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Sample records for saturation recovery epr

  1. Saturation recovery EPR and ELDOR at W-band for spin labels.

    PubMed

    Froncisz, Wojciech; Camenisch, Theodore G; Ratke, Joseph J; Anderson, James R; Subczynski, Witold K; Strangeway, Robert A; Sidabras, Jason W; Hyde, James S

    2008-08-01

    A reference arm W-band (94 GHz) microwave bridge with two sample-irradiation arms for saturation recovery (SR) EPR and ELDOR experiments is described. Frequencies in each arm are derived from 2 GHz synthesizers that have a common time-base and are translated to 94 GHz in steps of 33 and 59 GHz. Intended applications are to nitroxide radical spin labels and spin probes in the liquid phase. An enabling technology is the use of a W-band loop-gap resonator (LGR) [J.W. Sidabras, R.R. Mett, W. Froncisz, T.G. Camenisch, J.R. Anderson, J.S. Hyde, Multipurpose EPR loop-gap resonator and cylindrical TE(011) cavity for aqueous samples at 94 GHz, Rev. Sci. Instrum. 78 (2007) 034701]. The high efficiency parameter (8.2 GW(-1/2) with sample) permits the saturating pump pulse level to be just 5 mW or less. Applications of SR EPR and ELDOR to the hydrophilic spin labels 3-carbamoyl-2,2,5,5-tetra-methyl-3-pyrroline-1-yloxyl (CTPO) and 2,2,6,6,-tetramethyl-4-piperidone-1-oxyl (TEMPONE) are described in detail. In the SR ELDOR experiment, nitrogen nuclear relaxation as well as Heisenberg exchange transfer saturation from pumped to observed hyperfine transitions. SR ELDOR was found to be an essential method for measurements of saturation transfer rates for small molecules such as TEMPONE. Free induction decay (FID) signals for small nitroxides at W-band are also reported. Results are compared with multifrequency measurements of T(1e) previously reported for these molecules in the range of 2-35 GHz [J.S. Hyde, J.-J. Yin, W.K. Subczynski, T.G. Camenisch, J.J. Ratke, W. Froncisz, Spin label EPR T(1) values using saturation recovery from 2 to 35 GHz. J. Phys. Chem. B 108 (2004) 9524-9529]. The values of T(1e) decrease at 94 GHz relative to values at 35 GHz. PMID:18547848

  2. Resolving Conformational and Rotameric Exchange in Spin-Labeled Proteins Using Saturation Recovery EPR

    PubMed Central

    Bridges, Michael D.; Hideg, Kálmán

    2010-01-01

    The function of many proteins involves equilibria between conformational substates, and to elucidate mechanisms of function it is essential to have experimental tools to detect the presence of conformational substates and to determine the time scale of exchange between them. Site-directed spin labeling (SDSL) has the potential to serve this purpose. In proteins containing a nitroxide side chain (R1), multicomponent electron paramagnetic resonance (EPR) spectra can arise either from equilibria involving different conformational substates or rotamers of R1. To employ SDSL to uniquely identify conformational equilibria, it is thus essential to distinguish between these origins of multicomponent spectra. Here we show that this is possible based on the time scale for exchange of the nitroxide between distinct environments that give rise to multicomponent EPR spectra; rotamer exchange for R1 lies in the ≈0.1–1 μs range, while conformational exchange is at least an order of magnitude slower. The time scales of exchange events are determined by saturation recovery EPR, and in favorable cases, the exchange rate constants between substates with lifetimes of approximately 1–70 μs can be estimated by the approach. PMID:20157634

  3. Saturation recovery EPR and ELDOR at W-band for spin labels

    PubMed Central

    Froncisz, Wojciech; Camenisch, Theodore G.; Ratke, Joseph J.; Anderson, James R.; Subczynski, Witold K.; Strangeway, Robert A.; Sidabras, Jason W.; Hyde, James S.

    2008-01-01

    A reference-arm W-band (94 GHz) microwave bridge with two sample-irradiation arms for saturation recovery (SR) EPR and ELDOR experiments is described. Frequencies in each arm are derived from 2 GHz synthesizers that have a common time-base and are translated to 94 GHz in steps of 33 and 59 GHz. Intended applications are to nitroxide radical spin labels and spin probes in the liquid phase. An enabling technology is the use of a W-band loop-gap resonator (LGR) (J.W. Sidabras et al., Rev. Sci. Instrum. 78 (2007) 034701). The high efficiency parameter (8.2 GW−1/2 with sample) permits the saturating pump pulse level to be just 5 mW or less. Applications of SR EPR and ELDOR to the hydrophilic spin labels 3-carbamoyl-2,2,5,5-tetra-methyl-3-pyrroline-1-yloxyl (CTPO) and 2,2,6,6,-tetramethyl-4-piperidone-1-oxyl (TEMPONE) are described in detail. In the SR ELDOR experiment, nitrogen nuclear relaxation as well as Heisenberg exchange transfer saturation from pumped to observed hyperfine transitions. SR ELDOR was found to be an essential method for measurements of saturation transfer rates for small molecules such as TEMPONE. Free induction decay (FID) signals for small nitroxides at W-band are also reported. Results are compared with multifrequency measurements of T1e previously reported for these molecules in the range of 2 to 35 GHz (J.S. Hyde et al., J. Phys. Chem. B 108 (2004) 9524–9529). The values of T1e decrease at 94 GHz relative to values at 35 GHz. PMID:18547848

  4. Comparing continuous wave progressive saturation EPR and time domain saturation recovery EPR over the entire motional range of nitroxide spin labels.

    PubMed

    Nielsen, Robert D; Canaan, Stephane; Gladden, James A; Gelb, Michael H; Mailer, Colin; Robinson, Bruce H

    2004-07-01

    The measurement of spin-lattice relaxation rates from spin labels, such as nitroxides, in the presence and absence of spin relaxants provides information that is useful for determining biomolecular properties such as nucleic acid dynamics and the interaction of proteins with membranes. We compare X-band continuous wave (CW) and pulsed or time domain (TD) EPR methods for obtaining spin-lattice relaxation rates of spin labels across the entire range of rotational motion to which relaxation rates are sensitive. Model nitroxides and spin-labeled biological species are used to illustrate the potential complications that arise in extracting relaxation data under conditions typical to biological experiments. The effect of super hyperfine (SHF) structure is investigated for both CW and TD spectra. First and second harmonic absorption and dispersion CW spectra of the nitroxide spin label, TEMPOL, are all fit simultaneously to a model of SHF structure over a range of microwave amplitudes. The CW spectra are novel because all harmonics and microwave phases were acquired simultaneously using our homebuilt CW/TD spectrometer. The effect of the SHF structure on the pulsed free induction decay (FID) and pulsed saturation recovery spectrum is shown for both protonated and deuterated TEMPOL. We present novel pulsed saturation recovery measurements on biological molecules, including spin-lattice relaxation rates of spin-labeled proteins and spin-labeled double-stranded DNA. The impact of structure and dynamics on relaxation rates are discussed in the context of each of these examples. Collisional relaxation rates with oxygen and transition metal paramagnetic relaxants are extracted using both continuous wave and time domain methods. The extent of the errors inherent in the CW method and the advantages of pulsed methods for unambiguously measuring collisional relaxation rates are discussed. Spin-lattice relaxation rates, determined by both CW and pulsed methods, are used to determine

  5. Long-Range Distance Measurements in Proteins at Physiological Temperatures Using Saturation Recovery EPR Spectroscopy

    PubMed Central

    2015-01-01

    Site-directed spin labeling in combination with EPR is a powerful method for providing distances on the nm scale in biological systems. The most popular strategy, double electron–electron resonance (DEER), is carried out at cryogenic temperatures (50–80 K) to increase the short spin–spin relaxation time (T2) upon which the technique relies. A challenge is to measure long-range distances (20–60 Å) in proteins near physiological temperatures. Toward this goal we are investigating an alternative approach based on the distance-dependent enhancement of spin–lattice relaxation rate (T1–1) of a nitroxide spin label by a paramagnetic metal. With a commonly used nitroxide side chain (R1) and Cu2+, it has been found that interspin distances ≤25 Å can be determined in this way (Jun et al. Biochemistry2006, 45, 11666). Here, the upper limit of the accessible distance is extended to ≈40 Å using spin labels with long T1, a high-affinity 5-residue Cu2+ binding loop inserted into the protein sequence, and pulsed saturation recovery to measure relaxation enhancement. Time-domain Cu2+ electron paramagnetic resonance, quantum mechanical calculations, and molecular dynamics simulations provide information on the structure and geometry of the Cu2+ loop and indicate that the metal ion is well-localized in the protein. An important aspect of these studies is that both Cu2+/nitroxide DEER at cryogenic temperatures and T1 relaxation measurements at room temperature can be carried out on the same sample, allowing both validation of the relaxation method and assessment of the effect of freezing on protein structure. PMID:25290172

  6. Membrane fluidity profiles as deduced by saturation-recovery EPR measurements of spin-lattice relaxation times of spin labels

    PubMed Central

    Mainali, Laxman; Feix, Jimmy B.; Hyde, James S.; Subczynski, Witold K.

    2011-01-01

    There are no easily obtainable EPR spectral parameters for lipid spin labels that describe profiles of membrane fluidity. The order parameter, which is most often used as a measure of membrane fluidity, describes the amplitude of wobbling motion of alkyl chains relative to the membrane normal and does not contain explicitly time or velocity. Thus, this parameter can be considered as nondynamic. The spin-lattice relaxation rate (T−11) obtained from saturation-recovery EPR measurements of lipid spin labels in deoxygenated samples depends primarily on the rotational correlation time of the nitroxide moiety within the lipid bilayer. Thus, T−11 can be used as a convenient quantitative measure of membrane fluidity that reflects local membrane dynamics. T−11 profiles obtained for 1-palmitoyl-2-(n-doxylstearoyl)phosphatidylcholine (n-PC) spin labels in dimyristoylphosphatidylcholine (DMPC) membranes with and without 50 mol% cholesterol are presented in parallel with profiles of the rotational diffusion coefficient, R⊥, obtained from simulation of EPR spectra using Freed's model. These profiles are compared with profiles of the order parameter obtained directly from EPR spectra and with profiles of the order parameter obtained from simulation of EPR spectra. It is shown that T−11 and R⊥ profiles reveal changes in membrane fluidity that depend on the motional properties of the lipid alkyl chain. We find that cholesterol has a rigidifying effect only to the depth occupied by the rigid steroid ring structure and a fluidizing effect at deeper locations. These effects cannot be differentiated by profiles of the order parameter. All profiles in this study were obtained at X-band (9.5 GHz). PMID:21868272

  7. 20 °C, 9 GHz CW-EPR saturation measurements of five selected Alberta coals

    NASA Astrophysics Data System (ADS)

    Kudynska, J.; Buckmaster, H. A.; Duczmal, T.

    1991-12-01

    This paper reports the first determination of the spin-lattice (T_1) and spin-spin (T_2) relaxation times at 20 °C for two subbituminous and three hv bituminous selected Alberta coals using 9 GHz CW-EPR saturation measurements. Argand diagrammatic techniques were used to verify that the lineshapes were Lorentzian since the deviation was less than 4%. Consequently, it was assumed that the CW-EPR spectral resonances could be approximated to homogeneously broadened lineshapes and saturation techniques could be used to determine these relaxation times. The T_1 and T_2 relaxation times are in good agreement with values reported in the literature using saturation measurements, but two orders of magnitude shorter than those obtained using ESE because coal EPR spectral resonances are the unresolved superposition of comparatively narrow homogeneous resonances.

  8. The effects of dose and radiation quality on the shape and power saturation of the EPR signal in alanine.

    PubMed

    Ciesielski, B; Wielopolski, L

    1994-10-01

    Variations in the shape and the power saturation of EPR spectra of L-alanine irradiated with photons, electrons, neutrons and protons are reported. It is shown that the ratio of the intensities of the satellite lines attributable to "spin flips" and the central line depend on the EPR microwave power, and it is proposed as a quantitative measure of the signal saturation effect. Dependence of this ratio on the microwave power is affected by the radiation quality and for doses in excess of 10 kGy by the absorbed dose. At high doses of low-LET radiation these changes are attributed to a high local density of free radicals, while for low doses of high-LET radiation these are due to changes induced in the crystal lattice. Consequently, the conventional peak-to-peak amplitude measurement of the EPR signal intensity is inaccurate when used for high doses and for comparison between radiations with different beam quality. The possibility to determine radiation quality from an EPR measurement is discussed. PMID:7938443

  9. Doppler-resolved kinetics of saturation recovery

    SciTech Connect

    Forthomme, Damien; Hause, Michael L.; Yu, Hua -Gen; Dagdigian, Paul J.; Sears, Trevor J.; Hall, Gregory E.

    2015-04-08

    Frequency modulated laser transient absorption has been used to monitor the ground state rotational energy transfer rates of CN radicals in a double-resonance, depletion recovery experiment. When a pulsed laser is used to burn a hole in the equilibrium ground state population of one rotational state without velocity selection, the population recovery rate is found to depend strongly on the Doppler detuning of a narrow-band probe laser. Similar effects should be apparent for any relaxation rate process that competes effectively with velocity randomization. Alternative methods of extracting thermal rate constants in the presence of these non-thermal conditions are evaluated. Total recovery rate constants, analogous to total removal rate constants in an experiment preparing a single initial rotational level, are in good agreement with quantum scattering calculations, but are slower than previously reported experiments and show qualitatively different rotational state dependence between Ar and He collision partners. As a result, quasi-classical trajectory studies confirm that the differing rotational state dependence is primarily a kinematic effect.

  10. Doppler-resolved kinetics of saturation recovery

    DOE PAGESBeta

    Forthomme, Damien; Hause, Michael L.; Yu, Hua -Gen; Dagdigian, Paul J.; Sears, Trevor J.; Hall, Gregory E.

    2015-04-08

    Frequency modulated laser transient absorption has been used to monitor the ground state rotational energy transfer rates of CN radicals in a double-resonance, depletion recovery experiment. When a pulsed laser is used to burn a hole in the equilibrium ground state population of one rotational state without velocity selection, the population recovery rate is found to depend strongly on the Doppler detuning of a narrow-band probe laser. Similar effects should be apparent for any relaxation rate process that competes effectively with velocity randomization. Alternative methods of extracting thermal rate constants in the presence of these non-thermal conditions are evaluated. Totalmore » recovery rate constants, analogous to total removal rate constants in an experiment preparing a single initial rotational level, are in good agreement with quantum scattering calculations, but are slower than previously reported experiments and show qualitatively different rotational state dependence between Ar and He collision partners. As a result, quasi-classical trajectory studies confirm that the differing rotational state dependence is primarily a kinematic effect.« less

  11. Direct Oil Recovery from Saturated Carbon Nanotube Sponges.

    PubMed

    Li, Xiying; Xue, Yahui; Zou, Mingchu; Zhang, Dongxiao; Cao, Anyuan; Duan, Huiling

    2016-05-18

    Oil adsorption by porous materials is a major strategy for water purification and industrial spill cleanup; it is of great interest if the adsorbed oil can be safely recovered from those porous media. Here, direct oil recovery from fully saturated bulk carbon nanotube (CNT) sponges by displacing oil with water in controlled manner is shown. Surfactant-assisted electrocapillary imbibition is adopted to drive aqueous electrolyte into the sponge and extrude organic oil out continuously at low potentials (up to -1.2 V). More than 95 wt % of oil adsorbed within the sponge can be recovered, via a single electrocapillary process. Recovery of different oils with a wide range of viscosities is demonstrated, and the remaining CNT sponge can be reused with similar recovery capacity. A direct and efficient method is provided to recover oil from CNT sponges by water imbibition, which has many potential environmental and energy applications. PMID:27120687

  12. Relaxation time determinations by progressive saturation EPR: effects of molecular motion and Zeeman modulation for spin labels.

    PubMed

    Livshits, V A; Páli, T; Marsh, D

    1998-07-01

    The EPR spectra of nitroxide spin labels have been simulated as a function of microwave field, H1, taking into account both magnetic field modulation and molecular rotation. It is found that the saturation of the second integral, S, of the first harmonic in-phase absorption spectrum is approximated by that predicted for slow-passage conditions, that is, S approximately H1/1 + PH21, in all cases. This result is independent of the degree of inhomogeneous broadening. In general, the fitting parameter, P, depends not only on the T1 and T2 relaxation times, but also on the rate of molecular reorientation and on the modulation frequency. Calibrations for determining the relaxation times are established from the simulations. For a given modulation frequency and molecular reorientation rate, the parameter obtained by fitting the saturation curves is given by 1/P = a + 1/gamma2eT1 . Teff2, where Teff2 is the effective T2. For molecular reorientation frequencies in the range 2 x 10(7)-2 x 10(8) s-1, Teff2 is dominated by the molecular dynamics and is only weakly dependent on the intrinsic T02, allowing a direct estimation of T1. For reorientation frequencies outside this range, the (T1T2) product may be determined from the calibrations. The method is applied to determining relaxation times for spin labels undergoing different rates of rotational reorientation in a variety of environments, including those of biological relevance, and is verified experimentally by the relaxation rate enhancements induced by paramagnetic ions. PMID:9654471

  13. Recovery of ectomycorrhiza after 'nitrogen saturation' of a conifer forest.

    PubMed

    Högberg, Peter; Johannisson, Christian; Yarwood, Stephanie; Callesen, Ingeborg; Näsholm, Torgny; Myrold, David D; Högberg, Mona N

    2011-01-01

    Trees reduce their carbon (C) allocation to roots and mycorrhizal fungi in response to high nitrogen (N) additions, which should reduce the N retention capacity of forests. The time needed for recovery of mycorrhizas after termination of N loading remains unknown. Here, we report the long-term impact of N loading and the recovery of ectomycorrhiza after high N loading on a Pinus sylvestris forest. We analysed the N% and abundance of the stable isotope (15) N in tree needles and soil, soil microbial fatty acid biomarkers and fungal DNA. Needles in N-loaded plots became enriched in (15) N, reflecting decreased N retention by mycorrhizal fungi and isotopic discrimination against (15) N during loss of N. Meanwhile, needles in N-limited (control) plots became depleted in (15) N, reflecting high retention of (15) N by mycorrhizal fungi. N loading was terminated after 20yr. The δ(15) N and N% of the needles decreased 6yr after N loading had been terminated, and approached values in control plots after 15yr. This decrease, and the larger contributions compared with N-loaded plots of a fungal fatty acid biomarker and ectomycorrhizal sequences, suggest recovery of ectomycorrhiza. High N loading rapidly decreased the functional role of ectomycorrhiza in the forest N cycle, but significant recovery occurred within 6-15yr after termination of N loading. PMID:20880225

  14. Spin-Label CW Microwave Power Saturation and Rapid Passage with Triangular Non-Adiabatic Rapid Sweep (NARS) and Adiabatic Rapid Passage (ARP) EPR Spectroscopy

    PubMed Central

    Kittell, Aaron W.; Hyde, James S.

    2015-01-01

    Non-adiabatic rapid passage (NARS) electron paramagnetic resonance (EPR) spectroscopy was introduced by Kittell, A.W., Camenisch, T.G., Ratke, J.J. Sidabras, J.W., Hyde, J.S., 2011 as a general purpose technique to collect the pure absorption response. The technique has been used to improve sensitivity relative to sinusoidal magnetic field modulation, increase the range of inter-spin distances that can be measured under near physiological conditions, and enhance spectral resolution in copper (II) spectra. In the present work, the method is extended to CW microwave power saturation of spin-labeled T4 Lysozyme (T4L). As in the cited papers, rapid triangular sweep of the polarizing magnetic field was superimposed on slow sweep across the spectrum. Adiabatic rapid passage (ARP) effects were encountered in samples undergoing very slow rotational diffusion as the triangular magnetic field sweep rate was increased. The paper reports results of variation of experimental parameters at the interface of adiabatic and non-adiabatic rapid sweep conditions. Comparison of the forward (up) and reverse (down) triangular sweeps is shown to be a good indicator of the presence of rapid passage effects. Spectral turning points can be distinguished from spectral regions between turning points in two ways: differential microwave power saturation and differential passage effects. Oxygen accessibility data are shown under NARS conditions that appear similar to conventional field modulation data. However, the sensitivity is much higher, permitting, in principle, experiments at substantially lower protein concentrations. Spectral displays were obtained that appear sensitive to rotational diffusion in the range of rotational correlation times of 10−3 to 10−7 s in a manner that is analogous to saturation transfer spectroscopy. PMID:25917132

  15. Spin-label CW microwave power saturation and rapid passage with triangular non-adiabatic rapid sweep (NARS) and adiabatic rapid passage (ARP) EPR spectroscopy

    NASA Astrophysics Data System (ADS)

    Kittell, Aaron W.; Hyde, James S.

    2015-06-01

    Non-adiabatic rapid passage (NARS) electron paramagnetic resonance (EPR) spectroscopy was introduced by Kittell et al. (2011) as a general purpose technique to collect the pure absorption response. The technique has been used to improve sensitivity relative to sinusoidal magnetic field modulation, increase the range of inter-spin distances that can be measured under near physiological conditions (Kittell et al., 2012), and enhance spectral resolution in copper (II) spectra (Hyde et al., 2013). In the present work, the method is extended to CW microwave power saturation of spin-labeled T4 Lysozyme (T4L). As in the cited papers, rapid triangular sweep of the polarizing magnetic field was superimposed on slow sweep across the spectrum. Adiabatic rapid passage (ARP) effects were encountered in samples undergoing very slow rotational diffusion as the triangular magnetic field sweep rate was increased. The paper reports results of variation of experimental parameters at the interface of adiabatic and non-adiabatic rapid sweep conditions. Comparison of the forward (up) and reverse (down) triangular sweeps is shown to be a good indicator of the presence of rapid passage effects. Spectral turning points can be distinguished from spectral regions between turning points in two ways: differential microwave power saturation and differential passage effects. Oxygen accessibility data are shown under NARS conditions that appear similar to conventional field modulation data. However, the sensitivity is much higher, permitting, in principle, experiments at substantially lower protein concentrations. Spectral displays were obtained that appear sensitive to rotational diffusion in the range of rotational correlation times of 10-3 to 10-7 s in a manner that is analogous to saturation transfer spectroscopy.

  16. Spin-label CW microwave power saturation and rapid passage with triangular non-adiabatic rapid sweep (NARS) and adiabatic rapid passage (ARP) EPR spectroscopy.

    PubMed

    Kittell, Aaron W; Hyde, James S

    2015-06-01

    Non-adiabatic rapid passage (NARS) electron paramagnetic resonance (EPR) spectroscopy was introduced by Kittell et al. (2011) as a general purpose technique to collect the pure absorption response. The technique has been used to improve sensitivity relative to sinusoidal magnetic field modulation, increase the range of inter-spin distances that can be measured under near physiological conditions (Kittell et al., 2012), and enhance spectral resolution in copper (II) spectra (Hyde et al., 2013). In the present work, the method is extended to CW microwave power saturation of spin-labeled T4 Lysozyme (T4L). As in the cited papers, rapid triangular sweep of the polarizing magnetic field was superimposed on slow sweep across the spectrum. Adiabatic rapid passage (ARP) effects were encountered in samples undergoing very slow rotational diffusion as the triangular magnetic field sweep rate was increased. The paper reports results of variation of experimental parameters at the interface of adiabatic and non-adiabatic rapid sweep conditions. Comparison of the forward (up) and reverse (down) triangular sweeps is shown to be a good indicator of the presence of rapid passage effects. Spectral turning points can be distinguished from spectral regions between turning points in two ways: differential microwave power saturation and differential passage effects. Oxygen accessibility data are shown under NARS conditions that appear similar to conventional field modulation data. However, the sensitivity is much higher, permitting, in principle, experiments at substantially lower protein concentrations. Spectral displays were obtained that appear sensitive to rotational diffusion in the range of rotational correlation times of 10(-3) to 10(-7) s in a manner that is analogous to saturation transfer spectroscopy. PMID:25917132

  17. Direct reconstruction of T1 from k-space using a radial saturation-recovery sequence

    NASA Astrophysics Data System (ADS)

    Chen, Liyong; DiBella, Edward V. R.

    2011-03-01

    Contrast agent concentration ([CA]) must be known accurately to quantify dynamic contrast-enhanced (DCE) MR imaging. Accurate concentrations can be obtained if the longitudinal relaxation rate constant T1 is known both pre- and post-contrast injection. Post-contrast signal intensity in the images is often saturated and an approximation to T1 can be difficult to obtain. One method that has been proposed for accurate T1 estimation effectively acquires multiple images with different effective saturation recovery times (eSRTs) and fits the images to the equation for T1 recovery to obtain T1 values. This was done with a radial saturation-recovery sequence for 2D imaging of myocardial perfusion with DCE MRI. This multi-SRT method assumes that the signal intensity is constant for different readouts in each image. Here this assumption is not necessary as a model-based reconstruction method is proposed that directly reconstructs an image of T1 values from k-space. The magnetization for each ray at each readout pulse is modeled in the reconstruction with Bloch equations. Computer simulations based on a 72 ray cardiac DCE MRI acquisition were used to test the method. The direct model-based reconstruction gave accurate T1 values and was slightly more accurate than the multi-SRT method that used three sub-images.

  18. Toward Two-Color Sub-Doppler Saturation Recovery Kinetics in CN (x, v = 0, J)

    NASA Astrophysics Data System (ADS)

    Xu, Hong; Forthomme, Damien; Sears, Trevor; Hall, Gregory; Dagdigian, Paul

    2015-06-01

    Collision-induced rotational energy transfer among rotational levels of ground state CN (X 2σ+, v = 0) radicals has been probed by saturation recovery experiments, using high-resolution, polarized transient FM spectroscopy to probe the recovery of population and the decay of alignment following ns pulsed laser depletion of selected CN rotational levels. Despite the lack of Doppler selection in the pulsed depletion and the thermal distribution of collision velocities, the recovery kinetics are found to depend on the probed Doppler shift of the depleted signal. The observed Doppler-shift-dependent recovery rates are a measure of the velocity dependence of the inelastic cross sections, combined with the moderating effects of velocity-changing elastic collisions. New experiments are underway, in which the pulsed saturation is performed with sub-Doppler velocity selection. The time evolution of the spectral hole bleached in the initially thermal CN absorption spectrum can characterize speed-dependent inelastic collisions along with competing elastic velocity-changing collisions, all as a function of the initially bleached velocity group and rotational state. The initial time evolution of the depletion recovery spectrum can be compared to a stochastic model, using differential cross sections for elastic scattering as well as speed-dependent total inelastic cross sections, derived from ab initio scattering calculations. Progress to date will be reported. Acknowledgments: Work at Brookhaven National Laboratory was carried out under Contract No. DE-AC02-98CH10886 and DE-SC0012704 with the U.S. Department of Energy and supported by its Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences.

  19. Ultrafast recovery time and broadband saturable absorption properties of black phosphorus suspension

    SciTech Connect

    Wang, Yingwei; Huang, Guanghui; Chen, Jiazhang; Xiao, Si He, Jun; Mu, Haoran; Bao, Qiaoliang; Lin, Shenghuang

    2015-08-31

    As a new type of two-dimensional crystal material, black phosphorus (BP) exhibits excellent electronics and optical performance. Herein, we focus on carrier relaxation dynamics and nonlinear optical properties of BP suspension. Atomic force microscopy, transmission electron microscopy, and optical transmission spectrum are employed to characterize the structure and linear optical properties of the BP. Additionally, pump-probe experiments at wavelength of 1550 nm were carried out to study the carrier dynamics in BP suspension, and ultrafast recovery time was observed (τ{sub s} = 24 ± 2 fs). Furthermore, we demonstrate the saturable absorption signals by open aperture Z-scan experiments at wavelengths of 1550 nm, 532 nm, and 680 nm. The results indicate that BP has broadband saturable absorption properties and the nonlinear absorption coefficients were determined to be β{sub 2} = −0.20 ± 0.08 × 10{sup −3 }cm/GW (532 nm), β{sub 2} = −0.12 ± 0.05 × 10{sup −3 }cm/GW (680 nm), and β{sub 2} = −0.15 ± 0.09 × 10{sup −3 }cm/GW (1550 nm)

  20. TIME-LAPSE SEISMIC MODELING & INVERSION OF CO2 SATURATION FOR SEQUESTRATION AND ENHANCED OIL RECOVERY

    SciTech Connect

    Mark A. Meadows

    2006-03-31

    Injection of carbon dioxide (CO2) into subsurface aquifers for geologic storage/sequestration, and into subsurface hydrocarbon reservoirs for enhanced oil recovery, has become an important topic to the nation because of growing concerns related to global warming and energy security. In this project we developed new ways to predict and quantify the effects of CO2 on seismic data recorded over porous reservoir/aquifer rock systems. This effort involved the research and development of new technology to: (1) Quantitatively model the rock physics effects of CO2 injection in porous saline and oil/brine reservoirs (both miscible and immiscible). (2) Quantitatively model the seismic response to CO2 injection (both miscible and immiscible) from well logs (1D). (3) Perform quantitative inversions of time-lapse 4D seismic data to estimate injected CO2 distributions within subsurface reservoirs and aquifers. This work has resulted in an improved ability to remotely monitor the injected CO2 for safe storage and enhanced hydrocarbon recovery, predict the effects of CO2 on time-lapse seismic data, and estimate injected CO2 saturation distributions in subsurface aquifers/reservoirs. We applied our inversion methodology to a 3D time-lapse seismic dataset from the Sleipner CO2 sequestration project, Norwegian North Sea. We measured changes in the seismic amplitude and traveltime at the top of the Sleipner sandstone reservoir and used these time-lapse seismic attributes in the inversion. Maps of CO2 thickness and its standard deviation were generated for the topmost layer. From this information, we estimated that 7.4% of the total CO2 injected over a five-year period had reached the top of the reservoir. This inversion approach could also be applied to the remaining levels within the anomalous zone to obtain an estimate of the total CO2 injected.

  1. Preoperative mannitol infusion improves perioperative cerebral oxygen saturation and enhances postoperative recovery after laparoscopic cholecystectomy

    PubMed Central

    Mousa, Wesam F.; Mowafi, Hany A.; Al-Metwalli, Roshdi R.; Al-Ghamdi, Abdulmohsin A.; Al-Gameel, Haytham Z.

    2015-01-01

    Objectives: To test the effect of preoperative mannitol infusion on perioperative decreased cerebral oxygen saturation (rSO2) during laparoscopic cholecystectomy. Methods: Forty patients scheduled for laparoscopic cholecystectomy were enrolled in this study conducted at Dammam Hospital of the University, Dammam, Kingdom of Saudi Arabia from December 2013 to June 2014. Patients received either 0.5 g/kg of 20% intravenous mannitol infusion over 10 minutes before induction of anesthesia (group M), or an equal volume of normal saline instead (group C). Primary outcome variable was rSO2. Other variables included extubation time, clinical assessment of consciousness recovery using the Modified Observer’s Assessment of Alertness/Sedation Scale (OAA/S), and the mini-mental state examination (MMSE) for cognitive evaluation. Results: Anesthesia induction increased rSO2 in both groups. Pneumoperitoneum decreased rSO2 in group C, but not in group M. This drop in rSO2 in the group C reached its maximum 30 minutes after extubation, and was significantly less than the preinduction value. Time to extubation in group M was significantly shorter compared to group C (p=0.007). The OAAS in group M at 10 min after extubation was significantly higher compared to group C. No differences were found between the 2 groups in cognitive function as measured by MMSE score. Conclusion: Preoperative mannitol infusion maintains perioperative rSO2 during laparoscopic cholecystectomy and shortens extubation time with earlier resurgence of OAAS. PMID:26446331

  2. EPR imaging

    NASA Astrophysics Data System (ADS)

    Eaton, Sandra S.; Eaton, Gareth R.

    Useful EPR imaging has been achieved using simple gradient coils on a standard spectrometer. Resolution of less than 1 mm is possible without deconvolution of the resulting spectra. Examples are presented using DPPH and nitroxyl radicals.

  3. Increased endogenous ascorbyl free radical formation with singlet oxygen scavengers in reperfusion injury: an EPR and functional recovery study in rat hearts.

    PubMed

    Lee, J W; Bobst, E V; Wang, Y G; Ashraf, M M; Bobst, A M

    2000-12-01

    The objective of this study was to investigate the effect of singlet oxygen ((1)O2) scavengers on functional recovery and ascorbyl free radical (AFR) formation in isolated ischemic rat hearts. Hearts were subjected to 40 min. of global ischemia followed by 30 min. of reperfusion. Hemodynamics were measured as heart rate (HR), coronary flow (CF), left ventricular developed pressure (LVDP) and contractility (dP/dt). Electron paramagnetic resonance (EPR) spectroscopy was used to measure AFR release in coronary perfusate during the first two min. of reperfusion as a function of ROS scavengers. Relative to ischemic controls the administration of the (1)O2 scavengers 2,2,6,6-tetramethyl-4-piperidone x HCl (4-oxo-TEMP), carnosine (beta-alanyl-L-histidine) or a combination of the two significantly improved functional recovery as measured by LVDP. While no AFR signal was detected in coronary perfusate collected during preischemic perfusion with and without (1)O2 scavengers, the AFR background signal due to ischemia was significantly increased with the (1)O2 and *O2- scavengers. No such increase was observed with the hydroxyl radical (*OH) scavenger mannitol. Besides the AFR increase with the (1)O2 and *O2- scavengers the functional recovery was only significantly improved with the (1)O2 scavengers. In contrast to previous AFR studies we found with endogenous AFR that an increased AFR formation is not necessarily only reflecting increased oxidative stress but can also report improved functional recovery. Combining the hemodynamic data with increased AFR formation in the presence of several different ROS scavengers gives supportive evidence for (1)O2 also being involved in reperfusion injury. PMID:11156483

  4. Recovery of saturated video signals from vidicons by dynamic cathode biasing

    NASA Astrophysics Data System (ADS)

    Yates, G. J.

    1991-05-01

    Vidicons used for imaging of pulsed or transient light sources must instantaneously record gray scale images on photoconductive targets. Typical targets, which store photocharge proportional to the varying light intensity in the optical image, have larger positive charge storage capacity than the negative charge available from the electron beam used for neutralizing the target during read-out. Therefore, the target has much higher dynamic range, typically 3 to 5 times larger than the beam. The result is that several scans of the target are required to obtain all the charge from a fully charged target. For applications where only one scan of the target is permissible, this can result in reading the target data in saturated form, with the loss of gray scale information. However, with dynamic rebiasing of the vidicon cathode, the data can be recovered unsaturated. This technique is extremely powerful because it allows instantaneous adjustment after the target has been exposed to light pulses but before the target is read out. In effect, a real time gain or sensitivity control function is implemented by the technique. Alternatively, the technique can be viewed as a means to dynamically select strategic portions of the vidicon transfer curve for immediate read-out, which otherwise would either be saturated if read out immediate read-out, which otherwise would either be saturated if read out immediately or would require several read-outs. Although only transient imaging applications (usually with single field read-out) are addressed, the technique should find application in conventional continuous read-write TV cameras. The principle of operation, associated circuitry, and examples of image retrieval are presented.

  5. The estimation of recovery time of calf muscle oxygen saturation during exercise by using functional near infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Ansari, M. A.; Shojaeifar, M.; Mohajerani, E.

    2014-08-01

    Several methods of near infrared spectroscopy such as functional near infrared spectroscopy (fNIRS) and pulse oximetry have been applied for monitoring of tissue oxygenation or arterial oxygen saturation. Some vascular diseases can be diagnosed through measurements of tissue oxygenation. In this study, the temporal variation of oxygenation of calf muscle after exercise is studied by fNIRS. First, the accuracy of a low-cost fNIRS system is studied by measuring the oxygenation of a lipid phantom. Moreover, in-vivo study is performed to evaluate the precision of this system. Then, the variation of muscle oxygenation of four persons during exercise is measured and also the recovery time after walking/running is measured by this fNIRS system.

  6. Pulsed EPR Imaging of Nitroxides in Mice

    PubMed Central

    Hyodo, Fuminori; Matsumoto, Shingo; Devasahayam, Nallathamby; Dharmaraj, Christopher; Subramanian, Sankaran; Mitchell, James B.; Krishna, Murali C.

    2012-01-01

    Nitroxides, unlike trityl radicals, have shorter T2s which until now were not detectable by time-domain Electron Paramagnetic Resonance (EPR) spectrometer at 300 MHz pulsed EPR since their phase memory times were shorter than the spectrometer recovery times. In the current version of the time-domain EPR spectrometer with improved spectrometer recovery times, we tested the feasibility of detecting signals from nitroxide radicals. Several nitroxides and the trityl radical Oxo63 were tested. Among the nitroxides evaluated, deuterated 15N-Tempone (15N-PDT) was found to have the longest T2. The signal intensity profile as a function of concentration of these agents was evaluated and a bi-phasic behavior was observed; beyond a nitroxide concentration of 1.5 mM, signal intensity was found to decrease as a result of self-broadening. Imaging experiments were carried out with 15N-PDT in solutions equilibrated with 0, 5, 10 and 21% oxygen using the Single Point Imaging (SPI) modality in EPR. The image intensity in these tubes was found to depend on the oxygen concentration which in turn influences the T2 of 15N-PDT. In vivo experiments were demonstrated with 15N-PDT in anesthetized mice where the distribution and metabolism of 15N-PDT could be monitored. This study, for the first time shows the capability to image a cell-permeable nitroxide in mice using pulsed EPR in the SPI modality. PMID:19157932

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

    NASA Astrophysics Data System (ADS)

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

    2006-09-01

    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. 50 days, 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=2.0023±0.0003 and g⊥=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 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.

  8. Effects of Fluid Saturation on Gas Recovery from Class-3 Hydrate Accumulations Using Depressurization: Case Study of Yuan-An Ridge Site in Southwestern Offshore Taiwan

    NASA Astrophysics Data System (ADS)

    Huang, Yi-Jyun; Wu, Cheng-Yueh; Hsieh, Bieng-Zih

    2016-04-01

    Gas hydrates are crystalline compounds in which guest gas molecules are trapped in host lattices of ice crystals. In Taiwan, the significant efforts have recently begun to evaluate the reserves of hydrate because the vast accumulations of gas hydrates had been recognized in southwestern offshore Taiwan. Class-3 type hydrate accumulations are referred to an isolated hydrate layer without an underlying zone of mobile fluids, and the entire hydrate layer may be well within the hydrate stability zone. The depressurization method is a useful dissociation method for gas production from Class-3 hydrate accumulations. The dissociation efficiency is controlled by the responses of hydrate to the propagating pressure disturbance, and the pressure propagation is relating to the amount (or saturation) of the mobile fluid in pore space of the hydrate layer. The purpose of this study is to study the effects of fluid saturation on the gas recovery from a class-3 hydrate accumulation using depressurization method. The case of a class-3 hydrate deposit of Yuan-An Ridge in southwestern offshore Taiwan is studied. The numerical method was used in this study. The reservoir simulator we used to study the dissociation of hydrate and the production of gas was the STARS simulator developed by CMG, which coupled heat transfer, geo-chemical, geo-mechanical, and multiphase fluid flow mechanisms. The study case of Yuan-An Ridge is located in southwestern offshore Taiwan. The hydrate deposit was found by the bottom simulating reflectors (BSRs). The geological structure of the studied hydrate deposit was digitized to build the geological model (grids) of the case. The formation parameters, phase behavior data, rock and fluid properties, and formation's initial conditions were assigned sequentially to grid blocks, and the completion and operation conditions were designed to wellbore blocks to finish the numerical model. The changes of reservoir pressure, temperature, saturation due to the hydrate

  9. Pulsed EPR imaging of nitroxides in mice.

    PubMed

    Hyodo, Fuminori; Matsumoto, Shingo; Devasahayam, Nallathamby; Dharmaraj, Christopher; Subramanian, Sankaran; Mitchell, James B; Krishna, Murali C

    2009-04-01

    Nitroxides, unlike trityl radicals, have shorter T(2)s which until now were not detectable in vivo by a time-domain pulsed Electron Paramagnetic Resonance (EPR) spectrometer at 300 MHz since their phase memory times were shorter than the spectrometer recovery times. In the current version of the time-domain EPR spectrometer with improved spectrometer recovery times, the feasibility of detecting signals from nitroxide radicals was tested. Among the nitroxides evaluated, deuterated (15)N-Tempone ((15)N-PDT) was found to have the longest T(2). The signal intensity profile as a function of concentration of these agents was evaluated and a biphasic behavior was observed; beyond a nitroxide concentration of 1.5mM, signal intensity was found to decrease as a result of self-broadening. Imaging experiments were carried out with (15)N-PDT in solutions equilibrated with 0%, 5%, 10%, and 21% oxygen using the single point imaging (SPI) modality in EPR. The image intensity in these tubes was found to depend on the oxygen concentration which in turn influences the T(2) of (15)N-PDT. In vivo experiments were demonstrated with (15)N-PDT in anesthetized mice where the distribution and metabolism of (15)N-PDT could be monitored. This study, for the first time shows the capability to image a cell-permeable nitroxide in mice using pulsed EPR in the SPI modality. PMID:19157932

  10. 1.22 {mu}m GaInNAs Saturable Absorber Mirrors with Tailored Recovery Time

    SciTech Connect

    Puustinen, Janne; Guina, Mircea; Korpijaervi, Ville-Markus; Tukiainen, Antti; Kivistoe, Samuli; Pessa, Markus; Marcinkevicius, Saulius

    2010-11-10

    The effect of in-situ N-ion irradiation on the recombination dynamics of GaInNAs/GaAs semiconductor saturable absorber mirrors has been studied. The samples were fabricated by molecular beam epitaxy using a radio frequency plasma source for nitrogen incorporation in the absorber layers as well as for the irradiation. The recombination dynamics of irradiated samples were studied by pump-probe measurements. The recombination time of the absorbers could be reduced by increasing the irradiation time. The effect of the reduced recombination time on the pulse dynamics of a mode-locked laser setup was studied with a Bi-doped fibre laser. The pulse quality was found to improve with increased irradiation time and reduced recombination time, demonstrating the potential of the in-situ irradiation method for device applications.

  11. Nitrification cessation and recovery in an aerated saturated vertical subsurface flow treatment wetland: Field studies and microscale biofilm modeling.

    PubMed

    Murphy, Clodagh; Rajabzadeh, Amin R; Weber, Kela P; Nivala, Jaime; Wallace, Scott D; Cooper, David J

    2016-06-01

    In aerated treatment wetlands, oxygen availability is not a limiting factor in sustaining a high level of nitrification in wastewater treatment. In the case of an air blower failure, nitrification would cease, potentially causing adverse effects to the nitrifying bacteria. A field trial was completed investigating nitrification loss when aeration is switched off, and the system recovery rate after the aeration is switched back on. Loss of dissolved oxygen was observed to be more rapid than loss of nitrification. Nitrate was observed in the effluent long after the aeration was switched off (48h+). A complementary modeling study predicted nitrate diffusion out of biofilm over a 48h period. After two weeks of no aeration in the established system, nitrification recovered within two days, whereas nitrification establishment in a new system was previously observed to require 20-45days. These results suggest that once established resident nitrifying microbial communities are quite robust. PMID:26967335

  12. Spin labeling EPR.

    PubMed

    Klare, Johann P; Steinhoff, Heinz-Jürgen

    2009-01-01

    Site-directed spin labeling in combination with electron paramagnetic resonance spectroscopy has emerged as an efficient tool to elucidate the structure and conformational dynamics of biomolecules under native-like conditions. This article summarizes the basics as well as recent progress of site-directed spin labeling. Continuous wave EPR spectra analyses and pulse EPR techniques are reviewed with special emphasis on applications to the sensory rhodopsin-transducer complex mediating the photophobic response of the halophilic archaeum Natronomonas pharaonis and the photosynthetic reaction center from Rhodobacter sphaeroides R26. PMID:19728138

  13. Combining Steady-State and Dynamic Methods for Determining Absolute Signs of Hyperfine Interactions: Pulsed ENDOR Saturation and Recovery (PESTRE)

    PubMed Central

    Doan, Peter E.

    2010-01-01

    The underlying causes of asymmetric intensities in Davies pulsed ENDOR spectra that are associated with the signs of the hyperfine interaction are reinvestigated. The intensity variations in these asymmetric ENDOR patterns are best described as shifts in an apparent baseline intensity that occurs dynamically following on-resonance ENDOR transitions. We have developed an extremely straightforward multi-sequence protocol that is capable of giving the sign of the hyperfine interaction by probing a single ENDOR transition, without reference to its partner transition. This technique, Pulsed ENDOR Saturatation and Recovery (PESTRE) monitors dynamic shifts in the ‘baseline’ following measurements at a single RF frequency (single ENDOR peak), rather than observing anomalous ENDOR intensity differences between the two branches of an ENDOR response. These baseline shifts, referred to as dynamic reference levels (DRLs), can be directly tied to the electron spin manifold from which that ENDOR transition arises. The application of this protocol is demonstrated on 57Fe ENDOR of a 2Fe-2S ferredoxin. We use the 14N ENDOR transitions of the S = 3/2 [Fe(II)NO]2+ center of the non-heme iron enzyme, anthranilate dioxygenase (AntDO) to examine the details of the relaxation model using PESTRE. PMID:21075026

  14. Spin-label W-band EPR with seven-loop–six-gap resonator: Application to lens membranes derived from eyes of a single donor

    PubMed Central

    Mainali, Laxman; Sidabras, Jason W.; Camenisch, Theodore G.; Ratke, Joseph J.; Raguz, Marija; Hyde, James S.; Subczynski, Witold K.

    2014-01-01

    Spin-label W-band (94 GHz) EPR with a five-loop–four-gap resonator (LGR) was successfully applied to study membrane properties (L. Mainali, J.S. Hyde, W.K. Subczynski, Using spin-label W-band EPR to study membrane fluidity in samples of small volume, J. Magn. Reson. 226 (2013) 35–44). In that study, samples were equilibrated with the selected gas mixture outside the resonator in a sample volume ~100 times larger than the sensitive volume of the LGR and transferred to the resonator in a quartz capillary. A seven-loop–six-gap W-band resonator has been developed. This resonator permits measurements on aqueous samples of 150 nL volume positioned in a polytetrafluoroethylene (PTFE) gas permeable sample tube. Samples can be promptly deoxygenated or equilibrated with an air/nitrogen mixture inside the resonator, which is significant in saturation-recovery measurements and in spin-label oximetry. This approach was tested for lens lipid membranes derived from lipids extracted from two porcine lenses (single donor). Profiles of membrane fluidity and the oxygen transport parameter were obtained from saturation-recovery EPR using phospholipid analog spin-labels. Cholesterol analog spin-labels allowed discrimination of the cholesterol bilayer domain and acquisition of oxygen transport parameter profiles across this domain. Results were compared with those obtained previously for membranes derived from a pool of 100 lenses. Results demonstrate that EPR at W-band can be successfully used to study aqueous biological samples of small volume under controlled oxygen concentration. PMID:25541571

  15. Comparative study of some new EPR dosimeters

    NASA Astrophysics Data System (ADS)

    Alzimami, K. S.; Maghraby, Ahmed M.; Bradley, D. A.

    2014-02-01

    Investigations have been made of four new radiation dosimetry EPR candidates from the same family of materials: sulfamic acid, sulfanillic acid, homotaurine, and taurine. Mass energy attenuation coefficients, mass stopping power values and the time dependence of the radiation induced radicals are compared. Also investigated are the microwave saturation behavior and the effect of applied modulation amplitude on both peak-to-peak line width (WPP) and peak-to-peak signal height (HPP). The dosimeters are characterized by simple spectra and stable radiation-induced radicals over reasonable durations, especially in taurine dosimeters. Sulfamic acid dosimeters possessed the highest sensitivity followed by taurine and homotaurine and sulfanillic.

  16. Recovery

    NASA Video Gallery

    This video discusses the recovery events that occur in high-power rocketry and the various devices used in safely recovering the rocket. The video includes a discussion of black powder and ejection...

  17. [Recovery].

    PubMed

    Estingoy, Pierrette; Gilliot, Élodie; Parisot, Clément

    2015-01-01

    The historical fatalism of the impossibility of recovering from psychosis eased from the 1970s with the shaping of the idea of a possible recovery. Recovery is today the objective for the patient and caregivers. The key to achieving this lies in the encounter with Others. A collective approach, on the level of the institution, must be established. The aim is to create opportunities for the patient to express their doubts and feelings. PMID:26363659

  18. Rapid frequency scan EPR.

    PubMed

    Tseitlin, Mark; Rinard, George A; Quine, Richard W; Eaton, Sandra S; Eaton, Gareth R

    2011-08-01

    In rapid frequency scan EPR with triangular scans, sufficient time must be allowed to insure that the magnetization in the x, y plane decays to baseline at the end of the scan, which typically is about 5T(2) after the spins are excited. To permit relaxation of signals excited toward the extremes of the scan the total scan time required may be much longer than 5T(2). However, with periodic, saw-tooth excitation, the slow-scan EPR spectrum can be recovered by Fourier deconvolution of data recorded with a total scan period of 5T(2), even if some spins are excited later in the scan. This scan time is similar to polyphase excitation methods. The peak power required for either polyphase excitation or rapid frequency scans is substantially smaller than for pulsed EPR. The use of an arbitrary waveform generator (AWG) and cross loop resonator facilitated implementation of the rapid frequency scan experiments reported here. The use of constant continuous low B(1), periodic excitation waveform, and constant external magnetic field is similar to polyphase excitation, but could be implemented without the AWG that is required for polyphase excitation. PMID:21664848

  19. Rapid Frequency Scan EPR

    PubMed Central

    Tseitlin, Mark; Rinard, George A.; Quine, Richard W.; Eaton, Sandra S.; Eaton, Gareth R.

    2011-01-01

    In rapid frequency scan EPR with triangular scans, sufficient time must be allowed to insure that the magnetization in the x,y plane decays to baseline at the end of the scan, which typically is about 5 T2 after the spins are excited. To permit relaxation of signals excited toward the extremes of the scan the total scan time required may be much longer than 5 T2. However, with periodic, saw-tooth excitation, the slow-scan EPR spectrum can be recovered by Fourier deconvolution of data recorded with a total scan period of 5 T2, even if some spins are excited later in the scan. This scan time is similar to polyphase excitation methods. The peak power required for either polyphase excitation or rapid frequency scans is substantially smaller than for pulsed EPR. The use of an arbitrary waveform generator (AWG) and cross loop resonator facilitated implementation of the rapid frequency scan experiments reported here. The use of constant continuous low B1, periodic excitation waveform, and constant external magnetic field is similar to polyphase excitation, but could be implemented without the AWG that is required for polyphase excitation. PMID:21664848

  20. Absorption line CW EPR using an amplitude modulated longitudinal field.

    PubMed

    Fedin, Matvey; Gromov, Igor; Schweiger, Arthur

    2004-11-01

    In standard continuous wave electron paramagnetic resonance (CW-EPR) experiments, the first derivative of absorption lines is detected. This type of a line shape is caused by the magnetic field modulation and is usually an undesired feature, since the sensitivity of CW-EPR drastically decreases with increasing linewidth. A new approach is introduced, which allows for the measurement of absorption line EPR spectra in systems with broad inhomogeneous lines. The method makes use of multiple-photon transitions that are induced in spin systems when a transverse microwave and a longitudinal radio frequency field are simultaneously applied. The absorption lines are obtained by using amplitude modulation of the radio frequency field and slight saturation of the spectral lines. The basics of the new approach are discussed and experimental examples are given. PMID:15504685

  1. Broadband Transmission EPR Spectroscopy

    PubMed Central

    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

  2. Decolouration of H2SO4 leachate from phosphorus-saturated alum sludge using H2O2 and advanced oxidation processes in phosphorus recovery strategy.

    PubMed

    Zhao, X H; Zhao, Y Q

    2009-12-01

    As a part of attempt for phosphorus (P) recovery from P-saturated alum sludge, which was used as a low-cost P-adsorbent in treatment reed bed for wastewater treatment, decolouration of H(2)SO(4) leachate obtained from previous experiment, possessing a great deal of P, aluminum and red-brown coloured materials (RBCMs), by using H(2)O(2) and advanced oxidation processes (AOPs) was investigated. The use of H(2)O(2) and AOPs in the forms of Fenton (H(2)O(2)/Fe(2 +)) and photo-Fenton (UV/H(2)O(2)/Fe(2 +)) were tested. The changes in colour and total organic carbon (TOC) were taken place as a result of mineralization of RBCMs. The results revealed that all of these three processes examined were efficient. It was found that about 98% colour and 47% TOC can be removed under photo-Fenton treatment after 8 hours of UV irradiation.Correspondingly, the reaction rates of H(2)O(2) and Fenton systems were slow, but 100% colour and 59% TOC removal of H(2)O(2) process and 100% colour and 67% TOC reductions of Fenton process can be achieved after 72 hours of reaction. The changes of structure and molecular weight/size of RBCMs were also evaluated by HPLC and UV-vis spectroscopic analysis. From the results, some chromophores of RBCMs such as aromatic groups were appeared to be easily degraded to the smaller refractory components. Hence, based on the experimental results and considering the investment and expediency of operation, H(2)O(2) and Fenton oxidation could be suitable technologies for the treatment of the RBCMs derived from P-extraction stage by using H(2)SO(4) leaching. PMID:20183514

  3. Retrocausal models for EPR

    NASA Astrophysics Data System (ADS)

    Corry, Richard

    2015-02-01

    This paper takes up Huw Price's challenge to develop a retrocausal toy model of the Bell-EPR experiment. I develop three such models which show that a consistent, local, hidden-variables interpretation of the EPR experiment is indeed possible, and which give a feel for the kind of retrocausation involved. The first of the models also makes clear a problematic feature of retrocausation: it seems that we cannot interpret the hidden elements of reality in a retrocausal model as possessing determinate dispositions to affect the outcome of experiments. This is a feature which Price has embraced, but Gordon Belot has argued that this feature renders retrocausal interpretations "unsuitable for formal development", and the lack of such determinate dispositions threatens to undermine the motivation for hidden-variables interpretations in the first place. But Price and Belot are both too quick in their assessment. I show that determinate dispositions are indeed consistent with retrocausation. What is more, I show that the ontological economy allowed by retrocausation holds out the promise of a classical understanding of spin and polarization.

  4. Assessment of Lung Function in Asthma and COPD using Hyperpolarized 129Xe Chemical Shift Saturation Recovery Spectroscopy and Dissolved-Phase MR Imaging

    PubMed Central

    Qing, Kun; Mugler, John P.; Altes, Talissa A.; Jiang, Yun; Mata, Jaime F.; Miller, G. Wilson; Ruset, Iulian C.; Hersman, F. William; Ruppert, Kai

    2014-01-01

    Magnetic-resonance spectroscopy and imaging using hyperpolarized xenon-129 show great potential for evaluation of the most important function of the human lung -- gas exchange. In particular, Chemical Shift Saturation Recovery (CSSR) xenon-129 spectroscopy provides important physiological information for the lung as a whole by characterizing the dynamic process of gas exchange, while dissolved-phase xenon-129 imaging captures the time-averaged regional distribution of gas uptake by lung tissue and blood. Herein, we present recent advances in assessing lung function using CSSR spectroscopy and dissolved-phase imaging in a total of 45 subjects (23 healthy, 13 chronic obstructive pulmonary disease (COPD) and 9 asthma). From CSSR acquisitions, the COPD subjects showed red blood cell to tissue/plasma (RBC-to-TP) ratios below the average for the healthy subjects (p<0.001), but significantly higher septal wall thicknesses, as compared with the healthy subjects (p<0.005); the RBC-to-TP ratios for the asthmatics fell outside 2 standard deviations (either higher or lower) from the mean of the healthy subjects although there was no statistically significant difference for the average ratio of the study group as a whole. Similarly, from the 3D DP imaging acquisitions, we found all the ratios (TP-to-GP, RBC-to-GP, RBC-to-TP) measured in the COPD subjects were lower than those from the healthy subjects (p<0.05 for all ratios), while these ratios in the asthmatics differed considerably between subjects. Despite having been performed at different lung inflation levels, the RBC-to-TP ratios measured by CSSR and 3D DP imaging were fairly consistent with each other, with a mean difference of 0.037 (ratios from 3D DP imaging larger). In ten subjects the RBC-to-GP ratios obtained from the 3D DP imaging acquisitions were also highly correlated with their DLCO/Va ratios measured by pulmonary function testing (R=0.91). PMID:25146558

  5. Saturation meter

    DOEpatents

    Gregurech, S.

    1984-08-01

    A saturation meter for use in a pressurized water reactor plant comprising a differential pressure transducer having a first and second pressure sensing means and an alarm. The alarm is connected to the transducer and is preset to activate at a level of saturation prior to the formation of a steam void in the reactor vessel.

  6. EPR, Biology, and Consciousness

    NASA Astrophysics Data System (ADS)

    Goradia, Shantilal

    2006-03-01

    It seems that Darwin, in his concluding remark (1859, p490) ruled out the possibility of cosmic connection to evolution based on the fixed law of gravity, known then. More recent Dirac’s Large Number Hypothesis as described in http://www.arXiv.org/pdf/physics/0210040 v1 raises a possibility that the universal constant of gravity is decreasing and all coupling constants are increasing with time, so reported by some observations. Deeper investigation of the connection between evolution and the variation of the universal constant of gravity seems worthwhile to see if it impacts the passage of time in a stronger (gravitational according to the spirit of the above archive) field and affects the aging process, and explains locality and causality in random evolutionary mutations. If there is no physical locality and causality consistent with the special theory of relativity, there must be some spiritual locality and causality at superluminal speeds to explain the implicit hidden variables. Then there is a question of how to test spiritual locality and causality. Psychic effects and dream signals look promising, if they exist and can be tested with space age technology. This is neither about religion nor about Einstein’s orthodoxy in light of the spirit of EPR. This is about frontiers of science of the new millennium: biology, and consciousness.

  7. Using spin-label W-band EPR to study membrane fluidity profiles in samples of small volume

    NASA Astrophysics Data System (ADS)

    Mainali, Laxman; Hyde, James S.; Subczynski, Witold K.

    2013-01-01

    Conventional and saturation-recovery (SR) EPR at W-band (94 GHz) using phosphatidylcholine spin labels (labeled at the alkyl chain [n-PC] and headgroup [T-PC]) to obtain profiles of membrane fluidity has been demonstrated. Dimyristoylphosphatidylcholine (DMPC) membranes with and without 50 mol% cholesterol have been studied, and the results have been compared with similar studies at X-band (9.4 GHz) (L. Mainali, J.B. Feix, J.S. Hyde, W.K. Subczynski, J. Magn. Reson. 212 (2011) 418-425). Profiles of the spin-lattice relaxation rate (T1-1) obtained from SR EPR measurements for n-PCs and T-PC were used as a convenient quantitative measure of membrane fluidity. Additionally, spectral analysis using Freed's MOMD (microscopic-order macroscopic-disorder) model (E. Meirovitch, J.H. Freed J. Phys. Chem. 88 (1984) 4995-5004) provided rotational diffusion coefficients (R⊥ and R||) and order parameters (S0). Spectral analysis at X-band provided one rotational diffusion coefficient, R⊥. T1-1, R⊥, and R|| profiles reflect local membrane dynamics of the lipid alkyl chain, while the order parameter shows only the amplitude of the wobbling motion of the lipid alkyl chain. Using these dynamic parameters, namely T1-1, R⊥, and R||, one can discriminate the different effects of cholesterol at different depths, showing that cholesterol has a rigidifying effect on alkyl chains to the depth occupied by the rigid steroid ring structure and a fluidizing effect at deeper locations. The nondynamic parameter, S0, shows that cholesterol has an ordering effect on alkyl chains at all depths. Conventional and SR EPR measurements with T-PC indicate that cholesterol has a fluidizing effect on phospholipid headgroups. EPR at W-band provides more detailed information about the depth-dependent dynamic organization of the membrane compared with information obtained at X-band. EPR at W-band has the potential to be a powerful tool for studying membrane fluidity in samples of small volume, ˜30 n

  8. Migration from a prototype ePR for IA-MISS system to alpha version

    NASA Astrophysics Data System (ADS)

    Documet, Jorge R.; Le, Anh; Liu, Brent J.

    2010-03-01

    Last year we presented a paper that describes the design and clinical implementation of an ePR (Electronic Patient Record) system for Image-Assisted Minimally Invasive Spinal Surgery (IA-MISS). The goal of this ePR is to improve the workflow efficiency by providing all the necessary data of a surgical procedure from the preparation stage until the recovery stage. The mentioned ePR has been implemented and installed clinically and it has been in use for more than 16 months. In this paper, we will describe the migration process from a prototype version of the system to a more stable and easily-to-replicate alpha version.

  9. Planar microresonators for EPR experiments.

    PubMed

    Narkowicz, R; Suter, D; Stonies, R

    2005-08-01

    EPR resonators on the basis of standing-wave cavities are optimised for large samples. For small samples it is possible to design different resonators that have much better power handling properties and higher sensitivity. Other parameters being equal, the sensitivity of the resonator can be increased by minimising its size and thus increasing the filling factor. Like in NMR, it is possible to use lumped elements; coils can confine the microwave field to volumes that are much smaller than the wavelength. We discuss the design and evaluation of EPR resonators on the basis of planar microcoils. Our test resonators, which operate at a frequency of 14 GHz, have excellent microwave efficiency factors, achieving 24 ns pi/2 EPR pulses with an input power of 17 mW. The sensitivity tests with DPPH samples resulted in the sensitivity value 2.3 x 10(9) spins.G(-1) Hz(-1/2) at 300 K. PMID:15939642

  10. Planar microresonators for EPR experiments

    NASA Astrophysics Data System (ADS)

    Narkowicz, R.; Suter, D.; Stonies, R.

    2005-08-01

    EPR resonators on the basis of standing-wave cavities are optimised for large samples. For small samples it is possible to design different resonators that have much better power handling properties and higher sensitivity. Other parameters being equal, the sensitivity of the resonator can be increased by minimising its size and thus increasing the filling factor. Like in NMR, it is possible to use lumped elements; coils can confine the microwave field to volumes that are much smaller than the wavelength. We discuss the design and evaluation of EPR resonators on the basis of planar microcoils. Our test resonators, which operate at a frequency of 14 GHz, have excellent microwave efficiency factors, achieving 24 ns π/2 EPR pulses with an input power of 17 mW. The sensitivity tests with DPPH samples resulted in the sensitivity value 2.3 × 10 9 spins · G -1Hz -1/2 at 300 K.

  11. EPR and (57)Fe ENDOR investigation of 2Fe ferredoxins from Aquifex aeolicus.

    PubMed

    Cutsail, George E; Doan, Peter E; Hoffman, Brian M; Meyer, Jacques; Telser, Joshua

    2012-12-01

    We have employed EPR and a set of recently developed electron nuclear double resonance (ENDOR) spectroscopies to characterize a suite of [2Fe-2S] ferredoxin clusters from Aquifex aeolicus (Aae Fd1, Fd4, and Fd5). Antiferromagnetic coupling between the Fe(II), S = 2, and Fe(III), S = 5/2, sites of the [2Fe-2S](+) cluster in these proteins creates an S = 1/2 ground state. A complete discussion of the spin-Hamiltonian contributions to g includes new symmetry arguments along with references to related FeS model compounds and their symmetry and EPR properties. Complete (57)Fe hyperfine coupling (hfc) tensors for each iron, with respective orientations relative to g, have been determined by the use of "stochastic" continuous wave and/or "random hopped" pulsed ENDOR, with the relative utility of the two approaches being emphasized. The reported hyperfine tensors include absolute signs determined by a modified pulsed ENDOR saturation and recovery (PESTRE) technique, RD-PESTRE-a post-processing protocol of the "raw data" that comprises an ENDOR spectrum. The (57)Fe hyperfine tensor components found by ENDOR are nicely consistent with those previously found by Mössbauer spectroscopy, while accurate tensor orientations are unique to the ENDOR approach. These measurements demonstrate the capabilities of the newly developed methods. The high-precision hfc tensors serve as a benchmark for this class of FeS proteins, while the variation in the (57)Fe hfc tensors as a function of symmetry in these small FeS clusters provides a reference for higher-nuclearity FeS clusters, such as those found in nitrogenase. PMID:22872138

  12. Selective fermentation of carbohydrate and protein fractions of Scenedesmus, and biohydrogenation of its lipid fraction for enhanced recovery of saturated fatty acids.

