WorldWideScience

Sample records for photochemically induced dynamic

  1. 1H-NMR and photochemically-induced dynamic nuclear polarization studies on bovine pancreatic phospholipase A2

    NARCIS (Netherlands)

    Egmond, M.R.; Slotboom, A.J.; Haas, G.H. de; Dijkstra, Klaas; Kaptein, R.

    1980-01-01

    Proton-NMR resonances of trytophan 3 and tyrosine 69 in bovine pancreatic phospholipase A2, its pro-enzyme and in Ala1-transaminated protein were assigned using photochemically-induced dynamic nuclear polarization (photo-CIDNP) as such or in combination with spin-echo measurements. In addition

  2. 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

  3. Effect of heavy atoms on photochemically induced dynamic nuclear polarization in liquids

    Science.gov (United States)

    Okuno, Yusuke; Cavagnero, Silvia

    2018-01-01

    Given its short hyperpolarization time (∼10-6 s) and mostly non-perturbative nature, photo-chemically induced dynamic nuclear polarization (photo-CIDNP) is a powerful tool for sensitivity enhancement in nuclear magnetic resonance. In this study, we explore the extent of 1H-detected 13C nuclear hyperpolarization that can be gained via photo-CIDNP in the presence of small-molecule additives containing a heavy atom. The underlying rationale for this methodology is the well-known external-heavy-atom (EHA) effect, which leads to significant enhancements in the intersystem-crossing rate of selected photosensitizer dyes from photoexcited singlet to triplet. We exploited the EHA effect upon addition of moderate amounts of halogen-atom-containing cosolutes. The resulting increase in the transient triplet-state population of the photo-CIDNP sensitizer fluorescein resulted in a significant increase in the nuclear hyperpolarization achievable via photo-CIDNP in liquids. We also explored the internal-heavy-atom (IHA) effect, which is mediated by halogen atoms covalently incorporated into the photosensitizer dye. Widely different outcomes were achieved in the case of EHA and IHA, with EHA being largely preferable in terms of net hyperpolarization.

  4. 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).

  5. 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.

  6. Near-field photochemical and radiation-induced chemical fabrication of nanopatterns of a self-assembled silane monolayer

    Directory of Open Access Journals (Sweden)

    Ulrich C. Fischer

    2014-09-01

    Full Text Available A general concept for parallel near-field photochemical and radiation-induced chemical processes for the fabrication of nanopatterns of a self-assembled monolayer (SAM of (3-aminopropyltriethoxysilane (APTES is explored with three different processes: 1 a near-field photochemical process by photochemical bleaching of a monomolecular layer of dye molecules chemically bound to an APTES SAM, 2 a chemical process induced by oxygen plasma etching as well as 3 a combined near-field UV-photochemical and ozone-induced chemical process, which is applied directly to an APTES SAM. All approaches employ a sandwich configuration of the surface-supported SAM, and a lithographic mask in form of gold nanostructures fabricated through colloidal sphere lithography (CL, which is either exposed to visible light, oxygen plasma or an UV–ozone atmosphere. The gold mask has the function to inhibit the photochemical reactions by highly localized near-field interactions between metal mask and SAM and to inhibit the radiation-induced chemical reactions by casting a highly localized shadow. The removal of the gold mask reveals the SAM nanopattern.

  7. Photochemically induced dynamic nuclear polarization NMR study of yeast and horse muscle phosphoglycerate kinase

    International Nuclear Information System (INIS)

    Scheffler, J.E.; Cohn, M.

    1986-01-01

    A photochemically induced dynamic nuclear polarization (photo-CIDNP) study of yeast and horse muscle phosphoglycerate kinase with flavin dyes was undertaken to identify the histidine, tryptophan, and tyrosine resonances in the aromatic region of the simplified 1 H NMR spectra of these enzymes and to investigate the effect of substrates on the resonances observable by CIDNP. Identification of the CIDNP-enhanced resonances with respect to the type of amino acid residue has been achieved since only tyrosine yields emission peaks and the dye 8-aminoriboflavin enhances tryptophan but not histidine. By use of the known amino acid sequences and structures derived from X-ray crystallographic studies of the enzymes from the two species, assignment of the specific residues in the protein sequences giving rise to the CIDNP spectra was partially achieved. In addition, flavin dye accessibility was used to probe any changes in enzyme structure induced by substrate binding. The accessibility of a tyrosine to photoexcited flavin is reduced in the presence of MgATP. Since the tyrosine residues are located some distance from the MgATP binding site of the catalytic center, it is proposed either that this change is due to a distant conformational change or that a second metal-ATP site inferred from other studies lies close to one of the tyrosines. Horse muscle phosphoglycerate kinase exhibits seven resonances by CIDNP NMR. The addition of 3-phosphoglycerate and MgATP results in the appearance of two additional resonances in the CIDNP spectrum due to a histidine residue that is inaccessible to flavin in both the enzyme alone and its binary complex with 3-phosphoglycerate. The CIDNP spectra are consistent with the suggestions that binding of 3-phosphoglycerate alone is insufficient to effect domain movement and that binding of both substrates are required for conversion of the horse muscle enzyme to its catalytically active form

  8. 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)

  9. Sunlight-Induced Photochemical Degradation of Methylene Blue by Water-Soluble Carbon Nanorods

    Directory of Open Access Journals (Sweden)

    Anshu Bhati

    2016-01-01

    Full Text Available Water-soluble graphitic hollow carbon nanorods (wsCNRs are exploited for their light-driven photochemical activities under outdoor sunlight. wsCNRs were synthesized by a simple pyrolysis method from castor seed oil, without using any metal catalyst or template. wsCNRs exhibited the light-induced photochemical degradation of methylene blue used as a model pollutant by the generation of singlet oxygen species. Herein, we described a possible degradation mechanism of methylene blue under the irradiation of visible photons via the singlet oxygen-superoxide anion pathway.

  10. 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.

  11. 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...

  12. Light-induced hysteresis and recovery behaviors in photochemically activated solution-processed metal-oxide thin-film transistors

    Energy Technology Data Exchange (ETDEWEB)

    Jo, Jeong-Wan; Park, Sung Kyu, E-mail: yhkim76@skku.edu, E-mail: skpark@cau.ac.kr [School of Electrical and Electronics Engineering, Chung-Ang University, Seoul 156-756 (Korea, Republic of); Kim, Yong-Hoon, E-mail: yhkim76@skku.edu, E-mail: skpark@cau.ac.kr [School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

    2014-07-28

    In this report, photo-induced hysteresis, threshold voltage (V{sub T}) shift, and recovery behaviors in photochemically activated solution-processed indium-gallium-zinc oxide (IGZO) thin-film transistors (TFTs) are investigated. It was observed that a white light illumination caused negative V{sub T} shift along with creation of clockwise hysteresis in electrical characteristics which can be attributed to photo-generated doubly ionized oxygen vacancies at the semiconductor/gate dielectric interface. More importantly, the photochemically activated IGZO TFTs showed much reduced overall V{sub T} shift compared to thermally annealed TFTs. Reduced number of donor-like interface states creation under light illumination and more facile neutralization of ionized oxygen vacancies by electron capture under positive gate potential are claimed to be the origin of the less V{sub T} shift in photochemically activated TFTs.

  13. Photochemically induced carbon dioxide production as a mechanism for carbon loss from plant litter in arid ecosystems

    Science.gov (United States)

    Brandt, L. A.; Bohnet, C.; King, J. Y.

    2009-06-01

    We investigated the potential for abiotic mineralization to carbon dioxide (CO2) via photodegradation to account for carbon (C) loss from plant litter under conditions typical of arid ecosystems. We exposed five species of grass and oak litter collected from arid and mesic sites to a factorial design of ultraviolet (UV) radiation (UV pass, UV block), and sterilization under dry conditions in the laboratory. UV pass treatments produced 10 times the amount of CO2 produced in UV block treatments. CO2 production rates were unaffected by litter chemistry or sterilization. We also exposed litter to natural solar radiation outdoors on clear, sunny days close to the summer solstice at midlatitudes and found that UV radiation (280-400 nm) accounted for 55% of photochemically induced CO2 production, while shortwave visible radiation (400-500 nm) accounted for 45% of CO2 production. Rates of photochemically induced CO2 production on a per-unit-mass basis decreased with litter density, indicating that rates depend on litter surface area. We found no evidence for leaching, methane production, or facilitation of microbial decomposition as alternative mechanisms for significant photochemically induced C loss from litter. We conclude that abiotic mineralization to CO2 is the primary mechanism by which C is lost from litter during photodegradation. We estimate that CO2 production via photodegradation could be between 1 and 4 g C m-2 a-1 in arid ecosystems in the southwestern United States. Taken together with low levels of litter production in arid systems, photochemical mineralization to CO2 could account for a significant proportion of annual carbon loss from litter in arid ecosystems.

  14. Laser-induced photochemical enrichment of boron isotopes

    International Nuclear Information System (INIS)

    Freund, S.M.; Ritter, J.J.

    1976-01-01

    A boron trichloride starting material containing both boron-10 isotopes and boron-11 isotopes is selectively enriched in one or the other of these isotopes by a laser-induced photochemical method involving the reaction of laser-excited boron trichloride with either H 2 S or D 2 S. The method is carried out by subjecting a low pressure gaseous mixture of boron trichloride starting material and the sulfide to infrared radiation from a carbon dioxide TE laser. The wave length of the radiation is selected so as to selectively excite one or the other of boron-10 BCl 3 molecules or boron-11 BCl 3 molecules, thereby making them preferentially more reactive with the sulfide. The laser-induced reaction produces both a boron-containing solid phase reaction product and a gaseous phase containing mostly unreacted BCl 3 and small amounts of sulfhydroboranes. Pure boron trichloride selectively enriched in one of the isotopes is recovered as the primary product of the method from the gaseous phase by a multi-step recovery procedure. Pure boron trichloride enriched in the other isotope is recovered as a secondary product of the method by the subsequent chlorination of the solid phase reaction product followed by separation of BCl 3 from the mixture of gaseous products resulting from the chlorination

  15. Utilization of Photochemically Induced Fluorescence Detection for HPLC Determination of Genotoxic Impurities in the Vortioxetine Manufacturing Process.

    Science.gov (United States)

    Douša, Michal; Doubský, Jan; Srbek, Jan

    2016-07-01

    An analytical reversed-phase high-performance liquid chromatography (HPLC) method for the detection and quantitative determination of two genotoxic impurities at ppm level present in the vortioxetine manufacturing process is described. Applying the concept of threshold of toxicological concern, a limit of 75 ppm each for both genotoxic impurities was calculated based on the maximum daily dose of active pharmaceutical ingredients. The novel reversed-phase HPLC method with photochemically induced fluorescence detection was developed on XSELECT Charged Surface Hybrid Phenyl-Hexyl column using the mobile phase consisted a mixture of 10 mM ammonium formate pH 3.0 and acetonitrile. The elution was performed using an isocratic composition of 48:52 (v/v) at a flow rate of 1.0 mL/min. The photochemically induced fluorescence detection is based on the use of UV irradiation at 254 nm through measuring the fluorescence intensity at 300 nm and an excitation wavelength of 272 nm to produce fluorescent derivatives of both genotoxic impurities. The online photochemical conversion and detection is easily accomplished for two expected genotoxic impurities and provides a sufficiently low limit detection and quantification for the target analysis. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  16. 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.

  17. 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.; hide

    2018-01-01

    UV (ultraviolet) radiation can induce photochemical processes in the atmospheres of exoplanet and produce haze particles. Recent transmission spectra of super-Earths and mini-Neptunes have demonstrated the possibility that exoplanets have haze/cloud layers at high altitudes in their atmospheres. Haze particles play an important role in planetary atmospheres because they affect the chemistry, dynamics, and radiation flux in planetary atmospheres, and may provide a source of organic material to the surface which may impact the origin or evolution of life. However, very little information is known about photochemical processes in cool, high-metallicity exoplanetary atmospheres. We present here photochemical haze formation in laboratory simulation experiments with UV radiation; we explored temperatures ranging from 300 to 600 degrees Kelvin and a range of atmospheric metallicities (100 times, 1000 times, and 10000 times solar metallicity). We find that photochemical hazes are generated in all simulated atmospheres, but the haze production rates appear to be temperature dependent: the particles produced in each metallicity group decrease as the temperature increases. The images taken with an atomic force microscope (AFM) show that the particle size (15 nanometers to 190 nanometers) varies with temperature and metallicity. Our results provide useful laboratory data on the photochemical haze formation and particle properties, which can serve as critical inputs for exoplanet atmosphere modeling, and guide future observations of exoplanets with the Transiting Exoplanet Survey Satellite (TESS), the James Webb Space Telescope (JWST), and the Wide-Field Infrared Survey Telescope (WFIRST).

  18. Photochemical induced growth and aggregation of metal nanoparticles in diode-array spectrophotometer via excited dimethyl-sulfoxide.

    Science.gov (United States)

    Zidki, Tomer; Cohen, Haim; Meyerstein, Dan

    2010-10-21

    Ag(0) and Au(0) nanoparticles suspended in dilute aqueous solutions containing (CH(3))(2)SO are photochemically unstable. The light source of a diode-array spectrophotometer induces, within less than a minute, particle growth and aggregation. The results indicate that this process is triggered by UV light absorption by the (CH(3))(2)SO.

  19. 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.

  20. 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

  1. 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

  2. An optimal photochemical energy conversion and environmental effects in the reactive molecular dynamics; Optimale Photochemische Energiekonversion und Umgebungseffekte in Reaktiver Molekueldynamik

    Energy Technology Data Exchange (ETDEWEB)

    Fingerhut, Benjamin Philipp

    2011-02-08

    }-sigmatropic rearrangement is presented, which predicts that only in the (6-4) dinucleotide the Dewar is exclusively formed from an excited valence state, but not in the free base 5-methyl-2-pyrimidinone (5M2P) nor with a sliced backbone. The mechanism is elucidated by the analysis of conical intersections which show, that the photochemical deactivation of T(6-4)T is strongly influenced by the confinement in the dinucleotide, leading to T(Dewar)T formation, whereas in 5M2P the photophysical protection is ensured by a conical intersection seam. The implementation of the ONIOM-method into the non-adiabatic mixed quantum classical dynamics allows to follow the formation of the T(Dewar)T lesion as well as the competing photophysical relaxation. C=O-vibrations are identified as unambiguous spectroscopic probe of the 4{pi}-sigmatropic rearrangement for highly sensitive UV/VIS pump - IR probe experiments which were successful in following the reaction in real time. As a second photoreaction the ultrafast phototriggered reaction of benzhydryl cations with methanol is investigated. The mechanism of the laser induced generation of highly reactive benzhydryl cations from the precursor molecule diphenylmethyl chloride is derived by quantum chemical and quantum dynamical methods. For the competing reaction channels of ion pair and radical pair formation the interaction of different electronic states leads to ultrafast bond cleavage. The homolytic bond cleavage as a parallel reaction-channel is already accessible in the FC region by the participation of lone-pairs of the Cl-leaving group (n{sub p{sub x,z}}). Based on ab initio data a system Hamiltonian is derived which is suitable to describe the multidimensional dissociation process in a reduced reactive coordinate space. Quantum dynamical calculations show that bond cleavage induced by a Fourier limited femtosecond laser pulse provides the ion pair despite its higher potential energy and the existence of conical intersections. The subsequent

  3. 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.)

  4. Symbiont shuffling linked to differential photochemical dynamics of Symbiodinium in three Caribbean reef corals

    Science.gov (United States)

    Cunning, Ross; Silverstein, Rachel N.; Baker, Andrew C.

    2018-03-01

    Dynamic symbioses with functionally diverse dinoflagellate algae in the genus Symbiodinium may allow some reef corals to alter their phenotypes through `symbiont shuffling', or changes in symbiont community composition. In particular, corals may become more bleaching resistant by increasing the relative abundance of thermally tolerant Symbiodinium in clade D after bleaching. Despite the immediate relevance of this phenomenon to corals living in warming oceans—and to interventions aimed at boosting coral resilience—the mechanisms governing how, why, and when symbiont shuffling occurs are still poorly understood. Here, we performed controlled thermal bleaching and recovery experiments on three species of Caribbean corals hosting mixtures of D1a ( S. trenchii) and other symbionts in clades B or C. We show that the degree of symbiont shuffling is related to (1) the duration of stress exposure and (2) the difference in photochemical efficiency ( F v /F m) of co-occurring symbionts under stress (i.e., the `photochemical advantage' of one symbiont over the other). The advantage of D1a under stress was greatest in Montastraea cavernosa, intermediate in Siderastrea siderea, and lowest in Orbicella faveolata and correlated positively with the magnitude of shuffling toward D1a. In holobionts where D1a had less of an advantage over co-occurring symbionts (i.e., only slightly higher F v /F m under stress), a longer stress duration was required to elicit commensurate increases in D1a abundance. In fact, across these three coral species, 92.9% of variation in the degree of symbiont shuffling could be explained by the time-integrated photochemical advantage of D1a under heat stress. Although F v /F m is governed by numerous factors that this study is unable to resolve mechanistically, its strong empirical relationship with symbiont shuffling helps elucidate general features that govern this process in reef corals, which will help refine predictions of coral responses to

  5. UV radiation-induced photochemical damage of tryptophan in peptides, proteins and ocular lenses

    International Nuclear Information System (INIS)

    Hibbard, L.B.

    1985-01-01

    These studies were undertaken to investigate the possible involvement of the amino acid tryptophan in the near-ultraviolet radiation-induced photochemical alteration of peptides and proteins and the role tryptophan photolysis plays in ocular lens damage. Sample irradiations were performed to determine if tryptophan photolysis occurs with radiation in the UV-A region in comparison to photolysis induced by wavelengths in the normal absorption band of the amino acid (UV-B). Photolysis studies were carried out on free tryptophan and two dipeptides, tryptophyglycine and glycyltryptophan, in aqueous solutions at different pH values in the range 4.5-10.0 under aerated or anaerobic conditions. Rates of photolysis of these 290 nm-irradiated compounds, detected by observing tryptophan fluorescence intensity loss during irradiation, were compared and significant differences were observed for each compound which varied with pH and oxygen environment. Another series of experiments examined the photolysis of tryptophan residues in lens proteins in whole rat lenses induced by 290 nm and 298 nm dye laser radiation. Tryptophan residue photolysis was, once again, monitored by loss in tryptophan fluorescence intensity. A relationship was derived between tryptophan loss and photoproduct buildup during irradiation

  6. Effects of Edaravone, a Free Radical Scavenger, on Photochemically Induced Cerebral Infarction in a Rat Hemiplegic Model

    OpenAIRE

    Ikeda, Satoshi; Harada, Katsuhiro; Ohwatashi, Akihiko; Kamikawa, Yurie

    2013-01-01

    Edaravone is a free radical scavenger that protects the adjacent cortex during cerebral infarction. We created a hemiparetic model of cerebral thrombosis from a photochemically induced infarction with the photosensitive dye, rose bengal, in rats. We examined the effects of edaravone on recovery in the model. A total of 36 adult Wistar rats were used. The right sensorimotor area was irradiated with green light with a wavelength of 533?nm (10?mm diameter), and the rose bengal was injected intra...

  7. Photochemical reaction dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Moore, B.C. [Lawrence Berkeley Laboratory, Livermore, CA (United States)

    1993-12-01

    The purpose of the program is to develop a fundamental understanding of unimolecular and bimolecular reaction dynamics with application in combustion and energy systems. The energy dependence in ketene isomerization, ketene dissociation dynamics, and carbonyl substitution on organometallic rhodium complexes in liquid xenon have been studied. Future studies concerning unimolecular processes in ketene as well as energy transfer and kinetic studies of methylene radicals are discussed.

  8. 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.

  9. Molecular-beam studies of primary photochemical processes

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Y.T.

    1982-12-01

    Application of the method of molecular-beam photofragmentation translational spectroscopy to the investigation of primary photochemical processes of polyatomic molecules is described. Examples will be given to illustrate how information concerning the energetics, dynamics, and mechanism of dissociation processes can be obtained from the precise measurements of angular and velocity distributions of products in an experiment in which a well-defined beam of molecules is crossed with a laser.

  10. Molecular-beam studies of primary photochemical processes

    International Nuclear Information System (INIS)

    Lee, Y.T.

    1982-12-01

    Application of the method of molecular-beam photofragmentation translational spectroscopy to the investigation of primary photochemical processes of polyatomic molecules is described. Examples will be given to illustrate how information concerning the energetics, dynamics, and mechanism of dissociation processes can be obtained from the precise measurements of angular and velocity distributions of products in an experiment in which a well-defined beam of molecules is crossed with a laser

  11. Solar ultraviolet radiation induced variations in the stratosphere and mesosphere

    Science.gov (United States)

    Hood, L. L.

    1987-01-01

    The detectability and interpretation of short-term solar UV induced responses of middle atmospheric ozone, temperature, and dynamics are reviewed. The detectability of solar UV induced perturbations in the middle atmosphere is studied in terms of seasonal and endogenic dynamical variations. The interpretation of low-latitude ozone and possible temperature responses on the solar rotation time scale is examined. The use of these data to constrain or test photochemical model predictions is discussed.

  12. Development of a mouse model of neuropathic pain following photochemically induced ischemia in the sciatic nerve.

    Science.gov (United States)

    Hao, J X; Blakeman, K H; Yu, W; Hultenby, K; Xu, X J; Wiesenfeld-Hallin, Z

    2000-05-01

    A mouse model of neuropathic pain was developed by a photochemically induced ischemic nerve injury in normal male C57/BL6 mice. The ischemia was induced by unilateral irradiation of the sciatic nerve with an argon ion laser after intravenous administration of a photosensitizing dye, erythrosin B. The nerve injury resulted in a significant decrease in withdrawal threshold of the hindpaws to mechanical stimulation with von Frey hairs, as well as increased responsiveness to cold and heat stimulation. The mice, however, did not exhibit overt spontaneous pain-like behaviors. The evoked pain-related behaviors were observed bilaterally, although the ipsilateral changes were greater than on the contralateral side. The extent and time course of the behavioral changes were related to the duration of laser irradiation, with 1-min exposure producing the most consistent effect. Morphological examination at the light microscopic level revealed partial demyelination and axonal degeneration of the large myelinated fibers at the epicenter of the lesion 1 week postirradiation. The extent of the damage was correlated with the duration of irradiation. Injury and loss of unmyelinated fibers were also observed at the electronmicroscopic level. We conclude that an intravascular photochemical reaction leading to ischemia results in graded damage to the sciatic nerve in mice. Moreover, the nerve injury is associated with the development of abnormal pain-related behaviors. Both the behavioral and the morphological changes are correlated with the duration of irradiation. These results establish a mouse model of partial nerve injury with neuropathic pain-like behaviors which may be useful in studies using genetically modified mice. Copyright 2000 Academic Press.

  13. The study on laser photochemical process of Diazonaphthoquinon-Cresol system

    International Nuclear Information System (INIS)

    Wei Jie; Huang Yu Li; Wang Wenke

    1999-01-01

    The kinetic process of laser photochemical reaction of diazonaphthoquinon-cresol system was studied by using laser spectrophotofluorimetry and laser induced fluorescence attenuation method. The nonlinear relationship between photodecomposition rate of the sensitizer and laser power, exposure time and concentration of solutions was discussed in detail

  14. From small aromatic molecules to functional nanostructured carbon by pulsed laser-induced photochemical stitching

    Directory of Open Access Journals (Sweden)

    R. R. Gokhale

    2012-06-01

    Full Text Available A novel route employing UV laser pulses (KrF Excimer, 248 nm to cleave small aromatic molecules and stitch the generated free radicals into functional nanostructured forms of carbon is introduced. The process differs distinctly from any strategies wherein the aromatic rings are broken in the primary process. It is demonstrated that this pulsed laser-induced photochemical stitching (PLPS process when applied to routine laboratory solvents (or toxic chemical wastes when discarded Chlorobenzene and o-Dichlorobenzene yields Carbon Nanospheres (CNSs comprising of graphene-like sheets assembled in onion-like configurations. This room temperature process implemented under normal laboratory conditions is versatile and clearly applicable to the whole family of haloaromatic compounds without and with additions of precursors or other nanomaterials. We further bring out its applicability for synthesis of metal-oxide based carbon nanocomposites.

  15. 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 ...

  16. 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

  17. 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)

  18. 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.

  19. Photochemical Hydrogen Doping Induced Embedded Two-Dimensional Metallic Channel Formation in InGaZnO at Room Temperature.

    Science.gov (United States)

    Kim, Myeong-Ho; Lee, Young-Ahn; Kim, Jinseo; Park, Jucheol; Ahn, Seungbae; Jeon, Ki-Joon; Kim, Jeong Won; Choi, Duck-Kyun; Seo, Hyungtak

    2015-10-27

    The photochemical tunability of the charge-transport mechanism in metal-oxide semiconductors is of great interest since it may offer a facile but effective semiconductor-to-metal transition, which results from photochemically modified electronic structures for various oxide-based device applications. This might provide a feasible hydrogen (H)-radical doping to realize the effectively H-doped metal oxides, which has not been achieved by thermal and ion-implantation technique in a reliable and controllable way. In this study, we report a photochemical conversion of InGaZnO (IGZO) semiconductor to a transparent conductor via hydrogen doping to the local nanocrystallites formed at the IGZO/glass interface at room temperature. In contrast to thermal or ionic hydrogen doping, ultraviolet exposure of the IGZO surface promotes a photochemical reaction with H radical incorporation to surface metal-OH layer formation and bulk H-doping which acts as a tunable and stable highly doped n-type doping channel and turns IGZO to a transparent conductor. This results in the total conversion of carrier conduction property to the level of metallic conduction with sheet resistance of ∼16 Ω/□, room temperature Hall mobility of 11.8 cm(2) V(-1) sec(-1), the carrier concentration at ∼10(20) cm(-3) without any loss of optical transparency. We demonstrated successful applications of photochemically highly n-doped metal oxide via optical dose control to transparent conductor with excellent chemical and optical doping stability.

  20. 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.

  1. A plasmaless, photochemical etch process for porous organosilicate glass films

    Science.gov (United States)

    Ryan, E. Todd; Molis, Steven E.

    2017-12-01

    A plasmaless, photochemical etch process using ultraviolet (UV) light in the presence of NH3 or O2 etched porous organosilicate glass films, also called pSiCOH films, in a two-step process. First, a UV/NH3 or UV/O2 treatment removed carbon (mostly methyl groups bonded to silicon) from a pSiCOH film by demethylation to a depth determined by the treatment exposure time. Second, aqueous HF was used to selectively remove the demethylated layer of the pSiCOH film leaving the methylated layer below. UV in the presence of inert gas or H2 did not demethylate the pSiCOH film. The depth of UV/NH3 demethylation followed diffusion limited kinetics and possible mechanisms of demethylation are presented. Unlike reactive plasma processes, which contain ions that can damage surrounding structures during nanofabrication, the photochemical etch contains no damaging ions. Feasibility of the photochemical etching was shown by comparing it to a plasma-based process to remove the pSiCOH dielectric from between Cu interconnect lines, which is a critical step during air gap fabrication. The findings also expand our understanding of UV photon interactions in pSiCOH films that may contribute to plasma-induced damage to pSiCOH films.

  2. Selective laser-induced photochemical dry etching of semiconductors controlled by ion-bombardment-induced damage

    International Nuclear Information System (INIS)

    Ashby, C.I.H.; Myers, D.R.; Vook, F.L.

    1987-01-01

    When a photochemical dry etching process requires direct participation of photogenerated carriers in the chemical reaction, it is sensitive to the electronic properties of the semiconductor. For such solid-excitation-based dry etching processes, the balance between reaction and carrier recombination rates determines the practical utility of a particular reaction for device fabrication. The distance from the surface at which the photocarriers are generated by light adsorption is determined by the absorption coefficient. In the absence of an external bias potential, only those carriers formed within a diffusion length of the surface space-charge region will have an opportunity to drive the dry etching reaction. When the absorption coefficient is high, most of the photons generate carriers within a diffusion length from the surface space-charge region, and the etching rate is largely determined by the balance between the rate of the carrier-driven reaction and the surface recombination velocity. When the recombination rate of free carriers in the bulk of the semiconductor is high, the effective diffusion length is reduced and fewer of the carriers generated in the subsurface region ever reach the surface. An important effect of ion bombardment is the creation of many lattice defects that increase the rate of recombination of electrons and holes. When a sufficient number of defects, which act as recombination sites, are formed during ion implantation, the recombination of photogenerated carriers at these defects in the subsurface region can greatly reduce the number of carriers which can reach the surface and drive a photochemical etching reaction

  3. Quantum Mechanics/Molecular Mechanics Free Energy Maps and Nonadiabatic Simulations for a Photochemical Reaction in DNA: Cyclobutane Thymine Dimer.

    Science.gov (United States)

    Mendieta-Moreno, Jesús I; Trabada, Daniel G; Mendieta, Jesús; Lewis, James P; Gómez-Puertas, Paulino; Ortega, José

    2016-11-03

    The absorption of ultraviolet radiation by DNA may result in harmful genetic lesions that affect DNA replication and transcription, ultimately causing mutations, cancer, and/or cell death. We analyze the most abundant photochemical reaction in DNA, the cyclobutane thymine dimer, using hybrid quantum mechanics/molecular mechanics (QM/MM) techniques and QM/MM nonadiabatic molecular dynamics. We find that, due to its double helix structure, DNA presents a free energy barrier between nonreactive and reactive conformations leading to the photolesion. Moreover, our nonadiabatic simulations show that most of the photoexcited reactive conformations return to standard B-DNA conformations after an ultrafast nonradiative decay to the ground state. This work highlights the importance of dynamical effects (free energy, excited-state dynamics) for the study of photochemical reactions in biological systems.

  4. 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....

  5. A transthylakoid proton gradient and inhibitors induce a non-photochemical fluorescence quenching in unicellular algae Nannochloropsis sp.

    Science.gov (United States)

    Cao, Shaona; Zhang, Xiaowen; Xu, Dong; Fan, Xiao; Mou, Shanli; Wang, Yitao; Ye, Naihao; Wang, Wenqi

    2013-05-02

    Non-photochemical quenching (NPQ) of chlorophyll fluorescence is thought to be an indicator of an essential regulation and photoprotection mechanism against high-light stress in photosynthetic organisms. In this report, special chemicals were used to perturb the kinetics of the ΔpH build-up and the xanthophyll cycle (XC) in Nannochloropsis sp. We found that NPQ was stimulated rapidly on exposure to high light and relaxed rapidly in darkness. The ΔpH could be obligatory for NPQ and ΔpH alone was not sufficient to induce NPQ. The XC, being strictly mediated by ΔpH, was also essential for NPQ. The results demonstrate that the mechanism of NPQ in Nannochloropsis sp. resembled that of diatoms. Copyright © 2013 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

  6. 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

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

    Czech Academy of Sciences Publication Activity Database

    Niedzwiedzki, D.M.; Tronina, T.; Liu, H.; Staleva, H.; Komenda, Josef; Sobotka, Roman; Blankenship, R.E.; Polívka, T.

    2016-01-01

    Roč. 1857, č. 9 (2016), s. 1430-1439 ISSN 0005-2728 R&D Projects: GA ČR GBP501/12/G055 Institutional support: RVO:61388971 Keywords : Carotenoids * Non-photochemical quenching * Energy transfer Subject RIV: CE - Biochemistry Impact factor: 4.932, year: 2016

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

    OpenAIRE

    Fr?chette, Emmanuelle; Chang, Christine Yao-Yun; Ensminger, Ingo

    2016-01-01

    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 c...

  9. Photochemical Reactions of Particulate Organic Matter: Deciphering the Role of Direct and Indirect Processes

    Science.gov (United States)

    Carrasquillo, A. J.; Gelfond, C. E.; Kocar, B. D.

    2016-12-01

    Photochemical reactions of natural organic matter (NOM) represent potentially important pathways for biologically recalcitrant material to be chemically altered in aquatic systems. Irradiation can alter the physical state of organic matter by facilitating the cycling between the particulate (POM) and dissolved (DOM) pools, however, a molecular level understanding of this chemically dynamic system is currently lacking. Photochemical reactions of a target molecule proceed by the direct absorption of a photon, or through reaction with a second photolytically generated species (i.e. the hydroxyl radical, singlet oxygen, excited triplet state NOM, hydrogen peroxide, etc.). Here, we isolate the major direct and indirect photochemical reactions of a lignocellulose-rich POM material (Phragmites australis) to determine their relative importance in changing the the chemical structure of the parent POM, and in the production of DOM. We measured POM molecular structure using a combination of NMR and FTIR for bulk analyses and scanning transmission x-ray microscopy (STXM) for spatially resolved chemistry, while the chemical composition of photo-produced DOM was measured using ultra-high resolution mass spectrometry. Results are discussed in the context of the differences in chemical composition of both NOM pools resulting from the isolated photochemical pathways. All treatments result in an increase in DOM with reaction time, indicating that the larger POM matrix is likely fragmenting into smaller more soluble species. Spectroscopic measurements, on the other hand, point to functionalization reactions which increase the abundance of alcohol, acid, and carbonyl moieties in both carbon pools. This unique dataset provides new insight into how photochemical reactions alter the chemical composition of NOM while highlighting the relative importance of indirect pathways.

  10. Simulations of photochemical smog formation in complex urban areas

    Science.gov (United States)

    Muilwijk, C.; Schrijvers, P. J. C.; Wuerz, S.; Kenjereš, S.

    2016-12-01

    In the present study we numerically investigated the dispersion of photochemical reactive pollutants in complex urban areas by applying an integrated Computational Fluid Dynamics (CFD) and Computational Reaction Dynamics (CRD) approach. To model chemical reactions involved in smog generation, the Generic Reaction Set (GRS) approach is used. The GRS model was selected since it does not require detailed modeling of a large set of reactive components. Smog formation is modeled first in the case of an intensive traffic emission, subjected to low to moderate wind conditions in an idealized two-dimensional street canyon with a building aspect ratio (height/width) of one. It is found that Reactive Organic Components (ROC) play an important role in the chemistry of smog formation. In contrast to the NOx/O3 photochemical steady state model that predicts a depletion of the (ground level) ozone, the GRS model predicts generation of ozone. Secondly, the effect of direct sunlight and shadow within the street canyon on the chemical reaction dynamics is investigated for three characteristic solar angles (morning, midday and afternoon). Large differences of up to one order of magnitude are found in the ozone production for different solar angles. As a proof of concept for real urban areas, the integrated CFD/CRD approach is applied for a real scale (1 × 1 km2) complex urban area (a district of the city of Rotterdam, The Netherlands) with high traffic emissions. The predicted pollutant concentration levels give realistic values that correspond to moderate to heavy smog. It is concluded that the integrated CFD/CRD method with the GRS model of chemical reactions is both accurate and numerically robust, and can be used for modeling of smog formation in complex urban areas.

  11. Theoretical perspectives on electron transfer and charge separation events in photochemical water cleavage systems

    International Nuclear Information System (INIS)

    Kozak, J.J.; Lenoir, P.M.; Musho, M.K.; Tembe, B.L.

    1984-01-01

    We study in this paper the dynamics induced by models for photochemical water cleavage systems, focusing on the spatial and temporal factors influencing electron transfer and charge separation processes in such systems. The reaction-diffusion theory is formulated in full generality and the consequences explored in a number of spatio-temporal regimes, viz. the spatially homogeneous system in the long-time limit (i.e. the steady state for a well-stirred system), the spatially homogeneous system in evolution, and the spatially inhomogeneous system in evolution (where, in the latter study, we consider electron transfer at the cluster surface to be governed by a rate constant that reflects the localized nature of such processes). The results of numerical simulations are presented for all three cases and used to highlight the importance of heterogeneous environments in enhancing the cage escape yield of charge separated species, and to demonstrate the dependence of the hydrogen yield on the localization of electron-transfer processes in the vicinity of the microcatalyst surface

  12. Dispersion and photochemical evolution of reactive pollutants in street canyons

    Science.gov (United States)

    Kwak, Kyung-Hwan; Baik, Jong-Jin; Lee, Kwang-Yeon

    2013-05-01

    Dispersion and photochemical evolution of reactive pollutants in street canyons with canyon aspect ratios of 1 and 2 are investigated using a computational fluid dynamics (CFD) model coupled with the carbon bond mechanism IV (CBM-IV). Photochemical ages of NOx and VOC are expressed as a function of the NO2-to-NOx and toluene-to-xylene ratios, respectively. These are found to be useful for analyzing the O3 and OH oxidation processes in the street canyons. The OH oxidation process (O3 oxidation process) is more pronounced in the upper (lower) region of the street canyon with a canyon aspect ratio of 2, which is characterized by more (less) aged air. In the upper region of the street canyon, O3 is chemically produced as well as transported downward across the roof level, whereas O3 is chemically reduced in the lower region of the street canyon. The O3 chemical production is generally favorable when the normalized photochemical ages of NOx and VOC are larger than 0.55 and 0.28, respectively. The sensitivities of O3 chemical characteristics to NOx and VOC emission rates, photolysis rate, and ambient wind speed are examined for the lower and upper regions of the street canyon with a canyon aspect ratio of 2. The O3 concentration and the O3 chemical production rate divided by the O3 concentration increase as the NOx emission rate decreases and the VOC emission rate and photolysis rate increase. The O3 concentration is less sensitive to the ambient wind speed than to other factors considered. The relative importance of the OH oxidation process compared to the O3 oxidation process increases with increasing NOx emission rate and photolysis rate and decreasing VOC emission rate. In this study, both O3 and OH oxidation processes are found to be important in street-canyon scale chemistry. The methodology of estimating the photochemical ages can potentially be adopted to neighborhood scale chemistry.

  13. Probing and exploiting the chaotic dynamics of a hydrodynamic photochemical oscillator to implement all the basic binary logic functions

    Energy Technology Data Exchange (ETDEWEB)

    Hayashi, Kenta [Department of Mechanical Engineering, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu-shi, Shiga 525-8577 (Japan); Department of Chemistry, Biology, and Biotechnology, University of Perugia, 06123 Perugia (Italy); Gotoda, Hiroshi [Department of Mechanical Engineering, Tokyo University of Science, 6-3-1 Niijuku, Katsushika-ku, Tokyo 125-8585 (Japan); Gentili, Pier Luigi, E-mail: pierluigi.gentili@unipg.it [Department of Chemistry, Biology, and Biotechnology, University of Perugia, 06123 Perugia (Italy)

    2016-05-15

    The convective motions within a solution of a photochromic spiro-oxazine being irradiated by UV only on the bottom part of its volume, give rise to aperiodic spectrophotometric dynamics. In this paper, we study three nonlinear properties of the aperiodic time series: permutation entropy, short-term predictability and long-term unpredictability, and degree distribution of the visibility graph networks. After ascertaining the extracted chaotic features, we show how the aperiodic time series can be exploited to implement all the fundamental two-inputs binary logic functions (AND, OR, NAND, NOR, XOR, and XNOR) and some basic arithmetic operations (half-adder, full-adder, half-subtractor). This is possible due to the wide range of states a nonlinear system accesses in the course of its evolution. Therefore, the solution of the convective photochemical oscillator results in hardware for chaos-computing alternative to conventional complementary metal-oxide semiconductor-based integrated circuits.

  14. 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

  15. Generating and measuring photochemical changes inside the brain using optical fibers: exploring stroke.

    Science.gov (United States)

    Tsiminis, Georgios; Klarić, Thomas S; Schartner, Erik P; Warren-Smith, Stephen C; Lewis, Martin D; Koblar, Simon A; Monro, Tanya M

    2014-11-01

    We report here on the development of a method for inducing a stroke in a specific location within a mouse brain through the use of an optical fiber. By capturing the emitted fluorescence signal generated using the same fiber it is possible to monitor photochemical changes within the brain in real-time, and directly measure the concentration of the stroke-inducing dye, Rose Bengal, at the infarct site. This technique reduces the requirement for post-operative histology to determine if a stroke has successfully been induced within the animal, and therefore opens up the opportunity to explore the recovery of the brain after the stroke event.

  16. 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)

  17. 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...

  18. Dynamic light absorption of biomass-burning organic carbon photochemically aged under natural sunlight

    Science.gov (United States)

    Zhong, M.; Jang, M.

    2014-02-01

    Wood-burning aerosol produced under smoldering conditions was photochemically aged with different relative humidity (RH) and NOx conditions using a 104 m3 dual outdoor chamber under natural sunlight. Light absorption of organic carbon (OC) was measured over the course of photooxidation using a UV-visible spectrometer connected to an integrating sphere. At high RH, the color decayed rapidly. NOx slightly prolonged the color of wood smoke, suggesting that NOx promotes the formation of chromophores via secondary processes. Overall, the mass absorption cross section (integrated between 280 and 600 nm) of OC increased by 11-54% (except high RH) in the morning and then gradually decreased by 19-68% in the afternoon. This dynamic change in light absorption of wood-burning OC can be explained by two mechanisms: chromophore formation and sunlight bleaching. To investigate the effect of chemical transformation on light absorption, wood smoke particles were characterized using various spectrometers. The intensity of fluorescence, which is mainly related to polycyclic aromatic hydrocarbons (PAHs), rapidly decreased with time, indicating the potential bleaching of PAHs. A decline of levoglucosan concentrations evinced the change of primary organic aerosol with time. The aerosol water content measured by Fourier transform infrared spectroscopy showed that wood-burning aerosol became less hygroscopic as photooxidation proceeded. A similar trend in light absorption changes has been observed in ambient smoke aerosol originating from the 2012 County Line wildfire in Florida. We conclude that the biomass-burning OC becomes less light absorbing after 8-9 h sunlight exposure compared to fresh wood-burning OC.

  19. Dynamic light absorption of biomass burning organic carbon photochemically aged under natural sunlight

    Science.gov (United States)

    Zhong, M.; Jang, M.

    2013-08-01

    Wood burning aerosol produced under smoldering conditions was photochemically aged with different relative humidity (RH) and NOx conditions using a 104 m3 dual outdoor chamber under natural sunlight. Light absorption of organic carbon (OC) was measured over the course of photooxidation using a UV-visible spectrometer connected to an integrating sphere. At high RH, the color decayed rapidly. NOx slightly prolonged the color of wood smoke, suggesting that NOx promotes the formation of chromophores via secondary processes. Overall, the mass absorption cross-section (integrated between 280 nm and 600 nm) of OC increased by 11-54% (except high RH) in the morning and then gradually decreased by 19-68% in the afternoon. This dynamic change in light absorption of wood burning OC can be explained by two mechanisms: chromophore formation and sunlight bleaching. To investigate the effect of chemical transformation on light absorption, wood smoke particles were characterized using various spectrometers. The intensity of fluorescence, which is mainly related to polycyclic aromatic hydrocarbons (PAHs), rapidly decreased with time indicating the potential bleaching of PAHs. A decline of levoglucosan concentrations evinced the change of POA with time. The aerosol water content measured by Fourier transform infrared spectroscopy showed that wood burning aerosol became less hygroscopic as photooxidation proceeded. A similar trend in light absorption changes has been observed in ambient smoke aerosol originating from the 2012 County Line Wildfire in Florida. We conclude that the biomass burning OC becomes less light absorbing after 8-9 h sunlight exposure compared to fresh wood burning OC.

  20. 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

  1. 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

  2. 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.

  3. 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.

  4. Photochemical internalisation of chemotherapy potentiates killing of multidrug-resistant breast and bladder cancer cells

    OpenAIRE

    Adigbli, D. K.; Wilson, D. G. G.; Farooqui, N.; Sousi, E.; Risley, P.; Taylor, I.; MacRobert, A. J.; Loizidou, M.

    2007-01-01

    Multidrug resistance (MDR) is the major confounding factor in adjuvant solid tumour chemotherapy. Increasing intracellular amounts of chemotherapeutics to circumvent MDR may be achieved by a novel delivery method, photochemical internalisation (PCI). PCI consists of the co-administration of drug and photosensitiser; upon light activation the latter induces intracellular release of organelle-bound drug. We investigated whether co-administration of hypericin ( photosensitiser) with mitoxantrone...

  5. Photochemical internalisation of chemotherapy potentiates killing of multidrug-resistant breast and bladder cancer cells

    OpenAIRE

    Adigbli, D K; Wilson, D G G; Farooqui, N; Sousi, E; Risley, P; Taylor, I; MacRobert, A J; Loizidou, M

    2007-01-01

    Multidrug resistance (MDR) is the major confounding factor in adjuvant solid tumour chemotherapy. Increasing intracellular amounts of chemotherapeutics to circumvent MDR may be achieved by a novel delivery method, photochemical internalisation (PCI). PCI consists of the co-administration of drug and photosensitiser; upon light activation the latter induces intracellular release of organelle-bound drug. We investigated whether co-administration of hypericin (photosensitiser) with mitoxantrone ...

  6. Investigation of the photochemical changes of chlorogenic acids induced by ultraviolet light in model systems and in agricultural practice with Stevia rebaudiana cultivation as an example.

    Science.gov (United States)

    Karaköse, Hande; Jaiswal, Rakesh; Deshpande, Sagar; Kuhnert, Nikolai

    2015-04-08

    Mono- and diacyl chlorogenic acids undergo photochemical trans-cis isomerization under ultraviolet (UV) irradiation. The photochemical equilibrium composition was established for eight selected derivatives. In contrast to all other dicaffeoylquinic acid derivatives, cynarin (1,3-dicaffeoylquinic acid) undergoes a [2 + 2] photochemical cycloaddition reaction, constituting a first example of Schmidt's law in a natural product family. The relevance of photochemical isomerization in agricultural practice was investigated using 120 samples of Stevia rebaudiana leave samples grown under defined cultivation conditions. Ratios of cis to trans chlorogenic acids were determined in leaf samples and correlated with climatic and harvesting conditions. The data indicate a clear correlation between the formation of cis-caffeoyl derivatives and sunshine hours prior to harvesting and illustrate the relevance of UV exposure to plant material affecting its phytochemical composition.

  7. Photochemically induced deposition of protective alumina coatings onto UV emitting phosphors for Xe excimer discharge lamps

    International Nuclear Information System (INIS)

    Broxtermann, Mike; Jüstel, Thomas

    2016-01-01

    Highlights: • A UV-reactor for the pH induced precipitation of inorganic material is described. • The photolysis of Azide (N_3"−) leads to a steady pH increase used for precipitation. • A UV induced Al(OH)_3 precipitation is used to craft Al_2O_3 coatings onto YPO_4:Bi. • The influence of Al_2O_3 coated onto YPO_4:Bi with different thicknesses is discussed. • SEM, VUV-spectroscopy and ESA measurements were performed on Al_2O_3 coated samples. - Abstract: This work concerns the particle coating of the UV-C emitting phosphor YPO_4:Bi, targeting a stability enhancement of the phosphor material for Xe excimer lamp operation. To this end, the material is coated by the wide band gap material Al_2O_3. In order to obtain a thin and homogeneous coating layer, a novel process based on the photochemical cleavage of NaN_3 in water was developed. This results in a slow and continuous enhancement of the pH value due to ongoing NaOH formation, which results in the precipitation of Al(OH)_3 from an Al_2(SO_4)_3 _× 18H_2O solution. It turned out that the obtained particle coatings are of much better quality, i.e. homogeneity, compared to coatings made from a wet-chemical homogeneous precipitation process. The morphology and electrochemical properties of Al_2O_3 coated YPO_4:Bi are discussed on the basis of optical spectroscopy, ESA measurements, and SEM/EDX investigations.

  8. 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.

  9. 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.

  10. 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...

  11. Tropospheric Ozone and Photochemical Smog

    Science.gov (United States)

    Sillman, S.

    2003-12-01

    global background ozone can make the effects of local pollution events everywhere more acute, and can also cause ecological damage in remote locations that are otherwise unaffected by urban pollution. Ozone at the global scale is also related to greenhouse warming.This chapter provides an overview of photochemical smog at the urban and regional scale, focused primarily on ozone and including a summary of information about particulates. It includes the following topics: dynamics and extent of pollution events; health and ecological impacts; relation between ozone and precursor emissions, including hydrocarbons and nitrogen oxides (NOx); sources, composition, and fundamental properties of particulates; chemistry of ozone and related species; methods of interpretation based on ambient measurements; and the connection between air pollution events and the chemistry of the global troposphere. Because there are many similarities between the photochemistry of ozone during pollution events and the chemistry of the troposphere in general, this chapter will include some information about global tropospheric chemistry and the links between urban-scale and global-scale events. Additional treatment of the global troposphere is found in Volume 4 of this work. The chemistry of ozone formation discussed here is also related to topics discussed in greater detail elsewhere in this volume (see Chapters 9.10 and 9.12) and in Volume 4.

  12. 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)

  13. Polymers designed for laser ablation-influence of photochemical properties

    International Nuclear Information System (INIS)

    Lippert, T.; Dickinson, J.T.; Hauer, M.; Kopitkovas, G.; Langford, S.C.; Masuhara, H.; Nuyken, O.; Robert, J.; Salmio, H.; Tada, T.; Tomita, K.; Wokaun, A.

    2002-01-01

    The ablation characteristics of various polymers were studied at low and high fluences. The polymers can be divided into three groups, i.e. polymers containing triazene and ester groups, the same polymers without the triazene group, and polyimide as reference polymer. At high fluences similar ablation parameters, i.e. etch rates and effective absorption coefficients, were obtained for all polymers. The main difference is the absence of carbon deposits for the designed polymers. At low fluences (at 308 nm) very pronounced differences are detected. The polymers containing the photochemically most active group (triazene) exhibit the lowest threshold of ablation (as low as 25 mJ cm -2 ) and the highest etch rates (up to 3 μm/pulse), followed by the designed polyesters and then polyimide. The laser-induced decomposition of the designed polymers was studied by nanosecond-interferometry. Only the triazene-polymer reveals etching without any sign of surface swelling, which is observed for all other polymers. The etching of the triazene-polymer starts and ends with the laser pulse, clearly indicating photochemical etching. The triazene-polymer was also studied by time-of-flight mass spectrometry (TOF-MS). The intensities of the ablation fragments show pronounced differences between irradiation at the absorption band of the triazene group (308 nm) and irradiation at a shorter wavelength (248 nm)

  14. Controlling the photochemical reaction of an azastilbene derivative in water using a water-soluble pillar[6]arene.

    Science.gov (United States)

    Xia, Danyu; Wang, Pi; Shi, Bingbing

    2017-09-20

    Photochemistry plays an important role in our lives. It has also been a common tool in the laboratory to construct complicated systems from small molecules. Supramolecular chemistry provides an opportunity to solve some of the problems in controlling photochemical reactions via non-covalent interactions. By using confining media and weak interactions between the medium and the reactant molecule, the excited state behavior of molecules has been successfully manipulated. Pillararenes, a new class of macrocyclic hosts, have rarely been used in the field of photochemical investigations, such as the controlling of photo-induced reactions. Herein, we explore a synthetic macrocyclic host, a water-soluble pillar[6]arene, as a controlling tool to manipulate the photo-induced reactions (hydration) in water. A host-guest system in water based on a water-soluble pillar[6]arene and an azastilbene derivative, (E)-4,4'-dimethyl-4,4'-diazoniastilbene diiodide, has been constructed. Then this water-soluble pillar[6]arene was successfully employed to control the photohydration of the azastilbene derivative in water as a "protective agent".

  15. Photochemical Dynamics of Intramolecular Singlet Fission

    Science.gov (United States)

    Lin, Zhou; Iwasaki, Hikari; Van Voorhis, Troy

    2017-06-01

    Singlet fission (SF) converts a singlet exciton (S_1) into a pair of triplet ones (T_1) via a ``multi-exciton'' (ME) intermediate: S_1 \\longleftrightarrow ^1ME \\longleftrightarrow ^1(T_1T_1) \\longrightarrow 2T_1. In exothermic cases, e.g., crystalline pentacene or its derivatives, the quantum yield of SF can reach 200%. With SF doubling the electric current generated by an incident high-energy photon, the solar conversion efficiency in pentacene-based organic photovoltaics (OPVs) can exceed the Shockley-Queisser limit of 33.7%. The ME state is popularly considered to be a dimeric state with significant charge transfer (CT) character that is strongly coupled to both S_1 and ^1(T_1T_1), while this local model lacks strong support from full quantum dynamics studies. Intramolecular SF (ISF) occurring to covalently-bound dimers in the solution phase is an excellent model for a straightforward dynamics simulation of local excitons. In the present study, we investigate the ISF mechanisms for three covalently-bound dimers of pentacene derivatives, including ortho-, meta-, and para-bis(6,13-bis(triisopropylsilylethynyl)pentacene)benzene, in non-protic solvents. Specifically, we propagate the real-time, non-adiabatic quantum mechanical/molecular mechanical (QM/MM) dynamics on the potential energy surfaces associated with the states of S_1, ^1(T_1T_1) and CT. We explore how the energies of these ISF-relevant states and the non-adiabatic couplings between each other fluctuate with time and the instantaneous molecular configuration (e.g., intermonomer distance and orientation). We also quantitatively compare Condon and non-Condon ISF dynamics with solution-phase spectroscopic data. Our results allow us to understand the roles of CT energy levels in the ISF mechanism and propose a design strategy to maximize ISF efficiency. M. B. Smith and J. Michl, Chem. Rev. 110, 6891 (2010). W. Shockley and H. J. Queisser, J. Appl. Phys. 32, 510 (1961). T. C. Berkelbach, M. S. Hybertsen

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Self-induced temperature gradients in Brownian dynamics

    Science.gov (United States)

    Devine, Jack; Jack, M. W.

    2017-12-01

    Brownian systems often surmount energy barriers by absorbing and emitting heat to and from their local environment. Usually, the temperature gradients created by this heat exchange are assumed to dissipate instantaneously. Here we relax this assumption to consider the case where Brownian dynamics on a time-independent potential can lead to self-induced temperature gradients. In the same way that externally imposed temperature gradients can cause directed motion, these self-induced gradients affect the dynamics of the Brownian system. The result is a coupling between the local environment and the Brownian subsystem. We explore the resulting dynamics and thermodynamics of these coupled systems and develop a robust method for numerical simulation. In particular, by focusing on one-dimensional situations, we show that self-induced temperature gradients reduce barrier-crossing rates. We also consider a heat engine and a heat pump based on temperature gradients induced by a Brownian system in a nonequilibrium potential.

  1. Suppression of non-photochemical quenching in Arabidopsis leaves to a ionizing radiation

    International Nuclear Information System (INIS)

    Yu Ran Moon; Jin-Hong Kim; Min Hee Lee; Byung Yeoup Chung; Jae-Sung Kim

    2007-01-01

    Complete text of publication follows. Non-photochemical quenching (NPQ) of chlorophyll fluorescence has been known to be involved in a protection of photosystems against photoinhibition through a dissipation of excess light absorbed by photosynthetic pigments. In the present study, we aimed to elucidate the effects of a ionizing radiation on NPQ by comparing alterations in the development and release of NPQ after gamma-irradiation between the wild-type (WT) and the npq1-2 mutant of Arabidopsis. The npq1-2 mutant can't develop with a normal NPQ under excess light, since it is defective in its de-epoxidase activity for conversion of violaxanthin to zeaxanthin. Gamma-irradiation with a dose of 200 Gy inhibited the development of NPQ in both the WT and mutant but more noticeably in the latter. Moreover, Fv/Fm as an indice of the photochemical efficiency of photosystem II (PSII) was almost the same in both the WT and npq1-2 mutant throughout the post-irradiation period of 5 d. The obtained results will be also discussed with those from photoinhibition induced by non-ionizing radiations such as visible light and UV-B.

  2. Gas-to-particle conversion in the atmospheric environment by radiation-induced and photochemical reactions

    International Nuclear Information System (INIS)

    Vohra, K.G.

    1975-01-01

    During the last few years a fascinating new area of research involving ionizing radiations and photochemistry in gas-to-particle conversion in the atmosphere has been developing at a rapid pace. Two problems of major interest and concern in which this is of paramount importance are: (1) radiation induced and photochemical aerosol formation in the stratosphere and, (2) role of radiations and photochemistry in smog formation. The peak in cosmic ray intensity and significant solar UV flux in the stratosphere lead to complex variety of reactions involving major and trace constituents in this region of the atmosphere, and some of these reactions are of vital importance in aerosol formation. The problem is of great current interest because the pollutant gases from industrial sources and future SST operations entering the stratosphere could increase the aerosol burden in the stratosphere and affect the solar energy input of the troposphere with consequent ecological and climatic changes. On the other hand, in the nuclear era, the atmospheric releases from reactors and processing plants could lead to changes in the cloud nucleation behaviour of the environment and possible increase in smog formation in the areas with significant levels of radiations and conventional pollutants. A review of the earlier work, current status of the problem, and conventional pollutants. A review of the earlier work, current status of the problem, and some recent results of the experiments conducted in the author's laboratory are presented. The possible mechanisms of gas-to-particle conversion in the atmosphere have been explained

  3. On line photochemically induced excitation-emission-kinetic four-way data

    International Nuclear Information System (INIS)

    Jimenez Giron, A.; Duran-Meras, I.; Espinosa-Mansilla, A.; Munoz de la Pena, A.; Canada Canada, F.; Olivieri, A.C.

    2008-01-01

    The determination of folic acid and its two main serum metabolites, 5-methyltetrahydrofolic acid and tetrahydrofolic acid, has been accomplished using four-way data modelled by the third-order multivariate calibration methods unfolded and N-dimensional partial least-squares (U-PLS and N-PLS), in combination with the separate procedure known as residual trilinearization (RTL). The four-way data were acquired by following the photochemical reaction of these compounds by on line irradiation with a UV lamp. The excitation-emission matrices (EEMs) were recorded as a function of the irradiation time, using a fast scanning spectrofluorimeter. The method achieves selectivity from the different rates at which the corresponding photoproducts of the folic acid derivatives are formed and degraded. Several N-dimensional chemometric algorithms were used and the method was applied to the determination of these compounds in serum samples. The best algorithms to perform the multivariate calibration were U-PLS and N-PLS in combination with the separate residual trilinearization procedure, achieving the second-order advantage. The approach allows minimizing or eliminating traditionally time-consuming sample pre-treatments and can facilitate quantifying an analyte in its native environment

  4. Contribution of atmospheric processes affecting the dynamics of air pollution in South-Western Europe during a typical summertime photochemical episode

    Directory of Open Access Journals (Sweden)

    M. Gonçalves

    2009-02-01

    Full Text Available The southern Mediterranean region frequently experiences critical levels of photochemical pollutants during summertime. In order to account for the contribution of different atmospheric processes during this type of episodes, the WRF-ARW/HERMES/CMAQ modelling system was applied with high resolution (1 km2, 33 sigma vertical layers, 1 h to assess the different dynamics in a coastal environment and an inland-continental zone: the North-Eastern and Central Iberian Peninsula (NEIP and CIP, respectively. The former is characterized by a very complex terrain, while the latter behaves as a flat area, which clearly affects the pattern of local flows. A representative type of photochemical pollution episode (occurring over 78% of summer days which occurred during 17–18 June, 2004 is selected as the study period. The CMAQ Integrated Process Rate provides the hourly contributions of atmospheric processes to net O3, NOx and NMVOCs concentrations. The O3 photochemical formation occurs mainly in downwind areas from the main NOx emission sources during midday. At surface level it accounts for 50 to 75 μg m−3 h−1. The urban areas and main roads, as main sources of NOx emissions, act as O3 sinks, quenching up to −200 μg m−3 per hour during the traffic circulation peaks. The O3 concentration gradient generated, larger during daytime, increases the contribution of diffusion processes to ground-level O3 (up to 200 μg m−3 h−1 fluxes, mainly from upper vertical layers. The maximum positive contributions of gas-phase chemistry to O3 occur in the coastal domain at high levels (around 500 to 1500 m a.g.l., while in the continental domain they take place in the whole atmospheric column under the PBL. The transport of ozone precursors by advective flows determines the location of the maximum O

  5. 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.

  6. Photochemically induced deposition of protective alumina coatings onto UV emitting phosphors for Xe excimer discharge lamps

    Energy Technology Data Exchange (ETDEWEB)

    Broxtermann, Mike, E-mail: mike.b@fh-muenster.de; Jüstel, Thomas, E-mail: tj@fh-muenster.de

    2016-08-15

    Highlights: • A UV-reactor for the pH induced precipitation of inorganic material is described. • The photolysis of Azide (N{sub 3}{sup −}) leads to a steady pH increase used for precipitation. • A UV induced Al(OH){sub 3} precipitation is used to craft Al{sub 2}O{sub 3} coatings onto YPO{sub 4}:Bi. • The influence of Al{sub 2}O{sub 3} coated onto YPO{sub 4}:Bi with different thicknesses is discussed. • SEM, VUV-spectroscopy and ESA measurements were performed on Al{sub 2}O{sub 3} coated samples. - Abstract: This work concerns the particle coating of the UV-C emitting phosphor YPO{sub 4}:Bi, targeting a stability enhancement of the phosphor material for Xe excimer lamp operation. To this end, the material is coated by the wide band gap material Al{sub 2}O{sub 3}. In order to obtain a thin and homogeneous coating layer, a novel process based on the photochemical cleavage of NaN{sub 3} in water was developed. This results in a slow and continuous enhancement of the pH value due to ongoing NaOH formation, which results in the precipitation of Al(OH){sub 3} from an Al{sub 2}(SO{sub 4}){sub 3} {sub ×} 18H{sub 2}O solution. It turned out that the obtained particle coatings are of much better quality, i.e. homogeneity, compared to coatings made from a wet-chemical homogeneous precipitation process. The morphology and electrochemical properties of Al{sub 2}O{sub 3} coated YPO{sub 4}:Bi are discussed on the basis of optical spectroscopy, ESA measurements, and SEM/EDX investigations.

  7. 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 ⁎ .

  8. 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.

  9. Effects of Edaravone, a Free Radical Scavenger, on Photochemically Induced Cerebral Infarction in a Rat Hemiplegic Model

    Directory of Open Access Journals (Sweden)

    Satoshi Ikeda

    2013-01-01

    Full Text Available Edaravone is a free radical scavenger that protects the adjacent cortex during cerebral infarction. We created a hemiparetic model of cerebral thrombosis from a photochemically induced infarction with the photosensitive dye, rose bengal, in rats. We examined the effects of edaravone on recovery in the model. A total of 36 adult Wistar rats were used. The right sensorimotor area was irradiated with green light with a wavelength of 533 nm (10 mm diameter, and the rose bengal was injected intravenously to create an infarction. The edaravone group was injected intraperitoneally with edaravone (3 mg/kg, and the control group was injected with saline. The recovery process of the hemiplegia was evaluated with the 7-step scale of Fenny. The infarcted areas were measured after fixation. The recovery of the paralysis in the edaravone-treated group was significantly earlier than that in the untreated group. Seven days later, both groups were mostly recovered and had scores of 7, and the infarction region was significantly smaller in the edaravone-treated group. Edaravone reduced the infarction area and promoted the functional recovery of hemiparesis from cerebral thrombosis in a rat model. These findings suggest that edaravone treatment would be effective in clinical patients recovering from cerebral infarction.

