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NMR relaxation rates for protons in liquid water and neat acetonitrile were computed based on ab initio molecular dynamics (aiMD) with forces from Kohn-Sham (KS) theory as well as force-field (FF) based classical dynamics. Intra- and intermolecular dipole-dipole contributions were separated, and nearly quantitative agreement with experiment was obtained for water. Spin-rotation (SR) contributions to the intramolecular relaxation rate in acetonitrile were computed using nuclear SR coupling tensors obtained from KS theory. Their inclusion improved the total computed intramolecular rate to within a factor of two of experiment. Insufficient sampling of rare short-time collision events between neighboring acetonitrile molecules in the simulations is hypothesized as a major source of error in the intermolecular contributions.

To clarify the concentration dependence of visible fluorescence of Pr3+, a series of phosphate glass samples with Pr3+ concentration from 0.05 to 3.0 mol% were fabricated. Steady and dynamic spectroscopic characteristics of Pr3+-doped phosphate glasses were systematically investigated. When the Pr3+ concentration was small, only one visible fluorescence band can be observed at 596 nm, which was ascribed to the transition of 1D2 → 3H4. With increasing Pr3+ concentration from 0.05 to 0.5 mol%, since the multi-phonon relaxation rate of 3P0 was largely quicker than that of 1D2. Increasing Pr3+ concentration from 0.5 to 3 mol%, increasing two other fluorescence bands at 612 nm and 640 nm, which were assigned to the transitions of 3P0 → 3H6 and 3P0 → 3F2, respectively. It was due to the cross relaxation probability between [1D2: 1G4] and [3H4: 3F4] increased, which results in quicker decay rate of 1D2. The fluorescence lifetime of 1D2 decreased from 173 to 6 μs with increasing Pr3+ concentration from 0.1 to 3 mol%, which due to the cross relaxation probability between [1D2: 1G4] and [3H4: 3F4] increased, resulting in quicker decay rate of 1D2. Fitting the concentration dependence of fluorescence lifetime demonstrated that the cross relaxation arising from dipole-dipole interactions between Pr3+ ions.

Snowflakes and ordinary hexagonal ice were studied measuring water proton spin–lattice relaxation rate R1(ωI)-nuclear magnetic resonance dispersion (NMRD) profiles at proton Larmor frequencies ranging from 1 to 30 MHz and at different temperatures ranging from −2◦C to −10◦C. The spin–spin relaxation rate 1/ 1/T2(ωI) was determined at a single Larmor frequency of 16.3 MHz. The high-field wing of the proton R1(ωI)-NMRD profile was characterised by two parameters: a correlation time τc which described the dipole–dipole spectral density, and the relaxation rate at low fields R max real (0) which was determined from T 2 . The correlation time τc depended on the dynamic model used. A rotation diffusion model yield approximatively 3μs at −3◦C to about 5μs at 10◦C, whereas for a more realistic six-site discrete exchange model, the correlation times decreased slightly to about 80% for the same temperature interval. Proton dipole–dipole interactions were divided into intramolecular and intermolecular contributions where the intermolecular contribution was about 0.4–0.8 × the intramolecular contribution. It was not possible to discriminate between the dynamic models or to detect ice/water interface effects by comparing the NMRD data from snowflakes with ordinary hexagonal ice data.

We show that magnetic fluctuations can destroy the Hebel-Slichter peak in conventional superconductors. The Hebel-Slichter peak has previously been expected to survive even in the presence of strong electronic interactions. However, we show that antiferromagnetic fluctuations suppress the peak at q=0 in the imaginary part of the magnetic susceptibility χ′′+−(q,ω), which causes the Hebel-Slichter peak. This is of general interest as in many materials superconductivity is found near a magnetically ordered phase, and the absence of a Hebel-Slichter peak is taken as evidence of unconventional superconductivity in these systems. For example, no Hebel-Slichter peak is observed in the κ−(BEDT−TTF)2X organic superconductors but heat capacity measurements have been taken to indicate s-wave superconductivity. Similarly, experiments indicate nodeless superconductivity in many iron pnictide superconductors which exhibit no peak in the relaxation rate. If antiferromagnetic fluctuations destroy the putative Hebel-Slichter peak in organic superconductors, then the peak should be restored by applying a pressure, which is known to suppress antiferromagnetic correlations in these materials.

We present a microscopic study of a doped quantum spin liquid candidate, the hyperkagome ${\mathrm{Na}}_{3}{\mathrm{Ir}}_{3}{\mathrm{O}}_{8}$ compound, by using $^{23}\mathrm{Na}$ NMR. We determine the intrinsic behavior of the uniform q = 0 susceptibility via shift measurements and the dynamical response by probing the spin-lattice relaxation rate. Throughout the studied temperature range, the susceptibility is consistent with a semimetal behavior, though with electronic bands substantially modified by correlations. Remarkably, the antiferromagnetic fluctuations present in the insulating parent compound ${\mathrm{Na}}_{4}{\mathrm{Ir}}_{3}{\mathrm{O}}_{8}$ survive in the studied compound. The spin dynamics are consistent with ${120}^{\ensuremath{\circ}}$ excitation modes displaying short-range correlations.

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 c...