    PubMed

    Lai, YenJung Sean; Parameswaran, Prathap; Li, Ang; Aguinaga, Alyssa; Rittmann, Bruce E

    2016-02-01

    Biofuels derived from microalgae have promise as carbon-neutral replacements for petroleum. However, difficulty extracting microalgae-derived lipids and the co-extraction of non-lipid components add major costs that detract from the benefits of microalgae-based biofuel. Selective fermentation could alleviate these problems by managing microbial degradation so that carbohydrates and proteins are hydrolyzed and fermented, but lipids remain intact. We evaluated selective fermentation of Scenedesmus biomass in batch experiments buffered at pH 5.5, 7, or 9. Carbohydrates were fermented up to 45% within the first 6 days, protein fermentation followed after about 20 days, and lipids (measured as fatty acid methyl esters, FAME) were conserved. Fermentation of the non-lipid components generated volatile fatty acids, with acetate, butyrate, and propionate being the dominant products. Selective fermentation of Scenedesmus biomass increased the amount of extractable FAME and the ratio of FAME to crude lipids. It also led to biohydrogenation of unsaturated FAME to more desirable saturated FAME (especially to C16:0 and C18:0), and the degree of saturation was inversely related to the accumulation of hydrogen gas after fermentation. Moreover, the microbial communities after selective fermentation were enriched in bacteria from families known to perform biohydrogenation, i.e., Porphyromonadaceae and Ruminococcaceae. Thus, this study provides proof-of-concept that selective fermentation can improve the quantity and quality of lipids that can be extracted from Scenedesmus. PMID:26222672

  13. Distributed Saturation

    NASA Technical Reports Server (NTRS)

    Chung, Ming-Ying; Ciardo, Gianfranco; Siminiceanu, Radu I.

    2007-01-01

    The Saturation algorithm for symbolic state-space generation, has been a recent break-through in the exhaustive veri cation of complex systems, in particular globally-asyn- chronous/locally-synchronous systems. The algorithm uses a very compact Multiway Decision Diagram (MDD) encoding for states and the fastest symbolic exploration algo- rithm to date. The distributed version of Saturation uses the overall memory available on a network of workstations (NOW) to efficiently spread the memory load during the highly irregular exploration. A crucial factor in limiting the memory consumption during the symbolic state-space generation is the ability to perform garbage collection to free up the memory occupied by dead nodes. However, garbage collection over a NOW requires a nontrivial communication overhead. In addition, operation cache policies become critical while analyzing large-scale systems using the symbolic approach. In this technical report, we develop a garbage collection scheme and several operation cache policies to help on solving extremely complex systems. Experiments show that our schemes improve the performance of the original distributed implementation, SmArTNow, in terms of time and memory efficiency.

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

    PubMed

    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. PMID:26295168

  15. A cryogenic receiver for EPR.

    PubMed

    Narkowicz, R; Ogata, H; Reijerse, E; Suter, D

    2013-12-01

    Cryogenic probes have significantly increased the sensitivity of NMR. Here, we present a compact EPR receiver design capable of cryogenic operation. Compared to room temperature operation, it reduces the noise by a factor of ≈2.5. We discuss in detail the design and analyze the resulting noise performance. At low microwave power, the input noise density closely follows the emission of a cooled 50Ω resistor over the whole measurement range from 20K up to room temperature. To minimize the influence of the microwave source noise, we use high microwave efficiency (≈1.1-1.7mTW(-1/2)) planar microresonators. Their efficient conversion of microwave power to magnetic field permits EPR measurements with very low power levels, typically ranging from a few μW down to fractions of nW. PMID:24161681

  16. Protein rotational dynamics investigated with a dual EPR/optical molecular probe. Spin-labeled eosin.

    PubMed Central

    Cobb, C E; Hustedt, E J; Beechem, J M; Beth, A H

    1993-01-01

    An acyl spin-label derivative of 5-aminoeosin (5-SLE) was chemically synthesized and employed in studies of rotational dynamics of the free probe and of the probe when bound noncovalently to bovine serum albumin using the spectroscopic techniques of fluorescence anisotropy decay and electron paramagnetic resonance (EPR) and their long-lifetime counterparts phosphorescence anisotropy decay and saturation transfer EPR. Previous work (Beth, A. H., Cobb, C. E., and J. M. Beechem, 1992. Synthesis and characterization of a combined fluorescence, phosphorescence, and electron paramagnetic resonance probe. Society of Photo-Optical Instrumentation Engineers. Time-Resolved Laser Spectroscopy III. 504-512) has shown that the spin-label moiety only slightly altered the fluorescence and phosphorescence lifetimes and quantum yields of 5-SLE when compared with 5-SLE whose nitroxide had been reduced with ascorbate and with the diamagnetic homolog 5-acetyleosin. In the present work, we have utilized time-resolved fluorescence anisotropy decay and linear EPR spectroscopies to observe and quantitate the psec motions of 5-SLE in solution and the nsec motions of the 5-SLE-bovine serum albumin complex. Time-resolved phosphorescence anisotropy decay and saturation transfer EPR studies have been carried out to observe and quantitate the microseconds motions of the 5-SLE-albumin complex in glycerol/buffer solutions of varying viscosity. These latter studies have enabled a rigorous comparison of rotational correlation times obtained from these complementary techniques to be made with a single probe. The studies described demonstrate that it is possible to employ a single molecular probe to carry out the full range of fluorescence, phosphorescence, EPR, and saturation transfer EPR studies. It is anticipated that "dual" molecular probes of this general type will significantly enhance capabilities for extracting dynamics and structural information from macromolecules and their functional

  17. EPR-based material modelling of soils

    NASA Astrophysics Data System (ADS)

    Faramarzi, Asaad; Alani, Amir M.

    2013-04-01

    In the past few decades, as a result of the rapid developments in computational software and hardware, alternative computer aided pattern recognition approaches have been introduced to modelling many engineering problems, including constitutive modelling of materials. The main idea behind pattern recognition systems is that they learn adaptively from experience and extract various discriminants, each appropriate for its purpose. In this work an approach is presented for developing material models for soils based on evolutionary polynomial regression (EPR). EPR is a recently developed hybrid data mining technique that searches for structured mathematical equations (representing the behaviour of a system) using genetic algorithm and the least squares method. Stress-strain data from triaxial tests are used to train and develop EPR-based material models for soil. The developed models are compared with some of the well-known conventional material models and it is shown that EPR-based models can provide a better prediction for the behaviour of soils. The main benefits of using EPR-based material models are that it provides a unified approach to constitutive modelling of all materials (i.e., all aspects of material behaviour can be implemented within a unified environment of an EPR model); it does not require any arbitrary choice of constitutive (mathematical) models. In EPR-based material models there are no material parameters to be identified. As the model is trained directly from experimental data therefore, EPR-based material models are the shortest route from experimental research (data) to numerical modelling. Another advantage of EPR-based constitutive model is that as more experimental data become available, the quality of the EPR prediction can be improved by learning from the additional data, and therefore, the EPR model can become more effective and robust. The developed EPR-based material models can be incorporated in finite element (FE) analysis.

  18. A simplified apparatus for EPR imaging

    NASA Astrophysics Data System (ADS)

    Jingchuan, Deng; Kuixiang, Wang; Weiqing, Xu

    1996-06-01

    A simple apparatus for sub-surface electron paramagnetic resonance (EPR) imaging of a cut sample is described. A two-dimensional EPR image corresponding to the electron spin-density distribution of the DPPH test sample has been obtained by using a marginally oscillating self-detecting microwave frequency EPR spectrometer. Higher spatial resolution is obtained by using a deconvolution algorithm and the image processing technique of inverse filtering.

  19. Saturated fat (image)

    MedlinePlus

    ... saturated fats. Vegetable sources of saturated fat include coconut and palm oils. When looking at a food ... saturated fats. Vegetable sources of saturated fat include coconut and palm oils. When looking at a food ...

  20. EPR techniques for space biodosimetry

    SciTech Connect

    Haskell, E.; Hayes, R.; Kenner, G.; Sholom, S.; Chumak, V.

    1996-12-31

    Retrospective dosimetry of tooth enamel has become an increasingly complex and difficult discipline to undertake while still attaining accuracy. The paper provides a review of the major obstacles, advances and pertinent phenomenon associated with low level retrospective dosimetry of human tooth enamel. Also covered is the many sources of error in EPR dosimetry, their potential solutions, as well as the different analysis and scanning techniques in use with their prospective pros and cons. Prospective directions for new approaches, methods, and instruments are also reviewed.

  1. Overview of LBB implementation for the EPR

    SciTech Connect

    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.

  2. EPR STUDIES OF THERMALLY STERILIZED VASELINUM ALBUM.

    PubMed

    Ramos, Paweł; Pilawa, Barbara

    2015-01-01

    Electron paramagnetic resonance (EPR) spectroscopy was used for examination of free radicals in thermally treated vaselinum album (VA). Thermal treatment in hot air as sterilization process was tested. Conditions of thermal sterilization were chosen according to the pharmaceutical norms. Vaselinum album was heated at the following conditions (T--temperature, t--time): T = 160°C and t = 120 min, T = 170°C and t = 60 min and T = 180°C and t = 30 min. The aim of this work was to determine concentration and free radical properties of thermally sterilized VA. EPR analysis for VA was done 15 min after sterilization. EPR measurements were done at room temperature. EPR spectra were recorded in the range of microwave power of 2.2-70 mW. g-Factor, amplitudes (A) and line width (ΔBpp) of the spectra were determined. The shape of the EPR spectra was analyzed. Free radical concentration (N) in the heated samples was determined. EPR spectra were not obtained for the non heated VA. EPR spectra were detected for all thermally sterilized samples. The spectra revealed complex character, their asymmetry depends on microwave power. The lowest free radicals concentration was found for the VA sterilized at 180°C during 30 min. EPR spectroscopy is proposed as the method useful for optimization of sterilization process of drugs. PMID:26647625

  3. EPR dosimetry in chemically treated fingernails

    Technology Transfer Automated Retrieval System (TEKTRAN)

    By using EPR measurements of radiation-induced radicals it is possible to utilize human fingernails to estimate radiation dose after-the-fact. One of the potentially limiting factors in this approach is the presence of artifacts due to mechanically induced EPR signals (MIS) caused by mechanical str...

  4. Optimization of bicelle lipid composition and temperature for EPR spectroscopy of aligned membranes

    NASA Astrophysics Data System (ADS)

    McCaffrey, Jesse E.; James, Zachary M.; Thomas, David D.

    2015-01-01

    We have optimized the magnetic alignment of phospholipid bilayered micelles (bicelles) for EPR spectroscopy, by varying lipid composition and temperature. Bicelles have been extensively used in NMR spectroscopy for several decades, in order to obtain aligned samples in a near-native membrane environment and take advantage of the intrinsic sensitivity of magnetic resonance to molecular orientation. Recently, bicelles have also seen increasing use in EPR, which offers superior sensitivity and orientational resolution. However, the low magnetic field strength (less than 1 T) of most conventional EPR spectrometers results in homogeneously oriented bicelles only at a temperature well above physiological. To optimize bicelle composition for magnetic alignment at reduced temperature, we prepared bicelles containing varying ratios of saturated (DMPC) and unsaturated (POPC) phospholipids, using EPR spectra of a spin-labeled fatty acid to assess alignment as a function of lipid composition and temperature. Spectral analysis showed that bicelles containing an equimolar mixture of DMPC and POPC homogeneously align at 298 K, 20 K lower than conventional DMPC-only bicelles. It is now possible to perform EPR studies of membrane protein structure and dynamics in well-aligned bicelles at physiological temperatures and below.

  5. Saturated fat (image)

    MedlinePlus

    Saturated fat can raise blood cholesterol and can put you at risk for heart disease and stroke. You should ... limit any foods that are high in saturated fat. Sources of saturated fat include whole-milk dairy ...

  6. In Vivo EPR For Dosimetry

    PubMed Central

    Swartz, Harold M.; Burke, Greg; Coey, M.; Demidenko, Eugene; Dong, Ruhong; Grinberg, Oleg; Hilton, James; Iwasaki, Akinori; Lesniewski, Piotr; Kmiec, Maciej; Lo, Kai-Ming; Nicolalde, R. Javier; Ruuge, Andres; Sakata, Yasuko; Sucheta, Artur; Walczak, Tadeusz; Williams, Benjamin B.; Mitchell, Chad; Romanyukha, Alex; Schauer, David A.

    2007-01-01

    As a result of terrorism, accident, or war, populations potentially can be exposed to doses of ionizing radiation that could cause direct clinical effects within days or weeks. There is a critical need to determine the magnitude of the exposure to individuals so that those with significant risk have appropriate procedures initiated immediately, while those without a significant probability of acute effects can be reassured and removed from the need for further consideration in the medical/emergency system. In many of the plausible scenarios there is an urgent need to make the determination very soon after the event and while the subject is still present. In vivo EPR measurements of radiation-induced changes in the enamel of teeth is a method, perhaps the only such method, which can differentiate among doses sufficiently for classifying individuals into categories for treatment with sufficient accuracy to facilitate decisions on medical treatment. In its current state, the in vivo EPR dosimeter can provide estimates of absorbed dose with an error approximately ± 50 cGy over the range of interest for acute biological effects of radiation, assuming repeated measurements of the tooth in the mouth of the subject. The time required for acquisition, the lower limit, and the precision are expected to improve, with improvements in the resonator and the algorithm for acquiring and calculating the dose. The magnet system that is currently used, while potentially deployable, is somewhat large and heavy, requiring that it be mounted on a small truck or trailer. Several smaller magnets, including an intraoral magnet are under development, which would extend the ease of use of this technique. PMID:18591988

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

    PubMed

    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. PMID:24968092

  8. Shared experience in 13 local Danish EPR projects: the Danish EPR Observatory.

    PubMed

    Nøhr, C; Kristensen, M; Andersen, S K; Vingtoft, S; Lippert, S; Berstein, K; Bruun-Rasmussen, M

    2001-01-01

    In 1996 a national strategy for the development of electronic patient records (EPR) for the Danish hospitals and primary care was launched. An element in the strategy was to support a number of regional EPR development projects. The EPR-Observatory has in the two recent years collected data from the regional projects, dealing with the expectations in four areas: 1) Impact on organisational issues, 2) Benefits of EPR, 3) Integration of EPR with other information systems and 4) security aspects of EPR. Among the observations an increasing teamwork and im-proved knowledge about the patient was found. What was expected, but not found, was resistance to EPR, as a result of changes in skills and power. The most obvious benefits are increased data accessibility and improved decision ma-king. The most considerable disadvantage is an enormous growth in discontent with the systems performance and the fact, that all the projects are delayed. Many different types of integration solutions are chosen, because of a lack of a common model for integration. Generally the projects find, that EPJ yields increased security, but logistical problems arise in having the systems running 24 hours 7 days a week. Economical benefits cannot be documented. This relates to the fact, that the regional projects are stand-alone projects. The ongoing growth in discontent with the EPR-systems and the fact, that all the projects are delayed must be subject to further exploration. PMID:11604822

  9. EPR study of free radicals in bread

    NASA Astrophysics Data System (ADS)

    Yordanov, Nicola D.; Mladenova, Ralitsa

    2004-05-01

    The features of the recorded EPR spectra of paramagnetic species formed in bread and rusk are reported. The appearance of free radicals in them is only connected with their thermal treatment since the starting materials (flour and grains) exhibit very weak EPR signal. The obtained EPR spectra are complex and indicate that: (i) the relative number of paramagnetic species depends on the temperature and treating time of the raw product; (ii) the g-values are strongly temperature dependent with a tendency to coincide at t≥220 °C. Because of the relatively low (150-220 °C) temperature of thermal treatment, the studied free radicals can be assumed to appear in the course of the browning (Maillard) reaction and not to the carbonization of the material.

  10. Can EPR non-locality be geometrical?

    SciTech Connect

    Ne`eman, Y. |; Botero, A.

    1995-10-01

    The presence in Quantum Mechanics of non-local correlations is one of the two fundamentally non-intuitive features of that theory. The non-local correlations themselves fall into two classes: EPR and Geometrical. The non-local characteristics of the geometrical type are well-understood and are not suspected of possibly generating acausal features, such as faster-than-light propagation of information. This has especially become true since the emergence of a geometrical treatment for the relevant gauge theories, i.e. Fiber Bundle geometry, in which the quantum non-localities are seen to correspond to pure homotopy considerations. This aspect is reviewed in section 2. Contrary-wise, from its very conception, the EPR situation was felt to be paradoxical. It has been suggested that the non-local features of EPR might also derive from geometrical considerations, like all other non-local characteristics of QM. In[7], one of the authors was able to point out several plausibility arguments for this thesis, emphasizing in particular similarities between the non-local correlations provided by any gauge field theory and those required by the preservation of the quantum numbers of the original EPR state-vector, throughout its spatially-extended mode. The derivation was, however, somewhat incomplete, especially because of the apparent difference between, on the one hand, the closed spatial loops arising in the analysis of the geometrical non-localities, from Aharonov-Bohm and Berry phases to magnetic monopoles and instantons, and on the other hand, in the EPR case, the open line drawn by the positions of the two moving decay products of the disintegrating particle. In what follows, the authors endeavor to remove this obstacle and show that as in all other QM non-localities, EPR is somehow related to closed loops, almost involving homotopy considerations. They develop this view in section 3.

  11. Biophysical EPR Studies Applied to Membrane Proteins

    PubMed Central

    Sahu, Indra D; Lorigan, Gary A

    2015-01-01

    Membrane proteins are very important in controlling bioenergetics, functional activity, and initializing signal pathways in a wide variety of complicated biological systems. They also represent approximately 50% of the potential drug targets. EPR spectroscopy is a very popular and powerful biophysical tool that is used to study the structural and dynamic properties of membrane proteins. In this article, a basic overview of the most commonly used EPR techniques and examples of recent applications to answer pertinent structural and dynamic related questions on membrane protein systems will be presented. PMID:26855825

  12. Barium dithionate as an EPR dosemeter.

    PubMed

    Baran, M P; Bugay, O A; Kolesnik, S P; Maksimenko, V M; Teslenko, V V; Petrenko, T L; Desrosiers, M F

    2006-01-01

    Electron paramagnetic resonance (EPR) dosimetry is growing in popularity and this success has encouraged the search for other dosimetric materials. Previous studies of gamma-irradiated barium dithionate (BaS(2)O(6) x 2H(2)O) have shown promise for its use as a radiation dosemeter. This work studies in greater detail several essential attributes of the system. Special attention has been directed to the study of EPR response dependences on microwave power, irradiation temperature, minimum detectable dose and post-irradiation stability. PMID:16565205

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

    PubMed

    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. PMID:24423509

  14. Preparation of EPR/silica filler by a co-irradiation method forming PP/EPR/silica nanocomposites

    NASA Astrophysics Data System (ADS)

    Qian, Jun; Dang, Shuaiying; Huang, Zhijuan; Xu, Yongshen

    2012-01-01

    This paper presents a novel approach to prepare ethylene-propylene rubber (EPR)/silica filler by co-irradiation method forming polypropylene (PP)/EPR/silica nanocomposites. The grafting of maleic anhydride (MAH) on EPR was first studied by co-irradiation in the micro-suspension without any chemical initiator, and the effects of MAH concentration and the total co-irradiation dose on the graft degree of MAH were investigated. Then PP/EPR/silica nanocomposites were successfully prepared by blending of PP matrix and EPR/silica filler, which was obtained by co-irradiation using a mixture of EPR/MAH microsuspension in xylene and tetraethoxysilane/KH560 sol in formic acid. FTIR and SEM results showed that the reactions between MAH on EPR chains and KH560 surrounding silica particles were adopted to form the EPR/silica filler with strong bonding and well silica dispersion. Mechanical properties of PP/EPR/silica nanocomposites with different silica contents and the comparisons with PP, PP/EPR and PP/silica films were studied. The rigid silica particles were trapped in EPR shell and well dispersed in PP/EPR/silica nanocomposites with good compatibility and strong interfacial adhesion, achieving overall improvements in stiffness, strength and toughness compared with pure PP.

  15. Advanced tool kits for EPR security.

    PubMed

    Blobel, B

    2000-11-01

    Responding to the challenge for efficient and high quality health care, the shared care paradigm must be established in health. In that context, information systems such as electronic patient records (EPR) have to meet this paradigm supporting communication and interoperation between the health care establishments (HCE) and health professionals (HP) involved. Due to the sensitivity of personal medical information, this co-operation must be provided in a trustworthy way. To enable different views of HCE and HP ranging from management, doctors, nurses up to systems administrators and IT professionals, a set of models for analysis, design and implementation of secure distributed EPR has been developed and introduced. The approach is based on the popular UML methodology and the component paradigm for open, interoperable systems. Easy to use tool kits deal with both application security services and communication security services but also with the security infrastructure needed. Regarding the requirements for distributed multi-user EPRs, modelling and implementation of policy agreements, authorisation and access control are especially considered. Current developments for a security infrastructure in health care based on cryptographic algorithms as health professional cards (HPC), security services employing digital signatures, and health-related TTP services are discussed. CEN and ISO initiatives for health informatics standards in the context of secure and communicable EPR are especially mentioned. PMID:11154968

  16. Clinical EPR: Unique Opportunities and Some Challenges

    PubMed Central

    Swartz, Harold M.; Williams, Benjamin B.; Zaki, Bassem I.; Hartford, Alan C.; Jarvis, Lesley A.; Chen, Eunice; Comi, Richard J.; Ernstoff, Marc S.; Hou, Huagang; Khan, Nadeem; Swarts, Steven G.; Flood, Ann B.; Kuppusamy, Periannan

    2014-01-01

    Electron paramagnetic resonance (EPR) spectroscopy has been well established as a viable technique for measurement of free radicals and oxygen in biological systems, from in vitro cellular systems to in vivo small animal models of disease. However, the use of EPR in human subjects in the clinical setting, although attractive for a variety of important applications such as oxygen measurement, is challenged with several factors including the need for instrumentation customized for human subjects, probe and regulatory constraints. This paper describes the rationale and development of the first clinical EPR systems for two important clinical applications, namely, measurement of tissue oxygen (oximetry), and radiation dose (dosimetry) in humans. The clinical spectrometers operate at 1.2 GHz frequency and use surface loop resonators capable of providing topical measurements up to 1 cm depth in tissues. Tissue pO2 measurements can be carried out noninvasively and repeatedly after placement of an oxygen-sensitive paramagnetic material (currently India ink) at the site of interest. Our EPR dosimetry system is capable of measuring radiation-induced free radicals in the tooth of irradiated human subjects to determine the exposure dose. These developments offer potential opportunities for clinical dosimetry and oximetry, which include guiding therapy for individual patients with tumors or vascular disease, by monitoring of tissue oxygenation. Further work is in progress to translate this unique technology to routine clinical practice. PMID:24439333

  17. EPR: What has it taught us

    NASA Astrophysics Data System (ADS)

    Stapp, H. P.

    1985-05-01

    Eistein, Podoisky, and Rosen (EPR) paper is discussed. The EPR paper was counterproductive for the following reasons: (1) the work was quickly rebutted by Bohr and this rebuttal was accepted my most workers in the field; (2) scientists who adopted the position advocated by Bohr produced, useful theory, whereas those following the course suggested by EPR produced nothing of any certified practical value; (3) it was shown by Bell that the conclusion reached by EPR is incompatible with their assumptions. 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 was investigated. Because these systems are neither small enough to be treated as isolated between preparation and detection, nor large enough to be treated classically, they do not conform to the format demanded by the Copenhagen interpretation. 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. The task of enlarging the scope of quantum theory to cover these new situations, and comparing the empirical consequences of various ontological assumptions is discussed.

  18. Investigation of EPR signals on tooth enamel

    NASA Astrophysics Data System (ADS)

    Pavlenko, A.; Mironova-Ulmane, N.; Polakov, M.; Riekstina, D.

    2007-12-01

    Calcified tissues are involved in continues metabolic process in human organism exchanging a number of chemical elements with environment. The rate of biochemical reactions is tissue dependent and the slowest one at the tooth enamel, the most mineralized tissue of human organism. The long time stability and unique chemical composition make tooth enamel suitable for number of application. The assessment of individual radiation dose by Electron Paramagnetic Resonance (EPR) and evaluations of elemental composition by Instrumentation Neutron Activation Analysis (INAA) are the well known procedures where properties of tooth enamel intensively used. The current work is focused on investigation of EPR signals and determination of chemical composition on several teeth samples having different origin. The EPR spectra and INAA element content of milk tooth, caries tooth, and paradantose tooth have been compared to each other. The results showed that the intensity of EPR signal is much higher for the caries tooth than the for paradantose tooth that is in agreement with depleted Ca content.

  19. CORE SATURATION BLOCKING OSCILLATOR

    DOEpatents

    Spinrad, R.J.

    1961-10-17

    A blocking oscillator which relies on core saturation regulation to control the output pulse width is described. In this arrangement an external magnetic loop is provided in which a saturable portion forms the core of a feedback transformer used with the thermionic or semi-conductor active element. A first stationary magnetic loop establishes a level of flux through the saturation portion of the loop. A second adjustable magnet moves the flux level to select a saturation point giving the desired output pulse width. (AEC)

  20. RosettaEPR: An Integrated Tool for Protein Structure Determination from Sparse EPR Data

    PubMed Central

    Hirst, Stephanie J.; Alexander, Nathan; Mchaourab, Hassane S.; Meiler, Jens

    2010-01-01

    Site-directed spin labeling electron paramagnetic resonance (SDSL-EPR) is often used for the structural characterization of proteins that elude other techniques, such as X-ray crystallography and nuclear magnetic resonance (NMR). However, high-resolution structures are difficult to obtain due to uncertainty in the spin label location and sparseness of experimental data. Here, we introduce RosettaEPR, which has been designed to improve de novo high-resolution protein structure prediction using sparse SDSL-EPR distance data. The “motion-on-a-cone” spin label model is converted into a knowledge-based potential, which was implemented as a scoring term in Rosetta. RosettaEPR increased the fractions of correctly folded models (RMSDCα < 7.5Å) and models accurate at medium resolution (RMSDCα < 3.5Å) by 25%. The correlation of score and model quality increased from 0.42 when using no restraints to 0.51 when using bounded restraints and again to 0.62 when using RosettaEPR. This allowed for the selection of accurate models by score. After full-atom refinement, RosettaEPR yielded a 1.7Å model of T4-lysozyme, thus indicating that atomic detail models can be achieved by combining sparse EPR data with Rosetta. While these results indicate RosettaEPR’s potential utility in high-resolution protein structure prediction, they are based on a single example. In order to affirm the method’s general performance, it must be tested on a larger and more versatile dataset of proteins. PMID:21029778

  1. Critical condensate saturation in porous media

    SciTech Connect

    Wang, X.; Mohanty, K.K.

    1999-06-15

    The understanding of gas and condensate flow in porous media is critical to the optimum exploitation of gas-condensate reservoirs. Critical condensate saturation and relative permeabilities are the key parameters for the evaluation of possible recovery strategies. This work is aimed at developing a mechanistic network model for the critical condensate saturation in which phase trapping and connectivity in the pore corners are critically examined. Porous media are modeled by networks of pore bodies interconnected by pore throats. Bodies and throats are characterized by their connectivity, shapes, and radii distributions. Pore-level laws are identified from micromodel experiments with near-critical fluids. A nonzero critical condensate saturation can be obtained in the absence of contact angle hysteresis due to the converging-diverging nature of the throats. The critical saturation at which the condensate flows is found to be a function of pore geometry, water saturation, and interfacial tension (or the Bond number). The modified sphere-pack model underpredicts the critical condensate saturation of typical sandstones. The cubic model adequately predicts the critical saturation and its experimentally observed trends.

  2. Substoichiometry and Saturation Analysis

    ERIC Educational Resources Information Center

    Willett, J. E.; Servant, D. M.

    1977-01-01

    Two experiments are described and appropriate discussion is given to illustrate the use of substoichiometry and saturation analysis techniques with undergraduates. The first experiment is the determination of silver content in photographic film. The second is the estimation of a hormone concentration using saturation analysis and a commercially…

  3. Gluon saturation in a saturated environment

    SciTech Connect

    Kopeliovich, B. Z.; Potashnikova, I. K.; Schmidt, Ivan

    2011-07-15

    A bootstrap equation for self-quenched gluon shadowing leads to a reduced magnitude of broadening for partons propagating through a nucleus. Saturation of small-x gluons in a nucleus, which has the form of transverse momentum broadening of projectile gluons in pA collisions in the nuclear rest frame, leads to a modification of the parton distribution functions in the beam compared with pp collisions. In nucleus-nucleus collisions all participating nucleons acquire enhanced gluon density at small x, which boosts further the saturation scale. Solution of the reciprocity equations for central collisions of two heavy nuclei demonstrate a significant, up to several times, enhancement of Q{sub sA}{sup 2}, in AA compared with pA collisions.

  4. Gluon saturation in a saturated environment

    NASA Astrophysics Data System (ADS)

    Kopeliovich, B. Z.; Potashnikova, I. K.; Schmidt, Ivan

    2011-07-01

    A bootstrap equation for self-quenched gluon shadowing leads to a reduced magnitude of broadening for partons propagating through a nucleus. Saturation of small-x gluons in a nucleus, which has the form of transverse momentum broadening of projectile gluons in pA collisions in the nuclear rest frame, leads to a modification of the parton distribution functions in the beam compared with pp collisions. In nucleus-nucleus collisions all participating nucleons acquire enhanced gluon density at small x, which boosts further the saturation scale. Solution of the reciprocity equations for central collisions of two heavy nuclei demonstrate a significant, up to several times, enhancement of QsA2, in AA compared with pA collisions.

  5. EPR-based material modelling of soils considering volume changes

    NASA Astrophysics Data System (ADS)

    Faramarzi, Asaad; Javadi, Akbar A.; Alani, Amir M.

    2012-11-01

    In this paper an approach is presented for developing material models for soils based on evolutionary polynomial regression (EPR), taking into account its volumetric behaviour. EPR is a recently developed hybrid data mining technique that searches for structured mathematical equations (representing the behaviour of a system) using genetic algorithm and the least squares method. Stress-strain data from triaxial test are used to train and develop EPR-based material models for soil. The developed models are compared with some of the well known conventional material models. In particular, the capability of the developed EPR models in predicting volume change behaviour of soils is illustrated. It is also shown that the developed EPR-based material models can be incorporated in finite element (FE) analysis. Two geotechnical examples are presented to verify the developed EPR-based FE model (EPR-FEM). The results of the EPR-FEM are compared with those of a standard FEM where conventional constitutive models are used to describe the material behaviour. The results show that EPR-FEM can be successfully employed to analyse geotechnical engineering problems. The advantages of the proposed EPR models are highlighted.

  6. EPR Steering inequalities with Communication Assistance

    PubMed Central

    Nagy, Sándor; Vértesi, Tamás

    2016-01-01

    In this paper, we investigate the communication cost of reproducing Einstein-Podolsky-Rosen (EPR) steering correlations arising from bipartite quantum systems. We characterize the set of bipartite quantum states which admits a local hidden state model augmented with c bits of classical communication from an untrusted party (Alice) to a trusted party (Bob). In case of one bit of information (c = 1), we show that this set has a nontrivial intersection with the sets admitting a local hidden state and a local hidden variables model for projective measurements. On the other hand, we find that an infinite amount of classical communication is required from an untrusted Alice to a trusted Bob to simulate the EPR steering correlations produced by a two-qubit maximally entangled state. It is conjectured that a state-of-the-art quantum experiment would be able to falsify two bits of communication this way. PMID:26880376

  7. EPR Investigation of Irradiated Curry Powder

    SciTech Connect

    Duliu, O. G.; Ali, S. I.; Georgescu, R.

    2007-04-23

    Gamma-ray irradiated curry powder, a well priced oriental spice was investigated in order to establish the ability of EPR to detect the presence and time stability of free irradiation free-radicals. Accordingly, curry powder aliquots were irradiated with gradually increasing absorbed doses up to 11.3 kGy. The EPR spectra of all irradiated samples show the presence of al last two different species of free radicals, whose concentration increased monotonously with the absorbed doses. A 100 deg. C isothermal annealing of irradiated samples has shown a differential reduction of amplitude of various components of the 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 more than one year storage at room temperature, all of them being very useful in establishing the existence of any previous irradiation treatment.

  8. EPR Steering inequalities with Communication Assistance

    NASA Astrophysics Data System (ADS)

    Nagy, Sándor; Vértesi, Tamás

    2016-02-01

    In this paper, we investigate the communication cost of reproducing Einstein-Podolsky-Rosen (EPR) steering correlations arising from bipartite quantum systems. We characterize the set of bipartite quantum states which admits a local hidden state model augmented with c bits of classical communication from an untrusted party (Alice) to a trusted party (Bob). In case of one bit of information (c = 1), we show that this set has a nontrivial intersection with the sets admitting a local hidden state and a local hidden variables model for projective measurements. On the other hand, we find that an infinite amount of classical communication is required from an untrusted Alice to a trusted Bob to simulate the EPR steering correlations produced by a two-qubit maximally entangled state. It is conjectured that a state-of-the-art quantum experiment would be able to falsify two bits of communication this way.

  9. Deconvolution of sinusoidal rapid EPR scans.

    PubMed

    Tseitlin, Mark; Rinard, George A; Quine, Richard W; Eaton, Sandra S; Eaton, Gareth R

    2011-02-01

    In rapid scan EPR the magnetic field is scanned through the signal in a time that is short relative to electron spin relaxation times. Previously it was shown that the slow-scan lineshape could be recovered from triangular rapid scans by Fourier deconvolution. In this paper a general Fourier deconvolution method is described and demonstrated to recover the slow-scan lineshape from sinusoidal rapid scans. Since an analytical expression for the Fourier transform of the driving function for a sinusoidal scan was not readily apparent, a numerical method was developed to do the deconvolution. The slow scan EPR lineshapes recovered from rapid triangular and sinusoidal scans are in excellent agreement for lithium phthalocyanine, a trityl radical, and the nitroxyl radical, tempone. The availability of a method to deconvolute sinusoidal rapid scans makes it possible to scan faster than is feasible for triangular scans because of hardware limitations on triangular scans. PMID:21163677

  10. Deconvolution of Sinusoidal Rapid EPR Scans

    PubMed Central

    Tseitlin, Mark; Rinard, George A.; Quine, Richard W.; Eaton, Sandra S.; Eaton, Gareth R.

    2011-01-01

    In rapid scan EPR the magnetic field is scanned through the signal in a time that is short relative to electron spin relaxation times. Previously it was shown that the slow scan lineshape could be recovered from triangular rapid scans by Fourier deconvolution. In this paper a general Fourier deconvolution method is described and demonstrated to recover the slow scan lineshape from sinusoidal rapid scans. Since an analytical expression for the Fourier transform of the driving function for a sinusoidal scan was not readily apparent, a numerical method was developed to do the deconvolution. The slow scan EPR lineshapes recovered from rapid triangular and sinusoidal scans are in excellent agreement for lithium phthalocyanine, a trityl radical, and the nitroxyl radical, tempone. The availability of a method to deconvolute sinusoidal rapid scans makes it possible to scan faster than is feasible for triangular scans because of hardware limitations on triangular scans. PMID:21163677

  11. Bifunctional Spin Labeling of Muscle Proteins: Accurate Rotational Dynamics, Orientation, and Distance by EPR.

    PubMed

    Thompson, Andrew R; Binder, Benjamin P; McCaffrey, Jesse E; Svensson, Bengt; Thomas, David D

    2015-01-01

    While EPR allows for the characterization of protein structure and function due to its exquisite sensitivity to spin label dynamics, orientation, and distance, these measurements are often limited in sensitivity due to the use of labels that are attached via flexible monofunctional bonds, incurring additional disorder and nanosecond dynamics. In this chapter, we present methods for using a bifunctional spin label (BSL) to measure muscle protein structure and dynamics. We demonstrate that bifunctional attachment eliminates nanosecond internal rotation of the spin label, thereby allowing the accurate measurement of protein backbone rotational dynamics, including microsecond-to-millisecond motions by saturation transfer EPR. BSL also allows for accurate determination of helix orientation and disorder in mechanically and magnetically aligned systems, due to the label's stereospecific attachment. Similarly, labeling with a pair of BSL greatly enhances the resolution and accuracy of distance measurements measured by double electron-electron resonance (DEER). Finally, when BSL is applied to a protein with high helical content in an assembly with high orientational order (e.g., muscle fiber or membrane), two-probe DEER experiments can be combined with single-probe EPR experiments on an oriented sample in a process we call BEER, which has the potential for ab initio high-resolution structure determination. PMID:26477249

  12. Self-testing through EPR-steering

    NASA Astrophysics Data System (ADS)

    Šupić, Ivan; Hoban, Matty J.

    2016-07-01

    The verification of quantum devices is an important aspect of quantum information, especially with the emergence of more advanced experimental implementations of quantum computation and secure communication. Within this, the theory of device-independent robust self-testing via Bell tests has reached a level of maturity now that many quantum states and measurements can be verified without direct access to the quantum systems: interaction with the devices is solely classical. However, the requirements for this robust level of verification are daunting and require high levels of experimental accuracy. In this paper we discuss the possibility of self-testing where we only have direct access to one part of the quantum device. This motivates the study of self-testing via EPR-steering, an intermediate form of entanglement verification between full state tomography and Bell tests. Quantum non-locality implies EPR-steering so results in the former can apply in the latter, but we ask what advantages may be gleaned from the latter over the former given that one can do partial state tomography? We show that in the case of self-testing a maximally entangled two-qubit state, or ebit, EPR-steering allows for simpler analysis and better error tolerance than in the case of full device-independence. On the other hand, this improvement is only a constant improvement and (up to constants) is the best one can hope for. Finally, we indicate that the main advantage in self-testing based on EPR-steering could be in the case of self-testing multi-partite quantum states and measurements. For example, it may be easier to establish a tensor product structure for a particular party’s Hilbert space even if we do not have access to their part of the global quantum system.

  13. W-Band Frequency-Swept EPR

    PubMed Central

    Hyde, James S.; Strangeway, Robert A.; Camenisch, Theodore G.; Ratke, Joseph J.; Froncisz, Wojciech

    2010-01-01

    This paper describes a novel experiment on nitroxide radical spin labels using a multiarm EPR W-band bridge with a loop-gap resonator (LGR). We demonstrate EPR spectroscopy of spin labels by linear sweep of the microwave frequency across the spectrum. The high bandwidth of the LGR, about 1 GHz between 3 dB points of the microwave resonance, makes this new experiment possible. A frequency-tunable yttrium iron garnet (YIG) oscillator provides sweep rates as high as 1.8 × 105 GHz/s, which corresponds to 6.3 kT/s in magnetic field-sweep units over a 44 MHz range. Two experimental domains were identified. In the first, linear frequency sweep rates were relatively slow, and pure absorption and pure dispersion spectra were obtained. This appears to be a practical mode of operation at the present level of technological development. The main advantage is the elimination of sinusoidal magnetic field modulation. In the second mode, the frequency is swept rapidly across a portion of the spectrum, and then the frequency sweep is stopped for a readout period; FID signals from a swept line oscillate at a frequency that is the difference between the spectral position of the line in frequency units and the readout position. If there is more than one line, oscillations are superimposed. The sweep rates using the YIG oscillator were too slow, and the portion of the spectrum too narrow to achieve the full EPR equivalent of Fourier transform (FT) NMR. The paper discusses technical advances required to reach this goal. The hypothesis that trapezoidal frequency sweep is an enabling technology for FT EPR is supported by this study. PMID:20462775

  14. W-band frequency-swept EPR.

    PubMed

    Hyde, James S; Strangeway, Robert A; Camenisch, Theodore G; Ratke, Joseph J; Froncisz, Wojciech

    2010-07-01

    This paper describes a novel experiment on nitroxide radical spin labels using a multiarm EPR W-band bridge with a loop-gap resonator (LGR). We demonstrate EPR spectroscopy of spin labels by linear sweep of the microwave frequency across the spectrum. The high bandwidth of the LGR, about 1 GHz between 3 dB points of the microwave resonance, makes this new experiment possible. A frequency-tunable yttrium iron garnet (YIG) oscillator provides sweep rates as high as 1.8x10(5) GHz/s, which corresponds to 6.3 kT/s in magnetic field-sweep units over a 44 MHz range. Two experimental domains were identified. In the first, linear frequency sweep rates were relatively slow, and pure absorption and pure dispersion spectra were obtained. This appears to be a practical mode of operation at the present level of technological development. The main advantage is the elimination of sinusoidal magnetic field modulation. In the second mode, the frequency is swept rapidly across a portion of the spectrum, and then the frequency sweep is stopped for a readout period; FID signals from a swept line oscillate at a frequency that is the difference between the spectral position of the line in frequency units and the readout position. If there is more than one line, oscillations are superimposed. The sweep rates using the YIG oscillator were too slow, and the portion of the spectrum too narrow to achieve the full EPR equivalent of Fourier transform (FT) NMR. The paper discusses technical advances required to reach this goal. The hypothesis that trapezoidal frequency sweep is an enabling technology for FT EPR is supported by this study. PMID:20462775

  15. Tetrabromidocuprates(II)-Synthesis, Structure and EPR.

    PubMed

    Zabel, André; Winter, Alette; Kelling, Alexandra; Schilde, Uwe; Strauch, Peter

    2016-01-01

    Metal-containing ionic liquids (ILs) are of interest for a variety of technical applications, e.g., particle synthesis and materials with magnetic or thermochromic properties. In this paper we report the synthesis of, and two structures for, some new tetrabromidocuprates(II) with several "onium" cations in comparison to the results of electron paramagnetic resonance (EPR) spectroscopic analyses. The sterically demanding cations were used to separate the paramagnetic Cu(II) ions for EPR measurements. The EPR hyperfine structure in the spectra of these new compounds is not resolved, due to the line broadening resulting from magnetic exchange between the still-incomplete separated paramagnetic Cu(II) centres. For the majority of compounds, the principal g values (g‖ and g⊥) of the tensors could be determined and information on the structural changes in the [CuBr₄](2-) anions can be obtained. The complexes have high potential, e.g., as ionic liquids, as precursors for the synthesis of copper bromide particles, as catalytically active or paramagnetic ionic liquids. PMID:27104522

  16. EPR spin labeling measurements of thylakoid membrane fluidity during barley leaf senescence.

    PubMed

    Jajić, Ivan; Wiśniewska-Becker, Anna; Sarna, Tadeusz; Jemioła-Rzemińska, Małgorzata; Strzałka, Kazimierz

    2014-07-15

    Physical properties of thylakoid membranes isolated from barley were investigated by the electron paramagnetic resonance (EPR) spin labeling technique. EPR spectra of stearic acid spin labels 5-SASL and 16-SASL were measured as a function of temperature in secondary barley leaves during natural and dark-induced senescence. Oxygen transport parameter was determined from the power saturation curves of the spin labels obtained in the presence and absence of molecular oxygen at 25°C. Parameters of EPR spectra of both spin labels showed an increase in the thylakoid membrane fluidity during senescence, in the headgroup area of the membrane, as well as in its interior. The oxygen transport parameter also increased with age of barley, indicating easier diffusion of oxygen within the membrane and its higher fluidity. The data are consistent with age-related changes of the spin label parameters obtained directly by EPR spectroscopy. Similar outcome was also observed when senescence was induced in mature secondary barley leaves by dark incubation. Such leaves showed higher membrane fluidity in comparison with leaves of the same age, grown under light conditions. Changes in the membrane fluidity of barley secondary leaves were compared with changes in the levels of carotenoids (car) and proteins, which are known to modify membrane fluidity. Determination of total car and proteins showed linear decrease in their level with senescence. The results indicate that thylakoid membrane fluidity of barley leaves increases with senescence; the changes are accompanied with a decrease in the content of car and proteins, which could be a contributing factor. PMID:24974331

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

    NASA Astrophysics Data System (ADS)

    Yordanov, N. D.; Aleksieva, K.

    2007-06-01

    The shape and time stability of the electron paramagnetic resonance (EPR) spectra of non- and γ-irradiated papaya, melon, cherry and fig samples dehydrated via osmosis are reported. It is shown that non-irradiated samples are generally EPR silent whereas γ-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.

  18. Use of the Frank sequence in pulsed EPR.

    PubMed

    Tseitlin, Mark; Quine, Richard W; Eaton, Sandra S; Eaton, Gareth R; Halpern, Howard J; Ardenkjaer-Larsen, J-H

    2011-04-01

    The Frank polyphase sequence has been applied to pulsed EPR of triarylmethyl radicals at 25 6 MHz (9.1 mT 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. 1.5 mW in the application reported here) relative to standard pulsed EPR. A 0.2 mM aqueous solution of a triarylmethyl radical was studied using a 16 mm diameter cross-loop resonator to isolate the EPR signal detection system from the incident pulses. PMID:21371924

  19. Use of the Frank Sequence in Pulsed EPR

    PubMed Central

    Tseitlin, Mark; Quine, Richard W.; Eaton, Sandra S.; Eaton, Gareth R.; Halpern, Howard J.; Ardenkjaer-Larsen, J.-H.

    2011-01-01

    The Frank polyphase sequence has been applied to pulsed EPR of triarylmethyl radicals at 256 MHz (9.1 mT 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. 1.5 mW in the application reported here) relative to standard pulsed EPR. A 0.2 mM aqueous solution of a triarylmethyl radical was studied using a 16 mm diameter cross loop resonator to isolate the EPR signal detection system from the incident pulses. PMID:21371924

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed Central

    Olczyk, Pawel; Ramos, Pawel; Bernas, Marcin; Komosinska-Vassev, Katarzyna; Stojko, Jerzy; Pilawa, Barbara

    2013-01-01

    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. PMID:23781263

  2. EPR: what has it taught us

    SciTech Connect

    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.

  3. EPR investigations of gamma-irradiated novolacs

    NASA Astrophysics Data System (ADS)

    Schrödner, M.; Wünsche, P.; Lampe, I. v.

    EPR investigations of γ-irradiated phenol, p-chlorophenol, o-chlorophenol, 3,5-dichlorophenol and p-cresol novolac are presented. The elimination of a chlorine atom from the phenolic ring must be assumed in the case of chlorinated novolacs. The corresponding aryl radical could only be detected in the case of 3,5-dichlorophenol novolac in a large amount. Furthermore phenoxy and cyclohexadienyl radicals were found in the spectra. The radiation chemical as well as the resist sensitivity are enhanced by chlorination but there is no definite correlation between them.

  4. Saturation in coupled oscillators

    NASA Astrophysics Data System (ADS)

    Roman, Ahmed; Hanna, James

    2015-03-01

    We consider a weakly nonlinear system consisting of a resonantly forced oscillator coupled to an unforced oscillator. It has long been known that, for quadratic nonlinearities and a 2:1 resonance between the oscillators, a perturbative solution of the dynamics exhibits a phenomenon known as saturation. At low forcing, the forced oscillator responds, while the unforced oscillator is quiescent. Above a critical value of the forcing, the forced oscillator's steady-state amplitude reaches a plateau, while that of the unforced oscillator increases without bound. We show that, contrary to established folklore, saturation is not unique to quadratically nonlinear systems. We present conditions on the form of the nonlinear couplings and resonance that lead to saturation. Our results elucidate a mechanism for localization or diversion of energy in systems of coupled oscillators, and suggest new approaches for the control or suppression of vibrations in engineered systems.

  5. Case Studies in e-RPL and e-PR

    ERIC Educational Resources Information Center

    Cameron, Roslyn; Miller, Allison

    2014-01-01

    The use of ePortfolios for recognition of prior learning (e-RPL) and for professional recognition (e-PR) is slowly gaining in popularity in the VET sector however their use is sporadic across educational sectors, disciplines, educational institutions and professions. Added to this is an array of purposes and types of e-RPL and e-PR models and…

  6. Quantum Encryption Protocol Based on Continuous Variable EPR Correlations

    NASA Astrophysics Data System (ADS)

    He, Guang-Qiang; Zeng, Gui-Hua

    2006-07-01

    A quantum encryption protocol based on Gaussian-modulated continuous variable EPR correlations is proposed. The security is guaranteed by continuous variable EPR entanglement correlations produced by nondegenerate optical parametric amplifier (NOPA). For general beam splitter eavesdropping strategy, the mutual information I(α,epsilon) between Alice and Eve is calculated by employing Shannon information theory. Finally the security analysis is presented.

  7. EPR investigation of some gamma-irradiated excipients

    NASA Astrophysics Data System (ADS)

    Aleksieva, Katerina; Yordanov, Nicola D.

    2012-09-01

    The results of electron paramagnetic resonance (EPR) studies on some excipients: lactose, microcrystalline cellulose (avicel), starch, dioxosilane (aerosil), talc and magnesium stearate before and after gamma-irradiation are reported. Before irradiation, all samples are EPR silent except talc. After gamma-irradiation, they show complex spectra except magnesium stearate, which is EPR silent. Studies show the influence of gamma-irradiation on EPR spectra and stability of gamma-induced radicals. Analysis of the EPR spectrum of gamma-irradiated talc shows that this material is radiation insensitive. Only lactose forms stable-free radicals upon gamma sterilization and can be used for identification of radiation processing for a long time period thereafter.

  8. Pump for Saturated Liquids

    NASA Technical Reports Server (NTRS)

    Elliott, D. G.

    1986-01-01

    Boiling liquids pumped by device based on proven components. Expanding saturated liquid in nozzle and diverting its phases along separate paths in liquid/vapor separator raises pressure of liquid. Liquid cooled in process. Pump makes it unnecessary to pressurize cryogenic liquids in order to pump them. Problems of introducing noncondensable pressurizing gas avoided.

  9. Identification of gamma-irradiated fruit juices by EPR spectroscopy

    NASA Astrophysics Data System (ADS)

    Aleksieva, K. I.; Dimov, K. G.; Yordanov, N. D.

    2014-10-01

    The results of electron paramagnetic resonance (EPR) study on commercially available juices from various fruits and different fruit contents: 25%, 40%, 50%, and 100%, homemade juices, nectars and concentrated fruit syrups, before and after gamma-irradiation are reported. In order to remove water from non- and irradiated samples all juices and nectars were filtered; the solid residue was washed with alcohol and dried at room temperature. Only concentrated fruit syrups were dried for 60 min at 40 °C in a standard laboratory oven. All samples under study show a singlet EPR line with g=2.0025 before irradiation with exception of concentrated fruit syrups, which are EPR silent. Irradiation of juice samples gives rise to complex EPR spectra which gradually transferred to “cellulose-like” EPR spectrum from 25% to 100% fruit content. Concentrated fruit syrups show typical “sugar-like“ spectra due to added saccharides. All EPR spectra are characteristic and can prove radiation treatment. The fading kinetics of radiation-induced EPR signals were studied for a period of 60 days after irradiation.

  10. Capillary saturation and desaturation

    NASA Astrophysics Data System (ADS)

    Hilfer, R.; Armstrong, R. T.; Berg, S.; Georgiadis, A.; Ott, H.

    2015-12-01

    Capillary desaturation experiments produce disconnected (trapped) ganglia of mesoscopic sizes intermediate between pore size and system size. Experimental evidence for interactions between these mesoscale clusters during desaturation is analyzed and discussed within the established microscopic and macroscopic laws of Newton, Young-Laplace, and Darcy. A theoretical expression for capillary number correlations is introduced that seems to have remained unnoticed. It expresses capillary desaturation curves in terms of stationary capillary pressures and relative permeabilities. The theoretical expression shows that the plateau saturation in capillary desaturation curves may in general differ from the residual nonwetting saturation defined through the saturation limit of the main hysteresis loop. Hysteresis effects as well as the difference between wetting and nonwetting fluids are introduced into the analysis of capillary desaturation experiments. The article examines experiments with different desaturation protocols and discusses the existence of a mesoscopic length scale intermediate between pore scale and sample scale. The theoretical expression is derived entirely within the existing traditional theory of two-phase flow in porous media and compared to a recent experiment.

  11. EPR paradox, quantum nonlocality and physical reality

    NASA Astrophysics Data System (ADS)

    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

  12. Spin relaxation measurements using first-harmonic out-of-phase absorption EPR signals.

    PubMed

    Livshits, V A; Páli, T; Marsh, D

    1998-09-01

    The dependence on spin-lattice (T1) relaxation of the first-harmonic absorption EPR signal (V'1) detected in phase quadrature with the Zeeman modulation has been investigated both theoretically and experimentally for nitroxide spin labels. Spectral simulations were performed by iterative solution of the Bloch equations that contained explicitly both the modulation and microwave magnetic fields (T. Páli, V. A. Livshits, and D. Marsh, 1996, J. Magn. Reson. B 113, 151-159). It was found that, of the various non-linear EPR displays, the first-harmonic out-of-phase V'1-signal, recorded under conditions of partial saturation of the microwave absorption, is particularly favorable for determining spin-lattice relaxation enhancements because of its superior signal intensity and relative insensitivity to spin-spin (T2) relaxation. By varying the Zeeman modulation frequency it is also possible to tune the optimum sensitivity of the V'1-signal to different ranges of the T1-relaxation time. A Zeeman modulation frequency of 25 kHz appears to be particularly suited to spin label applications. Calibrations are given for the dependence on T1-relaxation time of both the amplitude and the second integral of the V'1-signal recorded under standard conditions. Experiments on different spin labels in solution and in membranes demonstrate the practical usable sensitivity of the V'1-signal, even at modulation frequencies of 25 kHz, and these are used to investigate the dependence on microwave field intensity, in comparison with theoretical predictions. The practicable sensitivity to spin-lattice relaxation enhancements is demonstrated experimentally for a spin-labeled membrane system in the presence of paramagnetic ions. The first-harmonic out-of-phase V'1-signal appears to be the non-linear CW EPR method of choice for determining T1-relaxation enhancements in spin-labeled systems. PMID:9740736

  13. Insights into the mechanism of X-ray-induced disulfide-bond cleavage in lysozyme crystals based on EPR, optical absorption and X-ray diffraction studies

    SciTech Connect

    Sutton, Kristin A.; Black, Paul J.; Mercer, Kermit R.; Garman, Elspeth F.; Owen, Robin L.; Snell, Edward H.; Bernhard, William A.

    2013-12-01

    Electron paramagnetic resonance (EPR) and online UV–visible absorption microspectrophotometry with X-ray crystallography have been used in a complementary manner to follow X-ray-induced disulfide-bond cleavage, to confirm a multi-track radiation-damage process and to develop a model of that process. Electron paramagnetic resonance (EPR) and online UV–visible absorption microspectrophotometry with X-ray crystallography have been used in a complementary manner to follow X-ray-induced disulfide-bond cleavage. Online UV–visible spectroscopy showed that upon X-irradiation, disulfide radicalization appeared to saturate at an absorbed dose of approximately 0.5–0.8 MGy, in contrast to the saturating dose of ∼0.2 MGy observed using EPR at much lower dose rates. The observations suggest that a multi-track model involving product formation owing to the interaction of two separate tracks is a valid model for radiation damage in protein crystals. The saturation levels are remarkably consistent given the widely different experimental parameters and the range of total absorbed doses studied. The results indicate that even at the lowest doses used for structural investigations disulfide bonds are already radicalized. Multi-track considerations offer the first step in a comprehensive model of radiation damage that could potentially lead to a combined computational and experimental approach to identifying when damage is likely to be present, to quantitate it and to provide the ability to recover the native unperturbed structure.

  14. Lorentz symmetry breaking effects on relativistic EPR correlations

    NASA Astrophysics Data System (ADS)

    Belich, H.; Furtado, C.; Bakke, K.

    2015-09-01

    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.

  15. EFFECT OF MICROWAVE POWER ON SHAPE OF EPR SPECTRA--APPLICATION TO EXAMINATION OF COMPLEX FREE RADICAL SYSTEM IN THERMALLY STERILIZED ACIDUM BORICUM.

    PubMed

    Ramos, Paweł; Pieprzyca, Małgorzata; Pilawa, Barbara

    2016-01-01

    Complex free radical system in thermally sterilized acidum boricum (AB) was studied. Acidum boricum was sterilized at temperatures and times given by pharmaceutical norms: 160 degrees C and 120 min, 170 degrees C and 60 min and 180 degrees C and 30 min. The advanced spectroscopic tests were performed. The EPR spectra of free radicals were measured as the first derivatives with microwaves of 9.3 GHz frequency and magnetic modulation of 100 kHz. The Polish X-band electron paramagnetic resonance spectrometer of Radiopan (Poznań) was used. EPR lines were not observed for the nonheated AB. The broad EPR asymmetric lines were obtained for all the heated AB samples. The influence of microwave power in the range of 2.2-70 mW on the shape of EPR spectra of the heated drug samples was tested. The following asymmetry parameters: A1/A2, A1-A2, B1/B2, and B1-B2, were analyzed. The changes of these parameters with microwave power were observed. The strong dependence of shape and its parameters on microwave power proved the complex character of free radical system in thermally sterilized AB. Changes of microwave power during the detection of EPR spectra indicated complex character of free radicals in AB sterilized in hot air under all the tested conditions. Thermolysis, interactions between free radicals and interactions of free radicals with oxygen may be responsible for the complex free radicals system in thermally treated AB. Usefulness of continuous microwave saturation of EPR lines and shape analysis to examine free radicals in thermally sterilized drugs was confirmed. PMID:27180421

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

    NASA Astrophysics Data System (ADS)

    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.

  17. Saturated Zone Colloid Transport

    SciTech Connect

    H. S. Viswanathan

    2004-10-07

    This scientific analysis provides retardation factors for colloids transporting in the saturated zone (SZ) and the unsaturated zone (UZ). These retardation factors represent the reversible chemical and physical filtration of colloids in the SZ. The value of the colloid retardation factor, R{sub col} is dependent on several factors, such as colloid size, colloid type, and geochemical conditions (e.g., pH, Eh, and ionic strength). These factors are folded into the distributions of R{sub col} that have been developed from field and experimental data collected under varying geochemical conditions with different colloid types and sizes. Attachment rate constants, k{sub att}, and detachment rate constants, k{sub det}, of colloids to the fracture surface have been measured for the fractured volcanics, and separate R{sub col} uncertainty distributions have been developed for attachment and detachment to clastic material and mineral grains in the alluvium. Radionuclides such as plutonium and americium sorb mostly (90 to 99 percent) irreversibly to colloids (BSC 2004 [DIRS 170025], Section 6.3.3.2). The colloid retardation factors developed in this analysis are needed to simulate the transport of radionuclides that are irreversibly sorbed onto colloids; this transport is discussed in the model report ''Site-Scale Saturated Zone Transport'' (BSC 2004 [DIRS 170036]). Although it is not exclusive to any particular radionuclide release scenario, this scientific analysis especially addresses those scenarios pertaining to evidence from waste-degradation experiments, which indicate that plutonium and americium may be irreversibly attached to colloids for the time scales of interest. A section of this report will also discuss the validity of using microspheres as analogs to colloids in some of the lab and field experiments used to obtain the colloid retardation factors. In addition, a small fraction of colloids travels with the groundwater without any significant retardation

  18. Sensitivity enhancement in pulse EPR distance measurements.

    PubMed

    Jeschke, G; Bender, A; Paulsen, H; Zimmermann, H; Godt, A

    2004-07-01

    Established pulse EPR approaches to the measurement of small dipole-dipole couplings between electron spins rely on constant-time echo experiments to separate relaxational contributions from dipolar time evolution. This requires a compromise between sensitivity and resolution to be made prior to the measurement, so that optimum data are only obtained if the magnitude of the dipole-dipole coupling is known beforehand to a good approximation. Moreover, the whole dipolar evolution function is measured with relatively low sensitivity. These problems are overcome by a variable-time experiment that achieves suppression of the relaxation contribution by reference deconvolution. Theoretical and experimental results show that this approach leads to significant sensitivity improvements for typical systems and experimental conditions. Further sensitivity improvements or, equivalently, an extension of the accessible distance range can be obtained by matrix deuteration or digital long-pass filtering of the time-domain data. Advantages and limitations of the new variable-time experiment are discussed by comparing it to the established analogous constant-time experiment for measurements of end-to-end distances of 5 and 7.5 nm on rod-like shape-persistent biradicals and for the measurement of a broadly distributed transmembrane distance in a doubly spin-labeled mutant of plant light harvesting complex II. PMID:15183350

  19. Pulsed EPR for studying silver clusters

    NASA Astrophysics Data System (ADS)

    Michalik, J.; Wasowicz, T.; Sadlo, J.; Reijerse, E. J.; Kevan, L.

    1996-01-01

    The cationic silver clusters of different nuclearity have been produced by radiolysis of zeolite A and SAPO molecular sieves containing Ag + as exchangeable cations. The pulsed EPR spectroscopy has been applied for studying the local environment of silver cluster in order to understand the mechanism of cluster formation and stabilization. The electron spin echo modulation (ESEM) results on Ag 6n+ cluster in dehydration zeolite A indicate that the hexameric silver is stabilized only in sodalite cages which are surrounded by α-cages containing no water molecules. Trimeric silver clusters formed in hydrated A zeolites strongly interact with water, thus the paramagnetic center can be considered as a cluster-water adduct. In SAPO-molecular sieves, silver clusters are formed only in the presence of adsorbed alcohol molecules. From ESEM it is determined that Ag 4n+ in SAPO-42 is stabilized in α-cages, where it is directly coordinated by two methanol molecules. Dimeric silver, Ag 2+ in SAPO-5 and SAPO-11 is located in 6-ring channels and interacts with three CH 3OH molecules, each in different 10-ring or 12-ring channels. The differences of Ag 2+ stability in SAPO-5 and SAPO-11 are also discussed.

