigate the hydrogen source term that results from the water injection into an uncovered core of a light-water reactor (LWR). The test bundle is made of 21 fuel rod simulators with a length of approximately 2.5 m. 20 fuel rod simulators are heated over a length of 1024 mm, the one unheated fuel rod simulator is located in the center of the test bundle. Heating is carried out electrically using 6-mm-diameter tungsten heating elements installed in the center of the rods and surrounded by annular ZrO 2 pellets. The rod cladding is identical to that used in LWRs: Zircaloy-4, 10.75 mm outside diameter, 0.725 mm wall thickness. The test bundle is instrumented with thermocouples attached to the cladding and the shroud at 17 different elevations with an axial distance between the thermocouples of 100 mm. During the entire test up to the cooldown phase, superheated steam together with the argon as carrier gas enters the test bundle at the bottom end and leaves the test section at the top together with the hydrogen that is produced in the zirconium-steam reaction. The hydrogen is analyzed by three different instruments: two mass spectrometers and a ''Caldos 7 G'' hydrogen measuring device (based on the principle of heat conductivity). Part I of this report describes the results of test QUENCH-04 performed in the QUENCH test facility at the Forschungszentrum Karlsruhe on June 30, 1999. The objective of the experiment QUENCH-04 was to investigate the reaction of the non-preoxidized rod cladding on cooldown by steam rather than quenching by water. Part II of the present report deals with the results of the SVECHA/QUENCH (S/Q) code application to the FZK QUENCH bundle tests. The adaptation of the S/Q code to such kind of calculations is described. The numerical procedure of the recalculation of the temperature test data, and the preparation for the S/Q code input is presented. In particular, the results of the QUENCH-01 and QUENCH-04 test

QUENCH: A software package for the determination of quenching curves in Liquid Scintillation counting

International Nuclear Information System (INIS)

Cassette, Philippe

2016-01-01

In Liquid Scintillation Counting (LSC), the scintillating source is part of the measurement system and its detection efficiency varies with the scintillator used, the vial and the volume and the chemistry of the sample. The detection efficiency is generally determined using a quenching curve, describing, for a specific radionuclide, the relationship between a quenching index given by the counter and the detection efficiency. A quenched set of LS standard sources are prepared by adding a quenching agent and the quenching index and detection efficiency are determined for each source. Then a simple formula is fitted to the experimental points to define the quenching curve function. The paper describes a software package specifically devoted to the determination of quenching curves with uncertainties. The experimental measurements are described by their quenching index and detection efficiency with uncertainties on both quantities. Random Gaussian fluctuations of these experimental measurements are sampled and a polynomial or logarithmic function is fitted on each fluctuation by χ"2 minimization. This Monte Carlo procedure is repeated many times and eventually the arithmetic mean and the experimental standard deviation of each parameter are calculated, together with the covariances between these parameters. Using these parameters, the detection efficiency, corresponding to an arbitrary quenching index within the measured range, can be calculated. The associated uncertainty is calculated with the law of propagation of variances, including the covariance terms. - Highlights: • The program “QUENCH” is devoted to the interpolation of quenching curves in LSC. • Functions are fitted to experimental data with uncertainties in both quenching and efficiency. • The parameters of the fitting function and the associated covariance matrix are evaluated. • The detection efficiency and uncertainty corresponding to a given quenching index is calculated.

Photochemical reactions of triplet benzophenone and anthraquinone molecules with amines in the gas phase

International Nuclear Information System (INIS)

Zalesskaya, G.A.; Sambor, E.G.; Belyi, N.N.

2004-01-01

The intermolecular photoinduced reactions between triplet ketone molecules and aliphatic amines and pyridine are studied by the quenching of delayed fluorescence of anthraquinone and benzophenone vapors by diethylamine, dibutylamine, cyclohexylamine, triethylamine, and pyridine. In the temperature range 423-573 K, the delayed fluorescence quenching rate constants k q are estimated from changes in the decay rate constant and the intensity of delayed fluorescence upon increasing pressure of bath gases. It is ascertained that, in the gas phase, the mixtures under study exhibit both a negative and a positive dependence of k q on temperature, which indicates that some photoinduced reactions do not have activation barriers. The rate constant k q is shown to increase with decreasing ionization potential of the electron donors. This points to the importance of interactions with charge transfer in the photoreaction of triplet ketone molecules with aliphatic amines and pyridine in the gas phase. The relationship between k q and the change in the free energy ΔG upon the photoinduced intermolecular electron transfer, which is the primary stage of the photochemical reaction, is studied. It is shown that the dependence k q (ΔG) for the donor-acceptor pairs under study is described well by the Marcus equation, in which the average vibrational energies of the donor and acceptor are taken into account for the estimate of ΔG

effects of various effects of various quenching media on quenching

African Journals Online (AJOL)

eobe

ABSTRACT. Evaluation of palm kernel oil, cotton seed oil and olive oil as quenching media of 0.509Wt%C medium carbon steel ... Quenching is an essential element in developing the .... machine, heat treatment furnace, Avery Denison Izod.

Decoupling photochemical Fe(II) oxidation from shallow-water BIF deposition

DEFF Research Database (Denmark)

Konhauser, Kurt; Amskold, Larry; Lalonde, Stefan

2007-01-01

to the rise of atmospheric oxygen and the development of a protective ozone layer, the Earth's surface was subjected to high levels of ultraviolet radiation. Bulk ocean waters that were anoxic at this time could have supported high concentrations of dissolved Fe(II). Under such conditions, dissolved ferrous...... for biology [Fran??ois, L.M., 1986, Extensive deposition of banded iron formations was possible without photosynthesis. Nature 320, 352-354]. Here, we evaluate the potential importance of photochemical oxidation using a combination of experiments and thermodynamic models. The experiments simulate......-type systems, then we are driven to conclude that oxide-facies BIF are the product of a rapid, non-photochemical oxidative process, the most likely candidates being direct or indirect biological oxidation, and that a significant fraction of BIF could have initially been deposited as ferrous minerals. ?? 2007...

Biochemical and molecular changes in response to aluminium-stress in highbush blueberry (Vaccinium corymbosum L.).

Science.gov (United States)

Inostroza-Blancheteau, Claudio; Reyes-Díaz, Marjorie; Aquea, Felipe; Nunes-Nesi, Adriano; Alberdi, Miren; Arce-Johnson, Patricio

2011-09-01

Aluminium (Al) stress is an important factor limiting crop yields in acid soils. Despite this, very little is known about the mechanisms of resistance to this stress in woody plants. To understand the mechanisms of Al-toxicity and response in blueberries, we compared the impact of Al-stress in Al-resistant and Al-sensitive genotypes using Vaccinium corymbosum L. (Ericaceae) as a plant model. We investigated the effect of Al-stress on the physiological performance, oxidative metabolism and expression of genes that encode antioxidant enzymes in two V. corymbosum cultivars maintained hydroponically with AlCl(3) (0 and 100 μM). Microscopic analyses of Al-treated root tips suggested a higher degree of Al-induced morphological injury in Bluegold (sensitive genotype) compared to Brigitta (resistant genotype). Furthermore, the results indicated that Brigitta had a greater ability to control oxidative stress under Al-toxicity, as reflected by enhancement of several antioxidative and physiological properties (radical scavenging activity: RSA, superoxide dismutase: SOD and catalase: CAT; maximum quantum yield: Fv/Fm, effective quantum yield: ФPSII, electron transport rate: ETR and non-photochemical quenching: NPQ). Finally, we analyzed the expression of genes homologous to GST and ALDH, which were identified in a global expression analysis. In the resistant genotype, the expression of these genes in response to Al-stress was greater in leaves than in roots. Copyright © 2011 Elsevier Masson SAS. All rights reserved.

Friend or foe? Reactive oxygen species production, scavenging and signaling in plant response to environmental stresses.

Science.gov (United States)

Czarnocka, Weronika; Karpiński, Stanisław

2018-01-10

In the natural environment, plants are exposed to a variety of biotic and abiotic stress conditions that trigger rapid changes in the production and scavenging of reactive oxygen species (ROS). The production and scavenging of ROS is compartmentalized, which means that, depending on stimuli type, they can be generated and eliminated in different cellular compartments such as the apoplast, plasma membrane, chloroplasts, mitochondria, peroxisomes, and endoplasmic reticulum. Although the accumulation of ROS is generally harmful to cells, ROS play an important role in signaling pathways that regulate acclimatory and defense responses in plants, such as systemic acquired acclimation (SAA) and systemic acquired resistance (SAR). However, high accumulations of ROS can also trigger redox homeostasis disturbance which can lead to cell death, and in consequence, to a limitation in biomass and yield production. Different ROS have various half-lifetimes and degrees of reactivity toward molecular components such as lipids, proteins, and nucleic acids. Thus, they play different roles in intra- and extra-cellular signaling. Despite their possible damaging effect, ROS should mainly be considered as signaling molecules that regulate local and systemic acclimatory and defense responses. Over the past two decades it has been proven that ROS together with non-photochemical quenching (NPQ), hormones, Ca 2+ waves, and electrical signals are the main players in SAA and SAR, two physiological processes essential for plant survival and productivity in unfavorable conditions. Copyright © 2018. Published by Elsevier Inc.

Magnet Quench 101

OpenAIRE

Bottura, L.

2014-01-01

This paper gives a broad summary of the physical phenomena associated with the quench of a superconducting magnet. This paper gives a broad summary of the physical phenomena associated with the quench of a superconducting magnet.

Numerical Analysis of Heat Transfer During Quenching Process

Science.gov (United States)

Madireddi, Sowjanya; Krishnan, Krishnan Nambudiripad; Reddy, Ammana Satyanarayana

2018-04-01

A numerical model is developed to simulate the immersion quenching process of metals. The time of quench plays an important role if the process involves a defined step quenching schedule to obtain the desired characteristics. Lumped heat capacity analysis used for this purpose requires the value of heat transfer coefficient, whose evaluation requires large experimental data. Experimentation on a sample work piece may not represent the actual component which may vary in dimension. A Fluid-Structure interaction technique with a coupled interface between the solid (metal) and liquid (quenchant) is used for the simulations. Initial times of quenching shows boiling heat transfer phenomenon with high values of heat transfer coefficients (5000-2.5 × 105 W/m2K). Shape of the work piece with equal dimension shows less influence on the cooling rate Non-uniformity in hardness at the sharp corners can be reduced by rounding off the edges. For a square piece of 20 mm thickness, with 3 mm fillet radius, this difference is reduced by 73 %. The model can be used for any metal-quenchant combination to obtain time-temperature data without the necessity of experimentation.

Quenching experiments on niobium

International Nuclear Information System (INIS)

Schwirtlich, I.A.; Schultz, H.; Max-Planck-Institut fuer Metallforschung, Stuttgart

1980-01-01

High-purity niobium wire specimens have been quenched in superfluid helium from near the melting point in order to obtain information on vacancies in this material. The quenched-in resistivity Δsub(pQ) for a quench from 2600 K was very small (approximately 0.3 x 10 -12 Ω m) and near the limit of detection. It is assumed that large quenching losses are responsible for the small quenched-in resistance. From the experimental cooling curve estimates have been made for the formation and migration enthalpies (Hsub(1V)sup(F), Hsub(1V)sup(M)), where Hsub(1V)sup(M)+Hsub(1V)sup(F)=Qsub(1V)sup(SD)=3.62 ev. For Ssub(1V)sup(F), the formation entropy, two different values were assumed. (author)

Fluctuation kinetics of fluorescence hopping quenching in the Nd3+:Y2O3 spherical nanoparticles

International Nuclear Information System (INIS)

Orlovskii, Yu.V.; Popov, A.V.; Platonov, V.V.; Fedorenko, S.G.; Sildos, I.; Osipov, V.V.

2013-01-01

We study the peculiarities of energy transfer kinetics from the 4 F 3/2 laser level in the Nd 3+ doped Y 2 O 3 spherical nanoparticles of monoclinic phase synthesized by laser ablation of solid targets with subsequent recondensation in flow of air at atmospheric pressure comparing to the similar bulk crystal. We show that the fluorescence quenching in the nanoparticles is determined by two processes depending on Nd 3+ concentration and the degree of dehydration. At concentrations less than 1% the fluorescence quenching is mainly determined by direct (static) quenching by vibrations of OH − molecular groups associated with oxygen vacancies. At concentrations greater than 1 at % quenching is due to energy migration over neodymium ions, followed by the Nd 3+ –OH − quenching. In the latter case, the first time in a solid-state impurity laser medium we observe non-stationary kinetics on the entire length of a time-dependent luminescence quenching, starting from static decay and ending with fluctuation kinetics of fluorescence hopping quenching. -- Highlights: ► We prepare monoclinic Nd 3+ :Y 2 O 3 spherical NPs of mean D=12 nm by laser ablation of solid targets. ► We detect the fluorescence quenching of Nd 3+ the 4 F 3/2 level by vibrations of OH – molecular groups. ► We find that at 0.1% of Nd 3+ the process of static quenching by vibrations of OH – dominates. ► We find that Nd 3+ –Nd 3+ energy migration accelerates the Nd 3+ –OH − quenching at 1% of Nd 3+ . ► We detect non-stationary quenching kinetics ending with fluctuation stage of hopping quenching

Simulation of quenches in SSC magnets with passive quench protection

International Nuclear Information System (INIS)

Koepke, K.

1985-06-01

The relative ease of protecting an SSC magnet following a quench and the implications of quench protection on magnet reliability and operation are necessary inputs in a rational magnet selection process. As it appears likely that the magnet selection will be made prior to full scale prototype testing, an alternative means is required to ascertain the surviveability of contending magnet types. This paper attempts to provide a basis for magnet selection by calculating the peak expected quench temperatures in the 3 T Design C magnet and the 6 T Design D magnet as a function of magnet length. A passive, ''cold diode'' protection system has been assumed. The relative merits of passive versus active protection systems have been discussed in a previous report. It is therefore assumed that - given the experience gained from the Tevatron system - that an active quench protection system can be employed to protect the magnets in the eventuality of unreliable cold diode function

Melt quenching and coolability by water injection from below: Co-injection of water and non-condensable gas

International Nuclear Information System (INIS)

Cho, Dae H.; Page, Richard J.; Abdulla, Sherif H.; Anderson, Mark H.; Klockow, Helge B.; Corradini, Michael L.

2006-01-01

The interaction and mixing of high-temperature melt and water is the important technical issue in the safety assessment of water-cooled reactors to achieve ultimate core coolability. For specific advanced light water reactor (ALWR) designs, deliberate mixing of the core melt and water is being considered as a mitigative measure, to assure ex-vessel core coolability. The goal of our work is to provide the fundamental understanding needed for melt-water interfacial transport phenomena, thus enabling the development of innovative safety technologies for advanced LWRs that will assure ex-vessel core coolability. The work considers the ex-vessel coolability phenomena in two stages. The first stage is the melt quenching process and is being addressed by Argonne National Lab and University of Wisconsin in modified test facilities. Given a quenched melt in the form of solidified debris, the second stage is to characterize the long-term debris cooling process and is being addressed by Korean Maritime University via test and analyses. In this paper, experiments on melt quenching by the injection of water from below are addressed. The test section represented one-dimensional flow-channel simulation of the bottom injection of water into a core melt in the reactor cavity. The melt simulant was molten lead or a lead alloy (Pb-Bi). For the experimental conditions employed (i.e., melt depth and water flow rates), it was found that: (1) the volumetric heat removal rate increased with increasing water mass flow rate and (2) the non-condensable gas mixed with the injected water had no impairing effect on the overall heat removal rate. Implications of these current experimental findings for ALWR ex-vessel coolability are discussed

LHC magnet quench protection system

Science.gov (United States)

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.

LHC magnet quench protection system

International Nuclear Information System (INIS)

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

1994-01-01

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

QUENCH: A software package for the determination of quenching curves in Liquid Scintillation counting.

Science.gov (United States)

Cassette, Philippe

2016-03-01

In Liquid Scintillation Counting (LSC), the scintillating source is part of the measurement system and its detection efficiency varies with the scintillator used, the vial and the volume and the chemistry of the sample. The detection efficiency is generally determined using a quenching curve, describing, for a specific radionuclide, the relationship between a quenching index given by the counter and the detection efficiency. A quenched set of LS standard sources are prepared by adding a quenching agent and the quenching index and detection efficiency are determined for each source. Then a simple formula is fitted to the experimental points to define the quenching curve function. The paper describes a software package specifically devoted to the determination of quenching curves with uncertainties. The experimental measurements are described by their quenching index and detection efficiency with uncertainties on both quantities. Random Gaussian fluctuations of these experimental measurements are sampled and a polynomial or logarithmic function is fitted on each fluctuation by χ(2) minimization. This Monte Carlo procedure is repeated many times and eventually the arithmetic mean and the experimental standard deviation of each parameter are calculated, together with the covariances between these parameters. Using these parameters, the detection efficiency, corresponding to an arbitrary quenching index within the measured range, can be calculated. The associated uncertainty is calculated with the law of propagation of variances, including the covariance terms. Copyright © 2015 Elsevier Ltd. All rights reserved.

Quenching effect on properties of Bi-Sr-Ca-Cu-O superconducting ceramics of various composition

International Nuclear Information System (INIS)

Amitin, E.B.; Gromilov, S.A.; Naumov, V.N.; Royak, A.Ya.; Starikov, M.A.

1989-01-01

Bismuth ceramics quenching effect on superconducting properties of samples of various composition is investigated. Two types of quenching effect on sample properties are detected: an increase of superconducting transition temperature T c by 15-20 K; broadening of temperature interval of the phase transition without anynatable T c displacement. X ray diffraction investigations have not detected sufficient differences in diffraction patterns of quenched and non-quenched samples. Within the limits of composition analysis by oxygen (±3%) no change of its content prior to and after quenching is detected. A correlation between the presence of an amorphous phase in a sample and the type of quenching effect is observed: T c increases in ceramics where an amorphous component is detected

Quenching of photoluminescence of colloidal ZnO nanocrystals by nitronyl nitroxide radicals

Energy Technology Data Exchange (ETDEWEB)

Stroyuk, Oleksandr L., E-mail: stroyuk@inphyschem-nas.kiev.ua [L.V. Pysarzhevsky Institute of Physical Chemistry of National Academy of Sciences of Ukraine, 31 Nauky avenue, 03028 Kyiv (Ukraine); Yakovenko, Anastasiya V.; Raevskaya, Oleksandra E. [L.V. Pysarzhevsky Institute of Physical Chemistry of National Academy of Sciences of Ukraine, 31 Nauky avenue, 03028 Kyiv (Ukraine); Plyusnin, Victor F. [Institute of Chemical Kinetics and Combustion of Siberian Branch of Russian Academy of Sciences, Novosibirsk (Russian Federation)

2014-11-15

Quenching of the photoluminescence of colloidal zinc oxide nanocrystals by a series of stable nitronyl nitroxide radicals was studied by means of stationary and time-resolved luminescence spectroscopy. Among the studied radicals the most efficient quenchers of the ZnO luminescence are the carboxyl-substituted species. The meta-substituted radical was found to be a more active quencher, than para-substituted one due to a closer proximity of the radical center to the nanocrystals surface. The PL quenching has a complex dynamic/static character. The dynamic quenching arises from photocatalytic radical reduction by ZnO conduction band electrons, while the static quenching is caused by adsorption of the photoreduction products on the nanocrystal surface. The non-substituted and OH-substituted radicals are inferior to the products of their photoreduction in capability of adsorption of the ZnO surface, and the quenching is dominated by interactions between the nanocrystals and photoreduced hydroxylamines. In case of COOH-substituted radicals, however, the radicals compete with the photoreduction products for the surface sites of ZnO nanocrystals resulting in a dynamic character of photoluminescence quenching.

Architecture of a software quench management system

International Nuclear Information System (INIS)

Jerzy M. Nogiec et al.

2001-01-01

Testing superconducting accelerator magnets is inherently coupled with the proper handling of quenches; i.e., protecting the magnet and characterizing the quench process. Therefore, software implementations must include elements of both data acquisition and real-time controls. The architecture of the quench management software developed at Fermilab's Magnet Test Facility is described. This system consists of quench detection, quench protection, and quench characterization components that execute concurrently in a distributed system. Collaboration between the elements of quench detection, quench characterization and current control are discussed, together with a schema of distributed saving of various quench-related data. Solutions to synchronization and reliability in such a distributed quench system are also presented

A Universal Protocol for Photochemical Covalent Immobilization of Intact Carbohydrates for the Preparation of Carbohydrate Microarrays

Science.gov (United States)

Wang, Huibin; Zhang, Yiming; Yuan, Xun; Chen, Yi; Yan, Mingdi

2010-01-01

A universal photochemical method has been established for the immobilization of intact carbohydrates and their analogues, and for the fabrication of carbohydrate microarrays. The method features the use of perfluorophenyl azide (PFPA)-modified substrates and the photochemical reaction of surface azido groups with printed carbohydrates. Various aldoses, ketoses, non-reducing sugars such as alditols and their derivatives can be directly arrayed on the PFPA-modified chips. The lectin-recognition ability of arrayed mannose, glucose and their oligo- and polysaccharides were confirmed using surface plasmon resonance imaging and laser-induced fluorescence imaging. PMID:21138274

A Precise determination of B(K) in quenched QCD

CERN Document Server

Dimopoulos, P.; Palombi, F.; Pena, C.; Sint, S.; Vladikas, A.

2006-01-01

The $B_K$ parameter is computed in quenched lattice QCD with Wilson twisted mass fermions. Two variants of tmQCD are used; in both of them the relevant $\\Delta S = 2$ four-fermion operator is renormalised multiplicatively. The renormalisation adopted is non-perturbative, with a Schroedinger functional renormalisation condition. Renormalisation group running is also non-perturbative, up to very high energy scales. In one of the two tmQCD frameworks the computations have been performed at the physical $K$-meson mass, thus eliminating the need of mass extrapolations. Simulations have been performed at several lattice spacings and the continuum limit was reached by combining results from both tmQCD regularisations. Finite volume effects have been partially checked and turned out to be small. Exploratory studies have also been performed with non-degenerate valence flavours. The final result for the RGI bag parameter, with all sources of uncertainty (except quenching) under control, is $\\hat B_K =0.789 \\pm 0.046$.

Thermal quenching of thermoluminescence in quartz samples of various origin

International Nuclear Information System (INIS)

Subedi, B.; Oniya, E.; Polymeris, G.S.; Afouxenidis, D.; Tsirliganis, N.C.; Kitis, G.

2011-01-01

The effect of thermal quenching stands among the most important properties in the thermoluminescence (TL) of quartz on which many applications of TL are based. Since the quartz samples used in various applications are all of different origin it is useful to investigate whether the values of the thermal quenching parameters, i.e. the activation energy for thermal quenching W and a parameter C which describes the ratio of non-radiative to radiative luminescence transitions, evaluated mainly in specific quartz samples can be extrapolated to quartz samples of unknown origin as well as to quartz samples which are annealed at high temperatures. In the present work the TL glow curve of a series of un-annealed and annealed natural and synthetic quartz samples were studied as a function of the heating rate between 0.25 K/s and 16 K/s. Using an indirect fitting method it was found that the thermal quenching parameters W and C in most of the quartz samples are very similar to the values accepted in the literature. Furthermore, in some cases the thermal quenching parameters W and C are not the same for all TL glow-peaks in the same glow-curve. Finally, the strong external treatment of annealing the quartz samples at very high temperature can also influence at least one of the thermal quenching parameters.

The Role of Quench-back in the Passive Quench Protection of Long Solenoids with Coil Sub-division

International Nuclear Information System (INIS)

Green, Michael A.; Guo, XingLong; Wang, Li; Pan, Heng; Wu, Hong

2009-01-01

This paper describes how a passive quench protection system can be applied to long superconducting solenoid magnets. When a solenoid coil is long compared to its thickness, the magnet quench process will be dominated by the time needed for uench propagation along the magnet length. Quench-back will permit a long magnet to quench more rapidly in a passive way. Quenchback from a conductive (low resistivity) mandrel is essential for spreading the quench along the length of a magnet. The andrel must be inductively coupled to the magnet circuit that is being quenched. Current induced in the mandrel by di/dt in the magnet produces heat in the mandrel, which in turn causes the superconducting coil wound on the mandrel to quench. Sub-divisions often employed to reduce the voltages to ground within the coil. This paper explores when it is possible for quench-back to be employed for passive quench protection. The role of sub-division of the coil is discussed for long magnets.

Effects of quenching and partial quenching on QCD penguin matrix elements

NARCIS (Netherlands)

Golterman, Maarten; Pallante, Elisabetta

2002-01-01

We point out that chiral transformation properties of penguin operators change in the transition from unquenched to (partially) quenched QCD. The way in which this affects the lattice determination of weak matrix elements can be understood in the framework of (partially) quenched chiral perturbation

Mechanisms of energy transfer and conversion in plant Light-Harvesting Complex II

Energy Technology Data Exchange (ETDEWEB)

Barros, Tiago Ferreira de

2009-09-24

The light-harvesting complex of photosystem II (LHC-II) is the major antenna complex in plant photosynthesis. It accounts for roughly 30% of the total protein in plant chloroplasts, which makes it arguably the most abundant membrane protein on Earth, and binds about half of plant chlorophyll (Chl). The complex assembles as a trimer in the thylakoid membrane and binds a total of 54 pigment molecules, including 24 Chl a, 18 Chl b, 6 lutein (Lut), 3 neoxanthin (Neo) and 3 violaxanthin (Vio). LHC-II has five key roles in plant photosynthesis. It: (1) harvests sunlight and transmits excitation energy to the reaction centres of photosystems II and I, (2) regulates the amount of excitation energy reaching each of the two photosystems, (3) has a structural role in the architecture of the photosynthetic supercomplexes, (4) contributes to the tight appression of thylakoid membranes in chloroplast grana, and (5) protects the photosynthetic apparatus from photo damage by non photochemical quenching (NPQ). A major fraction of NPQ is accounted for its energy-dependent component qE. Despite being critical for plant survival and having been studied for decades, the exact details of how excess absorbed light energy is dissipated under qE conditions remain enigmatic. Today it is accepted that qE is regulated by the magnitude of the pH gradient ({delta}pH) across the thylakoid membrane. It is also well documented that the drop in pH in the thylakoid lumen during high-light conditions activates the enzyme violaxanthin de-epoxidase (VDE), which converts the carotenoid Vio into zeaxanthin (Zea) as part of the xanthophyll cycle. Additionally, studies with Arabidopsis mutants revealed that the photosystem II subunit PsbS is necessary for qE. How these physiological responses switch LHC-II from the active, energy transmitting to the quenched, energy-dissipating state, in which the solar energy is not transmitted to the photosystems but instead dissipated as heat, remains unclear and is the

Quench propagation and quench detection in the TF system of JT-60SA

International Nuclear Information System (INIS)

Lacroix, Benoit; Duchateau, Jean-Luc; Meuris, Chantal; Ciazynski, Daniel; Nicollet, Sylvie; Zani, Louis; Polli, Gian-Mario

2013-01-01

Highlights: • The JT-60SA primary quench detection system will be based on voltage measurements. • The early quench propagation was studied in the JT-60SA TF conductor. • The impact of the conductor jacket on the hot spot criterion was quantified. • The detection parameters were investigated for different quench initiations. -- Abstract: In the framework of the JT-60SA project, France and Italy will provide to JAEA 18 Toroidal Field (TF) coils including NbTi cable-in-conduit conductors. During the tokamak operation, these coils could experience a quench, an incidental event corresponding to the irreversible transition from superconducting state to normal resistive state. Starting from a localized disturbance, the normal zone propagates along the conductor and dissipates a large energy due to Joule heating, which can cause irreversible damages. The detection has to be fast enough (a few seconds) to trigger the current discharge, so as to dump the stored magnetic energy into an external resistor. The JT-60SA primary quench detection system will be based on voltage measurements, which are the most rapid technology. The features of the detection system must be adjusted so as to detect the most probable quenches, while avoiding inopportune fast safety discharges. This requires a reliable simulation of the early quench propagation, performed in this study with the Gandalf code. The conductor temperature reached during the current discharge must be kept under a maximal value, according to the hot spot criterion. In the present study, a hot spot criterion temperature of 150 K was taken into account and the role of each conductor component (strands, helium and conduit) was analyzed. The detection parameters were then investigated for different hypotheses regarding the quench initiation

Emission sources of non-methane volatile organic compounds (NMVOCs) and their contribution to photochemical ozone (O3) formation at an urban atmosphere in western India.

Science.gov (United States)

Yadav, R.; Sahu, L. K.; Tripathi, N.; Pal, D.

2017-12-01

Atmospheric non-methane volatile organic compounds (NMVOCs) were measured at a sampling site in Udaipur city of western India during 2015 to recognize their pollution levels, variation characteristics, sources and photochemical reactivity. The samples were analyzed for NMVOCs using a Gas Chromatograph equipped with Flame Ionization Detector (GC/FID) and Thermal Desorption (TD) system. The main focus on understand the sources responsible for NMVOC emissions, and evaluating the role of the identified sources towards ozone formation. Hourly variations of various NMVOC species indicate that VOCs mixing ratios were influenced by photochemical removal with OH radicals for reactive species, secondary formation for oxygenated VOCs. In general, higher mixing ratios were observed during winter/pre-monsoon and lower levels during the monsoon season due to the seasonal change in meteorological, transport path of air parcel and boundary layer conditions. The high levels of propane (C3H8) and butane (C4H10) show the dominance of LPG over the study location. The correlation coefficients of typical NMVOC pairs (ethylene/propylene, propylene/isoprene, and ethane/propane) depicted that vehicular emission and natural gas leakages were important sources for atmospheric hydrocarbons in Udaipur. Based on the annual data, PMF analysis suggest the source factors namely biomass burning/ bio-fuel, automobile exhaust, Industrial/ natural gas/power plant emissions, petrol/Diesel, gasoline evaporation, and use of liquid petroleum gas (LPG) contribute to NMVOCs loading. The propylene-equivalent and ozone formation potential of NMVOCs have also been calculated in order to find out their OH reactivity and contribution to the photochemical ozone formation.

Photochemical reduction of uranyl ion with triphenylphosphine

International Nuclear Information System (INIS)

Brar, A.S.; Sidhu, M.S.; Sandhu, S.S.

1981-01-01

Photochemical reduction of uranyl ion with triphenylphosphine has been studied in acetone-water medium in the presence of sulphuric acid at 346nm, 400nm and 434nm wavelengths. The photochemical reduction is of second order and increases with increase in hydrogen ion concentration. Absorption spectra of uranyl ion in acidic medium and uranyl ion with triphenylphosphine do not show any ground state complex formation. The value of quantum yield increases with the wavelength of the radiation increase from 346 to 434nm. Plots of reciprocal of quantum yield for the formation of U(IV) versus reciprocal [triphenylphosphine] are linear. Products characterized by UV and visible, IR and TLC show the formation of U(IV) and triphenylphosphine oxide. On the basis of above observations mechanism of the photochemical reduction has been proposed. (author)

Temperature Profiles During Quenches in LHC Superconducting Dipole Magnets Protected by Quench Heaters

OpenAIRE

Maroussov, V; Sanfilippo, S; Siemko, A

1999-01-01

The efficiency of the magnet protection by quench heaters was studied using a novel method which derives the temperature profile in a superconducting magnet during a quench from measured voltage signals. In several Large Hadron Collider single aperture dipole models, temperature profiles and temperature gradients in the magnet coil have been evaluated in the case of protection by different sets of quench heaters and different powering and protection parameters. The influence of the insulation...