Photothermal effects can alter the response of an optical cavity, for example, by inducing self-locking behavior or unstable anomalies. The consequences of these effects are often regarded as parasitic and generally cause limited operational performance of the cavity. Despite their importance, however, photothermal parameters are usually hard to characterize precisely. In this work we use an optical cavity strongly coupled to photothermal effects to experimentally observe an optical back-action on the photothermal relaxation rate. This effect, reminiscent of the radiation-pressure-induced optical spring effect in cavity optomechanical systems, uses optical detuning as a fine control to change the photothermal relaxation process. The photothermal relaxation rate of the system can be accordingly modified by more than an order of magnitude. This approach offers an opportunity to obtain precise in-situ estimations of the parameters of the cavity, in a way that is compatible with a wide range of optical resonator platforms. Through this back-action effect we are able to determine the natural photothermal relaxation rate and the effective thermal conductivity of the cavity mirrors with unprecedented resolution., 11 pages, 4 figures

Objective To determine the variability, and preferred values, for normal liver longitudinal water proton relaxation rate R1 in the published literature. Methods Values of mean R1 and between-subject variance were obtained from literature searching. Weighted means were fitted to a heuristic and to a model. Results After exclusions, 116 publications (143 studies) remained, representing apparently normal liver in 3392 humans, 99 mice and 249 rats. Seventeen field strengths were included between 0.04 T and 9.4 T. Older studies tended to report higher between-subject coefficients of variation (CoV), but for studies published since 1992, the median between-subject CoV was 7.4%, and in half of those studies, measured R1 deviated from model by 8.0% or less. Discussion The within-study between-subject CoV incorporates repeatability error and true between-subject variation. Between-study variation also incorporates between-population variation, together with bias from interactions between methodology and physiology. While quantitative relaxometry ultimately requires validation with phantoms and analysis of propagation of errors, this survey allows investigators to compare their own R1 and variability values with the range of existing literature.

Quantitative relaxometry mapping—the measurement of water proton relaxation with MRI—provides a valuable imaging tool to characterize tissue, particularly in the brain. This topic is presented in terms of two parts: i) models that relate transverse or longitudinal relaxation to the structure and composition of neural tissue, such as the volume fraction of myelin and concentration of iron, and 2) MRI methods that can provide quantitative relaxation measurements. The simplest models relate one or more tissue characteristic to a single mono-exponential relaxation rate, which allows efficient measurements but faces limits in specificity and accuracy. Multi-exponential models offer a more complete characterization of tissue at the cost of efficiency in measurement. For any application, the user should appreciate potential shortcomings of the model and the precision of the measured relaxation parameters.

We investigate the strong field nuclear spin relaxation rate in $n$-type GaAs for doping densities from the quasi-insulating over the metal-to-insulator up to the quasimetallic regime. The rate measured at 6.5 K increases in the quasi-insulating regime with doping density due to nuclear spin diffusion to the donor electrons and shows a distinct maximum at the critical density of the Mott metal-to-insulator transition. The density dependence of the nuclear spin relaxation rate can be quantitatively calculated over the whole density regime taking into account the effective number of localized electrons and the interaction of free electrons via the Korringa mechanism. Only the nuclear spin relaxation rate of the very lowest doped sample shows a significant deviation from these calculations. Temperature-dependent measurements suggest in this case an additional nuclear spin relaxation channel which is negligible at higher doping densities and is linked to the electron spin relaxation time.

International audience; The freezing, melting and dynamics of supercooled water at different hydration of controlled porous glass (CPG) with mean pore sizes 10 nm, 30 nm, 50 nm and 70 nm are studied using differential scanning calorimetry (DSC) and deuteruim nuclear magnetic resonance (2 H-NMR). For saturated samples, the melting tempertaure follows the Gibbs-Thomson relation despite a clear linear decrease of the melting enthalpy when the transition is shifted due to confinement. For partially filled porous glasses the crystalization and melting temperatures as well as enthalpy are lower than for the saturated samples. 2 H-NMR confirms the existence of a non-crystallizable part of water adsorbed on the surface of pores. At room temperature, spin-lattice relaxation rate (1/T1) is proportional to the inverse of the mean pore size indicating that the relaxation is governed by a surface limited process. At low tempertaure relaxation rate follows the Vogel-Fulcher-Tammann (VFT) relation.

Momentum-conserving quasiparticle collisions in two-dimensional Fermi gases give rise to a large family of exceptionally long-lived excitation modes. The lifetimes of these modes exceed by a factor $(T_F/T)^2\gg 1$ the conventional Landau Fermi-liquid lifetimes $\tau\sim T_F/T^2$. The long-lived modes have a distinct angular structure, taking the form of $\cos m\theta$ and $\sin m\theta$ with odd $m$ values for a circular Fermi surface, with relaxation rate dependence on $m$ of the form $m^4\log m$, valid at not-too-large $m$. In contrast, the even-$m$ harmonics feature conventional lifetimes with a weak $m$ dependence. The long-time dynamics, governed by the long-lived modes, takes the form of angular (super)diffusion over the Fermi surface. Altogether, this leads to unusual long-time memory effects, defining an intriguing transport regime that lies between the conventional ballistic and hydrodynamic regimes., Comment: 29 pgs, 6 fgs

