WorldWideScience

Sample records for epr spectra sintez

  1. Quantitative analysis of dinuclear manganese(II) EPR spectra.

    Science.gov (United States)

    Golombek, Adina P; Hendrich, Michael P

    2003-11-01

    A quantitative method for the analysis of EPR spectra from dinuclear Mn(II) complexes is presented. The complex [(Me(3)TACN)(2)Mn(II)(2)(mu-OAc)(3)]BPh(4) (1) (Me(3)TACN=N, N('),N(")-trimethyl-1,4,7-triazacyclononane; OAc=acetate(1-); BPh(4)=tetraphenylborate(1-)) was studied with EPR spectroscopy at X- and Q-band frequencies, for both perpendicular and parallel polarizations of the microwave field, and with variable temperature (2-50K). Complex 1 is an antiferromagnetically coupled dimer which shows signals from all excited spin manifolds, S=1 to 5. The spectra were simulated with diagonalization of the full spin Hamiltonian which includes the Zeeman and zero-field splittings of the individual manganese sites within the dimer, the exchange and dipolar coupling between the two manganese sites of the dimer, and the nuclear hyperfine coupling for each manganese ion. All possible transitions for all spin manifolds were simulated, with the intensities determined from the calculated probability of each transition. In addition, the non-uniform broadening of all resonances was quantitatively predicted using a lineshape model based on D- and r-strain. As the temperature is increased from 2K, an 11-line hyperfine pattern characteristic of dinuclear Mn(II) is first observed from the S=3 manifold. D- and r-strain are the dominate broadening effects that determine where the hyperfine pattern will be resolved. A single unique parameter set was found to simulate all spectra arising for all temperatures, microwave frequencies, and microwave modes. The simulations are quantitative, allowing for the first time the determination of species concentrations directly from EPR spectra. Thus, this work describes the first method for the quantitative characterization of EPR spectra of dinuclear manganese centers in model complexes and proteins. The exchange coupling parameter J for complex 1 was determined (J=-1.5+/-0.3 cm(-1); H(ex)=-2JS(1).S(2)) and found to be in agreement with a

  2. Uncertainty analysis for absorption and first-derivative EPR spectra

    Science.gov (United States)

    Tseitlin, Mark; Eaton, Sandra S.; Eaton, Gareth R.

    2015-01-01

    Electron paramagnetic resonance (EPR) experimental techniques produce absorption or first-derivative spectra. Uncertainty analysis provides the basis for comparison of spectra obtained by different methods. In this study it was used to derive analytical equations to relate uncertainties for integrated intensity and line widths obtained from absorption or first-derivative spectra to the signal-to-noise ratio (SNR), with the assumption of white noise. Predicted uncertainties for integrated intensities and line widths are in good agreement with Monte Carlo calculations for Lorentzian and Gaussian lineshapes. Conservative low-pass filtering changes the noise spectrum, which can be modeled in the Monte Carlo simulations. When noise is close to white, the analytical equations provide useful estimates of uncertainties. For example, for a Lorentzian line with white noise, the uncertainty in the number of spins obtained from the first-derivative spectrum is 2.6 times greater than from the absorption spectrum at the same SNR. Uncertainties in line widths obtained from absorption and first-derivative spectra are similar. The impact of integration or differentiation on SNR and on uncertainties in fitting parameters was analyzed. Although integration of the first-derivative spectrum improves the apparent smoothness of the spectrum, it also changes the frequency distribution of the noise. If the lineshape of the signal is known, the integrated intensity can be determined more accurately by fitting the first-derivative spectrum than by first integrating and then fitting the absorption spectrum. Uncertainties in integrated intensities and line widths are less when the parameters are determined from the original data than from spectra that have been either integrated or differentiated. PMID:25774102

  3. Uncertainty analysis for absorption and first-derivative EPR spectra.

    Science.gov (United States)

    Tseitlin, Mark; Eaton, Sandra S; Eaton, Gareth R

    2012-11-01

    Electron paramagnetic resonance (EPR) experimental techniques produce absorption or first-derivative spectra. Uncertainty analysis provides the basis for comparison of spectra obtained by different methods. In this study it was used to derive analytical equations to relate uncertainties for integrated intensity and line widths obtained from absorption or first-derivative spectra to the signal-to-noise ratio (SNR), with the assumption of white noise. Predicted uncertainties for integrated intensities and line widths are in good agreement with Monte Carlo calculations for Lorentzian and Gaussian lineshapes. Conservative low-pass filtering changes the noise spectrum, which can be modeled in the Monte Carlo simulations. When noise is close to white, the analytical equations provide useful estimates of uncertainties. For example, for a Lorentzian line with white noise, the uncertainty in the number of spins obtained from the first-derivative spectrum is 2.6 times greater than from the absorption spectrum at the same SNR. Uncertainties in line widths obtained from absorption and first-derivative spectra are similar. The impact of integration or differentiation on SNR and on uncertainties in fitting parameters was analyzed. Although integration of the first-derivative spectrum improves the apparent smoothness of the spectrum, it also changes the frequency distribution of the noise. If the lineshape of the signal is known, the integrated intensity can be determined more accurately by fitting the first-derivative spectrum than by first integrating and then fitting the absorption spectrum. Uncertainties in integrated intensities and line widths are less when the parameters are determined from the original data than from spectra that have been either integrated or differentiated.

  4. Host material induced hyperfine structure of F{sup +} centres EPR spectra in CaS

    Energy Technology Data Exchange (ETDEWEB)

    Seeman, Viktor, E-mail: viktor.seeman@ut.ee; Dolgov, Sergei; Maaroos, Aarne

    2017-05-15

    The hyperfine structure (HFS) of F{sup +} centres in CaS single crystals due to the interaction with {sup 33}S and {sup 43}Ca nuclei was observed in EPR spectra for the first time. Angular variations of the HFS were measured for rotation of magnetic field in {100} and {110} crystallographic planes. Using measured orientation-dependent EPR spectra and the EPR NMR program, the parameters of the spin Hamiltonian were determined. In case of {sup 33}S nucleus there is a strong dependence of the F{sup +} centre EPR spectrum on the quadrupole term whereas for {sup 43}Ca nucleus this dependence is insignificant.

  5. Phase transitions reflected in HF-EPR spectra

    NARCIS (Netherlands)

    Horst, Eric van der

    2006-01-01

    EPR is a technique limited to unpaired electrons. Current state of the art set-ups operate at frequencies of 130 GHz or higher. The benefits are increased resolution and the ability to measure large D systems. Using EPR data combined with other techniques systems in which (magnetic) phase

  6. Effect of microwave power on EPR spectra of natural and synthetic dental biocompatible materials

    Directory of Open Access Journals (Sweden)

    Adamczyk Jakub

    2015-07-01

    Full Text Available Paramagnetic centers in the two exemplary synthetic and natural dental biocompatible materials applied in implantology were examined by the use of an X-band (9.3 GHz electron paramagnetic resonance (EPR spectroscopy. The EPR spectra were measured in the range of microwave power 2.2–70 mW. The aims of this work were to compare paramagnetic centers concentrations in different dental biocompatible materials and to determine the effect of microwave power on parameters of their EPR spectra. It is the very first and innovatory examination of paramagnetic centers in these materials. It was pointed out that paramagnetic centers existed in both natural (~1018 spin/g and synthetic (~1019 spin/g dental biocompatible materials, but the lower free radical concentration characterized the natural sample. Continuous microwave saturation of EPR spectra indicated that faster spin-lattice relaxation processes existed in synthetic dental biocompatible materials than in natural material. Linewidths (ΔBpp of the EPR spectra of the natural dental material slightly increased for the higher microwave powers. Such effect was not observed for the synthetic material. The broad EPR lines (ΔBpp: 2.4 mT, 3.9 mT, were measured for the natural and synthetic dental materials, respectively. Probably strong dipolar interactions between paramagnetic centers in the studied samples may be responsible for their line broadening. EPR spectroscopy is the useful experimental method in the examination of paramagnetic centers in dental biocompatible materials.

  7. EPR spectra induced by gamma-irradiation of some dry medical herbs

    Science.gov (United States)

    Yordanov, N. D.; Lagunov, O.; Dimov, K.

    2009-04-01

    The radiation-induced EPR spectra in some medical herbs are reported. The samples studied are: (i) leaves of nettle, common balm, peppermint and thyme; (ii) stalks of common balm, thyme, milfoil, yarrow and marigold; (iii) blossoms of yarrow and marigold; (iv) blossoms and leaves of hawthorn and tutsan; and (v) roots of common valerian, nettle, elecampane (black and white), restharrows and carlina. Before irradiation all samples exhibit one weak anisotropic singlet EPR line with effective g-value of 2.0050±0.0002. The radiation-induced spectra fall into three groups. EPR spectra of irradiated blossoms of yarrow and marigold, stalks of common balm, thyme, tutsan and yarrow as well as roots of common valerian, nettle and elecampane (black and white) show "cellulose-like" EPR spectrum typical for irradiated plants. It is characterized by one intense central line with g=2.0050±0.0005 and two weak satellite lines situated ca. 30 G left and right to it. EPR spectra of gamma-irradiated restharrows and carlina are complex. They may be represented by one triplet corresponding to the "cellulose-like" EPR spectrum, one relatively intense singlet, situated in the center of the spectrum, and five weak additional satellite lines left and right to the center. The last spectrum was assigned as "carbohydrate-like" type. Only one intense EPR singlet with g=2.0048±0.0005 was recorded after irradiation of leaves of nettle and common balm. The lifetime of the radiation-induced EPR spectra was followed for a period of 3 months.

  8. EPR spectra induced by gamma-irradiation of some dry medical herbs

    Energy Technology Data Exchange (ETDEWEB)

    Yordanov, N.D. [Laboratory EPR, Institute of Catalysis, Bulgarian Academy of Sciences, 1113 Sofia (Bulgaria)], E-mail: ndyepr@bas.bg; Lagunov, O. [Laboratory EPR, Institute of Catalysis, Bulgarian Academy of Sciences, 1113 Sofia (Bulgaria); Dimov, K. [Institute of Cryobiology and Food technology, 1162 Sofia (Bulgaria)

    2009-04-15

    The radiation-induced EPR spectra in some medical herbs are reported. The samples studied are: (i) leaves of nettle, common balm, peppermint and thyme; (ii) stalks of common balm, thyme, milfoil, yarrow and marigold; (iii) blossoms of yarrow and marigold; (iv) blossoms and leaves of hawthorn and tutsan; and (v) roots of common valerian, nettle, elecampane (black and white), restharrows and carlina. Before irradiation all samples exhibit one weak anisotropic singlet EPR line with effective g-value of 2.0050{+-}0.0002. The radiation-induced spectra fall into three groups. EPR spectra of irradiated blossoms of yarrow and marigold, stalks of common balm, thyme, tutsan and yarrow as well as roots of common valerian, nettle and elecampane (black and white) show 'cellulose-like' EPR spectrum typical for irradiated plants. It is characterized by one intense central line with g=2.0050{+-}0.0005 and two weak satellite lines situated ca. 30 G left and right to it. EPR spectra of gamma-irradiated restharrows and carlina are complex. They may be represented by one triplet corresponding to the 'cellulose-like' EPR spectrum, one relatively intense singlet, situated in the center of the spectrum, and five weak additional satellite lines left and right to the center. The last spectrum was assigned as 'carbohydrate-like' type. Only one intense EPR singlet with g=2.0048{+-}0.0005 was recorded after irradiation of leaves of nettle and common balm. The lifetime of the radiation-induced EPR spectra was followed for a period of 3 months.

  9. SimLabel: a graphical user interface to simulate continuous wave EPR spectra from site-directed spin labeling experiments.

    Science.gov (United States)

    Etienne, E; Le Breton, N; Martinho, M; Mileo, E; Belle, V

    2017-08-01

    Site-directed spin labeling (SDSL) combined with continuous wave electron paramagnetic resonance (cw EPR) spectroscopy is a powerful technique to reveal, at the residue level, structural transitions in proteins. SDSL-EPR is based on the selective grafting of a paramagnetic label on the protein under study, followed by cw EPR analysis. To extract valuable quantitative information from SDSL-EPR spectra and thus give reliable interpretation on biological system dynamics, numerical simulations of the spectra are required. Such spectral simulations can be carried out by coding in MATLAB using functions from the EasySpin toolbox. For non-expert users of MATLAB, this could be a complex task or even impede the use of such simulation tool. We developed a graphical user interface called SimLabel dedicated to run cw EPR spectra simulations particularly coming from SDSL-EPR experiments. Simlabel provides an intuitive way to visualize, simulate, and fit such cw EPR spectra. An example of SDSL-EPR spectra simulation concerning the study of an intrinsically disordered region undergoing a local induced folding is described and discussed. We believe that this new tool will help the users to rapidly obtain reliable simulated spectra and hence facilitate the interpretation of their results. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

  10. Orientation order and rotation mobility of nitroxide biradicals determined by quantitative simulation of EPR spectra.

    Science.gov (United States)

    Bogdanov, Alexey V; Vorobiev, Andrey Kh

    2016-11-16

    The problem of quantitative numerical simulation of electron paramagnetic resonance (EPR) spectra of biradical probes in both isotropic and aligned media was solved for the first time. The models suitable for the description of the spectra of the probes, both in the rigid limit and in the presence of rotational motions, were developed and successfully applied to model systems. The simulation of EPR spectra allows obtaining the following information about the molecular structure and dynamics: the values of orientation order parameters, the type of rotation mobility and its quantitative characteristics, and the sign and value of the spin exchange constant of the biradical. Model systems used in this work include solutions of nitroxide biradicals in a viscous solvent (squalane) in the range of temperatures 100-370 K and in the aligned liquid crystal n-octylcyanobiphenyl (8CB, 100-298.5 K). Unexpectedly, it was found that in 8CB the main orientation axis of the biradical molecule is perpendicular to the longest molecular axis.

  11. Synthesis, crystal structure and EPR spectra of tetraaquabis(methylisonicotinate) copper(II) disaccharinate single crystal

    Science.gov (United States)

    Çelik, Yunus; Bozkurt, Esat; Uçar, İbrahim; Karabulut, Bünyamin

    2011-10-01

    The crystal structure of the [Cu(mein)2(H2O)4]·(sac)2 complex (mein: methylisonicotinate, sac: saccharine) was investigated by single crystal X-ray diffraction technique. The vibrational spectrum was also discussed in relation with the other compounds containing methylisonicotinate and saccharinate complexes. The EPR spectra of [Cu(mein)2(H2O)4]·(sac)2 single crystal have been studied in the temperature range between 113 and 300 K in three mutually perpendicular planes and exhibit two sets of four hyperfine lines of Cu2+ ion. The ground state wave function of the Cu2+ ion is an admixture of dx2-y2 and dz2 states.

  12. Linear transformation of EPR spectra as a method proposed for improving identification of paramagnetic species in ceramic.

    Science.gov (United States)

    Dobosz, B; Krzyminiewski, R

    2007-04-01

    In the present paper the paramagnetic centres in pottery generated after gamma-irradiation were investigated. The computer resolution enhancement method (CREM) was used to increase the electron paramagnetic resonance (EPR) spectra resolution. The measurements were performed at room and liquid nitrogen temperatures. The paper shows the results of non-irradiated and gamma-irradiated pottery before and after resolution enhancement. Each EPR spectrum showed a multiple structure after the CREM procedure application. An aluminium hole centre [AlO(4)](0) has been ascribed to these lines. The g factors are: g(1)=2.0602, g(2)=2.0079, and g(3)=2.0019 and hyperfine splitting is A(1)=5.5G and A(2) approximately A(3)=6.3G.

  13. Linear transformation of EPR spectra as a method proposed for improving identification of paramagnetic species in ceramic

    Energy Technology Data Exchange (ETDEWEB)

    Dobosz, B. [Medical Physics Division, Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznan (Poland)]. E-mail: benia@hoth.amu.edu.pl; Krzyminiewski, R. [Medical Physics Division, Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznan (Poland)

    2007-04-15

    In the present paper the paramagnetic centres in pottery generated after {gamma}-irradiation were investigated. The computer resolution enhancement method (CREM) was used to increase the electron paramagnetic resonance (EPR) spectra resolution. The measurements were performed at room and liquid nitrogen temperatures. The paper shows the results of non-irradiated and {gamma}-irradiated pottery before and after resolution enhancement. Each EPR spectrum showed a multiple structure after the CREM procedure application. An aluminium hole centre [AlO{sub 4}]{sup 0} has been ascribed to these lines. The g factors are: g {sub 1}=2.0602, g {sub 2}=2.0079, and g {sub 3}=2.0019 and hyperfine splitting is A {sub 1}=5.5 G and A {sub 2}{approx}A {sub 3}=6.3 G.

  14. Consistent simulation of X- and Q-band EPR spectra of an unsymmetric dinuclear Mn2(II,III) complex.

    Science.gov (United States)

    Huang, Ping; Shaikh, Nizamuddin; Anderlund, Magnus F; Styring, Stenbjörn; Hammarström, Leif

    2006-05-01

    Simulation of X- and Q-band electron paramagnetic resonance (EPR) spectra of an unsymmetric dinuclear [Mn(2)(II,III)L(mu-OAc)(2)]ClO(4) complex (1), (L is the dianion of 2-{[N,N-bis(2-pyridylmethyl)amino]methyl}-6-{[N-(3,5-di-tert-butyl-2-hydroxybenzyl)-N-(2-pyridylmethyl)amino]methyl}-4-methylphenol) was performed using one consistent set of simulation parameters. Rhombic g-tensors and hyperfine tensors were necessary to obtain satisfactory simulation of the EPR spectra. The anisotropy of the effective hyperfine tensors of each individual (55)Mn ion was further analyzed in terms of intrinsic hyperfine tensors. Detailed analysis shows that the hyperfine anisotropy of the Mn(III) ion is a result of the Jahn-Teller effect and thus an inherent character. In contrast, the anomalous hyperfine anisotropy of the Mn(II) ion is attributed as being transferred from the Mn(III) ion through the spin exchange interaction. The anisotropy parameter for the Mn(II) is deduced as D(II)=-1.26+/-0.2cm(-1). This is the first reported D(II) value for a Mn(II) ion in a weakly exchange coupled mixed-valence Mn(2)(II,III) complex with a bis-mu-acetato-bridge. The [see text] electronic configuration of the Mn(III) ion in 1 is revealed by the negative sign of its intrinsic hyperfine tensor anisotropy, Deltaa(III)=a(z)-a(x,y)=-46cm(-1). Lower spectral resolution of the Q-band EPR spectrum as compared to the X-band EPR spectrum is associated to large line width broadening of the x- and y-components in contrast to the z-component. The origins of the unequal distribution of line width between the z- and x-, y-components are discussed.

  15. Analysis of various modifications in spectra analysis on accuracy of dose reconstructions in EPR dosimetry in tooth enamel

    Energy Technology Data Exchange (ETDEWEB)

    Ciesielski, B., E-mail: bciesiel@gumed.edu.pl [Department of Physics and Biophysics, Medical University of Gdansk, Debinki 1, 80-211 Gdansk (Poland); Kaminska, J. [Department of Oncology and Radiotherapy, Medical University of Gdansk, Debinki 7, 80-211 Gdansk (Poland); Emerich, K. [Department of Paediatric Dentistry, Medical University of Gdansk, Orzeszkowej 18, 80-208 Gdansk (Poland)

    2011-09-15

    The results of EPR measurements performed due to our participation in the 4th International Comparison of EPR Dosimetry using tooth enamel were used to analyze the effects of modifications in numerical analysis of the measured spectra on precision and accuracy of reconstructed doses. The studied modifications included effects of: (1) a use of Mn{sup 2+} standard, (2) variations in experimental native background signals of tooth enamel used for dose reconstructions, (3) signal filtration, (4) subtraction of empty tube spectra, and (5) variations in the spectra ranges used for calculations (fitting windows). It was shown, that the use of a Mn standard, for normalization of intensities of the recorded signals in the spectra processing, strongly increased the dosimetric accuracy. The regression lines of the doses reconstructed using different background spectra against nominal doses, obtained without Mn standard, had slopes about 30% higher and their scatter range was about 2 times higher than the same parameters obtained when Mn standard was applied in the spectra processing. Accuracy of the measured doses characterized by root mean square deviations from the nominal doses was 71 mGy for calculations with Mn standard and 241 mGy without normalization to Mn lines. Despite the large beneficial effect of the use of Mn standard on accuracy (root mean square deviations of the data, slope of the regression lines), it did not significantly improve the dosimetry performance characterized by the critical dose and detection limit. The smoothing of the spectra by 9 point filtration resulted in 1.6% increase of the reconstructed doses. The subtraction of empty tube spectrum had no effect on precision and accuracy of the dose reconstruction. The performance parameters were also practically insensitive to a choice of a width of the spectral window used for the analysis, provided it encompassed the {approx}1.6 mT range covering the main peaks of the radiation induced signal in

  16. UV/Vis, MCD and EPR Spectra of Mononuclear Manganese and Molybdenum Complexes

    OpenAIRE

    Westphal, Anne

    2012-01-01

    This PhD thesis deals with the spectroscopic characterization of the electronic structures of mononuclear manganese and molybdenum complexes. At this, in addition to UV/Vis absorption spectroscopy, electron paramagnetic resonance (EPR) and magnetic circular dichroism (MCD) spectroscopy were applied in this work. Additionally, new procedures for the general analysis of MCD C-term intensities were developed within the scope of this thesis. It is divided into four parts. Following a general p...

  17. Optical and EPR spectra of the thionitrosyl complex [Cr(OH2)5(NS)]2+

    DEFF Research Database (Denmark)

    Døssing, Anders Rørbæk; Dethlefsen, Johannes Wied

    2008-01-01

    . The optical data indicate that the NS ligand is a weaker p-acceptor than the NO ligand. The EPR parameters of [Cr(OH2)5(NS)]2+ were determined: giso, g¦ and g-: 1.96515, 1.92686(5) and 1.986860(8); Aiso(53Cr), A¦(53Cr) and A-(53Cr): 25.3´10-4, 38´10-4 and 18.5´10-4cm-1; Aiso(14N), A¦(14N) and A-(14N): 6...

  18. Microwave Saturation of Complex EPR Spectra and Free Radicals of Burnt Skin Treated with Apitherapeutic Agent

    Directory of Open Access Journals (Sweden)

    Pawel Olczyk

    2013-01-01

    Full Text Available The effect of microwave power on the complex electron paramagnetic resonance spectra of the burn matrix after the therapy with propolis was examined. The spectra were measured with microwaves in the range of 2.2–79 mW. Three groups of free radicals were found in the damaged skin samples. Their spectral lines evolve differently with the microwave power. In order to detect these free radical groups, the lineshape of the spectra was numerically analysed. The spectra were a superposition of three component lines. The best fit was obtained for the deconvolution of the experimental spectra into one Gauss and two Lorentz lines. The microwave power changes also the lineshape of the spectra of thermally injured skin treated with the conventional agent—silver sulphadiazine. The spectral changes were different for propolis and for silver sulphadiazine. The number of individual groups of free radicals in the wound bed after implementation of these two substances is not equal. It may be explained by a higher activity of propolis than of silver sulphadiazine as therapeutic agents.

  19. Theoretical studies of the optical and EPR spectra for VO^{2+} in Na_3C_6H_5O_7·2H_2O single crystal

    Directory of Open Access Journals (Sweden)

    Ch.-Y. Li

    2015-06-01

    Full Text Available On the basis of the perturbation formulas for a d^1 configuration ion in a tetragonal crystal field, the three optical absorption bands and electron paramagnetic resonance (EPR parameters (g factors g_i and hyperfine structure constants A_i for i = || and ⊥, respectively of VO^{2+} in Na_3C_6H_5O_7·2H_2O (TSCD single crystals were studied using the perturbation theory method. By simulating the calculated optical and EPR spectra to the observed values, local structure parameters and negative signs of the hyperfine structure constants A_i of the octahedral (VO_6^{8-} cluster in TSCD single crystal can be obtained.

  20. The role of ammonia molecules in [Cu(NH 3) 5](ClO 4) 2 structure in the crystal field averaging in Cu(II) EPR powder spectra

    Science.gov (United States)

    Piekara-Sady, Lidia; Bednarski, Waldemar

    2003-07-01

    The EPR results for [Cu(NH 3) 5](ClO 4) 2·0.1NH 3 above and below the phase transition temperature T c=142 K are reported. The comparison to the data reported so far revealed the role of 'free' ammonia (i.e. NH 3 molecules non-coordinated to Cu(II) ion) in the averaging process of anisotropic polycrystalline EPR spectra of five-coordinated Cu(II) complex. For T> TC, in the cubic structure, there is a dependence of gav value on the number of free ammonia molecule (0≤ x≤0.2) per one complex. Below TC, in tetragonal phase, for x≈0.1, there are two contributions to the EPR spectrum: the anisotropic one due to the rigid square pyramid coordination and isotropic one due to the centers where the averaging mechanism is efficient. For x=0.2, there is only isotropic spectrum in the tetragonal phase. Additionally, the 'aging' process of the freshly made sample has been observed as the increase in the intensity of the isotropic component, relative to the anisotropic one, in the low temperature phase. This behavior has been ascribed to free ammonia ordering process in tetragonal structure.

  1. Temperature dependence of the EPR spectra for the Ni{sub 1-x}Co{sub x}Fe{sub 2}O{sub 4} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    P, Silva; W, Braemer; F, Torres [Institute Venezolano de Investigaciones Cientificas, Centro de Fisica, Carretera Panamericana Km. 11, Aptdo. 20632 (Venezuela, Bolivarian Republic of); V, Sagredo; E, Perez, E-mail: silva@ivic.v [Universidad de Los Andes, Departamento de Fisica, Laboratorio de Magnetismo, Merida (Venezuela, Bolivarian Republic of)

    2010-01-01

    Electron Paramagnetic Resonance (EPR) was used to study, the temperature dependence, of the magnetic behavior of Ni{sub 1-x}Co{sub x}Fe{sub 2}O{sub 4} with 0.0 < x < 0.5, in the temperature range 80 < T < 700 K. Nanoparticles of sizes between 30 and 40 nm were obtained using the sol-gel method. The results show that the resonance field (H{sub R}) decrease while the linewidth (AH{sub PP}) increase, in the temperature range studied, when x is increased. The H{sub R} values for x = 0 are in agreement with a superparamagnetic phase in the temperature range studied, while for x = 0.2, H{sub R} and {Delta}H{sub PP} are in accordance with a ferri to superparamagnetic transition at T{approx}350 K, where T is related to the EPR blocking temperature of these samples. For sample with x = 0.5 this temperature is T{approx}470 K. These results are in good agreement with the magnetization and MOKE results. MOKE measurements as a function of temperature were made to corroborate EPR results.

  2. Nitrosyl hemoglobins: EPR above 80 K

    Energy Technology Data Exchange (ETDEWEB)

    Wajnberg, E.; Bemski, G.; El-Jaick, L.J.; Alves, O.C.

    1995-03-01

    The EPR spectra of nitrosyl hemoglobin and myoglobin in different conditions (native, denatured and lyophilized), as well as of hematin-NO were obtained in the temperature range of 80 K-280 K. There is a substantial and reversible.decrease of the areas of the EPR spectra of all the hemoglobin samples above 150 K. The interpretation of the results implies the existence of two conformational states in thermal equilibrium only one of which is EPR detectable. Thermodynamical parameters are determined for the hexa and penta-coordinated cases. (author). 25 refs, 3 figs.

  3. EPR spectroscopy of spices

    Directory of Open Access Journals (Sweden)

    R. T. Тimakova

    2016-01-01

    Full Text Available From 01 January 2017 you enter the interstate standard GOST 33271-2015 “Dry Spices, herbs and vegetable seasonings. Manual exposure in order to combat pathogens and other microorganisms” which States that the absorbed dose of radiation to the spices should be from 3 to 30 kGy. The study found that before the introduction of permissive legislative framework in the consumer market of Russia there are irradiated food products (chili, ground chili, ground spicy chili, black pepper. For radiation monitoring of food safety, we used the method of electron paramagnetic resonance (EPR, which allows quickly and with a high degree of reliability to establish the fact of irradiation. It is established that all samples of spices irradiated with dose of 12 kGy (technology radappertization gave typical spectra of the signals established by the method of electron paramagnetic resonance in the domestic EPR spectrometer, the intensity, amplitude and peak width of the EPR signal of samples of spices with the increase of irradiation dose increases. It is proven that repeated exposure no effect accumulation. Integration with 2017 Russia in the global practi ce of using radiation technologies of processing of food products and food raw materials with the purpose of extending shelf life confirms the need for a data Bank on the radiation sensitivity of various food products to determine the optimal doses and the eff ect of radiation doses on the shelf life and quality of products.

  4. Broadband transmission EPR spectroscopy.

    Directory of Open Access Journals (Sweden)

    Wilfred R Hagen

    Full Text Available EPR spectroscopy employs a resonator operating at a single microwave frequency and phase-sensitive detection using modulation of the magnetic field. The X-band spectrometer is the general standard with a frequency in the 9-10 GHz range. Most (biomolecular EPR spectra are determined by a combination of the frequency-dependent electronic Zeeman interaction and a number of frequency-independent interactions, notably, electron spin - nuclear spin interactions and electron spin - electron spin interactions, and unambiguous analysis requires data collection at different frequencies. Extant and long-standing practice is to use a different spectrometer for each frequency. We explore the alternative of replacing the narrow-band source plus single-mode resonator with a continuously tunable microwave source plus a non-resonant coaxial transmission cell in an unmodulated external field. Our source is an arbitrary wave digital signal generator producing an amplitude-modulated sinusoidal microwave in combination with a broadband amplifier for 0.8-2.7 GHz. Theory is developed for coaxial transmission with EPR detection as a function of cell dimensions and materials. We explore examples of a doublet system, a high-spin system, and an integer-spin system. Long, straigth, helical, and helico-toroidal cells are developed and tested with dilute aqueous solutions of spin label hydroxy-tempo. A detection limit of circa 5 µM HO-tempo in water at 800 MHz is obtained for the present setup, and possibilities for future improvement are discussed.

  5. Homogeneity and EPR metrics for assessment of regular grids used in CW EPR powder simulations

    Science.gov (United States)

    Crăciun, Cora

    2014-08-01

    CW EPR powder spectra may be approximated numerically using a spherical grid and a Voronoi tessellation-based cubature. For a given spin system, the quality of simulated EPR spectra depends on the grid type, size, and orientation in the molecular frame. In previous work, the grids used in CW EPR powder simulations have been compared mainly from geometric perspective. However, some grids with similar homogeneity degree generate different quality simulated spectra. This paper evaluates the grids from EPR perspective, by defining two metrics depending on the spin system characteristics and the grid Voronoi tessellation. The first metric determines if the grid points are EPR-centred in their Voronoi cells, based on the resonance magnetic field variations inside these cells. The second metric verifies if the adjacent Voronoi cells of the tessellation are EPR-overlapping, by computing the common range of their resonance magnetic field intervals. Beside a series of well known regular grids, the paper investigates a modified ZCW grid and a Fibonacci spherical code, which are new in the context of EPR simulations. For the investigated grids, the EPR metrics bring more information than the homogeneity quantities and are better related to the grids’ EPR behaviour, for different spin system symmetries. The metrics’ efficiency and limits are finally verified for grids generated from the initial ones, by using the original or magnetic field-constraint variants of the Spherical Centroidal Voronoi Tessellation method.

  6. EPR study on gamma-irradiated fruits dehydrated via osmosis

    Energy Technology Data Exchange (ETDEWEB)

    Yordanov, N.D. [Laboratory EPR, Institute of Catalysis, Bulgarian Academy of Sciences, 1113 Sofia (Bulgaria)]. E-mail: ndyepr@bas.bg; Aleksieva, K. [Laboratory EPR, Institute of Catalysis, Bulgarian Academy of Sciences, 1113 Sofia (Bulgaria)

    2007-06-15

    The shape and time stability of the electron paramagnetic resonance (EPR) spectra of non- and {gamma}-irradiated papaya, melon, cherry and fig samples dehydrated via osmosis are reported. It is shown that non-irradiated samples are generally EPR silent whereas {gamma}-irradiated exhibit 'sugar-like' EPR spectra. The recorded EPR spectra are monitored for a period of 7 months after irradiation (stored at low humidity and in the dark). The results suggest longer period of unambiguous identification of the radiation processing of osmose dehydrated fruits. Therefore, the Protocol EN 13708,2001 issued by CEN is fully applicable for the studied fruit samples.

  7. The structure, magnetism and EPR spectra of a (μ-thiophenolato)(μ-pyrazolato-N,N') double bridged dicopper(II) complex.

    Science.gov (United States)

    Khadir, Narjes; Boghaei, Davar M; Assoud, Abdeljalil; Nascimento, Otaciro R; Nicotina, Amanda; Ghivelder, Luis; Calvo, Rafael

    2015-02-07

    A new binuclear copper(ii) complex, namely [Cu2L(pz)(DMSO)], where L = 2,6-bis[(2-phenoxy)iminomethyl]-4-methylthiophenolate(3-) and pz = pyrazolate ligand, has been synthesized by a one-pot synthesis involving copper(ii) acetate monohydrate, the S-protected ligand precursor 2-(N,N-dimethylthiocarbamato)-5-methylisophthalaldehyde di-2'-hydroxy anil, (), and pyrazole, in which a metal-promoted S-deprotection reaction occurs during the formation of the complex. This was characterized by routine physicochemical studies, single crystal X-ray diffraction and electron paramagnetic resonance (EPR) techniques. The structure analysis reveals that there are copper centres in two different environments, a slightly distorted square planar and a distorted square-pyramidal, arranged in binuclear units. The EPR study of these binuclear units performed at 9.4 GHz in the temperature range between 4 and 293 K shows an antiferromagnetic interaction between Cu(II) ions, and allows evaluating g factors gx = 2.068(1), gy = 2.091(1) and gz = 2.165(1), with = 2.108(1), an exchange coupling parameter J0 = -26(1) cm(-1) (defined as ), and a zero field splitting of the ground triplet state described by D = 86(2) × 10(-4) cm(-1) and E = -48(3) × 10(-4) cm(-1). These results are discussed and compared with the existing literature.

  8. Broadband Transmission EPR Spectroscopy

    Science.gov (United States)

    Hagen, Wilfred R.

    2013-01-01

    EPR spectroscopy employs a resonator operating at a single microwave frequency and phase-sensitive detection using modulation of the magnetic field. The X-band spectrometer is the general standard with a frequency in the 9–10 GHz range. Most (bio)molecular EPR spectra are determined by a combination of the frequency-dependent electronic Zeeman interaction and a number of frequency-independent interactions, notably, electron spin – nuclear spin interactions and electron spin – electron spin interactions, and unambiguous analysis requires data collection at different frequencies. Extant and long-standing practice is to use a different spectrometer for each frequency. We explore the alternative of replacing the narrow-band source plus single-mode resonator with a continuously tunable microwave source plus a non-resonant coaxial transmission cell in an unmodulated external field. Our source is an arbitrary wave digital signal generator producing an amplitude-modulated sinusoidal microwave in combination with a broadband amplifier for 0.8–2.7 GHz. Theory is developed for coaxial transmission with EPR detection as a function of cell dimensions and materials. We explore examples of a doublet system, a high-spin system, and an integer-spin system. Long, straigth, helical, and helico-toroidal cells are developed and tested with dilute aqueous solutions of spin label hydroxy-tempo. A detection limit of circa 5 µM HO-tempo in water at 800 MHz is obtained for the present setup, and possibilities for future improvement are discussed. PMID:23555819

  9. Coordination modes between copper(II) and N-acetylneuraminic (sialic) acid from a 2D-simulation analysis of EPR spectra. Implications for copper mediation of sialoglycoconjugate chemistry relevant to human biology.

    Science.gov (United States)

    Fainerman-Melnikova, Marina; Szabó-Plánka, Terézia; Rockenbauer, Antal; Codd, Rachel

    2005-04-04

    The equilibrium distribution of species formed between Cu(II) and N-acetylneuraminic (sialic) acid (I, LH) at 298 K has been determined using a two-dimensional (2D) simulation analysis of electron paramagnetic resonance (EPR) spectra. In acidic solutions (pH values 11. It is proposed that [CuL]+ most likely features I coordinated via the deprotonated carboxylic acid group (O1) and the endocyclic oxygen atom (OR) forming a five-membered chelate ring. Select Cu(II)-I species of the form [CuLH-1] may feature I acting as a dianionic tridentate chelate, via oxygen atoms derived from O1, OR, and one deprotonated hydroxy group (O7 or O8) from the glycerol tail. Alternatively, I may coordinate Cu(II) in a bidentate fashion as the tert-2-hydroxycarboxylato (O1,O2) dianion. Spectra predicted for Cu(II)-I complexes in which I is coordinated in either a O1,OR {I1-} or O1,O2 {I2-} bidentate fashion {e.g., [CuL]+ (O1,O R), [CuL2] (bis-O1,O R), [CuLH-1] (isomer: O1, O2), [CuL2H-1]- (O1, O R; O1, O2), and [CuL2H-2]2- (isomer: bis-O1, O2)} have "irregular" EPR spectra that are ascribed to the existence of Cu(II)-I(monomer) Cu(II)-I(polymer) equilibria. The formation of polymeric Cu(II)-I species will be favored in these complexes because the glycerol-derived hydroxyl groups at the complex periphery (O, 7O, 8O9) are available for further Cu(II) binding. The presence of polymeric Cu(II)-I species is supported by EPR spectral data from solutions of Cu(II) and the homopolymer of I, colominic acid (Ipoly). Conversely, spectra predicted for Cu(II)-I complexes where I is coordinated in a {I2-} tridentate {e.g., [CuLH-1] (isomer: O1, O R, O7, or O8) and [CuL2H-2]2- (isomer: bis-O1,O R,O7, or O8)} or tetradentate fashion {I3-} {e.g., [CuLH-3]2- (O1, O R, O, 8O9)} are typical for mononuclear tetragonally elongated Cu(II) octahedra. In this latter series of complexes, the tendency toward the formation of polymeric Cu(II)-I analogues is small because the polydentate I effectively wraps up the

  10. EPR of exchange coupled systems

    CERN Document Server

    Bencini, Alessandro

    2012-01-01

    From chemistry to solid state physics to biology, the applications of Electron Paramagnetic Resonance (EPR) are relevant to many areas. This unified treatment is based on the spin Hamiltonian approach and makes extensive use of irreducible tensor techniques to analyze systems in which two or more spins are magnetically coupled. This edition contains a new Introduction by coauthor Dante Gatteschi, a pioneer and scholar of molecular magnetism.The first two chapters review the foundations of exchange interactions, followed by examinations of the spectra of pairs and clusters, relaxation in oligon

  11. Multifrequency EPR study on freeze-dried fruits before and after X-ray irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Yordanov, N.D. [Laboratory EPR, Institute of Catalysis, Bulgarian Academy of Sciences, 1113 Sofia (Bulgaria)]. E-mail: ndyepr@bas.bg; Aleksieva, K. [Laboratory EPR, Institute of Catalysis, Bulgarian Academy of Sciences, 1113 Sofia (Bulgaria); Dimitrova, A. [Laboratory EPR, Institute of Catalysis, Bulgarian Academy of Sciences, 1113 Sofia (Bulgaria); Georgieva, L. [Institute of Cryobiology and Food Technologies, 1162 Sofia (Bulgaria); Tzvetkova, E. [Institute of Cryobiology and Food Technologies, 1162 Sofia (Bulgaria)

    2006-09-15

    X-, K- and Q-band EPR studies on lyophilized whole pulp parts of blue plum, apricot, peach, melon as well as achens and pulp separately of strawberry before and after X-ray irradiation are reported. Before irradiation all samples show in X band a weak singlet EPR line with g=2.0030+/-0.0005, except melon, which is EPR silent. Immediately after irradiation all samples exhibit complex fruit-depending spectra, which decay with time and change to give, in ca. 50days, an asymmetric singlet EPR line with g=2.0041+/-0.0005. Only apricot pulp gave a typical ''sugar-like'' EPR spectrum. Singlet EPR lines recorded after irradiation in X -band are K- and Q-band resolved as typical anisotropic EPR spectra with g{sub ||}=2.0023+/-0.0003 and g{sub -}bar =2.0041+/-0.0005. In addition, K- and Q-band EPR spectra of all samples show a superposition with the six EPR lines of Mn{sup 2+} naturally present in the fruits. The saturation behavior of the EPR spectra of achens of lyophilized and fresh strawberry is also studied. The differences in g factors of samples before and after X-ray irradiation might be used for the identification of radiation processing of fruits in the case of pulp and the differences in the EPR saturation behavior might be used for the achens of strawberry.

  12. Identification of irradiated crab using EPR

    Energy Technology Data Exchange (ETDEWEB)

    Maghraby, A. [Radiation Dosimetry Department, National Institute for Standards (NIS), Ministry of Scientific Research, Haram, 12211- Giza, P.O. Box: 136 (Egypt)]. E-mail: maghrabism@yahoo.com

    2007-02-15

    EPR spectroscopy is a fast and powerful technique for the identification of irradiated food. Crab exoskeleton was divided into six parts: dactyl, cheliped, carapace, apron, swimming legs, and walking legs. Samples of the exoskeleton were prepared and irradiated to Cs-137 gamma radiation in the range (1.156-5.365 kGy). EPR spectra of unirradiated as well as irradiated samples were recorded and analyzed. Response to gamma radiation was plotted for each part of the exoskeleton, dactyl was found to be the most sensitive part, followed by the apron (38%), cheliped (37%), walking legs (30%), swimming legs (24%), and carapace (21%) relative to the dactyl response.

  13. An EPR Primer

    Indian Academy of Sciences (India)

    IAS Admin

    electron paramagnetic resonance (EPR) is given to help the uninitiated reader to get prepared to appreciate the following article. Electron paramagnetic resonance (EPR), also known as electron spin resonance, (ESR) is a form of spectroscopy dealing with electronic spin-state transitions. These transitions are caused.

  14. EPR study on tomatoes before and after gamma-irradiation

    Science.gov (United States)

    Aleksieva, K.; Georgieva, L.; Tzvetkova, E.; Yordanov, N. D.

    2009-09-01

    The results from the EPR studies on fresh, air-dried and lyophilized tomato samples before and after gamma-irradiation are reported. Before irradiation fresh and air-dried tomatoes exhibit one singlet EPR line characterized with common g-factor of 2.0048±0.0005, whereas freeze-dried tomato does not show any EPR spectrum. After irradiation, a typical "cellulose-like" triplet EPR spectrum appears in all samples, attributed to cellulose free radicals, generated by gamma-irradiation. It consists of intense central line with g=2.0048±0.0005 and two weak satellite lines separated ca. 3 mT left and right of it. In air-dried and lyophilized tomatoes the "cellulose-like" EPR spectrum is superimposed by an additional partly resolved carbohydrate spectrum. Fading measurements of the radiation-induced EPR signals indicate that the intensity of the EPR spectra of air-dried and freeze-dried tomato are reduced to about 50% after 50 days, whereas those of fresh irradiated tomatoes kept at 4 °C fade completely in 15 days. The reported results unambiguously show that the presence of two satellite lines in the EPR "cellulose-like" spectra of tomato samples can be used for identification of radiation processing.

  15. Computational and instrumental methods in EPR

    CERN Document Server

    Bender, Christopher J

    2006-01-01

    Computational and Instrumental Methods in EPR Prof. Bender, Fordham University Prof. Lawrence J. Berliner, University of Denver Electron magnetic resonance has been greatly facilitated by the introduction of advances in instrumentation and better computational tools, such as the increasingly widespread use of the density matrix formalism. This volume is devoted to both instrumentation and computation aspects of EPR, while addressing applications such as spin relaxation time measurements, the measurement of hyperfine interaction parameters, and the recovery of Mn(II) spin Hamiltonian parameters via spectral simulation. Key features: Microwave Amplitude Modulation Technique to Measure Spin-Lattice (T1) and Spin-Spin (T2) Relaxation Times Improvement in the Measurement of Spin-Lattice Relaxation Time in Electron Paramagnetic Resonance Quantitative Measurement of Magnetic Hyperfine Parameters and the Physical Organic Chemistry of Supramolecular Systems New Methods of Simulation of Mn(II) EPR Spectra: Single Cryst...

  16. EPR in characterization of seeds paramagnetic species

    Energy Technology Data Exchange (ETDEWEB)

    Luiz, A.P.C.; Mauro, M.F.F.L.; Portugal, K.O.; Barbana, V.M.; Guedes, C.L.B.; Mauro, E. di; Carneiro, C.E.A.; Zaia, D.A.M.; Prete, C.E.C. [Universidade Estadual de Londrina (UEL), PR (Brazil)

    2011-07-01

    Full text. In Brazil, since 1970s, renewable fuel programs has been developed in order to replace petroleum. Today a program that has been discussed is the bio diesel, which intend to replace diesel fuel, fossil oil, to bio diesel, renewal fuel. As seeds are the basis for production of oil and consequently processed into bio diesel, the goal of this work is to characterize and compare paramagnetic species present in the seeds by Electron Paramagnetic Resonance (EPR). Samples used in this study were seeds of sorghum, barley, corn, peanuts, soy beans, cotton, wheat, oats, mustard, rice, sunflower and turnip. Some paramagnetic species present in soil was also investigated as goethite (FeOOH), hematite (Fe{sub 2}O{sub 3}), magnetite (Fe{sub 3}O{sub 4}), and ferrihydrite (Fe{sub 5}HO{sub 8} {center_dot} 4H{sub 2}O), since, these species present in appreciable quantities in the soil can be present in the seeds and analyzed for comparison. The characterization of these species is essential to understand the EPR seeds spectra. Each sample is placed in a thin quartz tube 4 mm in diameter, and it is inserted into the cavity of the spectrometer at room temperature, at low temperature (77 K) and variable temperature using liquid nitrogen flow and hot flow through a compressor air. It was used as standard Mg O:Mn{sup 2+}, which is also inserted into the cavity. Shortly after the potency is regulated, frequency, amplitude and sweep the field. The spectroscopic analysis by EPR X-band ({approx} 9:5GHz), were performed at the Fluorescence and Electron Paramagnetic Resonance Laboratory, Exact Sciences Center, State University of Londrina, Parana state, Brazil, through an EPR spectrometer JEOL brand (JES-PE-3X). In the EPR spectra, spectroscopic factor or g factor and line width were determined in paramagnetic species. Studies from several seeds with EPR technique detected in all of them presence of same complex of Fe{sup 3+} present in the goethite at g {approx} 2, and in the seeds

  17. Biomolecular EPR spectroscopy

    CERN Document Server

    Hagen, Wilfred Raymond

    2008-01-01

    Comprehensive, Up-to-Date Coverage of Spectroscopy Theory and its Applications to Biological SystemsAlthough a multitude of books have been published about spectroscopy, most of them only occasionally refer to biological systems and the specific problems of biomolecular EPR (bioEPR). Biomolecular EPR Spectroscopy provides a practical introduction to bioEPR and demonstrates how this remarkable tool allows researchers to delve into the structural, functional, and analytical analysis of paramagnetic molecules found in the biochemistry of all species on the planet. A Must-Have Reference in an Intrinsically Multidisciplinary FieldThis authoritative reference seamlessly covers all important bioEPR applications, including low-spin and high-spin metalloproteins, spin traps and spin lables, interaction between active sites, and redox systems. It is loaded with practical tricks as well as do's and don'ts that are based on the author's 30 years of experience in the field. The book also comes with an unprecedented set of...

  18. Molecular structure and single crystal EPR spectra of bis(L-Valinato)copper(II) monohydrate, Cu[H 2NCH(CH 3) 2CHCO 2] 2·H 2O

    Science.gov (United States)

    Steren, C. A.; Calvo, R.; Castellano, E. E.; Fabiane, M. S.; Piro, O. E.

    1990-09-01

    A magnetic-structural study of the title compound, Cu(L-Val) 2·H 2O, employing EPR spectroscopy and X-ray diffraction methods is presented. The complex crystallizes in the space group C2 with a = 21.314(5) Å, b = 9.586(2) Å, c = 7.417(2) Å, β = 108.89(2)°, and Z=4. The Cu(II) ions, which are in a five-fold pyramidal coordination, with two valine molecules and a water oxygen (O w), are arranged in layers parallel to (100). Neighboring Cu(L-Val) 2·H 2O molecules in a layer are linked to each other by a net of O w-H…O and N-H…O hydrogen bonds. The single EPR line observed arises from the collapse of the resonances due to the two magnetically inequivalent Cu(II) ions in the lattice caused by the exchange interaction. The obtained g⌈ = 2.254(1) and g⊥ = 2.061(1) principal values of the molecular gyromagnetic tensor point to a d( x2- y2) orbital for the unpaired electron. The orientation of this orbital was also obtained from our EPR data. The angular variation of the resonance line width has contributions arising from the dipolar interaction modulated by exchange effects in a two-dimensional magnetic lattice, and from the incomplete collapse of the hyperfine structure. The EPR results are compared to those obtained in other copper amino acid complexes.

  19. EPR study on non- and gamma-irradiated herbal pills

    Science.gov (United States)

    Aleksieva, K.; Lagunov, O.; Dimov, K.; Yordanov, N. D.

    2011-06-01

    The results of EPR studies on herbal pills of marigold, hawthorn, yarrow, common balm, tutsan, nettle and thyme before and after gamma-irradiation are reported. Before irradiation all samples exhibit one weak singlet EPR line with a g-factor of 2.0048±0.0005. After irradiation herbal pills could be separated in two groups according to their EPR spectra. Radiation-induced free radicals in pills of marigold, yarrow, nettle, tutsan and thyme could be attributed mainly to saccharide excipients. Tablets of hawthorn and common balm show "cellulose-like" EPR spectrum, superimposed on partly resolved carbohydrate spectrum, due to the active part (herb) and inulin, which is present in the pills as an excipient. Fading study of the radiation-induced EPR signals confirms that sugar radicals are more stable than cellulose species. The reported results show that the presence of characteristic EPR spectra of herbal pills due to excipients or active part can be used as unambiguous proof of radiation processing within 35 or more days after irradiation.

  20. EPR study on non- and gamma-irradiated herbal pills

    Energy Technology Data Exchange (ETDEWEB)

    Aleksieva, K., E-mail: katerina_bas@abv.b [Institute of Catalysis, Bulgarian Academy of Sciences, 1113 Sofia (Bulgaria); Lagunov, O. [Institute of Catalysis, Bulgarian Academy of Sciences, 1113 Sofia (Bulgaria); Dimov, K. [Institute of Cryobiology and Food Technologies, 1162 Sofia (Bulgaria); Yordanov, N.D. [Institute of Catalysis, Bulgarian Academy of Sciences, 1113 Sofia (Bulgaria)

    2011-06-15

    The results of EPR studies on herbal pills of marigold, hawthorn, yarrow, common balm, tutsan, nettle and thyme before and after gamma-irradiation are reported. Before irradiation all samples exhibit one weak singlet EPR line with a g-factor of 2.0048{+-}0.0005. After irradiation herbal pills could be separated in two groups according to their EPR spectra. Radiation-induced free radicals in pills of marigold, yarrow, nettle, tutsan and thyme could be attributed mainly to saccharide excipients. Tablets of hawthorn and common balm show 'cellulose-like' EPR spectrum, superimposed on partly resolved carbohydrate spectrum, due to the active part (herb) and inulin, which is present in the pills as an excipient. Fading study of the radiation-induced EPR signals confirms that sugar radicals are more stable than cellulose species. The reported results show that the presence of characteristic EPR spectra of herbal pills due to excipients or active part can be used as unambiguous proof of radiation processing within 35 or more days after irradiation.

  1. EPR structure of the gamma irradiated alanine spectrum

    Energy Technology Data Exchange (ETDEWEB)

    Cabral P, A.; Jimenez D, H.; Urena N, F.; Galindo, S.; Bosch, P

    1992-03-15

    In this study is shown that the broadened five-line EPR pattern of the gamma irradiated alanine possibly decomposes into a more complex pattern when the recorded spectrum is subject to an operation of deconvolution. The EPR powder spectra of gamma irradiated DL- and L-alanine with and without binders are analysed. In all recorded spectra, each observed line is resolved into an asymmetrical triplet when a Gaussian distribution of 8.2 gauss width is removed, by deconvolution, from the observed spectrum. On the other hand, from a simple fitting analysis carried out on the original data, one encounters that some calculated relations between characteristic parameters, such as intensity ratios, deviate consistently from assumed height ratios. Both, from deconvolution and fitting results, a different structure is suggested for the observed broadened five-line EPR pattern of {gamma}-irradiated powder DL- and L-alanine. (Author)

  2. Quantitative EPR A Practitioners Guide

    CERN Document Server

    Eaton, Gareth R; Barr, David P; Weber, Ralph T

    2010-01-01

    This is the first comprehensive yet practical guide for people who perform quantitative EPR measurements. No existing book provides this level of practical guidance to ensure the successful use of EPR. There is a growing need in both industrial and academic research to provide meaningful and accurate quantitative EPR results. This text discusses the various sample, instrument and software related aspects required for EPR quantitation. Specific topics include: choosing a reference standard, resonator considerations (Q, B1, Bm), power saturation characteristics, sample positioning, and finally, putting all the factors together to obtain an accurate spin concentration of a sample.

  3. Magnetic properties of single crystal alpha-benzoin oxime: An EPR study

    Science.gov (United States)

    Sayin, Ulku; Dereli, Ömer; Türkkan, Ercan; Ozmen, Ayhan

    2012-02-01

    The electron paramagnetic resonance (EPR) spectra of gamma irradiated single crystals of alpha-benzoinoxime (ABO) have been examined between 120 and 440 K. Considering the dependence on temperature and the orientation of the spectra of single crystals in the magnetic field, we identified two different radicals formed in irradiated ABO single crystals. To theoretically determine the types of radicals, the most stable structure of ABO was obtained by molecular mechanic and B3LYP/6-31G(d,p) calculations. Four possible radicals were modeled and EPR parameters were calculated for the modeled radicals using the B3LYP method and the TZVP basis set. Calculated values of two modeled radicals were in strong agreement with experimental EPR parameters determined from the spectra. Additional simulated spectra of the modeled radicals, where calculated hyperfine coupling constants were used as starting points for simulations, were well matched with experimental spectra.

  4. The measurement of oxygen in vivo using EPR techniques

    Energy Technology Data Exchange (ETDEWEB)

    Swartz, Harold M. [Dartmouth Medical School, Hanover, NH 03755 (United States); Clarkson, Robert B. [College of Veterinary Medicine, University of Illinois, Urbana, IL 61801 (United States)

    1998-07-01

    The measurement of pO{sub 2} in vivo using EPR has some features which have already led to very useful applications and this approach is likely to have increasingly wide and effective use. It is based on the effect of oxygen on EPR spectra which provides a sensitive and accurate means to measure pO{sub 2} quantitatively. The development of oxygen-sensitive paramagnetic materials which are very stable, combined with instrumental developments, has been crucial to the in vivo applications of this technique. The physical basis and biological applications of in vivo EPR oximetry are reviewed, with particular emphasis on the use of EPR spectroscopy at 1 GHz using particulate paramagnetic materials for the repetitive and non-invasive measurement of pO{sub 2} in tissues. In vivo EPR has already produced some very useful results which have contributed significantly to solving important biological problems. The characteristics of EPR oximetry which appear to be especially useful are often complementary to existing techniques for measuring oxygen in tissues. These characteristics include the capability of making repeated measurements from the same site, high sensitivity to low levels of oxygen, and non-invasive options. The existing techniques are especially useful for studies in small animals, where the depth of measurements is not an overriding issue. In larger animals and potentially in human subjects, non-invasive techniques seem to be immediately applicable to study phenomena very near the surface (within 10 mm) while invasive techniques have some very promising uses. The clinical uses of EPR oximetry which seem especially promising and likely to be undertaken in the near future are long-term monitoring of the status and response to treatment of peripheral vascular disease and optimizing cancer therapy by enabling it to be modified on the basis of the pO{sub 2} measured in the tumour. (author)

  5. On the Correlation between EPR and Positron Annihilation Measurements on gamma-Irradiated Acetyl Methionine

    DEFF Research Database (Denmark)

    Eldrup, Morten Mostgaard; Lund-Thomsen, E.; Mogensen, O. E.

    1972-01-01

    The dose dependence of the relative EPR signal intensity and positron lifetime spectrum was measured for γ‐irradiated acetyl methionine in the dose range from 0 to 30 Mrad. Angular correlation measurements were performed for the doses 0 and 30 Mrad. The result of the irradiation was the creation...... of EPR centers and inhibition of positronium formation. For one sample, irradiated with a dose of 30 Mrad, EPR and positron lifetime spectra were followed over a period of 50 days after the irradiation. The inhibiting effect and the EPR signal intensity decreased with time. No simple correlation could...... be established between the number of EPR centers and the positron annihilation data, but other possible explanations are discussed....

  6. EPR study of Mn-implanted single crystal TiO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Gueler, S; Rameev, B [Department of Physics, Gebze Institute of Technology, 41400 Gebze-Kocaeli (Turkey); Khaibullin, R I; Aktas, B [Lab. of Radiation Physics, Kazan Physical-Technical Institute, 420029 Kazan (Russian Federation); Lopatin, O N, E-mail: sumeyra@gyte.edu.t [Faculty of Geology, Kazan State University, 420008 Kazan (Russian Federation)

    2009-03-01

    Single crystals of manganese-implanted TiO{sub 2} rutile have been investigated by electron paramagnetic resonance (EPR) technique at room temperature. ESR spectra have been interpreted to correspond to the transitions among the spin multiplet (S=3/2) of the paramagnetic Mn{sup 4+} ion. Characteristic six-line hyper-fine splitting of the ESR spectra resulting from the spin I=5/2 of the Mn{sup 55} nucleus has been observed. Analysis of EPR spectra shows that manganese in TiO{sub 2} rutile host substitutes for Ti{sup 4+} ions. Two equivalent Mn{sup 4+} centers have been observed in the EPR spectra in correspondence with two equivalent octahedral positions of Ti ions in the rutile structure. Parameters of the crystal field of orthorhombic symmetry on the Mn{sup 4+} centers have been obtained as result of computer modelling.

  7. EPR study of Mn-implanted single crystal TiO2

    Science.gov (United States)

    Güler, S.; Rameev, B.; Khaibullin, R. I.; Lopatin, O. N.; Aktaş, B.

    2009-03-01

    Single crystals of manganese-implanted TiO2 rutile have been investigated by electron paramagnetic resonance (EPR) technique at room temperature. ESR spectra have been interpreted to correspond to the transitions among the spin multiplet (S=3/2) of the paramagnetic Mn4+ ion. Characteristic six-line hyper-fine splitting of the ESR spectra resulting from the spin I=5/2 of the Mn55 nucleus has been observed. Analysis of EPR spectra shows that manganese in TiO2 rutile host substitutes for Ti4+ ions. Two equivalent Mn4+ centers have been observed in the EPR spectra in correspondence with two equivalent octahedral positions of Ti ions in the rutile structure. Parameters of the crystal field of orthorhombic symmetry on the Mn4+ centers have been obtained as result of computer modelling.

  8. EPR investigation of some desiccated Ascomycota and Basidiomycota gamma-irradiated mushrooms

    Energy Technology Data Exchange (ETDEWEB)

    Bercu, V., E-mail: vbercu@gmail.co [University of Bucharest, Department of Atomic and Nuclear Physics, P.O. Box MG-11, 077125 Magurele (Ilfov) (Romania); Negut, C.D., E-mail: dnegut@nipne.r [University of Bucharest, Department of Atomic and Nuclear Physics, P.O. Box MG-11, 077125 Magurele (Ilfov) (Romania); Horia Hulubei National Institute for Physics and Nuclear Engineering, P.O. Box MG-6, 077125 Magurele (Ilfov) (Romania); Duliu, O.G., E-mail: duliu@b.astral.r [University of Bucharest, Department of Atomic and Nuclear Physics, P.O. Box MG-11, 077125 Magurele (Ilfov) (Romania)

    2010-12-15

    The suitability of the EPR spectroscopy for detection of {gamma}-irradiation in five species of dried mushroom, currently used in gastronomy: yellow morel-Morchella esculenta, (L.) Pers. (Phylum Ascomycota), button mushroom-Agaricus bisporus (J.E.Lange), Agaricus haemorrhoidarius Fr., golden chantarelle-Cantharellus cibarius Fr., as well as oyster mushroom-Pleurotus ostreatus (Jacq. ex Fr.) (Phylum Basidiomycota) is presented and discussed. Although after irradiation at doses up to 11 kGy, all specimens presented well defined EPR spectra, only A. bisporus EPR signal was enough stable to make detection possible after 18 months.

  9. EPR investigation of some desiccated Ascomycota and Basidiomycota gamma-irradiated mushrooms

    Science.gov (United States)

    Bercu, V.; Negut, C. D.; Duliu, O. G.

    2010-12-01

    The suitability of the EPR spectroscopy for detection of γ-irradiation in five species of dried mushroom, currently used in gastronomy: yellow morel— Morchella esculenta, (L.) Pers. (Phylum Ascomycota), button mushroom— Agaricus bisporus (J.E.Lange), Agaricus haemorrhoidarius Fr., golden chantarelle— Cantharellus cibarius Fr., as well as oyster mushroom— Pleurotus ostreatus (Jacq. ex Fr.) (Phylum Basidiomycota) is presented and discussed. Although after irradiation at doses up to 11 kGy, all specimens presented well defined EPR spectra, only A. bisporus EPR signal was enough stable to make detection possible after 18 months.

  10. Single Crystal X- and Q-Band EPR Spectroscopy of a Binuclear Mn2(III,IV) Complex Relevant to the Oxygen-Evolving Complex of Photosystem II

    OpenAIRE

    Yano, Junko; Sauer, Kenneth; Girerd, Jean-Jacques; Yachandra, Vittal K.

    2004-01-01

    The anisotropic g and hyperfine tensors of the Mn di-μ-oxo complex, [Mn2(III,IV)O2(phen)4](PF6)3·CH3CN, were derived by single-crystal EPR measurements at X- and Q-band frequencies. This is the first simulation of EPR parameters from single-crystal EPR spectra for multinuclear Mn complexes, which are of importance in several metalloenzymes; one of them is the oxygen-evolving complex in photosystem II (PS II). Single-crystal [Mn2(III,IV)O2(phen)4](PF6)3·CH3CN EPR spectra showed distinct resolv...

  11. EPR investigation of some traditional oriental irradiated spices

    Energy Technology Data Exchange (ETDEWEB)

    Duliu, Octavian G. [University of Bucharest, Department of Atomic and Nuclear Physics, Magurele, C.P. MG-11, RO-077125 Bucharest (Romania)]. E-mail: duliu@pcnet.ro; Georgescu, Rodica [National Institute for Physics and Nuclear Engineering -Horia Hulubei, C.P. MG-6, RO-077125 Bucharest (Romania); Ali, Shaban Ibrahim [University of Bucharest, Department of Atomic and Nuclear Physics, Magurele, C.P. MG-11, RO-077125 Bucharest (Romania)

    2007-06-15

    The 9.50 GHz electron paramagnetic resonance (EPR) spectra of unirradiated and {sup 60}Co {gamma}-ray irradiated cardamom (Elettaria cardamomum L. Maton, Zingiberaceae), ginger ((Zingiber officinale Rosc., Zingiberaceae), and saffron (Crocus sativus L., Iridaceae) have been investigated at room temperature. All unirradiated spices presented a weak resonance line with g-factors around free-electron ones. After {gamma}-ray irradiation at an absorbed dose of up to 11.3 kGy, the presence of EPR spectra whose amplitude increase monotonously with the absorbed dose has been noticed with all spices. A 100 {sup o}C isothermal annealing of 11.3 kGy irradiated samples has shown a differential reduction of amplitude of various components that compose initial spectra, but even after 3.6 h of thermal treatment, the remaining amplitude represents no less then 30% of the initial ones. The same peculiarities have been noticed after 83 days storage at room temperature but after 340 days storage at ambient conditions only irradiated ginger displays a weak signal that differs from those of unirradiated sample. All these factors could be taken into account in establishing at which extent the EPR is suitable to evidence any irradiation treatment applied to these spices.

  12. EPR analysis and DFT computations of a series of polynitroxides.

    Science.gov (United States)

    Ottaviani, M Francesca; Modelli, Alberto; Zeika, Olaf; Jockusch, Steffen; Moscatelli, Alberto; Turro, Nicholas J

    2012-01-12

    Polynitroxides with varying numbers of nitroxide groups (one to four) derived from different aromatic core structures show intramolecular electron spin-spin coupling. The scope of this study is to establish an easy methodology for extracting structural, dynamical, and thermodynamical information from the EPR spectra of these polynitroxides which might find use as spin probes in complex systems, such as biological and host/guest systems, and as polarizing agents in dynamic nuclear polarization (DNP) applications. Density functional theory (DFT) calculations at the B3LYP/6-31G(d) level provided information on the structural details such as bond lengths and angles in the gas phase, which were compared with the single crystal X-ray diffraction data in the solid state. Polarizable continuum model (PCM) calculations were performed to account for solvent influences. The electron paramagnetic resonance (EPR) spectra of the polynitroxides in chloroform were analyzed in detail to extract information such as the percentages of different conformers, hyperfine coupling constants a, and rotational correlation times τ(c). The temperature dependence on the line shape of the EPR spectra gave thermodynamic parameters ΔH and ΔS for the conformational transitions. These parameters were found to depend on the number and relative positions of the nitroxide and other polar groups.

  13. EPR investigation of some traditional oriental irradiated spices

    Science.gov (United States)

    Duliu, Octavian G.; Georgescu, Rodica; Ali, Shaban Ibrahim

    2007-06-01

    The 9.50 GHz electron paramagnetic resonance (EPR) spectra of unirradiated and 60Co γ-ray irradiated cardamom ( Elettaria cardamomum L. Maton, Zingiberaceae), ginger (( Zingiber officinale Rosc., Zingiberaceae), and saffron ( Crocus sativus L., Iridaceae) have been investigated at room temperature. All unirradiated spices presented a weak resonance line with g-factors around free-electron ones. After γ-ray irradiation at an absorbed dose of up to 11.3 kGy, the presence of EPR spectra whose amplitude increase monotonously with the absorbed dose has been noticed with all spices. A 100 °C isothermal annealing of 11.3 kGy irradiated samples has shown a differential reduction of amplitude of various components that compose initial spectra, but even after 3.6 h of thermal treatment, the remaining amplitude represents no less then 30% of the initial ones. The same peculiarities have been noticed after 83 days storage at room temperature but after 340 days storage at ambient conditions only irradiated ginger displays a weak signal that differs from those of unirradiated sample. All these factors could be taken into account in establishing at which extent the EPR is suitable to evidence any irradiation treatment applied to these spices.

  14. EPR and optical absorption characteristics of sodic plagioclase from granite pegmatite in Kadavur, India

    Science.gov (United States)

    Anand, S. Vijay; Pandian, M. S.; Mithira, S.; Ravikumar, R. V. S. S. N.; Sambasiva Rao, P.

    The electron paramagnetic resonance (EPR) spectra of sodic plagioclase from dykes of granitic pegmatite occurring in the Kadavur area, Tamil Nadu, India, were examined at room temperature to identify paramagnetic impurities in a "low plagioclase" using EPR and optical techniques. The EPR spectra showed the presence of Fe(III) and Mn(II) impurities. After heating the plagioclase samples for various durations at 600 °C, it has been observed that the concentration of Mn(II) remained as such in one sample but completely disappeared in another sample, while there was no change in Fe(III) ion concentration after the heat treatment in either sample. Optical absorption spectra also showed Fe(II) and Fe(III) in addition to Ti(III) impurities in sodic plagioclase before heating, while after heating the relative concentration of Fe(II) and Fe(III) changed, accompanied by the disappearance of Ti(III).

  15. EPR and ENDOR spectroscopic study of the reactions of aromatic azides with gallium trichloride.

    Science.gov (United States)

    Bencivenni, Giorgio; Cesari, Riccardo; Nanni, Daniele; El Mkami, Hassane; Walton, John C

    2010-11-21

    The reactions of gallium trichloride with phenyl and deuterio-phenyl azides, as well as with 4-methoxyphenyl azide and deuterium isotopomers, were examined by product analysis, CW EPR spectroscopy and pulsed ENDOR spectroscopy. The products included the corresponding anilines together with 4-aminodiphenylamine type dimers, and polyanilines. Complex CW EPR spectra of the radical cations of the dimers [ArNHC(6)H(4)NH(2)](+)˙ and trimers [ArNHC(6)H(4)NHC(6)H(4)NH(2)](+)˙ were obtained. These EPR spectra were analysed with the help of data from the deuterium-substituted analogues as well as the pulse Davies ENDOR spectra. DFT computations of the radical cations provided corroborating evidence and suggested the unpaired electrons were accommodated in extensive π-delocalised orbitals. A mechanism to account for the reductive conversion of aromatic azides to the corresponding anilines and thence to the dimers and trimers is proposed.

  16. Crystallite arrangement of hydroxyapatite microcrystals in human tooth cementum as revealed by electron paramagnetic resonance (EPR)

    Energy Technology Data Exchange (ETDEWEB)

    Skaleric, U.; Gaspirc, B. [Univ. of Ljubljana, Jozef Stefan Inst., Center for Dental Research, Ljubljana (Slovenia); Cevc, P.; Schara, M. [Univ. of Ljubljana, Jozef Stefan Inst., EPR Center Ljubljana, Ljubljana (Slovenia)

    1998-08-01

    Human dental cementum was analyzed by electron paramagnetic resonance (EPR). The measured EPR powder spectra of {gamma}-irradiated cementum resembled those of {gamma}irradiated enamel. Both spectra were characterized by the same line shapes and g values. The position of the extreme first derivate peaks can be described by g{sub 1}=2.0023 and g{sub 2}=1.9971{+-}0.0002, and are assignable to the CO{sub 3}{sup 3-} center. The angular dependence of the cementum EPR spectra indicates a different arrangement of the hydroxyapatite microcrystals compared to that of enamel. A corresponding model of cementum micro-crystal alignment has been proposed. The methodology presented can be utilized for studying the mineralization process of root cementum and other mineralized tissues. (au) 14 refs.

  17. EPR study of deoxygenated high-temperature superconductors

    Indian Academy of Sciences (India)

    Abstract. High-Tc superconductors are EPR silent but on a little deoxygenation of the high-Tc materials and their constituents, they yield rich but complex spectra. Spectra of (1) CuO, (2) BaCuO2,. (3) CaCuO2, (4) Y2Cu2O5, (5) La2CuO4, (6) La2−x Mx CuO4 (M = Sr, Ba), (7) Y based-123, (8) Bi based-2201, 2212, 2223, ...

  18. EPR: the nuclear impasse; EPR: l'impasse nucleaire

    Energy Technology Data Exchange (ETDEWEB)

    Marillier, F. [Association Ecologiste Greenpeace (France)

    2008-07-01

    The questions relative to the climatic change constitute crucial challenges for the next ten years. In this context the author aims to show how the EPR project illustrates the nuclear french ''autism''. He presents and analyzes the international and environmental impacts of this obsolete technology, as a project useless and dangerous. (A.L.B.)

  19. EPR spectral investigation of radiation-induced radicals of gallic acid

    Energy Technology Data Exchange (ETDEWEB)

    Tuner, Hasan [Balikesir University, Department of Physics, Faculty of Art and Science, Balikesir (Turkey)

    2017-11-15

    In the present work, spectroscopic features of the radiation-induced radicals of gallic acid compounds were investigated using electron paramagnetic resonance (EPR) spectroscopy. While un-irradiated samples presented no EPR signal, irradiated samples exhibited an EPR spectrum consisting of an intense resonance line at the center and weak lines on both sides. Detailed microwave saturation investigations were carried out to determine the origin of the experimental EPR lines. It is concluded that the two side lines of the triplet satellite originate from forbidden ''spin-flip'' transitions. The spectroscopic and structural features of the radiation-induced radicals were determined using EPR spectrum fittings. The experimental EPR spectra of the two gallic acid compounds were consistent with the calculated EPR spectroscopic features of the proposed radicals. It is concluded that the most probable radicals are the cyclohexadienyl-type, O(OH){sub 2}C{sub 6}H{sub 2}COOH radicals for both compounds. (orig.)

  20. EPR study of VO/sup 2 +/ in some paramagnetic Tutton salt single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Upreti, G.C. (Indian Inst. of Tech., Kanpur. Dept. of Physics); Saraswat, R.S. (Indian Inst. of Tech., Kharagpur. Dept. of Physics)

    1984-04-01

    The EPR spectra of VO/sup 2 +/ in single crystals of some paramagnetic salts Me(II)(NH/sub 4/)/sub 2/(SO/sub 4/)/sub 2/x6H/sub 2/O (Me = Co, Fe, or Ni) and NiK/sub 2/(SO/sub 4/)/sub 2/x6H/sub 2/O have been recorded and analyzed. The vanadyl ions doped in Co and Fe double salt crystals showed sharp and well resolved EPR spectra consisting in two sets of eight-line hyperfine patterns. The spin-Hamiltonian parameters and the molecular orbital coefficients are given and the bonding in vanadyl complexes is discussed.

  1. Application of jade samples for high-dose dosimetry using the EPR technique

    Energy Technology Data Exchange (ETDEWEB)

    Teixeira, Maria Ines [Instituto de Pesquisas Energeticas e Nucleares/Comissao Nacional de Energia Nuclear Av. Prof. Lineu Prestes 2242, 05508-000, Sao Paulo (Brazil)], E-mail: miteixei@ipen.br; Melo, Adeilson P. [Instituto de Pesquisas Energeticas e Nucleares/Comissao Nacional de Energia Nuclear Av. Prof. Lineu Prestes 2242, 05508-000, Sao Paulo (Brazil); Centro Federal de Educacao Tecnologica de Sergipe, Aracaju (Brazil)], E-mail: adeilson_pessoa_melo@yahoo.com.br; Ferraz, Gilberto M. [Depto. de Fisica Nuclear, Instituto de Fisica, Universidade de Sao Paulo, Sao Paulo (Brazil)], E-mail: gmarconf@if.usp.br; Caldas, Linda V.E. [Instituto de Pesquisas Energeticas e Nucleares/Comissao Nacional de Energia Nuclear Av. Prof. Lineu Prestes 2242, 05508-000, Sao Paulo (Brazil)], E-mail: lcaldas@ipen.br

    2010-04-15

    The dosimeter characteristics of jade samples were studied for application in high-dose dosimetry. Jade is the common denomination of two silicates: jadeite and actinolite. The EPR spectra of different jade samples were obtained after irradiation with absorbed doses of 100 Gy up to 20 kGy. The jade samples present signals that increase with the absorbed dose (g-factors around 2.00); they can be attributed to electron centers. The EPR spectra obtained for the USA jade samples and their main dosimetric properties as reproducibility, calibration curves and energy dependence were investigated.