  20. High-Frequency EPR and ENDOR Spectroscopy on Semiconductor Quantum Dots

    PubMed Central

    Baranov, Pavel G.; de Mello Donegá, Celso; Schmidt, Jan

    2010-01-01

    is observed. Finally, it is shown that an almost complete dynamic nuclear polarization (DNP) of the 67Zn nuclear spins in the core of ZnO QDs and of the 1H nuclear spins in the Zn(OH)2 capping layer can be obtained. This DNP is achieved by saturating the EPR transition of SDs present in the QDs with resonant high-frequency microwaves at low temperatures. This nuclear polarization manifests itself as a hole and an antihole in the EPR absorption line of the SD in the QDs and a shift of the hole (antihole). The enhancement of the nuclear polarization opens the possibility to study semiconductor nanostructures with nuclear magnetic resonance techniques. PMID:20936163

  1. Correcting for accidental correlations in saturated avalanche photodiodes.

    PubMed

    Grieve, J A; Chandrasekara, R; Tang, Z; Cheng, C; Ling, A

    2016-02-22

    In this paper we present a general method for estimating rates of accidental coincidence between a pair of single photon detectors operated within their saturation regimes. By folding the effects of recovery time of both detectors and the detection circuit into an "effective duty cycle" we are able to accomodate complex recovery behaviour at high event rates. As an example, we provide a detailed high-level model for the behaviour of passively quenched avalanche photodiodes, and demonstrate effective background subtraction at rates commonly associated with detector saturation. We show that by post-processing using the updated model, we observe an improvement in polarization correlation visibility from 88.7% to 96.9% in our experimental dataset. This technique will be useful in improving the signal-to-noise ratio in applications which depend on coincidence measurements, especially in situations where rapid changes in flux may cause detector saturation. PMID:26907016

  2. Single-wall carbon nanotubes and peapods investigated by EPR.

    PubMed

    Corzilius, B; Dinse, K-P; Hata, K

    2007-12-14

    Single-wall carbon nanotubes (SWNT) prepared by the "super growth" method developed recently exhibit electron paramagnetic resonance (EPR) signals, which can be attributed to itinerant spins. EPR results indicate very low defect and catalyst concentrations in this superior material. Under these conditions EPR can be used to study details of charge transport properties over a wide temperature range, although the material is still very "heterogeneous" with respect to tube diameter and chirality. Non-resonant microwave absorption in the temperature range below 20 K is indicative for the opening of a small gap at the Fermi energy for tubes of metallic character, which is indicative for a transition into a superconducting state. Using SWNT filled partially with an endohedral spin probe like N@C(60), such "peapods" can be investigated "from the inside". Continuous-wave (cw) and pulsed EPR was used to investigate localization dynamics within the tubes or to check for interaction with itinerant electrons. Using SWNT grown by different methods, the dominant influence of tube diameter on fullerene dynamics was revealed by temperature dependent pulsed EPR experiments. These differences can be correlated with the interactions between the endohedral observer spin and spins on the SWNT. PMID:18167581

  3. Reading Recovery.

    ERIC Educational Resources Information Center

    Jones, Joanna R., Ed.

    1992-01-01

    This issue of the Arizona Reading Journal focuses on the theme "reading recovery" and includes the following articles: "Why Is an Inservice Programme for Reading Recovery Teachers Necessary?" (Marie M. Clay); "What Is Reading Recovery?" (Gay Su Pinnell); "Teaching a Hard To Teach Child" (Constance A. Compton); "Reading Recovery in Arizona--A…

  4. Macromolecular therapeutics in cancer treatment: the EPR effect and beyond.

    PubMed

    Maeda, Hiroshi

    2012-12-10

    In this review, I have discussed various issues of the cancer drug targeting primarily related to the EPR (enhanced permeability and retention) effect, which utilized nanomedicine or macromolecular drugs. The content goes back to the development of the first polymer-protein conjugate anticancer agent SMANCS and development of the arterial infusion in Lipiodol formulation into the tumor feeding artery (hepatic artery for hepatoma). The brief account on the EPR effect and its definition, factors involved, heterogeneity, and various methods of augmentation of the EPR effect, which showed remarkably improved clinical outcomes are also discussed. Various obstacles involved in drug developments and commercialization are also discussed through my personal experience and recollections. PMID:22595146

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

    SciTech Connect

    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.

  6. EPR Correlations, Bell Inequalities and Common Cause Systems

    NASA Astrophysics Data System (ADS)

    Hofer-Szabó, Gábor

    2014-03-01

    Standard common causal explanations of the EPR situation assume a so-called joint common cause system that is a common cause for all correlations. However, the assumption of a joint common cause system together with some other physically motivated assumptions concerning locality and no-conspiracy results in various Bell inequalities. Since Bell inequalities are violated for appropriate measurement settings, a local, non-conspiratorial joint common causal explanation of the EPR situation is ruled out. But why do we assume that a common causal explanation of a set of correlation consists in finding a joint common cause system for all correlations and not just in finding separate common cause systems for the different correlations? What are the perspectives of a local, non-conspiratorial separate common causal explanation for the EPR scenario? And finally, how do Bell inequalities relate to the weaker assumption of separate common cause systems?

  7. Effects of positional restraint on oxygen saturation and heart rate following exercise.

    PubMed

    Reay, D T; Howard, J D; Fligner, C L; Ward, R J

    1988-03-01

    This report assesses the effects on peripheral oxygen saturation and heart rate that positional restraint induces when a person is prone, handcuffed, and "hog-tied." Peripheral oxygen saturation and heart rate were monitored at rest, during exercise, and during recovery from exercise for 10 adult subjects. The effects of positional restraint produced a mean recovery time that was significantly prolonged. Consequently, the physiological effects produced by positional restraint should be recognized in deaths where such measures are used. PMID:3354518

  8. Determining the Topology of Integral Membrane Peptides Using EPR Spectroscopy

    PubMed Central

    Inbaraj, Johnson J.; Cardon, Thomas B.; Laryukhin, Mikhail; Grosser, Stuart M.

    2008-01-01

    This paper reports on the development of a new structural biology technique for determining the membrane topology of an integral membrane protein inserted into magnetically aligned phospholipid bilayers (bicelles) using EPR spectroscopy. The nitroxide spin probe, 2,2,6,6-tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid (TOAC) was attached to the pore-lining transmembrane domain (M2δ) of the nicotinic acetylcholine receptor (AChR) and incorporated into a bicelle. The corresponding EPR spectra revealed hyperfine splittings that were highly dependent on the macroscopic orientation of the bicelles with respect to the static magnetic field. The helical tilt of the peptide can be easily calculated using the hyperfine splittings gleaned from the orientational dependent EPR spectra. A helical tilt of 14° was calculated for the M2δ peptide with respect to the bilayer normal of the membrane, which agrees well with previous 15N solid-state NMR studies. The helical tilt of the peptide was verified by simulating the corresponding EPR spectra using the standardized MOMD approach. This new method is advantageous because: (1) bicelle samples are easy to prepare, (2) the helical tilt can be directly calculated from the orientational-dependent hyperfine splitting in the EPR spectra, and (3) EPR spectroscopy is approximately 1000 fold more sensitive than 15N solid-state NMR spectroscopy; thus, the helical tilt of an integral membrane peptide can be determined with only 100 μg of peptide. The helical tilt can be determined more accurately by placing TOAC spin labels at several positions with this technique. PMID:16848493

  9. Free-radical probes for functional in vivo EPR imaging

    NASA Astrophysics Data System (ADS)

    Subramanian, S.; Krishna, M. C.

    2007-02-01

    Electron paramagnetic resonance imaging (EPRI) is one of the recent functional imaging modalities that can provide valuable in vivo physiological information on its own merit and aids as a complimentary imaging technique to MRI and PET of tissues especially with respect to in vivo pO II (oxygen partial pressure), redox status and pharmacology. EPR imaging mainly deals with the measurement of distribution and in vivo dynamics and redox changes using special nontoxic paramagnetic spin probes that can be infused into the object of investigation. These spin probes should be characterized by simple EPR spectra, preferably with narrow EPR lines. The line width should be reversibly sensitive to the concentration of in vivo pO II with a linear dependence. Several non-toxic paramagnetic probes, some particulate and insoluble and others water-soluble and infusible (by intravenous or intramuscular injection) have been developed which can be effectively used to quantitatively assess tissue redox status, and tumor hypoxia. Quantitative assessment of the redox status of tissue in vivo is important in investigating oxidative stress, and that of tissue pO II is very important in radiation oncology. Other areas in which EPR imaging and oxymetry may help are in the investigation of tumorangiogenesis, wound healing, oxygenation of tumor tissue by the ingestion of oxygen-rich gases, etc. The correct choice of the spin probe will depend on the modality of measurement (whether by CW or time-domain EPR imaging) and the particular physiology interrogated. Examples of the available spin probes and some EPR imaging applications employing them are presented.

  10. EPR studies of gamma-irradiated taurine single crystals

    NASA Astrophysics Data System (ADS)

    Bulut, A.; Karabulut, B.; Tapramaz, R.; Köksal, F.

    2000-04-01

    An EPR study of gamma-irradiated taurine [C 2H 7NO 3S] single crystal was carried out at room temperature. The EPR spectra were recorded in the three at mutually perpendicular planes. There are two magnetically distinct sites in monoclinic lattice. The principle values of g and hyperfine constants for both sites were calculated. The results have indicated the presence of 32ṠO -2 and 33ṠO -2 radicals. The hyperfine values of 33ṠO -2 radical were used to obtain O-S-O bond angle for both sites.

  11. A new causal interpretation of EPR-B experiment

    NASA Astrophysics Data System (ADS)

    Gondran, Michel; Gondran, Alexandre

    2012-12-01

    In this paper we study a two-step version of EPR-B experiment, the Bohm version of the Einstein-Podolsky-Rosen experiment. Its theoretical resolution in space and time enables us to refute the classic "impossibility" to decompose a pair of entangled atoms into two distinct states, one for each atom. We propose a new causal interpretation of the EPR-B experiment where each atom has a position and a spin while the singlet wave function verifies the two-body Pauli equation. In conclusion we suggest a physical explanation of non-local influences, compatible with Einstein's point of view on relativity.

  12. Adaptive dynamics of saturated polymorphisms.

    PubMed

    Kisdi, Éva; Geritz, Stefan A H

    2016-03-01

    We study the joint adaptive dynamics of n scalar-valued strategies in ecosystems where n is the maximum number of coexisting strategies permitted by the (generalized) competitive exclusion principle. The adaptive dynamics of such saturated systems exhibits special characteristics, which we first demonstrate in a simple example of a host-pathogen-predator model. The main part of the paper characterizes the adaptive dynamics of saturated polymorphisms in general. In order to investigate convergence stability, we give a new sufficient condition for absolute stability of an arbitrary (not necessarily saturated) polymorphic singularity and show that saturated evolutionarily stable polymorphisms satisfy it. For the case [Formula: see text], we also introduce a method to construct different pairwise invasibility plots of the monomorphic population without changing the selection gradients of the saturated dimorphism. PMID:26676357

  13. EPR and Primitive Life: Dating and Visualizing the Organic Matter in the Oldest Rocks

    NASA Astrophysics Data System (ADS)

    Binet, L.; Gourier, D.; Skrzypczak-Bonduelle, A.; Delpoux, O.; Derenne, S.

    2007-03-01

    An EPR study of cherts of different ages showed that the age of the embedded fossil organic matter can be estimated from the EPR lineshape of the radicals. Nondestructive 3D visualization of bacterial mats is cherts in also possible by EPR imaging.

  14. Saturation current spikes eliminated in saturable core transformers

    NASA Technical Reports Server (NTRS)

    Schwarz, F. C.

    1971-01-01

    Unsaturating composite magnetic core transformer, consisting of two separate parallel cores designed so impending core saturation causes signal generation, terminates high current spike in converter primary circuit. Simplified waveform, demonstrates transformer effectiveness in eliminating current spikes.

  15. A hand-held EPR scanner for transcutaneous oximetry

    NASA Astrophysics Data System (ADS)

    Wolfson, Helen; Ahmad, Rizwan; Twig, Ygal; Blank, Aharon; Kuppusamy, Periannan

    2015-03-01

    Cutaneous (skin) oxygenation is an important prognostic factor for the treatment of chronic wounds, skin cancer, diabetes side effects, and limb amputation. Currently, there are no reliable methods for measuring this parameter. Oximetry, using electron paramagnetic resonance (EPR) spectroscopy, is emerging as a potential tool for clinical oximetry, including cutaneous applications. The problem with EPR oximetry, however, is that the conventional EPR design requires the use of a large magnet that can generate homogeneous field across the sample, making it unattractive for clinical practice. We present a novel approach that makes use of a miniature permanent magnet, combined with a small microwave resonator, to enable the acquisition of EPR signals from paramagnetic species placed on the skin. The instrumentation consists of a hand-held, modular, cylindrical probehead with overall dimensions of 36-mm diameter and 24-mm height, with 150-g weight. The probehead includes a Halbach array of 16 pieces (4×4×8 mm3) of Sm-Co permanent magnet and a loop-gap resonator (2.24 GHz). Preliminary measurements using a Hahn-echo pulse sequence (800 echos in 20 ms) showed a signalto- noise ratio of ~70 compared to ~435 in a homogenous magnet under identical settings. Further work is in progress to improve the performance of the probehead and to optimize the hand-held system for clinical use

  16. Numerical analysis of EPR spectra. 7. The simplex algorithm

    NASA Astrophysics Data System (ADS)

    Beckwith, Athelstan L. J.; Brumby, Steven

    The Simplex algorithm is well suited to the least-squares analysis of highly complex EPR spectra. The application of the algorithm to the analysis of the spectra of benzo[ a]pyrenyl-6-oxy, chloro(methoxycarbonyl)methyl, and cyano(methoxy)methyl free radicals is described.

  17. New ceramic EPR resonators with high dielectric permittivity.

    PubMed

    Golovina, Iryna; Geifman, Ilia; Belous, Anatolii

    2008-11-01

    New EPR resonators were developed by using a ceramic material with a high dielectric constant, epsilon=160. The resonators have a high quality factor, Q=10(3), and enhance the sensitivity of an EPR spectrometer up to 170 times. Some advantages of the new ceramic resonators are: (1) cheaper synthesis and simplified fabricating technology; (2) wider temperature range; and (3) ease of use. The ceramic material is produced with a titanate of complex oxides of rare-earth and alkaline metals, and has a perovskite type structure. The resonators were tested with X-band EPR spectrometers with cylindrical (TE(011)) and rectangular (TE(102)) cavities at 300 and 77K. We discovered that EPR signal strength enhancement depends on the dielectric constant of the material, resonator geometry and the size of the sample. Also, an unusual resonant mode was found in the dielectric resonator-metallic cavity structure. In this mode, the directions of microwave magnetic fields of the coupled resonators are opposite and the resonant frequency of the structure is higher than the frequency of empty metallic cavity. PMID:18815061

  18. Determination of tritium distribution in labeled compounds using EPR spectrometry

    SciTech Connect

    Postolache, C.; Matei, L.; Georgescu, R.

    2008-07-15

    Usually, the tritium distribution in a labeled compound is analyzed by T-NMR spectrometry. NMR equipment is expensive and its sensitivity is lower in comparison to EPR spectrometry. In this paper, the possibility of determining the distribution of tritium in a labeled molecule using self-radiolytic decay processes was analyzed. (authors)

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

    PubMed Central

    Ulmschneider, Martin B.; Searson, Peter C.

    2015-01-01

    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. PMID:25938565

  20. Development of a Hybrid EPR/NMR Coimaging System

    PubMed Central

    Samouilov, Alexandre; Caia, George L.; Kesselring, Eric; Petryakov, Sergey; Wasowicz, Tomasz; Zweier, Jay L.

    2010-01-01

    Electron paramagnetic resonance imaging (EPRI) is a powerful technique that enables spatial mapping of free radicals or other paramagnetic compounds; however, it does not in itself provide anatomic visualization of the body. Proton magnetic resonance imaging (MRI) is well suited to provide anatomical visualization. A hybrid EPR/NMR coimaging instrument was constructed that utilizes the complementary capabilities of both techniques, superimposing EPR and proton-MR images to provide the distribution of paramagnetic species in the body. A common magnet and field gradient system is utilized along with a dual EPR and proton-NMR resonator assembly, enabling coimaging without the need to move the sample. EPRI is performed at ~1.2 GHz/~40 mT and proton MRI is performed at 16.18 MHz/~380 mT; hence the method is suitable for whole-body coimaging of living mice. The gradient system used is calibrated and controlled in such a manner that the spatial geometry of the two acquired images is matched, enabling their superposition without additional postprocessing or marker registration. The performance of the system was tested in a series of phantoms and in vivo applications by mapping the location of a paramagnetic probe in the gastrointestinal (GI) tract of mice. This hybrid EPR/NMR coimaging instrument enables imaging of paramagnetic molecules along with their anatomic localization in the body. PMID:17659621

  1. Accurate Extraction of Nanometer Distances in Multimers by Pulse EPR

    PubMed Central

    Valera, Silvia; Ackermann, Katrin; Pliotas, Christos; Huang, Hexian; Naismith, James H.

    2016-01-01

    Abstract Pulse electron paramagnetic resonance (EPR) is gaining increasing importance in structural biology. The PELDOR (pulsed electron–electron double resonance) method allows extracting distance information on the nanometer scale. Here, we demonstrate the efficient extraction of distances from multimeric systems such as membrane‐embedded ion channels where data analysis is commonly hindered by multi‐spin effects. PMID:26865468

  2. EPR investigations of gamma-irradiated ground black pepper

    NASA Astrophysics Data System (ADS)

    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)< Ea( GIII)< Ea( GII). The EPR measurements performed 20 weeks after radiation process confirmed that a temperature increase from 298 to 353 K, caused a significant decrease of integral EPR signal intensity for γ-irradiated samples (˜40%), compared to the reference (non-irradiated) ground 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.

  3. Nonlinear Simulation of the Tooth Enamel Spectrum for EPR Dosimetry

    NASA Astrophysics Data System (ADS)

    Kirillov, V. A.; Dubovsky, S. V.

    2016-07-01

    Software was developed where initial EPR spectra of tooth enamel were deconvoluted based on nonlinear simulation, line shapes and signal amplitudes in the model initial spectrum were calculated, the regression coefficient was evaluated, and individual spectra were summed. Software validation demonstrated that doses calculated using it agreed excellently with the applied radiation doses and the doses reconstructed by the method of additive doses.

  4. New ceramic EPR resonators with high dielectric permittivity

    NASA Astrophysics Data System (ADS)

    Golovina, Iryna; Geifman, Ilia; Belous, Anatolii

    2008-11-01

    New EPR resonators were developed by using a ceramic material with a high dielectric constant, ɛ = 160. The resonators have a high quality factor, Q = 10 3, and enhance the sensitivity of an EPR spectrometer up to 170 times. Some advantages of the new ceramic resonators are: (1) cheaper synthesis and simplified fabricating technology; (2) wider temperature range; and (3) ease of use. The ceramic material is produced with a titanate of complex oxides of rare-earth and alkaline metals, and has a perovskite type structure. The resonators were tested with X-band EPR spectrometers with cylindrical (TE 011) and rectangular (TE 102) cavities at 300 and 77 K. We discovered that EPR signal strength enhancement depends on the dielectric constant of the material, resonator geometry and the size of the sample. Also, an unusual resonant mode was found in the dielectric resonator-metallic cavity structure. In this mode, the directions of microwave magnetic fields of the coupled resonators are opposite and the resonant frequency of the structure is higher than the frequency of empty metallic cavity.

  5. EPR Imaging at a Few Megahertz Using SQUID Detectors

    NASA Technical Reports Server (NTRS)

    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

  6. EPR/PTFE dosimetry for test reactor environments

    SciTech Connect

    Vehar, D.W.; Griffin, P.J.; Quirk, T.J.

    2011-07-01

    The use of Electron Paramagnetic Resonance (EPR) spectroscopy with materials such as alanine is well established as a technique for measurement of ionizing radiation absorbed dose in photon and electron fields such as Co-60, high-energy bremsstrahlung and electron-beam fields [1]. In fact, EPR/Alanine dosimetry has become a routine transfer standard for national standards bodies such as NIST and NPL. In 1992 the Radiation Metrology Laboratory (RML) at Sandia National Laboratories implemented EPR/Alanine capabilities for use in routine and calibration activities at its Co-60 and pulsed-power facilities. At that time it also investigated the usefulness of the system for measurement of absorbed dose in the mixed neutron/photon environments of reactors such as the Sandia Pulsed Reactor and the Annular Core Research Reactor used for hardness testing of electronics. The RML concluded that the neutron response of alanine was a sufficiently high fraction of the overall dosimeter response that the resulting uncertainties in the photon dose would be unacceptably large for silicon-device testing. However, it also suggested that non-hydrogenous materials such as polytetrafluoroethylene (PTFE) would exhibit smaller neutron response and might be useful in mixed environments. Preliminary research with PTFE in photon environments indicated considerable promise, but further development was not pursued at that time. Because of renewed interest in absorbed dose measurements that could better define the individual contributions of photon and neutron components to the overall dose delivered to a test object, the RML has re-initiated the development of an EPR/PTFE dosimetry system. This effort consists of three stages: 1) Identification of PTFE materials that may be suitable for dosimetry applications. It was speculated that the inconsistency of EPR signatures in the earlier samples may have been due to variability in PTFE manufacturing processes. 2) Characterization of dosimetry in

  7. Landsliding in partially saturated materials

    USGS Publications Warehouse

    Godt, J.W.; Baum, R.L.; Lu, N.

    2009-01-01

    [1] Rainfall-induced landslides are pervasive in hillslope environments around the world and among the most costly and deadly natural hazards. However, capturing their occurrence with scientific instrumentation in a natural setting is extremely rare. The prevailing thinking on landslide initiation, particularly for those landslides that occur under intense precipitation, is that the failure surface is saturated and has positive pore-water pressures acting on it. Most analytic methods used for landslide hazard assessment are based on the above perception and assume that the failure surface is located beneath a water table. By monitoring the pore water and soil suction response to rainfall, we observed shallow landslide occurrence under partially saturated conditions for the first time in a natural setting. We show that the partially saturated shallow landslide at this site is predictable using measured soil suction and water content and a novel unified effective stress concept for partially saturated earth materials. Copyright 2009 by the American Geophysical Union.

  8. Brine saturation technique for extracting light filth from ground cinnamon: intralaboratory study.

    PubMed

    Freeman, C C

    1985-01-01

    An intralaboratory study was performed using the new brine saturation technique for isolating light filth from ground cinnamon. Recoveries of light filth averaged greater than or equal to 96.5%. The excellent recovery plus improvements in safety and simplicity give this new technique considerable advantage over the present official method. PMID:4086431

  9. Graphene-clad microfibre saturable absorber for ultrafast fibre lasers

    NASA Astrophysics Data System (ADS)

    Liu, X. M.; Yang, H. R.; Cui, Y. D.; Chen, G. W.; Yang, Y.; Wu, X. Q.; Yao, X. K.; Han, D. D.; Han, X. X.; Zeng, C.; Guo, J.; Li, W. L.; Cheng, G.; Tong, L. M.

    2016-05-01

    Graphene, whose absorbance is approximately independent of wavelength, allows broadband light–matter interactions with ultrafast responses. The interband optical absorption of graphene can be saturated readily under strong excitation, thereby enabling scientists to exploit the photonic properties of graphene to realize ultrafast lasers. The evanescent field interaction scheme of the propagating light with graphene covered on a D-shaped fibre or microfibre has been employed extensively because of the nonblocking configuration. Obviously, most of the fibre surface is unused in these techniques. Here, we exploit a graphene-clad microfibre (GCM) saturable absorber in a mode-locked fibre laser for the generation of ultrafast pulses. The proposed all-surface technique can guarantee a higher efficiency of light–graphene interactions than the aforementioned techniques. Our GCM-based saturable absorber can generate ultrafast optical pulses within 1.5 μm. This saturable absorber is compatible with current fibre lasers and has many merits such as low saturation intensities, ultrafast recovery times, and wide wavelength ranges. The proposed saturable absorber will pave the way for graphene-based wideband photonics.

  10. Graphene-clad microfibre saturable absorber for ultrafast fibre lasers.

    PubMed

    Liu, X M; Yang, H R; Cui, Y D; Chen, G W; Yang, Y; Wu, X Q; Yao, X K; Han, D D; Han, X X; Zeng, C; Guo, J; Li, W L; Cheng, G; Tong, L M

    2016-01-01

    Graphene, whose absorbance is approximately independent of wavelength, allows broadband light-matter interactions with ultrafast responses. The interband optical absorption of graphene can be saturated readily under strong excitation, thereby enabling scientists to exploit the photonic properties of graphene to realize ultrafast lasers. The evanescent field interaction scheme of the propagating light with graphene covered on a D-shaped fibre or microfibre has been employed extensively because of the nonblocking configuration. Obviously, most of the fibre surface is unused in these techniques. Here, we exploit a graphene-clad microfibre (GCM) saturable absorber in a mode-locked fibre laser for the generation of ultrafast pulses. The proposed all-surface technique can guarantee a higher efficiency of light-graphene interactions than the aforementioned techniques. Our GCM-based saturable absorber can generate ultrafast optical pulses within 1.5 μm. This saturable absorber is compatible with current fibre lasers and has many merits such as low saturation intensities, ultrafast recovery times, and wide wavelength ranges. The proposed saturable absorber will pave the way for graphene-based wideband photonics. PMID:27181419

  11. Graphene-clad microfibre saturable absorber for ultrafast fibre lasers

    PubMed Central

    Liu, X. M.; Yang, H. R.; Cui, Y. D.; Chen, G. W.; Yang, Y.; Wu, X. Q.; Yao, X. K.; Han, D. D.; Han, X. X.; Zeng, C.; Guo, J.; Li, W. L.; Cheng, G.; Tong, L. M.

    2016-01-01

    Graphene, whose absorbance is approximately independent of wavelength, allows broadband light–matter interactions with ultrafast responses. The interband optical absorption of graphene can be saturated readily under strong excitation, thereby enabling scientists to exploit the photonic properties of graphene to realize ultrafast lasers. The evanescent field interaction scheme of the propagating light with graphene covered on a D-shaped fibre or microfibre has been employed extensively because of the nonblocking configuration. Obviously, most of the fibre surface is unused in these techniques. Here, we exploit a graphene-clad microfibre (GCM) saturable absorber in a mode-locked fibre laser for the generation of ultrafast pulses. The proposed all-surface technique can guarantee a higher efficiency of light–graphene interactions than the aforementioned techniques. Our GCM-based saturable absorber can generate ultrafast optical pulses within 1.5 μm. This saturable absorber is compatible with current fibre lasers and has many merits such as low saturation intensities, ultrafast recovery times, and wide wavelength ranges. The proposed saturable absorber will pave the way for graphene-based wideband photonics. PMID:27181419

  12. Saturation of CVD Diamond Detectors

    SciTech Connect

    Lucile S. Dauffy; Richard A. Lerche; Greg J. Schmid; Jeffrey A. Koch; Christopher Silbernagel

    2005-01-01

    A 5 x 0.25 mm Chemical Vapor Deposited (CVD) diamond detector, with a voltage bias of + 250V, was excited by a 400 nm laser (3.1 eV photons) in order to study the saturation of the wafer and its surrounding electronics. In a first experiment, the laser beam energy was increased from a few tens of a pJ to about 100 µJ, and the signal from the diamond was recorded until full saturation of the detection system was achieved. Clear saturation of the detection system was observed at about 40 V, which corresponds with the expected saturation at 10% of the applied bias (250V). The results indicate that the interaction mechanism of the 3.1 eV photons in the diamond (Ebandgap = 5.45 eV) is not a multi-photon process but is linked to the impurities and defects of the crystal. In a second experiment, the detector was irradiated by a saturating first laser pulse and then by a delayed laser pulse of equal or smaller amplitude with delays of 5, 10, and 20 ns. The results suggest that the diamond and associated electronics recover within 10 to 20 ns after a strong saturating pulse.

  13. Insights into the mechanism of X-ray-induced disulfide-bond cleavage in lysozyme crystals based on EPR, optical absorption and X-ray diffraction studies

    PubMed Central

    Sutton, Kristin A.; Black, Paul J.; Mercer, Kermit R.; Garman, Elspeth F.; Owen, Robin L.; Snell, Edward H.; Bernhard, William A.

    2013-01-01

    Electron paramagnetic resonance (EPR) and online UV–visible absorption microspectrophotometry with X-ray crystallography have been used in a complementary manner to follow X-ray-induced disulfide-bond cleavage. Online UV–visible spectroscopy showed that upon X-irradiation, disulfide radicalization appeared to saturate at an absorbed dose of approximately 0.5–0.8 MGy, in contrast to the saturating dose of ∼0.2 MGy observed using EPR at much lower dose rates. The observations suggest that a multi-track model involving product formation owing to the interaction of two separate tracks is a valid model for radiation damage in protein crystals. The saturation levels are remarkably consistent given the widely different experimental parameters and the range of total absorbed doses studied. The results indicate that even at the lowest doses used for structural investigations disulfide bonds are already radicalized. Multi-track considerations offer the first step in a comprehensive model of radiation damage that could potentially lead to a combined computational and experimental approach to identifying when damage is likely to be present, to quantitate it and to provide the ability to recover the native unperturbed structure. PMID:24311579

  14. RosettaEPR: Rotamer Library for Spin Label Structure and Dynamics

    PubMed Central

    Alexander, Nathan S.; Stein, Richard A.; Koteiche, Hanane A.; Kaufmann, Kristian W.; Mchaourab, Hassane S.; Meiler, Jens

    2013-01-01

    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. PMID:24039810

  15. Slow light and saturable absorption

    NASA Astrophysics Data System (ADS)

    Selden, A. C.

    2009-06-01

    Quantitative analysis of slow light experiments utilising coherent population oscillation (CPO) in a range of saturably absorbing media, including ruby and alexandrite, Er3+:Y2SiO5, bacteriorhodopsin, semiconductor quantum devices and erbium-doped optical fibres, shows that the observations may be more simply interpreted as saturable absorption phenomena. A basic two-level model of a saturable absorber displays all the effects normally associated with slow light, namely phase shift and modulation gain of the transmitted signal, hole burning in the modulation frequency spectrum and power broadening of the spectral hole, each arising from the finite response time of the non-linear absorption. Only where hole-burning in the optical spectrum is observed (using independent pump and probe beams), or pulse delays exceeding the limits set by saturable absorption are obtained, can reasonable confidence be placed in the observation of slow light in such experiments. Superluminal (“fast light”) phenomena in media with reverse saturable absorption (RSA) may be similarly explained.

  16. Transpolar potential saturation models compared

    NASA Astrophysics Data System (ADS)

    Siscoe, G.; Raeder, J.; Ridley, A. J.

    2004-09-01

    We compare four explanations of transpolar potential saturation: (1) the magnetic field at the stagnation point weakens, thereby limiting magnetic reconnection; (2) a dimple develops at the stagnation point, which limits the inflow rate to the reconnection line; (3) the magnetopause becomes blunt and the bow shock recedes, thus giving more room for the solar wind to flow around the magnetosphere, thereby reducing the need for magnetic reconnection; (4) the region 1 current system usurps the Chapman-Ferraro current system and saturates when the J × B force it generates balances solar wind ram pressure. The paper's point is that all four mechanisms involve a limit on the strength of the region 1 current system and that the criterion for the onset of transpolar potential saturation in each mechanism is that the region 1 current system generates a magnetic field that is about as strong as the dipole field at the dayside magnetopause. This circumstance prevents tests to discriminate between the four mechanisms based on predictions that relate to their dependencies on the region 1 current system. The group as a whole, however, can be tested to see whether their common criterion that relates the onset of transpolar potential saturation to the total current flowing in the region 1 system holds. The criterion can be formulated in terms of predictions that relate transpolar potential saturation to the strength of the interplanetary electric field, solar wind ram pressure, and ionospheric conductance. Published data analyses and MHD simulations reasonably confirm these predictions.

  17. Kinetic Measurements Using EPR Imaging with a Modulated Field Gradient

    NASA Astrophysics Data System (ADS)

    Herrling, Thomas; Fuchs, Jürgen; Groth, Norbert

    2002-01-01

    EPR imaging with modulated field gradient was applied for the investigation of fast diffusion processes. Three different imaging methods are possible: spectral-temporal, spatio-temporal, and spectral-spatial imaging. The time resolution is on the order of seconds and the spatial resolution is in the micrometer region. The efficiency of this imaging technique is demonstrated for the penetration of the spin probe Tempol in the skin of hairless mice biopsies. The skin is normally protected against the penetration of water soluble substances by the horny layer, a resistive thin lipophilic layer. Overcoming this horny layer for water soluble ingredients is one of the main practical problems for the topical application of pharmaceutics which could be investigated by EPR imaging. Different images represent the penetration behavior of the water soluble Tempol in the skin after treatment with the penetration enhancer DMSO (Dimethylsulfoxide) and after removing the horny layer.

  18. EPR dosimetry in a mixed neutron and gamma radiation field.

    PubMed

    Trompier, F; Fattibene, P; Tikunov, D; Bartolotta, A; Carosi, A; Doca, M C

    2004-01-01

    Suitability of Electron Paramagnetic Resonance (EPR) spectroscopy for criticality dosimetry was evaluated for tooth enamel, mannose and alanine pellets during the 'international intercomparison of criticality dosimetry techniques' at the SILENE reactor held in Valduc in June 2002, France. These three materials were irradiated in neutron and gamma-ray fields of various relative intensities and spectral distributions in order to evaluate their neutron sensitivity. The neutron response was found to be around 10% for tooth enamel, 45% for mannose and between 40 and 90% for alanine pellets according their type. According to the IAEA recommendations on the early estimate of criticality accident absorbed dose, analyzed results show the EPR potentiality and complementarity with regular criticality techniques. PMID:15353687

  19. EPR and electronic absorption spectra of copper bearing turquoise mineral

    NASA Astrophysics Data System (ADS)

    Sharma, K. B. N.; Moorthy, L. R.; Reddy, B. J.; Vedanand, S.

    1988-10-01

    Electron paramagnetic resonance and optical absorption spectra of turquoise have been studied both at room and low temperatures. It is concluded from the EPR spectra that the ground state of Cu 2+ ion in turquoise is 2A g(d x2- y2) and it is sited in an elongated rhombic octahedron (D 2π). The observed absorption bands at 14970 and 18354 cm -1 are assigned at 2A g→ 2B 1 g( dx2- y2→ xy) and 2A g→[ su2B 3g(d x 2-y 2→d yz) respectively assuming D 2π symmetry which are inconsistent with EPR studies. The three bands in the NIR region are attributed to combinations of fundamental modes of the H 2O molecule present in the sample.

  20. Saturation and pulsed FEL dynamics

    SciTech Connect

    Giannessi, L.; Mezi, L.

    1995-12-31

    The behavior of a FEL operating in the saturated pulsed regime, may be reproduced by the linear FEL integral equation, suitably modified to include saturation effects through a gain depression coefficient depending on the laser intensity. This simple method allows to evaluate several FEL parameters like gain, efficiency, band-width and optical pulse duration as functions of the optical cavity length, only with a numerical integration. The predictions have been compared with available experimental and numerical data, and the method has been applied to estimate the operating characteristics of some planned FEL experiments.

  1. Numerical analysis of EPR spectra. 8. Relative concentrations

    NASA Astrophysics Data System (ADS)

    Beckwith, Athelstan L. J.; Brumby, Steven

    A method for determining the relative concentrations of paramagnetic species in mixtures by least-squares analysis of the EPR spectra is described. The method is especially useful when the double integration method cannot be used because of overlap between the component spectra. In two examples, the relative steady-state concentrations of free radicals formed during the photolysis of dimethoxymethane/di- tert-butyl peroxide and cyclopropylmethyl methyl ether/di- tert-butyl peroxide/cyclopropane solutions are determined.

  2. Dosimetry Based on EPR Spectral Analysis of Fingernail Clippings

    PubMed Central

    Wilcox, Dean E.; He, Xiaoming; Gui, Jiang; Ruuge, Andres E.; Li, Hongbin; Williams, Benjamin B.; Swartz, Harold M.

    2009-01-01

    Exposure of fingernails and toenails to ionizing radiation creates radicals that are stable over a relatively long period (days to weeks) and characterized by an isotropic EPR signal at g = 2.003 (so-called radiation-induced signal, RIS). This signal in readily obtained fingernail parings has the potential to be used in screening a population for exposure to radiation and determining individual dose to guide medical treatment. However, the mechanical harvesting of fingernail parings also creates radicals and their EPR signals (so-called mechanically-induced signals, MIS) overlap the g ~ 2.0 region, interfering with efforts to quantify the RIS and, therefore, the radiation dose. Careful analysis of the time evolution and power-dependence of the EPR spectra of freshly cut fingernail parings has now resolved the MIS into three major components, including one that is described for the first time. It dominates the MIS soon after cutting, but decays within the first hour, and consists of a unique doublet that can be resolved from the RIS. The MIS obtained within the first few minutes after cutting is consistent among fingernail samples and provides an opportunity to achieve the two important dosimetry objectives. First, perturbation of the initial MIS by the presence of RIS in fingernails that have received a threshold dose of radiation leads to spectral signatures that can be used for rapid screening. Second, decomposition of the EPR spectra from irradiated fingernails into MIS and RIS components can be used to isolate and thus quantify the RIS for determining individual exposure dose. PMID:20065699

  3. Characterization of nuclear waste forms by EPR spectroscopy

    SciTech Connect

    Boatner, L.A.; Abraham, M.M.; Rappaz, M.

    1980-10-01

    Single crystals of LaPO/sub 4/ have been grown with the addition of various amounts of PW-4b simulated waste, and the EPR spectra of Gd/sup 3 +/ in these samples have been compared with that obtained for a pure LaPO/sub 4/ single crystal. The relationship between the average linewidth of two symmetric EPR transitions and their magnetic field separation for pure and PW-4b doped LaPO/sub 4/ crystals are shown quantitatively. These measurements were carried out for four different crystals and two different magnetic field orientations. Since the linewidth of each transition is proportional to its magnetic field separation from the central line, it can be concluded that the line broadening is inhomogeneous (i.e., the line broadening is due to a distribution of line positions with this distribution resulting from a distribution of impurities in the crystal). The sensitivity of Gd/sup 3 +/ linewidths to defects or strains is also under investigation as a means of detecting metamictization phenomena in orthophosphates. Mixed Ln/sub 1-x/An/sub x/PO/sub 4/ crystals, where Ln is a rare earth and An an actinide, have been grown and EPR spectra of Gd/sup 3 +/ in these systems are of considerable interest for detecting radiation damage created by ..cap alpha..-particles or recoil of the daughter nuclei. Although the examples of the application of EPR to waste form characterization described here have emphasized studies of lanthanide orthophosphates, the same techniques can be applied to perovskite, hollandite, zirconolite, etc. single crystals or powders or to amorphous materials.

  4. Implementing Diffie-Hellman key exchange using quantum EPR pairs

    NASA Astrophysics Data System (ADS)

    Mandal, Sayonnha; Parakh, Abhishek

    2015-05-01

    This paper implements the concepts of perfect forward secrecy and the Diffie-Hellman key exchange using EPR pairs to establish and share a secret key between two non-authenticated parties and transfer messages between them without the risk of compromise. Current implementations of quantum cryptography are based on the BB84 protocol, which is susceptible to siphoning attacks on the multiple photons emitted by practical laser sources. This makes BB84-based quantum cryptography protocol unsuitable for network computing environments. Diffie-Hellman does not require the two parties to be mutually authenticated to each other, yet it can provide a basis for a number of authenticated protocols, most notably the concept of perfect forward secrecy. The work proposed in this paper provides a new direction in utilizing quantum EPR pairs in quantum key exchange. Although, classical cryptography boasts of efficient and robust protocols like the Diffie-Hellman key exchange, in the current times, with the advent of quantum computing they are very much vulnerable to eavesdropping and cryptanalytic attacks. Using quantum cryptographic principles, however, these classical encryption algorithms show more promise and a more robust and secure structure for applications. The unique properties of quantum EPR pairs also, on the other hand, go a long way in removing attacks like eavesdropping by their inherent nature of one particle of the pair losing its state if a measurement occurs on the other. The concept of perfect forward secrecy is revisited in this paper to attribute tighter security to the proposed protocol.

  5. Advances in Probes and Methods for Clinical EPR Oximetry

    PubMed Central

    Hou, Huagang; Khan, Nadeem; Jarvis, Lesley A.; Chen, Eunice Y.; Williams, Benjamin B.; Kuppusamy, Periannan

    2015-01-01

    EPR oximetry, which enables reliable, accurate, and repeated measurements of the partial pressure of oxygen in tissues, provides a unique opportunity to investigate the role of oxygen in the pathogenesis and treatment of several diseases including cancer, stroke, and heart failure. Building on significant advances in the in vivo application of EPR oximetry for small animal models of disease, we are developing suitable probes and instrumentation required for use in human subjects. Our laboratory has established the feasibility of clinical EPR oximetry in cancer patients using India ink, the only material presently approved for clinical use. We now are developing the next generation of probes, which are both superior in terms of oxygen sensitivity and biocompatibility including an excellent safety profile for use in humans. Further advances include the development of implantable oxygen sensors linked to an external coupling loop for measurements of deep-tissue oxygenations at any depth, overcoming the current limitation of 10 mm. This paper presents an overview of recent developments in our ability to make meaningful measurements of oxygen partial pressures in human subjects under clinical settings. PMID:24729217

  6. EPR investigation of some traditional oriental irradiated spices

    NASA Astrophysics Data System (ADS)

    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.

  7. A Wire Crossed-Loop-Resonator for Rapid Scan EPR

    PubMed Central

    Rinard, George A.; Quine, Richard W.; Biller, Joshua R.; Eaton, Gareth R.

    2011-01-01

    A crossed-loop (orthogonal mode) resonator (CLR) was constructed of fine wire to achieve design goals for rapid scan in vivo EPR imaging at VHF frequencies (in practice, near 250 MHz). This application requires the resonator to have a very open design to facilitate access to the animal for physiological support during the image acquisition. The rapid scan experiment uses large amplitude magnetic field scans, and sufficiently large resonator and detection bandwidths to record the rapidly-changing signal response. Rapid-scan EPR is sensitive to RF/microwave source noise and to baseline changes that are coherent with the field scan. The sensitivity to source noise is a primary incentive for using a CLR to isolate the detected signal from the RF source noise. Isolation from source noise of 44 and 47 dB was achieved in two resonator designs. Prior results showed that eddy currents contribute to background problems in rapid scan EPR, so the CLR design had to minimize conducting metal components. Using fine (AWG 38) wire for the resonators decreased eddy currents and lowered the resonator Q, thus providing larger resonator bandwidth. Mechanical resonances at specific scan frequencies are a major contributor to rapid scan backgrounds. PMID:21603086

  8. Tetrabromidocuprates(II)—Synthesis, Structure and EPR

    PubMed Central

    Zabel, André; Winter, Alette; Kelling, Alexandra; Schilde, Uwe; Strauch, Peter

    2016-01-01

    Metal-containing ionic liquids (ILs) are of interest for a variety of technical applications, e.g., particle synthesis and materials with magnetic or thermochromic properties. In this paper we report the synthesis of, and two structures for, some new tetrabromidocuprates(II) with several “onium” cations in comparison to the results of electron paramagnetic resonance (EPR) spectroscopic analyses. The sterically demanding cations were used to separate the paramagnetic Cu(II) ions for EPR measurements. The EPR hyperfine structure in the spectra of these new compounds is not resolved, due to the line broadening resulting from magnetic exchange between the still-incomplete separated paramagnetic Cu(II) centres. For the majority of compounds, the principal g values (g‖ and g⊥) of the tensors could be determined and information on the structural changes in the [CuBr4]2− anions can be obtained. The complexes have high potential, e.g., as ionic liquids, as precursors for the synthesis of copper bromide particles, as catalytically active or paramagnetic ionic liquids. PMID:27104522

  9. Peptide-membrane Interactions by Spin-labeling EPR

    PubMed Central

    Smirnova, Tatyana I.; Smirnov, Alex I.

    2016-01-01

    Site-directed spin labeling (SDSL) in combination with Electron Paramagnetic Resonance (EPR) spectroscopy is a well-established method that has recently grown in popularity as an experimental technique, with multiple applications in protein and peptide science. The growth is driven by development of labeling strategies, as well as by considerable technical advances in the field, that are paralleled by an increased availability of EPR instrumentation. While the method requires an introduction of a paramagnetic probe at a well-defined position in a peptide sequence, it has been shown to be minimally destructive to the peptide structure and energetics of the peptide-membrane interactions. In this chapter, we describe basic approaches for using SDSL EPR spectroscopy to study interactions between small peptides and biological membranes or membrane mimetic systems. We focus on experimental approaches to quantify peptide-membrane binding, topology of bound peptides, and characterize peptide aggregation. Sample preparation protocols including spin-labeling methods and preparation of membrane mimetic systems are also described. PMID:26477253

  10. VHF EPR analysis of organic sulfur in coal. Technical report, December 1, 1991--February 29, 1992

    SciTech Connect

    Clarkson, R.B.; Belford, R.L.

    1992-08-01

    This is a report of the second quarter of a two-year investigation exploiting electron paramagnetic resonance (EPR), especially novel, very high frequency (VHF) spectroscopy techniques and instrumentation (the only high-modulation W-band EPR spectrometer in the world) developed earlier by these authors, to conduct further qualitative and quantitative studies of heteroatomic organic molecules in coal with particular emphasis on sulfur. New model compounds have been prepared in EPR-active forms and surveyed with X-band EPR. Previous W-band (96 GHz) VHF-EPR work is being extended to studies of these new model compounds as well as to a variety of coal and desulfurized coal samples. Typically, the model compounds under investigation and their analogues are found in coals as stable free radicals which give rise to an EPR signal.

  11. Light-induced EPR study of charge transfer in poly(3-hexylthiophene)/fullerene bulk heterojunction

    SciTech Connect

    Krinichnyi, V. I.; Yudanova, E. I.; Denisov, N. N.

    2009-07-28

    The first results of the light-induced EPR study of magnetic, relaxation, and dynamic parameters of charge carriers background photoinduced by optical photons (1.7-3.4 eV) in poly(3-hexylthiophene)/fullerene bulk heterojunctions are described. All magnetic resonance parameters for positively charged polaron and negatively charged fullerene ion-radical in radical pairs photoinduced in the composite were determined separately by the steady-state microwave saturation method. Paramagnetic susceptibility of charge carriers reflects their activation dynamics and exchange interaction. A decay of long-living radical pairs depends on the spatial distance between photoinduced charge carriers. The one-dimensional polaron diffusion along the polymer chain and fullerene rotation near the main molecular axis was shown to follow activation Elliot hopping model and to be governed by photon energy. The difference in activation energies of the charge carriers' dynamics and in their dependence on the exciting photon energy proves their noninteracting character in the polymer/fullerene composite. Main magnetic, relaxation and dynamics parameters of charge carriers are governed by the photon energy band due to inhomogeneity of distribution of polymer and fullerene domains in the composite.

  12. Recovery Online

    ERIC Educational Resources Information Center

    Clark, John R.

    2007-01-01

    Since the founding of Alcoholics Anonymous (AA) in 1935, programs offering opportunity for recovery from alcoholism and other addictions have undergone vast changes. The Internet has created nearly limitless opportunities for recovering people and those seeking recovery to find both meetings and places where they can gather virtually and discuss…

  13. EPR Study of [Cu(Him)4]·2Br Complex

    NASA Astrophysics Data System (ADS)

    Yıldırım, İ.; Karabulut, B.

    2016-04-01

    The single crystal of [Cu(Him)4]·2Br (Him: C3H4N2, imidazole) complex has been investigated at ambient temperature in three mutually perpendicular planes by EPR technique. The magnetic environments of [Cu(Him)4]·2Br complex have been identified by EPR technique. The study reveals the existence of two magnetically inequivalent Cu2+ sites. The principal values of g tensors were obtained. The EPR parameters show that the paramagnetic centers have rhombic symmetry.

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

    Cancer.gov

    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.

  15. Electron paramagnetic resonance- (EPR-) resolved kinetics of cryogenic nitric oxide recombination to cytochrome c oxidase and myoglobin.

    PubMed Central

    LoBrutto, R; Wei, Y H; Yoshida, S; Van Camp, H L; Scholes, C P; King, T E

    1984-01-01

    By the electron paramagnetic resonance (EPR) technique, recovery kinetics for nitric oxide (NO) to heme following cryogenic photolysis were studied for the nitrosylferrocytochrome a3 center in cytochrome c oxidase and for myoglobin. The recovery was nonexponential, as has been observed in previous cryogenic CO and O2 rebinding to heme systems. NO rebinding to heme a3 started near a temperature of 50 K and was related to a distribution of thermal activation energies. At the peak of the distribution the activation energy was 3.1 kcal/mol, and the preexponential in the recovery rate was 10(9.9) s-1. For recovery of NO back to the a3 heme, the activation energy was threefold less than that for CO where CO binds to nearby Cua3 following photolysis from heme a3, but was larger than the activation energy for CO, O2, and probably NO rebinding to myoglobin. NO ligand rebinding to myoglobin occurred at a temperature as low as 15 K and in a temperature regime where tunneling could occur. However, the rate of NO rebinding to myoglobin did increase with temperature in the 15-25 K range. PMID:6320917

  16. Implementing a new EPR lineshape parameter for organic radicals in carbonaceous matter

    PubMed Central

    2013-01-01

    Background Electron Paramagnetic Resonance (EPR) is a non-destructive, non-invasive technique useful for the characterization of organic moieties in primitive carbonaceous matter related to the origin of life. The classical EPR parameters are the peak-to-peak amplitude, the linewidth and the g factor; however, such parameters turn out not to suffice to fully determine a single EPR line. Results In this paper, we give the definition and practical implementation of a new EPR parameter based on the signal shape that we call the R10 factor. This parameter was originally defined in the case of a single symmetric EPR line and used as a new datation method for organic matter in the field of exobiology. Conclusion Combined to classical EPR parameters, the proposed shape parameter provides a full description of an EPR spectrum and opens the way to novel applications like datation. Such a parameter is a powerful tool for future EPR studies, not only of carbonaceous matter, but also of any substance which spectrum exhibits a single symmetric line. Reproducibility The paper is a literate program—written using Noweb within the Org-mode as provided by the Emacs editor— and it also describes the full data analysis pipeline that computes the R10 on a real EPR spectrum. PMID:23866970

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

    PubMed

    Nakagawa, Kouichi; Hara, Hideyuki

    2016-05-01

    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. PMID:26846304

  18. X- and Q-band EPR studies on fine powders of irradiated plants. New approach for detection of their radiation history by using Q-band EPR spectrometry

    NASA Astrophysics Data System (ADS)

    Yordanov, Nicola D.; Aleksieva, Katerina

    2004-01-01

    X- and Q-band EPR studies after γ-irradiation of some dry spices and aromatic herbs are reported. Before irradiation all samples show only one singlet line in X-band EPR, whereas the Q-band EPR spectrum of the same samples is a superposition of two individual spectra—one corresponding to the above EPR signal, with an anisotropic spectrum, and a second one consisting of six lines due to the Mn 2+ naturally present in plants. The radiation induced EPR signal due to cellulose free radicals was not detected after γ-irradiation, but only the increase of the natural signal present before the irradiation. The fading kinetic of this EPR signal was monitored in three cases—when samples were kept in plastic bags without any special conditioning after irradiation, when samples were covered with paraffin before irradiation and when samples were dried at 60°C for 1 h before irradiation. The studies show that stability of radiation induced EPR signals decreases in the order of: paraffin covered > heated before irradiation > kept at room conditions. The two EPR spectra in the Q-band—one with radiation dependent intensity and a second due to Mn 2+, which is radiation independent allow identification of previous radiation treatment based on the fact that Mn 2+ quantity in the sample is constant whereas the quantity of radiation-induced free radicals is temperature dependent. It was found that for irradiated samples the ratio between EPR intensity of the free radicals and that of Mn 2+ before and after heating decreases with 50-60% whereas for non-irradiated samples it is ca. 10-15%.

  19. Criteria for saturated magnetization loop

    NASA Astrophysics Data System (ADS)

    Harres, A.; Mikhov, M.; Skumryev, V.; Andrade, A. M. H. de; Schmidt, J. E.; Geshev, J.

    2016-03-01

    Proper estimation of magnetization curve parameters is vital in studying magnetic systems. In the present article, criteria for discrimination non-saturated (minor) from saturated (major) hysteresis loops are proposed. These employ the analysis of (i) derivatives of both ascending and descending branches of the loop, (ii) remanent magnetization curves, and (iii) thermomagnetic curves. Computational simulations are used in order to demonstrate their validity. Examples illustrating the applicability of these criteria to well-known real systems, namely Fe3O4 and Ni fine particles, are provided. We demonstrate that the anisotropy-field value estimated from a visual examination of an only apparently major hysteresis loop could be more than two times lower than the real one.

  20. Saturation of the turbulent dynamo.

    PubMed

    Schober, J; Schleicher, D R G; Federrath, C; Bovino, S; Klessen, R S

    2015-08-01

    The origin of strong magnetic fields in the Universe can be explained by amplifying weak seed fields via turbulent motions on small spatial scales and subsequently transporting the magnetic energy to larger scales. This process is known as the turbulent dynamo and depends on the properties of turbulence, i.e., on the hydrodynamical Reynolds number and the compressibility of the gas, and on the magnetic diffusivity. While we know the growth rate of the magnetic energy in the linear regime, the saturation level, i.e., the ratio of magnetic energy to turbulent kinetic energy that can be reached, is not known from analytical calculations. In this paper we present a scale-dependent saturation model based on an effective turbulent resistivity which is determined by the turnover time scale of turbulent eddies and the magnetic energy density. The magnetic resistivity increases compared to the Spitzer value and the effective scale on which the magnetic energy spectrum is at its maximum moves to larger spatial scales. This process ends when the peak reaches a characteristic wave number k☆ which is determined by the critical magnetic Reynolds number. The saturation level of the dynamo also depends on the type of turbulence and differs for the limits of large and small magnetic Prandtl numbers Pm. With our model we find saturation levels between 43.8% and 1.3% for Pm≫1 and between 2.43% and 0.135% for Pm≪1, where the higher values refer to incompressible turbulence and the lower ones to highly compressible turbulence. PMID:26382506

  1. Saturating the holographic entropy bound

    SciTech Connect

    Bousso, Raphael; Freivogel, Ben; Leichenauer, Stefan

    2010-10-15

    The covariant entropy bound states that the entropy, S, of matter on a light sheet cannot exceed a quarter of its initial area, A, in Planck units. The gravitational entropy of black holes saturates this inequality. The entropy of matter systems, however, falls short of saturating the bound in known examples. This puzzling gap has led to speculation that a much stronger bound, S < or approx. A{sup 3/4}, may hold true. In this note, we exhibit light sheets whose entropy exceeds A{sup 3/4} by arbitrarily large factors. In open Friedmann-Robertson-Walker universes, such light sheets contain the entropy visible in the sky; in the limit of early curvature domination, the covariant bound can be saturated but not violated. As a corollary, we find that the maximum observable matter and radiation entropy in universes with positive (negative) cosmological constant is of order {Lambda}{sup -1} ({Lambda}{sup -2}), and not |{Lambda}|{sup -3/4} as had hitherto been believed. Our results strengthen the evidence for the covariant entropy bound, while showing that the stronger bound S < or approx. A{sup 3/4} is not universally valid. We conjecture that the stronger bound does hold for static, weakly gravitating systems.

  2. Saturation diving; physiology and pathophysiology.

    PubMed

    Brubakk, Alf O; Ross, John A S; Thom, Stephen R

    2014-07-01

    In saturation diving, divers stay under pressure until most of their tissues are saturated with breathing gas. Divers spend a long time in isolation exposed to increased partial pressure of oxygen, potentially toxic gases, bacteria, and bubble formation during decompression combined with shift work and long periods of relative inactivity. Hyperoxia may lead to the production of reactive oxygen species (ROS) that interact with cell structures, causing damage to proteins, lipids, and nucleic acid. Vascular gas-bubble formation and hyperoxia may lead to dysfunction of the endothelium. The antioxidant status of the diver is an important mechanism in the protection against injury and is influenced both by diet and genetic factors. The factors mentioned above may lead to production of heat shock proteins (HSP) that also may have a negative effect on endothelial function. On the other hand, there is a great deal of evidence that HSPs may also have a "conditioning" effect, thus protecting against injury. As people age, their ability to produce antioxidants decreases. We do not currently know the capacity for antioxidant defense, but it is reasonable to assume that it has a limit. Many studies have linked ROS to disease states such as cancer, insulin resistance, diabetes mellitus, cardiovascular diseases, and atherosclerosis as well as to old age. However, ROS are also involved in a number of protective mechanisms, for instance immune defense, antibacterial action, vascular tone, and signal transduction. Low-grade oxidative stress can increase antioxidant production. While under pressure, divers change depth frequently. After such changes and at the end of the dive, divers must follow procedures to decompress safely. Decompression sickness (DCS) used to be one of the major causes of injury in saturation diving. Improved decompression procedures have significantly reduced the number of reported incidents; however, data indicate considerable underreporting of injuries

  3. EPR investigation of libration motion of spin labeled hemerythrin

    NASA Astrophysics Data System (ADS)

    Takacs, Istvan Mihaly; Mot, Augustin; Silaghi-Dumitrescu, Radu; Damian, Grigore

    2014-09-01

    Reported here are room-temperature continuous wave X-band Electron Paramagnetic Resonance (EPR) spectra of the non-heme di-iron protein hemerythrin (Hr), spin labeled at position 51C in different viscous media, illustrating the mobility and oligomeric recombination tendency of the Phascolopsis gouldii Hr. The mobility of a spin labeled Hr depends on the local viscosity and its connectivity to the nature of the molecular environment (glycerol, PEG4000 and BSA). This provides the basis for a tool useful in directly monitoring Hr in ex vivo samples upon injection within the bloodstream of test animals, for blood substitute research.

  4. EPR, NMR and molecular dynamics in fluoride glasses

    NASA Astrophysics Data System (ADS)

    Silly, G.; Buzaré, J. Y.; Bureau, B.; Legein, C.; Boulard, B.

    1999-11-01

    This paper deals with the method of investigation of local order in Transition Metal Fluoride Glasses that has been developed in the past few years using magnetic resonance techniques associated to molecular dynamics calculations. The results presented here will concern lead fluoride PZG (PbF2-ZnF2-GaF3) glasses of the PbF2-MtIIF2-MtIIIF3 family, but the method remains valid for any other disordered compound. The only limitations are that the sample may be doped with transition metal ions (S⩾1) for EPR measurements or contain quadrupolar nuclei (I⩾1) to perform NMR investigations.

  5. Mn distribution in natural sphalerites: a micronalytical and EPR study

    NASA Astrophysics Data System (ADS)

    di Benedetto, F.; Bernardini, G. P.; Cipriani, C.; Plant, D.; Romanelli, M.; Vaughan, D. J.

    2003-04-01

    Electron Paramagnetic Resonance (EPR) has been successfully applied to determine the local coordination and distribution of transition metal cations in sulphides and sulphosalts (Di Benedetto et al., 2002). Due to its enhanced sensitivity and element-specificity it is one of the best tools to monitor Mn(II) behaviour down to very low concentrations. In order to reach a fuller understanding of the spectroscopic results, a microanalytical study has also been undertaken by means of Electron Microprobe Analysis. Operating conditions were chosen to achieve the lowest possible detection limits, taking into account that Mn can replace Zn in the sphalerite lattice both as a minor and trace element, and that EPR can detect Mn(II) below the ppm range. Six natural samples from the Museo di Storia Naturale, Università di Firenze, were selected to have pure single crystals and avoid magnetically active phases associated with the sphalerite. The Mn concentration determined ranges between 30 and 14300 ppm and Mn content varies considerably within the same sample, leading to differences up to the 50% as compared to the mean value. X-ray images confirm Mn to be distributed with an unusual pattern, unrelated to the other common Zn-replacing cations, Fe and Cd, present in the samples. Powder EPR spectra reveal at least three different Mn(II) signals: two sextets, overlapping in all samples containing Mn as trace element, and a single line, present only in the more concentrated samples. While the latter have been attributed to an inhomogeneous Mn distribution, due to an enhanced Mn-Mn superexchange interaction, the difference between the two sextets, observed by means of EEPR investigations in a synthetic sphalerite (Di Benedetto et al., 2002), appears unrelated to the Mn concentration and may be attributed to small differences in the local coordination of Mn(II) ions. This, in turn, may be explained by the segregation of small amounts of Mn into polytypic domains, features which

  6. A Signal-to-Noise Standard for Pulsed EPR

    PubMed Central

    Eaton, Gareth R.; Eaton, Sandra S; Quine, Richard W.; Mitchell, Deborah; Kathirvelu, Velavan; Weber, Ralph T.

    2010-01-01

    A 2 mm diameter by 10 mm long cylinder of fused SiO2 (quartz) γ-irradiated to 1 kGy with 60Co contains about 2×1016 spins/cm3. It is proposed as a standard for monitoring signal-to-noise (S/N) performance of X-band pulsed EPR spectrometers. This sample yields S/N of about 25 on modern spin echo spectrometers, which permits measurement of both signal and noise under the same conditions with an 8-bit digitizer. PMID:20451433

  7. An EPR Experiment for the Undergraduate Physical Chemistry Laboratory

    NASA Astrophysics Data System (ADS)

    Butera, R. A.; Waldeck, D. H.

    2000-11-01

    An experiment that illustrates the principles of electron paramagnetic resonance spectroscopy in the undergraduate physical chemistry laboratory is described. Students measure the value of g for DPPH and use it to determine the value of g for two inorganic complexes, Cu(acac)2 and VO(acac)2. The students use two instruments: an instructional device that illustrates the principles of EPR and a commercial Varian E4 spectrometer. This approach allows an elucidation of the principles of the method and provides experience with a more sophisticated research-grade instrument.

  8. Geochemical constraints on the source of EPR MORBs

    NASA Astrophysics Data System (ADS)

    Tian, L.; Wang, Z.

    2015-12-01

    Geochemical variations of mid-ocean ridge basalts (MORBs) have long been attributed to the presence of compositionally distinct crustal and mantle components in their sources. The oxygen isotope composition of MORBs was proposed to be a valuable tracer of subducted crustal materials [1] since 18O/16O ratios are strongly fractioned during low-temperature water-rock interactions (e.g. seafloor alteration). Here, we present a study of combined oxygen isotopes, radiogenic isotopes, and trace elements on volcanic lavas sampled at both ridge axes and off-axis seamounts in the northern East Pacific Rise (EPR; 5-15°N). The chemical composition of these lavas ranges from normal-MORB to enriched-MORB, and the newly analyzed 18O/16O ratios of hand-picked fresh glasses from these 53 lavas were measured using laser-fluorination technique, with a typical precision of ±0.08‰ (1σ). Our results show that the δ18OSMOW values of EPR glasses span ~0.64‰ (from 5.08‰ to 5.72‰), with an average value of 5.53(±0.12, 1σ) ‰, which is comparable to results from previous survey of global MORBs (5.52±0.11‰) [1]. Two andesitic glasses show unusually lower δ18O values (5.08‰ and 5.27‰, respectively) and exhibit excess Cl addition ([Cl]>3000ppm), probably indicating an assimilation of seawater-derived component (e.g., saline brines or altered oceanic crust). Previous studies [2, 3, 4, 5] have shown the correlated variations of trace element ratios (e.g. La/Sm, and K2O/TiO2 element ratios) and radiogenic isotope compositions (e.g. 87Sr/86Sr, 143Nd/144Nd, Pb isotope ratios), suggesting the presence of at least two components in the source of EPR MORBs, an enriched component and depleted component. Our results show that δ18O values of these glasses lack statistically-significant correlations with other geochemical indicies in the same sample, suggesting that (1) the source of EPR MORBs has a uniform oxygen isotope composition, (2) the enriched components in the sources

  9. The effect of saturation path on three-phase relative permeability

    NASA Astrophysics Data System (ADS)

    Kianinejad, Amir; Chen, Xiongyu; DiCarlo, David A.