Nuclear quadrupole resonance (NQR) measurements were performed on the heavy-fermion superconductor ${\mathrm{Ce}}_{3}{\mathrm{PtIn}}_{11}$ with ${T}_{\mathrm{c}}=0.32\phantom{\rule{0.28em}{0ex}}\mathrm{K}$. The temperature dependence of both spin-lattice relaxation rate $1/{T}_{1}$ and NQR spectra evidences the occurrence of two successive magnetic transitions with ${T}_{\mathrm{N}1}\ensuremath{\simeq}2.2\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ and ${T}_{\mathrm{N}2}\ensuremath{\simeq}2.0\phantom{\rule{0.28em}{0ex}}\mathrm{K}$. In successive magnetic transitions, even though the magnetic moment at the Ce(2) site plays a major role, the magnetic moment at the Ce(1) site also contributes to some extent. While a commensurate antiferromagnetic ordered state appears for ${T}_{\mathrm{N}2}lTl{T}_{\mathrm{N}1}$, a partially incommensurate antiferromagnetic ordered state is suggested for $Tl{T}_{\mathrm{N}2}$.

ObjectiveThis prospective study investigated the feasibility of an optimized cardiovascular magnetic resonance (CMR) examination protocol using the motion-corrected (MOCO), balanced steady-state free precession (bSSFP), phase-sensitive inversion recovery (PSIR) sequence combined with a gadolinium contrast agent with a high relaxation rate in patients who cannot hold their breath.MethodsFifty-one patients with heart disease underwent CMR examinations twice and these were performed with different late gadolinium enhancement (LGE) imaging sequences (fast low-angle shot [FLASH] sequence vs. MOCO sequence) and different gadolinium contrast agents (gadopentetate dimeglumine vs. gadobenate dimeglumine) with a 48-hour interval. LGE image quality, total time spent in the whole study, and time taken to perform LGE imaging were compared for the two CMR examinations.ResultsLGE images with the MOCO bSSFP PSIR sequence showed significantly higher image quality compared with those with the segmented FLASH PSIR sequence. There was a significant difference between the total scan time for the two examinations and different LGE sequences.ConclusionsThe MOCO bSSFP PSIR sequence effectively improves the quality of LGE images. Changing the CMR scanning protocol by combining the MOCO bSSFP PSIR sequence with a gadolinium contrast agent with a high relaxation rate effectively shortens the scan time. Clinical trial registration number: ChiCTR-ROC-17013978.

We study the effect of a three-dimensional extremely short optical pulse in a medium with chiral carbon nanotubes on the order parameter of this medium. The possibility of the appearance of a phase transition in such a medium is shown. We investigate the dependence of the pulse shape on the relaxation rate of the order parameter and on the parameter β in the Landau expansion of free energy.

We performed $^{13}\mathrm{C}$-NMR measurements on an organic superconductor $\ensuremath{\lambda}\text{\ensuremath{-}}{(\mathrm{BETS})}_{2}{\mathrm{GaCl}}_{4}$ to investigate the superconducting (SC) gap symmetry, where BETS stands for bis(ethylenedithio)tetraselenafulvalene. As the temperature approaches 0 K, the Knight shift in the SC state decreases; the nuclear spin-lattice relaxation rate $1/{T}_{1}$ shows cubic temperature dependence below the SC transition temperature ${T}_{c}$ without a coherence peak. These results can be understood in terms of $d$-wave superconductivity. Moreover, an increase in $1/{T}_{1}T$ at lower temperatures was observed just above ${T}_{c}$; this behavior can be interpreted as an effect of spin-density-wave (SDW) fluctuation. We suggest that the $d$-wave superconductivity of $\ensuremath{\lambda}\text{\ensuremath{-}}{(\mathrm{BETS})}_{2}{\mathrm{GaCl}}_{4}$ originates from SDW fluctuation.

In this study, a new method was proposed to study the relaxation properties of carbon fiber reinforced plastics (CFRP) fabric under axial tension. Under the condition of constant temperature and humidity, six groups of 168 h stress relaxation tests were conducted. Considering the influence of the prestress level, the size of CFRP cloth, and the surface coating of CFRP cloth on the relaxation performance, the measures to reduce the relaxation loss were proposed. The relaxation rate calculation model was established based on the test results of the authors and other scholars and was validated through comparisons with the test results. The results indicate that the relaxation rate of CFRP cloth was between 1.92% and 6.1%. When the prestress level was smaller than 0.3 fu, the relaxation rate of CFRP cloth decreased with the increase of prestress level. When the prestress level was greater than 0.3 fu, the relaxation rate increased with the increase of the prestress level. Under the same conditions, the relaxation rate of the CFRP specimens coated with glue was smaller than the uncoated samples by 3.21&ndash, 6.28%. The calculation model could well estimate the relaxation rate of CFRP cloth.

Fluxonium qubits employ a chain of $N$ Josephson junctions in series. We investigate how the charge-noise induced coherence time ${T}_{2}$ of the qubit depends upon $N$, holding fixed the chain's effective capacitance and inductance. The pure dephasing rate decreases with $N$, but the relaxation rate increases. As a result, ${T}_{2}$ achieves a maximum. The optimal $N$ can be much smaller than the number typically chosen in experiments, implying that fluxonium qubits can be significantly simplified without compromising performance.