  2. EPR investigations of silicon carbide nanoparticles functionalized by acid doped polyaniline

    Science.gov (United States)

    Karray, Fekri; Kassiba, Abdelhadi

    2012-06-01

    Nanocomposites (SiC-PANI) based on silicon carbide nanoparticles (SiC) encapsulated in conducting polyaniline (PANI) are synthesized by direct polymerization of PANI on the nanoparticle surfaces. The conductivity of PANI and the nanocomposites was modulated by several doping levels of camphor sulfonic acid (CSA). Electron paramagnetic resonance (EPR) investigations were carried out on representative SiC-PANI samples over the temperature range [100-300 K]. The features of the EPR spectra were analyzed taking into account the paramagnetic species such as polarons with spin S=1/2 involved in two main environments realized in the composites as well as their thermal activation. A critical temperature range 200-225 K was revealed through crossover changes in the thermal behavior of the EPR spectral parameters. Insights on the electronic transport properties and their thermal evolutions were inferred from polarons species probed by EPR and the electrical conductivity in doped nanocomposites.

  3. Identification of slow relaxing spin components by pulse EPR techniques in graphene-related materials

    Directory of Open Access Journals (Sweden)

    Antonio Barbon

    2017-01-01

    Full Text Available Electron Paramagnetic Resonance (EPR is a powerful technique that is suitable to study graphene-related materials. The challenging ability requested to the spectroscopy is its capability to resolve the variety of structures, relatively similar, that are obtained in materials produced through different methods, but that also coexist inside a single sample. In general, because of the intrinsic inhomogeneity of the samples, the EPR spectra are therefore a superposition of spectra coming from different structures. We show that by pulse EPR techniques (echo-detected EPR, ESEEM and Mims ENDOR we can identify and characterize species with slow spin relaxing properties. These species are generally called molecular states, and are likely small pieces of graphenic structures of limited dimensions, thus conveniently described by a molecular approach. We have studied commercial reduced graphene oxide and chemically exfoliated graphite, which are characterized by different EPR spectra. Hyperfine spectroscopies enabled us to characterize the molecular components of the different materials, especially in terms of the interaction of the unpaired electrons with protons (number of protons and hyperfine coupling constants. We also obtained useful precious information about extent of delocalization of the molecular states.

  4. EPR and optical absorption studies on manganese ion doped in mixed alkali cadmium phosphate glasses

    Science.gov (United States)

    Giridhar, G.; Rangacharyulu, M.; Ravikumar, R. V. S. S. N.; Sambasiva Rao, P.

    2009-07-01

    Electron paramagnetic resonance (EPR) spectra of Mn(II) ions in cadmium phosphate glasses are presented with mixed alkali variation as xLi2O + (20 - x) Na2O + 20 CdO + 59.5 P2O5 + 0.5 MnO glass system with 5 EPR spectra of Mn(II) ions doped samples exhibit a sextet centered at g = 2·0. The optical absorption spectrum at room temperature shows three bands for Mn(II) ions in octahedral symmetry. The crystal field (Dq) and Racah parameters (B and C) are evaluated. From EPR and optical spectral studies reveals the nature of the bonding is dominantly ionic and its site symmetry is octahedral. At equal composition of alkali content, i.e. for x = 10 the glass system shows the mixed alkali effect.

  5. Pulsed EPR Spin-probe study of intracellular glasses in seed and pollen

    NARCIS (Netherlands)

    Buitink, J.; Dzuba, S.A.; Hoekstra, F.A.; Tsvetkov, Y.D.

    2000-01-01

    EPR spectra of 3-carboxy-proxyl (CP) in dry biological tissues exhibited a temperature-dependent change in the principal value A′zz of the hyperfine interaction tensor. The A′zz value changed sharply at a particular temperature that was dependent on water content. At elevated water contents, the

  6. The analogy in the formation of hardness salts and gallstones according to the EPR study

    Science.gov (United States)

    Pichugina, Alina; Tsyro, Larisa; Unger, Felix

    2017-11-01

    The article shows that the hardness salts contain the same crystalline phases as the bile stone pigment. The identity of EPR spectra of hardness salts and pigment of gallstones containing calcium carbonate was established. An analogy between the processes of formation of hardness salts and gallstones is played, in which particles with open spin-orbitals (fermions) play a decisive role.

  7. Single crystal EPR study of VO (II)-doped cadmium potassium ...

    Indian Academy of Sciences (India)

    Single crystal EPR studies of VO(II)-doped cadmium potassium phosphate hexahydrate (CPPH) have been carried out at room temperature. The angular variation spectra in the three orthogonal planes indicate that the paramagnetic impurity has entered the lattice only substitutionally in place of Cd(II). Spin Hamiltonian ...

  8. EPR and UV spectral study of gamma-irradiated white and burned sugar, fructose and glucose

    Science.gov (United States)

    Yordanov, Nicola D.; Georgieva, Elka

    2004-05-01

    The EPR and UV spectral properties of γ-irradiated white and burned sugar, fructose and glucose are studied with the accent on their suitability as dosimetric materials. It is shown that γ-irradiation of solid samples of white sugar and fructose yields stable EPR spectra whereas glucose signal remains time-dependent even 11 months later. Sugar and glucose exhibit linear EPR dose response in the region 0.44-21 kGy and fructose only up to ca. 10 kGy. The relative radiation sensitivity obtained for sugar and fructose is up to 10 kGy and slightly lower for glucose. Burned saccharides provide 2-3 orders of magnitude lower EPR radiation sensitivity making them not suitable for the proposed designation. According to the UV spectra water solutions of γ-irradiated solid white saccharides show well pronounced absorption bands at 267 and 286 nm for sugar and fructose with time-dependent intensities reaching steady values ca. 11 days after dissolution. The intensities of these absorption bands are in linear relation with the absorbed dose of γ-radiation. Glucose shows low sensitively because irradiation with 5.5 kGy yields only a shoulder at about 260-280 nm with decreasing to ca. 40% intensity in the first few days after dissolution. Excellent correlation between the intensities of the EPR- and UV-absorbed dose response is found for sugar and fructose in the region 0.44-10 kGy. This opens new possibilities for independent calibration the EPR dose response. Finally, the comparison suggests sugar as the best, universal material for EPR- and/or UV-dosimetry in the region 0.44-160 kGy.

  9. Preparation and applicability of fresh fruit samples for the identification of radiation treatment by EPR

    Energy Technology Data Exchange (ETDEWEB)

    Yordanov, Nicola D. [Laboratory EPR, Institute of Catalysis, Bulgarian Academy of Sciences, 1113 Sofia (Bulgaria)], E-mail: ndyepr@bas.bg; Aleksieva, Katerina [Laboratory EPR, Institute of Catalysis, Bulgarian Academy of Sciences, 1113 Sofia (Bulgaria)

    2009-03-15

    The results of electron paramagnetic resonance (EPR) study on fresh fruits (whole pulp of pears, apples, peaches, apricots, avocado, kiwi and mango) before and after gamma-irradiation are reported using two drying procedures before EPR investigation. In order to remove water from non-irradiated and irradiated samples of the first batch, the pulp of fresh fruits is pressed, and the solid residue is washed with alcohol and dried at room temperature. The fruits of the second batch are pressed and dried in a standard laboratory oven at 40 deg. C. The results obtained with both drying procedures are compared. All samples under study show a singlet EPR line with g=2.0048{+-}0.0005 before irradiation. Irradiation gives rise to typical 'cellulose-like' EPR spectrum featuring one intensive line with g=2.0048{+-}0.0005 and two very weak satellite lines situated 3 mT at left and right of the central line. Only mango samples show a singlet line after irradiation. The fading kinetics of radiation-induced EPR signal is studied for a period of 50 days after irradiation. When the irradiated fruit samples are stored in their natural state and dried just before each EPR measurement, the satellite lines are measurable for less than 17 days of storage. Irradiated fruit samples, when stored dried, lose for 50 days ca. 40% of their radiation-induced radicals if treated with alcohol or ca. 70% if dried in an oven. The reported results unambiguously show that the presence of the satellite lines in the EPR spectra could be used for identification of radiation processing of fresh fruits, thus extending the validity of European Protocol EN 1787 (2000). Foodstuffs-Detection of Irradiated Food Containing Cellulose by EPR Spectroscopy. European Committee for Standardisation. Brussels for dry herbs.

  10. Combining EPR spectroscopy and X-ray crystallography to elucidate the structure and dynamics of conformationally constrained spin labels in T4 lysozyme single crystals.

    Science.gov (United States)

    Consentius, Philipp; Gohlke, Ulrich; Loll, Bernhard; Alings, Claudia; Heinemann, Udo; Wahl, Markus C; Risse, Thomas

    2017-08-09

    Electron paramagnetic resonance (EPR) spectroscopy in combination with site-directed spin labeling is used to investigate the structure and dynamics of conformationally constrained spin labels in T4 lysozyme single crystals. Within a single crystal, the oriented ensemble of spin bearing moieties results in a strong angle dependence of the EPR spectra. A quantitative description of the EPR spectra requires the determination of the unit cell orientation with respect to the sample tube and the orientation of the spin bearing moieties within the crystal lattice. Angle dependent EPR spectra were analyzed by line shape simulations using the stochastic Liouville equation approach developed by Freed and co-workers and an effective Hamiltonian approach. The gain in spectral information obtained from the EPR spectra of single crystalline samples taken at different frequencies, namely the X-band and Q-band, allows us to discriminate between motional models describing the spectra of isotropic solutions similarly well. In addition, it is shown that the angle dependent single crystal spectra allow us to identify two spin label rotamers with very similar side chain dynamics. These results demonstrate the utility of single crystal EPR spectroscopy in combination with spectral line shape simulation techniques to extract valuable dynamic information not readily available from the analysis of isotropic systems. In addition, it will be shown that the loss of electron density in high resolution diffraction experiments at room temperature does not allow us to conclude that there is significant structural disorder in the system.

  11. EPR determination of the mechanism of the oxidation of alkenyl aminophosphites

    Energy Technology Data Exchange (ETDEWEB)

    Il' yasov, A.V.; Kibardin, A.M.; Morozov, V.I.; Gryaznov, P.I.; Vafina, A.A.; Pudovik, A.N.

    1987-10-20

    Aminophosphites that contain a vinyl group on the nitrogen atom are oxidized easily by atmospheric oxygen. Since it is important to clarify the nature of this reaction in order to understand the reactivity of organic phosphites, the authors have made an EPR study of the reaction of these phosphites with oxygen. Unstable intermediate paramagnetic reaction products were trapped in the presence of 2-methyl-nitrosopropane, ..cap alpha..-phenyl-N-tert-butylnitrone, and chloroaniline, compounds that served as spin traps. The hyperfine structure of the EPR spectra can be attributed to the interaction of an unpaired electron with nuclei of hydrogen, nitrogen, and phosphorus atoms.

  12. Overview of LBB implementation for the EPR

    Energy Technology Data Exchange (ETDEWEB)

    Cauquelin, C.

    1997-04-01

    This paper presents an overview of the use of leak-before-break (LBB) analysis for EPR reactors. EPR is an evolutionary Nuclear Island of the 4 loop x 1500 Mwe class currently in the design phase. Application of LBB to the main coolant lines and resulting design impacts are summarized. Background information on LBB analysis in France and Germany is also presented.

  13. VO2+ ions in zinc lead borate glasses studied by EPR and optical absorption techniques.

    Science.gov (United States)

    Prakash, P Giri; Rao, J Lakshmana

    2005-09-01

    Electron paramagnetic resonance (EPR) and optical absorption spectra of vanadyl ions in zinc lead borate (ZnO-PbO-B2O3) glass system have been studied. EPR spectra of all the glass samples exhibit resonance signals characteristic of VO2+ ions. The values of spin-Hamiltonian parameters indicate that the VO2+ ions in zinc lead borate glasses were present in octahedral sites with tetragonal compression and belong to C4V symmetry. The spin-Hamiltonian parameters g and A are found to be independent of V2O5 content and temperature but changing with ZnO content. The decrease in Deltag( parallel)/Deltag( perpendicular) value with increase in ZnO content indicates that the symmetry around VO2+ ions is more octahedral. The decrease in intensity of EPR signal above 10 mol% of V2O5 is attributed to a fall in the ratio of the number of V4+ ions (N4) to the number of V5+ ions (N5). The number of spins (N) participating in resonance was calculated as a function of temperature for VO2+ doped zinc lead borate glass sample and the activation energy was calculated. From the EPR data, the paramagnetic susceptibility was calculated at various temperatures and the Curie constant was evaluated from the 1/chi-T graph. The optical absorption spectra show single absorption band due to VO2+ ions in tetragonally distorted octahedral sites.

  14. EPR Dosimetry - Present and Future

    Energy Technology Data Exchange (ETDEWEB)

    Regulla, D.F. [GSF - National Research Centre for Environment and Health, Institute of Radiation Protection, 85764 Neuherberg (Germany)

    1999-07-01

    In the past, IAEA has played a central role in stipulating research and development in EPR high-dose standardisation as well as in coordinating and organising international dose intercomparison programs, within the Member States of the United Nations from the mid-seventies till today. The future tasks of EPR dosimetry seem to tend towards different subjects such as bio markers, biological radiation effects, post-accident dose reconstruction in the environment, and retrospective human dosimetry. The latter may be considered a promising tool for epidemiology on the way to re-define radiation risk of man for chronicle radiation exposures, based on e.g. South Ural civil population and radiation workers. There are on-going international activities in the field of standardising high-level dosimetry by the American Standards on Testing and Materials (Astm), and by the International Organisation of Standards (ISO). The International Commission on Radiation Units and Measurements (ICRU) is considering the establishment of relevant recommendations concerning industrial radiation processing, but also human dose reconstruction. (Author)

  15. Examination by EPR spectroscopy of free radicals in melanins isolated from A-375 cells exposed on valproic acid and cisplatin.

    Science.gov (United States)

    Chodurek, Ewa; Zdybel, Magdalena; Pilawa, Barbara; Dzierzewicz, Zofia

    2012-01-01

    Drug binding by melanin biopolymers influence the effectiveness of the chemotherapy, radiotherapy and photodynamic therapy. Free radicals of melanins take part in formation of their complex with drugs. The aim of this work was to determine the effect of the two compounds: valproic acid (VPA) and cisplatin (CPT) on free radicals properties of melanin isolated from A-375 melanoma cells. Free radicals were examined by an X-band (9.3 GHz) electron paramagnetic resonance (EPR) spectroscopy. EPR spectra were measured for the model synthetic eumelanin - DOPA-melanin, the melanin isolated from the control A-375 cells and these cells treated by VPA, CPT and both VPA and CPT. For all the examined samples broad EPR lines (deltaBpp: 0.48-0.68 mT) with g-factors of 2.0045-2.0060 characteristic for o-semiquinone free radicals were observed. Free radicals concentrations (N) in the tested samples, g-factors, amplitudes (A), integral intensities (I) and linewidths (deltaBpp) of the EPR spectra, were analyzed. The EPR lines were homogeneously broadened. Continuous microwave saturation of the EPR spectra indicated that slow spin-lattice relaxation processes existed in all the tested melanin samples. The relatively slowest spin-lattice relaxation processes characterized melanin isolated from A-375 cells treated with both VPA and CPT. The changes of the EPR spectra with increasing microwave power in the range of 2.2-70 mW were evaluated. Free radicals concentrations in the melanin from A-375 cells were higher than in the synthetic DOPA-melanin. The strong increase of free radicals concentration in the melanin from A-375 cells was observed after their treating by VPA. CPT also caused the increase of free radicals concentrations in the examined natural melanin. The free radicals concentration in melanin isolated from A-375 cells treated with both VPA and CPT was slightly higher than those in melanin from the control cells.

  16. Identification of irradiated oysters by EPR measurements on shells

    Energy Technology Data Exchange (ETDEWEB)

    Della Monaca, S., E-mail: sara.dellamonaca@iss.it [Istituto Superiore di Sanita, viale Regina Elena, 299 Rome (Italy); Fattibene, P.; Boniglia, C.; Gargiulo, R.; Bortolin, E. [Istituto Superiore di Sanita, viale Regina Elena, 299 Rome (Italy)

    2011-09-15

    In this paper the EPR spectra of the radicals induced in oyster shells after irradiation to (0.5-2) kGy ionizing radiation doses are analyzed. EPR spectra of irradiated shells showed the complex radical composition of biocarbonates, characterized by the presence of SO{sub 2}{sup -}, SO{sub 3}{sup -} and CO{sub 2}{sup -} radicals with different symmetries. In particular, the radiation-induced line at g = 2.0038, due to the g{sub x} component of the orthorhombic SO{sub 3}{sup -}, was well distinguishable from the rest of the spectrum. The g{sub x} component of the orthorhombic SO{sub 3}{sup -} was found to be intense and stable enough to allow the identification at least for the whole shelf life of the oyster. Furthermore, it is still well visible at low microwave powers for which the other signals are weak or non-visible and has a linear dose response in the (0.5-2) kGy range. A possible procedure protocol for the identification of irradiated oysters, can be based on acquisitions of the spectrum at low microwave power values (tenths of milliWatt) and low modulation amplitude values (0.03-0.05 mT) and on the identification of the g = 2.0038 signal as a proof of the ionizing radiation treatment performed on the sample.

  17. EPR, UV-Visible, and Near-Infrared Spectroscopic Characterization of Dolomite

    Directory of Open Access Journals (Sweden)

    S. Lakshmi Reddy

    2008-01-01

    Full Text Available Dolomite mineral samples having white and light green colors of Indian origin have been characterized by EPR, optical, and NIR spectroscopy. The optical spectrum exhibits a number of electronic bands due to presence of Fe(III ions in the mineral. From EPR studies, the parameters of g for Fe(III and g,A, and D for Mn(II are evaluated and the data confirm that the ions are in distorted octahedron. Optical absorption studies reveal that Fe(III is in distorted octahedron. The bands in NIR spectra are due to the overtones and combinations of water molecules. Thus EPR and optical absorption spectral studies have proven useful for the study of the solid state chemistry of dolomite.

  18. Harmonization of dosimetric information obtained by different EPR methods: Experience of the Techa river study

    Energy Technology Data Exchange (ETDEWEB)

    Volchkova, A. [Urals Research Center for Radiation Medicine, 68A, Vorovsky Str., 454076 Chelyabinsk (Russian Federation); Shishkina, E.A., E-mail: ElenaA.Shishkina@gmail.com [Urals Research Center for Radiation Medicine, 68A, Vorovsky Str., 454076 Chelyabinsk (Russian Federation); Ivanov, D. [Institute of Metal Physics, Russian Academy of Sciences, 18, S. Kovalevskoy Str., 620041 Yekaterinburg (Russian Federation); Timofeev, Yu. [Urals Research Center for Radiation Medicine, 68A, Vorovsky Str., 454076 Chelyabinsk (Russian Federation); Fattibene, P.; Della Monaca, S. [Istituto Superiore di Sanita and Istituto Nazionale di Fisica Nucleare, Viale Regina Elena 299, 00161 Rome (Italy); Wieser, A. [Helmholtz Zentrum Muenchen, German Research Centre for Environmental Health, D-85764 Neuherberg (Germany); Degteva, M.O. [Urals Research Center for Radiation Medicine, 68A, Vorovsky Str., 454076 Chelyabinsk (Russian Federation)

    2011-09-15

    Between 1949 and 1956 the Techa River (Southern Urals, Russia) was contaminated as a result of releases of radioactive waste by the Mayak Production Association. EPR dosimetry with tooth enamel has been used to estimate the external exposure of Techa riverside residents over the last 17 years. The database 'Tooth' of the Urals Research Center for Radiation Medicine (URCRM) has accumulated about 1000 EPR measurements of tooth enamel from the rural population of the Urals region. The teeth were investigated by laboratories of Russia, USA, Germany and Italy. Most of the enamel samples were measured several times in different laboratories. Each laboratory used different equipment and its own methods for sample preparation and EPR spectra analysis. Even measurements performed at the same laboratory over 10-15 years may not be assumed as uniform: methods change with time, and equipment is subject to aging. These two factors influenced EPR performance. The purpose of this study is, therefore, the harmonization of EPR data accumulated during long-term dosimetric investigations in the Southern Urals for further pooled analysis. The results will be used for external dose evaluation in the Techa River region.

  19. Study of dental enamel and synthetic hydroxyapatite irradiated by EPR at K-band

    Energy Technology Data Exchange (ETDEWEB)

    Santos, A.B. [Departamento Fisica e Matematica, FFCLRP, Universidade de Sao Paulo, 14040-901 Ribeirao Preto, SP (Brazil); Universidade Federal do Tocantins, 77020-120 Palmas, Tocantins (Brazil)]. E-mail: adevailton@uft.edu.br; Rossi, A.M. [Centro Brasileiro de Pesquisas Fisicas, 22290 180 Rio de Janeiro, RJ (Brazil); Baffa, O. [Departamento Fisica e Matematica, FFCLRP, Universidade de Sao Paulo, 14040-901 Ribeirao Preto, SP (Brazil)

    2005-02-01

    In this preliminary work the EPR spectra of a small dental enamel block and a synthetic B-type hydroxyapatite in powder form, both irradiated with gamma rays, were analyzed in K-band. The spectra of the dental enamel block allow the analysis of independent components with different angular orientations, while the study of the dosimetric properties of the synthetic hydroxyapatites showed good performance of this spectrometer. K-band spectra show better resolution when compared to X-band, while using significantly less sample material.

  20. Study of dental enamel and synthetic hydroxyapatite irradiated by EPR at K-band.

    Science.gov (United States)

    Santos, A B; Rossi, A M; Baffa, O

    2005-02-01

    In this preliminary work the EPR spectra of a small dental enamel block and a synthetic B-type hydroxyapatite in powder form, both irradiated with gamma rays, were analyzed in K-band. The spectra of the dental enamel block allow the analysis of independent components with different angular orientations, while the study of the dosimetric properties of the synthetic hydroxyapatites showed good performance of this spectrometer. K-band spectra show better resolution when compared to X-band, while using significantly less sample material.

  1. Detection of free radicals formed by in vitro metabolism of fluoride using EPR spectroscopy.

    Science.gov (United States)

    Pawłowska-Góral, Katarzyna; Pilawa, Barbara

    2011-10-01

    In many parts of the globe, where water contains large amount of fluoride, fluorosis is a serious public health problem. It is accompanied by many changes, not only in the bones, but practically in all organs of the body. Since it was discovered that oxidation stress, together with the peroxidation of lipids which accompanies it, results in many diseases, research has been carried out on this aspect of fluorosis. The findings, however, are incomplete and divergent. The aim of our study was to determine the presence of free radicals in hepatocytes exposed to fluoride in concentrations which do not lead to changes in the concentrations of calcium and magnesium ions. Free radical properties of hepatocytes incubated with fluoride were studied by an X-band electron paramagnetic resonance (EPR) spectroscopy. Hepatocytes are paramagnetic and broad unsymmetrical EPR spectra were obtained for them. Oxygen free radicals with g-factor of 2.0032 exist in hepatocytes. The effect of fluoride concentration and the time of incubation on free radicals amount in cells were examined. The amount of free radicals in hepatocytes increases with the increase of fluoride concentration for all the incubation times (10, 30, and 60 min). The amount of free radicals in hepatocytes decreases with the increase of time of incubation for all the used fluoride concentrations (0.002, 0.082, and 0.164 mmol/l). EPR spectra of the studied cells are homogeneously broadened. Continuous microwave saturation of EPR lines indicates that slow spin-lattice relaxation processes exist in the studied cells. Strong dipolar interactions responsible for the broadening (ΔB(pp): 1.45-1.87 mT) of the EPR spectra exist in the hepatocytes. Copyright © 2011 Elsevier Ltd. All rights reserved.

  2. EPR and photoluminescence study of irradiated anion-defective alumina single crystals

    Science.gov (United States)

    Kortov, V. S.; Ananchenko, D. V.; Konev, S. F.; Pustovarov, V. A.

    2017-09-01

    Electron paramagnetic resonance (EPR) and photoluminescence (PL) spectra of anion-defective alumina single crystals were measured. Exposure to a dose 10 Gy-1 kGy causes isotropic EPR signal of a complex form, this signal contains narrow and broad components. At the same time, in the PL spectrum alongside with a band of F+-centers (3.8 eV) an additional emission band with the maximum of 2.25 eV is registered. This band corresponds to aggregate F22+-centers which were create under irradiation. By comparing measurements in EPR and PL spectra with further stepped annealing in the temperature range of 773-1473 K of the samples exposed to the same doses, we were able to conclude that a narrow component of isotropic EPR signal is associated with the formation of paramagnetic F22+-centers under irradiation. A wide component can be caused by deep hole traps which are created by a complex defect (VAl2- - F+) with a localized hole.

  3. EPR Spectroscopy of Different Sol Concentration Synthesized Nanocrystalline-ZnO Thin Films

    Directory of Open Access Journals (Sweden)

    Manju Arora

    2015-01-01

    Full Text Available Nanocrystalline zinc oxide (nc-ZnO thin films were grown on p-type silicon substrate through spin coating by sol-gel process using different sol concentrations (10 wt.%, 15 wt.%, and 25 wt.%. These films were characterized by high resolution nondestructive X-ray diffraction (XRD, scanning electron microscopy (SEM with energy dispersive X-ray analysis (EDS attachment, and electron paramagnetic resonance (EPR techniques to understand variations in structural, morphological, and oxygen vacancy with respect to sol concentration. The film surface morphology changes from nanowall to nanorods on increasing sol concentration. EPR spectra revealed the systematic variation from ferromagnetic to paramagnetic nature in these nc-ZnO films. The broad EPR resonance signal arising from the strong dipolar-dipolar interactions among impurity defects present in nc-ZnO film deposited from 10 wt.% sol has been observed and a single strong narrow resonance signal pertaining to oxygen vacancies is obtained in 25 wt.% sol derived nc-ZnO film. The concentrations of impurity defects and oxygen vacancies are evaluated from EPR spectra, necessary for efficient optoelectronic devices development.

  4. A method to enhance the resolution of broadened spectra

    Energy Technology Data Exchange (ETDEWEB)

    Cabral P, A.; Jimenez D, H.; Torres V, M.; Azorin N, J.; Gutierrez C, A.; Gonzalez M, P.R.; Lopez E, J. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico); Fuentes Z, G.A.; Cordoba, A. [UAM-I, 09340 Mexico D.F. (Mexico)

    1992-02-15

    A deconvolution method to analyze line overlapping broadened spectra is presented. Two approximation expressions from which the user can remove, either a Lorentzian or a Gaussian line from observed spectra are utilized. Moessbauer spectra, EPR and Thermoluminescence spectroscopies are analyzed. It is shown that in each case, the de convolved spectrum may provide valuable data to get a much closer characterization of a substance. (Author)

  5. DOLOČITEV KINETIKE SINTEZE ACETILSALICILNE KISLINE

    OpenAIRE

    Dragojlović, Vesna

    2011-01-01

    Aspirin, znan tudi kot acetilsalicilna kislina (CH3COOC6H4COOH), je salicilna droga, ki se pogosto uporablja kot učinkovito sredstvo za lajšanje manjših bolečin, antipiretik za zmanjšanje vročine in protivnetno zdravilo. Namen diplomskega dela je bila sinteza aspirina in določitev reda reakcije. Potek reakcije smo zasledovali z opazovanjem spreminjanja specifične prevodnosti šibkega elektrolita, ocetne kisline (CH3COOH), v odvisnosti od časa. Kinetiko reakcije proizvodnje ocetne kisline kot s...

  6. RESULTS OF AN OPEN-LABEL COMPARATIVE RANDOMIZED CLINICAL TRIAL OF AXOGLATIRAN® FS (F-SINTEZ, RUSSIA EFFICIENCY AND SAFETY IN COMPARISON WITH COPAXONE®-TEVA (TEVA PHARMACEUTICAL INDUSTRIES LTD., ISRAEL IN PATIENTS WITH RELAPSING-REMITTING MULTIPLE SCLEROSIS

    Directory of Open Access Journals (Sweden)

    F. A. Khabirov

    2016-01-01

    Full Text Available Objective. Comparison of Axoglatiran® FS (F-Sintez,  Russia and Copaxone®-Teva (Teva Pharmaceutical Industries Ltd.,  Israel efficiency and safety in patients with relapsing-remitting multiple sclerosis. Materials and methods. In the study 150 patients with relapsing-remitting multiple sclerosis were randomized into 2 groups: patients in the 1st group (n = 100 received treatment with Axoglatiran® FS, patients in the 2nd group (n = 50 received treatment with Copaxone®-Teva. Vital signs of every patient in the study were monitored accompanied by physical examinations, neurological examinations with EDSS (Expanded Disability Status Scale and MSFC (Multiple Sclerosis Functional Composite evaluations, magnetic resonance imaging of the brain and lab tests. Results. Mean age (M ± SD of the patients in the 1st group was 32.8 ± 8.7 years (20–54  years, percentages of men and women were 34 and 66 % respectively, mean age of multiple sclerosis onset was 27.93 ± 7.72 years (11–48 years. Median (Me, lower and upper quartiles estimates [LQ; UQ] on the EDSS scale were 2 [1.5; 3.0] steps (1.0–4.5  steps. In the 2nd group mean age of the patients was 35.2 ± 9.5 years (18–57  years, percentages of men and women were 24 and 76 % respectively, mean age of multiple sclerosis onset was 26.5 ± 6.9 years (18–47  years, EDSS estimates were 2.25 [1.5; 3.5] steps (1–5  steps. In the 1st group 88 (88 % patients completed the study, in the 2nd  group 44 (88 % patients completed the study. Among them in 73 (82.95 % patients in the 1st group and 34 (77.27 % patients in the 2nd  group the disease didn’t exacerbate (p > 0.05. In both groups no progression according to the EDSS and MSFC scale was observed (p > 0.05. Magnetic resonance imaging data showed that dynamics of the total number of T2 lesions, contrast-enhancing T1 lesions, atrophy degree estimated using internuclear index were comparable in both groups (p > 0.05. Safety profiles of

  7. EPR Spectroscopy in Environmental Lichen-Indication

    Science.gov (United States)

    Bondarenko, P. V.; Nguyet, Le Thi Bich; Zhuravleva, S. E.; Trukhan, E. M.

    2017-09-01

    The paramagnetic properties of lichens were investigated using EPR spectroscopy and Xanthoria parietina (L.) Th. Fr. as a case study. It was found that the concentration of paramagnetic centers in lichen thalli increased as the air-pollution level increased. Possible formation mechanisms of the paramagnetic centers in lichens were discussed. The efficiency of using EPR spectroscopy to study lichens as environmental quality indicators was demonstrated.

  8. Applications of EPR in radiation research

    CERN Document Server

    Lund, Anders

    2014-01-01

    Applications of EPR in Radiation Research is a multi-author contributed volume presented in eight themes: I. Elementary radiation processes (in situ and low temperature radiolysis, quantum solids); II: Solid state radiation chemistry (crystalline, amorphous and heterogeneous systems); III: Biochemistry, biophysics and biology applications (radicals in biomaterials, spin trapping, free-radical-induced DNA damage); IV: Materials science (polymeric and electronic materials, materials for treatment of nuclear waste, irradiated food); V: Radiation metrology (EPR-dosimetry, retrospective and medical

  9. EPR oximetry of tumors in vivo in cancer therapy

    Science.gov (United States)

    Šentjurc, Marjeta; Čemažar, Maja; Serša, Gregor

    2004-05-01

    The partial oxygen pressure ( pO 2) in tumors is considered to be one of important factors that affect the response of tumors to different treatment. Therefore, we anticipate that the information about the variation of oxygen concentration in tumors can be used as a guide for individualizing radiotherapy, chemotherapy, and especially the combined therapies. There is thus a need to obtain quantitative data on the effects of different therapies on tumor oxygenation under in vivo conditions. One of the methods, which enable these measurements is EPR oximetry. In this work basic principles of the method will be described as well as some examples of tumor oxygenation changes after application of chemotherapeutic drugs (vinblastine, cisplatin, bleomycin) or electric pulses in combination with cisplatin or bleomycin to fibrosarcoma SA-1 tumors in mice. A paramagnetic probe, a char of Bubinga tree, was implanted into the tumor (center and periphery) and in the muscle or subcutis. EPR spectra line-width, which is proportional to oxygen concentration, was measured with time after the treatments. Tumor oxygenation was reduced for 58% of pretreatment value 1 h after intraperitoneal injection of 2.5 mg kg -1 VLB and returned to pretreatment level within 24 h. Reduction in oxygenation of muscle and subcutis was much smaller and returned to pretreatment value faster as in tumors. With cisplatin (4 mg kg -1) and bleomicyn (1 mg kg -1) the reduction was less than 15%, but increases in combined therapy to 70%. Similar reduction was observed also with electric pulses alone (eight pulses, 1300 V cm -1, 100 μs, 1 Hz) with fast recovery of 8 h. After electrochemotherapy the recovery was slower and occurs only after 48 h. This study demonstrates that EPR oximetry is a sensitive method for monitoring changes in tissue oxygenation after different treatments, which may have implications in controlling side effects of therapy and in the planning of combined treatments.

  10. EPR spectroscopy of a family of Cr(III) 7M(II) (M = Cd, Zn, Mn, Ni) "wheels": studies of isostructural compounds with different spin ground states

    DEFF Research Database (Denmark)

    Piligkos, Stergios; Weihe, Høgni; Bill, Eckhard

    2009-01-01

    spin states is observed.We present highly resolved multifrequency (X-, K-, Q- and W-band) continous wave EPR spectra of the heterooctametalic "wheels", [(CH(3))(2)NH(2)][Cr(III) (7)M(II)F(8)((CH(3))(3)CCOO)(16)], hereafter Cr(7)M, where M=Cd, Zn, Mn, and Ni. These experimental spectra provide rare...

  11. Single crystal X- and Q-band EPR spectroscopy of a binuclear Mn(2)(III,IV) complex relevant to the oxygen-evolving complex of photosystem II.

    Science.gov (United States)

    Yano, Junko; Sauer, Kenneth; Girerd, Jean-Jacques; Yachandra, Vittal K

    2004-06-23

    The anisotropic g and hyperfine tensors of the Mn di-micro-oxo complex, [Mn(2)(III,IV)O(2)(phen)(4)](PF(6))(3).CH(3)CN, were derived by single-crystal EPR measurements at X- and Q-band frequencies. This is the first simulation of EPR parameters from single-crystal EPR spectra for multinuclear Mn complexes, which are of importance in several metalloenzymes; one of them is the oxygen-evolving complex in photosystem II (PS II). Single-crystal [Mn(2)(III,IV)O(2)(phen)(4)](PF(6))(3).CH(3)CN EPR spectra showed distinct resolved (55)Mn hyperfine lines in all crystal orientations, unlike single-crystal EPR spectra of other Mn(2)(III,IV) di-micro-oxo bridged complexes. We measured the EPR spectra in the crystal ab- and bc-planes, and from these spectra we obtained the EPR spectra of the complex along the unique a-, b-, and c-axes of the crystal. The crystal orientation was determined by X-ray diffraction and single-crystal EXAFS (Extended X-ray Absorption Fine Structure) measurements. In this complex, the three crystallographic axes, a, b, and c, are parallel or nearly parallel to the principal molecular axes of Mn(2)(III,IV)O(2)(phen)(4) as shown in the crystallographic data by Stebler et al. (Inorg. Chem. 1986, 25, 4743). This direct relation together with the resolved hyperfine lines significantly simplified the simulation of single-crystal spectra in the three principal directions due to the reduction of free parameters and, thus, allowed us to define the magnetic g and A tensors of the molecule with a high degree of reliability. These parameters were subsequently used to generate the solution EPR spectra at both X- and Q-bands with excellent agreement. The anisotropic g and hyperfine tensors determined by the simulation of the X- and Q-band single-crystal and solution EPR spectra are as follows: g(x) = 1.9887, g(y) = 1.9957, g(z) = 1.9775, and hyperfine coupling constants are A(III)(x) = |171| G, A(III)(y) = |176| G, A(III)(z) = |129| G, A(IV)(x) = |77| G, A

  12. Solid-state NMR and EPR Spectroscopy of Mn2+ -Substituted ATP-Fueled Protein Engines.

    Science.gov (United States)

    Wiegand, Thomas; Lacabanne, Denis; Keller, Katharina; Cadalbert, Riccardo; Lecoq, Lauriane; Yulikov, Maxim; Terradot, Laurent; Jeschke, Gunnar; Meier, Beat H; Böckmann, Anja

    2017-03-13

    Paramagnetic metal ions deliver structural information both in EPR and solid-state NMR experiments, offering a profitable synergetic approach to study bio-macromolecules. We demonstrate the spectral consequences of Mg2+ / Mn2+ substitution and the resulting information contents for two different ATP:Mg2+ -fueled protein engines, a DnaB helicase from Helicobacter pylori active in the bacterial replisome, and the ABC transporter BmrA, a bacterial efflux pump. We show that, while EPR spectra report on metal binding and provide information on the geometry of the metal centers in the proteins, paramagnetic relaxation enhancements identified in the NMR spectra can be used to localize residues at the binding site. Protein engines are ubiquitous and the methods described herein should be applicable in a broad context. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. EPR dosimetric properties of nano-barium sulfate

    Science.gov (United States)

    Aboelezz, E.; Hassan, G. M.; Sharaf, M. A.; El-Khodary, A.

    2015-01-01

    Nano/micro BaSO4 were prepared through the co-precipitation method to measure ionizing radiation doses using electron paramagnetic resonance (EPR). The nano-BaSO4 sample was characterized using X-ray diffraction (XRD), and transmission electron microscopy (TEM) techniques. The dose response and fading properties of nano- and micro-phase BaSO4 were compared in EPR spectra. The prepared nano- and micro-BaSO4 samples have the same hole and electron centers, which may be attributed to SO4- and SO3-, respectively. The dosimetric signals for prepared nano- and micro-BaSO4 have spectroscopic splitting factor (g) with values 2.0025±0.0006 and 2.0027±0.0006, respectively. The nanocrystalline sample has a linear γ-ray dose response over the range 0.4 Gy-1 kGy. The performance parameters which including detection limit and critical level calculated from weighted and unweighted least-squares fitting. The sensitivity of nano-BaSO4 to γ-ray is one and a half times more than alanine. The lifetime and activation energy for nano-BaSO4 were estimated by conducting a thermal stability study, and were 5.7±1.1×104 years and 0.73±0.14 eV, respectively. The combined and expanded uncertainties accompanying measurements were ±3.89% and ±7.78%, respectively.

  14. EPR investigations of gamma-irradiated ground black pepper

    Science.gov (United States)

    Polovka, Martin; Brezová, Vlasta; Staško, Andrej; Mazúr, Milan; Suhaj, Milan; Šimko, Peter

    2006-02-01

    The γ-radiation treatment of ground black pepper samples resulted in the production of three paramagnetic species ( GI- GIII) which arise from a different origin and have different thermal behavior and stability. The axially symmetric spectra can be characterized by the spin Hamiltonian parameters: GI ( g⊥=2.0060, g∥=2.0032; A⊥=0.85 mT, A∥=0.70 mT) and GII ( g⊥=2.0060, g∥=2.0050; A⊥=0.50 mT, A∥=0.40 mT) assigned to carbohydrate radical structures. The parameters of EPR signal GIII ( g⊥=2.0029, g∥=2.0014; A⊥=3.00 mT, A∥=1.80 mT) possessed features characteristic of cellulose radical species. The activation energies, evaluated by Arrhenius analysis, are in order Ea( GI)black pepper, where a decrease of ˜13% was found. The influence of γ-radiation treatment on the radical-scavenging activities of aqueous and ethanol extracts of black pepper were investigated by both an EPR spin trapping technique and DPPH assay. No changes were detected in either the water or ethanol extracts for a γ-irradiation dose of 10 kGy.

  15. Multi-photon transitions and Rabi resonance in continuous wave EPR.

    Science.gov (United States)

    Saiko, Alexander P; Fedaruk, Ryhor; Markevich, Siarhei A

    2015-10-01

    The study of microwave-radiofrequency multi-photon transitions in continuous wave (CW) EPR spectroscopy is extended to a Rabi resonance condition, when the radio frequency of the magnetic-field modulation matches the Rabi frequency of a spin system in the microwave field. Using the non-secular perturbation theory based on the Bogoliubov averaging method, the analytical description of the response of the spin system is derived for all modulation frequency harmonics. When the modulation frequency exceeds the EPR linewidth, multi-photon transitions result in sidebands in absorption EPR spectra measured with phase-sensitive detection at any harmonic. The saturation of different-order multi-photon transitions is shown to be significantly different and to be sensitive to the Rabi resonance. The noticeable frequency shifts of sidebands are found to be the signatures of this resonance. The inversion of two-photon lines in some spectral intervals of the out-of-phase first-harmonic signal is predicted under passage through the Rabi resonance. The inversion indicates the transition from absorption to stimulated emission or vice versa, depending on the sideband. The manifestation of the primary and secondary Rabi resonance is also demonstrated in the time evolution of steady-state EPR signals formed by all harmonics of the modulation frequency. Our results provide a theoretical framework for future developments in multi-photon CW EPR spectroscopy, which can be useful for samples with long spin relaxation times and extremely narrow EPR lines. Copyright © 2015 Elsevier Inc. All rights reserved.

  16. EPR support for the ketyl radical-anion "triggered" [3,3]-sigmatropic rearrangement.

    Science.gov (United States)

    Enholm, Eric J; Battiste, Merle A; Gallagher, Maria; Moran, Kelley M; Alberti, Angelo; Guerra, Maurizio; Macciantelli, Dante

    2002-09-06

    New physical evidence to support a ketyl radical-anion mechanism for the [3,3]-sigmatropic rearrangement is presented. With use of EPR spectroscopy, spectra are observed that can be attributed to 8, an acyl radical-anion species resulting from a [3,3]-rearrangement; this also functions as a key intermediate in the process. The spectrum of an additional paramagnetic species resulting from further addition of tin-centered radicals to the reaction product was also observed.

  17. Free Radical Scavenging Activity of Drops and Spray Containing Propolis—An EPR Examination

    OpenAIRE

    Pawel Olczyk; Katarzyna Komosinska-Vassev; Pawel Ramos; Lukasz Mencner; Krystyna Olczyk; Barbara Pilawa

    2017-01-01

    The influence of heating at a temperature of 50 °C and UV-irradiation of propolis drops and spray on their free radical scavenging activity was determined. The kinetics of interactions of the propolis samples with DPPH free radicals was analyzed. Interactions of propolis drops and propolis spray with free radicals were examined by electron paramagnetic resonance spectroscopy. A spectrometer generating microwaves of 9.3 GHz frequency was used. The EPR spectra of the model DPPH free radicals we...

  18. Application of EPR spectroscopy to the examination of pro-oxidant activity of coffee.

    Science.gov (United States)

    Krakowian, Daniel; Skiba, Dominik; Kudelski, Adam; Pilawa, Barbara; Ramos, Paweł; Adamczyk, Jakub; Pawłowska-Góral, Katarzyna

    2014-05-15

    Free radicals present in coffee may be responsible for exerting toxic effects on an organism. The objectives of this work were to compare free radicals properties and concentrations in different commercially available coffees, in solid and liquid states, and to determine the effect of roasting on the formation of free radicals in coffee beans of various origins. The free radicals content of 15 commercially available coffees (solid and liquid) was compared and the impact of processing examined using electron paramagnetic resonance (EPR) spectroscopy at X-band (9.3 GHz). First derivative EPR spectra were measured at microwave power in the range of 0.7-70 mW. The following parameters were calculated for EPR spectra: amplitude (A), integral intensity (I), and line-width (ΔBpp); g-Factor was obtained from resonance condition. Our study showed that free radicals exist in green coffee beans (10(16) spin/g), roasted coffee beans (10(18) spin/g), and in commercially available coffee (10(17)-10(18) spin/g). Free radical concentrations were higher in solid ground coffee than in instant or lyophilised coffee. Continuous microwave saturation indicated homogeneous broadening of EPR lines from solid and liquid commercial coffee samples as well as green and roasted coffee beans. Slow spin-lattice relaxation processes were found to be present in all coffee samples tested, solid and liquid commercial coffees as well as green and roasted coffee beans. Higher free radicals concentrations were obtained for both the green and roasted at 240 °C coffee beans from Peru compared with those originating from Ethiopia, Brazil, India, or Colombia. Moreover, more free radicals occurred in Arabica coffee beans roasted at 240 °C than Robusta. EPR spectroscopy is a useful method of examining free radicals in different types of coffee. Copyright © 2013 Elsevier Ltd. All rights reserved.

  19. EFFECT OF CADMIUM(II) ON FREE RADICALS IN DOPA-MELANIN TESTED BY EPR SPECTROSCOPY.

    Science.gov (United States)

    Zdybel, Magdalena; Pilawa, Barbara; Chodurek, Ewa

    2015-01-01

    Electron paramagnetic resonance (EPR) spectroscopy may be applied to examine interactions of melanin with metal ions and drugs. In this work EPR method was used to examination of changes in free radical system of DOPA-melanin--the model eumelanin after complexing with diamagnetic cadmium(II) ions. Cadmium(II) may affect free radicals in melanin and drugs binding by this polymer, so the knowledge of modification of properties and free radical concentration in melanin is important to pharmacy. The effect of cadmium(II) in different concentrations on free radicals in DOPA-melanin was determined. EPR spectra of DOPA-melanin, and DOPA-melanin complexes with cadmium(II) were measured by an X-band (9.3 GHz) EPR spectrometer produced by Radiopan (Poznań, Poland) and the Rapid Scan Unit from Jagmar (Krak6w, Poland). The DOPA (3,4-dihydroxyphenylalanine) to metal ions molar ratios in the reaction mixtures were 2:1, 1:1, and 1: 2. High concentrations of o-semiquinone (g ~2.0040) free radicals (~10(21)-10(22) spin/g) characterize DOPA-melanin and its complexes with cadmium(II). Formation of melanin complexes with cadmium(II) increase free radical concentration in DOPA-melanin. The highest free radical concentration was obtained for DOPA-melanin-cadmium(II) (1:1) complexes. Broad EPR lines with linewidths: 0.37-0.73 mT, were measured. Linewidths increase after binding of cadmium(II) to melanin. Changes of integral intensities and linewidths with increasing microwave power indicate the homogeneous broadening of EPR lines, independently on the metal ion concentration. Slow spin-lattice relaxation processes existed in all the tested samples, their EPR lines saturated at low microwave powers. Cadmium(II) causes fastening of spin-lattice relaxation processes in DOPA-melanin. The EPR results bring to light the effect of cadmium(II) on free radicals in melanin, and probably as the consequence on drug binding to eumelanin.

  20. EPR (Electronic Patient Record Laboratory - Simulated Environment to Learn about a Hospital EPR System

    Directory of Open Access Journals (Sweden)

    Kazuko Yamamoto

    2011-03-01

    Full Text Available The “Electronic Patient Record (EPR Laboratory” is a computer based self-learning system developed for students to acquire practical skills and knowledge required to deal with EPRs. The system is designed to supplement conventional lectures on health information systems given as part of our undergraduate curriculum. Using the Laboratory, the students may learn not only operations of EPR systems but also the subjects connected with patient information handling, including privacy, security and health information ethics. The EPR Laboratory is composed of an eLearing system and an EPR system. The learning materials are arranged in units in the eLearning system, and in each unit, the student learns the materials and the EPR operations through practice. Tests are given at each end of unit, and if a student failed a test, the system shows which questions were answered incorrectly and indicates which parts of the unit he/she should review. For this purpose, we introduced a structure to the learning materials based on an information model. In this paper, the overview of the system, the simulated environment to learn patient flow, information flow and hospital workflow, fundamental EPR operations, and structured learning materials for the test and review cycle are described.

  1. Investigation of radical locations in various sesame seeds by CW EPR and 9-GHz EPR imaging.

    Science.gov (United States)

    Nakagawa, K; Hara, H

    2015-01-01

    We investigated the location of radical in various sesame seeds using continuous-wave (CW) electron paramagnetic resonance (EPR) and 9-GHz EPR imaging. CW EPR detected persistent radicals (single line) for various sesame seeds. The EPR linewidth of black sesame seeds was narrower than that of the irradiated white sesame seeds. A very small signal was detected for the white sesame seeds. Two-dimensional (2D) imaging using a 9-GHz EPR imager showed that radical locations vary for various sesame seeds. The paramagnetic species in black sesame seeds were located on the seed coat (skin) and in the hilum region. The signal with the highest intensity was obtained from the hilum part. A very low-intensity image was observed for the white sesame seeds. In addition, the 2D imaging of the irradiated white sesame seeds showed that free radicals were located throughout the entire seed. For the first time, CW EPR and 9-GHz EPR imaging showed the exact location of radical species in various sesame seeds.

  2. Application of EPR Spectroscopy to Examination of the Effect of Sterilization Process on Free Radicals in Different Herbs

    OpenAIRE

    Paw?owska-G?ral, Katarzyna; Ramos, Pawe?; Pilawa, Barbara; Kurzeja, Ewa

    2013-01-01

    Free radicals in the original and sterilized caraway, curry, curcuma and cardamom were studied. An X-band (9.3?GHz) electron paramagnetic resonance (EPR) spectroscopy was the experimental technique. Effect of microwave power in the range of 2.2?70?mW on amplitudes, linewidths, and lineshape parameters of the EPR spectra was tested. Free radicals concentrations in the non- and sterilized herb samples were compared. The aim of this work was to determine properties and concentration of free radi...

  3. Two-dimensional Pulsed EPR Studies of Vanadium-Exchanged ZSM-5

    Energy Technology Data Exchange (ETDEWEB)

    Woodworth, James F.; Bowman, Michael K.; Larsen, Sarah C.

    2004-10-14

    The pulsed electron paramagnetic resonance (EPR) technique of hyperfine sublevel correlation spectroscopy (HYSCORE) was used to obtain structural information about vanadium(VO2+) exchanged ZSM-5. HYSCORE spectra were obtained for vanadium exchanged ZSM-5 before and after dehydration and after adsorption of ammonia. For the hydrated samples, proton hyperfine coupling constants were measured and assigned to equatorial water ligands with orientations perpendicular and parallel to the equatorial plane. Nitrogen hyperfine coupling constants for adsorbed ammonia were also determined from the HYSCORE spectra. The results were compared with previous density functional theory (DFT) calculations of hyperfine coupling constants for vanadyl model complexes.

  4. Multifrequency Pulsed EPR Studies of Biologically Relevant Manganese(II) Complexes.

    Science.gov (United States)

    Stich, T A; Lahiri, S; Yeagle, G; Dicus, M; Brynda, M; Gunn, A; Aznar, C; Derose, V J; Britt, R D

    2007-03-01

    Electron paramagnetic resonance studies at multiple frequencies (MF EPR) can provide detailed electronic structure descriptions of unpaired electrons in organic radicals, inorganic complexes, and metalloenzymes. Analysis of these properties aids in the assignment of the chemical environment surrounding the paramagnet and provides mechanistic insight into the chemical reactions in which these systems take part. Herein, we present results from pulsed EPR studies performed at three different frequencies (9, 31, and 130 GHz) on [Mn(II)(H(2)O)(6)](2+), Mn(II) adducts with the nucleotides ATP and GMP, and the Mn(II)-bound form of the hammerhead ribozyme (MnHH). Through line shape analysis and interpretation of the zero-field splitting values derived from successful simulations of the corresponding continuous-wave and field-swept echo-detected spectra, these data are used to exemplify the ability of the MF EPR approach in distinguishing the nature of the first ligand sphere. A survey of recent results from pulsed EPR, as well as pulsed electron-nuclear double resonance and electron spin echo envelope modulation spectroscopic studies applied to Mn(II)-dependent systems, is also presented.

  5. Model compounds of humic acid and oxovanadium cations. Potentiometric titration and EPR spectroscopy studies

    Directory of Open Access Journals (Sweden)

    Mercê Ana Lucia Ramalho

    1999-01-01

    Full Text Available The stability constants and the isotropic EPR parameters Ao (hyperfine splitting constant and g o (g value were obtained by potentiometric titrations and EPR spectroscopy, respectively, of 85%v/v aqueous solutions of model compounds of humic acids - salicylic acid (SALA - and both nitrohumic acids, a laboratory artifact - nitrosalicylic acids, 3-nitrosalicylic acid (3-NSA, 5-nitrosalicylic acid (5-NSA and 3,5-dinitrosalicylic acid (3,5-DNSA and oxovanadium cations. It was possible to record EPR spectra of those model compounds and the ion VO2+ (V(IV, and the stability constants were obtained from a solution of VO3+ (V(V, the values for the logarithms of the stability constants ranging from 12.77 ± 0.04 to 7.06 ± 0.05 for the species ML, and from 9.90 ±0.04 to 4.06 ± 0.05 for the species ML2 according to the decrease in the acidity of the carboxylic and the hydroxyl groups in the aromatic ring of the model compounds studied as the -NO2 substituents were added. Species distribution diagrams were also obtained for the equilibria studied. The EPR parameters showed that as the logarithm of the overall stability constants increase, g o values also increase, while Ao values show a tendency to decrease.

  6. Mast-sipping in EPR trademark plants

    Energy Technology Data Exchange (ETDEWEB)

    Langenberger, Jan [AREVA NP GmbH, Erlangen (Germany). Fuel Service; Schienbein, Marcel; Geier, Roland [AREVA NP GmbH, Erlangen (Germany). Radiochemical Lab.

    2010-05-15

    For more than 20 years, AREVA applies and develops different sipping techniques to identify fuel assemblies with leaking fuel rods. For the EPR trademark reactors a Mast Sipping System with newest developments will be implemented considering radiation protection and latest standards requirements. The innovative EPR trademark Sipping System differs from previous systems in many ways. One of the main innovations is that all the necessary processes of the Sipping system have been fully digitized. Second, several ALARA design modifications have been implemented to meet the current radiation protection requirements. An additional implementable multilingual assistance program facilitates the handling of the system and helps to prevent incorrect operation. (orig.)

  7. TL and EPR dating: some applications

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, S. [Institute of Physics, University of Sao Paulo, Sao Paulo (Brazil)

    2006-07-01

    The intensity of thermoluminescence light emitted by a crystal is a function of radiation dose. The number of defects or of radicals in a crystal or organic substances is also a function of radiation dose. Since such defects or radicals present EPR signals, the EPR intensity is also a function of radiation dose. These facts are basis for radiation dosimetry and can be applied in dating of archaeological potteries or other materials, as well as in dating geological substances such as sediments, caves speleothemes, animal teeth and bones. Recent investigation on sensitized quartz based dosimeters and dating calcite covering ancient wall painting to find early settlers in Brazil will be presented. (Author)

  8. Models for the active site in galactose oxidase: Structure, spectra ...

    Indian Academy of Sciences (India)

    Models for the active site in galactose oxidase: Structure, spectra and redox of copper(II) complexes of certain phenolate ligands. Mathrubootham Vaidyanathan ... All the present complexes exhibit several electronic and EPR spectral features which are also similar to the enzyme. Further, to establish the structural and ...

  9. Synthesis, structure, redox and spectra of green iridium complexes ...

    Indian Academy of Sciences (India)

    TECS

    3. *For correspondence. Synthesis, structure, redox and spectra of green iridium complexes of tridentate azo-aromatic ligands. MANASHI PANDA,a CHAYAN DAS,a CHEN-HSIUNG HUNGb and. SREEBRATA ... Mn(II)7 and Fe(II)8 but also produces stable anionic ..... the EPR of the oxidized complexes were not suc- cessful ...

  10. Investigations of the electron paramagnetic resonance spectra of ...

    Indian Academy of Sciences (India)

    2015-11-27

    Nov 27, 2015 ... The EPR spectra for VO2+ in CaO–Al2O3–SiO2 system are calculated using complete diagonalization method (CDM) and perturbation theory method (PTM). The calculated results are in good agreement with the observed values. By comparing the calculated results by CDM and PTM in a wide range of ...

  11. Study on radiation-induced radicals giving rise to stable EPR signal suitable for the detection of irradiation in L-sorbose-containing fruits

    Directory of Open Access Journals (Sweden)

    Guzik Grzegorz P.

    2016-12-01

    Full Text Available The stable and complex EPR signals produced by the action of ionizing radiation on crystalline L-sorbose (C6H12O6 separated from rowan berries (Sorbus aucuparia were studied. Isothermal heating of the samples at the temperature close to the melting point of L-sorbose (140°C results in the modification and simplification of the EPR signal involved. In the EPR signal of heated L-sorbose, the isotropic quartet was distinguished. In the differential spectrum obtained by subtraction of normalized spectra of unheated and heated L-sorbose, the isotropic doublet was identified in addition. The DFT fitting offers the probable assignment of the EPR signals to specific radical structures.

  12. EPR-dosimetry of ionizing radiation

    Science.gov (United States)

    Popova, Mariia; Vakhnin, Dmitrii; Tyshchenko, Igor

    2017-09-01

    This article discusses the problems that arise during the radiation sterilization of medical products. It is propose the solution based on alanine EPR-dosimetry. The parameters of spectrometer and methods of absorbed dose calculation are given. In addition, the problems that arise during heavy particles irradiation are investigated.

  13. The EPR Paradox: Einstein Scrutinises Quantum Mechanics

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 5; Issue 4. The EPR Paradox: Einstein Scrutinises Quantum Mechanics. Arvind. General Article Volume 5 Issue 4 April 2000 pp 28-36. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/005/04/0028-0036 ...

  14. EPR spin trapping of protein radicals

    DEFF Research Database (Denmark)

    Davies, Michael Jonathan; Hawkins, Clare Louise

    2004-01-01

    Electron paramagnetic resonance (EPR) spin trapping was originally developed to aid the detection of low-molecular-mass radicals formed in chemical systems. It has subsequently found widespread use in biology and medicine for the direct detection of radical species formed during oxidative stress...

  15. Free Radical Scavenging Activity of Drops and Spray Containing Propolis-An EPR Examination.

    Science.gov (United States)

    Olczyk, Pawel; Komosinska-Vassev, Katarzyna; Ramos, Pawel; Mencner, Lukasz; Olczyk, Krystyna; Pilawa, Barbara

    2017-01-13

    The influence of heating at a temperature of 50 °C and UV-irradiation of propolis drops and spray on their free radical scavenging activity was determined. The kinetics of interactions of the propolis samples with DPPH free radicals was analyzed. Interactions of propolis drops and propolis spray with free radicals were examined by electron paramagnetic resonance spectroscopy. A spectrometer generating microwaves of 9.3 GHz frequency was used. The EPR spectra of the model DPPH free radicals were compared with the EPR spectra of DPPH in contact with the tested propolis samples. The antioxidative activity of propolis drops and propolis spray decreased after heating at the temperature of 50 °C. A UV-irradiated sample of propolis drops more weakly scavenged free radicals than an untreated sample. The antioxidative activity of propolis spray increased after UV-irradiation. The sample of propolis drops heated at the temperature of 50 °C quenched free radicals faster than the unheated sample. UV-irradiation weakly changed the kinetics of propolis drops or spray interactions with free radicals. EPR analysis indicated that propolis drops and spray should not be stored at a temperature of 50 °C. Propolis drops should not be exposed to UV-irradiation.

  16. EPR study of the formation of radicals in PP with antioxidants irradiated with gamma rays

    Energy Technology Data Exchange (ETDEWEB)

    Silva, P. [Instituto Venezolano de Investigaciones Cientificas, Centro de Fisica, Carretera Panamericana Km. 11, Caracas 1020-A (Venezuela)], E-mail: silva@ivic.ve; Albano, C. [Instituto Venezolano de Investigaciones Cientificas, Centro de Quimica, Universidad Central de Venezuela, Facultad de Ingenieria (Venezuela); Perera, R. [Departamento de Mecanica, Universidad Simon Bolivar (Venezuela)

    2007-12-15

    The behavior of different compounds of polypropylene (PP) with stabilizers such as buthyl-hydroxy-toluene (BHT), Chimassorb 944 (Hals) (CHIM), and a copolymer of styrene-butadiene-styrene (SBS) was studied using electron paramagnetic resonance (EPR). A characteristic spectra for pure PP irradiated in air was obtained for all the samples just after being irradiated [M. Dole, The Radiation Chemistry of Macromolecules, Vol. 2, Academic Press, 1973]. A change in the lineshape of the spectra from a pure PP's EPR signal to that of nitroxyl radical as a function of time was observed. The total free radical concentration (TFRC) decayed until approximately 800 h in the PP-HALS and until around 2000 h in all other cases, when the TFRC began to increase in all the cases, except in that of PP-BHT. In this last case, the EPR signal was not detectable after 4000 h. The BHT and the SBS diluted the free radical concentrations, being them smaller when they are present. The behavior observed in all the samples is consistent with the formation of nitroxyl radicals by gamma rays.

  17. EPR studies of free radicals decay and survival in gamma irradiated aminoglycoside antibiotics: sisomicin, tobramycin and paromomycin.

    Science.gov (United States)

    Wilczyński, Sławomir; Pilawa, Barbara; Koprowski, Robert; Wróbel, Zygmunt; Ptaszkiewicz, Marta; Swakoń, Jan; Olko, Paweł

    2012-02-14

    Radiation sterilization technology is more actively used now that any time because of its many advantages. Gamma radiation has high penetrating power, relatively low chemical reactivity and causes small temperature rise. But on the other hand radiosterilization can lead to radiolytic products appearing, in example free radicals. Free radicals in radiative sterilized sisomicin, tobramycin and paromomycin were studied by electron paramagnetic resonance (EPR) spectroscopy. Dose of gamma irradiation of 25kGy was used. Concentrations and properties of free radicals in irradiated antibiotics were studied. EPR spectra were recorded for samples stored in air and argon. For gamma irradiated antibiotics strong EPR lines were recorded. One- and two-exponential functions were fitted to experimental points during testing and researching of time influence of the antibiotics storage to studied parameters of EPR lines. Our study of free radicals in radiosterilized antibiotics indicates the need for characterization of medicinal substances prior to sterilization process using EPR values. We propose the concentration of free radicals and other spectroscopic parameters as useful factors to select the optimal type of sterilization for the individual drug. The important parameters are i.a. the τ time constants and K constants of exponential functions. Time constants τ give us information about the speed of free radicals concentration decrease in radiated medicinal substances. The constant K(0) shows the free radicals concentration in irradiated medicament after long time of storage. Copyright © 2011 Elsevier B.V. All rights reserved.

  18. AC susceptibility and EPR investigations of superspin dynamics in magnetite nanoparticles

    Science.gov (United States)

    Price, Alex D.

    In this investigation we use two complementary techniques to distinguish between superparamagnetic blocking (SPB) and superspin-glass (SSG) freezing phenomena in magnetite nanoparticles. While these manifestations of the superspin dynamics are fundamentally different, they have similar "signatures", especially in dc-magnetization experiments. Even if ac-susceptibility measurements are employed, careful use of mathematical models to analyze the data are needed to uncover which type of phenomena (SPB or SSG freezing) occurs within the material. Yet, by utilizing electron paramagnetic resonance (EPR) on a 10 nm Fe3O4 nano-powder as well as on a ferrofluid (based on the same nanoparticle ensemble) we found a very distinct difference in the absorption spectra between the two samples, which indicates markedly different EPR signatures from SPB and SSG freezing behaviors.

  19. An EPR line shape study of anisotropic rotational reorientation and slow tumbling in liquid and frozen jojoba oil

    Science.gov (United States)

    Hwang, J. S.; Al-Rashid, W. A.

    Spin probe investigation of jojoba oil was carried out by electron paramagnetic rresonance (EPR) spectroscopy. The spin probe used was 2,2,6,6-tetramethyl-4-piperidone- N-oxide. The EPR line shape studies were carried out in the lower temperature range of 192 to 275 K to test the applicability of the stochastic Liouville theory in the simulation of EPR line shapes where earlier relaxation theories do not apply. In an earlier study, this system was analysed by employing rotational diffusion at the fast-motional region. The results show that PD-Tempone exhibits asymmetric rotational diffusion with N = 3.3 at an axis z'= Y in the plane of the molecule and perpendicular to the NO bond direction. In this investigation we have extended the temperature range to lower temperatures and observed slow tumbling EPR spectra. It is shown that the stochastic Liouville method can be used to simulate all but two of the experimentally observed EPR spectra in the slow-motional region and details of the slow-motional line shape are sensitive to the anisotropy of rotation and showed good agreement for a moderate jump model. From the computer simulation of EPR line shapes it is found that the information obtained on τ R, and N in the motional-narrowing region can be extrapolated into the slow-tumbling region. It is also found that ln (τ R) is linear in 1/ T in the temperature range studied and the resulting activation energy for rotation is 51 kJ/mol. The two EPR spectra at 240 and 231 K were found to exhibit the effects of anisotropic viscosity observed by B IRELL for nitroxides oriented in tubular cavities in inclusion crystals in which the molecule is free to rotate about the long axis but with its rotation hindered about the other two axes because of the cavity geometry. These results proved that the slow-tumbling spectra were very sensitive to the effects of anisotropy in the viscosity.

  20. EPR study of gamma-irradiated amphi-phenylglyoxime single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Dereli, O., E-mail: odereli@selcuk.edu.t [A. Kelesoglu Education Faculty, Department of Physics, Selcuk University, Meram, 42090, Konya (Turkey); Tuerkkan, E. [A. Kelesoglu Education Faculty, Department of Physics, Selcuk University, Meram, 42090, Konya (Turkey); Ozmen, A.; Yueksel, H. [Science Faculty, Department of Physics, Selcuk University, Selcuklu, 42079, Konya (Turkey)

    2011-06-15

    Gamma-irradiated single crystals of Amphi-phenylglyoxime (APGO) were investigated using electron paramagnetic resonance (EPR) at different orientations in a magnetic field at room temperature (298 K). Considering the chemical structure and the experimental spectra of the irradiated single-crystals of APGO, we assumed that two different paramagnetic species, labeled as R{sup *} and R{sup **}, are either two iminoxy radicals formed by the abstraction of a H atom from different oxime branches or are different conformations of an iminoxy radical. Pursuant to this assumption, RA- and RB-type iminoxy radicals were modeled by the abstraction of H atoms from different oxime branches, and conformational analysis of these modeled radicals was performed using the semi-empirical AM1 and B3LYP/6-31+G(d,p) methods. EPR parameters were calculated for the modeled radicals using the B3LYP method and EPR-III basis set. Theoretically calculated values of the most stable conformers (RA-1 and RB-1) of the modeled radicals are in good agreement with the experimental EPR parameters determined from the spectra (differences in isotropic hyperfine coupling constant values <5%, and differences in isotropic g values fall into 1 ppt). Thus, from the findings of the present study, we strongly suggest that the experimentally observed R{sup *} and R{sup **} radicals in the single crystal of amphi-phenylglyoxime are the most stable conformers of RA- and RB-type modeled iminoxy radicals, respectively. The experimental g factors and hyperfine coupling constants were found to be anisotropic, with average values of g=2.0052, A({sup 14}N)=29.50 G, A({sup 1}H)=25.30 G for R{sup *}, and g=2.0057, A({sup 14}N)=34.50 G for R{sup **}.

  1. Application of EPR Spectroscopy to Examination of the Effect of Sterilization Process on Free Radicals in Different Herbs.

    Science.gov (United States)

    Pawłowska-Góral, Katarzyna; Ramos, Paweł; Pilawa, Barbara; Kurzeja, Ewa

    2013-03-01

    Free radicals in the original and sterilized caraway, curry, curcuma and cardamom were studied. An X-band (9.3 GHz) electron paramagnetic resonance (EPR) spectroscopy was the experimental technique. Effect of microwave power in the range of 2.2-70 mW on amplitudes, linewidths, and lineshape parameters of the EPR spectra was tested. Free radicals concentrations in the non- and sterilized herb samples were compared. The aim of this work was to determine properties and concentration of free radicals in steam sterilized caraway, curry, curcuma and cardamom. It was pointed out that free radicals (~10(18) spin/g) exist in both the original and sterilized herbs. Complex free radical system with oxygen and carbon paramagnetic centers characterizes the examined herbs. Homogeneously dipolar broadened EPR spectra were measured for all the tested herbs. Slow spin-lattice relaxation processes exist in the examined samples. Practical usefulness of EPR method in food technology was discussed.

  2. Electron paramagnetic resonance (EPR) in characterization of rocks and minerals

    Energy Technology Data Exchange (ETDEWEB)

    Valezi, D.F.; Mauro, E. di [Universidade Estadual de Londrina (UEL), PR (Brazil). Centro de Ciencias Exatas. Lab. de Fluorescencia e Ressonaancia Paramagnetica Eletronica (LAFLURPE); Zaia, D.A.M.; Carneiro, C.E.A. [Universidade Estadual de Londrina (UEL), PR (Brazil). Centro de Ciencias Exatas. Dept. de Quimica; Costa, A.C.S. da [Universidade Estadual de Maringa (UEM), PR (Brazil). Centro de Ciencias Agrarias. Dept. de Agronomia

    2011-07-01

    Full text. his work is based on the study of several stones and minerals from the Parana state, Brazil. They were analyzed by the Electron Paramagnetic Resonance (EPR) technique. The measurements were made on a spectrometer JEOL (JES-PE-3X), operating on X-band and at room temperature, with the exception of the mineral Goethite, which was measured with temperature variation. In all the samples were determined spectroscopic factors (or g factor) and line widths of paramagnetic species. A great number of the samples showed in their spectra, the presence of iron complexes. Phyllite and shale showed a resonance signal with approximately g = 2, and line width with about 1000 Gauss, which indicates the presence of the hematite mineral hematite in these rocks. Shale and coal samples showed the presence of free radical, it was identified as a very intense signal, centered at about g = 2.003. Phyllite sample showed in its spectra a resonance signal between the third and fourth line of the g marker (Mg O:Mn{sup 2+}) used in the measurements, and also a signal at g = 4.3, these characteristics may indicate the presence of Kaolinite in the sample. Limestone showed a signal with line width of about 600 Gauss, centered around g = 2, this signal is probably due to a mixture of ferrihydrite and some other compound, besides the presence of manganese, displaying a spectra with its six peculiar lines, due to hyperfine splitting. The two different types of limestone presented a overlap of two distinct spectra lines for the manganese, in the first limestone sample, rich in calcite, the existence of these different spectra is a result of the manganese substitution in a single site with different orientations of the calcite; the other limestone sample, this one abundant in dolomite, the existence of these different spectra is the result of the manganese substitution in different dolomite sites, taking the place of calcium and or of the magnesium. Now, we are focusing our research in the

  3. Inequality spectra

    Science.gov (United States)

    Eliazar, Iddo

    2017-03-01

    Inequality indices are widely applied in economics and in the social sciences as quantitative measures of the socioeconomic inequality of human societies. The application of inequality indices extends to size-distributions at large, where these indices can be used as general gauges of statistical heterogeneity. Moreover, as inequality indices are plentiful, arrays of such indices facilitate high-detail quantification of statistical heterogeneity. In this paper we elevate from arrays of inequality indices to inequality spectra: continuums of inequality indices that are parameterized by a single control parameter. We present a general methodology of constructing Lorenz-based inequality spectra, apply the general methodology to establish four sets of inequality spectra, investigate the properties of these sets, and show how these sets generalize known inequality gauges such as: the Gini index, the extended Gini index, the Rényi index, and hill curves.

  4. Full cycle rapid scan EPR deconvolution algorithm

    Science.gov (United States)

    Tseytlin, Mark

    2017-08-01

    Rapid scan electron paramagnetic resonance (RS EPR) is a continuous-wave (CW) method that combines narrowband excitation and broadband detection. Sinusoidal magnetic field scans that span the entire EPR spectrum cause electron spin excitations twice during the scan period. Periodic transient RS signals are digitized and time-averaged. Deconvolution of absorption spectrum from the measured full-cycle signal is an ill-posed problem that does not have a stable solution because the magnetic field passes the same EPR line twice per sinusoidal scan during up- and down-field passages. As a result, RS signals consist of two contributions that need to be separated and postprocessed individually. Deconvolution of either of the contributions is a well-posed problem that has a stable solution. The current version of the RS EPR algorithm solves the separation problem by cutting the full-scan signal into two half-period pieces. This imposes a constraint on the experiment; the EPR signal must completely decay by the end of each half-scan in order to not be truncated. The constraint limits the maximum scan frequency and, therefore, the RS signal-to-noise gain. Faster scans permit the use of higher excitation powers without saturating the spin system, translating into a higher EPR sensitivity. A stable, full-scan algorithm is described in this paper that does not require truncation of the periodic response. This algorithm utilizes the additive property of linear systems: the response to a sum of two inputs is equal the sum of responses to each of the inputs separately. Based on this property, the mathematical model for CW RS EPR can be replaced by that of a sum of two independent full-cycle pulsed field-modulated experiments. In each of these experiments, the excitation power equals to zero during either up- or down-field scan. The full-cycle algorithm permits approaching the upper theoretical scan frequency limit; the transient spin system response must decay within the scan

  5. EPR of transition metal ions in NZP ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Yegor`kova, O.; Kryukova-Orlova, A.I. [Univ. of Nizhnii Novgorod (Russian Federation); Stefanovsky, S.V. [SIA Radon, Moscow (Russian Federation)

    1995-12-31

    NZP-ceramics have been produced by different methods such as sol-gel, flux melting and sintering of dry salts or phosphates. Formation of NZP and related phases was confirmed by X-ray diffraction analysis. Electron paramagnetic resonance (EPR) was applied to evaluate a structure positions of paramagnetic ions and nature of radiation-induced centers. EPR responses from transition metal ions Fe{sup 3+} and Mn{sup 2+} with electron configuration 3d{sup 5} (ground state {sup 6}S{sub 5/2}) which occurred as impurities in raw materials were registered in powders of NZP-ceramics. Fine structure arising due to high spin iron complexes is well resolved. A part of Fe{sup 3+} ions substitutes for Zr{sup 4+} and another part of one substitutes for Na{sup +} ions in six-fold coordinated positions. A great value of hyperfine structure (hfs) constant (9.3 mT) shows a high ionic character of Mn-O bonds in the first coordination sphere. A coordination number is close to 6. Fine structure of Mn{sup 2+} ions are not well resolved. A comparison of the spectra of samples containing various alkali cations shows the substitution for cations in series of Li-Na-K-Rb-Cs does not result in fundamental variation in spectra except for CZP ceramics where the response with g=4.3 due to Fe{sup 3+} in strong ligand field rather than response with g=2.0 due to Fe{sup 3+} in weak field is observed. An investigation of some samples doped by 0.1...0.5 mole % of Fe{sup 3+} or Gd{sup 3+} has been carried out and principal spin-Hamiltonian parameters have been determined. The increase of Fe and Gd ions content as compared to impurity substituting for Zr and possibly Na in their own structural positions results in noticeable site distortion. Gamma irradiation of NZP ceramics results in formation of radiation-induced paramagnetic centers connected to phosphorus-oxygen. The nature and concentration of these centers depend on production method. The lowest defect concentration is in hot-pressed ceramics.

  6. High temperature EPR study of the M3Fe4V6O24 (M = Cu, Zn, Mg and Mn

    Directory of Open Access Journals (Sweden)

    Guskos Niko

    2016-09-01

    Full Text Available Electron paramagnetic resonance (EPR spectra of M3Fe4V6O24 (M = Cu, Zn, Mg and Mn compounds in high temperature range (293 K to 493 K have been investigated. The role of magnetic (Cu, Mn and non-magnetic (Zn, Mg ions in M3Fe4V6O24 structure in formation of magnetic resonance spectra was studied. Temperature dependence of EPR parameters: resonance field, linewidth and integrated intensity were examined. Similarities and differences in temperature behavior of these parameters has been discussed in terms of different relaxation mechanisms and magnetic interactions in the spin systems. An important role of additional magnetic ions (M = Mn or Cu in the M3Fe4V6O24 structure has been identified and its consequences considered.

