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Sample records for integrated paramagnetic resonance

  1. Electron paramagnetic resonance

    CERN Document Server

    Al'tshuler, S A

    2013-01-01

    Electron Paramagnetic Resonance is a comprehensive text on the field of electron paramagnetic resonance, covering both the theoretical background and the results of experiment. This book is composed of eight chapters that cover theoretical materials and experimental data on ionic crystals, since these are the materials that have been most extensively studied by the methods of paramagnetic resonance. The opening chapters provide an introduction to the basic principles of electron paramagnetic resonance and the methods of its measurement. The next chapters are devoted to the theory of spectra an

  2. Electron Paramagnetic Resonance Spectroscopy

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 20; Issue 11. Electron Paramagnetic Resonance Spectroscopy: Biological Applications. B G Hegde. General Article Volume 20 Issue 11 November 2015 pp 1017-1032. Fulltext. Click here to view fulltext PDF. Permanent link:

  3. 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 ...

  4. 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.

  5. 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.

  6. 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

  7. 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

  8. Theoretical study of the electron paramagnetic resonance ...

    Indian Academy of Sciences (India)

    conveniently investigated by means of electron paramagnetic resonance (EPR). In ... ion Ir2+ can experience the Jahn–Teller effect by means of vibration interaction, ... Similarly, k. (and k ) are the orbital reduction factors arising from the anisotropic interactions of the orbital angular momentum operator. From the cluster ...

  9. A superheterodyne spectrometer for electronic paramagnetic. Resonance

    International Nuclear Information System (INIS)

    Laffon, J.L.

    1963-12-01

    After a few generalities about electron paramagnetic resonance, a consideration of different experimental techniques authorises the choice of a particular type of apparatus. An EPR superheterodyne spectrometer built in the laboratory and having a novel circuit is described in detail. With this apparatus, many experimental results have been obtained and some of these are described as example. (author) [fr

  10. The application of electron paramagnetic resonance in biomedical research

    International Nuclear Information System (INIS)

    Qu Ximei; Wang Liqin; Zhang Wenyi; Liu Zhongchao; Cui Songye; Feng Xin; Jiaoling

    2013-01-01

    Electron paramagnetic resonance technique has been found more than half a century, for free radicals detection application, it has been applied to various research studies, and promotes the development of the biomedicine. This article summarized the various free radicals measurement by the electron paramagnetic resonance in biology tissue, and the application of the spin labeling and electron paramagnetic resonance imaging technology in biomedicine. (authors)

  11. Electron paramagnetic resonance of transition ions

    CERN Document Server

    Abragam, Anatole

    1970-01-01

    This book is a reissue of a classic Oxford text, and provides a comprehensive treatment of electron paramagnetic resonance of ions of the transition groups. The emphasis is on basic principles, with numerous references to publications containing further experimental results and more detailed developments of the theory. An introductory survey gives a general understanding, and a general survey presents such topics as the classical and quantum resonance equations, thespin-Hamiltonian, Endor, spin-spin and spin-lattice interactions, together with an outline of the known behaviour of ions of each

  12. 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

  13. Electron paramagnetic resonance dosimetry using synthetic hydroxyapatite

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Kwon; Kim, Hwi Young; Ye, Sung Joon [Seoul National University, Seoul (Korea, Republic of); Hirata, Hiroshi [Hokkaido University, Sapporo (Japan); Park, Jong Min [Seoul National University Hospital, Seoul (Korea, Republic of)

    2014-11-15

    The victims exposed doses under 3.5-4.0 Gy have chance to survive if treated urgently. To determine the priority of treatment among a large number of victims, the triage – distinguishing patients who need an urgent treatment from who may not be urgent – is necessary based on radiation biodosimetry. A current gold standard for radiation biodosimetry is the chromosomal assay using human lymphocytes. But this method requires too much time and skilled labors to cover the mass victims in radiation emergencies. Electron paramagnetic resonance (EPR) has been known for its capability of quantifying radicals in matters. EPR dosimetry is based on the measurement of stable radiation-induced radicals in tooth enamel. Hydroxyapatite (HAP) (Ca10(PO4)6(OH)2) contained in tooth enamel is a major probe for radiation dose reconstruction. This HAP dosimetry study was performed using a novel EPR spectrometer in Hokkaido University, Japan. The EPR dose-response curve was made using HAP samples. The blind test using 250 cGy samples showed the feasibility of EPR dosimetry for the triage purpose.

  14. 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)

  15. Electron paramagnetic resonance dosimetry in fingernails

    International Nuclear Information System (INIS)

    Romanyukha, Alex; Benevides, Luis A.; Reyes, Ricardo; Trompier, Francois; Clairand, Isabelle; Swartz, Harold M.

    2008-01-01

    Full text: Based on the capabilities of new instrumentation and the experience gained in the use of teeth for 'after-the-fact' dosimetry, we have undertaken a systematic electron paramagnetic resonance (EPR) study of irradiated fingernails. There have been only a modest number of previous studies of radiation-induced signals in fingernails. While these have given us some promising aspects, overall results have been inconsistent. The most significant problem of EPR fingernail dosimetry is the presence of two signals of non-radiation origin that overlap the radiation-induced signal (RIS), making it almost impossible to do dose measurements below 5 Gy. Historically, these two non-radiation components were named mechanically-induced signal (MIS) and background signal (BKS). In order to investigate them in detail, three different methods of MIS and BKS mutual isolation have been developed and implemented. Having applied these methods, we were able to understand that fingernail tissue, after cut, can be modeled as a deformed sponge, where the MIS and BKS are associated with the stress from elastic and plastic deformations respectively. A sponge has a unique mechanism of mechanical stress absorption, which is necessary for fingernails in order to perform its everyday function of protecting the fingertips from hits and trauma. Like a sponge, fingernails are also known to be an effective water absorber. When a sponge is saturated with water, it tends to restore to its original shape, and when it looses water, it becomes deformed again. The same happens to fingernail tissue. Our suggested interpretation of the mechanical deformation in fingernails gives also a way to distinguish between the MIS and RIS. Obtained results show that the MIS in irradiated fingernails can be almost completely eliminated without a significant change to the RIS by soaking the sample for 10 minutes in water. This is an ongoing study but even at its present state of development, it has shown that it

  16. Multifrequency Electron Paramagnetic Resonance Theory and Applications

    CERN Document Server

    Misra, Sushil K

    2011-01-01

    Filling the gap for a systematic, authoritative, and up-to-date review of this cutting-edge technique, this book covers both low and high frequency EPR, emphasizing the importance of adopting the multifrequency approach to study paramagnetic systems in full detail by using the EPR method. In so doing, it discusses not only the underlying theory and applications, but also all recent advances -- with a final section devoted to future perspectives.

  17. Introduction to Spin Label Electron Paramagnetic Resonance Spectroscopy of Proteins

    Science.gov (United States)

    Melanson, Michelle; Sood, Abha; Torok, Fanni; Torok, Marianna

    2013-01-01

    An undergraduate laboratory exercise is described to demonstrate the biochemical applications of electron paramagnetic resonance (EPR) spectroscopy. The beta93 cysteine residue of hemoglobin is labeled by the covalent binding of 3-maleimido-proxyl (5-MSL) and 2,2,5,5-tetramethyl-1-oxyl-3-methyl methanethiosulfonate (MTSL), respectively. The excess…

  18. 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

  19. New possibilities for using laser polarimetry technology to study electron paramagnetic resonance

    Energy Technology Data Exchange (ETDEWEB)

    Aleksandrov, E V; Zapasskii, V S

    1982-01-01

    Optical methods of recording electron paramagnetic resonance which arose in the early 50's as applied to the problem of recording the magnetic resonance of excited atoms is at the present time widely used in studying the electron paramagnetic resonance of the ground and excited states of free atoms and paramagnetic centers in condensed media. At the present time attention is devoted to the additional possibilities of optical methods of electron paramagnetic resonance which are realized using laser sources.

  20. Paramagnetic resonance and electronic conduction in organic semiconductors

    International Nuclear Information System (INIS)

    Nechtschein, M.

    1963-01-01

    As some organic bodies simultaneously display semi-conducting properties and a paramagnetism, this report addresses the study of conduction in organic bodies. The author first briefly recalls how relationships between conductibility and Electron Paramagnetic Resonance (EPR) can be noticed in a specific case (mineral and metallic semiconductors). He discusses published results related to paramagnetism and conductibility in organic bodies. He reviews various categories of organic bodies in which both properties are simultaneously present. He notably addresses radical molecular crystals, non-radical molecular crystals, charge transfer complexes, pyrolyzed coals, and pseudo-ferromagnetic organic structures. He discusses the issue of relationships between conduction (charge transfer by electrons) and ERP (which reveals the existence of non-paired electrons which provide free spins)

  1. Contribution to the study of electron paramagnetic resonance and relaxation

    International Nuclear Information System (INIS)

    Theobald, Jean-Gerard

    1962-01-01

    This research thesis reports an experimental work which comprises the development of a very practical and very sensitive electron paramagnetic resonance spectrometer, and the use of this equipment for the study of irradiated substances and carbons. By studying electronic resonance signals by fast modulation of the magnetic field, the author studied phenomena of quick passage in electronic resonance, and showed that the study of these phenomena requires observation systems with a particularly large bandwidth. He reports the measurement of the line width of packs of spins of inhomogeneous lines by two different methods [fr

  2. Radiation dosimetry in human bone using electron paramagnetic resonance

    International Nuclear Information System (INIS)

    Breen, S.L.

    1995-01-01

    Accurate measurements of dose in bone are required in order to improve the dosimetry of systemic radiotherapy for osseous metastases. Bone is an integrating dosimeter which records the radiation history of the skeleton. During irradiation, electrons become trapped in the crystalline component of bone mineral (hydroxyapatite). The traps are very stable; at room temperature, emptying of the traps occurs with a half-life of many years. The population of trapped unpaired electrons is proportional to the radiation dose administered to the bone and can be measured in excised bone samples using electron paramagnetic resonance (EPR). EPR spectra of synthetic hydroxyapatite, irradiated with Co-60, were obtained at room temperature and at 77 K. At room temperature, the radiation-induced signal, with a g-value of 2.001 ± 0.001 increased linearly with absorbed dose above a lower threshold of 3 Gy, up to doses of 200 Gy. In contrast with pure hydroxyapatite, EPR spectra of excised human bone showed a broad 'native' signal, due to the organic component of bone, which masks the dosimetrically important signal. This native signal is highly variable from sample to sample and precludes the use of EPR as an absolute dosimetry technique. However, after subtraction of the background signal, irradiated human bone showed a linear response with a lower limit of measurement similar to that of synthetic hydroxyapatite. Bone is an in vivo linear dosimeter which can be exploited to develop accurate estimates of the radiation dose delivered during systemic radiotherapy and teletherapy. However, improved sensitivity of the EPR dosimetry technique is necessary before it can be applied reliably in clinical situations. (author)

  3. Moessbauer effect and electron paramagnetic resonance studies on yeast aconitase

    International Nuclear Information System (INIS)

    Suzuki, Takashi; Maeda, Yutaka; Sakai, Hiroshi; Fujimoto, Shigeru; Morita, Yuhei.

    1975-01-01

    The Moessbauer effect and electron paramagnetic resonance (EPR) of yeast aconitase [EC 4.2.1.3] purified from the cells of Candida lipolytica (ATCC 20114) were measured. Moessbauer spectra suggested that yeast acontitase mostly contained two high-spin Fe(III) ions in an antiferromagnetically coupled binuclear complex that resembled oxidized 2 Fe ferredoxins, together with a small amount of high-spin Fe(II). EPR spectra recorded no signal at 77 0 K, but showed a slightly asymmetric signal centered at g=2.0 at 4.2 0 K, presumably due to the small amount of Fe(II) Fe(III) pairs. (auth.)

  4. Retrospective dosimetry of nail by Electron Paramagnetic Resonance

    International Nuclear Information System (INIS)

    Giannoni, Ricardo A.; Rodrigues Junior, Orlando

    2015-01-01

    The purpose of this study is to characterize samples of human nails, subjected to irradiation of high doses through Technical Electron Paramagnetic Resonance (EPR). The goal is to establish a dose/response relationship in order to assess dose levels absorbed by individuals exposed in radiation accidents situations, retrospectively. Samples of human nails were irradiated with gamma radiation, and received a dose of 20 Gy. EPR measurements performed on samples before irradiation identified EPR signals associated with defects caused by the mechanical action of the sample collection. After irradiation other species of free radicals, associated with the action of gamma radiation, have been identified

  5. In vivo imaging of a stable paramagnetic probe by pulsed-radiofrequency electron paramagnetic resonance spectroscopy

    DEFF Research Database (Denmark)

    Murugesan; Cook; Devasahayam

    1997-01-01

    , Recent advances in radiofrequency (RF) electronics have enabled the generation of pulses of the order of 10-50 ns. Such short pulses provide adequate spectral coverage for EPR studies at 300 MHz resonant frequency. Acquisition of free induction decays (FID) of paramagnetic species possessing...... inhomogeneously broadened narrow lines after pulsed excitation is feasible with an appropriate digitizer/averager. This report describes the use of time-domain RF EPR spectrometry and imaging for in vivo applications. FID responses were collected from a water-soluble, narrow line width spin probe within phantom...... samples in solution and also when infused intravenously in an anesthetized mouse. Using static magnetic field gradients and back-projection methods of image reconstruction, two-dimensional images of the spin-probe distribution were obtained in phantom samples as well as in a mouse. The resolution...

  6. Electron paramagnetic resonance in Cu-doped ZnO

    Science.gov (United States)

    Buchheit, R.; Acosta-Humánez, F.; Almanza, O.

    2016-04-01

    In this work, ZnO and Cu-doped ZnO nanoparticles (Zn1-xCuxO, x = 3%), with a calcination temperature of 500∘C were synthesized using the sol-gel method. The particles were analyzed using atomic absorption spectroscopy (AAS), X-ray diffraction (XRD) and electron paramagnetic resonance (EPR) at X-band, measurement in a temperature range from 90 K to room temperature. AAS confirmed a good correspondence between the experimental doping concentration and the theoretical value. XRD reveals the presence of ZnO phase in hexagonal wurtzite structure and a nanoparticle size for the samples synthesized. EPR spectroscopy shows the presence of point defects in both samples with g-values of g = 1.959 for shallow donors and g = 2.004 for ionized vacancies. It is important when these materials are required have been used as catalysts, as suggested that it is not necessary prepare them at higher temperature. A simulation of the Cu EPR signal using an anisotropic spin Hamiltonian was performed and showed good coincidence with the experimental spectra. It was shown that Cu2+ ions enter interstitial octahedral sites of orthorhombic symmetry in the wurtzite crystal structure. Temperature dependence of the EPR linewidth and signal intensity shows a paramagnetic behavior of the sample in the measurement range. A Néel temperature TN = 78 ± 19 K was determined.

  7. Data acquisition system for electronic paramagnetic resonance spectrophotometer

    International Nuclear Information System (INIS)

    Pena Eguiluz, R.

    1992-01-01

    In the Atomic and Molecular Physics Laboratory at the Physics Department of the Instituto Nacional de Investigaciones Nucleares (ININ), there is in operation an electronic paramagnetic resonance spectrometer (EPR). This equipment is utilized for determine, the distribution of the absorbed energy intensity for a sample of paramagnetic substance by means of the study and analysis of its emission lines spectrum. The useful information is provided as a graphic result showing the spectrum corresponding to the analyzed sample. In similar devices like this, the researchers problem, trying to get the important information, is a hard and imprecise work, thus, this process of find the ordinate magnitudes of a approximately two hundred points, equal spaced in the spectrum, is carried out completely by hand. After this, the information is captured and processed in a personal computer. As a solution for this problem, an interface in both aspects, hardware and software adaptable to a personal computer, was designed and constructed. This interface is able to: a) To get and digitized the analogical signal, that represents the corresponding spectrum curve. b) It stores the digitized information in files and c) It displays in graphic mode the stored data, and then these are normalized in order to be transferred to a statistics and analytical software packets (Author)

  8. Magnetic nanoparticle imaging using multiple electron paramagnetic resonance activation sequences

    International Nuclear Information System (INIS)

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

    2015-01-01

    Magnetic nanoparticles play an important role in several biomedical applications such as hyperthermia, drug targeting, and disease detection. To realize an effective working of these applications, the spatial distribution of the particles needs to be accurately known, in a non-invasive way. Electron Paramagnetic Resonance (EPR) is a promising and sensitive measurement technique for recovering these distributions. In the conventional approach, EPR is applied with a homogeneous magnetic field. In this paper, we employ different heterogeneous magnetic fields that allow to stabilize the solution of the associated inverse problem and to obtain localized spatial information. A comparison is made between the two approaches and our novel adaptation shows an average increase in reconstruction quality by 5% and is 12 times more robust towards noise. Furthermore, our approach allows to speed up the EPR measurements while still obtaining reconstructions with an improved accuracy and noise robustness compared to homogeneous EPR

  9. Tuner and radiation shield for planar electron paramagnetic resonance microresonators

    International Nuclear Information System (INIS)

    Narkowicz, Ryszard; Suter, Dieter

    2015-01-01

    Planar microresonators provide a large boost of sensitivity for small samples. They can be manufactured lithographically to a wide range of target parameters. The coupler between the resonator and the microwave feedline can be integrated into this design. To optimize the coupling and to compensate manufacturing tolerances, it is sometimes desirable to have a tuning element available that can be adjusted when the resonator is connected to the spectrometer. This paper presents a simple design that allows one to bring undercoupled resonators into the condition for critical coupling. In addition, it also reduces radiation losses and thereby increases the quality factor and the sensitivity of the resonator

  10. 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

  11. Application of electron paramagnetic resonance to identify irradiated soybean

    International Nuclear Information System (INIS)

    Bhaskar, S.; Behere, Arun; Sharma, Arun

    2006-01-01

    Full text: Electron paramagnetic resonance spectroscopy was applied to study free radicals in soy bean seed after gamma irradiation and to establish the potential of these radiation induced free radicals as the indicator of the radiation treatment. The radiation doses administered to the samples were 1 to 30 kGy. A stable doublet signal was detected at g = 2.0279 with hyperfine coupling constant of 2.8 mT, produced only by radiolysis. This signal can be used to identify irradiated soy bean seed samples. With the increase of the radiation dose the central line intensity and the intensities of the satellite lines showed almost a linear rise having linear correlation factors of 0.99724 and 0.99996, respectively. Thermal treatment at 373 deg K in air was studied. No line specific to thermolysis was observed. The spectrometer was operated with power 0.253 mW, microwave frequency 9.74 GHz, modulation frequency 100 kHz and scan range 10 mT. To study the stability of the signal, EPR spectra were obtained from the irradiated skin part of soy bean seeds samples following 1 and 90 days of storage after radiation treatment. The two satellite lines of g left = 2.0279 and g right 1.99529 were detected in all samples. This suggests that the signal is associated with a stable radical and therefore, the detection of a particular free radical as a marker of irradiation is proposed

  12. Effects of water on fingernail electron paramagnetic resonance dosimetry.

    Science.gov (United States)

    Zhang, Tengda; Zhao, Zhixin; Zhang, Haiying; Zhai, Hezheng; Ruan, Shuzhou; Jiao, Ling; Zhang, Wenyi

    2016-09-01

    Electron paramagnetic resonance (EPR) is a promising biodosimetric method, and fingernails are sensitive biomaterials to ionizing radiation. Therefore, kinetic energy released per unit mass (kerma) can be estimated by measuring the level of free radicals within fingernails, using EPR. However, to date this dosimetry has been deficient and insufficiently accurate. In the sampling processes and measurements, water plays a significant role. This paper discusses many effects of water on fingernail EPR dosimetry, including disturbance to EPR measurements and two different effects on the production of free radicals. Water that is unable to contact free radicals can promote the production of free radicals due to indirect ionizing effects. Therefore, varying water content within fingernails can lead to varying growth rates in the free radical concentration after irradiation-these two variables have a linear relationship, with a slope of 1.8143. Thus, EPR dosimetry needs to be adjusted according to the water content of the fingernails of an individual. When the free radicals are exposed to water, the eliminating effect will appear. Therefore, soaking fingernail pieces in water before irradiation, as many researchers have previously done, can cause estimation errors. In addition, nails need to be dehydrated before making accurately quantitative EPR measurements. © The Author 2016. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.

  13. Using an electron paramagnetic resonance method for testing motor oils

    Energy Technology Data Exchange (ETDEWEB)

    Krais, S; Tkac, T

    1982-01-01

    Using an ER-9 spectrometer from the Karl Zeiss company, the relative effectiveness is studied of antioxidation additives. Motor oils of the E group, M6AD, 465, M6AD, 466, M6AD 467, 15 W/40, S-3/2 M/4, R-950, which contain the antioxidation additive were tested in Petter AV-1 motors at a temperature of 50 degrees for 120 hours and Petter AVB at a temperature of 90 degrees for 53 hours. To measure the concentration of free radicals of the antioxidation additives one part of 2,2-diphenyl-1-picrylhydrazine (I), which forms stable dimagnetic products with the radicals of the antioxidation additives was introduced into each three parts of the oil. The reduction in the intensity of the signal of I was the measure of the radical concentration. The spectrum was taken for 1 to 2 minutes. The graphs of the dependence of the electron paramagnetic resonance on the test time and the concentration of I are built. The beginning and end of the induction period of oxidation of the oils and the change in the hourly activity of the PP was recorded.

  14. THz Electron Paramagnetic Resonance / THz Spectroscopy at BESSY II

    Directory of Open Access Journals (Sweden)

    Karsten Holldack

    2016-02-01

    Full Text Available The THz beamline at BESSY II employs high power broadband femto- to picosecond long THz pulses for magneto-optical THz and FIR studies. A newly designed set-up exploits the unique properties of ultrashort THz pulses generated by laser-energy modulation of electron bunches in the storage ring or alternatively from compressed electron bunches. Experiments from 0.15 to 5 THz (~ 5 – 150 cm-1 may be conducted at a user station equipped with a fully evacuated high resolution FTIR spectrometer (0.0063 cm-1, lHe cooled bolometer detectors, a THz TDS set-up and different sample environments, including a superconducting high field magnet (+11 T - 11T with variable temperature insert (1.5 K – 300 K, a sample cryostat and a THz attenuated total reflection chamber.  Main applications are Frequency Domain Fourier transform THz-Electron Paramagnetic Resonance (FD-FT THz-EPR, THz-FTIR spectroscopy and optical pump - THz probe time domain spectroscopy (TDS, with sub-ps time resolution.

  15. Cation Binding to Xanthorhodopsin: Electron Paramagnetic Resonance and Magnetic Studies.

    Science.gov (United States)

    Smolensky Koganov, Elena; Leitus, Gregory; Rozin, Rinat; Weiner, Lev; Friedman, Noga; Sheves, Mordechai

    2017-05-04

    Xanthorhodopsin (xR) is a member of the retinal protein family and acts as a proton pump in the cell membranes of the extremely halophilic eubacterium Salinibacter ruber. In addition to the retinal chromophore, xR contains a carotenoid, which acts as a light-harvesting antenna as it transfers 40% of the quanta it absorbs to the retinal. Our previous studies have shown that the CD and absorption spectra of xR are dramatically affected due to the protonation of two different residues. It is still unclear whether xR can bind cations. Electron paramagnetic resonance (EPR) spectroscopy used in the present study revealed that xR can bind divalent cations, such as Mn 2+ and Ca 2+ , to deionized xR (DI-xR). We also demonstrate that xR can bind 1 equiv of Mn 2+ to a high-affinity binding site followed by binding of ∼40 equiv in cooperative manner and ∼100 equiv of Mn 2+ that are weakly bound. SQUID magnetic studies suggest that the high cooperative binding of Mn 2+ cations to xR is due to the formation of Mn 2+ clusters. Our data demonstrate that Ca 2+ cations bind to DI-xR with a lower affinity than Mn 2+ , supporting the assumption that binding of Mn 2+ occurs through cluster formation, because Ca 2+ cations cannot form clusters in contrast to Mn 2+ .

  16. Enamel dose calculation by electron paramagnetic resonance spectral simulation technique

    International Nuclear Information System (INIS)

    Dong Guofu; Cong Jianbo; Guo Linchao; Ning Jing; Xian Hong; Wang Changzhen; Wu Ke

    2011-01-01

    Objective: To optimize the enamel electron paramagnetic resonance (EPR) spectral processing by using the EPR spectral simulation method to improve the accuracy of enamel EPR dosimetry and reduce artificial error. Methods: The multi-component superimposed EPR powder spectral simulation software was developed to simulate EPR spectrum models of the background signal (BS) and the radiation- induced signal (RS) of irradiated enamel respectively. RS was extracted from the multi-component superimposed spectrum of irradiated enamel and its amplitude was calculated. The dose-response curve was then established for calculating the doses of a group of enamel samples. The result of estimated dose was compared with that calculated by traditional method. Results: BS was simulated as a powder spectrum of gaussian line shape with the following spectrum parameters: g=2.00 35 and Hpp=0.65-1.1 mT, RS signal was also simulated as a powder spectrum but with axi-symmetric spectrum characteristics. The spectrum parameters of RS were: g ⊥ =2.0018, g ‖ =1.9965, Hpp=0.335-0.4 mT. The amplitude of RS had a linear response to radiation dose with the regression equation as y=240.74x + 76 724 (R 2 =0.9947). The expectation of relative error of dose estimation was 0.13. Conclusions: EPR simulation method has improved somehow the accuracy and reliability of enamel EPR dose estimation. (authors)

  17. Biophysical dose measurement using electron paramagnetic resonance in rodent teeth

    International Nuclear Information System (INIS)

    Khan, R.F.H.; Rink, W.J.; Boreham, D.R.

    2003-01-01

    Electron paramagnetic resonance (EPR) dosimetry of human tooth enamel has been widely used in measuring radiation doses in various scenarios. However, there are situations that do not involve a human victim (e.g. tests for suspected environmental overexposures, measurements of doses to experimental animals in radiation biology research, or chronology of archaeological deposits). For such cases we have developed an EPR dosimetry technique making use of enamel of teeth extracted from mice. Tooth enamel from both previously irradiated and unirradiated mice was extracted and cleaned by processing in supersaturated KOH aqueous solution. Teeth from mice with no previous irradiation history exhibited a linear EPR response to the dose in the range from 0.8 to 5.5 Gy. The EPR dose reconstruction for a preliminarily irradiated batch resulted in the radiation dose of (1.4±0.2) Gy, which was in a good agreement with the estimated exposure of the teeth. The sensitivity of the EPR response of mouse enamel to gamma radiation was found to be half of that of human tooth enamel. The dosimetric EPR signal of mouse enamel is stable up at least to 42 days after exposure to radiation. Dose reconstruction was only possible with the enamel extracted from molars and premolars and could not be performed with incisors. Electron micrographs showed structural variations in the incisor enamel, possibly explaining the large interfering signal in the non-molar teeth

  18. 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)

  19. Electrically-detected electron paramagnetic resonance of point centers in 6H-SiC nanostructures

    Czech Academy of Sciences Publication Activity Database

    Bagraev, N.T.; Gets, D.S.; Kalabukhova, E.N.; Klyachkin, L.E.; Malyarenko, A.M.; Mashkov, V.A.; Savchenko, Dariia; Shanina, B.D.

    2014-01-01

    Roč. 48, č. 11 (2014), s. 1467-1480 ISSN 1063-7826 R&D Projects: GA MŠk(CZ) LM2011029 Grant - others:SAFMAT(XE) CZ.2.16/3.1.00/22132 Institutional support: RVO:68378271 Keywords : electron paramagnetic resonance * electrically- detected electron paramagnetic resonance * 6H -SiC nanostructures * nitrogen-vacancy defect * point defect Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.739, year: 2014

  20. Electron paramagnetic resonance biophysical radiation dosimetry with tooth enamel

    International Nuclear Information System (INIS)

    Khan, Rao F.H.

    2003-01-01

    This thesis deals with the advancements made in the field of Electron Paramagnetic Resonance (EPR) for biophysical dosimetry with tooth enamel for accident, emergency, and retrospective radiation dose reconstruction. A methodology has been developed to measure retrospective radiation exposures in human tooth enamel. This entails novel sample preparation procedures with minimum mechanical treatment to reduce the preparation induced uncertainties, establish optimum measurement conditions inside the EPR cavity, post-process the measured spectrum with functional simulation of dosimetric and other interfering signals, and reconstruct dose. By using this technique, retrospective gamma exposures as low as 80±30 mGy have been successfully deciphered. The notion of dose modifier was introduced in EPR biodosimetry for low dose measurements. It has been demonstrated that by using the modified zero added dose (MZAD) technique for low radiation exposures, doses in 100 mGy ranges can be easily reconstructed in teeth that were previously thought useless for EPR dosimetry. Also, the use of a dose modifier makes robust dose reconstruction possible for higher radiation exposures. The EPR dosimetry technique was also developed for tooth samples extracted from rodents, which represent small tooth sizing. EPR doses in the molars, extracted from the mice irradiated with whole body exposures, were reassessed and shown to be correct within the experimental uncertainty. The sensitivity of human tooth enamel for neutron irradiation, obtained from the 3 MV McMaster K.N. Van de Graaff accelerator, was also studied. For the first time this work has shown that the neutron sensitivity of the tooth enamel is approximately 1/10th of the equivalent gamma sensitivity. Parametric studies for neutron dose rate and neutron energy within the available range of the accelerator, showed no impact on the sensitivity of the tooth enamel. Therefore, tooth enamel can be used as a dosimeter for both neutrons

  1. Electron paramagnetic resonance detection of carotenoid triplet states

    International Nuclear Information System (INIS)

    Frank, H.A.; Bolt, J.D.; deCosta, S.M.; Sauer, K.

    1980-01-01

    Triplet states of carotenoids have been detected by X-band electron paramagnetic resonance (EPR) and are reported here for the first time. The systems in which carotenoid triplets are observed include cells of photosynthetic bacteria, isolated bacteriochlorophyll-protein complexes, and detergent micelles which contain β-carotene. It is well known that if electron transfer is blocked following the initial acceptor in the bacterial photochemical reaction center, back reaction of the primary radical pair produces a bacteriochlorophyll dimer triplet. Previous optical studies have shown that in reaction centers containing carotenoids the bacteriochlorophyll dimer triplet sensitizes the carotenoid triplet. We have observed this carotenoid triplet state by EPR in reaction centers of Rhodopseudomonas sphaeroides, strain 2.4.1 (wild type), which contain the carotenoid spheroidene. The zero-field splitting parameters of the triplet spectrum are /D/ = 0.0290 +- 0.0005 cm -1 and /E/ = 0.0044 +-0.0006 cm -1 , in contrast with the parameters of the bacteriochlorophyll dimer triplet, which are /D/ = 0.0189 +- 0.0004 cm -1 and /E/ = 0.0032 +- 0.004 cm -1 . Bacteriochlorophyll in a light harvesting protein complex from Rps. sphaeroides, wild type, also sensitizes carotenoid triplet formation. In whole cells the EPR spectra vary with temperature between 100 and 10 K. Carotenoid triplets also have been observed by EPR in whole cells of Rps. sphaeroides and cells of Rhodospirillum rubrum which contain the carotenoid spirilloxanthin. Attempts to observe the triplet state EPR spectrum of β-carotene in numerous organic solvents failed. However, in nonionic detergent micelles and in phospholipid bilayer vesicles β-carotene gives a triplet state spectrum with /D/ = 0.0333 +- 0.0010 cm -1 and /E/ = 0.0037 +- 0.0010 cm -1 . 6 figures, 1 table

  2. Ferro-paramagnetic coupled resonant modes in GdEuCuO4

    International Nuclear Information System (INIS)

    Fainstein, A.; Tovar, M.

    1990-01-01

    Two paramagnetic resonances were observed in compound GdEuCuO 4 : one was originated in trivalent gadolinium paramagnetism, while the other is associated to a weak ferromagnetic mode in Cu-O planes. In this work, experimental results are presented that show an anisotropy and a strongly anomalous temperature dependence of Gd 3+ . A theoretical model was introduced which explains the data in terms of coupled ferro-paramagnetic resonant modes originated in spin exchange coupling of Cu and Gd. (Author). 9 refs., 4 figs

  3. Paramagnetic contrast media for magnetic resonance imaging of the central nervous system

    International Nuclear Information System (INIS)

    McNamara, M.T.

    1987-01-01

    Presently, a variety of radiofrequency (RF) and magnetic field gradient pulse sequences is used to manipulate magnetic resonance (MR) image contrast. Such manipulation may be performed by altering the RF pulse sequence repetition time (TR), the spin-echo delay time (TE), the inversion-delay time (TI), and the flip angle. The detection and characterization of a lesion or structure may thus be optimized. Although such contrast manipulation is noninvasive, magnetic resonance imaging (MRI) still suffers somewhat from lack of specificity. Also, the use of multiple imaging sequences to locate and characterize a lesion may prolong the imaging time and, thus, might place an economic burden on the system. Paramagnetic pharmaceuticals offer promise in this regard. They shorten tissue relaxation times, thus permitting the use of shorter imaging parameters, and in some circumstances, may obviate additional and more time-consuming pulse sequences. Paramagnetics could expand the sensitivity and specificity of MRI and provide functional information with regard to tissue perfusion, tissue viability, and blood-brain barrier integrity

  4. Point defects in crystalline zircon (zirconium silicate), ZrSiO4: electron paramagnetic resonance studies

    Science.gov (United States)

    Tennant, W. C.; Claridge, R. F. C.; Walsby, C. J.; Lees, N. S.

    This article outlines the present state of knowledge of paramagnetic defects in crystalline zircon as obtained mainly, but not exclusively, from electron paramagnetic resonance (EPR) studies in crystalline zircon (zirconium silicate, ZrSiO4). The emphasis is on single-crystal studies where, in principle, unambiguous analysis is possible. Firstly, the crystallography of zircon is presented. Secondly, the relationships between available crystal-site symmetries and the symmetries of observed paramagnetic species in zircon, and how these observations lead to unambiguous assignments of point-group symmetries for particular paramagnetic species are detailed. Next, spin-Hamiltonian (SH) analysis is discussed with emphasis on the symmetry relationships that necessarily exist amongst the Laue classes of the crystal sites in zircon, the paramagnetic species occupying those sites and the SH itself. The final sections of the article then survey the results of EPR studies on zircon over the period 1960-2002.

  5. Strongly driven electron spins using a Ku band stripline electron paramagnetic resonance resonator

    Science.gov (United States)

    Yap, Yung Szen; Yamamoto, Hiroshi; Tabuchi, Yutaka; Negoro, Makoto; Kagawa, Akinori; Kitagawa, Masahiro

    2013-07-01

    This article details our work to obtain strong excitation for electron paramagnetic resonance (EPR) experiments by improving the resonator's efficiency. The advantages and application of strong excitation are discussed. Two 17 GHz transmission-type, stripline resonators were designed, simulated and fabricated. Scattering parameter measurements were carried out and quality factor were measured to be around 160 and 85. Simulation results of the microwave's magnetic field distribution are also presented. To determine the excitation field at the sample, nutation experiments were carried out and power dependence were measured using two organic samples at room temperature. The highest recorded Rabi frequency was rated at 210 MHz with an input power of about 1 W, which corresponds to a π/2 pulse of about 1.2 ns.

  6. Electron paramagnetic resonance study on the ionizing radiation induced defects of the tooth enamel hydroxyapatite

    International Nuclear Information System (INIS)

    Oliveira, Liana Macedo de

    1995-01-01

    Hydroxyapatite is the main constituent of calcified tissues. Defects induced by ionizing radiations in this biomineral can present high stability and then, these are used as biological markers in radiological accidents, irradiated food identifying and geological and archaeological dating. In this work, paramagnetic centers induced on the enamel of the teeth by environmental ionizing radiation, are investigated by electron paramagnetic resonance (EPR). Decay thermal kinetic presents high complexity and shows the formation of different electron ligation energy centers and structures

  7. A superheterodyne spectrometer for electronic paramagnetic. Resonance; Spectrometre superheterodyne de resonance paramagnetique electronique

    Energy Technology Data Exchange (ETDEWEB)

    Laffon, J L [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1963-12-15

    After a few generalities about electron paramagnetic resonance, a consideration of different experimental techniques authorises the choice of a particular type of apparatus. An EPR superheterodyne spectrometer built in the laboratory and having a novel circuit is described in detail. With this apparatus, many experimental results have been obtained and some of these are described as example. (author) [French] Apres quelques generalites sur le phenomene de resonance paramagnetique electronique, une synthese des differentes techniques experimentales, permet de fixer le choix d'un type d'appareillage. Un spectrometre de RPE superheterodyne realise en laboratoire et comportant un circuit original est expose dans le detail. Cet appareil a permis de nombreux resultats experimentaux dont quelques-uns sont decrits a titre d'exemple. (auteur)

  8. Paramagnetic resonance and susceptibility of ilmenite, FeTiO3 crystal

    Science.gov (United States)

    Mcdonald, P. F.; Parasiris, A.; Pandey, R. K.; Gries, B. L.; Kirk, W. P.

    1991-01-01

    Large high-purity single crystals of FeTiO3 with ilmenite structure have been grown from a stoichiometric melt of Fe2O3 and TiO2 under an inert atmosphere using the modified Czochralski technique. Susceptibility and X-band paramagnetic resonance studies have been performed. Susceptibility measurements indicate a Neel temperature of about 59 K. The paramagnetic resonance spectrum for magnetic field perpendicular to the crystal c axis consists of a portion of a single, very intense approximately Lorentzian absorption line with its peak at about 600 G and half width at half maximum almost 1200 G. The absorption extends to zero magnetic field. For magnetic field approximately parallel to the c axis, the paramagnetic absorption is much smaller and may be considered a superposition of two approximately Lorentzian line shapes. The magnetic resonance measurements indicate a weak temperature dependence and large angular anisotropy.

  9. Magnetic resonance studies of isotopically labeled paramagnetic proteins: (2FE-2S) ferredoxins

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, H.; Xia, B.; Chae, Y.K.; Westler, W.M.; Markley, J.L. [Univ. of Wisconsin, Madison, WI (United States)

    1994-12-01

    Recent developments in NMR spectroscopy, especially multidimensional, multinuclear NMR techniques, have made NMR the most versatile tool available for studying protein structure and function in solution. Unlike diamagnetic proteins, paramagnetic proteins contain centers with unpaired electrons. These unpaired electrons interact with magnetic nuclei either through chemical bonds by a contact mechanism or through space by a pseudocontact mechanism. Such interactions make the acquisition and analysis of NMR spectra of paramagnetic proteins more challenging than those of diamagnetic proteins. Some NMR signals from paramagnetic proteins are shifted outside the chemical shift region characteristic of diamagnetic proteins; these {open_quotes}hyperfine-shifted{close_quotes} resonances originate from nuclei that interact with unpaired electrons from the paramagnetic center. The large chemical shift dispersion in spectra of paramagnetic proteins makes it difficult to excite the entire spectral window and leads to distortions in the baseline. Interactions with paramagnetic centers shorten T{sub 1} and T{sub 2} relaxation times of nuclei; the consequences are line broadening and lower spectral sensitivity. Scalar (through bond) and dipolar (through space) interactions between pairs of nuclei are what give rise to crosspeak signals in multi-dimensional NMR spectra of small diamagnetic proteins. When such interactions involve a nucleus that is strongly relaxed by interaction with a paramagnetic center, specialized methods may be needed for its detection or it may be completely undetectable by present nD NMR methods.

  10. 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.

  11. Electron paramagnetic resonance of the ns1 centers in crystals

    International Nuclear Information System (INIS)

    Nistor, S.V.; Ursu, I.

    1993-05-01

    The results of the EPR studies concerning the paramagnetic centers with ns 1 (N=n>2) outer electronic configuration contained in crystals are reviewed. Such centers, with 2 S 1/2 ground state, are produced by electron trapping at impurities of the IB and IIB group or by hole trapping at impurities of the IIIB and IV group of elements. The production and structural properties of such centers consisting of ns 1 ions (atoms) at various sites in the crystal lattice with different configurations of neighbouring defects are discussed in connection with their EPR characteristics. Tables containing the spin Hamiltonian parameters of all ns 1 centers reported in the literature until the end of year 1992 are given. (author). 146 refs, 14 tabs

  12. Biophysical dosimetry using electron paramagnetic resonance in human tooth

    International Nuclear Information System (INIS)

    Khan, R.F.H.; Boreham, D.R.; Rink, W.J.

    2002-01-01

    Accidental dosimetry utilizing radiation induced paramagnetic species in biophysical tissues like teeth is a technique; that can measure the amount of radiation exposure to an individual. The major problem in implementing this technique at low doses is the presence of native organic signal, and various other artifacts produced as a result of sample processing. After a series of experimental trials, we developed an optimum set of rules, which uses high temperature ultrasonic treatment of enamel in KOH, multiple sample rotation during in-cavity measurement of natural and calibrated added irradiations, and dose construction using a backward extrapolation method. By using this we report the successful dose reconstruction in a few of our laboratory samples in 100 mGy range (76.29 ± 30.14) mGy with reasonably low uncertainty. Keywords: biophysical dosimetry, human tooth enamel, low dose measurements, accidental dosimetry (author)

  13. Electron paramagnetic resonance field-modulation eddy-current analysis of silver-plated graphite resonators

    Science.gov (United States)

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

    2005-09-01

    Magnetic field modulation is often introduced into a cylindrical TE011 electron paramagnetic resonance (EPR) cavity through silver plating over a nonconductive substrate. The plating thickness must be many times the skin depth of the rf and smaller than the skin depth of the modulation. We derive a parameter that quantifies the modulation field penetration and find that it also depends on resonator dimensions. Design criteria based on this parameter are presented graphically. This parameter is then used to predict the behavior of eddy currents in substrates of moderate conductivity, such as graphite. The conductivity of the graphite permits improved plating uniformity and permits use of electric discharge machining (EDM) techniques to make the resonator. EDM offers precision tolerances of 0.005 mm and is suitable for small, complicated shapes that are difficult to machine by other methods. Analytic predictions of the modulation penetration are compared with the results of finite-element simulations. Simulated magnetic field modulation uniformity and penetration are shown for several elemental coils and structures including the plated graphite TE011 cavity. Fabrication and experimental testing of the structure are discussed. Spatial inhomogeneity of the modulation phase is also investigated by computer simulation. We find that the modulation phase is uniform to within 1% over the TE011 cavity. Structures of lower symmetry have increased phase nonuniformity.

  14. Contribution of electron paramagnetic resonance to the studies of hemoglobin: the nitrosylhemoglobin system

    International Nuclear Information System (INIS)

    Bemski, G.

    1995-03-01

    Since the initial work of Ingram Electron Paramagnetic Resonance contributed considerably to research in hemoglobins. Now, 40 years later some of the results of the application of EPR to nitrosyl hemoglobin (HbNO), are reviewed as an example of the diversity of information which this technique can provide are reviewed. (author). 34 refs, 7 figs

  15. Study of the arrangement of crystallites in γ-irradiated human enamel by electron paramagnetic resonance

    International Nuclear Information System (INIS)

    Cevc, P.; Schara, M.; Ravnik, C.; Skaleric, U.

    1976-01-01

    The arrangement of tooth enamel microcrystals has been studied on CO 3 3- bound electrons by paramagnetic resonance. It was found that noncarious human maxillary central incisors have a greater degree of alignment of tooth enamel microcrystals than the carious ones. The outermost surface layer of enamel showed a greater crystallite degree of alignment than other parts

  16. 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...

  17. Electron Paramagnetic Resonance and X-ray Diffraction of Boron- and Phosphorus-Doped Nanodiamonds

    Science.gov (United States)

    Binh, Nguyen Thi Thanh; Dolmatov, V. Yu.; Lapchuk, N. M.; Shymanski, V. I.

    2017-11-01

    Powders of boron- and phosphorus-doped detonation nanodiamonds and sintered pellets of non-doped nanodiamond powders were studied using electron paramagnetic resonance and x-ray diffraction. Doping of detonation nanodiamond crystals with boron and phosphorus was demonstrated to be possible. These methods could be used to diagnose diamond nanocrystals doped during shock-wave synthesis.

  18. A microwave resonator for limiting depth sensitivity for electron paramagnetic resonance spectroscopy of surfaces.

    Science.gov (United States)

    Sidabras, Jason W; Varanasi, Shiv K; Mett, Richard R; Swarts, Steven G; Swartz, Harold M; Hyde, James S

    2014-10-01

    A microwave Surface Resonator Array (SRA) structure is described for use in Electron Paramagnetic Resonance (EPR) spectroscopy. The SRA has a series of anti-parallel transmission line modes that provides a region of sensitivity equal to the cross-sectional area times its depth sensitivity, which is approximately half the distance between the transmission line centers. It is shown that the quarter-wave twin-lead transmission line can be a useful element for design of microwave resonators at frequencies as high as 10 GHz. The SRA geometry is presented as a novel resonator for use in surface spectroscopy where the region of interest is either surrounded by lossy material, or the spectroscopist wishes to minimize signal from surrounding materials. One such application is in vivo spectroscopy of human finger-nails at X-band (9.5 GHz) to measure ionizing radiation dosages. In order to reduce losses associated with tissues beneath the nail that yield no EPR signal, the SRA structure is designed to limit depth sensitivity to the thickness of the fingernail. Another application, due to the resonator geometry and limited depth penetration, is surface spectroscopy in coating or material science. To test this application, a spectrum of 1.44 μM of Mg(2+) doped polystyrene 1.1 mm thick on an aluminum surface is obtained. Modeling, design, and simulations were performed using Wolfram Mathematica (Champaign, IL; v. 9.0) and Ansys High Frequency Structure Simulator (HFSS; Canonsburg, PA; v. 15.0). A micro-strip coupling circuit is designed to suppress unwanted modes and provide a balanced impedance transformation to a 50 Ω coaxial input. Agreement between simulated and experimental results is shown.

  19. A microwave resonator for limiting depth sensitivity for electron paramagnetic resonance spectroscopy of surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Sidabras, Jason W.; Varanasi, Shiv K.; Hyde, James S. [Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin 53211 (United States); Mett, Richard R. [Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin 53211 (United States); Department of Physics and Chemistry, Milwaukee School of Engineering, Milwaukee, Wisconsin 53202 (United States); Swarts, Steven G. [Department of Radiation Oncology, University of Florida, Gainesville, Florida, 32610 (United States); Swartz, Harold M. [Department of Radiology, Geisel Medical School at Dartmouth, Hanover, New Hampshire 03755 (United States)

    2014-10-15

    A microwave Surface Resonator Array (SRA) structure is described for use in Electron Paramagnetic Resonance (EPR) spectroscopy. The SRA has a series of anti-parallel transmission line modes that provides a region of sensitivity equal to the cross-sectional area times its depth sensitivity, which is approximately half the distance between the transmission line centers. It is shown that the quarter-wave twin-lead transmission line can be a useful element for design of microwave resonators at frequencies as high as 10 GHz. The SRA geometry is presented as a novel resonator for use in surface spectroscopy where the region of interest is either surrounded by lossy material, or the spectroscopist wishes to minimize signal from surrounding materials. One such application is in vivo spectroscopy of human finger-nails at X-band (9.5 GHz) to measure ionizing radiation dosages. In order to reduce losses associated with tissues beneath the nail that yield no EPR signal, the SRA structure is designed to limit depth sensitivity to the thickness of the fingernail. Another application, due to the resonator geometry and limited depth penetration, is surface spectroscopy in coating or material science. To test this application, a spectrum of 1.44 μM of Mg{sup 2+} doped polystyrene 1.1 mm thick on an aluminum surface is obtained. Modeling, design, and simulations were performed using Wolfram Mathematica (Champaign, IL; v. 9.0) and Ansys High Frequency Structure Simulator (HFSS; Canonsburg, PA; v. 15.0). A micro-strip coupling circuit is designed to suppress unwanted modes and provide a balanced impedance transformation to a 50 Ω coaxial input. Agreement between simulated and experimental results is shown.

  20. Measurement of electron paramagnetic resonance using terahertz time-domain spectroscopy.

    Science.gov (United States)

    Kozuki, Kohei; Nagashima, Takeshi; Hangyo, Masanori

    2011-12-05

    We present a frequency-domain electron spin resonance (ESR) measurement system using terahertz time-domain spectroscopy. A crossed polarizer technique is utilized to increase the sensitivity in detecting weak ESR signals of paramagnets caused by magnetic dipole transitions between magnetic sublevels. We demonstrate the measurements of ESR signal of paramagnetic copper(II) sulfate pentahydrate with uniaxial anisotropy of the g-factor under magnetic fields up to 10 T. The lineshape of the obtained ESR signals agrees well with the theoretical predictions for a powder sample with the uniaxial anisotropy.

  1. Electron paramagnetic resonance study of Ce doped partially stabilized ZrO2 crystals

    Directory of Open Access Journals (Sweden)

    Mikhail А. Borik

    2017-09-01

    Full Text Available ZrO2 (PSZ solid solutions crystals stabilized with yttrium and cerium oxides have been studied using electron paramagnetic resonance (EPR in the X and Q ranges. Zr3+ have been observed centers in the as-annealed ZrO2 crystals stabilized only by yttrium oxide (2.8 mol% Y2O3. Another type of paramagnetic-O-centers appear as a result of CeO2 addition to ZrO2 crystals along with yttrium oxide. To estimate the concentration of Ce3+ ions in PZS crystals, we recorded the EPR spectra in the presence of a reference at 7 K. Paramagnetic Ce3+ ions have been identified and their relative amount in the PSZ crystals before and after high-temperature heat treatment has been assessed. Annealing in air leads decreases the concentration of Ce3+ ions for all the test compositions and changes the color of the crystals from red to white. After annealing of the sample 2.0Y0.8Ce3Zr, the amount of paramagnetic Ce3+ ions decreased approximately twofold. Paramagnetic centers from Ce3+ have not been detected in the specimen with a low cerium content of 0.1 mol% after annealing which indicates the complete transition of Ce3+ to the Ce4+ state. We show that the forming cerium paramagnetic centers are bound by strong exchange interactions. No angular dependence of the EPR lines of the paramagnetic Ce3+ cations on the applied external magnetic field has been observed. Probable origin of the absence of angular dependence is that the impurity rare-earth ions are located close to one another, forming impurity clusters with an effective spin of Seff=1/2.

  2. Electron paramagnetic resonance: A new method of quaternary dating

    International Nuclear Information System (INIS)

    Poupeau, G.; Rossi, A.; Teles, M.M.; Danon, J.

    1984-01-01

    Significant progress has occurred in the last years in quaternary geochronology. One of this is the emergence of a new dating approach, the Electron Spin Resonance Method. The aim of this paper is to briefly review the method and discuss some aspects of the work at CBPF. (Author) [pt

  3. Electron paramagnetic resonance: a new method of quaternary dating

    International Nuclear Information System (INIS)

    Poupeau, G.; Rossi, A.; Universidade Federal Rural do Rio de Janeiro; Telles, M.; Danon, J.

    1984-01-01

    Significant progress has occurred in the last years in quaternary geochronology. One of this is the emergence of a new dating approach, the Electron Spin Resonance Method. The aim of this paper is to briefly review the method and discuss some aspects of the work at CBPF. (Author) [pt

  4. 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...

  5. Handbook of multifrequency electron paramagnetic resonance data and techniques

    CERN Document Server

    Misra, Sushil K

    2014-01-01

    This handbook is aimed to deliver an up-to-date account of some of the recently developed experimental and theoretical methods in EPR, as well as a complete up-to-date listing of the experimentally determined values of multifrequency transition-ion spin Hamiltonian parameters by Sushil Misra, reported in the past 20 years, extending such a listing published by him in the Handbook on Electron Spin Resonance, volume 2. This extensive data tabulation makes up roughly 60% of the book`s content. It is complemented by the first full compilation of hyperfine splittings and g-factors for aminoxyl (nit

  6. Paramagnetic resonance and electronic conduction in organic semiconductors; Resonance paramagnetique et conduction electroniques dans les semi-conducteurs organiques

    Energy Technology Data Exchange (ETDEWEB)

    Nechtschein, M. [Commissariat a l' energie atomique et aux energies alternatives - CEA, Laboratoire de Resonance Magnetique (France)

    1963-07-01

    As some organic bodies simultaneously display semi-conducting properties and a paramagnetism, this report addresses the study of conduction in organic bodies. The author first briefly recalls how relationships between conductibility and Electron Paramagnetic Resonance (EPR) can be noticed in a specific case (mineral and metallic semiconductors). He discusses published results related to paramagnetism and conductibility in organic bodies. He reviews various categories of organic bodies in which both properties are simultaneously present. He notably addresses radical molecular crystals, non-radical molecular crystals, charge transfer complexes, pyrolyzed coals, and pseudo-ferromagnetic organic structures. He discusses the issue of relationships between conduction (charge transfer by electrons) and ERP (which reveals the existence of non-paired electrons which provide free spins)

  7. Thermally stimulated luminescence and electron paramagnetic resonance studies on uranium doped calcium phosphate

    CERN Document Server

    Natarajan, V; Veeraraghavan, R; Sastry, M D

    2003-01-01

    Thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR) studies on uranium doped calcium phosphate yielded mechanistic information on the observed glow peaks at 365, 410 and 450 K. TSL spectral studies of the glow peaks showed that UO sub 2 sup 2 sup + acts as the luminescent center. Electron paramagnetic resonance studies on gamma-irradiated samples revealed that the predominant radiation induced centers are H sup 0 , PO sub 4 sup 2 sup - , PO sub 3 sup 2 sup - and O sup - ion. Studies on the temperature dependence studies of the EPR spectra of samples annealed to different temperatures indicate the role of H sup 0 and PO sub 4 sup 2 sup - ions in the main glow peak at 410 K.

  8. Electron paramagnetic resonance spectrum of fresh fruits processed by gamma-rays

    International Nuclear Information System (INIS)

    Jesus, E.F.O. de; Lopes, R.T.

    1999-01-01

    Pulp of irradiated kiwi fruits, after extraction by ethyl alcohol of part of the water and sugars, has been analyzed by electron paramagnetic resonance in order to study the possibility of identifying irradiated fruits. The results allow to confirm that for a period of approximately 12 weeks a triplet with a coupling isotropic constant of 3.05 mT, intensity ratio 1:2:1 and a factor g=2,0026 is visible in irradiated fruits

  9. Evaluation by electronic paramagnetic resonance of the number of free radicals produced in irradiated rat bone

    International Nuclear Information System (INIS)

    Marble, G.; Valderas, R.

    1966-01-01

    The number of long half-life free radicals created by gamma irradiation in the bones of the rat has been determined from the electrons paramagnetic resonance spectrum. This number decreases slowly with time (calculated half life: 24 days). It is proportional to the dose of gamma radiation given to the rat. The method could find interesting applications in the field of biological dosimetry. (authors) [fr

  10. Electron spin resonance study of the demagnetization fields of the ferromagnetic and paramagnetic films

    Directory of Open Access Journals (Sweden)

    I.I. Gimazov, Yu.I. Talanov

    2015-12-01

    Full Text Available The results of the electron spin resonance study of the La1-xCaxMnO3 manganite and the diphenyl-picrylhydrazyl thin films for the magnetic field parallel and perpendicular to plane of the films are presented. The temperature dependence of the demagnetizing field is obtained. The parameters of the Curie-Weiss law are estimated for the paramagnetic thin film.

  11. Electron paramagnetic resonance investigations of carbon-doped β rhombohedral boron

    International Nuclear Information System (INIS)

    Gercke, U.; Siems, C.-D.

    1979-01-01

    Electron paramagnetic resonance (EPR) measurements at 9 and 35 GHz on polycrystalline β rhombohedral boron with various carbon contents resulted in partly resolved absorption spectra. At 300 K the spin density ratio of two lines (called D and E) showed a linear increase with the carbon content. This ratio is temperature dependent. The lines D and E are photo-EPR active with different quantum efficiencies at various temperatures. (Auth.)

  12. Semiconductor GaAs: electronic paramagnetic resonance new data

    International Nuclear Information System (INIS)

    Benchiguer, T.

    1994-04-01

    The topic of this study was to put to the fore, thanks to our electron spin resonance experiments, one charge transfer process, which was optically induced between the deep donor As + G a and the different acceptors, which were present in the material. We described these processes through a theoretical model, which we named charge transfer model. With this latter, we were able to trace a graph network, representing the As + G a concentration kinetics. Then we verified the compatibility of our model with one transport experiment. One experimental verification of our model were delivered, thanks to neutronic transmutation doping. The following stage was the study of defects, induced by thermal strains, to which the crystal was submitted during the cooling phase. At last we wanted to get round the non solved super hyperfine structure problem for GaAs by studying another III-V material for which she was resolved, namely gallium phosphide. (MML). 150 refs., 72 figs., 16 tabs., 3 annexes

  13. Investigation of lanthanide ions and other paramagnetic impurities in natural fluorite by electron paramagnetic resonance: examples of application to mining exploration and geochemistry

    International Nuclear Information System (INIS)

    Chatagnon, B.

    1981-01-01

    This research thesis reports the application to geology, and more particularly to geochemistry and mining exploration, of a physical method: the electron paramagnetic resonance (EPR). After a report of a bibliographical investigation on mineralogy and geochemistry of fluorite and lanthanides, as well as on paramagnetic centres observed by physicists in synthetic fluorite, the author reports an experimental work, and describes two examples of application of EPR: firstly, the exploration of radioactive ores, and secondly, with the joint use of neutron activation analysis, the characterization of the redox status of the hydrothermal solution which is at the origin of fluorinated mineralisation

  14. Comparative study between different nitrosyls hemoproteins using electron paramagnetic resonance; Estudo comparativo entre diferentes nitrosil hemoproteinas por ressonancia paramagnetica eletronica

    Energy Technology Data Exchange (ETDEWEB)

    Caracelli, Ignez

    1988-12-31

    Using the Electron Paramagnetic Resonance (EPR) technique, the properties of several nitrosyl hemoproteins were investigated as a function of temperature, pH and nitric oxide (NO) concentration. (author). 59 refs., 53 figs., 6 tabs.

  15. Investigations of a new nanostructured Si-material by spectral response and electron paramagnetic resonance

    Energy Technology Data Exchange (ETDEWEB)

    Kuznicki, Z.T.; Ley, M. [Laboratoire PHASE, CNRS UPR 292, 23 rue du Loess, F-67037 Strasbourg cedex 2 (France); Turek, P.; Bernard, M. [Institut Charles Sadron, CNRS UPR 22, 6 rue Boussingault, F-67083 Strasbourg cedex (France)

    2002-08-01

    Electron spin resonance (or electron paramagnetic resonance) was applied to analyze multi-interface solar cells with an active amorphized substructure inserted in the emitter. The nanostructure was realized by P ion implantation followed by an adequate thermal treatment to yield very sharp a-Si/c-Si heterointerfaces. The authors have investigated especially the substructure and the transition zones between the two Si phases, which is particularly interesting because of the stress induced by the density difference of the two Si phases. (Abstract Copyright[2002], Wiley Periodicals, Inc.)

  16. High field electron paramagnetic resonance spectroscopy under ultrahigh vacuum conditions—A multipurpose machine to study paramagnetic species on well defined single crystal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Rocker, J.; Cornu, D.; Kieseritzky, E.; Hänsel-Ziegler, W.; Freund, H.-J. [Fritz-Haber-Institut der MPG, Faradayweg 4-6, 14195 Berlin (Germany); Seiler, A. [Fritz-Haber-Institut der MPG, Faradayweg 4-6, 14195 Berlin (Germany); Laboratorium für Applikationen der Synchrotronstrahlung, KIT Campus Süd, Kaiserstr. 12, 76131 Karlsruhe (Germany); Bondarchuk, O. [Fritz-Haber-Institut der MPG, Faradayweg 4-6, 14195 Berlin (Germany); CIC energiGUNE, Parque Tecnologico, C/Albert Einstein 48, CP 01510 Minano (Alava) (Spain); Risse, T., E-mail: risse@chemie.fu-berlin.de [Fritz-Haber-Institut der MPG, Faradayweg 4-6, 14195 Berlin (Germany); Institut für Chemie und Biochemie, Freie Universität Berlin, Takustr. 3, 14195 Berlin (Germany)

    2014-08-01

    A new ultrahigh vacuum (UHV) electron paramagnetic resonance (EPR) spectrometer operating at 94 GHz to investigate paramagnetic centers on single crystal surfaces is described. It is particularly designed to study paramagnetic centers on well-defined model catalysts using epitaxial thin oxide films grown on metal single crystals. The EPR setup is based on a commercial Bruker E600 spectrometer, which is adapted to ultrahigh vacuum conditions using a home made Fabry Perot resonator. The key idea of the resonator is to use the planar metal single crystal required to grow the single crystalline oxide films as one of the mirrors of the resonator. EPR spectroscopy is solely sensitive to paramagnetic species, which are typically minority species in such a system. Hence, additional experimental characterization tools are required to allow for a comprehensive investigation of the surface. The apparatus includes a preparation chamber hosting equipment, which is required to prepare supported model catalysts. In addition, surface characterization tools such as low energy electron diffraction (LEED)/Auger spectroscopy, temperature programmed desorption (TPD), and infrared reflection absorption spectroscopy (IRAS) are available to characterize the surfaces. A second chamber used to perform EPR spectroscopy at 94 GHz has a room temperature scanning tunneling microscope attached to it, which allows for real space structural characterization. The heart of the UHV adaptation of the EPR experiment is the sealing of the Fabry-Perot resonator against atmosphere. To this end it is possible to use a thin sapphire window glued to the backside of the coupling orifice of the Fabry Perot resonator. With the help of a variety of stabilization measures reducing vibrations as well as thermal drift it is possible to accumulate data for a time span, which is for low temperature measurements only limited by the amount of liquid helium. Test measurements show that the system can detect paramagnetic

  17. Electron paramagnetic resonance investigation of polycrystalline CaCu3Ti4O12

    International Nuclear Information System (INIS)

    Mozzati, Maria Cristina; Azzoni, Carlo Bruno; Capsoni, Doretta; Bini, Marcella; Massarotti, Vincenzo

    2003-01-01

    Electron paramagnetic resonance (EPR) measurements on pure polycrystalline CaCu 3 Ti 4 O 12 have been performed and are discussed within a crystal-field approach. A symmetric signal centred at g = 2.15 is observed for T>25 K, with no evidence of hyperfine structure. At this temperature an antiferromagnetic transition is observed as confirmed by static magnetization data. Cu defective and 2% doped (V, Cr, Mn, La) samples were also prepared and considered, mainly to understand the nature of the observed paramagnetic centre. Substitutions in the octahedral sites, causing variations of the configuration in CuO 4 -TiO 6 -CuO 4 complexes, change the magnetic and EPR features. To justify the EPR response a strong copper-hole delocalization is suggested

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

    Energy Technology Data Exchange (ETDEWEB)

    Flores, Marco; Wajnberg, Eliane; Bemski, George

    1997-11-01

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

  19. Proton nuclear magnetic resonance in paramagnetic CoCl2.6H2O

    International Nuclear Information System (INIS)

    Oravcova, J.; Murin, J.; Rakos, M.; Olcak, D.