In Parkinson’s disease, the depletion of iron-rich dopaminergic neurons in nigrosome 1 of the substantia nigra precedes motor symptoms by two decades. Monitoring this neuronal depletion, at an early disease stage, is needed for early diagnosis. Magnetic resonance imaging (MRI) is particularly suitable for this task due to its sensitivity to iron. However, the exact mechanisms of MRI contrast in nigrosome 1 are not well understood, hindering the development of powerful biomarkers. We demonstrate that the dominant contribution to the effective transverse MRI relaxation rate in nigrosome 1 originates from iron accumulated in dopaminergic neurons. We link quantitatively to the product of cell density and local iron concentration in dopaminergic neurons, combining quantitative 3D iron histology, biophysical modeling, and quantitative MRI on post mortem brain tissue. It is now theoretically possible to monitor dopaminergic neuron depletion, in vivo, as an early diagnostic tool for Parkinson’s disease.

In this study, a stimulated-echo (STE) method was employed to robustify the cerebral vessel size estimation near air-tissue, bone-tissue interfaces, and large vessels. The proposed solution is to replace the relaxation rate change from gradient-echo (GRE) with that from STE with long diffusion time after the injection of an intravascular contrast agent, superparamagnetic iron oxide nanoparticles. The corresponding diffusion length of STE is shorter than the length over which the unwanted macroscopic field inhomogeneities but is still longer than the correlation length of the fields induced by small vessels. Therefore, the unwanted field inhomogeneities are refocused, while preserving microscopic susceptibility contrast from cerebral vessels. The mean vessel diameter (dimensionless) derived from the diffusion-time-varying STE method was compared to the mean vessel diameter obtained by a conventional spin-echo (SE) and GRE combination based on Monte-Carlo proton diffusion simulations and in vivo rat experiments at 7 ​T. The in vivo mean vessel diameter from the MRI experiments was directly compared to available reference mouse brain vasculature obtained by a knife-edge scanning microscope (KESM), which is considered to be the gold standard. Monte-Carlo simulation revealed that SE and GRE-based MR relaxation rate changes (ΔR2 and ΔR2∗, respectively) can be enhanced using single STE-based MR relaxation rate change (ΔRSTE) by regulating diffusion time, especially for small vessels. The in vivo mean vessel diameter from the STE method demonstrated a closer agreement with that from the KESM compared to the combined SE and GRE method, especially in the olfactory bulb and cortex. This study demonstrates that STE relaxation rate changes can be used as consistent measures for assessing small cerebral microvasculature, where macroscopic field inhomogeneity is severe and signal contamination from adjacent large vessels is significant.

Purpose Dynamic glucose-enhanced (DGE)-MRI based on chemical exchange-sensitive MRI, that is, glucoCEST and gluco-chemical exchange-sensitive spin-lock (glucoCESL), is intrinsically prone to motion-induced artifacts because the final DGE contrast relies on the difference of images, which were acquired with a time gap of several mins. In this study, identification of different types of motion-induced artifacts led to the development of a 3D acquisition protocol for DGE examinations in the human brain at 7 T with improved robustness in the presence of subject motion. Methods DGE-MRI was realized by the chemical exchange-sensitive spin-lock approach based either on relaxation rate in the rotating frame (R1ρ )-weighted or quantitative R1ρ imaging. A 3D image readout was implemented at 7 T, enabling retrospective volumetric coregistration of the image series and quantification of subject motion. An examination of a healthy volunteer without administration of glucose allowed for the identification of isolated motion-induced artifacts. Results Even after coregistration, significant motion-induced artifacts remained in the DGE contrast based on R1ρ -weighted images. This is due to the spatially varying sensitivity of the coil and was found to be compensated by a quantitative R1ρ approach. The coregistered quantitative approach allowed the observation of a clear increase of the DGE contrast in a patient with glioblastoma, which did not correlate with subject motion. Conclusion The presented 3D acquisition protocol enables DGE-MRI examinations in the human brain with improved robustness against motion-induced artifacts. Correction of motion-induced artifacts is of high importance for DGE-MRI in clinical studies where an unambiguous assignment of contrast changes due to an actual change in local glucose concentration is a prerequisite.

$^{7}\mathrm{Li}$ nuclear magnetic resonance and terahertz (THz) spectroscopies are used to probe magnetic excitations and their field dependence in the hyperhoneycomb Kitaev magnet $\ensuremath{\beta}\ensuremath{-}{\mathrm{Li}}_{2}{\mathrm{IrO}}_{3}$. Spin-lattice relaxation rate ($1/{T}_{1}$) measured down to 100 mK indicates the gapless nature of the excitations at low fields (below ${H}_{c}\ensuremath{\simeq}2.8$ T), in contrast to the gapped magnon excitations found in the honeycomb Kitaev magnet $\ensuremath{\alpha}\ensuremath{-}{\mathrm{RuCl}}_{3}$ at zero applied magnetic field. At higher temperatures in $\ensuremath{\beta}\ensuremath{-}{\mathrm{Li}}_{2}{\mathrm{IrO}}_{3}, 1/{T}_{1}$ passes through a broad maximum without any clear anomaly at the N\'eel temperature ${T}_{N}\ensuremath{\simeq}38$ K, suggesting the abundance of low-energy excitations that are indeed observed as two peaks in the THz spectra; both correspond to zone-center magnon excitations. At higher fields (above ${H}_{c}$), an excitation gap opens, and a redistribution of the THz spectral weight is observed without any indication of an excitation continuum, in contrast to $\ensuremath{\alpha}\ensuremath{-}{\mathrm{RuCl}}_{3}$ where an excitation continuum was reported.

