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Sample records for resonance epr oxygen

  1. Electron paramagnetic resonance (EPR) biodosimetry

    International Nuclear Information System (INIS)

    Desrosiers, Marc; Schauer, David A.

    2001-01-01

    Radiation-induced electron paramagnetic resonance (EPR) signals were first reported by Gordy et al. [Proc. Natl. Acad. Sci. USA 41 (1955) 983]. The application of EPR spectroscopy to ionizing radiation dosimetry was later proposed by Brady et al. [Health Phys. 15 (1968) 43]. Since that time EPR dosimetry has been applied to accident and epidemiologic dose reconstruction, radiation therapy, food irradiation, quality assurance programs and archaeological dating. Materials that have been studied include bone, tooth enamel, alanine and quartz. This review paper presents the fundamentals and applications of EPR biodosimetry. Detailed information regarding sample collection and preparation, EPR measurements, dose reconstruction, and data analysis and interpretation will be reviewed for tooth enamel. Examples of EPR biodosimetry application in accidental overexposures, radiopharmaceutical dose assessment and retrospective epidemiologic studies will also be presented

  2. Dynamic changes in oxygenation of intracranial tumor and contralateral brain during tumor growth and carbogen breathing: A multisite EPR oximetry with implantable resonators

    Science.gov (United States)

    Hou, Huagang; Dong, Ruhong; Li, Hongbin; Williams, Benjamin; Lariviere, Jean P.; Hekmatyar, S.K.; Kauppinen, Risto A.; Khan, Nadeem; Swartz, Harold

    2013-01-01

    Introduction Several techniques currently exist for measuring tissue oxygen; however technical difficulties have limited their usefulness and general application. We report a recently developed electron paramagnetic resonance (EPR) oximetry approach with multiple probe implantable resonators (IRs) that allow repeated measurements of oxygen in tissue at depths of greater than 10 mm. Methods The EPR signal to noise (S/N) ratio of two probe IRs was compared with that of LiPc deposits. The feasibility of intracranial tissue pO2 measurements by EPR oximetry using IRs was tested in normal rats and rats bearing intracerebral F98 tumors. The dynamic changes in the tissue pO2 were assessed during repeated hyperoxia with carbogen breathing. Results A 6–10 times increase in the S/N ratio was observed with IRs as compared to LiPc deposits. The mean brain pO2 of normal rats was stable and increased significantly during carbogen inhalation in experiments repeated for 3 months. The pO2 of F98 glioma declined gradually, while the pO2 of contralateral brain essentially remained the same. Although a significant increase in the glioma pO2 was observed during carbogen inhalation, this effect declined in experiments repeated over days. Conclusion EPR oximetry with IRs provides a significant increase in S/N ratio. The ability to repeatedly assess orthotopic glioma pO2 is likely to play a vital role in understanding the dynamics of tissue pO2 during tumor growth and therapies designed to modulate tumor hypoxia. This information could then be used to optimize chemoradiation by scheduling treatments at times of increased glioma oxygenation. PMID:22033225

  3. Cerebral Oxygenation of the Cortex and Striatum following Normobaric Hyperoxia and Mild Hypoxia in Rats by EPR Oximetry using Multi-Probe Implantable Resonators

    Science.gov (United States)

    Hou, Huagang; Li, Hongbin; Dong, Ruhong; Mupparaju, Sriram; Khan, Nadeem; Swartz, Harold

    2013-01-01

    Multi-site electron paramagnetic resonance (EPR) oximetry, using multi-probe implantable resonators, was used to measure the partial pressure of oxygen (pO2) in the brains of rats following normobaric hyperoxia and mild hypoxia. The cerebral tissue pO2 was measured simultaneously in the cerebral cortex and striatum in the same rats before, during, and after normobaric hyperoxia and mild hypoxia challenges. The baseline mean tissue pO2 values (±SE) were not significantly different between the cortex and striatum. During 30 min of 100% O2 inhalation, a statistically significant increase in tissue pO2 of all four sites was observed, however, the tissue pO2 of the striatum area was significantly higher than in the forelimb area of the cortex. Brain pO2 significantly decreased from the baseline value during 15 min of 15% O2 challenge. No differences in the recovery of the cerebral cortex and striatum pO2 were observed when the rats were allowed to breathe 30% O2. It appears that EPR oximetry using implantable resonators can provide information on pO2 under the experimental conditions needed for such a study. The levels of pO2 that occurred in these experiments are readily resolvable by multi-site EPR oximetry with multi-probe resonators. In addition, the ability to simultaneously measure the pO2 in several areas of the brain provides important information that could potentially help differentiate the pO2 changes that can occur due to global or local mechanisms. PMID:21445770

  4. IMPLANTABLE RESONATORS – A TECHNIQUE FOR REPEATED MEASUREMENT OF OXYGEN AT MULTIPLE DEEP SITES WITH IN VIVO EPR

    Science.gov (United States)

    Li, Hongbin; Hou, Huagang; Sucheta, Artur; Williams, Benjamin B.; Lariviere, Jean P.; Khan, Nadeem; Lesniewski, Piotr N.; Swartz, Harold M.

    2013-01-01

    EPR oximetry using implantable resonators allow measurements at much deeper sites than are possible with surface resonators (> 80 mm vs. 10 mm) and have greater sensitivity at any depth. We report here the development of an improvement of the technique that now enables us to obtain the information from multiple sites and at a variety of depths. The measurements from the various sites are resolved using a simple magnetic field gradient. In the rat brain multi-probe implanted resonators measured pO2 at several sites simultaneously for over 6 months to record under normoxic, hypoxic and hyperoxic conditions. This technique also facilitates measurements in moving parts of the animal such as the heart, because the orientation of the paramagnetic material relative to the sensitive small loop is not altered by the motion. The measured response is very fast, enabling measurements in real time of physiological and pathological changes such as experimental cardiac ischemia in the mouse heart. The technique also is quite useful for following changes in tumor pO2, including applications with simultaneous measurements in tumors and adjacent normal tissues. PMID:20204802

  5. Electron paramagnetic resonance (EPR) in medical dosimetry

    International Nuclear Information System (INIS)

    Schauer, David A.; Iwasaki, Akinori; Romanyukha, Alexander A.; Swartz, Harold M.; Onori, Sandro

    2006-01-01

    This paper describes the fundamentals of electron paramagnetic resonance (EPR) and its application to retrospective measurements of clinically significant doses of ionizing radiation. X-band is the most widely used in EPR dosimetry because it represents a good compromise between sensitivity, sample size and water content in the sample. Higher frequency bands (e.g., W and Q) provide higher sensitivity, but they are also greatly influenced by water content. L and S bands can be used for EPR measurements in samples with high water content but they are less sensitive than X-band. Quality control for therapeutic radiation facilities using X-band EPR spectrometry of alanine is also presented

  6. The measurement of oxygen in vivo using EPR techniques

    International Nuclear Information System (INIS)

    Swartz, Harold M.; Clarkson, Robert B.

    1998-01-01

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

  7. Concurrent Longitudinal EPR Monitoring of Tissue Oxygenation, Acidosis, and Reducing Capacity in Mouse Xenograft Tumor Models.

    Science.gov (United States)

    Bobko, Andrey A; Evans, Jason; Denko, Nicholas C; Khramtsov, Valery V

    2017-06-01

    Tissue oxygenation, extracellular acidity, and tissue reducing capacity are among crucial parameters of tumor microenvironment (TME) of significant importance for tumor pathophysiology. In this paper, we demonstrate the complementary application of particulate lithium octa-n-butoxy-naphthalocyanine and soluble nitroxide paramagnetic probes for monitoring of these TME parameters using electron paramagnetic resonance (EPR) technique. Two different types of therapeutic interventions were studied: hypothermia and systemic administration of metabolically active drug. In summary, the results demonstrate the utility of EPR technique for non-invasive concurrent longitudinal monitoring of physiologically relevant chemical parameters of TME in mouse xenograft tumor models, including that under therapeutic intervention.

  8. Reporting of quantitative oxygen mapping in EPR imaging

    Science.gov (United States)

    Subramanian, Sankaran; Devasahayam, Nallathamby; McMillan, Alan; Matsumoto, Shingo; Munasinghe, Jeeva P.; Saito, Keita; Mitchell, James B.; Chandramouli, Gadisetti V. R.; Krishna, Murali C.

    2012-01-01

    Oxygen maps derived from electron paramagnetic resonance spectral-spatial imaging (EPRI) are based upon the relaxivity of molecular oxygen with paramagnetic spin probes. This technique can be combined with MRI to facilitate mapping of pO 2 values in specific anatomic locations with high precision. The co-registration procedure, which matches the physical and digital dimensions of EPR and MR images, may present the pO 2 map at the higher MRI resolution, exaggerating the spatial resolution of oxygen, making it difficult to precisely distinguish hypoxic regions from normoxic regions. The latter distinction is critical in monitoring the treatment of cancer by radiation and chemotherapy, since it is well-established that hypoxic regions are three or four times more resistant to treatment compared to normoxic regions. The aim of this article is to describe pO 2 maps based on the intrinsic resolution of EPRI. A spectral parameter that affects the intrinsic spatial resolution of EPRI is the full width at half maximum (FWHM) height of the gradient-free EPR absorption line in frequency-encoded imaging. In single point imaging too, the transverse relaxation times (T2∗) limit the resolution since the signal decays by exp(-tp/T2∗) where the delay time after excitation pulse, t p, is related to the resolution. Although the spin densities of two point objects may be resolved at this separation, it is inadequate to evaluate quantitative changes of pO 2 levels since the linewidths are proportionately affected by pO 2. A spatial separation of at least twice this resolution is necessary to correctly identify a change in pO 2 level. In addition, the pO 2 values are blurred by uncertainties arising from spectral dimensions. Blurring due to noise and low resolution modulates the pO 2 levels at the boundaries of hypoxic and normoxic regions resulting in higher apparent pO 2 levels in hypoxic regions. Therefore, specification of intrinsic resolution and pO 2 uncertainties are

  9. Scope and limitations of the TEMPO/EPR method for singlet oxygen detection: the misleading role of electron transfer.

    Science.gov (United States)

    Nardi, Giacomo; Manet, Ilse; Monti, Sandra; Miranda, Miguel A; Lhiaubet-Vallet, Virginie

    2014-12-01

    For many biological and biomedical studies, it is essential to detect the production of (1)O2 and quantify its production yield. Among the available methods, detection of the characteristic 1270-nm phosphorescence of singlet oxygen by time-resolved near-infrared (TRNIR) emission constitutes the most direct and unambiguous approach. An alternative indirect method is electron paramagnetic resonance (EPR) in combination with a singlet oxygen probe. This is based on the detection of the TEMPO free radical formed after oxidation of TEMP (2,2,6,6-tetramethylpiperidine) by singlet oxygen. Although the TEMPO/EPR method has been widely employed, it can produce misleading data. This is demonstrated by the present study, in which the quantum yields of singlet oxygen formation obtained by TRNIR emission and by the TEMPO/EPR method are compared for a set of well-known photosensitizers. The results reveal that the TEMPO/EPR method leads to significant overestimation of singlet oxygen yield when the singlet or triplet excited state of the photosensitizer is efficiently quenched by TEMP, acting as electron donor. In such case, generation of the TEMP(+) radical cation, followed by deprotonation and reaction with molecular oxygen, gives rise to an EPR-detectable TEMPO signal that is not associated with singlet oxygen production. This knowledge is essential for an appropriate and error-free application of the TEMPO/EPR method in chemical, biological, and medical studies. Copyright © 2014 Elsevier Inc. All rights reserved.

  10. Physiological and pathophysiological reactive oxygen species as probed by EPR spectroscopy: the underutilized research window on muscle ageing.

    Science.gov (United States)

    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. © 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.

  11. Retrievable micro-inserts containing oxygen sensors for monitoring tissue oxygenation using EPR oximetry

    International Nuclear Information System (INIS)

    Dinguizli, M; Beghein, N; Gallez, B

    2008-01-01

    Tissue oxygenation is a crucial parameter in various physiopathological situations and can influence the therapeutic response of tumours. EPR oximetry is a reliable method for assessing and monitoring oxygen levels in vivo over long periods of time. Among the different paramagnetic oxygen sensors available for EPR oximetry, lithium phthalocyanine (LiPc) is a serious candidate for in vivo applications because of its narrow linewidth and its high signal-to-noise ratio. To enhance the biocompatibility of the sensors, fluoropolymer Teflon AF2400 was used to make cylindrical micro-inserts containing LiPc crystals. This new micro-pellet design has several advantages for in vivo studies, including the possibility of being able to choose the implant size, a high sensor content, the facility of in vivo insertion and complete protection with preservation of the oxygen sensor's characteristics. The response to oxygen and the kinetics of this response were tested using in vivo EPR: no differences were observed between micro-inserts and uncoated LiPc crystals. Pellets implanted in vivo in muscles conserved their responsiveness over a long period of time (∼two months), which is much longer than the few days of stability observed using LiPc crystals without protection by the implant. Finally, evaluation of the biocompatibility of the implants revealed no inflammatory reaction around the implantation area

  12. Injectable LiNc-BuO loaded microspheres as in vivo EPR oxygen sensors after co-implantation with tumor cells.

    Science.gov (United States)

    Frank, Juliane; Gündel, Daniel; Drescher, Simon; Thews, Oliver; Mäder, Karsten

    2015-12-01

    Electron paramagnetic resonance (EPR) oximetry is a technique which allows accurate and repeatable oxygen measurements. We encapsulated a highly oxygen sensitive particulate EPR spin probe into microparticles to improve its dispersibility and, hence, facilitate the administration. These biocompatible, non-toxic microspheres contained 5-10 % (w/w) spin probe and had an oxygen sensitivity of 0.60 ± 0.01 µT/mmHg. To evaluate the performance of the microparticles as oxygen sensors, they were co-implanted with syngeneic tumor cells in 2 different rat strains. Thus, tissue injury was avoided and the microparticles were distributed all over the tumor tissue. Dynamic changes of the intratumoral oxygen partial pressure during inhalation of 8 %, 21 %, or 100 % oxygen were monitored in vivo by EPR spectroscopy and quantified. Values were verified in vivo by invasive fluorometric measurements using Oxylite probes and ex vivo by pimonidazole adduct accumulation. There were no hints that the tumor physiology or tissue oxygenation had been altered by the microparticles. Hence, these microprobes offer great potential as oxygen sensors in preclinical research, not only for EPR spectroscopy but also for EPR imaging. For instance, the assessment of tissue oxygenation during therapeutic interventions might help understanding pathophysiological processes and lead to an individualized treatment planning or the use of formulations with hypoxia triggered release of active agents. Copyright © 2015 Elsevier Inc. All rights reserved.

  13. Structure and dynamics of paramagnetic transients by pulsed EPR and NMR detection of nuclear resonance

    International Nuclear Information System (INIS)

    Trifunac, A.D.

    1981-01-01

    Structure and dynamics of transient radicals in pulse radiolysis can be studied by time resolved EPR and NMR techniques. EPR study of kinetics and relaxation is illustrated. The NMR detection of nuclear resonance in transient radicals is a new method which allows the study of hyperfine coupling, population dynamics, radical kinetics, and reaction mechanism. 9 figures

  14. Cathodoluminescence (CL) and electron paramagnetic resonance (EPR) studies of clay minerals

    International Nuclear Information System (INIS)

    Goetze, J.; Ploetze, M.; Goette, T.; Neuser, R.D.; Richter, D.K.

    2002-01-01

    Sheet silicates of the serpentine-kaolin-group (serpentine, kaolinite, dickite, nacrite, halloysite), the talc-pyrophyllite-group (talc, pyrophyllite), the smectite-group (montmorillonite), and illite (as a mineral of the mica-group) were investigated to obtain information concerning their cathodoluminescence behavior. The study included analyses by cathodoluminescence (CL microscopy and spectroscopy), electron paramagnetic resonance (EPR), x-ray diffraction (XRD), scanning electron microscopy (SEM) and trace element analysis. In general, all dioctahedral clay minerals exhibit a visible CL. Kaolinite, dickite, nacrite and pyrophyllite have a characteristic deep blue CL, whereas halloysite emission is in the greenish-blue region. On the contrary, the trioctahedral minerals (serpentine, talc) and illite do not show visible CL. The characteristic blue CL is caused by an intense emission band around 400 nm (double peak with two maxima at 375 and 410 nm). EPR measurements indicate that his blue emission can be related to radiation induced defect centers (RID), which occur as electron holes trapped on apical oxygen (Si-O center) or located at the Al-O-Al group (Al substituting Si in the tetrahedron). Additional CL emission bands were detected at 580 nm in halloysite and kaolinite, and between 700 and 800 nm in kaolinite, dickite, nacrite and pyrophyllite. Time-resolved spectral CL measurements show typical luminescence kinetics for the different clay minerals, which enable differentiation between the various dioctahedral minerals (e.g. kaolinite and dickite), even in thin section. (author)

  15. Time-resolved EPR study of singlet oxygen in the gas phase.

    Science.gov (United States)

    Ruzzi, Marco; Sartori, Elena; Moscatelli, Alberto; Khudyakov, Igor V; Turro, Nicholas J

    2013-06-27

    X-band EPR spectra of singlet O2((1)Δg) and triplet O2((3)Σg(-)) were observed in the gas phase under low molecular-oxygen pressures PO2 = 0.175-0.625 Torr, T = 293-323 K. O2((1)Δg) was produced by quenching of photogenerated triplet sensitizers naphthalene C8H10, perdeuterated naphthalene, and perfluoronaphthalene in the gas phase. The EPR spectrum of O2((1)Δg) was also observed under microwave discharge. Integrated intensities and line widths of individual components of the EPR spectrum of O2((3)Σg(-)) were used as internal standards for estimating the concentration of O2 species and PO2 in the EPR cavity. Time-resolved (TR) EPR experiments of C8H10 were the main focus of this Article. Pulsed irradiation of C8H10 in the presence of O2((3)Σg(-)) allowed us to determine the kinetics of formation and decay for each of the four components of the O2((1)Δg) EPR signal, which lasted for only a few seconds. We found that the kinetics of EPR-component decay fit nicely to a biexponential kinetics law. The TR EPR 2D spectrum of the third component of the O2((1)Δg) EPR spectrum was examined in experiments using C8H10. This spectrum vividly presents the time evolution of an EPR component. The largest EPR signal and the longest lifetime of O2((1)Δg), τ = 0.4 s, were observed at medium pressure PO2 = 0.4 Torr, T = 293 K. The mechanism of O2((1)Δg) decay in the presence of photosensitizers is discussed. EPR spectra of O2((1)Δg) evidence that the spin-rotational states of O2((1)Δg) are populated according to Boltzmann distribution in the studied time range of 10-100 ms. We believe that this is the first report dealing with the dependence of O2((1)Δg) EPR line width on PO2 and T.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-07-01

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

  17. Nitrogen ligation to manganese in the photosynthetic oxygen-evolving complex: Continuous-wave and pulsed EPR studies of Photosystem II particles containing 14N or 15N

    International Nuclear Information System (INIS)

    DeRose, V.J.; Yachandra, V.K.; McDermott, A.E.; Britt, R.D.; Sauer, K.; Klein, M.P.

    1991-01-01

    The possibility of nitrogen ligation to the Mn in the oxygen-evolving complex from photosystem II was investigated with electron paramagnetic resonance (EPR) and electron spin echo envelope modulation (ESEEM) spectroscopies using 14 N- and 15 N-labeled preparations. Oxygen-evolving preparations were isolated from a thermophilic cyanobacterium, Synechococcus sp., grown on a medium containing either 14 NO 3 - or 15 NO - 3 as the sole source of nitrogen. The substructure on the multiline EPR signal, which arises from Mn in the S 2 state of the enzyme, was measured with continuous-wave EPR. No changes were detected in the substructure peak positions upon substitution of 15 N for 14 N, indicating that this substructure is not due to superhyperfine coupling from nitrogen ligands. To detect potential nitrogen ligands with superhyperfine couplings of lesser magnitude than could be observed with conventional EPR methods, electron spin-echo envelope modulation experiments were also performed on the multiline EPR signal. The Fourier transform of the light-minus-dark time domain ESEEM data shows a peak at 4.8 MHz in 14 N samples which is absent upon substitution with 15 N. This gives unambiguous evidence for weak hyperfine coupling of nitrogen to the Mn of the oxygen-evolving complex. Possible origins of this nitrogen interaction are discussed

  18. Detection and characterisation of radicals using electron paramagnetic resonance (EPR) spin trapping and related methods

    DEFF Research Database (Denmark)

    Davies, Michael Jonathan

    2016-01-01

    Electron paramagnetic resonance (EPR) spectroscopy (also known as electron spin resonance, ESR, or electron magnetic resonance, EMR, spectroscopy) is often described as the “gold standard” for the detection and characterisation of radicals in chemical, biological and medical systems. The article...... reviews aspects of EPR spectroscopy and discusses how this methodology and related techniques can be used to obtain useful information from biological systems. Consideration is given to the direct detection of radicals, the use of spin traps and the detection of nitric oxide, and the advantages...

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

    Science.gov (United States)

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

    2015-10-01

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

  20. Pulse Double-Resonance EPR Techniques for the Study of Metallobiomolecules.

    Science.gov (United States)

    Cox, Nicholas; Nalepa, Anna; Pandelia, Maria-Eirini; Lubitz, Wolfgang; Savitsky, Anton

    2015-01-01

    Electron paramagnetic resonance (EPR) spectroscopy exploits an intrinsic property of matter, namely the electron spin and its related magnetic moment. This can be oriented in a magnetic field and thus, in the classical limit, acts like a little bar magnet. Its moment will align either parallel or antiparallel to the field, giving rise to different energies (termed Zeeman splitting). Transitions between these two quantized states can be driven by incident microwave frequency radiation, analogous to NMR experiments, where radiofrequency radiation is used. However, the electron Zeeman interaction alone provides only limited information. Instead, much of the usefulness of EPR is derived from the fact that the electron spin also interacts with its local magnetic environment and thus can be used to probe structure via detection of nearby spins, e.g., NMR-active magnetic nuclei and/or other electron spin(s). The latter is exploited in spin labeling techniques, an exciting new area in the development of noncrystallographic protein structure determination. Although these interactions are often smaller than the linewidth of the EPR experiment, sophisticated pulse EPR methods allow their detection. A number of such techniques are well established today and can be broadly described as double-resonance methods, in which the electron spin is used as a reporter. Below we give a brief description of pulse EPR methods, particularly their implementation at higher magnetic fields, and how to best exploit them for studying metallobiomolecules. © 2015 Elsevier Inc. All rights reserved.

  1. Determination of the Antioxidant Status of the Skin by In Vivo-Electron Paramagnetic Resonance (EPR Spectroscopy

    Directory of Open Access Journals (Sweden)

    Silke Barbara Lohan

    2015-08-01

    Full Text Available Organisms produce free radicals which are essential for various metabolic processes (enzymatic oxidation, cellular respiration, signaling. Antioxidants are important chemical compounds that specifically prevent the oxidation of substances by scavenging radicals, especially reactive oxygen species (ROS. Made up of one or two unpaired electrons, ROS are free radicals that are highly reactive and can attack other metabolites. By using electron paramagnetic resonance (EPR spectroscopy, it is possible to measure paramagnetic substances such as free radicals. Therefore the dermal antioxidant activity can be determined by applying semi-stable radicals onto the skin and measuring the antioxidant-induced radical scavenging activity in the skin. In recent years, EPR has been developed as a spectroscopic method for determining the antioxidant status in vivo. Several studies have shown that an additional uptake of dietary supplements, such as carotenoids or vitamin C in physiological concentrations, provide a protective effect against free radicals. Using the EPR technique it could be demonstrated that the radical production in stress situations, such as irradiation with infrared and visible light, was reduced with time. However, not only the oral uptake of antioxidants, but also the topical application of antioxidants, e.g., a hyperforin-rich cream, is very useful against the development of oxidative stress. Regular application of a hyperforin-rich cream reduced radical formation. The skin lipids, which are very important for the barrier function of the skin, were also stabilized.

  2. Retrospective dosimetry by electronic paramagnetic resonance (EPR) in dental enamel

    International Nuclear Information System (INIS)

    Dubner, D.; Gisone, P.; Perez, M.R.; Davila, F.A.; Boveris, A.; Puntarulo, S.

    1998-01-01

    Biophysical dosimetry based on EPR in biological solid samples (like bone and teeth) or in organic materials (like textile fibres, sugar, etc.) is a complementary technique that could contribute, along with the biological dosimetry, to the retrospective evaluation of the absorbed dose in accidental situations. Dental enamel could be considered as the only tissue with structure and composition essentially constant over time: this characteristic feature allows its use as an index of radiation exposure since tooth retains indefinitely its radiation history. Samples of human molars were exposed to gamma-Rays (Co 60) with doses between 0,5 Gy to 10 Gy. After a chemical treatment of samples, enamel was removed by grinding with a dental drill and reduced to a fine powder. A characteristic EPR signal was detected at g=2.002. The dose effect curves were done using 20 mw of microwave power. Measurements were done both, with flat cells and disposable Pasteur pipettes allowing the use of lower amounts of sample. The intensity of the signal was proportional to the dose and linearity was verified in both cases. We discuss the applicability of this technique in evaluating radiation dose in accidental overexposures. (author) [es

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

    International Nuclear Information System (INIS)

    Skaleric, U.; Gaspirc, B.; Cevc, P.; Schara, M.

    1998-01-01

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

  4. Towards improving the detection limit of electron paramagnetic resonance (EPR) dosimetry of drywall (wallboard)

    Energy Technology Data Exchange (ETDEWEB)

    Mistry, R.; Thompson, J.W. [Dept. of Medical Physics and Applied Radiation Sciences, McMaster Univ., Hamilton, Ontario (Canada); Rink, W.J. [School of Geography and Earth Sciences, McMaster Univ., Hamilton, Ontario (Canada); Boreham, D. [Dept. of Medical Physics and Applied Radiation Sciences, McMaster Univ., Hamilton, Ontario (Canada)

    2009-07-01

    The intensity of the electron paramagnetic resonance (EPR) line corresponding to the carbonate free radical (CO{sub 3}{sup -}) in gypsum (CaSO{sub 4}{center_dot}2H{sub 2}O) drywall was previously shown to be proportional to absorbed dose. Heating irradiated drywall reduces the radiosensitive signal of the CO{sub 3}{sup -} radical. The response of the CO{sub 3}{sup -} EPR line to heat treatments is being studied in order to determine a background for an arbitrary drywall sample. Ultimately this is expected to improve the precision of dose measurements with drywall and to reduce the detection limit. Controlled heating of irradiated drywall was performed at temperatures between 50{sup o}C and 100{sup o}C. Although higher temperatures reduce the radiosensitive signal rapidly, the non-radiosensitive EPR signals are affected dramatically as well, presumably due to a phrase change from gypsum to plaster of Paris to anhydrite. (author)

  5. Electron paramagnetic resonance (EPR spectral components of spin-labeled lipids in saturated phospholipid bilayers: effect of cholesterol

    Directory of Open Access Journals (Sweden)

    Heverton Silva Camargos

    2013-01-01

    Full Text Available Electron paramagnetic resonance (EPR spectroscopy was used to study the main structural accommodations of spin labels in bilayers of saturated phosphatidylcholines with acyl chain lengths ranging from 16 to 22 carbon atoms. EPR spectra allowed the identification of two distinct spectral components in thermodynamic equilibrium at temperatures below and above the main phase transition. An accurate analysis of EPR spectra, using two fitting programs, enabled determination of the thermodynamic profile for these major probe accommodations. Focusing the analysis on two-component EPR spectra of a spin-labeled lipid, the influence of 40 mol % cholesterol in DPPC was studied.

  6. In vivo EPR oximetry using an isotopically-substituted nitroxide: Potential for quantitative measurement of tissue oxygen

    Science.gov (United States)

    Weaver, John; Burks, Scott R.; Liu, Ke Jian; Kao, Joseph P.Y.; Rosen, Gerald M.

    2017-01-01

    Variations in brain oxygen (O2) concentration can have profound effects on brain physiology. Thus, the ability to quantitate local O2 concentrations noninvasively in vivo could significantly enhance understanding of several brain pathologies. However, quantitative O2 mapping in the brain has proven difficult. The electron paramagnetic resonance (EPR) spectra of nitroxides are sensitive to molecular O2 and can be used to estimate O2 concentrations in aqueous media. We recently synthesized labile-ester-containing nitroxides, such as 3-acetoxymethoxycarbonyl-2,2,5,5-tetramethyl-1-pyrrolidinyloxyl (nitroxide 4), which accumulate in cerebral tissue after in situ hydrolysis, and thus enable spatial mapping of O2 concentrations in the mouse brain by EPR imaging. In an effort to improve O2 quantitation, we prepared 3-acetoxymethox ycarbonyl-2,2,5,5-tetra(2H3)methyl-1-(3,4,4-2H3,1-15N)pyrrolidinyloxyl (nitroxide 2), which proved to be a more sensitive probe than its normo-isotopic version for quantifying O2 in aqueous solutions of various O2 concentrations. We now demonstrate that this isotopically substituted nitroxide is ~2-fold more sensitive in vivo than the normo-isotopic nitroxide 4. Moreover, in vitro and in vivo EPR spectral-spatial imaging results with nitroxide 2 demonstrate significant improvement in resolution, reconstruction and spectral response to local O2 concentrations in cerebral tissue. Thus, isotopic-substituted nitroxides, such as 2, are excellent sensors for in vivo O2 quantitation in tissues, such as the brain. PMID:27567323

  7. EPR dating CO2- sites in tooth enamel apatites by ENDOR and triple resonance

    International Nuclear Information System (INIS)

    Vugman, N.V.; Rigby, S.E.J.

    1995-01-01

    In this work we combine electron paramagnetic resonance (EPR), high-resolution electron nucleus double resonance (ENDOR) and general triple resonance (GTR) spectroscopies, to study the local environment of the CO 2 - groups created by ionizing radiation in fossil tooth enamel. We demonstrate that the CO 2 - groups occupy slightly modified phosphate sites in the hydroxyapatite lattice. In quaternary shark enamel we found these groups to be interacting with water molecules in the apatite channels. The absence of water molecules as first neighbours in mammalian samples indicate, however, that these molecules are not significantly responsible for the stabilization of CO 2 - dating centers in enamel. (author)

  8. Flexible, wireless, inductively coupled surface coil resonator for EPR tooth dosimetry

    International Nuclear Information System (INIS)

    Schreiber, Wilson; Petryakov, Sergey V.; Kmiec, Maciej M.; Feldman, Matthew A.; Wood, Victoria A.; Boyle, Holly K.; Flood, Ann Barry; Williams, Benjamin B.; Swartz, Harold M.; Meaney, Paul M.

    2016-01-01

    Managing radiation injuries following a catastrophic event where large numbers of people may have been exposed to life-threatening doses of ionizing radiation relies on the availability of biodosimetry to assess whether individuals need to be triaged for care. Electron Paramagnetic Resonance (EPR) tooth dosimetry is a viable method to accurately estimate the amount of ionizing radiation to which an individual has been exposed. In the intended measurement conditions and scenario, it is essential that the measurement process be fast, straightforward and provides meaningful and accurate dose estimations for individuals in the expected measurement conditions. The sensing component of a conventional L-band EPR spectrometer used for tooth dosimetry typically consists of a surface coil resonator that is rigidly, physically attached to the coupler. This design can result in cumbersome operation, limitations in teeth geometries that may be measured and hinder the overall utility of the dosimeter. A novel surface coil resonator has been developed for the currently existing L-band (1.15 GHz) EPR tooth dosimeter for the intended use as a point of care device by minimally trained operators. This resonator development provides further utility to the dosimeter, and increases the usability of the dosimeter by non-expert operators in the intended use scenario. (authors)

  9. A Tunable Reentrant Resonator with Transverse Orientation of Electric Field for in Vivo EPR Spectroscopy

    Science.gov (United States)

    Chzhan, Michael; Kuppusamy, Periannan; Samouilov, Alexandre; He, Guanglong; Zweier, Jay L.

    1999-04-01

    There has been a need for development of microwave resonator designs optimized to provide high sensitivity and high stability for EPR spectroscopy and imaging measurements ofin vivosystems. The design and construction of a novel reentrant resonator with transversely oriented electric field (TERR) and rectangular sample opening cross section for EPR spectroscopy and imaging ofin vivobiological samples, such as the whole body of mice and rats, is described. This design with its transversely oriented capacitive element enables wide and simple setting of the center frequency by trimming the dimensions of the capacitive plate over the range 100-900 MHz with unloadedQvalues of approximately 1100 at 750 MHz, while the mechanical adjustment mechanism allows smooth continuous frequency tuning in the range ±50 MHz. This orientation of the capacitive element limits the electric field based loss of resonatorQobserved with large lossy samples, and it facilitates the use of capacitive coupling. Both microwave performance data and EPR measurements of aqueous samples demonstrate high sensitivity and stability of the design, which make it well suited forin vivoapplications.

  10. A high-resolution EPR-CT microscope using cavity-resonators equipped with small field gradient coils

    International Nuclear Information System (INIS)

    Miki, T.; Murata, T.; Kumai, H.; Yamashiro, A.

    1996-01-01

    Cylindrical cavity resonators equipped with field gradient coils were developed for two-dimensional EPR-CT microscope systems. The field gradient coils lie in four (or six) thin metal tubes placed along the direction of the microwave magnetic field in the cavity to minimize impact on the resonator's quality factor. Two pairs of the tubes carry a 100 kHz current for magnetic field modulation. This cavity has high spin-detection sensitivity and can provide EPR images with submillimeter resolution. In order to reconstruct better images from fewer projections, we used an algebraic reconstruction technique (ART) for the two-dimensional image reconstruction. The ART method may be suitable for not only spectral-spatial two-dimensional EPR imaging, but also spatio-temporal EPR imaging in dynamic spin systems. (author)

  11. Resonances in Electron Impact on Atomic Oxygen

    International Nuclear Information System (INIS)

    Yang, Wang; Ya-Jun, Zhou; Li-Guang, Jiao; Ratnavelu, Kuru

    2008-01-01

    The momentum-space coupled-channels-optical (CCO) method is used to study the resonances in electron-oxygen collision in the energy region of 9–12eV. Present results have shown agreement with the available experimental and theoretical results, and new positions of resonances are found by the comparison of total cross sections. (fundamental areas of phenomenology (including applications))

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

    Science.gov (United States)

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

  13. Frequency bandwidth extension by use of multiple Zeeman field offsets for electron spin-echo EPR oxygen imaging of large objects

    Science.gov (United States)

    Seifi, Payam; Epel, Boris; Sundramoorthy, Subramanian V.; Mailer, Colin; Halpern, Howard J.

    2011-01-01

    Purpose: Electron spin-echo (ESE) oxygen imaging is a new and evolving electron paramagnetic resonance (EPR) imaging (EPRI) modality that is useful for physiological in vivo applications, such as EPR oxygen imaging (EPROI), with potential application to imaging of multicentimeter objects as large as human tumors. A present limitation on the size of the object to be imaged at a given resolution is the frequency bandwidth of the system, since the location is encoded as a frequency offset in ESE imaging. The authors’ aim in this study was to demonstrate the object size advantage of the multioffset bandwidth extension technique.Methods: The multiple-stepped Zeeman field offset (or simply multi-B) technique was used for imaging of an 8.5-cm-long phantom containing a narrow single line triaryl methyl compound (trityl) solution at the 250 MHz imaging frequency. The image is compared to a standard single-field ESE image of the same phantom.Results: For the phantom used in this study, transverse relaxation (T2e) electron spin-echo (ESE) images from multi-B acquisition are more uniform, contain less prominent artifacts, and have a better signal to noise ratio (SNR) compared to single-field T2e images.Conclusions: The multi-B method is suitable for imaging of samples whose physical size restricts the applicability of the conventional single-field ESE imaging technique. PMID:21815379

  14. SU-C-BRD-05: Non-Invasive in Vivo Biodosimetry in Radiotherapy Patients Using Electron Paramagnetic Resonance (EPR) Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Bahar, N; Roberts, K; Stabile, F; Mongillo, N; Decker, RD; Wilson, LD; Husain, Z; Contessa, J; Carlson, DJ [Yale University School of Medicine, New Haven, Connecticut (United States); Williams, BB; Flood, AB; Swartz, HM [Geisel Medical School at Dartmouth University, Hanover, New Hampshire (United States)

    2015-06-15

    Purpose: Medical intervention following a major, unplanned radiation event can elevate the human whole body exposure LD50 from 3 to 7 Gy. On a large scale, intervention cannot be achieved effectively without accurate and efficient triage. Current methods of retrospective biodosimetry are restricted in capability and applicability; published human data is limited. We aim to further develop, validate, and optimize an automated field-deployable in vivo electron paramagnetic resonance (EPR) instrument that can fill this need. Methods: Ionizing radiation creates highly-stable, carbonate-based free radicals within tooth enamel. Using a process similar to nuclear magnetic resonance, EPR directly measures the presence of radiation-induced free radicals. We performed baseline EPR measurements on one of the upper central incisors of total body irradiation (TBI) and head and neck (H&N) radiotherapy patients before their first treatment. Additional measurements were performed between subsequent fractions to examine the EPR response with increasing radiation dose. Independent dosimetry measurements were performed with optically-stimulated luminescent dosimeters (OSLDs) and diodes to more accurately establish the relationship between EPR signal and delivered radiation dose. Results: 36 EPR measurements were performed over the course of four months on two TBI and four H & N radiotherapy patients. We observe a linear increase in EPR signal with increasing dose across the entirety of the tested range. A linear least squares-weighted fit of delivered dose versus measured signal amplitude yields an adjusted R-square of 0.966. The standard error of inverse prediction (SEIP) is 1.77 Gy. For doses up to 7 Gy, the range most relevant to triage, we calculate an SEIP of 1.29 Gy. Conclusion: EPR spectroscopy provides a promising method of retrospective, non-invasive, in vivo biodosimetry. Our preliminary data show an excellent correlation between predicted signal amplitude and delivered

  15. Structure and dynamics of paramagnetic transients by pulsed EPR and NMR detection of nuclear resonance. [Pulse radiolysis of methanol in D/sub 2/O

    Energy Technology Data Exchange (ETDEWEB)

    Trifunac, A.D.

    1981-01-01

    Structure and dynamics of transient radicals in pulse radiolysis can be studied by time resolved EPR and NMR techniques. EPR study of kinetics and relaxation is illustrated. The NMR detection of nuclear resonance in transient radicals is a new method which allows the study of hyperfine coupling, population dynamics, radical kinetics, and reaction mechanism. 9 figures.

  16. Electron paramagnetic resonance highlights that the oxygen effect contributes to the radiosensitizing effect of paclitaxel.

    Directory of Open Access Journals (Sweden)

    Fabienne Danhier

    Full Text Available BACKGROUND: Paclitaxel (PTX is a potent anti-cancer chemotherapeutic agent and is widely used in the treatments of solid tumors, particularly of the breast and ovaries. An effective and safe micellar formulation of PTX was used to administer higher doses of PTX than Taxol® (the current commercialized drug. We hypothesize that PTX-loaded micelles (M-PTX may enhance tumor radiosensitivity by increasing the tumor oxygenation (pO(2. Our goals were (i to evaluate the contribution of the "oxygen effect" to the radiosensitizing effect of PTX; (ii to demonstrate the therapeutic relevance of the combination of M-PTX and irradiation and (iii to investigate the underlying mechanisms of the observed oxygen effect. METHODOLOGY AND PRINCIPAL FINDINGS: We used (PEG-p-(CL-co-TMC polymeric micelles to solubilize PTX. pO(2 was measured on TLT tumor-bearing mice treated with M-PTX (80 mg/kg using electron paramagnetic resonance (EPR oximetry. The regrowth delay following 10 Gy irradiation 24 h after M-PTX treatment was measured. The tumor perfusion was assessed by the patent blue staining. The oxygen consumption rate and the apoptosis were evaluated by EPR oximetry and the TUNEL assay, respectively. EPR oximetry experiments showed that M-PTX dramatically increases the pO(2 24 h post treatment. Regrowth delay assays demonstrated a synergy between M-PTX and irradiation. M-PTX increased the tumor blood flow while cells treated with M-PTX consumed less oxygen and presented more apoptosis. CONCLUSIONS: M-PTX improved the tumor oxygenation which leads to synergy between this treatment and irradiation. This increased pO(2 can be explained both by an increased blood flow and an inhibition of O(2 consumption.

  17. Electron Paramagnetic Resonance pO2 Image Tumor Oxygen-Guided Radiation Therapy Optimization.

    Science.gov (United States)

    Epel, Boris; Maggio, Matt; Pelizzari, Charles; Halpern, Howard J

    2017-01-01

    Modern standards for radiation treatment do not take into account tumor oxygenation for radiation treatment planning. Strong correlation between tumor oxygenation and radiation treatment success suggests that oxygen-guided radiation therapy (OGRT) may be a promising enhancement of cancer radiation treatment. We have developed an OGRT protocol for rodents. Electron paramagnetic resonance (EPR) imaging is used for recording oxygen maps with high spatial resolution and excellent accuracy better than 1 torr. Radiation is delivered with an animal intensity modulated radiation therapy (IMRT) XRAD225Cx micro-CT/ therapy system. The radiation plan is delivered in two steps. First, a uniform 15% tumor control dose (TCD 15 ) is delivered to the whole tumor. In the second step, an additional booster dose amounting to the difference between TCD 98 and TCD 15 is delivered to radio-resistant, hypoxic tumor regions. Delivery of the booster dose is performed using a multiport conformal beam protocol. For radiation beam shaping we used individual radiation blocks 3D-printed from tungsten infused ABS polymer. Calculation of beam geometry and the production of blocks is performed next to the EPR imager, immediately after oxygen imaging. Preliminary results demonstrate the sub-millimeter precision of the radiation delivery and high dose accuracy. The efficacy of the radiation treatment is currently being tested on syngeneic FSa fibrosarcoma tumors grown in the legs of C3H mice.

  18. Uniform field loop-gap resonator and rectangular TEU02 for aqueous sample EPR at 94 GHz

    Science.gov (United States)

    Sidabras, Jason W.; Sarna, Tadeusz; Mett, Richard R.; Hyde, James S.

    2017-09-01

    In this work we present the design and implementation of two uniform-field resonators: a seven-loop-six-gap loop-gap resonator (LGR) and a rectangular TEU02 cavity resonator. Each resonator has uniform-field-producing end-sections. These resonators have been designed for electron paramagnetic resonance (EPR) of aqueous samples at 94 GHz. The LGR geometry employs low-loss Rexolite end-sections to improve the field homogeneity over a 3 mm sample region-of-interest from near-cosine distribution to 90% uniform. The LGR was designed to accommodate large degassable Polytetrafluorethylen (PTFE) tubes (0.81 mm O.D.; 0.25 mm I.D.) for aqueous samples. Additionally, field modulation slots are designed for uniform 100 kHz field modulation incident at the sample. Experiments using a point sample of lithium phthalocyanine (LiPC) were performed to measure both the uniformity of the microwave magnetic field and 100 kHz field modulation, and confirm simulations. The rectangular TEU02 cavity resonator employs over-sized end-sections with sample shielding to provide an 87% uniform field for a 0.1 × 2 × 6 mm3 sample geometry. An evanescent slotted window was designed for light access to irradiate 90% of the sample volume. A novel dual-slot iris was used to minimize microwave magnetic field perturbations and maintain cross-sectional uniformity. Practical EPR experiments using the application of light irradiated rose bengal (4,5,6,7-tetrachloro-2‧,4‧,5‧,7‧-tetraiodofluorescein) were performed in the TEU02 cavity. The implementation of these geometries providing a practical designs for uniform field resonators that continue resonator advancements towards quantitative EPR spectroscopy.

  19. Electron Paramagnetic Resonance Measurements of Reactive Oxygen Species by Cyclic Hydroxylamine Spin Probes.

    Science.gov (United States)

    Dikalov, Sergey I; Polienko, Yuliya F; Kirilyuk, Igor

    2018-05-20

    Oxidative stress contributes to numerous pathophysiological conditions such as development of cancer, neurodegenerative, and cardiovascular diseases. A variety of measurements of oxidative stress markers in biological systems have been developed; however, many of these methods are not specific, can produce artifacts, and do not directly detect the free radicals and reactive oxygen species (ROS) that cause oxidative stress. Electron paramagnetic resonance (EPR) is a unique tool that allows direct measurements of free radical species. Cyclic hydroxylamines are useful and convenient molecular probes that readily react with ROS to produce stable nitroxide radicals, which can be quantitatively measured by EPR. In this work, we critically review recent applications of various cyclic hydroxylamine spin probes in biology to study oxidative stress, their advantages, and the shortcomings. Recent Advances: In the past decade, a number of new cyclic hydroxylamine spin probes have been developed and their successful application for ROS measurement using EPR has been published. These new state-of-the-art methods provide improved selectivity and sensitivity for in vitro and in vivo studies. Although cyclic hydroxylamine spin probes EPR application has been previously described, there has been lack of translation of these new methods into biomedical research, limiting their widespread use. This work summarizes "best practice" in applications of cyclic hydroxylamine spin probes to assist with EPR studies of oxidative stress. Additional studies to advance hydroxylamine spin probes from the "basic science" to biomedical applications are needed and could lead to better understanding of pathological conditions associated with oxidative stress. Antioxid. Redox Signal. 28, 1433-1443.

  20. EPR-study of reversible oxygenation process of coordination compounds of cobalt(II) with S-substituted N1,N4-di(salicylidene)-isothiosemicarbazides

    International Nuclear Information System (INIS)

    Gerbeleu, N.V.; Revenko, M.D.; Rusu, V.G.; Shames, A.T.

    1987-01-01

    The reaction between molecular oxygen and coordination compounds of cobalt(II) with S-substituted N 1 ,N 4 -di(salicylidene)isothiosemicarbazides in dimethyl sulfoxide solution was studied by the EPR method. It was found that paramagnetic monomeric adducts and diamagnetic μ-peroxo-dimers are formed. The spin-Hamiltonian parameters of the EPR spectra of the initial cobalt complexes, as well as of the paramagnetic adducts were determined. The nature of the Co-O 2 bond is discussed

  1. EPR spectroscopic evidence for a tetranuclear manganese cluster as the site for photosynthetic oxygen evolution

    Energy Technology Data Exchange (ETDEWEB)

    Dismukes, G C; Ferris, K; Watnick, P

    1982-01-01

    It has been shown that EPR observations of a polynuclear Mn cluster in spinach chloroplasts can be interpreted in terms of a cluster containing three Mn(III) ions and one Mn(IV) ion within a tetranuclear complex. Both ferromagnetic and antiferromagnetic interactions appear to exist between the Mn ions, which exhibit deeply trapped discrete oxidation states, at least in this EPR active state. These results are discussed in terms of what is currently known about the polypeptide composition of the enzyme. A model of the oxidation state changes in the enzyme is proposed which is consistent with the EPR and protein isolation studies. Finally, a comparison between the electron-transporting metalloenzymes and the electron-storing metalloenzymes shows that the facile electron transfer kinetics observed in the former class and the slow kinetics observed in the latter class are consistent with the distinctly different electronic structures of these enzymes and their functional roles.

  2. Preliminary study on electron paramagnetic resonance (EPR) signal properties of mobile phone components for dose estimation in radiation accident

    Energy Technology Data Exchange (ETDEWEB)

    Park, Byeong Ryong; Ha, Wi Ho; Park, Sun Hoo; Lee, Jin Kyeong; Lee, Seung Sook [Korea Institute of Radiological and Medical Sciences, Seoul (Korea, Republic of)

    2015-12-15

    We have investigated the EPR signal properties in 12 components of two mobile phones (LCD, OLED) using electron paramagnetic resonance (EPR) spectrometer in this study.EPR measurements were performed at normal atmospheric conditions using Bruker EXEXSYS-II E500 spectrometer with X-band bridge, and samples were irradiated by {sup 137}C{sub s} gamma-ray source. To identify the presence of radiation-induced signal (RIS), the EPR spectra of each sample were measured unirradiated and irradiated at 50 Gy. Then, dose-response curve and signal intensity variating by time after irradiation were measured. As a result, the signal intensity increased after irradiation in all samples except the USIM plastic and IC chip. Among the samples, cover glass(CG), lens, light guide plate(LGP) and diffusion sheet have shown fine linearity (R{sup 2} > 0.99). Especially, the LGP had ideal characteristics for dosimetry because there were no signal in 0 Gy and high rate of increase in RIS. However, this sample showed weakness in fading. Signal intensity of LGP and Diffusion Sheet decreased by 50% within 72 hours after irradiation, while signals of Cover Glass and Lens were stably preserved during the short period of time. In order to apply rapidly EPR dosimetry using mobile phone components in large-scale radiation accidents, further studies on signal differences for same components of the different mobile phone, fading, pretreatment of samples and processing of background signal are needed. However, it will be possible to do dosimetry by dose-additive method or comparative method using unirradiated same product in small-scale accident.

  3. Electronic Paramagnetic Resonance (EPR) of free radicals induced by X-rays in pyrene

    International Nuclear Information System (INIS)

    Moya Partiti, C.S. de.

    1982-01-01

    Pyrene single crystals C 16 H 10 , irradiated by X-rays, at room temperature, were studied by EPR technique, to determine free radicals formed by radiation. The angular dependence of EPR spectra was explained by the presence of two kinds of radicals with an aditional hydrogen: 2-H 2 pyrene and 3-H 2 pyrene. It was studied the isothermic decay of the EPR signal and two typical values for the activation energy were found = (1,9+-0,1) eV and (1,93+-0,03) eV. (author) [pt

  4. Repeated assessment of orthotopic glioma pO2 by multi-site EPR oximetry: A technique with the potential to guide therapeutic optimization by repeated measurements of oxygen

    Science.gov (United States)

    Khan, Nadeem; Mupparaju, Sriram; Hou, Huagang; Williams, Benjamin B.; Swartz, Harold

    2011-01-01

    Tumor hypoxia plays a vital role in therapeutic resistance. Consequently, measurements of tumor pO2 could be used to optimize the outcome of oxygen-dependent therapies, such as, chemoradiation. However, the potential optimizations are restricted by the lack of methods to repeatedly and quantitatively assess tumor pO2 during therapies, particularly in gliomas. We describe the procedures for repeated measurements of orthotopic glioma pO2 by multi-site electron paramagnetic resonance (EPR) oximetry. This oximetry approach provides simultaneous measurements of pO2 at more than one site in the glioma and contralateral cerebral tissue. The pO2 of intracerebral 9L, C6, F98 and U251 tumors, as well as contralateral brain, were measured repeatedly for five consecutive days. The 9L glioma was well oxygenated with pO2 of 27 - 36 mm Hg, while C6, F98 and U251 glioma were hypoxic with pO2 of 7 - 12 mm Hg. The potential of multi-site EPR oximetry to assess temporal changes in tissue pO2 was investigated in rats breathing 100% O2. A significant increase in F98 tumor and contralateral brain pO2 was observed on day 1 and day 2, however, glioma oxygenation declined on subsequent days. In conclusion, EPR oximetry provides the capability to repeatedly assess temporal changes in orthotopic glioma pO2. This information could be used to test and optimize the methods being developed to modulate tumor hypoxia. Furthermore, EPR oximetry could be potentially used to enhance the outcome of chemoradiation by scheduling treatments at times of increase in glioma pO2. PMID:22079559

  5. Clinical EPR: Unique Opportunities and Some Challenges

    Science.gov (United States)

    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

  6. Studied by electron paramagnetic resonance (EPR) of polymethyl methacrylate (PMMA) irradiated with gamma photons from cobalt 60

    International Nuclear Information System (INIS)

    Jalali, Hajer

    2013-01-01

    Ionizing radiation is radiation able to deposit enough energy in the material through which they pass to create ionization. These ionizing radiations, when mastered, have many practical uses beneficial (areas of health, industry ...). Gamma rays are emitted by radioactive nuclei. The objective of our work is the study of polymethyl methacrylate (PMMA) irradiated by gamma photons from cobalt-60. To study the technique of radio spectroscopy (9 to 10Hz) electron paramagnetic resonance EPR is used. This technique is specific to characterize transient free radicals involved in chemical reactions such as oxidation, combustion, polymerization reactions ... We analyzed the EPR spectra three batch KS, EB, and JF our dosimeter according to the dose (high and low) and showed that the dosimetric response can be represented in exponential form (high dose) and linear form (low dose). We also studied the kinetics of decay of the EPR signal as a function of time (fading) and showed that the responses relating to stabilize after 20 min of irradiation.

  7. Medical application of EPR

    International Nuclear Information System (INIS)

    Eichhoff, Uwe; Hoefer, Peter

    2015-01-01

    Selected applications of continuous-wave EPR in medicine are reviewed. This includes detection of reactive oxygen and nitrogen species, pH measurements and oxymetry. Applications of EPR imaging are demonstrated on selected examples and future developments to faster imaging methods are discussed

  8. EPR oxygen imaging and hyperpolarized (13) C MRI of pyruvate metabolism as noninvasive biomarkers of tumor treatment response to a glycolysis inhibitor 3-bromopyruvate

    DEFF Research Database (Denmark)

    Matsumoto, Shingo; Saito, Keita; Yasui, Hironobu

    2013-01-01

    The hypoxic nature of tumors results in treatment resistance and poor prognosis. To spare limited oxygen for more crucial pathways, hypoxic cancerous cells suppress mitochondrial oxidative phosphorylation and promote glycolysis for energy production. Thereby, inhibition of glycolysis has...... the potential to overcome treatment resistance of hypoxic tumors. Here, EPR imaging was used to evaluate oxygen dependent efficacy on hypoxia-sensitive drug. The small molecule 3-bromopyruvate blocks glycolysis pathway by inhibiting hypoxia inducible enzymes and enhanced cytotoxicity of 3-bromopyruvate under...

  9. Oxygen-related 1-platinum defects in silicon: An electron paramagnetic resonance study

    Science.gov (United States)

    Juda, U.; Scheerer, O.; Höhne, M.; Riemann, H.; Schilling, H.-J.; Donecker, J.; Gerhardt, A.

    1996-09-01

    A monoclinic 1-platinum defect recently detected was investigated more thoroughly by electron paramagnetic resonance (EPR). The defect is one of the dominating defects in platinum doped silicon. With a perfect reproducibility it is observed in samples prepared from n-type silicon as well as from p-type silicon, in float zone (FZ) silicon as well as in Czochralski (Cz) silicon. Its concentration varies with the conditions of preparation and nearly reaches that of isolated substitutional platinum in Cz silicon annealed for 2 h at 540 °C after quenching from the temperature of platinum diffusion. Because of its concentration which in Cz-Si exceeds that in FZ-Si the defect is assumed to be oxygen-related though a hyperfine structure with 17O could not be resolved. The defect causes a level close to the valence band. This is concluded from variations of the Fermi level and from a discussion of the spin Hamiltonian parameters. In photo-EPR experiments the defect is coupled to recently detected acceptorlike self-interstitial related defects (SIRDs); their level position turns out to be near-midgap. These defects belong to the lifetime limiting defects in Pt-doped Si.

  10. Phenolic composition and related antioxidant properties in differently colored lettuces: a study by electron paramagnetic resonance (EPR) kinetics.

    Science.gov (United States)

    Pérez-López, Usue; Pinzino, Calogero; Quartacci, Mike Frank; Ranieri, Annamaria; Sgherri, Cristina

    2014-12-10

    Differently colored lettuce (Lactuca sativa L.) cultivars (green, green/red, and red) were studied to correlate their phenolic composition with their antioxidant kinetic behavior. Electron paramagnetic resonance (EPR) was employed to monitor decay kinetics of 1,1-diphenyl-2-picrylhydrazyl (DPPH(•)), which allowed the identification of three differently paced antioxidants. The results showed that as long as lettuce had higher red pigmentation, the hydrophilic antioxidant capacity increased together with the contents in free and conjugated phenolic acids, free and conjugated flavonoids, and anthocyanins. EPR allowed the identification of slow-rate antioxidants in green and green/red cultivars, intermediate-rate antioxidants in green, green/red, and red cultivars, and fast-rate antioxidants in green/red and red cultivars. At present, the different kinetic behaviors cannot be attributed to a specific antioxidant, but it is suggested that the flavonoid quercetin accounted for the majority of the intermediate-rate antioxidants, whereas the anthocyanins accounted for the majority of the fast-rate antioxidants.

  11. Demonstration using EPR spin-trapping of an oxygen-dependent, carbon-centered free radical generated by soybean lipoxygenase

    International Nuclear Information System (INIS)

    Carpenter, M.F.; Smith, F.L.

