Search

Eugenol–β‐cyclodextrin complex has been widely used because of the enhanced stability and conservation of the properties of eugenol. Applications in food and health sciences have been shown previously, which makes this complex an excellent model to understand and develop methodologies for the analysis and prediction of physical properties. In this work, the dynamics of eugenol incorporated into β‐cyclodextrin are presented, using NMR relaxation rates, and the predictive capabilities of molecular dynamics simulations are discussed. Results show a hindered rotation of eugenol around the principal inertial axes when located inside β‐cyclodextrin. Moreover, a translational movement of the whole complex is demonstrated. [ABSTRACT FROM AUTHOR]

Electron-piezoelectric phonon interaction provides a significant extrinsic channel for energy relaxation in a graphene sheet placed on a polar substrate. We report in this paper our analytical and numerical investigations on energy relaxation rate and power loss density in graphene sheet on a polar substrate considering the electron-piezoelectric phonon scattering channel in the Boltzmann transport approach. We overcome the earlier crude approximations made to achieve the reported analytical results and compare the obtained results for their compliance with the numerical findings for the graphene sheet on the GaAs substrate. The obtained analytical expression for energy relaxation rate is valid for all temperatures and electron energies. The analytical result for power loss density limits its validity for low electron densities (< 1 0 1 2 cm − 2). It is observed that the relaxation rate due to surface piezoelectric phonons in graphene on GaAs substrate is directly proportional to temperatures above ∼ 1 0 K , below which temperature independence is seen. Also, it is observed that the relaxation rate is linearly dependent on electron energy, E k at low temperatures, and E k independent at high temperatures. Moreover, the relaxation rate is electron density-independent for all (low to high) temperatures. The seemingly odd (from earlier reported behavior) temperature-independent, linearly dependent E k and n independent relaxation rate behavior for low temperatures is attributed to the approximation used so far in the phononic statistical occupation factor in deriving the relaxation rate in the low-temperature Bloch-Gruneisen (BG) regime. In undoped graphene, we have found that the power loss behavior follows a crossover from T e 5 to T e 4 behavior while moving from low (∼ 2 0 K) to high (∼ 1 0 0 0 K) electron temperature. This behavior contradicts the study by Zhang et al. [Phys. Rev. B 87, 075443 (2013)] and M. Ansari [Physica E: Low Dimens. Syst. Nanostruct. 131, 114722 (2021)] which reported low-temperature BG behavior of T e 3 . This behavior is again attributed to using BG regime approximation for statistical occupation factors. Our findings are in agreement with the experimental work by Chen et al. [Nature Nanotechnol.  3, 206 (2008)] and You et al. [Appl. Phys. Lett. 115, 043104 (2019)]. [ABSTRACT FROM AUTHOR]

The effect of an ionic core on the temperature relaxation in dense hot plasma of beryllium is studied using the pseudpotential model by Gericke et al [Phys. Rev. E 2010, 81, 065401(R)]. Employing the screened version of the ion pseudpotential [by Ramazanov et al, Phys. Plasmas 2021, 28 (9), 092702], we computed the quantum transport cross section for the electron‐ion collisions in dense beryllium plasma, where screening is taking into account using the density response function in the long‐wavelength regime. The results for the transport cross section are used to compute a generalised Coulomb logarithm and electron‐ion collision frequency. Utilizing the latter, we show the effect of the ionic core on the temperature relaxation. To understand the role of the ionic core, we compare the results with the data computed considering ions as point‐like charges. [ABSTRACT FROM AUTHOR]

Many body effects in the wetting layer (WL)-double quantum dot (DQD)-metal nanoparticle (MNP) structure have been studied by modeling the Coulomb scattering rates in this structure. The strong coupling between WL-DQD-MNPs was considered. An orthogonalized plane wave (OPW) is assumed between WL-QD transitions. The transition momenta are calculated accordingly to specify the normalized Rabi frequency on this structure, considering the strong coupling between the WL-DQD-MNP structures. This approach is important for realizing scattering rates, including in-and-out capture and relaxation rates, which are essential for specifying the type of structure used depending on the optimum value of the scattering time required to fit the application. The QD hole capture rate is the highest, and the hole capture times are the shortest. The relaxation times are less than the electron capture times by one order, while they are half of the hole capture times. The capture rates increase with increasing distance R between the DQDs and the MNP. High tunneling increases hole-capture rates and changes the relaxation rates, showing the importance of tunneling in controlling the scattering rates. [ABSTRACT FROM AUTHOR]

The relations for the optical characteristics of the composite nanoparticles of the type “metallic core – molecular aggregate shell” have been obtained in the work. The calculations of the frequency dependencies of the polarizability, absorption and scattering cross-sections, radiation efficiency and size dependencies of the frequencies of the hybrid plasmon-exciton resonances have been performed. An approximate approach to the determination of the size dependencies of the frequencies of the hybrid plasmon-exciton modes, the essence of which is to ignore the relaxation processes in the molecular aggregate shell and in metallic core, has been proposed. It has been demonstrated that the increase in the radius of metallic core results in the decrease in the highest frequency of plasmon-exciton resonance, while the next highest frequency increases. At the same time, the smallest of these frequencies decreases first, and when the content of metallic fraction becomes greater that 50 % of the volume of the entire particle, it begins to increase. The evolution of the maximums of the imaginary part of the polarizability with the change of the geometric parameters of the composite nanoparticle: the radius of metallic core and the thickness of the shell has been observed. It has been established that one of these maximums is situated in the near ultraviolet region, whereas the other two of them are in the visible part of the spectrum. Moreover, it should be pointed out the significant increase in the real and imaginary parts and the module of the polarizability under the increase in the radius of metallic core. The necessity of taking into account both absorption and scattering under the study of the optical properties of nanoparticles of the composition “metallic core – J-aggregate” is proved. It has been shown that the value of radiation efficiency in the optical frequency range is practically independent on the changes of the thickness and material of the shell, while the change of material and radius of metallic core has significant effect on its frequency dependence in the visible part of the spectrum. The feasibility of the practical use of the composite nanoparticles with golden core with the small radius, in which the radiation efficiency is close to one in the entire optical frequency range, has been established. [ABSTRACT FROM AUTHOR]