We analyse the dynamics of COVID-19 using computational modelling at multiple scales. For large scale analysis, we propose a 2-scale lattice extension of the classical SIR-type compartmental model with spatial interactions called the Lattice-SIRQL model. Computational simulations show that global quantifiers are not completely representative of the actual dynamics of the disease especially when mitigation measures such as quarantine and lockdown are applied. Furthermore, using real data of confirmed COVID-19 cases, we calibrate the Lattice-SIRQL model for 105 countries. The calibrated model is used to make country specific recommendations for lockdown relaxation and lockdown continuation. Finally, using an agent-based model we analyse the influence of cluster level relaxation rate and lockdown duration on disease spreading.

We have performed magnetic susceptibility $(\ensuremath{\chi})$, heat capacity $({C}_{p})$, and nuclear magnetic resonance (NMR) measurements on the layered compound ${\mathrm{Na}}_{2}{\mathrm{Mn}}_{3}{\mathrm{O}}_{7}$ in which the magnetic ${\mathrm{Mn}}^{4+}$ ions constitute a maple-leaf lattice. At high temperature, $\ensuremath{\chi}$ follows the Curie-Weiss (CW) law with CW temperature as high as 152 K and ${\mathrm{Mn}}^{4+}$ ions are found to be in the high-spin state $(S=\frac{3}{2})$. With decreasing temperature, $\ensuremath{\chi}$ passes through a broad maximum at 115 K and decreases rapidly at low temperature. A similar broad peak appears at around 62 K in the magnetic contribution to heat capacity $({C}_{m})$. The temperature dependence of $\ensuremath{\chi}$ and ${C}_{m}$ are the characteristics of an one-dimensional Heisenberg antiferromagnetic spin chain with a nonmagnetic ground state. The obtained values of spin-gap energy $({\mathrm{\ensuremath{\Delta}}}_{s})$ and nearest-neighbor antiferromagnetic exchange coupling $(J)$ are 28 and 27 K, respectively. There is no evidence of a long-range magnetic ordering down to 2 K in heat capacity data, in agreement with spin-singlet ground state. These observations are further corroborated by $^{23}\mathrm{Na}$ NMR studies through measurements of both the NMR shift and the spin-lattice relaxation rate.

We investigate the relaxation rate of the RNdS black hole perturbed by neutral massless scalar field in the eikonal limit. We find that the fastest relaxation rate of the composed system increases with the cosmological constant for all spacetime dimensions. We also find that, when the cosmological constant decreases from maximum value to zero, the corresponding critical charge of the four-dimensional RNdS black hole maximizing the relaxation rate of the composed system gradually decreases monotonically to $\bar{Q}=0.726$. However, for the higher dimensional systems, this is not the case and the critical charges decrease from maximum to zero., 8 pages, to appear in PLB

This paper reports on a highly accurate approach of magnetic resonance (MR) thermometry using iron oxide magnetic nanoparticles (MNPs) as temperature sensors. An empirical model for the description of the temperature dependent R 2 relaxation rate is proposed by taking into account the temperature sensitivity of the MNP magnetization. The temperature sensitivity of the MNP magnetization (η) and the temperature sensitivity of the R 2 relaxation rate (κ) are simulated with the proposed empirical models to investigate their dependence on the magnetic field and the particle size. Simulation results show the existence of optimal magnetic fields Hoη and Hoκ that maximize the temperature sensitivities η and κ. Furthermore, simulations and experiments demonstrate that the optimal magnetic field Hoη (Hoκ ) decreases with increasing the particle size. Experiments on temperature dependent R 2 relaxation rate are performed at different magnetic fields for MNP samples with different iron concentrations. Experimental results show that the proposed MR thermometry using MNPs as temperature sensors allows a temperature estimation accuracy of about 0.05 °C. We believe that the achieved approach of highly accurate MR thermometry is of great interest and significance to biomedicine and biology.