EMERGING TECHNOLOGY PROJECT BULLETIN: LASER INDUCED PHOTOCHEMICAL OXIDATIVE DESTRUCTION

Science.gov (United States)

The process developed by Energy and Environmental Engineering, Incorporated, is designed to photochemically oxidize organic compounds in wastewater by applying ultraviolet radiation using an Excimer laser. The photochemical reactor can destroy low to moderate concentrations...

Quench detection and behaviour in case of quench in the ITER magnet systems

International Nuclear Information System (INIS)

Coatanea-Gouachet, M.

2012-02-01

The quench of one of the ITER magnet system is an irreversible transition from superconducting to normal resistive state, of a conductor. This normal zone propagates along the cable in conduit conductor dissipating a large power. The detection has to be fast enough to dump out the magnetic energy and avoid irreversible damage of the systems. The primary quench detection in ITER is based on voltage detection, which is the most rapid detection. The very magnetically disturbed environment during the plasma scenario makes the voltage detection particularly difficult, inducing large inductive components in the coils and voltage compensations have to be designed to discriminate the resistive voltage associated with the quench. A conceptual design of the quench detection based on voltage measurements is proposed for the three majors magnet systems of ITER. For this, a clear methodology was developed. It includes the classical hot spot criterion, the quench propagation study using the commercial code Gandalf and the careful estimation of the inductive disturbances by developing the TrapsAV code. Specific solutions have been proposed for the compensation in the three ITER magnet systems and for the quench detection parameters, which are the voltage threshold (in the range of 0.1 V - 0.55 V) and the holding time (in the range of 1-1.4 s). The selected values, in particular the holding time, are sufficiently high to ensure the reliability of the system and avoid fast safety discharges not induced by a quench, which is a classical problem. (author)

Deciphering jet quenching with JEWEL

CERN Multimedia

CERN. Geneva

2018-01-01

In heavy ion collisions jets arising from the fragmentation of hard quarks and gluons experience strong modifications due to final state re-scattering. This so-called jet quenching is related to the emergence of collectivity and equilibration in QCD. I will give an introduction to jet quenching and its modeling in JEWEL, a Monte Carlo implementation of a dynamical model for jet quenching. I will then discuss examples highlighting how JEWEL can be used to elucidate the physical mechanisms relevant for jet quenching.  

Defect production in simulated cascades: cascade quenching and short-term annealing

International Nuclear Information System (INIS)

Heinisch, H.L.

1982-01-01

Defect production in high energy displacement cascades has been modeled using the computer code MARLOWE to generate the cascades and the stochastic computer code ALSOME to simulate the cascade quenching and short-term annealing of isolated cascades. The quenching is accomplished by using ALSOME with exaggerated values for defect mobilities and critical reaction distanes for recombination and clustering, which are in effect until the number of defect pairs is equal to the value determined from resistivity experiments at 4K. Then normal mobilities and reaction distances are used during short-term annealing to a point representative of Stage III recovery. Effects of cascade interactions at low fluences are also being investigated. The quenching parameter values were empirically determined for 30 keV cascades. The results agree well with experimental information throughout the range from 1 keV to 100 keV. Even after quenching and short-term annealing the high energy cascades behave as a collection of lower energy subcascades and lobes. Cascades generated in a crystal having thermal displacements were found to be in better agreement with experiments after quenching and annealing than those generated in a non-thermal crystal

Control dynamics of interaction quenched ultracold bosons in periodically driven lattices

Science.gov (United States)

Mistakidis, Simeon; Schmelcher, Peter; Group of Fundamental Processes in Quantum Physics Team

2016-05-01

The out-of-equilibrium dynamics of ultracold bosons following an interaction quench upon a periodically driven optical lattice is investigated. It is shown that an interaction quench triggers the inter-well tunneling dynamics, while for the intra-well dynamics breathing and cradle-like processes can be generated. In particular, the occurrence of a resonance between the cradle and tunneling modes is revealed. On the other hand, the employed periodic driving enforces the bosons in the mirror wells to oscillate out-of-phase and to exhibit a dipole mode, while in the central well the cloud experiences a breathing mode. The dynamical behaviour of the system is investigated with respect to the driving frequency revealing a resonant behaviour of the intra-well dynamics. To drive the system in a highly non-equilibrium state an interaction quench upon the driving is performed giving rise to admixtures of excitations in the outer wells, an enhanced breathing in the center and an amplification of the tunneling dynamics. As a result of the quench the system experiences multiple resonances between the inter- and intra-well dynamics at different quench amplitudes. Deutsche Forschungsgemeinschaft, SFB 925 ``Light induced dynamics and control of correlated quantum systems''.

Photochemical Assessment Monitoring Stations (PAMS)

Data.gov (United States)

U.S. Environmental Protection Agency — Photochemical Assessment Monitoring Stations (PAMS). This file provides information on the numbers and distribution (latitude/longitude) of air monitoring sites...

Interactions of hemin with bovine serum albumin and human hemoglobin: A fluorescence quenching study

Science.gov (United States)

Makarska-Bialokoz, Magdalena

2018-03-01

The binding interactions between hemin (Hmi) and bovine serum albumin (BSA) or human hemoglobin (HHb), respectively, have been examined in aqueous solution at pH = 7.4, applying UV-vis absorption, as well as steady-state, synchronous and three-dimensional fluorescence spectra techniques. Representative results received for both BSA and HHb intrinsic fluorescence proceeding from the interactions with hemin suggest the formation of stacking non-covalent and non-fluorescent complexes in both the Hmi-BSA and Hmi-HHb systems, with highly possible concurrent formation of a coordinate bond between a group on the protein surface and the metal in Hmi molecule. All the values of calculated parameters, the binding, fluorescence quenching and bimolecular quenching rate constants point to the involvement of static quenching in both the systems studied. The blue shift in the synchronous fluorescence spectra imply the participation of both tryptophan and tyrosine residues in quenching of BSA and HHb intrinsic fluorescence. Depicted outcomes suggest that hemin is supposedly able to influence the physiological functions of BSA and HHb, the most important blood proteins, particularly in case of its overuse.

Different physiological and photosynthetic responses of three cyanobacterial strains to light and zinc

International Nuclear Information System (INIS)

Xu, Kui; Juneau, Philippe

2016-01-01

Highlights: • The response mechanisms to high zinc was investigated among three cyanobacterial strains grown under two light regimes. • Photosystem II is more sensitive to high zinc compared to Photosystem I in the three studied strains. • High light increases the zinc uptake in two Microcystis aeruginosa strains, but not in Synechocystis sp.. • Combined high light and high zinc treatment is lethal for the toxic M. aeruginosa CPCC299. - Abstract: Zinc pollution of freshwater aquatic ecosystems is a problem in many countries, although its specific effects on phytoplankton may be influenced by other environmental factors. Light intensity varies continuously under natural conditions depending on the cloud cover and the season, and the response mechanisms of cyanobacteria to high zinc stress under different light conditions are not yet well understood. We investigated the effects of high zinc concentrations on three cyanobacterial strains (Microcystis aeruginosa CPCC299, M. aeruginosa CPCC632, and Synechocystis sp. FACHB898) grown under two light regimes. Under high light condition (HL), the three cyanobacterial strains increased their Car/Chl a ratios and non-photochemical quenching (NPQ), with CPCC299 showing the highest growth rate—suggesting a greater ability to adapt to those conditions as compared to the other two strains. Under high zinc concentrations the values of maximal (Φ_M) and operational (Φ'_M) photosystem II quantum yields, photosystem I quantum yield [Y(I)], and NPQ decreased. The following order of sensitivity to high zinc was established for the three strains studied: CPCC299 > CPCC632 > FACHB898. These different sensitivities can be partly explained by the higher internal zinc content observed in CPCC299 as compared to the other two strains. HL increased cellular zinc content and therefore increased zinc toxicity in both M. aeruginosa strains, although to a greater extent in CPCC299 than in CPCC632. Car/Chl a ratios decreased with high

Photochemically induced oscillations of aromatic pentazadienes

Energy Technology Data Exchange (ETDEWEB)

Kunz, T; Hahn, C; Wokaun, A [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

1997-06-01

Aromatic pentazadienes are used to enhance the laser induced ablation of standard polymers with low absorption in the UV. Therefore the photochemistry of substituted 1,5-diaryl-3-alkyl-1,4-pentazadiene monomers was studied with a pulsed excimer laser as irradiation source. The net photochemical reaction proceeds in an overall one-step pathway A{yields}B. Quantum yields for the laser decomposition were determined to be up to 10%. An oscillating behaviour of the absorption was found during the dark period following the irradiation. The temperature dependence of this dark reaction has been studied. An attempt to model this behaviour in terms of a non-linear coupling between heat released, heat transfer, and reaction kinetics will be described. (author) 4 figs., 4 refs.

Photochemical processes and ozone production in Finnish conditions

Energy Technology Data Exchange (ETDEWEB)

Laurila, T; Hakola, H [Finnish Meteorological Inst., Helsinki (Finland). Air Quality Dept.

1997-12-31

Photochemical ozone production is observed in March-September. Highest ozone concentrations and production efficiencies are observed in spring in the northern parts and in summer in the southern parts of the country. VOC concentrations are relatively low compared to continental areas in general. During the growing season a substantial part of the total reactive mass of VOCs is of biogenic origin. Large forest areas absorb ozone substantially, decreasing the ambient ozone concentrations in central and northern parts of Finland where long-range transport of ozone is relatively important compared to local production. The aim of the work conducted at Finnish Meteorological Institute has been to characterise concentrations of photochemically active species in the boundary layer and their photochemical formation and deposition including the effects on vegetation. Also interactions between the boundary layer and free troposphere of ozone have been studied. In the future, fluxes of both biogenic species and air pollutants will be measured and the models will be further developed so that the photochemical and micrometeorological processes could be better understood

Photochemical processes and ozone production in Finnish conditions

Energy Technology Data Exchange (ETDEWEB)

Laurila, T.; Hakola, H. [Finnish Meteorological Inst., Helsinki (Finland). Air Quality Dept.

1996-12-31

Photochemical ozone production is observed in March-September. Highest ozone concentrations and production efficiencies are observed in spring in the northern parts and in summer in the southern parts of the country. VOC concentrations are relatively low compared to continental areas in general. During the growing season a substantial part of the total reactive mass of VOCs is of biogenic origin. Large forest areas absorb ozone substantially, decreasing the ambient ozone concentrations in central and northern parts of Finland where long-range transport of ozone is relatively important compared to local production. The aim of the work conducted at Finnish Meteorological Institute has been to characterise concentrations of photochemically active species in the boundary layer and their photochemical formation and deposition including the effects on vegetation. Also interactions between the boundary layer and free troposphere of ozone have been studied. In the future, fluxes of both biogenic species and air pollutants will be measured and the models will be further developed so that the photochemical and micrometeorological processes could be better understood

Leaf and canopy photosynthesis of a chlorophyll deficient soybean mutant.

Science.gov (United States)

Sakowska, Karolina; Alberti, Giorgio; Genesio, Lorenzo; Peressotti, Alessandro; Delle Vedove, Gemini; Gianelle, Damiano; Colombo, Roberto; Rodeghiero, Mirco; Panigada, Cinzia; Juszczak, Radosław; Celesti, Marco; Rossini, Micol; Haworth, Matthew; Campbell, Benjamin W; Mevy, Jean-Philippe; Vescovo, Loris; Cendrero-Mateo, M Pilar; Rascher, Uwe; Miglietta, Franco

2018-03-02

The photosynthetic, optical, and morphological characteristics of a chlorophyll-deficient (Chl-deficient) "yellow" soybean mutant (MinnGold) were examined in comparison with 2 green varieties (MN0095 and Eiko). Despite the large difference in Chl content, similar leaf photosynthesis rates were maintained in the Chl-deficient mutant by offsetting the reduced absorption of red photons by a small increase in photochemical efficiency and lower non-photochemical quenching. When grown in the field, at full canopy cover, the mutants reflected a significantly larger proportion of incoming shortwave radiation, but the total canopy light absorption was only slightly reduced, most likely due to a deeper penetration of light into the canopy space. As a consequence, canopy-scale gross primary production and ecosystem respiration were comparable between the Chl-deficient mutant and the green variety. However, total biomass production was lower in the mutant, which indicates that processes other than steady state photosynthesis caused a reduction in biomass accumulation over time. Analysis of non-photochemical quenching relaxation and gas exchange in Chl-deficient and green leaves after transitions from high to low light conditions suggested that dynamic photosynthesis might be responsible for the reduced biomass production in the Chl-deficient mutant under field conditions. © 2018 John Wiley & Sons Ltd.

Quenches in large superconducting magnets

International Nuclear Information System (INIS)

Eberhard, P.H.; Alston-Garnjost, M.; Green, M.A.; Lecomte, P.; Smits, R.G.; Taylor, J.D.; Vuillemin, V.

1977-08-01

The development of large high current density superconducting magnets requires an understanding of the quench process by which the magnet goes normal. A theory which describes the quench process in large superconducting magnets is presented and compared with experimental measurements. The use of a quench theory to improve the design of large high current density superconducting magnets is discussed

Ultrafast spectroscopy tracks carotenoid configurations in the orange and red carotenoid proteins from cyanobacteria

Czech Academy of Sciences Publication Activity Database

Šlouf, V.; Kuznetsova, V.; Fuciman, M.; de Carbon, C.B.; Wilson, A.; Kirilowsky, D.; Polívka, Tomáš

2017-01-01

Roč. 131, č. 1 (2017), s. 105-117 ISSN 0166-8595 R&D Projects: GA ČR GBP501/12/G055 Institutional support: RVO:60077344 Keywords : Intramolecular charge-transfer state * Non-photochemical quenching * Orange carotenoid protein Subject RIV: BO - Biophysics OBOR OECD: Biophysics Impact factor: 3.864, year: 2016

Discharge quenching circuit for counters

International Nuclear Information System (INIS)

Karasik, A.S.

1982-01-01

A circuit for quenching discharges in gas-discharge detectors with working voltage of 3-5 kV based on transistors operating in the avalanche mode is described. The quenching circuit consists of a coordinating emitter follower, amplifier-shaper for avalanche key cascade control which changes potential on the counter electrodes and a shaper of discharge quenching duration. The emitter follower is assembled according to a widely used flowsheet with two transistors. The circuit permits to obtain a rectangular quenching pulse with front of 100 ns and an amplitude of up to 3.2 kV at duration of 500 μm-8 ms. Application of the quenching circuit described permits to obtain countering characteristics with the slope less than or equal to 0.02%/V and plateau extent greater than or equal to 300 V [ru

Analysis of the quench propagation along Nb$_{3}$Sn Rutherford cables with the THELMA code. Part II: application to the quench longitudinal propagation

CERN Document Server

Manfreda, G.; Bajas, H.; Perez, J.C.

2016-01-01

To improve the technology of the new generation of accelerator magnets, prototypes are being manufactured and tested in several laboratories. In parallel, many numerical analyses are being carried out to predict the magnets behaviour and interpret the experimental results. This paper focuses on the quench propagation velocity, which is a crucial parameter as regards the energy dissipation along the magnet conductor. The THELMA code, originally developed for cable-in-conduit conductors for fusion magnets, has been used to study such quench propagation. To this purpose, new code modules have been added to describe the Rutherford cable geometry, the material non-linear thermal properties and to describe the thermal conduction problem in transient regime. THELMA can describe the Rutherford cable at the strand level, modelling both the electrical and thermal contact resistances between strands and enabling the analysis of the effects of local hot spots and quench heaters. This paper describes the model application...

Thermalization in 2D critical quench and UV/IR mixing

Science.gov (United States)

Mandal, Gautam; Paranjape, Shruti; Sorokhaibam, Nilakash

2018-01-01

We consider quantum quenches in models of free scalars and fermions with a generic time-dependent mass m( t) that goes from m 0 to zero. We prove that, as anticipated in MSS [1], the post-quench dynamics can be described in terms of a state of the generalized Calabrese-Cardy form | ψ〉 = exp[- κ 2 H - ∑ n >2 ∞ κ n W n ]|Bd〉. The W n ( n = 2, 3, . . ., W 2 = H) here represent the conserved W ∞ charges and |Bd〉 represents a conformal boundary state. Our result holds irrespective of whether the pre-quench state is a ground state or a squeezed state, and is proved without recourse to perturbation expansion in the κ n 's as in MSS. We compute exact time-dependent correlators for some specific quench protocols m( t). The correlators explicitly show thermalization to a generalized Gibbs ensemble (GGE), with inverse temperature β = 4 κ 2, and chemical potentials μ n = 4 κ n . In case the pre-quench state is a ground state, it is possible to retrieve the exact quench protocol m( t) from the final GGE, by an application of inverse scattering techniques. Another notable result, which we interpret as a UV/IR mixing, is that the long distance and long time (IR) behaviour of some correlators depends crucially on all κ n 's, although they are highly irrelevant couplings in the usual RG parlance. This indicates subtleties in RG arguments when applied to non-equilibrium dynamics.

Highlighting the mechanisms by which proline can confer tolerance to salt stress in cakile maritima

International Nuclear Information System (INIS)

Messedi, D.; Farhani, F.; Hamed, K.B.; Trabelsi, N.; Ksouri, R.; Chedly Abdelly, C.; Athar, H.U.R.

2016-01-01

Cakile maritima is an oleaginous halophyte growing in the sandy dunes along the Tunisian coast. In order to investigate the role of proline in inducing high salinity tolerance (200 and 400 mM NaCl) in this halophyte, we studied several aspects of the salt responses of C. maritma under exogenous proline supply (20 mM). Salinity levels above 100 mM, reduced growth, photosynthetic activity, and quantum yield of photosystem II (FPSII), while increasing the non photochemical quenching (NPQ). Significant inhibition of the linear electron transport rate (ETR) was also observed in plants grown at 400 mM NaCl. In addition, polyphenol content, total antioxidant and DPPH scavenging activities increased due to increasing salinity stress, and the concentration of malondialdehyde (MDA) also increased. The application of proline counteracted all these adverse effects of salt stress in plants grown at 200 mM NaCl, while it improved some of these physiological attributes at 400 mM NaCl. In addition, contribution of Na+ for the osmotic adjustment decreased in the leaves of salt treated plants supplied with proline exogenously. Exogenous application of proline induced the accumulation of potassium, proline and soluble carbohydrates in salt stressed plants, particularly at 400 mM. This explained the reason of growth enhancement induced by proline application. All together, our Results showed that the beneficial effect of exogenous proline on the response of C. maritima to salinity was due to its role in the protection of chloroplast structures, antioxidant defenses and osmotic adjustment. (author)

Two Hymenophyllaceae species from contrasting natural environments exhibit a homoiochlorophyllous strategy in response to desiccation stress.

Science.gov (United States)

Flores-Bavestrello, Alejandra; Król, Marianna; Ivanov, Alexander G; Hüner, Norman P A; García-Plazaola, José Ignacio; Corcuera, Luis J; Bravo, León A

2016-02-01

Hymenophyllaceae is a desiccation tolerant family of Pteridophytes which are poikilohydric epiphytes. Their fronds are composed by a single layer of cells and lack true mesophyll cells and stomata. Although they are associated with humid and shady environments, their vertical distribution varies along the trunk of the host plant with some species inhabiting the drier sides with a higher irradiance. The aim of this work was to compare the structure and function of the photosynthetic apparatus during desiccation and rehydration in two species, Hymenophyllum dentatum and Hymenoglossum cruentum, isolated from a contrasting vertical distribution along the trunk of their hosts. Both species were subjected to desiccation and rehydration kinetics to analyze frond phenotypic plasticity, as well as the structure, composition and function of the photosynthetic apparatus. Minimal differences in photosynthetic pigments were observed upon dehydration. Measurements of ϕPSII (effective quantum yield of PSII), ϕNPQ (quantum yield of the regulated energy dissipation of PSII), ϕNO (quantum yield of non-regulated energy dissipation of PSII), and TL (thermoluminescence) indicate that both species convert a functional photochemical apparatus into a structure which exhibits maximum quenching capacity in the dehydrated state with minimal changes in photosynthetic pigments and polypeptide compositions. This dehydration-induced conversion in the photosynthetic apparatus is completely reversible upon rehydration. We conclude that H. dentatum and H. cruentum are homoiochlorophyllous with respect to desiccation stress and exhibited no correlation between inherent desiccation tolerance and the vertical distribution along the host tree trunk. Copyright © 2015 Elsevier GmbH. All rights reserved.

Nitrogen metabolism correlates with the acclimation of photosynthesis to short-term water stress in rice (Oryza sativa L.).

Science.gov (United States)

Zhong, Chu; Cao, Xiaochuang; Bai, Zhigang; Zhang, Junhua; Zhu, Lianfeng; Huang, Jianliang; Jin, Qianyu

2018-04-01

Nitrogen metabolism is as sensitive to water stress as photosynthesis, but its role in plant under soil drying is not well understood. We hypothesized that the alterations in N metabolism could be related to the acclimation of photosynthesis to water stress. The features of photosynthesis and N metabolism in a japonica rice 'Jiayou 5' and an indica rice 'Zhongzheyou 1' were investigated under mild and moderate soil drying with a pot experiment. Soil drying increased non-photochemical quenching (NPQ) and reduced photon quantum efficiency of PSII and CO 2 fixation in 'Zhongzheyou 1', whereas the effect was much slighter in 'Jiayou 5'. Nevertheless, the photosynthetic rate of the two cultivars showed no significant difference between control and water stress. Soil drying increased nitrate reducing in leaves of 'Zhongzheyou 1', characterized by enhanced nitrate reductase (NR) activity and lowered nitrate content; whereas glutamate dehydrogenase (GDH), glutamic-oxaloacetic transaminase (GOT) and glutamic-pyruvic transaminase (GPT) were relative slightly affected. 'Jiayou 5' plants increased the accumulation of nitrate under soil drying, although its NR activity was increased. In addition, the activities of GDH, GOT and GPT were typically increased under soil drying. Besides, amino acids and soluble sugar were significantly increased under mild and moderate soil drying, respectively. The accumulation of nitrate, amino acid and sugar could serve as osmotica in 'Jiayou 5'. The results reveal that N metabolism plays diverse roles in the photosynthetic acclimation of rice plants to soil drying. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

Photoacclimatory Responses of Zostera marina in the Intertidal and Subtidal Zones.

Science.gov (United States)

Park, Sang Rul; Kim, Sangil; Kim, Young Kyun; Kang, Chang-Keun; Lee, Kun-Seop

2016-01-01

Photoacclimatory responses of the seagrass Zostera marina in the intertidal and subtidal zones were investigated by measuring chlorophyll a fluorescence parameters, photosynthetic pigments, leaf δ13C values, and shoot morphology in two bay systems. Intertidal plants had higher carotenoid concentrations than subtidal plants to avoid photodamage under excess light conditions during the day. The maximum relative electron transport rate (rETRmax) and minimum saturation irradiance (Ek) of the intertidal plants were higher than those of the subtidal plants, whereas photosynthetic efficiency (α) and maximum quantum yield (Fv/Fm) were higher in subtidal plants. The intertidal plants also had significantly greater Stern-Volmer non-photochemical quenching (NPQ) than that of the subtidal plants. These results suggest that the subtidal plants photoacclimated to use limited light more efficiently, and the intertidal plants exhibited photosynthetic responses to minimize photodamage at excess irradiance. The δ13C values of leaf tissues were more negative in the intertidal plants than those in the subtidal plants, suggesting that the intertidal plants used atmospheric or dissolved CO2 for photosynthesis during emersion. Effective quantum yield (ΔF/Fm´) in the intertidal plants decreased more slowly after emersion than that in the subtidal plants, indicating higher desiccation tolerance of the intertidal plants. The intertidal plants also recovered more rapidly from desiccation damage than the subtidal plants, suggesting photosynthetic adaptation to desiccation stress. The photosynthetic plasticity of Z. marina in response to variable environmental conditions most likely allows this species to occur in the intertidal and subtidal zones.

Photoacclimatory Responses of Zostera marina in the Intertidal and Subtidal Zones.

Directory of Open Access Journals (Sweden)

Sang Rul Park

Full Text Available Photoacclimatory responses of the seagrass Zostera marina in the intertidal and subtidal zones were investigated by measuring chlorophyll a fluorescence parameters, photosynthetic pigments, leaf δ13C values, and shoot morphology in two bay systems. Intertidal plants had higher carotenoid concentrations than subtidal plants to avoid photodamage under excess light conditions during the day. The maximum relative electron transport rate (rETRmax and minimum saturation irradiance (Ek of the intertidal plants were higher than those of the subtidal plants, whereas photosynthetic efficiency (α and maximum quantum yield (Fv/Fm were higher in subtidal plants. The intertidal plants also had significantly greater Stern-Volmer non-photochemical quenching (NPQ than that of the subtidal plants. These results suggest that the subtidal plants photoacclimated to use limited light more efficiently, and the intertidal plants exhibited photosynthetic responses to minimize photodamage at excess irradiance. The δ13C values of leaf tissues were more negative in the intertidal plants than those in the subtidal plants, suggesting that the intertidal plants used atmospheric or dissolved CO2 for photosynthesis during emersion. Effective quantum yield (ΔF/Fm´ in the intertidal plants decreased more slowly after emersion than that in the subtidal plants, indicating higher desiccation tolerance of the intertidal plants. The intertidal plants also recovered more rapidly from desiccation damage than the subtidal plants, suggesting photosynthetic adaptation to desiccation stress. The photosynthetic plasticity of Z. marina in response to variable environmental conditions most likely allows this species to occur in the intertidal and subtidal zones.

Effects of fully open-air [CO2] elevation on leaf photosynthesis and ultrastructure of Isatis indigotica fort.

Science.gov (United States)

Hao, Xingyu; Li, Ping; Feng, Yongxiang; Han, Xue; Gao, Ji; Lin, Erda; Han, Yuanhuai

2013-01-01

Traditional Chinese medicine relies heavily on herbs, yet there is no information on how these herb plants would respond to climate change. In order to gain insight into such response, we studied the effect of elevated [CO2] on Isatis indigotica Fort, one of the most popular Chinese herb plants. The changes in leaf photosynthesis, chlorophyll fluorescence, leaf ultrastructure and biomass yield in response to elevated [CO2] (550±19 µmol mol(-1)) were determined at the Free-Air Carbon dioxide Enrichment (FACE) experimental facility in North China. Photosynthetic ability of I. indigotica was improved under elevated [CO2]. Elevated [CO2] increased net photosynthetic rate (P N), water use efficiency (WUE) and maximum rate of electron transport (J max) of upper most fully-expended leaves, but not stomatal conductance (gs), transpiration ratio (Tr) and maximum velocity of carboxylation (V c,max). Elevated [CO2] significantly increased leaf intrinsic efficiency of PSII (Fv'/Fm') and quantum yield of PSII(ΦPS II ), but decreased leaf non-photochemical quenching (NPQ), and did not affect leaf proportion of open PSII reaction centers (qP) and maximum quantum efficiency of PSII (Fv/Fm). The structural chloroplast membrane, grana layer and stroma thylakoid membranes were intact under elevated [CO2], though more starch grains were accumulated within the chloroplasts than that of under ambient [CO2]. While the yield of I. indigotica was higher due to the improved photosynthesis under elevated [CO2], the content of adenosine, one of the functional ingredients in indigowoad root was not affected.

The Quench Action

Science.gov (United States)

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.

Quench action approach for releasing the Néel state into the spin-1/2 XXZ chain

NARCIS (Netherlands)

Brockmann, M.; Wouters, B.; Fioretto, D.; De Nardis, J.; Vlijm, R.; Caux, J.-S.

2014-01-01

The steady state after a quantum quench from the Néel state to the anisotropic Heisenberg model for spin chains is investigated. Two methods that aim to describe the postquench non-thermal equilibrium, the generalized Gibbs ensemble and the quench action approach, are discussed and contrasted. Using

Quenching behaviour of hot zircaloy tube

International Nuclear Information System (INIS)

Chinchole, A.S.; Kulkarni, P.P.; Nayak, A.K.; Vijayan, P.K.

2015-01-01

The quenching process plays a very important role in case of safety of nuclear reactors. During large break Loss of Coolant Accident in a nuclear reactor, the cooling water from the system is lost. Under this condition, cold water is injected from emergency core cooling system. Quenching behaviour of such heated rod bundle is really complex. It is well known that nanofluids have better heat removal capability and high heat transfer coefficient owing to enhanced thermal properties. Alumina nano-particles result in better cooling abilities compared with the traditionally used quenching media. In this paper, the authors have carried out experiments on quenching behaviour of hot zircaloy tube with demineralized water and nanofluids. It was observed that, the tube got quenched within few seconds even with the presence of decay heat and shows slightly reduced quenching time compared with DM water. (author)

Quench Simulation Studies: Program documentation of SPQR

CERN Document Server

Sonnemann, F

2001-01-01

Quench experiments are being performed on prototypes of the superconducting magnets and busbars to determine the adequate design and protection. Many tests can only be understood correctly with the help of quench simulations that model the thermo-hydraulic and electrodynamic processes during a quench. In some cases simulations are the only method to scale the experimental results of prototype measurements to match the situation of quenching superconducting elements in the LHC. This note introduces the theoretical quench model and the use of the simulation program SPQR (Simulation Program for Quench Research), which has been developed to compute the quench process in superconducting magnets and busbars. The model approximates the heat balance equation with the finite difference method including the temperature dependence of the material parameters. SPQR allows the simulation of longitudinal quench propagation along a superconducting cable, the transverse propagation between adjacent conductors, heat transfer i...

Photochemical oxidation: A solution for the mixed waste dilemma

Energy Technology Data Exchange (ETDEWEB)

Prellberg, J.W.; Thornton, L.M.; Cheuvront, D.A. [Vulcan Peroxidation Systems, Inc., Tucson, AZ (United States)] [and others

1995-12-31

Numerous technologies are available to remove organic contamination from water or wastewater. A variety of techniques also exist that are used to neutralize radioactive waste. However, few technologies can satisfactorily address the treatment of mixed organic/radioactive waste without creating unacceptable secondary waste products or resulting in extremely high treatment costs. An innovative solution to the mixed waste problem is on-site photochemical oxidation. Liquid-phase photochemical oxidation has a long- standing history of successful application to the destruction of organic compounds. By using photochemical oxidation, the organic contaminants are destroyed on-site leaving the water, with radionuclides, that can be reused or disposed of as appropriate. This technology offers advantages that include zero air emissions, no solid or liquid waste formation, and relatively low treatment cost. Discussion of the photochemical process will be described, and several case histories from recent design testing, including cost analyses for the resulting full-scale installations, will be presented as examples.