Magnetic field gradients interfere with the coherence of the atomic ensemble and degrade the performance of the spin-exchange relaxation-free (SERF) atomic magnetometer. In this paper, the influence of magnetic field gradients is incorporated into the response model of single-beam atomic magnetometer, and the theoretical models of transverse relaxation rate, spin polarization and scale factor are established. Based on this model, we find that magnetic field gradients in different directions can cause varying degrees of degradation in the performance parameters of the magnetometer. The magnetic linewidths under different light power and magnetic field gradients are measured using the designed dedicated magnetic field gradients coils, and the spin polarization and magnetic field gradients relaxation rate are obtained through fitting. An unevenness and deviation of the curve are also observed in the experiments, indicating the presence of the magnetic field gradient of approximately 2 nT/cm in the magnetic shields. Furthermore, in a magnetic field gradient environment of 20 nT/cm, the mean of the long-term sensitivity decreased by 3.5 times and the standard deviation increased by 11 times. It shows that the magnetic field gradients will not only affect the signal-to-noise ratio, but also make the magnetometer more vulnerable to external interference when working. The sensitivity and stability of magnetometer will be greatly reduced. The research in this article provides a theoretical and experimental basis for eliminating the influence of magnetic field gradients and improving the accuracy of magnetic field measurements.

Abstract To investigate the diagnostic value of ultra‐small superparamagnetic Fe3O4 nanoparticles as dual modal contrast agent in rabbit orthotopic liver tumor. Twenty‐four New Zealand rabbits with orthotopic liver tumor were randomly divided into experimental group and control group. The experimental group contained 12 rabbits which intravenously injected with Fe3O4 nanoparticles and the control group contained 12 rabbits which intravenously injected with Gd‐DTPA. After injection, the cross‐sectional T1 and T2‐weighted scan images of experimental group and cross‐sectional T1‐weighted scan images of control group were obtained at the different timepoints (including 0, 5, 15, 20, 30, 45, 60, 75, 90, 120, 180, and 240 min) with a clinical 3.0 T MRI scanner. The SNR value of the tumor site and the normal liver site at different time points were calculated, respectively, and then the signal change value (CNR) of the tumor relative to the normal liver tissue was obtained. The r1 value of Fe3O4 nanoparticles was significantly higher than Gd‐DTPA (6.97 mM−1 s−1 for Fe3O4 nanoparticles and 4.75 mM−1 s−1 for Gd‐DTPA and only Fe3O4 nanoparticles exhibited the r2 relaxation rate which was 22.53 mM−1 s−1). In addition, the r2/r1 ratio of Fe3O4 was 3.23 which also demonstrated the strong MR relaxation characteristics of Fe3O4 nanoparticles. Compare with clinical used MRI contrast agent (Gd‐DTPA), the ultra‐small magnetic Fe3O4 nanoparticles not only showed the better T1 contrast enhancement but also exhibited the T1/T2 dual‐modal enhanced contrast ability, which could improve the accuracy and sensitivity of MRI diagnosis and realize the early diagnosis of diseases in prospect.

The behavior of the diagonal components of the dielectric tensor and the behavior of the absorption crosssection in the different frequency ranges for the composite cylindrical nanostructures "metallic core - graphene shell" have been studied. In order to obtain the calculation formulas one uses the relations for the longitudinal and transverse components of the dielectric tensors for metallic core and graphene shell, which are determined by Drude model and Cubo model correspondingly. The consideration is carried out in the frameworks of "equivalent" elongated spheroid approach, according to which the defining dimensional parameter is effective aspect ratio, calculated from the condition of the equality of the corresponding axial inertia moments for two-layer cylinder and the "equivalent" elongated spheroid. The numerical results have been obtained for the nanocylinders with the cores of different metals, different radius and with the different number of graphene layers. The variation of amplitude and the variation of the location of extremes of the real and imaginary parts of the transverse component of the dielectric tensor under the increase in radius of the metallic core and the thickness of the graphene shell have been analyzed. It has been shown that the variation of the radius of the core has the significantly greater influence on the properties of the polarizability resonances and absorption cross-section than the variation of the number of graphene layers. The reasons of the presence of two maxima of the absorption cross-section for the metal-graphene cylinders which differ in both amplitude and width and located in infrared, violet and near ultraviolet parts of the spectrum and their relation with the surface plasmonic resonances in the metallic core and with the terahertz plasmons of graphene have been found. The factors which have an effect on amplitude and on the shift of the maxima of the absorption cross-section have been found. The reasons of the different width of maxima, which are located in the different spectral intervals, have been determined. [ABSTRACT FROM AUTHOR]

This work aims to compare the effects of different yarn structures on the elastic properties. A new type of elastic core-spun yarn which is called tri-core (elastane/T400/elastane) yarn is introduced and tested for elastic properties after cyclic loading. The other yarn structures used are single-core/T400, single-core/lycra, dual-core (elastane/T400) yarn, and yarn without a core component (conventional). The five types of yarn structure were produced at three levels of yarn counts (10, 14, and 18 Ne). Elastic properties after cyclic loading including stress decay, permanent deformation, elastic recovery, and relaxation rate were calculated and statistically analyzed using two-way analysis of variance. The scanning electron microscopy images of the five structures used were produced to illustrate the structure of these yarns. The results determined that elastane/T400/elastane core-spun and single-core/T400 yarns have higher values for most of the elastic properties. It was found that yarn count and yarn structure significantly affect stress decay, while the yarn structure significantly affects permanent deformation and elastic recovery. On the other hand, yarn count significantly affects the relaxation rate. Data showed that the number of cyclic tests significantly influences yarn elastic recovery. [ABSTRACT FROM AUTHOR]