We report the inverse Laplace transform analysis of the $^{139}\mathrm{La}$ nuclear spin-lattice relaxation rate $1/{T}_{1}$ (${\mathrm{ILTT}}_{1}$ analysis) in charge-ordered ${\mathrm{La}}_{1.885}{\mathrm{Sr}}_{0.115}{\mathrm{CuO}}_{4}$ (${T}_{\mathrm{charge}}\ensuremath{\simeq}80$ K, ${T}_{c}\ensuremath{\simeq}{T}_{\mathrm{spin}}^{\mathrm{neutron}}=30$ K), and shed light on its magnetic inhomogeneity. We deduce the probability density function $P(1/{T}_{1})$ of the distributed $1/{T}_{1}$ (i.e., the histogram of distributed $1/{T}_{1}$) by taking the inverse Laplace transform of the experimentally observed nuclear magnetization recovery curve $M(t)$. We demonstrate that spin freezing sets in in some domains precisely below the onset of charge order at ${T}_{\mathrm{charge}}$, but their volume fraction grows only gradually toward ${T}_{c}$. Nearly a half of the sample volume exhibits properties expected for canonical high-${T}_{c}$ cuprates without charge order even near ${T}_{c}$. Our findings explain why charge order does not suppress ${T}_{c}$ of ${\mathrm{La}}_{1.885}{\mathrm{Sr}}_{0.115}{\mathrm{CuO}}_{4}$ as significantly as in ${\mathrm{La}}_{1.875}{\mathrm{Ba}}_{0.125}{\mathrm{CuO}}_{4}$.

We investigate the interplay between the lattice, charge, and spin dynamics in charge-ordered high ${T}_{c}$ cuprate ${\mathrm{La}}_{1.875}{\mathrm{Ba}}_{0.125}{\mathrm{CuO}}_{4}\phantom{\rule{4pt}{0ex}}({T}_{c}=4\phantom{\rule{0.16em}{0ex}}\mathrm{K})$ based on the inverse Laplace transform (ILT) analysis of the $^{139}\mathrm{La}$ nuclear spin-lattice relaxation rate $1/{T}_{1}$ (dubbed ${\mathrm{ILTT}}_{1}$ analysis hereafter). A major thrust of the ${\mathrm{ILTT}}_{1}$ analysis is that one can deduce the probability density function $P(1/{T}_{1})$ of distributed $1/{T}_{1}$. We demonstrate that $1/{T}_{1}^{\text{lm}}$, defined as the log mean (i.e., the center of gravity on a logarithmic scale) of $P(1/{T}_{1})$, can be well approximated by $1/{T}_{1}^{\text{str}}$ deduced from the phenomenological stretched fit; however, $P(1/{T}_{1})$ can provide much richer insight into how the lattice, charge, and spin fluctuations and their distribution develop near and below the long-range charge order at ${T}_{\text{charge}}\ensuremath{\sim}54\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. Upon entering the charge-ordered state, a divergent increase of $1/{T}_{1}^{\text{lm}}$ toward the spin ordering at ${T}_{\text{spin}}^{\ensuremath{\mu}\text{SR}}\ensuremath{\simeq}35\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ is accompanied by an asymmetric broadening of $P(1/{T}_{1})$. Even deep inside the charge-ordered state, $1/{T}_{1}$ at a gradually diminishing fraction of $^{139}\mathrm{La}$ sites continues to slow down as temperature is lowered, as expected for canonical superconducting ${\mathrm{CuO}}_{2}$ planes without enhanced spin fluctuations. The fraction of such canonical $^{139}\mathrm{La}$ sites almost disappears by $\ensuremath{\simeq}40\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. In contrast, nearly half of the $^{139}\mathrm{La}$ sites in ${\mathrm{La}}_{1.885}{\mathrm{Sr}}_{0.115}{\mathrm{CuO}}_{4}\phantom{\rule{4pt}{0ex}}({T}_{\text{charge}}\ensuremath{\simeq}80\phantom{\rule{0.16em}{0ex}}\mathrm{K})$ still exhibit the canonical behavior without enhanced spin fluctuations even near its ${T}_{c}=31\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. These contrasting behaviors explain why superconductivity in ${\mathrm{La}}_{1.875}{\mathrm{Ba}}_{0.125}{\mathrm{CuO}}_{4}$ is more strongly suppressed than in ${\mathrm{La}}_{1.885}{\mathrm{Sr}}_{0.115}{\mathrm{CuO}}_{4}$ despite the lower onset temperature of the charge order.

We have performed $^{13}\mathrm{C}$ NMR measurements on $\ensuremath{\lambda}\ensuremath{-}{(\mathrm{BEDT}\ensuremath{-}\mathrm{STF})}_{2}{\mathrm{FeCl}}_{4}$ to reveal the mechanism of unconventional paramagneticlike behavior observed in $\ensuremath{\lambda}$-type molecular $\ensuremath{\pi}\ensuremath{-}d$ systems. $^{13}\mathrm{C}$ NMR spectra and nuclear spin-lattice relaxation rate $1/{T}_{1}$ revealed that the $\ensuremath{\pi}$ and $3d$ electron systems undergo an antiferromagnetic transition simultaneously at 16 K with the assistance of the $\ensuremath{\pi}\ensuremath{-}d$ interaction. We found that the sublattice magnetizations of the $\ensuremath{\pi}$ and $3d$ spins show different temperature dependence below ${T}_{\mathrm{N}}$, which is derived from the magnetic coupling between the two sublattice systems with different magnetic natures. We discuss the relationship between the two different magnetization processes and the unconventional magnetic behavior in $\ensuremath{\lambda}$-type molecular $\ensuremath{\pi}\ensuremath{-}d$ system.