    1986-01-01

    Purified prostaglandin synthase produces a carbon-centered, oxygen-dependent free radical which they have shown forms a spin-trapped adduct with 4-POBN and has characteristic hyperfine spin coupling constants (hfsc). As production of this radical is cyclooxygenase-dependent, additional studies on radical production were done using soybean lipoxygenase. The latter generates a lipid substrate-derived free radical trapped by the EPR spin trap 4-POBN [α-(4-pyridyl 1-oxide)N-tert-butyl nitrone]. With linoleate as substrate, the hfsc are a/sub N/ = 15.5 G, a/sub β//sup H/ = 2.7 G. This signal is inhibited by ETYA, various antioxidants and heat inactivation of the enzyme. Additional hfsc are not seen when the enzyme is incubated in an 17 O 2 atmosphere, but the signal is inhibited by anaerobeosis. Substitution of 13 C 18 carbon free fatty acids from Chlorella pyrenoisdosa for linoleate produces 2 new lines for each of the original 6 observed with 12 C substrate; the new spectrum has hfsc of a/sub N/ = 16.0 G, a/sub β//sup H/ = 2.4 G, a/sub β/ 13 C = 4.2 G. This demonstrates that the radical is carbon centered and oxygen-dependent and appears not to be the same radical formed by enzymic hydrogen abstraction from the lipid substrate. This radical and the prostaglandin synthase-dependent radical appear to be nearly identical

  12. In vivo evidence of methamphetamine induced attenuation of brain tissue oxygenation as measured by EPR oximetry

    International Nuclear Information System (INIS)

    Weaver, John; Yang, Yirong; Purvis, Rebecca; Weatherwax, Theodore; Rosen, Gerald M.; Liu, Ke Jian

    2014-01-01

    Abuse of methamphetamine (METH) is a major and significant societal problem in the US, as a number of studies have suggested that METH is associated with increased cerebrovascular events, hemorrhage or vasospasm. Although cellular and molecular mechanisms involved in METH-induced toxicity are not completely understood, changes in brain O 2 may play an important role and contribute to METH-induced neurotoxicity including dopaminergic receptor degradation. Given that O 2 is the terminal electron acceptor for many enzymes that are important in brain function, the impact of METH on brain tissue pO 2 in vivo remains largely uncharacterized. This study investigated striatal tissue pO 2 changes in male C57BL/6 mice (16–20 g) following METH administration using EPR oximetry, a highly sensitive modality to measure pO 2 in vivo, in situ and in real time. We demonstrate that 20 min after a single injection of METH (8 mg/kg i.v.), the striatal pO 2 was reduced to 81% of the pretreatment level and exposure to METH for 3 consecutive days further attenuated striatal pO 2 to 64%. More importantly, pO 2 did not recover fully to control levels even 24 h after administration of a single dose of METH and continual exposure to METH exacerbates the condition. We also show a reduction in cerebral blood flow associated with a decreased brain pO 2 indicating an ischemic condition. Our findings suggests that administration of METH can attenuate brain tissue pO 2 , which may lead to hypoxic insult, thus a risk factor for METH-induced brain injury and the development of stroke in young adults. - Highlights: • Explored striatal tissue pO 2 in vivo after METH administration by EPR oximetry. • pO 2 was reduced by 81% after a single dose and 64% after 3 consecutive daily doses. • pO 2 did not recover fully to control levels even 24 h after a single dose. • Decrease in brain tissue pO 2 may be associated with a decrease in CBF. • Administration of methamphetamine may lead to hypoxic

  13. In vivo evidence of methamphetamine induced attenuation of brain tissue oxygenation as measured by EPR oximetry

    Energy Technology Data Exchange (ETDEWEB)

    Weaver, John, E-mail: jmweaver@salud.unm.edu [Center of Biomedical Research Excellence, College of Pharmacy, University of New Mexico Health Sciences Center, Albuquerque, NM 87131 (United States); Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico Health Sciences Center, Albuquerque, NM 87131 (United States); Yang, Yirong [Center of Biomedical Research Excellence, College of Pharmacy, University of New Mexico Health Sciences Center, Albuquerque, NM 87131 (United States); Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico Health Sciences Center, Albuquerque, NM 87131 (United States); Purvis, Rebecca [Center of Biomedical Research Excellence, College of Pharmacy, University of New Mexico Health Sciences Center, Albuquerque, NM 87131 (United States); Department of Neurology, University of New Mexico Health Sciences Center, Albuquerque, NM 87131 (United States); Weatherwax, Theodore [Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico Health Sciences Center, Albuquerque, NM 87131 (United States); Rosen, Gerald M. [Center for Biomedical Engineering and Technology, University of Maryland, Baltimore, MD 21201 (United States); Center for EPR Imaging In Vivo Physiology, University of Maryland, Baltimore, MD 21201 (United States); Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD 21201 (United States); Liu, Ke Jian [Center of Biomedical Research Excellence, College of Pharmacy, University of New Mexico Health Sciences Center, Albuquerque, NM 87131 (United States); Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico Health Sciences Center, Albuquerque, NM 87131 (United States); Department of Neurology, University of New Mexico Health Sciences Center, Albuquerque, NM 87131 (United States)

    2014-03-01

    Abuse of methamphetamine (METH) is a major and significant societal problem in the US, as a number of studies have suggested that METH is associated with increased cerebrovascular events, hemorrhage or vasospasm. Although cellular and molecular mechanisms involved in METH-induced toxicity are not completely understood, changes in brain O{sub 2} may play an important role and contribute to METH-induced neurotoxicity including dopaminergic receptor degradation. Given that O{sub 2} is the terminal electron acceptor for many enzymes that are important in brain function, the impact of METH on brain tissue pO{sub 2}in vivo remains largely uncharacterized. This study investigated striatal tissue pO{sub 2} changes in male C57BL/6 mice (16–20 g) following METH administration using EPR oximetry, a highly sensitive modality to measure pO{sub 2}in vivo, in situ and in real time. We demonstrate that 20 min after a single injection of METH (8 mg/kg i.v.), the striatal pO{sub 2} was reduced to 81% of the pretreatment level and exposure to METH for 3 consecutive days further attenuated striatal pO{sub 2} to 64%. More importantly, pO{sub 2} did not recover fully to control levels even 24 h after administration of a single dose of METH and continual exposure to METH exacerbates the condition. We also show a reduction in cerebral blood flow associated with a decreased brain pO{sub 2} indicating an ischemic condition. Our findings suggests that administration of METH can attenuate brain tissue pO{sub 2}, which may lead to hypoxic insult, thus a risk factor for METH-induced brain injury and the development of stroke in young adults. - Highlights: • Explored striatal tissue pO{sub 2}in vivo after METH administration by EPR oximetry. • pO{sub 2} was reduced by 81% after a single dose and 64% after 3 consecutive daily doses. • pO{sub 2} did not recover fully to control levels even 24 h after a single dose. • Decrease in brain tissue pO{sub 2} may be associated with a decrease in

  14. A dozen useful tips on how to minimise the influence of sources of error in quantitative electron paramagnetic resonance (EPR) spectroscopy-A review

    International Nuclear Information System (INIS)

    Mazur, Milan

    2006-01-01

    The principal and the most important error sources in quantitative electron paramagnetic resonance (EPR) measurements arising from sample-associated factors are the influence of the variation of the sample material (dielectric constant), sample size and shape, sample tube wall thickness, and sample orientation and positioning within the microwave cavity on the EPR signal intensity. Variation in these parameters can cause significant and serious errors in the primary phase of quantitative EPR analysis (i.e., data acquisition). The primary aim of this review is to provide useful suggestions, recommendations and simple procedures to minimise the influence of such primary error sources in quantitative EPR measurements. According to the literature, as well as results obtained in our EPR laboratory, the following are recommendations for samples, which are compared in quantitative EPR studies: (i) the shape of all samples should be identical; (ii) the position of the sample/reference in the cavity should be identical; (iii) a special alignment procedure for precise sample positioning within the cavity should be adopted; (iv) a special/consistent procedure for sample packing for a powder material should be used; (v) the wall thickness of sample tubes should be identical; (vi) the shape and wall thickness of quartz Dewars, where used, should be identical; (vii) where possible a double TE 104 cavity should be used in quantitative EPR spectroscopy; (viii) the dielectric properties of unknown and standard samples should be as close as possible; (ix) sample length less than double the cavity length should be used; (x) the optimised sample geometry for the X-band cavity is a 30 mm-length capillary with i.d. less then 1.5 mm; (xi) use of commercially distributed software for post-recording spectra manipulation is a basic necessity; and (xii) the sample and laboratory temperature should be kept constant during measurements. When the above recommendations and procedures were used

  15. Estimation of mean and median pO2 values for a composite EPR spectrum.

    Science.gov (United States)

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

    2008-06-01

    Electron paramagnetic resonance (EPR)-based oximetry is capable of quantifying oxygen content in samples. However, for a heterogeneous environment with multiple pO2 values, peak-to-peak linewidth of the composite EPR lineshape does not provide a reliable estimate of the overall pO2 in the sample. The estimate, depending on the heterogeneity, can be severely biased towards narrow components. To address this issue, we suggest a postprocessing method to recover the linewidth histogram which can be used in estimating meaningful parameters, such as the mean and median pO2 values. This information, although not as comprehensive as obtained by EPR spectral-spatial imaging, goes beyond what can be generally achieved with conventional EPR spectroscopy. Substantially shorter acquisition times, in comparison to EPR imaging, may prompt its use in clinically relevant models. For validation, simulation and EPR experiment data are presented.

  16. Noninvasive in vivo oximetric imaging by radiofrequency FT EPR

    NARCIS (Netherlands)

    Subramanian, S; Yamada, K; Irie, A; Murugesan, R; Cook, JA; Devasahayam, N; Van Dam, GM; Mitchell, JB; Krishna, MC

    A novel method, called relaxo-oximetry, for rapid spatially resolved in vivo measurements of oxygen concentration using time-domain radiofrequency (RF) electron paramagnetic resonance (EPR) is described. Time-domain data from triaryl methyl (TAM)-based single-electron contrast agents were processed

  17. Electronic paramagnetic resonance (EPR) of spices treated by gamma irradiation; Ressonancia paramagnetica eletronica (RPE) aplicada a analise de especiarias irradiadas (com radiacao gama)

    Energy Technology Data Exchange (ETDEWEB)

    Leal, Alexandre Soares; Rodrigues, Rogerio Rivail, E-mail: asleal@cdtn.b [Centro de Desenvolvimento de Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil). Serv. de Reator e Irradiacoes; Krambrock, Klaus; Guedes, Kassilio [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil)

    2004-07-15

    The treatment of food by ionizing radiation is a method that has been increased in many countries in substitution for the use of chemical products. The knowledge of safe and reliable techniques of detection of irradiated food is a factor that can contribute to the largest acceptance for the consuming market. This work presents the electron paramagnetic resonance (EPR) as method of detection of the irradiated spices rosemary and cilantro. The obtained results indicate that EPR can be used satisfactorily for that group of victuals in the identification of irradiated species and in the determination of the received dose. (author)

  18. In vivo evidence of methamphetamine induced attenuation of brain tissue oxygenation as measured by EPR oximetry

    Science.gov (United States)

    Weaver, John; Yang, Yirong; Purvis, Rebecca; Weatherwax, Theodore; Rosen, Gerald M.; Liu, Ke Jian

    2014-01-01

    Abuse of methamphetamine (METH) is a major and significant societal problem in the US, as a number of studies have suggested that METH is associated with increased cerebrovascular events, hemorrhage or vasospasm. Although cellular and molecular mechanisms involved in METH-induced toxicity are not completely understood, changes in brain O2 may play an important role and contribute to METH-induced neurotoxicity including dopaminergic receptor degradation. Given that O2 is the terminal electron acceptor for many enzymes that are important in brain function, the impact of METH on brain tissue pO2 in vivo remains largely uncharacterized. This study investigated striatal tissue pO2 changes in male C57BL/6 mice (16–20g) following METH administration using EPR oximetry, a highly sensitive modality to measure pO2 in vivo, in situ and in real time. We demonstrate that 20 min after a single injection of METH (8 mg/kg i.v.), the striatal pO2 was reduced to 81% of the pretreatment level and exposure to METH for 3 consecutive days further attenuated striatal pO2 to 64%. More importantly, pO2 did not recover fully to control levels even 24 hrs after administration of a single dose of METH. and continual exposure to METH exacerbates the condition. We also show a reduction in cerebral blood flow associated with a decreased brain pO2 indicating an ischemic condition. Our findings suggests that administration of METH can attenuate brain tissue pO2, which may lead to hypoxic insult, thus a risk factor for METH-induced brain injury and the development of stroke in young adults. PMID:24412707

  19. Electron paramagnetic resonance radiation dosimetry: possible inorganic alternatives to the EPR/alanine dosimeter

    International Nuclear Information System (INIS)

    Keizer, P.N.; Morton, J.R.; Preston, K.F.

    1991-01-01

    The intensity of the EPR spectrum of γ-irradiated L-α-alanine has been accepted by the International Atomic Energy Agency as a secondary standard for high-dose (10-100 000 Gy) dosimetry. The alanine dosimeter is not without its disadvantages, however, and in this article alternative EPR dosimeters are explored. These include SO 3 - in irradiated K 2 CH 2 (SO 3 ) 2 and CO 2 - in irradiated sodium formate (NaHCO 2 ), both of which have some advantages over CH 3 CHCO 2 - in L-α-alanine. Using as a readout parameter the peak-to-peak excursion of the strongest line, these systems have a four-fold sensitivity advantage over alanine. The radicals SO 3 - and CO 2 - are, moreover, found in a wide variety of matrices, and it may be possible to find one in which they are even stronger. The need to discover a dosimeter material sensitive enough to function in the 'clinical' dose range (below 10 Gy) is emphasized. (author)

  20. Brain magnetic resonance imaging with contrast dependent on blood oxygenation

    International Nuclear Information System (INIS)

    Ogawa, S.; Lee, T.M.; Kay, A.R.; Tank, D.W.

    1990-01-01

    Paramagnetic deoxyhemoglobin in venous blood is a naturally occurring contrast agent for magnetic resonance imaging (MRI). By accentuating the effects of this agent through the use of gradient-echo techniques in high yields, the authors demonstrate in vivo images of brain microvasculature with image contrast reflecting the blood oxygen level. This blood oxygenation level-dependent (BOLD) contrast follows blood oxygen changes induced by anesthetics, by insulin-induced hypoglycemia, and by inhaled gas mixtures that alter metabolic demand or blood flow. The results suggest that BOLD contrast can be used to provide in vivo real-time maps of blood oxygenation in the brain under normal physiological conditions. BOLD contrast adds an additional feature to magnetic resonance imaging and complement other techniques that are attempting to provide position emission tomography-like measurements related to regional neural activity

  1. A passive dual-circulator based transmit/receive switch for use with reflection resonators in pulse EPR

    Science.gov (United States)

    Subramanian, V. S.; Epel, Boris; Mailer, Colin; Halpern, Howard J.

    2009-01-01

    In order to protect the low noise amplifier (LNA) in the receive arm of a pulsed 250 MHz EPR bridge, it is necessary to install as much isolation as possible between the power exciting the spin system and the LNA when high power is present in the receive arm of the bridge, while allowing the voltage induced by the magnetization in the spin sample to be passed undistorted and undiminished to the LNA once power is reduced below the level that can cause a LNA damage. We discuss a combination of techniques to accomplish this involving the power-routing circulator in the bridge, a second circulator acting as an isolator with passive shunt PIN diodes immediately following the second circulator. The low resistance of the forward biased PIN diode passively generates an impedance mismatch at the second circulator output port during the high power excitation pulse and resonator ring down. The mismatch reflects the high power to the remaining port of the second circulator, dumping it into a system impedance matched load. Only when the power diminishes below the diode conduction threshold will the resistance of the PIN diode rise to a value much higher than the system impedance. This brings the device into conduction mode. We find that the present design passively limits the output power to 14 dBm independent of the input power. For high input power levels the isolation may exceed 60 dB. This level of isolation is sufficient to fully protect the LNA of pulse EPR bridge. PMID:20052312

  2. Reactive oxygen species' role in endothelial dysfunction by electron paramagnetic resonance

    Science.gov (United States)

    Wassall, Cynthia D.

    The endothelium is a single layer of cells lining the arteries and is involved in many physiological reactions which are responsible for vascular tone. Free radicals are important participants in these chemical reactions in the endothelium. Here we quantify free radicals, ex vivo, in biological tissue with continuous wave electron paramagnetic resonance (EPR). In all of the experiments in this thesis, we use a novel EPR spin trapping technique that has been developed for tissue segments. EPR spin trapping is often considered the 'gold standard' in reactive oxygen species (ROS) detection because of its sensitivity and non-invasive nature. In all experiments, tissue was placed in physiological saline solution with 190-mM PBN (N-tert -butyl-α-phenylnitrone), 10% by volume dimethyl-sulphoxide (DMSO) for cryopreservation, and incubated in the dark for between 30 minutes up to 2 hours at 37°C while gently being stirred. Tissue and supernatant were then loaded into a syringe and frozen at -80°C until EPR analysis. In our experiments, the EPR spectra were normalized with respect to tissue volume. Conducting experiments at liquid nitrogen temperature leads to some experimental advantages. The freezing of the spin adducts renders them stable over a longer period, which allows ample time to analyze tissue samples for ROS. The dielectric constant of ice is greatly reduced over its liquid counterpart; this property of water enables larger sample volumes to be inserted into the EPR cavity without overloading it and leads to enhanced signal detection. Due to Maxwell-Boltzmann statistics, the population difference goes up as the temperature goes down, so this phenomenon enhances the signal intensity as well. With the 'gold standard' assertion in mind, we investigated whether slicing tissue to assay ROS that is commonly used in fluorescence experiments will show more free radical generation than tissue of a similar volume that remains unsliced. Sliced tissue exhibited a 76

  3. Comparison of 250 MHz electron spin echo and continuous wave oxygen EPR imaging methods for in vivo applications

    Science.gov (United States)

    Epel, Boris; Sundramoorthy, Subramanian V.; Barth, Eugene D.; Mailer, Colin; Halpern, Howard J.

    2011-01-01

    Purpose: The authors compare two electron paramagnetic resonance imaging modalities at 250 MHz to determine advantages and disadvantages of those modalities for in vivo oxygen imaging. Methods: Electron spin echo (ESE) and continuous wave (CW) methodologies were used to obtain three-dimensional images of a narrow linewidth, water soluble, nontoxic oxygen-sensitive trityl molecule OX063 in vitro and in vivo. The authors also examined sequential images obtained from the same animal injected intravenously with trityl spin probe to determine temporal stability of methodologies. Results: A study of phantoms with different oxygen concentrations revealed a threefold advantage of the ESE methodology in terms of reduced imaging time and more precise oxygen resolution for samples with less than 70 torr oxygen partial pressure. Above∼100 torr, CW performed better. The images produced by both methodologies showed pO2 distributions with similar mean values. However, ESE images demonstrated superior performance in low pO2 regions while missing voxels in high pO2 regions. Conclusions: ESE and CW have different areas of applicability. ESE is superior for hypoxia studies in tumors. PMID:21626937

  4. Oxygen-enhanced magnetic resonance ventilation imaging of lung

    International Nuclear Information System (INIS)

    Ohno, Yoshiharu; Chen Qun; Hatabu, Hiroto

    2001-01-01

    The oxygen-enhanced magnetic resonance (MR) ventilation imaging is a new technique, and the full extent of its physiological significance has not been elucidated. This review article includes background on (1) respiratory physiology; (2) mechanism and optimization of oxygen-enhanced MR imaging technique; (3) recent applications in animal and human models; and (4) merits and demerits of the technique in comparison with hyperpolarized noble gas MR ventilation imaging. Application of oxygen-enhanced MR ventilation imaging to patients with pulmonary diseases has been very limited. However, we believe that further basic studies, as well as clinical applications of this new technique will define the real significance of oxygen-enhanced MR ventilation imaging in the future of pulmonary functional imaging and its usefulness for diagnostic radiology

  5. Monitoring of blood oxygenation in brain by resonance Raman spectroscopy

    DEFF Research Database (Denmark)

    Brazhe, Nadezda A; Thomsen, Kirsten; Lønstrup, Micael

    2018-01-01

    Blood oxygenation in cerebral vessels is an essential parameter to evaluate brain function and to investigate the coupling between local blood flow and neuronal activity. We apply resonance Raman spectroscopy in vivo to study hemoglobin oxygenation in cortex vessels of anesthetized ventilated mice....... We demonstrate that the pairs of Raman peaks at 1355 and1375 cm-1(symmetric vibrations of pyrrol half-rings in the heme molecule), 1552 and 1585 cm-1and 1602 and 1638 cm-1(vibrations of methine bridges in heme molecule) are reliable markers for quantitative estimation of the relative amount...

  6. Quantitative EPR A Practitioners Guide

    CERN Document Server

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

    2010-01-01

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

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

    Science.gov (United States)

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

    2010-01-01

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

  8. Contribution of Harold M. Swartz to In Vivo EPR and EPR Dosimetry.

    Science.gov (United States)

    Gallez, Bernard

    2016-12-01

    In 2015, we are celebrating half a century of research in the application of Electron Paramagnetic Resonance (EPR) as a biodosimetry tool to evaluate the dose received by irradiated people. During the EPR Biodose 2015 meeting, a special session was organized to acknowledge the pioneering contribution of Harold M. (Hal) Swartz in the field. The article summarizes his main contribution in physiology and medicine. Four emerging themes have been pursued continuously along his career since its beginning: (1) radiation biology; (2) oxygen and oxidation; (3) measuring physiology in vivo; and (4) application of these measurements in clinical medicine. The common feature among all these different subjects has been the use of magnetic resonance techniques, especially EPR. In this article, you will find an impressionist portrait of Hal Swartz with the description of the 'making of' this pioneer, a time-line perspective on his career with the creation of three National Institutes of Health-funded EPR centers, a topic-oriented perspective on his career with a description of his major contributions to Science, his role as a mentor and his influence on his academic children, his active role as founder of scientific societies and organizer of scientific meetings, and the well-deserved international recognition received so far. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  9. Contribution of Harold M. Swartz to In Vivo EPR and EPR Dosimetry

    International Nuclear Information System (INIS)

    Gallez, Bernard

    2016-01-01

    In 2015, we are celebrating half a century of research in the application of Electron Paramagnetic Resonance (EPR) as a biodosimetry tool to evaluate the dose received by irradiated people. During the EPR Biodose 2015 meeting, a special session was organized to acknowledge the pioneering contribution of Harold M. (Hal) Swartz in the field. The article summarizes his main contribution in physiology and medicine. Four emerging themes have been pursued continuously along his career since its beginning: (1) radiation biology; (2) oxygen and oxidation; (3) measuring physiology in vivo; and (4) application of these measurements in clinical medicine. The common feature among all these different subjects has been the use of magnetic resonance techniques, especially EPR. In this article, you will find an impressionist portrait of Hal Swartz with the description of the 'making of' this pioneer, a time-line perspective on his career with the creation of three National Institutes of Health-funded EPR centers, a topic-oriented perspective on his career with a description of his major contributions to Science, his role as a mentor and his influence on his academic children, his active role as founder of scientific societies and organizer of scientific meetings, and the well-deserved international recognition received so far. (author)

  10. Use of spin traps to detect superoxide production in living cells by electron paramagnetic resonance (EPR) spectroscopy.

    Science.gov (United States)

    Abbas, Kahina; Babić, Nikola; Peyrot, Fabienne

    2016-10-15

    Detection of superoxide produced by living cells has been an on-going challenge in biology for over forty years. Various methods have been proposed to address this issue, among which spin trapping with cyclic nitrones coupled to EPR spectroscopy, the gold standard for detection of radicals. This technique is based on the nucleophilic addition of superoxide to a diamagnetic cyclic nitrone, referred to as the spin trap, and the formation of a spin adduct, i.e. a persistent radical with a characteristic EPR spectrum. The first application of spin trapping to living cells dates back 1979. Since then, considerable improvements of the method have been achieved both in the structures of the spin traps, the EPR methodology, and the design of the experiments including appropriate controls. Here, we will concentrate on technical aspects of the spin trapping/EPR technique, delineating recent breakthroughs, inherent limitations, and potential artifacts. Copyright © 2016 Elsevier Inc. All rights reserved.

  11. Effect of absorbed dose and storage length on electron paramagnetic resonance (EPR) signal strength in irradiated alfalfa seeds

    International Nuclear Information System (INIS)

    Li Naining

    2006-01-01

    A kind of alfalfa seeds was irradiated by 1, 2, 3, 4 and 5 kGy at a dose rate of 6.288 kGy·h -1 in a self-shielded irradiator of 137 Cs gamma rays. The EPR spectra, which were measured subsequently between 0.3401 and 0.3501 T, showed that there was a direct proportional relationship between the EPR signal strength of free radicals produced by gamma irradiation in the alfalfa seeds and absorbed dose. The first derivative EPR spectra of the alfalfa seeds were very clear and easy to identify. However, the EPR signal strength of the peak-to-peak amplitude decreased rapidly and most of them decayed beyond 50% within 3 days after the seeds were irradiated. It tended to stabilize after half a month since the seeds were irradiated. the differences of the EPR signal strength between the irradiated and unirradiated alfalfa seeds still remained. All seeds were stored at ambient temperature for more than 3 months. Therefore, using EPR spectrometry technique to measure free radicals in alfalfa seeds as a means to determine whether the seeds have been irradiated or not is feasible, relatively fast and simple. (authors)

  12. Localization of dexamethasone within dendritic core-multishell (CMS) nanoparticles and skin penetration properties studied by multi-frequency electron paramagnetic resonance (EPR) spectroscopy.

    Science.gov (United States)

    Saeidpour, S; Lohan, S B; Anske, M; Unbehauen, M; Fleige, E; Haag, R; Meinke, M C; Bittl, R; Teutloff, C

    2017-07-01

    The skin and especially the stratum corneum (SC) act as a barrier and protect epidermal cells and thus the whole body against xenobiotica of the external environment. Topical skin treatment requires an efficient drug delivery system (DDS). Polymer-based nanocarriers represent novel transport vehicles for dermal application of drugs. In this study dendritic core-multishell (CMS) nanoparticles were investigated as promising candidates. CMS nanoparticles were loaded with a drug (analogue) and were applied to penetration studies of skin. We determined by dual-frequency electron paramagnetic resonance (EPR) how dexamethasone (Dx) labelled with 3-carboxy-2,2,5,5-tetramethyl-1-pyrrolidinyloxy (PCA) is associated with the CMS. The micro-environment of the drug loaded to CMS nanoparticles was investigated by pulsed high-field EPR at cryogenic temperature, making use of the fact that magnetic parameters (g-, A-matrices, and spin-lattice relaxation time) represent specific probes for the micro-environment. Additionally, the rotational correlation time of spin-labelled Dx was probed by continuous wave EPR at ambient temperature, which provides independent information on the drug environment. Furthermore, the penetration depth of Dx into the stratum corneum of porcine skin after different topical applications was investigated. The location of Dx in the CMS nanoparticles is revealed and the function of CMS as penetration enhancers for topical application is shown. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Detection of undistorted continuous wave (CW) electron paramagnetic resonance (EPR) spectra with non-adiabatic rapid sweep (NARS) of the magnetic field

    Science.gov (United States)

    Kittell, Aaron W.; Camenisch, Theodore G.; Ratke, Joseph J.; Sidabras, Jason W.; Hyde, James S.

    2011-01-01

    A continuous wave (CW) electron paramagnetic resonance (EPR) spectrum is typically displayed as the first harmonic response to the application of 100 kHz magnetic field modulation, which is used to enhance sensitivity by reducing the level of 1/f noise. However, magnetic field modulation of any amplitude causes spectral broadening and sacrifices EPR spectral intensity by at least a factor of two. In the work presented here, a CW rapid-scan spectroscopic technique that avoids these compromises and also provides a means of avoiding 1/f noise is developed. This technique, termed non-adiabatic rapid sweep (NARS) EPR, consists of repetitively sweeping the polarizing magnetic field in a linear manner over a spectral fragment with a small coil at a repetition rate that is sufficiently high that receiver noise, microwave phase noise, and environmental microphonics, each of which has 1/f characteristics, are overcome. Nevertheless, the rate of sweep is sufficiently slow that adiabatic responses are avoided and the spin system is always close to thermal equilibrium. The repetitively acquired spectra from the spectral fragment are averaged. Under these conditions, undistorted pure absorption spectra are obtained without broadening or loss of signal intensity. A digital filter such as a moving average is applied to remove high frequency noise, which is approximately equivalent in bandwidth to use of an integrating time constant in conventional field modulation with lock-in detection. Nitroxide spectra at L- and X-band are presented. PMID:21741868

  14. Electron paramagnetic resonance of radicals and metal complexes. 2. international conference of the Polish EPR Association. Warsaw 9-13 September 1996

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-12-31

    The conference of Electron Paramagnetic Resonance of Radicals and Metal Complexes has been held in Warsaw from 9 to 13 September 1996. It was the Second International Conference of the Polish EPR Association. The very extensive group of systems containing paramagnetic species has been studied by means of ESR or other magnetic techniques like ENDOR, Spin Echo etc. By radiation or photochemically generated radicals have been stabilized in low temperatures or being detected by means of very fast pulsed techniques. The chemical reactions, reaction kinetics of radicals as well as spin interaction with matrices have been studied and discussed. Over 100 lectures and posters have been presented.

  15. Electron paramagnetic resonance of radicals and metal complexes. 2. international conference of the Polish EPR Association. Warsaw 9-13 September 1996

    International Nuclear Information System (INIS)

    1996-01-01

    The conference of Electron Paramagnetic Resonance of Radicals and Metal Complexes has been held in Warsaw from 9 to 13 September 1996. It was the Second International Conference of the Polish EPR Association. The very extensive group of systems containing paramagnetic species has been studied by means of ESR or other magnetic techniques like ENDOR, Spin Echo etc. By radiation or photochemically generated radicals have been stabilized in low temperatures or being detected by means of very fast pulsed techniques. The chemical reactions, reaction kinetics of radicals as well as spin interaction with matrices have been studied and discussed. Over 100 lectures and posters have been presented

  16. Electron paramagnetic resonance of radicals and metal complexes. 2. international conference of the Polish EPR Association. Warsaw 9-13 September 1996

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-12-31

    The conference of Electron Paramagnetic Resonance of Radicals and Metal Complexes has been held in Warsaw from 9 to 13 September 1996. It was the Second International Conference of the Polish EPR Association. The very extensive group of systems containing paramagnetic species has been studied by means of ESR or other magnetic techniques like ENDOR, Spin Echo etc. By radiation or photochemically generated radicals have been stabilized in low temperatures or being detected by means of very fast pulsed techniques. The chemical reactions, reaction kinetics of radicals as well as spin interaction with matrices have been studied and discussed. Over 100 lectures and posters have been presented.

  17. Direct Measurements of Oxygen Gradients in Spheroid Culture System Using Electron Parametric Resonance Oximetry.

    Directory of Open Access Journals (Sweden)

    Laura M Langan

    Full Text Available Advanced in vitro culture from tissues of different origin includes three-dimensional (3D organoid micro structures that may mimic conditions in vivo. One example of simple 3D culture is spheroids; ball shaped structures typically used as liver and tumour models. Oxygen is critically important in physiological processes, but is difficult to quantify in 3D culture: and the question arises, how small does a spheroid have to be to have minimal micro-environment formation? This question is of particular importance in the growing field of 3D based models for toxicological assessment. Here, we describe a simple non-invasive approach modified for the quantitative measurement and subsequent evaluation of oxygen gradients in spheroids developed from a non-malignant fish cell line (i.e. RTG-2 cells using Electron Paramagnetic Resonance (EPR oximetry. Sonication of the paramagnetic probe Lithium phthalocyanine (LiPc allows for incorporation of probe particulates into spheroid during its formation. Spectra signal strength after incorporation of probe into spheroid indicated that a volume of 20 μl of probe (stock solution: 0.10 mg/mL is sufficient to provide a strong spectra across a range of spheroid sizes. The addition of non-toxic probes (that do not produce or consume oxygen report on oxygen diffusion throughout the spheroid as a function of size. We provide evidence supporting the use of this model over a range of initial cell seeding densities and spheroid sizes with the production of oxygen distribution as a function of these parameters. In our spheroid model, lower cell seeding densities (∼2,500 cells/spheroid and absolute size (118±32 μm allow control of factors such as pre-existing stresses (e.g. ∼ 2% normoxic/hypoxic interface for more accurate measurement of treatment response. The applied methodology provides an elegant, widely applicable approach to directly characterize spheroid (and other organoid cultures in biomedical and

  18. Dosimetry of an accident in mixed field (neutrons, photons) using the spectrometry by electronic paramagnetic resonance(EPR)

    International Nuclear Information System (INIS)

    Herve, M.L.

    2006-03-01

    In a radiological accident, the assessment of the dose received by the victim is relevant information for the therapeutic strategy. Two complementary dosimetric techniques based on physical means are used in routine practice in the laboratory: EPR spectroscopy performed on materials removed from the victim or gathered from the vicinity of the victim and Monte Carlo calculations. EPR dosimetry, has been used successfully several times in cases of photon or electron overexposures. Accidental exposure may also occur with a neutron component. The aim of this work is to investigate the potentiality of EPR dosimetry for mixed photon and neutron field exposure with different organic materials (ascorbic acid, sorbitol, glucose, galactose, fructose, mannose, lactose and sucrose). The influence of irradiation parameters (dose, dose rate, photon energy) and of environmental parameters (temperature of heating, light exposure) on the EPR signal amplitude was studied. To assess the neutron sensitivity, the materials were exposed to a mixed radiation field of experimental reactors with different neutron to photon ratios. The relative neutron sensitivity was found to range from 10% to 43% according to the materials. Prior knowledge of the ratio between the dose in samples measured by EPR spectrometry and organ or whole body dose obtained by calculations previously performed for these different configurations, makes it possible to give a first estimation of the dose received by the victim in a short delay. The second aim of this work is to provide data relevant for a quick assessment of the dose distribution in case of accidental overexposure based on EPR measurements performed on one or several points of the body. The study consists in determining by calculation the relation between the dose to the organs and whole body and the dose to specific points of the body, like teeth, bones or samples located in the pockets of victim clothes, for different external exposures corresponding

  19. Natural alpha recoil particle radiation and ionizing radiation sensitivities in quartz detected with EPR: implications for geochronometry

    International Nuclear Information System (INIS)

    Rink, W.J.; Odom, A.L.

    1991-01-01

    The electron paramagnetic resonance EPR signals in granitic quartz samples of known age are studied. Time-integrated alpha recoil activity and EPR signal intensity are more significantly correlated than sample age and EPR signal intensity. Neutron activation analysis for internal uranium and thorium in quartz are reported. Natural germanium EPR signals are observed in pegmatitic quartz samples and one granitic quartz. Pegmatitic quartz exhibits germanium EPR center growth competing strongly with E' center growth, apparently leading to depleted natural concentrations of E' centers. Calculations of lattice vacancy accumulation associated with alpha recoil damage are presented and compared with concentrations of paramagnetic oxygen vacancies in the quartz. Based on the results reported, the potential and problems associated with dating quartz are discussed, relating both to accumulated lattice damage and the additive dose methods. (author)

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

    Science.gov (United States)

    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.

  1. EPR oxygen imaging and hyperpolarized 13C MRI of pyruvate metabolism as non-invasive biomarkers of tumor treatment response to a glycolysis inhibitor 3-bromopyruvate

    Science.gov (United States)

    Matsumoto, Shingo; Saito, Keita; Yasui, Hironobu; Morris, H. Douglas; Munasinghe, Jeeva P.; Lizak, Martin; Merkle, Hellmut; Ardenkjaer-Larsen, Jan Henrik; Choudhuri, Rajani; Devasahayam, Nallathamby; Subramanian, Sankaran; Koretsky, Alan P.; Mitchell, James B.; Krishna, Murali C.

    2012-01-01

    The hypoxic nature of tumors results in treatment resistance and poor prognosis. To spare limited oxygen for more crucial pathways, hypoxic cancerous cells suppress mitochondrial oxidative phosphorylation, and promote glycolysis for energy production. Thereby, inhibition of glycolysis has the potential to overcome treatment resistance of hypoxic tumors. Here, EPR imaging was used to evaluate oxygen dependent efficacy on hypoxia-sensitive drug. The small molecule 3-bromopyruvate (3-BP) blocks glycolysis pathway by inhibiting hypoxia inducible enzymes, and enhanced cytotoxicity of 3-BP under hypoxic conditions has been reported in vitro. However, the efficacy of 3-BP was substantially attenuated in hypoxic tumor regions (pO2 < 10 mmHg) in vivo using squamous cell carcinoma (SCCVII)-bearing mouse model. Metabolic MRI studies using hyperpolarized 13C-labeled pyruvate showed that monocarboxylate transporter-1 (MCT1) is the major transporter for pyruvate and the analog 3-BP in SCCVII tumor. The discrepant results between in vitro and in vivo data were attributed to biphasic oxygen dependent expression of MCT1 in vivo. Expression of MCT1 was enhanced in moderately hypoxic (8–15 mmHg) tumor regions, but down regulated in severely hypoxic (< 5 mmHg) tumor regions. These results emphasize the importance of non-invasive imaging biomarkers to confirm the action of hypoxia-activated drugs. PMID:22692861

  2. EPR oxygen imaging and hyperpolarized 13C MRI of pyruvate metabolism as noninvasive biomarkers of tumor treatment response to a glycolysis inhibitor 3-bromopyruvate.

    Science.gov (United States)

    Matsumoto, Shingo; Saito, Keita; Yasui, Hironobu; Morris, H Douglas; Munasinghe, Jeeva P; Lizak, Martin; Merkle, Hellmut; Ardenkjaer-Larsen, Jan Henrik; Choudhuri, Rajani; Devasahayam, Nallathamby; Subramanian, Sankaran; Koretsky, Alan P; Mitchell, James B; Krishna, Murali C

    2013-05-01

    The hypoxic nature of tumors results in treatment resistance and poor prognosis. To spare limited oxygen for more crucial pathways, hypoxic cancerous cells suppress mitochondrial oxidative phosphorylation and promote glycolysis for energy production. Thereby, inhibition of glycolysis has the potential to overcome treatment resistance of hypoxic tumors. Here, EPR imaging was used to evaluate oxygen dependent efficacy on hypoxia-sensitive drug. The small molecule 3-bromopyruvate blocks glycolysis pathway by inhibiting hypoxia inducible enzymes and enhanced cytotoxicity of 3-bromopyruvate under hypoxic conditions has been reported in vitro. However, the efficacy of 3-bromopyruvate was substantially attenuated in hypoxic tumor regions (pO23-bromopyruvate in SCCVII tumor. The discrepant results between in vitro and in vivo data were attributed to biphasic oxygen dependent expression of monocarboxylate transporter-1 in vivo. Expression of monocarboxylate transporter-1 was enhanced in moderately hypoxic (8-15 mmHg) tumor regions but down regulated in severely hypoxic (<5 mmHg) tumor regions. These results emphasize the importance of noninvasive imaging biomarkers to confirm the action of hypoxia-activated drugs. Copyright © 2012 Wiley Periodicals, Inc.

  3. EPR-study of reversible oxygenation process of coordination compounds of cobalt(II) with S-substituted N/sup 1/,N/sup 4/-di(salicylidene)-isothiosemicarbazides

    Energy Technology Data Exchange (ETDEWEB)

    Gerbeleu, N.V.; Revenko, M.D.; Rusu, V.G.; Shames, A.T.

    1987-09-01

    The reaction between molecular oxygen and coordination compounds of cobalt(II) with S-substituted N/sup 1/,N/sup 4/-di(salicylidene)isothiosemicarbazides in dimethyl sulfoxide solution was studied by the EPR method. It was found that paramagnetic monomeric adducts and diamagnetic ..mu..-peroxo-dimers are formed. The spin-Hamiltonian parameters of the EPR spectra of the initial cobalt complexes, as well as of the paramagnetic adducts were determined. The nature of the Co-O/sub 2/ bond is discussed.

  4. The EPR reactor

    International Nuclear Information System (INIS)

    Lacoste, A.C.; Dupuy, Ph.; Gupta, O.; Perez, J.R.; Emond, D.; Cererino, G.; Rousseau, J.M.; Jeffroy, F.; Evrard, J.M.; Seiler, J.M.; Azarian, G.; Chaumont, B.; Dubail, A.; Fischer, M.; Tiippana, P.; Hyvarinen, J.; Zaleski, C.P.; Meritet, S.; Iglesias, F.; Vincent, C.; Massart, S.; Graillat, G.; Esteve, B.; Mansillon, Y.; Gatinol, C.; Carre, F.

    2005-01-01

    This document reviews economical and environmental aspects of the EPR project. The following topics are discussed: role and point of view of the French Nuclear Safety Authority on EPR, control of design and manufacturing of EPR by the French Nuclear Safety Authority, assessment by IRSN of EPR safety, research and development in support of EPR, STUK safety review of EPR design, standpoint on EPR, the place of EPR in the French energy policy, the place of EPR in EDF strategy, EPR spearhead of nuclear rebirth, the public debate, the local stakes concerning the building of EPR in France at Flamanville (Manche) and the research on fourth generation reactors. (A.L.B.)

  5. Inter-spin distance determination using L-band (1-2 GHz) non-adiabatic rapid sweep electron paramagnetic resonance (NARS EPR)

    Science.gov (United States)

    Kittell, Aaron W.; Hustedt, Eric J.; Hyde, James S.

    2014-01-01

    Site-directed spin-labeling electron paramagnetic resonance (SDSL EPR) provides insight into the local structure and motion of a spin probe strategically attached to a molecule. When a second spin is introduced to the system, macromolecular information can be obtained through measurement of inter-spin distances either by continuous wave (CW) or pulsed electron double resonance (ELDOR) techniques. If both methodologies are considered, inter-spin distances of 8 to 80 Å can be experimentally determined. However, there exists a region at the upper limit of the conventional X-band (9.5 GHz) CW technique and the lower limit of the four-pulse double electron-electron resonance (DEER) experiment where neither method is particularly reliable. The work presented here utilizes L-band (1.9 GHz) in combination with non-adiabatic rapid sweep (NARS) EPR to address this opportunity by increasing the upper limit of the CW technique. Because L-band linewidths are three to seven times narrower than those at X-band, dipolar broadenings that are small relative to the X-band inhomogeneous linewidth become observable, but the signal loss due to the frequency dependence of the Boltzmann factor, has made L-band especially challenging. NARS has been shown to increase sensitivity by a factor of five, and overcomes much of this loss, making L-band distance determination more feasible [1]. Two different systems are presented and distances of 18–30 Å have been experimentally determined at physiologically relevant temperatures. Measurements are in excellent agreement with a helical model and values determined by DEER. PMID:22750251

  6. Pharmaceutical applications of in vivo EPR

    International Nuclear Information System (INIS)

    Maeder, K.

    1998-01-01

    The aim of this article is to discuss the applications of in vivo EPR in the field of pharmacy. In addition to direct detection of free radical metabolites and measurement of oxygen, EPR can be used to characterize the mechanisms of drug release from biodegradable polymers. Unique information about drug concentration, the microenvironment (viscosity, polarity, pH) and biodistribution (by localized measurement or EPR Imaging) can be obtained. (author)

  7. Solid-support Electron Paramagnetic Resonance (EPR) Studies of Aβ40 Monomers Reveal a Structured State with Three Ordered Segments*

    Science.gov (United States)

    Gu, Lei; Ngo, Sam; Guo, Zhefeng

    2012-01-01

    Alzheimer disease is associated with the pathological accumulation of amyloid-β peptide (Aβ) in the brain. Soluble Aβ oligomers formed during early aggregation process are believed to be neurotoxins and causative agents in Alzheimer disease. Aβ monomer is the building block for amyloid assemblies. A comprehensive understanding of the structural features of Aβ monomer is crucial for delineating the mechanism of Aβ oligomerization. Here we investigated the structures of Aβ40 monomer using a solid-support approach, in which Aβ40 monomers are tethered on the solid support via an N-terminal His tag to prevent further aggregation. EPR spectra of tethered Aβ40 with spin labels at 18 different positions show that Aβ40 monomers adopt a completely disordered structure under denaturing conditions. Under native conditions, however, EPR spectra suggest that Aβ40 monomers adopt both a disordered state and a structured state. The structured state of Aβ40 monomer has three more ordered segments at 14–18, 29–30, and 38–40. Interactions between these segments may stabilize the structured state, which likely plays an important role in Aβ aggregation. PMID:22277652

  8. Monitoring Tumor Response to Carbogen Breathing by Oxygen-Sensitive Magnetic Resonance Parameters to Predict the Outcome of Radiation Therapy: A Preclinical Study

    Energy Technology Data Exchange (ETDEWEB)

    Cao-Pham, Thanh-Trang; Tran, Ly-Binh-An; Colliez, Florence; Joudiou, Nicolas [Université Catholique de Louvain, Louvain Drug Research Institute, Biomedical Magnetic Resonance Research Group, Brussels (Belgium); El Bachiri, Sabrina [Université Catholique de Louvain, IMMAQ Technological Platform, Methodology and Statistical Support, Louvain-la-Neuve (Belgium); Grégoire, Vincent [Université Catholique de Louvain, Institute of Experimental and Clinical Research, Center for Molecular Imaging, Radiotherapy and Oncology, Brussels (Belgium); Levêque, Philippe; Gallez, Bernard [Université Catholique de Louvain, Louvain Drug Research Institute, Biomedical Magnetic Resonance Research Group, Brussels (Belgium); Jordan, Bénédicte F., E-mail: benedicte.jordan@uclouvain.be [Université Catholique de Louvain, Louvain Drug Research Institute, Biomedical Magnetic Resonance Research Group, Brussels (Belgium)

    2016-09-01

    Purpose: In an effort to develop noninvasive in vivo methods for mapping tumor oxygenation, magnetic resonance (MR)-derived parameters are being considered, including global R{sub 1}, water R{sub 1}, lipids R{sub 1}, and R{sub 2}*. R{sub 1} is sensitive to dissolved molecular oxygen, whereas R{sub 2}* is sensitive to blood oxygenation, detecting changes in dHb. This work compares global R{sub 1}, water R{sub 1}, lipids R{sub 1}, and R{sub 2}* with pO{sub 2} assessed by electron paramagnetic resonance (EPR) oximetry, as potential markers of the outcome of radiation therapy (RT). Methods and Materials: R{sub 1}, R{sub 2}*, and EPR were performed on rhabdomyosarcoma and 9L-glioma tumor models, under air and carbogen breathing conditions (95% O{sub 2}, 5% CO{sub 2}). Because the models demonstrated different radiosensitivity properties toward carbogen, a growth delay (GD) assay was performed on the rhabdomyosarcoma model and a tumor control dose 50% (TCD50) was performed on the 9L-glioma model. Results: Magnetic resonance imaging oxygen-sensitive parameters detected the positive changes in oxygenation induced by carbogen within tumors. No consistent correlation was seen throughout the study between MR parameters and pO{sub 2}. Global and lipids R{sub 1} were found to be correlated to pO{sub 2} in the rhabdomyosarcoma model, whereas R{sub 2}* was found to be inversely correlated to pO{sub 2} in the 9L-glioma model (P=.05 and .03). Carbogen increased the TCD50 of 9L-glioma but did not increase the GD of rhabdomyosarcoma. Only R{sub 2}* was predictive (P<.05) for the curability of 9L-glioma at 40 Gy, a dose that showed a difference in response to RT between carbogen and air-breathing groups. {sup 18}F-FAZA positron emission tomography imaging has been shown to be a predictive marker under the same conditions. Conclusion: This work illustrates the sensitivity of oxygen-sensitive R{sub 1} and R{sub 2}* parameters to changes in tumor oxygenation. However, R{sub 1

  9. Monitoring Tumor Response to Carbogen Breathing by Oxygen-Sensitive Magnetic Resonance Parameters to Predict the Outcome of Radiation Therapy: A Preclinical Study

    International Nuclear Information System (INIS)

    Cao-Pham, Thanh-Trang; Tran, Ly-Binh-An; Colliez, Florence; Joudiou, Nicolas; El Bachiri, Sabrina; Grégoire, Vincent; Levêque, Philippe; Gallez, Bernard; Jordan, Bénédicte F.

    2016-01-01

    Purpose: In an effort to develop noninvasive in vivo methods for mapping tumor oxygenation, magnetic resonance (MR)-derived parameters are being considered, including global R_1, water R_1, lipids R_1, and R_2*. R_1 is sensitive to dissolved molecular oxygen, whereas R_2* is sensitive to blood oxygenation, detecting changes in dHb. This work compares global R_1, water R_1, lipids R_1, and R_2* with pO_2 assessed by electron paramagnetic resonance (EPR) oximetry, as potential markers of the outcome of radiation therapy (RT). Methods and Materials: R_1, R_2*, and EPR were performed on rhabdomyosarcoma and 9L-glioma tumor models, under air and carbogen breathing conditions (95% O_2, 5% CO_2). Because the models demonstrated different radiosensitivity properties toward carbogen, a growth delay (GD) assay was performed on the rhabdomyosarcoma model and a tumor control dose 50% (TCD50) was performed on the 9L-glioma model. Results: Magnetic resonance imaging oxygen-sensitive parameters detected the positive changes in oxygenation induced by carbogen within tumors. No consistent correlation was seen throughout the study between MR parameters and pO_2. Global and lipids R_1 were found to be correlated to pO_2 in the rhabdomyosarcoma model, whereas R_2* was found to be inversely correlated to pO_2 in the 9L-glioma model (P=.05 and .03). Carbogen increased the TCD50 of 9L-glioma but did not increase the GD of rhabdomyosarcoma. Only R_2* was predictive (P<.05) for the curability of 9L-glioma at 40 Gy, a dose that showed a difference in response to RT between carbogen and air-breathing groups. "1"8F-FAZA positron emission tomography imaging has been shown to be a predictive marker under the same conditions. Conclusion: This work illustrates the sensitivity of oxygen-sensitive R_1 and R_2* parameters to changes in tumor oxygenation. However, R_1 parameters showed limitations in terms of predicting the outcome of RT in the tumor models studied, whereas R_2* was found to be

  10. EPR spectroscopy of spices

    Directory of Open Access Journals (Sweden)

    R. T. Тimakova

    2016-01-01

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

  11. Methods of Blood Oxygen Level-Dependent Magnetic Resonance Imaging Analysis for Evaluating Renal Oxygenation

    Directory of Open Access Journals (Sweden)

    Fen Chen

    2018-03-01

    Full Text Available Blood oxygen level-dependent magnetic resonance imaging (BOLD MRI has recently been utilized as a noninvasive tool for evaluating renal oxygenation. Several methods have been proposed for analyzing BOLD images. Regional ROI selection is the earliest and most widely used method for BOLD analysis. In the last 20 years, many investigators have used this method to evaluate cortical and medullary oxygenation in patients with ischemic nephropathy, hypertensive nephropathy, diabetic nephropathy, chronic kidney disease (CKD, acute kidney injury and renal allograft rejection. However, clinical trials of BOLD MRI using regional ROI selection revealed that it was difficult to distinguish the renal cortico-medullary zones with this method, and that it was susceptible to observer variability. To overcome these deficiencies, several new methods were proposed for analyzing BOLD images, including the compartmental approach, fractional hypoxia method, concentric objects (CO method and twelve-layer concentric objects (TLCO method. The compartmental approach provides an algorithm to judge whether the pixel belongs to the cortex or medulla. Fractional kidney hypoxia, measured by using BOLD MRI, was negatively correlated with renal blood flow, tissue perfusion and glomerular filtration rate (GFR in patients with atherosclerotic renal artery stenosis. The CO method divides the renal parenchyma into six or twelve layers of thickness in each coronal slice of BOLD images and provides a R2* radial profile curve. The slope of the R2* curve associated positively with eGFR in CKD patients. Indeed, each method invariably has advantages and disadvantages, and there is generally no consensus method so far. Undoubtedly, analytic approaches for BOLD MRI with better reproducibility would assist clinicians in monitoring the degree of kidney hypoxia and thus facilitating timely reversal of tissue hypoxia.

  12. Genesis of Karl Popper's EPR-like experiment and its resonance amongst the physics community in the 1980s

    Science.gov (United States)

    Del Santo, Flavio

    2018-05-01

    I present the reconstruction of the involvement of Karl Popper in the community of physicists concerned with foundations of quantum mechanics, in the 1980s. At that time Popper gave active contribution to the research in physics, of which the most significant is a new version of the EPR thought experiment, alleged to test different interpretations of quantum mechanics. The genesis of such an experiment is reconstructed in detail, and an unpublished letter by Popper is reproduced in the present paper to show that he formulated his thought experiment already two years before its first publication in 1982. The debate stimulated by the proposed experiment as well as Popper's role in the physics community throughout 1980s is here analysed in detail by means of personal correspondence and publications.

  13. EPR dosimetry of irradiated human teeth

    International Nuclear Information System (INIS)

    Rodas Duran, J.E.; Panzeri, H.; Mascarenhas, S.

    1985-01-01

    The determination of the absorbed radiation dose in man may be made by Electron Paramagnetic Resonance (EPR) spectroscopy of dental enamel. We analysed the EPR signals for dental enamel submitted to gamma radiation in doses between 1 Gy and 25 Gy. We conclude that independent of the type of tooth analysed there exists a linear relation between the EPR signals and the absorbed doses. These studies were extended to enamel irradiated with gamma rays and with X rays in doses between 0.1 Gy and 0.6 Gy. The graph of the intensity of the EPR signals as a function of the dose has a slope of 0.22. This calibration may be used to calculate the absorbed dose for humans from a measurement of the EPR signal from small samples of enamel taken from any permanent tooth. Finally we comment on some EPR studies of effects of radiation of milk teeth. (author)

  14. EPR studies of melanin from Cladosporium cladosporioides

    International Nuclear Information System (INIS)

    Pilawa, B.; Buszman, E.; Latocha, M.; Wilczok, T.

    1996-01-01

    Free radical properties of Cladosporium cladosporioides mycelium and melanin, and synthetic eumelanin and pheomelanin were studied by electron paramagnetic resonance method. Single EPR line and complex EPR spectrum with hyperfine splitting were measured for model DOPA-melanin and cysteinyldopa-melanin, respectively. EPR spectra of Cladosporium cladosporioides samples and pheomelanin show the same character. The concentration of paramagnetic centers in melanins isolated from Cladosporium cladosporioides is considerably higher than that of crude mycelium, whereas the EPR line widths are lower for mycelium than for melanin samples. For all analyzed samples the increase of EPR signals intensity with the increase of microwave power, and the decrease of intensities after saturation were observed the low values of microwave power sufficient for EPR lines saturation demonstrate that the spin-lattice relaxation times of unpaired electrons in melanins are long. (author)

  15. EPR and DNP Properties of Certain Novel Single Electron Contrast Agents Intended for Oximetric Imaging

    DEFF Research Database (Denmark)

    Ardenkjær-Larsen, J. H.; Laursen, I; Leunbach, I.

    1998-01-01

    Parameters of relevance to oximetry with Overhauser magnetic resonance imaging (OMRI) have been measured for three single electron contrast agents of the triphenylmethyl type. The single electron contrast agents are stable and water soluble. Magnetic resonance properties of the agents have been...... examined with electron paramagnetic resonance (EPR), nuclear magnetic resonance (NMR), and dynamic nuclear polarization (DNP) at 9.5 mT in water, isotonic saline, plasma, and blood at 23 and 37°C. The relaxivities of the agents are about 0.2–0.4 mM−1s−1and the DNP enhancements extrapolate close...... to the dipolar limit. The agents have a single, narrow EPR line, which is analyzed as a Voigt function. The linewidth is measured as a function of the agent concentration and the oxygen concentration. The concentration broadenings are about 1–3 μT/mM and the Lorentzian linewidths at infinite dilution are less...

  16. A Quantitative Method to Monitor Reactive Oxygen Species Production by Electron Paramagnetic Resonance in Physiological and Pathological Conditions

    Science.gov (United States)

    Mrakic-Sposta, Simona; Gussoni, Maristella; Montorsi, Michela; Porcelli, Simone; Vezzoli, Alessandra

    2014-01-01

    The growing interest in the role of Reactive Oxygen Species (ROS) and in the assessment of oxidative stress in health and disease clashes with the lack of consensus on reliable quantitative noninvasive methods applicable. The study aimed at demonstrating that a recently developed Electron Paramagnetic Resonance microinvasive method provides direct evidence of the “instantaneous” presence of ROS returning absolute concentration levels that correlate with “a posteriori” assays of ROS-induced damage by means of biomarkers. The reliability of the choice to measure ROS production rate in human capillary blood rather than in plasma was tested (step I). A significant (P < 0.01) linear relationship between EPR data collected on capillary blood versus venous blood (R 2 = 0.95), plasma (R 2 = 0.82), and erythrocytes (R 2 = 0.73) was found. Then (step II) ROS production changes of various subjects' categories, young versus old and healthy versus pathological at rest condition, were found significantly different (range 0.0001–0.05 P level). The comparison of the results with antioxidant capacity and oxidative damage biomarkers concentrations showed that all changes indicating increased oxidative stress are directly related to ROS production increase. Therefore, the adopted method may be an automated technique for a lot of routine in clinical trials. PMID:25374651

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

    Science.gov (United States)

    Crăciun, Cora

    2014-08-01

    CW EPR powder spectra may be approximated numerically using a spherical grid and a Voronoi tessellation-based cubature. For a given spin system, the quality of simulated EPR spectra depends on the grid type, size, and orientation in the molecular frame. In previous work, the grids used in CW EPR powder simulations have been compared mainly from geometric perspective. However, some grids with similar homogeneity degree generate different quality simulated spectra. This paper evaluates the grids from EPR perspective, by defining two metrics depending on the spin system characteristics and the grid Voronoi tessellation. The first metric determines if the grid points are EPR-centred in their Voronoi cells, based on the resonance magnetic field variations inside these cells. The second metric verifies if the adjacent Voronoi cells of the tessellation are EPR-overlapping, by computing the common range of their resonance magnetic field intervals. Beside a series of well known regular grids, the paper investigates a modified ZCW grid and a Fibonacci spherical code, which are new in the context of EPR simulations. For the investigated grids, the EPR metrics bring more information than the homogeneity quantities and are better related to the grids' EPR behaviour, for different spin system symmetries. The metrics' efficiency and limits are finally verified for grids generated from the initial ones, by using the original or magnetic field-constraint variants of the Spherical Centroidal Voronoi Tessellation method. Copyright © 2014 Elsevier Inc. All rights reserved.

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

    Science.gov (United States)

    Crăciun, Cora

    2014-08-01

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

  19. EPR and Bell Locality

    OpenAIRE

    Norsen, Travis

    2004-01-01

    A new formulation of the EPR argument is presented, one which uses John Bell's mathematically precise local causality condition in place of the looser locality assumption which was used in the original EPR paper and on which Niels Bohr seems to have based his objection to the EPR argument. The new formulation of EPR bears a striking resemblance to Bell's derivation of his famous inequalities. The relation between these two arguments -- in particular, the role of EPR as part one of Bell's two-...

  20. EPR spectroscopic investigation of psoriatic finger nails.

    Science.gov (United States)

    Nakagawa, Kouichi; Minakawa, Satoko; Sawamura, Daisuke

    2013-11-01

    Nail lesions are common features of psoriasis and found in almost half of the patients. However, there is no feasible spectroscopic method evaluating changes and severity of nail psoriasis. EPR (electron paramagnetic resonance) might be feasible for evaluating nail conditions in the patients of psoriasis. Finger nails of five cases with nail psoriasis, (three females and two males) were examined. Nail samples were subjected to the EPR assay. The small piece of the finger nail (1.5 × 5 mm(2)) was incubated in ~50 μM 5-DSA (5-doxylstearic acid) aqueous solutions for about 60 min at 37°C. After rinsing and wiping off the excess 5-DSA solution, the nail samples were measured by EPR. EPR spectra were analyzed using the intensity ratio (Fast/Slow) of the two motions at the peaks of the lower magnetic field. We observed two distinguishable sites on the basis of the EPR results. In addition, the modern EPR calculation was performed to analyze the spectra obtained. The nail psoriasis-related region is 2~3 times higher than that of the control. The present EPR results show that there are two distinguishable sites in the nail. In the case of nail psoriasis, the fragile components are 2~3 times more than those of the control. Thus, the EPR method is thought to be a novel and reliable method of evaluating the nail psoriasis. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  1. EPR STUDIES OF THERMALLY STERILIZED VASELINUM ALBUM.

    Science.gov (United States)

    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.

  2. EPR dosimetry with tooth enamel: A review

    International Nuclear Information System (INIS)

    Fattibene, Paola; Callens, Freddy

    2010-01-01

    When tooth enamel is exposed to ionizing radiation, radicals are formed, which can be detected using electron paramagnetic resonance (EPR) techniques. EPR dosimetry using tooth enamel is based on the (presumed) correlation between the intensity or amplitude of some of the radiation-induced signals with the dose absorbed in the enamel. In the present paper a critical review is given of this widely applied dosimetric method. The first part of the paper is fairly fundamental and deals with the main properties of tooth enamel and some of its model systems (e.g., synthetic apatites). Considerable attention is also paid to the numerous radiation-induced and native EPR signals and the radicals responsible for them. The relevant methods for EPR detection, identification and spectrum analyzing are reviewed from a general point of view. Finally, the needs for solid-state modelling and studies of the linearity of the dose response are investigated. The second part is devoted to the practical implementation of EPR dosimetry using enamel. It concerns specific problems of preparation of samples, their irradiation and spectrum acquisition. It also describes how the dosimetric signal intensity and dose can be retrieved from the EPR spectra. Special attention is paid to the energy dependence of the EPR response and to sources of uncertainties. Results of and problems encountered in international intercomparisons and epidemiological studies are also dealt with. In the final section the future of EPR dosimetry with tooth enamel is analyzed.

  3. Spin states of reduced fullerenes (C60 and C120O) by CW and pulsed EPR

    International Nuclear Information System (INIS)

    Boas, J.F.; Drew, S.C.; Pilbrow, J.R.; Boyd, P.D.W.; Paul, P.; Reed, C.A.; Sun, D.

    2003-01-01

    Full text: The ESTN (Electron Spin Transient Nutation) EPR (Electron Paramagnetic Resonance) experiments reported at Wagga 2002 showed that the spin states of the reduced fullerenes C 120 O (2-), C 120 O (3-) and C 120 O (4-) were S = 1, S = 1/2 and S = 1 respectively. Further experiments using CW (Continuous Wave) EPR have confirmed the results of Paul et al. and have now shown that these states are the ground states of these anions. In the case of C 60 (3-), the recent CW and ESTN EPR experiments have shown that the electronic ground state of this anion is S = 1/2. The observation of ground states of low multiplicity for these anions is contrary to expectations based on MO calculations and the application of Hund's rules. A series of CW EPR experiments on C 60 (3-) have shown that some previous results may need to be re-interpreted. This arises from the delineation of the effects of microwave power, modulation amplitude and frequency, sample temperature and freezing rate on the EPR spectrum which is the combination of a broad line, attributed to C 60 (3-), and a 'spike' attributed to C 120 O impurities and other oxygen related species. Our results cast doubt on the existence of Jahn-Teller effects at low temperatures and of a low-lying spin quartet excited state

  4. Thermal induced EPR signals in tooth enamel

    International Nuclear Information System (INIS)

    Fattibene, P.; Aragno, D.; Onori, S.; Pressello, M.C.

    2000-01-01

    Electron paramagnetic resonance (EPR) spectroscopy was used to detect the effects of temperature on powdered human tooth enamel, not irradiated in the laboratory. Samples were heated at temperature between 350 and 450, at 600 and at 1000 deg. C, for different heating times, between 6 min and 39 h. Changes in the EPR spectra were detected, with the formation of new signals. Possible correlation between the changes in EPR spectra and modifications in the enamel and in the mineral phase of bone detected with other techniques is discussed. The implications for dosimetric applications of signals induced by overheating due to mechanical friction during sample preparation are underlined

  5. Perspectives of shaped pulses for EPR spectroscopy

    Science.gov (United States)

    Spindler, Philipp E.; Schöps, Philipp; Kallies, Wolfgang; Glaser, Steffen J.; Prisner, Thomas F.

    2017-07-01

    This article describes current uses of shaped pulses, generated by an arbitrary waveform generator, in the field of EPR spectroscopy. We show applications of sech/tanh and WURST pulses to dipolar spectroscopy, including new pulse schemes and procedures, and discuss the more general concept of optimum-control-based pulses for applications in EPR spectroscopy. The article also describes a procedure to correct for experimental imperfections, mostly introduced by the microwave resonator, and discusses further potential applications and limitations of such pulses.