  7. EPR-Bohr and Quantum Trajectories: Entaglement and Nonlocality

    OpenAIRE

    Floyd, Edward R.

    2010-01-01

    Quantum trajectories are used to investigate the EPR-Bohr debate in a modern sense by examining entanglement and nonlocality. We synthesize a single "entanglement molecule" from the two scattered particles of the EPR experiment. We explicitly investigate the behavior of the entanglement molecule rather than the behaviors of the two scattered particles to gain insight into the EPR-Bohr debate. We develop the entanglement molecule's wave function in polar form and its reduced action, both of wh...

  8. Clinical Electron Paramagnetic Resonance (EPR) Oximetry using India Ink

    OpenAIRE

    Williams, Benjamin B.; Khan, Nadeem; Zaki, Bassem; Hartford, Alan; Ernstoff, Marc S.; Swartz, Harold M.

    2010-01-01

    Electron paramagnetic resonance (EPR) oximetry can be used to provide direct absolute measurements of pO2 in living tissue using India ink as an O2 reporter. In vivo measurements are made using low frequency (1.2GHz) EPR spectroscopy and surface loop resonators, which enable measurements to be made at superficial sites through a non-invasive (after placing the ink in the tissues) and repeatable measurement procedure. Ongoing EPR oximetry studies in human subjects include measurement of subcut...

  9. EPR and 55Mn cw-ENDOR study of an antiferrogmagnetically coupled dinuclear manganese (Mn III Mn IV) complex

    Science.gov (United States)

    Zweygart, W.; Bittl, R.; Wieghardt, K.; Lubitz, W.

    1996-10-01

    X- and Q-band EPR and 55Mn cw-ENDOR experiments are reported on a binuclear oxo-bridged dimanganese Mn III Mn IV complex. Consistent simulations of spectra from both frequency bands using one parameter set for the orthorhombic g tensor and Mn III and Mn IV hyperfine tensors are achieved. Information on the manganese hyperfine couplings is independently obtained from 55Mn cw-ENDOR spectroscopy performed on both ions.

  10. EPR spectroscopy of the manganese cluster of photosystem II.

    Science.gov (United States)

    Haddy, Alice

    2007-06-01

    Electron paramagnetic resonance (EPR) spectroscopy is a valuable tool for understanding the oxidation state and chemical environment of the Mn4Ca cluster of photosystem II. Since the discovery of the multiline signal from the S2 state, EPR spectroscopy has continued to reveal details about the catalytic center of oxygen evolution. At present EPR signals from nearly all of the S-states of the Mn4Ca cluster, as well as from modified and intermediate states, have been observed. This review article describes the various EPR signals obtained from the Mn4Ca cluster, including the metalloradical signals due to interaction of the cluster with a nearby organic radical.

  11. Structural Characterization of Polymer-Clay Nanocomposites Prepared by Co-Precipitation Using EPR Techniques

    Directory of Open Access Journals (Sweden)

    Udo Kielmann

    2014-02-01

    Full Text Available Polymer-clay nanocomposites (PCNCs containing either a rubber or an acrylate polymer were prepared by drying or co-precipitating polymer latex and nanolayered clay (synthetic and natural suspensions. The interface between the polymer and the clay nanoparticles was studied by electron paramagnetic resonance (EPR techniques by selectively addressing spin probes either to the surfactant layer (labeled stearic acid or the clay surface (labeled catamine. Continuous-wave (CW EPR studies of the surfactant dynamics allow to define a transition temperature T* which was tentatively assigned to the order-disorder transition of the surfactant layer. CW EPR studies of PCNC showed that completely exfoliated nanoparticles coexist with agglomerates. HYSCORE spectroscopy in PCNCs showed couplings within the probe −assigned with DFT computations− and couplings with nuclei of the environment, 1H and 23Na for the surfactant layer probe, and 29Si, 7Li, 19F and 23Na for the clay surface probe. Analysis of these couplings indicates that the integrity of the surfactant layer is conserved and that there are sizeable ionic regions containing sodium ions directly beyond the surfactant layer. Simulations of the very weak couplings demonstrated that the HYSCORE spectra are sensitive to the composition of the clay and whether or not clay platelets stack.

  12. Light-induced EPR study of a direct light conversion by polymer/fullerene bulk heterojunctions

    Energy Technology Data Exchange (ETDEWEB)

    Krinichnyi, V.I.; Yudanova, E.I. [Institute of Problems of Chemical Physics, Chernogolovka (Russian Federation)

    2010-07-01

    Paramagnetic charge carriers photoinduced in poly(3-alkylthiophene)s modified by 6,6-phenyl-C{sub 61}-butanoic acid methyl ester (PCBM) and bis-PCBM by photons with the energy of 1.98 - 2.73 eV were investigated by X-band Light-Induced EPR (LEPR) method. LEPR spectra were attributed to non-interacting polarons and methanofullerene anion-radicals with different magnetic and relaxation parameters. A part of these charge carriers was proved to be trapping in a polymer matrix. The number of mobile charge carriers and their relaxation follow activation law. (orig.)

  13. EPR and UV/VIS spectroscopic investigations of VO2+ complexes and compounds formed in alkali pyrosulfates

    DEFF Research Database (Denmark)

    Rasmussen, Søren Birk; Eriksen, Kim Michael; Fehrmann, Rasmus

    2002-01-01

    The catalytically important molten salt-gas system M2S2O7-M2SO4-V2O5/SO2(g) (M = Na. K, Rb, Cs) has been investigated by X- and Q-band EPR spectroscopy. In order to obtain information about the V(IV) complex formation in the melts, samples rather dilute in V2O5 were quenched from the molten state...... at 450-460degreesC to 0degreesC. EPR spectra of the quenched samples were recorded on samples with alkali to vanadium (M/V) ratios 40, 80 and 160. The spectra show that two V(IV) complexes dominate in the melt regardless of the type of alkali metal ion. In systems with low activity of sulfate...... a paramagnetic V(IV) complex with g(parallel to) = 1.915, g(perpendicular to) = 1,978 and line widths 5-15 Gauss is observed. In systems saturated with M2SO4 the obtained EPR spectra show a paramagnetic complex with the g-tensors g(parallel to) = 1.930, g(perpendicular to) = 1.980 and line widths 20-60 Gauss...

  14. Locations of radical species in black pepper seeds investigated by CW EPR and 9 GHz EPR imaging

    Science.gov (United States)

    Nakagawa, Kouichi; Epel, Boris

    2014-10-01

    In this study, noninvasive 9 GHz electron paramagnetic resonance (EPR)-imaging and continuous wave (CW) EPR were used to investigate the locations of paramagnetic species in black pepper seeds without further irradiation. First, lithium phthalocyanine (LiPC) phantom was used to examine 9 GHz EPR imaging capabilities. The 9 GHz EPR-imager easily resolved the LiPC samples at a distance of ∼2 mm. Then, commercially available black pepper seeds were measured. We observed signatures from three different radical species, which were assigned to stable organic radicals, Fe3+, and Mn2+ complexes. In addition, no EPR spectral change in the seed was observed after it was submerged in distilled H2O for 1 h. The EPR and spectral-spatial EPR imaging results suggested that the three paramagnetic species were mostly located at the seed surface. Fewer radicals were found inside the seed. We demonstrated that the CW EPR and 9 GHz EPR imaging were useful for the determination of the spatial distribution of paramagnetic species in various seeds.

  15. Bismuth germanate as a perspective material for dielectric resonators in EPR spectroscopy

    Science.gov (United States)

    Ivanov, Mikhail Y.; Nadolinny, Vladimir A.; Bagryanskaya, Elena G.; Grishin, Yuriy A.; Fedin, Matvey V.; Veber, Sergey L.

    2016-10-01

    High purity bismuth germanate (Bi4(GeO4)3, BGO) is proposed and implemented as an alternative material for dielectric EPR resonators. A significant improvement of the absolute sensitivity can be readily achieved by substituting the alumina insert (ring) by BGO-made one in commercially available X-band EPR probeheads. Four BGO dielectric inserts of 2, 3, 4 and 5 mm inner diameter (ID) were made for comparison with standard 5 mm inner diameter alumina insert. All inserts were introduced into commercial Bruker EPR resonator ER 4118X-MD-5W1, and their performance was investigated. The Q-values of empty resonators, B1 saturation curves and continuous wave EPR spectra of DPPH (2,2-diphenyl-1-picrylhydrazyl) were measured and analyzed in a temperature range 6-300 K. BGO-made resonators were found superior in several important aspects. The background signals arising from BGO are much weaker compared to those of alumina at B = 0-0.6 T and T = 6-300 K; this is especially useful for measuring weak signals in the half-field region, as well as those near the central field. Moreover, mechanical properties of BGO allow easy fabrication of dielectric bodies having various shapes and sizes; in particular, small BGO resonators (e.g. ID = 2 or 3 mm) strongly enhance sensitivity for small samples due to increase of the filling factor. All these advantages have been also inspected in the pulse mode, proving that higher B1 fields and better filling factors can be achieved, contributing to the overall enhancement of the performance.

  16. EPR: what has it taught us

    Energy Technology Data Exchange (ETDEWEB)

    Stapp, H.P.

    1985-05-01

    This symposium commemorating the fiftieth anniversary of the paper of Einstein, Podolsky, and Rosen is a fitting place to review what that work and its sequels have taught us. Prima facie, the EPR paper appears to have been exceedingly counter-productive for the following reasons: (1) The work was quickly rebutted by Bohr, and this rebuttal was apparently accepted by most workers in the field. (2) Scientists who adopted the position advocated by Bohr have produced, in the intervening fifty years, a marvelous body of useful theory, whereas those following the course suggested by EPR have produced nothing of any certified practical value. (3) It has been shown by Bell that the conclusion reached by EPR is incompatible with their assumptions. Chemists and physicists have recently begun to examine the behavior of quantum mechanical systems that are very small, yet large enough to influence their environment in ways that appreciably modify their own behavior, vis-a-vis the behavior they would have if isolated. Because these systems are neither small enough to be treated as isolated (or as residing in a classically described environment) between preparation and detection, nor large enough to be treated classically, they do not conform to the format demanded by the Copenhagen interpretation. Indeed, the behavior of these systems depends on ontological considerations that were irrelevant in the situations covered by the Copenhagen interpretation, and that were systematically ignored in that interpretation. Scientists now face the task of enlarging the scope of quantum theory to cover these new situations, and comparing the empirical consequences of various ontological assumptions. 17 refs.

  17. Age of the Harrison Street Beast: Electron paramagnetic resonance spectra from tooth enamel

    Energy Technology Data Exchange (ETDEWEB)

    Weeks, R.A. [Vanderbilt Univ., Nashville, TN (United States). Dept. of Mechanical Engineering; Elam, J.M.; Davenport, C. [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Anthropology; Bogard, J.S. [Oak Ridge National Lab., TN (United States). Life Sciences Div.

    1998-04-01

    Workers doing road reconstruction in 1993 in Fort Wayne, Indiana, uncovered remains of a large skeleton and contacted archaeologists for assessment prior to continuing work. The archaeologists excavated the remains which were located in a 19-cm thick layer of blue glay, a pedological deposit which forms from wet, anaerobic environments associated with bogs. This glay layer was located some 2 meters below the current ground level (Davenport 1996). In this paper, the authors present the results of an EPR analysis of tooth enamel (biogenic hydroxyapatite) from the Harrison Street Beast. The objectives of this study are: (1) determine an age for the specimen through EPR analysis of molar tooth enamel; (2) resolve and identify the radiation sensitive EPR spectral components; and (3) develop a provisional model for the creation of radiation-sensitive components in the EPR spectra.

  18. Teaching the EPR paradox at high school?

    Science.gov (United States)

    Pospiech, Gesche

    1999-09-01

    The discovery of quantum mechanics at the beginning of our century led to a revolution of the physical world view. Modern experiments, made possible by new techniques on the border of the classical and the quantum regimes, offer new insights and better understanding of the quantum world and have an impact on new technological development. Therefore it seems important that students at university and in the final years of high school gain an appreciation of the principles of quantum mechanics. A suitable way seems to be through treatment of the EPR gedanken experiment (thought experiment).

  19. Single crystal EPR study of the dinuclear Cu(II) complex [Cu(tda)(phen)](2)·H(2)tda (tda = thiodiacetate, phen = phenanthroline): influence of weak interdimeric magnetic interactions.

    Science.gov (United States)

    Neuman, Nicolás I; Perec, Mireille; González, Pablo J; Passeggi, Mario C G; Rizzi, Alberto C; Brondino, Carlos D

    2010-12-23

    We report powder and single crystal EPR measurements of [Cu(tda)(phen)](2)·H(2)tda (tda = thiodiacetate, phen = phenanthroline) at 9.7 GHz. This compound consists of centrosymmetric copper(II) ion dimers, weakly ferromagnetically exchange-coupled (J = +3.2 cm(-1)), in which the dimeric units are linked by hydrophobic chemical paths involving the phen molecules. EPR revealed that the triplet spectra are collapsed by interdimeric exchange interactions mediated by that chemical path. Analysis and simulation of the single crystal EPR spectra were performed using Anderson's exchange narrowing model, together with statistical arguments. This approach allowed us to interpret the spectra modulated by the interdimeric interactions in situations of weak, intermediate, and strong exchange. We evaluated an interdimeric exchange constant J' = 0.0070(3) cm(-1), indicating that hydrophobic paths can transmit weak exchange interactions between centers at relatively long distances of the order of ∼10 Å.

  20. EPR and optical absorption studies of VO{sup 2+} ion doped magnesium citrate decahydrate single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Dwivedi, Prashant [Department of Physics, Kali Charan Nigam Institute of Technology, Banda 210001, UP (India); Kripal, Ram, E-mail: ram_kripal2001@rediffmail.co, E-mail: prashant_kcnit@rediffmail.co [EPR Laboratory, Department of Physics, University of Allahabad, Allahabad 211002 (India)

    2010-10-15

    An X-band electron paramagnetic resonance (EPR) study of VO{sup 2+} ions in magnesium citrate decahydrate single crystals was done at room temperature. Detailed EPR analysis indicated the presence of two magnetically inequivalent VO{sup 2+} sites. Both the vanadyl complexes were found to take up substitutional positions. The angular variation of the EPR spectra in three planes a{sup *}b, bc and ca{sup *} were used to determine principal g and A tensors. For the two sites the spin Hamiltonian parameters are site I: g{sub x}=2.0976, g{sub y}=1.9093, g{sub z}=1.9505, |A{sub x}|=73, |A{sub y}|=115, |A{sub z}|=237x10{sup -4} cm{sup -1}; site II: g{sub x}=2.0735, g{sub y}=1.9235, g{sub z}=1.9699, |A{sub x}|=72, |A{sub y}|=111, |A{sub z}|=233x10{sup -4} cm{sup -1}. An optical absorption study was also performed at room temperature, and absorption bands were assigned to various transitions. The theoretical band positions were estimated using energy expressions, and good agreement with experimental values was found. By correlating EPR and optical data, different molecular orbital coefficients were evaluated; the nature of the bonding in the crystal is discussed.

  1. EPR and optical absorption studies of paramagnetic molecular ion (VO2+) in Lithium Sodium Acid Phthalate single crystal

    Science.gov (United States)

    Subbulakshmi, N.; Kumar, M. Saravana; Sheela, K. Juliet; Krishnan, S. Radha; Shanmugam, V. M.; Subramanian, P.

    2017-12-01

    Electron Paramagnetic Resonance (EPR) spectroscopic studies of VO2+ ions as paramagnetic impurity in Lithium Sodium Acid Phthalate (LiNaP) single crystal have been done at room temperature on X-Band microwave frequency. The lattice parameter values are obtained for the chosen system from Single crystal X-ray diffraction study. Among the number of hyperfine lines in the EPR spectra only two sets are reported from EPR data. The principal values of g and A tensors are evaluated for the two different VO2+ sites I and II. They possess the crystalline field around the VO2+ as orthorhombic. Site II VO2+ ion is identified as substitutional in place of Na1 location and the other site I is identified as interstitial location. For both sites in LiNaP, VO2+ are identified in octahedral coordination with tetragonal distortion as seen from the spin Hamiltonian parameter values. The ground state of vanadyl ion in the LiNaP single crystal is dxy. Using optical absorption data the octahedral and tetragonal parameters are calculated. By correlating EPR and optical data, the molecular orbital bonding parameters have been discussed for both sites.

  2. Application of EPR spectroscopy to examine free radicals evolution during storage of the thermally sterilized Ungentum ophthalmicum.

    Science.gov (United States)

    Ramos, Paweł; Pilawa, Barbara

    2016-06-24

    Free radicals formed during thermal sterilization of the Ungentum ophthalmicum were examined by an X-band EPR spectroscopy. The influence of storage time (15 min; 1, 2 and 3 days after heating) on free radical properties and concentrations in this sample was determined. Thermal sterilization was done according to the pharmaceutical norms. The first-derivative EPR spectra with g-values about 2 were measured with magnetic modulation of 100 kHz in the range of microwave power 2.2-70 mW. The changes of amplitudes (A) and linewidths (ΔBpp) with microwave powers were evaluated. Free radicals in concentration ∼10(17) spin/g were formed during heating of the tested Ungentum. Free radical concentration decreased with increase in storage time, and reached values ∼10(17) spin/g after 3 days from sterilization. The tested U. ophthalmicum should not be sterilized at a temperature of 160 °C because of the free radicals formation, or it should be used 3 days after heating, when free radicals were considerably quenched. Free radical properties remain unchanged during storage of the Ungentum. The EPR lines of the U. ophthalmicum were homogeneously broadened and their linewidths (ΔBpp) increased with increase in microwave power. EPR spectroscopy is useful to examine free radicals to optimize sterilization process and storage conditions of ophthalmologic samples.

  3. EPR and optical absorption studies of Cu{sup 2+} ions doped magnesium citrate decahydrate single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Dwivedi, Prashant, E-mail: prashant_kcnit@rediffmail.co [Department of Physics, Kali Charan Nigam Institute of Technology, Banda (U.P.) 210001 (India); Kripal, Ram, E-mail: ram_kripal2001@rediffmail.co [EPR Laboratory, Department of Physics, University of Allahabad, 22/5A Katra Road, Allahabad, 211002 (India); Misra, Madan Gopal [EPR Laboratory, Department of Physics, University of Allahabad, 22/5A Katra Road, Allahabad, 211002 (India)

    2010-06-04

    X-band electron paramagnetic resonance (EPR) studies of Cu{sup 2+} ions in magnesium citrate decahydrate single crystals are done at room temperature. Detailed EPR analysis indicates the presence of only one Cu{sup 2+} site. Cu{sup 2+} is found to take up substitutional position at Mg site. The angular variation of the EPR spectra in three planes a*b, bc and ca* are used to determine principal g and A tensors. The spin Hamiltonian parameters are: g{sub x} = 2.0346, g{sub y} = 2.1400, g{sub z} = 2.3874, A{sub x} = 57, A{sub y} = 76, A{sub z} = 99 (x10{sup -4}) cm{sup -1}. The optical absorption study is also carried out at room temperature and absorption bands are assigned to various transitions. The theoretical band positions are estimated using energy expressions and a good agreement is obtained with the experimental values. By correlating EPR and optical data, different molecular orbital coefficients are evaluated and the nature of bonding in the complex is discussed.

  4. EPR study of free radicals in non- and gamma-irradiated nutritive supplements containing anthocyanins concentrate from lyophilized red wine

    Science.gov (United States)

    Mladenova, Ralitsa B.; Firzov, Cyril; Yordanov, Nicola D.

    2010-09-01

    Nutritive supplements Enoviton, Enoviton C and Enoviton CE containing standardized anthocyanins from lyophilized red wine, vitamins (some of them) and excipients were investigated by EPR spectrometry before and after gamma-irradiation. Non-irradiated samples exhibit one singlet line with g=2.0039±0.0002, most probably due to free radicals from anthocyanins. After irradiation with 10 kGy gamma-rays, tablets of Еnoviton, Еnoviton С and Еnoviton СЕ, all exhibit complex EPR signals centered at a g-value of g=2.0034. The EPR spectrum of irradiated Enoviton is different from that of Еnoviton С or Еnoviton СЕ due to the overlap of the spectra of microcrystalline cellulose and the background singlet spectrum present in all tablets with the EPR resonance due to irradiated ascorbic acid (in Еnoviton С and Еnoviton СЕ). Gamma-induced free radicals exhibit long time stability—for a six months period the intensity of central peak decrease with 30-40%.

  5. EPR study of free radicals in non- and gamma-irradiated nutritive supplements containing anthocyanins concentrate from lyophilized red wine

    Energy Technology Data Exchange (ETDEWEB)

    Mladenova, Ralitsa B., E-mail: ralitsa@ic.bas.b [Institute of Catalysis, Bulgarian Academy of Sciences, 1113 Sofia (Bulgaria); Firzov, Cyril [Institute of Cryobiology and Food Technology, 1162 Sofia (Bulgaria); Yordanov, Nicola D. [Institute of Catalysis, Bulgarian Academy of Sciences, 1113 Sofia (Bulgaria)

    2010-09-15

    Nutritive supplements Enoviton, Enoviton C and Enoviton CE containing standardized anthocyanins from lyophilized red wine, vitamins (some of them) and excipients were investigated by EPR spectrometry before and after gamma-irradiation. Non-irradiated samples exhibit one singlet line with g=2.0039{+-}0.0002, most probably due to free radicals from anthocyanins. After irradiation with 10 kGy gamma-rays, tablets of Enoviton, Enoviton S and Enoviton SE, all exhibit complex EPR signals centered at a g-value of g=2.0034. The EPR spectrum of irradiated Enoviton is different from that of Enoviton S or Enoviton SE due to the overlap of the spectra of microcrystalline cellulose and the background singlet spectrum present in all tablets with the EPR resonance due to irradiated ascorbic acid (in Enoviton S and Enoviton SE). Gamma-induced free radicals exhibit long time stability-for a six months period the intensity of central peak decrease with 30-40%.

  6. High resolution EPR applications to metalloenzymes and metals in medicine

    CERN Document Server

    Berliner, Lawrence

    2009-01-01

    EPR spectroscopy has an important role in the geometric structural characterization of the redox cofactors in metalloproteins and their electronic structure, as this is crucial for their reactivity. This title covers high-resolution EPR methods, iron proteins, nickel and copper enzymes, and metals in medicine.

  7. EPR and NMR spectroscopy on spin-labeled proteins

    NARCIS (Netherlands)

    Finiguerra, Michelina Giuseppina

    2011-01-01

    Spin labeling and electron paramagnetic resonance (EPR) have been employed to study structure and dynamics of proteins. The surface polarity of four single cysteine mutants of the Zn-azurin in frozen solution were studied using 275 GHz EPR (J-band), with the advantage compared to 9 GHz (X-band) and

  8. Use of the Frank sequence in pulsed EPR

    DEFF Research Database (Denmark)

    Tseitlin, Mark; Quine, Richard W.; Eaton, Sandra S.

    2011-01-01

    The Frank polyphase sequence has been applied to pulsed EPR of triarylmethyl radicals at 256MHz (9.1mT magnetic field), using 256 phase pulses. In EPR, as in NMR, use of a Frank sequence of phase steps permits pulsed FID signal acquisition with very low power microwave/RF pulses (ca. 1.5m......W in the application reported here) relative to standard pulsed EPR. A 0.2mM aqueous solution of a triarylmethyl radical was studied using a 16mm diameter cross-loop resonator to isolate the EPR signal detection system from the incident pulses. Keyword: Correlation spectroscopy,Multi-pulse EPR,Low power pulses...

  9. Applying the conventional moving average filter for estimation of low radiation doses using EPR spectroscopy: Benefits and drawbacks

    Science.gov (United States)

    Maghraby, Ahmed M.

    2014-02-01

    Alanine/EPR is the most common dosimetry system for high radiation doses because of its high stability and wide linear response, however, use of alanine in most of medical applications still require special sophisticated methodologies and techniques in order to extend alanine detection limit to low levels of radiation doses. One of these techniques is the use of digital processing of acquired alanine spectra for enhancing useful components in spectra while useless features are suppressed. Simple moving average filter (MA) impacts on alanine EPR spectra have been studied in terms of peak-to-peak height, peak-to-peak line width, and associated uncertainty. Three types of the used filter were investigated: upward MA, central MA, and downward MA filters, effects of each on the peak position for different values of filter width were studied. It was found that MA filter always lead to the reduction in signal intensity and the increase of line width of the central peak of alanine spectrum. Peak position also changes in cases of the upward MA and downward MA filters while no significant changes were observed in the case of central MA. Uncertainties associated to the averaging process were evaluated and plotted versus the filter width resulting in a linear relationship. Filter width value should be carefully selected in order to avoid probable distortion in processed spectra while gaining less noisy spectra with less associated uncertainties.

  10. XRD and EPR structural investigation of some zinc borate glasses doped with iron ions

    Science.gov (United States)

    Stefan, Razvan; Pascuta, Petru; Popa, Adriana; Raita, Oana; Indrea, Emil; Culea, Eugen

    2012-02-01

    Glasses in the system xFe2O3·(100-x) [45ZnO·55B2O3] (0≤x≤10 mol%) have been prepared by melting at 1200 °C and rapidly cooling at room temperature. The obtained samples were submitted to an additional thermal treatment at 570 °C for 12 h in order to relax the glass structure as well as to improve the local order. The as cast and heat treated samples were investigated using X-ray diffraction (XRD) and electron paramagnetic resonance (EPR) measurements. The XRD patterns of all the studied samples show their vitreous nature. Structural modifications occurring in the heat treated samples compared to the untreated ones have been pointed out. EPR spectra of untreated and heat treated samples revealed resonance absorptions centered at g≈2.0, g≈4.3 and g≈6.4. The compositional variation of the line intensity and linewidth of the absorptions from g≈4.3 and g≈2.0 have been interpreted in terms of the variation in the concentration of the Fe3+ ions and the interaction between the iron ions. The EPR spectra of the untreated samples containing 5 mol% Fe2O3 have been studied at different temperatures (110-290 K). The line intensity of the resonance signals decreases with increase in temperature whereas the linewidth is found to be independent of temperature. It was also found that the temperature variation of reciprocal line intensity obeys the Boltzmann law.

  11. Effect of VO2+ ions on the EPR and optical absorption investigations of lithium sulphate monohydrate single crystals for non linear optical applications

    Science.gov (United States)

    Juliet sheela, K.; Radha Krishnan, S.; Shanmugam, V. M.; Subramanian, P.

    2017-09-01

    Electron paramagnetic resonance (EPR) and optical absorption studies of VO2+ ions in Lithium Sulphate Monohydrate (LSMH) single crystal are carried out at room temperature. Single crystal rotations in each of the three mutually orthogonal crystalline planes, ac, ab, cb indicate three different vanadyl complexes. Three VO2+ ions of EPR spectra indicate among them, that two of them have (the intense two) entered the lattice substitutionally and the third one occupies the interstitial position. From the angular variation, the spin Hamiltonian parameters are evaluated. From the optical absorption spectrum containing four selected bands and EPR data, various bonding parameters are determined and the nature of bonding in the crystal is discussed. Also Second Harmonic Generation (SHG) studies are carried out to confirm the Non Linear Optical (NLO) properties of the given material.

  12. Effects of Mn and Fe impurities on the TL and EPR properties of artificial spodumene polycrystals under irradiation

    Science.gov (United States)

    Souza, S. O.; Ferraz, G. M.; Watanabe, S.

    2004-06-01

    It is known that natural spodumene crystals LiAlSi 2O 6 can vary in color due to contents of impurities. With the aim to study how the Fe and Mn impurities influence their thermally stimulated luminescence (TL) and electron paramagnetic resonance (EPR) spectra, we produced synthetic spodumene polycrystals with controlled amount of Fe and Mn. A mixture of SiO 2, Al 2O 3 and Li 2CO 3 was melted and cooled slowly to obtain a pure polycrystal, while a small amount of Fe or Mn has been added during this process. This way we produced the polycrystals which quality are fully adequate for present investigation, by low cost and quickly (comparing to sol-gel technique). We performed then the TL measurements in the temperature range from 0 to 500 °C, as well as the EPR at room temperature. Analyzing the TL glow curves and the EPR spectra, we concluded that the Fe "kills" the thermoluminescent centers in spodumene, while the Mn improves its TL response.

  13. Effects of Mn and Fe impurities on the TL and EPR properties of artificial spodumene polycrystals under irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Souza, S.O. E-mail: osusana@if.usp.br; Ferraz, G.M.; Watanabe, S

    2004-06-01

    It is known that natural spodumene crystals LiAlSi{sub 2}O{sub 6} can vary in color due to contents of impurities. With the aim to study how the Fe and Mn impurities influence their thermally stimulated luminescence (TL) and electron paramagnetic resonance (EPR) spectra, we produced synthetic spodumene polycrystals with controlled amount of Fe and Mn. A mixture of SiO{sub 2}, Al{sub 2}O{sub 3} and Li{sub 2}CO{sub 3} was melted and cooled slowly to obtain a pure polycrystal, while a small amount of Fe or Mn has been added during this process. This way we produced the polycrystals which quality are fully adequate for present investigation, by low cost and quickly (comparing to sol-gel technique). We performed then the TL measurements in the temperature range from 0 to 500 deg. C, as well as the EPR at room temperature. Analyzing the TL glow curves and the EPR spectra, we concluded that the Fe 'kills' the thermoluminescent centers in spodumene, while the Mn improves its TL response.

  14. Effect of UV irradiation on free radicals in synthetic melanin and melanin biopolymer from Sepia officinalis – EPR examination

    Directory of Open Access Journals (Sweden)

    Zdybel Magdalena

    2015-07-01

    Full Text Available Free radicals in synthetic melanin and melanin from Sepia officinalis were studied by electron paramagnetic resonance (EPR spectroscopy. The effect of time of ultraviolet (UV irradiation on free radicals in these melanins was tested. The samples were exposed to UV during 15, 30, and 60 minutes. EPR spectra were measured with microwaves from an X-band (9.3 GHz in the range of microwave power of 2.2–70 mW. The performed EPR examinations indicate that high concentrations (~1021–1022 spin/g of o-semiquinone free radicals with g factors of 2.0039–2.0045 exist in all the tested samples. For nonirradiated samples, free radical concentration was higher in natural melanin than in synthetic melanin. UV irradiation caused the increase of free radical concentrations in synthetic melanin samples and this effect depends on the time of irradiation. The largest free radical formation in the both melanins was obtained for 60 min of UV irradiation. Free radical concentrations after the UV irradiation of melanins during 30 min were lower than during irradiation by 15 min, and probably this effect was the result of recombination of the radiatively formed free radicals. EPR lines of the tested samples broadened with increasing microwave power, so these lines were homogeneously broadened. The two types of melanins differed in the time of spin-lattice relaxation processes. Slower spin-lattice relaxation processes exist in melanin from Sepia officinalis than in synthetic melanin. UV irradiation did not change the time of spin-lattice relaxation processes in the tested melanins. The performed studies confirmed the usefulness of EPR spectroscopy in cosmetology and medicine.

  15. Kinetics of elimination and distribution in blood and liver of biocompatible ferrofluids based on Fe{sub 3}O{sub 4} nanoparticles: An EPR and XRF study

    Energy Technology Data Exchange (ETDEWEB)

    Gamarra, L.F. [Instituto de Ensino e Pesquisa, Hospital Israelita Albert Einstein, Sao Paulo 05651-901 (Brazil); Instituto de Fisica, Universidade de Sao Paulo, Sao Paulo 05315-970 (Brazil)], E-mail: lgamarra@if.usp.br; Pontuschka, W.M. [Instituto de Fisica, Universidade de Sao Paulo, Sao Paulo 05315-970 (Brazil); Amaro, E. [Instituto de Ensino e Pesquisa, Hospital Israelita Albert Einstein, Sao Paulo 05651-901 (Brazil); Instituto de Radiologia, Faculdade de Medicina, Universidade de Sao Paulo, Sao Paulo 05403-001 (Brazil); Costa-Filho, A.J. [Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo, Sao Carlos 13560-970 (Brazil); Brito, G.E.S. [Instituto de Fisica, Universidade de Sao Paulo, Sao Paulo 05315-970 (Brazil); Vieira, E.D. [Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo, Sao Carlos 13560-970 (Brazil); Carneiro, S.M. [Laboratorio de Biologia Celular, Instituto Butantan, Sao Paulo 05503-900 (Brazil); Escriba, D.M. [Instituto de Fisica, Universidade de Sao Paulo, Sao Paulo 05315-970 (Brazil); Falleiros, A.M.F. [Centro de Ciencias Biologicas, Universidade Estadual de Londrina 86051-990 (Brazil); Salvador, V.L. [Centro de aplicacoes e Lasers, IPEN, Sao Paulo 05508-000 (Brazil)

    2008-05-01

    In this study, we evaluated the biodistribution and the elimination kinetics of a biocompatible magnetic fluid, Endorem{sup TM}, based on dextran-coated Fe{sub 3}O{sub 4} nanoparticles endovenously injected into Winstar rats. The iron content in blood and liver samples was recorded using electron paramagnetic resonance (EPR) and X-ray fluorescence (XRF) techniques. The EPR line intensity at g = 2.1 was found to be proportional to the concentration of magnetic nanoparticles and the best temperature for spectra acquisition was 298 K. Both EPR and XRF analysis indicated that the maximum concentration of iron in the liver occurred 95 min after the ferrofluid administration. The half-life of the magnetic nanoparticles (MNP) in the blood was (11.6 {+-} 0.6) min measured by EPR and (12.6 {+-} 0.6) min determined by XRF. These results indicate that both EPR and XRF are very useful and appropriate techniques for the study of kinetics of ferrofluid elimination and biodistribution after its administration into the organism.

  16. EPR paradox, quantum nonlocality and physical reality

    Science.gov (United States)

    Kupczynski, M.

    2016-03-01

    Eighty years ago Einstein, Podolsky and Rosen demonstrated that instantaneous reduction of wave function, believed to describe completely a pair of entangled physical systems, led to EPR paradox. The paradox disappears in statistical interpretation of quantum mechanics (QM) according to which a wave function describes only an ensemble of identically prepared physical systems. QM predicts strong correlations between outcomes of measurements performed on different members of EPR pairs in far-away locations. Searching for an intuitive explanation of these correlations John Bell analysed so called local realistic hidden variable models and proved that correlations consistent with these models satisfy Bell inequalities which are violated by some predictions of QM and by experimental data. Several different local models were constructed and inequalities proven. Some eminent physicists concluded that Nature is definitely nonlocal and that it is acting according to a law of nonlocal randomness. According to these law perfectly random, but strongly correlated events, can be produced at the same time in far away locations and a local and causal explanation of their occurrence cannot be given. We strongly disagree with this conclusion and we prove the contrary by analysing in detail some influential finite sample proofs of Bell and CHSH inequalities and so called Quantum Randi Challenges. We also show how one can win so called Bell's game without violating locality of Nature. Nonlocal randomness is inconsistent with local quantum field theory, with standard model in elementary particle physics and with causal laws and adaptive dynamics prevailing in the surrounding us world. The experimental violation of Bell-type inequalities does not prove the nonlocality of Nature but it only confirms a contextual character of quantum observables and gives a strong argument against counterfactual definiteness and against a point of view according to which experimental outcomes are produced

  17. Stability of X-band EPR signals from fingernails under vacuum storage

    Science.gov (United States)

    Sholom, Sergey; McKeever, Stephen

    2017-12-01

    EPR signals of different origin have been tested in human finger- and toe-nails with an X-band EPR technique for different conditions of nail storage. Three different signals were identified, namely a singlet at g = 2.005, a doublet at g = 2.004 with a splitting constant A = 1.8 mT, and an anisotropic signal at g1 = 2.057, g2 = 2.029 and g3 = 2.003 (positions of local extrema). All EPR spectra from nails, whether irradiated or mechanically stressed, can be described as a superposition of these three signals. The singlet is responsible for the background signal (BG), is the main component of radiation-induced signals (RIS) for low doses (100 Gy or lower) and also contributes to mechanically-induced signals (MIS). This signal is quite stable under vacuum storage, but can be reduced almost to zero by soaking in water. The behavior of this signal under ambient conditions depends on many factors, such as absorbed dose, air humidity, and ambient illumination intensity at the place of storage. The doublet arises after exposure of nails to high (few hundreds Gy and higher) doses or after mechanical stress of samples. Depending on how this signal was obtained, it may have bulk or surface locations with quite different stability properties. The surface-located doublet (generated on the nail edges during cutting or clipping) is quite unstable and decays over about two hours for samples stored at ambient conditions and within several seconds for samples immersed in water. The volume-distributed doublet decays within a few minutes in water, several hours at ambient conditions and several days in vacuum. The anisotropic signal may also be generated by both ionizing radiation and mechanical stress; this signal is quite stable in vacuum and decays over several days at ambient conditions or a few tens of minutes in water. The reference lines for the above-described three EPR signals were obtained and a procedure of spectra deconvolution was developed and tested on samples exposed

  18. New Amino-Acid-Based β-Phosphorylated Nitroxides for Probing Acidic pH in Biological Systems by EPR Spectroscopy.

    Science.gov (United States)

    Thétiot-Laurent, Sophie; Gosset, Gaëlle; Clément, Jean-Louis; Cassien, Mathieu; Mercier, Anne; Siri, Didier; Gaudel-Siri, Anouk; Rockenbauer, Antal; Culcasi, Marcel; Pietri, Sylvia

    2017-02-01

    There is increasing interest in measuring pH in biological samples by using nitroxides with pH-dependent electron paramagnetic resonance (EPR) spectra. Aiming to improve the spectral sensitivity (ΔaX ) of these probes (i.e., the difference between the EPR hyperfine splitting (hfs) in their protonated and unprotonated forms), we characterized a series of novel linear α-carboxy, α'-diethoxyphosphoryl nitroxides constructed on an amino acid core and featuring an (α or α')-C-H bond. In buffer, the three main hfs (aN , aH , and aP ) of their EPR spectra vary reversibly with pH and, from aP or aH titration curves, a two- to fourfold increase in sensitivity was achieved compared to reference imidazoline or imidazolidine nitroxides. The crystallized carboxylate 10 b (pKa ≈3.6), which demonstrated low cytotoxicity and good resistance to bioreduction, was applied to probe stomach acidity in rats. The results pave the way to a novel generation of highly sensitive EPR pH markers. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. EPR spectroscopy of a family of Cr(III) 7M(II) (M = Cd, Zn, Mn, Ni) "wheels": studies of isostructural compounds with different spin ground states.

    Science.gov (United States)

    Piligkos, Stergios; Weihe, Høgni; Bill, Eckhard; Neese, Frank; El Mkami, Hassane; Smith, Graham M; Collison, David; Rajaraman, Gopalan; Timco, Grigore A; Winpenny, Richard E P; McInnes, Eric J L

    2009-01-01

    Spinning wheels: The presented highly resolved multifrequency continuous wave EPR spectra (e.g., see figure) of the heterooctametalic "wheels" Cr(7)M provide rare examples of high nuclearity polymetallic systems where detailed information on the spin-Hamiltonian parameters of the ground and excited spin states is observed.We present highly resolved multifrequency (X-, K-, Q- and W-band) continous wave EPR spectra of the heterooctametalic "wheels", [(CH(3))(2)NH(2)][Cr(III) (7)M(II)F(8)((CH(3))(3)CCOO)(16)], hereafter Cr(7)M, where M=Cd, Zn, Mn, and Ni. These experimental spectra provide rare examples of high nuclearity polymetallic systems where detailed information on the spin-Hamiltonian parameters of the ground and excited spin states is observed. We interpret the EPR spectra by use of restricted size effective subspaces obtained by the rigorous solution of spin-Hamiltonians of dimension up to 10(5) by use of the Davidson algorithm. We show that transferability of spin-Hamiltonian parameters across complexes of the Cr(7)M family is possible and that the spin-Hamiltonian parameters of Cr(7)M do not have sharply defined values, but are rather distributed around a mean value.

  20. Reconfiguring Cooperative Work by Visualizing EPR on Large Projected Screens

    DEFF Research Database (Denmark)

    Simonsen, Jesper

    Simonsen, J. (2006): Reconfiguring Cooperative Work by Visualizing EPR on Large Projected Screens, Paper presented at the PDC 2006 workshop on: Reconfiguring Healthcare: Issues in Computer Supported Cooperative Work in Healthcare Environments. Participatory Design Conference, Trento, Italy, August...

  1. Detection of nanodiamonds in biological samples by EPR spectrometry.

    Science.gov (United States)

    Inzhevatkin, E V; Baron, A V; Maksimov, N G; Volkova, M B; Puzyr, A P; Bondar, V S

    2017-11-01

    In model experiments in vitro, the applicability of the EPR spectrometry method for the detection of modified nanodiamonds (MNDs) in blood and homogenates of mouse organs has been established. A characteristic signal (g = 2.003, ΔH ≈ 10 G) is observed in the samples of biomaterials containing MNDs, the intensity of which increases linearly with the concentration of nanoparticles in the range of 1.6-200 μg MNDs per 1 mL of the sample. The EPR method in biomaterials reveals the presence of intrinsic paramagnetic centers, signals from which are superimposed on the signal from the MNDs. However, the intensity of these signals is small, which makes it possible to register the MNDs using EPR spectrometry with the necessary accuracy. The data obtained open up the prospects of using the EPR method for studies of the interorgan distribution, accumulation, and elimination of MNDs during their intravenous injection into experimental animals.

  2. EPR-based distance measurements at ambient temperature

    Science.gov (United States)

    Krumkacheva, Olesya; Bagryanskaya, Elena

    2017-07-01

    Pulsed dipolar (PD) EPR spectroscopy is a powerful technique allowing for distance measurements between spin labels in the range of 2.5-10.0 nm. It was proposed more than 30 years ago, and nowadays is widely used in biophysics and materials science. Until recently, PD EPR experiments were limited to cryogenic temperatures (T biomolecules, the influence of a linker between the spin probe and biomolecule, and future opportunities.

  3. Lorentz symmetry breaking effects on relativistic EPR correlations

    Energy Technology Data Exchange (ETDEWEB)

    Belich, H. [Universidade Federal do Espirito Santo, Departamento de Fisica e Quimica, Vitoria, ES (Brazil); Furtado, C.; Bakke, K. [Universidade Federal da Paraiba, Departamento de Fisica, Caixa Postal 5008, Joao Pessoa, PB (Brazil)

    2015-09-15

    Lorentz symmetry breaking effects on relativistic EPR (Einstein-Podolsky-Rosen) correlations are discussed. From the modified Maxwell theory coupled to gravity, we establish a possible scenario of the Lorentz symmetry violation and write an effective metric for the Minkowski spacetime. Then we obtain the Wigner rotation angle via the Fermi-Walker transport of spinors and consider the WKB (Wentzel-Kramers-Brillouin) approximation in order to study the influence of Lorentz symmetry breaking effects on the relativistic EPR correlations. (orig.)

  4. ER=EPR, GHZ, and the Consistency of Quantum Measurements

    OpenAIRE

    Susskind, Leonard

    2014-01-01

    This paper illustrates various aspects of the ER=EPR conjecture.It begins with a brief heuristic argument, using the Ryu-Takayanagi correspondence, for why entanglement between black holes implies the existence of Einstein-Rosen bridges. The main part of the paper addresses a fundamental question: Is ER=EPR consistent with the standard postulates of quantum mechanics? Naively it seems to lead to an inconsistency between observations made on entangled systems by different observers. The resolu...

  5. EPR and NMR studies of amorphous aluminum borates

    NARCIS (Netherlands)

    Simon, S.; Pol, A. van der; Reijerse, E.J.; Kentgens, A.P.M.; Moorsel, G.J.M.P. van; Boer, E. de

    1994-01-01

    Amorphous aluminium borates, Al2(1–x)B2xO3 with O [less-than-or-eq]x[less-than-or-eq] 0.5, prepared from mixtures of aluminium nitrate, boric acid and glycerol, have been studied by EPR and 27Al MASNMR as a function of composition and heat-treatment temperature (Tt[less-than-or-eq] 860 °C). EPR

  6. SPIDYAN, a MATLAB library for simulating pulse EPR experiments with arbitrary waveform excitation

    Science.gov (United States)

    Pribitzer, Stephan; Doll, Andrin; Jeschke, Gunnar

    2016-02-01

    Frequency-swept chirp pulses, created with arbitrary waveform generators (AWGs), can achieve inversion over a range of several hundreds of MHz. Such passage pulses provide defined flip angles and increase sensitivity. The fact that spectra are not excited at once, but single transitions are passed one after another, can cause new effects in established pulse EPR sequences. We developed a MATLAB library for simulation of pulse EPR, which is especially suited for modeling spin dynamics in ultra-wideband (UWB) EPR experiments, but can also be used for other experiments and NMR. At present the command line controlled SPin DYnamics ANalysis (SPIDYAN) package supports one-spin and two-spin systems with arbitrary spin quantum numbers. By providing the program with appropriate spin operators and Hamiltonian matrices any spin system is accessible, with limits set only by available memory and computation time. Any pulse sequence using rectangular and linearly or variable-rate frequency-swept chirp pulses, including phase cycling can be quickly created. To keep track of spin evolution the user can choose from a vast variety of detection operators, including transition selective operators. If relaxation effects can be neglected, the program solves the Liouville-von Neumann equation and propagates spin density matrices. In the other cases SPIDYAN uses the quantum mechanical master equation and Liouvillians for propagation. In order to consider the resonator response function, which on the scale of UWB excitation limits bandwidth, the program includes a simple RLC circuit model. Another subroutine can compute waveforms that, for a given resonator, maintain a constant critical adiabaticity factor over the excitation band. Computational efficiency is enhanced by precomputing propagator lookup tables for the whole set of AWG output levels. The features of the software library are discussed and demonstrated with spin-echo and population transfer simulations.

  7. SPIDYAN, a MATLAB library for simulating pulse EPR experiments with arbitrary waveform excitation.

    Science.gov (United States)

    Pribitzer, Stephan; Doll, Andrin; Jeschke, Gunnar

    2016-02-01

    Frequency-swept chirp pulses, created with arbitrary waveform generators (AWGs), can achieve inversion over a range of several hundreds of MHz. Such passage pulses provide defined flip angles and increase sensitivity. The fact that spectra are not excited at once, but single transitions are passed one after another, can cause new effects in established pulse EPR sequences. We developed a MATLAB library for simulation of pulse EPR, which is especially suited for modeling spin dynamics in ultra-wideband (UWB) EPR experiments, but can also be used for other experiments and NMR. At present the command line controlled SPin DYnamics ANalysis (SPIDYAN) package supports one-spin and two-spin systems with arbitrary spin quantum numbers. By providing the program with appropriate spin operators and Hamiltonian matrices any spin system is accessible, with limits set only by available memory and computation time. Any pulse sequence using rectangular and linearly or variable-rate frequency-swept chirp pulses, including phase cycling can be quickly created. To keep track of spin evolution the user can choose from a vast variety of detection operators, including transition selective operators. If relaxation effects can be neglected, the program solves the Liouville-von Neumann equation and propagates spin density matrices. In the other cases SPIDYAN uses the quantum mechanical master equation and Liouvillians for propagation. In order to consider the resonator response function, which on the scale of UWB excitation limits bandwidth, the program includes a simple RLC circuit model. Another subroutine can compute waveforms that, for a given resonator, maintain a constant critical adiabaticity factor over the excitation band. Computational efficiency is enhanced by precomputing propagator lookup tables for the whole set of AWG output levels. The features of the software library are discussed and demonstrated with spin-echo and population transfer simulations. Copyright © 2016

  8. {sup 13}C NMR and EPR spectroscopic evaluation of oil shale mined soil recuperation

    Energy Technology Data Exchange (ETDEWEB)

    Santos, J.V. dos, E-mail: mangrich@ufpr.br [Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil); Mangrich, A.S. [Instituto Nacional de Ciencia e Tecnologia: Energia e Ambiente, Salvador, BA (Brazil); Pereira, B.F. [EMBRAPA Clima Temperado, Pelotas, RS (Brazil); Pillon, C.N. [EMBRAPA Clima Temperado, Pelotas, RS (Brazil). Estacao Experimental Cascata; Novotny, E.H. [EMBRAPA Solos, Rio de Janeiro, RJ (Brazil); Bonagamba, T.J. [Universidade de Sao Paulo (USP), Sao Carlos, SP (Brazil). Instituto de Fisica; Abbt-Braun, G.; Frimmel, F.H. [Engler-Bunte-Institut, Universitaet Karlsruhe, TH (Germany)

    2013-02-15

    In this work, native forest soil (NFS) organic matter (SOM) sample and SOM samples from a neighboring forest soil area of an oil shale mine which is being rehabilitated for thirty years (RFS) were analyzed. X-band electron paramagnetic resonance (EPR) and solid-state {sup 13}C nuclear magnetic resonance (NMR) spectroscopies were used to evaluate the soil reclamation of the Brazilian oil shale mining process. Two-dimensional heterospectral correlation studies of the results obtained from EPRand {sup 13}C NMR were used to obtain information about SOM structures and their interactions with residual paramagnetic metal ion. The signal of the residual metallic oxycation, VO{sup 2+} correlated positively with uronic acid-type hydrophilic organic structures, determined from the {sup 13}C NMR spectra, and correlated negatively with the organic free radical (OFR) signal associated with oxygen atoms (g = 2.0042). The hydrophobic aromatic structures correlate positively with the EPR OFR signal associated with carbon atoms (g = 2.0022). The data from the two spectroscopic magnetic techniques show that the used recuperation process is effective. (author)

  9. Radical Intermediates in Photoinduced Reactions on TiO2 (An EPR Spin Trapping Study

    Directory of Open Access Journals (Sweden)

    Dana Dvoranová

    2014-10-01

    Full Text Available The radical intermediates formed upon UVA irradiation of titanium dioxide suspensions in aqueous and non-aqueous environments were investigated applying the EPR spin trapping technique. The results showed that the generation of reactive species and their consecutive reactions are influenced by the solvent properties (e.g., polarity, solubility of molecular oxygen, rate constant for the reaction of hydroxyl radicals with the solvent. The formation of hydroxyl radicals, evidenced as the corresponding spin-adducts, dominated in the irradiated TiO2 aqueous suspensions. The addition of 17O-enriched water caused changes in the EPR spectra reflecting the interaction of an unpaired electron with the 17O nucleus. The photoexcitation of TiO2 in non-aqueous solvents (dimethylsulfoxide, acetonitrile, methanol and ethanol in the presence of 5,5-dimethyl-1-pyrroline N-oxide spin trap displayed a stabilization of the superoxide radical anions generated via electron transfer reaction to molecular oxygen, and various oxygen- and carbon-centered radicals from the solvents were generated. The character and origin of the carbon-centered spin-adducts was confirmed using nitroso spin trapping agents.

  10. The origin of split EPR signals in the Ca2+-depleted photosystem II.

    Science.gov (United States)

    Mino, Hiroyuki; Itoh, Shigeru

    2005-06-01

    A light-driven reaction model for the Ca2+-depleted Photosystem (PS) II is proposed to explain the split signal observed in electron paramagnetic resonance (EPR) spectra based on a comparison of EPR assignments with recent x-ray structural data. The split signal has a splitting linewidth of 160 G at around g = 2 and is seen upon illumination of the Ca2+-depleted PS II in the S2 state associated with complete or partial disappearance of the S2 state multiline signal. Another g=2 broad ESR signal with a 110 G linewidth was produced by 245 K illumination for a short period in the Ca2+-depleted PS II in S1 state. At the same time a normal YZ . radical signal was also efficiently trapped. The g=2 broad signal is attributed to an intermediate S1X. state in equilibrium with the trapped YZ . radical. Comparison with x-ray structural data suggests that one of the split signals (doublet signal) is attributable to interaction between His 190 and the YZ . radical, and other signals is attributable to interaction between His 337 and the manganese cluster, providing further clues as to the mechanism of water oxidation in photosynthetic oxygen evolution.

  11. Synthesis, XRD, TEM, EPR, and Optical Absorption Spectral Studies of CuZnO2 Nanocompound

    Directory of Open Access Journals (Sweden)

    T. Ravindra Reddy

    2014-01-01

    Full Text Available Synthesis of nano CuZnO2 compound is carried out by thermal decomposition method. The crystalline phase of the material is characterized by XRD. The calculated unit cell constants are a=3.1 Å and c=3.4786 Å and are of tetragonal structure. The unit cell constants are different from wurtzite (hexagonal which indicate that a nanocompound is formed. Further TEM images reveal that the metal ion is in tetragonal structure with oxygen ligands. The prepared CuZnO2 is then characterized for crystallite size analysis by employing transmission electron microscopy (TEM. The size is found to be 100 nm. Uniform bright rings are noticed in the TEM picture suggesting that the nanocrystals have preferential instead of random orientations. The selected-area electron diffraction (SAED pattern clearly indicates the formation of CuO-ZnO nanocompound. The nature of bonding is studied by electron paramagnetic resonance (EPR. The covalency character is about 0.74 and thus the compound is electrically less conductive. Optical absorption spectral studies suggest that Cu(II is placed in tetragonal elongation crystal field. The spin-orbit coupling constant, λ, is calculated using the EPR and optical absorption spectral results suggest some covalent bond between metal and ligand. Near infrared (NIR spectra are due to hydroxyl and water fundamentals.

  12. Growth, optical and EPR studies of {sup 151}Eu{sup 2+}:YAG single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Petrosyan, A.G., E-mail: pet@ipr.sci.am [Institute for Physical Research, National Academy of Sciences, Ashtarak, 0203 (Armenia); Asatryan, H.R. [Ioffe Physical-Technical Institute, Politekhnicheskaya ul. 26, St. Petersburg, 194021 (Russian Federation); Hovhannesyan, K.L.; Derdzyan, M.V. [Institute for Physical Research, National Academy of Sciences, Ashtarak, 0203 (Armenia); Feofilov, S.P. [Ioffe Physical-Technical Institute, Politekhnicheskaya ul. 26, St. Petersburg, 194021 (Russian Federation); Eganyan, A.V.; Sargsyan, R.S. [Institute for Physical Research, National Academy of Sciences, Ashtarak, 0203 (Armenia)

    2017-01-01

    Single crystals of {sup 151}Eu:YAG were grown by the vertical Bridgman method using Eu{sub 2}O{sub 3} with isotopic enrichment of {sup 151}Eu of 97.5%. Additional Hf{sup 4+}or Si{sup 4+} ions were introduced to favor a high concentrations of Eu{sup 2+}. As compared to Eu:YAG with natural isotope composition, the EPR spectra of YAG doped with {sup 151}Eu isotope show a reduced number of hyperfine structure components and a well-resolved structure of a bigger number of electronic transitions. Optical properties of obtained crystals and the effects of heat treatments under oxidizing and reducing conditions are reported. Based on the analysis of Eu{sup 3+} distribution in oxidized Eu,Hf:YAG, in comparison to that in Eu:YAG, the concentration of Eu{sup 2+} in as-grown Eu,Hf:YAG is determined. - Highlights: • YAG:Eu,Hf single crystals containing only {sup 151}Eu isotopes were prepared. • isotopic enriched crystals gave a well-resolved EPR hyperfine structure of Eu{sup 2+} centers. • the redox ratio was followed through the Eu{sup 2+} associated absorption band at 250 nm. • the band intensities at 378 nm correlate with the Eu{sup 2+} concentration.

  13. Redox reactions and the influence of natural Mn oxides on Cr oxidation in a contaminated site in northern Italy: evidence from Cr stable-isotopes and EPR spectroscopy

    OpenAIRE

    Marafatto F. F.; Petrini R.; Pinzino C.; Pezzetta E.; Slejko F.; Lutman A.

    2013-01-01

    Hexavalent chromium-contaminated groundwaters and sediments in northern Italy have been studied using the Cr stable-isotope systematics and electron spin resonance spectroscopy (ESR), in order to explore redox changes and soil-groundwater interactions. The isotopic data indicate a possible Cr(VI) source released into the environment from an industrial plant. EPR spectra on the sediments which constitute the aquifers show a broad asymmetric absorption due to coupled Fe(III) and coupled Cr(III)...

  14. The nature of the exchange coupling between high-spin Fe(III) heme o3 and CuBII in Escherichia coli quinol oxidase, cytochrome bo3: MCD and EPR studies.

    Science.gov (United States)

    Cheesman, Myles R; Oganesyan, Vasily S; Watmough, Nicholas J; Butler, Clive S; Thomson, Andrew J

    2004-04-07

    Fully oxidized cytochrome bo3 from Escherichia coli has been studied in its oxidized and several ligand-bound forms using electron paramagnetic resonance (EPR) and magnetic circular dichroism (MCD) spectroscopies. In each form, the spin-coupled high-spin Fe(III) heme o3 and CuB(II) ion at the active site give rise to similar fast-relaxing broad features in the dual-mode X-band EPR spectra. Simulations of dual-mode spectra are presented which show that this EPR can arise only from a dinuclear site in which the metal ions are weakly coupled by an anisotropic exchange interaction of J 1 cm-1. A variable-temperature and magnetic field (VTVF) MCD study is also presented for the cytochrome bo3 fluoride and azide derivatives. New methods are used to extract the contribution to the MCD of the spin-coupled active site in the presence of strong transitions from low-spin Fe(III) heme b. Analysis of the MCD data, independent of the EPR study, also shows that the spin-coupling within the active site is weak with J approximately 1 cm-1. These conclusions overturn a long-held view that such EPR signals in bovine cytochrome c oxidase arise from an S' = 2 ground state resulting from strong exchange coupling (J > 10(2) cm-1) within the active site.

  15. Theoretical investigation of the optical and EPR parameters for VO{sup 2+}ion in some complexes

    Energy Technology Data Exchange (ETDEWEB)

    Kalfaoglu, Emel [OndokuzMay Latin-Small-Letter-Dotless-I s University, Faculty of Sciences, Department of Physics, 55139 Kurupelit-Samsun (Turkey); Karabulut, Buenyamin, E-mail: bbulut@omu.edu.tr [OndokuzMay Latin-Small-Letter-Dotless-I s University, Faculty of Sciences, Department of Physics, 55139 Kurupelit-Samsun (Turkey)

    2012-04-15

    The molecular orbital coefficients and the EPR parameters of trisodium citrate dihydrate, sodium hydrogen oxalate monohydrate, potassium d-gluconate monohydrate and L-Alanine vanadyl complexes are calculated theoretically. Two d-d transition spectra and EPR parameters for the VO{sup 2+} complex are calculated theoretically by using crystal-field theory. The calculated g and A paramaters have indicated that paramagnetic center is axially symmetric. Having the relations of g{sub Parallel-To } Left-Pointing-Angle-Bracket g{sub Up-Tack } Left-Pointing-Angle-Bracket g{sub e} and A{sub Parallel-To } Right-Pointing-Angle-Bracket A{sub Up-Tack} for VO{sup 2+} ions, it can be concluded that VO{sup 2+} ions are located in distorted octahedral sites (C{sub 4v}) elongated along the z-axis and the ground state of the paramagnetic electron is d{sub xy}. - Highlights: Black-Right-Pointing-Pointer The EPR parameters and molecular orbital coefficients are calculated theoretically. Black-Right-Pointing-Pointer The g and A values of all complexes are found to be nearly axially symmetric. Black-Right-Pointing-Pointer The ground state of the paramagnetic electron is d{sub xy.}.

  16. Single crystals of DPPH grown from diethyl ether and carbon disulfide solutions - crystal structures, IR, EPR and magnetization studies.

    Science.gov (United States)

    Zilić, Dijana; Pajić, Damir; Jurić, Marijana; Molčanov, Krešimir; Rakvin, Boris; Planinić, Pavica; Zadro, Krešo

    2010-11-01

    Single crystals of the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) obtained from diethyl ether (ether) and carbon disulfide (CS₂) were characterized by the X-ray diffraction, IR, EPR and SQUID magnetization techniques. The X-ray structural analysis and IR spectra showed that the DPPH form crystallized from ether (DPPH1) is solvent free, whereas that one obtained from CS₂ (DPPH2) is a solvate of the composition 4DPPH·CS₂. Principal values of the g-tensor were estimated by the X-band EPR spectroscopy at room and low (10 K) temperatures. Magnetization studies revealed the presence of antiferromagnetically coupled dimers in both types of crystals. However, the way of dimerization as well as the strength of exchange couplings are different in the two DPPH samples, which is in accord with their crystal structures. The obtained results improved parameters accuracy and enabled better understanding of properties of DPPH as a standard sample in the EPR spectrometry. Copyright © 2010 Elsevier Inc. All rights reserved.

  17. THE ORIENTATION OF MEMBRANE BOUND RADICALS: AN EPR INVESTIGATION OF MAGNETICALLY ORDERED SPINACH CHLOROPLASTS

    Energy Technology Data Exchange (ETDEWEB)

    Dismukes, G. Charles; Sauer, Kenneth

    1978-03-01

    The orientation of membrane-bound radicals in spinach chloroplasts is examined by electron paramagnetic resonance (EPR) spectroscopy of chloroplasts oriented by magnetic fields. Several of the membrane-bound radicals which possess g-tensor anisotropy display EPR signals with a marked dependence on the orientation of the membranes relative to the applied EPR field. The fraction of oxidized and reduced plastocyanin, P-700, iron-sulfur proteins A and B, and the X center, an early acceptor of Photosystem I, can be controlled by the light intensity during steady-state illumination and can be trapped by cooling. The X center can be photoreduced and trapped in the absence of strong reductants and high pH, conditions previously found necessary for its detection. These results confirm its role as an early electron acceptor in P-700 photo-oxidation. X is oriented with its smallest principal g-tensor axis (g{sub x}) predominantly parallel to the normal to the thylakoid membrane, the same orientation as was found for an early electron acceptor based on time-resolved electron spin polarization studies. We propose that the X center is the first example of a high potential iron-sulfur protein which functions in electron transfer in its 'superreduced' state. We present evidence which suggests that iron-sulfur proteins A and B are 4Fe-4S clusters in an 8Fe-8S protein. Center B is oriented with g{sub y} predominantly normal to the membrane plane. The spectra of center A and plastocyanin do not show significant changes with sample orientation. In the case of plastocyanin, this may indicate a lack of molecular orientation. The absence of an orientation effect for reduced center A is reconcilable with a 4Fe-4S geometry, provided that the electron obtained upon reduction can be shared between any pair of Fe atoms in the center. Orientation of the 'Rieske' iron-sulfur protein is also observed. It has axial symmetry with g{parallel} close to the plane of the membrane

  18. CW-EPR study of 2,2,4,4-tetramethyl-3-pentanone oxime single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Sayin, Ulku; Yuksel, Huseyin; Ozmen, Ayhan [Physics Department, Selcuk University, Konya (Turkey); Birey, Mehmet, E-mail: birey@science.ankara.edu.t [Physics Department, Ankara University, Ankara (Turkey)

    2010-12-15

    The electron paramagnetic resonance (EPR) spectra of gamma irradiated single crystals of 2,2,4,4-tetramethyl-3-pentanone oxime (TPO) have been examined between temperatures of 125 and 450 K. The spectra were found to be both dependent on temperature and orientation of single crystals with magnetic field. We attributed radiation damage centers to iminoxy radicals (RC=N{sup {center_dot}}O). There are two similar group of splitting in the spectra because of conformational isomers (R1, R2) of iminoxy radicals produced by gamma irradiation of TPO. Determined g-factor and hyperfine coupling constants for R1 and R2 conformers were found anisotropic with the average values (g{sub iso}){sub R1}=2.01057, (g{sub iso}){sub R2}=2.009337, [(a{sub N}){sub iso}]{sub R1}=28.09 G, [(a{sub N}){sub iso}]{sub R2}=36.34 G, [(a{sub H}){sub iso}]{sub R2}=9.15 G, respectively.

  19. Identification and dosimetry of irradiated walnuts (Juglans regia) using EPR

    Science.gov (United States)

    Maghraby, A.; Salama, E.; Sami, A.; Mansour, A.; El-Sayed, M.

    2012-03-01

    Electron paramagnetic resonance (EPR) is an easy, fast, and reliable tool for identification of irradiated food. Untreated nuts may encounter hazards of carrying several pathogens or microbial contamination; walnuts are of specific importance due to their nutritional and medicinal values, and hence walnut processing via gamma irradiation is a necessary step. EPR was employed for the identification and dosimetry of Cs-137 gamma-irradiated walnuts (shells and kernels). Several important parameters were studied, such as spectral features, microwave power dependence of signal intensities, and short- and long-term time dependences. Responses of walnut shells and kernels to different radiation doses in the range 0-10 kGy were investigated. Results confirmed that EPR is a suitable tool for the identification and dosimetry of irradiated walnuts using either their shells or only kernels.

  20. ER=EPR, GHZ, and the consistency of quantum measurements

    Energy Technology Data Exchange (ETDEWEB)

    Susskind, Leonard [Stanford Institute for Theoretical Physics and Department of Physics, Stanford University, Stanford, CA (United States)

    2016-01-15

    This paper illustrates various aspects of the ER=EPR conjecture. It begins with a brief heuristic argument, using the Ryu-Takayanagi correspondence, for why entanglement between black holes implies the existence of Einstein-Rosen bridges. The main part of the paper addresses a fundamental question: Is ER=EPR consistent with the standard postulates of quantum mechanics? Naively it seems to lead to an inconsistency between observations made on entangled systems by different observers. The resolution of the paradox lies in the properties of multiple black holes, entangled in the Greenberger-Horne-Zeilinger pattern. The last part of the paper is about entanglement as a resource for quantum communication. ER=EPR provides a way to visualize protocols like quantum teleportation. In some sense teleportation takes place through the wormhole, but as usual, classical communication is necessary to complete the protocol. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Retrospective dosimetry using EPR and TL techniques: a status report

    Energy Technology Data Exchange (ETDEWEB)

    Haskell, E.H.

    1996-12-31

    Methods of retrospective dosimetry, including luminescence and electron paramagnetic resonance spectroscopy (EPR), rely on measurement of accident dose absorbed by naturally occurring materials - ceramics in the case of both thermoluminescence (TL) and optically stimulated luminescence (OSL) and organic materials and bio- minerals in the case of EPR. Each of these methods relies on measurement of radiation defects resulting from accidental exposure. Since defects also result from natural sources of radiation over the lifetime of a sample, analysis is usually restricted to materials for which the natural dose may be determined and subtracted from the measured cumulative dose. Luminescence dating techniques rely heavily on an accurate assessment of cumulative dose from natural radiation sources, and dating research has provided us with the bulk of our knowledge in this area. Virtually all of the work on natural dose determination can be directly applied to retrospective techniques. With EPR techniques the cumulative dose from diagnostic x- rays is also of importance.

  2. Structural characterization and electronic properties determination by high-field and high-frequency EPR of a series of five-coordinated Mn(II) complexes.

    Science.gov (United States)

    Mantel, Claire; Baffert, Carole; Romero, Isabel; Deronzier, Alain; Pécaut, Jacques; Collomb, Marie-Noëlle; Duboc, Carole

    2004-10-04

    The isolation, structural characterization, and electronic properties of a series of high-spin mononuclear five-coordinated Mn(II) complexes, [Mn(terpy)(X)(2)] (terpy = 2, 2':6',2' '-terpyridine; X = I(-) (1), Br(-) (2), Cl(-) (3), or SCN(-) (4)), are reported. The X-ray structures of the complexes reveal that the manganese ion lies in the center of a distorted trigonal bipyramid for complexes 1, 2, and 4, while complex 3 is better described as a distorted square pyramid. The electronic properties of 1-4 were investigated by high-field and high-frequency EPR spectroscopy (HF-EPR) performed between 5 and 30 K. The powder HF-EPR spectra have been recorded in high-field-limit conditions (95-285 GHz) (D EPR experiments, the sign of D was unambiguously determined. D is positive for the iodo and bromo complexes and negative for the chloro and thiocyano ones. A structural correlation is proposed. Each complex is characterized by a significant rhombicity with E/D values between 0.17 and 0.29, reflecting the distorted geometry observed around the manganese. Finally, we compared the spin Hamiltonian parameters of our five-coordinated complexes and those previously reported for other analogous series of dihalo four- and six-coordinated complexes. The effect of the coordination number and of the geometry of the Mn(II) complexes on the spin Hamiltonian parameters is discussed.

  3. EPR investigations on radiation induced chemical transformations in Pd(ClO4)2/i-PrOH/HClO4 system from 77 to 300 K.

    Science.gov (United States)

    Tripathi, S C; Kadam, R M; Kumar, Manmohan; Mittal, J P; Mishra, S P

    2005-12-01

    The EPR studies have been carried out on gamma irradiated samples of Pd(ClO4)2 in 9 M/4M HClO4 in the presence and absence of isopropanol [i-PrOH (5%, v/v)], in the temperature range of 77-300 K. The EPR studies revealed the formation of Pd+ complex, Pd3+ complex and several radicals such as H., OH., ClO3., ClO4. and O3- on radiolysis of these systems. Reduction of Pd2+ to Pd clusters could not be observed in the absence of i-PrOH and warming of the irradiated sample finally resulted in recovery of Pd2+ complex. However, in the presence of 5% i-PrOH, strongly oxidizing radicals like OH., ClO3. and ClO4. are suppressed and (CH3)2C.OH radical was produced along with reducing species like H.. EPR spectra in these strongly reducing conditions showed formation of Pd+ complex, which on heating above 230 K, disproportionated into Pd0 and Pd2+ complex and finally lead to formation of Pd metal aggregates. Simultaneously, pulse radiolysis technique has been employed as an alternative method to verify the EPR observations.

  4. Development of fire protection standards for the EPR project

    Energy Technology Data Exchange (ETDEWEB)

    Frank, H.J. [Nuclear Power International, Paris (France); Kaercher, M. [Electricite de France (EDF), 69 - Villeurbanne (France); Wittmann, R. [Siemens AG Energieerzeugung KWU, Erlangen (Germany)

    2000-05-01

    In 1989 Framatome and Siemens decided by setting up their joint subsidiary NPI (Nuclear Power International) to co-operate in designing a new European Pressurised Water Reactor, the EPR. French and German utilities decided to participate in this project. In parallel to the co-operation on supplier's and utility's side, the French and German safety authorities and safety experts wanted to work closely together in order to harmonise and further develop the outstanding safety standards in France and Germany. An organisation has been set up to elaborate common codes related to the EPR design, at the level of the French design and construction rules (RCC) of the German KTA safety standards and DIN standards for nuclear technology, the so-called EPR technical codes (ETC). In this context the decision was made to develop a new fire protection code, the ETC-F, which should be harmonised between France and Germany. The article gives an insight in the developing process of the ETC-F and an outlook on existing and perhaps further national activities. (orig.) [German] Mit der Gruendung der NPI (Nuclear Power International) im Jahr 1989 haben Framatome und Siemens ihre Zusammenarbeit bei der Entwicklung eines neuen Europaeischen Druckwasser-Reaktors (EPR) vereinbart und fuer dieses Projekt eine Beteiligung von Energieversorgungsunternehmen aus Frankreich und Deutschland erreicht. Zeitgleich hierzu haben sich atomrechtliche Genehmigungsbehoerden und Gutachter beider Laender abgesprochen, ebenfalls eng zusammen zu arbeiten, um ihre zukuenftigen Anforderungen nach Moeglichkeit zu harmonisieren. Fuer den EPR sollten deshalb gemeinsame Vorschriften, sog. 'EPR technical codes (ETCs)' erarbeitet werden, welche einen vergleichbaren Tiefgang, wie die bestehenden franzoesischen (RCC) und deutschen (KTA) sicherheitstechnischen Regeln sowie die deutschen kerntechnischen Industrienormen (DIN) haben sollten. Hierzu gehoerte auch eine Brandschutzvorschrift, der ETC

  5. Multi-frequency and high-field EPR study of manganese(III) protoporphyrin IX reconstituted myoglobin with an S=2 integer electron spin.

    Science.gov (United States)

    Horitani, Masaki; Yashiro, Haruhiko; Hagiwara, Masayuki; Hori, Hiroshi

    2008-04-01

    We investigate the electronic state of Mn(III) center with an integer electron spin S=2 in the manganese(III) protoporphyrin IX reconstituted myoglobin, Mn(III)Mb, by means of multi-frequency electron paramagnetic resonance (MFEPR) spectroscopy. Using a bimodal cavity resonator, X-band EPR signal from Mn(III) center in the Mn(III)Mb was observed near zero-field region. The temperature dependence of this signal indicates a negative axial zero-field splitting value, DEPR analysis shows that this signal is attributed to the transition between the closely spaced M(s)=+/-2 energy levels for the z-axis, corresponding to the heme normal. To determine the zero-field splitting (ZFS) parameters, EPR experiments on the Mn(III)Mb were performed at various temperatures for some frequencies between 30GHz and 130GHz and magnetic fields up to 14T. We observed several EPR spectra which are analyzed with a spin Hamiltonian for S=2, yielding highly accurate ZFS parameters; D=-3.79cm(-1) and |E|=0.08cm(-1) for an isotropic g=2.0. These ZFS parameters are compared with those in some Mn(III) complexes and Mn(III) superoxide dismutase (SOD), and effects on these parameters by the coordination and the symmetry of the ligands are discussed. To the best of our knowledge, these EPR spectra in the Mn(III)Mb are the very first MFEPR spectra at frequencies higher than Q-band in a metalloprotein with an integer spin.

  6. Continuous wave W- and D-Band EPR spectroscopy offer “sweet-spots” for characterizing conformational changes and dynamics in intrinsically disordered proteins

    Energy Technology Data Exchange (ETDEWEB)

    Casey, Thomas M.; Liu, Zhanglong; Esquiaqui, Jackie M.; Pirman, Natasha L.; Milshteyn, Eugene; Fanucci, Gail E., E-mail: fanucci@chem.ufl.edu

    2014-07-18

    Highlights: • W- and D-Band line shapes are sensitive to motions in the 0.1–2 ns time regime. • These frequencies effectively report on conformational dynamics of IDPs. • W-band spectra reflecting helical formation in IA{sub 3} is experimentally demonstrated. - Abstract: Site-directed spin labeling (SDSL) electron paramagnetic resonance (EPR) spectroscopy is a powerful tool for characterizing conformational sampling and dynamics in biological macromolecules. Here we demonstrate that nitroxide spectra collected at frequencies higher than X-band (∼9.5 GHz) have sensitivity to the timescale of motion sampled by highly dynamic intrinsically disordered proteins (IDPs). The 68 amino acid protein IA{sub 3}, was spin-labeled at two distinct sites and a comparison of X-band, Q-band (35 GHz) and W-band (95 GHz) spectra are shown for this protein as it undergoes the helical transition chemically induced by tri-fluoroethanol. Experimental spectra at W-band showed pronounced line shape dispersion corresponding to a change in correlation time from ∼0.3 ns (unstructured) to ∼0.6 ns (α-helical) as indicated by comparison with simulations. Experimental and simulated spectra at X- and Q-bands showed minimal dispersion over this range, illustrating the utility of SDSL EPR at higher frequencies for characterizing structural transitions and dynamics in IDPs.