    1978-01-01

    Nuclear magnetic resonance (NMR) is studied of protons of the crystal water of paramagnetic CoCl 2 .6H 2 O. The measurements were carried out on powdered samples at room temperature, for values of the external magnetic field ranging from 0.3 to 1.0 T. The NMR signals of protons of the crystal water exhibit asymmetric shape which changes with the applied external magnetic field. We found that the second moment of the resonance line shows a linear dependence on the square of the induction of the externally applied magnetic field. The cause of the asymmetry of the NMR line of protons of the crystal water and the dependence of the second moment of the resonance line on the induction of external magnetic field are interpreted. (author)

  20. Electron Paramagnetic Resonance of a Single NV Nanodiamond Attached to an Individual Biomolecule.

    Science.gov (United States)

    Teeling-Smith, Richelle M; Jung, Young Woo; Scozzaro, Nicolas; Cardellino, Jeremy; Rampersaud, Isaac; North, Justin A; Šimon, Marek; Bhallamudi, Vidya P; Rampersaud, Arfaan; Johnston-Halperin, Ezekiel; Poirier, Michael G; Hammel, P Chris

    2016-05-10

    Electron paramagnetic resonance (EPR), an established and powerful methodology for studying atomic-scale biomolecular structure and dynamics, typically requires in excess of 10(12) labeled biomolecules. Single-molecule measurements provide improved insights into heterogeneous behaviors that can be masked in ensemble measurements and are often essential for illuminating the molecular mechanisms behind the function of a biomolecule. Here, we report EPR measurements of a single labeled biomolecule. We selectively label an individual double-stranded DNA molecule with a single nanodiamond containing nitrogen-vacancy centers, and optically detect the paramagnetic resonance of nitrogen-vacancy spins in the nanodiamond probe. Analysis of the spectrum reveals that the nanodiamond probe has complete rotational freedom and that the characteristic timescale for reorientation of the nanodiamond probe is slow compared with the transverse spin relaxation time. This demonstration of EPR spectroscopy of a single nanodiamond-labeled DNA provides the foundation for the development of single-molecule magnetic resonance studies of complex biomolecular systems. Copyright © 2016 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  1. Electron paramagnetic resonance of atomic hydrogen (H0) centers in pink tourmaline from Brazil

    International Nuclear Information System (INIS)

    Camargo, M.B.

    1985-01-01

    A model for explaining the atom of hydrogen (H 0 ) in pink tourmaline irradiated with gamma rays is presented. The concentration of H 0 was evaluated and the H 0 lines using the electron paramagnetic resonance were analysed. The g factor and the hyperfine interaction constant were measured with accuracy and determined by matrix diagonalization of spin hamiltonian in vetor space of four dimensions, followed by an iterative calculation with quick convergence the local electric field produced by charges in the lattice was calculated and compared with the value obtained experimentally. (M.C.K.) [pt

  2. Al-doped MgB_2 materials studied using electron paramagnetic resonance and Raman spectroscopy

    International Nuclear Information System (INIS)

    Bateni, Ali; Somer, Mehmet; Erdem, Emre; Repp, Sergej; Weber, Stefan

    2016-01-01

    Undoped and aluminum (Al) doped magnesium diboride (MgB_2) samples were synthesized using a high-temperature solid-state synthesis method. The microscopic defect structures of Al-doped MgB_2 samples were systematically investigated using X-ray powder diffraction, Raman spectroscopy, and electron paramagnetic resonance. It was found that Mg-vacancies are responsible for defect-induced peculiarities in MgB_2. Above a certain level of Al doping, enhanced conductive properties of MgB_2 disappear due to filling of vacancies or trapping of Al in Mg-related vacancy sites.

  3. Er3+ impurities in KTiOPO4 studied by electron paramagnetic resonance

    International Nuclear Information System (INIS)

    Bravo, D; MartIn, A; Carvajal, J J; Aguilo, M; DIaz, F; Lopez, F J

    2006-01-01

    An electron paramagnetic resonance (EPR) study of Er 3+ ions in single crystals of KTiOPO 4 (KTP) is presented. The EPR spectra show the existence of eight different Er 3+ centres. The g-matrix has been determined for all eight centres from the analysis of the angular dependences of the spectrum in three planes of the crystal. This study provides strong evidence about incorporation of erbium in the low-symmetry K + sites of KTP. Possible reasons for the appearance of such a large number of Er 3+ centres are discussed

  4. Degradation of edible oil during food processing by ultrasound: electron paramagnetic resonance, physicochemical, and sensory appreciation.

    Science.gov (United States)

    Pingret, Daniella; Durand, Grégory; Fabiano-Tixier, Anne-Sylvie; Rockenbauer, Antal; Ginies, Christian; Chemat, Farid

    2012-08-08

    During ultrasound processing of lipid-containing food, some off-flavors can be detected, which can incite depreciation by consumers. The impacts of ultrasound treatment on sunflower oil using two different ultrasound horns (titanium and pyrex) were evaluated. An electron paramagnetic resonance study was performed to identify and quantify the formed radicals, along with the assessment of classical physicochemical parameters such as peroxide value, acid value, anisidine value, conjugated dienes, polar compounds, water content, polymer quantification, fatty acid composition, and volatiles profile. The study shows an increase of formed radicals in sonicated oils, as well as the modification of physicochemical parameters evidencing an oxidation of treated oils.

  5. Retrospective dosimetry of nail by Electron Paramagnetic Resonance; Dosimetria retrospectiva de unha por Ressonancia Paramagnetica Eletronica

    Energy Technology Data Exchange (ETDEWEB)

    Giannoni, Ricardo A., E-mail: giannoni@ird.gov.br [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil); Rodrigues Junior, Orlando, E-mail: rodrijr@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2015-07-01

    The purpose of this study is to characterize samples of human nails, subjected to irradiation of high doses through Technical Electron Paramagnetic Resonance (EPR). The goal is to establish a dose/response relationship in order to assess dose levels absorbed by individuals exposed in radiation accidents situations, retrospectively. Samples of human nails were irradiated with gamma radiation, and received a dose of 20 Gy. EPR measurements performed on samples before irradiation identified EPR signals associated with defects caused by the mechanical action of the sample collection. After irradiation other species of free radicals, associated with the action of gamma radiation, have been identified.

  6. Improving the calculation of electron paramagnetic resonance hyperfine coupling tensors for d-block metals

    DEFF Research Database (Denmark)

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

    2012-01-01

    Calculation of hyperfine coupling constants (HFCs) of Electron Paramagnetic Resonance from first principles can be a beneficial compliment to experimental data in cases where the molecular structure is unknown. We have recently investigated basis set convergence of HFCs in d-block complexes...... and obtained a set of basis functions for the elements Sc–Zn, which were saturated with respect to both the Fermi contact and spin-dipolar components of the hyperfine coupling tensor [Hedeg°ard et al., J. Chem. Theory Comput., 2011, 7, pp. 4077-4087]. Furthermore, a contraction scheme was proposed leading...

  7. Application of the Electron paramagnetic resonance to the ionizing radiation dosimetry

    International Nuclear Information System (INIS)

    Urena N, F.

    2000-01-01

    The Electron Paramagnetic Resonance (EPR) is defined as the resonant absorption of electromagnetic energy in paramagnetic substances by the spin transition of a non-pairing electron between different energy levels in presence of a magnetic field. (Slighter, 1989). One of the more important characteristic of EPR is that the electron spin levels are subdivided by the electron interaction with the magnetic dipoles of the nearby nucleus giving occasion for a spectral structure called hyperfine structure. In this kind of interactions two limit cases are distinguished: 1. when the non-pairing electron is located in a central ion surrounded of atoms belonging to coordinate molecules. 2. When a non-pairing electron interactioning in the same form with a number of equivalent nucleus, which is common in organic radicals, these will give as result spectra. Some EPR spectrometer can be used to dosimetric purposes by free radicals via. In this work, it is presented the application of EPR to dosimetry of ionizing radiations by free radicals via which allows to determinations of high doses. (Author)

  8. In vivo electron paramagnetic resonance oximetry and applications in the brain

    Directory of Open Access Journals (Sweden)

    John M Weaver

    2017-01-01

    Full Text Available Molecular oxygen (O2 is essential to brain function and mechanisms necessary to regulate variations in delivery or utilization of O2 are crucial to support normal brain homeostasis, physiology and energy metabolism. Any imbalance in cerebral tissue partial pressure of O2 (pO2 levels may lead to pathophysiological complications including increased reactive O2 species generation leading to oxidative stress when tissue O2 level is too high or too low. Accordingly, the need for oximetry methods, which assess cerebral pO2 in vivo and in real time, is imperative to understand the role of O2 in various metabolic and disease states, including the effects of treatment and therapy options. In this review, we provide a brief overview of the common in vivo oximetry methodologies for measuring cerebral pO2 . We discuss the advantages and limitations of oximetry methodologies to measure cerebral pO2 in vivo followed by a more in-depth review of electron paramagnetic resonance oximetry spectroscopy and imaging using several examples of current electron paramagnetic resonance oximetry applications in the brain.

  9. Hysteresis loops of spin-dependent electronic current in a paramagnetic resonant tunnelling diode

    International Nuclear Information System (INIS)

    Wójcik, P; Spisak, B J; Wołoszyn, M; Adamowski, J

    2012-01-01

    Nonlinear properties of the spin-dependent electronic transport through a semiconductor resonant tunnelling diode with a paramagnetic quantum well are considered. The spin-dependent Wigner–Poisson model of the electronic transport and the two-current Mott’s formula for the independent spin channels are applied to determine the current–voltage curves of the nanodevice. Two types of the electronic current hysteresis loops are found in the current–voltage characteristics for both the spin components of the electronic current. The physical interpretation of these two types of the electronic current hysteresis loops is given based on the analysis of the spin-dependent electron densities and the potential energy profiles. The differences between the current–voltage characteristics for both the spin components of the electronic current allow us to explore the changes of the spin polarization of the current for different electric fields and determine the influence of the electronic current hysteresis on the spin polarization of the current flowing through the paramagnetic resonant tunnelling diode. (paper)

  10. 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)

  11. Magnetic resonance force microscopy of paramagnetic electron spins at millikelvin temperatures.

    Science.gov (United States)

    Vinante, A; Wijts, G; Usenko, O; Schinkelshoek, L; Oosterkamp, T H

    2011-12-06

    Magnetic resonance force microscopy (MRFM) is a powerful technique to detect a small number of spins that relies on force detection by an ultrasoft magnetically tipped cantilever and selective magnetic resonance manipulation of the spins. MRFM would greatly benefit from ultralow temperature operation, because of lower thermomechanical noise and increased thermal spin polarization. Here we demonstrate MRFM operation at temperatures as low as 30 mK, thanks to a recently developed superconducting quantum interference device (SQUID)-based cantilever detection technique, which avoids cantilever overheating. In our experiment, we detect dangling bond paramagnetic centres on a silicon surface down to millikelvin temperatures. Fluctuations of such defects are supposedly linked to 1/f magnetic noise and decoherence in SQUIDs, as well as in several superconducting and single spin qubits. We find evidence that spin diffusion has a key role in the low-temperature spin dynamics.

  12. Electronic paramagnetic resonance in the Mn In X (X:Te,S) diluted magnetic semiconductor system

    International Nuclear Information System (INIS)

    Vincent, Bernardo; Betancourt, Luis; Sagredo, Vicente; Alcala, Rafael

    1996-01-01

    Semiconductor compounds wit the II-III-VI stoichiometry are very interesting materials since they present very good semiconducting characteristics and, along with strong magnetic properties, these II Mn In VI compounds have a great potential as opt and magneto-electronic devices. Among the possible magnetic properties of the materials is the presence of the spin-glass phase. Electron paramagnetic resonance is one of the techniques used to confirm this phase. The chosen crystals were chosen by chemical vapor transport. The absorption lines of these two families with 0.1 x 1 were all Lorentzian in shape and centred at g=2. A large broadening of the resonance line width was observed when lowering the temperature to below 80 K. This behaviour was fitted to the known existing models, and good values of the calculated parameters were obtained (author)

  13. Studying metal impurities (Mn2+, Cu2+, Fe3+) in calcium phosphates by electron paramagnetic resonance

    Science.gov (United States)

    Iskhakova, K.; Murzakhanov, F.; Mamin, G.; Putlyaev, V.; Klimashina, E.; Fadeeva, I.; Fomin, A.; Barinov, S.; Maltsev, A.; Bakhteev, S.; Yusupov, R.; Gafurov, M.; Orlinskii, S.

    2018-05-01

    Calcium phosphates (CaP) are exploited in many fields of science, including geology, chemistry, biology and medicine due to their abundance in the nature and presence in the living organism. Various analytical and biochemical methods are used for controlling their chemical content, structure, morphology, etc. Unfortunately, magnetic resonance techniques are usually not even considered as necessary tools for CaP inspection. Some aspects of application of the commercially realized electron paramagnetic resonance (EPR) approaches for characterization of CaP powders and ceramics (including the nanosized materails) such as hydroxyapatite and tricalcium phosphates of biogenic and synthetic origins containing intrinsic impurities or intentional dopants are demonstrated. The key features and advantages of the EPR techniques for CaP based materials characterization that could compliment the data obtained with the recognized analytical methods are pointed out.

  14. Chemistry of paramagnetic and diamagnetic contrast agents for Magnetic Resonance Imaging and Spectroscopy

    International Nuclear Information System (INIS)

    Perez-Mayoral, Elena; Negri, Viviana; Soler-Padros, Jordi; Cerdan, Sebastian; Ballesteros, Paloma

    2008-01-01

    We provide a brief overview of the chemistry and most relevant properties of paramagnetic and diamagnetic contrast agents (CAs) for Magnetic Resonance Imaging and Magnetic Resonance Spectroscopic Imaging. Paramagnetic CAs for MRI consist mainly of Gd(III) complexes from linear or macrocyclic polyaminopolycarboxylates. These agents reduce, the relaxation times T 1 and T 2 of the water protons in a concentration dependent manner, increasing selectively MRI contrast in those regions in which they accumulate. In most instances they provide anatomical information on the localization of lesions and in some specific cases they may allow to estimate some physiological properties of tissues including mainly vascular performance. Because of its ability to discriminate easily between normal and diseased tissue, extracellular pH (pH e ) has been added recently, to the battery of variables amenable to MRI investigation. A variety of Gd(III) containing macrocycles sensitive to pH, endogenous or exogenous polypeptides or even liposomes have been investigated for this purpose, using the pH dependence of their relaxivity or magnetization transfer rate constant (chemical exchange saturation transfer, CEST). Many environmental circumstances in addition to pH affect, however, relaxivity or magnetization transfer rate constants of these agents, making the results of pH measurements by MRI difficult to interpret. To overcome these limitations, our laboratory synthesized and developed a novel series of diamagnetic CAs for Magnetic Resonance Spectroscopic Imaging, a new family of monomeric and dimeric imidazolic derivatives able to provide unambiguous measurements of pH e , independent of water relaxivity, diffusion or exchange

  15. Chemistry of paramagnetic and diamagnetic contrast agents for Magnetic Resonance Imaging and Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Mayoral, Elena [Laboratorio de Sintesis Organica e Imagen Molecular por Resonancia Magnetica, Facultad de Ciencias, UNED, Paseo Senda del Rey 9, E-28040 Madrid (Spain); Departamento de Quimica Inorganica y Quimica Tecnica, Facultad de Ciencias, UNED, Paseo Senda del Rey 9, E-28040 Madrid (Spain); Negri, Viviana; Soler-Padros, Jordi [Laboratorio de Sintesis Organica e Imagen Molecular por Resonancia Magnetica, Facultad de Ciencias, UNED, Paseo Senda del Rey 9, E-28040 Madrid (Spain); Cerdan, Sebastian [Laboratorio de Imagen Espectroscopica por Resonancia Magnetica (LIERM), Instituto de Investigaciones Biomedicas ' Alberto Sols' , CSIC/UAM, c/Arturo Duperier 4, E-28029 Madrid (Spain); Ballesteros, Paloma [Laboratorio de Sintesis Organica e Imagen Molecular por Resonancia Magnetica, Facultad de Ciencias, UNED, Paseo Senda del Rey 9, E-28040 Madrid (Spain)], E-mail: pballesteros@ccia.uned.es

    2008-09-15

    We provide a brief overview of the chemistry and most relevant properties of paramagnetic and diamagnetic contrast agents (CAs) for Magnetic Resonance Imaging and Magnetic Resonance Spectroscopic Imaging. Paramagnetic CAs for MRI consist mainly of Gd(III) complexes from linear or macrocyclic polyaminopolycarboxylates. These agents reduce, the relaxation times T{sub 1} and T{sub 2} of the water protons in a concentration dependent manner, increasing selectively MRI contrast in those regions in which they accumulate. In most instances they provide anatomical information on the localization of lesions and in some specific cases they may allow to estimate some physiological properties of tissues including mainly vascular performance. Because of its ability to discriminate easily between normal and diseased tissue, extracellular pH (pH{sub e}) has been added recently, to the battery of variables amenable to MRI investigation. A variety of Gd(III) containing macrocycles sensitive to pH, endogenous or exogenous polypeptides or even liposomes have been investigated for this purpose, using the pH dependence of their relaxivity or magnetization transfer rate constant (chemical exchange saturation transfer, CEST). Many environmental circumstances in addition to pH affect, however, relaxivity or magnetization transfer rate constants of these agents, making the results of pH measurements by MRI difficult to interpret. To overcome these limitations, our laboratory synthesized and developed a novel series of diamagnetic CAs for Magnetic Resonance Spectroscopic Imaging, a new family of monomeric and dimeric imidazolic derivatives able to provide unambiguous measurements of pH{sub e}, independent of water relaxivity, diffusion or exchange.

  16. Characterisation of β-tricalcium phosphate-based bone substitute materials by electron paramagnetic resonance spectroscopy

    Science.gov (United States)

    Matković, Ivo; Maltar-Strmečki, Nadica; Babić-Ivančić, Vesna; Dutour Sikirić, Maja; Noethig-Laslo, Vesna

    2012-10-01

    β-TCP based materials are frequently used as dental implants. Due to their resorption in the body and direct contact with tissues, in order to inactivate bacteria, fungal spores and viruses, they are usually sterilized by γ-irradiation. However, the current literature provides little information about effects of the γ-irradiation on the formation and stability of the free radicals in the bone graft materials during and after sterilization procedure. In this work five different bone graft substitution materials, composed of synthetic beta tricalcium phosphate (β-TCP) and hydroxyapatite (HAP) present in the market were characterized by electron paramagnetic resonance (EPR) spectroscopy, X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). Paramagnetic species Mn2+, Fe3+, trapped H-atoms and CO2- radicals were detected in the biphasic material (60% HAP, 40% β-TCP), while in β-TCP materials only Mn2+ andor trapped hydrogen atoms were detected. EPR analysis revealed the details of the structure of these materials at the atomic level. The results have shown that EPR spectroscopy is a method which can be used to improve the quality control of bone graft materials after syntering, processing and sterilization procedure.

  17. Electron paramagnetic resonance of rhyolite and γ-irradiated trona minerals

    International Nuclear Information System (INIS)

    Koeksal, F.; Koeseoglu, R.; Basaran, E.

    2003-01-01

    Rhyolite from the ''Yellow Stone of Nevsehir'' and γ-irradiated trona from the Ankara Mine have been investigated by electron paramagnetic resonance at ambient temperature and at 113 K. Rhyolite was examined by X-ray powder diffraction and found to consist mainly of SiO 2 . Before γ-irradiation, the existing paramagnetic species in rhyolite were identified as PO 4 2- , CH 2 OH, CO 3 - , SO 2 - , CO 3 3- , and CO 2 - free radicals and Fe 3+ at ambient temperature. At 113 K SO 2 - , CO 3 3- , and CO 2 - radicals and Fe 3+ were observed. The γ-irradiation produced neither new species nor detectable effects on these free radicals. The disappearance of some of the radicals at 113 K is attributed to the freezing of their motions. Before γ-irradiation, the trona mineral shows only Mn 2+ lines, but after γ-irradiation it indicated the inducement of CO 3 3- and CO 2 - radicals at ambient temperature, 113 K, in addition to the Mn 2+ lines. The g and a values of the species were determined. (orig.)

  18. Coordination Environment of Copper Sites in Cu-CHA Zeolite Investigated by Electron Paramagnetic Resonance

    DEFF Research Database (Denmark)

    Godiksen, Anita; Stappen, Frederick N.; Vennestrøm, Peter N. R.

    2014-01-01

    Cu-CHA combines high activity for the selective catalytic reduction (SCR) reaction with better hydrothermal stability and selectivity compared to other copper-substituted zeolites. At the same time Cu-CHA offers an opportunity for unraveling the coordination environment of the copper centers since...... the zeolite framework is very simple with only one crystallographically independent tetrahedral site (T-site). In this study the results of an X-band electron paramagnetic resonance (EPR) investigation of ion-exchanged Cu-CHA zeolite with a Si/Al ratio of 14 ± 1 is presented. Different dehydration treatments...... of the EPR silent monomeric Cu2+ in copper-substituted zeolites is suggested to be copper species with an approximate trigonal coordination sphere appearing during the dehydration. After complete dehydration at 250 °C the majority of the EPR silent Cu2+ is suggested to exist as Cu2+–OH– coordinated to two...

  19. Detection of free radicals in γ-irradiated seasnail hard tissues by electron paramagnetic resonance

    International Nuclear Information System (INIS)

    Koeseoglu, Rahmi; Koeksal, Fevzi

    2003-01-01

    Gamma-irradiated seasnail (from family of Helix lukortium) hard tissues (CaCO 3 ) were investigated by electron paramagnetic resonance (EPR) at room temperature. The radicals produced by γ-irradiation in seasnail were attributed to orthorhombic C · O 2 - , freely rotating C · O 2 - , orthorhombic C · O 3 - , axial C · O 3 - , and axial C · O 3 3- free radicals. Unirradiated seasnail hard tissues also feature Mn 2+ ions in their EPR spectra. The hyperfine values were determined for the 13 C nucleus in the orthorhombic C · O 2 - and axial C · O 3 3- free radicals and for the manganese impurity ions. The g values of all the free radicals have been measured. The results were compared with the literature data for similar defects

  20. 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)

  1. High-Frequency Electron Paramagnetic Resonance Spectroscopy of Nitroxide-Functionalized Nanodiamonds in Aqueous Solution.

    Science.gov (United States)

    Akiel, R D; Stepanov, V; Takahashi, S

    2017-06-01

    Nanodiamond (ND) is an attractive class of nanomaterial for fluorescent labeling, magnetic sensing of biological molecules, and targeted drug delivery. Many of those applications require tethering of target biological molecules on the ND surface. Even though many approaches have been developed to attach macromolecules to the ND surface, it remains challenging to characterize dynamics of tethered molecule. Here, we show high-frequency electron paramagnetic resonance (HF EPR) spectroscopy of nitroxide-functionalized NDs. Nitroxide radical is a commonly used spin label to investigate dynamics of biological molecules. In the investigation, we developed a sample holder to overcome water absorption of HF microwave. Then, we demonstrated HF EPR spectroscopy of nitroxide-functionalized NDs in aqueous solution and showed clear spectral distinction of ND and nitroxide EPR signals. Moreover, through EPR spectral analysis, we investigate dynamics of nitroxide radicals on the ND surface. The demonstration sheds light on the use of HF EPR spectroscopy to investigate biological molecule-functionalized nanoparticles.

  2. Paramagnetic resonance of Mn4+ and Mn2+ centers in lanthanum gallate single crystals

    Science.gov (United States)

    Vazhenin, V. A.; Potapov, A. P.; Guseva, V. B.; Artyomov, M. Yu.

    2010-03-01

    An increase in the manganese concentration in lanthanum gallate in the range 0.5-5.0% has been found to result in a complete replacement of individual Mn4+ ions by Mn2+ ions. The relative concentrations and binding energies of individual Mn4+, Mn3+, and Mn2+ ions have been determined. The spin Hamiltonians of the Mn2+ and Mn4+ centers in the rhombohedral and orthorhombic phases, respectively, have been constructed and the orientation of the principal axes of the fine-structure tensor of Mn4+ at room temperature has been found. The possibility of using electron paramagnetic resonance for determining the rotation angles of oxygen octahedra of lanthanum gallate with respect to the perovskite structure has been discussed.

  3. Gamma-Irradiated seafoods: identification and dosimetry by electron paramagnetic resonance spectroscopy

    International Nuclear Information System (INIS)

    Desrosiers, M.F.

    1989-01-01

    Electron paramagnetic resonance (EPR) spectroscopy was used to measure the production of free radicals induced by 60Co γ-rays in shrimp exoskeleton, mussel shells, and fish bones. The EPR spectrum for irradiated shrimp shell was dose dependent and appeared to be derived from more than one radical. The major component of the radiation-induced spectrum resulted from radical formation in chitin, assigned by comparison with irradiated N-acetyl-D-glucosamine. Other measurements include the total yield of radicals formed as a function of dose and the longevity of the radiation-induced EPR signal. Similar measurements were made for mussel shells and fish bones, and the results are compared and discussed. It was concluded that irradiated shrimp (with shell attached) could definitely be identified by this technique; however, precise determination of absorbed dose was less straightforward. Positive identification of irradiated fish bones was also clearly distinguishable, and dosimetry by EPR appeared to be feasible. (author)

  4. Evaluation of adriamycin nephropathy by an in vivo electron paramagnetic resonance

    International Nuclear Information System (INIS)

    Oteki, Takaaki; Nagase, Sohji; Yokoyama, Hidekatsu; Ohya, Hiroaki; Akatsuka, Takao; Tada, Mika; Ueda, Atsushi; Hirayama, Aki; koyama, Akio

    2005-01-01

    A rat model for human minimal change nephropathy was obtained by the intravenous injection of adriamycin (ADR) at 5 mg/kg. By using an in vivo electron paramagnetic resonance (EPR) spectrometer operating at 700 MHz, the temporal changes in signal intensities of a nitroxide radical, 4-hydroxyl-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPOL), in the kidneys of rats with ADR nephropathy were investigated. The decay rate of the EPR signal intensity obtained in the kidney is indicative of the renal reducing ability. It was found that the reducing ability in the kidney declined on the 7th day after ADR administration and recovered after the 14th day. Impairment of the reducing ability occurred before the appearance of continuous urinary protein. The in vitro EPR study showed that this impairment of in vivo renal reducing ability is related to impairment of the reducing ability in the mitochondria

  5. Electron Paramagnetic Resonance Spectrometry and Imaging in Melanomas: Comparison between Pigmented and Nonpigmented Human Malignant Melanomas

    Directory of Open Access Journals (Sweden)

    Quentin Godechal

    2013-06-01

    Full Text Available It has been known for a long time that the melanin pigments present in normal skin, hair, and most of malignant melanomas can be detected by electron paramagnetic resonance (EPR spectrometry. In this study, we used EPR imaging as a tool to map the concentration of melanin inside ex vivo human pigmented and nonpigmented melanomas and correlated this cartography with anatomopathology. We obtained accurate mappings of the melanin inside pigmented human melanoma samples. The signal intensity observed on the EPR images correlated with the concentration of melanin within the tumors, visible on the histologic sections. In contrast, no EPR signal coming from melanin was observed from nonpigmented melanomas, therefore demonstrating the absence of EPR-detectable pigments inside these particular cases of skin cancer and the importance of pigmentation for further EPR imaging studies on melanoma.

  6. Quantitative detection of plasma-generated radicals in liquids by electron paramagnetic resonance spectroscopy

    International Nuclear Information System (INIS)

    Tresp, H; Hammer, M U; Winter, J; Reuter, S; Weltmann, K-D

    2013-01-01

    In this paper the qualitative and quantitative detection of oxygen radicals in liquids after plasma treatment with an atmospheric pressure argon plasma jet by electron paramagnetic resonance spectroscopy is investigated. Absolute values for · OH and O 2 ·- radical concentration and their net production rate in plasma-treated liquids are determined without the use of additional scavenging chemicals such as superoxide dismutase (SOD) or mannitol (D-MAN). The main oxygen-centred radical generation in PBS was found to originate from the superoxide radical. It is shown that hidden parameters such as the manufacturer of chemical components could have a big influence on the comparability and reproducibility of the results. Finally, the effect of a shielding gas device for the investigated plasma jet with a shielding gas composition of varying oxygen-to-nitrogen ratio on radical generation after plasma treatment of phosphate-buffered saline solution was investigated. (paper)

  7. Electron paramagnetic resonance of globin proteins - a successful match between spectroscopic development and protein research

    Science.gov (United States)

    Van Doorslaer, Sabine; Cuypers, Bert

    2018-02-01

    At the start of the twenty-first century, the research into the haem-containing globins got a considerable impetus with the discovery of three new mammalian globins: neuroglobin, cytoglobin and androglobin. Globins are by now found in all kingdoms of life and, in many cases, their functions are still under debate. This revival in globin research increased the demand for adequate physico-chemical research tools to determine the structure-function relationships of these proteins. From early days onwards, electron paramagnetic resonance (EPR) has been used in globin research. In recent decades, the field of EPR has been revolutionised with the introduction of many new pulsed and high-field EPR techniques. In this review, we highlight how EPR has become an essential tool in globin research, and how globins equally provide ideal model systems to push technical developments in EPR.

  8. 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)

  9. Electronic Paramagnetic Resonance of irradiated nails: challenges for a dosimetry in radiation accidents

    International Nuclear Information System (INIS)

    Giannoni, Ricardo A.; Rodrigues Junior, Orlando

    2014-01-01

    The purpose of this work is to characterize samples of human nails exposed to high doses of radiation, applying the technique of Electron Paramagnetic Resonance (EPR). The objective is to establish a dose response study that allow determine the absorbed dose by exposed individuals in situations of radiological accidents, in a retrospective form. Samples of human nails were collected and afterward irradiated with gamma radiation, and received dose of 20 Gy. The EPR measurement performed on the samples, before irradiation, permitted the signal identification of the components associated with effects caused by the mechanical stress during the fingernail cutting, the so-called mechanically induced signal (MIS). After the irradiation, different species of free radicals were identified, the so-called radiation induced signal (RIS). (author)

  10. 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)

  11. Retrospective radiation dosimetry using electron paramagnetic resonance in canine dental enamel

    International Nuclear Information System (INIS)

    Khan, Rao F.H.; Pekar, J.; Rink, W.J.; Boreham, D.R.

    2005-01-01

    Electron paramagnetic resonance (EPR) biodosimetry of human tooth enamel has been widely used for measuring radiation doses in various scenarios. We have now developed EPR dosimetry in tooth enamel extracted from canines. Molars and incisors from canines were cleaned by processing in supersaturated aqueous potassium hydroxide solution. The dosimetric signal in canine tooth enamel was found to increase linearly as a function of laboratory added dose from 0.44±0.02 to 4.42±0.22 Gy. The gamma radiation sensitivity of the canine molar enamel was found to be comparable to that of human tooth enamel. The dosimetric signal in canine enamel has been found to be stable up to at least 6 weeks after in vitro irradiation. A dosimetric signal variation of 10-25% was observed for canines ranging from in age 3 years to 16 year old

  12. Electrochemistry and electron paramagnetic resonance spectroscopy of cytochrome c and its heme-disrupted analogs.

    Science.gov (United States)

    Novak, David; Mojovic, Milos; Pavicevic, Aleksandra; Zatloukalova, Martina; Hernychova, Lenka; Bartosik, Martin; Vacek, Jan

    2018-02-01

    Cytochrome c (cyt c) is one of the most studied conjugated proteins due to its electron-transfer properties and ability to regulate the processes involved in homeostasis or apoptosis. Here we report an electrochemical strategy for investigating the electroactivity of cyt c and its analogs with a disrupted heme moiety, i.e. apocytochrome c (acyt c) and porphyrin cytochrome c (pcyt c). The electrochemical data are supplemented with low-temperature and spin-probe electron paramagnetic resonance (EPR) spectroscopy. The main contribution of this report is a complex evaluation of cyt c reduction and oxidation at the level of surface-localized amino acid residues and the heme moiety in a single electrochemical scan. The electrochemical pattern of cyt c is substantially different to both analogs acyt c and pcyt c, which could be applicable in further studies on the redox properties and structural stability of cytochromes and other hemeproteins. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Powderspec, a program for the efficient simulation of spectra of electron paramagnetic resonance of powders with orthorhombic symmetry

    International Nuclear Information System (INIS)

    Gonzalez T, L.; Beltran L, V.

    1991-09-01

    In this report a FORTRAN source program which simulates the second order powder pattern and spectrum of electron paramagnetic resonance (EPR) in crystal fields with orthorhombic symmetry using Gauss-Legendre quadratures is given. Also the commentaries which describe each step in detail are presented. (Author)

  14. Electron paramagnetic resonance study of copper impurity charge-states in PbWO.sub.4./sub. scintillator

    Czech Academy of Sciences Publication Activity Database

    Hofstaetter, A.; Laguta, V. V.; Meyer, B.K.; Nikl, Martin; Rosa, Jan; Zhu, R.Y.

    2004-01-01

    Roč. 38, - (2004), s. 703-706 ISSN 1350-4487 R&D Projects: GA AV ČR(CZ) KSK1010104 Keywords : electron paramagnetic resonance * tungstates * defects Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.664, year: 2004

  15. Progressive and resonant wave helices application to electron paramagnetic resonance; Helices a ondes progressives et resonnantes application a la resonance paramagnetique electronique

    Energy Technology Data Exchange (ETDEWEB)

    Volino, F [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1969-07-01

    We show that helices can be used as resonant systems. Their properties are theoretically and experimentally studied. We describe resonant helices for electron paramagnetic resonance in X-band and develop a comparison between their sensitivity and the sensitivity of a normal resonant cavity. For cylindrical samples less than 3 mm diameter, the helix is more sensitive and can produce more intense microwave magnetic fields. (author) [French] Il est montre que les helices peuvent etre utilisees comme systeme resonnant. Leurs proprietes sont discutees theoriquement et experimentalement. Des helices resonnantes en bande X pour la resonance paramagnetique electronique sont decrites et leur sensibilite est comparee a celle des cavites resonnantes. Pour des echantillons cylindriques de moins de 3 mm de diametre, l'helice est plus sensible et peut produire des champs magnetiques hyper fins plus intenses. (auteur)

  16. Progressive and resonant wave helices application to electron paramagnetic resonance; Helices a ondes progressives et resonnantes application a la resonance paramagnetique electronique

    Energy Technology Data Exchange (ETDEWEB)

    Volino, F. [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1969-07-01

    We show that helices can be used as resonant systems. Their properties are theoretically and experimentally studied. We describe resonant helices for electron paramagnetic resonance in X-band and develop a comparison between their sensitivity and the sensitivity of a normal resonant cavity. For cylindrical samples less than 3 mm diameter, the helix is more sensitive and can produce more intense microwave magnetic fields. (author) [French] Il est montre que les helices peuvent etre utilisees comme systeme resonnant. Leurs proprietes sont discutees theoriquement et experimentalement. Des helices resonnantes en bande X pour la resonance paramagnetique electronique sont decrites et leur sensibilite est comparee a celle des cavites resonnantes. Pour des echantillons cylindriques de moins de 3 mm de diametre, l'helice est plus sensible et peut produire des champs magnetiques hyper fins plus intenses. (auteur)

  17. Electron paramagnetic resonance and optical absorption of uranium ions diluted in CdF2 single crystals

    International Nuclear Information System (INIS)

    Pereira, J.J.C.R.

    1976-08-01

    The electron paramagnetic resonance (EPR) has been studied in conection with the optical absortion spectra of Uranium ions diluted in CdF 2 single crystals. Analyses of the EPR and optical absorption spectra obtained experimentally, and a comparison with known results in the isomorfic CaF 2 , SrF 2 and BaF 2 , allowed the identification of two paramagnetic centers associated with Uranium ions. These are the U(2+) ion in cubic symmetry having the triplet γ 5 as ground state, and the U(3+) ion in cubic symmetry having the dublet γ 6 as ground state. (Author) [pt

  18. Observation of Conducting Structures in Detonation Nanodiamond Powder by Electron Paramagnetic Resonance

    Science.gov (United States)

    Binh, Nguyen Thi Thanh; Dolmatov, V. Yu.; Lapchuk, N. M.

    2018-01-01

    We have used electron paramagnetic resonance (EPR) to study high-purity detonation nanodiamond (DND) powders at room temperature. In recording the EPR signal with g factor 2.00247 and line width 0.890 mT, with automatic frequency control locking the frequency of the microwave generator (klystron) to the frequency of the experimental cavity, we observed a change in the shape of the EPR signal from the DND powder due to formation of an anisotropic electrically conducting structure in the powder. The electrical conductivity of the DND sample is apparent in the Dysonian EPR lineshape (strongly asymmetric signal with g factor 2.00146 and line width 0.281 mT) together with an abrupt shift of the baseline at the time of resonant absorption, and in the decrease in the cavity Q due to nonresonant microwave absorption. The observed effect can be explained by transition of the DND powder from a dielectric state to a state with metallic conductivity, due to spin ordering in a preferred direction.

  19. New developments in high field electron paramagnetic resonance with applications in structural biology

    International Nuclear Information System (INIS)

    Bennati, Marina; Prisner, Thomas F

    2005-01-01

    Recent developments in microwave technologies have led to a renaissance of electron paramagnetic resonance (EPR) due to the implementation of new spectrometers operating at frequencies ≥90 GHz. EPR at high fields and high frequencies (HF-EPR) has been established up to THz (very high frequency (VHF) EPR) in continuous wave (cw) operation and up to about 300 GHz in pulsed operation. To date, its most prominent application field is structural biology. This review article first gives an overview of the theoretical basics and the technical aspects of HF-EPR methodologies, such as cw and pulsed HF-EPR, as well as electron nuclear double resonance at high fields (HF-ENDOR). In the second part, the article illustrates different application areas of HF-EPR in studies of protein structure and function. In particular, HF-EPR has delivered essential contributions to disentangling complex spectra of radical cofactors or reaction intermediates in photosynthetic reaction centres, radical enzymes (such as ribonucleotide reductase) and in metalloproteins. Furthermore, HF-EPR combined with site-directed spin labelling in membranes and soluble proteins provides new methods of investigating complex molecular dynamics and intermolecular distances

  20. Dosimetric properties of textile fibers: application of electron paramagnetic resonance dosimetry to an accidental gamma irradiation

    International Nuclear Information System (INIS)

    Kamenopoulou, V.

    1988-01-01

    The dosimetric properties of some twenty textile fibers have been studied in order to develop a method for determining the dose received in the case of an accidental gamma irradiation. Three textile fibers having properties most closely satisfying our needs were selected for detailed investigations: cotton, polypropylene and quartz. Electron Paramagnetic Resonance (EPR) readout techniques were used. In order to eliminate spectral anisotropy problems due to textile fiber inhomogeneities, a system has been developed to rotate samples in the resonant cavity during measurements. The structure, physical and chemical properties of cotton and polypropylene were investigated. A bibliographic study of the combined effects of light, heat and ionizing radiation on textile fibers was carried out. A linear relation exists between the EPR signal and the gamma ray dose received over a certain dose range. A method has been developed for preparing samples so as to reduce background noise not due to irradiation; in this way the detection threshold is lowered and a greater time stability obtained. Unknown doses corresponding to known spectra are determined by linear interpolation using a series of spectra obtained from the same fabric irradiated with known doses [fr

  1. Relaxation study of a paramagnetic ion by the observation of nuclear resonance signals

    International Nuclear Information System (INIS)

    Landesman, A.

    1960-01-01

    Dynamic polarization of protons in water containing the paramagnetic ion NO(SO 3 ) 2 was studied, both theoretically and experimentally, as a function of magnetic field. The enhancement of the proton polarization depends appreciably on the relaxation process of the electron spin and so enables us to decide which is the real relaxation process. We tried the two following processes: a) The electron spin is coupled with the nitrogen magnetic moment by hyperfine interaction; if this interaction has an anisotropic part, a relaxation process for the electronic spin will result through the Brownian motion of the ion. b) The relaxation of the electron spin takes place through spin-orbit coupling of the electron spin. Experimental results showed that the relaxation took place through the second process with the help of dynamic polarization we were able to study the relaxation of an electron spin in a liquid without using any electron resonance spectrometer, simply by observing the resonance of a nuclear spin coupled with the electron spin. Reprint of a paper published in Le Journal de Physique et le Radium, t. 20, p. 937-948, 1959 [fr

  2. Investigation of Mn Implanted LiNbO3 applying electron paramagnetic resonance technique

    International Nuclear Information System (INIS)

    Darwish, A.; Ila, D.; Poker, D.B.; Hensley, D.K.

    1997-10-01

    The effect of ion implantation on the LiNbO 3 crystal is studied using electron paramagnetic resonance spectroscopy (EPR). EPR measurements on these crystals were performed as a function of ion species Mn and Fe and fluence at room temperature. Also the effect of the laser illumination on the EPR signal was determined by illuminating the crystal in situ and measuring the decay and growth of the EPR signal. LiNbO 3 :Mn 2+ at a depth of approximately 200 nm was formed by implantation of 2.5 x 10 14 Mncm 2 and 1 x 10 17 Mn/cm 2 at 2 MeV. The implanted samples were compared with bulk doped crystals. It was found that the decay and growth of Mn EPR for the implanted crystal is very small compared with the bulk doped LiNbO 3 :Mn crystal. This was found to be primarily due to the spin concentration on the crystals. On the other, hand the decay time of the high fluence is about 40% slower than the decay of the low fluence implanted crystal

  3. Direct rate assessment of laccase catalysed radical formation in lignin by electron paramagnetic resonance spectroscopy

    DEFF Research Database (Denmark)

    Munk, Line; Andersen, Mogens Larsen; Meyer, Anne S.

    2017-01-01

    Laccases (EC 1.10.3.2) catalyse removal of an electron and a proton from phenolic hydroxyl groups, including phenolic hydroxyls in lignins, to form phenoxy radicals during reduction of O2. We employed electron paramagnetic resonance spectroscopy (EPR) for real time measurement of such catalytic...... to suspensions of the individual lignin samples produced immediate time and enzyme dose dependent increases in intensity in the EPR signal with g-values in the range 2.0047–2.0050 allowing a direct quantitative monitoring of the radical formation and thus allowed laccase enzyme kinetics assessment on lignin...... for the radical formation rate in organosolv lignin was determined by response surface methodology to pH 4.8, 33 °C and pH 5.8, 33 °C for the Tv laccase and the Mt laccase, respectively. The results verify direct radical formation action of fungal laccases on lignin without addition of mediators and the EPR...

  4. 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)

  5. Some recent multi-frequency electron paramagnetic resonance results on systems relevant for dosimetry and dating.

    Science.gov (United States)

    Callens, F; Vanhaelewyn, G; Matthys, P

    2002-04-01

    Electron Paramagnetic Resonance (EPR) applications like e.g. EPR dosimetry and dating, are usually performed at X-band frequencies because of practical reasons (cost, sample size, etc.). However, it is increasingly recognized that the radiation-induced EPR signals are strongly composite, what might affect dose/age estimates. A few recent examples from both the dosimetry and dating field, illustrating the problems, will be presented. The involved spectra are mainly due to carbonate-derived radicals (CO2-, CO3(3-), etc.). Measurements at higher microwave frequencies are often recommended to improve the insight into the spectra and/or the practical signal quantification. Recent results at Q- and W-band frequencies will show that a multi-frequency approach indeed opens many interesting perspectives in this field but also that each frequency may have specific (dis)advantages depending on the EPR probe and application involved. The discussion will concern carbonate-containing apatite single crystals, shells, modern and fossil tooth enamel.

  6. 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.

  7. Photoexcitation electron paramagnetic resonance studies on nickel-related defects in diamond

    CERN Document Server

    Pereira, R N; Neves, A J; Sobolev, N A

    2003-01-01

    Measurements of the electron paramagnetic resonance (EPR) upon photoexcitation are reported on Ni defects in diamonds grown with Ni-containing solvent/catalysts. The temperature dependence of the W8 EPR spectrum photoquenching shows that the relaxation of substitutional Ni sub s sup - upon electron ionization is very small, corroborating the interpretation that the previously reported photoinduced effects with thresholds at 2.5 and 3.0 eV correspond to two complementary photoionization transitions involving Ni sub s. Photoinduced behaviour of the NIRIM1 EPR centre favours the interstitial Ni sub i sup + model for this defect and suggests that the Ni sub i sup 0 sup / sup + level is located at 1.98 +- 0.03 eV below the conduction band. In N-doped diamond, Ni sub i is more likely to appear in the neutral state, undetectable by EPR, whereas at substitutional sites Ni sub s sup - is revealed. Observation of a strong AB2 EPR signal photoquenching and simultaneous detection of different spectral dependencies of the...

  8. 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.

  9. Electron paramagnetic resonance image reconstruction with total variation and curvelets regularization

    Science.gov (United States)

    Durand, Sylvain; Frapart, Yves-Michel; Kerebel, Maud

    2017-11-01

    Spatial electron paramagnetic resonance imaging (EPRI) is a recent method to localize and characterize free radicals in vivo or in vitro, leading to applications in material and biomedical sciences. To improve the quality of the reconstruction obtained by EPRI, a variational method is proposed to inverse the image formation model. It is based on a least-square data-fidelity term and the total variation and Besov seminorm for the regularization term. To fully comprehend the Besov seminorm, an implementation using the curvelet transform and the L 1 norm enforcing the sparsity is proposed. It allows our model to reconstruct both image where acquisition information are missing and image with details in textured areas, thus opening possibilities to reduce acquisition times. To implement the minimization problem using the algorithm developed by Chambolle and Pock, a thorough analysis of the direct model is undertaken and the latter is inverted while avoiding the use of filtered backprojection (FBP) and of non-uniform Fourier transform. Numerical experiments are carried out on simulated data, where the proposed model outperforms both visually and quantitatively the classical model using deconvolution and FBP. Improved reconstructions on real data, acquired on an irradiated distal phalanx, were successfully obtained.

  10. Determination of azide in biological fluids by use of electron paramagnetic resonance

    International Nuclear Information System (INIS)

    Minakata, Kayoko; Suzuki, Osamu

    2005-01-01

    A simple and sensitive method has been developed for the determination of azide ion (N 3 - ) in biological fluids and beverages. The procedure was based on the formation of a ternary complex Cu(N 3 ) 2 (4-methylpyridine) x in benzene, followed by its detection by electron paramagnetic resonance. The complex in benzene showed a characteristic four-peak hyperfine structure with a g-value of 2.115 at room temperature. Cu 2+ reacted with N 3 - most strongly among common metals found in biological fluids. Several anions and metal ions in biological fluids did not interfere with the determination of N 3 - in the presence of large amounts of Cu 2+ and oxidants. In the present method, N 3 - at the concentration from 5 μM to 2 mM in 100 μl solution could be determined with the detection limit of 20 ng. The recoveries were more than 95% for N 3 - added to 100 μl of blood, urine, milk and beverages at 200 μM. Our method is recommendable because it takes less than 10 min to determine N 3 - and the produced complex is quite stable

  11. Electron paramagnetic resonance measurements of absorbed dose in teeth from citizens of Ozyorsk

    Energy Technology Data Exchange (ETDEWEB)

    Wieser, A.; Semiochkina, N. [Helmholtz Zentrum Muenchen - German Research Center for Environmental Health, Institute of Radiation Protection, Neuherberg (Germany); Vasilenko, E.; Aladova, E.; Smetanin, M. [Southern Urals Biophysics Institute, Ozyorsk (Russian Federation); Fattibene, P. [Istituto Superiore di Sanita, Rome (Italy)

    2014-05-15

    In 1945, within the frame of the Uranium Project for the production of nuclear weapons, the Mayak nuclear facilities were constructed at the Lake Irtyash in the Southern Urals, Russia. The nuclear workers of the Mayak Production Association (MPA), who lived in the city of Ozyorsk, are the focus of epidemiological studies for the assessment of health risks due to protracted exposure to ionising radiation. Electron paramagnetic resonance measurements of absorbed dose in tooth enamel have already been used in the past, in an effort to validate occupational external doses that were evaluated in the Mayak Worker Dosimetry System. In the present study, 229 teeth of Ozyorsk citizens not employed at MPA were investigated for the assessment of external background exposure in Ozyorsk. The annually absorbed dose in tooth enamel from natural background radiation was estimated to be (0.7 ± 0.3) mGy. For citizens living in Ozyorsk during the time of routine noble gas releases of the MPA, which peaked in 1953, the average excess absorbed dose in enamel above natural background was (36 ± 29) mGy, which is consistent with the gamma dose obtained by model calculations. In addition, there were indications of possible accidental gaseous MPA releases that affected the population of Ozyorsk, during the early and late MPA operation periods, before 1951 and after 1960. (orig.)

  12. Electron paramagnetic resonance and optical properties of Cr3+ doped YAl3(BO3)4

    International Nuclear Information System (INIS)

    Wells, Jon-Paul R; Yamaga, Mitsuo; Han, Thomas P J; Honda, Makoto

    2003-01-01

    We report on the electron paramagnetic resonance (EPR) and optical absorption and fluorescence spectroscopy of YAl 3 (BO 3 ) 4 single crystals doped with 0.2 mol% of trivalent chromium. From EPR we determine that the Cr 3+ ions reside in sites of essentially octahedral symmetry with an orthorhombic distortion. The ground state 4 A 2 splitting is determined to be 2√D 2 + 3E 2 ∼ 1.05 ± 0.04 cm -1 , where D and E are fine-structure parameters, and we can attribute this splitting to the combined effect of a low-symmetry distortion and spin-orbit coupling. The g-values and fine-structure parameters D and E of the ground state 4 A 2 are measured to be g x ∼ g y ∼ g z = 1.978 ± 0.005, vertical bar D vertical bar = 0.52 ± 0.02 cm -1 and vertical bar E vertical bar 0.010 ± 0.005 cm -1 respectively. From 10 K optical absorption we have measured the position and crystal-field splittings of the 2 E, 2 T 1 , 4 T 2 , 2 T 2 and 4 T 1 states with the 4 T 2 and 4 T 1 levels appearing as vibronically broadened bands

  13. Electron paramagnetic resonance study of neutral Mg acceptors in β-Ga2O3 crystals

    Science.gov (United States)

    Kananen, B. E.; Halliburton, L. E.; Scherrer, E. M.; Stevens, K. T.; Foundos, G. K.; Chang, K. B.; Giles, N. C.

    2017-08-01

    Electron paramagnetic resonance (EPR) is used to directly observe and characterize neutral Mg acceptors ( M gGa0 ) in a β-Ga2O3 crystal. These acceptors, best considered as small polarons, are produced when the Mg-doped crystal is irradiated at or near 77 K with x rays. During the irradiation, neutral acceptors are formed when holes are trapped at singly ionized Mg acceptors ( M gGa- ). Unintentionally present Fe3+ (3d5) and Cr3+ (3d3) transition-metal ions serve as the corresponding electron traps. The hole is localized in a nonbonding p orbital on a threefold-coordinated oxygen ion adjacent to an Mg ion at a sixfold-coordinated Ga site. These M gGa0 acceptors (S = 1/2) have a slightly anisotropic g matrix (principal values are 2.0038, 2.0153, and 2.0371). There is also partially resolved 69Ga and 71Ga hyperfine structure resulting from unequal interactions with the two Ga ions adjacent to the hole. With the magnetic field along the a direction, hyperfine parameters are 2.61 and 1.18 mT for the 69Ga nuclei at the two inequivalent neighboring Ga sites. The M gGa0 acceptors thermally convert back to their nonparamagnetic M gGa- charge state when the temperature of the crystal is raised above approximately 250 K.

  14. New method to measure the carbamoylating activity of nitrosoureas by electron paramagnetic resonance spectroscopy.

    Science.gov (United States)

    Gadzheva, V; Ichimori, K; Raikov, Z; Nakazawa, H

    1997-08-01

    A new method for measuring the carbamoylating activity of nitrosoureas and isocyanates using electron paramagnetic resonance (EPR) spectroscopy is described. The extent and time course of carbamoylation reaction of chloroethyl isocyanate and a series of 9 nitrosoureas toward amino group of 4-amino-2,2,6,6-tetramethyl-piperidine-1-oxyl were examined with both the EPR method and the HPLC method which has been proposed by Brubaker et al. [Biochem. Pharmacol. 35:2359 (1986)]. Spin-labeled nitrosoureas we synthesized are included in this study since they have less toxicity or more efficiency than commercially available drug in some cases. The concentration of carbamoylated product was easily determined with the EPR spectra. There is a very high correlation (r = 0.982, t = 2.58, N = 10, p nitrosoureas showed lower carbamoylating activity than non-labeled analogues. The carbamoylating activity for these nitrosourea depended on the reactivity of isocyanate intermediate and almost independent of their half life. This rapid and simple EPR method is suitable for the detailed investigation of the rate and extent of carbamoylation reaction.

  15. Electron paramagnetic resonance of V4+ in the lanthanum and cerium orthophosphates

    International Nuclear Information System (INIS)

    Lima, J.C. de.

    1983-11-01

    The Electron Paramagnetic Resonance (EPR) spectrum of V 4+ was investigated in polycrystalline samples of lanthanum orthophosphate (LaPO 4 ) and cerium orthophosphate (CePO 4 ) doped with 0.2 wt % vanadium pentoxide (V 2 O 5 ). Measurements were performed at room temperature and 9.5 GHz. In LaPO 4 , two non-equivalent axial sites were inferred from the EPR spectra. The most stable of these two sites is probably substitutional. In CePO 4 , a single axial spectrum was observed. It was attributed to V 4+ in substitutional sites. A central, wide line was also seen; it was attributed to ferromagnetic clusters of vanadium ions. Photoacoustic absorption spectra were also recorded for the two compounds. The EPR and photoacoustic absorption data, when analyzed using the molecular orbital theory, show that for both lanthanum orthophosphate and cerium orthophosphate the ground orbital (d sub(x) 2 sub(-y) 2) of the unpainred electron is purely ionic, while the excited orbitals d sub(xy) and d sub(xz,yz) are partly covalent. The degree of covalency is higher for the d sub(xy) orbital. Finally, it should be pointed out that part of the theory used for the interpretation of the EPR and photoacoustic absorption spectra (study of the ligand field splitting of a d orbital in a site of distorted capped antiprism structure) was developed by the author in the present work and is therefore an original contribution. (Author) [pt

  16. Offline combination of pressurized fluid extraction and electron paramagnetic resonance spectroscopy for antioxidant activity of grape skin extracts assessment

    Czech Academy of Sciences Publication Activity Database

    Polovka, M.; Šťavíková, Lenka; Hohnová, Barbora; Karásek, Pavel; Roth, Michal

    2010-01-01

    Roč. 1217, č. 51 (2010), s. 7990-8000 ISSN 0021-9673 R&D Projects: GA ČR GA203/08/1536; GA MŠk LC06023 Institutional research plan: CEZ:AV0Z40310501 Keywords : pressurized fluid extraction * electron paramagnetic resonance spectroscopy * antioxidant activity Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 4.194, year: 2010

  17. 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

  18. Electron paramagnetic resonance study of lipid and protein membrane components of erythrocytes oxidized with hydrogen peroxide

    Energy Technology Data Exchange (ETDEWEB)

    Mendanha, S.A.; Anjos, J.L.V.; Silva, A.H.M.; Alonso, A. [Instituto de Física, Universidade Federal de Goiás, Goiânia, GO (Brazil)

    2012-04-05

    Electron paramagnetic resonance (EPR) spectroscopy of spin labels was used to monitor membrane dynamic changes in erythrocytes subjected to oxidative stress with hydrogen peroxide (H{sub 2}O{sub 2}). The lipid spin label, 5-doxyl stearic acid, responded to dramatic reductions in membrane fluidity, which was correlated with increases in the protein content of the membrane. Membrane rigidity, associated with the binding of hemoglobin (Hb) to the erythrocyte membrane, was also indicated by a spin-labeled maleimide, 5-MSL, covalently bound to the sulfhydryl groups of membrane proteins. At 2% hematocrit, these alterations in membrane occurred at very low concentrations of H{sub 2}O{sub 2} (50 µM) after only 5 min of incubation at 37°C in azide phosphate buffer, pH 7.4. Lipid peroxidation, suggested by oxidative hemolysis and malondialdehyde formation, started at 300 µM H{sub 2}O{sub 2} (for incubation of 3 h), which is a concentration about six times higher than those detected with the probes. Ascorbic acid and α-tocopherol protected the membrane against lipoperoxidation, but did not prevent the binding of proteins to the erythrocyte membrane. Moreover, the antioxidant (+)-catechin, which also failed to prevent the cross-linking of cytoskeletal proteins with Hb, was very effective in protecting erythrocyte ghosts from lipid peroxidation induced by the Fenton reaction. This study also showed that EPR spectroscopy can be useful to assess the molecular dynamics of red blood cell membranes in both the lipid and protein domains and examine oxidation processes in a system that is so vulnerable to oxidation.

  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. 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.

  1. Electron paramagnetic resonance study on n-type electron-irradiated 3C-SiC

    Energy Technology Data Exchange (ETDEWEB)

    Carlsson, P; Rabia, K; Son, N T; Janzen, E [Department of Physics, Chemistry and Biology, Linkoeping University, SE-581 83 Linkoeping (Sweden); Ohshima, T; Morishita, N; Itoh, H [Japan Atomic Energy Research Institute, Takasaki 370-1292 (Japan); Isoya, J [University of Tsukuba, Tsukuba 305-8550 (Japan)], E-mail: paca@ifm.liu.se

    2008-03-15

    Electron Paramagnetic Resonance (EPR) was used to study defects in n-type 3C-SiC films irradiated by 3-MeV electrons at room temperature with a dose of 2x10{sup 18} cm{sup -2}. After electron irradiation, two new EPR spectra with an effective spin S = 1, labeled L5 and L6, were observed. The L5 center has C{sub 3v} symmetry with g = 2.004 and a fine-structure parameter D = 436.5x10{sup -4} cm{sup -1}. The L5 spectrum was only detected under light illumination and it could not be detected after annealing at {approx}550{sup 0}C. The principal z-axis of the D tensor is parallel to the <111>-directions, indicating the location of spins along the Si-C bonds. Judging from the symmetry and the fact that the signal was detected under illumination in n-type material, the L5 center may be related to the divacancy in the neutral charge state. The L6 center has a C{sub 2v}-symmetry with an isotropic g-value of g = 2.003 and the fine structure parameters D = 547.7x10{sup -4} cm{sup -1} and E = 56.2x10{sup -4} cm{sup -1}. The L6 center disappeared after annealing at a rather low temperature ({approx}200 deg. C), which is substantially lower than the known annealing temperatures for vacancy-related defects in 3C-SiC. This highly mobile defect may be related to carbon interstitials.

  2. Primary Study about Intensity Signal of Electron Paramagnetic Resonance in vivo Tooth Dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Hoon; Gang, Seo Gon; Kim, Jeong In; Lee, Byung Il [KHNP Radiation Health Institute, Gyeongju (Korea, Republic of)

    2017-04-15

    The signal of Electron Paramagnetic Resonance(EPR) dosimetry system using human tooth has been well introduced as one of the efficient tool to evaluate radiation exposure. But, EPR dosimetry, even in the case of classical in vitro EPR system using tooth sample(measured molars), was regarded as having big signal fluctuation. One of reason for such difficulty in getting accurate intensity was the big effect of organic materials mixed in enamel part of teeth samples. They are mainly caused by the adaptation process of system itself to the movement of measured human subject. Generally, when we measured human teeth in vivo, five of six teeth spectrum were gathered and averaged for real evaluation. The these spectrum are measured under very different environment like angle of external magnet making magnetic filed with teeth(incisor). Random movement of these signals should be considered in different view point to understand and compare each EPR in vivo EPR spectrum. The peak to peak value of obtained five or six in vivo EPR system to get averaged value for final quantity of free radicals in hydroxy apatite crystal construction in enamel part of human teeth looks so randomly changed without regulation. But, in overall view, the EPR signal, especially at no irradiation level, is almost same for every measurement trial which is mainly composed of big noise and very small signal from real free radicals. The peak to peak value of obtained five or six in vivo EPR system to get averaged value for final quantity of free radicals in hydroxy apatite crystal construction in enamel part of human teeth looks so randomly changed without regulation.