  10. Effects of edaravone, a free radical scavenger, on photochemically induced cerebral infarction in a rat hemiplegic model.

    Science.gov (United States)

    Ikeda, Satoshi; Harada, Katsuhiro; Ohwatashi, Akihiko; Kamikawa, Yurie

    2013-01-01

    Edaravone is a free radical scavenger that protects the adjacent cortex during cerebral infarction. We created a hemiparetic model of cerebral thrombosis from a photochemically induced infarction with the photosensitive dye, rose bengal, in rats. We examined the effects of edaravone on recovery in the model. A total of 36 adult Wistar rats were used. The right sensorimotor area was irradiated with green light with a wavelength of 533 nm (10 mm diameter), and the rose bengal was injected intravenously to create an infarction. The edaravone group was injected intraperitoneally with edaravone (3 mg/kg), and the control group was injected with saline. The recovery process of the hemiplegia was evaluated with the 7-step scale of Fenny. The infarcted areas were measured after fixation. The recovery of the paralysis in the edaravone-treated group was significantly earlier than that in the untreated group. Seven days later, both groups were mostly recovered and had scores of 7, and the infarction region was significantly smaller in the edaravone-treated group. Edaravone reduced the infarction area and promoted the functional recovery of hemiparesis from cerebral thrombosis in a rat model. These findings suggest that edaravone treatment would be effective in clinical patients recovering from cerebral infarction.

  11. 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.

  12. Photochemical key steps in the synthesis of surfactants from furfural-derived intermediates.

    Science.gov (United States)

    Gassama, Abdoulaye; Ernenwein, Cédric; Hoffmann, Norbert

    2009-01-01

    Furfural is oxidized to 2[5H]-furanone by using hydrogen peroxide or to 5-hydroxy-2[5H]-furanone by using photo-oxygenation. An amine function is introduced by photochemically induced radical addition of tertiairy amines, some of which carry an n-alkyl side chain as hydrophobic moiety. These amines are produced from fatty aldehydes and cyclic secondary amines. The resulting adducts are transformed into amphoteric surfactants possessing an ammonium and a carboxylate function. Amphoteric (pK(N) and isoelectric point) and surfactant properties such as the critical micelle concentration and the adsorption efficiency are determined.

  13. 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...

  14. Magnetic field induced dynamical chaos.

    Science.gov (United States)

    Ray, Somrita; Baura, Alendu; Bag, Bidhan Chandra

    2013-12-01

    In this article, we have studied the dynamics of a particle having charge in the presence of a magnetic field. The motion of the particle is confined in the x-y plane under a two dimensional nonlinear potential. We have shown that constant magnetic field induced dynamical chaos is possible even for a force which is derived from a simple potential. For a given strength of the magnetic field, initial position, and velocity of the particle, the dynamics may be regular, but it may become chaotic when the field is time dependent. Chaotic dynamics is very often if the field is time dependent. Origin of chaos has been explored using the Hamiltonian function of the dynamics in terms of action and angle variables. Applicability of the present study has been discussed with a few examples.

  15. 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

  16. Photochemical and Spectroscopic Effects Resulting from Excimer Laser Excitation.

    Science.gov (United States)

    Wang, Xuan Xiao

    I. Photochemical production of ozone from pure oxygen using excimer lasers. Production of ozone was observed from experiments when oxygen was under a broadband pulsed KrF laser radiation. The production process was found to be autocatalytic. Mechanisms for the ozone formation were proposed. Experimental results over a range of oxygen pressure and laser pulse energy (irradiance) provided evidences in favor of the proposed mechanisms. Experiments were also numerically modeled. Good agreement between the experimental and the numerical results were observed, which provided further evidence to support the proposed mechanisms. Cross sections for some photochemical processes in the mechanisms were estimated. Production of ozone from pure oxygen under a ArF excimer laser radiation (193 nm) was also studied and numerically modeled. Effects of ambient water vapor on ozone production were investigated. Experimental results showed a fast ozone destruction when water vapor was present in the cell. However, numerical results obtained from the well-known OH and HO _2 chain ozone destruction mechanism predicted a slower ozone destruction. Possible reasons for the discrepancy are discussed. II. Resonance-enhanced multiphoton ionization of N_2 at 193 and 248 nm detected by N_sp{2}{+} fluorescence. Using a broadband excimer laser operating at 193 and 248 nm multiphoton ionization at high pressures in air and pure nitrogen has been detected by fluorescence from N_sp{2}{+} in the B-X firstnegative system. Measurements of the fluorescence intensity as a function of beam irradiance indicate resonance in N_2 at the energy of two 193 nm photons (2 + 1 REMPI) and three 248 nm photons (3 + 1 REMPI). Possible intermediate states are discussed. III. Excimer laser-induced fluorescence from some organic solvents. Fluorescence was observed from vapor phase benzene, toluene, p-xylene, benzyl chloride, methyl benzoate, acetic anhydride, ether, methanol, ethyl acetone, acetone, and 2-butanone using

  17. 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....

  18. 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...

  19. 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)

  20. Facilitated beam-walking recovery during acute phase by kynurenic acid treatment in a rat model of photochemically induced thrombosis causing focal cerebral ischemia.

    Science.gov (United States)

    Abo, Masahiro; Yamauchi, Hideki; Suzuki, Masahiko; Sakuma, Mio; Urashima, Mitsuyoshi

    We previously demonstrated the presence of activated areas in the non-injured contralateral sensorimotor cortex in addition to the ipsilateral sensorimotor cortex of the area surrounding a brain infarction, using a rat model of focal photochemically induced thrombosis (PIT) and functional magnetic resonance imaging. Using this model, we next applied gene expression profiling to screen key molecules upregulated in the activated area. RNA was extracted from the ipsilateral and contralateral sensorimotor cortex to the focal brain infarction and from the sham controlled cortex, and hybridized to gene-expression profiling arrays containing 1,322 neurology-related genes. Results showed that glycine receptors were upregulated in both the ipsilateral and contralateral cortex to the focal ischemic lesion. To prove the preclinical significance of upregulated glycine receptors, kynurenic acid, an endogenous antagonist to glycine receptors on neuronal cells, was administered intrathecally. As a result, the kynurenic acid significantly improved behavioral recovery within 10 days from paralysis induced by the focal PIT (p beam walking. These results suggest that intrathecal administration of a glycine receptor antagonist may facilitate behavioral recovery during the acute phase after brain infarction. Copyright (c) 2006 S. Karger AG, Basel.

  1. 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

  2. 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 }.

  3. Geometric origin of dynamically induced freezing of quantum evolution

    International Nuclear Information System (INIS)

    Matos-Abiague, A.; Berakdar, J.

    2006-01-01

    The phenomenon of dynamical, field-induced freezing of quantum evolution is discussed. It occurs when a time-dependent state is dynamically driven in such a way that the evolution of the corresponding wave function is effectively localized within a small region in the projective Hilbert space. As a consequence, the dynamics of the system is frozen and the expectation values of all physical observables hardly change with time. Necessary and sufficient conditions for inducing dynamical freezing are inferred from a general analysis of the geometry of quantum evolution. The relevance of the dynamical freezing for a sustainable in time, dynamical control is discussed and exemplified by a study of the coherent control of the kicked rotor motion

  4. Inducible Laryngeal Obstruction: Excessive Dynamic Airway Collapse vs. Inducible Laryngeal Obstruction

    Science.gov (United States)

    2017-10-20

    REPORT TYPE 10/20/2017 Poster 4. TITLE AND SUBTITLE Inducible Laryngeal Obstrnction: Excessive Dynamic Airway Collapse vs. Inducible Laryngeal...REPORT b.ABSTRACT c. THIS PAGE ABSTRACT OF PAGES 3. DATES COVERED (From - To) 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER

  5. Photophysical and photochemical effects in ultrafast laser patterning of CVD graphene

    International Nuclear Information System (INIS)

    Bobrinetskiy, Ivan; Otero, Nerea; Romero, Pablo M; Emelianov, Aleksei; Komarov, Ivan; Nasibulin, Albert

    2016-01-01

    The micro-scale patterns in graphene on Si/SiO 2 substrate were fabricated using ultrashort 515 nm laser pulses. For both picosecond and femtosecond laser pulses two competitive processes, based on photo-thermal (ablation) and photochemical (oxidation/etching) effects, were observed. The laser-induced etching of graphene starts just below the threshold energy of graphene ablation: 1.7 nJ per 280 fs pulse and 2.7 µ J per 30 ps pulse. Whilst etching is not sensitive to thermal properties of graphene and provides uniform patterns, the ablation, in contrast, is highly affected by defects in the graphene structure like wrinkles and bilayer islands. The mechanisms of ultrafast laser interaction with graphene are discussed. (letter)

  6. Current-induced dynamics in carbon atomic contacts

    DEFF Research Database (Denmark)

    Lu, Jing Tao; Gunst, Tue; Brandbyge, Mads

    2011-01-01

    voltage, which can be used to explore current-induced vibrational instabilities due the NC/BP forces. Furthermore, using tight-binding and the Brenner potential we illustrate how Langevin-type molecular-dynamics calculations including the Joule heating effect for the carbon-chain systems can be performed...... be used to explore current-induced dynamics and instabilities. We find instabilities at experimentally relevant bias and gate voltages for the carbon-chain system. © 2011 Lü et al....... carbon chain connecting electrically gated graphene electrodes. This illustrates how the device stability can be predicted solely from the modes obtained from the Langevin equation, including the current-induced forces. We point out that the gate offers control of the current, independent of the bias...

  7. Induced topological pressure for topological dynamical systems

    International Nuclear Information System (INIS)

    Xing, Zhitao; Chen, Ercai

    2015-01-01

    In this paper, inspired by the article [J. Jaerisch et al., Stochastics Dyn. 14, 1350016, pp. 1-30 (2014)], we introduce the induced topological pressure for a topological dynamical system. In particular, we prove a variational principle for the induced topological pressure

  8. Photochemical products causing fluorescence enhancement for 6H-benzo[cd]pyren-6-one in de-aerated and pre-irradiated solutions

    Energy Technology Data Exchange (ETDEWEB)

    Yagishita, M., E-mail: yagishita.mayuko@nies.go.jp [Department of Environmental Science, Faculty of Science, Toho University, 2-2-1 Miyama, Funabashi, Chiba 274-8510 (Japan); National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba-City, Ibaraki 305-8506 (Japan); Nakajima, D. [National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba-City, Ibaraki 305-8506 (Japan); Ohshima, S. [Department of Environmental Science, Faculty of Science, Toho University, 2-2-1 Miyama, Funabashi, Chiba 274-8510 (Japan)

    2016-11-15

    Polycyclic aromatic ketones emit very weak fluorescence, but their fluorescence is significantly enhanced by about one hundred times after preliminary irradiation of their degassed solution. To investigate the mechanism of such fluorescence enhancement, liquid chromatography/time-of-flight mass spectrometry measurements were performed for degassed methanol, ethanol, and acetonitrile solutions of 6H-benzo[cd]pyren-6-one (naphthanthrone), in which fluorescence enhancement had been induced. As a result, two kinds of photochemical products were identified as the substance causing fluorescence enhancement: they were produced by dehydrogenation and dehydration of adducts of a solvent molecule to naphthanthrone. On the basis of the findings, the mechanism of the fluorescence enhancement of naphthanthrone was discussed. Fluorescence enhancement; 6H-benzo[cd]pyren-6-one; Polycyclic aromatic ketones; Liquid chromatography-mass spectrometry; Photochemical reaction.

  9. Photochemical products causing fluorescence enhancement for 6H-benzo[cd]pyren-6-one in de-aerated and pre-irradiated solutions

    International Nuclear Information System (INIS)

    Yagishita, M.; Nakajima, D.; Ohshima, S.

    2016-01-01

    Polycyclic aromatic ketones emit very weak fluorescence, but their fluorescence is significantly enhanced by about one hundred times after preliminary irradiation of their degassed solution. To investigate the mechanism of such fluorescence enhancement, liquid chromatography/time-of-flight mass spectrometry measurements were performed for degassed methanol, ethanol, and acetonitrile solutions of 6H-benzo[cd]pyren-6-one (naphthanthrone), in which fluorescence enhancement had been induced. As a result, two kinds of photochemical products were identified as the substance causing fluorescence enhancement: they were produced by dehydrogenation and dehydration of adducts of a solvent molecule to naphthanthrone. On the basis of the findings, the mechanism of the fluorescence enhancement of naphthanthrone was discussed. Fluorescence enhancement; 6H-benzo[cd]pyren-6-one; Polycyclic aromatic ketones; Liquid chromatography-mass spectrometry; Photochemical reaction

  10. 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.

  11. 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.

  12. 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)

  13. Dynamic Behavior of Fault Slip Induced by Stress Waves

    Directory of Open Access Journals (Sweden)

    Guang-an Zhu

    2016-01-01

    Full Text Available Fault slip burst is a serious dynamic hazard in coal mining. A static and dynamic analysis for fault slip was performed to assess the risk of rock burst. A numerical model FLAC3D was established to understand the stress state and mechanical responses of fault rock system. The results obtained from the analysis show that the dynamic behavior of fault slip induced by stress waves is significantly affected by mining depth, as well as dynamic disturbance intensity and the distance between the stope and the fault. The isolation effect of the fault is also discussed based on the numerical results with the fault angle appearing to have the strongest influence on peak vertical stress and velocity induced by dynamic disturbance. By taking these risks into account, a stress-relief technology using break-tip blast was used for fault slip burst control. This technique is able to reduce the stress concentration and increase the attenuation of dynamic load by fracturing the structure of coal and rock. The adoption of this stress-relief method leads to an effective reduction of fault slip induced rock burst (FSIRB occurrence.

  14. 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.

  15. Vegetation dynamics induced by phreatophyte--aquifer interactions.

    Science.gov (United States)

    Ridolfi, Luca; D'Odorico, Paolo; Laio, Francesco

    2007-09-21

    The dynamics of phreatophyte vegetation are strongly coupled to those of the shallow phreatic aquifers from which phreatophytes extract water. Vegetation is able to influence the depth of the water table, which, in turn, can induce stress in vegetation. These interactions are likely to affect the composition and structure of phreatophyte plant communities, as well as their successional dynamics. Despite the environmental and economical value of many wetland plant ecosystems around the world, the impact of vegetation-water table interactions on ecosystem succession and interspecies competition in phreatophyte plant communities remains poorly understood. This study develops a minimalistic modelling framework to investigate the dynamics of two phreatophyte species, and their interactions with the water table. In spite of its simplicity, the model exhibits a remarkable variety of dynamical behaviors, especially when the water table depth is forced by external drivers. It is shown that, even when one of the two species is dominant with respect to the other, these two species can coexist showing periodic, quasi-periodic, and chaotic dynamics. Moreover, in the presence of a random environmental forcing, noise-induced coexistence may emerge.

  16. Synthesis of silver nanoprisms: A photochemical approach using light emission diodes

    International Nuclear Information System (INIS)

    Saade, Jamil; Araújo, Cid B. de

    2014-01-01

    We report a simplified photochemical methodology for fabrication of silver nanoprisms (Ag-NPs). The particles, synthesized in aqueous solution, were produced by illumination with narrow band and low cost Light Emission Diodes (LEDs) and exhibit Localized Surface Plasmon Resonances (LSPR) from the blue to the near-infrared. The new methodology consists of one pot synthesis that uses only three chemical reagents and allows good control of the sizes and the aspect ratios of triangular Ag-NPs. Reduction of silver ions by trisodium citrate (TSC), catalyzed on silver seeds, is exploited to synthesize and to control the growth of the Ag-NPs. The growth kinetics of the particles was characterized by monitoring the LSPR absorption band during several hours under continuous illumination. Optical absorption, transmission electron microscopy (TEM), electron diffraction and zeta potential measurements were performed to characterize the shape and size of the Ag-NPs and the colloid stability during its synthesis and aging. The TEM images and extinction spectra revealed Ag-NPs with good size dispersion and narrow LSPR bands with great potential for applications in nanotechnology. - Highlights: • Efficient method to synthesize Ag nanoprisms using only three chemical reagents. • Practicality: it removes the needs for some steps used in photochemical synthesis. • Zeta Potential measurements revealed the best conditions for colloids stability. • Non-coherent-radiation-induced dipoles cause aggregation of similar nanoprisms. • Data confirmed step-like-structures on the nanoprisms surface due to their aging

  17. 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.

  18. 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.

  19. Reversible-Deactivation Radical Polymerization of Methyl Methacrylate Induced by Photochemical Reduction of Various Copper Catalysts

    Directory of Open Access Journals (Sweden)

    Jaroslav Mosnáček

    2014-11-01

    Full Text Available Photochemically mediated reversible-deactivation radical polymerization of methyl methacrylate was successfully performed using 50–400 ppm of various copper compounds such as CuSO4·5H2O, copper acetate, copper triflate and copper acetylacetonate as catalysts. The copper catalysts were reduced in situ by irradiation at wavelengths of 366–546 nm, without using any additional reducing agent. Bromopropionitrile was used as an initiator. The effects of various solvents and the concentration and structure of ligands were investigated. Well-defined polymers were obtained when at least 100 or 200 ppm of any catalyst complexed with excess tris(2-pyridylmethylamine as a ligand was used in dimethyl sulfoxide as a solvent.

  20. Photochemical reaction products in air pollution

    Energy Technology Data Exchange (ETDEWEB)

    Stephens, E R; Darley, E F; Taylor, O C; Scott, W E

    1961-01-01

    Isolation and purification of peroxyacetyl nitrate (PAN) from artificial photochemical reaction of olefins and NO/sub x/ in air are analyzed. Olefin splits at the double bond, one end forming carbonyl compound and the other yielding PAN, among others. At concentrations below 1 ppM, PAN causes plant damage. At a concentration of about 1 ppM, PAN is a strong eye irritant.

  1. 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.

  2. New electrochemical and photochemical systems for water and wastewater treatment

    International Nuclear Information System (INIS)

    Sarria, Victor M; Parra, Sandra; Rincon, Angela G; Torres, Ricardo A; Pulgarin, Cesar

    2005-01-01

    With the increasing pressure on a more effective use of water resources, the development of appropriate water treatment technologies become more and more important. Photochemical and electrochemical oxidation processes have been proposed in recent years as an attractive alternative for the treatment of contaminated water containing anthropogenic substances hardly biodegradable as well as to purify and disinfect drinking waters. The aim of this paper is to present some of our last results demonstrating that electrochemical, photochemical, and the coupling of these processes with biological systems are very promising alternatives for the improvement of the water quality

  3. Carrier-lifetime-controlled selective etching process for semiconductors using photochemical etching

    International Nuclear Information System (INIS)

    Ashby, C.I.H.; Myers, D.R.

    1992-01-01

    This patent describes a process for selectively photochemically etching a semiconductor material. It comprises introducing at least one impurity into at least one selected region of a semiconductor material to be etched to increase a local impurity concentration in the at least one selected region relative to an impurity concentration in regions of the semiconductor material adjacent thereto, for reducing minority carrier lifetimes within the at least one selected region relative to the adjacent regions for thereby providing a photochemical etch-inhibiting mask at the at least one selected region; and etching the semiconductor material by subjecting the surface of the semiconductor material to a carrier-driven photochemical etching reaction for selectively etching the regions of the semiconductor material adjacent the at least one selected region having the increase impurity concentration; wherein the step of introducing at least one impurity is performed so as not to produce damage to the at least one selected region before any etching is performed

  4. Disulfonated tetraphenyl chlorin (TPCS2a)-induced photochemical internalisation of bleomycin in patients with solid malignancies: a phase 1, dose-escalation, first-in-man trial.

    Science.gov (United States)

    Sultan, Ahmed A; Jerjes, Waseem; Berg, Kristian; Høgset, Anders; Mosse, Charles A; Hamoudi, Rifat; Hamdoon, Zaid; Simeon, Celia; Carnell, Dawn; Forster, Martin; Hopper, Colin

    2016-09-01

    Photochemical internalisation, a novel minimally invasive treatment, has shown promising preclinical results in enhancing and site-directing the effect of anticancer drugs by illumination, which initiates localised chemotherapy release. We assessed the safety and tolerability of a newly developed photosensitiser, disulfonated tetraphenyl chlorin (TPCS2a), in mediating photochemical internalisation of bleomycin in patients with advanced and recurrent solid malignancies. In this phase 1, dose-escalation, first-in-man trial, we recruited patients (aged ≥18 to internalisation were either local, resulting from the local inflammatory process, or systemic, mostly as a result of the skin-photosensitising effect of TPCS2a. The most common grade 3 or worse adverse events were unexpected higher transient pain response (grade 3) localised to the treatment site recorded in nine patients, and respiratory failure (grade 4) noted in two patients. One dose-limiting toxicity was reported in the 1·0 mg/kg cohort (skin photosensitivity [grade 2]). Dose-limiting toxicities were reported in two of three patients at a TPCS2a dose of 1·5 mg/kg (skin photosensitivity [grade 3] and wound infection [grade 3]); thus, the maximum tolerated dose of TPCS2a was 1·0 mg/kg. Administration of TPCS2a was found to be safe and tolerable by all patients. No deaths related to photochemical internalisation treatment occurred. TPCS2a-mediated photochemical internalisation of bleomycin is safe and tolerable. We identified TPCS2a 0·25 mg/kg as the recommended treatment dose for future trials. PCI Biotech. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. 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.

  6. Repair processes for photochemical damage in mammalian cells

    International Nuclear Information System (INIS)

    Cleaver, J.E.

    1974-01-01

    Repair processes for photochemical damage in cells following uv irradiation are reviewed. Cultured fibroblast cells from human patients with xeroderma pigmentosum were used as an example to illustrate aspects of repair of injuries to DNA and proteins. (250 references) (U.S.)

  7. True Triaxial Experimental Study of Rockbursts Induced By Ramp and Cyclic Dynamic Disturbances

    Science.gov (United States)

    Su, Guoshao; Hu, Lihua; Feng, Xiating; Yan, Liubin; Zhang, Gangliang; Yan, Sizhou; Zhao, Bin; Yan, Zhaofu

    2018-04-01

    A modified rockburst testing system was utilized to reproduce rockbursts induced by ramp and cyclic dynamic disturbances with a low-intermediate strain rate of 2 × 10-3-5 × 10-3 s-1 in the laboratory. The experimental results show that both the ramp and cyclic dynamic disturbances play a significant role in inducing rockbursts. In the tests of rockbursts induced by a ramp dynamic disturbance, as the static stress before the dynamic disturbance increases, both the strength of specimens and the kinetic energy of the ejected fragments first increase and then decrease. In the tests of rockbursts induced by a cyclic dynamic disturbance, there exists a rockburst threshold of the static stress and the dynamic disturbance amplitude, and the kinetic energy of the ejected fragments first increases and then decreases as the cyclic dynamic disturbance frequency increases. The main differences between rockbursts induced by ramp dynamic disturbances and those induced by cyclic dynamic disturbances are as follows: the rockburst development process of the former is characterized by an impact failure feature, while that of the latter is characterized by a fatigue failure feature; the damage evolution curve of the specimen of the former has a leap-developing form with a significant catastrophic feature, while that of the latter has an inverted S-shape with a remarkable fatigue damage characteristic; the energy mechanism of the former involves the ramp dynamic disturbance giving extra elastic strain energy to rocks, while that of the latter involves the cyclic dynamic disturbance decreasing the ultimate energy storage capacity of rocks.

  8. Photochemical oxidant transport - Mesoscale lake breeze and synoptic-scale aspects

    Science.gov (United States)

    Lyons, W. A.; Cole, H. S.

    1976-01-01

    Data from routine ozone monitoring in southeastern Wisconsin and limited monitoring of the Milwaukee area by the Environmental Protection Agency are examined. Hourly averages as high as 30 pphm have been recorded in southeastern Wisconsin, and high readings have been reported in rural regions throughout the state. The observations indicate that photochemical oxidants and their nitrogen oxide and reactive hydrocarbon precursers advect from Chicago and northern Indiana into southeastern Wisconsin. There is evidence that synoptic-scale transport of photochemical oxidants occurs, allowing the pollution of entire anticyclones. These results cast doubt on the validity of the Air Quality Control Regions established by amendment to the Clean Air Act of 1970.

  9. Temporal Changes in Photochemically Labile DOM and Implications for Carbon Budgets in Peatland Aquatic Systems

    Science.gov (United States)

    Pickard, A.

    2015-12-01

    Aquatic systems in peatland catchments are subject to high loading of dissolved organic matter (DOM) from surrounding terrestrial environments. However the significance of photochemical transformation of DOM in peatland carbon budgets remains poorly constrained. In this study UV irradiation experiments were conducted on water samples collected over one year from two contrasting systems in Scotland: a stream draining a peatland with high levels of DOM and a reservoir draining a peat catchment with low levels of DOM. Further samples were collected from the high DOM system during two storm events. After experimental exposure, optical and chemical analyses were employed to determine photochemical lability of the DOM pool. At both sites irradiation-induced decreases in dissolved organic carbon (DOC) as a percentage of the total carbon pool were greatest in winter, suggesting that DOM was depleted in photo-reactive molecules in summer. Seasonal variability in DOC was high at the stream site and was positively correlated with CO₂ and CO photoproduction (r2 = 0.81 and 0.83, respectively; pLignin phenol analyses indicate considerable contribution of peat to the DOM pool at the stream site, particularly during summer. Whilst DOC concentrations did not vary greatly during storm events, UV-Vis absorbance indicators did, signifying changing DOM source material from activation of different hydrological pathways. The most photo-reactive DOM occurred 5-10 hours after peak discharge, suggesting that storms replenish photochemically labile DOM in headwater streams. Conservative estimates using data from this study suggest that up to 7% of the DOM pool of peatland streams can be lost (primarily as CO₂ and CO) upon exposure to 8 hours of environmentally representative UV irradiation. Further investigation in field campaigns under natural UV exposure are underway to assess the importance of photodegradation of DOM as a loss pathway of carbon based gases from aquatic systems.

  10. Hydrogen bond dynamics governs the effective photoprotection mechanism of plant phenolic sunscreens.

    Science.gov (United States)

    Liu, Fang; Du, Likai; Lan, Zhenggang; Gao, Jun

    2017-02-15

    Sinapic acid derivatives are important sunscreen species in natural plants, which could provide protection from solar UV radiation. Using a combination of ultrafast excited state dynamics, together with classical molecular dynamics studies, we demonstrate that there is direct coupling of hydrogen bond motion with excited state photoprotection dynamics as part of the basic mechanism in solution. Beyond the intra-molecular degree of freedom, the inter-molecular motions on all timescales are potentially important for the photochemical or photophysical events, ranging from the ultrafast hydrogen bond motion to solvent rearrangements. This provides not only an enhanced understanding of the anomalous experimental spectroscopic results, but also the key idea in the development of sunscreen agents with improved photo-chemical properties. We suggest that the hydrogen bond dynamics coupled excited state photoprotection mechanism may also be possible in a broad range of bio-related molecules in the condensed phase.

  11. Trapping Dynamics in Photosystem I-Light Harvesting Complex I of Higher Plants Is Governed by the Competition Between Excited State Diffusion from Low Energy States and Photochemical Charge Separation.

    Science.gov (United States)

    Molotokaite, Egle; Remelli, William; Casazza, Anna Paola; Zucchelli, Giuseppe; Polli, Dario; Cerullo, Giulio; Santabarbara, Stefano

    2017-10-26

    The dynamics of excited state equilibration and primary photochemical trapping have been investigated in the photosystem I-light harvesting complex I isolated from spinach, by the complementary time-resolved fluorescence and transient absorption approaches. The combined analysis of the experimental data indicates that the excited state decay is described by lifetimes in the ranges of 12-16 ps, 32-36 ps, and 64-77 ps, for both detection methods, whereas faster components, having lifetimes of 550-780 fs and 4.2-5.2 ps, are resolved only by transient absorption. A unified model capable of describing both the fluorescence and the absorption dynamics has been developed. From this model it appears that the majority of excited state equilibration between the bulk of the antenna pigments and the reaction center occurs in less than 2 ps, that the primary charge separated state is populated in ∼4 ps, and that the charge stabilization by electron transfer is completed in ∼70 ps. Energy equilibration dynamics associated with the long wavelength absorbing/emitting forms harbored by the PSI external antenna are also characterized by a time mean lifetime of ∼75 ps, thus overlapping with radical pair charge stabilization reactions. Even in the presence of a kinetic bottleneck for energy equilibration, the excited state dynamics are shown to be principally trap-limited. However, direct excitation of the low energy chlorophyll forms is predicted to lengthen significantly (∼2-folds) the average trapping time.

  12. Photochemical Creation of Fluorescent Quantum Defects in Semiconducting Carbon Nanotube Hosts.

    Science.gov (United States)

    Wu, Xiaojian; Kim, Mijin; Kwon, Hyejin; Wang, YuHuang

    2018-01-15

    Quantum defects are an emerging class of synthetic single-photon emitters that hold vast potential for near-infrared imaging, chemical sensing, materials engineering, and quantum information processing. Herein, we show that it is possible to optically direct the synthetic creation of molecularly tunable fluorescent quantum defects in semiconducting single-walled carbon nanotube hosts through photochemical reactions. By exciting the host semiconductor with light that resonates with its electronic transition, we find that halide-containing aryl groups can covalently bond to the sp 2 carbon lattice. The introduced quantum defects generate bright photoluminescence that allows tracking of the reaction progress in situ. We show that the reaction is independent of temperature but correlates strongly with the photon energy used to drive the reaction, suggesting a photochemical mechanism rather than photothermal effects. This type of photochemical reactions opens the possibility to control the synthesis of fluorescent quantum defects using light and may enable lithographic patterning of quantum emitters with electronic and molecular precision. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Sun-induced chlorophyll fluorescence and photochemical reflectance index improve remote-sensing gross primary production estimates under varying nutrient availability in a typical Mediterranean savanna ecosystem

    Science.gov (United States)

    Perez-Priego, O.; Guan, J.; Rossini, M.; Fava, F.; Wutzler, T.; Moreno, G.; Carvalhais, N.; Carrara, A.; Kolle, O.; Julitta, T.; Schrumpf, M.; Reichstein, M.; Migliavacca, M.

    2015-11-01

    This study investigates the performances of different optical indices to estimate gross primary production (GPP) of herbaceous stratum in a Mediterranean savanna with different nitrogen (N) and phosphorous (P) availability. Sun-induced chlorophyll fluorescence yield computed at 760 nm (Fy760), scaled photochemical reflectance index (sPRI), MERIS terrestrial-chlorophyll index (MTCI) and normalized difference vegetation index (NDVI) were computed from near-surface field spectroscopy measurements collected using high spectral resolution spectrometers covering the visible near-infrared regions. GPP was measured using canopy chambers on the same locations sampled by the spectrometers. We tested whether light-use efficiency (LUE) models driven by remote-sensing quantities (RSMs) can better track changes in GPP caused by nutrient supplies compared to those driven exclusively by meteorological data (MM). Particularly, we compared the performances of different RSM formulations - relying on the use of Fy760 or sPRI as a proxy for LUE and NDVI or MTCI as a fraction of absorbed photosynthetically active radiation (fAPAR) - with those of classical MM. Results showed higher GPP in the N-fertilized experimental plots during the growing period. These differences in GPP disappeared in the drying period when senescence effects masked out potential differences due to plant N content. Consequently, although MTCI was closely related to the mean of plant N content across treatments (r2 = 0.86, p < 0.01), it was poorly related to GPP (r2 = 0.45, p < 0.05). On the contrary sPRI and Fy760 correlated well with GPP during the whole measurement period. Results revealed that the relationship between GPP and Fy760 is not unique across treatments, but it is affected by N availability. Results from a cross-validation analysis showed that MM (AICcv = 127, MEcv = 0.879) outperformed RSM (AICcv =140, MEcv = 0.8737) when soil moisture was used to constrain the seasonal dynamic of LUE. However

  14. 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

  15. Molecular beam studies of reaction dynamics

    International Nuclear Information System (INIS)

    Lee, Yuan T.

    1991-03-01

    The major thrust of this research project is to elucidate detailed dynamics of simple elementary reactions that are theoretically important and to unravel the mechanism of complex chemical reactions or photochemical processes that play important roles in many macroscopic processes. Molecular beams of reactants are used to study individual reactive encounters between molecules or to monitor photodissociation events in a collision-free environment. Most of the information is derived from measurement of the product fragment energy, angular, and state distributions. Recent activities are centered on the mechanisms of elementary chemical reactions involving oxygen atoms with unsaturated hydrocarbons, the dynamics of endothermic substitution reactions, the dependence of the chemical reactivity of electronically excited atoms on the alignment of excited orbitals, the primary photochemical processes of polyatomic molecules, intramolecular energy transfer of chemically activated and locally excited molecules, the energetics of free radicals that are important to combustion processes, the infrared-absorption spectra of carbonium ions and hydrated hydronium ions, and bond-selective photodissociation through electric excitation

  16. Molecular beam studies of reaction dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Y.T. [Lawrence Berkeley Laboratory, CA (United States)

    1993-12-01

    The major thrust of this research project is to elucidate detailed dynamics of simple elementary reactions that are theoretically important and to unravel the mechanism of complex chemical reactions or photochemical processes that play important roles in many macroscopic processes. Molecular beams of reactants are used to study individual reactive encounters between molecules or to monitor photodissociation events in a collision-free environment. Most of the information is derived from measurement of the product fragment energy, angular, and state distributions. Recent activities are centered on the mechanisms of elementary chemical reactions involving oxygen atoms with unsaturated hydrocarbons, the dynamics of endothermic substitution reactions, the dependence of the chemical reactivity of electronically excited atoms on the alignment of excited orbitals, the primary photochemical processes of polyatomic molecules, intramolecular energy transfer of chemically activated and locally excited molecules, the energetics of free radicals that are important to combustion processes, the infrared-absorption spectra of carbonium ions and hydrated hydronium ions, and bond-selective photodissociation through electric excitation.

  17. Preparation of UO{sub 2}, ThO{sub 2} and (Th,U)O{sub 2} pellets from photochemically-prepared nano-powders

    Energy Technology Data Exchange (ETDEWEB)

    Pavelková, Tereza [Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Břehová 7, 115 19 Praha 1 (Czech Republic); Čuba, Václav, E-mail: vaclav.cuba@fjfi.cvut.cz [Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Břehová 7, 115 19 Praha 1 (Czech Republic); Visser-Týnová, Eva de [Nuclear Research and Consultancy Group (NRG), Research & Innovation, Westerduinweg 3, 1755 LE Petten (Netherlands); Ekberg, Christian [Nuclear Chemistry/Industrial Materials Recycling, Chalmers University of Technology, SE-412 96 Göteborg (Sweden); Persson, Ingmar [Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences, P.O. Box 7015, SE-750 07 Uppsala (Sweden)

    2016-02-15

    Photochemically-induced preparation of nano-powders of crystalline uranium and/or thorium oxides and their subsequent pelletizing has been investigated. The preparative method was based on the photochemically induced formation of amorphous solid precursors in aqueous solution containing uranyl and/or thorium nitrate and ammonium formate. The EXAFS analyses of the precursors shown that photon irradiation of thorium containing solutions yields a compound with little long-range order but likely “ThO{sub 2} like” and the irradiation of uranium containing solutions yields the mixture of U(IV) and U(VI) compounds. The U-containing precursors were carbon free, thus allowing direct heat treatment in reducing atmosphere without pre-treatment in the air. Subsequent heat treatment of amorphous solid precursors at 300–550 °C yielded nano-crystalline UO{sub 2}, ThO{sub 2} or solid (Th,U)O{sub 2} solutions with high purity, well-developed crystals with linear crystallite size <15 nm. The prepared nano-powders of crystalline oxides were pelletized without any binder (pressure 500 MPa), the green pellets were subsequently sintered at 1300 °C under an Ar:H{sub 2} (20:1) mixture (UO{sub 2} and (Th,U)O{sub 2} pellets) or at 1600 °C in ambient air (ThO{sub 2} pellets). The theoretical density of the sintered pellets varied from 91 to 97%. - Highlights: • Photochemically prepared UO{sub 2}/ThO{sub 2} nano-powders were pelletized. • The nano-powders of crystalline oxides were pelletized without any binder. • Pellets were sintered at 1300 °C (UO{sub 2} and (Th,U)O{sub 2}) or 1600 °C (ThO{sub 2} pellets). • The theoretical density of the sintered pellets varies from 91 to 97%.

  18. Photochemical internalisation of a macromolecular protein toxin using a cell penetrating peptide-photosensitiser conjugate.

    Science.gov (United States)

    Wang, Julie T-W; Giuntini, Francesca; Eggleston, Ian M; Bown, Stephen G; MacRobert, Alexander J

    2012-01-30

    Photochemical internalisation (PCI) is a site-specific technique for improving cellular delivery of macromolecular drugs. In this study, a cell penetrating peptide, containing the core HIV-1 Tat 48-57 sequence, conjugated with a porphyrin photosensitiser has been shown to be effective for PCI. Herein we report an investigation of the photophysical and photobiological properties of a water soluble bioconjugate of the cationic Tat peptide with a hydrophobic tetraphenylporphyrin derivative. The cellular uptake and localisation of the amphiphilic bioconjugate was examined in the HN5 human head and neck squamous cell carcinoma cell line. Efficient cellular uptake and localisation in endo/lysosomal vesicles was found using fluorescence detection, and light-induced, rupture of the vesicles resulting in a more diffuse intracellular fluorescence distribution was observed. Conjugation of the Tat sequence with a hydrophobic porphyrin thus enables cellular delivery of an amphiphilic photosensitiser which can then localise in endo/lysosomal membranes, as required for effective PCI treatment. PCI efficacy was tested in combination with a protein toxin, saporin, and a significant reduction in cell viability was measured versus saporin or photosensitiser treatment alone. This study demonstrates that the cell penetrating peptide-photosensitiser bioconjugation strategy is a promising and versatile approach for enhancing the therapeutic potential of bioactive agents through photochemical internalisation. Copyright © 2011 Elsevier B.V. All rights reserved.

  19. 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.

  20. The chitosan - Porphyrazine hybrid materials and their photochemical properties.

    Science.gov (United States)

    Chełminiak-Dudkiewicz, Dorota; Ziegler-Borowska, Marta; Stolarska, Magdalena; Sobotta, Lukasz; Falkowski, Michal; Mielcarek, Jadwiga; Goslinski, Tomasz; Kowalonek, Jolanta; Węgrzynowska-Drzymalska, Katarzyna; Kaczmarek, Halina

    2018-04-01

    Three magnesium sulfanyl porphyrazines differing in the size of peripheral substituents (3,5-dimethoxybenzylsulfanyl, (3,5-dimethoxybenzyloxy)benzylsulfanyl, 3,5-bis[(3,5-bis[(3,5-dimethoxybenzyloxy)benzyloxy]benzylsulfanyl) were exposed to visible and ultraviolet radiation (UV A + B + C) in order to determine their photochemical properties. The course of photochemical reactions in dimethylformamide solutions and the ability of the systems to generate singlet oxygen were studied by UV-Vis spectroscopy, which additionally gave information on aggregation processes. The porphyrazines were found to be stable upon visible light irradiation conditions, but when exposed to high energy UV radiation, the efficient photodegradation of these macrocycles was observed. Therefore, these three magnesium sulfanyl porphyrazines were incorporated into chitosan matrix. The obtained thin films of chitosan doped with porphyrazines were subjected to polychromatic UV-radiation and studied by spectroscopic methods (UV-Vis, FTIR), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Application of chitosan as a polymer matrix for porphyrazines was found to be successful method that effectively stopped the unwelcome degradation of macrocycles, thus worth considering for their photoprotection. In addition, the surface properties of the hybrid material were determined by contact angle measurements and calculation of surface free energy. Intermolecular interactions between these novel porphyrazines and chitosan were detected. The mechanism of photochemical reactions occurring in studied systems has been discussed. Copyright © 2018 Elsevier B.V. All rights reserved.

  1. Enhanced Indirect Photochemical Transformation of Histidine and Histamine through Association with Chromophoric Dissolved Organic Matter.

    Science.gov (United States)

    Chu, Chiheng; Lundeen, Rachel A; Remucal, Christina K; Sander, Michael; McNeill, Kristopher

    2015-05-05

    Photochemical transformations greatly affect the stability and fate of amino acids (AAs) in sunlit aquatic ecosystems. Whereas the direct phototransformation of dissolved AAs is well investigated, their indirect photolysis in the presence of chromophoric dissolved organic matter (CDOM) is poorly understood. In aquatic systems, CDOM may act both as sorbent for AAs and as photosensitizer, creating microenvironments with high concentrations of photochemically produced reactive intermediates, such as singlet oxygen (1O2). This study provides a systematic investigation of the indirect photochemical transformation of histidine (His) and histamine by 1O2 in solutions containing CDOM as a function of solution pH. Both His and histamine showed pH-dependent enhanced phototransformation in the CDOM systems as compared to systems in which model, low-molecular-weight 1O2 sensitizers were used. Enhanced reactivity resulted from sorption of His and histamine to CDOM and thus exposure to elevated 1O2 concentrations in the CDOM microenvironment. The extent of reactivity enhancement depended on solution pH via its effects on the protonation state of His, histamine, and CDOM. Sorption-enhanced reactivity was independently supported by depressed rate enhancements in the presence of a cosorbate that competitively displaced His and histamine from CDOM. Incorporating sorption and photochemical transformation processes into a reaction rate prediction model improved the description of the abiotic photochemical transformation rates of His in the presence of CDOM.

  2. Curcumin prevents cisplatin-induced renal alterations in mitochondrial bioenergetics and dynamic.

    Science.gov (United States)

    Ortega-Domínguez, Bibiana; Aparicio-Trejo, Omar Emiliano; García-Arroyo, Fernando E; León-Contreras, Juan Carlos; Tapia, Edilia; Molina-Jijón, Eduardo; Hernández-Pando, Rogelio; Sánchez-Lozada, Laura Gabriela; Barrera-Oviedo, Diana; Pedraza-Chaverri, José

    2017-09-01

    Cisplatin is widely used as chemotherapeutic agent for treatment of diverse types of cancer, however, acute kidney injury (AKI) is an important side effect of this treatment. Diverse mechanisms have been involved in cisplatin-induced AKI, such as oxidative stress, apoptosis and mitochondrial damage. On the other hand, curcumin is a polyphenol extracted from the rhizome of Curcuma longa L. Previous studies have shown that curcumin protects against the cisplatin-induced AKI; however, it is unknown whether curcumin can reduce alterations in mitochondrial bioenergetics and dynamic in this model. It was found that curcumin prevents cisplatin-induced: (a) AKI and (b) alterations in the following mitochondrial parameters: bioenergetics, ultrastructure, hydrogen peroxide production and dynamic. In fact, curcumin prevented the increase of mitochondrial fission 1 protein (FIS1), the decrease of optic atrophy 1 protein (OPA1) and the decrease of NAD + -dependent deacetylase sirtuin-3 (SIRT3), a mitochondrial dynamic regulator as well as the increase in the mitophagy associated proteins parkin and phosphatase and tensin homologue (PTEN)-induced putative kinase protein 1 (PINK1). In conclusion, the protective effect of curcumin in cisplatin-induced AKI was associated with the prevention of the alterations in mitochondrial bioenergetics, ultrastructure, redox balance, dynamic, and SIRT3 levels. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Nuclear dynamics in heavy ion induced fusion-fission reactions

    International Nuclear Information System (INIS)

    Kapoor, S.S.

    1992-01-01

    Heavy ion induced fission and fission-like reactions evolve through a complex nuclear dynamics encountered in the medium energy nucleus-nucleus collisions. In the recent years, measurements of the fragment-neutron and fragment-charged particle angular correlations in heavy ion induced fusion-fission reactions, have provided new information on the dynamical times of nuclear deformations of the initial dinuclear complex to the fission saddle point and the scission point. From the studies of fragment angular distributions in heavy ion induced fission it has been possible to infer the relaxation times of the dinuclear complex in the K-degree of freedom and our recent measurements on the entrance channel dependence of fragment anisotropies have provided an experimental signature of the presence of fissions before K-equilibration. This paper reviews recent experimental and theoretical status of the above studies with particular regard to the questions relating to dynamical times, nuclear dissipation and the effect of nuclear dissipation on the K-distributions at the fission saddle in completely equilibrated compound nucleus. (author). 19 refs., 9 figs

  4. Photochemically-induced ischemia of the rat sciatic nerve produces a dose-dependent and highly reproducible mechanical, heat and cold allodynia, and signs of spontaneous pain.

    Science.gov (United States)

    Kupers, R; Yu, W; Persson, J K; Xu, X J; Wiesenfeld-Hallin, Z

    1998-05-01

    Sensory abnormalities and changes in spontaneous behavior were examined after a photochemically induced ischemic lesion of the rat sciatic nerve. Male adult rats were anesthetized and the sciatic nerve was exposed. After the intravenous injection of a photosensitizing dye, erythrosin B, the exposed nerve was irradiated just proximal to the nerve trifurcation with light from an argon laser. Three different irradiation times were used, 30 s, 1 and 2 min. In sham-operated rats, the exposed sciatic nerve was irradiated for 2 min without prior injection of the erythrosin B. Rats were tested for the presence of mechanical, cold and heat allodynia or hyperalgesia. All the animals in the 1- and 2-min irradiation groups developed mechanical, cold and heat allodynia after nerve irradiation. A significant dose-dependent effect of laser exposure time was observed for all modalities tested (2 min > 1 min > 30 s = sham). The maximum effects were observed at 3 and 7 days postirradiation and remained present for up to 10 weeks. No significant contralateral effects were observed in any of the groups. In three separate groups of rats (1, 2 and 4 min of laser exposure), the presence of possible signs of spontaneous pain (paw shaking, paw elevation and freezing behavior) was tested. A significant and exposure time-dependent increase in spontaneous paw elevation and paw shaking was observed which was maximal at week 1, but resolved at 4 weeks (4 min > 2 min > 1 min > sham). In addition, animals in all ischemic groups, but not in the sham group, showed a significant increase in freezing behavior up to 4 weeks after nerve irradiation. Light microscopic evaluation of nerves removed 7 days post-irradiation, i.e. when maximal allodynia was observed, showed clear evidence of demyelination of large myelinated fibers. These data indicate that photochemically-induced peripheral nerve ischemia is associated with abnormal pain-related behaviors, including mechanical, thermal and cold allodynia

  5. Photochemical pollution indicators; Les indicateurs de la pollution photochimique. La mesure des composes azotes

    Energy Technology Data Exchange (ETDEWEB)

    Perros, P E; Marion, T [Paris-7 Univ., 75 (France). Laboratoire Interuniversitaire des Systemes Atmospheriques

    1998-11-01

    The number of photochemical pollution is generally based on the observation of ozone and nitrogen oxides concentration levels. So, the measurement of photochemical pollution indicators becomes essential to better understand the involved phenomena, and at the end to enable its reduction control and strategy. In this paper, we focus on the measurements of nitrogen compounds (NO{sub x} PAN, HNO{sub 3}). (authors) 24 refs.

  6. Formation dynamics of UV and EUV induced hydrogen plasma

    NARCIS (Netherlands)

    Dolgov, A.A.; Lee, Christopher James; Yakushev, O.; Lopaev, D.V.; Abrikosov, A.; Krivtsun, V.M.; Zotovich, A.; Bijkerk, F.

    2014-01-01

    The comparative study of the dynamics of ultraviolet (UV) and extreme ultraviolet (EUV) induced hydrogen plasma was performed. It was shown that for low H2 pressures and bias voltages, the dynamics of the two plasmas are significantly different. In the case of UV radiation, the plasma above the

  7. Photochemical degradation of alachlor in water

    Directory of Open Access Journals (Sweden)

    Tajana Đurkić

    2017-01-01

    Full Text Available This study investigates the photochemical degradation of alachlor, a chloroacetanilide herbicide. All experiments were conducted in ultra-pure deionized water (ASTM Type I quality using direct ultraviolet (UV photolysis and the UV/H2O2 advanced oxidation process. The direct UV photolysis and UV/H2O2 experiments were conducted in a commercial photochemical reactor with a quartz reaction vessel equipped with a 253.7 nm UV low pressure mercury lamp (Philips TUV 16 W. The experimental results demonstrate that UV photolysis was very effective for alachlor degradation (up to 97% removal using a high UV fluence of 4200 mJ/cm2. The UV/H2O2 process promoted alachlor degradation compared to UV photolysis alone, with a high degree of decomposition (97% achieved at a significantly lower UV fluence of 600 mJ/cm2 when combined with 1 mg H2O2/L. The application of UV photolysis alone with a UV fluence of 600 mJ/cm2 gave a negligible 4% alachlor degradation. The photo degradation of alachlor, in both direct UV photolysis and the UV/H2O2 process, followed pseudo first-order kinetics. The degradation rate constant was about 6 times higher for the UV/H2O2 process than for UV photolysis alone.

  8. Photochemically Synthesized Polyimides

    Science.gov (United States)

    Meador, Michael A.; Tyson, Daniel S.

    2008-01-01

    An alternative to the conventional approach to synthesis of polyimides involves the use of single monomers that are amenable to photopolymerization. Heretofore, the synthesis of polyimides has involved multiple-monomer formulations and heating to temperatures that often exceed 250 C. The present alternative approach enables synthesis under relatively mild conditions that can include room temperature. The main disadvantages of the conventional approach are the following: Elevated production temperatures can lead to high production costs and can impart thermal stresses to the final products. If the proportions of the multiple monomeric ingredients in a given batch are not exactly correct, the molecular weight and other physical properties of the final material could be reduced from their optimum or desired values. To be useful in the alternative approach, a monomer must have a molecular structure tailored to exploit Diels-Alder trapping of a photochemically generated ortho-quinodimethane. (In a Diels-Alder reaction, a diene combines with a dienophile to form molecules that contain six-membered rings.) In particular, a suitable monomer (see figure) contains ortho-methylbenzophenone connected to a dienophile (in this case, a maleimide) through a generic spacer group. Irradiation with ultraviolet light gives rise to a photochemical intermediate the aforementioned ortho-quinodimethane from the ortho-methylbenzophenone. This group may react with the dienophile on another such monomer molecule to produce an oligomer that, in turn may react in a stepgrowth manner to produce a polyimide. This approach offers several advantages in addition to those mentioned above: The monomer can be stored for a long time because it remains unreactive until exposed to light. Because the monomer is the only active starting ingredient, there is no need for mixing, no concern for ensuring correct proportions of monomers, and the purity of the final product material is inherently high. The use

  9. Photochemical exchange reactions of thymine, uracil and their nucleosides with selected amino acids

    International Nuclear Information System (INIS)

    Shetlar, M.D.; Taylor, J.A.; Hom, K.

    1984-01-01

    The photoinduced exchange reactions of thymine with lysine at basic pH, using 254 nm light, have been studied. Three products have been isolated, namely, 6-amino-2-(1-thyminyl)hexanoic acid (Ia), 2-amino-6-(1-thyminyl)hexanoic acid (IIa) and 1-amino-5-(1-thyminyl)pentane (IIIa). Compound IIIa was shown to be a secondary product, produced by photochemical decarboxylation of Ia. Photochemical reaction of thymine with glycine and alanine at basic pH led, respectively, to formation of 2-(1-thyminyl)acetic acid (Ic) and 2-(1-thyminyl)propionic acid (Id). Compounds Ic and Id underwent photolysis to produce the decarboxylated secondary products 1-methylthymine and 1-ethylthymine, respectively. Thymidine reacts photochemically with glycine and alanine to produce the same products. Irradiation of DNA in the presence of lysine at basic pH led to the formation of the same products formed in the thymine-lysine system, namely Ia, IIa and IIIa. Uracil was found to undergo analogous photochemical exchange reactions with lysine to form 6-amino-2-(1-uracilyl)hexanoic acid (Ib), and 2-amino-6-(1-uracilyl)hexanoic acid (IIb). Compound Ib was found to undergo photodecarboxylation to form 1-amino-5-(1-uracilyl)pentane (IIIb), analogous to the secondary photoreaction of Ia. Photoreaction of uracil with 1,5-diaminopentane (cadaverine) likewise led to formation of IIIb. (author)

  10. Theoretical study of ultraviolet induced photodissociation dynamics of sulfuric acid

    Energy Technology Data Exchange (ETDEWEB)

    Murakami, Tatsuhiro; Ohta, Ayumi; Suzuki, Tomoya; Ikeda, Kumiko [Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioi-Cho, Chiyoda-ku, Tokyo 102-8554 (Japan); Danielache, Sebastian O. [Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioi-Cho, Chiyoda-ku, Tokyo 102-8554 (Japan); Earth-Life Science Institute (ELSI), Tokyo Institute of Technology (Japan); Department of Environmental Science and Techonology, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Yoohama 226-8502 (Japan); Nanbu, Shinkoh, E-mail: shinkoh.nanbu@sophia.ac.jp [Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioi-Cho, Chiyoda-ku, Tokyo 102-8554 (Japan)

    2015-05-01

    Highlights: • Photodissociation dynamics of H{sub 2}SO{sub 4} at low-lying electronically excited states were investigated. • Photochemical processes were simulated by on-the-fly ab initio MD. • Sulfuric acid after the excitation to the S{sub 1} state dissociated to HSO{sub 4}(1{sup 2}A″) + H({sup 2}S). • Sulfuric acid after the excitation to the S{sub 2} state dissociated to HSO{sub 4}(2{sup 2}A″) + H({sup 2}S). • The energy region of the UV spectra where NMD fractionation may occur is predicted. - Abstract: Photodissociation dynamics of sulfuric acid after excitation to the first and second excited states (S{sub 1} and S{sub 2}) were studied by an on-the-fly ab initio molecular dynamics simulations based on the Zhu–Nakamura version of the trajectory surface hopping (ZN-TSH). Forces acting on the nuclear motion were computed on-the-fly by CASSCF method with Dunning’s augmented cc-pVDZ basis set. It was newly found that the parent molecule dissociated into two reaction-channels (i) HSO{sub 4}(1{sup 2}A″) + H({sup 2}S) by S{sub 1}-excitation, and (ii) HSO{sub 4}(2{sup 2}A″) + H({sup 2}S) by S{sub 2}-excitation. The direct dissociation dynamics yield products different from the SO{sub 2} + 2OH fragments often presented in the literature. Both channels result in the same product and differs only in the electronic state of the HSO{sub 4} fragment{sub .} The trajectories running on S{sub 2} do not hop with S{sub 0} and a nonadiabatic transition happens at the S{sub 2}–S{sub 1} conical intersection located at a longer OH bond-length than the S{sub 1}–S{sub 0} intersection producing an electronic excited state (2{sup 2}A″) of HSO{sub 4} product.

  11. Photochemical production of ozone and control strategy for Southern Taiwan

    Science.gov (United States)

    Shiu, Chein-Jung; Liu, Shaw Chen; Chang, Chih-Chung; Chen, Jen-Ping; Chou, Charles C. K.; Lin, Chuan-Yao; Young, Chea-Yuan

    An observation-based method (OBM) is developed to evaluate the ozone (O 3) production efficiency (O 3 molecules produced per NO x molecule consumed) and O 3 production rate ( P(O 3)) during a field campaign in southern Taiwan. The method can also provide an estimate of the concentration of OH. A key step in the method is to use observed concentrations of two aromatic hydrocarbons, namely ethylbenzene and m, p-xylene, to estimate the degree of photochemical processing and amounts of photochemically consumed NO x and NMHCs by OH. In addition, total oxidant (O 3+NO 2) instead of O 3 itself turns out to be very useful for representing ozone production in the OBM approach. The average O 3 production efficiency during the field campaign in Fall (2003) is found to be about 10.2±3.9. The relationship of P(O 3) with NO x is examined and compared with a one-dimensional (1D) photochemical model. Values of P(O 3) derived from the OBM are slightly lower than those calculated in the 1D model. However, OH concentrations estimated by the OBM are about a factor of 2 lower than the 1D model. Fresh emissions, which affect the degree of photochemical processing appear to be a major cause of the underestimate. We have developed a three-dimensional (3D) OBM O 3 production diagram that resembles the EKMA ozone isopleth diagram to study the relationship of the total oxidant versus O 3 precursors. The 3D OBM O 3 production diagram suggests that reducing emissions of NMHCs are more effective in controlling O 3 than reducing NO x. However, significant uncertainties remain in the OBM, and considerable more work is required to minimize these uncertainties before a definitive control strategy can be reached. The observation-based approach provides a good alternative to measuring peroxy radicals for evaluating the production of O 3 and formulating O 3 control strategy in urban and suburban environments.

  12. Changes in optical characteristics of surface microlayers in the Peruvian upwelling region hint to photochemically and microbially-mediated DOM turnover

    Science.gov (United States)

    Engel, A.; Galgani, L.

    2016-02-01

    The coastal upwelling system off Peru is characterized by high biological activity and associated subsurface oxygen minimum zone, leading to an enhanced emission of atmospheric trace gases. High biological productivity in the water column may promote the establishment of enriched organic surface films, key environments for processes regulating gas fluxes across the water-air interface. During M91 cruise to the Peruvian upwelling, we focused our attention on the composition of the sea-surface microlayer (SML), the oceanic uppermost boundary directly subject to high solar radiation, often enriched in specific organic compounds of biological origin like Chromophoric Dissolved Organic Matter (CDOM) and marine gels. In the SML, the continuous photochemical and microbial recycling of organic matter may strongly influence gas exchange between marine systems and the atmosphere. In order to understand organic matter cycling in surface films, we analyzed SML and underlying water samples in 38 stations determining DOC concentrations, amino acids composition, marine gels, CDOM and bacterial abundance as indicators of photochemical and microbial alteration processes. CDOM composition was characterized by spectral slopes (S) values and Excitation-Emission Matrix fluorescence (EEMs), which allow to track changes in molecular weight (MW) of DOM, and to determine potential DOM sources. Profound changes in spectral slope properties were observed suggesting smaller MW CDOM in the SML compared to underlying water. Microbial and photochemical degradation are likely the main drivers for organic matter cycling in the top layer of the ocean. Consequences on the formation of inorganic and organic species highly relevant for air-sea gas exchange and for climate dynamics will be discussed.

  13. 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

  14. Ammonia removal from leachate by photochemical process using H2O2

    Directory of Open Access Journals (Sweden)

    Giovani Archanjo Brota

    2010-08-01

    Full Text Available In this work, it was studied the optimization of the photochemical process using H2O2/UV in order to reduce the concentration of ammonia in leachate. It was used landfills leachate previously treated in the development of studies. A photochemical reactor with the capacity of 1.7 liters equipped with refrigeration system and recirculation of leachate was employed in the research. The influence of temperature, the light bulb power, the concentration of H2O2 and treatment time were tested during the study. A removal of 97% of ammonia was observed at 90 min.

  15. Photochemical Aryl Radical Cyclizations to Give (E-3-Ylideneoxindoles

    Directory of Open Access Journals (Sweden)

    Michael Gurry

    2014-09-01

    Full Text Available (E-3-Ylideneoxindoles are prepared in methanol in reasonable to good yields, as adducts of photochemical 5-exo-trig of aryl radicals, in contrast to previously reported analogous radical cyclizations initiated by tris(trimethylsilylsilane and azo-initiators that gave reduced oxindole adducts.

  16. Implications of imprecision in kinetic rate data for photochemical model calculations

    Energy Technology Data Exchange (ETDEWEB)

    Stewart, R.W.; Thompson, A.M. [National Aeronautics and Space Administration, Greenbelt, MD (United States). Goddard Space Flight Center

    1997-12-31

    Evaluation of uncertainties in photochemical model calculations is of great importance to scientists performing assessment modeling. A major source of uncertainty is the measurement imprecision inherent in photochemical reaction rate data that modelers rely on. A rigorous method of evaluating the impact of data imprecision on computational uncertainty is the study of error propagation using Monte Carlo techniques. There are two problems with the current implementation of the Monte Carlo method. First, there is no satisfactory way of accounting for the variation of imprecision with temperature in 1, 2, or 3D models; second, due to its computational expense, it is impractical in 3D model studies. These difficulties are discussed. (author) 4 refs.

  17. Implications of imprecision in kinetic rate data for photochemical model calculations

    Energy Technology Data Exchange (ETDEWEB)

    Stewart, R W; Thompson, A M [National Aeronautics and Space Administration, Greenbelt, MD (United States). Goddard Space Flight Center

    1998-12-31

    Evaluation of uncertainties in photochemical model calculations is of great importance to scientists performing assessment modeling. A major source of uncertainty is the measurement imprecision inherent in photochemical reaction rate data that modelers rely on. A rigorous method of evaluating the impact of data imprecision on computational uncertainty is the study of error propagation using Monte Carlo techniques. There are two problems with the current implementation of the Monte Carlo method. First, there is no satisfactory way of accounting for the variation of imprecision with temperature in 1, 2, or 3D models; second, due to its computational expense, it is impractical in 3D model studies. These difficulties are discussed. (author) 4 refs.

  18. Laser-induced vibrational dynamics of ozone in solid argon

    DEFF Research Database (Denmark)

    Hansen, Flemming Yssing; Amstrup, B.; Henriksen, Niels Engholm

    1997-01-01

    We consider the vibrational dynamics, induced by an intense infrared laser pulse, in an ozone molecule with isotopic substitution, that is, (OOO)-O-16-O-16-O-18 and compare the dynamics in the gas phase and in solid ar on. not perturbed by argon on a time-scale of a few picoseconds and selective...

  19. Parvovirus induced alterations in nuclear architecture and dynamics.

    Directory of Open Access Journals (Sweden)

    Teemu O Ihalainen

    2009-06-01

    Full Text Available The nucleus of interphase eukaryotic cell is a highly compartmentalized structure containing the three-dimensional network of chromatin and numerous proteinaceous subcompartments. DNA viruses induce profound changes in the intranuclear structures of their host cells. We are applying a combination of confocal imaging including photobleaching microscopy and computational methods to analyze the modifications of nuclear architecture and dynamics in parvovirus infected cells. Upon canine parvovirus infection, expansion of the viral replication compartment is accompanied by chromatin marginalization to the vicinity of the nuclear membrane. Dextran microinjection and fluorescence recovery after photobleaching (FRAP studies revealed the homogeneity of this compartment. Markedly, in spite of increase in viral DNA content of the nucleus, a significant increase in the protein mobility was observed in infected compared to non-infected cells. Moreover, analysis of the dynamics of photoactivable capsid protein demonstrated rapid intranuclear dynamics of viral capsids. Finally, quantitative FRAP and cellular modelling were used to determine the duration of viral genome replication. Altogether, our findings indicate that parvoviruses modify the nuclear structure and dynamics extensively. Intranuclear crowding of viral components leads to enlargement of the interchromosomal domain and to chromatin marginalization via depletion attraction. In conclusion, parvoviruses provide a useful model system for understanding the mechanisms of virus-induced intranuclear modifications.