Human mesenchymal stem cells (hMSCs) were labeled with Dotarem or (Gd-DOTA)2- EM7 (EM7Gd2) via electroporation (EP). Cellular transmission electron microscopy (TEM) reveals free distribution of Gd agents and formation of EM7Gd2 clusters in the cytosol. Cellular magnetic resonance imaging (MRI) reveals that the free Gd agents induce MRI signal enhancement effect due to its fast exocytosis and subsequent interaction with intercellular water molecules. The EM7Gd2 clusters exhibits a longer intracellular retention time and induce a persistent MRI signal reduction effect. The cellular MRI results are interpreted by taking into account both T1 and T2 relaxation rates and their correlation with cellular binding structures of Dotarem and EM7Gd2.

Enzymatic activity is a pivotal factor in cancer progression, necessitating the development of in vivo imaging techniques for precise enzyme localization and quantification within tumors. Magnetic resonance imaging (MRI), known for its non-invasive nature and excellent soft tissue contrast, is vital in molecular imaging. However, current molecular MRI methods need improved accuracy and sensitivity. Interest in enzyme-catalyzed MRI probes has surged due to their unique specificity and catalytic efficiency. These probes are activated by abnormal enzyme expression in lesion tissue, enabling a signal transition from inactive to active. This "OFF-to-ON" activation aims to improve tumor imaging fidelity and the target-to-background signal ratio. This review synthesizes the latest developments in enzyme-catalyzed MRI probes, focusing on three key de-sign strategies: enzyme-catalyzed self-assembly, disassembly, and distance-dependent magnetic resonance tuning. We elucidate the practical applications of these probes in tumor enzyme monitoring and address the ongoing challenges and future directions in this burgeoning field. • Enzymatic activity is pivotal in cancer progression, necessitating methods to localize and quantify enzymes in living cancer cells for cancer imaging. • Enhancement of imaging specificity and sensitivity by enzyme-catalyzed MRI probes has been summarized, paving new avenues for advanced tumor imaging techniques. • Design strategies of enzyme-catalyzed MRI probes are summarized, including self-assembly, disassembly, and distance-dependent magnetic resonance tuning (MRET), highlighting their applications in tumor imaging. • Challenges and prospects have been discussed to further advance enzyme-catalyzed MRI probes towards clinical applications. [ABSTRACT FROM AUTHOR]

A theoretical analysis of thermal conductivity of high-temperature superconductor cuprates, Pr1.3−xLa0.7CexCuO4 (PLCCO), has been successfully investigated. In this formulation, the idea of relaxation times and other scattering processes has been developed from frequency (energy) line widths using a quantum dynamical method. The major emphasis of this study is on the influence of phonon-dopant atom scattering on the thermal conductivity of Ce-doped PLCCO, as well as other prominent scattering processes such as electron-phonon, cubic and quartic anharmonic phonon, cubic and quartic phonon interference, and so on. The proposed theory has achieved a satisfactory agreement between theory and experiment. [ABSTRACT FROM AUTHOR]

The frequency dependences of polarizability, absorption and scattering cross sections, and optical radiation efficiency of nanotubes of different metals and different sizes are studied. Expressions for the frequencies of longitudinal and transverse surface plasmon resonances are obtained. The relationship between the theory proposed and the plasmon hybridization model is discussed. The evolution of the polarizability maxima, as well as the absorption and scattering cross sections, upon a change in the geometric parameters and morphology of the core and the shell, is traced. [ABSTRACT FROM AUTHOR]

Traditional practice of suppressing low-frequency noise in atomic magnetometers is mainly through the application of magnetic field modulation, while magnetic fields of this kind introduce extra transverse relaxation, which results in a decrease of sensitivity. In this study, a novel method of measuring relaxation rate induced by spin-destruction, wall collisions and modulation magnetic fields is proposed. The optical pumping model is studied both in optical-thin and optical-thick vapor cell through the analysis of total relaxation, thus the optical pumping rate can be separated from total relaxation by analyzing the optical depth. Furthermore, based on the analysis of optical pumping rate and relaxation rate, the polarization of the electron ensemble was evaluated. A compact magnetometer with single-beam configuration is developed for the proof of concept, and the experimental results show good agreements with theoretical calculation. Our method provides a simple and feasible approach to in-situ measurement of transverse relaxation rate and optical pumping rate with physical structure of the device untouched, which is especially advantageous for designing and optimizing compact atomic magnetometers. [ABSTRACT FROM AUTHOR]

The thermal conductivity of high temperature superconductor cuprates (Zn-doped yttrium barium copper oxide (YBCO), YBa2(Cu1−xZnx)3O7−δ) is successfully analyzed in the temperature range of 0–200 K. Despite the fact that several theories have been offered to assess the thermal conductivity of high temperature superconductors since the pioneering work of Bardeen, Rickayzen, and Tewordt until now, a satisfactory solution has yet to be found. The idea of relaxation time and various scattering mechanisms has been developed from frequency line widths using a quantum dynamical approach in this current formulation. The influence of phonon–dopant atom scattering on the thermal conductivity of Zn-doped YBCO has been investigated in this study. This proposed theory has been able to achieve successful agreement between theory and experiment. [ABSTRACT FROM AUTHOR]

Using limit transitions in the general relations for the surface relaxation and radiation damping rates in a prolate and an oblate ellipsoidal nanoparticle, the corresponding expressions for rod-shaped and disk-shaped particles are obtained. The frequency dependences of the statistically averaged efficiencies of the absorption and scattering of electromagnetic radiation by nanoparticles of different shapes are calculated. Calculations were performed for Au, Ag, Cu, and Pt nanostructures. The effect of the shape and material of the nanoparticle on the number and position of the maxima and the absorption and scattering efficiency is analyzed. It is found that the presence of two maxima in the frequency dependence of the scattering efficiency for nanodisks is associated with the manifestation of a longitudinal and transverse surface plasmon resonance. [ABSTRACT FROM AUTHOR]