Method of making gold thiolate and photochemically functionalized microcantilevers

Science.gov (United States)

Boiadjiev, Vassil I [Knoxville, TN; Brown, Gilbert M [Knoxville, TN; Pinnaduwage, Lal A [Knoxville, TN; Thundat, Thomas G [Knoxville, TN; Bonnesen, Peter V [Knoxville, TN; Goretzki, Gudrun [Nottingham, GB

2009-08-25

Highly sensitive sensor platforms for the detection of specific reagents, such as chromate, gasoline and biological species, using microcantilevers and other microelectromechanical systems (MEMS) whose surfaces have been modified with photochemically attached organic monolayers, such as self-assembled monolayers (SAM), or gold-thiol surface linkage are taught. The microcantilever sensors use photochemical hydrosilylation to modify silicon surfaces and gold-thiol chemistry to modify metallic surfaces thereby enabling individual microcantilevers in multicantilever array chips to be modified separately. Terminal vinyl substituted hydrocarbons with a variety of molecular recognition sites can be attached to the surface of silicon via the photochemical hydrosilylation process. By focusing the activating UV light sequentially on selected silicon or silicon nitride hydrogen terminated surfaces and soaking or spotting selected metallic surfaces with organic thiols, sulfides, or disulfides, the microcantilevers are functionalized. The device and photochemical method are intended to be integrated into systems for detecting specific agents including chromate groundwater contamination, gasoline, and biological species.

Analysis of stability and quench in HTS devices-New approaches

International Nuclear Information System (INIS)

Vysotsky, V.S.; Sytnikov, V.E.; Rakhmanov, A.L.; Ilyin, Y.

2006-01-01

R and D of HTS devices are in their full steam-more magnets and devices are developed with larger sizes. But analysis of their stability and quench was still old fashioned, based on normal zone determination, analysis of its appearance and propagation. Some peculiarities of HTS make this traditional, quite impractical and inconvenient approach to consideration of HTS devices stability and quench development using normal zone origination and propagation analysis. The novel approaches were developed that consider the HTS device as a cooled medium with non-linear parameters with no mentioning of 'superconductivity' in the analysis. The approach showed its effectiveness and convenience to analyze the stability and quench development in HTS devices. In this paper the analysis of difference between HTS and LTS quench, dependent on index n and specific heat comparison, is followed by the short approach descriptions and by the consequences from it for the HTS devices design. The further development of the method is presented for the analysis of long HTS objects where 'blow-up' regimes may happen. This is important for design and analysis of HTS power cables operations under overloading conditions

Light-induced dissociation of antenna complexes in the symbionts of scleractinian corals correlates with sensitivity to coral bleaching

Czech Academy of Sciences Publication Activity Database

Hill, R.; Larkum, A. W. D.; Prášil, Ondřej; Kramer, D. M.; Szabó, M.; Kumar, V.; Ralph, P. J.

2012-01-01

Roč. 31, č. 4 (2012), s. 963-975 ISSN 0722-4028 R&D Projects: GA AV ČR IAA601410907; GA MŠk(CZ) ED2.1.00/03.0110 Institutional support: RVO:61388971 Keywords : Photoprotection * Non-photochemical quenching * Xanthophyll cycle Subject RIV: EE - Microbiology, Virology Impact factor: 3.662, year: 2012

Quench protection analysis of the Mu2e production solenoid

International Nuclear Information System (INIS)

Kashikhin, Vadim; Ambrosio, Giorgio; Andreev, Nikolai; Lamm, Michael; Nicol, Thomas; Orris, Darryl; Page, Thomas

2014-01-01

The Muon-to-Electron conversion experiment (Mu2e), under development at Fermilab, seeks to detect direct muon to electron conversion to provide evidence for a process violating muon and electron lepton number conservation that cannot be explained by the Standard Model of particle physics. The Mu2e magnet system consists of three large superconducting solenoids. In case of a quench, the stored magnetic energy is extracted to an external dump circuit. However, because of the fast current decay, a significant fraction of the energy dissipates inside of the cryostat in the coil support shells made of structural aluminum, and in the radiation shield. A 3D finite-element model of the complete cold-mass was created in order to simulate the quench development and understand the role of the quench-back. The simulation results are reported at the normal and non-standard operating conditions

Quench protection analysis of the Mu2e production solenoid

Science.gov (United States)

Kashikhin, Vadim; Ambrosio, Giorgio; Andreev, Nikolai; Lamm, Michael; Nicol, Thomas; Orris, Darryl; Page, Thomas

2014-01-01

The Muon-to-Electron conversion experiment (Mu2e), under development at Fermilab, seeks to detect direct muon to electron conversion to provide evidence for a process violating muon and electron lepton number conservation that cannot be explained by the Standard Model of particle physics. The Mu2e magnet system consists of three large superconducting solenoids. In case of a quench, the stored magnetic energy is extracted to an external dump circuit. However, because of the fast current decay, a significant fraction of the energy dissipates inside of the cryostat in the coil support shells made of structural aluminum, and in the radiation shield. A 3D finite-element model of the complete cold-mass was created in order to simulate the quench development and understand the role of the quench-back. The simulation results are reported at the normal and non-standard operating conditions.

Exact solution for the quench dynamics of a nested integrable system

Science.gov (United States)

Mestyán, Márton; Bertini, Bruno; Piroli, Lorenzo; Calabrese, Pasquale

2017-08-01

Integrable models provide an exact description for a wide variety of physical phenomena. For example nested integrable systems contain different species of interacting particles with a rich phenomenology in their collective behavior, which is the origin of the unconventional phenomenon of spin-charge separation. So far, however, most of the theoretical work in the study of non-equilibrium dynamics of integrable systems has focussed on models with an elementary (i.e. not nested) Bethe ansatz. In this work we explicitly investigate quantum quenches in nested integrable systems, by generalizing the application of the quench action approach. Specifically, we consider the spin-1 Lai-Sutherland model, described, in the thermodynamic limit, by the theory of two different species of Bethe-ansatz particles, each one forming an infinite number of bound states. We focus on the situation where the quench dynamics starts from a simple matrix product state for which the overlaps with the eigenstates of the Hamiltonian are known. We fully characterize the post-quench steady state and perform several consistency checks for the validity of our results. Finally, we provide predictions for the propagation of entanglement and mutual information after the quench, which can be used as signature of the quasi-particle content of the model.

Rapid Quench in an Electrostatic Levitator

Science.gov (United States)

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.

MSFC Electrostatic Levitator (ESL) Rapid Quench System

Science.gov (United States)

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.

Concentration quenching in Nd-doped glasses

International Nuclear Information System (INIS)

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

1984-01-01

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

Eficiência fotoquímica de gramíneas forrageiras tropicais submetidas à deficiência hídrica Photochemical efficiency of tropical forage grasses submitted to water deficit

Directory of Open Access Journals (Sweden)

Manoel Messias Pereira da Silva

2006-02-01

, nilograss (Acroceras macrum Stapf. and angola grass (Brachiaria purpurascens [Raddi] Henr. were submitted to moderate drought. The characteristics of chlorophyll a fluorescence (inicial fluorescence, Fo; maximum fluorescence, Fm; photochemistry efficiency, Fv/F­m; photochemical quenching, qP; non-photochemical quenching, qN and relative electron transport rate, ETR were investigated in an experiment carried out in greenhouse, using plastic pots. The experimental treatments were allocated in a randomized complete blocks design, with three replications. The values of Fo and Fm decreased in all species after 10 days of drought, this effect being more evident in nilograss and setariagrass. The Fv/Fm values for nilograss and setariagrass decreased dramatically while that one for hemarthriagrass did not differ from the control. This results suggest a lower photochemical efficiency of photosynthesis in nilograss and setariagrass under water stress compared to hemarthriagrass and to the hea,lthy plants. The highest values of qN were observed for hemarthriagraas and angolagrass. This showed that the increased capacity to dissipate the excessive energy to drive photosynthesis was satisfactory to maintain a low reduction state of the primary electron acceptor of the photosystem II (measured as qP. In general, ETR curves in response to increasing photosynthetic photon flux differed from control to stressed plants, especially for nilograss. In this species, a serious damage caused by water stress provoked a significant reduction to the efficiency of the electron transporters of PSII.

Problems with the quenched approximation in the chiral limit

International Nuclear Information System (INIS)

Sharpe, S.R.

1992-01-01

In the quenched approximation, loops of the light singlet meson (the η') give rise to a type of chiral logarithm absent in full QCD. These logarithms are singular in the chiral limit, throwing doubt upon the utility of the quenched approximation. In previous work, I summed a class of diagrams, leading to non-analytic power dependencies such as left-angle anti ψψ right-angle ∝ m q -δ /(1+δ) I suggested, however, that these peculiar results could be redefined away. Here I give an alternative derivation of the results, based on the renormalization group, and argue that they cannot be redefined away. I discuss the evidence (or lack thereof) for such effects in numerical data

Synthesis and photochemical properties of a novel iron-sulfur-nitrosyl cluster derivatized with the pendant chromophore protoporphyrin IX.

Science.gov (United States)

Conrado, Christa L; Wecksler, Stephen; Egler, Christian; Magde, Douglas; Ford, Peter C

2004-09-06

The novel Roussin red-salt ester (PPIX-RSE) with a pendant porphyrin chromophore was prepared and investigated as a precursor for the photochemical generation of nitric oxide. PPIX-RSE has the general formula Fe(2)(NO)(4)[(mu-S,mu-S')P] (where (S,S')P is the bis(2-thiolatoethyl) diester of protoporphyrin IX. The photoexcitation of PPIX-RSE with 436- or 546-nm light in an aerated chloroform solution led to the photodecomposition of the cluster with the respective quantum yields (5.2 +/- 0.7) x 10(-4) and (2.5 +/- 0.5 x 10(-4)) and the concomitant release of NO. PPIX-RSE is a significantly more effective NO generator at longer wavelength excitation than are other Fe(2)(mu-SR)(2)(NO)(4) esters for which R is a simple alkyl group such as CH(3)CH(2)- because of the much higher absorptivity of the pendant PPIX chromophore at these wavelengths and a modestly higher quantum yield. Fluorescence intensity and lifetime data indicate that the photoexcited porphyrin of PPIX-RSE is largely quenched by the energy transfer to the Fe(2)S(2)(NO)(4) cluster's core. However, a small fraction of this emission is not quenched, and it is proposed that PPIX-RSE may exist in solution as two conformers.

Participation of the Halogens in Photochemical Reactions in Natural and Treated Waters

Directory of Open Access Journals (Sweden)

Yi Yang

2017-10-01

Full Text Available Halide ions are ubiquitous in natural waters and wastewaters. Halogens play an important and complex role in environmental photochemical processes and in reactions taking place during photochemical water treatment. While inert to solar wavelengths, halides can be converted into radical and non-radical reactive halogen species (RHS by sensitized photolysis and by reactions with secondary reactive oxygen species (ROS produced through sunlight-initiated reactions in water and atmospheric aerosols, such as hydroxyl radical, ozone, and nitrate radical. In photochemical advanced oxidation processes for water treatment, RHS can be generated by UV photolysis and by reactions of halides with hydroxyl radicals, sulfate radicals, ozone, and other ROS. RHS are reactive toward organic compounds, and some reactions lead to incorporation of halogen into byproducts. Recent studies indicate that halides, or the RHS derived from them, affect the concentrations of photogenerated reactive oxygen species (ROS and other reactive species; influence the photobleaching of dissolved natural organic matter (DOM; alter the rates and products of pollutant transformations; lead to covalent incorporation of halogen into small natural molecules, DOM, and pollutants; and give rise to certain halogen oxides of concern as water contaminants. The complex and colorful chemistry of halogen in waters will be summarized in detail and the implications of this chemistry for global biogeochemical cycling of halogen, contaminant fate in natural waters, and water purification technologies will be discussed.

2-Diazo-1-(4-hydroxyphenyl)ethanone: a versatile photochemical and synthetic reagent.

Science.gov (United States)

Senadheera, Sanjeewa N; Evans, Anthony S; Toscano, John P; Givens, Richard S

2014-02-01

α-Diazo arylketones are well-known substrates for Wolff rearrangement to phenylacetic acids through a ketene intermediate by either thermal or photochemical activation. Likewise, α-substituted p-hydroxyphenacyl (pHP) esters are substrates for photo-Favorskii rearrangements to phenylacetic acids by a different pathway that purportedly involves a cyclopropanone intermediate. In this paper, we show that the photolysis of a series of α-diazo-p-hydroxyacetophenones and p-hydroxyphenacyl (pHP) α-esters both generate the identical rearranged phenylacetates as major products. Since α-diazo-p-hydroxyacetophenone (1a, pHP N2) contains all the necessary functionalities for either Wolff or Favorskii rearrangement, we were prompted to probe this intriguing mechanistic dichotomy under conditions favorable to the photo-Favorskii rearrangement, i.e., photolysis in hydroxylic media. An investigation of the mechanism for conversion of 1a to p-hydroxyphenyl acetic acid (4a) using time-resolved infrared (TRIR) spectroscopy clearly demonstrates the formation of a ketene intermediate that is subsequently trapped by solvent or nucleophiles. The photoreaction of 1a is quenched by oxygen and sensitized by triplet sensitizers and the quantum yields for 1a-c range from 0.19 to a robust 0.25. The lifetime of the triplet, determined by Stern-Volmer quenching, is 31 ns with a rate for appearance of 4a of k = 7.1 × 10(6) s(-1) in aq. acetonitrile (1 : 1 v : v). These studies establish that the primary rearrangement pathway for 1a involves ketene formation in accordance with the photo-Wolff rearrangement. Furthermore we have also demonstrated the synthetic utility of 1a as an esterification and etherification reagent with a variety of substituted α-diazo-p-hydroxyacetophenones, using them as synthons for efficiently coupling it to acids and phenols to produce pHP protect substrates.

2-Diazo-1-(4-hydroxyphenyl)ethanone: A Versatile Photochemical and Synthetic Reagenta

Science.gov (United States)

Senadheera, Sanjeewa N.; Evans, Anthony S.; Toscano, John P.; Givens, Richard S.

2014-01-01

α-Diazo arylketones are well-known substrates for Wolff rearrangement to phenylacetic acids through a ketene intermediate by either thermal or photochemical activation. Likewise, α-substituted p-hydroxyphenacyl (pHP) esters are substrates for photo-Favorskii rerrangements to phenylacetic acids by a different pathway that purportedly involves a cyclopropanone intermediate. In this paper, we show that the photolysis of a series of α-diazo-p-hydroxyacetophenones and p-hydroxyphenacyl (pHP) α-esters both generate the identical rearranged phenylacetates as major products. Since α-diazo-p-hydroxyacetophenone (1a, pHP N2) contains all the necessary functionalities for either Wolff or Favorskii rearrangement, we were prompted to probe this intriguing mechanistic dichotomy under conditions favorable to the photo-Favorskii reangement, i.e., photolysis in hydroxylic media. An investigation of the mechanism for conversion of 1a to p-hydroxyphenyl acetic acid (4a) using time-resolved infrared (TRIR) spectroscopy clearly demonstrates the formation of a ketene intermediate that is subsequently trapped by solvent or nucleophiles. The photoreaction of 1a is quenched by oxygen and sensitized by triplet sensitizers and the quantum yields for 1a–c range from 0.19 to a robust 0.25. The lifetime of the triplet, determined by Stern-Volmer quenching, is 15 ns with a rate for appearance of 4a of k = 7,1 × 106 s−1 in aq. acetonitrile (1:1 v:v). These studies establish that the primary rearrangement pathway for 1a involves ketene formation in accordance with the photo-Wolff rearrangement. Furthermore we have also demonstrated the synthetic utility of 1a as an esterification and etherification reagent with a variety of substituted α-diazo-p-hydroxyacetophenones, using them as synthons for efficiently coupling it to acids and phenols to produce pHP protect substrates. PMID:24305682

Application of Best Estimate Approach for Modelling of QUENCH-03 and QUENCH-06 Experiments

Directory of Open Access Journals (Sweden)

Tadas Kaliatka

2016-04-01

In this article, the QUENCH-03 and QUENCH-06 experiments are modelled using ASTEC and RELAP/SCDAPSIM codes. For the uncertainty and sensitivity analysis, SUSA3.5 and SUNSET tools were used. The article demonstrates that applying the best estimate approach, it is possible to develop basic QUENCH input deck and to develop the two sets of input parameters, covering maximal and minimal ranges of uncertainties. These allow simulating different (but with the same nature tests, receiving calculation results with the evaluated range of uncertainties.

Action Spectrum of Photoinhibition in the Diatom Phaeodactylum tricornutum.

Science.gov (United States)

Havurinne, Vesa; Tyystjärvi, Esa

2017-12-01

Light-dependent electron transfer is necessary for photosynthesis, but light also damages PSII. Light-induced damage to PSII is called photoinhibition, and the damaging reactions of photoinhibition are still under debate. Diatoms possess an exotic combination of light-harvesting pigments, Chls a/c and fucoxanthin, making them an interesting platform for studying the photoreceptors of photoinhibition. We first confirmed the direct proportionality of photoinhibition to the photon flux density of incident light in the diatom Phaeodactylum tricornutum. Phaeodactylum is known for its efficient non-photochemical quenching, and the effect of this photoprotective mechanism on photoinhibition was tested. Photoinhibition proceeded essentially at the same rate in blue-light-grown Phaeodactylum cells that are capable of non-photochemical quenching and in red-light-grown, non-photochemical quenching-deficient cells. To obtain more insight into how the pigment composition of diatoms affects photoinhibition, we measured the action spectrum of photoinhibition in Phaeodactylum. In visible light, the action spectrum resembled the absorption spectrum of Phaeodactylum, and UV radiation caused much more photoinhibition than visible light. Comparison of the action spectrum of photoinhibition with the absorption spectrum and the excitation spectrum of 77 K PSII fluorescence emission confirmed that photosynthetic pigments are involved in photoinhibition, but the photoinhibitory efficiency of red light is weak, suggesting that the role of light-harvesting pigments as light receptors of photoinhibition is secondary. Finally, we compared photoinhibition in Phaeodactylum with that in other photosynthetic organisms, and our data indicate that the PSII reaction centers of Phaeodactylum are not particularly well protected against the primary damage of photoinhibition. © The Author 2017. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights

Quenching and recovery experiments on molybdenum

International Nuclear Information System (INIS)

Schwirtlich, I.A.; Schultz, H.; Max-Planck-Institut fuer Metallforschung, Stuttgart

1980-01-01

Quenching experiments in superfluid helium have been performed on high-purity wire specimens obtained from a Mo single crystal with a residual resistance ratio of 40 000. Quenching from various temperatures near the melting point to 1.5 K resulted in quenched-in resistivities which are interpreted in terms of quenched-in vacancies. The following parameters were derived: Hsub(1V)sup(F) = 3.2 eV (formation enthalpy of monovacancies) and Ssub(1V)sup(F) = 1.5 k (formation entropy). The recovery of the quenched-in resistivity showed a recovery stage at 520 K, which is compatible with a migration enthalpy of Hsub(1V)sup(M) = 1.35 eV. The results are compared with recently published positron annihilation data. (author)

Quantum quenches in a holographic Kondo model

Science.gov (United States)

Erdmenger, Johanna; Flory, Mario; Newrzella, Max-Niklas; Strydom, Migael; Wu, Jackson M. S.

2017-04-01

We study non-equilibrium dynamics and quantum quenches in a recent gauge/gravity duality model for a strongly coupled system interacting with a magnetic impurity with SU( N ) spin. At large N , it is convenient to write the impurity spin as a bilinear in Abrikosov fermions. The model describes an RG flow triggered by the marginally relevant Kondo operator. There is a phase transition at a critical temperature, below which an operator condenses which involves both an electron and an Abrikosov fermion field. This corresponds to a holographic superconductor in AdS2 and models the impurity screening. We quench the Kondo coupling either by a Gaussian pulse or by a hyperbolic tangent, the latter taking the system from the condensed to the uncondensed phase or vice-versa. We study the time dependence of the condensate induced by this quench. The timescale for equilibration is generically given by the leading quasinormal mode of the dual gravity model. This mode also governs the formation of the screening cloud, which is obtained as the decrease of impurity degrees of freedom with time. In the condensed phase, the leading quasinormal mode is imaginary and the relaxation of the condensate is over-damped. For quenches whose final state is close to the critical point of the large N phase transition, we study the critical slowing down and obtain the combination of critical exponents zν = 1. When the final state is exactly at the phase transition, we find that the exponential ringing of the quasinormal modes is replaced by a power-law behaviour of the form ˜ t - a sin( b log t). This indicates the emergence of a discrete scale invariance.

Seasonal photochemical transformations of nitrogen species in a forest stream and lake.

Directory of Open Access Journals (Sweden)

Petr Porcal

Full Text Available The photochemical release of inorganic nitrogen from dissolved organic matter is an important source of bio-available nitrogen (N in N-limited aquatic ecosystems. We conducted photochemical experiments and used mathematical models based on pseudo-first-order reaction kinetics to quantify the photochemical transformations of individual N species and their seasonal effects on N cycling in a mountain forest stream and lake (Plešné Lake, Czech Republic. Results from laboratory experiments on photochemical changes in N speciation were compared to measured lake N budgets. Concentrations of organic nitrogen (Norg; 40-58 µmol L-1 decreased from 3 to 26% during 48-hour laboratory irradiation (an equivalent of 4-5 days of natural solar insolation due to photochemical mineralization to ammonium (NH4+ and other N forms (Nx; possibly N oxides and N2. In addition to Norg mineralization, Nx also originated from photochemical nitrate (NO3- reduction. Laboratory exposure of a first-order forest stream water samples showed a high amount of seasonality, with the maximum rates of Norg mineralization and NH4+ production in winter and spring, and the maximum NO3- reduction occurring in summer. These photochemical changes could have an ecologically significant effect on NH4+ concentrations in streams (doubling their terrestrial fluxes from soils and on concentrations of dissolved Norg in the lake. In contrast, photochemical reactions reduced NO3- fluxes by a negligible (<1% amount and had a negligible effect on the aquatic cycle of this N form.

Photochemical Copper Coating on 3D Printed Thermoplastics

Science.gov (United States)

Yung, Winco K. C.; Sun, Bo; Huang, Junfeng; Jin, Yingdi; Meng, Zhengong; Choy, Hang Shan; Cai, Zhixiang; Li, Guijun; Ho, Cheuk Lam; Yang, Jinlong; Wong, Wai Yeung

2016-08-01

3D printing using thermoplastics has become very popular in recent years, however, it is challenging to provide a metal coating on 3D objects without using specialized and expensive tools. Herein, a novel acrylic paint containing malachite for coating on 3D printed objects is introduced, which can be transformed to copper via one-step laser treatment. The malachite containing pigment can be used as a commercial acrylic paint, which can be brushed onto 3D printed objects. The material properties and photochemical transformation processes have been comprehensively studied. The underlying physics of the photochemical synthesis of copper was characterized using density functional theory calculations. After laser treatment, the surface coating of the 3D printed objects was transformed to copper, which was experimentally characterized by XRD. 3D printed prototypes, including model of the Statue of Liberty covered with a copper surface coating and a robotic hand with copper interconnections, are demonstrated using this painting method. This composite material can provide a novel solution for coating metals on 3D printed objects. The photochemical reduction analysis indicates that the copper rust in malachite form can be remotely and photo-chemically reduced to pure copper with sufficient photon energy.

lessons learned from the QUENCH program at FZK

International Nuclear Information System (INIS)

Steinbrueck, M.; Grosse, M.; Sepold, L.; Stuckert, J.

2011-01-01

The paper gives an overview on the main outcome of the QUENCH program at FZK, including complementary bundle experiments and separate-effects tests. The major objective of the program is to deliver experimental and analytical data to support development and validation of quench and quench-related models as used in code systems. So far, 15 integral bundle QUENCH experiments with 21-31 electrically heated fuel rod simulators of 2.5 m length have been conducted. The following parameters and their influence on bundle degradation and reflood have been investigated: degree of pre-oxidation, temperature at initiation of reflood, flooding rate, influence of neutron absorber materials (B 4 C, AgInCd), air ingress, and the influence of the type of cladding alloy. In six tests reflood of the bundle caused a temporary temperature excursion connected with the release of a significant amount of hydrogen, typically 2 orders of magnitude greater than in those tests with 'successful' quenching in which cool-down was immediately achieved. Comprehensive formation, relocation, and oxidation of melt were observed in all tests with escalation. The temperature boundary between rapid cooldown and temperature escalation was typically 2100-2200 K in the 'normal' quench tests, i.e. tests without absorber and/or steam starvation. Tests with absorber and/or steam starvation were found to lead to temperature escalations at lower temperatures. All phenomena occurring in the bundle tests have been additionally investigated in parametric and more systematic separate-effects tests. Oxidation kinetics of various cladding alloys, including advanced ones, have been determined over a wide temperature range (873-1773 K) in different atmospheres (steam, oxygen, air, and their mixtures). Hydrogen absorption by different zirconium alloys was investigated in detail, recently also using neutron radiography as non-destructive method for determination of hydrogen distribution in claddings

40 CFR 52.2426 - Photochemical Assessment Monitoring Stations (PAMS) Program.

Science.gov (United States)

2010-07-01

... Stations (PAMS) Program. 52.2426 Section 52.2426 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... § 52.2426 Photochemical Assessment Monitoring Stations (PAMS) Program. On November 23, 1994 Virginia's... Photochemical Assessment Monitoring Stations (PAMS) Program as a state implementation plan (SIP) revision, as...

Changes in activities of both photosystems and the regulatory effect of cyclic electron flow in field-grown cotton (Gossypium hirsutum L) under water deficit.

Science.gov (United States)

Yi, Xiao-Ping; Zhang, Ya-Li; Yao, He-Sheng; Han, Ji-Mei; Chow, Wah Soon; Fan, Da-Yong; Zhang, Wang-Feng

2018-01-01

To clarify the influence of water deficit on the functionality of the photosynthetic apparatus of cotton plants, leaf gas exchange, chlorophyll a fluorescence, and P700 redox state were examined in field-grown cotton Gossypium hirsutum L. cv. Xinluzao 45. In addition, we measured changes in the P515 signal and analyzed the activity of ATP synthase and the trans-thylakoid proton gradient (ΔpH). With increasing water deficit, the net CO 2 assimilation rate (A N ) and stomatal conductance (g s ) significantly decreased, but the maximum quantum efficiency of PSII photochemistry (F v /F m ) did not change. The photochemical activity of photosystem II (PSII) was reflected by the photochemical quenching coefficient (qP), quantum efficiency of photosystem II [Y(II)], and electron transport rate through PSII [ETR(II)], while the activity of photosystem I (PSI) was reflected by the quantum efficiency of photosystem I [Y(I)] and the electron transport rate through PSI [ETR(I)]. Both activities were maintained under mild water deficit, but were slightly decreased under moderate water deficit. Under moderate water deficit, cyclic electron flow (CEF), the fraction of absorbed light dissipated thermally via the ΔpH- and xanthophyll-regulated process [Y(NPQ)], and the fraction of P700 oxidized under a given set of conditions [Y(ND)] increased. Our results suggest that the activities of both photosystems are stable under mild water deficit and decrease only slightly under moderate water deficit. Moderate water deficit stimulates CEF, and the stimulation of CEF is essential for protecting PSI and PSII against photoinhibition. Copyright © 2017 Elsevier GmbH. All rights reserved.

The mass dependence of dwarf satellite galaxy quenching

International Nuclear Information System (INIS)

Slater, Colin T.; Bell, Eric F.

2014-01-01

We combine observations of the Local Group with data from the NASA-Sloan Atlas to show the variation in the quenched fraction of satellite galaxies from low-mass dwarf spheroidals and dwarf irregulars to more massive dwarfs similar to the Magellanic Clouds. While almost all of the low-mass (M * ≲ 10 7 M ☉ ) dwarfs are quenched, at higher masses the quenched fraction decreases to approximately 40%-50%. This change in the quenched fraction is large and suggests a sudden change in the effectiveness of quenching that correlates with satellite mass. We combine this observation with models of satellite infall and ram pressure stripping to show that the low-mass satellites must quench within 1-2 Gyr of pericenter passage to maintain a high quenched fraction, but that many more massive dwarfs must continue to form stars today even though they likely fell into their host >5 Gyr ago. We also characterize how the susceptibility of dwarfs to ram pressure must vary as a function of mass if it is to account for the change in quenched fractions. Though neither model predicts the quenching effectiveness a priori, this modeling illustrates the physical requirements that the observed quenched fractions place on possible quenching mechanisms.

Supramolecular structures for photochemical energy conversion. Technical progress report, 1993--1996

Energy Technology Data Exchange (ETDEWEB)

NONE

1996-06-01

This research project is concerned with the design, synthesis and study by photochemical and spectroscopic methods of complex molecular devices that mimic some important aspects of photosynthetic electron and energy transfer. Properly engineered molecules of this type can functionally mimic photosynthetic light harvesting (singlet-singlet energy transfer between chromophores), photoprotection from light-initiated singlet oxygen damage (triplet-triplet energy transfer from chlorophylls to carotenoid polyenes), and, most importantly, photoinduced multistep electron transfer to generate charge-separated states that preserve some of the photon energy as chemical potential. During the last three years, progress has been made on several fronts, all of which are related to the overall goal. A biomimetic system based on carotenoid-porphyrin-quinone triads has been constructed that demonstrates photoinduced transmembrane charge separation which in turn drives transmembrane proton transfer. Another investigation has focused on the use of proton transfer reactions to stabilize the initial products of photoinduced electron transfer and thereby increase the yield of long-lived charge separation. A third study has investigated the influence of rigid molecular geometries and short donor-acceptor separations on photoinduced electron transfer reactions. Finally, generation and quenching of singlet molecular oxygen by chlorophyll aggregates has been studied. All four studies are described and results are discussed.

Universal post-quench prethermalization at a quantum critical point

Science.gov (United States)

Orth, Peter P.; Gagel, Pia; Schmalian, Joerg

2015-03-01

We consider an open system near a quantum critical point that is suddenly moved towards the critical point. The bath-dominated diffusive non-equilibrium dynamics after the quench is shown to follow scaling behavior, governed by a critical exponent that emerges in addition to the known equilibrium critical exponents. We determine this exponent and show that it describes universal prethermalized coarsening dynamics of the order parameter in an intermediate time regime. Implications of this quantum critical prethermalization are a powerlaw rise of order and correlations after an initial collapse of the equilibrium state and a crossover to thermalization that occurs arbitrarily late for sufficiently shallow quenches. [1] P. Gagel, P. P. Orth, J. Schmalian, Phys.Rev. Lett. (in press) arXiv:1406.6387

$B_K$ from quenched QCD with exact chiral symmetry

CERN Document Server

Garron, N; Hölbling, C; Lellouch, L P; Rebbi, C; Garron, Nicolas; Giusti, Leonardo; Hoelbling, Christian; Lellouch, Laurent; Rebbi, Claudio

2004-01-01

We present a calculation of the standard model Delta S=2 matrix element relevant to indirect CP violation in K->pipi decays which uses Neuberger's chiral formulation of lattice fermions. The computation is performed in the quenched approximation on a 16^3x32 lattice that has a lattice spacing asim 0.1 fm. The resulting bare matrix element is renormalized non-perturbatively. Our main result is B_K^{RGI}=0.87(8)^{+2+14}_{-1-14}, where the first error is statistical, the second is systematic and the third is an estimate of the uncertainty associated with the quenched approximation and with the fact that our kaons are composed of degenerate s and d quarks with masses sim m_s/2.