  20. Advanced oxidation treatment and photochemical fate of selected antidepressant pharmaceuticals in solutions of Suwannee River humic acid

    Energy Technology Data Exchange (ETDEWEB)

    Santoke, Hanoz, E-mail: hsantoke@uci.edu [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@uci.edu [Urban Water Research Center, Department of Civil and Environmental Engineering, University of California, Irvine, Irvine, CA 92697-2175 (United States); Department of Environmental Science and Engineering, Fudan University, Shanghai, 200433 (China); Cooper, William J., E-mail: wcooper@uci.edu [Urban Water Research Center, Department of Civil and Environmental Engineering, University of California, Irvine, Irvine, CA 92697-2175 (United States); Peake, Barrie M., E-mail: bpeake@chemistry.otago.ac.nz [Chemistry Department, University of Otago, P.O. Box 56, Dunedin 9054 (New Zealand)

    2012-05-30

    Highlights: Black-Right-Pointing-Pointer We elucidate the photochemical degradation of three antidepressant pharmaceuticals. Black-Right-Pointing-Pointer Hydroxyl radical is the most significant contributor to the degradation. Black-Right-Pointing-Pointer Excited state dissolved organic matter also plays a significant role for duloxetine. Black-Right-Pointing-Pointer Tentative reaction byproducts are identified. - Abstract: Antidepressant pharmaceuticals have recently been detected at low concentrations in wastewater and surface water. This work reports studies of the direct and indirect photochemical fate and treatment by advanced oxidation of three antidepressant compounds (duloxetine, venlafaxine and bupropion) in solutions of humic acid in order to elucidate their behavior in the natural environment prior to reaching a water treatment facility and potentially entering a potable water supply. Humic acid solution was prepared by adding to distilled water a known amount of organic matter as a photosensitizer. All three antidepressants react very rapidly with hydroxyl radicals ({center_dot}OH) and hydrated electrons (e{sup -}{sub aq}) with rate constants of {approx}10{sup 8} to 10{sup 10} M{sup -1} s{sup -1}, but significantly slower with singlet oxygen ({sup 1}{Delta}O{sub 2}) ({approx}10{sup 3} to 10{sup 5} M{sup -1} s{sup -1}). The steady-state concentrations of {center_dot}OH and {sup 1}{Delta}O{sub 2}, in a sample of humic acid solution were measured and used with the second order rate constants to show that the hydroxyl radical was an order of magnitude more effective than the singlet oxygen in the solar-induced photochemical degradation of the antidepressants. Excited state dissolved organic matter also accounted for a substantial portion of degradation of duloxetine, decreasing its half-life by 27% under solar irradiation. Several reaction pathways and by-products arising from the photodegradation were identified using gamma-irradiation followed by LC

  1. Photochemical and microbial alterations of DOM spectroscopic properties in the estuarine system Ria de Aveiro.

    Science.gov (United States)

    Santos, L; Santos, E B H; Dias, J M; Cunha, A; Almeida, A

    2014-08-01

    The influence of photochemical transformations of chromophoric dissolved organic matter (CDOM) on microbial communities was evaluated in the estuarine system Ria de Aveiro. Two sites, representative of the marine and brackish water zones of the estuary, were surveyed regularly in order to determine seasonal and vertical profiles of variation of CDOM properties. Optical parameters of CDOM indicative of aromaticity and molecular weight were used to establish CDOM sources, and microbial abundance and activity was characterized. Additionally, microcosm experiments were performed in order to simulate photochemical reactions of CDOM and to evaluate microbial responses to light-induced changes in CDOM composition. The CDOM of the two estuarine zones showed different spectral characteristics, with significantly higher values of the specific ultra-violet absorbance at 254 nm (SUVA254) (5.5 times) and of the absorption coefficient at 350 nm (a350) (12 times) and lower SR (S275-295/S350-400) ratio at brackish water compared with the marine zone, reflecting the different amounts and prevailing sources of organic matter, as well as distinct riverine and oceanic influences. At the marine zone, the abundance of bacteria and the activity of Leu-AMPase correlated with a350 and a254, suggesting a microbial contribution to the HMW CDOM pool. The irradiation of DOM resulted in a decrease of the values of a254 and a350 and an increase of the slope S275-295 and of the ratios E2 : E3 (a250/a365) and SR, which in turn increase its bioavailability. However, the extent of photoinduced transformations and microbial responses was dependent on the initial optical characteristics of CDOM. In Ria de Aveiro both photochemical and microbial processes yielded optical changes in CDOM and the overall results of these combined processes determine the fate of CDOM in the estuarine system and have an influence on local productivity and in adjacent coastal areas.

  2. The photochemical reaction of hydrocarbons under extreme thermobaric conditions

    Science.gov (United States)

    Serovaiskii, Aleksandr; Kolesnikov, Anton; Mukhina, Elena; Kutcherov, Vladimir

    2017-10-01

    The photochemical reaction of hydrocarbons was found to play an important role in the experiments with the synthetic petroleum conducted in Diamond Anvil Cell (DAC). Raman spectroscopy with a green laser (514.5 nm) was used for in situ sample analysis. This photochemical effect was investigated in the pressure range of 0.7-5 GPa, in the temperature interval from the ambient conditions to 450°C. The power of laser used in these experiment series was from 0.05 W to 0.6 W. The chemical transformation was observed when the necessary threshold pressure (~2.8 GPa) was reached. This transformation correlated with the luminescence appearance on the Raman spectra and a black opaque spot in the sample was observed in the place where the laser focus was forwarded. The exposure time and laser power (at least in the 0.1-0.5 W range) did not play a role in the 0.1-0.5 GPa range.

  3. 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...

  4. Photochemical Reactivity of Dissolved Organic Matter in Boreal Lakes

    Science.gov (United States)

    Gu, Y.; Vuorio, K.; Tiirola, M.; Perämäki, S.; Vahatalo, A.

    2016-12-01

    Boreal lakes are rich in dissolved organic matter (DOM) that terrestrially derived from forest soil and wetland, yet little is known about potential for photochemical transformation of aquatic DOM in boreal lakes. Transformation of chromophoric dissolved organic matter (CDOM) can decrease water color and enhance microbial mineralization, affecting primary production and respiration, which both affect the CO2 balance of the lakes. We used laboratory solar radiation exposure experiments with lake water samples collected from 54 lakes located in Finland and Sweden, representing different catchment composition and watershed location to assess photochemical reactivity of DOM. The pH of water samples ranged from 5.4 to 8.3, and the concentrations of dissolved iron (Fe) were between samples received simulated solar radiation corresponding to a daily dose of sunlight, and photomineralization of dissolved organic carbon (DOC) to dissolved inorganic carbon (DIC) was measured for determination of spectral apparent quantum yields (AQY). During irradiation, photobleaching decreased the absorption coefficients of CDOM at 330 nm between 4.9 and 79 m-1 by 0.5 to 11 m-1. Irradiation generated DIC from 2.8 to 79 μmol C L-1. The AQY at 330 nm ranged between 31 and 273 ×10-6 mol C mol photons-1 h-1, which was correlated positively with concentration of dissolved Fe, and negatively with pH. Further statistical analyze indicated that the interaction between pH and Fe may explain much of the photochemical reactivity of DOM in the examined lakes, and land cover concerns main catchment areas also can have impact on the photoreaction process. This study may suggest how environmental conditions regulate DOM photomineralization in boreal lakes.

  5. Effect of latitude on the potential for formation of photochemical smog

    Energy Technology Data Exchange (ETDEWEB)

    Neiboer, H [Central Laboratorium TNO, Delft, Netherlands; Carter, W P.L.; Lloyd, A C; Pitts, Jr, J N

    1976-01-01

    The effect of latitude on the potential for the formation of photochemical smog has been assessed. Calculations suggest that at the summer solstice, the integrated sunlight intensity at Rotterdam or Fairbanks (Alaska) is very similar to that in Los Angeles. Computations carried out, assuming the same pollutant emission inventory for the three locations, showed that ozone and PAN dosages depend more on the integrated light intensity than on the nature of the light intensity distribution with time. Therefore, if factors such as emissions and meteorological conditions are equal, the potential for significant photochemical smog formation during the summer months is similar for Los Angeles (34/sup 0/N) and northern cities such as Rotterdam (52/sup 0/N) and Nome or Fairbanks, Alaska (65/sup 0/N).

  6. Photochemical Synthesis and Properties of Colloidal Copper, Silver and Gold Adsorbed on Quartz

    International Nuclear Information System (INIS)

    Loginov, Anatoliy V.; Gorbunova, Valentina V.; Boitsova, Tatiana B.

    2002-01-01

    Original methods for the photochemical production of stable copper, silver and gold colloids in the form of films on quartz, and dispersion in liquids were devised. It is shown that photochemical synthesis of colloidal metals is a difficult multiphase process, and includes the formation of low-valence forms of Cu(I), Au(I) and nonmetal clusters, colloidal particles and their agglomerates. Cluster stabilization and further growth to colloidal particles are achieved by adsorption onto the solid surface (quartz) or by increasing the viscosity of photolyte. In the absence of these methods of stabilization, the processes of intermediate reoxidation to Cu(II) and Au(III) and agglomeration of Ag and Au colloids proceed in a photolyte. Adsorption and the rate of cluster growth on a quartz surface are speeded up by the action of monochromatic UV light. Experimental models of the mechanism of colloidal formation are suggested. The dependence of the growth rate and the properties of the colloids on conditions of the photochemical procedure (energy and light intensity, concentration of initial complex) has been established

  7. Global emissions and models of photochemically active compounds

    International Nuclear Information System (INIS)

    Penner, J.E.; Atherton, C.S.; Graedel, T.E.

    1993-01-01

    Anthropogenic emissions from industrial activity, fossil fuel combustion, and biomass burning are now known to be large enough (relative to natural sources) to perturb the chemistry of vast regions of the troposphere. A goal of the IGAC Global Emissions Inventory Activity (GEIA) is to provide authoritative and reliable emissions inventories on a 1 degree x 1 degree grid. When combined with atmospheric photochemical models, these high quality emissions inventories may be used to predict the concentrations of major photochemical products. Comparison of model results with measurements of pertinent species allows us to understand whether there are major shortcomings in our understanding of tropospheric photochemistry, the budgets and transport of trace species, and their effects in the atmosphere. Through this activity, we are building the capability to make confident predictions of the future consequences of anthropogenic emissions. This paper compares IGAC recommended emissions inventories for reactive nitrogen and sulfur dioxide to those that have been in use previously. We also present results from the three-dimensional LLNL atmospheric chemistry model that show how emissions of anthropogenic nitrogen oxides might potentially affect tropospheric ozone and OH concentrations and how emissions of anthropogenic sulfur increase sulfate aerosol loadings

  8. Photochemical and other air pollutions in the Netherlands

    Energy Technology Data Exchange (ETDEWEB)

    Floor, H.

    1975-01-01

    Together with the State Institute of Public Health and the Royal Dutch Meteorological Institute, the Institute of Phytopathological Research continued investigations on incidence of air pollution in the country. The main purpose is to measure the effects of air pollution on indicator plants and to detect over the years which components separately or perhaps together damage indicator plants. In 1974, the network of experimental fields in the Netherlands was completed. From April until October, 29 fields were inspected weekly for typical symptoms of air pollution. Just as in the preceding year O3 caused most injury of the photochemical air pollutants, as shown by Spinacia oleracea and Nicotiana tabacum. Other photochemical air pollutants like PAN, and the pollutants SO2, NO/sub x/ and ethylene caused little injury to the indicator plants Urtica urens, Poa annua, Medicago sativa, Petunia nyctaginiflora and Solanum tuberosum. Symptoms of damage on Tulipa gesneriana, Gladiolus gandavensis and Freesia refracta indicated air pollution by HF in all experimental fields, but especially in the south of the country. The F determination in the air by means of the limed paper method established the results with the indicator plants.

  9. Photochemical stability of electrochromic polymers and devices

    DEFF Research Database (Denmark)

    Jensen, Jacob; Madsen, Morten Vesterager; Krebs, Frederik C

    2013-01-01

    The stability of fully printed flexible organic electrochromics based on 11 different conjugated polymers is explored from the fundamental chemical degradation level to the operational device level. The photochemical stability of the electrochromic polymers (ECPs) is studied enabling an analysis ...... based on flexible barrier substrates exhibit increased stability and are indeed viable in devices such as shading elements, light management systems, displays with low switching speed requirements and signage. © 2013 The Royal Society of Chemistry....

  10. Cherenkov light as a source of photochemical reactions in irradiated solutions of nitrile of malachite green

    Energy Technology Data Exchange (ETDEWEB)

    Stuglik, Z; Grodkowski, J

    1986-10-01

    Experimental data on photochemical activity of Cherenkov light are presented. Malachite green leucocyanide was used to detect the photochemical effects. The G value of Cherenkov light from the region 200-330 nm (number of quanta formed per 100 eV absorbed energy of ionizing radiation) in ethanol was estimated to be in the range of 0.0027-0.049. 14 references.

  11. Cherenkov light as a source of photochemical reactions in irradiated solutions of nitrile of malachite green

    International Nuclear Information System (INIS)

    Stuglik, Z.; Grodkowski, J.

    1986-01-01

    Experimental data on photochemical activity of Cherenkov light are presented. Malachite green leucocyanide was used to detect the photochemical effects. The G value of Cherenkov light from the region 200-330 nm (number of quanta formed per 100 eV absorbed energy of ionizing radiation) in ethanol was estimated to be in the range of 0.0027-0.049. (author)

  12. 40 CFR 52.430 - Photochemical Assessment Monitoring Stations (PAMS) Program.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 3 2010-07-01 2010-07-01 false Photochemical Assessment Monitoring Stations (PAMS) Program. 52.430 Section 52.430 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Natural Resources & Environmental Control submitted a plan for the establishment and implementation of a...

  13. 40 CFR 52.480 - Photochemical Assessment Monitoring Stations (PAMS) Program.

    Science.gov (United States)

    2010-07-01

    ... of Columbia's Department of Consumer and Regulatory Affairs submitted a plan for the establishment... 40 Protection of Environment 3 2010-07-01 2010-07-01 false Photochemical Assessment Monitoring Stations (PAMS) Program. 52.480 Section 52.480 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY...

  14. 40 CFR 52.1080 - Photochemical Assessment Monitoring Stations (PAMS) Program.

    Science.gov (United States)

    2010-07-01

    ... Stations (PAMS) Program. 52.1080 Section 52.1080 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... § 52.1080 Photochemical Assessment Monitoring Stations (PAMS) Program. On March 24, 1994 Maryland's... Assessment Monitoring Stations (PAMS) Program as a state implementation plan (SIP) revision, as required by...

  15. Photochemical technique for reduction of uranium and subsequently plutonium in the Purex process

    International Nuclear Information System (INIS)

    Goldstein, M.; Barker, J.J.; Gangwer, T.

    1976-09-01

    A photochemical modification of the Purex process is described in which a purified side stream of UO 2 ++ ion is reduced to U +4 outside the radioactive area of the reprocessing plant. The U +4 is then cycled back to step 2 of the Purex process to reduce the plutonium and effect separation within the partitioning column. This process is shown to be very energy efficient and compatible with existing conventional lamp technology. Preliminary cost estimates of the energy requirements for photon production are essentially negligible. Conceptual systems and photochemical reactor designs are presented. Potential benefits of this system are discussed

  16. Influence of photochemical transformations upon optic-spectral characteristics of iodine cadmium crystals with copper dopant

    International Nuclear Information System (INIS)

    Novosad, S.S.

    2000-01-01

    The influence of photochemical transformations upon absorption. X-ray, photo- and thermostimulated luminescence of crystals CdI 2 :CuI, CdI 2 :CuI and CdI 2 :CuO grown by Stockbarger - Czochralski method has been studied. The photochemical reactions in crystals of iodine cadmium with the dopant of copper leads to reducing the intensity of X-ray, photo- and thermostimulated luminescence, the appearance of new luminescent centers is not observed

  17. Photochemical and photocatalytic evaluation of 1D titanate/TiO{sub 2} based nanomaterials

    Energy Technology Data Exchange (ETDEWEB)

    Conceição, D.S.; Ferreira, D.P. [Centro de Química-Física Molecular and IN-Institute of Nanoscience and Nanotechnology Instituto Superior Técnico, Universidade de Lisboa Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Graça, C.A.L. [Universidade de São Paulo, Avenida Prof. Luciano Gualberto, tr. 3, 380 São Paulo (Brazil); Júlio, M.F.; Ilharco, L.M. [Centro de Química-Física Molecular and IN-Institute of Nanoscience and Nanotechnology Instituto Superior Técnico, Universidade de Lisboa Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Velosa, A.C. [Instituto Nacional de Tecnologia, Av. Venezuela 82, Rio de Janeiro (Brazil); Santos, P.F. [Centro de Química, Vila Real Universidade de Trás-os-Montes e Alto Douro, 5001-801 Vila Real (Portugal); Vieira Ferreira, L.F., E-mail: lfvieiraferreira@tecnico.ulisboa.pt [Centro de Química-Física Molecular and IN-Institute of Nanoscience and Nanotechnology Instituto Superior Técnico, Universidade de Lisboa Av. Rovisco Pais, 1049-001 Lisboa (Portugal)

    2017-01-15

    Highlights: • 1D titanate based nanomaterials were prepared via a hydrothermal approach. • The structural and photochemical evaluation of the nanomaterials was performed. • A fluorescent dye was used as a surface probe in visible excitation conditions. • Amicarbazone was used as the model contaminant for photodegradation studies. - Abstract: One-dimensional (1D) titanate based nanomaterials were synthesized following an alkaline hydrothermal approach of commercial TiO{sub 2} nanopowder. The morphological features of all materials were monitored by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and also Brunauer-Emmett-Teller (BET) technique. In addition the photochemical behaviour of these nanostructured materials were evaluated with the use of laser induced luminescence (LIL), ground-state diffuse reflectance (GSDR), and laser-flash photolysis in diffuse reflectance mode (DRLFP). The mixed titanate/TiO{sub 2} nanowires presented the least intense fluorescence spectra, suggesting the presence of surficial defects that can extend the lifetime of the excited charge carriers. A fluorescent ‘rhodamine-like’ dye was adsorbed onto different materials and examined via photoexcitation in the visible range to study the self-photosensitization mechanism. The presence of the radical cation of the dye and the degradation kinetics, when compared with a neutral substrate—cellulose, provided significant evidences regarding the photoactivity of the different materials. Regarding all the materials under study, the nanowires exhibited a strong photocatalytic efficiency, for the adsorbed fluorescent probe. The photocatalytic mechanism was also considered by studying the photodegradation capability of the titanate based materials in the presence of an herbicide, Amicarbazone, after ultraviolet (UVA) photoexcitation.

  18. Multicharged Ion-induced simple molecule fragmentation dynamics

    International Nuclear Information System (INIS)

    Tarisien, M.

    2003-10-01

    The aim of this work is to study the dynamics of swift multicharged ion-induced fragmentation of diatomic (CO) and triatomic (CO 2 ) molecules. Performed at the GANIL facility, this study used the Recoil Ion Momentum Spectroscopy technique (RIMS), which consists of a time-of-flight mass spectrometer, coupled with a multi-hit capability position sensitive detector (delay line anode). The high-resolution measurement of the kinetic energy distribution released (KER) during the CO fragmentation points out the limitation of the Coulomb Explosion Model, revealing, for example, the di-cation CO 2 + electronic state contribution in the case of C + /O + fragmentation pathway. Furthermore, the multi-ionization cross section dependence with the orientation of the internuclear axis of CO is compared with a geometrical model calculation. Finally, different behaviours are observed for the dissociation dynamics of a triatomic molecule (CO 2 ). While triple ionization leads mainly to a synchronous concerted fragmentation dynamics, a weak fraction of dissociating molecule follows a sequential dynamics involving CO 2 + metastable states. In the case of double ionization, (CO 2 ) 2+ di-cation dissociation dynamics is asynchronously concerted and has been interpreted using a simple model involving an asymmetrical vibration of the molecule. (author)

  19. 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.)

  20. Photochemical reactions of aqueous plutonium systems

    International Nuclear Information System (INIS)

    Friedman, H.A.; Toth, L.M.; Bell, J.T.

    1977-01-01

    The photochemical shift of the Pu 4+ disproportionation equilibrium in aqueous perchloric acid solutions has been measured and shown to be reversible. Ratios of equilibrium quotients between light and dark conditions have been measured for 0.01 M Pu ion concentrations in 0.53 to 1.24 N acid solutions exposed to 0.5 Watt of UV light. The photodecomposition of time- and temperature-aged Pu(IV) polymers in perchloric and nitric acid solutions have been examined as a function of aging conditions. Effects similar to those seen previously for fresh polymers have been observed in the aged perchloric acid solutions. (author)

  1. Fabrication of self-written waveguide in photosensitive polyimide resin by controlling photochemical reaction of photosensitizer

    International Nuclear Information System (INIS)

    Yamashita, K.; Kuro, T.; Oe, K.; Mune, K.; Tagawa, K.; Naitou, R.; Mochizuki, A.

    2004-01-01

    We have investigated optical properties of photosensitive polyimide appropriating for long self-written waveguide fabrication. From systematic measurements of absorption properties, it was found that photochemical reaction of photosensitizer dissolved in the photosensitive polyimide resins relates to transparency after the exposure, which limits the length of the fabricated self-written waveguide. By controlling the photochemical reaction, in which the photosensitive polyimide resin has sufficient transparency during exposure, four times longer self-written waveguide core was fabricated

  2. Nonequilibrium photochemical reactions induced by lasers. Technical progress report

    International Nuclear Information System (INIS)

    Steinfeld, J.I.

    1978-04-01

    Research has progressed in six principal subject areas of interest to DOE advanced (laser) isotope separation efforts. These are (1) Infrared double resonance spectroscopy of molecules excited by multiple infrared photon absorption, particularly SF 6 and vinyl chloride. (2) Infrared multiphoton excitation of metastable triplet-state molecules, e.g., biacetyl. (3) An Information Theory analysis of multiphoton excitation and collisional deactivation has been carried out. (4) The mechanism of infrared energy deposition and multiphoton-induced reactions in chlorinated ethylene derivatives; and RRKM (statistical) model accounts for all observed behavior of the system, and a deuterium-specific reaction pathway has been identified. (5) Diffusion-enhanced laser isotope separation in N 16 O/N 18 O. (6) A technical evaluation of laser-induced chemistry and isotope separation

  3. Effect of photochemical ageing on the ice nucleation properties of diesel and wood burning particles

    Directory of Open Access Journals (Sweden)

    C. Chou

    2013-01-01

    Full Text Available A measurement campaign (IMBALANCE conducted in 2009 was aimed at characterizing the physical and chemical properties of freshly emitted and photochemically aged combustion particles emitted from a log wood burner and diesel vehicles: a EURO3 Opel Astra with a diesel oxidation catalyst (DOC but no particle filter and a EURO2 Volkswagen Transporter TDI Syncro without emission aftertreatment. Ice nucleation experiments in the deposition and condensation freezing modes were conducted with the Portable Ice Nucleation Chamber (PINC at three nominal temperatures, −30 °C, −35 °C and −40 °C. Freshly emitted diesel particles showed ice formation only at −40 °C in the deposition mode at 137% relative humidity with respect to ice (RHi and 92% relative humidity with respect to water (RHw, and photochemical ageing did not play a role in modifying their ice nucleation behaviour. Only one diesel experiment where α-pinene was added for the ageing process, showed an ice nucleation enhancement at −35 °C. Wood burning particles also act as ice nuclei (IN at −40 °C in the deposition mode at the same conditions as for diesel particles and photochemical ageing also did not alter the ice formation properties of the wood burning particles. Unlike diesel particles, wood burning particles form ice via condensation freezing at −35 °C whereas no ice nucleation was observed at −30 °C. Photochemical ageing did not affect the ice nucleation ability of the diesel and wood burning particles at the three different temperatures investigated but a broader range of temperatures below −40 °C need to be investigated in order to draw an overall conclusion on the effect of photochemical ageing on deposition/condensation ice nucleation across the entire temperature range relevant to cold clouds.

  4. [Estimation of Time-Dependent microRNA Expression Patterns in Brain Tissue, Leukocytes, and Blood Plasma of Rats under Photochemically Induced Focal Cerebral Ischemia].

    Science.gov (United States)

    Gusar, V A; Timofeeva, A V; Zhanin, I S; Shram, S I; Pinelis, V G

    2017-01-01

    miRNA expression over different time periods (24 and 48 h) using the quantitative RT-PCR and deep sequencing has been evaluated in a model of photochemically induced thrombosis. A combination of two approaches allowed us to determine the miRNA expression patterns caused by ischemia. Nine miRNAs, including let-7f-5p, miR-221-3p, miR-21-5p, miR-30c-5p, miR-30a-3p, miR-223-3p, miR-23a-3p, miR-22-5p, and miR-99a-5p, were differentially expressed in brain tissue and leukocytes of rats 48 h after onset of ischemia. In addition, six miRNAs were differentially expressed in the brain tissue and blood plasma of rats 24 h after exposure, among which miR-145-3p and miR-375-3p were downregulated and miR-19a-3p, miR-92a-3p, miR-188-5p, and miR-532-5p were upregulated. In our opinion, miR-188-5p and miR-532-5p may be considered to be new potential markers of ischemic injury. The level of miRNA expression tended to increase 48 h after the onset of ischemia in brain tissue and leukocytes, which reflects not only the local response in brain tissue due to inflammation, vascular endothelial dysfunction, and disorders of the permeability of the blood-brain barrier, but also the systemic response of the organism to multifactor molecular processes induced by ischemic injury.

  5. 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

  6. Analysis of thermally induced magnetization dynamics in spin-transfer nano-oscillators

    Energy Technology Data Exchange (ETDEWEB)

    D' Aquino, M., E-mail: daquino@uniparthenope.it [Department of Technology, University of Naples ' Parthenope' , 80143 Naples (Italy); Serpico, C. [Department of Engineering, University of Naples Federico II, 80125 Naples (Italy); Bertotti, G. [Istituto Nazionale di Ricerca Metrologica 10135 Torino (Italy); Bonin, R. [Politecnico di Torino - Sede di Verres, 11029 Verres (Aosta) (Italy); Mayergoyz, I.D. [ECE Department and UMIACS, University of Maryland, College Park, MD 20742 (United States)

    2012-05-01

    The thermally induced magnetization dynamics in the presence of spin-polarized currents injected into a spin-valve-like structure used as microwave spin-transfer nano-oscillator (STNO) is considered. Magnetization dynamics is described by the stochastic Landau-Lifshitz-Slonczewski (LLS) equation. First, it is shown that, in the presence of thermal fluctuations, the spectrum of the output signal of the STNO exhibits multiple peaks at low and high frequencies. This circumstance is associated with the occurrence of thermally induced transitions between stationary states and magnetization self-oscillations. Then, a theoretical approach based on the separation of time-scales is developed to obtain a stochastic dynamics only in the slow state variable, namely the energy. The stationary distribution of the energy and the aforementioned transition rates are analytically computed and compared with the results of direct integration of the LLS dynamics, showing very good agreement.

  7. 40 CFR 52.2035 - Photochemical Assessment Monitoring Stations (PAMS) Program.

    Science.gov (United States)

    2010-07-01

    ... Stations (PAMS) Program. 52.2035 Section 52.2035 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY...) Pennsylvania § 52.2035 Photochemical Assessment Monitoring Stations (PAMS) Program. On September 23, 1994... (PAMS) Program as a state implementation plan (SIP) revision, as required by section 182(c)(1) of the...

  8. Heparin Assisted Photochemical Synthesis of Gold Nanoparticles and Their Performance as SERS Substrates

    Science.gov (United States)

    Rodríguez-Torres, Maria del Pilar; Díaz-Torres, Luis Armando; Romero-Servin, Sergio

    2014-01-01

    Reactive and pharmaceutical-grade heparins were used as biologically compatible reducing and stabilizing agents to photochemically synthesize colloidal gold nanoparticles. Aggregates and anisotropic shapes were obtained photochemically under UV black-light lamp irradiation (λ = 366 nm). Heparin-functionalized gold nanoparticles were characterized by Scanning Electron Microscopy and UV-Vis spectroscopy. The negatively charged colloids were used for the Surface Enhanced Raman Spectroscopy (SERS) analysis of differently charged analytes (dyes). Measurements of pH were taken to inspect how the acidity of the medium affects the colloid-analyte interaction. SERS spectra were taken by mixing the dyes and the colloidal solutions without further functionalization or addition of any aggregating agent. PMID:25342319

  9. Development and first evaluation of micro-calgrid: a 3-D, urban-canopy-scale photochemical model

    International Nuclear Information System (INIS)

    Stern, R.; Yamartino, R.J.

    2001-01-01

    This paper details the development and first application of the MICRO-CALGRID (MCG), micro-scale photochemical model. The MCG model treats individual buildings as obstacles with impenetrable surfaces, rather than as roughness elements; is driven by the flow and turbulence fields generated by the MISKAM Navier-Stokes model, the emissions generated by the German MOBILEV model, and the concentration inflow boundary conditions generated by the urban-scale CALGRID model; includes a detailed treatment of vehicle-induced turbulence; and is equipped with three chemistry schemes (SAPRC-93, CB-4, and an analytic solution for Chapman cycle chemistry). The MCG model is exercised in both its 2-D and 3-D modes. Also described is a MCG application to a 5-day episode measured within a busy street canyon in Berlin, Germany. Concentrations of all measured pollutants (CO, NO, NO 2 , benzene, SO 2 and TSP) were well reproduced by the MCG model. NO 2 performance appeared adequate using the simpler analytic chemistry solution; however, inclusion of vehicle-induced turbulence was found to improve model performance statistics. (Author)

  10. Delay-Induced Consensus and Quasi-Consensus in Multi-Agent Dynamical Systems

    NARCIS (Netherlands)

    Yu, Wenwu; Chen, Guanrong; Cao, Ming; Ren, Wei

    2013-01-01

    This paper studies consensus and quasi-consensus in multi-agent dynamical systems. A linear consensus protocol in the second-order dynamics is designed where both the current and delayed position information is utilized. Time delay, in a common perspective, can induce periodic oscillations or even

  11. Temporal dynamics of distinct CA1 cell populations during unconscious state induced by ketamine.

    Directory of Open Access Journals (Sweden)

    Hui Kuang

    2010-12-01

    Full Text Available Ketamine is a widely used dissociative anesthetic which can induce some psychotic-like symptoms and memory deficits in some patients during the post-operative period. To understand its effects on neural population dynamics in the brain, we employed large-scale in vivo ensemble recording techniques to monitor the activity patterns of simultaneously recorded hippocampal CA1 pyramidal cells and various interneurons during several conscious and unconscious states such as awake rest, running, slow wave sleep, and ketamine-induced anesthesia. Our analyses reveal that ketamine induces distinct oscillatory dynamics not only in pyramidal cells but also in at least seven different types of CA1 interneurons including putative basket cells, chandelier cells, bistratified cells, and O-LM cells. These emergent unique oscillatory dynamics may very well reflect the intrinsic temporal relationships within the CA1 circuit. It is conceivable that systematic characterization of network dynamics may eventually lead to better understanding of how ketamine induces unconsciousness and consequently alters the conscious mind.

  12. Engineering photochemical smog through convection towers

    Energy Technology Data Exchange (ETDEWEB)

    Elliott, S.; Prueitt, M.L.; Bossert, J.E.; Mroz, E.J.; Krakowski, R.A.; Miller, R.L. [Los Alamos National Lab., NM (United States); Jacobson, M.Z.; Turco, R.P. [Los Alamos National Lab., NM (United States)]|[Univ. of California, Los Angeles, CA (United States). Atmospheric Sciences Dept.

    1995-02-01

    Reverse convection towers have attracted attention as a medium for cleansing modern cities. Evaporation of an aqueous mist injected at the tower opening could generate electrical power by creating descent, and simultaneously scavenge unsightly and unhealthful particulates. The study offered here assesses the influence to tower water droplets on the photochemical component of Los Angeles type smog. The primary radical chain initiator OH is likely removed into aqueous phases well within the residence time of air in the tower, and then reacts away rapidly. Organics do not dissolve, but nighttime hydrolysis of N{sub 2}O{sub 5} depletes the nitrogen oxides. A lack of HOx would slow hydrocarbon oxidation and so also ozone production. Lowering of NOx would also alter ozone production rates, but the direction is uncertain. SO{sub 2} is available in sufficient quantities in some urban areas to react with stable oxidants, and if seawater were the source of the mist, the high pH would lead to fast sulfur oxidation kinetics. With an accommodation coefficient of 10{sup {minus}3}, however, ozone may not enter the aqueous phase efficiently. Even if ozone is destroyed or its production suppressed, photochemical recovery times are on the order of hours, so that tower processing must be centered on a narrow midday time window. The cost of building the number of structures necessary for this brief turnover could be prohibitive. The increase in humidity accompanying mist evaporation could be controlled with condensers, but might otherwise counteract visibility enhancements by recreating aqueous aerosols. Quantification of the divergent forcings convection towers must exert upon the cityscape would call for coupled three dimensional modeling of transport, microphysics, and photochemistry. 112 refs.

  13. Bipyridine based metallogels: an unprecedented difference in photochemical and chemical reduction in the in situ nanoparticle formation.

    Science.gov (United States)

    Tatikonda, Rajendhraprasad; Bertula, Kia; Nonappa; Hietala, Sami; Rissanen, Kari; Haukka, Matti

    2017-02-28

    Metal co-ordination induced supramolecular gelation of low molecular weight organic ligands is a rapidly expanding area of research due to the potential in creating hierarchically self-assembled multi-stimuli responsive materials. In this context, structurally simple O-methylpyridine derivatives of 4,4'-dihydroxy-2,2'-bipyridine ligands are reported. Upon complexation with Ag(i) ions in aqueous dimethyl sulfoxide (DMSO) solutions the ligands spontaneously form metallosupramolecular gels at concentrations as low as 0.6 w/v%. The metal ions induce the self-assembly of three dimensional (3D) fibrillar networks followed by the spontaneous in situ reduction of the Ag-centers to silver nanoparticles (AgNPs) when exposed to daylight. Significant size and morphological differences of the AgNP's was observed between the standard chemical and photochemical reduction of the metallogels. The gelation ability, the nanoparticle formation and rheological properties were found to be depend on the ligand structure, while the strength of the gels is affected by the water content of the gels.

  14. Synthesis of fluorescent metal nanoparticles in aqueous solution by photochemical reduction

    KAUST Repository

    Kshirsagar, Prakash; Sangaru, Shiv; Brunetti, Virgilio; Malvindi, Maria Ada Da; Pompa, Pier Paolo

    2014-01-01

    A facile green chemistry approach for the synthesis of sub-5 nm silver and gold nanoparticles is reported. The synthesis was achieved by a photochemical method using tyrosine as the photoreducing agent. The size of the gold and silver nanoparticles

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

    NARCIS (Netherlands)

    Su, Y.; Straathof, N.J.W.; Hessel, V.; Noel, T.

    2014-01-01

    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

  16. Photophysics of conjugated polymers: interplay between Förster energy migration and defect concentration in shaping a photochemical funnel in PPV.

    Science.gov (United States)

    Saini, Sangeeta; Bagchi, Biman

    2010-07-21

    Recent single molecule experiments have suggested the existence of a photochemical funnel in the photophysics of conjugated polymers, like poly[2-methoxy-5-(2'-ethylhexyl)oxy-1,4-phenylenevinylene] (MEH-PPV). The funnel is believed to be a consequence of the presence of conformational or chemical defects along the polymer chain and efficient non-radiative energy transfer among different chromophore segments. Here we address the effect of the excitation energy dynamics on the photophysics of PPV. The PPV chain is modeled as a polymer with the length distribution of chromophores given either by a Gaussian or by a Poisson distribution. We observe that the Poisson distribution of the segment lengths explains the photophysics of PPV better than the Gaussian distribution. A recently proposed version of an extended 'particle-in-a-box' model is used to calculate the exciton energies and the transition dipole moments of the chromophores, and a master equation to describe the excitation energy transfer among different chromophores. The rate of energy transfer is assumed to be given here, as a first approximation, by the well-known Förster expression. The observed excitation population dynamics confirms the photochemical funneling of excitation energy from shorter to longer chromophores of the polymer chain. The time scale of spectral shift and energy transfer for our model polymer, with realistic values of optical parameters, is in the range of 200-300 ps. We find that the excitation energy may not always migrate towards the longest chromophore segments in the polymer chain as the efficiency of energy transfer between chromophores depends on the separation distance between the two and their relative orientation.

  17. Remote sensing techniques to monitor nitrogen-driven carbon dynamics in field corn

    Science.gov (United States)

    Corp, Lawrence A.; Middleton, Elizabeth M.; Campbell, Petya K. E.; Huemmrich, K. Fred; Cheng, Yen-Ben; Daughtry, Craig S. T.

    2009-08-01

    Patterns of change in vegetation growth and condition are one of the primary indicators of the present and future ecological status of the globe. Nitrogen (N) is involved in photochemical processes and is one of the primary resources regulating plant growth. As a result, biological carbon (C) sequestration is driven by N availability. Large scale monitoring of photosynthetic processes are currently possible only with remote sensing systems that rely heavily on passive reflectance (R) information. Unlike R, fluorescence (F) emitted from chlorophyll is directly related to photochemical reactions and has been extensively used for the elucidation of the photosynthetic pathways. Recent advances in passive fluorescence instrumentation have made the remote acquisition of solar-induced fluorescence possible. The goal of this effort is to evaluate existing reflectance and emerging fluorescence methodologies for determining vegetation parameters related to photosynthetic function and carbon sequestration dynamics in plants. Field corn N treatment levels of 280, 140, 70, and 0 kg N / ha were sampled from an intensive test site for a multi-disciplinary project, Optimizing Production Inputs for Economic and Environmental Enhancement (OPE). Aircraft, near-ground, and leaf-level measurements were used to compare and contrast treatment effects within this experiment site assessed with both reflectance and fluorescence approaches. A number of spectral indices including the R derivative index D730/D705, the normalized difference of R750 vs. R705, and simple ratio R800/R750 differentiated three of the four N fertilization rates and yielded high correlations to three important carbon parameters: C:N, light use efficiency, and grain yield. These results advocate the application of hyperspectral sensors for remotely monitoring carbon cycle dynamics in terrestrial ecosystems.

  18. 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.

  19. Photochemical synthesis of biomolecules under anoxic conditions

    Science.gov (United States)

    Folsome, C.; Brittain, A.; Zelko, M.

    1983-01-01

    The long-wavelength UV anoxic photosynthesis of uracil, various sugars (including deoxyribose and glycoaldehyde), amino acids, and other organic photoproducts is reported. The reactions were conducted in a mixture of water, calcium carbonate, hydrazine, and formaldehyde which were subjected to 24 hr or 72 hr radiation. Product yields were greatest when the hydrazine/formaldehyde ratio was one, and when the reactant concentrations were low. These data suggest that organic products can be formed in variety from those amounts of formaldehyde and hydazine precursors which are themselves formed under anoxic UV photochemical conditions.

  20. Applications of laser-induced gratings to spectroscopy and dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Rohlfing, E.A. [Sandia National Laboratories, Livermore, CA (United States)

    1993-12-01

    This program has traditionally emphasized two principal areas of research. The first is the spectroscopic characterization of large-amplitude motion on the ground-state potential surface of small, transient molecules. The second is the reactivity of carbonaceous clusters and its relevance to soot and fullerene formation in combustion. Motivated initially by the desire to find improved methods of obtaining stimulated emission pumping (SEP) spectra of transients, most of our recent work has centered on the use of laser-induced gratings or resonant four-wave mixing in free-jet expansions. These techniques show great promise for several chemical applications, including molecular spectroscopy and photodissociation dynamics. The author describes recent applications of two-color laser-induced grating spectroscopy (LIGS) to obtain background-free SEP spectra of transients and double resonance spectra of nonfluorescing species, and the use of photofragment transient gratings to probe photodissociation dynamics.

  1. Enhancing endosomal escape of transduced proteins by photochemical internalisation.

    Directory of Open Access Journals (Sweden)

    Kevin Mellert

    Full Text Available Induced internalisation of functional proteins into cultured cells has become an important aspect in a rising number of in vitro and in vivo assays. The endo-lysosomal entrapment of the transduced proteins remains the major problem in all transduction protocols. In this study we compared the efficiency, cytotoxicity and protein targeting of different commercially available transduction reagents by transducing a well-studied fluorescently labelled protein (Atto488-bovine serum albumin into cultured human sarcoma cells. The amount of internalised protein and toxicity differed between the different reagents, but the percentage of transduced cells was consistently high. Furthermore, in all protocols the signals of the transduced Atto488-BSA were predominantly punctual consistent with an endosomal localisation. To overcome the endosomal entrapment, the transduction protocols were combined with a photochemical internalisation (PCI treatment. Using this combination revealed that an endosomal disruption is highly effective in cell penetrating peptide (CPP mediated transduction, whereas lipid-mediated transductions lead to a lower signal spreading throughout the cytosol. No change in the signal distribution could be achieved in treatments using non-lipid polymers as a transduction reagent. Therefore, the combination of protein transduction protocols based on CPPs with the endosomolytic treatment PCI can facilitate protein transduction experiments in vitro.

  2. Enhancing endosomal escape of transduced proteins by photochemical internalisation.

    Science.gov (United States)

    Mellert, Kevin; Lamla, Markus; Scheffzek, Klaus; Wittig, Rainer; Kaufmann, Dieter

    2012-01-01

    Induced internalisation of functional proteins into cultured cells has become an important aspect in a rising number of in vitro and in vivo assays. The endo-lysosomal entrapment of the transduced proteins remains the major problem in all transduction protocols. In this study we compared the efficiency, cytotoxicity and protein targeting of different commercially available transduction reagents by transducing a well-studied fluorescently labelled protein (Atto488-bovine serum albumin) into cultured human sarcoma cells. The amount of internalised protein and toxicity differed between the different reagents, but the percentage of transduced cells was consistently high. Furthermore, in all protocols the signals of the transduced Atto488-BSA were predominantly punctual consistent with an endosomal localisation. To overcome the endosomal entrapment, the transduction protocols were combined with a photochemical internalisation (PCI) treatment. Using this combination revealed that an endosomal disruption is highly effective in cell penetrating peptide (CPP) mediated transduction, whereas lipid-mediated transductions lead to a lower signal spreading throughout the cytosol. No change in the signal distribution could be achieved in treatments using non-lipid polymers as a transduction reagent. Therefore, the combination of protein transduction protocols based on CPPs with the endosomolytic treatment PCI can facilitate protein transduction experiments in vitro.

  3. Nickel films: Nonselective and selective photochemical deposition and properties

    International Nuclear Information System (INIS)

    Smirnova, N.V.; Boitsova, T.B.; Gorbunova, V.V.; Alekseeva, L.V.; Pronin, V.P.; Kon'uhov, G.S.

    2006-01-01

    Nickel films deposited on quartz surfaces by the photochemical reduction of a chemical nickel plating solution were studied. It was found that the deposition of the films occurs after an induction period, the length of which depends on the composition of the photolyte and the light intensity. Ni particles with a mean diameter of 20-30 nm were detected initially by transmission electron microscopy. The particles then increased in size (50 nm) upon irradiation and grouped into rings consisting of 4-5 particles. Irradiation with high-intensity light produces three-dimensional films. The calculated extinction coefficient of the nickel film was found to be 4800 L mol -1 cm -1 . Electron diffraction revealed that the prepared amorphous nickel films crystallize after one day of storage. It was determined that the films exhibit catalytic activity in the process of nickel deposition from nickel plating solution. The catalytic action remains for about 5-7 min after exposure of the films to air. The processes of selective and nonselective deposition of the nickel films are discussed. The use of poly(butoxy titanium) in the process of selective photochemical deposition enables negative and positive images to be prepared on quartz surfaces

  4. Photochemical epoxidation of olefins by visible light in a redox system involving Sb(V) tetraphenylporphyrin and water

    Energy Technology Data Exchange (ETDEWEB)

    Inoue, Haruo; Hida, Mitsuhiko (Tokyo Metropolitan Univ. (Japan))

    1989-03-25

    The authors explore electron donors from the viewpoint of solar energy storage. Much attention has been focused on how a water molecule can be incorporated into electron donor system. In this paper, the authors describe a photochemical epoxidation of alkene sensitized by Sb(V)-, P(V)-, Sn(IV)-, Ge(IV)- tetraphenylporphyrin (TPP) with higher oxidation potential than 1.0 Volts vs. NHE in redox systems with a water molecule as an electron donor. The water molecule acts as an electron donor, and alkene acts as an oxygen atom acceptor in this photoredox system. Epoxidation of alkenes usually requires strong oxidizing agents either by the thermal or photochemical method. This is the first example of the photochemical epoxide formation from alkene and water without any strong oxidizing agent. 1 fig.

  5. L-Cysteine Capped CdSe Quantum Dots Synthesized by Photochemical Route.

    Science.gov (United States)

    Singh, Avinash; Kunwar, Amit; Rath, M C

    2018-05-01

    L-cysteine capped CdSe quantum dots were synthesized via photochemical route in aqueous solution under UV photo-irradiation. The as grown CdSe quantum dots exhibit broad fluorescence at room temperature. The CdSe quantum dots were found to be formed only through the reactions of the precursors, i.e., Cd(NH3)2+4 and SeSO2-3 with the photochemically generated 1-hydroxy-2-propyl radicals, (CH3)2COH radicals, which are formed through the process of H atom abstraction by the photoexcited acetone from 2-propanol. L-Cysteine was found to act as a suitable capping agent for the CdSe quantum dots and increases their biocompatability. Cytotoxicty effects of these quantum dots were evaluated in Chinese Hamster Ovary (CHO) epithelial cells, indicated a significant lower level for the L-cysteine capped CdSe quantum dots as compare to the bare ones.

  6. Photochemical immobilization of anthraquinone conjugated oligonucleotides and PCR amplicons on solid surfaces

    DEFF Research Database (Denmark)

    Koch, T.; Jacobsen, N.; Fensholdt, J.

    2000-01-01

    Ligand immobilization on solid surfaces is an essential step in fields such as diagnostics, bio sensor manufacturing, and new material sciences in general. In this paper a photochemical approach based on anthraquinone as the chromophore is presented. Photochemical procedures offer special...... advantages as they are able to generate highly reactive species in an orientation specific manner. As presented here, anthraquinone (AQ) mediated covalent DNA immobilization appears to be superior to currently known procedures. A synthetic procedure providing AQ-phosphoramidites is presented. These reagents...... facilitate AQ conjugation during routine DNA synthesis, thus enabling the AQ-oligonucleotides to be immobilized in a very convenient and efficient manner. AQ-conjugated PCR primers can be used directly in PCR. When the PCR is performed in solution, the amplicons can be immobilized after the PCR. Moreover...

  7. Is the ipsilateral cortex surrounding the lesion or the non-injured contralateral cortex important for motor recovery in rats with photochemically induced cortical lesions?

    Science.gov (United States)

    Takata, Kotaro; Yamauchi, Hideki; Tatsuno, Hisashi; Hashimoto, Keiji; Abo, Masahiro

    2006-01-01

    To determine whether the ipsilateral cortex surrounding the lesion or the non-injured contralateral cortex is important for motor recovery after brain damage in the photochemically initiated thrombosis (PIT) model. We induced PIT in the sensorimotor cortex in rats and examined the recovery of motor function using the beam-walking test. In 24 rats, the right sensorimotor cortex was lesioned after 2 days of training for the beam-walking test (group 1). After 10 days, PIT was induced in the left sensorimotor cortex. Eight additional rats (group 2) received 2 days training in beam walking, then underwent the beam-walking test to evaluate function. After 10 days of testing, the left sensorimotor cortex was lesioned and recovery was monitored by the beam-walking test for 8 days. In group 1 animals, left hindlimb function caused by a right sensorimotor cortex lesion recovered within 10 days after the operation. Right hindlimb function caused by the left-side lesion recovered within 6 days. In group 2, right hindlimb function caused by induction of the left-side lesion after a total of 12 days of beam-walking training and testing recovered within 6 days as with the double PIT model. The training effect may be relevant to reorganization and neuromodulation. Motor recovery patterns did not indicate whether motor recovery was dependent on the ipsilateral cortex surrounding the lesion or the cortex of the contralateral side. The results emphasize the need for selection of appropriate programs tailored to the area of cortical damage in order to enhance motor functional recovery in this model. Copyright 2006 S. Karger AG, Basel.

  8. New model for surface fracture induced by dynamical stress

    OpenAIRE

    Andersen, J. V.; Lewis, L. J.

    1997-01-01

    We introduce a model where an isotropic, dynamically-imposed stress induces fracture in a thin film. Using molecular dynamics simulations, we study how the integrated fragment distribution function depends on the rate of change and magnitude of the imposed stress, as well as on temperature. A mean-field argument shows that the system becomes unstable for a critical value of the stress. We find a striking invariance of the distribution of fragments for fixed ratio of temperature and rate of ch...

  9. Studies on the photochemical and thermal dissociation synthesis of krypton difluoride

    Energy Technology Data Exchange (ETDEWEB)

    Kinkead, S.A.; FitzPatrick, J.R.; Foropoulos, J. Jr.; Kissane, R.J.; Purson, J.D.

    1993-08-01

    Like dioxygen difluoride (O{sub 2}F{sub 2}), KrF{sub 2} can be produced by thermal dissociation or photochemical synthesis from the elements; however, the yields are invariably much less than those obtained for O{sub 2}F{sub 2}. For example, while irradiation of liquid O{sub 2}/F{sub 2} mixtures at {minus}196{degrees}C through a sapphire window with an unfiltered 1,000W uv lamp provides in excess of 3g of O{sub 2}F{sub 2} per hour, the yield of KrF{sub 2} under identical circumstances is approximately 125 mg/hr. In this report, the yield of KrF{sub 2} in quartz and Pyrex{trademark} photochemical reactors has been examined as a function of irradiation wavelength, irradiation power, and Kr: F{sub 2} mole ratio. The uv-visible spectrum of KrF{sub 2} has also been recorded for comparison with earlier work, and the quantum yield for photodissociation at two wavelengths determined. The synthesis of KrF{sub 2} using large thermal gradients has also been examined using resistively heated nickel filaments to thermally dissociate the F{sub 2} in close proximity to liquid nitrogen-cooled metal surfaces. As a net result, KrF{sub 2} has been produced in yields in excess of 1.75 g/hr for extended periods in photochemical systems, and 2.3 g/hr for shorter periods in thermally dissociative reactors. This paper summarizes the results of examining parametrically several different types of reactors for efficiency of producing krypton difluoride.

  10. Photochemical versus biological production of methyl iodide during Meteor 55

    Science.gov (United States)

    Richter, U.; Wallace, D.

    2003-04-01

    The flux of methyl iodide from sea to air represents the largest flux of iodine from the ocean to the atmosphere. Surface water concentrations and hence fluxes are particularly high in tropical regions. This flux may be responsible for the enrichment of iodine in the marine aerosol and may contribute to important processes in the marine boundary layer, including particle formation. Methyl iodide is commonly referred to as a biogenic gas, with both macroalgae and phytoplankton identified as important sources. On the other hand experimental and field data have shown the importance of photochemical production that is not necessarily associated directly with biological activity. During the Meteor cruise 55 along 11°N in the tropical Atlantic Ocean, a series of experiments were conducted to examine the biological vs. photochemical production of methyl iodide. A total of eight separate experiments were conducted. Production of CH3I in quartz glass flasks during 24 hour incubations (dark and natural sunlight) was measured under three experimental treatments: untreated seawater, filtered seawater (0.1 um pore size filter to exclude most phytoplankton and bacteria), and seawater that was poisoned with mercuric chloride. There were two clear findings from these experiments: (1) methyl iodide production was significantly higher in all the incubations that were exposed to the light than in the dark incubations; (2) there was no significant difference between CH3I production under the three experimental treatments. These results argue very strongly for the primary importance of photochemical production of CH3I as opposed to biogenic production at least for the tropical open ocean surface waters. Further experiments are required to investigate the reactants involved, their sources, the wavelength and depth dependence of production, etc. as well as (possibly related) sink processes.

  11. 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

  12. Current-induced atomic dynamics, instabilities, and Raman signals

    DEFF Research Database (Denmark)

    Lu, Jing Tao; Brandbyge, Mads; Hedegard, Per

    2012-01-01

    We derive and employ a semiclassical Langevin equation obtained from path integrals to describe the ionic dynamics of a molecular junction in the presence of electrical current. The electronic environment serves as an effective nonequilibrium bath. The bath results in random forces describing Joule...... heating, current-induced forces including the nonconservative wind force, dissipative frictional forces, and an effective Lorentz-type force due to the Berry phase of the nonequilibrium electrons. Using a generic two-level molecular model, we highlight the importance of both current-induced forces...... and Joule heating for the stability of the system. We compare the impact of the different forces, and the wide-band approximation for the electronic structure on our result. We examine the current-induced instabilities (excitation of runaway "waterwheel" modes) and investigate the signature...

  13. Concurrency-Induced Transitions in Epidemic Dynamics on Temporal Networks.

    Science.gov (United States)

    Onaga, Tomokatsu; Gleeson, James P; Masuda, Naoki

    2017-09-08

    Social contact networks underlying epidemic processes in humans and animals are highly dynamic. The spreading of infections on such temporal networks can differ dramatically from spreading on static networks. We theoretically investigate the effects of concurrency, the number of neighbors that a node has at a given time point, on the epidemic threshold in the stochastic susceptible-infected-susceptible dynamics on temporal network models. We show that network dynamics can suppress epidemics (i.e., yield a higher epidemic threshold) when the node's concurrency is low, but can also enhance epidemics when the concurrency is high. We analytically determine different phases of this concurrency-induced transition, and confirm our results with numerical simulations.

  14. Concurrency-Induced Transitions in Epidemic Dynamics on Temporal Networks

    Science.gov (United States)

    Onaga, Tomokatsu; Gleeson, James P.; Masuda, Naoki

    2017-09-01

    Social contact networks underlying epidemic processes in humans and animals are highly dynamic. The spreading of infections on such temporal networks can differ dramatically from spreading on static networks. We theoretically investigate the effects of concurrency, the number of neighbors that a node has at a given time point, on the epidemic threshold in the stochastic susceptible-infected-susceptible dynamics on temporal network models. We show that network dynamics can suppress epidemics (i.e., yield a higher epidemic threshold) when the node's concurrency is low, but can also enhance epidemics when the concurrency is high. We analytically determine different phases of this concurrency-induced transition, and confirm our results with numerical simulations.

  15. Dynamic strain-induced transformation: An atomic scale investigation

    International Nuclear Information System (INIS)

    Zhang, H.; Pradeep, K.G.; Mandal, S.; Ponge, D.; Springer, H.; Raabe, D.

    2015-01-01

    Phase transformations provide the most versatile access to the design of complex nanostructured alloys in terms of grain size, morphology, local chemical constitution etc. Here we study a special case of deformation induced phase transformation. More specifically, we investigate the atomistic mechanisms associated with dynamic strain-induced transformation (DSIT) in a dual-phased multicomponent iron-based alloy at high temperatures. DSIT phenomena and the associated secondary phase nucleation were observed at atomic scale using atom probe tomography. The obtained local chemical composition was used for simulating the nucleation process which revealed that DSIT, occurring during load exertion, proceeds by a diffusion-controlled nucleation process

  16. An On-the-Fly Surface-Hopping Program JADE for Nonadiabatic Molecular Dynamics of Polyatomic Systems: Implementation and Applications.

    Science.gov (United States)

    Du, Likai; Lan, Zhenggang

    2015-04-14

    Nonadiabatic dynamics simulations have rapidly become an indispensable tool for understanding ultrafast photochemical processes in complex systems. Here, we present our recently developed on-the-fly nonadiabatic dynamics package, JADE, which allows researchers to perform nonadiabatic excited-state dynamics simulations of polyatomic systems at an all-atomic level. The nonadiabatic dynamics is based on Tully's surface-hopping approach. Currently, several electronic structure methods (CIS, TDHF, TDDFT(RPA/TDA), and ADC(2)) are supported, especially TDDFT, aiming at performing nonadiabatic dynamics on medium- to large-sized molecules. The JADE package has been interfaced with several quantum chemistry codes, including Turbomole, Gaussian, and Gamess (US). To consider environmental effects, the Langevin dynamics was introduced as an easy-to-use scheme into the standard surface-hopping dynamics. The JADE package is mainly written in Fortran for greater numerical performance and Python for flexible interface construction, with the intent of providing open-source, easy-to-use, well-modularized, and intuitive software in the field of simulations of photochemical and photophysical processes. To illustrate the possible applications of the JADE package, we present a few applications of excited-state dynamics for various polyatomic systems, such as the methaniminium cation, fullerene (C20), p-dimethylaminobenzonitrile (DMABN) and its primary amino derivative aminobenzonitrile (ABN), and 10-hydroxybenzo[h]quinoline (10-HBQ).

  17. Dynamics and mechanisms of chemotherapy-induced ovarian follicular depletion in women of fertile age

    DEFF Research Database (Denmark)

    Rosendahl, Mikkel; Andersen, Claus Yding; la Cour Freiesleben, Nina

    2010-01-01

    To study ovarian follicular dynamics during chemotherapy to understand the mechanisms behind chemotherapy-induced ovarian follicular depletion and to evaluate whether pretreatment levels of ovarian reserve markers were predictive of the posttreatment levels.......To study ovarian follicular dynamics during chemotherapy to understand the mechanisms behind chemotherapy-induced ovarian follicular depletion and to evaluate whether pretreatment levels of ovarian reserve markers were predictive of the posttreatment levels....

  18. Ozone budgets from the Dynamics and Chemistry of Marine Stratocumulus experiment

    Science.gov (United States)

    Kawa, S. R.; Pearson, R., Jr.

    1989-01-01

    Measurements from the Dynamics and Chemistry of marine Stratocumulus experiment have been used to study components of the regional ozone budget. The surface destruction rate is determined by eddy correlation of ozone and vertical velocity measured by a low-flying aircraft. Significant variability is found in the measured surface resistance; it is partially correlated with friction velocity but appears to have other controlling influences as well. The mean resistance is 4190 s/m which is higher (slower destruction) than most previous estimates for seawater. Flux and mean measurements throughout the marine boundary layer are used to estimate the net rate of in situ photochemical production/destruction of ozone. Averaged over the flights, ozone concentration is found to be near steady state, and a net of photochemical destruction of 0.02-0.07 ng/cu m per sec is diagnosed. This is an important confirmation of photochemical model results for the remote marine boundary layer. Ozone vertical distributions above the boundary layer show a strongly layered structure with very sharp gradients. These distributions are possibly related to the stratospheric ozone source.

  19. Ultrafast Dynamics in Light-Driven Molecular Rotary Motors Probed by Femtosecond Stimulated Raman Spectroscopy

    NARCIS (Netherlands)

    Hall, Christopher R.; Conyard, Jamie; Heisler, Ismael A.; Jones, Garth; Frost, James; Browne, Wesley R.; Feringa, Ben L.; Meech, Stephen R.

    2017-01-01

    Photochemical isomerization in sterically crowded chiral alkenes is the driving force for molecular rotary motors in nanoscale machines. Here the excited-state dynamics and structural evolution of the prototypical light-driven rotary motor are followed on the ultrafast time scale by femtosecond

  20. Water Treatment Process Intensification by Combination of Electrochemical and Photochemical Methods

    Czech Academy of Sciences Publication Activity Database

    Krystyník, Pavel; Klusoň, Petr; Tito, D.N.

    2015-01-01

    Roč. 94, SI (2015), s. 85-92 ISSN 0255-2701 R&D Projects: GA MPO(CZ) FR-TI1/065; GA TA ČR TA03010548 Institutional support: RVO:67985858 Keywords : electrocoagulation * photochemical oxidation * TOC removal Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 2.154, year: 2015

  1. Intraluminal bubble dynamics induced by lithotripsy shock wave

    Science.gov (United States)

    Song, Jie; Bai, Jiaming; Zhou, Yufeng

    2016-12-01

    Extracorporeal shock wave lithotripsy (ESWL) has been the first option in the treatment of calculi in the upper urinary tract since its introduction. ESWL-induced renal injury is also found after treatment and is assumed to associate with intraluminal bubble dynamics. To further understand the interaction of bubble expansion and collapse with the vessel wall, the finite element method (FEM) was used to simulate intraluminal bubble dynamics and calculate the distribution of stress in the vessel wall and surrounding soft tissue during cavitation. The effects of peak pressure, vessel size, and stiffness of soft tissue were investigated. Significant dilation on the vessel wall occurs after contacting with rapid and large bubble expansion, and then vessel deformation propagates in the axial direction. During bubble collapse, large shear stress is found to be applied to the vessel wall at a clinical lithotripter setting (i.e. 40 MPa peak pressure), which may be the mechanism of ESWL-induced vessel rupture. The decrease of vessel size and viscosity of soft tissue would enhance vessel deformation and, consequently, increase the generated shear stress and normal stresses. Meanwhile, a significantly asymmetric bubble boundary is also found due to faster axial bubble expansion and shrinkage than in radial direction, and deformation of the vessel wall may result in the formation of microjets in the axial direction. Therefore, this numerical work would illustrate the mechanism of ESWL-induced tissue injury in order to develop appropriate counteractive strategies for reduced adverse effects.

  2. Photochemical reactions in biological systems: probing the effect of the environment by means of hybrid quantum chemistry/molecular mechanics simulations.

    Science.gov (United States)

    Boggio-Pasqua, Martial; Burmeister, Carl F; Robb, Michael A; Groenhof, Gerrit

    2012-06-14

    Organisms have evolved a wide variety of mechanisms to utilize and respond to light. In many cases, the biological response is mediated by structural changes that follow photon absorption in a protein complex. The initial step in such cases is normally the photoisomerization of a highly conjugated prosthetic group. To understand better the factors controlling the isomerization, we perform atomistic molecular dynamics simulations. In this perspective article we briefly review the key theoretical concepts of photochemical reactions and present a practical simulation scheme for simulating photochemical reactions in biomolecular systems. In our scheme, a multi-configurational quantum mechanical description is used to model the electronic rearrangement for those parts of the system that are involved in the photon absorption. For the remainder, typically consisting of the apo-protein and the solvent, a simple force field model is used. The interactions in the systems are thus computed within a hybrid quantum/classical framework. Forces are calculated on-the-fly, and a diabatic surface hopping procedure is used to model the excited-state decay. To demonstrate how this method is used we review our studies on photoactivation of the photoactive yellow protein, a bacterial photoreceptor. We will show what information can be obtained from the simulations, and, by comparing to recent experimental findings, what the limitations of our simulations are.

  3. 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

  4. 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

  5. Investigating the pathway for the photochemical formation of VOCs in presence of an organic monolayer at the air/water interface.