  6. Rapid-scan EPR imaging.

    Science.gov (United States)

    Eaton, Sandra S; Shi, Yilin; Woodcock, Lukas; Buchanan, Laura A; McPeak, Joseph; Quine, Richard W; Rinard, George A; Epel, Boris; Halpern, Howard J; Eaton, Gareth R

    2017-07-01

    In rapid-scan EPR the magnetic field or frequency is repeatedly scanned through the spectrum at rates that are much faster than in conventional continuous wave EPR. The signal is directly-detected with a mixer at the source frequency. Rapid-scan EPR is particularly advantageous when the scan rate through resonance is fast relative to electron spin relaxation rates. In such scans, there may be oscillations on the trailing edge of the spectrum. These oscillations can be removed by mathematical deconvolution to recover the slow-scan absorption spectrum. In cases of inhomogeneous broadening, the oscillations may interfere destructively to the extent that they are not visible. The deconvolution can be used even when it is not required, so spectra can be obtained in which some portions of the spectrum are in the rapid-scan regime and some are not. The technology developed for rapid-scan EPR can be applied generally so long as spectra are obtained in the linear response region. The detection of the full spectrum in each scan, the ability to use higher microwave power without saturation, and the noise filtering inherent in coherent averaging results in substantial improvement in signal-to-noise relative to conventional continuous wave spectroscopy, which is particularly advantageous for low-frequency EPR imaging. This overview describes the principles of rapid-scan EPR and the hardware used to generate the spectra. Examples are provided of its application to imaging of nitroxide radicals, diradicals, and spin-trapped radicals at a Larmor frequency of ca. 250MHz. Copyright © 2017 Elsevier Inc. All rights reserved.

  7. Assessment of performance parameters for EPR dosimetry with tooth enamel

    International Nuclear Information System (INIS)

    Wieser, A.; Fattibene, P.; Shishkina, E.A.; Ivanov, D.V.; De Coste, V.; Guettler, A.; Onori, S.

    2008-01-01

    In the framework of a comparison between three laboratories, electron paramagnetic resonance (EPR) signal-to-dose response curves were measured for sets of 30 tooth enamel samples and the variance of EPR measurements in dependence on absorbed dose was evaluated, in nine combinations of laboratory of sample preparation and EPR evaluation, respectively. As a test for benchmarking of EPR evaluation, the parameters 'critical dose' and 'limit of detection' were proposed as performance parameters following definitions from chemical-metrology, and a model function was suggested for analytical formulation of the dependence of the variance of EPR measurement on absorbed dose. First estimates of limits of detection by weighted and unweighted fitting resulted in the range 101-552 and 67-561 mGy, respectively, and were generally larger with weighted than with unweighted fitting. Indication was found for the influence of methodology of sample preparation and applied EPR measurement parameters on performance of EPR dosimetry with tooth enamel

  8. High-field EPR on membrane proteins - crossing the gap to NMR.

    Science.gov (United States)

    Möbius, Klaus; Lubitz, Wolfgang; Savitsky, Anton

    2013-11-01

    In this review on advanced EPR spectroscopy, which addresses both the EPR and NMR communities, considerable emphasis is put on delineating the complementarity of NMR and EPR concerning the measurement of molecular interactions in large biomolecules. From these interactions, detailed information can be revealed on structure and dynamics of macromolecules embedded in solution- or solid-state environments. New developments in pulsed microwave and sweepable cryomagnet technology as well as ultrafast electronics for signal data handling and processing have pushed to new horizons the limits of EPR spectroscopy and its multifrequency extensions concerning the sensitivity of detection, the selectivity with respect to interactions, and the resolution in frequency and time domains. One of the most important advances has been the extension of EPR to high magnetic fields and microwave frequencies, very much in analogy to what happens in NMR. This is exemplified by referring to ongoing efforts for signal enhancement in both NMR and EPR double-resonance techniques by exploiting dynamic nuclear or electron spin polarization via unpaired electron spins and their electron-nuclear or electron-electron interactions. Signal and resolution enhancements are particularly spectacular for double-resonance techniques such as ENDOR and PELDOR at high magnetic fields. They provide greatly improved orientational selection for disordered samples that approaches single-crystal resolution at canonical g-tensor orientations - even for molecules with small g-anisotropies. Exchange of experience between the EPR and NMR communities allows for handling polarization and resolution improvement strategies in an optimal manner. Consequently, a dramatic improvement of EPR detection sensitivity could be achieved, even for short-lived paramagnetic reaction intermediates. Unique structural and dynamic information is thus revealed that can hardly be obtained by any other analytical techniques. Micromolar

  9. Using 3.05 MeV resonance for determination of oxygen impurities

    International Nuclear Information System (INIS)

    Burkova, I.E.; Polyanskij, V.N.; Yatis, A.A.

    1983-01-01

    The method of determining oxygen impurities behind thin films using the isolated resonance in the 16 O(α, α) 16 O reaction at E=3.048 MeV with the width GITA approximately 20 keV, is considered. Cross section in resonance is σsUb(R) = 0.95 b apd it increases cross section of Rutherford scattering by the factor of 25. The conclusion is made on the possibility of using 3.048 MeV resonance when investigating Me-Si film structures

  10. Electron paramagnetic resonance (EPR) of antiferromagnetic nanoparticles of La1-xSrxCrO3 (0.000 ≤ x ≤ 0.020) synthesized by combustion reaction

    International Nuclear Information System (INIS)

    Franco, Adolfo; Santana, Ricardo C.

    2010-01-01

    Nanocrystalline particles of La 1-x Sr x CrO 3 (0.000 ≤ x ≤ 0.020) compounds were synthesized in order to investigate the antiferromagnetic (AFM) to paramagnetic (PM) phase transition temperature, g-factor, line width and intensity by electron paramagnetic resonance (EPR). All samples were synthesized by combustion reaction method using strontium nitrate, lanthanum nitrate, chromium nitrate and urea as fuel without subsequent heat treatment. X-ray diffraction patterns of all systems showed broad peaks consistent with orthorhombic structure of LaCrO 3 . The absence of extra reflections in the diffraction patterns of as-prepared materials ensures the phase purity. The average crystallite sizes determined from the prominent (1 1 2) peak of the diffraction using Scherrer's equation was independent of the addition of Sr 2+ ions; being ca. 31-29 nm for x = 0.000 and 0.020, respectively. The EPR line width and intensity were found to be dependent on Sr 2+ addition and temperature. However, the AFM-PM transition temperature was found to be independent of strontium concentration, being ca. 296 K. In the PM phase, g-factor was nearly temperature independent with increasing of x. The EPR results indicated that the addition of Sr 2+ ions may induce creation of Cr 3+ -Cr 4+ clusters.

  11. EPR of uranium ions

    International Nuclear Information System (INIS)

    Ursu, I.; Lupei, V.

    1984-02-01

    A review of the electron paramagnetic resonance data on the uranium ions is given. After a general account of the electronic structure of the uranium free atoms and ions, the influence of the external fields (magnetic field, crystal fields) is discussed. The main information obtained from EPR studies on the uranium ions in crystals are emphasized: identification of the valence and of the ground electronic state, determination of the structure of the centers, crystal field effects, role of the intermediate coupling and of the J-mixing, role of the covalency, determination of the nuclear spin, maqnetic dipole moment and electric quadrupole moment of the odd isotopes of uranium. These data emphasize the fact that the actinide group has its own identity and this is accutely manifested at the beginning of the 5fsup(n) series encompassed by the uranium ions. (authors)

  12. EPR Oximetry Sensor-Developing a TAM Derivative for In Vivo Studies.

    Science.gov (United States)

    Boś-Liedke, Agnieszka; Walawender, Magdalena; Woźniak, Anna; Flak, Dorota; Gapiński, Jacek; Jurga, Stefan; Kucińska, Małgorzata; Plewiński, Adam; Murias, Marek; Elewa, Marwa; Lampp, Lisa; Imming, Peter; Tadyszak, Krzysztof

    2018-06-01

    Oxygenation is one of the most important physiological parameters of biological systems. Low oxygen concentration (hypoxia) is associated with various pathophysiological processes in different organs. Hypoxia is of special importance in tumor therapy, causing poor response to treatment. Triaryl methyl (TAM) derivative radicals are commonly used in electron paramagnetic resonance (EPR) as sensors for quantitative spatial tissue oxygen mapping. They are also known as magnetic resonance imaging (MRI) contrast agents and fluorescence imaging compounds. We report the properties of the TAM radical tris(2,3,5,6-tetrachloro-4-carboxy-phenyl)methyl, (PTMTC), a potential multimodal (EPR/fluorescence) marker. PTMTC was spectrally analyzed using EPR and characterized by estimation of its sensitivity to the oxygen in liquid environment suitable for intravenous injection (1 mM PBS, pH = 7.4). Further, fluorescent emission of the radical was measured using the same solvent and its quantum yield was estimated. An in vitro cytotoxicity examination was conducted in two cancer cell lines, HT-29 (colorectal adenocarcinoma) and FaDu (squamous cell carcinoma) and followed by uptake studies. The stability of the radical in different solutions (PBS pH = 7.4, cell media used for HT-29 and FaDu cells culturing and cytotoxicity procedure, full rat blood and blood plasma) was determined. Finally, a primary toxicity test of PTMTC was carried out in mice. Results of spectral studies confirmed the multimodal properties of PTMTC. PTMTC was demonstrated to be not absorbed by cancer cells and did not interfere with luciferin-luciferase based assays. Also in vitro and in vivo tests showed that it was non-toxic and can be freely administrated till doses of 250 mg/kg BW via both i.v. and i.p. injections. This work illustrated that PTMTC is a perfect candidate for multimodal (EPR/fluorescence) contrast agent in preclinical studies.

  13. Resonant electron attachment to mixed hydrogen/oxygen and deuterium/oxygen clusters

    Science.gov (United States)

    Renzler, Michael; Kranabetter, Lorenz; Barwa, Erik; Grubwieser, Lukas; Scheier, Paul; Ellis, Andrew M.

    2017-11-01

    Low energy electron attachment to mixed (H2)x/(O2)y clusters and their deuterated analogs has been investigated for the first time. These experiments were carried out using liquid helium nanodroplets to form the clusters, and the effect of the added electron was then monitored via mass spectrometry. There are some important differences between electron attachment to the pure clusters and to the mixed clusters. A particularly notable feature is the formation of HO2- and H2O- ions from an electron-induced chemical reaction between the two dopants. The chemistry leading to these anions appears to be driven by electron resonances associated with H2 rather than O2. The electron resonances for H2 can lead to dissociative electron attachment (DEA), just as for the free H2 molecule. However, there is evidence that the resonance in H2 can also lead to rapid electron transfer to O2, which then induces DEA of the O2. This kind of excitation transfer has not, as far as we are aware, been reported previously.

  14. EPR and NMR spectroscopy on spin-labeled proteins

    NARCIS (Netherlands)

    Finiguerra, Michelina Giuseppina

    2011-01-01

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

  15. Pre-clinical evaluation of OxyChip for long-term EPR oximetry.

    Science.gov (United States)

    Hou, Huagang; Khan, Nadeem; Gohain, Sangeeta; Kuppusamy, M Lakshmi; Kuppusamy, Periannan

    2018-03-16

    Tissue oxygenation is a critical parameter in various pathophysiological situations including cardiovascular disease and cancer. Hypoxia can significantly influence the prognosis of solid malignancies and the efficacy of their treatment by radiation or chemotherapy. Electron paramagnetic resonance (EPR) oximetry is a reliable method for repeatedly assessing and monitoring oxygen levels in tissues. Lithium octa-n-butoxynaphthalocyanine (LiNc-BuO) has been developed as a probe for biological EPR oximetry, especially for clinical use. However, clinical applicability of LiNc-BuO crystals is hampered by potential limitations associated with biocompatibility, biodegradation, or migration of individual bare crystals in tissue. To overcome these limitations, we have embedded LiNc-BuO crystals in polydimethylsiloxane (PDMS), an oxygen-permeable biocompatible polymer and developed an implantable/retrievable form of chip, called OxyChip. The chip was optimized for maximum spin density (40% w/w of LiNc-BuO in PDMS) and fabricated in a form suitable for implantation using an 18-G syringe needle. In vitro evaluation of the OxyChip showed that it is robust and highly oxygen sensitive. The dependence of its EPR linewidth to oxygen was linear and highly reproducible. In vivo efficacy of the OxyChip was evaluated by implanting it in rat femoris muscle and following its response to tissue oxygenation for up to 12 months. The results revealed preservation of the integrity (size and shape) and calibration (oxygen sensitivity) of the OxyChip throughout the implantation period. Further, no inflammatory or adverse reaction around the implantation area was observed thereby establishing its biocompatibility and safety. Overall, the results demonstrated that the newly-fabricated high-sensitive OxyChip is capable of providing long-term measurements of oxygen concentration in a reliable and repeated manner under clinical conditions.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2007-06-15

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

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

    International Nuclear Information System (INIS)

    Yordanov, N.D.; Aleksieva, K.

    2007-01-01

    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. EPR study on gamma-irradiated fruits dehydrated via osmosis

    Science.gov (United States)

    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.

  19. A web-based database for EPR centers in semiconductors

    International Nuclear Information System (INIS)

    Umeda, T.; Hagiwara, S.; Katagiri, M.; Mizuochi, N.; Isoya, J.

    2006-01-01

    We develop a web-based database system for electron paramagnetic resonance (EPR) centers in semiconductors. This database is available to anyone at http://www.kc.tsukuba.ac.jp/div-media/epr/. It currently has more than 300 records of the spin-Hamiltonian parameters for major known EPR centers. One can upload own new records to the database or can use simulation tools powered by EPR-NMR(C). Here, we describe the features and objectives of this database, and mention some future plans

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

    NARCIS (Netherlands)

    Mathies, Guinevere

    2012-01-01

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

  1. Use of the Frank sequence in pulsed EPR

    DEFF Research Database (Denmark)

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

    2011-01-01

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

  2. Quantification of oxygen and carbon in high Tc superconducting films by (α,α) elastic resonance technique

    International Nuclear Information System (INIS)

    Vizkelethy, G.; Revesz, P.

    1993-01-01

    The quantification of oxygen and carbon in high-temperature (T c ) superconducting oxide thin films was made by employing elastic resonance in He backscattering analysis. A method combining the oxygen resonance technique and channeling was presented for measuring the nature of the oxygen disorder near the surface and the interface in a YBCO superconducting film grown on an MgO substrate. The oxygen resonance technique was used to quantify the oxygen profiling in the metal/YBCO contacts, showing that Zr and Nb act as sinks to oxygen from YBCO films and are oxidized in the forms Zr/ZrO 2 /YBCO/MgO and Nb 0.2 O/YBCO/MgO after annealing in a vacuum at 350 o C. We combined the carbon and oxygen resonances to determine the carbon contamination and oxygen concentration changes on the YBCO surface after coating and baking the photoresist. Residual carbon on the surface and a thin layer of oxygen depletion near the YBCO surface have been observed. The residual carbon in Bi 2 Sr 2 CaCu 2 O 8 films made by the decomposition of metallo-organic precursors was quantified using carbon resonance. (author)

  3. Computational and instrumental methods in EPR

    CERN Document Server

    Bender, Christopher J

    2006-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Daniel eNohr

    2015-09-01

    Full Text Available Electron paramagnetic resonance (EPR spectroscopy is a well-established spectroscopic method for the examination of paramagnetic molecules. Proteins can contain paramagnetic moieties in form of stable cofactors, transiently formed intermediates, or spin labels artificially introduced to cysteine sites. The focus of this review is to evaluate potential scopes of application of EPR to the emerging field of optogenetics. The main objective for EPR spectroscopy in this context is to unravel the complex mechanisms of light-active proteins, from their primary photoreaction to downstream signal transduction. An overview of recent results from the family of flavin-containing, blue-light dependent photoreceptors is given. In detail, mechanistic similarities and differences are condensed from the three classes of flavoproteins, the cryptochromes, LOV (Light-oxygen-voltage, and BLUF (blue-light using FAD domains. Additionally, a concept that includes spin-labeled proteins and examination using modern pulsed EPR is introduced, which allows for a precise mapping of light-induced conformational changes.

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

    Science.gov (United States)

    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.

  6. Trichloroethylene Radicals: An EPR/SPIN Trapping Study

    National Research Council Canada - National Science Library

    Steel-Goodwin, Linda

    1995-01-01

    .... As part of the process to develop environmental and health effects criteria for base clean-up the initial radicals produced by TCE were studied by electron paramagnetic resonance spectroscopy (EPR...

  7. EPR and NMR detection of transient radicals and reaction products

    International Nuclear Information System (INIS)

    Trifunac, A.D.

    1981-01-01

    Magnetic resonance methods in radiation chemistry are illustrated. The most recent developments in pulsed EPR and NMR studies in pulse radiolysis are outlined with emphasis on the study of transient radicals and their reaction products. 12 figures

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

    Science.gov (United States)

    Nakagawa, K; Hara, H

    2015-01-01

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

  9. Evaluation of Renal Blood Flow and Oxygenation in CKD Using Magnetic Resonance Imaging.

    Science.gov (United States)

    Khatir, Dinah S; Pedersen, Michael; Jespersen, Bente; Buus, Niels H

    2015-09-01

    Animal studies suggest that progression of chronic kidney disease (CKD) is related to renal hypoxia. With renal blood supply determining oxygen delivery and sodium absorption being the main contributor to oxygen consumption, we describe the relationship between renal oxygenation, renal artery blood flow, and sodium absorption in patients with CKD and healthy controls. Cross-sectional study. 62 stable patients with CKD stages 3 to 4 (mean age, 61±13 [SD] years) and 24 age- and sex-matched controls. CKD versus control status. Renal artery blood flow, tissue oxygenation (relative changes in deoxyhemoglobin concentration of the renal medulla [MR2*] and cortex [CR2*]), and sodium absorption. Renal artery blood flow was determined by phase-contrast magnetic resonance imaging (MRI); MR2* and CR2* were determined by blood oxygen level-dependent MRI. Ultrafiltered and reabsorbed sodium were determined from measured glomerular filtration rate (mGFR) and 24-hour urine collections. mGFR in patients was 37% that of controls (36±15 vs 97±23 mL/min/1.73 m(2); P renal artery blood flow was 72% that of controls (319 vs 443 mL/min; P renal artery blood flow or sodium absorption. Increasing arterial blood oxygen tension by breathing 100% oxygen had very small effects on CR2*, but reduced MR2* in both groups. Only renal artery blood flow was determined and thus regional perfusion could not be related to CR2* or MR2*. In CKD, reductions of mGFR and reabsorbed sodium are more than double that of renal artery blood flow, whereas cortical and medullary oxygenation are within the range of healthy persons. Reduction in glomerular filtration fraction may prevent renal hypoxia in CKD. Copyright © 2015 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.

  10. The EPR detection of radiation treated foodstuffs

    International Nuclear Information System (INIS)

    Stachowicz, W.; Burlinska, G.; Michalik, J.; Ostrowski, K.; Dziedzic-Goclawska, A.

    1993-01-01

    The short paper by a Polish study group describes the results of the use of Electron Paramagnetic Resonance (EPR) Spectroscopy in the detection of irradiation to food. Pultry, fresh-water fish and sea fish as well as various fruits and yellow boletus are dealt with in some detail. (VHE) [de

  11. EPR of exchange coupled systems

    CERN Document Server

    Bencini, Alessandro

    2012-01-01

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

  12. EPR investigations on technetium compounds

    International Nuclear Information System (INIS)

    Abram, U.; Munze, R.; Kirmse, R.; Stach, J.

    1986-01-01

    Stimulated by the widespread use of the isotope /sup 99m/Tc in the field of nuclear medicine, there has been a substantial growth of interest in the chemistry of this man-made element. A particular need emerges for analytical methods allowing solution investigations of coordination compounds of technetium with low substance use. Considering these facts, Electron Paramagnetic Resonance Spectroscopy (EPR) appears to be a very suitable method because only very small amounts of the compounds are needed (lower than 1 mg). The resulting spectra give information regarding the valence state, symmetry and bonding properties of the compounds under study

  13. Quantification of Regional Myocardial Oxygenation by Magnetic Resonance Imaging: Validation with Positron Emission Tomography

    Science.gov (United States)

    McCommis, Kyle S.; Goldstein, Thomas A.; Abendschein, Dana R.; Herrero, Pilar; Misselwitz, Bernd; Gropler, Robert J.; Zheng, Jie

    2011-01-01

    Background A comprehensive evaluation of myocardial ischemia requires measures of both oxygen supply and demand. Positron emission tomography (PET) is currently the gold standard for such evaluations, but its use is limited due to its ionizing radiation, limited availability, and high cost. A cardiac magnetic resonance imaging (MRI) method was developed for assessing myocardial oxygenation. The purpose of this study was to evaluate and validate this technique compared to PET during pharmacologic stress in a canine model of coronary artery stenosis. Methods and Results Twenty-one beagles and small mongrel dogs without coronary artery stenosis (controls), or with moderate to severe acute coronary artery stenosis underwent MRI and PET imaging at rest and during dipyridamole vasodilation or dobutamine stress to induce a wide range of changes in cardiac perfusion and oxygenation. MRI first-pass perfusion imaging was performed to quantify myocardial blood flow (MBF) and volume (MBV). The MRI blood-oxygen-level-dependent (BOLD) technique was used to determine the myocardial oxygen extraction fraction (OEF) during pharmacologic hyperemia. Myocardial oxygen consumption (MVO2) was determined by Fick’s law. In the same dogs, 15O-water and 11C-acetate were used to measure MBF and MVO2, respectively, by PET. Regional assessments were performed for both MR and PET. MRI data correlated nicely with PET values for MBF (R2 = 0.79, P < 0.001), MVO2 (R2 = 0.74, P < 0.001), and OEF (R2 = 0.66, P < 0.01). Conclusions Cardiac MRI methods may provide an alternative to radionuclide imaging in settings of myocardial ischemia. Our newly developed quantitative MRI oxygenation imaging technique may be a valuable non-invasive tool to directly evaluate myocardial energetics and efficiency. PMID:19933371

  14. EPR study of sagitta otoliths of Sciaenidae fish

    International Nuclear Information System (INIS)

    Beneditto, Ana Paula Madeira di; Franco, Roberto Weider de Assis

    2011-01-01

    Full text. Otoliths are crystalline structures of calcium carbonate (CaCO 3 ) located in the inner ear of bone fish that are responsible for balance maintenance in the water column and sense of direction. The bio mineralization of these structures occurs during the fish development; when the otolith growth layers are formed. In this work, electron paramagnetic resonance (EPR) spectroscopy is applied to study the sagitta otoliths via manganese (Mn 2+ ) spectra, since in calcium carbonates the Mn 2+ ion is a natural substitutional impurity at Ca 2+ sites. The sagitta otoliths of the Sciaenidae fish Paralonchurus brasiliensis, commonly known as cabeca dura (47 samples), and Stellifer rastrifer, known as cangoa (22 samples), were obtained from specimens captured in coastal areas of Rio de Janeiro State, southeastern Brazil: Atafona (21 deg 37'S), Farol de Sao Tome (22 deg 05'S) and Rio das Ostras (22 deg 30'S). EPR spectra of sagitta otoliths were obtained in X-band (9GHz) at room temperature. The EPR spectra are typical of Mn 2+ in aragonite powder, associated to an occupation of Ca 2+ site with nine nearest neighbor oxygen atoms. It is well established in the literature that the otolith core is constituted by calcite, which is covered by aragonite during the fish growth. However, otoliths of younger fishes showed similar EPR spectra when compared to the older ones, indicating that aragonite is the main bio mineral structure in both maturity stages. In a previous work, these two Sciaenidae species presented significant differences in sagitta otoliths shape, which were related to environmental differences (e.g. water temperature, nutrients, depth) among the sampling sites (Atafona, Farol de Sao Tome and Rio das Ostras). Meanwhile, we do not observed differences in the EPR spectra, indicating that the aragonite crystallization process and the occupation of manganese are not related with the environment where these fish species are living. Then, we can infer that the

  15. EPR study of sagitta otoliths of Sciaenidae fish

    Energy Technology Data Exchange (ETDEWEB)

    Beneditto, Ana Paula Madeira di; Franco, Roberto Weider de Assis [Universidade Estadual do Norte Fluminense (UENF), RJ (Brazil)

    2011-07-01

    Full text. Otoliths are crystalline structures of calcium carbonate (CaCO{sub 3}) located in the inner ear of bone fish that are responsible for balance maintenance in the water column and sense of direction. The bio mineralization of these structures occurs during the fish development; when the otolith growth layers are formed. In this work, electron paramagnetic resonance (EPR) spectroscopy is applied to study the sagitta otoliths via manganese (Mn{sup 2+}) spectra, since in calcium carbonates the Mn{sup 2+} ion is a natural substitutional impurity at Ca{sup 2+} sites. The sagitta otoliths of the Sciaenidae fish Paralonchurus brasiliensis, commonly known as cabeca dura (47 samples), and Stellifer rastrifer, known as cangoa (22 samples), were obtained from specimens captured in coastal areas of Rio de Janeiro State, southeastern Brazil: Atafona (21 deg 37'S), Farol de Sao Tome (22 deg 05'S) and Rio das Ostras (22 deg 30'S). EPR spectra of sagitta otoliths were obtained in X-band (9GHz) at room temperature. The EPR spectra are typical of Mn{sup 2+} in aragonite powder, associated to an occupation of Ca{sup 2+} site with nine nearest neighbor oxygen atoms. It is well established in the literature that the otolith core is constituted by calcite, which is covered by aragonite during the fish growth. However, otoliths of younger fishes showed similar EPR spectra when compared to the older ones, indicating that aragonite is the main bio mineral structure in both maturity stages. In a previous work, these two Sciaenidae species presented significant differences in sagitta otoliths shape, which were related to environmental differences (e.g. water temperature, nutrients, depth) among the sampling sites (Atafona, Farol de Sao Tome and Rio das Ostras). Meanwhile, we do not observed differences in the EPR spectra, indicating that the aragonite crystallization process and the occupation of manganese are not related with the environment where these fish species

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

    International Nuclear Information System (INIS)

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

    2014-01-01

    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. - Highlights: • The EPR analysis of juices, nectars and syrups proves that the sample has been irradiated. • Two sample preparation procedures were used. • The stability of the radiation induced EPR signals was studied over 2 months. • Application of European standards can be extended for irradiated juices and syrups

  17. Determination of formal redox potentials in aqueous solution of copper(II) complexes with ligands having nitrogen and oxygen donor atoms and comparison with their EPR and UV-Vis spectral features.

    Science.gov (United States)

    Tabbì, Giovanni; Giuffrida, Alessandro; Bonomo, Raffaele P

    2013-11-01

    Formal redox potentials in aqueous solution were determined for copper(II) complexes with ligands having oxygen and nitrogen as donor atoms. All the chosen copper(II) complexes have well-known stereochemistries (pseudo-octahedral, square planar, square-based pyramidal, trigonal bipyramidal or tetrahedral) as witnessed by their reported spectroscopic, EPR and UV-visible (UV-Vis) features, so that a rough correlation between the measured redox potential and the typical geometrical arrangement of the copper(II) complex could be established. Negative values have been obtained for copper(II) complexes in tetragonally elongated pseudo-octahedral geometries, when measured against Ag/AgCl reference electrode. Copper(II) complexes in tetrahedral environments (or flattened tetrahedral geometries) show positive redox potential values. There is a region, always in the field of negative redox potentials which groups the copper(II) complexes exhibiting square-based pyramidal arrangements. Therefore, it is suggested that a measurement of the formal redox potential could be of great help, when some ambiguities might appear in the interpretation of spectroscopic (EPR and UV-Vis) data. Unfortunately, when the comparison is made between copper(II) complexes in square-based pyramidal geometries and those in square planar environments (or a pseudo-octahedral) a little perturbed by an equatorial tetrahedral distortion, their redox potentials could fall in the same intermediate region. In this case spectroscopic data have to be handled with great care in order to have an answer about a copper complex geometrical characteristics. © 2013.

  18. Adult and newborn rat inner retinal oxygenation during carbogen and 100% oxygen breathing. Comparison using magnetic resonance imaging delta Po2 mapping.

    Science.gov (United States)

    Berkowitz, B A

    1996-09-01

    To test the hypothesis that breathing carbogen (95% O2-5% CO2) oxygenates the inner retina better than breathing 100% oxygen using an magnetic resonance imaging (MRI) method that noninvasively measures inner retinal oxygenation in normal adult and newborn rats. Urethane-anesthetized adult and newborn (day 18) rats were studied. Sequential images were acquired in room air combined with either 100% oxygen or carbogen breathing. Normalized vitreous signal intensity changes were converted to oxygen tension changes (delta PO2) either on a pixel-by-pixel basis or in specific regions of interest. Systemic levels of hyperoxia during carbogen or 100% oxygen breathing were not significantly different (P > 0.05). In the adult rat, a significant difference (P = 0.017) was found in the preretinal vitreous delta PO2 during the breathing of either carbogen (130 +/- 9 mm Hg, mean +/- SEM; n = 5) or 100% oxygen (88 +/- 16 mm Hg; n = 5). Agreement was found between the MRI-determined delta PO2 values and literature oxygen microelectrodes data. In the newborn rat, significant differences (P delta PO2 were found during carbogen (164 +/- 23 mm Hg; n = 3) and oxygen breathing (91 +/- 8 mm Hg; n = 3). MRI delta PO2 mapping demonstrated for the first time that in the normal adult and newborn rat eye, carbogen breathing oxygenates the inner retina better than 100% oxygen breathing.

  19. Dosimetry of an accident in mixed field (neutrons, photons) using the spectrometry by electronic paramagnetic resonance(EPR); Dosimetrie d'accident en champ mixte (neutrons, photons) utilisant la spectrometrie par resonance paramagnetique electronique (RPE)

    Energy Technology Data Exchange (ETDEWEB)

    Herve, M.L

    2006-03-15

    In a radiological accident, the assessment of the dose received by the victim is relevant information for the therapeutic strategy. Two complementary dosimetric techniques based on physical means are used in routine practice in the laboratory: EPR spectroscopy performed on materials removed from the victim or gathered from the vicinity of the victim and Monte Carlo calculations. EPR dosimetry, has been used successfully several times in cases of photon or electron overexposures. Accidental exposure may also occur with a neutron component. The aim of this work is to investigate the potentiality of EPR dosimetry for mixed photon and neutron field exposure with different organic materials (ascorbic acid, sorbitol, glucose, galactose, fructose, mannose, lactose and sucrose). The influence of irradiation parameters (dose, dose rate, photon energy) and of environmental parameters (temperature of heating, light exposure) on the EPR signal amplitude was studied. To assess the neutron sensitivity, the materials were exposed to a mixed radiation field of experimental reactors with different neutron to photon ratios. The relative neutron sensitivity was found to range from 10% to 43% according to the materials. Prior knowledge of the ratio between the dose in samples measured by EPR spectrometry and organ or whole body dose obtained by calculations previously performed for these different configurations, makes it possible to give a first estimation of the dose received by the victim in a short delay. The second aim of this work is to provide data relevant for a quick assessment of the dose distribution in case of accidental overexposure based on EPR measurements performed on one or several points of the body. The study consists in determining by calculation the relation between the dose to the organs and whole body and the dose to specific points of the body, like teeth, bones or samples located in the pockets of victim clothes, for different external exposures corresponding

  20. X-ray absorption spectroscopy and EPR studies of oriented spinach thylakoid preparations

    Energy Technology Data Exchange (ETDEWEB)

    Andrews, J.C. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry]|[Lawrence Berkeley Lab., CA (United States). Structural Biology Div.

    1995-08-01

    In this study, oriented Photosystem II (PS II) particles from spinach chloroplasts are studied with electron paramagnetic resonance (EPR) and x-ray absorption spectroscopy (XAS) to determine more details of the structure of the oxygen evolving complex (OEC). The nature of halide binding to Mn is also studied with Cl K-edge and Mn EXAFS (extended x-ray absorption fine structure) of Mn-Cl model compounds, and with Mn EXAFS of oriented PS II in which Br has replaced Cl. Attention is focused on the following: photosynthesis and the oxygen evolving complex; determination of mosaic spread in oriented photosystem II particles from signal II EPR measurement; oriented EXAFS--studies of PS II in the S{sub 2} state; structural changes in PS II as a result of treatment with ammonia: EPR and XAS studies; studies of halide binding to Mn: Cl K-edge and Mn EXAFS of Mn-Cl model compounds and Mn EXAFS of oriented Br-treated photosystem II.

  1. 1H nuclear magnetic resonance studies of sarcoplasmic oxygenation in the red cell-perfused rat heart

    OpenAIRE

    Jelicks, L.A.; Wittenberg, B.A.

    1995-01-01

    The proximal histidine N delta H proton of deoxymyoglobin experiences a large hyperfine shift resulting in its 1H nuclear magnetic resonance (NMR) signal appearing at approximately 76 ppm (at 35 degrees C), downfield of the diamagnetic spectral region. 1H NMR of this proton is used to monitor sarcoplasmic oxygen pressure in isolated perfused rat heart. This method monitors intracellular oxygenation in the whole heart and does not reflect oxygenation in a limited region. The deoxymyoglobin res...

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

    Science.gov (United States)

    Nakagawa, Kouichi; Epel, Boris

    2014-10-15

    In this study, noninvasive 9GHz 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 9GHz EPR imaging capabilities. The 9GHz EPR-imager easily resolved the LiPC samples at a distance of ∼2mm. Then, commercially available black pepper seeds were measured. We observed signatures from three different radical species, which were assigned to stable organic radicals, Fe(3+), and Mn(2+) complexes. In addition, no EPR spectral change in the seed was observed after it was submerged in distilled H2O for 1h. 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 9GHz EPR imaging were useful for the determination of the spatial distribution of paramagnetic species in various seeds. Copyright © 2014 Elsevier B.V. All rights reserved.

  3. Comparison of continuous wave, spin echo, and rapid scan EPR of irradiated fused quartz

    International Nuclear Information System (INIS)

    Mitchell, Deborah G.; Quine, Richard W.; Tseitlin, Mark; Meyer, Virginia; Eaton, Sandra S.; Eaton, Gareth R.

    2011-01-01

    The E' defect in irradiated fused quartz has spin lattice relaxation times (T 1 ) about 100-300 μs and spin-spin relaxation times (T 2 ) up to about 200 μs, depending on the concentration of defects and other species in the sample. These long relaxation times make it difficult to record an unsaturated continuous wave (CW) electron paramagnetic resonance (EPR) signal that is free of passage effects. Signals measured at X-band (∼9.5 GHz) by three EPR methods: conventional slow-scan field-modulated EPR, rapid scan EPR, and pulsed EPR, were compared. To acquire spectra with comparable signal-to-noise, both pulsed and rapid scan EPR require less time than conventional CW EPR. Rapid scan spectroscopy does not require the high power amplifiers that are needed for pulsed EPR. The pulsed spectra, and rapid scan spectra obtained by deconvolution of the experimental data, are free of passage effects.

  4. A magnetic resonance study of 3d transition metals and thermal donors in silicon

    International Nuclear Information System (INIS)

    Wezep, D.A. van.

    1986-01-01

    This thesis describes a study of 3d-transition metal impurities in silicon (titanium and iron in particular) and a study of oxygen-related heat-treatment centers in silicon, both carried out mainly by magnetic resonances techniques like EPR and ENDOR. 119 refs.; 31 figs.; 14 tabs

  5. One-way EPR steering and genuine multipartite EPR steering

    Science.gov (United States)

    He, Qiongyi; Reid, Margaret D.

    2012-11-01

    We propose criteria and experimental strategies to realise the Einstein-Podolsky-Rosen (EPR) steering nonlocality. One-way steering can be obtained where there is asymmetry of thermal noise on each system. We also present EPR steering inequalities that act as signatures and suggest how to optimise EPR correlations in specific schemes so that the genuine multipartite EPR steering nonlocality (EPR paradox) can also possibly be realised. The results presented here also apply to the spatially separated macroscopic atomic ensembles.

  6. Assessment of tumor energy and oxygenation status by bioluminescence, nuclear magnetic resonance spectroscopy, and cryospectrophotometry.

    Science.gov (United States)

    Mueller-Klieser, W; Schaefer, C; Walenta, S; Rofstad, E K; Fenton, B M; Sutherland, R M

    1990-03-15

    The energy and oxygenation status of tumors from two murine sarcoma lines (KHT, RIF-1) and two human ovarian carcinoma xenograft lines (MLS, OWI) were assessed using three independent techniques. Tumor energy metabolism was investigated in vivo by 31P nuclear magnetic resonance spectroscopy. After nuclear magnetic resonance measurements, tumors were frozen in liquid nitrogen to determine the tissue ATP concentration by imaging bioluminescence and to register the intracapillary oxyhemoglobin (HbO2) saturation using the cryospectrophotometric method. There was a positive correlation between the nucleoside triphosphate beta/total resonance ratio or a negative correlation between the Pi/total resonance ratio and the model ATP concentration obtained by bioluminescence, respectively. This was true for small tumors with no extended necrosis irrespective of tumor type. Moreover, a positive correlation was obtained between the HbO2 saturations and the ATP concentration measured with bioluminescence. The results demonstrate the potential of combined studies using noninvasive, integrating methods and high-resolution imaging techniques for characterizing the metabolic milieu in tumors.

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

    International Nuclear Information System (INIS)

    Tuner, Hasan

    2017-01-01

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

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

    Science.gov (United States)

    Tuner, Hasan

    2017-11-01

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

  9. Noninvasive assessment of tissue-engineered graft viability by oxygen-17 magnetic resonance spectroscopy.

    Science.gov (United States)

    Einstein, Samuel A; Weegman, Bradley P; Kitzmann, Jennifer P; Papas, Klearchos K; Garwood, Michael

    2017-05-01

    Transplantation of macroencapsulated tissue-engineered grafts (TEGs) is being investigated as a treatment for type 1 diabetes, but there is a critical need to measure TEG viability both in vitro and in vivo. Oxygen deficiency is the most critical issue preventing widespread implementation of TEG transplantation and delivery of supplemental oxygen (DSO) has been shown to enhance TEG survival and function in vivo. In this study, we demonstrate the first use of oxygen-17 magnetic resonance spectroscopy ( 17 O-MRS) to measure the oxygen consumption rate (OCR) of TEGs and show that in addition to providing therapeutic benefits to TEGs, DSO with 17 O 2 can also enable measurements of TEG viability. Macroencapsulated TEGs containing βTC3 murine insulinoma cells were prepared with three fractional viabilities and provided with 17 O 2 . Cellular metabolism of 17 O 2 into nascent mitochondrial water (H 2 17 O) was monitored by 17 O-MRS and, from the measured data, OCR was calculated. For comparison, OCR was simultaneously measured on a separate, but equivalent sample of cells with a well-established stirred microchamber technique. OCR measured by 17 O-MRS agreed well with measurements made in the stirred microchamber device. These studies confirm that 17 O-MRS can quantify TEG viability noninvasively. Biotechnol. Bioeng. 2017;114: 1118-1121. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  10. Pancreas Oxygen Persufflation Increases ATP Levels as Shown by Nuclear Magnetic Resonance

    Science.gov (United States)

    Scott, W.E.; Weegman, B.P.; Ferrer-Fabrega, J.; Stein, S.A.; Anazawa, T.; Kirchner, V.A.; Rizzari, M.D.; Stone, J.; Matsumoto, S.; Hammer, B.E.; Balamurugan, A.N.; Kidder, L.S.; Suszynski, T.M.; Avgoustiniatos, E.S.; Stone, S.G.; Tempelman, L.A.; Sutherland, D.E.R.; Hering, B.J.; Papas, K.K.

    2010-01-01

    Background Islet transplantation is a promising treatment for type 1 diabetes. Due to a shortage of suitable human pancreata, high cost, and the large dose of islets presently required for long-term diabetes reversal; it is important to maximize viable islet yield. Traditional methods of pancreas preservation have been identified as suboptimal due to insufficient oxygenation. Enhanced oxygen delivery is a key area of improvement. In this paper, we explored improved oxygen delivery by persufflation (PSF), ie, vascular gas perfusion. Methods Human pancreata were obtained from brain-dead donors. Porcine pancreata were procured by en bloc viscerectomy from heparinized donation after cardiac death donors and were either preserved by either two-layer method (TLM) or PSF. Following procurement, organs were transported to a 1.5-T magnetic resonance (MR) system for 31P nuclear magnetic resonance spectroscopy to investigate their bioenergetic status by measuring the ratio of adenosine triphosphate to inorganic phosphate (ATP:Pi) and for assessing PSF homogeneity by MRI. Results Human and porcine pancreata can be effectively preserved by PSF. MRI showed that pancreatic tissue was homogeneously filled with gas. TLM can effectively raise ATP:Pi levels in rat pancreata but not in larger porcine pancreata. ATP:Pi levels were almost undetectable in porcine organs preserved with TLM. When human or porcine organs were preserved by PSF, ATP:Pi was elevated to levels similar to those observed in rat pancreata. Conclusion The methods developed for human and porcine pancreas PSF homogeneously deliver oxygen throughout the organ. This elevates ATP levels during preservation and may improve islet isolation outcomes while enabling the use of marginal donors, thus expanding the usable donor pool. PMID:20692395

  11. EPR: Evidence and fallacy.

    Science.gov (United States)

    Nichols, Joseph W; Bae, You Han

    2014-09-28

    The enhanced permeability and retention (EPR) of nanoparticles in tumors has long stood as one of the fundamental principles of cancer drug delivery, holding the promise of safe, simple and effective therapy. By allowing particles preferential access to tumors by virtue of size and longevity in circulation, EPR provided a neat rationale for the trend toward nano-sized drug carriers. Following the discovery of the phenomenon by Maeda in the mid-1980s, this rationale appeared to be well justified by the flood of evidence from preclinical studies and by the clinical success of Doxil. Clinical outcomes from nano-sized drug delivery systems, however, have indicated that EPR is not as reliable as previously thought. Drug carriers generally fail to provide superior efficacy to free drug systems when tested in clinical trials. A closer look reveals that EPR-dependent drug delivery is complicated by high tumor interstitial fluid pressure (IFP), irregular vascular distribution, and poor blood flow inside tumors. Furthermore, the animal tumor models used to study EPR differ from clinical tumors in several key aspects that seem to make EPR more pronounced than in human patients. On the basis of this evidence, we believe that EPR should only be invoked on a case-by-case basis, when clinical evidence suggests the tumor type is susceptible. Copyright © 2014 Elsevier B.V. All rights reserved.

  12. EPR and development of quantum electronics

    International Nuclear Information System (INIS)

    Manenkov, A A

    2011-01-01

    A role of electron paramagnetic resonance in development of quantum electronics is discussed. Basic principles and history of masers are briefly described. Spin-levels of paramagnetic ions in crystals as a very suitable object for active media of solid-state masers (called as EPR-masers) and physical processes in EPR-masers (population inversion of energy states) are analyzed. This analysis demonstrates a significant role of relaxation processes in multi-level spin-systems for efficient maser action. In this context peculiarities of spin-lattice and spin-spin cross relaxation processes in multi-level systems are analyzed. Development of EPR-masers and their application in radioastronomy and far-space communication systems are briefly described.

  13. Nitroxyl Modified Tobacco Mosaic Virus as a Metal-Free High-Relaxivity MRI and EPR Active Superoxide Sensor.

    Science.gov (United States)

    Dharmarwardana, Madushani; Martins, André F; Chen, Zhuo; Palacios, Philip M; Nowak, Chance M; Welch, Raymond P; Li, Shaobo; Luzuriaga, Michael A; Bleris, Leonidas; Pierce, Brad S; Sherry, A Dean; Gassensmith, Jeremiah J

    2018-05-29

    Superoxide overproduction is known to occur in multiple disease states requiring critical care; yet, noninvasive detection of superoxide in deep tissue remains a challenge. Herein, we report a metal-free magnetic resonance imaging (MRI) and electron paramagnetic resonance (EPR) active contrast agent prepared by "click conjugating" paramagnetic organic radical contrast agents (ORCAs) to the surface of tobacco mosaic virus (TMV). While ORCAs are known to be reduced in vivo to an MRI/EPR silent state, their oxidation is facilitated specifically by reactive oxygen species-in particular, superoxide-and are largely unaffected by peroxides and molecular oxygen. Unfortunately, single molecule ORCAs typically offer weak MRI contrast. In contrast, our data confirm that the macromolecular ORCA-TMV conjugates show marked enhancement for T 1 contrast at low field (<3.0 T) and T 2 contrast at high field (9.4 T). Additionally, we demonstrated that the unique topology of TMV allows for a "quenchless fluorescent" bimodal probe for concurrent fluorescence and MRI/EPR imaging, which was made possible by exploiting the unique inner and outer surface of the TMV nanoparticle. Finally, we show TMV-ORCAs do not respond to normal cellular respiration, minimizing the likelihood for background, yet still respond to enzymatically produced superoxide in complicated biological fluids like serum.

  14. The EPR paradox revisited

    International Nuclear Information System (INIS)

    Cantrell, C.D.; Scully, M.O.

    1978-01-01

    Einstein, Podolsky and Rosen (EPR) argued in 1935 that quantum mechanics fails to give an adequate description of physical reality, and also cannot give a consistent wave-function description of certain phenomena. The authors show that a calculation based upon the reduced density matrix removes the formal inconsistency pointed out by EPR. The spirit of the present paper is that of a pedagogical review. (Auth.)

  15. EPR paradox revisited

    Energy Technology Data Exchange (ETDEWEB)

    Cantrell, C.D.; Scully, M.O.

    1978-07-01

    Einstein, Podolsky, and Rosen (EPR) argued in 1935 that quantum mechanics fails to give an adequate description of physical reality, and also cannot give a consistent wave-function description of certain phenomena. It is shown that a calculation based upon the reduced density matrix removes the formal inconsistency pointed out by EPR. The spirit of the present paper is that of a pedagogical review.

  16. A Comparative Evaluation of EPR and OxyLite Oximetry Using a Random Sampling of pO2 in a Murine Tumor

    Science.gov (United States)

    Vikram, Deepti S.; Bratasz, Anna; Ahmad, Rizwan; Kuppusamy, Periannan

    2015-01-01

    Methods currently available for the measurement of oxygen concentrations (oximetry) in viable tissues differ widely from each other in their methodological basis and applicability. The goal of this study was to compare two novel methods, particulate-based electron paramagnetic resonance (EPR) and OxyLite oximetry, in an experimental tumor model. EPR oximetry uses implantable paramagnetic particulates, whereas OxyLite uses fluorescent probes affixed on a fiber-optic cable. C3H mice were transplanted with radiation-induced fibrosarcoma (RIF-1) tumors in their hind limbs. Lithium phthalocyanine (LiPc) microcrystals were used as EPR probes. The pO2 measurements were taken from random locations at a depth of ~3 mm within the tumor either immediately or 48 h after implantation of LiPc. Both methods revealed significant hypoxia in the tumor. However, there were striking differences between the EPR and OxyLite readings. The differences were attributed to the volume of tissue under examination and the effect of needle invasion at the site of measurement. This study recognizes the unique benefits of EPR oximetry in terms of robustness, repeatability and minimal invasiveness. PMID:17705635

  17. EPR Dosimetry in Irradiated Fingernails

    International Nuclear Information System (INIS)

    Spinella, M.R.; Dubner, D.L.; Bof, E.

    2010-01-01

    The Electron Paramagnetic Resonance (EPR) is being transformed in a complementary tool of biologically-based methods for evaluation of dose after accidental radiation exposure. Many efforts are being carried out in laboratories to evaluate the performance of different materials for its use in EPR doses measurements and for improving the current methods for spectrum analysis and calibration curves determinations. In our country the EPR techniques have been used in different areas with dosimetric (alanine) and non dosimetric purposes. Now we are performing the first studies to obtain properly dose response curves to be used for accidental dose assessments through irradiated fingernails. It is by now well known that the fingernails present two types of signals, a background one (BKS), originated in elastic and inelastic mechanical deformations and the radio induced one (RIS), object of interest (I). In this work we will present some of the previous studies performed to characterize the fingernail samples and we analyse the additive dose method for data obtained employing the technique of the substraction of the spectrum recorded at two different microwave powers in order to reduce the BKS signal. Fingernail samples collected from different donors were treated by soaking in water during 10 min and 5 min drying on paper towel and the BKS signals were studied previously its irradiation. The statistical analysis (R statistics) show a distribution with a Standard Deviation of 24% respects to its media. During these studies we also conserved in freezer for more than 6 months irradiated fingernails that, were periodically measured and the statistical analysis of the peak to peak amplitude show a normal distribution through the Quantile correlation test with a SD 11% respected to its median. (authors)

  18. An X-band Co2+ EPR study of Zn1-xCoxO (x=0.005-0.1) nanoparticles prepared by chemical hydrolysis methods using diethylene glycol and denaturated alcohol at 5 K

    Science.gov (United States)

    Misra, Sushil K.; Andronenko, S. I.; Srinivasa Rao, S.; Chess, Jordan; Punnoose, A.

    2015-11-01

    EPR investigations on two types of dilute magnetic semiconductor (DMS) ZnO nanoparticles doped with 0.5-10% Co2+ ions, prepared by two chemical hydrolysis methods, using: (i) diethylene glycol ((CH2CH2OH)2O) (NC-rod-like samples), and (ii) denatured ethanol (CH3CH2OH) solutions (QC-spherical samples), were carried out at X-band (9.5 GHz) at 5 K. The analysis of EPR data for NC samples revealed the presence of several types of EPR lines: (i) two types, intense and weak, of high-spin Co2+ ions in the samples with Co concentration >0.5%; (ii) surface oxygen vacancies, and (iii) a ferromagnetic resonance (FMR) line. QC samples exhibit an intense FMR line and an EPR line due to high-spin Co2+ ions. FMR line is more intense, than the corresponding line exhibited by NC samples. These EPR spectra varied for sample with different doping concentrations. The magnetic states of these samples as revealed by EPR spectra, as well as the origin of ferromagnetism DMS samples are discussed.

  19. Monitoring Oxygen Levels in Orthotopic Human Glioma Xenograft Following Carbogen Inhalation and Chemotherapy by Implantable Resonator Based Oximetry

    Science.gov (United States)

    Hou, Huagang; Nemani, Venkata Krishnamurthy; Du, Gaixin; Montano, Ryan; Song, Rui; Gimi, Barjor; Swartz, Harold M.; Eastman, Alan; Khan, Nadeem

    2014-01-01

    Hypoxia is a critical hallmark of glioma, and significantly compromises treatment efficacy. Unfortunately, techniques for monitoring glioma pO2 to facilitate translational research are lacking. Furthermore, poor prognoses of patients with malignant glioma, in particular glioblastoma multiforme, warrant effective strategies that can inhibit hypoxia and improve treatment outcome. EPR oximetry using implantable resonators was implemented for monitoring pO2 in normal cerebral tissue and U251 glioma in mice. Breathing carbogen (95% O2 + 5% CO2) was tested for hyperoxia in the normal brain and glioma xenografts. A new strategy to inhibit glioma growth by rationally combining gemcitabine and MK-8776, a cell cycle checkpoint inhibitor, was also investigated. The mean pO2 of left and right hemisphere were approximately 56 – 69 mmHg in the normal cerebral tissue of mice. The mean baseline pO2 of U251 glioma on the first and fifth day of measurement was 21.9 ± 3.7 and 14.1 ± 2.4 mmHg, respectively. The mean brain pO2 including glioma increased by at least 100% on carbogen inhalation, although the response varied between the animals over days. Treatment with gemcitabine + MK-8776 significantly increased pO2 and inhibited glioma growth assessed by MRI. In conclusion, EPR oximetry with implantable resonators can be used to monitor the efficacy of carbogen inhalation and chemotherapy on orthotopic glioma in mice. The increase in glioma pO2 of mice breathing carbogen can be used to improve treatment outcome. The treatment with gemcitabine + MK-8776 is a promising strategy that warrants further investigation. PMID:25111969

  20. Monitoring oxygen levels in orthotopic human glioma xenograft following carbogen inhalation and chemotherapy by implantable resonator-based oximetry.

    Science.gov (United States)

    Hou, Huagang; Krishnamurthy Nemani, Venkata; Du, Gaixin; Montano, Ryan; Song, Rui; Gimi, Barjor; Swartz, Harold M; Eastman, Alan; Khan, Nadeem

    2015-04-01

    Hypoxia is a critical hallmark of glioma, and significantly compromises treatment efficacy. Unfortunately, techniques for monitoring glioma pO2 to facilitate translational research are lacking. Furthermore, poor prognosis of patients with malignant glioma, in particular glioblastoma multiforme, warrant effective strategies that can inhibit hypoxia and improve treatment outcome. EPR oximetry using implantable resonators was implemented for monitoring pO2 in normal cerebral tissue and U251 glioma in mice. Breathing carbogen (95% O2 + 5% CO2 ) was tested for hyperoxia in the normal brain and glioma xenografts. A new strategy to inhibit glioma growth by rationally combining gemcitabine and MK-8776, a cell cycle checkpoint inhibitor, was also investigated. The mean pO2 of left and right hemisphere were ∼56-69 mmHg in the normal cerebral tissue of mice. The mean baseline pO2 of U251 glioma on the first and fifth day of measurement was 21.9 ± 3.7 and 14.1 ± 2.4 mmHg, respectively. The mean brain pO2 including glioma increased by at least 100% on carbogen inhalation, although the response varied between the animals over days. Treatment with gemcitabine + MK-8776 significantly increased pO2 and inhibited glioma growth assessed by MRI. In conclusion, EPR oximetry with implantable resonators can be used to monitor the efficacy of carbogen inhalation and chemotherapy on orthotopic glioma in mice. The increase in glioma pO2 of mice breathing carbogen can be used to improve treatment outcome. The treatment with gemcitabine + MK-8776 is a promising strategy that warrants further investigation. © 2014 UICC.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-11-15

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

  2. Development of Selective Excitation Methods in Nuclear Magnetic Resonance: Investigation of Hemoglobin Oxygenation in Erythrocytes Using Proton and Phosphorus -31 Nuclear Magnetic Resonance

    Science.gov (United States)

    Fetler, Bayard Keith

    1993-01-01

    Nuclear magnetic resonance (NMR) offers a potential method for making measurements of the percent oxygenation of hemoglobin (Hb) in living tissue non-invasively. As a demonstration of the feasibility of such measurements, we measured the percent oxygenation of Hb in red blood cells (erythrocytes) using resonances in the proton-NMR (^1H-NMR) spectrum which are characteristic of oxyhemoglobin (oxy-Hb) and deoxyhemoglobin (deoxy-Hb), and are due to the unique magnetic properties of these molecules. To perform these measurements, we developed a new NMR method of selectively exciting signals in a region of interest with uniform phase and amplitude, while suppressing the signal of the water resonance. With this method, we are able to make exact calculations distinguishing between uniform phase excitation produced at large flip-angles using the non-linear properties of the Bloch equations, and uniform phase excitation produced at small flip-angles using asymmetric pulse excitation functions. We measured the percent oxygenation of three characteristic ^1H-NMR resonances of Hb: two from deoxy-Hb, originating from the N_delta H protons of histidine residue F8, which occur at different frequencies for the alpha and beta chains of Hb; and one from oxy-Hb, originating from the gamma_2 -CH_3 protons of valine residue E11. We performed experiments both on fresh erythrocytes and on erythrocytes depleted of 2,3-diphosphoglycerate (2,3-DPG), and found that oxygen is more tightly bound to Hb in the former case. In both fresh and 2,3-DPG-depleted samples, we found that: (i) from the deoxy-Hb marker resonances, there is a small but significant difference in the oxygen saturation between the alpha and beta chains; (ii) the decrease in the areas of the deoxy-Hb marker resonances correlates well with the increase in the percent oxygenation of Hb as measured optically; (iii) the area of the oxy-Hb marker resonance may be up to ~15% less than the optically measured Hb saturation. We are

  3. Pulsed-High Field/High-Frequency EPR Spectroscopy

    Science.gov (United States)

    Fuhs, Michael; Moebius, Klaus

    Pulsed high-field/high-frequency electron paramagnetic resonance (EPR) spectroscopy is used to disentangle many kinds of different effects often obscured in continuous wave (cw) EPR spectra at lower magnetic fields/microwave frequencies. While the high magnetic field increases the resolution of G tensors and of nuclear Larmor frequencies, the high frequencies allow for higher time resolution for molecular dynamics as well as for transient paramagnetic intermediates studied with time-resolved EPR. Pulsed EPR methods are used for example for relaxation-time studies, and pulsed Electron Nuclear DOuble Resonance (ENDOR) is used to resolve unresolved hyperfine structure hidden in inhomogeneous linewidths. In the present article we introduce the basic concepts and selected applications to structure and mobility studies on electron transfer systems, reaction centers of photosynthesis as well as biomimetic models. The article concludes with an introduction to stochastic EPR which makes use of an other concept for investigating resonance systems in order to increase the excitation bandwidth of pulsed EPR. The limited excitation bandwidth of pulses at high frequency is one of the main limitations which, so far, made Fourier transform methods hardly feasible.

  4. Biomolecular EPR spectroscopy

    CERN Document Server

    Hagen, Wilfred Raymond

    2008-01-01

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

  5. An EPR investigation of SiO{sub x} films with columnar structure

    Energy Technology Data Exchange (ETDEWEB)

    Bratus' , V., E-mail: v_bratus@isp.kiev.ua [V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine, Kyiv 03680 (Ukraine); Indutnyi, I.; Shepeliavyi, P. [V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine, Kyiv 03680 (Ukraine); Torchynska, T. [ESFM-Instituto Politécnico Nacional, México D.F. 07738 (Mexico)

    2014-11-15

    The results of electron paramagnetic resonance (EPR) study of obliquely deposited porous SiO{sub x} films before and after thermal annealing in vacuum at 950 °C are presented. The low intensity slightly asymmetrical and featureless EPR line with a g-value of 2.0044 and a linewidth of 0.77 mT has been detected in as-sputtered films and attributed to dangling bonds of silicon atoms in amorphous SiO{sub x} domains with x=0.8. Successive annealing results in decreasing this line and the appearance of an intense EPR line with g=2.0025, linewidth of 0.11 mT and a hyperfine doublet with 1.6 mT splitting. According to the parameters this spectrum has been attributed to the EX center, a hole delocalized over four non-bridging oxygen atoms grouped around a Si vacancy in SiO{sub 2}. The impact of chemical treatment before annealing and duration of anneals on the defect system is discussed.

  6. Electron Spin Resonance Spectroscopy for Studying the Generation and Scavenging of Reactive Oxygen Species by Nanomaterials

    Science.gov (United States)

    Yin, Jun-Jie; Zhao, Baozhong; Xia, Qingsu; Fu, Peter P.

    2013-09-01

    One fundamental mechanism widely described for nanotoxicity involves oxidative damage due to generation of free radicals and other reactive oxygen species. Indeed, the ability of nanoscale materials to facilitate the transfer of electrons, and thereby promote oxidative damage or in some instances provide antioxidant protection, may be a fundamental property of these materials. Any assessment of a nanoscale material's safety must therefore consider the potential for toxicity arising from oxidative damage. Therefore, rapid and predictive methods are needed to assess oxidative damage elicited by nanoscale materials. The use of electron spin resonance (ESR) to study free radical related bioactivity of nanomaterials has several advantages for free radical determination and identification. Specifically it can directly assess antioxidant quenching or prooxidant generation of relevant free radicals and reactive oxygen species. In this chapter, we have reported some nonclassical behaviors of the electron spin relaxation properties of unpaired electrons in different fullerenes and the investigation of anti/prooxidant activity by various types of nanomaterials using ESR. In addition, we have reviewed the mechanisms of free radical formation photosensitized by different nanomaterials. This chapter also included the use of spin labels, spin traps and ESR oximetry to systematically examine the enzymatic mimetic activities of nanomaterials.

  7. In Vivo pO2 Imaging of Tumors: Oxymetry with Very Low-Frequency Electron Paramagnetic Resonance.

    Science.gov (United States)

    Epel, Boris; Halpern, Howard J

    2015-01-01

    For over a century, it has been known that tumor hypoxia, regions of a tumor with low levels of oxygenation, are important contributors to tumor resistance to radiation therapy and failure of radiation treatment of cancer. Recently, using novel pulse electron paramagnetic resonance (EPR) oxygen imaging, near absolute images of the partial pressure of oxygen (pO2) in tumors of living animals have been obtained. We discuss here the means by which EPR signals can be obtained in living tissues and tumors. We review development of EPR methods to image the pO2 in tumors and the potential for the pO2 image acquisition in human subjects. © 2015 Elsevier Inc. All rights reserved.

  8. In vivo pO2 imaging of tumors: Oxymetry with very low frequency Electron Paramagnetic Resonance

    Science.gov (United States)

    Epel, Boris; Halpern, Howard J.

    2016-01-01

    For over a century it has been known that tumor hypoxia, regions of a tumor with low levels of oxygenation, are important contributors to tumor resistance to radiation therapy and failure of radiation treatment of cancer. Recently, using novel pulse electron paramagnetic resonance (EPR) oxygen imaging, near absolute images of the partial pressure of oxygen (pO2) in tumors of living animals have been obtained. We discuss here the means by which EPR signals can be obtained in living tissues and tumors. We review development of EPR methods to image the pO2 in tumors and the potential for the pO2 image acquisition in human subjects. PMID:26477263

  9. EPR paradox revisited

    Energy Technology Data Exchange (ETDEWEB)

    Klippert, R. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil)

    1999-07-01

    In a seminal paper from 1935 Einstein, Podolsky and Rosen produced one of the most powerful weapon against the unpredictability of the world ensured by quantum mechanics. The recent production of entangled states, with all its possible future applications in quantum computation, re-open the possibility of testing EPR states on physical grounds. The present intends to present a challenge to the wedding of classical (special) relativity with quantum mechanics, the so called relativistic quantum mechanics. Making use of the same apparatus devised in EPR, it is shown that non local quantum states are incompatible with either their possibility of being measured or else with Lorentz invariance (or even with both). (author)

  10. Investigation of EPR signals on tooth enamel

    Energy Technology Data Exchange (ETDEWEB)

    Pavlenko, A; Mironova-Ulmane, N; Polakov, M; Riekstina, D [Institute of Solid State Physics, University of Latvia, Riga (Latvia)

    2007-12-15

    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.