• In biological tissue, paramagnetic and diamagnetic inclusions often occur co-located. • Especially in in vivo applications, a separation would be desirable. • A dedicated phantom with isotropic dia- and paramagnetic substructure is presented. • Measured susceptibility values and relaxation rates are compared with theoretical values. • The proposed phantom allows for the validation of QSM and source separation algorithms. A phantom is presented in this study that allows for an experimental evaluation of QSM reconstruction algorithms. The phantom contains susceptibility producing particles with dia- and paramagnetic properties embedded in an MRI visible medium and is suitable to assess the performance of algorithms that attempt to separate isotropic dia- and paramagnetic susceptibility at the sub-voxel level. The phantom was built from calcium carbonate (diamagnetic) and tungsten carbide particles (paramagnetic) embedded in gelatin and surrounded by agarose gel. Different mass fractions and mixing ratios of both susceptibility sources were used. Gradient echo data were acquired at 1.5 T, 3 T and 7 T. Susceptibility maps were calculated using the MEDI toolbox and relaxation rates Δ R 2 ∗ were determined using exponential fitting. Relaxation rates as well as susceptibility values generally coincide with the theoretical values for particles fulfilling the assumptions of the the static dephasing regime with stronger deviations for relaxation rates at higher field strength and for high susceptibility values. MRI raw data are available for free academic use as supplementary material. In this study, a susceptibility phantom is presented that might find its application in the development and quantitative validation of current and future QSM reconstruction algorithms which aim to separate the influence of isotropic dia- and paramagnetic substructure in quantitative susceptibility mapping. [ABSTRACT FROM AUTHOR]

As an important tool in microwave detection, quantum sensing techniques have been studied in a broad range of fields such as microwave electrometry and microwave magnetic field detection. In this work, we measure the relaxation rate of Rb atoms in vapor cells using a Rabi-resonance-based quantum sensing technique. The characterizations of the Rabi resonance line shape with different experimental parameters are investigated. The relaxation rate of the vapor cell can be obtained with the Rabi resonance line shape. [ABSTRACT FROM AUTHOR]

Alkali metal-noble gas comagnetometers operated in the regime of spin-exchange relaxation-free (SERF) have been widely used in fundamental physics tests and rotation sensing as gyroscope. Spin-exchange relaxation is an important systematic bias of the comagnetometer, which could limit sensitivity significantly. However, the suppression effect of the spin-exchange relaxation has not been examined quantitatively so far. Herein, we systematically investigate the relaxation of the alkali metal atoms and find that the spin-exchange relaxation is not completely eliminated under the normal operating condition of the K-Rb-21Ne comagnetometer. In addition to the optical pumping rate, the spin-exchange relaxation still plays a dominant role in the broadening of electron Zeeman resonances due to the large electron magnetic field. This is the first demonstration that the alkali metal atoms are operated in the near-SERF regime in the alkali metal-noble gas comagnetometer with a large election magnetic field, which will shed light on the way to reduce the relaxation of the alkali metal atoms and enhance the sensitivity of the comagnetometer. [ABSTRACT FROM AUTHOR]

Multichannel spin-exchange relaxation-free (SERF) atomic magnetometers (AMs) have broad application prospects in array biomagnetic measurement systems because of their high spatial resolution. This study proposed an efficient and high-quality beam-splitting method based on a diffractive optical element (DOE), which enables multichannel SERF AM to maintain ultrahigh consistency with a channel interval of 3.27 mm. Based on the relaxation rate model under zero-field resonance, the minor differences in the magnetic linewidth of each channel were analyzed. The experimental results demonstrated ultra-high consistency of the magnetic field measurement signals between multiple channels, with a nonlinear error of less than 0.1%. The optimal sensitivity for a single channel was 11.9 fT/Hz 1 / 2 @31.5 Hz, and 9.3 fT/Hz 1 / 2 @31.5 Hz in the first-order gradiometer mode. The structure also satisfied the requirements of long-term high stability and high sensitivity, which are expected to further obtain more measurement channels. This method plays a critical role in improving the accuracy of magnetocardiography (MCG) and magnetoencephalography (MEG) systems. [Display omitted] • Implemented a highly consistent method of beam splitting in a magnetometer. • The distance between channels of the multichannel atomic magnetometer is 3.27 mm. • After beam splitting, the nonlinear error of each channel is less than 0.1%. • The sensitivity of a single channel is 11.9 fT/Hz 1 / 2 @31.5 Hz. • The sensitivity can reach 9.3 fT/Hz 1 / 2 @31.5 Hz in a first-order gradiometer mode. [ABSTRACT FROM AUTHOR]

Magnetic field gradients interfere with the coherence of the atomic ensemble and degrade the performance of the spin-exchange relaxation-free (SERF) atomic magnetometer. In this paper, the influence of magnetic field gradients is incorporated into the response model of single-beam atomic magnetometer, and the theoretical models of transverse relaxation rate, spin polarization and scale factor are established. Based on this model, we find that magnetic field gradients in different directions can cause varying degrees of degradation in the performance parameters of the magnetometer. The magnetic linewidths under different light power and magnetic field gradients are measured using the designed dedicated magnetic field gradients coils, and the spin polarization and magnetic field gradients relaxation rate are obtained through fitting. An unevenness and deviation of the curve are also observed in the experiments, indicating the presence of the magnetic field gradient of approximately 2 nT/cm in the magnetic shields. Furthermore, in a magnetic field gradient environment of 20 nT/cm, the mean of the long-term sensitivity decreased by 3.5 times and the standard deviation increased by 11 times. It shows that the magnetic field gradients will not only affect the signal-to-noise ratio, but also make the magnetometer more vulnerable to external interference when working. The sensitivity and stability of magnetometer will be greatly reduced. The research in this article provides a theoretical and experimental basis for eliminating the influence of magnetic field gradients and improving the accuracy of magnetic field measurements. • The models of the influence of MFGs on the parameters of the OPMs are established. • The experimental results are in good agreement with the proposed equations. • The asymmetry of the curve indicates the presence of residual MFGs. • The MFGs make the OPM more vulnerable to interference from the external environment. [ABSTRACT FROM AUTHOR]