  7. Characterizing EPR-mediated passive drug targeting using contrast-enhanced functional ultrasound imaging

    NARCIS (Netherlands)

    Theek, B.; Gremse, F.; Kunjachan, S.; Fokong, S.; Pola, R.; Pechar, M.; Deckers, R.; Storm, Gerrit; Ehling, J.; Kiessling, F.; Lammers, Twan Gerardus Gertudis Maria

    2014-01-01

    The Enhanced Permeability and Retention (EPR) effect is extensively used in drug delivery research. Taking into account that EPR is a highly variable phenomenon, we have here set out to evaluate if contrast-enhanced functional ultrasound (ceUS) imaging can be employed to characterize EPR-mediated

  8. High-frequency EPR on high-spin transition-metal sites

    NARCIS (Netherlands)

    Mathies, Guinevere

    2012-01-01

    The electronic structure of transition-metal sites can be probed by electron-paramagnetic-resonance (EPR) spectroscopy. The study of high-spin transition-metal sites benefits from EPR spectroscopy at frequencies higher than the standard 9.5 GHz. However, high-frequency EPR is a developing field. In

  9. Magnetic properties and electronic structure of manganese-based blue pigments: a high-frequency and -field EPR study.

    Science.gov (United States)

    Krzystek, J; Telser, Joshua; Li, Jun; Subramanian, M A

    2015-09-21

    A variety of new oxide-based materials based on hexagonal phase of YInO3 have been recently described. In some of these materials, the In(III) ions are substituted by Mn(III), which finds itself in a trigonal-bipyramidal (TBP) coordination environment. While YInO3 is colorless and YMnO3 is black, mixed systems YIn1-xMnxO3 (0.02 EPR) in its high-frequency and -field version (HFEPR), a technique ideally suited for transition metal ions such as Mn(III) that, in contrast to, for example, Mn(II), are difficult to study by EPR at (conventional) low frequency and field. YIn1-xMnxO3 with 0.02 < x < 0.2 exhibited high-quality HFEPR spectra up to room temperature that could be interpreted as arising from isolated S = 2 paramagnets. A simple ligand-field model, based on the structure and optical spectra, explains the spin Hamiltonian parameters provided by HFEPR, which were D = +3.0 cm(-1), E = 0; g⊥ = 1.99, g∥ = 2.0. This study demonstrates the general applicability of a combined spectroscopic and classical theoretical approach to understanding the electronic structure of novel materials containing paramagnetic dopants. Moreover, HFEPR complements optical and other experimental methods as being a sensitive probe of dopant level.

  10. Magnetic, catalytic, EPR and electrochemical studies on binuclear ...

    Indian Academy of Sciences (India)

    Unknown

    Spectral, catalytic, magnetic, EPR and electrochemical studies have been ... attention in recent years, particularly to understand the redox function of copper ... Binuclear Cu(II) complexes with 3,4-disubstituted phenol. 3. 2.2 Materials. All solvents and reagents were obtained from commercial source. Ethanol and methanol.

  11. Copenhagen vs Everett, Teleportation, and ER=EPR

    OpenAIRE

    Susskind, Leonard

    2016-01-01

    Quantum gravity may have as much to tell us about the foundations and interpretation of quantum mechanics as it does about gravity. The Copenhagen interpretation of quantum mechanics and Everett's Relative State Formulation are complementary descriptions which in a sense are dual to one another. My purpose here is to discuss this duality in the light of the of ER=EPR conjecture.

  12. The EPR Paradox: Einstein Scrutinises Quantum Mechanics -28 ...

    Indian Academy of Sciences (India)

    he detailed the Copenhagen interpretation of quantum mechanics. He argued that the EPR paradox does not prove the incompleteness of quantum theory and that the statement "in no way disturbing the system" has to be interpreted differently in quantum mechanics. A measurement on particle P1 changes the very circum-.

  13. Electrical transport and EPR investigations: A comparative study for ...

    Indian Academy of Sciences (India)

    A detailed comparative study of electron paramagnetic resonance (EPR) in conjunction with d.c. electrical conductivity has been undertaken to know about the charge transport mechanism in polyaniline (PANI) doped with monovalent and multivalent protonic acids. This work is in continuation of our previous work for further ...

  14. Which Parts of a Clinical Process EPR Needs Special Configuration

    DEFF Research Database (Denmark)

    Barlach, Anders; Simonsen, Jesper

    2007-01-01

    which screen types in a clinical process that can be standard configured and which are subject to initial as well as on-going re-configuration. Methods and results: A pilot-project implementing a fully functional clinical process EPR was configured and used at a neurological ward, replacing all paper...

  15. Quantitative Analysis of the Enhanced Permeation and Retention (EPR Effect.

    Directory of Open Access Journals (Sweden)

    Andrew D Wong

    Full Text Available Tumor vasculature is characterized by a variety of abnormalities including irregular architecture, poor lymphatic drainage, and the upregulation of factors that increase the paracellular permeability. The increased permeability is important in mediating the uptake of an intravenously administered drug in a solid tumor and is known as the enhanced permeation and retention (EPR effect. Studies in animal models have demonstrated a cut-off size of 500 nm - 1 µm for molecules or nanoparticles to extravasate into a tumor, however, surprisingly little is known about the kinetics of the EPR effect. Here we present a pharmacokinetic model to quantitatively assess the influence of the EPR effect on the uptake of a drug into a solid tumor. We use pharmacokinetic data for Doxil and doxorubicin from human clinical trials to illustrate how the EPR effect influences tumor uptake. This model provides a quantitative framework to guide preclinical trials of new chemotherapies and ultimately to develop design rules that can increase targeting efficiency and decrease unwanted side effects in normal tissue.

  16. Antioxidant Capacity: Experimental Determination by EPR Spectroscopy and Mathematical Modeling.

    Science.gov (United States)

    Polak, Justyna; Bartoszek, Mariola; Chorążewski, Mirosław

    2015-07-22

    A new method of determining antioxidant capacity based on a mathematical model is presented in this paper. The model was fitted to 1000 data points of electron paramagnetic resonance (EPR) spectroscopy measurements of various food product samples such as tea, wine, juice, and herbs with Trolox equivalent antioxidant capacity (TEAC) values from 20 to 2000 μmol TE/100 mL. The proposed mathematical equation allows for a determination of TEAC of food products based on a single EPR spectroscopy measurement. The model was tested on the basis of 80 EPR spectroscopy measurements of herbs, tea, coffee, and juice samples. The proposed model works for both strong and weak antioxidants (TEAC values from 21 to 2347 μmol TE/100 mL). The determination coefficient between TEAC values obtained experimentally and TEAC values calculated with proposed mathematical equation was found to be R(2) = 0.98. Therefore, the proposed new method of TEAC determination based on a mathematical model is a good alternative to the standard EPR method due to its being fast, accurate, inexpensive, and simple to perform.

  17. Characterization of Monomeric MnII/III/IV–Hydroxo Complexes from X- and Q-Band Dual Mode Electron Paramagnetic Resonance (EPR) Spectroscopy

    Science.gov (United States)

    Gupta, Rupal; Taguchi, Taketo; Borovik, A. S.; Hendrich, Michael P.

    2013-01-01

    Manganese–hydroxo species have been implicated in C–H bond activation performed by metalloenzymes, but the electronic properties of many of these intermediates are not well characterized. The present work presents a detailed characterization of three Mnn–OH complexes (where n = II, III, and IV) of the tris[(N′-tert-butylureaylato)-N-ethylene]aminato ([H3buea]3−) ligand using X- and Q-band dual mode electron paramagnetic resonance (EPR). Quantitative simulations for the [MnIIH3buea(OH)]2− complex demonstrated the ability to characterize similar MnII species commonly present in the resting states of manganese-containing enzymes. The spin states of the MnIII and MnIV complexes determined from EPR spectroscopy are S = 2 and 3/2, respectively, as expected for the C3 symmetry imposed by the [H3buea]3− ligand. Simulations of the spectra indicated the constant presence of two MnIV species in solutions of [MnIVH3buea(OH)] complex. The simulations of perpendicular- and parallel-mode EPR spectra allow determination of zero-field splitting and hyperfine parameters for all complexes. For the MnIII and MnIV complexes, density functional theory calculations are used to determine the isotropic Mn hyperfine values, to compare the excited electronic state energies, and to give theoretical estimates of the zero-field energy. PMID:24156406

  18. Characterization of monomeric Mn(II/III/IV)-hydroxo complexes from X- and Q-band dual mode electron paramagnetic resonance (EPR) spectroscopy.

    Science.gov (United States)

    Gupta, Rupal; Taguchi, Taketo; Borovik, A S; Hendrich, Michael P

    2013-11-04

    Manganese-hydroxo species have been implicated in C-H bond activation performed by metalloenzymes, but the electronic properties of many of these intermediates are not well characterized. The present work presents a detailed characterization of three Mn(n)-OH complexes (where n = II, III, and IV) of the tris[(N'-tert-butylureaylato)-N-ethylene]aminato ([H3buea](3-)) ligand using X- and Q-band dual mode electron paramagnetic resonance (EPR). Quantitative simulations for the [Mn(II)H3buea(OH)](2-) complex demonstrated the ability to characterize similar Mn(II) species commonly present in the resting states of manganese-containing enzymes. The spin states of the Mn(III) and Mn(IV) complexes determined from EPR spectroscopy are S = 2 and 3/2, respectively, as expected for the C3 symmetry imposed by the [H3buea](3-) ligand. Simulations of the spectra indicated the constant presence of two Mn(IV) species in solutions of [Mn(IV)H3buea(OH)] complex. The simulations of perpendicular- and parallel-mode EPR spectra allow determination of zero-field splitting and hyperfine parameters for all complexes. For the Mn(III) and Mn(IV) complexes, density functional theory calculations are used to determine the isotropic Mn hyperfine values, to compare the excited electronic state energies, and to give theoretical estimates of the zero-field energy.

  19. Nuclear spin-lattice relaxation in nitroxide spin-label EPR

    DEFF Research Database (Denmark)

    Marsh, Derek

    2016-01-01

    that the definition of nitrogen nuclear relaxation rate Wn commonly used in the CW-EPR literature for 14N-nitroxyl spin labels is inconsistent with that currently adopted in time-resolved EPR measurements of saturation recovery. Redefinition of the normalised 14N spin-lattice relaxation rate, b = Wn/(2We), preserves...... the expressions used for CW-EPR, whilst rendering them consistent with expressions for saturation recovery rates in pulsed EPR. Furthermore, values routinely quoted for nuclear relaxation times that are deduced from EPR spectral diffusion rates in 14N-nitroxyl spin labels do not accord with conventional analysis...

  20. EPR Imaging at a Few Megahertz Using SQUID Detectors

    Science.gov (United States)

    Hahn, Inseob; Day, Peter; Penanen, Konstantin; Eom, Byeong Ho

    2010-01-01

    An apparatus being developed for electron paramagnetic resonance (EPR) imaging operates in the resonance-frequency range of about 1 to 2 MHz well below the microwave frequencies used in conventional EPR. Until now, in order to obtain sufficient signal-to-noise radios (SNRs) in conventional EPR, it has been necessary to place both detectors and objects to be imaged inside resonant microwave cavities. EPR imaging has much in common with magnetic resonance imaging (MRI), which is described briefly in the immediately preceding article. In EPR imaging as in MRI, one applies a magnetic pulse to make magnetic moments (in this case, of electrons) precess in an applied magnetic field having a known gradient. The magnetic moments precess at a resonance frequency proportional to the strength of the local magnetic field. One detects the decaying resonance-frequency magnetic- field component associated with the precession. Position is encoded by use of the known relationship between the resonance frequency and the position dependence of the magnetic field. EPR imaging has recently been recognized as an important tool for non-invasive, in vivo imaging of free radicals and reduction/oxidization metabolism. However, for in vivo EPR imaging of humans and large animals, the conventional approach is not suitable because (1) it is difficult to design and construct resonant cavities large enough and having the required shapes; (2) motion, including respiration and heartbeat, can alter the resonance frequency; and (3) most microwave energy is absorbed in the first few centimeters of tissue depth, thereby potentially endangering the subject and making it impossible to obtain adequate signal strength for imaging at greater depth. To obtain greater penetration depth, prevent injury to the subject, and avoid the difficulties associated with resonant cavities, it is necessary to use lower resonance frequencies. An additional advantage of using lower resonance frequencies is that one can use

  1. EPR studies of free radicals in A-2058 human melanoma cells treated by valproic acid and 5,7-dimethoxycoumarin.

    Science.gov (United States)

    Zdybel, Magdalena; Chodurek, Ewa; Pilawa, Barbara

    2014-01-01

    Free radicals in A-2058 human melanoma cells were studied by the use of electron paramagnetic resonance (EPR) spectroscopy. The aim of this work was to determine the changes in relative free radical concentrations in tumor A-2058 cells after treatment by valproic acid (VPA) and 5,7-dimethoxycoumarin (DMC). The influences of VPA and DMC on free radicals in A-2058 cells were compared with those for human melanoma malignum A-375 and G-361 cells, which were tested by us earlier. Human malignant melanoma A-2058 cells were exposed to interactions with VPA, DMC, and both VPA and DMC. The tumor cells A-2058 were purchased from LGC Standards (Lomianki, Poland), and they were grown in the standard conditions: at 37°C and in an atmosphere containing 95% air and 5% CO2, in the Minimum Essential Medium Eagle (MEM, Sigma-Aldrich). The A-2058 cells were incubated with VPA (1 mM) and DMC (10 μM) for 4 days. The first-derivative EPR spectra of the control A-2058 cells, and the cells treated with VPA, DMC, and both VPA and DMC, were measured by the electron paramagnetic resonance spectrometer of Radiopan (Poznań, Poland) with microwaves from an X-band (9.3 GHz). The parameters of the EPR lines: amplitudes (A), integral intensities (I), line widths (ΔBpp), and g-factors, were analyzed. The changes of amplitudes and line widths with microwave power increasing from 2.2 to 70 mW were drawn evaluated, o-Semiquinone free radicals of melanin biopolymer are mainly responsible for the EPR lines of A-2058 melanoma malignum cells. The amounts of free radicals in A-2058 cells treated with VPA, and both VPA and DMC, were lower than in the untreated control cells. Application of the tested substances (VPA, and both VPA and DMC) as the antitumor compounds was discussed. DMC without VPA did not decrease free radicals concentration in A-2058 cells. The studies con-firmed that EPR spectroscopy may be used to examine interactions of free radicals with antitumor compounds.

  2. An X-band Co{sup 2+} EPR study of Zn{sub 1−x}Co{sub x}O (x=0.005–0.1) nanoparticles prepared by chemical hydrolysis methods using diethylene glycol and denaturated alcohol at 5 K

    Energy Technology Data Exchange (ETDEWEB)

    Misra, Sushil K., E-mail: skmisra@alcor.concordia.ca [Physics Department, Concordia University, Montreal, QC, Canada H3G 1M8 (Canada); Andronenko, S.I. [Physics Institute, Kazan Federal University, Kazan 420008 (Russian Federation); Srinivasa Rao, S.; Chess, Jordan; Punnoose, A. [Department of Physics, Boise State University, Boise, ID 83725-1570 (United States)

    2015-11-15

    EPR investigations on two types of dilute magnetic semiconductor (DMS) ZnO nanoparticles doped with 0.5–10% Co{sup 2+} ions, prepared by two chemical hydrolysis methods, using: (i) diethylene glycol ((CH{sub 2}CH{sub 2}OH){sub 2}O) (NC-rod-like samples), and (ii) denatured ethanol (CH{sub 3}CH{sub 2}OH) solutions (QC-spherical samples), were carried out at X-band (9.5 GHz) at 5 K. The analysis of EPR data for NC samples revealed the presence of several types of EPR lines: (i) two types, intense and weak, of high-spin Co{sup 2+} ions in the samples with Co concentration >0.5%; (ii) surface oxygen vacancies, and (iii) a ferromagnetic resonance (FMR) line. QC samples exhibit an intense FMR line and an EPR line due to high-spin Co{sup 2+} ions. FMR line is more intense, than the corresponding line exhibited by NC samples. These EPR spectra varied for sample with different doping concentrations. The magnetic states of these samples as revealed by EPR spectra, as well as the origin of ferromagnetism DMS samples are discussed. - Highlights: • 5 K X band Co{sup 2+} EPR investigations on QC and NC ZnO dilute magnetic semiconductor nanoparticles. • NC and QC samples exhibited high-spin Co{sup 2+} EPR lines and ferromagnetic resonance line. • NC sample also exhibit line due surface oxygen vacancies. • FMR line is more intense in QC than that in NC samples. • Magnetic states and the origin of ferromagnetism are discussed.

  3. Direct synthesis, crystal structures, high-field EPR, and magnetic studies of heterometallic polymers containing manganese(II) carboxylates interconnected by [Cu(en)2]2+.

    Science.gov (United States)

    Makhankova, Valeriya G; Beznischenko, Asya O; Kokozay, Vladimir N; Zubatyuk, Roman I; Shishkin, Oleg V; Jezierska, Julia; Ozarowski, Andrew

    2008-06-02

    Two heterometallic polymers containing cations [Cu(en)2]2+ and either the [Mn(mal)2(H2O)2]2- (1) or [Mn2(succ)2Cl2]n2n- (2) anions (mal=malonate and succ=succinate) were investigated by X-ray crystallography, high-field electron paramagnetic resonance (EPR) spectroscopy, and magnetic susceptibility measurements. Magnetic susceptibility and EPR spectra characteristic of antiferromagnetically coupled Mn2+-Mn2+ pairs were observed in 2, and the exchange integral J=31 cm(-1) (H=JS1S2) as well as the zero-field-splitting parameter D=-3.046 cm(-1) in the triplet state of the dimanganese entity was determined.

  4. High-dose neutron irradiation of MgAl{sub 2}O{sub 4} spinel: effects of post-irradiation thermal annealing on EPR and optical absorption

    Energy Technology Data Exchange (ETDEWEB)

    Ibarra, A. [EURATOM/CIEMAT Fusion Association, Inst. Investigacion Basica, Av. Complutense, 22, E-28040 Madrid (Spain)]. E-mail: angel.ibarra@ciemat.es; Bravo, D. [Departamento de Fisica de Materiales, Facultad de Ciencias (C-IV), Universidad Autonoma de Madrid, Cantoblanco, E-28049 Madrid (Spain); Lopez, F.J. [Departamento de Fisica de Materiales, Facultad de Ciencias (C-IV), Universidad Autonoma de Madrid, Cantoblanco, E-28049 Madrid (Spain); Garner, F.A. [Pacific Northwest National Laboratory, Richland, WA (United States)

    2005-02-01

    Electron paramagnetic resonance (EPR) and optical absorption spectra were measured during thermal annealing of stoichiometric MgAl{sub 2}O{sub 4} spinel that was previously irradiated in the Materials Open Test Assembly in the Fast Flux Test Facility (FFTF/MOTA) at {approx}680 K to {approx}50 dpa. Both F and F{sup +} centres are to persist up to very high temperatures (over 1000 K) suggesting the operation of an annealing mechanism controlled by the thermal stability of extended defects. Using X-ray irradiation following the different annealing steps it was shown that an optical absorption band at 37,000 cm{sup -1} is related to a sharp EPR band at g = 2.0005 and that the defect causing these effects is the F{sup +} centre.

  5. EPR investigations of Mn 2+, Fe 3+ ions and carbonaceous radicals in atmospheric particulate aerosols during their transport over the eastern coast of the English Channel

    Science.gov (United States)

    Ledoux, Frédéric; Zhilinskaya, Elena; Bouhsina, Saâd; Courcot, Lucie; Bertho, Marie-Laure; Aboukaı̈s, Antoine; Puskaric, Emile

    Electron paramagnetic resonance (EPR) spectroscopy was used to follow the evolution of the chemical forms of manganese and study other paramagnetic species in the atmospheric particulate aerosols at Wimereux, a French station located on the eastern coast of the English Channel. In parallel, Graphite Furnace Atomic Absorption Spectrometry (GFAAS) was used to measure the metal concentrations. Fe concentration values are common in North Sea sites, but those of Mn are quite higher due to the presence of an important local source of Mn. EPR spectra have evidenced isolated Fe 3+ and Mn 2+ ions and carbonaceous products with variable intensities according to the wind directions. Amounts of paramagnetic species and carbonaceous products are maximum for continental winds and minimum for marine winds. Three Mn types were identified depending on the sampling distance from the source of emission and the size of the particles.

  6. EPR and optical absorption of VO{sup 2+} impurity in lithium potassium sulphate single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Kripal, Ram, E-mail: ram_kripal2001@rediffmail.co [Department of Physics, University of Allahabad, Allahabad 211002 (India); Maurya, Manju, E-mail: mmanju8@yahoo.co.i [Department of Physics, University of Allahabad, Allahabad 211002 (India)

    2009-05-01

    Electron paramagnetic resonance (EPR) and optical absorption studies of VO{sup 2+} doped lithium potassium sulphate single crystals are carried out at room temperature. The angular variation of the spectra is studied in the crystallographic a*b, bc and ca* plane. Vanadyl is found to have fixed orientations in the lattice and there are two magnetically inequivalent complexes in the lattice. The spin Hamiltonian parameters obtained from single crystal data for the two sites are, Site I: g{sub xx}=2.0015+-0.0002, g{sub yy}=1.9835+-0.0002, g{sub zz}=1.9211+-0.0002, A{sub xx}=(48+-2)x10{sup -4} cm{sup -1}, A{sub yy}=(64+-2)x10{sup -4} cm{sup -1}, A{sub zz}=(169+-2)x10{sup -4} cm{sup -1}, Site II: g{sub xx}=2.0019+-0.0002, g{sub yy}=1.9796+-0.0002, g{sub zz} =1.9225+-0.0002, A{sub xx}=(48+-2)x10{sup -4} cm{sup -1}, A{sub yy}=(83+-2)x10{sup -4} cm{sup -1}, A{sub zz}=(178+-2)x10{sup -4} cm{sup -1}. The first three bands observed in optical absorption spectrum are attributed to d-d transitions and the last band is probably charge transfer band. The band positions are calculated using energy expressions and compared with the observed values to confirm the transitions. Crystal field parameter (D{sub q}) and tetragonal parameters (D{sub s} and D{sub t}) are also evaluated. Using EPR and optical results, the molecular orbital parameters of VO{sup 2+} ions in the lattice are evaluated with a tetragonal symmetry approximation (because the rhombic part is small) and the nature of bonding in the complex is discussed.

  7. Solute distribution and stability in emulsion-based delivery systems: an EPR study.

    Science.gov (United States)

    Yucel, Umut; Elias, Ryan J; Coupland, John N

    2012-07-01

    Oil-in-water emulsions and related systems are often used to deliver hydrophobic solutes in foods, personal care products, and pharmaceuticals. Recent work has considered the use of crystalline lipid carrier particles (i.e., solid lipid nanoparticles, SLN) to control the availability of the solute; however, there is little direct evidence for the localization of small molecules in these systems. Alkanes (10 wt.% tetradecane or eicosane) containing the spin probe 4-phenyl-2,2,5,5-tetramethyl-3-imidazoline-1-oxyl (PTMIO, 200 ppm) were homogenized into sodium caseinate solution (1 wt.%) to produce fine or coarse droplets (0.2 μm or 1.3 μm, respectively) and cooled to 21.5 °C where eicosane is crystalline and tetradecane is liquid. Analysis of the resulting EPR spectra revealed populations of probe in two discrete environments (i.e., aqueous and lipid). PTMIO is largely hydrophobic with 77% and 70% present in the coarse and fine liquid lipid droplets (i.e., tetradecane droplets), respectively. In the solid droplets (i.e., eicosane), all of the probe was excluded from the droplets into the aqueous environment. In all cases, the mobility of the probe in both lipid and aqueous environments was affected by the droplet surface; thus, we hypothesize that the majority of the probe molecules are associated with the droplet interface. The PTMIO was reduced to an EPR-silent form by the addition of iron/ascorbate to the aqueous phase, and the apparent rate constant of the reaction was proportional to the fraction of the spin probe in the aqueous phase. Based on these findings, we propose that droplet crystallization excludes solute molecules from the droplet core to the aqueous environment where they interact with the droplet surface. Copyright © 2012 Elsevier Inc. All rights reserved.

  8. Phenylbutazone Oxidation via Cu,Zn-SOD Peroxidase Activity: An EPR Study.

    Science.gov (United States)

    Aljuhani, Naif; Whittal, Randy M; Khan, Saifur R; Siraki, Arno G

    2015-07-20

    We investigated the effect of Cu,Zn-superoxide dismutase (Cu,Zn-SOD)-peroxidase activity on the oxidation of the nonsteroidal anti-inflammatory drug phenylbutazone (PBZ). We utilized electron paramagnetic resonance (EPR) spectroscopy to detect free radical intermediates of PBZ, UV-vis spectrophotometry to monitor PBZ oxidation, oxygen analysis to determine the involvement of C-centered radicals, and LC/MS to determine the resulting metabolites. Using EPR spectroscopy and spin-trapping with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), we found that the spin adduct of CO3(•-) (DMPO/(•)OH) was attenuated with increasing PBZ concentrations. The resulting PBZ radical, which was assigned as a carbon-centered radical based on computer simulation of hyperfine splitting constants, was trapped by both DMPO and MNP spin traps. Similar to Cu,Zn-SOD-peroxidase activity, an identical PBZ carbon-centered radical was also detected with the presence of both myeloperoxidase (MPO/H2O2) and horseradish peroxidase (HRP/H2O2). Oxygen analysis revealed depletion in oxygen levels when PBZ was oxidized by SOD peroxidase-activity, further supporting carbon radical formation. In addition, UV-vis spectra showed that the λmax for PBZ (λ = 260 nm) declined in intensity and shifted to a new peak that was similar to the spectrum for 4-hydroxy-PBZ when oxidized by Cu,Zn-SOD-peroxidase activity. LC/MS evidence supported the formation of 4-hydroxy-PBZ when compared to that of a standard, and 4-hydroperoxy-PBZ was also detected in significant yield. These findings together indicate that the carbonate radical, a product of SOD peroxidase activity, appears to play a role in PBZ metabolism. Interestingly, these results are similar to findings from heme peroxidase enzymes, and the context of this metabolic pathway is discussed in terms of a mechanism for PBZ-induced toxicity.

  9. Linking Cr₃ triangles through phosphonates and lanthanides: synthetic, structural, magnetic and EPR studies.

    Science.gov (United States)

    Zangana, Karzan H; Pineda, Eufemio Moreno; Vitorica-Yrezabal, Iñigo J; McInnes, Eric J L; Winpenny, Richard E P

    2014-09-21

    The preparation and structural characterisation of five 3d-4f mixed metal phosphonate cages with general formula [Cr(III)6Ln(III)2(μ3-O)2(H2O)2(O3P(t)Bu)4(O2C(t)Bu)12(HO(i)Bu)2((i)PrNH2)2] where Ln(III) = La, 1; Tb, 3; Dy, 4; Ho, 5 and [Cr(III)6Gd(III)2(μ3-O)2(H2O)2(O3P(t)Bu)4(O2C(t)Bu)12(HO(i)Bu)4] (2) are reported. The structure contains two oxo-centred {Cr3} triangles, bridged by phosphonates and lanthanides. The magnetic behaviour of 1 has been modelled as two non-interacting isosceles triangles, involving two antiferromagnetic interactions (J1 = -8.8 cm(-1)) with a smaller ferromagnetic interaction for the unique edge of the triangle (J2 = +1.3 cm(-1)) giving an isolated S = 3/2 ground state per triangle. The quartet ground state has been proven through simulation of electron paramagnetic resonance (EPR) spectra obtained at the X- and Q-band. EPR simulations have also resulted in the introduction of small single-ion Zero Field Splitting (ZFS) parameters D = ±0.19 cm(-1) and rhombic term E = ±0.02 cm(-1), which are consistent with strong exchange limit calculations for an isolated S = 3/2 (D = ±0.22 and E = ±0.018 cm(-1)).

  10. Structure and dynamics of a conformationally constrained nitroxide side chain and applications in EPR spectroscopy.

    Science.gov (United States)

    Fleissner, Mark R; Bridges, Michael D; Brooks, Evan K; Cascio, Duilio; Kálai, Tamás; Hideg, Kálmán; Hubbell, Wayne L

    2011-09-27

    A disulfide-linked nitroxide side chain (R1) is the most widely used spin label for determining protein topology, mapping structural changes, and characterizing nanosecond backbone motions by site-directed spin labeling. Although the internal motion of R1 and the number of preferred rotamers are limited, translating interspin distance measurements and spatial orientation information into structural constraints is challenging. Here, we introduce a highly constrained nitroxide side chain designated RX as an alternative to R1 for these applications. RX is formed by a facile cross-linking reaction of a bifunctional methanethiosulfonate reagent with pairs of cysteine residues at i and i + 3 or i and i + 4 in an α-helix, at i and i + 2 in a β-strand, or with cysteine residues in adjacent strands in a β-sheet. Analysis of EPR spectra, a crystal structure of RX in T4 lysozyme, and pulsed electron-electron double resonance (ELDOR) spectroscopy on an immobilized protein containing RX all reveal a highly constrained internal motion of the side chain. Consistent with the constrained geometry, interspin distance distributions between pairs of RX side chains are narrower than those from analogous R1 pairs. As an important consequence of the constrained internal motion of RX, spectral diffusion detected with ELDOR reveals microsecond internal motions of the protein. Collectively, the data suggest that the RX side chain will be useful for distance mapping by EPR spectroscopy, determining spatial orientation of helical segments in oriented specimens, and measuring structural fluctuations on the microsecond time scale.

  11. EPR and optical absorption spectral studies on sphalerite mineral

    Science.gov (United States)

    Seshamaheswaramma, K.; Reddy, G. Udayabhaskara; Reddy, A. Varada; Lakshmi Reddy, S.; Frost, R. L.; Endo, Tamio

    2011-10-01

    The mineral sphalerite (Zn,Fe)S has been characterized by a combination of X-ray diffraction, EPR and NIR spectroscopy. The optical absorption spectrum of mineral sphalerite is due to an iron impurity only, which is in a distorted octahedral environment. The g = 2.2 is attributed to iron and g and A value observed in the spectrum 1.999 and 6.0 mT are assigned to Mn(II) impurity in the mineral. These results indicate that iron and Mn(II) impurity have entered the lattice by substitution. The EPR results confirm the presence of manganese in a distorted octahedral environment. It is evident from the chemical analysis that iron is present in higher concentrations. NIR results are due to the presence of water and sulphide fundamentals which also support the formula of the mineral. No sulphate in the sphalerite mineral was observed.

  12. Frequency modulation effects in EPR and dynamic nuclear polarisation

    CERN Document Server

    Kiselev, Yu F

    1996-01-01

    We elaborate on new effects in electron paramagnetic resonance and dynamic nuclear polarisation, recently discovered in the large polarized target of SMC at CERN, and validate our theoretical concepts by experiment. The phenomena, called by us 'frequency modulation effects', appear in a target cavity in the presence of strong frequency modulated microwave field which excites the electron magnetic dipole transitions. The system exhibits properties similar to an optical interferometer, whose arms can be adjusted by a steady magnetic field. The EPR spectrum of the cavity intensity shows satellites at monochromatic irradiation; these satellites disappear when the microwave frequency is modulated. It is shown that on the edges of the EPR line the absorption of the frequency modulated field is strongly enchanced due to a new mechanism of magnetic losses. This contributes also to the average dynamic deuteron polarization which is increased by a dramatic factor of 1.7 giving the highest ever deuteron polarization exc...

  13. Identification and dose assessment of irradiated cumin by EPR spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Abdel-Fattah, A.A. E-mail: atef_fattah@hotmail.com

    2002-03-01

    The use of electron paramagnetic resonance spectroscopy to accurately distinguish irradiated from unirradiated cumin and assess the absorbed dose to radiation-processed cumin is examined. The results were successful for identifying both irradiated and unirradiated cumin. Additive reirradiation of the cumin produces a reproducible dose response function, which can be used to assess the initial dose by back-extrapolation. Third-degree polynomial and exponential functions were used to fit the EPR signal/dose curves. It was found that the 3rd degree polynomial function provides satisfactory results without correction for decay of free radicals. The exponential fit to the data cannot be used without correction of decay of free radicals. The stability of the radiation-induced EPR signal of irradiated cumin was studied over a storage period of 6 months. The additive reirradiation of some samples was carried out at different storage times (10, 20 and 30 days) after initial irradiation.

  14. Substitutional and surface Mn2+ centers in cubic ZnS:Mn nanocrystals. A correlated EPR and photoluminescence study

    Science.gov (United States)

    Stefan, M.; Nistor, S. V.; Ghica, D.; Mateescu, C. D.; Nikl, M.; Kucerkova, R.

    2011-01-01

    The EPR, radioluminescence, and photoluminescence of cubic ZnS (cZnS) nanocrystals (NCs) with a narrow size distribution centered at 2 nm, doped with 0.1, 0.2, and 0.5at.% Mn2+ ions were investigated. Besides the main lines from substitutional Mn2+ ions localized in the core of the NCs next to a stacking defect, the EPR spectra exhibited two broader hyperfine sextets, attributed to the so-called Mn(II) and Mn(III) surface centers, which could be separated by adequate thermal treatments. The contribution to the photoluminescence from the Mn2+ ions at various sites was further determined from the analysis of the steady-state and time-resolved photoluminescence data from cZnS:Mn NCs subjected to thermal treatments and from cZnS:Mn single crystals. Thus, the main emission consisting of two intense overlapping bands peaking at 596 and 630 nm was attributed to the 4T1-6A1 transition of the substitutional Mn2+ ions in the core of the cZnS nanocrystals and to residual aggregated Mn2+ ions, respectively, the last ones being responsible for a broad EPR line observed in the X-band spectrum. The Mn(II) and Mn(III) centers, consisting of Mn2+ ions in the oxidized and hydrolyzed surface layer of the NCs, respectively, are only indirectly involved in the energy transfer to the substitutional Mn2+ centers, very likely through pairs interaction.

  15. state hybrid hemoglobins as revealed by optical, EPR and ...

    Indian Academy of Sciences (India)

    Unknown

    EPR examinations of these hybrids show that both in R state-[Cu(II)-Fe(II)] and T state-[Cu(II)-Ni(II)] hybrids at neutral pH and in the absence of IHP, CuPPIX, ... ion environment: Species 1, a five-coordinated Cu2+ complex with strong proximal histidine bond and spe- .... with those of copper and nickel-reconstituted hemo-.

  16. EPR = ER, scattering amplitude and entanglement entropy change

    Energy Technology Data Exchange (ETDEWEB)

    Seki, Shigenori, E-mail: sigenori@hanyang.ac.kr [Research Institute for Natural Science, Hanyang University, Seoul 133-791 (Korea, Republic of); Sin, Sang-Jin, E-mail: sjsin@hanyang.ac.kr [Department of Physics, Hanyang University, Seoul 133-791 (Korea, Republic of)

    2014-07-30

    We study the causal structure of the minimal surface of the four-gluon scattering, and find a world-sheet wormhole parametrized by Mandelstam variables, thereby demonstrate the EPR = ER relation for gluon scattering. We also propose that scattering amplitude is the change of the entanglement entropy by generalizing the holographic entanglement entropy of Ryu–Takayanagi to the case where two regions are divided in space–time.

  17. EPR study of spermine interaction with multilamellar phosphatidylcholine liposomes.

    Science.gov (United States)

    Momo, F; Wisniewska, A; Stevanato, R

    1995-11-22

    The interaction of spermine with egg-yolk phosphatidylcholine liposomes was investigated. The EPR spin labeling technique evidenced that spermine induces modifications of some membrane functions of biological interest like water permeability and is a possible modulator of diffusion processes for charged and polar molecules. The association constant for a hypothesized complex between spermine and the phosphate group of phosphatidylcholine was evaluated by enzymatic methods.

  18. Copenhagen vs Everett, teleportation, and ER=EPR

    Energy Technology Data Exchange (ETDEWEB)

    Susskind, Leonard [Stanford Institute for Theoretical Physics and Department of Physics, Stanford University, Stanford, CA (United States)

    2016-06-15

    Quantum gravity may have as much to tell us about the foundations and interpretation of quantum mechanics as it does about gravity. The Copenhagen interpretation of quantum mechanics and Everett's Relative State Formulation are complementary descriptions which in a sense are dual to one another. My purpose here is to discuss this duality in the light of the of ER=EPR conjecture. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. Clinical electron paramagnetic resonance (EPR) oximetry using India ink.

    Science.gov (United States)

    Williams, Benjamin B; Khan, Nadeem; Zaki, Bassem; Hartford, Alan; Ernstoff, Marc S; Swartz, Harold M

    2010-01-01

    Electron paramagnetic resonance (EPR) oximetry can be used to provide direct absolute measurements of pO(2) in living tissue using India ink as an O(2) reporter. In vivo measurements are made using low frequency (1.2 GHz) EPR spectroscopy and surface loop resonators, which enable measurements to be made at superficial sites through a non-invasive (after placing the ink in the tissues) and repeatable measurement procedure. Ongoing EPR oximetry studies in human subjects include measurement of subcutaneous pO(2) in the feet of healthy volunteers to develop procedures that could be used in the treatment of peripheral vascular disease and oximetry in tumors during courses of radiation and chemotherapy, to follow pO(2) so oxygen-dependent therapies can be optimized. In each case, we aim to provide quantitative measurements of tissue pO(2) which will aid physicians in the characterization of disease status and the effects of therapeutic measures, so that treatments can be applied with optimal effectiveness by taking into account the oxygen-dependent aspects of the therapy. The overall goal is to enhance clinical outcomes. Oximetry measurements of subcutaneous tissue on dorsal and plantar foot surfaces have been made in 9 volunteers, with measurements ongoing for each and the longest set of measurements carried out successfully over the last 5 years. Tumor oximetry measurements have been performed in tumor tissues of 10 patients during courses of radiation and chemotherapy. Tumor types include melanoma, basal cell, soft tissue sarcoma, and lymphoma, and measurement sites have ranged from the feet to the scalp. These studies demonstrate the feasibility of EPR oximetry in a clinical setting and the potential for more widespread use in the treatment of these and other oxygen-dependent diseases.

  20. Karl R. Popper, 1992: About the EPR controversy

    Science.gov (United States)

    Combourieu, Marie-Christine

    1992-10-01

    Sir K. R. Popper's experimental schemes challenge the Copenhagen interpretation of quantum theory, principally Heisenberg's indeterminacy relations and the EPR paradox. “The so-called Einstein-Podolsky-Rosen paradox is not a paradox. It is a theoretical statement in expectation of an interpretation,” says K. R. Popper in this interview. “My experiment ought to be a classical experiment. It is very simple and free from any additional assumption. It should really be done.”

  1. TL, EPR and optical absorption in natural grossular crystal

    Energy Technology Data Exchange (ETDEWEB)

    Yauri, J.M. [Institute of Physics, University of Sao Paulo, Rua do Matao, Travessa R, 187, CEP 05508-900, Sao Paulo (Brazil); Department of Physics, University of San Agustin, Av. Independencia S/N, Arequipa (Peru); Cano, N.F. [Institute of Physics, University of Sao Paulo, Rua do Matao, Travessa R, 187, CEP 05508-900, Sao Paulo (Brazil)], E-mail: nilocano@dfn.if.usp.br; Watanabe, S. [Institute of Physics, University of Sao Paulo, Rua do Matao, Travessa R, 187, CEP 05508-900, Sao Paulo (Brazil)

    2008-10-15

    Grossular is one of six members of silicate Garnet group. Two samples GI and GII have been investigated concerning their luminescence thermally stimulated (TL). EPR and optical absorption and the measurements were carried out to find out whether or not same point defects are responsible for all three properties. Although X-rays diffraction analysis has shown that both GI and GII have practically the same crystal structure of a standard grossular crystal, they presented different behavior in many aspects. The TL glow curve shape, TL response to radiation dose, the effect of annealing at high temperatures before irradiation, the dependence of UV bleaching parameters on peak temperature, all of them differ going from GI to GII. The EPR signals around g=2.0 as well as at g=4.3 and 6.0 have much larger intensity in GI than in GII. Very high temperature (>800 deg. C) annealing causes large increase in the bulk background absorption in GI, however, only very little in GII. In the cases of EPR and optical absorption, the difference in their behavior can be attributed to Fe{sup 3+} ions; however, in the TL case one cannot and the cause was not found as yet.

  2. Spectra of stable sonoluminescence

    Science.gov (United States)

    Lewis, Stephen D.

    1992-12-01

    The continuous emission of picosecond pulses of light has been observed to originate from a bubble trapped at the pressure antinode of a resonant sound field in water and in water/glycerin mixtures. The spectra of this light in several solutions has been measured with a scanning monochrometer/photomultiplier detector system. The spectra are broadband and show strong emission in the UV region. A comparison of this measurement to two other independently produced spectra is made. The spectra are also modeled by a blackbody radiation distribution to determine an effective blackbody temperature and a size is deduced as if Sonoluminescence were characterized by blackbody radiation.

  3. Assessment of an alanine EPR dosimetry technique with enhanced precision and accuracy

    CERN Document Server

    Hayes, R B; Wieser, A; Romanyukha, A A; Hardy, B L; Barrus, J K

    2000-01-01

    Dose reconstruction in the course of a series of blind tests demonstrated that an accuracy of 10 mGy for low doses and 1% for high doses can be achieved using EPR spectroscopy. This was accomplished using a combination of methodologies including polynomial filtration of the EPR spectrum, dosimeter rotation during scanning, use of an EPR standard fixed into the resonator and subtraction of all nonradiogenic signals. Doses were reconstructed over the range of 0.01-1000 Gy using this compound spectral EPR analysis. This EPR technique, being equally applicable to fractionated doses (such as those delivered during multiple radiotherapy treatments), was verified to exhibit dose reciprocity. Irradiated alanine dosimeters which were stored exhibited compound spectral EPR signal fading of ca 3% over 9 months. All error estimates given in this paper are given at the 1 standard deviation level and unless otherwise specified do not account for uncertainties in source calibration.

  4. Preferential location of lidocaine and etidocaine in lecithin bilayers as determined by EPR, fluorescence and 2H NMR.

    Science.gov (United States)

    de Paula, Eneida; Schreier, Shirley; Jarrell, Harold C; Fraceto, Leonardo Fernandes

    2008-01-01

    We have examined the effect of the uncharged species of lidocaine (LDC) and etidocaine (EDC) on the acyl chain moiety of egg phosphatidylcholine liposomes. Changes in membrane organization caused by both anesthetics were detected through the use of EPR spin labels (5, 7 and 12 doxyl stearic acid methyl ester) or fluorescence probes (4, 6, 10, 16 pyrene-fatty acids). The disturbance caused by the LA was greater when the probes were inserted in more external positions of the acyl chain and decreased towards the hydrophobic core of the membrane. The results indicate a preferential insertion of LDC at the polar interface of the bilayer and in the first half of the acyl chain, for EDC. Additionally, (2)H NMR spectra of multilamellar liposomes composed by acyl chain-perdeutero DMPC and EPC (1:4 mol%) allowed the determination of the segmental order (S(mol)) and dynamics (T(1)) of the acyl chain region. In accordance to the fluorescence and EPR results, changes in molecular orientation and dynamics are more prominent if the LA preferential location is more superficial, as for LDC while EDC seems to organize the acyl chain region between carbons 2-8, which is indicative of its positioning. We propose that the preferential location of LDC and EDC inside the bilayers creates a "transient site", which is related to the anesthetic potency since it could modulate the access of these molecules to their binding site(s) in the voltage-gated sodium channel.

  5. EPR studies of chromium(V) intermediates generated via reduction of chromium(VI) by DOPA and related catecholamines

    DEFF Research Database (Denmark)

    Pattison, D I; Lay, P A; Davies, Michael Jonathan

    2000-01-01

    The reductions of K2Cr2O7 by catecholamines, DOPA, DOPA-beta,beta-d2, N-acetyl-DOPA, alpha-methyl-DOPA, dopamine, adrenaline, noradrenaline, catechol, 1,2-dihydroxybenzoic acid (DHBA), and 4-tert-butylcatechol (TBC), produce a number of Cr(V) electron paramagnetic resonance (EPR) signals. These s......The reductions of K2Cr2O7 by catecholamines, DOPA, DOPA-beta,beta-d2, N-acetyl-DOPA, alpha-methyl-DOPA, dopamine, adrenaline, noradrenaline, catechol, 1,2-dihydroxybenzoic acid (DHBA), and 4-tert-butylcatechol (TBC), produce a number of Cr(V) electron paramagnetic resonance (EPR) signals...... previously but have been reassigned as octahedral Cr(V) species with mixed catechol-derived ligands, [CrV(semiquinone)2(catecholate)]+. Experiments with excess K2Cr2O7 show complex behavior with the catecholamines and TBC. Several weak Cr(V) signals are detected after mixing, and the spectra evolve over time...... to yield relatively stable substrate-dependent signals at g(iso) approximately 1.980. These signals have been attributed to [Cr(O)L2](L = diolato) species, in which the Cr is coordinated to two cyclized catecholamine ligands and an oxo ligand. Isotopic labeling studies with DOPA (ring or side chain...

  6. Public debate about the EPR nuclear power plant at Flamanville; Debat public sur la centrale nucleaire EPR a Flamanville

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2005-07-01

    The project of building of he EPR reactor at Flamanville (Manche, France) has been submitted to the public debate. This document includes a presentation of the project and of the rules of the public debate, a synthesis of the file made by the prime contractor (EDF), a synthesis of the collective book of national actors concerned by the project (a group of associations for environment protection, Areva company, the ministries of economy and ecology, Global Chance, association of pro-nuclear ecologists (AEPN), 'Sortir du Nucleaire' (out-of nuclear) network, group of scientists for the information about nuclear (GSIEN), association for the promotion of the Flamanville site (Proflam), French nuclear energy society (SFEN) in association with 'Sauvons le Climat' (let's save climate), regional collective association 'EPR non merci, ni ailleurs, ni ici' (EPR, no thanks, neither elsewhere, nor here), NegaWatt), and 5 detailed books of actors: ACRO (association for the control of radioactivity in Western France), CFDT and CGT syndicates, the economic and social council of Basse Normandie region, and Proflam. (J.S.)

  7. In Vivo Imaging of Tissue Physiological Function using EPR Spectroscopy | NCI Technology Transfer Center | TTC

    Science.gov (United States)

    Electron paramagnetic resonance (EPR) is a technique for studying chemical species that have one or more unpaired electrons.  The current invention describes Echo-based Single Point Imaging (ESPI), a novel EPR image formation strategy that allows in vivo imaging of physiological function.  The National Cancer Institute's Radiation Biology Branch is seeking statements of capability or interest from parties interested in in-licensing an in vivo imaging using Electron paramagnetic resonance (EPR) to measure active oxygen species.

  8. Spin dynamics evidenced by EPR in Sn{sub 1-x}Mn{sub x}O{sub 2} nanoparticles annealed at different temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Popa, A.; Toloman, D. [National Institute for Research and Development of Isotopic and Molecular Technologies, Donath 65-103, 400293 Cluj-Napoca (Romania); Raita, O., E-mail: oana.raita@itim-cj.ro [National Institute for Research and Development of Isotopic and Molecular Technologies, Donath 65-103, 400293 Cluj-Napoca (Romania); Stan, M. [National Institute for Research and Development of Isotopic and Molecular Technologies, Donath 65-103, 400293 Cluj-Napoca (Romania); Vasile, B.S. [University ' Politehnica' , Faculty of Applied Chemistry and Material Science, Department of Science and Engineering of Oxide Materials and Nanomaterials, 1-7 Gh. Polizu, 011061 Bucharest (Romania); Leostean, C.; Giurgiu, L.M. [National Institute for Research and Development of Isotopic and Molecular Technologies, Donath 65-103, 400293 Cluj-Napoca (Romania)

    2013-02-25

    Highlights: Black-Right-Pointing-Pointer The mean size of individual nanoparticles was investigated by TEM. Black-Right-Pointing-Pointer The annealed temperature influence on Mn{sup 2+} and Mn{sup 4+} ions content was investigated. Black-Right-Pointing-Pointer A ferromagnetic phase was identified by EPR and his origin was explained. - Abstract: This article reports the effects of the annealing temperature on the structural, morphological and spin dynamic properties of SnO{sub 2} samples doped with 0.005 Mn. The samples were annealed at 400, 600, 700 and 800 Degree-Sign C and analyzed by XRD, TEM, XPS and EPR spectroscopy. The XRD spectra show that the average crystallite size increases with the increase of the annealing temperature. The particles size and morphology were characterized by TEM microscopy. The valence bands of Mn were investigated by measuring the XPS spectra of Mn 2p core-level doublet. Regardless of the annealing temperature, the observed EPR spectra are due to (i) Mn{sup 2+} ions either interstitially situated on the particle surfaces or isolated ones located substitutionally at Sn sites and (ii) Mn{sup 4+} ions which substitute for Sn{sup 4+} in SnO{sub 2} lattice. The effects of the annealing temperature on the relative fractions of Mn{sup 2+} and Mn{sup 4+} ions are presented and discussed. In Sn{sub 1-x}Mn{sub x}O{sub 2} (x = 0.005) sample annealed at 400 Degree-Sign C, a FMR line was identified and attributed to a ferromagnetic phase.

  9. Comparison of EPR-visible Cu(2+) sites in pMMO from Methylococcus capsulatus (Bath) and Methylomicrobium album BG8.

    Science.gov (United States)

    Lemos, S S; Perille Collins, M L; Eaton, S S; Eaton, G R; Antholine, W E

    2000-08-01

    X-band (9.1 GHz) and S-band (3.4 GHz) electron paramagnetic resonance (EPR) spectra for particulate methane monooxygenase (pMMO) in whole cells from Methylococcus capsulatus (Bath) grown on (63)Cu and (15)N were obtained and compared with previously reported spectra for pMMO from Methylomicrobium album BG8. For both M. capsulatus (Bath) and M. album BG8, two nearly identical Cu(2+) EPR signals with resolved hyperfine coupling to four nitrogens are observed. The EPR parameters for pMMO from M. capsulatus (Bath) (g( parallel) = 2.244, A( parallel) = 185 G, and A(N) = 19 G for signal one; g( parallel) = 2.246, A( parallel) = 180 G, and A(N) = 19 G for signal two) and for pMMO from M. album BG8 (g( parallel) = 2.243, A( parallel) = 180 G, and A(N) = 18 G for signal one; g( parallel) = 2. 251, A( parallel) = 180 G, and A(N) = 18 G for signal two) are very similar and are characteristic of type 2 Cu(2+) in a square planar or square pyramidal geometry. In three-pulse electron spin echo envelope modulation (ESEEM) data for natural-abundance samples, nitrogen quadrupolar frequencies due to the distant nitrogens of coordinated histidine imidazoles were observed. The intensities of the quadrupolar combination bands indicate that there are three or four coordinated imidazoles, which implies that most, if not all, of the coordinated nitrogens detected in the continuous wave spectra are from histidine imidazoles.

  10. EPR and luminescence studies of the radiation induced Eu.sup.2+./sup. centers in the EuAl.sub.3./sub.(BO.sub.3./sub.).sub.4./sub. single crystals

    Czech Academy of Sciences Publication Activity Database

    Prokhorov, Andriy; Chernush, L.F.; Babin, Vladimir; Buryi, Maksym; Savchenko, Dariia; Lančok, Ján; Nikl, Martin; Prokhorov, A.D.

    2017-01-01

    Roč. 66, Apr (2017), s. 428-433 ISSN 0925-3467 R&D Projects: GA MŠk LO1409; GA MŠk LM2015088 Institutional support: RVO:68378271 Keywords : EPR spectra * multiferroics * rare-earth * luminescence * aluminum borates * X-ray irradiation * spin Hamiltonian parameters * superposition model Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.238, year: 2016

  11. Research on EPR measurement methods of sucrose used in radiation accident dose reconstruction.

    Science.gov (United States)

    Ding, Yanqiu; Jiao, Ling; Zhang, Wenyi; Zhou, Li; Zhang, Xiaodong; Zhang, Liang'an

    2010-03-01

    Sucrose is a convenient, common, tissue-equivalent material suitable for electron paramagnetic resonance (EPR) dosimetry of ionising radiation. A number of publications have reported on the dosimetric properties of sucrose and their use in radiation accident dose reconstruction. However, previous studies did not include specially the description of measurement methods of sucrose by EPR. The aim of this work is to introduce particularly the EPR measurement methods of sucrose. In this regard, practical considerations of sample size, microwave power, modulation amplitude, EPR spectrum and signal stability are discussed.

  12. Eksplorativ analyse av EPR-spektre av alanin og Gorilla® Glass

    OpenAIRE

    Jåstad, Eirik Ogner

    2016-01-01

    Elektron Paramagnetisk Resonans (EPR) spektroskopi er en måleteknikk som tar opp spektre som kan brukes til å estimere absorbert stråledose, såkalt EPR-dosimetri. EPR-dosimetri måler mengden frie radikaler i et materiale, som er proporsjonalt med den absorberte dosen. De fleste frie radikaler er kortlivede ved romtemperatur, dette er en utfordring ved EPR-dosimetri. Et materiale som ofte brukes i dosimetri er aminosyren L-α-alanin. Alanin egner seg for planlagte eksponeringer, men ikke nødven...

  13. Alternative chitosan-based EPR dosimeter applicable for a relatively wide range of gamma radiation doses

    Science.gov (United States)

    Piroonpan, Thananchai; Katemake, Pichayada; Panritdam, Eagkapong; Pasanphan, Wanvimol

    2017-12-01

    Chitosan biopolymer is proposed as an alternative EPR dosimeter. Its ability to be EPR dosimeter was studied in comparison with the conventional alanine, sugars (i.e., glucose and sucrose), formate derivatives (i.e., lithium (Li), magnesium (Mg), and calcium (Ca) formate). Ethylene vinyl acetate (EVA) and paraffin were used as binder for the preparation of composite EPR dosimeter. Dose responses of all materials were investigated in a wide dose range of radiation doses, i.e., low-level (0-1 kGy), medium-level (1-10 kGy) and high-level (10-100 kGy). The EPR dosimeter properties were studied under different parameters, i.e., microwave power, materials contents, absorbed doses, storage conditions and post-irradiation effects. Li-formate showed a simple EPR spectrum and exhibited superior radiation response for low-dose range; whereas chitosan and sucrose exhibited linear dose response in all studied dose ranges. The EPR signals of chitosan exhibited similar stability as glucose, Li-formate and alanine at ambient temperature after irradiation as long as a year. All EPR signals of the studied materials were affected post-irradiation temperature and humidity after gamma irradiation. The EPR signal of chitosan exhibited long-term stability and it was not sensitive to high storage temperatures and humidity values after irradiation. Chitosan has a good merit as the alternative bio-based material for a stable EPR dosimeter in a wide range of radiation-absorbed doses.

  14. A Regional PD Strategy for EPR Systems: Evidence-Based IT Development

    DEFF Research Database (Denmark)

    Simonsen, Jesper; Hertzum, Morten

    2006-01-01

    One of the five regions in Denmark has initiated a remark-able and alternative strategy for the development of Elec-tronic Patient Record (EPR) systems. This strategy is driven by Participatory Design (PD) experiments and based on evidence of positive effects on the clinical practice when using EPR...... systems. We present this PD strategy and our related research on evidence-based IT development. We report from a newly completed PD experiment with EPR in the region conducted through a close collaboration compris-ing a neurological stroke unit, the region’s EPR unit, the vendor, as well as the authors....

  15. An advanced EPR stopped-flow apparatus based on a dielectric ring resonator

    Science.gov (United States)

    Lassmann, Günter; Schmidt, Peter Paul; Lubitz, Wolfgang

    2005-02-01

    A novel EPR stopped-flow accessory is described which allows time-dependent cw-EPR measurements of rate constants of reactions involving paramagnetic species after rapid mixing of two liquid reagents. The EPR stopped-flow design represents a state-of-the-art, computer controlled fluid driving system, a miniresonant EPR structure with an integrated small ball mixer, and a stopping valve. The X-band EPR detection system is an improved version of that reported by Sienkiewicz et al. [Rev. Sci. Instr. 65 (1994) 68], and utilizes a resonator with two stacked ceramic dielectric rings separated by a variable spacer. The resonator with the mode TE( H) 011 is tailored particularly for conditions of fast flowing and rapidly stopped aqueous solutions, and for a high time resolution. The short distance between the ball mixer and the small EPR active volume (1.8 μl) yields a measured dead time of 330 μs. A compact assembly of all parts results in minimization of disturbing microphonics. The computer controlled driving system from BioLogic with two independent stepping motors was optimized for EPR stopped-flow with a hard-stop valve. Performance tests on the EPR spectrometer ESP 300E from BRUKER using redox reactions of nitroxide radicals revealed the EPR stopped-flow accessory as an advanced, versatile, and reliable instrument with high reproducibility.

  16. Non-invasive in vivo evaluation of in situ forming PLGA implants by benchtop magnetic resonance imaging (BT-MRI) and EPR spectroscopy.

    Science.gov (United States)

    Kempe, Sabine; Metz, Hendrik; Pereira, Priscila G C; Mäder, Karsten

    2010-01-01

    In the present study, we used benchtop magnetic resonance imaging (BT-MRI) for non-invasive and continuous in vivo studies of in situ forming poly(lactide-co-glycolide) (PLGA) implants without the use of contrast agents. Polyethylene glycol (PEG) 400 was used as an alternative solvent to the clinically used NMP. In addition to BT-MRI, we applied electron paramagnetic resonance (EPR) spectroscopy to characterize implant formation and drug delivery processes in vitro and in vivo. We were able to follow key processes of implant formation by EPR and MRI. Because EPR spectra are sensitive to polarity and mobility, we were able to follow the kinetics of the solvent/non-solvent exchange and the PLGA precipitation. Due to the high water affinity of PEG 400, we observed a transient accumulation of water in the implant neighbourhood. Furthermore, we detected the encapsulation by BT-MRI of the implant as a response of the biological system to the polymer, followed by degradation over a period of two months. We could show that MRI in general has the potential to get new insights in the in vivo fate of in situ forming implants. The study also clearly shows that BT-MRI is a new viable and much less expensive alternative for superconducting MRI machines to monitor drug delivery processes in vivo in small mammals. Copyright 2009 Elsevier B.V. All rights reserved.

  17. Thermodynamic basis of electron transfer in dihydroorotate dehydrogenase B from Lactococcus lactis: analysis by potentiometry, EPR spectroscopy, and ENDOR spectroscopy.

    Science.gov (United States)

    Mohsen, Al-Walid A; Rigby, Stephen E J; Jensen, Kaj Frank; Munro, Andrew W; Scrutton, Nigel S

    2004-06-01

    signal is assigned to the formation of a spin interacting state between the FMN semiquinone species and the reduced 2Fe-2S center. Reduction of DHODB using an excess of NADH or dihydroorotate produces EPR spectra that are distinct from those produced by dithionite. From potentiometric studies, the reduction of the 2Fe-2S center and the reduction of the FMN occur concomitantly. The study provides a detailed thermodynamic framework for electron transfer in this complex iron-sulfur flavoprotein.

  18. Effects of Mn and Fe impurities in the TL and EPR properties of artificial spodumene polycrystals under irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Souza, S.O.; Watanabe, S. [Universidade de Sao Paulo (IF/USP), SP (Brazil). Inst. de Fisica

    2003-07-01

    Full text: A mixture of 57,75% SiO{sub 2}, 24,50% Al{sub 2}O{sub 3} and 17,75 Li{sub 2}CO{sub 3} was melted in a crucible at 1480 deg C during 2h and cooled slowly to obtain pure spodumene (LiAlSi{sub 2}O{sub 6}) polycrystal. A test to obtain the glass transition was presented no suddenly change in the curve, which indicates that the product from the melting was polycrystal without glass phase. The X ray diffraction has shown that portions contained {beta}-spodumene. The same procedure was realized to obtain {beta}-spodumene with Mn and Fe impurities. The polycrystals were investigated as to them TL and EPR properties. After gamma-ray irradiation between 50 and 5000 Gy dose, TL glow peaks at 175, 325 and 410 deg C, in the pure sample, grow. Including 0,075% of Fe{sub 2}O{sub 3} in the mixture, the TL peaks intensity diminish around 35%, besides new TL peaks appear at 215 and 285 deg C. With 0.5% of Fe{sub 2}O{sub 3} the intensity of this peak is 97% minor. The inclusion of 0.54% of MnO in initial mixture also made the whole TL be diminished 30% related to the pure sample and created peaks at 194, 210, 340 and 415 deg C. The EPR spectrum of samples presents many signals. Small amount of Fe, probably included during the heating or grinding process, gives rise to a characteristic Fe{sup 3+} line at g= 4,27 in the pure sample. The most interesting feature of the spectra is the lines between 3000 and 4000 Gauss, which are strong in the pure sample, but almost disappear in the sample with 0,50% of Fe{sub 2}O{sub 3}. While the EPR line at g=2.006 grows as the dose grows, the line at g=2.026 diminish at same rate. Comparing the behaviour of 175 TL peak and these EPR lines, they are very different. It means they are probably due to distinct defects. One needs future data to know the complete traps nature. (author)

  19. CW EPR and 9 GHz EPR imaging investigation of stable paramagnetic species and their antioxidant activities in dry shiitake mushroom (Lentinus edodes).

    Science.gov (United States)

    Nakagawa, Kouichi; Hara, Hideyuki

    2016-01-01

    We investigated the antioxidant activities and locations of stable paramagnetic species in dry (or drying) shiitake mushroom (Lentinus edodes) using continuous wave (CW) electron paramagnetic resonance (EPR) and 9 GHz EPR imaging. CW 9 GHz EPR detected paramagnetic species (peak-to-peak linewidth (ΔHpp) = 0.57 mT) in the mushroom. Two-dimensional imaging of the sharp line using a 9 GHz EPR imager showed that the species were located in the cap and shortened stem portions of the mushroom. No other location of the species was found in the mushroom. However, radical locations and concentrations varied along the cap of the mushroom. The 9 GHz EPR imaging determined the exact location of stable paramagnetic species in the shiitake mushroom. Distilled water extracts of the pigmented cap surface and the inner cap of the mushroom showed similar antioxidant activities that reduced an aqueous solution of 0.1 mM 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl. The present results suggest that the antioxidant activities of the edible mushroom extracts are much weaker than those of ascorbic acid. Thus, CW EPR and EPR imaging revealed the location and distribution of stable paramagnetic species and the antioxidant activities in the shiitake mushroom for the first time.

  20. EPR study of complex formation between copper (II) ions and sympathomimetic amines in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Preoteasa, E.A. [Inst. of Atomic Physics, IFIN, Bucharest (Romania); Duliu, O.G.; Grecu, V.V. [Bucharest, Univ. (Romania). Dept. of Atomic and Nuclear Physics

    1997-07-01

    The complex formation between sympathomimetic amines (SA): adrenaline (AD), noradrenaline (NA), dopamine (DA), ephedrine (ED) and p-tyramine (pTA), and Cu(II) ion in aqueous solution has been studied by X-band EPR at room temperature. Excepting pTA, all investigated SA yielded two types of complexes in different pH domains. All complexes consistent with a ligand fields having a distorted octahedral symmetry, i.e., hexacoordination of Cu(II). The covalence coefficient calculated from the isotropic g and A values has shown strong ionic sigma-type ligand bonds. A structural model with the Cu(II) ion bound by four catecholic O(hydroxy) atoms for the low pH complexes of AD, NA and DA is proposed. For the high pH complexes of the former compounds as well as for both Ed complexes, the authors suppose Cu(II) bound by two N (amino) and two O (hydroxy) atoms. The spectra are consistent to water binding on the longitudinal octahedron axis in all compounds excepting the high pH complex of Ed, where OH2- ions are bound. Possible implications for the SA-cell receptors interactions are discussed.

  1. EPR dosimetry of radiation background in the Urals region

    Energy Technology Data Exchange (ETDEWEB)

    Shishkina, E.A.; Degteva, M.O.; Shved, V.A. [Urals Research Center for Radiation Medicine, 48-A Vorovsky, Chelyabinsk 454076 (Russian Federation); Fattibene, P.; Onori, S. [Istituto Superiore di Sanita and Istituto Nazionale di Fisica Nucleare (Italy); Wieser, A. [GSF, Forschungszentrum fuer Umwelt und Gesundheit, Ingolstaedter Landstr (Germany); Ivanov, D.V.; Bayankin, S.N. [Institute of Metal Physics, Russian Academy of Sciences (Russian Federation); Knyazev, V.A.; Vasilenko, E.I.; Gorelov, M. [ZAO, Closed Corporation ' Company GEOSPETSECOLOGIA' (Russian Federation)

    2006-07-01

    Method of Electron Paramagnetic Resonance is extensively applied to individual retrospective dosimetry. The background dose is unavoidable component of cumulative absorbed dose in the tooth enamel accumulated during the lifetime of donor. Estimation of incidental radiation dose using tooth enamel needs in extraction of background dose. Moreover, the variation of background doses in the population is a limited factor for reliable detection of additional irradiation especially for low dose level. Therefore the accurate knowledge of the natural background radiation dose is a critical element of EPR studies of exposed populations. In the Urals region the method applies for such two large cohorts as the workers of Mayak (Ozersk citizens) and Techa River riverside inhabitants (rural population). Current study aimed to investigate the Urals radiation background detected by EPR spectrometry. For this aim two group of unexposed Urals residents were separated, viz: citizens of Ozersk and rural inhabitants of Chelyabinsk region. Comparison of two investigated territories has demonstrated that from the point of view of radiation background it is impossible to assume the Urals population as uniform. The reliable difference between the urban and rural residents has been found. The average background doses of Ozersk donors is in average 50 mGy higher than those detected for rural residents. The individual variability of background doses for Osersk has been higher than in the rural results. The difference in background dose levels between two population results in different limits of accidental dose detection and individualization. The doses for 'Mayak' workers (Ozyorsk citizens) can be classed as anthropogenic if the EPR measurements exceed 120 mGy for teeth younger than 40 years, and 240 mGy for teeth older than 70 years. The anthropogenic doses for Techa River residents (rural population) would be higher than 95 mGy for teeth younger than 50 years and 270 mGy for

  2. EPR Characterization of the Triheme Cytochrome from Geobacter sulfurreducens.

    Science.gov (United States)

    Ponomarenko, Nina; Niklas, Jens; Pokkuluri, Phani Raj; Poluektov, Oleg G; Tiede, David Michael

    2018-01-03

    Periplasmic cytochrome A (PpcA) is a representative of a broad class of multi-heme cytochromes functioning as protein "nanowires" for storage and extracellular transfer of multiple electrons in the δ-proteobacterium Geobacter sulfurreducens. PpcA contains three bis-His coordinated hemes held in a spatial arrangement that is highly conserved among the multi-heme cytochromes c3 and c7 families, carries low potential hemes and is notable for having one of the lowest number of amino acids utilized to maintain a characteristic protein fold and site specific heme function. Low temperature X-band EPR spectroscopy has been used to characterize the electronic configuration of the Fe(III) and the ligation mode for each heme. The three sets of EPR signals are assigned to individual hemes in the 3D crystal structure. The relative energy levels of the Fe(III) 3d orbitals for individual hemes was estimated from the principal g values. The observed g tensor anisotropy was used as a probe of electronic structure of each heme and differences were determined by specifics of axial ligation. To ensure unambiguous assignment of highly anisotropic low spin (HALS) signal to individual hemes, EPR analyses of iron atom electronic configurations have been supplemented with investigation of porphyrin macrocycles by 1D 1H NMR chemical shift patterns for the methyl substituents. Within optimized geometry of hemes in PpcA the magnetic interactions between hemes were found to be minimal, similar to c3 family of tetraheme cytochromes.

  3. Low temperature EPR investigation of Co{sup 2+} ion doped into rutile TiO{sub 2} single crystal: Experiments and simulations

    Energy Technology Data Exchange (ETDEWEB)

    Zerentürk, A. [Department of Physics, Marmara University, 34722 Kadıköy, Istanbul (Turkey); Açıkgöz, M., E-mail: muhammed.acikgoz@eng.bau.edu.tr [Bahcesehir University, Faculty of Engineering and Natural Sciences, Besiktas Campus, 34349 Besiktas, Istanbul (Turkey); Kazan, S.; Yıldız, F.; Aktaş, B. [Department of Physics, Gebze Technical University, 41400 Gebze, Kocaeli (Turkey)

    2017-02-01

    In this paper, we present the results of X-band EPR spectra of Co{sup 2+} ion doped rutile (TiO{sub 2}) which is one of the most promising memristor material. We obtained the angular variation of spectra in three mutually perpendicular planes at liquid helium (7–13 K) temperatures. Since the impurity ions have ½ effective spin and 7/2 nuclear spin, a relatively simple spin Hamiltonian containing only electronic Zeeman and hyperfine terms was utilized. Two different methods were used in theoretical analysis. Firstly, a linear regression analysis of spectra based on perturbation theory was studied. However, this approach is not sufficient for analyzing Co{sup +2} spectra and leads to complex eigenvectors for G and A tensors due to large anisotropy of eigenvalues. Therefore, all spectra were analyzed again with exact diagonalization of spin Hamiltonian and the high accuracy eigenvalues and eigenvectors of G and A tensors were obtained by taking into account the effect of small sample misalignment from the exact crystallographic planes due to experimental conditions. Our results show that eigen-axes of g and A tensors are parallel to crystallographic directions. Hence, our EPR experiments proves that Co{sup 2+} ions substitute for Ti{sup 4+} ions in lattice. The obtained principal values of g tensor are g{sub x}=2.110(6), g{sub y}=5.890(2), g{sub z}=3.725(7) and principal values of hyperfine tensor are A{sub x}=42.4, A{sub y}=152.7, A{sub z}=26 (in 10{sup −4}/cm). - Highlights: • X-band EPR spectra of Co{sup 2+} ion doped rutile (TiO{sub 2}) investigated at 7–13 K. • Two different methods were used in theoretical analysis. • The presence of two structurally equivalent centers for Co{sup 2+} ions observed. • It is concluded that impurity ions substitute for Ti{sup 4+} ion.

  4. EPR study on copper- and vanadium complexes with substituted phthalocyanines

    Energy Technology Data Exchange (ETDEWEB)

    Shklyaev, A.A.; Selyutin, G.E.; Shakot' ko, N.I.; Mikhalenko, S.A. (Nauchno-Issledovatel' skij Inst. Organicheskikh Poluproduktov i Krasitelej, Moscow (USSR))

    1984-06-01

    The structure of binuclear associates of substituted vanadyl- and copper-phthalocyanines is investigated. The EPR study has shown that metal phthalocyanine protonation in acid media (CH/sub 2/Cl/sub 2/, Py, H/sub 2/SO/sub 4/, toluence, etc) is accompanied by destabilization of bonds of the central ion with a polycyclic ligand. Substituted copper- and vanadyl phthalocyanines form dimerized associates where M-M interatmic distance varies in a wide range from 4.1 to 12 A.

  5. Medical reference dosimetry using EPR measurements of alanine

    DEFF Research Database (Denmark)

    Helt-Hansen, Jakob; Rosendal, F.; Kofoed, I.M.

    2009-01-01

    Background. Electron spin resonance (EPR) is used to determine the absorbed dose of alanine dosimeters exposed to clinical photon beams in a solid-water phantom. Alanine is potentially suitable for medical reference dosimetry, because of its near water equivalence over a wide energy spectrum, low...... methods the proposed algorithm can be applied without normalisation of phase shifts caused by changes in the g-value of the cavity. The study shows that alanine dosimetry is a suitable candidate for medical reference dosimetry especially for quality control applications....

  6. SAWYER ASTEROID SPECTRA

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set contains 94 optical asteroid spectra obtained by Scott Sawyer as part of his Ph.D. dissertation at the University of Texas at Austin. Observational...

  7. Competing interactions and dimensional crossover in (Er{sub 0.5}Y{sub 0.5}){sub 2}Cu{sub 2}O{sub 5} studied by EPR

    Energy Technology Data Exchange (ETDEWEB)

    Typek, J. [Institute of Physics, Szczecin University of Technology, Al. Piastow 17, 70-310 Szczecin (Poland)]. E-mail: typjan@ps.pl

    2007-08-16

    Copper spin dynamics in (Er{sub 0.5}Y{sub 0.5}){sub 2}Cu{sub 2}O{sub 5} solid solution has been investigated by electron paramagnetic resonance (EPR) technique. The temperature dependence of the EPR integrated intensity of the resonance line has showed a pronounced maximum at low temperatures and has vanished at the transition to the antiferromagnetic ordering at T {sub N} = 11 K. The temperature at which the EPR integrated intensity reaches maximum was different for the heating and cooling runs. Study of the product of integrated intensity and temperature has allowed determination of the dominating interactions in a particular temperature range. A model used previously to describe the AFM modes in the antiferromagnetic state of Y{sub 2}Cu{sub 2}O{sub 5} was applied to explain the observed changes in the EPR spectra. A dimensional crossover from 2D to 3D magnetic behaviour was observed at 55 K and interpreted in terms of the spin correlation length.

  8. EPR of photochromic Mo3+ in SrTiO3

    NARCIS (Netherlands)

    Kool, Th.W.

    2010-01-01

    In single crystals of SrTiO_3, a paramagnetic center, characterized by S = 3/2 and hyperfine interaction with an I = 5/2 nuclear spin has been observed in the temperature range 4.2K-77K by means of EPR. The impurity center is attributed to Mo3+. No additional line splitting in the EPR spectrum due

  9. EPR study of positive holes on phenylene vinylene chains : from dimer to polymer

    NARCIS (Netherlands)

    Zezin, AA; Feldman, [No Value; Warman, JM; Wildeman, J; Hadziioannou, G

    2004-01-01

    Isolated radical cations of substituted oligomers and polymers of phenylene vinylenes (PV) produced by irradiation in glassy toluene solutions were characterized by EPR. It was shown that the linewidth of the EPR signal from radical cations in oligomers decreased with increasing the number of repeat

  10. Design and testing of a 750MHz CW-EPR digital console for small animal imaging.

    Science.gov (United States)

    Sato-Akaba, Hideo; Emoto, Miho C; Hirata, Hiroshi; Fujii, Hirotada G

    2017-11-01

    This paper describes the development of a digital console for three-dimensional (3D) continuous wave electron paramagnetic resonance (CW-EPR) imaging of a small animal to improve the signal-to-noise ratio and lower the cost of the EPR imaging system. A RF generation board, an RF acquisition board and a digital signal processing (DSP) & control board were built for the digital EPR detection. Direct sampling of the reflected RF signal from a resonator (approximately 750MHz), which contains the EPR signal, was carried out using a band-pass subsampling method. A direct automatic control system to reduce the reflection from the resonator was proposed and implemented in the digital EPR detection scheme. All DSP tasks were carried out in field programmable gate array ICs. In vivo 3D imaging of nitroxyl radicals in a mouse's head was successfully performed. Copyright © 2017 Elsevier Inc. All rights reserved.

  11. Preliminary study for precision dosimetry using electron paramagnetic resonance (EPR) in radiotherapy applications

    Energy Technology Data Exchange (ETDEWEB)

    Shehzadi, N. N.; Kim, I. J.; Yi, C. Y. [Center for Ionizing Radiation, Korea Research for Standards and Science, Daejeon (Korea, Republic of)

    2015-10-15

    EPR (Electron paramagnetic resonance) dosimetry for radiotherapy dose range (1-10 Gy) is still being established.Alanine is an important material for EPR dosimetry because in terms of density and radiation absorption properties, it is water equivalent. High repeatability and high reproducibility of alanine spectrum measurement makes it possible to estimate the irradiation dose accurately. This baseline study has been carried out to establish precision EPR dosimetry in therapeutic photon range. For that purpose, an EPR dosimetry system has been setup and repeatability as well as reproducibility of measurements using alanine dosimeter have been evaluated. Effect of anisotropy of alanine dosimeter in spectrometer cavity has also been observed. EPR dosimetry system is set up at KRISS. It is found that reproducibility of the system at therapeutic photon range is 1.5 % - 6.6 %.