  3. Analysis of Gamma-irradiated Soybean Components by Electron Paramagnetic Resonance

    International Nuclear Information System (INIS)

    Oliveira, M.R. R. de; Quadrado, M.G.O.; Mastro, N.L. del

    2007-01-01

    Soybean (Glycine max) seeds contain besides oil and protein, important phytochemicals that have been shown in recent years to offer important health benefits. Soybean contains at least six classes of antioxidant compounds: flavonol, isoflavones, anthocyanins, proanthocyanidins, tocopherols, and poly carboxylic acids. An increasing number of studies have documented the significant value of many classes of these compounds, mainly isoflavones, not only as potent antioxidants, but also as antitumor agents and cardio protective compounds. Food irradiation is gaining increasing attention around the world but it is not a worldwide approved treatment yet. Electron paramagnetic resonance, EPR, is considered the most important technique to detect free-radicals on food. Results from a previous work showed that irradiated soybean could be detected by EPR only when higher doses were employed. This study was undertaken to investigate the radiation response of the diverse parts of the soy seed: hull or seed coat, cotyledons, hilum and hypocotyl axis or germ, from different soybean cultivars. Soybean samples were obtained from the National Soybean Research Center (Embrapa-Soja), Londrina, Brazil, separated in their components and gamma-irradiated in a Gamma cell 220 (AECL) with doses of 0.1 and 2.0 kGy at a dose rate of 2.9 kGy/h. EPR measurements were performed on an X-band spectrometer (ER 041 XG Microwave Bridge, Bruker). Both irradiation and EPR measurements were performed at room temperature (20-25 C). The results showed that the EPR signal intensity correlated with the ionizing radiation dose, although different cultivars presented differences in their radiation response. The main EPR peak corresponding to free radical presented differences in shape and intensity. The hull and the hilum presented signals higher and easier to be analyzed than the whole bean, indicating strong differences in radiation sensitivity of soybean components. (Author)

  4. Interpretation of the Electron Paramagnetic Resonance Spectra of Copper(II)-Tyrosine Complex

    Science.gov (United States)

    Xu, Xiao-Hui; Kuang, Min-Quan

    2017-12-01

    The electron paramagnetic resonance (EPR) spectra of [Cu(l-tyrosine)2]n (CuA) were interpreted based on the fourth-order perturbation treatments where the contributions due to the local distortion, ligand orbit and spin-orbit coupling were included. The calculated band transitions d_{x^2} - y^2 to dxy (≈16412 cm-1) and d_{z^2} (≈14845 cm-1) agree well with the band analysis results (d_{x^2} - y^2 \\to d_{xy} ≈16410 and d_{x^2} - y^2 \\to d_{z^2} ≈14850 cm-1). The unresolved separations d_{x^2} - y^2 \\to d_{xz} and d_{x^2} - y^2 \\to d_{yz} in the absorption spectra were evaluated as 26283 and 26262 cm-1, respectively. For CuA, copper chromophores in 1,3-diaminorpropane isophtalate copper(II) complex (CuB) and N-methyl-1,2-diaminoetaane-bis copper(II) polymer (CuC), the transition d_{x^2} - y^2 \\to d_{xy} (=E1≈10Dq) suffered an increase with a decrease in R̅L which was evaluated as the mean value of the copper-ligand bond lengths. The correlations between the tetragonal elongation ratio ρ (=(Rz-R̅L)/R̅L) (or the ratio G=(gz-ge)/((gx+gy)/2-ge)) and the g isotropy gav (=(gx+gy+gz)/3) (or the covalency factor N) for CuA, CuB and CuC were acquired and all the results were discussed.

  5. Primary Study about Intensity Signal of Electron Paramagnetic Resonance in vivo Tooth Dosimetry

    International Nuclear Information System (INIS)

    Choi, Hoon; Gang, Seo Gon; Kim, Jeong In; Lee, Byung Il

    2017-01-01

    The signal of Electron Paramagnetic Resonance(EPR) dosimetry system using human tooth has been well introduced as one of the efficient tool to evaluate radiation exposure. But, EPR dosimetry, even in the case of classical in vitro EPR system using tooth sample(measured molars), was regarded as having big signal fluctuation. One of reason for such difficulty in getting accurate intensity was the big effect of organic materials mixed in enamel part of teeth samples. They are mainly caused by the adaptation process of system itself to the movement of measured human subject. Generally, when we measured human teeth in vivo, five of six teeth spectrum were gathered and averaged for real evaluation. The these spectrum are measured under very different environment like angle of external magnet making magnetic filed with teeth(incisor). Random movement of these signals should be considered in different view point to understand and compare each EPR in vivo EPR spectrum. The peak to peak value of obtained five or six in vivo EPR system to get averaged value for final quantity of free radicals in hydroxy apatite crystal construction in enamel part of human teeth looks so randomly changed without regulation. But, in overall view, the EPR signal, especially at no irradiation level, is almost same for every measurement trial which is mainly composed of big noise and very small signal from real free radicals. The peak to peak value of obtained five or six in vivo EPR system to get averaged value for final quantity of free radicals in hydroxy apatite crystal construction in enamel part of human teeth looks so randomly changed without regulation.

  6. Electron paramagnetic resonance and density-functional theory studies of Cu(II)-bis(oxamato) complexes.

    Science.gov (United States)

    Bräuer, Björn; Weigend, Florian; Fittipaldi, Maria; Gatteschi, Dante; Reijerse, Edward J; Guerri, Annalisa; Ciattini, Samuele; Salvan, Georgeta; Rüffer, Tobias

    2008-08-04

    In this work we present the investigation of the influence of electronic and structural variations induced by varying the N,N'-bridge on the magnetic properties of Cu(II)- bis(oxamato) complexes. For this study the complexes [Cu(opba)] (2-) ( 1, opba = o-phenylene- bis(oxamato)), [Cu(nabo)] (2-) ( 2, nabo = 2,3-naphthalene- bis(oxamato)), [Cu(acbo)] (2-) ( 3, acbo = 2,3-anthrachinone- bis(oxamato)), [Cu(pba)] (2-) ( 4, pba = propylene- bis(oxamato)), [Cu(obbo)] (2-) ( 5, obbo = o-benzyl- bis(oxamato)), and [Cu(npbo)] (2-) ( 6, npbo = 1,8-naphthalene- bis(oxamato)), and the respective structurally isomorphic Ni(II) complexes ( 8- 13) have been prepared as ( (n)Bu 4N) (+) salts. The new complex ( (n)Bu 4N) 2[Cu(R-bnbo)].2H 2O ( 7, R-bnbo = (R)-1,1'-binaphthalene-2,2'- bis(oxamato)) was synthesized and is the first chiral complex in the series of Cu(II)-bis(oxamato) complexes. The molecular structure of 7 has been determined by single crystal X-ray analysis. The Cu(II) ions of the complexes 1- 7 are eta (4)(kappa (2) N, kappa (2) O) coordinated with a more or less distorted square planar geometry for 1- 6 and a distorted tetrahedral geometry for 7. Using pulsed Electron Nuclear Double Resonance on complex 6, detailed information about the relative orientation of the hyperfine ( A) and nuclear quadrupole tensors ( Q) of the coordinating nitrogens with respect to the g tensor were obtained. Electron Paramagnetic Resonance studies in the X, Q, and W-band at variable temperatures were carried out to extract g and A values of N ligands and Cu ion for 1- 7. The hyperfine values were interpreted in terms of spin population on the corresponding atoms. The obtained trends of the spin population for the monomeric building blocks were shown to correlate to the trends obtained in the dependence of the exchange interaction of the corresponding trinuclear complexes on their geometry.

  7. Electron paramagnetic resonance investigation of polycrystalline CaCu{sub 3}Ti{sub 4}O{sub 12}

    Energy Technology Data Exchange (ETDEWEB)

    Mozzati, Maria Cristina [INFM-Dipartimento di Fisica ' Alessandro Volta' , Universita di Pavia, via Bassi 6, I-27100 Pavia (Italy); Azzoni, Carlo Bruno [INFM-Dipartimento di Fisica ' Alessandro Volta' , Universita di Pavia, via Bassi 6, I-27100 Pavia (Italy); Capsoni, Doretta [Dipartimento di Chimica Fisica ' Mario Rolla' , Universita di Pavia and IENI-CNR, Sezione di Pavia, viale Taramelli 16, I-27100 Pavia (Italy); Bini, Marcella [Dipartimento di Chimica Fisica ' Mario Rolla' , Universita di Pavia and IENI-CNR, Sezione di Pavia, viale Taramelli 16, I-27100 Pavia (Italy); Massarotti, Vincenzo [Dipartimento di Chimica Fisica ' Mario Rolla' , Universita di Pavia and IENI-CNR, Sezione di Pavia, viale Taramelli 16, I-27100 Pavia (Italy)

    2003-11-05

    Electron paramagnetic resonance (EPR) measurements on pure polycrystalline CaCu{sub 3}Ti{sub 4}O{sub 12} have been performed and are discussed within a crystal-field approach. A symmetric signal centred at g = 2.15 is observed for T>25 K, with no evidence of hyperfine structure. At this temperature an antiferromagnetic transition is observed as confirmed by static magnetization data. Cu defective and 2% doped (V, Cr, Mn, La) samples were also prepared and considered, mainly to understand the nature of the observed paramagnetic centre. Substitutions in the octahedral sites, causing variations of the configuration in CuO{sub 4}-TiO{sub 6}-CuO{sub 4} complexes, change the magnetic and EPR features. To justify the EPR response a strong copper-hole delocalization is suggested.

  8. High-resolution mapping of 1D and 2D dose distributions using X-band electron paramagnetic resonance imaging

    International Nuclear Information System (INIS)

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

    2014-01-01

    Electron paramagnetic resonance imaging (EPRI) was performed to visualise 2D dose distributions of homogeneously irradiated potassium dithionate tablets and to demonstrate determination of 1D dose profiles along the height of the tablets. Mathematical correction was applied for each relative dose profile in order to take into account the inhomogeneous response of the resonator using X-band EPRI. The dose profiles are presented with the spatial resolution of 0.6 mm from the acquired 2D images; this value is limited by pixel size, and 1D dose profiles from 1D imaging with spatial resolution of 0.3 mm limited by the intrinsic line-width of potassium dithionate. In this paper, dose profiles from 2D reconstructed electron paramagnetic resonance (EPR) images using the Xepr software package by Bruker are focussed. The conclusion is that using potassium dithionate, the resolution 0.3 mm is sufficient for mapping steep dose gradients if the dosemeters are covering only ±2 mm around the centre of the resonator. (authors)

  9. Signature of ferro–paraelectric transition in biferroic LuCrO{sub 3} from electron paramagnetic resonance and non-resonant microwave absorption

    Energy Technology Data Exchange (ETDEWEB)

    Alvarez, G., E-mail: memodin@yahoo.com [Escuela Superior de Física y Matemáticas del Instituto Politécnico Nacional, U.P.A.L.M, Edificio 9, Av. Instituto Politécnico Nacional S/N, San Pedro Zacatenco, México DF 07738 (Mexico); Montiel, H. [Centro de Ciencias Aplicadas y Desarrollo Tecnológico de la Universidad Nacional Autónoma de México, Cd. Universitaria, A.P. 70-186, México DF 04510 (Mexico); Durán, A. [Centro de Nanociencias y Nanotecnología de la Universidad Nacional Autónoma de México, Km. 107, Carretera Tijuana-Ensenada, Apartado Postal 14, C.P. 22800 Ensenada, B.C. México (Mexico); Conde-Gallardo, A. [Departamento de Física, CINVESTAV-IPN, A.P. 14-740, México DF 07360 (Mexico); Zamorano, R. [Escuela Superior de Física y Matemáticas del Instituto Politécnico Nacional, U.P.A.L.M, Edificio 9, Av. Instituto Politécnico Nacional S/N, San Pedro Zacatenco, México DF 07738 (Mexico)

    2014-12-15

    An electron paramagnetic resonance (EPR) study in the polycrystalline biferroic LuCrO{sub 3} is carried out at X-band (8.8–9.8 GHz) in the 295–510 K temperature range. For all the temperatures, the EPR spectra show a single broad line attributable to Cr{sup 3+} (S = 3/2) ions. The onset of a ferro–paraelectric transition has been determined from the temperature dependence of the parameters deduced from EPR spectra: the peak-to-peak linewidth (ΔH{sub pp}), the g-factor and the integral intensity (I{sub EPR}). Magnetically modulated microwave absorption spectroscopy (MAMMAS) and low-field microwave absorption (LFMA) are used to give further information on this material, where these techniques give also evidence of the ferro–paraelectric transition; indicating a behavior in agreement with a diffuse phase transition. - Highlights: • LuCrO{sub 3} powders are obtained via auto-ignition synthesis. • EPR is employed to study the onset of the ferro–paraelectric transition. • MAMMAS and LFMA techniques are used to give further information on this material.

  10. Signature of ferro–paraelectric transition in biferroic LuCrO3 from electron paramagnetic resonance and non-resonant microwave absorption

    International Nuclear Information System (INIS)

    Alvarez, G.; Montiel, H.; Durán, A.; Conde-Gallardo, A.; Zamorano, R.

    2014-01-01

    An electron paramagnetic resonance (EPR) study in the polycrystalline biferroic LuCrO 3 is carried out at X-band (8.8–9.8 GHz) in the 295–510 K temperature range. For all the temperatures, the EPR spectra show a single broad line attributable to Cr 3+ (S = 3/2) ions. The onset of a ferro–paraelectric transition has been determined from the temperature dependence of the parameters deduced from EPR spectra: the peak-to-peak linewidth (ΔH pp ), the g-factor and the integral intensity (I EPR ). Magnetically modulated microwave absorption spectroscopy (MAMMAS) and low-field microwave absorption (LFMA) are used to give further information on this material, where these techniques give also evidence of the ferro–paraelectric transition; indicating a behavior in agreement with a diffuse phase transition. - Highlights: • LuCrO 3 powders are obtained via auto-ignition synthesis. • EPR is employed to study the onset of the ferro–paraelectric transition. • MAMMAS and LFMA techniques are used to give further information on this material

  11. Electron paramagnetic resonance studies on silver atoms and clusters in regularly interstratified clay minerals

    International Nuclear Information System (INIS)

    Yamada, H.; Tamura, K.; Shimomura, S.; Sadlo, J.; Turek, J.; Michalik, J.

    2004-01-01

    The formation and stabilization of reduced silver species in the regularly interstratified clay minerals, trioctahedral smectite/chlorite (tri-Sm/Ch) and dioctahedral smectite/mica (di-Sm/M), have been studied by electron paramagnetic resonance (EPR) spectroscopy. Both minerals loaded with Ag + cations after degassing and dehydration were γ-irradiated at 77 K and monitored by EPR as the temperature increased. Some samples were exposed to water or methanol vapor after dehydration. In both hydrated and dehydrated samples only the doublets to Ag 0 atoms were observed with no evidence of the formation of Ag clusters. However, the EPR parameter of silver atoms in both matrices are different. In tri-Sm/Ch the narrow anisotropic EPR lines overlap with the broader isotropic lines, whereas in di-Sm/M only broad lines are recorded. The hyperfine splitting - A iso (Ag 0 ) is larger in tri-Sm/Ch than in di-Sm/M. Also the stability of Ag 0 in both clay minerals is distinctly different. Ag 0 doublet in di-Sm/M disappears completely above 230 K, Whereas in tri-Sm/Ch it is still recorded at 310 K. It is proposed, basing on the EPR results that Ag 0 atoms appear at different sites in both matrices: - in tri-Sm/Ch in the middle of smectite interlayer and in hexagonal cavities in the silicate sheets of tetrahedron layer and in di-Sm.M in hexagonal cavities only. When samples had been exposed to methanol before irradiation, the silver clusters become stabilized in the interlayer sites. In tri-Sm/M matrix the silver dimer Ag 2 + formed by gamma-irradiation at 77 K is transformed to tetrameric cluster, Ag 4 + at 150 K. In di-Sm/M the radiation-induced silver agglomeration proceeds in a similar way, but with a slower rate and Ag tetramer is formed only above 190 K. In both clay minerals, Ag 4 + clusters decay above 250 K. (author)

  12. The Resonance Integral of Gold

    Energy Technology Data Exchange (ETDEWEB)

    Jirlow, K; Johansson, E

    1959-04-15

    The resonance activation integral of gold has been determined, by means of cadmium ratio measurements of thin foils in a neutron beam. Comparison was made with a 1/v detector, and the neutron spectra were measured with a chopper. The resonance integral, RI, is defined as {integral}{sub 0.5}{sup {infinity}}{sigma}{sub r}(E)dE/E, where {sigma}{sub r}(E) is the differenc between the total absorption cross section and the 1/v part. An experimental value of 1490 {+-} 40 barns has been obtained. RI has also been computed from resonance parameter data with the result 1529 {+-} 70 barns.

  13. Conventional electron paramagnetic resonance of Mn2+ in synthetic hydroxyapatite at different concentrations of the doped manganese

    Science.gov (United States)

    Murzakhanov, F.; Mamin, G.; Voloshin, A.; Klimashina, E.; Putlyaev, V.; Doronin, V.; Bakhteev, S.; Yusupov, R.; Gafurov, M.; Orlinskii, S.

    2018-05-01

    Powders of synthetic hydroxyapatite doped with Mn2+ ions in concentrations from 0.05 till 5 wt. % were investigated by conventional electron paramagnetic resonance (EPR). The parameters of the spin-Hamiltonian are derived. Partially resolved hyperfine structure in the magnetic fields corresponding to g ≈ 4.3 and g ≈ 9.4 is observed. The narrowing of the central peak with concentration is reported. A possibility to use the linewidth and intensity of the central peak for concentration measurements are discussed. The results could be used for the identification and qualification of Mn2+ in oil, mining and ore formations.

  14. Electron paramagnetic resonance g-tensors from state interaction spin-orbit coupling density matrix renormalization group

    Science.gov (United States)

    Sayfutyarova, Elvira R.; Chan, Garnet Kin-Lic

    2018-05-01

    We present a state interaction spin-orbit coupling method to calculate electron paramagnetic resonance g-tensors from density matrix renormalization group wavefunctions. We apply the technique to compute g-tensors for the TiF3 and CuCl42 - complexes, a [2Fe-2S] model of the active center of ferredoxins, and a Mn4CaO5 model of the S2 state of the oxygen evolving complex. These calculations raise the prospects of determining g-tensors in multireference calculations with a large number of open shells.

  15. X-ray photoelectron spectroscopy and paramagnetic resonance evidence for shock-induced intramolecular bond breaking in some energetic solids

    Science.gov (United States)

    Owens, F. J.; Sharma, J.

    1980-03-01

    Solid samples of 1,3,5, trinitro 1,3,5, triazacyclohexane (RDX), trinitrotoluene (TNT), and ammonium nitrate were subjected to shock pulses of strength and duration less than the threshold to cause detonation. The recovered shocked samples were studied by x-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR). The results of these measurements indicate that the shock pulse either broke or altered the internal bonds of the molecules of the solid. The results of the shock decomposition are compared with measurements of the uv and slow thermal decomposition of these materials using the same experimental techniques.

  16. Pulse-electron paramagnetic resonance of Cr.sup.3+./sup. centers in SrTiO.sub.3./sub..

    Czech Academy of Sciences Publication Activity Database

    Azamat, Dmitry; Dejneka, Alexandr; Lančok, Ján; Trepakov, Vladimír; Jastrabík, Lubomír; Badalyan, A. G.

    2013-01-01

    Roč. 113, č. 17 (2013), "174106-1"-"174106-6" ISSN 0021-8979 R&D Projects: GA MŠk(CZ) LM2011029; GA TA ČR TA01010517; GA ČR GAP108/12/1941 Grant - others:SAFMAT(XE) CZ.2.16/3.1.00/22132 Institutional support: RVO:68378271 Keywords : pulse-electron paramagnetic resonance * Cr3+ centers in SrTiO 3 Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.185, year: 2013

  17. 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.

  18. Moessbauer, electron paramagnetic resonance and magnetic susceptibility studies of photosensitive nitrile hydratase from Rhodococcus sp. N-771

    International Nuclear Information System (INIS)

    Nagamune, Teruyuki; Honda, Jun; Kobayashi, Yoshio; Sasabe, Hiroyuki; Endo, Isao; Ambe, Fumitoshi; Teratani, Yoshitaka; Hirata, Akira

    1992-01-01

    Moessbauer, magnetic susceptibility and electron paramagnetic resonance (EPR) studies of inactive and photoactivated NHase enzymes were performed to elucidate the electronic change of non-heme two-iron atom center of the enzyme by photoactivation. These spectroscopic investigations revealed that both the two iron atoms of the active NHase could be assigned to low-spin ferric state, and those of the inactive NHase could each be assigned to low-spin ferric and low-spin ferrous ones. From these results, it was concluded that one of the non-heme iron atoms is oxidized in the inactive NHase during photoactivation. (orig.)

  19. Al-doped MgB{sub 2} materials studied using electron paramagnetic resonance and Raman spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Bateni, Ali; Somer, Mehmet, E-mail: emre.erdem@physchem.uni-freiburg.de, E-mail: msomer@ku.edu.tr [Department of Chemistry, Koç University, Rumelifeneri Yolu, Sariyer, Istanbul (Turkey); Erdem, Emre, E-mail: emre.erdem@physchem.uni-freiburg.de, E-mail: msomer@ku.edu.tr; Repp, Sergej [Institut für Physikalische Chemie, Universität Freiburg, Albertstr. 21, Freiburg (Germany); Weber, Stefan [Institut für Physikalische Chemie, Universität Freiburg, Albertstr. 21, Freiburg (Germany); Freiburg Institute for Advanced Studies (FRIAS), Universität Freiburg, Albertstr. 19, Freiburg (Germany)

    2016-05-16

    Undoped and aluminum (Al) doped magnesium diboride (MgB{sub 2}) samples were synthesized using a high-temperature solid-state synthesis method. The microscopic defect structures of Al-doped MgB{sub 2} samples were systematically investigated using X-ray powder diffraction, Raman spectroscopy, and electron paramagnetic resonance. It was found that Mg-vacancies are responsible for defect-induced peculiarities in MgB{sub 2}. Above a certain level of Al doping, enhanced conductive properties of MgB{sub 2} disappear due to filling of vacancies or trapping of Al in Mg-related vacancy sites.

  20. Development and validation of an ex vivo electron paramagnetic resonance fingernail bio-dosimetric method

    International Nuclear Information System (INIS)

    He, Xiaoming; Swarts, Steven G.; Marsh, Stephen D.; Demidenko, Eugene; Flood, Ann B.; Grinberg, Oleg; Gui, Jiang; Mariani, Michael; Ruuge, Andres E.; Tipikin, Dmitry; Swartz, Harold M.; Sidabras, Jason W.; Wilcox, Dean E.

    2014-01-01

    There is an imperative need to develop methods that can rapidly and accurately determine individual exposure to radiation for screening (triage) populations and guiding medical treatment in an emergency response to a large-scale radiological/nuclear event. To this end, a number of methods that rely on dose-dependent chemical and/or physical alterations in biomaterials or biological responses are in various stages of development. One such method, ex vivo electron paramagnetic resonance (EPR) nail dosimetry using human nail clippings, is a physical bio-dosimetry technique that takes advantage of a stable radiation-induced signal (RIS) in the keratin matrix of fingernails and toenails. This dosimetry method has the advantages of ubiquitous availability of the dosimetric material, easy and non-invasive sampling, and the potential for immediate and rapid dose assessment. The major challenge for ex vivo EPR nail dosimetry is the overlap of mechanically induced signals and the RIS. The difficulties of analysing the mixed EPR spectra of a clipped irradiated nail were addressed in the work described here. The following key factors lead to successful spectral analysis and dose assessment in ex vivo EPR nail dosimetry: (1) obtaining a thorough understanding of the chemical nature, the decay behaviour, and the microwave power dependence of the EPR signals, as well as the influence of variation in temperature, humidity, water content, and O 2 level; (2) control of the variability among individual samples to achieve consistent shape and kinetics of the EPR spectra; (3) use of correlations between the multiple spectral components; and (4) use of optimised modelling and fitting of the EPR spectra to improve the accuracy and precision of the dose estimates derived from the nail spectra. In the work described here, two large clipped nail datasets were used to test the procedures and the spectral fitting model of the results obtained with it. A 15-donor nail set with 90 nail samples

  1. 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

  2. Changes in mitochondrial functioning with electromagnetic radiation of ultra high frequency as revealed by electron paramagnetic resonance methods.

    Science.gov (United States)

    Burlaka, Anatoly; Selyuk, Marina; Gafurov, Marat; Lukin, Sergei; Potaskalova, Viktoria; Sidorik, Evgeny

    2014-05-01

    To study the effects of electromagnetic radiation (EMR) of ultra high frequency (UHF) in the doses equivalent to the maximal permitted energy load for the staffs of the radar stations on the biochemical processes that occur in the cell organelles. Liver, cardiac and aorta tissues from the male rats exposed to non-thermal UHF EMR in pulsed and continuous modes were studied during 28 days after the irradiation by the electron paramagnetic resonance (EPR) methods including a spin trapping of superoxide radicals. The qualitative and quantitative disturbances in electron transport chain (ETC) of mitochondria are registered. A formation of the iron-nitrosyl complexes of nitric oxide (NO) radicals with the iron-sulphide (FeS) proteins, the decreased activity of FeS-protein N2 of NADH-ubiquinone oxidoreductase complex and flavo-ubisemiquinone growth combined with the increased rates of superoxide production are obtained. (i) Abnormalities in the mitochondrial ETC of liver and aorta cells are more pronounced for animals radiated in a pulsed mode; (ii) the alterations in the functioning of the mitochondrial ETC cause increase of superoxide radicals generation rate in all samples, formation of cellular hypoxia, and intensification of the oxide-initiated metabolic changes; and (iii) electron paramagnetic resonance methods could be used to track the qualitative and quantitative changes in the mitochondrial ETC caused by the UHF EMR.

  3. Magnetic resonance tomography of the orbit: First experiences with the paramagnetic contrast medium gadolinium-DTPA

    International Nuclear Information System (INIS)

    Markl, A.; Vogl, T.; Scheidhauer, K.; Riedel, K.G.; Oeckler, R.

    1986-01-01

    In 21 patients with orbital mass lesions MRI was performed before and after administration of paramagnetic contrast medium, gadolinium-DPTA. In comparison to the plain scan the differentiation of the tumorous tissue against the surrounding structures was improved after application of contrast medium despite a partially moderate increase in signal intensity. Especially highly vascular tumors and vessel diseases show a significant contrast enhancement. With increasing experience in larger number of patients a tissue differentiation seems to be possible. (orig.) [de

  4. Anomalous magnetism and electron paramagnetic resonance spectroscopy of the ZrNi1-xCrxSn solid solution

    International Nuclear Information System (INIS)

    Stadnyk, Y.V.; Skolozdra, R.V.; Gorelenko, Y.K.; Romaka, L.P.; Jankowska-Frydel, A.; Grinberg, M.

    2000-01-01

    The static magnetic properties and electron paramagnetic resonance (EPR) spectra of ZrNi 1-x Cr x Sn solid solution (0 pp =(120±5)G type and g=1.980±0.001, peak-to-peak width ΔH pp =(10±1)G, respectively. They have been attributed to Cr 3+ ions in Ni-sites of the lattice coupled by magnetic dipolar interaction (type I) and to exchange coupled Cr 3+ pairs or clusters of more than two Cr 3+ ions (type II). The third line detected in the samples with x=0.3,0.4 characterised by g eff =2.0003±0.0001 and ΔH pp =(3.0±0.5)G has been interpreted as conduction electron spin resonance (CESR). (orig.)

  5. A compensating point defect in carbon-doped GaN substrates studied with electron paramagnetic resonance spectroscopy

    Science.gov (United States)

    Willoughby, W. R.; Zvanut, M. E.; Paudel, Subash; Iwinska, M.; Sochacki, T.; Bockowski, M.

    2018-04-01

    Electron paramagnetic resonance (EPR) spectroscopy was used to investigate a type of point defect present in 1019 cm-3 carbon-doped GaN substrates grown by hydride vapor phase epitaxy. A broad, isotropic resonance at g ˜ 1.987 was observed at 3.5 K, and the EPR intensity increased with illumination at energies greater than 2.75 eV and decreased with photon energies greater than 0.95 eV. The latter is consistent with a deep level of 0.95 eV above the valence band maximum and implies that the associated defect likely participates in donor compensation. The ionization energy for this defect is close to the predicted value for the (-/0) transition level of CN and transition levels associated with Ga vacancies such as VGa and VGa-ON-2H.

  6. The Resonance Integral of Niobium

    Energy Technology Data Exchange (ETDEWEB)

    Hellstrand, E; Lundgren, G

    1962-08-15

    The resonance integral of niobium has been studied by both pile oscillator and activation techniques. A value of 8.15b {+-} 0.65 b was obtained for the infinitely dilute integral. In addition, the variation of the resonance integral with foil thickness has been measured for thicknesses in the range 0.06 mm to 1.36 mm. A separate study of the half-life of the isomeric state in {sup 94}Nb yielded a value T{sub 1/2} = 6.30 - 0.03 m which is about 5 % lower than the value given in literature.

  7. A study on the retrospective dosimetry using electron paramagnetic resonance spectroscopy of tooth enamel

    International Nuclear Information System (INIS)

    Hong, Dae Seok

    2004-02-01

    Retrospective dosimetry is a process that is a part of dose reconstruction for estimation of exposed dose occurred years before the estimation. Dose reconstruction may be required in a variety of situations such as acute accidental exposure, suspected chronic overexposure and reassessment of occupational exposure. The techniques for retrospective can be classified as biological method and physical method. As a distinct physical technique for dose reconstruction, EPR (Electron Paramagnetic Resonance) or ESR (Electron Spin Resonance) dosimetry has been widely used. In EPR dosimetry, electrons generated by the interaction of material with radiation and trapped in lattice are measured by microwave absorption spectroscopy. Among the materials used for EPR dosimetry, tooth enamel has a high sensitivity for ionising radiation and since the tooth follows the carrier in all situations, it can act as a lifetime-dosimeter. And it is considered as one of the important biological samples. In many countries, there have been a lot of studies and practical applications on EPR dosimetry with tooth enamel. This technique has been applied for A-bomb survivors, Techa riverside population, Chernobyl cleanup workers and so on. Also there were two times of international comparison of the results of EPR dosimetry with tooth enamel in 1996 and 2000 respectively. But the experts have yet to reach a consensus on the best method. So, a lot of methods have been used for the separation of enamel from teeth and this may influence the dose evaluation. With the factors affecting EPR spectrum, this can effect on the results of dose reconstructed. In this study, factors affecting the EPR spectrum of tooth are experimented first. Anisotropy of radiation induced CO 2 - radical is negligible at low doses, but it become important at high doses. It can induce errors in dose estimation up to 40% at dose range of 5Gy. So, crushing process is essential in dose estimation. But, since sample grinding can

  8. Electron paramagnetic resonance of isolated Assub(Ga)+ antisite defect in neutron-transmutation doped semi-insulating GaAs

    International Nuclear Information System (INIS)

    Manasreh, M.O.; McDonald, P.F.; Kivlighn, S.A.; Minton, J.T.; Covington, B.C.

    1988-01-01

    The isolated Assub(Ga) antisite defect produced by the neutron-transmutation doping in semi-insulating GaAs was studied using the electron paramagnetic resonance technique. The results show that the optically induced quenching of the isolated Assub(Ga) + antisite defect is quite different from that of the EL2 center. Illumination with white light seems to always reduce the electron paramagnetic resonance spectrum suggesting that depopulation of the EL2 center does not introduce a noticeable change in the Assub(Ga) + antisite concentration. (author)

  9. Comparison of neutron and gamma irradiation effects on KU1 fused silica monitored by electron paramagnetic resonance

    Energy Technology Data Exchange (ETDEWEB)

    Bravo, D. [Department Fisica de Materiales, Universidad Autonoma de Madrid, E-28049 Madrid (Spain)], E-mail: david.bravo@uam.es; Lagomacini, J.C. [Department Fisica de Materiales, Universidad Autonoma de Madrid, E-28049 Madrid (Spain); Leon, M.; Martin, P. [Materiales para Fusion, CIEMAT, Avda. Complutense 22, E-28040 Madrid (Spain); Martin, A. [Department Fisica e Instalaciones, ETS Arquitectura UPM, E-28040 Madrid (Spain); Lopez, F.J. [Department Fisica de Materiales, Universidad Autonoma de Madrid, E-28049 Madrid (Spain); Ibarra, A. [Materiales para Fusion, CIEMAT, Avda. Complutense 22, E-28040 Madrid (Spain)

    2009-06-15

    Electron paramagnetic resonance (EPR) studies have been carried out on KU1 fused silica irradiated with neutrons at fluences 10{sup 21} and 10{sup 22} n/m{sup 2}, and gamma-ray doses up to 12 MGy. The effects of post-irradiation thermal annealing treatments, up to 850 deg. C, have also been investigated. Paramagnetic oxygen-related defects (POR and NBOHC) and E'-type defects have been identified and their concentration has been measured as a function of neutron fluence, gamma dose and post-irradiation annealing temperature. It is found that neutrons at the highest fluence generate a much higher concentration of defects (mainly E' and POR, both at concentrations about 5 x 10{sup 18} spins/cm{sup 3}) than gamma irradiations at the highest dose (mainly E' at a concentration about 4 x 10{sup 17} spins/cm{sup 3}). Moreover, for gamma-irradiated samples a lower treatment temperature (about 400 deg. C) is required to annihilate most of the observed defects than for neutron-irradiated ones (about 600 deg. C)

  10. 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.

  11. 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.

  12. Utility decay rates of T1-weighted magnetic resonance imaging contrast based on redox-sensitive paramagnetic nitroxyl contrast agents

    International Nuclear Information System (INIS)

    Matsumoto, Ken-ichiro

    2009-01-01

    The availability and applicability of the combination of paramagnetic nitroxyl contrast agent and T 1 -weighted gradient echo (GE)-based dynamic magnetic resonance imaging (MRI) measurement for redox imaging are described. The time courses of T 1 -weighted GE MRI signal intensities according to first-order paramagnetic loss of a nitroxyl contrast agent were simulated for several experimental conditions. The apparent decay rate calculated based on decreasing T 1 -weighted MRI contrast (k MRI ) can show an approximate value of the original decay rate (k true ) discretionarily given for simulation with suitable experimental parameters. The difference between k MRI and k true can be sufficiently small under T 1 -weighted spoiled gradient echo (SPGR) scan conditions (repetition time=75 ms, echo time=3 ms, and flip angle=45deg), with a conventional redox-sensitive nitroxyl contrast agent, such as 4-hydroxy-2,2,6,6,-tetramethylpiperidine-N-oxyl (TEMPOL) and/or 3-carbamoyl-2,2,5,5-tetramethylpyrrolidine-N-oxyl (carbamoyl-PROXYL), and with intravenous (i.v.) doses of below 1.5 γmol/g body weight (b.w.) for mice. The results of this simulation suggest that the k MRI of nitroxyl contrast agents can be the primary index of redox status under biological conditions. (author)

  13. Magnetic resonance imaging using paramagnetic contrast agents in the clinical evaluation of myocardial infarction. Chapter 15

    International Nuclear Information System (INIS)

    Dijkman, P.R.M. van; Wall, E.E. van der

    1992-01-01

    MRI is noninvasive and specific method for production of high resolution tomographic images in blocks of 3D information. Apart from scintigraphic techniques and computed tomography for evaluation of myocardial ischemia and infarcts, MRI has emerged as a new diagnostic technique to study the extent of anatomical and functional abnormalities in patients with coronary artery disease. Conventional noncontrast MRI can identify acute-infarcted myocardial areas, although the difficulty in identifying myocardial ischemia and infarct with noncontrast MRI suggests a potential role for contrast enhanced MRI. Use of the paramagnetic contrast agent gadolinium diethylene triamine pentaacetic acid (Gd-DTPA) improves depiction of infarcted myocardium on T1-weighted spin -echo MR images that are obtained soon after acute myocardial infarction. This is of particular interest for the estimation of myocardial infarct size. Furthermore, ultrafast subsecond imaging, in combination with Gd-DTPA, offers the potential to analyze cardiac first pass and myocardial perfusion. The development of nontoxic paramagnetic contrast agents which are selectively taken up by viable myocardium would be helpful in assessing the presence of ischemic/infarcted myocardium salvage by MRI following reperfusion. (author). 58 refs., 6 figs

  14. 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.

  15. 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

  16. Electron paramagnetic resonance and Raman spectroscopy studies on carbon-doped MgB2 superconductor nanomaterials

    International Nuclear Information System (INIS)

    Bateni, Ali; Somer, Mehmet; Erdem, Emre; Repp, Sergej; Weber, Stefan; Acar, Selcuk; Kokal, Ilkin; Häßler, Wolfgang

    2015-01-01

    Undoped and carbon-doped magnesium diboride (MgB 2 ) samples were synthesized using two sets of mixtures prepared from the precursors, amorphous nanoboron, and as-received amorphous carbon-doped nanoboron. The microscopic defect structures of carbon-doped MgB 2 samples were systematically investigated using X-ray powder diffraction, Raman and electron paramagnetic resonance spectroscopy. Mg vacancies and C-related dangling-bond active centers could be distinguished, and sp 3 -hybridized carbon radicals were detected. A strong reduction in the critical temperature T c was observed due to defects and crystal distortion. The symmetry effect of the latter is also reflected on the vibrational modes in the Raman spectra

  17. Electron paramagnetic resonance and Raman spectroscopy studies on carbon-doped MgB{sub 2} superconductor nanomaterials

    Energy Technology Data Exchange (ETDEWEB)

    Bateni, Ali; Somer, Mehmet, E-mail: emre.erdem@physchem.uni-freiburg.de, E-mail: msomer@ku.edu.tr [Department of Chemistry, Koc University, RumelifeneriYolu, Sariyer, Istanbul (Turkey); Erdem, Emre, E-mail: emre.erdem@physchem.uni-freiburg.de, E-mail: msomer@ku.edu.tr; Repp, Sergej; Weber, Stefan [Institut für Physikalische Chemie, Universität Freiburg, Albertstr. 21, 79104 Freiburg (Germany); Acar, Selcuk; Kokal, Ilkin [Pavezyum Kimya Sanayi Dış Ticaret LTD. ŞTI., Tuzla, Istanbul (Turkey); Häßler, Wolfgang [Leibniz Institute for Solid State and Materials Research Dresden (IFW), P.O. Box 270116, 01171 Dresden (Germany)

    2015-04-21

    Undoped and carbon-doped magnesium diboride (MgB{sub 2}) samples were synthesized using two sets of mixtures prepared from the precursors, amorphous nanoboron, and as-received amorphous carbon-doped nanoboron. The microscopic defect structures of carbon-doped MgB{sub 2} samples were systematically investigated using X-ray powder diffraction, Raman and electron paramagnetic resonance spectroscopy. Mg vacancies and C-related dangling-bond active centers could be distinguished, and sp{sup 3}-hybridized carbon radicals were detected. A strong reduction in the critical temperature T{sub c} was observed due to defects and crystal distortion. The symmetry effect of the latter is also reflected on the vibrational modes in the Raman spectra.

  18. 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

  19. NATO Advanced Research Workshop on Nuclear Magnetic Resonance of Paramagnetic Macromolecules

    CERN Document Server

    1995-01-01

    Since A. Kowalsky's first report of the spectrum of cytochrome c in 1965, interest in the detection, assignment and interpretation of paramagnetic molecules has surged, especially in the last decade. Two classes of systems have played a key role in the development of the field: heme proteins and iron-sulfur proteins. These two systems are unique in many respects, one of which is that they contain well-defined chromophores, each of which can be studied in detail outside the protein matrix. They are the most successfully studied macromolecules, and the first eight and last six of the seventeen contributions to this book deal with heme and/or iron-sulfur proteins. The middle three chapters survey the progress on, and significant promise of, more difficult systems which do not possess a chromophore, but which have nevertheless yielded remarkable insights into their structure.

  20. Electron paramagnetic resonance and electron-nuclear double resonance study of the neutral copper acceptor in ZnGeP sub 2 crystals

    CERN Document Server

    Stevens, K T; Setzler, S D; Schünemann, P G; Pollak, T M

    2003-01-01

    Electron paramagnetic resonance (EPR) and electron-nuclear double resonance have been used to characterize the neutral copper acceptor in ZnGeP sub 2 crystals. The copper substitutes for zinc and behaves as a conventional acceptor (i.e. the 3d electrons do not play a dominant role). Because of a high degree of compensation from native donors, the copper acceptors in our samples were initially in the nonparamagnetic singly ionized state (Cu sub Z sub n sup -). The paramagnetic neutral state (Cu sub Z sub n sup 0) was observed when the crystals were exposed to 632.8 nm or 1064 nm laser light while being held at a temperature below 50 K. The g matrix of the neutral copper acceptor is axial g sub p sub a sub r = 2.049 and g sub p sub e sub r sub p = 2.030), with the unique principal direction parallel to the tetragonal c axis of the crystal. The hyperfine and nuclear quadrupole matrices also exhibit c-axis symmetry (A sub p sub a sub r = 87.6 MHz, A sub p sub e sub r sub p = 34.8 MHz and P = 0.87 MHz for sup 6 su...

  1. Development of an electron paramagnetic resonance methodology for studying the photo-generation of reactive species in semiconductor nano-particle assembled films

    Science.gov (United States)

    Twardoch, Marek; Messai, Youcef; Vileno, Bertrand; Hoarau, Yannick; Mekki, Djamel E.; Felix, Olivier; Turek, Philippe; Weiss, Jean; Decher, Gero; Martel, David

    2018-06-01

    An experimental approach involving electron paramagnetic resonance is proposed for studying photo-generated reactive species in semiconductor nano-particle-based films deposited on the internal wall of glass capillaries. This methodology is applied here to nano-TiO2 and allows a semi-quantitative analysis of the kinetic evolutions of radical production using a spin scavenger probe.

  2. AgInS{sub 2}-ZnS nanocrystals: Evidence of bistable states using light-induced electron paramagnetic resonance and photoluminescence

    Energy Technology Data Exchange (ETDEWEB)

    Nobre, Sonia S.; Renard, Olivier; Chevallier, Theo; Le Blevennec, Gilles [Laboratoire d' Innovation pour les Technologies des Energies Nouvelles et les Nanomateriaux, Departement de Technologie des Nano-Materiaux, Service d' Elaboration de Nanomateriaux, Laboratoire de Synthese et Integration des Nanomateriaux, CEA-Grenoble (France); Lombard, Christian; Pepin-Donat, Brigitte [Laboratoire Structure et Proprietes d' Architecture Moleculaire (UMR 5819) CEA-CNRS - UJF/INAC/CEA-Grenoble (France)

    2014-04-15

    The precursor (AgIn){sub x} Zn{sub 2(1-x)}(S{sub 2}CN(C{sub 2}H{sub 5}){sub 2}){sub 4} was used to prepared AgInS{sub 2}-ZnS nanocrystals with different compositions (x = 0.4 and x = 0.7) and with different time of reaction (10 min and 75 min). The photoluminescence features of the nanocrystals were addressed by combining steady-state spectroscopy and light-induced electron paramagnetic resonance. Both techniques showed the contribution of at least two components for the emission, previously assigned to surface and intrinsic states. Light-induced electron paramagnetic resonance allowed detection of the photocreation both of irreversible paramagnetic species that are likely responsible for the nano-crystals degradation assigned to surface states and of reversible paramagnetic species assigned to intrinsic states. Moreover, reversible bistable paramagnetic states were observed. This Letter provides a scheme that might be useful in addressing the well-known problem of aging of the nanocrystals. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  3. 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.

  4. 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

  5. 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.

  6. In vivo colocalization of 2-nitroimidazole EF5 fluorescence intensity and electron paramagnetic resonance oximetry in mouse tumors

    International Nuclear Information System (INIS)

    Mahy, Pierre; Bast, Marc de; Gallez, Bernard; Gueulette, John; Koch, Cameron J.; Scalliet, Pierre; Gregoire, Vincent

    2003-01-01

    Background and purpose: The primary objective of this study was to establish in vivo the relationship between 2-2-nitro-1H-imidazol-1yl-N-(2,2,3,3,3-pentafluoropropyl)-acetamide (EF5) adduct formation and intratumoral oxygen concentrations measured by electron paramagnetic resonance (EPR) in a tumor model mimicking a clinical situation. The secondary objective was an attempt to calibrate in situ the immunofluorescence (IF) signal with EPR oximetry. Materials and methods: IM syngeneic fibrosarcoma (NFSA) bearing C3H mice were used. Three days after injection of a paramagnetic charcoal into the tumor, the mice were anesthetized, injected with the hypoxic marker EF5, and monitored every 20 min for 3 h with a low-frequency EPR spectrometer. Animals were allowed to breath either under 21 or 100% O 2 . Tumors were then harvested, frozen, cut into sections including the charcoal and processed for EF5 adducts detection using monoclonal antibodies. Slices were viewed with a fluorescence microscope and 190x140 μm areas surrounding the charcoal were digitized and analyzed with the NIH-Image and Adobe Photoshop TM software. The fluorescence intensity (FI) was measured in the whole pictures and in strips of 10 μm around the charcoal. Results: EF5 binding increased with decreasing pO 2 , most substantially at pO 2 below 5 mm Hg. Baseline (ambient air) pO 2 reached 3.2±2.1 mm Hg in NFSA tumors. It increased to 9.8±3.2 mm Hg under 100% O 2 . A statistically significant correlation was observed on an individual tumor basis between the FI in the first 10 μm strip around the charcoal and the pO 2 determined by EPR oximetry (Wilcoxon signed rank test: P 2 in an in vivo environment under biologically-relevant pO 2 values of less than 10 mm Hg

  7. Coiled-coil formation of the membrane-fusion K/E peptides viewed by electron paramagnetic resonance.

    Directory of Open Access Journals (Sweden)

    Pravin Kumar

    Full Text Available The interaction of the complementary K (Ac-(KIAALKE3-GW-NH2 and E (Ac-(EIAALEK3-GY-NH2 peptides, components of the zipper of an artificial membrane fusion system (Robson Marsden H. et al. Angew Chemie Int Ed. 2009 is investigated by electron paramagnetic resonance (EPR. By frozen solution continuous-wave EPR and double electron-electron resonance (DEER, the distance between spin labels attached to the K- and to the E-peptide is measured. Three constructs of spin-labelled K- and E-peptides are used in five combinations for low temperature investigations. The K/E heterodimers are found to be parallel, in agreement with previous studies. Also, K homodimers in parallel orientation were observed, a finding that was not reported before. Comparison to room-temperature, solution EPR shows that the latter method is less specific to detect this peptide-peptide interaction. Combining frozen solution cw-EPR for short distances (1.8 nm to 2.0 nm and DEER for longer distances thus proves versatile to detect the zipper interaction in membrane fusion. As the methodology can be applied to membrane samples, the approach presented suggests itself for in-situ studies of the complete membrane fusion process, opening up new avenues for the study of membrane fusion.

  8. A Ku band pulsed electron paramagnetic resonance spectrometer using an arbitrary waveform generator for quantum control experiments at millikelvin temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Yap, Yung Szen, E-mail: yungszen@utm.my [Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama-cho, Toyonaka-shi, Osaka 560-8531 (Japan); Faculty of Science, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Tabuchi, Yutaka [Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Meguro-ku, Tokyo 153-8904 (Japan); Negoro, Makoto; Kagawa, Akinori; Kitagawa, Masahiro, E-mail: kitagawa@ee.es.osaka-u.ac.jp [Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama-cho, Toyonaka-shi, Osaka 560-8531 (Japan)

    2015-06-15

    We present a 17 GHz (Ku band) arbitrary waveform pulsed electron paramagnetic resonance spectrometer for experiments down to millikelvin temperatures. The spectrometer is located at room temperature, while the resonator is placed either in a room temperature magnet or inside a cryogen-free dilution refrigerator; the operating temperature range of the dilution unit is from ca. 10 mK to 8 K. This combination provides the opportunity to perform quantum control experiments on electron spins in the pure-state regime. At 0.6 T, spin echo experiments were carried out using γ-irradiated quartz glass from 1 K to 12.3 mK. With decreasing temperatures, we observed an increase in spin echo signal intensities due to increasing spin polarizations, in accordance with theoretical predictions. Through experimental data fitting, thermal spin polarization at 100 mK was estimated to be at least 99%, which was almost pure state. Next, to demonstrate the ability to create arbitrary waveform pulses, we generate a shaped pulse by superposing three Gaussian pulses of different frequencies. The resulting pulse was able to selectively and coherently excite three different spin packets simultaneously—a useful ability for analyzing multi-spin system and for controlling a multi-qubit quantum computer. By applying this pulse to the inhomogeneously broadened sample, we obtain three well-resolved excitations at 8 K, 1 K, and 14 mK.

  9. Magnetic resonance tomography for focal lesions in the liver using the para-magnetic contrast medium gadolinium DTPA

    International Nuclear Information System (INIS)

    Hamm, B.; Roemer, T.; Felix, R.; Wolf, K.J.; Klinikum Charlottenburg, Berlin

    1986-01-01

    The use of the para-magnetic contrast medium gadolinium DTPA for magnetic resonance tomography of focal lesions in the liver was investigated in 31 patients. Two dosage schedules of the contrast medium (0.1 and 0.2 mmol/kg body weight) were used with field strengths of 0.35 and 0.5 Tesla. Using T 1 sequences, gadolinium DTPA showed increased signal intensity in the liver and in tumours, but this was significantly more marked in the tumour. On T 1 spin-echo sequences, previously iso-intense lesions became visible after administration of contrast. On the other hand, contrast-enhanced lesions were less well seen on inversion recovery sequences because of a reduction in the contrast between tumour and liver tissue. The contrast between tumour and liver tissue was not improved by gadolinium DTPA in comparison with precontrast inversion recovery sequences and T 2 spin-echo sequences. The perfusion of intra-hepatic tumours could be elucidated by magnetic resonance tomography after the administration of gadolinium DTPA. (orig.) [de

  10. Free radicals produced by the oxidation of gallic acid: An electron paramagnetic resonance study

    Directory of Open Access Journals (Sweden)

    Wagner Brett A

    2010-08-01

    Full Text Available Abstract Background Gallic acid (3,4,5-trihydroxybenzoic acid is found in a wide variety of plants; it is extensively used in tanning, ink dyes, as well as in the manufacturing of paper. The gallate moiety is a key component of many functional phytochemicals. In this work electron paramagnetic spectroscopy (EPR was used to detect the free radicals generated by the air-oxidation of gallic acid. Results We found that gallic acid produces two different radicals as a function of pH. In the pH range between 7-10, the spectrum of the gallate free radical is a doublet of triplets (aH = 1.00 G, aH = 0.23 G, aH = 0.28 G. This is consistent with three hydrogens providing hyperfine splitting. However, in a more alkaline environment, pH >10, the hyperfine splitting pattern transforms into a 1:2:1 pattern (aH (2 = 1.07 G. Using D2O as a solvent, we demonstrate that the third hydrogen (i.e. aH = 0.28 G at lower pH is a slowly exchanging hydron, participating in hydrogen bonding with two oxygens in ortho position on the gallate ring. The pKa of this proton has been determined to be 10. Conclusions This simple and novel approach permitted the understanding of the prototropic equilibrium of the semiquinone radicals generated by gallic acid, a ubiquitous compound, allowing new insights into its oxidation and subsequent reactions.

  11. 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

  12. Study by magnetic resonance and relaxation of carbon 13 of some paramagnetic coordination complexes

    International Nuclear Information System (INIS)

    Ronfard-Haret, Jean-Claude

    1977-01-01

    This research thesis reports the study of coordination complexes by using NMR. After a brief recall of the theoretical background required for the processing of experimental data (hyper-fine coupling and magnetic resonance, spin density distribution, chemical displacement, dipolar, scalar and electronic relaxation), the author describes the conditions in which experiments have been performed and presents measurement methods (pulsed nuclear magnetic resonance, relaxation time measurement, determination of hyper-fine coupling constants, spectrometers and reactants). The next chapters address the study of different coordination complexes: [(pyridine-N-oxide) 2 Ni(acetylacetonate) 2 ], carbon 13 in alkyl-anilines-Ni II, complexation of 1- and 2-aminonaphthalene by transition ions, complexation of pyridine-N-oxide by the nickel Ni ++ ion in presence of water

  13. Electron spin resonance of paramagnetic defects and related charge carrier traps in complex oxide scintillators

    Czech Academy of Sciences Publication Activity Database

    Laguta, Valentyn; Nikl, Martin

    2013-01-01

    Roč. 250, č. 2 (2013), s. 254-260 ISSN 0370-1972 R&D Projects: GA MŠk(CZ) LM2011029; GA ČR GAP204/12/0805; GA AV ČR IAA100100810 Grant - others:SAFMAT(XE) CZ.2.16/3.1.00/22132 Institutional support: RVO:68378271 Keywords : scintillators * point defects * electron spin resonance * polarons Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.605, year: 2013

  14. 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.

  15. Assessing topology and surface orientation of an antimicrobial peptide magainin 2 using mechanically aligned bilayers and electron paramagnetic resonance spectroscopy.

    Science.gov (United States)

    Mayo, Daniel J; Sahu, Indra D; Lorigan, Gary A

    2018-07-01

    Aligned CW-EPR membrane protein samples provide additional topology interactions that are absent from conventional randomly dispersed samples. These samples are aptly suited to studying antimicrobial peptides because of their dynamic peripheral topology. In this study, four consecutive substitutions of the model antimicrobial peptide magainin 2 were synthesized and labeled with the rigid TOAC spin label. The results revealed the helical tilts to be 66° ± 5°, 76° ± 5°, 70° ± 5°, and 72° ± 5° for the TOAC substitutions H7, S8, A9, and K10 respectively. These results are consistent with previously published literature. Using the EPR (electron paramagnetic resonance) mechanical alignment technique, these substitutions were used to critically assess the topology and surface orientation of the peptide with respect to the membrane. This methodology offers a rapid and simple approach to investigate the structural topology of antimicrobial peptides. Copyright © 2018 Elsevier B.V. All rights reserved.

  16. 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

    2018-04-20

    The advent of hybrid scanners, combining complementary modalities, has revolutionized imaging; enhancing 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). The PET radiotracers can provide important information about cellular parameters, such as glucose metabolism. While EPR probes can provide assessment of tissue microenvironment, measuring parameters such as oxygenation and pH, for example. A combined PET/EPRI scanner has the promise to provide new insights not attainable with current imagers by simultaneous acquisition of multiple components of tissue microenvironments. In this investigation, a prototype system was created by combing two existing scanners, modified for simultaneous imaging. 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 PET and EPR tracers. The resulting images demonstrated the ability to obtain contemporaneous PET and ERP images without cross-modality interference. The next step in this project is the construction of pre-clinical PET/EPRI scanner for multi-parametric assessment of physiologically important parameters of tissue microenvironments. . © 2018 Institute of Physics and Engineering in Medicine.

  17. 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.

  18. Electron paramagnetic resonance study of conformational effects in alkyl-substituted 2-cyclohexanonyl radicals in an adamantane matrix

    International Nuclear Information System (INIS)

    Walter, H.F.

    1975-01-01

    Electron paramagnetic resonance spectra have been obtained for radicals produced by x-irradiation of cyclohexanone and various alkyl-substituted cyclohexanones trapped in an adamantane matrix. Temperature variation of these spectra permits determination of the enthalpy and entropy of activation for interconversion between the two half-chair conformations. In those cases where the two conformations have intrinsically different energies, the enthalpy and entropy differences between conformations are determined. For 2-cyclohexanonyl radical, the enthalpy of activation is 3.90 +- 0.07 kcal/mole and the entropy of activation is -2.3 +- 0.3 e.u. Methyl substitution on C 3 or C 5 gives a radical with activation parameters similar to the parent radical, indicating moderate realignment of atoms during the conformational change. Methyl substitution on C 4 gives a radical with lower activation parameters, which are interpreted to indicate conformational change mainly be a folding along the diagonal through the radical site. Larger groups attached to C 3 influence enthalpy and entropy differences between conformations much less than when they are attached to C 5 . Very large groups attached to C 5 apparently flatten the ring; it is not known whether or not this is a matrix effect. Deuteration seems to cause a slight reduction in the activation parameters for 2-cyclohexanonyl radical

  19. Clearance and Biodistribution of Liposomally Encapsulated Nitroxides: A Model for Targeted Delivery of Electron Paramagnetic Resonance Imaging Probes to Tumors

    Science.gov (United States)

    Burks, Scott R.; Legenzov, Eric A.; Rosen, Gerald M.

    2011-01-01

    Electron paramagnetic resonance (EPR) imaging using nitroxides as molecular probes is potentially a powerful tool for the detection and physiological characterization of micrometastatic lesions. Encapsulating nitroxides in anti-HER2 immunoliposomes at high concentrations to take advantage of the “self-quenching” phenomenon of nitroxides allows generation of robust EPR signals in HER2-overexpressing breast tumor cells with minimal background from indifferent tissues or circulating liposomes. We investigated the in vivo pharmacological properties of nitroxides encapsulated in sterically stabilized liposomes designed for long circulation times. We show that circulation times of nitroxides can be extended from hours to days; this increases the proportion of liposomes in circulation to enhance tumor targeting. Furthermore, nitroxides encapsulated in sterically stabilized anti-HER2 immunoliposomes can be delivered to HER2-overexpressing tumors at micromolar concentrations, which should be imageable by EPR. Lastly, after in vivo administration, liposomally encapsulated nitroxide signal also appears in the liver, spleen, and kidneys. Although these organs are spatially distinct and would not hinder tumor imaging in our model, understanding nitroxide signal retention in these organs is essential for further improvements in EPR imaging contrast between tumors and other tissues. These results lay the foundation to use liposomally delivered nitroxides and EPR imaging to visualize tumor cells in vivo. PMID:21737567

  20. Electron paramagnetic resonance of Na, [(FeEDTA)2oJ-12H20] crystal electrons

    International Nuclear Information System (INIS)

    Esquivel, Darci Motta de Souza

    1974-01-01

    Crystals of Na [(Fe EDTA) 2 o] ·12H 2 0 were investigated by means of electron paramagnetic resonance spectroscopy. The spectra were obtained at various temperatures and crystals orientations. These spectra are very complex with many absorption bands. As the crystal orientation with respect to the magnetic field was changed the variations of the intensity and number of bands were recorded. The antiferromagnetic coupling between the iron atoms in the bridge Fe - 0 - Fe gives rise to states with total spin quantum number S= 0, 1, 2, 3, 4 and 5. Analyses of the EPR spectra as a function of temperature provided a means for the identification of the EPR absorption bands attributed to the states with S = 2. It was also possible to calculate the exchange parameter value J = 300 K. From the study of bands angular dependence in relation to the crystal orientation in the magnetic field it was found that the magnetic crystal axes X, Y, Z and the crystals axes a, b, c are related as (a, b, c) = (Y, Z, X) ! with a precision of 5 deg. Also the crystalline distortion parameters were calculated D = 0.21 ± 0.02 cm 1 ; E = 0.015 ± 0.005 cm 1 . (author)

  1. Site selective substitution Pt for Ti in KTiOPO{sub 4}:Ga crystals revealed by electron paramagnetic resonance

    Energy Technology Data Exchange (ETDEWEB)

    Grachev, V.; Meyer, M.; Jorgensen, J.; Malovichko, G. [Department of Physics, Montana State University, Bozeman, Montana 59717 (United States); Hunt, A. W. [Idaho Accelerator Center, Idaho State University, Pocatello, Idaho 83209 (United States)

    2014-07-28

    Electron Paramagnetic Resonance at low temperatures has been used to characterize potassium titanyl phosphate (KTiOPO{sub 4}) single crystals grown by different techniques. Irradiation with 20 MeV electrons performed at room temperature and liquid nitrogen temperature caused an appearance of electrons and holes. Platinum impurities act as electron traps in KTiOPO{sub 4} creating Pt{sup 3+} centers. Two different Pt{sup 3+} centers were observed, Pt(A) and Pt(D). The Pt(A) centers are dominant in undoped samples, whereas Pt(D)—in Ga-doped KTP crystals. Superhyperfine structure registered for Pt(D) centers was attributed to interactions of platinum electrons with {sup 39}K and two {sup 31}P nuclei in their surroundings. In both Pt(A) and Pt(D) centers, Pt{sup 3+} ions substitute for Ti{sup 4+} ions, but with a preference to one of two electrically distinct crystallographic positions. The site selective substitution can be controlled by the Ga-doping.

  2. 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.

  3. 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

  4. Investigation of Antioxidant Activity of Pomegranate Juices by Means of Electron Paramagnetic Resonance and UV-Vis Spectroscopy.

    Science.gov (United States)

    Kozik, Violetta; Jarzembek, Krystyna; Jędrzejowska, Agnieszka; Bąk, Andrzej; Polak, Justyna; Bartoszek, Mariola; Pytlakowska, Katarzyna

    2015-01-01

    Pomegranate fruit (Punica granatum L.) is a source of numerous phenolic compounds, and it contains flavonoids such as anthocyanins, anthocyanidins, cyanidins, catechins and other complexes of flavonoids, ellagitannins, and hydrolyzed tannins. Pomegranate juice shows antioxidant, antiproliferative, and anti-atherosclerotic properties. The antioxidant capacity (TEAC) of the pomegranate juices was measured using electron paramagnetic resonance (EPR) spectroscopy and 1,1-diphenyl-2-picrylhydrazyl (DPPH•) as a source of free radicals, and the total phenolic (TP) content was measured using UV-Vis spectroscopy. All the examined pomegranate juices exhibited relatively high antioxidant properties. The TEAC values determined by means of EPR spectroscopy using Trolox (TE) as a free radical scavenger were in the range of 463.12 to 1911.91 μmol TE/100 mL juice. The TP content measured by the Folin-Ciocalteu method, using gallic acid (GA) as a free radical scavenger, widely varied in the investigated pomegranate juice samples and ranged from 1673.62 to 5263.87 mg GA/1 L juice. The strongest antioxidant properties were observed with the fresh pomegranate juices obtained from the fruits originating from Israel, Lebanon, and Azerbaijan. Correlation analysis of numerical data obtained by means of EPR spectroscopy (TEAC) and UV-Vis spectroscopy (TP) gave correlation coefficient (r)=0.90 and determination coefficient (r2)=0.81 (P<0.05).

  5. Investigation of some parameters influencing the sensitivity of human tooth enamel to gamma radiation using electron paramagnetic resonance

    International Nuclear Information System (INIS)

    El-Faramawy, N.