    2015-11-01

    Simulation and fluid flow prediction of many petroleum-enhanced oil recovery methods as well as environmental processes such as carbon dioxide (CO2) geological storage or underground water resources remediation requires accurate modeling and determination of relative permeability under different saturation histories. Based on this critical need, several three-phase relative permeability models were developed to predict relative permeability; however, for practical purposes most of them require a variety of parameters introducing undesired complexity to the models. In this work, we attempt to find out if there is a simpler way to express this functionality. To do so, we experimentally measure three-phase, water/oil/gas, relative permeability in a 1 m long water-wet sand pack, under several saturation flow paths to cover the entire three-phase saturation space. We obtain the in situ saturations along the sand pack using a CT scanner and then determine the relative permeabilities of liquid phases directly from the measured in situ saturations using an unsteady state method. The measured data show that at a specific saturation, the oil relative permeability varies significantly (up to two orders of magnitude), depending on the path through saturation space. The three-phase relative permeability data are modeled using standard relative permeability models, Corey-type, and Saturation Weighted Interpolation (SWI). Our measured data suggest that three-phase oil relative permeability in water-wet media is only a function of its own saturation if the residual oil saturation is treated as a function of two saturations. We determine that residual saturation is the key parameter in modeling three-phase relative permeability (effect of saturation history).

  10. Solution-phase EPR studies of single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Chen, J.; Hu, H.; Hamon, M. A.; Itkis, M. E.; Haddon, R. C.

    1999-01-01

    We report EPR studies on pristine, purified, shortened and soluble SWNTs in various solution phases. Some of these samples give rise to strong, sharp EPR signals, and this technique is useful for monitoring the presence of SWNTs in aqueous and organic solvents. The soluble SWNTs carry about 1 unpaired electron per 10000 carbon atoms and give a free electron g-value.

  11. Saturation of repeated quantum measurements

    NASA Astrophysics Data System (ADS)

    Haapasalo, Erkka; Heinosaari, Teiko; Kuramochi, Yui

    2016-08-01

    We study sequential measurement scenarios where the system is repeatedly subjected to the same measurement process. We first provide examples of such repeated measurements where further repetitions of the measurement do not increase our knowledge on the system after some finite number of measurement steps. We also prove, however, that repeating the Lüders measurement of an unsharp two-outcome observable never saturates in this sense, and we characterize the observable measured in the limit of infinitely many repetitions. Our result implies that a repeated measurement can be used to correct the inherent noise of an unsharp observable.

  12. Gluon Evolution and Saturation Proceedings

    SciTech Connect

    McLerran, L.D.

    2010-05-26

    Almost 40 years ago, Gribov and colleagues at the Leningrad Nuclear Physics Institute developed the ideas that led to the Dokhsitzer-Gribov-Altarelli-Parisi the Baltisky-Fadin-Kuraev-Lipatov equations. These equations describe the evolution of the distributions for quarks and gluon inside a hadron to increased resolution scale of a probe or to smaller values of the fractional momentum of a hadronic constituent. I motivate and discuss the generalization required of these equations needed for high energy processes when the density of constituents is large. This leads to a theory of saturation realized by the Color Glass Condensate

  13. Alcoholic extraction enables EPR analysis to characterize radiation-induced cellulosic signals in spices.

    PubMed

    Ahn, Jae-Jun; Sanyal, Bhaskar; Akram, Kashif; Kwon, Joong-Ho

    2014-11-19

    Different spices such as turmeric, oregano, and cinnamon were γ-irradiated at 1 and 10 kGy. The electron paramagnetic resonance (EPR) spectra of the nonirradiated samples were characterized by a single central signal (g = 2.006), the intensity of which was significantly enhanced upon irradiation. The EPR spectra of the irradiated spice samples were characterized by an additional triplet signal at g = 2.006 with a hyperfine coupling constant of 3 mT, associated with the cellulose radical. EPR analysis on various sample pretreatments in the irradiated spice samples demonstrated that the spectral features of the cellulose radical varied on the basis of the pretreatment protocol. Alcoholic extraction pretreatment produced considerable improvements of the EPR signals of the irradiated spice samples relative to the conventional oven and freeze-drying techniques. The alcoholic extraction process is therefore proposed as the most suitable sample pretreatment for unambiguous detection of irradiated spices by EPR spectroscopy. PMID:25347931

  14. EPR Studies of Gating Mechanisms in Ion Channels

    PubMed Central

    Chakrapani, Sudha

    2015-01-01

    Ion channels open and close in response to diverse stimuli, and the molecular events underlying these processes are extensively modulated by ligands of both endogenous and exogenous origin. In the past decade, high-resolution structures of several channel types have been solved, providing unprecedented details of the molecular architecture of these membrane proteins. Intrinsic conformational flexibility of ion channels critically governs their functions. However, the dynamics underlying gating mechanisms and modulations are obscured in the information from crystal structures. While nuclear magnetic resonance spectroscopic methods allow direct measurements of protein dynamics, they are limited by the large size of these membrane protein assemblies in detergent micelles or lipid membranes. Electron paramagnetic resonance (EPR) spectroscopy has emerged as a key biophysical tool to characterize structural dynamics of ion channels and to determine stimulus-driven conformational transition between functional states in a physiological environment. This review will provide an overview of the recent advances in the field of voltage- and ligand-gated channels and highlight some of the challenges and controversies surrounding the structural information available. It will discuss general methods used in site-directed spin labeling and EPR spectroscopy and illustrate how findings from these studies have narrowed the gap between high-resolution structures and gating mechanisms in membranes, and have thereby helped reconcile seemingly disparate models of ion channel function. PMID:25950970

  15. Double-stacked dielectric resonator for sensitive EPR measurements.

    PubMed

    Jaworski, M; Sienkiewicz, A; Scholes, C P

    1997-01-01

    A new approximate method for predicting the resonant frequencies and for solving the field distribution problem of a cylindrical dielectric resonator (DR) is developed. The model proposed in this paper bridges the gap between rigorous and accurate finite-element or Green function-based numerical methods on the one hand and on the other hand, simple approximate solutions in which the field distribution can be described analytically, but the resulting frequency is accurate within a few percent only. In the method described here, the approximate solution for the microwave field distribution is modified by substituting different values of the radial separation constants inside and outside of the diskshaped DR. The model is generalized for the double-stacked DR structure and enables one to introduce corrections that take into account the presence of the shielding walls and of the cylindrical sample hole. Good agreement is found between experimental and calculated results for both the single and double-stacked structures that are designed around commercially available X-band DRs (9-10 GHz). For the resonant frequency of the lowest transverse-electric TEzero1 delta mode that is commonly used for EPR measurements, the accuracy of the method is better than 1%. Experimentally measured resonator filling factors are also in good agreement with those theoretically estimated. Both the theory and the experimental results suggest that the double-stacked DR structure with finite spacing between the ceramic cylinders is the most suitable for EPR measurements of long lossy samples. PMID:9169212

  16. EPR study of gamma-irradiated single crystal 4-phenylsemicarbazide

    NASA Astrophysics Data System (ADS)

    Sayin, U.; Türkkan, E.; Dereli, Ö.; Yüksel, H.; Birey, M.

    2010-08-01

    Single crystals of 4-phenylsemicarbazide (4PSC) were investigated using an electron paramagnetic resonance (EPR) technique, with γ irradiation of the crystals at different orientations in the magnetic field between temperatures of 120 and 450 K, and the spectra were found to be temperature independent. Taking into consideration the chemical structure and the experimental spectra of the irradiated single crystal 4PSC, we assumed that one or more paramagnetic species were produced, each having an unpaired electron delocalized in the phenyl ring. Pursuant to this assumption, six possible radicals were modeled using the B3LYP/6-311+G(d) level of density-functional theory. EPR parameters were calculated for these modeled radicals using the B3LYP method and TZVP basis set. The calculated hyperfine coupling constants were used as starting points for simulations. The experimental and simulated spectra for each of the three crystallographic axes were well matched for the modeled radical R6. We thus identified the R6 (C 6H 5NH) radical as a paramagnetic species produced in 4PSC. The experimental g-factor and hyperfine coupling constants of the C 6H 5NH radical were found to be anisotropic, with the average values g=2.00431, aNHN(8)=8.85 G, aNHH(9)=16.85 G, ao,pH(14,16,20)=6.47 G, and amH(18,19)=2.80 G.

  17. EPR Spectroscopic Studies of [FeFe]-Hydrogenase Maturation

    PubMed Central

    Suess, Daniel L. M.

    2015-01-01

    Proton reduction and H2 oxidation are key elementary reactions for solar fuel production. Hydrogenases interconvert H+ and H2 with remarkable efficiency and have therefore received much attention in this context. For [FeFe]-hydrogenases, catalysis occurs at a unique cofactor called the H-cluster. In this article, we discuss ways in which EPR spectroscopy has elucidated aspects of the bioassembly of the H-cluster, with a focus on four case studies: EPR spectroscopic identification of a radical en route to the CO and CN− ligands of the H-cluster, tracing 57Fe from the maturase HydG into the H-cluster, characterization of the auxiliary Fe–S cluster in HydG, and isotopic labeling of the CN− ligands of HydA for electronic structure studies of its Hox state. Advances in cell-free maturation protocols have enabled several of these mechanistic studies, and understanding H-cluster maturation may in turn provide insights leading to improvements in hydrogenase production for biotechnological applications. PMID:26508821

  18. W/O microemulsions as dendrimer nanocarriers: an EPR study.

    PubMed

    Rokach, Shifra; Ottaviani, Maria Francesca; Shames, Alexander I; Nir, Ido; Aserin, Abraham; Garti, Nissim

    2012-10-18

    A complex system, based on a dendrimer solubilized in the aqueous core of water-in-oil microemulsion, may combine the advantages of both dendrimers and microemulsions to provide better control of drug release. We report for the first time the use of EPR technique to determine the effect of solubilized dendrimer on the structure of the microemulsion. The solubilized poly(propyleneimine) (PPI-G2) interacts with sodium bis(2-ethylhexyl) sulfosuccinate (AOT). EPR analysis provided information on polarity, microviscosity, and molecular order of the systems. Polarity and microviscosity increased from unloaded water-in-oil microemulsion to the system loaded with 0.2 wt % PPI-G2, but remained unchanged with higher PPI-G2 loads. The degree of order also increased with 0.2 wt % PPI-G2 with only minor additional increase with larger quantities (25 wt %) of PPI-G2. Variations in pH only slightly affected the structure of microemulsion in the absence and presence of the loaded dendrimers. Aliphatic oils with longer lipophilic chains enhanced the structural order of the microemulsion. On increasing water content, polarity and degree of order increased. PPI-G2 dendrimer in small loads is attracted by the negatively charged AOT and thus intercalates in the interface of the droplets. Yet, at higher PPI-G2 loads, the excess molecules are solubilized in the water core. PMID:22989387

  19. Antioxidant properties of tea investigated by EPR spectroscopy.

    PubMed

    Polovka, Martin; Brezová, Vlasta; Stasko, Andrej

    2003-10-01

    The antioxidant properties of green, black and mixed (fruit) tea samples of different origin were investigated by means of EPR spectroscopy. A six line EPR spectrum of solid tea samples indicates the presence of Mn(II) ions and it is superimposed with a sharp singlet line attributed to semiquinone radical species (Delta H(pp)=1 mT; g=2.0022). Antioxidant properties of aqueous tea extracts in H(2)O(2)/NaOH/dimethylsulfoxide system generating reactive radicals (*OH, O(2)*-), *CH(3)) were followed by spin trapping technique. In addition, antioxidant capacity of these samples was assessed using stable radicals 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPOL). Typically, the highest antioxidant potential to terminate superoxide radicals was found in green teas, followed by black and fruity teas. The pro-oxidant activity of green teas evidenced by spin traps was promoted in samples with higher Mn(II) and ascorbic acid concentrations. Various sources of free radicals used in the antioxidant tests due to their specific action show different termination rates in the presence of the individual tea samples. PMID:14516911

  20. Waste heat recovery method and apparatus

    SciTech Connect

    Farnia, Kh.

    1984-05-01

    An apparatus and method are disclosed for the recovery of sensible heat from a hot tar-free gas produced in a coal gasification process and in combined-cycle power generation. The recovered heat is utilized to generate a flow of superheated steam which may be used in the gasification plant. The apparatus includes a first boiler and a superheater fabricated from materials susceptible to damage from thermal shock when a flow of the tar-free gas having a temperature in excess of a predetermined safety temperature is introduced to the superheater when it is dry. The first boiler, filled with a flow of saturated water, initially receives the flow of gas. Within the first boiler, the gas indirectly heats the water converting it to a flow of saturated steam and reducing the gas temperature below the safety temperature. The reduced temperature gas is passed to the superheater and the saturated steam is passed to the superheater. The gas heats the saturated steam in the superheater to convert it to superheated steam and the temperature of the gas is further reduced. The gas flows to a second boiler for converting a flow of saturated water to saturated steam and further reducing the gas temperature. The saturated steam from the second boiler is passed to the superheater and the gas flows to an economizer for converting a flow of unsaturated water to saturated water for the boilers and reducing the temperature of the gas to a final temperature.

  1. VHF EPR analysis of organic sulfur in coal. Final technical report, September 1, 1991--August 31, 1992

    SciTech Connect

    Clarkson, R.B.; Belford, R.L.

    1992-12-31

    The development of very High Frequency Electron Paramagnetic Resonance (VHF-EPR) into an analytical technique that holds great promise for the non-destructive determination of the amount and structure of organic sulfur in both native and desulfurized coal advanced considerably during the past year. The VHF-EPR spectrometer built with funds from the CRSC is one of two operating near 96 GHz, and the only such instrument in the United States. Earlier work has shown that W-band spectra of Illinois coals and separated macerals shows good sensitivity to forms of organic sulfur present. This work has been extended to improve the use of W-band spectra to provide quantitative as well as qualitative information regarding different sulfur species and, in collaboration with other researchers, their fate during various desulfurizing techniques. A key approach is to synthesize various model compounds, both those from known precursors and those made as sulfurized chars, and to compare their respective W-band spectra (1) with each other, (2) with the predictions of theoretical models, and (3) with the W-band spectra of coal specimens. The quantitative measurement of aromatic sulfur in these compounds has improved as different methods of calibration and indexing are evaluated. Work is also being conducted on apparent variations in spectral line-shapes on evacuation of coal samples. Corroborations of many aspects of W-band organic sulfur interpretation in both raw and desulfurized coals as well as in model compounds are also being carried out by microanalysis and by high-temperature mass spectroscopy. The determination of populations of groups or species of aromatic sulfur molecules is being refined. Especially promising are methods to improve discrimination by differing saturation rates, and by second-derivative spectra.

  2. Redox intermediates of flavonoids and caffeic acid esters from propolis: an EPR spectroscopy and cyclic voltammetry study.

    PubMed

    Rapta, P; Misík, V; Stasko, A; Vrábel, I

    1995-05-01

    The redox properties of flavonoids: chrysin (1), tectochrysin (2), galangin (3), isalpinin (4), pinostrobin (5), pinobanksin (6), pinobanksin-3-acetate (7), and of caffeic acid ester (8) and diacetylcaffeic acid ester (9), all isolated from propolis, were investigated by cyclic voltammetry in acetonitrile. The choice of aprotic solvent lowered the reactivity of the radical intermediates and made possible to identify redox steps and intermediates not detected so far. The oxidation potentials (vs. saturated calomel electrode) of the investigated compounds were in the region of 1.5 V for 3 and 4; 1.9 V for 1, 2, and 5; 2.0 V for 6 and 7; 1.29 V for 8; and 2.3 V for 9. These oxidation potentials were mainly influenced by the presence of a double bond in 2,3-position and substituent R1 in position 3. Comparison with our earlier data revealed that flavonoids, 1-4, and caffeic acid ester 8 with lower oxidation potentials showed the maximal lipid antioxidant activity, whereas those with higher potentials (5, 6, 7, and 9) are less active. On reduction of 1-9 several one-electron-steps were typically observed in the potential regions: -1.5 V, -1.8 V, and -2 V. where in simultaneous EPR experiments anion radicals of 1 and 3 were observed with the center of unpaired spin density on ring A. Upon oxidation of flavonoids 1-4 carbonyl carbon-centered radicals, .C(O)R, were identified as consecutive products using the EPR spin trapping technique. PMID:7797098

  3. Perception of saturation in natural scenes.

    PubMed

    Schiller, Florian; Gegenfurtner, Karl R

    2016-03-01

    We measured how well perception of color saturation in natural scenes can be predicted by different measures that are available in the literature. We presented 80 color images of natural scenes or their gray-scale counterparts to our observers, who were asked to choose the pixel from each image that appeared to be the most saturated. We compared our observers' choices to the predictions of seven popular saturation measures. For the color images, all of the measures predicted perception of saturation quite well, with CIECAM02 performing best. Differences between the measures were small but systematic. When gray-scale images were viewed, observers still chose pixels whose counterparts in the color images were saturated above average. This indicates that image structure and prior knowledge can be relevant to perception of saturation. Nevertheless, our results also show that saturation in natural scenes can be specified quite well without taking these factors into account. PMID:26974924

  4. Stochastic excitation and Hadamard correlation spectroscopy with bandwidth extension in RF FT-EPR

    PubMed Central

    Pursley, Randall H.; Kakareka, John; Salem, Ghadi; Devasahayam, Nallathamby; Subramanian, Sankaran; Tschudin, Rolf G.; Krishna, Murali C.; Pohida, Thomas J.

    2012-01-01

    The application of correlation spectroscopy employing stochastic excitation and the Hadamard transform to time-domain Fourier transform electron paramagnetic resonance (FT-EPR) spectroscopy in the radiofrequency (RF) band is described. An existing, time-domain FT-EPR spectrometer system with a Larmor frequency (Lf) of 300 MHz was used to develop this technique by incorporating a pseudo-random pulse sequence generator to output the maximum length binary sequence (MLBS, 10- and 11-bit). Software developed to control the EPR system setup, acquire the signals, and post process the data, is outlined. The software incorporates the Hadamard transform algorithm to perform the required cross-correlation of the acquired signal and the MLBS after stochastic excitation. To accommodate the EPR signals, bandwidth extension was accomplished by sampling at a rate many times faster than the RF pulse repetition rate, and subsequent digital signal processing of the data. The results of these experiments showed that there was a decrease in the total acquisition time, and an improved free induction decay (FID) signal-to-noise (S/N) ratio compared to the conventional coherent averaging approach. These techniques have the potential to reduce the RF pulse power to the levels used in continuous wave (CW) EPR while retaining the advantage of time-domain EPR methods. These methods have the potential to facilitate the progression to in vivo FT-EPR imaging of larger volumes. PMID:12762981

  5. Active cancellation - A means to zero dead-time pulse EPR

    NASA Astrophysics Data System (ADS)

    Franck, John M.; Barnes, Ryan P.; Keller, Timothy J.; Kaufmann, Thomas; Han, Songi

    2015-12-01

    The necessary resonator employed in pulse electron paramagnetic resonance (EPR) rings after the excitation pulse and creates a finite detector dead-time that ultimately prevents the detection of signal from fast relaxing spin systems, hindering the application of pulse EPR to room temperature measurements of interesting chemical or biological systems. We employ a recently available high bandwidth arbitrary waveform generator (AWG) to produce a cancellation pulse that precisely destructively interferes with the resonant cavity ring-down. We find that we can faithfully detect EPR signal at all times immediately after, as well as during, the excitation pulse. This is a proof of concept study showcasing the capability of AWG pulses to precisely cancel out the resonator ring-down, and allow for the detection of EPR signal during the pulse itself, as well as the dead-time of the resonator. However, the applicability of this approach to conventional EPR experiments is not immediate, as it hinges on either (1) the availability of low-noise microwave sources and amplifiers to produce the necessary power for pulse EPR experiment or (2) the availability of very high conversion factor micro coil resonators that allow for pulse EPR experiments at modest microwave power.

  6. Active cancellation - A means to zero dead-time pulse EPR.

    PubMed

    Franck, John M; Barnes, Ryan P; Keller, Timothy J; Kaufmann, Thomas; Han, Songi

    2015-12-01

    The necessary resonator employed in pulse electron paramagnetic resonance (EPR) rings after the excitation pulse and creates a finite detector dead-time that ultimately prevents the detection of signal from fast relaxing spin systems, hindering the application of pulse EPR to room temperature measurements of interesting chemical or biological systems. We employ a recently available high bandwidth arbitrary waveform generator (AWG) to produce a cancellation pulse that precisely destructively interferes with the resonant cavity ring-down. We find that we can faithfully detect EPR signal at all times immediately after, as well as during, the excitation pulse. This is a proof of concept study showcasing the capability of AWG pulses to precisely cancel out the resonator ring-down, and allow for the detection of EPR signal during the pulse itself, as well as the dead-time of the resonator. However, the applicability of this approach to conventional EPR experiments is not immediate, as it hinges on either (1) the availability of low-noise microwave sources and amplifiers to produce the necessary power for pulse EPR experiment or (2) the availability of very high conversion factor micro coil resonators that allow for pulse EPR experiments at modest microwave power. PMID:26507308

  7. The view from the trenches: part 2-technical considerations for EPR screening.

    PubMed

    Nicolalde, Roberto J; Gougelet, Robert M; Rea, Michael; Williams, Benjamin B; Dong, Ruhong; Kmiec, Maciej M; Lesniewski, Piotr N; Swartz, Harold M

    2010-02-01

    There is growing awareness of the need for methodologies that can be used retrospectively to provide the biodosimetry needed to carry out screening and triage immediately after an event in which large numbers of people have potentially received clinically significant doses of ionizing radiation. The general approach to developing such methodologies has been a technology centric one, often ignoring the system integrations considerations that are key to their effective use. In this study an integrative approach for the evaluation and development of a physical biodosimetry technology was applied based on in vivo electron paramagnetic resonance (EPR) dosimetry. The EPR measurements are based on physical changes in tissues whose magnitudes are not affected by the factors that can confound biologically-based assessments. In this study the use of a pilot simulation exercise to evaluate an experimental EPR system and gather stakeholders' feedback early on in the development process is described. The exercise involved: ten non-irradiated participants, representatives from a local fire department; Department of Homeland Security certified exercise evaluators, EPR experts, physicians; and a human factors engineer. Stakeholders were in agreement that the EPR technology in its current state of development could be deployed for the screening of mass casualties. Furthermore, stakeholders' recommendations will be prioritized and incorporated in future developments of the EPR technique. While the results of this exercise were aimed specifically at providing feedback for the development of EPR dosimetry for screening mass casualties, the methods and lessons learned are likely to be applicable to other biodosimetric methods. PMID:20065674

  8. EPR pairing dynamics in Hubbard model with resonant U

    PubMed Central

    Zhang, X. Z.; Song, Z.

    2016-01-01

    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. PMID:26728282

  9. Carotenoid cation radicals: electrochemical, optical, and EPR study

    SciTech Connect

    Grant, J.L.; Kramer, V.J.; Ding, R.; Kispert, L.D.

    1988-03-30

    The general aim of this investigation is to determine whether carotenoid cation radicals can be produced, and stabilized, electrochemically. Hence, the authors have undertaken a detailed study of the electrooxidation of various carotenoids (..beta..-carotene (I), ..beta..-apo-8'-carotenal (II), and canthaxanthin (III) using the techniques of cyclic voltammetry, controlled-potential electrolysis (cpe) in conjunction with optical spectroscopy, and EPR spectroscopy coupled with in situ electrolysis. They report the successful generation of carotenoid cation radicals via electrochemical oxidation and, furthermore, the stabilization of these radicals for several minutes in CH/sub 2/Cl/sub 2/ and C/sub 2/H/sub 4/Cl/sub 2/ solvents.

  10. EPR Oximetry in Three Spatial Dimensions using Sparse Spin Distribution

    PubMed Central

    Som, Subhojit; Potter, Lee C.; Ahmad, Rizwan; Vikram, Deepti S.; Kuppusamy, Periannan

    2008-01-01

    A method is presented to use continuous wave electron paramagnetic resonance imaging for rapid measurement of oxygen partial pressure in three spatial dimensions. A particulate paramagnetic probe is employed to create a sparse distribution of spins in a volume of interest. Information encoding location and spectral linewidth is collected by varying the spatial orientation and strength of an applied magnetic gradient field. Data processing exploits the spatial sparseness of spins to detect voxels with nonzero spin and to estimate the spectral linewidth for those voxels. The parsimonious representation of spin locations and linewidths permits an order of magnitude reduction in data acquisition time, compared to four-dimensional tomographic reconstruction using traditional spectral-spatial imaging. The proposed oximetry method is experimentally demonstrated for a lithium octa-n-butoxy naphthalocyanine (LiNc-BuO) probe using an L-band EPR spectrometer. PMID:18538600

  11. N-Player Quantum Games in an EPR Setting

    PubMed Central

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

    2012-01-01

    The -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 -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’ payoff matrices are then defined using linear functions so that common two-player games can be easily extended to the -player case and permit analytic expressions for the Nash equilibrium. As a specific example, we solve the Prisoners’ Dilemma game for general . 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. PMID:22606258

  12. Implementing EPR Dosimetry for Life-Threatening Incidents

    PubMed Central

    Flood, Ann Barry; Bhattacharyya, Shayan; Nicolalde, R. Javier; Swartz, Harold M.

    2007-01-01

    Starting with the assumption that a device to detect unplanned radiation exposures is technically superior to current technology, we examine the additional stakeholders and processes that must be considered to move the device from the lab into use. The use is to provide reliable information to triage people for early treatment of exposure to ionizing radiation that could lead to the Acute Radiation Syndrome. The scenario is a major accident or terrorist event that leaves a large number of people potentially exposed, with the resulting need to identify those to treat promptly or not. In vivo EPR dosimetry is the exemplar of such a technique. Three major areas are reviewed: policy considerations, regulatory clearance, and production of the device. Our analysis of policy-making indicates that the current system is very complex, with multiple significant decision-makers who may have conflicting agendas. Adoption of new technologies by policy-makers is further complicated because many sources of expert input already have made public stances or have reasons to prefer current solutions, e.g., some may have conflicts of interest in approving new devices because they are involved with the development or adoption of competing techniques. Regulatory clearance is complicated by not being able to collect evidence via clinical trials of its intended use, but pathways for approval for emergency use are under development by the FDA. The production of the new device could be problematical if the perceived market is too limited, particularly for private manufacturers; for in vivo EPR dosimetry the potential for other uses may be a mitigating factor. Overall we conclude that technical superiority of a technique does not in itself assure its rapid and effective adoption, even where the need is great and the alternatives are not satisfactory for large populations. Many important steps remain to achieve the goals of approval and adoption for use. PMID:18591990

  13. EPR retrospective dosimetry with fingernails: report on first application cases.

    PubMed

    Trompier, Francois; Queinnec, François; Bey, Eric; De Revel, Thierry; Lataillade, Jean Jacques; Clairand, Isabelle; Benderitter, Marc; Bottollier-Depois, Jean-François

    2014-06-01

    For localized irradiation to hands, in case of sources accidentally handled, it is very difficult to estimate the dose distribution by calculation. Doses may reach several tens of grays, and the dose distribution is usually very heterogeneous. Until recently, doses in such situations could be estimated only by analysis of bone biopsies using Electron Paramagnetic Resonance (EPR) spectroscopy. This technique was used previously on surgical wastes or after amputation of a finger. In this case, the dose information was available in one or a few locations on the hand only, due to the limited number of biopsy fragments usually collected. The idea to measure free radicals (FRs) induced by radiation in nails to estimate a dose is not new, but up to now, no application cases were reported. As a matter of fact, the EPR analysis of nails is complex due to the presence of intrinsic signals and parasitic signals induced by the mechanical stress (when nails are collected), which overlaps the radio-induced components. In addition, the radio-induced FRs identified up to now are unstable and very sensitive to humidity. In these conditions, it was difficult to foresee any application for dosimetry with fingernails. Recently, stable radio-induced FRs in nails has been identified and an associated protocol for dose assessment developed. This protocol has been applied by the Institut de Radioprotection et de Sûreté Nucléaire on fingernail samples from victims of three different radiological accidents that occurred between 2008 and 2012 in different places. PMID:24776914

  14. Measuring tissue oxygen saturation using NIR spectroscopy

    NASA Astrophysics Data System (ADS)

    Sircan-Kucuksayan, Aslinur; Uyuklu, Mehmet; Canpolat, Murat

    2014-05-01

    Tissue oxygen saturation (StO2) is known quite useful parameter for medical applications. A spectroscopic method has been developed to diagnose pathologic tissues due to lack of normal blood circulation by measuring tissue oxygen saturation. In the study, human blood samples with different level of oxygen saturations have been prepared and spectra were taken using an optical fiber probe to investigate correlation between the oxygen saturations and the spectra. The experimental set up for the spectroscopic measurements was consists of a miniature NIR light spectrometer, an optical fiber probe, a halogen-tungsten light source and a laptop. A linear correlation between the oxygen saturation of the blood samples and the ratio of the light of wavelengths 660 nm to 790 nm has been found from the spectra. Then, oxygen saturations of the blood samples were estimated from the spectroscopic measurements within an error of 2.9%. Furthermore, it has been shown that the linear dependence between the ratio and the oxygen saturation of the blood samples was valid for the blood samples with different hematocrits. Tissue oxygen saturation has been estimated from the spectroscopic measurements were taken from the fingers of healthy volunteers using the correlation between the spectra and blood oxygen saturation. The tissue StO2 measured was 80% as expected. The technique developed to measure tissue oxygen saturation has potential to diagnose premalignant tissues, follow up prognosis of cancerous tissues, and evaluation of ischemia reperfusion tissues.

  15. EPR as an analytical tool in assessing the mineral nutrients and irradiated food products-vegetables

    NASA Astrophysics Data System (ADS)

    Prasuna, C. P. Lakshmi; Chakradhar, R. P. S.; Rao, J. L.; Gopal, N. O.

    2008-12-01

    EPR spectral investigations of some commonly available vegetables in south India, which are of global importance like Daucus carota (carrot), Cyamopsis tetragonoloba (cluster beans), Coccinia indica (little gourd) and Beta vulgaris (beet root) have been carried out. In all the vegetable samples a free radical corresponding to cellulose radical is observed. Almost all the samples under investigation exhibit Mn ions in different oxidation states. The temperature variation EPR studies are done and are discussed in view of the paramagnetic oxidation states. The radiation-induced defects have also been assessed by using the EPR spectra of such irradiated food products.

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

    NASA Astrophysics Data System (ADS)

    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.

  17. Bell Correlated and EPR States in the Framework of Jordan Algebras

    NASA Astrophysics Data System (ADS)

    Hamhalter, Jan; Sobotíková, Veronika

    2016-03-01

    We study Bell inequalities and EPR states in the context of Jordan algebras. We show that the set of states violating Bell inequalities across two operator commuting nonmodular Jordan Banach algebras is norm dense in the global state space. It generalizes hitherto known results in quantum field theory in several directions. We propose new Jordan quantity for incommensurable observables in a given state, introduce the concept of EPR state for Jordan structures, and study relationship between EPR states and Bell correlated states. Our analysis shows crucial role of spin factors and Pauli spin matrices for studying noncommutative properties of states and observables.

  18. EPR dosimetric properties of 2-methylalanine pellet for radiation processing application

    NASA Astrophysics Data System (ADS)

    Soliman, Y. S.; Ali, Laila I.; Moustafa, H.; Tadros, Soad M.

    2014-09-01

    The dosimetric characteristics of γ-radiation induced free radicals in 2-methylalanine (2MA) pellet dosimeter are investigated using electron paramagnetic resonance (EPR) in the high-dose range of 1-100 kGy. The EPR spectrum of γ-irradiated 2MA exhibits an isotropic EPR signal with seven lines. The dosimeter response is humidity independent in the range of 33-76% relative humidity. The manufactured dosimeter is typically adipose tissue equivalent in the energy level of 0.1-15 MeV. The overall uncertainty (2σ) of the dosimeter is less than 6.9%.

  19. Optimal strategies for tests of EPR-Steering with no detection loophole

    NASA Astrophysics Data System (ADS)

    Evans, David A.; Wiseman, Howard M.

    2014-12-01

    It has been shown in earlier works that the vertices of Platonic solids are good measurement choices for tests of EPR-Steering. Such measurements are regularly spaced, and measurement diversity is a good feature for making EPR-Steering inequalities easier to violate with entangled states. However, such measurements are provably suboptimal. By scrutinising not only the average results, but also the measurement statistics of cheating strategies in a Local Hidden State model, we outline a method for devising optimal strategies for EPR-Steering tests with no detection loophole.

  20. Microwave (EPR) measurements of the penetration depth measurements of high-Tc superconductors

    NASA Technical Reports Server (NTRS)

    Dalal, N. S.; Rakvin, B.; Mahl, T. A.; Bhalla, A. S.; Sheng, Z. Z.

    1991-01-01

    The use is discussed of electron paramagnetic resonance (EPR) as a quick and easily accessible method for measuring the London penetration depth, lambda for the high T sub c superconductors. The method uses the broadening of the EPR signal, due to the emergence of the magnetic flux lattice, of a free radical adsorbed on the surface of the sample. The second moment, of the EPR signal below T sub c is fitted to the Brandt equation for a simple triangular lattice. The precision of this method compares quite favorably with those of the more standard methods such as micro sup(+)SR, neutron scattering, and magnetic susceptibility.

  1. Method for enhanced oil recovery

    DOEpatents

    Comberiati, Joseph R.; Locke, Charles D.; Kamath, Krishna I.

    1980-01-01

    The present invention is directed to an improved method for enhanced recovery of oil from relatively "cold" reservoirs by carbon dioxide flooding. In oil reservoirs at a temperature less than the critical temperature of 87.7.degree. F. and at a pore pressure greater than the saturation pressure of carbon dioxide at the temperature of the reservoir, the carbon dioxide remains in the liquid state which does not satisfactorily mix with the oil. However, applicants have found that carbon dioxide can be vaporized in situ in the reservoir by selectively reducing the pore pressure in the reservoir to a value less than the particular saturated vapor pressure so as to greatly enhance the mixing of the carbon dioxide with the oil.

  2. Power flow control using distributed saturable reactors

    DOEpatents

    Dimitrovski, Aleksandar D.

    2016-02-13

    A magnetic amplifier includes a saturable core having a plurality of legs. Control windings wound around separate legs are spaced apart from each other and connected in series in an anti-symmetric relation. The control windings are configured in such a way that a biasing magnetic flux arising from a control current flowing through one of the plurality of control windings is substantially equal to the biasing magnetic flux flowing into a second of the plurality of control windings. The flow of the control current through each of the plurality of control windings changes the reactance of the saturable core reactor by driving those portions of the saturable core that convey the biasing magnetic flux in the saturable core into saturation. The phasing of the control winding limits a voltage induced in the plurality of control windings caused by a magnetic flux passing around a portion of the saturable core.

  3. Reproducibility of muscle oxygen saturation.

    PubMed

    Thiel, C; Vogt, L; Himmelreich, H; Hübscher, M; Banzer, W

    2011-04-01

    The present study evaluated the reproducibility of tissue oxygenation in relation to oxygen consumption (VO2) across cycle exercise intensities in a test-retest design. 12 subjects (25.7±2.1 years; 24.7±1.9 kg · m(-2)) twice performed an incremental bicycle exercise protocol, while tissue oxygen saturation (StO2) in the vastus lateralis muscle was monitored by a commercially available NIRS unit and VO2 determined by an open-circuit indirect calorimetric system. Coefficients of variation across rest, workloads corresponding to 25, 50 and 75% of individual maximum capacity, and maximum load were 5.8, 4.6, 6.1, 8.0, 11.0% (StO2) and 7.6, 6.0, 3.7, 3.4, 3.1% (VO2), respectively. 95 % CI of relative test-retest differences ranged from -5.6 to +5.4% at 25% load to -17.2 to +7.5% at maximum load for StO2 and from -7.3 to +7.7% at rest to -3.3 to +3.2% at maximum load for VO2. With advancing exercise intensity, within-subject variability of StO2 was augmented, whereas VO2 variability slightly attenuated. NIRS measurements at higher workloads need to be interpreted with caution. PMID:21271493

  4. Casimir experiments showing saturation effects

    SciTech Connect

    Sernelius, Bo E.

    2009-10-15

    We address several different Casimir experiments where theory and experiment disagree. First out is the classical Casimir force measurement between two metal half spaces; here both in the form of the torsion pendulum experiment by Lamoreaux and in the form of the Casimir pressure measurement between a gold sphere and a gold plate as performed by Decca et al.; theory predicts a large negative thermal correction, absent in the high precision experiments. The third experiment is the measurement of the Casimir force between a metal plate and a laser irradiated semiconductor membrane as performed by Chen et al.; the change in force with laser intensity is larger than predicted by theory. The fourth experiment is the measurement of the Casimir force between an atom and a wall in the form of the measurement by Obrecht et al. of the change in oscillation frequency of a {sup 87}Rb Bose-Einstein condensate trapped to a fused silica wall; the change is smaller than predicted by theory. We show that saturation effects can explain the discrepancies between theory and experiment observed in all these cases.

  5. Impact of the track density versus linear density trade-off on the read channel: TCPR4 versus EPR4

    NASA Astrophysics Data System (ADS)

    Sayiner, Necip

    1995-12-01

    The areal density on a magnetic recording medium can be increased by increasing the linear bit density, or by increasing the track density, or, more commonly, by a combination of both. Equalizing the signal to a higher order partial response polynomial (i.e. EPR4), and employing a trellis code in conjunction with a PR4 channel (i.e. TCPR4) are among the techniques to achieve this goal by providing performance gains over a PR4 system. In this study, the potential increases in linear and track densities that could be afforded by EPR4 and TCPR4 are investigated by simulating a read channel model which incorporates the effects of non-ideal timing recovery, A/D conversion, and finite register-lengths, using spinstand data. In order to quantify the effects of the increased track density, intertrack interference (ITI) is taken into account in evaluating the performance, by defining the interference as a function of the track misregistration. The trade-offs concerning the equalizer loss due to a higher linear bit density and the SNR loss due to a narrower track, as a function of PW50/T, are addressed. The measure of performance used captures the coding gain, the rate loss due to coding, the loss of the equalizer, and the degradation due to ITI. Assuming similar hardware complexity for the detectors, the two alternatives are compared in terms of the areal density increase they provide over a range of user bit densities that are of current practical interest.

  6. Self isolating high frequency saturable reactor

    DOEpatents

    Moore, James A.

    1998-06-23

    The present invention discloses a saturable reactor and a method for decoupling the interwinding capacitance from the frequency limitations of the reactor so that the equivalent electrical circuit of the saturable reactor comprises a variable inductor. The saturable reactor comprises a plurality of physically symmetrical magnetic cores with closed loop magnetic paths and a novel method of wiring a control winding and a RF winding. The present invention additionally discloses a matching network and method for matching the impedances of a RF generator to a load. The matching network comprises a matching transformer and a saturable reactor.

  7. Adiabatic and fast passage ultra-wideband inversion in pulsed EPR

    NASA Astrophysics Data System (ADS)

    Doll, Andrin; Pribitzer, Stephan; Tschaggelar, René; Jeschke, Gunnar

    2013-05-01

    We demonstrate that adiabatic and fast passage ultra-wideband (UWB) pulses can achieve inversion over several hundreds of MHz and thus enhance the measurement sensitivity, as shown by two selected experiments. Technically, frequency-swept pulses are generated by a 12 GS/s arbitrary waveform generator and upconverted to X-band frequencies. This pulsed UWB source is utilized as an incoherent channel in an ordinary pulsed EPR spectrometer. We discuss experimental methodologies and modeling techniques to account for the response of the resonator, which can strongly limit the excitation bandwidth of the entire non-linear excitation chain. Aided by these procedures, pulses compensated for bandwidth or variations in group delay reveal enhanced inversion efficiency. The degree of bandwidth compensation is shown to depend critically on the time available for excitation. As a result, we demonstrate optimized inversion recovery and double electron electron resonance (DEER) experiments. First, virtually complete inversion of the nitroxide spectrum with an adiabatic pulse of 128 ns length is achieved. Consequently, spectral diffusion between inverted and non-inverted spins is largely suppressed and the observation bandwidth can be increased to increase measurement sensitivity. Second, DEER is performed on a terpyridine-based copper (II) complex with a nitroxide-copper distance of 2.5 nm. As previously demonstrated on this complex, when pumping copper spins and observing nitroxide spins, the modulation depth is severely limited by the excitation bandwidth of the pump pulse. By using fast passage UWB pulses with a maximum length of 64 ns, we achieve up to threefold enhancement of the modulation depth. Associated artifacts in distance distributions when increasing the bandwidth of the pump pulse are shown to be small.

  8. EPR spectroscopy of protein microcrystals oriented in a liquid crystalline polymer medium

    NASA Astrophysics Data System (ADS)

    Caldeira, Jorge; Figueirinhas, João Luis; Santos, Celina; Godinho, Maria Helena

    2004-10-01

    Correlation of the g-tensor of a paramagnetic active center of a protein with its structure provides a unique experimental information on the electronic structure of the metal site. To address this problem, we made solid films containing metalloprotein ( Desulfovibrio gigas cytochrome c3) microcrystals. The microcrystals in a liquid crystalline polymer medium (water/hydroxypropylcellulose) were partially aligned by a shear flow. A strong orientation effect of the metalloprotein was observed by EPR spectroscopy and polarizing optical microscopy. The EPR spectra of partially oriented samples were simulated, allowing for molecular orientation distribution function determination. The observed effect results in enhanced sensitivity and resolution of the EPR spectra and provides a new approach towards the correlation of spectroscopic data, obtained by EPR or some other technique, with the three-dimensional structure of a protein or a model compound.

  9. Preparation and EPR characterization of N@C60 and N@C70 based peapods

    NASA Astrophysics Data System (ADS)

    Corzilius, B.; Gembus, A.; Weiden, N.; Dinse, K.-P.

    2005-09-01

    Using the quartet spin of encased nitrogen atoms as an electron paramagnetic resonance (EPR) probe, it is possible to examine the fullerene/nanotube interactions in a peapod. A purification method is developed which allows low temperature filling of nanotubes with endohedral fullerenes. The paramagnetic impurities of undoped single wall carbon nanotubes (SWNT) are characterized via EPR resulting in a broad superparamagnetic signal of the remaining catalyst particles and a rather narrow signal of carbonaceous material. Comparison of EPR spectra of several nitrogen endohedral doped peapods with their analogues obtained in a solid fullerene matrix shows a significant broadening of N@C60 and N@C70 EPR signals. This broadening is related to a non-vanishing zero-field splitting caused by deformation of the fullerene cage upon encapsulation.

  10. Crystal field effect on EPR and optical absorption properties of natural green zoisite.

    PubMed

    Javier-Ccallata, Henry; Watanabe, Shigueo

    2013-03-01

    In this study the electron paramagnetic resonance (EPR) and optical absorption (OA) of natural crystal of zoisite were investigated after γ ((60)Co) irradiation and high temperature annealing. EPR measurements show that the zoisite from Tefilo Otoni MG Brazil contain Cr(3+), Fe(3+) and Mn(2+) ions and occupy distorted Al(3+) octahedral and tetrahedral sites which are subjected to the action of a strong crystal field in axial direction. Absorption bands which in principle give rise to sets of EPR lines between 500 and 2500 G were found using the deconvolution method. The application of high doses of gamma ray and high temperature annealing has shown no significant effects on EPR and OA spectra. Spin-allowed, spin-forbidden and crystal field parameters were calculated for 3d(3) configuration and interpreted using the spin Hamiltonian formalism containing axial and rhombic terms in low symmetries. PMID:23291113

  11. Variable temperature EPR studies of Illinois No. 6 coal treated with donor and acceptor molecules

    SciTech Connect

    Thompson, R.L.; Rothenberger, K.S.; Retcofsky, H.L.

    1996-10-01

    Variable, temperature EPR studies of Illinois No. 6 coal, its pyridine extract, and samples of each after treatment with known donor and acceptor molecules are reported. The purpose of the study was to explore the origin of the EPR signals near g = 2 and to assess the contribution of certain non-bonded interactions in coal. Curie Law behavior is exhibited for each sample indicating that the EPR signals are dominated by doublet state radicals. No evidence for thermally accessible, low-lying triplet states, such as those found in some charge-transfer complexes, was found. Infrared spectroscopy reveals, however, that some electron density is transferred from the coal after treatment with acceptors such as TCNQ and TCNE. EPR studies of chromat graphic fractions of the pyridine extract (approximately five percent of the whole coal), both untreated and treated with TTF and TCNE, indicated some minor contributions of low-lying triplet states.

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

    NASA Astrophysics Data System (ADS)

    Bao, Ning; Pollack, Jason; Remmen, Grant N.

    2015-11-01

    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.

  13. Nitrite binding to globins: linkage isomerism, EPR silence and reductive chemistry

    PubMed Central

    Silaghi-Dumitrescu, Radu; Svistunenko, Dimitri A.; Cioloboc, Daniela; Bischin, Cristina; Scurtu, Florina; Cooper, Chris E.

    2014-01-01

    The nitrite adducts of globins can potentially bind via O- or N- linkage to the heme iron. We have used EPR (electron paramagnetic resonance) and DFT (density functional theory) to explore these binding modes to myoglobin and hemoglobin. We demonstrate that the nitrite adducts of both globins have detectable EPR signals; we provide an explanation for the difficulty in detecting these EPR features, based on uniaxial state considerations. The EPR and DFT data show that both nitrite linkage isomers can be present at the same time and that the two isomers are readily interconvertible in solution. The millisecond-scale process of nitrite reduction by Hb is investigated in search of the elusive Fe(II)-nitrite adduct. PMID:25172022

  14. Characterizing Active Pharmaceutical Ingredient Binding to Human Serum Albumin by Spin-Labeling and EPR Spectroscopy.

    PubMed

    Hauenschild, Till; Reichenwallner, Jörg; Enkelmann, Volker; Hinderberger, Dariush

    2016-08-26

    Drug binding to human serum albumin (HSA) has been characterized by a spin-labeling and continuous-wave (CW) EPR spectroscopic approach. Specifically, the contribution of functional groups (FGs) in a compound on its albumin-binding capabilities is quantitatively described. Molecules from different drug classes are labeled with EPR-active nitroxide radicals (spin-labeled pharmaceuticals (SLPs)) and in a screening approach CW-EPR spectroscopy is used to investigate HSA binding under physiological conditions and at varying ratios of SLP to protein. Spectral simulations of the CW-EPR spectra allow extraction of association constants (KA ) and the maximum number (n) of binding sites per protein. By comparison of data from 23 SLPs, the mechanisms of drug-protein association and the impact of chemical modifications at individual positions on drug uptake can be rationalized. Furthermore, new drug modifications with predictable protein binding tendency may be envisaged. PMID:27460503

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

    NASA Astrophysics Data System (ADS)

    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.

  16. Einstein locality, EPR locality, and the significance for science of the nonlocal character of quantum theory

    SciTech Connect

    Stapp, H.P.

    1985-10-01

    The immense difference between Einstein locality and EPR locality is discussed. The latter provides a basis for establishing the nonlocal character of quantum theory, whereas the former does not. A model representing Heisenberg's idea of physical reality is introduced. It is nondeterministic and holistic: the objects, measuring devices, and their environment are treated as an inseparable entity, with, however, macroscopically localizable attributes. The EPR principle that no disturbance can propagate faster than light is imposed without assuming any structure incompatible with orthodox quantum thinking. This locality requirement renders the model incompatible with rudimentary predictions of quantum theory. A more general proof not depending on any model is also given. A recent argument that purports to show that quantum theory is compatible with EPR locality is examined. It illustrates the importance of the crucial one-world assumption. The significance for science of the failure of EPR locality is discussed.

  17. Does deformation saturate seismic anisotropy?

    NASA Astrophysics Data System (ADS)

    Tatham, D. J.; Lloyd, G. E.; Butler, R. W.; Casey, M.

    2006-12-01

    The progressive simple shear deformation that characterizes ductile fault zones in the crust involves both rotation and intensification of the strain ellipsoid. These mathematic predictions have been confirmed repeatedly by finite strain determinations in outcrop studies of natural shear zones and used to test geodynamic models of mountain belts. Seismic anisotropy (SA) methods offer the opportunity to pursue these approaches in situ. First however, we must calibrate the magnitude and orientation of the SA ellipsoid against naturally deformed tectonites of known strain state and microstructure. Here we present data from a field analogue of mafic ductile crust in an amphibolite-facies shear zone developed in a deformed mafic dyke embedded within the Lewisian Gneiss (Badcall, NW Scotland). Deflection of pre-existing linear and planar elements and attenuation of the dyke into the shear zone are used to determine the strain gradient. Specimens collected along this gradient were used to establish the geometric fabric intensity defined by different minerals (hornblende grain alignment and ellipticity of plagioclase clots). Finally, petrophysical properties were calculated for the specimens using the SEM-EBSD measured populations of lattice preferred orientations (LPO) for all mineral phases. It is the hornblende-plagioclase LPO, combined in their modal proportions and modulated by the individual mineral single crystal elastic properties, which define the SA profile across the shear zone. Hornblende develops a strong preferred dimensional orientation and hence LPO at shear strains of about 2, whereas the plagioclase LPO remains close to random regardless of bulk strain. The modelled SA of the samples is dominated therefore by the amphibole LPO. Although the values of bulk shear strain vary across the shear zone (0 at the margins to greater than 12 in the centre), the calculated intensity of SA saturates at a shear strain of about 2. These results, if typical of large

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    Yordanov, Nicola D.; Aleksieva, Katerina

    2009-03-01

    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 °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.

  20. Gamma-irradiated dry fruits. An example of a wide variety of long-time dependent EPR spectra

    NASA Astrophysics Data System (ADS)

    Yordanov, Nicola D.; Pachova, Zdravka

    2006-03-01

    EPR spectra of dry, sugar containing fruits—raisins, sultanas, figs, dates, peaches, blue plums and chokeberry recorded before and after irradiation with gamma-rays, are reported. It is shown that weak singlet EPR line with 2.0031 ± 0.0005 can be recorded before irradiation of seeds, stones or skin of chokeberry, figs and raisins as well as flesh of blue plum, raisins and peaches. EPR signals of various shape are distinguished after irradiation in different parts of the fruits, as well as in randomly cut pieces of them: Seeds of raisins, chokeberry and figs give a singlet line. Stones from blue plums and peaches exhibit typical "cellulose-like" EPR signal consisting of an intense singlet line with g = 2.0033 ± 0.0005 and 2 week satellite lines situated ca. 30 G left and right to it. Stones of dates are the only sample in which "sugar-like" spectrum is recorded. Skin of raisins and figs exhibits "sugar-like" EPR spectrum whereas that of dates and chokeberry—a singlet line. Under the same experimental conditions skin of sultanas, peaches and blue plums are EPR silent. Flesh of raisins, sultanas, figs, dates and peaches exhibits "sugar-like" EPR spectrum, flesh of blue plums gives a singlet EPR line and that of chokeberry is EPR silent. As a result, randomly cut pieces of dry fruits suitable for EPR studies, containing various constituents, exhibit different in shape and intensity EPR spectra. Kinetic studies followed for 1 year on the time stability of all reported EPR signals indicate that intensity ratio between the simultaneously appearing EPR signals in particular fruit varies from 1:20 immediately after irradiation to 1:0.5 at the end of the period. These observations open a new possibility for identification of irradiated fruits - using the magnitude of the intensity ratio to find the approximate date of radiation processing in the first ca. 30-100 days.

  1. Transport de paires EPR dans des structures mesoscopiques

    NASA Astrophysics Data System (ADS)

    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

  2. EPR and ENDOR studies of point defects in lithium tetraborate crystals

    NASA Astrophysics Data System (ADS)

    Buchanan, Douglas A.

    Lithium tetraborate (Li2B4O7 or LTB) is a promising material for both radiation dosimetry and neutron detection applications. LTB crystals can be grown pure or doped with different impurities including transition-metal and rare-earth ions. Research in this dissertation focuses on undoped LTB crystals and LTB crystals doped with copper and silver. Electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) are used to characterize point defects in the lithium tetraborate crystals. Thermoluminescence (TL), photoluminescence (PL), photoluminescence excitation (PLE), and optical absorption (OA) are also used. An intrinsic hole trap associated with lithium vacancies is characterized with EPR and ENDOR and its thermal stability is determined using thermoluminescence. A "perturbed" hole trap due to Ag2+ ions is characterized in doped crystals using EPR data alone. This method is tested on a previously studied hole center where both EPR and ENDOR were used. New x-ray induced centers are identified in copper-doped crystals. These include two Cu 2+ hole centers and two Cu0 electron centers. These centers are characterized with EPR and their thermal stability explains TL peaks in glow curves. Finally, a comprehensive study utilizing EPR, OA, PL, and PLE data provide convincing explanations for the absorption and emission features of silver-doped crystals.

  3. Alanine-EPR as a transfer standard dosimetry system for low energy X radiation

    NASA Astrophysics Data System (ADS)

    Khoury, H. J.; da Silva, E. J.; Mehta, K.; de Barros, V. S.; Asfora, V. K.; Guzzo, P. L.; Parker, A. G.

    2015-11-01

    The purpose of this paper is to evaluate the use of alanine-EPR as a transfer standard dosimetry system for low energy X radiation, such as that in RS-2400, which operates in the range from 25 to 150 kV and 2 to 45 mA. Two types of alanine dosimeters were investigated. One is a commercial alanine pellets from Aérial-Centre de Ressources Technologiques, France and one was prepared in our laboratory (LMRI-DEN/UFPE). The EPR spectra of the irradiated dosimeters were recorded in the Nuclear Energy Department of UFPE, using a Bruker EMX10 EPR spectrometer operating in the X-band. The alanine-EPR dosimetry system was calibrated in the range of 20-220 Gy in this X-ray field, against an ionization chamber calibrated at the relevant X-ray energy with traceability to PTB. The results showed that both alanine dosimeters presented a linear dose response the same sensitivity, when the EPR signal was normalized to alanine mass. The total uncertainty in the measured dose was estimated to be about 3%. The results indicate that it is possible to use the alanine-EPR dosimetry system for validation of a low-energy X ray irradiator, such as RS-2400.

  4. EPR and IR spectral investigations on some leafy vegetables of Indian origin

    NASA Astrophysics Data System (ADS)

    Prasuna, C. P. Lakshmi; Chakradhar, R. P. S.; Rao, J. L.; Gopal, N. O.

    2009-09-01

    EPR spectral investigations have been carried out on four edible leafy vegetables of India, which are used as dietary component in day to day life. In Rumex vesicarius leaf sample, EPR spectral investigations at different temperatures indicate the presence of anti-ferromagnetically coupled Mn(IV)-Mn(IV) complexes. EPR spectra of Trigonella foenum graecum show the presence of Mn ions in multivalent state and Fe 3+ ions in rhombic symmetry. EPR spectra of Basella rubra indicate the presence of Mn(IV)-O-Mn(IV) type complexes. The EPR spectra of Basella rubra have been studied at different temperatures. It is found that the spin population for the resonance signal at g = 2.06 obeys the Boltzmann distribution law. The EPR spectra of Moringa oliefera leaves show the presence of Mn 2+ ions. Radiation induced changes in free radical of this sample have also been studied. The FT-IR spectra of Basella rubra and Moringa oliefera leaves show the evidences for the protein matrix bands and those corresponding to carboxylic C dbnd O bonds.

  5. EPR and IR spectral investigations on some leafy vegetables of Indian origin.

    PubMed

    Prasuna, C P Lakshmi; Chakradhar, R P S; Rao, J L; Gopal, N O

    2009-09-15

    EPR spectral investigations have been carried out on four edible leafy vegetables of India, which are used as dietary component in day to day life. In Rumex vesicarius leaf sample, EPR spectral investigations at different temperatures indicate the presence of anti-ferromagnetically coupled Mn(IV)-Mn(IV) complexes. EPR spectra of Trigonella foenum graecum show the presence of Mn ions in multivalent state and Fe(3+) ions in rhombic symmetry. EPR spectra of Basella rubra indicate the presence of Mn(IV)-O-Mn(IV) type complexes. The EPR spectra of Basella rubra have been studied at different temperatures. It is found that the spin population for the resonance signal at g=2.06 obeys the Boltzmann distribution law. The EPR spectra of Moringa oliefera leaves show the presence of Mn(2+) ions. Radiation induced changes in free radical of this sample have also been studied. The FT-IR spectra of Basella rubra and Moringa oliefera leaves show the evidences for the protein matrix bands and those corresponding to carboxylic CO bonds. PMID:19546024

  6. Photosynthetic reaction center of green sulfur bacteria studied by EPR

    SciTech Connect

    Nitschke, W.; Rutherford, A.W. ); Fieler, U. )

    1990-04-24

    Membrane preparations of two species of the green sulfur bacteria Chlorobium have been studied be EPR. Three signals were detected which were attributed to iron-sulfur centers acting as electron acceptors in the photosynthetic reaction center. (1) A signal from a center designated F{sub B}, was photoinduced at 4K. (2) A similar signal, F{sub A}, was photoinduced in addition to the F{sub B} signal upon a short period of illumination at 200 K. (3) Further illumination at 200 K resulted in the appearance of a broad feature at g=1.78. This is attributed to the g{sub x} component of an iron-sulfur center designated F{sub X}. The designations of these signals as F{sub B}, F{sub A}, and F{sub X} are based on their spectroscopic similarities to signals in photosystem I (PS I). The orientation dependence of these EPR signals in ordered Chlorobium membrane multilayers is remarkably similar to that of their PS I homologues. A magnetic interaction between the reduced forms of F{sub B} and F{sub A} occurs, which is also very similar to that seen in PS I. The triplet state of P{sub 840}, the primary electron donor, could be photoinduced at 4 K in samples which had been preincubated with sodium dithionite and methyl viologen and then preilluminated at 200 K. The preillumination reduces the iron-sulfur centers while the preincubation is thought to result in the inactivation of an earlier electron acceptor. Orientation studies of the triplet signal in ordered multilayers indicate that the bacteriochlorophylls which act as the primary electron donor in Chlorobium are arranged with a structural geometry almost identical with that of the special pair in purple bacteria. The Chlorobium reaction center appears to be similar in some respects to both PS I and to the purple bacterial reaction center. This is discussed with regard to the evolution of the different types of reaction centers from a common ancestor.

  7. Calibration of helical tomotherapy machine using EPR/alanine dosimetry

    SciTech Connect

    Perichon, Nicolas; Garcia, Tristan; Francois, Pascal; Lourenco, Valerie; Lesven, Caroline; Bordy, Jean-Marc

    2011-03-15

    Purpose: Current codes of practice for clinical reference dosimetry of high-energy photon beams in conventional radiotherapy recommend using a 10x10 cm{sup 2} square field, with the detector at a reference depth of 10 cm in water and 100 cm source to surface distance (SSD) (AAPM TG-51) or 100 cm source-to-axis distance (SAD) (IAEA TRS-398). However, the maximum field size of a helical tomotherapy (HT) machine is 40x5 cm{sup 2} defined at 85 cm SAD. These nonstandard conditions prevent a direct implementation of these protocols. The purpose of this study is twofold: To check the absorbed dose in water and dose rate calibration of a tomotherapy unit as well as the accuracy of the tomotherapy treatment planning system (TPS) calculations for a specific test case. Method: Both topics are based on the use of electron paramagnetic resonance (EPR) using alanine as transfer dosimeter between the Laboratoire National Henri Becquerel (LNHB) {sup 60}Co-{gamma}-ray reference beam and the Institut Curie's HT beam. Irradiations performed in the LNHB reference {sup 60}Co-{gamma}-ray beam allowed setting up the calibration method, which was then implemented and tested at the LNHB 6 MV linac x-ray beam, resulting in a deviation of 1.6% (at a 1% standard uncertainty) relative to the reference value determined with the standard IAEA TRS-398 protocol. Results: HT beam dose rate estimation shows a difference of 2% with the value stated by the manufacturer at a 2% standard uncertainty. A 4% deviation between measured dose and the calculation from the tomotherapy TPS was found. The latter was originated by an inadequate representation of the phantom CT-scan values and, consequently, mass densities within the phantom. This difference has been explained by the mass density values given by the CT-scan and used by the TPS which were not the true ones. Once corrected using Monte Carlo N-Particle simulations to validate the accuracy of this process, the difference between corrected TPS

  8. Pulsed EPR characterization of encapsulated atomic hydrogen in octasilsesquioxane cages.

    PubMed

    Mitrikas, George

    2012-03-21

    Hydrogen atoms encapsulated in molecular cages are potential candidates for quantum computing applications. They provide the simplest two-spin system where the 1s electron spin, S = 1/2, is hyperfine-coupled to the proton nuclear spin, I = 1/2, with a large isotropic hyperfine coupling (A = 1420.40575 MHz for a free atom). While hydrogen atoms can be trapped in many matrices at cryogenic temperatures, it has been found that they are exceptionally stable in octasilsesquioxane cages even at room temperature [Sasamori et al., Science, 1994, 256, 1691]. Here we present a detailed spin-lattice and spin-spin relaxation study of atomic hydrogen encapsulated in Si(8)O(12)(OSiMe(2)H)(8) using X-band pulsed EPR spectroscopy. The spin-lattice relaxation times T(1) range between 1.2 s at 20 K and 41.8 μs at room temperature. The temperature dependence of the relaxation rate shows that for T < 60 K the spin-lattice relaxation is best described by a Raman process with a Debye temperature of θ(D) = 135 K, whereas for T > 100 K a thermally activated process with activation energy E(a) = 753 K (523 cm(-1)) prevails. The phase memory time T(M) = 13.9 μs remains practically constant between 200 and 300 K and is determined by nuclear spin diffusion. At lower temperatures T(M) decreases by an order of magnitude and exhibits two minima at T = 140 K and T = 60 K. The temperature dependence of T(M) between 20 and 200 K is attributed to dynamic processes that average inequivalent hyperfine couplings, e.g. rotation of the methyl groups of the cage organic substituents. The hyperfine couplings of the encapsulated proton and the cage (29)Si nuclei are obtained through numerical simulations of field-swept FID-detected EPR spectra and HYSCORE experiments, respectively. The results are discussed in terms of existing phenomenological models based on the spherical harmonic oscillator and compared to those of endohedral fullerenes. PMID:22323086

  9. Interpreting HSE Contents of Planetary Basalts: The Importance of Sulfide Saturation and Under-Saturation

    NASA Technical Reports Server (NTRS)

    Righter, K.

    2000-01-01

    Highly siderophile elements provide important constraints on planetary differentiation due to their siderophile behavior. Their interpretation in terms of planetary differentiation models has so far overlooked the importance of sulfide saturation and under-saturation.

  10. NITROGEN SATURATION IN NORTHERN FOREST ECOSYSTEMS

    EPA Science Inventory

    In this article we provide a formal definition of nitrogen saturation and set forth a series of testable hypotheses regarding the states of forest ecosystem response to chronic nitrogen deposition. hese hypotheses are used to suggest early indicators of nitrogen saturation and to...

  11. Seismic determination of saturation in fractured reservoirs

    USGS Publications Warehouse

    Brown, R.L.; Wiggins, M.L.; Gupta, A.

    2002-01-01

    Detecting the saturation of a fractured reservoir using shear waves is possible when the fractures have a geometry that induces a component of movement perpendicular to the fractures. When such geometry is present, vertically traveling shear waves can be used to examine the saturation of the fractured reservoir. Tilted, corrugated, and saw-tooth fracture models are potential examples.

  12. Zircon Saturation Re-Revisited

    NASA Astrophysics Data System (ADS)

    Boehnke, P.; Trail, D.; Schmitt, A. K.; Watson, E. B.; Harrison, M.