  12. Structural, EPR, photo and thermoluminescence properties of ZnO:Fe nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Reddy, A. Jagannatha [Department of Physics, M. S. Ramaiah Institute of Technology, Bangalore 560 054 (India); Kokila, M.K. [Department of Physics, Bangalore University, Bangalore 560 056 (India); Nagabhushana, H., E-mail: bhushanvl@rediffmail.com [Prof C.N.R. Rao Centre for Nano Research, Tumkur University, Tumkur 572 103 (India); Sharma, S.C. [Prof C.N.R. Rao Centre for Nano Research, Tumkur University, Tumkur 572 103 (India); Rao, J.L. [Department of Physics, S.V. University, Tirupathi 517 502 (India); Shivakumara, C. [Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560 012 (India); Nagabhushana, B.M. [Department of Chemistry, M. S. Ramaih Institute of Technology, Bangalore 560 054 (India); Chakradhar, R.P.S., E-mail: sreechakra72@yahoo.com [CSIR-National Aerospace Laboratories, Bangalore 560017 (India)

    2012-04-16

    Highlights: Black-Right-Pointing-Pointer ZnO:Fe nanopowders were prepared by LSC method. Black-Right-Pointing-Pointer PXRD, SEM, TEM, FTIR, UV-Vis, Raman, EPR, PL and TL studies were carried out. Black-Right-Pointing-Pointer Single well resolved TL glow peak at {approx}368 Degree-Sign C was observed. Black-Right-Pointing-Pointer The trap parameters have been evaluated and discussed. - Abstract: Zn{sub (1-x)}Fe{sub (x)}O{sub (1+0.5x)} (x = 0.5-5 mol%) nanoparticles were synthesized by a low temperature solution combustion route. The structural characterization of these nanoparticles by PXRD, SEM and TEM confirmed the phase purity of the samples and indicated a reduction in the particle size with increase in Fe content. A small increase in micro strain in the Fe doped nanocrystals is observed from W-H plots. EPR spectrum exhibits an intense resonance signal with effective g values at g Almost-Equal-To 2.0 with a sextet hyperfine structure (hfs) besides a weak signal at g Almost-Equal-To 4.13. The signal at g Almost-Equal-To 2.0 with a sextet hyperfine structure might be due to manganese impurity where as the resonance signal at g Almost-Equal-To 4.13 is due to iron. The optical band gap E{sub g} was found to decrease with increase of Fe content. Raman spectra exhibit two non-polar optical phonon (E{sub 2}) modes at low and high frequencies at 100 and 435 cm{sup -1} in Fe doped samples. These modes broaden and disappear with increase of Fe dopant concentration. TL measurements of {gamma}-irradiated (1-5 kGy) samples show a main glow peak at 368 Degree-Sign C at a warming rate of 6.7 Degree-Sign Cs{sup -1}. The thermal activation parameters were estimated from Glow peak shape method. The average activation energy was found to be in the range 0.34-2.81 eV.

  13. Dosimetry of stereotactic radiosurgery using lithium formate EPR dosimeters

    Science.gov (United States)

    Waldeland, Einar; Hörling, Magnus; Olaug Hole, Eli; Sagstuen, Einar; Malinen, Eirik

    2010-04-01

    Small lithium formate EPR (electron paramagnetic resonance) dosimeters (diameter 3 mm, height 2 mm) were produced and employed for 2D dosimetry of stereotactic radiosurgery (SRS). An anthropomorphic head phantom with an in-house made insert holding 45 lithium formate dosimeters was used. A spherical target was outlined centrally in planning CT images of the head and an SRS dose plan with three arcs was made using the iPlan planning system. Beam collimation was achieved with the BrainLAB m3 micro-MLC. The minimum target dose was 15 Gy. The planned dose distribution was compared to measurements. For dosimetry, a dosimeter calibration series was generated with doses from 1 to 20 Gy. At the treatment unit, three replicate measurement series were performed. The measurements gave on average 2.2% lower dose at the plateau of the dose distribution compared to the dose plan. Larger differences were seen in the penumbra, where the dose plan underestimated the dose gradients. By repeated measurements, the systematic and random error in the SRS delivery was estimated to less than 1 mm. In conclusion, the planning system produced an intracranial dose distribution with tolerable accuracy. Furthermore, small lithium formate EPR dosimeters were useful for measuring SRS dose distributions.

  14. New Developments in Spin Labels for Pulsed Dipolar EPR

    Directory of Open Access Journals (Sweden)

    Alistair J. Fielding

    2014-10-01

    Full Text Available Spin labelling is a chemical technique that enables the integration of a molecule containing an unpaired electron into another framework for study. Given the need to understand the structure, dynamics, and conformational changes of biomacromolecules, spin labelling provides a relatively non-intrusive technique and has certain advantages over X-ray crystallography; which requires high quality crystals. The technique relies on the design of binding probes that target a functional group, for example, the thiol group of a cysteine residue within a protein. The unpaired electron is typically supplied through a nitroxide radical and sterically shielded to preserve stability. Pulsed electron paramagnetic resonance (EPR techniques allow small magnetic couplings to be measured (e.g., <50 MHz providing information on single label probes or the dipolar coupling between multiple labels. In particular, distances between spin labels pairs can be derived which has led to many protein/enzymes and nucleotides being studied. Here, we summarise recent examples of spin labels used for pulse EPR that serve to illustrate the contribution of chemistry to advancing discoveries in this field.

  15. Identification of irradiated food by EPR-spectroscopy and tomography

    Energy Technology Data Exchange (ETDEWEB)

    Groth, N. (KAI e.V., Tomographie-Labor, Berlin (Germany)); Anders, B. (Technische Fachhochschule Berlin (Germany). Fachbereich Mathematik/Physik); Maerzke, A. (Forschungsstelle fuer Ortsaufloesende Messtechnik e.V., Berlin (Germany)); Nitschke, S. (KAI e.V., Tomographie-Labor, Berlin (Germany)); Schlawe, R. (Forschungsstelle fuer Ortsaufloesende Messtechnik e.V., Berlin (Germany)); Herrling, T. (KAI e.V., Tomographie-Labor, Berlin (Germany))

    1993-01-01

    Food irradiation is used to kill harmful microorganisms (e.g. salmonella), this improving food safety and extending the shelf-life. The electron paramagnetic resonance (EPR) detection of stable, radiation-induced free radicals within the matrix of calcified tissue is well established. An extention of this technique to food provides in suitable cases one of the most promissing methods for detecting that irradiation has been performed. It provides an excellent method for the identification of irradiated foods containing bones or calcified cuticle even in the absence of unirradiated controls. Bones of chicken, pepper grains and lentils were also identified as irradiated some weeks after radiation treatment. The method is rapid and can detect very low doses. With EPR - Tomography the 2D spatial distribution of the irradiation induced stable radicals in the cross section of a chicken bone was measured. The use of ionising radiation to treat certain foodstuffs is increasingly of interest and there is a need to determine wether irradiation has occured, and to what extent. (orig.)

  16. SIMULACIÓN DEL ESPECTRO EPR DEL RADICAL CO2-

    Directory of Open Access Journals (Sweden)

    Eduar Enrique Carvajal Taborda

    2013-09-01

    Full Text Available La  dosimetría EPR se basa en el hecho de que las radiaciones ionizantes interaccionan con el tejido mineralizado, en este caso es esmalte dental y tejido óseo, generan los radicales CO2- estables a temperatura ambiente y de larga vida cuya concentración depende de la dosis recibida. La cuantificación de estos radicales libres se hace por EPR, cuyo espectro característico consta de dos líneas, una muy intensa y otra de menor intensidad. En este trabajo identificamos teóricamente estas dos líneas solucionando el Hamiltoniano de espín electrónico y  simulando el espectro experimental, encontramos que el espectro ERP del radical CO2- es producido por la interacción del espín del electrón desapareado con el campo magnético externo y que el radical CO2- está ubicado en una simetría local axial.

  17. EPR and ligand field studies of iron superoxide dismutases and iron-substituted manganese superoxide dismutases: relationships between electronic structure of the active site and activity.

    Science.gov (United States)

    Renault, J P; Verchère-Béaur, C; Morgenstern-Badarau, I; Yamakura, F; Gerloch, M

    2000-06-12

    The problem of metal selectivity of iron/manganese superoxide dismutases (SODs) is addressed through the electronic structures of active sites using electron paramagnetic resonance and ligand field calculations. Studies of wild-type iron(III) SOD (FeSOD) from Escherichia coli and from Methanobacterium thermoautotrophicum and iron-substituted manganese(III) SOD (Fe(sub)MnSOD) from E. coli and from Serratia marcescens are reported. EPR spectroscopy of wild-type enzymes shows transitions within all three Kramers doublets identified by their g values. From the temperature dependence of the observed transitions, the zero-field splitting is found to be negative, D = -2 +/- 0.2 cm-1. The electronic structure is typical of a distorted trigonal bipyramid, all the EPR features being reproduced by ligand field analysis. This unique and necessary electronic structure characterizes wild-type enzymes whatever their classification from the amino acid sequence into iron or manganese types, as E. coli FeSOD or M. thermoautotrophicum FeSOD. In iron-substituted manganese SODs, reduced catalytic activity is found. We describe how inhomogeneity of all reported substituted MnSODs might explain the activity decrease. EPR spectra of substituted enzymes show several overlapping components. From simulation of these spectra, one component is identified which shares the same electronic structure of the wild-type FeSODs, with the proportion depending on pH. Ligand field calculations were performed to investigate distortions of the active site geometry which induce variation of the excitation energy of the lowest quartet state. The corresponding coupling between the ground state and the excited state is found to be maximum in the geometry of the native SODs. We conjecture that such coupling should be considered in the electron-transfer process and in the contribution of the typical electronic structure of FeSOD to the activity.

  18. Stable radicals and biochemical compounds in embryos and endosperm of wheat grains differentiating sensitive and tolerant genotypes--EPR and Raman studies.

    Science.gov (United States)

    Kurdziel, Magdalena; Dłubacz, Aleksandra; Wesełucha-Birczyńska, Aleksandra; Filek, Maria; Łabanowska, Maria

    2015-07-01

    The aim of this study was to uncover the specific species in grains that might differentiate the wheat genotypes according to their tolerance to oxidative stress. Measurements by EPR and Raman spectroscopy techniques were used to examine whole grains and their parts (embryo, endosperm, seed coat) originating from four wheat genotypes with differing tolerance to drought stress. Raman spectra showed that, in spite of the similar amounts of proteins in whole grains from tolerant and sensitive genotypes, in tolerant ones they were accumulated mainly in embryos. Moreover, in embryos from these grains, a higher content of unsaturated fatty acids was observed. Endosperm of grains from the tolerant genotype, richer with starch than that of sensitive one, exhibited higher content of amylopectin. Detailed analysis of EPR signals and simulation procedures of the spectra allowed the estimation of the nature of interactions of Fe(III) and Mn(II) with organic and inorganic structures of grains and the character of organic stable radicals. Three types of these radicals: carbohydrate, semiquinone and phenoxyl, were identified. The amounts of these radicals were higher in grains of sensitive genotypes, mostly because of differences in carbohydrate radical content in endosperm. Taking into account the level of radical concentration and greater capacity for radical formation in grains from plants of lower tolerance to stress, the content of radicals, especially of a carbohydrate nature, was considered as a marker of the plant resistance to stress conditions. Copyright © 2015 Elsevier GmbH. All rights reserved.

  19. Mn7 species with an S = 29/2 ground state: high-frequency EPR studies of a species at the classical/quantum spin interface.

    Science.gov (United States)

    Wang, Zhenxing; van Tol, Johan; Taguchi, Taketo; Daniels, Matthew R; Christou, George; Dalal, Naresh S

    2011-11-09

    A high spin (S) compound has been synthesized whose properties straddle the interface between the classical and quantum mechanical spin descriptions. The cluster [Mn(7)O(4)(pdpm)(6)(N(3))(4)](ClO(4))(2) (Mn(7)) has an unprecedented core structure comprising an octahedral [Mn(III)(6)(μ(4)-O)(μ(3)-O)(3)(μ(3)-N(3))(4)](6+) unit with one of its faces capped by a Mn(II) ion. Magnetization and susceptibility studies indicate an S = (29/2) ground state, the maximum possible. Variable-temperature, high-frequency electron paramagnetic resonance (HF-EPR) spectra on powder and single-crystal samples of Mn(7) exhibit sharp spectral features characteristic of a quantum spin that are well resolved in a certain temperature range but which transform to a continuum of peaks characteristic of a classical spin in another; these features have been well reproduced by computer simulations. A fast Fourier transform analysis of the sharp spectral features and the low temperature EPR spectra suggests that more than one spin state are involved.

  20. Highly-Efficient Charge Separation and Polaron Delocalization in Polymer-Fullerene Bulk-Heterojunctions: A Comparative Multi-Frequency EPR & DFT Study

    Science.gov (United States)

    Niklas, Jens; Mardis, Kristy L.; Banks, Brian P.; Grooms, Gregory M.; Sperlich, Andreas; Dyakonov, Vladimir; Beaupré, Serge; Leclerc, Mario; Xu, Tao; Yu, Luping; Poluektov, Oleg G.

    2016-01-01

    The ongoing depletion of fossil fuels has led to an intensive search for additional renewable energy sources. Solar-based technologies could provide sufficient energy to satisfy the global economic demands in the near future. Photovoltaic (PV) cells are the most promising man-made devices for direct solar energy utilization. Understanding the charge separation and charge transport in PV materials at a molecular level is crucial for improving the efficiency of the solar cells. Here, we use light-induced EPR spectroscopy combined with DFT calculations to study the electronic structure of charge separated states in blends of polymers (P3HT, PCDTBT, and PTB7) and fullerene derivatives (C60-PCBM and C70-PCBM). Solar cells made with the same composites as active layers show power conversion efficiencies of 3.3% (P3HT), 6.1% (PCDTBT), and 7.3% (PTB7), respectively. Under illumination of these composites, two paramagnetic species are formed due to photo-induced electron transfer between the conjugated polymer and the fullerene. They are the positive, P+, and negative, P-, polarons on the polymer backbone and fullerene cage, respectively, and correspond to radical cations and radical anions. Using the high spectral resolution of high-frequency EPR (130 GHz), the EPR spectra of these species were resolved and principal components of the g-tensors were assigned. Light-induced pulsed ENDOR spectroscopy allowed the determination of 1H hyperfine coupling constants of photogenerated positive and negative polarons. The experimental results obtained for the different polymer-fullerene composites have been compared with DFT calculations, revealing that in all three systems the positive polaron is distributed over distances of 40 - 60 Å on the polymer chain. This corresponds to about 15 thiophene units for P3HT, approximately three units PCDTBT, and about three to four units for PTB7. No spin density delocalization between neighboring fullerene molecules was detected by EPR. Strong

  1. Effect of Ca2+/Sr2+ substitution on the electronic structure of the oxygen-evolving complex of photosystem II: a combined multifrequency EPR, 55Mn-ENDOR, and DFT study of the S2 state.

    Science.gov (United States)

    Cox, Nicholas; Rapatskiy, Leonid; Su, Ji-Hu; Pantazis, Dimitrios A; Sugiura, Miwa; Kulik, Leonid; Dorlet, Pierre; Rutherford, A William; Neese, Frank; Boussac, Alain; Lubitz, Wolfgang; Messinger, Johannes

    2011-03-16

    The electronic structures of the native Mn(4)O(x)Ca cluster and the biosynthetically substituted Mn(4)O(x)Sr cluster of the oxygen evolving complex (OEC) of photosystem II (PSII) core complexes isolated from Thermosynechococcus elongatus, poised in the S(2) state, were studied by X- and Q-band CW-EPR and by pulsed Q-band (55)Mn-ENDOR spectroscopy. Both wild type and tyrosine D less mutants grown photoautotrophically in either CaCl(2) or SrCl(2) containing media were measured. The obtained CW-EPR spectra of the S(2) state displayed the characteristic, clearly noticeable differences in the hyperfine pattern of the multiline EPR signal [Boussac et al. J. Biol. Chem.2004, 279, 22809-22819]. In sharp contrast, the manganese ((55)Mn) ENDOR spectra of the Ca and Sr forms of the OEC were remarkably similar. Multifrequency simulations of the X- and Q-band CW-EPR and (55)Mn-pulsed ENDOR spectra using the Spin Hamiltonian formalism were performed to investigate this surprising result. It is shown that (i) all four manganese ions contribute to the (55)Mn-ENDOR spectra; (ii) only small changes are seen in the fitted isotropic hyperfine values for the Ca(2+) and Sr(2+) containing OEC, suggesting that there is no change in the overall spin distribution (electronic coupling scheme) upon Ca(2+)/Sr(2+) substitution; (iii) the changes in the CW-EPR hyperfine pattern can be explained by a small decrease in the anisotropy of at least two hyperfine tensors. It is proposed that modifications at the Ca(2+) site may modulate the fine structure tensor of the Mn(III) ion. DFT calculations support the above conclusions. Our data analysis also provides strong support for the notion that in the S(2) state the coordination of the Mn(III) ion is square-pyramidal (5-coordinate) or octahedral (6-coordinate) with tetragonal elongation. In addition, it is shown that only one of the currently published OEC models, the Siegbahn structure [Siegbahn, P. E. M. Acc. Chem. Res.2009, 42, 1871-1880, Pantazis

  2. Atomic Spectra Database (ASD)

    Science.gov (United States)

    SRD 78 NIST Atomic Spectra Database (ASD) (Web, free access)   This database provides access and search capability for NIST critically evaluated data on atomic energy levels, wavelengths, and transition probabilities that are reasonably up-to-date. The NIST Atomic Spectroscopy Data Center has carried out these critical compilations.

  3. EPR pairing dynamics in Hubbard model with resonant U.

    Science.gov (United States)

    Zhang, X Z; Song, Z

    2016-01-05

    We study the dynamics of the collision between two fermions in Hubbard model with on-site interaction strength U. The exact solution shows that the scattering matrix for two-wavepacket collision is separable into two independent parts, operating on spatial and spin degrees of freedom, respectively. The S-matrix for spin configuration is equivalent to that of Heisenberg-type pulsed interaction with the strength depending on U and relative group velocity vr. This can be applied to create distant EPR pair, through a collision process for two fermions with opposite spins in the case of |vr/U| = 1, without the need for temporal control and measurement process. Multiple collision process for many particles is also discussed.

  4. Quantum secure direct communication by EPR pairs and entanglement swapping

    CERN Document Server

    Gao, T; Yan, F L; 10.1393/ncb/i2004-10090-1

    2004-01-01

    We present, a quantum secure direct communication scheme achieved by swapping quantum entanglement. In this scheme a set of ordered Einstein-Podolsky-Rosen (HPIl) pairs is used as a quantum information channel for sending secret messages directly. After insuring the safety of the quantum channel, the sender Alice encodes the secret messages directly by applying a series local operations on her particle sequences according to their stipulation. Using three EPR pairs, three bits of secret classical information can be faithfully transmitted from Alice to remote Bob without revealing any information to a potential eavesdropper. By both Alice and Bob's GHZ state measurement results, Bob is able to read out the encoded secret messages directly. The protocol is completely secure if perfect quantum channel is used, because there is not a transmission of the qubits carrying the secret message between Alice and Bob in the public channel.

  5. N-player quantum games in an EPR setting.

    Science.gov (United States)

    Chappell, James M; Iqbal, Azhar; Abbott, Derek

    2012-01-01

    The N-player quantum games are analyzed that use an Einstein-Podolsky-Rosen (EPR) experiment, as the underlying physical setup. In this setup, a player's strategies are not unitary transformations as in alternate quantum game-theoretic frameworks, but a classical choice between two directions along which spin or polarization measurements are made. The players' strategies thus remain identical to their strategies in the mixed-strategy version of the classical game. In the EPR setting the quantum game reduces itself to the corresponding classical game when the shared quantum state reaches zero entanglement. We find the relations for the probability distribution for N-qubit GHZ and W-type states, subject to general measurement directions, from which the expressions for the players' payoffs and mixed Nash equilibrium are determined. Players' N x N payoff matrices are then defined using linear functions so that common two-player games can be easily extended to the N-player case and permit analytic expressions for the Nash equilibrium. As a specific example, we solve the Prisoners' Dilemma game for general N ≥ 2. We find a new property for the game that for an even number of players the payoffs at the Nash equilibrium are equal, whereas for an odd number of players the cooperating players receive higher payoffs. By dispensing with the standard unitary transformations on state vectors in Hilbert space and using instead rotors and multivectors, based on Clifford's geometric algebra (GA), it is shown how the N-player case becomes tractable. The new mathematical approach presented here has wide implications in the areas of quantum information and quantum complexity, as it opens up a powerful way to tractably analyze N-partite qubit interactions.

  6. N-player quantum games in an EPR setting.

    Directory of Open Access Journals (Sweden)

    James M Chappell

    Full Text Available The N-player quantum games are analyzed that use an Einstein-Podolsky-Rosen (EPR experiment, as the underlying physical setup. In this setup, a player's strategies are not unitary transformations as in alternate quantum game-theoretic frameworks, but a classical choice between two directions along which spin or polarization measurements are made. The players' strategies thus remain identical to their strategies in the mixed-strategy version of the classical game. In the EPR setting the quantum game reduces itself to the corresponding classical game when the shared quantum state reaches zero entanglement. We find the relations for the probability distribution for N-qubit GHZ and W-type states, subject to general measurement directions, from which the expressions for the players' payoffs and mixed Nash equilibrium are determined. Players' N x N payoff matrices are then defined using linear functions so that common two-player games can be easily extended to the N-player case and permit analytic expressions for the Nash equilibrium. As a specific example, we solve the Prisoners' Dilemma game for general N ≥ 2. We find a new property for the game that for an even number of players the payoffs at the Nash equilibrium are equal, whereas for an odd number of players the cooperating players receive higher payoffs. By dispensing with the standard unitary transformations on state vectors in Hilbert space and using instead rotors and multivectors, based on Clifford's geometric algebra (GA, it is shown how the N-player case becomes tractable. The new mathematical approach presented here has wide implications in the areas of quantum information and quantum complexity, as it opens up a powerful way to tractably analyze N-partite qubit interactions.

  7. Investigations for the EPR-concept - KAPOOL and KATS experiments

    Energy Technology Data Exchange (ETDEWEB)

    Engel, G.; Eppinger, B.; Fieg, G.; Schmidt-Stiefel, S. [Forschungszentrum Karlsruhe GmbH Technik und Umwelt (Germany). Inst. fuer Kern- und Energietechnik; Messainguiral, C.; Prothmann, N.; Raupp, D.; Schuetz, W. [Forschungszentrum Karlsruhe GmbH Technik und Umwelt (Germany). Inst. fuer Reaktorsicherheit; Stegmaier, U. [Forschungszentrum Karlsruhe GmbH Technik und Umwelt (Germany). Inst. fuer Materialforschung 1 - Angewandte Werkstoffphysik; Massier, H. [Forschungszentrum Karlsruhe GmbH Technik und Umwelt (Germany). Inst. fuer Hochleistungsimpuls- und Mikrowellentechnik; Stern, G.; Veser, A. [Fa. Pro-Science (Germany)

    2000-08-01

    The objective of the KAPOOL and KATS experiments is to investigate basic phenomena in connection with the EPR melt spreading and cooling concept. High-temperature Al{sub 2}O{sub 3}- and Fe-melts produced by the thermite reaction are used to simulate the oxidic and metallic components of the core melt. Two KAPOOL tests have been performed to study the interaction of the oxidic melt with the release gate which is situated between the cavity and the spreading compartment. These tests have been analyzed with the HEATING-5 code and compared with the experimental results. With test KATS-17 (spreading onto dry concrete for the oxide melt, spreading onto concrete with 1 mm water level for the metallic melt) the series of two-dimensional spreading experiments has been finished. KATS-15 (2-dim spreading on dry ceramics) has been analyzed with the code CORFLOW. (orig.) [German] In den KAPOOL- und KATS-Experimenten werden grundlegende Phaenomene des EPR-Konzepts zur Ausbreitung und Kuehlung der Kernschmelze untersucht. Die oxidische und metallische Komponente der Kernschmelze werden dabei durch mittels der Thermit-Reaktion erzeugte Al{sub 2}O{sub 3}- und Fe-Schmelzen simuliert. In zwei KAPOOL-Tests wurde die Wechselwirkung der oxidischen Schmelze mit dem Schmelztor untersucht, das den Ausbreitungsraum von der Kaverne trennt. Diese Experimente wurden mit Hilfe des HEATING-5 Codes analysiert und mit den experimentellen Resultaten verglichen. Mit KATS-17 (2-dim Ausbreitung der Oxidschmelze auf trockenen Beton, 2-dim Ausbreitung der metallischen Schmelze auf Beton mit einer 1 mm Wasserschicht) wurde die Serie der zwei-dimensionalen Ausbreitungsexperimente abgeschlossen. KATS-15 (2-dim Ausbreitung auf einer trockenen Keramikflaeche) wurde mit Hilfe des CORFLOW-Codes analysiert. (orig.)

  8. A variable temperature EPR study of Mn(2+)-doped NH(4)Cl(0.9)I(0.1) single crystal at 170 GHz: zero-field splitting parameter and its absolute sign.

    Science.gov (United States)

    Misra, Sushil K; Andronenko, Serguei I; Chand, Prem; Earle, Keith A; Paschenko, Sergei V; Freed, Jack H

    2005-06-01

    EPR measurements have been carried out on a single crystal of Mn(2+)-doped NH(4)Cl(0.9)I(0.1) at 170-GHz in the temperature range of 312-4.2K. The spectra have been analyzed (i) to estimate the spin-Hamiltonian parameters; (ii) to study the temperature variation of the zero-field splitting (ZFS) parameter; (iii) to confirm the negative absolute sign of the ZFS parameter unequivocally from the temperature-dependent relative intensities of hyperfine sextets at temperatures below 10K; and (iv) to detect the occurrence of a structural phase transition at 4.35K from the change in the structure of the EPR lines with temperature below 10K.

  9. EPR investigations of Mn{sup 2+}, Fe{sup 3+} ions and carbonaceous radicals in atmospheric particulate aerosols during their transport over the eastern coast of the English Channel

    Energy Technology Data Exchange (ETDEWEB)

    Ledoux, F.; Bouhsina, S.; Courcot, L.; Bertho, M.L.; Puskaric, E. [Universite du Littoral Cote d' Opale, Wimereaux (France). Lab. Interdisciplinaire en Sciences de l' Environnement; Zhilinskaya, E.; Aboukais, A. [Universite du Littoral Cote d' Opale, Wimereaux (France). Lab. de Catalyse et Environnement

    2002-07-01

    Electron paramagnetic resonance (EPR) spectroscopy was used to follow the evolution of the chemical forms of manganese and study other paramagnetic species in the atmospheric particulate aerosols at Wimereux, a French station located on the eastern coast of the English Channel. In parallel, Graphite Furnace Atomic Absorption Spectrometry (GFAAS) was used to measure the metal concentrations. Fe concentration values are common in North Sea sites, but those of Mn are quite higher due to the presence of an important local source of Mn. EPR spectra have evidenced isolated Fe{sup 3+} and Mn{sup 2+} ions and carbonaceous products with variable intensities according to the wind directions. Amounts of paramagnetic species and carbonaceous products are maximum for continental winds and minimum for marine winds. Three Mn types were identified depending on the sampling distance from the source of emission and the size of the particles. (Author)

  10. User acceptance by individuals of health telematics from distributed EPRs associated with knowledge couplers.

    Science.gov (United States)

    Scherrer, J R; Spahni, S; Boyer, C

    2000-01-01

    The patient in a hospital bed is also a private individual that might access his or her own Electronic Patient Record (EPR) in association with additional tools that are able to show critical up-to-date knowledge about diagnoses, clinical investigations or treatments. The distributed EPRs are shown here in full production with the DOMED application of DIOGENE 2. Besides, in order to facilitate an easier understanding of the EPRs by the patient, the HON Web Site services are at his or her disposal in this respect at the same terminal.

  11. Radiolysis of proteins in the solid state: an approach by EPR and product analysis.

    Science.gov (United States)

    Terryn, Hélène; Deridder, Véronique; Sicard-Roselli, Cécile; Tilquin, Bernard; Houée-Levin, Chantal

    2005-05-01

    Radio-induced modifications in proteins have been studied using several techniques. Electron paramagnetic resonance (EPR) was used to characterize free radicals, and analysis methods (high-performance liquid chromatography, capillary electrophoresis) were employed to visualize final degraded forms. Whereas EPR indicates that perthiyl radicals are formed, analysis does not detect any compound in which such bonds would be broken. Since EPR signals decay with time, it is concluded that rearrangements occur at subsequent steps, in which the solvent used during the analysis might play a role.

  12. Identification of irradiated fruit from the pectin-derived EPR signal

    Energy Technology Data Exchange (ETDEWEB)

    Deighton, N.; Glidewell, S.M.; Goodman, B.A.; McMillan, G.P.; Perombelon, M.C.M. [Scottish Crop Research Inst., Dundee (United Kingdom)

    1996-12-31

    An EPR method based upon the observation of an unidentified multiline spectrum has been reported for the detection of irradiated fruit (dried papaya, banana, dates). A similar long-lived EPR spectrum after irradiation of dried amorphous apple pectin (BDH, 6% methyl ester) suggesting that pectin might be the origin of the signal in the dried fruit. Compositions of pectins vary greatly according to source and also with the age of the fruit itself. Therefore, a series of pectins of citrus fruit and potato tuber origin have been investigated to examine the effects of different levels of esterification on the irradiation-induced EPR signal. (author).

  13. Tissue interfaces dosimetry in small field radiotherapy with alanine/EPR mini dosimeters and Monte Carlo-Penelope simulation

    Energy Technology Data Exchange (ETDEWEB)

    Vega R, J. L.; Nicolucci, P.; Baffa, O. [Universidade de Sao Paulo, FFCLRP, Departamento de Fisica, Av. Bandeirantes 3900, Bairro Monte Alegre, 14040-901 Ribeirao Preto, Sao Paulo (Brazil); Chen, F. [Universidade Federale do ABC, CCNH, Rua Santa Adelia 166, Bangu, 09210-170 Santo Andre, Sao Paulo (Brazil); Apaza V, D. G., E-mail: josevegaramirez@yahoo.es [Universidad Nacional de San Agustin de Arequipa, Departamento de Fisica, Arequipa (Peru)

    2014-08-15

    The dosimetry system based on alanine mini dosimeters plus K-Band EPR spectrometer was tested in the tissue-interface dosimetry through the percentage depth-dose (Pdd) determination for 3 x 3 cm{sup 2} and 1 x 1 cm{sup 2} radiation fields sizes. The alanine mini dosimeters were produced by mechanical pressure from a mixture of 95% L-alanine and 5% polyvinyl alcohol (Pva) acting as binder. Nominal dimensions of these mini dosimeters were 1 mm diameter and 3 mm length as well as 3 - 4 mg mass. The EPR spectra of the mini dosimeters were registered using a K-Band (24 GHz) EPR spectrometer. The mini dosimeters were placed in a nonhomogeneous phantom and irradiated with 20 Gy in a 6 MV PRIMUS Siemens linear accelerator, with a source-to-surface distance of 100 cm using the small fields previously mentioned. The cylindrical non-homogeneous phantom was comprised of several disk-shaped plates of different materials in the sequence acrylic-bone cork-bone-acrylic, with dimensions 15 cm diameter and 1 cm thick. The plates were placed in descending order, starting from top with four acrylic plates followed by two bone plates plus eight cork plates plus two bone plates and finally, four acrylic plates (4-2-8-2-4). Pdd curves from the treatment planning system and from Monte Carlo simulation with Penelope code were determined. Mini dosimeters Pdd results show good agreement with Penelope, better than 95% for the cork homogeneous region and 97.7% in the bone heterogeneous region. In the first interface region, between acrylic and bone, it can see a dose increment of 0.6% for mini dosimeters compared to Penelope. At the second interface, between bone and cork, there is 9.1% of dose increment for mini dosimeter relative to Penelope. For the third (cork-bone) and fourth (bone-acrylic) interfaces, the dose increment for mini dosimeters compared to Penelope was 4.1% both. (Author)

  14. 2D FTIR correlation spectroscopy and EPR analysis of Urtica dioica leaves from areas of different environmental pollution.

    Science.gov (United States)

    Moskal, Paulina; Wesełucha-Birczyńska, Aleksandra; Łabanowska, Maria; Kurdziel, Magdalena; Filek, Maria

    2018-01-15

    Leaves of Urtica dioica collected from two areas of different environmental pollution were analysed by fourier transform infrared spectroscopy (FTIR) and electron paramagnetic resonance (EPR) spectroscopy. Analysis of FTIR spectra allows to describe main component of plant like proteins, lipids and carbohydrates. Although the FTIR spectra of plants from these two geographical locations of different environmental pollution appear to be relatively similar, 2D correlation shows completely different patterns. Synchronous and asynchronous correlation maps showed sequences of changes occurring during development of plant, manly in Amide I and Amide II, lignin, lipids and cellulose. In addition, 2D analysis revealed another sequence of changes as the function of plant growth depending on the degree of the environmental pollution. Two various kinds of paramagnetic species, transition metal ions (Mn(II), Fe(III)) and stable organic radicals (chlorophyll, semiquinone, tyrosyl and carbon centered) were found in leaves of nettle collected at different stages of development and growing in clean and polluted environment. In plants growing in polluted area the injuries of protein molecules bonding metal ions and the disturbances of photosynthesis and redox equilibrium in cells, as well as instability of polysaccharide structure of cell walls were observed. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Raman, IR, UV-vis and EPR characterization of two copper dioxolene complexes derived from L-dopa and dopamine.

    Science.gov (United States)

    Barreto, Wagner J; Barreto, Sônia R G; Ando, Rômulo A; Santos, Paulo S; DiMauro, Eduardo; Jorge, Thiago

    2008-12-15

    The anionic complexes [Cu(L(1-))3](1-), L(-)=dopasemiquinone or L-dopasemiquinone, were prepared and characterized. The complexes are stable in aqueous solution showing intense absorption bands at ca. 605 nm for Cu(II)-L-dopasemiquinone and at ca. 595 nm for Cu(II)-dopasemiquinone in the UV-vis spectra, that can be assigned to intraligand transitions. Noradrenaline and adrenaline, under the same reaction conditions, did not yield Cu-complexes, despite the bands in the UV region showing that noradrenaline and adrenaline were oxidized during the process. The complexes display a resonance Raman effect, and the most enhanced bands involve ring modes and particularly the nuCC+nuCO stretching mode at ca. 1384 cm(-1). The free radical nature of the ligands and the oxidation state of the Cu(II) were confirmed by the EPR spectra that display absorptions assigned to organic radicals with g=2.0005 and g=2.0923, and for Cu(II) with g=2.008 and g=2.0897 for L-dopasemiquinone and dopasemiquinone, respectively. The possibility that dopamine and L-dopa can form stable and aqueous-soluble copper complexes at neutral pH, whereas noradrenaline and adrenaline cannot, may be important in understanding how Cu(II)-dopamine crosses the cellular membrane as proposed in the literature to explain the role of copper in Wilson disease.

  16. 2D FTIR correlation spectroscopy and EPR analysis of Urtica dioica leaves from areas of different environmental pollution

    Science.gov (United States)

    Moskal, Paulina; Wesełucha-Birczyńska, Aleksandra; Łabanowska, Maria; Kurdziel, Magdalena; Filek, Maria

    2018-01-01

    Leaves of Urtica dioica collected from two areas of different environmental pollution were analysed by fourier transform infrared spectroscopy (FTIR) and electron paramagnetic resonance (EPR) spectroscopy. Analysis of FTIR spectra allows to describe main component of plant like proteins, lipids and carbohydrates. Although the FTIR spectra of plants from these two geographical locations of different environmental pollution appear to be relatively similar, 2D correlation shows completely different patterns. Synchronous and asynchronous correlation maps showed sequences of changes occurring during development of plant, manly in Amide I and Amide II, lignin, lipids and cellulose. In addition, 2D analysis revealed another sequence of changes as the function of plant growth depending on the degree of the environmental pollution. Two various kinds of paramagnetic species, transition metal ions (Mn(II), Fe(III)) and stable organic radicals (chlorophyll, semiquinone, tyrosyl and carbon centered) were found in leaves of nettle collected at different stages of development and growing in clean and polluted environment. In plants growing in polluted area the injuries of protein molecules bonding metal ions and the disturbances of photosynthesis and redox equilibrium in cells, as well as instability of polysaccharide structure of cell walls were observed.

  17. EPR spectroscopy and catalase activity of manganese-bound DNA-binding protein from nutrient starved cells.

    Science.gov (United States)

    Hayden, Joshua Allen; Hendrich, Michael P

    2010-06-01

    DNA-binding proteins from nutrient-starved cells (DPS) protect cells from oxidative stress by removing H(2)O(2) and iron. A new class of DPS-like proteins has recently been identified, with DPS-like protein from Sulfolobus solfataricus (SsDPS) being the best characterized to date. SsDPS protects cells from oxidative stress and is upregulated in response to H(2)O(2) but also in response to iron depletion. The ferroxidase active site of SsDPS is structurally similar to the active sites of manganese catalase and rat liver arginase. The present work shows that the ferroxidase center in SsDPS binds two Mn(2+) ions with K (D) = (1/K (1) K (2))(1/2) = 48(3) microM. The binding constant of the second Mn(2+) is significantly higher than that of the first, inducing dinuclear Mn(II) cluster formation for all but the lowest concentrations of added Mn(2+). In competition experiments, equimolar amounts of Fe(2+) were unable to displace the bound manganese. EPR spectroscopy of the Mn(2) (2+) cluster showed signals comparable to those of other characterized dimanganese clusters. The exchange coupling for the cluster was determined, J = -1.4(3) cm(-1) (H = -2JS (1) S (2)), and is within the range expected for a mu(1,1)-carboxylato bridge between the manganese ions. Manganese-bound SsDPS showed catalase activity at a rate 10-100 times slower than for manganese catalases. EPR spectra of SsDPS after addition of H(2)O(2) showed the appearance of an intermediate in the reaction with H(2)O(2).

  18. A deployable in vivo EPR tooth dosimeter for triage after a radiation event involving large populations

    Energy Technology Data Exchange (ETDEWEB)

    Williams, Benjamin B., E-mail: Benjamin.B.Williams@dartmouth.edu [Dartmouth Physically Based Biodosimetry Center for Medical Countermeasures Against Radiation (Dart-Dose CMCR), Dartmouth Medical School, Hanover, NH 03768 (United States); Section of Radiation Oncology, Department of Medicine, Dartmouth Hitchcock Medical Center, Lebanon, NH (United States); Dong, Ruhong [Dartmouth Physically Based Biodosimetry Center for Medical Countermeasures Against Radiation (Dart-Dose CMCR), Dartmouth Medical School, Hanover, NH 03768 (United States); Flood, Ann Barry [Dartmouth Physically Based Biodosimetry Center for Medical Countermeasures Against Radiation (Dart-Dose CMCR), Dartmouth Medical School, Hanover, NH 03768 (United States); Clin-EPR, LLC, Lyme, NH (United States); Grinberg, Oleg [Clin-EPR, LLC, Lyme, NH (United States); Kmiec, Maciej; Lesniewski, Piotr N.; Matthews, Thomas P.; Nicolalde, Roberto J.; Raynolds, Tim [Dartmouth Physically Based Biodosimetry Center for Medical Countermeasures Against Radiation (Dart-Dose CMCR), Dartmouth Medical School, Hanover, NH 03768 (United States); Salikhov, Ildar K. [Clin-EPR, LLC, Lyme, NH (United States); Swartz, Harold M. [Dartmouth Physically Based Biodosimetry Center for Medical Countermeasures Against Radiation (Dart-Dose CMCR), Dartmouth Medical School, Hanover, NH 03768 (United States); Clin-EPR, LLC, Lyme, NH (United States)

    2011-09-15

    In order to meet the potential need for emergency large-scale retrospective radiation biodosimetry following an accident or attack, we have developed instrumentation and methodology for in vivo electron paramagnetic resonance spectroscopy to quantify concentrations of radiation-induced radicals within intact teeth. This technique has several very desirable characteristics for triage, including independence from confounding biologic factors, a non-invasive measurement procedure, the capability to make measurements at any time after the event, suitability for use by non-expert operators at the site of an event, and the ability to provide immediate estimates of individual doses. Throughout development there has been a particular focus on the need for a deployable system, including instrumental requirements for transport and field use, the need for high throughput, and use by minimally trained operators. Numerous measurements have been performed using this system in clinical and other non-laboratory settings, including in vivo measurements with unexposed populations as well as patients undergoing radiation therapies. The collection and analyses of sets of three serially-acquired spectra with independent placements of the resonator, in a data collection process lasting approximately 5 min, provides dose estimates with standard errors of prediction of approximately 1 Gy. As an example, measurements were performed on incisor teeth of subjects who had either received no irradiation or 2 Gy total body irradiation for prior bone marrow transplantation; this exercise provided a direct and challenging test of our capability to identify subjects who would be in need of acute medical care. -- Highlights: > Advances in radiation biodosimetry are needed for large-scale emergency response. > Radiation-induced radicals in tooth enamel can be measured using in vivo EPR. > A novel transportable spectrometer was applied in the laboratory and at remote sites. > The current instrument

  19. Spectra, Winter 2014

    Science.gov (United States)

    2014-01-01

    additional copies or more information, please email spectra@nrl.navy.mil. LEADINGEDGE 1 Contents 30 Navy Launches UAV from Submerged Submarine 31...the splash, Test Sub submerged and started moving underwater. Flying WANDA With the success of Test Sub, the Flimmer team applied the lessons to...coated for corrosion- proofing against the acidic environ- ment in the fuel cell and then welded together. Looking at the complexity of developing

  20. Pattern recognition in spectra

    Science.gov (United States)

    Gebran, M.; Paletou, F.

    2017-06-01

    We present a new automated procedure that simultaneously derives the effective temperature Teff, surface gravity log g, metallicity [Fe/H], and equatorial projected rotational velocity ve sin i for stars. The procedure is inspired by the well-known PCA-based inversion of spectropolarimetric full-Stokes solar data, which was used both for Zeeman and Hanle effects. The efficiency and accuracy of this procedure have been proven for FGK, A, and late type dwarf stars of K and M spectral types. Learning databases are generated from the Elodie stellar spectra library using observed spectra for which fundamental parameters were already evaluated or with synthetic data. The synthetic spectra are calculated using ATLAS9 model atmospheres. This technique helped us to detect many peculiar stars such as Am, Ap, HgMn, SiEuCr and binaries. This fast and efficient technique could be used every time a pattern recognition is needed. One important application is the understanding of the physical properties of planetary surfaces by comparing aboard instrument data to synthetic ones.

  1. Estimating Spectra from Photometry

    Science.gov (United States)

    Bryce Kalmbach, J.; Connolly, Andrew J.

    2017-12-01

    Measuring the physical properties of galaxies such as redshift frequently requires the use of spectral energy distributions (SEDs). SED template sets are, however, often small in number and cover limited portions of photometric color space. Here we present a new method to estimate SEDs as a function of color from a small training set of template SEDs. We first cover the mathematical background behind the technique before demonstrating our ability to reconstruct spectra based upon colors and then compare our results to other common interpolation and extrapolation methods. When the photometric filters and spectra overlap, we show that the error in the estimated spectra is reduced by more than 65% compared to the more commonly used techniques. We also show an expansion of the method to wavelengths beyond the range of the photometric filters. Finally, we demonstrate the usefulness of our technique by generating 50 additional SED templates from an original set of 10 and by applying the new set to photometric redshift estimation. We are able to reduce the photometric redshifts standard deviation by at least 22.0% and the outlier rejected bias by over 86.2% compared to original set for z ≤ 3.

  2. Searching for biosignatures using electron paramagnetic resonance (EPR) analysis of manganese oxides.

    Science.gov (United States)

    Kim, Soon Sam; Bargar, John R; Nealson, Kenneth H; Flood, Beverly E; Kirschvink, Joseph L; Raub, Timothy D; Tebo, Bradley M; Villalobos, Mario

    2011-10-01

    Manganese oxide (Mn oxide) minerals from bacterial sources produce electron paramagnetic resonance (EPR) spectral signatures that are mostly distinct from those of synthetic simulants and abiogenic mineral Mn oxides. Biogenic Mn oxides exhibit only narrow EPR spectral linewidths (∼500 G), whereas abiogenic Mn oxides produce spectral linewidths that are 2-6 times broader and range from 1200 to 3000 G. This distinction is consistent with X-ray structural observations that biogenic Mn oxides have abundant layer site vacancies and edge terminations and are mostly of single ionic species [i.e., Mn(IV)], all of which favor narrow EPR linewidths. In contrast, abiogenic Mn oxides have fewer lattice vacancies, larger particle sizes, and mixed ionic species [Mn(III) and Mn(IV)], which lead to the broader linewidths. These properties could be utilized in the search for extraterrestrial physicochemical biosignatures, for example, on Mars missions that include a miniature version of an EPR spectrometer.

  3. USE OF-EPR-DL FIELD TEST EQUIPMENT FOR DETECTION OF SIGMA PHASE

    Directory of Open Access Journals (Sweden)

    Abraão Danilo Gomes Barreto

    2014-06-01

    Full Text Available This work has objective to correlate the intergranular corrosion susceptibility test named EPR-DL (Electrochemical Potentiokinetic Reactivation of Double Loop with the sigma phase formation and other phases. It has been used samples from a UNS S32760 steel pipe for conducting various aging heat treatments. Held isothermal heat treatment at 850°C for 1 min, 10 min, 30 min, 1 h, 1h30min and 10 h. Each heat treated sample and as received were tested using the electrochemical polarization reactivation of double loop technique (EPR-DL. It was possible the detection of deleterious phases with DL-EPR portable cell. The EPR-DL test of some samples showed a second peak of reactivation in which the results showed that this peak might be associated with ferrite or be related to the presence of chi phase

  4. Wormhole and entanglement (non-)detection in the ER=EPR correspondence

    Energy Technology Data Exchange (ETDEWEB)

    Bao, Ning [Institute for Quantum Information and Matter, California Institute of Technology,Pasadena, CA 91125 (United States); Walter Burke Institute for Theoretical Physics, California Institute of Technology,Pasadena, CA 91125 (United States); Pollack, Jason; Remmen, Grant N. [Walter Burke Institute for Theoretical Physics, California Institute of Technology,Pasadena, CA 91125 (United States)

    2015-11-19

    The recently proposed ER=EPR correspondence postulates the existence of wormholes (Einstein-Rosen bridges) between entangled states (such as EPR pairs). Entanglement is famously known to be unobservable in quantum mechanics, in that there exists no observable (or, equivalently, projector) that can accurately pick out whether a generic state is entangled. Many features of the geometry of spacetime, however, are observables, so one might worry that the presence or absence of a wormhole could identify an entangled state in ER=EPR, violating quantum mechanics, specifically, the property of state-independence of observables. In this note, we establish that this cannot occur: there is no measurement in general relativity that unambiguously detects the presence of a generic wormhole geometry. This statement is the ER=EPR dual of the undetectability of entanglement.

  5. Radicals as EPR probes of magnetization of gadolinium stearate Langmuir-Blodgett film

    DEFF Research Database (Denmark)

    Koksharov, Y.A.; Bykov, I.V.; Malakho, A.P.

    2002-01-01

    the Gd and Y stearate LB films. Placing the small BDPA crystal on the film surface we have found that for the Gd LB sample the effective g-value of the radical's resonance depends on the film orientation in respect to the external magnetic field direction. The relative shift of the EPR signal......In the present work we have applied the method of the EPR spin probes which allows performing simultaneously EPR and magnetization measurements to the investigation of magnetism of the Cid stearate Langmuir-Blodgett (LB) films. For this purpose we have prepared and studied by the EPR technique...... corresponded to the magnetization of the film along the field direction. Such effect has not been observed for the Y stearate LB film. The data obtained give an experimental proof for the room temperature. magnetic ordering in the! gadolinium stearate LB film....

  6. Comparative EPR studies of free radicals in melanin synthesized by Bacillus weihenstephanensis soil strains

    Science.gov (United States)

    Zdybel, Magdalena; Pilawa, Barbara; Drewnowska, Justyna M.; Swiecicka, Izabela

    2017-07-01

    EPR spectroscopy was used to examine the properties of and free radical concentrations in atypical water-soluble melanin-like pigments from Bacillus weihenstephanensis strains. The same EPR spectral shape was observed in bacterial melanins as in eumelanin. The EPR lines were homogeneously broadened. Continuous microwave saturation of the EPR lines indicated slow spin-lattice relaxation processes in the samples. Strong dipolar interactions characterized the tested melanin samples. Higher free radical concentrations were found in bacterial melanin than in synthetic melanin. The free radical concentrations in melanin from B. weihenstephanensis increased in the following order: strain JAS 81/4 < JAS 83/3 < JAS 86/1 < JAS 39/1.

  7. Multifrequency Pulsed EPR Studies of Biologically Relevant Manganese(II) Complexes

    OpenAIRE

    Stich, T. A.; Lahiri, S.; Yeagle, G.; Dicus, M.; Brynda, M.; Gunn, A; Aznar, C.; DeRose, V.J.; Britt, R. D.

    2007-01-01

    Electron paramagnetic resonance studies at multiple frequencies (MF EPR) can provide detailed electronic structure descriptions of unpaired electrons in organic radicals, inorganic complexes, and metalloenzymes. Analysis of these properties aids in the assignment of the chemical environment surrounding the paramagnet and provides mechanistic insight into the chemical reactions in which these systems take part. Herein, we present results from pulsed EPR studies performed at three different fre...

  8. FPGA based digital signal processing for EPR spectroscopy with an application to MRI

    OpenAIRE

    Duraiswamy, Punithavathi

    2011-01-01

    Electron Paramagnetic Resonance (EPR), a magnetic resonance technique similar to nuclear magnetic resonance, detects paramagnetic species such as free radicals. Like Magnetic Resonance Imaging (MRI), EPR can be implemented as an imaging technique for small animals and potentially human applications both in pulsed and continuous wave mode. Typical frequencies used for in vivo applications are about 300 MHz with a corresponding static magnetic field of about 100 G (10mT). As demonstrated with h...

  9. Experimental demonstration of frequency-degenerate bright EPR beams with a self-phase-locked OPO.

    Science.gov (United States)

    Keller, G; D'Auria, V; Treps, N; Coudreau, T; Laurat, J; Fabre, C

    2008-06-23

    We report the first experimental observation of bright EPR beams produced by a type-II optical parametric oscillator operating above threshold at frequency degeneracy. The degenerate operation is obtained by introducing a birefringent plate inside the cavity resulting in phase locking. After filtering the pump noise, which plays a critical role, continuous-variable EPR correlations between the orthogonally polarized signal and idler beams are demonstrated.

  10. New Methods of Simulation of Mn(II) EPR Spectra: Single Crystals, Polycrystalline and Amorphous (Biological) Materials

    Science.gov (United States)

    Misra, Sushil K.

    Biological systems exhibit properties of amorphous materials. The Mn(II) ion in amorphous materials is characterized by distributions of spin-Hamiltonian parameters around mean values. It has a certain advantage over other ions, being one of the most abundant elements on the earth. The extent to which living organisms utilize manganese varies from one organism to the other. There is a fairly high concentration of the Mn(II) ion in green plants, which use it in the O2 evolution reaction of photosynthesis (Sauer, 1980). Structure-reactivity relationships in Mn(II)-O2 complexes are given in a review article by Coleman and Taylor (1980). Manganese is a trace requirement in animal nutrition; highly elevated levels of manganese in the diet can be toxic, probably because of an interference with iron homeostasis (Underwood, 1971). On the other hand, animals raised with a dietary deficiency of manganese exhibit severe abnormalities in connective tissue; these problems have been attributed to the obligatory role of Mn(II) in mucopolysaccharide metabolism (Leach, 1971). Mn(II) has been detected unequivocally in living organisms.

  11. EPR safety. Consideration of the internal and external hazards in the safety studies; Surete du reacteur EPR. Prise en compte des agressions internes et externes dans les etudes de surete EPR

    Energy Technology Data Exchange (ETDEWEB)

    Gueguin, H. [Electricite de France (EDF-DIN), Centre National d' Equipement Nucleaire, Service Controle Commande, 92 - Montrouge (France)

    2008-04-15

    The author presents the main points of the Preliminary Safety Report of EDF on the EPR reactor safety. It concerns the considerations of the internal (fire, flood, explosions, pipes failures) and external (earthquakes, airplane falls, explosions, exceptional natural disasters, extreme meteorological conditions) damages. It presents how the safety report takes into account the aggression. (A.L.B.)

  12. Transport de paires EPR dans des structures mesoscopiques

    Science.gov (United States)

    Dupont, Emilie

    Dans cette these, nous nous sommes particulierement interesses a la propagation de paires EPR1 delocalisees et localisees, et a l'influence d'un supraconducteur sur le transport de ces paires. Apres une introduction de cette etude, ainsi que du cadre scientifique qu'est l'informatique quantique dans lequel elle s'inscrit, nous allons dans le chapitre 1 faire un rappel sur le systeme constitue de deux points quantiques normaux entoures de deux fils supraconducteurs. Cela nous permettra d'introduire une methode de calcul qui sera reutilisee par la suite, et de trouver egalement le courant Josephson produit par ce systeme transforme en SQUID-dc par l'ajout d'une jonction auxiliaire. Le SQUID permet de mesurer l'etat de spin (singulet ou triplet), et peut etre forme a partir d'autres systemes que nous etudierons ensuite. Dans le chapitre 2, nous rappellerons l'etude detaillee d'un intricateur d'Andreev faite par un groupe de Bale. La matrice T, permettant d'obtenir le courant dans les cas ou les electrons sont separes spatialement ou non, sera etudiee en detail afin d'en faire usage au chapitre suivant. Le chapitre 3 est consacre a l'etude de l'influence du bruit sur le fonctionnement de l'intricateur d'Andreev. Ce bruit modifie la forme du courant jusqu'a aboutir a d'autres conditions de fonctionnement de l'intricateur. En effet, le bruit present sur les points quantiques peut perturber le transport des paires EPR par l'intermediaire des degres de liberte. Nous montrerons que, du fait de l'"intrication" entre la charge de la paire et le bruit, la paire est detruite pour des temps longs. Cependant, le resultat le plus important sera que le bruit perturbe plus le transport des paires delocalisees, qui implique une resonance de Breit-Wigner a deux particules. Le transport parasite n'implique pour sa part qu'une resonance de Breit-Wigner a une particule. Dans le chapitre 4, nous reviendrons au systeme constitue de deux points quantiques entoures de deux fils

  13. Characterization of lithium formate EPR dosimeters for high dose applications – comparison with alanine

    DEFF Research Database (Denmark)

    Waldeland, Einar; Helt-Hansen, Jakob; Malinen, Eirik

    2011-01-01

    Lithium formate and l-α-alanine (alanine) EPR dosimeters were irradiated to doses from 100 Gy to 100 kGy. The irradiations were mainly performed at a Gammacell irradiator with dose rate of approximately 5.5 kGy h−1. Both the peak-to-peak amplitude of the first derivative EPR spectrum and the area...... under the EPR absorption spectrum were extracted, and the resulting dose dependence of these EPR signal intensity parameters were analyzed. The dependence of the peak-to-peak width of the central resonance in the first derivative EPR spectrum on the dose was also elucidated. In addition, the dependence...... on dose rate and irradiation temperature for the two materials was measured. Dosimeters were given doses from 100 Gy to 10 kGy at two different Gammacells with dose rates of 5.5 kGy h−1 and 0.6 kGy h−1, respectively, and the results were compared. Furthermore, the EPR signal intensities for dosimeters...

  14. Using ANN and EPR models to predict carbon monoxide concentrations in urban area of Tabriz

    Directory of Open Access Journals (Sweden)

    Mohammad Shakerkhatibi

    2015-09-01

    Full Text Available Background: Forecasting of air pollutants has become a popular topic of environmental research today. For this purpose, the artificial neural network (AAN technique is widely used as a reliable method for forecasting air pollutants in urban areas. On the other hand, the evolutionary polynomial regression (EPR model has recently been used as a forecasting tool in some environmental issues. In this research, we compared the ability of these models to forecast carbon monoxide (CO concentrations in the urban area of Tabriz city. Methods: The dataset of CO concentrations measured at the fixed stations operated by the East Azerbaijan Environmental Office along with meteorological data obtained from the East Azerbaijan Meteorological Bureau from March 2007 to March 2013, were used as input for the ANN and EPR models. Results: Based on the results, the performance of ANN is more reliable in comparison with EPR. Using the ANN model, the correlation coefficient values at all monitoring stations were calculated above 0.85. Conversely, the R2 values for these stations were obtained <0.41 using the EPR model. Conclusion: The EPR model could not overcome the nonlinearities of input data. However, the ANN model displayed more accurate results compared to the EPR. Hence, the ANN models are robust tools for predicting air pollutant concentrations.

  15. Antibacterial ethylene propylene rubber impregnated with silver nanopowder: AgNP@EPR

    Directory of Open Access Journals (Sweden)

    Marzieh Miranzadeh

    2016-01-01

    Full Text Available Following our interest in reaching for a molded rubber article with possible detergent contact applications, durable silver nanopowder (AgNP is synthesized by arc discharge, then mixed with varying ratios of ethylene propylene rubber (EPR, affording novel AgNP@EPR nanocomposites. X-ray diffraction (XRD patterns of AgNP as well as AgNP@EPR show no trace of impurity, while scanning electron microscopy (SEM indicates an average diameter of 50 nm for the former. Transmission electron microscopy (TEM images while confirm the SEM results, show quite a few 5 nm AgNP particles lying beside some micro crumbs. Our DC arc discharge technique involves explosion of movable silver anode and static cathode by a current pulse between 5 to 10 A cm-2. A solution blending method is employed for preparation of AgNP@EPR nanocomposites. The AgNP is first dispersed in toluene using an ultrasonic homogenizer, and then thoroughly mixed with EPR in the same solvent whose removal gives nanocomposites of 2, 4, 6 and 8 vol% AgNP in EPR,  showing strong antibacterial activity against both Escherichia coli and Staphylococcus aureus.

  16. Butanolic fraction of Moringa oleifera Lam. (Moringaceae) attenuates isoprotrenol-induced cardiac necrosis and oxidative stress in rats: an EPR study.

    Science.gov (United States)

    Panda, Sunanda

    2015-01-01

    The preventive effect of Moringa oleifera polyphenolic fraction (MOPF) on cardiac damage was evaluated in isoproterenol (ISO) induced cardiotoxicity model of Wistar rats. Male rats in different groups were treated with MOPF orally at the dose of 50, 100 and 150 mg/kg/day for 28 days and were subsequently administered (s.c.) with ISO (85 mg/kg body weight) for the last two days. At the end of the experiment levels of serum troponin-T, creatine kinase-MB, lactate dehydrogenase, content of malondialdehyde (MDA), activities/levels of different cellular antioxidants were estimated in control and experimental groups. Additionally, scavenging potential to the hydroxyl radical of the fraction was measured by electron paramagnetic resonance (EPR). ISO administered rats showed significant increase in the levels of serum troponin-I, creatine kinase, lactate dehydrogenase, and heart tissue MDA content. Furthermore, marked reduction in the activities of antioxidants such as superoxide dismutase, catalase, glutathione peroxidase and reduced glutathione levels were observed. EPR study showed an increase in signal intensity in ISO-induced rats. Triphenyl tetrazolium chloride (TTC) staining of heart section revealed a marked increase in infarcted area in ISO-induced rats. Histological features of the heart also indicated a disruption in the structure of cardiac myofibrils in these animals. MOPF (100 mg/kg body weight) pretreatment prevented all these adverse effects of ISO. Present results show that the rich polyphenolic content of Moringa oleifera significantly reduced the myocardial damage and decreased the oxidative stress, possibly through hydroxyl radical scavenging activity as evidenced from the EPR spectra.

  17. A comparative study of the effect of cholesterol on bicelle model membranes using X-band and Q-band EPR spectroscopy.

    Science.gov (United States)

    Ghimire, Harishchandra; Inbaraj, Johnson J; Lorigan, Gary A

    2009-08-01

    X-band and Q-band electron paramagnetic resonance (EPR) spectroscopic techniques were used to investigate the structure and dynamics of cholesterol containing phospholipid bicelles based upon molecular order parameters (S(mol)), orientational dependent hyperfine splittings and line shape analysis of the corresponding EPR spectra. The nitroxide spin-label 3-beta-doxyl-5-alpha-cholestane (cholestane) was incorporated into DMPC/DHPC bicelles to report the alignment of bicelles in the static magnetic field. The influence of cholesterol on aligned phospholipid bicelles in terms of ordering, the ease of alignment, phase transition temperature have been studied comparatively at X-band and Q-band. At a magnetic field of 1.25 T (Q-band), bicelles with 20 mol% cholesterol aligned at a much lower temperature (313 K), when compared to 318 K at a 0.35 T field strength for X-band, showed better hyperfine splitting values (18.29 G at X-band vs. 18.55 G at Q-band for perpendicular alignment and 8.25 G at X-band vs. 7.83 G at Q-band for the parallel alignment at 318 K) and have greater molecular order parameters (0.76 at X-band vs. 0.86 at Q-band at 318 K). Increasing cholesterol content increased the bicelle ordering, the bicelle-alignment temperature and the gel to liquid crystalline phase transition temperature. We observed that Q-band is more effective than X-band for studying aligned bicelles, because it yielded a higher ordered bicelle system for EPR spectroscopic studies.

  18. Control spectra for Quito

    Science.gov (United States)

    Aguiar, Roberto; Rivas-Medina, Alicia; Caiza, Pablo; Quizanga, Diego

    2017-03-01

    The Metropolitan District of Quito is located on or very close to segments of reverse blind faults, Puengasí, Ilumbisí-La Bota, Carcelen-El Inca, Bellavista-Catequilla and Tangahuilla, making it one of the most seismically dangerous cities in the world. The city is divided into five areas: south, south-central, central, north-central and north. For each of the urban areas, elastic response spectra are presented in this paper, which are determined by utilizing some of the new models of the Pacific Earthquake Engineering Research Center (PEER) NGA-West2 program. These spectra are calculated considering the maximum magnitude that could be generated by the rupture of each fault segment, and taking into account the soil type that exists at different points of the city according to the Norma Ecuatoriana de la Construcción (2015). Subsequently, the recurrence period of earthquakes of high magnitude in each fault segment is determined from the physical parameters of the fault segments (size of the fault plane and slip rate) and the pattern of recurrence of type Gutenberg-Richter earthquakes with double truncation magnitude (Mmin and Mmax) is used.

  19. Arbitrary waveform modulated pulse EPR at 200 GHz

    Science.gov (United States)

    Kaminker, Ilia; Barnes, Ryan; Han, Songi

    2017-06-01

    We report here on the implementation of arbitrary waveform generation (AWG) capabilities at ∼200 GHz into an Electron Paramagnetic Resonance (EPR) and Dynamic Nuclear Polarization (DNP) instrument platform operating at 7 T. This is achieved with the integration of a 1 GHz, 2 channel, digital to analog converter (DAC) board that enables the generation of coherent arbitrary waveforms at Ku-band frequencies with 1 ns resolution into an existing architecture of a solid state amplifier multiplier chain (AMC). This allows for the generation of arbitrary phase- and amplitude-modulated waveforms at 200 GHz with >150 mW power. We find that the non-linearity of the AMC poses significant difficulties in generating amplitude-modulated pulses at 200 GHz. We demonstrate that in the power-limited regime of ω1 10 MHz) spin manipulation in incoherent (inversion), as well as coherent (echo formation) experiments. Highlights include the improvement by one order of magnitude in inversion bandwidth compared to that of conventional rectangular pulses, as well as a factor of two in improvement in the refocused echo intensity at 200 GHz.

  20. A new paramagnetic hyperfine structure effect in manganese tetramers. The origin of "multiline" EPR signals from an S 2 state of a photosynthetic water-splitting enzyme

    Science.gov (United States)

    Kusunoki, Masami

    1992-09-01

    A new theory of EPR spectra for singlet states of Mn tetramers, allowing spin-hybridizations for component composite spins, is developed to elucidate the origin of the "multiline" EPR signals from the Mn clusters in an S 2 state of photosystem II. By computer simulation it is shown that the Mn cluster most probably exists in the Mn(III, IV, IV, IV) oxidation state with a strong-antiferromagnetic exchange interaction ( JabSa· Sb) between a pair of Mn(III) and Mn(IV) ions and the other weak or intermediate ones satisfying the relations, (3/2) p01 (2 Jac-2 Jad+ Jbd- Jbc) cos 2θ=[ Jcd- Jac- Jad+ 1/2( Jbc+ Jbd)] sin 2θ≫0, where p01=1.291 and θ, a polar angle of the spin—state vector in the x- y plane of Scd=0 and Scd=1 spin configurations, is ≈ 38°-39° in control samples.

  1. Free radical formation in chloramphenicol heated at different temperatures and the best thermal sterilization conditions - application of EPR spectroscopy and UV spectrophotometry.

    Science.gov (United States)

    Ramos, Paweł; Pilawa, Barbara

    2016-12-12

    Free radicals in thermally treated chloramphenicol were examined by electron paramagnetic resonance (EPR) spectroscopy. The parameters and shape of EPR spectra were analysed and free radical concentrations were obtained in the tested drug samples. Chloramphenicol was thermally sterilized at pharmacopeia conditions: 100 °C (120 min). Sterilization was also carried out at different conditions, 110 °C (60 min) and 120 °C (30 min), for comparison with pharmacopeia settings. Microbiological analysis was performed on the samples to confirm sterility. The aim of this work was to determine the concentration of free radicals in chloramphenicol following thermal sterilization at pharmacopeia conditions and compare this with other sets of conditions [110 °C (60 min) and 120 °C (30 min)]. The best conditions of thermal sterilization are determined as those that kill microorganisms and produce the lowest amounts of free radicals in this drug. It was concluded that the optimal temperatures and times for the thermal sterilization of chloramphenicol are 100 °C and 120 min and 110 °C and 60 min. A temperature of 120 °C coupled with a heating time of 30 min was rejected for thermal sterilization because of the high amount of free radicals produced by the drug samples.

  2. Redox reactions and the influence of natural Mn oxides on Cr oxidation in a contaminated site in northern Italy: evidence from Cr stable-isotopes and EPR spectroscopy

    Directory of Open Access Journals (Sweden)

    Marafatto F. F.

    2013-04-01

    Full Text Available Hexavalent chromium-contaminated groundwaters and sediments in northern Italy have been studied using the Cr stable-isotope systematics and electron spin resonance spectroscopy (ESR, in order to explore redox changes and soil-groundwater interactions. The isotopic data indicate a possible Cr(VI source released into the environment from an industrial plant. EPR spectra on the sediments which constitute the aquifers show a broad asymmetric absorption due to coupled Fe(III and coupled Cr(III ions and a well resolved hyperfine structure due to manganese ions, resulting from Mn(IV and Mn(II. The isotopic and EPR data support the hypothesis of Cr(III being oxidized by Mn oxides which are widespread in the aquifer, possibly related to the oscillation of the phreatic level. The obtained results highlight the usefulness of chromium stable isotopes as environmental tracers and support the observations that naturally occurring Mn oxides in soils may catalize Cr oxidation from the stable Cr(III form to the toxic Cr(VI soluble form, yielding valuable information in planning remediation interventions.

  3. Characterization of complexes metal-polymer by electron paramagnetic resonance (EPR); Caracterizacao de complexos polimero-metal por ressonancia paramagnetica eletronica (RPE)

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Venina dos; Crespo, Janaina S.; Zeni, Mara [Universidade de Caxias do Sul, RS (Brazil). Centro de Ciencias Exatas e Tecnologia. Dept. de Fisica e Quimica]. E-mail: vsantos2@ucs.br; Mangrich, Antonio S. [Parana Univ., Curitiba, PR (Brazil). Dept. de Quimica

    2003-07-01

    In this work polymeric films of the polyvinyl alcohol (Pva) containing manganese ions (II) were investigated and analysed with enzymes were immobilized from photochemical process. The coordination and structural analysis of the compounds (Pva, Pva-Mn{sup 2+} and Pva-Mn{sup 2+}-enzyme) were all characterized by Electron Paramagnetic Resonance (EPR) and Infrared Spectroscopy (IR). The results EPR shows that the Pva is diamagnetic, films Pva-Mn{sup 2+} present specters complex of external sphere (g=2; A=96G). The commercial enzyme (DeniLite{sup TM} II S) presents a state triplet where two Cu{sup 2+} interact ferromagnetically. The enzyme when immobilized in the Pva-Mn{sup 2+} it causes to only one small widening of the line due the presence of the Cu{sup 2+}. The Pva-Mn{sup 2+} films present in the IR spectra an absorption at 715 cm{sup -1} attributed at the deformation in the PVA-Mn{sup 2+} complex in plane and out of plane. (author)

  4. Synthesis, X-ray crystal structure, and EPR study of [Na(H 2O) 2] 2[VO(H 2O) 5][SiW 12O 40]·4H 2O

    Science.gov (United States)

    Tézé, André; Marchal-Roch, Catherine; So, Hyunsoo; Fournier, Michel; Hervé, Gilbert

    2001-03-01

    The vanadyl salt [Na(H 2O) 2] 2[VO(H 2O) 5][SiW 12O 40]·4H 2O has been synthesized in mild conditions by cationic exchanges from dodecasilicotungstic acid. Structural determination and EPR study have been achieved on single crystals. They are tetragonal, space group P4/ n with a=14.7759(1), c=10.4709(2) Å, V=2286(1) Å 3 and Z=2. A three-dimensional framework built from Keggin anions [SiW 12O 40] 4- linked by sodium cations in (110) and ( 1 1¯0 ) planes generates channels along the c axis in which are localized aquo vanadyl complexes [VO(H 2O) 5] 2+ and water molecules. Single crystal EPR spectra show eight hyperfine lines of the vanadium atom ( I=7/2) which are split into 1:2:1 pattern when the magnetic field is parallel to the c axis. The triplet pattern may be attributed to weak dipolar interactions between the nearest-neighbor vanadium atoms which are 10.47 Å apart in the infinite chain. A ring model was used to simulate the spectrum, and a very small antiferromagnetic exchange interaction was determined accurately . The EPR parameters determined are gx= gy=1.980, gz=1.9336, Ax= Ay=0.0072 cm -1, and Az=0.01805 cm -1, J=-0.00025 cm -1.

  5. A study of the x-irradiated Cs sub 5 H sub 3 (SO sub 4) sub 4 centre dot H sub 2 O crystal by EPR in the 80-415 K temperature range

    CERN Document Server

    Waplak, S; Baranov, A I; Shuvalov, L A

    1997-01-01

    The EPR spectra of the x-irradiated fast proton conductor Cs sub 5 H sub 3 (SO sub 4) sub 4 centre dot H sub 2 O were investigated in the temperature range of 80-415 K. Two kinds of paramagnetic SO sub 4 sup - centres with different proton configurations below about 370 K and freeze-out behaviour of one of them below about 200 K were observed. The role of acid proton dynamics with respect to the glassy-like transition is discussed. (author)

  6. EPR spectroscopy as a tool in homogeneous catalysis research

    NARCIS (Netherlands)

    Goswami, M.; Chirila, A.; Rebreyend, C.; de Bruin, B.

    2015-01-01

    In the context of homogeneous catalysis, open-shell systems are often quite challenging to characterize. Nuclear magnetic resonance (NMR) spectroscopy is the most frequently applied tool to characterize organometallic compounds, but NMR spectra are usually broad, difficult to interpret and often

  7. Consensus structures of the Mo(v) sites of sulfite-oxidizing enzymes derived from variable frequency pulsed EPR spectroscopy, isotopic labelling and DFT calculations.

    Science.gov (United States)

    Enemark, John H

    2017-10-10

    Sulfite-oxidizing enzymes from eukaryotes and prokaryotes have five-coordinate distorted square-pyramidal coordination about the molybdenum atom. The paramagnetic Mo(v) state is easily generated, and over the years four distinct CW EPR spectra have been identified, depending upon enzyme source and the reaction conditions, namely high and low pH (hpH and lpH), phosphate inhibited (Pi) and sulfite (or blocked). Extensive studies of these paramagnetic forms of sulfite-oxidizing enzymes using variable frequency pulsed electron spin echo (ESE) spectroscopy, isotopic labeling and density functional theory (DFT) calculations have led to the consensus structures that are described here. Errors in some of the previously proposed structures are corrected.

  8. EPR UNIFORM FIELD SIGNAL ENHANCEMENT BY DIELECTRIC TUBES IN CAVITIES.

    Science.gov (United States)

    Hyde, James S; Mett, Richard R

    2017-12-01

    The dielectric tube resonator (DTR) for EPR spectroscopy is introduced. It is defined as a metallic cylindrical TE011 microwave cavity that contains a dielectric tube centered on the axis of the cylinder. Contour plots of dimensions of the metallic cylinder to achieve resonance at 9.5 GHz are shown for quartz, sapphire, and rutile tubes as a function of wall thickness and average radius. These contour plots were developed using analytical equations and confirmed by finite element modeling. They can be used in two ways: design of the metallic cylinder for use at 9.5 GHz that incorporates a readily available tube such as a sapphire tube intended for NMR, or design of a custom procured tube for optimized performance for specific sample-size constraints. The charts extend to the limiting condition where the dielectric fills the tube. However, the structure at this limit is not a dielectric resonator due to the metal wall and does not radiate. In addition, the uniform field (UF) DTR is introduced. Development of the UF resonator starting with a dielectric tube resonator is shown. The diameter of the tube remains constant along the cavity axis, and the diameter of the cylindrical metallic enclosure increases at the ends of the cavity to satisfy the uniform field condition. This structure has advantages over the previously developed UF TE011 resonators: higher resonator efficiency parameter Λ, convenient overall size when using sapphire tubes, and higher quality data for small samples. The DTR and UF DTR structures fill the gap between free space and dielectric resonator limits in a continuous manner.