    2008-01-01

    Electron paramagnetic resonance (EPR) has been successfully used as a physical technique for gamma radiation dose reconstruction using calcified tissues. To minimize potential discrepancies between EPR readings in future studies, the effects of cavity response factor, tooth position and donor gender on the estimated gamma radiation dose were studied. It was found that the EPR response per sample mass used for assessment of doses in teeth outside of the 70-100 mg range should be corrected by a factor which is a function of the sample mass. In the EPR measurements, the difference in sensitivity of different tooth positions to γ-radiation was taken into consideration. It was determined that among all the premolars and molars tooth positions, the relative standard deviation of sensitivity was 6.5%, with the wisdom teeth and the first molars having the highest and lowest sensitivity to γ-radiation, respectively. The current results reveal no effect of the donor gender on the sensitivity to γ-radiation. (author)

  6. Electron paramagnetic resonance evidence of hydroxyl radical generation and oxidative damage induced by tetrabromobisphenol A in Carassius auratus

    Energy Technology Data Exchange (ETDEWEB)

    Shi Huahong [State Key Laboratory of Pollution Control and Resource Reuse, Nanjing University, Nanjing 210093 (China)]. E-mail: huahongshi@tom.com; Wang Xiaorong [State Key Laboratory of Pollution Control and Resource Reuse, Nanjing University, Nanjing 210093 (China); Luo Yi [State Key Laboratory of Pollution Control and Resource Reuse, Nanjing University, Nanjing 210093 (China); Su Yan [State Key Laboratory of Pollution Control and Resource Reuse, Nanjing University, Nanjing 210093 (China)

    2005-09-30

    Tetrabromobisphenol A (TBBPA) is one of the most widely used brominated flame retardants (BFRs). To confirm its putative oxidative stress-inducing activity, freshwater fish Carassius auratus were injected intraperitoneally with TBBPA. One experiment lasted 3 h to 28 days after a single injection of 100 mg/kg TBBPA, and the other lasted 24 h after a single injection of 0-300 mg/kg TBBPA. Reactive oxygen species (ROS) were trapped by phenyl-tert-butyl nitrone (PBN) and detected by electron paramagnetic resonance (EPR). Protein carbonyl (PCO) and lipid peroxidation product (LPO) content were also determined. A six-line EPR spectrum was detected in the sample prepared in air, and a multiple one was obtained in nitrogen. The observed spectrum in nitrogen fits the simulation one with PBN/{center_dot}OCH{sub 3} and PBN/{center_dot}CH{sub 3} quite well. As compared to the control group, TBBPA significantly induced ROS production marked by the intensity of the prominent spectra in liver and bile. TBBPA (100 mg/kg) also significantly increased PCO content in liver starting 24 h and LPO content 3 days after injection. Either PCO or LPO content showed significant relation with ROS production. Based on the hyperfine constants and shape of the spectrum, ROS induced by TBBPA was determined as {center_dot}OH. The results clearly indicated that TBBPA could induce {center_dot}OH generation and result in oxidative damage in liver of C. auratus.

  7. Kissing G domains of MnmE monitored by X-ray crystallography and pulse electron paramagnetic resonance spectroscopy.

    Directory of Open Access Journals (Sweden)

    Simon Meyer

    2009-10-01

    Full Text Available MnmE, which is involved in the modification of the wobble position of certain tRNAs, belongs to the expanding class of G proteins activated by nucleotide-dependent dimerization (GADs. Previous models suggested the protein to be a multidomain protein whose G domains contact each other in a nucleotide dependent manner. Here we employ a combined approach of X-ray crystallography and pulse electron paramagnetic resonance (EPR spectroscopy to show that large domain movements are coupled to the G protein cycle of MnmE. The X-ray structures show MnmE to be a constitutive homodimer where the highly mobile G domains face each other in various orientations but are not in close contact as suggested by the GDP-AlF(x structure of the isolated domains. Distance measurements by pulse double electron-electron resonance (DEER spectroscopy show that the G domains adopt an open conformation in the nucleotide free/GDP-bound and an open/closed two-state equilibrium in the GTP-bound state, with maximal distance variations of 18 A. With GDP and AlF(x, which mimic the transition state of the phosphoryl transfer reaction, only the closed conformation is observed. Dimerization of the active sites with GDP-AlF(x requires the presence of specific monovalent cations, thus reflecting the requirements for the GTPase reaction of MnmE. Our results directly demonstrate the nature of the conformational changes MnmE was previously suggested to undergo during its GTPase cycle. They show the nucleotide-dependent dynamic movements of the G domains around two swivel positions relative to the rest of the protein, and they are of crucial importance for understanding the mechanistic principles of this GAD.

  8. Imaging in Vivo Extracellular pH with a Single Paramagnetic Chemical Exchange Saturation Transfer Magnetic Resonance Imaging Contrast Agent

    Directory of Open Access Journals (Sweden)

    Guanshu Liu

    2012-01-01

    Full Text Available The measurement of extracellular pH (pHe has potential utility for cancer diagnoses and for assessing the therapeutic effects of pH-dependent therapies. A single magnetic resonance imaging (MRI contrast agent that is detected through paramagnetic chemical exchange saturation transfer (PARACEST was designed to measure tumor pHe throughout the range of physiologic pH and with magnetic resonance saturation powers that are not harmful to a mouse model of cancer. The chemical characterization and modeling of the contrast agent Yb3+-1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid, 10-o-aminoanilide (Yb-DO3A-oAA suggested that the aryl amine of the agent forms an intramolecular hydrogen bond with a proximal carboxylate ligand, which was essential for generating a practical chemical exchange saturation transfer (CEST effect from an amine. A ratio of CEST effects from the aryl amine and amide was linearly correlated with pH throughout the physiologic pH range. The pH calibration was used to produce a parametric pH map of a subcutaneous flank tumor on a mouse model of MCF-7 mammary carcinoma. Although refinements in the in vivo CEST MRI methodology may improve the accuracy of pHe measurements, this study demonstrated that the PARACEST contrast agent can be used to generate parametric pH maps of in vivo tumors with saturation power levels that are not harmful to a mouse model of cancer.

  9. Proton nuclear magnetic resonance imaging of regionally ischemic canine hearts: effects of paramagnetic proton signal enhancement

    International Nuclear Information System (INIS)

    Brady, T.J.; Goldman, M.R.; Pykett, I.L.; Buonanno, F.S.; Kistler, J.P.; Newhouse, J.H.; Burt, C.T.; Hinshaw, W.S.; Pohost, G.M.

    1982-01-01

    In a study to evaluate the potential of proton nuclear magnetic resonance (NMR) imaging with and without manganese contrast enhancement for detecting acute myocardial infarction, 12 dogs underwent 90-minute occlusion of the left circumflex coronary artery. Transverse-section NMR images of the excised, nonbeating heart were obtained at 1-cm intervals using the steady-state-free-precession (SSFP) technique. All NMR images revealed detailed structure of the heart. The three hearts without manganese showed no difference in intensity between the normal and the ischemic posterior regions, whereas those with manganese demonstrated a clearly demarcated zone of reduced signal intensity consistent with the ischemic zone. It is concluded that high-resolution tomograms of the excised canine myocardium can be obtained using proton NMR imaging. With the SSFP imaging technique, proton signal enhancement with manganese infusion is necessary to differentiate between ischemic and nonischemic myocardium after 90 minutes of coronary occlusion

  10. 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

  11. Electron paramagnetic resonance study of exchange coupled Ce.sup.3+./sup. ions in Lu.sub.2./sub.SiO.sub.5./sub. single crystal scintillator

    Czech Academy of Sciences Publication Activity Database

    Buryi, Maksym; Laguta, Valentyn; Rosa, Jan; Nikl, Martin

    2016-01-01

    Roč. 90, Jul (2016), s. 23-26 ISSN 1350-4487 R&D Projects: GA ČR GAP204/12/0805; GA MŠk(CZ) LM2011029; GA MŠk LO1409 Institutional support: RVO:68378271 Keywords : electron paramagnetic resonance * scintillators * lutetium oxyorthosilicate * exchange coupled ions * cerium ions Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.442, year: 2016

  12. Electron paramagnetic resonance of gamma irradiated (CH3)3NHClO4 and CH3NH3ClO4 single crystals

    International Nuclear Information System (INIS)

    Yavuz, Metin; Koeksal, Fevzi

    1999-01-01

    Gamma irradiation damage centers in (CH 3 ) 3 NHClO 4 and CH 3 NH 3 ClO 4 single crystals have been investigated at room temperature by the electron paramagnetic resonance (EPR) technique. It has been found that γ-irradiation produces the (CH 3 ) 3 N + radical in the first, and NH + 3 and ClO 3 radicals in the second compound. The EPR parameters of the observed radicals have been determined and discussed

  13. Initial deposition and electron paramagnetic resonance defects characterization of TiO{sub 2} films prepared using successive ionic layer adsorption and reaction method

    Energy Technology Data Exchange (ETDEWEB)

    Wu Yiyong, E-mail: wuyiyong2001@yahoo.com.cn [National Key Laboratory of Materials Behaviors and Evaluation Technology in Space Environments, Harbin Institute of Technology, P.O. 432, Nan gang District, Harbin, 150080 (China); Shi Yaping [National Key Laboratory of Materials Behaviors and Evaluation Technology in Space Environments, Harbin Institute of Technology, P.O. 432, Nan gang District, Harbin, 150080 (China); Harbin University of Commerce, P.O. 493, Song bei District, Harbin, 150028 (China); Xu Xianbin; Sun Chengyue [National Key Laboratory of Materials Behaviors and Evaluation Technology in Space Environments, Harbin Institute of Technology, P.O. 432, Nan gang District, Harbin, 150080 (China)

    2012-06-01

    Successive ionic layer adsorption and reaction (SILAR) technique was considered promisingly to deposit ultra thin titanium dioxide (TiO{sub 2}) films under ambient condition. In this paper, the growth process, structures and paramagnetic defects of the films were characterized by complementary techniques of atomic force microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and electron paramagnetic resonance spectroscopy. The results indicate that on glass substrate the SILAR TiO{sub 2} film nucleates in an island mode within the initial five deposition cycles but grows in a layer-by-layer mode afterwards. The growth rate was measured as 4.6 A/cycle. In the as-deposited films, a kind of paramagnetic defects is detected at g (2.0029) and it can be attributed to oxygen vacancies. These as-received oxygen vacancies could be annealed out at 473 K. Ultraviolet irradiation on the as-deposited films can also decrease the density of the defects. The relative mechanisms on the phenomenon were discussed in this paper. - Highlights: Black-Right-Pointing-Pointer TiO{sub 2} films are deposited on glass at 25 Degree-Sign C by successive ionic layer adsorption and reaction method with a rate of 4.6 A/cycle. Black-Right-Pointing-Pointer The films nucleate in an island mode initially but grow in a layer mode afterwards. Black-Right-Pointing-Pointer The SILAR TiO{sub 2} films nucleation period is five cycles. Black-Right-Pointing-Pointer Electron paramagnetic resonance spectroscopy shows that TiO{sub 2} films paramagnetic defects are attributed to oxygen vacancies. Black-Right-Pointing-Pointer They will decrease by anneal or ultraviolet radiation and form hydroxyl or superoxide radicals.

  14. Initial deposition and electron paramagnetic resonance defects characterization of TiO2 films prepared using successive ionic layer adsorption and reaction method

    International Nuclear Information System (INIS)

    Wu Yiyong; Shi Yaping; Xu Xianbin; Sun Chengyue

    2012-01-01

    Successive ionic layer adsorption and reaction (SILAR) technique was considered promisingly to deposit ultra thin titanium dioxide (TiO 2 ) films under ambient condition. In this paper, the growth process, structures and paramagnetic defects of the films were characterized by complementary techniques of atomic force microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and electron paramagnetic resonance spectroscopy. The results indicate that on glass substrate the SILAR TiO 2 film nucleates in an island mode within the initial five deposition cycles but grows in a layer-by-layer mode afterwards. The growth rate was measured as 4.6 Å/cycle. In the as-deposited films, a kind of paramagnetic defects is detected at g (2.0029) and it can be attributed to oxygen vacancies. These as-received oxygen vacancies could be annealed out at 473 K. Ultraviolet irradiation on the as-deposited films can also decrease the density of the defects. The relative mechanisms on the phenomenon were discussed in this paper. - Highlights: ► TiO 2 films are deposited on glass at 25 °C by successive ionic layer adsorption and reaction method with a rate of 4.6 Å/cycle. ► The films nucleate in an island mode initially but grow in a layer mode afterwards. ► The SILAR TiO 2 films nucleation period is five cycles. ► Electron paramagnetic resonance spectroscopy shows that TiO 2 films paramagnetic defects are attributed to oxygen vacancies. ► They will decrease by anneal or ultraviolet radiation and form hydroxyl or superoxide radicals.

  15. Polynuclear water-soluble dinitrosyl iron complexes with cysteine or glutathione ligands: electron paramagnetic resonance and optical studies.

    Science.gov (United States)

    Vanin, Anatoly F; Poltorakov, Alexander P; Mikoyan, Vasak D; Kubrina, Lyudmila N; Burbaev, Dosymzhan S

    2010-09-15

    Electron paramagnetic resonance and optical spectrophotometric studies have demonstrated that low-molecular dinitrosyl iron complexes (DNICs) with cysteine or glutathione exist in aqueous solutions in the form of paramagnetic mononuclear (capital EM, Cyrillic-DNICs) and diamagnetic binuclear complexes (B-DNICs). The latter represent Roussin's red salt esters and can be prepared by treatment of aqueous solutions of Fe(2+) and thiols (small er, Cyrilliccapital EN, Cyrillic 7.4) with gaseous nitric oxide (NO) at the thiol:Fe(2+) ratio 1:1. capital EM, Cyrillic-DNICs are synthesized under identical conditions at the thiol:Fe(2+) ratios above 20 and produce an EPR signal with an electronic configuration {Fe(NO)(2)}(7) at g(aver.)=2.03. At neutral pH, aqueous solutions contain both M-DNICs and B-DNICs (the content of the latter makes up to 50% of the total DNIC pool). The concentration of B-DNICs decreases with a rise in pH; at small er, Cyrilliccapital EN, Cyrillic 9-10, the solutions contain predominantly M-DNICs. The addition of thiol excess to aqueous solutions of B-DNICs synthesized at the thiol:Fe(2+) ratio 1:2 results in their conversion into capital EM, Cyrillic-DNICs, the total amount of iron incorporated into M-DNICs not exceeding 50% of the total iron pool in B-DNICs. Air bubbling of cys-capital EM, Cyrillic-DNIC solutions results in cysteine oxidation-controlled conversion of capital EM, Cyrillic-DNICs first into cys-B-DNICs and then into the EPR-silent compound capital HA, Cyrillic able to generate a strong absorption band at 278 nm. In the presence of glutathione or cysteine excess, compound capital HA, Cyrillic is converted into B-DNIC/M-DNIC and is completely decomposed under effect of the Fe(2+) chelator small o, Cyrillic-phenanthroline or N-methyl-d-glucamine dithiocarbamate (MGD). Moreover, MGD initiates the synthesis of paramagnetic mononitrosyl iron complexes with MGD. It is hypothesized that compound capital HA, Cyrillic represents a polynuclear

  16. Comprehensive high frequency electron paramagnetic resonance studies of single molecule magnets

    Science.gov (United States)

    Lawrence, Jonathan D.

    This dissertation presents research on a number of single molecule magnet (SMM) compounds conducted using high frequency, low temperature magnetic resonance spectroscopy of single crystals. By developing a new technique that incorporated other devices such as a piezoelectric transducer or Hall magnetometer with our high frequency microwaves, we were able to collect unique measurements on SMMs. This class of materials, which possess a negative, axial anisotropy barrier, exhibit unique magnetic properties such as quantum tunneling of a large magnetic moment vector. There are a number of spin Hamiltonians used to model these systems, the most common one being the giant spin approximation. Work done on two nickel systems with identical symmetry and microenvironments indicates that this model can contain terms that lack any physical significance. In this case, one must turn to a coupled single ion approach to model the system. This provides information on the nature of the exchange interactions between the constituent ions of the molecule. Additional studies on two similar cobalt systems show that, for these compounds, one must use a coupled single ion approach since the assumptions of the giant spin model are no longer valid. Finally, we conducted a collection of studies on the most famous SMM, Mn12Ac. Three different techniques were used to study magnetization dynamics in this system: stand-alone HFEPR in two different magnetization relaxation regimes, HFEPR combined with magnetometry, and HFEPR combined with surface acoustic waves. All of this research gives insight into the relaxation mechanisms in Mn12Ac.

  17. Electron paramagnetic resonance and electron-nuclear double-resonance study of Ti sup 3 sup + centres in KTiOPO sub 4

    CERN Document Server

    Setzler, S D; Fernelius, N C; Scripsick, M P; Edwards, G J; Halliburton, L E

    2003-01-01

    Electron paramagnetic resonance and electron-nuclear double resonance have been used to characterize four Ti sup 3 sup + centres in undoped crystals of potassium titanyl phosphate (KTiOPO sub 4 or KTP). These 3d sup 1 defects (S = 1/2) are produced by ionizing radiation (either 60 kV x-rays or 355 nm photons from a tripled Nd:YAG laser), and form when the regular Ti sup 4 sup + ions in the crystal trap an electron. Two of these trapped-electron centres are only observed in hydrothermally grown KTP and the other two are dominant in flux-grown KTP. Both of the Ti sup 3 sup + centres in hydrothermally grown crystals have a neighbouring proton (i.e. an OH sup - molecule). In the flux-grown crystals, one of the Ti sup 3 sup + centres is adjacent to an oxygen vacancy and the other centre is tentatively attributed to a self-trapped electron (i.e. a Ti sup 3 sup + centre with no stabilizing entity nearby). The g matrix and phosphorus hyperfine matrices are determined for all four Ti sup 3 sup + centres, and the proto...

  18. Electron paramagnetic resonance and electron-nuclear double-resonance study of Ti{sup 3+} centres in KTiOPO{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Setzler, S D [BAE Systems, Nashua, NH 03061 (United States); Stevens, K T [Northrop Grumman, Space Technology, Synoptics, Charlotte, NC 28273 (United States); Fernelius, N C [Air Force Research Laboratory, Materials and Manufacturing Directorate, AFRL/MLPSO, Wright-Patterson AFB, OH 45433 (United States); Scripsick, M P [Nova Phase, Newton, NJ 07860 (United States); Edwards, G J [Department of Physics, West Virginia University, Morgantown, WV 26506 (United States); Halliburton, L E [Department of Physics, West Virginia University, Morgantown, WV 26506 (United States)

    2003-06-18

    Electron paramagnetic resonance and electron-nuclear double resonance have been used to characterize four Ti{sup 3+} centres in undoped crystals of potassium titanyl phosphate (KTiOPO{sub 4} or KTP). These 3d{sup 1} defects (S = 1/2) are produced by ionizing radiation (either 60 kV x-rays or 355 nm photons from a tripled Nd:YAG laser), and form when the regular Ti{sup 4+} ions in the crystal trap an electron. Two of these trapped-electron centres are only observed in hydrothermally grown KTP and the other two are dominant in flux-grown KTP. Both of the Ti{sup 3+} centres in hydrothermally grown crystals have a neighbouring proton (i.e. an OH{sup -} molecule). In the flux-grown crystals, one of the Ti{sup 3+} centres is adjacent to an oxygen vacancy and the other centre is tentatively attributed to a self-trapped electron (i.e. a Ti{sup 3+} centre with no stabilizing entity nearby). The g matrix and phosphorus hyperfine matrices are determined for all four Ti{sup 3+} centres, and the proton hyperfine matrix is determined for the two centres associated with OH{sup -} ions. These Ti{sup 3+} centres contribute to the formation of the grey tracks often observed in KTP crystals used to generate the second harmonic of high-power, near-infrared lasers.

  19. Topology and immersion depth of an integral membrane protein by paramagnetic rates from dissolved oxygen.

    Science.gov (United States)

    Al-Abdul-Wahid, M Sameer; Verardi, Raffaello; Veglia, Gianluigi; Prosser, R Scott

    2011-09-01

    In studies of membrane proteins, knowledge of protein topology can provide useful insight into both structure and function. In this work, we present a solution NMR method for the measurement the tilt angle and average immersion depth of alpha helices in membrane proteins, from analysis of the paramagnetic relaxation rate enhancements arising from dissolved oxygen. No modification to the micelle or protein is necessary, and the topology of both transmembrane and amphipathic helices are readily determined. We apply this method to the measure the topology of a monomeric mutant of phospholamban (AFA-PLN), a 52-residue membrane protein containing both an amphipathic and a transmembrane alpha helix. In dodecylphosphocholine micelles, the amphipathic helix of AFA-PLN was found to have a tilt angle of 87° ± 1° and an average immersion depth of 13.2 Å. The transmembrane helix was found to have an average immersion depth of 5.4 Å, indicating residues 41 and 42 are closest to the micelle centre. The resolution of paramagnetic relaxation rate enhancements from dissolved oxygen compares favourably to those from Ni (II), a hydrophilic paramagnetic species.

  20. Topology and immersion depth of an integral membrane protein by paramagnetic rates from dissolved oxygen

    International Nuclear Information System (INIS)

    Al-Abdul-Wahid, M. Sameer; Verardi, Raffaello; Veglia, Gianluigi; Prosser, R. Scott

    2011-01-01

    In studies of membrane proteins, knowledge of protein topology can provide useful insight into both structure and function. In this work, we present a solution NMR method for the measurement the tilt angle and average immersion depth of alpha helices in membrane proteins, from analysis of the paramagnetic relaxation rate enhancements arising from dissolved oxygen. No modification to the micelle or protein is necessary, and the topology of both transmembrane and amphipathic helices are readily determined. We apply this method to the measure the topology of a monomeric mutant of phospholamban (AFA-PLN), a 52-residue membrane protein containing both an amphipathic and a transmembrane alpha helix. In dodecylphosphocholine micelles, the amphipathic helix of AFA-PLN was found to have a tilt angle of 87° ± 1° and an average immersion depth of 13.2 Å. The transmembrane helix was found to have an average immersion depth of 5.4 Å, indicating residues 41 and 42 are closest to the micelle centre. The resolution of paramagnetic relaxation rate enhancements from dissolved oxygen compares favourably to those from Ni (II), a hydrophilic paramagnetic species.

  1. Effects of pre-irradiation annealing at high temperature on optical absorption and electron paramagnetic resonance of natural pumpellyite mineral

    International Nuclear Information System (INIS)

    Javier-Ccallata, Henry; Filho, Luiz Tomaz; Sartorelli, Maria L.; Watanabe, Shigueo

    2013-01-01

    Highlights: •Natural pumpellyite mineral presents superposition bands around 900 and 1060 nm due Fe 2+ and Fe 3+ . •High temperature annealing influences the EPR and OA spectra. •The behavior of EPR line for 800 and 900 °C can be attributed to forbidden dd transitions due the Fe 3+ . -- Abstract: Natural silicate mineral of pumpellyite, Ca 2 MgAl 2 (SiO 4 )(Si 2 O 7 )(OH) 2 ·(H 2 O), point group A2/m, has been studied concerning high temperature annealing and γ-radiation effects on Optical Absorption (OA) and Electron Paramagnetic Resonance (EPR) properties. Chemical analysis revealed that besides Si, Al, Ca and Mg, other oxides i.e., Fe, Mn, Na, K, Ti and P are present in the structure as impurities. OA measurements of natural and annealed pumpellyite revealed several bands in the visible region due to spin forbidden transitions of Fe 2+ and Fe 3+ . The behaviour of bands around 900 and 1060 nm, with pre-annealing and γ radiation dose, indicating a transition Fe 2+ → e − + Fe 3+ . On the other hand, EPR measurements reveal six lines of Mn 2+ , and satellites due to hyperfine interaction, superimposed on the signal of Fe 3+ around of g = 2. For heat treatment from 800 °C the signal grows significantly and for 900 °C a strong signal of Fe 3+ hides all Mn 2+ lines. The strong growth of this signal indicates that the transitions are due to Fe 3+ dipole–dipole interactions

  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. Electron paramagnetic resonance and AC susceptibility studies of Mn and Gd doped 1:2:3 superconductors

    International Nuclear Information System (INIS)

    La Robina, M.A.

    1997-01-01

    For many years superconductivity was considered to be a low temperature phenomenon occurring below ∼ 25K. All this changed in April 1986 when J. G. Bednorz and K. A. Muller showed that the oxide La 2-x Ba x CuO 4 becomes a superconductor at ∼ 30K. Later in December 1986 the oxides La 2-x Sr x CuO 4 and La 2-x Ba x CuO 4 synthesised under high pressure, were shown to superconduct at ∼ 40K and ∼ 50K, respectively. Finally in February 1987, Chu synthesised the classic superconductor YBa 2 Cu 3 O 6.8 , the so-called 1:2:3 material, which has a critical temperature circa 92K. In this thesis, electron paramagnetic resonance (EPR) and susceptibility measurements are reported on various superconductors. In 1987 Bowden et al., showed that pure phase 1:2:3 samples are characterised by an absence of Cu EPR signals. This contrasts sharply with the Green phase material, Y 2 Ba 1 Cu 1 O 5 , which shows a very large EPR signal with a g eff of 2.08. In an attempt to induce EPR signals, Mn doped 1:2:3 samples have been synthesised and characterised with EPR , AC susceptibility, XRD and SEM measurements. It is shown that Mn EPR signals are not evident in the Mn doped samples with a g eff of 2.09. Also, below T c the EPR signals of the lightly doped Mn samples vanish. It is argued that this is due to fluxoids motion within the superconductor, which gives rise to very large non-reproducible signals. It is suggested that the signals originate from Cu, impurity contaminants and multiple phases produced when the 1:2:3 superconductor is doped with Manganese (author)

  4. Effects of pre-irradiation annealing at high temperature on optical absorption and electron paramagnetic resonance of natural pumpellyite mineral

    Energy Technology Data Exchange (ETDEWEB)

    Javier-Ccallata, Henry, E-mail: henrysjc@gmail.com [Escuela de Ingeniería Electrónica y Telecomunicaciones, Universidad Alas Peruanas Filial Arequipa, Urb. D. A. Carrión G-14, J. L. Bustamante y Rivero, Arequipa (Peru); Laboratório de Sistemas Nanoestruturados, Departamento de Física, Universidade Federal de Santa Catarina, Florianópolis, Santa Catarina (Brazil); Filho, Luiz Tomaz [Departamento de Física Nuclear, Instituto de Física, Universidade de São Paulo, Rua do Matão, travessa R, 187, CEP 05508-900 São Paulo, SP (Brazil); Faculdade de Tecnologia e Ciências Exatas, Universidade São Judas Tadeu, Rua Taquari 546, São Paulo, SP (Brazil); Sartorelli, Maria L. [Laboratório de Sistemas Nanoestruturados, Departamento de Física, Universidade Federal de Santa Catarina, Florianópolis, Santa Catarina (Brazil); Watanabe, Shigueo [Departamento de Física Nuclear, Instituto de Física, Universidade de São Paulo, Rua do Matão, travessa R, 187, CEP 05508-900 São Paulo, SP (Brazil)

    2013-09-15

    Highlights: •Natural pumpellyite mineral presents superposition bands around 900 and 1060 nm due Fe{sup 2+}and Fe{sup 3+}. •High temperature annealing influences the EPR and OA spectra. •The behavior of EPR line for 800 and 900 °C can be attributed to forbidden dd transitions due the Fe{sup 3+}. -- Abstract: Natural silicate mineral of pumpellyite, Ca{sub 2}MgAl{sub 2}(SiO{sub 4})(Si{sub 2}O{sub 7})(OH){sub 2}·(H{sub 2}O), point group A2/m, has been studied concerning high temperature annealing and γ-radiation effects on Optical Absorption (OA) and Electron Paramagnetic Resonance (EPR) properties. Chemical analysis revealed that besides Si, Al, Ca and Mg, other oxides i.e., Fe, Mn, Na, K, Ti and P are present in the structure as impurities. OA measurements of natural and annealed pumpellyite revealed several bands in the visible region due to spin forbidden transitions of Fe{sup 2+} and Fe{sup 3+}. The behaviour of bands around 900 and 1060 nm, with pre-annealing and γ radiation dose, indicating a transition Fe{sup 2+} → e{sup −} + Fe{sup 3+}. On the other hand, EPR measurements reveal six lines of Mn{sup 2+}, and satellites due to hyperfine interaction, superimposed on the signal of Fe{sup 3+} around of g = 2. For heat treatment from 800 °C the signal grows significantly and for 900 °C a strong signal of Fe{sup 3+} hides all Mn{sup 2+} lines. The strong growth of this signal indicates that the transitions are due to Fe{sup 3+} dipole–dipole interactions.

  5. Electron paramagnetic resonance and optical absorption study of V{sup 4+} centres in YVO{sub 4} crystals

    Energy Technology Data Exchange (ETDEWEB)

    Garces, N Y [Department of Physics, West Virginia University, Morgantown, WV 26506 (United States); Stevens, K T [Northrop Grumman Space Technology, Synoptics, Charlotte, NC 28273 (United States); Foundos, G K [Northrop Grumman Space Technology, Synoptics, Charlotte, NC 28273 (United States); Halliburton, L E [Department of Physics, West Virginia University, Morgantown, WV 26506 (United States)

    2004-10-06

    Electron paramagnetic resonance (EPR) has been used to characterize three distinct V{sup 4+} centres in undoped Czochralski-grown yttrium orthovanadate (YVO{sub 4}) crystals. These EPR signals are observed at low temperatures, and their average c-axis splittings between adjacent {sup 51}V hyperfine lines are 40 G, 123 G, and 140 G. We refer to these centres as [V{sup 4+}]{sub A}, [V{sup 4+}]{sub B}, and [V{sup 4+}]{sub C}, respectively. The [V{sup 4+}]{sub A} and [V{sup 4+}]{sub B} centres are present in as-grown crystals. Exposure at 77 K to ionizing radiation (x-rays or an ultraviolet laser beam) destroys these centres and creates the [V{sup 4+}]{sub C} centres. The as-grown state of the crystal is restored upon returning to room temperature. Angular dependence data are used to determine the principal values and principal directions of the g tensor and the {sup 51}V hyperfine tensor for each of the centres. We suggest that the [V{sup 4+}]{sub A} centre is a V{sup 4+} ion adjacent to an oxygen vacancy and that the [V{sup 4+}]{sub B} centre is a V{sup 4+} ion substituting for a Y{sup 3+} ion (i.e. a vanadium antisite defect). The [V{sup 4+}]{sub C} centre is assigned to a V{sup 4+} ion at a regular vanadium site with a nearby stabilizing defect, possibly a Zr{sup 4+} on a Y{sup 3+} site. In as-grown crystals, there is a correlation between the number of [V{sup 4+}]{sub A} centres and the intensity (at 380 nm) of a broad near-edge optical absorption band. This band, now associated with oxygen vacancies, gives YVO{sub 4} a 'yellow' appearance.

  6. A versatile and modular quasi optics-based 200 GHz dual dynamic nuclear polarization and electron paramagnetic resonance instrument

    Science.gov (United States)

    Siaw, Ting Ann; Leavesley, Alisa; Lund, Alicia; Kaminker, Ilia; Han, Songi

    2016-03-01

    Solid-state dynamic nuclear polarization (DNP) at higher magnetic fields (>3 T) and cryogenic temperatures (∼2-90 K) has gained enormous interest and seen major technological advances as an NMR signal enhancing technique. Still, the current state of the art DNP operation is not at a state at which sample and freezing conditions can be rationally chosen and the DNP performance predicted a priori, but relies on purely empirical approaches. An important step towards rational optimization of DNP conditions is to have access to DNP instrumental capabilities to diagnose DNP performance and elucidate DNP mechanisms. The desired diagnoses include the measurement of the "DNP power curve", i.e. the microwave (MW) power dependence of DNP enhancement, the "DNP spectrum", i.e. the MW frequency dependence of DNP enhancement, the electron paramagnetic resonance (EPR) spectrum, and the saturation and spectral diffusion properties of the EPR spectrum upon prolonged MW irradiation typical of continuous wave (CW) DNP, as well as various electron and nuclear spin relaxation parameters. Even basic measurements of these DNP parameters require versatile instrumentation at high magnetic fields not commercially available to date. In this article, we describe the detailed design of such a DNP instrument, powered by a solid-state MW source that is tunable between 193 and 201 GHz and outputs up to 140 mW of MW power. The quality and pathway of the transmitted and reflected MWs is controlled by a quasi-optics (QO) bridge and a corrugated waveguide, where the latter couples the MW from an open-space QO bridge to the sample located inside the superconducting magnet and vice versa. Crucially, the versatility of the solid-state MW source enables the automated acquisition of frequency swept DNP spectra, DNP power curves, the diagnosis of MW power and transmission, and frequency swept continuous wave (CW) and pulsed EPR experiments. The flexibility of the DNP instrument centered around the QO MW

  7. 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

  8. A versatile and modular quasi optics-based 200GHz dual dynamic nuclear polarization and electron paramagnetic resonance instrument.

    Science.gov (United States)

    Siaw, Ting Ann; Leavesley, Alisa; Lund, Alicia; Kaminker, Ilia; Han, Songi

    2016-03-01

    Solid-state dynamic nuclear polarization (DNP) at higher magnetic fields (>3T) and cryogenic temperatures (∼ 2-90K) has gained enormous interest and seen major technological advances as an NMR signal enhancing technique. Still, the current state of the art DNP operation is not at a state at which sample and freezing conditions can be rationally chosen and the DNP performance predicted a priori, but relies on purely empirical approaches. An important step towards rational optimization of DNP conditions is to have access to DNP instrumental capabilities to diagnose DNP performance and elucidate DNP mechanisms. The desired diagnoses include the measurement of the "DNP power curve", i.e. the microwave (MW) power dependence of DNP enhancement, the "DNP spectrum", i.e. the MW frequency dependence of DNP enhancement, the electron paramagnetic resonance (EPR) spectrum, and the saturation and spectral diffusion properties of the EPR spectrum upon prolonged MW irradiation typical of continuous wave (CW) DNP, as well as various electron and nuclear spin relaxation parameters. Even basic measurements of these DNP parameters require versatile instrumentation at high magnetic fields not commercially available to date. In this article, we describe the detailed design of such a DNP instrument, powered by a solid-state MW source that is tunable between 193 and 201 GHz and outputs up to 140 mW of MW power. The quality and pathway of the transmitted and reflected MWs is controlled by a quasi-optics (QO) bridge and a corrugated waveguide, where the latter couples the MW from an open-space QO bridge to the sample located inside the superconducting magnet and vice versa. Crucially, the versatility of the solid-state MW source enables the automated acquisition of frequency swept DNP spectra, DNP power curves, the diagnosis of MW power and transmission, and frequency swept continuous wave (CW) and pulsed EPR experiments. The flexibility of the DNP instrument centered around the QO MW

  9. Assignment of hyperfine shifted haem methyl carbon resonances in paramagnetic low-spin met-cyano complex of sperm whale myoglobin

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, Yasuhiko

    1987-09-28

    The hyperfine shifted resonances arising from all four individual haem carbons of the paramagnetic low-spin met-cyano complex of sperm whale myoglobin have been clearly identified and assigned for the first time with the aid of /sup 1/H-/sup 13/C heteronuclear chemical shift correlated spectroscopy. Alteration of the in-plane symmetry of the electronic structure of haem induced by the ligation of proximal histidyl imidazole spreads the haem carbon resonances to 32 ppm at 22/sup 0/C, indicating the sensitivity of those resonances to the haem electronic/molecular structure. Those resonances are potentially powerful probes in characterizing the nature of haem electronic structure. 25 refs.; 2 figs.; 1 table.

  10. Electron Paramagnetic Resonance Imaging

    Indian Academy of Sciences (India)

    IAS Admin

    Sankaran Subramanian and Murali C Krishna ... the National Cancer Institute, .... They are non-toxic and can be injected intravenously or intraperitoneally for EPR ..... Consumption of green vegetables, green tea, Vitamin E, polyphenols, ...

  11. Electron Paramagnetic Resonance Spectroscopy

    Indian Academy of Sciences (India)

    IAS Admin

    the EPR technique can be used to elucidate the structural reorganization taking place in a ... including cellular maintenance, immunity and reproduction. The ... derstand the function of a particular protein involved in various cellular events, it is ...

  12. Electron Paramagnetic Resonance Imaging

    Indian Academy of Sciences (India)

    IAS Admin

    is Professor of Chemistry at. IIT Madras. ... speeding up the CW imaging by special novel methods. How- ever, the ... presence of gradients which are applied in two or three dimen- sions and ... optics and mechanical engineer- ing stands for ...

  13. An analytical approximation for resonance integral

    International Nuclear Information System (INIS)

    Magalhaes, C.G. de; Martinez, A.S.

    1985-01-01

    It is developed a method which allows to obtain an analytical solution for the resonance integral. The problem formulation is completely theoretical and based in concepts of physics of general character. The analytical expression for integral does not involve any empiric correlation or parameter. Results of approximation are compared with pattern values for each individual resonance and for sum of all resonances. (M.C.K.) [pt

  14. Effects of thermal annealing on the radiation produced electron paramagnetic resonance spectra of bovine and equine tooth enamel: Fossil and modern

    International Nuclear Information System (INIS)

    Weeks, Robert A.; Bogard, James S.; Elam, J. Michael; Weinand, Daniel C.; Kramer, Andrew

    2003-01-01

    The concentration of stable radiation-induced paramagnetic states in fossil teeth can be used as a measure of sample age. Temperature excursions >100 deg. C, however, can cause the paramagnetic state clock to differ from the actual postmortem time. We have heated irradiated enamel from both fossilized bovid and modern equine (MEQ) teeth for 30 min in 50 deg. C increments from 100 to 300 deg. C, measuring the electron paramagnetic resonance (EPR) spectrum after each anneal, to investigate such effects. Samples were irradiated again after the last anneal, with doses of 300-1200 Gy from 60 Co photons, and measured. Two unirradiated MEQ samples were also annealed for 30 min at 300 deg. C, one in an evacuated EPR tube and the other in a tube open to the atmosphere, and subsequently irradiated. The data showed that hyperfine components attributed to the alanine radical were not detected in the irradiated MEQ sample until after the anneals. The spectrum of the MEQ sample heated in air and then irradiated was similar to that of the heat treated fossil sample. We conclude that the hyperfine components are due to sample heating to temperatures/times >100 deg. C/30 min and that similarities between fossil and MEQ spectra after the 300 deg. C/30 min MEQ anneal are also due to sample heating. We conclude that the presence of the hyperfine components in spectra of fossil tooth enamel indicate that such thermal events occurred either at the time of death, or during the postmortem history

  15. Electron paramagnetic resonance investigations of Fe3+ doped layered TiInS2 and TiGaSe2 single crystals

    International Nuclear Information System (INIS)

    Faik, Mikailov; Bulat, Rameev; Sinan, Kazan; Bekir, Aktash; Faik, Mikailov; Bulat, Rameev

    2005-01-01

    Full text : TiInS 2 and TiGaSe 2 single crystals doped by paramagnetic Fe ions have been studied at room temperature by Electron Paramagnetic Resonance (EPR) technique. A fine structure of EPR spectra of paramagnetic Fe 3 + ions was observed. The spectra were interpreted to correspond to the transitions among spin multiplet which are splitted by the local ligand crystal field (CF) of orthorhombic symmetry. Four equivalent Fe 3 + centers have been observed in the EPR spectra and the local symmetry of crystal field at the Fe 3 + site and CF parameters were determined. It was established that symmetry axis of the axial component in the CF is making an angle of about 48 and 43 degree with the plane of layers of TiInS 2 and TiGaSe 2 crystals respectively. Experimental results indicate that the Fe ions substitute In (GA) at the center of InS 4 (GaSe 4 ) tetrahedrons, and the rhombic distortion of the CF is caused by the TI ions located in the trigonal cavities between the tethedral complexes

  16. Integral data analysis for resonance parameters determination

    International Nuclear Information System (INIS)

    Larson, N.M.; Leal, L.C.; Derrien, H.

    1997-09-01

    Neutron time-of-flight experiments have long been used to determine resonance parameters. Those resonance parameters have then been used in calculations of integral quantities such as Maxwellian averages or resonance integrals, and results of those calculations in turn have been used as a criterion for acceptability of the resonance analysis. However, the calculations were inadequate because covariances on the parameter values were not included in the calculations. In this report an effort to correct for that deficiency is documented: (1) the R-matrix analysis code SAMMY has been modified to include integral quantities of importance, (2) directly within the resonance parameter analysis, and (3) to determine the best fit to both differential (microscopic) and integral (macroscopic) data simultaneously. This modification was implemented because it is expected to have an impact on the intermediate-energy range that is important for criticality safety applications

  17. Evaluation of temperature dependent neutron resonance integrals

    International Nuclear Information System (INIS)

    Menon, S.V.G.; Sahni, D.C.

    1975-01-01

    The Fourier transform method is extended for evaluating temperature dependent resonance integrals and Doppler coefficients. With the temperature dependent cross-sections, the slowing-down equation is transformed into a Fredholm integral equation of second kind. A method of solution is presented using the familiar Gauss-Hermite quadrature formulae. As a byproduct of the above technique, a fast and accurate method for computing the resonance integral J-function is given. (orig.) [de

  18. Experimental Model for Retrospective Assessment of X-Ray Exposures in Dento-Maxillary Radiology Measured by Electron Paramagnetic Resonance in Tooth Enamel

    Directory of Open Access Journals (Sweden)

    Ioana Costina DÂNŞOREANU

    2009-12-01

    Full Text Available Electron paramagnetic resonance (EPR dosimetry of human tooth enamel has been widely used in measuring radiation doses in various scenarios. For experimental purposes in X-ray diagnostic or therapy human persons can not be involved. For such cases we have developed an EPR dosimetry technique making use of enamel of molars extracted from pigs. The method can evaluate doses and dose-profiles of irradiated teeth at low level as 50 – 100 mGy (in air. EPR-spectra acquisition, data processing and dose assessment were done using non-dedicated equipment, devices and software.

  19. Electron paramagnetic resonance study of the Ce.sup.3+./sup. pair centers in YAlO.sub.3./sub.:Ce scintillator crystals

    Czech Academy of Sciences Publication Activity Database

    Buryi, Maksym; Laguta, Valentyn; Mihóková, Eva; Novák, Pavel; Nikl, Martin

    2015-01-01

    Roč. 92, č. 22 (2015), "224105-1"-"224105-10" ISSN 1098-0121 R&D Projects: GA MŠk LO1409; GA MŠk(CZ) LM2011029; GA ČR GAP204/12/0805 Grant - others:SAFMAT(XE) CZ.2.16/3.1.00/22132 Institutional support: RVO:68378271 Keywords : electron paramagnetic resonance * scintillator * pair of ions * density functional theory calculation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.736, year: 2014

  20. Defect structure in lithium-doped polymer-derived SiCN ceramics characterized by Raman and electron paramagnetic resonance spectroscopy.

    Science.gov (United States)

    Erdem, Emre; Mass, Valentina; Gembus, Armin; Schulz, Armin; Liebau-Kunzmann, Verena; Fasel, Claudia; Riedel, Ralf; Eichel, Rüdiger-A

    2009-07-21

    Lithium-doped polymer-derived silicon carbonitride ceramics (SiCN:Li) synthesized at various pyrolysis temperatures, have been investigated by means of multifrequency and multipulse electron paramagnetic resonance (EPR) and Raman spectroscopy in order to determine different defect states that may impact the materials electronic properties. In particular, carbon- and silicon-based 'dangling bonds' at elevated, as well as metallic networks containing Li0 in the order of 1 microm at low pyrolysis temperatures have been observed in concentrations ranging between 10(14) and 10(17) spins mg(-1).

  1. 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)

  2. Electron paramagnetic resonance and neutron activation study of lanthanide ions behaviour in fluorite. Application to the geochemical study of Montroc and Burc veins (Tarn)

    International Nuclear Information System (INIS)

    Meary, Alain

    1983-01-01

    In order to obtain a better understanding of fluorite deposits, rare earth impurities have been analyzed for a large number of samples taken from cross-sections of several low temperature hydrothermal veins; two types of measurements have been used: Electron Paramagnetic Resonance (EPR) and Neutron Activation Analysis (NAA). This enabled us to measure a 'deficit of spins' relative to the total lanthanide concentration, this deficit reveals that the paramagnetic center observed by EPR is not the only mode of incorporation. For Gd no marked deficit is observed; that is the ratio of spin concentrations to total concentration [Gd 3+ ]/[Gd total ] is close to 1 in all the samples; on the other hand, the ratios [Eu 2+ ]/[Eu total ], [Ce 3- F i - ]/[Ce total ], and [Yb 3+ ]/ [Yb total ] exhibit large variations. The first result suggests that the major part of the lanthanides in the samples is incorporated in the crystal lattice and that clustering of lanthanides ions is not important. Deficit of spins observed for Ce and Nd are probably due to the dissociation of paramagnetic complexes Ce 3+ -F i - and Nd 3+ -F i - ; for Eu, it may be attributed to the oxidized state Eu 3+ . Moreover, the sign and the amplitude of the anomaly exhibited by Eu in the normalized lanthanides spectra may be correlated with the majority valence state of Eu in the crystal: a marked positive anomaly belongs to a deficit of paramagnetic divalent Eu and, inversely, if divalent Eu is the majority valence state, the Eu anomaly appears to be negative. The results obtained for the Montroc vein are consistent with a model involving discontinuous injections of hydrothermal solutions. They may be connected to variations of oxygen fugacity arising from cooling of these solutions and from precipitation of sulfides during fluorite precipitation. (author) [fr

  3. Integrated unaligned resonant modulator tuning

    Energy Technology Data Exchange (ETDEWEB)

    Zortman, William A.; Lentine, Anthony L.

    2017-10-03

    Methods and systems for tuning a resonant modulator are disclosed. One method includes receiving a carrier signal modulated by the resonant modulator with a stream of data having an approximately equal number of high and low bits, determining an average power of the modulated carrier signal, comparing the average power to a predetermined threshold, and operating a tuning device coupled to the resonant modulator based on the comparison of the average power and the predetermined threshold. One system includes an input structure, a plurality of processing elements, and a digital control element. The input structure is configured to receive, from the resonant modulator, a modulated carrier signal. The plurality of processing elements are configured to determine an average power of the modulated carrier signal. The digital control element is configured to operate a tuning device coupled to the resonant modulator based on the average power of the modulated carrier signal.

  4. Electron Paramagnetic Resonance: Elementary Theory and Practical Applications, Second Edition (John A. Weil and James R. Bolton)

    Science.gov (United States)

    Williams, Ffrancon

    2009-01-01

    The detection of electron magnetic resonance by Zavoiskii in the mid 1940s (1) ushered in a golden age of physical and chemical applications. Perhaps no single book did more to stimulate this development of EPR spectroscopy than the classic text by Wertz and Bolton (2) , which appeared in 1972. A revised version, with John A. Weil added as a co-author, was published by Wiley in 1994. This 2007 text is formally described as the second edition of the 1994 version. Wertz died shortly after the publication of the 1994 edition leaving Weil and Bolton as authors. In noting that the senior author (JAW) takes most of the responsibility for the content of this 2007 version, the Preface refers to it at one point as the "third edition", which of course is precisely how older readers will regard it. The main thrust of the book is decidedly on the physical aspects of EPR, so that it nicely complements the more chemical emphasis provided in the recent comprehensive text by Gerson and Hüber (3) . As the authors remark, the 2007 edition does not differ dramatically from the 1994 version. The titles of the 13 chapters remain the same except for chapter 11, which now refers to the "Noncontinuous" instead of the "Time-Dependent" Excitation of Spins. Recent developments are generally accommodated by a few extra pages in each chapter. Thus, chapter 1 on Basic Principles of Paramagnetic Resonance has been expanded from 31 to 36 pages to introduce the topics of parallel-field EPR, time-resolved EPR, "computerology", and EPR imaging. Chapter 2 on Magnetic Interactions is essentially unchanged while chapter 3 on Isotropic Hyperfine Effects has been expanded to include new sections on Deviations from the Simple Multinomial Scheme (3.7) and Some Interesting π-Type Free Radicals (3.9). Section 3.9 provides a useful corrective to the notion that the EPR method can detect and characterize almost any type of radical species. This welcome touch of realism is nicely illustrated by mentioning

  5. Resonance integral calculations for high temperature reactors

    International Nuclear Information System (INIS)

    Blake, J.P.H.

    1960-02-01

    Methods of calculation of resonance integrals of finite dilution and temperature are given for both, homogeneous and heterogeneous geometries, together with results obtained from these methods as applied to the design of high temperature reactors. (author)

  6. Electron paramagnetic resonance studies of manganese centers in SrTiO.sub.3./sub.: Non-Kramers Mn.sup.3+./sup. ions and spin-spin coupled Mn.sup.4+./sup. dimers

    Czech Academy of Sciences Publication Activity Database

    Azamat, Dmitry; Dejneka, Alexandr; Lančok, Ján; Trepakov, Vladimír; Jastrabík, Lubomír; Badalyan, A. G.

    2012-01-01

    Roč. 111, č. 10 (2012), "104119-1"-"104119-6" ISSN 0021-8979. [International Symposium on Integrated Functionalities (ISIF) /22./. San Juan, Puerto Rico , 13.06.2010-16.06.2010] R&D Projects: GA TA ČR TA01010517; GA MŠk(CZ) LM2011029; GA ČR GAP108/12/1941 Grant - others:SAFMAT(CZ) CZ.2.16/3.1.00/22132 Institutional research plan: CEZ:AV0Z10100522 Keywords : electron paramagnetic resonance * X- and Q-band * SrTiO 3 doped with Mn Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.210, year: 2012

  7. Application of the Electron paramagnetic resonance to the ionizing radiation dosimetry; Aplicacion de la Resonancia paramagnetica electronica a la dosimetria de las radiaciones ionizantes

    Energy Technology Data Exchange (ETDEWEB)

    Urena N, F. [Instituto Nacional de Investigaciones Nucleares, Km. 36.5 Carretera Mexico-Toluca, 52045 Salazar, Estado de Mexico (Mexico)

    2000-07-01

    The Electron Paramagnetic Resonance (EPR) is defined as the resonant absorption of electromagnetic energy in paramagnetic substances by the spin transition of a non-pairing electron between different energy levels in presence of a magnetic field. (Slighter, 1989). One of the more important characteristic of EPR is that the electron spin levels are subdivided by the electron interaction with the magnetic dipoles of the nearby nucleus giving occasion for a spectral structure called hyperfine structure. In this kind of interactions two limit cases are distinguished: 1. when the non-pairing electron is located in a central ion surrounded of atoms belonging to coordinate molecules. 2. When a non-pairing electron interactioning in the same form with a number of equivalent nucleus, which is common in organic radicals, these will give as result spectra. Some EPR spectrometer can be used to dosimetric purposes by free radicals via. In this work, it is presented the application of EPR to dosimetry of ionizing radiations by free radicals via which allows to determinations of high doses. (Author)

  8. Parallel image-acquisition in continuous-wave electron paramagnetic resonance imaging with a surface coil array: Proof-of-concept experiments

    Science.gov (United States)

    Enomoto, Ayano; Hirata, Hiroshi

    2014-02-01

    This article describes a feasibility study of parallel image-acquisition using a two-channel surface coil array in continuous-wave electron paramagnetic resonance (CW-EPR) imaging. Parallel EPR imaging was performed by multiplexing of EPR detection in the frequency domain. The parallel acquisition system consists of two surface coil resonators and radiofrequency (RF) bridges for EPR detection. To demonstrate the feasibility of this method of parallel image-acquisition with a surface coil array, three-dimensional EPR imaging was carried out using a tube phantom. Technical issues in the multiplexing method of EPR detection were also clarified. We found that degradation in the signal-to-noise ratio due to the interference of RF carriers is a key problem to be solved.

  9. Effects of thermal annealing on the radiation produced electron paramagnetic resonance spectra of bovine and equine tooth enamel: Fossil and modern

    Science.gov (United States)

    Weeks, Robert A.; Bogard, James S.; Elam, J. Michael; Weinand, Daniel C.; Kramer, Andrew

    2003-06-01

    The concentration of stable radiation-induced paramagnetic states in fossil teeth can be used as a measure of sample age. Temperature excursions >100 °C, however, can cause the paramagnetic state clock to differ from the actual postmortem time. We have heated irradiated enamel from both fossilized bovid and modern equine (MEQ) teeth for 30 min in 50 °C increments from 100 to 300 °C, measuring the electron paramagnetic resonance (EPR) spectrum after each anneal, to investigate such effects. Samples were irradiated again after the last anneal, with doses of 300-1200 Gy from 60Co photons, and measured. Two unirradiated MEQ samples were also annealed for 30 min at 300 °C, one in an evacuated EPR tube and the other in a tube open to the atmosphere, and subsequently irradiated. The data showed that hyperfine components attributed to the alanine radical were not detected in the irradiated MEQ sample until after the anneals. The spectrum of the MEQ sample heated in air and then irradiated was similar to that of the heat treated fossil sample. We conclude that the hyperfine components are due to sample heating to temperatures/times >100 °C/30 min and that similarities between fossil and MEQ spectra after the 300 °C/30 min MEQ anneal are also due to sample heating. We conclude that the presence of the hyperfine components in spectra of fossil tooth enamel indicate that such thermal events occurred either at the time of death, or during the postmortem history.

  10. A numerical method for resonance integral calculations

    International Nuclear Information System (INIS)

    Tanbay, Tayfun; Ozgener, Bilge

    2013-01-01

    A numerical method has been proposed for resonance integral calculations and a cubic fit based on least squares approximation to compute the optimum Bell factor is given. The numerical method is based on the discretization of the neutron slowing down equation. The scattering integral is approximated by taking into account the location of the upper limit in energy domain. The accuracy of the method has been tested by performing computations of resonance integrals for uranium dioxide isolated rods and comparing the results with empirical values. (orig.)

  11. Multilayer Integrated Film Bulk Acoustic Resonators

    CERN Document Server

    Zhang, Yafei

    2013-01-01

    Multilayer Integrated Film Bulk Acoustic Resonators mainly introduces the theory, design, fabrication technology and application of a recently developed new type of device, multilayer integrated film bulk acoustic resonators, at the micro and nano scale involving microelectronic devices, integrated circuits, optical devices, sensors and actuators, acoustic resonators, micro-nano manufacturing, multilayer integration, device theory and design principles, etc. These devices can work at very high frequencies by using the newly developed theory, design, and fabrication technology of nano and micro devices. Readers in fields of IC, electronic devices, sensors, materials, and films etc. will benefit from this book by learning the detailed fundamentals and potential applications of these advanced devices. Prof. Yafei Zhang is the director of the Ministry of Education’s Key Laboratory for Thin Films and Microfabrication Technology, PRC; Dr. Da Chen was a PhD student in Prof. Yafei Zhang’s research group.

  12. Effects of diffusion and surface interactions on the line shape of electron paramagnetic resonances in the presence of a magnetic field gradient

    International Nuclear Information System (INIS)

    Schaden, M.; Zhao, K. F.; Wu, Z.

    2007-01-01

    In an evanescent wave magnetometer the Zeeman polarization is probed at micrometer to submicrometer distances from the cell surface. The electron paramagnetic resonance lines of an evanescent wave magnetometer in the presence of a magnetic field gradient exhibit edge enhancement seen previously in nuclear magnetic resonance lines. We present a theoretical model that describes quantitatively the shape of the magnetic resonance lines of an evanescent wave magnetometer under a wide range of experimental conditions. It accounts for diffusion broadening in the presence of a magnetic field gradient as well as interactions of spin polarized Rb atoms with the coated Pyrex glass surfaces. Depending on the field gradient, cell thickness, and buffer gas pressure, the resonance line may have the form of a single asymmetric peak or two peaks localized near the front and back surfaces in frequency space. The double-peaked response depends on average characteristics of the surface interactions. Its shape is sensitive to the dwell time, relaxation probability, and average phase shift of adsorbed spin polarized Rb atoms

  13. Study of the radiolysis of tetracycline hydrochloride in powder form, in aqueous solutions and in benzyl alcohol, at 77K, by electron paramagnetic resonance spectroscopy

    International Nuclear Information System (INIS)

    Guedes, S.M.L.

    1984-01-01

    The radiolysis of tetracycline hydrochloride in powder form, dissolved in benzyl alcohol and in acid, neutral and alkaline aerated aqueous solutions at 77K is studied by electron paramagnetic resonance spectroscopy. Mechanisms of reactions that occur in the radiolysis of these systems are proposed and some aspects of the reactions that occurs with electrons and with hydrogen atoms at 77K are investigated, since tetracycline hydrochloride captures both paramagnetic species. Also discussed is the influence of some factors in the migration of these species at 77K, such as: the position of solutes, the crystalline structure of the solvent, the kinetic energy of the species and the angle of incidence in the channeling. The rate constants for the reaction between the electron and physical and chemical traps which are present in the alkaline aerated aqueous solutions, at 77k, are calculated. The values found are, respectively: k=9.6 x 10 15 1 mol -1 s -1 and k= 1.8 x 10 10 1 mol -1 s -1 . (Author) [pt

  14. Oxidation of carbon monoxide cocatalyzed by palladium(0) and the H(5)PV(2)Mo(10)O(40) polyoxometalate probed by electron paramagnetic resonance and aerobic catalysis.

    Science.gov (United States)

    Goldberg, Hila; Kaminker, Ilia; Goldfarb, Daniella; Neumann, Ronny

    2009-08-17

    The H(5)PV(2)Mo(10)O(40) polyoxometalate and Pd/Al(2)O(3) were used as co-catalysts under anaerobic conditions for the activation and oxidation of CO to CO(2) by an electron transfer-oxygen transfer mechanism. Upon anaerobic reduction of H(5)PV(2)Mo(10)O(40) with CO in the presence of Pd(0) two paramagnetic species were observed and characterized by continuous wave electron paramagnetic resonance (CW-EPR) and hyperfine sublevel correlation (HYSCORE) spectroscopic measurements. Major species I (65-70%) is assigned to a species resembling a vanadyl cation that is supported on the polyoxometalate and showed a bonding interaction with (13)CO. Minor species II (30-35%) is attributed to a reduced species where the vanadium(IV) atom is incorporated in the polyoxometalate framework but slightly distanced from the phosphate core. Under aerobic conditions, CO/O(2), a nucleophilic oxidant was formed as elucidated by oxidation of thianthrene oxide as a probe substrate. Oxidation reactions performed on terminal alkenes such as 1-octene yielded a complicated mixture of products that was, however, clearly a result of alkene epoxidation followed by subsequent reactions of the intermediate epoxide. The significant competing reaction was a hydrocarbonylation reaction that yielded a approximately 1:1 mixture of linear/branched carboxylic acids.

  15. Resonance integral of cylindrical absorber; Rezonantni integral cilindricnog absorbera

    Energy Technology Data Exchange (ETDEWEB)

    Slipicevic, K [Elektrotehnicki fakultet, Belgrade (Yugoslavia)

    1968-07-01

    This paper presents the procedure for calculating effective resonance integral for cylindrical rod which enables derivation of improved spatial distribution of source neutron flux. Application of this new expression for penetration factor, simultaneously with Doppler broadening of Breight-Wigner line enabled derivation of new equation for resonance integral which is valid for the whole range of surface-volume ratio of the rod, has correct boundary conditions and gives as special, results same as Wigner and Pomeranchuk. Functions for correcting the effects of interference of potential and resonance dissipation are derived separately.

  16. Theoretical studies of the local structure and electron paramagnetic resonance parameters for tetragonal VO{sup 2+} in C{sub 6}H{sub 7}KO{sub 7}

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Ping [Chongqing Jiaotong Univ. (China). School of Science; Li, Ling [Sichuan University of Arts and Science, Dazhou (China). Dept. of Maths and Finance-Economics

    2015-07-01

    The optical spectra, electron paramagnetic resonance parameters (i.e., the spin Hamiltonian parameters, including paramagnetic g factors and the hyperfine structure constants A{sub i}) and the local distortion structure for the tetragonal VO{sup 2+} in C{sub 6}H{sub 7}KO{sub 7} are theoretically studied based on the crystal-field theory and three-order perturbation formulas of a 3d{sup 1} centre in tetragonal site. The magnitude of orbital reduction factor, core polarisation constant κ, and local structure parameters are obtained by fitting the calculated optical spectra and electron paramagnetic resonance parameters to the experimental values. The theoretical results are in reasonable agreement with the experimental values.

  17. Unified explanation for optical and electron paramagnetic resonance spectra of Cr sup 3 sup + ions in LiNbO sub 3 crystals

    CERN Document Server

    Zhao, M G

    1997-01-01

    An approximately microscopic model is developed for the Cr sup 3 sup + -6O sup 2 sup - cluster and applied to study the optical data and electron paramagnetic resonance (EPR) g-factors and the zero-field splitting D-value in LiNbO sub 3 :Cr sup 3 sup +. Analysis of the optical and EPR data indicate that Cr sup 3 sup + ions substitute at Nb sites and Nb-vacancy (Li) sites simultaneously. The results are in good agreement with the experimental findings. This means that the optical and EPR data and the substitution site of Cr sup 3 sup + ions in LiNbO sub 3 can be interpreted uniformly. (author)

  18. 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.

  19. Use of electron paramagnetic resonance dosimetry with tooth enamel for retrospective dose assessment. Report of a co-ordinated research project

    CERN Document Server

    2002-01-01

    Electron paramagnetic resonance (EPR) dosimetry is a physical method for the assessment of absorbed dose from ionising radiation. It is based on the measurement of stable radiation induced radicals in human calcified tissues (primarily in tooth enamel). EPR dosimetry with teeth is now firmly established in retrospective dosimetry. It is a powerful method for providing information on exposure to ionising radiation many years after the event, since the 'signal' is 'stored' in the tooth or the bone. This technique is of particular relevance to relatively low dose exposures or when the results of conventional dosimetry are not available (e.g. in accidental circumstances). The use of EPR dosimetry, as an essential tool for retrospective assessment of radiation exposure is an important part of radioepidemiological studies and also provides data to select appropriate countermeasures based on retrospective evaluation of individual doses. Despite well established regulations and protocols for maintaining radiation pro...

  20. Electronic Paramagnetic Resonance of irradiated nails: challenges for a dosimetry in radiation accidents; Ressonancia Paramagnetica Eletronica de unhas irradiadas: desafios para uma dosimetria em acidentes radiologicos

    Energy Technology Data Exchange (ETDEWEB)

    Giannoni, Ricardo A., E-mail: giannoni@ird.gov.br [Instituto de Radioprotecao e Dosimetria, (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil); Rodrigues Junior, Orlando [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2014-07-01

    The purpose of this work is to characterize samples of human nails exposed to high doses of radiation, applying the technique of Electron Paramagnetic Resonance (EPR). The objective is to establish a dose response study that allow determine the absorbed dose by exposed individuals in situations of radiological accidents, in a retrospective form. Samples of human nails were collected and afterward irradiated with gamma radiation, and received dose of 20 Gy. The EPR measurement performed on the samples, before irradiation, permitted the signal identification of the components associated with effects caused by the mechanical stress during the fingernail cutting, the so-called mechanically induced signal (MIS). After the irradiation, different species of free radicals were identified, the so-called radiation induced signal (RIS). (author)

  1. The influence of microscopic disorder on electron paramagnetic resonance spectra of Eu2+ ions in Pb1-xGexTe

    International Nuclear Information System (INIS)

    Radzynski, T; Lusakowski, A; Swiatek, K; Story, T

    2009-01-01

    In mixed crystals, because of the different ionic radii of cations or anions and the randomness in the placement of ions of different kinds, the crystal lattice is locally deformed. Such local deformations have significant influence on the ground state splitting of magnetic ions. Because this ground state splitting is responsible for the position of the electron paramagnetic resonance (EPR) lines, microscopic disorder is one of the factors which lead to the broadening of the lines, and eventually to their disappearance. This paper is devoted to semi-quantitative analysis of the influence of microscopic disorder on EPR spectra. The theory is compared against measurements performed on mono-crystalline Pb 1-x Ge x Te epitaxial layers containing Eu 2+ ions for different germanium and europium contents. With increasing germanium content we observe gradual disappearance of the EPR lines, although macroscopically, on the basis of x-ray diffraction analysis, each layer might have been considered as a perfect crystal.