Quench simulation of SMES consisting of some superconducting coils

International Nuclear Information System (INIS)

Noguchi, S.; Oga, Y.; Igarashi, H.

2011-01-01

A chain of quenches may be caused by a quench of one element coil when SMES is consists of many element coils. To avoid the chain of quenches, the energy stored in element coil has to be quickly discharged. The cause of the chain of the quenches is the short time constant of the decreasing current of the quenched coil. In recent years, many HTS superconducting magnetic energy storage (HTS-SMES) systems are investigated and designed. They usually consist of some superconducting element coils due to storing excessively high energy. If one of them was quenched, the storage energy of the superconducting element coil quenched has to be immediately dispersed to protect the HTS-SMES system. As the result, the current of the other element coils, which do not reach to quench, increases since the magnetic coupling between the quenched element coil and the others are excessively strong. The increase of the current may cause the quench of the other element coils. If the energy dispersion of the element coil quenched was failed, the other superconducting element coil would be quenched in series. Therefore, it is necessary to investigate the behavior of the HTS-SMES after quenching one or more element coils. To protect a chain of quenches, it is also important to investigate the time constant of the coils. We have developed a simulation code to investigate the behavior of the HTS-SMES. By the quench simulation, it is indicated that a chain of quenches is caused by a quench of one element coil.

Iron oxides photochemical dissolution

International Nuclear Information System (INIS)

Blesa, M.A.; Litter, M.I.

1987-01-01

This work was intended to study the light irradiation influence of diverse wave-lengths on iron oxides dissolution in aqueous solutions. The objectives of this work were: the exploration of photochemical processes with the aim of its eventual application in: a) decontamination and chemical cleaning under special conditions; b) materials for solar energy conversion. (Author)

Quenching reactions of electronically excited atoms

International Nuclear Information System (INIS)

Setser, D.W.

2001-01-01

The two-body, thermal quenching reactions of electronically excited atoms are reviewed using excited states of Ar, Kr, and Xe atoms as examples. State-specific interstate relaxation and excitation-transfer reactions with atomic colliders are discussed first. These results then are used to discuss quenching reactions of excited-state atoms with diatomic and polyatomic molecules, the latter have large cross sections, and the reactions can proceed by excitation transfer and by reactive quenching. Excited states of molecules are not considered; however, a table of quenching rate constants is given for six excited-state molecules in an appendix

Quench/reflood modeling in MELCOR

International Nuclear Information System (INIS)

Gauntt, R.O.

2001-01-01

The authors describe the reactor accident simulation model MELCOR. It comprises hydrodynamic investigations on reactor core quenching, hydrogen generation in the reactor core vessel, quench front advances. Preliminary comparisons to data are reasonable but need further validation. (uke)

Inheritance of photochemical air pollution tolerance in petunias

Energy Technology Data Exchange (ETDEWEB)

Hanson, G.P.; Addis, D.H.; Thorne, L.

1976-12-01

Seven commercial inbred lines of pink flowered multiflora petunia (Petunia hybrida Vilm.) which differed widely in degrees of tolerance to photochemical oxidants were crossed in all possible combinations to yield a complete diallel cross. Sibling representatives of all 49 possible hybrids were then separately subjected to ozone (O/sub 3/), peroxyacetyl nitrate (PAN), and ambient oxidants at Arcadia, California. The seedlings were scored for tolerance to each pollutant and the inheritance of tolerance to each pollutant was studied. At the ambient levels of photochemical oxidants encountered, PAN more severely injured the petunias than did the O/sub 3/ component. Hybrids tolerant to one oxidant were not necessarily tolerant to the other. The genes which contributed photochemical oxidant tolerance in petunia acted primarily in an additive manner with some indication of partial dominance for tolerance. Gene interaction was evident in the expression of petunia sensitivity to PAN.

Simulation of photoreactive transients and of photochemical transformation of organic pollutants in sunlit boreal lakes across 14 degrees of latitude: A photochemical mapping of Sweden.

Science.gov (United States)

Koehler, Birgit; Barsotti, Francesco; Minella, Marco; Landelius, Tomas; Minero, Claudio; Tranvik, Lars J; Vione, Davide

2018-02-01

Lake water constituents, such as chromophoric dissolved organic matter (CDOM) and nitrate, absorb sunlight which induces an array of photochemical reactions. Although these reactions are a substantial driver of pollutant degradation in lakes they are insufficiently understood, in particular on large scales. Here, we provide for the first time comprehensive photochemical maps covering a large geographic region. Using photochemical kinetics modeling for 1048 lakes across Sweden we simulated the steady-state concentrations of four photoreactive transient species, which are continuously produced and consumed in sunlit lake waters. We then simulated the transient-induced photochemical transformation of organic pollutants, to gain insight into the relevance of the different photoreaction pathways. We found that boreal lakes were often unfavorable environments for photoreactions mediated by hydroxyl radicals (OH) and carbonate radical anions (CO 3 - ), while photoreactions mediated by CDOM triplet states ( 3 CDOM*) and, to a lesser extent, singlet oxygen ( 1 O 2 ) were the most prevalent. These conditions promote the photodegradation of phenols, which are used as plastic, medical drug and herbicide precursors. When CDOM concentrations increase, as is currently commonly the case in boreal areas such as Sweden, 3 CDOM* will also increase, promoting its importance in photochemical pathways even more. Copyright © 2017 Elsevier Ltd. All rights reserved.

Quantum quenches in a holographic Kondo model

Energy Technology Data Exchange (ETDEWEB)

Erdmenger, Johanna [Max-Planck-Institut für Physik (Werner-Heisenberg-Institut),Föhringer Ring 6, 80805, Munich (Germany); Institut für Theoretische Physik und Astrophysik, Julius-Maximilians-Universität Würzburg,Am Hubland, 97074 Würzburg (Germany); Flory, Mario [Max-Planck-Institut für Physik (Werner-Heisenberg-Institut),Föhringer Ring 6, 80805, Munich (Germany); Institute of Physics, Jagiellonian University,Łojasiewicza 11, 30-348 Kraków (Poland); Newrzella, Max-Niklas; Strydom, Migael [Max-Planck-Institut für Physik (Werner-Heisenberg-Institut),Föhringer Ring 6, 80805, Munich (Germany); Wu, Jackson M. S. [Department of Physics and Astronomy, University of Alabama,Tuscaloosa, AL 35487 (United States)

2017-04-10

We study non-equilibrium dynamics and quantum quenches in a recent gauge/ gravity duality model for a strongly coupled system interacting with a magnetic impurity with SU(N) spin. At large N, it is convenient to write the impurity spin as a bilinear in Abrikosov fermions. The model describes an RG flow triggered by the marginally relevant Kondo operator. There is a phase transition at a critical temperature, below which an operator condenses which involves both an electron and an Abrikosov fermion field. This corresponds to a holographic superconductor in AdS{sub 2} and models the impurity screening. We quench the Kondo coupling either by a Gaussian pulse or by a hyperbolic tangent, the latter taking the system from the condensed to the uncondensed phase or vice-versa. We study the time dependence of the condensate induced by this quench. The timescale for equilibration is generically given by the leading quasinormal mode of the dual gravity model. This mode also governs the formation of the screening cloud, which is obtained as the decrease of impurity degrees of freedom with time. In the condensed phase, the leading quasinormal mode is imaginary and the relaxation of the condensate is over-damped. For quenches whose final state is close to the critical point of the large N phase transition, we study the critical slowing down and obtain the combination of critical exponents zν=1. When the final state is exactly at the phase transition, we find that the exponential ringing of the quasinormal modes is replaced by a power-law behaviour of the form ∼t{sup −a}sin (blog t). This indicates the emergence of a discrete scale invariance.

Trends in photochemical smog in the Cape Peninsula and the ...

African Journals Online (AJOL)

There has been growing public concern over reports of increasing air pollution in the Cape Peninsula. Attention has been focused on the 'brown haze' and on photochemical smog. Because of deficiencies in the monitoring equipment, information on trends in photochemical smog levels over the past decade is limited.

Quenched Large Deviations for Simple Random Walks on Percolation Clusters Including Long-Range Correlations

Science.gov (United States)

Berger, Noam; Mukherjee, Chiranjib; Okamura, Kazuki

2018-03-01

We prove a quenched large deviation principle (LDP) for a simple random walk on a supercritical percolation cluster (SRWPC) on {Z^d} ({d ≥ 2}). The models under interest include classical Bernoulli bond and site percolation as well as models that exhibit long range correlations, like the random cluster model, the random interlacement and the vacant set of random interlacements (for {d ≥ 3}) and the level sets of the Gaussian free field ({d≥ 3}). Inspired by the methods developed by Kosygina et al. (Commun Pure Appl Math 59:1489-1521, 2006) for proving quenched LDP for elliptic diffusions with a random drift, and by Yilmaz (Commun Pure Appl Math 62(8):1033-1075, 2009) and Rosenbluth (Quenched large deviations for multidimensional random walks in a random environment: a variational formula. Ph.D. thesis, NYU, arXiv:0804.1444v1) for similar results regarding elliptic random walks in random environment, we take the point of view of the moving particle and prove a large deviation principle for the quenched distribution of the pair empirical measures of the environment Markov chain in the non-elliptic case of SRWPC. Via a contraction principle, this reduces easily to a quenched LDP for the distribution of the mean velocity of the random walk and both rate functions admit explicit variational formulas. The main difficulty in our set up lies in the inherent non-ellipticity as well as the lack of translation-invariance stemming from conditioning on the fact that the origin belongs to the infinite cluster. We develop a unifying approach for proving quenched large deviations for SRWPC based on exploiting coercivity properties of the relative entropies in the context of convex variational analysis, combined with input from ergodic theory and invoking geometric properties of the supercritical percolation cluster.

Photochemically consumed hydrocarbons and their relationship with ozone formation in two megacities of China

Science.gov (United States)

Chang, C.; Wang, J.; Liu, S.; Shao, M.; Zhang, Y.; Zhu, T.; Shiu, C.; Lai, C.

2010-12-01

Two on-site continuous measurements of ozone and its precursors in two megacities of China were carried out in an urban site of Beijing and a suburban site near Guangzhou in the Pearl River Delta (PRD) to estimate precursor consumption and to assess its relationship with oxidant (O3+NO2) formation level. An observation-based method (OBM) with the precursor consumption concept was adopted to assess the relationship between oxidant production and amounts of photochemically consumed non-methane hydrocarbons (NMHCs). In this approach, the ratio of ethylbenzene to m,p-xylenes was used to estimate the degree of photochemical processing, as well as the amounts of photochemically consumed NMHCs by reacting with OH. By trying to correlate the observed oxidant with the observed NMHC concentration, the two areas both revealed nearly no to low correlation between them. However, it existed fair to good correlations (R2=0.68 for Beijing, 0.53 for PRD) between the observed oxidant level and the degree of photochemical processing (ethylbenzene/m,p-xylenes). Furthermore, after taking the approach of consumption to estimate the consumed amounts of NMHCs, an interesting finding reveals that the definite correlation existed between the observed oxidant level and the total consumed NMHCs. The good correlations (R2=0.83 for Beijing, 0.81 for PRD) implies that the ambient oxidant level correlated to the amount of consumed NMHCs. The results of the two megacities in China by using the OBM with the precursor consumption concept can provide another pathway to explore the relationship between photochemically produced oxidant and consumed precursors, and will be helpful to validate model results and to reduce uncertainty of model predictions. However, the method has some room for uncertainty, as injection of fresh precursor emissions and additional boundary ozone involved, etc. could affect the estimation of consumed NMHCs and observed oxidant levels. Assistance of approaches in assessing the

40 CFR 1065.675 - CLD quench verification calculations.

Science.gov (United States)

2010-07-01

... 40 Protection of Environment 32 2010-07-01 2010-07-01 false CLD quench verification calculations... POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Calculations and Data Requirements § 1065.675 CLD quench verification calculations. Perform CLD quench-check calculations as follows: (a) Perform a CLD analyzer quench...

Statistical Diagnosis Method of Conductor Motions in Superconducting Magnets to Predict their Quench Performance

CERN Document Server

Khomenko, B A; Rijllart, A; Sanfilippo, S; Siemko, A

2001-01-01

Premature training quenches are usually caused by the transient energy released within the magnet coil as it is energised. Two distinct varieties of disturbances exist. They are thought to be electrical and mechanical in origin. The first type of disturbance comes from non-uniform current distribution in superconducting cables whereas the second one usually originates from conductor motions or micro-fractures of insulating materials under the action of Lorentz forces. All of these mechanical events produce in general a rapid variation of the voltages in the so-called quench antennas and across the magnet coil, called spikes. A statistical method to treat the spatial localisation and the time occurrence of spikes will be presented. It allows identification of the mechanical weak points in the magnet without need to increase the current to provoke a quench. The prediction of the quench level from detailed analysis of the spike statistics can be expected.

Thermal and mechanical effects of quenches on Nb3Sn high field hadron collider magnets

International Nuclear Information System (INIS)

Ryuji, Yamada

2001-01-01

Thermal and its resulting mechanical stress due to quenches inside short and long epoxy impregnated Nb 3 Sn high field magnets are studied with a quench simulation program, Kuench, and ANSYS program. For the protection of a long high field magnet, we have to use heaters to dump the stored energy uniformly inside the magnet, after detection of a spontaneous quench. The time delay of starting a forced quench with heaters, is estimated using ANSYS. Using this information, the thermal distribution in two-dimensional magnet cross section is studied. First a one meter model magnet with a dump resistor is used to estimate the effects and then a 10 meter long magnet is studied. The two-dimensional temperature distributions in the magnet cross sections are recorded every 5 ms, and visually displayed. With this visual animation displays we can understand intuitively the thermal and quench propagation in 2-dimensional field. The quenching cables get heated locally much more than the surrounding material and non-quenching conductor cables. With a one meter magnet with a dump resistor of 30 mOmega, typically only the quench starting cables and its neighbor cables get heated up to 100 K without significant effects from the heaters. With a10 meter magnet, heaters cause the quenches to most of the conductor blocks. The quench initiating cables get up to 250 to 300 K in 100 ms, but the surrounding and wedges are not heated up significantly. This causes the excessive stress in the quenching conductors and in their insulation material locally. The stress and strain in the conductor as well as in the insulation become excessive, and they are studied using the ANSYS stress analysis, using Von Mises criterion. It is concluded that for the one meter magnet with the presented cross section and configuration, the thermal effects due to the quench is tolerable. But we need much more quench study and improvements in the design for the extended ten meter long magnet [1

Single photon detection with self-quenching multiplication

Science.gov (United States)

Zheng, Xinyu (Inventor); Cunningham, Thomas J. (Inventor); Pain, Bedabrata (Inventor)

2011-01-01

A photoelectronic device and an avalanche self-quenching process for a photoelectronic device are described. The photoelectronic device comprises a nanoscale semiconductor multiplication region and a nanoscale doped semiconductor quenching structure including a depletion region and an undepletion region. The photoelectronic device can act as a single photon detector or a single carrier multiplier. The avalanche self-quenching process allows electrical field reduction in the multiplication region by movement of the multiplication carriers, thus quenching the avalanche.

Assessment of diphenylcyclopropenone for photochemically induced mutagenicity in the Ames assay

Energy Technology Data Exchange (ETDEWEB)

Wilkerson, M.G.; Connor, T.H.; Henkin, J.; Wilkin, J.K.; Matney, T.S.

1987-10-01

The photochemical conversion of diphenylcyclopropenone to diphenylacetylene has recently been reported. Diphenylcyclopropenone is used in the treatment of alopecia areata and is nonmutagenic in a limited Ames assay. We examined diphenylcyclopropenone and diphenylacetylene, as well as synthetic precursors of diphenylcyclopropenone--dibenzylketone and alpha,alpha'-dibromodibenzylketone--for mutagenicity against TA100, TA98, TA102, UTH8413, and UTH8414. All compounds were nonmutagenic except alpha,alpha'-dibromodibenzylketone, which was a potent mutagen in TA100 with and without S-9 activation. The effect of photochemical activation of diphenylcyclopropenone in the presence of bacteria demonstrated mutagenicity in UTH8413 (two times background) at 10 micrograms/plate with S-9 microsomal activation. 8-Methoxypsoralen produces a mutagenic response in TA102 at 0.1 microgram/plate with 60 seconds of exposure to 350 nm light. In vitro photochemically activated Ames assay with S-9 microsomal fraction may enhance the trapping of short-lived photochemically produced high-energy mutagenic intermediates. This technique offers exciting opportunities to trap high-energy intermediates that may play an important role in mutagenesis. This method can be applied to a variety of topically applied dermatologic agents, potentially subjected to photochemical changes in normal use.

Quench propagation in the SSC dipole magnets

International Nuclear Information System (INIS)

Lopez, G.; Snitchler, G.

1990-09-01

The effects of quench propagation are modeled in 40mm and 50mm diameter collider dipole magnet designs. A comparative study of the cold diode (passive) and quench heater (active) protection schemes will be presented. The SSCQ modeling program accurately simulates the axial quench velocity and uses phenomenological time delays for turn-to-turn transverse propagation. The axial quench velocity is field dependent and consequently, each conductor's quench profile is tracked separately. No symmetry constraints are employed and the distribution of the temperatures along the conductor differs from the adiabatic approximation. A single magnet has a wide margin of self protection which suggests that passive protection schemes must be considered. 6 refs., 3 figs., 1 tab

Luminescence quenching by heavy metal ions of probes based on anthracene, pyrene, and eosin in human serum albumin

Science.gov (United States)

Naumova, E. V.; Melnikov, A. G.; Melnikov, G. V.

2013-05-01

Fluorescence and phosphorescence quenching processes of polar and non-polar luminescent probes associated with human serum albumin (HSA) in phosphate buffer at pH 7.4 were studied. Stern-Volmer quenching constants of anthracene and pyrene fluorescence and eosin phosphorescence and rate constants for quenching of eosin triplet states were determined. The polarity index of pyrene bound to HSA was obtained as a function of thallium nitrate concentration. The influences of structural changes in the proteins that were stimulated by heavy-metal salts and of screening of protein charges by salt ions on quenching processes of singlet and triplet states of the probes were found.

Simulation of the Quench-06 experiment with Scdapsim; Simulacion del experimento Quench-06 con Scdapsim

Energy Technology Data Exchange (ETDEWEB)

Angel M, E. del; Nunez C, A.; Amador G, R. [CNSNS, Dr. Barragan No. 779, 03020 Mexico D.F. (Mexico)]. e-mail: edangelm@cnsns.gob.mx

2003-07-01

The present work describes the pattern of the called Quench installation developed and used by the National Commission of Nuclear Security and Safeguards (CNSNS) for their participation in the International Standard Problem 45 (ISP), organized by the Nuclear Energy Agency (NEA). The exercise consisted on the simulation of the denominated experiment Quench-06 carried out in the experimental installation Quench located in the Forschungszentrum laboratory in Karlsruhe, Germany. The experiment Quench-06 consisted on simulating the sudden and late injection of water in a fuel assemble for a pressurized reactor (PWR). The CNSNS uses the version bd of the SCDAPSIM code developed by the company Innovative Software Systems (ISS) to simulate this experiment. The obtained results showed that the code is able to predict the experiment partially when overestimating the hydrogen production and of the partial fused of some fuel pellets, but predicting correctly the damage in the shroud. (Author)

Minimum Quench Energy and Early Quench Development in NbTi Superconducting Strands

CERN Document Server

Breschi, M; Boselli, M; Bottura, Luca; Devred, Arnaud; Ribani, P L; Trillaud, F

2007-01-01

The stability of superconducting wires is a crucial task in the design of safe and reliable superconducting magnets. These magnets are prone to premature quenches due to local releases of energy. In order to simulate these energy disturbances, various heater technologies have been developed, such as coated tips, graphite pastes, and inductive coils. The experiments studied in the present work have been performed using a single-mode diode laser with an optical fiber to illuminate the superconducting strand surface. Minimum quench energies and voltage traces at different magnetic flux densities and transport currents have been measured on an LHC-type, Cu/NbTi wire bathed in pool boiling helium I. This paper deals with the numerical analysis of the experimental data. In particular, a coupled electromagnetic and thermal model has been developed to study quench development and propagation, focusing on the influence of heat exchange with liquid helium.

Experimental methods for quenching structures in lunar-analog silicate melts - Variations as a function of quench media and composition

International Nuclear Information System (INIS)

Dyar, M.D.

1984-01-01

Compositions analogous to lunar green, orange, and brown glasses were synthesized under consistent conditions, then quenched into a variety of different media when the samples were removed from the furnace. Iron valence and coordination are a direct function of quench media used, spanning the range from brine/ice (most effective quench), water, butyl phthalate, silicone oil, liquid nitrogen, highly reducing CO-CO2 gas, to air (least efficient quench). In the green and brown glasses, Fe(3+) in four-fold and six-fold coordination is observed in the slowest-quenched samples Fe(2+) coordination varies directly with quench efficiency. Less pronounced changes were observed in the Ti-rich orange glass. Therefore the remote-sensed spectrum of a glass-bearing regolith on the moon may be influenced by the process by which the glass cooled, and extreme caution must be used when comparing spectra of synthetic glass analogs with real lunar glasses

Computational quench model applicable to the SMES/CICC

Science.gov (United States)

Luongo, Cesar A.; Chang, Chih-Lien; Partain, Kenneth D.

1994-07-01

A computational quench model accounting for the hydraulic peculiarities of the 200 kA SMES cable-in-conduit conductor has been developed. The model is presented and used to simulate the quench on the SMES-ETM. Conclusions are drawn concerning quench detection and protection. A plan for quench model validation is presented.

The quench detector on magnetic modulator for the UNK quench protection system

International Nuclear Information System (INIS)

Bolotin, I.M.; Enbaev, A.V.; Erokhin, A.N.; Gridasov, V.I.; Priyma, M.V.; Sychev, V.A.; Vasiliev, L.M.

1992-01-01

When designing and constructing superconducting high energy accelerators, the development of the Quench Detection System (QDS) for superconducting (SC) magnets becomes an important and critical problem. At present there is experience in developing such systems for the Tevatron (FNAL, USA) and HERA (Hamburg, Germany). The machines for more than 3 TeV-the UNK (Russia) and SSC (USA), which are presently under construction, have very large circumferences, 21 and 87 km, respectively. The QDS's, similar to those of the Tevatron, require a larger part of the active components of the electronic equipment be placed in the machine tunnel close to the magnets, and protected from irradiation or additional surface buildings will have to be constructed. In either case the cost of such a QDS increases. In addition the former ones reliability decreases and maintenance becomes more difficult. For such machines, a QDS in which the quench signal, in each superconducting magnet (SCM) or groups of SCM'S, is extracted with the help of a bridge circuit (BC) appears to be more suitable. The half coils of SCM's are connected as two arms of the bridge and the resistors placed in the vacuum vessels of the magnet cryostats are connected to the other two. The off-balance signal of each BC is enhanced with the help of magnetic amplifiers. This note describes the experimental prototype of a bridge-type Quench Detector (QD) based on a magnetic amplifier Magnetic Modulator (MM) type, allowing one not only to detect a quench in a SCM, but also making feasible a wider system capability, namely: to record the signals from all SC elements during a quench for further analysis of its causes; to check the presence of short circuits of the ring electromagnet bus relative to the cryostats and to localize their position

The interrelationship between the lower oxygen limit, chlorophyll fluorescence and the xanthophyll cycle in plants.

Science.gov (United States)

Wright, A Harrison; DeLong, John M; Gunawardena, Arunika H L A N; Prange, Robert K

2011-03-01

The lower oxygen limit (LOL) in plants may be identified through the measure of respiratory gases [i.e. the anaerobic compensation point (ACP) or the respiratory quotient breakpoint (RQB)], but recent work shows it may also be identified by a sudden rise in dark minimum fluorescence (F(o)). The interrelationship between aerobic respiration and fermentative metabolism, which occur in the mitochondria and cytosol, respectively, and fluorescence, which emanates from the chloroplasts, is not well documented in the literature. Using spinach (Spinacia oleracea), this study showed that F(o) and photochemical quenching (q(P)) remained relatively unchanged until O(2) levels dropped below the LOL. An over-reduction of the plastoquinone (PQ) pool is believed to increase F(o) under dark + anoxic conditions. It is proposed that excess cytosolic reductant due to inhibition of the mitochondria's cytochrome oxidase under low-O(2), may be the primary reductant source. The maximum fluorescence (F(m)) is largely unaffected by low-O(2) in the dark, but was severely quenched, mirroring changes to the xanthophyll de-epoxidation state (DEPS), under even low-intensity light (≈4 μmol m(-2) s(-1)). In low light, the low-O(2)-induced increase in F(o) was also quenched, likely by non-photochemical and photochemical means. The degree of quenching in the light was negatively correlated with the level of ethanol fermentation in the dark. A discussion detailing the possible roles of cyclic electron flow, the xanthophyll cycle, chlororespiration and a pathway we termed 'chlorofermentation' were used to interpret fluorescence phenomena of both spinach and apple (Malus domestica) over a range of atmospheric conditions under both dark and low-light.

Ultra-trace determination of iodine in sediments and biological material using UV photochemical generation-inductively coupled plasma mass spectrometry

Energy Technology Data Exchange (ETDEWEB)

Grinberg, Patricia [Institute for National Measurements Standards, National Research Council Canada, Ottawa, Ontario, K1A 0R6 (Canada)], E-mail: patricia.grinberg@nrc.ca; Sturgeon, Ralph E. [Institute for National Measurements Standards, National Research Council Canada, Ottawa, Ontario, K1A 0R6 (Canada)

2009-03-15

Several sample preparation techniques have been evaluated for the determination of iodine using UV-photochemical generation-quadrupole inductively coupled plasma mass spectrometry. Thermal decomposition of samples at 1000 {sup o}C followed by capture of the liberated iodine in dilute acetic acid permitted subsequent UV-photochemical generation of a volatile iodine species that serves to enhance sensitivity 25-fold over conventional solution nebulization, delivering reagent blank detection limits of 8.75 pg g{sup -1127}I and 0.075 pg g{sup -1129}I for solid samples (400 mg test mass). The methodology was validated through determination of total iodine in several Standard Reference Materials, including NIST 1572 Citrus leaves, NIST 1549 Non-fat milk powder, NIST 1566a Oyster tissue and NIST 2709 San Joaquin Soil. Liberation of iodine from samples and its collection as well as photochemical generation were quantitative, permitting calibration to be achieved using standards prepared in dilute acetic acid.

Quasiparticle explanation of ``weak thermalization'' regime under quench in a non-integrable quantum spin chain

Science.gov (United States)

Lin, Cheng-Ju; Motrunich, Olexei

Eigenstate Thermalization Hypothesis provides one picture of thermalization in a quantum system by looking at individual eigenstates. However, it is also important to consider how local observables reach equilibrium values dynamically. Quench protocol is one of the settings to study such questions. A recent numerical study [Banuls, Cirac, and Hastings, Phys. Rev. Lett. 106, 050405 (2011)] of a nonintegrable quantum Ising model with longitudinal field under such quench setting found different behaviors under different initial quantum states. One particular case termed ``weak thermalization'' regime showed apparently persistent oscillations of some observables. Here we provide an explanation of such oscillations. We use perturbation theory near the ground state of the model, and identify the oscillation frequency as the quasiparticle mass. With this quasiparticle picture, we can then address the long-time behavior of the oscillations.

Photochemical reduction of CO{sub 2} to fuels and chemicals

Energy Technology Data Exchange (ETDEWEB)

DuBois, D. [National Renewable Energy Lab., Golden, CO (United States); Eisenberg, R. [Univ. of Rochester, NY (United States); Fujita, E. [Brookhaven National Lab., Upton, NY (United States)

1996-09-01

Photochemical reduction of CO{sub 2} represents a potentially useful approach to developing a sustainable source of carbon-based chemicals, fuels, and materials. In this report the present status of photochemical CO{sub 2} reduction is assessed, areas that need to be better understood for advancement are identified, and approaches to overcoming barriers are suggested. Because of the interdisciplinary nature of this field, assessments of three closely interrelated areas are given including integrated photochemical systems for catalytic CO{sub 2} reduction, thermal catalytic CO{sub 2} reactions, and electrochemical CO{sub 2} reduction. The report concludes with a summary and assessment of potential impacts of this area on chemical and energy technologies.

PHOTOCHEMICAL HEATING OF DENSE MOLECULAR GAS

Energy Technology Data Exchange (ETDEWEB)

Glassgold, A. E. [Astronomy Department, University of California, Berkeley, CA 94720 (United States); Najita, J. R. [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States)

2015-09-10

Photochemical heating is analyzed with an emphasis on the heating generated by chemical reactions initiated by the products of photodissociation and photoionization. The immediate products are slowed down by collisions with the ambient gas and then heat the gas. In addition to this direct process, heating is also produced by the subsequent chemical reactions initiated by these products. Some of this chemical heating comes from the kinetic energy of the reaction products and the rest from collisional de-excitation of the product atoms and molecules. In considering dense gas dominated by molecular hydrogen, we find that the chemical heating is sometimes as large, if not much larger than, the direct heating. In very dense gas, the total photochemical heating approaches 10 eV per photodissociation (or photoionization), competitive with other ways of heating molecular gas.

The composition dependence of the photochemical reactivity of strontium barium titanate

Science.gov (United States)

Bhardwaj, Abhilasha

The efficiency of particulate water photolysis catalysts is impractically low due to the recombination of intermediate species and charge carriers. The back reaction can occur easily if the oxidation and reduction sites on the surface of the catalyst are not far enough apart. It is hypothesized that it will be possible to increase the separation of the sites of the two half reactions and reduce the recombination of photogenerated charge carriers by using a ferroelectric material with permanent internal dipolar fields. This separation of the reaction sites may significantly increase the efficiency of the process. The present work compares the photochemical reactivities of ferroelectric and nonferroelectric materials (SrxBa1-xTiO 3, 0.0≤ x ≤1.0) with similar composition and structure. The reactivities are compared by measuring the color change of methylene blue dye after the aqueous dye solution reacts on the surface of ceramic sample pellets as a result of exposure to UV light. The reactivities are also compared by measuring the amount of silver that is formed when an aqueous AgNO3 solution photochemically reacts on the surface. The change in the color of the dye is measured by diffuse reflectance spectroscopy and absorbance measurements. The amount of silver is measured by atomic force microscopy. The photochemical reactivity of SrxBa1-xTiO3 shows a local maximum at the composition of the ferroelectric to non-ferroelectric transition. Also, the reactivities decrease as BaTiO3 and SrTiO3 become less pure. The dominant factors causing this trend in reactivities of SrxBa1-xTiO3 are the dielectric constant and alloy scattering. It is found that higher values of the dielectric constant increase the photochemical reactivity by enlarging the space charge region. The increase in alloy scattering in SrxBa1-xTiO 3 solid solutions as x increases from zero or decreases from 1, has adverse effect on reactivity. There are other factors such as ferroelectric polarization

Quenches in the superconducting magnet CELLO

International Nuclear Information System (INIS)

Hassenzahl, W.V.