    Science.gov (United States)

    Tinel, Liselotte; Rossignol, Stéphanie; Ciuraru, Raluca; George, Christian

    2015-04-01

    unsaturated aldehydes were detected and a reaction pathway, initiated by a H-abstraction of the surfactant by the excited HA*, has been proposed. This mechanism infers that the presence of the surface microlayer will enhance protonation and self-reactions, leading to the formation of dimers as suggested in [6]. These products could explain the formation of the unsaturated products observed. To confirm the hypothesis of an initiative step of H-abstraction, the system was simplified using OH radicals, generated by the photolysis of H2O2, in presence of an artificial organic layer of nonanoic acid. The VOCs produced, monitored by PTR/SRI-TOF-MS in NO+ and H3O+ ionization mode, were less abundant compared to the system with HA, but the same classes of products could be observed, including oxidation products such as aldehydes but also unsatured products like dienes. The underlying water was sampled before and after the experiment and analysed by HR-ESI-MS, showing mostly enrichment of oxidative products, such as hydroxy- and keto-acids immediately derived from the photochemical oxidation of the nonanoic acid layer. These products, showing lower volatility and higher polarity, partition preferentially to the bulk water. The results of this simplified system confirm the reaction mechanism proposed and the role an organic layer can play in the photochemical formation of VOCs, which could influence the marine boundary layer chemistry. 1. Peter S. Liss, R.A.D., ed. Sea Surface and Global Change. 1997, Cambridge University Press: Cambridge. 509. 2. Griffith, E.C. and V. Vaida, In situ observation of peptide bond formation at the water-air interface. Proceedings of the National Academy of Sciences, 2012. 109(39): p. 15697-15701. 3. Sinreich, R., et al., Ship-based detection of glyoxal over the remote tropical Pacific Ocean. Atmospheric Chemistry and Physics, 2010. 10(23): p. 11359-11371. 4. Kieber, R.J., X.L. Zhou, and K. Mopper, Formation of carbonyl-compounds from uv-induced

  6. Dynamic correlation of photo-excited electrons: Anomalous levels induced by light–matter coupling

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Xiankai [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, P.O. Box 800-204, Shanghai 201800 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Huai, Ping, E-mail: huaiping@sinap.ac.cn [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, P.O. Box 800-204, Shanghai 201800 (China); Song, Bo, E-mail: bosong@sinap.ac.cn [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, P.O. Box 800-204, Shanghai 201800 (China)

    2014-04-01

    Nonlinear light–matter coupling plays an important role in many aspects of modern physics, such as spectroscopy, photo-induced phase transition, light-based devices, light-harvesting systems, light-directed reactions and bio-detection. However, excited states of electrons are still unclear for nano-structures and molecules in a light field. Our studies unexpectedly present that light can induce anomalous levels in the electronic structure of a donor–acceptor nanostructure with the help of the photo-excited electrons transferring dynamically between the donor and the acceptor. Furthermore, the physics underlying is revealed to be the photo-induced dynamical spin–flip correlation among electrons. These anomalous levels can significantly enhance the electron current through the nanostructure. These findings are expected to contribute greatly to the understanding of the photo-excited electrons with dynamic correlations, which provides a push to the development and application of techniques based on photosensitive molecules and nanostructures, such as light-triggered molecular devices, spectroscopic analysis, bio-molecule detection, and systems for solar energy conversion.

  7. Spin-motive Force Induced by Domain Wall Dynamics in the Antiferromagnetic Spin Valve

    Science.gov (United States)

    Sugano, Ryoko; Ichimura, Masahiko; Takahashi, Saburo; Maekawa, Sadamichi; Crest Collaboration

    2014-03-01

    In spite of no net magnetization in antiferromagnetic (AF) textures, the local magnetic properties (Neel magnetization) can be manipulated in a similar fashion to ferromagnetic (F) ones. It is expected that, even in AF metals, spin transfer torques (STTs) lead to the domain wall (DW) motion and that the DW motion induces spin-motive force (SMF). In order to study the Neel magnetization dynamics and the resultant SMF, we treat the nano-structured F1/AF/F2 junction. The F1 and F2 leads behave as a spin current injector and a detector, respectively. Each F lead is fixed in the different magnetization direction. Torsions (DW in AF) are introduced reflecting the fixed magnetization of two F leads. We simulated the STT-induced Neel magnetization dynamics with the injecting current from F1 to F2 and evaluate induced SMF. Based on the adiabatic electron dynamics in the AF texture, Langevin simulations are performed at finite temperature. This research was supported by JST, CREST, Japan.

  8. 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

  9. Photochemical Microscale Electrophoresis Allows Fast Quantification of Biomolecule Binding.

    Science.gov (United States)

    Möller, Friederike M; Kieß, Michael; Braun, Dieter

    2016-04-27

    Intricate spatiotemporal patterns emerge when chemical reactions couple to physical transport. We induce electrophoretic transport by a confined photochemical reaction and use it to infer the binding strength of a second, biomolecular binding reaction under physiological conditions. To this end, we use the photoactive compound 2-nitrobenzaldehyde, which releases a proton upon 375 nm irradiation. The charged photoproducts locally perturb electroneutrality due to differential diffusion, giving rise to an electric potential Φ in the 100 μV range on the micrometer scale. Electrophoresis of biomolecules in this field is counterbalanced by back-diffusion within seconds. The biomolecule concentration is measured by fluorescence and settles proportionally to exp(-μ/D Φ). Typically, binding alters either the diffusion coefficient D or the electrophoretic mobility μ. Hence, the local biomolecule fluorescence directly reflects the binding state. A fit to the law of mass action reveals the dissociation constant of the binding reaction. We apply this approach to quantify the binding of the aptamer TBA15 to its protein target human-α-thrombin and to probe the hybridization of DNA. Dissociation constants in the nanomolar regime were determined and match both results in literature and in control experiments using microscale thermophoresis. As our approach is all-optical, isothermal and requires only nanoliter volumes at nanomolar concentrations, it will allow for the fast screening of biomolecule binding in low volume multiwell formats.

  10. 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.

  11. Ultrafast Excited State Dynamics in Molecular Motors : Coupling of Motor Length to Medium Viscosity

    NARCIS (Netherlands)

    Conyard, Jamie; Stacko, Peter; Chen, Jiawen; McDonagh, Sophie; Hall, Christopher R.; Laptenok, Sergey P.; Browne, Wesley R.; Feringa, Ben L.; Meech, Stephen R.

    2017-01-01

    Photochemically driven molecular motors convert the energy of incident radiation to intramolecular rotational motion. The motor molecules considered here execute four step unidirectional rotational motion. This comprises a pair of successive light induced isomerizations to a metastable state

  12. Ozonolysis and Subsequent Photolysis of unsaturated organic molecules: Model Systems for Photochemical Aging of Organic Aerosol Particles

    Science.gov (United States)

    Park, J.; Gomez, A. L.; Walser, M. L.; Lin, A.; Nizkorodov, S. A.

    2005-12-01

    Chemical and photochemical aging of organic species adsorbed on aerosol particle surfaces is believed to have a significant effect on cloud condensation properties of atmospheric aerosols. Ozone initiated oxidation reactions of thin films of undecylenic acid and alkene-terminated self assembled monolayers (SAMs) on SiO2 surface were investigated using a combination of spectroscopic and mass spectrometric techniques. Photolysis of the oxidized film in the tropospheric actinic region (λ>290 nm) readily produces formaldehyde and formic acid as gas-phase products. Photodissociation action spectra of the oxidized film suggest that organic peroxides are responsible for the enhanced photochemical activity. The presence of peroxides in the oxidized sample was confirmed by mass-spectrometric analysis and by an iodometric test. Significant polymerization resulting from secondary reactions of Criegee radicals during ozonolysis of the film is also observed. The reaction mechanism and its implications for photochemical aging of atmospheric aerosol particles will be discussed.

  13. Organic photochemical reactions on solid surfaces: Enrichment and separation of isotopes. Final report. SBIR-1988, Phase 2

    International Nuclear Information System (INIS)

    Ruderman, W.; Fehlner, J.; Spencer, J.

    1988-01-01

    The objectives of the Phase II program were to: (1) investigate organic photochemical reactions on solid porous silica surfaces, (2) utilize the magnetic isotope effect to develop a (13)C enrichment process using a fluidized bed reactor, and (3) investigate the possibility of enrichment of heavier isotopes having a nuclear spin. Although researchers were able to demonstrate a continuous fluidized bed (13)C enrichment process, analysis showed that the process could not compete with low temperature distillation of CO because of the high cost of the starting material, dibenzylketone (DBK), and the difficulty of converting the photochemical decomposition products back to DBK. However, the process shows promise for the separation of heavier isotopes such as (29)Si. The photochemical studies led to the discovery that the selectivity for terminal chlorination of alkanes can be increased more than 25 fold by sorbing the alkanes on ZSM-5 zeolites in a fluidized bed. The selectivity is ascribed to the presence of interfaces within the crystals

  14. Particle number concentration, size distribution and chemical composition during haze and photochemical smog episodes in Shanghai.

    Science.gov (United States)

    Wang, Xuemei; Chen, Jianmin; Cheng, Tiantao; Zhang, Renyi; Wang, Xinming

    2014-09-01

    The aerosol number concentration and size distribution as well as size-resolved particle chemical composition were measured during haze and photochemical smog episodes in Shanghai in 2009. The number of haze days accounted for 43%, of which 30% was severe (visibilitysmog episodes, about 5.89 times and 4.29 times those of clean days. The particle volume concentration and surface concentration in haze, photochemical smog and clean days were 102, 49, 15μm(3)/cm(3) and 949, 649, 206μm(2)/cm(3), respectively. As haze events got more severe, the number concentration of particles smaller than 50nm decreased, but the particles of 50-200nm and 0.5-1μm increased. The diurnal variation of particle number concentration showed a bimodal pattern in haze days. All soluble ions were increased during haze events, of which NH4(+), SO4(2-) and NO3(-) increased greatly, followed by Na(+), K(+), Ca(2+) and Cl(-). These ions were very different in size-resolved particles during haze and photochemical smog episodes. Copyright © 2014. Published by Elsevier B.V.

  15. Photochemical recombination of deep centers in silicon: decay of donor-acceptor pairs

    International Nuclear Information System (INIS)

    Adilov, K.A.

    1991-01-01

    Processes of photochemical recombination of deep impurity centers (DIC) in p-Si alloyed by Te, Zn and Fe occuring at 300-350 K under irradiation by super-low-energy light from δ 14 -10 17 quantum/cm 2 )Xs intensity impurity absorption range, are considered

  16. Atmospheric photochemical reactivity and ozone production at two sites in Hong Kong: Application of a Master Chemical Mechanism-photochemical box model

    Science.gov (United States)

    Ling, Z. H.; Guo, H.; Lam, S. H. M.; Saunders, S. M.; Wang, T.

    2014-09-01

    A photochemical box model incorporating the Master Chemical Mechanism (v3.2), constrained with a full suite of measurements, was developed to investigate the photochemical reactivity of volatile organic compounds at a semirural site (Mount Tai Mo Shan (TMS)) and an urban site (Tsuen Wan (TW)) in Hong Kong. The levels of ozone (O3) and its precursors, and the magnitudes of the reactivity of O3 precursors, revealed significant differences in the photochemistry at the two sites. Simulated peak hydroperoxyl radical (HO2) mixing ratios were similar at TW and TMS (p = 0.05), while the simulated hydroxyl radical (OH) mixing ratios were much higher at TW (p TMS, but at TW, both HCHO and O3 photolyses were found to be major contributors. By contrast, radical-radical reactions governed HOx radical losses at TMS, while at TW, the OH + NO2 reaction was found to dominate in the morning and the radical-radical reactions at noon. Overall, the conversion of NO to NO2 by HO2 dictated the O3 production at the two sites, while O3 destruction was dominated by the OH + NO2 reaction at TW, and at TMS, O3 photolysis and the O3 + HO2 reaction were the major mechanisms. The longer OH chain length at TMS indicated that more O3 was produced for each radical that was generated at this site.

  17. Vegetation Function and Physiology: Photosynthesis, Fluorescence and Non-photochemical Quenching (NPQ)

    Science.gov (United States)

    Zhang, Q.; Yao, T.

    2017-12-01

    Photosynthesis is a basic physiological function of vegetation that relies on PAR provided through photosynthetic pigments (mainly chlorophyll) for plant growth and biomass accumulation. Vegetation chlorophyll (chl) content and non-chlorophyll (non-chl) components vary with plant functional types (PFTs) and growing stages. The PAR absorbed by canopy chlorophyll (APARchl) is associated with photosynthesis (i.e., gross primary production, GPP) while the PAR absorbed by canopy non-chl components (APARnon-chl) is not associated with photosynthesis. Under non-optimal environmental conditions, vegetation is "stressed" and both photosynthesis (GPP) and light use efficiency are reduced, therefore, excess portions of APARchl are discarded as fluorescence or non-photochemical quenching (NPQ). The photochemical reflectance index (PRI) is a measurement related to NPQ. Both PRI and yield of solar induced chlorophyll fluorescence (SIFyield = SIF/APARchl) have been proposed as possible bio-indicators of LUEchl. We have successfully developed an algorithm to distinguish between chlorophyll and non-chl components of vegetation, and to retrieve fractional absorptions of PAR by chlorophyll (fAPARchl) and by non-chl components (fAPARnon-chl) with surface reflectance of MODIS bands 1 - 7. A method originally pioneered by Hanan et al. (2002) has been used to retrieve fAPAR for vegetation photosynthesis (fAPARPSN) at flux tower sites based on the light response curve of tower net ecosystem exchange (NEE) and incident PAR at low light intensity. We have also retrieved the PRI from MODIS data (bands 11 and 1) and have derived SIFyield with the Global Ozone Monitoring Experiment - 2 (GOME-2) SIF data. We find that fAPARPSN at flux tower sites matches well with site fAPARchl, and ratio fAPARnon-chl/fAPARchl varies largely. APARchl can explain >=78% variation in seasonal GPP . We disentangle the possible impact of fAPARchl on PRI from physiological stress response, disentangle the possible

  18. A model assessment of the ability of lake water in Terra Nova Bay, Antarctica, to induce the photochemical degradation of emerging contaminants.

    Science.gov (United States)

    Minella, Marco; Maurino, Valter; Minero, Claudio; Vione, Davide

    2016-11-01

    The shallow lakes located in Terra Nova Bay, Antarctica, are free from ice for only up to a couple of months (mid December to early/mid February) during the austral summer. In the rest of the year, the ice cover shields the light and inhibits the photochemical processes in the water columns. Previous work has shown that chromophoric dissolved organic matter (CDOM) in these lakes is very reactive photochemically. A model assessment is here provided of lake-water photoreactivity in field conditions, based on experimental data of lake water absorption spectra, chemistry and photochemistry obtained previously, taking into account the water depth and the irradiation conditions of the Antarctic summer. The chosen sample contaminants were the solar filter benzophenone-3 and the antimicrobial agent triclosan, which have very well known photoreactivity and have been found in a variety of environmental matrices in the Antarctic continent. The two compounds would have a half-life time of just a few days or less in the lake water during the Antarctic summertime, largely due to reaction with CDOM triplet states ((3)CDOM*). In general, pollutants that occur in the ice and could be released to lake water upon ice melting (around or soon after the December solstice) would be quickly photodegraded if they undergo fast reaction with (3)CDOM*. With some compounds, the important (3)CDOM* reactions might favour the production of harmful secondary pollutants, such as 2,8-dichlorodibenzodioxin from the basic (anionic) form of triclosan. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. Studies of Silyl-Transfer Photochemical Reactions of N-[(Trimethylsilyl)alkyl]saccharins

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Dae Won; Oh, Sun Wha; Park, Hea Jung; Yoon, Ung Chan [Pusan National University, Busan (Korea, Republic of); Kim, Dong Uk [Daegu National University of Education, Daegu (Korea, Republic of); Xue, Jin Ying [Harbin Normal University, Harbin (China); Mariano, Patrick S. [University of New Mexico, Albuquerque (United States)

    2010-09-15

    Photochemical studies of N-[(trimethylsilyl)alkyl]saccharins were carried out to investigate their photochemical behavior. Depending on the nature of the substrate and the solvent system employed, reactions of these substances can take place by either SET-promoted silyl migration from carbon to either the amide carbonyl or sulfonyl oxygen or by a N-S homolysis route. The results of the current studies show that an azomethine ylide, arising from a SET-promoted silyl migration pathway, is generated in photoreactions of N-[(trimethylsilyl)methyl]saccharin and this intermediate reacts to give various photoproducts depending on the conditions employed. In addition, irradiation of N-[(trimethylsily)ethyl]saccharin produces an excited state that reacts through two pathways, the relative importance is governed by solvent polarity and protic nature. Finally, photoirradiation of N-[(trimethylsilyl)propyl]saccharin in a highly polar solvent system comprised of 35% aqueous MeOH gives rise to formation of a tricyclic pyrrolizidine and saccharin that generated via competitive SET-promoted silyl transfer and γ-hydrogen abstraction pathways.

  20. Studies of Silyl-Transfer Photochemical Reactions of N-[(Trimethylsilyl)alkyl]saccharins

    International Nuclear Information System (INIS)

    Cho, Dae Won; Oh, Sun Wha; Park, Hea Jung; Yoon, Ung Chan; Kim, Dong Uk; Xue, Jin Ying; Mariano, Patrick S.

    2010-01-01

    Photochemical studies of N-[(trimethylsilyl)alkyl]saccharins were carried out to investigate their photochemical behavior. Depending on the nature of the substrate and the solvent system employed, reactions of these substances can take place by either SET-promoted silyl migration from carbon to either the amide carbonyl or sulfonyl oxygen or by a N-S homolysis route. The results of the current studies show that an azomethine ylide, arising from a SET-promoted silyl migration pathway, is generated in photoreactions of N-[(trimethylsilyl)methyl]saccharin and this intermediate reacts to give various photoproducts depending on the conditions employed. In addition, irradiation of N-[(trimethylsily)ethyl]saccharin produces an excited state that reacts through two pathways, the relative importance is governed by solvent polarity and protic nature. Finally, photoirradiation of N-[(trimethylsilyl)propyl]saccharin in a highly polar solvent system comprised of 35% aqueous MeOH gives rise to formation of a tricyclic pyrrolizidine and saccharin that generated via competitive SET-promoted silyl transfer and γ-hydrogen abstraction pathways

  1. Molecular dynamics studies of the ion beam induced crystallization in silicon

    International Nuclear Information System (INIS)

    Marques, L.A.; Caturla, M.J.; Huang, H.

    1995-01-01

    We have studied the ion bombardment induced amorphous-to-crystal transition in silicon using molecular dynamics techniques. The growth of small crystal seeds embedded in the amorphous phase has been monitored for several temperatures in order to get information on the effect of the thermal temperature increase introduced by the incoming ion. The role of ion-induced defects on the growth has been also studied

  2. A framework of induced hyperspace dynamical systems equipped with the hit-or-miss topology

    International Nuclear Information System (INIS)

    Wang Yangeng; Wei Guo; Campbell, William H.; Bourquin, Steven

    2009-01-01

    For any dynamical system (E,d,f), where E is Hausdorff locally compact second countable (HLCSC), let F (resp., 2 E ) denote the space of all closed subsets (resp., non-empty closed subsets) of E equipped with the hit-or-miss topology τ f . Both F and 2 E are again HLCSC (F actually compact), thus metrizable. Let ρ be such a metric (three metrics available). The main purpose is to determine the conditions on f that ensure the continuity of the induced hyperspace maps 2 f :F→F and 2 f :2 E →2 E defined by 2 f (F)=f(F). With this setting, the induced hyperspace systems (F,ρ,2 f ) and (2 E ,ρ,2 f ) are compact and locally compact dynamical systems, respectively. Consequently, dynamical properties, particularly metric related dynamical properties, of the given system (E,d,f) can be explored through these hyperspace systems. In contrast, when the Vietoris topology τ v is equipped on 2 E , the space of the induced hyperspace topological dynamical system (2 E ,τ v ,2 f ) is not metrizable if E is not compact metrizable, e.g., E=R n , implying that metric related dynamical concepts cannot be defined for (2 E ,τ v ,2 f ). Moreover, two examples are provided to illustrate the advantages of the hit-or-miss topology as compared to the Vietoris topology.

  3. Photochemical Cyclopolymerization of Polyimides in Ultraviolet Ridgidizing Composites for Use in Inflatable Structures, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This innovation uses photochemical cyclopolymerization of polyimides to manufacture ultraviolet rigidizable composites for use in RIS (ridgidizing inflatable)...

  4. A Highly Effective Photochemical System for Complex Treatment of Heavily Contaminated Wastewaters

    Czech Academy of Sciences Publication Activity Database

    Krystyník, Pavel; Klusoň, Petr; Hejda, S.; Mašín, P.; Tito, D.N.

    2014-01-01

    Roč. 86, č. 11 (2014), s. 2212-2220 ISSN 1061-4303 R&D Projects: GA MPO(CZ) FR-TI1/065 Institutional support: RVO:67985858 Keywords : advanced oxidation processes * photochemical oxidation * wastewater treatment Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 0.865, year: 2014

  5. Dynamics of defect-induced dark solitons in an exciton-polariton condensate

    Science.gov (United States)

    Opala, Andrzej; Pieczarka, Maciej; Bobrovska, Nataliya; Matuszewski, Michał

    2018-04-01

    We study theoretically the emission of dark solitons induced by a moving defect in a nonresonantly pumped exciton-polariton condensate. The number of created dark solitons per unit of time is found to be strongly dependent on the pump power. We relate the observed dynamics of this process to the oscillations of the drag force experienced by the condensate. We investigate the stability of the polariton quantum fluid and present various types of dynamics depending on the condensate and moving obstacle parameters. Furthermore, we provide analytical expressions for dark soliton dynamics using the variational method adapted to the nonequilibrium polariton system. The determined dynamical equations are found to be in excellent agreement with the results of numerical simulations.

  6. Nuclear dynamics of radiation-induced foci in euchromatin and heterochromatin

    International Nuclear Information System (INIS)

    Chiolo, Irene; Tang, Jonathan; Georgescu, Walter; Costes, Sylvain V.

    2013-01-01

    Repair of double strand breaks (DSBs) is essential for cell survival and genome integrity. While much is known about the molecular mechanisms involved in DSB repair and checkpoint activation, the roles of nuclear dynamics of radiation-induced foci (RIF) in DNA repair are just beginning to emerge. Here, we summarize results from recent studies that point to distinct features of these dynamics in two different chromatin environments: heterochromatin and euchromatin. We also discuss how nuclear architecture and chromatin components might control these dynamics, and the need of novel quantification methods for a better description and interpretation of these phenomena. These studies are expected to provide new biomarkers for radiation risk and new strategies for cancer detection and treatment

  7. Nuclear dynamics of radiation-induced foci in euchromatin and heterochromatin

    Energy Technology Data Exchange (ETDEWEB)

    Chiolo, Irene; Tang, Jonathan; Georgescu, Walter; Costes, Sylvain V.

    2013-10-01

    Repair of double strand breaks (DSBs) is essential for cell survival and genome integrity. While much is known about the molecular mechanisms involved in DSB repair and checkpoint activation, the roles of nuclear dynamics of radiation-induced foci (RIF) in DNA repair are just beginning to emerge. Here, we summarize results from recent studies that point to distinct features of these dynamics in two different chromatin environments: heterochromatin and euchromatin. We also discuss how nuclear architecture and chromatin components might control these dynamics, and the need of novel quantification methods for a better description and interpretation of these phenomena. These studies are expected to provide new biomarkers for radiation risk and new strategies for cancer detection and treatment.

  8. Biological diversity of photosynthetic reaction centers and the solid-state photo-CIDNP effect

    NARCIS (Netherlands)

    Roy, Esha

    2007-01-01

    Photosynthetic reaction centers (RCs) from plants, heliobacteria and green sulphur bacteria has been investigated with photochemically induced dynamic nuclear polarization (photo-CIDNP) MAS NMR. In photosystem (PS) I of spinach, all signals appear negative which is proposed by a predominance of the

  9. Reduction of Guanosyl Radical by Cysteine and Cysteine-Glycine Studied by Time-Resolved CIDNP

    NARCIS (Netherlands)

    Morozova, O.B.; Kaptein, R.; Yurkovskaya, A.V.

    2012-01-01

    As a model for chemical DNA repair, reduction of guanosyl radicals in the reaction with cysteine or the dipeptide cysteine-glycine has been studied by time-resolved chemically induced dynamic nuclear polarization (CIDNP). Radicals were generated photochemically by pulsed laser irradiation of a

  10. Quantum chaos induced by nonadiabatic coupling in wave-packet dynamics

    International Nuclear Information System (INIS)

    Higuchi, Hisashi; Takatsuka, Kazuo

    2002-01-01

    The effect of nonadiabatic coupling due to breakdown of the Born-Oppenheimer approximation on chaos is investigated. A couple of measures (indicators) that detect the extent of chaos in wave-packet dynamics on coupled potential functions are devised. Using them, we show that chaos is indeed induced by a nonadiabatic coupling in individual time-dependent wave-packet dynamics. This chaos is genuinely of quantum nature, since it arises from bifurcation and merging of a wave packet at the quasicrossing region of two coupled potential functions

  11. Photochemical degradation of the carbapenem antibiotics imipenem and meropenem in aqueous solutions under solar radiation.

    Science.gov (United States)

    Reina, Alejandro Cabrera; Martínez-Piernas, Ana B; Bertakis, Yannis; Brebou, Christina; Xekoukoulotakis, Nikolaos P; Agüera, Ana; Sánchez Pérez, José Antonio

    2018-01-01

    This paper deals with the photochemical fate of two representative carbapenem antibiotics, namely imipenem and meropenem, in aqueous solutions under solar radiation. The analytical method employed for the determination of the target compounds in various aqueous matrices, such as ultrapure water, municipal wastewater treatment plant effluents, and river water, at environmentally relevant concentrations, was liquid chromatography coupled with hybrid triple quadrupole-linear ion trap-mass spectrometry. The absorption spectra of both compounds were measured in aqueous solutions at pH values from 6 to 8, and both compounds showed a rather strong absorption band centered at about 300 nm, while their molar absorption coefficient was in the order from 9 × 10 3 -10 4  L mol -1  cm -1 . The kinetics of the photochemical degradation of the target compounds was studied in aqueous solutions under natural solar radiation in a solar reactor with compound parabolic collectors. It was found that the photochemical degradation of both compounds at environmentally relevant concentrations follows first order kinetics and the quantum yield was in the order of 10 -3  mol einsten -1 . Several parameters were studied, such as solution pH, the presence of nitrate ions and humic acids, and the effect of water matrix. In all cases, it was found that the presence of various organic and inorganic constituents in the aqueous matrices do not contribute significantly, either positively or negatively, to the photochemical degradation of both compounds under natural solar radiation. In a final set of photolysis experiments, the effect of the level of irradiance was studied under simulated solar radiation and it was found that the quantum yield for the direct photodegradation of both compounds remained practically constant by changing the incident solar irradiance from 28 to 50 W m -2 . Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Photochemical reaction of Si-substituted ethynylsilanes with 1,2-ethanedithiol

    Energy Technology Data Exchange (ETDEWEB)

    Voronkov, M.G.; Brodskaya, E.I.; Kalabin, G.A.; Vlasova, N.N.; Yarosh, O.G.; Zhila, G.Y.

    1985-12-01

    The authors investigate the chief products of the photochemical reactions of Si-substituted ethynylsilanes with 1,2,-ethanedithiol at 60-70 C. It is found that the chief products are 2-triorganylsilyl-substituted 1,4-dithiacyclopentanes and 1,4-dithiacyclohexanes. On lowering the temperature to -30 C, formation of bis (triorganylsilyl)-substituted 1,4,7,10-tetrathiacyclododecanes occurs along with the abo ve-mentioned five- and six-membered heterocycles.

  13. Femtosecond photodissociation dynamics of I studied by ion imaging

    DEFF Research Database (Denmark)

    Larsen, J.J.; Bjerre, N.; Mørkbak, N.J.

    1998-01-01

    on imaging is employed to analyze the fragments from timed Coulomb explosion studies of femtosecond (fs) molecular dynamics. The technique provides high detection efficiency and direct recording of the two-dimensional velocity of all ionized fragments. We illustrate the approach by studying...... agreement with quantum mechanical wave packet simulations. We discuss the perspectives for extending the studies to photochemical reactions of small polyatomic molecules...

  14. 5-FU resistant EMT-like pancreatic cancer cells are hypersensitive to photochemical internalization of the novel endoglin-targeting immunotoxin CD105-saporin.

    Science.gov (United States)

    Lund, Kaja; Olsen, Cathrine Elisabeth; Wong, Judith Jing Wen; Olsen, Petter Angell; Solberg, Nina Therese; Høgset, Anders; Krauss, Stefan; Selbo, Pål Kristian

    2017-12-19

    Development of resistance to 5-fluorouracil (5-FU) is a major problem in treatment of various cancers including pancreatic cancer. In this study, we reveal important resistance mechanisms and photochemical strategies to overcome 5-FU resistance in pancreatic adenocarcinoma. 5-FU resistant (5-FUR), epithelial-to-mesenchymal-like sub-clones of the wild type pancreatic cancer cell line Panc03.27 were previously generated in our lab. We investigated the cytotoxic effect of the endosomal/lysosomal-localizing photosensitizer TPCS 2a (fimaporfin) combined with light (photochemical treatment, PCT) using MTS viability assay, and used fluorescence microscopy to show localization of TPCS 2a and to investigate the effect of photodamage of lysosomes. Flow cytometric analysis was performed to investigate uptake of photosensitizer and to assess intracellular ROS levels. Expression and localization of LAMP1 was assessed using RT-qPCR, western blotting, and structured illumination microscopy. MTS viability assay was used to assess the effect of combinations of 5-FU, chloroquine (CQ), and photochemical treatment. Expression of CD105 was investigated using RT-qPCR, western blotting, flow cytometry, and fluorescence microscopy, and co-localization of TPCS 2a and anti-CD105-saporin was assessed using microscopy. Lastly, the MTS assay was used to investigate cytotoxic effects of photochemical internalization (PCI) of the anti-CD105-immunotoxin. The 5-FUR cell lines display hypersensitivity to PCT, which was linked to increased uptake of TPCS 2a , altered lysosomal distribution, lysosomal photodamage and increased expression of the lysosomal marker LAMP-1 in the 5-FUR cells. We show that inhibition of autophagy induced by either chloroquine or lysosomal photodamage increases the sensitivity to 5-FU in the resistant cells. The three 5-FUR sub-clones overexpress Endoglin (CD105). Treatment with the immunotoxin anti-CD105-saporin alone significantly reduced the viability of the CD105

  15. Photochemical alteration of organic carbon draining permafrost soils shifts microbial metabolic pathways and stimulates respiration.

    Science.gov (United States)

    Ward, Collin P; Nalven, Sarah G; Crump, Byron C; Kling, George W; Cory, Rose M

    2017-10-03

    In sunlit waters, photochemical alteration of dissolved organic carbon (DOC) impacts the microbial respiration of DOC to CO 2 . This coupled photochemical and biological degradation of DOC is especially critical for carbon budgets in the Arctic, where thawing permafrost soils increase opportunities for DOC oxidation to CO 2 in surface waters, thereby reinforcing global warming. Here we show how and why sunlight exposure impacts microbial respiration of DOC draining permafrost soils. Sunlight significantly increases or decreases microbial respiration of DOC depending on whether photo-alteration produces or removes molecules that native microbial communities used prior to light exposure. Using high-resolution chemical and microbial approaches, we show that rates of DOC processing by microbes are likely governed by a combination of the abundance and lability of DOC exported from land to water and produced by photochemical processes, and the capacity and timescale that microbial communities have to adapt to metabolize photo-altered DOC.The role of dissolved organic carbon (DOC) photo-alteration in the microbial respiration of DOC to CO 2 is unclear. Here, the authors show that the impact of this mechanism depends on whether photo-alteration of DOC produces or removes molecules used by native microbial communities prior to light exposure.

  16. 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.

  17. Numerical results on noise-induced dynamics in the subthreshold regime for thermoacoustic systems

    Science.gov (United States)

    Gupta, Vikrant; Saurabh, Aditya; Paschereit, Christian Oliver; Kabiraj, Lipika

    2017-03-01

    Thermoacoustic instability is a serious issue in practical combustion systems. Such systems are inherently noisy, and hence the influence of noise on the dynamics of thermoacoustic instability is an aspect of practical importance. The present work is motivated by a recent report on the experimental observation of coherence resonance, or noise-induced coherence with a resonance-like dependence on the noise intensity as the system approaches the stability margin, for a prototypical premixed laminar flame combustor (Kabiraj et al., Phys. Rev. E, 4 (2015)). We numerically investigate representative thermoacoustic models for such noise-induced dynamics. Similar to the experiments, we study variation in system dynamics in response to variations in the noise intensity and in a critical control parameter as the systems approach their stability margins. The qualitative match identified between experimental results and observations in the representative models investigated here confirms that coherence resonance is a feature of thermoacoustic systems. We also extend the experimental results, which were limited to the case of subcritical Hopf bifurcation, to the case of supercritical Hopf bifurcation. We identify that the phenomenon has qualitative differences for the systems undergoing transition via subcritical and supercritical Hopf bifurcations. Two important practical implications are associated with the findings. Firstly, the increase in noise-induced coherence as the system approaches the onset of thermoacoustic instability can be considered as a precursor to the instability. Secondly, the dependence of noise-induced dynamics on the bifurcation type can be utilised to distinguish between subcritical and supercritical bifurcation prior to the onset of the instability.

  18. Cancellation Effects in CSR Induced Bunch Transverse Dynamics in Bends

    International Nuclear Information System (INIS)

    Li, R.

    2002-01-01

    The partial cancellation between the effect of centrifugal space charge force on transverse bunch dynamics and the potential energy effect has been a long-standing controversial issue in the study of coherent synchrotron radiation (CSR) induced bunch dynamics in bends. In this paper, we clarify our definition of the ''centrifugal space charge force,'' and discuss the meaning of the ''cancellation effect'' and its general application. We further use simulation to demonstrate the cancellation in both steady state and transient regimes, and show the behavior of the effective transverse force

  19. Thermally induced all-optical inverter and dynamic hysteresis loops in graphene oxide dispersions.

    Science.gov (United States)

    Melle, Sonia; Calderón, Oscar G; Egatz-Gómez, Ana; Cabrera-Granado, E; Carreño, F; Antón, M A

    2015-11-01

    We experimentally study the temporal dynamics of amplitude-modulated laser beams propagating through a water dispersion of graphene oxide sheets in a fiber-to-fiber U-bench. Nonlinear refraction induced in the sample by thermal effects leads to both phase reversing of the transmitted signals and dynamic hysteresis in the input-output power curves. A theoretical model including beam propagation and thermal lensing dynamics reproduces the experimental findings.

  20. A review of photochemical approaches for the treatment of a wide range of pesticides.

    Science.gov (United States)

    Reddy, P Venkata Laxma; Kim, Ki-Hyun

    2015-03-21

    Pesticides are renowned as some of the most pernicious chemicals known to humankind. Nine out of twelve most hazardous and persistent organic chemicals on planet have been identified as pesticides and their derivatives. Because of their strong recalcitrant nature, it often becomes a difficult task to treat them by conventional approaches. It is well perceived that many factors can interfere with the degradation of pesticides under ambient conditions, e.g., media, light intensity, humic content, and other biological components. However, for the effective treatment of pesticides, photochemical methods are viewed as having clear and perceivable advantages. In this article, we provide a review of the fundamental characteristics of photochemical approaches for pesticide treatment and the factors governing their capacity and potential in such a process. Copyright © 2014 Elsevier B.V. All rights reserved.

  1. Estimation of flow stress of radiation induced F/M steels using molecular dynamics and discrete dislocation dynamics approach

    International Nuclear Information System (INIS)

    More, Ameya; Dutta, B.K.; Durgaprasad, P.V.; Arya, A.K.

    2012-01-01

    Fe-Cr based Ferritic/Martensitic (F/M) steels are the candidate structural materials for future fusion reactors. In this work, a multi-scale approach comprising atomistic Molecular Dynamics (MD) simulations and Discrete Dislocation Dynamics (DDD) simulations are used to model the effect of irradiation dose on the flow stress of F/M steels. At the atomic scale, molecular dynamics simulations are used to study the dislocation interaction with irradiation induced defects, i.e. voids and He bubbles. Whereas, the DDD simulations are used to estimate the change in flow stress of the material as a result of irradiation hardening. (author)

  2. UV inactivation of enzymes in supramolecular complexes of biological membranes. The phenomenon of photochemical allotropy

    International Nuclear Information System (INIS)

    Konev, S.V.; Volotovskij, I.D.; Sheiko, L.M.

    1978-01-01

    The photosensitivity of erythrocyte acetylcholinesterase (AChE) is different in its free and membrane-bound states. The modification of the structure of membraneous lipids by phospholipases A 2 , C and D or by cholesterol depletion is accompanied by a change in AChE photosensitivity. UV light was demonstrated to induce cooperative structural transitions in the erythrocyte membrane. This follows from the data obtained by circular dichroism and solubilization in detergents. In contrast to free AChE, UV light acts on the membraneous enzyme as a mixed inhibitor (simultaneous change in Vsub(max) and Ksub(m)). The anomalous behaviour of membrane-bound enzyme, termed the phenomenon of photochemical allotropy, is associated with a modification of the structure within the microenvironment of the residual AChE. The phenomenon depends on membrane integrity, and disappears after treatment of erythrocyte ghosts with ultrasound, trypsin, phospholipases and neuraminidase and remains unchanged in cholesterol-depleted membranes. The nature and localization of events responsible for this phenomenon are discussed. (author)

  3. Research on Greenhouse-Gas-Induced Climate Change

    Energy Technology Data Exchange (ETDEWEB)

    Schlesinger, M. E.

    2001-07-15

    During the 5 years of NSF grant ATM 95-22681 (Research on Greenhouse-Gas-Induced Climate Change, $1,605,000, 9/15/1995 to 8/31/2000) we have performed work which we are described in this report under three topics: (1) Development and Application of Atmosphere, Ocean, Photochemical-Transport, and Coupled Models; (2) Analysis Methods and Estimation; and (3) Climate-Change Scenarios, Impacts and Policy.

  4. Complete synchronization of the global coupled dynamical network induced by Poisson noises.

    Science.gov (United States)

    Guo, Qing; Wan, Fangyi

    2017-01-01

    The different Poisson noise-induced complete synchronization of the global coupled dynamical network is investigated. Based on the stability theory of stochastic differential equations driven by Poisson process, we can prove that Poisson noises can induce synchronization and sufficient conditions are established to achieve complete synchronization with probability 1. Furthermore, numerical examples are provided to show the agreement between theoretical and numerical analysis.

  5. Circumvention of resistance to photodynamic therapy in doxorubicin-resistant sarcoma by photochemical internalization of gelonin.

    Science.gov (United States)

    Olsen, Cathrine Elisabeth; Berg, Kristian; Selbo, Pål Kristian; Weyergang, Anette

    2013-12-01

    A wide range of anti-cancer therapies have been shown to induce resistance upon repetitive treatment and such adapted resistance may also cause cross-resistance to other treatment modalities. We here show that MES-SA/Dx5 cells with adapted resistance to doxorubicin (DOX) are cross-resistant to photodynamic therapy (PDT). A DOX-induced increased expression of the reactive oxygen species (ROS)-scavenging proteins glutathione peroxidase (GPx) 1 and GPx4 in MES-SA/Dx5 cells was indicated as the mechanism of resistance to PDT in line with the reduction in PDT-generated ROS observed in this cell line. ROS-induced p38 activation was, in addition, shown to be reduced to one-third of the signal of the parental MES-SA cells 2h after PDT, and addition of the p38 inhibitor SB203580 confirmed p38 activation as a death signal after PDT in the MES-SA cells. The MES-SA/Dx5 cells were also cross-resistant to ionizing radiation in agreement with the increased GPx1 and GPx4 expression. Surprisingly, PDT-induced endo/lysosomal release of the ribosome-inactivating protein gelonin (photochemical internalization (PCI)) was more effective in the PDT-resistant MES-SA/Dx5 cells, as measured by synergy calculations in both cell lines. Analysis of death-inducing signaling indicated a low activation of caspase-3 and a strong PARP I cleavage after PDT and PCI in both cell lines. The PARP I activation was, however, stronger after PCI than after PDT in the MES-SA cells, but not in the MES-SA/Dx5 cells, and therefore cannot explain the strong PCI effect in the MES-SA/Dx5 cells. In conclusion PCI of recombinant gelonin circumvents ROS resistance in an apoptosis-independent manner. © 2013 Elsevier Inc. All rights reserved.

  6. Nonlinear absorption dynamics using field-induced surface hopping: zinc porphyrin in water.

    Science.gov (United States)

    Röhr, Merle I S; Petersen, Jens; Wohlgemuth, Matthias; Bonačić-Koutecký, Vlasta; Mitrić, Roland

    2013-05-10

    We wish to present the application of our field-induced surface-hopping (FISH) method to simulate nonlinear absorption dynamics induced by strong nonresonant laser fields. We provide a systematic comparison of the FISH approach with exact quantum dynamics simulations on a multistate model system and demonstrate that FISH allows for accurate simulations of nonlinear excitation processes including multiphoton electronic transitions. In particular, two different approaches for simulating two-photon transitions are compared. The first approach is essentially exact and involves the solution of the time-dependent Schrödinger equation in an extended manifold of excited states, while in the second one only transiently populated nonessential states are replaced by an effective quadratic coupling term, and dynamics is performed in a considerably smaller manifold of states. We illustrate the applicability of our method to complex molecular systems by simulating the linear and nonlinear laser-driven dynamics in zinc (Zn) porphyrin in the gas phase and in water. For this purpose, the FISH approach is connected with the quantum mechanical-molecular mechanical approach (QM/MM) which is generally applicable to large classes of complex systems. Our findings that multiphoton absorption and dynamics increase the population of higher excited states of Zn porphyrin in the nonlinear regime, in particular in solution, provides a means for manipulating excited-state properties, such as transient absorption dynamics and electronic relaxation. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Induced gravity and the attractor dynamics of dark energy/dark matter

    International Nuclear Information System (INIS)

    Cervantes-Cota, Jorge L.; Putter, Roland de; Linder, Eric V.

    2010-01-01

    Attractor solutions that give dynamical reasons for dark energy to act like the cosmological constant, or behavior close to it, are interesting possibilities to explain cosmic acceleration. Coupling the scalar field to matter or to gravity enlarges the dynamical behavior; we consider both couplings together, which can ameliorate some problems for each individually. Such theories have also been proposed in a Higgs-like fashion to induce gravity and unify dark energy and dark matter origins. We explore restrictions on such theories due to their dynamical behavior compared to observations of the cosmic expansion. Quartic potentials in particular have viable stability properties and asymptotically approach general relativity

  8. In situ airborne measurements of aerosol optical properties during photochemical pollution events

    Science.gov (United States)

    Mallet, M.; van Dingenen, R.; Roger, J. C.; Despiau, S.; Cachier, H.

    2005-02-01

    Dry aerosol optical properties (scattering, absorbing coefficients, and single scattering albedo) were derived from in situ airborne measurements during two photochemical pollution events (25 and 26 June) observed during the Experience sur Site pour Contraindre les Modeles de Pollution atmospherique et de Transport d'Emissions (ESCOMPTE) experiment. Two flights were carried out during daytime (one during the morning and one at noon) over a domain, allowing the investigation of how an air pollution event affects the particle optical properties. Both horizontal distribution and vertical profiles are presented. Results from the horizontal mapping show that plumes of enhanced scattering and absorption are formed in the planetary boundary layer (PBL) during the day in the sea breeze-driven outflow of the coastal urban-industrial area of Marseille-Fos de Berre. The domain-averaged scattering coefficient (at 550 nm) over land σs changes from 35 (28) Mm-1 during land breeze to 63 (43) Mm-1 during sea breeze on 25 June (26 June), with local maxima reaching > 100 Mm-1. The increase in the scattering coefficient is associated with new particle formation, indicative of secondary aerosol formation. Simultaneously, the domain-averaged absorption coefficient increases from 5.6 (3.4) Mm-1 to 9.3 (8.0) Mm-1. The pollution plume leads to strong gradients in the single scattering albedo ωo over the domain studied, with local values as low as 0.73 observed inside the pollution plume. The role of photochemistry and secondary aerosol formation during the 25 June case is shown to increase ωo and to make the aerosol more `reflecting' while the plume moves away from the sources. The lower photochemical activity, observed in the 26 June case, induces a relatively higher contribution of black carbon, making the aerosol more absorbing. Results from vertical profiles at a single near-urban location in the domain indicate that the changes in optical properties happen almost entirely within

  9. Memory-induced nonlinear dynamics of excitation in cardiac diseases.

    Science.gov (United States)

    Landaw, Julian; Qu, Zhilin

    2018-04-01

    Excitable cells, such as cardiac myocytes, exhibit short-term memory, i.e., the state of the cell depends on its history of excitation. Memory can originate from slow recovery of membrane ion channels or from accumulation of intracellular ion concentrations, such as calcium ion or sodium ion concentration accumulation. Here we examine the effects of memory on excitation dynamics in cardiac myocytes under two diseased conditions, early repolarization and reduced repolarization reserve, each with memory from two different sources: slow recovery of a potassium ion channel and slow accumulation of the intracellular calcium ion concentration. We first carry out computer simulations of action potential models described by differential equations to demonstrate complex excitation dynamics, such as chaos. We then develop iterated map models that incorporate memory, which accurately capture the complex excitation dynamics and bifurcations of the action potential models. Finally, we carry out theoretical analyses of the iterated map models to reveal the underlying mechanisms of memory-induced nonlinear dynamics. Our study demonstrates that the memory effect can be unmasked or greatly exacerbated under certain diseased conditions, which promotes complex excitation dynamics, such as chaos. The iterated map models reveal that memory converts a monotonic iterated map function into a nonmonotonic one to promote the bifurcations leading to high periodicity and chaos.

  10. Bioavialability of Dom Photochemically Released from Resuspended Sediments

    Science.gov (United States)

    Avery, G. B., Jr.; Rainey, D. H.; Mead, R. N.; Skrabal, S. A.; Kieber, R. J.; Felix, J. D.; Helms, J. R.

    2016-02-01

    Little is known regarding the bioavailability of dissolved organic matter (DOM) released photochemically from resuspended estuarine sediments. Sediments were collected from two sites along the Cape Fear River estuary, NC, USA, size fractionated in 0.2 µm filtered Gulf Stream seawater and exposed to simulated sunlight for six hours. Light exposed samples resulted in increases of dissolved organic carbon (DOC) (34 ± 3 µM), chromophoric dissolved organic matter (CDOM) (a300nm, 2.7 m-1), and fluorescent dissolved organic matter (FDOM) (78.6 quinine sulfate equivalents (QSE)) compared to dark controls. Ultra high resolution mass spectrometric characterization indicated the photoreleased DOM was more oxidized and condensed based upon van Kreevlan analysis. Samples were then filtered and inoculated to a final ratio of 4% with coastal water sample filtered through a100 µm net to remove larger grazing organisms and particles while keeping most of bacterial community intact. All three parameters were monitored during a 30 day-long incubation in the dark to assess biological consumption and alteration. Previously light exposed samples had double (20 vs. 9 µM) the amount of DOC consumed compared to samples not previously exposed to light and twice the loss of CDOM (a300nm, 0.6 vs. 0.3 m-1) compared to samples not previously exposed to light. Previously light exposed samples resulted in a threefold loss of FDOM (9.5 QSE) compared to samples not previously exposed to light (2.8 QSE). Results of this study are important because they demonstrate dissolved organic matter released photochemically from resuspended sediments is more bioavailable than ambient material likely fueling secondary productivity and impacting ecosystem functioning in coastal regions.

  11. Line-shape theory and molecular dynamics in collision-induced light scattering

    International Nuclear Information System (INIS)

    Balucani, U.; Tognetti, V.; Vallauri, R.

    1979-01-01

    Molecular-dynamics studies in argon at 148 amagats are presented for gaining information on the dynamical properties responsible for the depolarized light scattering from simple fluids. The total and pair-correlation functions are computed within the simple dipole--induced-dipole model of polarizability anisotropy. The pair spectral shape is derived. These results are compared with a theoretical analysis based on a continued-fraction approach. The necessary frequency moments are calculated both in the low-density limit and taking into account first-order density corrections, and compared with the molecular-dynamics data. The agreement between the theoretical spectra and molecular-dynamics data shows the validity of the memory-function approach. The comparison with the real experimental results allows one to test the relevant physical contributions to the polarizability anisotropy

  12. Separation of the mercury isotopes by the indirect photochemical method

    International Nuclear Information System (INIS)

    Botter nee Bergheaud, F.; Scaringella nee Desnoyer, M.; Wacongne, M.

    1976-01-01

    A method of photochemical separation of the mercury isotopes by the so-called indirect route in which a gas stream of oxygen and butadiene containing a mixture of mercury isotopes is passed through one or a number of vessels placed in series. The gas stream is irradiated by a lamp containing mercury which is depleted in one or a number of the isotopes and said isotopes are recovered in a trap placed downstream of the vessel or vessels

  13. APEX (Aqueous Photochemistry of Environmentally occurring Xenobiotics): a free software tool to predict the kinetics of photochemical processes in surface waters.

    Science.gov (United States)

    Bodrato, Marco; Vione, Davide

    2014-04-01

    The APEX software predicts the photochemical transformation kinetics of xenobiotics in surface waters as a function of: photoreactivity parameters (direct photolysis quantum yield and second-order reaction rate constants with transient species, namely ˙OH, CO₃(-)˙, (1)O₂ and the triplet states of chromophoric dissolved organic matter, (3)CDOM*), water chemistry (nitrate, nitrite, bicarbonate, carbonate, bromide and dissolved organic carbon, DOC), and water depth (more specifically, the optical path length of sunlight in water). It applies to well-mixed surface water layers, including the epilimnion of stratified lakes, and the output data are average values over the considered water column. Based on intermediate formation yields from the parent compound via the different photochemical pathways, the software can also predict intermediate formation kinetics and overall yield. APEX is based on a photochemical model that has been validated against available field data of pollutant phototransformation, with good agreement between model predictions and field results. The APEX software makes allowance for different levels of knowledge of a photochemical system. For instance, the absorption spectrum of surface water can be used if known, or otherwise it can be modelled from the values of DOC. Also the direct photolysis quantum yield can be entered as a detailed wavelength trend, as a single value (constant or average), or it can be defined as a variable if unknown. APEX is based on the free software Octave. Additional applications are provided within APEX to assess the σ-level uncertainty of the results and the seasonal trend of photochemical processes.

  14. 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.

  15. Bubble dynamics and bubble-induced turbulence of a single-bubble chain

    Science.gov (United States)

    Lee, Joohyoung; Park, Hyungmin

    2016-11-01

    In the present study, the bubble dynamics and liquid-phase turbulence induced by a chain of bubbles injected from a single nozzle have been experimentally investigated. Using a high-speed two-phase particle image velociemtry, measurements on the bubbles and liquid-phase velocity field are conducted in a transparent tank filled with water, while varying the bubble release frequency from 0.1 to 35 Hz. The tested bubble size ranges between 2.0-3.2 mm, and the corresponding bubble Reynolds number is 590-1100, indicating that it belongs to the regime of path instability. As the release frequency increases, it is found that the global shape of bubble dispersion can be classified into two regimes: from asymmetric (regular) to axisymmetric (irregular). In particular, at higher frequency, the wake vortices of leading bubbles cause an irregular behaviour of the following bubble. For the liquid phase, it is found that a specific trend on the bubble-induced turbulence appears in a strong relation to the above bubble dynamics. Considering this, we try to provide a theoretical model to estimate the liquid-phase turbulence induced by a chain of bubbles. Supported by a Grant funded by Samsung Electronics, Korea.

  16. Enhanced cellular delivery of cell-penetrating peptide-peptide nucleic acid conjugates by photochemical internalization

    DEFF Research Database (Denmark)

    Shiraishi, Takehiko; Nielsen, Peter E

    2011-01-01

    (antisense activity) is still limited by endocytotic entrapment. We have shown that this low bioavailability can be greatly improved by combining CPP-PNA conjugate administration with a photochemical internalization technique using photosensitizers such as aluminum phthalocyanine (AlPcS(2a...

  17. 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.

  18. Photochemical degradation of PCBs in snow.

    Science.gov (United States)

    Matykiewiczová, Nina; Klánová, Jana; Klán, Petr

    2007-12-15

    This work represents the first laboratory study known to the authors describing photochemical behavior of persistent organic pollutants in snow at environmentally relevant concentrations. The snow samples were prepared by shock freezing of the corresponding aqueous solutions in liquid nitrogen and were UV-irradiated in a photochemical cold chamber reactor at -25 degrees C, in which simultaneous monitoring of snow-air exchange processeswas also possible. The main photodegradation pathway of two model snow contaminants, PCB-7 and PCB-153 (c approximately 100 ng kg(-1)), was found to be reductive dehalogenation. Possible involvement of the water molecules of snow in this reaction has been excluded by performing the photolyses in D2O snow. Instead, trace amounts of volatile organic compounds have been proposed to be the major source of hydrogen atom in the reduction, and this hypothesis was confirmed by the experiments with deuterated organic cocontaminants, such as d6-ethanol or d8-tetrahydrofuran. It is argued that bimolecular photoreduction of PCBs was more efficient or feasible than any other phototransformations under the experimental conditions used, including the coupling reactions. The photodegradation of PCBs, however, competed with a desorption process responsible for the pollutant loss from the snow samples, especially in case of lower molecular-mass congeners. Organic compounds, apparently largely located or photoproduced on the surface of snow crystals, had a predisposition to be released to the air but, at the same time, to react with other species in the gas phase. It is concluded that physicochemical properties of the contaminants and trace co-contaminants, their location and local concentrations in the matrix, and the wavelength and intensity of radiation are the most important factors in the evaluation of organic contaminants' lifetime in snow. Based on the results, it has been estimated that the average lifetime of PCBs in surface snow, connected

  19. Application of chaos theory to the particle dynamics of asymmetry-induced transport

    Science.gov (United States)

    Eggleston, D. L.

    2018-03-01

    The techniques of chaos theory are employed in an effort to better understand the complex single-particle dynamics of asymmetry-induced transport in non-neutral plasmas. The dynamical equations are re-conceptualized as describing time-independent trajectories in a four-dimensional space consisting of the radius r, rotating frame angle ψ, axial position z, and axial velocity v. Results include the identification of an integral of the motion, fixed-point analysis of the dynamical equations, the construction and interpretation of Poincaré sections to visualize the dynamics, and, for the case of chaotic motion, numerical calculation of the largest Lyapunov exponent. Chaotic cases are shown to be associated with the overlap of resonance islands formed by the applied asymmetry.

  20. Low Density Supersonic Decelerator (LDSD) Supersonic Flight Dynamics Test (SFDT) Plume Induced Environment Modelling

    Science.gov (United States)

    Mobley, B. L.; Smith, S. D.; Van Norman, J. W.; Muppidi, S.; Clark, I

    2016-01-01

    Provide plume induced heating (radiation & convection) predictions in support of the LDSD thermal design (pre-flight SFDT-1) Predict plume induced aerodynamics in support of flight dynamics, to achieve targeted freestream conditions to test supersonic deceleration technologies (post-flight SFDT-1, pre-flight SFDT-2)

  1. Summary of photochemical and radiative data used in the LLNL one-dimensional transport-kinetics model of the troposphere and stratosphere: 1982

    International Nuclear Information System (INIS)

    Connell, P.S.; Wuebbles, D.J.

    1983-01-01

    This report summarizes the contents and sources of the photochemical and radiative segment of the LLNL one-dimensional transport-kinetics model of the troposphere and stratosphere. Data include the solar flux incident at the top of the atmosphere, absorption spectra for O 2 , O 3 and NO 2 , and effective absorption coefficients for about 40 photolytic processes as functions of wavelength and, in a few cases, temperature and pressure. The current data set represents understanding of atmospheric photochemical processes as of late 1982 and relies largely on NASA Evaluation Number 5 of Chemical Kinetics and Photochemical Data for Use in Stratospheric Modeling, JPL Publication 82-57 (DeMore et al., 1982). Implementation in the model, including the treatment of multiple scattering and cloud cover, is discussed in Wuebbles (1981)

  2. Volatile organic compounds (VOCs) in photochemically aged air from the eastern and western Mediterranean

    Science.gov (United States)

    Derstroff, Bettina; Hüser, Imke; Bourtsoukidis, Efstratios; Crowley, John N.; Fischer, Horst; Gromov, Sergey; Harder, Hartwig; Janssen, Ruud H. H.; Kesselmeier, Jürgen; Lelieveld, Jos; Mallik, Chinmay; Martinez, Monica; Novelli, Anna; Parchatka, Uwe; Phillips, Gavin J.; Sander, Rolf; Sauvage, Carina; Schuladen, Jan; Stönner, Christof; Tomsche, Laura; Williams, Jonathan

    2017-08-01

    During the summertime CYPHEX campaign (CYprus PHotochemical EXperiment 2014) in the eastern Mediterranean, multiple volatile organic compounds (VOCs) were measured from a 650 m hilltop site in western Cyprus (34° 57' N/32° 23' E). Periodic shifts in the northerly Etesian winds resulted in the site being alternately impacted by photochemically processed emissions from western (Spain, France, Italy) and eastern (Turkey, Greece) Europe. Furthermore, the site was situated within the residual layer/free troposphere during some nights which were characterized by high ozone and low relative humidity levels. In this study we examine the temporal variation of VOCs at the site. The sparse Mediterranean scrub vegetation generated diel cycles in the reactive biogenic hydrocarbon isoprene, from very low values at night to a diurnal median level of 80-100 pptv. In contrast, the oxygenated volatile organic compounds (OVOCs) methanol and acetone exhibited weak diel cycles and were approximately an order of magnitude higher in mixing ratio (ca. 2.5-3 ppbv median level by day, range: ca. 1-8 ppbv) than the locally emitted isoprene and aromatic compounds such as benzene and toluene. Acetic acid was present at mixing ratios between 0.05 and 4 ppbv with a median level of ca. 1.2 ppbv during the daytime. When data points directly affected by the residual layer/free troposphere were excluded, the acid followed a pronounced diel cycle, which was influenced by various local effects including photochemical production and loss, direct emission, dry deposition and scavenging from advecting air in fog banks. The Lagrangian model FLEXPART was used to determine transport patterns and photochemical processing times (between 12 h and several days) of air masses originating from eastern and western Europe. Ozone and many OVOC levels were ˜ 20 and ˜ 30-60 % higher, respectively, in air arriving from the east. Using the FLEXPART calculated transport time, the contribution of photochemical

  3. Determination of total mercury and methylmercury in biological samples by photochemical vapor generation

    Energy Technology Data Exchange (ETDEWEB)

    Vieira, Mariana A.; Ribeiro, Anderson S.; Curtius, Adilson J. [Universidade Federal de Santa Catarina, Departamento de Quimica, Florianopolis, SC (Brazil); Sturgeon, Ralph E. [National Research Council Canada, Institute for National Measurement Standards, Ottawa, ON (Canada)

    2007-06-15

    Cold vapor atomic absorption spectrometry (CV-AAS) based on photochemical reduction by exposure to UV radiation is described for the determination of methylmercury and total mercury in biological samples. Two approaches were investigated: (a) tissues were digested in either formic acid or tetramethylammonium hydroxide (TMAH), and total mercury was determined following reduction of both species by exposure of the solution to UV irradiation; (b) tissues were solubilized in TMAH, diluted to a final concentration of 0.125% m/v TMAH by addition of 10% v/v acetic acid and CH{sub 3}Hg{sup +} was selectively quantitated, or the initial digests were diluted to 0.125% m/v TMAH by addition of deionized water, adjusted to pH 0.3 by addition of HCl and CH{sub 3}Hg{sup +} was selectively quantitated. For each case, the optimum conditions for photochemical vapor generation (photo-CVG) were investigated. The photochemical reduction efficiency was estimated to be {proportional_to}95% by comparing the response with traditional SnCl{sub 2} chemical reduction. The method was validated by analysis of several biological Certified Reference Materials, DORM-1, DORM-2, DOLT-2 and DOLT-3, using calibration against aqueous solutions of Hg{sup 2+}; results showed good agreement with the certified values for total and methylmercury in all cases. Limits of detection of 6 ng/g for total mercury using formic acid, 8 ng/g for total mercury and 10 ng/g for methylmercury using TMAH were obtained. The proposed methodology is sensitive, simple and inexpensive, and promotes ''green'' chemistry. The potential for application to other sample types and analytes is evident. (orig.)

  4. Analysis of the unresolved organic fraction in atmospheric aerosols with ultrahigh-resolution mass spectrometry and nuclear magnetic resonance spectroscopy: organosulfates as photochemical smog constituents.

    Science.gov (United States)

    Schmitt-Kopplin, Philippe; Gelencsér, Andras; Dabek-Zlotorzynska, Ewa; Kiss, Gyula; Hertkorn, Norbert; Harir, Mourad; Hong, Yang; Gebefügi, Istvan

    2010-10-01

    Complementary molecular and atomic signatures obtained from Fourier transform ion cyclotron resonance (FTICR) mass spectra and NMR spectra provided unequivocal attribution of CHO, CHNO, CHOS, and CHNOS molecular series in secondary organic aerosols (SOA) and high-resolution definition of carbon chemical environments. Sulfate esters were confirmed as major players in SOA formation and as major constituents of its water-soluble fraction (WSOC). Elevated concentrations of SO(2), sulfate, and photochemical activity were shown to increase the proportion of SOA sulfur-containing compounds. Sulfonation of CHO precursors by means of heterogeneous reactions between carbonyl derivatives and sulfuric acid in gas-phase photoreactions was proposed as a likely formation mechanism of CHOS molecules. In addition, photochemistry induced oligomerization processes of CHOS molecules. Methylesters found in methanolic extracts of a SOA subjected to strong photochemical exposure were considered secondary products derived from sulfate esters by methanolysis. The relative abundance of nitrogen-containing compounds (CHNO and CHNOS series) appeared rather dependent on local effects such as biomass burning. Extensive aliphatic branching and disruption of extended NMR spin-systems by carbonyl derivatives and other heteroatoms were the most significant structural motifs in SOA. The presence of heteroatoms in elevated oxidation states suggests a clearly different SOA formation trajectory in comparison with established terrestrial and aqueous natural organic matter.