  2. Resonance integral analytical calculation considering shadowing effect

    International Nuclear Information System (INIS)

    Monteiro, M.A.M.; Martinez, A.S.

    1990-01-01

    It is presented a method for the Resonance Integral Calculation in the fuel and moderator regions, including the shadowing effect. This effect appears due to the presence of several fuel rods in a infinite moderator region. The method is based on the approximations to the J (ξ, β) function and theirs partial derivatives in relation to β. The dependence of the Resonance Integral in the J (ξ, β) comes from the rational approximation to the neutron escape probability. The final results were obtained in a very simple and fast way, and they show the good accuracy of the method. (author)

  3. In-depth magnetic characterization of a [2 × 2] Mn(III) square grid using SQUID magnetometry, inelastic neutron scattering, and high-field electron paramagnetic resonance spectroscopy

    DEFF Research Database (Denmark)

    Konstantatos, Andreas; Bewley, Robert; Barra, Anne Laure

    2016-01-01

    . Combined inelastic neutron scattering (INS) and electron paramagnetic resonance (EPR) experiments provided the necessary information in order to successfully model the magnetic properties of Mn4. The resulting model takes into account both the magnitude and the relative orientations of the single...

  4. Powderspec, a program for the efficient simulation of spectra of electron paramagnetic resonance of powders with orthorhombic symmetry; Powderspec, un programa para la simulacion eficiente de espectros de resonancia paramagnetica electronica de polvos con simetria ortorrombica

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez T, L.; Beltran L, V

    1991-09-15

    In this report a FORTRAN source program which simulates the second order powder pattern and spectrum of electron paramagnetic resonance (EPR) in crystal fields with orthorhombic symmetry using Gauss-Legendre quadratures is given. Also the commentaries which describe each step in detail are presented. (Author)

  5. Electron paramagnetic resonance study on the ionizing radiation induced defects of the tooth enamel hydroxyapatite; Estudo por ressonancia paramagnetica eletronica de defeitos induzidos pelas radiacoes ionizantes na hidroxiapatita do esmalte dentario

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Liana Macedo de

    1995-01-01

    Hydroxyapatite is the main constituent of calcified tissues. Defects induced by ionizing radiations in this biomineral can present high stability and then, these are used as biological markers in radiological accidents, irradiated food identifying and geological and archaeological dating. In this work, paramagnetic centers induced on the enamel of the teeth by environmental ionizing radiation, are investigated by electron paramagnetic resonance (EPR). Decay thermal kinetic presents high complexity and shows the formation of different electron ligation energy centers and structures 65 refs., 40 figs., 5 tabs.

  6. Anti-HER2 immunoliposomes for selective delivery of electron paramagnetic resonance imaging probes to HER2-overexpressing breast tumor cells

    Science.gov (United States)

    Burks, Scott R.; Macedo, Luciana F.; Barth, Eugene D.; Tkaczuk, Katherine H.; Martin, Stuart S.; Rosen, Gerald M.; Halpern, Howard J.; Brodie, Angela M.

    2014-01-01

    Electron paramagnetic resonance (EPR) imaging is an emerging modality that can detect and localize paramagnetic molecular probes (so-called spin probes) in vivo. We previously demonstrated that nitroxide spin probes can be encapsulated in liposomes at concentrations exceeding 100 mM, at which nitroxides exhibit a concentration-dependent quenching of their EPR signal that is analogous to the self-quenching of fluorescent molecules. Therefore, intact liposomes encapsulating high concentrations of nitroxides exhibit greatly attenuated EPR spectral signals, and endocytosis of such liposomes represents a cell-activated contrast-generating mechanism. After endocytosis, the encapsulated nitroxide is liberated and becomes greatly diluted in the intracellular milieu. This dequenches the nitroxides to generate a robust intracellular EPR signal. It is therefore possible to deliver a high concentration of nitroxides to cells while minimizing background signal from unendocytosed liposomes. We report here that intracellular EPR signal can be selectively generated in a specific cell type by exploiting its expression of Human Epidermal Growth Factor Receptor 2 (HER2). When targeted by anti-HER2 immunoliposomes encapsulating quenched nitroxides, Hc7 cells, which are novel HER2-overexpressing cells derived from the MCF7 breast tumor cell line, endocytose the liposomes copiously, in contrast to the parent MCF7 cells or control CV1 cells, which do not express HER2. HER2-dependent liposomal delivery enables Hc7 cells to accumulate 750 μM nitroxide intracellularly. Through the use of phantom models, we verify that this concentration of nitroxides is more than sufficient for EPR imaging, thus laying the foundation for using EPR imaging to visualize HER2-overexpressing Hc7 tumors in animals. PMID:20066490

  7. Native and induced triplet nitrogen-vacancy centers in nano- and micro-diamonds: Half-field electron paramagnetic resonance fingerprint

    Energy Technology Data Exchange (ETDEWEB)

    Shames, A. I., E-mail: sham@bgu.ac.il [Department of Physics, Ben-Gurion University of the Negev, Be' er-Sheva 84105 (Israel); Osipov, V. Yu.; Vul’, A. Ya. [Ioffe Physical-Technical Institute, Polytechnicheskaya 26, 194021 St. Petersburg (Russian Federation); Bardeleben, H.-J. von [Institut des Nano Sciences de Paris-INSP, Université Pierre et Marie Curie/UMR 7588 au CNRS, 7500 Paris (France); Boudou, J.-P.; Treussart, F. [Laboratoire Aimé Cotton, CNRS, Université Paris-Sud and ENS Cachan, 91405 Orsay (France)

    2014-02-10

    Multiple frequency electron paramagnetic resonance (EPR) study of small (4–25 nm) nanodiamonds obtained by various dynamic synthesis techniques reveals systematic presence in the half-field (HF) region a distinctive doublet fingerprint consisting of resolved g{sub HF1} = 4.26 and g{sub HF2} = 4.00 signals. This feature is attributed to “forbidden” ΔM{sub S} = 2 transitions in EPR spectra of two native paramagnetic centers of triplet (S = 1) origin designated as TR1 and TR2, characterized by zero field splitting values D{sub 1} = 0.0950 ± 0.002 cm{sup −1} and D{sub 2} = 0.030 ± 0.005 cm{sup −1}. Nanodiamonds of ∼50 nm particle size, obtained by crushing of Ib type nitrogen rich synthetic diamonds, show only HF TR2 signal whereas the same sample undergone high energy (20 MeV) electron irradiation and thermal annealing demonstrates rise of HF TR1 signal. The same HF TR1 signals appear in the process of fabrication of fluorescent nanodiamonds from micron-size synthetic diamond precursors. Results obtained allow unambiguous attribution of the half-field TR1 EPR signals with g{sub HF1} = 4.26, observed in nano- and micron-diamond powders, to triplet negatively charged nitrogen-vacancy centers. These signals are proposed as reliable and convenient fingerprints in both qualitative and quantitative study of fluorescent nano- and micron-diamonds.

  8. Native and induced triplet nitrogen-vacancy centers in nano- and micro-diamonds: Half-field electron paramagnetic resonance fingerprint

    International Nuclear Information System (INIS)

    Shames, A. I.; Osipov, V. Yu.; Vul’, A. Ya.; Bardeleben, H.-J. von; Boudou, J.-P.; Treussart, F.

    2014-01-01

    Multiple frequency electron paramagnetic resonance (EPR) study of small (4–25 nm) nanodiamonds obtained by various dynamic synthesis techniques reveals systematic presence in the half-field (HF) region a distinctive doublet fingerprint consisting of resolved g HF1  = 4.26 and g HF2  = 4.00 signals. This feature is attributed to “forbidden” ΔM S  = 2 transitions in EPR spectra of two native paramagnetic centers of triplet (S = 1) origin designated as TR1 and TR2, characterized by zero field splitting values D 1  = 0.0950 ± 0.002 cm −1 and D 2  = 0.030 ± 0.005 cm −1 . Nanodiamonds of ∼50 nm particle size, obtained by crushing of Ib type nitrogen rich synthetic diamonds, show only HF TR2 signal whereas the same sample undergone high energy (20 MeV) electron irradiation and thermal annealing demonstrates rise of HF TR1 signal. The same HF TR1 signals appear in the process of fabrication of fluorescent nanodiamonds from micron-size synthetic diamond precursors. Results obtained allow unambiguous attribution of the half-field TR1 EPR signals with g HF1  = 4.26, observed in nano- and micron-diamond powders, to triplet negatively charged nitrogen-vacancy centers. These signals are proposed as reliable and convenient fingerprints in both qualitative and quantitative study of fluorescent nano- and micron-diamonds

  9. Evaluation by electronic paramagnetic resonance of the number of free radicals produced in irradiated rat bone; Evaluation par resonance paramagnetique electronique du nombre de radicaux libres produits dans l'os de rat irradie

    Energy Technology Data Exchange (ETDEWEB)

    Marble, G; Valderas, R [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1966-07-01

    The number of long half-life free radicals created by gamma irradiation in the bones of the rat has been determined from the electrons paramagnetic resonance spectrum. This number decreases slowly with time (calculated half life: 24 days). It is proportional to the dose of gamma radiation given to the rat. The method could find interesting applications in the field of biological dosimetry. (authors) [French] Le nombre de radicaux libres a vie longue crees par irradiation gamma dans l'os de rat a ete determine a partir du spectre de resonance paramagnetique electronique. Ce nombre decroit lentement avec le temps (demi-vie calculee {approx_equal} 24 jours). IL est proportionnel a la dose de rayonnement gamma delivree au rat. La methode pourra trouver en dosimetrie biologique des applications interessantes. (auteurs)

  10. Evaluation by electronic paramagnetic resonance of the number of free radicals produced in irradiated rat bone; Evaluation par resonance paramagnetique electronique du nombre de radicaux libres produits dans l'os de rat irradie

    Energy Technology Data Exchange (ETDEWEB)

    Marble, G.; Valderas, R. [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1966-07-01

    The number of long half-life free radicals created by gamma irradiation in the bones of the rat has been determined from the electrons paramagnetic resonance spectrum. This number decreases slowly with time (calculated half life: 24 days). It is proportional to the dose of gamma radiation given to the rat. The method could find interesting applications in the field of biological dosimetry. (authors) [French] Le nombre de radicaux libres a vie longue crees par irradiation gamma dans l'os de rat a ete determine a partir du spectre de resonance paramagnetique electronique. Ce nombre decroit lentement avec le temps (demi-vie calculee {approx_equal} 24 jours). IL est proportionnel a la dose de rayonnement gamma delivree au rat. La methode pourra trouver en dosimetrie biologique des applications interessantes. (auteurs)

  11. 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

  12. Electron-spin-resonance study of radiation-induced paramagnetic defects in oxides grown on (100) silicon substrates

    International Nuclear Information System (INIS)

    Kim, Y.Y.; Lenahan, P.M.

    1988-01-01

    We have used electron-spin resonance to investigate radiation-induced point defects in Si/SiO 2 structures with (100) silicon substrates. We find that the radiation-induced point defects are quite similar to defects generated in Si/SiO 2 structures grown on (111) silicon substrates. In both cases, an oxygen-deficient silicon center, the E' defect, appears to be responsible for trapped positive charge. In both cases trivalent silicon (P/sub b/ centers) defects are primarily responsible for radiation-induced interface states. In earlier electron-spin-resonance studies of unirradiated (100) substrate capacitors two types of P/sub b/ centers were observed; in oxides prepared in three different ways only one of these centers, the P/sub b/ 0 defect, is generated in large numbers by ionizing radiation

  13. Experimental assessment of absorbed dose to mineralized bone tissue from internal emitters: An electron paramagnetic resonance study

    International Nuclear Information System (INIS)

    Desrosiers, M.F.

    1994-01-01

    EPR resonances attributable to radiation-induced centers in hydroxyapatite were not detectable in bone samples supplied by the USTUR. These centers are the basis for imaging and dose assessment. Presumable, the short range of the alpha particles emitted precluded the formation of appreciable amounts of hydroxyapatite centers. However, one bone sample did offer a suggestion of hydroxyapatite centers and newly-developed methods to extract this information will be pursued

  14. 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.

  15. Electron paramagnetic resonance investigations of alpha-Al sub 2 O sub 3 powders doped with Fe sup 3 sup + ions: experiments and simulations

    CERN Document Server

    Buzare, J Y; Klein, J; Scholz, G; Stoesser, R; Nofz, M

    2002-01-01

    Electron paramagnetic resonance (EPR) of Fe sup 3 sup + ions in Al sub 2 O sub 3 is studied in powder samples prepared by different routes and/or modified by thermal or mechanical treatments, with different doping levels and grain sizes. The measurements are performed in various frequency bands (S, X, K, Q and W) and with bimodal detection in X-band. Simulations of the spectra are achieved with a code designed for computing EPR powder spectra described by any spin Hamiltonian including second-, fourth-and sixth-order ZFS terms (S <= 7/2). The linewidths, intensities and lineshapes are accounted for. The lineshape is Gaussian at low Fe sup 3 sup + concentration whereas it is Lorentzian for higher concentration. The linewidths are interpreted as the superimposition of three main contributions: intrinsic linewidth, dipolar broadening and broadening due to lattice imperfections. The latter is tentatively interpreted in terms of quadrupolar spin Hamiltonian parameter distributions treated using first-order pert...

  16. Artifact suppression in electron paramagnetic resonance imaging of 14N- and 15N-labeled nitroxyl radicals with asymmetric absorption spectra

    Science.gov (United States)

    Takahashi, Wataru; Miyake, Yusuke; Hirata, Hiroshi

    2014-10-01

    This article describes an improved method for suppressing image artifacts in the visualization of 14N- and 15N-labeled nitroxyl radicals in a single image scan using electron paramagnetic resonance (EPR). The purpose of this work was to solve the problem of asymmetric EPR absorption spectra in spectral processing. A hybrid function of Gaussian and Lorentzian lineshapes was used to perform spectral line-fitting to successfully separate the two kinds of nitroxyl radicals. This approach can process the asymmetric EPR absorption spectra of the nitroxyl radicals being measured, and can suppress image artifacts due to spectral asymmetry. With this improved visualization method and a 750-MHz continuous-wave EPR imager, a temporal change in the distributions of a two-phase paraffin oil and water/glycerin solution system was visualized using lipophilic and hydrophilic nitroxyl radicals, i.e., 2-(14-carboxytetradecyl)-2-ethyl-4,4-dimethyl-3-oxazolidinyloxy (16-DOXYL stearic acid) and 4-hydroxyl-2,2,6,6-tetramethylpiperidine-d17-1-15N-1-oxyl (TEMPOL-d17-15N). The results of the two-phase separation experiment verified that reasonable artifact suppression could be achieved by the present method that deals with asymmetric absorption spectra in the EPR imaging of 14N- and 15N-labeled nitroxyl radicals.

  17. New opportunities of the application of natural herb and spice extracts in plant oils: application of electron paramagnetic resonance in examining the oxidative stability.

    Science.gov (United States)

    Kozłowska, Mariola; Szterk, Arkadiusz; Zawada, Katarzyna; Ząbkowski, Tomasz

    2012-09-01

    The aim of this study was to establish the applicability of natural water-ethanol extracts of herbs and spices in increasing the oxidative stability of plant oils and in the production of novel food. Different concentrations (0, 100, 300, 500, and 700 ppm) of spice extracts and butylated hydroxyanisole (BHA) (100 ppm) were added to the studied oils. The antioxidant activity of spice extracts was determined with electron paramagnetic resonance (EPR) spectroscopy using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical assay. The study showed that the extracts significantly increased the oxidative stability of the examined oils when compared to one of the strongest synthetic antioxidants--BHA. The applied simple production technology and addition of herb and spice extracts to plant oils enabled enhancement of their oxidative stability. The extracts are an alternative to the oils aromatized with an addition of fresh herbs, spices, and vegetables because it did not generate additional flavors thus enabling the maintenance of the characteristic ones. Moreover, it will increase the intake of natural substances in human diet, which are known to possess anticarcinogenic properties. © 2012 Institute of Food Technologists®

  18. Optical and electron paramagnetic resonance studies of the excited triplet states of UV-B absorbers: 2-ethylhexyl salicylate and homomenthyl salicylate.

    Science.gov (United States)

    Sugiyama, Kazuto; Tsuchiya, Takumi; Kikuchi, Azusa; Yagi, Mikio

    2015-09-26

    The energy levels and lifetimes of the lowest excited triplet (T1) states of UV-B absorbers, 2-ethylhexyl salicylate (EHS) and homomenthyl salicylate (HMS), and their deprotonated anions (EHS(-) and HMS(-)) were determined through measurements of phosphorescence and electron paramagnetic resonance (EPR) spectra in rigid solutions at 77 K. The observed T1 energies of EHS and HMS are higher than those of butylmethoxydibenzoylmethane, the most widely used UV-A absorber, and octyl methoxycinnamate, the most widely used UV-B absorber. The T1 states of EHS, HMS, EHS(-) and HMS(-) were assigned to almost pure (3)ππ* state from the observed T1 lifetimes and zero-field splitting parameters. EHS and HMS with an intramolecular hydrogen bond show a photoinduced phosphorescence enhancement in ethanol at 77 K. The EPR signals of the T1 states of EHS and HMS also increase in intensity with UV-irradiation time (photoinduced EPR enhancement). The T1 lifetimes of EHS and HMS at room temperature were determined through triplet-triplet absorption measurements in ethanol. The quantum yields of singlet oxygen production by EHS and HMS were determined by using time-resolved near-IR phosphorescence.

  19. Application of Numerical Analysis of the Shape of Electron Paramagnetic Resonance Spectra for Determination of the Number of Different Groups of Radicals in the Burn Wounds

    Directory of Open Access Journals (Sweden)

    Paweł Olczyk

    2017-01-01

    Full Text Available Background. The evidence exists that radicals are crucial agents necessary for the wound regeneration helping to enhance the repair process. Materials and methods. The lineshape of the electron paramagnetic resonance (EPR spectra of the burn wounds measured with the low microwave power (2.2 mW was numerically analyzed. The experimental spectra were fitted by the sum of two and three lines. Results. The number of the lines in the EPR spectrum corresponded to the number of different groups of radicals in the natural samples after thermal treatment. The component lines were described by Gaussian and Lorentzian functions. The spectra of the burn wounds were superposition of three lines different in shape and in linewidths. The best fitting was obtained for the sum of broad Gaussian, broad Lorentzian, and narrow Lorentzian lines. Dipolar interactions between the unpaired electrons widened the broad Gaussian and broad Lorentzian lines. Radicals with the narrow Lorentzian lines existed mainly in the tested samples. Conclusions. The spectral shape analysis may be proposed as a useful method for determining the number of different groups of radicals in the burn wounds.

  20. Measurement of differences in pO2 in response to perfluorocarbon/carbogen in FSa and NFSa murine fibrosarcomas with low-frequency electron paramagnetic resonance oximetry.

    Science.gov (United States)

    Halpern, H J; Yu, C; Peric, M; Barth, E D; Karczmar, G S; River, J N; Grdina, D J; Teicher, B A

    1996-05-01

    We have used very low-frequency electron paramagnetic resonance (EPR) oximetry to measure the change in oxygen concentration (delta pO2) due to change in breathing atmosphere in FSa and NFSa fibrosarcomas implanted in the legs of C3H mice infused with perfluoro-octylbromine (PFOB). Measurements in each tumor were made before and after the administration of the high-density (47% v/v) perfluorocarbon PFOB, perflubron (Alliance Pharmaceutical Corporation, San Diego, CA). Measurements in each tumor were also made, after the administration of the PFOB, both before (PFOB/air) and after the administration of carbogen (95% O2 + 5% CO2, PFOB/carbogen). Large changes (delta p02) relative to PFOB/air oxygenation were seen with the administration of PFOB/carbogen. No significant difference in oxygen concentration was seen between air-breathing mice with and without PFOB. The mean delta pO2 for FSa tumors was 13 +/- 6 torr, while the mean for NFSa fibrosarcomas was 28 +/- 7 torr. There were such large intertumor differences that the trend toward a smaller change in the more hypoxic FSa tumors was not significant (P = 0.13). This paper describes a novel method of measuring differences in oxygenation in tumor tissues. The results of such measurements indicate large differences in pO2 response to different breathing atmospheres in PFOB-infused tumors of similar histology. The intertumor delta pO2 differences may correlate with differences in radiation response.

  1. Investigation of 3C-SiC/SiO2 interfacial point defects from ab initio g-tensor calculations and electron paramagnetic resonance measurements

    Science.gov (United States)

    Nugraha, T. A.; Rohrmueller, M.; Gerstmann, U.; Greulich-Weber, S.; Stellhorn, A.; Cantin, J. L.; von Bardeleben, J.; Schmidt, W. G.; Wippermann, S.

    SiC is widely used in high-power, high-frequency electronic devices. Recently, it has also been employed as a building block in nanocomposites used as light absorbers in solar energy conversion devices. Analogous to Si, SiC features SiO2 as native oxide that can be used for passivation and insulating layers. However, a significant number of defect states are reported to form at SiC/SiO2 interfaces, limiting mobility and increasing recombination of free charge carriers. We investigated the growth of oxide on different 3C-SiC surfaces from first principles. Carbon antisite Csi defects are found to be strongly stabilized in particular at the interface, because carbon changes its hybridization from sp3 in the SiC-bulk to sp2 at the interface, creating a dangling bond inside a porous region of the SiO2 passivating layer. Combining ab initio g-tensor calculations and electron paramagnetic resonance (EPR) measurements, we show that Csi defects explain the measured EPR signatures, while the hyperfine structure allows to obtain local structural information of the oxide layer. Financial support from BMBF NanoMatFutur Grant 13N12972 and DFG priority program SPP-1601 is gratefully acknowledged.

  2. Microstructure evaluation of dermally applicable liquid crystals as a function of water content and temperature: Can electron paramagnetic resonance provide complementary data?

    Science.gov (United States)

    Matjaž, Mirjam Gosenca; Mravljak, Janez; Rogač, Marija Bešter; Šentjurc, Marjeta; Gašperlin, Mirjana; Pobirk, Alenka Zvonar

    2017-11-30

    Insight into the microstructure of lyotropic liquid crystals (LCs) is of crucial importance for development of novel dermal delivery systems. Our aim was to evaluate the phase behaviour of dermally applicable LCs composed of isopropyl myristate/Tween 80/lecithin/water, along the dilution line, where phase transitions are predominantly driven by increased water content. Additionally, identification of LC temperature dependence is of great importance for skin application. Selected LCs were evaluated using electron paramagnetic resonance (EPR) plus conventionally used methods of polarization microscopy, small-angle X-ray scattering, differential scanning calorimetry, and rheological measurements. Depending on water content, LCs formed diverse microstructures, from (pseudo)hexagonal (LC1) and lamellar (LC2-LC7) liquid crystalline phases that possibly co-exist with rod-like micelles (LC4-LC7), to a transitional micellar phase (LC8). Furthermore, the LCs microstructure remained unaltered within the tested temperature range. EPR was shown to detect microstructural transitions of LCs and to provide complementary data to other techniques. These data thus confirm the applicability of EPR as a complementary technique for better understanding of LC microstructural transitions that are expected to contribute greatly to studies oriented towards the drug release characteristics from such systems. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Electron paramagnetic resonance studies of a new luminescent material based on CaB{sub 6}O{sub 10}:Pb

    Energy Technology Data Exchange (ETDEWEB)

    Franca, L. V. S.; Oliveira, L. C.; Baffa, O., E-mail: leofranca@usp.br [Universidade de Sao Paulo, FFCLRP, Departamento de Fisica, Av. Bandeirantes 3900, CEP 14040-901, Bairro Monte Alegre, Ribeirao Preto, Sao Paulo (Brazil)

    2017-10-15

    A new photostimulable phosphor based on Pb-doped CaB{sub 6}O{sub 10} was recently synthesized and its luminescence properties studied. This material is very promising exhibiting high sensitivity to ionizing radiation, comparable or surpassing commercially available luminescence materials such LiF:Mg,Ti and Al{sub 2}O{sub 3}:C with a dominant thermoluminescence (Tl) peak at ∼180 degrees Celsius and an optically stimulated luminescence (OSL) signal that can be ∼99% read within ∼ 20s under current experimental conditions. The radioluminescence, Tl and OSL signals are dominated by an emission band at ∼320 nm, probably associated with {sup 3}P{sub 1} → {sup 1}S{sub 0} transition of Pb{sup 2+}. However, the involvement of the Pb dopant in the trapping process is not completely clear and Electron Paramagnetic Resonance (EPR) spectroscopy is being used to study the valence states of the Pb ion before and after irradiation. EPR measurements were carried out using a Jeol FX200 X-band spectrometer at liquid nitrogen temperature. The material was irradiated with a dose of 500 Gy using a 160 kV X-ray tube. The EPR spectrum shows the appearance of a symmetrical central line at g ∼ 2.0 and a line at high field at g ∼ 1.2 with orthorhombic symmetry. This study is under way with more experiments to correlate these findings with the luminescence properties. (Author)

  4. Brain redox imaging in the pentylenetetrazole (PTZ)-induced kindling model of epilepsy by using in vivo electron paramagnetic resonance and a nitroxide imaging probe.

    Science.gov (United States)

    Emoto, Miho C; Yamato, Mayumi; Sato-Akaba, Hideo; Yamada, Ken-ichi; Fujii, Hirotada G

    2015-11-03

    Much evidence supports the idea that oxidative stress is involved in the pathogenesis of epilepsy, and therapeutic interventions with antioxidants are expected as adjunct antiepileptic therapy. The aims of this study were to non-invasively obtain spatially resolved redox data from control and pentylenetetrazole (PTZ)-induced kindled mouse brains by electron paramagnetic resonance (EPR) imaging and to visualize the brain regions that are sensitive to oxidative damage. After infusion of the redox-sensitive imaging probe 3-methoxycarbonyl-2,2,5,5-tetramethyl-piperidine-1-oxyl (MCP), a series of EPR images of PTZ-induced mouse heads were measured. Based on the pharmacokinetics of the reduction reaction of MCP in the mouse heads, the pixel-based rate constant of its reduction reaction was calculated as an index of redox status in vivo and mapped as a redox map. The obtained redox map showed heterogeneity in the redox status in PTZ-induced mouse brains compared with control. The co-registered image of the redox map and magnetic resonance imaging (MRI) for both control and PTZ-induced mice showed a clear change in the redox status around the hippocampus after PTZ. To examine the role of antioxidants on the brain redox status, the levels of antioxidants were measured in brain tissues of control and PTZ-induced mice. Significantly lower concentrations of glutathione in the hippocampus of PTZ-kindled mice were detected compared with control. From the results of both EPR imaging and the biochemical assay, the hippocampus was found to be susceptible to oxidative damage in the PTZ-induced animal model of epilepsy. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  5. Jahn-Teller glass formation in beta-lithium ammonium sulfate monocrystals studied by means of the electron paramagnetic resonance of Mn sup 2 sup + and Cu sup 2 sup + ions

    CERN Document Server

    Waplak, S

    2002-01-01

    The EPR (electron paramagnetic resonance) spectra of non-Jahn-Teller (JT) Mn sup 2 sup + and JT Cu sup 2 sup + ions have been studied for alpha- or beta-LAS structure modification in the temperature range of 4.2-480 K. The experimental evidence for JT glass with frozen-in random strain fields due to the presence of the JT Cu sup 2 sup + ions is presented.

  6. Strong quadrupole interaction in electron paramagnetic resonance. Study of the indium hexacyanide (III) in KCl irradiated with electrons

    International Nuclear Information System (INIS)

    Vugman, N.V.

    1973-08-01

    The radiation effects in ]Ir III (CN) 6 ] 3- diamagnetic complexe inserted in the KCl lattice and irradiated with electrons of 2MeV by electron spin resonance (ESR) are analysed. Formulas for g and A tensors in the ligand field approximation, are derivated to calculate non coupling electron density in the metal. The X polarization field of inner shells is positive, indicating a 6s function mixture in the non coupling electron molecular orbital. The observed hyperfine structure is assigned to 4 equivalent nitrogen and one non equivalent nitrogen. This hypothesis is verified by experience of isotope substitution with 15 N. The s and p spin density in ligands are calculated and discussed in terms of molecular obitals. The effects of strong quadrupole interaction into the EPR spectra of ]Ir II (CN) 5 ] 3- complex are analysed by MAGNSPEC computer program to diagonalize the Spin Hamiltonian of the system. Empiric rules for EPR espectrum interpretation with strong quadrupole interaction. A review of EPR technique and a review of main concepts of crystal-field and ligand field theories, are also presented. (M.C.K.) [pt

  7. The resonance integral of thorium metal rods

    Energy Technology Data Exchange (ETDEWEB)

    Hellstrand, E; Weitman, J

    1960-03-15

    The resonance integral for thorium metal rods of different diameters has been determined by the activation method. The irradiations took place in the central channel of the reactor R1, where the energy dependence of the neutron flux had earlier been investigated with a fast chopper up to about 1 keV. The absolute calibration was made with gold as a standard. The true resonance integral for gold was taken from the literature as 1,500 {+-} 35 b. The experimental values for thorium were fitted to two alternative expressions with the following results: RI = (1.70 + 15.9{radical}(S/M)) {+-} 5.5%; RI 17.3{radical}(S/M + 0.06) {+-} 5.5 %. The measurements were made for S/M values in the range 0.14 - 0.87 cm{sup 2}/g. The main contribution to the margin of errors arises from the uncertainties in the cross sections used and in the correction for the departure of the neutron energy distribution from the 1/E form.

  8. Proportional-Integral-Resonant AC Current Controller

    Directory of Open Access Journals (Sweden)

    STOJIC, D.

    2017-02-01

    Full Text Available In this paper an improved stationary-frame AC current controller based on the proportional-integral-resonant control action (PIR is proposed. Namely, the novel two-parameter PIR controller is applied in the stationary-frame AC current control, accompanied by the corresponding parameter-tuning procedure. In this way, the proportional-resonant (PR controller, common in the stationary-frame AC current control, is extended by the integral (I action in order to enable the AC current DC component tracking, and, also, to enable the DC disturbance compensation, caused by the voltage source inverter (VSI nonidealities and by nonlinear loads. The proposed controller parameter-tuning procedure is based on the three-phase back-EMF-type load, which corresponds to a wide range of AC power converter applications, such as AC motor drives, uninterruptible power supplies, and active filters. While the PIR controllers commonly have three parameters, the novel controller has two. Also, the provided parameter-tuning procedure needs only one parameter to be tuned in relation to the load and power converter model parameters, since the second controller parameter is directly derived from the required controller bandwidth value. The dynamic performance of the proposed controller is verified by means of simulation and experimental runs.

  9. Design principles and theory of paramagnetic fluorine-labelled lanthanide complexes as probes for (19)F magnetic resonance: a proof-of-concept study.

    Science.gov (United States)

    Chalmers, Kirsten H; De Luca, Elena; Hogg, Naomi H M; Kenwright, Alan M; Kuprov, Ilya; Parker, David; Botta, Mauro; Wilson, J Ian; Blamire, Andrew M

    2010-01-04

    The synthesis and spectroscopic properties of a series of CF(3)-labelled lanthanide(III) complexes (Ln=Gd, Tb, Dy, Ho, Er, Tm) with amide-substituted ligands based on 1,4,7,10-tetraazacyclododecane are described. The theoretical contributions of the (19)F magnetic relaxation processes in these systems are critically assessed and selected volumetric plots are presented. These plots allow an accurate estimation of the increase in the rates of longitudinal and transverse relaxation as a function of the distance between the Ln(III) ion and the fluorine nucleus, the applied magnetic field, and the re-rotational correlation time of the complex, for a given Ln(III) ion. Selected complexes exhibit pH-dependent chemical shift behaviour, and a pK(a) of 7.0 was determined in one example based on the holmium complex of an ortho-cyano DO3A-monoamide ligand, which allowed the pH to be assessed by measuring the difference in chemical shift (varying by over 14 ppm) between two (19)F resonances. Relaxation analyses of variable-temperature and variable-field (19)F, (17)O and (1)H NMR spectroscopy experiments are reported, aided by identification of salient low-energy conformers by using density functional theory. The study of fluorine relaxation rates, over a field range of 4.7 to 16.5 T allowed precise computation of the distance between the Ln(III) ion and the CF(3) reporter group by using global fitting methods. The sensitivity benefits of using such paramagnetic fluorinated probes in (19)F NMR spectroscopic studies are quantified in preliminary spectroscopic and imaging experiments with respect to a diamagnetic yttrium(III) analogue.

  10. R(+-Thioctic Acid Effects on Oxidative Stress and Peripheral Neuropathy in Type II Diabetic Patients: Preliminary Results by Electron Paramagnetic Resonance and Electroneurography

    Directory of Open Access Journals (Sweden)

    Simona Mrakic-Sposta

    2018-01-01

    Full Text Available Objectives. Diabetic neuropathy is the most common complication of diabetes. The idea of alterations in energy metabolism in diabetes is emerging. The biogenic antioxidant R(+-thioctic acid has been successfully used in the treatment of diabetic polyneuropathic (DPN patients. Methods. The effects of R(+-thioctic acid (1 tablet, 1.6 g administration were evaluated in 12 DPN patients at baseline and at 15, 30, 60, and 120 administration days throughout the assessment of oxidative stress (OxS; ROS production rate by electron paramagnetic resonance (EPR technique; and oxidative damage biomarkers (thiobarbituric acid reactive substances (TBARS and protein carbonyls (PC, electroneurography (ENG and visual analogue scale. Results. Supplementation induced significant changes (p<0.05 at 30 and 60 days. ROS production rate up to −16%; TBARS (−31%, PC (−38%, and TAC up to +48%. Motor nerve conduction velocity in SPE and ulnar nerves (+22% and +16% and sensor conduction velocity in sural and median nerves (+22% and +5%. Patients reported a general wellness sensation improvement (+35% at 30 days: lower limb pain sensation (−40% and upper limbs (−23%. Conclusion. The results strongly indicate that an increased antioxidant capacity plays an important role in OxS, nerve conduction velocity, pain, and general wellness improvement. Nevertheless, the effects of the antioxidant compound were found positive up to 60 days. Then, a hormesis effect was observed. Novelty of the research would be a challenge for investigators to carefully address issues, including dose range factors, appropriate administration time, and targeting population to counteract possible “boomerang effects.” The great number of monitored parameters would firmly stress these conclusions.

  11. Experimental determination of the radial dose distribution in high gradient regions around 192Ir wires: Comparison of electron paramagnetic resonance imaging, films, and Monte Carlo simulations

    International Nuclear Information System (INIS)

    Kolbun, N.; Leveque, Ph.; Abboud, F.; Bol, A.; Vynckier, S.; Gallez, B.

    2010-01-01

    Purpose: The experimental determination of doses at proximal distances from radioactive sources is difficult because of the steepness of the dose gradient. The goal of this study was to determine the relative radial dose distribution for a low dose rate 192 Ir wire source using electron paramagnetic resonance imaging (EPRI) and to compare the results to those obtained using Gafchromic EBT film dosimetry and Monte Carlo (MC) simulations. Methods: Lithium formate and ammonium formate were chosen as the EPR dosimetric materials and were used to form cylindrical phantoms. The dose distribution of the stable radiation-induced free radicals in the lithium formate and ammonium formate phantoms was assessed by EPRI. EBT films were also inserted inside in ammonium formate phantoms for comparison. MC simulation was performed using the MCNP4C2 software code. Results: The radical signal in irradiated ammonium formate is contained in a single narrow EPR line, with an EPR peak-to-peak linewidth narrower than that of lithium formate (∼0.64 and 1.4 mT, respectively). The spatial resolution of EPR images was enhanced by a factor of 2.3 using ammonium formate compared to lithium formate because its linewidth is about 0.75 mT narrower than that of lithium formate. The EPRI results were consistent to within 1% with those of Gafchromic EBT films and MC simulations at distances from 1.0 to 2.9 mm. The radial dose values obtained by EPRI were about 4% lower at distances from 2.9 to 4.0 mm than those determined by MC simulation and EBT film dosimetry. Conclusions: Ammonium formate is a suitable material under certain conditions for use in brachytherapy dosimetry using EPRI. In this study, the authors demonstrated that the EPRI technique allows the estimation of the relative radial dose distribution at short distances for a 192 Ir wire source.

  12. Electron paramagnetic resonance spin label titration: a novel method to investigate random and site-specific immobilization of enzymes onto polymeric membranes with different properties

    International Nuclear Information System (INIS)

    Butterfield, D. Allan; Colvin, Joshua; Liu Jiangling; Wang Jianquan; Bachas, Leonidas; Bhattacharrya, Dibakar

    2002-01-01

    The immobilization of biological molecules onto polymeric membranes to produce biofunctional membranes is used for selective catalysis, separation, analysis, and artificial organs. Normally, random immobilization of enzymes onto polymeric membranes leads to dramatic reduction in activity due to chemical reactions involved in enzyme immobilization, multiple-point binding, etc., and the extent of activity reduction is a function of membrane hydrophilicity (e.g. activity in cellulosic membrane >> polysulfone membrane). We have used molecular biology to effect site-specific immobilization of enzymes in a manner that orients the active site away from the polymeric membrane surface, thus resulting in higher enzyme activity that approaches that in solution and in increased stability of the enzyme relative to the enzyme in solution. A prediction of this site-specific method of enzyme immobilization, which in this study with subtilisin and organophosphorus hydrolase consists of a fusion tag genetically added to these enzymes and subsequent immobilization via the anti-tag antibody and membrane-bound protein A, is that the active site conformation will more closely resemble that of the enzyme in solution than is the case for random immobilization. This hypothesis was confirmed using a new electron paramagnetic resonance (EPR) spin label active site titration method that determines the amount of spin label bound to the active site of the immobilized enzyme. This value nearly perfectly matched the enzyme activity, and the results suggested: (a) a spectroscopic method for measuring activity and thus the extent of active enzyme immobilization in membrane, which may have advantages in cases where optical methods can not be used due to light scattering interference; (b) higher spin label incorporation (and hence activity) in enzymes that had been site-specifically immobilized versus random immobilization; (c) higher spin label incorporation in enzymes immobilized onto hydrophilic

  13. Development of double-pulse lasers ablation system and electron paramagnetic resonance spectroscopy for direct spectral analysis of manganese doped PVA polymer

    Science.gov (United States)

    Khalil, A. A. I.; Morsy, M. A.; El-Deen, H. Z.

    2017-11-01

    Series of manganese-co-precipitated poly (vinyl alcohol) (PVA) polymer were quantitatively and qualitatively analyzed using laser ablation system (LAS) based on double-pulse laser induced breakdown spectroscopy (DP-LIBS) and electron paramagnetic resonance (EPR) spectroscopy. The collinear nanosecond laser beams of 266 and 1064 nm were optimized to focus on the surface of the PVA polymer target. Both laser beams were employed to estimate the natural properties of the excited Mn-PVA plasma, such as electron number density (Ne), electron temperature (Te), and Mn concentration. Individual transition lines of manganese (Mn), carbon (C), lithium (Li), hydrogen (H) and oxygen (O) atoms are identified based on the NIST spectral database. The results show better responses with DP-LIBS than the single-pulse laser induced breakdown spectroscopy (SP-LIBS). On the other hand, the EPR investigation shows characteristic broad peak of Mn-nano-particles (Mn-NPs) in the range of quantum dots of superparamagnetic materials. The line width (peak-to-peak, ΔHpp) and g-value of the observed Mn-EPR peak are ∼20 mT and 2.0046, respectively. The intensities of Mn-emission line at a wavelength 403.07 nm and the Mn-EPR absorption peak were used to accurate quantify the Mn-content in the polymer matrix. The results produce linear trends within the studied concentration range with regression coefficient (R2) value of ∼0.99, and limit of detection (LOD) of 0.026 mol.% and 0.016 mol.%, respectively. The LOD values are at a fold change of about -0.2 of the studied lowest mol.%. The proposed protocols of trace element detection are of significant advantage and can be applied to the other metal analysis.

  14. Copper doping of ZnO crystals by transmutation of {sup 64}Zn to {sup 65}Cu: An electron paramagnetic resonance and gamma spectroscopy study

    Energy Technology Data Exchange (ETDEWEB)

    Recker, M. C.; McClory, J. W., E-mail: John.McClory@afit.edu; Holston, M. S.; Golden, E. M.; Giles, N. C. [Department of Engineering Physics, Air Force Institute of Technology, Wright-Patterson Air Force Base, Ohio 45433 (United States); Halliburton, L. E. [Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506 (United States)

    2014-06-28

    Transmutation of {sup 64}Zn to {sup 65}Cu has been observed in a ZnO crystal irradiated with neutrons. The crystal was characterized with electron paramagnetic resonance (EPR) before and after the irradiation and with gamma spectroscopy after the irradiation. Major features in the gamma spectrum of the neutron-irradiated crystal included the primary 1115.5 keV gamma ray from the {sup 65}Zn decay and the positron annihilation peak at 511 keV. Their presence confirmed the successful transmutation of {sup 64}Zn nuclei to {sup 65}Cu. Additional direct evidence for transmutation was obtained from the EPR of Cu{sup 2+} ions (where {sup 63}Cu and {sup 65}Cu hyperfine lines are easily resolved). A spectrum from isolated Cu{sup 2+} (3d{sup 9}) ions acquired after the neutron irradiation showed only hyperfine lines from {sup 65}Cu nuclei. The absence of {sup 63}Cu lines in this Cu{sup 2+} spectrum left no doubt that the observed {sup 65}Cu signals were due to transmuted {sup 65}Cu nuclei created as a result of the neutron irradiation. Small concentrations of copper, in the form of Cu{sup +}-H complexes, were inadvertently present in our as-grown ZnO crystal. These Cu{sup +}-H complexes are not affected by the neutron irradiation, but they dissociate when a crystal is heated to 900 °C. This behavior allowed EPR to distinguish between the copper initially in the crystal and the copper subsequently produced by the neutron irradiation. In addition to transmutation, a second major effect of the neutron irradiation was the formation of zinc and oxygen vacancies by displacement. These vacancies were observed with EPR.

  15. Copper doping of ZnO crystals by transmutation of 64Zn to 65Cu: An electron paramagnetic resonance and gamma spectroscopy study

    International Nuclear Information System (INIS)

    Recker, M. C.; McClory, J. W.; Holston, M. S.; Golden, E. M.; Giles, N. C.; Halliburton, L. E.

    2014-01-01

    Transmutation of 64 Zn to 65 Cu has been observed in a ZnO crystal irradiated with neutrons. The crystal was characterized with electron paramagnetic resonance (EPR) before and after the irradiation and with gamma spectroscopy after the irradiation. Major features in the gamma spectrum of the neutron-irradiated crystal included the primary 1115.5 keV gamma ray from the 65 Zn decay and the positron annihilation peak at 511 keV. Their presence confirmed the successful transmutation of 64 Zn nuclei to 65 Cu. Additional direct evidence for transmutation was obtained from the EPR of Cu 2+ ions (where 63 Cu and 65 Cu hyperfine lines are easily resolved). A spectrum from isolated Cu 2+ (3d 9 ) ions acquired after the neutron irradiation showed only hyperfine lines from 65 Cu nuclei. The absence of 63 Cu lines in this Cu 2+ spectrum left no doubt that the observed 65 Cu signals were due to transmuted 65 Cu nuclei created as a result of the neutron irradiation. Small concentrations of copper, in the form of Cu + -H complexes, were inadvertently present in our as-grown ZnO crystal. These Cu + -H complexes are not affected by the neutron irradiation, but they dissociate when a crystal is heated to 900 °C. This behavior allowed EPR to distinguish between the copper initially in the crystal and the copper subsequently produced by the neutron irradiation. In addition to transmutation, a second major effect of the neutron irradiation was the formation of zinc and oxygen vacancies by displacement. These vacancies were observed with EPR.

  16. Copper doping of ZnO crystals by transmutation of 64Zn to 65Cu: An electron paramagnetic resonance and gamma spectroscopy study

    Science.gov (United States)

    Recker, M. C.; McClory, J. W.; Holston, M. S.; Golden, E. M.; Giles, N. C.; Halliburton, L. E.

    2014-06-01

    Transmutation of 64Zn to 65Cu has been observed in a ZnO crystal irradiated with neutrons. The crystal was characterized with electron paramagnetic resonance (EPR) before and after the irradiation and with gamma spectroscopy after the irradiation. Major features in the gamma spectrum of the neutron-irradiated crystal included the primary 1115.5 keV gamma ray from the 65Zn decay and the positron annihilation peak at 511 keV. Their presence confirmed the successful transmutation of 64Zn nuclei to 65Cu. Additional direct evidence for transmutation was obtained from the EPR of Cu2+ ions (where 63Cu and 65Cu hyperfine lines are easily resolved). A spectrum from isolated Cu2+ (3d9) ions acquired after the neutron irradiation showed only hyperfine lines from 65Cu nuclei. The absence of 63Cu lines in this Cu2+ spectrum left no doubt that the observed 65Cu signals were due to transmuted 65Cu nuclei created as a result of the neutron irradiation. Small concentrations of copper, in the form of Cu+-H complexes, were inadvertently present in our as-grown ZnO crystal. These Cu+-H complexes are not affected by the neutron irradiation, but they dissociate when a crystal is heated to 900 °C. This behavior allowed EPR to distinguish between the copper initially in the crystal and the copper subsequently produced by the neutron irradiation. In addition to transmutation, a second major effect of the neutron irradiation was the formation of zinc and oxygen vacancies by displacement. These vacancies were observed with EPR.

  17. Electron paramagnetic resonance and optical properties of Cr{sup 3+} doped YAl{sub 3}(BO{sub 3}){sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Wells, Jon-Paul R [Department of Physics and Astronomy, University of Sheffield, Sheffield (United Kingdom); Yamaga, Mitsuo [Department of Mathematical and Design Engineering, Gifu University, Gifu (Japan); Han, Thomas P J [Department of Physics, University of Strathclyde, Glasgow (United Kingdom); Honda, Makoto [Faculty of Science, Naruto University of Education, Naruto (Japan)

    2003-01-29

    We report on the electron paramagnetic resonance (EPR) and optical absorption and fluorescence spectroscopy of YAl{sub 3}(BO{sub 3}){sub 4} single crystals doped with 0.2 mol% of trivalent chromium. From EPR we determine that the Cr{sup 3+} ions reside in sites of essentially octahedral symmetry with an orthorhombic distortion. The ground state {sup 4}A{sub 2} splitting is determined to be 2{radical}D{sup 2} + 3E{sup 2} {approx} 1.05 {+-} 0.04 cm{sup -1}, where D and E are fine-structure parameters, and we can attribute this splitting to the combined effect of a low-symmetry distortion and spin-orbit coupling. The g-values and fine-structure parameters D and E of the ground state {sup 4}A{sub 2} are measured to be g{sub x} {approx} g{sub y} {approx} g{sub z} = 1.978 {+-} 0.005, vertical bar D vertical bar = 0.52 {+-} 0.02 cm{sup -1} and vertical bar E vertical bar 0.010 {+-} 0.005 cm{sup -1} respectively. From 10 K optical absorption we have measured the position and crystal-field splittings of the {sup 2}E, {sup 2}T{sub 1}, {sup 4}T{sub 2}, {sup 2}T{sub 2} and {sup 4}T{sub 1} states with the {sup 4}T{sub 2} and {sup 4}T{sub 1} levels appearing as vibronically broadened bands.

  18. An electron paramagnetic resonance study on Sm{sup 3+} and Yb{sup 3+} in KY{sub 3}F{sub 10} crystals

    Energy Technology Data Exchange (ETDEWEB)

    Yamaga, M. [Department of Electrical and Electronic Engineering, Faculty of Engineering, Gifu University, Gifu (Japan); Honda, M. [Faculty of Science, Naruto University of Education, Naruto, Tokushima (Japan); Wells, J.P.R. [FELIX Free Electron Laser Facility, FOM-Institute for Plasma Physics, Rijnhuizen, Nieuwegein (Netherlands); Han, T.P.J.; Gallagher, H.G. [Department of Physics and Applied Physics, University of Strathclyde, Glasgow (United Kingdom)

    2000-10-09

    Electron paramagnetic resonance (EPR) spectra of Sm{sup 3+} and Yb{sup 3+} ions in KY{sub 3}F{sub 10} single crystals have been measured at X-band microwave frequencies and low temperatures. The EPR lines have been fitted to a tetragonal spin Hamiltonian to determine effective g-values (g{sub parallel},g{sub perpendicular}). The observed g-values, (g{sub parallel} = 0.714(2),g{sub perpendicular} = 0.11(1)), for Sm{sup 3+} are in agreement with those calculated via crystal-field J-mixing of the first excited-state multiplet {sup 6}H{sub 7/2} into the groundstate multiplet {sup 6}H{sub 5/2} of Sm{sup 3+} as the second-order perturbation. On the other hand, the observed g-values, (g{sub parallel}=5.363(5), g{sub perpendicular}=1.306(2)) for Yb{sup 3+} are coincident with those calculated via mixing in only the groundstate multiplet {sup 2}F{sub 7/2} as the first-order perturbation because the first excited-state multiplet {sup 2}F{sub 5/2} lies above {approx}10,000 cm{sup -1} from the groundstate. The groundstate eigenfunctions of Sm{sup 3+} and Yb{sup 3+} obtained from the EPR results are close to those calculated from a C{sub 4v} symmetry crystal-field analysis applied to their optical transitions. The distortions of the Sm{sup 3+} and Yb{sup 3+} complexes in KY{sub 3}F{sub 10} are discussed in the term of the crystal-field Hamiltonian in comparison with LiYF{sub 4}. (author)

  19. Enzyme kinetics, inhibitors, mutagenesis and electron paramagnetic resonance analysis of dual-affinity nitrate reductase in unicellular N(2)-fixing cyanobacterium Cyanothece sp. PCC 8801.

    Science.gov (United States)

    Wang, Tung-Hei; Chen, Yung-Han; Huang, Jine-Yung; Liu, Kang-Cheng; Ke, Shyue-Chu; Chu, Hsiu-An

    2011-11-01

    The assimilatory nitrate reductase (NarB) of N(2)-fixing cyanobacterium Cyanothece sp. PCC 8801 is a monomeric enzyme with dual affinity for substrate nitrate. We purified the recombinant NarB of Cyanothece sp. PCC 8801 and further investigated it by enzyme kinetics analysis, site-directed mutagenesis, inhibitor kinetics analysis, and electron paramagnetic resonance (EPR) spectroscopy. The NarB showed 2 kinetic regimes at pH 10.5 or 8 and electron-donor conditions methyl viologen or ferredoxin (Fd). Fd-dependent NR assay revealed NarB with very high affinity for nitrate (K(m)1, ∼1μM; K(m)2, ∼270μM). Metal analysis and EPR results showed that NarB contains a Mo cofactor and a [4Fe-4S] cluster. In addition, the R352A mutation on the proposed nitrate-binding site of NarB greatly altered both high- and low-affinity kinetic components. Furthermore, the effect of azide on the NarB of Cyanothece sp. PCC 8801 was more complex than that on the NarB of Synechococcus sp. PCC 7942 with its single kinetic regime. With 1mM azide, the kinetics of the wild-type NarB was transformed from 2 kinetic regimes to hyperbolic kinetics, and its activity was enhanced significantly under medium nitrate concentrations. Moreover, EPR results also suggested a structural difference between the two NarBs. Taken together, our results show that the NarB of Cyanothece sp. PCC 8801 contains only a single Mo-catalytic center, and we rule out that the enzyme has 2 independent, distinct catalytic sites. In addition, the NarB of Cyanothece sp. PCC 8801 may have a regulatory nitrate-binding site. Copyright © 2011 Elsevier Masson SAS. All rights reserved.

  20. Hydrogen interstitial in H-ion implanted ZnO bulk single crystals: Evaluation by elastic recoil detection analysis and electron paramagnetic resonance

    Energy Technology Data Exchange (ETDEWEB)

    Kaida, T.; Kamioka, K.; Nishimura, T. [College of Engineering and Research Center of Ion Beam Technology, Hosei University, Koganei, Tokyo 184-8584 (Japan); Kuriyama, K., E-mail: kuri@ionbeam.hosei.ac.jp [College of Engineering and Research Center of Ion Beam Technology, Hosei University, Koganei, Tokyo 184-8584 (Japan); Kushida, K. [Department of Arts and Sciences, Osaka Kyoiku University, Kashiwara, Osaka 582-8582 (Japan); Kinomura, A. [National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568 (Japan)

    2015-12-15

    The origins of low resistivity in H ion-implanted ZnO bulk single crystals are evaluated by elastic recoil detection analysis (ERDA), electron paramagnetic resonance (EPR), and Van der Pauw methods. The H-ion implantation (peak concentration: 5.0 × 10{sup 15} cm{sup −2}) into ZnO is performed using a 500 keV implanter. The maximum of the concentration of the implanted H estimated by a TRIM simulation is at 3600 nm in depth. The resistivity decreases from ∼10{sup 3} Ω cm for un implanted ZnO to 6.5 Ω cm for as-implanted, 2.3 × 10{sup −1} Ω cm for 200 °C annealed, and 3.2 × 10{sup −1} Ω cm for 400 °C annealed samples. The ERDA measurements can evaluate the concentration of hydrogens which move to the vicinity of the surface (surface to 300 nm or 100 nm) because of the diffusion by the annealing at 200 °C and 400 °C. The hydrogen concentration near the surface estimated using the 2.0 MeV helium beam is ∼3.8 × 10{sup 13} cm{sup −2} for annealed samples. From EPR measurements, the oxygen vacancy of +charge state (V{sub o}{sup +}) is observed in as-implanted samples. The V{sub o}{sup +} related signal (g = 1.96) observed under no illumination disappears after successive illumination with a red LED and appears again with a blue light illumination. The activation energy of as-implanted, 200 °C annealed, and 400 °C annealed samples estimated from the temperature dependence of carrier concentration lies between 29 meV and 23 meV, suggesting the existence of H interstitial as a shallow donor level.

  1. Higher-order Zeeman and spin terms in the electron paramagnetic resonance spin Hamiltonian; their description in irreducible form using Cartesian, tesseral spherical tensor and Stevens' operator expressions

    International Nuclear Information System (INIS)

    McGavin, Dennis G; Tennant, W Craighead

    2009-01-01

    In setting up a spin Hamiltonian (SH) to study high-spin Zeeman and high-spin nuclear and/or electronic interactions in electron paramagnetic resonance (EPR) experiments, it is argued that a maximally reduced SH (MRSH) framed in tesseral combinations of spherical tensor operators is necessary. Then, the SH contains only those terms that are necessary and sufficient to describe the particular spin system. The paper proceeds then to obtain interrelationships between the parameters of the MRSH and those of alternative SHs expressed in Cartesian tensor and Stevens operator-equivalent forms. The examples taken, initially, are those of Cartesian and Stevens' expressions for high-spin Zeeman terms of dimension BS 3 and BS 5 . Starting from the well-known decomposition of the general Cartesian tensor of second rank to three irreducible tensors of ranks 0, 1 and 2, the decomposition of Cartesian tensors of ranks 4 and 6 are treated similarly. Next, following a generalization of the tesseral spherical tensor equations, the interrelationships amongst the parameters of the three kinds of expressions, as derived from equivalent SHs, are determined and detailed tables, including all redundancy equations, set out. In each of these cases the lowest symmetry, 1-bar Laue class, is assumed and then examples of relationships for specific higher symmetries derived therefrom. The validity of a spin Hamiltonian containing mixtures of terms from the three expressions is considered in some detail for several specific symmetries, including again the lowest symmetry. Finally, we address the application of some of the relationships derived here to seldom-observed low-symmetry effects in EPR spectra, when high-spin electronic and nuclear interactions are present.

  2. Membrane Disruption Mechanism of a Prion Peptide (106-126) Investigated by Atomic Force Microscopy, Raman and Electron Paramagnetic Resonance Spectroscopy.

    Science.gov (United States)

    Pan, Jianjun; Sahoo, Prasana K; Dalzini, Annalisa; Hayati, Zahra; Aryal, Chinta M; Teng, Peng; Cai, Jianfeng; Rodriguez Gutierrez, Humberto; Song, Likai

    2017-05-18

    A fragment of the human prion protein spanning residues 106-126 (PrP106-126) recapitulates many essential properties of the disease-causing protein such as amyloidogenicity and cytotoxicity. PrP106-126 has an amphipathic characteristic that resembles many antimicrobial peptides (AMPs). Therefore, the toxic effect of PrP106-126 could arise from a direct association of monomeric peptides with the membrane matrix. Several experimental approaches are employed to scrutinize the impacts of monomeric PrP106-126 on model lipid membranes. Porous defects in planar bilayers are observed by using solution atomic force microscopy. Adding cholesterol does not impede defect formation. A force spectroscopy experiment shows that PrP106-126 reduces Young's modulus of planar lipid bilayers. We use Raman microspectroscopy to study the effect of PrP106-126 on lipid atomic vibrational dynamics. For phosphatidylcholine lipids, PrP106-126 disorders the intrachain conformation, while the interchain interaction is not altered; for phosphatidylethanolamine lipids, PrP106-126 increases the interchain interaction, while the intrachain conformational order remains similar. We explain the observed differences by considering different modes of peptide insertion. Finally, electron paramagnetic resonance spectroscopy shows that PrP106-126 progressively decreases the orientational order of lipid acyl chains in magnetically aligned bicelles. Together, our experimental data support the proposition that monomeric PrP106-126 can disrupt lipid membranes by using similar mechanisms found in AMPs.

  3. Large Mn25 single-molecule magnet with spin S = 51/2: magnetic and high-frequency electron paramagnetic resonance spectroscopic characterization of a giant spin state.

    Science.gov (United States)

    Murugesu, Muralee; Takahashi, Susumu; Wilson, Anthony; Abboud, Khalil A; Wernsdorfer, Wolfgang; Hill, Stephen; Christou, George

    2008-10-20

    The synthesis and structural, spectroscopic, and magnetic characterization of a Mn25 coordination cluster with a large ground-state spin of S = 51/2 are reported. Reaction of MnCl2 with pyridine-2,6-dimethanol (pdmH2) and NaN3 in MeCN/MeOH gives the mixed valence cluster [Mn25O18(OH)2(N3)12(pdm)6(pdmH)6]Cl2 (1; 6Mn(II), 18Mn(III), Mn(IV)), which has a barrel-like cage structure. Variable temperature direct current (dc) magnetic susceptibility data were collected in the 1.8-300 K temperature range in a 0.1 T field. Variable-temperature and -field magnetization (M) data were collected in the 1.8-4.0 K and 0.1-7 T ranges and fit by matrix diagonalization assuming only the ground state is occupied at these temperatures. The fit parameters were S = 51/2, D = -0.020(2) cm(-1), and g = 1.87(3), where D is the axial zero-field splitting parameter. Alternating current (ac) susceptibility measurements in the 1.8-8.0 K range and a 3.5 G ac field oscillating at frequencies in the 50-1500 Hz range revealed a frequency-dependent out-of-phase (chi(M)'') signal below 3 K, suggesting 1 to be a single-molecule magnet (SMM). This was confirmed by magnetization vs dc field sweeps, which exhibited hysteresis loops but with no clear steps characteristic of resonant quantum tunneling of magnetization (QTM). However, magnetization decay data below 1 K were collected and used to construct an Arrhenius plot, and the fit of the thermally activated region above approximately 0.5 K gave U(eff)/k = 12 K, where U(eff) is the effective relaxation barrier. The g value and the magnitude and sign of the D value were independently confirmed by detailed high-frequency electron paramagnetic resonance (HFEPR) spectroscopy on polycrystalline samples. The combined studies confirm both the high ground-state spin S = 51/2 of complex 1 and that it is a SMM that, in addition, exhibits QTM.

  4. Determination of g-tensors of low-symmetry Nd{sup 3+} centers in LiNbO{sub 3} by rectification of angular dependence of electron paramagnetic resonance spectra

    Energy Technology Data Exchange (ETDEWEB)

    Grachev, V., E-mail: grachev@physics.montana.edu; Malovichko, G. [Physics Department, Montana State University, Bozeman, Montana 59717 (United States); Munro, M. [Quantel Laser, Bozeman, Montana 59715 (United States); Kokanyan, E. [Institute of Physical Researches, Ashtarak (Armenia)

    2015-07-28

    Two procedures for facilitation of line tracing and deciphering of complicated spectra of electron paramagnetic resonance (EPR) were developed: a correction of microwave frequencies for every orientation of external magnetic field on the base of known values of g-tensor components for a reference paramagnetic center and followed rectification of measured angular dependences using plots of effective deviation of g{sup 2}-factors of observed lines from effective g{sup 2}-factors of the reference center versus angles or squared cosines of angles describing magnetic field orientations. Their application to EPR spectra of nearly stoichiometric lithium niobate crystals doped with neodymium allowed identifying two axial and six different low-symmetry Nd{sup 3+} centers, to determine all components of their g-tensors, and to propose common divacancy models for a whole family of Nd{sup 3+} centers.

  5. Iterative resonance self-shielding methods using resonance integral table in heterogeneous transport lattice calculations

    International Nuclear Information System (INIS)

    Hong, Ser Gi; Kim, Kang-Seog

    2011-01-01

    This paper describes the iteration methods using resonance integral tables to estimate the effective resonance cross sections in heterogeneous transport lattice calculations. Basically, these methods have been devised to reduce an effort to convert resonance integral table into subgroup data to be used in the physical subgroup method. Since these methods do not use subgroup data but only use resonance integral tables directly, these methods do not include an error in converting resonance integral into subgroup data. The effective resonance cross sections are estimated iteratively for each resonance nuclide through the heterogeneous fixed source calculations for the whole problem domain to obtain the background cross sections. These methods have been implemented in the transport lattice code KARMA which uses the method of characteristics (MOC) to solve the transport equation. The computational results show that these iteration methods are quite promising in the practical transport lattice calculations.