    2011-12-01

    Zircon saturation in silicate melts has been utilized for magma thermometry and predicting the survival of zircon xenocrysts in crustal melts for nearly 30 years. The original calibration, which assumed only compositional (M = [2Ca+Na+K]/[AlxSi]) and temperature controls, was bolstered by subsequent experimental investigations and thermometry of volcanic rocks and glasses. These latter studies, while confirming the general predictions of the model, suggested that other environmental parameters (e.g., pressure, H 2O, halogens, [Fe], oxygen fugacity, etc.) might have second-order effects. Given the tremendous advances in micro-analytical capabilities over the intervening three decades, we have returned to this question with a view to obtaining a refined zircon solubility calibration as a function of P, T, [H2O] and FM (= [Na+K+2(Ca+Mg+Fe)]/[AlxSi]). Detailed SEM imaging of the original low-temperature crystallization experiments (1.2-2.1 kbar) revealed limitations of this approach and we chose instead to use a new experimental design in which shattered Mud Tank zircon is infiltrated by melts of selected composition and water contents. 10 kbar hydrothermal experiments (925o and 850oC) were run for sufficiently long durations (2 to 3 days) to ensure microscale diffusive equilibration of Zr released by zircon dissolution into the intercrystalline melt pools. Sectioned run products were analyzed by SIMS ion imaging of selected areas where glass is exposed in close proximity to or surrounded by Mud Tank zircon fragments. Ion imaging has the advantage of permitting high spatial resolution (3 μm) analysis of the glasses allowing assessment of Zr equilibration. Using synthetic glass standards, we found [Zr] in anhydrous glasses to be enhanced by ca. 20% relative to hydrous (at 6 wt.% H2O). Our new experiments and re-analysis of the earlier glasses broadly reproduce the original calibration, albeit with substantially enhanced (factor of five) precision compared to the

  13. Patterning via optical saturable transitions

    NASA Astrophysics Data System (ADS)

    Cantu, Precious

    For the past 40 years, optical lithography has been the patterning workhorse for the semiconductor industry. However, as integrated circuits have become more and more complex, and as device geometries shrink, more innovative methods are required to meet these needs. In the far-field, the smallest feature that can be generated with light is limited to approximately half the wavelength. This, so called far-field diffraction limit or the Abbe limit (after Prof. Ernst Abbe who first recognized this), effectively prevents the use of long-wavelength photons >300nm from patterning nanostructures <100nm. Even with a 193nm laser source and extremely complicated processing, patterns below ˜20nm are incredibly challenging to create. Sources with even shorter wavelengths can potentially be used. However, these tend be much more expensive and of much lower brightness, which in turn limits their patterning speed. Multi-photon reactions have been proposed to overcome the diffraction limit. However, these require very large intensities for modest gain in resolution. Moreover, the large intensities make it difficult to parallelize, thus limiting the patterning speed. In this dissertation, a novel nanopatterning technique using wavelength-selective small molecules that undergo single-photon reactions, enabling rapid top-down nanopatterning over large areas at low-light intensities, thereby allowing for the circumvention of the far-field diffraction barrier is developed and experimentally verified. This approach, which I refer to as Patterning via Optical Saturable Transitions (POST) has the potential for massive parallelism, enabling the creation of nanostructures and devices at a speed far surpassing what is currently possible with conventional optical lithographic techniques. The fundamental understanding of this technique goes beyond optical lithography in the semiconductor industry and is applicable to any area that requires the rapid patterning of large-area two or three

  14. Reactivity of some vanadium oxides: An EPR and XRD study

    SciTech Connect

    Occhiuzzi, Manlio

    2005-05-15

    V{sub 2}O{sub 5}, VO{sub 2} and V{sub 2}O{sub 3} fresh samples and at different times after purchase or preparation (aged samples) were investigated by chemical analysis, redox treatments, XRD and EPR. The ageing process through a reaction with water and oxygen slowly oxidize crystalline VO{sub 2} and V{sub 2}O{sub 3}, leading to a quasi-amorphous phase with bariandite structure (V{sub 10}O{sub 24}.12H{sub 2}O). The role of water is the progressive demolition of the compact structures and formation of hydrated phase. Kinetic study of VO{sub 2} oxidation by O{sub 2} and O{sub 2}+H{sub 2}O mixture indicates that increasing the temperature up to 723K the effect of water becomes less important. The reaction leads to partially oxidized products with decreasing water content: bariandite at room temperature, V{sub 3}O{sub 7}.H{sub 2}O at 383K and V{sub 3}O{sub 7} at 723K. Kinetic investigation of V{sub 2}O{sub 5} reduction by CO at 633-723K showed that the reduction process proceeds trough the formation of V{sup 4+} and of electrons delocalized in the conduction band.

  15. Noise Analysis of EPR Spectrometers with Cryogenic Microwave Preamplifiers

    NASA Astrophysics Data System (ADS)

    Pfenninger, S.; Froncisz, W.; Hyde, J. S.

    Studies are reported on the sensitivity of an EPR spectrometer utilizing a cryogenic preamplifier (0.5 dB noise figure, 35 K equivalent noise temperature). Three cases are considered: (a) resonator matched in a CW experiment, (b) resonator Q spoiled by overcoupling, and (c) resonator matched in pulse experiments. Contributions to the system noise because of losses in the microwave bridge have been determined quantitatively: the equivalent noise temperature of the receiver chain rises from 35 to 100 K. It is suggested that improved system performance can be achieved by cooling major components of the microwave bridge. It is particularly advantageous to cool the load resistor at port 1 of the circulator. Measurements of source noise are reported. This noise contribution becomes increasingly apparent as the system noise is decreased, but can be suppressed by use of loop-gap resonators. Analysis is carried out in a mixed engineering vocabulary of output noise temperature and equivalent noise temperature, which are temperatures referred to the output and input of the circuit, respectively. It is suggested that this is an appropriate analytical approach when there are multiple paths that feed noise to the output of the circuit with different physical temperatures of the input load resistor for each path.

  16. EPR characterisation of platinum nanoparticle functionalised carbon nanotube hybrid materials.

    PubMed

    Dennany, Lynn; Sherrell, Peter; Chen, Jun; Innis, Peter C; Wallace, Gordon G; Minett, Andrew I

    2010-04-28

    The use of nanostructured carbon materials as electrodes for energy storage and conversion is an expanding area of research in recent years. Herein, platinum nanoparticles have been deposited onto both multi-walled and single-walled carbon nanotubes (CNTs) via a microwave assisted polyol reduction method. This interaction has been probed with electron paramagnetic resonance (EPR) and Raman spectroscopies to elucidate the charge/electron transfer interactions between the Pt nanoparticles and the CNTs. Observed shifts in the g factors of the CNTs are indicative of such an electronic interaction, strongly suggesting the covalent attachment of the nanoparticles to the carboxylic groups on the CNTs, formed during the microwave-assisted reduction process. The Pt decorated CNTs show a dramatic increase in electrochemical behaviour in terms of high reversible capacity and relatively stable cycle performance compared to unmodified CNTs increasing their applicability in energy storage devices. For instance, significant increases in the electrochemical double layer capacitance are observed for the CNT-NP composite electrode. PMID:20379504

  17. Boron dose determination for BNCT using Fricke and EPR dosimetry

    SciTech Connect

    Wielopolski, L.; Ciesielski, B.

    1995-02-01

    In Boron Neutron Capture Therapy (BNCT) the dominant dose delivered to the tumor is due to {alpha} and {sup 7}Li charged particles resulting from a neutron capture by {sup 10}B and is referred to herein as the boron dose. Boron dose is directly attributable to the following two independent factors, one boron concentration and the neutron capture energy dependent cross section of boron, and two the energy spectrum of the neutrons that interact with boron. The neutron energy distribution at a given point is dictated by the incident neutron energy distribution, the depth in tissue, geometrical factors such as beam size and patient`s dimensions. To account for these factors can be accommodated by using Monte Carlo theoretical simulations. However, in conventional experimental BNCT dosimetry, e.g., using TLDs or ionization chambers, it is only possible to estimate the boron dose. To overcome some of the limitations in the conventional dosimetry, modifications in ferrous sulfate dosimetry (Fricke) and Electron Paramagnetic Resonance (EPR) dosimetry in alanine, enable to measure specifically boron dose in a mixed gamma neutron radiation fields. The boron dose, in either of the dosimeters, is obtained as a difference between measurements with boronated and unboronated dosimeters. Since boron participates directly in the measurements, the boron dosimetry reflects the true contribution, integral of the neutron energy spectrum with boron cross section, of the boron dose to the total dose. Both methods are well established and used extensively in dosimetry, they are presented briefly here.

  18. Implementation of GPU-Accelerated Back Projection for EPR imaging

    PubMed Central

    Qiao, Zhiwei; Redler, Gage; Epel, Boris; Qian, Yuhua; Halpern, Howard

    2016-01-01

    Electron paramagnetic resonance (EPR) Imaging (EPRI) is a robust method for measuring in vivo oxygen concentration (pO2). For 3D pulse EPRI, a commonly used reconstruction algorithm is the filtered backprojection (FBP) algorithm, in which the backprojection process is computationally intensive and may be time consuming when implemented on a CPU. A multistage implementation of the backprojection can be used for acceleration, however it is not flexible (requires equal linear angle projection distribution) and may still be time consuming. In this work, single-stage backprojection is implemented on a GPU (Graphics Processing Units) having 1152 cores to accelerate the process. The GPU implementation results in acceleration by over a factor of 200 overall and by over a factor of 3500 if only the computing time is considered. Some important experiences regarding the implementation of GPU-accelerated backprojection for EPRI are summarized. The resulting accelerated image reconstruction is useful for real-time image reconstruction monitoring and other time sensitive applications. PMID:26410654

  19. Free radical generation induced by ultrasound in red wine and model wine: An EPR spin-trapping study.

    PubMed

    Zhang, Qing-An; Shen, Yuan; Fan, Xue-hui; Martín, Juan Francisco García; Wang, Xi; Song, Yun

    2015-11-01

    Direct evidence for the formation of 1-hydroxylethyl radicals by ultrasound in red wine and air-saturated model wine is presented in this paper. Free radicals are thought to be the key intermediates in the ultrasound processing of wine, but their nature has not been established yet. Electron paramagnetic resonance (EPR) spin trapping with 5,5-dimethyl-l-pyrrolin N-oxide (DMPO) was used for the detection of hydroxyl free radicals and 1-hydroxylethyl free radicals. Spin adducts of hydroxyl free radicals were detected in DMPO aqueous solution after sonication while 1-hydroxylethyl free radical adducts were observed in ultrasound-processed red wine and model wine. The latter radical arose from ethanol oxidation via the hydroxyl radical generated by ultrasound in water, thus providing the first direct evidence of the formation of 1-hydroxylethyl free radical in red wine exposed to ultrasound. Finally, the effects of ultrasound frequency, ultrasound power, temperature and ultrasound exposure time were assessed on the intensity of 1-hydroxylethyl radical spin adducts in model wine. PMID:26186825

  20. Light-induced EPR study of charge transfer in P3HT/bis-PCBM bulk heterojunctions

    NASA Astrophysics Data System (ADS)

    Krinichnyi, Victor I.; Yudanova, Eugenia I.

    2011-06-01

    Radical pairs, polarons and fullerene anion radicals photoinduced by photons with energy of 1.98 - 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 (LEPR) method in a wide temperature range. A part of photoinduced polarons are pinned in trap sites which number and depth are governed by an ordering of the polymer/fullerene system and energy of initiating photons. It was shown that dynamics and recombination of mobile polarons and counter fullerene anion radicals are governed by their exchange- and multi-trap assisted diffusion. Relaxation and dynamics parameters of both the charge carriers were determined separately by the steady-state saturation method. These parameters are governed by structure and conformation of the carriers' microenvironment as well as by the energy of irradiating photons. Longitudinal diffusion of polarons was shown to depend on lattice phonons of crystalline domains embedded into an amorphous polymer matrix. The energy barrier required for polaron interchain hopping is higher than that its intrachain diffusion. Pseudorotation of fullerene derivatives in a polymer matrix was shown to follow the activation Pike model.

  1. Saturated anionic phospholipids enhance transdermal transport by electroporation.

    PubMed Central

    Sen, Arindam; Zhao, Ya-Li; Hui, Sek Wen

    2002-01-01

    Anionic phospholipids, but not cationic or neutral phospholipids, were found to enhance the transdermal transport of molecules by electroporation. When added as liposomes to the milieus of water-soluble molecules to be delivered through the epidermis of porcine skin by electroporation, these phospholipids enhance, by one to two orders of magnitude, the transdermal flux. Encapsulation of molecules in liposomes is not necessary. Dimyristoylphosphatidylserine (DMPS), phosphatidylserine from bovine brain (brain-PS), dioleoylphosphatidylserine (DOPS), and dioleoylphosphatidylglycerol (DOPG) were used to test factors affecting the potency of anionic lipid transport enhancers. DMPS with saturated acyl chains was found to be a much more potent transport enhancer than those with unsaturated acyl chains (DOPS and DOPG). There was no headgroup preference. Saturated DMPS was also more effective in delaying resistance recovery after pulsing, and with a greater affinity in the epidermis after pulsing. Using fluorescent carboxyl fluorescein and fluorescein isothiocyanate (FITC)-labeled Dextrans as test water-soluble molecules for transport, and rhodamine-labeled phospholipids to track anionic phospholipids, we found, by conventional and confocal fluorescence microscopy, that transport of water-soluble molecules was localized in local transport spots or regions (LTRs) created by the electroporation pulses. Anionic phospholipids, especially DMPS, were located at the center of the LTRs and spanned the entire thickness of the stratum corneum (SC). The degree of saturation of anionic phospholipids made no difference in the densities of LTRs created. We deduce that, after being driven into the epidermis by negative electric pulses, saturated anionic phospholipids mix and are retained better by the SC lipids. Anionic lipids prefer loose layers or vesicular rather than multilamellar forms, thereby prolonging the structural recovery of SC lipids to the native multilamellar form. In the

  2. CW- and pulsed-EPR of carbonaceous matter in primitive meteorites: solving a lineshape paradox.

    PubMed

    Delpoux, Olivier; Gourier, Didier; Binet, Laurent; Vezin, Hervé; Derenne, Sylvie; Robert, François

    2008-05-01

    Insoluble organic matter (IOM) of Orgueil and Tagish Lake meteorites are studied by CW-EPR and pulsed-EPR spectroscopies. The EPR line is due to polycyclic paramagnetic moieties concentrated in defect-rich regions of the IOM, with concentrations of the order of 4x10(19) spin/g. CW-EPR reveals two types of paramagnetic defects: centres with S=1/2, and centres with S=0 ground state and thermally accessible triple state S=1. In spite of the Lorentzian shape of the EPR and its narrowing upon increasing the spin concentration, the EPR line is not in the exchange narrowing regime as previously deduced from multi-frequency CW-EPR [L. Binet, D. Gourier, Appl. Magn. Reson. 30 (2006) 207-231]. It is inhomogeneously broadened as demonstrated by the presence of nuclear modulations in the spin-echo decay. The line narrowing, similar to an exchange narrowing effect, is the result of an increasing contribution of the narrow line of the triplet state centres in addition to the broader line of doublet states. Hyperfine sublevel correlation spectroscopy (HYSCORE) of hydrogen and (13)C nuclei indicates that IOM* centres are small polycyclic moieties that are moderately branched with aliphatic chains, as shown by the presence of aromatic hydrogen atoms. On the contrary the lack of such aromatic hydrogen in triplet states suggests that these radicals are most probably highly branched. Paramagnetic centres are considerably enriched in deuterium, with D/H approximately 1.5+/-0.5x10(-2) of the order of values existing in interstellar medium. PMID:18024197

  3. Electronically Tunable Surface-Coil-Type Resonator for L-Band EPR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Hirata, Hiroshi; Walczak, Tadeusz; Swartz, Harold M.

    2000-01-01

    The automatic frequency control (AFC) circuit in conventional electron paramagnetic resonance (EPR) spectrometers automatically tunes the microwave source to the resonance frequency of the resonator. The circuit works satisfactorily for samples stable enough that the geometric relations in the resonance structure do not change in a significant way. When EPR signals are measured during in vivo experiments with small rodents, however, the distance between the signal source and the surface-coil detector can change rapidly. When a conventional AFC circuit keeps the oscillator tuned to the resonator under those conditions, the resultant frequency change may exceed ±5 MHz and markedly shift the position of the EPR signal. Such a shift results in unacceptable effects on the spectra, especially when the experimenter is dealing with narrow EPR lines. The animal movement also causes a mismatching of the resonator and the 50-ohm transmission line. Direct results of this mismatching are increased noise; shifts in the position of the baseline; and a high probability of overdriving the signal preamplifier with consequent loss of the EPR signal. We therefore designed, built, and tested a new surface-coil resonator using varactor diodes for tuning the resonance frequency to the fixed frequency oscillator and for capacitive matching of the resonator to the 50-ohm transmission line. The performance of the automatic matching system was tested in vivo by measuring EPR spectra of lithium phthalocyanine implanted in rats. Stability and sensitivity of the spectrometer were evaluated by measuring EPR spectra with and without the use of the automatic matching system. The overall experimental performance of the spectrometer was found to significantly improve during in vivo experiments using the automatic matching system. Excellent matching between the 50-ohm transmission line and the resonator was maintained under all experimental circumstances that were tested. This should allow us now to

  4. Scintillation probe with photomultiplier tube saturation indicator

    DOEpatents

    Ruch, Jeffrey F.; Urban, David J.

    1996-01-01

    A photomultiplier tube saturation indicator is formed by supplying a supplemental light source, typically an light emitting diode (LED), adjacent to the photomultiplier tube. A switch allows the light source to be activated. The light is forwarded to the photomultiplier tube by an optical fiber. If the probe is properly light tight, then a meter attached to the indicator will register the light from the LED. If the probe is no longer light tight, and the saturation indicator is saturated, no signal will be registered when the LED is activated.

  5. Reading Recovery. [Fact Sheets].

    ERIC Educational Resources Information Center

    Reading Recovery Council of North America, Columbus, OH.

    This set of 10 fact sheets (each 2 to 4 pages long) addresses aspects of Reading Recovery, a program that helps children to be proficient readers and writers by the end of the first grade. It discusses the basic facts of Reading Recovery; Reading Recovery for Spanish literacy; Reading Recovery lessons; Reading Recovery professional development;…

  6. The Perturbational MO Method for Saturated Systems.

    ERIC Educational Resources Information Center

    Herndon, William C.

    1979-01-01

    Summarizes a theoretical approach using nonbonding MO's and perturbation theory to correlate properties of saturated hydrocarbons. Discussion is limited to correctly predicted using this method. Suggests calculations can be carried out quickly in organic chemistry. (Author/SA)

  7. Ultrafast saturation of resonant optical processes

    NASA Astrophysics Data System (ADS)

    Patnaik, Anil K.; Roy, Sukesh; Gord, James R.

    2014-12-01

    A generalized formulation is presented for determining the saturation thresholds for optical processes excited by ultrafast pulses based on the pulse area of the excitation pulse. It is demonstrated that the threshold of driving-pulse intensity for absorption and fluorescence saturation in a two-level system is inversely proportional to the square of the duration of the excitation pulse. These results are obtained from both a simplified analytical solution assuming a Gaussian excitation pulse shape and a detailed numerical calculation based on density-matrix equations. The calculation is generalized further to obtain the saturation condition for a two-photon Raman process by defining a two-photon pulse area both analytically and numerically. These results not only provide predictive capabilities for determining thresholds of signal saturation using ultrashort durations with arbitrary pulse shapes and durations but also open up possibilities for predetermining the threshold intensities of various resonant nonlinear processes.

  8. Introduction to the physics of saturation

    NASA Astrophysics Data System (ADS)

    Kovchegov, Yuri V.

    2013-03-01

    In these lectures I present the main pillars of saturation physics: Glauber-Mueller multiple rescatterings, quasi-classical McLerran-Venugopalan model, and the nonlinear BK and JIMWLK small-x evolution equations.

  9. Position tracking control of saturated LSRM.

    PubMed

    Dolinar, Drago; Stumberger, Gorazd; Milanovic, Miro

    2004-10-01

    This paper deals with the tracking control design of a linear synchronous reluctance motor (LSRM) drive. An extended nonlinear dynamic LSRM model with magnetic saturation included is used in the control design and practical realization, in order to improve tracking performances at very low speeds of motion. Iron core saturation is included in the extended model with the experimentally determined flux linkages given as functions of the direct and quadrature axes currents. Experimental results show that the proposed input-output linearizing tracking control with included saturation behaves considerably better than the one without saturation, introducing smaller position and speed errors and better motor stiffness, on account of the increased computational complexity. PMID:15535392

  10. Microwave and optical saturable absorption in graphene.

    PubMed

    Zheng, Zhiwei; Zhao, Chujun; Lu, Shunbin; Chen, Yu; Li, Ying; Zhang, Han; Wen, Shuangchun

    2012-10-01

    We report on the first experiments on saturable absorption in graphene at microwave frequency band. Almost independent of the incident frequency, microwave absorbance of graphene always decreases with increasing the power and reaches at a constant level for power larger than 80 µW, evidencing the microwave saturable absorption property of graphene. Optical saturable absorption of the same graphene sample was also experimentally confirmed by an open-aperture Z-scan technique by one laser at telecommunication band and another pico-second laser at 1053 nm, respectively. Herein, we are able to conclude that graphene is indeed a broadband saturable absorber that can operate at both microwave and optical band. PMID:23188285

  11. Combinatorics of saturated secondary structures of RNA.

    PubMed

    Clote, P

    2006-11-01

    Following Zuker (1986), a saturated secondary structure for a given RNA sequence is a secondary structure such that no base pair can be added without violating the definition of secondary structure, e.g., without introducing a pseudoknot. In the Nussinov-Jacobson energy model (Nussinov and Jacobson, 1980), where the energy of a secondary structure is -1 times the number of base pairs, saturated secondary structures are local minima in the energy landscape, hence form kinetic traps during the folding process. Here we present recurrence relations and closed form asymptotic limits for combinatorial problems related to the number of saturated secondary structures. In addition, Python source code to compute the number of saturated secondary structures having k base pairs can be found at the web servers link of bioinformatics.bc.edu/clotelab/. PMID:17147486

  12. EPR/alanine dosimetry for two therapeutic proton beams

    NASA Astrophysics Data System (ADS)

    Marrale, Maurizio; Carlino, Antonio; Gallo, Salvatore; Longo, Anna; Panzeca, Salvatore; Bolsi, Alessandra; Hrbacek, Jan; Lomax, Tony

    2016-02-01

    In this work the analysis of the electron paramagnetic resonance (EPR) response of alanine pellets exposed to two different clinical proton beams employed for radiotherapy is performed. One beam is characterized by a passive delivery technique and is dedicated to the eyes treatment (OPTIS2 beam line). Alanine pellets were irradiated with a 70 MeV proton beam corresponding to 35 mm range in eye tissue. We investigated how collimators with different sizes and shape used to conform the dose to the planned target volume influence the delivered dose. For this purpose we performed measurements with varying the collimator size (Output Factor) and the results were compared with those obtained with other dosimetric techniques (such as Markus chamber and diode detector). This analysis showed that the dosimeter response is independent of collimator diameter if this is larger than or equal to 10 mm. The other beam is characterized by an active spot-scanning technique, the Gantry1 beam line (maximum energy 230 MeV), and is used to treat deep-seated tumors. The dose linearity of alanine response in the clinical dose range was tested and the alanine dose response at selected locations in depth was measured and compared with the TPS planned dose in a quasi-clinical scenario. The alanine response was found to be linear in the dose in the clinical explored range (from 10 to 70 Gy). Furthermore, a depth dose profile in a quasi-clinical scenario was measured and compared to the dose computed by the Treatment Planning System PSIPLAN. The comparison of calibrated proton alanine measurements and TPS dose shows a difference under 1% in the SOBP and a "quenching" effect up to 4% in the distal part of SOBP. The positive dosimetric characteristics of the alanine pellets confirm the feasibility to use these detectors for "in vivo" dosimetry in clinical proton beams.

  13. Parton Saturation and the Color Glass Condensate

    NASA Astrophysics Data System (ADS)

    Kovchegov, Yuri V.

    2007-03-01

    We review recent developments in the field of parton saturation and the Color Glass Condensate. We discuss the classical gluon fields of McLerran-Venugopalan model. We explain how small- x non-linear quantum evolution corrections can be included into the total cross section for deep inelastic scattering. We proceed by reviewing saturation physics predictions for the particle production in p( d) A collisions and conclude by demonstrating how such predictions were confirmed by the RHIC experiments.

  14. Determining the saturation scale in nuclei

    SciTech Connect

    Kopeliovich, B. Z.; Potashnikova, I. K.; Schmidt, Ivan

    2010-03-15

    The saturation momentum seen in the nuclear infinite-momentum frame is directly related to transverse momentum broadening of partons propagating through the medium in the nuclear rest frame. Calculation of broadening within the color dipole approach, including the effects of saturation in the nucleus, gives rise to an equation which describes well the data on broadening in the Drell-Yan reaction and heavy quarkonium production.

  15. Photoionization of phenothiazine: EPR detection of reactions of the polarized solvated electron

    SciTech Connect

    Turro, N.J.; Khudyakov, I.V.; Willigen, H. van

    1995-12-13

    Photoionization of phenothiazine (PTH) and reactions of the solvated electron with some electron acceptors were studied with steady state and time-resolved EPR and transient optical absorption techniques. Time-resolved EPR spectra from the phenothiazine cation radical (PTH{sup .+}) and hydrated electron (e{sub aq}{sup -}) formed in sodium 1-dodecylsulfate (SDS) micellar solution were observed in emission. By contrast, PTH{sup .+} formed by photoionization of PTH in alcohols gives absorptive EPR signals. The spin polarization carried by the hydrated electron in SDS solutions can be transferred effectively to a stable nitroxyl free radical 3-carboxy-2,2,5, 5-tetramethyl-1-pyrrolidinyloxyl (N{sup .-}) present in the bulk aqueous phase. EPR and flash photolysis measurements show that this electron spin polarization transfer process proceeds with a rate which is approximately five times faster than the chemical reaction between e{sub aq}{sup -} and N{sup .-}. The marked difference in rates is attributed to differences in spin-statistical factors and difference in reaction radii for spin exchange compared to reaction. In alcohol solutions of PTH and a nitroxyl stable radical (2,2,6, 6-tetramethylpyperidin-1-oxyl, TEMPO), excitation of PTH also results in emissive polarization of the EPR spectrum of the stable radical. 46 refs., 12 figs.

  16. Site Directed Spin Labeling and EPR Spectroscopic Studies of Pentameric Ligand-Gated Ion Channels.

    PubMed

    Basak, Sandip; Chatterjee, Soumili; Chakrapani, Sudha

    2016-01-01

    Ion channel gating is a stimulus-driven orchestration of protein motions that leads to transitions between closed, open, and desensitized states. Fundamental to these transitions is the intrinsic flexibility of the protein, which is critically modulated by membrane lipid-composition. To better understand the structural basis of channel function, it is necessary to study protein dynamics in a physiological membrane environment. Electron Paramagnetic Resonance (EPR) spectroscopy is an important tool to characterize conformational transitions between functional states. In comparison to NMR and X-ray crystallography, the information obtained from EPR is intrinsically of lower resolution. However, unlike in other techniques, in EPR there is no upper-limit to the molecular weight of the protein, the sample requirements are significantly lower, and more importantly the protein is not constrained by the crystal lattice forces. Therefore, EPR is uniquely suited for studying large protein complexes and proteins in reconstituted systems. In this article, we will discuss general protocols for site-directed spin labeling and membrane reconstitution using a prokaryotic proton-gated pentameric Ligand-Gated Ion Channel (pLGIC) from Gloeobacter violaceus (GLIC) as an example. A combination of steady-state Continuous Wave (CW) and Pulsed (Double Electron Electron Resonance-DEER) EPR approaches will be described that will enable a complete quantitative characterization of channel dynamics. PMID:27403967

  17. Identification of the EPR signal of S₂⁻ in green ultramarine pigments.

    PubMed

    Raulin, Katarzyna; Gobeltz, Noëlle; Vezin, Hervé; Touati, Nadia; Ledé, Bertrand; Moissette, Alain

    2011-05-28

    Green and blue ultramarine pigments are characterized by the sodalite structure Na(6)(Al(6)Si(6)O(24)) and colored inserted species. These chromophores are sulfur species: S(3)(-) (blue) and S(2)(-) (yellow). Both radicals are encapsulated inside the β-cages. They contribute to the EPR spectrum of ultramarine pigments. The well-known strong EPR signal observed in all ultramarine pigments Continuous-Wave (CW) spectra has long been assigned to S(3)(-) (g = 2.029). In contrast, the S(2)(-) contribution is still subject to controversy because its signal in ultramarine pigments was not resolved even at low temperature in CW-EPR experiments. In this study, we identify unambiguously for the first time by CW-EPR and field sweep-echo detected (FS-ED) EPR the signal of S(2)(-) in ultramarine pigments and we determine its tensor components: g(1) = 2.69(6), g(2) = 2.03(4) and g(3) = 1.86(4). PMID:21468420

  18. Determination of methemoglobin in human blood after ionising radiation by EPR

    NASA Astrophysics Data System (ADS)

    Polakovs, M.; Mironova-Ulmane, N.; Pavlenko, A.; Aboltins, A.

    2015-03-01

    In the present work presents results of investigations of radiation influence on blood of patients examined by radio-isotopes diagnosis (Tc99m), blood of Chernobyl clean-up workers and human blood irradiated by LINAC using Electron Paramagnetic Resonance (EPR). The EPR spectroscopy reveals information on electronic states of transition metal ions, particularly Fe3+ in different spin states. It is shown that EPR spectra of blood of patients before examination has signal from metal-protein transferrin (g=4.3) and after administration of radioisotope proves signal of Fe3+ (methemaglobin) in the high spin state (g=6.0). The EPR spectra of Chernobyl liquidator display number of signals including low and high state of ion Fe3+ (g = 2.0 and g=6.0), and transferrin (g=4.3). The EPR spectra of irradiated human blood by LINAC (linear accelerator) have only signal Fe3+ (methemaglobin) in low-spin state with g = 2.0.

  19. Quantitative Interpretation of Multifrequency Multimode EPR Spectra of Metal Containing Proteins, Enzymes, and Biomimetic Complexes.

    PubMed

    Petasis, Doros T; Hendrich, Michael P

    2015-01-01

    Electron paramagnetic resonance (EPR) spectroscopy has long been a primary method for characterization of paramagnetic centers in materials and biological complexes. Transition metals in biological complexes have valence d-orbitals that largely define the chemistry of the metal centers. EPR spectra are distinctive for metal type, oxidation state, protein environment, substrates, and inhibitors. The study of many metal centers in proteins, enzymes, and biomimetic complexes has led to the development of a systematic methodology for quantitative interpretation of EPR spectra from a wide array of metal containing complexes. The methodology is now contained in the computer program SpinCount. SpinCount allows simulation of EPR spectra from any sample containing multiple species composed of one or two metals in any spin state. The simulations are quantitative, thus allowing determination of all species concentrations in a sample directly from spectra. This chapter will focus on applications to transition metals in biological systems using EPR spectra from multiple microwave frequencies and modes. PMID:26478486

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

    NASA Astrophysics Data System (ADS)

    Kassiba, A.; Makowska-Janusik, M.; Mehdi, A.

    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 TiO2, 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 TiO2, and in general to give a valuable feedback to improve the synthesis routes of smart materials.

  1. New Developed Cylindrical TM010 Mode EPR Cavity for X-Band In Vivo Tooth Dosimetry

    PubMed Central

    Junwang, Guo; Qingquan, Yuan; Jianbo, Cong; Lei, Ma; Guofu, Dong; Guoshan, Yang; Ke, Wu

    2014-01-01

    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. PMID:25222483

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

    PubMed

    Junwang, Guo; Qingquan, Yuan; Jianbo, Cong; Lei, Ma; Guofu, Dong; Guoshan, Yang; Ke, Wu

    2014-01-01

    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. PMID:25222483

  3. Single-headed binding of a spin-labeled-HMM-ADP complex to F-actin. Saturation transfer electron paramagnetic resonance and sedimentation studies.

    PubMed Central

    Manuck, B A; Seidel, J C; Gergely, J

    1986-01-01

    The interaction of actin and spin-labeled heavy meromyosin (MSL-HMM) was studied in the presence and absence of adenosine diphosphate or 5'-adenyl-yl-imidodiphosphate (AMPPNP) to determine the contributions of single and double-headed binding. The extent of single-headed binding to actin was deduced from a comparison of the fraction of immobilized heads (fi) with the fraction of bound molecules (fs) determined by saturation-transfer EPR (ST-EPR) and sedimentation, respectively. The ST-EPR measurements depend on the reduced motion of the spin label rigidly bound to the HMM heads upon the interaction of the latter with actin. During titration of acto-MSL-HMM with nucleotide, we measured changes in fi and fs brought about by dissociation of MSL-HMM from actin. On titration with ADP, fs changed very little, remaining above 0.8, while fi decreased to approximately 0.5 at 10mM ADP, a result consistent with extensive single-headed binding of MSL-HMM to actin. On titration with AMPPNP, single-headed binding was not detected; viz., fi and fs decreased in parallel. It was not necessary to postulate a nucleotide induced state of the bound heads, differing in motional properties from that of rigor heads, to account for the results. PMID:3017466

  4. Heart Attack Recovery FAQs

    MedlinePlus

    ... Pressure High Blood Pressure Tools & Resources Stroke More Heart Attack Recovery FAQs Updated:Aug 24,2016 Most people ... recovery. View an animation of a heart attack . Heart Attack Recovery Questions and Answers What treatments will I ...

  5. Brine saturation technique for extraction of light filth from rubbed and ground sage: intralaboratory study.

    PubMed

    Freeman, C C

    1981-05-01

    An intralaboratory study was made of a new and widely applicable technique for isolating light filth from rubbed and ground sage. The technique eliminated the hazardous, costly, and lengthy pretreatment and isolation procedures of the current methodology and resulted in considerably better recoveries. Overall recovery of all filth elements introduced as spikes was 99.3% on the first trapping. The basic principle of the procedure is product saturation with brine, followed by trapping of the filth elements from tap water with oliver oil. PMID:7240080

  6. SATURATED ZONE IN-SITU TESTING

    SciTech Connect

    P.W. REIMUS

    2004-11-08

    The purpose of this scientific analysis is to document the results and interpretations of field experiments that test and validate conceptual flow and radionuclide transport models in the saturated zone (SZ) near Yucca Mountain, Nevada. The test interpretations provide estimates of flow and transport parameters used in the development of parameter distributions for total system performance assessment (TSPA) calculations. These parameter distributions are documented in ''Site-Scale Saturated Zone Flow Model (BSC 2004 [DIRS 170037]), Site-Scale Saturated Zone Transport'' (BSC 2004 [DIRS 170036]), Saturated Zone Colloid Transport (BSC 2004 [DIRS 170006]), and ''Saturated Zone Flow and Transport Model Abstraction'' (BSC 2004 [DIRS 170042]). Specifically, this scientific analysis contributes the following to the assessment of the capability of the SZ to serve as part of a natural barrier for waste isolation for the Yucca Mountain repository system: (1) The bases for selection of conceptual flow and transport models in the saturated volcanics and the saturated alluvium located near Yucca Mountain. (2) Results and interpretations of hydraulic and tracer tests conducted in saturated fractured volcanics at the C-wells complex near Yucca Mountain. The test interpretations include estimates of hydraulic conductivities, anisotropy in hydraulic conductivity, storativities, total porosities, effective porosities, longitudinal dispersivities, matrix diffusion mass transfer coefficients, matrix diffusion coefficients, fracture apertures, and colloid transport parameters. (3) Results and interpretations of hydraulic and tracer tests conducted in saturated alluvium at the Alluvial Testing Complex (ATC) located at the southwestern corner of the Nevada Test Site (NTS). The test interpretations include estimates of hydraulic conductivities, storativities, total porosities, effective porosities, longitudinal dispersivities, matrix diffusion mass transfer coefficients, and colloid

  7. Methodology for increased precision in saturation transfer electron paramagnetic resonance studies of rotational dynamics.

    PubMed Central

    Squier, T C; Thomas, D D

    1986-01-01

    Microsecond rotational motions of nitroxide spin labels are measured primarily with saturation transfer electron paramagnetic resonance (ST-EPR). In the present study we have used model system experiments to quantitatively evaluate different ST-EPR spectral parameters, both in-phase and out-of-phase, with an emphasis on techniques for suppressing the interference from weakly immobilized probes. Analyses of both systematic and random errors show that maximum sensitivity to small changes in correlation time and minimum ambiguity of interpretation are best achieved by combining measurements of both spectral line-shape, i.e., the ratio of line-heights, and spectral intensity, i.e., the absolute amplitude of either a position within a spectrum or a spectral integral. Errors in the measurement of correlation times for the two types of parameters tend to be complementary. Integrated intensity parameters are particularly useful in measuring microsecond probe motions in the presence of weakly immobilized components. We confirm that integrated intensity parameters are sometimes effective in rejecting signals from weakly immobilized probes, but the effectiveness of this rejection is more limited than previously supposed and depends on the type of parameter being measured. We describe procedures for evaluating and minimizing errors due to weakly immobilized probes, emphasizing the advantages of a new kind of intensity parameter obtained from integrated in-phase spectra. We provide detailed descriptions of experimental procedures, along with calibration plots of the most useful spectral parameters vs. rotational correlation time, which should make it possible for workers in other laboratories, using different instruments and sample geometries, to reproduce spectra quantitatively and to make accurate correlation time measurements. PMID:3013330

  8. A reinvestigation of EXAFS and EPR spectroscopic measurements of chromium(VI) reduction by coir pith.

    PubMed

    Suksabye, Parinda; Worasith, Niramon; Thiravetyan, Paitip; Nakajima, Akira; Goodman, Bernard A

    2010-08-15

    New measurements using extended X-ray absorption fine structure (EXAFS) and electron paramagnetic resonance (EPR) techniques are consistent with Cr in the Cr(III) oxidation state as the main product from the adsorption of Cr(VI) on coir pith. These confirm the previous X-ray measurements, but differ from the results of previous EPR studies, which indicated that Cr(V) was the main form of Cr. The reason for this discrepancy is the presence of a broad signal from Cr(III) in an unsymmetrical environment that was missed previously; the Cr(V) component is in fact only a minor reaction product. As a result of this problem with spectral acquisition and interpretation, some simple recommendations are presented for conducting EPR investigations on natural systems. PMID:20452728

  9. Copper ESEEM and HYSCORE through ultra-wideband chirp EPR spectroscopy

    SciTech Connect

    Segawa, Takuya F.; Doll, Andrin; Pribitzer, Stephan; Jeschke, Gunnar

    2015-07-28

    The main limitation of pulse electron paramagnetic resonance (EPR) spectroscopy is its narrow excitation bandwidth. Ultra-wideband (UWB) excitation with frequency-swept chirp pulses over several hundreds of megahertz overcomes this drawback. This allows to excite electron spin echo envelope modulation (ESEEM) from paramagnetic copper centers in crystals, whereas up to now, only ESEEM of ligand nuclei like protons or nitrogens at lower frequencies could be detected. ESEEM spectra are recorded as two-dimensional correlation experiments, since the full digitization of the electron spin echo provides an additional Fourier transform EPR dimension. Thus, UWB hyperfine-sublevel correlation experiments generate a novel three-dimensional EPR-correlated nuclear modulation spectrum.

  10. Photonic EPR State from Quadratic Waveguide Array with Alternating Positive and Negative Couplings

    NASA Astrophysics Data System (ADS)

    Ying, Yang; Ping, Xu; Liang-Liang, Lu; Shi-Ning, Zhu

    2016-02-01

    We propose the generation of photonic EPR state from quadratic waveguide array. Both the propagation constant and the nonlinearity in the array are designed to possess a periodical modulation along the propagation direction. This ensures that the photon pairs can be generated efficiently through the quasi-phase-matching spontaneous parametric down conversion by holding the spatial EPR entanglement in the fashion of correlated position and anticorrelated momentum. The Schmidt number which denotes the degree of EPR entanglement is calculated and it can approach a high value when the number of illuminated waveguide channels and the length of the waveguide array are properly chosen. These results suggest the quadratic waveguide array as a compact platform for engineering photonic quantum states in a high-dimensional Hilbert space. Supported by the State Key Program for Basic Research in China under Grant No. 2012CB921802, the National Natural Science Foundations of China under Grant Nos. 91321312, 11321063 and 11422438

  11. Copper ESEEM and HYSCORE through ultra-wideband chirp EPR spectroscopy.

    PubMed

    Segawa, Takuya F; Doll, Andrin; Pribitzer, Stephan; Jeschke, Gunnar

    2015-07-28

    The main limitation of pulse electron paramagnetic resonance (EPR) spectroscopy is its narrow excitation bandwidth. Ultra-wideband (UWB) excitation with frequency-swept chirp pulses over several hundreds of megahertz overcomes this drawback. This allows to excite electron spin echo envelope modulation (ESEEM) from paramagnetic copper centers in crystals, whereas up to now, only ESEEM of ligand nuclei like protons or nitrogens at lower frequencies could be detected. ESEEM spectra are recorded as two-dimensional correlation experiments, since the full digitization of the electron spin echo provides an additional Fourier transform EPR dimension. Thus, UWB hyperfine-sublevel correlation experiments generate a novel three-dimensional EPR-correlated nuclear modulation spectrum. PMID:26233121

  12. Fault Current Distribution and Pole Earth Potential Rise (EPR) Under Substation Fault

    NASA Astrophysics Data System (ADS)

    Nnassereddine, M.; Rizk, J.; Hellany, A.; Nagrial, M.

    2013-09-01

    New high-voltage (HV) substations are fed by transmission lines. The position of these lines necessitates earthing design to ensure safety compliance of the system. Conductive structures such as steel or concrete poles are widely used in HV transmission mains. The earth potential rise (EPR) generated by a fault at the substation could result in an unsafe condition. This article discusses EPR based on substation fault. The pole EPR assessment under substation fault is assessed with and without mutual impedance consideration. Split factor determination with and without the mutual impedance of the line is also discussed. Furthermore, a simplified formula to compute the pole grid current under substation fault is included. Also, it includes the introduction of the n factor which determines the number of poles that required earthing assessments under substation fault. A case study is shown.

  13. EPR/alanine pellets with low Gd content for neutron dosimetry.

    PubMed

    Marrale, M; Brai, M; Longo, A; Panzeca, S; Carlino, A; Tranchina, L; Tomarchio, E; Parlato, A; Buttafava, A; Dondi, D; Zeffiro, A

    2014-10-01

    This paper reports on results obtained by electron paramagnetic resonance (EPR) measurements and Monte Carlo (MC) simulation on a blend of alanine added with low content of gadolinium oxide (5 % by weight) to improve the sensitivity to thermal neutron without excessively affecting tissue equivalence. The sensitivity is enhanced by this doping procedure of more an order of magnitude. The results are compared with those obtained with the addition of boric acid (50 % by weight) where boron is in its natural isotopic composition in order to produce low-cost EPR dosemeters. The gadolinium addition influences neutron sensitivity more than the boron addition. The presence of additives does not substantially change the fading of the EPR signal induced by neutrons. The MC simulations agree the experimental results in case of gadolinium addition. PMID:24262924

  14. Saccharides as Prospective Immobilizers of Nucleic Acids for Room-Temperature Structural EPR Studies.

    PubMed

    Kuzhelev, Andrey A; Shevelev, Georgiy Yu; Krumkacheva, Olesya A; Tormyshev, Victor M; Pyshnyi, Dmitrii V; Fedin, Matvey V; Bagryanskaya, Elena G

    2016-07-01

    Pulsed dipolar electron paramagnetic resonance (EPR) spectroscopy is a powerful tool for structural studies of biomolecules and their complexes. This method, whose applicability has been recently extended to room temperatures, requires immobilization of the studied biosystem to prevent averaging of dipolar couplings; at the same time, the modification of native conformations by immobilization must be avoided. In this work, we provide first demonstration of room-temperature EPR distance measurements in nucleic acids using saccharides trehalose, sucrose, and glucose as immobilizing media. We propose an approach that keeps structural conformation and unity of immobilized double-stranded DNA. Remarkably, room-temperature electron spin dephasing time of triarylmethyl-labeled DNA in trehalose is noticeably longer compared to previously used immobilizers, thus providing a broader range of available distances. Therefore, saccharides, and especially trehalose, can be efficiently used as immobilizers of nucleic acids, mimicking native conditions and allowing wide range of structural EPR studies at room temperatures. PMID:27320083

  15. Pulsed EPR of P1 centers in synthetic diamond under bichromatic excitation conditions

    NASA Astrophysics Data System (ADS)

    Fedoruk, G. G.; Saiko, A. P.; Markevich, S. A.; Poklonskaya, O. N.

    2009-03-01

    The dynamics of the interaction of P1 centers in synthetic diamond with a bichromatic radiation, representing microwave (MW) and radio frequency (RF) fields in a configuration characteristic of the stationary EPR spectroscopy with modulated magnetic field, has been studied using the transient nutation technique. It is demonstrated that a thermobaric treatment of the crystal leads to an increase in the phase relaxation time of P1 centers. Additional increase in this relaxation time is observed under the conditions of a nutation resonance, where the RF field frequency is close to the effective Rabi frequency in the MW field. These data are taken into account in considering the inversion of the EPR lines of P1 centers that was recently discovered in the stationary EPR.

  16. Characterization by XRD and electron paramagnetic resonance (EPR) of waste materials from 'Cerro Matoso' Mine (Colombia)

    SciTech Connect

    Hernandez, Y.; Carriazo, J.G.; Almanza, O. . E-mail: oaalmanzam@unal.edu.co

    2006-07-15

    Materials from a mining process, in which ferronickel metal extraction is the principal aim, were studied. The residual solid (scum) obtained in this process leads to large-scale accumulation of a vitreous material (pollutant) which creates an environmental problem. These materials were characterized by EPR, X-ray diffraction and X-ray fluorescence. The results indicate that the analyzed solids are rich in Fe{sub 2}O{sub 3} and NiO among other oxides. The scum material shows diffraction signals corresponding to the minerals enstatite (pyroxene) and {alpha}-alumina. Moreover, the scum EPR analysis showed a broad line around g = 2.1 corresponding to Fe{sup 3+} clusters in a complex glassy matrix. An analysis of EPR at different temperatures was also performed. The objective of this work, as a first exploratory stage, is to develop a better understanding of the residual solids in order to identify potential applications.

  17. A proposed model to include a residual NAPL saturation in a hysteretic capillary pressure saturation relationship

    NASA Astrophysics Data System (ADS)

    Van Geel, P. J.; Roy, S. D.

    2002-09-01

    A residual non-aqueous phase liquid (NAPL) present in the vadose zone can act as a contaminant source for many years as the compounds of concern partition to infiltrating groundwater and air contained in the soil voids. Current pressure-saturation-relative permeability relationships do not include a residual NAPL saturation term in their formulation. This paper presents the results of series of two- and three-phase pressure cell experiments conducted to evaluate the residual NAPL saturation and its impact on the pressure-saturation relationship. A model was proposed to incorporate a residual NAPL saturation term into an existing hysteretic three-phase parametric model developed by Parker and Lenhard [Water Resour. Res. 23(12) (1987) 2187], Lenhard and Parker [Water Resour. Res. 23(12) (1987) 2197] and Lenhard [J. Contam. Hydrol. 9 (1992) 243]. The experimental results indicated that the magnitude of the residual NAPL saturation was a function of the maximum total liquid saturation reached and the water saturation. The proposed model to incorporate a residual NAPL saturation term is similar in form to the entrapment model proposed by Parker and Lenhard, which was based on an expression presented by Land [Soc. Pet. Eng. J. (June 1968) 149].

  18. Saturation and isotopic replacement of deuterium in low-Z material

    SciTech Connect

    Doyle, B.L.; Wampler, W.R.; Brice, D.K.; Picraux, S.T.

    1980-01-01

    The saturation and replacement of hydrogen isotopes implanted into TiC, TiB/sub 2/, VB/sub 2/, B/sub 4/C, B, Si, and C has been examined experimentally and modeled theoretically. The deuterium saturation concentrations for these materials varied from .16 to .57. A new isotopic replacement model is presented which predicts isotopic trapping and exchange on the basis of the depth dependence of the implanted ions and the experimentally determined hydrogen saturation concentration. Our results indicate that, for these materials used as coatings on components in a D-T fueled tokamak, T recovery by ion induced replacement with H or D should be feasible and that T buildup will be at tolerable levels.

  19. Solid state ``self-calibrated'' EPR-dosimeters—advantageous and shortcomings

    NASA Astrophysics Data System (ADS)

    Peimel-Stuglik, Z.; Fabisiak, S.

    2006-03-01

    EPR dosimetry method with α-alanine as radiation sensitive material (RSM) is widely used in high dose dosimetry laboratories. However, it is not suitable for routine industrial applications mainly because of difficult EPR measurement procedure. In order to simplify quantitative EPR dosimetry measurements Yordanov and Gancheva developed so-called "self-calibrated" (sc) dosimeters consists of RSM (α-alanine, sugar, other ones), Mn 2+/MgO as internal EPR intensity standard (IES) and a binder. The aim of this work was to check dosimetric properties of two experimental batches of sc EPR dosimeters with α-alanine and sugar as RSM, Mn 2+/MgO as IES and paraffin as a binder. The percentage content of the components was 60, 5 and 35% (w/w), respectively. It was established that the investigated alanine sc-dosimeters are about two times more sensitive than the sugar ones. The dose-response coefficient, Kdr of sc-alanine dosimeters was stable in all investigated dose range from 1 to 23 kGy. The Kdr-value of sugar sc-dosimeters decreased with the dose what was in a contradiction to the results pointed to the high stability of radiation generated sugar radicals. The observed effect arose probably from the special chemical procedure used for the sc-sugar dosimeters production. The results confirmed an expectation that the position of sc dosimeter in the cavity is not important factor for accurate dose evaluation. It allows to read-out dosimetric signals in shorter time, with lower uncertainty and on less sophisticate EPR-spectrometers than that commonly used till now. The main shortcomings of sc dosimeters are: (a) the limitation of RSM suitable for sc dosimeters to these ones having strictly linear signal to dose characteristic; (b) necessity to assure very good homogeneity of dosimeter material; and (c) the cost of IES present in the amount of some percent in each sc dosimeter.

  20. 75 FR 16203 - Advisory Committee on Reactor Safeguards (ACRS); Meeting of the ACRS Subcommittee on EPR; Notice...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-31

    ... From the Federal Register Online via the Government Publishing Office NUCLEAR REGULATORY COMMISSION Advisory Committee on Reactor Safeguards (ACRS); Meeting of the ACRS Subcommittee on EPR; Notice of Meeting The ACRS Subcommittee on the U.S. Evolutionary Power Reactor (EPR) will hold a meeting on April 20-21, 2010, at 11545 Rockville Pike, T2-...

  1. Optimal weighted suprathreshold stochastic resonance with multigroup saturating sensors

    NASA Astrophysics Data System (ADS)

    Xu, Liyan; Duan, Fabing; Abbott, Derek; McDonnell, Mark D.

    2016-09-01

    Suprathreshold stochastic resonance (SSR) describes a noise-enhanced effect that occurs, not in a single element, but rather in an array of nonlinear elements when the signal is no longer subthreshold. Within the context of SSR, we investigate the optimization problem of signal recovery through an array of saturating sensors where the response of each element can be optimally weighted prior to summation, with a performance measure of mean square error (MSE). We consider groups of sensors. Individual sensors within each group have identical parameters, but each group has distinct parameters. We find that optimally weighting the sensor responses provides a lower MSE in comparison with the unweighted case for weak and moderate noise intensities. Moreover, as the slope parameter of the nonlinear sensors increases, the MSE superiority of the optimally weighted array shows a peak, and then tends to a fixed value. These results indicate that SSR with optimal weights, as a general mechanism of enhancement by noise, is of potential interest to signal recovery.

  2. EPR study of free radicals in some drugs γ-irradiated in the solid state

    NASA Astrophysics Data System (ADS)

    Ambroż, H. B.; 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 γ-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 — 4.5×10 17 spins per gram and the lowest for nimodipine — 2.1×10 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.

  3. Pulsed EPR Distance Measurements in Soluble Proteins by Site-directed Spin-labeling (SDSL)

    PubMed Central

    de Vera, Ian Mitchelle S.; Blackburn, Mandy E.; Galiano, Luis; Fanucci, Gail E.

    2015-01-01

    The resurgence of pulsed electron paramagnetic resonance (EPR) in structural biology centers on recent improvements in distance measurements using the double electron-electron resonance (DEER) technique. This unit focuses on EPR-based distance measurements by site-directed spin-labeling (SDSL) of engineered cysteine residues in soluble proteins, with HIV-1 protease used as a model. To elucidate conformational changes in proteins, experimental protocols were optimized and existing data analysis programs were employed to derive distance distribution profiles. Experimental considerations, sample preparation and error analysis for artifact suppression are also outlined here. PMID:24510645

  4. The first international intercomparison of EPR-dosimetry with teeth: first results.

    PubMed

    Chumak, V; Bailiff, I; Baran, N; Bugai, A; Dubovsky, S; Fedosov, I; Finin, V; Haskell, E; Hayes, R; Ivannikov, A; Kenner, G; Kirillov, V; Khamidova, L; Kolesnik, S; Liidja, G; Likhtarev, I; Lippmaa, E; Maksimenko, V; Meijer, A; Minenko, V; Pasalskaya, L; Past, J; Puskar, J; Radchuk, V; Wieser, A

    1996-01-01

    Intercomparison of EPR-dosimetric techniques using tooth enamel had been performed in order to check whether the results produced by different laboratories are consistent and accurate. Participants were supposed to evaluate doses applied to pulverized enamel samples, using routine techniques from their laboratories. The intercomparison has demonstrated a great variety of methods used for dose reconstruction. Peculiarities of experimental approaches are discussed systematically in terms of procedure for recording the EPR-spectra, determination of the amplitude of the radiation induced signal, determination of the dose, and error propagation. PMID:9022185

  5. Use of polyphase continuous excitation based on the Frank sequence in EPR.

    PubMed Central

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

    2011-01-01

    Polyphase continuous excitation based on the Frank sequence is suggested as an alternative to single pulse excitation in EPR. The method allows reduction of the source power, while preserving the excitation bandwidth of a single pulse. For practical EPR implementation the use of a cross-loop resonator is essential to provide isolation between the spin system and the resonator responses to the excitation. Provided that a line broadening of about 5% is acceptable, the cumulative turning angle of the magnetization vector generated by the excitation sequence can be quite large and can produce signal amplitudes that are comparable to that achieved with a higher power 90° pulse. PMID:21737326

  6. Use of polyphase continuous excitation based on the Frank sequence in EPR.

    PubMed

    Tseitlin, Mark; Quine, Richard W; Eaton, Sandra S; Eaton, Gareth R

    2011-08-01

    Polyphase continuous excitation based on the Frank sequence is suggested as an alternative to single pulse excitation in EPR. The method allows reduction of the source power, while preserving the excitation bandwidth of a single pulse. For practical EPR implementation the use of a cross-loop resonator is essential to provide isolation between the spin system and the resonator responses to the excitation. Provided that a line broadening of about 5% is acceptable, the cumulative turning angle of the magnetization vector generated by the excitation sequence can be quite large and can produce signal amplitudes that are comparable to that achieved with a higher power 90° pulse. PMID:21737326

  7. EPR, mass, IR, electronic, and magnetic studies on copper(II) complexes of semicarbazones and thiosemicarbazones

    NASA Astrophysics Data System (ADS)

    Chandra, Sulekh; Gupta, Lokesh Kumar

    2005-01-01

    Copper(II) complexes having the general composition Cu(L) 2X 2 [where L = isopropyl methyl ketone semicarbazone (LLA), isopropyl methyl ketone thiosemicarbazone (LLB), 4-aminoacetophenone semicarbazone (LLC), and 4-aminoacetophenone thiosemicarbazone (LLD) and X = Cl -, 1/2SO 42-] have been synthesized. All the Cu(II) complexes reported here have been characterized by elemental analyses, molar conductance, magnetic moment susceptibility, EI mass, 1H NMR, IR, EPR, and electronic spectral studies. All the complexes were found to have magnetic moments corresponding to one unpaired electrons. The possible geometries of the complexes were assigned on the basis of EPR, electronic, and infrared spectral studies.

  8. EPR evidence of extrinsic symmetry-breaking defects in nominally pure KTaO3

    NASA Astrophysics Data System (ADS)

    Pechenyi, A. P.; Glinchuk, M. D.; Azzoni, C. B.; Scardina, F.; Paleari, A.

    1995-05-01

    EPR measurements on nominally pure (undoped) KTaO3 single crystals at low temperature (4.2 K) are reported. Evidence is brought of impurity defects analyzed through the experimental spin-Hamiltonian parameters. Axial EPR spectra of Fe3+ in different cation positions are detected. An orthorhombic spectrum is found and attributed to Fe3+ substituting for K+ ions and involving nearby potassium vacancies as charge compensators. Manganese impurities are also observed following illumination of the sample to cause a change of the Mn valence state.

  9. EPR study of VO2+ doped glycine zinc sulphate single crystal

    NASA Astrophysics Data System (ADS)

    Prabakaran, R.; Subramanian, P.

    2015-06-01

    Single crystals Of GZS:VO2+ were grown by slow evaporation of solvent at room temperature. The EPR study was carried out at room temperature. Single crystal rotations in each of the three mutually orthogonal planes indicate single site occupation of VO2+ in the lattice. g and A tensors were calculated from the recorded EPR spectra. The principal values of g and A indicates existence of rhombic symmetry around the VO2+ ion. From the direction cosines of the g and A tensors, the locations of VO2+ in the lattice have been identified as substitutional site.

  10. EPR dosimetry of teeth in past and future accidents: a prospective look at a retrospective method

    SciTech Connect

    Haskell, E.H.; Kenner, G.H.; Hayes, R.B.; Chumak, V.; Shalom, S.

    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.

  11. EPR detection of the flux distribution in ceramic high-T c superconductors

    NASA Astrophysics Data System (ADS)

    Rakvin, B.; Požek, M.; Dulčić, A.

    1989-10-01

    EPR measurements were made on adsorbed diphenyl picrylhydrazil (DPPH) at the surface of a ceramic high- T c superconductor YBa 2Cu 3O 7. A significant broadening of the EPR linewidth was observed below the superconducting transition temperature T c. It is interpreted as a broadening due to the spatial distribution of the flux in the superconducting mixed state which is developed at the resonant magnetic field H 0 (H Cl ≪ H 0 ≪ H C2). The penetration depth of the magnetic field can be determined by this simple technique.

  12. Current and Noise Saturation in Graphene Superlattice

    NASA Astrophysics Data System (ADS)

    Yang, Wei; Lu, Xiaobo; Berthou, Simon; Wilmart, Quentin; Boukhicha, Mohamed; Voisin, Christophe; Zhang, Guangyu; Placais, Bernard

    One of the merits of graphene is that the Fermi level can be easily tuned by electrical gating, which render charge carriers n type or p type, or even insulating around the Dirac point (DP). By aligning graphene on top of Boron Nitride (BN), the presence of graphene superlattice makes transport properties even more versatile owning to the emergence of secondary Dirac points (SDPs). Here we present a study of high electric field performance of graphene superlattice obtained from epitaxial approach. By using microwave cavity, noise produced from graphene by joule heating is recorded up to 5GHz. Current and noise saturation are observed and investigated. Depending on Fermi energy, saturation can be attributed to intrinsic optical or remote surface polar phonon scattering at a doping far away from DP, while no saturation are found around DP. Moreover, noise saturation is identified around Fermi energy between DP and SDP, which can be attributed to the influence of van Hove singularity arising from the superlattice. Lastly, saturation due to the bias induced shift of DP, or so called Dirac fermion pinch-off, is well observed by local top gate technique. EU Graphene flagship project (Contract No. 604391).

  13. Planetary cratering 2: Studies of saturation equilibrium

    NASA Astrophysics Data System (ADS)

    Hartmann, William K.; Gaskell, Robert W.

    1997-01-01

    A realistic computer model has been developed to display images of imaginary cratered surfaces, taking into account empirically measured input size distributions of primary and secondary craters, ejecta blanket morphology including feathering with distance, obliteration due to ejecta from outside the imaged area, lighting effects, etc. The model allows us to track surface evolution of morphology as new craters are added. Using the model as well as lunar photos, we have studied the approach to saturation equilibrium (defined as a condition when no further proportionate increase in crater density occurs as input cratering increases). We find that an identifiable saturation equilibrium occurs close to a level previously identified for this state (Hartmann 1984), typically fluctuating around a crater density from about 0.4 to 2 times that level. This result is fairly robust vis-a-vis the range of model parameters we have chosen. Flooding, basin ejecta blankets, and other obliterative effects can introduce structure and oscillations within this range, even after saturation equilibrium is achieved. These findings may constrain or revise certain earlier interpretations of satellite and planet surface evolution and impactor populations which were predicated on the assumed absence of saturation equilibrium. In our fourth experimental run, we found that suppression of "sandblasting" by sub-resolution impacts allows the smallest secondaries to rise above the saturation equilibrium line, a result that might be relevant to a similar situation on Gaspra and perhaps some other asteroids.

  14. A secure and efficient password-based user authentication scheme using smart cards for the integrated EPR information system.

    PubMed

    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. PMID:23553734

  15. Saturable inductor and transformer structures for magnetic pulse compression

    DOEpatents

    Birx, Daniel L.; Reginato, Louis L.

    1990-01-01

    Saturable inductor and transformer for magnetic compression of an electronic pulse, using a continuous electrical conductor looped several times around a tightly packed core of saturable inductor material.

  16. Lipid order, saturation and surface property relationships: a study of human meibum saturation.

    PubMed

    Mudgil, Poonam; Borchman, Douglas; Yappert, Marta C; Duran, Diana; Cox, Gregory W; Smith, Ryan J; Bhola, Rahul; Dennis, Gary R; Whitehall, John S

    2013-11-01

    Tear film stability decreases with age however the cause(s) of the instability are speculative. Perhaps the more saturated meibum from infants may contribute to tear film stability. The meibum lipid phase transition temperature and lipid hydrocarbon chain order at physiological temperature (33 °C) decrease with increasing age. It is reasonable that stronger lipid-lipid interactions could stabilize the tear film since these interactions must be broken for tear break up to occur. In this study, meibum from a pool of adult donors was saturated catalytically. The influence of saturation on meibum hydrocarbon chain order was determined by infrared spectroscopy. Meibum is in an anhydrous state in the meibomian glands and on the surface of the eyelid. The influence of saturation on the surface properties of meibum was determined using Langmuir trough technology. Saturation of native human meibum did not change the minimum or maximum values of hydrocarbon chain order so at temperatures far above or below the phase transition of human meibum, saturation does not play a role in ordering or disordering the lipid hydrocarbon chains. Saturation did increase the phase transition temperature in human meibum by over 20 °C, a relatively high amount. Surface pressure-area studies showing the late take off and higher maximum surface pressure of saturated meibum compared to native meibum suggest that the saturated meibum film is quite molecularly ordered (stiff molecular arrangement) and elastic (molecules are able to rearrange during compression and expansion) compared with native meibum films which are more fluid agreeing with the infrared spectroscopic results of this study. In saturated meibum, the formation of compacted ordered islands of lipids above the surfactant layer would be expected to decrease the rate of evaporation compared to fluid and more loosely packed native meibum. Higher surface pressure observed with films of saturated meibum compared to native meibum

  17. Economical analysis of saturation mutagenesis experiments.

    PubMed

    Acevedo-Rocha, Carlos G; Reetz, Manfred T; Nov, Yuval

    2015-01-01

    Saturation mutagenesis is a powerful technique for engineering proteins, metabolic pathways and genomes. In spite of its numerous applications, creating high-quality saturation mutagenesis libraries remains a challenge, as various experimental parameters influence in a complex manner the resulting diversity. We explore from the economical perspective various aspects of saturation mutagenesis library preparation: We introduce a cheaper and faster control for assessing library quality based on liquid media; analyze the role of primer purity and supplier in libraries with and without redundancy; compare library quality, yield, randomization efficiency, and annealing bias using traditional and emergent randomization schemes based on mixtures of mutagenic primers; and establish a methodology for choosing the most cost-effective randomization scheme given the screening costs and other experimental parameters. We show that by carefully considering these parameters, laboratory expenses can be significantly reduced. PMID:26190439

  18. Economical analysis of saturation mutagenesis experiments

    PubMed Central

    Acevedo-Rocha, Carlos G.; Reetz, Manfred T.; Nov, Yuval

    2015-01-01

    Saturation mutagenesis is a powerful technique for engineering proteins, metabolic pathways and genomes. In spite of its numerous applications, creating high-quality saturation mutagenesis libraries remains a challenge, as various experimental parameters influence in a complex manner the resulting diversity. We explore from the economical perspective various aspects of saturation mutagenesis library preparation: We introduce a cheaper and faster control for assessing library quality based on liquid media; analyze the role of primer purity and supplier in libraries with and without redundancy; compare library quality, yield, randomization efficiency, and annealing bias using traditional and emergent randomization schemes based on mixtures of mutagenic primers; and establish a methodology for choosing the most cost-effective randomization scheme given the screening costs and other experimental parameters. We show that by carefully considering these parameters, laboratory expenses can be significantly reduced. PMID:26190439

  19. Interger multiplication with overflow detection or saturation

    SciTech Connect

    Schulte, M.J.; Balzola, P.I.; Akkas, A.; Brocato, R.W.