  5. Photochemical fate and eco-genotoxicity assessment of the drug etodolac

    Energy Technology Data Exchange (ETDEWEB)

    Passananti, Monica [Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario Monte S. Angelo, via Cintia, 4, 80126 Napoli (Italy); Clermont Université, Université Blaise Pascal, Institut de Chimie de Clermont-Ferrand (ICCF) UMR 6296, BP 10448, F-63000 Clermont-Ferrand (France); Lavorgna, Margherita [Dipartimento di Scienze e Tecnologie Ambientali, Biologiche e Farmaceutiche, Seconda Università di Napoli, Via Vivaldi 43, I-81100 Caserta (Italy); Iesce, Maria Rosaria, E-mail: iesce@unina.it [Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario Monte S. Angelo, via Cintia, 4, 80126 Napoli (Italy); DellaGreca, Marina [Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario Monte S. Angelo, via Cintia, 4, 80126 Napoli (Italy); Brigante, Marcello [Clermont Université, Université Blaise Pascal, Institut de Chimie de Clermont-Ferrand (ICCF) UMR 6296, BP 10448, F-63000 Clermont-Ferrand (France); Criscuolo, Emma [Dipartimento di Scienze e Tecnologie Ambientali, Biologiche e Farmaceutiche, Seconda Università di Napoli, Via Vivaldi 43, I-81100 Caserta (Italy); Cermola, Flavio [Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario Monte S. Angelo, via Cintia, 4, 80126 Napoli (Italy); Isidori, Marina, E-mail: marina.isidori@unina2.it [Dipartimento di Scienze e Tecnologie Ambientali, Biologiche e Farmaceutiche, Seconda Università di Napoli, Via Vivaldi 43, I-81100 Caserta (Italy)

    2015-06-15

    The photochemical behavior of etodolac was investigated under various irradiation conditions. Kinetic data were obtained after irradiation of 10{sup −4} M aqueous solutions by UVB, UVA and direct exposure to sunlight. The Xenon lamp irradiation was used in order to determine the photodegradation quantum yield under sun-simulated condition (ϕ{sub sun}). The value was determined to be = 0.10 ± 0.01. In order to obtain photoproducts and for mechanistic purposes, experiments were carried out on more concentrated solutions by exposure to sunlight and to UVA and UVB lamps. The drug underwent photooxidative processes following an initial oxygen addition to the double bond of the five membered ring and was mainly converted into a spiro compound and a macrolactam. Ecotoxicity tests were performed on etodolac, its photostable spiro derivative and its sunlight irradiation mixture on two different aquatic trophic levels, plants (algae) and invertebrates (rotifers and crustaceans). Mutagenesis and genotoxicity were detected on bacterial strains. The results showed that only etodolac had long term effects on rotifers although at concentrations far from environmental detection values. A mutagenic and genotoxic potential was found for its derivative. - Highlights: • Photochemical transformation of etodolac occurs in the environment. • Etodolac was slightly toxic in the long term for some aquatic organisms. • A mutagenic and genotoxic potential was found for etodolac photostable derivative.

  6. Distributed Dynamic Traffic Modeling and Implementation Oriented Different Levels of Induced Travelers

    Directory of Open Access Journals (Sweden)

    Yan Liu

    2015-01-01

    Full Text Available In order to respond to the variable state of traffic network in time, a distributed dynamic traffic assignment strategy is proposed which can improve the intelligent traffic management. The proposed dynamic assignment method is based on utility theory and is oriented to different levels of induced users. A distributed model based on the marginal utility is developed which combines the advantages of both decentralized paradigm and traveler preference, so as to provide efficient and robust dynamic traffic assignment solutions under uncertain network conditions. Then, the solution algorithm including subroute update and subroute calculation is proposed. To testify the effectiveness of the proposed model in optimizing traffic network operation and minimizing traveler’s cost on different induced levels, a sequence numerical experiment is conducted. In the experiment, there are two test environments: one is in different network load conditions and the other is in different deployment coverage of local agents. The numerical results show that the proposed model not only can improve the running efficiency of road network but also can significantly decrease the average travel time.

  7. Dynamical photo-induced electronic properties of molecular junctions

    Science.gov (United States)

    Beltako, K.; Michelini, F.; Cavassilas, N.; Raymond, L.

    2018-03-01

    Nanoscale molecular-electronic devices and machines are emerging as promising functional elements, naturally flexible and efficient, for next-generation technologies. A deeper understanding of carrier dynamics in molecular junctions is expected to benefit many fields of nanoelectronics and power devices. We determine time-resolved charge current flowing at the donor-acceptor interface in molecular junctions connected to metallic electrodes by means of quantum transport simulations. The current is induced by the interaction of the donor with a Gaussian-shape femtosecond laser pulse. Effects of the molecular internal coupling, metal-molecule tunneling, and light-donor coupling on photocurrent are discussed. We then define the time-resolved local density of states which is proposed as an efficient tool to describe the absorbing molecule in contact with metallic electrodes. Non-equilibrium reorganization of hybridized molecular orbitals through the light-donor interaction gives rise to two phenomena: the dynamical Rabi shift and the appearance of Floquet-like states. Such insights into the dynamical photoelectronic structure of molecules are of strong interest for ultrafast spectroscopy and open avenues toward the possibility of analyzing and controlling the internal properties of quantum nanodevices with pump-push photocurrent spectroscopy.

  8. Kinetic analyses and mathematical modeling of primary photochemical and photoelectrochemical processes in plant photosystems

    NARCIS (Netherlands)

    Vredenberg, W.J.

    2011-01-01

    In this paper the model and simulation of primary photochemical and photo-electrochemical reactions in dark-adapted intact plant leaves is presented. A descriptive algorithm has been derived from analyses of variable chlorophyll a fluorescence and P700 oxidation kinetics upon excitation with

  9. A single exposure to photochemical smog causes airway irritation and cardiac dysrhythmia in mice

    Science.gov (United States)

    The data presented here shows that a single exposure to photochemical smog causes airway irritation and cardiac dysrhythmia in mice. Smog, which is a complex mixture of particulate matter and gaseous irritants (ozone, sulfur dioxide, reactive aldehydes), as well as components whi...

  10. APPLICATION OF BAYESIAN MONTE CARLO ANALYSIS TO A LAGRANGIAN PHOTOCHEMICAL AIR QUALITY MODEL. (R824792)

    Science.gov (United States)

    Uncertainties in ozone concentrations predicted with a Lagrangian photochemical air quality model have been estimated using Bayesian Monte Carlo (BMC) analysis. Bayesian Monte Carlo analysis provides a means of combining subjective "prior" uncertainty estimates developed ...

  11. The role of dynamically induced variability in the recent warming trend slowdown over the Northern Hemisphere.

    Science.gov (United States)

    Guan, Xiaodan; Huang, Jianping; Guo, Ruixia; Lin, Pu

    2015-07-30

    Since the slowing of the trend of increasing surface air temperature (SAT) in the late 1990 s, intense interest and debate have arisen concerning the contribution of human activities to the warming observed in previous decades. Although several explanations have been proposed for the warming-trend slowdown (WTS), none has been generally accepted. We investigate the WTS using a recently developed methodology that can successfully identify and separate the dynamically induced and radiatively forced SAT changes from raw SAT data. The dynamically induced SAT changes exhibited an obvious cooling effect relative to the warming effect of the adjusted SAT in the hiatus process. A correlation analysis suggests that the changes are dominated primarily by the North Atlantic Oscillation (NAO), Pacific Decadal Oscillation (PDO), and Atlantic Multidecadal Oscillation (AMO). Our results confirm that dynamically induced variability caused the WTS. The radiatively forced SAT changes are determined mainly by anthropogenic forcing, indicating the warming influence of greenhouse gases (GHGs), which reached levels of 400 ppm during the hiatus period. Therefore, the global SAT will not remain permanently neutral. The increased radiatively forced SAT will be amplified by increased dynamically induced SAT when the natural mode returns to a warming phase in the next period.

  12. Dynamics and composition of the Asian summer monsoon anticyclone

    Science.gov (United States)

    Gottschaldt, Klaus-Dirk; Schlager, Hans; Baumann, Robert; Sinh Cai, Duy; Eyring, Veronika; Graf, Phoebe; Grewe, Volker; Jöckel, Patrick; Jurkat-Witschas, Tina; Voigt, Christiane; Zahn, Andreas; Ziereis, Helmut

    2018-04-01

    This study places HALO research aircraft observations in the upper-tropospheric Asian summer monsoon anticyclone (ASMA) into the context of regional, intra-annual variability by hindcasts with the ECHAM/MESSy Atmospheric Chemistry (EMAC) model. The observations were obtained during the Earth System Model Validation (ESMVal) campaign in September 2012. Observed and simulated tracer-tracer relations reflect photochemical O3 production as well as in-mixing from the lower troposphere and the tropopause layer. The simulations demonstrate that tropospheric trace gas profiles in the monsoon season are distinct from those in the rest of the year, and the measurements reflect the main processes acting throughout the monsoon season. Net photochemical O3 production is significantly enhanced in the ASMA, where uplifted precursors meet increased NOx, mainly produced by lightning. An analysis of multiple monsoon seasons in the simulation shows that stratospherically influenced tropopause layer air is regularly entrained at the eastern ASMA flank and then transported in the southern fringe around the interior region. Radial transport barriers of the circulation are effectively overcome by subseasonal dynamical instabilities of the anticyclone, which occur quite frequently and are of paramount importance for the trace gas composition of the ASMA. Both the isentropic entrainment of O3-rich air and the photochemical conversion of uplifted O3-poor air tend to increase O3 in the ASMA outflow.

  13. Photochemical cycle of bacteriorhodopsin studied by resonance Raman spectroscopy.

    Science.gov (United States)

    Stockburger, M; Klusmann, W; Gattermann, H; Massig, G; Peters, R

    1979-10-30

    Individual species of the photochemical cycle of bacteriorhodopsin, a retinal-protein complex of Halobacteria, were studied in aqueous suspensions of the "purple membrane" at room temperature by resonance Raman (RR) spectroscopy with flow systems. Two pronounced deuterium shifts were found in the RR spectra of the all-trans complex BR-570 in H2O-D2O suspensions. The first is ascribed to C=NH+ (C=ND+) stretching vibrations of the protonated Schiff base which links retinal to opsin. The second is assigned tentatively to an "X-H" ("X-D") bending mode, where "X" is an atom which carries an exchangeable proton. A RR spectrum of the 13-cis-retinal complex "BR-548" could be deduced from spectra of the dark-adapted purple membrane. The RR spectrum of the M-412 intermediate was monitored in a double-beam pump-probe experiment. The main vibrational features of the intermediate M' in the reaction M-412 in equilibrium hv M' leads to delta BR-570 could be deduced from a photostationary mixture of M-412 and M'. Difference procedures were applied to obtain RR spectra of the L-550 intermediate and of two new long-lived species, R1'-590 and R2-550. From kinetic data it is suggested that T1'-590 links the proton-translocating cycle to the "13-cis" cycle of BR-548. The protonation and isomeric states of the different species are discussed in light of the new spectroscopic and kinetic data. It is found that conformational changes during the photochemical cycle play an important role.

  14. Effects of Biological and Photochemical Degradation on the Optical Properties of CDOM Exported to Coastal Marine Environments

    National Research Council Canada - National Science Library

    Moran, Mary

    2004-01-01

    .... This project quantitatively assessed the ability of coastal ocean bacteria to degrade and produce CDOM and investigated the synergistic interactions between bacterial degradation and photochemical...

  15. Chlorophyll loss associated with heat-induced senescence in bentgrass.

    Science.gov (United States)

    Jespersen, David; Zhang, Jing; Huang, Bingru

    2016-08-01

    Heat stress-induced leaf senescence is characterized by the loss of chlorophyll from leaf tissues. The objectives of this study were to examine genetic variations in the level of heat-induced leaf senescence in hybrids of colonial (Agrostis capillaris)×creeping bentgrass (Agrostis stolonifera) contrasting in heat tolerance, and determine whether loss of leaf chlorophyll during heat-induced leaf senescence was due to suppressed chlorophyll synthesis and/or accelerated chlorophyll degradation in the cool-season perennial grass species. Plants of two hybrid backcross genotypes ('ColxCB169' and 'ColxCB190') were exposed to heat stress (38/33°C, day/night) for 28 d in growth chambers. The analysis of turf quality, membrane stability, photochemical efficiency, and chlorophyll content demonstrated significant variations in the level of leaf senescence induced by heat stress between the two genotypes, with ColXCB169 exhibiting a lesser degree of decline in chlorophyll content, photochemical efficiency and membrane stability than ColXCB190. The assays of enzymatic activity or gene expression of several major chlorophyll-synthesizing (porphobilinogen deaminase, Mg-chelatase, protochlorophyllide-reductase) and chlorophyll-degrading enzymes (chlorophyllase, pheophytinase, and chlorophyll-degrading peroxidase) indicated heat-induced decline in leaf chlorophyll content was mainly due to accelerated chlorophyll degradation, as manifested by increased gene expression levels of chlorophyllase and pheophytinase, and the activity of pheophytinase (PPH), while chlorophyll-synthesizing genes and enzymatic activities were not differentially altered by heat stress in the two genotypes. The analysis of heat-induced leaf senescence of pph mutants of Arabidopsis further confirmed that PPH could be one enzymes that plays key roles in regulating heat-accelerated chlorophyll degradation. Further research on enzymes responsible in part for the loss of chlorophyll during heat-induced

  16. Synthetic tetracycline-inducible regulatory networks: computer-aided design of dynamic phenotypes

    Directory of Open Access Journals (Sweden)

    Kaznessis Yiannis N

    2007-01-01

    Full Text Available Abstract Background Tightly regulated gene networks, precisely controlling the expression of protein molecules, have received considerable interest by the biomedical community due to their promising applications. Among the most well studied inducible transcription systems are the tetracycline regulatory expression systems based on the tetracycline resistance operon of Escherichia coli, Tet-Off (tTA and Tet-On (rtTA. Despite their initial success and improved designs, limitations still persist, such as low inducer sensitivity. Instead of looking at these networks statically, and simply changing or mutating the promoter and operator regions with trial and error, a systematic investigation of the dynamic behavior of the network can result in rational design of regulatory gene expression systems. Sophisticated algorithms can accurately capture the dynamical behavior of gene networks. With computer aided design, we aim to improve the synthesis of regulatory networks and propose new designs that enable tighter control of expression. Results In this paper we engineer novel networks by recombining existing genes or part of genes. We synthesize four novel regulatory networks based on the Tet-Off and Tet-On systems. We model all the known individual biomolecular interactions involved in transcription, translation, regulation and induction. With multiple time-scale stochastic-discrete and stochastic-continuous models we accurately capture the transient and steady state dynamics of these networks. Important biomolecular interactions are identified and the strength of the interactions engineered to satisfy design criteria. A set of clear design rules is developed and appropriate mutants of regulatory proteins and operator sites are proposed. Conclusion The complexity of biomolecular interactions is accurately captured through computer simulations. Computer simulations allow us to look into the molecular level, portray the dynamic behavior of gene regulatory

  17. Photochemical oxidants: state of the science.

    Science.gov (United States)

    Kley, D; Kleinmann, M; Sanderman, H; Krupa, S

    1999-01-01

    Atmospheric photochemical processes resulting in the production of tropospheric ozone (O(3)) and other oxidants are described. The spatial and temporal variabilities in the occurrence of surface level oxidants and their relationships to air pollution meteorology are discussed. Models of photooxidant formation are reviewed in the context of control strategies and comparisons are provided of the air concentrations of O(3) at select geographic locations around the world. This overall oxidant (O(3)) climatology is coupled to human health and ecological effects. The discussion of the effects includes both acute and chronic responses, mechanisms of action, human epidemiological and plant population studies and briefly, efforts to establish cause-effect relationships through numerical modeling. A short synopsis is provided of the interactive effects of O(3) with other abiotic and biotic factors. The overall emphasis of the paper is on identifying the current uncertainties and gaps in our understanding of the state of the science and some suggestions as to how they may be addressed.

  18. 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)

  19. Efficient photochemical generation of peroxycarboxylic nitric anhydrides with ultraviolet light-emitting diodes

    Science.gov (United States)

    Rider, N. D.; Taha, Y. M.; Odame-Ankrah, C. A.; Huo, J. A.; Tokarek, T. W.; Cairns, E.; Moussa, S. G.; Liggio, J.; Osthoff, H. D.

    2015-07-01

    Photochemical sources of peroxycarboxylic nitric anhydrides (PANs) are utilized in many atmospheric measurement techniques for calibration or to deliver an internal standard. Conventionally, such sources rely on phosphor-coated low-pressure mercury (Hg) lamps to generate the UV light necessary to photo-dissociate a dialkyl ketone (usually acetone) in the presence of a calibrated amount of nitric oxide (NO) and oxygen (O2). In this manuscript, a photochemical PAN source in which the Hg lamp has been replaced by arrays of ultraviolet light-emitting diodes (UV-LEDs) is described. The output of the UV-LED source was analyzed by gas chromatography (PAN-GC) and thermal dissociation cavity ring-down spectroscopy (TD-CRDS). Using acetone, diethyl ketone (DIEK), diisopropyl ketone (DIPK), or di-n-propyl ketone (DNPK), respectively, the source produces peroxyacetic (PAN), peroxypropionic (PPN), peroxyisobutanoic (PiBN), or peroxy-n-butanoic nitric anhydride (PnBN) from NO in high yield (> 90 %). Box model simulations with a subset of the Master Chemical Mechanism (MCM) were carried out to rationalize product yields and to identify side products. The present work demonstrates that UV-LED arrays are a viable alternative to current Hg lamp setups.

  20. Role of nitrite in the photochemical formation of radicals in the snow.

    Science.gov (United States)

    Jacobi, Hans-Werner; Kleffmann, Jörg; Villena, Guillermo; Wiesen, Peter; King, Martin; France, James; Anastasio, Cort; Staebler, Ralf

    2014-01-01

    Photochemical reactions in snow can have an important impact on the composition of the atmosphere over snow-covered areas as well as on the composition of the snow itself. One of the major photochemical processes is the photolysis of nitrate leading to the formation of volatile nitrogen compounds. We report nitrite concentrations determined together with nitrate and hydrogen peroxide in surface snow collected at the coastal site of Barrow, Alaska. The results demonstrate that nitrite likely plays a significant role as a precursor for reactive hydroxyl radicals as well as volatile nitrogen oxides in the snow. Pollution events leading to high concentrations of nitrous acid in the atmosphere contributed to an observed increase in nitrite in the surface snow layer during nighttime. Observed daytime nitrite concentrations are much higher than values predicted from steady-state concentrations based on photolysis of nitrate and nitrite indicating that we do not fully understand the production of nitrite and nitrous acid in snow. The discrepancy between observed and expected nitrite concentrations is probably due to a combination of factors, including an incomplete understanding of the reactive environment and chemical processes in snow, and a lack of consideration of the vertical structure of snow.

  1. 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.

  2. Applications of the Regional Atmospheric Modeling System (RAMS) to provide input to photochemical grid models for the Lake Michigan Ozone Study (LMOS)

    Energy Technology Data Exchange (ETDEWEB)

    Lyons, W.A.; Tremback, C.J.; Pielke, R.A. [ASTeR, Inc., Ft. Collins, CO (United States); Eastman, J.L. [Colorado State Univ., Ft. Collins, CO (United States)

    1994-12-31

    In spite of stringent emission controls, numerous exceedances of the US ozone air quality standard have continued in the Lake Michigan region, especially during the very hot summers of 1987 and 1988. Analyses revealed that exceedances of the 120 PPB hourly standard were 400% more likely at monitors located within 20 km of the lakeshore. While the role of Lake Michigan in exacerbating regional air quality problems has been investigated for almost 20 years, the relative impacts of various phenomena upon regional photochemical air quality have yet to be quantified. In order to design a defensible regional emission control policy, LMOS sponsored the development of a comprehensive regional photochemical modeling system. This is comprised of an emission model, an advanced regional photochemical model, and a prognostic meteorological model.

  3. Systems and methods for solar energy storage, transportation, and conversion utilizing photochemically active organometallic isomeric compounds and solid-state catalysts

    Science.gov (United States)

    Vollhardt, K. Peter C.; Segalman, Rachel A; Majumdar, Arunava; Meier, Steven

    2015-02-10

    A system for converting solar energy to chemical energy, and, subsequently, to thermal energy includes a light-harvesting station, a storage station, and a thermal energy release station. The system may include additional stations for converting the released thermal energy to other energy forms, e.g., to electrical energy and mechanical work. At the light-harvesting station, a photochemically active first organometallic compound, e.g., a fulvalenyl diruthenium complex, is exposed to light and is photochemically converted to a second, higher-energy organometallic compound, which is then transported to a storage station. At the storage station, the high-energy organometallic compound is stored for a desired time and/or is transported to a desired location for thermal energy release. At the thermal energy release station, the high-energy organometallic compound is catalytically converted back to the photochemically active organometallic compound by an exothermic process, while the released thermal energy is captured for subsequent use.

  4. Chemical Kinetics and Photochemical Data for Use in Stratospheric Modeling. Evaluation No. 12

    Science.gov (United States)

    DeMore, W. B.; Sander, S. P.; Golden, D. M.; Hampson, R. F.; Kurylo, M. J.; Howard, C. J.; Ravishankara, A. R.; Kolb, C. E.; Molina, M. J.

    1997-01-01

    This is the twelfth in a series of evaluated sets of rate constants and photochemical cross sections compiled by the NASA Panel for Data Evaluation. The primary application of the data is in the modeling of stratospheric processes, with special emphasis on the ozone layer and its possible perturbation by anthropogenic and natural phenomena.

  5. Ultraviolet-B irradiation of seeds affects photochemical and reproductive performance of the arid-environment ephemeral Dimorphotheca pluvialis

    International Nuclear Information System (INIS)

    Musil, C.F.

    1994-01-01

    A higher polyphenolic content and thicker sclerenchymatous cylinder in the pericarp of ray than of disc seed morphs (diaspores) of Dimorphotheca pluvialis (L.) Moench (Asteraceae) could limit possible damage to the embryo during long-term seed exposure to solar UV-B radiation. This hypothesis was tested by irradiating sun-dried disc and ray diaspores continuously for 6 weeks with four different doses of biologically effective UV radiation, viz 0.0, 0.2, 9.46 and 11.97 kj m −2 8 hr −1 of visible (> 400 nm), UV-A (320–400 nm), ambient and enhanced UV-B (280–320 nm) radiation, respectively. Total effective UV-B doses approximated those received over an 18-week period following seed dispersal at this species' northerly distribution limit (26° 38′ S), at normal ozone levels (ambient UV-B) and anticipated 20% ozone depletion (enhanced UV-B). Irradiation of diaspores with enhanced UV-B improved germination in both seed morphs. However, disc diaspores exhibited a greater fractional increase in germination than ray diaspores. Disc and ray plants grown from diaspores irradiated with enhanced UV-B exhibited decreased photochemical efficiency (reduced variable to maximal fluorescence, F v /F m ), but only disc plants showed decreased potential photosynthetic activity (reduced areas over fluorescence curves, A fd ). This was accompanied by increased diaspore production and reduced diaspore mass. Irradiation of diaspores with photoreactivating UV-A produced a contrasting response (increased F v /F m and A fd , accompanied by decreased diaspore production) in disc plants only. Altered photochemical and reproductive performance, and visibly diminished leaf pigmentation, in disc plants indicated increased sensitivity to photoinhibition, a possible consequence of UV-B induced cellular (membrane and DNA) damage in seeds. (author)

  6. Proposal to realize a cost breakthrough in carbon-13 production by photochemical separation

    International Nuclear Information System (INIS)

    Marling, J.B.

    1979-10-01

    A cost breakthrough can now be made in photochemical production of the rare stable isotope carbon-13. This cost breakthrough is achieved by CO 2 laser infrared multiple-photon dissociation of any of several halocarbons (Freon derivatives) such as CF 3 Cl, CF 3 Br, or CF 2 Cl 2 . The single-step carbon-13 enrichment factor for this process is approximately 50, yielding 30% pure C-13 in one step, or up to 97% pure C-13 in two steps. A three-fold carbon-13 cost reduction to below $20/gram is expected to be achieved in a small laboratory-scale demonstration facility capable of producing 4 to 8 kg/year of carbon-13, using presently available pulsed CO 2 TEA lasers at an average power level of 50 watts. Personnel costs dominate the attainable C-13 production costs in a small photochemical enrichment facility. A price reduction to $2/gm carbon-13 is feasible at carbon-13 production levels of 100 to 1000 kg/year, dominated by the Freon raw material costs

  7. Simplified dynamic analysis to evaluate liquefaction-induced lateral deformation of earth slopes: a computational fluid dynamics approach

    Science.gov (United States)

    Jafarian, Yaser; Ghorbani, Ali; Ahmadi, Omid

    2014-09-01

    Lateral deformation of liquefiable soil is a cause of much damage during earthquakes, reportedly more than other forms of liquefaction-induced ground failures. Researchers have presented studies in which the liquefied soil is considered as viscous fluid. In this manner, the liquefied soil behaves as non-Newtonian fluid, whose viscosity decreases as the shear strain rate increases. The current study incorporates computational fluid dynamics to propose a simplified dynamic analysis for the liquefaction-induced lateral deformation of earth slopes. The numerical procedure involves a quasi-linear elastic model for small to moderate strains and a Bingham fluid model for large strain states during liquefaction. An iterative procedure is considered to estimate the strain-compatible shear stiffness of soil. The post-liquefaction residual strength of soil is considered as the initial Bingham viscosity. Performance of the numerical procedure is examined by using the results of centrifuge model and shaking table tests together with some field observations of lateral ground deformation. The results demonstrate that the proposed procedure predicts the time history of lateral ground deformation with a reasonable degree of precision.

  8. Interaction of light and atmospheric photochemical products (smog) within plants. [Phaseolius vulgaris; Petunia hydrida

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, O C; Dugger, W M; Cardiff, E A; Darley, E F

    1961-12-02

    Damage to plants from ozone and peroxyacetyl nitrate, two photochemically formed components of smog, has been described. However, variations in symptom expression and the degree of damage caused by a given concentration of these components, whether of synthetic or natural origin, have complicated development of an adequate biological assay method for these materials. These observed variations in symptomatology have implicated stomatal action, inorganic nutrition temperature, genetics, ascorbic acid content, physiological age of tissue and photoperiod. Plants grown under artificial illumination differ in their response to the photochemically formed pollutants as compared with plants grown in the greenhouse. Interactions between light and oxidants from the polluted atmosphere within plants, as reported here, might well explain some of the variabilities in symptomatology observed in earlier controlled experiments as well as the unexplained natural variability observed in the Los Angeles area. The results presented also emphasize the importance of standardizing plant growth conditions for future work of this nature. 10 references.

  9. Photochemical charges separation and photoelectric properties of flexible solar cells with two types of heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xiangyang, E-mail: lxy081276@126.com, E-mail: yzgu@henu.edu.cn; Wang, Shun; Zheng, Haiwu; Cheng, Xiuying; Gu, Yuzong, E-mail: lxy081276@126.com, E-mail: yzgu@henu.edu.cn [Institute of Microsystems Physics and School of Physics and Electronics, Henan University, Kaifeng 475004 (China)

    2015-12-14

    Photochemical charges generation, separation, and transport at nanocrystal interfaces are central to energy conversion for solar cells. Here, Zn{sub 2}SnO{sub 4} nanowires/Cu{sub 4}Bi{sub 4}S{sub 9} (ZTO/CBS), ZTO nanowires/CBS-reduced graphene oxide (ZTO/CBS-RGO), and bulk heterojunction (BHJ) solar cells were measured. The signals of steady state and electric field-induced surface photovoltage indicate that RGO with high electron mobility can evidently improve the photovoltaic response. Besides, ZTO/CBS and ZTO/CBS-RGO cells exhibit the excellent performance and the highest efficiencies of 1.2% and 2.8%, respectively. The internal relations of photoelectric properties to some factors, such as film thickness, direct paths, RGO conductive network, energy level matching, etc., were discussed in detail. Qualitative and quantitative analyses further verified the comprehensive effect of RGO and other factors. Importantly, the fine bendable characteristic of BHJ solar cells with excellent efficiency and facile, scalable production gives the as-made flexible solar cells device potential for practical application in future.

  10. Volatile organic compounds (VOCs in photochemically aged air from the eastern and western Mediterranean

    Directory of Open Access Journals (Sweden)

    B. Derstroff

    2017-08-01

    Full Text Available During the summertime CYPHEX campaign (CYprus PHotochemical EXperiment 2014 in the eastern Mediterranean, multiple volatile organic compounds (VOCs were measured from a 650 m hilltop site in western Cyprus (34° 57′ N/32° 23′ E. Periodic shifts in the northerly Etesian winds resulted in the site being alternately impacted by photochemically processed emissions from western (Spain, France, Italy and eastern (Turkey, Greece Europe. Furthermore, the site was situated within the residual layer/free troposphere during some nights which were characterized by high ozone and low relative humidity levels. In this study we examine the temporal variation of VOCs at the site. The sparse Mediterranean scrub vegetation generated diel cycles in the reactive biogenic hydrocarbon isoprene, from very low values at night to a diurnal median level of 80–100 pptv. In contrast, the oxygenated volatile organic compounds (OVOCs methanol and acetone exhibited weak diel cycles and were approximately an order of magnitude higher in mixing ratio (ca. 2.5–3 ppbv median level by day, range: ca. 1–8 ppbv than the locally emitted isoprene and aromatic compounds such as benzene and toluene. Acetic acid was present at mixing ratios between 0.05 and 4 ppbv with a median level of ca. 1.2 ppbv during the daytime. When data points directly affected by the residual layer/free troposphere were excluded, the acid followed a pronounced diel cycle, which was influenced by various local effects including photochemical production and loss, direct emission, dry deposition and scavenging from advecting air in fog banks. The Lagrangian model FLEXPART was used to determine transport patterns and photochemical processing times (between 12 h and several days of air masses originating from eastern and western Europe. Ozone and many OVOC levels were  ∼  20 and  ∼  30–60 % higher, respectively, in air arriving from the east. Using the FLEXPART

  11. 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)

  12. SMOG CHAMBERS: A TOOL TO EXAMINE EFFECTS OF PHOTOCHEMICALLY AGED AIR POLLUTANTS ON BIOLOGICAL SYSTEMS

    Science.gov (United States)

    Irradiative exposure chambers or 'Smog chambers' have been used at the University of North Carolina for over 30 years to study photochemically active mixtures of volatile organic compounds and their transformation products (a significant sub-set of Hazardous Air Pollutants, HAPs)...

  13. Effect of Photochemical Transformation on Dissolved Organic Carbon Concentration and Bioavailability from Watersheds with Varying Landcover

    Science.gov (United States)

    Vermilyea, A.; Sanders, A.; Vazquez, E.

    2017-12-01

    The transformation of freshwater dissolved organic carbon (DOC) can have important implications for water quality, aquatic ecosystem health, and our climate. DOC is an important nutrient for heterotrophic microorganisms near the base of the aquatic food chain and the extent of conversion of DOC to CO2 is a critical piece of the global carbon cycle. Photochemical pathways have the potential to transform recalcitrant DOC into more labile forms that can then be converted to smaller DOC molecules and eventually be completely mineralized to CO2. This may lead to a DOC pool with different bioavailability depending on the structural composition of the original DOC pool and the mechanistic pathways undergone during transformation. This study aimed to measure the changes in DOC concentration and bioavailability due solely to photochemical processes in three watersheds of northern Vermont, USA that have varied land cover, land use (LCLU) attributes. Our hypothesis was that photochemical transformations will lead to (1) an overall loss of DOC due to mineralization to CO2 and (2) a relative increase in the bioavailable fraction of DOC. Additionally, the influence of LCLU and base flow versus storm flow on both mineralization rates and changes in DOC bioavailability was investigated. Irradiation of filtered samples in quartz vessels under sunlight led to small changes in DOC concentration over time, but significant changes in DOC bioavailability. In general, fluorescence excitation-emission matrices (EEMs) showed a shift from an initially more humic-like DOC pool, to a more protein-like (bioavailable) DOC pool. Specific UV index (SUVA) along with bioavailable DOC (BDOC) incubations were also used to characterize DOC and its bioavailability. There were only small differences in the DOC transformation that took place among sites, possibly due to only small differences in the initial bioavailability and fluorescent properties between water samples. Photochemical transformation

  14. Magnetization dynamics induced by Rashba effect in a Permalloy nanodisk

    Energy Technology Data Exchange (ETDEWEB)

    Li, Huanan; Hua, Zhong, E-mail: jiyonghnli@126.com; Li, Dongfei

    2017-02-15

    Magnetic vortex dynamics mediated by spin-polarized ac current of different amplitudes and frequencies are investigated by micromagnetic simulations in a system lacking structure inversion symmetry. Micromagnetic calculations reveal that the critical current density required to induce vortex core reversal may be decreased to below 10{sup 10} A m{sup −2} due to strong transverse magnetic field by Rashba effect. We also find the spin torque of ac current plays a trivial role in magnetic vortex dynamics in a broken inversion symmetry system when the current density is on the order of 10{sup 10} A m{sup −2} and the current with frequency close to the vortex eigenfrequency is the most efficient for reversal.

  15. Dynamic evolution characteristics of mining-induced fractures in overlying strata detected by radon

    International Nuclear Information System (INIS)

    Zhang Wei; Ma Liqiang; Wang Xufeng; Fang Gangwei; Zhang Dongsheng

    2011-01-01

    For environment protection in mining areas in northwest China, we developed a CTSRM (comprehensive test system by radon measurement) to measure radon radioactivity and detect dynamic evolution characteristics of mining-induced fractures in overlying strata. It was used to simulate the relationship between the dynamic evolution characteristics and radon concentrations of No. 33201 coalface at Bulianta coal mine in Inner Mongolia, and feasibility of the method was validate. (authors)

  16. HANDBOOK ON ADVANCED PHOTOCHEMICAL OXIDATION ...

    Science.gov (United States)

    This handbook summarizes commercial-scale system performance and cost data for advanced photochemical oxidation (APO) treatment of contaminated water, air, and solids. Similar information from pilot- and bench-scale evaluations of APO processes is also included to supplement the commercial-scale data. Performance and cost data is summarized for various APO processes, including vacuum ultraviolet (VUV) photolysis, ultraviolet (UV)/oxidation, photo-Fenton, and dye- or semiconductor-sensitized APO processes. This handbook is intended to assist engineering practitioners in evaluating the applicability of APO processes and in selecting one or more such processes for site-specific evaluation.APO has been shown to be effective in treating contaminated water and air. Regarding contaminated water treatment, UV/oxidation has been evaluated for the most contaminants, while VUV photolysis has been evaluated for the fewest. Regarding contaminated air treatment, the sensitized APO processes have been evaluated for the most contaminants, while VUV photolysis has been evaluated for the fewest.APO processes for treating contaminated solids generally involve treatment of contaminated slurry or leachate generated using an extraction process such as soil washing. APO has been shown to be effective in treating contaminated solids, primarily at the bench-scale level. Information

  17. Photochemical reduction of uranyl nitrate

    Energy Technology Data Exchange (ETDEWEB)

    Duerksen, W.K.

    1993-10-20

    The photochemical reduction of uranyl nitrate solutions to tetravalent uranium was investigated as a means of producing uranium dioxide feed for the saltless direct oxide reduction (SDOR) process. At high uranium concentrations, reoxidation of U{sup +4} occurs rapidly. The kinetics of the nitric oxidation of tetravalent uranium depend on the concentrations of hydrogen ion, nitrate ion, nitrous acid, and tetravalent uranium in the same manner as was reported elsewhere for the nitrate oxidation of PU{sup +3}. Reaction rate data were successfully correlated with a mechanism in which nitrogen dioxide is the reactive intermediate. Addition of a nitrous acid scavenger suppresses the reoxidation reaction. An immersion reactor employing a mercury vapor lamp gave reduction times fast enough for routine production usage. Precipitation techniques for conversion of aqueous U(NO{sub 3}){sub 4} to hydrous UO{sub 2} were evaluated. Prolonged dewatering times tended to make the process time consuming. Use of 3- to 4-M aqueous NaOH gave the best dewatering times observed. Reoxidation of the UO{sub 2} by water of hydration was encountered, which required the drying process to be carried out under a reducing atmosphere.

  18. Silver nanocrystals by hyperbranched polyurethane-assisted photochemical reduction of Ag+

    International Nuclear Information System (INIS)

    Lu, H.W.; Liu, S.H.; Wang, X.L.; Qian, X.F.; Yin, J.; Zhu, Z.K.

    2003-01-01

    Silver nanoparticles in hyperbranched polyurethane (HP) matrix were prepared by means of UV irradiation at room temperature. HP was found to play a key role in the photochemical reduction of silver ions and the formation of nanosized particles. Transmission electron microscopic (TEM) analysis showed that silver nanoparticles were homogeneously dispersed in HP matrix. The absorption peaks due to the surface plasmon resonance of the obtained silver nanoparticles were observed at about 430 nm in the ultraviolet-visible (UV-Vis) absorption spectra. X-ray powder diffraction (XRD) was also used to characterize the obtained nanoparticles

  19. Dynamics of synchrotron VUV-induced intracluster reactions

    Energy Technology Data Exchange (ETDEWEB)

    Grover, J.R. [Brookhaven National Laboratory, Upton, NY (United States)

    1993-12-01

    Photoionization mass spectrometry (PIMS) using the tunable vacuum ultraviolet radiation available at the National Synchrotron Light Source is being exploited to study photoionization-induced reactions in small van der Waals mixed complexes. The information gained includes the observation and classification of reaction paths, the measurement of onsets, and the determination of relative yields of competing reactions. Additional information is obtained by comparison of the properties of different reacting systems. Special attention is given to finding unexpected features, and most of the reactions investigated to date display such features. However, understanding these reactions demands dynamical information, in addition to what is provided by PIMS. Therefore the program has been expanded to include the measurement of kinetic energy release distributions.

  20. Application of photochemical technologies for treatment of landfill leachate

    International Nuclear Information System (INIS)

    Meeroff, Daniel E.; Bloetscher, Frederick; Reddy, D.V.; Gasnier, François; Jain, Swapnil; McBarnette, André; Hamaguchi, Hatsuko

    2012-01-01

    Highlights: ► Photochemical iron-mediated aeration and TiO 2 photocatalysis for leachate treatment. ► Removal efficiency tested on COD, BOD 5 , color, ammonia, and lead. ► Contact times for 90% removal were 10–200 h for PIMA ► Contact times for 90% removal were 3–37 h for TiO 2 photocatalysis. ► Pre-filtration is not necessary. - Abstract: Because of widely varying practices in solid waste management, an all-inclusive solution to long-term management of landfill leachate is currently not available. There is a major technological need for sustainable, economical options for safe discharge of leachate to the environment. Two potential on-site pretreatment technologies, photochemical iron-mediated aeration (PIMA) and TiO 2 photocatalysis were compared for treatment of landfill leachate at laboratory scale. Results of bench scale testing of real landfill leachate with PIMA and TiO 2 photocatalysis showed up to 86% conversion of refractory COD to complete mineralization, up to 91% removal of lead, up to 71% removal of ammonia without pH adjustment, and up to 90% effective color removal with detention times between 4 and 6 h, in field samples. The estimated contact times for 90% removal of COD, ammonia, lead, and color were found to be on the order of 10–200 h for PIMA and 3–37 h for TiO 2 photocatalysis. Testing with actual leachate samples showed 85% TiO 2 photocatalyst recovery efficiency with no loss in performance after multiple (n > 4 uses). Pre-filtration was not found to be necessary for effective treatment using either process.

  1. 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.

  2. Source characterization and dynamic fault modeling of induced seismicity

    Science.gov (United States)

    Lui, S. K. Y.; Young, R. P.

    2017-12-01

    In recent years there are increasing concerns worldwide that industrial activities in the sub-surface can cause or trigger damaging earthquakes. In order to effectively mitigate the damaging effects of induced seismicity, the key is to better understand the source physics of induced earthquakes, which still remain elusive at present. Furthermore, an improved understanding of induced earthquake physics is pivotal to assess large-magnitude earthquake triggering. A better quantification of the possible causes of induced earthquakes can be achieved through numerical simulations. The fault model used in this study is governed by the empirically-derived rate-and-state friction laws, featuring a velocity-weakening (VW) patch embedded into a large velocity-strengthening (VS) region. Outside of that, the fault is slipping at the background loading rate. The model is fully dynamic, with all wave effects resolved, and is able to resolve spontaneous long-term slip history on a fault segment at all stages of seismic cycles. An earlier study using this model has established that aseismic slip plays a major role in the triggering of small repeating earthquakes. This study presents a series of cases with earthquakes occurring on faults with different fault frictional properties and fluid-induced stress perturbations. The effects to both the overall seismicity rate and fault slip behavior are investigated, and the causal relationship between the pre-slip pattern prior to the event and the induced source characteristics is discussed. Based on simulation results, the subsequent step is to select specific cases for laboratory experiments which allow well controlled variables and fault parameters. Ultimately, the aim is to provide better constraints on important parameters for induced earthquakes based on numerical modeling and laboratory data, and hence to contribute to a physics-based induced earthquake hazard assessment.

  3. 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.

  4. Mitochondrial Dynamics Decrease Prior to Axon Degeneration Induced by Vincristine and are Partially Rescued by Overexpressed cytNmnat1.

    Directory of Open Access Journals (Sweden)

    Gregory Berbusse

    2016-07-01

    Full Text Available Axon degeneration is a prominent feature of various neurodegenerative diseases, such as Parkinson’s and Alzheimer’s, and is often characterized by aberrant mitochondrial dynamics. Mitochondrial fission, fusion, and motility have been shown to be particularly important in progressive neurodegeneration. Thus we investigated these imperative dynamics, as well as mitochondrial fragmentation in vincristine induced axon degradation in cultured DRG neurons. CytNmnat1 inhibits axon degeneration in various paradigms including vincristine toxicity. The mechanism of its protection is not yet fully understood; therefore, we also investigated the effect of cytNmnat1 on mitochondrial dynamics in vincristine treated neurons. We observed that vincristine treatment decreases the rate of mitochondrial fission, fusion and motility and induces mitochondrial fragmentation. These mitochondrial events precede visible axon degeneration. Overexpression of cytNmnat1 inhibits axon degeneration and preserves the normal mitochondrial dynamics and motility in vincristine treated neurons. We suggest the alterations in mitochondrial structure and dynamics are early events which lead to axon degeneration and cytNmnat1 blocks axon degeneration by halting the vincristine induced changes to mitochondrial structure and dynamics.

  5. Pressure Dependent Product Formation in the Photochemically Initiated Allyl + Allyl Reaction

    Directory of Open Access Journals (Sweden)

    Thomas Zeuch

    2013-11-01

    Full Text Available Photochemically driven reactions involving unsaturated radicals produce a thick global layer of organic haze on Titan, Saturn’s largest moon. The allyl radical self-reaction is an example for this type of chemistry and was examined at room temperature from an experimental and kinetic modelling perspective. The experiments were performed in a static reactor with a volume of 5 L under wall free conditions. The allyl radicals were produced from laser flash photolysis of three different precursors allyl bromide (C3H5Br, allyl chloride (C3H5Cl, and 1,5-hexadiene (CH2CH(CH22CHCH2 at 193 nm. Stable products were identified by their characteristic vibrational modes and quantified using FTIR spectroscopy. In addition to the (re- combination pathway C3H5+C3H5 → C6H10 we found at low pressures around 1 mbar the highest final product yields for allene and propene for the precursor C3H5Br. A kinetic analysis indicates that the end product formation is influenced by specific reaction kinetics of photochemically activated allyl radicals. Above 10 mbar the (re- combination pathway becomes dominant. These findings exemplify the specificities of reaction kinetics involving chemically activated species, which for certain conditions cannot be simply deduced from combustion kinetics or atmospheric chemistry on Earth.

  6. Action spectrum for photochemical retinal pigment epithelium (RPE) disruption in an in vivo monkey model

    Science.gov (United States)

    Zhang, Jie; Sabarinathan, Ranjani; Bubel, Tracy; Williams, David R.; Hunter, Jennifer J.

    2016-03-01

    Observations of RPE disruption and autofluorescence (AF) photobleaching at light levels below the ANSI photochemical maximum permissible exposure (MPE) (Morgan et al., 2008) indicates a demand to modify future light safety standards to protect the retina from harm. To establish safe light exposures, we measured the visible light action spectrum for RPE disruption in an in vivo monkey model with fluorescence adaptive optics retinal imaging. Using this high resolution imaging modality can provide insight into the consequences of light on a cellular level and allow for longitudinal monitoring of retinal changes. The threshold retinal radiant exposures (RRE) for RPE disruption were determined for 4 wavelengths (460, 488, 544, and 594 nm). The anaesthetized macaque retina was exposed to a uniform 0.5° × 0.5° field of view (FOV). Imaging within a 2° × 2° FOV was performed before, immediately after and at 2 week intervals for 10 weeks. At each wavelength, multiple RREs were tested with 4 repetitions each to determine the threshold for RPE disruption. For qualitative analysis, RPE disruption is defined as any detectable change from the pre exposure condition in the cell mosaic in the exposed region relative to the corresponding mosaic in the immediately surrounding area. We have tested several metrics to evaluate the RPE images obtained before and after exposure. The measured action spectrum for photochemical RPE disruption has a shallower slope than the current ANSI photochemical MPE for the same conditions and suggests that longer wavelength light is more hazardous than other measurements would suggest.

  7. Dynamics of rain-induced pollutographs of solubles in sewers.

    Science.gov (United States)

    Rutsch, M; Müller, I; Krebs, P

    2005-01-01

    When looking at acute receiving water impacts due to combined sewer overflows the characteristics of the background diurnal sewage flux variation may influence the peak loads from combined sewer overflows (CSO) and wastewater treatment plant (WWTP) effluent significantly. In this paper, effects on the dynamic compounds transported in the sewer, on CSO discharges and WWTP loading are evaluated by means of hydrodynamic simulations. The simulations are based on different scenarios for diurnal dry-weather flow variations induced by different infiltration rates.

  8. Optical wall dynamics induced by coexistence of monostable and bistable spatial regions.

    Science.gov (United States)

    Odent, V; Louvergneaux, E; Clerc, M G; Andrade-Silva, I

    2016-11-01

    When nonequilibrium extended homogeneous systems exhibit multistability, it leads to the presence of domain walls between the existing equilibria. Depending on the stability of the steady states, the dynamics differs. Here, we consider the interface dynamics in the case of a spatially inhomogeneous system, namely, an optical system where the control parameter is spatially Gaussian. Then interfaces connect the monostable and the bistable nonuniform states that are associated with two distinct spatial regions. The coexistence of these two regions of different stability induces relaxation dynamics and the propagation of a wall with a time-dependent speed. We emphasize analytically these two dynamical behaviors using a generic bistable model. Experimentally, an inhomogeneous Gaussian light beam traveling through either a dye-doped liquid crystal cell or a Kerr cavity depicts these behaviors, in agreement with the theoretical predictions.

  9. Dynamic actuation of glassy polymersomes through isomerization of a single azobenzene unit at the block copolymer interface

    Science.gov (United States)

    Molla, Mijanur Rahaman; Rangadurai, Poornima; Antony, Lucas; Swaminathan, Subramani; de Pablo, Juan J.; Thayumanavan, S.

    2018-06-01

    Nature has engineered exquisitely responsive systems where molecular-scale information is transferred across an interface and propagated over long length scales. Such systems rely on multiple interacting, signalling and adaptable molecular and supramolecular networks that are built on dynamic, non-equilibrium structures. Comparable synthetic systems are still in their infancy. Here, we demonstrate that the light-induced actuation of a molecularly thin interfacial layer, assembled from a hydrophilic- azobenzene -hydrophobic diblock copolymer, can result in a reversible, long-lived perturbation of a robust glassy membrane across a range of over 500 chemical bonds. We show that the out-of-equilibrium actuation is caused by the photochemical trans-cis isomerization of the azo group, a single chemical functionality, in the middle of the interfacial layer. The principles proposed here are implemented in water-dispersed nanocapsules, and have implications for on-demand release of embedded cargo molecules.

  10. 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.

  11. 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.

  12. Efficient photochemical generation of peroxycarboxylic nitric anhydrides with ultraviolet light emitting diodes

    Science.gov (United States)

    Rider, N. D.; Taha, Y. M.; Odame-Ankrah, C. A.; Huo, J. A.; Tokarek, T. W.; Cairns, E.; Moussa, S. G.; Liggio, J.; Osthoff, H. D.

    2015-01-01

    Photochemical sources of peroxycarboxylic nitric anhydrides (PANs) are utilized in many atmospheric measurement techniques for calibration or to deliver an internal standard. Conventionally, such sources rely on phosphor-coated low-pressure mercury (Hg) lamps to generate the UV light necessary to photo-dissociate a dialkyl ketone (usually acetone) in the presence of a calibrated amount of nitric oxide (NO) and oxygen (O2). In this manuscript, a photochemical PAN source in which the Hg lamp has been replaced by arrays of ultraviolet light-emitting diodes (UV-LEDs) is described. The output of the UV-LED source was analyzed by gas chromatography (PAN-GC) and thermal dissociation cavity ring-down spectroscopy (TD-CRDS). Using acetone, diethyl ketone (DIEK), diisopropyl ketone (DIPK), or di-n-propyl ketone (DNPK), respectively, the source produces peroxyacetic (PAN), peroxypropionic (PPN), peroxyisobutanoic (PiBN), or peroxy-n-butanoic nitric anhydride (PnBN) from NO in high yield (> 90%). Box model simulations with a subset of the Master Chemical Mechanism (MCM) were carried out to rationalize products yields and to identify side products. The use of UV-LED arrays offers many advantages over conventional Hg lamp setups, including greater light output over a narrower wavelength range, lower power consumption, and minimal generation of heat.

  13. Under-the-barrier dynamics in laser-induced relativistic tunneling.

    Science.gov (United States)

    Klaiber, Michael; Yakaboylu, Enderalp; Bauke, Heiko; Hatsagortsyan, Karen Z; Keitel, Christoph H

    2013-04-12

    The tunneling dynamics in relativistic strong-field ionization is investigated with the aim to develop an intuitive picture for the relativistic tunneling regime. We demonstrate that the tunneling picture applies also in the relativistic regime by introducing position dependent energy levels. The quantum dynamics in the classically forbidden region features two time scales, the typical time that characterizes the probability density's decay of the ionizing electron under the barrier (Keldysh time) and the time interval which the electron spends inside the barrier (Eisenbud-Wigner-Smith tunneling time). In the relativistic regime, an electron momentum shift as well as a spatial shift along the laser propagation direction arise during the under-the-barrier motion which are caused by the laser magnetic field induced Lorentz force. The momentum shift is proportional to the Keldysh time, while the wave-packet's spatial drift is proportional to the Eisenbud-Wigner-Smith time. The signature of the momentum shift is shown to be present in the ionization spectrum at the detector and, therefore, observable experimentally. In contrast, the signature of the Eisenbud-Wigner-Smith time delay disappears at far distances for pure quasistatic tunneling dynamics.

  14. The Photochemical Conversion of Surrogate Emissions for Use in Toxicological Studies: Role of Particulate- and Gas-Phase Products

    Data.gov (United States)

    U.S. Environmental Protection Agency — The production of photochemical atmospheres under controlled conditions in an irradiation chamber permits the manipulation of parameters that influence the resulting...

  15. Integrated Science Assessment (ISA) of Ozone and Related Photochemical Oxidants (Second External Review Draft, Sep 2011)

    Science.gov (United States)

    EPA has released the Integrated Science Assessment of Ozone and Related Photochemical Oxidants (Second External Review Draft) for independent peer review and public review. This draft document represents a concise synthesis and evaluation of the most policy-relevant scienc...

  16. Application of a Three-Layer Photochemical Box Model in an Athens Street Canyon.

    Science.gov (United States)

    Proyou, Athena G; Ziomas, Loannis C; Stathopoulos, Antony

    1998-05-01

    The aim of this paper is to show that a photochemical box model could describe the air pollution diurnal profiles within a typical street canyon in the city of Athens. As sophisticated three-dimensional dispersion models are computationally expensive and they cannot serve to simulate pollution levels in the scale of an urban street canyon, a suitably modified three-layer photochemical box model was applied. A street canyon of Athens with heavy traffic was chosen to apply the aforementioned model. The model was used to calculate pollutant concentrations during two days with meteorological conditions favoring pollutant accumulation. Road traffic emissions were calculated based on existing traffic load measurements. Meteorological data, as well as various pollutant concentrations, in order to compare with the model results, were provided by available measurements. The calculated concentrations were found to be in good agreement with measured concentration levels and show that, when traffic load and traffic composition data are available, this model can be used to predict pollution episodes. It is noteworthy that high concentrations persisted, even after additional traffic restriction measures were taken on the second day because of the high pollution levels.

  17. Partial coupling and differential regulation of biologically and photochemically labile dissolved organic carbon across boreal aquatic networks

    Science.gov (United States)

    Lapierre, J.-F.; del Giorgio, P. A.

    2014-10-01

    Despite the rapidly increasing volume of research on the biological and photochemical degradation of DOC (dissolved organic carbon) in aquatic environments, little is known of the large-scale patterns in biologically and photochemically degradable DOC (BDOC and PDOC, respectively) in continental watersheds, and on the links that exist between these two key properties that greatly influence the flow of carbon from continents to oceans. Here we explored the patterns in the concentrations and proportions of BDOC and PDOC across hundreds of boreal lakes, rivers and wetlands spanning a large range of system trophic status and terrestrial influence, and compared the drivers of these two reactive pools of DOC at the landscape level. Using standardized incubations of natural waters, we found that the concentrations of BDOC and PDOC covaried across all systems studied but were nevertheless related to different pools of dissolved organic matter (DOM; identified by fluorescence analyses) in ambient waters. Concentrations of nutrients and protein-like fluorescent DOM (FDOM) explained nearly half of the variation in BDOC, whereas PDOC was exclusively predicted by DOM optical properties, consistent with the photochemical degradability of specific FDOM pools that we experimentally determined. The concentrations of colored DOM (CDOM), which we use here as a proxy of terrestrial influence, almost entirely accounted for the observed relationship between FDOM and the concentrations of both BDOC and PDOC. The concentrations of CDOM and of the putative biolabile fluorescence component shifted from complete decoupling in clear-water environments to strong coupling in darker streams and wetlands. This suggests a baseline autochthonous BDOC pool fueled by internal production that is gradually overwhelmed by land-derived BDOC as terrestrial influence increases across landscape gradients. The importance of land as a major source of both biologically and photochemically degradable DOC for

  18. Photochemical Internalization of Peptide Antigens Provides a Novel Strategy to Realize Therapeutic Cancer Vaccination

    Directory of Open Access Journals (Sweden)

    Markus Haug

    2018-04-01

    Full Text Available Effective priming and activation of tumor-specific CD8+ cytotoxic T lymphocytes (CTLs is crucial for realizing the potential of therapeutic cancer vaccination. This requires cytosolic antigens that feed into the MHC class I presentation pathway, which is not efficiently achieved with most current vaccination technologies. Photochemical internalization (PCI provides an emerging technology to route endocytosed material to the cytosol of cells, based on light-induced disruption of endosomal membranes using a photosensitizing compound. Here, we investigated the potential of PCI as a novel, minimally invasive, and well-tolerated vaccination technology to induce priming of cancer-specific CTL responses to peptide antigens. We show that PCI effectively promotes delivery of peptide antigens to the cytosol of antigen-presenting cells (APCs in vitro. This resulted in a 30-fold increase in MHC class I/peptide complex formation and surface presentation, and a subsequent 30- to 100-fold more efficient activation of antigen-specific CTLs compared to using the peptide alone. The effect was found to be highly dependent on the dose of the PCI treatment, where optimal doses promoted maturation of immature dendritic cells, thus also providing an adjuvant effect. The effect of PCI was confirmed in vivo by the successful induction of antigen-specific CTL responses to cancer antigens in C57BL/6 mice following intradermal peptide vaccination using PCI technology. We thus show new and strong evidence that PCI technology holds great potential as a novel strategy for improving the outcome of peptide vaccines aimed at triggering cancer-specific CD8+ CTL responses.

  19. Photochemical degradation of chromophoric-dissolved organic matter exposed to simulated UV-B and natural solar radiation

    NARCIS (Netherlands)

    Zhang, Y.; Liu, M.; Qin, B.; Feng, S.

    2009-01-01

    Photochemical degradation of chromophoric-dissolved organic matter (CDOM) by UV-B radiation decreases CDOM absorption in the UV region and fluorescence intensity, and alters CDOM composition. CDOM absorption, fluorescence, and the spectral slope indicating the CDOM composition were studied using

  20. Diagnostic Evaluation of Ozone Production and Horizontal Transport in a Regional Photochemical Air Quality Modeling System

    Science.gov (United States)

    A diagnostic model evaluation effort has been performed to focus on photochemical ozone formation and the horizontal transport process since they strongly impact the temporal evolution and spatial distribution of ozone (O3) within the lower troposphere. Results from th...

  1. Sulfidic photochemical passivation of GaAs surfaces in alcoholic solutions

    International Nuclear Information System (INIS)

    Simonsmeier, T.; Ivankov, A.; Bauhofer, W.

    2005-01-01

    We report on a remarkable enhancement of the passivation effect of sulfidic solutions through illumination with above band gap light. Luminescence measurements on GaAs surfaces which have been illuminated during chemical passivation reveal in comparison to nonilluminated samples a further reduction of their surface density of states as well as a significantly increased stability of the passivation. Investigations with photoelectron spectroscopy show that illumination leads to a nearly complete removal of oxides on the surface. Measurements on Schottky diodes which have been manufactured with photochemically passivated GaAs indicate a noticeable decrease in band bending and a depinning of the Fermi level

  2. Application of photochemical technologies for treatment of landfill leachate

    Energy Technology Data Exchange (ETDEWEB)

    Meeroff, Daniel E., E-mail: dmeeroff@fau.edu [Department of Civil, Environmental and Geomatics Engineering, Florida Atlantic University, Boca Raton, FL (United States); Bloetscher, Frederick; Reddy, D.V.; Gasnier, Francois; Jain, Swapnil; McBarnette, Andre; Hamaguchi, Hatsuko [Department of Civil, Environmental and Geomatics Engineering, Florida Atlantic University, Boca Raton, FL (United States)

    2012-03-30

    Highlights: Black-Right-Pointing-Pointer Photochemical iron-mediated aeration and TiO{sub 2} photocatalysis for leachate treatment. Black-Right-Pointing-Pointer Removal efficiency tested on COD, BOD{sub 5}, color, ammonia, and lead. Black-Right-Pointing-Pointer Contact times for 90% removal were 10-200 h for PIMA Black-Right-Pointing-Pointer Contact times for 90% removal were 3-37 h for TiO{sub 2} photocatalysis. Black-Right-Pointing-Pointer Pre-filtration is not necessary. - Abstract: Because of widely varying practices in solid waste management, an all-inclusive solution to long-term management of landfill leachate is currently not available. There is a major technological need for sustainable, economical options for safe discharge of leachate to the environment. Two potential on-site pretreatment technologies, photochemical iron-mediated aeration (PIMA) and TiO{sub 2} photocatalysis were compared for treatment of landfill leachate at laboratory scale. Results of bench scale testing of real landfill leachate with PIMA and TiO{sub 2} photocatalysis showed up to 86% conversion of refractory COD to complete mineralization, up to 91% removal of lead, up to 71% removal of ammonia without pH adjustment, and up to 90% effective color removal with detention times between 4 and 6 h, in field samples. The estimated contact times for 90% removal of COD, ammonia, lead, and color were found to be on the order of 10-200 h for PIMA and 3-37 h for TiO{sub 2} photocatalysis. Testing with actual leachate samples showed 85% TiO{sub 2} photocatalyst recovery efficiency with no loss in performance after multiple (n > 4 uses). Pre-filtration was not found to be necessary for effective treatment using either process.

  3. Stacking effect on the ferroelectric properties of PZT/PLZT multilayer thin films formed by photochemical metal-organic deposition

    International Nuclear Information System (INIS)

    Park, Hyeong-Ho; Park, Hyung-Ho; Hill, Ross H.

    2004-01-01

    The ferroelectric properties of lead zirconate titanate (PZT) and lanthanum-doped lead zirconate titanate (PLZT) multilayer films formed by photochemical metal-organic deposition (PMOD) using photosensitive precursors have been characterized. The substitution of La for Pb was reported to induce improved ferroelectric properties, especially fatigue resistance, through the reduction of oxygen vacancies. The relation between La-substitution and the ferroelectric properties was investigated by characterization of the effect of the order of stacking four ferroelectric layers of PZT or PLZT in the multilayer films 4-PZT, PZT/2-PLZT/PZT, PLZT/2-PZT/PLZT, and 4-PLZT. The films with the PLZT layer at the top and bottom showed an improvement in the fatigue resistance. It was revealed that defect dipole such as O vacancy was reduced at the ferroelectric/Pt interface by doping with La. Also, the bottom layer, just on Pt substrate had a significant influence on the surface microstructure and growth orientation of ferroelectric film

  4. Active Self-Assembled Spinners: dynamic crystals, transport and induced surface flows

    Science.gov (United States)

    Snezhko, Alexey; Kokot, Gasper

    Strongly interacting colloids driven out-of-equilibrium by an external periodic forcing often develop nontrivial collective dynamics. Active magnetic colloids proved to be excellent model experimental systems to explore emergent behavior and active (out-of-equilibrium) self-assembly phenomena. Ferromagnetic micro-particles, suspended at a liquid interface and energized by a rotational homogeneous alternating magnetic field applied along the supporting interface, spontaneously form ensembles of synchronized self-assembled spinners with well-defined characteristic length. The size and the torque of an individual self-assembled spinner are controlled by the frequency of the driving magnetic field. Experiments reveal a rich collective dynamics in large ensembles of synchronized magnetic spinners that spontaneously form dynamic spinner lattices at the interface in a certain range of the excitation parameters. Non-trivial dynamics inside of the formed spinner lattices is observed. Transport of passive cargo particles and structure of the underlying self-induced surface flows is analyzed. The research was supported by the U.S. DOE, Office of Basic Energy Sciences, Division of Materials Science and Engineering.

  5. Direct current (DC) resistivity and induced polarization (IP) monitoring of active layer dynamics at high temporal resolution

    DEFF Research Database (Denmark)

    Doetsch, Joseph; Ingeman-Nielsen, Thomas; Christiansen, Anders V.

    2015-01-01

    With permafrost thawing and changes in active layer dynamics induced by climate change, interactions between biogeochemical and thermal processes in the ground are of great importance. Here, active layer dynamics have been monitored using direct current (DC) resistivity and induced polarization (IP...... in resistivity. While the freezing horizon generally moves deeper with time, some variations in the freezing depth are observed along the profile. Comparison with depth-specific soil temperature indicates an exponential relationship between resistivity and below-freezing temperature. Time-lapse inversions...