  6. Calculation of resonance integral for fuel cluster

    International Nuclear Information System (INIS)

    Remsak, S.

    1969-01-01

    The procedure for calculating the shielding correction, formulated in the previous paper [6], was broadened and applied for a cluster of cylindrical rods. The sam analytical method as in the previous paper was applied. A combination of Gauss method with the method of Almgren and Porn used for solving the same type of integral was used to calculate the geometry functions. CLUSTER code was written for ZUSE-Z-23 computer to calculate the shielding corrections for pairs of fuel rods in the cluster. Computing time for one pair of fuel rods depends on the number of closely placed rod, and for two closely placed rods it is about 3 hours. Calculations were done for clusters containing 7 and 19 UO 2 rods. results show that calculated values of resonance integrals are somewhat higher than the values obtained by Helstrand empirical formula. Taking into account the results for two rods from the previous paper it can be noted that the calculated and empirical values for clusters with 2 and 7 rods are in agreement since the deviations do not exceed the limits of experimental error (±2%). In case of larger cluster with 19 rods deviations are higher than the experimental error. Most probably the calculated values exceed the experimental ones result from the fact that in this paper the shielding correction is calculated only in the region up to 1 keV [sr

  7. The Dependence of the Resonance Integral on the Doppler Effect

    Energy Technology Data Exchange (ETDEWEB)

    Rosen, J

    1960-12-15

    The Doppler sensitive contributions to the resonance integral for metal and oxide cylinders have been calculated using tables compiled by Adler, Hinman and Nordheim. The temperatures 20, 200, 350, 500 and 650 deg C have been investigated for the pure metal and 20, 300, 600, 900 and 1200 deg C for the oxide. Contributions from the separate resonances in the resolved region and for certain energies in the unresolved region are accounted for in detail. Integration over adequate statistical distributions has been carried out for the resonance parameters in the unresolved region. The increase in the resonance integral at elevated temperatures due to the Doppler effect is given separately in tables and diagrams.

  8. 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

  9. Use of electron paramagnetic resonance dosimetry with tooth enamel for retrospective dose assessment. Report of a co-ordinated research project

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2002-12-01

    Electron paramagnetic resonance (EPR) dosimetry is a physical method for the assessment of absorbed dose from ionising radiation. It is based on the measurement of stable radiation induced radicals in human calcified tissues (primarily in tooth enamel). EPR dosimetry with teeth is now firmly established in retrospective dosimetry. It is a powerful method for providing information on exposure to ionising radiation many years after the event, since the 'signal' is 'stored' in the tooth or the bone. This technique is of particular relevance to relatively low dose exposures or when the results of conventional dosimetry are not available (e.g. in accidental circumstances). The use of EPR dosimetry, as an essential tool for retrospective assessment of radiation exposure is an important part of radioepidemiological studies and also provides data to select appropriate countermeasures based on retrospective evaluation of individual doses. Despite well established regulations and protocols for maintaining radiation protection dose limits, the assurance that these limits will not be exceeded cannot be guaranteed, thus providing new challenges for development of accurate methods of individual dose assessment. To meet some of these challenges, in 1998 the IAEA initiated a co-ordinated research project (CRP) with the objective to review the available methods, current research and development in EPR biodosimetry technology, which may be of practical use. The major goal of this CRP was to investigate the use of EPR biodosimetry for reconstruction of absorbed dose in tooth enamel with the aim of providing Member States with up-to-date, and generally agreed upon advice regarding the most suitable procedures and the best focus for their research. The co-ordinated research project was conducted over four years and this publication presents the results and findings by a group of investigators from different countries. The available cytogenetic methods for radiation dose assessment were

  10. Use of electron paramagnetic resonance dosimetry with tooth enamel for retrospective dose assessment. Report of a co-ordinated research project

    International Nuclear Information System (INIS)

    2002-12-01

    Electron paramagnetic resonance (EPR) dosimetry is a physical method for the assessment of absorbed dose from ionising radiation. It is based on the measurement of stable radiation induced radicals in human calcified tissues (primarily in tooth enamel). EPR dosimetry with teeth is now firmly established in retrospective dosimetry. It is a powerful method for providing information on exposure to ionising radiation many years after the event, since the 'signal' is 'stored' in the tooth or the bone. This technique is of particular relevance to relatively low dose exposures or when the results of conventional dosimetry are not available (e.g. in accidental circumstances). The use of EPR dosimetry, as an essential tool for retrospective assessment of radiation exposure is an important part of radioepidemiological studies and also provides data to select appropriate countermeasures based on retrospective evaluation of individual doses. Despite well established regulations and protocols for maintaining radiation protection dose limits, the assurance that these limits will not be exceeded cannot be guaranteed, thus providing new challenges for development of accurate methods of individual dose assessment. To meet some of these challenges, in 1998 the IAEA initiated a co-ordinated research project (CRP) with the objective to review the available methods, current research and development in EPR biodosimetry technology, which may be of practical use. The major goal of this CRP was to investigate the use of EPR biodosimetry for reconstruction of absorbed dose in tooth enamel with the aim of providing Member States with up-to-date, and generally agreed upon advice regarding the most suitable procedures and the best focus for their research. The co-ordinated research project was conducted over four years and this publication presents the results and findings by a group of investigators from different countries. The available cytogenetic methods for radiation dose assessment were

  11. Hyperbolic-cosine waveguide tapers and oversize rectangular waveguide for reduced broadband insertion loss in W-band electron paramagnetic resonance spectroscopy. II. Broadband characterization

    Energy Technology Data Exchange (ETDEWEB)

    Sidabras, Jason W.; Anderson, James R.; Mainali, Laxman; Hyde, James S. [Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226 (United States); Strangeway, Robert A. [Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226 (United States); Department of Electrical Engineering and Computer Science, Milwaukee School of Engineering, Milwaukee, Wisconsin 53201 (United States); Mett, Richard R. [Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226 (United States); Department of Chemistry and Physics, Milwaukee School of Engineering, Milwaukee, Wisconsin 53201 (United States)

    2016-03-15

    Experimental results have been reported on an oversize rectangular waveguide assembly operating nominally at 94 GHz. It was formed using commercially available WR28 waveguide as well as a pair of specially designed tapers with a hyperbolic-cosine shape from WR28 to WR10 waveguide [R. R. Mett et al., Rev. Sci. Instrum. 82, 074704 (2011)]. The oversize section reduces broadband insertion loss for an Electron Paramagnetic Resonance (EPR) probe placed in a 3.36 T magnet. Hyperbolic-cosine tapers minimize reflection of the main mode and the excitation of unwanted propagating waveguide modes. Oversize waveguide is distinguished from corrugated waveguide, overmoded waveguide, or quasi-optic techniques by minimal coupling to higher-order modes. Only the TE{sub 10} mode of the parent WR10 waveguide is propagated. In the present work, a new oversize assembly with a gradual 90° twist was implemented. Microwave power measurements show that the twisted oversize waveguide assembly reduces the power loss in the observe and pump arms of a W-band bridge by an average of 2.35 dB and 2.41 dB, respectively, over a measured 1.25 GHz bandwidth relative to a straight length of WR10 waveguide. Network analyzer measurements confirm a decrease in insertion loss of 2.37 dB over a 4 GHz bandwidth and show minimal amplitude distortion of approximately 0.15 dB. Continuous wave EPR experiments confirm these results. The measured phase variations of the twisted oversize waveguide assembly, relative to an ideal distortionless transmission line, are reduced by a factor of two compared to a straight length of WR10 waveguide. Oversize waveguide with proper transitions is demonstrated as an effective way to increase incident power and the return signal for broadband EPR experiments. Detailed performance characteristics, including continuous wave experiment using 1 μM 2,2,6,6-tetramethylpiperidine-1-oxyl in aqueous solution, provided here serve as a benchmark for other broadband low-loss probes in

  12. Disorder and intermolecular interactions in a family of tetranuclear Ni(II) complexes probed by high-frequency electron paramagnetic resonance.

    Science.gov (United States)

    Lawrence, Jon; Yang, En-Che; Edwards, Rachel; Olmstead, Marilyn M; Ramsey, Chris; Dalal, Naresh S; Gantzel, Peter K; Hill, Stephen; Hendrickson, David N

    2008-03-17

    High-frequency electron paramagnetic resonance (HFEPR) data are presented for four closely related tetranuclear Ni(II) complexes, [Ni(hmp)(MeOH)Cl]4.H2O (1a), [Ni(hmp)(MeOH)Br]4.H2O (1b), [Ni(hmp)(EtOH)Cl]4.H2O (2), and [Ni(hmp)(dmb)Cl]4 (3) (where hmp(-) is the anion of 2-hydroxymethylpyridine and dmb is 3,3'-dimethyl-1-butanol), which exhibit magnetic bistability (hysteresis) and fast magnetization tunneling at low temperatures, properties which suggest they are single-molecule magnets (SMMs). The HFEPR spectra confirm spin S = 4 ground states and dominant uniaxial anisotropy (DSz(2), D SMM. The individual fine structure peaks (due to zero-field splitting) for complexes 1a, 1b, and 2 are rather broad. They also exhibit further (significant) splitting, which can be explained by the fact that there exists two crystallographically distinct Ni 4 sites in the lattices for these complexes, with associated differences in metal-ligand bond lengths and different zero-field splitting (ZFS) parameters. The broad EPR lines, meanwhile, may be attributed to ligand and solvent disorder, which results in additional distributions of microenvironments. In the case of complex 3, there are no solvate molecules in the structure, and only one distinct Ni 4 molecule in the lattice. Consequently, the HFEPR data for complex 3 are extremely sharp. As the temperature of a crystal of complex 3 is decreased, the HFEPR spectrum splits abruptly at approximately 46 K into two patterns with very slightly different ZFS parameters. Heat capacity data suggest that this is caused by a structural transition at 46.6 K. A single-crystal X-ray structure at 12(2) K indicates large thermal parameters on the terminal methyl groups of the dmb (3,3-dimethyl-1-butanol) ligand. Most likely there exists dynamic disorder of parts of the dmb ligand above 46.6 K; an order-disorder structural phase transition at 46.6 K then removes some of the motion. A further decrease in temperature (<6 K) leads to further fine

  13. Hyperbolic-cosine waveguide tapers and oversize rectangular waveguide for reduced broadband insertion loss in W-band electron paramagnetic resonance spectroscopy. II. Broadband characterization

    International Nuclear Information System (INIS)

    Sidabras, Jason W.; Anderson, James R.; Mainali, Laxman; Hyde, James S.; Strangeway, Robert A.; Mett, Richard R.

    2016-01-01

    Experimental results have been reported on an oversize rectangular waveguide assembly operating nominally at 94 GHz. It was formed using commercially available WR28 waveguide as well as a pair of specially designed tapers with a hyperbolic-cosine shape from WR28 to WR10 waveguide [R. R. Mett et al., Rev. Sci. Instrum. 82, 074704 (2011)]. The oversize section reduces broadband insertion loss for an Electron Paramagnetic Resonance (EPR) probe placed in a 3.36 T magnet. Hyperbolic-cosine tapers minimize reflection of the main mode and the excitation of unwanted propagating waveguide modes. Oversize waveguide is distinguished from corrugated waveguide, overmoded waveguide, or quasi-optic techniques by minimal coupling to higher-order modes. Only the TE 10 mode of the parent WR10 waveguide is propagated. In the present work, a new oversize assembly with a gradual 90° twist was implemented. Microwave power measurements show that the twisted oversize waveguide assembly reduces the power loss in the observe and pump arms of a W-band bridge by an average of 2.35 dB and 2.41 dB, respectively, over a measured 1.25 GHz bandwidth relative to a straight length of WR10 waveguide. Network analyzer measurements confirm a decrease in insertion loss of 2.37 dB over a 4 GHz bandwidth and show minimal amplitude distortion of approximately 0.15 dB. Continuous wave EPR experiments confirm these results. The measured phase variations of the twisted oversize waveguide assembly, relative to an ideal distortionless transmission line, are reduced by a factor of two compared to a straight length of WR10 waveguide. Oversize waveguide with proper transitions is demonstrated as an effective way to increase incident power and the return signal for broadband EPR experiments. Detailed performance characteristics, including continuous wave experiment using 1 μM 2,2,6,6-tetramethylpiperidine-1-oxyl in aqueous solution, provided here serve as a benchmark for other broadband low-loss probes in

  14. Semiconductor GaAs: electronic paramagnetic resonance new data; GaAs semi-isolant: nouvelles donnees de resonance paramagnetique electronique

    Energy Technology Data Exchange (ETDEWEB)

    Benchiguer, T.

    1994-04-01

    The topic of this study was to put to the fore, thanks to our electron spin resonance experiments, one charge transfer process, which was optically induced between the deep donor As{sup +}{sub G}a and the different acceptors, which were present in the material. We described these processes through a theoretical model, which we named charge transfer model. With this latter, we were able to trace a graph network, representing the As{sup +}{sub G}a concentration kinetics. Then we verified the compatibility of our model with one transport experiment. One experimental verification of our model were delivered, thanks to neutronic transmutation doping. The following stage was the study of defects, induced by thermal strains, to which the crystal was submitted during the cooling phase. At last we wanted to get round the non solved super hyperfine structure problem for GaAs by studying another III-V material for which she was resolved, namely gallium phosphide. (MML). 150 refs., 72 figs., 16 tabs., 3 annexes.

  15. Evidence of emerging Griffiths singularity in La{sub 0.5} Sr{sub 0.5} MnO{sub 3} nanocrystalline probed by magnetization and electron paramagnetic resonance

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xiyuan [Department of Applied Physics, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Fan, Jiyu, E-mail: jiyufan@nuaa.edu.cn [Department of Applied Physics, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Xu, Lisa [Department of Applied Physics, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Tong, Wei [High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei 230031 (China); Hu, Dazhi [Department of Applied Physics, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); He, Xun [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Zhang, Lei; Pi, Li; Zhang, Yuheng [High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei 230031 (China)

    2016-06-01

    We present an investigation of Griffiths singularity in La{sub 0.5} Sr{sub 0.5} MnO{sub 3} nanocrystalline by means of magnetic susceptibility and electron paramagnetic resonance (EPR). An unusual platform was found in paramagnetic region. Based on the analysis of EPR spectrum and magnetization variation across the whole temperature range of phase transition, we confirm it is due to the presence of Griffiths singularity rather than a superparamagnetic state in the nanocrystalline system. Such a singularity phase is constituted with some correlated ferromagnetic clusters which embed in paramagnetic matrix. Although they form ferromagnetic spin correlation, the system do not yield any spontaneous magnetization. According to core–shell model, the emergence of Griffiths singularity can be considered due to the presence of local ferromagnetic fluctuations originated from surface spin disorder as the sample size is confined to nanoscale. - Highlights: • Griffiths singularity rather than superparamagnetism occurs in La{sub 0.5}Sr{sub 0.5}MnO{sub 3} nanoparticals. • The sample’s size reduced to nanoscale results in the short-range ferromagnetic interaction. • The core-shell model is used to understand the formation of Griffiths phase in nanometer La{sub 0.5}Sr{sub 0.5}MnO{sub 3}.

  16. Paramagnetic defects in hydrogenated amorphous carbon powders

    International Nuclear Information System (INIS)

    Keeble, D J; Robb, K M; Smith, G M; Mkami, H El; Rodil, S E; Robertson, J

    2003-01-01

    Hydrogenated amorphous carbon materials typically contain high concentrations of paramagnetic defects, the density of which can be quantified by electron paramagnetic resonance (EPR). In this work EPR measurements near 9.5, 94, and 189 GHz have been performed on polymeric and diamond-like hydrogenated amorphous carbon (a-C:H) powder samples. A similar single resonance line was observed at all frequencies for the two forms of a-C:H studied. No contributions to the spectrum from centres with resolved anisotropic g-values as reported earlier were detected. An increase in linewidth with microwave frequency was observed. Possible contributions to this frequency dependence are discussed

  17. Integrated polymer micro-ring resonators for optical sensing applications

    OpenAIRE

    Girault , Pauline; Lorrain , Nathalie; Poffo , Luiz; Guendouz , Mohammed; Lemaitre , Jonathan; Carré , Christiane; Gadonna , Michel; Bosc , Dominique; Vignaud , Guillaume

    2015-01-01

    International audience; Micro-resonators (MR) have become a key element for integrated optical sensors due to their integration capability and their easy fabrication with low cost polymer materials. Nowadays, there is a growing need on MRs as highly sensitive and selective functions especially in the areas of food and health. The context of this work is to implement and study integrated micro-ring resonators devoted to sensing applications. They are fabricated by processing SU8 polymer as cor...

  18. Influence of resonance parameters' correlations on the resonance integral uncertainty; 55Mn case

    International Nuclear Information System (INIS)

    Zerovnik, Gasper; Trkov, Andrej; Capote, Roberto; Rochman, Dimitri

    2011-01-01

    For nuclides with a large number of resonances the covariance matrix of resonance parameters can become very large and expensive to process in terms of the computation time. By converting covariance matrix of resonance parameters into covariance matrices of background cross-section in a more or less coarse group structure a considerable amount of computer time and memory can be saved. The question is how important is the information that is discarded in the process. First, the uncertainty of the 55 Mn resonance integral was estimated in narrow resonance approximation for different levels of self-shielding using Bondarenko method by random sampling of resonance parameters according to their covariance matrices from two different 55 Mn evaluations: one from Nuclear Research and Consultancy Group NRG (with large uncertainties but no correlations between resonances), the other from Oak Ridge National Laboratory (with smaller uncertainties but full covariance matrix). We have found out that if all (or at least significant part of the) resonance parameters are correlated, the resonance integral uncertainty greatly depends on the level of self-shielding. Second, it was shown that the commonly used 640-group SAND-II representation cannot describe the increase of the resonance integral uncertainty. A much finer energy mesh for the background covariance matrix would have to be used to take the resonance structure into account explicitly, but then the objective of a more compact data representation is lost.

  19. Effect of ultraviolet irradiation on free radical scavenging activity of immunosuppressants used in lung transplantation and comparative electron paramagnetic resonance study of kinetics of their interactions with model free radicals.

    Science.gov (United States)

    Stanjek-Cichoracka, A; Żegleń, S; Ramos, P; Pilawa, B; Wojarski, J

    2018-06-01

    The immunosuppressive drugs used in solid organ transplantation or autoimmunological processes were studied by electron paramagnetic resonance (EPR) spectroscopy to estimate their free radical scavenging activity. The interactions of immunosuppressants with free radicals were examined by an X-band (9.3 GHz) EPR spectroscopy and a model of DPPH free radicals. The EPR spectra of DPPH and DPPH interacting with individual drugs were compared. Kinetic studies were performed, and the effect of ultraviolet (UV) irradiation on the free radical scavenging activity of the tested drugs was determined. The free radical scavenging activity of non-irradiated drugs decreased in the order: rapamycin > mycophenolate mofetil > ciclosporin > tacrolimus. UV irradiation increased the free radical scavenging activity of all the tested immunosuppressive drugs, and the effect was highest for tacrolimus. For the non-irradiated samples, the speed of free radical interactions decreased in the order: ciclosporin > tacrolimus > mycophenolate mofetil > rapamycin. UV irradiation only slightly affected the speed of interactions of the immunosuppressive drugs with the model DPPH free radicals. Electron paramagnetic resonance spectroscopy is useful for obtaining information on interactions of immunosuppressive drugs with free radicals. We hypothesized that the long-term immunosuppressive effects of these drugs after transplantation or during autoimmune disorders may be mediated by anti-inflammatory action in addition to the known receptor/cell cycle inhibition. © 2018 John Wiley & Sons Ltd.

  20. Disappearance of electron-hole asymmetry in nanoparticles of Nd1−xCaxMnO3(x=0.6,0.4): magnetization and electron paramagnetic resonance evidence

    International Nuclear Information System (INIS)

    Bhagyashree, K. S.; Bhat, S. V.

    2015-01-01

    We study and compare magnetic and electron paramagnetic resonance behaviors of bulk and nanoparticles of Nd 1−x Ca x MnO 3 in hole doped (x=0.4;NCMOH) and electron doped (x=0.6;NCMOE) samples. NCMOH in bulk form shows a complex temperature dependence of magnetization M(T), with a charge ordering transition at ∼250 K, an antiferromagnetic (AFM) transition at ∼150 K, and a transition to a canted AFM phase/mixed phase at ∼80 K. Bulk NCMOE behaves quite differently with just a charge ordering transition at ∼280 K, thus providing a striking example of the so called electron-hole asymmetry. While our magnetization data on bulk samples are consistent with the earlier reports, the new results on the nanoparticles bring out drastic effects of size reduction. They show that M(T) behaviors of the two nanosamples are essentially similar in addition to the absence of the charge order in them thus providing strong evidence for vanishing of the electron-hole asymmetry in nanomanganites. This conclusion is further corroborated by electron paramagnetic resonance studies which show that the large difference in the “g” values and their temperature dependences found for the two bulk samples disappears as they approach a common behavior in the corresponding nanosamples

  1. Electronic paramagnetic resonance in the Mn In X (X:Te,S) diluted magnetic semiconductor system; Resonancia paramagnetica electronica en el sistema semiconductor magnetico diluido Cd Mn In X (X:Te,S)

    Energy Technology Data Exchange (ETDEWEB)

    Vincent, Bernardo; Betancourt, Luis; Sagredo, Vicente [Universidad de los Andes, Merida (Venezuela). Dept. de Fisica; Alcala, Rafael [Zaragoza Univ. (Spain). Dept. de Fisica de la Materia Condensada

    1997-12-31

    Semiconductor compounds wit the II-III-VI stoichiometry are very interesting materials since they present very good semiconducting characteristics and, along with strong magnetic properties, these II Mn In VI compounds have a great potential as opt and magneto-electronic devices. Among the possible magnetic properties of the materials is the presence of the spin-glass phase. Electron paramagnetic resonance is one of the techniques used to confirm this phase. The chosen crystals were chosen by chemical vapor transport. The absorption lines of these two families with 0.1 x 1 were all Lorentzian in shape and centred at g=2. A large broadening of the resonance line width was observed when lowering the temperature to below 80 K. This behaviour was fitted to the known existing models, and good values of the calculated parameters were obtained (author). 18 refs., 2 figs., 2 tabs.

  2. Fabrication of resonant micro cantilevers with integrated transparent fluidic channel

    DEFF Research Database (Denmark)

    Khan, Faheem; Schmid, Silvan; Davis, Zachary James

    2011-01-01

    Microfabricated cantilevers are proving their potential as excellent tools for analysis applications. In this paper, we describe the design, fabrication and testing of resonant micro cantilevers with integrated transparent fluidic channels. The cantilevers have been devised to measure the density...

  3. Model-free nuclear magnetic resonance study of intermolecular free energy landscapes in liquids with paramagnetic Ln3+ spotlights: theory and application to Arg-Gly-Asp.

    Science.gov (United States)

    Fries, Pascal H

    2012-01-28

    We propose an easily applicable method for investigating the pair distribution function of a lanthanide Ln(3+) complex LnL (L = ligand) with respect to any solvent or solute molecule A carrying observable nuclear spins. Let r be the distance of Ln(3+) to the observed nuclear spin I. We derive a simple expression of the experimental value of the configurational average of 1/r(6) in terms of longitudinal paramagnetic relaxation (rate) enhancements (PREs) of the spin I measured on a standard high-resolution NMR spectrometer and due to well-chosen concentrations of LnL complexes in which Ln(3+) is a fast-relaxing paramagnetic lanthanide or the slowly-relaxing gadolinium Gd(3+). The derivation is justified in the general case of a molecule A which is by turns in a bound state where it follows the complex and a free state where it moves independently. It rests on the expression of the underlying PRE theory in terms of the angle-dependent pair distribution function of LnL and A. The simplifications of this theory in the high-field regime and under the condition of fast exchange between bound and free states are carefully discussed. We also show that original information on the angle dependence of the molecular pair distribution function can be gained from the measured paramagnetic dipolar shifts induced by complexed fast-relaxing Ln(3+) ions. The method is illustrated by the case study of the anionic Lnttha(3-) = [Ln(3+)(ttha)](3-) (ttha(6-) = triethylene tetraamine hexacetate) complex interacting with the biologically important tripeptide Arg-Gly-Asp (RGD) which carries peripheral ionic groups. The usefulness of an auxiliary reference outer sphere probe solute is emphasized. © 2012 American Institute of Physics

  4. Paramagnetic pharmaceuticals for functional studies

    International Nuclear Information System (INIS)

    Hall, L.D.; Hogan, P.G.

    1987-01-01

    It has been suggested that limitations of the Magnetic Resonance Imaging (MRI) method may be minimised by the use of ''image contrast'' agents. These are exogenous chemicals administered to the patient which, by influencing the magnetic resonance properties of the water in the region of the pathology, serve to heighten the contrast between that tissue and its surroundings. At present the most widely used agent is gadolinium-DTPA (Gd-DTPA). This appears to have many desirable features and its development provides a textbook example for the early stages of any future development. All compounds used so far can be subdivided into one of the following categories: Paramagnetic metal species; Ferromagnetic metal species; Stable free radicals; Oxygen carriers; Susceptibility agents; and Density substitution agents. The authors summarise briefly these chemical substances and their reported uses

  5. 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.

  6. Electron paramagnetic resonance and optical spectroscopy of Yb sup 3 sup + ions in SrF sub 2 and BaF sub 2; an analysis of distortions of the crystal lattice near Yb sup 3 sup +

    CERN Document Server

    Falin, M L; Latypov, V A; Leushin, A M

    2003-01-01

    SrF sub 2 and BaF sub 2 crystals, doped with the Yb sup 3 sup + ions, have been investigated by electron paramagnetic resonance and optical spectroscopy. As-grown crystals of SrF sub 2 and BaF sub 2 show the two paramagnetic centres for the cubic (T sub c) and trigonal (T sub 4) symmetries of the Yb sup 3 sup + ions. Empirical diagrams of the energy levels were established and the potentials of the crystal field were determined. Information was obtained on the SrF sub 2 and BaF sub 2 phonon spectra from the electron-vibrational structure of the optical spectra. The crystal field parameters were used to analyse the crystal lattice distortions in the vicinity of the impurity ion and the F sup - ion compensating for the excess positive charge in T sub 4. Within the frames of a superposition model, it is shown that three F sup - ions from the nearest surrounding cube, located symmetrically with respect to the C sub 3 axis from the side of the ion-compensator, approach the impurity ion and cling to the axis of the...

  7. Integrated MEMS/NEMS Resonant Cantilevers for Ultrasensitive Biological Detection

    Directory of Open Access Journals (Sweden)

    Xinxin Li

    2009-01-01

    Full Text Available The paper reviews the recent researches implemented in Chinese Academy of Sciences, with achievements on integrated resonant microcantilever sensors. In the resonant cantilevers, the self-sensing elements and resonance exciting elements are both top-down integrated with silicon micromachining techniques. Quite a lot of effort is focused on optimization of the resonance mode and sensing structure for improvement of sensitivity. On the other hand, to enable the micro-cantilevers specifically sensitive to bio/chemical molecules, sensing materials are developed and modified on the cantilever surface with a self-assembled monolayer (SAM based bottom-up construction and surface functionalization. To improve the selectivity of the sensors and depress environmental noise, multiple and localized surface modifications are developed. The achieved volume production capability and satisfactory detecting resolution to trace-level biological antigen of alpha-fetoprotein (AFP give the micro-cantilever sensors a great promise for rapid and high-resoluble detection.

  8. Determination of space-energy distribution of resonance neutrons in reactor lattice cell and calculation of resonance integrals

    International Nuclear Information System (INIS)

    Zmijarevic, I.

    1980-01-01

    Space-energy distribution of resonance neutrons in reactor lattice cell was determined by solving the Boltzmann equation by spherical harmonics method applying P-3 approximation. Computer code SPLET used for these calculations is described. Resonance absorption and calculation of resonance integrals are described as well. Effective resonance integral values for U-238 resonance at 6.7 Ev are calculated for heavy water reactor cell with metal, oxide and carbide fuel elements

  9. Analysis and Modeling of Integrated Magnetics for LLC resonant Converters

    DEFF Research Database (Denmark)

    Li, Mingxiao; Ouyang, Ziwei; Zhao, Bin

    2017-01-01

    Shunt-inserted transformers are widely used toobtain high leakage inductance. This paper investigates thismethod in depth to make it applicable to integrate resonantinductor for the LLC resonant converters. The analysis andmodel of magnetizing inductance and leakage inductance forshunt...... transformers can provide a significantdifference. The way to obtain the desirable magnetizing andleakage inductance value for LLC resonant converters issimplified by the creation of air gaps together with a magneticshunt. The calculation and relation are validated by finiteelement analysis (FEA) simulations...

  10. Path-integral approach to resonant electron-molecule scattering

    International Nuclear Information System (INIS)

    Winterstetter, M.; Domcke, W.

    1993-01-01

    A path-integral formulation of resonant electron-molecule scattering is developed within the framework of the projection-operator formalism of scattering theory. The formation and decay of resonances is treated in real time as a quantum-mechanical electronic-tunneling process, modified by the coupling of the electronic motion with the nuclear degrees of freedom. It is shown that the electronic continuum can be summed over in the path-integral formulation, resulting formally in the path integral for an effective two-state system with coupling to vibrations. The harmonic-oscillator approximation is adopted for the vibrational motion in the present work. Approximation methods are introduced which render the numerical evaluation of the sum over paths feasible for up to ∼10 3 elementary time slices. The theory is numerically realized for simple but nontrivial models representing the 2 Π g d-wave shape resonance in e - +N 2 collisions and the 2 Σ u + p-wave shape resonance in e - +H 2 collisions, respectively. The accuracy of the path-integral results is assessed by comparison with exact numerical reference data for these models. The essential virtue of the path-integral approach is the fact that the computational effort scales at most linearly with the number of vibrational degrees of freedom. The path-integral method is thus well suited to treat electron collisions with polyatomic molecules and molecular aggregates

  11. X-ray Crystallographic, Multifrequency Electron Paramagnetic Resonance, and Density Functional Theory Characterization of the Ni(P(Cy)2N(tBu)2)2(n+) Hydrogen Oxidation Catalyst in the Ni(I) Oxidation State.

    Science.gov (United States)

    Niklas, Jens; Westwood, Mark; Mardis, Kristy L; Brown, Tiara L; Pitts-McCoy, Anthony M; Hopkins, Michael D; Poluektov, Oleg G

    2015-07-06

    The Ni(I) hydrogen oxidation catalyst [Ni(P(Cy)2N(tBu)2)2](+) (1(+); P(Cy)2N(tBu)2 = 1,5-di(tert-butyl)-3,7-dicyclohexyl-1,5-diaza-3,7-diphosphacyclooctane) has been studied using a combination of electron paramagnetic resonance (EPR) techniques (X-, Q-, and D-band, electron-nuclear double resonance, hyperfine sublevel correlation spectroscopy), X-ray crystallography, and density functional theory (DFT) calculations. Crystallographic and DFT studies indicate that the molecular structure of 1(+) is highly symmetrical. EPR spectroscopy has allowed determination of the electronic g tensor and the spin density distribution on the ligands, and revealed that the Ni(I) center does not interact strongly with the potentially coordinating solvents acetonitrile and butyronitrile. The EPR spectra and magnetic parameters of 1(+) are found to be distinctly different from those for the related compound [Ni(P(Ph)2N(Ph)2)2](+) (4(+)). One significant contributor to these differences is that the molecular structure of 4(+) is unsymmetrical, unlike that of 1(+). DFT calculations on derivatives in which the R and R' groups are systematically varied have allowed elucidation of structure/substituent relationships and their corresponding influence on the magnetic resonance parameters.

  12. Levitation in paramagnetic liquids

    Energy Technology Data Exchange (ETDEWEB)

    Dunne, P.A. [School of Physics and CRANN, Trinity Collge, Dublin 2 (Ireland)]. E-mail: pdunne2@tcd.ie; Hilton, J. [School of Physics and CRANN, Trinity Collge, Dublin 2 (Ireland); Coey, J.M.D. [School of Physics and CRANN, Trinity Collge, Dublin 2 (Ireland)

    2007-09-15

    Magnetic levitation of diamagnetic and paramagnetic substances in a paramagnetic liquid is explored. Materials ranging from graphite to tin and copper can be made to float at ambient temperature in concentrated solutions of dysprosium nitrate, when an electromagnet or four-block permanent magnet array is used to produce a gradient field. Simulations illustrate the stable regions for levitation above the permanent magnets; and a novel eight-block configuration is proposed, which allows denser materials such as gold or lead to be levitated.

  13. Levitation in paramagnetic liquids

    International Nuclear Information System (INIS)

    Dunne, P.A.; Hilton, J.; Coey, J.M.D.

    2007-01-01

    Magnetic levitation of diamagnetic and paramagnetic substances in a paramagnetic liquid is explored. Materials ranging from graphite to tin and copper can be made to float at ambient temperature in concentrated solutions of dysprosium nitrate, when an electromagnet or four-block permanent magnet array is used to produce a gradient field. Simulations illustrate the stable regions for levitation above the permanent magnets; and a novel eight-block configuration is proposed, which allows denser materials such as gold or lead to be levitated

  14. Integrated Microfluidic Sensor System with Magnetostrictive Resonators

    KAUST Repository

    Liang, Cai; Kosel, Jü rgen; Gooneratne, Chinthaka

    2011-01-01

    The present embodiments describe a method that integrates a magnetostrictive sensor with driving and detecting elements into a microfluidic chip to detect a chemical, biochemical or biomedical species. These embodiments may also measure the properties of a fluid such as viscosity, pH values. The whole system can be referred to lab-on-a-chip (LOC) or micro-total-analysis-systems (.mu.TAS). In particular, this present embodiments include three units, including a microfluidics unit, a magnetostrictive sensor, and driving/detecting elements. An analyzer may also be provided to analyze an electrical signal associated with a feature of a target specimen.

  15. Integrated Microfluidic Sensor System with Magnetostrictive Resonators

    KAUST Repository

    Liang, Cai

    2011-12-08

    The present embodiments describe a method that integrates a magnetostrictive sensor with driving and detecting elements into a microfluidic chip to detect a chemical, biochemical or biomedical species. These embodiments may also measure the properties of a fluid such as viscosity, pH values. The whole system can be referred to lab-on-a-chip (LOC) or micro-total-analysis-systems (.mu.TAS). In particular, this present embodiments include three units, including a microfluidics unit, a magnetostrictive sensor, and driving/detecting elements. An analyzer may also be provided to analyze an electrical signal associated with a feature of a target specimen.

  16. An attempt to explain the uranium 238 resonance integral discrepancy

    International Nuclear Information System (INIS)

    Tellier, H.; Grandotto, M.

    1978-01-01

    Studies on uranium 238 resonance integral discrepancy were carried out for light water reactor physics. It was shown that using recently published resonance parameters and substituting a multilevel formalism to the usual Breit and Wigner formula reduced the well known discrepancy between two values of the uranium 238 effective resonance integral: the value calculated with the nuclear data and the one deduced from critical experiments. Since the cross section computed with these assumptions agrees quite well with the Oak-Ridge transmission data, it was used to obtain the self-shielding effect and the capture rate in light water lattices. The multiplication factor calculated with this method is found very close to the experimental value. Preliminary results for a set of benchmarks relative to several types of thermal neutron reactors lead to very low discrepancies. The reactivity loss is only 130 x 10 -5 instead of 650 x 10 -5 in the case of the usual libraries and the single level formula

  17. Demonstrating Paramagnetism Using Liquid Nitrogen.

    Science.gov (United States)

    Simmonds, Ray; And Others

    1994-01-01

    Describes how liquid nitrogen is attracted to the poles of neodymium magnets. Nitrogen is not paramagnetic, so the attraction suggests that the liquid nitrogen contains a small amount of oxygen, which causes the paramagnetism. (MVL)

  18. Nonlinear resonance in Duffing oscillator with fixed and integrative ...

    Indian Academy of Sciences (India)

    We study the nonlinear resonance, one of the fundamental phenomena in nonlinear oscillators, in a damped and periodically-driven Duffing oscillator with two types of time-delayed feedbacks, namely, fixed and integrative. Particularly, we analyse the effect of the time-delay parameter and the strength of the ...

  19. Photonic crystal resonator integrated in a microfluidic system

    DEFF Research Database (Denmark)

    Rodrigues de Sousa Nunes, Pedro André; Mortensen, Niels Asger; Kutter, Jörg Peter

    2008-01-01

    We report on a novel optofluidic system consisting of a silica-based 1D photonic crystal, integrated planar waveguides, and electrically insulated fluidic channels. An array of pillars in a microfluidic channel designed for electrochromatography is used as a resonator for on-column label...

  20. Nonlinear resonance in Duffing oscillator with fixed and integrative ...

    Indian Academy of Sciences (India)

    2012-03-02

    Mar 2, 2012 ... Abstract. We study the nonlinear resonance, one of the fundamental phenomena in nonlinear oscillators, in a damped and periodically-driven Duffing oscillator with two types of time-delayed feedbacks, namely, fixed and integrative. Particularly, we analyse the effect of the time-delay parameter α and the ...

  1. On kinetics of paramagnetic radiation defects accumulation in beryllium ceramics

    International Nuclear Information System (INIS)

    Polyakov, A.I.; Ryabikin, Yu.A.; Zashkvara, O.V.; Bitenbaev, M.I.; Petykhov, Yu.V.

    1999-01-01

    Results of paramagnetic radiation defects concentration dependence study in beryllium ceramics from gamma-irradiation dose ( 60 Co) within interval 0-100 Mrem are cited. Obtained dose dependence has form of accumulation curve with saturation typical of for majority of solids (crystals, different polymers, organic substances and others) , in which under irradiation occur not only formation of paramagnetic radiation defects, but its destruction due to recombination and interaction with radiation fields. Analysis of accumulation curve by the method of distant asymptotics allows to determine that observed in gamma-irradiated beryllium ceramics double line of electron spin resonance is forming of two types of paramagnetic radiation defects. It was defined, that sum paramagnetic characteristics of beryllium ceramics within 1-100 Mrad gamma- irradiation dose field change insignificantly and define from first type of paramagnetic radiation defects

  2. Aluminum and gallium nuclei as microscopic probes for pulsed electron-nuclear double resonance diagnostics of electric-field gradient and spin density in garnet ceramics doped with paramagnetic ions

    Science.gov (United States)

    Uspenskaya, Yu. A.; Mamin, G. V.; Babunts, R. A.; Badalyan, A. G.; Edinach, E. V.; Asatryan, H. R.; Romanov, N. G.; Orlinskii, S. B.; Khanin, V. M.; Wieczorek, H.; Ronda, C.; Baranov, P. G.

    2018-03-01

    The presence of aluminum and gallium isotopes with large nuclear magnetic and quadrupole moments in the nearest environment of impurity ions Mn2+ and Ce3+ in garnets made it possible to use hyperfine and quadrupole interactions with these ions to determine the spatial distribution of the unpaired electron and the gradient of the electric field at the sites of aluminum and gallium in the garnet lattice. High-frequency (94 GHz) electron spin echo detected electron paramagnetic resonance and electron-nuclear double resonance measurements have been performed. Large difference in the electric field gradient and quadrupole splitting at octahedral and tetrahedral sites allowed identifying the positions of aluminum and gallium ions in the garnet lattice and proving that gallium first fills tetrahedral positions in mixed aluminum-gallium garnets. This should be taken into account in the development of garnet-based scintillators and lasers. It is shown that the electric field gradient at aluminum nuclei near Mn2+ possessing an excess negative charge in the garnet lattice is ca. 2.5 times larger than on aluminum nuclei near Ce3+.

  3. 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.

  4. Paramagnetic contrast material

    International Nuclear Information System (INIS)

    McNamara, M.T.

    1987-01-01

    Paramagnetic contrast materials have certainly demonstrated clinical utility in a variety of organ systems for improved detection of various neoplastic, inflammatory, infectious, and physiologic abnormalities. Although the more commonly employed extracellular agents, such as Gd-DTPA, have been quite safe and useful, particularly in the CNS, it is almost certain that other substances will achieve more success in various other organs, such as iron oxides in the reticuloendothelial system and persisting extracellular agents in the cardiovascular system. Finally, as MRI technology continues to evolve, producing such exciting new sequences as gradient-echo fast scans, the roles of currently existing and newly discovered paramagnetic pharmaceuticals must be continuously reevaluated both to obtain maximum clinical benefit and to guide the search for newer agents that may further optimize the diagnostic efficacy of MRI

  5. Trispyrazolylborate Complexes: An Advanced Synthesis Experiment Using Paramagnetic NMR, Variable-Temperature NMR, and EPR Spectroscopies

    Science.gov (United States)

    Abell, Timothy N.; McCarrick, Robert M.; Bretz, Stacey Lowery; Tierney, David L.

    2017-01-01

    A structured inquiry experiment for inorganic synthesis has been developed to introduce undergraduate students to advanced spectroscopic techniques including paramagnetic nuclear magnetic resonance and electron paramagnetic resonance. Students synthesize multiple complexes with unknown first row transition metals and identify the unknown metals by…

  6. Integrating out resonances in strongly-coupled electroweak scenarios

    Directory of Open Access Journals (Sweden)

    Rosell Ignasi

    2017-01-01

    Full Text Available Accepting that there is a mass gap above the electroweak scale, the Electroweak Effective Theory (EWET is an appropriate tool to describe this situation. Since the EWET couplings contain information on the unknown high-energy dynamics, we consider a generic strongly-coupled scenario of electroweak symmetry breaking, where the known particle fields are coupled to heavier states. Then, and by integrating out these heavy fields, we study the tracks of the lightest resonances into the couplings. The determination of the low-energy couplings (LECs in terms of resonance parameters can be made more precise by considering a proper short-distance behaviour on the Lagrangian with heavy states, since the number of resonance couplings is then reduced. Notice that we adopt a generic non-linear realization of the electroweak symmetry breaking with a singlet Higgs.

  7. Study of the nature and of the properties of paramagnetic centers observed by electron spin resonance in conjugated polymers; Etude de la nature des propriete des centres paramagnetiques observes par resonance paramagnetique electronique dans les polymeres conjugues

    Energy Technology Data Exchange (ETDEWEB)

    Nechtschein, M [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1967-06-15

    Conjugated polymers contain paramagnetic centers. It is established that these centers are free radicals and a model which defines their electronic structure is proposed. The interactions between these centers are studied, notably by dynamic polarisation experiments. Finally it is shown that the centers have catalytic properties. (author) [French] Les polymeres conjugues contiennent des centres paramagnetiques. L'origine radicalaire de ces centres est etablie et un modele precisant leur structure electronique est propose. Les interactions entre ces centres sont etudiees, notamment a l'aide d'experiences de polarisation dynamique. Des proprietes catalytiques sont mises en evidence. (auteur)

  8. Study of the nature and of the properties of paramagnetic centers observed by electron spin resonance in conjugated polymers; Etude de la nature des propriete des centres paramagnetiques observes par resonance paramagnetique electronique dans les polymeres conjugues

    Energy Technology Data Exchange (ETDEWEB)

    Nechtschein, M. [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1967-06-15

    Conjugated polymers contain paramagnetic centers. It is established that these centers are free radicals and a model which defines their electronic structure is proposed. The interactions between these centers are studied, notably by dynamic polarisation experiments. Finally it is shown that the centers have catalytic properties. (author) [French] Les polymeres conjugues contiennent des centres paramagnetiques. L'origine radicalaire de ces centres est etablie et un modele precisant leur structure electronique est propose. Les interactions entre ces centres sont etudiees, notamment a l'aide d'experiences de polarisation dynamique. Des proprietes catalytiques sont mises en evidence. (auteur)

  9. Electronically Tunable Fully Integrated Fractional-Order Resonator

    KAUST Repository

    Tsirimokou, Georgia

    2017-03-20

    A fully integrated implementation of a parallel fractional-order resonator which employs together a fractional order capacitor and a fractional-order inductor is proposed in this paper. The design utilizes current-controlled Operational Transconductance Amplifiers as building blocks, designed and fabricated in AMS 0:35m CMOS process, and based on a second-order approximation of a fractional-order differentiator/ integrator magnitude optimized in the range 10Hz–700Hz. An attractive benefit of the proposed scheme is its electronic tuning capability.

  10. Electronically Tunable Fully Integrated Fractional-Order Resonator

    KAUST Repository

    Tsirimokou, Georgia; Psychalinos, Costas; Elwakil, Ahmed S.; Salama, Khaled N.

    2017-01-01

    A fully integrated implementation of a parallel fractional-order resonator which employs together a fractional order capacitor and a fractional-order inductor is proposed in this paper. The design utilizes current-controlled Operational Transconductance Amplifiers as building blocks, designed and fabricated in AMS 0:35m CMOS process, and based on a second-order approximation of a fractional-order differentiator/ integrator magnitude optimized in the range 10Hz–700Hz. An attractive benefit of the proposed scheme is its electronic tuning capability.

  11. Diamond electro-optomechanical resonators integrated in nanophotonic circuits

    Energy Technology Data Exchange (ETDEWEB)

    Rath, P.; Ummethala, S.; Pernice, W. H. P., E-mail: wolfram.pernice@kit.edu [Institute of Nanotechnology, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen (Germany); Diewald, S. [Center for Functional Nanostructures, Karlsruhe Institute of Technology, 76131 Karlsruhe (Germany); Lewes-Malandrakis, G.; Brink, D.; Heidrich, N.; Nebel, C. [Fraunhofer Institute for Applied Solid State Physics, Tullastr. 72, 79108 Freiburg (Germany)

    2014-12-22

    Diamond integrated photonic devices are promising candidates for emerging applications in nanophotonics and quantum optics. Here, we demonstrate active modulation of diamond nanophotonic circuits by exploiting mechanical degrees of freedom in free-standing diamond electro-optomechanical resonators. We obtain high quality factors up to 9600, allowing us to read out the driven nanomechanical response with integrated optical interferometers with high sensitivity. We are able to excite higher order mechanical modes up to 115 MHz and observe the nanomechanical response also under ambient conditions.

  12. Integrated polymer micro-ring resonators for optical sensing applications

    Science.gov (United States)

    Girault, Pauline; Lorrain, Nathalie; Poffo, Luiz; Guendouz, Mohammed; Lemaitre, Jonathan; Carré, Christiane; Gadonna, Michel; Bosc, Dominique; Vignaud, Guillaume

    2015-03-01

    Micro-resonators (MR) have become a key element for integrated optical sensors due to their integration capability and their easy fabrication with low cost polymer materials. Nowadays, there is a growing need on MRs as highly sensitive and selective functions especially in the areas of food and health. The context of this work is to implement and study integrated micro-ring resonators devoted to sensing applications. They are fabricated by processing SU8 polymer as core layer and PMATRIFE polymer as lower cladding layer. The refractive index of the polymers and of the waveguide structure as a function of the wavelength is presented. Using these results, a theoretical study of the coupling between ring and straight waveguides has been undertaken in order to define the MR design. Sub-micronic gaps of 0.5 μm to 1 μm between the ring and the straight waveguides have been successfully achieved with UV (i-lines) photolithography. Different superstrates such as air, water, and aqueous solutions with glucose at different concentrations have been studied. First results show a good normalized transmission contrast of 0.98, a resonator quality factor around 1.5 × 104 corresponding to a coupling ratio of 14.7%, and ring propagation losses around 5 dB/cm. Preliminary sensing experiments have been performed for different concentrations of glucose; a sensitivity of 115 ± 8 nm/RIU at 1550 nm has been obtained with this couple of polymers.

  13. The thermal neutron absorption cross-sections, resonance integrals and resonance parameters of silicon and its stable isotopes

    International Nuclear Information System (INIS)

    Story, J.S.

    1969-09-01

    The data available up to the end of November 1968 on the thermal neutron absorption cross-sections, resonance absorption integrals, and resonance parameters of silicon and its stable isotopes are collected and discussed. Estimates are given of the mean spacing of the energy levels of the compound nuclei near the neutron binding energy. It is concluded that the thermal neutron absorption cross-section and resonance absorption integral of natural silicon are not well established. The data on these two parameters are somewhat correlated, and three different assessments of the resonance integral are presented which differ over-all by a factor of 230. Many resonances have been detected by charged particle reactions which have not yet been observed in neutron cross-section measurements. One of these resonances of Si 2 8, at E n = 4 ± 5 keV might account for the large resonance integral which is derived, very uncertainly, from integral data. The principal source of the measured resonance integral of Si 3 0 has not yet been located. The thermal neutron absorption cross-section of Si 2 8 appears to result mainly from a negative energy resonance, possibly the resonance at E n = - 59 ± 5 keV detected by the Si 2 8 (d,p) reaction. (author)

  14. Charge order suppression, emergence of ferromagnetism and absence of exchange bias effect in Bi0.25Ca0.75MnO3 nanoparticles: Electron paramagnetic resonance and magnetization studies

    Science.gov (United States)

    Singh, Geetanjali; Bhat, S. V.

    2012-06-01

    We report the results of magnetization and electron paramagnetic resonance (EPR) studies on nanoparticles (average diameter ˜ 30 nm) of Bi0.25Ca0.75MnO3 (BCMO) and compare them with the results on bulk BCMO. The nanoparticles were prepared using the nonaqueous sol-gel technique and characterized by XRD and TEM analysis. Magnetization measurements were carried out with a commercial physical property measurement system (PPMS). While the bulk BCMO exhibits a charge ordering transition at ˜230 K and an antiferromagnetic (AFM) transition at ˜130 K, in the nanoparticles, the CO phase is seen to have disappeared and a transition to a ferromagnetic (FM) state is observed at Tc ˜ 120 K. However, interestingly, the exchange bias effect observed in other nanomanganite ferromagnets is absent in BCMO nanoparticles. EPR measurements were carried out in the X-band between 8 and 300 K. Lineshape fitting to a Lorentzian with two terms (accounting for both the clockwise and anticlockwise rotations of the microwave field) was employed to obtain the relevant EPR parameters as functions of temperature. The results confirm the occurrence of ferromagnetism in the nanoparticles of BCMO.

  15. Understanding the magnetic behavior of heat treated CaO-P2O5-Na2O-Fe2O3-SiO2 bioactive glass using electron paramagnetic resonance studies

    Science.gov (United States)

    Shankhwar, Nisha; Kothiyal, G. P.; Srinivasan, A.

    2014-09-01

    Bioactive glass of composition 41CaO-44SiO2-4P2O5-8Fe2O3-3Na2O has been heat treated in the temperature (TA) range of 750-1150 °C for time periods (tA) ranging from 1 h to 3 h to yield magnetic bioactive glass ceramics (MBCs). X-ray diffraction studies indicate the presence of bone mineral (hydroxyapatite and wollastonite) and magnetic (magnetite and α-hematite) phases in nanocrystalline form in the MBCs. Electron paramagnetic resonance (EPR) study was carried out to understand the variation in saturation magnetization and coercivity of the MBCs with TA and tA. These studies reveal the nature and amount of iron ions present in the MBCs and their interaction in the glassy oxide matrix as a function of annealing parameters. The deterioration in the magnetic properties of the glass heat treated above 1050 °C is attributed to the crystallization of the non-magnetic α-hematite phase. These results are expected to be useful in the application of these MBCs as thermoseeds in hyperthermia treatment of cancer.

  16. Adsorption and collective paramagnetism

    CERN Document Server

    Selwood, Pierce W

    1962-01-01

    Adsorption and Collective Paramagnetism describes a novel method for studying chemisorption. The method is based on the change in the number of unpaired electrons in the adsorbent as chemisorption occurs. The method is applicable to almost all adsorbates, but it is restricted to ferromagnetic adsorbents such as nickel, which may be obtained in the form of very small particles, that is to say, to ferromagnetic adsorbents with a high specific surface. While almost all the data used illustratively have been published elsewhere this is the first complete review of the subject. The book is addresse

  17. The Effective Resonance Integral of Thorium Oxide Rods

    Energy Technology Data Exchange (ETDEWEB)

    Weitman, J

    1962-12-15

    The effective resonance integral of thorium oxide rods has been determined as a function of their surface to mass ratio. The range of S/M values covered is 0.15 - 0.65 cm/g. An experimental technique based on the comparison of activities obtained in thermal and slowing-down neutron fluxes was employed. The shape of the resonance neutron spectrum was determined from measurements with a fast chopper and from calculations, permitting deduction of a correction factor which relates the experimental values to the ideal 1/E case. The results are summarized by the following expression: RI{sub ThO{sub 2}} (5.0 + 15.6{radical}(S/M{sub ThO{sub 2}})) {+-} 5% The main contribution to the margin of error arises from the uncertainties in the 1.5 % spectral correction applied in the 1.5 b '1/v' part deducted and in the 1520 b infinite dilution integral of gold, used as a standard. In order to compare the consistency of Dresner's first equivalence theorem and Nordheim's numerical calculations relative to our results, the resonance integral values for thorium metal rods obtained previously by Hellstrand and Weitman have been recalculated, using recent cross section and spectrum data. The new formula is Rl{sub Th} = (3.3 + 16.1{radical}(S/M{sub Th})) {+-} 5%. It differs from the old one mainly because of the proved non-1/v behaviour of the thorium cross section below the first resonance.

  18. Coupling thermal atomic vapor to an integrated ring resonator

    International Nuclear Information System (INIS)

    Ritter, R; Kübler, H; Pfau, T; Löw, R; Gruhler, N; Pernice, W H P

    2016-01-01

    Strongly interacting atom–cavity systems within a network with many nodes constitute a possible realization for a quantum internet which allows for quantum communication and computation on the same platform. To implement such large-scale quantum networks, nanophotonic resonators are promising candidates because they can be scalably fabricated and interconnected with waveguides and optical fibers. By integrating arrays of ring resonators into a vapor cell we show that thermal rubidium atoms above room temperature can be coupled to photonic cavities as building blocks for chip-scale hybrid circuits. Although strong coupling is not yet achieved in this first realization, our approach provides a key step towards miniaturization and scalability of atom–cavity systems. (paper)

  19. measurements of the absorption resonance integrals by reactor oscillator method

    International Nuclear Information System (INIS)

    Markovic, V.; Kocic, A.

    1965-12-01

    Experimental values of resonance integrals for silver vary significantly dependent on authors. That is why we have chosen this sample to measure RI. On the other hand, nuclear fuel (for example natural uranium) still represents an interesting objective for research in reactor physics. Measurements of natural uranium are done as a function of S/M. Measurements were done by amplitude reactor oscillator ROB-1/5 with precision from 0.5% - 2% dependent on the conditions of the oscillator. Measurements were completed at the heavy water reactor RB with 2% enriched uranium fuel [fr

  20. Ultrasonic series resonant converter with integrated L-C-T

    CSIR Research Space (South Africa)

    Smit, MC

    1995-01-01

    Full Text Available primary plate separation, w G bifilar primary 2EOE,NpW(h + To - T;) d C= where d plate width. Fig. 8. SPICE model of discrete component converter ~ 21 B. Spice Simulation The objective of the simulation is to show that the integrated structure... reacts in the same way as a discrete series inductor capacitor and transformer would do, and in turn agrees with the experimental results. Fig. 8 shows the SPICE circuit model of the discrete component series resonant converter. Inductance L...

  1. Size-dependent concentration of N0 paramagnetic centres in HPHT nanodiamonds

    OpenAIRE

    Yavkin, Boris V; Mamin, Georgy V; Gafurov, Marat R.; Orlinskii, Sergei B.

    2015-01-01

    Size-calibrated commercial nanodiamonds synthesized by high-pressure high-temperature (HPHT) technique were studied by high-frequency W and conventional X band electron paramagnetic resonance (EPR) spectroscopy. The numbers of spins in the studied samples were estimated. The core-shell model of the HPHT nanodiamonds was proposed to explain the observed dependence of the concentration of the N0 paramagnetic centers. Two other observed paramagnetic centers are attributed to the two types of str...

  2. Two-frequency radiospectrometer for studying paramagnetics under a strong magnetic field

    International Nuclear Information System (INIS)

    Vertii, A.A.; Gudym, I.Y.; Ivanchenko, I.V.

    1994-01-01

    A two-frequency radiospectrometer for studying electron paramagnetic resonance in the 120-150-GHz band and nuclear magnetic resonance in the 180-200-MHz band is described. The spectrometer is used to measure the properties of paramagnetics by a double-resonance technique in a magnetic field of up to 5 T at a temperature ranging from 1.7 to 20 degrees K

  3. Syntheses, X-ray structures, solid state high-field electron paramagnetic resonance, and density-functional theory investigations on chloro and aqua Mn(II) mononuclear complexes with amino-pyridine pentadentate ligands.

    Science.gov (United States)

    Hureau, Christelle; Groni, Sihem; Guillot, Régis; Blondin, Geneviève; Duboc, Carole; Anxolabéhère-Mallart, Elodie

    2008-10-20

    The two pentadentate amino-pyridine ligands L5(2) and L5(3) (L5(2) and L5(3) stand for the N-methyl-N,N',N'-tris(2-pyridylmethyl)ethane-1,2-diamine and the N-methyl-N,N',N'-tris(2-pyridylmethyl)propane-1,3-diamine, respectively) were used to synthesize four mononuclear Mn(II) complexes, namely [(L5(2))MnCl](PF6) (1(PF6)), [(L5(3))MnCl](PF6) (2(PF6)), [(L5(2))Mn(OH2)](BPh4)2 (3(BPh4)2), and [(L5(3))Mn(OH2)](BPh4)2 (4(BPh4)2). The X-ray diffraction studies revealed different configurations for the ligand L5(n) (n = 2, 3) depending on the sixth exogenous ligand and/or the counterion. Solid state high-field electron paramagnetic resonance spectra were recorded on complexes 1-4 as on previously described mononuclear Mn(II) systems with tetra- or hexadentate amino-pyridine ligands. Positive and negative axial zero-field splitting (ZFS) parameters D were determined whose absolute values ranged from 0.090 to 0.180 cm(-1). Density-functional theory calculations were performed unraveling that, in contrast with chloro systems, the spin-spin and spin-orbit coupling contributions to the D-parameter are comparable for mixed N,O-coordination sphere complexes.

  4. Electrochemical and Electron Paramagnetic Resonance Study of the Mechanism of Oxidation of Phenazine-di-N-oxide in the Presence of Isopropyl alcohol at Glassy Carbon and Single-Walled Carbon Nanotube Electrodes

    International Nuclear Information System (INIS)

    Kulakovskaya, S.I.; Kulikov, A.V.; Sviridova, L.N.; Stenina, E.V.

    2014-01-01

    Graphical abstract: - Highlights: • The mechanism of oxidation of phenazine-di-N-oxide in the presence of isopropyl alcohol was studied. • The results are explained in terms of the E 1 C 1 E 2 C 2 mechanism of the two-stage electrode process. • The total two-electron catalytic oxidation of i-PrOH in the complex with the phenazine-di-N-oxide radical cation was assumed to occur. - Abstract: The mechanism of oxidation of phenazine-di-N-oxide in the presence of isopropyl alcohol was studied by cyclic voltammetry at glassy carbon (GC) and single-walled carbon nanotubes (SWCNT) electrodes in 0.1 M LiClO 4 solutions in acetonitrile. The adsorption of phenazine-di-N-oxide at SWCNT electrode in 0.1 M LiClO 4 solution in acetonitrile was investigated by measurement of the dependence of the differential double layer capacitance of the electrode C on potential E. The effect of isopropyl alcohol on the shape of cyclic voltammograms (CVs) of phenazine-di-N-oxide and the intensity of Electron Paramagnetic Resonance (EPR) signal of its radical cation was investigated. The catalytic currents were recorded at the oxidation of phenazine-di-N-oxide at SWCNT and GC electrodes in the presence of isopropyl alcohol. The results were explained in terms of the E 1 C 1 E 2 C 2 mechanism of two-stage electrode process characterized by catalytic current recorded at the second electrode stage. The overall two-electron catalytic oxidation of isopropyl alcohol in complex with the phenazine-di-N-oxide radical cation was assumed to occur. It was shown that SWCNT electrodes can be used in the electrocatalytic oxidation of organic compounds in the presence of electrochemically generated phenazine-di-N-oxide radical cation

  5. Effects of hydrostatic pressure and temperature on the electron paramagnetic resonance spectrum of off-centre Jahn-Teller [CuF sub 4 F sub 4] sup 6 sup - complexes in SrF sub 2 crystal

    CERN Document Server

    Ulanov, V A; Hoffmann, S K; Zaripov, M M

    2003-01-01

    Pressure and temperature variations of the spin-Hamiltonian parameters and electron paramagnetic resonance (EPR) linewidths of non-central Jahn-Teller [CuF sub 4 F sub 4] sup 6 sup - complexes in SrF sub 2 crystal were studied by continuous-wave EPR. It was found that the static spin-Hamiltonian parameters, found at T = 85 K and at normal pressure (g sub | sub | = 2.491, g sub p sub e sub r sub p sub e sub n sub d sub i sub c sub u sub l sub a sub r = 2.083, a sub p sub a sub r sub a sub l sub l sub e sub l = 360, a sub p sub e sub r sub p sub e sub n sub d sub i sub c sub u sub l sub a sub r = 26, A sub x sub ' sub ' = 96, A sub y sub ' sub ' = 99, A sub z sub ' sub ' = 403 and beta sub e sub x sub p = 17 diameter), are slightly changed with hydrostatic pressure and, at T = 85 K and P = 550 MPa, become equal to g sub | sub | = 2.489, g sub p sub e sub r sub p sub e sub n sub d sub i sub c sub u sub l sub a sub r = 2.083, a sub | sub | 348, a sub p sub e sub r sub p sub e sub n sub d sub i sub c sub u sub l s...

  6. Paramagnetic centers in nanocrystalline TiC/C system

    International Nuclear Information System (INIS)

    Guskos, N.; Bodziony, T.; Maryniak, M.; Typek, J.; Biedunkiewicz, A.