Most previous stress relaxation tests were based on steel wires and steel strands. This test performed 1,000 h of stress relaxation test on stainless steel cables and Galfan-coated steel cables with diameters of Ø14 , Ø20 , and Ø26 mm. Three different initial tension levels were tested, and three control values of 30%, 50%, and 70% of the ultimate tensile strength of the cable were used as the load control points. The stress relaxation tests were carried out in a factory building, and the temperature was not strictly controlled. The stress relaxation of the cable is the stress relaxation under the combined action of temperature relaxation, stress relaxation, and time relaxation. To make the research more valuable, the thermal expansion coefficient of the cable was used to eliminate the influence of temperature on the stress relaxation test, and the data were adjusted to correspond to 30°C. The test results were analyzed, and formulas for calculating the tension loss of steel cables were established. The results showed that the exponential equation of time logarithm can better express the relation between tension loss and time. The relation between the coefficients and the initial tensile force was established. This test also compared the relaxation properties of stainless steel cables and Galfan-coated steel cables. For steel cables with the same initial tension level and the same diameter, the Galfan-coated steel cables had much larger relaxation rates than the stainless steel cables. [ABSTRACT FROM AUTHOR]

We propose a novel method for measuring relaxation rates and Fermi-contact fields of the electron and nuclear spin ensembles rapidly and synchronously in spin-exchange relaxation-free (SERF) atomic comagnetometers based on the transient response. The transient response model of the comagnetometer is established by solving a set of Bloch equations. The decay rates and oscillation frequencies of the transient response as functions of the longitudinal magnetic field are investigated theoretically and experimentally. The total relaxation rate of the nuclear spin ensemble is obtained from its decay rate. A linear model is presented with a detailed mathematical derivation based on the decay rates and oscillation frequencies of the spin ensembles. The Fermi-contact fields of the spin ensembles and the slowing-down factor are extracted from the slope and intercept of the linear model. The total relaxation rate of the electron spins is obtained from the decay rates of the spin ensembles and the measured slowing-down factor. The validity of this method is further checked by the magnetic resonance (MR) method from a perspective of the electron resonance linewidth. Identification of these systematic parameters paves the way for operating the comagnetometers efficiently as well as the practical applications of the comagnetometers. [ABSTRACT FROM AUTHOR]

Tissue microstructure can influence quantitative magnetic resonance imaging such as relaxation rate measurements. Consequently, relaxation rate mapping can provide useful information on tissue microstructure. In this work, the theory on relaxation mechanisms of the change of the relaxation rate ∆R 2 ⁎ in the presence of spherical susceptibility sources in a spin bearing medium is validated in simulations and phantom experiments for the coexistence of two species of susceptibility sources. The influence of coexisting spherical perturbers with magnetic susceptibilitys of different signs was evaluated in Monte Carlo simulations including diffusion effects in the surrounding medium. Simulations were compared with relaxometry measurements at 1.5 Tesla and at 3 Tesla. The phantoms used to validate the simulations were built from agarose gel containing calcium carbonate and tungsten carbide particles of different size and concentration. The Monte Carlo simulations showed, that the change in relaxation rate only depends on the overall amount of susceptibility producing structures in the simulation volume and no difference was found, if mixtures of positive and negative particles were simulated. Phantom measurements within the static dephasing regime showed linear additivity of the effects from positive and negative susceptibility sources that were present within the same voxel. In summary, both the simulations and the phantom measurements showed that changes in the relaxation rate Δ R 2 ⁎ add up linearly for spherical particles with different susceptibilities within the same voxel if the conditions for the static dephasing regime are fulfilled. If particles with different susceptibilities have both different sizes and violate the conditions of the static dephasing regime, effects on relaxation rates might no longer be linear. [ABSTRACT FROM AUTHOR]

The impact of periodic freezing-thawing cycling on the stress-relaxation behavior of expansive soil, which was discovered during the construction of the Harbin-Jiamusi high-speed railway, was investigated in this paper. The laboratory tests associated with this study involved X-ray diffraction (XRD), thermal analysis, and direct shear testing. Test results indicate that shear stress decreases gradually in line with the number of freeze-thaw (F-T) cycling (NFT). When the NFT exceeds 7, F-T cycling no longer has any observably significant influence on the shear stress. The relaxation rate decreases during the first F-T cycle, after which almost no appreciable effect from F-T cycling is visible. It is concluded that, during the relaxation process, the shear stress decreases gradually and tends towards a stable value. A three stage process for the stress relaxation of soil samples affected by F-T cycling was observed: instantaneous relaxation; attenuated relaxation; and steady relaxation. Based on the experimental results, a disturbed state concept (DSC)-based stress-relaxation model for expansive soil exposed to freeze-thaw cycling was proposed. Close agreement between the experimental data and results predicted according to the model confirms the model's validity. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Diffusion and susceptibility effects around vessels are considered. • The Bloch-Torrey-equation is exactly solved around randomly distributed vessels. • The gradient echo relaxation rate is obtained for arbitrary vessel sizes. Abstract We analyze the gradient echo signal in the presence of blood vessel networks. Both, diffusion and susceptibility effects are analytically emphasized within the Bloch-Torrey equation. Solving this equation, we present the first exact description of the local magnetization around a single vessel. This allows us to deduce the gradient echo signal of parallel vessels randomly distributed in a plane, which is valid for arbitrary mean vessel diameters in the range of physiological relevant blood volume fractions. Thus, the results are potentially relevant for gradient echo measurements of blood vessel networks with arbitrary vessel size. [ABSTRACT FROM AUTHOR]