    2000-01-11

    High-speed multiplication is frequently used in general-purpose and application-specific computer systems. These systems often support integer multiplication, where two n-bit integers are multiplied to produce a 2n-bit product. To prevent growth in word length, processors typically return the n least significant bits of the product and a flag that indicates whether or not overflow has occurred. Alternatively, some processors saturate results that overflow to the most positive or most negative representable number. This paper presents efficient methods for performing unsigned or two's complement integer multiplication with overflow detection or saturation. These methods have significantly less area and delay than conventional methods for integer multiplication with overflow detection and saturation.

  20. Dilatant hardening of fluid-saturated sandstone

    NASA Astrophysics Data System (ADS)

    Makhnenko, Roman Y.; Labuz, Joseph F.

    2015-02-01

    The presence of pore fluid in rock affects both the elastic and inelastic deformation processes, yet laboratory testing is typically performed on dry material even though in situ the rock is often saturated. Techniques were developed for testing fluid-saturated porous rock under the limiting conditions of drained, undrained, and unjacketed response. Confined compression experiments, both conventional triaxial and plane strain, were performed on water-saturated Berea sandstone to investigate poroelastic and inelastic behavior. Measured drained response was used to calibrate an elasto-plastic constitutive model that predicts undrained inelastic deformation. The experimental data show good agreement with the model: dilatant hardening in undrained triaxial and plane strain compression tests under constant mean stress was predicted and observed.

  1. Saturation transfer electron paramagnetic resonance study of the mobility of myosin heads in myofibrils under conditions of partial dissociation.

    PubMed Central

    Ishiwata, S; Manuck, B A; Seidel, J C; Gergely, J

    1986-01-01

    The rotational motion of rigidly spin-labeled myosin heads of glycerinated myofibrils as reflected in saturation-transfer EPR spectra behaves to a first approximation as though the heads consist of two populations with different rotational motions. An immobilized fraction has a correlation time (tau 2) of approximately 0.5 ms, comparable to that of spin-labeled subfragment-1 (S1) bound to thin filaments, while a mobile fraction has a tau 2 of 10 microseconds, comparable to that of the heads of purified myosin filaments. The effects of nonhydrolyzable ATP analogues, potassium pyrophosphate (PPi), or adenylyl imidodiphosphate, Ca2+, temperature, or ionic strength on the spectra can be analyzed in terms of the fraction of myosin heads immobilized by attachment to thin filaments, without requiring changes in the motion of either attached or detached heads. PMID:3013329

  2. Studies of non-isothermal flow in saturated and partially saturated porous media

    SciTech Connect

    Ho, C.K.; Maki, K.S.; Glass, R.J.

    1993-12-31

    Physical and numerical experiments have been performed to investigate the behavior of nonisothermal flow in two-dimensional saturated and partially saturated porous media. The physical experiments were performed to identify non-isothermal flow fields and temperature distributions in fully saturated, half-saturated, and residually saturated two-dimensional porous media with bottom heating and top cooling. Two counter-rotating liquid-phase convective cells were observed to develop in the saturated regions of all three cases. Gas-phase convection was also evidenced in the unsaturated regions of the partially saturated experiments. TOUGH2 numerical simulations of the saturated case were found to be strongly dependent on the assumed boundary conditions of the physical system. Models including heat losses through the boundaries of the test cell produced temperature and flow fields that were in better agreement with the observed temperature and flow fields than models that assumed insulated boundary conditions. A sensitivity analysis also showed that a reduction of the bulk permeability of the porous media in the numerical simulations depressed the effects of convection, flattening the temperature profiles across the test cell.

  3. Studies of non-isothermal flow in saturated and partially saturated porous media

    SciTech Connect

    Ho, C.K.; Maki, K.S.; Glass, R.J.

    1994-12-31

    Coupled thermal and hydrologic flow processes in unsaturated fractured rocks are important in the evaluation of Yucca Mountain as a potential repository for high level nuclear waste. Physical and numerical experiments have been performed to investigate the behavior of non-isothermal flow in two-dimensional saturated and partially saturated porous media. The physical experiments were performed to identify non-isothermal flow fields and temperature distributions in fully saturated, half-saturated, and residually saturated two-dimensional porous media with bottom heating and top cooling. Two counter-rotating liquid-phase convective cells were observed to develop in the saturated regions of all three cases. Gas-phase convection was also evidenced in the unsaturated regions of the partially saturated experiments. TOUGH2 numerical simulations of the saturated case were found to be strongly dependent on the assumed boundary conditions of the physical system. Models including heat losses through the boundaries of the test cell produced temperature and flow fields that were in better agreement with the observed temperature and flow fields than models that assumed insulated boundary conditions. A sensitivity analysis also showed that a reduction of the bulk permeability of the porous media in the numerical simulations depressed the effect of convection, flattening the temperature profiles across the test cell.

  4. Computational Modeling of Seismic Wave Propagation Velocity-Saturation Effects in Porous Rocks

    NASA Astrophysics Data System (ADS)

    Deeks, J.; Lumley, D. E.

    2011-12-01

    Compressional and shear velocities of seismic waves propagating in porous rocks vary as a function of the fluid mixture and its distribution in pore space. Although it has been possible to place theoretical upper and lower bounds on the velocity variation with fluid saturation, predicting the actual velocity response of a given rock with fluid type and saturation remains an unsolved problem. In particular, we are interested in predicting the velocity-saturation response to various mixtures of fluids with pressure and temperature, as a function of the spatial distribution of the fluid mixture and the seismic wavelength. This effect is often termed "patchy saturation' in the rock physics community. The ability to accurately predict seismic velocities for various fluid mixtures and spatial distributions in the pore space of a rock is useful for fluid detection, hydrocarbon exploration and recovery, CO2 sequestration and monitoring of many subsurface fluid-flow processes. We create digital rock models with various fluid mixtures, saturations and spatial distributions. We use finite difference modeling to propagate elastic waves of varying frequency content through these digital rock and fluid models to simulate a given lab or field experiment. The resulting waveforms can be analyzed to determine seismic traveltimes, velocities, amplitudes, attenuation and other wave phenomena for variable rock models of fluid saturation and spatial fluid distribution, and variable wavefield spectral content. We show that we can reproduce most of the published effects of velocity-saturation variation, including validating the Voigt and Reuss theoretical bounds, as well as the Hill "patchy saturation" curve. We also reproduce what has been previously identified as Biot dispersion, but in fact in our models is often seen to be wave multi-pathing and broadband spectral effects. Furthermore, we find that in addition to the dominant seismic wavelength and average fluid patch size, the

  5. Beyond nonlinear saturation of backward Raman amplifiers

    DOE PAGESBeta

    Barth, Ido; Toroker, Zeev; Balakin, Alexey A.; Fisch, Nathaniel J.

    2016-06-27

    Backward Raman amplification is limited by relativistic nonlinear dephasing resulting in saturation of the leading spike of the amplified pulse. We employed pump detuning in order to mitigate the relativistic phase mismatch and to overcome the associated saturation. In an amplified pulse can then be reshaped into a monospike pulse with little precursory power ahead of it, with the maximum intensity increasing by a factor of two. Finally, this detuning can be employed advantageously both in regimes where the group velocity dispersion is unimportant and where the dispersion is important but small.

  6. Beyond nonlinear saturation of backward Raman amplifiers.

    PubMed

    Barth, Ido; Toroker, Zeev; Balakin, Alexey A; Fisch, Nathaniel J

    2016-06-01

    Backward Raman amplification is limited by relativistic nonlinear dephasing resulting in saturation of the leading spike of the amplified pulse. Pump detuning is employed to mitigate the relativistic phase mismatch and to overcome the associated saturation. The amplified pulse can then be reshaped into a monospike pulse with little precursory power ahead of it, with the maximum intensity increasing by a factor of two. This detuning can be employed advantageously both in regimes where the group velocity dispersion is unimportant and where the dispersion is important but small. PMID:27415380

  7. Beyond nonlinear saturation of backward Raman amplifiers

    NASA Astrophysics Data System (ADS)

    Barth, Ido; Toroker, Zeev; Balakin, Alexey A.; Fisch, Nathaniel J.

    2016-06-01

    Backward Raman amplification is limited by relativistic nonlinear dephasing resulting in saturation of the leading spike of the amplified pulse. Pump detuning is employed to mitigate the relativistic phase mismatch and to overcome the associated saturation. The amplified pulse can then be reshaped into a monospike pulse with little precursory power ahead of it, with the maximum intensity increasing by a factor of two. This detuning can be employed advantageously both in regimes where the group velocity dispersion is unimportant and where the dispersion is important but small.

  8. Site-Scale Saturated Zone Flow Model

    SciTech Connect

    G. Zyvoloski

    2003-12-17

    The purpose of this model report is to document the components of the site-scale saturated-zone flow model at Yucca Mountain, Nevada, in accordance with administrative procedure (AP)-SIII.lOQ, ''Models''. This report provides validation and confidence in the flow model that was developed for site recommendation (SR) and will be used to provide flow fields in support of the Total Systems Performance Assessment (TSPA) for the License Application. The output from this report provides the flow model used in the ''Site-Scale Saturated Zone Transport'', MDL-NBS-HS-000010 Rev 01 (BSC 2003 [162419]). The Site-Scale Saturated Zone Transport model then provides output to the SZ Transport Abstraction Model (BSC 2003 [164870]). In particular, the output from the SZ site-scale flow model is used to simulate the groundwater flow pathways and radionuclide transport to the accessible environment for use in the TSPA calculations. Since the development and calibration of the saturated-zone flow model, more data have been gathered for use in model validation and confidence building, including new water-level data from Nye County wells, single- and multiple-well hydraulic testing data, and new hydrochemistry data. In addition, a new hydrogeologic framework model (HFM), which incorporates Nye County wells lithology, also provides geologic data for corroboration and confidence in the flow model. The intended use of this work is to provide a flow model that generates flow fields to simulate radionuclide transport in saturated porous rock and alluvium under natural or forced gradient flow conditions. The flow model simulations are completed using the three-dimensional (3-D), finite-element, flow, heat, and transport computer code, FEHM Version (V) 2.20 (software tracking number (STN): 10086-2.20-00; LANL 2003 [161725]). Concurrently, process-level transport model and methodology for calculating radionuclide transport in the saturated zone at Yucca Mountain using FEHM V 2.20 are being

  9. Oxygen Saturation Targeting and Bronchopulmonary Dysplasia.

    PubMed

    Darlow, Brian A; Morley, Colin J

    2015-12-01

    Oxygen saturation targeting is widely used in neonatal intensive care, but the optimal target range in very preterm infants has been uncertain and is the subject of recent debate and research. This review briefly discusses the technology of oxygen monitoring and the role of oxygen toxicity in preterm infants. The background to the recent trials of oxygen saturation targeting in acute and continuing care of very preterm infants is reviewed, and the findings and implications of the recent trials, particularly with respect to bronchopulmonary dysplasia, are discussed. PMID:26593080

  10. Aerobic microbial enhanced oil recovery

    SciTech Connect

    Torsvik, T.; Gilje, E.; Sunde, E.

    1995-12-31

    In aerobic MEOR, the ability of oil-degrading bacteria to mobilize oil is used to increase oil recovery. In this process, oxygen and mineral nutrients are injected into the oil reservoir in order to stimulate growth of aerobic oil-degrading bacteria in the reservoir. Experiments carried out in a model sandstone with stock tank oil and bacteria isolated from offshore wells showed that residual oil saturation was lowered from 27% to 3%. The process was time dependent, not pore volume dependent. During MEOR flooding, the relative permeability of water was lowered. Oxygen and active bacteria were needed for the process to take place. Maximum efficiency was reached at low oxygen concentrations, approximately 1 mg O{sub 2}/liter.

  11. Waterflood oil recovery under mixed-wet conditions: laboratory observations

    NASA Astrophysics Data System (ADS)

    Tanino, Y.; Blunt, M. J.

    2013-12-01

    As an aqueous phase displaces a non-aqueous phase in a uniformly water-wet porous medium, a portion of the latter becomes immobilized by capillary forces as discontinuous pore-scale ganglia. This phenomenon, known as capillary trapping, has received renewed attention in recent years as a mechanism through which injected CO_2 may be secured against advection in a geological storage site. Here, we consider the impact of wettability on capillary trapping in oil/brine/rock systems. In uniformly water-wet rock, it is well established that residual oil saturation increases monotonically with its initial saturation. In contrast, salient features of mixed-wet rock, in which parts of the pore surface are oil-wet while the rest is water-wet, are not well established. We present laboratory measurements of remaining oil saturation in a limestone in its original, water-wet state and under mixed-wet conditions established systematically using organic acid. Under water-wet conditions, the remaining oil saturation increases linearly with its initial saturation. Under mixed-wet conditions, the remaining saturation displays three distinct regimes: as the initial oil saturation increases from 0, the remaining saturation increases, decreases, and finally increases again. These observations may have important implications for enhanced oil recovery, groundwater remediation, and injection schemes at carbon storage sites where contact with injected CO_2 alters the wettability of the grain surface.

  12. Evaluation of arterial oxygen saturation in pregnant patients and their newborns.

    PubMed

    Porter, K B; Goldhamer, R; Mankad, A; Peevy, K; Gaddy, J; Spinnato, J A

    1988-03-01

    Continuous oxygen saturation measurements were obtained in 103 pregnant patients and 96 of their newborns by a pulse oximeter during the peripartum period. The parturients received narcotic sedation; epidural, spinal, or general anesthesia; or no analgesia. Seventy-nine patients had oxygen saturation levels over 90% (mean 97.6%), and 24 had one or more oxygen saturation levels less than or equal to 90% (mean 95.6%, P = .001). For all neonates, the mean oxygen saturation was in the "hypoxic range" at one minute (77.6 +/- 11.48%), five minutes (84.4 +/- 7.64%), and ten minutes (89.4 +/- 6.29%). More desaturation episodes were noted in mothers exposed to a central nervous system depressant (P = .041). When mothers with and without desaturation events were compared, no differences were found for age, parity, race, hematocrit, smoking, hypotensive episodes, or delivery route. More maternal desaturation episodes occurred during transport (P = .0016) and while in the recovery room (P = .0003) than in other study periods. Maternal peripartum desaturation events occurred without adverse neonatal effect when prompt treatment was provided. Neonatal hemoglobin oxygen saturation less than or equal to 90% is commonly found within ten minutes after birth and does not always merit the designation of "hypoxia." PMID:3347419

  13. EPR and optical absorption studies of Cu2+ doped lithium maleate dihydrate single crystal

    NASA Astrophysics Data System (ADS)

    Kripal, Ram; Pandey, Shri Devi

    Electron paramagnetic resonance (EPR) study of Cu2+ doped lithium maleate dihydrate single crystal is done at liquid nitrogen temperature (LNT). Four hyperfine lines are observed in all directions, i.e. only a single site is observed. The spin Hamiltonian parameters are determined from EPR spectra: gx=2.100±0.002, gy=2.162±0.002, gz=2.215±0.002, Ax=(55±5)×10-4 cm-1, Ay=(52±5)×10-4 cm-1, Az=(50±5)×10-4 cm-1. The results indicate that the copper ion enters the lattice interstitially. Using the spin Hamiltonian parameters obtained from EPR study the ground state wave function of Cu2+ ion in the lattice is determined. The optical absorption study of Cu2+ doped lithium maleate dihydrate at room temperature is also performed. With the help of optical and EPR data, the nature of bonding in the complex is discussed.

  14. How can EPR spectroscopy help to unravel molecular mechanisms of flavin-dependent photoreceptors?

    PubMed Central

    Nohr, Daniel; Rodriguez, Ryan; Weber, Stefan; Schleicher, Erik

    2015-01-01

    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. PMID:26389123

  15. EPR techniques to probe insertion and conformation of spin-labeled proteins in lipid bilayers.

    PubMed

    Bordignon, Enrica; Polyhach, Yevhen

    2013-01-01

    Electron paramagnetic resonance (EPR) spectroscopy of spin-labeled membrane proteins is a valuable biophysical technique to study structural details and conformational transitions of proteins close to their physiological environment, e.g., in liposomes, membrane bilayers, and nanodiscs. Unlike in nuclear magnetic resonance spectroscopy, having only one or few specific side chains labeled at a time with paramagnetic probes makes the size of the object under investigation irrelevant in terms of technique sensitivity. As a drawback, extensive site-directed mutagenesis is required in order to analyze the properties of the protein under investigation. EPR can provide detailed information on side chain dynamics of large membrane proteins or protein complexes embedded in membranes with an exquisite sensitivity for flexible regions and on water accessibility profiles across the membrane bilayer. Moreover, distances between the two spin-labeled side chains in membrane proteins can be detected with high precision in the 1.5-6 nm range at cryogenic temperatures. The application of EPR to membrane proteins still presents some challenges in terms of sample preparation, sensitivity, and data interpretation; thus no ready-to-go methodological recipes can be given. However this chapter describes the state of the art in the application of nitroxide-based site-directed spin labeling EPR to membrane proteins, with specific focus on the different types of information which can be obtained with continuous wave and pulsed techniques and on the challenges in sample preparation and data analysis for functional and structural membrane protein studies. PMID:23404283

  16. EPR policies for electronics in developing Asia: an adapted phase-in approach.

    PubMed

    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. PMID:21730041

  17. Increasing sensitivity of pulse EPR experiments using echo train detection schemes

    NASA Astrophysics Data System (ADS)

    Mentink-Vigier, F.; Collauto, A.; Feintuch, A.; Kaminker, I.; Tarle, V.; Goldfarb, D.

    2013-11-01

    Modern pulse EPR experiments are routinely used to study the structural features of paramagnetic centers. They are usually performed at low temperatures, where relaxation times are long and polarization is high, to achieve a sufficient Signal/Noise Ratio (SNR). However, when working with samples whose amount and/or concentration are limited, sensitivity becomes an issue and therefore measurements may require a significant accumulation time, up to 12 h or more. As the detection scheme of practically all pulse EPR sequences is based on the integration of a spin echo - either primary, stimulated or refocused - a considerable increase in SNR can be obtained by replacing the single echo detection scheme by a train of echoes. All these echoes, generated by Carr-Purcell type sequences, are integrated and summed together to improve the SNR. This scheme is commonly used in NMR and here we demonstrate its applicability to a number of frequently used pulse EPR experiments: Echo-Detected EPR, Davies and Mims ENDOR (Electron-Nuclear Double Resonance), DEER (Electron-Electron Double Resonance|) and EDNMR (Electron-Electron Double Resonance (ELDOR)-Detected NMR), which were combined with a Carr-Purcell-Meiboom-Gill (CPMG) type detection scheme at W-band. By collecting the transient signal and integrating a number of refocused echoes, this detection scheme yielded a 1.6-5 folds SNR improvement, depending on the paramagnetic center and the pulse sequence applied. This improvement is achieved while keeping the experimental time constant and it does not introduce signal distortion.

  18. High-pressure EPR reveals conformational equilibria and volumetric properties of spin-labeled proteins

    PubMed Central

    McCoy, John; Hubbell, Wayne L.

    2011-01-01

    Identifying equilibrium conformational exchange and characterizing conformational substates is essential for elucidating mechanisms of function in proteins. Site-directed spin labeling has previously been employed to detect conformational changes triggered by some event, but verifying conformational exchange at equilibrium is more challenging. Conformational exchange (microsecond–millisecond) is slow on the EPR time scale, and this proves to be an advantage in directly revealing the presence of multiple substates as distinguishable components in the EPR spectrum, allowing the direct determination of equilibrium constants and free energy differences. However, rotameric exchange of the spin label side chain can also give rise to multiple components in the EPR spectrum. Using spin-labeled mutants of T4 lysozyme, it is shown that high-pressure EPR can be used to: (i) demonstrate equilibrium between spectrally resolved states, (ii) aid in distinguishing conformational from rotameric exchange as the origin of the resolved states, and (iii) determine the relative partial molar volume () and isothermal compressibility () of conformational substates in two-component equilibria from the pressure dependence of the equilibrium constant. These volumetric properties provide insight into the structure of the substates. Finally, the pressure dependence of internal side-chain motion is interpreted in terms of volume fluctuations on the nanosecond time scale, the magnitude of which may reflect local backbone flexibility. PMID:21205903

  19. EPR and ENDOR of Nd^3+ in congruent and stoichiometric LiNbO3

    NASA Astrophysics Data System (ADS)

    Grachev, Valentin; Malovichko, Galina; Munro, Mark

    2007-05-01

    Since many years Lithium Niobate (LN) is of great interest for both fundamental science and applications because of the unusual richness of its ferro-, pyro- and piezoelectric properties. Conventional LN crystals, grown from a congruent melt with lithium deficiency, contain some percent of intrinsic defects. Samples grown under special conditions from melts, to which potassium has been added, have reduced contents of intrinsic defects and lower disorder (stoichiometric samples). Both congruent and stoichiometric crystals doped with neodymium were studied with the help of the electron paramagnetic resonance, EPR. Tremendous narrowing of the EPR lines in stoichiometric samples in comparison with congruent ones allowed us to distinguish four non-equivalent centers, as well as line splitting caused by hyperfine interaction of neodymium electrons with nuclear spins of magnetic isotopes ^143Nd and ^145Nd. One of the centers has axial C3 symmetry, whereas others have lowest C1 symmetry due to presence of intrinsic defects or/and charge compensation defects in the near neighborhood of Nd^3+. Narrow EPR lines allowed us also to investigate Electron Nuclear Double Resonance (ENDOR). Structures of the Nd^3+ centers derived from the EPR/ENDOR data and effects produced by micro- and macro-imperfections of LN crystals are discussed. To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2007.NWS07.C1.4

  20. 34 GHz EPR FTIR spectra of chromatographically separated Boscan asphaltene fractions

    SciTech Connect

    Malhotra, V.M. ); Buckmaster, H.A. )

    1989-03-01

    The authors report on their re-examination of the 34 GHz and Fourier transform infrared (FTIR) measurements on three fractions of Boxcan asphaltene separated by the gel permeation chromatography (GPC) technique. The authors attempted to determine various types of vanadium coordination in GPC fractions by their partial combustion and subsequent EPR AND FTIR measurements.

  1. Estimation of the absorbed dose in radiation-processed food. 4. EPR measurements on eggshell

    SciTech Connect

    Desrosiers, M.F.; Le, F.G. ); Harewood, P.M.; Josephson, E.S. ); Montesalvo, M. )

    1993-09-01

    Fresh whole eggs treated with ionizing radiation for Salmonellae control testing. The eggshell was then removed and examined by electron paramagnetic resonance (EPR) spectroscopy to determine if EPR could be used to (1) distinguish irradiated from unirradiated eggs and (2) assess the absorbed dose. No EPR signals were detected in unirradiated eggs, while strong signals were measurable for more than 200 days after irradiation. Although a number of EPR signals were measured, the most intense resonance (g = 2.0019) was used for dosimetry throughout the study. This signal was observed to increase linearly with dose (up to [approximately]6 kGy), which decayed [approximately]20% within the first 5 days after irradiation and remained relatively constant thereafter. The standard added-dose method was used to assess, retrospectively, the dose to eggs processed at 0.2, 0.7, and 1.4 kGy. Relatively good results were obtained when measurement was made on the day the shell was reirradiated; with this procedure estimates were better for shell processed at the lower doses.

  2. DFT calculations of EPR parameters of transition metal complexes: Implications for catalysis

    SciTech Connect

    Saladino, Alexander C.; Larsen, Sarah C.

    2005-07-15

    Transition metal and ligand hyperfine coupling constants for paramagnetic vanadium and copper model complexes have been calculated using DFT methods that are available in commercial software packages. Variations in EPR parameters with ligand identity and ligand orientation are two of the trends that have been investigated with DFT calculations. For example, the systematic variation of the vanadium hyperfine coupling constant with orientation for an imidazole ligand in a VO2+ complex has been observed experimentally and has also been reproduced by DFT calculations. Similarly, changes in the vanadium hyperfine coupling constant with ligand binding have been calculated using model complexes and DFT methods. DFT methods were also used to calculate ligand hyperfine coupling constants in transition metal systems. The variation of the proton hyperfine coupling constant with water ligand orientation was investigated for [VO(H2O)5]2+ and the results were used to interpret high resolution EPR data of VO2+-exchanged zeolites. Nitrogen hyperfine and quadrupole coupling constants for VO2+ model complexes were calculated and compared with experimental data. The computational results were used to enhance the interpretation of the EPR data for vanadium-exchanged zeolites which are promising catalytic materials. The implications of the DFT calculations of EPR parameters with respect to catalysis will be discussed

  3. EPR on Y-ceramics and Bi-vitroceramics doped with S state paramagnetic ions

    NASA Astrophysics Data System (ADS)

    Simon, Simion; Ilonca, Gheorghe; Barbur, Ioan; Ardelean, Ioan; Redac, Radu

    1989-12-01

    The effect of Gd doping and of thermal history on the EPR spectra from Y 1-xGd xBa 2Cu 3O 7-δ ceramics and, for the first time, from Bi 2-xGd xSr 2Ca 2O z vitroceramics was investigated. The results were correlated with the superconducting properties of the studied samples.

  4. Sonoporation enhances liposome accumulation and penetration in tumors with low EPR.

    PubMed

    Theek, Benjamin; Baues, Maike; Ojha, Tarun; Möckel, Diana; Veettil, Seena Koyadan; Steitz, Julia; van Bloois, Louis; Storm, Gert; Kiessling, Fabian; Lammers, Twan

    2016-06-10

    The Enhanced Permeability and Retention (EPR) effect is a highly variable phenomenon. To enhance EPR-mediated passive drug targeting to tumors, several different pharmacological and physical strategies have been evaluated over the years, including e.g. TNFα-treatment, vascular normalization, hyperthermia and radiotherapy. Here, we systematically investigated the impact of sonoporation, i.e. the combination of ultrasound (US) and microbubbles (MB), on the tumor accumulation and penetration of liposomes. Two different MB formulations were employed, and their ability to enhance liposome accumulation and penetration was evaluated in two different tumor models, which are both characterized by relatively low levels of EPR (i.e. highly cellular A431 epidermoid xenografts and highly stromal BxPC-3 pancreatic carcinoma xenografts). The liposomes were labeled with two different fluorophores, enabling in vivo computed tomography/fluorescence molecular tomography (CT-FMT) and ex vivo two-photon laser scanning microscopy (TPLSM). In both models, in spite of relatively high inter- and intra-individual variability, a trend towards improved liposome accumulation and penetration was observed. In treated tumors, liposome concentrations were up to twice as high as in untreated tumors, and sonoporation enhanced the ability of liposomes to extravasate out of the blood vessels into the tumor interstitium. These findings indicate that sonoporation may be a useful strategy for improving drug targeting to tumors with low EPR. PMID:26878973

  5. Recognising Workplace Learning: The Emerging Practices of e-RPL and e-PR

    ERIC Educational Resources Information Center

    Cameron, Roslyn

    2012-01-01

    Purpose: The use of e-portfolios in recognition of prior learning (RPL) processes in workplace and professional practice contexts has attracted little attention in the literature due to its emergent nature. This study seeks to explore the growing incidence of e-portfolio-based RPL (e-RPL) and professional recognition (e-PR) processes in Australia…

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

    PubMed Central

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

    2011-01-01

    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 frequencies (9, 31, and 130 GHz) on [Mn(II)(H2O)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. PMID:22190766

  7. Tight binding study of transition ions in silicon and E.P.R. spectra

    NASA Astrophysics Data System (ADS)

    Pecheur, P.; Toussaint, G.

    1983-02-01

    A tight binding scheme is used to study the electronic structure of transition ions in silicon. Self consistency and spin polarization are introduced in a simple way. Results are obtained for interstitial and substitutional Cr, Mn and Fe impurities. They are compared to E.P.R. experiments and cluster Xα results.

  8. Electronic paramagnetic resonance (EPR) for the study of ascorbyl radical and lipid radicals in marine organisms.

    PubMed

    González, Paula Mariela; Aguiar, María Belén; Malanga, Gabriela; Puntarulo, Susana

    2013-08-01

    Electron paramagnetic resonance (EPR) spectroscopy detects the presence of radicals of biological interest, such as ascorbyl radical (A(•)) and lipid radicals. A(•) is easily detectable by EPR even in aqueous solution at room-temperature. Under oxidative conditions leading to changes in total ascorbate (AH(-)) content, the A(•)/AH(-) ratio could be used to estimate early oxidative stress in the hydrophilic milieu. This methodology was applied to a wide range of aquatic systems including algae, sea urchin, limpets, bivalves and fish, under physiological and oxidative stress conditions as well. The A(•)/AH(-) ratio reflected the state of one part of the oxidative defense system and provided an early and simple diagnosis of environmental stressing conditions. Oxidative damage to lipids was assessed by the EPR-sensitive adduct formation that correlates well with cell membrane damage with no interference from other biological compounds. Probe instability, tissue metabolism, and lack of spin specificity are drawback factors for employing EPR for in vivo determination of free radicals. However, the dependability of this technique, mostly by combining it with other biochemical strategies, enhances the value of these procedures as contributors to the knowledge of oxidative condition in aquatic organisms. PMID:23485428

  9. EPR Studies of Spin-Spin Exchange Processes: A Physical Chemistry Experiment.

    ERIC Educational Resources Information Center

    Eastman, Michael P.

    1982-01-01

    Theoretical background, experimental procedures, and analysis of experimental results are provided for an undergraduate physical chemistry experiment on electron paramagnetic resonance (EPR) linewidths. Source of line broadening observed in a spin-spin exchange process between radicals formed in aqueous solutions of potassium peroxylamine…

  10. EPR study of free-radical structure and conformation in pyridoxine hydrochloride single crystal

    NASA Astrophysics Data System (ADS)

    Masiakowski, Jerzy T.; Krzyminiewski, Ryszard; Pietrzak, Jerzy

    1985-05-01

    Numerical analysis of experimental EPR spectra of γ-irradiated single crystals of pyridoxine hydrochloride (vitamin B 6) allowed determination of the structure of the radical formed. Six hyperfine couplings were distinguished. The geometrical model of the radical was found to be in good agreement with the geometry expected from the crystal structure. Semi-empirical INDO and CNDO calculations were performed.

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

    PubMed

    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. PMID:16043053

  12. CALCULATING THE PH OF CALCIUM CARBONATE SATURATION

    EPA Science Inventory

    Two new expressions for the pH of saturation (pH subs) were derived. One is a simplified equation developed from an aqueous carbonate equilibrium system in which correction for ionic strength was considered. The other is a more accurate quadratic formula that involves computerize...

  13. Multi-spectral imaging of oxygen saturation

    NASA Astrophysics Data System (ADS)

    Savelieva, Tatiana A.; Stratonnikov, Aleksander A.; Loschenov, Victor B.

    2008-06-01

    The system of multi-spectral imaging of oxygen saturation is an instrument that can record both spectral and spatial information about a sample. In this project, the spectral imaging technique is used for monitoring of oxygen saturation of hemoglobin in human tissues. This system can be used for monitoring spatial distribution of oxygen saturation in photodynamic therapy, surgery or sports medicine. Diffuse reflectance spectroscopy in the visible range is an effective and extensively used technique for the non-invasive study and characterization of various biological tissues. In this article, a short review of modeling techniques being currently in use for diffuse reflection from semi-infinite turbid media is presented. A simple and practical model for use with a real-time imaging system is proposed. This model is based on linear approximation of the dependence of the diffuse reflectance coefficient on relation between absorbance and reduced scattering coefficient. This dependence was obtained with the Monte Carlo simulation of photon propagation in turbid media. Spectra of the oxygenated and deoxygenated forms of hemoglobin differ mostly in the red area (520 - 600 nm) and have several characteristic points there. Thus four band-pass filters were used for multi-spectral imaging. After having measured the reflectance, the data obtained are used for fitting the concentration of oxygenated and free hemoglobin, and hemoglobin oxygen saturation.

  14. Saturated Vapour Pressure and Refrigeration - Part I

    ERIC Educational Resources Information Center

    Bunker, C. A.

    1973-01-01

    The first part of a two-part article describes an experimental approach that can be used in teaching the concept of saturated vapour pressure. This leads to a discussion of refrigeration cycles in the second part of the article. (JR)

  15. Saturation Advertising and the Repetition Effect.

    ERIC Educational Resources Information Center

    Baddeley, A. D.; Bekerian, D. A.

    1980-01-01

    An investigation of a saturation advertising campaign to acquaint the public with changes in radio wavelengths showed that repeated presentation of material does not lead to learning unless appropriate encoding occurs. Such encoding will occur when subjects are allowed to use previously acquired learning strategies. (PMJ)

  16. Fullerene Transport in Saturated Porous Media

    EPA Science Inventory

    We investigated the effects of background solution chemistry and residence time within the soil column on the transport of aqu/C60 through saturated ultrapure quartz sand columns. Aqu/C60 breakthrough curves were obtained under different pore water velocities, solution pHs, and i...

  17. The Effect of CO2-Saturated Brines on the Hydraulic and Mechanical Behavior of Dunite

    NASA Astrophysics Data System (ADS)

    Lisabeth, H. P.; Zhu, W.; Kelemen, P. B.

    2013-12-01

    Carbon dioxide is increasingly being used as an industrial chemical, both in enhanced oil and gas recovery and in pilot and proposed carbon capture and storage projects. Due to the high reactivity of carbon dioxide, particularly with mafic and ultramafic minerals, a better understanding of the effects of CO2-rock interaction is necessary for the safe and effective implementation of these technologies. In order to explore the effect of CO2-rock interaction on the hydraulic and mechanical behavior of ultramafic rocks, we performed hydrostatic creep tests on thermally cracked dunites saturated with distilled water and CO2-saturated brines of varying composition to observe the effect of the presence of CO2 in pore fluid on the compaction behavior and permeability evolution of the samples. Pore fluids used in these tests were distilled water, CO2-saturated 0.6 M NaHCO3 brine, and CO2-saturated 1.5 M NaHCO3 brine. Experiments were performed at room temperature and 423 K, with a confining pressure of 15 MPa and a pore fluid pressure of 10 MPa. In-situ permeability measurements were taken throughout the experiment. At the end of three day hydrostatic tests, samples were axially deformed at a constant strain rate of 10-5 s-1 to the point of failure to assess the effects of compaction and reaction on the mechanical behavior of the samples. Samples saturated with distilled water compact with a monotonic decrease in compaction rate throughout the tests, while samples saturated with CO2-brine display an increase in compaction rate toward the end of tests. All samples exhibit a modest reduction in permeability throughout the compaction. Samples saturated with CO2-brine appear to accommodate more axial shortening before the onset of dilatancy in axial deformation tests. Optical microscopy and SEM analyses were performed on the samples and reveal interplay between dissolution, precipitation and mechanical cracking.

  18. A Potential Cost Effective Liquefaction Mitigation Countermeasure: Induced Partial Saturation

    SciTech Connect

    Bian Hanbing; Jia Yun; Shahrour, Isam

    2008-07-08

    This work is devoted to illustrate the potential liquefaction mitigation countermeasure: Induced Partial Saturation. Firstly the potential liquefaction mitigation method is briefly introduced. Then the numerical model for partially saturated sandy soil is presented. At last the dynamic responses of liquefiable free filed with different water saturation is given. It shows that the induced partial saturation is efficiency for preventing the liquefaction.

  19. Calcite saturation in eastern UK rivers.

    PubMed

    Neal, Colin

    2002-01-23

    Calcite saturation in eastern UK rivers is assessed in relation to the potential kinetic inhibition of calcite precipitation. Two well established inhibitors are considered: soluble reactive phosphorus (SRP, i.e. inorganic monomeric phosphorus); and dissolved organic carbon (DOC). The rivers show a range of calcite saturation levels from approximately 1hundredth to approximately 100-fold. The greatest range occurs for the northernmost river considered, the Tweed, where the waters range from highly unsaturated to highly oversaturated. The lowest range occurs for the most southerly rivers (the Great Ouse and the Thames) where the waters are consistently oversaturated with respect to calcite. The contrasting patterns relate to a greater diversity of water quality within the northern regions. Thus, during the winter, the main waters are derived from the upland areas with acidic soils and low weathering rates. During the summer baseflow periods, groundwater inputs are more important and high photosynthesis results in particularly high pHs and calcite oversaturation. In contrast, for the southern rivers, the main source of water during both the summer baseflow and the winter highflow periods comes from calcium carbonate rich aquifer sources. Statistical analysis of pH vs. the logarithm of the calcite saturation index for each river indicates strong linear features with individual gradients of approximately 1. This linearity results from an autocorrelation (the logarithm of the saturation index is calculated from the pH) and this indicates that calcite solubility controls are not operative in any of the rivers examined. A comparison of calcite saturation levels and SRP and DOC concentrations show a pattern inconsistent with kinetic hindrance, although some structure is observed, probably due to the mixing reactions between point and diffuse sources of water with contrasting chemistry. PMID:11846076

  20. Gamma-irradiated dry fruits. An example of a wide variety of long-time dependent EPR spectra.

    PubMed

    Yordanov, Nicola D; Pachova, Zdravka

    2006-03-13

    EPR spectra of dry, sugar containing fruits--raisins, sultanas, figs, dates, peaches, blue plums and chokeberry recorded before and after irradiation with gamma-rays, are reported. It is shown that weak singlet EPR line with 2.0031+/-0.0005 can be recorded before irradiation of seeds, stones or skin of chokeberry, figs and raisins as well as flesh of blue plum, raisins and peaches. EPR signals of various shape are distinguished after irradiation in different parts of the fruits, as well as in randomly cut pieces of them: As a result, randomly cut pieces of dry fruits suitable for EPR studies, containing various constituents, exhibit different in shape and intensity EPR spectra. Kinetic studies followed for 1 year on the time stability of all reported EPR signals indicate that intensity ratio between the simultaneously appearing EPR signals in particular fruit varies from 1:20 immediately after irradiation to 1:0.5 at the end of the period. These observations open a new possibility for identification of irradiated fruits - using the magnitude of the intensity ratio to find the approximate date of radiation processing in the first ca. 30-100 days. PMID:16497546

  1. Electronic structure of the primary electron donor of Blastochloris viridis heterodimer mutants : high field EPR study.

    SciTech Connect

    Ponomarenko, N. S.; Poluektov, O. G.; Bylina, E. J.; Norris, J. R.; Chemical Sciences and Engineering Division; Univ. of Chicago

    2010-09-01

    High-field electron paramagnetic resonance (HF EPR) has been employed to investigate the primary electron donor electronic structure of Blastochloris viridis heterodimer mutant reaction centers (RCs). In these mutants the amino acid substitution His(M200)Leu or His(L173)Leu eliminates a ligand to the primary electron donor, resulting in the loss of a magnesium in one of the constituent bacteriochlorophylls (BChl). Thus, the native BChl/BChl homodimer primary donor is converted into a BChl/bacteriopheophytin (BPhe) heterodimer. The heterodimer primary donor radical in chemically oxidized RCs exhibits a broadened EPR line indicating a highly asymmetric distribution of the unpaired electron over both dimer constituents. Observed triplet state EPR signals confirm localization of the excitation on the BChl half of the heterodimer primary donor. Theoretical simulation of the triplet EPR lineshapes clearly shows that, in the case of mutants, triplet states are formed by an intersystem crossing mechanism in contrast to the radical pair mechanism in wild type RCs. Photooxidation of the mutant RCs results in formation of a BPhe anion radical within the heterodimer pair. The accumulation of an intradimer BPhe anion is caused by the substantial loss of interaction between constituents of the heterodimer primary donor along with an increase in the reduction potential of the heterodimer primary donor D/D{sup +} couple. This allows oxidation of the cytochrome even at cryogenic temperatures and reduction of each constituent of the heterodimer primary donor individually. Despite a low yield of primary donor radicals, the enhancement of the semiquinone-iron pair EPR signals in these mutants indicates the presence of kinetically viable electron donors.

  2. EPR Methods for Biological Cu(II): L-Band CW and NARS

    PubMed Central

    Bennett, Brian; Kowalski, Jason

    2016-01-01

    Copper has many roles in biology that involve the change of coordination sphere and/or oxidation state of the copper ion. Consequently, the study of copper in heterogeneous environments is an important area in biophysics. EPR is a primary technique for the investigation of paramagnetic copper, which is usually the isolated Cu(II) ion, but sometimes as Cu(II) in different oxidation states of multi-transition ion clusters. The gross geometry of the coordination environment of Cu(II) can often be determined from a simple inspection of the EPR spectrum, recorded in the traditional X-band frequency range (9 – 10 GHz). Identification and quantitation of the coordinating ligand atoms, however, is not so straightforward. In particular, analysis of the superhyperfine structure on the EPR spectrum, to determine the number of coordinated nitrogen atoms, is fraught with difficulty at X-band, despite the observation that the overwhelming number of EPR studies of Cu(II) in the literature have been carried out at X-band. Greater reliability has been demonstrated at S-band (3 – 4 GHz), using the low-field parallel (gz) features. However, analysis relies on clear identification of the outermost superhyperfine line, which has the lowest intensity of all the spectral features. Computer simulations have subsequently indicated that the much more intense perpendicular region of the spectrum can be reliably interpreted at L-band (2 GHz). The present work describes the development of L-band EPR of Cu(II) into a routine method, that is applicable to biological samples. PMID:26478491

  3. Advanced space recovery systems

    NASA Technical Reports Server (NTRS)

    Wailes, William K.

    1989-01-01

    The design evolution of a space recovery system designed by a NASA-contracted study is described, with particular attention given to the design of a recovery system for a propulsion/avionics module (P/AM), which weighs 60,000 lb at the recovery initiation and achieves subsonic terminal descent at or above 50,000 ft msl. The components of the recovery system concept are described together with the operational sequences of the recovery. The recovery system concept offers low cost, low weight, good performance, a potential for pinpoint landing, and an operational flexibility.

  4. Cotransport of viruses and clay particles in water saturated and unsaturated porous media

    NASA Astrophysics Data System (ADS)

    Chrysikopoulos, C. V.; Syngouna, V. I.

    2014-12-01

    This experimental study examines the effects of clay colloids on the transport of viruses in variably saturated porous media. All cotransport experiments were conducted in both saturated and partially saturated columns packed with glass beads, using bacteriophages MS2 and ΦΧ174 as model viruses, and kaolinite (KGa-1b) and montmorillonite (STx-1b) as model clay colloids. The various experimental collision efficiencies were determined using the classical colloid filtration theory. The experimental data indicated that the mass recovery of viruses and clay colloids decreased as the water saturation decreased. Temporal moments of the various breakthrough concentrations collected, suggested that the presence of clays significantly influenced virus transport and irreversible deposition onto glass beads. The mass recovery of both viruses, based on total effluent virus concentrations, was shown to reduce in the presence of suspended clay particles. Furthermore, the transport of suspended virus and clay-virus particles was retarded, compared to the conservative tracer. Under unsaturated conditions both clay particles hindered the transport of the two viruses considered in this work. Moreover, the surface properties of viruses, clays and glass beads were employed for the construction of classical DLVO and capillary potential energy profiles, and the results suggested that capillary forces play a significant role on colloid retention. It was estimated that the capillary potential energy of MS2 is lower than that of ΦΧ174, and the capillary potential energy ofKGa-1b is lower than that of STx-1b, assuming that the protrusion distance through the water filmis the same for each pair of particles. Moreover, the capillary potential energy is several orders of magnitude greater than the DLVO energy potential. Figure 1Schematic illustration of the various concentrations involved in the cotransport experiments for: (a) saturated and (b) unsaturated porous media.

  5. Saturated Zone In-Situ Testing

    SciTech Connect

    P. W. Reimus; M. J. Umari

    2003-12-23

    The purpose of this scientific analysis is to document the results and interpretations of field experiments that have been conducted to test and validate conceptual flow and radionuclide transport models in the saturated zone (SZ) near Yucca Mountain. The test interpretations provide estimates of flow and transport parameters that are used in the development of parameter distributions for Total System Performance Assessment (TSPA) calculations. These parameter distributions are documented in the revisions to the SZ flow model report (BSC 2003 [ 162649]), the SZ transport model report (BSC 2003 [ 162419]), the SZ colloid transport report (BSC 2003 [162729]), and the SZ transport model abstraction report (BSC 2003 [1648701]). Specifically, this scientific analysis report provides the following information that contributes to the assessment of the capability of the SZ to serve as a barrier for waste isolation for the Yucca Mountain repository system: (1) The bases for selection of conceptual flow and transport models in the saturated volcanics and the saturated alluvium located near Yucca Mountain. (2) Results and interpretations of hydraulic and tracer tests conducted in saturated fractured volcanics at the C-wells complex near Yucca Mountain. The test interpretations include estimates of hydraulic conductivities, anisotropy in hydraulic conductivity, storativities, total porosities, effective porosities, longitudinal dispersivities, matrix diffusion mass transfer coefficients, matrix diffusion coefficients, fracture apertures, and colloid transport parameters. (3) Results and interpretations of hydraulic and tracer tests conducted in saturated alluvium at the Alluvium Testing Complex (ATC), which is located at the southwestern corner of the Nevada Test Site (NTS). The test interpretations include estimates of hydraulic conductivities, storativities, total porosities, effective porosities, longitudinal dispersivities, matrix diffusion mass transfer coefficients, and

  6. Disaster Recovery Planning.

    ERIC Educational Resources Information Center

    Wilkins, Jeannine W.

    1985-01-01

    Every school needs an effective disaster recovery plan that is flexible, comprehensive and designed to take into account unexpected disasters. Presents guidelines for preparing such a plan, with immediate and long-range recovery procedures. (MD)

  7. Recovery Act Milestones

    SciTech Connect

    Rogers, Matt

    2009-01-01

    Every 100 days, the Department of Energy is held accountable for a progress report on the American Recovery and Reinvestment Act. Update at 200 days, hosted by Matt Rogers, Senior Advisor to Secretary Steven Chu for Recovery Act Implementation.

  8. Recovery Act Milestones

    ScienceCinema

    Rogers, Matt

    2013-05-29

    Every 100 days, the Department of Energy is held accountable for a progress report on the American Recovery and Reinvestment Act. Update at 200 days, hosted by Matt Rogers, Senior Advisor to Secretary Steven Chu for Recovery Act Implementation.

  9. Controls on Highly Siderophile Element Concentrations in Martian Basalt: Sulfide Saturation and Under-Saturation

    NASA Technical Reports Server (NTRS)

    Righter, Kevin

    2009-01-01

    Highly siderophile elements (HSE; Re, Au and the platinum group elements) in shergottites exhibit a wide range from very high, similar to the terrestrial mantle, to very low, similar to sulfide saturated mid ocean ridge basalt (e.g., [1]). This large range has been difficult to explain without good constraints on sulfide saturation or under-saturation [2]. A new model for prediction of sulfide saturation places new constraints on this problem [3]. Shergottite data: For primitive shergottites, pressure and temperature estimates are between 1.2-1.5 GPa, and 1350-1470 C [4]. The range of oxygen fugacities is from FMQ-2 to IW, where the amount of Fe2O3 is low and thus does not have a significant effect on the S saturation values. Finally, the bulk compositions of shergottites have been reported in many recent studies (e.g., [5]). All of this information will be used to test whether shergottites are sulfide saturated [3]. Modeling values and results: The database for HSE partition coefficients has been growing with many new data for silicates and oxides [6-8] to complement a large sulfide database [9- 11]. Combining these data with simple batch melting models allows HSE contents of mantle melts to be estimated for sulfide-bearing vs. sulfide-free mantle. Combining such models with fractional crystallization modeling (e.g., [12]) allows HSE contents of more evolved liquids to be modeled. Most primitive shergottites have high HSE contents (and low S contents) that can be explained by sulfide under-saturated melting of the mantle. An exception is Dhofar 019 which has high S contents and very low HSE contents suggesting sulfide saturation. Most evolved basaltic shergottites have lower S contents than saturation, and intermediate HSE contents that can be explained by olivine, pyroxene, and chromite fractionation. An exception is EET A79001 lithology B, which has very low HSE contents and S contents higher than sulfide saturation values . evidence for sulfide saturation

  10. HEAVY AND THERMAL OIL RECOVERY PRODUCTION MECHANISMS

    SciTech Connect

    Anthony R. Kovscek

    2002-07-01

    This technical progress report describes work performed from April 1 through June 30, 2002, for the project ''Heavy and Thermal Oil Recovery Production Mechanisms.'' We investigate a broad spectrum of topics related to thermal and heavy-oil recovery. Significant results were obtained in the areas of multiphase flow and rock properties, hot-fluid injection, improved primary heavy oil recovery, and reservoir definition. The research tools and techniques used are varied and span from pore-level imaging of multiphase fluid flow to definition of reservoir-scale features through streamline-based history-matching techniques. Briefly, experiments were conducted to image at the pore level matrix-to-fracture production of oil from a fractured porous medium. This project is ongoing. A simulation studied was completed in the area of recovery processes during steam injection into fractured porous media. We continued to study experimentally heavy-oil production mechanisms from relatively low permeability rocks under conditions of high pressure and high temperature. High temperature significantly increased oil recovery rate and decreased residual oil saturation. Also in the area of imaging production processes in laboratory-scale cores, we use CT to study the process of gas-phase formation during solution gas drive in viscous oils. Results from recent experiments are reported here. Finally, a project was completed that uses the producing water-oil ratio to define reservoir heterogeneity and integrate production history into a reservoir model using streamline properties.

  11. Space Charge Saturated Sheath Regime and Electron Temperature Saturation in Hall Thrusters

    SciTech Connect

    Y. Raitses; D. Staack; A. Smirnov; N.J. Fisch

    2005-03-16

    Secondary electron emission in Hall thrusters is predicted to lead to space charge saturated wall sheaths resulting in enhanced power losses in the thruster channel. Analysis of experimentally obtained electron-wall collision frequency suggests that the electron temperature saturation, which occurs at high discharge voltages, appears to be caused by a decrease of the Joule heating rather than by the enhancement of the electron energy loss at the walls due to a strong secondary electron emission.

  12. Flux saturation length of sediment transport.

    PubMed

    Pähtz, Thomas; Kok, Jasper F; Parteli, Eric J R; Herrmann, Hans J

    2013-11-22

    Sediment transport along the surface drives geophysical phenomena as diverse as wind erosion and dune formation. The main length scale controlling the dynamics of sediment erosion and deposition is the saturation length Ls, which characterizes the flux response to a change in transport conditions. Here we derive, for the first time, an expression predicting Ls as a function of the average sediment velocity under different physical environments. Our expression accounts for both the characteristics of sediment entrainment and the saturation of particle and fluid velocities, and has only two physical parameters which can be estimated directly from independent experiments. We show that our expression is consistent with measurements of Ls in both aeolian and subaqueous transport regimes over at least 5 orders of magnitude in the ratio of fluid and particle density, including on Mars. PMID:24313529

  13. Attitude control with active actuator saturation prevention

    NASA Astrophysics Data System (ADS)

    Forbes, James Richard

    2015-02-01

    Spacecraft attitude control in the presence of actuator saturation is considered. The attitude controller developed has two components: a proportional component and an angular velocity component. The proportional control has a special form that depends on the attitude parameterization. The angular velocity control is realized by a strictly positive real system with its own input nonlinearity. The strictly positive real system can filter noise in the angular velocity measurement. With this control architecture the torques applied to the body are guaranteed to be below a predetermined value, thus preventing saturation of the actuators. The closed-loop equilibrium point corresponding to the desired attitude is shown to be asymptotically stable. Additionally, the control law does not require specific knowledge of the body's inertia properties, and is therefore robust to such modelling errors.

  14. Flux Saturation Length of Sediment Transport

    NASA Astrophysics Data System (ADS)

    Pähtz, Thomas; Kok, Jasper F.; Parteli, Eric J. R.; Herrmann, Hans J.

    2013-11-01

    Sediment transport along the surface drives geophysical phenomena as diverse as wind erosion and dune formation. The main length scale controlling the dynamics of sediment erosion and deposition is the saturation length Ls, which characterizes the flux response to a change in transport conditions. Here we derive, for the first time, an expression predicting Ls as a function of the average sediment velocity under different physical environments. Our expression accounts for both the characteristics of sediment entrainment and the saturation of particle and fluid velocities, and has only two physical parameters which can be estimated directly from independent experiments. We show that our expression is consistent with measurements of Ls in both aeolian and subaqueous transport regimes over at least 5 orders of magnitude in the ratio of fluid and particle density, including on Mars.

  15. Saturated solar ponds: 3. Experimental verification

    SciTech Connect

    Subhakar, D.; Murthy, S.S. )

    1994-12-01

    An experimental saturated solar pond is constructed using magnesium chloride salt. The temperature and concentration gradients are developed by heating the pond from the bottom and adding finely powdered salt from the top. The development of a temperature profile in the pond exposed to direct sunlight and its daily variation are studied. The predictions of the temperature profiles, using the authors' mathematical model, match the experiments better than the concentration profiles.

  16. Saturation Measurements of a Visible SASE FEL

    SciTech Connect

    Carr, Roger

    2002-08-14

    VISA (Visible to Infrared SASE Amplifier) is an FEL designed to obtain high gain at a radiation wavelength of 800 nm. Large gain is achieved by driving the FEL with the 71 MeV, high brightness beam of the Accelerator Test Facility (ATF) and using a novel, strong focusing, 4 m long undulator with a gap of 6 mm and a period of 1.8 cm. We report measurements of exponential gain, saturation, and spectra of the FEL radiation intensity.

  17. Saturation Measurements of a Visible SASE FEL

    NASA Astrophysics Data System (ADS)

    Tremaine, A.; Frigola, P.; Murokh, A.; Pellegrini, C.; Reiche, S.

    2002-08-01

    VISA (Visible to Infrared SASE Amplifier) is an FEL designed to obtain high gain at a radiation wavelength of 800 nm. Large gain is achieved by driving the FEL with the 71 MeV, high brightness beam of the Accelerator Test Facility (ATF) and using a novel, strong focusing, 4m long undulator with a gap of 6 mm and a period of 1.8 cm. We report measurements of exponential gain, saturation, and spectra of the FEL radiation intensity.

  18. HYDRAULIC CONDUCTIVITY OF ESSENTIALLY SATURATED PEAT

    SciTech Connect

    Nichols, R

    2008-02-27

    The Savannah River National Laboratory measured the hydraulic conductivity of peat samples using method ASTM D4511-00. Four samples of peat were packed into 73mm diameter plastic tubes and saturated from the bottom up with water. The columns were packed with Premier ProMoss III TBK peat to a dry density of approximately 0.16 gm/cc (10 lb/ft3). One column was packed using oven dried peat and the other 3 were packed using as delivered peat. The oven dried sample was the most difficult to saturate. All of the peat samples expanded during saturation resulting in a sample length (L) that was longer than when the sample was initially packed. Table 1 contains information related to the column packing. After saturation the hydraulic conductivity test was conducted using the apparatus shown in Figure 1. Three of the samples were tested at 2 different flow conductions, 1 high and 1 low. Table 2 and Figure 2 contain the results of the hydraulic conductivity testing. Each test was run for a minimum of 40 minutes to allow the test conditions to stabilize. The hydraulic conductivity at the end of each test is reported as the hydraulic conductivity for that test. The hydraulic conductivity of the 4 peat samples is 0.0052 {+-} 0.0009 cm/sec. This result compares well with the hydraulic conductivity measured in the pilot scale peat bed after approximately 2 months of operation. The similarity in results between the dry pack sample and moist pack samples shows the moisture content at the time of packing had a minimal effect on the hydraulic conductivity. Additionally, similarity between the results shows the test is reproducible. The hydraulic conductivity results are similar to those reported by other tests of peat samples reported in the literature.

  19. Youth in Recovery

    ERIC Educational Resources Information Center

    de Miranda, John; Williams, Greg

    2011-01-01

    Young people are entering long-term recovery probably in greater numbers than ever before. A key word here is "probably" because we know precious little about the phenomenon of young people who recover from alcohol and drug addition. This article is a preliminary exploration of youth in recovery. It reviews several types of recovery support…

  20. What Is "No Recovery?"

    ERIC Educational Resources Information Center

    Kauffman, Jeffrey

    2008-01-01

    Thanatologists, as Balk recently commented (Balk, 2004), have been saying that there is no recovery from bereavement, or that we should not speak of bereavement as leading to a recovery. The term recovery has a high level of plasticity and can be shaped to fit diverse meanings, including contradictory meanings. We will sort our way through some of…

  1. Enhanced oil recovery update

    SciTech Connect

    Smith, R.V

    1989-03-01

    Technology continues to grow in the realm of enhanced oil recovery. Since 1950 several processes have proven economic for oil recovery. Others are still in their infancy and must be custom designed for each reservoir. This paper gives a general overview of these processes. The author focuses on the latest technology and the outlook for enhanced oil recovery operations.

  2. Multipactor saturation in parallel-plate waveguides

    SciTech Connect

    Sorolla, E.; Mattes, M.

    2012-07-15

    The saturation stage of a multipactor discharge is considered of interest, since it can guide towards a criterion to assess the multipactor onset. The electron cloud under multipactor regime within a parallel-plate waveguide is modeled by a thin continuous distribution of charge and the equations of motion are calculated taking into account the space charge effects. The saturation is identified by the interaction of the electron cloud with its image charge. The stability of the electron population growth is analyzed and two mechanisms of saturation to explain the steady-state multipactor for voltages near above the threshold onset are identified. The impact energy in the collision against the metal plates decreases during the electron population growth due to the attraction of the electron sheet on the image through the initial plate. When this growth remains stable till the impact energy reaches the first cross-over point, the electron surface density tends to a constant value. When the stability is broken before reaching the first cross-over point the surface charge density oscillates chaotically bounded within a certain range. In this case, an expression to calculate the maximum electron surface charge density is found whose predictions agree with the simulations when the voltage is not too high.

  3. Saturated Dispersive Extinction Theory of Red Shift

    NASA Astrophysics Data System (ADS)

    Wang, Ling Jun

    2012-03-01

    The Dispersive Extinction Theory (DET) proposed by WangfootnotetextWang, Ling Jun, Physics Essays, 18, No. 2, (2005). offers an alternative to the Big Bang. According to DET, the cosmic red shift is caused by the dispersive extinction of the star light during the propagation from the stars to the earth, instead of being caused by the Doppler shift due to the expansion of the universe.footnotetextHubble, E., Astrophys. J. 64, 321 (1926).^,footnotetextHubble, E., The Realm of the Nebulae, (Yale University Press, New Haven, 1936). DET allows an infinite, stable, non expanding universe, and is immune of the fundamental problems inherent to the Big Bang such as the horizon problem, the extreme violation of the conservation of mass, energy and charge, and the geocentric nature which violates the principle of relativity.footnotetextWang, Ling Jun, Physics Essays, 20, No. 2, (2007). The scenario dealt with in Reference (1) is a one in which the extinction by the space medium is not saturated. This work deals with a different scenario when the extinction is saturated. The saturated extinction causes limited energy loss, and the star light can travel a much greater distance than in the unsaturated scenario.

  4. Digitally generated excitation and near-baseband quadrature detection of rapid scan EPR signals

    PubMed Central

    Quine, Richard W.; Rinard, George A.; Eaton, Sandra S.; Eaton, Gareth R.

    2014-01-01

    The use of multiple synchronized outputs from an AWG provides the opportunity to perform EPR experiments differently than by conventional EPR. We report a method for reconstructing the quadrature EPR spectrum from periodic signals that are generated with sinusoidal magnetic field modulation such as continuous wave (CW), multiharmonic, or rapid scan experiments. The signal is down-converted to an intermediate frequency (IF) that is less than the field scan or field modulation frequency and then digitized in a single channel. This method permits use of a high-pass analog filter before digitization to remove the strong non-EPR signal at the IF, that might otherwise overwhelm the digitizer. The IF is the difference between two synchronized X-band outputs from a Tektronix AWG 70002A arbitrary waveform generator (AWG), one of which is for excitation and the other is the reference for down-conversion. To permit signal averaging, timing was selected to give an exact integer number of full cycles for each frequency. In the experiments reported here the IF was 5 kHz and the scan frequency was 40 kHz. To produce sinusoidal rapid scans with a scan frequency eight times IF, a third synchronized output generated a square wave that was converted to a sine wave. The timing of the data acquisition with a Bruker SpecJet II was synchronized by an external clock signal from the AWG. The baseband quadrature signal in the frequency domain was reconstructed. This approach has the advantages that (i) the non-EPR response at the carrier frequency is eliminated, (ii) both real and imaginary EPR signals are reconstructed from a single physical channel to produce an ideal quadrature signal, and (iii) signal bandwidth does not increase relative to baseband detection. Spectra were obtained by deconvolution of the reconstructed signals for solid BDPA (1,3-bisdiphenylene-2-phenylallyl) in air, 0.2 mM trityl OX63 in water, 15N perdeuterated tempone, and a nitroxide with a 0.5 G partially

  5. Digitally generated excitation and near-baseband quadrature detection of rapid scan EPR signals.

    PubMed

    Tseitlin, Mark; Yu, Zhelin; Quine, Richard W; Rinard, George A; Eaton, Sandra S; Eaton, Gareth R

    2014-10-30

    The use of multiple synchronized outputs from an arbitrary waveform generator (AWG) provides the opportunity to perform EPR experiments differently than by conventional EPR. We report a method for reconstructing the quadrature EPR spectrum from periodic signals that are generated with sinusoidal magnetic field modulation such as continuous wave (CW), multiharmonic, or rapid scan experiments. The signal is down-converted to an intermediate frequency (IF) that is less than the field scan or field modulation frequency and then digitized in a single channel. This method permits use of a high-pass analog filter before digitization to remove the strong non-EPR signal at the IF, that might otherwise overwhelm the digitizer. The IF is the difference between two synchronized X-band outputs from a Tektronix AWG 70002A, one of which is for excitation and the other is the reference for down-conversion. To permit signal averaging, timing was selected to give an exact integer number of full cycles for each frequency. In the experiments reported here the IF was 5kHz and the scan frequency was 40kHz. To produce sinusoidal rapid scans with a scan frequency eight times IF, a third synchronized output generated a square wave that was converted to a sine wave. The timing of the data acquisition with a Bruker SpecJet II was synchronized by an external clock signal from the AWG. The baseband quadrature signal in the frequency domain was reconstructed. This approach has the advantages that (i) the non-EPR response at the carrier frequency is eliminated, (ii) both real and imaginary EPR signals are reconstructed from a single physical channel to produce an ideal quadrature signal, and (iii) signal bandwidth does not increase relative to baseband detection. Spectra were obtained by deconvolution of the reconstructed signals for solid BDPA (1,3-bisdiphenylene-2-phenylallyl) in air, 0.2mM trityl OX63 in water, (15)N perdeuterated tempone, and a nitroxide with a 0.5G partially-resolved proton

  6. Digitally generated excitation and near-baseband quadrature detection of rapid scan EPR signals

    NASA Astrophysics Data System (ADS)

    Tseitlin, Mark; Yu, Zhelin; Quine, Richard W.; Rinard, George A.; Eaton, Sandra S.; Eaton, Gareth R.