    2008-01-01

    Electron paramagnetic resonance is applied to study the defect centers in nanocrystalline titanium carbide dispersed in carbon matrix (TiC x /C) synthesized by the non-hydrolytic sol-gel process. The presence of Ti 3+ paramagnetic centers is identified below 120 K along with a minor contribution from localized defect spins coupled with the conduction electron system in the carbon matrix. The temperature dependence of the resonance intensity of the latter signal indicates weak antiferromagnetic interactions. The presence of paramagnetic centers connected with trivalent titanium is suggested to be the result of chemical disorder, which can be further related to the observed anomalous behavior of conductivity, hardness, and corrosion resistance of nanocrystalline TiC x /C

  7. 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

  8. 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

  9. Electron paramagnetic resonance line shifts and line shape changes due to heisenberg spin exchange and dipole-dipole interactions of nitroxide free radicals in liquids 8. Further experimental and theoretical efforts to separate the effects of the two interactions.

    Science.gov (United States)

    Peric, Mirna; Bales, Barney L; Peric, Miroslav

    2012-03-22

    The work in part 6 of this series (J. Phys. Chem. A 2009, 113, 4930), addressing the task of separating the effects of Heisenberg spin exchange (HSE) and dipole-dipole interactions (DD) on electron paramagnetic resonance (EPR) spectra of nitroxide spin probes in solution, is extended experimentally and theoretically. Comprehensive measurements of perdeuterated 2,2,6,6-tetramethyl-4-oxopiperidine-1-oxyl (pDT) in squalane, a viscous alkane, paying special attention to lower temperatures and lower concentrations, were carried out in an attempt to focus on DD, the lesser understood of the two interactions. Theoretically, the analysis has been extended to include the recent comprehensive treatment by Salikhov (Appl. Magn. Reson. 2010, 38, 237). In dilute solutions, both interactions (1) introduce a dispersion component, (2) broaden the lines, and (3) shift the lines. DD introduces a dispersion component proportional to the concentration and of opposite sign to that of HSE. Equations relating the EPR spectral parameters to the rate constants due to HSE and DD have been derived. By employing nonlinear least-squares fitting of theoretical spectra to a simple analytical function and the proposed equations, the contributions of the two interactions to items 1-3 may be quantified and compared with the same parameters obtained by fitting experimental spectra. This comparison supports the theory in its broad predictions; however, at low temperatures, the DD contribution to the experimental dispersion amplitude does not increase linearly with concentration. We are unable to deduce whether this discrepancy is due to inadequate analysis of the experimental data or an incomplete theory. A new key aspect of the more comprehensive theory is that there is enough information in the experimental spectra to find items 1-3 due to both interactions; however, in principle, appeal must be made to a model of molecular diffusion to separate the two. The permanent diffusion model is used to

  10. Simulation of electron spin resonance spectroscopy in diverse environments: An integrated approach

    Science.gov (United States)

    Zerbetto, Mirco; Polimeno, Antonino; Barone, Vincenzo

    2009-12-01

    We discuss in this work a new software tool, named E-SpiReS (Electron Spin Resonance Simulations), aimed at the interpretation of dynamical properties of molecules in fluids from electron spin resonance (ESR) measurements. The code implements an integrated computational approach (ICA) for the calculation of relevant molecular properties that are needed in order to obtain spectral lines. The protocol encompasses information from atomistic level (quantum mechanical) to coarse grained level (hydrodynamical), and evaluates ESR spectra for rigid or flexible single or multi-labeled paramagnetic molecules in isotropic and ordered phases, based on a numerical solution of a stochastic Liouville equation. E-SpiReS automatically interfaces all the computational methodologies scheduled in the ICA in a way completely transparent for the user, who controls the whole calculation flow via a graphical interface. Parallelized algorithms are employed in order to allow running on calculation clusters, and a web applet Java has been developed with which it is possible to work from any operating system, avoiding the problems of recompilation. E-SpiReS has been used in the study of a number of different systems and two relevant cases are reported to underline the promising applicability of the ICA to complex systems and the importance of similar software tools in handling a laborious protocol. Program summaryProgram title: E-SpiReS Catalogue identifier: AEEM_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEEM_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GPL v2.0 No. of lines in distributed program, including test data, etc.: 311 761 No. of bytes in distributed program, including test data, etc.: 10 039 531 Distribution format: tar.gz Programming language: C (core programs) and Java (graphical interface) Computer: PC and Macintosh Operating system: Unix and Windows Has the code been vectorized or

  11. Integrated refractive index optical ring resonator detector for capillary electrophoresis.

    Science.gov (United States)

    Zhu, Hongying; White, Ian M; Suter, Jonathan D; Zourob, Mohammed; Fan, Xudong

    2007-02-01

    We developed a novel miniaturized and multiplexed, on-capillary, refractive index (RI) detector using liquid core optical ring resonators (LCORRs) for future development of capillary electrophoresis (CE) devices. The LCORR employs a glass capillary with a diameter of approximately 100 mum and a wall thickness of a few micrometers. The circular cross section of the capillary forms a ring resonator along which the light circulates in the form of the whispering gallery modes (WGMs). The WGM has an evanescent field extending into the capillary core and responds to the RI change due to the analyte conducted in the capillary, thus permitting label-free measurement. The resonating nature of the WGM enables repetitive light-analyte interaction, significantly enhancing the LCORR sensitivity. This LCORR architecture achieves dual use of the capillary as a sensor head and a CE fluidic channel, allowing for integrated, multiplexed, and noninvasive on-capillary detection at any location along the capillary. In this work, we used electro-osmotic flow and glycerol as a model system to demonstrate the fluid transport capability of the LCORRs. In addition, we performed flow speed measurement on the LCORR to demonstrate its flow analysis capability. Finally, using the LCORR's label-free sensing mechanism, we accurately deduced the analyte concentration in real time at a given point on the capillary. A sensitivity of 20 nm/RIU (refractive index units) was observed, leading to an RI detection limit of 10-6 RIU. The LCORR marries photonic technology with microfluidics and enables rapid on-capillary sample analysis and flow profile monitoring. The investigation in this regard will open a door to novel high-throughput CE devices and lab-on-a-chip sensors in the future.

  12. Photo-electon paramagnetic resonance and photoacoustic

    Indian Academy of Sciences (India)

    journal of. January 2002 physics pp. 101–111. Non-equilibrium effects in copper ... the EPR intensity of Nd3·ion on exposure to CVL and the kinetics involved in .... equalization of the population of + and spin states, which has the same effect as .... This gives further proof that the observed effects are not associated with mere.

  13. Analog implementation of an integral resonant control scheme

    International Nuclear Information System (INIS)

    Pereira, E; Moheimani, S O R; Aphale, S S

    2008-01-01

    Integral resonant control (IRC) has been introduced as a high performance controller design methodology for flexible structures with collocated actuator–sensor pairs. IRC has a simple structure and is capable of achieving significant damping, over several modes, while guaranteeing closed-loop stability of the system in the presence of unmodeled out-of-bandwidth dynamics. IRC can be an ideal controller for various industrial damping applications, if packaged in a simple easy-to-implement electronic module. This work proposes an analog implementation of the IRC scheme using a single Op-Amp circuit. The objective is to show that with simple analog realization of the modified IRC scheme, it is possible to damp a large number of vibration modes. A brief discussion about the modeling, circuit considerations, implementation and experimental results is presented in order to validate the usefulness and practicality of the proposed analog IRC implementation. (technical note)

  14. X-Band Electron Paramagnetic Resonance Comparison of Mononuclear Mn(IV)-oxo and Mn(IV)-hydroxo Complexes and Quantum Chemical Investigation of Mn(IV) Zero-Field Splitting.

    Science.gov (United States)

    Leto, Domenick F; Massie, Allyssa A; Colmer, Hannah E; Jackson, Timothy A

    2016-04-04

    X-band electron paramagnetic resonance (EPR) spectroscopy was used to probe the ground-state electronic structures of mononuclear Mn(IV) complexes [Mn(IV)(OH)2(Me2EBC)](2+) and [Mn(IV)(O)(OH)(Me2EBC)](+). These compounds are known to effect C-H bond oxidation reactions by a hydrogen-atom transfer mechanism. They provide an ideal system for comparing Mn(IV)-hydroxo versus Mn(IV)-oxo motifs, as they differ by only a proton. Simulations of 5 K EPR data, along with analysis of variable-temperature EPR signal intensities, allowed for the estimation of ground-state zero-field splitting (ZFS) and (55)Mn hyperfine parameters for both complexes. From this analysis, it was concluded that the Mn(IV)-oxo complex [Mn(IV)(O)(OH)(Me2EBC)](+) has an axial ZFS parameter D (D = +1.2(0.4) cm(-1)) and rhombicity (E/D = 0.22(1)) perturbed relative to the Mn(IV)-hydroxo analogue [Mn(IV)(OH)2(Me2EBC)](2+) (|D| = 0.75(0.25) cm(-1); E/D = 0.15(2)), although the complexes have similar (55)Mn values (a = 7.7 and 7.5 mT, respectively). The ZFS parameters for [Mn(IV)(OH)2(Me2EBC)](2+) were compared with values obtained previously through variable-temperature, variable-field magnetic circular dichroism (VTVH MCD) experiments. While the VTVH MCD analysis can provide a reasonable estimate of the magnitude of D, the E/D values were poorly defined. Using the ZFS parameters reported for these complexes and five other mononuclear Mn(IV) complexes, we employed coupled-perturbed density functional theory (CP-DFT) and complete active space self-consistent field (CASSCF) calculations with second-order n-electron valence-state perturbation theory (NEVPT2) correction, to compare the ability of these two quantum chemical methods for reproducing experimental ZFS parameters for Mn(IV) centers. The CP-DFT approach was found to provide reasonably acceptable values for D, whereas the CASSCF/NEVPT2 method fared worse, considerably overestimating the magnitude of D in several cases. Both methods were poor in

  15. Measurement of the effect of the lattice pitch on the effective resonance integral of natural uranium

    Energy Technology Data Exchange (ETDEWEB)

    Krcevinac, S; Takac, S [Institut za nuklearne nauke ' Boris Kidric' , Vinca, Belgrade (Yugoslavia)

    1966-07-01

    The analytical theory of resonance absorption, as well as the numerical Monte Carlo method, allows calculation of the resonance integral. However, it is based on specific approximations so it may be used accurately enough in a limited number of cases. Likewise, insufficiently accurate know ledge of the basic nuclear constants (e.g. resonance parameters, etc.) used as input data in analytical calculation, leads to inaccurate determination of the resonance integral.. Therefore, experimental determination of the effective resonance integral is still indispensable. In some cases the experimental results are used as the exclusive source of information, or as the basis for the semiempirical technique of calculation, and in others as a check of the new theoretical procedures. There are several experimental methods of direct determination of the resonance integral: the activation method (1,2), the reactor oscillator and the danger coefficient method. Indirectly, using the results of critical experiments, it is possible to determine correlated values of the effective resonance integral. The present work investigates the dependence of the effective resonance integral on the lattice pitch. Theoretically, the dependence is determined starting from Wigner's rational approximation in which the lattice is characterized by the effective ratio (S/M) {sup X}. Later this allows correlation between the lattice resonance integral and the resonance integral of the single rod (the rod in infinite medium). Using two approximations for Dancoff's factor we give the measured functional dependence of the effective resonance integral on the effective (S/M){sup X} ratio. To determine the resonance integral experimentally we used the activation method and the differential technique of measuring absorption distribution in U{sup 2}38. Since, because of the use of cadmium in determining the cadmium ratio in the fuel rod the effective lattice pitch cannot be defined with certain reliability, besides

  16. Investigation of the biochemical state of paramagnetic ions in vivo using the magnetic field dependence of 1/T1 of tissue protons (NMRD profile): applications to contrast agents for magnetic resonance imaging

    International Nuclear Information System (INIS)

    Koenig, S.H.; Brown, R.D. III; Spiller, M.; Wolf, G.L.

    1988-01-01

    Nuclear magnetic relaxation dispersion (NMRD) profiles of protons are obtained in homogenous aqueous solutions of the paramagnetic ions, Mn 2+ and Gd 3+ and their chelate and macromolecular complexes in vitro, giving information regarding the biochemical state of these ions. Similarly NMRD profiles of protons of excised rabbit tissues containing Mn 2+ and Gd 3+ complexes are obtained. These NMRD profiles are shown to be very useful for determining the fate of potentially useful paramagnetic NMR imaging contrast agents in vivo. (U.K.)

  17. Antiferromagnetic–paramagnetic state transition of NiO synthesized by pulsed laser deposition

    CSIR Research Space (South Africa)

    Nkosi, SS

    2013-01-01

    Full Text Available respectively from Raman spectroscopy study. These particle sizes are known be affected by substrate temperature during the deposition. Electron spin resonance (ESR) results demonstrated a strange antiferromagnetic to paramagnetic transition at a room...

  18. Integrated variable projection approach (IVAPA) for parallel magnetic resonance imaging.

    Science.gov (United States)

    Zhang, Qiao; Sheng, Jinhua

    2012-10-01

    Parallel magnetic resonance imaging (pMRI) is a fast method which requires algorithms for the reconstructing image from a small number of measured k-space lines. The accurate estimation of the coil sensitivity functions is still a challenging problem in parallel imaging. The joint estimation of the coil sensitivity functions and the desired image has recently been proposed to improve the situation by iteratively optimizing both the coil sensitivity functions and the image reconstruction. It regards both the coil sensitivities and the desired images as unknowns to be solved for jointly. In this paper, we propose an integrated variable projection approach (IVAPA) for pMRI, which integrates two individual processing steps (coil sensitivity estimation and image reconstruction) into a single processing step to improve the accuracy of the coil sensitivity estimation using the variable projection approach. The method is demonstrated to be able to give an optimal solution with considerably reduced artifacts for high reduction factors and a low number of auto-calibration signal (ACS) lines, and our implementation has a fast convergence rate. The performance of the proposed method is evaluated using a set of in vivo experiment data. Copyright © 2012 Elsevier Ltd. All rights reserved.

  19. TUZ, Resonance Integrals in Unresolved Region, Various Temperature, From Porter-Thomas Distribution

    International Nuclear Information System (INIS)

    Kuncir, G.F.

    1969-01-01

    1 - Nature of physical problem solved: TUZ computes resonance integrals for a wide variety of temperatures, compositions, and geometries for the unresolved resonances. 2 - Method of solution: The resonances are considered to be defined by an average over the Porter-Thomas distribution of neutron widths

  20. Vacuum Gap Microstrip Microwave Resonators for 2.5-D Integration in Quantum Computing

    International Nuclear Information System (INIS)

    Lewis, Rupert M.; Henry, Michael David; Schroeder, Katlin

    2017-01-01

    We demonstrate vacuum gap λ/2 microwave resonators as a route toward higher integration in superconducting qubit circuits. The resonators are fabricated from pieces on two silicon chips bonded together with an In-Sb bond. Measurements of the devices yield resonant frequencies in good agreement with simulations. Furthermore, we discuss creating low loss circuits in this geometry.

  1. New methodology for analytical calculation of resonance integrals in an heterogeneous medium

    International Nuclear Information System (INIS)

    Campos, T.P.R. de; Martinez, A.S.

    1986-01-01

    A new methodology for analytical calculation of Resonance Integral in a typical fuel cell is presented. The expression obtained for the Resonance Integral presents the advantage of being analytical. Its constituent terms are combinations of the well known function J(xi,β) with its partial derivatives in regard to β. This is a general expression for all types of resonance. The parameters used in this method depend on the resonance type and are obtained as a function of the parameter lambda. A simple expression, depending on resonance parameters is proposed for this variable. (Author) [pt

  2. 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.

  3. Flexible optical network components based on densely integrated microring resonators

    NARCIS (Netherlands)

    Geuzebroek, D.H.

    2005-01-01

    This thesis addresses the design, realization and characterization of reconfigurable optical network components based on multiple microring resonators. Since thermally tunable microring resonators can be used as wavelength selective space switches, very compact devices with high complexity and

  4. ZUT, Resonance Integrals in Resolved Region at Various Temperature, Escape Probability Calculation

    International Nuclear Information System (INIS)

    Kuncir, G.F.

    1984-01-01

    1 - Nature of physical problem solved: ZUT computes resonance integrals from resonance parameters for a wide variety of temperatures, compositions, and geometries for the resolved resonances. 2 - Method of solution: The form used permits specification of escape probability as a function of the lump dimension and the mean free path. The absorber term may be treated by the integral method, the narrow resonance or the infinite mass approximation. Moderator terms may be represented either by the full integral method (IM) or the asymptotic (NR) form

  5. Integrated optics ring-resonator chemical sensor with polymer transduction layer

    Science.gov (United States)

    Ksendzov, A.; Homer, M. L.; Manfreda, A. M.

    2004-01-01

    An integrated optics chemical sensor based on a ring resonator with an ethyl cellulose polymer coating has been demonstrated. The measured sensitivity to isopropanol in air is 50 ppm-the level immediately useful for health-related air quality monitoring. The resonator was fabricated using SiO2 and SixNy materials. The signal readout is based on tracking the wavelength of a resonance peak. The resonator layout optimisation for sensing applications is discussed.

  6. Measurement of the effect of the lattice pitch on the effective resonance integral of natural uranium

    Energy Technology Data Exchange (ETDEWEB)

    Krcevinac, S; Takac, S [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Yugoslavia)

    1966-04-15

    The present work investigates the dependence of the effective resonance integral on the lattice pitch. Theoretically, the dependence is determined starting from Wigner's rational approximation in which the lattice is characterized by the effective ratio (s/M). Later this allows correlation between the lattice resonance integral and the resonance integral of the single rod (the rod in infinite medium). Using two approximations for Dancoff's factor we give the measured functional dependence of the effective resonance integral on the effective (s/M) ratio. The activation method and the differential technique of measuring absorption distribution in U-238 are used to determine the resonance integral experimentally. Since the effective lattice pitch cannot be defined with certain reliability, due to the use of cadmium in determining the cadmium ratio in the fuel rod, besides other perturbing effects, the method of comparing thermal activations of U-238 and a suitable thermal detector are used to determine the cadmium ratio.

  7. Measurement of the effect of the lattice pitch on the effective resonance integral of natural uranium

    International Nuclear Information System (INIS)

    Krcevinac, S.; Takac, S.

    1966-04-01

    The present work investigates the dependence of the effective resonance integral on the lattice pitch. Theoretically, the dependence is determined starting from Wigner's rational approximation in which the lattice is characterized by the effective ratio (s/M). Later this allows correlation between the lattice resonance integral and the resonance integral of the single rod (the rod in infinite medium). Using two approximations for Dancoff's factor we give the measured functional dependence of the effective resonance integral on the effective (s/M) ratio. The activation method and the differential technique of measuring absorption distribution in U-238 are used to determine the resonance integral experimentally. Since the effective lattice pitch cannot be defined with certain reliability, due to the use of cadmium in determining the cadmium ratio in the fuel rod, besides other perturbing effects, the method of comparing thermal activations of U-238 and a suitable thermal detector are used to determine the cadmium ratio

  8. Resonant-cantilever bio/chemical sensors with an integrated heater for both resonance exciting optimization and sensing repeatability enhancement

    International Nuclear Information System (INIS)

    Yu Haitao; Li Xinxin; Gan Xiaohua; Liu Yongjing; Liu Xiang; Xu Pengcheng; Li Jungang; Liu Min

    2009-01-01

    With an integrated resonance exciting heater and a self-sensing piezoresistor, resonant micro-cantilever bio/chemical sensors are optimally designed and fabricated by micromachining techniques. This study is emphasized on the optimization of the integrated heating resistor. Previous research has put the heater at either the cantilever clamp end, the midpoint or the free end. Aiming at sufficiently high and stable resonant amplitude, our research indicates that the optimized location of the thermal-electric exciting resistor is the clamp end instead of other positions. By both theoretical analysis and resonance experiments where three heating resistors are placed at the three locations of the fabricated cantilever, it is clarified that the clamp end heating provides the most efficient resonance excitation in terms of resonant amplitude, Q-factor and resonance stability. Besides, the optimized combination of dc bias and ac voltage is determined by both analysis and experimental verification. With the optimized heating excitation, the resonant cantilever is used for biotin–avidin-specific detection, resulting in a ±0.1 Hz ultra-low noise floor of the frequency signal and a 130 fg mass resolution. In addition to resonance excitation, the heater is used to heat up the cantilever for speed-up desorption after detection that helps rapid and repeated sensing to chemical vapor. The clamp end is determined (by simulation) as the optimal heating location for uniform temperature distribution on the cantilever. Using the resonant cantilever, a rapid and repeated sensing experiment on dimethyl methylphosphonate (DMMP) vapor shows that a short-period heating at the detection interval significantly quickens the signal recovery and enhances the sensing repeatability

  9. From VHF to UHF CMOS-MEMS Monolithically Integrated Resonators

    DEFF Research Database (Denmark)

    Teva, Jordi; Berini, Abadal Gabriel; Uranga, A.

    2008-01-01

    This paper presents the design, fabrication and characterization of microresonators exhibiting resonance frequencies in the VHF and UHF bands, fabricated using the available layers of the standard and commercial CMOS technology, AMS-0.35mum. The resonators are released in a post-CMOS process cons...

  10. Paramagnetic epoxy resin

    Directory of Open Access Journals (Sweden)

    E. C. Vazquez Barreiro

    2017-01-01

    Full Text Available This work illustrates that macrocycles can be used as crosslinking agents for curing epoxy resins, provided that they have appropriate organic functionalities. As macrocycles can complex metal ions in their structure, this curing reaction allows for the introduction of that metal ion into the resin network. As a result, some characteristic physical properties of the metallomacrocycle could be transferred to the new material. The bisphenol A diglycidyl ether (BADGE, n = 0 and hemin (a protoporphyrin IX containing the Fe(III ion, and an additional chloride ligand have been chosen. The new material has been characterized by differential scanning calorimetry (DSC, thermogravimetric analysis (TGA, Fourier Transform Infrared (FT-IR, Nuclear Magnetic Resonance (NMR, Transmission Electron Microscopy (TEM, and magnetic susceptibility measurements. Fe(III remains in the high-spin state during the curing process and, consequently, the final material exhibits the magnetic characteristics of hemin. The loss of the chlorine atom ligand during the cure of the resin allows that Fe(III can act as Lewis acid, catalyzing the crosslinking reactions. At high BADGE n = 0/hemin ratios, the formation of ether and ester bonds occurs simultaneously during the process.

  11. The effect of non-uniform fuel rod temperatures on effective resonance integrals

    International Nuclear Information System (INIS)

    Reichel, A.

    1961-06-01

    The effective resonance integral for heterogeneous lattices can be reduced to the effective resonance integral for an equivalent homogeneous system with a fairly well defined error depending on lump size and geometry. This report investigates the effect of a radial parabolic temperature variation in cylindrical lumps on the equivalent homogeneous effective resonance integral. Also determined is the equivalent uniform temperature to be taken in the usual formulae to allow for non-uniform fuel rod temperature. This effective temperature is found to be T eff. = T s + 4/9 (T c - T s ) where T s and T c are the surface and central temperatures of the lump. (author)

  12. Set up of a method for the adjustment of resonance parameters on integral experiments

    International Nuclear Information System (INIS)

    Blaise, P.

    1996-01-01

    Resonance parameters for actinides play a significant role in the neutronic characteristics of all reactor types. All the major integral parameters strongly depend on the nuclear data of the isotopes in the resonance-energy regions.The author sets up a method for the adjustment of resonance parameters taking into account the self-shielding effects and restricting the cross section deconvolution problem to a limited energy region. (N.T.)

  13. Paramagnetic metal complexes as potential relaxation agents for NMR imaging

    International Nuclear Information System (INIS)

    Coroiu, Ilioara; Demco, D. E.; Darabont, Al.; Bogdan, M.

    1997-01-01

    The development of nuclear magnetic resonance (NMR) imaging technique as a clinical diagnostic modality has prompted the need for a new class of pharmaceuticals. These drugs must be administered to a patient in order to enhance the image contrast between the normal and diseased tissue and/or indicate the status of organ function or blood flow. Paramagnetic compounds are presently undergoing extensive evaluation as contrast agents in magnetic resonance imaging (MRI). These agents increase contrast in MRI by differentially localizing in tissue where they increase the relaxation rates of nearby water protons. The longitudinal R 1 and transverse R 2 relaxivities were measured as a function of molar concentrations for some new paramagnetic complexes like the following: dysprosium, erbium and gadolinium citrates, gadolinium methylene diphosphonate, dysprosium and gadolinium iminodiacetate, manganese para-aminobenzoate and copper nicotinate. The available theoretical approaches for quantitative understanding are presented. (authors)

  14. Dynamical magnetic response of paramagnetic CeFe-2

    International Nuclear Information System (INIS)

    Rainford, B.D.; McK Paul, D.; Warwick Univ., Coventry

    1988-01-01

    Inelastic neutron scattering has been used to study the energy dependence of the paramagnetic response from CeFe 2 . Our results, when integrated over energy, are in excellent agreement with the polarised neutron experiments of Deportes et al., but the correlation length obtained by fitting the data to a double Lorentzian scattering function is significantly smaller than that derived previously

  15. Measurement of resonance integral of the 90Sr(n,γ)91Sr reaction

    International Nuclear Information System (INIS)

    Nakamura, Shoji; Furutaka, Kazuyoshi; Wada, Hiroaki; Katoh, Toshio; Harada, Hideo; Fujii, Toshiyuki; Yamana, Hajimu

    2001-01-01

    To obtain fundamental data for research on nuclear transmutation method of radioactive wastes, the resonance integral (I 0 ) of the 90 Sr(n,γ) 91 Sr reaction was measured with an activation method. (author)

  16. The evaluated neutron cross sections and resonance integrals of fission products with Z = 57-62

    International Nuclear Information System (INIS)

    Fedorova, A.F.; Pisanko, Zh.I.; Novoselov, G.M.

    1976-01-01

    Neutron cross sections at a neutron velocity of V=2200 m/s, and resonance integrals for fission products with Z=57-71 are estimated. In obtaining the recommended values the results of the neutron cross sections and resonance integrals for elements used as references were normalized in accordance with the latest adjusted values. In the course of estimation, preference was given to the more accurate methods for obtaining the measured values and to the more recent investigations

  17. The evaluated neutron cross sections and resonance integrals of fission products with Z=63-71

    International Nuclear Information System (INIS)

    Fedorova, A.F.; Pisanko, Zh.I.; Novoselov, G.M.

    1976-01-01

    Neutron cross sections at a neutron velocity of V=2200 m/s, and the resonance integrals for fission products with Z=63-71 are estimated. In obtaining the recommended values the results were normalized of the neutron cross sections and resonance integrals for elements used as references in accordance with the latest adjusted values. In the course of estimation, preference was given to the more accurate measuring methods and the more recent investigations. Scientific publications up to 1975 have been used

  18. Model for paramagnetic Fermi systems

    International Nuclear Information System (INIS)

    Ainsworth, T.L.; Bedell, K.S.; Brown, G.E.; Quader, K.F.

    1983-01-01

    We develop a mode for paramagnetic Fermi liquids. This model has both direct and induced interactions, the latter including both density-density and current-current response. The direct interactions are chosen to reproduce the Fermi liquid parameters F/sup s/ 0 , F/sup a/ 0 , F/sup s/ 1 and to satify the forward scattering sum rule. The F/sup a/ 1 and F/sup s/,a/sub l/ for l>1 are determined self-consistently by the induced interactions; they are checked aginst experimental determinations. The model is applied in detail to liquid 3 He, using data from spin-echo experiments, sound attenuation, and the velocities of first and zero sound. Consistency with experiments gives definite preferences for values of m. The model is also applied to paramagnetic metals. Arguments are given that this model should provide a basis for calculating effects of magnetic fields

  19. Size-dependent concentration of N0 paramagnetic centres in HPHT nanodiamonds

    Directory of Open Access Journals (Sweden)

    B.V. Yavkin, G.V. Mamin, M.R. Gafurov, S.B. Orlinskii

    2015-12-01

    Full Text Available Size-calibrated commercial nanodiamonds synthesized by high-pressure high-temperature (HPHT technique were studied by high-frequency W- and conventional X-band electron paramagnetic resonance (EPR spectroscopy. The numbers of spins in the studied samples were estimated. The core-shell model of the HPHT nanodiamonds was proposed to explain the observed dependence of the concentration of the N0 paramagnetic centers. Two other observed paramagnetic centers are attributed to the two types of structures in the nanodiamond shell.

  20. Control of integrated micro-resonator wavelength via balanced homodyne locking.

    Science.gov (United States)

    Cox, Jonathan A; Lentine, Anthony L; Trotter, Douglas C; Starbuck, Andrew L

    2014-05-05

    We describe and experimentally demonstrate a method for active control of resonant modulators and filters in an integrated photonics platform. Variations in resonance frequency due to manufacturing processes and thermal fluctuations are corrected by way of balanced homodyne locking. The method is compact, insensitive to intensity fluctuations, minimally disturbs the micro-resonator, and does not require an arbitrary reference to lock. We demonstrate long-term stable locking of an integrated filter to a laser swept over 1.25 THz. In addition, we show locking of a modulator with low bit error rate while the chip temperature is varied from 5 to 60° C.

  1. Significantly improving nuclear resonance fluorescence non-destructive assay by using the integral resonance transmission method and photofission

    International Nuclear Information System (INIS)

    Angell, Christopher T.; Hayakawa, Takehito; Shizuma, Toshiyuki; Hajima, Ryoichi

    2013-01-01

    Non-destructive assay (NDA) of 239 Pu in spent nuclear fuel or melted fuel using a γ-ray beam is possible using self absorption and the integral resonance transmission method. The method uses nuclear resonance absorption where resonances in 239 Pu remove photons from the beam, and the selective absorption is detected by measuring the decrease in scattering in a witness target placed in the beam after the fuel, consisting of the isotope of interest, namely 239 Pu. The method is isotope specific, and can use photofission or scattered γ-rays to assay the 239 Pu. It overcomes several problems related to NDA of melted fuel, including the radioactivity of the fuel, and the unknown composition and geometry. This talk will explain the general method, and how photofission can be used to assay specific isotopes, and present example calculations. (author)

  2. Enhanced Wireless Power Transmission Using Strong Paramagnetic Response.

    Science.gov (United States)

    Ahn, Dukju; Kiani, Mehdi; Ghovanloo, Maysam

    2014-03-01

    A method of quasi-static magnetic resonant coupling has been presented for improving the power transmission efficiency (PTE) in near-field wireless power transmission, which improves upon the state of the art. The traditional source resonator on the transmitter side is equipped with an additional resonator with a resonance frequency that is tuned substantially higher than the magnetic field excitation frequency. This additional resonator enhances the magnetic dipole moment and the effective permeability of the power transmitter, owing to a phenomenon known as the strong paramagnetic response. Both theoretical calculations and experimental results show increased PTE due to amplification of the effective permeability. In measurements, the PTE was improved from 57.8% to 64.2% at the nominal distance of 15 cm when the effective permeability was 2.6. The power delivered to load was also improved significantly, with the same 10 V excitation voltage, from 0.38 to 5.26 W.

  3. High Frequency LLC Resonant Converter with Magnetic Shunt Integrated Planar Transformer

    DEFF Research Database (Denmark)

    Li, Mingxiao; Ouyang, Ziwei; Andersen, Michael A. E.

    2018-01-01

    High Frequency LLC requires a smaller resonant inductance which is usually implemented by transformer leakage inductance. However, this small resonant inductance is difficult to deal with a wide input voltage range. This paper proposes a new method to implement a larger resonant inductance by using...... a magnetic shunt integrated into planar transformer. The switching frequency can be greatly narrowed by designing a smaller inductance ratio of magnetizing inductance to resonant inductance. Since this method can well deal with a wide input voltage range without adding extra inductor and increasing the size...... of the transformer, the power density can be improved. The precise leakage inductance calculation method for this transformer and detailed LLC converter design procedure are presented. A 280-380V and 48V-100W half bridge LLC resonant converter with 1 MHz resonant frequency is built to verify the design methodology....

  4. Resonance integral analytical calculation considering shadowing effect. Calculo analitico da integral de ressonancia considerando o efeito de sombreamento

    Energy Technology Data Exchange (ETDEWEB)

    Monteiro, M A.M. [NUCLEN, Rio de Janeiro, RJ (Brazil); Martinez, A S [Universidade Federal, Rio de Janeiro, RJ (Brazil). Coordenacao dos Programas de Pos-graduacao de Engenharia

    1990-01-01

    It is presented a method for the Resonance Integral Calculation in the fuel and moderator regions, including the shadowing effect. This effect appears due to the presence of several fuel rods in a infinite moderator region. The method is based on the approximations to the J ({xi}, {beta}) function and theirs partial derivatives in relation to {beta}. The dependence of the Resonance Integral in the J ({xi}, {beta}) comes from the rational approximation to the neutron escape probability. The final results were obtained in a very simple and fast way, and they show the good accuracy of the method. (author).

  5. Non-integrability of first order resonances in Hamiltonian systems in three degrees of freedom

    Science.gov (United States)

    Christov, Ognyan

    2012-02-01

    The normal forms of the Hamiltonian 1:2: ω resonances to degree three for ω = 1, 3, 4 are studied for integrability. We prove that these systems are non-integrable except for the discrete values of the parameters which are well known. We use the Ziglin-Morales-Ramis method based on the differential Galois theory.

  6. Photo-Detectors Integrated with Resonant Tunneling Diodes

    Directory of Open Access Journals (Sweden)

    José M. L. Figueiredo

    2013-07-01

    Full Text Available We report on photo-detectors consisting of an optical waveguide that incorporates a resonant tunneling diode (RTD. Operating at wavelengths around 1.55 μm in the optical communications C band we achieve maximum sensitivities of around 0.29 A/W which is dependent on the bias voltage. This is due to the nature of RTD nonlinear current-voltage characteristic that has a negative differential resistance (NDR region. The resonant tunneling diode photo-detector (RTD-PD can be operated in either non-oscillating or oscillating regimes depending on the bias voltage quiescent point. The oscillating regime is apparent when the RTD-PD is biased in the NDR region giving rise to electrical gain and microwave self-sustained oscillations Taking advantage of the RTD’s NDR distinctive characteristics, we demonstrate efficient detection of gigahertz (GHz modulated optical carriers and optical control of a RTD GHz oscillator. RTD-PD based devices can have applications in generation and optical control of GHz low-phase noise oscillators, clock recovery systems, and fiber optic enabled radio frequency communication systems.

  7. Sound Transmission Loss Through a Corrugated-Core Sandwich Panel with Integrated Acoustic Resonators

    Science.gov (United States)

    Schiller, Noah H.; Allen, Albert R.; Zalewski, Bart F; Beck, Benjamin S.

    2014-01-01

    The goal of this study is to better understand the effect of structurally integrated resonators on the transmission loss of a sandwich panel. The sandwich panel has facesheets over a corrugated core, which creates long aligned chambers that run parallel to the facesheets. When ports are introduced through the facesheet, the long chambers within the core can be used as low-frequency acoustic resonators. By integrating the resonators within the structure they contribute to the static load bearing capability of the panel while also attenuating noise. An analytical model of a panel with embedded resonators is derived and compared with numerical simulations. Predictions show that acoustic resonators can significantly improve the transmission loss of the sandwich panel around the natural frequency of the resonators. In one configuration with 0.813 m long internal chambers, the diffuse field transmission loss is improved by more than 22 dB around 104 Hz. The benefit is achieved with no added mass or volume relative to the baseline structure. The embedded resonators are effective because they radiate sound out-of-phase with the structure. This results in destructive interference, which leads to less transmitted sound power.

  8. Indium phosphide-based monolithically integrated PIN waveguide photodiode readout for resonant cantilever sensors

    Energy Technology Data Exchange (ETDEWEB)

    Siwak, N. P. [Department of Electrical and Computer Engineering, Institute for Systems Research, University of Maryland, College Park, Maryland 20742 (United States); Laboratory for the Physical Sciences, 8050 Greenmead Drive, College Park, Maryland 20740 (United States); Fan, X. Z.; Ghodssi, R. [Department of Electrical and Computer Engineering, Institute for Systems Research, University of Maryland, College Park, Maryland 20742 (United States); Kanakaraju, S.; Richardson, C. J. K. [Laboratory for the Physical Sciences, 8050 Greenmead Drive, College Park, Maryland 20740 (United States)

    2014-10-06

    An integrated photodiode displacement readout scheme for a microelectromechanical cantilever waveguide resonator sensing platform is presented. III-V semiconductors are used to enable the monolithic integration of passive waveguides with active optical components. This work builds upon previously demonstrated results by measuring the displacement of cantilever waveguide resonators with on-chip waveguide PIN photodiodes. The on-chip integration of the readout provides an additional 70% improvement in mass sensitivity compared to off-chip photodetector designs due to measurement stability and minimized coupling loss. In addition to increased measurement stability, reduced packaging complexity is achieved due to the simplicity of the readout design. We have fabricated cantilever waveguides with integrated photodetectors and experimentally characterized these cantilever sensors with monolithically integrated PIN photodiodes.

  9. Simulation thermique de l'évolution diagénétique des kérogènes : étude par résonance paramagnétique électronique Thermal Simulation of the Diagenetic Evolution of Kerogens: Electron Paramagnetic Resonance Analysis

    Directory of Open Access Journals (Sweden)

    Villey M.

    2006-11-01

    Full Text Available Dans cet article sont exposés les résultats obtenus en résonance paramagnétique électronique (RPE sur des séries chauffées en laboratoire, d'échantillons de kérogènes, illustrant les trois lignées évolutives. L'évolution de ces kérgènes est caractérisée par la susceptibilité paramagnétique, la largeur et la forme de la raie RPE et le facteur de décomposition spectrale g. Ces résultats sont, d'une part comparés à ceux obtenus (sur les mêmes échantillons en microscopie électronique à haute résolution, en spectroscopie infra-rouge, en analyse thermique et élémentaire, d'autre part confrontés aux données RPE de kérogènes différents précédemment étudiés. Enfin, le modèle d'évolution d'un carbonisat proposé par la microscopie électronique est ici complété. This article describes the results obtained by electron paramagnetic resonance (EPR analysis of heated series of kerogen samples in the laboratory to illustrate three evolutive lines. The evolution of these kerogens is characterized by paramagnet susceptibility, the width and shape of the EPR line and the spectral decomposition factor g. These results are compared with those obtained (with the same samples by high-resolution electron microscopy, infrared spectroscopy and thermal and elemental analysis. They are also compared with EPR data from previous kerogen analyses. The evolution model of a carbonizate proposed by electron microscopy is completed here.

  10. Micro-resonators based on integrated polymer technology for optical sensing

    OpenAIRE

    Girault , Pauline; Lemaitre , Jonathan; Guendouz , Mohammed; Lorrain , Nathalie; Poffo , Luiz; Gadonna , Michel; Bosc , Dominique

    2014-01-01

    International audience; Research on sensors has experienced a noticeable development over the last decades especially in label free optical biosensors. However, compact sensors without markers for rapid, reliable and inexpensive detection of various substances induces a significant research of new technological solutions. The context of this work is the development of a sensor based on easily integrated and inexpensive micro-resonator (MR) component in integrated optics, highly sensitive and ...

  11. INTER, ENDF/B Thermal Cross-Sections, Resonance Integrals, G-Factors Calculation

    International Nuclear Information System (INIS)

    Dunford, Charles L.

    2007-01-01

    1 - Description of program or function: INTER calculates thermal cross sections, g-factors, resonance integrals, fission spectrum averaged cross sections and 14.0 MeV (or other energy) cross sections for major reactions in an ENDF-6 or ENDF-5 format data file. Version 7.01 (Jan 2005): set success flag after return from beginning. 2 - Method of solution: INTER performs integrations by using the trapezoidal rule

  12. Measurement and Evaluation of the Activation Resonance Integral of 146Nd, 148Nd and 150Nd

    International Nuclear Information System (INIS)

    Ricabarra, M. D.; Turjanski, R.; Ricabarra, G. H.

    2012-01-01

    Values of the ratio of the reduced activation resonance integral to the thermal cross section, I'/σ 0 of 146 Nd, 148 Nd and 150 Nd were determined relative to gold by measuring cadmium ratios. A lithium-drifted germanium gamma ray spectrometer was used to resolve the activities of the irradiated samples. The results are for 146 Nd I'/σ 0 = 1.42±0.1 0 and with an assumed σ 0 = 1.4 barn, I' = 1 .99±0.20; for 148 Nd I'/ σ 0 = 4.22±0.1 4 and with an assumed σ 0 = 2.5 barn, I' = 10.5±0. 9 barn, and for 150 Nd I'/σ 0 = 13.7±0. 8 and with an assumed σ 0 = 1.2 barn, I' = 16.4±2.8. The resolved and unresolved epithermal integrals of 146 Nd, 148 Nd and 150 Nd were calculated. Values of the spectral correction factor were also calculated, so the resonance integral could be obtained from the epithermal integral data measured in our reactor spectrum in this experiment. Epithermal integral and spectral correction factors are listed in the text. The most important result of this investigation is that the 148 Nd activation reduced resonance integral is about half of the previously recommended value and consequently the radiative width for 148 Nd is also about half of the previously accepted value. (author)

  13. Influence of the resonance integral value on the fuel cycle characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Graziani, G; Trauwaert, E

    1972-04-24

    The problem that is considered here is to determine what can be done about a variation in resonance integral when the complete geometry of the reactor and of the fuel elements are fixed, leaving as only free parameters the amount of heavy metal and the enrichment to put in the fuel pins.

  14. Low insertion loss SOI microring resonator integrated with nano-taper couplers

    DEFF Research Database (Denmark)

    Pu, Minhao; Frandsen, Lars Hagedorn; Ou, Haiyan

    2009-01-01

    We demonstrate a microring resonator working at TM mode integrated with nano-taper couplers with 3.6dB total insertion loss. The measured insertion loss of the nano-taper coupler was only 1.3dB for TM mode....

  15. Resonance integral calculations for isolated rods containing oxides of 238U and 232Th

    International Nuclear Information System (INIS)

    Baker, V.C.; Marable, J.H.

    1980-02-01

    Results of resonance integral calculations for UO 2 and ThO 2 isolated rods are discussed. The calculations were performed with ENDF/B-IV cross-section data and the multigroup transport code ANISN. The findings reported demonstrate by comparison with semiempirical relationships (based on experimentally derived results) the suitability of the method used for determining resonance integrals. The calculations were based on a cylindrical rod in an H 2 O moderator of large radius. Multigroup cross sections were obtained by a MINX-SPHINX-AMMPX sequence, and ANISN was used to account for the neutron flux and capture rates. A special approach was used to determine a neutron source distribution such that the flux in the moderator region was forced to behave in an asymptotic way; thus, the ideal resonance integral experiment could be calculated. The UO 2 resonance integrals calculated were in exceptionally good agreement with experimental values based on isolated rods. The ThO 2 results were approximately 6% lower than experimental values, and efforts to understand the discrepancy are discussed. 8 figures, 7 tables

  16. Magnetically integrated high step-up resonant DC-DC converter for distributed photovoltaic systems

    DEFF Research Database (Denmark)

    Vinnikov, Dmitri; Chub, Andrii; Liivik, Elizaveta

    2017-01-01

    In this paper magnetically integrated resonant single-switch quasi-Z-source DC-DC converter is evaluated as a candidate topology for the low-cost photovoltaic microconverter. The derivation of the topology and its basic operation principle are explained. Generalized design guidelines...

  17. Monolithic integration of a resonant tunneling diode and a quantum well semiconductor laser

    Science.gov (United States)

    Grave, I.; Kan, S. C.; Griffel, G.; Wu, S. W.; Sa'Ar, A.

    1991-01-01

    A monolithic integration of a double barrier AlAs/GaAs resonant tunneling diode and a GaAs/AlGaAs quantum well laser is reported. Negative differential resistance and negative differential optical response are observed at room temperature. The device displays bistable electrical and optical characteristics which are voltage controlled. Operation as a two-state optical memory is demonstrated.

  18. Thermal neutron cross sections and resonance integrals for the 1994 handbook of chemistry and physics

    International Nuclear Information System (INIS)

    Holden, N.E.

    1994-01-01

    A re-evaluation of all thermal neutron cross sections and neutron resonance integrals has been performed, utilizing the previous database of the ''Barn Book'' and all of the more recently published experiments. Only significant changes or previously undetermined values are recorded in this report. The source for each value is also recorded in the accompanying table

  19. Electron paramagnetic resonance study of radicals formed by radiolysis at 77 K of nitroalkanes and of their solutions in organic glasses. Chromatography analysis of radiolysis products of nitromethane in ethanol solution in a vitreous medium

    International Nuclear Information System (INIS)

    Rosilio, C.

    1969-01-01

    With a view to explaining the formation of the final products resulting from the photolysis and the radiolysis of nitro-alkanes, we have attempted to identify the paramagnetic species formed as intermediates during the radiolysis. Our work has covered the structure and the reactivity of the radicals formed by 7 irradiation of the nitrogen containing derivatives at 77 K, and on the mechanism of formation and of disappearance of these radicals in the various matrices used. The radicals resulting from the removal of a hydrogen atom in the α position of the NO 2 group, and the radicals resulting from addition reactions on the nitrogen group characterized by an unpaired electron on the nitrogen have been identified, either during the radiolysis of pure nitroalkanes, or during the radiolysis of nitro-alkanes in solution in organic glasses at 77 K. A study has been made of the conformation and the movements of radicals in the matrices, and the mechanism of formation of the observed radicals produced generally by the capture by the nitro-alkanes of primary radiolysis species. The nitro-alkanes in ethanol solution can behave as traps both for electrons and for free radicals. The study of the radiolysis of nitro-alkanes in solution in a polar ethanol glass has been completed with chemical analyses on the final radiolysis products; it has been possible to deduce the capture efficiency of trapped electrons and of free radicals by nitro-alkanes in ethanol. For this we have determined the radio-chemical yields of hydrogen, acetaldehyde and glycol as a function of the capture agent concentration, for the nitro-methane-ethanol system. A mechanism for the disappearance of the observed radicals is proposed. (author) [fr

  20. On kinetics of paramagnetic radiation defects accumulation in beryllium ceramics; O kinetike nakopleniya paramagnitnykh radiatsionnykh defektov v berillievykh keramikakh

    Energy Technology Data Exchange (ETDEWEB)

    Polyakov, A I; Ryabikin, Yu A; Zashkvara, O V; Bitenbaev, M I; Petykhov, Yu V [Fiziko-Tekhnicheskij Inst., Almaty (Kazakhstan); Inst. Atomnoj Ehnergii, Kurchatov (Kazakhstan)

    1999-07-01

    Results of paramagnetic radiation defects concentration dependence study in beryllium ceramics from gamma-irradiation dose ({sup 60}Co) within interval 0-100 Mrem are cited. Obtained dose dependence has form of accumulation curve with saturation typical of for majority of solids (crystals, different polymers, organic substances and others) , in which under irradiation occur not only formation of paramagnetic radiation defects, but its destruction due to recombination and interaction with radiation fields. Analysis of accumulation curve by the method of distant asymptotics allows to determine that observed in gamma-irradiated beryllium ceramics double line of electron spin resonance is forming of two types of paramagnetic radiation defects. It was defined, that sum paramagnetic characteristics of beryllium ceramics within 1-100 Mrad gamma- irradiation dose field change insignificantly and define from first type of paramagnetic radiation defects.

  1. 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....

  2. Multi-photon Rabi oscillations in high spin paramagnetic impurity

    International Nuclear Information System (INIS)

    Bertaina, S; Groll, N; Chen, L; Chiorescu, I

    2011-01-01

    We report on multiple photon monochromatic quantum oscillations (Rabi oscillations) observed by pulsed EPR (Electron Paramagnetic Resonance) of Mn 2+ (S = 5/2) impurities in MgO. We find that when the microwave magnetic field is similar or large than the anisotropy splitting, the Rabi oscillations have a spectrum made of many frequencies not predicted by the S = l/2 Rabi model. We show that these new frequencies come from multiple photon coherent manipulation of the multi-level spin impurity. We develop a model based on the crystal field theory and the rotating frame approximation, describing the observed phenomenon with a very good agreement.

  3. Development of polarization magneto-optics of paramagnetic crystals

    International Nuclear Information System (INIS)

    Zapasskij, V.S.; Feofilov, P.P.

    1975-01-01

    The present status of the polarization magnetooptics of crystals containing paramagnetic ion impurities is reviewed. The paper discusses methods of measurement of circular magnetic anisotropy and results obtained in recent years in the field of conventional magnetooptical studies, e.g., magnetooptical activity in absorption spectra for intrinsic and impurity defects in crystals, luminescence magnetic circular polarization, anisotropy of magnetooptical activity in cubic crystals. The main emphasis is placed on new trends in polarization magnetooptics: studies of interactions of a spin system with a lattice, in particular, spin-lattice relaxation and spin memory effect, experiments in the double radiooptical resonance, studies of optical spin relaxation, nonlinear magnetooptical effects, etc

  4. Evaluation of thermal neutron cross-sections and resonance integrals of protactinium, americium, curium, and berkelium isotopes

    International Nuclear Information System (INIS)

    Belanova, T.S.

    1994-12-01

    Data on the thermal neutron fission and capture cross-sections as well as their corresponding resonance integrals are reviewed and analysed. The data are classified according to the form of neutron spectra under investigation. The weighted mean values of the cross-sections and resonance integrals for every type of neutron spectra were adopted as evaluated data. (author). 87 refs, 2 tabs

  5. An NMR strategy for fragment-based ligand screening utilizing a paramagnetic lanthanide probe

    International Nuclear Information System (INIS)

    Saio, Tomohide; Ogura, Kenji; Shimizu, Kazumi; Yokochi, Masashi; Burke, Terrence R.; Inagaki, Fuyuhiko

    2011-01-01

    A nuclear magnetic resonance-based ligand screening strategy utilizing a paramagnetic lanthanide probe is presented. By fixing a paramagnetic lanthanide ion to a target protein, a pseudo-contact shift (PCS) and a paramagnetic relaxation enhancement (PRE) can be observed for both the target protein and its bound ligand. Based on PRE and PCS information, the bound ligand is then screened from the compound library and the structure of the ligand–protein complex is determined. PRE is an isotropic paramagnetic effect observed within 30 Å from the lanthanide ion, and is utilized for the ligand screening in the present study. PCS is an anisotropic paramagnetic effect providing long-range (∼40 Å) distance and angular information on the observed nuclei relative to the paramagnetic lanthanide ion, and utilized for the structure determination of the ligand–protein complex. Since a two-point anchored lanthanide-binding peptide tag is utilized for fixing the lanthanide ion to the target protein, this screening method can be generally applied to non-metal-binding proteins. The usefulness of this strategy was demonstrated in the case of the growth factor receptor-bound protein 2 (Grb2) Src homology 2 (SH2) domain and its low- and high-affinity ligands.

  6. "Cul-de-sac" microstrip resonators for high-speed integrated optical commutator switches

    Science.gov (United States)

    Jaeger, Nicolas A.; Chen, Mingche

    1993-04-01

    A novel microstrip resonator structure for use with integrated Y-branch optical modulators fabricated in Ti:LiNbO3 is proposed. The legs of the structure are intended to act as the electrodes of the modulator, with light being directed into each of the output waveguides of the Y-branch on alternate half-cycles of the standing wave excited in the resonator; forming an optical commutator switch. Such resonators having Al2O3 substrates were designed, fabricated, and tested. Measurements on one such resonator, operating at 7.12 GHz and having an unloaded quality factor of 123, indicating that 50 V should develop across the ends of its legs for 35 mW dissipated power; the corresponding values, from the model used to design the resonator, were 179, 50 V,and 24 mW, respectively. Using the model it is shown that a similar resonator fabricated on LiNbO3 should be able to develop about 50 V for 100 mW dissipated power at 15 GHz.

  7. Wireless passive polymer-derived SiCN ceramic sensor with integrated resonator/antenna

    Science.gov (United States)

    Li, Yan; Yu, Yuxi; San, Haisheng; Wang, Yansong; An, Linan

    2013-10-01

    This paper presents a passive wireless polymer-derived silicon carbonitride (SiCN) ceramic sensor based on cavity radio frequency resonator together with integrated slot antenna. The effect of the cavity sensor dimensions on the Q-factor and resonant frequency is investigated by numerical simulation. A sensor with optimal dimensions is designed and fabricated. It is demonstrated that the sensor signal can be wirelessly detected at distances up to 20 mm. Given the high-temperature stability of the SiCN, the sensor is very promising for high-temperature wireless sensing applications.

  8. Decay of paramagnetic centers in polyacetylene

    International Nuclear Information System (INIS)

    Hola, O.

    1994-01-01

    The time dependences of the relative concentration of spins in irradiated and unirradiated samples of polyacetylene have been studied. Similar courses of the decay of paramagnetic centers were observed in both types of samples. (author) 6 refs.; 1 fig

  9. Integrated phononic crystal resonators based on adiabatically-terminated phononic crystal waveguides

    Directory of Open Access Journals (Sweden)

    Razi Dehghannasiri

    2016-12-01

    Full Text Available In this letter, we demonstrate a new design for integrated phononic crystal (PnC resonators based on confining acoustic waves in a heterogeneous waveguide-based PnC structure. In this architecture, a PnC waveguide that supports a single mode at the desired resonance frequencies is terminated by two waveguide sections with no propagating mode at those frequencies (i.e., have mode gap. The proposed PnC resonators are designed through combining the spatial-domain and the spatial-frequency domain (i.e., the k-domain analysis to achieve a smooth mode envelope. This design approach can benefit both membrane-based and surface-acoustic-wave-based architectures by confining the mode spreading in k-domain that leads to improved electromechanical excitation/detection coupling and reduced loss through propagating bulk modes.

  10. Symmetric Imidazolium-Based Paramagnetic Ionic Liquids

    Science.gov (United States)

    2017-11-29

    Charts N/A Unclassified Unclassified Unclassified SAR 14 Kamran Ghiassi N/A 1 Symmetric Imidazolium-Based Paramagnetic Ionic Liquids Kevin T. Greeson...NUMBER (Include area code) 29 November 2017 Briefing Charts 01 November 2017 - 30 November 2017 Symmetric Imidazolium-Based Paramagnetic Ionic ... Liquids K. Greeson, K. Ghiassi, J. Alston, N. Redeker, J. Marcischak, L. Gilmore, A. Guenthner Air Force Research Laboratory (AFMC) AFRL/RQRP 9 Antares

  11. Electron paramagnetic resonance of Na, [(FeEDTA){sub 2}oJ-12H{sub 2}0] crystal electrons; Ressonancia paramagnetica de eletrons de cristais de Na, [(FeEDTA){sub 2}oJ-12H{sub 2}0

    Energy Technology Data Exchange (ETDEWEB)

    Esquivel, Darci Motta de Souza

    1974-07-01

    Crystals of Na [(Fe EDTA){sub 2}o] {center_dot}12H{sub 2}0 were investigated by means of electron paramagnetic resonance spectroscopy. The spectra were obtained at various temperatures and crystals orientations. These spectra are very complex with many absorption bands. As the crystal orientation with respect to the magnetic field was changed the variations of the intensity and number of bands were recorded. The antiferromagnetic coupling between the iron atoms in the bridge Fe - 0 - Fe gives rise to states with total spin quantum number S= 0, 1, 2, 3, 4 and 5. Analyses of the EPR spectra as a function of temperature provided a means for the identification of the EPR absorption bands attributed to the states with S = 2. It was also possible to calculate the exchange parameter value J = 300 K. From the study of bands angular dependence in relation to the crystal orientation in the magnetic field it was found that the magnetic crystal axes X, Y, Z and the crystals axes a, b, c are related as (a, b, c) = (Y, Z, X) {exclamation_point} with a precision of 5 deg. Also the crystalline distortion parameters were calculated D = 0.21 {+-} 0.02 cm{sup 1}; E = 0.015 {+-} 0.005 cm{sup 1}. (author)

  12. Towards a fully integrated optical gyroscope using whispering gallery modes resonators

    Science.gov (United States)

    Amrane, T.; Jager, J.-B.; Jager, T.; Calvo, V.; Léger, J.-M.

    2017-11-01

    Since the developments of lasers and the optical fibers in the 70s, the optical gyroscopes have been subject to an intensive research to improve both their resolution and stability performances. However the best optical gyroscopes currently on the market, the ring laser gyroscope and the interferometer fiber optic gyroscope are still macroscopic devices and cannot address specific applications where size and weight constraints are critical. One solution to overcome these limitations could be to use an integrated resonator as a sensitive part to build a fully Integrated Optical Resonant Gyroscope (IORG). To keep a high rotation sensitivity, which is usually degraded when downsizing this kind of optical sensors based on the Sagnac effect, the resonator has to exhibit a very high quality factor (Q): as detailed in equation (1) where the minimum rotation rate resolution for an IORG is given as a function of the resonator characteristics (Q and diameter D) and of the global system optical system characteristics (i.e. SNR and bandwidth B), the higher the Q×D product, the lower the resolution.

  13. Laser magnetic resonance spectroscopy

    International Nuclear Information System (INIS)

    Ferrari, C.A.

    1985-01-01

    The technique of laser resonance magnetic resonance allows one to study the high-resolution spectroscopy of transient paramagnetic species, viz, atoms, radicals, and molecular ions. This article is a brief exposition of the method, describing the principles, instrumentation and applicability of the IR and FIR-LMR and shows results of HF + . (Author) [pt

  14. Multilevel effect in uranium-238 and thorium-232 effective neutron capture resonance integrals

    International Nuclear Information System (INIS)

    Tellier, H.

    1981-01-01

    Until now, there has been a discrepancy between the computed and the measured values of the /sup 238/U effective capture integral. Recently, several new measurements of the resonance parameters were carried out and the use of a multilevel formalism was suggested to compute the /sup 238/U cross sections. This paper shows that the simultaneous use of recent parameters and the Reich-Moore formalism explain the discrepancy. 31 refs

  15. Role of paramagnetic chromium in chromium(VI)-induced damage in cultured mammalian cells.

    OpenAIRE

    Sugiyama, M

    1994-01-01

    Chromium(VI) compounds are known to be potent toxic and carcinogenic agents. Because chromium(VI) is easily taken up by cells and is subsequently reduced to chromium(III), the formation of paramagnetic chromium such as chromium(V) and chromium(III) is believed to play a role in the adverse biological effects of chromium(VI) compounds. The present report, uses electron spin resonance (ESR) spectroscopy; the importance of the role of paramagnetic chromium in chromium(VI)-induced damage in intac...

  16. Susceptibility cancellation of a microcoil wound with a paramagnetic-liquid-filled copper capillary

    Science.gov (United States)

    Takeda, Kazuyuki; Takasaki, Tomoya; Takegoshi, K.

    2015-09-01

    Even though microcoils improve the sensitivity of NMR measurement of tiny samples, magnetic-field inhomogeneity due to the bulk susceptibility effect of the coil material can cause serious resonance-line broadening. Here, we propose to fabricate the microcoil using a thin, hollow copper capillary instead of a wire and fill paramagnetic liquid inside the capillary, so as to cancel the diamagnetic contribution of the copper. Susceptibility cancellation is demonstrated using aqueous solution of NiSO4. In addition, the paramagnetic liquid serves as coolant when it is circulated through the copper capillary, effectively transferring the heat generated by radiofrequency pulses.

  17. 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...

  18. Single-frequency, fully integrated, miniature DPSS laser based on monolithic resonator

    Science.gov (United States)

    Dudzik, G.; Sotor, J.; Krzempek, K.; Soboń, G.; Abramski, K. M.

    2014-02-01

    We present a single frequency, stable, narrow linewidth, miniature laser sources operating at 532 nm (or 1064 nm) based on a monolithic resonators. Such resonators utilize birefringent filters formed by YVO4 beam displacer and KTP or YVO4 crystals to force single frequency operation at 532 nm or 1064 nm, respectively. In both configurations Nd:YVO4 gain crystal is used. The resonators dimensions are 1x1x10.5 mm3 and 1x1x8.5 mm3 for green and infrared configurations, respectively. Presented laser devices, with total dimensions of 40x52x120 mm3, are fully equipped with driving electronics, pump diode, optical and mechanical components. The highly integrated (36x15x65 mm3) low noise driving electronics with implemented digital PID controller was designed. It provides pump current and resonator temperature stability of ±30 μA@650 mA and ±0,003ºC, respectively. The laser parameters can be set and monitored via the USB interface by external application. The developed laser construction is universal. Hence, the other wavelengths can be obtained only by replacing the monolithic resonator. The optical output powers in single frequency regime was at the level of 42 mW@532 nm and 0.5 W@1064 nm with the long-term fluctuations of ±0.85 %. The linewidth and the passive frequency stability under the free running conditions were Δν < 100 kHz and 3ṡ10-9@1 s integration time, respectively. The total electrical power supply consumption of laser module was only 4 W. Presented compact, single frequency laser operating at 532 nm and 1064 nm may be used as an excellent source for laser vibrometry, interferometry or seed laser for fiber amplifiers.

  19. 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)

  20. Thermal neutron capture and resonance integral cross sections of {sup 45}Sc

    Energy Technology Data Exchange (ETDEWEB)

    Van Do, Nguyen; Duc Khue, Pham; Tien Thanh, Kim [Institute of Physics, Vietnam Academy of Science and Technology, 10 Dao Tan, Hanoi (Viet Nam); Thi Hien, Nguyen [Institute of Physics, Vietnam Academy of Science and Technology, 10 Dao Tan, Hanoi (Viet Nam); Department of Physics and Center for High Energy Physics, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Kim, Guinyun, E-mail: gnkim@knu.ac.kr [Department of Physics and Center for High Energy Physics, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Kim, Kwangsoo [Department of Physics and Center for High Energy Physics, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Shin, Sung-Gyun; Cho, Moo-Hyun [Department of Advanced Nuclear Engineering, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Lee, Manwoo [Research Center, Dongnam Institute of Radiological and Medical Science, Busan 619-953 (Korea, Republic of)

    2015-11-01

    The thermal neutron cross section (σ{sub 0}) and resonance integral (I{sub 0}) of the {sup 45}Sc(n,γ){sup 46}Sc reaction have been measured relative to that of the {sup 197}Au(n,γ){sup 198}Au reaction by means of the activation method. High-purity natural scandium and gold foils without and with a cadmium cover of 0.5 mm thickness were irradiated with moderated pulsed neutrons produced from the Pohang Neutron Facility (PNF). The induced activities in the activated foils were measured with a high purity germanium (HPGe) detector. In order to improve the accuracy of the experimental results the counting losses caused by the thermal (G{sub th}) and resonance (G{sub epi}) neutron self-shielding, the γ-ray attenuation (F{sub g}) and the true γ-ray coincidence summing effects were made. In addition, the effect of non-ideal epithermal spectrum was also taken into account by determining the neutron spectrum shape factor (α). The thermal neutron cross-section and resonance integral of the {sup 45}Sc(n,γ){sup 46}Sc reaction have been determined relative to the reference values of the {sup 197}Au(n,γ){sup 198}Au reaction, with σ{sub o,Au} = 98.65 ± 0.09 barn and I{sub o,Au} = 1550 ± 28 barn. The present thermal neutron cross section has been determined to be σ{sub o,Sc} = 27.5 ± 0.8 barn. According to the definition of cadmium cut-off energy at 0.55 eV, the present resonance integral cross section has been determined to be I{sub o,Sc} = 12.4 ± 0.7 barn. The present results are compared with literature values and discussed.