  11. EPR Imaging at a Few Megahertz Using SQUID Detectors

    Science.gov (United States)

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

    2010-01-01

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

  12. Superhigh-frequency circuit for the EPR spectrometer with rectifier screening

    International Nuclear Information System (INIS)

    Zhizhchenko, G.A.; Tsvirko, L.V.

    1983-01-01

    The hamodyne SHF circuit of a 3-cm EPR spectrometer with a reflecting resonator is described. The optimum operating mode of SHF-rectifier at a constant phase difference is automatically assured in the circuit. The circuit employs a reflecting p-i-n- attenuator and a SHF-rectifier sereen which simplify the spectrometer tuming. The circuit is used in a miniature EPR radiospectrometer Minsk EPR-6-type

  13. Dynamic oxygen-enhanced magnetic resonance imaging of the lung in asthma—Initial experience

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Wei-Juan, E-mail: weijuan.zhang@postgrad.manchester.ac.uk [Centre for Imaging Sciences, The University of Manchester, Oxford Road, Manchester M13 9PT (United Kingdom); Biomedical Imaging Institute, The University of Manchester, Oxford Road, Manchester M13 9PT (United Kingdom); Niven, Robert M., E-mail: robert.niven@uhsm.nhs.uk [North West Lung Research Centre, University Hospital of South Manchester, Southmoor Road, Manchester M23 9LT (United Kingdom); Young, Simon S., E-mail: Simon.Young1@astrazeneca.com [Personalised Healthcare and Biomarkers, AstraZeneca R and D, Alderley Park, Macclesfield SK10 4TF (United Kingdom); Liu, Yu-Zhen, E-mail: yu-zhen.liu@astrazeneca.com [Personalised Healthcare and Biomarkers, AstraZeneca R and D, Alderley Park, Macclesfield SK10 4TF (United Kingdom); Parker, Geoffrey J.M., E-mail: Geoff.parker@manchester.ac.uk [Centre for Imaging Sciences, The University of Manchester, Oxford Road, Manchester M13 9PT (United Kingdom); Biomedical Imaging Institute, The University of Manchester, Oxford Road, Manchester M13 9PT (United Kingdom); Bioxydyn Limited, Rutherford House, Pencroft Way, Manchester M15 6SZ (United Kingdom); Naish, Josephine H., E-mail: Josephine.naish@manchester.ac.uk [Centre for Imaging Sciences, The University of Manchester, Oxford Road, Manchester M13 9PT (United Kingdom); Biomedical Imaging Institute, The University of Manchester, Oxford Road, Manchester M13 9PT (United Kingdom)

    2015-02-15

    Highlights: • Oxygen-enhanced MRI may have a role in the estimation of disease severity in asthma. • Heterogeneity of parameter maps reflects localized functional impairment in asthma. • OE-MRI provides non-ionising, spatial and temporal information on oxygen delivery. - Abstract: Objectives: To prospectively estimate the feasibility and reproducibility of dynamic oxygen-enhanced magnetic resonance imaging (OE-MRI) in the assessment of regional oxygen delivery, uptake and washout in asthmatic lungs. Materials and methods: The study was approved by the National Research Ethics Committee and written informed consent was obtained. Dynamic OE-MRI was performed twice at one month apart on four mild asthmatic patients (23 ± 5 years old, FEV{sub 1} = 96 ± 3% of predicted value) and six severe asthmatic patients (41 ± 12 years old, FEV{sub 1} = 60 ± 14% of predicted value) on a 1.5 T MR scanner using a two-dimensional T{sub 1}-weighted inversion-recovery turbo spin echo sequence. The enhancing fraction (EF), the maximal change in the partial pressure of oxygen in lung tissue (ΔPO{sub 2max{sub l}}) and arterial blood of the aorta (ΔPO{sub 2max{sub a}}), and the oxygen wash-in (τ{sub up{sub l}}, τ{sub up{sub a}}) and wash-out (τ{sub down{sub l}}, τ{sub down{sub a}}) time constants were extracted and compared between groups using the independent-samples t-test (two-tailed). Correlations between imaging readouts and clinical measurements were assessed by Pearson's correlation analysis. Bland–Altman analysis was used to estimate the levels of agreement between the repeat scans and the intra-observer agreement in the MR imaging readouts. Results: The severe asthmatic group had significantly smaller EF (70 ± 16%) and median ΔPO{sub 2max{sub l}} (156 ± 52 mmHg) and significantly larger interquartile range of τ{sub up{sub l}} (0.84 ± 0.26 min) than the mild asthmatic group (95 ± 3%, P = 0.014; 281 ± 40 mmHg, P = 0.004; 0.20 ± 0.07 min, P = 0

  14. Dynamic oxygen-enhanced magnetic resonance imaging of the lung in asthma—Initial experience

    International Nuclear Information System (INIS)

    Zhang, Wei-Juan; Niven, Robert M.; Young, Simon S.; Liu, Yu-Zhen; Parker, Geoffrey J.M.; Naish, Josephine H.

    2015-01-01

    Highlights: • Oxygen-enhanced MRI may have a role in the estimation of disease severity in asthma. • Heterogeneity of parameter maps reflects localized functional impairment in asthma. • OE-MRI provides non-ionising, spatial and temporal information on oxygen delivery. - Abstract: Objectives: To prospectively estimate the feasibility and reproducibility of dynamic oxygen-enhanced magnetic resonance imaging (OE-MRI) in the assessment of regional oxygen delivery, uptake and washout in asthmatic lungs. Materials and methods: The study was approved by the National Research Ethics Committee and written informed consent was obtained. Dynamic OE-MRI was performed twice at one month apart on four mild asthmatic patients (23 ± 5 years old, FEV 1 = 96 ± 3% of predicted value) and six severe asthmatic patients (41 ± 12 years old, FEV 1 = 60 ± 14% of predicted value) on a 1.5 T MR scanner using a two-dimensional T 1 -weighted inversion-recovery turbo spin echo sequence. The enhancing fraction (EF), the maximal change in the partial pressure of oxygen in lung tissue (ΔPO 2max l ) and arterial blood of the aorta (ΔPO 2max a ), and the oxygen wash-in (τ up l , τ up a ) and wash-out (τ down l , τ down a ) time constants were extracted and compared between groups using the independent-samples t-test (two-tailed). Correlations between imaging readouts and clinical measurements were assessed by Pearson's correlation analysis. Bland–Altman analysis was used to estimate the levels of agreement between the repeat scans and the intra-observer agreement in the MR imaging readouts. Results: The severe asthmatic group had significantly smaller EF (70 ± 16%) and median ΔPO 2max l (156 ± 52 mmHg) and significantly larger interquartile range of τ up l (0.84 ± 0.26 min) than the mild asthmatic group (95 ± 3%, P = 0.014; 281 ± 40 mmHg, P = 0.004; 0.20 ± 0.07 min, P = 0.001, respectively). EF, median ΔPO 2max l and τ down l and the interquartile range of τ up l

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

    Science.gov (United States)

    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.

  16. Detection of reactive oxygen species in isolated, perfused lungs by electron spin resonance spectroscopy

    Directory of Open Access Journals (Sweden)

    Schudt Christian

    2005-07-01

    Full Text Available Abstract Background The sources and measurement of reactive oxygen species (ROS in intact organs are largely unresolved. This may be related to methodological problems associated with the techniques currently employed for ROS detection. Electron spin resonance (ESR with spin trapping is a specific method for ROS detection, and may address some these technical problems. Methods We have established a protocol for the measurement of intravascular ROS release from isolated buffer-perfused and ventilated rabbit and mouse lungs, combining lung perfusion with the spin probe l-hydroxy-3-carboxy-2,2,5,5-tetramethylpyrrolidine (CPH and ESR spectroscopy. We then employed this technique to characterize hypoxia-dependent ROS release, with specific attention paid to NADPH oxidase-dependent superoxide formation as a possible vasoconstrictor pathway. Results While perfusing lungs with CPH over a range of inspired oxygen concentrations (1–21 %, the rate of CP• formation exhibited an oxygen-dependence, with a minimum at 2.5 % O2. Addition of superoxide dismutase (SOD to the buffer fluid illustrated that a minor proportion of this intravascular ROS leak was attributable to superoxide. Stimulation of the lungs by injection of phorbol-12-myristate-13-acetate (PMA into the pulmonary artery caused a rapid increase in CP• formation, concomitant with pulmonary vasoconstriction. Both the PMA-induced CPH oxidation and the vasoconstrictor response were largely suppressed by SOD. When the PMA challenge was performed at different oxygen concentrations, maximum superoxide liberation and pulmonary vasoconstriction occurred at 5 % O2. Using a NADPH oxidase inhibitor and NADPH-oxidase deficient mice, we illustrated that the PMA-induced superoxide release was attributable to the stimulation of NADPH oxidases. Conclusion The perfusion of isolated lungs with CPH is suitable for detection of intravascular ROS release by ESR spectroscopy. We employed this technique to

  17. EPR: the nuclear impasse

    International Nuclear Information System (INIS)

    Marillier, F.

    2008-01-01

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

  18. Software for evaluation of EPR-dosimetry performance

    International Nuclear Information System (INIS)

    Shishkina, E.A.; Timofeev, Yu.S.; Ivanov, D.V.

    2014-01-01

    Electron paramagnetic resonance (EPR) with tooth enamel is a method extensively used for retrospective external dosimetry. Different research groups apply different equipment, sample preparation procedures and spectrum processing algorithms for EPR dosimetry. A uniform algorithm for description and comparison of performances was designed and implemented in a new computer code. The aim of the paper is to introduce the new software 'EPR-dosimetry performance'. The computer code is a user-friendly tool for providing a full description of method-specific capabilities of EPR tooth dosimetry, from metrological characteristics to practical limitations in applications. The software designed for scientists and engineers has several applications, including support of method calibration by evaluation of calibration parameters, evaluation of critical value and detection limit for registration of radiation-induced signal amplitude, estimation of critical value and detection limit for dose evaluation, estimation of minimal detectable value for anthropogenic dose assessment and description of method uncertainty. (authors)

  19. EPR of radiation defects in lithium-oxyfluoride glass ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Fedotovs, A; Rogulis, U; Sarakovskis, A; Dimitrocenko, L, E-mail: andris-f@navigator.l [Institute of Solid State Physics, University of Latvia, Kengaraga st. 8, LV-1063, Riga (Latvia)

    2010-11-01

    We studied oxyfluoride composites based on lithium silicate glasses with yttrium fluorides and rare-earth dopants. The electron paramagnetic resonance (EPR) has been used to obtain information about radiation induced defects in these materials. Spectra have been measured before and after X-ray irradiation at room temperature and at liquid nitrogen temperature. Fluoride crystallites within samples were created by means of thermal treatment at specific temperatures. EPR spectra of radiation induced defects in oxyfluoride glass ceramics, in which crystallites have not been yet created, show no explicit hfs interaction of fluorine nuclei. However, in glass ceramics, which already contains fluoride crystallites, the hfs characteristic to fluorine nuclei appears in the EPR spectra. EPR hyperfine structure could be explained within a model of an F-type centre in YF{sub 3} crystalline phase.

  20. EPR of radiation defects in lithium-oxyfluoride glass ceramics

    Science.gov (United States)

    Fedotovs, A.; Rogulis, U.; Sarakovskis, A.; Dimitrocenko, L.

    2010-11-01

    We studied oxyfluoride composites based on lithium silicate glasses with yttrium fluorides and rare-earth dopants. The electron paramagnetic resonance (EPR) has been used to obtain information about radiation induced defects in these materials. Spectra have been measured before and after X-ray irradiation at room temperature and at liquid nitrogen temperature. Fluoride crystallites within samples were created by means of thermal treatment at specific temperatures. EPR spectra of radiation induced defects in oxyfluoride glass ceramics, in which crystallites have not been yet created, show no explicit hfs interaction of fluorine nuclei. However, in glass ceramics, which already contains fluoride crystallites, the hfs characteristic to fluorine nuclei appears in the EPR spectra. EPR hyperfine structure could be explained within a model of an F-type centre in YF3 crystalline phase.

  1. Kinetics of oxygen exchange between bisulfite ion and water as studied by oxygen-17 nuclear magnetic resonance spectroscopy

    International Nuclear Information System (INIS)

    Horner, D.A.

    1984-08-01

    The nuclear magnetic relaxation times of oxygen-17 have been measured in aqueous sodium bisulfite solutions in the pH range from 2.5 to 5 as a function of temperature, pH, and S(IV) concentration, at an ionic strength of 1.0 m. The rate law for oxygen exchange between bisulfite ion and water was obtained from an analysis of the data, and is consistent with oxygen exchange occurring via the reaction SO 2 + H 2 O right reversible H + + SHO 3 - . The value of k/sub -1/ is in agreement with relaxation measurements. Direct spectroscopic evidence was found for the existence of two isomers of bisulfite ion: one with the proton bonded to the sulfur (HSO 3 - ) and the other with the proton bonded to an oxygen (SO 3 H - ). (The symbol SHO 3 - in the above chemical equation refers to both isomeric forms of bisulfite ion.) The relative amounts of the two isomers were determined as a function of temperature, and the rate and mechanism of oxygen exchange between the two was investigated. One of the two isomers, presumably SO 3 H - , exchanges oxygens with water much more rapidly than does the other. A two-pulse sequence was developed which greatly diminished the solvent peak in the NMR spectrum

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

    Science.gov (United States)

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

    2017-11-01

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

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

    Science.gov (United States)

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

    2017-11-01

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

  4. Epr, structural characteristics and intramolecular movements of some phenoxyl radicals in toluene

    OpenAIRE

    Nizameev, I.; Pudovkin, M.; Kadirov, M.

    2010-01-01

    The method of electron paramagnetic resonance (EPR) spectroscopy was used for studying magnetic and dynamic properties of phenoxyl radicals in toluene at 170-370 K. Characteristics of intramolecular motion and structure of phenoxyl radicals were determined from the temperature dependence of EPR spectra. For all the given compounds the activation energies of transitions between the conformers were calculated.

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

    Science.gov (United States)

    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. Copyright © 2015 Elsevier Inc. All rights reserved.

  6. Investigation of the generation of singlet oxygen in ensembles of photoexcited silicon nanocrystals by electron paramagnetic resonance spectroscopy

    International Nuclear Information System (INIS)

    Konstantinova, E. A.; Demin, V. A.; Timoshenko, V. Yu.

    2008-01-01

    The generation of singlet oxygen is investigated and its concentration upon photoexcitation of silicon nanocrystals in porous silicon layers is determined using electron paramagnetic resonance spectroscopy. The relaxation times of spin centers, i.e., silicon dangling bonds, in vacuum and in an oxygen atmosphere in the dark and under illumination of the samples are measured for the first time. It is revealed that the spin-lattice relaxation in porous silicon is retarded as compared to that in a single-crystal substrate. From analyzing experimental data, a microscopic model is proposed for interaction of oxygen molecules in the triplet state and spin centers at the surface of silicon nanocrystals. The results obtained have demonstrated that porous silicon holds promise for the use as a photosensitizer of molecular oxygen in biomedical applications

  7. Multisite EPR oximetry from multiple quadrature harmonics.

    Science.gov (United States)

    Ahmad, R; Som, S; Johnson, D H; Zweier, J L; Kuppusamy, P; Potter, L C

    2012-01-01

    Multisite continuous wave (CW) electron paramagnetic resonance (EPR) oximetry using multiple quadrature field modulation harmonics is presented. First, a recently developed digital receiver is used to extract multiple harmonics of field modulated projection data. Second, a forward model is presented that relates the projection data to unknown parameters, including linewidth at each site. Third, a maximum likelihood estimator of unknown parameters is reported using an iterative algorithm capable of jointly processing multiple quadrature harmonics. The data modeling and processing are applicable for parametric lineshapes under nonsaturating conditions. Joint processing of multiple harmonics leads to 2-3-fold acceleration of EPR data acquisition. For demonstration in two spatial dimensions, both simulations and phantom studies on an L-band system are reported. Copyright © 2011 Elsevier Inc. All rights reserved.

  8. Subpicosecond oxygen trapping in the heme pocket of the oxygen sensor FixL observed by time-resolved resonance Raman spectroscopy.

    Science.gov (United States)

    Kruglik, Sergei G; Jasaitis, Audrius; Hola, Klara; Yamashita, Taku; Liebl, Ursula; Martin, Jean-Louis; Vos, Marten H

    2007-05-01

    Dissociation of oxygen from the heme domain of the bacterial oxygen sensor protein FixL constitutes the first step in hypoxia-induced signaling. In the present study, the photodissociation of the heme-O2 bond was used to synchronize this event, and time-resolved resonance Raman (TR(3)) spectroscopy with subpicosecond time resolution was implemented to characterize the heme configuration of the primary photoproduct. TR(3) measurements on heme-oxycomplexes are highly challenging and have not yet been reported. Whereas in all other known six-coordinated heme protein complexes with diatomic ligands, including the oxymyoglobin reported here, heme iron out-of-plane motion (doming) occurs faster than 1 ps after iron-ligand bond breaking; surprisingly, no sizeable doming is observed in the oxycomplex of the Bradyrhizobium japonicum FixL sensor domain (FixLH). This assessment is deduced from the absence of the iron-histidine band around 217 cm(-1) as early as 0.5 ps. We suggest that efficient ultrafast oxygen rebinding to the heme occurs on the femtosecond time scale, thus hindering heme doming. Comparing WT oxy-FixLH, mutant proteins FixLH-R220H and FixLH-R220Q, the respective carbonmonoxy-complexes, and oxymyoglobin, we show that a hydrogen bond of the terminal oxygen atom with the residue in position 220 is responsible for the observed behavior; in WT FixL this residue is arginine, crucially implicated in signal transmission. We propose that the rigid O2 configuration imposed by this residue, in combination with the hydrophobic and constrained properties of the distal cavity, keep dissociated oxygen in place. These results uncover the origin of the "oxygen cage" properties of this oxygen sensor protein.

  9. EPR in characterization of seeds paramagnetic species

    International Nuclear Information System (INIS)

    Luiz, A.P.C.; Mauro, M.F.F.L.; Portugal, K.O.; Barbana, V.M.; Guedes, C.L.B.; Mauro, E. di; Carneiro, C.E.A.; Zaia, D.A.M.; Prete, C.E.C.

    2011-01-01

    Full text. In Brazil, since 1970s, renewable fuel programs has been developed in order to replace petroleum. Today a program that has been discussed is the bio diesel, which intend to replace diesel fuel, fossil oil, to bio diesel, renewal fuel. As seeds are the basis for production of oil and consequently processed into bio diesel, the goal of this work is to characterize and compare paramagnetic species present in the seeds by Electron Paramagnetic Resonance (EPR). Samples used in this study were seeds of sorghum, barley, corn, peanuts, soy beans, cotton, wheat, oats, mustard, rice, sunflower and turnip. Some paramagnetic species present in soil was also investigated as goethite (FeOOH), hematite (Fe 2 O 3 ), magnetite (Fe 3 O 4 ), and ferrihydrite (Fe 5 HO 8 · 4H 2 O), since, these species present in appreciable quantities in the soil can be present in the seeds and analyzed for comparison. The characterization of these species is essential to understand the EPR seeds spectra. Each sample is placed in a thin quartz tube 4 mm in diameter, and it is inserted into the cavity of the spectrometer at room temperature, at low temperature (77 K) and variable temperature using liquid nitrogen flow and hot flow through a compressor air. It was used as standard Mg O:Mn 2+ , which is also inserted into the cavity. Shortly after the potency is regulated, frequency, amplitude and sweep the field. The spectroscopic analysis by EPR X-band (∼ 9:5GHz), were performed at the Fluorescence and Electron Paramagnetic Resonance Laboratory, Exact Sciences Center, State University of Londrina, Parana state, Brazil, through an EPR spectrometer JEOL brand (JES-PE-3X). In the EPR spectra, spectroscopic factor or g factor and line width were determined in paramagnetic species. Studies from several seeds with EPR technique detected in all of them presence of same complex of Fe 3+ present in the goethite at g ∼ 2, and in the seeds exist free radicals at g = 2:004, at room temperature

  10. EPR in characterization of seeds paramagnetic species

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-07-01

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

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

    DEFF Research Database (Denmark)

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

    2002-01-01

    In the present work we have applied the method of the EPR spin probes which allows performing simultaneously EPR and magnetization measurements to the investigation of magnetism of the Cid stearate Langmuir-Blodgett (LB) films. For this purpose we have prepared and studied by the EPR technique...... the Gd and Y stearate LB films. Placing the small BDPA crystal on the film surface we have found that for the Gd LB sample the effective g-value of the radical's resonance depends on the film orientation in respect to the external magnetic field direction. The relative shift of the EPR signal...

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

    Science.gov (United States)

    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.

  13. Tumour oxygen dynamics measured simultaneously by near-infrared spectroscopy and 19F magnetic resonance imaging in rats

    International Nuclear Information System (INIS)

    Xia Mengna; Kodibagkar, Vikram; Liu Hanli; Mason, Ralph P

    2006-01-01

    Simultaneous near-infrared spectroscopy (NIRS) and magnetic resonance imaging (MRI) were used to investigate the correlation between tumour vascular oxygenation and tissue oxygen tension dynamics in rat breast 13762NF tumours with respect to hyperoxic gas breathing. NIRS directly detected global variations in the oxygenated haemoglobin concentration (Δ[HbO 2 ]) within tumours and oxygen tension (pO 2 ) maps were achieved using 19 F MRI of the reporter molecule hexafluorobenzene. Multiple correlations were examined between rates and magnitudes of vascular (Δ[HbO 2 ]) and tissue (pO 2 ) responses. Significant correlations were found between response to oxygen and carbogen breathing using either modality. Comparison of results for the two methods showed a correlation between the vascular perfusion rate ratio and the mean pO 2 values (R 2 > 0.7). The initial rates of increase of Δ[HbO 2 ] and the slope of dynamic pO 2 response, d(pO 2 )/dt, of well-oxygenated voxels in response to hyperoxic challenge were also correlated. These results demonstrate the feasibility of simultaneous measurements using NIRS and MRI. As expected, the rate of pO 2 response to oxygen is primarily dependent upon the well perfused rather than poorly perfused vasculature

  14. Dancing with the Electrons: Time-Domain and CW In Vivo EPR Imaging

    Directory of Open Access Journals (Sweden)

    Murali C. Krishna

    2008-01-01

    Full Text Available The progress in the development of imaging the distribution of unpaired electrons in living systems and the functional and the potential diagnostic dimensions of such an imaging process, using Electron Paramagnetic Resonance Imaging (EPRI, is traced from its origins with emphasis on our own work. The importance of EPR imaging stems from the fact that many paramagnetic probes show oxygen dependent spectral broadening. Assessment of in vivo oxygen concentration is an important factor in radiation oncology in treatment-planning and monitoring treatment-outcome. The emergence of narrow-line trairylmethyl based, bio-compatible spin probes has enabled the development of radiofrequency time-domain EPRI. Spectral information in time-domain EPRI can be achieved by generating a time sequence of T2* or T2 weighted images. Progress in CW imaging has led to the use of rotating gradients, more recently rapid scan with direct detection, and a combination of all the three. Very low field MRI employing Dynamic Nuclear polarization (Overhauser effect is also employed for monitoring tumor hypoxia, and re-oxygenation in vivo. We have also been working on the co-registration of MRI and time domain EPRI on mouse tumor models at 300 MHz using a specially designed resonator assembly. The mapping of the unpaired electron distribution and unraveling the spectral characteristics by using magnetic resonance in presence of stationary and rotating gradients in indeed ‘dancing with the (unpaired electrons’, metaphorically speaking.

  15. Dancing with the Electrons: Time-Domain and CW EPR Imaging

    Directory of Open Access Journals (Sweden)

    Sankaran Subramanian

    2008-01-01

    Full Text Available The progress in the development of imaging the distribution of unpaired electrons in living systems and the functional and the potential diagnostic dimensions of such an imaging process, using Electron Paramagnetic Resonance Imaging (EPRI, is traced from its origins with emphasis on our own work. The importance of EPR imaging stems from the fact that many paramagnetic probes show oxygen dependent spectral broadening. Assessment of in vivo oxygen concentration is an important factor in radiation oncology in treatment-planning and monitoring treatment-outcome. The emergence of narrow-line trairylmethyl based, bio-compatible spin probes has enabled the development of radiofrequency time-domain EPRI. Spectral information in time-domain EPRI can be achieved by generating a time sequence of T 2 * or T 2 weighted images. Progress in CW imaging has led to the use of rotating gradients, more recently rapid scan with direct detection, and a combination of all the three. Very low field MRI employing Dynamic Nuclear polarization (Overhauser effect is also employed for monitoring tumor hypoxia, and re-oxygenation in vivo . We have also been working on the co-registration of MRI and time domain EPRI on mouse tumor models at 300 MHz using a specially designed resonator assembly. The mapping of the unpaired electron distribution and unraveling the spectral characteristics by using magnetic resonance in presence of stationary and rotating gradients in indeed ‘dancing with the ( unpaired electrons’, metaphorically speaking.

  16. Oxygen 18 concentration profile measurements near the surface by 18O(p,α)15N resonance reaction

    International Nuclear Information System (INIS)

    Amsel, G.; David, D.

    1975-01-01

    The method of spectrum reduction in nuclear reaction microanalysis does not allow to obtain depth resolutions better than the order of 2000A. Resolutions of the order of 200A may be obtained by using the narrow resonance technique, when applied to thin films. The latter technique was extended to thick targets, with deep concentration profiles presenting a sharp gradient near the surface. This method is presented and illustrated by the study of 18 O profiles in oxygen diffusion measurements in growing ZrO 2 , using the 629keV resonance of the reaction 18 O(p,α) 15 N [fr

  17. EPR (European Pressurized Reactor)

    International Nuclear Information System (INIS)

    2015-01-01

    This document presents the EPR (European Pressurized Reactor), a modernised version of PWRs which uses nuclear fission. It indicates to which category it belongs (third generation). It briefly describes its operation: recalls on nuclear fission, electricity production in a nuclear reactor. It presents and comments its characteristics: power, thermal efficiency, redundant systems for safety control, double protective enclosure, expected lifetime, use of MOX fuel, modular design. It discusses economic stakes (expected higher nuclear electricity competitiveness, but high construction costs), and safety challenges (design characteristics, critics by nuclear safety authorities about the safety data processing system). It presents the main involved actors (Areva, EDF) and competitors in the field of advanced reactors (Rosatom with its VVER 1200, General Electric with its ABWR and its ESBWR, Mitsubishi with its APWR, Westinghouse with its AP100) while outlining the importance of certifications and delays to obtain them. After having evoked key data on EPR fuel consumption, it indicates reactors under construction, evokes potential markets and perspectives

  18. 13C NMR and EPR spectroscopic evaluation of oil shale mined soil recuperation

    International Nuclear Information System (INIS)

    Santos, J.V. dos; Mangrich, A.S.; Pereira, B.F.; Pillon, C.N.; Bonagamba, T.J.

    2013-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-02-15

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

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

    CERN Document Server

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

    2000-01-01

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

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

    International Nuclear Information System (INIS)

    Hayes, Robert B.; Haskell, E.H.; Wieser, Albrecht; Romanyukha, Alexander A.; Hardy, Byron L.; Barrus, Jeffrey K.

    2000-01-01

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

  2. EPR, kvantemekanik og Bohr

    OpenAIRE

    Nielsen, Morten Klockmann

    2007-01-01

    Dette projekt omhandler området hvor filosofi og fysik smelter sammen. Kvantemekanikkens tilblivelse fik en hård medfart hvilket diskussionerne mellem især Albert Einstein og Niels Bohr vidner om. De var hovedpersoner i striden om hvordan kvantemekanikken skulle fortolkes, og diskussionen kulminerede i 1935 hvor Einstein sammen med kollegerne Podolsky og Rosen offentliggjorde en artikel med titlen “Can Quantum-Mechanical Description of Physical Reality Be Considered Complete?” (EPR-artiklen)....

  3. EPR a strategic choice

    International Nuclear Information System (INIS)

    2003-01-01

    How can we answer to the increasing demand of electric power, resulting of the demographic evolution and needed to the economic development, without exhausting the fossil resources? The answers are function of the countries and imply an optimization of the production and the consumption. This document published by the Areva Group aims to show the advantages of the nuclear energy: economical and environmental advantages. A special chapter is devoted to the European Pressurized Reactor, EPR. (A.L.B.)

  4. Accurate Cross Sections for Excitation of Resonance Transitions in Atomic Oxygen

    Science.gov (United States)

    Tayal, S. S.

    2004-01-01

    Electron collision excitation cross sections for the resonance 2p(sup)4 (sup 3)P-2p(sup 3)3s (sup 3)S(sup 0), 2p(sup 4) (sup 3)P-2p(sup 3)3d (sup 3)D(sup 0), 2p4 (sup 3)P-2p(sup 3)3s (sup 3)D(sup 0), 2p(sup 4) (sup 3)P-2p(sup 3)3s (sup 3)P(sup 0) and 2p(sup 4) (sup 3)P-2s2p(sup 5) (sup 3)P(sup 0) transitions have been calculated by using the R matrix with a pseudostates approach for incident electron energies from near threshold to 100 eV. The excitation of these transition sgives rise to strong atomic oxygen emission features at 1304, 1027, 989, 878, and 792 Angstrom in the spectra of several planetary atmospheres. We included 22 spectroscopic bound and autoionizing states and 30 pseudostates in the close-coupling expansion. The target wave functions are chosen to properly account for the important correlation and relaxation effects. The effect of coupling to the continuum is included through the use of pseudostates. The contribution of the ionization continuum is significant for resonance transitions. Measured absolute direct excitation cross sections of 0 I are reported by experimental groups from the Jet Propulsion Laboratory and Johns Hopkins University. Good agreement is noted for the 2p(sup)4 (sup 3)P-2p(sup 3)3s (sup 3)S(sup 0) transition (lambda 1304 Ang) with measured cross sections from both groups that agree well with each other. There is disagreement between experiments for other transitions. Our results support the measured cross sections from the Johns Hopkins University for the 2p(sup 4) (sup 3)P-2p(sup 3)3d (sup 3)D(sup 0) and 2p4 (sup 3)P-2p(sup 3)3s (sup 3)D(sup 0) transitions, while for the 2p4 (sup 3)P-2p(sup 3)3s (sup 3)D(sup 0) transition the agreement is switched to the measured cross sections from the Jet Propulsion Laboratory.

  5. EPR spectroscopy at DNP conditions

    International Nuclear Information System (INIS)

    Heckmann, J.; Goertz, St.; Meyer, W.; Radtke, E.; Reicherz, G.

    2004-01-01

    In terms of dynamic nuclear polarization (DNP) studies and systematic target material research it is crucial to know the EPR lineshape of the DNP relevant paramagnetic centers. Therefore in Bochum an EPR spectrometer has been implemented into the 4 He evaporation DNP facility in order to perform EPR studies at DNP conditions (B=2.5 T, T=1 K). The spectrometer hardware and performance as well as first results are presented

  6. Emergency EPR and OSL dosimetry with table vitamins and minerals.

    Science.gov (United States)

    Sholom, S; McKeever, S W S

    2016-12-01

    Several table vitamins, minerals and L-lysine amino acid have been preliminarily tested as potential emergency dosemeters using electron paramagnetic resonance (EPR) and optically stimulated luminescence (OSL) techniques. Radiation-induced EPR signals were detected in samples of vitamin B2 and L-lysine while samples of multivitamins of different brands as well as mineral Mg demonstrated prominent OSL signals after exposure to ionizing radiation doses. Basic dosimetric properties of the radiation-sensitive substances were studied, namely dose response, fading of the EPR or OSL signals and values of minimum measurable doses (MMDs). For EPR-sensitive samples, the EPR signal is converted into units of dose using a linear dose response and correcting for fading using the measured fading dependence. For OSL-sensitive materials, a multi-aliquot, enhanced-temperature protocol was developed to avoid the problem of sample sensitization and to minimize the influence of signal fading. The sample dose in this case is also evaluated using the dose response and fading curves. MMDs of the EPR-sensitive samples were below 2 Gy while those of the OSL-sensitive materials were below 500 mGy as long as the samples are analyzed within 1 week after exposure. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  7. EPR and Optical Characterization of Photorefractive Materials Used in Agile Laser Protection

    National Research Council Canada - National Science Library

    Halliburton, Larry

    2003-01-01

    .... The specific materials investigated were LiNbO3 and LiTaO3. The experimental techniques used to characterize these crystals were optical absorption, thermoluminescence, and electron paramagnetic resonance (EPR...

  8. EPR imaging of dose distributions aiming at applications in radiation therapy

    International Nuclear Information System (INIS)

    Lund, E.; Kolbun, N.; Adolfsson, E.; Gustafsson, H.

    2014-01-01

    A one-dimensional electron paramagnetic resonance (EPR) imaging method for visualisation of dose distributions in photon fields has been developed. Pressed pellets of potassium dithionate were homogeneously irradiated in a 60 Co radiation field to 600 Gy. The EPR analysis was performed with an X-Band (9.6 GHz) Bruker E540 EPR and EPR imaging spectrometer equipped with an E540 GC2X two-axis X-band gradient coil set with gradients along the y axis (along the sample tube) and z axis (along B 0 ) and an ER 4108TMHS resonator. Image reconstruction, including deconvolution, baseline corrections and corrections for the resonator sensitivity, was performed using an in-house-developed Matlab code for the purpose to have a transparent and complete algorithm for image reconstruction. With this method, it is possible to visualise a dose distribution with an accuracy of ∼5 % within ±5 mm from the centre of the resonator. (authors)

  9. ISS protocol for EPR tooth dosimetry

    International Nuclear Information System (INIS)

    Onori, S.; Aragno, D.; Fattibene, P.; Petetti, E.; Pressello, M.C.

    2000-01-01

    The accuracy in Electron Paramagnetic Resonance (EPR) dose reconstruction with tooth enamel is affected by sample preparation, dosimetric signal amplitude evaluation and unknown dose estimate. Worldwide efforts in the field of EPR dose reconstruction with tooth enamel are focused on the optimization of the three mentioned steps in dose assessment. In the present work, the protocol implemented at ISS in the framework of the European Community Nuclear Fission Safety project 'Dose Reconstruction' is presented. A combined mechanical-chemical procedure for ground enamel sample preparation is used. The signal intensity evaluation is carried out with powder spectra simulation program. Finally, the unknown dose is evaluated individually for each sample with the additive dose method. The unknown dose is obtained by subtracting a mean native dose from the back-extrapolated dose. As an example of the capability of the ISS protocol in unknown dose evaluation, the results obtained in the framework of the 2nd International Intercomparison on EPR tooth enamel dosimetry are reported

  10. A fast method for ionized food identification: EPR

    International Nuclear Information System (INIS)

    Raffi, J.; Rubel, G.

    1990-01-01

    Electronic paramagnetic resonance allows the detection of ionized food only after dry storage, avoiding reaction of radicals with water. Dry and solid parts are used for analysis (bones for meat and fish, kernels for fruits). Dosimetry is possible by EPR spectrometry of alanine-L fixed on products treated in industrial irradiators [fr

  11. Copper(II) Thiosemicarbazone Complexes and Their Proligands upon UVA Irradiation: An EPR and Spectrophotometric Steady-State Study.

    Science.gov (United States)

    Hricovíni, Michal; Mazúr, Milan; Sîrbu, Angela; Palamarciuc, Oleg; Arion, Vladimir B; Brezová, Vlasta

    2018-03-21

    X- and Q-band electron paramagnetic resonance (EPR) spectroscopy was used to characterize polycrystalline Cu(II) complexes that contained sodium 5-sulfonate salicylaldehyde thiosemicarbazones possessing a hydrogen, methyl, ethyl, or phenyl substituent at the terminal nitrogen. The ability of thiosemicarbazone proligands to generate superoxide radical anions and hydroxyl radicals upon their exposure to UVA irradiation in aerated aqueous solutions was evidenced by the EPR spin trapping technique. The UVA irradiation of proligands in neutral or alkaline solutions and dimethylsulfoxide (DMSO) caused a significant decrease in the absorption bands of aldimine and phenolic chromophores. Mixing of proligand solutions with the equimolar amount of copper(II) ions resulted in the formation of 1:1 Cu(II)-to-ligand complex, with the EPR and UV-Vis spectra fully compatible with those obtained for the dissolved Cu(II) thiosemicarbazone complexes. The formation of the complexes fully inhibited the photoinduced generation of reactive oxygen species, and only subtle changes were found in the electronic absorption spectra of the complexes in aqueous and DMSO solutions upon UVA steady-state irradiation. The dark redox activity of copper(II) complexes and proligand/Cu(II) aqueous solutions towards hydrogen peroxide which resulted in the generation of hydroxyl radicals, was confirmed by spin trapping experiments.

  12. EPR spin trapping of protein radicals

    DEFF Research Database (Denmark)

    Davies, Michael Jonathan; Hawkins, Clare Louise

    2004-01-01

    Electron paramagnetic resonance (EPR) spin trapping was originally developed to aid the detection of low-molecular-mass radicals formed in chemical systems. It has subsequently found widespread use in biology and medicine for the direct detection of radical species formed during oxidative stress...... tumbling radicals are often broad and relatively poor in distinctive features, a number of techniques have been developed that allow a wealth of information to be obtained about the nature, site, and reactions of such radicals. This article summarizes recent developments in this area and reviews selected...... examples of radical formation on proteins....

  13. Dosimetry of ionizing radiations by Electron paramagnetic resonance

    International Nuclear Information System (INIS)

    Azorin N, J.

    2005-01-01

    In this work, some historical and theoretical aspects about the Electron Paramagnetic Resonance (EPR), its characteristics, the resonance detection, the paramagnetic species, the radiation effects on inorganic and organic materials, the diagrams of the instrumentation for the EPR detection, the performance of an EPR spectrometer, the coherence among EPR and dosimetry and, practical applications as well as in the food science there are presented. (Author)

  14. EPR design for maintenance

    International Nuclear Information System (INIS)

    Krugmann, U.

    1998-01-01

    Preventive maintenance is very important in achieving high plant availability. For the European Pressurized Reactor (EPR) preventive maintenance has been carefully addressed in the design stage. This is particularly necessary because of the traditionally different maintenance strategies employed in France and Germany. This paper emphasizes the following features introduced in the ERP design to minimize the duration of the refueling outage: (1) containment accessibility during power operation; (2) overall plant layout to facilitate inspections and maintenances within the containment; and (3) safety system design for enabling preventive maintenance during power operation. (author)

  15. Molecular packing and magnetic properties of lithium naphthalocyanine crystals: hollow channels enabling permeability and paramagnetic sensitivity to molecular oxygen

    Science.gov (United States)

    Pandian, Ramasamy P.; Dolgos, Michelle; Marginean, Camelia; Woodward, Patrick M.; Hammel, P. Chris; Manoharan, Periakaruppan T.; Kuppusamy, Periannan

    2009-01-01

    The synthesis, structural framework, magnetic and oxygen-sensing properties of a lithium naphthalocyanine (LiNc) radical probe are presented. LiNc was synthesized in the form of a microcrystalline powder using a chemical method and characterized by electron paramagnetic resonance (EPR) spectroscopy, magnetic susceptibility, powder X-ray diffraction analysis, and mass spectrometry. X-Ray powder diffraction studies revealed a structural framework that possesses long, hollow channels running parallel to the packing direction. The channels measured approximately 5.0 × 5.4 Å2 in the two-dimensional plane perpendicular to the length of the channel, enabling diffusion of oxygen molecules (2.9 × 3.9 Å2) through the channel. The powdered LiNc exhibited a single, sharp EPR line under anoxic conditions, with a peak-to-peak linewidth of 630 mG at room temperature. The linewidth was sensitive to surrounding molecular oxygen, showing a linear increase in pO2 with an oxygen sensitivity of 31.2 mG per mmHg. The LiNc microcrystals can be further prepared as nano-sized crystals without the loss of its high oxygen-sensing properties. The thermal variation of the magnetic properties of LiNc, such as the EPR linewidth, EPR intensity and magnetic susceptibility revealed the existence of two different temperature regimes of magnetic coupling and hence differing columnar packing, both being one-dimensional antiferromagnetic chains but with differing magnitudes of exchange coupling constants. At a temperature of ∼50 K, LiNc crystals undergo a reversible phase transition. The high degree of oxygen-sensitivity of micro- and nano-sized crystals of LiNc, combined with excellent stability, should enable precise and accurate measurements of oxygen concentration in biological systems using EPR spectroscopy. PMID:19809598

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

    Science.gov (United States)

    Bourbin, Mathilde; Du, Yann Le; Binet, Laurent; Gourier, Didier

    2013-07-17

    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. 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. 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. 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.

  17. Factors Determining the Oxygen Permeability of Biological Membranes: Oxygen Transport Across Eye Lens Fiber-Cell Plasma Membranes.

    Science.gov (United States)

    Subczynski, Witold Karol; Widomska, Justyna; Mainali, Laxman

    2017-01-01

    Electron paramagnetic resonance (EPR) spin-label oximetry allows the oxygen permeability coefficient to be evaluated across homogeneous lipid bilayer membranes and, in some cases, across coexisting membrane domains without their physical separation. The most pronounced effect on oxygen permeability is observed for cholesterol, which additionally induces the formation of membrane domains. In intact biological membranes, integral proteins induce the formation of boundary and trapped lipid domains with a low oxygen permeability. The effective oxygen permeability coefficient across the intact biological membrane is affected not only by the oxygen permeability coefficients evaluated for each lipid domain but also by the surface area occupied by these domains in the membrane. All these factors observed in fiber cell plasma membranes of clear human eye lenses are reviewed here.

  18. Use of rapid-scan EPR to improve detection sensitivity for spin-trapped radicals.

    Science.gov (United States)

    Mitchell, Deborah G; Rosen, Gerald M; Tseitlin, Mark; Symmes, Breanna; Eaton, Sandra S; Eaton, Gareth R

    2013-07-16

    The short lifetime of superoxide and the low rates of formation expected in vivo make detection by standard continuous wave (CW) electron paramagnetic resonance (EPR) challenging. The new rapid-scan EPR method offers improved sensitivity for these types of samples. In rapid-scan EPR, the magnetic field is scanned through resonance in a time that is short relative to electron spin relaxation times, and data are processed to obtain the absorption spectrum. To validate the application of rapid-scan EPR to spin trapping, superoxide was generated by the reaction of xanthine oxidase and hypoxanthine with rates of 0.1-6.0 μM/min and trapped with 5-tert-butoxycarbonyl-5-methyl-1-pyrroline-N-oxide (BMPO). Spin trapping with BMPO to form the BMPO-OOH adduct converts the very short-lived superoxide radical into a more stable spin adduct. There is good agreement between the hyperfine splitting parameters obtained for BMPO-OOH by CW and rapid-scan EPR. For the same signal acquisition time, the signal/noise ratio is >40 times higher for rapid-scan than for CW EPR. Rapid-scan EPR can detect superoxide produced by Enterococcus faecalis at rates that are too low for detection by CW EPR. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  19. Toward 2D and 3D imaging of magnetic nanoparticles using EPR measurements.

    Science.gov (United States)

    Coene, A; Crevecoeur, G; Leliaert, J; Dupré, L

    2015-09-01

    Magnetic nanoparticles (MNPs) are an important asset in many biomedical applications. An effective working of these applications requires an accurate knowledge of the spatial MNP distribution. A promising, noninvasive, and sensitive technique to visualize MNP distributions in vivo is electron paramagnetic resonance (EPR). Currently only 1D MNP distributions can be reconstructed. In this paper, the authors propose extending 1D EPR toward 2D and 3D using computer simulations to allow accurate imaging of MNP distributions. To find the MNP distribution belonging to EPR measurements, an inverse problem needs to be solved. The solution of this inverse problem highly depends on the stability of the inverse problem. The authors adapt 1D EPR imaging to realize the imaging of multidimensional MNP distributions. Furthermore, the authors introduce partial volume excitation in which only parts of the volume are imaged to increase stability of the inverse solution and to speed up the measurements. The authors simulate EPR measurements of different 2D and 3D MNP distributions and solve the inverse problem. The stability is evaluated by calculating the condition measure and by comparing the actual MNP distribution to the reconstructed MNP distribution. Based on these simulations, the authors define requirements for the EPR system to cope with the added dimensions. Moreover, the authors investigate how EPR measurements should be conducted to improve the stability of the associated inverse problem and to increase reconstruction quality. The approach used in 1D EPR can only be employed for the reconstruction of small volumes in 2D and 3D EPRs due to numerical instability of the inverse solution. The authors performed EPR measurements of increasing cylindrical volumes and evaluated the condition measure. This showed that a reduction of the inherent symmetry in the EPR methodology is necessary. By reducing the symmetry of the EPR setup, quantitative images of larger volumes can be

  20. Toward 2D and 3D imaging of magnetic nanoparticles using EPR measurements

    International Nuclear Information System (INIS)

    Coene, A.; Crevecoeur, G.; Dupré, L.; Leliaert, J.

    2015-01-01

    Purpose: Magnetic nanoparticles (MNPs) are an important asset in many biomedical applications. An effective working of these applications requires an accurate knowledge of the spatial MNP distribution. A promising, noninvasive, and sensitive technique to visualize MNP distributions in vivo is electron paramagnetic resonance (EPR). Currently only 1D MNP distributions can be reconstructed. In this paper, the authors propose extending 1D EPR toward 2D and 3D using computer simulations to allow accurate imaging of MNP distributions. Methods: To find the MNP distribution belonging to EPR measurements, an inverse problem needs to be solved. The solution of this inverse problem highly depends on the stability of the inverse problem. The authors adapt 1D EPR imaging to realize the imaging of multidimensional MNP distributions. Furthermore, the authors introduce partial volume excitation in which only parts of the volume are imaged to increase stability of the inverse solution and to speed up the measurements. The authors simulate EPR measurements of different 2D and 3D MNP distributions and solve the inverse problem. The stability is evaluated by calculating the condition measure and by comparing the actual MNP distribution to the reconstructed MNP distribution. Based on these simulations, the authors define requirements for the EPR system to cope with the added dimensions. Moreover, the authors investigate how EPR measurements should be conducted to improve the stability of the associated inverse problem and to increase reconstruction quality. Results: The approach used in 1D EPR can only be employed for the reconstruction of small volumes in 2D and 3D EPRs due to numerical instability of the inverse solution. The authors performed EPR measurements of increasing cylindrical volumes and evaluated the condition measure. This showed that a reduction of the inherent symmetry in the EPR methodology is necessary. By reducing the symmetry of the EPR setup, quantitative images of

  1. A 5 tesla superconducting magnet and cryostats for an EPR/FMR spectrometer

    NARCIS (Netherlands)

    Reuvekamp, E.M.C.M.; Gerritsma, G.J.; ten Kate, Herman H.J.; van de Klundert, L.J.M.

    1988-01-01

    A description is given of the cryogenic part of an electron paramagnetic resonance (EPR)/ferromagnetic resonance (FMR) spectrometer using Ka-band (26.5-40 GHz) and U-band (40-60 GHz) frequencies for resonance measurements on large magnetic thin-films. The unit has two cryostats; the first has a

  2. Advances in Probes and Methods for Clinical EPR Oximetry

    Science.gov (United States)

    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

  3. Macrophages Under Low Oxygen Culture Conditions Respond to Ion Parametric Resonance Magnetic Fields

    Science.gov (United States)

    Macrophages, when entering inflamed tissue, encounter low oxygen tension due to the impairment of blood supply and/or the massive infiltration of cells that consume oxygen. Previously, we showed that such macrophages release more bacteriotoxic hydrogen peroxide (H202) when expose...

  4. Correlation between near-infrared spectroscopy and magnetic resonance imaging of rat brain oxygenation modulation

    International Nuclear Information System (INIS)

    Chen Yu; Tailor, Dharmesh R; Intes, Xavier; Chance, Britton

    2003-01-01

    We measure the tissue oxygen and haemoglobin concentrations in the rat brain during modulation of inhaled oxygen concentration (FiO 2 ), using non-invasive frequency domain near-infrared oximetry. The rise in oxygenated haemoglobin concentration and the decline in deoxygenated haemoglobin concentration are demonstrated in correspondence with the modulation of FiO 2 , which is changed from 20% to 100% in increments of 20%. Furthermore, the tissue oxygenation saturation also shows the corresponding trend and changes ranging from approximately 70% to 90%. The relative changes in deoxygenated haemoglobin concentration are compared to the blood-oxygenation-level-dependent (BOLD) MRI signal recorded during a similar FiO 2 protocol. A linear relationship with high correlation coefficient between the relative changes in the BOLD MRI signal and the NIRS signal is observed

  5. Correlation between near-infrared spectroscopy and magnetic resonance imaging of rat brain oxygenation modulation

    Energy Technology Data Exchange (ETDEWEB)

    Chen Yu [Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA (United States); Tailor, Dharmesh R [Department of Bioengineering, University of Pennsylvania, Philadelphia, PA (United States); Intes, Xavier [Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA (United States); Chance, Britton [Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA (United States)

    2003-02-21

    We measure the tissue oxygen and haemoglobin concentrations in the rat brain during modulation of inhaled oxygen concentration (FiO{sub 2}), using non-invasive frequency domain near-infrared oximetry. The rise in oxygenated haemoglobin concentration and the decline in deoxygenated haemoglobin concentration are demonstrated in correspondence with the modulation of FiO{sub 2}, which is changed from 20% to 100% in increments of 20%. Furthermore, the tissue oxygenation saturation also shows the corresponding trend and changes ranging from approximately 70% to 90%. The relative changes in deoxygenated haemoglobin concentration are compared to the blood-oxygenation-level-dependent (BOLD) MRI signal recorded during a similar FiO{sub 2} protocol. A linear relationship with high correlation coefficient between the relative changes in the BOLD MRI signal and the NIRS signal is observed.

  6. Full cycle rapid scan EPR deconvolution algorithm.

    Science.gov (United States)

    Tseytlin, Mark

    2017-08-01

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

  7. EPR study of gamma and neutron irradiation effects on KU1, KS-4V and Infrasil 301 silica glasses

    International Nuclear Information System (INIS)

    Lagomacini, Juan C.; Bravo, David; Leon, Monica; Martin, Piedad; Ibarra, Angel; Martin, Agustin; Lopez, Fernando J.

    2011-01-01

    Electron paramagnetic resonance (EPR) studies have been carried out on KU1 and KS-4V high purity quartz glasses and commercial silica Infrasil 301, irradiated with gamma rays up to a dose of 11.6 MGy and neutron fluences of 10 21 and 10 22 n/m 2 . Gamma irradiations produce a much higher concentration of defect centres (mainly E', POR and NBOHC) for KU1 and I301 than for KS-4V silica. In contrast, neutron irradiation at the highest fluence produces similar concentrations in all silica types. These results agree to a good extent with those obtained in previous optical absorption measurements. Moreover, oxygen-related centres (POR and NBOHC) have been well characterized by means of electron paramagnetic resonance.

  8. EPR study of gamma and neutron irradiation effects on KU1, KS-4V and Infrasil 301 silica glasses

    Energy Technology Data Exchange (ETDEWEB)

    Lagomacini, Juan C., E-mail: jc.lagomacini@uam.es [Dept. Fisica de Materiales, Universidad Autonoma de Madrid, E-28049 Madrid (Spain); Bravo, David [Dept. Fisica de Materiales, Universidad Autonoma de Madrid, E-28049 Madrid (Spain); Leon, Monica; Martin, Piedad; Ibarra, Angel [Materiales para Fusion, CIEMAT, Avda. Complutense 22, E-28040 Madrid (Spain); Martin, Agustin [Dept. Fisica e Instalaciones, ETS Arquitectura UPM, E-28040 Madrid (Spain); Lopez, Fernando J. [Dept. Fisica de Materiales, Universidad Autonoma de Madrid, E-28049 Madrid (Spain)

    2011-10-01

    Electron paramagnetic resonance (EPR) studies have been carried out on KU1 and KS-4V high purity quartz glasses and commercial silica Infrasil 301, irradiated with gamma rays up to a dose of 11.6 MGy and neutron fluences of 10{sup 21} and 10{sup 22} n/m{sup 2}. Gamma irradiations produce a much higher concentration of defect centres (mainly E', POR and NBOHC) for KU1 and I301 than for KS-4V silica. In contrast, neutron irradiation at the highest fluence produces similar concentrations in all silica types. These results agree to a good extent with those obtained in previous optical absorption measurements. Moreover, oxygen-related centres (POR and NBOHC) have been well characterized by means of electron paramagnetic resonance.

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

    International Nuclear Information System (INIS)

    Haskell, E.H.

    1996-01-01

    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

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

    Energy Technology Data Exchange (ETDEWEB)

    Haskell, E.H.

    1996-12-31

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

  11. A High Sensitivity EPR Technique for Alanine Dosimetry (invited paper)

    International Nuclear Information System (INIS)

    Haskell, E.H.; Hayes, R.B.; Kenner, G.H.

    1998-01-01

    Uncertainties of ± 5 mGy were achieved in the measurement of alanine dosemeters using optimised EPR parameters, instrumentation, spectral manipulation and subtraction techniques. Modulation amplitude and microwave power were adjusted to combine resonances of two neighbouring alanine signals. Instrumental variations were minimised by combining and subtracting pre- and post-measurement spectra of the empty EPR tube. A spectrum of the native signal of non-dosed alanine was generated from a single batch of dosemeters and subtracted from spectra of the irradiated dosemeters, also from the same batch. Field alignment was adjusted with the use of an in-cavity Mn ++ standard. A constant rotation goniometer was used to eliminate anisotropies in the EPR tube and alanine samples. Finally, digital filters were applied to the resulting spectra. (author)

  12. Megalophallus as a sequela of priapism in sickle cell anemia: use of blood oxygen level-dependent magnetic resonance imaging.

    Science.gov (United States)

    Kassim, A A; Umans, H; Nagel, R L; Fabry, M E

    2000-09-01

    Priapism is a common complication of sickle cell anemia. We report a little known sequela of priapism: painless megalophallus, with significant penile enlargement. The patient had had an intense episode of priapism 9 years previously and his penis remained enlarged. Blood oxygen level-dependent magnetic resonance imaging revealed enlarged, hypoxic corpora cavernosa. Megalophallus probably resulted from permanent loss of elasticity of the tunica albuginea due to severe engorgement during the episode of priapism. This sequela needs to be recognized by physicians because no intervention is necessary and sexual function seems to remain intact.

  13. Physical and Instrumental Considerations in the Use of Lithium Phthalocyanine for Measurements of the Concentration of the Oxygen

    Science.gov (United States)

    Smirnov, A. I.; Norby, S. W.; Walczak, T.; Liu, K. J.; Swartz, H. M.

    The use of crystals of lithium phthalocyanine (LiPc) to measure the concentration of oxygen in vivo and in vitro by electron paramagnetic resonance leads to experimental constraints due to the very narrow EPR lines that may occur (as narrow as 11-13 mG in the absence of O 2), distortions induced by the automatic frequency control system, anisotropy in the spectra (orientation-dependent linewidth is 11-17 mG in the absence of O 2), microwave power saturation, and the effect of physiological motion. These constraints can be overcome if recognized. This article highlights the experimental and theoretical basis of these properties of the EPR signal of LiPc and suggests some technical solutions. It is most important to recognize that paramagnetic species such as LiPc present problems that are not commonly encountered in EPR spectroscopy.

  14. Centers responsible for the TL peaks of willemite mineral estimated by EPR analysis

    Energy Technology Data Exchange (ETDEWEB)

    Gundu Rao, T.K. [Instituto de Física, Universidade de São Paulo, Rua do Matão, Travessa R, 187, CEP 05508-090, São Paulo, SP (Brazil); Cano, Nilo F., E-mail: nilo.cano@unifesp.br [Departamento de Ciências do Mar, Universidade Federal de São Paulo, Rua Doutor Carvalho de Mendonça, 144, CEP 11070-102, Santos, SP (Brazil); Silva-Carrera, Betzabel N.; Ferreira, Reinaldo M. [Instituto de Física, Universidade de São Paulo, Rua do Matão, Travessa R, 187, CEP 05508-090, São Paulo, SP (Brazil); Javier-Ccallata, Henry S., E-mail: henrysjc@gmail.com [Escuela Profesional de Física, Facultad de Ciencias Naturales y Formales, Universidad Nacional de San Agustín (UNSA), Av. Independencia S/N, Arequipa (Peru); Watanabe, Shigueo, E-mail: watanabe@if.usp.br [Instituto de Física, Universidade de São Paulo, Rua do Matão, Travessa R, 187, CEP 05508-090, São Paulo, SP (Brazil)

    2016-09-15

    The mineral willemite (Zn{sub 2}SiO{sub 4}) exhibits five thermoluminescence (TL) peaks approximately at 160, 225, 260, 310 and 400 °C. Electron paramagnetic resonance (EPR) studies were carried out to study the defect centers induced in the mineral by gamma irradiation and also to identify the centers responsible for the TL process. Room temperature EPR spectrum of irradiated mineral is a superposition of at least four distinct centers. One of the centers (center I) with an isotropic g factor 2.0114 is attributable to an intrinsic O{sup −} type center and the center correlates with the TL peak at 160 °C. Center II exhibiting hyperfine lines is also tentatively assigned to an O{sup −} ion and is related to the low temperature TL peak at 160 °C. Center III is characterized by an axially symmetric g-tensor with principal values g{sub ||}=2.0451 and g{sub ⊥}=2.011 and is identified as an O{sub 2}{sup −} ion. This center appears to be related to 160, 225 and 260 °C TL peaks. Center IV with principal g-values g{sub ||}=2.0025 and g{sub ⊥}=2.0088 is attributed to an F{sup +}-type center (singly ionized oxygen vacancy) and is the likely recombination center for TL peaks between 160 and 310 °C.

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

    Directory of Open Access Journals (Sweden)

    T. Ravindra Reddy

    2014-01-01

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

  16. Gold atoms and clusters on MgO(100) films; an EPR and IRAS study

    Science.gov (United States)

    Yulikov, M.; Sterrer, M.; Risse, T.; Freund, H.-J.

    2009-06-01

    Single gold atoms deposited on single crystalline MgO(1 0 0) films grown on Mo(1 0 0) are characterized by electron paramagnetic resonance spectroscopy as well as IR spectroscopy using CO as probe molecules. In this article we describe the first angular dependent measurements to determine the principal hyperfine components of a secondary hyperfine interaction, namely, with 17O of the MgO. The values determined here are in perfect agreement with theoretical expectations and corroborate the previously reported binding mechanism of Au atoms on the oxygen anions of the MgO terrace. The temperature dependent EPR data reveal an onset of Au atom mobility at about 80 K while the formation of Au particles occurs only above 125 K. By an analysis of the EPR line width in combination with STM measurements it is possible to deduce an increase of the interatomic distance above 80 K. The Au/CO complexes show a somewhat smaller temperature stability as compared to the Au atoms. The observed thermal stability is in perfect agreement with theoretical predictions for CO desorption.

  17. Chirp echo Fourier transform EPR-detected NMR.

    Science.gov (United States)

    Wili, Nino; Jeschke, Gunnar

    2018-04-01

    A new ultra-wide band (UWB) pulse EPR method is introduced for observing all nuclear frequencies of a paramagnetic center in a single shot. It is based on burning spectral holes with a high turning angle (HTA) pulse that excites forbidden transitions and subsequent detection of the hole pattern by a chirp echo. We term this method Chirp Echo Epr SpectroscopY (CHEESY)-detected NMR. The approach is a revival of FT EPR-detected NMR. It yields similar spectra and the same type of information as electron-electron double resonance (ELDOR)-detected NMR, but with a multiplex advantage. We apply CHEESY-detected NMR in Q band to nitroxides and correlate the hyperfine spectrum to the EPR spectrum by varying the frequency of the HTA pulse. Furthermore, a selective π pulse before the HTA pulse allows for detecting hyperfine sublevel correlations between transitions of one nucleus and for elucidating the coupling regime, the same information as revealed by the HYSCORE experiment. This is demonstrated on hexaaquamanganese(II). We expect that CHEESY-detected NMR is generally applicable to disordered systems and that our results further motivate the development of EPR spectrometers capable of coherent UWB excitation and detection, especially at higher fields and frequencies. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

  18. Chirp echo Fourier transform EPR-detected NMR

    Science.gov (United States)

    Wili, Nino; Jeschke, Gunnar

    2018-04-01

    A new ultra-wide band (UWB) pulse EPR method is introduced for observing all nuclear frequencies of a paramagnetic center in a single shot. It is based on burning spectral holes with a high turning angle (HTA) pulse that excites forbidden transitions and subsequent detection of the hole pattern by a chirp echo. We term this method Chirp Echo Epr SpectroscopY (CHEESY)-detected NMR. The approach is a revival of FT EPR-detected NMR. It yields similar spectra and the same type of information as electron-electron double resonance (ELDOR)-detected NMR, but with a multiplex advantage. We apply CHEESY-detected NMR in Q band to nitroxides and correlate the hyperfine spectrum to the EPR spectrum by varying the frequency of the HTA pulse. Furthermore, a selective π pulse before the HTA pulse allows for detecting hyperfine sublevel correlations between transitions of one nucleus and for elucidating the coupling regime, the same information as revealed by the HYSCORE experiment. This is demonstrated on hexaaquamanganese(II). We expect that CHEESY-detected NMR is generally applicable to disordered systems and that our results further motivate the development of EPR spectrometers capable of coherent UWB excitation and detection, especially at higher fields and frequencies.