  9. Wideband frequency-swept excitation in pulsed EPR spectroscopy

    Science.gov (United States)

    Doll, Andrin; Jeschke, Gunnar

    2017-07-01

    Excitation of electron spins with monochromatic rectangular pulses is limited to bandwidths that are smaller than the spectral widths of most organic radicals and much smaller than the spectral widths of transition and rare earth metal ions. With frequency-swept pulses, bandwidths of up to 800 MHz have previously been attained for excitation and detection of spin packets at frequencies of about 9.6 GHz and bandwidths of up to 2.5 GHz in a polarization transfer experiment at frequencies of about 34 GHz. The remaining limitations, mainly due to resonator bandwidth and due to pulse length restrictions are discussed. Flip angles for state-space rotations on passage of a transition can generally be computed from the critical adiabaticity by the Landau-Zener-Stückelberg-Majorana expression. For hyperbolic secant pulses, the Demkov-Kunike model describes excitation for spin packets within and outside the sweep range. Well within the sweep range, the Bloch-Siegert phase shift is proportional to critical adiabaticity to a very good approximation. Because of the dependence of both flip angle and coherence phase on critical adiabaticity, it is advantageous to use pairs of amplitude and frequency modulation functions that provide such offset-independent adiabaticity. Compensation for the resonator response function should restore offset-independent adiabaticity. Whereas resonance offsets and Bloch-Siegert phase can be refocused at certain pulse length ratios, phase dispersion in coupled spin systems cannot generally be refocused. Based on the bandwidth limitations that arise from spin dynamics, requirements are derived for a spectrometer that achieves precise spin control over wide bands. The design of such a spectrometer and hardware characterization by EPR experiments are discussed.

  10. EPR in functional structures based on doped (nano, meso)-porous silica and titanium dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Kassiba, A [Laboratoire de Physique de l' Etat Condense LPEC, UMRCNRS 6087 Universite du Maine, Avenue Olivier Messiaen 72085 Le Mans Cedex 9 France (France); Makowska-Janusik, M [Institute of Physics, Al Armii Krajowej 13/15, Akademina Im Jana Dlugosz w Czestochowa, 42200 (Poland); Mehdi, A, E-mail: kassiba@univ-lemans.fr [Institut Charles Gerhardt, UMR 5253 Chimie Moleculaire et Organisation du Solide, Universite Montpellier II Place E Bataillon, 34095 Montpellier Cedex 5 (France)

    2011-04-01

    EPR investigations are performed on mesoporous silica (SBA15) functionalized by Nickel-cyclam complexes (1,4,8,11-tetraazacyclotetradecane groups chelating nickel ions) and on mesoporous titanium dioxide with nitrogen doping. For functionalized silica, the magnetic behaviour of organometallic groups, their mutual interactions and dispersion in the host matrices are compared with respect to the doping rates and the synthesis procedures. The relaxation processes were analyzed from the thermal evolution of the paramagnetic spin susceptibilities and EPR line-widths. Particularly, some samples show the formation of clusters where phonon assisted one dimensional (1D) ferromagnetic ordering occurs below 45 K. For the mesoporous TiO{sub 2}, systematic EPR investigations were performed on two main classes of materials with regard to the porosity degrees. The EPR experiments point out the efficiency of EPR method to probe the degree of functionalization of mesoporous silica or the nitrogen doping achievement in TiO{sub 2}, and in general to give a valuable feedback to improve the synthesis routes of smart materials.

  11. New developed cylindrical TM010 mode EPR cavity for X-band in vivo tooth dosimetry.

    Directory of Open Access Journals (Sweden)

    Guo Junwang

    Full Text Available EPR tooth in vivo dosimetry is an attractive approach for initial triage after unexpected nuclear events. An X-band cylindrical TM010 mode resonant cavity was developed for in vivo tooth dosimetry and used in EPR applications for the first time. The cavity had a trapezoidal measuring aperture at the exact position of the cavity's cylindrical wall where strong microwave magnetic field H1 concentrated and weak microwave electric field E1 distributed. Theoretical calculations and simulations were used to design and optimize the cavity parameters. The cavity features were evaluated by measuring DPPH sample, intact incisor samples embed in a gum model and the rhesus monkey teeth. The results showed that the cavity worked at designed frequency and had the ability to make EPR spectroscopy in relative high sensitivity. Sufficient modulation amplitude and microwave power could be applied into the aperture. Radiation induced EPR signal could be observed remarkably from 1 Gy irradiated intact incisor within only 30 seconds, which was among the best in scan time and detection limit. The in vivo spectroscopy was also realized by acquiring the radiation induced EPR signal from teeth of rhesus monkey whose teeth was irradiated by dose of 2 Gy. The results suggested that the cavity was sensitive to meet the demand to assess doses of significant level in short time. This cavity provided a very potential option for the development of X-band in vivo dosimetry.

  12. A special JMR issue: Methodological advances in EPR spectroscopy and imaging

    Science.gov (United States)

    2017-07-01

    Since about five decades, EPR spectroscopy provides important insights into the electronic structure of metalloproteins and transition-metal based catalysts. Somewhat later this spectroscopy was also applied to the study of electron transfer processes, often in radical enzymes. The study of diamagnetic proteins and nucleic acids with site-directed spin labeling (SDSL) techniques became really popular in the 1990s and early in the new millennium. The same applies to applications of pulsed EPR techniques to metalloproteins, although the pioneering work in this field by Mims and Peisach dates back to the early 1970s. Pulsed dipolar spectroscopy for the measurement of distance distributions in the nanometer range has become the major EPR-based tool in structural biology during the past 15 years and is still expanding its scope. EPR (or ESR) imaging may appear to be overshadowed by (nuclear) MRI, as it has not yet found clinical application. However, development of EPR-based imaging modalities has recently gained much momentum as they can provide information that is inaccessible by any established imaging technology.

  13. Temperature dependence of Q-band electron paramagnetic resonance spectra of nitrosyl heme proteins

    Energy Technology Data Exchange (ETDEWEB)

    Flores, Marco; Wajnberg, Eliane; Bemski, George

    1997-11-01

    The Q-band (35 GHz) electron paramagnetic resonance (EPR) spectra of nitrosyl hemoglobin (Hb N O) and nitrosyl myoglobin (Mb NO) were studied as a function of temperature between 19 K and 200 K. The spectra of both heme proteins show classes of variations as a function of temperature. The first one has previously been associated with the existence of two paramagnetic species, one with rhombic and the other with axial symmetry. The second one manifests itself in changes in the g-factors and linewidths of each species. These changes are correlated with the conformational substates model and associate the variations of g-values with changes in the angle of the N(his)-Fe-N (NO) bond in the rhombic species and with changes in the distance between Fe and N of the proximal (F8) histidine in the axial species. (author) 24 refs., 6 figs.

  14. HF-EPR, Raman, UV/VIS light spectroscopic, and DFT studies of the ribonucleotide reductase R2 tyrosyl radical from Epstein-Barr virus.

    Directory of Open Access Journals (Sweden)

    Ane B Tomter

    Full Text Available Epstein-Barr virus (EBV belongs to the gamma subfamily of herpes viruses, among the most common pathogenic viruses in humans worldwide. The viral ribonucleotide reductase small subunit (RNR R2 is involved in the biosynthesis of nucleotides, the DNA precursors necessary for viral replication, and is an important drug target for EBV. RNR R2 generates a stable tyrosyl radical required for enzymatic turnover. Here, the electronic and magnetic properties of the tyrosyl radical in EBV R2 have been determined by X-band and high-field/high-frequency electron paramagnetic resonance (EPR spectroscopy recorded at cryogenic temperatures. The radical exhibits an unusually low g₁-tensor component at 2.0080, indicative of a positive charge in the vicinity of the radical. Consistent with these EPR results a relatively high C-O stretching frequency associated with the phenoxyl radical (at 1508 cm⁻¹ is observed with resonance Raman spectroscopy. In contrast to mouse R2, EBV R2 does not show a deuterium shift in the resonance Raman spectra. Thus, the presence of a water molecule as a hydrogen bond donor moiety could not be identified unequivocally. Theoretical simulations showed that a water molecule placed at a distance of 2.6 Å from the tyrosyl-oxygen does not result in a detectable deuterium shift in the calculated Raman spectra. UV/VIS light spectroscopic studies with metal chelators and tyrosyl radical scavengers are consistent with a more accessible dimetal binding/radical site and a lower affinity for Fe²⁺ in EBV R2 than in Escherichia coli R2. Comparison with previous studies of RNR R2s from mouse, bacteria, and herpes viruses, demonstrates that finely tuned electronic properties of the radical exist within the same RNR R2 Ia class.

  15. High-frequency EPR investigation of X-ray storage SrBPO{sub 5}:Eu phosphor

    Energy Technology Data Exchange (ETDEWEB)

    Nakamura, T. E-mail: tctnaka@ipc.shizuoka.ac.jp; Takeyama, T.; Takahashi, N.; Jagannathan, R.; Karthikeyani, A.; Smith, G.M.; Riedi, P.C

    2003-05-01

    High-frequency EPR (HFEPR) spectra of the SrBPO{sub 5}:Eu with stillwellite structure, which was prepared using EuCl{sub 3}.6H{sub 2}O as a dopant, have been examined in order to clarify the Eu sites in it. They showed an intense doublet at 3.3 T corresponding to g=2.0 as is expected for the {sup 8}S state ions. Also, weak satellites were observed on both sides of the central doublet signal symmetrically. This means that microwave energy at 90 GHz is sufficiently larger than the zero-field splitting. Taking into account the crystal structure of stillwellite and the earlier PL investigation, a single Eu{sup 2+} site was assumed for the HFEPR simulation. As a result, it was found that HFEPR spectrum simulated using g=1.98161, vertical bar D vertical bar =0.130 T and {lambda} vertical bar E/D vertical bar =0.06 reasonably agrees well with the experimental one, supporting that the Eu{sup 2+} occupies the Sr site. The large vertical bar D vertical bar value small {lambda} value obtained implies that the crystal field surrounding Eu{sup 2+} has a strong axial field with weak rhombic distortion.

  16. Structure of the biliverdin radical intermediate in phycocyanobilin:ferredoxin oxidoreductase identified by high-field EPR and DFT.

    Science.gov (United States)

    Stoll, Stefan; Gunn, Alexander; Brynda, Marcin; Sughrue, Wesley; Kohler, Amanda C; Ozarowski, Andrew; Fisher, Andrew J; Lagarias, J Clark; Britt, R David

    2009-02-11

    The cyanobacterial enzyme phycocyanobilin:ferredoxin oxidoreductase (PcyA) catalyzes the two-step four-electron reduction of biliverdin IXalpha to phycocyanobilin, the precursor of biliprotein chromophores found in phycobilisomes. It is known that catalysis proceeds via paramagnetic radical intermediates, but the structure of these intermediates and the transfer pathways for the four protons involved are not known. In this study, high-field electron paramagnetic resonance (EPR) spectroscopy of frozen solutions and single crystals of the one-electron reduced protein-substrate complex of two PcyA mutants D105N from the cyanobacteria Synechocystis sp. PCC6803 and Nostoc sp. PCC7120 are examined. Detailed analysis of Synechocystis D105N mutant spectra at 130 and 406 GHz reveals a biliverdin radical with a very narrow g tensor with principal values 2.00359(5), 2.00341(5), and 2.00218(5). Using density-functional theory (DFT) computations to explore the possible protonation states of the biliverdin radical, it is shown that this g tensor is consistent with a biliverdin radical where the carbonyl oxygen atoms on both the A and the D pyrrole rings are protonated. This experimentally confirms the reaction mechanism recently proposed (Tu, et al. Biochemistry 2007, 46, 1484).

  17. The structure of the biliverdin radical intermediate in phycocyanobilin:ferredoxin oxidoreductase identified by high-field EPR and DFT

    Science.gov (United States)

    Stoll, Stefan; Gunn, Alexander; Brynda, Marcin; Sughrue, Wesley; Kohler, Amanda C.; Ozarowski, Andrew; Fisher, Andrew J.; Lagarias, J. Clark; Britt, R. David

    2009-01-01

    The cyanobacterial enzyme phycocyanobilin:ferredoxin oxidoreductase (PcyA) catalyzes the two-step four-electron reduction of biliverdin IXα to phycocyanobilin, the precursor of biliprotein chromophores found in phycobilisomes. It is known that catalysis proceeds via paramagnetic radical intermediates, but the structure of these intermediates and the transfer pathways for the four protons involved are not known. In this study, high-field electron paramagnetic resonance (EPR) spectroscopy of frozen solutions and single crystals of the one-electron reduced protein-substrate complex of two PcyA mutants D105N from the cyanobacteria Synechocystis sp. PCC6803 and Nostoc sp. PCC7120 are examined. Detailed analysis of Synechocystis D105N mutant spectra at 130 GHz and 406 GHz reveals a biliverdin radical with a very narrow g tensor with principal values 2.00359(5), 2.00341(5) and 2.00218(5). Using density-functional theory (DFT) computations to explore the possible protonation states of the biliverdin radical, it is shown that this g tensor is consistent with a biliverdin radical where the carbonyl oxygen atoms on both the A and the D pyrrole rings are protonated. This experimentally confirms the reaction mechanism recently proposed (Tu et al, Biochemistry 2007, 46, 1484). PMID:19159240

  18. EPR properties of some new cadmium and rare-earth molybdates, molybdato-tungstates and their solid solutions

    Energy Technology Data Exchange (ETDEWEB)

    Kaczmarek, S.M., E-mail: skaczmarek@zut.edu.pl [Faculty of Mechanical Engineering and Mechatronics, Institute of Physics, West Pomeranian University of Technology, Al. Piastow 17, 70-310 Szczecin (Poland); Leniec, G.; Fuks, H. [Faculty of Mechanical Engineering and Mechatronics, Institute of Physics, West Pomeranian University of Technology, Al. Piastow 17, 70-310 Szczecin (Poland); Tomaszewicz, E.; Dabrowska, G. [Department of Inorganic and Analytical Chemistry, West Pomeranian University of Technology, Al. Piastow 42, 71-065 Szczecin (Poland); Skibinski, T. [Faculty of Mechanical Engineering and Mechatronics, Institute of Physics, West Pomeranian University of Technology, Al. Piastow 17, 70-310 Szczecin (Poland)

    2012-04-15

    Highlights: Black-Right-Pointing-Pointer Some new molybdato-tungstates of rare earths were synthesized and investigated. Black-Right-Pointing-Pointer EPR and XRD of the obtained phases revealed scheelite-like structures. Black-Right-Pointing-Pointer Rare-earths ions enter at axial symmetry sites convenient for phosphors or lasers. - Abstract: A reactivity in the solid state between CdMoO{sub 4} and RE{sub 2}(MoO{sub 4}){sub 3} or RE{sub 2}(WO{sub 4}){sub 3}, where RE = Nd, Sm, Dy, was investigated using X-ray diffraction and electron paramagnetic resonance techniques. Obtained phases have shown scheelite-like structure, congruent melting and axial or close to axial symmetry of RE{sup 3+} ions. The main type of magnetic interactions in samples under studies is proved to be ferromagnetic one. Besides RE{sup 3+} ions, isolated and paired centers o molybdenum (5+) were found in the electron paramagnetic resonance spectra.

  19. Sequencing BPS spectra

    Energy Technology Data Exchange (ETDEWEB)

    Gukov, Sergei [Walter Burke Institute for Theoretical Physics, California Institute of Technology,1200 E California Blvd, Pasadena, CA 91125 (United States); Max-Planck-Institut für Mathematik,Vivatsgasse 7, D-53111 Bonn (Germany); Nawata, Satoshi [Walter Burke Institute for Theoretical Physics, California Institute of Technology,1200 E California Blvd, Pasadena, CA 91125 (United States); Centre for Quantum Geometry of Moduli Spaces, University of Aarhus,Nordre Ringgade 1, DK-8000 (Denmark); Saberi, Ingmar [Walter Burke Institute for Theoretical Physics, California Institute of Technology,1200 E California Blvd, Pasadena, CA 91125 (United States); Stošić, Marko [CAMGSD, Departamento de Matemática, Instituto Superior Técnico,Av. Rovisco Pais, 1049-001 Lisbon (Portugal); Mathematical Institute SANU,Knez Mihajlova 36, 11000 Belgrade (Serbia); Sułkowski, Piotr [Walter Burke Institute for Theoretical Physics, California Institute of Technology,1200 E California Blvd, Pasadena, CA 91125 (United States); Faculty of Physics, University of Warsaw,ul. Pasteura 5, 02-093 Warsaw (Poland)

    2016-03-02

    This paper provides both a detailed study of color-dependence of link homologies, as realized in physics as certain spaces of BPS states, and a broad study of the behavior of BPS states in general. We consider how the spectrum of BPS states varies as continuous parameters of a theory are perturbed. This question can be posed in a wide variety of physical contexts, and we answer it by proposing that the relationship between unperturbed and perturbed BPS spectra is described by a spectral sequence. These general considerations unify previous applications of spectral sequence techniques to physics, and explain from a physical standpoint the appearance of many spectral sequences relating various link homology theories to one another. We also study structural properties of colored HOMFLY homology for links and evaluate Poincaré polynomials in numerous examples. Among these structural properties is a novel “sliding” property, which can be explained by using (refined) modular S-matrix. This leads to the identification of modular transformations in Chern-Simons theory and 3d N=2 theory via the 3d/3d correspondence. Lastly, we introduce the notion of associated varieties as classical limits of recursion relations of colored superpolynomials of links, and study their properties.

  20. Electronic structure of a weakly antiferromagnetically coupled Mn(II)Mn(III) model relevant to manganese proteins: a combined EPR, 55Mn-ENDOR, and DFT study.

    Science.gov (United States)

    Cox, Nicholas; Ames, William; Epel, Boris; Kulik, Leonid V; Rapatskiy, Leonid; Neese, Frank; Messinger, Johannes; Wieghardt, Karl; Lubitz, Wolfgang

    2011-09-05

    An analysis of the electronic structure of the [Mn(II)Mn(III)(μ-OH)-(μ-piv)(2)(Me(3)tacn)(2)](ClO(4))(2) (PivOH) complex is reported. It displays features that include: (i) a ground 1/2 spin state; (ii) a small exchange (J) coupling between the two Mn ions; (iii) a mono-μ-hydroxo bridge, bis-μ-carboxylato motif; and (iv) a strongly coupled, terminally bound N ligand to the Mn(III). All of these features are observed in structural models of the oxygen evolving complex (OEC). Multifrequency electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR) measurements were performed on this complex, and the resultant spectra simulated using the Spin Hamiltonian formalism. The strong field dependence of the (55)Mn-ENDOR constrains the (55)Mn hyperfine tensors such that a unique solution for the electronic structure can be deduced. Large hyperfine anisotropy is required to reproduce the EPR/ENDOR spectra for both the Mn(II) and Mn(III) ions. The large effective hyperfine tensor anisotropy of the Mn(II), a d(5) ion which usually exhibits small anisotropy, is interpreted within a formalism in which the fine structure tensor of the Mn(III) ion strongly perturbs the zero-field energy levels of the Mn(II)Mn(III) complex. An estimate of the fine structure parameter (d) for the Mn(III) of -4 cm(-1) was made, by assuming the intrinsic anisotropy of the Mn(II) ion is small. The magnitude of the fine structure and intrinsic (onsite) hyperfine tensor of the Mn(III) is consistent with the known coordination environment of the Mn(III) ion as seen from its crystal structure. Broken symmetry density functional theory (DFT) calculations were performed on the crystal structure geometry. DFT values for both the isotropic and the anisotropic components of the onsite (intrinsic) hyperfine tensors match those inferred from the EPR/ENDOR simulations described above, to within 5%. This study demonstrates that DFT calculations provide reliable estimates for spectroscopic

  1. EPR approaches to heterogeneous catalysis. The chemistry of titanium in heterogeneous catalysts and photocatalysts.

    Science.gov (United States)

    Morra, Elena; Giamello, Elio; Chiesa, Mario

    2017-07-01

    Paramagnetic species are often involved in catalytic or photocatalytic reactions occurring at the solid-gas interface of heterogeneous catalysts. In this contribution we will provide an overview of the wealth and breadth of information that can be obtained from EPR in the characterization of paramagnetic species in such systems, illustrating the advantages that modern pulsed EPR methodologies can offer in monitoring the elementary processes occurring within the coordination sphere of surface transition-metal ions. To do so we selected three representative systems, where titanium ions in low oxidation states act as active catalytic sites, trying to outline the methodological approaches which characterize the application of EPR techniques and the questions that can be answered and addressed relative to the characterization of heterogeneous catalytic materials. Copyright © 2017 Elsevier Inc. All rights reserved.

  2. EPR approaches to heterogeneous catalysis. The chemistry of titanium in heterogeneous catalysts and photocatalysts

    Science.gov (United States)

    Morra, Elena; Giamello, Elio; Chiesa, Mario

    2017-07-01

    Paramagnetic species are often involved in catalytic or photocatalytic reactions occurring at the solid-gas interface of heterogeneous catalysts. In this contribution we will provide an overview of the wealth and breadth of information that can be obtained from EPR in the characterization of paramagnetic species in such systems, illustrating the advantages that modern pulsed EPR methodologies can offer in monitoring the elementary processes occurring within the coordination sphere of surface transition-metal ions. To do so we selected three representative systems, where titanium ions in low oxidation states act as active catalytic sites, trying to outline the methodological approaches which characterize the application of EPR techniques and the questions that can be answered and addressed relative to the characterization of heterogeneous catalytic materials.

  3. BCL::MP-Fold: membrane protein structure prediction guided by EPR restraints

    CERN Document Server

    Fischer, Axel Walter; Woetzel, Nils; Karakas, Mert; Weiner, Brian; Meiler, Jens

    2015-01-01

    For many membrane proteins the determination of their topology remains a challenge for methods like X-ray crystallography and nuclear magnetic resonance (NMR) spectroscopy. Electron paramagnetic resonance (EPR) spectroscopy has evolved as an alternative technique to study structure and dynamics of membrane proteins. The present study demonstrates the feasibility of membrane protein topology determination using limited EPR distance and accessibility measurements. The BCL::MP-Fold (BioChemical Library membrane protein fold) algorithm assembles secondary structure elements (SSEs) in the membrane using a Monte Carlo Metropolis (MCM) approach. Sampled models are evaluated using knowledge-based potential functions and agreement with the EPR data and a knowledge-based energy function. Twenty-nine membrane proteins of up to 696 residues are used to test the algorithm. The RMSD100 value of the most accurate model is better than 8{\\AA} for twenty-seven, better than 6{\\AA} for twenty-two and better than 4{\\AA} for fifte...

  4. A password-based user authentication scheme for the integrated EPR information system.

    Science.gov (United States)

    Wu, Zhen-Yu; Chung, Yufang; Lai, Feipei; Chen, Tzer-Shyong

    2012-04-01

    With the rapid development of the Internet, digitization and electronic orientation are required in various applications of our daily life. For e-medicine, establishing Electronic patient records (EPRs) for all the patients has become the top issue during the last decade. Simultaneously, constructing an integrated EPR information system of all the patients is beneficial because it can provide medical institutions and the academia with most of the patients' information in details for them to make correct decisions and clinical decisions, to maintain and analyze patients' health. Also beneficial to doctors and scholars, the EPR system can give them record linkage for researches, payment audits, or other services bound to be developed and integrated into medicine. To tackle the illegal access and to prevent the information from theft during transmission over the insecure Internet, we propose a password-based user authentication scheme suitable for information integration.

  5. EPR and optical absorption studies on VO 2+ ions in calcium fumarate trihydrate single crystals

    Science.gov (United States)

    Kripal, Ram; Mishra, Indrajeet; Gupta, S. K.; Arora, Manju

    2010-01-01

    Electron Paramagnetic Resonance (EPR) studies of VO 2+ ions in calcium fumarate trihydrate single crystals have been done at room temperature. EPR analysis indicates the presence of two magnetically inequivalent VO 2+ sites. For the two sites the spin Hamiltonian parameters are, Site I: g x = 1.9689 ,g y = 2.0087 ,g z = 1.9344, A x = 73 ,A y = 88 ,A z = 202; Site II: g x = 1.9675 ,g y = 2.0100 ,g z = 1.9346 ,A x = 75 ,A y = 90, A z = 206 (×10 -4) cm -1. The optical absorption study is also carried out at room temperature. By correlating EPR and optical data the nature of bonding in the crystal is discussed. The three-line superhyperfine structure has been attributed to two protons.

  6. EPR persistence measurements of UV-induced melanin free radicals in whole skin

    Energy Technology Data Exchange (ETDEWEB)

    Collins, B.; Poehler, T.O. [Johns Hopkins Univ., Baltimore, MD (United States); Bryden, W.A. [Johns Hopkins Univ., Laurel, MD (United States). Applied Physics Lab.

    1995-09-01

    Electron paramagnetic resonance is used to detect the formation of free radicals caused by exposure to ultraviolet radiation in chemically untreated rabbit skin. A fast jump in EPR signal level, occurring over a few seconds, is observed immediately after a skin sample is exposed to UV. This is followed by a slower increase toward an elevated steady-state signal over a period of hours as the skin is continuously exposed to a UV light source. Upon cessation of UV light exposure, EPR signal levels undergo an abrupt drop followed by a slower decay toward natural levels. Elevated free radical concentrations following UV exposure are found to persist for several hours in whole skin. These results are consistent with time resolved EPR measurements of photoinduced radicals in various natural melanins. (Author).

  7. "Assessing the RAFT equilibrium constant via model systems: an EPR study"--response to a comment.

    Science.gov (United States)

    Meiser, Wibke; Buback, Michael

    2012-08-14

    We have presented an EPR-based approach for deducing the RAFT equilibrium constant, K(eq), of a dithiobenzoate-mediated system [Meiser, W. and Buback M. Macromol. Rapid Commun. 2011, 32, 1490]. Our value is by four orders of magnitude below K(eq) from ab initio calculations for the identical monomer-free system. Junkers et al. [Macromol. Rapid Commun. 2011, 32, 1891] claim that our EPR approach would be model dependent and our data could be equally well fitted by assuming slow addition of radicals to the RAFT agent and slow fragmentation of the so-obtained intermediate radical as well as high cross-termination rate. By identification of all side products, our EPR-based method is shown to be model independent and to provide reliable K(eq) values, which demonstrate the validity of the intermediate radical termination model. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. EPR and FTIR Characterization of Paramagnetic Transition Metal Ions in Fossil Fuels: Tar Sands

    Science.gov (United States)

    Shepherd, Robert Anthony

    The techniques of EPR and FTIR spectroscopy have been applied to the bitumen and mineral fractions of a tar sand sample originating from Circle Cliffs, Utah to detect and identify paramagnetic transition metal ions present, indicate whether or not they are organically bound, and determine the identities of the complexes in which they occur. An EPR spectrum of the bitumen reveals the presence of V('4+) at a site of axial symmetry. Fitting the spectrum to the second order perturbation solution of the spin Hamiltonian indicates that the spectrum originates from vanadyl etioporphyrin. An EPR spectrum characteristic of Mn('2+) in a carbonate lattice was observed for the mineral component. A quantitative analysis of the mineral components, conducted using FTIR spectroscopy, shows the tar sand mineral fraction consists of the two clays, kaolinite and illite, quartz, gypsum, and one carbonate, dolomite. A computer simulation of the EPR spectrum positively identifies the Mn('2+) host as polycrystalline dolomite, shows the ions are at two crystallographically distinct sites in the dolomite lattice, and gives the relative population at each site. A second feature observed in the EPR spectrum of the mineral fraction is a broad line at g = 4.2 which is attributed to Fe('3+) in kaolinite. A third and final feature observed in the EPR spectrum of the tar sand mineral fraction is a broad line at g = 2. The temperature-dependent behavior of this line suggests that it is due to Fe('3+) in amorphous iron oxides and wustite, two compounds that commonly coat kaolinite surfaces.

  9. Optical and EPR studies of iron bearing phosphate minerals: satterlyite and gormanite from Yukon Territory, Canada

    Science.gov (United States)

    Chandrasekhar, A. V.; Ramanaiah, M. Venkata; Reddy, B. J.; Reddy, Y. P.; Rao, P. S.; Ravikumar, R. V. S. S. N.

    2003-07-01

    The iron phosphate minerals satterlyite and gormanite have been investigated by EPR and optical absorption studies. The optical results indicate the presence of ferrous and ferric ions in both minerals. In gormanite the site symmetry of Fe(III) is near octahedral whereas in satterlyite it is tetragonally distorted. On the other hand, the Fe(II) ions are in tetragonally distorted octahedral site in both minerals. In satterlyite the EPR results indicate the presence of the ferric ion in a tetragonally distorted state together with a small percentage of Mn(II). Crystal field (Dq) and interelectronic parameters (B and C) are evaluated.

  10. EPR study of free radicals in some drugs {gamma}-irradiated in the solid state

    Energy Technology Data Exchange (ETDEWEB)

    Ambroz, H.B. E-mail: ambroz@orange.ichtj.waw.pl; Kornacka, E.M.; Marciniec, B.; Ogrodowczyk, M.; Przybytniak, G.K

    2000-06-01

    A range of drugs in the form of microcrystalline powder was exposed to {gamma}-radiation. EPR measurements proved that all of them contained various paramagnetic species after 4 and 8 weeks of storage. We observed following radical concentrations, stable up to 4 weeks: the highest for ifosfamide -- 4.5x10{sup 17} spins per gram and the lowest for nimodipine -- 2.1x10{sup 16} spins per gram. Three drugs exhibited very weak EPR signals before irradiation, not detectable quantitatively. Some spectroscopic properties and suggestions concerning possible structure of the radicals are given in our paper. (author)

  11. Characterisation of prehnite by EPMA, Mössbauer, optical absorption and EPR spectroscopic methods.

    Science.gov (United States)

    Reddy, N C Gangi; Fayazyddin, S Md; Reddy, R Rama Subba; Reddy, G Siva; Reddy, S Lakshmi; Rao, P Sambasiva; Reddy, B Jagannatha

    2005-11-01

    A sample of prehnite from Rayalaseema zone of Andhra Pradesh, India containing about 2.565 wt.% Fe(2)O(3) is used in the present work. The mineral has been characterized by EPMA, optical absorption, EPR, NIR and Mössbauer techniques. Mössbauer studies confirm the presence of iron as an impurity in two sites. An EPR study on powder sample confirm the presence of Fe(III) impurity in the mineral. Optical absorption spectrum also indicates that Fe(III) impurity is present in two sites with octahedral structure. NIR results are due to water fundamentals.

  12. Characterization of KCNE1 inside Lipodisq Nanoparticles for EPR Spectroscopic Studies of Membrane Proteins.

    Science.gov (United States)

    Sahu, Indra D; Zhang, Rongfu; Dunagan, Megan M; Craig, Andrew F; Lorigan, Gary A

    2017-06-01

    EPR spectroscopic studies of membrane proteins in a physiologically relevant native membrane-bound state are extremely challenging due to the complexity observed in inhomogeneity sample preparation and dynamic motion of the spin-label. Traditionally, detergent micelles are the most widely used membrane mimetics for membrane proteins due to their smaller size and homogeneity, providing high-resolution structure analysis by solution NMR spectroscopy. However, it is often difficult to examine whether the protein structure in a micelle environment is the same as that of the respective membrane-bound state. Recently, lipodisq nanoparticles have been introduced as a potentially good membrane mimetic system for structural studies of membrane proteins. However, a detailed characterization of a spin-labeled membrane protein incorporated into lipodisq nanoparticles is still lacking. In this work, lipodisq nanoparticles were used as a membrane mimic system for probing the structural and dynamic properties of the integral membrane protein KCNE1 using site-directed spin labeling EPR spectroscopy. The characterization of spin-labeled KCNE1 incorporated into lipodisq nanoparticles was carried out using CW-EPR titration experiments for the EPR spectral line shape analysis and pulsed EPR titration experiment for the phase memory time (Tm) measurements. The CW-EPR titration experiment indicated an increase in spectral line broadening with the addition of the SMA polymer which approaches close to the rigid limit at a lipid to polymer weight ratio of 1:1, providing a clear solubilization of the protein-lipid complex. Similarly, the Tm titration experiment indicated an increase in Tm values with the addition of SMA polymer and approaches ∼2 μs at a lipid to polymer weight ratio of 1:2. Additionally, CW-EPR spectral line shape analysis was performed on six inside and six outside the membrane spin-label probes of KCNE1 in lipodisq nanoparticles. The results indicated significant

  13. FTIR and EPR spectroscopic investigation of calcium-silicate glasses with iron and dysprosium

    Science.gov (United States)

    Eniu, D.; Gruian, C.; Vanea, E.; Patcas, L.; Simon, V.

    2015-03-01

    The sol-gel derived 50SiO2ṡ30CaOṡ10Fe2O3ṡ10Dy2O3 system was subjected to heat treatments at 500, 800 and 1200 °C in order to obtain crystalline phases of interest for biomedical applications. The structural changes were investigated by Fourier transform infrared spectroscopy (FTIR) and electron paramagnetic resonance (EPR). Both FTIR and EPR results support the development of wollastonite, hematite and magnetite crystalline phases desirable for samples bioactivity and heating possibility for hyperthermia treatment. Dysprosium addition was considered for subsequent radioactivation of the samples that could extend their application to thermoradiotherapy.

  14. Correlated four-component EPR g-tensors for doublet molecules

    DEFF Research Database (Denmark)

    Vad, M.S.; Pedersen, M.N.; Nørager, A.

    2013-01-01

    The first correlated ab initio four-component calculations of electron paramagnetic resonance (EPR) g-tensors for doublet radicals are reported. We have implemented a first-order degenerate perturbation theory approach based on the four-component Dirac-Coulomb Hamiltonian and fully relativistic...... configuration interaction wave functions in the DIRAC program package. We find that the correlation effects on the g-tensors can be sufficiently well described with manageable basis sets of triple-zeta quality and manageable configuration spaces. The new fully relativistic EPR module in DIRAC should be useful...

  15. EPR dosimetry of teeth in past and future accidents: a prospective look at a retrospective method

    Energy Technology Data Exchange (ETDEWEB)

    Haskell, E.H.; Kenner, G.H.; Hayes, R.B. [Utah Univ., Salt Lake City, UT (United States). Center for Applied Dosimetry; Chumak, V.; Shalom, S. [All-Union Scientific Centre of Radiation Medicine, Kiev (Ukraine)

    1996-01-01

    Electron paramagnetic resonance spectroscopy (EPR) of tooth enamel is a relatively new technique for retrospective dosimetry that in the past two years has seen increasing effort towards its development and evaluation. Efforts have centered on determining the accuracy which may be achieved with current measurement techniques as well as the minimum doses detectable. The study was focused on evaluating some factors which influence the accuracy of EPR dosimetry of enamel. Reported are studies on sample intercomparisions, instrumental considerations, and effects of dental x-rays, environmental sunlight and ultraviolet radiation.

  16. A secure and efficient password-based user authentication scheme using smart cards for the integrated EPR information system.

    Science.gov (United States)

    Lee, Tian-Fu; Chang, I-Pin; Lin, Tsung-Hung; Wang, Ching-Cheng

    2013-06-01

    The integrated EPR information system supports convenient and rapid e-medicine services. A secure and efficient authentication scheme for the integrated EPR information system provides safeguarding patients' electronic patient records (EPRs) and helps health care workers and medical personnel to rapidly making correct clinical decisions. Recently, Wu et al. proposed an efficient password-based user authentication scheme using smart cards for the integrated EPR information system, and claimed that the proposed scheme could resist various malicious attacks. However, their scheme is still vulnerable to lost smart card and stolen verifier attacks. This investigation discusses these weaknesses and proposes a secure and efficient authentication scheme for the integrated EPR information system as alternative. Compared with related approaches, the proposed scheme not only retains a lower computational cost and does not require verifier tables for storing users' secrets, but also solves the security problems in previous schemes and withstands possible attacks.

  17. Polypropylene/ethylene-propylene rubber (PP/EPR blends for the automotive industry: Basic correlations between EPR-design and shrinkage

    Directory of Open Access Journals (Sweden)

    G. D. Potter

    2014-04-01

    Full Text Available The influence of the phase morphology on the shrinkage of injection molded plates from reactor based PP/EPR blends was investigated using a model series. The morphology of the dispersed phase – in terms of size and shape of the rubber particles as determined from scanning electron microscopy (SEM – was found to correlate fairly well with the shrinkage determined in the flow and transverse direction of injection molded plates. In this respect it turned out to be elementary to consider the anisotropy of the particles rather than their average size alone. Additionally, the effect of the EPR design on the coefficient of linear thermal expansion (CLTE was evaluated and brought into a relationship with the blend morphology.

  18. Characteristics and economy of the European reactor of pressurized water (EPR); Caracteristicas y economia del reactor europeo de agua a presion (EPR)

    Energy Technology Data Exchange (ETDEWEB)

    Ortiz V, J.; Ramirez S, J.R.; Palacios H, J.C. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico)]. e-mail: jov@nuclear.inin.mx

    2005-07-01

    The high current costs of the fossil fuels, have propitiated that the industries of electric power generation in the world reconsider the nuclear option as medium of generation. In Europe, the more recently contracted nuclear power plant is that of Olkiluoto-III in Finland that waits it enters in operation at the end of 2009. The reactor that will be installed in this power plant will be a prototype of pressurized water reactor of the companies AREVA and EDF. In this work they are described the reactor EPR and the major components of the nuclear power plant as well as the main characteristics of safety and the flexibility of the operation of the EPR. The supposed costs reported in different sources of information are also described and calculated with information provided by the manufacturer company. (Author)

  19. EPR dosimetry in tooth enamel by x radiation; Dosimetria EPR en esmalte dental irradiado con rayos X

    Energy Technology Data Exchange (ETDEWEB)

    Dubner, Diana; Perez, Maria del Rosario; Gisone, P. [Autoridad Regulatoria Nuclear, Buenos Aires (Argentina)] E-mail: ddubner@cae.arn.gov.ar; Fainstein, C.; Winkler, E. [Comision Nacional de Energia Atomica (CNEA), San Carlos de Bariloche (Argentina). Centro Atomico Bariloche]|[Universidad Nacional de Cuyo, Mendoza (Argentina). Inst. Balseiro; Saravi, Margarita [Comision Nacional de Energia Atomica (CNEA) (Argentina). Centro Atomico Ezeiza; Davila, Francisco [Ateneo Argentino de Odontologia, Buenos Aires (Argentina)

    2001-07-01

    Tooth enamel, extracted from molars, was irradiated with 66 keV X-rays, with doses up to 1 Gy. The preparation of the powder samples is described, as well as the protocol for the acquisition and processing of the spectra. The radiation induced paramagnetism is measured, at room temperature, by ESR spectroscopy. The ESR spectra is well described considering two paramagnetic species, with magnetic moments (in units of Bohr magnetrons) g=2,0041, and g1=2,0018, g2=1,9972. The ESR data (peak-to-peak amplitude per mg, hpp/mg, vs dose D), for doses 0 Gy

  20. Resonance Raman spectra of metallooctaethylporphyrin cation radicals with a/sub 1u/ and a/sub 2u/ orbital character

    Energy Technology Data Exchange (ETDEWEB)

    Kim, D.; Miller, L.A.; Rakhit, G.; Spiro, T.G.

    1986-07-17

    Resonance Raman (RR) spectra are reported for radical cations of M/sup II/OEP (OEP = octaethylporphyrin; M = Zn, Mg, Ni, Cu) and for the perchlorate and bromide salts of (Co/sup III/OEP)/sup +/, produced by electrochemical and/or chemical oxidation. The enhancement patterns obtained with B (4067 A) and Q (5682 A) band excitation (except M = Zn and Mg, for which fluorescence overwhelms the Q band RR spectra) permitted assignment of most of the porphyrin skeletal modes above 1000 cm/sup -1/, and frequency shifts relative to the unoxidized porphyrins have been cataloged. Those radicals, magnesium(II), zinc(II), and cobalt(III) bromides, whose EPR spectra have been assigned on the basis of electron removal from an a/sub lu/ molecular orbital show a common pattern of shifts, while those with a/sub 2u/-type EPR spectra, nickel(II) and cobalt(III) perchlorates, show a different pattern. The Cu/sup II/ radical, whose visible absorption spectrum resembles that of other a/sub 2u/ radicals, likewise has an a/sub 2u/ RR frequency shift pattern. The largest shifts are shown by the most prominent RR bands in the B-band-excited spectra, nu/sub 4/ (C/sub a/N breathing, primarily) and nu/sub 2/ (C/sub b/C/sub b/ breathing, primarily).

  1. Electronic structure and spectroscopic properties of mononuclear manganese(III) Schiff base complexes: a systematic study on [Mn(acen)X] complexes by EPR, UV/vis, and MCD spectroscopy (X = Hal, NCS).

    Science.gov (United States)

    Westphal, Anne; Klinkebiel, Arne; Berends, Hans-Martin; Broda, Henning; Kurz, Philipp; Tuczek, Felix

    2013-03-04

    The manganese(III) Schiff base complexes [Mn(acen)X] (H2acen: N,N'-ethylenebis(acetylacetone)imine, X: I(-), Br(-), Cl(-), NCS(-)) are considered as model systems for a combined study of the electronic structure using vibrational, UV/vis absorption, parallel-mode electron paramagnetic resonance (EPR) and low-temperature magnetic circular dichroism (MCD) spectroscopy. By variation of the co-ligand X, the influence of the axial ligand field within a given square-pyramidal coordination geometry on the UV/vis, EPR, and MCD spectra of the title compounds is investigated. Between 25000 and 35000 cm(-1), the low-temperature MCD spectra are dominated by two very intense, oppositely signed pseudo-A terms, referred to as "double pseudo-A terms", which change their signs within the [Mn(acen)X] series dependent on the axial ligand X. Based on molecular orbital (MO) and symmetry considerations, these features are assigned to π(n.b.)(s, a) → yz, z(2) ligand-to-metal charge transfer transitions. The individual MCD signs are directly determined from the calculated MOs of the [Mn(acen)X] complexes. The observed sign change is explained by an inversion of symmetry among the π(n.b.)(s, a) donor orbitals which leads to an interchange of the positive and negative pseudo-A terms constituting the "double pseudo-A term".

  2. Raman spectra of lithium compounds

    Science.gov (United States)

    Gorelik, V. S.; Bi, Dongxue; Voinov, Y. P.; Vodchits, A. I.; Gorshunov, B. P.; Yurasov, N. I.; Yurasova, I. I.

    2017-11-01

    The paper is devoted to the results of investigating the spontaneous Raman scattering spectra in the lithium compounds crystals in a wide spectral range by the fibre-optic spectroscopy method. We also present the stimulated Raman scattering spectra in the lithium hydroxide and lithium deuteride crystals obtained with the use of powerful laser source. The symmetry properties of the lithium hydroxide, lithium hydroxide monohydrate and lithium deuteride crystals optical modes were analyzed by means of the irreducible representations of the point symmetry groups. We have established the selection rules in the Raman and infrared absorption spectra of LiOH, LiOH·H2O and LiD crystals.

  3. Study of Thermal Properties of Mixed (PP/EPR/ABS with Five Model Compatibilizers

    Directory of Open Access Journals (Sweden)

    Pierre Marcel Anicet Noah

    2016-01-01

    Full Text Available The influences of incorporating compatibilizers E-EA-MAH, E-MA-GMA, E-AM, SEBS KRATON G, or PP-g-MAH on the thermal properties of mixed (polypropylene/ethylene propylene rubber/acrylonitrile butadiene styrene (PP/EPR/ABS have been investigated. DSC investigations have revealed that the incorporation of 5% of ABS in the copolymer (PP/EPR does not fundamentally affect the thermal properties of the basic copolymer; additionally, the addition of 1.5% of each of the compatibilizers in the basic mixture does not significantly alter the crystallization temperature values and the melting of the -P- sequences. There is a variation of melting enthalpy values of the -P- sequences of 18.23% using SEBS KRATON G and of 10.38% using E-AM-GMA. When the rate of each of the compatibilizers increases to 5%, overall crystallization enthalpies of -P- sequences are almost kept unchanged, except for the case of using the compatibilizer E-AM-GMA with a variation of 8.42%. There is a minor variation of the melting enthalpy of -P- sequences with higher levels of compatibilizer. The incorporation of 5% ABS copolymer in the PP/EPR does not significantly alter the thermal properties of the basic structure of (PP/EPR/ABS.

  4. In Vivo EPR Resolution Enhancement Using Techniques Known from Quantum Computing Spin Technology.

    Science.gov (United States)

    Rahimi, Robabeh; Halpern, Howard J; Takui, Takeji

    2017-01-01

    A crucial issue with in vivo biological/medical EPR is its low signal-to-noise ratio, giving rise to the low spectroscopic resolution. We propose quantum hyperpolarization techniques based on 'Heat Bath Algorithmic Cooling', allowing possible approaches for improving the resolution in magnetic resonance spectroscopy and imaging.

  5. High-frequency EPR and ENDOR spectroscopy on semiconductor quantum dots

    NARCIS (Netherlands)

    Baranov, P.G.; Orlinskii, S.B.; de Mello Donega, C.|info:eu-repo/dai/nl/125593899; Schmidt, J.

    2010-01-01

    It is shown that high-frequency electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) spectroscopy are excellent tools for the investigation of the electronic properties of semiconductor quantum dots (QDs). The great attractions of these techniques are that, in contrast

  6. EPR policies for electronics in developing Asia: an adapted phase-in approach.

    Science.gov (United States)

    Akenji, Lewis; Hotta, Yasuhiko; Bengtsson, Magnus; Hayashi, Shiko

    2011-09-01

    The amount of e-waste is growing rapidly in developing countries, and the health and environmental problems resulting from poor management of this waste have become a concern for policy makers. In response to these challenges, a number of Asian developing countries have been inspired by policy developments in OECD countries, and have drafted legislations based on the principle of extended producer responsibility (EPR). However, the experiences from developed countries show that a successful implementation of EPR policies requires adequate institutions and sufficient administrative capacity. Even advanced countries are thus facing difficulties. This paper concludes from existing literature and from the authors' own observations that there seems to be a mismatch between the typical policy responses to e-waste problems in developing Asia and the capacity for successful implementation of such policies. It also notes that the e-waste situation in developing Asian countries is further complicated by a number of additional factors, such as difficulties in identifying producers, import of used electronic products and e-waste (sometimes illegal), and the existence of a strong informal waste sector. Given these challenges, the authors conclude that comprehensive EPR policy schemes of the kind that have been implemented in some advanced countries are not likely to be effective. The paper therefore proposes an alternative phase-in approach whereby developing Asian countries are able to move gradually towards EPR systems. It argues that this approach would be more feasible, and discusses what could be the key building blocks of each implementation stage.

  7. CO{sub 2} doped γ-irradiated hydroxyapatite for EPR dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Ziaie, Farhood [Nuclear Science and Technology Resesarch Institute, Tehran (Iran, Islamic Republic of). Radiation Application Research School

    2014-11-15

    Synthetic nano-structure hydroxyapatite samples were doped by carbon in furnace via exposing to CO{sub 2} circulating gas in different time of 30, 120, and 360 min under 100 C and 400 C of temperatures. FTIR, TEM and XRD analyses results confirmed the doping of carbonate group to the hydroxyapatite structure. The samples were irradiated in absorbed doses of 2, 5, 10, 20, 50, and 80 kGy using a {sup 60}Co γ-ray source and subjected to EPR measurement, subsequently. The EPR signal intensities were constructed as a function of radiation dose, were compared with the results of raw sample and were studied from dosimetric point of view. The obtained results show a considerable increment in EPR signal intensities of the samples which were treated at 400 C. At the doses less than 20 kGy the carbon doped samples show a better EPR respond. This is much better for doses below 5 kGy in comparison to the raw samples and the response is quite linear.

  8. Irradiated bivalve mollusks: Use of EPR spectroscopy for identification and dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Alberti, Angelo, E-mail: aalberti@isof.cnr.it [CNR-ISOF, Area della Ricerca di Bologna, Via P. Gobetti 101, Bologna I-40129 (Italy); Chiaravalle, Eugenio [Istituto Zooprofilattico Sperimentale della Puglia e Basilicata, Via Manfredonia 20, Foggia I-71100 (Italy); Fuochi, Piergiorgio; Macciantelli, Dante [CNR-ISOF, Area della Ricerca di Bologna, Via P. Gobetti 101, Bologna I-40129 (Italy); Mangiacotti, Michele, E-mail: michelemangiacotti@libero.it [Istituto Zooprofilattico Sperimentale della Puglia e Basilicata, Via Manfredonia 20, Foggia I-71100 (Italy); Marchesani, Giuliana [Istituto Zooprofilattico Sperimentale della Puglia e Basilicata, Via Manfredonia 20, Foggia I-71100 (Italy); Plescia, Elena [CNR-ISOF, Area della Ricerca di Bologna, Via P. Gobetti 101, Bologna I-40129 (Italy)

    2011-12-15

    High energy radiation treatment of foodstuff for microbial control and shelf-life extension is being used in many countries. However, for consumer protection and information, the European Union has adopted the Directives 1999/2/EC and 1999/3/EC to harmonize the rules concerning the treatment and trade of irradiated foods in EU countries. Among the validated methods to detect irradiated foods the EU directives also include Electron Paramagnetic Resonance (EPR/ESR) spectroscopy. We describe herein the use of EPR for identification of four species of bivalve mollusks, i.e. brown Venus shells (Callista chione), clams (Tapes semidecussatus), mussels (Mytilus galloprovincialis) and oysters (Ostrea edulis) irradiated with {sup 60}Co {gamma}-rays. EPR could definitely identify irradiated seashells due to the presence of long-lived free radicals, primarily CO{sub 2}{sup -}, CO{sub 3}{sup 3-}, SO{sub 2}{sup -} and SO{sub 3}{sup -} radical anions. The presence of other organic free radicals, believed to originate from conchiolin, a scleroprotein present in the shells, was also ascertained. The use of one of these radicals as a marker for irradiation of brown Venus shells and clams can be envisaged. We also propose a dosimetric protocol for the reconstruction of the administered dose in irradiated oysters. - Highlights: > EPR spectroscopy is confirmed a valuable identification tool for irradiated mollusks. > A conchiolin-derived radical can be used as irradiation marker for some mollusks. > A reliable protocol is outlined for dose reconstruction of irradiated oysters.

  9. On the use of locally dense basis sets in the calculation of EPR hyperfine couplings

    DEFF Research Database (Denmark)

    Milhøj, Birgitte Olai; Hedegård, Erik D.; Sauer, Stephan P. A.

    2013-01-01

    The usage of locally dense basis sets in the calculation of Electron Paramagnetic Resonance (EPR) hyperne coupling constants is investigated at the level of Density Functional Theory (DFT) for two model systems of biologically important transition metal complexes: One for the active site in the c...

  10. On the use of Locally Dense Basis Sets in the Calculation of EPR Hyperfine Couplings

    DEFF Research Database (Denmark)

    Hedegård, Erik D.; Sauer, Stephan P. A.; Milhøj, Birgitte O.

    2013-01-01

    The usage of locally dense basis sets in the calculation of Electron Paramagnetic Resonance (EPR) hyperne coupling constants is investigated at the level of Density Functional Theory (DFT) for two model systems of biologically important transition metal complexes: One for the active site in the c...

  11. Measuring precarious employment in times of crisis: the revised Employment Precariousness Scale (EPRES in Spain

    Directory of Open Access Journals (Sweden)

    Alejandra Vives

    2015-09-01

    Conclusion: The revised version of the EPRES demonstrated good metric properties and improved sensitivity to worker vulnerability and employment instability among permanent workers. Furthermore, it was sensitive to increased levels of precariousness in some dimensions despite decreases in others, demonstrating responsiveness to the context of the economic crisis affecting the Spanish labour market.

  12. Single crystal EPR studies of Mn (II) doped into zinc ammonium ...

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 62; Issue 1. Single crystal EPR studies of Mn(II) doped into zinc ammonium phosphate hexahydrate (ZnNH4PO4⋅6H2O): A case of interstitial site for bio-mineral analogue. H Anandalakshmi K Velavan I Sougandi Venkatesan P Sambasiva Rao. Research Articles ...

  13. Simple group password-based authenticated key agreements for the integrated EPR information system.

    Science.gov (United States)

    Lee, Tian-Fu; Chang, I-Pin; Wang, Ching-Cheng

    2013-04-01

    The security and privacy are important issues for electronic patient records (EPRs). The goal of EPRs is sharing the patients' medical histories such as the diagnosis records, reports and diagnosis image files among hospitals by the Internet. So the security issue for the integrated EPR information system is essential. That is, to ensure the information during transmission through by the Internet is secure and private. The group password-based authenticated key agreement (GPAKE) allows a group of users like doctors, nurses and patients to establish a common session key by using password authentication. Then the group of users can securely communicate by using this session key. Many approaches about GAPKE employ the public key infrastructure (PKI) in order to have higher security. However, it not only increases users' overheads and requires keeping an extra equipment for storing long-term secret keys, but also requires maintaining the public key system. This investigation presents a simple group password-based authenticated key agreement (SGPAKE) protocol for the integrated EPR information system. The proposed SGPAKE protocol does not require using the server or users' public keys. Each user only remembers his weak password shared with a trusted server, and then can obtain a common session key. Then all users can securely communicate by using this session key. The proposed SGPAKE protocol not only provides users with convince, but also has higher security.

  14. How can EPR spectroscopy help to unravel molecular mechanisms of flavin-dependent photoreceptors?

    Directory of Open Access Journals (Sweden)

    Daniel eNohr

    2015-09-01

    Full Text Available Electron paramagnetic resonance (EPR spectroscopy is a well-established spectroscopic method for the examination of paramagnetic molecules. Proteins can contain paramagnetic moieties in form of stable cofactors, transiently formed intermediates, or spin labels artificially introduced to cysteine sites. The focus of this review is to evaluate potential scopes of application of EPR to the emerging field of optogenetics. The main objective for EPR spectroscopy in this context is to unravel the complex mechanisms of light-active proteins, from their primary photoreaction to downstream signal transduction. An overview of recent results from the family of flavin-containing, blue-light dependent photoreceptors is given. In detail, mechanistic similarities and differences are condensed from the three classes of flavoproteins, the cryptochromes, LOV (Light-oxygen-voltage, and BLUF (blue-light using FAD domains. Additionally, a concept that includes spin-labeled proteins and examination using modern pulsed EPR is introduced, which allows for a precise mapping of light-induced conformational changes.

  15. single crystal EPR studies of Mn(II) doped into zinc ammonium ...

    Indian Academy of Sciences (India)

    -sulphato-aquotris(imidazole) cadmium(II), the paramagnetic ion enters substi- tutionally into the host lattice giving rise to two magnetically inequivalent sites. [9]. single crystal EPR study of Mn(II)-doped magnesium bis(hydrogen maleate) hexahydrate confirms that the impurity ion not only occupies the magnesium site.

  16. Detection and characterisation of radicals using electron paramagnetic resonance (EPR) spin trapping and related methods

    DEFF Research Database (Denmark)

    Davies, Michael Jonathan

    2016-01-01

    Electron paramagnetic resonance (EPR) spectroscopy (also known as electron spin resonance, ESR, or electron magnetic resonance, EMR, spectroscopy) is often described as the “gold standard” for the detection and characterisation of radicals in chemical, biological and medical systems. The article...

  17. A 5 tesla superconducting magnet and cryostats for an EPR/FMR spectrometer

    NARCIS (Netherlands)

    Reuvekamp, E.M.C.M.; Gerritsma, G.J.; ten Kate, Herman H.J.; van de Klundert, L.J.M.

    1988-01-01

    A description is given of the cryogenic part of an electron paramagnetic resonance (EPR)/ferromagnetic resonance (FMR) spectrometer using Ka-band (26.5-40 GHz) and U-band (40-60 GHz) frequencies for resonance measurements on large magnetic thin-films. The unit has two cryostats; the first has a

  18. Interpretation of wave energy spectra

    National Research Council Canada - National Science Library

    Thompson, E.F

    1980-01-01

    Guidelines for interpreting nondirectional wave energy spectra and presented. A simple method is given for using the spectrum to estimate a significant height and period for each major wave train in most sea states...

  19. Infrared spectra of mineral species

    CERN Document Server

    Chukanov, Nikita V

    2014-01-01

    This book details more than 3,000 IR spectra of more than 2,000 mineral species collected during last 30 years. It features full descriptions and analytical data of each sample for which IR spectrum was obtained.

  20. Pileup correction of microdosimetric spectra

    CERN Document Server

    Langen, K M; Lennox, A J; Kroc, T K; De Luca, P M

    2002-01-01

    Microdosimetric spectra were measured at the Fermilab neutron therapy facility using low pressure proportional counters operated in pulse mode. The neutron beam has a very low duty cycle (<0.1%) and consequently a high instantaneous dose rate which causes distortions of the microdosimetric spectra due to pulse pileup. The determination of undistorted spectra at this facility necessitated (i) the modified operation of the proton accelerator to reduce the instantaneous dose rate and (ii) the establishment of a computational procedure to correct the measured spectra for remaining pileup distortions. In support of the latter effort, two different pileup simulation algorithms using analytical and Monte-Carlo-based approaches were developed. While the analytical algorithm allows a detailed analysis of pileup processes it only treats two-pulse and three-pulse pileup and its validity is hence restricted. A Monte-Carlo-based pileup algorithm was developed that inherently treats all degrees of pileup. This algorithm...

  1. Photon spectra from WIMP annihilation

    OpenAIRE

    Ruiz Cembranos, José Alberto; Cruz Dombriz, Álvaro de la; Dobado González, Antonio; Lineros, R. A.; López Maroto, Antonio

    2010-01-01

    If the present dark matter in the Universe annihilates into standard model particles, it must contribute to the fluxes of cosmic rays that are detected on the Earth and, in particular, to the observed gamma-ray fluxes. The magnitude of such a contribution depends on the particular dark matter candidate, but certain features of the produced photon spectra may be analyzed in a rather model-independent fashion. In this work we provide the complete photon spectra coming from WIMP annihilation int...

  2. Well-Known Mediators of Selective Oxidation with Unknown Electronic Structure: Metal-Free Generation and EPR Study of Imide-N-oxyl Radicals.

    Science.gov (United States)

    Krylov, Igor B; Kompanets, Mykhailo O; Novikova, Katerina V; Opeida, Iosip O; Kushch, Olga V; Shelimov, Boris N; Nikishin, Gennady I; Levitsky, Dmitri O; Terent'ev, Alexander O

    2016-01-14

    Nitroxyl radicals are widely used in chemistry, materials sciences, and biology. Imide-N-oxyl radicals are subclass of unique nitroxyl radicals that proved to be useful catalysts and mediators of selective oxidation and CH-functionalization. An efficient metal-free method was developed for the generation of imide-N-oxyl radicals from N-hydroxyimides at room temperature by the reaction with (diacetoxyiodo)benzene. The method allows for the production of high concentrations of free radicals and provides high resolution of their EPR spectra exhibiting the superhyperfine structure from benzene ring protons distant from the radical center. An analysis of the spectra shows that, regardless of the electronic effects of the substituents in the benzene ring, the superhyperfine coupling constant of an unpaired electron with the distant protons at positions 4 and 5 of the aromatic system is substantially greater than that with the protons at positions 3 and 6 that are closer to the N-oxyl radical center. This is indicative of an unusual character of the spin density distribution of the unpaired electron in substituted phthalimide-N-oxyl radicals. Understanding of the nature of the electron density distribution in imide-N-oxyl radicals may be useful for the development of commercial mediators of oxidation based on N-hydroxyimides.

  3. Saturation transfer EPR (ST-EPR) for dating biocarbonates containing large amount of Mn{sup 2+}: separation of SO{sub 3}{sup -} and CO{sub 2}{sup -} lines and geochronology of Brazilian fish fossil

    Energy Technology Data Exchange (ETDEWEB)

    Sastry, M.D.; Andrade, M.B.; Watanabe, Shigueo E-mail: watanabe@if.usp.br

    2003-04-01

    A method using saturation transfer EPR (ST-EPR) is shown to be feasible for detecting EPR signal of radiation-induced defects in biocarbonates containing large amount of Mn{sup 2+}. The ST-EPR measurements conducted at room temperature on fish fossil of Brazilian origin, enabled the identification of CO{sub 2}{sup -} and SO{sub 3}{sup -} radical ions, by partially suppressing the intense signal from Mn{sup 2+} when the signal are detected 90 deg. out of phase with magnetic field modulating signal and at high microwave power (50 mW). Using these signals the age of fish fossil is estimated to be (36{+-}5) Ma.

  4. Retrospective individual dosimetry using luminescence and EPR after radiation accidents; Retroperspektive individuelle Dosimetrie mit Lumineszenz - und EPR-Messungen fuer den Notfallschutz

    Energy Technology Data Exchange (ETDEWEB)

    Goeksu, H.Y.; Wieser, A.; Ulanovsky, A. [GSF - Forschungszentrum fuer Umwelt und Gesundheit GmbH, Neuherberg (Germany)

    2007-07-01

    doses requires further investigation. Applicability of suggested procedure need to be tested under factory conditions using the latest material and card technology. Feasibility of production of such cards on an industrial scale is discussed. Alternatively individual dose after emergency situations can be reconstructed by assessment of absorbed dose in human tooth enamel by electron paramagnetic resonance (EPR) measurements. From absorbed dose in tooth enamel the effective dose and dose in organs can be reconstructed in consideration of photon energy response characteristic of teeth, and photon energy spectrum and geometry of the exposure field. In this project the applicability of EPR measurements with teeth was extended by reducing the detection threshold and computation of the photon energy response characteristic of deciduous teeth. It is shown that current limitation of EPR measurement with teeth at low absorbed dose is caused by incomplete consideration of the EPR spectrum of nonradiation induced (initial) radicals. By adding further components for simulation of the initial EPR spectrum in the dose evaluation procedure, the critical value for detection of absorbed dose in tooth enamel could be decreased to 19 mGy. Dose conversion coefficients for deciduous teeth in dependence of photon energy and exposure geometry were computed by Monte Carlo simulation using a mathematical child phantom. For use with luminescence measurements with chip cards and EPR measurements with teeth a software was established that allows conversion of the measured dose to integral free-in-air kerma, tissue dose or dose water in dependence on exposure scenario. (orig.)

  5. Membrane remodeling by amyloidogenic and non-amyloidogenic proteins studied by EPR

    Science.gov (United States)

    Varkey, Jobin; Langen, Ralf

    2017-07-01

    The advancement in site-directed spin labeling of proteins has enabled EPR studies to expand into newer research areas within the umbrella of protein-membrane interactions. Recently, membrane remodeling by amyloidogenic and non-amyloidogenic proteins has gained a substantial interest in relation to driving and controlling vital cellular processes such as endocytosis, exocytosis, shaping of organelles like endoplasmic reticulum, Golgi and mitochondria, intracellular vesicular trafficking, formation of filopedia and multivesicular bodies, mitochondrial fusion and fission, and synaptic vesicle fusion and recycling in neurotransmission. Misregulation in any of these processes due to an aberrant protein (mutation or misfolding) or alteration of lipid metabolism can be detrimental to the cell and cause disease. Dissection of the structural basis of membrane remodeling by proteins is thus quite necessary for an understanding of the underlying mechanisms, but it remains a formidable task due to the difficulties of various common biophysical tools in monitoring the dynamic process of membrane binding and bending by proteins. This is largely since membranes generally complicate protein structure analysis and this problem is amplified for structural analysis in the presence of different types of membrane curvatures. Recent EPR studies on membrane remodeling by proteins show that a significant structural information can be generated to delineate the role of different protein modules, domains and individual amino acids in the generation of membrane curvature. These studies also show how EPR can complement the data obtained by high resolution techniques such as X-ray and NMR. This perspective covers the application of EPR in recent studies for understanding membrane remodeling by amyloidogenic and non-amyloidogenic proteins that is useful for researchers interested in using or complimenting EPR to gain better understanding of membrane remodeling. We also discuss how a single

  6. Enactment of a decree for a EPR unit on the Flamanville site; Publication du decret sur l'EPR a Flamanville

    Energy Technology Data Exchange (ETDEWEB)

    Anon

    2007-03-15

    The decree allowing the construction of a EPR (European Pressurized Reactor) on the Flamanville site has been enacted through publishing in the official gazette on the 11. April 2007. This decree sets the technical specifications concerning: nuclear safety, radiation protection and environment protection that will have to be followed during the operating life of the reactor. This decree is the last step before construction works begin, this 1650 MWe reactor is expected to enter into service by 2012. The regional administrative jurisdiction has rejected 3 requests in annulment claimed by associations, upon the grounds that the 1986 law on the coastline development is not relevant in this case. (A.C.)

  7. Projects of Iberdrola Engineering and Construction on the Flamanville 3 EPR; Proyectos de Iberdrola Ingenieria y construccion en el EPR de Flamanville 3

    Energy Technology Data Exchange (ETDEWEB)

    Zornoza, J.; Dumas, H.; Sesma, J. L.; Cubian, B.; Diaz, J. I.

    2013-06-01

    Iberdrola Engineering and Construction is participating during the last 5 years in 5 projects on the Flamanville 3 EPR, both in the nuclear island and conventional island and the pump house. These projects represent a challenge from the technical point of view due to the high requirements applicable to the project because of the experience feedback of the operator EDF and of compliance with new regulations that have emerged since the completion of the last nuclear power station in France. This paper presents the description of these projects, as well as its current status. (Author)

  8. High-field (high-frequency) EPR spectroscopy and structural characterization of a novel manganese(III) corrole

    OpenAIRE

    Bendix, Jesper; Gray, Harry B.; Golubkov, Galina; Gross, Zeev

    2000-01-01

    The X-ray structure, magnetic susceptibility, and high-field (high-frequency) EPR spectrum of manganese 5,10,15-tris(pentafluorophenyl) corrole unambiguously establish that the complex contains an isolated, slightly rhombic, manganese(III) center.

  9. An EPR study of the intramolecular dynamics in o-semiquinonic nickel complexes with a diphosphorous pincer ligand.

    Science.gov (United States)

    Kozhanov, Konstantin A; Bubnov, Michael P; Cherkasov, Vladimir K; Fukin, Georgy K; Abakumov, Gleb A

    2003-10-21

    Square pyramidal o-semiquinonic nickel complexes with 2,6-bis(diphenylphosphinomethyl)phenyl have a flexible coordination sphere and exist in solution as the mixture of tautomers rapidly, according to EPR time scale, interconverting at room temperature.

  10. QUALITATIVE INTERPRETATION OF GALAXY SPECTRA

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez Almeida, J.; Morales-Luis, A. B. [Instituto de Astrofisica de Canarias, E-38205 La Laguna, Tenerife (Spain); Terlevich, R.; Terlevich, E. [Instituto Nacional de Astrofisica, Optica y Electronica, Tonantzintla, Puebla (Mexico); Cid Fernandes, R., E-mail: jos@iac.es, E-mail: abml@iac.es, E-mail: rjt@ast.cam.ac.uk, E-mail: eterlevi@inaoep.mx, E-mail: cid@astro.ufsc.br [Departamento de Fisica-CFM, Universidade Federal de Santa Catarina, P.O. Box 476, 88040-900 Florianopolis, SC (Brazil)

    2012-09-10

    We describe a simple step-by-step guide to qualitative interpretation of galaxy spectra. Rather than an alternative to existing automated tools, it is put forward as an instrument for quick-look analysis and for gaining physical insight when interpreting the outputs provided by automated tools. Though the recipe is for general application, it was developed for understanding the nature of the Automatic Spectroscopic K-means-based (ASK) template spectra. They resulted from the classification of all the galaxy spectra in the Sloan Digital Sky Survey data release 7, thus being a comprehensive representation of the galaxy spectra in the local universe. Using the recipe, we give a description of the properties of the gas and the stars that characterize the ASK classes, from those corresponding to passively evolving galaxies, to H II galaxies undergoing a galaxy-wide starburst. The qualitative analysis is found to be in excellent agreement with quantitative analyses of the same spectra. We compare the mean ages of the stellar populations with those inferred using the code STARLIGHT. We also examine the estimated gas-phase metallicity with the metallicities obtained using electron-temperature-based methods. A number of byproducts follow from the analysis. There is a tight correlation between the age of the stellar population and the metallicity of the gas, which is stronger than the correlations between galaxy mass and stellar age, and galaxy mass and gas metallicity. The galaxy spectra are known to follow a one-dimensional sequence, and we identify the luminosity-weighted mean stellar age as the affine parameter that describes the sequence. All ASK classes happen to have a significant fraction of old stars, although spectrum-wise they are outshined by the youngest populations. Old stars are metal-rich or metal-poor depending on whether they reside in passive galaxies or in star-forming galaxies.

  11. RosettaTMH: a method for membrane protein structure elucidation combining EPR distance restraints with assembly of transmembrane helices

    Directory of Open Access Journals (Sweden)

    Andrew Leaver-Fay

    2015-12-01

    Full Text Available Membrane proteins make up approximately one third of all proteins, and they play key roles in a plethora of physiological processes. However, membrane proteins make up less than 2% of experimentally determined structures, despite significant advances in structure determination methods, such as X-ray crystallography, nuclear magnetic resonance spectroscopy, and cryo-electron microscopy. One potential alternative means of structure elucidation is to combine computational methods with experimental EPR data. In 2011, Hirst and others introduced RosettaEPR and demonstrated that this approach could be successfully applied to fold soluble proteins. Furthermore, few computational methods for de novo folding of integral membrane proteins have been presented. In this work, we present RosettaTMH, a novel algorithm for structure prediction of helical membrane proteins. A benchmark set of 34 proteins, in which the proteins ranged in size from 91 to 565 residues, was used to compare RosettaTMH to Rosetta’s two existing membrane protein folding protocols: the published RosettaMembrane folding protocol (“MembraneAbinitio” and folding from an extended chain (“ExtendedChain”. When EPR distance restraints are used, RosettaTMH+EPR outperforms ExtendedChain+EPR for 11 proteins, including the largest six proteins tested. RosettaTMH+EPR is capable of achieving native-like folds for 30 of 34 proteins tested, including receptors and transporters. For example, the average RMSD100SSE relative to the crystal structure for rhodopsin was 6.1 ± 0.4 Å and 6.5 ± 0.6 Å for the 449-residue nitric oxide reductase subunit B, where the standard deviation reflects variance in RMSD100SSE values across ten different EPR distance restraint sets. The addition of RosettaTMH and RosettaTMH+EPR to the Rosetta family of de novo folding methods broadens the scope of helical membrane proteins that can be accurately modeled with this software suite.

  12. EPR experiment and 2-photon interferometry: Report of a 2-photon interference experiment

    Science.gov (United States)

    Shih, Y. H.; Rubin, M. H.; Sergienko, A. V.

    1992-01-01

    After a very brief review of the historical Einstein, Podolsky, and Rosen (EPR) experiments, a new two-photon interference type EPR experiment is reported. A two-photon state was generated by optical parametric down conversion. Pairs of light quanta with degenerate frequency but divergent directions of propagation were sent to two independent Michelson interferometers. First and second order interference effectors were studied. Different than other reports, we observed that the second order interference visibility vanished when the optical path difference of the interferometers were much less than the coherence length of the pumping laser beam. However, we also observed that the second order interference behaved differently depending on whether the interferometers were set at equal or different optical path differences.

  13. Analysis of two-player quantum games in an EPR setting using Clifford's geometric algebra.

    Directory of Open Access Journals (Sweden)

    James M Chappell

    Full Text Available The framework for playing quantum games in an Einstein-Podolsky-Rosen (EPR type setting is investigated using the mathematical formalism of geometric algebra (GA. The main advantage of this framework is that the players' strategy sets remain identical to the ones in the classical mixed-strategy version of the game, and hence the quantum game becomes a proper extension of the classical game, avoiding a criticism of other quantum game frameworks. We produce a general solution for two-player games, and as examples, we analyze the games of Prisoners' Dilemma and Stag Hunt in the EPR setting. The use of GA allows a quantum-mechanical analysis without the use of complex numbers or the Dirac Bra-ket notation, and hence is more accessible to the non-physicist.

  14. The Interplay of manganese and nitrate in hydroxyapatite nanoparticles as revealed by pulsed EPR and DFT.

    Science.gov (United States)

    Gafurov, Marat; Biktagirov, Timur; Mamin, Georgy; Klimashina, Elena; Putlayev, Valery; Kuznetsova, L; Orlinskii, Sergei

    2015-08-21

    The interplay of oppositely charged substitutions in the structure of hydroxyapatite (HAp) nanopowders is investigated on the atomic level by pulsed electron paramagnetic resonance (EPR) technique and ab initio density functional theory calculations. Benefits of EPR to determine Mn(2+) ions in nano-HAp samples are demonstrated. A simple approach based on the measurements of electron spin relaxation times allowed observing the strong influence of fast-relaxing Mn(2+) ions on the relaxation characteristics of the nitrate ions (NO3(-)/NO3(2-)) incorporated in trace amounts. Based on the results of ab initio calculations, we show the propensity of Mn(2+) and NO3(-)/NO3(2-) to associate within the HAp crystal lattice. This could have a direct impact on the functional properties of the material especially to resorption and ion exchange. Furthermore, such an effect can increase a propensity of undesired impurities to incorporate into the doped nanocrystals.

  15. The design and integration of retinal CAD-SR to diabetes patient ePR system

    Science.gov (United States)

    Wu, Huiqun; Wei, Yufang; Liu, Brent J.; Shang, Yujuan; Shi, Lili; Jiang, Kui; Dong, Jiancheng

    2017-03-01

    Diabetic retinopathy (DR) is one of the serious complications of diabetes that could lead to blindness. Digital fundus camera is often used to detect retinal changes but the diagnosis relies too much on ophthalmologist's experience. Based on our previously developed algorithms for quantifying retinal vessels and lesions, we developed a computer aided detection-structured report (CAD-SR) template and implemented it into picture archiving and communication system (PACS). Furthermore, we mapped our CAD-SR into HL7 CDA to integrate CAD findings into diabetes patient electronic patient record (ePR) system. Such integration could provide more quantitative features from fundus image into ePR system, which is valuable for further data mining researches.

  16. A Novel Approach to Separating EPR Lines Arising from Species with Different Transition Moments

    Science.gov (United States)

    Hofbauer, Wulf; Bittl, Robert

    2000-12-01

    In pulsed EPR, spectral contributions from several species in one sample can be separated based on different EPR transition probabilities. This is usually done by monitoring the Rabi nutations in a 2D experiment. By using long pulses, the FID and echo shapes of species with different transition probabilities differ significantly, including temporal shifts of the observed echo signals in a two-pulse ESE experiment. These shifts can be used to disentangle spectral components in a 1D field-swept ESE experiment by choosing an appropriate detection time. This approach is demonstrated by experiments on a sample containing Mn2+ and Cr3+ centers as well as on an exchange-coupled Mn(III)/Mn(IV) system with Mn2+ contaminations.

  17. EPR, optical and superposition model study of Mn2+ doped L+ glutamic acid

    Science.gov (United States)

    Kripal, Ram; Singh, Manju

    2015-12-01

    Electron paramagnetic resonance (EPR) study of Mn2+ doped L+ glutamic acid single crystal is done at room temperature. Four interstitial sites are observed and the spin Hamiltonian parameters are calculated with the help of large number of resonant lines for various angular positions of external magnetic field. The optical absorption study is also done at room temperature. The energy values for different orbital levels are calculated, and observed bands are assigned as transitions from 6A1g(s) ground state to various excited states. With the help of these assigned bands, Racah inter-electronic repulsion parameters B = 869 cm-1, C = 2080 cm-1 and cubic crystal field splitting parameter Dq = 730 cm-1 are calculated. Zero field splitting (ZFS) parameters D and E are calculated by the perturbation formulae and crystal field parameters obtained using superposition model. The calculated values of ZFS parameters are in good agreement with the experimental values obtained by EPR.