  1. Integrability of the Gross-Pitaevskii equation with Feshbach resonance management

    International Nuclear Information System (INIS)

    Zhao Dun; Luo Honggang; Chai Huayue

    2008-01-01

    In this Letter we study the integrability of a class of Gross-Pitaevskii equations managed by Feshbach resonance in an expulsive parabolic external potential. By using WTC test, we find a condition under which the Gross-Pitaevskii equation is completely integrable. Under the present model, this integrability condition is completely consistent with that proposed by Serkin, Hasegawa, and Belyaeva [V.N. Serkin, A. Hasegawa, T.L. Belyaeva, Phys. Rev. Lett. 98 (2007) 074102]. Furthermore, this integrability can also be explicitly shown by a transformation, which can convert the Gross-Pitaevskii equation into the well-known standard nonlinear Schroedinger equation. By this transformation, each exact solution of the standard nonlinear Schroedinger equation can be converted into that of the Gross-Pitaevskii equation, which builds a systematical connection between the canonical solitons and the so-called nonautonomous ones. The finding of this transformation has a significant contribution to understanding the essential properties of the nonautonomous solitons and the dynamics of the Bose-Einstein condensates by using the Feshbach resonance technique

  2. Analysis and optimization of acoustic wave micro-resonators integrating piezoelectric zinc oxide layers

    Science.gov (United States)

    Mortada, O.; Zahr, A. H.; Orlianges, J.-C.; Crunteanu, A.; Chatras, M.; Blondy, P.

    2017-02-01

    This paper reports on the design, simulation, fabrication, and test results of ZnO-based contour-mode micro-resonators integrating piezoelectric zinc oxide (ZnO) layers. The inter-digitated (IDT) type micro-resonators are fabricated on ZnO films and suspended top of 2 μm thick silicon membranes using silicon-on insulator technology. We analyze several possibilities of increasing the quality factor (Q) and the electromechanical coupling coefficient (kt2) of the devices by varying the numbers and lengths of the IDT electrodes and using different thicknesses of the ZnO layer. We designed and fabricated IDTs of different finger numbers (n = 25, 40, 50, and 80) and lengths (L = 100/130/170/200 μm) for three different thicknesses of ZnO films (200, 600, and 800 nm). The measured Q factor confirms that reducing the length and the number of IDT fingers enables us to reach better electrical performances at resonant frequencies around 700 MHz. The extracted results for an optimized micro-resonator device having an IDT length of 100 μm and 40 finger electrodes show a Q of 1180 and a kt2 of 7.4%. We demonstrate also that the reduction of the ZnO thickness from 800 nm to 200 nm increases the quality factor from 430 to 1600, respectively, around 700 MHz. Experimental data are in very good agreement with theoretical simulations of the fabricated devices

  3. Integration of Resonant Coil for Wireless Power Transfer and Implantable Antenna for Signal Transfer

    Directory of Open Access Journals (Sweden)

    Dong-Wook Seo

    2016-01-01

    Full Text Available We propose the integration of the resonant coil for wireless power transfer (WPT and the implantable antenna for physiological signal transfer. The integration allows for a compact biomedical implantable system such as electrocardiogram (ECG recorder and pacemaker. While the resonant coils resonate at the frequency of 13.56 MHz for the WPT, the implantable antenna works in the medical implant communications service (MICS band of 402–405 MHz for wireless communications. They share the narrow substrate area of a bar-type shape; the coil has the current path on the outer part of the substrate and the meandered planar inverted-F antenna (PIFA occupies the inside of the coil. To verify the potentials of the proposed structure, a prototype is fabricated and tested in vitro. The power transfer efficiency (PTE of about 20% is obtained at a distance of 15 mm and the antenna gain of roughly −40 dBi is achieved.

  4. Electron paramagnetic resonance study of paramagnetic centers in carbon-fumed silica adsorbent

    Czech Academy of Sciences Publication Activity Database

    Savchenko, Dariia; Shanina, B.D.; Kalabukhova, E.N.; Sitnikov, A.A.; Lysenko, V.S.; Tertykh, V.A.

    2014-01-01

    Roč. 115, č. 13 (2014), "133704-1"-"133704-7" ISSN 0021-8979 R&D Projects: GA MŠk(CZ) LM2011029 Grant - others:SAFMAT(XE) CZ.2.16/3.1.00/22132 Institutional support: RVO:68378271 Keywords : EPR * carbosil * confinement effect * carbon-related defect Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.183, year: 2014

  5. Integrated nanohole array surface plasmon resonance sensing device using a dual-wavelength source

    International Nuclear Information System (INIS)

    Escobedo, C; Vincent, S; Choudhury, A I K; Campbell, J; Gordon, R; Brolo, A G; Sinton, D

    2011-01-01

    In this paper, we demonstrate a compact integrated nanohole array-based surface plasmon resonance sensing device. The unit includes a LED light source, driving circuitry, CCD detector, microfluidic network and computer interface, all assembled from readily available commercial components. A dual-wavelength LED scheme was implemented to increase spectral diversity and isolate intensity variations to be expected in the field. The prototype shows bulk sensitivity of 266 pixel intensity units/RIU and a limit of detection of 6 × 10 −4 RIU. Surface binding tests were performed, demonstrating functionality as a surface-based sensing system. This work is particularly relevant for low-cost point-of-care applications, especially those involving multiple tests and field studies. While nanohole arrays have been applied to many sensing applications, and their suitability to device integration is well established, this is the first demonstration of a fully integrated nanohole array-based sensing device.

  6. PARAssign-paramagnetic NMR assignments of protein nuclei on the basis of pseudocontact shifts

    Energy Technology Data Exchange (ETDEWEB)

    Skinner, Simon P., E-mail: skinnersp@chem.leidenuniv.nl [Leiden University, Gorlaeus Laboratories, Leiden Institute of Chemistry (Netherlands); Moshev, Mois, E-mail: mois@monomon.me [Leiden University, Leiden Institute of Advanced Computer Science (Netherlands); Hass, Mathias A. S., E-mail: hassmas@chem.leidenuniv.nl; Ubbink, Marcellus, E-mail: m.ubbink@chem.leidenuniv.nl [Leiden University, Gorlaeus Laboratories, Leiden Institute of Chemistry (Netherlands)

    2013-04-15

    The use of paramagnetic NMR data for the refinement of structures of proteins and protein complexes is widespread. However, the power of paramagnetism for protein assignment has not yet been fully exploited. PARAssign is software that uses pseudocontact shift data derived from several paramagnetic centers attached to the protein to obtain amide and methyl assignments. The ability of PARAssign to perform assignment when the positions of the paramagnetic centers are known and unknown is demonstrated. PARAssign has been tested using synthetic data for methyl assignment of a 47 kDa protein, and using both synthetic and experimental data for amide assignment of a 14 kDa protein. The complex fitting space involved in such an assignment procedure necessitates that good starting conditions are found, both regarding placement and strength of paramagnetic centers. These starting conditions are obtained through automated tensor placement and user-defined tensor parameters. The results presented herein demonstrate that PARAssign is able to successfully perform resonance assignment in large systems with a high degree of reliability. This software provides a method for obtaining the assignments of large systems, which may previously have been unassignable, by using 2D NMR spectral data and a known protein structure.

  7. Buckling of paramagnetic chains in soft gels

    Science.gov (United States)

    Huang, Shilin; Pessot, Giorgio; Cremer, Peet; Weeber, Rudolf; Holm, Christian; Nowak, Johannes; Odenbach, Stefan; Menzel, Andreas M.; Auernhammer, Günter K.

    We study the magneto-elastic coupling behavior of paramagnetic chains in soft polymer gels exposed to external magnetic fields. To this end, a laser scanning confocal microscope is used to observe the morphology of the paramagnetic chains together with the deformation field of the surrounding gel network. The paramagnetic chains in soft polymer gels show rich morphological shape changes under oblique magnetic fields, in particular a pronounced buckling deformation. The details of the resulting morphological shapes depend on the length of the chain, the strength of the external magnetic field, and the modulus of the gel. Based on the observation that the magnetic chains are strongly coupled to the surrounding polymer network, a simplified model is developed to describe their buckling behavior. A coarse-grained molecular dynamics simulation model featuring an increased matrix stiffness on the surfaces of the particles leads to morphologies in agreement with the experimentally observed buckling effects.

  8. New design of a triplexer using ring resonator integrated with directional coupler based on photonic crystals

    Science.gov (United States)

    Wu, Yaw-Dong; Shih, Tien-Tsorng; Lee, Jian-Jang

    2009-11-01

    In this paper, we proposed the design of directional coupler integrated with ring resonator based on two-dimensional photonic crystals (2D PCs) to develop a triplexer filter. It can be widely used as the fiber access network element for multiplexer-demultiplexer wavelength selective in fiber-to-the-home (FTTH) communication systems. The directional coupler is chosen to separate the wavelengths of 1490nm and 1310nm. The ring resonator separates the wavelength of 1550nm. The transmission efficiency is larger than 90%. Besides, the total size of propose triplexer is only 19μm×12μm. We present simulation results using the finite-difference time-domain (FDTD) method for the proposed structure.

  9. RESONANCE

    Indian Academy of Sciences (India)

    small bar magnets. NMR spectroscopy .... that the integrated area for the methylene .... in a network of spins. .... Schematic representation of the type of short (broken arrows) and medium-range .... we can define between cities and towns in the.

  10. Paramagnetism: an alternative view. Pt. 1

    International Nuclear Information System (INIS)

    Oudet, X.

    1991-01-01

    A new calculation of the paramagnetic susceptibility χ is proposed on the basis of the statistical distribution of the thermal energy using the mean value U of this energy as statistical variable. This allows us to replace the molecular field by an equivalent energy barrier that the paramagnetic moment of an atom has to cross to contribute to χ. The variation of χ with U, or T as well, shows a maximum when there is no magnetic order. The asymptotic character of the Curie-Weiss law appears in close connection with that of the Dulong and Petit law. (orig.)

  11. The temperature coefficient of the resonance integral for uranium metal and oxide

    Energy Technology Data Exchange (ETDEWEB)

    Blomberg, P; Hellstrand, E; Homer, S

    1960-06-15

    The temperature coefficient of the resonance integral in uranium metal and oxide has been measured over a wide temperature range for rods with three different diameters. The results for metal agree with most earlier results from activation measurements but differ as much as a factor of two from results obtained with reactivity methods. For oxide only one measurement has been reported recently. Our value is considerably lower than the result of that measurement. The experiments will continue in order to find the reason for the large discrepancy mentioned above.

  12. The temperature coefficient of the resonance integral for uranium metal and oxide

    International Nuclear Information System (INIS)

    Blomberg, P.; Hellstrand, E.; Homer, S.

    1960-06-01

    The temperature coefficient of the resonance integral in uranium metal and oxide has been measured over a wide temperature range for rods with three different diameters. The results for metal agree with most earlier results from activation measurements but differ as much as a factor of two from results obtained with reactivity methods. For oxide only one measurement has been reported recently. Our value is considerably lower than the result of that measurement. The experiments will continue in order to find the reason for the large discrepancy mentioned above

  13. Conformally integrated stent cell resonators for wireless monitoring of peripheral artery disease

    KAUST Repository

    Viswanath, Anupam

    2013-01-01

    This paper presents the design and in vitro evaluation of magnetoelastic sensors intended for wireless monitoring of tissue accumulation in peripheral artery stents. The sensors, shaped like stent cells, are fabricated from 28-μm thick foils of magnetoelastic Ni-Fe alloy and are conformally integrated with the stent. The typical sensitivity to viscosity is 427 ppm/cP over a 1.1-8.6 cP range. The sensitivity to mass loading is typically 63,000-65000 ppm/mg with resonant frequency showing an 8.1% reduction for an applied mass that is 15% of the unloaded mass of the sensor. © 2013 IEEE.

  14. Resonance

    Indian Academy of Sciences (India)

    Administrator

    Refresher Course in. Experimental Physics. Refresher Course on. Advanced in Biophysics. IISc Young Science. Fellowship Programme. Inside Back Cover. Flowering Trees. (Credit: K Sankara Rao,IISc,. Bangalore). 97. 83. Classics. REFLECTIONS. 71 Integrative Microbiology – The Third Golden Age. Moselio Schaechter.

  15. Chip-integrated optical power limiter based on an all-passive micro-ring resonator

    Science.gov (United States)

    Yan, Siqi; Dong, Jianji; Zheng, Aoling; Zhang, Xinliang

    2014-10-01

    Recent progress in silicon nanophotonics has dramatically advanced the possible realization of large-scale on-chip optical interconnects integration. Adopting photons as information carriers can break the performance bottleneck of electronic integrated circuit such as serious thermal losses and poor process rates. However, in integrated photonics circuits, few reported work can impose an upper limit of optical power therefore prevent the optical device from harm caused by high power. In this study, we experimentally demonstrate a feasible integrated scheme based on a single all-passive micro-ring resonator to realize the optical power limitation which has a similar function of current limiting circuit in electronics. Besides, we analyze the performance of optical power limiter at various signal bit rates. The results show that the proposed device can limit the signal power effectively at a bit rate up to 20 Gbit/s without deteriorating the signal. Meanwhile, this ultra-compact silicon device can be completely compatible with the electronic technology (typically complementary metal-oxide semiconductor technology), which may pave the way of very large scale integrated photonic circuits for all-optical information processors and artificial intelligence systems.

  16. Recent results on some columnar paramagnetic metallomesogens

    Indian Academy of Sciences (India)

    A broader view on some physical properties of columnar paramagnetic ... was evident by X-ray crystal structure determination in the solid state on a homologous ... leading to interfacial polarization as described for other LC materials before [9]. ... dodecyloxy tail on the phenyl rings) was described to exhibit a Colho phase ...

  17. Microassembly using a Cluster of Paramagnetic Microparticles

    NARCIS (Netherlands)

    Khalil, I.S.M.; Brink, F.V; Sardan Sukas, Ö.; Misra, Sarthak

    2013-01-01

    We use a cluster of paramagnetic microparticles to carry out a wireless two-dimensional microassembly operation. A magnetic-based manipulation system is used to control the motion of the cluster under the influence of the applied magnetic fields. Wireless motion control of the cluster is implemented

  18. Depolarization of diffusing spins by paramagnetic impurities

    International Nuclear Information System (INIS)

    Schillaci, M.E.; Hutson, R.L.; Heffner, R.H.; Leon, M.; Dodds, S.A.; Estle, T.L.

    1981-01-01

    We study the depolarization of diffusing spins (muons) interacting with dilute paramagnetic impurities in a solid using a simple computational model which properly treats the muon motion and preserves correct muon-impurity distances. Long-range (dipolar) and nearest-neighbor (contact) interactions are treated together. Diffusion parameters are deduced and model comparisons made for AuGd (300 ppm). (orig.)

  19. Dual excitation acoustic paramagnetic logging tool

    Energy Technology Data Exchange (ETDEWEB)

    Vail, III, William B. (Bothell, WA)

    1989-01-01

    New methods and apparatus are disclosed which allow measurement of the presence of oil and water in gelogical formations using a new physical effect called the Acoustic Paramagnetic Logging Effect (APLE). The presence of petroleum in formation causes a slight increase in the earth's magnetic field in the vicinity of the reservoir. This is the phenomena of paramagnetism. Application of an acoustic source to a geological formation at the Larmor frequency of the nucleous present causes the paramagnetism of the formation to disappear. This results in a decrease in the earth's magnetic field in the vicinity of the oil bearing formation. Repetitively frequency sweeping the acoustic source through the Larmor frequency of the nucleons present (approx. 2 kHz) causes an amplitude modulation of the earth's magnetic field which is a consequence of the APLE. The amplitude modulation of the earth's magnetic field is measured with an induction coil gradiometer and provides a direct measure of the amount of oil and water in the excitation zone of the formation. The phase of the signal is used to infer the longitudinal relaxation times of the fluids present, which results in the ability in general to separate oil and water and to measure the viscosity of the oil present. Such measurements may be preformed in open boreholes and in cased well bores. The Dual Excitation Acoustic Paramagnetic Logging Tool employing two acoustic sources is also described.

  20. Measurement of the effective resonance integral of natural uranium; Merenje efektivnog rezonantnog integrala prirodnog urana

    Energy Technology Data Exchange (ETDEWEB)

    Markovic, V; Kocic, A [Institute of nuclear sciences Boris Kidric, Vinca, Beograd (Yugoslavia)

    1965-12-15

    Good understanding of the nuclear properties of the materials in the reactor core is essential for reactor operation. One of the fundamental properties is the resonance absorption of the fuel, which is directly included in the reactor calculation through resonance escape probability and influences the choice of the materials quality in the core. This paper describes the measurement of resonance absorption integral of the natural uranium as a function of the S/M ratio. Improved experiment planning and analysis of results, as well as improvement of the ROB-1 reactor oscillator device related to the interpretation of results and decrease of reactor drift variations during measurement enabled higher precision of results compared to previous experiments. Poznavanje osobina nuklearnih karakteristika materijala koji ulaze u jezgro nuklearnog reaktora predstavlja bitan faktor u njegovom rezimu rada. Jedna od osnovnih je svakako rezonantna apsorpcija goriva, cija velicina - preko faktora rezonantnog izbegavanja - direktno ulazi u proracun nuklearnih reaktora i utice na izbor kvaliteta materijala koji ga sacinjavaju. U radu se opisuje merenje rezonantnog apsorpcionog integrala prirodnog urana u funkciji odnosa S/M. Bolja postavka eksperimenta i interpretacija rezultata, s jedne strane, i poboljsanje uredjaja reaktorskog oscilatora ROB-1 /1/ u pogledu analize podataka i smanjenja promene drifta reaktora u toku merenja, s druge strane, daju znacaj ovom radu u pogledu dobijanja preciznijih rezultata u odnosu na ranije /2/ (author)

  1. 1 million-Q optomechanical microdisk resonators for sensing with very large scale integration

    Science.gov (United States)

    Hermouet, M.; Sansa, M.; Banniard, L.; Fafin, A.; Gely, M.; Allain, P. E.; Santos, E. Gil; Favero, I.; Alava, T.; Jourdan, G.; Hentz, S.

    2018-02-01

    Cavity optomechanics have become a promising route towards the development of ultrasensitive sensors for a wide range of applications including mass, chemical and biological sensing. In this study, we demonstrate the potential of Very Large Scale Integration (VLSI) with state-of-the-art low-loss performance silicon optomechanical microdisks for sensing applications. We report microdisks exhibiting optical Whispering Gallery Modes (WGM) with 1 million quality factors, yielding high displacement sensitivity and strong coupling between optical WGMs and in-plane mechanical Radial Breathing Modes (RBM). Such high-Q microdisks with mechanical resonance frequencies in the 102 MHz range were fabricated on 200 mm wafers with Variable Shape Electron Beam lithography. Benefiting from ultrasensitive readout, their Brownian motion could be resolved with good Signal-to-Noise ratio at ambient pressure, as well as in liquid, despite high frequency operation and large fluidic damping: the mechanical quality factor reduced from few 103 in air to 10's in liquid, and the mechanical resonance frequency shifted down by a few percent. Proceeding one step further, we performed an all-optical operation of the resonators in air using a pump-probe scheme. Our results show our VLSI process is a viable approach for the next generation of sensors operating in vacuum, gas or liquid phase.

  2. Resonant passive–active vibration absorber with integrated force feedback control

    International Nuclear Information System (INIS)

    Høgsberg, Jan; Brodersen, Mark L; Krenk, Steen

    2016-01-01

    A general format of a two-terminal vibration absorber is constructed by placing a passive unit in series with a hybrid unit, composed of an active actuator in parallel with a second passive element. The displacement of the active actuator is controlled by an integrated feedback control with the difference in force between the two passive elements as input. This format allows passive and active contributions to be combined arbitrarily within the hybrid unit, which results in a versatile absorber format with guaranteed closed-loop stability. This is demonstrated for resonant absorbers with inertia realized passively by a mechanical inerter or actively by the integrated force feedback. Accurate calibration formulae are presented for two particular absorber configurations and the performance is subsequently demonstrated with respect to both equal modal damping and effective response reduction. (technical note)

  3. Photonic crystal ring resonator based optical filters for photonic integrated circuits

    International Nuclear Information System (INIS)

    Robinson, S.

    2014-01-01

    In this paper, a two Dimensional (2D) Photonic Crystal Ring Resonator (PCRR) based optical Filters namely Add Drop Filter, Bandpass Filter, and Bandstop Filter are designed for Photonic Integrated Circuits (PICs). The normalized output response of the filters is obtained using 2D Finite Difference Time Domain (FDTD) method and the band diagram of periodic and non-periodic structure is attained by Plane Wave Expansion (PWE) method. The size of the device is minimized from a scale of few tens of millimeters to the order of micrometers. The overall size of the filters is around 11.4 μm × 11.4 μm which is highly suitable of photonic integrated circuits

  4. Micro-resonators based on integrated polymer technology for optical sensing

    Science.gov (United States)

    Girault, Pauline; Lemaitre, Jonathan; Guendouz, Mohammed; Lorrain, Nathalie; Poffo, Luiz; Gadonna, Michel; Bosc, Dominique

    2014-05-01

    Research on sensors has experienced a noticeable development over the last decades especially in label free optical biosensors. However, compact sensors without markers for rapid, reliable and inexpensive detection of various substances induce a significant research of new technological solutions. The context of this work is the development of a sensor based on easily integrated and inexpensive micro-resonator (MR) component in integrated optics, highly sensitive and selective mainly in the areas of health and food. In this work, we take advantage of our previous studies on filters based on micro-resonators (MR) to experiment a new couple of polymers in the objective to use MR as a sensing function. MRs have been fabricated by processing SU8 polymer as core and PMATRIFE polymer as cladding layer of the waveguide. The refractive index contrast reaches 0.16 @ 1550 nm. Sub-micronic ring waveguides gaps from 0.5 to 1 μm have been successfully achieved with UV (i-line) photolithography. This work confirms our forecasts, published earlier, about the resolution that can be achieved. First results show a good extinction coefficient of ~17 dB, a quality factor around 104 and a finesse of 12. These results are in concordance with the theoretical study and they allow us to validate our technology with this couple of polymers. Work is going on with others lower cladding materials that will be used to further increase refractive index contrast for sensing applications.

  5. Integration of structural and functional magnetic resonance imaging in amyotrophic lateral sclerosis.

    Science.gov (United States)

    Douaud, Gwenaëlle; Filippini, Nicola; Knight, Steven; Talbot, Kevin; Turner, Martin R

    2011-12-01

    Amyotrophic lateral sclerosis as a system failure is a concept supported by the finding of consistent extramotor as well as motor cerebral pathology. The functional correlates of the structural changes detected using advanced magnetic resonance imaging techniques such as diffusion tensor imaging and voxel-based morphometry have not been extensively studied. A group of 25 patients with amyotrophic lateral sclerosis was compared to healthy control subjects using a multi-modal neuroimaging approach comprising T(1)-weighted, diffusion-weighted and resting-state functional magnetic resonance imaging. Using probabilistic tractography, a grey matter connection network was defined based upon the prominent corticospinal tract and corpus callosum involvement demonstrated by white matter tract-based spatial statistics. This 'amyotrophic lateral sclerosis-specific' network included motor, premotor and supplementary motor cortices, pars opercularis and motor-related thalamic nuclei. A novel analysis protocol, using this disease-specific grey matter network as an input for a dual-regression analysis, was then used to assess changes in functional connectivity directly associated with this network. A spatial pattern of increased functional connectivity spanning sensorimotor, premotor, prefrontal and thalamic regions was found. A composite of structural and functional magnetic resonance imaging measures also allowed the qualitative discrimination of patients from controls. An integrated structural and functional connectivity approach therefore identified apparently dichotomous processes characterizing the amyotrophic lateral sclerosis cerebral network failure, in which there was increased functional connectivity within regions of decreased structural connectivity. Patients with slower rates of disease progression showed connectivity measures with values closer to healthy controls, raising the possibility that functional connectivity increases might not simply represent a

  6. Thermoluminescence, infrared reflectivity and electron paramagnetic resonance properties of hemimorphite

    Energy Technology Data Exchange (ETDEWEB)

    Gallegos, E.A. [Institute of Physics, University of Sao Paulo, Rua do Matao, Travessa R, 187, CEP 05508-900, Sao Paulo, SP (Brazil); Cano, N.F. [Institute of Physics, University of Sao Paulo, Rua do Matao, Travessa R, 187, CEP 05508-900, Sao Paulo, SP (Brazil)], E-mail: nilocano@dfn.if.usp.br; Watanabe, S.; Chubaci, J.F.D. [Institute of Physics, University of Sao Paulo, Rua do Matao, Travessa R, 187, CEP 05508-900, Sao Paulo, SP (Brazil)

    2009-01-15

    Silicate mineral hemimorphite has been investigated concerning its TL, IR and EPR properties. A broad TL peak around 180 deg. C and a weaker and narrower peak around 360 deg. C were found in a sample annealed at 600 deg. C for 1 h and then irradiated. The deconvolution using the CGCD method revealed peaks around 132, 169, 222 and 367 deg. C. The reflectivity measurements showed several bands in the NIR region due to H{sub 2}O, OH and Al-OH complexes. No band was observed in the visible region. The thermal treatments were carried out from {approx}110 to 940 deg. C and dehydration was observed, first causing a diminishing optical absorption in general and the disappearance of water and hydroxyl absorption bands. The EPR spectrum of natural hemimorphite, presented Cu{sup 2+} signals at g = 2.4 and g = 2.1 plus E{sub 1}' signal superposed to Fe{sup 3+} signal around g = 2.0.

  7. Electron paramagnetic resonance parameters and local structure for ...

    Indian Academy of Sciences (India)

    HUA-MING ZHANG. 1. , GUANG-DUO LU. 1 ... the above ZFSs, the local structure information for the impurity Gd. 3+ is obtained, i.e., .... parameters, extended X-ray absorption fine-structure (EXAFS) measurements and crystal-field spectrum ...

  8. 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

  9. Electron paramagnetic resonance studies of defects in dilute magnetic alloys

    International Nuclear Information System (INIS)

    Suss, J.T.; Raizman, A.

    1980-01-01

    The EPR spectrum of erbium was used to study the effects of cold-working (rolling and mechanical polishing) in dilute gold-erbium alloys. Variation in the EPR linewidth, intensity and asymmetry parameter (A/B ratio) were investigated. Most of the results could be interpreted in terms of segregation of erbium ions to subgrain boundaries (dislocations) in a surface layer of a few thousand Angstroms. (author)

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

    Indian Academy of Sciences (India)

    1Department of Physics, Baoji University of Arts and Science, Baoji 721007, Shaanxi,. China. 2College of Chemistry and .... for V 4+ in free state. By diagonalizing the complete energy matrix, the values of g , g⊥, A and A⊥ can be obtained using eqs (4)–(7). The calculated results are listed in table 1. 2.2 PTM method.

  11. Electron paramagnetic resonance study of ternary Cu compounds ...

    Indian Academy of Sciences (India)

    field modulation, and ∼19mW of microwave power. .... using EasySpin,38 a program working under Matlab39 as ... simulations obtained as explained in the text. σ denote the qua- ..... the exchange narrowing process is the collapse of reso-.

  12. On the internal resonant modes in marching-on-in-time solution of the time domain electric field integral equation

    KAUST Repository

    Shi, Yifei

    2013-08-01

    Internal resonant modes are always observed in the marching-on-in-time (MOT) solution of the time domain electric field integral equation (EFIE), although \\'relaxed initial conditions,\\' which are enforced at the beginning of time marching, should in theory prevent these spurious modes from appearing. It has been conjectured that, numerical errors built up during time marching establish the necessary initial conditions and induce the internal resonant modes. However, this conjecture has never been proved by systematic numerical experiments. Our numerical results in this communication demonstrate that, the internal resonant modes\\' amplitudes are indeed dictated by the numerical errors. Additionally, it is shown that in a few cases, the internal resonant modes can be made \\'invisible\\' by significantly suppressing the numerical errors. These tests prove the conjecture that the internal resonant modes are induced by numerical errors when the time domain EFIE is solved by the MOT method. © 2013 IEEE.

  13. On the internal resonant modes in marching-on-in-time solution of the time domain electric field integral equation

    KAUST Repository

    Shi, Yifei; Bagci, Hakan; Lu, Mingyu

    2013-01-01

    Internal resonant modes are always observed in the marching-on-in-time (MOT) solution of the time domain electric field integral equation (EFIE), although 'relaxed initial conditions,' which are enforced at the beginning of time marching, should in theory prevent these spurious modes from appearing. It has been conjectured that, numerical errors built up during time marching establish the necessary initial conditions and induce the internal resonant modes. However, this conjecture has never been proved by systematic numerical experiments. Our numerical results in this communication demonstrate that, the internal resonant modes' amplitudes are indeed dictated by the numerical errors. Additionally, it is shown that in a few cases, the internal resonant modes can be made 'invisible' by significantly suppressing the numerical errors. These tests prove the conjecture that the internal resonant modes are induced by numerical errors when the time domain EFIE is solved by the MOT method. © 2013 IEEE.

  14. Fano-type coupling of a bound paramagnetic state with 2D continuum

    International Nuclear Information System (INIS)

    Rozhansky, I. V.; Averkiev, N. S.; Lähderanta, E.

    2013-01-01

    We analyze an effect of a bound impurity state located at a tunnel distance from a quantum well (QW). The study is focused on the resonance case when the bound state energy lies within the continuum of the QW states. Using the developed theory we calculate spin polarization of 2D holes induced by paramagnetic (Mn) delta-layer in the vicinity of the QW and indirect exchange interaction between two impurities located at a tunnel distance from electron gas

  15. On the paramagnetism of spin in the classical limit

    International Nuclear Information System (INIS)

    Hogreve, H.

    1985-12-01

    We consider particles with spin 1/2 in external electromagnetic fields. Although in many quantum mechanical situations they show a paramagnetic behaviour, within non-relativistic quantum theory a universal paramagnetic influence of spin fails to be true in general. Here we investigate the paramagnetism of spin in the framework of a classical theory. Applying previous results for the classical limit slash-h→O we obtain a classical expression corresponding to the quantum partition function of Hamiltonians with spin variables. For this classical partition function simple estimates lead to a paramagnetic inequality which demonstrates that indeed in the classical limit the spin shows a general paramagnetic behaviour. (author)

  16. Study of actinide paramagnetism in solution

    International Nuclear Information System (INIS)

    Autillo, Matthieu

    2015-01-01

    The physiochemical properties of actinide (An) solutions are still difficult to explain, particularly the behavioral differences between An(III) and Ln(III). The study of actinide paramagnetic behavior may be a 'simple' method to analyze the electronic properties of actinide elements and to obtain information on the ligand-actinide interaction. The objective of this PhD thesis is to understand the paramagnetic properties of these elements by magnetic susceptibility measurements and chemical shift studies. Studies on actinide electronic properties at various oxidation states in solution were carried out by magnetic susceptibility measurements in solution according to the Evans method. Unlike Ln(III) elements, there is no specific theory describing the magnetic properties of these ions in solution. To obtain accurate data, the influence of experimental measurement technique and radioactivity of these elements was analyzed. Then, to describe the electronic structure of their low energy states, the experimental results were complemented with quantum chemical calculations from which the influence of the ligand field was studied. Finally, these interpretations were applied to better understand the variations in the magnetic properties of actinide cations in chloride and nitrate media. Information about ligand-actinide interactions may be determined from an NMR chemical shift study of actinide complexes. Indeed, modifications induced by a paramagnetic complex can be separated into two components. The first component, a Fermi contact contribution (δ_c) is related to the degree of covalency in coordination bonds with the actinide ions and the second, a dipolar contribution (δ_p_c) is related to the structure of the complex. The paramagnetic induced shift can be used only if we can isolate these two terms. To achieve this study on actinide elements, we chose to work with the complexes of dipicolinic acid (DPA). Firstly, to characterize the geometrical parameters, a

  17. Paramagnetic form factors from itinerant electron theory

    International Nuclear Information System (INIS)

    Cooke, J.F.; Liu, S.H.; Liu, A.J.

    1985-01-01

    Elastic neutron scattering experiments performed over the past two decades have provided accurate information about the magnetic form factors of paramagnetic transition metals. These measurements have traditionally been analyzed in terms of an atomic-like theory. There are, however, some cases where this procedure does not work, and there remains the overall conceptual problem of using an atomistic theory for systems where the unpaired-spin electrons are itinerant. We have recently developed computer codes for efficiently evaluating the induced magnetic form factors of fcc and bcc itinerant electron paramagnets. Results for the orbital and spin contributions have been obtained for Cr, Nb, V, Mo, Pd, and Rh based on local density bands. By using calculated spin enhancement parameters, we find reasonable agreement between theory and neutron form factor data. In addition, these zero parameter calculations yield predictions for the bulk susceptibility on an absolute scale which are in reasonable agreement with experiment in all treated cases except palladium

  18. Role of spinning electrons in paramagnetic phenomena

    International Nuclear Information System (INIS)

    Bose, D.M.

    1986-06-01

    An attempt is made to explain paramagnetic phenomena without assuming the orientation of a molecule or ion in a magnetic field. Only the spin angular momentum is assumed to be responsible. A derivative of the Gurie-Langevin law and the magnetic moments of ions are given as a function of the number of electrons in an inner, incomplete shell. An explanation of Gerlach's experiments with iron and nickel vapors is attempted. An explanation of magnetomechanical experiments with ferromagnetic elements is given

  19. Methodologies for Wind Turbine and STATCOM Integration in Wind Power Plant Models for Harmonic Resonances Assessment

    DEFF Research Database (Denmark)

    Freijedo Fernandez, Francisco Daniel; Chaudhary, Sanjay Kumar; Guerrero, Josep M.

    2015-01-01

    -domain. As an alternative, a power based averaged modelling is also proposed. Type IV wind turbine harmonic signature and STATCOM active harmonic mitigation are considered for the simulation case studies. Simulation results provide a good insight of the features and limitations of the proposed methodologies.......This paper approaches modelling methodologies for integration of wind turbines and STATCOM in harmonic resonance studies. Firstly, an admittance equivalent model representing the harmonic signature of grid connected voltage source converters is provided. A simplified type IV wind turbine modelling...... is then straightforward. This linear modelling is suitable to represent the wind turbine in the range of frequencies at which harmonic interactions are likely. Even the admittance method is suitable both for frequency and time domain studies, some limitations arise in practice when implementing it in the time...

  20. Thermal neutron capture cross sections resonance integrals and g-factors

    International Nuclear Information System (INIS)

    Mughabghab, S.F.

    2003-02-01

    The thermal radiative capture cross sections and resonance integrals of elements and isotopes with atomic numbers from 1 to 83 (as well as 232 Th and 238 U) have been re-evaluated by taking into consideration all known pertinent data published since 1979. This work has been undertaken as part of an IAEA co-ordinated research project on 'Prompt capture gamma-ray activation analysis'. Westcott g-factors for radiative capture cross sections at a temperature of 300K were computed by utilizing the INTER code and ENDF-B/VI (Release 8) library files. The temperature dependence of the Westcott g-factor is illustrated for 113 Cd, 124 Xe and 157 Gd at temperatures of 150, 294 and 400K. Comparisons have also been made of the newly evaluated capture cross sections of 6 Li, 7 Li, 12 C and 207 Pb with those determined by the k 0 method. (author)

  1. An EPR study on tea: Identification of paramagnetic species, effect of heat and sweeteners

    Science.gov (United States)

    Bıyık, Recep; Tapramaz, Recep

    2009-10-01

    Tea ( Camellia Sinensis) is the most widely consumed beverage in the world, and is known to be having therapeutic, antioxidant and nutritional effects. Electron paramagnetic resonance (EPR) spectral studies made on the tea cultivated along the shore of Black Sea, Turkey, show Mn 2+ and Fe 3+ centers in green tea leaves and in black tea extract. Dry black tea flakes and dry extract show additional sharp line attributed to semiquinone radical. The origins of the paramagnetic species in black tea are defined and discussed. Effect of humidity and heat are investigated. It is observed that dry extract of black tea melts at 100 °C and the semiquinone radical lives up to 140 °C while Mn 2+ sextet disappears just above 100 °C in tea extract. Natural and synthetics sweeteners have different effects on the paramagnetic centers. White sugar (sucrose) quenches the Mn 2+ and semiquinone lines in black tea EPR spectrum, and glucose, fructose, lactose and maltose quench Fe 3+ line while synthetic sweeteners acesulfam potassium, aspartame and sodium saccharine do not have any effect on paramagnetic species in tea.

  2. Integrated Geophysical Measurements for Bioremediation Monitoring: Combining Spectral Induced Polarization, Nuclear Magnetic Resonance and Magnetic Methods

    Energy Technology Data Exchange (ETDEWEB)

    Keating, Kristina [Rutgers Univ., Newark, NJ (United States). Dept. of Earth and Environmental Sciences; Slater, Lee [Rutgers Univ., Newark, NJ (United States). Dept. of Earth and Environmental Sciences; Ntarlagiannis, Dimitris [Rutgers Univ., Newark, NJ (United States). Dept. of Earth and Environmental Sciences; Williams, Kenneth H. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Earth Sciences Division

    2015-02-24

    This documents contains the final report for the project "Integrated Geophysical Measurements for Bioremediation Monitoring: Combining Spectral Induced Polarization, Nuclear Magnetic Resonance and Magnetic Methods" (DE-SC0007049) Executive Summary: Our research aimed to develop borehole measurement techniques capable of monitoring subsurface processes, such as changes in pore geometry and iron/sulfur geochemistry, associated with remediation of heavy metals and radionuclides. Previous work has demonstrated that geophysical method spectral induced polarization (SIP) can be used to assess subsurface contaminant remediation; however, SIP signals can be generated from multiple sources limiting their interpretation value. Integrating multiple geophysical methods, such as nuclear magnetic resonance (NMR) and magnetic susceptibility (MS), with SIP, could reduce the ambiguity of interpretation that might result from a single method. Our research efforts entails combining measurements from these methods, each sensitive to different mineral forms and/or mineral-fluid interfaces, providing better constraints on changes in subsurface biogeochemical processes and pore geometries significantly improving our understanding of processes impacting contaminant remediation. The Rifle Integrated Field Research Challenge (IFRC) site was used as a test location for our measurements. The Rifle IFRC site is located at a former uranium ore-processing facility in Rifle, Colorado. Leachate from spent mill tailings has resulted in residual uranium contamination of both groundwater and sediments within the local aquifer. Studies at the site include an ongoing acetate amendment strategy, native microbial populations are stimulated by introduction of carbon intended to alter redox conditions and immobilize uranium. To test the geophysical methods in the field, NMR and MS logging measurements were collected before, during, and after acetate amendment. Next, laboratory NMR, MS, and SIP measurements

  3. Molecular orbital calculations of the unpaired electron distribution and electric field gradients in divalent paramagnetic Ir complexes

    International Nuclear Information System (INIS)

    Nogueira, S.R.; Vugman, N.V.; Guenzburger, D.

    1988-01-01

    Semi-empirical Molecular Orbital calculations were performed for the paramagnetic complex ions [Ir(CN) 5 ] 3- , [Ir(CN) 5 Cl] 4- and [Ir(CN) 4 Cl 2 ] 4- . Energy levels schemes and Mulliken-type populations were obtained. The distribution of the unpaired spin over the atoms in the complexes was derived, and compared to data obtained from Electron Paramagnetic Resonance spectra with the aid of a Ligand Field model. The electric field gradients at the Ir nucleus were calculated and compared to experiment. The results are discussed in terms of the chemical bonds formed by Ir and the ligands. (author) [pt

  4. Pulse advancement and delay in an integrated optical two-port ring-resonator circuit: direct experimental observations

    NARCIS (Netherlands)

    Uranus, H.P.; Zhuang, L.; Roeloffzen, C.G.H.; Hoekstra, Hugo

    We report experimental observations of the negative-group-velocity (v_g) phenomenon in an integrated-optical two-port ring-resonator circuit. We demonstrate that when the v_g is negative, the (main) peak of output pulse appears earlier than the peak of a reference pulse, while for a positive v_g,

  5. Audiovisual functional magnetic resonance imaging adaptation reveals multisensory integration effects in object-related sensory cortices.

    Science.gov (United States)

    Doehrmann, Oliver; Weigelt, Sarah; Altmann, Christian F; Kaiser, Jochen; Naumer, Marcus J

    2010-03-03

    Information integration across different sensory modalities contributes to object recognition, the generation of associations and long-term memory representations. Here, we used functional magnetic resonance imaging adaptation to investigate the presence of sensory integrative effects at cortical levels as early as nonprimary auditory and extrastriate visual cortices, which are implicated in intermediate stages of object processing. Stimulation consisted of an adapting audiovisual stimulus S(1) and a subsequent stimulus S(2) from the same basic-level category (e.g., cat). The stimuli were carefully balanced with respect to stimulus complexity and semantic congruency and presented in four experimental conditions: (1) the same image and vocalization for S(1) and S(2), (2) the same image and a different vocalization, (3) different images and the same vocalization, or (4) different images and vocalizations. This two-by-two factorial design allowed us to assess the contributions of auditory and visual stimulus repetitions and changes in a statistically orthogonal manner. Responses in visual regions of right fusiform gyrus and right lateral occipital cortex were reduced for repeated visual stimuli (repetition suppression). Surprisingly, left lateral occipital cortex showed stronger responses to repeated auditory stimuli (repetition enhancement). Similarly, auditory regions of interest of the right middle superior temporal gyrus and sulcus exhibited repetition suppression to auditory repetitions and repetition enhancement to visual repetitions. Our findings of crossmodal repetition-related effects in cortices of the respective other sensory modality add to the emerging view that in human subjects sensory integrative mechanisms operate on earlier cortical processing levels than previously assumed.

  6. Silicon-Nitride-based Integrated Optofluidic Biochemical Sensors using a Coupled-Resonator Optical Waveguide

    Directory of Open Access Journals (Sweden)

    Jiawei eWANG

    2015-04-01

    Full Text Available Silicon nitride (SiN is a promising material platform for integrating photonic components and microfluidic channels on a chip for label-free, optical biochemical sensing applications in the visible to near-infrared wavelengths. The chip-scale SiN-based optofluidic sensors can be compact due to a relatively high refractive index contrast between SiN and the fluidic medium, and low-cost due to the complementary metal-oxide-semiconductor (CMOS-compatible fabrication process. Here, we demonstrate SiN-based integrated optofluidic biochemical sensors using a coupled-resonator optical waveguide (CROW in the visible wavelengths. The working principle is based on imaging in the far field the out-of-plane elastic-light-scattering patterns of the CROW sensor at a fixed probe wavelength. We correlate the imaged pattern with reference patterns at the CROW eigenstates. Our sensing algorithm maps the correlation coefficients of the imaged pattern with a library of calibrated correlation coefficients to extract a minute change in the cladding refractive index. Given a calibrated CROW, our sensing mechanism in the spatial domain only requires a fixed-wavelength laser in the visible wavelengths as a light source, with the probe wavelength located within the CROW transmission band, and a silicon digital charge-coupled device (CCD / CMOS camera for recording the light scattering patterns. This is in sharp contrast with the conventional optical microcavity-based sensing methods that impose a strict requirement of spectral alignment with a high-quality cavity resonance using a wavelength-tunable laser. Our experimental results using a SiN CROW sensor with eight coupled microrings in the 680nm wavelength reveal a cladding refractive index change of ~1.3 × 10^-4 refractive index unit (RIU, with an average sensitivity of ~281 ± 271 RIU-1 and a noise-equivalent detection limit (NEDL of 1.8 ×10^-8 RIU ~ 1.0 ×10^-4 RIU across the CROW bandwidth of ~1 nm.

  7. Magnetic resonance of phase transitions

    CERN Document Server

    Owens, Frank J; Farach, Horacio A

    1979-01-01

    Magnetic Resonance of Phase Transitions shows how the effects of phase transitions are manifested in the magnetic resonance data. The book discusses the basic concepts of structural phase and magnetic resonance; various types of magnetic resonances and their underlying principles; and the radiofrequency methods of nuclear magnetic resonance. The text also describes quadrupole methods; the microwave technique of electron spin resonance; and the Mössbauer effect. Phase transitions in various systems such as fluids, liquid crystals, and crystals, including paramagnets and ferroelectrics, are also

  8. Tunable paramagnetic relaxation enhancements by [Gd(DPA)3]3- for protein structure analysis

    International Nuclear Information System (INIS)

    Yagi, Hiromasa; Loscha, Karin V.; Su, Xun-Cheng; Stanton-Cook, Mitchell; Huber, Thomas; Otting, Gottfried

    2010-01-01

    Paramagnetic relaxation enhancements (PRE) present a powerful source of structural information in nuclear magnetic resonance (NMR) studies of proteins and protein-ligand complexes. In contrast to conventional PRE reagents that are covalently attached to the protein, the complex between gadolinium and three dipicolinic acid (DPA) molecules, [Gd(DPA) 3 ] 3- , can bind to proteins in a non-covalent yet site-specific manner. This offers straightforward access to PREs that can be scaled by using different ratios of [Gd(DPA) 3 ] 3- to protein, allowing quantitative distance measurements for nuclear spins within about 15 A of the Gd 3+ ion. Such data accurately define the metal position relative to the protein, greatly enhancing the interpretation of pseudocontact shifts induced by [Ln(DPA) 3 ] 3- complexes of paramagnetic lanthanide (Ln 3+ ) ions other than gadolinium. As an example we studied the quaternary structure of the homodimeric GCN4 leucine zipper.

  9. Tunable superconducting resonators with integrated trap structures for coupling with ultracold atomic gases

    Energy Technology Data Exchange (ETDEWEB)

    Ferdinand, Benedikt; Wiedmaier, Dominik; Koelle, Dieter; Kleiner, Reinhold [Physikalisches Institut and Center for Quantum Science in LISA+, Universitaet Tuebingen (Germany); Bothner, Daniel [Physikalisches Institut and Center for Quantum Science in LISA+, Universitaet Tuebingen (Germany); Kavli Institute of Nanoscience, Delft University of Technology, Delft (Netherlands)

    2016-07-01

    We intend to investigate a hybrid quantum system where ultracold atomic gases play the role of a long-living quantum memory, coupled to a superconducting qubit via a coplanar waveguide transmission line resonator. As a first step we developed a resonator chip containing a Z-shaped trapping wire for the atom trap. In order to suppress parasitic resonances due to stray capacitances, and to achieve good ground connection we use hybrid superconductor - normal conductor chips. As an additional degree of freedom we add a ferroelectric capacitor making the resonators voltage-tunable. We furthermore show theoretical results on the expected coupling strength between resonator and atomic cloud.

  10. About kinetics of paramagnetic radiation malformations in beryllium ceramics

    International Nuclear Information System (INIS)

    Polyakov, A.I.; Ryabinkin, Yu.A.; Zashkvara, O.V.; Bitenbaev, M.I.; Petukhov, Yu.V.

    1999-01-01

    This paper [1] specifies that γ-radiation of the beryllium-oxide-based ceramics results in development of paramagnetic radiation malformations emerging the ESR spectrum in form of doublet with the splitting rate of oestrasid Δ∼1.6 and g-factor of 2.008. This report presents evaluation outcomes of dependence of paramagnetic radiation malformations concentration in beryllium ceramics on gamma-radiation dose ( 60 Co) within the range of 0-100 Mrad. Total paramagnetic parameters of beryllium ceramics in the range 0-100 Mrad of gamma-radiation dose varied slightly, and were specified by the first type of paramagnetic radiation malformations

  11. Design of a Miniaturized X-Band Diplexer Based on Novel One-Third-Mode Substrate Integrated Resonator Filters

    Science.gov (United States)

    Zhang, Hao; Kang, Wei; Wu, Wen

    2017-12-01

    In this paper, a miniaturized diplexer designed with two novel one-third-mode substrate integrated resonator (OTMSIR) filters has been presented. The one-third triangular resonator cavity with two transmission zeros (TZs) and two transmission poles is investigated. TZs are implemented by taking cross couplings of lower order modes in this design. The diplexer is then obtained by integrating two different sizes of OTMSIR filters with a common T-junction structure. A X-band diplexer operating at 10 GHz and 11.5 GHz is designed on a substrate with a dielectric constant of 3.55 to verify the above design concept. This novel structure features more compact size, better transmission performance, higher out of band rejection and easier integration compared with other circuits. A good agreement is obtained between the simulations and the measured results.

  12. Integrated Optic Surface Plasmon Resonance Measurements in a Borosilicate Glass Substrate

    Directory of Open Access Journals (Sweden)

    Antonino Parisi

    2008-11-01

    Full Text Available The surface plasmon resonance (SPR technique is a well-known optical method that can be used to measure the refractive index of organic nano-layers adsorbed on a thin metal film. Although there are many configurations for measuring biomolecular interactions, SPR-based techniques play a central role in many current biosensing experiments, since they are the most suited for sensitive and quantitative kinetic measurements. Here we give some results from the analysis and numerical elaboration of SPR data from integrated optics experiments in a particular borosilicate glass, chosen for its composition offering the rather low refractive index of 1.4701 at 633 nm wavelength. These data regard the flow over the sensing region (metal window of different solutions with refractive indexes in the range of interest (1.3÷1.5 for the detection of contaminants in aqueous solutions. After a discussion of the principles of SPR, of the metal window design optimization by means of optical interaction numerical modeling, and of waveguide fabrication techniques, we give a description of system setup and experimental results. Optimum gold film window thickness and width in this guided-wave configuration has been for the first time derived and implemented on an integrated optic prototype device. Its characterization is given by means of the real time waveguide output intensity measurements, which correspond to the interaction between the sensing gold thin film window and the flowing analyte. The SPR curve was subsequently inferred. Finally, a modified version of the device is reported, with channel waveguides arranged in a Y-junction optical circuit, so that laser source stability requirements are lowered by a factor of 85 dB, making possible the use of low cost sources in practical applications.

  13. Set up of a method for the adjustment of resonance parameters on integral experiments; Mise au point d`une methode d`ajustement des parametres de resonance sur des experiences integrales

    Energy Technology Data Exchange (ETDEWEB)

    Blaise, P.

    1996-12-18

    Resonance parameters for actinides play a significant role in the neutronic characteristics of all reactor types. All the major integral parameters strongly depend on the nuclear data of the isotopes in the resonance-energy regions.The author sets up a method for the adjustment of resonance parameters taking into account the self-shielding effects and restricting the cross section deconvolution problem to a limited energy region. (N.T.).

  14. Magneto-Optical Properties of Paramagnetic Superrotors

    Science.gov (United States)

    Milner, A. A.; Korobenko, A.; Floß, J.; Averbukh, I. Sh.; Milner, V.

    2015-07-01

    We study the dynamics of paramagnetic molecular superrotors in an external magnetic field. An optical centrifuge is used to create dense ensembles of oxygen molecules in ultrahigh rotational states. In is shown, for the first time, that the gas of rotating molecules becomes optically birefringent in the presence of a magnetic field. The discovered effect of "magneto-rotational birefringence" indicates the preferential alignment of molecular axes along the field direction. We provide an intuitive qualitative model, in which the influence of the applied magnetic field on the molecular orientation is mediated by the spin-rotation coupling. This model is supported by the direct imaging of the distribution of molecular axes, the demonstration of the magnetic reversal of the rotational Raman signal, and by numerical calculations.

  15. Integrated test plan ResonantSonic drilling system technology demonstration-1995, at the Hanford Site: Revision 1

    International Nuclear Information System (INIS)

    McLellan, G.W.

    1994-01-01

    This integrated test plan describes the demonstration test of the ResonantSonic drilling system. This demonstration is part of the Office of Technology Development's Volatile Organic Compound Arid Integrated Demonstration (VOC-Arid ID). Two main purposes of this demonstration are (1) to continue testing the ResonantSonic drilling system compatibility with the Hanford Site waste characterization programs, and (2) to transfer this method for use at the Hanford Site, other government sites, and the private sector. The ResonantSonic method is a dry drilling technique. Field testing of this method began in July 1993. During the next four months, nine holes were drilled, and continuous core samples were retrieved. Penetration rates were 2 to 3 times the baseline, and the operational downtime rate was less than 10%. Successfully demonstrated equipment refinements included a prototype 300 series ResonantSonic head, a new drill rod design for 18-centimeter diameter pipe, and an automated pipe handling system. Various configurations of sampling equipment and drill bits were tested, depending on geologic conditions. The principal objective of the VOC-Arid ID is to determine the viability of emerging technologies that can be used to characterize, remediate, and/or monitor arid or semiarid sites containing VOCs (e.g., carbon tetrachloride) with or without associated metal and radionuclide contamination

  16. Thermal properties of paramagnetic solid helium 3

    International Nuclear Information System (INIS)

    Goldstein, L.

    1983-01-01

    It was shown in recent work that over a limited molar volume range and at asymptotically high temperatures the thermal modulations of the pressure along isochores of paramagnetic solid 3 He could be accounted for through the formalism of the Heisenberg model of an antiferromagnetically interacting localized spin- 1/2 system. The internal consistency of this formalism requires the characteristic exchange-interaction parameter of the model derived from pressure modulation data to be identical with that appearing in the other thermal properties of this quantum solid. In a restricted temperature region where the spin excitations are the dominant thermal excitations of the solid, heat capacity data yield exchange-interaction parameters in fair agreement with those derived from pressures along isochores of larger molar volume. At higher temperatures, within well-defined limitations, thermal excitations involve both spin and phononexcitations. Here, because of the opposite temperature variations of the spin and phonon heat capacity components, the ensuing heat capacity minimum determines exactly the exchange-energy parameter and the relevant limiting Debye temperature as a function of the measured temperature location and value of the heat capacity extremum along the experimentally explored isochore. The exchange-energy parameters so derived display larger deviations from their predicted pressure-based values than those resulting from the lower temperature but still asymptotic spin-only heat capacities. At the present time, ambiguities in the experimental determinations of the characteristic Weiss temperatures of the asymptotic paramagnetic susceptibilities prevent one from deriving exchange-energy parameters with them. The present work leads to the prediction, within the limitations of the model formalism, of thermal properties of magnetized solid 3 He

  17. {sup 41}K(n, {gamma}){sup 42}K thermal and resonance integral cross section measurements

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira, F.A. Jr.; Maidana, N.L.; Vanin, V.R. [Sao Paulo Univ., SP (Brazil). Lab. do Acelerador Linear; Dias, M.S.; Koskinas, M.F. [IPEN-CNEN, Sao Paulo, SP (Brazil). Lab. de Metrolgia Nuclear; Lopez-Pino, N. [Instituto Superior de Tecnolgias y Ciencias Aplicadas (InSTEC), Habana (Cuba)

    2012-07-01

    We measured the {sup 41}K thermal neutron absorption and resonance integral cross sections after the irradiation of KNO{sub 3} samples near the core of the IEA-R1 IPEN pool-type research reactor. Bare and cadmium-covered targets were irradiated in pairs with Au-Al alloy flux-monitors. The residual activities were measured by gamma-ray spectroscopy with a HPGe detector, with special care to avoid the {sup 42}K decay {beta}{sup -} emission effects on the spectra. The gamma-ray self-absorption was corrected with the help of MCNP simulations. We applied the Westcott formalism in the average neutron flux determination and calculated the depression coefficients for thermal and epithermal neutrons due to the sample thickness with analytical approximations. We obtained 1.57(4) b and 1.02(4) b, for thermal and resonance integral cross sections, respectively, with correlation coefficient equal to 0.39.

  18. Gd-doped GaN studied with element specificity: Very small polarization of Ga, paramagnetism of Gd and the formation of magnetic clusters

    Energy Technology Data Exchange (ETDEWEB)

    Ney, A., E-mail: ney@maglomat.d [Fachbereich Physik and Center for Nanointegration Duisburg-Essen (CeNIDE), Universitaet Duisburg-Essen, Lotharstr. 1, D-47057 Duisburg (Germany); Kammermeier, T.; Ollefs, K.; Ney, V.; Ye, S. [Fachbereich Physik and Center for Nanointegration Duisburg-Essen (CeNIDE), Universitaet Duisburg-Essen, Lotharstr. 1, D-47057 Duisburg (Germany); Dhar, S. [Fachbereich Physik and Center for Nanointegration Duisburg-Essen (CeNIDE), Universitaet Duisburg-Essen, Lotharstr. 1, D-47057 Duisburg (Germany); Paul-Drude-Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, D-10117 Berlin (Germany); Ploog, K.H. [Paul-Drude-Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, D-10117 Berlin (Germany); Roever, M.; Malindretos, J.; Rizzi, A. [IV. Physikalisches Institut and Virtual Institute of Spinelectronics (VISel), Georg August Universitaet Goettingen, D-37077 Goettingen (Germany); Wilhelm, F.; Rogalev, A. [European Synchrotron Radiation Facility (ESRF), 6 Rue Jules Horowitz, BP 220, 38043 Grenoble Cedex (France)

    2010-05-15

    Element specific X-ray linear dichroism (XLD), X-ray magnetic circular dichroism (XMCD) at the Ga K- and Ga and Gd L{sub 3}-edges and magnetic resonance measurements have been carried out on Gd:GaN grown by molecular beam epitaxy with different Gd concentrations. XMCD studies at the Ga K-edge reveal only a very weak magnetic polarization, which is too small to account for the colossal moments reported before by SQUID. In the dilute limit we can show by XLD that the majority of the Gd dopant atoms go to substitutional Ga sites. XMCD studies demonstrate that the Gd sublattice behaves paramagnetic which is in contrast to integral SQUID measurements. The absence of ferromagnetic order at room temperature is corroborated by magnetic resonance studies. First signatures of phase separation are visible. At higher Gd concentrations phase separation is found by XLD. In such samples ferromagnetic-like order is consistently found by SQUID, XMCD and magnetic resonance which is characteristic for a blocked superparamagnetic ensemble. In turn, phase separated ferromagnetic Gd/GdN clusters cannot account for magnetic order observed at and above 300 K by SQUID.

  19. A Novel Paramagnetic Substrate for Detecting Myeloperoxidase Activity in Vivo

    Directory of Open Access Journals (Sweden)

    Mohammed S. Shazeeb

    2012-09-01

    Full Text Available Bis-phenylamides and bis-hydroxyindolamides of diethylenetriaminepentaacetic acid-gadolinium (DTPA(Gd are paramagnetic reducing substrates of peroxidases that enable molecular imaging of peroxidase activity in vivo. Specifically, gadolinium chelates of bis-5-hydroxytryptamide-DTPA (bis-5HT-DTPA(Gd have been used to image localized inflammation in animal models by detecting neutrophil-derived myeloperoxidase (MPO activity at the inflammation site. However, in other preclinical disease models, bis-5HT-DTPA(Gd presents technical challenges due to its limited solubility in vivo. Here we report a novel MPO-sensing probe obtained by replacing the reducing substrate serotonin (5-HT with 5-hydroxytryptophan (HTrp. Characterization of the resulting probe (bis-HTrp-DTPA(Gd in vitro using nuclear magnetic resonance spectroscopy and enzyme kinetic analysis showed that bis-HTrp-DTPA(Gd (1 improves solubility in water; (2 acts as a substrate for both horseradish peroxidase and MPO enzymes; (3 induces cross-linking of proteins in the presence of MPO; (4 produces oxidation products, which bind to plasma proteins; and (5 unlike bis-5HT-DTPA(Gd, does not follow first-order reaction kinetics. In vivo magnetic resonance imaging (MR! in mice demonstrated that bis-HTrp-DTPA(Gd was retained for up to 5 days in MPO-containing sites and cleared faster than bis-5HT-DTPA(Gd from MPO-negative sites. Bis-HTrp-DTPA(Gd should offer improvements for MR! of MPO-mediated inflammation in vivo, especially in high-field MR!, which requires a higher dose of contrast agent.

  20. A novel paramagnetic substrate for detecting myeloperoxidase activity in vivo.

    Science.gov (United States)

    Shazeeb, Mohammed S; Xie, Yang; Gupta, Suresh; Bogdanov, Alexei A

    2012-01-01

    Bis-phenylamides and bis-hydroxyindolamides of diethylenetriaminepentaacetic acid-gadolinium (DTPA(Gd)) are paramagnetic reducing substrates of peroxidases that enable molecular imaging of peroxidase activity in vivo. Specifically, gadolinium chelates of bis-5-hydroxytryptamide-DTPA (bis-5HT-DTPA(Gd)) have been used to image localized inflammation in animal models by detecting neutrophil-derived myeloperoxidase (MPO) activity at the inflammation site. However, in other preclinical disease models, bis-5HT-DTPA(Gd) presents technical challenges due to its limited solubility in vivo. Here we report a novel MPO-sensing probe obtained by replacing the reducing substrate serotonin (5-HT) with 5-hydroxytryptophan (HTrp). Characterization of the resulting probe (bis-HTrp-DTPA(Gd)) in vitro using nuclear magnetic resonance spectroscopy and enzyme kinetic analysis showed that bis-HTrp-DTPA(Gd) (1) improves solubility in water; (2) acts as a substrate for both horseradish peroxidase and MPO enzymes; (3) induces cross-linking of proteins in the presence of MPO; (4) produces oxidation products, which bind to plasma proteins; and (5) unlike bis-5HT-DTPA(Gd), does not follow first-order reaction kinetics. In vivo magnetic resonance imaging (MRI) in mice demonstrated that bis-HTrp-DTPA(Gd) was retained for up to 5 days in MPO-containing sites and cleared faster than bis-5HT-DTPA(Gd) from MPO-negative sites. Bis-HTrp-DTPA(Gd) should offer improvements for MRI of MPO-mediated inflammation in vivo, especially in high-field MRI, which requires a higher dose of contrast agent.