  19. Development of a new dosimeter of EPR based on lactose

    International Nuclear Information System (INIS)

    Cruz C, L.; Torijano C, E.; Azorin N, J.; Aguirre G, F.; Cruz Z, E.

    2014-08-01

    50 years have passed since was proposed using the amino acid alanine as dosimeter advantage the phenomenon of electron paramagnetic resonance (EPR); this dosimetric method has reached a highly competitive level regarding others dosimetry classic methods, for example the thermoluminescence or the use of Fricke dosimeters, to measure high dose of radiation. In this type of materials, the free radicals induced by the radiation are stable and their concentration is proportional to the absorbed dose may be determined by the amplitude pick to pick of the first derived of the EPR absorption spectrum. The obtained results studying the EPR response of lactose tablets elaborated in the Universidad Autonoma Metropolitana, Unidad Iztapalapa are presented. The tablets were irradiated with gamma radiation of 60 Co in the irradiator Gamma beam 651-Pt of the Instituto de Ciencias Nucleares de la Universidad Nacional Autonoma de Mexico to a dose rate of 8 kGy-h -1 and their EPR response in a EPR spectrometer e-scan Bruker. The obtained response in function of the dose was lineal in the interval of 1 at 10 kGy. The lactose sensibility was compared with the l-alanine, used as reference, and the result was consistently 0.25 of this. Due to the linearity shown in the interval of used dose and their low production cost, we conclude that the lactose is a promissory option for the dosimetry of high dose of radiation. (author)

  20. Microstrip resonators for electron paramagnetic resonance experiments

    Science.gov (United States)

    Torrezan, A. C.; Mayer Alegre, T. P.; Medeiros-Ribeiro, G.

    2009-07-01

    In this article we evaluate the performance of an electron paramagnetic resonance (EPR) setup using a microstrip resonator (MR). The design and characterization of the resonator are described and parameters of importance to EPR and spin manipulation are examined, including cavity quality factor, filling factor, and microwave magnetic field in the sample region. Simulated microwave electric and magnetic field distributions in the resonator are also presented and compared with qualitative measurements of the field distribution obtained by a perturbation technique. Based on EPR experiments carried out with a standard marker at room temperature and a MR resonating at 8.17 GHz, the minimum detectable number of spins was found to be 5×1010 spins/GHz1/2 despite the low MR unloaded quality factor Q0=60. The functionality of the EPR setup was further evaluated at low temperature, where the spin resonance of Cr dopants present in a GaAs wafer was detected at 2.3 K. The design and characterization of a more versatile MR targeting an improved EPR sensitivity and featuring an integrated biasing circuit for the study of samples that require an electrical contact are also discussed.

  1. Microstrip resonators for electron paramagnetic resonance experiments.

    Science.gov (United States)

    Torrezan, A C; Mayer Alegre, T P; Medeiros-Ribeiro, G

    2009-07-01

    In this article we evaluate the performance of an electron paramagnetic resonance (EPR) setup using a microstrip resonator (MR). The design and characterization of the resonator are described and parameters of importance to EPR and spin manipulation are examined, including cavity quality factor, filling factor, and microwave magnetic field in the sample region. Simulated microwave electric and magnetic field distributions in the resonator are also presented and compared with qualitative measurements of the field distribution obtained by a perturbation technique. Based on EPR experiments carried out with a standard marker at room temperature and a MR resonating at 8.17 GHz, the minimum detectable number of spins was found to be 5 x 10(10) spins/GHz(1/2) despite the low MR unloaded quality factor Q0=60. The functionality of the EPR setup was further evaluated at low temperature, where the spin resonance of Cr dopants present in a GaAs wafer was detected at 2.3 K. The design and characterization of a more versatile MR targeting an improved EPR sensitivity and featuring an integrated biasing circuit for the study of samples that require an electrical contact are also discussed.

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

    Science.gov (United States)

    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.

  3. EPR Flamanville 3, Site Management

    International Nuclear Information System (INIS)

    Menager, Antoine

    2014-01-01

    Antoine Menager, the EPR Flamanville 3 Site Manager described the organization and the management of the Flamanville site during the construction phase. He placed emphasis on Health and Safety, Environmental and Social Responsibility and on Nuclear Safety and Quality

  4. Functional magnetic resonance imaging (fMRI) for fetal oxygenation during maternal hypoxia: initial results

    International Nuclear Information System (INIS)

    Wedegaertner, U.; Adam, G.; Tchirikov, M.; Schroeder, H.; Koch, M.

    2002-01-01

    Purpose: To investigate the potential of fMRI to measure changes in fetal tissue oxygenation during acute maternal hypoxia in fetal lambs. Material and Methods: Two ewes carrying singleton fetuses (gestational age 125 and 131 days) underwent MR imaging under inhalation anesthesia. BOLD imaging of the fetal brain, liver and myocardium was performed during acute maternal hypoxia (oxygen replaced by N 2 O). Maternal oxygen saturation and heart rate were monitored by a pulse-oxymeter attached to the maternal tongue. Results: Changes of fetal tissue oxygenation during maternal hypoxia were clearly visible with BOLD MRI. Signal intensity decreases were more distinct in liver and heart (∝40%) from control than in the fetal brain (∝10%). Conclusions: fMRI is a promising diagnostic tool to determine fetal tissue oxygenation and may open new opportunities in monitoring fetal well being in high risk pregnancies complicated by uteroplacentar insufficiency. Different signal changes in liver/heart and brain may reflect a centralization of the fetal blood flow. (orig.) [de

  5. Oxygen depth profiling in Kr+-implanted polycrystalline alpha titanium by means of 16O(α,α)16O resonance scattering

    International Nuclear Information System (INIS)

    Nsengiyumva, S.; Riviere, J.P.; Raji, A.T.; Comrie, C.M.; Britton, D.T.; Haerting, M.

    2011-01-01

    The 16 O(α,α) 16 O resonance scattering was applied to study the effects of ion implantation on the oxygen distribution in the near surface region of polycrystalline titanium implanted with 180 keV krypton ions at fluences, ranging between 1 x 10 14 and 5 x 10 15 Kr + /cm 2 . Two sample sets were chosen: as-received polycrystalline titanium discs rolled and annealed in half-hard condition which had a thick oxygen layer and similar samples in which this surface layer was removed by polishing. An increase of the mean oxygen concentration observed in both unpolished and polished samples at low fluence suggests a knock-on implantation of surface oxygen atoms. At high fluence, an overall decrease in the mean oxygen concentration and mean oxygen depth suggests an out-diffusion of near-surface oxygen atoms.

  6. Oxygen depth profiling in Kr{sup +}-implanted polycrystalline alpha titanium by means of {sup 16}O({alpha},{alpha}){sup 16}O resonance scattering

    Energy Technology Data Exchange (ETDEWEB)

    Nsengiyumva, S., E-mail: schadnse@hotmail.com [Department of Physics, University of Cape Town, Rondebosch 7701 (South Africa); Department of Physics and Electronics, Rhodes University, Grahamstown 6140 (South Africa); Department of Physics, Kigali Institute of Education, P.O. Box 5039 Kigali (Rwanda); Riviere, J.P. [Laboratoire de Physique des Materiaux UMR6630-CNRS, 86960 (France); Raji, A.T.; Comrie, C.M.; Britton, D.T.; Haerting, M. [Department of Physics, University of Cape Town, Rondebosch 7701 (South Africa)

    2011-07-15

    The {sup 16}O({alpha},{alpha}){sup 16}O resonance scattering was applied to study the effects of ion implantation on the oxygen distribution in the near surface region of polycrystalline titanium implanted with 180 keV krypton ions at fluences, ranging between 1 x 10{sup 14} and 5 x 10{sup 15} Kr{sup +}/cm{sup 2}. Two sample sets were chosen: as-received polycrystalline titanium discs rolled and annealed in half-hard condition which had a thick oxygen layer and similar samples in which this surface layer was removed by polishing. An increase of the mean oxygen concentration observed in both unpolished and polished samples at low fluence suggests a knock-on implantation of surface oxygen atoms. At high fluence, an overall decrease in the mean oxygen concentration and mean oxygen depth suggests an out-diffusion of near-surface oxygen atoms.

  7. Towards EPR (European pressurized reactor)

    International Nuclear Information System (INIS)

    Anon.

    2003-01-01

    According to the French industry minister, it is nonsense continuing delaying the construction of an EPR prototype because France needs it in order to renew timely its park of nuclear reactors. The renewing is expected to begin in 2020 and will be assured with third generation reactors like EPR. A quick launching of the EPR prototype is necessary to have it being in service by 2012, the feedback operating experience that will be accumulated over the 8 years that will follow will be necessary to optimize the industrial version and to have it ready by 2020. The EPR reactor has indisputable assets: modern, safer, more competitive and it will produce less wastes than present nuclear reactors. The construction cost of an EPR prototype is estimated to 3 milliard Euros and the nuclear industry operators propose to finance it completely. The EPR prototype does not jeopardize the ambitious French program about renewable energy sources, France is committed to produce 21% of its electricity from renewable energies by 2010 and 10 milliard Euros will be invested over this period on wind energy. Nuclear energy and alternative energies must be considered as 2 aspects of a diversified energy policy. (A.C.)

  8. Synergistic combination of hyperoxygenation and radiotherapy by repeated assessments of tumor pO2 with EPR oximetry

    International Nuclear Information System (INIS)

    Hou, H.; Dong, R.; Lariviere, J.P.; Mupparaju, S.P.; Swartz, H.M.; Khan, N.

    2011-01-01

    The effect of hyperoxygenation with carbogen (95% O 2 +5% CO 2 ) inhalation on radiation-induced fibrosarcoma (RIF-1) tumor pO 2 and its consequence on growth inhibition with fractionated radiotherapy is reported. The temporal changes in the tumor pO 2 were assessed by in vivo Electron Paramagnetic Resonance (EPR) oximetry in mice breathing 30% O 2 or carbogen and the tumors were irradiated with 4 Gy/day for 5 consecutive days; a protocol that emulates the clinical application of carbogen. The RIF-1 tumors were hypoxic with a tissue pO 2 of 5-9 mmHg. Carbogen (CB) breathing significantly increased tumor pO 2 , with a maximum increase at 22.9-31.2 min on days 1-5, however, the magnitude of increase in pO 2 declined on day 5. Radiotherapy during carbogen inhalation (CB/RT) resulted in a significant tumor growth inhibition from day 3 to day 6 as compared to 30%O 2 /RT and carbogen (CB/Sham RT) groups. The results provide unambiguous quantitative information on the effect of carbogen inhalation on tumor pO 2 over the course of 5 days. Tumor growth inhibition in the CB/RT group confirms that the tumor oxygenation with carbogen was radiobiologically significant. Repeated tumor pO 2 measurements by EPR oximetry can provide temporal information that could be used to improve therapeutic outcomes by scheduling doses at times of improved tumor oxygenation. (author)

  9. Synergistic combination of hyperoxygenation and radiotherapy by repeated assessments of tumor pO2 with EPR oximetry

    Science.gov (United States)

    HOU, Huagang; DONG, Ruhong; LARIVIERE, Jean P.; MUPPARAJU, Sriram P.; SWARTZ, Harold M.; KHAN, Nadeem

    2013-01-01

    The effect of hyperoxygenation with carbogen (95% O2 + 5% CO2) inhalation on RIF-1 tumor pO2 and its consequence on growth inhibition with fractionated radiotherapy is reported. The temporal changes in the tumor pO2 were assessed by in vivo Electron Paramagnetic Resonance (EPR) oximetry in mice breathing 30% O2 or carbogen and the tumors were irradiated with 4 Gy/day for 5 consecutive days; a protocol that emulates the clinical application of carbogen. The RIF-1 tumors were hypoxic with a tissue pO2 of 5 – 9 mm Hg. Carbogen (CB) breathing significantly increased tumor pO2, with a maximum increase at 22.9 – 31.2 min on days 1 – 5, however, the magnitude of increase in pO2 declined on day 5. Radiotherapy during carbogen inhalation (CB/RT) resulted in a significant tumor growth inhibition from day 3 to day 6 as compared to 30%O2/RT and carbogen (CB/Sham RT) groups. The results provide unambiguous quantitative information on the effect of carbogen inhalation on tumor pO2 over the course of 5 days. Tumor growth inhibition in the CB/RT group confirms that the tumor oxygenation with carbogen was radiobiologically significant. Repeated tumor pO2 measurements by EPR oximetry can provide temporal information that could be used to improve therapeutic outcomes by scheduling doses at times of improved tumor oxygenation. PMID:21799293

  10. EPR and X-ray diffraction investigation of some Greek marbles and limestones

    International Nuclear Information System (INIS)

    Duliu, Octavian; Grecu, Maria Nicoleta; Cristea, Corina

    2009-01-01

    Twelve different marble and limestone samples collected from well-known Greek quarries have been investigated by X-ray diffraction and electron paramagnetic resonance (EPR). X-ray diffraction spectra permitted to determine both major (calcite and dolomite) and minor (quartz or magnesite) mineralogical components. EPR has been used to investigate the same samples unirradiated and after 10 kGy gamma-ray irradiation. The unirradiated samples display typical EPR spectra of Mn 2+ in calcite and dolomite as well as a superposition of these while some samples displayed EPR free radicals signals of centers (low field signal) and centers (high field signal). From X-ray diffraction and EPR spectra it was possible to extract numerical values of several numerical parameters such as dolomite to calcite ratio, EPR intensity parameter, and low field to high field EPR signals intensity ratio. These values as well as the correlation coefficients between the digital functions that described the low field Mn 2+ ions EPR line have been used as entry data for cluster analysis to quantify the resemblance and differences between analyzed samples. (authors)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-11-15

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

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

    Science.gov (United States)

    Nakagawa, Kouichi; Hara, Hideyuki

    2016-01-01

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

  13. An EPR methodology for measuring the London penetration depth for the ceramic superconductors

    Science.gov (United States)

    Rakvin, B.; Mahl, T. A.; Dalal, N. S.

    1990-01-01

    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 utilizes 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.

  14. EPR by Areva. EPR the 1600+ MWe reactor

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2008-07-01

    This brochure presents the GEN III+ EPR reactor designed by the Areva and Siemens consortium. The EPR reactor is a direct descendent of the well-proven N4 and KONVOI reactors, the most modern reactors in France and Germany. The EPR was designed by teams from KWU/Siemens and Framatome, EDF in France and the major German utilities, working in collaboration with both French and German safety authorities. The EPR integrates the results of decades of R and D programs, in particular those performed by the CEA (French Atomic Energy Commission) and the Karlsruhe Research Center in Germany. The EPR benefits from the experience of several thousand reactor-years of operation of pressurized water reactor technology. This experience has put 87 AREVA PWRs online throughout the world. Innovative Features: - An outer shell covering the reactor building, the spent fuel building and two of the four safeguard buildings provides protection against large commercial or military aircraft crash. - A heavy neutron reflector that surrounds the reactor core lowers uranium consumption. - An axial economizer inside the steam generator allows a high level of steam pressure and therefore high plant efficiency. - A core catcher allows passive collection and retention of the molten core should the reactor vessel fail in the highly unlikely event of a core melt. - A digital technology and a fully computerized control room with an operator friendly man-machine interface improve the reactor protection system.

  15. EPR by Areva. EPR the 1600+ MWe reactor

    International Nuclear Information System (INIS)

    2008-01-01

    This brochure presents the GEN III+ EPR reactor designed by the Areva and Siemens consortium. The EPR reactor is a direct descendent of the well-proven N4 and KONVOI reactors, the most modern reactors in France and Germany. The EPR was designed by teams from KWU/Siemens and Framatome, EDF in France and the major German utilities, working in collaboration with both French and German safety authorities. The EPR integrates the results of decades of R and D programs, in particular those performed by the CEA (French Atomic Energy Commission) and the Karlsruhe Research Center in Germany. The EPR benefits from the experience of several thousand reactor-years of operation of pressurized water reactor technology. This experience has put 87 AREVA PWRs online throughout the world. Innovative Features: - An outer shell covering the reactor building, the spent fuel building and two of the four safeguard buildings provides protection against large commercial or military aircraft crash. - A heavy neutron reflector that surrounds the reactor core lowers uranium consumption. - An axial economizer inside the steam generator allows a high level of steam pressure and therefore high plant efficiency. - A core catcher allows passive collection and retention of the molten core should the reactor vessel fail in the highly unlikely event of a core melt. - A digital technology and a fully computerized control room with an operator friendly man-machine interface improve the reactor protection system

  16. Development and Validation of Noninvasive Magnetic Resonance Relaxometry for the In Vivo Assessment of Tissue-Engineered Graft Oxygenation.

    Science.gov (United States)

    Einstein, Samuel A; Weegman, Bradley P; Firpo, Meri T; Papas, Klearchos K; Garwood, Michael

    2016-11-01

    Techniques to monitor the oxygen partial pressure (pO 2 ) within implanted tissue-engineered grafts (TEGs) are critically necessary for TEG development, but current methods are invasive and inaccurate. In this study, we developed an accurate and noninvasive technique to monitor TEG pO 2 utilizing proton ( 1 H) or fluorine ( 19 F) magnetic resonance spectroscopy (MRS) relaxometry. The value of the spin-lattice relaxation rate constant (R 1 ) of some biocompatible compounds is sensitive to dissolved oxygen (and temperature), while insensitive to other external factors. Through this physical mechanism, MRS can measure the pO 2 of implanted TEGs. We evaluated six potential MRS pO 2 probes and measured their oxygen and temperature sensitivities and their intrinsic R 1 values at 16.4 T. Acellular TEGs were constructed by emulsifying porcine plasma with perfluoro-15-crown-5-ether, injecting the emulsion into a macroencapsulation device, and cross-linking the plasma with a thrombin solution. A multiparametric calibration equation containing R 1 , pO 2 , and temperature was empirically generated from MRS data and validated with fiber optic (FO) probes in vitro. TEGs were then implanted in a dorsal subcutaneous pocket in a murine model and evaluated with MRS up to 29 days postimplantation. R 1 measurements from the TEGs were converted to pO 2 values using the established calibration equation and these in vivo pO 2 measurements were simultaneously validated with FO probes. Additionally, MRS was used to detect increased pO 2 within implanted TEGs that received supplemental oxygen delivery. Finally, based on a comparison of our MRS data with previously reported data, ultra-high-field (16.4 T) is shown to have an advantage for measuring hypoxia with 19 F MRS. Results from this study show MRS relaxometry to be a precise, accurate, and noninvasive technique to monitor TEG pO 2 in vitro and in vivo.

  17. Measurement of rotational dynamics by the simultaneous nonlinear analysis of optical and EPR data.

    OpenAIRE

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

    1993-01-01

    In the preceding companion article in this issue, an optical dye and a nitroxide radical were combined in a new dual function probe, 5-SLE. In this report, it is demonstrated that time-resolved optical anisotropy and electron paramagnetic resonance (EPR) data can be combined in a single analysis to measure rotational dynamics. Rigid-limit and rotational diffusion models for simulating nitroxide EPR data have been incorporated into a general non-linear least-squares procedure based on the Marq...

  18. Evaluation of the original dose in irradiated dried fruit by EPR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    D' Oca, Maria Cristina, E-mail: mcristina.doca@unipa.it [Dipartimento Farmacochimico, Tossicologico e Biologico, Universita di Palermo, via Archirafi 32, 90123 Palermo (Italy); Bartolotta, Antonio [Dipartimento Farmacochimico, Tossicologico e Biologico, Universita di Palermo, via Archirafi 32, 90123 Palermo (Italy)

    2011-09-15

    The electron paramagnetic resonance spectroscopy (EPR) is one of the physical methods, recommended by the European Committee for Standardization, for the identification of irradiated food containing cellulose, such as dried fruit. In this work the applicability of EPR as identification method of irradiated pistachios, hazelnuts, peanuts, chestnuts, pumpkin seeds is evaluated; the time stability of the radiation induced signal is studied and the single aliquot additive dose method is used to evaluate the dose in the product.

  19. Evaluation of the original dose in irradiated dried fruit by EPR spectroscopy

    International Nuclear Information System (INIS)

    D'Oca, Maria Cristina; Bartolotta, Antonio

    2011-01-01

    The electron paramagnetic resonance spectroscopy (EPR) is one of the physical methods, recommended by the European Committee for Standardization, for the identification of irradiated food containing cellulose, such as dried fruit. In this work the applicability of EPR as identification method of irradiated pistachios, hazelnuts, peanuts, chestnuts, pumpkin seeds is evaluated; the time stability of the radiation induced signal is studied and the single aliquot additive dose method is used to evaluate the dose in the product.

  20. Functional magnetic resonance imaging (fMRI) for fetal oxygenation during maternal hypoxia: initial results

    Energy Technology Data Exchange (ETDEWEB)

    Wedegaertner, U.; Adam, G. [Abt. fuer Diagnostische und Interventionelle Radiologie, Klinik und Poliklinik fuer Radiologie, UKE Hamburg (Germany); Tchirikov, M.; Schroeder, H. [Abt. fuer experimentelle Gynaekologie der Universitaetsfrauenklinik, Klinik und Poliklinik fuer Frauenheilkunde, UKE, Hamburg (Germany); Koch, M. [Klinik und Poliklinik fuer Neurologie, UKE Hamburg (Germany)

    2002-06-01

    Purpose: To investigate the potential of fMRI to measure changes in fetal tissue oxygenation during acute maternal hypoxia in fetal lambs. Material and Methods: Two ewes carrying singleton fetuses (gestational age 125 and 131 days) underwent MR imaging under inhalation anesthesia. BOLD imaging of the fetal brain, liver and myocardium was performed during acute maternal hypoxia (oxygen replaced by N{sub 2}O). Maternal oxygen saturation and heart rate were monitored by a pulse-oxymeter attached to the maternal tongue. Results: Changes of fetal tissue oxygenation during maternal hypoxia were clearly visible with BOLD MRI. Signal intensity decreases were more distinct in liver and heart ({proportional_to}40%) from control than in the fetal brain ({proportional_to}10%). Conclusions: fMRI is a promising diagnostic tool to determine fetal tissue oxygenation and may open new opportunities in monitoring fetal well being in high risk pregnancies complicated by uteroplacentar insufficiency. Different signal changes in liver/heart and brain may reflect a centralization of the fetal blood flow. (orig.) [German] Ziel: Untersuchung des Potentiales der funktionellen MRT (BOLD) in der Darstellung von Veraenderungen in der Sauerstoffsaettigung fetaler Gewebe waehrend akuter materner Hypoxie bei fetalen Laemmern. Material und Methoden: Die MR-Untersuchung wurde an zwei Mutterschafen mit 125 und 131 Tage alten Feten in Inhalationsnarkose durchgefuehrt. Die BOLD Messungen von fetaler Leber, Myokard und Gehirn erfolgten waehrend einer akuten Hypoxiephase des Muttertieres, in der Sauerstoff durch N{sub 2}O ersetzt wurde. Die materne Sauerstoffsaettigung und Herzfrequenz wurde durch ein Pulsoxymeter ueberwacht. Ergebnisse: Aenderungen der fetalen Gewebsoxygenierung waehrend einer akuten Hypoxiephase der Mutter waren mit der BOLD-MR-Bildgebung deutlich darstellbar. In der fetalen Leber und dem Myokard zeigte sich ein staerkerer Signalabfall um ca. 40% von den Kontrollwerten als im fetalen

  1. Medical reference dosimetry using EPR measurements of alanine

    DEFF Research Database (Denmark)

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

    2009-01-01

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

  2. Longitudinal Assessment of Renal Perfusion and Oxygenation in Transplant Donor-Recipient Pairs Using Arterial Spin Labeling and Blood Oxygen Level-Dependent Magnetic Resonance Imaging.

    Science.gov (United States)

    Niles, David J; Artz, Nathan S; Djamali, Arjang; Sadowski, Elizabeth A; Grist, Thomas M; Fain, Sean B

    2016-02-01

    The aims of this study were to assess renal function in kidney transplant recipients and their respective donors over 2 years using arterial spin labeling (ASL) and blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) and to prospectively evaluate the effect of losartan on functional MRI measures in recipients. The study included 15 matched pairs of renal transplant donors and recipients. Arterial spin labeling and BOLD MRI of the kidneys were performed on donors before transplant surgery (baseline) and on both donors and recipients at 3 months, 1 year, and 2 years after transplant. After 3 months, 7 of the 15 recipients were prescribed 25 to 50 mg/d losartan for the remainder of the study. A linear mixed-effects model was used to evaluate perfusion, R2*, estimated glomerular filtration rate, and fractional excretion of sodium for changes across time or associated with losartan treatment. In donors, cortical perfusion in the remaining kidney decreased by 50 ± 19 mL/min per 100 g (11.8%) between baseline and 2 years (P donors and to 14.6 ± 4.3 mL/min per 1.73 m (33.3%; P donors, and they indicate a potentially beneficial effect of losartan in recipients.

  3. The EPR layout design

    International Nuclear Information System (INIS)

    Mast, U.; Le Carrer, P.Y.

    2001-01-01

    General: The European Pressurised Water Reactor (EPR) is a French - German development for the next generation of Pressurised Water Reactor. The new reactor design is based on the experiences of operation and design of nuclear power plants in both countries. The EPR fulfils enhanced safety standards, higher availability and a longer service life. Utilities aspects: For the Utilities one important requirement is the reduction of personnel exposure during maintenance and in-service inspection. The other significant requirement is of economic nature. The main points influencing costs, which have also impact on the layout, are: outage times, accessibility of the reactor building and the available maintenance and set down areas. The Utilities have also required to load the spent fuel assemblies into the shipping cask from the bottom of the fuel pool, because of the exclusion of the drop of the cask and in order to avoid contamination at the outer cask shell. Layout and safety aspects: All safety relevant Nuclear Island (NI) buildings are designed against design earthquake as well as explosion pressure wave. The protection against Airplane Crash (APC) is realised by civil and layout dispositions. The Reactor Building, the Safeguard Buildings division 2 and 3 and the Fuel Building are protected by concrete structures. The other safety relevant nuclear buildings are protected by geographical separation. Important safety requirements are the further reduction of the probability of severe accidents and the mitigation of such an accident on the plant area. For that, a spreading area for molten corium, a channel from the reactor pit to the spreading area and the In Containment Refuelling Water Storage Tank (IRWST) for flooding and initial cooling of the corium, were implemented in the design of the Reactor Building. Layout results: The following buildings are arranged on a common raft to protect them against design earthquake: Reactor Building (RB), Safeguard Buildings (SAB

  4. Cerebral misery perfusion diagnosed using hypercapnic blood-oxygenation-level-dependent contrast functional magnetic resonance imaging: a case report

    Directory of Open Access Journals (Sweden)

    D'Souza Olympio

    2010-02-01

    Full Text Available Abstract Introduction Cerebral misery perfusion represents a failure of cerebral autoregulation. It is an important differential diagnosis in post-stroke patients presenting with collapses in the presence of haemodynamically significant cerebrovascular stenosis. This is particularly the case when cortical or internal watershed infarcts are present. When this condition occurs, further investigation should be done immediately. Case presentation A 50-year-old Caucasian man presented with a stroke secondary to complete occlusion of his left internal carotid artery. He went on to suffer recurrent seizures. Neuroimaging demonstrated numerous new watershed-territory cerebral infarcts. No source of arterial thromboembolism was demonstrable. Hypercapnic blood-oxygenation-level-dependent-contrast functional magnetic resonance imaging was used to measure his cerebrovascular reserve capacity. The findings were suggestive of cerebral misery perfusion. Conclusions Blood-oxygenation-level-dependent-contrast functional magnetic resonance imaging allows the inference of cerebral misery perfusion. This procedure is cheaper and more readily available than positron emission tomography imaging, which is the current gold standard diagnostic test. The most evaluated treatment for cerebral misery perfusion is extracranial-intracranial bypass. Although previous trials of this have been unfavourable, the results of new studies involving extracranial-intracranial bypass in high-risk patients identified during cerebral perfusion imaging are awaited. Cerebral misery perfusion is an important and under-recognized condition in which emerging imaging and treatment modalities present the possibility of practical and evidence-based management in the near future. Physicians should thus be aware of this disorder and of recent developments in diagnostic tests that allow its detection.

  5. Dosimetry of ionizing radiations by Electron paramagnetic resonance; Dosimetria de radiaciones ionizantes por resonancia paramagnetica electronica

    Energy Technology Data Exchange (ETDEWEB)

    Azorin N, J [UAM-I, Av. San Rafael Atlixco 186, 09340 Mexico D.F. (Mexico)

    2005-07-01

    In this work, some historical and theoretical aspects about the Electron Paramagnetic Resonance (EPR), its characteristics, the resonance detection, the paramagnetic species, the radiation effects on inorganic and organic materials, the diagrams of the instrumentation for the EPR detection, the performance of an EPR spectrometer, the coherence among EPR and dosimetry and, practical applications as well as in the food science there are presented. (Author)

  6. Resonance

    DEFF Research Database (Denmark)

    Petersen, Nils Holger

    2014-01-01

    A chapter in a book about terminology within the field of medievalism: the chapter discusses the resonance of medieval music and ritual in modern (classical) music culture and liturgical practice.......A chapter in a book about terminology within the field of medievalism: the chapter discusses the resonance of medieval music and ritual in modern (classical) music culture and liturgical practice....

  7. The EPR in a few words: all you need to know about the EPR nuclear reactor

    International Nuclear Information System (INIS)

    2009-01-01

    After a brief presentation of the EPR (European - or Evolutionary - Pressurized Reactor) type nuclear reactor, this paper, proposed by the collective group 'Stop EPR', develops the following points: EPR is as dangerous as other reactors; EPR flouts democracy; France's energy demand do not need the construction of EPRs; the construction of EPRs is not a factor of economical and social development; EPR should not be constructed neither in France nor elsewhere and the present building sites should be cancelled; the EPR will not help France to increase its energy independence and protect itself from oil price increases; choosing the EPR is incompatible with the large investments to be made in energy conservation and renewable energies; the EPR is not a solution to climate change; the VHV line corridor that will starts at Flamanville is not justified and poses risks to the environment and public health

  8. EPR analysis of biomaterials

    International Nuclear Information System (INIS)

    Sukhodub, L.

    2001-01-01

    There is the review of electron spin resonance application for paramagnetic individual investigation in biomaterials. Especially the bone tissue and tooth enamel can be taken into account. The material composition (e.g. Mn 2+ and Cr 3+ ions) can be measured, also after irradiation (X, γ radiations) when paramagnetic signal appears as a result of physical radiation effects

  9. EPR: Some History and Clarification

    Science.gov (United States)

    Fine, Arthur

    2002-04-01

    Locality, separation and entanglement 1930s style. We’ll explore the background to the 1935 paper by Einstein, Podolsky and Rosen, how it was composed, the actual argument of the paper, the principles used, and how the paper was received by Schroedinger, and others.We’ll also look at Bohr’s response: the extent to which Bohr connects with what Einstein was after in EPR and the extent to EPR marks a shift in Bohr’s thinking about the quantum theory.

  10. Some ideas on the EPR

    International Nuclear Information System (INIS)

    2003-01-01

    Facing the debate and controversial between partisans and opponents of the European Pressurized Reactor construction, the SFP energy Group aims to offer some reflexions. In this framework the following topics are discussed: the french nuclear park and its replacement, the energy costs, the nuclear reactors profitability, the generation IV reactors. The paper examines then the EPR technology and its cost to conclude on the advantage of an EPR construction, in the case of an energy policy based on the nuclear. This last point seems to be the real challenge of the problem. (A.L.B.)

  11. EPR in B physics and elsewhere

    International Nuclear Information System (INIS)

    Lipkin, H.J.; Tel Aviv Univ.; Argonne National Lab., IL

    1997-01-01

    The application of Einstein-Podolsky-Rosen correlations in Υ(4s) → B anti B decays to research in CP violation is the first and probably only use of EPR as a technique for research in new physics. Elsewhere highly sophisticated EPR projects question EPR and test its predictions to look for violations of quantum mechanics, hidden variables, Bell''s inequalities, etc

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

    Science.gov (United States)

    Polak, Justyna; Bartoszek, Mariola; Chorążewski, Mirosław

    2015-07-22

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

  13. Water-resistant alanine-EPR dosimeter alanpol

    International Nuclear Information System (INIS)

    Peimel-Stuglik, Zofia; Bryl-Sandelewska, Teresa; Mirkowski, Krzysztof; Sartowska, Bozena

    2009-01-01

    Alanpol-water-resistant alanine-electron paramagnetic resonance (EPR) dosimeter consisted of cheap DL-α-alanine (9.8-27%) suspended in polyethylene matrix was presented. The rods (O=2.8 mm) were extruded from a hot mixture of alanine and low-density polyethylene. No grinding or crushing was used for alanine preparation. An orientation of cylindrical crystals, up to 300 μm long in parallel to the rod axis was responsible for some differences in a shape of EPR signal. These differences had no negative consequences for dosimetric applications. Signal-to-dose dependence was linear up to 10 kGy. Standard deviation of dosimetric answer was up to ±1.8% and up to 2.4% for dosimeters with 9.8% and 27% of DL-α-alanine, respectively. Irradiation temperature coefficient for both dosimeters was equal 0.2%/ deg. C. Hydrophobic properties of polyethylene and small number of alanine crystals located on the surface of the rod led to high resistance of dosimeters to water and humidity. The 24 h soaking of irradiated dosimeters in liquid water-reduced EPR signals by 3-4% and by 2-3% for dosimeters with 27% and 9.8% of DL-α-alanine, respectively. Three month storage time of irradiated dosimeters in room conditions decreases EPR signal for ∼3%.

  14. Pulse EPR distance measurements to study multimers and multimerisation

    Science.gov (United States)

    Ackermann, Katrin; Bode, Bela E.

    2018-06-01

    Pulse dipolar electron paramagnetic resonance (PD-EPR) has become a powerful tool for structural biology determining distances on the nanometre scale. Recent advances in hardware, methodology, and data analysis have widened the scope to complex biological systems. PD-EPR can be applied to systems containing lowly populated conformers or displaying large intrinsic flexibility, making them all but intractable for cryo-electron microscopy and crystallography. Membrane protein applications are of particular interest due to the intrinsic difficulties for obtaining high-resolution structures of all relevant conformations. Many drug targets involved in critical cell functions are multimeric channels or transporters. Here, common approaches for introducing spin labels for PD-EPR cause the presence of more than two electron spins per multimeric complex. This requires careful experimental design to overcome detrimental multi-spin effects and to secure sufficient distance resolution in presence of multiple distances. In addition to obtaining mere distances, PD-EPR can also provide information on multimerisation degrees allowing to study binding equilibria and to determine dissociation constants.

  15. Advances in magnetic resonance 10

    CERN Document Server

    Waugh, John S

    2013-01-01

    Advances in Magnetic Resonance, Volume 10, presents a variety of contributions to the theory and practice of magnetic resonance. The book contains three chapters that examine superoperators in magnetic resonance; ultrasonically modulated paramagnetic resonance; and the utility of electron paramagnetic resonance (EPR) and electron-nuclear double-resonance (ENDOR) techniques for studying low-frequency modes of atomic fluctuations and their significance for understanding the mechanism of structural phase transitions in solids.

  16. Gas enhanced magnetic resonance angiography of the cerebrum using carbon dioxide and oxygen - preliminary results

    DEFF Research Database (Denmark)

    Pedersen, Mads Møller; Hansen, Kristoffer Lindskov; Ohlhues, Anders

    Purpose/introduction Standard imaging of the cerebral arteries is performed using intravenous contrast in CT angiography and x-ray angiography. Magnetic resonance angiography (MRA) of the cerebral arteries using intravenous contrast media does not perform well. Contrast in the venous bed...... and Methods Two healthy volunteers were scanned during inhalation of three different gas mixtures: Gas I (air), Gas II (5% CO2, 21 % O2, 74 % N2), Gas III (5% CO2, 95% O2). For each gas mixture a time of flight (TOF) series on the cerebral arteries was performed. Following each TOF series an ECG-gated phase...... contrast sequence was performed to calculate volume flow in the common carotid arteries. MRA data was acquired with a 1.5 T Siemens VISION MR-system (SIEMENS Medical Systems, Germany) using a standard circularly polarized head coil. Reconstructed images of TOF series and volume flow measurements were...

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

    Energy Technology Data Exchange (ETDEWEB)

    Marillier, F [Association Ecologiste Greenpeace (France)

    2008-07-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Marillier, F. [Association Ecologiste Greenpeace (France)

    2008-07-01

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

  19. Four-channel surface coil array for sequential CW-EPR image acquisition

    Science.gov (United States)

    Enomoto, Ayano; Emoto, Miho; Fujii, Hirotada; Hirata, Hiroshi

    2013-09-01

    This article describes a four-channel surface coil array to increase the area of visualization for continuous-wave electron paramagnetic resonance (CW-EPR) imaging. A 776-MHz surface coil array was constructed with four independent surface coil resonators and three kinds of switches. Control circuits for switching the resonators were also built to sequentially perform EPR image acquisition for each resonator. The resonance frequencies of the resonators were shifted using PIN diode switches to decouple the inductively coupled coils. To investigate the area of visualization with the surface coil array, three-dimensional EPR imaging was performed using a glass cell phantom filled with a solution of nitroxyl radicals. The area of visualization obtained with the surface coil array was increased approximately 3.5-fold in comparison to that with a single surface coil resonator. Furthermore, to demonstrate the applicability of this surface coil array to animal imaging, three-dimensional EPR imaging was performed in a living mouse with an exogenously injected nitroxyl radical imaging agent.

  20. Enhanced accuracy of the microwave field strength measurement in a CW-EPR by pulsed modulation technique

    Science.gov (United States)

    Rakvin, B.; Carić, D.; Kveder, M.

    2018-02-01

    The microwave magnetic field strength, B1, in the cavity of a conventional continuous wave electron paramagnetic resonance, CW-EPR, spectrometer was measured by employing modulation sidebands, MS, in the EPR spectrum. MS spectrum in CW-EPR is produced by applying the modulation frequency, ωrf, which exceeds the linewidth, δB, given in frequency units. An amplitude-modulated CW-EPR, AM-CW-EPR, was selected as detection method. Theoretical description of AM-CW-EPR spectrum was modified by adding Bloch-Siegert-like shift obtained by taking into account the cumulative effect of the non-resonant interactions between the driving fields and the spin system. This approach enables to enhance the precision of B1 measurement. In order to increase the sensitivity of the method when saturation effects, due to higher intensity of B1, decrease the resolution of AM-CW-EPR spectrum, detection at the second harmonic of CW-EPR has been employed.

  1. Enhanced accuracy of the microwave field strength measurement in a CW-EPR by pulsed modulation technique.

    Science.gov (United States)

    Rakvin, B; Carić, D; Kveder, M

    2018-02-01

    The microwave magnetic field strength, B 1 , in the cavity of a conventional continuous wave electron paramagnetic resonance, CW-EPR, spectrometer was measured by employing modulation sidebands, MS, in the EPR spectrum. MS spectrum in CW-EPR is produced by applying the modulation frequency, ω rf , which exceeds the linewidth, δB, given in frequency units. An amplitude-modulated CW-EPR, AM-CW-EPR, was selected as detection method. Theoretical description of AM-CW-EPR spectrum was modified by adding Bloch-Siegert-like shift obtained by taking into account the cumulative effect of the non-resonant interactions between the driving fields and the spin system. This approach enables to enhance the precision of B 1 measurement. In order to increase the sensitivity of the method when saturation effects, due to higher intensity of B 1 , decrease the resolution of AM-CW-EPR spectrum, detection at the second harmonic of CW-EPR has been employed. Copyright © 2018 Elsevier Inc. All rights reserved.

  2. High altitude may alter oxygen availability and renal metabolism in diabetics as measured by hyperpolarized [1-1C]pyruvate magnetic resonance imaging

    DEFF Research Database (Denmark)

    Laustsen, Christoffer; Lycke, Sara; Palm, Fredrik

    2014-01-01

    inspired oxygen did not alter renal metabolism in the control group. Reduced oxygen availability in the diabetic kidney altered energy metabolism by increasing lactate and alanine formation by 23% and 34%, respectively, whereas the bicarbonate flux was unchanged. Thus, the increased prevalence and severity......The kidneys account for about 10% of the whole body oxygen consumption, whereas only 0.5% of the total body mass. It is known that intrarenal hypoxia is present in several diseases associated with development of kidney disease, including diabetes, and when renal blood flow is unaffected....... The importance of deranged oxygen metabolism is further supported by deterioration of kidney function in patients with diabetes living at high altitude. Thus, we argue that reduced oxygen availability alters renal energy metabolism. Here, we introduce a novel magnetic resonance imaging (MRI) approach to monitor...

  3. Electronic Structure of ZnO Quantum Dots studied by High-frequency EPR, ESE, ENDOR and ODMR Spectroscopy

    NARCIS (Netherlands)

    Baranov, P.G.; Romanov, N.G.; Bundakova, A.P.; de Mello-Donega, Celso; Schmidt, J.

    2016-01-01

    High-frequency electron paramagnetic resonance (EPR), electron spin echo (ESE), electron-nuclear double resonance (ENDOR) and optically detected magnetic resonance (ODMR) were applied for the investigation of the electronic properties of ZnO colloidal quantum dots (QDs) which consist of a ZnO

  4. THE VIEW FROM THE TRENCHES: PART 2–TECHNICAL CONSIDERATIONS FOR EPR SCREENING

    Science.gov (United States)

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

    2014-01-01

    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

  5. The sensitivity analysis of tooth enamel to the absorbed dose for the application to EPR dosimetry

    International Nuclear Information System (INIS)

    Hong, Dae Seok; Lee, Kun Jai; Cho, Young Hwan

    2002-01-01

    Electron Paramagnetic Resonance (EPR) spectroscopy is one of the methods applicable to retrospective dosimetry. The retrospective dosimetry is a process that is a part of dose reconstruction for estimation of exposed dose occurred years before the estimation. Many techniques can be used to the retrospective dosimetry. As a physical method, EPR analysis of biological material measures the quantity of free radicals generated in the material from the interaction of radiation and material. Since the later 80s, in many countries, EPR dosimetry with tooth enamel has been studied and applied for the retrospective dosimetry. In the consideration of the biological materials for EPR dosimetry, human fingernail, hair, bone and tooth are generally considered. The tooth can be separated as enamel, dentine and cementum. Among the three parts, enamel shows the best sensitivity to the absorbed dose and is most widely used. In this study, the characteristics of tooth enamel for EPR dosimetry is examined and experimented. At the experiment, for easy separation, tooth was cut into 4 parts and then each part is treated by ultrasonic vibration in NaOH liquid to reduce mechanically induced noise in the corresponding signal. After the separation of the enamel from dentine, background EPR signal is measured and then radiation-induced EPR spectrum is estimated

  6. EPR correlations and EPW distributions

    International Nuclear Information System (INIS)

    Bell, J.S.

    1995-01-01

    In the case of two free spin-zero particles, the wave function originally considered by Einstein, Podolsky and Rosen to exemplify EPR correlations has a non-negative Wigner distribution. This distribution gives an explicitly local account of the correlations. For an irreducible non-locality, more elaborate wave functions are required, with Wigner distributions which are not non-negative. (author)

  7. EPR measurements in irradiated polyacetylene

    International Nuclear Information System (INIS)

    Hola, O.; Foeldesova, M.

    1990-01-01

    The influence of γ-irradiation on the paramagnetic properties of polyacetylene, and the dependence of the EPR spectra on the radiation dose in samples of irradiated polyacetylene were studied. The measurements show that no essential changes of the spin mobility occurred during irradiation. (author) 3 refs.; 2 figs

  8. EPR study of human hair

    Czech Academy of Sciences Publication Activity Database

    Křížová, Jana; Káfuňková, Eva; Stopka, Pavel

    2005-01-01

    Roč. 99, č. 14 (2005), s. 217-218 ISSN 0009-2770 R&D Projects: GA MZd(CZ) NL7567; GA MZd(CZ) NB7377 Institutional research plan: CEZ:AV0Z40320502 Keywords : EPR Subject RIV: CA - Inorganic Chemistry Impact factor: 0.445, year: 2005

  9. Characterization of Melanin Radicals in Paraffin-embedded Malignant Melanoma and Nevus Pigmentosus Using X-band EPR and EPR Imaging.

    Science.gov (United States)

    Nakagawa, Kouichi; Minakawa, Satoko; Sawamura, Daisuke; Hara, Hideyuki

    2017-01-01

    Continuous wave electron paramagnetic resonance (CW EPR) and X-band (9 GHz) EPR imaging (EPRI) were used to nondestructively investigate the possible differentiation between malignant melanoma (MM) and nevus pigmentosus (NP) melanin radicals in paraffin-embedded specimens. The EPR spectra of both samples were analyzed using linewidth, spectral pattern, and X-band EPRI. The CW-EPR spectra of the MM showed an additional signal overlap. Eumelanin- and pheomelanin-related radicals were observed in the MM specimens. The EPR results revealed that the peak-to-peak linewidths (ΔH pp ) of paraffin-embedded MM and NP samples were 0.65 ± 0.01 and 0.69 ± 0.01 mT, respectively. The g-value was 2.005 for both samples. Moreover, the two-dimensional (2D) EPRI of the MM showed different signal intensities at the different tumor stages, unlike the NP, which displayed fewer variations in signal intensity. Thus, the present results suggest that EPR and 2D EPRI can be useful for characterization of the two melanin radicals in the MM and for determination of their size and concentration.

  10. Skew Projection of Echo-Detected EPR Spectra for Increased Sensitivity and Resolution

    Science.gov (United States)

    Bowman, Michael K.; Krzyaniak, Matthew D.; Cruce, Alex A.; Weber, Ralph T.

    2013-01-01

    The measurement of EPR spectra during pulsed EPR experiments is commonly accomplished by recording the integral of the electron spin echo as the applied magnetic field is stepped through the spectrum. This approach to echo-detected EPR spectral measurement (ED-EPR) limits sensitivity and spectral resolution and can cause gross distortions in the resulting spectra because some of the information present in the electron spin echo is discarded in such measurements. However, Fourier Transformation of echo shapes measured at a series of magnetic field values followed by skew projection onto either a magnetic field or resonance frequency axis can increase both spectral resolution and sensitivity without the need to trade one against the other. Examples of skew-projected spectra with single crystals, glasses and powders show resolution improvements as large as a factor of seven with sensitivity increases of as much as a factor of five. PMID:23644351

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

    Science.gov (United States)

    Karray, Fekri; Kassiba, Abdelhadi

    2012-06-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Karray, Fekri [Laboratoire des materiaux Ceramiques Composites et Polymeres, Faculte des Sciences de Sfax, BP 802, 3018 Sfax (Tunisia); Kassiba, Abdelhadi, E-mail: kassiba@univ-lemans.fr [Institute of Molecules and Materials of Le Mans (I3M), UMR-CNRS 6283, Universite du Maine, 72085 Le Mans (France)

    2012-06-15

    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.

  13. Use of EPR to Solve Biochemical Problems

    Science.gov (United States)

    Sahu, Indra D.; McCarrick, Robert M.; Lorigan, Gary A.

    2013-01-01

    EPR spectroscopy is a very powerful biophysical tool that can provide valuable structural and dynamic information on a wide variety of biological systems. The intent of this review is to provide a general overview for biochemists and biological researchers on the most commonly used EPR methods and how these techniques can be used to answer important biological questions. The topics discussed could easily fill one or more textbooks; thus, we present a brief background on several important biological EPR techniques and an overview of several interesting studies that have successfully used EPR to solve pertinent biological problems. The review consists of the following sections: an introduction to EPR techniques, spin labeling methods, and studies of naturally occurring organic radicals and EPR active transition metal systems which are presented as a series of case studies in which EPR spectroscopy has been used to greatly further our understanding of several important biological systems. PMID:23961941

  14. Electron paramagnetic resonance imaging of tumor hypoxia: enhanced spatial and temporal resolution for in vivo pO2 determination.

    Science.gov (United States)

    Matsumoto, Ken-ichiro; Subramanian, Sankaran; Devasahayam, Nallathamby; Aravalluvan, Thirumaran; Murugesan, Ramachandran; Cook, John A; Mitchell, James B; Krishna, Murali C

    2006-05-01

    The time-domain (TD) mode of electron paramagnetic resonance (EPR) data collection offers a means of estimating the concentration of a paramagnetic probe and the oxygen-dependent linewidth (LW) to generate pO2 maps with minimal errors. A methodology for noninvasive pO2 imaging based on the application of TD-EPR using oxygen-induced LW broadening of a triarylmethyl (TAM)-based radical is presented. The decay of pixel intensities in an image is used to estimate T2*, which is inversely proportional to pO2. Factors affecting T2* in each pixel are critically analyzed to extract the contribution of dissolved oxygen to EPR line-broadening. Suitable experimental and image-processing parameters were obtained to produce pO2 maps with minimal artifacts. Image artifacts were also minimized with the use of a novel data collection strategy using multiple gradients. Results from a phantom and in vivo imaging of tumor-bearing mice validated this novel method of noninvasive oximetry. The current imaging protocols achieve a spatial resolution of approximately 1.0 mm and a temporal resolution of approximately 9 s for 2D pO2 mapping, with a reliable oxygen resolution of approximately 1 mmHg (0.12% oxygen in gas phase). This work demonstrates that in vivo oximetry can be performed with good sensitivity, accuracy, and high spatial and temporal resolution.

  15. Synoviocytes, not chondrocytes, release free radicals after cycles of anoxia/re-oxygenation

    International Nuclear Information System (INIS)

    Schneider, Nicole; Mouithys-Mickalad, Ange L.; Lejeune, Jean-Philippe; Deby-Dupont, Ginette P.; Hoebeke, Maryse; Serteyn, Didier A.

    2005-01-01

    By oxymetry and electron paramagnetic resonance (EPR), we investigated the effects of repeated anoxia/re-oxygenation (A/R) periods on the respiration and production of free radicals by synoviocytes (rabbit HIG-82 cell line and primary equine synoviocytes) and equine articular chondrocytes. Three periods of 20 min anoxia followed by re-oxygenation were applied to 10 7 cells; O 2 consumption was measured before anoxia and after each re-oxygenation. After the last A/R, cellular free radical formation was investigated by EPR spectroscopy with spin trapping technique (n = 3 for each cell line). Both types of synoviocytes showed a high O 2 consumption, which was slowered after anoxia. By EPR with the spin trap POBN, we proved a free radical formation. Results were similar for equine and rabbit synoviocytes. For chondrocytes, we observed a low O 2 consumption, unchanged by anoxia, and no free radical production. These observations suggest an oxidant activity of synoviocytes, potentially important for the onset of osteoarthritis

  16. Introduction lecture to magnetic resonance

    International Nuclear Information System (INIS)

    Conard, J.

    1980-01-01

    This lecture deals with all that is common either to electron paramagnetic resonance (E.P.R.) or to nuclear magnetic resonance (N.M.R.). It will present, in an as elementary form as possible, the main concepts used in magnetic resonance emphasizing some aspects, specific for interface science. (orig./BHO)

  17. EPR Technology as Sensitive Method for Oxidative Stress Detection in Primary and Secondary Keratinocytes Induced by Two Selected Nanoparticles.

    Science.gov (United States)

    Lohan, S B; Ahlberg, S; Mensch, A; Höppe, D; Giulbudagian, M; Calderón, M; Grether-Beck, S; Krutmann, J; Lademann, J; Meinke, M C

    2017-12-01

    Exogenous factors can cause an imbalance in the redox state of biological systems, promoting the development of oxidative stress, especially reactive oxygen species (ROS). To monitor the intensity of ROS production in secondary keratinocytes (HaCaT) by diesel exhaust particles and thermoresponsive nanogels (tNG), electron paramagnetic resonance (EPR) spectroscopy after 1 and 24 h of incubation, respectively, was applied. Their cytotoxicity was analyzed by a cell viability assay (XTT). For tNG an increase in the cell viability and ROS production of 10% was visible after 24 h, whereas 1 h showed no effect. A ten times lower concentration of diesel exhaust particles exhibited no significant toxic effects on HaCaT cells for both incubation times, thus normal adult human keratinocytes (NHK) were additionally analyzed by XTT and EPR spectroscopy. Here, after 24 h a slight increase of 18% in metabolic activity was observed. However, this effect could not be explained by the ROS formation. A slight increase in the ROS production was only visible after 1 h of incubation time for HaCaT (9%) and NHK (14%).

  18. EPR, mu-Raman and Crystallographic properties of spinel type ZnCr{sub 2}O{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Vargas-Hernandez, C; Almanza, O; Jurado, J F, E-mail: cvargash@unal.edu.c [Universidad Nacional de Colombia, Manizales-Colombia Laboratorio de Propiedades Opticas de Materiales-POM (Colombia)

    2009-05-01

    Structural, vibrational and electron paramagnetic resonance (EPR) analysis for compound ZnCr{sub 2}O{sub 4} are shown in this work. These types of materials are used in technological applications as humidity sensors and piezoelectric devices. The compound was obtained by mean of solid state reaction technique from binary precursors ZnO and Cr{sub 2}O{sub 3}. After three thermal treatments the sample structure was monitoring using X ray diffraction (XRD), the spinel cubic phase has been indexed within O{sup 7}{sub h}(Fd3m) spatial group. It is observed normal spinel phase. Micro-Raman analysis revealed bands for normal vibration modes of Zn and Cr atoms in tetrahedral and octahedral environments formed by oxygen atoms at approximately 400 and 900 cm{sup -1}, respectively. Bands around 941 cm{sup -1} are associated possibly to vacancies in the tetrahedral and octahedral sites due to interaction between Zn and Cr ions. EPR signal from 150 to 300 K isothermals indicates a transition between inverse spinel to normal spinel type in a central field around 3350 G. A signal at approximately 3400 G corresponding to the C'r{sup +3} in tetrahedral sites is observed near the central field.

  19. CW EPR parameters reveal cytochrome P450 ligand binding modes.

    Science.gov (United States)

    Lockart, Molly M; Rodriguez, Carlo A; Atkins, William M; Bowman, Michael K

    2018-06-01

    Cytochrome P450 (CYP) monoxygenses utilize heme cofactors to catalyze oxidation reactions. They play a critical role in metabolism of many classes of drugs, are an attractive target for drug development, and mediate several prominent drug interactions. Many substrates and inhibitors alter the spin state of the ferric heme by displacing the heme's axial water ligand in the resting enzyme to yield a five-coordinate iron complex, or they replace the axial water to yield a nitrogen-ligated six-coordinate iron complex, which are traditionally assigned by UV-vis spectroscopy. However, crystal structures and recent pulsed electron paramagnetic resonance (EPR) studies find a few cases where molecules hydrogen bond to the axial water. The water-bridged drug-H 2 O-heme has UV-vis spectra similar to nitrogen-ligated, six-coordinate complexes, but are closer to "reverse type I" complexes described in older liteature. Here, pulsed and continuous wave (CW) EPR demonstrate that water-bridged complexes are remarkably common among a range of nitrogenous drugs or drug fragments that bind to CYP3A4 or CYP2C9. Principal component analysis reveals a distinct clustering of CW EPR spectral parameters for water-bridged complexes. CW EPR reveals heterogeneous mixtures of ligated states, including multiple directly-coordinated complexes and water-bridged complexes. These results suggest that water-bridged complexes are under-represented in CYP structural databases and can have energies similar to other ligation modes. The data indicates that water-bridged binding modes can be identified and distinguished from directly-coordinated binding by CW EPR. Copyright © 2018 Elsevier Inc. All rights reserved.

  20. Accelerated dynamic EPR imaging using fast acquisition and compressive recovery.

    Science.gov (United States)

    Ahmad, Rizwan; Samouilov, Alexandre; Zweier, Jay L

    2016-12-01

    Electron paramagnetic resonance (EPR) allows quantitative imaging of tissue redox status, which provides important information about ischemic syndromes, cancer and other pathologies. For continuous wave EPR imaging, however, poor signal-to-noise ratio and low acquisition efficiency limit its ability to image dynamic processes in vivo including tissue redox, where conditions can change rapidly. Here, we present a data acquisition and processing framework that couples fast acquisition with compressive sensing-inspired image recovery to enable EPR-based redox imaging with high spatial and temporal resolutions. The fast acquisition (FA) allows collecting more, albeit noisier, projections in a given scan time. The composite regularization based processing method, called spatio-temporal adaptive recovery (STAR), not only exploits sparsity in multiple representations of the spatio-temporal image but also adaptively adjusts the regularization strength for each representation based on its inherent level of the sparsity. As a result, STAR adjusts to the disparity in the level of sparsity across multiple representations, without introducing any tuning parameter. Our simulation and phantom imaging studies indicate that a combination of fast acquisition and STAR (FASTAR) enables high-fidelity recovery of volumetric image series, with each volumetric image employing less than 10 s of scan. In addition to image fidelity, the time constants derived from FASTAR also match closely to the ground truth even when a small number of projections are used for recovery. This development will enhance the capability of EPR to study fast dynamic processes that cannot be investigated using existing EPR imaging techniques. Copyright © 2016 Elsevier Inc. All rights reserved.

  1. On the use of Locally Dense Basis Sets in the Calculation of EPR Hyperfine Couplings

    DEFF Research Database (Denmark)

    Hedegård, Erik D.; Sauer, Stephan P. A.; Milhøj, Birgitte O.

    2013-01-01

    The usage of locally dense basis sets in the calculation of Electron Paramagnetic Resonance (EPR) hyperne coupling constants is investigated at the level of Density Functional Theory (DFT) for two model systems of biologically important transition metal complexes: One for the active site in the c......The usage of locally dense basis sets in the calculation of Electron Paramagnetic Resonance (EPR) hyperne coupling constants is investigated at the level of Density Functional Theory (DFT) for two model systems of biologically important transition metal complexes: One for the active site...

  2. On the use of locally dense basis sets in the calculation of EPR hyperfine couplings

    DEFF Research Database (Denmark)

    Milhøj, Birgitte Olai; Hedegård, Erik D.; Sauer, Stephan P. A.

    2013-01-01

    The usage of locally dense basis sets in the calculation of Electron Paramagnetic Resonance (EPR) hyperne coupling constants is investigated at the level of Density Functional Theory (DFT) for two model systems of biologically important transition metal complexes: One for the active site in the c......The usage of locally dense basis sets in the calculation of Electron Paramagnetic Resonance (EPR) hyperne coupling constants is investigated at the level of Density Functional Theory (DFT) for two model systems of biologically important transition metal complexes: One for the active site...

  3. Study of dosimetric properties of acetylsalicylic acid in pharmaceutical preparations by EPR spectroscopy

    International Nuclear Information System (INIS)

    Juarez-Calderon, J.M.; Negron-Mendoza, A.; Ramos-Bernal, S.; Gomez-Vidales, V.

    2009-01-01

    Electron paramagnetic resonance (EPR) was used to investigate the dosimetric properties of two pharmaceutical preparations containing acetylsalicylic acid, Aspirin R and Cafiaspirin R . The EPR spectra of the irradiated samples were found to have an asymmetric absorption characterized by a major resonance at g = 2.0033. Dose response was investigated between dose ranges of 2 to 95 kGy for 60 Co-gamma rays. Fading characteristics and dependence on temperature irradiation were also studied. We suggest that commercial Aspirin R and Cafiaspirin R tablets can be used as dosimeters in the case of a short accident. (author)

  4. Study of dosimetric properties of acetylsalicylic acid in pharmaceutical preparations by EPR spectroscopy

    International Nuclear Information System (INIS)

    Juarez Calderon, J.M.; Negron Mendoza, A.; Ramos Bernal, S.; Gomez Vidales, V.