Abstract Most studies of brain iron relied on the effect of the iron on magnetic resonance (MR) relaxation properties, such as R 2 ∗ , and bulk tissue magnetic susceptibility, as measured by quantitative susceptibility mapping (QSM). The present study exploited the dependence of R 2 ∗ and magnetic susceptibility on physical interactions at different length-scales to retrieve information about the tissue microenvironment, rather than the iron concentration. We introduce a method for the simultaneous analysis of brain tissue magnetic susceptibility and R 2 ∗ that aims to isolate those biophysical mechanisms of R 2 ∗ -contrast that are associated with the micro- and mesoscopic distribution of iron, referred to as the Iron Microstructure Coefficient (IMC). The present study hypothesized that changes in the deep gray matter (DGM) magnetic microenvironment associated with aging and pathological mechanisms of multiple sclerosis (MS), such as changes of the distribution and chemical form of the iron, manifest in quantifiable contributions to the IMC. To validate this hypothesis, we analyzed the voxel-based association between R 2 ∗ and magnetic susceptibility in different DGM regions of 26 patients with multiple sclerosis and 33 age- and sex-matched normal controls. Values of the IMC varied significantly between anatomical regions, were reduced in the dentate and increased in the caudate of patients compared to controls, and decreased with normal aging, most strongly in caudate, globus pallidus and putamen. Highlights • Voxel-wise analysis of R 2 * and susceptibility reveals their differential dependency on brain iron. • The Iron Microstructure Coefficient (IMC) varies with brain regions and decreases with age. • Multiple Sclerosis is associated with increased IMC in dentate and decreased IMC in caudate. [ABSTRACT FROM AUTHOR]

Abstract We investigate the semiclassical electronic transport properties of the bilayer silicene-like systems in the presence of charged impurity. The trigonal warping due to the interlayer hopping, and its effect to the band structure of bilayer silicene is discussed. Besides the trigonal warping, the external field also gives rise to the anisotropic effect of the mobility (at finite temperature) which can be explored by the Boltzmann theory. The dynamical polarization as well as the scattering wave vector-dependent screening within random phase approximation are very important in determining the scattering behavior as well as the self-consistent transport. We detailedly discuss the transport behavior under the short- or long-range potential. The phonon scattering with the acoustic phonon mode which dominants at high temperature is also studied within the density functional theory (DFT). Our results are also valid for the bilayer graphene or bilayer MoS 2 , and other bilayer systems which with strong interlayer coupling. [ABSTRACT FROM AUTHOR]

Abstract The surfactant coated cobalt ferrite (CoFe 2 O 4) samples were synthesized at different temperatures by different synthesis routes. The oleic acid (OA) coated cobalt ferrite sample synthesized at 80 °C by co-precipitation route while, sodium dodecyl sulfate (SDS) and cetyl-trimethyl ammonium-bromide (CTAB) cobalt ferrite samples were synthesized at 140 °C and 180 °C by hydrothermal process respectively. The average crystallite size of 14.9 ± 0.2 nm, 19.1 ± 0.3 nm and 21.3 ± 0.2 nm at higher intensity peak (311) of X-ray diffraction pattern (XRD) for CF-OA, CF-SDS, and CF-CTAB sample respectively were estimated using Lorentz fitting profile of experimental data. Transmission electron microscopy (TEM) images show randomly oriented nanoparticles of the irregular shape of CF-OA sample, globular shape for CF-SDS and rhomboidal shape of CF-CTAB sample respectively. The average particle size of 15.7, 22.7 and 30.1 nm for CF-OA, CF-SDS and CF-CTAB sample were estimated using TEM analysis. FTIR spectra of all samples confirmed the coating of surfactant on the surface of cobalt ferrite nanoparticles. The temperature dependence electron paramagnetic resonance (EPR) spectra of all samples in the non-magnetic matrix were measured in the temperature range (100 K–300 K). The linewidth and g-factor from their EPR signal were increased significantly with increase in particle size of the sample. The spin-spin relaxation time T 2 was estimated from linewidth of EPR signal of the sample. The spin-spin relaxation time T 2 decreased with increase in linewidth as an increase in particle size of the sample. The linewidth of EPR signal was decided by dipolar interactions between nanoparticles and super-exchange interaction between metal cations at tetrahedral and octahedral sites of the CoFe 2 O 4 sample. Graphical abstract Image 1 Highlights • Surface modification of cobalt ferrite nanoparticles by various surfactants. • Temperature dependence linewidth by Electron paramagnetic resonance (EPR). • Interpretation of linewidth in terms of dipolar interaction and super-exchange interaction. • Estimation of spin-spin relaxation time T 2 and relaxation rate R 2 using linewidth parameter. [ABSTRACT FROM AUTHOR]

Fast-field-cycling nuclear magnetic resonance (FFC-NMR) is a powerful technique for non-destructively probing the properties of fluids contained within the pores of porous materials. FFC-NMR measures the spin−lattice relaxation rate R 1 ( f ) as a function of NMR frequency f over the kHz to MHz range. The shape and magnitude of the R 1 ( f ) dispersion curve is exquisitely sensitive to the relative motion of pairs of spins over time scales of picoseconds to microseconds. To extract information on the nano-scale dynamics of spins, it is necessary to identify a model that describes the relative motion of pairs of spins, to translate the model dynamics to a prediction of R 1 ( f ) and then to fit to the experimental dispersion. The principles underpinning one such model, the 3 τ model, are described here. We present a new fitting package using the 3 τ model, called 3TM, that allows users to achieve excellent fits to experimental relaxation rates over the full frequency range to yield five material properties and much additional derived information. 3TM is demonstrated on historic data for mortar and plaster paste samples.