    2014-12-01

    The use of multiple synchronized outputs from an arbitrary waveform generator (AWG) provides the opportunity to perform EPR experiments differently than by conventional EPR. We report a method for reconstructing the quadrature EPR spectrum from periodic signals that are generated with sinusoidal magnetic field modulation such as continuous wave (CW), multiharmonic, or rapid scan experiments. The signal is down-converted to an intermediate frequency (IF) that is less than the field scan or field modulation frequency and then digitized in a single channel. This method permits use of a high-pass analog filter before digitization to remove the strong non-EPR signal at the IF, that might otherwise overwhelm the digitizer. The IF is the difference between two synchronized X-band outputs from a Tektronix AWG 70002A, one of which is for excitation and the other is the reference for down-conversion. To permit signal averaging, timing was selected to give an exact integer number of full cycles for each frequency. In the experiments reported here the IF was 5 kHz and the scan frequency was 40 kHz. To produce sinusoidal rapid scans with a scan frequency eight times IF, a third synchronized output generated a square wave that was converted to a sine wave. The timing of the data acquisition with a Bruker SpecJet II was synchronized by an external clock signal from the AWG. The baseband quadrature signal in the frequency domain was reconstructed. This approach has the advantages that (i) the non-EPR response at the carrier frequency is eliminated, (ii) both real and imaginary EPR signals are reconstructed from a single physical channel to produce an ideal quadrature signal, and (iii) signal bandwidth does not increase relative to baseband detection. Spectra were obtained by deconvolution of the reconstructed signals for solid BDPA (1,3-bisdiphenylene-2-phenylallyl) in air, 0.2 mM trityl OX63 in water, 15N perdeuterated tempone, and a nitroxide with a 0.5 G partially

  7. Residual-oil-saturation-technology test, Bell Creek Field, Montana. Final report

    SciTech Connect

    Not Available

    1981-06-01

    A field test was conducted of the technology available to measure residual oil saturation following waterflood secondary oil recovery processes. The test was conducted in a new well drilled solely for that purpose, located immediately northwest of the Bell Creek Micellar Polymer Pilot. The area where the test was conducted was originally drilled during 1968, produced by primary until late 1970, and was under line drive waterflood secondary recovery until early 1976, when the area was shut in at waterflood depletion. This report presents the results of tests conducted to determine waterflood residual oil saturation in the Muddy Sandstone reservoir. The engineering techniques used to determine the magnitude and distribution of the remaining oil saturation included both pressure and sidewall cores, conventional well logs (Dual Laterolog - Micro Spherically Focused Log, Dual Induction Log - Spherically Focused Log, Borehole Compensated Sonic Log, Formation Compensated Density-Compensated Neutron Log), Carbon-Oxygen Logs, Dielectric Logs, Nuclear Magnetism Log, Thermal Decay Time Logs, and a Partitioning Tracer Test.

  8. Cotransport of Pseudomonas putida and kaolinite particles through water-saturated columns packed with glass beads

    NASA Astrophysics Data System (ADS)

    Vasiliadou, Ioanna A.; Chrysikopoulos, Constantinos V.

    2011-02-01

    This study is focused on Pseudomonas putida bacteria transport in porous media in the presence of suspended kaolinite clay particles. Experiments were performed with bacteria and kaolinite particles separately to determine their individual transport characteristics in water-saturated columns packed with glass beads. The results indicated that the mass recovery of bacteria and clay particles decreased as the pore water velocity decreased. Batch experiments were carried out to investigate the attachment of Pseudomonas putida onto kaolinite particles. The attachment process was adequately described by a Langmuir isotherm. Finally, bacteria and kaolinite particles were injected simultaneously into a packed column in order to investigate their cotransport behavior. The experimental data suggested that the presence of clay particles significantly inhibited the transport of bacteria in water-saturated porous media. The observed reduction of Pseudomonas putida recovery in the column outflow was attributed to bacteria attachment onto kaolinite particles, which were retained onto the solid matrix of the column. A mathematical model was developed to describe the transport of bacteria in the presence of suspended clay particles in one-dimensional water-saturated porous media. Model simulations were in good agreement with the experimental results.

  9. Recovery of light, non-aqueous phase liquid from porous media: laboratory experiments and model validation

    NASA Astrophysics Data System (ADS)

    Waddill, Dan W.; Parker, Jack C.

    1997-07-01

    Laboratory experiments were conducted to measure flow of a light, non-aqueous phase liquid (LNAPL or simply "oil") in porous media. The objective of these experiments was to measure oil recovery as influenced by hysteresis, the oil-water capillary fringe, and an oil seepage face. Oil was infiltrated and allowed to redistribute across the horizontal length of a two-dimensional tank filled with medium sand. The first experiment involved oil recovery without water pumping, while the second experiment involved oil recovery with water pumping to increase the gradient toward the recovery well. Observed oil recovery compared favorably with the predictions of a numerical model (ARMOS). A dual-energy gamma radiation attenuation system monitored oil and water saturations throughout the experiments, while hydrophobic tensiometers measured the location of the air-oil table (Z ao). The experimental distribution of oil saturations suggested the need to incorporate an oil-water capillary fringe in the calculation of oil trapping in the saturated zone. Measurements of Z ao indicated that hysteresis influenced the liquid saturation-pressure relationships. When the effects of hysteresis were incorporated into the model, predicted and measured values of Z ao came into agreement, especially at early times during the recovery process. Experimental data also suggested the presence of an oil seepage face at the pumping well, but model results were not sensitive to this factor. Oil saturation measurements at later times suggested that the oil may have experienced delayed yield, an effect that was not modeled explicitly. A sensitivity analysis revealed that oil recovery predictions were most affected by horizontal hydraulic conductivity, fluid scaling parameters βao and βow, and van Genuchten α, n, and Sm. Overall, the numerical model appeared to match measured data for oil saturation, pressure, and recovery under two sets of boundary conditions.

  10. Battleground Energy Recovery Project

    SciTech Connect

    Bullock, Daniel

    2011-12-31

    In October 2009, the project partners began a 36-month effort to develop an innovative, commercial-scale demonstration project incorporating state-of-the-art waste heat recovery technology at Clean Harbors, Inc., a large hazardous waste incinerator site located in Deer Park, Texas. With financial support provided by the U.S. Department of Energy, the Battleground Energy Recovery Project was launched to advance waste heat recovery solutions into the hazardous waste incineration market, an area that has seen little adoption of heat recovery in the United States. The goal of the project was to accelerate the use of energy-efficient, waste heat recovery technology as an alternative means to produce steam for industrial processes. The project had three main engineering and business objectives: Prove Feasibility of Waste Heat Recovery Technology at a Hazardous Waste Incinerator Complex; Provide Low-cost Steam to a Major Polypropylene Plant Using Waste Heat; and Create a Showcase Waste Heat Recovery Demonstration Project.

  11. Correcting for Incomplete Saturation and Off-Resonance Effects in Multiple-Site Saturation-Transfer Kinetic Measurements

    NASA Astrophysics Data System (ADS)

    Kingsley, Peter B.; Monahan, W. Gordon

    2000-09-01

    The effects of incomplete saturation and off-resonance irradiation on nuclear magnetic resonance saturation-transfer measurements of three-site chemical-exchange rates are discussed. A new method that uses double-saturation measurements is compared with two published methods, one that uses single-saturation measurements and one that uses a single-saturation measurement and a double-saturation measurement. Several formulas are compared for measuring the exchange rate constant kDE for exchange from a detected spin D to an exchanging spin E in the presence of exchange from spin D to a competing spin C. For each method, formulas are derived with corrections for incomplete saturation or off-resonance effects, with both corrections, and with neither correction. Exact formulas are available for three exchanging sites with incomplete saturation if there are no off-resonance effects. Off-resonance corrections are imperfect even with complete saturation.

  12. VHF EPR quantitation and speciation of organic sulfur in coal. Technical report, 1 March--31 May 1994

    SciTech Connect

    Clarkson, R.B.; Belford, R.L.

    1994-09-01

    The existence of free electrons in coals` natural state offers a great attraction for Electron Paramagnetic Resonance (EPR) analysis to aid in the study of the structure and composition of coal. This direct and non-destructive approach to coal analysis has been hindered by the problem of resolution using the conventional 9.5 GHz EPR spectrometers. In the past few years, the authors have developed techniques including W-band Very High Frequency EPR spectroscopy as a means of determining the quantity and structure of organic sulfur in native and desulfurized coals. The state-of-the-art 95 GHz (W-band) EPR spectrometer which they have constructed shows a well resolved spectrum including the interaction between unpaired electrons and the heteroatom like sulfur. The spectra also provide quantitative as well as qualitative information regarding different sulfur species. In this quarter, the authors have been concentrating their efforts on developing a new standard protocol in handling and preparing the coal samples for EPR measurements to provide a quantitative comparison between the EPR spectra of coal in the natural state and desulfurized. Sixteen new coal samples, both native and desulfurized, have been provided to us as well as to the University of Kentucky for analysis by XANES. These samples have been run in both laboratories. The results from these samples, which were kept in an oxygen-free environment, are compared to those of 10 previous samples, which were air-oxidized. Significant differences in the EPR spectra of air-oxidized and oxygen free samples are noted; results from Kentucky are not yet available. Desulfurized samples show a significant decrease in organic sulfur as measured by the VHF-EPR method.

  13. Vhf EPR quantitation and speciation of organic sulfur in coal. [Quarterly] technical report, December 1, 1993--February 28, 1994

    SciTech Connect

    Clarkson, R.B.; Belford, R.I.

    1994-06-01

    The existence of free electrons in coals` natural site offers a great attraction for Electron Paramagnetic Resonance (EPR) analysis to aid in the study of the structure and composition of coal. This direct and non-destructive approach to coal analysis has been hindered by the problem of resolution using the conventional 9.5 GHz EPR spectrometers. In the past few years, we have developed techniques including W-band Very High Frequency EPR spectroscopy as a means of determining the quantity and structure of organic sulfur in native and desulfurized coals. The state of the art 95 GHz (W-band) EPR spectrometer which we have constructed shows a well resolved spectrum including the interaction between unpaired electrons and the heteroatom like sulfur. The spectra also provide quantitative as well as qualitative information regarding different sulfur species. In collaboration with researchers at the University of Kentucky, we are also analyzing the result of desulfurization techniques on the presence of various sulfur species in coal. In the past, we have tried to synthesize various model compounds comparing their W-band spectra with other models, the predictions of theoretical models, and with the W-band spectra of coal specimens. In this quarter, we have been concentrating our efforts on developing a new standard protocol in handling and preparing the coal samples for EPR measurements to provide a quantitative comparison between the EPR spectra of coal in the natural state and desulfurized. Ten coal samples, both native and desulfurized, have been provided to us. These samples have been run in both laboratories. The simulation of coal EPR spectra has been carried out using several mathematical models. EPR results now are being compared with XANES data.

  14. Degradation of saturation output of the COTS array charge-coupled devices induced by total dose radiation damage

    NASA Astrophysics Data System (ADS)

    Wang, Zujun; Chen, Wei; Huang, Shaoyan; Liu, Minbo; He, Baoping; Sheng, Jiangkun

    2014-07-01

    Experiments of total dose radiation effects on COTS array charge-coupled device (CCD) and annealing measurements are shown. Degradations of saturation output voltage at different bias conditions are analyzed, and their mechanisms induced by radiation are also demonstrated. Degradations of saturation output imaging at different total doses and the recovery after annealing are also compared. The phenomena of imaging degradation induced by total dose irradiation are analyzed. The camera imaging quality of resolution test card degraded by total dose irradiation is also analyzed. Finally, integration research from the irradiation-sensitive parameter degradation to the camera imaging degradation of the array CCD is achieved.

  15. The direct and inverse problems of an air-saturated porous cylinder submitted to acoustic radiation

    NASA Astrophysics Data System (ADS)

    Ogam, Erick; Depollier, Claude; Fellah, Z. E. A.

    2010-09-01

    Gas-saturated porous skeleton materials such as geomaterials, polymeric and metallic foams, or biomaterials are fundamental in a diverse range of applications, from structural materials to energy technologies. Most polymeric foams are used for noise control applications and knowledge of the manner in which the energy of sound waves is dissipated with respect to the intrinsic acoustic properties is important for the design of sound packages. Foams are often employed in the audible, low frequency range where modeling and measurement techniques for the recovery of physical parameters responsible for energy loss are still few. Accurate acoustic methods of characterization of porous media are based on the measurement of the transmitted and/or reflected acoustic waves by platelike specimens at ultrasonic frequencies. In this study we develop an acoustic method for the recovery of the material parameters of a rigid-frame, air-saturated polymeric foam cylinder. A dispersion relation for sound wave propagation in the porous medium is derived from the propagation equations and a model solution is sought based on plane-wave decomposition using orthogonal cylindrical functions. The explicit analytical solution equation of the scattered field shows that it is also dependent on the intrinsic acoustic parameters of the porous cylinder, namely, porosity, tortuosity, and flow resistivity (permeability). The inverse problem of the recovery of the flow resistivity and porosity is solved by seeking the minima of the objective functions consisting of the sum of squared residuals of the differences between the experimental and theoretical scattered field data.

  16. Theoretical investigation of the optical and EPR parameters for VO 2+ion in some complexes

    NASA Astrophysics Data System (ADS)

    Kalfaoğlu, Emel; Karabulut, Bünyamin

    2012-04-01

    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 VO2+ 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∥A⊥ for VO2+ ions, it can be concluded that VO2+ ions are located in distorted octahedral sites (C4v) elongated along the z-axis and the ground state of the paramagnetic electron is dxy.

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

    NASA Astrophysics Data System (ADS)

    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.

  18. EPR study of gamma irradiated DL-methionine sulfone single crystals

    NASA Astrophysics Data System (ADS)

    Karabulut, Bünyamin; Yıldırım, İlkay

    2015-12-01

    Electron paramagnetic resonance (EPR) study of gamma irradiated dl-2-amino-4-(Methylsulfonyl) butyric acid (dl-methionine sulfone, hereafter dl-ABA) single crystals and powder was performed at room temperature. It has been found that this compound indicates the existence of C. O2- and N. H2 radicals after γ-irradiation. While g and hyperfine splitting values for the N. H2 radical were observed, for the C. O2- radical, only the g factor was measured. The EPR spectra have shown that N. H2 radical has two groups each having two distinct sites and C. O2- radical has one site. The principal g and hyperfine values for all sites were analyzed.

  19. Identification and dose assessment of irradiated cardamom and cloves by EPR spectrometry

    NASA Astrophysics Data System (ADS)

    Beshir, W. B.

    2014-03-01

    The use of electron paramagnetic resonance spectroscopy to accurately distinguish irradiated from unirradiated cardamom and cloves and assesses the absorbed dose to radiation processed cardamom and cloves are examined. The results were successful for identifying both irradiated and unirradiated cardamom and cloves. Additive reirradiation of cardamom and cloves produces reproducible dose-response functions, which can be used to assess the initial dose by back-extrapolation. Third degree polynomial function was used to fit the EPR signal/dose curves. It was found that this 3rd degree polynomial function provides satisfactory results without correction of decay for free radicals. The stability of the radiation induced EPR signal of irradiated cardamom and cloves were studied over a storage period of almost 8 months.

  20. Analysis of Two-Player Quantum Games in an EPR Setting Using Clifford's Geometric Algebra

    PubMed Central

    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. PMID:22279525

  1. Nano-emulsions of fluorinated trityl radicals as sensors for EPR oximetry

    NASA Astrophysics Data System (ADS)

    Charlier, N.; Driesschaert, B.; Wauthoz, N.; Beghein, N.; Préat, V.; Amighi, K.; Marchand-Brynaert, J.; Gallez, B.

    2009-04-01

    This article reports the development and evaluation of two nano-emulsions (F45T-03/HFB and F15T-03/PFOB) containing fluorinated trityl radicals dissolved in perfluorocarbons. Preparation with a high-pressure homogenizer conferred sub-micronic size to both nano-emulsions. In vitro and in vivo EPR spectroscopy showed that the nano-emulsions had much greater oxygen sensitivity than the hydrophilic trityl, CT-03. In vivo experiments in rodents confirmed the ability of the nano-emulsions to follow the changes in oxygen concentration after induced ischemia. Histological evaluation of the tissue injected with the nano-emulsions revealed some acute toxicity for the F45T-03/HFB nano-emulsion but none for the F15T-03/PFOB nano-emulsion. These new formulations should be considered for further EPR oximetry experiments in pathophysiological situations where subtle changes in tissue oxygenation are expected.

  2. Nano-emulsions of fluorinated trityl radicals as sensors for EPR oximetry.

    PubMed

    Charlier, N; Driesschaert, B; Wauthoz, N; Beghein, N; Préat, V; Amighi, K; Marchand-Brynaert, J; Gallez, B

    2009-04-01

    This article reports the development and evaluation of two nano-emulsions (F45T-03/HFB and F15T-03/PFOB) containing fluorinated trityl radicals dissolved in perfluorocarbons. Preparation with a high-pressure homogenizer conferred sub-micronic size to both nano-emulsions. In vitro and in vivo EPR spectroscopy showed that the nano-emulsions had much greater oxygen sensitivity than the hydrophilic trityl, CT-03. In vivo experiments in rodents confirmed the ability of the nano-emulsions to follow the changes in oxygen concentration after induced ischemia. Histological evaluation of the tissue injected with the nano-emulsions revealed some acute toxicity for the F45T-03/HFB nano-emulsion but none for the F15T-03/PFOB nano-emulsion. These new formulations should be considered for further EPR oximetry experiments in pathophysiological situations where subtle changes in tissue oxygenation are expected. PMID:19128993

  3. Characterisation of nanohybrids of porphyrins with metallic and semiconducting carbon nanotubes by EPR and optical spectroscopy.

    PubMed

    Cambré, Sofie; Wenseleers, Wim; Culin, Jelena; Van Doorslaer, Sabine; Fonseca, Antonio; Nagy, Janos B; Goovaerts, Etienne

    2008-09-15

    Single-walled carbon nanotubes (SWCNTs) are noncovalently functionalised with octaethylporphyrins (OEPs) and the resulting nanohybrids are isolated from the free OEPs. Electron paramagnetic resonance (EPR) spectroscopy of cobalt(II)OEP, adsorbed on the nanotube walls by pi-pi-stacking, demonstrates that the CNTs act as electron acceptors. EPR is shown to be very effective in resolving the different interactions for metallic and semiconducting tubes. Moreover, molecular oxygen is shown to bind selectively to nanohybrids with semiconducting tubes. Water solubilisation of the porphyrin/CNT nanohybrids using bile salts, after applying a thorough washing procedure, yields solutions in which at least 99% of the porphyrins are interacting with the CNTs. Due to this purification, we observe, for the first time, the isolated absorption spectrum of the interacting porphyrins, which is strongly red-shifted compared to the free porphyrin absorption. In addition a quasi-complete quenching of the porphyrin fluorescence is also observed. PMID:18712730

  4. Frequency domain Fourier transform THz-EPR on single molecule magnets using coherent synchrotron radiation.

    PubMed

    Schnegg, Alexander; Behrends, Jan; Lips, Klaus; Bittl, Robert; Holldack, Karsten

    2009-08-21

    Frequency domain Fourier transform THz electron paramagnetic resonance (FD-FT THz-EPR) based on coherent synchrotron radiation (CSR) is presented as a novel tool to ascertain very large zero field splittings in transition metal ion complexes. A description of the FD-FT THz-EPR at the BESSY II storage ring providing CSR in a frequency range from 5 cm(-1) up to 40 cm(-1) at external magnetic fields from -10 T to +10 T is given together with first measurements on the single molecule magnet Mn(12)Ac where we studied DeltaM(S) = +/-1 spin transition energies as a function of the external magnetic field and temperature. PMID:19639156

  5. New chemometric approach MCR-ALS to unmix EPR spectroscopic data from complex mixtures

    NASA Astrophysics Data System (ADS)

    Fadel, Maya Abou; de Juan, Anna; Touati, Nadia; Vezin, Hervé; Duponchel, Ludovic

    2014-11-01

    Electron paramagnetic resonance (EPR) spectra of mixtures are often difficult to interpret due to the superposition of spectral contribution of various species present in the complex materials. It is challenging to accurately identify the number of pure compounds present and to extract their pure spectra. In this study, the powerful chemometric method, multivariate curve resolution-alternating least squares (MCR-ALS), is applied to identify different paramagnetic centers. This method is used to simultaneously extract, with no prior knowledge, the pure spectra and the corresponding concentration profiles of all the compounds in the unknown and unresolved mixtures. The goal of our work is to apply, for the first time, this new chemometrics methodology, MCR-ALS, on EPR spectroscopic data in order to characterize a series of distinct but strongly overlapping spectra of various paramagnetic species.

  6. Dating sediment deposits on Montalvanian carvings using EPR and TL methods

    NASA Astrophysics Data System (ADS)

    Sastry, M. D.; Sullasi, Henry S. L.; Camargo, Fabiola; Watanabe, Shigueo; Prous, André P. P.; Silva, Martha M. C.

    2004-01-01

    About 30 years ago a rock shelter with engravings by early settlers was found at Montalvânia, northern end of state of Minas Gerais, Brazil. Lower part of engravings was covered with thin deposit of calcite mixed with quartz grains, due to occasional flood. This mixture of two minerals was dated by thermoluminescence and electron paramagnetic resonance using in both cases, additive method. The accumulated dose DAC, that is, natural radioactivity and cosmic rays radiation dose that induces TL and EPR signal intensity has been found to be around 50 Gy both by TL and EPR methods. The annual radiation dose rate was estimated to be about 1.027 mGy/a from knowledge of uranium, thorium and potassium content determined by inductively coupled plasma-mass spectrometer system. The age of this calcite plus quartz deposits was estimated to be about 50 ka.

  7. Temperature dependent electron paramagnetic resonance (EPR) of SrZrO3

    NASA Astrophysics Data System (ADS)

    Gupta, Santosh K.; Pathak, Nimai; Ghosh, P. S.; Rajeshwari, B.; Natarajan, V.; Kadam, R. M.

    2015-10-01

    SrZrO3 (SZO), a distorted perovskite was synthesized using gel-combustion route employing citric acid as a fuel and ammonium nitrate as oxidizer followed by characterization using X-ray diffraction (XRD) and electron paramagnetic resonance (EPR). Purity of the sample is confirmed by inductively coupled plasma atomic emission spectroscopy (ICP-AES) analysis. Broadening and shift of the resonance field position in EPR spectrum to the lower field was observed as the temperature is lowered; which is the characteristic of ferromagnetic resonance spectra. The value of Curie-Weiss temperature obtained for SZO particles is 8.7 K. The positive sign of the Curie-Weiss temperature indicates that some of the spins are ferromagnetically coupled in this sample. Theoretical investigation using density functional theory (DFT) calculation revealed that Vacancy at zirconium site contribute maximum to the magnetic moment.

  8. EPR experiment and 2-photon interferometry: Report of a 2-photon interference experiment

    NASA Technical Reports Server (NTRS)

    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.

  9. EPR and magnetic studies of a novel copper metal organic framework (STAM-I)

    NASA Astrophysics Data System (ADS)

    EL Mkami, H.; Mohideen, M. I. H.; Pal, C.; McKinlay, A.; Scheimann, O.; Morris, R. E.

    2012-08-01

    The magnetic interaction between dinuclear copper (II) in a new copper carboxylate compound, STAM-1, has been investigated by means of EPR and SQUID measurements. The powder EPR spectra, measured at 9.80 and 34.5 GHz and at different temperatures, show the typical lines of the triplet state (S = 1), attributed to Cu2+-Cu2+ dimers, in addition of a temperature dependent central lines. The zero field splitting parameters obtained are |Dobs| = 0.337 cm-1 and E ˜ 0. Magnetic susceptibility data, performed in the range 1.8-300 K, shows a strong antiferromagnetic exchange coupling between the Cu2+ centers in the paddle-wheel units with the exchange coupling constant 2J = -334 ± 4 cm-1.

  10. High precision EPR dosimetry as a reference tool for validation of other techniques.

    PubMed

    Chumak, V V; Sholom, S V; Bakhanova, E V; Pasalskaya, L F; Musijachenko, A V

    2005-02-01

    We present here a particular application area for EPR dosimetry with teeth--use as a source of reference dose values for validation/verification of other retrospective dosimetry techniques and existing dose records. The conditions of application of EPR dosimetry in this role as well as practical design of such studies are shown. Particular attention is given to the requirements to the techniques in terms of precision and throughput, as well as to the issue of availability of samples for analysis and practical solution of this problem. Practical application of this approach is illustrated by several examples of completed validation sub-studies, which were performed in the framework of large-scale post-Chernobyl epidemiological studies. PMID:15607440

  11. EPR and polarography of nitroazoles. 6. 3-Nitro-1,2,4-triazoles

    SciTech Connect

    Vakul'skaya, T.I.; Rakhmatulina, T.N.; Pevzner, M.S.; Kofman, T.P.; Lopyrev, V.A.

    1987-09-01

    The electrochemical reduction of eight 3-nitro-1,2,4-triazole derivatives in acetonitrile was investigated by polarography and EPR spectroscopy. Two different signals were recorded in the EPR spectra in the electrochemical reduction of derivative I. The first signal shows up at the potentials of the second wave with a hyperfine structure corresponding to coupling of an unpaired electron with five nitrogen atoms and to a symmetrical distribution of the spin density as shown. Electrochemical generation of the ion radicals was realized in special electrochemical cells that had been previously deoxygenated by successive freezing and thawing of solutions in vacuo and were then filled with argon purified over potassium-sodium alloy.

  12. Special aspects of the temperature dependence of EPR absorption of chemically carbonized polyvinylidene fluoride derivatives

    NASA Astrophysics Data System (ADS)

    Zhivulin, V. E.; Pesin, L. A.; Ivanov, D. V.

    2016-01-01

    The temperature dependences of electron paramagnetic resonance (EPR) absorption of two samples of chemically carbonized derivatives of polyvinylidene fluoride (PVDF) synthesized under different conditions have been measured in the range of 100-300 K. It has been found that the temperature dependence of the integrated intensity of the EPR signal of both samples is nonmonotonic and does not obey the classical Curie dependence characteristic of free radicals. An analytical expression that is consistent with experimental data and suggests the presence of an activation component of paramagnetism in the test samples has been obtained. The presence of a term independent of temperature in this equation also indicates the paramagnetic contribution of free electrons. The magnitude of the activation energy of the singlet-triplet transitions has been evaluated: δ = 0.067 eV. The HYSCORE spectra of chemically carbonized PVDF derivatives have been obtained for the first time.

  13. Theoretical studies of EPR spectra and defect structure for Er3+ center in lithium niobate.

    PubMed

    Chai, Rui-Peng; Kuang, Xiao-Yu; Duan, Mei-Ling; Zhang, Cai-Xia

    2010-09-15

    The optical and EPR spectra of octahedral Er(3+) center in LiNbO(3) have been studied by diagonalizing 364 x 364 complete energy matrices. The new set of crystal-field parameters that can well account for the Stark levels and EPR parameters have been obtained for Er(3+) ions in LiNbO(3). Simultaneously, by simulating the most reliable six-order parameter B(60) obtained, we have presented the evidence that the Er(3+) ions do not occupy the actual Li(+) site, but have a displacement along the C(3)-axis away from the Li(+) center by about 0.0454 nm. The conclusion is well in accord with that drawn by earlier workers. PMID:20541458

  14. Chitosan gallate as a novel potential polysaccharide antioxidant: an EPR study.

    PubMed

    Pasanphan, Wanvimol; Buettner, Garry R; Chirachanchai, Suwabun

    2010-01-11

    A novel biopolymer-based antioxidant, chitosan conjugated with gallic acid (chitosan galloylate, chitosan-GA), is proposed. Electron paramagnetic resonance (EPR) demonstrates a wide range of antioxidant activity for chitosan-GA as evidenced from its reactions with oxidizing free radicals, that is, 1,1-diphenyl-2-picryl-hydrazyl (DPPH), horseradish peroxidase (HRP)-H(2)O(2), carbon-centered alkyl radicals, and hydroxyl radicals. The EPR spectrum of the radical formed on chitosan-GA was attributed to the semiquinone radical of the gallate moiety. The stoichiometry and effective concentration (EC(50)) of the DPPH free radical with chitosan-GA show that the radical scavenging capacity is maintained even after thermal treatment at 100 degrees C for an hour. Although the degree of substitution of GA on chitosan was about 15%, its antioxidant capacity, that is, the reaction with carbon-centered and hydroxyl radicals, is comparable to that of GA. PMID:19889400

  15. Physiological and pathophysiological reactive oxygen species as probed by EPR spectroscopy: the underutilized research window on muscle ageing.

    PubMed

    A Abdel-Rahman, Engy; Mahmoud, Ali M; Khalifa, Abdulrahman M; Ali, Sameh S

    2016-08-15

    Reactive oxygen and nitrogen species (ROS and RNS) play crucial roles in triggering, mediating and regulating physiological and pathophysiological signal transduction pathways within the cell. Within the cell, ROS efflux is firmly controlled both spatially and temporally, making the study of ROS dynamics a challenging task. Different approaches have been developed for ROS assessment; however, many of these assays are not capable of direct identification or determination of subcellular localization of different ROS. Here we highlight electron paramagnetic resonance (EPR) spectroscopy as a powerful technique that is uniquely capable of addressing questions on ROS dynamics in different biological specimens and cellular compartments. Due to their critical importance in muscle functions and dysfunction, we discuss in some detail spin trapping of various ROS and focus on EPR detection of nitric oxide before highlighting how EPR can be utilized to probe biophysical characteristics of the environment surrounding a given stable radical. Despite the demonstrated ability of EPR spectroscopy to provide unique information on the identity, quantity, dynamics and environment of radical species, its applications in the field of muscle physiology, fatiguing and ageing are disproportionately infrequent. While reviewing the limited examples of successful EPR applications in muscle biology we conclude that the field would greatly benefit from more studies exploring ROS sources and kinetics by spin trapping, protein dynamics by site-directed spin labelling, and membrane dynamics and global redox changes by spin probing EPR approaches. PMID:26801204

  16. DUAL FREQUENCY RESONATOR FOR 1.2 GHZ EPR/16.2 MHZ NMR CO-IMAGING

    PubMed Central

    Petryakov, Sergey; Samouilov, Alexandre; Kesselring, Eric; Caia, George L.; Sun, Ziqi; Zweier, Jay L.

    2010-01-01

    The development of a dual frequency resonator that enables both EPR and proton NMR imaging within the same resonator, magnet and gradient system is described. A novel design allows the same resonator to perform both EPR and proton NMR operation without moving resonator cables or switches. The resonator is capable of working at frequencies of 16.18 MHz for proton NMR and 1.2 GHz for EPR and is optimized for isolated rat heart experiments, measuring 22 mm in inner diameter and 19 mm in length. In EPR mode, the resonator functions as a one loop two gap resonator, electrically coupled through a half wavelength inverter. In NMR mode, it functions a single turn coil. Using the same loop for both modalities maximizes filling factor at both frequencies. Placing the tuning and switching controls away from the resonator prevents any inadvertent movement that would cause errors of EPR and NMR co-imaging registration. The resonator enabled good quality EPR and proton MRI of isolated rat hearts with precise registration. PMID:20434379

  17. SINGLE LOOP - MULTI GAP RESONATOR FOR WHOLE BODY EPR IMAGING OF MICE AT 1.2 GHZ

    PubMed Central

    Petryakov, Sergey; Samouilov, Alexandre; Kesselring, Eric; Wasowicz, Tomasz; Caia, George L.; Zweier, Jay L.

    2009-01-01

    For whole body EPR imaging of small animals, typically low frequencies of 250–750 MHz have been used due to the microwave losses at higher frequencies and the challenges in designing suitable resonators to accommodate these large lossy samples. However, low microwave frequency limits the obtainable sensitivity. L-band frequencies can provide higher sensitivity, and have been commonly used for localized in vivo EPR spectroscopy. Therefore, it would be highly desirable to develop an L-band microwave resonator suitable for in vivo whole body EPR imaging of small animals such as living mice. A 1.2 GHz 16 gap resonator with inner diameter of 43 mm and 48 mm length was designed and constructed for whole body EPR imaging of small animals. The resonator has good field homogeneity and stability to animal induced motional noise. Resonator stability was achieved with electrical and mechanical design utilizing a fixed position double coupling loop of novel geometry, thus minimizing the number of moving parts. Using this resonator, high quality EPR images of lossy phantoms and living mice were obtained. This design provides good sensitivity, ease of sample access, excellent stability and uniform B1 field homogeneity for in vivo whole body EPR imaging of mice at 1.2 GHz. PMID:17625940

  18. Spin relaxation measurements using first-harmonic out-of-phase absorption EPR signals: rotational motion effects.

    PubMed

    Livshits, V A; Marsh, D

    2000-07-01

    A recent survey of nonlinear continuous-wave (CW) EPR methods revealed that the first-harmonic absorption EPR signal, detected 90 degrees out of phase with respect to the Zeeman modulation (V(1)(')-EPR), is the most appropriate for determining spin-lattice relaxation enhancements of spin labels (V. A. Livshits, T. Páli, and D. Marsh, 1998, J. Magn. Reson. 134, 113-123). The sensitivity of such V(1)(')-EPR spectra to molecular rotational motion is investigated here by spectral simulations for nitroxyl spin labels, over the entire range of rotational correlation times. Determination of the effective spin-lattice relaxation times is less dependent on rotational mobility than for other nonlinear CW EPR methods, especially at a Zeeman modulation frequency of 25 kHz which is particularly appropriate for spin labels. This relative insensitivity to molecular motion further enhances the usefulness of the V(1)(')-EPR method. Calibrations of the out-of-phase to in-phase spectral intensity (and amplitude) ratios are given as a function of spin-lattice relaxation time, for the full range of spin-label rotational correlation times. Experimental measurements on spin labels in the slow, intermediate, and fast motional regimes of molecular rotation are used to test and validate the method. PMID:10873499

  19. Saturation dynamics and working limits of saturated absorption cavity ringdown spectroscopy.

    PubMed

    Sadiek, Ibrahim; Friedrichs, Gernot

    2016-08-17

    Cavity ringdown spectroscopy (CRDS) in the linear absorption regime is a well-established method for sensitive trace gas detection, but only a few studies have addressed quantitative measurements in the presence of a saturated sample. In fact, saturation is usually avoided in order to escape from the required complex modeling of the saturation process that depends on the characteristics of the absorbing species, its interaction with the surrounding gas as well as on the temporal and spectral characteristics of the cavity excitation. Conversely, the novel saturated-absorption cavity ringdown spectroscopy approach (SCAR/Sat-CRDS) takes advantage of sample saturation in order to allow one to extract both the gas absorption and the empty cavity loss rates from a single ringdown event. Using a new continuous-wave infrared CRD spectrometer equipped with a tunable narrow-bandwidth high-power OPO laser system and a 18 bit digitizer, the transient dynamics of absorption saturation and the working limits of the Sat-CRDS approach in terms of its ability to extract reliable trace gas concentrations have been experimentally studied in this work. Using a strong methane transition as a test case, the excitation power P0 and saturation power PS have been systematically varied to explore a wide range of saturation regimes. At pressures 5 μbar < p < 2 mbar, the saturation intensity revealed a nearly linear pressure dependence showing that non-collisional processes contribute to the overall relaxation. A ratio of P0/PS ≈ 15 turned out to be optimal with working limits of 5 < P0/PS < 300. Moreover, the ratio of the absorption and empty cavity loss rates, γg/γc, has been varied to test the dynamic range of the method. At γg > γc, a pronounced coupling between the two parameters has been observed. Finally, a standard error analysis was performed revealing that the Sat-CRDS approach holds its advantages over conventional CRDS implementations in particular when the attainable

  20. Highly Active Titanocene Catalysts for Epoxide Hydrosilylation: Synthesis, Theory, Kinetics, EPR Spectroscopy.

    PubMed

    Henriques, Dina Schwarz G; Zimmer, Katharina; Klare, Sven; Meyer, Andreas; Rojo-Wiechel, Elena; Bauer, Mirko; Sure, Rebecca; Grimme, Stefan; Schiemann, Olav; Flowers, Robert A; Gansäuer, Andreas

    2016-06-27

    A catalytic system for titanocene-catalyzed epoxide hydrosilylation is described. It features a straightforward preparation of titanocene hydrides that leads to a reaction with low catalyst loading, high yields, and high selectivity of radical reduction. The mechanism was studied by a suite of methods, including kinetic studies, EPR spectroscopy, and computational methods. An unusual resting state leads to the observation of an inverse rate order with respect to the epoxide. PMID:27125466

  1. Electrostatic influence on rotational mobilities of sol-gel-encapsulated solutes by NMR and EPR spectroscopies.

    PubMed

    Wheeler, Korin E; Lees, Nicholas S; Gurbiel, Ryszard J; Hatch, Shelby L; Nocek, Judith M; Hoffman, Brian M

    2004-10-20

    The rotational mobilities of small solute molecules encapsulated in tetramethyl orthosilicate (TMOS) sol-gels have been investigated by EPR spectroscopy of encapsulated nitroxide probes and by high-resolution NMR spectroscopic measurements of transferred NOE's (trNOE's), of T(1)'s, and of T(1)'s in the rotating frame (T(1)rho). The two spectroscopic methods are sensitive to motions on different time scales and hence, are nicely complementary. Suites of neutral, positively, and negatively charged nitroxide probes (EPR) and of simple diamagnetic small molecules (NMR) were selected to disclose influences of electrostatic interactions with the sol-gel walls and to probe the presence of multiple populations of molecules in distinct regions of the sol-gel pores. For neutral and negatively charged solute probes, both techniques disclose a single population with a significantly increased average rotational correlation time, which we interpret at least in part as resulting from exchange between free-volume and transiently immobilized surface populations. The electrostatic attraction between cationic probes and the negatively charged sol-gel walls causes the positively charged probes to be more effectively immobilized and/or causes a greater percentage of probes to undergo this transient immobilization. The EPR spectra directly disclose a population of cationic probes which are immobilized on the X-band EPR time scale: tau(c) greater than or approximately equal 10(-7) s. However, NMR measurements of trNOE's and of T(1)rho demonstrate that this population does exchange with the free-volume probes on the slower time scale of NMR. This approach is equally applicable to the study of solutes within other types of confined spaces, as well. PMID:15479102

  2. Synthesis and EPR Characterization of Exohedrally Perfluoroalkylated Paramagnetic Lanthanum Metallofullerenes: A Fluorous Phase Approach

    NASA Astrophysics Data System (ADS)

    Tagmatarchis, Nikos; Taninaka, Atsushi; Shinohara, Hisanori; Prato, Maurizio

    2002-10-01

    A strategy to chemically derivatize the outer sphere of endohedral metallofullerenes by using a modern organic technique that utilizes a fluorous synthesis-partitioning approach has been developed. The newly synthesized materials were found to be paramagnetic species and were characterized by electron paramagnetic resonance spectroscopy (EPR), laser desorption time-of-flight spectrometry (LD-TOF) and electronic absorption spectroscopy (UV-VIS-NIR). The systematic study of exohedrally derivatized endohedral metallofullerenes should ultimately provide technologically intriguing novel nano-materials.

  3. Ionizable Nitroxides for Studying Local Electrostatic Properties of Lipid Bilayers and Protein Systems by EPR

    PubMed Central

    Voinov, Maxim A.; Smirnov, Alex I.

    2016-01-01

    Electrostatic interactions are known to play one of the major roles in the myriad of biochemical and biophysical processes. In this Chapter we describe biophysical methods to probe local electrostatic potentials of proteins and lipid bilayer systems that is based on an observation of reversible protonation of nitroxides by EPR. Two types of the electrostatic probes are discussed. The first one includes methanethiosulfonate derivatives of protonatable nitroxides that could be used for highly specific covalent modification of the cysteine’s sulfhydryl groups. Such spin labels are very similar in magnetic parameters and chemical properties to conventional MTSL making them suitable for studying local electrostatic properties of protein-lipid interfaces. The second type of EPR probes is designed as spin-labeled phospholipids having a protonatable nitroxide tethered to the polar head group. The probes of both types report on their ionization state through changes in magnetic parameters and a degree of rotational averaging, thus, allowing one to determine the electrostatic contribution to the interfacial pKa of the nitroxide, and, therefore, determining the local electrostatic potential. Due to their small molecular volume these probes cause a minimal perturbation to the protein or lipid system while covalent attachment secure the position of the reporter nitroxides. Experimental procedures to characterize and calibrate these probes by EPR and also the methods to analyze the EPR spectra by least-squares simulations are also outlined. The ionizable nitroxide labels and the nitroxide-labeled phospholipids described so far cover an exceptionally wide pH range from ca. 2.5 to 7.0 pH units making them suitable to study a broad range of biophysical phenomena especially at the negatively charged lipid bilayer surfaces. The rationale for selecting proper electrostatically neutral interface for calibrating such probes and example of studying surface potential of lipid bilayer is

  4. Microbial enhanced oil recovery and compositions therefor

    DOEpatents

    Bryant, Rebecca S.

    1990-01-01

    A method is provided for microbial enhanced oil recovery, wherein a combination of microorganisms is empirically formulated based on survivability under reservoir conditions and oil recovery efficiency, such that injection of the microbial combination may be made, in the presence of essentially only nutrient solution, directly into an injection well of an oil bearing reservoir having oil present at waterflood residual oil saturation concentration. The microbial combination is capable of displacing residual oil from reservoir rock, which oil may be recovered by waterflooding without causing plugging of the reservoir rock. Further, the microorganisms are capable of being transported through the pores of the reservoir rock between said injection well and associated production wells, during waterflooding, which results in a larger area of the reservoir being covered by the oil-mobilizing microorganisms.

  5. [New Method of Measuring Arterial Oxygen Saturation].

    PubMed

    Li, Gang; Bao, Lei; Zhou, Mei; Lin, Ling; Liu, Rui; Zhao, Chun-jie

    2016-01-01

    The traditional method of measuring arterial oxygen saturation is that R value, the ratio of alternating component of the logarithmic photoplethysmography, is firstly computed and then the linear regression model is established by experiment. The R value computation is a dimension reduction process based on Lambert-beer law, which aims at eliminating the influence of optical path and minimizing the impact of individual differences. When taking scattering into consideration, the dimension reduction process loses information, introduces the system error and limits the precision of measurement. In order to reduce the measurement error resulting from the scattering effects, this paper presents a new method that the peak and valley values of dual-wavelength logarithmic photoplethysmography waves are used as the independent variables to develop a linear regression model to predict the arterial oxygen saturation. During the experiment, the in-vivo measurements were carried out on 23 healthy volunteer and 133 samples of photoplethysmography waves and the reference value of oxygen saturation were recorded. To compare the predictive performance between the new method and the R value method, 90 samples were randomly selected as modeling sets and the remaining 43 samples were used as prediction sets. Random selection of modeling sets and prediction are executed 10 times. The average related coefficients of the prediction sets of the new method and the R value method are 0.890 6 and 0.846 8, and the average root mean square errors are 0.889 6% and 1.037 3% respectively. Results indicate that the performance of the new method is better than the one of the R value method, and the predictivemodel based on 4 parameters can improve the stability and accuracy of measurement. And the new method has guiding significance to the measurement of human body's blood physiological information based on limited wavelength spectrum data. PMID:27228767

  6. The 9 GHz EPR Imager for Thin Materials: an Application to Surface Detection

    PubMed Central

    Nakagawa, Kouichi; Ohba, Yasunori; Epel, Boris; Hirata, Hitoshi

    2015-01-01

    A 9 GHz EPR imager that is capable of imaging surface area of the thin-materials has been built. The EPR imager resolved samples spaced by 1 mm. The developed TE111 cavity was able to detect easily ~1.1 mM aqueous TEMPOL solution in ~1.0 mm (i.d.) glass capillary placed just above the cavity. The theoretical sensitivity of the TE111 cavity was estimated to be ~1.3-fold in comparison with the JEOL TE011 cavity considering the same quality factor (Q). The sensitivity measured using the TEMPOL solution showed ~0.33 of that for the JEOL cavity, which was in a qualitative agreement with the calculations considering the difference in the filling factors of the cavities. The relatively low measured sensitivity of the TE111 cavity is due to utilization of microwave field leakage from a small hole in the cavity wall. More importantly, the TE111 cavity does not require inserting sample into the inner volume of the cavity as well as placing samples into EPR tubes. Therefore, we can use the maximum imager microwave power to gain the sample signal intensity. PMID:22864516

  7. EPR study of Cu2+ ion doped orotato(nicotinamid)cobalt(II) single crystal

    NASA Astrophysics Data System (ADS)

    Yıldırım, İ.; Karabulut, B.; Büyükgüngör, O.

    2016-01-01

    We have studied the Cu2+ ion doped orotato(nicotinamid)cobalt(II) complex by using EPR spectroscopy and X-ray diffraction. The single crystal is triclinic with the space group P 1 ‾ . The unit cell dimensions of the crystal are a = 7.2785(4) Å, b = 10.2349(5) Å, c = 12.7372(6) Å, α = 69.297(4)°, β = 74.791(4)° and γ = 76.995(4)°, with Z = 2. We analyzed the EPR spectra of both single crystal and powder of the complex at room temperature. EPR analysis indicates the presence of only one Cu2+ site. We obtained the spin Hamiltonian parameters from the single crystal data for the complex. The spin Hamiltonian parameters are gx = 2.032, gy = 2.116, gz = 2.319, Ax = 28 G, Ay = 66 G, Az = 126 G. These data indicate that the symmetry of paramagnetic center is rhombic. We constructed the ground state wave function of the Cu2+ ion.

  8. Analysis of Influenza A Virus NS1 Dimer Interfaces in Solution by Pulse EPR Distance Measurements

    PubMed Central

    2014-01-01

    Pulsed electron–electron double resonance (PELDOR) is an electron paramagnetic resonance (EPR) spectroscopy technique for nanometer distance measurements between paramagnetic centers such as radicals. PELDOR has been recognized as a valuable tool to approach structural questions in biological systems. In this manuscript, we demonstrate the value of distance measurements for differentiating competing structural models on the dimerization of the effector domain (ED) of the non-structural protein 1 (NS1) of the influenza A virus. Our results show NS1 to be well amenable to nanometer distance measurements by EPR, yielding high quality data. In combination with mutants perturbing protein dimerization and in silico prediction based on crystal structures, we can exclude one of two potential dimerization interfaces. Furthermore, our results lead to a viable hypothesis of a NS1 ED:ED interface which is flexible through rotation around the vector interconnecting the two native cysteines. These results prove the high value of pulse EPR as a complementary method for structural biology. PMID:25148246

  9. EPR investigation of gamma irradiated single crystal guaifenesin: A combined experimental and computational study

    NASA Astrophysics Data System (ADS)

    Tasdemir, Halil Ugur; Sayin, Ulku; Türkkan, Ercan; Ozmen, Ayhan

    2016-04-01

    Gamma irradiated single crystal of Guaifenesin (Glyceryl Guaiacolate), an important expectorant drug, were investigated with Electron Paramagnetic Resonance (EPR) spectroscopy between 123 and 333 K temperature at different orientations in the magnetic field. Considering the chemical structure and the experimental spectra of the gamma irradiated single crystal of guaifenesin sample, we assumed that alkoxy or alkyl-type paramagnetic species may be produced by irradiation. Depending on this assumption, eight possible alkoxy and alkyl-type radicals were modeled and EPR parameters of these modeled radicals were calculated using the B3LYP/6-311++G(d,p)-level of density functional theory (DFT). Theoretically calculated values of alkyl-type modeled radical(R3) are in good agreement with experimentally determined EPR parameters of single crystal. Furthermore, simulation spectra which are obtained by using the theoretical initial values are well matched with the experimental spectra. It was determined that a stable Cα •H2αCβHβCγH2γ (R3) alkyl radical was produced in the host crystal as a result of gamma irradiation.

  10. Entanglement conservation, ER=EPR, and a new classical area theorem for wormholes

    NASA Astrophysics Data System (ADS)

    Remmen, Grant N.; Bao, Ning; Pollack, Jason

    2016-07-01

    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.

  11. Tetrachloridocuprates(II)—Synthesis and Electron Paramagnetic Resonance (EPR) Spectroscopy

    PubMed Central

    Winter, Alette; Zabel, André; Strauch, Peter

    2012-01-01

    Ionic liquids (ILs) on the basis of metal containing anions and/or cations are of interest for a variety of technical applications e.g., synthesis of particles, magnetic or thermochromic materials. We present the synthesis and the results of electron paramagnetic resonance (EPR) spectroscopic analyses of a series of some new potential ionic liquids based on tetrachloridocuprates(II), [CuCl4]2−, with different sterically demanding cations: hexadecyltrimethylammonium 1, tetradecyltrimethylammonium 2, tetrabutylammonium 3 and benzyltriethylammonium 4. The cations in the new compounds were used to achieve a reasonable separation of the paramagnetic Cu(II) ions for EPR spectroscopy. The EPR hyperfine structure was not resolved. This is due to the exchange broadening, resulting from still incomplete separation of the paramagnetic Cu(II) centers. Nevertheless, the principal values of the electron Zeemann tensor (g║ and g┴) of the complexes could be determined. Even though the solid substances show slightly different colors, the UV/Vis spectra are nearly identical, indicating structural changes of the tetrachloridocuprate moieties between solid state and solution. The complexes have a promising potential e.g., as high temperature ionic liquids, as precursors for the formation of copper chloride particles or as catalytic paramagnetic ionic liquids. PMID:22408411

  12. Cr3+-Doped Yb3Ga5O12 Nanophosphor: Synthesis, Optical, EPR, Studies

    NASA Astrophysics Data System (ADS)

    Singh, Vijay; Sivaramaiah, G.; Rao, J. L.; Singh, N.; Pathak, M. S.; Jirimali, H. D.; Singh, Pramod K.; Srivastava, Anoop K.; Dhoble, S. J.; Mohapatra, M.

    2016-08-01

    Gallium garnets of lanthanides are multifunctional materials especially known for their complicated structure and magnetic properties. In addition, with a suitable transition metal dopant ion, these matrices have been proved to be excellent materials for lasers. In particular, gallium garnet of ytterbium (Yb3Ga5O12) is known to possess excellent properties with regards to these applications. In this connection, Yb3Ga5O12 doped with Cr3+ nanophosphors were synthesized by a solution combustion route. The synthesized material was characterized by powder x-ray diffraction and scanning electron microscopy for phase purity and homogenous morphology. In order to ascertain the oxidation state of the doped ion, diffuse reflectance (DRF), photoluminescence (PL) and electron paramagnetic resonance (EPR) experiments were performed on the sample. The DRF and PL data suggested the stabilisation of the trivalent Cr ion in the matrix. The EPR spectra exhibited two resonance signals with effective g values at g ≈ 7.6 and 4. The EPR data corroborated the DRF and PL results, suggesting the stabilisation of Cr3+ in the matrix at octahedral-type geometries.

  13. Skeletal Muscle Oxygenation Measured by EPR Oximetry Using a Highly Sensitive Polymer-Encapsulated Paramagnetic Sensor.

    PubMed

    Hou, H; Khan, N; Nagane, M; Gohain, S; Chen, E Y; Jarvis, L A; Schaner, P E; Williams, B B; Flood, A B; Swartz, H M; Kuppusamy, P

    2016-01-01

    We have incorporated LiNc-BuO, an oxygen-sensing paramagnetic material, in polydimethylsiloxane (PDMS), which is an oxygen-permeable, biocompatible, and stable polymer. We fabricated implantable and retrievable oxygen-sensing chips (40 % LiNc-BuO in PDMS) using a 20-G Teflon tubing to mold the chips into variable shapes and sizes for in vivo studies in rats. In vitro EPR measurements were used to test the chip's oxygen response. Oxygen induced linear and reproducible line broadening with increasing partial pressure (pO2). The oxygen response was similar to that of bare (unencapsulated) crystals and did not change significantly on sterilization by autoclaving. The chips were implanted in rat femoris muscle and EPR oximetry was performed repeatedly (weekly) for 12 weeks post-implantation. The measurements showed good reliability and reproducibility over the period of testing. These results demonstrated that the new formulation of OxyChip with 40 % LiNc-BuO will enable the applicability of EPR oximetry for long-term measurement of oxygen concentration in tissues and has the potential for clinical applications. PMID:27526163

  14. Moving Difference (MDIFF) Non-adiabatic rapid sweep (NARS) EPR of copper(II)

    PubMed Central

    Hyde, James S.; Bennett, Brian; Kittell, Aaron W.; Kowalski, Jason M.; Sidabras, Jason W.

    2014-01-01

    Non Adiabatic Rapid Sweep (NARS) EPR spectroscopy has been introduced for application to nitroxide-labeled biological samples (AW Kittell et al, (2011)). Displays are pure absorption, and are built up by acquiring data in spectral segments that are concatenated. In this paper we extend the method to frozen solutions of copper-imidazole, a square planar copper complex with four in-plane nitrogen ligands. Pure absorption spectra are created from concatenation of 170 5-gauss segments spanning 850 G at 1.9 GHz. These spectra, however, are not directly useful since nitrogen superhyperfine couplings are barely visible. Application of the moving difference (MDIFF) algorithm to the digitized NARS pure absorption spectrum is used to produce spectra that are analogous to the first harmonic EPR. The signal intensity is about 4 times higher than when using conventional 100 kHz field modulation, depending on line shape. MDIFF not only filters the spectrum, but also the noise, resulting in further improvement of the SNR for the same signal acquisition time. The MDIFF amplitude can be optimized retrospectively, different spectral regions can be examined at different amplitudes, and an amplitude can be used that is substantially greater than the upper limit of the field modulation amplitude of a conventional EPR spectrometer, which improves the signal-to-noise ratio of broad lines. PMID:24036469

  15. Electron paramagnetic resonance (EPR) study of free radicals in irradiated zinc poly methacrylate

    NASA Astrophysics Data System (ADS)

    Galindo, S.; Ureña-Núñez, F.

    2015-06-01

    We report the analysis of the X-band EPR spectrum of the free radical species formed in Zn(II) polymethacrylate (Zn(II) PMA), after degradation was induced in this polymer by 60Co γ- radiation at room temperature. We begin by describing the synthesis and characterization of our samples and its polymerization before applying them several doses to induce degradation. Doses from 10 to 100 kGy in steps of 10 kGy were applied to the samples. At 10 kGy dose, the EPR spectrum shows the superimposed spectra of two species, namely: a typical pattern of an axially symmetrical singlet and a broad symmetric single line. The former can be attributed to peroxide radicals. After applying further doses, the EPR spectra of the samples display a series of superimposed lines on top of the mentioned axial singlet and the broad line. In these spectra, we recognize three sets of lines: a weak doublet, a quartet and quintet in addition to the already detected axially symmetrical line and the broad singlet. These can be assigned to scission radicals trapped in the polymeric matrix.

  16. Semiquinone and ascorbyl radicals in the gut fluids of caterpillars measured with EPR spectrometry.

    PubMed

    Barbehenn, R V; Poopat, U; Spencer, B

    2003-01-01

    The biological activity of phenolic compounds ingested by caterpillars is commonly believed to result from their oxidation, although the products of oxidation have been well-characterized in only a few cases. The initial oxidation products of phenols (semiquinone or phenoxyl radicals) can be measured with electron paramagnetic resonance (EPR) spectrometry. In this study semiquinone radicals formed from tannic acid and gallic acid in the gut fluids of two species of caterpillars were measured. In Orgyia leucostigma, in which ingested phenols are not oxidized, semiquinone radicals were absent or at very low intensities. By contrast, in Malacosoma disstria, in which ingested phenols are oxidized, high semiquinone radical intensities were measured. In the absence of detectable levels of semiquinone radicals, ascorbyl radicals were detected in the EPR spectra instead. High molar ratios of ascorbate to phenols in an artificial diet produced ascorbyl radicals in the midgut fluids of both species, while diets containing low molar ratios produced semiquinone radicals. Similar results were obtained in M. disstria fed the leaves of red oak or sugar maple. The results of this study provide further evidence that ascorbate is an essential antioxidant that prevents the oxidation of phenols in the gut fluids of caterpillars, and demonstrate that EPR spectrometry is a valuable method for determining the degree of oxidative activation of phenols ingested by herbivorous insects. PMID:12459207

  17. Assessment of quality of quartz crystals by EPR and γ-ray diffraction

    NASA Astrophysics Data System (ADS)

    Nienhaus, K.; Stegger, P.; Lehmann, G.; Schneider, J. R.

    1986-03-01

    Natural amethysts from amygdoidal cavities and from fissures as well as synthetic iron-doped quartz crystals of different origins were studied by EPR and γ-ray diffraction. Anisotropic broadening proportional to the slopes of the transitions consistent with a distribution of orientations, most likely due to a mosaic structure, was observed in the EPR spectra of Fe 3+. This broadening was considerably smaller or completely absent in natural amethysts from fissures as well as in a synthetic crystal grown from NH 4F solution. From this broadening average distributions of orientations could be evaluated for substitutional Fe 3+ in good overall agreement with those obtained for the whole crystals by γ-ray diffraction. Thus Fe 3+ is a good probe for the overall quality of the crystals, but the γ-ray diffraction experiments clearly show predominance of a few orientations rather than a random distribution. In the quartz samples of high perfection a hyperfine splitting from an alkali nucleus could be resolved in the EPR spectra of substitutional Fe 3+ at low temperatures and a contribution of vibrations to the minimum linewidths was also observed.

  18. Multifrequency EPR Studies of Manganese Catalases Provide a Complete Description of Proteinaceous Nitrogen Coordination

    PubMed Central

    Stich, Troy A.; Whittaker, James W.; Britt, R. David

    2012-01-01

    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 14N 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, while 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 sp2-hybridized nitrogens coordinating equatorially to high-valent 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. PMID:20055466

  19. A more secure anonymous user authentication scheme for the integrated EPR information system.

    PubMed

    Wen, Fengtong

    2014-05-01

    Secure and efficient user mutual authentication is an essential task for integrated electronic patient record (EPR) information system. Recently, several authentication schemes have been proposed to meet this requirement. In a recent paper, Lee et al. proposed an efficient and secure password-based authentication scheme used smart cards for the integrated EPR information system. This scheme is believed to have many abilities to resist a range of network attacks. Especially, they claimed that their scheme could resist lost smart card attack. However, we reanalyze the security of Lee et al.'s scheme, and show that it fails to protect off-line password guessing attack if the secret information stored in the smart card is compromised. This also renders that their scheme is insecure against user impersonation attacks. Then, we propose a new user authentication scheme for integrated EPR information systems based on the quadratic residues. The new scheme not only resists a range of network attacks but also provides user anonymity. We show that our proposed scheme can provide stronger security. PMID:24760224

  20. Applications of pulsed EPR spectroscopy to structural studies of sulfite oxidizing enzymes

    SciTech Connect

    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. Are entangled particles connected by wormholes? Evidence for the ER =EPR conjecture from entropy inequalities

    NASA Astrophysics Data System (ADS)

    Gharibyan, Hrant; Penna, Robert F.

    2014-03-01

    If spacetime is built out of quantum bits, does the shape of space depend on how the bits are entangled? The ER =EPR conjecture relates the entanglement entropy of a collection of black holes to the cross sectional area of Einstein-Rosen (ER) bridges (or wormholes) connecting them. We show that the geometrical entropy of classical ER bridges satisfies the subadditivity, triangle, strong subadditivity, and Cadney-Linden-Winter inequalities. These are nontrivial properties of entanglement entropy, so this is evidence for ER =EPR. We further show that the entanglement entropy associated with classical ER bridges has nonpositive tripartite information. This is not a property of entanglement entropy, in general. For example, the entangled four qubit pure state |GHZ4⟩=(|0000⟩+|1111⟩)/√2 has positive tripartite information, so this state cannot be described by a classical ER bridge. Large black holes with massive amounts of entanglement between them can fail to have a classical ER bridge if they are built out of |GHZ4⟩ states. States with nonpositive tripartite information are called monogamous. We conclude that classical ER bridges require monogamous EPR correlations.

  2. Irradiated bivalve mollusks: Use of EPR spectroscopy for identification and dosimetry

    NASA Astrophysics Data System (ADS)

    Alberti, Angelo; Chiaravalle, Eugenio; Fuochi, Piergiorgio; Macciantelli, Dante; Mangiacotti, Michele; Marchesani, Giuliana; Plescia, Elena

    2011-12-01

    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 60Co γ-rays. EPR could definitely identify irradiated seashells due to the presence of long-lived free radicals, primarily CO2-, CO33-, SO2- and SO3- 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.

  3. EPR and impedance spectroscopic investigations on lithium bismuth borate glasses containing nickel and vanadium ions.

    PubMed

    Yadav, Arti; Khasa, Satish; Hooda, Ashima; Dahiya, Manjeet S; Agarwal, Ashish; Chand, Prem

    2016-03-15

    Glasses having composition 7NiO∙23Li2O∙20Bi2O3∙50B2O3, 7V2O5∙23Li2O∙20Bi2O3∙50B2O3 and x(2NiO∙V2O5)∙(30-x)Li2O∙50B2O3∙20Bi2O3 (with x=0, 2, 5, 7 & 10 mol%) prepared through melt-quench route are explored by analyzing density, impedance spectroscopy and electron paramagnetic resonance (EPR). It is found that both density and molar volume increase with an increase in substitution of 2NiO∙V2O5 in the base glass matrix. Different dielectric parameters viz. dielectric loss (ε), electrical modulus (M), loss tangent (tanδ) etc. are evaluated and their variations with frequency and temperature are analyzed which reveals that these glasses exhibit a non-Debye relaxation behavior. A phenomenal description of the capacitive behavior is obtained by considering the circuitry as a parallel combination of bulk resistance (Rb) and constant phase element (CPE). The conduction mechanism is found to follow Quantum Mechanical Tunneling (QMT) model. Spin Hamiltonian Parameters (SHPs) and covalency rates are calculated from the EPR spectra of vanadyl ion. The observed EPR spectra confirmed that V(4+) ion exists as vanadyl ion in the octahedral coordination with tetragonal compression. PMID:26748341

  4. Ionizable Nitroxides for Studying Local Electrostatic Properties of Lipid Bilayers and Protein Systems by EPR.

    PubMed

    Voinov, Maxim A; Smirnov, Alex I

    2015-01-01

    Electrostatic interactions are known to play a major role in the myriad of biochemical and biophysical processes. Here, we describe biophysical methods to probe local electrostatic potentials of proteins and lipid bilayer systems that are based on an observation of reversible protonation of nitroxides by electron paramagnetic resonance (EPR). Two types of probes are described: (1) methanethiosulfonate derivatives of protonatable nitroxides for highly specific covalent modification of the cysteine's sulfhydryl groups and (2) spin-labeled phospholipids with a protonatable nitroxide tethered to the polar head group. The probes of both types report on their ionization state through changes in magnetic parameters and degree of rotational averaging, thus, allowing the electrostatic contribution to the interfacial pKa of the nitroxide, and, therefore, the local electrostatic potential to be determined. Due to their small molecular volume, these probes cause a minimal perturbation to the protein or lipid system. Covalent attachment secures the position of the reporter nitroxides. Experimental procedures to characterize and calibrate these probes by EPR, and also the methods to analyze the EPR spectra by simulations are outlined. The ionizable nitroxide labels and the nitroxide-labeled phospholipids described so far cover an exceptionally wide range of ca. 2.5-7.0 pH units, making them suitable to study a broad range of biophysical phenomena, especially at the negatively charged lipid bilayer surfaces. The rationale for selecting proper electrostatically neutral interface for probe calibration, and examples of lipid bilayer surface potential studies, are also described. PMID:26477252

  5. X-ray absorption spectroscopy and EPR studies of oriented spinach thylakoid preparations

    SciTech Connect

    Andrews, J.C. |

    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.