    2008-01-01

    Electron paramagnetic resonance (EPR) was used to investigate the dosimetric properties of two pharmaceutical preparations containing acetylsalicylic acid, Aspirin (trademark) and Cafiaspirin (trademark). The EPR spectra of the irradiated samples were found to have an asymmetric absorption characterized by a major resonance at g = 2.0033. Dose response was investigated between dose ranges of 2 to 40 kGy for 60 Co-gamma rays. Fading characteristics and dependence on temperature irradiation were also studied. We suggest that commercial Aspirin (trademark) and Cafiaspirin (trademark) tablets can be used as dosimeters for industrial processes. (author)

  5. EPR investigation of some traditional oriental irradiated spices

    International Nuclear Information System (INIS)

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

    2007-01-01

    The 9.50 GHz electron paramagnetic resonance (EPR) spectra of unirradiated and 60 Co 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 o C isothermal annealing of 11.3 kGy irradiated samples has shown a differential reduction of amplitude of various components that compose initial spectra, but even after 3.6 h of thermal treatment, the remaining amplitude represents no less then 30% of the initial ones. The same peculiarities have been noticed after 83 days storage at room temperature but after 340 days storage at ambient conditions only irradiated ginger displays a weak signal that differs from those of unirradiated sample. All these factors could be taken into account in establishing at which extent the EPR is suitable to evidence any irradiation treatment applied to these spices

  6. EPR investigation of some traditional oriental irradiated spices

    Energy Technology Data Exchange (ETDEWEB)

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

    2007-06-15

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

  7. EPR investigation of some traditional oriental irradiated spices

    Science.gov (United States)

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

    2007-06-01

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

  8. EPR-technical codes - a common basis for the EPR

    International Nuclear Information System (INIS)

    Zaiss, W.; Appell, B.

    1997-01-01

    The design and construction of Nuclear Power Plants implies a full set of codes and standards to define the construction rules of components and equipment. Rules are existing and are currently implemented, respectively in France and Germany (mainly RCCs and KTA safety standards). In the frame of the EPR-project, the common objective requires an essential industrial work programme between engineers from both countries to elaborate a common set of codes and regulations. These new industrial rules are called the ETCs (EPR Technical Codes). In the hierarchy the ETCs are - in case of France - on the common level of basic safety rules (RFS), design and construction rules (RCC) and - in Germany - belonging to RSK guidelines and KTA safety standards. A set of six ETCs will be elaborated to cover: safety and process, mechanical components, electrical equipment, instrumentation and control, civil works, fire protection. (orig.)

  9. The Flamanville 3 EPR reactor; Le reacteur EPR Flamanville 3

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2007-07-01

    On April 10. 2007, the french government authorized EDF to create on the site of Flamanville ( La Manche) a nuclear base installation containing a pressurized water EPR type reactor. This nuclear reactor, conceived by AREVA NP and EDF, is the first copy of a generation susceptible to replace later, at least partly, the French nuclear reactors at present in operation.Within the framework of its mission of technical support of the Authority of Nuclear Safety ( A.S.N.), the I.R.S.N. widely contributed successively: to define the general objectives of safety assigned to this new generation of pressurized water nuclear reactors; to analyze the options of safety proposed by EDF for the EPR project; To deepen, upstream to the authorization of creation, the evaluation of the step of safety and the measures of conception retained by EDF that have to allow to respect the objectives of safety which were notified to it. (N.C.)

  10. Resonances

    DEFF Research Database (Denmark)

    an impetus or drive to that account: change, innovation, rupture, or discontinuity. Resonances: Historical Essays on Continuity and Change explores the historiographical question of the modes of interrelation between these motifs in historical narratives. The essays in the collection attempt to realize...

  11. A transferability study of the EPR-tooth-dosimetry technique

    International Nuclear Information System (INIS)

    Sholom, S.; Chumak, V.; Desrosiers, M.; Bouville, A.

    2006-01-01

    The transferability of a measurement protocol from one laboratory to another is an important feature of any mature, standardised protocol. The electron paramagnetic resonance (EPR)-tooth dosimetry technique that was developed in Scientific Center for Radiation Medicine, AMS (Ukraine) (SCRM) for routine dosimetry of Chernobyl liquidators has demonstrated consistent results in several inter-laboratory measurement comparisons. Transferability to the EPR dosimetry laboratory at the National Inst. of Standards and Technology (NIST) was examined. Several approaches were used to test the technique, including dose reconstruction of SCRM-NIST inter-comparison samples. The study has demonstrated full transferability of the technique and the possibility to reproduce results in a different laboratory environment. (authors)

  12. EPR of divalent manganese in non-Kramers hosts

    Energy Technology Data Exchange (ETDEWEB)

    Lech, J.; Slezak, A. [Institute of Physics, Technical University of Czestochowa, Czestochowa (Poland)

    1997-12-31

    Various interactions which lead to the observation of sharp EPR spectra of the high half-integer spin impurity Mn{sup 2+} (S=5/2) in paramagnetic hosts with integer spins S=1 and S=2 have been studied. Studies have been carried out on the basis of data extracted from experimental EPR spectra of Mn{sup 2+} in single crystal of divalent nickel Ni{sup 2+} (S=1) and Fe{sup 2+} (S=1) perchlorate hexahydrates. It has been shown that dipolar host-host and host-guest couplings broaden resonance lines of Mn{sup 2+}. Narrowing of the lines in the both crystals can be mainly attributed to the host-guest exchange interactions and quenching of the host spins. 19 refs, 3 figs, 1 tab.

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

    Science.gov (United States)

    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.

  14. EPR compared to international requirements (Mainly EUR)

    International Nuclear Information System (INIS)

    Broecker, B.

    1996-01-01

    A number of European Utilities have entered an agreement to write common requirements dedicated to future light water nuclear power plants to be built in Europe. The activities are known under the sign EUR (European Utilities Requirements). EPR, the future European Pressurized water Reactor, is the first installation of this type which will be operational from the year 2000 onwards, must fulfill the European requirements. EPR will serve as a test whether these requirements are realistic and well balanced. At the basic design stage of EPR, this paper concentrates on four main topics: the requirements which are new compared with existing reactors and which put a major challenge to the designer; the requirements today still open and the way they can be met by the EPR or not; the points for which already today the EPR special requirements exceed the EUR; the examples where the design of the EPR has given feedback which has led to a change of the EUR. EPR and EUR are different approaches to the reactor of the future. EUR is a set of requirements which leaves a flexibility to the designer while EPR is a real project which defines the technical solutions. EPR will fulfill the EUR and will at the same time serve as a test whether these requirements are realistic. EPR will also fulfill international requirements with minor changes. (J.S.). 7 figs

  15. Hydrogen Analyses in the EPR

    International Nuclear Information System (INIS)

    Worapittayaporn, S.; Eyink, J.; Movahed, M.

    2008-01-01

    In severe accidents with core melting large amounts of hydrogen may be released into the containment. The EPR provides a combustible gas control system to prevent hydrogen combustion modes with the potential to challenge the containment integrity due to excessive pressure and temperature loads. This paper outlines the approach for the verification of the effectiveness and efficiency of this system. Specifically, the justification is a multi-step approach. It involves the deployment of integral codes, lumped parameter containment codes and CFD codes and the use of the sigma criterion, which provides the link to the broad experimental data base for flame acceleration (FA) and deflagration to detonation transition (DDT). The procedure is illustrated with an example. The performed analyses show that hydrogen combustion at any time does not lead to pressure or temperature loads that threaten the containment integrity of the EPR. (authors)

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

    Science.gov (United States)

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

    2017-08-01

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

  17. Bioactivity characterization of 45S5 bioglass using TL, OSL and EPR: Comparison with the case of 58S sol-gel bioactive glass

    Energy Technology Data Exchange (ETDEWEB)

    Polymeris, G.S., E-mail: gspolymeris@ankara.edu.tr [Ankara University, Institute of Nuclear Sciences, 06100 Beşevler, Ankara (Turkey); Giannoulatou, V. [Ankara University, Institute of Nuclear Sciences, 06100 Beşevler, Ankara (Turkey); Solid State Section, Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Kyriakidou, A. [Solid State Section, Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Sfampa, I.K. [Nuclear Physics Laboratory, Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Theodorou, G.S. [Solid State Section, Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Şahiner, E.; Meriç, N. [Ankara University, Institute of Nuclear Sciences, 06100 Beşevler, Ankara (Turkey); Kitis, G. [Nuclear Physics Laboratory, Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Paraskevopoulos, K.M. [Solid State Section, Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece)

    2017-01-01

    The current work exploits the effective application of thermoluminescence (TL), optically stimulated luminescence (OSL) and the possibility of applying Electron Paramagnetic Resonance (EPR) for the discrimination between different bioactive responses in the case of the 45S5 bioactive glass (SiO{sub 2} 45, Na{sub 2}O 24.5, CaO 24.5, P{sub 2}O{sub 5} 6 in wt%), which was synthesized through melting process. These techniques are suggested mainly due to their low spectroscopic detection thresholds. The original 45S5 in grain size range of 20–40 μm was immersed in the Simulated Body Fluid (SBF) for various different immersion times ranging over one week. In this work the 110 °C TL peak, a specific OSL component and the EPR signal at g = 2.013 ascribed to oxygen hole center (OHC) are used due to their sensitivity to the different bioactive responses. For all luminescence and EPR components, the intensity plot versus immersion time yields sharp discontinuities, resulting in effective probes regarding the timescale for both the beginning as well as the end of the procedure of the crystalline HCAp formation respectively. On the contrary to the smooth decreasing pattern of both luminescence entities, the peak to peak amplitude of the EPR signal indicates an initial increase for the initial 16 min of immersion, followed by a further decrease throughout the immersion time duration. The discontinuities monitored for both sensitivity of TL, OSL and EPR, in conjunction with the discontinuities monitored for the sensitization of TL and OSL, when plotted versus immersion time, provide an individual time scale for each one of the chemical reactions involved in the five steps of the aforementioned procedure. According to the authors' best knowledge, scarce characterization techniques could provide this time scale frame, while it is the first time that such an application of OSL and EPR is attempted. Finally, the bioactive response of the 45S5 bioglass was compared with that

  18. EPR-based material modelling of soils

    Science.gov (United States)

    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.

  19. Probing Microenvironment in Ionic Liquids by Time-Resolved EPR of Photoexcited Triplets.

    Science.gov (United States)

    Ivanov, M Yu; Veber, S L; Prikhod'ko, S A; Adonin, N Yu; Bagryanskaya, E G; Fedin, M V

    2015-10-22

    Unusual physicochemical properties of ionic liquids (ILs) open vistas for a variety of new applications. Herewith, we investigate the influence of microviscosity and nanostructuring of ILs on spin dynamics of the dissolved photoexcited molecules. We use two most common ILs [Bmim]PF6 and [Bmim]BF4 (with its close analogue [C10mim]BF4) as solvents and photoexcited Zn tetraphenylporphyrin (ZnTPP) as a probe. Time-resolved electron paramagnetic resonance (TR EPR) is employed to investigate spectra and kinetics of spin-polarized triplet ZnTPP in the temperature range 100-270 K. TR EPR data clearly indicate the presence of two microenvironments of ZnTPP in frozen ILs at 100-200 K, being manifested in different spectral shapes and different spin relaxation rates. For one of these microenvironments TR EPR data is quite similar to those obtained in common frozen organic solvents (toluene, glycerol, N-methyl-2-pyrrolidone). However, the second one favors the remarkably slow relaxation of spin polarization, being much longer than in the case of common solvents. Additional experiments using continuous wave EPR and stable nitroxide as a probe confirmed the formation of heterogeneities upon freezing of ILs and complemented TR EPR results. Thus, TR EPR of photoexcited triplets can be effectively used for probing heterogeneities and nanostructuring in frozen ILs. In addition, the increase of polarization lifetime in frozen ILs is an interesting finding that might allow investigation of short-lived intermediates inaccessible otherwise.

  20. Pulsed EPR analysis of tooth enamel samples exposed to UV and {gamma}-radiations

    Energy Technology Data Exchange (ETDEWEB)

    Marrale, M., E-mail: marrale@unipa.it [Dipartimento di Fisica, Universita di Palermo, Viale delle Scienze, Edificio 18, 90128 Palermo (Italy); Gruppo V Sezione INFN, Catania, Italy and Unita CNISM, Palermo (Italy); Longo, A.; Brai, M. [Dipartimento di Fisica, Universita di Palermo, Viale delle Scienze, Edificio 18, 90128 Palermo (Italy); Gruppo V Sezione INFN, Catania (Italy) and Unita CNISM, Palermo (Italy); Barbon, A.; Brustolon, M. [Dipartimento di Scienze Chimiche, Universita degli Studi di Padova, Via Marzolo 1, 35131 Padova (Italy); Fattibene, P. [Istituto Superiore di Sanita, Viale Regina Elena 299, 00161 Rome (Italy)

    2011-09-15

    The electron paramagnetic resonance (EPR) spectroscopy is widely applied for retrospective dosimetric purposes by means of quantitative detection of radicals in tooth enamel and bone samples. In this work we report a study by cw and pulsed EPR on two samples of human tooth enamel respectively irradiated by UV (254 nm) and {gamma}-exposed. The continuous wave (cw) EPR spectra have shown the usual presence in both samples of two types of CO{sub 2}{sup -} radicals, with axial and orthorombic g tensors. We have obtained the electron spin echo detected EPR (ED-EPR) spectra at 80 K of the two samples, and we have shown that they are suitable to mark the difference between the effects produced by the different irradiations. At low temperature the contribution to the ED-EPR spectrum of the mobile radical with the axial g tensor is still present in the UV irradiated sample, but not in the {gamma}-irradiated one, where its dynamics is too slow to average the g tensor. We have moreover studied the two-pulse electron spin echo decay on varying the microwave power, a well established method for measuring the Instantaneous Diffusion. We have found that the spectral diffusion parameter is almost the same for both radiation types, whereas the Instantaneous Diffusion is significantly larger for {gamma}-exposed samples than for UV irradiated ones. This difference is due to a higher local microscopic concentration of free radicals for samples irradiated with {gamma} photons.

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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-03-15

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

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

    International Nuclear Information System (INIS)

    Yordanov, Nicola D.; Aleksieva, Katerina

    2009-01-01

    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 deg. C. The results obtained with both drying procedures are compared. All samples under study show a singlet EPR line with g=2.0048±0.0005 before irradiation. Irradiation gives rise to typical 'cellulose-like' EPR spectrum featuring one intensive line with g=2.0048±0.0005 and two very weak satellite lines situated 3 mT at left and right of the central line. Only mango samples show a singlet line after irradiation. The fading kinetics of radiation-induced EPR signal is studied for a period of 50 days after irradiation. When the irradiated fruit samples are stored in their natural state and dried just before each EPR measurement, the satellite lines are measurable for less than 17 days of storage. Irradiated fruit samples, when stored dried, lose for 50 days ca. 40% of their radiation-induced radicals if treated with alcohol or ca. 70% if dried in an oven. The reported results unambiguously show that the presence of the satellite lines in the EPR spectra could be used for identification of radiation processing of fresh fruits, thus extending the validity of European Protocol EN 1787 (2000). Foodstuffs-Detection of Irradiated Food Containing Cellulose by EPR Spectroscopy. European Committee for Standardisation. Brussels for dry herbs

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

    Science.gov (United States)

    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.

  5. Magnetic Resonance Imaging-Derived Renal Oxygenation and Perfusion During Continuous, Steady-State Angiotensin-II Infusion in Healthy Humans.

    Science.gov (United States)

    van der Bel, René; Coolen, Bram F; Nederveen, Aart J; Potters, Wouter V; Verberne, Hein J; Vogt, Liffert; Stroes, Erik S G; Krediet, C T Paul

    2016-03-28

    The role of kidney hypoxia is considered pivotal in the progression of chronic kidney disease. A widely used method to assess kidney oxygenation is blood oxygen level dependent (BOLD)-magnetic resonance imaging (MRI), but its interpretation remains problematic. The BOLD-MRI signal is the result of kidney oxygen consumption (a proxy of glomerular filtration) and supply (ie, glomerular perfusion). Therefore, we hypothesized that with pharmacological modulation of kidney blood flow, renal oxygenation, as assessed by BOLD-MRI, correlates to filtration fraction (ie, glomerular filtration rate/effective renal plasma flow) in healthy humans. Eight healthy volunteers were subjected to continuous angiotensin-II infusion at 0.3, 0.9, and 3.0 ng/kg per minute. At each dose, renal oxygenation and blood flow were assessed using BOLD and phase-contrast MRI. Subsequently, "gold standard" glomerular filtration rate/effective renal plasma flow measurements were performed under the same conditions. Renal plasma flow decreased dose dependently from 660±146 to 467±103 mL/min per 1.73 m(2) (F[3, 21]=33.3, PMRI, we showed that cortical oxygenation measured by BOLD MRI relates poorly to glomerular filtration rate but is associated with filtration fraction. For future studies, there may be a need to include renal plasma flow measurements when employing renal BOLD-MRI. © 2016 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.

  6. Oxygen vacancies at the spinel/perovskite γ-Al{sub 2}O{sub 3}/SrTiO{sub 3} heterointerface probed by resonant photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Schuetz, Philipp; Pfaff, Florian; Zapf, Michael; Gabel, Judith; Dudy, Lenart; Berner, Goetz; Sing, Michael; Claessen, Ralph [Physikalisches Institut and Roentgen Center for Complex Material Systems (RCCM), Universitaet Wuerzburg (Germany); Chen, Yunzhong; Pryds, Nini [Department of Energy Conversion and Storage, Technical University of Denmark, Risoe (Denmark); Schlueter, Christoph; Lee, Tien-Lin [Diamond Light Source Ltd., Harwell Science and Innovation Campus, Didcot (United Kingdom)

    2016-07-01

    The spinel/perovskite heterointerface between the band insulators γ-Al{sub 2}O{sub 3} and SrTiO{sub 3} hosts a two-dimensional electron system (2DES) with exceptionally high electron mobility. Soft x-ray resonant photoelectron spectroscopy at the Ti L absorption edge is used to probe the Ti 3d derived interface states. Marked differences in the resonance behavior are found for the SrTiO{sub 3} valence band and the different interface states, which are observed in the band gap of SrTiO{sub 3}. A comparison to X-ray absorption spectra of Ti 3d{sup 0} and Ti 3d{sup 1} systems reveals the presence of different types of electronic states with Ti 3d character, i.e., oxygen vacancy induced, trapped in-gap states and itinerant states contributing to the 2DES. Exposure to low doses of oxygen during irradiation allows for the reversible manipulation of the oxygen stoichiometry, thus revealing the presence of an oxygen vacancy-induced state, which is characteristic for this spinel/perovskite interface.

  7. EPR investigation of some irradiated traditional oriental spices

    International Nuclear Information System (INIS)

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

    2005-01-01

    The X-band EPR spectra of unirradiated and 60 Co gamma ray irradiated cardamom (Elettaria cardamomum L. Maton, Zingiberaceae), ginger ((Zingiber officinale Rosc., Zingiberaceae), saffron (Crocus sativus L., Iridaceae), and curry have been investigated at room temperature. All unirradiated spices presented a weak resonance line with g-factors around free-electron ones, most probably due to the presence of semiquinones, previously reported to have paramagnetic properties. After gamma ray irradiation at absorbed dose up to 11.3 kGy we have noticed in all spices the presence of complex EPR spectra consisting of a superposition of at last two different paramagnetic species whose amplitude increase monotonously with the absorbed dose. A 100 deg. C isothermal annealing of 11.3 kGy irradiated samples has shown a differential reduction of amplitude of various components that form the initial spectra, but even after 5 h of thermal treatment, the remaining amplitude represents no less than 40% from the initial ones, testifying for a good thermal stability. The presences of initial EPR spectra as well as the remaining amplitude after isothermal annealing are very useful in identifying any irradiation treatment applied to this category of species. (authors)

  8. Peptide-membrane Interactions by Spin-labeling EPR

    Science.gov (United States)

    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

  9. High-frequency EPR of surface impurities on nanodiamond

    Science.gov (United States)

    Peng, Zaili; Stepanov, Viktor; Takahashi, Susumu

    Diamond is a fascinating material, hosting nitrogen-vacancy (NV) defect centers with unique magnetic and optical properties. There have been many reports that suggest the existence of paramagnetic impurities near surface of various kinds of diamonds. Electron paramagnetic resonance (EPR) investigation of mechanically crushed nanodiamonds (NDs) as well as detonation NDs revealed g 2 like signals that are attributed to structural defects and dangling bonds near the diamond surface. In this presentation, we investigate paramagnetic impurities in various sizes of NDs using high-frequency (HF) continuous wave (cw) and pulsed EPR spectroscopy. Strong size dependence on the linewidth of HF cw EPR spectra reveals the existence of paramagnetic impurities in the vicinity of the diamond surface. We also study the size dependence of the spin-lattice and spin-spin relaxation times (T1 and T2) of single substitutional nitrogen defects in NDs Significant deviations from the temperature dependence of the phonon-assisted T1 process were observed in the ND samples, and were attributed to the contribution from the surface impurities. This work was supported by the Searle Scholars Program and the National Science Foundation (DMR-1508661 and CHE-1611134).

  10. ENDOR-Induced EPR of Disordered Systems: Application to X-Irradiated Alanine.

    Science.gov (United States)

    Kusakovskij, Jevgenij; Maes, Kwinten; Callens, Freddy; Vrielinck, Henk

    2018-02-15

    The electron paramagnetic resonance (EPR) spectra of radiation-induced radicals in organic solids are generally composed of multiple components that largely overlap due to their similar weak g anisotropy and a large number of hyperfine (HF) interactions. Such properties make these systems difficult to study using standard cw EPR spectroscopy even in single crystals. Electron-nuclear double-resonance (ENDOR) spectroscopy is a powerful and widely used complementary technique. In particular, ENDOR-induced EPR (EIE) experiments are useful for separating the overlapping contributions. In the present work, these techniques were employed to study the EPR spectrum of stable radicals in X-irradiated alanine, which is widely used in dosimetric applications. The principal values of all major proton HF interactions of the dominant radicals were determined by analyzing the magnetic field dependence of the ENDOR spectrum at 50 K, where the rotation of methyl groups is frozen. Accurate simulations of the EPR spectrum were performed after the major components were separated using an EIE analysis. As a result, new evidence in favor of the model of the second dominant radical was obtained.

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

    Science.gov (United States)

    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…

  12. Effect of ferroelastic domain pattern changes on the EPR spectra in TDM

    Science.gov (United States)

    Zapart, W.; Zapart, M. B.

    2011-09-01

    This article presents polarized light microscopy studies of the ferroelastic domain structure and the analysis of electron paramagnetic resonance spectra of Cr3+ admixture ions in trigonal double molybdates. The correlation has been found between abnormal EPR lineshape and domain structure in ferroelastic phases of these crystals.

  13. In Vivo EPR Resolution Enhancement Using Techniques Known from Quantum Computing Spin Technology.

    Science.gov (United States)

    Rahimi, Robabeh; Halpern, Howard J; Takui, Takeji

    2017-01-01

    A crucial issue with in vivo biological/medical EPR is its low signal-to-noise ratio, giving rise to the low spectroscopic resolution. We propose quantum hyperpolarization techniques based on 'Heat Bath Algorithmic Cooling', allowing possible approaches for improving the resolution in magnetic resonance spectroscopy and imaging.

  14. Dating by electron paramagnetic resonance

    International Nuclear Information System (INIS)

    Poupeau, G.; Rossi, A.M.

    1984-01-01

    Some natural materials behave like dosimeters in front of the ionizing particle flux coming from environmental radioactivity and the cosmic radiation. This property is used for the dating by Electron Paramagnetic Resonance (EPR). Before presenting the basic principles of the EPR analysis and the dating method which uses such a phenomenous, it is reviewed several types of application currently in course of development. (L.C.) [pt

  15. EPR project construction cost control

    International Nuclear Information System (INIS)

    Duflo, D.; Pouget-Abadie, X.; Dufour, A.; Kauffmann, G.

    2001-01-01

    The EPR project is now managed by EDF in cooperation with the German Utilities. The main engineering activities for this period are related to the preparation of construction project management, deepening of some safety issues, definition of the project technical reference. The EPR project concerns the so-called reference unit, that is an isolated first-off unit, with unit electrical power of about 1500 MW. The construction costs evaluated are those of the nuclear island, the conventional island, site facilities, installation work and the administrative buildings. The EPR project construction cost evaluation method applies to all the equipment installed and commissioned. It requires the availability of a preliminary project detailed enough to identify the bill of quantities. To these quantities are then assigned updated unit prices that are based either on cost bases for similar and recent facilities or taken from request for quotation for similar equipment or result from gains due to contractual conditions benefiting from simplifications in the functional and technical specifications. The input and output data are managed in a model that respects the breakdown on which the evaluation method is based. The structural organization of this method reflects a functional breakdown on the one hand (nuclear island, conventional island, common site elements) and on the other hand a breakdown according to equipment or activity (civil engineering, mechanics, electricity, instrumentation and control). This paper discusses the principle and the method of construction cost evaluation carried out, the cost data base and input and output parameters as well as results and oncoming cost analysis tasks. (author)

  16. Electron paramagnetic resonance and dynamic nuclear polarization of char suspensions: surface science and oximetry

    International Nuclear Information System (INIS)

    Clarkson, R.B.; Odintsov, B.M.; Ceroke, P.J.; Ardenkjaer-Larsen, J.H.; Fruianu, M.; Belford, R.L.

    1998-01-01

    Carbon chars have been synthesized in our laboratory from a variety of starting materials, by means of a highly controlled pyrolysis technique. These chars exhibit electron paramagnetic resonance (EPR) line shapes which change with the local oxygen concentration in a reproducible and stable fashion; they can be calibrated and used for oximetry. Biological stability and low toxicity make chars good sensors for in vivo measurements. Scalar and dipolar interactions of water protons at the surfaces of chars may be utilized to produce dynamic nuclear polarization (DNP) of the 1 H nuclear spin population in conjunction with electron Zeeman pumping. Low-frequency EPR, DNP and DNP-enhanced MRI all show promise as oximetry methods when used with carbon chars. (author)

  17. EPR dosimetric properties of nano-barium sulfate

    International Nuclear Information System (INIS)

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

    2015-01-01

    Nano/micro BaSO 4 were prepared through the co-precipitation method to measure ionizing radiation doses using electron paramagnetic resonance (EPR). The nano-BaSO 4 sample was characterized using X-ray diffraction (XRD), and transmission electron microscopy (TEM) techniques. The dose response and fading properties of nano- and micro-phase BaSO 4 were compared in EPR spectra. The prepared nano- and micro-BaSO 4 samples have the same hole and electron centers, which may be attributed to SO 4 − and SO 3 − , respectively. The dosimetric signals for prepared nano- and micro-BaSO 4 have spectroscopic splitting factor (g) with values 2.0025±0.0006 and 2.0027±0.0006, respectively. The nanocrystalline sample has a linear γ-ray dose response over the range 0.4 Gy–1 kGy. The performance parameters which including detection limit and critical level calculated from weighted and unweighted least-squares fitting. The sensitivity of nano-BaSO 4 to γ-ray is one and a half times more than alanine. The lifetime and activation energy for nano-BaSO 4 were estimated by conducting a thermal stability study, and were 5.7±1.1×10 4 years and 0.73±0.14 eV, respectively. The combined and expanded uncertainties accompanying measurements were ±3.89% and ±7.78%, respectively. - Highlights: • Preparation of nano-BaSO 4 using the co-precipitation method. • Study of the dosimetric properties of nano-barium sulfate using the EPR technique. • Comparison between a new EPR dosimeter using nano-materials and standard alanine. • Calculation of the uncertainty budget for nano-BaSO 4

  18. Overview of LBB implementation for the EPR

    International Nuclear Information System (INIS)

    Cauquelin, C.

    1997-01-01

    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

  19. Overview of LBB implementation for the EPR

    Energy Technology Data Exchange (ETDEWEB)

    Cauquelin, C.

    1997-04-01

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

  20. Electron paramagnetic resonance spectral study of [Mn(acs){sub 2}(2–pic){sub 2}(H{sub 2}O){sub 2}] single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Kocakoç, Mehpeyker, E-mail: mkocakoc@cu.edu.tr [Çukurova University (Turkey); Tapramaz, Recep, E-mail: recept@omu.edu.tr [Ondokuz Mayıs University (Turkey)

    2016-03-25

    Acesulfame potassium salt is a synthetic and non-caloric sweetener. It is also important chemically for its capability of being ligand in coordination compounds, because it can bind over Nitrogen and Oxygen atoms of carbonyl and sulfonyl groups and ring oxygen. Some acesulfame containing transition metal ion complexes with mixed ligands exhibit solvato and thermo chromic properties and these properties make them physically important. In this work single crystals of Mn{sup +2} ion complex with mixed ligand, [Mn(acs){sub 2}(2-pic){sub 2}(H{sub 2}O){sub 2}], was studied with electron paramagnetic resonance (EPR) spectroscopy. EPR parameters were determined. Zero field splitting parameters indicated that the complex was highly symmetric. Variable temperature studies showed no detectable chance in spectra.

  1. EPR meeting international safety standards with margin

    International Nuclear Information System (INIS)

    Mazurkiewicz, S.M.; Brauns, J.; Blombach, J.

    2005-01-01

    The EPR provides technology that offers a solution to the market's need for safe, economic power. The EPR was originally developed through a joint effort between Framatome ANP and Siemens by incorporating the best technological features from the French and German nuclear reactor fleets into a cost-competitive product capable of international licensing. As such, the EPR is a global product with commercial units currently being built in Finland at the Olkiluoto site, and planned for France, at the Flamanville site. Framatome ANP has recently proposed four EPR units to China in response to a request for vendor bids. In addition, Framatome ANP has announced their intent to pursue design certification with the United States Nuclear Regulatory Commission (NRC). This paper discusses how EPR's innovative safety philosophy ensures compliance with international safety standards for advanced light-water reactors (ALWRs). (author)

  2. EPR meeting international safety standards with margin

    International Nuclear Information System (INIS)

    Mazurkiewicz, S.M.; Brauns, J.; Blombach, J.

    2005-01-01

    The EPR provides technology that offers a solution to the market's need for safe, economic power. The EPR was originally developed through a joint effort between Framatome ANP and Siemens by incorporating the best technological features from the French and German nuclear reactor fleets into a cost-competitive product capable of international licensing. As such, the EPR is a global product with commercial units currently being built in Finland at the Olkiluoto site, and planned for France, at the Flamanville site. Framatome ANP has recently proposed four EPR units to China in response to a request for vendor bids. In addition, Framatome ANP has announced their intent to pursue design certification in with the United States Nuclear Regulatory Commission (NRC). This paper discusses how EPR's innovative safety philosophy ensures compliance with international safety standards for advanced light-water reactors (ALWRs). (author)

  3. Effects of breathing a hyperoxic hypercapnic gas mixture on blood oxygenation and vascularity of head-and-neck tumors as measured by magnetic resonance imaging

    International Nuclear Information System (INIS)

    Rijpkema, Mark; Kaanders, Johannes H.A.M.; Joosten, Frank; Kogel, Albert J. van der; Heerschap, Arend

    2002-01-01

    Purpose: For head-and-neck tumors, breathing a hyperoxic hypercapnic gas mixture and administration of nicotinamide has been shown to result in a significantly improved tumor response to accelerated radiotherapy (ARCON, Accelerated Radiotherapy with CarbOgen and Nicotinamide). This may be caused by improved tumor oxygenation, possibly mediated by vascular effects. In this study, both blood oxygenation and vascular effects of breathing a hyperoxic hypercapnic gas mixture (98% O 2 +2% CO 2 ) were assessed by magnetic resonance imaging (MRI) in patients with head-and-neck tumors. Methods and Materials: Tumor vascularity and oxygenation were investigated by dynamic gadolinium contrast-enhanced MRI and blood oxygen level dependent (BOLD) MRI, respectively. Eleven patients with primary head-and-neck tumors were each measured twice; with and without breathing the hyperoxic hypercapnic gas mixture. Results: BOLD MR imaging revealed a significant increase of the MRI time constant of transverse magnetization decay (T 2 *) in the tumor during hypercapnic hyperoxygenation, which correlates to a decrease of the deoxyhemoglobin concentration. No changes in overall tumor vascularity were observed, as measured by the gadolinium contrast uptake rate in the tumor. Conclusion: Breathing a hyperoxic hypercapnic gas mixture improves tumor blood oxygenation in patients with head-and-neck tumors, which may contribute to the success of the ARCON therapy

  4. Electron Paramagnetic Resonance Imaging

    Indian Academy of Sciences (India)

    Twentieth century bore witness to remarkable scientists whohave advanced our understanding of the brain. Among them,EPR (Electron Paramagnetic Resonance) imaging is particularlyuseful in monitoring hypoxic zones in tumors which arehighly resistant to radiation and chemotherapeutic treatment.This first part of the ...

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

    Energy Technology Data Exchange (ETDEWEB)

    Haskell, E.H.; Kenner, G.H.; Hayes, R.B. [Utah Univ., Salt Lake City, UT (United States). Center for Applied Dosimetry; Chumak, V.; Shalom, S. [All-Union Scientific Centre of Radiation Medicine, Kiev (Ukraine)

    1996-01-01

    Electron paramagnetic resonance spectroscopy (EPR) of tooth enamel is a relatively new technique for retrospective dosimetry that in the past two years has seen increasing effort towards its development and evaluation. Efforts have centered on determining the accuracy which may be achieved with current measurement techniques as well as the minimum doses detectable. The study was focused on evaluating some factors which influence the accuracy of EPR dosimetry of enamel. Reported are studies on sample intercomparisions, instrumental considerations, and effects of dental x-rays, environmental sunlight and ultraviolet radiation.

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

    International Nuclear Information System (INIS)

    Haskell, E.H.; Kenner, G.H.; Hayes, R.B.

    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

  7. Kinetic study of UV-irradiated amorphous sulfur by EPR spectroscopy

    International Nuclear Information System (INIS)

    El Mkami, H.; Smith, G.M.

    2005-01-01

    Electron paramagnetic resonance (EPR) spectroscopy is used to investigate UV-irradiation damage in amorphous sulfur by examining post-irradiation kinetics as a function of UV-exposure time. The kinetic study is described by first-order concurrent reactions where the sulfur, as reactant, undergoes two parallel processes leading to the formation of two distinct defects called S 1 * and S 2 *. The temperature dependence of the EPR intensities of the signals, related to these defects, is used in the kinetic study

  8. EPR study of the free radicals in the spices and pigments turmeric and saffron

    International Nuclear Information System (INIS)

    Troup, G.J.; Hutton, D.R.; Hunter, C.A.; Hewitt, D.; Mulinacci, N.; Romani, A.; Giaccherini, K. Anon

    2000-01-01

    Full text: The spices Turmeric (curcuma longa) and Saffron (crocus sativus) have also been used as pigments. The EPR spectrum of each shows a readily detectable free radical signal. EPR spectra of the available pure chief active colorants in solid form also give free radical signals. Curcumin (turmeric) is a 'linear' symmetric phenolic, so is expected to do so. The peptide turmerin (commercially unavailable), containing sulphur, may also contribute to the ESR signal. Crocetin (saffron) is a 'linear' molecule, related to the beta-carotenes, which do not give free radical signals: but it does, presumably because of its particular resonant structure properties

  9. Validating and analyzing EPR hyperfine coupling constants with density functional theory

    DEFF Research Database (Denmark)

    Hedegård, Erik D.; Kongsted, Jacob; Sauer, Stephan P. A.

    2013-01-01

    Electron Paramagnetic Resonance (EPR) is a central spectroscopic technique for compounds with non-zero spin. The effective parameters from the EPR spin-Hamiltonian can today be calculated from rst principles using quantum chemical methods. We focus here on the hyperne coupling tensor, A, which....... Unfortunately both organometallic and traditional coordination complexes show a completely different behavior, where the core contributions to AKiso either are comparable (“class 2”) or far exceed (“class 3”) the contributions from the frontier orbitals. Agreement with experiment can for these complexes only...

  10. Detection by EPR method of radiation treatment in dried fruits containing crystalline sugar

    International Nuclear Information System (INIS)

    Lehner, K.; Stachowicz, W.

    2006-01-01

    The results of EPR (electron paramagnetic resonance) measurements are presented on the detection ability and stability of radiation induced sugar-born radicals in the samples of dried (dehydrated) fruits available in the market and related to doses of 0.5, 1 and 3 kGy, respectively. The experiments have been conducted during 12 months of storage. Measurements were done with an EPR - 10 MINI spectrometer in X band (frequency of microwaves 9.5 GHz), St. Petersburg Instruments Ltd. The aim of the work was to prove the reliability of acceptability of the method in routine control of irradiated food. (author)

  11. EPR dosimetry - present and future

    International Nuclear Information System (INIS)

    Regulla, D.F.

    1999-01-01

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

  12. EPR Dosimetry - Present and Future

    Energy Technology Data Exchange (ETDEWEB)

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

    1999-07-01

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

  13. EPR Dosimetry - Present and Future

    International Nuclear Information System (INIS)

    Regulla, D.F.

    1999-01-01

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

  14. EPR Study of Vanadium Ion in Zinc-Boro-Vanadate Glasses

    International Nuclear Information System (INIS)

    Renuka, C.; Gowda, V. C. Veeranna; Chakradhar, R. P. S.; Reddy, C. Narayana

    2011-01-01

    This paper describes EPR studies on x V 2 O 5 -(40-x)ZnO-60B 2 O 3 (where x 5, 10, 15 and 20 mol %) glass system. These studies indicate a strong compositional dependent trend and existence of characteristic boro-vanadate groups in these glasses. The EPR spectra show a distinct hyperfine structure of 51 V. Spectral analysis shows that the vanadium is present in the glass as vanadyl ion [VO] 2+ at tetragonally distorted octahedral site. The decrease of A || and A perpendicular with increase of V 2 O 5 concentration suggests an increase in the covalence between the central atom and the surrounding oxygen ligands.

  15. Oxidative response of human monocytes and macrophages cultured under low oxygen culture conditions to ion parametric resonance magnetic fields.

    Science.gov (United States)

    INTRODUCTION One proposed mechanism of action of electromagnetic fields (EMFs) on biological systems is the Ion Parametric Resonance (IPR) model, which has been experimentally validated in neuronal PC-12 cells [1, 2]. It proposes that when applied EMFs are tuned to resonate with...

  16. EPR studies of excited state exchange and crystal-field effects in rare earth compounds

    International Nuclear Information System (INIS)

    Huang, C.Y.; Sugawara, K.; Cooper, B.R.

    1976-01-01

    EPR in excited crystal-field states of Tm 3+ , Pr 3+ , and Tb 3+ in singlet-ground-state systems and in the excited state of Ce 3+ in CeP are reviewed. Because one is looking at a crystal-field excited state resonance, the exchange, even if isotropic, does not act as a secular perturbation. This means that one obtains different effects and has access to more information about the dynamic effects of exchange than in conventional paramagnetic resonance experiments. The Tm and Pr monopnictides studied are paramagnetic at all temperatures. The most striking feature of the behavior of the GAMMA 5 /sup (2)/ EPR in the Tm compounds is the presence of an anomalous maximum in the temperature dependence of the g-factor. The relationship of this effect to anisotropic exchange is discussed. The results of the EPR of the excited GAMMA 5 /sup (2)/ level of Tb 3 + (g-factor becomes very large at T/sub N/ in antiferromagnetic TbX (X = P, As, Sb) and that of the excited GAMMA 8 level of Ce 3+ in antiferromagnetic CeP will also be reported. For sufficient dilution of the Tb 3+ in the terbium monopnictides, the systems become paramagnetic (Van Vleck paramagnets) down to 0 0 K. The Tb 3+ excited state resonance EPR in Tb/sub 0.1/ La/sub 0.9/P was studied as an example of behavior in such systems. 10 fig

  17. Temporal variation in the response of tumors to hyperoxia with breathing carbogen and oxygen

    Science.gov (United States)

    Hou, Hua-gang; Khan, Nadeem; Du, Gai-xin; Hodge, Sassan; Swartz, Harold M.

    2016-01-01

    The effect of hyperoxygenation with carbogen (95% O2 + 5% CO2) and 100% oxygen inhalation on partial pressure of oxygen (pO2) of radiation-induced fibrosarcoma (RIF-1) tumor was investigated. RIF-1 tumors were innoculated in C3H mice, and aggregates of oximetry probe, lithium phthalocyanine (LiPc), was implanted in each tumor. A baseline tumor pO2 was measured by electron paramagnetic resonance (EPR) oximetry for 20 minutes in anesthetized mice breathing 30% O2 and then the gas was switched to carbogen or 100 % oxygen for 60 minutes. These experiments were repeated for 10 days. RIF-1 tumors were hypoxic with a baseline tissue pO2 of 6.2–8.3 mmHg in mice breathing 30% O2. Carbogen and 100% oxygen significantly increased tumor pO2 on days 1 to 5, with a maximal increase at approximately 32–45 minutes on each day. However, the extent of increase in pO2 from the baseline declined significantly on day 5 and day 10. The results provide quantitative information on the effect of hyperoxic gas inhalation on tumor pO2 over the course of 10 days. EPR oximetry can be effectively used to repeatedly monitor tumor pO2 and test hyperoxic methods for potential clinical applications. PMID:27867481

  18. Temporal variation in the response of tumors to hyperoxia with breathing carbogen and oxygen

    Directory of Open Access Journals (Sweden)

    Hua-gang Hou

    2016-01-01

    Full Text Available The effect of hyperoxygenation with carbogen (95% O 2 + 5% CO 2 and 100% oxygen inhalation on partial pressure of oxygen (pO 2 of radiation-induced fibrosarcoma (RIF-1 tumor was investigated. RIF-1 tumors were innoculated in C3H mice, and aggregates of oximetry probe, lithium phthalocyanine (LiPc, was implanted in each tumor. A baseline tumor pO 2 was measured by electron paramagnetic resonance (EPR oximetry for 20 minutes in anesthetized mice breathing 30% O 2 and then the gas was switched to carbogen or 100 % oxygen for 60 minutes. These experiments were repeated for 10 days. RIF-1 tumors were hypoxic with a baseline tissue pO 2 of 6.2-8.3 mmHg in mice breathing 30% O 2 . Carbogen and 100% oxygen significantly increased tumor pO 2 on days 1 to 5, with a maximal increase at approximately 32-45 minutes on each day. However, the extent of increase in pO 2 from the baseline declined significantly on day 5 and day 10. The results provide quantitative information on the effect of hyperoxic gas inhalation on tumor pO 2 over the course of 10 days. EPR oximetry can be effectively used to repeatedly monitor tumor pO 2 and test hyperoxic methods for potential clinical applications.

  19. Various approaches in EPR identification of gamma-irradiated plant foodstuffs: A review.

    Science.gov (United States)

    Aleksieva, Katerina I; Yordanov, Nicola D

    2018-03-01

    Irradiation of food in the world is becoming a preferred method for their sterilization and extending their shelf life. For the purpose of trade with regard to the rights of consumers is necessary marking of irradiated foodstuffs, and the use of appropriate methods for unambiguous identification of radiation treatment. One-third of the current standards of the European Union to identify irradiated foods use the method of the Electron Paramagnetic Resonance (EPR) spectroscopy. On the other hand the current standards for irradiated foods of plant origin have some weaknesses that led to the development of new methodologies for the identification of irradiated food. New approaches for EPR identification of radiation treatment of herbs and spices when the specific signal is absent or disappeared after irradiation are discussed. Direct EPR measurements of dried fruits and vegetables and different pretreatments for fresh samples are reviewed. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. International intercomparison of dose measurements using EPR spectrometry of tooth enamel

    International Nuclear Information System (INIS)

    Wieser, A.; Chumak, V.; Pasalskaya, L.; Pavlenko, J.; Sholom, S.; Bailiff, I.; Baran, N.; Bougai, A.; Kolesnik, S.; Maksimenko, V.; Brik, A.; Matyash, M.; Scherbina, O.; Dubovsky, S.; Kirillov, V.; Minenko, V.; Finin, V.; Haskell, E.; Hayes, R.; Kenner, G.; Ivannikov, A.; Skvortsov, V.; Stepanenko, V.; Liidja, G.; Lippmaa, E.; Past, J.; Puskar, J.; Meijer, A.; Radchuk, V.; Vaher, Ue.

    1996-01-01

    Electron paramagnetic resonance (EPR) dosimetry with teeth is the only solid state dosimetry method that allows for direct measurement of the individual dose. It is considered to be a very promising tool for retrospective individual dosimetry after accidental radioactive releases. It will help to make a reliable assessment of the radiation risk. A number of laboratories are engaged in retrospective EPR dosimetry with teeth. There is consequently a need to develop a programme of intercalibration and intercomparison to check whether the results produced by different laboratories are either consistent or accurate. The Commission of the European Communities has initiated the project ECP10 entitled, Retrospective Dosimetry and Dose reconstruction. Within the joint Eu/CIS project the 1st International Intercomparison of EPR Dosimetry with Teeth' was started in 1994. Nine research laboratories were involved from Germany, Russia, Belarus, Ukraine, Estonia and USA

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

    Energy Technology Data Exchange (ETDEWEB)

    Segawa, Takuya F.; Doll, Andrin; Pribitzer, Stephan; Jeschke, Gunnar, E-mail: gjeschke@ethz.ch [ETH Zurich, Laboratory of Physical Chemistry, Vladimir-Prelog-Weg 2, CH-8093 Zurich (Switzerland)

    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.

  2. EPR dosimetry for actual and suspected overexposures during radiotherapy treatments in Poland

    International Nuclear Information System (INIS)

    Trompier, F.; Sadlo, J.; Michalik, J.; Stachowicz, W.; Mazal, A.; Clairand, I.; Rostkowska, J.; Bulski, W.; Kulakowski, A.; Sluszniak, J.; Gozdz, S.; Wojcik, A.

    2007-01-01

    EPR dosimetry on bone samples was recently used for actual and suspected overexposures during radiotherapy treatments performed in Poland. In 2001 five breast-cancer patients undergoing radiotherapy in the Bialystok Oncology Center, Poland, were overexposed. The overexposure was due to a defective safety interlock and an obsolete safety system of the linear accelerator. For the three most exposed patients, pieces of rib bones removed during surgical reconstruction of the chest wall and skin transplantation allowed an estimation of the accident doses by electron paramagnetic resonance (EPR) spectrometry. The doses delivered during the accident were as high as 60-80 Gy. In 2005, a patient treated in Kielce Holy Cross Cancer Center exhibited similar deep necroses of the chest wall but 6 years following a 'standard upper mantel fields' radiotherapy for Hodgkin's disease. In order to investigate the possible late effect of an overexposure as necrosis origin, the delivered dose was afterward estimated by EPR dosimetry performed on a rib sample

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

    International Nuclear Information System (INIS)

    Collins, B.; Poehler, T.O.; Bryden, W.A.

    1995-01-01

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

  4. Detection and identification of nitrogen defects in nanodiamond as studied by EPR

    Energy Technology Data Exchange (ETDEWEB)

    Soltamova, A.A.; Ilyin, I.V. [Ioffe Physical Technical Institute, Politechnicheskaya, 26, St. Petersburg 194021 (Russian Federation); Baranov, P.G., E-mail: pavel.baranov@mail.ioffe.r [Ioffe Physical Technical Institute, Politechnicheskaya, 26, St. Petersburg 194021 (Russian Federation); Vul' , A.Ya.; Kidalov, S.V.; Shakhov, F.M. [Ioffe Physical Technical Institute, Politechnicheskaya, 26, St. Petersburg 194021 (Russian Federation); Mamin, G.V.; Orlinskii, S.B.; Silkin, N.I.; Salakhov, M.Kh. [Kazan State University, Federal Center of Shared Usage for Physicochemical Measurements, Kazan 420008 (Russian Federation)

    2009-12-15

    Electron paramagnetic resonance (EPR) and electron spin echo (ESE) at X-band and at high-frequency W-band (95 GHz) have been used to study defects in natural diamond nanocrystals, detonation nanodiamond (ND) with a size of approx4.5 nm and detonation ND after high-temperature, high-pressure sintering with a size of approx8.5 nm. Atomic nitrogen centers N{sup 0} and nitrogen pairs N{sub 2}{sup +} have been detected and identified and their structure has been unambiguously determined by means of the high frequency EPR and ESE in natural diamond nanocrystals. In detonation ND and detonation ND after sintering atomic nitrogen centers N{sup 0} have been discovered in nanodiamond core. In addition EPR signal of multi-vacancy centers with spin 3/2 seems to be observed in diamond core of detonation ND.

  5. Radiation sensitivity and EPR dosimetric potential of gallic acid and its esters

    International Nuclear Information System (INIS)

    Tuner, Hasan; Oktay Bal, M.; Polat, Mustafa

    2015-01-01

    In the preset work the radiation sensitivities of Gallic Acid anhydrous and monohydrate, Octyl, Lauryl, and Ethyl Gallate (GA, GAm, OG, LG, and EG) were investigated in the intermediate (0.5–20 kGy) and low radiation (<10 Gy) dose range using Electron Paramagnetic Resonance (EPR) spectroscopy. While OG, LG, and EG are presented a singlet EPR spectra, their radiation sensitivity found to be very different in the intermediate dose range. At low radiation dose range (<10 Gy) only LG is found to be present a signal that easily distinguished from the noise signals. The intermediate and low dose range radiation sensitivities are compared using well known EPR dosimeter alanine. The radiation yields (G) of the interested material were found to be 1.34×10 −2 , 1.48×10 −2 , 4.14×10 −2 , and 6.03×10 −2 , 9.44×10 −2 for EG, GA, GAm, OG, and LG, respectively at the intermediate dose range. It is found that the simple EPR spectra and the noticeable EPR signal of LG make it a promising dosimetric material to be used below 10 Gy of radiation dose. - Highlights: • Radiation sensitivity of gallic acid and its esters were studied in intermediate and low radiation dose range using EPR. • While the irradiated samples of GA were presented complex EPR spectra the esters presented singlet ESR spectra. • Samples were compared to alanine in terms of the dosimetric point of view. • The radiation sensitivities of the investigated materials were very low at intermediate doses. • Lauryl ester of gallic acid was found to present a good sensitivity below 10 Gy

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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 4 × 10 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 13C nuclei indicates that IOM rad 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 ≈ 1.5 ± 0.5 × 10 -2 of the order of values existing in interstellar medium.

  8. Isolation of EPR spectra and estimation of spin-states in two-component mixtures of paramagnets.

    Science.gov (United States)

    Chabbra, Sonia; Smith, David M; Bode, Bela E

    2018-04-26

    The presence of multiple paramagnetic species can lead to overlapping electron paramagnetic resonance (EPR) signals. This complication can be a critical obstacle for the use of EPR to unravel mechanisms and aid the understanding of earth abundant metal catalysis. Furthermore, redox or spin-crossover processes can result in the simultaneous presence of metal centres in different oxidation or spin states. In this contribution, pulse EPR experiments on model systems containing discrete mixtures of Cr(i) and Cr(iii) or Cu(ii) and Mn(ii) complexes demonstrate the feasibility of the separation of the EPR spectra of these species by inversion recovery filters and the identification of the relevant spin states by transient nutation experiments. We demonstrate the isolation of component spectra and identification of spin states in a mixture of catalyst precursors. The usefulness of the approach is emphasised by monitoring the fate of the chromium species upon activation of an industrially used precatalyst system.

  9. In vivo EPR extracellular pH-metry in tumors using a triphosphonated trityl radical.

    Science.gov (United States)

    Marchand, Valérie; Levêque, Philippe; Driesschaert, Benoit; Marchand-Brynaert, Jacqueline; Gallez, Bernard

    2017-06-01

    The ability to assess the extracellular pH (pHe) is an important issue in oncology, because extracellular acidification is associated with tumor aggressiveness and resistance to cytotoxic therapies. In this study, a stable triphosphonated triarylmethyl (TPTAM) radical was qualified as a pHe electron paramagnetic resonance (EPR) molecular reporter. Calibration of hyperfine splitting as a function of pH was performed using a 1.2-GHz EPR spectrometer. Gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) was used as an extracellular paramagnetic broadening agent to assess the localization of TPTAM when incubated with cells. In vivo EPR pH-metry was performed in MDA, SiHa, and TLT tumor models and in muscle. Bicarbonate therapy was used to modulate the tumor pHe. EPR measurements were compared with microelectrode readouts. The hyperfine splitting of TPTAM was strongly pH-dependent around the pKa of the probe (pKa = 6.99). Experiments with Gd-DTPA demonstrated that TPTAM remained in the extracellular compartment. pHe was found to be more acidic in the MDA, SiHa, and TLT tumor models compared with muscle. Treatment of animals by bicarbonate induced an increase in pHe in tumors: similar variations in pHe were found when using in vivo EPR or invasive microelectrodes measurements. This study demonstrates the potential usefulness of TPTAM for monitoring pHe in tumors. Magn Reson Med 77:2438-2443, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

  10. A combined positron emission tomography (PET)-electron paramagnetic resonance imaging (EPRI) system: initial evaluation of a prototype scanner

    Science.gov (United States)

    Tseytlin, Mark; Stolin, Alexander V.; Guggilapu, Priyaankadevi; Bobko, Andrey A.; Khramtsov, Valery V.; Tseytlin, Oxana; Raylman, Raymond R.

    2018-05-01

    The advent of hybrid scanners, combining complementary modalities, has revolutionized the application of advanced imaging technology to clinical practice and biomedical research. In this project, we investigated the melding of two complementary, functional imaging methods: positron emission tomography (PET) and electron paramagnetic resonance imaging (EPRI). PET radiotracers can provide important information about cellular parameters, such as glucose metabolism. While EPR probes can provide assessment of tissue microenvironment, measuring oxygenation and pH, for example. Therefore, a combined PET/EPRI scanner promises to provide new insights not attainable with current imagers by simultaneous acquisition of multiple components of tissue microenvironments. To explore the simultaneous acquisition of PET and EPR images, a prototype system was created by combining two existing scanners. Specifically, a silicon photomultiplier (SiPM)-based PET scanner ring designed as a portable scanner was combined with an EPRI scanner designed for the imaging of small animals. The ability of the system to obtain simultaneous images was assessed with a small phantom consisting of four cylinders containing both a PET tracer and EPR spin probe. The resulting images demonstrated the ability to obtain contemporaneous PET and EPR images without cross-modality interference. Given the promising results from this initial investigation, the next step in this project is the construction of the next generation pre-clinical PET/EPRI scanner for multi-parametric assessment of physiologically-important parameters of tissue microenvironments.

  11. Correlation between single-trial visual evoked potentials and the blood oxygenation level dependent response in simultaneously recorded electroencephalography-functional magnetic resonance imaging

    DEFF Research Database (Denmark)

    Fuglø, Dan; Pedersen, Henrik; Rostrup, Egill

    2012-01-01

    in different occipital and extraoccipital cortical areas not explained by the boxcar regressor. The results suggest that the P1-N2 regressor is the best EEG-based regressor to model the visual paradigm, but when looking for additional effects like habituation or attention modulation that cannot be modeled......To compare different electroencephalography (EEG)-based regressors and their ability to predict the simultaneously recorded blood oxygenation level dependent response during blocked visual stimulation, simultaneous EEG-functional magnetic resonance imaging in 10 healthy volunteers was performed....... The performance of different single-trial EEG regressors was compared in terms of predicting the measured blood oxygenation level dependent response. The EEG-based regressors were the amplitude and latency of the primary positive (P1) and negative (N2) peaks of the visual evoked potential, the combined P1-N2...

  12. Nitrosyl hemoglobins: EPR above 80 K

    Energy Technology Data Exchange (ETDEWEB)

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

    1995-03-01

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

  13. Nitrosyl hemoglobins: EPR above 80 K

    International Nuclear Information System (INIS)

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

    1995-03-01

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

  14. EPR ohmic heating energy storage

    International Nuclear Information System (INIS)

    Heck, F.M.; Stillwagon, R.E.; King, E.I.

    1977-01-01

    The Ohmic Heating (OH) Systems for all the Experimental Power Reactor (EPR) designs to date have all used temporary energy storage to assist in providing the OH current charge required to build up the plasma current. The energies involved (0.8 x 10 9 J to 1.9 x 10 9 J) are so large as to make capacitor storage impractical. Two alternative approaches are homopolar dc generators and ac generators. Either of these can be designed for pulse duty and can be made to function in a manner similar to a capacitor in the OH circuit and are therefore potential temporary energy storage devices for OH systems for large tokamaks. This study compared total OH system costs using homopolar and ac generators to determine their relative merits. The total system costs were not significantly different for either type of machine. The added flexibility and the lower maintenance of the ac machine system make it the more attractive approach

  15. All-atom molecular dynamics simulations of spin labelled double and single-strand DNA for EPR studies.

    Science.gov (United States)

    Prior, C; Danilāne, L; Oganesyan, V S

    2018-05-16

    We report the first application of fully atomistic molecular dynamics (MD) simulations to the prediction of electron paramagnetic resonance (EPR) spectra of spin labelled DNA. Models for two structurally different DNA spin probes with either the rigid or flexible position of the nitroxide group in the base pair, employed in experimental studies previously, have been developed. By the application of the combined MD-EPR simulation methodology we aimed at the following. Firstly, to provide a test bed against a sensitive spectroscopic technique for the recently developed improved version of the parmbsc1 force field for MD modelling of DNA. The predicted EPR spectra show good agreement with the experimental ones available from the literature, thus confirming the accuracy of the currently employed DNA force fields. Secondly, to provide a quantitative interpretation of the motional contributions into the dynamics of spin probes in both duplex and single-strand DNA fragments and to analyse their perturbing effects on the local DNA structure. Finally, a combination of MD and EPR allowed us to test the validity of the application of the Model-Free (M-F) approach coupled with the partial averaging of magnetic tensors to the simulation of EPR spectra of DNA systems by comparing the resultant EPR spectra with those simulated directly from MD trajectories. The advantage of the M-F based EPR simulation approach over the direct propagation techniques is that it requires motional and order parameters that can be calculated from shorter MD trajectories. The reported MD-EPR methodology is transferable to the prediction and interpretation of EPR spectra of higher order DNA structures with novel types of spin labels.

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

    Science.gov (United States)

    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. Radiation-induced electron paramagnetic resonance signal and soybean isoflavones content

    International Nuclear Information System (INIS)

    Oliveira, Marcos R.R. de; Mandarino, José M.G.; Mastro, Nelida L. del

    2012-01-01

    Electron Paramagnetic Resonance (EPR) is a well-known spectroscopic technique that detects paramagnetic centers and can detect free radicals with high sensitivity. In food, free radicals can be generated by several commonly used industrial processes, such as radiosterilization or heat treatment. EPR spectroscopy is used to detect radioinduced free radicals in food. In this work the relation between EPR signal induced by gamma irradiation treatment and soybean isoflavones content was investigated. Present results did not show correlation between total isoflavones content and the EPR signal. Nevertheless, some isoflavone contents had a negative correlation with the radiation-induced EPR signal. - Highlights: ► Electron Paramagnetic Resonance (EPR) detects free radicals. ► Ionizing radiation as free radicals inducer. ► Total soybean isoflvones do not correlate with radiation-induced EPR intensity but a soybean glucosyl glucoside isoflavone does.

  18. Radiation sensitivity and EPR dosimetric potential of gallic acid and its esters

    Science.gov (United States)

    Tuner, Hasan; Oktay Bal, M.; Polat, Mustafa

    2015-02-01

    In the preset work the radiation sensitivities of Gallic Acid anhydrous and monohydrate, Octyl, Lauryl, and Ethyl Gallate (GA, GAm, OG, LG, and EG) were investigated in the intermediate (0.5-20 kGy) and low radiation (<10 Gy) dose range using Electron Paramagnetic Resonance (EPR) spectroscopy. While OG, LG, and EG are presented a singlet EPR spectra, their radiation sensitivity found to be very different in the intermediate dose range. At low radiation dose range (<10 Gy) only LG is found to be present a signal that easily distinguished from the noise signals. The intermediate and low dose range radiation sensitivities are compared using well known EPR dosimeter alanine. The radiation yields (G) of the interested material were found to be 1.34×10-2, 1.48×10-2, 4.14×10-2, and 6.03×10-2, 9.44×10-2 for EG, GA, GAm, OG, and LG, respectively at the intermediate dose range. It is found that the simple EPR spectra and the noticeable EPR signal of LG make it a promising dosimetric material to be used below 10 Gy of radiation dose.

  19. Ion Channel Conformation and Oligomerization Assessment by Site-Directed Spin Labeling and Pulsed-EPR.

    Science.gov (United States)

    Pliotas, Christos

    2017-01-01

    Mechanosensitive (MS) ion channels are multimeric integral membrane proteins that respond to increased lipid bilayer tension by opening their nonselective pores to release solutes and relieve increased cytoplasmic pressure. These systems undergo major conformational changes during gating and the elucidation of their mechanism requires a deep understanding of the interplay between lipids and proteins. Lipids are responsible for transmitting lateral tension to MS channels and therefore play a key role in obtaining a molecular-detail model for mechanosensation. Site-directed spin labeling combined with electron paramagnetic resonance (EPR) spectroscopy is a powerful spectroscopic tool in the study of proteins. The main bottleneck for its use relates to challenges associated with successful isolation of the protein of interest, introduction of paramagnetic labels on desired sites, and access to specialized instrumentation and expertise. The design of sophisticated experiments, which combine a variety of existing EPR methodologies to address a diversity of specific questions, require knowledge of the limitations and strengths, characteristic of each particular EPR method. This chapter is using the MS ion channels as paradigms and focuses on the application of different EPR techniques to ion channels, in order to investigate oligomerization, conformation, and the effect of lipids on their regulation. The methodology we followed, from the initial strategic selection of mutants and sample preparation, including protein purification, spin labeling, reconstitution into lipid mimics to the complete set-up of the pulsed-EPR experiments, is described in detail. © 2017 Elsevier Inc. All rights reserved.