We continue the investigation of kinetic models of a system in contact via stochastic interactions with several spatially homogeneous thermal reservoirs at different temperatures. Considering models different from those investigated in Carlen et al. (Braz J Probab Stat 29:372-386, 2015), we explicitly compute the unique spatially uniform non-equilibrium steady state (NESS) and prove that it is approached exponentially fast from any uniform initial state. This leaves open the question of whether there exist NESS that are not spatially uniform. Making a further simplification of our models, we then prove non-existence of such NESS and exponential approach to the unique spatially uniform NESS (with a computably boundable rate). The method of proof relies on refined Doeblin estimates and other probabilistic techniques, and is quite different form the analysis in Carlen et al. (Braz J Probab Stat 29:372-386, 2015) that was based on contraction mapping methods. [ABSTRACT FROM AUTHOR]

We discuss the dynamics of a bilayer membrane with partial slip boundary conditions between the monolayers and the bulk fluid. Using Onsager’s variational principle to account for the associated dissipations, we derive the coupled dynamic equations for the membrane height and the excess lipid density. The newly introduced friction coefficients appear in the renormalized fluid viscosities. For ordinary lipid bilayer membranes, we find that it is generally justified to ignore the effects of permeation and parallel slip at the membrane surface. [ABSTRACT FROM AUTHOR]

Measurements on magnetization and relaxation have been carried out on an optimally doped Ba 1 − x K x BiO 3 + δ single crystal with T c = 31.3 K. Detailed analysis is undertaken on the data. Both the dynamical relaxation and conventional relaxation have been measured leading to the self-consistent determination of the magnetization relaxation rate. It is found that the data are well described by the collective pinning model leading to the glassy exponent of about μ  ≈  1.64–1.68 with the magnetic fields of 1 and 3 T. The analysis based on Maley’s method combining with the conventional relaxation data allows us to determine the current dependent activation energy U which yields a μ value of about 1.23–1.29 for the magnetic fields of 1 and 3 T. The second magnetization peaks appear in wide temperature region from 2 K to 24 K. The separation between the second peak field and the irreversibility field becomes narrow when temperature is increased. When the two fields are close to each other, we find that the second peak evolves into a step-like transition of magnetization. Finally, we present a vortex phase diagram and demonstrate that the vortex dynamics in Ba 1 − x K x BiO 3 can be used as a model system for studying the collective vortex pining. [ABSTRACT FROM AUTHOR]

ABSTRACT In the electrospinning process, the measurement of extension rate of the straight jet is not an easy task. In this study, the diameter profile of the tapering straight jet is determined with a laser light-scattering technique. Afterwards, the jet extension rate ( [ABSTRACT FROM AUTHOR]

The miniaturised spin-exchange relaxation-free (SERF) magnetometer has promising applications in biomagnetic measurements owing to its ultrasensitive magnetic field measurement capacity. In this paper, we propose a single-beam parameter-optimised SERF magnetometer that operates below the relaxation rate saturation region. Based on the relaxation rate model under zero-field resonance, the relationship between the magnetometer optimal working point and multiphysical parameters, including the optical power density, cell temperature, and nitrogen density, was studied. The experimental results verified the accuracy of the law deduced from the model. By adjusting the parameters according to our experimental results, a sensitivity of 17 fT/Hz 1 / 2 (@31.5Hz) and bandwidth of 110 Hz were obtained optimally in a 5.5 cm 3 magnetometer. The superiority of the optimised parameters in the miniaturised SERF magnetometer is verified. We found that the relaxation rate saturation region results from light absorption saturation, which leads to a performance decline of the SERF magnetometer. This relaxation rate saturation phenomenon widely exists in miniaturised SERF magnetometers, and the study of this phenomenon is helpful for further applications in arrayed integration of biomagnetic measurement. [Display omitted] • The relaxation rate model under zero-field resonance is systematically established. • Multiphysical parameters in atomic magnetometer are optimised based on this model. • A relaxation rate saturation phenomenon causing performance degradation was observed. • The optimal sensitivity is 17 fT/Hz1/2 (@31.5Hz) with a bandwidth of 110 Hz. [ABSTRACT FROM AUTHOR]

Magnetic iron oxide nanoparticles are relatively advanced nanomaterials, and are widely used in biology, physics and medicine, especially as contrast agents for magnetic resonance imaging. Characterization of the properties of magnetic nanoparticles plays an important role in the application of magnetic particles. As a contrast agent, the relaxation rate directly affects image enhancement. We characterized a series of monodispersed magnetic nanoparticles using different methods and measured their relaxation rates using a 0.47 T low-field Nuclear Magnetic Resonance instrument. Generally speaking, the properties of magnetic nanoparticles are closely related to their particle sizes; however, neither longitudinal relaxation rate r 1 nor transverse relaxation rate r 2 changes monotonously with the particle size d . Therefore, size can affect the magnetism of magnetic nanoparticles, but it is not the only factor. Then, we defined the relaxation rates r i ′ (i = 1 or 2) using the induced magnetization of magnetic nanoparticles, and found that the correlation relationship between r 1 ′ relaxation rate and r 1 relaxation rate is slightly worse, with a correlation coefficient of R 2 = 0.8939, while the correlation relationship between r 2 ′ relaxation rate and r 2 relaxation rate is very obvious, with a correlation coefficient of R 2 = 0.9983. The main reason is that r 2 relaxation rate is related to the magnetic field inhomogeneity, produced by magnetic nanoparticles; however r 1 relaxation rate is mainly a result of the direct interaction of hydrogen nucleus in water molecules and the metal ions in magnetic nanoparticles to shorten the T 1 relaxation time, so it is not directly related to magnetic field inhomogeneity.