  6. Using of Photochemical H2O2/UVC Decontamination Cell for Heavily Polluted Waters

    Czech Academy of Sciences Publication Activity Database

    Žebrák, R.; Mašín, P.; Klusoň, Petr; Krystyník, Pavel

    2014-01-01

    Roč. 2014, č. 2 (2014), s. 55-62 ISSN 1804-0195. [Symposium ODPADOVÉ FÓRUM 2014. Hustopeče u Brna, 23.042014-23.04.2013] R&D Projects: GA MPO(CZ) FR-TI1/065 Institutional support: RVO:67985858 Keywords : photochemical oxidation * remediation * pilot scale Subject RIV: CI - Industrial Chemistry, Chemical Engineering http://www.wasteforum.cz/

  7. Photochemical reductions of benzil and benzoin in the presence of triethylamine and TiO2 photocatalyst

    International Nuclear Information System (INIS)

    Park, Joon Woo; Kim, Eun Kyung; Koh Park, Kwang Hee

    2002-01-01

    This paper reports the photochemical reduction of benzil 1 to benzoin 2 and the reduction of 2 to hydrobenzoin 4 in deoxygenated solvents in the presence of triethylamine (TEA) and/or TiO 2 . Without TEA or TiO 2 , the photolysis of 1 resulted in very low yield of 2. The presence of TEA or TiO 2 increased the rate of disappearance of 1 and the yield of 2, which were further increased considerably by the presence of water. The photoreduction of 1 to 2 proceeds through an electron transfer to 1 from TEA or hole-scavenged excited TiO 2 followed by protonation. In the reaction medium of 88:7:2:3 CH 3 CN/CH 3 OH/H 2 O/TEA with 2.5 mg/mL of TiO 2 , the yield of 2 was as high as 85% at 50% conversion of 1. The photolysis of 2 in homogeneous media resulted in photo-cleavage to benzoyl and hydroxybenzyl radicals, which are mostly converted to benzaldehyde. The reduction product 4 is formed in low yield through the dimerization of hydroxybenzyl radicals. The addition of TEA increased the conversion rate of 2 and the yield of 4 significantly. This was attributed to the scavenging effect of TEA for benzoyl radical to produce N,N-diethylbenzamide and the photoreduction of benzaldehyde in the presence of TEA. The ratio of (±) and meso isomers of 4 obtained from the photochemical reaction is about 1.1. This ratio is the same as that from the photochemical reduction of benzaldehyde in the presence of TEA. In the TiO 2 -sensitized photochemical reduction of 2, meso-4 was obtained in moderate yield. The reduction of 2 to 4 proceeds through two consecutive electron/proton transfer processes on the surface of the photocatalyst without involvement of α-cleavage. The radical 11 initially formed from 2 by one electron/proton process can also combine with hydroxy methyl radical, which is generated after hole trapping of excited TiO 2 by methanol, to product 1,2-diphenylpropenone after dehydration reaction

  8. Photochemical Energy Storage and Electrochemically Triggered Energy Release in the Norbornadiene-Quadricyclane System: UV Photochemistry and IR Spectroelectrochemistry in a Combined Experiment.

    Science.gov (United States)

    Brummel, Olaf; Waidhas, Fabian; Bauer, Udo; Wu, Yanlin; Bochmann, Sebastian; Steinrück, Hans-Peter; Papp, Christian; Bachmann, Julien; Libuda, Jörg

    2017-07-06

    The two valence isomers norbornadiene (NBD) and quadricyclane (QC) enable solar energy storage in a single molecule system. We present a new photoelectrochemical infrared reflection absorption spectroscopy (PEC-IRRAS) experiment, which allows monitoring of the complete energy storage and release cycle by in situ vibrational spectroscopy. Both processes were investigated, the photochemical conversion from NBD to QC using the photosensitizer 4,4'-bis(dimethylamino)benzophenone (Michler's ketone, MK) and the electrochemically triggered cycloreversion from QC to NBD. Photochemical conversion was obtained with characteristic conversion times on the order of 500 ms. All experiments were performed under full potential control in a thin-layer configuration with a Pt(111) working electrode. The vibrational spectra of NBD, QC, and MK were analyzed in the fingerprint region, permitting quantitative analysis of the spectroscopic data. We determined selectivities for both the photochemical conversion and the electrochemical cycloreversion and identified the critical steps that limit the reversibility of the storage cycle.

  9. Photo-oxidative damage to isolated rat liver mitochondria induced by phenothiazines

    Directory of Open Access Journals (Sweden)

    T. RODRIGUES

    2009-01-01

    Full Text Available

    Photosensitization is a well-known side-effect of phenothiazines that could involve photochemically promoted oxidative damage to mitochondria, leading to the impairment of metabolic functions and apoptosis. In this work, for the first time, we investigated the effects of photoexcited thioridazine (TR, trifluoperazine (TFP and fluphenazine (FP on isolated rat liver mitochondria. Under UV irradiation, the presence of these phenothiazines led to a dose-dependent lack of the respiratory control ratio. These effects were not accompanied by significant swelling and oxidation of protein thiol groups but were accompanied by lipid peroxidation. Lycopene and sorbate, well-known quenchers of singlet oxygen and triplet species, respectively, were ineffective at protecting mitochondrial lipids against the damage promoted by the excited phenothiazines, suggesting that photochemically-produced cation radicals were the prooxidant species. Corroborating this proposal, butylated hydroxytoluene (BHT completely inhibited the lipid peroxidation induced by UV irradiation in the presence of phenothiazines. These novel results make a significant contribution to the understanding of the photochemical properties of phenothiazines in biological systems. Keywords: Trifluoperazine, thioridazine, fluphenazine, rat liver mitochondria, oxidative stress, photochemistry, photodamage, respiratory chain.

  10. Binding of carbon dioxide to metal macrocycles: Toward a mechanistic understanding of electrochemical and photochemical carbon dioxide reduction

    Energy Technology Data Exchange (ETDEWEB)

    Fujita, E.

    1993-01-01

    Efforts were made to find effective catalysts for photochemical and electrochemical reduction of CO[sub 2]. We are studying the factors controlling excited-state lifetimes, electron-transfer rates to mediators/catalysts, properties of reduced mediators, binding of small molecules to reduced mediators, and reactivity of the mediators to yield the desired products. This document describes some of the results of binding on CO[sub 2] to metal macrocycles. The electrocatalytic activity of cobalt macrocycle complexes in reduction of CO[sub 2] in CO[sub 2]-saturated water at the Hg electrode is being studied. We are ready to study the mechanism and kinetics of the photochemical CO[sub 2] reduction in order to design more efficient photo-energy conversion systems. 19 refs.

  11. Binding of carbon dioxide to metal macrocycles: Toward a mechanistic understanding of electrochemical and photochemical carbon dioxide reduction

    Energy Technology Data Exchange (ETDEWEB)

    Fujita, E.

    1993-07-01

    Efforts were made to find effective catalysts for photochemical and electrochemical reduction of CO{sub 2}. We are studying the factors controlling excited-state lifetimes, electron-transfer rates to mediators/catalysts, properties of reduced mediators, binding of small molecules to reduced mediators, and reactivity of the mediators to yield the desired products. This document describes some of the results of binding on CO{sub 2} to metal macrocycles. The electrocatalytic activity of cobalt macrocycle complexes in reduction of CO{sub 2} in CO{sub 2}-saturated water at the Hg electrode is being studied. We are ready to study the mechanism and kinetics of the photochemical CO{sub 2} reduction in order to design more efficient photo-energy conversion systems. 19 refs.

  12. Two-dimensional NMR and photo-CIDNP studies of the insulin monomer: Assignment of aromatic resonances with application to protein folding, structure, and dynamics

    International Nuclear Information System (INIS)

    Weiss, M.A.; Shoelson, S.E.; Nguyen, D.T.; O'Shea, E.; Karplus, M.; Khait, I.; Neuringer, L.J.; Inouye, K.; Frank, B.H.; Beckage, M.

    1989-01-01

    The aromatic 1 H NMR resonances of the insulin monomer are assigned at 500 MHz by comparative studies of chemically modified and genetically altered variants, including a mutant insulin (PheB25 → Leu) associated with diabetes mellitus. The two histidines, three phenylalanines, and four tyrosines are observed to be in distinct local environments; their assignment provides sensitive markers for studies of tertiary structure, protein dynamics, and protein folding. The environments of the tyrosine residues have also been investigated by photochemically induced dynamic nuclear polarization (photo-CIDNP) and analyzed in relation to packing constrains in the crystal structures of insulin. Dimerization involving specific B-chain interactions is observed with increasing protein concentration and is shown to depend on temperature, pH, and solvent composition. The differences between proinsulin and mini-proinsulin suggest a structural mechanism for the observation that the fully reduced B29-A1 analogue folds more efficiently than proinsulin to form the correct pattern of disulfide bonds. These results are discussed in relation to molecular mechanics calculations of insulin based on the available crystal structures

  13. Direct current (DC) resistivity and Induced Polarization (IP) monitoring of active layer dynamics at high temporal resolution

    DEFF Research Database (Denmark)

    Doetsch, J.; Fiandaca, G.; Ingeman-Nielsen, Thomas

    2015-01-01

    With permafrost thawing and changes in active layer dynamics induced by climate change, interactions between biogeochemical and thermal processes in the ground are of great importance. Here, active layer dynamics have been monitored using direct current (DC) resistivity and induced polarization (IP...... the soil freezing as a strong increase in resistivity. While the freezing horizon generally moves deeper with time, some variations in the freezing depth are observed along the profile. Comparison with depth-specific soil temperature indicates an exponential relationship between resistivity and below...

  14. Evaluated kinetic and photochemical data for atmospheric chemistry: Supplement VIII, halogen species evaluation for atmospheric chemistry

    International Nuclear Information System (INIS)

    Atkinson, R.; Baulch, D.L.; Cox, R.A.; Hampson, R.F. Jr.; Kerr, J.A.; Rossi, M.J.; Troe, J.

    2000-01-01

    This paper updates and extends part of the previous data base of critical evaluations of the kinetics and photochemistry of gas-phase chemical reactions of neutral species involved in atmospheric chemistry [J. Phys. Chem. Ref. Data 9, 295 (1980); 11, 327 (1982); 13, 1259 (1984); 18, 881 (1989); 21, 1125 (1992); 26, 521 (1997); 26, 1329 (1997); 28, 191 (1999)]. The present evaluation is limited to the inorganic halogen family of atmospherically important reactions. The work has been carried out by the authors under the auspices of the IUPAC Subcommittee on Gas Phase Kinetic Data Evaluation for Atmospheric Chemistry. Data sheets have been prepared for 102 thermal and photochemical reactions, containing summaries of the available experimental data with notes giving details of the experimental procedures. For each thermal reaction, a preferred value of the rate coefficient at 298 K is given together with a temperature dependence where possible. The selection of the preferred value is discussed and estimates of the accuracies of the rate coefficients and temperature coefficients have been made for each reaction. For each photochemical reaction the data sheets list the preferred values of the photoabsorption cross sections and the quantum yields of the photochemical reactions together with comments on how they were selected. The data sheets are intended to provide the basic physical chemical data needed as input for calculations that model atmospheric chemistry. A table summarizing the preferred rate data is provided, together with an appendix listing the available values of enthalpies of formation of the reactant and product species

  15. Photochemical synthesis of copper nanoparticles incorporated in poly(vinyl pyrrolidone)

    International Nuclear Information System (INIS)

    Giuffrida, Salvatore; Costanzo, Lucia L.; Ventimiglia, Giorgio; Bongiorno, Corrado

    2008-01-01

    The effect of the presence of poly(vinyl pyrrolidone) (PVP) on the copper nanoparticle formation, obtained by UV irradiation of ethanol solution of Cu(acac) 2 (acac = 2,4-pentanedionato), was investigated. At 254 nm, in conditions of light completely absorbed by complex, the PVP exhibited protective and stabilizing effects, as shown by the formation of a colloidal copper solution and by a block of the heterogeneous process, which leads to thin film formation on the quartz walls. The colloidal solution was tested for several months by plasmon position and it was found that it remained unaltered in inert atmosphere, but returned to the starting complex on contact with air. The PVP ability to control the particle size was investigated by carrying out photoreduction sensitized by Hacac at 254 and 300 nm, in the presence of PVP concentration varying from 0 to 0.2 M. In this range it was possible to obtain copper nanoparticles of dimensions decreasing from 30 to 4 nm. Besides this, the PVP (0.005-0.05 M) role as sensitizer was investigated by irradiating solutions of Cu(acac) 2 at 300 nm which is an inactive wavelength for copper reduction by direct light absorption. It was found that the PVP was an efficient sensitizer of the copper photoreduction. The nanoparticles were characterized by plasmon band, Trasmission Electron Microscope (TEM) as well as Dynamic Light Scattering (DSL) analysis. The overall results evidence the advantages of the PVP use in the nanoparticle copper formation through the photochemical technique such as the exclusive formation of colloidal copper, their size control, stable colloidal solution and complete return to the starting complex.

  16. Switching dynamics in reaction networks induced by molecular discreteness

    International Nuclear Information System (INIS)

    Togashi, Yuichi; Kaneko, Kunihiko

    2007-01-01

    To study the fluctuations and dynamics in chemical reaction processes, stochastic differential equations based on the rate equation involving chemical concentrations are often adopted. When the number of molecules is very small, however, the discreteness in the number of molecules cannot be neglected since the number of molecules must be an integer. This discreteness can be important in biochemical reactions, where the total number of molecules is not significantly larger than the number of chemical species. To elucidate the effects of such discreteness, we study autocatalytic reaction systems comprising several chemical species through stochastic particle simulations. The generation of novel states is observed; it is caused by the extinction of some molecular species due to the discreteness in their number. We demonstrate that the reaction dynamics are switched by a single molecule, which leads to the reconstruction of the acting network structure. We also show the strong dependence of the chemical concentrations on the system size, which is caused by transitions to discreteness-induced novel states

  17. Synthesis of fluorescent metal nanoparticles in aqueous solution by photochemical reduction

    KAUST Repository

    Kshirsagar, Prakash

    2014-01-06

    A facile green chemistry approach for the synthesis of sub-5 nm silver and gold nanoparticles is reported. The synthesis was achieved by a photochemical method using tyrosine as the photoreducing agent. The size of the gold and silver nanoparticles was about 3 and 4 nm, respectively. The nanoparticles were characterized using x-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy and photoluminescence spectroscopy. Both silver and gold nanoparticles synthesized by this method exhibited fluorescence properties and their use for cell imaging applications has been demonstrated. © 2014 IOP Publishing Ltd.

  18. Considerations on photochemical genotoxicity. II: Report of the 2009 International Workshop on Genotoxicity Testing Working Group

    NARCIS (Netherlands)

    Lynch, A.M.; Guzzie, P.J.; Bauer, D.; Gocke, E.; Itoh, S.; Jacobs, A.; Krul, C.A.M.; Schepky, A.; Tanaka, N.; Kasper, P.

    2011-01-01

    A workshop to reappraise the previous IWGT recommendations for photogenotoxicity testing [E. Gocke, L. Muller, P.J. Guzzie, S. Brendler-Schwaab, S. Bulera, C.F. Chignell, L.M. Henderson, A. Jacobs, H. Murli, R.D. Snyder, N. Tanaka, Considerations on photochemical genotoxicity: report of the

  19. Sub-nanometer glass surface dynamics induced by illumination

    International Nuclear Information System (INIS)

    Nguyen, Duc; Nienhaus, Lea; Haasch, Richard T.; Lyding, Joseph; Gruebele, Martin

    2015-01-01

    Illumination is known to induce stress and morphology changes in opaque glasses. Amorphous silicon carbide (a-SiC) has a smaller bandgap than the crystal. Thus, we were able to excite with 532 nm light a 1 μm amorphous surface layer on a SiC crystal while recording time-lapse movies of glass surface dynamics by scanning tunneling microscopy (STM). Photoexcitation of the a-SiC surface layer through the transparent crystal avoids heating the STM tip. Up to 6 × 10 4 s, long movies of surface dynamics with 40 s time resolution and sub-nanometer spatial resolution were obtained. Clusters of ca. 3-5 glass forming units diameter are seen to cooperatively hop between two states at the surface. Photoexcitation with green laser light recruits immobile clusters to hop, rather than increasing the rate at which already mobile clusters hop. No significant laser heating was observed. Thus, we favor an athermal mechanism whereby electronic excitation of a-SiC directly controls glassy surface dynamics. This mechanism is supported by an exciton migration-relaxation-thermal diffusion model. Individual clusters take ∼1 h to populate states differently after the light intensity has changed. We believe the surrounding matrix rearranges slowly when it is stressed by a change in laser intensity, and clusters serve as a diagnostic. Such cluster hopping and matrix rearrangement could underlie the microscopic mechanism of photoinduced aging of opaque glasses

  20. Dynamics of laser-induced magnetization in Ce-doped yttrium aluminum garnet

    International Nuclear Information System (INIS)

    Kolesov, Roman

    2007-01-01

    Circularly polarized short laser pulse induces nonequilibrium population of spin levels in the excited state of Ce 3+ -ion embedded in yttrium aluminium garnet crystal and, consequently, the magnetization of the crystal associated with spin polarization. Dynamic behavior of laser-induced magnetization is studied as a function of the external magnetic field. It reveals spin oscillations attributed to the effect of hyperfine magnetic field produced by 27 Al nuclei on the Ce 3+ spin. A simple theoretical model explaining spin oscillations is presented. It shows that circularly polarized light induces spin coherence at the transition between Zeeman sublevels of Ce 3+ ion in the lowest 5d state. Temporal shape of laser-induced magnetization signal reveals the following parameters of this state: (1) the spin-lattice relaxation constant is ≅2x10 7 s -1 , (2) inhomogeneous spin dephasing time is ≅4 ns, and (3) the g tensor of the state seems to be isotropic with the g factor being in the range 0.7-0.9. In addition, the width of the local hyperfine field distribution is ≅40 G

  1. The Social Network of Tracer Variations and O(100) Uncertain Photochemical Parameters in the Community Atmosphere Model

    Science.gov (United States)

    Lucas, D. D.; Labute, M.; Chowdhary, K.; Debusschere, B.; Cameron-Smith, P. J.

    2014-12-01

    Simulating the atmospheric cycles of ozone, methane, and other radiatively important trace gases in global climate models is computationally demanding and requires the use of 100's of photochemical parameters with uncertain values. Quantitative analysis of the effects of these uncertainties on tracer distributions, radiative forcing, and other model responses is hindered by the "curse of dimensionality." We describe efforts to overcome this curse using ensemble simulations and advanced statistical methods. Uncertainties from 95 photochemical parameters in the trop-MOZART scheme were sampled using a Monte Carlo method and propagated through 10,000 simulations of the single column version of the Community Atmosphere Model (CAM). The variance of the ensemble was represented as a network with nodes and edges, and the topology and connections in the network were analyzed using lasso regression, Bayesian compressive sensing, and centrality measures from the field of social network theory. Despite the limited sample size for this high dimensional problem, our methods determined the key sources of variation and co-variation in the ensemble and identified important clusters in the network topology. Our results can be used to better understand the flow of photochemical uncertainty in simulations using CAM and other climate models. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and supported by the DOE Office of Science through the Scientific Discovery Through Advanced Computing (SciDAC).

  2. Understanding of the mode of action of Fe(III)-EDDHA as iron chlorosis corrector based on its photochemical and redox behavior.

    Science.gov (United States)

    Gómez-Gallego, Mar; Pellico, Daniel; Ramírez-López, Pedro; Mancheño, María J; Romano, Santiago; de la Torre, María C; Sierra, Miguel A

    2005-10-07

    The very low reduction potential of the chelate Fe(III)-EDDHA (EDDHA = ethylenediamine N,N'-bis(2-hydroxy)phenylacetic acid) makes it unreactive in photochemically or chemically induced electron transfer processes. The lack of reactivity of this complex toward light invalidates photodegradation as an alternative mechanism for environmental elimination. However, in spite of its low reduction potential, the biological reduction of Fe(III)-EDDHA is very effective. Based on electrochemical measurements, it is proposed that Fe(III)-EDDHA itself is not the substrate of the enzyme ferric chelate reductase. Likely, at the more acidic pH in the vicinity of the roots, the ferric chelate in a closed form (FeL-) could generate a vacant coordination site that leads to an open hexacoordinate species (FeHL) where the reduction of the metal by the enzyme takes place.

  3. The photochemical stability of the Venus atmosphere against UV radiation

    International Nuclear Information System (INIS)

    Mills, F.P.; Slanger, T.G.; Allen, M.

    2004-01-01

    Full text: One unresolved question regarding the Venus atmosphere is what chemical mechanism(s) stabilize its primary constituent (CO 2 ) against UV radiation. CO 2 photolyzes on the day side into CO and O after absorbing photons at 2 rather than recombining with CO to form CO 2 , and the intense night side O 2 airglow observed quantitatively supports this. CO and O 2 are photochemically stable in an otherwise pure CO 2 atmosphere so significant abundances of CO and O 2 could accumulate on Venus if no catalytic mechanism existed to speed the reformation of CO 2 . However, the observational upper limit on ground state O 2 is equivalent to 2 from CO and O 2 . Recent laboratory work verified the existence of the ClC(O)OO catalytic mechanism that has been used in photochemical models since the early 1980s. However, there are significant uncertainties in the rates for the component steps of this catalytic mechanism. An alternative mechanism for production of CO 2 that has not previously been modeled but which could be competitive with the ClCO(O)O mechanism is the reaction CO + O 2 (c 1 Σ - u ) → CO 2 + O( 1 D) or O( 1 S), Reaction (1). A range of values for Reaction (1) will be examined in model calculations to compare with observational (UV to IR) constraints and to assess under what conditions this mechanism is competitive with the ClC(O)OO catalytic mechanism. The sensitivity of the results to uncertainties in the CO 2 UV absorption cross section also will be examined

  4. Volatile Organic Compounds from Logwood Combustion: Emissions and Transformation under Dark and Photochemical Aging Conditions in a Smog Chamber.

    Science.gov (United States)

    Hartikainen, Anni; Yli-Pirilä, Pasi; Tiitta, Petri; Leskinen, Ari; Kortelainen, Miika; Orasche, Jürgen; Schnelle-Kreis, Jürgen; Lehtinen, Kari E J; Zimmermann, Ralf; Jokiniemi, Jorma; Sippula, Olli

    2018-04-17

    Residential wood combustion (RWC) emits high amounts of volatile organic compounds (VOCs) into ambient air, leading to formation of secondary organic aerosol (SOA), and various health and climate effects. In this study, the emission factors of VOCs from a logwood-fired modern masonry heater were measured using a Proton-Transfer-Reactor Time-of-Flight Mass Spectrometer. Next, the VOCs were aged in a 29 m 3 Teflon chamber equipped with UV black lights, where dark and photochemical atmospheric conditions were simulated. The main constituents of the VOC emissions were carbonyls and aromatic compounds, which accounted for 50%-52% and 30%-46% of the detected VOC emission, respectively. Emissions were highly susceptible to different combustion conditions, which caused a 2.4-fold variation in emission factors. The overall VOC concentrations declined considerably during both dark and photochemical aging, with simultaneous increase in particulate organic aerosol mass. Especially furanoic and phenolic compounds decreased, and they are suggested to be the major precursors of RWC-originated SOA in all aging conditions. On the other hand, dark aging produced relatively high amounts of nitrogen-containing organic compounds in both gas and particulate phase, while photochemical aging increased especially the concentrations of certain gaseous carbonyls, particularly acid anhydrides.

  5. Exciton model and quantum molecular dynamics in inclusive nucleon-induced reactions

    International Nuclear Information System (INIS)

    Bevilacqua, Riccardo; Pomp, Stephan; Watanabe, Yukinobu

    2011-01-01

    We compared inclusive nucleon-induced reactions with two-component exciton model calculations and Kalbach systematics; these successfully describe the production of protons, whereas fail to reproduce the emission of composite particles, generally overestimating it. We show that the Kalbach phenomenological model needs to be revised for energies above 90 MeV; agreement improves introducing a new energy dependence for direct-like mechanisms described by the Kalbach model. Our revised model calculations suggest multiple preequilibrium emission of light charged particles. We have also compared recent neutron-induced data with quantum molecular dynamics (QMD) calculations complemented by the surface coalescence model (SCM); we observed that the SCM improves the predictive power of QMD. (author)

  6. Dynamical isospin effects in nucleon-induced reactions

    International Nuclear Information System (INIS)

    Ou Li; Li Zhuxia; Wu Xizhen

    2008-01-01

    The isospin effects in proton-induced reactions on isotopes of 112-132 Sn and the corresponding β-stable isobars are studied by means of the improved quantum molecular dynamics model and some sensitive probes for the density dependence of the symmetry energy at subnormal densities are proposed. The beam energy range is chosen to be 100-300 MeV. Our study shows that the system size dependence of the reaction cross sections for p+ 112-132 Sn deviates from the Carlson's empirical expression obtained by fitting the reaction cross sections for proton on nuclei along the β-stability line and sensitively depends on the stiffness of the symmetry energy. We also find that the angular distribution of elastic scattering for p+ 132 Sn at large impact parameters is very sensitive to the density dependence of the symmetry energy, which is uniquely due to the effect of the symmetry potential with no mixture of the effect from the isospin dependence of the nucleon-nucleon cross sections. The isospin effects in neutron-induced reactions are also studied and it is found that the effects are just opposite to that in proton-induced reactions. We find that the difference between the peaks of the angular distributions of elastic scattering for p+ 132 Sn and n+ 132 Sn at E p,n =100 MeV and b=7.5 fm is positive for soft symmetry energy U sym sf and negative for super-stiff symmetry energy U sym nlin and close to zero for linear density dependent symmetry energy U sym lin , which seems very useful for constraining the density dependence of the symmetry energy at subnormal densities

  7. Dynamic RSA for the evaluation of inducible micromotion of Oxford UKA during step-up and step-down motion.

    Science.gov (United States)

    Horsager, Kristian; Kaptein, Bart L; Rømer, Lone; Jørgensen, Peter B; Stilling, Maiken

    2017-06-01

    Background and purpose - Implant inducible micromotions have been suggested to reflect the quality of the fixation interface. We investigated the usability of dynamic RSA for evaluation of inducible micromotions of the Oxford Unicompartmental Knee Arthroplasty (UKA) tibial component, and evaluated factors that have been suggested to compromise the fixation, such as fixation method, component alignment, and radiolucent lines (RLLs). Patients and methods - 15 patients (12 men) with a mean age of 69 (55-86) years, with an Oxford UKA (7 cemented), were studied after a mean time in situ of 4.4 (3.6-5.1) years. 4 had tibial RLLs. Each patient was recorded with dynamic RSA (10 frames/second) during a step-up/step-down motion. Inducible micromotions were calculated for the tibial component with respect to the tibia bone. Postoperative component alignment was measured with model-based RSA and RLLs were measured on screened radiographs. Results - All tibial components showed inducible micromotions as a function of the step-cycle motion with a mean subsidence of up to -0.06 mm (95% CI: -0.10 to -0.03). Tibial component inducible micromotions were similar for cemented fixation and cementless fixation. Patients with tibial RLLs had 0.5° (95% CI: 0.18-0.81) greater inducible medio-lateral tilt of the tibial component. There was a correlation between postoperative posterior slope of the tibial plateau and inducible anterior-posterior tilt. Interpretation - All patients had inducible micromotions of the tibial component during step-cycle motion. RLLs and a high posterior slope increased the magnitude of inducible micromotions. This suggests that dynamic RSA is a valuable clinical tool for the evaluation of functional implant fixation.

  8. Crossfit analysis: a novel method to characterize the dynamics of induced plant responses.

    Science.gov (United States)

    Jansen, Jeroen J; van Dam, Nicole M; Hoefsloot, Huub C J; Smilde, Age K

    2009-12-16

    Many plant species show induced responses that protect them against exogenous attacks. These responses involve the production of many different bioactive compounds. Plant species belonging to the Brassicaceae family produce defensive glucosinolates, which may greatly influence their favorable nutritional properties for humans. Each responding compound may have its own dynamic profile and metabolic relationships with other compounds. The chemical background of the induced response is therefore highly complex and may therefore not reveal all the properties of the response in any single model. This study therefore aims to describe the dynamics of the glucosinolate response, measured at three time points after induction in a feral Brassica, by a three-faceted approach, based on Principal Component Analysis. First the large-scale aspects of the response are described in a 'global model' and then each time-point in the experiment is individually described in 'local models' that focus on phenomena that occur at specific moments in time. Although each local model describes the variation among the plants at one time-point as well as possible, the response dynamics are lost. Therefore a novel method called the 'Crossfit' is described that links the local models of different time-points to each other. Each element of the described analysis approach reveals different aspects of the response. The crossfit shows that smaller dynamic changes may occur in the response that are overlooked by global models, as illustrated by the analysis of a metabolic profiling dataset of the same samples.

  9. A box model study on photochemical interactions between VOCs and reactive halogen species in the marine boundary layer

    Directory of Open Access Journals (Sweden)

    K. Toyota

    2004-01-01

    Full Text Available A new chemical scheme is developed for the multiphase photochemical box model SEAMAC (size-SEgregated Aerosol model for Marine Air Chemistry to investigate photochemical interactions between volatile organic compounds (VOCs and reactive halogen species in the marine boundary layer (MBL. Based primarily on critically evaluated kinetic and photochemical rate parameters as well as a protocol for chemical mechanism development, the new scheme has achieved a near-explicit description of oxidative degradation of up to C3-hydrocarbons (CH4, C2H6, C3H8, C2H4, C3H6, and C2H2 initiated by reactions with OH radicals, Cl- and Br-atoms, and O3. Rate constants and product yields for reactions involving halogen species are taken from the literature where available, but the majority of them need to be estimated. In particular, addition reactions of halogen atoms with alkenes will result in forming halogenated organic intermediates, whose photochemical loss rates are carefully evaluated in the present work. Model calculations with the new chemical scheme reveal that the oceanic emissions of acetaldehyde (CH3CHO and alkenes (especially C3H6 are important factors for regulating reactive halogen chemistry in the MBL by promoting the conversion of Br atoms into HBr or more stable brominated intermediates in the organic form. The latter include brominated hydroperoxides, bromoacetaldehyde, and bromoacetone, which sequester bromine from a reactive inorganic pool. The total mixing ratio of brominated organic species thus produced is likely to reach 10-20% or more of that of inorganic gaseous bromine species over wide regions over the ocean. The reaction between Br atoms and C2H2 is shown to be unimportant for determining the degree of bromine activation in the remote MBL. These results imply that reactive halogen chemistry can mediate a link between the oceanic emissions of VOCs and the behaviors of compounds that are sensitive to halogen chemistry such as dimethyl

  10. Partial coupling and differential regulation of biologically and photo-chemically labile dissolved organic carbon across boreal aquatic networks

    Science.gov (United States)

    Lapierre, J.-F.; del Giorgio, P. A.

    2014-05-01

    Despite the rapidly increasing volume of research on the biological and photochemical degradation of DOC in aquatic environments, little is known on the large-scale patterns in biologically and photo-chemically degradable DOC (Bd-DOC and Pd-DOC, respectively) in continental watersheds, and on the links that exist between these two key properties that greatly influence the flow of carbon from continents to oceans. Here we explore the patterns of Bd- and Pd-DOC across hundreds of boreal lakes, rivers and wetlands spanning a large range of system trophy and terrestrial influence, and compared the drivers of these two reactive pools of DOC at the landscape level. Using standardized incubations of natural waters, we found that the concentrations of Bd- and Pd-DOC co-varied across all systems studied but were nevertheless related to different pools of dissolved organic matter (DOM, identified by fluorescence analyses) in ambient waters. A combination of nutrients and protein-like DOM explained nearly half of the variation in Bd-DOC, whereas Pd-DOC was exclusively predicted by DOM optical properties, consistent with the photochemical degradability of specific fluorescent DOM (FDOM) pools that we experimentally determined. The concentrations of colored DOM (CDOM), a proxy of terrestrial influence, almost entirely accounted for the observed relationship between FDOM and the concentrations of both Bd- and Pd-DOC. The concentrations of CDOM and of the putative bio-labile fluorescence component shifted from complete decoupling in clear-water environments to strong coupling in browner streams and wetlands. This suggests a baseline autochthonous Bd-DOC pool fuelled by internal production that is gradually overwhelmed by land-derived Bd-DOC as terrestrial influence increases across landscape gradients. The importance of land as a major source of both biologically and photo-chemically degradable DOC for continental watersheds resulted in a partial coupling of those carbon pools in

  11. Effect of Si ion irradiation on polycrystalline CdS thin film grown from novel photochemical deposition technique

    International Nuclear Information System (INIS)

    Soundeswaran, S.; Senthil Kumar, O.; Ramasamy, P.; Kabi Raj, D.; Avasthi, D.K.; Dhanasekaran, R.

    2005-01-01

    CdS thin films have been deposited from aqueous solution by photochemical reactions. The solution contains Cd(CH 3 COO) 2 and Na 2 S 2 O 3 , and pH is controlled in an acidic region by adding H 2 SO 4 . The solution is illuminated with light from a high-pressure mercury-arc lamp. CdS thin films are formed on a glass substrate by the heterogeneous nucleation and the deposited thin films have been subjected to high-energy Si ion irradiations. Si ion irradiation has been performed with an energy of 80 MeV at fluences of 1x10 11 , 1x10 12 , 1x10 13 and 1x10 14 ions/cm 2 using tandem pelletron accelerator. The irradiation-induced changes in CdS thin films are studied using XRD, Raman spectroscopy and photoluminescence. Broadening of the PL emission peak were observed with increasing irradiation fluence, which could be attributed to the band tailing effect of the Si ion irradiation. The lattice disorder takes place at high Si ion fluences

  12. Transfusion of pooled buffy coat platelet components prepared with photochemical pathogen inactivation treatment: the euroSPRITE trial

    NARCIS (Netherlands)

    D.J. van Rhenen (Dirk Jan); S. Marblie (Stephane); M. Laforet (Michel); K. Davis (Kathryn); M. Conlan (Maureen); B. Lioure (Bruno); H. Gulliksson (Hans); J.P. Cazenave; P. Metzel (Peyton); D. Pamphilon (Derwood); L. Corash (Laurence); J. Flament (Jocelyne); P. Ljungman (Per); H. Kluter; H. Vermeij (Hans); V. Mayaudon (Veronique); L. Lin (Lily); M.C. Kappers-Klunne (Mies); D. Buchholz (Don); G.E. de Greef (Georgine)

    2003-01-01

    textabstractA nucleic acid-targeted photochemical treatment (PCT) using amotosalen HCl (S-59) and ultraviolet A (UVA) light was developed to inactivate viruses, bacteria, protozoa, and leukocytes in platelet components. We conducted a controlled, randomized, double-blinded trial in thrombocytopenic

  13. Photochemical water splitting mediated by a C1 shuttle

    KAUST Repository

    Alderman, N. P.

    2016-10-31

    The possibility of performing photochemical water splitting in a two-stage system, separately releasing the H and O components, has been probed with two separate catalysts and in combination with a formaldehyde/formate shuttling redox couple. In the first stage, formaldehyde releases hydrogen vigorously in the presence of an Na[Fe(CN)]·10HO catalyst, selectively affording the formate anion. In the second stage, the formate anion is hydro-genated back to formaldehyde by water and in the presence of a BiWO photocatalyst whilst releasing oxygen. Both stages operate at room temperature and under visible light irradiation. The two separate photocatalysts are compatible since water splitting can also be obtained in one-pot experiments with simultaneous H/O evolution.

  14. Energy and Molecules from Photochemical/Photocatalytic Reactions. An Overview

    Directory of Open Access Journals (Sweden)

    Davide Ravelli

    2015-01-01

    Full Text Available Photocatalytic reactions have been defined as those processes that require both a (not consumed catalyst and light. A previous definition was whether such reactions brought a system towards or away from the (thermal equilibrium. This consideration brings in the question whether a part of the photon energy is incorporated into the photochemical reaction products. Data are provided for representative organic reactions involving or not molecular catalysts and show that energy storage occurs only when a heavily strained structure is generated, and in that case only a minor part of photon energy is actually stored (ΔG up to 25 kcal·mol−1. The green role of photochemistry/photocatalysis is rather that of forming highly reactive intermediates under mild conditions.

  15. Photochemical water splitting mediated by a C1 shuttle

    KAUST Repository

    Alderman, N. P.; Sommers, J. M.; Viasus, C. J.; Wang, C. H T; Peneau, V.; Gambarotta, S.; Vidjayacoumar, B.; Al-Bahily, K. A.

    2016-01-01

    The possibility of performing photochemical water splitting in a two-stage system, separately releasing the H and O components, has been probed with two separate catalysts and in combination with a formaldehyde/formate shuttling redox couple. In the first stage, formaldehyde releases hydrogen vigorously in the presence of an Na[Fe(CN)]·10HO catalyst, selectively affording the formate anion. In the second stage, the formate anion is hydro-genated back to formaldehyde by water and in the presence of a BiWO photocatalyst whilst releasing oxygen. Both stages operate at room temperature and under visible light irradiation. The two separate photocatalysts are compatible since water splitting can also be obtained in one-pot experiments with simultaneous H/O evolution.

  16. Disorder-induced amorphization of intermetallic compounds: A molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Massobrio, C. (Ecole Polytechnique Federale, Lausanne (Switzerland). Inst. de Physique Experimentale); Pontikis, V.; Doan, N.V.; Martin, G. (CEA Centre d' Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette (France). Dept. de Physique des Particules Elementaires)

    The reaction of the crystalline compound NiZr{sub 2} to imposed chemical disorder has been studied by molecular dynamics in the isobaric canonical ensemble. The cohesive energy used is inspired by the second moment apporoximation of the local density of states in the tight binding model. Imposed chemical disorder induced swelling (3% for full disorder, 1% for 10% disorder). Above 10% disorder, the crystalline structure athermally collapses to an amorphous state which retains much of the local chemical order. (orig.).

  17. Disorder-induced amorphization of intermetallic compounds: A molecular dynamics study

    International Nuclear Information System (INIS)

    Massobrio, C.; Pontikis, V.; Doan, N.V.; Martin, G.

    1991-01-01

    The reaction of the crystalline compound NiZr 2 to imposed chemical disorder has been studied by molecular dynamics in the isobaric canonical ensemble. The cohesive energy used is inspired by the second moment apporoximation of the local density of states in the tight binding model. Imposed chemical disorder induced swelling (3% for full disorder, 1% for 10% disorder). Above 10% disorder, the crystalline structure athermally collapses to an amorphous state which retains much of the local chemical order. (orig.)

  18. Aromatic amino acids and ultraviolet induced photoelectric effects in bilayer membranes

    Energy Technology Data Exchange (ETDEWEB)

    Huebner, J S; Arrieta, R T [University of North Florida, Jacksonville (USA); Naval Medical Research Inst., Bethesda, MD (USA))

    1982-04-01

    Ultraviolet light flashes induced voltage transients across bilayer lipid membranes when aromatic amino acids were adsorbed to one side of the membrane. These photo-effects varied with the chromophore structure, the aqueous solution salt concentration, pH and oxygen partial pressure. These photo-effects are attributed to the migration of electrically charged photochemical intermediates in the membrane, and provide a new method for studying the effects of UV light on membranes.

  19. Photochemical reactions between mercury (Hg) and dissolved organic matter decrease Hg bioavailability and methylation.

    Science.gov (United States)

    Luo, Hong-Wei; Yin, Xiangping; Jubb, Aaron M; Chen, Hongmei; Lu, Xia; Zhang, Weihua; Lin, Hui; Yu, Han-Qing; Liang, Liyuan; Sheng, Guo-Ping; Gu, Baohua

    2017-01-01

    Atmospheric deposition of mercury (Hg) to surface water is one of the dominant sources of Hg in aquatic environments and ultimately drives methylmercury (MeHg) toxin accumulation in fish. It is known that freshly deposited Hg is more readily methylated by microorganisms than aged or preexisting Hg; however the underlying mechanism of this process is unclear. We report that Hg bioavailability is decreased by photochemical reactions between Hg and dissolved organic matter (DOM) in water. Photo-irradiation of Hg-DOM complexes results in loss of Sn(II)-reducible (i.e. reactive) Hg and up to an 80% decrease in MeHg production by the methylating bacterium Geobacter sulfurreducens PCA. Loss of reactive Hg proceeded at a faster rate with a decrease in the Hg to DOM ratio and is attributed to the possible formation of mercury sulfide (HgS). These results suggest a new pathway of abiotic photochemical formation of HgS in surface water and provide a mechanism whereby freshly deposited Hg is readily methylated but, over time, progressively becomes less available for microbial uptake and methylation. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Creating Metamaterial Building Blocks with Directed Photochemical Metallization of Silver onto DNA Origami Templates.

    Science.gov (United States)

    Hossen, Md Mir; Bendickson, Lee; Palo, Pierre; Yao, Zhiqi; Nilsen-Hamilton, Marit; Hillier, Andrew C

    2018-06-07

    DNA origami can be used to create a variety of complex and geometrically unique nanostructures that can be further modified to produce building blocks for applications such as in optical metamaterials. We describe a method for creating metal-coated nanostructures using DNA origami templates and a photochemical metallization technique. Triangular DNA origami were fabricated and coated with a thin metal layer by photochemical silver reduction while either in solution or supported on a surface. The DNA origami template serves as a localized photosensitizer to facilitate reduction of silver ions directly from solution onto the DNA surface. The metallizing process is shown to result in a conformal metal coating, which grows in height to a self-limiting value with increasing photoreduction steps. Although this coating process results in a slight decrease in the triangle dimensions, the overall template shape is retained. Notably, this coating method exhibits characteristics of self-limiting and defect-filling growth, which results in a metal nanostructure that maps the shape of the original origami template with a continuous and uniform metal layer and stops growing once all available DNA sites are exhausted. © 2018 IOP Publishing Ltd.

  1. Modelling the influence of thermal effects induced by radio frequency electric field on the dynamics of the ATPase nano-biomolecular motors.

    Science.gov (United States)

    Lohrasebi, A; Mohamadi, S; Fadaie, S; Rafii-Tabar, H

    2012-07-01

    We model the dynamics of the F(0) component of the F(0)F(1)-ATPase mitochondrion-based nano-motor operating in a stochastically-fluctuating medium that represents the intracellular environment. The stochastic dynamics are modeled via Langevin equation of motion wherein fluctuations are treated as white noise. We have investigated the influence of an applied alternating electric field on the rotary motion of the F(0) rotor in such an environment. The exposure to the field induces a temperature rise in the mitochondrion's membrane, within which the F(0) is embedded. The external field also induces an electric potential that promotes a change in the mitochondrion's transmembrane potential (TMP). Both the induced temperature and the change in TMP contribute to a change in the dynamics of the F(0). We have found that for external fields in the radio frequency (RF) range, normally present in the environment and encountered by biological systems, the contribution of the induced thermal effects, relative to that of the induced TMP, to the dynamics of the F(0) is more significant. The changes in the dynamics of the F(0) part affect the frequency of the rotary motion of the F(0)F(1)-ATPase protein motor which, in turn, affects the production rate of the ATP molecules. Copyright © 2011 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

  2. A practical MGA-ARIMA model for forecasting real-time dynamic rain-induced attenuation

    Science.gov (United States)

    Gong, Shuhong; Gao, Yifeng; Shi, Houbao; Zhao, Ge

    2013-05-01

    novel and practical modified genetic algorithm (MGA)-autoregressive integrated moving average (ARIMA) model for forecasting real-time dynamic rain-induced attenuation has been established by combining genetic algorithm ideas with the ARIMA model. It is proved that due to the introduction of MGA into the ARIMA(1,1,7) model, the MGA-ARIMA model has the potential to be conveniently applied in every country or area by creating a parameter database used by the ARIMA(1,1,7) model. The parameter database is given in this paper based on attenuation data measured in Xi'an, China. The methods to create the parameter databases in other countries or areas are offered, too. Based on the experimental results, the MGA-ARIMA model has been proved practical for forecasting dynamic rain-induced attenuation in real time. The novel model given in this paper is significant for developing adaptive fade mitigation technologies at millimeter wave bands.

  3. Thermal shock induced dynamics of a spacecraft with a flexible deploying boom

    Science.gov (United States)

    Shen, Zhenxing; Li, Huijian; Liu, Xiaoning; Hu, Gengkai

    2017-12-01

    The dynamics in the process of deployment of a flexible extendible boom as a deployable structure on the spacecraft is studied. For determining the thermally induced vibrations of the boom subjected to an incident solar heat flux, an axially moving thermal-dynamic beam element based on the absolute nodal coordinate formulation which is able to precisely describe the large displacement, rotation and deformation of flexible body is presented. For the elastic forces formulation of variable-length beam element, the enhanced continuum mechanics approach is adopted, which can eliminate the Poisson locking effect, and take into account the tension-bending-torsion coupling deformations. The main body of the spacecraft, modeled as a rigid body, is described using the natural coordinates method. In the derived nonlinear thermal-dynamic equations of rigid-flexible multibody system, the mass matrix is time-variant, and a pseudo damping matrix which is without actual energy dissipation, and a heat conduction matrix which is relative to the moving speed and the number of beam element are arisen. Numerical results give the dynamic and thermal responses of the nonrotating and spinning spacecraft, respectively, and show that thermal shock has a significant influence on the dynamics of spacecraft.

  4. Chemical Kinetics and Photochemical Data for Use in Atmospheric Studies: Evaluation Number 18

    Science.gov (United States)

    Burkholder, J. B.; Sander, S. P.; Abbatt, J. P. D.; Barker, J. R.; Huie, R. E.; Kolb, C. E.; Kurylo, M. J.; Orkin, V. L.; Wilmouth, D. M.; Wine, P. H.

    2015-01-01

    This is the eighteenth in a series of evaluated sets of rate constants, photochemical cross sections, heterogeneous parameters, and thermochemical parameters compiled by the NASA Panel for Data Evaluation. The data are used primarily to model stratospheric and upper tropospheric processes, with particular emphasis on the ozone layer and its possible perturbation by anthropogenic and natural phenomena. The evaluation is available in electronic form from the following Internet URL: http://jpldataeval.jpl.nasa.gov/

  5. Interfacial electrochemistry of colloidal ruthenium dioxide and catalysis of the photochemical generation of hydrogen from water

    NARCIS (Netherlands)

    Kleijn, J.M.

    1987-01-01

    The formation of hydrogen from water using solar energy is a very attractive research topic, because of the potential use of hydrogen as an alternative, clean fuel. It has been shown by many workers in the field that photochemical hydrogen generation can be achieved in an aqueous system,

  6. Photochemical reductions of benzil and benzoin in the presence of triethylamine and TiO{sub 2} photocatalyst

    Energy Technology Data Exchange (ETDEWEB)

    Park, Joon Woo; Kim, Eun Kyung [Ewha Womans Univ., Seoul (Korea, Republic of); Koh Park, Kwang Hee [Chungnam National Univ., Daejon (Korea, Republic of)

    2002-09-01

    This paper reports the photochemical reduction of benzil 1 to benzoin 2 and the reduction of 2 to hydrobenzoin 4 in deoxygenated solvents in the presence of triethylamine (TEA) and/or TiO{sub 2}. Without TEA or TiO{sub 2}, the photolysis of 1 resulted in very low yield of 2. The presence of TEA or TiO{sub 2} increased the rate of disappearance of 1 and the yield of 2, which were further increased considerably by the presence of water. The photoreduction of 1 to 2 proceeds through an electron transfer to 1 from TEA or hole-scavenged excited TiO{sub 2} followed by protonation. In the reaction medium of 88:7:2:3 CH{sub 3}CN/CH{sub 3}OH/H{sub 2}O/TEA with 2.5 mg/mL of TiO{sub 2}, the yield of 2 was as high as 85% at 50% conversion of 1. The photolysis of 2 in homogeneous media resulted in photo-cleavage to benzoyl and hydroxybenzyl radicals, which are mostly converted to benzaldehyde. The reduction product 4 is formed in low yield through the dimerization of hydroxybenzyl radicals. The addition of TEA increased the conversion rate of 2 and the yield of 4 significantly. This was attributed to the scavenging effect of TEA for benzoyl radical to produce N,N-diethylbenzamide and the photoreduction of benzaldehyde in the presence of TEA. The ratio of ({+-}) and meso isomers of 4 obtained from the photochemical reaction is about 1.1. This ratio is the same as that from the photochemical reduction of benzaldehyde in the presence of TEA. In the TiO{sub 2}-sensitized photochemical reduction of 2, meso-4 was obtained in moderate yield. The reduction of 2 to 4 proceeds through two consecutive electron/proton transfer processes on the surface of the photocatalyst without involvement of {alpha}-cleavage. The radical 11 initially formed from 2 by one electron/proton process can also combine with hydroxy methyl radical, which is generated after hole trapping of excited TiO{sub 2} by methanol, to product 1,2-diphenylpropenone after dehydration reaction.

  7. Effect of strain-induced precipitation on dynamic recrystallization in Mg–Al–Sn alloys

    International Nuclear Information System (INIS)

    Kabir, Abu Syed Humaun; Sanjari, Mehdi; Su, Jing; Jung, In-Ho; Yue, Stephen

    2014-01-01

    Two different amounts of tin (Sn) were added to a Mg–3 wt% Al binary alloy to form different amounts of precipitates during hot deformation. The thermodynamic modeling software, FactSage ™ , was used to calculate the amounts of Sn to generate the desired relative levels of precipitation. The alloys were deformed at four different temperatures and three different strain rates to generate different amounts of precipitates. The objective was to study the effect of these precipitates on dynamic recrystallization. The results indicated that the formation of strain-induced precipitates is a function of deformation temperature, strain, and strain rate. The findings also revealed that higher amounts of precipitates reduced the volume fraction of dynamic recrystallization and refined the dynamically recrystallized grain size

  8. High performance oligomers: synthesis and photochemical properties of calix(n)arene containing various photoreactive groups

    International Nuclear Information System (INIS)

    Nishikubo, T.; Kameyama, A.

    1999-01-01

    Photoreactive calix(n)arenes containing radical polymerizable (meth)acrylate groups, and catatonically polymerizable vinyl ether, propargyl ether, oxirane and oxetane groups were synthesized by certain reactions of calix(n)arenes with the corresponding (meth)acrylic acid derivatives, vinyl ether compound, epibromohydrin and oxetane derivatives, respectively. The photochemical reaction of these calix(n)arene derivatives were also examined

  9. Modulation of photochemical damage in normal and malignant cells by naturally occurring compounds.

    Science.gov (United States)

    Lee, Yuan-Hao; Kumar, Neeru C; Glickman, Randolph D

    2012-01-01

    Certain phytochemicals, such as the stilbene, resveratrol (RES, found in red grapes and berries), and the triterpenoid, ursolic acid (UA, found in waxy berries and herbs such as rosemary and oregano), have antioxidant, anti-inflammatory and antiproliferative effects. Two human-derived cell lines, hTERT-RPE with a nonmalignant phenotype derived from retinal pigment epithelium, and ATCC CRL-11147 derived from a malignant skin melanoma, were used as in vitro models of photooxidative stress produced by exposure to the broadband output of a 150 W Hg vapor arc lamp at an irradiance of 19-26 mW cm(-2). In untreated cells, UV-VIS broadband light exposure produced a loss of proliferative ability, an activation of NF-κB and an increase in protein carbonyl adducts at 24 h postexposure. Pretreatment of the cells with RES or UA at 1-2 μmsignificantly reduced the amount of phosphorylated NF-κB at 24 h postexposure. RES pretreatment reduced the burden of light-induced protein carbonyl adducts by up to 25% in exposed cells. UA treatment markedly increased the sensitivity of melanoma cells to UV radiation, while conferring some photoprotection to RPE cells. These observations indicate that phytochemicals modulate the cellular response to photochemical stress by interacting with specific cell-signaling pathways. © 2012 Wiley Periodicals, Inc. Photochemistry and Photobiology © 2012 The American Society of Photobiology.

  10. Chemical characteristics of fulvic acids from Arctic surface waters: Microbial contributions and photochemical transformations

    Science.gov (United States)

    Cory, Rose M.; McKnight, Diane M.; Chin, Yu-Ping; Miller, Penney; Jaros, Chris L.

    2007-12-01

    Dissolved organic matter (DOM) originating from the extensive Arctic tundra is an important source of organic material to the Arctic Ocean. Chemical characteristics of whole water dissolved organic matter (DOM) and the fulvic acid fraction of DOM were studied from nine surface waters in the Arctic region of Alaska to gain insight into the extent of microbial and photochemical transformation of this DOM. All the fulvic acids had a strong terrestrial/higher plant signature, with uniformly depleted δ13C values of -28‰, and low fluorescence indices around 1.3. Several of the measured chemical characteristics of the Arctic fulvic acids were related to water residence time, a measure of environmental exposure to sunlight and microbial activity. For example, fulvic acids from Arctic streams had higher aromatic contents, higher specific absorbance values, lower nitrogen content, lower amino acid-like fluorescence and were more depleted in δ15N relative to fulvic acids isolated from lake and coastal surface waters. The differences in the nitrogen signature between the lake and coastal fulvic acids compared to the stream fulvic acids indicated that microbial contributions to the fulvic acid pool increased with increasing water residence time. The photo-lability of the fulvic acids was positively correlated with water residence time, suggesting that the fulvic acids isolated from source waters with larger water residence times (i.e., lakes and coastal waters) have experienced greater photochemical degradation than the stream fulvic acids. In addition, many of the initial differences in fulvic acid chemical characteristics across the gradient of water residence times were consistent with changes observed in fulvic acid photolysis experiments. Taken together, results from this study suggest that photochemical processes predominantly control the chemical character of fulvic acids in Arctic surface waters. Our findings show that hydrologic transport in addition to

  11. Distinct retrosplenial cortex cell populations and their spike dynamics during ketamine-induced unconscious state.

    Directory of Open Access Journals (Sweden)

    Grace E Fox

    Full Text Available Ketamine is known to induce psychotic-like symptoms, including delirium and visual hallucinations. It also causes neuronal damage and cell death in the retrosplenial cortex (RSC, an area that is thought to be a part of high visual cortical pathways and at least partially responsible for ketamine's psychotomimetic activities. However, the basic physiological properties of RSC cells as well as their response to ketamine in vivo remained largely unexplored. Here, we combine a computational method, the Inter-Spike Interval Classification Analysis (ISICA, and in vivo recordings to uncover and profile excitatory cell subtypes within layers 2&3 and 5&6 of the RSC in mice within both conscious, sleep, and ketamine-induced unconscious states. We demonstrate two distinct excitatory principal cell sub-populations, namely, high-bursting excitatory principal cells and low-bursting excitatory principal cells, within layers 2&3, and show that this classification is robust over the conscious states, namely quiet awake, and natural unconscious sleep periods. Similarly, we provide evidence of high-bursting and low-bursting excitatory principal cell sub-populations within layers 5&6 that remained distinct during quiet awake and sleep states. We further examined how these subtypes are dynamically altered by ketamine. During ketamine-induced unconscious state, these distinct excitatory principal cell subtypes in both layer 2&3 and layer 5&6 exhibited distinct dynamics. We also uncovered different dynamics of local field potential under various brain states in layer 2&3 and layer 5&6. Interestingly, ketamine administration induced high gamma oscillations in layer 2&3 of the RSC, but not layer 5&6. Our results show that excitatory principal cells within RSC layers 2&3 and 5&6 contain multiple physiologically distinct sub-populations, and they are differentially affected by ketamine.

  12. Space Shuttle Main Engine Low Pressure Oxidizer Turbo-Pump Inducer Dynamic Environment Characterization through Water Model and Hot-Fire Testing

    Science.gov (United States)

    Arellano, Patrick; Patton, Marc; Schwartz, Alan; Stanton, David

    2006-01-01

    The Low Pressure Oxidizer Turbopump (LPOTP) inducer on the Block II configuration Space Shuttle Main Engine (SSME) experienced blade leading edge ripples during hot firing. This undesirable condition led to a minor redesign of the inducer blades. This resulted in the need to evaluate the performance and the dynamic environment of the redesign, relative to the current configuration, as part of the design acceptance process. Sub-scale water model tests of the two inducer configurations were performed, with emphasis on the dynamic environment due to cavitation induced vibrations. Water model tests were performed over a wide range of inlet flow coefficient and pressure conditions, representative of the scaled operating envelope of the Block II SSME, both in flight and in ground hot-fire tests, including all power levels. The water test hardware, facility set-up, type and placement of instrumentation, the scope of the test program, specific test objectives, data evaluation process and water test results that characterize and compare the two SSME LPOTP inducers are discussed. In addition, dynamic characteristics of the two water models were compared to hot fire data from specially instrumented ground tests. In general, good agreement between the water model and hot fire data was found, which confirms the value of water model testing for dynamic characterization of rocket engine turbomachinery.

  13. The evolution of photochemical smog in a power plant plume

    Science.gov (United States)

    Luria, Menachem; Valente, Ralph J.; Tanner, Roger L.; Gillani, Noor V.; Imhoff, Robert E.; Mueller, Stephen F.; Olszyna, Kenneth J.; Meagher, James F. Present address: Aeronomy Laboratory, NOAA, 325 Broadway, Boulder CO 80303, USA.)

    The evolution of photochemical smog in a plant plume was investigated with the aid of an instrumented helicopter. Air samples were taken in the plume of the Cumberland Power Plant, located in central Tennessee, during the afternoon of 16 July 1995 as part of the Southern Oxidants Study - Nashville Middle Tennessee Ozone Study. Twelve cross-wind air sampling traverses were made at six distance groups from 35 to 116 km from the source. During the sampling period the winds were from the west-northwest and the plume drifted towards the city of Nashville TN. Ten of the traverses were made upwind of the city, where the power plant plume was isolated, and two traverses downwind of the city when the plumes were possibly mixed. The results revealed that even six hours after the release, excess ozone production was limited to the edges of the plume. Only when the plume was sufficiently dispersed, but still upwind of Nashville, was excess ozone (up to 109 ppbv, 50-60 ppbv above background levels) produced in the center of the plume. The concentrations image of the plume and a Lagrangian particle model suggests that portions of the power plant plume mixed with the urban plume. The mixed urban power plant plume began to regenerate O 3 that peaked at 120 ppbv at a short distance (15-25 km) downwind of Nashville. Ozone productivity (the ratio of excess O 3 to NO y and NO z) in the isolated plume was significantly lower compared with that found in the city plume. The production of nitrate, a chain termination product, was significantly higher in the power plant plume compared to the mixed plume, indicating shorter chain length of the photochemical smog chain reaction mechanism.

  14. The evolution of photochemical smog in a power plant plume

    International Nuclear Information System (INIS)

    Luria, M.; The Hebrew University, Jerusalem; Valente, R.J.; Tanner, R.L.; Imhoff, R.E.; Mueller, S.F.; Olszyna, K.J.; Meagher, J.F.; Gillani, N.V.; University of Alabama, Huntsville, AL

    1999-01-01

    The evolution of photochemical smog in a plant plume was investigated with the aid of an instrumented helicopter. Air samples were taken in the plume of the Cumberland Power Plant, located in central Tennessee, during the afternoon of 16 July 1995 as part of the Southern Oxidants Study - Nashville Middle Tennessee Ozone Study. Twelve cross-wind air sampling traverses were made at six distance groups from 35 to 116 km from the source. During the sampling period the winds were from the west-northwest and the plume drifted towards the city of Nashville TN. Ten of the traverses were made upwind of the city, where the power plant plume was isolated, and two traverses downwind of the city when the plumes were possibly mixed. The results revealed that even six hours after the release, excess ozone production was limited to the edges of the plume. Only when the plume was sufficiently dispersed, but still upwind of Nashville, was excess ozone (up to 109 ppbv, 50-60 ppbv above background levels) produced in the center of the plume. The concentrations image of the plume and a Lagrangian particle model suggests that portions of the power plant plume mixed with the urban plume. The mixed urban power plant plume began to regenerate O 3 that peaked at 120 ppbv at a short distance (15-25 km) downwind of Nashville. Ozone productivity (the ratio of excess O 3 to NO y and NO z ) in the isolated plume was significantly lower compared with that found in the city plume. The production of nitrate, a chain termination product, was significantly higher in the power plant plume compared to the mixed plume, indicating shorter chain length of the photochemical smog chain reaction mechanism. (author)

  15. Redox reaction in photochemical and ionizing irradiation systems

    International Nuclear Information System (INIS)

    Slama-Schwok, A.

    1985-09-01

    This work presents a basic study of electron transfer reactions which could be involved in appropriate systems for photochemical conversion and storage of solar energy. The aim was to extend the knowledge to new photosensitizers and quenchers and to compare them with the most popular photosensitizers-quenchers system, i.e. a rubidium complex. The photosensitizer studied here is an irridium complex. We studied in this work the air oxidation of bromide to Br 3 - and H 2 O 2 using the irridium complex as the sensitizer. The reducing properties of the reduced irridium complex photosensitizer were studied, using the pulse radiolysis techniques. In conclusion, the oxidation reduction properties of the irridium and its lowest excited state correspond to most of the photosensitizer for electron transfer reactions. The energy temporary present in the charge separation products can be stored using appropriate environment such as polyelectrolytes

  16. Crossfit analysis: a novel method to characterize the dynamics of induced plant responses

    Directory of Open Access Journals (Sweden)

    Smilde Age K

    2009-12-01

    Full Text Available Abstract Background Many plant species show induced responses that protect them against exogenous attacks. These responses involve the production of many different bioactive compounds. Plant species belonging to the Brassicaceae family produce defensive glucosinolates, which may greatly influence their favorable nutritional properties for humans. Each responding compound may have its own dynamic profile and metabolic relationships with other compounds. The chemical background of the induced response is therefore highly complex and may therefore not reveal all the properties of the response in any single model. Results This study therefore aims to describe the dynamics of the glucosinolate response, measured at three time points after induction in a feral Brassica, by a three-faceted approach, based on Principal Component Analysis. First the large-scale aspects of the response are described in a 'global model' and then each time-point in the experiment is individually described in 'local models' that focus on phenomena that occur at specific moments in time. Although each local model describes the variation among the plants at one time-point as well as possible, the response dynamics are lost. Therefore a novel method called the 'Crossfit' is described that links the local models of different time-points to each other. Conclusions Each element of the described analysis approach reveals different aspects of the response. The crossfit shows that smaller dynamic changes may occur in the response that are overlooked by global models, as illustrated by the analysis of a metabolic profiling dataset of the same samples.