By using mostly the muon-spin rotation/relaxation ($\ensuremath{\mu}\mathrm{SR}$) technique, we investigate the superconductivity (SC) of ${\mathrm{Nb}}_{5}{\mathrm{Ir}}_{3\ensuremath{-}x}{\mathrm{Pt}}_{x}\mathrm{O}$ ($x=0$ and 1.6) alloys, with ${T}_{c}=10.5$ and 9.1 K, respectively. At a macroscopic level, their superconductivity was studied by electrical resistivity, magnetization, and specific-heat measurements. In both compounds, the electronic specific heat and the low-temperature superfluid density data suggest a nodeless SC. The superconducting gap value and the specific heat discontinuity at ${T}_{c}$ are larger than that expected from BCS theory in the weak-coupling regime, indicating strong-coupling superconductivity in the ${\mathrm{Nb}}_{5}{\mathrm{Ir}}_{3\ensuremath{-}x}{\mathrm{Pt}}_{x}\mathrm{O}$ family. In ${\mathrm{Nb}}_{5}{\mathrm{Ir}}_{3}\mathrm{O}$, multigap SC is evidenced by the field dependence of the electronic specific heat coefficient and the superconducting Gaussian relaxation rate, as well as by the temperature dependence of the upper critical field. Pt substitution suppresses one of the gaps, and ${\mathrm{Nb}}_{5}{\mathrm{Ir}}_{1.4}{\mathrm{Pt}}_{1.6}\mathrm{O}$ becomes a single-gap superconductor. By combining our extensive experimental results, we provide evidence for a multiple- to single-gap SC crossover in the ${\mathrm{Nb}}_{5}{\mathrm{Ir}}_{3\ensuremath{-}x}{\mathrm{Pt}}_{x}\mathrm{O}$ family.

We scrutinize the magnetic properties of $\kappa$-(BEDT-TTF)$_2$Hg(SCN)$_2$Cl through its first-order metal-insulator transition at $T_{\rm CO}=30$ K by means of $^1$H nuclear magnetic resonance (NMR). While in the metal we find Fermi-liquid behavior with temperature-independent $(T_1T)^{-1}$, the relaxation rate exhibits a pronounced enhancement when charge order sets in. The NMR spectra remain unchanged through the transition and no magnetic order stabilizes down to 25 mK. Similar to the isostructural spin-liquid candidates $\kappa$-(BEDT-TTF)$_2$Cu$_2$(CN)$_3$ and $\kappa$-(BEDT-TTF)$_2$Ag$_2$(CN)$_3$, $T_1^{-1}$ acquires a dominant maximum (here around 5 K). Field-dependent experiments identify the low-temperature feature as a dynamic inhomogeneity contribution that is typically dominant over the intrinsic relaxation but gets suppressed with magnetic field., Comment: 6 pages, 4 figures; Supplemental Material: 3 pages, 2 figures, 1 table

BACKGROUND: Acute limb ischemia (ALI) can lead to death and amputation. Evaluating the severity of ischemia is important but difficult, through current methods of examination. The purpose of this research was to demonstrate the feasibility of magnetic resonance imaging (MRI) susceptibility-based imaging techniques for use in assessing muscle oxygenation alterations in ALI. METHODS: ALI animal models were established in 11 rabbits. Their left iliac arteries were embolized by microspheres. MRI scans were conducted 24 hours before (Pre) and 1 hour (Post 1) and 3 hours (Post 2) after the procedure. A susceptibility model was used to calculate skeletal muscle oxygenation extraction fraction (SMOEF) and relaxation rate (R2’). T2 weighted (T2w) imaging and diffusion-weighted (DW) imaging were performed. RESULTS: The average calf muscle SMOEF in the embolized hindlimbs increased from 0.43±0.02 (Pre) to 0.48±0.02 (Post 1) and 0.50±0.02 (Post 2), both P0.05). No abnormal signals were observed in the anatomical T2w images at Post 1 and Post 2. CONCLUSIONS: This study demonstrates the feasibility of using SMOEF for the assessment of oxygenation alterations in ALI models. SMOEF is more sensitive than T2w and DW imaging in detecting acute muscle ischemia at an early stage.

Short-term high frequency electrostimulation (8-10 Hz) of the isolated isovolumic rat heart rapidly increased the rate of pressure rise and drop and the diastolic pressure. At the same time, the relaxation rate constant (RRC), being independent of the developed pressure, remained unaltered. These findings suggested that diastolic pressure rise was not caused by incomplete myocardial relaxation. Doxorubicin (3 μM) moderately reduced the developed pressure, but the relaxation rate constant remained unchanged. The dynamics and degree of changes in all indicators of the cardiac contractile function in high-frequency stimulation were the same as in control. It can be hypothesized that the initial effect of doxorubicin was not related to ionic transport system disturbances in cardiomyocytes.