Copyright of Journal of Measurement Science & Instrumentation is the property of Journal of Measurement Science & Instrumentation and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The purpose of this study is to demonstrate the feasibility of dynamic renal R2/ R2′/ R2* measurements based on a method, denoted psMASE-ME, in which a periodic 180° pulse-shifting multi-echo asymmetric spin echo (psMASE) sequence, combined with a moving estimation (ME) strategy, is adopted. Following approval by the institutional animal care and use committee, a block design of respiratory challenge with interleaved air and carbogen (97% O2, 3% CO2) breathing was employed in nine rabbits. Parametrical R2/ R2′/ R2* maps were computed and average R2/ R2′/ R2* values were measured in regions of interest in the renal medulla and cortex. Bland-Altman plots showed good agreement between the proposed method and reference standards of multi-echo spin echo and multi-echo gradient echo sequences. Renal R2, R2′ and R2* decreased significantly from 16.2 ± 4.4 s−1, 9.8 ± 5.2 s−1 and 25.9 ± 5.0 s−1 to 14.9 ± 4.4 s−1 ( p < 0.05), 8.5 ± 4.1 s−1 ( p < 0.05) and 23.4 ± 4.8 s−1 ( p < 0.05) in the cortex when switching the gas mixture from room air to carbogen. In the renal medulla, R2, R2′ and R2* also decreased significantly from 12.9 ± 4.7 s−1, 15.1 ± 5.8 s−1 and 27.9 ± 5.3 s−1 to 11.8 ± 4.5 s−1 ( p < 0.05), 14.2 ± 4.2 s−1 ( p < 0.05) and 25.8 ± 5.1 s−1 ( p < 0.05). No statistically significant differences in relative R2, R2′ and R2* changes were observed between the cortex and medulla ( p = 0.72 for R2, p = 0.39 for R2′ and p = 0.61 for R2*). The psMASE-ME method for dynamic renal R2/ R2′/ R2* measurements, together with the respiratory challenge, has potential use in the evaluation of renal oxygenation in many renal diseases [ABSTRACT FROM AUTHOR]

The relaxation rates of thermal and hot quasiparticles when scatter with each other are calculated. The transition probabilities at low temperatures express in terms of Bogoliubov coefficients, singlet and triplet scattering amplitudes and dimensionless Landau parameters. Comparison of the theoretical and experimental results gives the values of two Landaus parameters .

Objective: To quantify gestation-dependent longitudinal changes in the magnetic resonance transverse relaxation time (T2) parameter of the major constituent regions of the mouse placenta and to evaluate their relative contributions to changes in overall placental T2.Methods: Timed-pregnant CD-1 mice underwent magnetic resonance imaging at 7.0 T field strength, on gestational day 13 (GD13), GD15 and GD17. T2 of the placenta and its constituent high and low blood perfusion regions were quantified. A linear mixed-effects model was used to fit the T2 across gestation, and the significance of coefficients was tested.Results: A decrease in the T2 values of the placenta and its constituent regions was observed across gestation. The temporal change in T2 was estimated to be -1.85 ms/GD (p < 0.0001) for the placenta, -1.00 ms/GD (p < 0.001) for the high-perfusion zones (HPZs) and -1.66 ms/GD (p < 0.0001) for the low-perfusion zones (LPZs).Conclusion: T2 of the constituent zones of the murine placenta decreases with advancing gestation. While the T2 of the LPZ is smaller than that of the HPZ, there is no difference in their decrease rate relative to that of the whole placenta (p = 0.24). The results suggest an increased role of constituent volume fractions in affecting overall gestation-dependent placental T2 decrease in mice. [ABSTRACT FROM AUTHOR]

We present a theoretical analysis of exciton transfer and decoherence effects in a photosynthetic dimer interacting with collective (correlated) and local (uncorrelated) protein-solvent environments. Our approach is based on the framework of the spin-boson model. We derive explicitly the thermal relaxation and decoherence rates of the exciton transfer process, valid for arbitrary temperatures and for arbitrary (in particular, large) interaction constants between the dimer and the environments. We establish a generalization of the Marcus formula, giving reaction rates for dimer levels possibly individually and asymmetrically coupled to environments. We identify rigorously parameter regimes for the validity of the generalized Marcus formula. The existence of long living quantum coherences at ambient temperatures emerges naturally from our approach. [ABSTRACT FROM AUTHOR]

Catastrophic earthquakes on platforms determine the relevance of the development of criteria for the identification of locations and assessment of the intensity and frequency of such events. The low accuracy of data on historical earthquakes and the short series of instrumental observations, as well as the lack of representative statistics, lead to mixed assessments of seismic hazards using deterministic and probabilistic methods and complicates the risk-oriented safety regulation of nuclear power plants (NPP). In order to solve this problem, we propose a method for the assessment of the expected magnitude-frequency relationships based on the uniform model of the Earth's crust, taking into account the dependence of earthquake limiting magnitudes on the strain conditions, size, and type of the source (Bugaev and Spivak, 2002; Bugaev, 2011). The uniform model of the Earth's crust reflects discrete properties of the Earth's crust, including earthquake sources and the areas of their nucleation (for example, see (Sadovskii, 1979) and others). In (Bugaev, 2014), the method is considered in relation to the assessment of expected magnitude-frequency relationships of the seismically active area. In this paper, the method is used to assess magnitude-frequency relationships, taking into account the geodynamic and seismic conditions of some areas of the East European (EEP) and North American (NAP) platforms. The similarities and differences of the magnitude-frequency relationships that define the long-term and current seismic hazard for the EEP and NAP are found. In particular, it is pointed out that it is relevant to set criteria for when recommendations should be issued for the implementation of organizational and technical NPP security measures, based on the results of seismological monitoring. [ABSTRACT FROM AUTHOR]