  17. Potential biosignatures in super-Earth atmospheres II. Photochemical responses.

    Science.gov (United States)

    Grenfell, J L; Gebauer, S; Godolt, M; Palczynski, K; Rauer, H; Stock, J; von Paris, P; Lehmann, R; Selsis, F

    2013-05-01

    Spectral characterization of super-Earth atmospheres for planets orbiting in the habitable zone of M dwarf stars is a key focus in exoplanet science. A central challenge is to understand and predict the expected spectral signals of atmospheric biosignatures (species associated with life). Our work applies a global-mean radiative-convective-photochemical column model assuming a planet with an Earth-like biomass and planetary development. We investigated planets with gravities of 1g and 3g and a surface pressure of 1 bar around central stars with spectral classes from M0 to M7. The spectral signals of the calculated planetary scenarios have been presented by in an earlier work by Rauer and colleagues. The main motivation of the present work is to perform a deeper analysis of the chemical processes in the planetary atmospheres. We apply a diagnostic tool, the Pathway Analysis Program, to shed light on the photochemical pathways that form and destroy biosignature species. Ozone is a potential biosignature for complex life. An important result of our analysis is a shift in the ozone photochemistry from mainly Chapman production (which dominates in Earth's stratosphere) to smog-dominated ozone production for planets in the habitable zone of cooler (M5-M7)-class dwarf stars. This result is associated with a lower energy flux in the UVB wavelength range from the central star, hence slower planetary atmospheric photolysis of molecular oxygen, which slows the Chapman ozone production. This is important for future atmospheric characterization missions because it provides an indication of different chemical environments that can lead to very different responses of ozone, for example, cosmic rays. Nitrous oxide, a biosignature for simple bacterial life, is favored for low stratospheric UV conditions, that is, on planets orbiting cooler stars. Transport of this species from its surface source to the stratosphere where it is destroyed can also be a key process. Comparing 1g with

  18. Femtosecond Laser Irradiation of Plasmonic Nanoparticles in Polymer Matrix: Implications for Photothermal and Photochemical Material Alteration

    Directory of Open Access Journals (Sweden)

    Anton A. Smirnov

    2014-11-01

    Full Text Available We analyze the opportunities provided by the plasmonic nanoparticles inserted into the bulk of a transparent medium to modify the material by laser light irradiation. This study is provoked by the advent of photo-induced nano-composites consisting of a typical polymer matrix and metal nanoparticles located in the light-irradiated domains of the initially homogeneous material. The subsequent irradiation of these domains by femtosecond laser pulses promotes a further alteration of the material properties. We separately consider two different mechanisms of material alteration. First, we analyze a photochemical reaction initiated by the two-photon absorption of light near the plasmonic nanoparticle within the matrix. We show that the spatial distribution of the products of such a reaction changes the symmetry of the material, resulting in the appearance of anisotropy in the initially isotropic material or even in the loss of the center of symmetry. Second, we analyze the efficiency of a thermally-activated chemical reaction at the surface of a plasmonic particle and the distribution of the product of such a reaction just near the metal nanoparticle irradiated by an ultrashort laser pulse.

  19. Vacuolar and cytoskeletal dynamics during elicitor-induced programmed cell death in tobacco BY-2 cells.

    Science.gov (United States)

    Higaki, Takumi; Kadota, Yasuhiro; Goh, Tatsuaki; Hayashi, Teruyuki; Kutsuna, Natsumaro; Sano, Toshio; Hasezawa, Seiichiro; Kuchitsu, Kazuyuki

    2008-09-01

    Responses of plant cells to environmental stresses often involve morphological changes, differentiation and redistribution of various organelles and cytoskeletal network. Tobacco BY-2 cells provide excellent model system for in vivo imaging of these intracellular events. Treatment of the cell cycle-synchronized BY-2 cells with a proteinaceous oomycete elicitor, cryptogein, induces highly synchronous programmed cell death (PCD) and provide a model system to characterize vacuolar and cytoskeletal dynamics during the PCD. Sequential observation revealed dynamic reorganization of the vacuole and actin microfilaments during the execution of the PCD. We further characterized the effects cryptogein on mitotic microtubule organization in cell cycle-synchronized cells. Cryptogein treatment at S phase inhibited formation of the preprophase band, a cortical microtubule band that predicts the cell division site. Cortical microtubules kept their random orientation till their disruption that gradually occurred during the execution of the PCD twelve hours after the cryptogein treatment. Possible molecular mechanisms and physiological roles of the dynamic behavior of the organelles and cytoskeletal network in the pathogenic signal-induced PCD are discussed.

  20. Sunscreen protection against ultraviolet radiation-induced pyrimidine dimers in mouse epidermal DNA

    International Nuclear Information System (INIS)

    Ley, R.D.

    1997-01-01

    Solar ultraviolet radiation (UVR) induces a number of pathologic conditions of mammalian skin including erythema, oedema, hyperplasia, sunburn cell formation and skin cancer. Consequently, UVR-induced DNA damage has been implicated as one of the photochemical events that results in the formation of these pathological changes. The ability of sunscreens to protect against UVR-induced DNA damage has not been well characterized especially with UVA (320-400 nm) wavelengths and UVA absorbers. In this paper we present results of a study aimed at determining the efficacy of two sunscreens at preventing the induction of pyrmidine dimers in basal cell DNA of mice exposed to solar-simulated UVR (SSUV) wavelengths (290-400 nm) or to UVA (320-400 nm). (author)

  1. Sunscreen protection against ultraviolet radiation-induced pyrimidine dimers in mouse epidermal DNA

    Energy Technology Data Exchange (ETDEWEB)

    Ley, R.D. [The Lovelace Institutes, Albuqeurque, NM (United States). Photomdecine Program; Fourtanier, A. [L`Oreal, Advanced Research, Clichy (France)

    1997-06-01

    Solar ultraviolet radiation (UVR) induces a number of pathologic conditions of mammalian skin including erythema, oedema, hyperplasia, sunburn cell formation and skin cancer. Consequently, UVR-induced DNA damage has been implicated as one of the photochemical events that results in the formation of these pathological changes. The ability of sunscreens to protect against UVR-induced DNA damage has not been well characterized especially with UVA (320-400 nm) wavelengths and UVA absorbers. In this paper we present results of a study aimed at determining the efficacy of two sunscreens at preventing the induction of pyrmidine dimers in basal cell DNA of mice exposed to solar-simulated UVR (SSUV) wavelengths (290-400 nm) or to UVA (320-400 nm). (author).

  2. Dynamic behaviour and shock-induced martensite transformation in near-beta Ti-5553 alloy under high strain rate loading

    Directory of Open Access Journals (Sweden)

    Wang Lin

    2015-01-01

    Full Text Available Ti-5553 alloy is a near-beta titanium alloy with high strength and high fracture toughness. In this paper, the dynamic behaviour and shock-induced martensite phase transformation of Ti-5553 alloy with alpha/beta phases were investigated. Split Hopkinson Pressure Bar was employed to investigate the dynamic properties. Microstructure evolutions were characterized by Scanning Electronic Microscopy and Transmission Electron Microscope. The experimental results have demonstrated that Ti-5553 alloy with alpha/beta phases exhibits various strain rate hardening effects, both failure through adiabatic shear band. Ti-5553 alloy with Widmannstatten microstructure exhibit more obvious strain rate hardening effect, lower critical strain rate for ASB nucleation, compared with the alloy with Bimodal microstructures. Under dynamic compression, shock-induced beta to alpha” martensite transformation occurs.

  3. Odd-parity currents induced by dynamic deformations in graphene-like systems

    International Nuclear Information System (INIS)

    Zhang, Kai; Zhang, Erhu; Chen, Huawei; Zhang, Shengli

    2016-01-01

    Reduced (3  +  1)-dimensional Dirac systems with inter-pseudo-spin and inter-valley scattering are employed to investigate current responses to (chiral) gauge fields in graphene-like systems. From (chiral) current—(chiral) current correlation functions, we derive the current responses. Except for electric currents induced by external gauge fields, we find the inter-valley scattering can break the topological nature of odd-parity currents. Given the proper conditions, this property can help us realize valley-polarized electric currents. Through the dynamic deformations generating the chiral gauge fields, we find the vortex-like currents while their profiles can be tuned by superposition of some deformations. In particular, we find a more manageable approach to realize the topological electric current by choosing a linear dynamic deformation. (paper)

  4. Photochemically enhanced microbial degradation of environmental pollutants

    International Nuclear Information System (INIS)

    Katayama, A.; Matsumura, F.

    1991-01-01

    Biodegradation of persistent halogenated organic pollutants is of great interest from the viewpoint of its potential use to cleanup the contaminated sites and industrial waste streams on-site (i.e., in situ remediation). Recent studies have shown that lignin-degrading white rot fungi possess capabilities to degrade a variety of highly recalcitrant and toxic compounds. On the other hand, photodegradation by sunlight or ultraviolet light (UV) has not been considered as a potential technology to detoxify the contaminated sites, in spite of the availability of extensive research data, because of its limited reaching ability to subsurface locations. In view of the urgent needs for the development of technology to deal with mounting problems of toxic wastes, the authors have decided to experiment with the ideas of combining photochemical and microbial technologies. The main obstacle in developing such simultaneous combination systems has been the susceptibilities of microorganisms in general to UV irradiation. To overcome this problem, the authors have developed an ultraviolet- and fungicide-resistant strain of white rot fungus and now report their results

  5. Decomposition of oxalate precipitates by photochemical reaction

    International Nuclear Information System (INIS)

    Yoo, J.H.; Kim, E.H.

    1998-01-01

    A photo-radiation method was applied to decompose oxalate precipitates so that it can be dissolved into dilute nitric acid. This work has been studied as a part of partitioning of minor actinides. Minor actinides can be recovered from high-level wastes as oxalate precipitates, but they tend to be coprecipitated together with lanthanide oxalates. This requires another partitioning step for mutual separation of actinide and lanthanide groups. In this study, therefore, the photochemical decomposition mechanism of oxalates in the presence of nitric acid was elucidated by experimental work. The decomposition of oxalates was proved to be dominated by the reaction with hydroxyl radical generated from the nitric acid, rather than with nitrite ion also formed from nitrate ion. The decomposition rate of neodymium oxalate, which was chosen as a stand-in compound representing minor actinide and lanthanide oxalates, was found to be 0.003 M/hr at the conditions of 0.5 M HNO 3 and room temperature when a mercury lamp was used as a light source. (author)

  6. Decomposition of oxalate precipitates by photochemical reaction

    International Nuclear Information System (INIS)

    Jae-Hyung Yoo; Eung-Ho Kim

    1999-01-01

    A photo-radiation method was applied to decompose oxalate precipitates so that it can be dissolved into dilute nitric acid. This work has been studied as a part of partitioning of minor actinides. Minor actinides can be recovered from high-level wastes as oxalate precipitates, but they tend to be coprecipitated together with lanthanide oxalates. This requires another partitioning step for mutual separation of actinide and lanthanide groups. In this study, therefore, some experimental work of photochemical decomposition of oxalate was carried out to prove its feasibility as a step of partitioning process. The decomposition of oxalic acid in the presence of nitric acid was performed in advance in order to understand the mechanistic behaviour of oxalate destruction, and then the decomposition of neodymium oxalate, which was chosen as a stand-in compound representing minor actinide and lanthanide oxalates, was examined. The decomposition rate of neodymium oxalate was found as 0.003 mole/hr at the conditions of 0.5 M HNO 3 and room temperature when a mercury lamp was used as a light source. (author)

  7. Multi-mode-multi-state quantum dynamics of key five-membered heterocycles: spectroscopy and ultrafast internal conversion

    International Nuclear Information System (INIS)

    Koeppel, H.; Gromov, E.V.; Trofimov, A.B.

    2004-01-01

    The multi-mode and multi-state vibronic interactions in the heterocyclic molecules furan, pyrrole, thiophene and their radical cations are investigated theoretically, employing a linear vibronic coupling scheme. The underlying system parameters are determined from large-scale ab initio computations. Previous time-independent dynamical calculations on the radical cations are extended by wave-packet propagations (using the MCTDH method) confirming the strong nonadiabatic coupling effects. For the singlet excited states of furan and thiophene quantum dynamical calculations are presented which go beyond the two-state approximation frequently applied in the literature. The characteristic spectral structures are well reproduced, especially in the case of furan. The implications of these results on the photochemical reaction dynamics of these species are discussed

  8. Photochemical studies on aromatic γ,δ-epoxy ketones: efficient synthesis of benzocyclobutanones and indanones.

    Science.gov (United States)

    Shao, Yutian; Yang, Chao; Gui, Weijun; Liu, Yang; Xia, Wujiong

    2012-04-11

    Irradiation of terminal aromatic γ,δ-epoxy ketones with a 450 W UV lamp led to Norrish type II cyclization/semi-pinacol rearrangement cascade reaction which formed the benzocyclobutanones containing a full-carbon quaternary center, whereas irradiation of substituted aromatic γ,δ-epoxy ketones led to the indanones through a photochemical epoxy rearrangement and 1,5-biradicals cyclization tandem reaction. This journal is © The Royal Society of Chemistry 2012

  9. Molecular orbital study of iron pentacarbonyl and its photochemical fragments Fe(CO) sub(n)

    International Nuclear Information System (INIS)

    Guenzburger, D.J.R.; Saitovitch, E.M.B.; De Paoli, M.-A.; Manella, H.

    1982-01-01

    Self-consistent Molecular Orbital calculations were performed for Fe(CO) 5 and its photofragments Fe(CO) sub(n), 1 5 , photoelectron and optical spectra are analysed, and photochemical behaviour is discussed. The Moessbauer isomer shifts and quadrupole splittings are investigated. In the case of Fe(CO) 5 and Fe(CO) 4 , the values derived for these hyperfine interactions are compared to experimental measurements reported in a polyethylene matrix. (Author) [pt

  10. Synthesis of fluorescent metal nanoparticles in aqueous solution by photochemical reduction

    International Nuclear Information System (INIS)

    Kshirsagar, Prakash; Brunetti, Virgilio; Malvindi, Maria Ada; Pompa, Pier Paolo; Sangaru, Shiv Shankar

    2014-01-01

    A facile green chemistry approach for the synthesis of sub-5 nm silver and gold nanoparticles is reported. The synthesis was achieved by a photochemical method using tyrosine as the photoreducing agent. The size of the gold and silver nanoparticles was about 3 and 4 nm, respectively. The nanoparticles were characterized using x-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy and photoluminescence spectroscopy. Both silver and gold nanoparticles synthesized by this method exhibited fluorescence properties and their use for cell imaging applications has been demonstrated. (paper)

  11. Large-scale photochemical reactions of nanocrystalline suspensions: a promising green chemistry method.

    Science.gov (United States)

    Veerman, Marcel; Resendiz, Marino J E; Garcia-Garibay, Miguel A

    2006-06-08

    Photochemical reactions in the solid state can be scaled up from a few milligrams to 10 grams by using colloidal suspensions of a photoactive molecular crystal prepared by the solvent shift method. Pure products are recovered by filtration, and the use of H(2)O as a suspension medium makes this method a very attractive one from a green chemistry perspective. Using the photodecarbonylation of dicumyl ketone (DCK) as a test system, we show that reaction efficiencies in colloidal suspensions rival those observed in solution. [reaction: see text

  12. Catalysis of photochemical hydrogen production by metal dithiolenes in aqueous organic solvents

    International Nuclear Information System (INIS)

    Zeug, N.

    1983-01-01

    Photolysis(lambda>=248 nm) of zinc ditetrabutylammonium-bis(cis-1,2-dicyano-1,2-dithiol-ethylene) in mixtures of water with 2,5-dihydrofuran (2,5-DHF) or tetrahydroguran (THF) gives rise to catalytic production of hydrogen. The mechanisms of this process were studied here. The photochemical and thermal properties of zinc dithiolene were studied along with the analogous cadmium and mercury complexes. It could be shown that zinc dithiolene is in fact only the precursor to the actual catalyst which has been identified elsewhere as zinc sulphide. (orig./GG) [de

  13. Computational fluid-dynamic model of laser-induced breakdown in air

    International Nuclear Information System (INIS)

    Dors, Ivan G.; Parigger, Christian G.

    2003-01-01

    Temperature and pressure profiles are computed by the use of a two-dimensional, axially symmetric, time-accurate computational fluid-dynamic model for nominal 10-ns optical breakdown laser pulses. The computational model includes a kinetics mechanism that implements plasma equilibrium kinetics in ionized regions and nonequilibrium, multistep, finite-rate reactions in nonionized regions. Fluid-physics phenomena following laser-induced breakdown are recorded with high-speed shadowgraph techniques. The predicted fluid phenomena are shown by direct comparison with experimental records to agree with the flow patterns that are characteristic of laser spark decay

  14. UV-photochemical vapor generation of selenium for atomic absorption spectrometry: Optimization and 75Se radiotracer efficiency study

    Czech Academy of Sciences Publication Activity Database

    Rybínová, M.; Musil, Stanislav; Červený, J.; Vobecký, Miloslav; Rychlovský, P.

    2016-01-01

    Roč. 123, SEP (2016), s. 134-142 ISSN 0584-8547 R&D Projects: GA ČR GA14-23532S Institutional support: RVO:68081715 Keywords : UV-photochemical vapor generation * Selenium * 75Se radiotracer Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 3.241, year: 2016

  15. Development of advanced technologies for photochemical tritium recovery. Bi-quarterly program report, 1 April-30 September 1980

    International Nuclear Information System (INIS)

    Herman, I.P.; Marling, J.B.

    1980-01-01

    The laboratory facility for photochemical tritium separation research has been completed. Methods for synthesizing the mono-tritiated halogenated methanes have been developed. Notably, CTF 3 has been synthesized and spectrally analyzed. The CTF 3 vibrational frequencies are found to be in quite good agreement with earlier calculations

  16. Photosynthesis by isolated chloroplasts. IV. General concept and comparison of three photochemical reactions

    Energy Technology Data Exchange (ETDEWEB)

    Arnon, D I; Allen, M B; Whatley, F R

    1956-01-01

    Procedures are described for the preparation of chloroplasts capable of carrying out three photochemical reactions, each representing an increasingly complex phase of photosynthesis: photolysis of water (Hill reaction), esterification of inorganic phosphate into adenosine triphosphate (photosynthetic phosphorylation) and the reduction of carbon dioxide to the level of carbohydrates with a simultaneous evolution of oxygen. The three photochemical reactions were separable by variations in the technique for preparation of chloroplasts and by differential inhibition by several reagents. Inhibition of a more complex phase of photosynthesis does not affect the simpler one which precedes it and, conversely, the inhibition of a simpler phase of photosynthesis is paralleled by an inhibition of the more complex phase which follows. Reversible inhibition of CO/sub 2/ fixation and photosynthetic phosphorylation, but not of photolysis, by sulfhydryl group inhibitors suggests that sulfhydryl compounds (enzymes, cofactors, or both) are involved in phosphorylation and CO/sub 2/ fixation, but not in the primary conversion of light into chemical energy as measured by the Hill reaction. Evidence is presented in support of the conclusion that the synthesis of ATP by green cells occurs at two distinct sites: anaerobically in chloroplasts by photosynthetic phosphorylation, and acrobically in smaller cytoplasmic particles, presumably mitochondria, by oxidative phosphorylation independent of light. A general scheme of photosynthesis by chloroplasts, consistent with these findings, is presented. 44 references, 8 figures, 4 tables.

  17. Dynamic photosynthesis in different environmental conditions.

    Science.gov (United States)

    Kaiser, Elias; Morales, Alejandro; Harbinson, Jeremy; Kromdijk, Johannes; Heuvelink, Ep; Marcelis, Leo F M

    2015-05-01

    Incident irradiance on plant leaves often fluctuates, causing dynamic photosynthesis. Whereas steady-state photosynthetic responses to environmental factors have been extensively studied, knowledge of dynamic modulation of photosynthesis remains scarce and scattered. This review addresses this discrepancy by summarizing available data and identifying the research questions necessary to advance our understanding of interactions between environmental factors and dynamic behaviour of photosynthesis using a mechanistic framework. Firstly, dynamic photosynthesis is separated into sub-processes related to proton and electron transport, non-photochemical quenching, control of metabolite flux through the Calvin cycle (activation states of Rubisco and RuBP regeneration, and post-illumination metabolite turnover), and control of CO₂ supply to Rubisco (stomatal and mesophyll conductance changes). Secondly, the modulation of dynamic photosynthesis and its sub-processes by environmental factors is described. Increases in ambient CO₂ concentration and temperature (up to ~35°C) enhance rates of photosynthetic induction and decrease its loss, facilitating more efficient dynamic photosynthesis. Depending on the sensitivity of stomatal conductance, dynamic photosynthesis may additionally be modulated by air humidity. Major knowledge gaps exist regarding environmental modulation of loss of photosynthetic induction, dynamic changes in mesophyll conductance, and the extent of limitations imposed by stomatal conductance for different species and environmental conditions. The study of mutants or genetic transformants for specific processes under various environmental conditions could provide significant progress in understanding the control of dynamic photosynthesis. © The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

  18. Lévy stable noise-induced transitions: stochastic resonance, resonant activation and dynamic hysteresis

    International Nuclear Information System (INIS)

    Dybiec, Bartłomiej; Gudowska-Nowak, Ewa

    2009-01-01

    A standard approach to analysis of noise-induced effects in stochastic dynamics assumes a Gaussian character of the noise term describing interaction of the analyzed system with its complex surroundings. An additional assumption about the existence of timescale separation between the dynamics of the measured observable and the typical timescale of the noise allows external fluctuations to be modeled as temporally uncorrelated and therefore white. However, in many natural phenomena the assumptions concerning the above mentioned properties of 'Gaussianity' and 'whiteness' of the noise can be violated. In this context, in contrast to the spatiotemporal coupling characterizing general forms of non-Markovian or semi-Markovian Lévy walks, so called Lévy flights correspond to the class of Markov processes which can still be interpreted as white, but distributed according to a more general, infinitely divisible, stable and non-Gaussian law. Lévy noise-driven non-equilibrium systems are known to manifest interesting physical properties and have been addressed in various scenarios of physical transport exhibiting a superdiffusive behavior. Here we present a brief overview of our recent investigations aimed at understanding features of stochastic dynamics under the influence of Lévy white noise perturbations. We find that the archetypal phenomena of noise-induced ordering are robust and can be detected also in systems driven by memoryless, non-Gaussian, heavy-tailed fluctuations with infinite variance

  19. Ozone modeling for compliance planning: A synopsis of ''The Use of Photochemical Air Quality Models for Evaluating Emission Control Strategies: A Synthesis Report''

    International Nuclear Information System (INIS)

    Blanchard, C.L.

    1992-12-01

    The 1990 federal Clean Air Act Amendments require that many nonattainment areas use gridded, photochemical air quality models to develop compliance plans for meeting the ambient ozone standard. Both industry and regulatory agencies will need to consider explicitly the strengths and limitations of the models. Photochemical air quality models constitute the principal tool available for evaluating the relative effectiveness of alternative emission control strategies. Limitations in the utility of modeling results stem from the uncertainty and bias of predictions for modeled episodes, possible compensating errors, limitations in the number of modeled episodes, and incompatibility between deterministic model predictions and the statistical form of the air quality standard for ozone. If emissions estimates (including naturally produced ''biogenic'' emissions) are accurate, intensive aerometric data are available, and an evaluation of performance (including diagnostic evaluations) is successfully completed, gridded photochemical airquality models can determine (1) the types of emission controls - VOC, NO x , or both - that would be most effective for reducing ozone concentrations, and (2) the approximate magnitudes - to within about 20--40% - of the estimated ozone reductions

  20. Controlling laser-induced magnetization reversal dynamics in a rare-earth iron garnet across the magnetization compensation point

    Science.gov (United States)

    Deb, Marwan; Molho, Pierre; Barbara, Bernard; Bigot, Jean-Yves

    2018-04-01

    In this work we explore the ultrafast magnetization dynamics induced by femtosecond laser pulses in a doped film of gadolinium iron garnet over a broad temperature range including the magnetization compensation point TM. By exciting the phonon-assisted 6S→4G and 6S→4P electronic d -d transitions simultaneously by one- and two-photon absorption processes, we find out that the transfer of heat energy from the lattice to the spin has, at a temperature slightly below TM, a large influence on the magnetization dynamics. In particular, we show that the speed and the amplitude of the magnetization dynamics can be strongly increased when increasing either the external magnetic field or the laser energy density. The obtained results are explained by a magnetization reversal process across TM. Furthermore, we find that the dynamics has unusual characteristics which can be understood by considering the weak spin-phonon coupling in magnetic garnets. These results open new perspectives for controlling the magnetic state of magnetic dielectrics using an ultrashort optically induced heat pulse.

  1. The coupling of mechanical dynamics and induced currents in plates and surfaces

    International Nuclear Information System (INIS)

    Weissenburger, D.W.; Bialek, J.M.

    1986-10-01

    Significant mechanical reactions and deflections may be produced when electrical eddy currents induced in a conducting structure by transformer-like electromotive forces interact with background magnetic fields. Additional eddy currents induced by structural motion through the background fields modify both the mechanical and electrical dynamic behavior of the system. The observed effects of these motional eddy currents are sometimes referred to as magnetic damping and magnetic stiffness. This paper addresses the coupled structural deformation and eddy currents in flat plates and simple two-dimensional surfaces in three-space. A coupled system of equations has been formulated using finite element techniques for the mechanical aspects and a mesh network method for the electrical aspects of the problem

  2. Chemical composition and photochemical reactivity of exhaust from aircraft turbine engines

    Directory of Open Access Journals (Sweden)

    C. W. Spicer

    1994-08-01

    Full Text Available Assessment of the environmental impact of aircraft emissions is required by planners and policy makers. Seveal areas of concern are: 1. exposure of airport workers and urban residents to toxic chemicals emitted when the engines operate at low power (idle and taxi on the ground; 2. contributions to urban photochemical air pollution of aircraft volatile organic and nitrogen oxides emissions from operations around airports; and 3. emissions of nitrogen oxides and particles during high-altitude operation. The environmental impact of chemicals emitted from jet aircraft turbine engines has not been firmly established due to lack of data regarding emission rates and identities of the compounds emitted. This paper describes an experimental study of two different aircraft turbine engines designed to determine detailed organic emissions, as well as emissions of inorganic gases. Emissions were measured at several engine power settings. Measurements were made of detailed organic composition from C1 through C17, CO, CO2, NO, NOx, and polycyclic aromatic hydrocarbons. Measurements were made using a multi-port sampling pro be positioned directly behind the engine in the exhaust exit plane. The emission measurements have been used to determine the organic distribution by carbon number and the distribution by compound class at each engine power level. The sum of the organic species was compared with an independent measurement of total organic carbon to assess the carbon mass balance. A portion of the exhaust was captured and irradiated in outdoor smog chambers to assess the photochemical reactivity of the emissions with respect to ozone formation. The reactivity of emissions from the two engines was apportioned by chemical compound class.

  3. Ferric ion mediated photochemical decomposition of perfluorooctanoic acid (PFOA) by 254 nm UV light

    International Nuclear Information System (INIS)

    Wang Yuan; Zhang Pengyi; Pan Gang; Chen Hao

    2008-01-01

    The great enhancement of ferric ion on the photochemical decomposition of environmentally persistent perfluorooctanoic acid (PFOA) under 254 nm UV light was reported. In the presence of 10 μM ferric ion, 47.3% of initial PFOA (48 μM) was decomposed and the defluorination ratio reached 15.4% within 4 h reaction time. While the degradation and defluorination ratio greatly increased to 80.2% and 47.8%, respectively, when ferric ion concentration increased to 80 μM, and the corresponding half-life was shortened to 103 min. Though the decomposition rate was significantly lowered under nitrogen atmosphere, PFOA was efficiently decomposed too. Other metal ions like Cu 2+ and Zn 2+ also slightly improved the photochemical decomposition of PFOA under irradiation of 254 nm UV light. Besides fluoride ion, other intermediates during PFOA decomposition including formic acid and five shorter-chain perfluorinated carboxylic acids (PFCAs) with C7, C6, C5, C4 and C3, respectively, were identified and quantified by IC or LC/MS. The mixture of PFOA and ferric ion had strong absorption around 280 nm. It is proposed that PFOA coordinates with ferric ion to form a complex, and its excitation by 254 nm UV light leads to the decomposition of PFOA in a stepwise way

  4. 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

  5. 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.

  6. Mercury dynamics in the Rocky Mountain, Colorado, snowpack

    Directory of Open Access Journals (Sweden)

    X. Faïn

    2013-06-01

    Full Text Available Gaseous elemental mercury (GEM was monitored at the Niwot Ridge (NWT Long-Term Ecological Research (LTER site (Colorado, USA, 40° N from interstitial air extracted from the snowpack at depths ranging from the snow surface to 10 cm above the soil. A highly dynamic cycling of mercury (Hg in this mid-latitude snowpack was observed. Patterns were driven by both GEM production in surface snow and GEM destruction in the deeper snowpack layers. Thorough mixing and vertical transport processes were observed through the snowpack. GEM was photochemically produced near the snow-air interface throughout the entire winter, leading to enhanced GEM levels in interstitial air of surface snow of up to 8 ng m−3. During low-wind periods, GEM in surface snow layers remained significantly above ambient air levels at night as well, which may indicate a potential weak GEM production overnight. Analyses of vertical GEM gradients in the snowpack show that surface GEM enhancements efficiently propagated down the snowpack, with a temporal lag in peak GEM levels observed with increasing depth. Downward diffusion was responsible for much of these patterns, although vertical advection also contributed to vertical redistribution. Destruction of GEM in the lower snowpack layers was attributed to dark oxidation of GEM. Analysis of vertical GEM / CO2 flux ratios indicated that this GEM destruction occurred in the snow and not in the underlying soil. The strong, diurnal patterns of photochemical GEM production at the surface ultimately lead to re-emission losses of deposited Hg back to the atmosphere. The NWT data show that highest GEM surface production and re-emissions occur shortly after fresh snowfall, which possibly resupplies photoreducible Hg to the snowpack, and that photochemical GEM reduction is not radiation-limited as it is strong even on cloudy days.

  7. Birefringence induced by pp-wave modes in an electromagnetically active dynamic aether

    International Nuclear Information System (INIS)

    Alpin, Timur Yu.; Balakin, Alexander B.

    2017-01-01

    In the framework of the Einstein-Maxwell-aether theory we study the birefringence effect, which can occur in the pp-wave symmetric dynamic aether. The dynamic aether is considered to be a latently birefringent quasi-medium, which displays this hidden property if and only if the aether motion is non-uniform, i.e., when the aether flow is characterized by the non-vanishing expansion, shear, vorticity or acceleration. In accordance with the dynamo-optical scheme of description of the interaction between electromagnetic waves and the dynamic aether, we shall model the susceptibility tensors by the terms linear in the covariant derivative of the aether velocity four-vector. When the pp-wave modes appear in the dynamic aether, we deal with a gravitationally induced degeneracy removal with respect to hidden susceptibility parameters. As a consequence, the phase velocities of electromagnetic waves possessing orthogonal polarizations do not coincide, thus displaying the birefringence effect. Two electromagnetic field configurations are studied in detail: longitudinal and transversal with respect to the aether pp-wave front. For both cases the solutions are found, which reveal anomalies in the electromagnetic response on the action of the pp-wave aether mode. (orig.)

  8. Birefringence induced by pp-wave modes in an electromagnetically active dynamic aether

    Energy Technology Data Exchange (ETDEWEB)

    Alpin, Timur Yu.; Balakin, Alexander B. [Kazan Federal University, Department of General Relativity and Gravitation, Institute of Physics, Kazan (Russian Federation)

    2017-10-15

    In the framework of the Einstein-Maxwell-aether theory we study the birefringence effect, which can occur in the pp-wave symmetric dynamic aether. The dynamic aether is considered to be a latently birefringent quasi-medium, which displays this hidden property if and only if the aether motion is non-uniform, i.e., when the aether flow is characterized by the non-vanishing expansion, shear, vorticity or acceleration. In accordance with the dynamo-optical scheme of description of the interaction between electromagnetic waves and the dynamic aether, we shall model the susceptibility tensors by the terms linear in the covariant derivative of the aether velocity four-vector. When the pp-wave modes appear in the dynamic aether, we deal with a gravitationally induced degeneracy removal with respect to hidden susceptibility parameters. As a consequence, the phase velocities of electromagnetic waves possessing orthogonal polarizations do not coincide, thus displaying the birefringence effect. Two electromagnetic field configurations are studied in detail: longitudinal and transversal with respect to the aether pp-wave front. For both cases the solutions are found, which reveal anomalies in the electromagnetic response on the action of the pp-wave aether mode. (orig.)

  9. Effects of Photo-chemically Activated Alkylating Agents of the FR900482 Family on Chromatin

    OpenAIRE

    Subramanian, Vidya; Ducept, Pascal; Williams, Robert M.; Luger, Karolin

    2007-01-01

    Bioreductive alkylating agents are an important class of clinical antitumor antibiotics that cross-link and mono-alkylate DNA. Here we use a synthetic photochemically activated derivative of FR400482 to investigate the molecular mechanism of this class of drugs in a biologically relevant context. We find that the organization of DNA into nucleosomes effectively protects it against drug-mediated cross-linking, while permitting mono-alkylation. This modification has the potential to form covale...

  10. Dynamic response of infrastructure to environmentally induced loads analysis, measurements, testing, and design

    CERN Document Server

    Manolis, George

    2017-01-01

    This book provides state of the art coverage of important current issues in the analysis, measurement, and monitoring of the dynamic response of infrastructure to environmental loads, including those induced by earthquake motion and differential soil settlement. The coverage is in five parts that address numerical methods in structural dynamics, soil–structure interaction analysis, instrumentation and structural health monitoring, hybrid experimental mechanics, and structural health monitoring for bridges. Examples that give an impression of the scope of the topics discussed include the seismic analysis of bridges, soft computing in earthquake engineering, use of hybrid methods for soil–structure interaction analysis, effects of local site conditions on the inelastic dynamic analysis of bridges, embedded models in wireless sensor networks for structural health monitoring, recent developments in seismic simulation methods, and seismic performance assessment and retrofit of structures. Throughout, the empha...

  11. Investigation on Surface Roughness of Inconel 718 in Photochemical Machining

    Directory of Open Access Journals (Sweden)

    Nitin D. Misal

    2017-01-01

    Full Text Available The present work is focused on estimating the optimal machining parameters required for photochemical machining (PCM of an Inconel 718 and effects of these parameters on surface topology. An experimental analysis was carried out to identify optimal values of parameters using ferric chloride (FeCl3 as an etchant. The parameters considered in this analysis are concentration of etchant, etching time, and etchant temperature. The experimental analysis shows that etching performance as well as surface topology improved by appropriate selection of etching process parameters. Temperature of the etchant found to be dominant parameter in the PCM of Inconel 718 for surface roughness. At optimal etching conditions, surface roughness was found to be 0.201 μm.

  12. Changes in mitochondrial dynamics during ceramide-induced cardiomyocyte early apoptosis.

    Science.gov (United States)

    Parra, Valentina; Eisner, Veronica; Chiong, Mario; Criollo, Alfredo; Moraga, Francisco; Garcia, Alejandra; Härtel, Steffen; Jaimovich, Enrique; Zorzano, Antonio; Hidalgo, Cecilia; Lavandero, Sergio

    2008-01-15

    In cells, mitochondria are organized as a network of interconnected organelles that fluctuate between fission and fusion events (mitochondrial dynamics). This process is associated with cell death. We investigated whether activation of apoptosis with ceramides affects mitochondrial dynamics and promotes mitochondrial fission in cardiomyocytes. Neonatal rat cardiomyocytes were incubated with C(2)-ceramide or the inactive analog dihydro-C(2)-ceramide for up to 6 h. Three-dimensional images of cells loaded with mitotracker green were obtained by confocal microscopy. Dynamin-related protein-1 (Drp-1) and mitochondrial fission protein 1 (Fis1) distribution and levels were studied by immunofluorescence and western blot. Mitochondrial membrane potential (DeltaPsi(m)) and cytochrome c (cyt c) distribution were used as indexes of early activation of apoptosis. Cell viability and DNA fragmentation were determined by propidium iodide staining/flow cytometry, whereas cytotoxicity was evaluated by lactic dehydrogenase activity. To decrease the levels of the mitochondrial fusion protein mitofusin 2, we used an antisense adenovirus (AsMfn2). C(2)-ceramide, but not dihydro-C(2)-ceramide, promoted rapid fragmentation of the mitochondrial network in a concentration- and time-dependent manner. C(2)-ceramide also increased mitochondrial Drp-1 and Fis1 content, Drp-1 colocalization with Fis1, and caused early activation of apoptosis. AsMfn2 accentuated the decrease in DeltaPsi(m) and cyt c redistribution induced by C(2)-ceramide. Doxorubicin, which induces cardiomyopathy and apoptosis through ceramide generation, also stimulated mitochondrial fragmentation. Ceramides stimulate mitochondrial fission and this event is associated with early activation of cardiomyocyte apoptosis.

  13. Induced Unbalance as a Method for Improving the Dynamic Stability of High-Speed Turbochargers

    KAUST Repository

    Gordon Kirk, R.; Alsaeed, Ali A.

    2011-01-01

    The high-speed diesel engine turbocharger is known to have subsynchronous vibrations for a wide speed range. The bearing fluid-film instability is the main source of the vibration. The nonlinear forces inside the bearings are causing the rotor to whirl in a limit cycle. This study presents a new method for improving the dynamic stability by inducing the turbocharger rotor unbalance in order to suppress the subsynchronous vibration. The finite-element model of the turbocharger with floating-ring bearings is numerically solved for the nonlinear time-transient response. Both compressor and turbine added unbalance are induced and the dynamic stability is computed. The turbocharger model with linearized floating-ring bearings is also solved for eigenvalues to predict the modes of instability. The linear analysis demonstrates that the forward whirling mode of the floating-ring at the compressor end also becomes unstable at the higher turbocharger speeds, in addition to the unstable forward conical and cylindrical modes. The numerical predictions are also compared to the former experimental results of a similar turbocharger. The results of the study show that the subsynchronous frequency amplitude of the dominant first mode is reduced when inducing either the compressor or the turbine unbalance at a certain level. © 2011 R. Gordon Kirk and Ali A. Alsaeed.

  14. Synthesis, optical properties and residual strain effect of GaN nanowires generated via metal-assisted photochemical electroless etching

    KAUST Repository

    Najar, Adel; Shafa, Muhammad; Anjum, Dalaver H.

    2017-01-01

    Herein, we report on the studies of GaN nanowires (GaN NWs) prepared via a metal-assisted photochemical electroless etching method with Pt as the catalyst. It has been found that etching time greatly influences the growth of GaN NWs. The density

  15. Swimming attenuates d-galactose-induced brain aging via suppressing miR-34a-mediated autophagy impairment and abnormal mitochondrial dynamics.

    Science.gov (United States)

    Kou, Xianjuan; Li, Jie; Liu, Xingran; Chang, Jingru; Zhao, Qingxia; Jia, Shaohui; Fan, Jingjing; Chen, Ning

    2017-06-01

    microRNAs (miRNAs) have been reported to be involved in many neurodegenerative diseases. To explore the regulatory role of miR-34a in aging-related diseases such as Alzheimer's disease (AD) during exercise intervention, we constructed a rat model with d-galactose (d-gal)-induced oxidative stress and cognitive impairment coupled with dysfunctional autophagy and abnormal mitochondrial dynamics, determined the mitigation of cognitive impairment of d-gal-induced aging rats during swimming intervention, and evaluated miR-34a-mediated functional status of autophagy and abnormal mitochondrial dynamics. Meanwhile, whether the upregulation of miR-34a can lead to dysfunctional autophagy and abnormal mitochondrial dynamics was confirmed in human SH-SY5Y cells with silenced miR-34a by the transfection of a miR-34a inhibitor. Results indicated that swimming intervention could significantly attenuate cognitive impairment, prevent the upregulation of miR-34a, mitigate the dysfunctional autophagy, and inhibit the increase of dynamin-related protein 1 (DRP1) in d-gal-induced aging model rats. In contrast, the miR-34a inhibitor in cell model not only attenuated D-gal-induced the impairment of autophagy but also decreased the expression of DRP1 and mitofusin 2 (MFN2). Therefore, swimming training can delay brain aging of d-gal-induced aging rats through attenuating the impairment of miR-34a-mediated autophagy and abnormal mitochondrial dynamics, and miR-34a could be the novel therapeutic target for aging-related diseases such as AD. NEW & NOTEWORTHY In the present study, we have found that the upregulation of miR-34a is the hallmark of aging or aging-related diseases, which can result in dysfunctional autophagy and abnormal mitochondrial dynamics. In contrast, swimming intervention can delay the aging process by rescuing the impaired functional status of autophagy and abnormal mitochondrial dynamics via the suppression of miR-34a. Copyright © 2017 the American Physiological Society.

  16. The molecular dynamics simulation of ion-induced ripple growth

    International Nuclear Information System (INIS)

    Suele, P.; Heinig, K.-H.

    2009-01-01

    The wavelength-dependence of ion-sputtering induced growth of repetitive nanostructures, such as ripples has been studied by molecular dynamics (MD) simulations in Si. The early stage of the ion erosion driven development of ripples has been simulated on prepatterned Si stripes with a wavy surface. The time evolution of the height function and amplitude of the sinusoidal surface profile has been followed by simulated ion-sputtering. According to Bradley-Harper (BH) theory, we expect correlation between the wavelength of ripples and the stability of them. However, we find that in the small ripple wavelength (λ) regime BH theory fails to reproduce the results obtained by molecular dynamics. We find that at short wavelengths (λ 35 nm is stabilized in accordance with the available experimental results. According to the simulations, few hundreds of ion impacts in λ long and few nanometers wide Si ripples are sufficient for reaching saturation in surface growth for for λ>35 nm ripples. In another words, ripples in the long wavelength limit seems to be stable against ion-sputtering. A qualitative comparison of our simulation results with recent experimental data on nanopatterning under irradiation is attempted.

  17. Molecular Dynamics Studies of Thermal Induced Chemistry in Tatb

    Science.gov (United States)

    Quenneville, J.; Germann, T. C.; Thompson, A. P.; Kober, E. M.

    2007-12-01

    A reactive force field (ReaxFF) is used with molecular dynamics to probe the chemistry induced by intense heating (`accelerated cook-off') of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB). Large-system simulations are desired for TATB because of the high degree of carbon clustering expected in this material. Using small, 32-molecule simulations, we calculate the reaction rate as a function of temperature and compare the Arrhenius-predicted activation energy with experiment. Decomposition product evolution (mainly N2, H2O, CO2 and graphitic carbon clusters) is followed using a 576-molecule larger simulation, which also illustrates the effect of system size on both carbon clustering and reaction rate.

  18. Vortex-induced dynamic loads on a non-spinning volleyball

    Science.gov (United States)

    Qing-ding, Wei; Rong-sheng, Lin; Zhi-jie, Liu

    1988-09-01

    An experiment on vortex-induced dynamic loads on a non-spinning Volleyball was conducted in a wind tunnel. The flow past the Volleyball was visualized, and the aerodynamic load was measured by use of a strain gauge balance. The separation on the Volleyball was measured with hot-film. The experimental results suggest that under the action of an unstable tail vortex system the separation region is changeable, and that the fluctuation of drag and lateral forces is the same order of magnitude as the mean drag, no matter whether the seam of the Volleyball is symmetric or asymmetric, with regard to the flow. Based on the experimental data a numerical simulation of Volleyball swerve motion was made.

  19. Total OH reactivity study from VOC photochemical oxidation in the SAPHIR chamber

    Science.gov (United States)

    Yu, Z.; Tillmann, R.; Hohaus, T.; Fuchs, H.; Novelli, A.; Wegener, R.; Kaminski, M.; Schmitt, S. H.; Wahner, A.; Kiendler-Scharr, A.

    2015-12-01

    It is well known that hydroxyl radicals (OH) act as a dominant reactive species in the degradation of VOCs in the atmosphere. In recent field studies, directly measured total OH reactivity often showed poor agreement with OH reactivity calculated from VOC measurements (e.g. Nölscher et al., 2013; Lu et al., 2012a). This "missing OH reactivity" is attributed to unaccounted biogenic VOC emissions and/or oxidation products. The comparison of total OH reactivity being directly measured and calculated from single component measurements of VOCs and their oxidation products gives us a further understanding on the source of unmeasured reactive species in the atmosphere. This allows also the determination of the magnitude of the contribution of primary VOC emissions and their oxidation products to the missing OH reactivity. A series of experiments was carried out in the atmosphere simulation chamber SAPHIR in Jülich, Germany, to explore in detail the photochemical degradation of VOCs (isoprene, ß-pinene, limonene, and D6-benzene) by OH. The total OH reactivity was determined from the measurement of VOCs and their oxidation products by a Proton Transfer Reaction Time of Flight Mass Spectrometer (PTR-TOF-MS) with a GC/MS/FID system, and directly measured by a laser-induced fluorescence (LIF) at the same time. The comparison between these two total OH reactivity measurements showed an increase of missing OH reactivity in the presence of oxidation products of VOCs, indicating a strong contribution to missing OH reactivity from uncharacterized oxidation products.

  20. A novel photochemical machining process for magnesium aerospace and biomedical microengineering applications

    International Nuclear Information System (INIS)

    Allen, D M; Simpkins, M; Almond, H

    2010-01-01

    Research was carried out to evaluate the feasibility of fabricating perforated (filigree) magnesium microcomponents with metal wire widths of the order of the metal thickness using a photochemical machining (PCM) process. Experimentally, it has been demonstrated for the first time that metal wire widths of 0.15 mm can be achieved within a 2D, 0.25 mm thick magnesium foil to fabricate microcomponents for use as micro air vehicle (MAV) wings or stents through a bespoke PCM process. This etching process differs significantly from the industrial etching process used currently to manufacture magnesium letterpress printing plates and embossing dies

  1. Study on flow-induced acoustic resonance in symmetrically located side-branches using dynamic PIV technique

    International Nuclear Information System (INIS)

    Li, Yanrong; Inagaki, Terumi; Nishi, Yasuyuki; Someya, Satoshi; Okamoto, Koji

    2014-01-01

    Flow-induced acoustic resonance in a piping system containing closed coaxial side-branches was investigated experimentally. Resonance characteristics of the piping system were examined by a microphone. The results revealed that the resonance frequencies of the shear layer instability were locked in corresponding to the natural frequencies of the side-branches. Phase-averaged velocity fields were obtained two-dimensionally in the junction of coaxial side-branches by dynamic particle image velocimetry (PIV), while the acoustic resonance was induced at the first and second hydrodynamic modes. Patterns of jet correspond to two hydrodynamic modes were derived from the phase-averaged velocity fields. The dynamic PIV can acquire time-series velocity fluctuations, then, two-dimensional phase delay maps under resonance and off-resonance conditions in the junction of coaxial side-branches were obtained. Experimental results show that the proposed phase delay map method costs less experiment and computation time and achieves a better accuracy and repetition than the phase-locking technique. In addition, the phase delay map method can obtain phase difference under the different frequency components. This is important when two different acoustic modes were induced in one experimental condition. (author)

  2. Dynamic cerebral autoregulation to induced blood pressure changes in human experimental and clinical sepsis

    DEFF Research Database (Denmark)

    Berg, Ronan M G; Plovsing, Ronni R; Bailey, Damian M

    2016-01-01

    (-1) ; P = 0·91 versus baseline; P = 0·14 versus LPS]. While our findings support the concept that dynamic cerebral autoregulation is enhanced during the very early stages of sepsis, they remain inconclusive with regard to more advanced stages of disease, because thigh-cuff deflation failed to induce...... (Ps...

  3. Changes in the anisotropy of oriented membrane dynamics induced by myelin basic protein

    Energy Technology Data Exchange (ETDEWEB)

    Natali, F. [OGG-INFM, Grenoble (France); Gliozzi, A.; Rolandi, R.; Relini, A. [Dipartimento di Fisica and Istituto Nazionale per la Fisica della Materia, Universita di Genova (Italy); Cavatorta, P.; Deriu, A. [Dipartimento di Fisica and Istituto Nazionale per la Fisica della Materia, Universita di Parma (Italy); Fasano, A. [Dipartimento di Biochimica e Biologia Molecolare, Universita di Bari (Italy); Riccio, P. [Dipartimento di Biologia D.B.A.F., Universita della Basilicata, Potenza (Italy)

    2002-07-01

    We report recent results showing the evidence of the effect induced by physiological amounts of myelin basic protein (MBP) on the dynamics of dimyristoyl L-a-phosphatidic acid (DMPA) membranes. Incoherent elastic neutron scattering scans, performed over a wide temperature range, have shown that the anisotropy of motions in oriented membranes is significantly enhanced by the presence of MBP. (orig.)

  4. Characterization of photochemical pollution at different elevations in mountainous areas in Hong Kong

    Directory of Open Access Journals (Sweden)

    H. Guo

    2013-04-01

    Full Text Available To advance our understanding on the factors that affect photochemical pollution at different elevations in mountainous areas, concurrent systematic field measurements (September to November 2010 were conducted at a mountain site and at an urban site at the foot of the mountain in Hong Kong. The mixing ratios of air pollutants were greater at the foot of the mountain (i.e., Tsuen Wan urban site, TW than near the summit (i.e., Tai Mao Shan mountain site, TMS, expect for ozone. In total, only one O3 episode day was observed at TW, whereas twenty-one (21 O3 episode days were observed at TMS. The discrepancy of O3 at the two sites was attributed to the mixed effects of NO titration, vertical meteorological conditions, regional transport and mesoscale circulations. The lower NO levels at TMS and the smaller differences of "oxidant" Ox (O3 + NO2 between the two sites suggested that variations of O3 at the two sites were partly attributed to different degree of NO titration. In addition, analysis of vertical structure of meteorological variables revealed that the inversion layer at the range of altitudes of 500–1000 m might be another factor that caused the high O3 levels at TMS. Furthermore, analyses of the wind fields, the levels of air pollutants in different air flows, ratios of different trace gases and the correlation between variability and the lifetime of VOCs (volatile organic compounds indicated that high O3 concentrations at TMS were somewhat influenced by regional air masses from the highly polluted Pearl River delta (PRD region. In particular, the diurnal profiles and correlations of gaseous pollutants suggested influence of mesoscale circulations, which is confirmed using the Master Chemical Mechanism moving box model (Mbox and the Weather Research and Forecasting (WRF model. By investigating the correlations of observed O3 and NOx* and the relationships of O3 and its precursors by an observation-based model (OBM, as well as the ratios

  5. Nuclear magnetic resonance in pulse radiolysis. Chemically induced dynamic nuclear polarization

    International Nuclear Information System (INIS)

    Trifunac, A.D.; Johnson, K.W.; Lowers, R.H.

    1976-01-01

    Nuclear magnetic resonance and chemically induced dynamic nuclear polarization (CIDNP) were applied to the study of pulse radiolysis. Samples were irradiated with a 3-MeV electron beam from the Argonne Van de Graaff accelerator in an EPR magnet (approximately 4000 G) which had axial holes for beam access. A fast flow system transferred the irradiated solution to the rotating 5-mm NMR sample tube. The NMR spectra of mixtures of sodium acetate and methanol were presented to demonstrate the features of the CIDNP in pulse radiolysis

  6. Radiation-Induced Chemical Dynamics in Ar Clusters Exposed to Strong X-Ray Pulses

    Science.gov (United States)

    Kumagai, Yoshiaki; Jurek, Zoltan; Xu, Weiqing; Fukuzawa, Hironobu; Motomura, Koji; Iablonskyi, Denys; Nagaya, Kiyonobu; Wada, Shin-ichi; Mondal, Subhendu; Tachibana, Tetsuya; Ito, Yuta; Sakai, Tsukasa; Matsunami, Kenji; Nishiyama, Toshiyuki; Umemoto, Takayuki; Nicolas, Christophe; Miron, Catalin; Togashi, Tadashi; Ogawa, Kanade; Owada, Shigeki; Tono, Kensuke; Yabashi, Makina; Son, Sang-Kil; Ziaja, Beata; Santra, Robin; Ueda, Kiyoshi

    2018-06-01

    We show that electron and ion spectroscopy reveals the details of the oligomer formation in Ar clusters exposed to an x-ray free electron laser (XFEL) pulse, i.e., chemical dynamics triggered by x rays. With guidance from a dedicated molecular dynamics simulation tool, we find that van der Waals bonding, the oligomer formation mechanism, and charge transfer among the cluster constituents significantly affect ionization dynamics induced by an XFEL pulse of moderate fluence. Our results clearly demonstrate that XFEL pulses can be used not only to "damage and destroy" molecular assemblies but also to modify and transform their molecular structure. The accuracy of the predictions obtained makes it possible to apply the cluster spectroscopy, in connection with the respective simulations, for estimation of the XFEL pulse fluence in the fluence regime below single-atom multiple-photon absorption, which is hardly accessible with other diagnostic tools.

  7. Photochemical decoration of silver nanoparticles on graphene oxide nanosheets and their optical characterization

    Energy Technology Data Exchange (ETDEWEB)

    Lan, Nguyen Thi; Chi, Do Thi; Dinh, Ngo Xuan; Hung, Nguyen Duy; Lan, Hoang [Department of Nanoscience and Nanotechnology, Advanced Institute for Science and Technology (AIST), Hanoi University of Science and Technology (HUST), No. 1 Dai Co Viet Street, Hai Ba Trung District, Hanoi (Viet Nam); Tuan, Pham Anh [Vietnam Metrology Institute, 08 Hoang Quoc Viet Road, Cau Giay District, Hanoi (Viet Nam); Thang, Le Hong [School of Materials Science and Engineering, Hanoi University of Science and Technology (HUST), 01 Dai Co Viet Street, Hai Ba Trung District, Hanoi (Viet Nam); Trung, Nguyen Ngoc [School of Engineering Physics, Hanoi University of Science and Technology (HUST), 01 Dai Co Viet Street, Hai Ba Trung District, Hanoi (Viet Nam); Hoa, Nguyen Quang [Department of Physics, Hanoi University of Science, 334 Nguyen Trai, Thanh Xuan, Hanoi (Viet Nam); Huy, Tran Quang [Laboratory for Ultrastructure and Bionanotechnology (LUBN), National Institute of Hygiene and Epidemiology (NIHE), No. 1 Yecxanh Street, Hai Ba Trung District, Hanoi (Viet Nam); Quy, Nguyen Van [International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology (HUST), 01 Dai Co Viet Street, Hai Ba Trung District, Hanoi (Viet Nam); Duong, Thanh-Tung [Department of Materials Engineering, Chungnam National University, Daeduk Science Town, 305-764 Daejeon (Korea, Republic of); Phan, Vu Ngoc [Department of Nanoscience and Nanotechnology, Advanced Institute for Science and Technology (AIST), Hanoi University of Science and Technology (HUST), No. 1 Dai Co Viet Street, Hai Ba Trung District, Hanoi (Viet Nam); Le, Anh-Tuan, E-mail: tuan.leanh1@hust.edu.vn [Department of Nanoscience and Nanotechnology, Advanced Institute for Science and Technology (AIST), Hanoi University of Science and Technology (HUST), No. 1 Dai Co Viet Street, Hai Ba Trung District, Hanoi (Viet Nam)

    2014-12-05

    Highlights: • A photochemical method for effective decoration of the Ag-NPs on GO nanosheets is presented. • The average size of the Ag-NPs on the GO nanosheets obtained ∼6–7 nm with uniform size distribution. • Surface interaction of Ag-NPs with GO nanosheets leads to surface plasmon-enhanced luminescence. - Abstract: Nanohybrid materials based on silver nanoparticles (Ag-NPs) and graphene oxide (GO) are attracting considerable research interest because of their potential many applications including surface-enhanced Raman scattering, catalysis, sensors, biomedicine and antimicrobials. In this study, we established a simple and effective method of preparing a finely dispersed Ag-GO aqueous solution using modified Hummer and photochemical technique. The Ag-NPs formation on GO nanosheets was analyzed by X-ray diffraction, transmission electron microscopy, Raman spectroscopy, and Fourier-transform infrared spectroscopy. The average size of Ag-NPs on the GO nanosheets was approximately 6–7 nm with nearly uniform size distribution. The Ag-GO nanohybrid also exhibits an adsorption band at 435 nm because of the presence of Ag-NPs on the GO nanosheets. Photoluminescence emission of the Ag-GO nanohybrid was found at 400 and 530 nm, which can be attributed to the interaction between the luminescence of exploited GO nanosheets and localized surface plasmon resonance from metallic Ag-NPs. The observed excellent optical properties of the as-prepared Ag-GO nanohybrid showed a significant potential for optoelectronics applications.

  8. PHOTOCHEMICAL AIR POLLUTION IN THE NORTH OF PORTUGAL: A HIGH TROPOSHERIC OZONE EPISODE

    Science.gov (United States)

    Monteiro, A.; Carvalho, A.; Tchepel, O.; Ferreira, J.; Martins, H.; Miranda, A.; Borrego, C.; Saavedra, S.; Rodríguez, A.; Souto, J. A.

    2009-12-01

    Very high concentrations of ozone are continuously measured at the monitoring station at Lamas d’Olo, located at the North of Portugal,. A particular high photochemical episode occurred between 11 and 13 of July 2005, registering ozone hourly maximum values above 350 µg.m-3. This ozone-rich episode is investigated in this paper, in order to identify its origin and formation. Besides the analysis of both meteorological and air quality monitoring datasets, a numerical modelling approach, based on MM5-CAMx system, was used to simulate the dispersion and transport (horizontal and vertical) of the photochemical pollutants and its precursors. A cross spectrum analysis of the meteorological and air quality time series was performed, in the frequency domain, to establish the relationships between ozone data measured at Lamas d’Olo with air quality data from neighbourhood stations and meteorological parameters. Results point out different behaviour/contribution between the analysed sites. Moreover, different contributions of the u and v wind component on the ozone concentration fluctuations were found suggesting the presence a mountain breeze circulation and a north synoptic transport. The preliminary modelling results pointed out that the vertical transport of pollutants are responsible for the measured high concentrations, combined with particular meteorological conditions, related to the planetary boundary layer (PBL) development. The pollutants transported and existent at high vertical levels are captured/trapped when the PBL height reaches its daily maximum, and extremely high ozone ground level concentrations are consequently measured.

  9. Photochemical decoration of silver nanoparticles on graphene oxide nanosheets and their optical characterization

    International Nuclear Information System (INIS)

    Lan, Nguyen Thi; Chi, Do Thi; Dinh, Ngo Xuan; Hung, Nguyen Duy; Lan, Hoang; Tuan, Pham Anh; Thang, Le Hong; Trung, Nguyen Ngoc; Hoa, Nguyen Quang; Huy, Tran Quang; Quy, Nguyen Van; Duong, Thanh-Tung; Phan, Vu Ngoc; Le, Anh-Tuan

    2014-01-01

    Highlights: • A photochemical method for effective decoration of the Ag-NPs on GO nanosheets is presented. • The average size of the Ag-NPs on the GO nanosheets obtained ∼6–7 nm with uniform size distribution. • Surface interaction of Ag-NPs with GO nanosheets leads to surface plasmon-enhanced luminescence. - Abstract: Nanohybrid materials based on silver nanoparticles (Ag-NPs) and graphene oxide (GO) are attracting considerable research interest because of their potential many applications including surface-enhanced Raman scattering, catalysis, sensors, biomedicine and antimicrobials. In this study, we established a simple and effective method of preparing a finely dispersed Ag-GO aqueous solution using modified Hummer and photochemical technique. The Ag-NPs formation on GO nanosheets was analyzed by X-ray diffraction, transmission electron microscopy, Raman spectroscopy, and Fourier-transform infrared spectroscopy. The average size of Ag-NPs on the GO nanosheets was approximately 6–7 nm with nearly uniform size distribution. The Ag-GO nanohybrid also exhibits an adsorption band at 435 nm because of the presence of Ag-NPs on the GO nanosheets. Photoluminescence emission of the Ag-GO nanohybrid was found at 400 and 530 nm, which can be attributed to the interaction between the luminescence of exploited GO nanosheets and localized surface plasmon resonance from metallic Ag-NPs. The observed excellent optical properties of the as-prepared Ag-GO nanohybrid showed a significant potential for optoelectronics applications

  10. Chloroplastic and stomatal aspects of ozone-induced reduction of net photosynthesis in plants

    Energy Technology Data Exchange (ETDEWEB)

    Torsethaugen, Gro

    1998-09-01

    The present thesis relates to ozone-induced reduction of photosynthesis in plants. As a photochemical oxidant O{sub 3} is formed by the interaction of hydrocarbons, nitrogen oxides and oxygen in sunlight. Ozone (O{sub 3}) is the most phytotoxic of all the air pollutants and is known to reduce plant growth and net photosynthesis, cause stomatal closure, induce visible injury, accelerate senescence and induce or inhibit transcription of a variety of genes with a corresponding increase/decrease in protein products. The underlying cellular mechanisms for many of these changes are unknown. Following fields are investigated: Ozone-induced reduction of net photosynthesis; ozone and the photosynthetic apparatus in the chloroplasts; ozone and stomata; ozone effects on plant membranes; protection against ozone injury in plants. 249 refs., 22 figs., 4 tabs.

  11. Transient dynamics in cavity electromagnetically induced transparency with ion Coulomb crystals

    Science.gov (United States)

    Albert, Magnus; Dantan, Aurélien; Drewsen, Michael

    2018-03-01

    We experimentally investigate the transient dynamics of an optical cavity field interacting with large ion Coulomb crystals in a situation of electromagnetically induced transparency (EIT). EIT is achieved by injecting a probe field at the single photon level and a more intense control field with opposite circular polarization into the same mode of an optical cavity to couple Zeeman substates of a metastable level in ? ions. The EIT interaction dynamics are investigated both in the frequency-domain - by measuring the probe field steady state reflectivity spectrum - and in the time-domain - by measuring the progressive buildup of transparency. The experimental results are observed to be in excellent agreement with theoretical predictions taking into account the inhomogeneity of the control field in the interaction volume, and confirm the high degree of control on light-matter interaction that can be achieved with ion Coulomb crystals in optical cavities.