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

    Science.gov (United States)

    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. Copyright © 2014 Elsevier Inc. All rights reserved.

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

    Science.gov (United States)

    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. © 2015 Elsevier Inc. All rights reserved.

  2. Physically-based biodosimetry using in vivo EPR of teeth in patients undergoing total body irradiation

    Science.gov (United States)

    Williams, Benjamin B.; Dong, Ruhong; Nicolalde, Roberto J.; Matthews, Thomas P.; Gladstone, David J.; Demidenko, Eugene; Zaki, Bassem I.; Salikhov, Ildar K.; Lesniewski, Piotr N.; Swartz, Harold M.

    2014-01-01

    Purpose The ability to estimate individual exposures to radiation following a large attack or incident has been identified as a necessity for rational and effective emergency medical response. In vivo electron paramagnetic resonance (EPR) spectroscopy of tooth enamel has been developed to meet this need. Materials and methods A novel transportable EPR spectrometer, developed to facilitate tooth dosimetry in an emergency response setting, was used to measure upper incisors in a model system, in unirradiated subjects, and in patients who had received total body doses of 2 Gy. Results A linear dose response was observed in the model system. A statistically significant increase in the intensity of the radiation-induced EPR signal was observed in irradiated versus unirradiated subjects, with an estimated standard error of dose prediction of 0.9 + 0.3 Gy. Conclusions These results demonstrate the current ability of in vivo EPR tooth dosimetry to distinguish between subjects who have not been irradiated and those who have received exposures that place them at risk for acute radiation syndrome. Procedural and technical developments to further increase the precision of dose estimation and ensure reliable operation in the emergency setting are underway. With these developments EPR tooth dosimetry is likely to be a valuable resource for triage following potential radiation exposure of a large population. PMID:21696339

  3. The Third International Intercomparison on EPR Tooth Dosimetry: Part 2, final analysis

    International Nuclear Information System (INIS)

    Wieser, A.; Debuyst, R.; Fattibene, P.; Meghzifene, A.; Onori, S.; Bayankin, S. N.; Brik, A.; Bugay, A.; Chumak, V.; Ciesielski, B.; Hoshi, M.; Imata, H.; Ivannikov, A.; Ivanov, D.; Junczewska, M.; Miyazawa, C.; Penkowski, M.; Pivovarov, S.; Romanyukha, A.; Romanyukha, L.; Schauer, D.; Scherbina, O.; Schultka, K.; Sholom, S.; Skvortsov, V.; Stepanenko, V.; Thomas, J. A.; Tielewuhan, E.; Toyoda, S.; Trompier, F.

    2006-01-01

    The objective of the Third International Intercomparison on EPR Tooth Dosimetry was to evaluate laboratories performing tooth enamel dosimetry <300 mGy. Final analysis of results included a correlation analysis between features of laboratory dose reconstruction protocols and dosimetry performance. Applicability of electron paramagnetic resonance (EPR) tooth dosimetry at low dose was shown at two applied dose levels of 79 and 176 mGy. Most (9 of 12) laboratories reported the dose to be within 50 mGy of the delivered dose of 79 mGy, and 10 of 12 laboratories reported the dose to be within 100 mGy of the delivered dose of 176 mGy. At the high-dose tested (704 mGy) agreement within 25% of the delivered dose was found in 10 laboratories. Features of EPR dose reconstruction protocols that affect dosimetry performance were found to be magnetic field modulation amplitude in EPR spectrum recording, EPR signal model in spectrum deconvolution and duration of latency period for tooth enamel samples after preparation. (authors)

  4. Evaluation by EPR of potential antioxidant components of 60Co-irradiated varieties of soybean

    International Nuclear Information System (INIS)

    Oliveira, Marcos Ronaldo Ramos de

    2009-01-01

    Brazil is today the second main producer of soybean in the world with a planted ground of about 21 million hectares and an annual production of 60 million tons in 2008, being slight more than a fourth of the annual production. The presence of flavonoids, particularly isoflavones in soybean products has been related as important for human health. It has been suggested that flavonoids play a role in the protection of plants by screening vital cellular components from damaging UV radiation. Electron paramagnetic resonance (EPR) spectroscopy can measure free radicals produced by dissociation molecules resulting from irradiation. It has been successfully employed for the detection of some irradiated food products. Twenty one Brazilian soybean cultivars from two crops were gamma-irradiated with a 60 Co source and evaluated by EPR. Correlation coefficients were made among the central EPR signal (g = 2.0039) and the total and partial isoflavones contents. There was no correlation with total contents, though glicitein and acetyl-daidzin showed a negative correlation. Even 7 months after irradiation the intensity of central EPR signal were high enough to distinguish the irradiated samples. EPR measurements of separated parts of the grain were more efficient for that purpose, particularly from hilum and coat. The radiation did not change substantially the total isoflavone contents, although there were some evidences suggesting some conversion of glycosides to aglycones. (author)

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

    Directory of Open Access Journals (Sweden)

    Guo Junwang

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

  6. Investigating Pigment Radicals in Black Rice Using HPLC and Multi-EPR.

    Science.gov (United States)

    Nakagawa, Kouichi; Maeda, Hayato

    2017-01-01

    We investigated the location and distribution of paramagnetic species in black and white rice using electron paramagnetic resonance (EPR), X-band (9 GHz) EPR imaging (EPRI), and HPLC. EPR primarily detected two paramagnetic species in black rice, which were identified as a stable radical and Mn 2+ species, based on the g values and hyperfine components of the EPR signals. The signal from the stable radical appeared at g ≈ 2.00 and was relatively strong and stable. Subsequent noninvasive two-dimensional (2D) EPRI revealed that this stable radical was primarily located in the pigmented region of black rice, while very few radicals were observed in the rice interior. Pigments extracted from black rice were analyzed using HPLC; the major compound was found to be cyanidin-3-glucoside. EPR and HPLC results indicate that the stable radical was only found within the pigmented region of the rice, and that it could either be cyanidin-3-glucoside, or one of its oxidative decomposition products.

  7. Nano-emulsions of fluorinated trityl radicals as sensors for EPR oximetry

    Science.gov (United States)

    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.

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

    Directory of Open Access Journals (Sweden)

    Ane B Tomter

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

  9. Using rapid scan EPR to improve the detection limit of quantitative EPR by more than one order of magnitude

    OpenAIRE

    Möser, J.; Lips, K.; Tseytlin, M.; Eaton, G.; Eaton, S.; Schnegg, A

    2017-01-01

    X band rapid scan EPR was implemented on a commercially available Bruker ELEXSYS E580 spectrometer. Room temperature rapid scan and continuous wave EPR spectra were recorded for amorphous silicon powder samples. By comparing the resulting signal intensities the feasibility of performing quantitative rapid scan EPR is demonstrated. For different hydrogenated amorphous silicon samples, rapid scan EPR results in signal to noise improvements by factors between 10 and 50. Rapid scan EPR is thus ca...

  10. New loophole for the EPR paradox

    OpenAIRE

    Feldmann, Michel

    1999-01-01

    We exhibit a classical model free from any paradox which exactly simulates the spin EPR test. We conclude that Bell's inequality violation is a strictly classical phenomenon, contrary to a general belief.

  11. Spin entanglement, decoherence and Bohm's EPR paradox

    OpenAIRE

    Cavalcanti, E. G.; Drummond, P. D.; Bachor, H. A.; Reid, M. D.

    2007-01-01

    We obtain criteria for entanglement and the EPR paradox for spin-entangled particles and analyse the effects of decoherence caused by absorption and state purity errors. For a two qubit photonic state, entanglement can occur for all transmission efficiencies. In this case, the state preparation purity must be above a threshold value. However, Bohm's spin EPR paradox can be achieved only above a critical level of loss. We calculate a required efficiency of 58%, which appears achievable with cu...

  12. Applications of EPR in radiation research

    CERN Document Server

    Lund, Anders

    2014-01-01

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

  13. EPR Spectroscopy in Environmental Lichen-Indication

    Science.gov (United States)

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

    2017-09-01

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

  14. EPR of alanine irradiated by neutrons

    International Nuclear Information System (INIS)

    Pivovarov, S.P.; Seredavina, T.A.; Zhdanov, S.V.; Mul'gin, S.I.; Zhakparov, R.K.

    2001-01-01

    In the work the first results of EPR studies of alanine, irradiated with diverse doses at neutron cyclotron generator different conditions and on the critical reactor stand are presented. A dose linearity dependence of EPR signal is observing, the methods of γ-background contribution separation are discussed. Obtain results is giving the basis to recommendation of alanine as an effective detector irradiation. However it is demanded the farther study on clarification of radiation sensitivity value dependence on the neutron energy spectrum form

  15. Some examples of utilization of electron paramagnetic resonance in biology

    International Nuclear Information System (INIS)

    Bemski, G.

    1982-10-01

    A short outline of the fundamentals of electron paramagnetic resonance (EPR) is presented and is followed by examples of the application of EPR to biology. These include use of spin labels, as well as of ENDOR principally to problems of heme proteins, photosynthesis and lipids. (Author) [pt

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

    Science.gov (United States)

    Fischer, Axel W.; Alexander, Nathan S.; Woetzel, Nils; Karakaş, Mert; Weiner, Brian E.; Meiler, Jens

    2016-01-01

    For many membrane proteins, the determination of their topology remains a challenge for methods like X-ray crystallography and nuclear magnetic resonance (NMR) spectroscopy. Electron paramagnetic resonance (EPR) spectroscopy has evolved as an alternative technique to study structure and dynamics of membrane proteins. The present study demonstrates the feasibility of membrane protein topology determination using limited EPR distance and accessibility measurements. The BCL::MP-Fold algorithm assembles secondary structure elements (SSEs) in the membrane using a Monte Carlo Metropolis (MCM) approach. Sampled models are evaluated using knowledge-based potential functions and agreement with the EPR data and a knowledge-based energy function. Twenty-nine membrane proteins of up to 696 residues are used to test the algorithm. The protein-size-normalized root-mean-square-deviation (RMSD100) value of the most accurate model is better than 8 Å for twenty-seven, better than 6 Å for twenty-two, and better than 4 Å for fifteen out of twenty-nine proteins, demonstrating the algorithm’s ability to sample the native topology. The average enrichment could be improved from 1.3 to 2.5, showing the improved discrimination power by using EPR data. PMID:25820805

  17. EPR spectroscopy as a potential approach to identify irradiated food and radiation dosimetry - an overview

    International Nuclear Information System (INIS)

    Sanyal, Bhaskar; Chawla, S.P.

    2017-01-01

    The need for reliable and routine tests to determine whether or not food has been irradiated has arisen as a result of the progress made in commercialization of the food irradiation technology. The effectiveness of food irradiation depends on proper delivery of absorbed dose and its reliable measurement. Electron Paramagnetic Resonance (EPR) spectroscopy has been established as an essential tool both for detection of irradiated food and radiation measurements. This presentation demonstrates the behavior of the radicals produced in irradiated cashew nut and orange. In addition the role of EPR spectroscopy will be discussed to understand thermoluminescence behavior of CaSO 4 dosimeter. Cashew nut and orange samples were exposed to gamma radiation in the dose range of 0.25 to 2 kGy. CaSO 4 crystals were irradiated at 0.5-7 kGy. Electron Paramagnetic Resonance (EPR) spectroscopy was carried out using EMX model EPR spectrometer (BRUKER, Germany) with a microwave frequency of 9.42 GHz

  18. Blood oxygen level dependent magnetic resonance imaging for detecting pathological patterns in lupus nephritis patients: a preliminary study using a decision tree model.

    Science.gov (United States)

    Shi, Huilan; Jia, Junya; Li, Dong; Wei, Li; Shang, Wenya; Zheng, Zhenfeng

    2018-02-09

    Precise renal histopathological diagnosis will guide therapy strategy in patients with lupus nephritis. Blood oxygen level dependent (BOLD) magnetic resonance imaging (MRI) has been applicable noninvasive technique in renal disease. This current study was performed to explore whether BOLD MRI could contribute to diagnose renal pathological pattern. Adult patients with lupus nephritis renal pathological diagnosis were recruited for this study. Renal biopsy tissues were assessed based on the lupus nephritis ISN/RPS 2003 classification. The Blood oxygen level dependent magnetic resonance imaging (BOLD-MRI) was used to obtain functional magnetic resonance parameter, R2* values. Several functions of R2* values were calculated and used to construct algorithmic models for renal pathological patterns. In addition, the algorithmic models were compared as to their diagnostic capability. Both Histopathology and BOLD MRI were used to examine a total of twelve patients. Renal pathological patterns included five classes III (including 3 as class III + V) and seven classes IV (including 4 as class IV + V). Three algorithmic models, including decision tree, line discriminant, and logistic regression, were constructed to distinguish the renal pathological pattern of class III and class IV. The sensitivity of the decision tree model was better than that of the line discriminant model (71.87% vs 59.48%, P decision tree model was equivalent to that of the line discriminant model (63.87% vs 63.73%, P = 0.939) and higher than that of the logistic regression model (63.87% vs 38.0%, P decision tree model was greater than that of the line discriminant model (0.765 vs 0.629, P Decision tree models constructed using functions of R2* values may facilitate the prediction of renal pathological patterns.

  19. EPR dosimetry of radiation background in the Urals region

    Energy Technology Data Exchange (ETDEWEB)

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

    2006-07-01

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

  20. EPR dosimetry of radiation background in the Urals region

    International Nuclear Information System (INIS)

    Shishkina, E.A.; Degteva, M.O.; Shved, V.A.; Fattibene, P.; Onori, S.; Wieser, A.; Ivanov, D.V.; Bayankin, S.N.; Knyazev, V.A.; Vasilenko, E.I.; Gorelov, M.

    2006-01-01

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

  1. Non-invasive determination of the irradiation dose in fingers using low-frequency EPR

    International Nuclear Information System (INIS)

    Zdravkova, M; Crokart, N; Trompier, F; Beghein, N; Gallez, B; Debuyst, R

    2004-01-01

    Several reports in the literature have described the effects of radiation in workers who exposed their fingers to intense radioactive sources. The radiation injuries occurring after local exposure to a high dose (20 to 100 Gy) could lead to the need for amputation. Follow-up of victims needs to be more rational with a precise knowledge of the irradiated area that risks tissue degradation and necrosis. It has been described previously that X-band electron paramagnetic resonance (EPR) spectroscopy could be used to assess the dose in irradiated amputated fingers. Here, we propose the use of low-frequency EPR spectroscopy to evaluate non-invasively the absorbed dose. Low-frequency microwaves are indeed less absorbed by water and penetrate more deeply into living material (∼10 mm in tissues using 1 GHz spectrometers). This work presents preliminary results obtained with baboon and human fingers compared with human dry phalanxes placed inside a surface-coil resonator. The EPR signal increased linearly with the dose. The ratio of the slopes of the dry bone to whole finger linear regression lines was around 5. The detection limit achievable with the present spectrometer and resonator is around 60 Gy, which is well within the range of accidentally exposed fingers. It is likely that the detection limit could be improved in the future, thanks to further technical spectrometer and resonator developments as well as to appropriate spectrum deconvolution into native and dosimetric signals

  2. Gold nanoring-enhanced generation of singlet oxygen: an intricate correlation with surface plasmon resonance and polyelectrolyte bilayers

    Czech Academy of Sciences Publication Activity Database

    Hu, Y.; Kaňka, Jiří; Liu, K.; Yang, Y.; Wang, H.; Du, H.

    2016-01-01

    Roč. 6, č. 106 (2016), s. 104819-104826 ISSN 2046-2069 R&D Projects: GA ČR(CZ) GBP205/12/G118 Institutional support: RVO:67985882 Keywords : Singlet oxygen * Fluorescence * Gold nanorings Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 3.108, year: 2016

  3. New strategy to identify radicals in a time evolving EPR data set by multivariate curve resolution-alternating least squares

    Energy Technology Data Exchange (ETDEWEB)

    Fadel, Maya Abou [LASIR CNRS UMR 8516, Université Lille 1, Sciences et Technologies, 59655 Villeneuve d' Ascq Cedex (France); Juan, Anna de [Chemometrics Group, Section of Analytical Chemistry, Universitat de Barcelona, Diagonal 645, 08028 Barcelona (Spain); Vezin, Hervé [LASIR CNRS UMR 8516, Université Lille 1, Sciences et Technologies, 59655 Villeneuve d' Ascq Cedex (France); Duponchel, Ludovic, E-mail: ludovic.duponchel@univ-lille1.fr [LASIR CNRS UMR 8516, Université Lille 1, Sciences et Technologies, 59655 Villeneuve d' Ascq Cedex (France)

    2016-12-01

    Electron paramagnetic resonance (EPR) spectroscopy is a powerful technique that is able to characterize radicals formed in kinetic reactions. However, spectral characterization of individual chemical species is often limited or even unmanageable due to the severe kinetic and spectral overlap among species in kinetic processes. Therefore, we applied, for the first time, multivariate curve resolution-alternating least squares (MCR-ALS) method to EPR time evolving data sets to model and characterize the different constituents in a kinetic reaction. Here we demonstrate the advantage of multivariate analysis in the investigation of radicals formed along the kinetic process of hydroxycoumarin in alkaline medium. Multiset analysis of several EPR-monitored kinetic experiments performed in different conditions revealed the individual paramagnetic centres as well as their kinetic profiles. The results obtained by MCR-ALS method demonstrate its prominent potential in analysis of EPR time evolved spectra. - Highlights: • A new strategy to identify radicals in a time evolving EPR data set. • Extraction of pure EPR spectral signatures and corresponding kinetic profiles. • The proposed method does not require any prior knowledge of the chemical system. • A multiset analysis in order to decrease rotational ambiguity.

  4. Feasibility assessment of using oxygen-enhanced magnetic resonance imaging for evaluating the effect of pharmacological treatment in COPD

    Energy Technology Data Exchange (ETDEWEB)

    Morgan, Alexandra R., E-mail: alex.morgan@bioxydyn.com [Bioxydyn Ltd, Manchester (United Kingdom); Centre for Imaging Sciences and Biomedical Imaging Institute, Manchester Academic Health Sciences Centre, University of Manchester, Manchester (United Kingdom); Parker, Geoff J.M.; Roberts, Caleb [Bioxydyn Ltd, Manchester (United Kingdom); Centre for Imaging Sciences and Biomedical Imaging Institute, Manchester Academic Health Sciences Centre, University of Manchester, Manchester (United Kingdom); Buonaccorsi, Giovanni A.; Maguire, Niall C. [Bioxydyn Ltd, Manchester (United Kingdom); Hubbard Cristinacce, Penny L. [Centre for Imaging Sciences and Biomedical Imaging Institute, Manchester Academic Health Sciences Centre, University of Manchester, Manchester (United Kingdom); Singh, Dave; Vestbo, Jørgen [University of Manchester, Medicines Evaluation Unit, Manchester Academic Health Sciences Centre, University Hospital of South Manchester, Manchester (United Kingdom); Bjermer, Leif [Department of Respiratory Medicine and Allergology, Skåne University Hospital, Lund (Sweden); Jögi, Jonas [Department of Clinical Physiology, Skåne University Hospital and Lund University, Lund (Sweden); Taib, Ziad; Sarv, Janeli; Bruijnzeel, Piet L.B.; Olsson, Lars E.; Bondesson, Eva [AstraZeneca R and D, Mölndal (Sweden); Nihlén, Ulf [Department of Respiratory Medicine and Allergology, Skåne University Hospital, Lund (Sweden); AstraZeneca R and D, Mölndal (Sweden); McGrath, Deirdre M. [Centre for Imaging Sciences and Biomedical Imaging Institute, Manchester Academic Health Sciences Centre, University of Manchester, Manchester (United Kingdom); Young, Simon S. [AstraZeneca R and D, Alderley Park (United Kingdom); and others

    2014-11-15

    Highlights: • We investigate physiologic response to standard COPD treatment regimes using OE-MRI. • We assess the potential role of OE-MRI in future drug development studies. • In COPD, OE-MRI parameters showed response to single-dose formoterol. • OE-MRI parameters showed response to 8-week formoterol/budesonide treatment. • OE-MRI measurements are feasible in a small-scale multi-center trial setting. - Abstract: Objectives: Oxygen-enhanced MRI (OE-MRI) biomarkers have potential value in assessment of COPD, but need further evaluation before treatment-induced changes can be interpreted. The objective was to evaluate how OE-MRI parameters of regional ventilation and oxygen uptake respond to standard pharmacological interventions in COPD, and how the response compares to that of gold standard pulmonary function tests. Materials and methods: COPD patients (n = 40), mean FEV{sub 1} 58% predicted normal, received single-dose inhaled formoterol 9 μg, or placebo, followed by 8 weeks treatment bid with a combination of budesonide and formoterol Turbuhaler{sup ®} 320/9 μg or formoterol Turbuhaler{sup ®}. OE-MRI biomarkers were obtained, as well as X-ray computed tomography (CT) biomarkers and pulmonary function tests, in a two-center study. An ANCOVA statistical model was used to assess effect size of intervention measurable in OE-MRI parameters of lung function. Results: OE-MRI data were successfully acquired at both study sites. 8-week treatment with budesonide/formoterol significantly decreased lung wash-out time by 31% (p < 0.01), decreased the change in lung oxygen level upon breathing pure oxygen by 13% (p < 0.05) and increased oxygen extraction from the lung by 58% (p < 0.01). Single-dose formoterol increased both lung wash-out time (+47%, p < 0.05) and lung oxygenation time (+47%, p < 0.05). FEV{sub 1} was improved by single-dose formoterol (+12%, p < 0.001) and 8 weeks of budesonide/formoterol (+ 18%, p < 0.001), consistent with published studies

  5. Feasibility assessment of using oxygen-enhanced magnetic resonance imaging for evaluating the effect of pharmacological treatment in COPD

    International Nuclear Information System (INIS)

    Morgan, Alexandra R.; Parker, Geoff J.M.; Roberts, Caleb; Buonaccorsi, Giovanni A.; Maguire, Niall C.; Hubbard Cristinacce, Penny L.; Singh, Dave; Vestbo, Jørgen; Bjermer, Leif; Jögi, Jonas; Taib, Ziad; Sarv, Janeli; Bruijnzeel, Piet L.B.; Olsson, Lars E.; Bondesson, Eva; Nihlén, Ulf; McGrath, Deirdre M.; Young, Simon S.

    2014-01-01

    Highlights: • We investigate physiologic response to standard COPD treatment regimes using OE-MRI. • We assess the potential role of OE-MRI in future drug development studies. • In COPD, OE-MRI parameters showed response to single-dose formoterol. • OE-MRI parameters showed response to 8-week formoterol/budesonide treatment. • OE-MRI measurements are feasible in a small-scale multi-center trial setting. - Abstract: Objectives: Oxygen-enhanced MRI (OE-MRI) biomarkers have potential value in assessment of COPD, but need further evaluation before treatment-induced changes can be interpreted. The objective was to evaluate how OE-MRI parameters of regional ventilation and oxygen uptake respond to standard pharmacological interventions in COPD, and how the response compares to that of gold standard pulmonary function tests. Materials and methods: COPD patients (n = 40), mean FEV 1 58% predicted normal, received single-dose inhaled formoterol 9 μg, or placebo, followed by 8 weeks treatment bid with a combination of budesonide and formoterol Turbuhaler ® 320/9 μg or formoterol Turbuhaler ® . OE-MRI biomarkers were obtained, as well as X-ray computed tomography (CT) biomarkers and pulmonary function tests, in a two-center study. An ANCOVA statistical model was used to assess effect size of intervention measurable in OE-MRI parameters of lung function. Results: OE-MRI data were successfully acquired at both study sites. 8-week treatment with budesonide/formoterol significantly decreased lung wash-out time by 31% (p < 0.01), decreased the change in lung oxygen level upon breathing pure oxygen by 13% (p < 0.05) and increased oxygen extraction from the lung by 58% (p < 0.01). Single-dose formoterol increased both lung wash-out time (+47%, p < 0.05) and lung oxygenation time (+47%, p < 0.05). FEV 1 was improved by single-dose formoterol (+12%, p < 0.001) and 8 weeks of budesonide/formoterol (+ 18%, p < 0.001), consistent with published studies. Conclusions: In COPD

  6. Detection of Redox Imbalance in Normal Lymphocytes with Induced Mitochondrial Dysfunction - EPR Study.

    Science.gov (United States)

    Georgieva, Ekaterina; Zhelev, Zhivko; Aoki, Ichio; Bakalova, Rumiana; Higashi, Tatsuya

    2016-10-01

    The present study describes a new approach for direct imaging of redox status in live cells using paramagnetic spin-probes, which allows evaluation of the level of oxidative stress due to overproduction of superoxide. The method is based on redox cycling of cell/mitochondria-penetrating nitroxide radicals (e.g. mito-TEMPO) and their electron-paramagnetic resonance (EPR) contrast, which makes them useful molecular sensors for analysis of redox status and oxidative stress in cells and tissues. Oxidative stress was induced in normal human lymphocytes by treatment with 2-methoxyestradiol and rotenone (ME/Rot) at different concentrations. This combination provokes mitochondrial dysfunction, which is accompanied by overproduction of superoxide. The EPR measurements were performed in dynamics on X-Band spectrometer after addition of mito-TEMPO to cell suspensions. The intensity of the EPR signal in untreated cells decreased significantly, which indicates a conversion of paramagnetic mito-TEMPO to its non-contrast diamagnetic form (hydroxylamine - mito-TEMPOH) due to reduction. In ME/Rot-treated cells, the signal decreased more slowly and to a lower level with increasing the concentration of ME/Rot. These data indicate an induction of oxidative stress in the cells in a concentration-dependent manner. A very good positive correlation between the intensity of EPR signal of mito-TEMPO and the intracellular level of superoxide was found, analyzed by conventional dihydroethidium test (R=0.9143, pEPR imaging of the superoxide level in live cells, as well as for EPR imaging of mitochondrial dysfunction and metabolic activity, accompanied by superoxide imbalance. Copyright© 2016 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.

  7. EPR and optical absorption studies of Cr3+ ions in potassium sodium dl-tartrate tetrahydrate

    International Nuclear Information System (INIS)

    Kripal, Ram; Singh, Pragya; Shukla, Santwana

    2011-01-01

    EPR spectra of Cr 3+ ions doped in potassium sodium dl-tartrate tetrahydrate single crystals are recorded at 77 K. The spin Hamiltonian and zero field parameters g, |D| and |E| are measured from the resonance lines obtained at various rotations of the magnetic field. The values obtained are: g x =1.9257±0.0002, g y =1.9720±0.0002, g z =2.0102±0.0002, |D|=313±2 (x10 -4 ) cm -1 and |E|=101±2 (x10 -4 ) cm -1 . From the results of EPR study, the site symmetry of Cr 3+ ion in the crystal is discussed. The optical absorption at room temperature is also studied. From the observed band positions, the crystal field splitting parameter (D q ) and the Racah inter-electronic repulsion parameters (B and C) are evaluated. The bonding parameters are obtained by correlating optical and EPR data and the nature of bonding in the crystal is discussed. -- Research Highlights: → EPR spectra of Cr 3+ ions doped in potassium sodium dl-tartrate tetrahydrate single crystals are done at 77 K. → The spin Hamiltonian and zero field parameters g, |D| and |E| are measured. From the results of EPR study, the site symmetry of Cr 3+ ion in the crystal is discussed. → The optical absorption at room temperature is also studied and the crystal field splitting parameter (D q ) as well as the Racah inter-electronic repulsion parameters (B and C) is evaluated. → The bonding parameters are obtained by correlating optical and EPR data and the nature of bonding in the crystal is discussed.

  8. EPR and optical study of Mn{sup 2+} doped monohydrated dipotassium stannic chloride

    Energy Technology Data Exchange (ETDEWEB)

    Kripal, Ram, E-mail: ram_kripal2001@rediffmail.com; Singh, Manju

    2014-11-15

    Highlights: • EPR study of Mn{sup 2+}: DPSC crystal is done at room temperature. • The spin Hamiltonian parameters for two Mn{sup 2+} sites are determined. • The optical absorption study is also done. • The nature of metal–ligand bonding is discussed on the basis of EPR and optical data. • Theoretical zero-field splitting parameters match well with the experimental values. - Abstract: Electron paramagnetic resonance (EPR) study at room temperature (RT) is used to investigate the property of Mn{sup 2+} doped monohydrated dipotassium stannic chloride (K{sub 2}SnCl{sub 4}⋅H{sub 2}O) single crystal. EPR spectra show that there exist two substitutional sites, the spin Hamiltonian parameters for which are determined. The optical absorption study is also done at room temperature in the wavelength range 195–1100 nm. The observed bands are assigned as transitions from {sup 6}A{sub 1g}(S) ground state to various excited states. These bands are fitted with four parameters, namely Racah inter-electronic repulsion parameters B = 792 cm{sup −1}, C = 2278 cm{sup −1}; cubic crystal field splitting parameter Dq = 700 cm{sup −1} and Trees correction α = 76 cm{sup −1}. The nature of metal–ligand bonding is discussed on the basis of EPR and optical data. Superposition model (SPM) is used to find out the crystal field (CF) parameters and the perturbation formulae are used to obtain zero-field splitting (ZFS) parameters. Theoretically calculated ZFS parameters match well with the experimental values obtained from EPR study.

  9. In vivo intracellular oxygen dynamics in murine brain glioma and immunotherapeutic response of cytotoxic T cells observed by fluorine-19 magnetic resonance imaging.

    Directory of Open Access Journals (Sweden)

    Jia Zhong

    Full Text Available Noninvasive biomarkers of anti-tumoral efficacy are of great importance to the development of therapeutic agents. Tumor oxygenation has been shown to be an important indicator of therapeutic response. We report the use of intracellular labeling of tumor cells with perfluorocarbon (PFC molecules, combined with quantitative ¹⁹F spin-lattice relaxation rate (R₁ measurements, to assay tumor cell oxygen dynamics in situ. In a murine central nervous system (CNS GL261 glioma model, we visualized the impact of Pmel-1 cytotoxic T cell immunotherapy, delivered intravenously, on intracellular tumor oxygen levels. GL261 glioma cells were labeled ex vivo with PFC and inoculated into the mouse striatum. The R₁ of ¹⁹F labeled cells was measured using localized single-voxel magnetic resonance spectroscopy, and the absolute intracellular partial pressure of oxygen (pO₂ was ascertained. Three days after tumor implantation, mice were treated with 2×10⁷ cytotoxic T cells intravenously. At day five, a transient spike in pO₂ was observed indicating an influx of T cells into the CNS and putative tumor cell apoptosis. Immunohistochemistry and quantitative flow cytometry analysis confirmed that the pO₂ was causally related to the T cells infiltration. Surprisingly, the pO₂ spike was detected even though few (∼4×10⁴ T cells actually ingress into the CNS and with minimal tumor shrinkage. These results indicate the high sensitivity of this approach and its utility as a non-invasive surrogate biomarker of anti-cancer immunotherapeutic response in preclinical models.

  10. A novel microfluidic rapid freeze-quench device for trapping reactions intermediates for high field EPR analysis.

    Science.gov (United States)

    Kaufmann, Royi; Yadid, Itamar; Goldfarb, Daniella

    2013-05-01

    Rapid freeze quench electron paramagnetic resonance (RFQ)-EPR is a method for trapping short lived intermediates in chemical reactions and subjecting them to EPR spectroscopy investigation for their characterization. Two (or more) reacting components are mixed at room temperature and after some delay the mixture is sprayed into a cold trap and transferred into the EPR tube. A major caveat in using commercial RFQ-EPR for high field EPR applications is the relatively large amount of sample needed for each time point, a major part of which is wasted as the dead volume of the instrument. The small sample volume (∼2μl) needed for high field EPR spectrometers, such as W-band (∼3.5T, 95GHz), that use cavities calls for the development of a microfluidic based RFQ-EPR apparatus. This is particularly important for biological applications because of the difficulties often encountered in producing large amounts of intrinsically paramagnetic proteins and spin labeled nucleic acid and proteins. Here we describe a dedicated microfluidic based RFQ-EPR apparatus suitable for small volume samples in the range of a few μl. The device is based on a previously published microfluidic mixer and features a new ejection mechanism and a novel cold trap that allows collection of a series of different time points in one continuous experiment. The reduction of a nitroxide radical with dithionite, employing the signal of Mn(2+) as an internal standard was used to demonstrate the performance of the microfluidic RFQ apparatus. Copyright © 2013 Elsevier Inc. All rights reserved.

  11. RosettaTMH: a method for membrane protein structure elucidation combining EPR distance restraints with assembly of transmembrane helices

    Directory of Open Access Journals (Sweden)

    Andrew Leaver-Fay

    2015-12-01

    Full Text Available Membrane proteins make up approximately one third of all proteins, and they play key roles in a plethora of physiological processes. However, membrane proteins make up less than 2% of experimentally determined structures, despite significant advances in structure determination methods, such as X-ray crystallography, nuclear magnetic resonance spectroscopy, and cryo-electron microscopy. One potential alternative means of structure elucidation is to combine computational methods with experimental EPR data. In 2011, Hirst and others introduced RosettaEPR and demonstrated that this approach could be successfully applied to fold soluble proteins. Furthermore, few computational methods for de novo folding of integral membrane proteins have been presented. In this work, we present RosettaTMH, a novel algorithm for structure prediction of helical membrane proteins. A benchmark set of 34 proteins, in which the proteins ranged in size from 91 to 565 residues, was used to compare RosettaTMH to Rosetta’s two existing membrane protein folding protocols: the published RosettaMembrane folding protocol (“MembraneAbinitio” and folding from an extended chain (“ExtendedChain”. When EPR distance restraints are used, RosettaTMH+EPR outperforms ExtendedChain+EPR for 11 proteins, including the largest six proteins tested. RosettaTMH+EPR is capable of achieving native-like folds for 30 of 34 proteins tested, including receptors and transporters. For example, the average RMSD100SSE relative to the crystal structure for rhodopsin was 6.1 ± 0.4 Å and 6.5 ± 0.6 Å for the 449-residue nitric oxide reductase subunit B, where the standard deviation reflects variance in RMSD100SSE values across ten different EPR distance restraint sets. The addition of RosettaTMH and RosettaTMH+EPR to the Rosetta family of de novo folding methods broadens the scope of helical membrane proteins that can be accurately modeled with this software suite.

  12. New Developments in Spin Labels for Pulsed Dipolar EPR

    Directory of Open Access Journals (Sweden)

    Alistair J. Fielding

    2014-10-01

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

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

    International Nuclear Information System (INIS)

    Groth, N.; Anders, B.; Nitschke, S.; Schlawe, R.; Herrling, T.

    1993-01-01

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

  14. Potential use of wallboard (drywall) for EPR retrospective dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, Jeroen W. [Department of Medical Physics and Applied Radiation Sciences, McMaster University, 1280 Main St. West, Hamilton ON L8S 4K1 (Canada)], E-mail: thompjw@mcmaster.ca; Atiya, Ibrahim Abu [Department of Medical Physics and Applied Radiation Sciences, McMaster University, 1280 Main St. West, Hamilton ON L8S 4K1 (Canada)], E-mail: abuatii@mcmaster.ca; Rink, W. Jack [School of Geography and Earth Sciences, McMaster University, 1280 Main St. West, Hamilton ON L8S 4K1 (Canada)], E-mail: rinkwj@mcmaster.ca; Boreham, Doug [Department of Medical Physics and Applied Radiation Sciences, McMaster University, 1280 Main St. West, Hamilton ON L8S 4K1 (Canada)], E-mail: boreham@mcmaster.ca

    2009-03-15

    Concern regarding the possibility of criminal or terrorist use of nuclear materials has led to an interest in developing the capability to measure radiation dose in a variety of natural and manufactured materials. Electron paramagnetic resonance (EPR) measurements of radiation dose following a radiological incident may aid in screening affected populations (triage) and in reconstruction of doses following accidents. One such EPR dosimeter is wallboard (drywall), a common construction material composed largely of gypsum (calcium sulphate dihydrate). We have identified the CO{sub 3}{sup -} and SO{sub 3}{sup -} dose-sensitive lines in drywall and developed a measurement protocol using the intensity of CO{sub 3}{sup -} line. Proper background subtraction is a major difficulty, and we demonstrate a procedure based on alignment of a contaminant Mn{sup 2+} line. As a proof-of-concept, a wallboard panel was irradiated with a {sup 60}Co source, and a two-dimensional map of the absorbed dose was measured. While most aliquots yielded reasonably accurate doses, a spatially contiguous region of apparent dose-insensitivity in one panel was identified.

  15. Study of the EPR and Moessbauer spectra of iron phosphites

    International Nuclear Information System (INIS)

    Ebert, M.; Kavan, L.

    1978-01-01

    The EPR and Moessbauer spectra of polycrystalline samples of ferrous phosphites FeHPO 3 .3H 2 O, FeH 2 P 2 O 5 , FeH 4 P 2 O 6 .1/2H 2 O, FeH 10 P 4 O 12 .4H 2 O and ferric phosphites Fe 2 (HPO 3 ) 3 .9h 2 O, FeH 3 P 2 O 6 .3H 2 O and Fe 4 H 33 P 15 O 45 .6H 2 O were studied. The hydrogen bonds present in hydrogen phosphite anions (polyorthophosphites) produce a decrease in the electron density on the oxygen atom in the anion and thus also a decrease in the crystal field strength with an increasing P/Fe ratio. These changes are reflected not only in the Dq values but also in the g-factors, Moessbauer isomeric shifts and quadropole splitting values. The Moessbauer spectra were measured at laboratory temperature with a Co-57/Pd source (the time for measuring one sample was about 24 hrs) and evaluated on a Hewlett-Packard computer. The EPR spectra of the polycristalline samples were measured at laboratory temperature in the 3 cm region. (T.I.)

  16. Nanodiamond graphitization: a magnetic resonance study

    International Nuclear Information System (INIS)

    Panich, A M; Shames, A I; Sergeev, N A; Olszewski, M; McDonough, J K; Mochalin, V N; Gogotsi, Y

    2013-01-01

    We report on the first nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) study of the high-temperature nanodiamond-to-onion transformation. 1 H, 13 C NMR and EPR spectra of the initial nanodiamond samples and those annealed at 600, 700, 800 and 1800 ° C were measured. For the samples annealed at 600 to 800 ° C, our NMR data reveal the early stages of the surface modification, as well as a progressive increase in sp 2 carbon content with increased annealing temperature. Such quantitative experimental data were recorded for the first time. These findings correlate with EPR data on the sensitivity of the dangling bond EPR line width to air content, progressing with rising annealing temperature, that evidences consequent graphitization of the external layers of the diamond core. The sample annealed at 1800 ° C shows complete conversion of nanodiamond particles into carbon onions. (paper)

  17. Thermal oxidation of 6H-SiC studied by oxygen isotopic tracing and narrow nuclear resonance profiling

    International Nuclear Information System (INIS)

    Trimaille, Isabelle.; Ganem, Jean-Jacques; Vickridge, Ian C.; Rigo, Serge; Battistig, Gabor; Szilagyi, Edit; Baumvol, Israel J.; Radtke, Claudio; Stedile, Fernanda C.

    2004-01-01

    We show that on SiC (0 0 0 1-bar) (the fast-oxidizing carbon face), at 1100 deg. C and 100 mbar, the oxide exhibits an initial fast growth regime, followed by a constant growth rate confirming previous results that oxide growth is not limited by diffusion of the oxidizing species or reaction products through the oxide. At 1100 deg. C, in this linear regime, the growth rate also exhibits a linear dependence with oxygen pressure. The silicon face shows sub-linear pressure dependence. A simple oxidation model is ruled out since, on both SiC faces, sequential 16 O 2 / 18 O 2 / 16 O 2 oxidations show that oxygen fixed in the oxide, near the SiC/SiO 2 interface moves during subsequent growth

  18. Thermal oxidation of 6H-SiC studied by oxygen isotopic tracing and narrow nuclear resonance profiling

    Energy Technology Data Exchange (ETDEWEB)

    Trimaille, Isabelle. E-mail: trimaille@gps.jussieu.fr; Ganem, Jean-Jacques; Vickridge, Ian C.; Rigo, Serge; Battistig, Gabor; Szilagyi, Edit; Baumvol, Israel J.; Radtke, Claudio; Stedile, Fernanda C

    2004-06-01

    We show that on SiC (0 0 0 1-bar) (the fast-oxidizing carbon face), at 1100 deg. C and 100 mbar, the oxide exhibits an initial fast growth regime, followed by a constant growth rate confirming previous results that oxide growth is not limited by diffusion of the oxidizing species or reaction products through the oxide. At 1100 deg. C, in this linear regime, the growth rate also exhibits a linear dependence with oxygen pressure. The silicon face shows sub-linear pressure dependence. A simple oxidation model is ruled out since, on both SiC faces, sequential {sup 16}O{sub 2}/{sup 18}O{sub 2}/{sup 16}O{sub 2} oxidations show that oxygen fixed in the oxide, near the SiC/SiO{sub 2} interface moves during subsequent growth.

  19. EPR, optical and superposition model study of Mn2+ doped L+ glutamic acid

    Science.gov (United States)

    Kripal, Ram; Singh, Manju

    2015-12-01

    Electron paramagnetic resonance (EPR) study of Mn2+ doped L+ glutamic acid single crystal is done at room temperature. Four interstitial sites are observed and the spin Hamiltonian parameters are calculated with the help of large number of resonant lines for various angular positions of external magnetic field. The optical absorption study is also done at room temperature. The energy values for different orbital levels are calculated, and observed bands are assigned as transitions from 6A1g(s) ground state to various excited states. With the help of these assigned bands, Racah inter-electronic repulsion parameters B = 869 cm-1, C = 2080 cm-1 and cubic crystal field splitting parameter Dq = 730 cm-1 are calculated. Zero field splitting (ZFS) parameters D and E are calculated by the perturbation formulae and crystal field parameters obtained using superposition model. The calculated values of ZFS parameters are in good agreement with the experimental values obtained by EPR.

  20. EPR Dosimetry for ageing effect in NPP

    International Nuclear Information System (INIS)

    Choi, Hoon; Lim, Young Ki; Kim, Jong Seog; Jung, Sun Chul

    2005-01-01

    As one of the retrospective dosimetry method, EPR spectroscopy has been studied by many research up to theses days. As a dosimeter for EPR spectroscopy, Alanine is already a well known dosimeter in the field of radiation therapy and dose assessment in radiological accident by its characteristics as good linearity in a wide range of energy level and extremely low signal fading on time. Through technical document of IAEA, the EPR dosimetry method using alanine sample was published in 2000 after research by coordinated project on management of ageing of in-containment I and C cables. Although alanine sample is regarded as a good EPR dosimeter like above ageing assessment field, actually the assessment of radiation should be done at least for two fuel cycles, because of its relatively low irradiation environment in almost all spots in power plant. So, for getting more accurate detection value of radiation, another material is tested for being put in simultaneously inside the power plant with alanine. The test result for lithium formate monohydrate (HCO 2 LiH 2 0) was presented below for checking its possibility for being applied as EPR dosimeter for this project

  1. Retrospective individual dosimetry using luminescence and EPR after radiation accidents

    International Nuclear Information System (INIS)

    Goeksu, H.Y.; Wieser, A.; Ulanovsky, A.

    2007-01-01

    requires further investigation. Applicability of suggested procedure need to be tested under factory conditions using the latest material and card technology. Feasibility of production of such cards on an industrial scale is discussed. Alternatively individual dose after emergency situations can be reconstructed by assessment of absorbed dose in human tooth enamel by electron paramagnetic resonance (EPR) measurements. From absorbed dose in tooth enamel the effective dose and dose in organs can be reconstructed in consideration of photon energy response characteristic of teeth, and photon energy spectrum and geometry of the exposure field. In this project the applicability of EPR measurements with teeth was extended by reducing the detection threshold and computation of the photon energy response characteristic of deciduous teeth. It is shown that current limitation of EPR measurement with teeth at low absorbed dose is caused by incomplete consideration of the EPR spectrum of nonradiation induced (initial) radicals. By adding further components for simulation of the initial EPR spectrum in the dose evaluation procedure, the critical value for detection of absorbed dose in tooth enamel could be decreased to 19 mGy. Dose conversion coefficients for deciduous teeth in dependence of photon energy and exposure geometry were computed by Monte Carlo simulation using a mathematical child phantom. For use with luminescence measurements with chip cards and EPR measurements with teeth a software was established that allows conversion of the measured dose to integral free-in-air kerma, tissue dose or dose water in dependence on exposure scenario. (orig.)

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

    Science.gov (United States)

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

    2014-05-15

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

  3. Spectra processing at tooth enamel dosimetry: Analytical description of EPR spectrum at different microwave power

    International Nuclear Information System (INIS)

    Tieliewuhan, E.; Ivannikov, A.; Zhumadilov, K.; Nalapko, M.; Tikunov, D.; Skvortsov, V.; Stepanenko, V.; Toyoda, S.; Tanaka, K.; Endo, S.; Hoshi, M.

    2006-01-01

    Variation of the electron paramagnetic resonance (EPR) spectrum of the human tooth enamel recorded at different microwave power is investigated. The analytical models describing the native and the radiation-induced signals in the enamel are proposed, which fit the experimental spectra in wide range of microwave power. These models are designed to use for processing the spectra of irradiated enamel at determination of the absorbed dose from the intensity of the radiation-induced signal

  4. Characterization of the factors having an influence on the evolution of the EPR signal of irradiated alanine

    International Nuclear Information System (INIS)

    Feaugas-Le-Berre, Valerie

    1999-01-01

    EPR/alanine dosimetry has been used by the LNHB (Laboratoire National Henri Becquerel) since many years for applied metrology. This technic is based on the measurement of the EPR signal of the free radicals induced in alanine by irradiation. The aim of this work is to characterize the factors having an influence on the evolution of the amplitude of the EPR signal of irradiated alanine to limit the uncertainties on the determination of the absorbed dose. The first step of this work has been the choice of the dosimeter. A bibliographic study completed by experiments on the response of alanine isomers to the dose and on its stability with time has lead us to choose L-α-alanine powder as dosimeter. The influence of the recording parameter of the spectrometer on the characteristics of the EPR spectrum has then been studied. This has enabled us to optimize the recording conditions of EPR spectra. As the angular anisotropy of the EPR signal limits the measurements reproducibility, an experimental protocol has been defined to solve this problem. The repeatability of the measurements has been enhanced by modifying the spectrometer and using an internal standard constituted of single crystals of CuSO 4 .5H 2 O. As the amplitude of the EPR signal is sensitive to the measurement temperature, a method of normalization of the results to 20 C has been determined. We have studied the influence of an irradiation parameter and of environmental parameters. We have shown that the EPR signal amplitude increases with irradiation temperature. The EPR signal amplitude and its evolution vary strongly with storage conditions (temperature and moisture) of the dosimeter before and after irradiation. The presence of moisture in alanine powder leads to a loss of signal amplitude. The dosimeters exposition to light also entails a loss of amplitude. Oxygen does not influence the EPR spectrum of alanine. We have noticed that the EPR signal amplitude of samples stored in absence of moisture

  5. L-026: EPR-First Responders: Action Guides Extinguishing Fire Brigades

    International Nuclear Information System (INIS)

    2011-01-01

    This conference will cover how and when to apply the Fire Brigades. Instructions and guidelines within the IAEA-EPR-First Responders to be used to guide the fire fighting brigade in a radiological emergency response to radioactive material in a manner that will minimize risks while performing the task. It will take into consideration the use of several types of monitoring equipment such as oxygen level meters, sight explosive, chemical meters and radiation detectors

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

    Indian Academy of Sciences (India)

    Magnetic, catalytic, EPR and electrochemical studies on binuclear copper(II) complexes ... to the oxidation of 3,5-di--butylcatechol to the corresponding quinone. ... EPR spectral studies in methanol solvent show welldefined four hyperfine ...

  7. Selfcalibrated alanine/EPR dosimeters. A new generation of solid state/EPR dosimeters

    International Nuclear Information System (INIS)

    Yordanov, N.D.; Gancheva, V.

    1999-01-01

    Alanine/EPR dosimeters are well established as secondary, reference dosimeters for high-energy radiation. However, there are various sources of uncertainty in the evaluation of absorbed dose. This arises primarily from the necessity to calibrate each EPR spectrometer and each batch of dosimeters before their use. In order to overcome this disadvantage, a new generation alanine/EPR dosimeter has been developed, and its possibilities as a radiation detector are reported. Principally, it is a mixture of alanine, some quantity of EPR active substance, and a binding material. The EPR active substance, acting as an internal EPR standard, is chosen to have EPR parameters which are independent of the irradiation dose. The simultaneous recording of the spectra of both the sample and the standard under the same experimental conditions and the estimation of the ratio I alanine /I Mn as a function of the absorbed dose strongly reduces the uncertainties. The response of these dosimeters for 60 Co γ-radiation exhibits excellent linearity and reproducibility in the range of absorbed dose, 10 2 - 5 x 10 4 Gy. (author)

  8. EPR spectra of some irradiated polycrystalline perrhenate

    International Nuclear Information System (INIS)

    Zaitseva, N.G.; Constantinescu, M.; Georgescu, R.; Constantinescu, O.

    1978-10-01

    An EPR study of the paramagnetic centers formed by γ, electron and neutron irradiation of the NaReO 4 and KReO 4 was made. In the EPR spectra of the powder samples irradiated γ, with electrons and neutrons, the presence of three types of paramagnetic centers was observed. From the EPR parameters, the centers were attributed to the ReOsub(4)sup(.), ReOsub(3)sup(.) and ReOsub(2)sup(.) radicals respectively. The lower intensity of the spectra observed by KReO 4 samples irradiation showed a higher radioresistance of the KReO 4 than that of NaReO 4 . A radiolitical scheme taking into account the paramagnetic centers formation was proposed. (author)

  9. Relativistic Nonlocality and the EPR Paradox

    Science.gov (United States)

    Chamberlain, Thomas

    2014-03-01

    The exact violation of Bell's Inequalities is obtained with a local realistic model for spin. The model treats one particle that comprises a quantum ensemble and simulates the EPR data one coincidence at a time as a product state. Such a spin is represented by operators σx , iσy ,σz in its body frame rather than the usual set of σX ,σY ,σZ in the laboratory frame. This model, assumed valid in the absence of a measuring probe, contains both quantum polarizations and coherences. Each carries half the EPR correlation, but only half can be measured using coincidence techniques. The model further predicts the filter angles that maximize the spin correlation in EPR experiments.

  10. Pressurized water reactors: the EPR project

    International Nuclear Information System (INIS)

    Py, J.P.; Yvon, M.

    2007-01-01

    EPR (originally 'European pressurized water reactor', and now 'evolutionary power reactor') is a model of reactor initially jointly developed by French and German engineers which fulfills the particular safety specifications of both countries but also the European utility requirements jointly elaborated by the main European power companies under the initiative of Electricite de France (EdF). Today, two EPR-based reactors are under development: one is under construction in Finland and the other, Flamanville 3 (France), received its creation permit decree on April 10, 2007. This article presents, first, the main objectives of the EPR, and then, describes the Flamanville 3 reactor: reactor type and general conditions, core and conditions of operation, primary and secondary circuits with their components, main auxiliary and recovery systems, man-machine interface and instrumentation and control system, confinement and serious accidents, arrangement of buildings. (J.S.)

  11. Spin entanglement, decoherence and Bohm's EPR paradox.

    Science.gov (United States)

    Cavalcanti, E G; Drummond, P D; Bachor, H A; Reid, M D

    2009-10-12

    We obtain criteria for entanglement and the EPR paradox for spin-entangled particles and analyse the effects of decoherence caused by absorption and state purity errors. For a two qubit photonic state, entanglement can occur for all transmission efficiencies. In this case, the state preparation purity must be above a threshold value. However, Bohm's spin EPR paradox can be achieved only above a critical level of loss. We calculate a required efficiency of 58%, which appears achievable with current quantum optical technologies. For a macroscopic number of particles prepared in a correlated state, spin entanglement and the EPR paradox can be demonstrated using our criteria for efficiencies eta > 1/3 and eta > 2/3 respectively. This indicates a surprising insensitivity to loss decoherence, in a macroscopic system of ultra-cold atoms or photons.

  12. EPR of impurity ions in disordered solids

    International Nuclear Information System (INIS)

    Kliava, J.

    1986-01-01

    The state of the art in the EPR spectroscopy of disordered solids is reviewed and theoretical aspects of the EPR shape in disordered systems are discussed. Emphasis is placed on the concept of the joint probability density of the spin Hamiltonian parameters. A survey of experimental data is provided on distributions of spin Hamiltonian parametes obtained using computer simulation techniques. A quantitative information is given on the short-range ordering in disordered materials available from EPR studies. A procedure of extracting such type of data which consists in a transformation from the distribution of the spin Hamiltonian parameters to that of atomic coordinates in the surrounding of a paramagnetic center is outlined. Numerical estimates of the degree of continuous disorder are reviewed

  13. EPR study of free radicals in bread

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    Zdybel, Magdalena; Pilawa, Barbara; Chodurek, Ewa

    2015-01-01

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

  15. Can EPR non-locality be geometrical?

    International Nuclear Information System (INIS)

    Ne'eman, Y.

    1995-01-01

    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

  16. Reconstruction for Time-Domain In Vivo EPR 3D Multigradient Oximetric Imaging—A Parallel Processing Perspective

    Directory of Open Access Journals (Sweden)

    Christopher D. Dharmaraj

    2009-01-01

    Full Text Available Three-dimensional Oximetric Electron Paramagnetic Resonance Imaging using the Single Point Imaging modality generates unpaired spin density and oxygen images that can readily distinguish between normal and tumor tissues in small animals. It is also possible with fast imaging to track the changes in tissue oxygenation in response to the oxygen content in the breathing air. However, this involves dealing with gigabytes of data for each 3D oximetric imaging experiment involving digital band pass filtering and background noise subtraction, followed by 3D Fourier reconstruction. This process is rather slow in a conventional uniprocessor system. This paper presents a parallelization framework using OpenMP runtime support and parallel MATLAB to execute such computationally intensive programs. The Intel compiler is used to develop a parallel C++ code based on OpenMP. The code is executed on four Dual-Core AMD Opteron shared memory processors, to reduce the computational burden of the filtration task significantly. The results show that the parallel code for filtration has achieved a speed up factor of 46.66 as against the equivalent serial MATLAB code. In addition, a parallel MATLAB code has been developed to perform 3D Fourier reconstruction. Speedup factors of 4.57 and 4.25 have been achieved during the reconstruction process and oximetry computation, for a data set with 23×23×23 gradient steps. The execution time has been computed for both the serial and parallel implementations using different dimensions of the data and presented for comparison. The reported system has been designed to be easily accessible even from low-cost personal computers through local internet (NIHnet. The experimental results demonstrate that the parallel computing provides a source of high computational power to obtain biophysical parameters from 3D EPR oximetric imaging, almost in real-time.

  17. Reconstruction for time-domain in vivo EPR 3D multigradient oximetric imaging--a parallel processing perspective.

    Science.gov (United States)

    Dharmaraj, Christopher D; Thadikonda, Kishan; Fletcher, Anthony R; Doan, Phuc N; Devasahayam, Nallathamby; Matsumoto, Shingo; Johnson, Calvin A; Cook, John A; Mitchell, James B; Subramanian, Sankaran; Krishna, Murali C

    2009-01-01

    Three-dimensional Oximetric Electron Paramagnetic Resonance Imaging using the Single Point Imaging modality generates unpaired spin density and oxygen images that can readily distinguish between normal and tumor tissues in small animals. It is also possible with fast imaging to track the changes in tissue oxygenation in response to the oxygen content in the breathing air. However, this involves dealing with gigabytes of data for each 3D oximetric imaging experiment involving digital band pass filtering and background noise subtraction, followed by 3D Fourier reconstruction. This process is rather slow in a conventional uniprocessor system. This paper presents a parallelization framework using OpenMP runtime support and parallel MATLAB to execute such computationally intensive programs. The Intel compiler is used to develop a parallel C++ code based on OpenMP. The code is executed on four Dual-Core AMD Opteron shared memory processors, to reduce the computational burden of the filtration task significantly. The results show that the parallel code for filtration has achieved a speed up factor of 46.66 as against the equivalent serial MATLAB code. In addition, a parallel MATLAB code has been developed to perform 3D Fourier reconstruction. Speedup factors of 4.57 and 4.25 have been achieved during the reconstruction process and oximetry computation, for a data set with 23 x 23 x 23 gradient steps. The execution time has been computed for both the serial and parallel implementations using different dimensions of the data and presented for comparison. The reported system has been designed to be easily accessible even from low-cost personal computers through local internet (NIHnet). The experimental results demonstrate that the parallel computing provides a source of high computational power to obtain biophysical parameters from 3D EPR oximetric imaging, almost in real-time.

  18. Comparison of Langmuir probe and multipole resonance probe measurements in argon, hydrogen, nitrogen, and oxygen mixtures in a double ICP discharge

    Science.gov (United States)

    Fiebrandt, Marcel; Oberberg, Moritz; Awakowicz, Peter

    2017-07-01

    The results of a Multipole Resonance Probe (MRP) are compared to a Langmuir probe in measuring the electron density in Ar, H2, N2, and O2 mixtures. The MRP was designed for measurements in industry processes, i.e., coating or etching. To evaluate a possible influence on the MRP measurement due to molecular gases, different plasmas with increasing molecular gas content in a double inductively coupled plasma at 5 Pa and 10 Pa at 500 W are used. The determined electron densities from the MRP and the Langmuir probe slightly differ in H2 and N2 diluted argon plasmas, but diverge significantly with oxygen. In pure molecular gas plasmas, electron densities measured with the MRP are always higher than those measured with the Langmuir Probe, in particular, in oxygen containing mixtures. The differences can be attributed to etching of the tungsten wire in the Ar:O2 mixtures and rf distortion in the pure molecular discharges. The influence of a non-Maxwellian electron energy distribution function, negative ions or secondary electron emission seems to be of no or only minor importance.

  19. Using rapid-scan EPR to improve the detection limit of quantitative EPR by more than one order of magnitude.

    Science.gov (United States)

    Möser, J; Lips, K; Tseytlin, M; Eaton, G R; Eaton, S S; Schnegg, A

    2017-08-01

    X-band rapid-scan EPR was implemented on a commercially available Bruker ELEXSYS E580 spectrometer. Room temperature rapid-scan and continuous-wave EPR spectra were recorded for amorphous silicon powder samples. By comparing the resulting signal intensities the feasibility of performing quantitative rapid-scan EPR is demonstrated. For different hydrogenated amorphous silicon samples, rapid-scan EPR results in signal-to-noise improvements by factors between 10 and 50. Rapid-scan EPR is thus capable of improving the detection limit of quantitative EPR by at least one order of magnitude. In addition, we provide a recipe for setting up and calibrating a conventional pulsed and continuous-wave EPR spectrometer for rapid-scan EPR. Copyright © 2017 Elsevier Inc. All rights reserved.

  20. Alanine EPR dosimetry of therapeutic irradiators

    International Nuclear Information System (INIS)

    Bugay, O.; Bartchuk, V.; Kolesnik, S.; Mazin, M.; Gaponenko, H.

    1999-01-01

    The high-dose alanine EPR dosimetry is a very precise method in the dose range 1-100 kGy. The system is used generally as the standard high-dose transfer dosimetry in many laboratories. This is comparatively expensive technique so it is important to use it as a more universal dosimetry system also in the middle and low dose ranges. The problems of the middle-dose alanine dosimetry are discussed and the solution of several problems is proposed. The alanine EPR dosimetry has been applied to the dose measurements of medical irradiators in the Kiev City Oncology Center. (author)

  1. Identification of irradiated crab using EPR

    Energy Technology Data Exchange (ETDEWEB)

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

    2007-02-15

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

  2. Krótka (prehistoria argumentu EPR

    Directory of Open Access Journals (Sweden)

    Tadeusz Pabjan

    2010-12-01

    Full Text Available The 1935 thought experiment of Einstein, Podolsky and Rosen is one of the most important episodes in the history of the dispute about the correct interpretation of quantum mechanics. The present paper deals with the origin of the EPR paper and discusses some other thought experiments that preceded the formulation of the Einstein-Podolsky-Rosen argument. Special attention is paid to the evolution of a simply photon-box experiment, which was devised by Einstein in 1930 and then modified by him several times before 1935. It is argued that the scheme of the original EPR argument is in fact contained in these few seminal experiments.