1979-01-01

The superconducting magnet CELLO was tested with currents up to 3200 A at Saclay and has been installed at DESY in Hamburg where it will be used for particle physics experiments requiring colliding beams of electrons and positrons. The testing of this unique, large, one-layer solenoid provides an excellent opportunity to evaluate the theory of quench propagation under adiabatic conditions, that is, in a coil in which the conductors are not in direct contact with helium. In an early test of this coil, quenches that occurred, gives the details of the damaged conductor, and includes an analysis of the quenches. Observed axial quench velocities are compared to the calculated values based on both measurements and calculations of the thermal conductivity of the fabricated coil

Role of Ions in the Regulation of Light-Harvesting

Czech Academy of Sciences Publication Activity Database

Kaňa, Radek; Govindjee, G.

2016-01-01

Roč. 7, DEC 16 (2016), s. 1849 ISSN 1664-462X R&D Projects: GA ČR(CZ) GA16-10088S; GA MŠk(CZ) LO1416; GA MŠk(CZ) ED2.1.00/19.0392 Institutional support: RVO:61388971 Keywords : ions * non-photochemical quenching * state transitions Subject RIV: EA - Cell Biology Impact factor: 4.298, year: 2016

Wave form of current quench during disruptions in tokamaks

International Nuclear Information System (INIS)

Sugihara, Masayoshi; Gribov, Yuri; Shimada, Michiya; Lukash, Victor; Kawano, Yasunori; Yoshino, Ryuji; Miki, Nobuharu; Ohmori, Junji; Khayrutdinov, Rustam

2003-01-01

The time dependence of the current decay during the current quench phase of disruptions, which can significantly influence the electro-magnetic force on the in-vessel components due to the induced eddy currents, is investigated using data obtained in JT-60U experiments in order to derive a relevant physics guideline for the predictive simulations of disruptions in ITER. It is shown that an exponential decay can fit the time dependence of current quench for discharges with large quench rate (fast current quench). On the other hand, for discharges with smaller quench rate (slow current quench), a linear decay can fit the time dependence of current quench better than exponential. (author)

Photochemical heavy-atom effects

International Nuclear Information System (INIS)

Koziar, J.C.; Cowan, D.O.

1978-01-01

The effects of halogenated solvents such as n-butyl chloride, n-propyl bromide, and ethyl iodide, on the photochemistry of several aromatic compounds are reviewed. Dimerization of acenaphthylene is discussed in terms of spin -orbit coupling induced by the solvents. Appropriate wave functions are given for both the solvents and the compound. Cycloaddition reactions, electrocyclic rearrangements, and photochemical cis-trans isomerization are also considered

An experimental simulation study of debris quenching in a radially stratified porous bed

International Nuclear Information System (INIS)

Sehgal, B.R.; Nayak, A.K.; Stepanyan, A.

2004-01-01

During a severe accident condition in a nuclear power plant, the core melt can fail the reactor vessel and relocate into the containment basement. In some accident management schemes, the vessel cavity is flooded with water. For these a particulate debris bed is likely to form on the cavity floor due to melt break-up in water. . In this situation, the coolability of debris bed on the containment floor is a crucial issue. This is because the debris bed still generates the decay heat and if it is uncoolable, it can eventually remelt and react with concrete basement generating a lot of noncondensable gases and pressurising the containment. Hence, it is important to cool the debris bed as an accident management programme. The main parameters affecting the coolability of the debris bed are its porosity which is a function of the size and shape of the particles which constitute the debris bed, the operating condition such as water flooding from the top or bottom of debris bed, water temperature and non-condensable gas generated during bed-concrete interactions. It is found from previous studies that the debris bed has a non-uniform particle distribution or a porosity stratification. This can happen both in radial and axial plane. For example, the bed can have a lower porosity at the centre and higher porosity at the periphery. It is of interest to investigate the quenching phenomena in such configurations so as to find an effective means of quenching the heat generating bed. While most of the previous investigations mainly concentrate on quenching of a homogenous or axially stratified particulate bed with volumetric heat generation, there are almost no studies on the above phenomena in a radially stratified porous bed. So the objective of this paper is to investigate the quenching phenomena in a radially stratified bed. To simulate the phenomena, we conducted experiments in an experimental facility named as POMECO (POrous MEdia COolability). The facility has a square

Nitrate limitation and ocean acidification interact with UV-B to reduce photosynthetic performance in the diatom Phaeodactylum tricornutum

Science.gov (United States)

Li, W.; Gao, K.; Beardall, J.

2015-04-01

It has been proposed that ocean acidification (OA) will interact with other environmental factors to influence the overall impact of global change on biological systems. Accordingly we investigated the influence of nitrogen limitation and OA on the physiology of diatoms by growing the diatom Phaeodactylum tricornutum Bohlin under elevated (1000 μatm; high CO2 - HC) or ambient (390 μatm; low CO2 - LC) levels of CO2 with replete (110 μmol L-1; high nitrate - HN) or reduced (10 μmol L-1; low nitrate - LN) levels of NO3- and subjecting the cells to solar radiation with or without UV irradiance to determine their susceptibility to UV radiation (UVR, 280-400 nm). Our results indicate that OA and UVB induced significantly higher inhibition of both the photosynthetic rate and quantum yield under LN than under HN conditions. UVA or/and UVB increased the cells' non-photochemical quenching (NPQ) regardless of the CO2 levels. Under LN and OA conditions, activity of superoxide dismutase and catalase activities were enhanced, along with the highest sensitivity to UVB and the lowest ratio of repair to damage of PSII. HC-grown cells showed a faster recovery rate of yield under HN but not under LN conditions. We conclude therefore that nutrient limitation makes cells more prone to the deleterious effects of UV radiation and that HC conditions (ocean acidification) exacerbate this effect. The finding that nitrate limitation and ocean acidification interact with UV-B to reduce photosynthetic performance of the diatom P. tricornutum implies that ocean primary production and the marine biological C pump will be affected by OA under multiple stressors.

Assessing ambient ozone injury in olive (Olea europaea L.) plants by using the antioxidant ethylenediurea (EDU) in Saudi Arabia.

Science.gov (United States)

Basahi, J M; Ismail, I M; Haiba, N S; Hassan, I A; Lorenzini, G

2016-06-01

The antiozonant chemical, ethylenediurea (N-[2-(2-oxo-1-imidazolidinyl)ethyl]-N'-phenylurea, abbreviated as EDU), was applied as stem injections or soil drenches to 5-year-old containerized plants of olive (Olea europaea L. cultivar Kalamata) in growth chambers in order to assess its ameliorative effects against realistic ozone (O3) stress. Visible injury symptoms were reduced greatly in individuals treated with EDU, with injection applications having greater protection than soil drenches. EDU application caused increases in the measured ecophysiological parameters compared to untreated individuals. In particular, the stem injection protected plants against photosynthetic impairment (unchanged net photosynthetic rates and intercellular CO2 concentration, in comparison to plants grown in filtered air). EDU application increased the protection of PSII from ambient O3 oxidative stress, although it did not retain the proportion of redox state of QA, pigment composition of photosynthetic apparatus and size of light-harvesting complex of PSII. However, the stem injection of plants with EDU induced lower non-photochemical quenching (NPQ) values in comparison to ambient air (-2 %), indicating a better photoprotection of PSII in comparison to soil drench application. EDU application caused increases in the morphological and biometric parameters compared to individuals exposed to ambient air. To the best of our knowledge, this is the first study highlighting the protection of Kalamata olive trees due to EDU in terms of growth, yield, visible injury, and photosynthetic performance. Furthermore, this study proved that EDU could be a low-cost and a low-technology efficient tool for assessing O3 effects on plant performances in the field in Saudi Arabia.

Response of the diatom Phaeodactylum tricornutum to photooxidative stress resulting from high light exposure.

Directory of Open Access Journals (Sweden)

Nuno Domingues

Full Text Available The response of microalgae to photooxidative stress resulting from high light exposure is a well-studied phenomenon. However, direct analyses of photosystem II (PSII D1 protein (the main target of photoinhibition in diatoms are scarce. In this study, the response of the diatom model species Phaeodactylum tricornutum to short-term exposure to high light was examined and the levels of D1 protein determined immunochemically. Low light (LL acclimated cells (40 µmol photons m(-2 s(-1 subjected to high light (HL, 1,250 µmol photons m(-2 s(-1 showed rapid induction of non-photochemical quenching (NPQ and ca. 20-fold increase in diatoxanthin (DT concentration. This resulted from the conversion of diadinoxanthin (DD to DT through the activation of the DD-cycle. D1 protein levels under LL decreased about 30% after 1 h of the addition of lincomycin (LINC, a chloroplast protein synthesis inhibitor, showing significant D1 degradation and repair under low irradiance. Exposure to HL lead to a 3.2-fold increase in D1 degradation rate, whereas average D1 repair rate was 1.3-x higher under HL than LL, leading to decreased levels of D1 protein under HL. There were significant effects of both HL and LINC on P. tricornutum maximum quantum yield of PSII (F(v/F(m, showing a reduction of active PSII reaction centres. Partial recovery of F(v/F(m in the dark demonstrates the photosynthetic resilience of this diatom to changes in the light regime. P. tricornutum showed high allocation of total protein to D1 and an active D1-repair cycle to limit photoinhibition.

Studies on halogen quenching through the Stern-Volmer plot

International Nuclear Information System (INIS)

Takiue, Makoto; Ishikawa, Hiroaki.

1978-01-01

The quenching effect for halogenated benzenes, methanes and ethanes have been investigated. The halogen quenching was accurately measured using the internal conversion electrons emitted from 113 Sn-sup(113m)In. From the quenching constants determined by the Stern-Volmer plots with respect to various halogen quenchers, the following results have been obtained. (1) The quenching constants increase with the number of halogen substituents, so as linearly in halogenated benzenes and exponentially in halogenated methanes and ethanes. Even the isomers of halogenides have different quenching constants. (2) There is a linearity between logarithm of the quenching constant and a polarographic half-wave reduction potential. (3) Electron excitation provides larger quenching constants than UV excitation for halogenated methanes. Based on these results, the mechanism of halogen quenching have been discussed in connection with the exciplex formation. (auth.)

Photochemical transformations accelerated in continuous-flow reactors: basic concepts and applications.

Science.gov (United States)

Su, Yuanhai; Straathof, Natan J W; Hessel, Volker; Noël, Timothy

2014-08-18

Continuous-flow photochemistry is used increasingly by researchers in academia and industry to facilitate photochemical processes and their subsequent scale-up. However, without detailed knowledge concerning the engineering aspects of photochemistry, it can be quite challenging to develop a suitable photochemical microreactor for a given reaction. In this review, we provide an up-to-date overview of both technological and chemical aspects associated with photochemical processes in microreactors. Important design considerations, such as light sources, material selection, and solvent constraints are discussed. In addition, a detailed description of photon and mass-transfer phenomena in microreactors is made and fundamental principles are deduced for making a judicious choice for a suitable photomicroreactor. The advantages of microreactor technology for photochemistry are described for UV and visible-light driven photochemical processes and are compared with their batch counterparts. In addition, different scale-up strategies and limitations of continuous-flow microreactors are discussed. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Quenching behaviour for a singular predator–prey model

International Nuclear Information System (INIS)

Ducrot, Arnaud; Guo, Jong-Shenq

2012-01-01

In this paper, we study the quenching behaviour for a system of two reaction–diffusion equations arising in the modelling of the spatio-temporal interaction of prey and predator populations in fragile environment. We first provide some sufficient conditions on the initial data to have finite time quenching. Then we classify the initial data to distinguish type I quenching and type II quenching, by introducing a delicate energy functional along with the help of some a priori estimates. Finally, we present some results on the quenching set. It can be a singleton, the whole domain, or a compact subset of the domain

Quench dynamics of two coupled zig-zag ion chains

Energy Technology Data Exchange (ETDEWEB)

Klumpp, Andrea, E-mail: andrea.klumpp@physnet.uni-hamburg.de [Zentrum für Optische Quantentechnologien, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg (Germany); Liebchen, Benno [SUPA, School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3FD (United Kingdom); Schmelcher, Peter [Zentrum für Optische Quantentechnologien, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg (Germany); The Hamburg Centre for Ultrafast Imaging, Luruper Chaussee 149, 22761 Hamburg (Germany)

2016-08-06

We explore the non-equilibrium dynamics of two coupled zig-zag chains of trapped ions in a double well potential. Following a quench of the potential barrier between both wells, the induced coupling between both chains due to the long-range interaction of the ions leads to the complete loss of order in the radial direction. The resulting dynamics is however not exclusively irregular but leads to phases of motion during which various ordered structures appear with ions arranged in arcs, lines and crosses. We quantify the emerging order by introducing a suitable measure and complement our analysis of the ion dynamics using a normal mode analysis showing a decisive population transfer between only a few distinguished modes. - Highlights: • Novel dynamical phenomenology of two coupled zig-zag ion chains following a trap quench is explored. • Transient ordered ion configurations are unraveled in non-equilibrium dynamics dominated by irregular behavior. • A measure for the diagnosis of this transient order is introduced and applied. • Energy transfer between a few eigen modes is identified as the key mechanism for the occurrence of the ordered configurations.

SU-F-T-164: Investigation of PRESAGE Formulation On Signal Quenching in a Proton Beam

Energy Technology Data Exchange (ETDEWEB)

Carroll, M; Alqathami, M; Ibbott, G [UT MD Anderson Cancer Center, Houston, TX (United States)

2016-06-15

Purpose: The radiochromic polyurethane PRESAGE by Heuris Pharma has had limited applications with protons because of a dose response dependence on LET resulting in signal quenching in the Bragg peak. This is due to the radical initiator, a halocarbon, radically recombining in high-LET irradiations. This study investigated the use of alternative halocarbons at various chemical concentrations to determine their significance in signal quenching. Methods: PRESAGE was manufactured in-house and cast in small volume cuvettes (1×1×4cm^3). Several compositions were evaluated to determine the influence of the radical initiator component. Mixtures contained one of two halocarbons, chloroform or bromoform, at concentrations of 5%/10%/15%(w/w). A large volume, cylindrical PRESAGE dosimeter made following the mixture described by Heuris Pharma, 4cm(D)×8.5cm(H), was irradiated with 200-MeV protons to study regions of low- and high-LET along a 10cm spread out Bragg peak isodose profile. Depths corresponding to regions of low quenching (<3%) and high quenching (>20%) were determined. These depths were used for cuvette placement in a solid water phantom. Samples of each formulation were placed at each depth and irradiated to doses between 0 and 10Gy. Results: The cuvettes indicated different levels of quenching for different radical initiator types, concentrations, and total doses. Chloroform formulations showed reduced quenching from 29%(5%-w/w) to 21%(15%-w/w) while bromoform reduced quenching from 27%(5%-w/w) to 17%(15%-w/w). The reduction in quenching was found to be non-linear with concentration of radical initiator. A quenching dose-dependency was also found that changed with formulation. In all cases, quenching was relatively consistent from 0–5Gy but increased at 10Gy. The quenching decreased as concentrations of radical initiator increased. Conclusion: The radical initiator component in PRESAGE is correlated with the signal quenching observed in proton irradiations and

Heater induced quenches in SSC [Superconducting Super Collider] model dipoles

International Nuclear Information System (INIS)

Hassenzahl, W.V.

1986-10-01

A 1-m long SSC dipole constructed at the Lawrence Berkeley laboratory was subjected to a series of heater induced quenches to determine: axial quench propagation velocities, transverse quench propagation, and conductor temperature rise. Quenches were produced by 3 heaters at different locations in the magnet and at several currents. The results of these studies are described and are compared to previously published theoretical studies of quenches on the SSC dipoles. These results are shown to be in agreement with the calculations of the program ''QUENCH'', which includes an increase of the quench velocity during the first few milliseconds of the quench

Photochemical fate of beta-blockers in NOM enriched waters

International Nuclear Information System (INIS)

Wang, Ling; Xu, Haomin; Cooper, William J.; Song, Weihua

2012-01-01

Beta-blockers, prescribed for the treatment of high blood pressure and for long-term use after a heart attack, have been detected in surface and ground waters. This study examines the photochemical fate of three beta-blockers, atenolol, metoprolol, and nadolol. Hydrolysis accounted for minor losses of these beta-blockers in the pH range 4–10. The rate of direct photolysis at pH 7 in a solar simulator varied from 6.1 to 8.9 h −1 at pH 7. However, the addition of a natural organic matter (NOM) isolate enhanced the photochemical loss of all three compounds. Indirect photochemical fate, generally described by reactions with hydroxyl radical (·OH) and singlet oxygen ( 1 ΔO 2 ), and, the direct reaction with the triplet excited state, 3 NOM ⁎ , also varied but collectively appeared to be the major loss factor. Bimolecular reaction rate constants of the three beta-blockers with 1 ΔO 2 and ·OH were measured and accounted for 0.02–0.04% and 7.2–38.9% of their loss, respectively. These data suggest that the 3 NOM ⁎ contributed 50.6–85.4%. Experiments with various 3 NOM ⁎ quenchers supported the hypothesis that it was singly the most important reaction. Atenolol was chosen for more detailed investigation, with the photoproducts identified by LC–MS analysis. The results suggested that electron-transfer could be an important mechanism in photochemical fate of beta-blockers in the presence of NOM. - Highlights: ► Photochemical degradation of beta-blockers in the simulated natural waters. ► Reactive Oxygen Species play a minor role in the indirect photodegradation. ► The loss of beta-blockers results from direct reaction with 3 DOM ⁎ .

Surface retention and photochemical reactivity of the diphenylether herbicide oxyfluorfen.

Science.gov (United States)

Scrano, Laura; Bufo, Sabino A; Cataldi, Tommaso R I; Albanis, Triantafyllos A

2004-01-01

The photochemical behavior of oxyfluorfen [2-chloro-1-(3-etoxy-4-nitrophenoxy)-4-(trifluoromethyl) benzene] on two Greek soils was investigated. Soils were sampled from Nea Malgara and Preveza regions, characterized by a different organic matter content. Soils were spiked with the diphenyl-ether herbicide and irradiation experiments were performed either in the laboratory with a solar simulator (xenon lamp) or outside, under natural sunlight irradiation; other soil samples were kept in the dark to control the retention reaction. Kinetic parameters of both retention and photochemical reactions were calculated using zero-, first- and second- (Langmuir-Hinshelwood) order equations, and best fit was checked through statistical analysis. The soil behaviors were qualitatively similar but quantitatively different, with the soil sampled from the Nea Malgara region much more sorbent as compared with Preveza soil. All studied reactions followed second-order kinetics and photochemical reactions were influenced by retaining capability of the soils. The contributions of the photochemical processes to the global dissipation rates were also calculated. Two main metabolites were identified as 2-chloro-1-(3-ethoxy-4-hydroxyphenoxy)-4-(trifluoromethyl)benzene and 2-chloro-1- (3-hydroxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene.

Enhanced photoprotection by protein-bound vs free xanthophyll pools: a comparative analysis of chlorophyll b and xanthophyll biosynthesis mutants.

Science.gov (United States)

Dall'Osto, Luca; Cazzaniga, Stefano; Havaux, Michel; Bassi, Roberto

2010-05-01

When light absorbed by plants exceeds the capacity of photosynthesis, the xanthophyll violaxanthin is reversibly de-epoxidized to zeaxanthin in the so-called xanthophyll cycle. Zeaxanthin plays a key role in the protection of photosynthetic organisms against excess light, by promoting rapidly reversible (qE) and long-term (qI) quenching of excited chlorophylls, and preventing lipid oxidation. The photoprotective role of zeaxanthin, either free or bound to light-harvesting complexes (Lhcs), has been investigated by using mutants lacking Chl b (ch1) and/or specific xanthophyll species (npq, lut2). The ch1 mutation causes (1) the absence of Lhcb proteins; (2) strong reduction of the feedback de-excitation (qE); and (3) accumulation of xanthophylls as free pigments into thylakoids. Ch1 mutants showed extreme sensitivity to photo-oxidative stress in high light, due to higher singlet oxygen (¹O₂) release. The double mutant ch1npq1 was more sensitive to photo-oxidation than ch1, showing that zeaxanthin does protect lipids even when free in the membrane. Nevertheless, lack of zeaxanthin had a much stronger impact on the level of lipid peroxidation in Lhcs-containing plants (WT vs npq1) with respect to Lhc-less plants (ch1 vs ch1npq1), implying that its protective effect is enhanced by interaction with antenna proteins. It is proposed that the antioxidant capacity of zeaxanthin is empowered in the presence of PSII-LHCs-Zea complexes, while its effect on enhancement of qE only provides a minor contribution. Comparison of the sensitivity of WT vs npq1 plants to exogenous ¹O₂ suggests that besides the scavenging of ¹O₂, at least one additional mechanism is involved in chloroplast photoprotection.

Advanced active quenching circuit for ultra-fast quantum cryptography.

Science.gov (United States)

Stipčević, Mario; Christensen, Bradley G; Kwiat, Paul G; Gauthier, Daniel J

2017-09-04

Commercial photon-counting modules based on actively quenched solid-state avalanche photodiode sensors are used in a wide variety of applications. Manufacturers characterize their detectors by specifying a small set of parameters, such as detection efficiency, dead time, dark counts rate, afterpulsing probability and single-photon arrival-time resolution (jitter). However, they usually do not specify the range of conditions over which these parameters are constant or present a sufficient description of the characterization process. In this work, we perform a few novel tests on two commercial detectors and identify an additional set of imperfections that must be specified to sufficiently characterize their behavior. These include rate-dependence of the dead time and jitter, detection delay shift, and "twilighting". We find that these additional non-ideal behaviors can lead to unexpected effects or strong deterioration of the performance of a system using these devices. We explain their origin by an in-depth analysis of the active quenching process. To mitigate the effects of these imperfections, a custom-built detection system is designed using a novel active quenching circuit. Its performance is compared against two commercial detectors in a fast quantum key distribution system with hyper-entangled photons and a random number generator.

An Integrative Study of Photochemical Air Pollution in Hong Kong: an Overview

Science.gov (United States)

Wang, T.

2014-12-01

Hong Kong is situated in the Pearl River delta of Southern China. This region has experienced phenomenal economic growth in the past 30 years. Emissions of large amount of pollutants from urban areas and various industries coupled with subtropical climate have led to frequent occurrences of severe photochemical air pollution. Despite the long-term control efforts of the Hong Kong government, the atmospheric levels of ozone have been increasing in the past decade. To obtain an updated and more complete understanding of photochemical smog, an integrative study has been conducted during 2010-2014. Several intensive measurement campaigns were carried out at urban, suburban and rural sites in addition to the routine observations at fourteen air quality monitoring stations in Hong Kong. Meteorological, photochemical, and chemical-transport modeling studies were conducted to investigate the causes/processes of elevated photochemical pollution . The main activities of this study were to (1) examine the situation and trends of photochemical air pollution in Hong Kong, (2) understand some underlying chemical processes in particular the poorly-understood heterogeneous processes of reactive nitrogen oxides, (3) quantify the local, regional, and super-regional contributions to the ozone pollution in Hong Kong, and (4) review the control policy and make further recommendations based on the science. This paper will give an overview of this study and present some key results on the trends and chemistry of the photochemical pollution in this polluted subtropical region.

SDSS-IV MaNGA: faint quenched galaxies - I. Sample selection and evidence for environmental quenching

Science.gov (United States)

Penny, Samantha J.; Masters, Karen L.; Weijmans, Anne-Marie; Westfall, Kyle B.; Bershady, Matthew A.; Bundy, Kevin; Drory, Niv; Falcón-Barroso, Jesús; Law, David; Nichol, Robert C.; Thomas, Daniel; Bizyaev, Dmitry; Brownstein, Joel R.; Freischlad, Gordon; Gaulme, Patrick; Grabowski, Katie; Kinemuchi, Karen; Malanushenko, Elena; Malanushenko, Viktor; Oravetz, Daniel; Roman-Lopes, Alexandre; Pan, Kaike; Simmons, Audrey; Wake, David A.

2016-11-01

Using kinematic maps from the Sloan Digital Sky Survey (SDSS) Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey, we reveal that the majority of low-mass quenched galaxies exhibit coherent rotation in their stellar kinematics. Our sample includes all 39 quenched low-mass galaxies observed in the first year of MaNGA. The galaxies are selected with Mr > -19.1, stellar masses 109 M⊙ 1.9. They lie on the size-magnitude and σ-luminosity relations for previously studied dwarf galaxies. Just six (15 ± 5.7 per cent) are found to have rotation speeds ve, rot 5 × 1010 M⊙), supporting the hypothesis that galaxy-galaxy or galaxy-group interactions quench star formation in low-mass galaxies. The local bright galaxy density for our sample is ρproj = 8.2 ± 2.0 Mpc-2, compared to ρproj = 2.1 ± 0.4 Mpc-2 for a star-forming comparison sample, confirming that the quenched low-mass galaxies are preferentially found in higher density environments.

Electro- and photochemical switching of dithienylethene self-assembled monolayers on gold electrodes

DEFF Research Database (Denmark)

Browne, W.R.; Kudernac, T.; Katsonis, N.

2008-01-01

forms of the dithienylethene SAMs is examined and found to be sensitive to the molecular structure of the switch. For the three dithienylethenes, the electrochemical behavior with respect to electrochemical ring opening/closing is retained in the SAMs. In contrast, a marked dependence on the nature...... of the anchoring group is observed upon immobilization in terms of the retention of the photochemical properties observed in solution. For the meta-thiophenol anchor both photochemical ring opening and closing are observed in the SAM, while for the thienyl-thiol-anchored switches the photochemically properties...

Photochemical organonitrate formation in wet aerosols

Science.gov (United States)

Lim, Yong Bin; Kim, Hwajin; Kim, Jin Young; Turpin, Barbara J.

2016-10-01

Water is the most abundant component of atmospheric fine aerosol. However, despite rapid progress, multiphase chemistry involving wet aerosols is still poorly understood. In this work, we report results from smog chamber photooxidation of glyoxal- and OH-containing ammonium sulfate or sulfuric acid particles in the presence of NOx and O3 at high and low relative humidity. Particles were analyzed using ultra-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS). During the 3 h irradiation, OH oxidation products of glyoxal that are also produced in dilute aqueous solutions (e.g., oxalic acids and tartaric acids) were formed in both ammonium sulfate (AS) aerosols and sulfuric acid (SA) aerosols. However, the major products were organonitrogens (CHNO), organosulfates (CHOS), and organonitrogen sulfates (CHNOS). These were also the dominant products formed in the dark chamber, indicating non-radical formation. In the humid chamber (> 70 % relative humidity, RH), two main products for both AS and SA aerosols were organonitrates, which appeared at m / z- 147 and 226. They were formed in the aqueous phase via non-radical reactions of glyoxal and nitric acid, and their formation was enhanced by photochemistry because of the photochemical formation of nitric acid via reactions of peroxy radicals, NOx and OH during the irradiation.

Photochemical Approaches to Complex Chemotypes: Applications in Natural Product Synthesis

Science.gov (United States)

2016-01-01

The use of photochemical transformations is a powerful strategy that allows for the formation of a high degree of molecular complexity from relatively simple building blocks in a single step. A central feature of all light-promoted transformations is the involvement of electronically excited states, generated upon absorption of photons. This produces transient reactive intermediates and significantly alters the reactivity of a chemical compound. The input of energy provided by light thus offers a means to produce strained and unique target compounds that cannot be assembled using thermal protocols. This review aims at highlighting photochemical transformations as a tool for rapidly accessing structurally and stereochemically diverse scaffolds. Synthetic designs based on photochemical transformations have the potential to afford complex polycyclic carbon skeletons with impressive efficiency, which are of high value in total synthesis. PMID:27120289

Quench simulation in the thin superconducting solenoid

International Nuclear Information System (INIS)

Tominaka, T.; Takasaki, M.; Wake, M.; Yamada, R.

1983-07-01

The propagation velocities of a normal zone were calculated for a 1 mdiameter x 1 m superconducting solenoid and for a 3 mdiameter x 5 m thin solenoid based on a simple model using the one-dimensional thermal equation. The quench back effect can be observed in certain conditions. The quench of the large thin solenoid was also simulated by using the computer program 'QUENCH'. (author)

Mode-coupling of interaction quenched ultracold bosons in periodically driven lattices

Science.gov (United States)

Mistakidis, Simeon; Schmelcher, Peter

2016-05-01

The out-of-equilibrium dynamics of interaction quenched finite ultracold bosonic ensembles in periodically driven one-dimensional optical lattices is investigated. As a first attempt a brief analysis of the dynamics caused exclusively by the periodically driven lattice is presented and the induced low-lying modes are introduced. It is shown that the periodic driving enforces the bosons in the outer wells to exhibit out-of-phase dipole-like modes, while in the central well the cloud experiences a local-breathing mode. The dynamical behavior of the system is investigated with respect to the driving frequency, revealing a resonant-like behavior of the intra-well dynamics. Subsequently, we drive the system to a highly non-equilibrium state by performing an interaction quench upon the periodically driven lattice. This protocol gives rise to admixtures of excitations in the outer wells, an enhanced breathing in the center and an amplification of the tunneling dynamics. As a result (of the quench) the system experiences multiple resonances between the inter- and intra-well dynamics at different quench amplitudes. Finally, our study reveals that the position of the resonances can be adjusted e.g. via the driving frequency or the atom number manifesting their many-body nature. Deutsche Forschungsgemeinschaft (DFG) in the framework of the SFB 925 ``Light induced dynamics and control of correlated quantum systems''.