Selective inversion recovery (SIR) is a quantitative magnetization transfer (qMT) method that provides estimates of parameters related to myelin content in white matter, namely the macromolecular pool-size-ratio (PSR) and the spin-lattice relaxation rate of the free pool (R1f), without the need for independent estimates of ∆B0, B1+, and T1. Although the feasibility of performing SIR in the human brain has been demonstrated, the scan times reported previously were too long for whole-brain applications. In this work, we combined optimized, short-TR acquisitions, SENSE/partial-Fourier accelerations, and efficient 3D readouts (turbo spin-echo, SIR-TSE; echo-planar imaging, SIR-EPI; and turbo field echo, SIR-TFE) to obtain whole-brain data in 18, 10, and 7 min for SIR-TSE, SIR-EPI, SIR-TFE, respectively. Based on numerical simulations, all schemes provided accurate parameter estimates in large, homogenous regions; however, the shorter SIR-TFE scans underestimated focal changes in smaller lesions due to blurring. Experimental studies in healthy subjects (n = 8) yielded parameters that were consistent with literature values and repeatable across scans (coefficient of variation: PSR = 2.2–6.4%, R1f = 0.6–1.4%) for all readouts. Overall, SIR-TFE parameters exhibited the lowest variability, while SIR-EPI parameters were adversely affected by susceptibility-related image distortions. In patients with relapsing remitting multiple sclerosis (n = 2), focal changes in SIR parameters were observed in lesions using all three readouts; however, contrast was reduced in smaller lesions for SIR-TFE, which was consistent with the numerical simulations. Together, these findings demonstrate that efficient, accurate, and repeatable whole-brain SIR can be performed using 3D TFE, EPI, or TSE readouts; however, the appropriate readout should be tailored to the application.

We characterize spin-wave propagation and its modification by an electrical current in permalloy($\mathrm{Py}$)/$\mathrm{Pt}$ bilayers with $\mathrm{Py}$ thickness between 4 and 20 nm. First, we analyze the frequency nonreciprocity of surface spin waves and extract from it the interfacial Dzyaloshinskii-Moriya interaction constant ${D}_{s}$ accounting for an additional contribution due to asymmetric surface anisotropies. Second, we measure the spin-wave relaxation rate and deduce from it the $\mathrm{Py}$/$\mathrm{Pt}$ spin-mixing conductance ${g}_{\mathrm{eff}}^{\ensuremath{\uparrow}\ensuremath{\downarrow}}$. Last, applying a dc electrical current, we extract the spin Hall conductivity ${\ensuremath{\sigma}}_{\mathrm{SH}}$ from the change of spin-wave relaxation rate due to the spin Hall spin-transfer torque. We obtain a consistent picture of the spin-wave propagation data for different film thicknesses using a single set of parameters ${D}_{s}=0.25$ pJ/m, ${g}_{\mathrm{eff}}^{\ensuremath{\uparrow}\ensuremath{\downarrow}}=3.2\ifmmode\times\else\texttimes\fi{}{10}^{19}\phantom{\rule{0.2em}{0ex}}{\mathrm{m}}^{\ensuremath{-}2}$ and ${\ensuremath{\sigma}}_{\mathrm{SH}}=4\ifmmode\times\else\texttimes\fi{}{10}^{5}$ S/m.

The mechanisms that modulate the kinetics of muscle relaxation are critically important for muscle function. A prime example of the impact of impaired relaxation kinetics is nemaline myopathy caused by mutations in KBTBD13 (NEM6). In addition to weakness, NEM6 patients have slow muscle relaxation, compromising contractility and daily life activities. The role of KBTBD13 in muscle is unknown, and the pathomechanism underlying NEM6 is undetermined. A combination of transcranial magnetic stimulation–induced muscle relaxation, muscle fiber– and sarcomere-contractility assays, low-angle x-ray diffraction, and superresolution microscopy revealed that the impaired muscle-relaxation kinetics in NEM6 patients are caused by structural changes in the thin filament, a sarcomeric microstructure. Using homology modeling and binding and contractility assays with recombinant KBTBD13, Kbtbd13-knockout and Kbtbd13(R408C)-knockin mouse models, and a GFP-labeled Kbtbd13-transgenic zebrafish model, we discovered that KBTBD13 binds to actin — a major constituent of the thin filament — and that mutations in KBTBD13 cause structural changes impairing muscle-relaxation kinetics. We propose that this actin-based impaired relaxation is central to NEM6 pathology.

We consider the simplest model for $T$ - linear growth of resistivity in metals. It is shown that the so called "Planckian" limit for the temperature dependent relaxation rate of electrons follows from a certain procedure for representation of experimental data on resistivity and, in this sense, is a kind of delusion., 5 pages, 1 figure

The field of medical science is also revolutionized with the emergence of nanotechnology where the use of nanomaterials offers many applications especially for the diagnosis of different diseases and their treatment. For example, these nanomaterials offer enhanced contrast agent properties by modulating the relaxation rate of water protons under certain applied fields. Consequently, a more detailed visualization of different tissues and organelles is possible, which can be used to identify any abnormalities in the organism. In the meantime, these nanomaterials can also be used to deliver different types of drugs in the body at particular sites with minimum side effects. In this way, nanomaterials can be used for the diagnosis and treatment of different diseases through minimum invasion in the body. In this chapter, different types of nanomaterials, their synthesis methods, and the use for diagnosis of different diseases will be discussed.

In this chapter, we present the spin-lattice relaxation rate of quantum spin liquid. Also, we analyze optical conductivity with the goal to demonstrate experimental manifestation of the new state of matter.