  3. Biophysical EPR Studies Applied to Membrane Proteins

    Science.gov (United States)

    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

  4. Identification of irradiated crab using EPR

    International Nuclear Information System (INIS)

    Maghraby, A.

    2007-01-01

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

  5. TL and EPR dating: some applications

    Energy Technology Data Exchange (ETDEWEB)

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

    2006-07-01

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

  6. Holographic EPR Pairs, Wormholes and Radiation

    OpenAIRE

    Chernicoff, Mariano; Güijosa, Alberto; Pedraza, Juan F.

    2013-01-01

    As evidence for the ER=EPR conjecture, it has recently been observed that the string that is holographically dual to an entangled quark-antiquark pair separating with (asymptotically) uniform acceleration has a wormhole on its worldsheet. We point out that a two-sided horizon and a wormhole actually appear for much more generic quark-antiquark trajectories, which is consistent with the fact that the members of an EPR pair need not be permanently out of causal contact. The feature that determi...

  7. Mast-sipping in EPR trademark plants

    International Nuclear Information System (INIS)

    Langenberger, Jan; Schienbein, Marcel; Geier, Roland

    2010-01-01

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

  8. Irradiated bivalve mollusks: Use of EPR spectroscopy for identification and dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Alberti, Angelo, E-mail: aalberti@isof.cnr.it [CNR-ISOF, Area della Ricerca di Bologna, Via P. Gobetti 101, Bologna I-40129 (Italy); Chiaravalle, Eugenio [Istituto Zooprofilattico Sperimentale della Puglia e Basilicata, Via Manfredonia 20, Foggia I-71100 (Italy); Fuochi, Piergiorgio; Macciantelli, Dante [CNR-ISOF, Area della Ricerca di Bologna, Via P. Gobetti 101, Bologna I-40129 (Italy); Mangiacotti, Michele, E-mail: michelemangiacotti@libero.it [Istituto Zooprofilattico Sperimentale della Puglia e Basilicata, Via Manfredonia 20, Foggia I-71100 (Italy); Marchesani, Giuliana [Istituto Zooprofilattico Sperimentale della Puglia e Basilicata, Via Manfredonia 20, Foggia I-71100 (Italy); Plescia, Elena [CNR-ISOF, Area della Ricerca di Bologna, Via P. Gobetti 101, Bologna I-40129 (Italy)

    2011-12-15

    High energy radiation treatment of foodstuff for microbial control and shelf-life extension is being used in many countries. However, for consumer protection and information, the European Union has adopted the Directives 1999/2/EC and 1999/3/EC to harmonize the rules concerning the treatment and trade of irradiated foods in EU countries. Among the validated methods to detect irradiated foods the EU directives also include Electron Paramagnetic Resonance (EPR/ESR) spectroscopy. We describe herein the use of EPR for identification of four species of bivalve mollusks, i.e. brown Venus shells (Callista chione), clams (Tapes semidecussatus), mussels (Mytilus galloprovincialis) and oysters (Ostrea edulis) irradiated with {sup 60}Co {gamma}-rays. EPR could definitely identify irradiated seashells due to the presence of long-lived free radicals, primarily CO{sub 2}{sup -}, CO{sub 3}{sup 3-}, SO{sub 2}{sup -} and SO{sub 3}{sup -} radical anions. The presence of other organic free radicals, believed to originate from conchiolin, a scleroprotein present in the shells, was also ascertained. The use of one of these radicals as a marker for irradiation of brown Venus shells and clams can be envisaged. We also propose a dosimetric protocol for the reconstruction of the administered dose in irradiated oysters. - Highlights: > EPR spectroscopy is confirmed a valuable identification tool for irradiated mollusks. > A conchiolin-derived radical can be used as irradiation marker for some mollusks. > A reliable protocol is outlined for dose reconstruction of irradiated oysters.

  9. Identification and dose assessment of irradiated cardamom and cloves by EPR spectrometry

    International Nuclear Information System (INIS)

    Beshir, W.B.

    2014-01-01

    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. The calculated G-value (The number of radicals per 100 eV of absorbed energy) for cardamom and cloves was found 0.07±0.01 and 0.055±0.01, respectively. - Highlights: • The EPR analysis of cardamom and cloves prove the sample has been irradiated or not. • Dose additive can be used for evaluation of the absorbed dose in cardamom and cloves. • The 3rd polynomial function can be used to fit the data and the estimated dose. • The stability of the radiation induced EPR signal of irradiated cardamom and cloves were studied over 2 months

  10. The evaluation of new and isotopically labeled isoindoline nitroxides and an azaphenalene nitroxide for EPR oximetry

    Science.gov (United States)

    Khan, Nadeem; Blinco, James P.; Bottle, Steven E.; Hosokawa, Kazuyuki; Swartz, Harold M.; Micallef, Aaron S.

    2011-01-01

    Isoindoline nitroxides are potentially useful probes for viable biological systems, exhibiting low cytotoxicity, moderate rates of biological reduction and favorable Electron Paramagnetic Resonance (EPR) characteristics. We have evaluated the anionic (5-carboxy-1,1,3,3-tetramethylisoindolin-2-yloxyl; CTMIO), cationic (5-(N,N,N-trimethylammonio)-1,1,3,3-tetramethylisoindolin-2-yloxyl iodide, QATMIO) and neutral (1,1,3,3-tetramethylisoindolin-2-yloxyl; TMIO) nitroxides and their isotopically labeled analogues (2H12- and/or 2H12-15N-labeled) as potential EPR oximetry probes. An active ester analogue of CTMIO, designed to localize intracellularly, and the azaphenalene nitroxide 1,1,3,3-tetramethyl-2,3-dihydro-2-azaphenalen-2-yloxyl (TMAO) were also studied. While the EPR spectra of the unlabeled nitroxides exhibit high sensitivity to O2 concentration, deuteration resulted in a loss of superhyperfine features and a subsequent reduction in O2 sensitivity. Labeling the nitroxides with 15N increased the signal intensity and this may be useful in decreasing the detection limits for in vivo measurements. The active ester nitroxide showed approximately 6% intracellular localization and low cytotoxicity. The EPR spectra of TMAO nitroxide indicated an increased rigidity in the nitroxide ring, due to dibenzo-annulation. PMID:21665499

  11. Radiation dose estimation by tooth enamel EPR dosimetry for residents of Dolon and Bodene

    International Nuclear Information System (INIS)

    Zhumadilov, Kassym; Ivannikov, Alexander; Apsalikov, Kazbek N.

    2006-01-01

    The method of electron paramagnetic resonance (EPR) dosimetry was applied to the enamel of the teeth extracted from the residents of the Dolon and Bodene settlements of the Beskaragay district, which is the area adjacent to the radioactive fallout of the most contaminating nuclear test of 1949. The individual accidental radiation doses due to the fallout were obtained from the amplitude of the radiation induced EPR signal from the CO 2- radical using the calibration method, after determining the parameters of EPR measurements to obtain the best reproducibility of the signal intensities. It was shown that after subtracting the natural background dose from the total absorbed dose obtained by EPR the residents of Dolon and Bodene received accidental radiation doses up to 356 mGy with an average value of 74.1 ± 45.5 mGy before 1949 while the younger population received up to about 100 mGy with an average value of 11.5 ± 37.7 mGy. (author)

  12. Field-swept pulsed electron paramagnetic resonance of Cr3+-doped ZBLAN fluoride glass

    International Nuclear Information System (INIS)

    Drew, S.C.; Pilbrow, J.R.; Newman, P.J.; MacFarlane, D.R.

    2001-01-01

    Field-swept pulsed electron paramagnetic resonance (EPR) spectra of a ZBLAN fluoride glass doped with a low concentration of Cr 3+ are obtained using echo-detected EPR and hole-burning free induction decay detection. We review the utility of the pulsed EPR technique in generating field-swept EPR spectra, as well as some of the distorting effects that are peculiar to the pulsed detection method. The application of this technique to Cr 3+ -doped ZBLAN reveals that much of the broad resonance extending from g eff =5.1 to g eff =1.97, characteristic of X-band continuous wave EPR of Cr 3+ in glasses, is absent. We attribute this largely to the variation in nutation frequencies across the spectrum that result from sites possessing large fine structure interactions. The description of the spin dynamics of such sites is complicated and we discuss some possible approaches to the simulation of the pulsed EPR spectra. (author)

  13. Design of the EPR containment

    International Nuclear Information System (INIS)

    Appell, B.; Zaiss, W.

    1996-01-01

    In order to respect the safety objectives set for the EPR (European Pressurized water Reactor), the confinement function must be designed to guard against in the design uncontrolled releases in the environment in all conditions taken into account and to preserve its structural integrity. The concept chosen is a double-wall confinement with technology identical derived from the current French N4 containments and the associated systems ensuring the isolation and the control of leaks. The basic principles aiming to minimize leaks are as follows: no direct leak; state-of-the-art leak tight design of the systems and components passing through the containment building; recovery of potential leaks through the inner wall and the penetration sleeves in the inter-wall space; recovery in the peripheral buildings; and specific measures if necessary. The inner wall is a prestressed concrete shell (55 tendons cables arranged in two horizontal layers and a vertical layer for the barrel) without liner, of free volume 90000 m 3 , an internal diameter of 48 m and 1.3 m thickness. The free volume is chosen so as to rule out the risk of global detonation and the use of catalytic recombiners limits the risk of hydrogen explosion. The design pressure (6.5 bar abs) and temperature of the inner wall are defined for a given volume by the set of three conditions: Pee-4 conditions such as LOCA or SLB, global deflagration of hydrogen and core melt scenario. The rate of leakage in accident conditions from the inner wall must not be higher than 1% per day. The chosen concept must enable satisfactory leak tightness to be preserved for beyond design conditions in order to have margins and to guard against phenomenological uncertainties. The possibility of adding an internal composite liner is being studied. A large scale mockup is being built to validate the hypothesis and methods of leak rates of the inner wall and for the performance testing of the composite liner. The outer wall, made of

  14. MDEP Common Position No EPR-01 - Common positions on the EPR instrumentation and controls design

    International Nuclear Information System (INIS)

    2010-01-01

    The purpose of the EPR Working Group (EPRWG) of the Multinational Design Evaluation Program (MDEP) is to identify common positions among the regulators reviewing the EPR Instrumentation and Controls (I and C) Systems in order to: 1. Promote understanding of each country 's regulatory decisions and basis for the decisions, 2. Enhance communication among the members and with external stakeholders, 3. Identify areas where harmonization and convergence of regulations, standards, and guidance can be achieved or improved, and 4. Supports standardization of new reactor designs. Since January 2008, the EPR I and C Technical Expert Subgroup (TESG) members met five times to exchange information regarding their country 's review of the EPR I and C design. The EPR I and C TESG consists of regulators from China, Canada, Finland, France, the United Kingdom, and the United States. The information exchange includes presentation of each country 's review status and technical issues, sharing of guidance documents, and sharing of regulatory decision documents. The TESG focused on the following four core areas of the EPR I and C design: 1. I and C System Independence (particularly for data communications), 2. Level of Defense and Diversity (back-up systems), 3. Qualification/quality of digital platforms, 4. Categorization/classification of systems and functions. As meetings were conducted, some areas were emphasized more depending on the significance of the issues for each country. During the TESG interactions, it became apparent that there were aspects of the EPR design where the countries had common agreement. On November 2, 2009, three of the subgroup countries, France, Finland and the United Kingdom, issued a joint regulatory position on the EPR I and C design as result of the 'Groupe Permanent' meeting in France. This statement of common positions expands upon that joint regulatory position

  15. Polymer therapeutics and the EPR effect.

    Science.gov (United States)

    Maeda, Hiroshi

    History of the EPR (enhanced permeability and retention) effect is discussed, which goes back to the analyses of molecular pathology in bacterial infection and edema (extravasation) formation. The first mediator we found for extravasation was bradykinin. Later on, were found nitric oxide and superoxide, then formation of peroxynitrite, that activates procollagenase. In this inflammatory setting many other vascular mediators are involved that are also common to cancer vasculature. Obviously cancer vasculature is defective architechtally, and this makes macromolecular drugs more permeable through the vascular wall. The importance of this pathophysiological event of EPR effect can be applied to macromolecular drug-delivery, or tumor selective delivery, which takes hours to achieve in the primary as well as metastatic tumors, not to mention of the inflamed tissues. The retention of the EPR means that such drugs will be retained in tumor tissues more than days to weeks. This was demonstrated initially, and most dramatically, using SMANCS, a protein-polymer conjugated-drug dissolved in lipid contrast medium (Lipiodol) by administering intraarterially. For disseminating the EPR concept globally, or in the scientific community, Professor Ruth Duncan played a key role at the early stage, as she worked extensively on polymer- therapeutics, and knew its importance.

  16. Teaching the EPR Paradox at High School?

    Science.gov (United States)

    Pospiech, Gesche

    1999-01-01

    Argues the importance of students at university and in the final years of high school gaining an appreciation of the principles of quantum mechanics. Presents the EPR gedanken experiment (thought experiment) as a method of teaching the principles of quantum mechanics. (Author/CCM)

  17. EPR: outlines of research and development

    International Nuclear Information System (INIS)

    Anon.

    1996-01-01

    The articles give an overview of the research and development presently under way for the future pressurized water reactors to be constructed in Europe, and particularly the French and German EPR (European Pressurized Reactor). Such an analysis deals essentially with respect to the pressurized water reactors now in operation. (author)

  18. EPR-dosimetry of ionizing radiation

    Science.gov (United States)

    Popova, Mariia; Vakhnin, Dmitrii; Tyshchenko, Igor

    2017-09-01

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

  19. EPR application in medicine and biology

    Czech Academy of Sciences Publication Activity Database

    Stopka, Pavel; Křížová, Jana; Káfuňková, Eva

    2005-01-01

    Roč. 99, č. 14 (2005), s. 190-192 ISSN 0009-2770 R&D Projects: GA MZd(CZ) NB7377; GA MZd(CZ) NL7567 Institutional research plan: CEZ:AV0Z40320502 Keywords : EPR application Subject RIV: CA - Inorganic Chemistry Impact factor: 0.445, year: 2005

  20. Zavoisky and the Discovery of EPR

    Indian Academy of Sciences (India)

    IAS Admin

    moved to Kazan. In 1926, after finishing the nine-year secondary ... year student, he got a patent for an invention. Zavoisky was ... Early Attempts at NMR and Interruption by World War II ... band modulation) and, in some cases, he did not even apply the constant ... was awarded the Lenin Prize for the discovery of EPR. In the.

  1. An X- and Q-band Fe3+ EPR study of nanoparticles of magnetic semiconductor Zn1-xFexO

    Science.gov (United States)

    Misra, Sushil K.; Andronenko, S. I.; Thurber, A.; Punnoose, A.; Nalepa, A.

    2014-08-01

    EPR studies on two types of nanoparticles of Fe3+ doped, 0.1-10%, ZnO, NL and QJ, prepared using similar chemical hydrolysis methods, in diethylene glycol, and in denatured ethanol solutions, respectively, were carried out at X-band (~9.5 GHz) at 77 K and at Q-band (~34.0 GHz) at 10, 80, and 295 K. To interpret the experimental results, EPR spectra were simulated by exact diagonalization of the spin-Hamiltonian matrix to identify the Fe ions at different magnetically active sites in these samples. The simulation for NL samples revealed that they contained (i) Fe3+ ions, which substituted for Zn ions, the zero-field splitting (ZFS) parameter which has a large distribution over the sample due to oxygen vacancies in the second coordination sphere; (ii) EPR signal from surface oxygen defects; and (iii) ferromagnetically (FM) coupled Fe ions with concentration of Fe more than 1%. The EPR spectra for QJ samples are very different from those for NL samples, exhibiting only rather intense FM EPR lines. The FM and EPR spectra in NL and/or QJ samples are found to vary strongly with differences in the surface morphology of nanoparticles.

  2. Production of a recombinant phospholipase A2 in Escherichia coli using resonant acoustic mixing that improves oxygen transfer in shake flasks.

    Science.gov (United States)

    Valdez-Cruz, Norma A; Reynoso-Cereceda, Greta I; Pérez-Rodriguez, Saumel; Restrepo-Pineda, Sara; González-Santana, Jesus; Olvera, Alejandro; Zavala, Guadalupe; Alagón, Alejandro; Trujillo-Roldán, Mauricio A

    2017-07-25

    Shake flasks are widely used during the development of bioprocesses for recombinant proteins. Cultures of recombinant Escherichia coli with orbital mixing (OM) have an oxygen limitation negatively affecting biomass growth and recombinant-protein production. With the aim to improve mixing and aeration in shake flask cultures, we analyzed cultures subjected to OM and the novel resonant acoustic mixing (RAM) by applying acoustic energy to E. coli BL21-Gold (DE3): a producer of recombinant phospholipase A2 (rPLA2) from Micrurus laticollaris snake venom. Comparing OM with RAM (200 rpm vs. 7.5g) at the same initial volumetric oxygen transfer coefficient (k L a ≈ 80 h -1 ) ~69% less biomass was obtained with OM compared with RAM. We analyzed two more conditions increasing agitation until maximal speed (12.5 and 20g), and ~1.6- and ~1.4-fold greater biomass was obtained as compared with cultures at 7.5g. Moreover, the specific growth rate was statistically similar in all cultures carried out in RAM, but ~1.5-fold higher than that in cultures carried out under OM. Almost half of the glucose was consumed in OM, whereas between 80 and 100% of the glucose was consumed in RAM cultures, doubling biomass per glucose yields. Differential organic acid production was observed, but acetate production was prevented at the maximal RAM (20g). The amount of rPLA2 in both, OM and RAM cultures, represented 38 ± 5% of the insoluble protein. A smaller proportion of α-helices and β-sheet of purified inclusion bodies (IBs) were appreciated by ATR-FTIR from cultures carried out under OM, than those from RAM. At maximal agitation by RAM, internal E. coli localization patterns of protein aggregation changed, as well as, IBs proteolytic degradation, in conjunction with the formation of small external vesicles, although these changes did not significantly affect the cell survival response. In moderate-cell-density recombinant E. coli BL21-Gold (DE3) cultures, the agitation increases in

  3. New Generation of self-calibrated SS/EPR dosimeters: Alanine/EPR dosimeters

    International Nuclear Information System (INIS)

    Yordanov, N.D.; Gancheva, V.

    1999-01-01

    A new type of solid state/EPR dosimeters is described. Principally, it contains radiation sensitive diamagnetic material, some quantity of EPR active, but radiation insensitive, substance (for example Mn 2+ /MgO) and a binding material. In the present case alanine is used as a radiation sensitive substance. With this dosimeter, the EPR spectra of alanine and Mn 2+ are simultaneously recorded and the calibration graph represents the ratio of alanine versus Mn 2+ EPR signal intensity as a function of absorbed dose. In this way the reproducibility of the results is expected to be improved significantly including their intercomparison among different laboratories. Homogeneity of the prepared dosimeters and their behaviour (fading of EPR signals with time, influence of different meteorological conditions) show satisfactory reproducibility and stability with time. Because two different EPR active samples are recorded simultaneously, the influence of some instrument setting parameters (microwave power, modulation amplitude and modulation frequency) on the ratio I alanine /I Mn is also investigated. (author)

  4. EPR and optical absorption studies of VO2+ doped L-alanine (C3H7NO2) single crystals

    International Nuclear Information System (INIS)

    Biyik, Recep

    2009-01-01

    VO 2+ doped L-alanine (C 3 H 7 NO 2 ) single crystals and powders are examined by electron paramagnetic resonance (EPR) and optical absorption spectroscopy. Three magnetically different sites are resolved from angular variations of L-alanine single crystal EPR spectra. In some specific orientations each VO 2+ line splits into three superhyperfine lines with intensities of 1:2:1 and maximum splitting value of 2.23 mT. The local symmetries of VO 2+ complex sites are nearly axial. The optical absorption spectra show three bands. Spin Hamiltonian parameters are measured and molecular orbital coefficients are calculated by correlating EPR and optical absorption data for the central vanadyl ion.

  5. EPR Evidence of Liquid Water in Ice: An Intrinsic Property of Water or a Self-Confinement Effect?

    Science.gov (United States)

    Thangswamy, Muthulakshmi; Maheshwari, Priya; Dutta, Dhanadeep; Rane, Vinayak; Pujari, Pradeep K

    2018-06-01

    Liquid water (LW) existence in pure ice below 273 K has been a controversial aspect primarily because of the lack of experimental evidence. Recently, electron paramagnetic resonance (EPR) has been used to study deeply supercooled water in a rapidly frozen polycrystalline ice. The same technique can also be used to probe the presence of LW in polycrystalline ice that has formed through a more conventional, slow cooling one. In this context, the present study aims to emphasize that in case of an external probe involving techniques such as EPR, the results are influenced by the binary phase (BP) diagram of the probe-water system, which also predicts the existence of LW domains in ice, up to the eutectic point. Here we report the results of our such EPR spin-probe studies on water, which demonstrate that smaller the concentration of the probe stronger is the EPR evidence of liquid domains in polycrystalline ice. We used computer simulations based on stochastic Liouville theory to analyze the lineshapes of the EPR spectra. We show that the presence of the spin probe modifies the BP diagram of water, at very low concentrations of the spin probe. The spin probe thus acts, not like a passive reporter of the behavior of the solvent and its environment, but as an active impurity to influence the solvent. We show that there exists a lower critical concentration, below which BP diagram needs to be modified, by incorporating the effect of confinement of the spin probe. With this approach, we demonstrate that the observed EPR evidence of LW domains in ice can be accounted for by the modified BP diagram of the probe-water system. The present work highlights the importance of taking cognizance of the possibility of spin probes affecting the host systems, when interpreting the EPR (or any other probe based spectroscopic) results of phase transitions of host, as its ignorance may lead to serious misinterpretations.

  6. Understanding the dosimetric powder EPR spectrum of sucrose by identification of the stable radiation-induced radicals

    International Nuclear Information System (INIS)

    Vrielinck, H.; Vanhaelewyn, G.; Matthys, P.; Callens, F.; Kusakovskij, J.

    2014-01-01

    Sucrose, the main component of table sugar, present in nearly every household and quite radiation sensitive, is considered as an interesting emergency dosemeter. Another application of radiation-induced radicals in sugars is the detection of irradiation in sugar-containing foodstuffs. The complexity of electron paramagnetic resonance (EPR) spectra of radicals in these materials, as a result of many hyperfine interactions and the multi-compositeness of the spectra of individual sugars, complicate dose assessment and the improvement of protocols for control and identification of irradiated sugar-containing foodstuffs using EPR. A thorough understanding of the EPR spectrum of individual irradiated sugars is desirable when one wants to reliably use them in a wide variety of dosimetric applications. Recently, the dominant room temperature stable radicals in irradiated sucrose have been thoroughly characterised using EPR, electron nuclear double resonance (ENDOR) and ENDOR-induced EPR. These radicals were structurally identified by comparing their proton hyperfine and g-tensors with the results of Density Functional Theory calculations for test radical structures. In this paper, the authors use the spin Hamiltonian parameters determined in these studies to simulate powder EPR spectra at the standard X-band (9.5 GHz), commonly used in applications, and at higher frequencies, up to J-band (285 GHz), rendering spectra with higher resolution. A few pitfalls in the simulation process are highlighted. The results indicate that the major part of the dosimetric spectrum can be understood in terms of three dominant radicals, but as-yet unidentified radicals also contribute in a non-negligible way. (authors)

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

    Science.gov (United States)

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

    2012-02-14

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

  8. Development of a new dosimeter of EPR based on lactose; Desarrollo de un nuevo dosimetro de RPE basado en lactosa

    Energy Technology Data Exchange (ETDEWEB)

    Cruz C, L.; Torijano C, E.; Azorin N, J.; Aguirre G, F. [Universidad Autonoma Metropolitana, Unidad Iztapalapa, Av. San Rafael Atlixco 186, Col. Vicentina, 09340 Mexico D. F. (Mexico); Cruz Z, E., E-mail: eftc@xanum.uam.mx [UNAM, Instituto de Ciencias Nucleares, Circuito Exterior, Ciudad Universitaria, 04510 Mexico D. F. (Mexico)

    2014-08-15

    50 years have passed since was proposed using the amino acid alanine as dosimeter advantage the phenomenon of electron paramagnetic resonance (EPR); this dosimetric method has reached a highly competitive level regarding others dosimetry classic methods, for example the thermoluminescence or the use of Fricke dosimeters, to measure high dose of radiation. In this type of materials, the free radicals induced by the radiation are stable and their concentration is proportional to the absorbed dose may be determined by the amplitude pick to pick of the first derived of the EPR absorption spectrum. The obtained results studying the EPR response of lactose tablets elaborated in the Universidad Autonoma Metropolitana, Unidad Iztapalapa are presented. The tablets were irradiated with gamma radiation of {sup 60}Co in the irradiator Gamma beam 651-Pt of the Instituto de Ciencias Nucleares de la Universidad Nacional Autonoma de Mexico to a dose rate of 8 kGy-h{sup -1} and their EPR response in a EPR spectrometer e-scan Bruker. The obtained response in function of the dose was lineal in the interval of 1 at 10 kGy. The lactose sensibility was compared with the l-alanine, used as reference, and the result was consistently 0.25 of this. Due to the linearity shown in the interval of used dose and their low production cost, we conclude that the lactose is a promissory option for the dosimetry of high dose of radiation. (author)

  9. EPR spectral changes of nitrosil hemes and their relation to the hemoglobin T-R transition

    International Nuclear Information System (INIS)

    Louro, S.R.W.; Ribeiro, P.C.; Bemski, G.

    1980-09-01

    EPR spectra of nitrosil-hemes were used to study the quaternary structure of hemoglobin. Human adult hemoglobin has been titrated with nitric oxide at pH 7.0 and 25 0 C. After the equilibration of NO among the α and β subunits the samples were frozen for EPR measurements. The spectra were fitted by linear combinations of three standard signals: the first arising from NO - β hemes and the other two arising from NO - α hemes of molecules in the high and low affinity conformations. The fractional amounts of α subunits exhibiting the high affinity spectrum fitted the two-state model with L = 7 x 10 6 , and csup(α) sub(NO) and csup(β) sub(NO) approximately 0.01. Hemoglobin has been marked with nitric oxide at one chain using low-saturation amounts of nitric oxide. The EPR spectra were studied as a function of oxygen saturation. Linear combinations of the three standard signals above fitted these spectra. The fractions of molecules exhibiting the high affinity spectrum fitted the two-state model with L = 7 x 10 6 , csub(O 2 ) = 0.0033 and csup(α) sub(NO) = 0.08, instead of csup(α) sub(NO) = 0.01.Thus, the two state model is not adequate to describe the conformational transition of these hybrids. The results are evidence of the nonequivalence between oxygen and nitric oxide as ligands. (Author) [pt

  10. Electron paramagnetic resonance studies on conformation states and metal ion exchange properties of vanadium bromoperoxidase

    International Nuclear Information System (INIS)

    de Boer, E.; Boon, K.; Wever, R.

    1988-01-01

    An electron paramagnetic resonance (EPR) study was carried out to examine structural aspects of vanadium-containing bromoperoxidase from the brown seaweed Ascophyllum nodosum. At high pH, the reduced form of bromoperoxidase showed an apparently axially symmetric EPR signal with 16 hyperfine lines. When the pH was lowered, a new EPR spectrum was formed. When EPR spectra of the reduced enzyme were recorded in the pH range from 4.2 to 8.4, it appeared that these changes were linked to a functional group with an apparent pK/sub a/ of about 5.4. In D 2 O this value for the pK/sub a/ was 5.3. It is suggested that these effects arise from protonation of histidine or aspartate/glutamate residues near the metal ion. The values for the isotropic hyperfine coupling constant of the reduced enzyme at both high and low pH are also consistent with a ligand field containing nitrogen and/or oxygen donor atoms. When reduced bromoperoxidase was dissolved in D 2 O or H 2 17 O instead of H 2 16 O, vanadium (IV) hyperfine line widths were markedly affected, demonstrating that water is a ligand of the metal ion. Together with previous work these findings suggest that vanadium (IV) is not involved in catalytic turnover and confirm the model in which the vanadium (V) ion of the native enzyme only serves to bind both hydrogen peroxide and bromide. After excess vanadate was added to a homogeneous preparation of purified bromoperoxidase, the extent of vanadium bound to the protein increased from 0.5 to 1.1, with a concomitant enhancement of enzymic activity. Finally, it is demonstrated that both vanadate (VO 4 3- ) and molybdate (MoO 4 2- ) compete for the same site on apobromoperoxidase

  11. Investigation of anisotropy in EPR spectra of radiation defects in irradiated beryllium ceramics

    International Nuclear Information System (INIS)

    Polyakov, A.I.; Ryabikin, Yu.A.; Zashkvara, O. V.; Bitenbaev, M.I.; Petukhov, Yu. V.

    2004-01-01

    Full text: In this work results of analysis of anisotropy and hyperfine structure in EPR spectra of paramagnetic defects in irradiated samples of beryllium ceramics are presented. To explain peculiarities in a shape and parameters of the EPR spectrum hyperfine structure in beryllium ceramics, we have analyzed several versions of model representations for the radiation-induced paramagnetic defects uniformly distributed in a sample as well as for cluster defects which hyperfine structure is determined by interactions between electrons and nuclei of impurity atoms (S=1/2) and which are characterized by anisotropy in the g factors. Calculations of a shape of the uniformly widened EPR spectra are carried out by the model of random interactions between electron spins. The EPR spectra, widened at the expense of anisotropy in the g factors, are calculated by the following equation: g(Δ)=[2(ω-ω 0 )+α] -1/2 , where ω 0 =γH 0 , α is the quantify proportional to the anisotropy shift. To describe wings of spectral lines, where the equation doesn't work, we use the Gaussian function. To determine the frequency of precession of electron spins packages with local concentration N loc , the following expression is used: ω=ω 0 +1/2α(3cos 2 θ-1), where θ is an angle between the symmetry axis and the direction of the external magnetic field. It is shown that the best agreement between the calculated and experimental EPR spectra is observed with the following computational model: paramagnetic radiation defects are distributed uniformly over a ceramics sample, and the g factors of its EPR spectra have the anisotropy typical for dipole-dipole interaction in powder samples. By results of the data we obtained, it's clear that in future we'll need in more detailed information than that published in scientific journals about formation of the paramagnetic defect EPR spectra structure in beryllium oxides and ceramics at the expense of resonance line hyperfine splitting on atoms of

  12. Investigation of anisotropy in EPR spectra of radiation defects in irradiated beryllium ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Polyakov, A I; Ryabikin, Yu A; Zashkvara, O V; Bitenbaev, M I; Petukhov, Yu V [Inst. of Physics and Technology, Almaty (Kazakhstan)

    2004-07-01

    Full text: In this work results of analysis of anisotropy and hyperfine structure in EPR spectra of paramagnetic defects in irradiated samples of beryllium ceramics are presented. To explain peculiarities in a shape and parameters of the EPR spectrum hyperfine structure in beryllium ceramics, we have analyzed several versions of model representations for the radiation-induced paramagnetic defects uniformly distributed in a sample as well as for cluster defects which hyperfine structure is determined by interactions between electrons and nuclei of impurity atoms (S=1/2) and which are characterized by anisotropy in the g factors. Calculations of a shape of the uniformly widened EPR spectra are carried out by the model of random interactions between electron spins. The EPR spectra, widened at the expense of anisotropy in the g factors, are calculated by the following equation: g({delta})=[2({omega}-{omega}{sub 0})+{alpha}]{sup -1/2}, where {omega}{sub 0}={gamma}H{sub 0}, {alpha} is the quantify proportional to the anisotropy shift. To describe wings of spectral lines, where the equation doesn't work, we use the Gaussian function. To determine the frequency of precession of electron spins packages with local concentration N{sub loc}, the following expression is used: {omega}={omega}{sub 0}+1/2{alpha}(3cos{sup 2}{theta}-1), where {theta} is an angle between the symmetry axis and the direction of the external magnetic field. It is shown that the best agreement between the calculated and experimental EPR spectra is observed with the following computational model: paramagnetic radiation defects are distributed uniformly over a ceramics sample, and the g factors of its EPR spectra have the anisotropy typical for dipole-dipole interaction in powder samples. By results of the data we obtained, it's clear that in future we'll need in more detailed information than that published in scientific journals about formation of the paramagnetic defect EPR spectra structure in

  13. Using the methods of radiospectroscopy (EPR, NMR) to study the nature of the defect structure of solid solutions based on lead zirconate titanate (PZT).

    Science.gov (United States)

    Bykov, Igor; Zagorodniy, Yuriy; Yurchenko, Lesya; Korduban, Alexander; Nejezchleb, Karel; Trachevsky, Vladimir; Dimza, Vilnis; Jastrabik, Lubomir; Dejneka, Alexander

    2014-08-01

    The nature of intrinsic and impurity point defects in lead zirconate titanate (PZT) ceramics has been explored. Using electron paramagnetic resonance (EPR), nuclear magnetic resonance (NMR), and X-ray photoelectron spectroscopy (XPS) methods, several impurity sites have been identified in the materials, including the Fe(3+)-oxygen vacancy (VO) complex and Pb ions. Both of these centers are incorporated into the PZT lattice. The Fe(3+) –VО paramagnetic complex serves as a sensitive probe of the local crystal field in the ceramic; the symmetry of this defect roughly correlates with PZT phase diagram as the composition is varied from PbTiO3 to PbZrO3. NMR spectra (207)Pb in PbTiO3, PbZrO3, and PZT with iron content from 0 to 0.4 wt% showed that increasing the iron concentration leads to a distortion of the crystal structure and to improvement of the electrophysical parameters of the piezoceramics. This is due to the formation of a phase which has a higher symmetry, but at high concentrations of iron (>0.4 wt%), it leads to sharp degradation of electrophysical parameters.

  14. Braked rotation of CH3 group in L-alanine monocrystals: temperature transformation of EPR spectrum

    International Nuclear Information System (INIS)

    Lemanov, V.V.; Sochava, L.S.

    2003-01-01

    EPR spectra temperature transformation of the irradiated alanine crystals is used for studying rotation of CH 3 methyl group in L-alamine monocrystals. 60 Co (2 x 10 4 Gy dose) was applied as a γ-radiation source. The simple method of experimental data processing which is reduced to obtaining the resonance lines width dependence on the temperature is used for the quantitative analysis of the spectrum temperature transformation. Temperature dependence of the CH 3 group rotation frequency is identified on the basis of these data. Activation energy U = 0.18 eV and pre-exponential multiplier ω 0 = 10 13 s -1 are determined from the EPR spectra temperature transformation which are in good agreement with values obtained earlier from the measurements of the proton spin-lattice relaxation in alanine polycrystal samples [ru

  15. Pyruvate induces transient tumor hypoxia by enhancing mitochondrial oxygen consumption and potentiates the anti-tumor effect of a hypoxia-activated prodrug TH-302.

    Directory of Open Access Journals (Sweden)

    Yoichi Takakusagi

    Full Text Available BACKGROUND: TH-302 is a hypoxia-activated prodrug (HAP of bromo isophosphoramide mustard that is selectively activated within hypoxic regions in solid tumors. Our recent study showed that intravenously administered bolus pyruvate can transiently induce hypoxia in tumors. We investigated the mechanism underlying the induction of transient hypoxia and the combination use of pyruvate to potentiate the anti-tumor effect of TH-302. METHODOLOGY/RESULTS: The hypoxia-dependent cytotoxicity of TH-302 was evaluated by a viability assay in murine SCCVII and human HT29 cells. Modulation in cellular oxygen consumption and in vivo tumor oxygenation by the pyruvate treatment was monitored by extracellular flux analysis and electron paramagnetic resonance (EPR oxygen imaging, respectively. The enhancement of the anti-tumor effect of TH-302 by pyruvate treatment was evaluated by monitoring the growth suppression of the tumor xenografts inoculated subcutaneously in mice. TH-302 preferentially inhibited the growth of both SCCVII and HT29 cells under hypoxic conditions (0.1% O2, with minimal effect under aerobic conditions (21% O2. Basal oxygen consumption rates increased after the pyruvate treatment in SCCVII cells in a concentration-dependent manner, suggesting that pyruvate enhances the mitochondrial respiration to consume excess cellular oxygen. In vivo EPR oxygen imaging showed that the intravenous administration of pyruvate globally induced the transient hypoxia 30 min after the injection in SCCVII and HT29 tumors at the size of 500-1500 mm(3. Pretreatment of SCCVII tumor bearing mice with pyruvate 30 min prior to TH-302 administration, initiated with small tumors (∼ 550 mm(3, significantly delayed tumor growth. CONCLUSIONS/SIGNIFICANCE: Our in vitro and in vivo studies showed that pyruvate induces transient hypoxia by enhancing mitochondrial oxygen consumption in tumor cells. TH-302 therapy can be potentiated by pyruvate pretreatment if started at the

  16. Pyruvate induces transient tumor hypoxia by enhancing mitochondrial oxygen consumption and potentiates the anti-tumor effect of a hypoxia-activated prodrug TH-302.

    Science.gov (United States)

    Takakusagi, Yoichi; Matsumoto, Shingo; Saito, Keita; Matsuo, Masayuki; Kishimoto, Shun; Wojtkowiak, Jonathan W; DeGraff, William; Kesarwala, Aparna H; Choudhuri, Rajani; Devasahayam, Nallathamby; Subramanian, Sankaran; Munasinghe, Jeeva P; Gillies, Robert J; Mitchell, James B; Hart, Charles P; Krishna, Murali C

    2014-01-01

    TH-302 is a hypoxia-activated prodrug (HAP) of bromo isophosphoramide mustard that is selectively activated within hypoxic regions in solid tumors. Our recent study showed that intravenously administered bolus pyruvate can transiently induce hypoxia in tumors. We investigated the mechanism underlying the induction of transient hypoxia and the combination use of pyruvate to potentiate the anti-tumor effect of TH-302. The hypoxia-dependent cytotoxicity of TH-302 was evaluated by a viability assay in murine SCCVII and human HT29 cells. Modulation in cellular oxygen consumption and in vivo tumor oxygenation by the pyruvate treatment was monitored by extracellular flux analysis and electron paramagnetic resonance (EPR) oxygen imaging, respectively. The enhancement of the anti-tumor effect of TH-302 by pyruvate treatment was evaluated by monitoring the growth suppression of the tumor xenografts inoculated subcutaneously in mice. TH-302 preferentially inhibited the growth of both SCCVII and HT29 cells under hypoxic conditions (0.1% O2), with minimal effect under aerobic conditions (21% O2). Basal oxygen consumption rates increased after the pyruvate treatment in SCCVII cells in a concentration-dependent manner, suggesting that pyruvate enhances the mitochondrial respiration to consume excess cellular oxygen. In vivo EPR oxygen imaging showed that the intravenous administration of pyruvate globally induced the transient hypoxia 30 min after the injection in SCCVII and HT29 tumors at the size of 500-1500 mm(3). Pretreatment of SCCVII tumor bearing mice with pyruvate 30 min prior to TH-302 administration, initiated with small tumors (∼ 550 mm(3)), significantly delayed tumor growth. Our in vitro and in vivo studies showed that pyruvate induces transient hypoxia by enhancing mitochondrial oxygen consumption in tumor cells. TH-302 therapy can be potentiated by pyruvate pretreatment if started at the appropriate tumor size and oxygen concentration.

  17. In vivo evaluation of different alterations of redox status by studying pharmacokinetics of nitroxides using magnetic resonance techniques

    Science.gov (United States)

    Bačić, Goran; Pavićević, Aleksandra; Peyrot, Fabienne

    2015-01-01

    Free radicals, particularly reactive oxygen species (ROS), are involved in various pathologies, injuries related to radiation, ischemia-reperfusion or ageing. Unfortunately, it is virtually impossible to directly detect free radicals in vivo, but the redox status of the whole organism or particular organ can be studied in vivo by using magnetic resonance techniques (EPR and MRI) and paramagnetic stable free radicals – nitroxides. Here we review results obtained in vivo following the pharmacokinetics of nitroxides on experimental animals (and a few in humans) under various conditions. The focus was on conditions where the redox status has been altered by induced diseases or harmful agents, clearly demonstrating that various EPR/MRI/nitroxide combinations can reliably detect metabolically induced changes in the redox status of organs. These findings can improve our understanding of oxidative stress and provide a basis for studying the effectiveness of interventions aimed to modulate oxidative stress. Also, we anticipate that the in vivo EPR/MRI approach in studying the redox status can play a vital role in the clinical management of various pathologies in the years to come providing the development of adequate equipment and probes. PMID:26827126

  18. In vivo evaluation of different alterations of redox status by studying pharmacokinetics of nitroxides using magnetic resonance techniques

    Directory of Open Access Journals (Sweden)

    Goran Bačić

    2016-08-01

    Full Text Available Free radicals, particularly reactive oxygen species (ROS, are involved in various pathologies, injuries related to radiation, ischemia-reperfusion or ageing. Unfortunately, it is virtually impossible to directly detect free radicals in vivo, but the redox status of the whole organism or particular organ can be studied in vivo by using magnetic resonance techniques (EPR and MRI and paramagnetic stable free radicals – nitroxides. Here we review results obtained in vivo following the pharmacokinetics of nitroxides on experimental animals (and a few in humans under various conditions. The focus was on conditions where the redox status has been altered by induced diseases or harmful agents, clearly demonstrating that various EPR/MRI/nitroxide combinations can reliably detect metabolically induced changes in the redox status of organs. These findings can improve our understanding of oxidative stress and provide a basis for studying the effectiveness of interventions aimed to modulate oxidative stress. Also, we anticipate that the in vivo EPR/MRI approach in studying the redox status can play a vital role in the clinical management of various pathologies in the years to come providing the development of adequate equipment and probes.

  19. Identification and Quantification of Copper Sites in Zeolites by Electron Paramagnetic Resonance Spectroscopy

    DEFF Research Database (Denmark)

    Godiksen, Anita; Vennestrøm, Peter N. R.; Rasmussen, Søren Birk

    2017-01-01

    Recent quantitative electron paramagnetic resonance spectroscopy (EPR) data on different copper species present in copper exchanged CHA zeolites are presented and put into context with the literature on other copper zeolites. Results presented herein were obtained using ex situ and in situ EPR...

  20. The investigation of lithium formate hydrate, sodium dithionate and N-methyl taurine as clinical EPR dosimeters

    International Nuclear Information System (INIS)

    Lelie, S.; Hole, E.O.; Duchateau, M.; Schroeyers, W.; Schreurs, S.; Verellen, D.

    2013-01-01

    Introduction: EPR-dosimetry using L-α-alanine is an established method for measuring high doses of ionizing radiation. However, since a minimum dose of approximately 4 Gy is required to achieve sufficient low uncertainties (1–2%) for clinical application, alternative dosimeter materials are being inquired. Lithium formate (LiFo) monohydrate has been studied by several groups and has revealed several promising properties in the low dose region (<4 Gy). The fading properties, however, are somewhat unpredictable, and depend on properties not yet fully uncovered. This paper reports the results from a study of lithium formate hydrate and N-methyl taurine as potential low dose EPR dosimeters. Methods and materials: Pellet shaped dosimeters of lithium formate monohydrate, lithium formate hydrate, sodium dithionate and N-methyl taurine were produced using a manual Weber press, L-α-alanine was obtained from Harwell dosimeters and irradiated using 60 kV and 6 MV X-ray beams, and Co-60 gamma-rays to a dose of 30 Gy and dose ranges of 0.5–100 Gy and 2–20 Gy respectively. The dosimeters were measured using an Electron Paramagnetic Resonance (EPR)-spectrometer. The detector responses for 6 MV and Co-60 radiation beams, the fading behaviors and signal shape in time were investigated. Results: Lithium formate monohydrate and lithium formate hydrate are apparently associated with near identical EPR-spectra (mainly one broad line), and the same spectrum arises for all radiation energies investigated. The shape of the EPR resonance remains constant with time, but the intensities decreases, and the fading is more prominent for the monohydrate than for the hydrate. The EPR resonance associated with N-methyl taurine is more complex than the resonance associated with LiFo and it changes with time, implying radical transitions and growth. Conclusions: The study showed that lithium formate hydrate is a strong candidate for EPR dosimetry with slightly better fading characteristics

  1. EPR evidence for thermally excited triplet states in exinite, vitrinite and inertinite separated from bituminous coal

    Energy Technology Data Exchange (ETDEWEB)

    Slowik, G.P.; Wojtowicz, W.; Wieckowski, A.B. [University of Zielona Gora, Zielona Gora (Poland). Inst. of Physics

    2005-07-01

    In this work we have made an electron spin resonance (EPR) study of macerals obtained from the lithotype clarain separated from Polish medium-rank coal (85.6 wt.% C). For three macerals (exinite, vitrinite, and inertinite), the temperature dependence of intensity of EPR spectra in the temperature range of 100-373 K was investigated. The experimentally obtained EPR spectra of macerals were fitted by curves of the derivatives of the Gaussian and Lorentzian functions. The best fitting was obtained, when the experimental EPR spectra were assumed to be a superposition of three lines, for exinite and vitrinite - a broad Gaussian (G), a broad Lorentzian (L1) and a narrow Lorentzian (L3) line, but for inertinite of two lines - a narrow Lorentzian (L2) and a narrow Lorentzian (L3) line. The computer-assisted fitting has shown that each individual component line has similar values of resonance field, but different linewidths and amplitudes. The temperature dependence of line intensity I of the broad Gaussian (G) and narrow Lorentzian (L2 and L3) lines fulfils the Curie law in the form I = C/T or IT = C, whereas the broad Lorentzian (L1) line does not fulfil the Curie law. In the last case the temperature dependence of the Lorentzian (L1) component was fitted by the relation I = C/T + B/(T(3 + exp(J/kT))) or IT C + B/(3 + exp(J/kT))), valid for thermally excited triplet states (S = 1). For exinite and vitrinite the curves presenting the temperature dependence of the product IT versus temperature T were resolved into two curves, one for paramagnetic centres in the doublet state (S = ), and the other for paramagnetic centres in the thermally excited triplet state (S = 1).

  2. The Relationship Between Dopamine Neurotransmitter Dynamics and the Blood-Oxygen-Level-Dependent (BOLD Signal: A Review of Pharmacological Functional Magnetic Resonance Imaging

    Directory of Open Access Journals (Sweden)

    Tyler J. Bruinsma

    2018-04-01

    Full Text Available Functional magnetic resonance imaging (fMRI is widely used in investigations of normal cognition and brain disease and in various clinical applications. Pharmacological fMRI (pharma-fMRI is a relatively new application, which is being used to elucidate the effects and mechanisms of pharmacological modulation of brain activity. Characterizing the effects of neuropharmacological agents on regional brain activity using fMRI is challenging because drugs modulate neuronal function in a wide variety of ways, including through receptor agonist, antagonist, and neurotransmitter reuptake blocker events. Here we review current knowledge on neurotransmitter-mediated blood-oxygen-level dependent (BOLD fMRI mechanisms as well as recently updated methodologies aimed at more fully describing the effects of neuropharmacologic agents on the BOLD signal. We limit our discussion to dopaminergic signaling as a useful lens through which to analyze and interpret neurochemical-mediated changes in the hemodynamic BOLD response. We also discuss the need for future studies that use multi-modal approaches to expand the understanding and application of pharma-fMRI.

  3. Study of paramagnetic defect centers in as-grown and annealed TiO2 anatase and rutile nanoparticles by a variable-temperature X-band and high-frequency (236 GHz) EPR.

    Science.gov (United States)

    Misra, S K; Andronenko, S I; Tipikin, D; Freed, J H; Somani, V; Prakash, Om

    2016-03-01

    Detailed EPR investigations on as-grown and annealed TiO 2 nanoparticles in the anatase and rutile phases were carried out at X-band (9.6 GHz) at 77, 120-300 K and at 236 GHz at 292 K. The analysis of EPR data for as-grown and annealed anatase and rutile samples revealed the presence of several paramagnetic centers: Ti 3+ , O - , adsorbed oxygen (O 2 - ) and oxygen vacancies. On the other hand, in as-grown rutile samples, there were observed EPR lines due to adsorbed oxygen (O 2 - ) and the Fe 3+ ions in both Ti 4+ substitutional positions, with and without coupling to an oxygen vacancy in the near neighborhood. Anatase nanoparticles were completely converted to rutile phase when annealed at 1000° C, exhibiting EPR spectra similar to those exhibited by the as-grown rutile nanoparticles. The high-frequency (236 GHz) EPR data on anatase and rutile samples, recorded in the region about g = 2.0 exhibit resolved EPR lines, due to O - and O 2 - ions enabling determination of their g-values with higher precision, as well as observation of hyperfine sextets due to Mn 2+ and Mn 4+ ions in anatase.

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

    DEFF Research Database (Denmark)

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

    2000-01-01

    The reductions of K2Cr2O7 by catecholamines, DOPA, DOPA-beta,beta-d2, N-acetyl-DOPA, alpha-methyl-DOPA, dopamine, adrenaline, noradrenaline, catechol, 1,2-dihydroxybenzoic acid (DHBA), and 4-tert-butylcatechol (TBC), produce a number of Cr(V) electron paramagnetic resonance (EPR) signals. These s......The reductions of K2Cr2O7 by catecholamines, DOPA, DOPA-beta,beta-d2, N-acetyl-DOPA, alpha-methyl-DOPA, dopamine, adrenaline, noradrenaline, catechol, 1,2-dihydroxybenzoic acid (DHBA), and 4-tert-butylcatechol (TBC), produce a number of Cr(V) electron paramagnetic resonance (EPR) signals...... deuteration or enrichment with 15N), and simulation of the signals, show that the superhyperfine couplings originate from the side chain protons, confirming that the catecholamine ligands are cyclized. At pH 3.5, a major short-lived EPR signal is observed for many of the substrates at g(iso) approximately 1......) species with a sixth ligand (e.g. H2O). Addition of catalase or deoxygenation of the solutions did not affect the main EPR signals. When the substrates were in excess (pH > 4.5), primary and secondary (cyclized) semiquinones were also detected. Semiquinone stabilization by Zn(II) complexation yielded...

  5. Steering, Entanglement, Nonlocality, and the EPR Paradox

    Science.gov (United States)

    Wiseman, Howard; Jones, Steve; Andrew, Doherty

    2007-06-01

    The concept of steering was introduced by Schroedinger in 1935 as a generalization of the EPR paradox for arbitrary pure bipartite entangled states and arbitrary measurements by one party. Until now, it has never been rigorously defined, so it has not been known (for example) what mixed states are steerable (that is, can be used to exhibit steering). We provide an operational definition, from which we prove (by considering Werner states and Isotropic states) that steerable states are a strict subset of the entangled states, and a strict superset of the states that can exhibit Bell-nonlocality. For arbitrary bipartite Gaussian states we derive a linear matrix inequality that decides the question of steerability via Gaussian measurements, and we relate this to the original EPR paradox.

  6. The long way to the EPR

    International Nuclear Information System (INIS)

    Berke, C.

    1997-01-01

    At the joint conference organized by the German Kerntechnische Gesellschaft (KTG) e.V. and the French Societe Francaise d'Energie Nucleaire (SFEN) in Cologne, the announcement was made on October 20, 1997 that Jean Claude Leny will be appointed Honorary Member of KTG. For reasons of ill health the new honorary member was prevented from attending the conference. In his place, Claus Berke sketched the history of the European Pressurized Water Reactor (EPR) and presented an overview of nuclear development in France and in Germany. Developing one standard reactor model in the primary objective of German-French cooperation in reactor development. The EPR is to replace the present nuclear generating units in France and Germany after the end of their planned service life, and is to be marketed as a standard export line. (orig.) [de

  7. EPR becomes reality at Finland's Olkiluoto 3

    International Nuclear Information System (INIS)

    Gueldner, R.; Giese, U.

    2005-01-01

    The EPR is a third-generation pressurized water reactor (PWR). Its development was started in 1992 by Framatome and Siemens within a Franco-German partnership. Since 2001 this work has been continued by Framatome ANP, which was formed when the two companies merged their nuclear businesses. The French company AREVA, world market leader in nuclear technology, holds a 66% share in Framatome ANP, with Siemens owning 34%. From the very start, development of the EPR was focused on improving plant safety and economics even further. The new reactor development was jointly financed together with the leading power utilities of both countries. The first steps towards realization of an EPR nuclear power plant were taken at Olkiluoto, Finland in 2004, consisting of initial preparation of the construction site. By mid-February 2005 the local municipality - Eurajoki - had issued a construction permit, and the Finnish Government a construction license pursuant to the Finnish Nuclear Energy Act. This had been preceded by a preliminary safety assessment prepared by the Finnish Radiation and Nuclear Safety Authority (STUK) for the Finnish Ministry of Trade and Industry in which STUK verified that it did not see any safety-related issues opposing issuance of the nuclear construction license. STUK emphasized that the evolutionary design of the EPR had been further improved by AREVA compared to the previous product lines. Concreting work began this spring and the unit will start commercial operation in 2009. Construction of an EPR has also been given the political go-ahead in France. According to the utility Electricite de France (EDF) the new reactor will be built as a forerunner of a later series at the site of Flamanville in Normandy. Construction is scheduled to begin in 2007. An EPR nuclear power plant has a rated electric capacity of around 1600 MW, depending on specific site conditions. Being the product of intense bilateral cooperation the EPR combines the technological

  8. A theoretical interpretation of EPR and ENDOR

    International Nuclear Information System (INIS)

    Matos, M.O.M. de.

    1975-08-01

    To interpret the EPR and ENDOR results of the U 2 center in SrF 2 , two wavefunctions are proposed to describe the unpaired electron of the defect. Use is made of two different models in order to obtain the wavefunctions: the Heitler-London and that of molecular orbitals models. The Pauli repulsion (overlap of wavefunctions) is discussed as well as covalency mechanisms and their influence in the calculation of the hyperfine constants due to magnetic interaction of the unpaired electron and the magnetic nucleus of the cristal. A small amount of covalency between the ground state of the interstitial Hydrogen atom and the 2p shell of the F - ions of the first cristaline shell is introduced fenomenologically in the molecular orbitals model. Both methods are discussed by comparing the theoretical calculations of the hyperfine constants with the measured experimental values obtained with the EPR and ENDOR techniques. (Author) [pt

  9. Holographic EPR pairs, wormholes and radiation

    Science.gov (United States)

    Chernicoff, Mariano; Güijosa, Alberto; Pedraza, Juan F.

    2013-10-01

    As evidence for the ER = EPR conjecture, it has recently been observed that the string that is holographically dual to an entangled quark-antiquark pair separating with (asymptotically) uniform acceleration has a wormhole on its worldsheet. We point out that a two-sided horizon and a wormhole actually appear for much more generic quark-antiquark trajectories, which is consistent with the fact that the members of an EPR pair need not be permanently out of causal contact. The feature that determines whether the causal structure of the string worldsheet is trivial or not turns out to be the emission of gluonic radiation by the dual quark and antiquark. In the strongly-coupled gauge theory, it is only when radiation is emitted that one obtains an unambiguous separation of the pair into entangled subsystems, and this is what is reflected on the gravity side by the existence of the worldsheet horizon.

  10. Teichmuller Space Resolution of the EPR Paradox

    Science.gov (United States)

    Winterberg, Friedwardt

    2013-04-01

    The mystery of Newton's action-at-a-distance law of gravity was resolved by Einstein with Riemann's non-Euclidean geometry, which permitted the explanation of the departure from Newton's law for the motion of Mercury. It is here proposed that the similarly mysterious non-local EPR-type quantum correlations may be explained by a Teichmuller space geometry below the Planck length, for which an experiment for its verification is proposed.

  11. Steering, Entanglement, Nonlocality, and the EPR Paradox

    OpenAIRE

    Wiseman, H. M.; Jones, S. J.; Doherty, A. C.

    2006-01-01

    The concept of steering was introduced by Schrodinger in 1935 as a generalization of the EPR paradox for arbitrary pure bipartite entangled states and arbitrary measurements by one party. Until now, it has never been rigorously defined, so it has not been known (for example) what mixed states are steerable (that is, can be used to exhibit steering). We provide an operational definition, from which we prove (by considering Werner states and Isotropic states) that steerable states are a strict ...

  12. Seventy Years of the EPR Paradox

    Science.gov (United States)

    Kupczynski, Marian

    2006-11-01

    In spite of the fact that statistical predictions of quantum theory (QT) can only be tested if large amount of data is available a claim has been made that QT provides the most complete description of an individual physical system. Einstein's opposition to this claim and the paradox he presented in the article written together with Podolsky and Rosen in 1935 inspired generations of physicists in their quest for better understanding of QT. Seventy years after EPR article it is clear that without deep understanding of the character and limitations of QT one may not hope to find a meaningful unified theory of all physical interactions, manipulate qubits or construct a quantum computer.. In this paper we present shortly the EPR paper, the discussion, which followed it and Bell inequalities (BI). To avoid various paradoxes we advocate purely statistical contextual interpretation (PSC) of QT. According to PSC a state vector is not an attribute of a single electron, photon, trapped ion or quantum dot. A value of an observable assigned to a physical system has only a meaning in a context of a particular physical experiment PSC does not provide any mental space-time picture of sub phenomena. The EPR paradox is avoided because the reduction of the state vector in the measurement process is a passage from a description of the whole ensemble of the experimental results to a particular sub-ensemble of these results. We show that the violation of BI is neither a proof of the completeness of QT nor of its non-locality. Therefore we rephrase the EPR question and ask whether QT is "predictably "complete or in other words does it provide the complete description of experimental data. To test the "predictable completeness" it is not necessary to perform additional experiments it is sufficient to analyze more in detail the existing experimental data by using various non-parametric purity tests and other specific statistical tools invented to study the fine structure the time-series.

  13. Seventy Years of the EPR Paradox

    OpenAIRE

    Kupczynski, Marian

    2007-01-01

    In spite of the fact that statistical predictions of quantum theory (QT) can only be tested if large amount of data is available a claim has been made that QT provides the most complete description of an individual physical system. Einstein's opposition to this claim and the paradox he presented in the article written together with Podolsky and Rosen in 1935 inspired generations of physicists in their quest for better understanding of QT. Seventy years after EPR article it is clear that witho...

  14. Is the EPR paradox really a paradox?

    OpenAIRE

    Tartaglia, A.

    1998-01-01

    The EPR paradox and the meaning of the Bell inequality are discussed. It is shown that considering the quantum objects as carrying with them ''instruction kits'' telling them what to do when meeting a measurement apparatus any paradox disappears. In this view the quantum state is characterized by the prescribed behaviour rather than by the specific value a parameter assumes as a result of an interaction.

  15. Should the EPR be financed by industrialists?

    International Nuclear Information System (INIS)

    Jemain, A.

    2005-01-01

    As a reciprocal arrangement, the industrialists should be invited to contribute to the financing of the new generation reactor EPR (European pressurized reactor) which will be built in Flamanville (Manche, France). In exchange to their financial participation, the industrialists will receive the contractual warranty of stable electricity prices during 10 to 15 years periods. This short paper presents the opposite opinion of two representative of French industries concerning this proposal. Short paper. (J.S.)

  16. EPR Test with Photons and Kaons Analogies

    CERN Document Server

    Gisin, Nicolas

    2001-01-01

    We present a unified formalism describing EPR test using spin 1/2 particles, photons and kaons. This facilitates the comparison between existing experiments using photons and kaons. It underlines the similarities between birefringence and polarization dependent losses that affects experiments using optical fibers and mixing and decay that are intrinsic to the kaons. We also discuss the limitation these two characteristics impose on the testing of Bell's inequality.

  17. On Popper's new EPR-Experiment

    International Nuclear Information System (INIS)

    Bedford, D.; Selleri, F.

    1985-01-01

    It is scientifically reasonable to search for particular statistical ensembles to which the standard quantum rules (like Heisenberg relations) do not apply: these rules would instead be applicable to more general statistical ensembles (which might be called ''standard quantum ensembles''). Along these lines, Popper has recently proposed what he calls ''a new version of the EPR experiment'' in which the Copenhagen and statistical interpretations of quantum mechanics apparently lead to distinguishably different predictions

  18. Self-testing through EPR-steering

    International Nuclear Information System (INIS)

    Šupić, Ivan; Hoban, Matty J

    2016-01-01

    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. (paper)

  19. The Finnish EPR dependent on a bridge

    International Nuclear Information System (INIS)

    Dupin, L.

    2010-01-01

    A new conflict has emerged between the main contractor Areva and its client TVO, the Finnish energy group. The qualification of a handling bridge has delayed the OL3 project of third EPR reactor at Olkiluoto, Finland. The disagreement concerns the testing procedure and may induce a two year delay in the completion of the project which is now planned for 2012 instead of 2010 initially. (J.S.)

  20. The EPR operators are trained on simulator

    International Nuclear Information System (INIS)

    Maincent, G.

    2009-01-01

    Three years before the EPR reactor of Flamanville (Normandie, France) is generating its very first kilowatt hours, Electricite de France has started to train its teams on a simulator which reproduces the man-machine interface of the future nuclear power plant. The simulator used is an evolutive tool specific to the Flamanville reactor and capable to test about 20 different accidental situations. (J.S.)