SU-F-T-164: Investigation of PRESAGE Formulation On Signal Quenching in a Proton Beam

International Nuclear Information System (INIS)

Carroll, M; Alqathami, M; Ibbott, G

2016-01-01

Purpose: The radiochromic polyurethane PRESAGE by Heuris Pharma has had limited applications with protons because of a dose response dependence on LET resulting in signal quenching in the Bragg peak. This is due to the radical initiator, a halocarbon, radically recombining in high-LET irradiations. This study investigated the use of alternative halocarbons at various chemical concentrations to determine their significance in signal quenching. Methods: PRESAGE was manufactured in-house and cast in small volume cuvettes (1×1×4cm^3). Several compositions were evaluated to determine the influence of the radical initiator component. Mixtures contained one of two halocarbons, chloroform or bromoform, at concentrations of 5%/10%/15%(w/w). A large volume, cylindrical PRESAGE dosimeter made following the mixture described by Heuris Pharma, 4cm(D)×8.5cm(H), was irradiated with 200-MeV protons to study regions of low- and high-LET along a 10cm spread out Bragg peak isodose profile. Depths corresponding to regions of low quenching ( 20%) were determined. These depths were used for cuvette placement in a solid water phantom. Samples of each formulation were placed at each depth and irradiated to doses between 0 and 10Gy. Results: The cuvettes indicated different levels of quenching for different radical initiator types, concentrations, and total doses. Chloroform formulations showed reduced quenching from 29%(5%-w/w) to 21%(15%-w/w) while bromoform reduced quenching from 27%(5%-w/w) to 17%(15%-w/w). The reduction in quenching was found to be non-linear with concentration of radical initiator. A quenching dose-dependency was also found that changed with formulation. In all cases, quenching was relatively consistent from 0–5Gy but increased at 10Gy. The quenching decreased as concentrations of radical initiator increased. Conclusion: The radical initiator component in PRESAGE is correlated with the signal quenching observed in proton irradiations and formulation adjustments

Variation of Quench Propagation Velocities in YBCO Cables

CERN Document Server

Härö, E.; Stenvall, A.; 10.1007/s10948-015-2976-y

2015-01-01

changes during the quench. Due to the large temperature margin between the operation and the current sharing temperatures, the normal zone does not propagate with the temperature front. This means that the temperature will rise in a considerably larger volume when compared to the quenched volume. Thus, the evolution of the temperature distribution below current sharing temperature Tcs after the quench onset affects the normal zone propagation velocity in HTS more than in LTS coils. This can be seen as an acceleration of the quench propagation velocities while the quench evolves when margin to Tcs is high. In this paper we scrutinize quench propagation in a stack of YBCO cables with an in-house finite element method software which solves the heat diffusion equation. We compute the longitudinal and transverse normal zone propagation velocities at various distances from the hot spot to demonstrate the distance-variation...

A dichotomy in satellite quenching around L* galaxies

Science.gov (United States)

Phillips, John I.; Wheeler, Coral; Boylan-Kolchin, Michael; Bullock, James S.; Cooper, Michael C.; Tollerud, Erik J.

2014-01-01

We examine the star formation properties of bright (˜0.1 L*) satellites around isolated ˜L* hosts in the local Universe using spectroscopically confirmed systems in the Sloan Digital Sky Survey Data Release 7. Our selection method is carefully designed with the aid of N-body simulations to avoid groups and clusters. We find that satellites are significantly more likely to be quenched than a stellar mass-matched sample of isolated galaxies. Remarkably, this quenching occurs only for satellites of hosts that are themselves quenched: while star formation is unaffected in the satellites of star-forming hosts, satellites around quiescent hosts are more than twice as likely to be quenched than stellar-mass-matched field samples. One implication of this is that whatever shuts down star formation in isolated, passive L* galaxies also play at least an indirect role in quenching star formation in their bright satellites. The previously reported tendency for `galactic conformity' in colour/morphology may be a by-product of this host-specific quenching dichotomy. The Sérsic indices of quenched satellites are statistically identical to those of field galaxies with the same specific star formation rates, suggesting that environmental and secular quenching give rise to the same morphological structure. By studying the distribution of pairwise velocities between the hosts and satellites, we find dynamical evidence that passive host galaxies reside in dark matter haloes that are ˜45 per cent more massive than those of star-forming host galaxies of the same stellar mass. We emphasize that even around passive hosts, the mere fact that galaxies become satellites does not typically result in star formation quenching: we find that only ˜30 per cent of ˜0.1L* galaxies that fall in from the field are quenched around passive hosts, compared with ˜0 per cent around star-forming hosts.

Southern Africa - a giant natural photochemical reactor

CSIR Research Space (South Africa)

Diab, RD

2006-04-01

Full Text Available photochemical reactor’ are abundant sources of ozone precursors (biomass burning, lightning, biogenic and urban-industrial sources), and meteorological conditions that promote anticyclonic recirculation on a subhemispheric scale....

Photosynthetic activity, photoprotection and photoinhibition in intertidal microphytobenthos as studied in situ using variable chlorophyll fluorescence

Science.gov (United States)

Serôdio, João; Vieira, Sónia; Cruz, Sónia

2008-06-01

The photosynthetic activity of microphytobenthos biofilms was studied in situ on an intertidal mudflat of the Ria de Aveiro, Portugal. Time series of physical variables characterizing the microenvironment at the sediment photic zone (incident solar irradiance, temperature, salinity), photophysiological parameters and productive biomass of undisturbed microalgal assemblages were measured during daytime low-tide periods along one spring-neap tidal cycle, with the objective of (1) characterizing the short-term variability in photosynthetic activity in situ, (2) relating it with the changing environmental conditions and (3) with the operation of physiologically (xanthophyll cycle) and behaviorally (vertical migration) based photoprotective processes, and (4) assessing the occurrence of photoinhibition. Pulse Amplitude Modulated (PAM) fluorometry was applied to measure photosynthetic activity (the effective and maximum quantum yield of photosystem II, Δ F/ Fm' and Fv/ Fm; the photosynthesis index EFY; rapid light-response curves (RLC)), the photoprotective operation of the xanthophyll cycle and photoinhibition (non-photochemical quenching, NPQ; quantum efficiency of open RCs, Fv'/ Fm'), and vertical migration (productive biomass, Fo). The photosynthetic activity was found to be strongly affected by the cumulative light dose received during the morning low-tide periods. The fluorescence indices Δ F/ Fm', EFY, Fv'/ Fm' and RLC parameters were more depressed under high irradiances when clear sky was present during the morning low tide than when foggy conditions reduced the light dose received during a comparable period. Productive biomass exhibited maximum values in the first hours of the morning, followed by a steep decrease when irradiance reached moderate levels, due to the downward migration of the microalgae. This photophobic migratory response appeared to display a photoprotective role, allowing Δ F/ Fm' to remain near optimum values until irradiance reached

Different physiological and photosynthetic responses of three cyanobacterial strains to light and zinc

Energy Technology Data Exchange (ETDEWEB)

Xu, Kui; Juneau, Philippe, E-mail: juneau.philippe@uqam.ca

2016-01-15

Highlights: • The response mechanisms to high zinc was investigated among three cyanobacterial strains grown under two light regimes. • Photosystem II is more sensitive to high zinc compared to Photosystem I in the three studied strains. • High light increases the zinc uptake in two Microcystis aeruginosa strains, but not in Synechocystis sp.. • Combined high light and high zinc treatment is lethal for the toxic M. aeruginosa CPCC299. - Abstract: Zinc pollution of freshwater aquatic ecosystems is a problem in many countries, although its specific effects on phytoplankton may be influenced by other environmental factors. Light intensity varies continuously under natural conditions depending on the cloud cover and the season, and the response mechanisms of cyanobacteria to high zinc stress under different light conditions are not yet well understood. We investigated the effects of high zinc concentrations on three cyanobacterial strains (Microcystis aeruginosa CPCC299, M. aeruginosa CPCC632, and Synechocystis sp. FACHB898) grown under two light regimes. Under high light condition (HL), the three cyanobacterial strains increased their Car/Chl a ratios and non-photochemical quenching (NPQ), with CPCC299 showing the highest growth rate—suggesting a greater ability to adapt to those conditions as compared to the other two strains. Under high zinc concentrations the values of maximal (Φ{sub M}) and operational (Φ'{sub M}) photosystem II quantum yields, photosystem I quantum yield [Y(I)], and NPQ decreased. The following order of sensitivity to high zinc was established for the three strains studied: CPCC299 > CPCC632 > FACHB898. These different sensitivities can be partly explained by the higher internal zinc content observed in CPCC299 as compared to the other two strains. HL increased cellular zinc content and therefore increased zinc toxicity in both M. aeruginosa strains, although to a greater extent in CPCC299 than in CPCC632. Car/Chl a ratios

Photochemical reactions of actinide ions

International Nuclear Information System (INIS)

Tomiyasu, Hiroshi

1995-01-01

This paper reviews the results of photochemical studies of actinide ions, which have been performed in our research group for past several years as follows: I) behavior of the excited uranyl(VI) ion; II) photo-reductions of the uranyl ion with organic and inorganic compounds; III) photo-oxidations of uranium(IV) and plutonium(III) in nitric acid solutions. (author)

Evaluating analytical ionization quenching correction models for 3D liquid organic scintillator detector

Science.gov (United States)

Alsanea, F.; Beddar, S.

2017-05-01

Proton therapy offers dosimetric advantage over conventional photon therapy due to the finite range of the proton beam, which improves dose conformity. However, one of the main challenges of proton beam therapy is verification of the complex treatment plans delivered to a patient. Thus, 3D measurements are needed to verify the complex dose distribution. A 3D organic scintillator detector is capable of such measurements. However, organic scintillators exhibit a non-linear relation to the ionization density called ionization quenching. The ionization quenching phenomenon in organic scintillators must be accounted for to obtain accurate dose measurements. We investigated the energy deposition by secondary electrons (EDSE) model to explain ionization quenching in 3D liquid organic scintillator when exposed to proton beams. The EDSE model was applied to volumetric scintillation measurement of proton pencil beam with energies of 85.6, 100.9, 144.9 and 161.9 MeV. The quenching parameter in EDSE model ρq was determined by plotting the total light output vs the initial energy of the ion. The results were compared to the Birks semi-empirical formula of scintillation light emission.

Quantum Quenches in a Spinor Condensate

International Nuclear Information System (INIS)

Lamacraft, Austen

2007-01-01

We discuss the ordering of a spin-1 condensate when quenched from its paramagnetic phase to its ferromagnetic phase by reducing the magnetic field. We first elucidate the nature of the equilibrium quantum phase transition. Quenching rapidly through this transition reveals XY ordering either at a specific wave vector, or the ''light-cone'' correlations familiar from relativistic theories, depending on the end point of the quench. For a quench proceeding at a finite rate the ordering scale is governed by the Kibble-Zurek mechanism. The creation of vortices through growth of the magnetization fluctuations is also discussed. The long-time dynamics again depends on the end point, conserving the order parameter in a zero field, but not at a finite field, with differing exponents for the coarsening of magnetic order. The results are discussed in the light of a recent experiment by Sadler et al

Superconducting synchrotron power supply and quench protection scheme

International Nuclear Information System (INIS)

Stiening, R.; Flora, R.; Lauckner, R.; Tool, G.

1978-01-01

The power supply and quench protection scheme for the proposed Fermilab 6 km circumference superconducting synchrotron is described. Specifically, the following points are discussed: (1) the 46 MW thyristor power supply; (2) the 3 x 10 8 J emergency energy dump; (3) the distributed microprocessing system for the detection of quenches; (4) the thyristor network for shunting current around quenched magnets; and (5) the heaters internal to the magnets which cause rapid propagation of quenches. Test results on prototype systems are given

Implicit time-dependent finite different algorithm for quench simulation

International Nuclear Information System (INIS)

Koizumi, Norikiyo; Takahashi, Yoshikazu; Tsuji, Hiroshi

1994-12-01

A magnet in a fusion machine has many difficulties in its application because of requirement of a large operating current, high operating field and high breakdown voltage. A cable-in-conduit (CIC) conductor is the best candidate to overcome these difficulties. However, there remained uncertainty in a quench event in the cable-in-conduit conductor because of a difficulty to analyze a fluid dynamics equation. Several scientists, then, developed the numerical code for the quench simulation. However, most of them were based on an explicit time-dependent finite difference scheme. In this scheme, a discrete time increment is strictly restricted by CFL (Courant-Friedrichs-Lewy) condition. Therefore, long CPU time was consumed for the quench simulation. Authors, then, developed a new quench simulation code, POCHI1, which is based on an implicit time dependent scheme. In POCHI1, the fluid dynamics equation is linearlized according to a procedure applied by Beam and Warming and then, a tridiagonal system can be offered. Therefore, no iteration is necessary to solve the fluid dynamics equation. This leads great reduction of the CPU time. Also, POCHI1 can cope with non-linear boundary condition. In this study, comparison with experimental results was carried out. The normal zone propagation behavior was investigated in two samples of CIC conductors which had different hydraulic diameters. The measured and simulated normal zone propagation length showed relatively good agreement. However, the behavior of the normal voltage shows a little disagreement. These results indicate necessity to improve the treatment of the heat transfer coefficient in the turbulent flow region and the electric resistivity of the copper stabilizer in high temperature and high field region. (author)

A simple holographic scenario for gapped quenches

Energy Technology Data Exchange (ETDEWEB)

Lopez, Esperanza; Bosch, Guillermo Milans del [Instituto de Física Teórica IFT UAM/CSIC, Universidad Autónoma de Madrid,28049 Cantoblanco, Madrid (Spain)

2017-02-24

We construct gravitational backgrounds dual to a family of field theories parameterized by a relevant coupling. They combine a non-trivial scalar field profile with a naked singularity. The naked singularity is necessary to preserve Lorentz invariance along the boundary directions. The singularity is however excised by introducing an infrared cutoff in the geometry. The holographic dictionary associated to the infrared boundary is developed. We implement quenches between two different values of the coupling. This requires considering time dependent boundary conditions for the scalar field both at the AdS boundary and the infrared wall.

Influence of temperature to quenching on liquid scintillation measurement

CERN Document Server

Kato, T

2003-01-01

The amount of quench is measured with liquid scintillation spectrometer changing the temperature of the sample. The range of the changed temperature is between 0 deg C and 35 deg C. The measurement is carried out for three kinds of unquenched standard, two quenched standards and fifteen kinds of scintillation cocktail and the mixed sample. It is confirmed that the amount of quench increases for all samples as the temperature rises. The influence of the changed amount of quench to the quench correction is examined. (author)

Quench simulations for superconducting elements in the LHC accelerator

Science.gov (United States)

Sonnemann, F.; Schmidt, R.

2000-08-01

The design of the protection system for the superconducting elements in an accelerator such as the large Hadron collider (LHC), now under construction at CERN, requires a detailed understanding of the thermo-hydraulic and electrodynamic processes during a quench. A numerical program (SPQR - simulation program for quench research) has been developed to evaluate temperature and voltage distributions during a quench as a function of space and time. The quench process is simulated by approximating the heat balance equation with the finite difference method in presence of variable cooling and powering conditions. The simulation predicts quench propagation along a superconducting cable, forced quenching with heaters, impact of eddy currents induced by a magnetic field change, and heat transfer through an insulation layer into helium, an adjacent conductor or other material. The simulation studies allowed a better understanding of experimental quench data and were used for determining the adequate dimensioning and protection of the highly stabilised superconducting cables for connecting magnets (busbars), optimising the quench heater strip layout for the main magnets, and studying quench back by induced eddy currents in the superconductor. After the introduction of the theoretical approach, some applications of the simulation model for the LHC dipole and corrector magnets are presented and the outcome of the studies is compared with experimental data.

Photochemically induced emission tuning of conductive polumers used in OLEDs

Energy Technology Data Exchange (ETDEWEB)

Vasilopoulou, M [NCSR ' Demokritos' , Institute of Microelectronics, POB 60228, 153 10 Agia Paraskevi, Attiki (Greece); Pistolis, G [Institute of Physical Chemistry, NCSR ' Demokritos' Athens 153 10 (Greece); Argitis, P [NCSR ' Demokritos' , Institute of Microelectronics, POB 60228, 153 10 Agia Paraskevi, Attiki (Greece)

2005-01-01

The present work focuses on the use of novel patterning technology schemes for the fabrication of OLED-based displays and in particular on the definition of two colour emitting pixels in one polymeric conducting layer. The approach adopted to this end is based on photochemically induced emition tuning. On the basis of this approach a novel photolithographic patterning technique was developed, aiming at the considerable simplification of the display fabrication process and on the performance improvement. We prepared electroluminescent devices that are emitting blue colour ({lambda}{sub max} 413 nm) with a turnon voltage about 12-15 V. In other devices we introduce a dispersed dye (1-[4-(dimethylamino)phenyl]-6-phenylhexatriene) and a series of photoacid generators (onium salts) in the polymeric layer and, by using an appropriate photochemical transformation through a photomask in a single layer, we were able to change the colour to desirable direction, since the parent compound and its photochemical product have distinguishable luminescence spectra (green and blue colour respectively). We were able to produce two of the three primary colours in a single layer of a conductive polymer by using a photochemical transformation based on photoacid induced emission change. A series of photoacid generators were evaluated.

Quench detection by fluid dynamic means in cable-in-conduit superconductors

International Nuclear Information System (INIS)

Dresner, L.

1988-01-01

The tight confinement of the helium in cable-in-conduit superconductors creates protection problems because of the pressure rise that can occur during a quench. But the same pressure rise offers the possibility of a non-electrical means of detecting incipient quenches by monitoring the outflow from the various hydraulic paths of the magnet. If the method is to work, the signal must be large enough to be detected unambiguously at an early time, and must not depend too strongly on the length, Joule power density, or rate of growth of the initial normal zone. This paper explores by calculation the degree to which these conditions can be met. The Westinghouse Large Coil Task coil is used as an example

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

Energy Technology Data Exchange (ETDEWEB)

Gilmore, A.M.; Hazlett, T.L.; Govindjee [Univ. of Illinois, Urbana, IL (United States)

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.

Quenching of the He/sub μ/ +(2s) atom

International Nuclear Information System (INIS)

Russell, J.E.

1986-01-01

Quenching of the metastable 2s state of the He/sub μ/ + atom in helium gas is discussed. The first part of the discussion, which is devoted entirely to processes occurring after the He/sub μ/ + has become bound to one or more ordinary helium atoms, is based partly on Cohen's calculations of rates of vibrational quenching and partly on estimates obtained in the present paper of rates of Burbidge--de Borde quenching and Ruderman quenching. It is concluded that Burbidge--de Borde quenching or Ruderman quenching, or both, are likely to be more effective than Cohen quenching if the vibrational level of the bound system is low. A recent experiment by von Arb et al. is then analyzed in the light of this conclusion. The analysis is based on the reported absence, or near absence, of Auger electrons accompanying 2s quenching. While it is agreed that the Cohen mechanism occurring in the molecular ion HeHe/sub μ/ + remains the most likely explanation of the experiment, it is concluded that the quenching occurs in comparatively high levels. It is then argued that this conclusion is in accord with some theoretical investigations of three-body association reactions and also with some elementary considerations regarding the relaxation of highly excited diatomic molecules, and it is further concluded that the quenching is most likely to occur in states with very low rotational quantum number and vibrational quantum number 8≤v≤14

Quench dynamics in SRF cavities: can we locate the quench origin with 2nd sound?

International Nuclear Information System (INIS)

Maximenko, Yulia; Segatskov, Dmitri A.

2011-01-01

A newly developed method of locating quenches in SRF cavities by detecting second-sound waves has been gaining popularity in SRF laboratories. The technique is based on measurements of time delays between the quench as determined by the RF system and arrival of the second-sound wave to the multiple detectors placed around the cavity in superfluid helium. Unlike multi-channel temperature mapping, this approach requires only a few sensors and simple readout electronics; it can be used with SRF cavities of almost arbitrary shape. One of its drawbacks is that being an indirect method it requires one to solve an inverse problem to find the location of a quench. We tried to solve this inverse problem by using a parametric forward model. By analyzing the data we found that the approximation where the second-sound emitter is a near-singular source does not describe the physical system well enough. A time-dependent analysis of the quench process can help us to put forward a more adequate model. We present here our current algorithm to solve the inverse problem and discuss the experimental results.

Detection of Second Sound in He-II for Thermal Quench Mapping of Superconducting Radio Frequency Accelerating Cavities

OpenAIRE

Stegmaier, Tobias; Grohmann, Steffen; Kind, Matthias; Furci, Hernán; Koettig, Torsten; Peters, Benedikt

2018-01-01

The development of future particle accelerators requires intensive testing of superconducting radio frequency cavities with different sizes and geometries. Non-contact thermometry quench localisation techniques proved to be beneficial for the localisation of surface defects that can originate a quench (sudden loss of superconducting state). These techniques are based on the detection of second sound in helium II. Transition Edge Sensors (TES) are highly sensitive thin film thermometers with f...

Heat transfer to a dispersed two-phase flow and detailed quench front velocity research

International Nuclear Information System (INIS)

Boer, T.C. de; Molen, S.B. van der

1985-01-01

A programme to obtain a data base for 'Boildown and Reflood' computer code development and to obtain information on the influence of non-uniform temperature and/or power profile on the quench front velocity and prequench heat transfer, including unheated wall and grid effects, has been undertaken. It is in two parts. In the first (for the tube, annulus and a 4-rod bundle) an early wetting of the unheated shroud is shown. This leads to an increase in quench front velocity and in liquid transport downstream from the quench front. For the inverted annular flow regime the extended Bromley correlation gives good agreement with the experimental data. In the second part (36-rod bundle reflood test programme) the wall-temperature differences in the radial direction gives rise to heat transfer processes which are described and explained. (U.K.)

System and method for quench protection of a superconductor

Science.gov (United States)

Huang, Xianrui; Sivasubramaniam, Kiruba Haran; Bray, James William; Ryan, David Thomas

2008-03-11

A system and method for protecting a superconductor from a quench condition. A quench protection system is provided to protect the superconductor from damage due to a quench condition. The quench protection system comprises a voltage detector operable to detect voltage across the superconductor. The system also comprises a frequency filter coupled to the voltage detector. The frequency filter is operable to couple voltage signals to a control circuit that are representative of a rise in superconductor voltage caused by a quench condition and to block voltage signals that are not. The system is operable to detect whether a quench condition exists in the superconductor based on the voltage signal received via the frequency filter and to initiate a protective action in response.

Approximate photochemical dynamics of azobenzene with reactive force fields

Science.gov (United States)

Li, Yan; Hartke, Bernd

2013-12-01

We have fitted reactive force fields of the ReaxFF type to the ground and first excited electronic states of azobenzene, using global parameter optimization by genetic algorithms. Upon coupling with a simple energy-gap transition probability model, this setup allows for completely force-field-based simulations of photochemical cis→trans- and trans→cis-isomerizations of azobenzene, with qualitatively acceptable quantum yields. This paves the way towards large-scale dynamics simulations of molecular machines, including bond breaking and formation (via the reactive force field) as well as photochemical engines (presented in this work).

Bar quenching in gas-rich galaxies

Science.gov (United States)

Khoperskov, S.; Haywood, M.; Di Matteo, P.; Lehnert, M. D.; Combes, F.

2018-01-01

Galaxy surveys have suggested that rapid and sustained decrease in the star-formation rate (SFR), "quenching", in massive disk galaxies is frequently related to the presence of a bar. Optical and near-IR observations reveal that nearly 60% of disk galaxies in the local universe are barred, thus it is important to understand the relationship between bars and star formation in disk galaxies. Recent observational results imply that the Milky Way quenched about 9-10 Gyr ago, at the transition between the cessation of the growth of the kinematically hot, old, metal-poor thick disk and the kinematically colder, younger, and more metal-rich thin disk. Although perhaps coincidental, the quenching episode could also be related to the formation of the bar. Indeed the transfer of energy from the large-scale shear induced by the bar to increasing turbulent energy could stabilize the gaseous disk against wide-spread star formation and quench the galaxy. To explore the relation between bar formation and star formation in gas rich galaxies quantitatively, we simulated gas-rich disk isolated galaxies. Our simulations include prescriptions for star formation, stellar feedback, and for regulating the multi-phase interstellar medium. We find that the action of stellar bar efficiently quenches star formation, reducing the star-formation rate by a factor of ten in less than 1 Gyr. Analytical and self-consistent galaxy simulations with bars suggest that the action of the stellar bar increases the gas random motions within the co-rotation radius of the bar. Indeed, we detect an increase in the gas velocity dispersion up to 20-35 km s-1 at the end of the bar formation phase. The star-formation efficiency decreases rapidly, and in all of our models, the bar quenches the star formation in the galaxy. The star-formation efficiency is much lower in simulated barred compared to unbarred galaxies and more rapid bar formation implies more rapid quenching.

Optimization of a quench detection system for superconducting magnets

International Nuclear Information System (INIS)

Borlein, M.

2004-12-01

Subject of this report is the detection of a quench in a superconducting magnet. For the safe operation of superconducting magnets one of the most important issues is the quench detection system which controls the superconducting state of the magnet and triggers a safety discharge if necessary. If it comes to a breakdown of the superconductivity (quench), the magnet has to be discharged very quickly to avoid any damage or danger for the magnet or its environment. First an introducing overview is given. Next different methods of quench detection will be presented, partially on the basis of existing quench detection systems and the applicability of these methods in different states of the magnet operation will be shown. The different quench detection methods are compared and evaluated partially by using test experiments described in the appendix. As an application example this report contains a proposal for the quench detection system for the Wendelstein 7-X facility, actually built by the Institute for Plasma Physics, Garching [de

Quench simulations for superconducting elements in the LHC accelerator

CERN Document Server

Sonnemann, F

2000-01-01

The design of he protection system for he superconducting elements in an accel- erator such as the Large Hadron Collider (LHC),now under construction at CERN, requires a detailed understanding of the hermo-hydraulic and electrodynamic pro- cesses during a quench.A numerical program (SPQR -Simulation Program for Quench Research)has been developed o evaluate temperature and voltage dis ri- butions during a quench as a func ion of space and ime.The quench process is simulated by approximating the heat balance equation with the finite di fference method in presence of variable cooling and powering conditions.The simulation predicts quench propagation along a superconducting cable,forced quenching with heaters,impact of eddy curren s induced by a magnetic field change,and heat trans- fer hrough an insulation layer in o helium,an adjacen conductor or other material. The simulation studies allowed a better understanding of experimental quench data and were used for determining the adequ...

Photochemical synthesis of UO2 nanoparticles

International Nuclear Information System (INIS)

Rath, M.C.; Keny, Sangeeta; Naik, D.B.

2014-01-01

UO 2 nanoparticles have been recently synthesized by us from aqueous solutions of uranyl nitrate through radiolytic method on high-energy electron beam irradiation. In this study, the synthesis of UO 2 nanoparticles through photochemical method is reported which is a complementary route to radiation chemical method

Photochemical fate of beta-blockers in NOM enriched waters

Energy Technology Data Exchange (ETDEWEB)

Wang, Ling; Xu, Haomin; Cooper, William J. [Urban Water Research Center, Department of Civil and Environmental Engineering, University of California, Irvine, Irvine, CA 92697-2175 (United States); Song, Weihua, E-mail: wsong@fudan.edu.cn [Department of Environmental Science and Engineering, Fudan University, Shanghai 200433 (China)

2012-06-01

Beta-blockers, prescribed for the treatment of high blood pressure and for long-term use after a heart attack, have been detected in surface and ground waters. This study examines the photochemical fate of three beta-blockers, atenolol, metoprolol, and nadolol. Hydrolysis accounted for minor losses of these beta-blockers in the pH range 4-10. The rate of direct photolysis at pH 7 in a solar simulator varied from 6.1 to 8.9 h{sup -1} at pH 7. However, the addition of a natural organic matter (NOM) isolate enhanced the photochemical loss of all three compounds. Indirect photochemical fate, generally described by reactions with hydroxyl radical ({center_dot}OH) and singlet oxygen ({sup 1}{Delta}O{sub 2}), and, the direct reaction with the triplet excited state, {sup 3}NOM{sup Low-Asterisk }, also varied but collectively appeared to be the major loss factor. Bimolecular reaction rate constants of the three beta-blockers with {sup 1}{Delta}O{sub 2} and {center_dot}OH were measured and accounted for 0.02-0.04% and 7.2-38.9% of their loss, respectively. These data suggest that the {sup 3}NOM{sup Low-Asterisk} contributed 50.6-85.4%. Experiments with various {sup 3}NOM{sup Low-Asterisk} quenchers supported the hypothesis that it was singly the most important reaction. Atenolol was chosen for more detailed investigation, with the photoproducts identified by LC-MS analysis. The results suggested that electron-transfer could be an important mechanism in photochemical fate of beta-blockers in the presence of NOM. - Highlights: Black-Right-Pointing-Pointer Photochemical degradation of beta-blockers in the simulated natural waters. Black-Right-Pointing-Pointer Reactive Oxygen Species play a minor role in the indirect photodegradation. Black-Right-Pointing-Pointer The loss of beta-blockers results from direct reaction with {sup 3}DOM{sup Low-Asterisk }.

ITER Side Correction Coil Quench model and analysis

Science.gov (United States)

Nicollet, S.; Bessette, D.; Ciazynski, D.; Duchateau, J. L.; Gauthier, F.; Lacroix, B.

2016-12-01

Previous thermohydraulic studies performed for the ITER TF, CS and PF magnet systems have brought some important information on the detection and consequences of a quench as a function of the initial conditions (deposited energy, heated length). Even if the temperature margin of the Correction Coils is high, their behavior during a quench should also be studied since a quench is likely to be triggered by potential anomalies in joints, ground fault on the instrumentation wires, etc. A model has been developed with the SuperMagnet Code (Bagnasco et al., 2010) for a Side Correction Coil (SCC2) with four pancakes cooled in parallel, each of them represented by a Thea module (with the proper Cable In Conduit Conductor characteristics). All the other coils of the PF cooling loop are hydraulically connected in parallel (top/bottom correction coils and six Poloidal Field Coils) are modeled by Flower modules with equivalent hydraulics properties. The model and the analysis results are presented for five quench initiation cases with/without fast discharge: two quenches initiated by a heat input to the innermost turn of one pancake (case 1 and case 2) and two other quenches initiated at the innermost turns of four pancakes (case 3 and case 4). In the 5th case, the quench is initiated at the middle turn of one pancake. The impact on the cooling circuit, e.g. the exceedance of the opening pressure of the quench relief valves, is detailed in case of an undetected quench (i.e. no discharge of the magnet). Particular attention is also paid to a possible secondary quench detection system based on measured thermohydraulic signals (pressure, temperature and/or helium mass flow rate). The maximum cable temperature achieved in case of a fast current discharge (primary detection by voltage) is compared to the design hot spot criterion of 150 K, which includes the contribution of helium and jacket.

Fuel rod quenching with oxidation and precursory cooling

International Nuclear Information System (INIS)

Davidi, A.; Elias, E.; Olek, S.