  18. Electrochemical behaviour of gold modified with contaminated TMP amine adlayers studied by STM, CV, EPR

    Energy Technology Data Exchange (ETDEWEB)

    Krukowski, P. [Division of Physics and Technology of Nanometric Structures, Solid State Physics Department, University of Lodz, Pomorska 149/153, 90-236 Lodz (Poland)], E-mail: pkrukowski@std2.phys.uni.lodz.pl; Kowalczyk, P.J. [Division of Physics and Technology of Nanometric Structures, Solid State Physics Department, University of Lodz, Pomorska 149/153, 90-236 Lodz (Poland); Krzyczmonik, P. [Department of General and Inorganic Chemistry, University of Lodz, Narutowicza 68, 90-136 Lodz (Poland); Olejniczak, W.; Klusek, Z.; Puchalski, M. [Division of Physics and Technology of Nanometric Structures, Solid State Physics Department, University of Lodz, Pomorska 149/153, 90-236 Lodz (Poland); Gwozdzinski, K. [Department of Molecular Biophysics, University of Lodz, Banacha 12/16, 90-237 Lodz (Poland)

    2009-01-15

    Scanning tunnelling microscopy (STM), cyclic voltammetry (CV) and electron paramagnetic resonance spectroscopy (EPR) were used to investigate the influence of the TMP amine derivative on Au (1 1 1). The STM results show that the gold surface covered by the adlayer of the TMP derivative is easily modified (holes formation) after increasing the bias voltage to 0.5 V. The CV and EPR results show the electrochemical origin of observed STM topography changes. It is suggested that TMP could be oxidized to the nitroxyl TEMPO radical which adsorbs on Au in the form of an oxoammonium cation. Such an oxoammonium cation at the potential of 0.5 V forms a permanent complex of gold and the nitroxyl radical which could be easily desorbed during STM imaging.

  19. Analysis of two-player quantum games in an EPR setting using Clifford's geometric algebra.

    Science.gov (United States)

    Chappell, James M; Iqbal, Azhar; Abbott, Derek

    2012-01-01

    The framework for playing quantum games in an Einstein-Podolsky-Rosen (EPR) type setting is investigated using the mathematical formalism of geometric algebra (GA). The main advantage of this framework is that the players' strategy sets remain identical to the ones in the classical mixed-strategy version of the game, and hence the quantum game becomes a proper extension of the classical game, avoiding a criticism of other quantum game frameworks. We produce a general solution for two-player games, and as examples, we analyze the games of Prisoners' Dilemma and Stag Hunt in the EPR setting. The use of GA allows a quantum-mechanical analysis without the use of complex numbers or the Dirac Bra-ket notation, and hence is more accessible to the non-physicist.

  20. EPR studies of carbonaceous compounds deposited on Al-MCM-41

    Energy Technology Data Exchange (ETDEWEB)

    Nowak, L.; Lezanska, M.; Rozwadowski, M.; Rozploch, F.; Marciniak, W

    2002-11-30

    Electron paramagnetic resonance (EPR) spectroscopy was used to investigate carbonaceous compounds deposited on aluminosilicate mesoporous molecular sieves of the MCM-41 type during conversion of cyclohexene at various temperatures. The amount of the deposited coke grew with the increasing Al content of the catalysts and with the decreasing reaction temperature. The deposits caused a reduction in both the surface area and pore volume of the Al-MCM-41 materials. The measurements showed that the EPR lines were complex. The performed analysis revealed a hyperfine structure the envelope of which was of the Gaussian shape. It was found that the spin concentration increased and the peak-to-peak width ({delta}B{sub pp}) decreased with the increasing reaction temperature.

  1. In vivo preclinical cancer and tissue engineering applications of absolute oxygen imaging using pulse EPR

    Science.gov (United States)

    Epel, Boris; Kotecha, Mrignayani; Halpern, Howard J.

    2017-07-01

    The value of any measurement and a fortiori any measurement technology is defined by the reproducibility and the accuracy of the measurements. This implies a relative freedom of the measurement from factors confounding its accuracy. In the past, one of the reasons for the loss of focus on the importance of imaging oxygen in vivo was the difficulty in obtaining reproducible oxygen or pO2 images free from confounding variation. This review will briefly consider principles of electron paramagnetic oxygen imaging and describe how it achieves absolute oxygen measurements. We will provide a summary review of the progress in biomedical EPR imaging, predominantly in cancer biology research, discuss EPR oxygen imaging for cancer treatment and tissue graft assessment for regenerative medicine applications.

  2. EPR investigation on radiation-induced graft copolymerization of styrene onto polyethylene: Energy transfer effects

    Energy Technology Data Exchange (ETDEWEB)

    Salih, M.A. [Dipartimento di Chimica Generale, Universita di Pavia, 27100 Pavia (Italy); Buttafava, A. [Dipartimento di Chimica Generale, Universita di Pavia, 27100 Pavia (Italy); Ravasio, U. [Dipartimento di Chimica Generale, Universita di Pavia, 27100 Pavia (Italy); Dipartimento di Ingegneria Nucleare, Politecnico di Milan (Italy); Mariani, M. [Dipartimento di Ingegneria Nucleare, Politecnico di Milan (Italy); Faucitano, A. [Dipartimento di Chimica Generale, Universita di Pavia, 27100 Pavia (Italy)]. E-mail: antonio.faucitano@unipv.it

    2007-08-15

    In this paper, energy transfer phenomena concerning the in-source graft copolymerization of styrene onto LDPE were investigated through the EPR analysis of the radical intermediates. The model solution experiments have shown a substantial deviation of the experimental G (radicals) values with respect to the additivity law, which reflect the negative effect of the styrene monomer concentration on the initiation rate of the graft copolymerization. The EPR measurements performed on polyethylene-co-styrene graft copolymers of various composition following low-temperature vacuum gamma irradiation have confirmed the decrease of the total radical yields with increasing the styrene concentration. The effect was partly attributed to the heterogeneity of the graft copolymer matrix and to the lack of molecular mobility in the solid state at low temperature, which prevents the attainment of the favourable geometrical configurations in intermolecular energy and charge transfer events.

  3. Quantum Chemical Investigations of Structure, Bonding and EPR Parameters of Manganese Complexes relevant to Photosystem II

    OpenAIRE

    Schinzel, Sandra

    2009-01-01

    Im Wasser-oxidierenden Cluster („oxygen-evolving complex“, OEC) des Photosystem II findet sich die primäre Quelle der Sauerstoffproduktion der Erde. Der OEC katalysiert in grünen Pflanzen unter Absorption von Sonnenlicht die Vierelektronen-Oxidation von Wasser zu Sauerstoff in einer zyklischen Sequenz von Oxidationszuständen (Kok-Zyklus). In dieser Arbeit wurden Strukturen, Spindichteverteilungen sowie EPR-Parameter ein-, zwei- und vierkerniger Mangankomplexe, die in Bezug auf den OEC modelli...

  4. Multifrequency EPR Studies of Manganese Catalases Provide a Complete Description of Proteinaceous Nitrogen Coordination

    OpenAIRE

    Stich, Troy A.; Whittaker, James W.; Britt, R. David

    2010-01-01

    Pulse electron paramagnetic resonance (EPR) spectroscopy is employed at two very different excitation frequencies, 9.77 and 30.67 GHz, in the study of the nitrogen coordination environment of the Mn(III)Mn(IV) state of the dimanganese-containing catalases from Lactobacillus plantarum and Thermus thermophilus. Consistent with previous studies, the lower-frequency results reveal one unique histidine nitrogen-Mn cluster interaction. For the first time, a second, more strongly hyperfine-coupled 1...

  5. Very-Low-Frequency Electron Paramagnetic Resonance (EPR) Imaging of Nitroxide-Loaded Cells

    OpenAIRE

    Kao, Joseph P. Y.; Barth, Eugene D.; Burks, Scott R.; Smithback, Philip; Mailer, Colin; Ahn, Kang-Hyun; Halpern, Howard J.; Rosen, Gerald M

    2007-01-01

    Recent advances in electron paramagnetic resonance (EPR) imaging have made it possible to image, in real time in vivo, cells that have been labeled with nitroxide spin probes. We previously reported that cells can be loaded to high (millimolar) intracellular concentrations with (2,2,5,5-tetramethylpyrrolidin-1-oxyl-3-ylmethyl)amine-N,N-diacetic acid by incubation with the corresponding acetoxymethyl (AM) ester. Furthermore, the intracellular lifetime (t1/e) of this nitroxide is 114 min—suffic...

  6. Emergency Preservation and Resuscitation for Cardiac Arrest from Trauma (EPR-CAT)

    Science.gov (United States)

    2015-10-01

    Award Number: W81XWH-07-1-0682 TITLE: Emergency Preservation and Resuscitation for Cardiac Arrest from Trauma (EPR-CAT) PRINCIPAL INVESTIGATOR...COVERED (From - To) 26 SEP 2014 – 25 SEP 2015 4. TITLE AND SUBTITLE Emergency Preservation and Resuscitation for Cardiac Arrest 5a. CONTRACT NUMBER From...study. It was felt that patients who arrive at the hospital with a pulse, but then develop cardiac arrest in the operating room, rather than in the

  7. CONFORMATIONAL EQUILIBRIA OF BULGED SITES IN DUPLEX DNA STUDIED BY EPR SPECTROSCOPY

    OpenAIRE

    Smith, Alyssa L.; Cekan, Pavol; Brewood, Greg P.; Okonogi, Tamara M.; Alemayehu, Saba; Hustedt, Eric J.; Benight, Albert S.; Sigurdsson, Snorri Th.; Robinson, Bruce H.

    2009-01-01

    Conformational flexibility in nucleic acids provides a basis for complex structures, binding, and signaling. One-base bulges directly neighboring single-base mismatches in nucleic acids can be present in a minimum of two distinct conformations, complicating the examination of the thermodynamics by calorimetry or UV-monitored melting techniques. To provide additional information about such structures, we demonstrate how electron paramagnetic resonance (EPR) active spin-labeled base analogues, ...

  8. Assessing dimerisation degree and cooperativity in a biomimetic small-molecule model by pulsed EPR

    OpenAIRE

    Ackermann, Katrin; Giannoulis, Angeliki; Cordes, David Bradford; Slawin, Alexandra Martha Zoya; Bode, Bela Ernest

    2015-01-01

    AG acknowledges a postgraduate fellowship by the EPSRC funded doctoral training centre ‘integrated magnetic resonance’. BEB is grateful for an EaStCHEM Hirst Academic Fellowship by the School of Chemistry, St Andrews, and funding from the People Programme (Marie Curie Actions) of the European Union’s Seventh Framework Programme (REA 334496). Pulsed electron paramagnetic resonance (EPR) spectroscopy is gaining increasing importance as a complementary biophysical technique in structural biol...

  9. EPR Oximetry Sensor-Developing a TAM Derivative for In Vivo Studies.

    Science.gov (United States)

    Boś-Liedke, Agnieszka; Walawender, Magdalena; Woźniak, Anna; Flak, Dorota; Gapiński, Jacek; Jurga, Stefan; Kucińska, Małgorzata; Plewiński, Adam; Murias, Marek; Elewa, Marwa; Lampp, Lisa; Imming, Peter; Tadyszak, Krzysztof

    2017-09-04

    Oxygenation is one of the most important physiological parameters of biological systems. Low oxygen concentration (hypoxia) is associated with various pathophysiological processes in different organs. Hypoxia is of special importance in tumor therapy, causing poor response to treatment. Triaryl methyl (TAM) derivative radicals are commonly used in electron paramagnetic resonance (EPR) as sensors for quantitative spatial tissue oxygen mapping. They are also known as magnetic resonance imaging (MRI) contrast agents and fluorescence imaging compounds. We report the properties of the TAM radical tris(2,3,5,6-tetrachloro-4-carboxy-phenyl)methyl, (PTMTC), a potential multimodal (EPR/fluorescence) marker. PTMTC was spectrally analyzed using EPR and characterized by estimation of its sensitivity to the oxygen in liquid environment suitable for intravenous injection (1 mM PBS, pH = 7.4). Further, fluorescent emission of the radical was measured using the same solvent and its quantum yield was estimated. An in vitro cytotoxicity examination was conducted in two cancer cell lines, HT-29 (colorectal adenocarcinoma) and FaDu (squamous cell carcinoma) and followed by uptake studies. The stability of the radical in different solutions (PBS pH = 7.4, cell media used for HT-29 and FaDu cells culturing and cytotoxicity procedure, full rat blood and blood plasma) was determined. Finally, a primary toxicity test of PTMTC was carried out in mice. Results of spectral studies confirmed the multimodal properties of PTMTC. PTMTC was demonstrated to be not absorbed by cancer cells and did not interfere with luciferin-luciferase based assays. Also in vitro and in vivo tests showed that it was non-toxic and can be freely administrated till doses of 250 mg/kg BW via both i.v. and i.p. injections. This work illustrated that PTMTC is a perfect candidate for multimodal (EPR/fluorescence) contrast agent in preclinical studies.

  10. Synthesis and EPR studies of the first water-soluble N@C60 derivative.

    Science.gov (United States)

    Cornes, Stuart P; Zhou, Shen; Porfyrakis, Kyriakos

    2017-11-28

    The first water-soluble derivative of the paramagnetic endohedral fullerene N@C60 has been prepared through the covalent attachment of a single addend containing two permethylated β-cyclodextrin units to the surface of the carbon cage. The line width of the derivative's EPR signal is highly sensitive to both the nature of the solvent and the presence of Cu(ii) ions in solution.

  11. Fluorescence Spectra of Highlighter Inks

    Science.gov (United States)

    Birriel, Jennifer J.; King, Damon

    2018-01-01

    Fluorescence spectra excited by laser pointers have been the subject of several papers in "TPT". These papers all describe a fluorescence phenomenon in which the reflected laser light undergoes a change in color: this color change results from the combination of some partially reflected laser light and additional colors generated by…

  12. Correlation Functions and Power Spectra

    DEFF Research Database (Denmark)

    Larsen, Jan

    2006-01-01

    The present lecture note is a supplement to the textbook Digital Signal Processing by J. Proakis and D.G. Manolakis used in the IMM/DTU course 02451 Digital Signal Processing and provides an extended discussion of correlation functions and power spectra. The definitions of correlation functions...

  13. INFRARED SPECTRA, THERMOGRAVIMETRIC ANALYSIS AND ...

    African Journals Online (AJOL)

    Preferred Customer

    characterized by melting point, molar conductivity, magnetic moment, elemental analysis, infrared spectra and thermal analyses. ... methyl-quinazolinone and the final products of the thermogravimetric analysis were recorded on a Perkin-Elmer FT-IR type ..... [Cu(CH3COO)(L)3]. CuO + 5C +12C2H2 + 4NO + NH3 + 0.5N2.

  14. Multifrequency EPR studies of manganese catalases provide a complete description of proteinaceous nitrogen coordination.

    Science.gov (United States)

    Stich, Troy A; Whittaker, James W; Britt, R David

    2010-11-18

    Pulse electron paramagnetic resonance (EPR) spectroscopy is employed at two very different excitation frequencies, 9.77 and 30.67 GHz, in the study of the nitrogen coordination environment of the Mn(III)Mn(IV) state of the dimanganese-containing catalases from Lactobacillus plantarum and Thermus thermophilus. Consistent with previous studies, the lower-frequency results reveal one unique histidine nitrogen-Mn cluster interaction. For the first time, a second, more strongly hyperfine-coupled (14)N atom is unambiguously observed through the use of higher frequency/higher field EPR spectroscopy. The low excitation frequency spectral features are rationalized as arising from the interaction of a histidine nitrogen that is bound to the Mn(IV) ion, and the higher excitation frequency features are attributed to the histidine nitrogen bound to the Mn(III) ion. These results allow for the computation of intrinsic hyperfine coupling constants, which range from 2.2 to 2.9 MHz, for sp(2)-hybridized nitrogens coordinating equatorially to high-valence Mn ions. The relevance of these findings is discussed in the context of recent results from analogous higher frequency EPR studies of the Mn cluster in photosystem II and other exchange-coupled, transition metal-containing systems.

  15. Photochemistry of naphthalene diimides: EPR study of free radical formation via photoredox process.

    Science.gov (United States)

    Reszka, Krzysztof J; Takayama, Masami; Sik, Robert H; Chignell, Colin F; Saito, Isao

    2005-01-01

    Earlier studies have shown that on exposure to UVA, hydroperoxynaphthalene diimide (IA) generates hydroxyl radicals, induces DNA strand scission, and kills cells. Here we employed electron paramagnetic resonance (EPR) and spin trapping to investigate the free radical photochemistry of IA and that of related naphthalene diimides, which are devoid of the hydroperoxyl moiety (N,N'-bis[2-methyl]-1,4,5,8-naphthaldiimide [IB], N,N'-bis[2-thiomethyl-2-methoxyethyl]-1,4,5,8-naphthaldiimide [IC]) and therefore are unable to generate hydroxyl radicals. It is shown that on UV irradiation (>300 nm) in air-free methanol or ethanol solutions all these naphthalene diimides undergo one-electron reduction to corresponding anion radicals, positively identified by EPR. With EPR and a spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO), we found that the photogeneration of the naphthalene diimide radicals is concomitant with the formation of radicals from the solvents, presumably through electron/hydrogen atom abstraction by photoactivated diimides. Irradiation of IA, IB or IC in the presence of oxygen generates superoxide, which was detected as a DMPO adduct. The high photoreactivity of IB and IC supports the notion that hydroperoxide IA can induce oxidative damage via photoprocesses that are independent of *OH generation. These observations could be pertinent to the application of naphthalene diimides as selective photonucleases, PDT anticancer agents or both.

  16. Entanglement conservation, ER=EPR, and a new classical area theorem for wormholes

    Energy Technology Data Exchange (ETDEWEB)

    Remmen, Grant N. [Walter Burke Institute for Theoretical PhysicsCalifornia Institute of Technology, Pasadena, CA 91125 (United States); Bao, Ning [Walter Burke Institute for Theoretical PhysicsCalifornia Institute of Technology, Pasadena, CA 91125 (United States); Institute for Quantum Information and Matter,California Institute of Technology, Pasadena, CA 91125 (United States); Pollack, Jason [Walter Burke Institute for Theoretical PhysicsCalifornia Institute of Technology, Pasadena, CA 91125 (United States)

    2016-07-11

    We consider the question of entanglement conservation in the context of the ER=EPR correspondence equating quantum entanglement with wormholes. In quantum mechanics, the entanglement between a system and its complement is conserved under unitary operations that act independently on each; ER=EPR suggests that an analogous statement should hold for wormholes. We accordingly prove a new area theorem in general relativity: for a collection of dynamical wormholes and black holes in a spacetime satisfying the null curvature condition, the maximin area for a subset of the horizons (giving the largest area attained by the minimal cross section of the multi-wormhole throat separating the subset from its complement) is invariant under classical time evolution along the outermost apparent horizons. The evolution can be completely general, including horizon mergers and the addition of classical matter satisfying the null energy condition. This theorem is the gravitational dual of entanglement conservation and thus constitutes an explicit characterization of the ER=EPR duality in the classical limit.

  17. Simultaneous EPR and optical spectroscopy of pure and Rh-doped barium calcium titanate crystals

    Science.gov (United States)

    Grachev, Valentin; Malovichko, Galina; Schirmer, Ortwin

    2003-03-01

    The large electro-optic coefficients and high holographic sensitivity of barium calcium titanate (Ba0.77Ca0.23TiO3, BCT) make it promising candidate for various applications, since it has no drawback related to the phase transition at 280 K like barium titanate. The nominally pure and Rh doped BCT crystals were investigated with the help of optical absorption spectroscopy, light induced absorption change measurements and electron paramagnetic resonance (EPR) in the temperature range between 4.2 and 300 K. Analyzing angular dependencies of the EPR lines we succeed to identify low-symmetry and nearly cubic centers of iron trace impurity. Four other paramagnetic defects were found after illumination: Ti3+, Rh2+, O- and Pt3+. All these defects are participants of charge transfer processes. At the light energy E about 1.3 eV the holes abandon Ti4+ creating the paramagnetic electronic Ti3+. At E > 2.3 eV O2- ions capture the holes and create hole O- centers and simultaneously Ti3+ concentration increases. Nearly located non-controlled or intentionally introduced impurities (Sr, K, Na, Ca...) may serve as pins for the fixation of the electrons and holes. Additional correlated changes were found at E > 3.2 eV (band-band transition), when EPR lines of Rh2+, Pt3+ appear and intensities of Ti3+, O- and Fe3+ essentially increase. Models of defects involved in these light induced processes are proposed.

  18. Bacterial recovery and recycling of tellurium from tellurium-containing compounds by Pseudoalteromonas sp. EPR3.

    Science.gov (United States)

    Bonificio, W D; Clarke, D R

    2014-11-01

    Tellurium-based devices, such as photovoltaic (PV) modules and thermoelectric generators, are expected to play an increasing role in renewable energy technologies. Tellurium, however, is one of the scarcest elements in the earth's crust, and current production and recycling methods are inefficient and use toxic chemicals. This study demonstrates an alternative, bacterially mediated tellurium recovery process. We show that the hydrothermal vent microbe Pseudoalteromonas sp. strain EPR3 can convert tellurium from a wide variety of compounds, industrial sources and devices into metallic tellurium and a gaseous tellurium species. These compounds include metallic tellurium (Te(0)), tellurite (TeO3(2-)), copper autoclave slime, tellurium dioxide (TeO2), tellurium-based PV material (cadmium telluride, CdTe) and tellurium-based thermoelectric material (bismuth telluride, Bi2Te3). Experimentally, this was achieved by incubating these tellurium sources with the EPR3 in both solid and liquid media. Despite the fact that many of these tellurium compounds are considered insoluble in aqueous solution, they can nonetheless be transformed by EPR3, suggesting the existence of a steady state soluble tellurium concentration during tellurium transformation. These experiments provide insights into the processes of tellurium precipitation and volatilization by bacteria, and their implications on tellurium production and recycling. © 2014 The Society for Applied Microbiology.

  19. Delocalisation of photoexcited triplet states probed by transient EPR and hyperfine spectroscopy

    Science.gov (United States)

    Richert, Sabine; Tait, Claudia E.; Timmel, Christiane R.

    2017-07-01

    Photoexcited triplet states play a crucial role in photochemical mechanisms: long known to be of paramount importance in the study of photosynthetic reaction centres, they have more recently also been shown to play a major role in a number of applications in the field of molecular electronics. Their characterisation is crucial for an improved understanding of these processes with a particular focus on the determination of the spatial distribution of the triplet state wavefunction providing information on charge and energy transfer efficiencies. Currently, active research in this field is mostly focussed on the investigation of materials for organic photovoltaics (OPVs) and organic light emitting diodes (OLEDs). As the properties of triplet states and their spatial extent are known to have a major impact on device performance, a detailed understanding of the factors governing triplet state delocalisation is at the basis of the further development and improvement of these devices. Electron Paramagnetic Resonance (EPR) has proven a valuable tool in the study of triplet state properties and both experimental methods as well as data analysis and interpretation techniques have continuously improved over the last few decades. In this review, we discuss the theoretical and practical aspects of the investigation of triplet states and triplet state delocalisation by transient continuous wave and pulse EPR and highlight the advantages and limitations of the presently available techniques and the current trends in the field. Application of EPR in the study of triplet state delocalisation is illustrated on the example of linear multi-porphyrin chains designed as molecular wires.

  20. Applications of pulsed EPR spectroscopy to structural studies of sulfite oxidizing enzymes

    Energy Technology Data Exchange (ETDEWEB)

    Klein, Eric L.; Astashkin, Andrei V.; Raitsimring, Arnold M.; Enemark, John H.

    2013-01-01

    Sulfite oxidizing enzymes (SOEs), including sulfite oxidase (SO) and bacterial sulfite dehydrogenase (SDH), catalyze the oxidation of sulfite (SO32-) to sulfate (SO42-). The active sites of SO and SDH are nearly identical, each having a 5-coordinate, pseudo-square-pyramidal Mo with an axial oxo ligand and three equatorial sulfur donor atoms. One sulfur is from a conserved Cys residue and two are from a pyranopterindithiolene (molybdopterin, MPT) cofactor. The identity of the remaining equatorial ligand, which is solvent-exposed, varies during the catalytic cycle. Numerous in vitro studies, particularly those involving electron paramagnetic resonance (EPR) spectroscopy of the Mo(V) states of SOEs, have shown that the identity and orientation of this exchangeable equatorial ligand depends on the buffer pH, the presence and concentration of certain anions in the buffer, as well as specific point mutations in the protein. Until very recently, however, EPR has not been a practical technique for directly probing specific structures in which the solvent-exposed, exchangeable ligand is an O, OH-, H2O, SO32-, or SO42- group, because the primary O and S isotopes (16O and 32S) are magnetically silent (I = 0). This review focuses on the recent advances in the use of isotopic labeling, variable-frequency high resolution pulsed EPR spectroscopy, synthetic model compounds, and DFT calculations to elucidate the roles of various anions, point mutations, and steric factors in the formation, stabilization, and transformation of SOE active site structures.

  1. X-ray absorption spectroscopy and EPR studies of oriented spinach thylakoid preparations

    Energy Technology Data Exchange (ETDEWEB)

    Andrews, J.C. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry]|[Lawrence Berkeley Lab., CA (United States). Structural Biology Div.

    1995-08-01

    In this study, oriented Photosystem II (PS II) particles from spinach chloroplasts are studied with electron paramagnetic resonance (EPR) and x-ray absorption spectroscopy (XAS) to determine more details of the structure of the oxygen evolving complex (OEC). The nature of halide binding to Mn is also studied with Cl K-edge and Mn EXAFS (extended x-ray absorption fine structure) of Mn-Cl model compounds, and with Mn EXAFS of oriented PS II in which Br has replaced Cl. Attention is focused on the following: photosynthesis and the oxygen evolving complex; determination of mosaic spread in oriented photosystem II particles from signal II EPR measurement; oriented EXAFS--studies of PS II in the S{sub 2} state; structural changes in PS II as a result of treatment with ammonia: EPR and XAS studies; studies of halide binding to Mn: Cl K-edge and Mn EXAFS of Mn-Cl model compounds and Mn EXAFS of oriented Br-treated photosystem II.

  2. Development of next-generation macromolecular drugs based on the EPR effect: challenges and pitfalls.

    Science.gov (United States)

    Nakamura, Hideaki; Fang, Jun; Jun, Fang; Maeda, Hiroshi

    2015-01-01

    A major problem with conventional antitumor therapeutics is nonselective delivery of cytotoxic drugs to normal vital organs and tissues but little delivery to tumor tissues. Here, the authors describe the tumor selective delivery of antitumor drugs by taking advantage of nano-sized drugs and the means to augment it further. Based on the enhanced permeability and retention (EPR) effect, the mechanism for more efficient universal tumor delivery using macromolecular drugs to cover wider tumor types than single molecular target is discussed. Unique properties of solid tumor vasculature in the tumor tissue are discussed, especially leakiness of the blood vessels and factors involved and impaired clearance of macromolecular drugs from the tumor interstitium via the lymphatic system. The criteria for such macromolecular drugs or nanomedicines for effective accumulation at tumor sites is commented on as well as the importance of long plasma retention time of such drugs and a need to release active principles from nanoparticles at target sites. Methods to augment the EPR effect and tumor delivery (2 - 3 times) and its application to photodynamic therapy are also discussed. Tumor selective delivery of antitumor drugs based on the EPR effect can be accomplished and augmented by modulating the tumor environment. This methodology is favorable not only for tumor therapy but also for tumor imaging.

  3. Non-invasive determination of the irradiation dose in fingers using low-frequency EPR

    Energy Technology Data Exchange (ETDEWEB)

    Zdravkova, M [Laboratory of Biomedical Magnetic Resonance, Universite catholique de Louvain, UCL, Avenue Hippocrate, 10, B-1200 Brussels (Belgium); Crokart, N [Laboratory of Biomedical Magnetic Resonance, Universite catholique de Louvain, UCL, Avenue Hippocrate, 10, B-1200 Brussels (Belgium); Trompier, F [Service de Dosimetrie Externe, Departement de Radioprotection et de Protection de l' Homme, Institut de Radioprotection et de Surete Nucleaire, IRSN, BP no 17, F-92262 Fontenay-aux-Roses Cedex (France); Beghein, N [Laboratory of Biomedical Magnetic Resonance, Universite catholique de Louvain, UCL, Avenue Hippocrate, 10, B-1200 Brussels (Belgium); Gallez, B [Laboratory of Biomedical Magnetic Resonance, Universite catholique de Louvain, UCL, Avenue Hippocrate, 10, B-1200 Brussels (Belgium); Debuyst, R [Laboratory of Biomedical Magnetic Resonance, Universite catholique de Louvain, UCL, Avenue Hippocrate, 10, B-1200 Brussels (Belgium)

    2004-07-07

    Several reports in the literature have described the effects of radiation in workers who exposed their fingers to intense radioactive sources. The radiation injuries occurring after local exposure to a high dose (20 to 100 Gy) could lead to the need for amputation. Follow-up of victims needs to be more rational with a precise knowledge of the irradiated area that risks tissue degradation and necrosis. It has been described previously that X-band electron paramagnetic resonance (EPR) spectroscopy could be used to assess the dose in irradiated amputated fingers. Here, we propose the use of low-frequency EPR spectroscopy to evaluate non-invasively the absorbed dose. Low-frequency microwaves are indeed less absorbed by water and penetrate more deeply into living material ({approx}10 mm in tissues using 1 GHz spectrometers). This work presents preliminary results obtained with baboon and human fingers compared with human dry phalanxes placed inside a surface-coil resonator. The EPR signal increased linearly with the dose. The ratio of the slopes of the dry bone to whole finger linear regression lines was around 5. The detection limit achievable with the present spectrometer and resonator is around 60 Gy, which is well within the range of accidentally exposed fingers. It is likely that the detection limit could be improved in the future, thanks to further technical spectrometer and resonator developments as well as to appropriate spectrum deconvolution into native and dosimetric signals.

  4. Camel molar tooth enamel response to gamma rays using EPR spectroscopy.

    Science.gov (United States)

    El-Faramawy, N A; El-Somany, I; Mansour, A; Maghraby, A M; Eissa, H; Wieser, A

    2017-10-12

    Tooth enamel samples from molar teeth of camel were prepared using a combined procedure of mechanical and chemical tooth treatment. Based on electron paramagnetic resonance (EPR) spectroscopy, the dose response of tooth enamel samples was examined and compared to that of human enamel. The EPR dose response of the tooth enamel samples was obtained through irradiation to gamma doses from 1 Gy up to 100 kGy. It was found that the radiation-induced EPR signal increased linearly with gamma dose for all studied tooth enamel samples, up to about 15 kGy. At higher doses, the dose response curve leveled off. The results revealed that the location of the native signal of camel tooth enamel was similar to that of enamel from human molars at 2.00644, but different from that of enamel from cows and goats. In addition, the peak-to-peak width (ΔH pp) for human and camel molar teeth was similar. It was also found that the response of camel enamel to gamma radiation was 36% lower than that of human enamel. In conclusion, the results indicate the suitability of camel teeth for retrospective gamma dosimetry.

  5. Mapping ischemic risk region and necrosis in the isolated heart using EPR imaging.

    Science.gov (United States)

    Velayutham, Murugesan; Li, Haiquan; Kuppusamy, Periannan; Zweier, Jay L

    2003-06-01

    Reperfusion of ischemic tissue is a common event in the treatment of heart attack and stroke. To study disease pathogenesis, methods are required to measure tissue perfusion and area at risk, as well as localized regions of injury. While histology can provide this information, its destructive nature precludes assessment of time course. Thus, there is a critical need for a noninvasive technique to obtain this information. To map myocardial redox state as a possible index of cellular ischemia and viability, electron paramagnetic resonance (EPR) imaging experiments were performed on isolated rat hearts before and after the onset of regional ischemia using nitroxide spin labels. With coronary artery occlusion, the EPR images clearly showed the risk region as a void of lower intensity that reversed upon reperfusion. The extent of risk region in the heart was similar in EPR imaging and histological measurements. The unique information obtained regarding the time course of changes in redox metabolism of the risk region and normal myocardium can provide important insights regarding the mechanisms of myocardial injury during and following ischemia. Copyright 2003 Wiley-Liss, Inc.

  6. 240 GHz EPR Studies of Intrinsic Defects in 4H SiC

    Science.gov (United States)

    Konovalov, V. V.; Zvanut, M. E.; van Tol, J.; Brunel, L.-C.

    2002-03-01

    Intrinsic defects may strongly influence the conductivity and optical behavior of SiC. Several groups have reported 9.5 GHz EPR studies of a carbon vacancy in electron irradiated p-type and as-grown nominally semi-insulating SiC. Recently, Son et al. interpreted two lines in a 95 GHz EPR spectrum as a carbon vacancy and silicon antisite. We report 240 GHz EPR studies of intrinsic defects in as-grown 4H SiC provided by Cree Inc. The ID-1 line we observed earlier at 9.5 GHz and assigned to a carbon vacancy was resolved at 240 GHz into two lines, ID-1a and ID-1b. As the temperature decreased from 80 to 4 K, with H//c-axis the g-value of ID-1a remained constant at 2.00307, but the g-value of ID-1b decreased from 2.00272 to 2.00235. Concomitantly, the intensity of ID-1a decreased while that of ID-1b increased. Although our data are close to Son’s 95 GHz spectrum, preliminary interpretation of the highly resolved lines obtained at 240 GHz does not suggest a silicon antisite. Illumination with IR light quenches both ID-1a and ID-1b simultaneously, indicating close defect levels. The work is supported by the ONR.

  7. EPR-Spin Trapping and Flow Cytometric Studies of Free Radicals Generated Using Cold Atmospheric Argon Plasma and X-Ray Irradiation in Aqueous Solutions and Intracellular Milieu.

    Science.gov (United States)

    Uchiyama, Hidefumi; Zhao, Qing-Li; Hassan, Mariame Ali; Andocs, Gabor; Nojima, Nobuyuki; Takeda, Keigo; Ishikawa, Kenji; Hori, Masaru; Kondo, Takashi

    2015-01-01

    Electron paramagnetic resonance (EPR)-spin trapping and flow cytometry were used to identify free radicals generated using argon-cold atmospheric plasma (Ar-CAP) in aqueous solutions and intracellularly in comparison with those generated by X-irradiation. Ar-CAP was generated using a high-voltage power supply unit with low-frequency excitation. The characteristics of Ar-CAP were estimated by vacuum UV absorption and emission spectra measurements. Hydroxyl (·OH) radicals and hydrogen (H) atoms in aqueous solutions were identified with the spin traps 5,5-dimethyl-1-pyrroline N-oxide (DMPO), 3,3,5,5-tetramethyl-1-pyrroline-N-oxide (M4PO), and phenyl N-t-butylnitrone (PBN). The occurrence of Ar-CAP-induced pyrolysis was evaluated using the spin trap 3,5-dibromo-4-nitrosobenzene sulfonate (DBNBS) in aqueous solutions of DNA constituents, sodium acetate, and L-alanine. Human lymphoma U937 cells were used to study intracellular oxidative stress using five fluorescent probes with different affinities to a number of reactive species. The analysis and quantification of EPR spectra revealed the formation of enormous amounts of ·OH radicals using Ar-CAP compared with that by X-irradiation. Very small amounts of H atoms were detected whereas nitric oxide was not found. The formation of ·OH radicals depended on the type of rare gas used and the yield correlated inversely with ionization energy in the order of krypton > argon = neon > helium. No pyrolysis radicals were detected in aqueous solutions exposed to Ar-CAP. Intracellularly, ·OH, H2O2, which is the recombination product of ·OH, and OCl- were the most likely formed reactive oxygen species after exposure to Ar-CAP. Intracellularly, there was no practical evidence for the formation of NO whereas very small amounts of superoxides were formed. Despite the superiority of Ar-CAP in forming ·OH radicals, the exposure to X-rays proved more lethal. The mechanism of free radical formation in aqueous solutions and an

  8. EPR-Spin Trapping and Flow Cytometric Studies of Free Radicals Generated Using Cold Atmospheric Argon Plasma and X-Ray Irradiation in Aqueous Solutions and Intracellular Milieu.

    Directory of Open Access Journals (Sweden)

    Hidefumi Uchiyama

    Full Text Available Electron paramagnetic resonance (EPR-spin trapping and flow cytometry were used to identify free radicals generated using argon-cold atmospheric plasma (Ar-CAP in aqueous solutions and intracellularly in comparison with those generated by X-irradiation. Ar-CAP was generated using a high-voltage power supply unit with low-frequency excitation. The characteristics of Ar-CAP were estimated by vacuum UV absorption and emission spectra measurements. Hydroxyl (·OH radicals and hydrogen (H atoms in aqueous solutions were identified with the spin traps 5,5-dimethyl-1-pyrroline N-oxide (DMPO, 3,3,5,5-tetramethyl-1-pyrroline-N-oxide (M4PO, and phenyl N-t-butylnitrone (PBN. The occurrence of Ar-CAP-induced pyrolysis was evaluated using the spin trap 3,5-dibromo-4-nitrosobenzene sulfonate (DBNBS in aqueous solutions of DNA constituents, sodium acetate, and L-alanine. Human lymphoma U937 cells were used to study intracellular oxidative stress using five fluorescent probes with different affinities to a number of reactive species. The analysis and quantification of EPR spectra revealed the formation of enormous amounts of ·OH radicals using Ar-CAP compared with that by X-irradiation. Very small amounts of H atoms were detected whereas nitric oxide was not found. The formation of ·OH radicals depended on the type of rare gas used and the yield correlated inversely with ionization energy in the order of krypton > argon = neon > helium. No pyrolysis radicals were detected in aqueous solutions exposed to Ar-CAP. Intracellularly, ·OH, H2O2, which is the recombination product of ·OH, and OCl- were the most likely formed reactive oxygen species after exposure to Ar-CAP. Intracellularly, there was no practical evidence for the formation of NO whereas very small amounts of superoxides were formed. Despite the superiority of Ar-CAP in forming ·OH radicals, the exposure to X-rays proved more lethal. The mechanism of free radical formation in aqueous solutions and

  9. Synthesis, microstructure and EPR of CaMnO{sub 3} and Eu{sub x}Ca{sub 1-x}MnO{sub 3} manganite, obtained by coprecipitation

    Energy Technology Data Exchange (ETDEWEB)

    Santiago T, M.; Hernandez C, L.; Legorreta G, F. [Universidad Autonoma del Estado de Hidalgo, AACTyM, Carretera Pachuca-Tulancingo Km 4.5, 42074 Pachuca, Hidalgo (Mexico); Montiel S, H. [UNAM, Centro de Ciencias Aplicadas y Desarrollo Tecnologico, Departamento de Tecnociencias, Ciudad Universitaria, 04510 Mexico D. F. (Mexico); Alvarez L, G. [IPN, Escuela Superior de Fisica y Matematicas, Departamento de Fisica, U. P. Adolfo Lopez Mateos, Edif. 9, Col. Lindavista, 07738 Mexico D. F. (Mexico); Flores G, M. A., E-mail: mar200878@hotmail.com [Universidad Politecnica de Pachuca, Laboratorio de Nanotecnologia y Bioelectromagnetismo Aplicado, Carretera Pachuca-Cd. Sahagun Km 20, Ex-Hacienda de Santa Barbara, 43830 Zempoala, Hidalgo (Mexico)

    2011-07-01

    The synthesis of CaMnO{sub 3} and Eu{sub x}Ca{sub 1-x}MnO{sub 3} obtained by coprecipitation method is showed. The synthesized samples were characterized by X-ray diffraction and scanning electronic microscopy, the powders showed orthorhombic structure and pnma space group. When it was doped with Europium, their morphology tendency was spherical. Measurements were carried out on electron paramagnetic resonance (EPR) with constant frequency = 9.4 GHz (band X) and dc magnetic field (H dc) 0-0.8 T, measurements were at 300 K and 77 K. EPR spectra showed significant differences between both samples, indicating that the substitution of divalent alkaline earth cations by trivalent rare earth ions, allowing the formation of a mixed valence state of manganese, Mn{sup 3+} and Mn{sup 4+}. A 77 K, the manganite of concentration x = 0.30 had a magnetic ordering, noted by the presence of hysteresis. (Author)

  10. Characterization of Cu-exchanged SSZ-13: a comparative FTIR, UV-Vis, and EPR study with Cu-ZSM-5 and Cu-β with similar Si/Al and Cu/Al ratios.

    Science.gov (United States)

    Giordanino, Filippo; Vennestrøm, Peter N R; Lundegaard, Lars F; Stappen, Frederick N; Mossin, Susanne; Beato, Pablo; Bordiga, Silvia; Lamberti, Carlo

    2013-09-21

    Cu-SSZ-13 has been characterized by different spectroscopic techniques and compared with Cu-ZSM-5 and Cu-β with similar Si/Al and Cu/Al ratios and prepared by the same ion exchange procedure. On vacuum activated samples, low temperature FTIR spectroscopy allowed us to appreciate a high concentration of reduced copper centres, i.e. isolated Cu(+) ions located in different environments, able to form Cu(+)(N2), Cu(+)(CO)n (n = 1, 2, 3), and Cu(+)(NO)n (n = 1, 2) upon interaction with N2, CO and NO probe molecules, respectively. Low temperature FTIR, DRUV-Vis and EPR analysis on O2 activated samples revealed the presence of different Cu(2+) species. New data and discussion are devoted to (i) [Cu-OH](+) species likely balanced by one framework Al atom; (ii) mono(μ-oxo)dicopper [Cu2(μ-O)](2+) dimers observed in Cu-ZSM-5 and Cu-β, but not in Cu-SSZ-13. UV-Vis-NIR spectra of O2 activated samples reveal an intense and finely structured d-d quadruplet, unique to Cu-SSZ-13, which is persistent under SCR conditions. This differs from the 22,700 cm(-1) band of the mono(μ-oxo)dicopper species of the O2 activated Cu-ZSM-5, which disappears under SCR conditions. The EPR signal intensity sets Cu-β apart from the others.

  11. Anglinių nanostruktūrų sintezė ir dangų gamyba

    OpenAIRE

    Stankevičienė, Inga

    2012-01-01

    Unikaliomis savybėmis pasižyminčios anglinės nanostruktūros panaudojamos dangų ir plėvelių gamyboje, kurios pritaikomos nanoelektronikoje, biotechnologijoje ir kitose srityse. Šio darbo tikslas buvo susintetinti daugiasienius anglinius nanovamzdelius ir grafito oksidą, pagaminti ir ištirti jų dangas. Mūsų laboratorijoje daugiasieniai angliniai nanovamzdeliai buvo susintetinti cheminio nusodinimo iš garų fazės metodu. Susintetinto produkto valymui nuo katalizatoriaus priemaišų pirmą kartą ...

  12. Ultraviolet Fluorescence Spectra of Fingerprints

    Directory of Open Access Journals (Sweden)

    Naoki Saitoh

    2005-01-01

    Full Text Available We have studied inherent fluorescence spectra and imaging of fingerprints in the deep ultraviolet (UV region with a nanosecond-pulsed Nd-YAG laser system that consists of a tunable laser, a cooled CCD camera, and a grating spectrometer. In this paper, we have studied UV fluorescence spectra of fingerprints under 266-nm illumination. Fluorescence spectra of fingerprints have two main peaks, around 330 nm (peak A and 440 nm (peak B. At first, when a fingerprint has just been pressed, peak A is dominant. However, its intensity reduces as the total illumination time increases. On the other hand, peak B is weak at first. It appears after enough 266-nm illumination and its intensity increases as time elapses. After 3 h of illumination, peak A almost diminishes and peak B becomes dominant. By leaving the fingerprint under a fluorescent lamp in a room without laser illumination, peak A can be restored partly, while the intensity of peak B still increases.Time-resolved fluorescence spectra were also measured for these two peaks. The lifetime of each peak is 2.0 nsec (peak A and 6.2 nsec (peak B on average. Both peaks seem to consist of several components with different lifetimes. In the case of peak A, the 330-nm peak decays fast and a new component at 360 nm becomes dominant when the delay time exceeds 20 nsec. In the case of peak B, unlike peak A, no clear peak separation is observed, but the peak position seems to move from 440 to 460 nm when the delay time becomes larger.

  13. Catalogue of representative meteor spectra

    Science.gov (United States)

    Vojáček, V.; Borovička, J.; Koten, P.; Spurný, P.; Štork, R.

    2015-08-01

    Aims: We present a library of low-resolution meteor spectra that includes sporadic meteors, members of minor meteor showers, and major meteor showers. These meteors are in the magnitude range from +2 to -3, corresponding to meteoroid sizes from 1 mm to 10 mm. Methods: Parallel double-station video observations allowed us to compute heliocentric orbits for all meteors. Most observations were performed during the periods of activity of major meteor showers in the years between 2006 and 2012. Spectra are classified according to relative intensities of the low-temperature emission lines of Mg, Na, and Fe. Results: Shower meteors were found to be of normal composition, except for Southern δ Aquariids and some members of the Geminid shower, neither of which have Na in the meteor spectra. Variations in Na content are typical for the Geminid shower. Three populations of Na-free mereoroids were identified. The first population are iron meteorites, which have an asteroidal-chondritic origin, but one meteoroid with low perihelion (0.11 AU) was found among the iron meteorites. The second population were Sun-approaching meteoroids in which sodium is depleted by thermal desorption. The third population were Na-free meteoroids of cometary origin. Long exposure to cosmic rays on the surface of comets in the Oort cloud and disintegration of this crust might be the origin of this population of meteoroids. Spectra (Figs. 17-30) are only, Tables 4-6 are also available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/580/A67

  14. Application of Numerical Analysis of the Shape of Electron Paramagnetic Resonance Spectra for Determination of the Number of Different Groups of Radicals in the Burn Wounds

    Directory of Open Access Journals (Sweden)

    Paweł Olczyk

    2017-01-01

    Full Text Available Background. The evidence exists that radicals are crucial agents necessary for the wound regeneration helping to enhance the repair process. Materials and methods. The lineshape of the electron paramagnetic resonance (EPR spectra of the burn wounds measured with the low microwave power (2.2 mW was numerically analyzed. The experimental spectra were fitted by the sum of two and three lines. Results. The number of the lines in the EPR spectrum corresponded to the number of different groups of radicals in the natural samples after thermal treatment. The component lines were described by Gaussian and Lorentzian functions. The spectra of the burn wounds were superposition of three lines different in shape and in linewidths. The best fitting was obtained for the sum of broad Gaussian, broad Lorentzian, and narrow Lorentzian lines. Dipolar interactions between the unpaired electrons widened the broad Gaussian and broad Lorentzian lines. Radicals with the narrow Lorentzian lines existed mainly in the tested samples. Conclusions. The spectral shape analysis may be proposed as a useful method for determining the number of different groups of radicals in the burn wounds.

  15. Structured near-infrared Magnetic Circular Dichroism spectra of the Mn4CaO5 cluster of PSII in T. vulcanus are dominated by Mn(IV) d-d 'spin-flip' transitions.

    Science.gov (United States)

    Morton, Jennifer; Chrysina, Maria; Craig, Vincent S J; Akita, Fusamichi; Nakajima, Yoshiki; Lubitz, Wolfgang; Cox, Nicholas; Shen, Jian-Ren; Krausz, Elmars

    2018-02-01

    Photosystem II passes through four metastable S-states in catalysing light-driven water oxidation. Variable temperature variable field (VTVH) Magnetic Circular Dichroism (MCD) spectra in PSII of Thermosynochococcus (T.) vulcanus for each S-state are reported. These spectra, along with assignments, provide a new window into the electronic and magnetic structure of Mn4CaO5. VTVH MCD spectra taken in the S2 state provide a clear g=2, S=1/2 paramagnetic characteristic, which is entirely consistent with that known by EPR. The three features, seen as positive (+) at 749nm, negative (-) at 773nm and (+) at 808nm are assigned as 4A→2E spin-flips within the d3 configuration of the Mn(IV) centres present. This assignment is supported by comparison(s) to spin-flips seen in a range of Mn(IV) materials. S3 exhibits a more intense (-) MCD peak at 764nm and has a stronger MCD saturation characteristic. This S3 MCD saturation behaviour can be accurately modelled using parameters taken directly from analyses of EPR spectra. We see no evidence for Mn(III) d-d absorption in the near-IR of any S-state. We suggest that Mn(IV)-based absorption may be responsible for the well-known near-IR induced changes induced in S2 EPR spectra of T. vulcanus and not Mn(III)-based, as has been commonly assumed. Through an analysis of the nephelauxetic effect, the excitation energy of S-state dependent spin-flips seen may help identify coordination characteristics and changes at each Mn(IV). A prospectus as to what more detailed S-state dependent MCD studies promise to achieve is outlined. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. SU-C-BRD-05: Non-Invasive in Vivo Biodosimetry in Radiotherapy Patients Using Electron Paramagnetic Resonance (EPR) Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Bahar, N; Roberts, K; Stabile, F; Mongillo, N; Decker, RD; Wilson, LD; Husain, Z; Contessa, J; Carlson, DJ [Yale University School of Medicine, New Haven, Connecticut (United States); Williams, BB; Flood, AB; Swartz, HM [Geisel Medical School at Dartmouth University, Hanover, New Hampshire (United States)

    2015-06-15

    Purpose: Medical intervention following a major, unplanned radiation event can elevate the human whole body exposure LD50 from 3 to 7 Gy. On a large scale, intervention cannot be achieved effectively without accurate and efficient triage. Current methods of retrospective biodosimetry are restricted in capability and applicability; published human data is limited. We aim to further develop, validate, and optimize an automated field-deployable in vivo electron paramagnetic resonance (EPR) instrument that can fill this need. Methods: Ionizing radiation creates highly-stable, carbonate-based free radicals within tooth enamel. Using a process similar to nuclear magnetic resonance, EPR directly measures the presence of radiation-induced free radicals. We performed baseline EPR measurements on one of the upper central incisors of total body irradiation (TBI) and head and neck (H&N) radiotherapy patients before their first treatment. Additional measurements were performed between subsequent fractions to examine the EPR response with increasing radiation dose. Independent dosimetry measurements were performed with optically-stimulated luminescent dosimeters (OSLDs) and diodes to more accurately establish the relationship between EPR signal and delivered radiation dose. Results: 36 EPR measurements were performed over the course of four months on two TBI and four H & N radiotherapy patients. We observe a linear increase in EPR signal with increasing dose across the entirety of the tested range. A linear least squares-weighted fit of delivered dose versus measured signal amplitude yields an adjusted R-square of 0.966. The standard error of inverse prediction (SEIP) is 1.77 Gy. For doses up to 7 Gy, the range most relevant to triage, we calculate an SEIP of 1.29 Gy. Conclusion: EPR spectroscopy provides a promising method of retrospective, non-invasive, in vivo biodosimetry. Our preliminary data show an excellent correlation between predicted signal amplitude and delivered

  17. Development of a new dosimeter of EPR based on lactose; Desarrollo de un nuevo dosimetro de RPE basado en lactosa

    Energy Technology Data Exchange (ETDEWEB)

    Cruz C, L.; Torijano C, E.; Azorin N, J.; Aguirre G, F. [Universidad Autonoma Metropolitana, Unidad Iztapalapa, Av. San Rafael Atlixco 186, Col. Vicentina, 09340 Mexico D. F. (Mexico); Cruz Z, E., E-mail: eftc@xanum.uam.mx [UNAM, Instituto de Ciencias Nucleares, Circuito Exterior, Ciudad Universitaria, 04510 Mexico D. F. (Mexico)

    2014-08-15

    50 years have passed since was proposed using the amino acid alanine as dosimeter advantage the phenomenon of electron paramagnetic resonance (EPR); this dosimetric method has reached a highly competitive level regarding others dosimetry classic methods, for example the thermoluminescence or the use of Fricke dosimeters, to measure high dose of radiation. In this type of materials, the free radicals induced by the radiation are stable and their concentration is proportional to the absorbed dose may be determined by the amplitude pick to pick of the first derived of the EPR absorption spectrum. The obtained results studying the EPR response of lactose tablets elaborated in the Universidad Autonoma Metropolitana, Unidad Iztapalapa are presented. The tablets were irradiated with gamma radiation of {sup 60}Co in the irradiator Gamma beam 651-Pt of the Instituto de Ciencias Nucleares de la Universidad Nacional Autonoma de Mexico to a dose rate of 8 kGy-h{sup -1} and their EPR response in a EPR spectrometer e-scan Bruker. The obtained response in function of the dose was lineal in the interval of 1 at 10 kGy. The lactose sensibility was compared with the l-alanine, used as reference, and the result was consistently 0.25 of this. Due to the linearity shown in the interval of used dose and their low production cost, we conclude that the lactose is a promissory option for the dosimetry of high dose of radiation. (author)

  18. [Analysis of three-dimensional fluorescence overlapping spectra using differential spectra and independent component analysis].

    Science.gov (United States)

    Yu, Shao-Hui; Zhang, Yu-Jun; Zhao, Nan-Jing; Xiao, Xue; Wang, Huan-Bo; Yin, Gao-Fang

    2013-01-01

    The analysis of multi-component three-dimensional fluorescence overlapping spectra is always very difficult. In view of the advantage of differential spectra and based on the calculation principle of two-dimensional differential spectra, the three-dimensional fluorescence spectra with both excitation and emission spectra is fully utilized. Firstly, the excitation differential spectra and emission differential spectra are respectively computed after unfolding the three-dimensional fluorescence spectra. Then the excitation differential spectra and emission differential spectra of the single component are obtained by analyzing the multicomponent differential spectra using independent component analysis. In this process, the use of cubic spline increases the data points of excitation spectra, and the roughness penalty smoothing reduces the noise of emission spectra which is beneficial for the computation of differential spectra. The similarity indices between the standard spectra and recovered spectra show that independent component analysis based on differential spectra is more suitable for the component recognition of three-dimensional fluorescence overlapping spectra.

  19. Study of EPR, optical properties and electrical conductivity of vanadyl doped Bi2O3.PbO.B2O3 glasses.

    Science.gov (United States)

    Gahlot, P S; Agarwal, A; Seth, V P; Sanghi, S; Gupta, S K; Arora, M

    2005-04-01

    Heavy metal based oxide glasses having composition xBi(2)O(3).(0.30 - x)PbO.0.70B(2)O(3) have been prepared (0.00 melt-quenching technique. Electron paramagnetic resonance (EPR), optical spectra and dc conductivity of these glasses have been studied. Spin Hamiltonian parameters (SHP) of VO(2+) ions, dipolar hyperfine parameter, P and Fermi contact interaction parameter, K, molecular orbital coefficients (alpha(2) and gamma(2)) and optical band gap have been calculated. It is observed that in these glasses, the tetragonal nature of V(4+)O(6) complex increases with Bi(2)O(3) content. Increase in Bi(2)O(3):PbO ratio results in the contraction of 3d(xy) orbit of the unpaired electron in the vanadium ion, and the SHP are dependent on the theoretical optical basicity, Lambda(th). In present glasses, the conductivity (activation energy) first decreases (increases) with increase in mol% of Bi(2)O(3) content upto x = 0.08 and then shows a maxima (minima) at x = 0.10 and then starts decreasing (increasing) upto x < or = 0.15 with mol% of Bi(2)O(3) content.

  20. Synthesis, physicochemical and spectroscopic characterization of copper(II)-polysaccharide pullulan complexes by UV-vis, ATR-FTIR, and EPR.

    Science.gov (United States)

    Mitić, Zarko; Cakić, Milorad; Nikolić, Goran M; Nikolić, Ružica; Nikolić, Goran S; Pavlović, Radmila; Santaniello, Enzo

    2011-02-15

    Bioactive copper(II) complexes with polysaccharides, like pullulan and dextran, are important in both veterinary and human medicine for the treatment of hypochromic microcitary anemia and hypocupremia. In aqueous alkaline solutions, Cu(II) ion forms complexes with the exopolysaccharide pullulan and its reduced low-molecular derivative. The metal content and the solution composition depend on pH, temperature, and time of the reaction. The complexing process begins in a weak alkali solution (pH >7) and involves OH groups of pullulan monomer (glucopyranose) units. Complexes of Cu(II) ion with reduced low-molecular pullulan (RLMP, M(w) 6000 g mol(-1)) were synthesized in water solutions, at the boiling temperature and at different pH values ranging from 7.5 to 12. The Cu(II) complex formation with RLMP was analyzed by UV-vis spectrophotometry and other physicochemical methods. Spectroscopic characterizations (ATR-FTIR, FT-IRIS, and EPR) and spectra-structure correlation of Cu(II)-RLMP complexes were also carried out. Copyright © 2010 Elsevier Ltd. All rights reserved.

  1. Infrared Spectra of Polycyclic Aromatic Hydrocarbons (PAHs)

    Science.gov (United States)

    Bauschlicher, Charles W., Jr.; Bakes, E. L. O.

    2000-01-01

    We have computed the synthetic infrared spectra of some polycyclic aromatic hydrocarbons containing up to 54 carbon atoms. The species studied include ovalene, circumcoronene, dicoronylene, and hexabenzocoronene. We report spectra for anions, neutrals, cations, and multiply charged cations.

  2. Resonance Raman and EPR spectroscopic studies on heme-heme oxygenase complexes.

    Science.gov (United States)

    Sun, J; Wilks, A; Ortiz de Montellano, P R; Loehr, T M

    1993-12-28

    The binding of ferrous and ferric hemes and manganese(II)- and manganese(III)-substituted hemes to heme oxygenase has been investigated by optical absorption, resonance Raman, and EPR spectroscopy. The results are consistent with the presence of a six-coordinate heme moiety ligated to an essential histidine ligand and a water molecule. The latter ionizes with a pKa approximately 8.0 to give a mixture of high-spin and low-spin six-coordinate hydroxo adducts. Addition of excess cyanide converts the heme to a hexacoordinate low-spin species. The resonance Raman spectrum of the ferrous heme-heme oxygenase complex and that of the Mn(II)protoporphyrin-heme oxygenase complex shows bands at 216 and 212 cm-1, respectively, that are assigned to the metal-histidine stretching mode. The EPR spectrum of the oxidized heme-heme oxygenase complex has a strongly axial signal with g parallel of approximately 6 and g perpendicular approximately 2. 14NO and 15NO adducts of ferrous heme-heme oxygenase exhibit EPR hyperfine splittings of approximately 20 and approximately 25 Gauss, respectively. In addition, both nitrosyl complexes show additional superhyperfine splittings of approximately 7 Gauss from spin-spin interaction with the proximal histidine nitrogen. The heme environment in the heme-heme oxygenase enzyme-substrate complex has spectroscopic properties similar to those of the heme in myoglobin. Hence, there is neither a strongly electron-donating fifth (proximal) ligand nor an electron-withdrawing network on the distal side of the heme moiety comparable to that for cytochromes P-450 and peroxidases. This observation has profound implications about the nature of the oxygen-activating process in the heme-->biliverdin reaction that are discussed in this paper.

  3. Cooper-pair splitter: towards an efficient source of spin-entangled EPR pairs

    Science.gov (United States)

    Schonenberger, Christian

    2011-03-01

    In quantum mechanics the properties of two and more particles can be entangled. In basic science pairs of entangled particles, so called Einstein-Podolsky-Rosen (EPR) pairs, play a special role as toy objects for fundamental studies. They provide such things as ``spooky interaction at distance,'' but they also enable secure encoding and teleportation and are thus important for applications in quantum information technology. Whereas EPR pairs of photons can be generated by parametric down conversion (PDC) in a crystal, a similar source for EPR pairs of electrons does not exists yet. In several theory papers, it has been suggested to use a superconductor for this purpose. The superconducting ground state is formed by a condensate of Cooper-pairs which are electron pairs in a spin-singlet state. Since there are many Cooper pairs in a metallic superconductor like Al, the main tasks are to extract Cooper pairs one by one and to split them into different arms. A controlled and efficient splitting is possible if one makes use of Coulomb interaction. This has recently be demonstrated by two groups [2-4] using hybrid quantum-dot devices with both superconducting and normal metal contacts. In the present talk, I will discuss the Cooper-pair splitter results from the Basel-Budapest-Copenhagen team and compare with the other experiments. As an outlook we discuss approaches that aim at entanglement detection. The Cooper pair splitter holds great promises because very large splitting efficiencies approaching 100% and large pair current rates appear feasible. This work has been done by L. Hofstetter, S. Csonka, A. Geresdi, M. Aagesen, J. Nygard and C. Schönenberger

  4. NANOSCOPIC MOLECULAR CLUSTER V15: HIGH-FIELD EPR AND MAGNETIZATION AT ULTRA-LOW TEMPERATURES

    Directory of Open Access Journals (Sweden)

    Boris Tsukerblat

    2007-06-01

    Full Text Available n this paper we give a short overview of our efforts in the understanding of the magnetic properties of the fascinating nanoscopic cluster K6[VIV15As6O42(H2O]·8H2O (hereafter V15 exhibiting layers of magnetization. We analyze EPR and adiabatic magnetization of the V15 cluster with a triangular VIV3 array causing spin frustration. A model for V15 includes isotropic and antisymmetric (AS exchange interactions in the general form compatible with the trigonal symmetry. Orientation of the AS vector (but not only its absolute value is shown to play an important physical role in spin-frustrated systems. We were able to reach perfect fit to the experimental data on the stepwise dependence of magnetization vs. field at ultra-low temperatures. Furthermore, it was possible for the first time to estimate precisely two components of the AS vector coupling constant, namely, in-plane component and the perpendicular part. We show that only intramultiplet transitions in EPR are allowed when the vector of AS exchange is normal to the plane of vanadium triangle, meanwhile the in-plane part of AS exchange gives rise to a series of weak intermultiplet transitions. Experimental data on high-frequency EPR of V15 at low temperatures are discussed. The spin-vibronic effects in trimeric spin frustrated clusters are also studied and an important role of the interplay between the AS exchange and Jahn-Teller interaction is revealed. The results clarify the concept of spin-frustration in view of its magnetic and spectroscopic manifestations in metal clusters.

  5. Lipid peroxidation and water penetration in lipid bilayers: a W-band EPR study.

    Science.gov (United States)

    Conte, Elena; Megli, Francesco Maria; Khandelia, Himanshu; Jeschke, Gunnar; Bordignon, Enrica

    2013-02-01

    Lipid peroxidation plays a key role in the alteration of cell membrane's properties. Here we used as model systems multilamellar vesicles (MLVs) made of the first two products in the oxidative cascade of linoleoyl lecithin, namely 1-palmitoyl-2-(13-hydroperoxy-9,11-octadecanedienoyl)-lecithin (HpPLPC) and 1-palmitoyl-2-(13-hydroxy-9,11-octadecanedienoyl)-lecithin (OHPLPC), exhibiting a hydroperoxide or a hydroxy group at position 13, respectively. The two oxidized lipids were used either pure or in a 1:1 molar ratio mixture with untreated 1-palmitoyl-2-linoleoyl-lecithin (PLPC). The model membranes were doped with spin-labeled lipids to study bilayer alterations by electron paramagnetic resonance (EPR) spectroscopy. Two different spin-labeled lipids were used, bearing the doxyl ring at position (n) 5 or 16: γ-palmitoyl-β-(n-doxylstearoyl)-lecithin (n-DSPPC) and n-doxylstearic acid (n-DSA). Small changes in the acyl chain order in the sub-polar region and at the methyl-terminal induced by lipid peroxidation were detected by X-band EPR. Concomitantly, the polarity and proticity of the membrane bilayer in those regions were investigated at W band in frozen samples. Analysis of the g(xx) and A(zz) parameters revealed that OHPLPC, but mostly HpPLPC, induced a measurable increase in polarity and H-bonding propensity in the central region of the bilayer. Molecular dynamics simulation performed on 16-DSA in the PLPC-HpPLPC bilayer revealed that water molecules are statistically favored with respect to the hydroperoxide groups to interact with the nitroxide at the methyl-terminal, confirming that the H-bonds experimentally observed are due to increased water penetration in the bilayer. The EPR and MD data on model membranes demonstrate that cell membrane damage by oxidative stress cause alteration of water penetration in the bilayer. Copyright © 2012 Elsevier B.V. All rights reserved.

  6. Water accessibility in a membrane-inserting peptide comparing Overhauser DNP and pulse EPR methods

    Energy Technology Data Exchange (ETDEWEB)

    Segawa, Takuya F., E-mail: takuya.segawa@alumni.ethz.ch; Doppelbauer, Maximilian; Garbuio, Luca; Doll, Andrin; Polyhach, Yevhen O.; Jeschke, Gunnar, E-mail: gjeschke@ethz.ch [Laboratory of Physical Chemistry, ETH Zurich, Vladimir-Prelog-Weg 2, CH-8093 Zurich (Switzerland)

    2016-05-21

    Water accessibility is a key parameter for the understanding of the structure of biomolecules, especially membrane proteins. Several experimental techniques based on the combination of electron paramagnetic resonance (EPR) spectroscopy with site-directed spin labeling are currently available. Among those, we compare relaxation time measurements and electron spin echo envelope modulation (ESEEM) experiments using pulse EPR with Overhauser dynamic nuclear polarization (DNP) at X-band frequency and a magnetic field of 0.33 T. Overhauser DNP transfers the electron spin polarization to nuclear spins via cross-relaxation. The change in the intensity of the {sup 1}H NMR spectrum of H{sub 2}O at a Larmor frequency of 14 MHz under a continuous-wave microwave irradiation of the nitroxide spin label contains information on the water accessibility of the labeled site. As a model system for a membrane protein, we use the hydrophobic α-helical peptide WALP23 in unilamellar liposomes of DOPC. Water accessibility measurements with all techniques are conducted for eight peptides with different spin label positions and low radical concentrations (10–20 μM). Consistently in all experiments, the water accessibility appears to be very low, even for labels positioned near the end of the helix. The best profile is obtained by Overhauser DNP, which is the only technique that succeeds in discriminating neighboring positions in WALP23. Since the concentration of the spin-labeled peptides varied, we normalized the DNP parameter ϵ, being the relative change of the NMR intensity, by the electron spin concentration, which was determined from a continuous-wave EPR spectrum.

  7. BPS spectra from BPS graphs

    OpenAIRE

    Gabella, Maxime

    2017-01-01

    I present a simple graphical method to find the BPS spectra of $A_1$ theories of class S. BPS graphs provide a bridge between spectral networks and BPS quivers, the two main frameworks for the study of BPS states. Here I show how to essentially read off from a BPS graph the quantum spectrum generator (or BPS monodromy), expressed as a product of quantum dilogarithms. Thanks to the framed wall-crossing phenomenon for line defects, the determination of the BPS spectrum reduces to the computatio...

  8. Splitting spacetime and cloning qubits: linking no-go theorems across the ER=EPR duality

    Energy Technology Data Exchange (ETDEWEB)

    Bao, Ning [Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, CA 91125 (United States); Walter Burke Institute for Theoretical Physics, California Institute of Technology, Pasadena, CA 91125 (United States); Pollack, Jason; Remmen, Grant N. [Walter Burke Institute for Theoretical Physics, California Institute of Technology, Pasadena, CA 91125 (United States)

    2015-11-15

    We analyze the no-cloning theorem in quantum mechanics through the lens of the proposed ER=EPR (Einstein-Rosen = Einstein-Podolsky-Rosen) duality between entanglement and wormholes. In particular, we find that the no-cloning theorem is dual on the gravity side to the no-go theorem for topology change, violating the axioms of which allows for wormhole stabilization and causality violation. Such a duality between important no-go theorems elucidates the proposed connection between spacetime geometry and quantum entanglement. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. 2'-Alkynylnucleotides: A Sequence- and Spin Label-Flexible Strategy for EPR Spectroscopy in DNA.

    Science.gov (United States)

    Haugland, Marius M; El-Sagheer, Afaf H; Porter, Rachel J; Peña, Javier; Brown, Tom; Anderson, Edward A; Lovett, Janet E

    2016-07-27

    Electron paramagnetic resonance (EPR) spectroscopy is a powerful method to elucidate molecular structure through the measurement of distances between conformationally well-defined spin labels. Here we report a sequence-flexible approach to the synthesis of double spin-labeled DNA duplexes, where 2'-alkynylnucleosides are incorporated at terminal and internal positions on complementary strands. Post-DNA synthesis copper-catalyzed azide-alkyne cycloaddition (CuAAC) reactions with a variety of spin labels enable the use of double electron-electron resonance experiments to measure a number of distances on the duplex, affording a high level of detailed structural information.

  10. Free radicals in virgin olive oil: a spin trapping EPR study

    OpenAIRE

    Avramiotis, S.; Georgalaki, M.; Cazianis, C.T.; Sotiroudis, Theodore G.; Xenakis, Aristotelis

    2008-01-01

    The spin trap 5.5-dimethyl-1-pyrroline-N-oxide (DMPO) has been used as a probe for monitoring the oxidation properties of virgin olive oil and the detection of free radicals produced in the oil during storage. When DMPO is added in an olive oil sample (or in oxidised triolein) a 12-line Electron Paramagnetic Resonance (EPR) signal is recorded suggesting the trapping of alkoxyl radicals In presence of ethanol the formation of hydroxyl radicals is also detected. The 12-line spectrum changes gra...

  11. Oxidative stress and aging: a non-invasive EPR investigation in human volunteers.

    Science.gov (United States)

    Valgimigli, Luca; Sapone, Andrea; Canistro, Donatella; Broccoli, Massimiliano; Gatta, Luigi; Soleti, Antonio; Paolini, Moreno

    2015-04-01

    The oxidative stress theory of aging has brought to the implicit expectation that oxidative stress increases with aging. Unfortunately, a broad investigation in humans is missing due to limitations of conventional oxidative stress status (OSS) analyses. Here we show that the OSS measured in peripheral blood of 247 healthy volunteers, aged 2 days-104 years, using the electron paramagnetic resonance "EPR-radical probe" technique, negatively correlated with age (-1.1 %/year; p < 0.0001) both by simple and multiple linear regression analyses and that it was only marginally affected by sex. These findings stimulate further mechanistic studies.

  12. EPR-based approach for the localization of paramagnetic metal ions in biomolecules.

    Science.gov (United States)

    Abdullin, Dinar; Florin, Nicole; Hagelueken, Gregor; Schiemann, Olav

    2015-02-02

    Metal ions play an important role in the catalysis and folding of proteins and oligonucleotides. Their localization within the three-dimensional fold of such biomolecules is therefore an important goal in understanding structure-function relationships. A trilateration approach for the localization of metal ions by means of long-range distance measurements based on electron paramagnetic resonance (EPR) is introduced. The approach is tested on the Cu(2+) center of azurin, and factors affecting the precision of the method are discussed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. [Laser flash photolysis, EPR and Raman studies of liquids at elevated pressures

    Energy Technology Data Exchange (ETDEWEB)

    Eyring, E.M.

    1992-01-01

    The proposed research will solve a number of analytical chemical problems in solutions with measurement techniques that benefit from the use of elevated hydrostatic pressures: stopped-flow spectrophotometry (Gd[sup 3+] + L(ligand), [RuL[sub 5]H[sub 2]O][sup 2+], laser flash photolysis of Mo(CO)[sub 6] + L, flash photolysis of binuclear metalloproteins), EPR spectroscopy (Gd[sup 3+] ion-exchanged into ETS-10 and ETAS-10 molecular sieves), laser flash photolysis kinetic studies of Mo(CO)[sub 6]-2,2'-bipyridine, and electrochemical studies of metalloporphyrins using resonance Raman spectroscopy.

  14. [Laser flash photolysis, EPR and Raman studies of liquids at elevated pressures

    Energy Technology Data Exchange (ETDEWEB)

    Eyring, E.M.

    1992-10-01

    The proposed research will solve a number of analytical chemical problems in solutions with measurement techniques that benefit from the use of elevated hydrostatic pressures: stopped-flow spectrophotometry (Gd{sup 3+} + L(ligand), [RuL{sub 5}H{sub 2}O]{sup 2+}, laser flash photolysis of Mo(CO){sub 6} + L, flash photolysis of binuclear metalloproteins), EPR spectroscopy (Gd{sup 3+} ion-exchanged into ETS-10 and ETAS-10 molecular sieves), laser flash photolysis kinetic studies of Mo(CO){sub 6}-2,2`-bipyridine, and electrochemical studies of metalloporphyrins using resonance Raman spectroscopy.

  15. Nursing documentation with NANDA and NIC in a comprehensive HIS/EPR system.

    Science.gov (United States)

    Flø, Kåre

    2006-01-01

    DIPS nursing documentation system facilitates that nurses can write several types of notes into the EPR. Within these notes the nurses can register NANDA diagnoses and NIC interventions with nursing activities. To choose NANDA and NIC the nurse can use a search engine, or she can choose a relevant Care plan guideline and pick the suggested diagnoses and interventions from there. Diagnoses and interventions with nursing activities registered are presented in a Care plan. When a nurse writes a note for a patient she will always be presented the Care plan and she can easy evaluate and update the Care plan.

  16. Semi-Loss-Tolerant Strong Coin Flipping Protocol Using EPR Pairs

    OpenAIRE

    Ma, Jia-Jun; Guo, Fen-Zhuo; Yang, Qian; Li, Yan-Bing; Wen, Qiao-Yan

    2011-01-01

    In this paper, we present a quantum strong coin flipping protocol. In this protocol, an EPR pair and a quantum memory storage are made use of, and losses in the quantum communication channel and quantum memory storage are all analyzed. We obtain the bias in the fair scenario as a function of $p$, where $p$ is the probability that the particle in Bob's quantum memory storage is lost, which means our bias varies as the degree of losses in the quantum memory storage changes. Therefore we call ou...

  17. Moessbauer- and EPR-Snapshots of an Enzymatic Reaction: The Cytochrome P450 Reaction Cycle

    Energy Technology Data Exchange (ETDEWEB)

    Schuenemann, V. [University of Luebeck, Institute of Physics (Germany); Jung, C. [Max-Delbrueck-Center for Molecular Medicine (Germany); Lendzian, F. [Technical University, PC 14, Max-Volmer Laboratory for Biophysical Chemistry (Germany); Barra, A.-L. [Grenoble High Magnetic Field Laboratory (France); Teschner, T.; Trautwein, A. X. [University of Luebeck, Institute of Physics (Germany)

    2004-12-15

    In this communication we present a complimentary Moessbauer- and EPR-study of the time dependance of the reaction of substrate free P450cam with peracetic acid within a time region ranging from 8 ms up to 5 min. An Fe(IV) species as well as a tyrosyl radical residing on the amino acid residue Tyr96 have been identified as reaction intermediates. These species possibly are formed by the reduction of compound I by means of transferring an electron from Tyr 96 to the heme moiety.

  18. In Situ EPR Studies of Reaction Pathways in Titania Photocatalyst-Promoted Alkylation of Alkenes

    Directory of Open Access Journals (Sweden)

    Shona Rhydderch

    2015-03-01

    Full Text Available In situ EPR spectroscopy at cryogenic temperatures has been used to observe and identify paramagnetic species produced when titania is irradiated in the presence of reactants used in the photocatalytic alkylation of maleimide with t-butyl carboxylic acid or phenoxyacetic acid. It is shown that maleimide acts as an acceptor of conduction band electrons. Valence band holes oxidise t-butyl carboxylic acid to the t-butyl radical and phenoxyacetic acid to the phenoxyacetic acid radical cation. In the presence of maleimide, the phenoxymethyl radical is formed from phenoxyacetic acid. The relevance of these observations to the mechanisms of titania photocatalyst-promoted alkylation of alkenes is discussed.

