Detection of gravity wave signals with drift of the geometric dimensions of the detector

A technique for thermal compensation of drift in the resonator length in a gravity wave detector is described. © 2008 Springer Science+Business Media, Inc

Radiation-induced stable radicals in calcium phosphates: Results of multifrequency epr, ednmr, eseem, and endor studies

This article presents the results of a study of radiation-induced defects in various synthetic calcium phosphate (CP) powder materials (hydroxyapatite—HA and octacalcium phosphate—OCP) by electron paramagnetic resonance (EPR) spectroscopy at the X, Q, and W-bands (9, 34, 95 GHz for the microwave frequencies, respectively). Currently, CP materials are widely used in orthopedics and dentistry owing to their high biocompatibility and physico-chemical similarity with human hard tissue. It is shown that in addition to the classical EPR techniques, other experimental approaches such as ELDOR-detected NMR (EDNMR), electron spin echo envelope modulation (ESEEM), and electronnuclear double resonance (ENDOR) can be used to analyze the electron–nuclear interactions of CP powders. We demonstrated that the value and angular dependence of the quadrupole interaction for14 N nuclei of a nitrate radical can be determined by the EDNMR method at room temperature. The ESEEM technique has allowed for a rapid analysis of the nuclear environment and estimation of the structural positions of radiation-induced centers in various crystal matrices. ENDOR spectra can provide information about the distribution of the nitrate radicals in the OCP structure. © 2021 by the authors. Licensee MDPI, Basel, Switzerland. Published under the CC BY 4.0 license.Authors would like to thank the Russian Foundation for Basic Research, project no. 18-29-11086. Institute of Solid State Physics, University of Latvia as the Center of Excellence received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01–2016-2017- TeamingPhase2 under grant agreement No. 739508, project CAMART2

Connection Between the Carotid Plaque Instability and Paramagnetic Properties of the Intrinsic Mn²⁺ Ions

© 2016, Springer Science+Business Media New York.The pulsed W-band (the microwave frequency of 94 GHz, magnetic field of 3.4 T) electron paramagnetic resonance (EPR) comparative studies of a series of 20 atherosclerotic plaques (AP) obtained during carotid endarterectomy in patients with atherosclerosis is presented. The AP stability was established by ultrasound angiography. In all of the obtained species EPR spectra due to the presence of Mn2+ ions in a crystal matrix of hydroxyapatites (HAp) is observed. The existence of HAp in plaque fragments is confirmed by X-ray diffraction analyses. The spectral parameters of Mn2+ are ascribed to two possible locations in the HAp constituent of the atherosclerotic plaques. The difference in the electronic relaxation times of T2e for Mn2+ ions in stable and unstable plaques is observed that can indicate the more homogeneous distribution of Mn2+ in stable plaques as compared to unstable species. The results can be potentially used for the understanding the mechanisms of pathological calcifications and AP stability

W-band EPR of vanadyl complexes aggregates on the surface of Al<inf>2</inf>O<inf>3</inf>

© 2018 Institute of Physics Publishing. All rights reserved. Structural characterization of metalloporphyrins, asphaltenes and their aggregates in complex systems such as native hydrocarbons is in the focus of scientific and industrial interests since many years. We present W-band (95 GHz) electron paramagnetic resonance (EPR) study in the magnetic field of about 3.4 T and temperature of 100 K for Karmalinskoe oil, asphaltens and asphaltenes deposited on the surface of Al2O3. Features of the obtained spectra are described. Shift to the higher frequencies allows to separate spectrally the contributions from paramagnetic complexes of different origin and define the EPR parameters more accurately comparing to the conventional X-band (9 GHz). Changes of the EPR parameters are tracked. We suggest that the proposed approach can be used for the investigation of structure of vanadyl complexes aggregates in crude oil and their fractions

W-band EPR of vanadyl complexes aggregates on the surface of Al<inf>2</inf>O<inf>3</inf>

© 2018 Institute of Physics Publishing. All rights reserved. Structural characterization of metalloporphyrins, asphaltenes and their aggregates in complex systems such as native hydrocarbons is in the focus of scientific and industrial interests since many years. We present W-band (95 GHz) electron paramagnetic resonance (EPR) study in the magnetic field of about 3.4 T and temperature of 100 K for Karmalinskoe oil, asphaltens and asphaltenes deposited on the surface of Al2O3. Features of the obtained spectra are described. Shift to the higher frequencies allows to separate spectrally the contributions from paramagnetic complexes of different origin and define the EPR parameters more accurately comparing to the conventional X-band (9 GHz). Changes of the EPR parameters are tracked. We suggest that the proposed approach can be used for the investigation of structure of vanadyl complexes aggregates in crude oil and their fractions

HYSCORE Spectroscopy to Resolve Electron–Nuclear Structure of Vanadyl Porphyrins in Asphaltenes from the Athabasca Oil Sands In Situ Conditions

The purpose of this work is to analyze the electron–nuclear interactions of the vanadyl-porphyrin (VP) complexes in oil asphaltenes. Asphaltenes from the Athabasca oil sands were studied by HYperfine Sublevel CORrelation Spectroscopy (HYSCORE) electron paramagnetic resonance (EPR). It makes it possible to resolve and interpret complex hyperfine spectra of intrinsic VP with strong and weak hyperfine interactions between the electron magnetic moment and various nuclear spins (1H, 14N, 51V). The main parameters of spin-Hamiltonian for the VP spin system are determined. The axially symmetric structure of the VP complexes is revealed, and the local nuclear environment of the paramagnetic center is investigated. The results can be used for the study of asphaltene electron–nuclear structure and asphaltene aggregates with the aim of elucidating asphaltenes’ transformation(s) under the influence of external treatment

Molecular Dynamics and Proton Hyperpolarization via Synthetic and Crude Oil Porphyrin Complexes in Solid and Solution States

The use of vanadyl porphyrins either in synthetic compounds or naturally occurring in asphaltenes is investigated as a source of proton hyperpolarization via dynamic nuclear polarization (DNP) in nuclear magnetic resonance (NMR) experiments. The features of dynamics and location of the vanadyl VO2+ complex in aggregates within the oil asphaltene molecules are studied by means of DNP, electron paramagnetic resonance (EPR), and NMR field cycling relaxometry. Both the solid effect and Overhauser DNP were observed for the asphaltene solution in benzene, as well as in the solution and solid states for synthetic compounds. By comparison with a solution of synthetic vanadyl porphyrins, it is shown that vanadyl porphyrins in asphaltene aggregates are localized outside of the interface of the asphaltene aggregates and more exposed to the maltene molecules than "free"carbon-centered radicals associated with the core of asphaltene molecules. The perceptible contribution of scalar interaction is observed in solutions for both synthetic and asphaltene vanadyl porphyrins

Mineral–Polymer Composites Based on Hydroxyapatite and Polyvinylpyrrolidone for Medical Applications

© 2019, Pleiades Publishing, Ltd. Abstract: Hydroxyapatite (HA)–polyvinylpyrrolidone (PVP) nanocomposites with the HA/PVP ratio of 3.6–14.5 were synthesized by chemical precipitation from solutions of calcium nitrate and ammonium hydrogen phosphate in a PVP solution. The phase composition, size of coherent scattering regions, and size and morphology of HA particles were determined after heat treatment of the products of synthesis. The chemical interaction of the composite components was established by ESR spectroscopy on exposure to laser radiation at 355 nm