1999-01-01

During a loss-of-coolant-accident in LWR fuel rods may be temporarily exposed thus reaching high temperature levels. The injection of cold water into the core, while providing the necessary cooling to prevent melting may also generate steam inducing exothermal oxidation of the cladding. A number of high temperature quenching experiments [I] have demonstrated that during the early phase of the quenching process, the rate of hydrogen generation increased markedly and the surface temperatures rose rapidly. These effects are believed to result from thermal stresses breaking up the oxide layer on the zircalloy cladding, thus exposing the inner surface to oxidizing atmosphere. Steam reacts exothermally with the metallic components of the newly formed surface causing temporarily local temperature escalation. The main objective of this study is to develop and assess a one-dimensional time-dependent rewetting model to address the problem of quenching of hot surfaces undergoing exothermic oxidation reactions. Addressing a time-dependent problem is an important aspect of the work since it is believed that the progression of a quench-front along a hot oxidizing surface is an unsteady process. Several studies dealing with time-dependent rewetting problems have been published, e.g. [2]-[5], but none considers oxidation reactions downstream of the quench-front. The main difficulty in solving time-dependent rewetting problems stems from the fact that either the quench-front velocity or the quench-front positions constitute a time-dependent eigenvalue of the problem. The model is applied to describe the interrelated processes of cooling and exothermic steam-metal reactions at the vapor zirconium-cladding interface during quenching of degraded fuel rods. A constant heat transfer coefficient is assumed upstream of the quenching front whereas the combined effect of oxidation and post dry-out cooling is described by prescribing a heat flux distribution of general form downstream. The

Characterization of plasma current quench at JET

International Nuclear Information System (INIS)

Riccardo, V; Barabaschi, P; Sugihara, M

2005-01-01

Eddy currents generated during the fastest disruption current decays represent the most severe design condition for medium and small size in-vessel components of most tokamaks. Best-fit linear and instantaneous plasma current quench rates have been extracted for a set of recent JET disruptions. Contrary to expectations, the current quench rate spectrum of high and low thermal energy disruptions is not substantially different. For most of the disruptions with the highest instantaneous current quench rate an exponential fit of the early phase of the current decay provides a more accurate estimate of the maximum current decay velocity. However, this fit is only suitable to model the fastest events, for which the current quench is dominated by radiation losses rather than the plasma motion

Photochemical reactions of nucleic acids and their constituents of photobiological relevance

International Nuclear Information System (INIS)

Saito, I.; Sugiyama, H.; Matsuura, T.

1983-01-01

A review is given of the papers published from 1977 to May 1983 on the UV-induced photochemical reactions of nucleic acids and their constituents of photobiological relevance where the structures of photoproducts have been fully characterized. Among the topics discussed are photoadditions relevant to nucleic acid-protein photocrosslinking, photoreactions with psoralens and nucleic acids and photochemical reactions of polynucleotides. (U.K.)

Effects of quench rate and natural ageing on the age hardening behaviour of aluminium alloy AA6060

Energy Technology Data Exchange (ETDEWEB)

Strobel, Katharina, E-mail: katharina.strobel@aol.com [CAST Co-operative Research Centre, Department of Materials Engineering, Monash University, Clayton, Victoria 3800 (Australia); Lay, Matthew D.H., E-mail: mlay@fbrice.com [CSIRO Manufacturing Flagship, Clayton, Victoria 3169 (Australia); Easton, Mark A., E-mail: mark.easton@rmit.edu.au [CAST Co-operative Research Centre, Department of Materials Engineering, Monash University, Clayton, Victoria 3800 (Australia); Sweet, Lisa, E-mail: lisa.sweet@monash.edu [CAST Co-operative Research Centre, Department of Materials Engineering, Monash University, Clayton, Victoria 3800 (Australia); Zhu, Suming, E-mail: suming.zhu@rmit.edu.au [CAST Co-operative Research Centre, Department of Materials Engineering, Monash University, Clayton, Victoria 3800 (Australia); Parson, Nick C., E-mail: nick.parson@riotinto.com [Rio Tinto Alcan, Arvida Research and Development Centre, 1955, Mellon Blvd, Jonquière, Québec G7S 4K8 (Canada); Hill, Anita J., E-mail: anita.hill@csiro.au [CSIRO Manufacturing Flagship, Clayton, Victoria 3169 (Australia)

2016-01-15

Quench sensitivity in Al–Mg–Si alloys has been largely attributed to the solute loss at the heterogeneous nucleation sites, primarily dispersoids, during slow cooling after extrusion. As such, the number density of dispersoids, the solute type and concentration are considered to be the key variables for the quench sensitivity. In this study, quench sensitivity and the influence of natural ageing in a lean Al–Mg–Si alloy, AA6060, which contains few dispersoids, have been investigated by hardness measurement, thermal analysis, transmission electron microscopy (TEM) and positron annihilation lifetime spectroscopy (PALS). It is shown that the quench sensitivity in this alloy is associated with the degree of supersaturation of vacancies after cooling. Due to vacancy annihilation and clustering during natural ageing, the quench sensitivity is more pronounced after a short natural ageing time (30 min) compared to a longer natural ageing time (24 h). Therefore, prolonged natural ageing not only leads to an increase in hardness, but can also have a positive effect on the quench sensitivity of lean Al–Mg–Si alloys. - Highlights: • Significant quench sensitivity observed in AA6060 alloy after 30 min natural ageing • Prolonged natural ageing increased hardness and reduced QS. • Low dispersoid density leads to insignificant QS from non-hardening precipitates. • Vacancy supersaturation identified as a contributor to QS.

Effects of quench rate and natural ageing on the age hardening behaviour of aluminium alloy AA6060

International Nuclear Information System (INIS)

Strobel, Katharina; Lay, Matthew D.H.; Easton, Mark A.; Sweet, Lisa; Zhu, Suming; Parson, Nick C.; Hill, Anita J.

2016-01-01

Quench sensitivity in Al–Mg–Si alloys has been largely attributed to the solute loss at the heterogeneous nucleation sites, primarily dispersoids, during slow cooling after extrusion. As such, the number density of dispersoids, the solute type and concentration are considered to be the key variables for the quench sensitivity. In this study, quench sensitivity and the influence of natural ageing in a lean Al–Mg–Si alloy, AA6060, which contains few dispersoids, have been investigated by hardness measurement, thermal analysis, transmission electron microscopy (TEM) and positron annihilation lifetime spectroscopy (PALS). It is shown that the quench sensitivity in this alloy is associated with the degree of supersaturation of vacancies after cooling. Due to vacancy annihilation and clustering during natural ageing, the quench sensitivity is more pronounced after a short natural ageing time (30 min) compared to a longer natural ageing time (24 h). Therefore, prolonged natural ageing not only leads to an increase in hardness, but can also have a positive effect on the quench sensitivity of lean Al–Mg–Si alloys. - Highlights: • Significant quench sensitivity observed in AA6060 alloy after 30 min natural ageing • Prolonged natural ageing increased hardness and reduced QS. • Low dispersoid density leads to insignificant QS from non-hardening precipitates. • Vacancy supersaturation identified as a contributor to QS.

Quench Tests of LHC Magnets with Beam: Studies on Beam Loss development and determination of Quench levels

CERN Document Server

Priebe, A; Sapinski, M

The application of superconducting materials in the field of high energy accelerator physics not only opens the doors to the generation of the magnetic fields unattainable to normal conductors but also demands facing new challenges. A transition fromthe superconducting state, which is characterized by a resistance-free flow of the electric current, to the normal conducting state is called quenching. This process might be extremely dangerous and even lead to destruction of amagnet superconducting coil if no protecting actions are taken. Therefore, the knowledge of a magnet quench level, i.e. amount of energy which causes the transition to the resistive state, is crucial for the safety and operational efficiency of the accelerator. Regarding that, specific thresholds are incorporated to dedicated quench prevention systems in order to suppress the origin of detected energy perturbation, for example beam losses, or mitigate the consequences of the quenching process by dissipating the energy stored in the magnetic...

Quench behavior of a superconducting accelerator magnet

International Nuclear Information System (INIS)

McInturff, A.D.; Sampson, W.B.; Garber, M.; Dahl, P.F.

1980-01-01

Data are presented on the minimum energy required to cause quenches to propagate in an accelerator dipole magnet. The amount of stored energy dissipated into the magnet was measured as a function of dipole excitation current. This in turn determines the maximum coil temperature reached in a given magnet. Quench velocities in the longitudinal direction of the conductor were as high as 11m/sec. The azimuthal velocities or turn to turn velocities were found to be a function of the number of fiberglass layers of insulation that the quench had to cross and were on the order of a few tens of centimeters/sec. The field shape of a given magnet was found to be unchanged for more than 100 quenches. The coil to coil connection and inter-coil splice resistances were found to be less than a namo-ohm and therefore of litle consequence in the cryogenic load considerations. No definitive answers were found on how to decrease the rate of training (130 Gauss/Quench average) required from 4.OT to 5.1T

Quenching phenomena in natural circulation loop

International Nuclear Information System (INIS)

Umekawa, Hisashi; Ozawa, Mamoru; Ishida, Naoki

1995-01-01

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

Quenching phenomena in natural circulation loop

Energy Technology Data Exchange (ETDEWEB)

Umekawa, Hisashi; Ozawa, Mamoru [Kansai Univ., Osaka (Japan); Ishida, Naoki [Daihatsu Motor Company, Osaka (Japan)

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.

(Talk) Investigating The Star Formation Quenching Across Cosmic Time - A Methodology To Select Galaxies Just After The Quenching Of Star Formation

Science.gov (United States)

Citro, Annalisa; Pozzetti, Lucia; Quai, Salvatore; Moresco, Michele; Vallini, Livia; Cimatti, Andrea

2017-06-01

We propose a method aimed at identifing galaxies in the short evolutionary phase in which they quench their star-formation (SF). We rely on high- to low-ionization emission line ratios, which rapidly disappear after the SF halt due to the softening of the UV ionizing radiation. In particular, we focus on [O III] 5007/Halpha and [Ne III] 3869/[O II] 3727, simulating their time evolution by means of the CLOUDY photoionization code. We find that these two emission line ratios are able to trace the quenching on very short time-scales (i.e. 10-80 Myr), depending on if a sharp or a smoother SF quenching is assumed. We adopt the [N II] 6584/[O II] 3727 ratio as metallicity diagnostic to mitigate the metallicity degeneracy which affects our method. Using a Sloan Digital Sky Survey galaxy sample, we identify 11 examples of extreme quenching candidates within the [O III] 5007/Halpha vs. [N II] 6584/[O II] 3727 plane, characterized by faint [Ne III] 3869, blue dust-corrected spectra and blue (u-r) colours, as expected if the quenching occurred in the recent past. Our results also suggest that the observed fractions of quenching candidates can be used to constrain the quenching mechanism at work and its time-scales.

Novel water-air circulation quenching process for AISI 4140 steel

Science.gov (United States)

Zheng, Liyun; Zheng, Dawei; Zhao, Lixin; Wang, Lihui; Zhang, Kai

2013-11-01

AISI 4140 steel is usually used after quenching and tempering. During the heat treatment process in industry production, there are some problems, such as quenching cracks, related to water-cooling and low hardness due to oil quenching. A water-air circulation quenching process can solve the problems of quenching cracks with water and the high cost quenching with oil, which is flammable, unsafe and not enough to obtain the required hardness. The control of the water-cooling and air-cooling time is a key factor in the process. This paper focuses on the quenching temperature, water-air cycle time and cycle index to prevent cracking for AISI 4140 steel. The optimum heat treatment parameters to achieve a good match of the strength and toughness of AISI 4140 steel were obtained by repeated adjustment of the water-air circulation quenching process parameters. The tensile strength, Charpy impact energy at -10 °C and hardness of the heat treated AISI 4140 steel after quenching and tempering were approximately 1098 MPa, 67.5 J and 316 HB, respectively.

Quenching and recovery experiments on tungsten

International Nuclear Information System (INIS)

Rasch, K.D.; Siegel, R.W.; Schultz, H.

1976-01-01

A short summary is given of new results concerning transmission electron microscopy and resistivity measurements on quenched tungsten. These results give evidence for the first time that the quenching and annealing of high purity tungsten leads to vacancy--defect clustering resulting in small voids observable in the electron microscope. 21 references

High-Field Quench Behavior and Protection of $Bi_2 Sr_2 Ca Cu_2 O_x$ Coils: Minimum and Maximum Quench Detection Voltages

Energy Technology Data Exchange (ETDEWEB)

Shen, Tengming [Fermilab; Ye, Liyang [NCSU, Raleigh; Turrioni, Daniele [Fermilab; Li, Pei [Fermilab

2015-01-01

Small insert coils have been built using a multifilamentary Bi2Sr2CaCu2Ox round wire, and characterized in background fields to explore the quench behaviors and limits of Bi2Sr2CaCu2Ox superconducting magnets, with an emphasis on assessing the impact of slow normal zone propagation on quench detection. Using heaters of various lengths to initiate a small normal zone, a coil was quenched safely more than 70 times without degradation, with the maximum coil temperature reaching 280 K. Coils withstood a resistive voltage of tens of mV for seconds without quenching, showing the high stability of these coils and suggesting that the quench detection voltage shall be greater than 50 mV to not to falsely trigger protection. The hot spot temperature for the resistive voltage of the normal zone to reach 100 mV increases from ~40 K to ~80 K with increasing the operating wire current density Jo from 89 A/mm2 to 354 A/mm2 whereas for the voltage to reach 1 V, it increases from ~60 K to ~140 K, showing the increasing negative impact of slow normal zone propagation on quench detection with increasing Jo and the need to limit the quench detection voltage to < 1 V. These measurements, coupled with an analytical quench model, were used to access the impact of the maximum allowable voltage and temperature upon quench detection on the quench protection, assuming to limit the hot spot temperature to <300 K.

Galaxies in the act of quenching star formation

Science.gov (United States)

Quai, Salvatore; Pozzetti, Lucia; Citro, Annalisa; Moresco, Michele; Cimatti, Andrea

2018-04-01

Detecting galaxies when their star-formation is being quenched is crucial to understand the mechanisms driving their evolution. We identify for the first time a sample of quenching galaxies selected just after the interruption of their star formation by exploiting the [O III] λ5007/Hα ratio and searching for galaxies with undetected [O III]. Using a sample of ˜174000 star-forming galaxies extracted from the SDSS-DR8 at 0.04 ≤ z growth of the quiescent population at these redshifts. Their main properties (i.e. star-formation rate, colours and metallicities) are comparable to those of the star-forming population, coherently with the hypothesis of recent quenching, but preferably reside in higher-density environments.Most candidates have morphologies similar to star-forming galaxies, suggesting that no morphological transformation has occurred yet. From a survival analysis we find a low fraction of candidates (˜ 0.58% of the star-forming population), leading to a short quenching timescale of tQ ˜ 50 Myr and an e-folding time for the quenching history of τQ ˜ 90 Myr, and their upper limits of tQ < 0.76 Gyr and τQ <1.5 Gyr, assuming as quenching galaxies 50% of objects without [O III] (˜7.5%).Our results are compatible with a 'rapid' quenching scenario of satellites galaxies due to the final phase of strangulation or ram-pressure stripping. This approach represents a robust alternative to methods used so far to select quenched galaxies (e.g. colours, specific star-formation rate, or post-starburst spectra).

Quenched lattice QCD with domain wall fermions and the chiral limit

International Nuclear Information System (INIS)

Blum, T.; Wingate, M.; Chen, P.; Christ, N.; Cristian, C.; Fleming, G.; Kaehler, A.; Liao, X.; Liu, G.; Malureanu, C.; Mawhinney, R.; Siegert, G.; Sui, C.; Wu, L.; Zhestkov, Y.; Dawson, C.; Soni, A.; Ohta, S.; Vranas, P.

2004-01-01

Quenched QCD simulations on three volumes 8 3 x, 12 3 x and 16 3 x32 and three couplings β=5.7, 5.85 and 6.0 using domain wall fermions provide a consistent picture of quenched QCD. We demonstrate that the small induced effects of chiral symmetry breaking inherent in this formulation can be described by a residual mass (m res ) whose size decreases as the separation between the domain walls (L s ) is increased. However, at stronger couplings much larger values of L s are required to achieve a given physical value of m res . For β=6.0 and L s =16, we find m res /m s =0.033(3), while for β=5.7, and L s =48, m res /m s =0.074(5), where m s is the strange quark mass. These values are significantly smaller than those obtained from a more naive determination in our earlier studies. Important effects of topological near zero modes which should afflict an accurate quenched calculation are easily visible in both the chiral condensate and the pion propagator. These effects can be controlled by working at an appropriately large volume. A non-linear behavior of m π 2 in the limit of small quark mass suggests the presence of additional infrared subtlety in the quenched approximation. Good scaling is seen both in masses and in f π over our entire range, with inverse lattice spacing varying between 1 and 2 GeV

Numerical Study of Quench Protection for Fast-Ramping Accelerator Magnets

CERN Document Server

Schwerg, N; Mess, K-N; Russenschuck, S

2009-01-01

The quench module of the ROXIE field computation program has been presented at previous conferences. In this paper we discuss recently implemented features that allow quench simulation of fast-ramping superconducting magnets. As the reliability of quench detection during the ramps depends on the signal to noise ratio, we simulate the influence of detection thresholds and the propagation of undetected quenches during the ramps. We also study the effect of an increased copper content and the feasibility of a self-protected magnet surviving a powering cycle with an undetected quench and without quench heater firing or energy-extraction system.

Quench antenna for superconducting particle accelerator magnets

International Nuclear Information System (INIS)

Ogitsu, T.; Devred, A.; Kim, K.

1993-10-01

We report on the design, fabrication, and test of an assembly of stationary pickup coils which can be used to localize quench origins. After describing the pickup coils configuration, we develop a simple model of current redistribution which allows interpretation of the measured voltages and determination of the turn of the magnet coil in which the quench started. The technique is illustrated by analyzing the data from a quench of a 5-cm-aperture, 15-m-long SSC dipole magnet prototype

Fluorescence quenching of fluorescein by Merocyanine 540 in liposomes

International Nuclear Information System (INIS)

Toprak, Mahmut; Meryem Aydin, Burcu; Arik, Mustafa; Onganer, Yavuz

2011-01-01

The fluorescence quenching of fluorescein (FL) by merociyanine 540 (MC540) was examined in L-egg lecithin phosphatidycholine (PC) liposomes using spectroscopic methods. The type of quenching mechanism (dynamic or static) was evaluated using the Stern-Volmer plots. Findings were also supported by the temperature studies and florescence decay measurements. The Stern-Volmer equation was utilized to calculate bimolecular quenching constants (K q ). Furthermore, the bimolecular quenching constant of the quencher in the liposomes (K SV ), partition coefficient (K p ), binding constant (K), and corresponding thermodynamic parameters ΔH, ΔS, and ΔG were calculated. The quenching property was also used in determining quantitatively (K p ) the partition coefficient of Merociyanini 540 in PC liposome.The obtained data indicated that static quenching occurred in the system and the K SV values decreased with increasing lipid concentration. In addition, thermodynamic analysis suggested that van der Waals interactions and hydrogen bonding were the main acting forces between fluorescein and merociyanine 540 molecules in the medium. - Highlights: → Fluorescence quenching of FL by MC540 in liposome system was analyzed. → Fluorescence quenching mechanism of FL by MC540 was consistent with the static model. → Binding FL to MC540 was spontaneous and carried out by hydrogen bond and van der Waals forces.

FPGA-based quench detection system for super-FRS super-ferric dipole prototype

International Nuclear Information System (INIS)

Yang Tongjun; Wu Wei; Yao Qinggao; Yuan Ping; He Yuan; Han Shaofei; Ma Lizhen

2011-01-01

The quench detection system for Super-FRS super-ferric dipole prototype magnet of FAIR has been designed and built. The balance bridge was used to detect quench signal. In order to avoid blind zone of quench detection, two independent bridges were used. NI PXI-7830R FPGA was used to implement filter to quench signal and algorithm of quench decision and to produce quench trigger signal. Pre-sample technique was used in quench data acquisition. The data before and after quench could be recorded for analysis later. The test result indicated that the quench of the dipole's superconducting coil could be reliably detected by the quench detection module. (authors)

N-acetylcysteine induced quenching of red fluorescent oligonucleotide-stabilized silver nanoclusters and the application in pharmaceutical detection

International Nuclear Information System (INIS)

Wang, Xinyi; Lin, Ruoyun; Xu, Zhihan; Huang, Hongduan; Li, Limei; Liu, Feng; Li, Na; Yang, Xiaoda

2013-01-01

Graphical abstract: -- Highlights: •A new method for nanomolar NAC determination with LOD of 50 nM was reported. •The combined mechanism for NAC quenching with static dominating was suggested. •DNA-Ag NC structure changed with addition of NAC, proved by spectroscopic studies. -- Abstract: In this work, we reported a new, simple and sensitive method for determination of N-acetylcysteine (NAC) based on quenching of the red fluorescence of oligonuleotide-protected silver nanoculsters (Ag NCs) with the quantum yield of 68.3 ± 0.3%. This method was successfully used for the assay of NAC granules presenting a linear range from 100 nM to 1200 nM (LOD of 50 nM) with minimal interferences from potential coexisting substances. It is for the first time that quenching performance of the thiol-containing compound was found to follow a non-linear Stern–Volmer profile, indicative of a complicated quenching mechanism with static quenching dominating, in which DNA-template of Ag NCs was partly replaced by NAC, as elucidated by spectral investigations. This study extended the analytical application of silver nanoclusters as well as provided a more insightful understanding of the quenching mechanism of thiol-compounds on the fluorescence of Ag NCs

A review of post-column photochemical reaction systems coupled to electrochemical detection in HPLC

International Nuclear Information System (INIS)

Fedorowski, Jennifer; LaCourse, William R.

2010-01-01

Post-column photochemical reaction systems have developed into a common approach for enhancing conventional methods of detection in HPLC. Photochemical reactions as a means of 'derivatization' have a significant number of advantages over chemical reaction-based methods, and a significant effort has been demonstrated to develop an efficient photochemical reactor. When coupled to electrochemical (EC) detection, the technique allows for the sensitive and selective determination of a variety of compounds (e.g., organic nitro explosives, beta-lactam antibiotics, sulfur-containing antibiotics, pesticides and insecticides). This review will focus on developments and methods using post-column photochemical reaction systems followed by EC detection in liquid chromatography. Papers are presented in chronological order to emphasize the evolution of the approach and continued importance of the application.

Processing of the quench detection signals in W7-X

International Nuclear Information System (INIS)

Birus, Dietrich; Schneider, Matthias; Rummel, Thomas; Fricke, Marko; Petry, Klaus; Ebersoldt, Andreas

2009-01-01

The Wendelstein 7-X (W7-X) project uses superconductive coils for generation of the magnetic field to keep the plasma. One of the important safety systems is the protection against quench events. The quench detection system of W7-X protects the superconducting coils, the superconducting bus bar sections and the high temperature superconductor of the current leads against the damage because of a quench and against the high stress by a fast discharge of the magnet system. Therefore, the present design of the quench detection system (QDS) uses a two-stage safety concept for discharging the magnetic system. This paper describes the present design of the system assembly from the quench detection unit (QDU) for the detection of the quench to the quench detection interface (QDI) to implement the two-stage safety concept.

Heating the quenched Eguchi-Kawai model

Energy Technology Data Exchange (ETDEWEB)

Klinkhamer, F.R. (Rijksuniversiteit Leiden (Netherlands). Sterrewacht)

1983-05-30

We consider the Eguchi-Kawaii reduction, in the momentum-quenched prescription, of the SU(N) lattice gauge theory for N -> infinite and address the problem of how finite temperature might be incorporated. This is of interest in order to establish quark deconfinement at high temperatures. We also show that different quenching procedures may be inequivalent.

Novel Naphthalene Based Lariat-Type Crown Ethers Using Direct Single Electron Transfer Photochemical Strategy

International Nuclear Information System (INIS)

Park, Hea Jung; Sung, Nam Kyung; Kim, Su Rhan; Kim, Su Rhan; Ahn, So Hyun; Yoon, Ung Chan; Cho, Dae Won; Mariano, Patrick S.

2013-01-01

This study explored a direct SET-photochemical strategy to construct a new family of thioene conjugated-naphthalamide fluorophore based lariat-crown ethers which show strong binding properties towards heavy metal ions. Irradiations of designed nitrogen branched (trimethylsilyl)methylthio-terminated polyethylenoxy-tethered naphthalimides in acidic methanol solutions have led to highly efficient photocyclization reactions to generate naphthalamide based lariat type thiadiazacrown ethers directly in chemo- and regio-selective manners which undergo very facile secondary dehydration reactions during separation processes to produce their corresponding amidoenethio ether cyclic products tethered with electron donating diethyleneoxy- and diethyenethio-side arm chains. Fluorescence and metal cation binding properties of the lariat type enamidothio products were examined. The photocyclized amidoenethio products, thioene conjugated naphthalamide fluorophore containing lariat-thiadiazacrowns exhibited strong fluorescence emissions in region of 330-450 nm along with intramolecular exciplex emissions in region of 450-560 nm with their maxima at 508 nm. Divalent cation Hg 2+ and Pb 2+ showed strong binding to sulfur atom(s) in side arm chain and atoms in enethiadiazacrown ether rings which led to significant enhancement of fluorescence from its chromophore singlet excited state and concomitant quenching of exciplex emission. The dual fluorescence emission responses towards divalent cations might provide a new guide for design and development of fluorescence sensors for detecting those metals

Highly efficient destruction of squamous carcinoma cells of the head and neck by photochemical internalization of Ranpirnase.

Science.gov (United States)

Liebers, Nora; Holland-Letz, Tim; Welschof, Mona; Høgset, Anders; Jäger, Dirk; Arndt, Michaela A E; Krauss, Jürgen

2017-11-01

Photochemical Internalization is a novel drug delivery technology for cancer treatment based on the principle of Photodynamic Treatment. Using a photosensitizer that locates in endocytic vesicles membranes of tumor cells, Photochemical internalization enables cytosolic release of endocytosed antitumor agents in a site-specific manner. The purpose of the present in-vitro study was to explore whether Photochemical Internalization is able to enhance the efficacy of Ranpirnase, a cytotoxic amphibian ribonuclease, for eradication of squamous cell carcinoma of the head and neck. Cell viability was measured in 8 primary human cell lines of squamous cell carcinoma of the head and neck after treatment with Ranpirnase and Photochemical Internalization. For Photochemical Internalization the photosensitizer disulfonated tetraphenyl porphine was incubated with tumor cells followed by exposure to blue light (435 nm). Our study demonstrates significant enhancement of antitumor activity of Ranpirnase by Photochemical Internalization. Treatment responses were heterogeneous between the primary cancer cell lines. Combining Photochemical Internalization with Ranpirnase resulted in 4.6 to 1,940-fold increased cytotoxicity when compared with the ribonuclease alone (P Internalization in squamous cell carcinoma of the head and neck.

Validation of Quench Simulation and Simulation of the TWIN Solenoid

CERN Document Server

Pots, Rosalinde Hendrika

2015-01-01

For the Future Circular Collider at CERN a multi-purpose detector is proposed. The 6T TWIN Solenoid, a very large magnet system with a stored energy of 53 GJ, is being designed. It is important to protect the magnet against quenches in the system. Therefore several existing quench protection systems are evaluated and simulations have be performed on quenches in the TWIN Solenoid. The simulations on quenches in the TWIN Solenoid have been performed with promising results; the hotspot temperatures do not exceed 120 K and layer to layer voltages stay below 500 V. Adding quench heaters to the system might improve the quench protection system further.

Supersymmetric Field Theory of Non-Equilibrium Thermodynamic System

OpenAIRE

Olemskoi, Alexander I.; Brazhnyi, Valerii A.

1998-01-01

On the basis of Langevin equation the optimal SUSY field scheme is formulated to discribe a non-equilibrium thermodynamic system with quenched disorder and non-ergodicity effects. Thermodynamic and isothermal susceptibilities, memory parameter and irreversible response are determined at different temperatures and quenched disorder intensities.

Forced convective post CHF heat transfer and quenching

International Nuclear Information System (INIS)

Nelson, R.A.

1980-01-01

This paper discusses mechanisms in the post-CHF region which provide understanding and qualitative prediction capability for several current forced convective heat transfer problems. In the area of nuclear reactor safety, the mechanisms are important in the prediction of fuel rod quenches for the reflood phase, blowdown phase, and possibly some operational transients with dryout. Results using the mechanisms to investigate forced convective quenching are presented. Data reduction of quenching experiments is discussed, and the way in which the quenching transient may affect the results of different types of quenching experiments is investigated. This investigation provides an explanation of how minimum wall superheats greater than the homogeneous nucleation temperature result, as well as how these may appear to be either hydrodynamically or thermodynamically controlled. Finally, the results of a parametric study of the effects of the mechanisms upon the LOFT L2-3 hotpin calculation are presented

Heating the quenched Eguchi-Kawai model

International Nuclear Information System (INIS)

Klinkhamer, F.R.

1983-01-01

We consider the Eguchi-Kawaii reduction, in the momentum-quenched prescription, of the SU(N) lattice gauge theory for N -> infinite and address the problem of how finite temperature might be incorporated. This is of interest in order to establish quark deconfinement at high temperatures. We also show that different quenching procedures may be inequivalent. (orig.)

Degraded Core Quench: Summary of Progress 1996-1999 - Executive Summary

International Nuclear Information System (INIS)

Haste, T.J.; Trambauer, K.

2000-01-01

A status report on experiments and modelling relating to quench of degraded cores was issued by CSNI in August 1996, following the publication of the In-Vessel Core Degradation Code Validation Matrix. In response to a request by PWG2 through the TG-DCC, a review of progress since then to June 1999 has been performed. The scope is broadly the same as before, restricted to mainly rod-like geometries and not considering pure debris bed configurations. The scope has been increased slightly to include a VVER bundle quench experiment, CODEX-3, which falls within the parameter range of the Western bundle experiments performed to date. The same format has been adopted as before, with the experimental results for bundle and separate-effects tests being summarised in separate tables, updated from the earlier report. This review shows further evolutionary progress made in understanding the phenomena of fuel rod quench under severe accident conditions. The successful performance of commissioning and four main tests in the new bundle QUENCH facility at FZ Karlsruhe has provided valuable new data, supplemented by the VVER test CODEX-3 at AEKI Budapest. Temperature excursions and excess hydrogen production were only observed for quench from high temperature (2300 K) with a non pre-oxidised bundle (2 relevant tests); for quench from lower temperatures (1750-1870 K) and with pre-oxidation (50- 500 μm oxide) smooth cooling with no significant excess hydrogen production was observed (3 relevant tests). When cooling a non pre-oxidised bundle from 1870 K rapidly by steam, no significant excursion was observed (1 test). These new lower temperature bundle tests have usefully extended the parameter range down from that previously covered (quench temperature 2150 K and above, no pre-oxidation, temperature excursions/excess hydrogen production always observed), and have shown that there are conditions for quench from high temperature where excess temperatures and hydrogen production do not

Quench start localization in full-length SSC R ampersand D dipoles

International Nuclear Information System (INIS)

Devred, A.; Chapman, M.; Cortella, J.; Desportes, A.; Kaugerts, J.; Kirk, T.; Mirk, K.; Schermer, R.; Tompkins, J.C.; Turner, J.; Bleadon, M.; Brown, B.C.; Hanft, R.; Kuchnir, M.; Lamm, M.; Mantsch, P.; Mazur, P.O.; Orris, D.; Peoples, J.; Strait, J.; Tool, G.; Caspi, S.; Gilbert, W.; Meuser, R.; Peters, C.; Rechen, J.; Royet, J.; Scanlan, R.; Taylor, C.; Zbasnik, J.