  19. Electron-phonon interaction spectra in beryllium

    Energy Technology Data Exchange (ETDEWEB)

    Najdyuk, Yu.G.; Shklyarevskij, O.I. (AN Ukrainskoj SSR, Kharkov. Fiziko-Tekhnicheskij Inst. Nizkikh Temperatur)

    1982-09-01

    Micro-contact (MC) method was used to investigate spectra of electron-phonon interaction (EPI) in berillium. MC spectra and the known dependences of phonon state density in this metal have been compared in detail. It is shown that the MC spectra can be used for refining the berillium phonon spectrum. The EPI integral parameter has been determined in the free electron model.

  20. Hierarchical resolution of power spectra

    Science.gov (United States)

    Badii, R.; Finardi, M.; Broggi, G.; Sepúlveda, M. A.

    1992-09-01

    We identify the basic ingredients determining the structure of the power spectra of non-linear dynamical systems in a hierarchical order of importance. The analysis, performed with the help of symbolic methods, shows that dynamical invariants such as topological and metric properties of the symbolic orbits explain the main qualitative features of the spectra, whereas the coordinate-dependent values of the observable itself represent a less relevant contribution. Consideration of simple dynamical models with increasing number of topological transition rules evidences the formation of coherent structures (peaks) and explains their position and size. By constructing the parse tree of the allowed symbolic itineraries, it is possible to estimate conditional probabilities by considering orbits belonging to adjacent tree levels. Accordingly, a Markov transition matrix is obtained for each level l and is used to generate signals with statistical properties which approximate those of the actual one increasingly better for l → ∞. A considerable improvement is achieved by recoding the original signal in terms of variable-length words and by re-applying the above procedure to the transformed signal, which is equivalent to a renormalization operation of the associated dynamical map. The accuracy of the estimates is directly related to the convergence of the scaling function for the conditional probabilities. Analytic results are presented for the simplest five Markov models arising from piecewise-linear, continuous, one-dimensional maps. Numerical studies have been performed for the logistic and Hénon maps and for the Lorenz system.

  1. Beyond the EPR: Complementary roles of the hospital-wide electronic health record and clinical departmental systems

    Science.gov (United States)

    2009-01-01

    Background Many hospital departments have implemented small clinical departmental systems (CDSs) to collect and use patient data for documentation as well as for other department-specific purposes. As hospitals are implementing institution-wide electronic patient records (EPRs), the EPR is thought to be integrated with, and gradually substitute the smaller systems. Many EPR systems however fail to support important clinical workflows. Also, successful integration of systems has proven hard to achieve. As a result, CDSs are still in widespread use. This study was conducted to see which tasks are supported by CDSs and to compare this to the support offered by the EPR. Methods Semi-structured interviews with users of 16 clinicians using 15 different clinical departmental systems (CDS) at a Medium-sized University hospital in Norway. Inductive analysis of transcriptions from the audio taped interviews. Results The roles of CDSs were complementary to those of the hospital-wide EPR system. The use of structured patient data was a characteristic feature. This facilitated quality development and supervision, tasks that were poorly supported by the EPR system. The structuring of the data also improved filtering of information to better support clinical decision-making. Because of the high value of the structured patient data, the users put much effort in maintaining their integrity and representativeness. Employees from the departments were also engaged in the funding, development, implementation and maintenance of the systems. Conclusion Clinical departmental systems are vital to the activities of a clinical hospital department. The development, implementation and clinical use of such systems can be seen as bottom-up, user-driven innovations. PMID:19523198

  2. Multiscale climate emulator of multimodal wave spectra: MUSCLE-spectra

    Science.gov (United States)

    Rueda, Ana; Hegermiller, Christie A.; Antolinez, Jose A. A.; Camus, Paula; Vitousek, Sean; Ruggiero, Peter; Barnard, Patrick L.; Erikson, Li H.; Tomás, Antonio; Mendez, Fernando J.

    2017-02-01

    Characterization of multimodal directional wave spectra is important for many offshore and coastal applications, such as marine forecasting, coastal hazard assessment, and design of offshore wave energy farms and coastal structures. However, the multivariate and multiscale nature of wave climate variability makes this complex problem tractable using computationally expensive numerical models. So far, the skill of statistical-downscaling model-based parametric (unimodal) wave conditions is limited in large ocean basins such as the Pacific. The recent availability of long-term directional spectral data from buoys and wave hindcast models allows for development of stochastic models that include multimodal sea-state parameters. This work introduces a statistical downscaling framework based on weather types to predict multimodal wave spectra (e.g., significant wave height, mean wave period, and mean wave direction from different storm systems, including sea and swells) from large-scale atmospheric pressure fields. For each weather type, variables of interest are modeled using the categorical distribution for the sea-state type, the Generalized Extreme Value (GEV) distribution for wave height and wave period, a multivariate Gaussian copula for the interdependence between variables, and a Markov chain model for the chronology of daily weather types. We apply the model to the southern California coast, where local seas and swells from both the Northern and Southern Hemispheres contribute to the multimodal wave spectrum. This work allows attribution of particular extreme multimodal wave events to specific atmospheric conditions, expanding knowledge of time-dependent, climate-driven offshore and coastal sea-state conditions that have a significant influence on local nearshore processes, coastal morphology, and flood hazards.

  3. Scikit-spectra: Explorative Spectroscopy in Python

    Directory of Open Access Journals (Sweden)

    Adam Hughes

    2015-06-01

    Full Text Available Scikit-spectra is an intuitive framework for explorative spectroscopy in Python. Scikit-spectra leverages the Pandas library for powerful data processing to provide datastructures and an API designed for spectroscopy. Utilizing the new IPython Notebook widget system, scikit-spectra is headed towards a GUI when you want it, API when you need it approach to spectral analysis. As an application, analysis is presented of the surface-plasmon resonance shift in a solution of gold nanoparticles induced by proteins binding to the gold’s surface. Please refer to the scikit-spectra website for full documentation and support: http://hugadams.github.io/scikit-spectra/

  4. High-frequency and -field EPR spectroscopy of tris(2,4-pentanedionato)manganese(III): investigation of solid-state versus solution Jahn-Teller effects.

    Science.gov (United States)

    Krzystek, J; Yeagle, Gregory J; Park, Ju-Hyun; Britt, R David; Meisel, Mark W; Brunel, Louis-Claude; Telser, Joshua

    2003-07-28

    High-frequency and -field electron paramagnetic resonance (HFEPR) spectroscopy of a classical coordination complex, Mn(acac)(3) (Hacac = 2,4-pentanedione), has been performed on both solid powder and frozen solution (in CH(2)Cl(2)/toluene, 3:2 v/v) samples. Parallel mode detection X-band EPR spectra exhibiting resolved (55)Mn hyperfine coupling were additionally obtained for frozen solutions. Magnetic susceptibility and field-dependent magnetization measurements were also made on powder samples. Analysis of the entire EPR data set for the frozen solution allowed extraction of the relevant spin Hamiltonian parameters: D = -4.52(2); |E| = 0.25(2) cm(-1); g(iso) = 1.99(1). The somewhat lower quality solid-state HFEPR data and the magnetic measurements confirmed these parameters. These parameters are compared to those for other complexes of Mn(III) and to previous studies on Mn(acac)(3) using X-ray crystallography, solution electronic absorption spectroscopy, and powder magnetic susceptibility. Crystal structures have been reported for Mn(acac)(3) and show tetragonal distortion, as expected for this Jahn-Teller ion (Mn(3+), 3d(4)). However, in one case, the molecule exhibits axial compression and, in another, axial elongation. The current HFEPR studies clearly show the negative sign of D, which corresponds to an axial (tetragonal) elongation in frozen solution. The correspondence among solution and solid-state HFEPR data, solid-state magnetic measurements, and an HFEPR study by others on a related complex indicates that the form of Mn(acac)(3) studied here exhibits axial elongation in all cases. Such tetragonal elongation has been found for Mn(3+) and Cr(2+) complexes with homoleptic pseudooctahedral geometry as well as for Mn(3+) in square pyramidal geometry. This taken together with the results obtained here for Mn(acac)(3) in frozen solution indicates that axial elongation could be considered the "natural" form of Jahn-Teller distortion for octahedral high-spin 3d(4

  5. EPR Line Shifts and Line Shape Changes Due to Heisenberg Spin Exchange and Dipole-Dipole Interactions of Nitroxide Free Radicals in Liquids: 8. Further Experimental and Theoretical Efforts to Separate the Effects of the Two Interactions

    Science.gov (United States)

    Peric, Mirna; Bales, Barney L; Peric, Miroslav

    2012-01-01

    The work in Part 6 of this series (J. Phys. Chem. A 2009, 113, 4930), addressing the task of separating the effects of Heisenberg spin exchange (HSE) and dipole-dipole (DD) interactions on EPR spectra of nitroxide spin probes in solution, is extended experimentally and theoretically. Comprehensive measurements of perdeuterated 2,2,6,6-tetramethyl-4-oxopiperidine-1-oxyl (pDT) in squalane, a viscous alkane, paying special attention to lower temperatures and lower concentrations were carried out in an attempt to focus on DD, the lesser understood of the two interactions. Theoretically, the analysis has been extended to include the recent comprehensive treatment by Salikhov (Appl. Magn. Reson. 2010, 38, 237). In dilute solutions, both interactions (1) introduce a dispersion component, (2) broaden the lines, and (3) shift the lines. DD introduces a dispersion component proportional to the concentration and of opposite sign to that of HSE. Equations relating the EPR spectral parameters to the rate constants due HSE and DD have been derived. By employing non-linear least-squares fitting of theoretical spectra to a simple analytical function and the proposed equations, the contributions of the two interactions to items (1)–(3) may be quantified and compared with the same parameters obtained by fitting experimental spectra. This comparison supports the theory in its broad predictions, however, at low temperatures, the DD contribution to the experimental dispersion amplitude does not increase linearly with concentration. We are unable to deduce if this discrepancy is due to inadequate analysis of the experimental data or an incomplete theory. A key new aspect of the more comprehensive theory is that there is enough information in the experimental spectra to find items (1)–(3) due to both interactions; however, in principle, appeal must be made to a model of molecular diffusion to separate the two. The permanent diffusion model is used to illustrate the separation in this

  6. Enhanced bacterial tumor delivery by modulating the EPR effect and therapeutic potential of Lactobacillus casei.

    Science.gov (United States)

    Fang, Jun; Liao, Long; Yin, Hongzhuan; Nakamura, Hideaki; Shin, Takashi; Maeda, Hiroshi

    2014-10-01

    Bacteria of micrometer size could accumulate in tumor based on enhanced permeability and retention (EPR) effect. We report here Lactobacillus casei (L. casei), a nonpathogenic facultatively anaerobic bacterium, preferentially accumulated in tumor tissues after intravenously (i.v.) injection; at 24 h, live bacteria were found more in the tumor, whereas the bacteria in normal tissues including the liver and spleen were cleared rapidly. The tumor-selective accumulation and growth of L. casei is probably due to the EPR effect and the hypoxic tumor environment. Moreover, the bacterial tumor delivery was significantly increased by a nitric oxide (NO) donor nitroglycerin (NG, 10-70 times) and an angiotensin II converting enzyme inhibitor, enalapril (6-18 times). Consequently significant suppression of tumor growth was found in a colon cancer C26 model, and more remarkable antitumor effect was achieved when L. casei was combined with NG, probably by modulating the host nonspecific immune responses; tumor necrosis factor-α significantly increased in tumor after the treatment, as well as NO synthase activity and myleoperoxidase activity. These findings suggest the potential of L. casei as a candidate for targeted bacterial antitumor therapy, especially in combine with NG or other vascular mediators. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

  7. SOM assembly of hydroxynaphthoquinone and its oxime: Polymorphic X-ray structures and EPR studies

    Science.gov (United States)

    Todkary, Ashwini V.; Dalvi, Rupali; Salunke-Gawali, Sunita; Linares, Jorge; Varret, François; Marrot, Jérôme; Yakhmi, Jatinder V.; Bhadbhade, Mohan; Srinivas, D.; Gejji, Shridhar P.; Rane, Sandhya Y.

    2006-01-01

    Investigation on solvent-induced polymorphism in X-ray structures of 2-hydroxy-1,4-naphthoquinone (Lawsone) 1, is carried out. In protic methanol, 1 crystallizes in monoclinic space group P21/c (1a) comprising of 2D hydrogen bonded network via cyclic dimers. In aprotic solvent such as acetone on the other hand, 1 exhibits orthorhombic space group Pna 21 (1b) and emerges with 1D catemeric chain. Solvent-induced topological isomerism of cyclic dimers and helical catemeric chains arising from (i) bifurcated intra- and inter molecular hydrogen bondings viz. Osbnd H ⋯Odbnd C interactions between C(2) hydroxyl and C(1), C(4) carbonyls, (ii) Csbnd H ⋯O interactions viz. C(3)sbnd H ⋯O(1)C(1) have been discussed. A signal for radical in 1 at g = 2.0058 is signatured by EPR spectrum and it's oxime derivative viz. 2-hydroxy-4-naphthoquinone-1-oxime 2, in solid state shows biradical and monoradical formation with aggregation of dimer and monomer due to non-covalent hydrogen bonds. Zero field split parameters for 2 are estimated to be D = 215 G, Ex = 13 G, Ey = 47 G at 298 K. A half field signal at 77 K indicates triplet ground state. Frozen glass EPR of 2 resolves as regioregular dimeric-monomeric species showing hyperfine interactions with 1-oximino nitrogen in dimer Abar(14N) = 15.5 G].

  8. Combining crystallography and EPR: crystal and solution structures of the multidomain cochaperone DnaJ

    Energy Technology Data Exchange (ETDEWEB)

    Barends, Thomas R. M., E-mail: thomas.barends@mpimf-heidelberg.mpg.de [MPI for Medical Research, Heidelberg (Germany); Brosi, Richard W. W. [Freie Universitat Berlin, Berlin (Germany); Steinmetz, Andrea; Scherer, Anna; Hartmann, Elisabeth; Eschenbach, Jessica; Lorenz, Thorsten [MPI for Medical Research, Heidelberg (Germany); Seidel, Ralf [MPI for Molecular Physiology, Dortmund (Germany); Shoeman, Robert L.; Zimmermann, Sabine [MPI for Medical Research, Heidelberg (Germany); Bittl, Robert [Freie Universitat Berlin, Berlin (Germany); Schlichting, Ilme; Reinstein, Jochen [MPI for Medical Research, Heidelberg (Germany)

    2013-08-01

    The crystal structure of the N-terminal part of T. thermophilus DnaJ unexpectedly showed an ordered GF domain and guided the design of a construct enabling the first structure determination of a complete DnaJ cochaperone molecule. By combining the crystal structures with spin-labelling EPR and cross-linking in solution, a dynamic view of this flexible molecule was developed. Hsp70 chaperones assist in a large variety of protein-folding processes in the cell. Crucial for these activities is the regulation of Hsp70 by Hsp40 cochaperones. DnaJ, the bacterial homologue of Hsp40, stimulates ATP hydrolysis by DnaK (Hsp70) and thus mediates capture of substrate protein, but is also known to possess chaperone activity of its own. The first structure of a complete functional dimeric DnaJ was determined and the mobility of its individual domains in solution was investigated. Crystal structures of the complete molecular cochaperone DnaJ from Thermus thermophilus comprising the J, GF and C-terminal domains and of the J and GF domains alone showed an ordered GF domain interacting with the J domain. Structure-based EPR spin-labelling studies as well as cross-linking results showed the existence of multiple states of DnaJ in solution with different arrangements of the various domains, which has implications for the function of DnaJ.

  9. The principle of relativity, superluminality and EPR experiments. "Riserratevi sotto coverta ..."

    Science.gov (United States)

    Cocciaro, B.

    2015-07-01

    The principle of relativity claims the invariance of the results for experiments carried out in inertial reference frames if the system under examination is not in interaction with the outside world. In this paper it is analysed a model suggested by J. S. Bell, and later developed by P. H. Eberhard, D. Bohm and B. Hiley on the basis of which the EPR correlations would be due to superluminal exchanges between the various parts of the entangled system under examination. In the model the existence of a privileged reference frame (PF) for the propagation of superluminal signals is hypothesized so that these superluminal signals may not give rise to causal paradoxes. According to this model, in an EPR experiment, the entangled system interacts with the outer world since the result of the experiment depends on an entity (the reference frame PF) that is not prepared by the experimenter. The existence of this privileged reference frame makes the model non invariant for Lorentz transformations. In this paper, in opposition to what claimed by the authors mentioned above, the perfect compatibility of the model with the theory of relativity is strongly maintained since, as already said, the principle of relativity does not require that the results of experiments carried out on systems interacting with the outside world should be invariant.

  10. The 4th international comparison on EPR dosimetry with tooth enamel

    Energy Technology Data Exchange (ETDEWEB)

    Fattibene, P., E-mail: paola.fattibene@iss.it [Istituto Superiore di Sanita, Department of Technology and Health, Viale Regina Elena 299, I-00162 Rome (Italy); Wieser, A. [Helmholtz Zentrum Muenchen, Neuherberg D-85764 (Germany); Adolfsson, E. [Linkoeping University, SE-58185 Linkoeping (Sweden); Benevides, L.A. [Naval Dosimetry Center, Bethesda MD 20889-5600 (United States); Brai, M. [University of Palermo, I-90128 Palermo (Italy); Callens, F. [Ghent University, B-9000 Gent (Belgium); Chumak, V. [Research Center for Radiation Medicine AMS, 04050 Kiev (Ukraine); Ciesielski, B. [Medical University of Gdansk, 80-211 Gdansk (Poland); Della Monaca, S. [Istituto Superiore di Sanita, Department of Technology and Health, Viale Regina Elena 299, I-00162 Rome (Italy); Regina Elena Institute, I-00144 Rome (Italy); Emerich, K. [Medical University of Gdansk, 80-211 Gdansk (Poland); Department of Paediatric Dentistry, 80-208 Gdansk (Poland); Gustafsson, H. [Linkoeping University, SE-58185 Linkoeping (Sweden); Hirai, Y. [Radiation Effects Research Foundation, Minami-ku, Hiroshima 732-0815 (Japan); Hoshi, M. [Hiroshima University, Minami-ku, Hiroshima 734-8553 (Japan); Israelsson, A. [Linkoeping University, SE-58185 Linkoeping (Sweden); Ivannikov, A. [Medical Radiological Research Center, Obninsk, Kaluga region (Russian Federation); Ivanov, D. [Institute of Metal Physics, Yekaterinburg 620041 (Russian Federation); Kaminska, J. [Medical University of Gdansk, 80-211 Gdansk (Poland); Ke, Wu [Beijing Institute of Radiation Medicine, Beijing 100850 (China); Lund, E. [Linkoeping University, SE-58185 Linkoeping (Sweden); Marrale, M. [University of Palermo, I-90128 Palermo (Italy)

    2011-09-15

    This paper presents the results of the 4th International Comparison of in vitro electron paramagnetic resonance dosimetry with tooth enamel, where the performance parameters of tooth enamel dosimetry methods were compared among sixteen laboratories from all over the world. The participating laboratories were asked to determine a calibration curve with a set of tooth enamel powder samples provided by the organizers. Nine molar teeth extracted following medical indication from German donors and collected between 1997 and 2007 were prepared and irradiated at the Helmholtz Zentrum Muenchen. Five out of six samples were irradiated at 0.1, 0.2, 0.5, 1.0 and 1.5 Gy air kerma; and one unirradiated sample was kept as control. The doses delivered to the individual samples were unknown to the participants, who were asked to measure each sample nine times, and to report the EPR signal response, the mass of aliquots measured, and the parameters of EPR signal acquisition and signal evaluation. Critical dose and detection limit were calculated by the organizers on the basis of the calibration-curve parameters obtained at every laboratory. For calibration curves obtained by measuring every calibration sample three times, the mean value of the detection limit was 205 mGy, ranging from 56 to 649 mGy. The participants were also invited to provide the signal response and the nominal dose of their current dose calibration curve (wherever available), the critical dose and detection limit of which were also calculated by the organizers.

  11. Integrity of the reactor coolant boundary of the European pressurized water reactor (EPR)

    Energy Technology Data Exchange (ETDEWEB)

    Goetsch, D.; Bieniussa, K.; Schulz, H.; Jalouneix, J.

    1997-04-01

    This paper is an abstract of the work performed in the frame of the development of the IPSN/GRS approach in view of the EPR conceptual safety features. EPR is a pressurized water reactor which will be based on the experience gained by utilities and designers in France and in Germany. The reactor coolant boundary of a PWR includes the reactor pressure vessel (RPV), those parts of the steam generators (SGs) which contain primary coolant, the pressurizer (PSR), the reactor coolant pumps (RCPs), the main coolant lines (MCLs) with their branches as well as the other connecting pipes and all branching pipes including the second isolation valves. The present work covering the integrity of the reactor coolant boundary is mainly restricted to the integrity of the main coolant lines (MCLs) and reflects the design requirements for the main components of the reactor coolant boundary. In the following the conceptual aspects, i.e. design, manufacture, construction and operation, will be assessed. A main aspect is the definition of break postulates regarding overall safety implications.

  12. Minimization of actinide waste by multi-recycling of thoriated fuels in the EPR reactor

    Directory of Open Access Journals (Sweden)

    Nuttin A.

    2012-02-01

    Full Text Available The multi-recycling of innovative uranium/thorium oxide fuels for use in the European Pressurized water Reactor (EPR has been investigated. If increasing quantities of 238U, the fertile isotope in standard UO2 fuel, are replaced by 232Th, then a greater yield of new fissile material (233U is produced during the cycle than would otherwise be the case. This leads to economies of natural uranium of around 45% if the uranium in the spent fuel is multi-recycled. In addition we show that minor actinide and plutonium waste inventories are reduced and hence waste radio-toxicities and decay heats are up to a factor of 20 lower after 103 years. Two innovative fuel types named S90 and S20, ThO2 mixed with 90% and 20% enriched UO2 respectively, are compared as an alternative to standard uranium oxide (UOX and uranium/plutonium mixed oxide (MOX fuels at the longest EPR fuel discharge burn-ups of 65 GWd/t. Fissile and waste inventories are examined, waste radio-toxicities and decay heats are extracted and safety feedback coefficients are calculated.

  13. Oxidation processes in Sicilian olive oils investigated by a combination of optical and EPR spectroscopy.

    Science.gov (United States)

    Ricca, Mariaelena; Foderà, Vito; Vetri, Valeria; Buscarino, Gianpiero; Montalbano, Maria; Leone, Maurizio

    2012-10-01

    Extra virgin olive oil (EVOO) is recognized as one of the healthiest foods for its high content of antioxidants, which forestall and slow down radical formation. Free radical-initiated oxidation is considered one of the main causes of rancidity in fats and oils. As a consequence, reliable protocols for the investigation of oil oxidation based on selective, noninvasive, and fast methods are highly desirable. Here we report an experimental approach based on UV-Vis absorbance, steady-state fluorescence, and electron paramagnetic resonance (EPR) spectroscopy for studying oxidation processes induced by temperature for a period up to 35 d on Sicilian EVOO samples. We followed the decrease in β-carotene content during incubation time and observed changes in polyphenols and tocopherols during the oxidation processes, focusing on the time scale of those changes. Using EPR spectroscopy, the free radical formation in different oil samples is reported, providing a fingerprint for both the antioxidant content and temporal features of the oxidation process at its early stage. We monitor β-carotene and chlorophyll in an auto-oxidation process. A protocol based on spectroscopic measurements is presented and can be used for the quality control process of commercial olive oil. © 2012 Institute of Food Technologists®

  14. Measuring precarious employment in times of crisis: the revised Employment Precariousness Scale (EPRES) in Spain.

    Science.gov (United States)

    Vives, Alejandra; González, Francisca; Moncada, Salvador; Llorens, Clara; Benach, Joan

    2015-01-01

    This study examines the psychometric properties of the revised Employment Precariousness Scale (EPRES-2010) in a context of economic crisis and growing unemployment. Data correspond to salaried workers with a contract (n=4,750) from the second Psychosocial Work Environment Survey (Spain, 2010). Analyses included acceptability, scale score distributions, Cronbach's alpha coefficient and exploratory factor analysis. Response rates were 80% or above, scores were widely distributed with reductions in floor effects for temporariness among permanent workers and for vulnerability. Cronbach's alpha coefficients were 0.70 or above; exploratory factor analysis confirmed the theoretical allocation of 21 out of 22 items. The revised version of the EPRES demonstrated good metric properties and improved sensitivity to worker vulnerability and employment instability among permanent workers. Furthermore, it was sensitive to increased levels of precariousness in some dimensions despite decreases in others, demonstrating responsiveness to the context of the economic crisis affecting the Spanish labour market. Copyright © 2015 SESPAS. Published by Elsevier Espana. All rights reserved.

  15. Contribution of major lipophilic antioxidants to the antioxidant activity of basil extracts: an EPR study.

    Science.gov (United States)

    Sgherri, Cristina; Pinzino, Calogero; Navari-Izzo, Flavia; Izzo, Riccardo

    2011-04-01

    The present research analyses the contribution of some lipid antioxidants to the antioxidant activity of lipophilic extracts from basil by an electron paramagnetic resonance (EPR) study using the stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH). DPPH assay is considered an easy and accurate method with regard to measuring the antioxidant activity of plant extracts and EPR has already been employed to determine antioxidant activities of lipophilic plant extracts. Lipid extracts were obtained from basil grown hydroponically for 20 or 35 days from sowing and in soil for 35 days from sowing. Fast and slow rate constants were distinguishable in the decay kinetics of DPPH mixture added with lipid extract. Antioxidants with kinetics characterized by a fast decay rate were tocopherols and chlorophylls, whereas those characterized by a slow decay rate were carotenoids, among which were β-carotene, lutein, β-apo-8'-carotenal and zeaxanthin. The 20-day hydroponically grown sample, which showed higher contents of tocopherol, chlorophyll and carotenoid molecules, was the sample endowed with the higher content of fast lipophilic antioxidants (FLA) and slow lipophilic antioxidants (SLA). The three samples showed different compositions of FLA and SLA, giving rise to different decay kinetics. Despite the differences, in all samples tocopherol contributed about 0.3% to the bulk of FLA, whereas the figure for chlorophyll was about 40%, evidencing the relevant but little-studied role of chlorophyll as an antioxidant. Copyright © 2011 Society of Chemical Industry.

  16. An EPR study on tea: Identification of paramagnetic species, effect of heat and sweeteners

    Science.gov (United States)

    Bıyık, Recep; Tapramaz, Recep

    2009-10-01

    Tea ( Camellia Sinensis) is the most widely consumed beverage in the world, and is known to be having therapeutic, antioxidant and nutritional effects. Electron paramagnetic resonance (EPR) spectral studies made on the tea cultivated along the shore of Black Sea, Turkey, show Mn 2+ and Fe 3+ centers in green tea leaves and in black tea extract. Dry black tea flakes and dry extract show additional sharp line attributed to semiquinone radical. The origins of the paramagnetic species in black tea are defined and discussed. Effect of humidity and heat are investigated. It is observed that dry extract of black tea melts at 100 °C and the semiquinone radical lives up to 140 °C while Mn 2+ sextet disappears just above 100 °C in tea extract. Natural and synthetics sweeteners have different effects on the paramagnetic centers. White sugar (sucrose) quenches the Mn 2+ and semiquinone lines in black tea EPR spectrum, and glucose, fructose, lactose and maltose quench Fe 3+ line while synthetic sweeteners acesulfam potassium, aspartame and sodium saccharine do not have any effect on paramagnetic species in tea.

  17. L'argument Einstein Podolsky Rosen (EPR) paradoxe, alternative et demonstration

    CERN Document Server

    Roussel, P

    2003-01-01

    En physique quantique, l'absence d'observation d'etats de superposition ne devrait etre une surprise pour personne, que les objets soient microscopiques ou macroscopiques. Cela n'en etait pas une pour Schroedinger. L'experience de pensee "du chat" parmi bien d'autres arguments le montre clairement. On ne doit pas aujourd'hui lui faire dire le contraire. L'article EPR (A.Einstein, B.Podolsky,N.Rosen, ecrit en 1935), qui est a l'origine de l'intervention de Schroedinger et du developpement d'une problematique qui se prolonge jusqu'a aujourd'hui, est analyse. Avec Schroedinger, Bohr, Wigner et jusqu'a aujourd'hui, la reponse a EPR a ete le recours renouvele a l'observateur finalement caracterise par sa conscience. Deux elements nouveaux sont apparus: d'une part un developpement experimental et theorique impressionnant avec l'optique quantique et les manipulations d'atomes, d'autre part la proposition du concept de decoherence susceptible d'expliquer le passage du microscopique au macroscopique et par la d'apport...

  18. SOM assembly of hydroxynaphthoquinone and its oxime: polymorphic X-ray structures and EPR studies.

    Science.gov (United States)

    Todkary, Ashwini V; Dalvi, Rupali; Salunke-Gawali, Sunita; Linares, Jorge; Varret, François; Marrot, Jérôme; Yakhmi, Jatinder V; Bhadbhade, Mohan; Srinivas, D; Gejji, Shridhar P; Rane, Sandhya Y

    2006-01-01

    Investigation on solvent-induced polymorphism in X-ray structures of 2-hydroxy-1,4-naphthoquinone (Lawsone) 1, is carried out. In protic methanol, 1 crystallizes in monoclinic space group P2(1)/c (1a) comprising of 2D hydrogen bonded network via cyclic dimers. In aprotic solvent such as acetone on the other hand, 1 exhibits orthorhombic space group Pna 2(1) (1b) and emerges with 1D catemeric chain. Solvent-induced topological isomerism of cyclic dimers and helical catemeric chains arising from (i) bifurcated intra- and inter molecular hydrogen bondings viz. O-H...O=C interactions between C(2) hydroxyl and C(1), C(4) carbonyls, (ii) C-H...O interactions viz. C(3)-H...O(1)C(1) have been discussed. A signal for radical in 1 at g = 2.0058 is signatured by EPR spectrum and it's oxime derivative viz. 2-hydroxy-4-naphthoquinone-1-oxime 2, in solid state shows biradical and monoradical formation with aggregation of dimer and monomer due to non-covalent hydrogen bonds. Zero field split parameters for 2 are estimated to be D = 215 G, Ex = 13 G, Ey = 47 G at 298 K. A half field signal at 77 K indicates triplet ground state. Frozen glass EPR of 2 resolves as regioregular dimeric-monomeric species showing hyperfine interactions with 1-oximino nitrogen in dimer A (14N) = 15.5 G].

  19. Temperature study of magnetic resonance spectra of co-modified (Co,N-TiO2 nanocomposites

    Directory of Open Access Journals (Sweden)

    Guskos Nikos

    2016-06-01

    Full Text Available The (nCo,N-TiO2 (n = 1, 5 and 10 wt.% of Co nanocomposites were investigated by magnetic resonance spectroscopy in 4 K to 290 K range. Analyses of ferromagnetic/electron paramagnetic resonance (FMR/EPR spectra in terms of four Callen lineshape components revealed the existence of two types of magnetic centers, one derived from metallic cobalt nanoparticles in superparamagnetic (SPM phase and the other from cobalt clusters in the TiO2 lattice. Additionally, at low temperature the EPR spectrum arising from Ti3+ ions was also registered. Both relaxations of the Landau-Lifshitz type and the Bloch-Bloembergen type played an important role at high temperature in determining the linewidths and the latter relaxation was prevailing at low temperature. Analysis of the integrated intensity showed that the SPM signal is due to small size FM cobalt nanoparticles while the paramagnetic signal from Co clusters originates from those nanoparticles in which the concentration of magnetic polarons is below the percolation threshold.

  20. Reflectance spectra of primitive chondrites

    Science.gov (United States)

    Trigo-Rodríguez, J. M.; Moyano-Cambero, C. E.; Llorca, J.

    2013-05-01

    We are studying a wide sample of pristine carbonaceous chondrites from the NASA Antarctic collection in order to get clues on the physico-chemical processes occurred in the parent bodies of these meteorites. We are obtaining laboratory reflectance spectra of different groups of carbonaceous chondrites, but here we focus in CM and CI chondrites. We discuss the main spectral features that can be used to identify primitive carbonaceous asteroids by remote sensing techniques. Two different spectrometers were used covering the entire 0.3 to 30 μm electromagnetic window. Only a handful of Near Earth Objects (NEOs) exhibit bands or features clearly associated with aqueous alteration. Among them are the target asteroids of Osiris Rex and Marco Polo-R missions.

  1. Graviton spectra in string cosmology

    Energy Technology Data Exchange (ETDEWEB)

    Galluccio, Massimo [Osservatorio Astronomico di Roma (Roma-IT); Litterio, Marco [Istituto Astronomico dell' Universita (Roma-IT); Occhionero, Franco [Osservatorio Astronomico di Roma (Roma-IT)

    1996-08-01

    We propose to uncover the signature of a stringy era in the primordial Universe by searching for a prominent peak in the relic graviton spectrum. This feature, which in our specific model terminates an ω³ increase and initiates an ω⁻⁷ decrease, is induced during the so far overlooked bounce of the scale factor between the collapsing deflationary era (or pre-Big Bang) and the expanding inflationary era (or post-Big Bang). We evaluate both analytically and numerically the frequency and the intensity of the peak and we show that they may likely fall in the realm of the new generation of interferometric detectors. The existence of a peak is at variance with ordinarily monotonic (either increasing or decreasing) graviton spectra of canonical cosmologies; its detection would therefore offer strong support to string cosmology.

  2. High-field EPR spectroscopy applied to biological systems: characterization of molecular switches for electron and ion transfer.

    Science.gov (United States)

    Möbius, K; Savitsky, A; Schnegg, A; Plato, M; Fuchst, M

    2005-01-07

    The last decade witnessed a tremendous growth in combined efforts of biologists, chemists and physicists to understand the dominant factors determining the specificity and directionality of transmembrane transfer processes in proteins. A large variety of experimental techniques is being used including X-ray and neutron diffraction, but also time-resolved optical, infrared and magnetic resonance spectroscopy. This is done in conjunction with genetic engineering strategies to construct site-specific mutants for controlled modification of the proteins. As a general perception of these efforts, the substantial influence of weak interactions within the protein and its membrane interfaces is recognized. The weak interactions are subject to subtle changes during the reaction cycle owing to the inherent flexibility of the protein-membrane complex. Specific conformational changes accomplish molecular-switch functions for the transfer process to proceed with optimum efficiency. Characteristic examples of time varying non-bonded interactions are specific H-patterns and/or polarity effects of the microenvironment. The present perception has emerged from the coupling of newly developed spectroscopic techniques - and advanced EPR certainly deserves credit in this respect - with newly developed computational strategies to interpret the experimental data in terms of protein structure and dynamics. By now, the partners of this coupling, particularly high-field EPR spectroscopy and DFT-based quantum theory, have reached a level of sophistication that applications to large biocomplexes are within reach. In this review, a few large paradigm biosystems are surveyed which were explored lately in our laboratory. Taking advantage of the improved spectral and temporal resolution of high-frequency/high-field EPR at 95 GHz/3.4 T and 360 GHz/12.9 T, as compared to conventional X-band EPR (9.5 GHz/0.34 T), three biosystems are characterized with respect to structure and dynamics: (1) Light

  3. The E.P.R. (European Water Pressurized Reactor): a choice from the past that should close future?; L'EPR: un choix du passe qui fermerait l'avenir?

    Energy Technology Data Exchange (ETDEWEB)

    Marignac, Y

    2003-11-15

    The present note discusses, by opening questions, different counter-arguments, of the French energy policy such the attempt to adapt the E.P.R., a technological project conceived in an old policy frame, to actual economical and environmental realities. (N.C.)

  4. Recent pulsed EPR studies of the photosystem II oxygen-evolving complex: implications as to water oxidation mechanisms.

    Science.gov (United States)

    Britt, R David; Campbell, Kristy A; Peloquin, Jeffrey M; Gilchrist, M Lane; Aznar, Constantino P; Dicus, Michelle M; Robblee, John; Messinger, Johannes

    2004-04-12

    The pulsed electron paramagnetic resonance (EPR) methods of electron spin echo envelope modulation (ESEEM) and electron spin echo-electron nuclear double resonance (ESE-ENDOR) are used to investigate the structure of the Photosystem II oxygen-evolving complex (OEC), including the paramagnetic manganese cluster and its immediate surroundings. Recent unpublished results from the pulsed EPR laboratory at UC-Davis are discussed, along with aspects of recent publications, with a focus on substrate and cofactor interactions. New data on the proximity of exchangeable deuterons around the Mn cluster poised in the S(0)-state are presented and interpreted. These pulsed EPR results are used in an evaluation of several recently proposed mechanisms for PSII water oxidation. We strongly favor mechanistic models where the substrate waters bind within the OEC early in the S-state cycle. Models in which the O-O bond is formed by a nucleophilic attack by a Ca(2+)-bound water on a strong S(4)-state electrophile provide a good match to the pulsed EPR data.

  5. Testing and linearity calibration of films of phenol compounds exposed to thermal neutron field for EPR dosimetry.

    Science.gov (United States)

    Gallo, S; Panzeca, S; Longo, A; Altieri, S; Bentivoglio, A; Dondi, D; Marconi, R P; Protti, N; Zeffiro, A; Marrale, M

    2015-12-01

    This paper reports the preliminary results obtained by Electron Paramagnetic Resonance (EPR) measurements on films of IRGANOX® 1076 phenols with and without low content (5% by weight) of gadolinium oxide (Gd2O3) exposed in the thermal column of the Triga Mark II reactor of LENA (Laboratorio Energia Nucleare Applicata) of Pavia (Italy). Thanks to their size, the phenolic films here presented are good devices for the dosimetry of beams with high dose gradient and which require accurate knowledge of the precise dose delivered. The dependence of EPR signal as function of neutron dose was investigated in the fluence range between 10(11) cm(-2) and 10(14) cm(-2). Linearity of EPR response was found and the signal was compared with that of commercial alanine films. Our analysis showed that gadolinium oxide (5% by weight) can enhance the thermal neutron sensitivity more than 18 times. Irradiated dosimetric films of phenolic compound exhibited EPR signal fading of about 4% after 10 days from irradiation. Copyright © 2015 Elsevier Ltd. All rights reserved.

  6. Electronic Structure of ZnO Quantum Dots studied by High-frequency EPR, ESE, ENDOR and ODMR Spectroscopy

    NARCIS (Netherlands)

    Baranov, P.G.; Romanov, N.G.; Bundakova, A.P.; de Mello-Donega, Celso; Schmidt, J.

    2016-01-01

    High-frequency electron paramagnetic resonance (EPR), electron spin echo (ESE), electron-nuclear double resonance (ENDOR) and optically detected magnetic resonance (ODMR) were applied for the investigation of the electronic properties of ZnO colloidal quantum dots (QDs) which consist of a ZnO

  7. 3D printed sample holder for in-operando EPR spectroscopy on high temperature polymer electrolyte fuel cells

    Science.gov (United States)

    Niemöller, Arvid; Jakes, Peter; Kayser, Steffen; Lin, Yu; Lehnert, Werner; Granwehr, Josef

    2016-08-01

    Electrochemical cells contain electrically conductive components, which causes various problems if such a cell is analyzed during operation in an EPR resonator. The optimum cell design strongly depends on the application and it is necessary to make certain compromises that need to be individually arranged. Rapid prototyping presents a straightforward option to implement a variable cell design that can be easily adapted to changing requirements. In this communication, it is demonstrated that sample containers produced by 3D printing are suitable for EPR applications, with a particular emphasis on electrochemical applications. The housing of a high temperature polymer electrolyte fuel cell (HT-PEFC) with a phosphoric acid doped polybenzimidazole membrane was prepared from polycarbonate by 3D printing. Using a custom glass Dewar, this fuel cell could be operated at temperatures up to 140 °C in a standard EPR cavity. The carbon-based gas diffusion layer showed an EPR signal with a characteristic Dysonian line shape, whose evolution could be monitored in-operando in a non-invasive manner.

  8. Light-induced EPR study of charge transfer in P3HT/bis-PCBM bulk heterojunctions

    National Research Council Canada - National Science Library

    Krinichnyi, Victor I; Yudanova, Eugenia I

    2011-01-01

    ... – 2.73 eV in bulk heterojunctions formed by poly(3-hexylthiophene) (P3HT) with bis(1-[3-(methoxycarbonyl)propyl]-1-phenyl)-[6.6]C62 (bis-PCBM) fullerene derivative have been studied by direct light-induced EPR...

  9. STRUCTURAL AND DYNAMIC PROPERTIES OF SOLID-SOLUTIONS OF BAF2 AND GDF3 - AN EPR STUDY

    NARCIS (Netherlands)

    DENHARTOG, HW

    Results of EPR experiments on solid solutions of barium and gadolinium fluoride in the temperature range 300 to 900 K are presented. At room temperature the Gd-ions are located predominantly at trigonal sites. If the temperature is increased, the interstitial fluoride ions are found to dissociate

  10. Reconstruction of the first-derivative EPR spectrum from multiple harmonics of the field-modulated continuous wave signal.

    Science.gov (United States)

    Tseitlin, Mark; Eaton, Sandra S; Eaton, Gareth R

    2011-04-01

    Selection of the amplitude of magnetic field modulation for continuous wave electron paramagnetic resonance (EPR) often is a trade-off between sensitivity and resolution. Increasing the modulation amplitude improves the signal-to-noise ratio, S/N, at the expense of broadening the signal. Combining information from multiple harmonics of the field-modulated signal is proposed as a method to obtain the first derivative spectrum with minimal broadening and improved signal-to-noise. The harmonics are obtained by digital phase-sensitive detection of the signal at the modulation frequency and its integer multiples. Reconstruction of the first-derivative EPR line is done in the Fourier conjugate domain where each harmonic can be represented as the product of the Fourier transform of the 1st derivative signal with an analytical function. The analytical function for each harmonic can be viewed as a filter. The Fourier transform of the 1st derivative spectrum can be calculated from all available harmonics by solving an optimization problem with the goal of maximizing the S/N. Inverse Fourier transformation of the result produces the 1st derivative EPR line in the magnetic field domain. The use of modulation amplitude greater than linewidth improves the S/N, but does not broaden the reconstructed spectrum. The method works for an arbitrary EPR line shape, but is limited to the case when magnetization instantaneously follows the modulation field, which is known as the adiabatic approximation. Copyright © 2011 Elsevier Inc. All rights reserved.

  11. Structure of high-resolution NMR spectra

    CERN Document Server

    Corio, PL

    2012-01-01

    Structure of High-Resolution NMR Spectra provides the principles, theories, and mathematical and physical concepts of high-resolution nuclear magnetic resonance spectra.The book presents the elementary theory of magnetic resonance; the quantum mechanical theory of angular momentum; the general theory of steady state spectra; and multiple quantum transitions, double resonance and spin echo experiments.Physicists, chemists, and researchers will find the book a valuable reference text.

  12. Calculation of reactor antineutrino spectra in TEXONO

    CERN Document Server

    Chen Dong Liang; Mao Ze Pu; Wong, T H

    2002-01-01

    In the low energy reactor antineutrino physics experiments, either for the researches of antineutrino oscillation and antineutrino reactions, or for the measurement of abnormal magnetic moment of antineutrino, the flux and the spectra of reactor antineutrino must be described accurately. The method of calculation of reactor antineutrino spectra was discussed in detail. Furthermore, based on the actual circumstances of NP2 reactors and the arrangement of detectors, the flux and the spectra of reactor antineutrino in TEXONO were worked out

  13. Using PEGylated magnetic nanoparticles to describe the EPR effect in tumor for predicting therapeutic efficacy of micelle drugs.

    Science.gov (United States)

    Chen, Ling; Zang, Fengchao; Wu, Haoan; Li, Jianzhong; Xie, Jun; Ma, Ming; Gu, Ning; Zhang, Yu

    2018-01-08

    Micelle drugs based on a polymeric platform offer great advantages over liposomal drugs for tumor treatment. Although nearly all of the nanomedicines approved in the clinical use can passively target to the tumor tissues on the basis of an enhanced permeability and retention (EPR) effect, the nanodrugs have shown heterogenous responses in the patients. This phenomenon may be traced back to the EPR effect of tumor, which is extremely variable in the individuals from extensive studies. Nevertheless, there is a lack of experimental data describing the EPR effect and predicting its impact on therapeutic efficacy of nanoagents. Herein, we developed 32 nm magnetic iron oxide nanoparticles (MION) as a T2-weighted contrast agent to describe the EPR effect of each tumor by in vivo magnetic resonance imaging (MRI). The MION were synthesized by a thermal decomposition method and modified with DSPE-PEG2000 for biological applications. The PEGylated MION (Fe3O4@PEG) exhibited high r2 of 571 mM-1 s-1 and saturation magnetization (Ms) of 94 emu g-1 Fe as well as long stability and favorable biocompatibility through the in vitro studies. The enhancement intensities of the tumor tissue from the MR images were quantitatively measured as TNR (Tumor/Normal tissue signal Ratio) values, which were correlated with the delay of tumor growth after intravenous administration of the PLA-PEG/PTX micelle drug. The results demonstrated that the group with the smallest TNR values (TNR enhanced by Fe3O4@PEG (d = 32 nm) could be used to predict the therapeutic efficacy of the micelle drugs (d ≤ 32 nm) in a certain period of time. Fe3O4@PEG has a potential to serve as an ideal MRI contrast agent to visualize the EPR effect in patients for accurate medication guidance of micelle drugs in the future treatment of tumors.

  14. A secure effective dynamic group password-based authenticated key agreement scheme for the integrated EPR information system

    Directory of Open Access Journals (Sweden)

    Vanga Odelu

    2016-01-01

    Full Text Available With the rapid growth of the Internet, a lot of electronic patient records (EPRs have been developed for e-medicine systems. The security and privacy issues of EPRs are important for the patients in order to understand how the hospitals control the use of their personal information, such as name, address, e-mail, medical records, etc. of a particular patient. Recently, Lee et al. proposed a simple group password-based authenticated key agreement protocol for the integrated EPR information system (SGPAKE. However, in this paper, we show that Lee et al.’s protocol is vulnerable to the off-line weak password guessing attack and as a result, their scheme does not provide users’ privacy. To withstand this security weakness found in Lee et al.’s scheme, we aim to propose an effective dynamic group password-based authenticated key exchange scheme for the integrated EPR information system, which retains the original merits of Lee et al.’s scheme. Through the informal and formal security analysis, we show that our scheme provides users’ privacy, perfect forward security and known-key security, and also protects online and offline password guessing attacks. Furthermore, our scheme efficiently supports the dynamic group password-based authenticated key agreement for the integrated EPR information system. In addition, we simulate our scheme for the formal security verification using the widely-accepted AVISPA (Automated Validation of Internet Security Protocols and Applications tool and show that our scheme is secure against passive and active attacks.

  15. Internal in vitro dosimetry for fish using hydroxyapatite-based EPR detectors

    Energy Technology Data Exchange (ETDEWEB)

    Ivanov, D.V. [Urals Division of Russian Academy of Sciences, Institute of Metal Physics, Yekaterinburg (Russian Federation); Ural Federal University, Yekaterinburg (Russian Federation); Shishkina, E.A.; Osipov, D.I.; Pryakhin, E.A. [Urals Research Center for Radiation Medicine, Chelyabinsk (Russian Federation); Razumeev, R.A. [Ural Federal University, Yekaterinburg (Russian Federation)

    2015-08-15

    A number of aquatic ecosystems were exposed to ionizing radiation as a result of the activities of the Mayak Production Association in the Southern Urals, former Soviet Union, in the 1950s. Currently, fishes inhabiting contaminated lakes are being actively studied. These investigations need dosimetric support. In the present paper the results of a pilot study for elaborating an EPR dosimeter which can be used for internal dosimetry in vitro are described. Biological hydroxyapatite is proposed here to be used as a detecting substance. More specifically, small hydroxyapatite grains are proposed for use as point detectors fixed in a solid matrix. After having been pelletized, the detectors were covered by Mylar and placed in the body of a fish to be stored in the fridge for several months. Application of the detectors for internal fish dosimetry demonstrated that the enamel sensitivity is sufficient for passive detection of ionizing radiation in fishes inhabiting contaminated lakes in the Southern Urals. (orig.)

  16. Analyzing three-player quantum games in an EPR type setup.

    Science.gov (United States)

    Chappell, James M; Iqbal, Azhar; Abbott, Derek

    2011-01-01

    We use the formalism of Clifford Geometric Algebra (GA) to develop an analysis of quantum versions of three-player non-cooperative games. The quantum games we explore are played in an Einstein-Podolsky-Rosen (EPR) type setting. In this setting, the players' strategy sets remain identical to the ones in the mixed-strategy version of the classical game that is obtained as a proper subset of the corresponding quantum game. Using GA we investigate the outcome of a realization of the game by players sharing GHZ state, W state, and a mixture of GHZ and W states. As a specific example, we study the game of three-player Prisoners' Dilemma.

  17. Analyzing three-player quantum games in an EPR type setup.

    Directory of Open Access Journals (Sweden)

    James M Chappell

    Full Text Available We use the formalism of Clifford Geometric Algebra (GA to develop an analysis of quantum versions of three-player non-cooperative games. The quantum games we explore are played in an Einstein-Podolsky-Rosen (EPR type setting. In this setting, the players' strategy sets remain identical to the ones in the mixed-strategy version of the classical game that is obtained as a proper subset of the corresponding quantum game. Using GA we investigate the outcome of a realization of the game by players sharing GHZ state, W state, and a mixture of GHZ and W states. As a specific example, we study the game of three-player Prisoners' Dilemma.

  18. EPR and DNP Properties of Certain Novel Single Electron Contrast Agents Intended for Oximetric Imaging

    DEFF Research Database (Denmark)

    Ardenkjær-Larsen, J. H.; Laursen, I; Leunbach, I.

    1998-01-01

    Parameters of relevance to oximetry with Overhauser magnetic resonance imaging (OMRI) have been measured for three single electron contrast agents of the triphenylmethyl type. The single electron contrast agents are stable and water soluble. Magnetic resonance properties of the agents have been...... examined with electron paramagnetic resonance (EPR), nuclear magnetic resonance (NMR), and dynamic nuclear polarization (DNP) at 9.5 mT in water, isotonic saline, plasma, and blood at 23 and 37°C. The relaxivities of the agents are about 0.2–0.4 mM−1s−1and the DNP enhancements extrapolate close...... than 1 μT in water at room temperature. The longitudinal electron spin relaxation rate is calculated from the DNP enhancement curves. The oxygen broadening in water is about 50 μT/mM O2at 37°C. These agents have good properties for oximetry with OMRI....

  19. An EPR spin probe method for characterizing changes in the accessible regions of coal upon oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Sady, W.; Kispert, L.D.; Spears, D.R.

    1992-09-01

    Eight Argonne Premium Coal Samples (APCS) were weathered in air and the structural and chemical changes that upon swelling with toluene and pyridine were, examined by an EPR spin probe method developed in this laboratory. Under mild oxidation conditions and swelling with toluene large structural changes were observed for lignite (Beulah-Zap) which suggested the collapse of the coal structure. This did not occur for higher rank coal. Upon oxidation and swelling with toluene and pyridine an increase occurred in the amino substituted spin probe concentration for coals with the carbon percent above 80%. A maximum was found for the creation of 5 {Angstrom} diameter pores upon swelling with pyridine at 85% C.

  20. An EPR spin probe method for characterizing changes in the accessible regions of coal upon oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Sady, W.; Kispert, L.D.; Spears, D.R.

    1992-01-01

    Eight Argonne Premium Coal Samples (APCS) were weathered in air and the structural and chemical changes that upon swelling with toluene and pyridine were, examined by an EPR spin probe method developed in this laboratory. Under mild oxidation conditions and swelling with toluene large structural changes were observed for lignite (Beulah-Zap) which suggested the collapse of the coal structure. This did not occur for higher rank coal. Upon oxidation and swelling with toluene and pyridine an increase occurred in the amino substituted spin probe concentration for coals with the carbon percent above 80%. A maximum was found for the creation of 5 {Angstrom} diameter pores upon swelling with pyridine at 85% C.

  1. Evalution of the EPR effect in dogs with spontaneous tumors and its implications on nanotherapies

    DEFF Research Database (Denmark)

    Andresen, Thomas Lars

    2013-01-01

    Nanoparticles are well established as effective drug delivery systems and have potential in biomedical imaging as a diagnostic tool. We have recently developed a highly efficient method for utilizing liposomes as agents in positron emission tomography (PET) imaging giving high resolution images...... and allowing direct quantification of liposome tissue distribution and blood clearance. Our approach is based on remote loading of a copper-radionuclide (64Cu) into preformed liposomes and copper entrapment by an encapsulated copper-chelator. We show that the 64Cu-liposomes provide quantitative in vivo imaging...... in canines with spontaneous tumors using PET. Seven canines with spontaneous tumors were included in the study where the main focus was to evaluate the EPR effect in large animals with spontaneous tumors and the performance of the developed liposome imaging agent. None of the included dogs displayed any...

  2. EPR dosimetry of teeth in past and future accidents. A prospective look at a retrospective method

    Energy Technology Data Exchange (ETDEWEB)

    Haskell, E.; Kenner, G.; Hayes, R. [Center for Applied Dosimetry, Salt Lake City, UT (United States); Chumak, V.; Shalom, S.

    1996-12-31

    Accurate assessments of doses received by individuals exposed to radiation from nuclear accidents and incidents such as those at Hiroshima and Nagasaki, the Nevada test site, Chelyabinsk and Mayak are required for epidemiological studies seeking to establish relationships between radiation dose and health effects. One method of retrospective dosimetry which allows for measurement of cumulative gamma ray doses received by exposed individuals is electron paramagnetic resonance spectroscopy (EPR) of tooth enamel. Tooth enamel stores and retains, indefinitely, information on absorbed radiation dose; and teeth are available in every population as a result of dental extraction for medical reasons including periodontal disease and impacted wisdom teeth. In the case of children, deciduous teeth, which are shed between the ages of 7 and 13, can be a very important dosimetric source if documented collection is implemented shortly following an accident. (author)

  3. EPR dosimetry teeth in past and future accidents: A prospective look at a retrospective method

    Energy Technology Data Exchange (ETDEWEB)

    Haskell, E.; Kenner, G.; Hayes, R. [Univ. of Utah, Salt Lake City, UT (United States). Center for Applied Dosimetry; Chumak, V.; Shalom, S. [Scientific Center for Radiation Medicine, Kiev (Ukraine)

    1997-03-01

    Accurate assessments of doses received by individuals exposed to radiation from nuclear accidents and incidents such as those at Hiroshima and Nagasaki, the Nevada test site, Cheliabinsk and Mayak are required for epidemiological studies seeking to establish relationships between radiation dose and health effects. One method of retrospective dosimetry which allows for measurement of cumulative gamma ray doses received by exposed individuals is electron paramagnetic resonance spectroscopy (EPR) of tooth enamel. Tooth enamel stores and retains, indefinitely, information on absorbed radiation dose. And teeth are available in every population as a result of dental extraction for medical reasons including periodontal disease and impacted wisdom teeth. In the case of children, deciduous teeth, which are shed between the ages of 7 and 13, can be a very important dosimetric source if documented collection is implemented shortly following an accident.

  4. EPR characterization of Mn(ii) complexes for distance determination with pulsed dipolar spectroscopy.

    Science.gov (United States)

    Keller, Katharina; Zalibera, Michal; Qi, Mian; Koch, Vanessa; Wegner, Julia; Hintz, Henrik; Godt, Adelheid; Jeschke, Gunnar; Savitsky, Anton; Yulikov, Maxim

    2016-09-14

    The four Mn(ii) complexes Mn-DOTA, Mn-TAHA, Mn-PyMTA, and Mn-NO3Py were characterized by electron paramagnetic resonance (EPR), electron-nuclear double resonance (ENDOR), and relaxation measurements, to predict their relative performance in the EPR pulse dipolar spectroscopy (PDS) experiments. High spin density localization on the metal ions was proven by ENDOR on 1H, D, 14N, and 55Mn nuclei. The transverse relaxation of the Mn(ii) complexes appears to be slow enough for PDS-based spin-spin distance determination. Rather advantageous ratios of T1/Tm were measured allowing for good relaxation induced dipolar modulation enhancement (RIDME) performance and, in general, fast shot repetitions in any PDS experiment. Relaxation properties of the Mn(ii) complexes correlate with the strengths of their zero field splitting (ZFS). Further, a comparison of Mn(ii)-DOTA and Gd(iii)-DOTA based spin labels is presented. The RIDME technique to measure nanometer-range Mn(ii)-Mn(ii) distances in biomolecules is discussed as an alternative to the well-known DEER technique that often appears challenging in cases of metal-metal distance measurements. The use of a modified kernel function that includes dipolar harmonic overtones allows model-free computation of the Mn(ii)-Mn(ii) distance distributions. Mn(ii)-Mn(ii) distances are computed from RIDME data of Mn-rulers consisting of two Mn-PyMTA complexes connected by a rodlike spacer of defined length. Level crossing effects seem to have only a weak influence on the distance distributions computed from this set of Mn(ii)-Mn(ii) RIDME data.

  5. RosettaEPR: rotamer library for spin label structure and dynamics.

    Directory of Open Access Journals (Sweden)

    Nathan S Alexander

    Full Text Available An increasingly used parameter in structural biology is the measurement of distances between spin labels bound to a protein. One limitation to these measurements is the unknown position of the spin label relative to the protein backbone. To overcome this drawback, we introduce a rotamer library of the methanethiosulfonate spin label (MTSSL into the protein modeling program Rosetta. Spin label rotamers were derived from conformations observed in crystal structures of spin labeled T4 lysozyme and previously published molecular dynamics simulations. Rosetta's ability to accurately recover spin label conformations and EPR measured distance distributions was evaluated against 19 experimentally determined MTSSL labeled structures of T4 lysozyme and the membrane protein LeuT and 73 distance distributions from T4 lysozyme and the membrane protein MsbA. For a site in the core of T4 lysozyme, the correct spin label conformation (Χ1 and Χ2 is recovered in 99.8% of trials. In surface positions 53% of the trajectories agree with crystallized conformations in Χ1 and Χ2. This level of recovery is on par with Rosetta performance for the 20 natural amino acids. In addition, Rosetta predicts the distance between two spin labels with a mean error of 4.4 Å. The width of the experimental distance distribution, which reflects the flexibility of the two spin labels, is predicted with a mean error of 1.3 Å. RosettaEPR makes full-atom spin label modeling available to a wide scientific community in conjunction with the powerful suite of modeling methods within Rosetta.

  6. The acid-catalyzed interaction of melanin with nitrite ions. An EPR investigation

    Directory of Open Access Journals (Sweden)

    Matuszak Zenon

    2015-07-01

    Full Text Available The interaction of synthetic dihydroxyphenylalanine (DOPA melanin (DM with nitrite ions, NO2−, in the pH 3.6–7.0 range, has been investigated using electron paramagnetic resonance (EPR. We found that especially at pH <5.5 (from ca. 5.5 to 3.6 the reaction of DM with nitrite generated large quantities of new melanin radicals, which implies the involvement of nitrous acid, HNO2, in the radical formation process. Measurements carried out at constant pH of 3.6 showed that the melanin signal increased together with nitrite concentration, reaching a plateau level which was more than fourfold larger compared to the initial signal amplitude observed in a nitrite-free buffer of the same pH. The effects of nitrite and DM concentrations on the melanin-free radical content were also investigated. It is proposed that the radicals are generated by one electron oxidation of melanin ortho-hydroquinone groups to ortho-semiquinones by HNO2 or related nitrogen oxides such as NO2• radicals. The possible involvement of nitric oxide (•NO and peroxynitrite (ONOO− in DM oxidation was also examined. In air-free solutions, nitric oxide per se did not generate melanin radicals; however, in the presence of oxygen a marked increase in the melanin EPR signal intensity was observed. This result is interpreted in terms of the generation of radicals via the oxidation of DM by peroxynitrite. Our findings suggest that melanin can function as a natural scavenger of nitrous acid and some nitrous acid-derived species. This property may be relevant to physiological functions of melanin pigments in vivo.

  7. EPR spin trapping of free radicals produced by bleomycin and ascorbate.

    Science.gov (United States)

    Buettner, G R; Moseley, P L

    1993-01-01

    In the presence of ascorbate, bleomycin (BLM) is converted to a redox-inactive form that is incapable of inducing DNA strand scission. We have employed EPR spin trapping with 5,5-dimethylpyrroline-1-oxide (DMPO) to examine free radical production during this process. The introduction of ascorbate to an Fe(III)BLM-DMPO system results in the formation of three EPR observable free radicals. One of these radicals is the resonance-stabilized ascorbate free radical (aH = 1.8 G) that is not spin trapped by DMPO; the other two are the result of DMPO spin trapping. These radicals appear to be two carbon-centered radicals, DMPO/.CR1, (aN1 = 15.75 G, aH1 = 22.30 G, aN/aH = 0.706) and DMPO/.CR2 (aN2 = 15.20 G, aH2 = 19.20 G, aN/aH = 0.79). Although it is not possible to identify the exact structures of the carbon-centered radicals that are spin trapped, the hyperfine splittings, as well as the aN/aH values, are characteristic of the presence of electron-withdrawing groups, such as the oxygen atom when attached to the carbon atom. In fact, these parameters are characteristic of DMPO spin trapping results obtained when sugars are subjected to oxidative insult from HO.. Thus, these BLM-ascorbate produced radicals may well be derived from the sugar moiety of BLM.

  8. Bridging the Gap Between the Social and the Technical: The Enrolment of Socio-Technical Information Architects to Cope with the Two-Level Model of EPR Systems.

    Science.gov (United States)

    Pedersen, Rune

    2017-01-01

    This is a project proposal derived from an urge to re-define the governance of ICT in healthcare towards regional and national standardization of the patient pathways. The focus is on a two-levelled approach for governing EPR systems where the clinicians' model structured variables and patient pathways. The overall goal is a patient centric EPR portfolio. This paper define and enlighten the need for establishing the socio- technical architect role necessary to obtain the capabilities of a modern structured EPR system. Clinicians are not capable to moderate between the technical and the clinical.

  9. An image-intensive ePR for image-guided minimally invasive spine surgery applications including real-time intra-operative image acquisition, archival, and display

    Science.gov (United States)

    Documet, Jorge R.; Le, Anh; Liu, Brent; Huang, H. K.; Chiu, John

    2009-02-01

    Recent developments in medical imaging informatics have improved clinical workflow in Radiology enterprise but gaps remain in the clinical workflow from diagnosis to surgical treatment through post-operative follow-up. One solution to bridge this gap is the development of an electronic patient record (ePR) that integrates key imaging and informatics data during the pre, intra, and post-operative phases of clinical workflow. We present an ePR system based on standards and tailored to the clinical application for image-guided minimally invasive spinal surgery (MISS). The ePR system has been implemented in a clinical environment for a half-year.

  10. Orientation of the tetranuclear manganese cluster and tyrosine Z in the O(2)-evolving complex of photosystem II: An EPR study of the S(2)Y(Z)(*) state in oriented acetate-inhibited photosystem II membranes.

    Science.gov (United States)

    Lakshmi, K V; Eaton, S S; Eaton, G R; Brudvig, G W

    1999-09-28

    Inhibitory treatment by acetate, followed by illumination and rapid freezing, is known to trap the S(2)Y(Z)(*) state of the O(2)-evolving complex (OEC) in photosystem II (PS II). An EPR spectrum of this state exhibits broad split signals due to the interaction of the tyrosyl radical, Y(Z)(*), with the S = 1/2 S(2) state of the Mn(4) cluster. We present a novel approach to analyze S(2)Y(Z)(*) spectra of one-dimensionally (1-D) oriented acetate-inhibited PS II membranes to determine the magnitude and relative orientation of the S(2)Y(Z)(*) dipolar vector within the membrane. Although there exists a vast body of EPR data on isolated spins in oriented membrane sheets, the present study is the first of its kind on dipolar-coupled electron spin pairs in such systems. We demonstrate the feasibility of the technique and establish a rigorous treatment to account for the disorder present in partially oriented 1-D membrane preparations. We find that (i) the point-dipole distance between Y(Z)(*) and the Mn(4) cluster is 7.9 +/- 0.2 A, (ii) the angle between the interspin vector and the thylakoid membrane normal is 75 degrees, (iii) the g(z)()-axis of the Mn(4) cluster is 70 degrees away from the membrane normal and 35 degrees away from the interspin vector, and (iv) the exchange interaction between the two spins is -275 x 10(-)(4) cm(-)(1), which is antiferromagnetic. Due to the sensitivity of EPR line shapes of oriented spin-coupled pairs to the interspin distance, the present study imposes a tighter constraint on the Y(Z)-Mn(4) point-dipole distance than obtained from randomly oriented samples. The geometric constraints obtained from the 1-D oriented sample are combined with published models of the structure of Mn-depleted PS II to propose a location of the Mn(4) cluster. A structure in which Y(Z) is hydrogen bonded to a manganese-bound hydroxide ligand is consistent with available data and favors maximal orbital overlap between the two redox center that would facilitate

  11. Mass Spectra of Tetraselenafulvalenes, Diselenadithiafulvalenes and Tetrathiafulvalenes

    DEFF Research Database (Denmark)

    Andersen, Jan Rud; Egsgaard, Helge; Larsen, Elfinn

    1978-01-01

    The mass spectra of 13 heterofulvalenes are reported. The spectra show great similarities within the selenium and within the sulphur series. The main difference between the selenium and the sulphur compounds results from the more facile loss of selenium compared with sulphur, and from the first...

  12. Spectra of Velocity components over Complex Terrain

    DEFF Research Database (Denmark)

    Panofsky, H. A.; Larko, D.; Lipschut, R.

    1982-01-01

    Spectra have been measured over a variety of types of complex terrain: on tops of hills and escarpments, over land downstream of a water surface, and over rolling terrain. Differences between spectra over many types of complex terrain, and over uniform terrain, can be explained by these hypotheses...

  13. Resolution enhancement in second-derivative spectra.

    Science.gov (United States)

    Czarnecki, Mirosław A

    2015-01-01

    Derivative spectroscopy is a powerful tool for the resolution enhancement in infrared, near-infrared, Raman, ultraviolet-visible, nuclear magnetic resonance, electron paramagnetic resonance, and fluorescence spectroscopy. Despite its great significance in analytical chemistry, not all aspects of the applications of this method have been explored as yet. This is the first systematic study of the parameters that influence the resolution enhancement in the second derivative spectra. The derivative spectra were calculated with the Savitzky-Golay method with different window size (5, 15, 25) and polynomial order (2, 4). The results obtained in this work show that the resolution enhancement in the second derivative spectra strongly depends on the data spacing in the original spectra, window size, polynomial order, and peak profile. As shown, the resolution enhancement is related to variations in the width of the peaks upon the differentiation. The present study reveals that in order to maximize the separation of the peaks in the second derivative spectra, the original spectra should be recorded at high resolution and differentiated using a small window size and high polynomial order. However, working with the real spectra one has to compromise between the noise reduction and optimization of the resolution enhancement in the second derivative spectra.

  14. Aircraft Measurements of Atmospheric Kinetic Energy Spectra

    DEFF Research Database (Denmark)

    Lundtang Petersen, Erik; Lilly, D. K.

    1983-01-01

    Wind velocity data obtained from a jet airliner are used to construct kinetic energy spectra over the range of wavelengths from 2.5 to 2500 km. The spectra exhibit an approximate -5/3 slope for wavelengths of less than about 150 km, steepening to about -2.2 at larger scales. These results support...

  15. Decomposition of spectra using maximum autocorrelation factors

    DEFF Research Database (Denmark)

    Larsen, Rasmus

    2001-01-01

    This paper addresses the problem of generating a low dimensional representation of the variation present in a set of spectra, e.g. reflection spectra recorded from a series of objects. The resulting low dimensional description may subseque ntly be input through variable selection schemes into cla......This paper addresses the problem of generating a low dimensional representation of the variation present in a set of spectra, e.g. reflection spectra recorded from a series of objects. The resulting low dimensional description may subseque ntly be input through variable selection schemes...... Fourier decomposition these new variables are located in frequency as well as well wavelength. The proposed algorithm is tested on 100 samples of NIR spectra of wheat....

  16. General Notes on Processes and Their Spectra

    Directory of Open Access Journals (Sweden)

    Gustav Cepciansky

    2012-01-01

    Full Text Available The frequency spectrum performs one of the main characteristics of a process. The aim of the paper is to show the coherence between the process and its own spectrum and how the behaviour and properties of a process itself can be deduced from its spectrum. Processes are categorized and general principles of their spectra calculation and recognition are given. The main stress is put on power spectra of electric and optic signals, as they also perform a kind of processes. These spectra can be directly measured, observed and examined by means of spectral analyzers and they are very important characteristics which can not be omitted at transmission techniques in telecommunication technologies. Further, the paper also deals with non electric processes, mainly with processes and spectra at mass servicing and how these spectra can be utilised in praxis.

  17. Optical absorption spectra of Ag-11 isomers

    DEFF Research Database (Denmark)

    Martinez, Jose Ignacio; Fernandez, E. M.

    2009-01-01

    The optical absorption spectra of the three most; stable structural isomers of the Ag-11 cluster were calculated using the time-dependent, density functional theory within the Casida formalism. The slightly different, spectra, of the isomers may permit the identification of the ground-stale confi......The optical absorption spectra of the three most; stable structural isomers of the Ag-11 cluster were calculated using the time-dependent, density functional theory within the Casida formalism. The slightly different, spectra, of the isomers may permit the identification of the ground......-stale configuration predominantly present in the laboratory beams based on a direct comparison between the calculated photoabsorptiou response for the Ag-11 isomers and the measured spectra of medium-size silver clusters trapped in noble gas Ar and Ne matrices at different, temperatures. This assignment is confirmed...

  18. Effect of methanobactin on the activity and electron paramagnetic resonance spectra of the membrane-associated methane monooxygenase in Methylococcus capsulatus Bath.

    Science.gov (United States)

    Choi, Dong W; Antholine, William E; Do, Young S; Semrau, Jeremy D; Kisting, Clint J; Kunz, Ryan C; Campbell, Damon; Rao, Vinay; Hartsel, Scott C; DiSpirito, Alan A

    2005-10-01

    Improvements in the purification of methanobactin (mb) from either Methylosinus trichosporium OB3b(T) or Methylococcus capsulatus Bath resulted in preparations that stimulated methane-oxidation activity in both whole-cell and cell-free fractions of Methylococcus capsulatus Bath expressing the membrane-associated methane monooxygenase (pMMO). By using washed membrane factions with pMMO activities in the 290 nmol propylene oxidized min(-1) (mg protein)(-1) range, activities approaching 400 nmol propylene oxidized min(-1) (mg protein)(-1) were commonly observed following addition of copper-containing mb (Cu-mb), which represented 50-75 % of the total whole-cell activity. The stimulation of methane-oxidation activity by Cu-mb was similar to or greater than that observed with equimolar concentrations of Cu(II), without the inhibitory effects observed with high copper concentrations. Stimulation of pMMO activity was not observed with copper-free mb, nor was it observed when the copper-to-mb ratio was <0.5 Cu atoms per mb. The electron paramagnetic resonance (EPR) spectra of mb differed depending on the copper-to-mb ratio. At copper-to-mb ratios of <0.4 Cu(II) per mb, Cu(II) addition to mb showed an initial coordination by both sulfur and nitrogen, followed by reduction to Cu(I) in <2 min. At Cu(II)-to-mb ratios between 0.4 and 0.9 Cu(II) per mb, the intensity of the Cu(II) signal in EPR spectra was more representative of the Cu(II) added and indicated more nitrogen coordination. The EPR spectral properties of mb and pMMO were also examined in the washed membrane fraction following the addition of Cu(II), mb and Cu-mb in the presence or absence of reductants (NADH or duroquinol) and substrates (CH4 and/or O2). The results indicated that Cu-mb increased electron flow to the pMMO, increased the free radical formed following the addition of O2 and decreased the residual free radical following the addition of O2 plus CH4. The increase in pMMO activity and EPR spectral changes

  19. EPR spectroscopic characterization of the manganese center and a free radical in the oxalate decarboxylase reaction: identification of a tyrosyl radical during turnover.

    Science.gov (United States)

    Chang, Christopher H; Svedruzic, Drazenka; Ozarowski, Andrzej; Walker, Lee; Yeagle, Gregory; Britt, R David; Angerhofer, Alexander; Richards, Nigel G J

    2004-12-17

    Several molecular mechanisms for cleavage of the oxalate carbon-carbon bond by manganese-dependent oxalate decarboxylase have recently been proposed involving high oxidation states of manganese. We have examined the oxalate decarboxylase from Bacillus subtilis by electron paramagnetic resonance in perpendicular and parallel polarization configurations to test for the presence of such species in the resting state and during enzymatic turnover. Simulation and the position of the half-field Mn(II) line suggest a nearly octahedral metal geometry in the resting state. No spectroscopic signature for Mn(III) or Mn(IV) is seen in parallel mode EPR for samples frozen during turnover, consistent either with a large zero-field splitting in the oxidized metal center or undetectable levels of these putative high-valent intermediates in the steady state. A narrow, featureless g = 2.0 species was also observed in perpendicular mode in the presence of substrate, enzyme, and dioxygen. Additional splittings in the signal envelope became apparent when spectra were taken at higher temperatures. Isotopic editing resulted in an altered line shape only when tyrosine residues of the enzyme were specifically deuterated. Spectral processing confirmed multiple splittings with isotopically neutral enzyme that collapsed to a single prominent splitting in the deuterated enzyme. These results are consistent with formation of an enzyme-based tyrosyl radical upon oxalate exposure. Modestly enhanced relaxation relative to abiological tyrosyl radicals was observed, but site-directed mutagenesis indicated that conserved tyrosine residues in the active site do not host the unpaired spin. Potential roles for manganese and a peripheral tyrosyl radical during steady-state turnover are discussed.

  20. EPR response of sucrose and microcrystalline cellulose to measure high doses of gamma radiation; Respuesta EPR de sacarosa y celulosa micro cristalina para medir altas dosis de radiacion gamma

    Energy Technology Data Exchange (ETDEWEB)

    Torijano, E.; Cruz, L.; Gutierrez, G.; Azorin, J.; Aguirre, F. [Universidad Autonoma Metropolitana, Unidad Iztapalapa, Av. San Rafael Atlixco 186, Col. Vicentina, 09340 Mexico D. F. (Mexico); Cruz Z, E., E-mail: eftc@xanum.uam.mx [UNAM, Instituto de Ciencias Nucleares, Circuito Exterior, Ciudad Universitaria, 04510 Mexico D. F. (Mexico)

    2015-10-15

    Solid dosimeters of sucrose and microcrystalline cellulose (Avicel Ph-102) were prepared, following the same process, in order to compare their EPR response against that of the l-alanine dosimeters considered as reference. All lots of dosimeters were irradiated with gamma radiation in Gamma beam irradiator with 8 kGy/h of the Nuclear Sciences Institute of UNAM. Doses ranged from 1 to 10 kGy respectively. We found that both the response of sucrose as microcrystalline cellulose were linear; however, the response intensity was, on average, twenty times more for sucrose. Comparing this against the EPR response of l-alanine in the range of doses, it was found that the response to sucrose is a third part; and microcrystalline cellulose is a sixtieth, approximately. The results agree with those found in the literature for sucrose, leaving open the possibility of investigating other dosage ranges for cellulose. (Author)