  12. Study of the photochemical isomerization of ergosterol

    International Nuclear Information System (INIS)

    Mermet-Bouvier, Rene

    1972-01-01

    The photochemical reaction scheme of Ergosterol-Vitamin D 2 was studied. The schemes proposed in published literature are described together with earlier methods used for the analysis and determination. The method used is then discussed. In the first part, the factors concerning the changes occurring in molecular systems exposed to radiation, and the formalism used, are examined. Investigations of linear molecular systems and their applications to the reaction scheme of Ergosterol-Vitamin D 2 are discussed. The properties which enable the last three reaction schemes proposed in the literature to be distinguished are described. In the second part, the experimental analytical methods and the determinations made of the different isomers formed are presented. Chromatographic techniques (thin films, columns, gaseous phase) suitable for separating the various isomeric species are used. The existence of 8 isomers was established as well as a transformation occurring in one of them. The ultraviolet and infrared spectra were obtained. A reaction scheme is proposed (in which all the quantum yield values are given) from comparisons between the calculated and experimental values of the eigenvalue of the absolute minimum value λ m and the eigenvector corresponding to V m . (author) [fr

  13. Photochemical transformation of benzotriazole, relevant to sunlit surface waters: Assessing the possible role of triplet-sensitised processes

    International Nuclear Information System (INIS)

    Bianco, Angelica; Fabbri, Debora; Minella, Marco; Brigante, Marcello; Mailhot, Gilles; Maurino, Valter; Minero, Claudio; Vione, Davide

    2016-01-01

    The corrosion inhibitor 1H-benzotriazole (pK a = 8.4) can exist in two different forms in natural waters, and photochemical transformation is a potentially significant attenuation pathway for both of them. Depending on conditions, the modelled half-life times range from some days/weeks to several months. In sunlit water bodies, the acidic (neutral) form would undergo direct photolysis (accounting for up to 7% of total phototransformation) and, most notably, reaction with the hydroxyl radicals ( · OH) and the triplet states of chromophoric dissolved organic matter ( 3 CDOM*). The basic (anionic) form would undergo significant transformation with · OH and 3 CDOM*. The · OH reactions would be more important at low dissolved organic carbon (DOC) and the 3 CDOM* processes at high DOC. In the presence of highly reactive triplet-state model compounds, the two benzotriazole forms react with similar rate constants. In this case, they would show comparable half-life times in surface-water environments. With less reactive triplet states, the rate constant of the anionic form can be a couple of orders of magnitude higher than that of the neutral one. Under these circumstances, the neutral form could be considerably more photostable than the anionic one at high DOC. Therefore, depending on 3 CDOM* reactivity, the solution pH may or may not play an important role in the photoattenuation kinetics of 1H-benzotriazole in sunlit natural waters, especially at high DOC. Both forms of benzotriazole yield hydroxyderivatives as their main transformation intermediates under all the relevant photochemical reaction pathways. These intermediates could be formed via · OH-induced hydroxylation, or upon electron abstraction followed by reaction with water. Differently from UVC irradiation data reported in previous studies, the concentration of aniline upon excitation of 1H-benzotriazole under environmentally significant UV wavelengths was always below the detection limit of the analytical

  14. High-precision spectrometer for studies of ion-induced and spontaneous fission dynamics

    International Nuclear Information System (INIS)

    Batenkov, O.; Elmgren, K.; Majorov, M.; Blomgren, J.; Conde, H.; Hultqvist, S.; Olsson, N.; Rahm, J.; Ramstroem, E.; Smirnov, S.; Veshikov, A.

    1997-01-01

    A spectrometer has been designed and built to investigate the dynamics of spontaneous and ion-induced fission processes. It consists of 8 neutron detectors surrounding a low mass scattering chamber containing the fissionable targets and two fission fragment telescopes. The spectrometer measures neutron spectra, and energy and angular correlations of neutrons, as well as kinetic energy, mass, and relative angle of fission fragments. A 252 Cf fission reference source is used for calibration. (orig.)

  15. Chemical composition and photochemical reactivity of exhaust from aircraft turbine engines

    Directory of Open Access Journals (Sweden)

    T. F. Lyon

    Full Text Available Assessment of the environmental impact of aircraft emissions is required by planners and policy makers. Seveal areas of concern are: 1. exposure of airport workers and urban residents to toxic chemicals emitted when the engines operate at low power (idle and taxi on the ground; 2. contributions to urban photochemical air pollution of aircraft volatile organic and nitrogen oxides emissions from operations around airports; and 3. emissions of nitrogen oxides and particles during high-altitude operation. The environmental impact of chemicals emitted from jet aircraft turbine engines has not been firmly established due to lack of data regarding emission rates and identities of the compounds emitted. This paper describes an experimental study of two different aircraft turbine engines designed to determine detailed organic emissions, as well as emissions of inorganic gases. Emissions were measured at several engine power settings. Measurements were made of detailed organic composition from C1 through C17, CO, CO2, NO, NOx, and polycyclic aromatic hydrocarbons. Measurements were made using a multi-port sampling pro be positioned directly behind the engine in the exhaust exit plane. The emission measurements have been used to determine the organic distribution by carbon number and the distribution by compound class at each engine power level. The sum of the organic species was compared with an independent measurement of total organic carbon to assess the carbon mass balance. A portion of the exhaust was captured and irradiated in outdoor smog chambers to assess the photochemical reactivity of the emissions with respect to ozone formation. The reactivity of emissions from the two engines was apportioned by chemical compound class.

  16. The susceptibility of the retina to photochemical damage from visible light

    Science.gov (United States)

    Hunter, Jennifer J; Morgan, Jessica I W; Merigan, William H; Sliney, David H; Sparrow, Janet R; Williams, David R

    2011-01-01

    The photoreceptor/RPE complex must maintain a delicate balance between maximizing the absorption of photons for vision and retinal image quality while simultaneously minimizing the risk of photodamage when exposed to bright light. We review the recent discovery of two new effects of light exposure on the photoreceptor/RPE complex in the context of current thinking about the causes of retinal phototoxicity. These effects are autofluorescence photobleaching in which exposure to bright light reduces lipofuscin autofluorescence and, at higher light levels, RPE disruption in which the pattern of autofluorescence is permanently altered following light exposure. Both effects occur following exposure to visible light at irradiances that were previously thought to be safe. Photopigment, retinoids involved in the visual cycle, and bisretinoids in lipofuscin have been implicated as possible photosensitizers for photochemical damage. The mechanism of RPE disruption may follow either of these paths. On the other hand, autofluorescence photobleaching is likely an indicator of photooxidation of lipofuscin. The permanent changes inherent in RPE disruption might require modification of the light safety standards. AF photobleaching recovers after several hours although the mechanisms by which this occurs are not yet clear. Understanding the mechanisms of phototoxicity is all the more important given the potential for increased susceptibility in the presence of ocular diseases that affect either the visual cycle and/or lipofuscin accumulation. In addition, knowledge of photochemical mechanisms can improve our understanding of some disease processes that may be influenced by light exposure, such as some forms of Leber’s congenital amaurosis, and aid in the development of new therapies. Such treatment prior to intentional light exposures, as in ophthalmic examinations or surgeries, could provide an effective preventative strategy. PMID:22085795

  17. Obesity May Not Induce Dynamic Stability Disadvantage during Overground Walking among Young Adults.

    Science.gov (United States)

    Liu, Zhong-Qi; Yang, Feng

    2017-01-01

    Obesity has been related to postural instability during static standing. It remains unknown how obesity influences stability during dynamic movements like gait. The primary aim of this study was to investigate the effects of obesity on dynamic gait stability control in young adults during gait. Forty-four young adults (21 normal-weight and 23 obese) participated in this study. Participants walked five times at their self-selected gait speeds on a linear walkway. Their full-body kinematics were gathered by a motion capture system. Compared with normal-weight group, individuals with obesity walked more slowly with a shorter but wider step. People with obesity also spent an elongated double stance phase than those with normal weight. A reduced gait speed decreases the body center of mass's velocity relative to the base of support, leading to a reduction in dynamic stability. On the other hand, a shortened step in accompanying with a less backward-leaning trunk has the potential to bring the center of mass closer to the base of support, resulting in an increase in dynamic stability. As the result of these adaptive changes to the gait pattern, dynamic gait stability among people with obesity did not significantly differ from the one among people with normal weight. Obesity seems to not be inducing dynamic stability disadvantage in young adults during level overground walking. These findings could provide insight into the mechanisms of stability control among people affected by obesity during dynamic locomotion.

  18. Open burning of rice, corn and wheat straws: primary emissions, photochemical aging, and secondary organic aerosol formation

    Science.gov (United States)

    Fang, Zheng; Deng, Wei; Zhang, Yanli; Ding, Xiang; Tang, Mingjin; Liu, Tengyu; Hu, Qihou; Zhu, Ming; Wang, Zhaoyi; Yang, Weiqiang; Huang, Zhonghui; Song, Wei; Bi, Xinhui; Chen, Jianmin; Sun, Yele; George, Christian; Wang, Xinming

    2017-12-01

    Agricultural residues are among the most abundant biomass burned globally, especially in China. However, there is little information on primary emissions and photochemical evolution of agricultural residue burning. In this study, indoor chamber experiments were conducted to investigate primary emissions from open burning of rice, corn and wheat straws and their photochemical aging as well. Emission factors of NOx, NH3, SO2, 67 non-methane hydrocarbons (NMHCs), particulate matter (PM), organic aerosol (OA) and black carbon (BC) under ambient dilution conditions were determined. Olefins accounted for > 50 % of the total speciated NMHCs emission (2.47 to 5.04 g kg-1), indicating high ozone formation potential of straw burning emissions. Emission factors of PM (3.73 to 6.36 g kg-1) and primary organic carbon (POC, 2.05 to 4.11 gC kg-1), measured at dilution ratios of 1300 to 4000, were lower than those reported in previous studies at low dilution ratios, probably due to the evaporation of semi-volatile organic compounds under high dilution conditions. After photochemical aging with an OH exposure range of (1.97-4.97) × 1010 molecule cm-3 s in the chamber, large amounts of secondary organic aerosol (SOA) were produced with OA mass enhancement ratios (the mass ratio of total OA to primary OA) of 2.4-7.6. The 20 known precursors could only explain 5.0-27.3 % of the observed SOA mass, suggesting that the major precursors of SOA formed from open straw burning remain unidentified. Aerosol mass spectrometry (AMS) signaled that the aged OA contained less hydrocarbons but more oxygen- and nitrogen-containing compounds than primary OA, and carbon oxidation state (OSc) calculated with AMS resolved O / C and H / C ratios increased linearly (p < 0.001) with OH exposure with quite similar slopes.

  19. Effect of the R dependence of laser-induced polarizability on molecular dynamic alignment in an intense femtosecond laser field

    International Nuclear Information System (INIS)

    Chen Jianxin; Cui Xiaomei; Huang Bomin; Wu Hongchun; Zhuo Shuangmu

    2006-01-01

    In the rotation equation of the angle θ between the molecular axis and the laser polarization direction, the dependence of laser-induced polarizability on the molecular internuclear distance R is considered. The effect of the R dependence of laser-induced polarizability on molecular dynamic alignment in an intense femtosecond laser field is investigated with 20 and 100 fs laser pulses for N 2 molecules and with 60 and 100 fs laser pulses for Br 2 molecules at intensities of 5x10 14 W cm -2 and 5x10 15 W cm -2 . This effect exists and only occurs during the dissociative process after the molecule is ionized. It enhances the degrees of molecular dynamic alignment and is more significant in reorienting the angular distributions of molecules towards the laser polarization direction in the conditions of high laser intensity and short pulse length. Compared with the N 2 molecule, the effect of the R dependence of laser-induced polarizability on molecular dynamic alignment for Br 2 is stronger. The reasons are presented and discussed

  20. Singlet Oxygen Sensor Green: Photochemical Behavior in Solution and in a Mammalian Cell

    DEFF Research Database (Denmark)

    Gollmer, Anita; Arnbjerg, Jacob; Blaikie, Frances Helen

    2011-01-01

    The development of efficient and selective luminescent probes for reactive oxygen species, particularly for singlet molecular oxygen, is currently of great importance. In this study, the photochemical behavior of Singlet Oxygen Sensor Green® (SOSG), a commercially available fluorescent probe...... of the reaction between SOSG and singlet oxygen is, itself, an efficient singlet oxygen photosensitizer. Second, SOSG appears to efficiently bind to proteins which, in turn, can influence uptake by a cell as well as behavior in the cell. As such, incorrect use of SOSG can yield misleading data on yields...

  1. [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

  2. Photochemical addition of amino acids and peptides to homopolyribonucleotides of the major DNA bases

    International Nuclear Information System (INIS)

    Shetlar, M.D.; Hom, K.; Carbone, J.; Moy, D.; Steady, E.; Watanabe, M.

    1984-01-01

    The photochemical quantum yields for addition of glycine and the L-amino acids commonly occurring in proteins to polyadenylic acid, polycytidylic acid, polyguanylic acid and polyribothymidylic acid have been determined in deoxygenated phosphate buffer using a fluorescamine assay technique. Polyadenylic acid was reactive with eleven of the twenty amino acids tested, with phenylalanine, tyrosine, glutamine, lysine and asparagine having the highest quantum yields. Polyguanylic acid reacted with sixteen amino acids; phenylalanine, arginine, cysteine, tyrosine, and lysine displayed the largest quantum yields. Polycytidylic acid showed reactivity with fifteen amino acids with lysine, phenylalanine, cysteine, tyrosine and arginine having the greatest quantum yields. Polyribothymidylic acid, reactive with fifteen of nineteen amino acids surveyed, showed the highest quantum yields for cysteine, phenylalanine, tyrosine, lysine and asparagine. None of the polynucleotides were reactive with aspartic acid or glutamic acid. The quantum yields for photoaddition of eighteen dipeptides of the form gycyl X (X being an amino acid), and of L-alanyl-L-tryptophan, L-seryl-L-seryl-L-serine, L-threonyl-L-threonyl-L-threonine, L-cystine-bis-glycine, and Nsup(α)-acetyllysine to polyadenylic acid, polycytidylic acid and polyguanylic acid were measured. All were found to add photochemically to each of these polymers. Polyribothymidylic acid, tested with eleven peptides and with Nsup(α)-acetyllysine, was found to be reactive with all. (author)

  3. Photochemical transformation of phenylurea herbicides in surface waters: a model assessment of persistence, and implications for the possible generation of hazardous intermediates.

    Science.gov (United States)

    Fabbri, Debora; Minella, Marco; Maurino, Valter; Minero, Claudio; Vione, Davide

    2015-01-01

    This work models the phototransformation kinetics in surface waters of five phenylurea herbicides (diuron, fenuron, isoproturon, metoxuron and chlortoluron), for which important photochemical parameters are available in the literature (direct photolysis quantum yields and reaction rate constants with ·OH, CO3(-·) and the triplet states of chromophoric dissolved organic matter, (3)CDOM*). Model calculations suggest that isoproturon and metoxuron would be the least photochemically persistent and diuron the most persistent compound. Reactions with ·OH and (3)CDOM* would be the main phototransformation pathways for all compounds in the majority of environmental conditions. Reaction with CO3(-) could be important in waters with low dissolved organic carbon (DOC), while direct photolysis would be negligible for fenuron, quite important for chlortoluron, and somewhat significant for the other compounds. The direct photolysis of metoxuron and diuron is known to increase toxicity, and such a photoreaction pathway would be enhanced at intermediate DOC values (1-4 mg C L(1)). The reaction between phenylureas and ·OH is known to produce toxic intermediates, differently from (3)CDOM*. Therefore, the shift of reactivity from ·OH to (3)CDOM* with increasing DOC could reduce the environmental impact of photochemical transformation. Copyright © 2014 Elsevier Ltd. All rights reserved.

  4. Flash photolysis of cutinase

    DEFF Research Database (Denmark)

    Neves Petersen, Teresa; Klitgaard, Søren; Skovsen, Esben

    2009-01-01

    Aromatic amino acids play an important role in ultraviolet (UV)-induced photochemical reactions in proteins. In this work, we aim at gaining insight into the photochemical reactions induced by near-UV light excitation of aromatic residues that lead to breakage of disulfide bridges in our model en...... of the formed species and their lifetimes is important for the understanding of UV-induced reactions in humans that lead to light-induced diseases, e.g., skin cancer and cataract formation.......Aromatic amino acids play an important role in ultraviolet (UV)-induced photochemical reactions in proteins. In this work, we aim at gaining insight into the photochemical reactions induced by near-UV light excitation of aromatic residues that lead to breakage of disulfide bridges in our model...... of RSSR *-. Additional mechanisms that may lead to the near disappearance of Trp(*) are discussed. Our study provides insight into one key UV-light-induced reaction in cutinase, i.e., light-induced disruption of disulphide bridges mediated by the excitation of aromatic residues. Knowledge about the nature...

  5. Ligand-Induced Dynamics of Neurotrophin Receptors Investigated by Single-Molecule Imaging Approaches

    Science.gov (United States)

    Marchetti, Laura; Luin, Stefano; Bonsignore, Fulvio; de Nadai, Teresa; Beltram, Fabio; Cattaneo, Antonino

    2015-01-01

    Neurotrophins are secreted proteins that regulate neuronal development and survival, as well as maintenance and plasticity of the adult nervous system. The biological activity of neurotrophins stems from their binding to two membrane receptor types, the tropomyosin receptor kinase and the p75 neurotrophin receptors (NRs). The intracellular signalling cascades thereby activated have been extensively investigated. Nevertheless, a comprehensive description of the ligand-induced nanoscale details of NRs dynamics and interactions spanning from the initial lateral movements triggered at the plasma membrane to the internalization and transport processes is still missing. Recent advances in high spatio-temporal resolution imaging techniques have yielded new insight on the dynamics of NRs upon ligand binding. Here we discuss requirements, potential and practical implementation of these novel approaches for the study of neurotrophin trafficking and signalling, in the framework of current knowledge available also for other ligand-receptor systems. We shall especially highlight the correlation between the receptor dynamics activated by different neurotrophins and the respective signalling outcome, as recently revealed by single-molecule tracking of NRs in living neuronal cells. PMID:25603178

  6. Photochemical and microbial degradation technologies to remove toxic chemicals

    International Nuclear Information System (INIS)

    Matsumura, F.; Katayama, A.

    1992-01-01

    An effort was made to apply photochemical degradation technology on biodegradation processes to increase the bioremediation potential of microbial actions. For this purpose, we have chosen Phanerochaete chrysosporium, a wood decaying white-rot fungus and a variety of chlorinated pesticides and aromatics as study materials. By using UV-irradiation and benomyl (a commonly used fungicide) as selection methods, a strain of UV-resistant P. chrysosporium was developed. This strain was found to be capable of rapidly degrading these chlorinated chemicals when they were incubated in N-deficient medium which received 1 hr/day of UV-irradiation. UV-irradiation either at 300 or 254 nm showed the beneficial effect of speeding up the rate of degradation on most of test chemicals with the exception of toxaphene and HCH (hexachlorocyclohexane). By adding fresh glucose to the medium it was possible to maintain high degradation capacity for several weeks

  7. Photochemical and microbial degradation technologies to remove toxic chemicals

    Energy Technology Data Exchange (ETDEWEB)

    Matsumura, F.; Katayama, A.

    1992-07-01

    An effort was made to apply photochemical degradation technology on biodegradation processes to increase the bioremediation potential of microbial actions. For this purpose, we have chosen Phanerochaete chrysosporium, a wood decaying white-rot fungus and a variety of chlorinated pesticides and aromatics as study materials. By using UV-irradiation and benomyl (a commonly used fungicide) as selection methods, a strain of UV-resistant P. chrysosporium was developed. This strain was found to be capable of rapidly degrading these chlorinated chemicals when they were incubated in N-deficient medium which received 1 hr/day of UV-irradiation. UV-irradiation either at 300 or 254 nm showed the beneficial effect of speeding up the rate of degradation on most of test chemicals with the exception of toxaphene and HCH (hexachlorocyclohexane). By adding fresh glucose to the medium it was possible to maintain high degradation capacity for several weeks.

  8. Laboratory investigation of photochemical oxidation of organic aerosol from wood fires 2: analysis of aerosol mass spectrometer data

    Directory of Open Access Journals (Sweden)

    A. P. Grieshop

    2009-03-01

    Full Text Available Experiments were conducted to investigate the effects of photo-oxidation on organic aerosol (OA in dilute wood smoke by exposing emissions from soft- and hard-wood fires to UV light in a smog chamber. This paper focuses on changes in OA composition measured using a unit-mass-resolution quadrupole Aerosol Mass Spectrometer (AMS. The results highlight how photochemical processing can lead to considerable evolution of the mass, volatility and level of oxygenation of biomass-burning OA. Photochemical oxidation produced substantial new OA, more than doubling the OA mass after a few hours of aging under typical summertime conditions. Aging also decreased the volatility of the OA and made it progressively more oxygenated. The results also illustrate strengths of, and challenges with, using AMS data for source apportionment analysis. For example, the mass spectra of fresh and aged BBOA are distinct from fresh motor-vehicle emissions. The mass spectra of the secondary OA produced from aging wood smoke are very similar to those of the oxygenated OA (OOA that dominates ambient AMS datasets, further reinforcing the connection between OOA and OA formed from photo-chemistry. In addition, aged wood smoke spectra are similar to those from OA created by photo-oxidizing dilute diesel exhaust. This demonstrates that the OOA observed in the atmosphere can be produced by photochemical aging of dilute emissions from different types of combustion systems operating on fuels with modern or fossil carbon. Since OOA is frequently the dominant component of ambient OA, the similarity of spectra of aged emissions from different sources represents an important challenge for AMS-based source apportionment studies.

  9. Topology of a dissipative spin: Dynamical Chern number, bath-induced nonadiabaticity, and a quantum dynamo effect

    Science.gov (United States)

    Henriet, Loïc; Sclocchi, Antonio; Orth, Peter P.; Le Hur, Karyn

    2017-02-01

    We analyze the topological deformations of the ground state manifold of a quantum spin-1/2 in a magnetic field H =H (sinθ cosϕ ,sinθ sinϕ ,cosθ ) induced by a coupling to an ohmic quantum dissipative environment at zero temperature. From Bethe ansatz results and a variational approach, we confirm that the Chern number associated with the geometry of the reduced spin ground state manifold is preserved in the delocalized phase for α <1 . We report a divergence of the Berry curvature at αc=1 for magnetic fields aligned along the equator θ =π /2 . This divergence is caused by the complete quenching of the transverse magnetic field by the bath associated with a gap closing that occurs at the localization Kosterlitz-Thouless quantum phase transition in this model. Recent experiments in quantum circuits have engineered nonequilibrium protocols to access topological properties from a measurement of a dynamical Chern number defined via the out-of-equilibrium spin expectation values. Applying a numerically exact stochastic Schrödinger approach we find that, for a fixed field sweep velocity θ (t )=v t , the bath induces a crossover from (quasi)adiabatic to nonadiabatic dynamical behavior when the spin bath coupling α increases. We also investigate the particular regime H /ωc≪v /H ≪1 with large bath cutoff frequency ωc, where the dynamical Chern number vanishes already at α =1 /2 . In this regime, the mapping to an interacting resonance level model enables us to analytically describe the behavior of the dynamical Chern number in the vicinity of α =1 /2 . We further provide an intuitive physical explanation of the bath-induced breakdown of adiabaticity in analogy to the Faraday effect in electromagnetism. We demonstrate that the driving of the spin leads to the production of a large number of bosonic excitations in the bath, which strongly affect the spin dynamics. Finally, we quantify the spin-bath entanglement and formulate an analogy with an effective

  10. Bibliographic study of photophysical and photochemical properties of laser dyes

    International Nuclear Information System (INIS)

    Doizi, D.

    1986-06-01

    Laser isotope separation of uranium requires high power and precise wave length. This report is a bibliographic and experimental study of the photophysical and photochemical properties of seven commercial laser dyes which have an emission wavelength in the range 5500-6500 A: Rhodamine 110 or 560, rhodamine 6G or 590, rhodamine B or 610, rhodamine 101 or 640, sulforhodamine B or kiton red 620, sulforhodamine 101 or 640 and DCM or LC 6500. Absorption and emission cross section values, fluorescence lifetimes and quantum yields in various solvents are indicated. For each dye, a non exhaustive list of laboratory experiments made with two types of pump sources: Nd YAG (532) and copper vapor laser is given. When it is known, the toxicity of the dyes is mentioned [fr

  11. Photochemical internalization (PCI) of bleomycin is equally effective in two dissimilar leiomyosarcoma xenografts in athymic mice.

    Science.gov (United States)

    Sellevold, Simen; Peng, Qian; Fremstedal, Ane Sofie Viset; Berg, Kristian

    2017-12-01

    Photochemical internalization (PCI) is a novel technique for delivery of active macromolecules into cancerous cells, via light activation of a specific photosensitizer and a low dose systemic drug. Numerous pre-clinical studies and one clinical trial have confirmed the treatment potential in carcinomas. Soft tissue sarcomas are rare and generally resistant to radio- and chemotherapy. Due to treatment resistance and surgical morbidity in sarcoma care, we seek to increase knowledge on PCI effects in sarcomas by studying two different, but closely related leiomyosarcomas. MES-SA and SK-LMS-1 tumours were established in the leg muscles of athymic mice. Treatment effects after AlPcS 2a -PCI of bleomycin, PCI with no drug (photodynamic therapy, PDT) and control groups were evaluated by: 1) assessment of tumour growth, 2) uptake of contrast agent during MRI and 3) histopathology. PCI of bleomycin induced a similar and significant increase in time to reach the end point in both tumour models, while neither responded to AlPcS 2a -PDT. In the MES-SA tumours PCI reduced the growth rate, while in the SK-LMS-1 tumours the growth was blocked for 12days followed by exponential growth close to that of untreated tumours. SK-LMS-1 tumours were more homogenously and better vascularized than MES-SA. After PCI the vascular shutdown was more complete in the SK-LMS-1 tumours than in the MES-SA tumours. AlPcS2a-based PCI, but not PDT, induced significant tumour growth delay in the evaluated sarcomas. Cellular responsiveness to bleomycin and tumour vascularity are identified as predictive markers for PCI treatment effects. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Recurring dynamically induced thinning during 1985 to 2010 on Upernavik Isstrøm, West Greenland

    DEFF Research Database (Denmark)

    Khan, Shfaqat Abbas; Kjaer, K.H.; Korsgaard, N.J.

    2013-01-01

    elevation satellite laser altimeter data supplemented with altimeter surveys from NASA's Airborne Topographic Mapper during 2002 to 2010. To assess thinning prior to 2002, we analyze aerial photographs from 1985. We document at least two distinct periods of dynamically induced ice loss during 1985 to 2010...

  13. Influence of a photochemical reaction on the controlled potential coulometric determination of plutonium in a mixture with uranium

    International Nuclear Information System (INIS)

    Le Duigou, Y.; Leidert, W.

    1976-01-01

    Data are provided in support of a photochemical reaction which takes place simultaneously with the electrochemical reduction of quadrivalent plutonium during the controlled potential coulometric determination of plutonium in a mixture with uranium. The interfering effect of this reaction is overcome by placing the cell in a dark environment. (orig.) [de

  14. Picosecond dynamics of the glutamate receptor in response to agonist-induced vibrational excitation.

    Science.gov (United States)

    Kubo, Minoru; Shiomitsu, Eiji; Odai, Kei; Sugimoto, Tohru; Suzuki, Hideo; Ito, Etsuro

    2004-02-01

    Conformational changes of proteins are dominated by the excitation and relaxation processes of their vibrational states. To elucidate the mechanism of receptor activation, the conformation dynamics of receptors must be analyzed in response to agonist-induced vibrational excitation. In this study, we chose the bending vibrational mode of the guanidinium group of Arg485 of the glutamate receptor subunit GluR2 based on our previous studies, and we investigated picosecond dynamics of the glutamate receptor caused by the vibrational excitation of Arg485 via molecular dynamics simulations. The vibrational excitation energy in Arg485 in the ligand-binding site initially flowed into Lys730, and then into the J-helix at the subunit interface of the ligand-binding domain. Consequently, the atomic displacement in the subunit interface around an intersubunit hydrogen bond was evoked in about 3 ps. This atomic displacement may perturb the subunit packing of the receptor, triggering receptor activation. Copyright 2003 Wiley-Liss, Inc.

  15. Photochemical degradation of atenolol, carbamazepine, meprobamate, phenytoin and primidone in wastewater effluents

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Mei Mei [Civil, Environmental and Architectural Engineering, 428 UCB, University of Colorado, Boulder, CO 80309 (United States); Southern Nevada Water Authority (SNWA), P.O. Box 99954, Las Vegas, NV 89193-9954 (United States); Trenholm, Rebecca [Southern Nevada Water Authority (SNWA), P.O. Box 99954, Las Vegas, NV 89193-9954 (United States); Rosario-Ortiz, Fernando L., E-mail: Fernando.rosario@colorado.edu [Civil, Environmental and Architectural Engineering, 428 UCB, University of Colorado, Boulder, CO 80309 (United States)

    2015-01-23

    Highlights: • The photochemical degradation of 5 compounds was evaluated in wastewater effluents. • Attenuation by sensitized photolysis was the most important degradation pathway. • Hydroxyl radical accounted for most of the degradation for aliphatic compounds. • Other transient oxidants could also significantly impact the degradation of the compounds. - Abstract: The photochemical degradation of five pharmaceuticals was examined in two secondary wastewater effluents. The compounds, which included atenolol, carbamazepine, meprobamate, phenytoin and primidone, were evaluated for both direct and sensitized photolysis. In the two wastewaters, direct photolysis did not lead to significant compound degradation; however, sensitized photolysis was an important removal pathway for the five pharmaceuticals. Upon solar irradiation, hydroxyl radical (HO·) was quantified using the hydroxylation of benzene and singlet oxygen ({sup 1}O{sub 2}) formation was monitored following the degradation of furfuryl alcohol. Degradation via sensitized photolysis was observed following five-day exposures for atenolol (69–91%), carbamazepine (67–98%), meprobamate (16–52%), phenytoin (44–85%), and primidone (34–88%). Varying removal is likely a result of the differences in reactivity with transient oxidants. Averaged steady state HO· concentrations ranged from 1.2 to 4.0 × 10{sup −16} M, whereas the concentrations of {sup 1}O{sub 2} were 6.0–7.6 × 10{sup −14} M. Partial removal due to presence of HO· indicates it was not the major sink for most compounds examined. Other transient oxidants, such as {sup 1}O{sub 2} and triplet state effluent organic matter, are likely to play important roles in fates of these compounds.

  16. Source reconciliation of atmospheric gas-phase and particle-phase pollutants during a severe photochemical smog episode.

    Science.gov (United States)

    Schauer, James J; Fraser, Matthew P; Cass, Glen R; Simoneit, Bernd R T

    2002-09-01

    A comprehensive organic compound-based receptor model is developed that can simultaneously apportion the source contributions to atmospheric gas-phase organic compounds, semivolatile organic compounds, fine particle organic compounds, and fine particle mass. The model is applied to ambient data collected at four sites in the south coast region of California during a severe summertime photochemical smog episode, where the model determines the direct primary contributions to atmospheric pollutants from 11 distinct air pollution source types. The 11 sources included in the model are gasoline-powered motor vehicle exhaust, diesel engine exhaust, whole gasoline vapors, gasoline headspace vapors, organic solvent vapors, whole diesel fuel, paved road dust, tire wear debris, meat cooking exhaust, natural gas leakage, and vegetative detritus. Gasoline engine exhaust plus whole gasoline vapors are the predominant sources of volatile organic gases, while gasoline and diesel engine exhaust plus diesel fuel vapors dominate the emissions of semivolatile organic compounds from these sources during the episode studied at all four air monitoring sites. The atmospheric fine particle organic compound mass was composed of noticeable contributions from gasoline-powered motor vehicle exhaust, diesel engine exhaust, meat cooking, and paved road dust with smaller but quantifiable contributions from vegetative detritus and tire wear debris. In addition, secondary organic aerosol, which is formed from the low-vapor pressure products of gas-phase chemical reactions, is found to be a major source of fine particle organic compound mass under the severe photochemical smog conditions studied here. The concentrations of secondary organic aerosol calculated in the present study are compared with previous fine particle source apportionment results for less intense photochemical smog conditions. It is shown that estimated secondary organic aerosol concentrations correlate fairly well with the

  17. Mechanisms of shock-induced dynamic friction

    International Nuclear Information System (INIS)

    Winter, R E; Ball, G J; Keightley, P T

    2006-01-01

    The mechanism of shock-induced dynamic friction has been explored through an integrated programme of experiments and numerical simulations. A novel experimental technique has been developed for observing the sub-surface deformation in aluminium when sliding against a steel anvil at high velocity and pressure. The experimental observations suggest that slight differences in conditions at the interface between the metals affect frictional behaviour even at the very high-velocity, high-pressure regime studied here. However, a clear finding from the experimental work is the presence of two distinct modes of deformation termed deep and shallow. The deep deformation is observed in a region of the aluminium specimen where the interfacial velocity is relatively low and the shallow deformation is observed in a region where the interfacial velocity is higher. A 1D numerical treatment is presented which predicts the existence of two mechanisms for dynamic friction termed 'asymptotic melting' and 'slide-then-lock'. In both modes there is a warm-up phase in which the interface temperature is increased by frictional heating. For high initial sliding velocity, this is followed by the onset of the asymptotic melting state, in which the temperature is almost constant and melting is approached asymptotically. This mechanism produces low late-time frictional stress and shallow deformation. For lower initial sliding velocity, the warm-up terminates in a violent work hardening event that locks the interface and launches a strong plastic shear wave into the weaker material. This slide-then-lock mechanism is characterized by sustained high frictional stress and deep plastic deformation. These predicted mechanisms offer a plausible and consistent explanation for the abrupt transitions in the depth of sub-surface deformation observed in the experiments. A key conclusion arising from the current work is that the frictional stress does not vary smoothly with pressure or sliding velocity

  18. Results of photochemical modeling sensitivity analyses in the Lake Michigan region: Current status of Lake Michigan Ozone Control Program (LMOP) modeling

    Energy Technology Data Exchange (ETDEWEB)

    Dolwick, P.D. [Lake Michigan Air Directors Consortium, Des Plaines, IL (United States); Kaleel, R.J. [Illinois Environmental Protection Agency, Springfield, IL (United States); Majewski, M.A. [Wisconsin Dept. of Natural Resources, Madison, WI (United States)

    1994-12-31

    The four states that border Lake Michigan are cooperatively applying a state-of-the-art nested photochemical grid model to assess the effects of potential emission control strategies on reducing elevated tropospheric ozone concentrations in the region to levels below the national ambient air quality standard. In order to provide an extensive database to support the application of the photochemical model, a substantial data collection effort known as the Lake Michigan Ozone Study (LMOS) was completed during the summer of 1991. The Lake Michigan Ozone Control Program (LMOP) was established by the States of Illinois, Wisconsin, Michigan, and Indiana to carry out the application of the modeling system developed from the LMOS, in terms of developing the attainment demonstrations required from this area by the Clean Air Act Amendments of 1990.

  19. Photochemical and electrochemical studies on lanthanide complexes of 6-(hydroxymethylpyridine- 2-carboxaldehyde[2- methyl-pyrimidine-4,6-diyl] bis-hydrazone

    Directory of Open Access Journals (Sweden)

    María Alejandra Fernandez

    2014-01-01

    Full Text Available Herein we report the synthesis of the 6-(hydroxymethylpyridine-2- carboxaldehyde[2-methyl-pyrimidine- 4,6-diyl]bis-hydrazone by a condensation reaction between 6-(hydroxymethyl picolinaldehyde with 4,6-(bis-hydrazino-2- methylpyrimidine. This bis-hydrazone can be visualized as a two-arm system which exhibits photochemical induced [E,E]/[E,Z]/[Z,Z’] isomerizations and double coordination to metal centers. Configurational changes, upon UV light irradiation, were followed over time by 1 H NMR, establishing that isomerization, in both arms, is a consecutive reaction that follows first-order kinetics (k1 = 4.06 x 10-4 s-1 and k2 = 2.80 x 10-4 s-1. Furthermore, the synthesis of bis-hydrazone metal complexes with La (III and Sm (III ions was achieved; subsequently, the absorption and emission properties of these complexes were studied, determining the fluorescence quantum yields, La= 0.2024 and Sm= 0.1413. Electrochemical studies of the complexes were conducted by square wave voltammetry, demonstrating that the bis-hydrazone and its complexes are electroactive species between +1.5 and -2.5 V.

  20. Applications of high order harmonic radiation to UVX-solids interaction: high excitation density in electronic relaxation dynamics and surface damaging

    International Nuclear Information System (INIS)

    De Grazia, M.

    2007-12-01

    The new sources of radiation in the extreme-UV (X-UV: 10-100 nm), which deliver spatially coherent, ultra-short and intense pulses, allow studying high flux processes and ultra-fast dynamics in various domains. The thesis work presents two applications of the high-order laser harmonics (HH) to solid state physics. In Part I, we describe the optimization of the harmonic for studies of X-UV/solids interaction. In Part II, we investigate effects of high excitation density in the dynamics of electron relaxation in dielectric scintillator crystals - tungstates and fluorides, using time-resolved luminescence spectroscopy. Quenching of luminescence at short time gives evidence of the competition between radiative and non-radiative recombination of self-trapped excitons (STE). The non-radiative channel is identified to mutual interaction of STE at high excitation density. In Part III, we study the X-UV induced damage mechanism in various materials, either conductor (amorphous carbon) or insulators (organic polymers, e.g., PMMA). In PMMA-Plexiglas, in the desorption regime (0.2 mJ/cm 2 , i.e., below damage threshold), the surface modifications reflect X-UV induced photochemical processes that are tentatively identified, as a function of dose: at low dose, polymer chain scission followed by the blow-up of the volatile, low-molecular fragments leads to crater formation; at high dose, cross-linking in the near-surface layer of remaining material leads to surface hardening. These promising results have great perspectives considering the performances already attained and planned in the next future in the development of the harmonic sources. (author)

  1. European scale modeling of sulfur, oxidized nitrogen and photochemical oxidants. Model development and evaluation for the 1994 growing season

    Energy Technology Data Exchange (ETDEWEB)

    Langner, J.; Bergstroem, R. [Swedish Meteorological and Hydrological Inst., Norrkoeping (Sweden); Pleijel, K. [Swedish Environmental Research Inst., Goeteborg (Sweden)

    1998-09-01

    A chemical mechanism, including the relevant reactions leading to the production of ozone and other photochemical oxidants, has been implemented in the MATCH regional tracer transport/chemistry/deposition model. The aim has been to develop a model platform that can be used as a basis for a range of regional scale studies involving atmospheric chemistry, including assessment of the importance of different sources of pollutants to the levels of photochemical oxidants and air pollutant forecasting. Meteorological input data to the model were taken from archived output from the operational version of HIRLAM at SMHI. Evaluation of model calculations over Europe for a six month period in 1994 for a range of chemical components show good results considering known sources of error and uncertainties in input data and model formulation. With limited further work the system is sufficiently good to be applied for scenario studies and for regional scale air pollutant forecasts 42 refs, 24 figs, 17 tabs

  2. Photochemical stability of π-conjugated polymers for polymer solar cells: a rule of thumb

    DEFF Research Database (Denmark)

    Manceau, Matthieu; Bundgaard, Eva; Carlé, Jon Eggert

    2011-01-01

    A comparative photochemical stability study of a wide range of π-conjugated polymers relevant to polymer solar cells is presented. The behavior of each material has been investigated under simulated sunlight (1 sun, 1000 W m−2, AM 1.5G) and ambient atmosphere. Degradation was monitored during age...... ageing combining UV-visible and infrared spectroscopies. From the comparison of the collected data, the influence of the polymer chemical structure on its stability has been discussed. General rules relative to the polymer structure–stability relationship are proposed....

  3. Aqueous photochemical degradation of hydroxylated PAHs: Kinetics, pathways, and multivariate effects of main water constituents

    Energy Technology Data Exchange (ETDEWEB)

    Ge, Linke; Na, Guangshui [Key Laboratory for Ecological Environment in Coastal Areas (SOA), National Marine Environmental Monitoring Center, Dalian 116023 (China); Chen, Chang-Er [Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ (United Kingdom); Li, Jun [Key Laboratory for Ecological Environment in Coastal Areas (SOA), National Marine Environmental Monitoring Center, Dalian 116023 (China); College of Marine Science, Shanghai Ocean University, Shanghai 201306 (China); Ju, Maowei; Wang, Ying; Li, Kai [Key Laboratory for Ecological Environment in Coastal Areas (SOA), National Marine Environmental Monitoring Center, Dalian 116023 (China); Zhang, Peng, E-mail: pzhang@nmemc.org.cn [Key Laboratory for Ecological Environment in Coastal Areas (SOA), National Marine Environmental Monitoring Center, Dalian 116023 (China); Yao, Ziwei [Key Laboratory for Ecological Environment in Coastal Areas (SOA), National Marine Environmental Monitoring Center, Dalian 116023 (China)

    2016-03-15

    Hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) are contaminants of emerging concern in the aquatic environment, so it is of great significance to understand their environmental transformation and toxicity. This study investigated the aqueous photochemical behavior of four OH-PAHs, 9-Hydroxyfluorene (9-OHFL), 2-Hydroxyfluorene, 9-Hydroxyphenanthrene and 1-Hydroxypyrene, under simulated sunlight irradiation (λ > 290 nm). It was observed that their photodegradation followed the pseudo-first-order kinetics. Based on the determined quantum yields, their calculated solar apparent photodegradation half-lives in surface waters at 45° N latitude ranged from 0.4 min for 9-Hydroxyphenanthrene to 7.5 × 10{sup 3} min for 9-OHFL, indicating that the OH-PAHs would intrinsically photodegrade fast in sunlit surface waters. Furthermore, 9-OHFL as an example was found to undergo direct photolysis, and self-sensitized photooxidation via ·OH rather than {sup 1}O{sub 2} in pure water. The potential photoreactions involved photoinduced hydroxylation, dehydrogenation and isomerization based on product identification by GC–MS/MS. 9-OHFL photodegraded slower in natural waters than in pure water, which was attributed to the integrative effects of the most photoreactive species, such as Fe(III), NO{sub 3}{sup −}, Cl{sup −} and humic acid. The photomodified toxicity was further examined using Vibrio fischeri, and it was found that the toxicity of photolyzed 9-OHFL did not decrease significantly (p > 0.05) either in pure water or in seawater, implying the comparable or higher toxicity of some intermediates. These results are important for assessing the fate and risks of OH-PAHs in surface waters. - Graphical abstract: Aqueous photochemical behavior of 4 hydroxylated PAHs is first reported on revealing the kinetics, mechanisms, toxicity, and multivariate effects of water constituents. - Highlights: • It is first reported on aqueous photochemical behavior of 4 hydroxylated

  4. Applying green chemistry to the photochemical route to artemisinin

    Science.gov (United States)

    Amara, Zacharias; Bellamy, Jessica F. B.; Horvath, Raphael; Miller, Samuel J.; Beeby, Andrew; Burgard, Andreas; Rossen, Kai; Poliakoff, Martyn; George, Michael W.

    2015-06-01

    Artemisinin is an important antimalarial drug, but, at present, the environmental and economic costs of its semi-synthetic production are relatively high. Most of these costs lie in the final chemical steps, which follow a complex acid- and photo-catalysed route with oxygenation by both singlet and triplet oxygen. We demonstrate that applying the principles of green chemistry can lead to innovative strategies that avoid many of the problems in current photochemical processes. The first strategy combines the use of liquid CO2 as solvent and a dual-function solid acid/photocatalyst. The second strategy is an ambient-temperature reaction in aqueous mixtures of organic solvents, where the only inputs are dihydroartemisinic acid, O2 and light, and the output is pure, crystalline artemisinin. Everything else—solvents, photocatalyst and aqueous acid—can be recycled. Some aspects developed here through green chemistry are likely to have wider application in photochemistry and other reactions.

  5. Applying green chemistry to the photochemical route to artemisinin.

    Science.gov (United States)

    Amara, Zacharias; Bellamy, Jessica F B; Horvath, Raphael; Miller, Samuel J; Beeby, Andrew; Burgard, Andreas; Rossen, Kai; Poliakoff, Martyn; George, Michael W

    2015-06-01

    Artemisinin is an important antimalarial drug, but, at present, the environmental and economic costs of its semi-synthetic production are relatively high. Most of these costs lie in the final chemical steps, which follow a complex acid- and photo-catalysed route with oxygenation by both singlet and triplet oxygen. We demonstrate that applying the principles of green chemistry can lead to innovative strategies that avoid many of the problems in current photochemical processes. The first strategy combines the use of liquid CO2 as solvent and a dual-function solid acid/photocatalyst. The second strategy is an ambient-temperature reaction in aqueous mixtures of organic solvents, where the only inputs are dihydroartemisinic acid, O2 and light, and the output is pure, crystalline artemisinin. Everything else-solvents, photocatalyst and aqueous acid-can be recycled. Some aspects developed here through green chemistry are likely to have wider application in photochemistry and other reactions.

  6. Prediction of dynamic loads and induced vibrations in stall

    Energy Technology Data Exchange (ETDEWEB)

    Thirstrup Petersen, J.; Aagaard Madsen, H. [Risoe National Lab. (Denmark); Bjoerck, A. [Aeronautical Research Inst. of Sweden (Sweden); Enevoldsen, P. [Bonus Energy A/S (Denmark); Oeye, S. [The Technical Univ. of Denmark (Denmark); Ganander, H. [Teknikgruppen AB (Sweden); Winkelaar, D. [Netherlands Energy Research Foundation (Netherlands)

    1998-05-01

    Results from research in an EC Joule-III project and from national projects are presented. The objectives are improvement of design methods for stall regulated wind turbines with emphasis on stall induced vibrations and dynamic stall. The primary concern is limitation of the edgewise vibrations in the fundamental blade natural mode shape, which have caused trouble on modern wind turbines of approximate size 500 kW nominal power and 40 m rotor diameter. A theoretical study of quasi-steady aerodynamics confirms that the vibrations are driven basically by energy supplied from the aerodynamic forces during stalled operation. This energy exchange is equivalent to negative aerodynamic damping. The theoretical approach identifies the main parameters controlling the phenomenon. These parameters describe the steady and the dynamic airfoil characteristics, the overall aerodynamic layout of the blade, e.g. chord length and twist, the structural properties of the blade, e.g. structural damping and properties controlling the resulting vibration direction. Furthermore, full aeroelastic calculations and comparison with measurements show that the properties of the supporting structure, i.e. the main shaft, the nacelle and the tower, are important, as the global vibration of the rotor on its support may exchange energy with the blade vibration, when the blade natural frequency is close to one of the frequencies of the coupled rotor tilt-yaw mode shapes, usually denoted the global rotor whirl frequencies. It is confirmed that the influence of changing the primary design parameters can be determined by use of qualified aeroelastic calculations. Presented design guidelines therefore build on both the simple quasi-steady models, which can be used for the preliminary choice of the design variables mentioned above, and on full aeroelastic calculations. The aeroelastic calculations refine the design basis and should be used for choosing the final design variables and for final

  7. Dissociation dynamics of CH3I in electric spark induced breakdown revealed by time-resolved laser induced breakdown spectroscopy

    International Nuclear Information System (INIS)

    Wang, Yang; Liu, Wei-long; Song, Yun-fei; Duo, Li-ping; Liu, Yu-qiang; Yang, Yan-qiang

    2015-01-01

    Highlights: • Emission of electric spark dissociation of CH 3 I is similar to its fs LIBS. • We use fs laser induced breakdown as a simulation for electric spark dissociation. • The I 2 molecule formation is directly observed in the time-resolved LIBS. • Bimolecular collision of I ∗ and CH 3 I is responsible for the formation of I 2 . - Abstract: The electric discharge spark dissociation of gas CH 3 I is found to be similar to its femtosecond laser photodissociation. The almost identical spectra of the two processes show that their initial ionization conditions are very similar. The initial ionization followed by molecular fragmentation is proposed as the dissociation mechanism, in which the characteristic emissions of I + , CH 3 , CH 2 , CH, H, and I 2 are identified as the dissociation products. The emission band of 505 nm I 2 is clearly observed in the time-resolved laser induced breakdown spectroscopy (LIBS). The dynamic curve indicates that I 2 ∗ molecules are formed after the delay time of ∼4.7 ns. The formation of I 2 ∗ molecule results from the bimolecular collision of the highly excited iodine atom I ∗ ( 4 P) and CH 3 I molecule. This dynamical information can help understand the process of electric discharge spark dissociation of CH 3 I

  8. Photochemical sensitization by azathioprine and its metabolites. Part 3. A direct EPR and spin-trapping study of light-induced free radicals from 6-mercaptopurine and its oxidation products.

    Science.gov (United States)

    Moore, D E; Sik, R H; Bilski, P; Chignell, C F; Reszka, K J

    1994-12-01

    Sunlight has been implicated in the high incidence of skin cancer found in patients receiving 6-mercaptopurine (PSH) in the form of its pro-drug azathioprine. In this study we have used EPR spectroscopy in conjunction with the spin-trapping technique to determine whether PSH and its metabolic or photochemical oxidation products generate highly reactive free radicals upon UV irradiation. When an aqueous anaerobic solution (pH 5 or 9) of PSH (pKa = 7.7) and either 2-methyl-2-nitrosopropane (MNP) or nitromethane (NM) were irradiated (lambda > 300 nm) with a Xe arc lamp, the corresponding purine-6-thiyl (PS.) radical adduct and the reduced form of the spin trap (MNP/H. or CH3NO2.-) were observed. However, no radical adducts were detected when PSH and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) were irradiated (lambda = 320 nm) in oxygen-free buffer. These findings suggest that PSH does not photoionize but that instead MNP and NM are reduced by direct electron transfer from excited state PSH, 1.3(PSH)*. In aerobic solution, oxygen can act as an electron acceptor and the O2.- and PS. radicals are formed and trapped by DMPO. 6-Mercaptopurine did photoionize when irradiated with a Nd:YAG laser at 355 nm as evidenced by the appearance of the DMPO/H.(eq- + H+) adduct, which decreased in intensity in the presence of N2O. 1.3(6-Mercaptopurine)* oxidized ascorbate, formate and reduced glutathione to the corresponding ascorbyl, CO2.- or glutathiyl radicals. The photochemical behavior of 6-thioxanthine and 6-thiouric acid was similar to PSH. However, the excited states of these metabolic oxidation products exhibited stronger reducing properties than 1.3(PSH)*.(ABSTRACT TRUNCATED AT 250 WORDS)

  9. Mercury in Arctic snow: Quantifying the kinetics of photochemical oxidation and reduction

    Energy Technology Data Exchange (ETDEWEB)

    Mann, E.A. [Department of Environmental Science, Acadia University, Wolfville, NS (Canada); Environmental Science Programme, Memorial University of Newfoundland, St. John' s, NL (Canada); Mallory, M.L. [Department of Biology, Acadia University, Wolfville, NS (Canada); Ziegler, S.E. [Environmental Science Programme, Memorial University of Newfoundland, St. John' s, NL (Canada); Tordon, R. [Environment Canada, Dartmouth, NS (Canada); O' Driscoll, N.J., E-mail: nelson.odriscoll@acadiau.ca [Department of Environmental Science, Acadia University, Wolfville, NS (Canada)

    2015-03-15

    Controlled experiments were performed with frozen and melted Arctic snow to quantify relationships between mercury photoreaction kinetics, ultra violet (UV) radiation intensity, and snow ion concentrations. Frozen (− 10 °C) and melted (4 °C) snow samples from three Arctic sites were exposed to UV (280–400 nm) radiation (1.26–5.78 W · m{sup −2}), and a parabolic relationship was found between reduction rate constants in frozen and melted snow with increasing UV intensity. Total photoreduced mercury in frozen and melted snow increased linearly with greater UV intensity. Snow with the highest concentrations of chloride and iron had larger photoreduction and photooxidation rate constants, while also having the lowest Hg(0) production. Our results indicate that the amount of mercury photoreduction (loss from snow) is the highest at high UV radiation intensities, while the fastest rates of mercury photoreduction occurred at both low and high intensities. This suggests that, assuming all else is equal, earlier Arctic snow melt periods (when UV intensities are less intense) may result in less mercury loss to the atmosphere by photoreduction and flux, since less Hg(0) is photoproduced at lower UV intensities, thereby resulting in potentially greater mercury transport to aquatic systems with snowmelt. - Highlights: • Mercury photochemical kinetics were studied in frozen and melted Arctic snow. • UV-induced photoreduction and photooxidation rate constants were quantified. • Chloride ion, iron, and DOC influence mercury photoreactions in snow. • Frozen and melted snow have different mercury photoreduction characteristics. • Kinetic information provided can be used to model mercury fate in the Arctic.

  10. Mercury in Arctic snow: Quantifying the kinetics of photochemical oxidation and reduction

    International Nuclear Information System (INIS)

    Mann, E.A.; Mallory, M.L.; Ziegler, S.E.; Tordon, R.; O'Driscoll, N.J.

    2015-01-01

    Controlled experiments were performed with frozen and melted Arctic snow to quantify relationships between mercury photoreaction kinetics, ultra violet (UV) radiation intensity, and snow ion concentrations. Frozen (− 10 °C) and melted (4 °C) snow samples from three Arctic sites were exposed to UV (280–400 nm) radiation (1.26–5.78 W · m −2 ), and a parabolic relationship was found between reduction rate constants in frozen and melted snow with increasing UV intensity. Total photoreduced mercury in frozen and melted snow increased linearly with greater UV intensity. Snow with the highest concentrations of chloride and iron had larger photoreduction and photooxidation rate constants, while also having the lowest Hg(0) production. Our results indicate that the amount of mercury photoreduction (loss from snow) is the highest at high UV radiation intensities, while the fastest rates of mercury photoreduction occurred at both low and high intensities. This suggests that, assuming all else is equal, earlier Arctic snow melt periods (when UV intensities are less intense) may result in less mercury loss to the atmosphere by photoreduction and flux, since less Hg(0) is photoproduced at lower UV intensities, thereby resulting in potentially greater mercury transport to aquatic systems with snowmelt. - Highlights: • Mercury photochemical kinetics were studied in frozen and melted Arctic snow. • UV-induced photoreduction and photooxidation rate constants were quantified. • Chloride ion, iron, and DOC influence mercury photoreactions in snow. • Frozen and melted snow have different mercury photoreduction characteristics. • Kinetic information provided can be used to model mercury fate in the Arctic

  11. Infrared laser-induced chemical reactions

    International Nuclear Information System (INIS)

    Katayama, Mikio

    1978-01-01

    The experimental means which clearly distinguishes between infrared ray-induced reactions and thermal reactions has been furnished for the first time when an intense monochromatic light source has been obtained by the development of infrared laser. Consequently, infrared laser-induced chemical reactions have started to develop as one field of chemical reaction researches. Researches of laser-induced chemical reactions have become new means for the researches of chemical reactions since they were highlighted as a new promising technique for isotope separation. Specifically, since the success has been reported in 235 U separation using laser in 1974, comparison of this method with conventional separation techniques from the economic point of view has been conducted, and it was estimated by some people that the laser isotope separation is cheaper. This report briefly describes on the excitation of oscillation and reaction rate, and introduces the chemical reactions induced by CW laser and TEA CO 2 laser. Dependence of reaction yield on laser power, measurement of the absorbed quantity of infrared ray and excitation mechanism are explained. Next, isomerizing reactions are reported, and finally, isotope separation is explained. It was found that infrared laser-induced chemical reactions have the selectivity for isotopes. Since it is evident that there are many examples different from thermal and photo-chemical reactions, future collection of the data is expected. (Wakatsuki, Y.)

  12. Photochemical generation of highly destabilized vinyl cations: the effects of alpha- and beta-trifluoromethyl versus alpha- and beta-methyl substituents

    NARCIS (Netherlands)

    Alem, van K.; Belder, G.; Lodder, G.; Zuilhof, H.

    2005-01-01

    The photochemical reactions in methanol of the vinylic halides 1-4, halostyrenes with a methyl or a trifluoromethyl substituent at the - or -position, have been investigated quantitatively. Next to E/Z isomerization, the reactions are formation of vinyl radicals, leading to reductive dehalogenation

  13. Photochemical reactions of neptunium in nitric acid solution containing photocatalyst

    International Nuclear Information System (INIS)

    Fukasawa, Tetsuo; Kawamura, Fumio

    1991-01-01

    Photochemical oxidation and reduction behaviors of neptunium were preliminarily investigated in 3 mol/l nitric acid solution. Nitric acid of 3 mol/l simulated the high level waste solution from a spent fuel reprocessing process. Concentrations of Np(V), Np(VI) and nitrous acid were determined with a photospectrometer, and solution potential with an electrode. Without additives, Np(VI) was reduced to Np(V) by nitrous acid which was photolytically generated from nitric acid. With a scavenger for nitrous acid, Np(V) was oxidized to extractable Np(VI) by a photolytically generated oxidizing reagent which were predicted by the solution potential measurement. The reduction rate was higher than the oxidation rate because of the larger quantity and higher reactivity of nitrous acid than an oxidizing reagent. Photocatalyst was proved to be effective for the oxidation of Np(V) to Np(VI). (author)

  14. Femtosecond-laser induced dynamics of CO on Ru(0001): Deep insights from a hot-electron friction model including surface motion

    Science.gov (United States)

    Scholz, Robert; Floß, Gereon; Saalfrank, Peter; Füchsel, Gernot; Lončarić, Ivor; Juaristi, J. I.

    2016-10-01

    A Langevin model accounting for all six molecular degrees of freedom is applied to femtosecond-laser induced, hot-electron driven dynamics of Ru(0001)(2 ×2 ):CO. In our molecular dynamics with electronic friction approach, a recently developed potential energy surface based on gradient-corrected density functional theory accounting for van der Waals interactions is adopted. Electronic friction due to the coupling of molecular degrees of freedom to electron-hole pairs in the metal are included via a local density friction approximation, and surface phonons by a generalized Langevin oscillator model. The action of ultrashort laser pulses enters through a substrate-mediated, hot-electron mechanism via a time-dependent electronic temperature (derived from a two-temperature model), causing random forces acting on the molecule. The model is applied to laser induced lateral diffusion of CO on the surface, "hot adsorbate" formation, and laser induced desorption. Reaction probabilities are strongly enhanced compared to purely thermal processes, both for diffusion and desorption. Reaction yields depend in a characteristic (nonlinear) fashion on the applied laser fluence, as well as branching ratios for various reaction channels. Computed two-pulse correlation traces for desorption and other indicators suggest that aside from electron-hole pairs, phonons play a non-negligible role for laser induced dynamics in this system, acting on a surprisingly short time scale. Our simulations on precomputed potentials allow for good statistics and the treatment of long-time dynamics (300 ps), giving insight into this system which hitherto has not been reached. We find generally good agreement with experimental data where available and make predictions in addition. A recently proposed laser induced population of physisorbed precursor states could not be observed with the present low-coverage model.

  15. Protonation-induced ultrafast torsional dynamics in 9-anthrylbenzimidazole: a pH activated molecular rotor.

    Science.gov (United States)

    Nandi, Amitabha; Kushwaha, Archana; Das, Dipanwita; Ghosh, Rajib

    2018-03-07

    We report the photophysical properties and excited state dynamics of 9-anthrylbenzimidazole (ANBI) which exhibits protonation-induced molecular rotor properties. In contrast to the highly emissive behavior of neutral ANBI, protonation of the benzimidazole group of ANBI induces efficient nonradiative deactivation by ultrafast torsional motion around the bond connecting the anthracene and benzimidazole units, as revealed by ultrafast transient absorption and fluorescence spectroscopy. Contrary to viscosity-independent fluorescence of neutral dyes, protonated ANBI is shown to display linear variation of emission yield and lifetime with solvent viscosity. The protonation-induced molecular rotor properties in the studied system are shown to be driven by enhanced charge transfer and are corroborated by quantum chemical calculations. Potential application as a microviscosity sensor of acidic regions in a heterogeneous environment by these proton-activated molecular rotor properties of ANBI is discussed.

  16. 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)

  17. 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.

  18. Dual active layer a-IGZO TFT via homogeneous conductive layer formation by photochemical H-doping.

    Science.gov (United States)

    Jeong, Seung-Ki; Kim, Myeong-Ho; Lee, Sang-Yeon; Seo, Hyungtak; Choi, Duck-Kyun

    2014-01-01

    In this study, InGaZnO (IGZO) thin film transistors (TFTs) with a dual active layer (DAL) structure are fabricated by inserting a homogeneous embedded conductive layer (HECL) in an amorphous IGZO (a-IGZO) channel with the aim of enhancing the electrical characteristics of conventional bottom-gate-structure TFTs. A highly conductive HECL (carrier concentration at 1.6 × 10(13) cm(-2), resistivity at 4.6 × 10(-3) Ω∙cm, and Hall mobility at 14.6 cm(2)/Vs at room temperature) is fabricated using photochemical H-doping by irradiating UV light on an a-IGZO film. The electrical properties of the fabricated DAL TFTs are evaluated by varying the HECL length. The results reveal that carrier mobility increased proportionally with the HECL length. Further, a DAL TFT with a 60-μm-long HECL embedded in an 80-μm-long channel exhibits comprehensive and outstanding improvements in its electrical properties: a saturation mobility of 60.2 cm(2)/Vs, threshold voltage of 2.7 V, and subthreshold slope of 0.25 V/decade against the initial values of 19.9 cm(2)/Vs, 4.7 V, and 0.45 V/decade, respectively, for a TFT without HECL. This result confirms that the photochemically H-doped HECL significantly improves the electrical properties of DAL IGZO TFTs.

  19. Construction of a photochemical reactor combining a CCD spectrophotometer and a LED radiation source.

    Science.gov (United States)

    Gombár, Melinda; Józsa, Éva; Braun, Mihály; Ősz, Katalin

    2012-10-01

    An inexpensive photoreactor using LED light sources and a fibre-optic CCD spectrophotometer as a detector was built by designing a special cell holder for standard 1.000 cm cuvettes. The use of this device was demonstrated by studying the aqueous photochemical reaction of 2,5-dichloro-1,4-benzoquinone. The developed method combines the highly quantitative data collection of CCD spectrophotometers with the possibility of illuminating the sample independently of the detecting light beam, which is a substantial improvement of the method using diode array spectrophotometers as photoreactors.

  20. Static and Dynamic Water Motion-Induced Instability in Oxide Thin-Film Transistors and Its Suppression by Using Low-k Fluoropolymer Passivation.

    Science.gov (United States)

    Choi, Seungbeom; Jo, Jeong-Wan; Kim, Jaeyoung; Song, Seungho; Kim, Jaekyun; Park, Sung Kyu; Kim, Yong-Hoon

    2017-08-09

    Here, we report static and dynamic water motion-induced instability in indium-gallium-zinc-oxide (IGZO) thin-film transistors (TFTs) and its effective suppression with the use of a simple, solution-processed low-k (ε ∼ 1.9) fluoroplastic resin (FPR) passivation layer. The liquid-contact electrification effect, in which an undesirable drain current modulation is induced by a dynamic motion of a charged liquid such as water, can cause a significant instability in IGZO TFTs. It was found that by adopting a thin (∼44 nm) FPR passivation layer for IGZO TFTs, the current modulation induced by the water-contact electrification was greatly reduced in both off- and on-states of the device. In addition, the FPR-passivated IGZO TFTs exhibited an excellent stability to static water exposure (a threshold voltage shift of +0.8 V upon 3600 s of water soaking), which is attributed to the hydrophobicity of the FPR passivation layer. Here, we discuss the origin of the current instability caused by the liquid-contact electrification as well as various static and dynamic stability tests for IGZO TFTs. On the basis of our findings, we believe that the use of a thin, solution-processed FPR passivation layer is effective in suppressing the static and dynamic water motion-induced instabilities, which may enable the realization of high-performance and environment-stable oxide TFTs for emerging wearable and skin-like electronics.