1989-04-01

Full-length SSC R ampersand D dipole magnets instrumented with four voltage taps on each turn of the inner quarter coils have been tested. These voltage taps enable accurate location of the point at which the quenches start and detailed studies of quench development in the coil. Attention here is focused on localizing the quench source. After recalling the basic mechanism of a quench (why it occurs and how it propagates), the method of quench origin analysis is described: the quench propagation velocity on the turn where the quench occurs is calculated, and the quench location is then verified by reiterating the analysis on the adjacent turns. Last, the velocity value, which appears to be higher than previously measured, is discussed

Mechanical stress analysis during a quench in CLIQ protected 16 T dipole magnets designed for the future circular collider

Science.gov (United States)

Zhao, Junjie; Prioli, Marco; Stenvall, Antti; Salmi, Tiina; Gao, Yuanwen; Caiffi, Barbara; Lorin, Clement; Marinozzi, Vittorio; Farinon, Stefania; Sorbi, Massimo

2018-07-01

Protecting the magnets in case of a quench is a challenge for the 16 T superconducting dipole magnets presently designed for the 100 TeV: Future Circular Collider (FCC). These magnets are driven to the foreseen technological limits in terms of critical current, mechanical strength and quench protection. The magnets are protected with CLIQ (Coupling-Loss Induced Quench) system, which is a recently developed quench protection method based on discharging a capacitor bank across part of the winding. The oscillation of the magnet currents and the dissipation of the high stored energy into the windings cause electrodynamic forces and thermal stresses, which may need to be considered in the magnet mechanical design. This paper focuses on mechanical stress analysis during a quench of the 16 T cos-θ and block type dipole magnets. A finite element model allowed studying the stress due to the non-uniform temperature and current distribution in the superconducting coils. Two different CLIQ configurations were considered for the cos-θ design and one for the block type magnet. The analyses of the mechanical behavior of two magnets during a quench without or with hot spot turn were separately carried out. The simulation results show that the stress related to a quench should be considered when designing a high field magnet.

The effect of quenched disorder in neutral theories

International Nuclear Information System (INIS)

Borile, Claudio; Maritan, Amos; Muñoz, Miguel A

2013-01-01

We study systems with two symmetric absorbing states, such as the voter model and its variations, which have been broadly used as minimal neutral models in genetics, population ecology, sociology, etc. We analyze the effects of a key ingredient inevitably present in most real applications: random-field-like quenched disorder. In accord with simulations and previous findings, coexistence between the two competing states/opinions turns out to be strongly favored by disorder in the standard voter model; actually, a disorder-induced phase transition is generated for any finite system size in the presence of an arbitrarily small spontaneous-inversion rate (preventing absorbing states from being stable). For nonlinear versions of the voter model a general theory (by Al Hammal et al) explains that the spontaneous breaking of the up/down symmetry and an absorbing state phase transition can occur either together or separately, giving rise to two different scenarios. Here, we show that the presence of quenched disorder in nonlinear voter models does not allow the separation of the up–down (Ising-like) symmetry breaking from the active-to-absorbing phase transition in low-dimensional systems: both phenomena can occur only simultaneously, as a consequence of the well-known Imry–Ma argument generalized to these non-equilibrium problems. When the two phenomena occur in unison, resulting in a genuinely non-equilibrium (‘generalized voter’) transition, the Imry–Ma argument is violated and the symmetry can be spontaneously broken even in low dimensions. (paper)

Modelling of QUENCH-03 and QUENCH-06 Experiments Using RELAP/SCDAPSIM and ASTEC Codes

Directory of Open Access Journals (Sweden)

Tadas Kaliatka

2014-01-01

Full Text Available To prevent total meltdown of the uncovered and overheated core, the reflooding with water is a necessary accident management measure. Because these actions lead to the generation of hydrogen, which can cause further problems, the related phenomena are investigated performing experiments and computer simulations. In this paper, for the experiments of loss of coolant accidents, performed in Forschungszentrum Karlsruhe, QUENCH-03 and QUENCH-06 are modelled using RELAP5/SCDAPSIM and ASTEC codes. The performed benchmark allowed analysing different modelling features. The recommendations for the model development are presented.

Exercise enhanced functional recovery and expression of GDNF after photochemically induced cerebral infarction in the rat.

Science.gov (United States)

Ohwatashi, Akihiko; Ikeda, Satoshi; Harada, Katsuhiro; Kamikawa, Yurie; Yoshida, Akira

2013-01-01

Exercise has been considered to affect the functional recovery from central nervous damage. Neurotrophic factors have various effects on brain damage. However, the effects of exercise for expression of GDNF on functional recovery with brain damage are not well known. We investigated the difference in functional recovery between non-exercise and beam-walking exercise groups, and the expression of GDNF in both groups after photochemical infarction. Adult male Wistar rats (N = 64) were used. Animals were divided into two groups: non-exercise (N = 35), and beam-walking exercise (N = 29). All rats underwent surgical photochemical infarction. The rats of the beam-walking group were trained every day to walk on a narrow beam after a one-day recovery period and those of the non-exercise group were left to follow a natural course. Animals were evaluated for hind limb function every day using a beam-walking task with an elevated narrow beam. The number of GDNF-like immunoreactive cells in the temporal cortex surrounding the lesion was counted 1, 3, 5, and 7 days after the infarction. Functional recovery of the beam-walking exercise group was significantly earlier than that of the non-exercise group. At 3 days after infarction, the number of GDNF-positive cells in the temporal cortex surrounding the infarction was significantly increased in the beam-walking exercise group compared with that in the non-exercise group. In the exercise group, motor function was remarkably recovered with the increased expression of GDNF-like immunoreactive cells. Our results suggested that a rehabilitative approach increased the expression of GDNF and facilitated functional recovery from cerebral infarction.

UV-B photoreceptor-mediated protection of the photosynthetic machinery in Chlamydomonas reinhardtii

Science.gov (United States)

Allorent, Guillaume; Lefebvre-Legendre, Linnka; Chappuis, Richard; Kuntz, Marcel; Truong, Thuy B.; Niyogi, Krishna K.; Goldschmidt-Clermont, Michel

2016-01-01

Life on earth is dependent on the photosynthetic conversion of light energy into chemical energy. However, absorption of excess sunlight can damage the photosynthetic machinery and limit photosynthetic activity, thereby affecting growth and productivity. Photosynthetic light harvesting can be down-regulated by nonphotochemical quenching (NPQ). A major component of NPQ is qE (energy-dependent nonphotochemical quenching), which allows dissipation of light energy as heat. Photodamage peaks in the UV-B part of the spectrum, but whether and how UV-B induces qE are unknown. Plants are responsive to UV-B via the UVR8 photoreceptor. Here, we report in the green alga Chlamydomonas reinhardtii that UVR8 induces accumulation of specific members of the light-harvesting complex (LHC) superfamily that contribute to qE, in particular LHC Stress-Related 1 (LHCSR1) and Photosystem II Subunit S (PSBS). The capacity for qE is strongly induced by UV-B, although the patterns of qE-related proteins accumulating in response to UV-B or to high light are clearly different. The competence for qE induced by acclimation to UV-B markedly contributes to photoprotection upon subsequent exposure to high light. Our study reveals an anterograde link between photoreceptor-mediated signaling in the nucleocytosolic compartment and the photoprotective regulation of photosynthetic activity in the chloroplast. PMID:27930292

UV-B photoreceptor-mediated protection of the photosynthetic machinery in Chlamydomonas reinhardtii.

Science.gov (United States)

Allorent, Guillaume; Lefebvre-Legendre, Linnka; Chappuis, Richard; Kuntz, Marcel; Truong, Thuy B; Niyogi, Krishna K; Ulm, Roman; Goldschmidt-Clermont, Michel

2016-12-20

Life on earth is dependent on the photosynthetic conversion of light energy into chemical energy. However, absorption of excess sunlight can damage the photosynthetic machinery and limit photosynthetic activity, thereby affecting growth and productivity. Photosynthetic light harvesting can be down-regulated by nonphotochemical quenching (NPQ). A major component of NPQ is qE (energy-dependent nonphotochemical quenching), which allows dissipation of light energy as heat. Photodamage peaks in the UV-B part of the spectrum, but whether and how UV-B induces qE are unknown. Plants are responsive to UV-B via the UVR8 photoreceptor. Here, we report in the green alga Chlamydomonas reinhardtii that UVR8 induces accumulation of specific members of the light-harvesting complex (LHC) superfamily that contribute to qE, in particular LHC Stress-Related 1 (LHCSR1) and Photosystem II Subunit S (PSBS). The capacity for qE is strongly induced by UV-B, although the patterns of qE-related proteins accumulating in response to UV-B or to high light are clearly different. The competence for qE induced by acclimation to UV-B markedly contributes to photoprotection upon subsequent exposure to high light. Our study reveals an anterograde link between photoreceptor-mediated signaling in the nucleocytosolic compartment and the photoprotective regulation of photosynthetic activity in the chloroplast.

Quench protection in superconducting magnets

International Nuclear Information System (INIS)

Shajii, A.; Freidberg, J.P.

1993-01-01

The purpose of this obviously non-plasma physics research is to demonstrate that many of the powerful and sophisticated theoretical techniques widely used by the plasma physics community can be applied to engineering problems of direct interest to the magnetic fusion program. Quench protection is such a problem. If a sudden pulse of energy is delivered (usually by accident) to a small section of a superconducting magnet, it may go normal. Under such conditions, the magnet current flows in the surrounding copper matrix, which is essentially in parallel with the superconductor. Although the copper is a good conductor, it still dissipates ohmic power, further adding to the energy input. It is important to detect the quench as early as possible in order to shut off the current, thereby preventing irreversible damage to the conductor. This a non-trivial problem since the cables comprising a coil can be as long as one kilometer. The theory presented here starts with a set of multi-dimensional Navier-Stokes and heat transport equations for the coupled system of helium coolant, superconducting/copper cable, and surrounding jacket. A combination of multiple time scale expansions and asymptotic analysis reduces the problem to a nonlinear fourth order system of 1-D plus time equations. A code has been written whose numerical results are in excellent agreement with more complex engineering codes. There is at least an order of magnitude savings in CPU over the existing codes where a typical run requires one hour Cray CPU. By investigating a number of different cases the authors have been able to introduce further analytic approximations which reduce the problem to quasi-analytic form, a set of three ODE's in time. The results here too are in excellent agreement with the engineering code and requires only several seconds of CPU time. More important, the critical dimensionless parameters have been identified, as well as practical scaling information for the magnet design

Partially quenched gauge theories and an application to staggered fermions

International Nuclear Information System (INIS)

Bernard, C.W.; Golterman, M.F.L.

1994-01-01

We extend our Lagrangian technique for chiral perturbation theory for quenched QCD to include theories in which only some of the quarks are quenched. We discuss the relationship between the partially quenched theory and a theory in which only the unquenched quarks are present. We also investigate the peculiar infrared divergences associated with the η' in the quenched approximation, and find the conditions under which such divergences can appear in a partially quenched theory. We then apply our results to staggered fermion QCD in which the square root of the fermion determinant is taken, using the observation that this should correspond to a theory with four quarks, two of which are quenched

Validation of photosynthetic-fluorescence parameters as biomarkers for isoproturon toxic effect on alga Scenedesmus obliquus.

Science.gov (United States)

Dewez, David; Didur, Olivier; Vincent-Héroux, Jonathan; Popovic, Radovan

2008-01-01

Photosynthetic-fluorescence parameters were investigated to be used as valid biomarkers of toxicity when alga Scenedesmus obliquus was exposed to isoproturon [3-(4-isopropylphenyl)-1,1-dimethylurea] effect. Chlorophyll fluorescence induction of algal cells treated with isoproturon showed inactivation of photosystem II (PSII) reaction centers and strong inhibition of PSII electron transport. A linear correlation was found (R2>or=0.861) between the change of cells density affected by isoproturon and the change of effective PSII quantum yield (PhiM'), photochemical quenching (qP) and relative photochemical quenching (qP(rel)) values. The cells density was also linearly dependent (R2=0.838) on the relative unquenched fluorescence parameter (UQF(rel)). Non-linear correlation was found (R2=0.937) only between cells density and the energy transfer efficiency from absorbed light to PSII reaction center (ABS/RC). The order of sensitivity determined by the EC-50% was: UQF(rel)>PhiM'>qP>qP(rel)>ABS/RC. Correlations between cells density and those photosynthetic-fluorescence parameters provide supporting evidence to use them as biomarkers of toxicity for environmental pollutants.

Investigation of thermal quenching and abnormal thermal quenching in mixed valence Eu co-doped LaAlO{sub 3} phosphor

Energy Technology Data Exchange (ETDEWEB)

Chen, Jingjing [Tianjin Key Laboratory for Photoelectric Materials and Devices, School of Materials Science and Engineering, Tianjin University of Technology, Tianjin 300384 (China); Zhao, Yang [China academy of civil aviation science and technology, Beijing 100028 (China); Mao, Zhiyong, E-mail: mzhy1984@163.com [Tianjin Key Laboratory for Photoelectric Materials and Devices, School of Materials Science and Engineering, Tianjin University of Technology, Tianjin 300384 (China); Wang, Dajian [Tianjin Key Laboratory for Photoelectric Materials and Devices, School of Materials Science and Engineering, Tianjin University of Technology, Tianjin 300384 (China); Bie, Lijian, E-mail: ljbie@tjut.edu.cn [Tianjin Key Laboratory for Photoelectric Materials and Devices, School of Materials Science and Engineering, Tianjin University of Technology, Tianjin 300384 (China)

2017-06-15

Temperature dependent luminescence of mixed valence Eu co-doped LaAlO{sub 3} phosphors are deeply investigated in this work. Different temperature properties of Eu{sup 2+} and Eu{sup 3+} luminescence are observed as the phosphor excited by different incident light. Eu{sup 3+} luminescence shows normal thermal quenching when excited at 320 nm and abnormal thermal quenching as the excitation light changed into 365 nm, while Eu{sup 2+} luminescence exhibits a normal thermal quenching independent on the incident excitation lights. The origin of these novel normal/abnormal thermal quenching phenomena are analyzed and discussed by the excitation-emission processes in terms of the configuration coordinate model. The presented important experimental and analysis results give insights into the temperature properties of phosphors.

Photochemical Haze Formation in the Atmospheres of Super-Earths and Mini-Neptunes

Science.gov (United States)

He, Chao; Hoerst, Sarah M.; Lewis, Nikole K.; Yu, Xinting; Moses, Julianne I.; Kempton, Eliza M.- R.; Marley, Mark S.; McGuiggan, Patricia; Morley, Caroline V.; Valenti, Jeff A.;

The LHC quench protection system

CERN Multimedia

2009-01-01

The new quench protection system (QPS) has the crucial roles of providing an early warning for any part of the superconducting coils and busbars that develop high resistance, as well as triggering the switch-off of the machine. Over 2000 new detectors will be installed around the LHC to make sure every busbar segment between magnets is monitored and protected. One of the major consolidation activities for the LHC is the addition of two new detectors to the quench protection system. A magnet quench occurs when part of the superconducting cable becomes normally-conducting. When the protection system detects an increased resistance the huge amount of energy stored in the magnet chains is safely extracted and ‘dumped’ into specially designed resistors. In the case of the main dipole chain, the stored energy in a single LHC sector is roughly the same as the kinetic energy of a passenger jet at cruising speed. The first new detector is designed to monitor the superconducting...

The influence of aerosols on photochemical smog in Mexico City

Energy Technology Data Exchange (ETDEWEB)

Castro, T.; Mar, B. [UNAM, Mexico, Centro de Ciencias de la Atmosfera (Mexico); Madronich, S.; Rivale, S. [National Center for Atmospheric Research, Boulder, CO (United States); Muhlia, A. [UNAM, Mexico, Inst. de Geofysica (Mexico)

2001-04-01

Aerosols in the Mexico City atmosphere can have a non-negligible effect on the ultraviolet radiation field and hence on the formation of photochemical smog. We used estimates of aerosol optical depths from sun photometer observations in a detailed radiative transfer model, to calculate photolysis rate coefficients (J{sub NO2}) for the key reaction NO{sub 2}+h{nu}{yields}NO+O ({lambda}<430nm). The calculated values are in good agreement with previously published measurements of J{sub NO2} at two sites in Mexico City: Palacio de Mineria (19 degrees 25'59''N, 99 degrees 07'58''W, 2233masl), and IMP (19 degrees 28'48''N, 99 degrees 11'07''W, 2277masl) and in Tres Marias, a town near Mexico City (19 degrees 03'N, 99 degrees 14'W, 2810masl). In particular, the model reproduces very well the contrast between the two urban sites and the evidently much cleaner Tres Marias site. For the measurement days, reductions in surface J{sub NO2} by 10-30% could be attributed to the presence of aerosols, with considerable uncertainty due largely to lack of detailed data on aerosol optical properties at ultraviolet wavelengths (esp. the single scattering albedo). The potential impact of such large reductions in photolysis rates on surface ozone concentrations is illustrated with a simple zero-dimensional photochemical model. (Author)

Quench propagation across the copper wedges in SSC dipoles

International Nuclear Information System (INIS)

Ghosh, A.K.; Robins, K.E.; Sampson, W.B.

1986-01-01

The effect of copper wedges on quench propagation in SSC windings has been studied. The results indicate that the turn-to-turn quench transit time for conductors separated by an insulated copper wedge can be predicted with reasonable accuracy from the bulk quench properties and the mean wedge thickness

Quench protection and safety of the ATLAS central solenoid

CERN Document Server

Makida, Y; Haruyama, T; ten Kate, H H J; Kawai, M; Kobayashi, T; Kondo, T; Kondo, Y; Mizumaki, S; Olesen, G; Sbrissa, E; Yamamoto, A; Yamaoka, H

2002-01-01

Fabrication of the ATLAS central solenoid was completed and the performance test has been carried out. The solenoid was successfully charged up to 8.4 kA, which is 10% higher than the normal operational current of 7.6 kA. Two methods for quench protection, pure aluminum strips accelerating quench propagation and quench protection heaters distributing normal zones, are applied in order to safely dissipate the stored energy. In this paper, quench characteristics and protection methods of the ATLAS central solenoid are described. (14 refs).

NASA MSFC Electrostatic Levitator (ESL) Rapid Quench System

Science.gov (United States)

SanSoucie, Michael P.; Craven, Paul D.

2014-01-01

Electrostatic levitation, a form of containerless processing, is an important tool in materials research. Levitated specimens are free from contact with a container; therefore, heterogeneous nucleation on container walls is not possible. This allows studies of deeply undercooled melts. Furthermore, studies of high-temperature, highly reactive materials are also possible. Studies of the solidification and crystallization of undercooled melts is vital to the understanding of microstructure development, particularly the formation of alloys with unique properties by rapid solidification. The NASA Marshall Space Flight Center (MSFC) Electrostatic Levitator (ESL) lab has recently been upgraded to allow for rapid quenching of levitated materials. The ESL Rapid Quench System uses a small crucible-like vessel that can be partially filled with a low melting point material, such as a Gallium alloy, as a quench medium. An undercooled sample can be dropped into the vessel to rapidly quench the sample. A carousel with nine vessels sits below the bottom electrode assembly. This system allows up to nine rapid quenches before having to break vacuum and remove the vessels. 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 initial results are presented.

On the rapid melt quenching

International Nuclear Information System (INIS)

Usatyuk, I.I.; Novokhatskij, I.A.; Kaverin, Yu.F.

1994-01-01

Specific features of instrumentation of traditionally employed method of melt spinning (rapid quenching), its disadvantages being discussed, were analyzed. The necessity of the method upgrading as applied to the problems of studying fine structure of molten metals and glasses was substantiated. The principle flowsheet of experimental facility for extremely rapid quenching of the melts of metals is described, specificity of its original functional units being considered. The sequence and character of all the principal stages of the method developed were discussed. 18 refs.; 3 figs

Photochemical Internalization of Bleomycin Before External-Beam Radiotherapy Improves Locoregional Control in a Human Sarcoma Model

International Nuclear Information System (INIS)

Norum, Ole-Jacob; Bruland, Oyvind Sverre; Gorunova, Ludmila; Berg, Kristian

2009-01-01

Purpose: The aim of this study was to explore the tumor growth response of the combination photochemical internalization and external-beam radiotherapy. Photochemical internalization is a technology to improve the utilization of therapeutic macromolecules in cancer therapy by photochemical release of endocytosed macromolecules into the cytosol. Methods and Materials: A human sarcoma xenograft TAX-1 was inoculated subcutaneously into nude mice. The photosensitizer AlPcS 2a and bleomycin were intraperitoneally administrated 48 h and 30 min, respectively, before diode laser light exposure at 670 nm (20 J/cm 2 ). Thirty minutes or 7 days after photochemical treatment, the animals were subjected to 4 Gy of ionizing radiation. Results: Using photochemical internalization of bleomycin as an adjunct to ionizing radiation increased the time to progression for the tumors from 17 to 33 days as compared with that observed with photodynamic therapy combined with ionizing radiation as well as for radiochemotherapy with bleomycin. The side effects observed when photochemical internalization of bleomycin was given shortly before ionizing radiation were eliminated by separating the treatment modalities in time. Conclusion: Photochemical internalization of bleomycin combined with ionizing radiation increased the time to progression and showed minimal toxicity and may therefore reduce the total radiation dose necessary to obtain local tumor control while avoiding long-term sequelae from radiotherapy.

40 CFR 86.327-79 - Quench checks; NOX analyzer.

Science.gov (United States)

2010-07-01

... any flow rate into the reaction chamber. This includes, but is not limited to, sample capillary, ozone... Quench checks; NOX analyzer. (a) Perform the reaction chamber quench check for each model of high vacuum reaction chamber analyzer prior to initial use. (b) Perform the reaction chamber quench check for each new...

Quench detection, protection and simulation studies on SST-1 magnets

International Nuclear Information System (INIS)

Sharma, Aashoo N.; Khristi, Yohan; Pradhan, Subrata; Doshi, Kalpesh; Prasad, Upendra; Banaudha, Moni; Varmora, Pankaj; Praghi, Bhadresh R.

2015-01-01

Steady-state Superconducting Tokamak-1 (SST-1) is India's first tokamak with superconducting toroidal field (TF) and Poloidal Field (PF) magnets. These magnets are made with NbTi based Cable-In-Conduit-Conductors. The quench characteristic of SST-1 CICC has been extensively studied both analytically and using simulation codes. Dedicated experiments like model coil test program, TF coil test program and laboratory experiments were conducted to fully characterize the performance of the CICC and the magnets made using this CICC. Results of quench experiments performed during these tests have been used to design the SST-1 quench detection and protection system. Simulation results of TF coil quenches and slow propagation quench of TF busbars have been used to further optimize these systems during the SST-1 tokamak operation. Redundant hydraulic based quench detection is also proposed for the TF coil quench detection. This paper will give the overview of these development and simulation activities. (author)

Photochemical smog incident on June 30, 1973

Energy Technology Data Exchange (ETDEWEB)

Hata, S

1973-01-01

The first photochemical smog incident in Shizuoka prefecture (June 30, 1973) started in Hamamatsu and extended 100 km northeast as far as Fujinomiya city. This not only involved an extraordinarily large area, but the type of smog was different from that in Tokyo and Osaka. The victims were all pupils exercising at the time in the playgrounds. In Hamamatsu, 1050 children were involved and complained of eye irritation and pain, throat pain, coughs, and headaches between 2 and 3 pm, but there were no serious effects. The damages to agricultural produce were extensive and 70% of the total rice fields (1656 hectares), and 40 hectares of green scallions were affected. In Shizuoka, 716 children were affected about 5:30 pm, but in Fujinomiya, which is located further northeast, 16 children were affected about 4 pm. The movement of the damages, the locations, the extent of damages, and the direction of the wind, were puzzling in the light of the normal pattern of photochemical smogs, and the pollution sources could not be the coastal industrial area or automobile exhaust gases. Meteorological factors were similar to the usual photochemical smog conditions, but the locations of the cities involved and the wind direction from the sea suggested that the pollution source was the Pacific Ocean. Since the wind above 1000 m was northeast, circulation of industrial pollutants by the sea breeze is a possible explanation. The maximum concentration of oxidants was about 0.2 ppm in all areas except for Hamamatsu, where it was a little over 0.2 ppm.

Non-Photochemical Quenching in Cryptophyte Alga Rhodomonas salina Is Located in Chlorophyll a/c Antennae

Czech Academy of Sciences Publication Activity Database

Kaňa, Radek; Kotabová, Eva; Sobotka, Roman; Prášil, Ondřej

2012-01-01

Roč. 7, č. 1 (2012), e29700 E-ISSN 1932-6203 Institutional research plan: CEZ:AV0Z50200510 Keywords : PHOTOPROTECTIVE ENERGY -DISSIPATION * LIGHT- HARVESTING COMPLEX * DIATOM PHAEODACTYLUM-TRICORNUTUM Subject RIV: EE - Microbiology, Virology Impact factor: 3.730, year: 2012

Short initial length quench on CICC of ITER TF coils

Energy Technology Data Exchange (ETDEWEB)

Nicollet, S.; Ciazynski, D.; Duchateau, J.-L.; Lacroix, B. [CEA, IRFM, F-13108 Saint-Paul-lez-Durance (France); Bessette, D.; Rodriguez-Mateos, F. [ITER Organization, Route de Vinon sur Verdon, 13115 Saint Paul Lez Durance (France); Coatanea-Gouachet, M. [ELC Engineering, 350 chemin du Verladet, F-13290 Les Milles (France); Gauthier, F. [Soditech Ingenierie, 4 bis allée des Gabians, ZI La Frayère, 06150 Cannes (France)

2014-01-29

Previous quench studies performed for the International Thermonuclear Experimental Reactor (ITER) Toroidal Field (TF) Coils have led to identify two extreme families of quench: first 'severe' quenches over long initial lengths in high magnetic field, and second smooth quenches over short initial lengths in low field region. Detailed analyses and results on smooth quench propagation and detectability on one TF Cable In Conduit Conductor (CICC) with a lower propagation velocity are presented here. The influence of the initial quench energy is shown and results of computations with either a Fast Discharge (FD) of the magnet or without (failure of the voltage quench detection system) are reported. The influence of the central spiral of the conductor on the propagation velocity is also detailed. In the cases of a regularly triggered FD, the hot spot temperature criterion of 150 K (with helium and jacket) is fulfilled for an initial quench length of 1 m, whereas this criterion is exceed (Tmax ≈ 200 K) for an extremely short length of 5 cm. These analyses were carried out using both the Supermagnet(trade mark, serif) and Venecia codes and the comparisons of the results are also discussed.

Short initial length quench on CICC of ITER TF coils

International Nuclear Information System (INIS)

Nicollet, S.; Ciazynski, D.; Duchateau, J.-L.; Lacroix, B.; Bessette, D.; Rodriguez-Mateos, F.; Coatanea-Gouachet, M.; Gauthier, F.

2014-01-01

Previous quench studies performed for the International Thermonuclear Experimental Reactor (ITER) Toroidal Field (TF) Coils have led to identify two extreme families of quench: first 'severe' quenches over long initial lengths in high magnetic field, and second smooth quenches over short initial lengths in low field region. Detailed analyses and results on smooth quench propagation and detectability on one TF Cable In Conduit Conductor (CICC) with a lower propagation velocity are presented here. The influence of the initial quench energy is shown and results of computations with either a Fast Discharge (FD) of the magnet or without (failure of the voltage quench detection system) are reported. The influence of the central spiral of the conductor on the propagation velocity is also detailed. In the cases of a regularly triggered FD, the hot spot temperature criterion of 150 K (with helium and jacket) is fulfilled for an initial quench length of 1 m, whereas this criterion is exceed (Tmax ≈ 200 K) for an extremely short length of 5 cm. These analyses were carried out using both the Supermagnet(trade mark, serif) and Venecia codes and the comparisons of the results are also discussed

NDH-Mediated Cyclic Electron Flow Around Photosystem I is Crucial for C4 Photosynthesis.

Science.gov (United States)

Ishikawa, Noriko; Takabayashi, Atsushi; Noguchi, Ko; Tazoe, Youshi; Yamamoto, Hiroshi; von Caemmerer, Susanne; Sato, Fumihiko; Endo, Tsuyoshi

2016-10-01

C 4 photosynthesis exhibits efficient CO 2 assimilation in ambient air by concentrating CO 2 around ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) through a metabolic pathway called the C 4 cycle. It has been suggested that cyclic electron flow (CEF) around PSI mediated by chloroplast NADH dehydrogenase-like complex (NDH), an alternative pathway of photosynthetic electron transport (PET), plays a crucial role in C 4 photosynthesis, although the contribution of NDH-mediated CEF is small in C 3 photosynthesis. Here, we generated NDH-suppressed transformants of a C 4 plant, Flaveria bidentis, and showed that the NDH-suppressed plants grow poorly, especially under low-light conditions. CO 2 assimilation rates were consistently decreased in the NDH-suppressed plants under low and medium light intensities. Measurements of non-photochemical quenching (NPQ) of Chl fluorescence, the oxidation state of the reaction center of PSI (P700) and the electrochromic shift (ECS) of pigment absorbance indicated that proton translocation across the thylakoid membrane is impaired in the NDH-suppressed plants. Since proton translocation across the thylakoid membrane induces ATP production, these results suggest that NDH-mediated CEF plays a role in the supply of ATP which is required for C 4 photosynthesis. Such a role is more crucial when the light that is available for photosynthesis is limited and the energy production by PET becomes rate-determining for C 4 photosynthesis. Our results demonstrate that the physiological contribution of NDH-mediated CEF is greater in C 4 photosynthesis than in C 3 photosynthesis, suggesting that the mechanism of PET in C 4 photosynthesis has changed from that in C 3 photosynthesis accompanying the changes in the mechanism of CO 2 assimilation. © The Author 2016. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Smooth and fast versus instantaneous quenches in quantum field theory

Science.gov (United States)

Das, Sumit R.; Galante, Damián A.; Myers, Robert C.

2015-08-01

We examine in detail the relationship between smooth fast quantum quenches, characterized by a time scale δ t, and instantaneous quenches, within the framework of exactly solvable mass quenches in free scalar field theory. Our earlier studies [1, 2] highlighted that the two protocols remain distinct in the limit δ t → 0 because of the relation of the quench rate to the UV cut-off, i.e., 1 /δ t ≪ Λ always holds in the fast smooth quenches while 1 /δ t ˜ Λ for instantaneous quenches. Here we study UV finite quantities like correlators at finite spatial distances and the excess energy produced above the final ground state energy. We show that at late times and large distances (compared to the quench time scale) the smooth quench correlator approaches that for the instantaneous quench. At early times, we find that for small spatial separation and small δ t, the correlator scales universally with δ t, exactly as in the scaling of renormalized one point functions found in earlier work. At larger separation, the dependence on δ t drops out. The excess energy density is finite (for finite mδ t) and scales in a universal fashion for all d. However, the scaling behaviour produces a divergent result in the limit mδ t → 0 for d ≥ 4, just as in an instantaneous quench, where it is UV divergent for d ≥ 4. We argue that similar results hold for arbitrary interacting theories: the excess energy density produced is expected to diverge for scaling dimensions Δ > d/2.

Solvent refined coal reactor quench system

Science.gov (United States)

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.

History of Giant Resonances and Quenching

CERN Document Server

Arima, A

1999-01-01