  6. Dental radiography: tooth enamel EPR dose assessment from Rando phantom measurements

    NASA Astrophysics Data System (ADS)

    Aragno, D.; Fattibene, P.; Onori, S.; Aragno, D.; Fattibene, P.

    2000-09-01

    Electron paramagnetic resonance dosimetry of tooth enamel is now established as a suitable method for individual dose reconstruction following radiation accidents. The accuracy of the method is limited by some confounding factors, among which is the dose received due to medical x-ray irradiation. In the present paper the EPR response of tooth enamel to endoral examination was experimentally evaluated using an anthropomorphic phantom. The dose to enamel for a single exposure of a typical dental examination performed with a new x-ray generation unit working at 65 kVp gave rise to a CO2- signal of intensity similar to that induced by a dose of about 2 mGy of 60Co. EPR measurements were performed on the entire tooth with no attempt to separate buccal and lingual components. Also the dose to enamel for an orthopantomography exam was estimated. It was derived from TLD measurements as equivalent to 0.2 mGy of 60Co. In view of application to risk assessment analysis, in the present work the value for the ratio of the reference dose at the phantom surface measured with TLD to the dose at the tooth measured with EPR was determined.

  7. EPR and impedance spectroscopic investigations on lithium bismuth borate glasses containing nickel and vanadium ions

    NASA Astrophysics Data System (ADS)

    Yadav, Arti; Khasa, Satish; Hooda, Ashima; Dahiya, Manjeet S.; Agarwal, Ashish; Chand, Prem

    2016-03-01

    Glasses having composition 7NiO • 23Li2O • 20Bi2O3 • 50B2O3, 7V2O5 • 23Li2O • 20Bi2O3 • 50B2O3 and x(2NiO • V2O5) • (30 - x)Li2O • 50B2O3 • 20Bi2O3 (with x = 0, 2, 5, 7 & 10 mol%) prepared through melt-quench route are explored by analyzing density, impedance spectroscopy and electron paramagnetic resonance (EPR). It is found that both density and molar volume increase with an increase in substitution of 2NiO • V2O5 in the base glass matrix. Different dielectric parameters viz. dielectric loss (ε), electrical modulus (M), loss tangent (tanδ) etc. are evaluated and their variations with frequency and temperature are analyzed which reveals that these glasses exhibit a non-Debye relaxation behavior. A phenomenal description of the capacitive behavior is obtained by considering the circuitry as a parallel combination of bulk resistance (Rb) and constant phase element (CPE). The conduction mechanism is found to follow Quantum Mechanical Tunneling (QMT) model. Spin Hamiltonian Parameters (SHPs) and covalency rates are calculated from the EPR spectra of vanadyl ion. The observed EPR spectra confirmed that V4 + ion exists as vanadyl ion in the octahedral coordination with tetragonal compression.

  8. EPR study of Cu(2+) ion doped orotato(nicotinamid)cobalt(II) single crystal.

    PubMed

    Yıldırım, I; Karabulut, B; Büyükgüngör, O

    2016-01-01

    We have studied the Cu(2+) ion doped orotato(nicotinamid)cobalt(II) complex by using EPR spectroscopy and X-ray diffraction. The single crystal is triclinic with the space group P1‾. The unit cell dimensions of the crystal are a=7.2785(4)Å, b=10.2349(5)Å, c=12.7372(6)Å, α=69.297(4)°, β=74.791(4)° and γ=76.995(4)°, with Z=2. We analyzed the EPR spectra of both single crystal and powder of the complex at room temperature. EPR analysis indicates the presence of only one Cu(2+) site. We obtained the spin Hamiltonian parameters from the single crystal data for the complex. The spin Hamiltonian parameters are gx=2.032, gy=2.116, gz=2.319, Ax=28G, Ay=66G, Az=126G. These data indicate that the symmetry of paramagnetic center is rhombic. We constructed the ground state wave function of the Cu(2+) ion. PMID:25704568

  9. Modeling EPR powder spectra using numerical diagonalization of the spin hamiltonian

    PubMed

    Morin; Bonnin

    1999-02-01

    A new modeling code, ZFSFIT (standing for Zero Field Splitting FITting), written in FORTRAN 77 is proposed. It is designed for computing and fitting EPR powder spectra described by any spin Hamiltonian including second- and fourth-order ZFS terms (S EPR powder line positions recorded at distinct frequencies improves the accuracy of the refined EPR parameters. Superhyperfine effects as well as broadening effects due to site-to-site distribution of g-, A-, and ZFS parameters are treated using first-order perturbation theory and can also be refined. Parameters for several distinct centers can be fitted simultaneously, allowing quantification of their relative amounts in the sample. After a description of the algorithm, determination of second- and fourth-order ZFS parameters of Cr3+, Mn2+, and Fe3+ centers in low-symmetry sites in minerals are treated, including first evidence of structural Fe3+ centers in alphaAl(OH)3. The code is available without charge to academic users from the authors. Copyright 1999 Academic Press. PMID:9986760

  10. EPR observation of first point defects in cubic boron nitride crystalline powders

    NASA Astrophysics Data System (ADS)

    Nistor, S. V.; Stefan, M.; Schoemaker, D.; Dinca, G.

    2000-05-01

    An X-band electron paramagnetic resonance (EPR) study of nominally pure, diamond-like cubic boron nitride (c-BN) crystalline powders, has led to the first identification of a spectrum attributed to two related paramagnetic species. The composite EPR spectrum can be observed only in dark brown colored powders known to contain excess of boron. It consists of two superimposed lorentzian components, called D1 and D2, centered at g1=2.0063 and g2=2.0084, with peak-to-peak linewidths of 3.3 and 17.9 mT, respectively. The temperature dependence of the integrated intensities, their linewidths and intensity ratio D2/D1 allows one to conclude that the narrow line D1 originates from EPR transitions inside a S=1/2 ground doublet and the broad line D2 from transitions inside the excited levels of another center. Evidence suggests that both centers are boron related paramagnetic species.

  11. EPR and transient capacitance studies on electron-irradiated silicon solar cells

    NASA Technical Reports Server (NTRS)

    Lee, Y. H.; Cheng, L. J.; Mooney, P. M.; Corbett, J. W.

    1977-01-01

    One and two ohm-cm solar cells irradiated with 1 MeV electrons at 30 C were studied using both EPR and transient capacitance techniques. In 2 ohm-cm cells, Si-G6 and Si-G15 EPR spectra and majority carrier trapping levels at (E sub V + 0.23) eV and (E sub V + 0.38) eV were observed, each of which corresponded to the divacancy and the carbon-oxygen-vacancy complex, respectively. In addition, a boron-associated defect with a minority carrier trapping level at (E sub C -0.27) eV was observed. In 1 ohm-cm cells, the G15 spectrum and majority carrier trap at (E sub V + 0.38) eV were absent and an isotropic EPR line appeared at g = 1.9988 (+ or - 0.0003); additionally, a majority carrier trapping center at (E sub V + 0.32) eV, was found which could be associated with impurity lithium. The formation mechanisms of these defects are discussed according to isochronal annealing data in electron-irradiated p-type silicon.

  12. Some plant leaves have orientation-dependent EPR and NMR spectra.

    PubMed

    McCain, D C; Selig, T C; Govindjee; Markley, J L

    1984-02-01

    Proton nuclear magnetic resonance ((1)H NMR) spectra of leaves from 50 plant species were obtained at a spectrometer frequency of 470 MHz. Water present in leaf samples gives rise to characteristic spectral patterns. Most species show only one broad (1)H NMR peak; however, the leaves of some plants display complex, orientation-dependent spectra in which a common three-line pattern is discerned. The pattern varies with the angle between the leaf surface and the external magnetic field. Proton relaxation measurements show the presence of at least two water compartments in the leaves. The compartments are responsible for different components of the spectral pattern. EPR spectra, obtained at 35 GHz and at a temperature of -180 degrees C, of plant leaf sections are dominated by the strong signals of manganous ions. We find that most plant leaves have isotropic Mn(2+) EPR spectra. However, in some species (including ones that exhibit orientation-dependent (1)H NMR spectra) we detect orientation-dependent intensities in the forbidden lines; the spectra indicate that Mn(2+) ions occupy binding sites with axial or lower symmetry on nonrandomly oriented membranes. Both the NMR and the EPR results suggest that the chloroplasts of some plants are preferentially aligned with respect to the leaf surface. PMID:16593413

  13. The MSPICE simulation of a saturating transformer

    NASA Astrophysics Data System (ADS)

    Maclean, David N.

    A transformer is simulated using a nonlinear saturating magnetic model. Hysteresis and gradual smooth reduction of core permeability are achieved with standard SPICE networks and functions. The equations that define the nonlinear inductance and the MSPICE circuits used to simulate them are derived. A hierarchy of circuit complexity that is based on the structured logic design subcircuit method is used. An example of a push-pull buck regulator being operated in an unbalanced condition is given. Noise ripple on the input power cable generates a dc offset current in the transformer. The example demonstrates how avionics power equipment can be evaluated for large-signal ac, dc, and transient behavior.

  14. Saturation point structure of marine stratocumulus clouds

    NASA Technical Reports Server (NTRS)

    Boers, Reinout; Betts, Alan K.

    1988-01-01

    An investigation of the microstructure of a Pacific stratocumulus capped boundary layer is presented. A complex structure of three branches, identified using conserved variable diagrams, is found to correspond well to a conceptual model for the unstable, radiatively cooled cloud topped boundary layer. A simple conditional sampling method was used to identify saturation point pairs for ascending and descending branches of the internal boundary layer circulation. Results indicate a primary circulation scale of 5 km and provide a reasonable cloud top entrainment rate of 1 cm/s.

  15. Separation and isolation of saturated and unsaturated 5-n-alk(en)ylresorcinols from rye bran.

    PubMed

    Patzke, Hannes; Schulze-Kaysers, Nadine; Schieber, Andreas

    2016-03-18

    Alkylresorcinols (AR) are a class of phenolic lipids which are found in a number of plants and microorganisms and which are associated with various biological activities. In view of the very limited availability of reference compounds, we developed a process for the isolation of AR from rye bran. For this purpose, a crude extract was subjected to deep bed filtration at -80 °C, whereby the crystallized saturated AR were separated from the unsaturated homologues. Highly purified, individual compounds were subsequently isolated by semi-preparative HPLC. In contrast to previously published approaches, the method reported here is relatively easy to perform and allows the recovery of saturated and unsaturated AR of high purity. Furthermore, it is superior to argentation chromatography because it does not necessitate the removal of silver ions for subsequent bioassays. PMID:26895830

  16. Development of semiconductor saturable absorbers for use in photonic analog-to-digital converters

    NASA Astrophysics Data System (ADS)

    Hayduk, Michael J.; Bussjager, Rebecca J.; Johns, Steven T.; Gerhardstein, Cheryl M.; Wicks, Gary W.

    2001-07-01

    Wide bandwidth and high-resolution analog to digital converters (ADCs) are required for the next generation of sensor systems. Progress at advancing the electronic ADC modules has been very slow due in large part to the difficulties in fabricating the electronic circuitry required for very high resolution and high sampling rate converters. It is anticipated that the use of photonic ADCs will far surpass the performance of electronic ADCs in terms of both sampling speed and resolution. We have recently designed a novel photonic ADC module that incorporates the use of semiconductor saturable absorbers to perform the data quantization at speeds in the tens of GHz regime. Experimental material characterization results including the nonlinear transmission and the recovery time of the semiconductor saturable absorbers use din the data conversion process will be presented. Different material parameters will also be analyzed including the effects of low temperature growth, band-edge position, and strain on these material properties.

  17. Development of SGTR Recovery Strategy

    SciTech Connect

    Ju Han Lee; Se Chang Kim; Jong Joo Sohn; Jong Tae Seo

    2004-07-01

    The Steam Generator Tube Rupture (SGTR) recovery guideline of the Korean Standard Nuclear Power Plant (KSNP) Emergency Operating Guidelines (EOG) provides operator actions which must be accomplished in the event of a SGTR. The goal of the guideline is to safely establish Shutdown Cooling System (SCS) entry conditions while minimizing radiological releases to the environment and maintaining adequate core cooling. The current KSNP SGTR EOG uses the strategy that requires immediate rapid cooldown of Reactor Coolant System (RCS) using Atmospheric Dump Valves (ADVs) on both steam generators to a temperature lower than the saturation temperature corresponding to the lowest Main Steam Safety Valves (MSSVs) opening setpoint, followed by an isolation of the affected steam generator. This strategy helps to prevent unnecessary lifting and possible stuck-open of MSSVs on the affected steam generator side after isolation. Generally, the safety analysis for SGTR is performed based on the automatic mitigation actions provided by the engineered safety features and operator actions as directed in the SGTR EOG. For a conservatism, this analysis assumes a Loss of Off-site Power (LOOP) and a postulated single-failure of stuck-open ADV which is used for the initial rapid RCS cooldown. However, a concern on the radiological release through the stuck-open ADV can be eliminated by changing the SGTR recovery strategy. Therefore, a feasibility study has been performed to develop a new SGTR recovery strategy which requires an immediate isolation of the affected steam generator followed by a rapid cooldown of RCS using the ADV on the intact steam generator only. The results of the analyses have been evaluated from the standpoint of the total amount of radiological release to the environment and the possibility of overfill of the affected steam generator. The best-estimate analysis results with the new SGTR recovery strategy show that the amount of radiological release to the environment can

  18. Seismoelectric wave propagation numerical modelling in partially saturated materials

    NASA Astrophysics Data System (ADS)

    Warden, S.; Garambois, S.; Jouniaux, L.; Brito, D.; Sailhac, P.; Bordes, C.

    2013-09-01

    To better understand and interpret seismoelectric measurements acquired over vadose environments, both the existing theory and the wave propagation modelling programmes, available for saturated materials, should be extended to partial saturation conditions. We propose here an extension of Pride's equations aiming to take into account partially saturated materials, in the case of a water-air mixture. This new set of equations was incorporated into an existing seismoelectric wave propagation modelling code, originally designed for stratified saturated media. This extension concerns both the mechanical part, using a generalization of the Biot-Gassmann theory, and the electromagnetic part, for which dielectric permittivity and electrical conductivity were expressed against water saturation. The dynamic seismoelectric coupling was written as a function of the streaming potential coefficient, which depends on saturation, using four different relations derived from recent laboratory or theoretical studies. In a second part, this extended programme was used to synthesize the seismoelectric response for a layered medium consisting of a partially saturated sand overburden on top of a saturated sandstone half-space. Subsequent analysis of the modelled amplitudes suggests that the typically very weak interface response (IR) may be best recovered when the shallow layer exhibits low saturation. We also use our programme to compute the seismoelectric response of a capillary fringe between a vadose sand overburden and a saturated sand half-space. Our first modelling results suggest that the study of the seismoelectric IR may help to detect a sharp saturation contrast better than a smooth saturation transition. In our example, a saturation contrast of 50 per cent between a fully saturated sand half-space and a partially saturated shallow sand layer yields a stronger IR than a stepwise decrease in saturation.

  19. Incorporating carbon saturation concepts and nitrogen retention theory

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Recent advances in soil C saturation concepts have increased our understanding of soil C storage and mineralization without explicit links to N retention and saturation theories. Here, we exploit a soil texture gradient to test hypotheses that link C saturation with soil 15N retention and nitrifica...

  20. Saturable and Reverse Saturable Absorption in Nanocomposite Films of Naphthol Green B Dye-polymer System

    NASA Astrophysics Data System (ADS)

    Devi, S. Maya; Sreeja, S.; Frobel, P. G. Louie; Suresh, S. R.; Muneera, C. I.

    2011-10-01

    Naphthol Green B dye-polyvinyl alcohol composite films were fabricated and their nonlinear absorption properties were investigated using the Z-scan technique under excitation with 5ns laser light pulses at 532 nm. The samples displayed a switchover from saturable absorption to reverse saturable absorption with increase in either intensity or concentration. The measured values of β and IS were found to be of the order of 10-7 cm/W and 109 W/cm2 respectively. The atomic force microscopic analysis of the composite films revealed homogeneous distribution of aggregated nanoclusters marked by a low average surface roughness ≈1.8 nm.

  1. Preliminary Saturated-Zone Flow Model

    SciTech Connect

    1997-06-10

    This milestone consists of an updated fully 3D model of ground-water flow within the saturated zone at Yucca Mountain, Nevada. All electronic files pertaining to this deliverable have been transferred via ftp transmission to Steve Bodnar (M and O) and the technical data base. The model was developed using a flow and transport simulator, FEHMN, developed at Los Alamos National Laboratory, and represents a collaborative effort between staff from the US Geological Survey and Los Alamos National Laboratory. The model contained in this deliverable is minimally calibrated and represents work in progress. The flow model developed for this milestone is designed to feed subsequent transport modeling studies at Los Alamos which also use the FEHMN software. In addition, a general-application parameter estimation routine, PEST, was used in conjunction with FEHMN to reduce the difference between observed and simulated values of hydraulic head through the adjustment of model variables. This deliverable in large part consists of the electronic files for Yucca Mountain Site saturated-zone flow model as it existed as of 6/6/97, including the executable version of FEHMN (accession no. MOL.19970610.0204) used to run the code on a Sun Ultrasparc I workstation. It is expected that users of the contents of this deliverable be knowledgeable about the oration of FEHMN.

  2. Flux saturation length of sediment transport

    NASA Astrophysics Data System (ADS)

    Pähtz, T.; Kok, J. F.

    2013-12-01

    Sediment transport along the surface ("bedload", "saltation") drives geophysical phenomena as diverse as wind erosion and dune formation. The main length-scale controlling the dynamics of sediment erosion and deposition is the saturation length L, which characterizes the flux response to a change in transport conditions. L partially determines the dynamics of bedforms, such as dunes, for instance by dictating the wavelength of elementary dunes on a sediment surface and the minimal size of crescent-shaped barchan dunes. Here, we present an analytical model predicting L as a function of the average sediment velocity under different physical environments. Our model accounts for both the characteristics of sediment entrainment and the saturation of particle and fluid velocities, and has only two physical parameters which we estimated directly from independent experiments. We show that our model is consistent with measurements of L in both aeolian and subaqueous transport regimes over at least five orders of magnitude in the ratio of fluid and particle density, including on Mars.

  3. Salt-saturated concrete strength and permeability

    SciTech Connect

    Pfeifle, T.W.

    1996-11-01

    Laboratory-scale experiments applicable to the use of salt-saturated concrete as a seal material for a transuranic waste repository have been completed. Nitrogen gas permeability measurements were made using a flexible-wall permeameter, a confining pressure of 1 MPa, and gas pressure gradients ranging from 0.3 MPa to 0.75 MPa. Results show that salt-saturated concrete has very low intrinsic permeability with values ranging from 9.4 {times} 10{sup {minus}22} m{sup 2} to 9.7 {times} 10{sup {minus}17} m{sup 2}. Strength and deformation characteristics were investigated under conditions of triaxial compression with confining pressures ranging from 0 to 15 MPa using either axial strain-rate or axial stress-rate control and show that the failure strength of concrete increases with confining pressure which can be adequately described through pressure-sensitive failure criteria. Axial, radial, and volumetric strains were also measured during each test and these data were used to determine elastic properties. Experimental results are applicable in the design and analysis of scale-related functions and apply to other concrete structures subjected to compressive loadings such as dams and prestressed structural members.

  4. Particle correlations in saturated QCD matter

    SciTech Connect

    Baier, Rudolf; Kovner, Alex; Nardi, Marzia; Wiedemann, Urs Achim

    2005-11-01

    We study quantitatively angular correlations in the two-particle spectrum produced by an energetic probe scattering off a dense hadronic target with sizable saturation momentum. To this end, two-parton inclusive cross sections for arbitrary projectiles with small color charge density are derived in the eikonal formalism. Our results are the following: For large momenta of the observed particles, the perturbative limit with characteristic back-to-back correlation is recovered. As the trigger momenta get closer to the saturation scale Q{sub s}, the angular distribution broadens. When the momenta are significantly smaller than Q{sub s}, the azimuthal distribution is broad but still peaked back-to-back. However, in a narrow momentum range (0.5 divide 1.5)Q{sub s}, we observe that the azimuthal correlation splits into a double peak with maxima displaced away from 180 deg. We argue that it is the soft multiple scattering physics that is responsible for the appearance of this shift in the angle of maximal correlation. We also point out that when the physical size of the projectile is particularly small, the double peak structure persists in a significantly wider range of final state momenta.

  5. Response of lithium formate EPR dosimeters at photon energies relevant to the dosimetry of brachytherapy

    SciTech Connect

    Adolfsson, Emelie; Alm Carlsson, Gudrun; Grindborg, Jan-Erik; Gustafsson, Haakan; Lund, Eva; Carlsson Tedgren, Aasa

    2010-09-15

    Purpose: To investigate experimentally the energy dependence of the detector response of lithium formate EPR dosimeters for photon energies below 1 MeV relative to that at {sup 60}Co energies. High energy photon beams are used in calibrating dosimeters for use in brachytherapy since the absorbed dose to water can be determined with high accuracy in such beams using calibrated ion chambers and standard dosimetry protocols. In addition to any differences in mass-energy absorption properties between water and detector, variations in radiation yield (detector response) with radiation quality, caused by differences in the density of ionization in the energy imparted (LET), may exist. Knowledge of an eventual deviation in detector response with photon energy is important for attaining high accuracy in measured brachytherapy dose distributions. Methods: Lithium formate EPR dosimeters were irradiated to known levels of air kerma in 25-250 kV x-ray beams and in {sup 137}Cs and {sup 60}Co beams at the Swedish Secondary Standards Dosimetry Laboratory. Conversions from air kerma free in air into values of mean absorbed dose to the detectors were made using EGSnrc MC simulations and x-ray energy spectra measured or calculated for the actual beams. The signals from the detectors were measured using EPR spectrometry. Detector response (the EPR signal per mean absorbed dose to the detector) relative to that for {sup 60}Co was determined for each beam quality. Results: Significant decreases in the relative response ranging from 5% to 6% were seen for x-ray beams at tube voltages {<=}180 kV. No significant reduction in the relative response was seen for {sup 137}Cs and 250 kV x rays. Conclusions: When calibrated in {sup 60}Co or MV photon beams, corrections for the photon energy dependence of detector response are needed to achieve the highest accuracy when using lithium formate EPR dosimeters for measuring absorbed doses around brachytherapy sources emitting photons in the energy

  6. SITE-SCALE SATURATED ZONE TRANSPORT

    SciTech Connect

    S. KELLER

    2004-11-03

    This work provides a site-scale transport model for calculating radionuclide transport in the saturated zone (SZ) at Yucca Mountain, for use in the abstractions model in support of ''Total System Performance Assessment for License Application'' (TSPA-LA). The purpose of this model report is to provide documentation for the components of the site-scale SZ transport model in accordance with administrative procedure AP-SIII.10Q, Models. The initial documentation of this model report was conducted under the ''Technical Work Plan For: Saturated Zone Flow and Transport Modeling and Testing'' (BSC 2003 [DIRS 163965]). The model report has been revised in accordance with the ''Technical Work Plan For: Natural System--Saturated Zone Analysis and Model Report Integration'', Section 2.1.1.4 (BSC 2004 [DIRS 171421]) to incorporate Regulatory Integration Team comments. All activities listed in the technical work plan that are appropriate to the transport model are documented in this report and are described in Section 2.1.1.4 (BSC 2004 [DIRS 171421]). This report documents: (1) the advection-dispersion transport model including matrix diffusion (Sections 6.3 and 6.4); (2) a description and validation of the transport model (Sections 6.3 and 7); (3) the numerical methods for simulating radionuclide transport (Section 6.4); (4) the parameters (sorption coefficient, Kd ) and their uncertainty distributions used for modeling radionuclide sorption (Appendices A and C); (5) the parameters used for modeling colloid-facilitated radionuclide transport (Table 4-1, Section 6.4.2.6, and Appendix B); and (6) alternative conceptual models and their dispositions (Section 6.6). The intended use of this model is to simulate transport in saturated fractured porous rock (double porosity) and alluvium. The particle-tracking method of simulating radionuclide transport is incorporated in the finite-volume heat and mass transfer numerical analysis (FEHM) computer code, (FEHM V2.20, STN: 10086

  7. PREDICTIVE MODELS. Enhanced Oil Recovery Model

    SciTech Connect

    Ray, R.M.

    1992-02-26

    PREDICTIVE MODELS is a collection of five models - CFPM, CO2PM, ICPM, PFPM, and SFPM - used in the 1982-1984 National Petroleum Council study of enhanced oil recovery (EOR) potential. Each pertains to a specific EOR process designed to squeeze additional oil from aging or spent oil fields. The processes are: 1 chemical flooding; 2 carbon dioxide miscible flooding; 3 in-situ combustion; 4 polymer flooding; and 5 steamflood. CFPM, the Chemical Flood Predictive Model, models micellar (surfactant)-polymer floods in reservoirs, which have been previously waterflooded to residual oil saturation. Thus, only true tertiary floods are considered. An option allows a rough estimate of oil recovery by caustic or caustic-polymer processes. CO2PM, the Carbon Dioxide miscible flooding Predictive Model, is applicable to both secondary (mobile oil) and tertiary (residual oil) floods, and to either continuous CO2 injection or water-alternating gas processes. ICPM, the In-situ Combustion Predictive Model, computes the recovery and profitability of an in-situ combustion project from generalized performance predictive algorithms. PFPM, the Polymer Flood Predictive Model, is switch-selectable for either polymer or waterflooding, and an option allows the calculation of the incremental oil recovery and economics of polymer relative to waterflooding. SFPM, the Steamflood Predictive Model, is applicable to the steam drive process, but not to cyclic steam injection (steam soak) processes. The IBM PC/AT version includes a plotting capability to produces a graphic picture of the predictive model results.

  8. Intermediate water recovery system

    NASA Technical Reports Server (NTRS)

    Deckman, G.; Anderson, A. R. (Editor)

    1973-01-01

    A water recovery system for collecting, storing, and processing urine, wash water, and humidity condensates from a crew of three aboard a spacecraft is described. The results of a 30-day test performed on a breadboard system are presented. The intermediate water recovery system produced clear, sterile, water with a 96.4 percent recovery rate from the processed urine. Recommendations for improving the system are included.

  9. Apollo Recovery Operations

    NASA Technical Reports Server (NTRS)

    Interbartolo, Michael

    2009-01-01

    Objectives include: a) Describe the organization of recovery force command and control and landing areas; b) Describe the function and timeline use of the Earth Landing System (ELS); c) Describe Stable 1 vs Stable 2 landing configurations and the function of the Command Module Uprighting System; d) Explain the activities of the helicopter and swimmer teams in egress and recovery of the crew; e)Explain the activities of the swimmer teams and primary recovery ship in recovery of the Command Module; and f) Describe several landing incidents that occurred during Apollo.

  10. Brine saturation technique for extraction of light filth from rubbed, ground, and whole sage: collaborative study.

    PubMed

    Freeman, C C

    1985-01-01

    A new approach to the isolation of light filth from the 3 commercial forms of sage was studied collaboratively. It incorporates a simple isopropanol defatting, followed by saturation of the product with brine by alternately heating and cooling, and subsequent trapping of filth from tap water with olive oil. This method circumvents the use of hazardous, expensive solvents and more time-consuming pretreatment procedures. Overall recoveries were 92.1% for rodent hair and 78.7% for insect fragments on clean, easy-to-read papers. An additional blending step was necessary to obtain satisfactory recovery of rodent hair fragments from whole sage. The method has been adopted official first action for light filth in rubbed and ground sage only. PMID:4055634

  11. Nitroxide free radical clearance in the live rat monitored by radio-frequency CW-EPR and PEDRI

    NASA Astrophysics Data System (ADS)

    Alecci, Marcello; Seimenis, Ioannis; McCallum, Stephen J.; Lurie, David J.; Foster, Margaret A.

    1998-07-01

    The use of RF (100 to 300 MHz) PEDRI and CW-EPR techniques allows the in vivo study of large animals such as whole rats and rabbits. Recently a PEDRI instrument was modified to also allow CW-EPR spectroscopy with samples of similar size and under the same experimental conditions. In the present study, this CW-EPR and PEDRI apparatus was used to assess the feasibility of the detection of a pyrrolidine nitroxide free radical (2,2,5,5,-tetramethylpyrrolidine-1-oxyl-3-carboxylic acid, PCA) in the abdomen of rats. In particular, we have shown that after the PCA administration ( b.w.): (i) the PCA EPR linewidth does not show line broadening due to concentration effects; (ii) a similar PCA up-take phase is observed by EPR and PEDRI; and (iii) the PCA half-lives in the whole abdomen of rats measured with the CW-EPR (, , n = 10) and PEDRI (, , n = 4) techniques were not significantly different ( p>0.05). These results show, for the first time, that information about PCA pharmacokinetics obtained by CW-EPR is the same as that from PEDRI under the same experimental conditions.

  12. EPR study of free radicals in cotton fiber for its potential use as a fortuitous dosimeter in radiological accidents

    NASA Astrophysics Data System (ADS)

    Sudprasert, W.; Insuan, P.; Khamkhrongmee, S.

    2015-05-01

    Electron paramagnetic resonance (EPR) spectroscopy was applied to characterize radiation-induced free radicals in the cotton fiber in order to determine the possibility for using cotton as a fortuitous dosimeter in accidental exposures to radiation. Cotton fabrics were irradiated at 0.1, 0.5, 1, 2, 10, 50 and 500 Gy using a 137Cs gamma source. The irradiated samples were then stored in the dark under controlled environmental conditions for 1, 15, 35 and 60 days. The EPR spectra were observed in samples using a Bruker EMX X-band spectrometer equipped with a TE102 rectangular cavity. The EPR signal intensities of irradiated samples were determined from peak-to-peak amplitudes of EPR spectra and compared to those of unirradiated samples. The following optimum parameters were used: 100 kHz modulation frequency, 9.84 GHz microwave frequency, 1.8 mT modulation amplitude, 1.0 mW microwave power, 655 ms time constant, 41 ms conversion time and 41.98 s sweep time. The EPR spectra of unirradiated samples showed a singlet line with g = 2.006 due to pre-existing stable organic radicals in the cotton fibers, whereas those of irradiated samples showed the same pattern with different signal intensities according to the doses. Irradiation increased the signal intensity in a dose dependent manner. The signal intensity exhibited an exponential decay with storage time from 1 to 60 days. Obviously, the degree of fading of EPR intensity did not depend on the absorbed dose from 0.1 - 50 Gy. The maximum fading was about 60% at 60 days of storage for irradiated samples at all doses. However, this post-irradiation signal appeared to be detectable for up to 60 days. The EPR study results indicated the potential of using cotton as a fortuitous dosimeter in radiological accidents.

  13. VHF EPR analysis of organic sulfur in coal. Final technical report, September 1, 1992--August 31, 1993

    SciTech Connect

    Clarkson, R.B.; Belford, R.L.

    1993-12-31

    A direct and non-destructive technique called very High Frequency Electron Paramagnetic Resonance (VHF EPR) utilizing instrumentation and application techniques developed in this laboratory, is proving to be a practical and sensitive analytical method for the organic sulfur in coal. Research during this past year (1992--1993) was very successful in terms of obtaining spectrochemical information on organic sulfur in coal both quantitatively (amount of organic sulfur) and qualitatively (form and distribution of organic sulfur). Starting in this funding year, the authors have begun to develop and use a two-species model (non-exchanging and axially symmetric) for the simulation of VHF EPR coal spectra. Such a model provides quantitative information on the total concentration of sulfur species that can be directly related to the organic sulfur content as measured by conventional chemical methods. Utilizing the newly developed method, they have analyzed the VHF EPR spectra from some sub-bituminous coals containing organic sulfur in the range from 2% to 12% and a number of maceral blends. Excellent quantitative agreement is achieved between VHF EPR results and chemical analyses. In addition, the modelling of VHF EPR spectra of coal provides detailed spectral parameters. These parameters can be related to the molecular structures of the paramagnetic species giving rise to the EPR signals, as demonstrated by our study of the model compounds. The foundation of VHF EPR analysis of aromatic sulfur radicals has been firmly established based on careful investigations of the molecular and electronic structures of the thiophenic model compounds. The results validate the theoretical soundness of the method and carry important practical implications.

  14. Wave Dispersion and Attenuation in Partially Saturated Sandstones

    NASA Astrophysics Data System (ADS)

    Nie, Jian-Xin; Yang, Ding-Hui; Yang, Hui-Zhu

    2004-03-01

    We investigate the wave dispersion and attenuation in partially water-saturated sandstones based on the improved Biot/squirt (BISQ) model in which the saturation is introduced. Numerical experiments indicate that the phase velocity of the fast P-wave decreases as the saturation increases in the low-frequency range (102-104 Hz), and reaches the minimum at the full-saturation state. The behaviour of the phase velocity varying with the saturation in the high-frequency range (104-106 Hz), however, is opposite to that in the low-frequency range. The peak value of P-wave attenuation increases with increasing saturation, and is the maximum at the fully saturated state. Numerical models and experiments show that the improved BISQ model is better than the traditional Gassmann-Biot model.

  15. CT imaging of enhanced oil recovery experiments

    SciTech Connect

    Gall, B.L.

    1992-12-01

    X-ray computerized tomography (Cr) has been used to study fluid distributions during chemical enhanced oil recovery experiments. Four CT-monitored corefloods were conducted, and oil saturation distributions were calculated at various stages of the experiments. Results suggested that this technique could add significant information toward interpretation and evaluation of surfactant/polymer EOR recovery methods. CT-monitored tracer tests provided information about flow properties in the core samples. Nonuniform fluid advance could be observed, even in core that appeared uniform by visual inspection. Porosity distribution maps based on CT density calculations also showed the presence of different porosity layers that affected fluid movement through the cores. Several types of CT-monitored corefloods were conducted. Comparisons were made for CT-monitored corefloods using chemical systems that were highly successful in reducing residual oil saturations in laboratory experiments and less successful systems. Changes were made in surfactant formulation and in concentration of the mobility control polymer. Use of a poor mobility control agent failed to move oil that was not initially displaced by the injected surfactant solution; even when a good'' surfactant system was used. Use of a less favorable surfactant system with adequate mobility control could produce as much oil as the use of a good surfactant system with inadequate mobility control. The role of mobility control, therefore, becomes a critical parameter for successful application of chemical EOR. Continuation of efforts to use CT imaging in connection with chemical EOR evaluations is recommended.

  16. CT imaging of enhanced oil recovery experiments

    SciTech Connect

    Gall, B.L.

    1992-12-01

    X-ray computerized tomography (Cr) has been used to study fluid distributions during chemical enhanced oil recovery experiments. Four CT-monitored corefloods were conducted, and oil saturation distributions were calculated at various stages of the experiments. Results suggested that this technique could add significant information toward interpretation and evaluation of surfactant/polymer EOR recovery methods. CT-monitored tracer tests provided information about flow properties in the core samples. Nonuniform fluid advance could be observed, even in core that appeared uniform by visual inspection. Porosity distribution maps based on CT density calculations also showed the presence of different porosity layers that affected fluid movement through the cores. Several types of CT-monitored corefloods were conducted. Comparisons were made for CT-monitored corefloods using chemical systems that were highly successful in reducing residual oil saturations in laboratory experiments and less successful systems. Changes were made in surfactant formulation and in concentration of the mobility control polymer. Use of a poor mobility control agent failed to move oil that was not initially displaced by the injected surfactant solution; even when a ``good`` surfactant system was used. Use of a less favorable surfactant system with adequate mobility control could produce as much oil as the use of a good surfactant system with inadequate mobility control. The role of mobility control, therefore, becomes a critical parameter for successful application of chemical EOR. Continuation of efforts to use CT imaging in connection with chemical EOR evaluations is recommended.

  17. Comparison of the effects of the CHESS sequence and the SPAIR sequence for fat saturation

    NASA Astrophysics Data System (ADS)

    Dong, Kyung-Rae; Goo, Eun-Hoe; Kweon, Dae-Cheol; Chung, Woon-Kwan; Lee, Jong-Woong

    2013-06-01

    This study compared the abilities of the chemical-shift selective saturation(CHESS) and the spectrally-adiabatic inversion recovery (SPAIR) fat-saturation techniques to resolve the recent problems in fat saturation caused by areas of changing volume such as the head and the neck and by metal artifacts when T1 fat-saturation techniques representing the anatomical images and T2 fat-saturation techniques representing pathological images are used. To compare the abilities of CHESS and SPAIR, we acquired images of the head and the neck and of the pelvis, and we compared the contrast-to-noise ratios (CNRs) and the signal-to-noise ratios (SNRs) of the signals from the flexed body parts. Images were taken of the abdomens, heads and necks, and pelvises of 15 men and 15 women (30 in total). In all scanning techniques, the SNRs and the CNRs were calculated based on a quantitative analysis method with a view to obtaining uniform data. According to the study results, the CNRs of the SPAIR and the CHESS techniques for the pelvis in the T1-weighted image were 55.10 and 67.23, respectively. The SNRs of the SPAIR technique were70.61 for muscle and 15.50 for fat whereas the SNRs of the CHESS technique were 79.23 for muscle and 12.00 for fat. For the pelvis in the T2-weighted image, the CNRs of the SPAIR and the CHESS technique were 12.50 and 16.66, respectively. The SNRs of the SPAIR technique were 16.98 for muscle and 5.14 for fat. In contrast, the SNRs of the CHESS technique were 27.90 for muscle and 11.23 for fat. Consequently, the signal intensity was higher in the CHESS than in the SPAIR technique. Nevertheless, with regard to the clinical usefulness, the image quality was higher in the SPAIR technique than in the CHESS technique.

  18. Retinal Vessel Oxygen Saturation during 100% Oxygen Breathing in Healthy Individuals

    PubMed Central

    Olafsdottir, Olof Birna; Eliasdottir, Thorunn Scheving; Kristjansdottir, Jona Valgerdur; Hardarson, Sveinn Hakon; Stefánsson, Einar

    2015-01-01

    Purpose To detect how systemic hyperoxia affects oxygen saturation in retinal arterioles and venules in healthy individuals. Methods Retinal vessel oxygen saturation was measured in 30 healthy individuals with a spectrophotometric retinal oximeter (Oxymap T1). Oximetry was performed during breathing of room air, 100% oxygen (10 minutes, 6L/min) and then again room air (10 minutes recovery). Results Mean oxygen saturation rises modestly in retinal arterioles during 100% oxygen breathing (94.5%±3.8 vs. 92.0%±3.7% at baseline, p<0.0001) and dramatically in retinal venules (76.2%±8.0% vs. 51.3%±5.6%, p<0.0001). The arteriovenous difference decreased during 100% oxygen breathing (18.3%±9.0% vs. 40.7%±5.7%, p<0.0001). The mean diameter of arterioles decreased during 100% oxygen breathing compared to baseline (9.7±1.4 pixels vs. 10.3±1.3 pixels, p<0.0001) and the same applies to the mean venular diameter (11.4±1.2 pixels vs. 13.3±1.5 pixels, p<0.0001). Conclusions Breathing 100% oxygen increases oxygen saturation in retinal arterioles and more so in venules and constricts them compared to baseline levels. The dramatic increase in oxygen saturation in venules reflects oxygen flow from the choroid and the unusual vascular anatomy and oxygen physiology of the eye. PMID:26042732

  19. Superfluid helium in fully saturated porous media

    SciTech Connect

    Huang, K. ); Meng, H. )

    1993-09-01

    The flow of superfluid [sup 4]He through spongelike media at full saturation is modeled by the flow of current through an Ohmic network with random resistors. Solving Kirchhoff's equations leads to the conclusion that the superfluid critical point is a percolation threshold, with critical exponent 1.7. The fractal dimension of the percolating cluster is 2.6. These lead to a specific-heat exponent [alpha]=[minus]5.4, by the Josephson hyperscaling relation. Existing experiments apparently do not cover the critical region. Instead, they measure mean-field'' exponents, whose values for Vycor, aerogel, and xerogel can all be reproduced by choosing appropriate distribution functions for the resistors.

  20. Induction of phase II enzymes and hsp70 genes by copper sulfate through the electrophile-responsive element (EpRE): insights obtained from a transgenic zebrafish model carrying an orthologous EpRE sequence of mammalian origin.

    PubMed

    Almeida, Daniela Volcan; Nornberg, Bruna Félix da Silva; Geracitano, Laura A; Barros, Daniela Martí; Monserrat, José Maria; Marins, Luis Fernando

    2010-09-01

    We have evaluated the homology of the electrophile-responsive element (EpRE) core sequence, a binding site for the Nrf2 transcription factor, in the proximal promoters of the mouse and zebrafish glutathione-S-transferase (gst), glutamate cysteine ligase catalytic subunit (gclc) and heat shock protein 70 (hsp70) genes. The EpRE sites identified for both species in the three analyzed genes showed a high similarity with the putative EpRE core sequence. We also produced a transgenic zebrafish model carrying a transgene comprised of the luciferase (luc) reporter gene under transcriptional control of a mouse EpRE sequence. This transgenic model was exposed to copper sulfate, and the reporter gene was significantly activated. The endogenous gst, gclc and hsp70 zebrafish genes were analyzed in the EpRE-Luc transgenic zebrafish and showed an expression pattern similar to that of the reporter transgene used. Our results demonstrate that EpRE is conserved between mouse and zebrafish for detoxification-related genes and that the development of genetically modified models using this responsive element to drive the expression of reporter genes can be an important tool in understanding the action mechanism of aquatic pollutants. PMID:19116768

  1. Saturated Free Fatty Acids Induce Cholangiocyte Lipoapoptosis

    PubMed Central

    Natarajan, Sathish Kumar; Ingham, Sally A.; Mohr, Ashley M.; Wehrkamp, Cody J.; Ray, Anuttoma; Roy, Sohini; Cazanave, Sophie C.; Phillippi, Mary Anne; Mott, Justin L.

    2015-01-01

    Recent studies have identified a cholestatic variant of nonalcoholic fatty liver disease (NAFLD) with portal inflammation and ductular reaction. Based on reports of biliary damage, as well as increased circulating free fatty acids (FFAs) in NAFLD, we hypothesized the involvement of cholangiocyte lipoapoptosis as a mechanism of cellular injury. Here, we demonstrate that the saturated FFAs palmitate and stearate induced robust and rapid cell death in cholangiocytes. Palmitate and stearate induced cholangiocyte lipoapoptosis in a concentration-dependent manner in multiple cholangiocyte-derived cell lines. The mechanism of lipoapoptosis relied on the activation of caspase 3/7 activity. There was also a significant up-regulation of the proapoptotic BH3-containing protein, PUMA. In addition, palmitate-induced cholangiocyte lipoapoptosis involved a time-dependent increase in the nuclear localization of forkhead family of transcription factor 3 (FoxO3). We show evidence for posttranslational modification of FoxO3, including early (6 hours) deacetylation and dephosphorylation that coincide with localization of FoxO3 in the nuclear compartment. By 16 hours, nuclear FoxO3 is both phosphorylated and acetylated. Knockdown studies confirmed that FoxO3 and its downstream target, PUMA, were critical for palmitate- and stearate-induced cholangiocyte lipoapoptosis. Interestingly, cultured cholangiocyte-derived cells did not accumulate appreciable amounts of neutral lipid upon FFA treatment. Conclusion Our data show that the saturated FFAs palmitate and stearate induced cholangiocyte lipoapoptosis by way of caspase activation, nuclear translocation of FoxO3, and increased proapoptotic PUMA expression. These results suggest that cholangiocyte injury may occur through lipoapoptosis in NAFLD and nonalcoholic steatohepatitis patients. PMID:24753158

  2. A capacitive electrode with fast recovery feature.

    PubMed

    Spinelli, Enrique; Haberman, Marcelo; García, Pablo; Guerrero, Federico

    2012-08-01

    Capacitive electrodes (CEs) allow for acquiring biopotentials without galvanic contact, avoiding skin preparation and the use of electrolytic gel. The signal quality provided by present CEs is similar to that of standard wet electrodes, but they are more sensitive to electrostatic charge interference and motion artifacts, mainly when biopotentials are picked up through clothing and coupling capacitances are reduced to tens of picofarads. When artifacts are large enough to saturate the preamplifier, several seconds (up to tens) are needed to recover a proper baseline level, and during this period biopotential signals are irremediably lost. To reduce this problem, a CE that includes a fast-recovery (FR) circuit is proposed. It works directly on the coupling capacitor, recovering the amplifier from saturation while preserving ultra-high input impedance, as a CE requires. A prototype was built and tested acquiring ECG signals. Several experimental data are presented, which show that the proposed circuit significantly reduces record segment losses due to amplifier saturation when working in real environments. PMID:22813845

  3. Direct laboratory observation of fluid distribution and its influence on acoustic properties of patchy saturated rocks

    NASA Astrophysics Data System (ADS)

    Lebedev, M.; Clennell, B.; Pervukhina, M.; Shulakova, V.; Mueller, T.; Gurevich, B.

    2009-04-01

    predictions of White's model. The results illustrate the non-unique relationships between saturation and velocity in sandstones dependent on texture and fluid displacement history: fuller understanding of these phenomena is needed for accurate assessment of time lapse seismic measurements, be they for oil and gas recovery or for CO2 disposal purposes. Gassmann, F., 1951, Elastic waves through a packing of spheres. Geophysics 16, 673-685; Mavko, G., T. Mukerji, and J. Dvorkin, 1998, The Rock Physics Handbook: Tools for seismic analysis in porous media: Cambridge University Press. Wood, A. W., 1955, A Textbook of Sound, The MacMillan Co., New York, 360 pp. Hill, R., 1963, Elastic properties of reinforced solids: some theoretical principles. J. Mech. Phys. Solids, 11, 357-372. Hill, R., 1952, The elastic behavior of crystalline aggregates. Proc. Physical Soc., London, A65, 349-354. J. Toms, T.M. Mueller, B. Gurevich, 2007 Seismic attenuation in porous rocks with random patchy saturation. Geophysical Prospecting, 55, 671-678.

  4. SU-C-BRD-05: Non-Invasive in Vivo Biodosimetry in Radiotherapy Patients Using Electron Paramagnetic Resonance (EPR) Spectroscopy

    SciTech Connect

    Bahar, N; Roberts, K; Stabile, F; Mongillo, N; Decker, RD; Wilson, LD; Husain, Z; Contessa, J; Carlson, DJ; Williams, BB; Flood, AB; Swartz, HM

    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

  5. Use of multi-coil parallel-gap resonators for co-registration EPR/NMR imaging

    NASA Astrophysics Data System (ADS)

    Kawada, Yuuki; Hirata, Hiroshi; Fujii, Hirodata

    2007-01-01

    This article reports experimental investigations on the use of RF resonators for continuous-wave electron paramagnetic resonance (cw-EPR) and proton nuclear magnetic resonance (NMR) imaging. We developed a composite resonator system with multi-coil parallel-gap resonators for co-registration EPR/NMR imaging. The resonance frequencies of each resonator were 21.8 MHz for NMR and 670 MHz for EPR. A smaller resonator (22 mm in diameter) for use in EPR was placed coaxially in a larger resonator (40 mm in diameter) for use in NMR. RF magnetic fields in the composite resonator system were visualized by measuring a homogeneous 4-hydroxy-2,2,6,6-tetramethyl-piperidinooxy (4-hydroxy-TEMPO) solution in a test tube. A phantom of five tubes containing distilled water and 4-hydroxy-TEMPO solution was also measured to demonstrate the potential usefulness of this composite resonator system in biomedical science. An image of unpaired electrons was obtained for 4-hydroxy-TEMPO in three tubes, and was successfully mapped on the proton image for five tubes. Technical problems in the implementation of a composite resonator system are discussed with regard to co-registration EPR/NMR imaging for animal experiments.

  6. EPR and ab initio calculation study on the EI4 center in 4H- and 6H-SiC

    SciTech Connect

    Carlsson, P.; Son, N. T.; Janzen, E.; Gali, A.; Isoya, J.; Morishita, N.; Ohshima, T.; Magnusson, B.

    2010-12-15

    We present results from electron paramagnetic resonance (EPR) studies of the EI4 EPR center in 4H- and 6H-SiC. The EPR signal of the EI4 center was found to be drastically enhanced in electron-irradiated high-purity semi-insulating materials after annealing at 700-750 deg. C. Strong EPR signals of the EI4 center with minimal interferences from other radiation-induced defects in irradiated high-purity semi-insulating materials allowed our more detailed study of the hyperfine (hf) structures. An additional large-splitting {sup 29}Si hf structure and {sup 13}C hf lines of the EI4 defect were observed. Comparing the data on the hf interactions and the annealing behavior obtained from EPR experiments and from ab initio supercell calculations of different carbon-vacancy-related complexes, we suggest a complex between a carbon vacancy-carbon antisite and a carbon vacancy at the third-neighbor site of the antisite in the neutral charge state, (V{sub C}-C{sub Si}V{sub C}){sup 0}, as a new defect model for the EI4 center.

  7. Elastic Waves Push Residual Organic Fluids From Saturated Rock

    NASA Astrophysics Data System (ADS)

    Beresnev, I. A.; Vigil, R. D.; Li, W.

    2004-12-01

    With world oil reserves dwindling and production shifting to increasingly forbidding environments, the emphasis is greater than ever on the more efficient extraction of the existing oil. Yet typically up to two-thirds of the U. S. domestic oil is abandoned underground. Elastic waves have been observed to increase productivity of oil wells, although the reason for the vibratory motion mobilizing the residual organic fluids has remained unclear. Residual oil is entrapped as blobs or ganglia in narrow pore constrictions due to the resisting capillary forces that prevent free motion of non-wetting fluids driven by water. A finite external pressure gradient, exceeding an "unplugging" threshold, is needed to carry the residual ganglia through. We show that vibrations help overcome the resistance of capillary forces by adding an oscillatory inertial forcing to the external gradient; when the vibratory forcing acts along the gradient and the threshold is exceeded, instant "unplugging" occurs. This mechanism predicts the mobilization effect to be proportional to the amplitude and inversely proportional to the frequency of vibrations. We observe this dependence in a laboratory experiment, in which residual saturation of an organic fluid is created in a glass micromodel, and mobilization of the dyed ganglia is monitored using digital photography. We also directly demonstrate the release of an entrapped ganglion from a pore constriction by the application of vibrations in a computational fluid-dynamics simulation. The technologies that can utilize this phenomenon are not limited to enhanced oil recovery, but also apply to the remediation of groundwater contaminated by leaks from underground storage tanks and surface spills of organic fluids.

  8. Complex Dyke Emplacement at the Hyper-Inflated EPR 16°N Segment

    NASA Astrophysics Data System (ADS)

    Dyment, J.; Deschamps, A.; Gente, P.; Agranier, A.; Aquilon-Robles, A.; Benoit, M.; Hémond, Ch.; Janin, M.; Maia, M.; Rodrigues-Leon, L.; Szitkar, F.; Thibaud, R.; Tilot, V.; Parisub Scientific Party

    2010-12-01

    The EPR segment located between 15°22’N and 16°15’N (hereafter referred as EPR 16°N) presents a very wide (~13 km at the widest) and quite shallow (~2300 m) axial dome and is clearly over-inflated with respect to typical magmatically robust segments of the EPR. This segment is located at the intersection of the EPR with the Mathematician seamount chain, suggesting some kind of ridge-hotspot interaction which would account for the over-inflation. As a consequence of such an interaction, it has also been suggested that the ridge axis may episodically relocate further west to maintain the ridge-hotspot connection. Cruise Parisub of R/V L’Atalante took place in March-April 2010 and used Deep Sea Submersible Nautile and Autonomous Underwater Vehicle Aster-X to study this problem. The area was surveyed using L’Atalante new Simrad EM 122 echo-sounder, and a few sea-surface magnetic profiles were added to the existing data set. A higher resolution swath was achieved at a slower speed on the axial dome. AUV Aster-X completed a 30 x 4 km wide survey of the axial zone at an altitude of 70 m, collecting high resolution multibeam bathymetry and imagery, magnetics, and nephelometry. A total of 24 successful Nautile dives was carried out with videos and photos, rock sampling, and magnetic data collection, making an axial cross section up to 300 ka off-axis to investigate the inferred ridge jumps (10 Nautile dives), and a set of along axis dives to identify the active volcanic axis and search for active and fossil hydrothermal sites (13 Nautile dives). During these dives, several active and inactive hydrothermal vents have been discovered. In this presentation, we focus on the AUV survey. Unlike most fast spreading centres, which display one clear axial graben at the summit of the axial dome, the hyper-inflated dome at 16°N presents a complex set of several grabens, among which it is difficult to decipher which one are volcanically active and may be considered as the

  9. EPR of layered magnetic metal-amino acid salts. II. Cu(L-Met) 2

    NASA Astrophysics Data System (ADS)

    Levstein, P. R.; Steren, C. A.; Gennaro, A. M.; Calvo, R.

    1988-03-01

    Single crystals of bis(L-methioninato)copper(II), Cu(L-Met) 2, were studied by EPR at 9.7 and 33.6 GHz, at 300 K. The position and the peak-to-peak linewidth of the single observed EPR line were measured in three perpendicular planes of the samples. This single resonance is due to the collapse of the resonances of the two magnetically inequivalent copper ions in the lattice caused by the exchange interaction. The components of the molecular g tensor for isolated copper ions were obtained using a model which assumes axial symmetry. The results indicate that the unpaired electron occupies the d( x2 - y2) orbital, and the orientation of the molecule obtained from the EPR data agrees with the crystallographic result. The linewidth data support a model which assumes exchange narrowing of the magnetic dipolar interaction in a two-dimensional magnetic lattice, an incomplete collapse of the hyperfine structure, and a frequency-dependent contribution in the planes where the g factors for the two sites of copper are different. An analysis of this latter contribution, allows to evaluate an exchange coupling constant | J'| = 0.10 K between inequivalent copper neighbors. Besides, the analysis of the hyperfine contribution to the linewidth gives | J| = 0.18 K for the average value of the exchange interaction of one copper ion with its six nearest neighbors within the layer. Concerning the possible superexchange paths between inequivalent copper ions, we suggest they can be of two types: the CuNH…OCu one, involving hydrogen bonds between equatorial nitrogens and equatorial oxygens, and the other consisting of CuOCOCu carboxylate bridges involving apical and equatorial oxygens. They are discussed in view of the experimental results.

  10. Application of Electron Paramagnetic Resonance (EPR) Oximetry to Monitor Oxygen in Wounds in Diabetic Models

    PubMed Central

    Desmet, Céline M.; Lafosse, Aurore; Vériter, Sophie; Porporato, Paolo E.; Sonveaux, Pierre; Dufrane, Denis; Levêque, Philippe; Gallez, Bernard

    2015-01-01

    A lack of oxygen is classically described as a major cause of impaired wound healing in diabetic patients. Even if the role of oxygen in the wound healing process is well recognized, measurement of oxygen levels in a wound remains challenging. The purpose of the present study was to assess the value of electron paramagnetic resonance (EPR) oximetry to monitor pO2 in wounds during the healing process in diabetic mouse models. Kinetics of wound closure were carried out in streptozotocin (STZ)-treated and db/db mice. The pO2 was followed repeatedly during the healing process by 1 GHz EPR spectroscopy with lithium phthalocyanine (LiPc) crystals used as oxygen sensor in two different wound models: a full-thickness excisional skin wound and a pedicled skin flap. Wound closure kinetics were dramatically slower in 12-week-old db/db compared to control (db/+) mice, whereas kinetics were not statistically different in STZ-treated compared to control mice. At the center of excisional wounds, measurements were highly influenced by atmospheric oxygen early in the healing process. In pedicled flaps, hypoxia was observed early after wounding. While reoxygenation occurred over time in db/+ mice, hypoxia was prolonged in the diabetic db/db model. This observation was consistent with impaired healing and microangiopathies observed using intravital microscopy. In conclusion, EPR oximetry using LiPc crystals as the oxygen sensor is an appropriate technique to follow wound oxygenation in acute and chronic wounds, in normal and diabetic animals. Nevertheless, the technique is limited for measurements in pedicled skin flaps and cannot be applied to excisional wounds in which diffusion of atmospheric oxygen significantly affects the measurements. PMID:26659378

  11. Mapping Local Protein Electrostatics by EPR of pH-Sensitive Thiol-Specific Nitroxide† ¶

    PubMed Central

    Voinov, Maxim A.; Ruuge, Andres; Reznikov, Vladimir A.; Grigor’ev, Igor A.; Smirnov, Alex I.

    2013-01-01

    A first thiol-specific pH-sensitive nitroxide spin label of the imidazolidine series -methanethiosulfonic acid S-(1-oxyl-2,2,3,5,5-pentamethylimidazolidin-4-ylmethyl) ester (IMTSL) - has been synthesized and characterized. X- (9 GHz) and W-band (94 GHz) EPR spectral parameters of the new spin label in its free form and covalently attached to an amino acid cysteine and a tripeptide glutathione were studied as a function of pH and solvent polarity. pKa value of protonatable tertiary amino group of the spin label was found to be unaffected by other ionizable groups present in side chains of unstructured small peptides. The W-band EPR spectra were shown to allow for pKa determination from precise g-factor measurements. Is has been demonstrated that high accuracy of pKa determination for pH-sensitive nitroxides could be achieved regardless the frequency of measurements or the regime of spin exchange: fast at X-band and slow at W-band. IMTSL was found to react specifically with a model protein - iso-1-cytochrome c from yeast Saccharomyces cerevisiae - giving EPR spectra very similar to those of the most commonly employed cysteine-specific label MTSL. CD data indicated no perturbations to the overall protein structure upon IMTSL labeling. It was found that for IMTSL, giso correlates linearly with Aiso but the slopes are different for the neutral and charged forms of the nitroxide. This finding was attributed to the solvent effects on the spin density at the oxygen atom of the N–O group and on the excitation energy of the oxygen lone-pair orbital. PMID:18426227

  12. Water accessibility in a membrane-inserting peptide comparing Overhauser DNP and pulse EPR methods

    NASA Astrophysics Data System (ADS)

    Segawa, Takuya F.; Doppelbauer, Maximilian; Garbuio, Luca; Doll, Andrin; Polyhach, Yevhen O.; Jeschke, Gunnar

    2016-05-01

    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 1H NMR spectrum of H2O 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 ɛ, being the relative change of the NMR intensity, by the electron spin concentration, which was determined from a continuous-wave EPR spectrum.

  13. Application of Electron Paramagnetic Resonance (EPR) Oximetry to Monitor Oxygen in Wounds in Diabetic Models.

    PubMed

    Desmet, Céline M; Lafosse, Aurore; Vériter, Sophie; Porporato, Paolo E; Sonveaux, Pierre; Dufrane, Denis; Levêque, Philippe; Gallez, Bernard

    2015-01-01

    A lack of oxygen is classically described as a major cause of impaired wound healing in diabetic patients. Even if the role of oxygen in the wound healing process is well recognized, measurement of oxygen levels in a wound remains challenging. The purpose of the present study was to assess the value of electron paramagnetic resonance (EPR) oximetry to monitor pO2 in wounds during the healing process in diabetic mouse models. Kinetics of wound closure were carried out in streptozotocin (STZ)-treated and db/db mice. The pO2 was followed repeatedly during the healing process by 1 GHz EPR spectroscopy with lithium phthalocyanine (LiPc) crystals used as oxygen sensor in two different wound models: a full-thickness excisional skin wound and a pedicled skin flap. Wound closure kinetics were dramatically slower in 12-week-old db/db compared to control (db/+) mice, whereas kinetics were not statistically different in STZ-treated compared to control mice. At the center of excisional wounds, measurements were highly influenced by atmospheric oxygen early in the healing process. In pedicled flaps, hypoxia was observed early after wounding. While reoxygenation occurred over time in db/+ mice, hypoxia was prolonged in the diabetic db/db model. This observation was consistent with impaired healing and microangiopathies observed using intravital microscopy. In conclusion, EPR oximetry using LiPc crystals as the oxygen sensor is an appropriate technique to follow wound oxygenation in acute and chronic wounds, in normal and diabetic animals. Nevertheless, the technique is limited for measurements in pedicled skin flaps and cannot be applied to excisional wounds in which diffusion of atmospheric oxygen significantly affects the measurements. PMID:26659378

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

    PubMed

    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. PMID:26773526

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

    NASA Astrophysics Data System (ADS)

    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.

  16. Lipid peroxidation and water penetration in lipid bilayers: a W-band EPR study.

    PubMed

    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. PMID:23036933

  17. Algorithm for selection of optimized EPR distance restraints for de novo protein structure determination

    PubMed Central

    Kazmier, Kelli; Alexander, Nathan S.; Meiler, Jens; Mchaourab, Hassane S.

    2010-01-01

    A hybrid protein structure determination approach combining sparse Electron Paramagnetic Resonance (EPR) distance restraints and Rosetta de novo protein folding has been previously demonstrated to yield high quality models (Alexander et al., 2008). However, widespread application of this methodology to proteins of unknown structures is hindered by the lack of a general strategy to place spin label pairs in the primary sequence. In this work, we report the development of an algorithm that optimally selects spin labeling positions for the purpose of distance measurements by EPR. For the α-helical subdomain of T4 lysozyme (T4L), simulated restraints that maximize sequence separation between the two spin labels while simultaneously ensuring pairwise connectivity of secondary structure elements yielded vastly improved models by Rosetta folding. 50% of all these models have the correct fold compared to only 21% and 8% correctly folded models when randomly placed restraints or no restraints are used, respectively. Moreover, the improvements in model quality require a limited number of optimized restraints, the number of which is determined by the pairwise connectivities of T4L α-helices. The predicted improvement in Rosetta model quality was verified by experimental determination of distances between spin labels pairs selected by the algorithm. Overall, our results reinforce the rationale for the combined use of sparse EPR distance restraints and de novo folding. By alleviating the experimental bottleneck associated with restraint selection, this algorithm sets the stage for extending computational structure determination to larger, traditionally elusive protein topologies of critical structural and biochemical importance. PMID:21074624

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

    NASA Astrophysics Data System (ADS)

    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.

  19. Water accessibility in a membrane-inserting peptide comparing Overhauser DNP and pulse EPR methods.

    PubMed

    Segawa, Takuya F; Doppelbauer, Maximilian; Garbuio, Luca; Doll, Andrin; Polyhach, Yevhen O; Jeschke, Gunnar

    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 (1)H NMR spectrum of H2O 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. PMID:27208942

  20. Cooper-pair splitter: towards an efficient source of spin-entangled EPR pairs

    NASA Astrophysics Data System (ADS)

    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