Magnetic Resonance Letters最新文献

{"title":"Numerical simulation study on the effect of temperature on the restricted diffusion in porous media","authors":"Zhen Xie ,&nbsp;Lizhi Xiao ,&nbsp;Sihui Luo ,&nbsp;Guangzhi Liao","doi":"10.1016/j.mrl.2023.03.007","DOIUrl":"10.1016/j.mrl.2023.03.007","url":null,"abstract":"<div><p>It is of great significance to study how temperature affects the restricted diffusion in pores for an accurate evaluation of reservoir physical properties by using nuclear magnetic resonance (NMR) diffusion-transverse relaxation (<em>D</em>-<em>T</em>₂) spectrum under reservoir temperature conditions. In this paper, we simulate the restricted diffusion and two-dimensional (2D) NMR <em>D</em>-<em>T</em>₂ spectra of water molecules at different temperatures using random-walk method. The one-dimensional (1D) restricted diffusion simulation results show that the diffusion coefficient in the pore at room temperature decays with the diffusion time and eventually reaches a plateau. Under the condition of long-time diffusion, the ratio of restricted diffusion coefficient to bulk diffusion coefficient at different temperatures tends to be the same constant. With the increase in temperature, the simulated <em>D</em>-<em>T</em>₂ spectra also gradually move upward. The simulated <em>D</em>-<em>T</em>₂ spectra at all temperatures are consistent with the Padé interpolation equation. In addition, the results calculated by Padé interpolation equation demonstrate that the degree of temperature influence on the <em>D</em>-<em>T</em>₂ spectrum of rock is quantitatively related to the pore radius, porosity and cementation index.</p></div>","PeriodicalId":93594,"journal":{"name":"Magnetic Resonance Letters","volume":"3 2","pages":"Pages 118-126"},"PeriodicalIF":0.0,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45975296","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"NMR relaxation and diffusion studies to probe the motional dynamics of risperidone within PLGA microsphere","authors":"Deepak Kumar ,&nbsp;Samanwita Pal","doi":"10.1016/j.mrl.2023.03.005","DOIUrl":"10.1016/j.mrl.2023.03.005","url":null,"abstract":"<div><p>The present study aims to investigate the motional dynamics of risperidone within polylactic co-glycolic acid (PLGA) microsphere by employing solution state ¹H and ¹⁹F nuclear magnetic resonance (NMR) measurements. Risperidone, a second-generation fluorinated antipsychotic drug used for the treatment of schizophrenia is commercially marketed as PLGA microsphere formulation resulting in prolonged release of the drug in solution. Although the current trend in the pharmaceutical market is to develop drug formulation with long-acting release (LAR) products, complete physicochemical characterization of such formulations are scarce. Especially the effects of microsphere encapsulation on the motional properties and diffusion behavior of the drugs are not discussed adequately in any of the earlier reports. We therefore, have employed NMR relaxation and diffusion measurements to decipher the interaction of PLGA cavity water with risperidone. A detailed analysis of NMR relaxation rates confirmed the event of encapsulation and the presence of local motion in the non-fluorinated end of risperidone. Further, the relaxation data indicated a significant alteration in ¹⁹F chemical shift anisotropy (CSA) and CSA/dipole-dipole (DD) cross-correlated relaxation mechanism and decreased effect of solvent relaxation pointing out reduced water concentration within the microsphere cavity. ¹H and ¹⁹F diffusion coefficients of risperidone led to the information about hydrodynamic radius of risperidone in free and encapsulated states. Measurement of hydrodynamic radius supported the presence of limited water in PLGA cavity allowing higher translational mobility of risperidone after the encapsulation.</p></div>","PeriodicalId":93594,"journal":{"name":"Magnetic Resonance Letters","volume":"3 2","pages":"Pages 197-205"},"PeriodicalIF":0.0,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41282243","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Binary fluids in mesoporous materials: Phase separation studied by NMR relaxation and diffusion","authors":"Siegfried Stapf,&nbsp;Niklas Siebert,&nbsp;Timo Spalek,&nbsp;Vincent Hartmann,&nbsp;Bulat Gizatullin,&nbsp;Carlos Mattea","doi":"10.1016/j.mrl.2023.03.002","DOIUrl":"10.1016/j.mrl.2023.03.002","url":null,"abstract":"<div><p>Relaxation and diffusion measurements were carried out on single and binary liquids filling the pore space of controlled porous glass Vycor with an average pore size of about 4 nm. The dispersion of the longitudinal relaxation time <em>T</em>₁ is discussed as a means to identify liquid-surface interaction based on existing models developed for metal-free glass surfaces. In addition, the change of <em>T</em>₁ and <em>T</em>₂ with respect to their bulk values is discussed, in particular <em>T</em>₂ serves as a probe for the strength of molecular interactions. As the native glass surface is polar and contains a large amount of hydroxyl groups, a pronounced interaction of polar and protic adsorbate liquids is expected; however, the <em>T</em>₁ dispersion, and the corresponding reduction of <em>T</em>₂, are also observed for non-polar liquids such as alkanes and cyclohexane. Deuterated liquids are employed for simplifying data analysis in binary systems, but also for separating the respective contributions of intra- and intermolecular interactions to the overall relaxation rate. Despite the lack of paramagnetic impurities in the glass material, ¹H and ²H relaxation dispersions of equivalent molecules are frequently found to differ from each other, suggesting intermolecular relaxation mechanisms for the ¹H nuclei. The variation of the <em>T</em>₁ dispersion when comparing single and binary systems gives clear evidence for the preferential adsorption of one of the two liquids, suggesting complete phase separation in several cases. Measurement of the apparent tortuosity by self-diffusion experiments supports the concept of a local variation of sample composition within the porespace.</p></div>","PeriodicalId":93594,"journal":{"name":"Magnetic Resonance Letters","volume":"3 2","pages":"Pages 108-117"},"PeriodicalIF":0.0,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48055350","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Low-field, high-gradient NMR shows diffusion contrast consistent with localization or motional averaging of water near surfaces","authors":"Nathan H. Williamson ,&nbsp;Velencia J. Witherspoon ,&nbsp;Teddy X. Cai ,&nbsp;Rea Ravin ,&nbsp;Ferenc Horkay ,&nbsp;Peter J. Basser","doi":"10.1016/j.mrl.2023.03.009","DOIUrl":"10.1016/j.mrl.2023.03.009","url":null,"abstract":"<div><p>Nuclear magnetic resonance (NMR) measurements of water diffusion have been extensively used to probe microstructure in porous materials, such as biological tissue, however primarily using pulsed gradient spin echo (PGSE) methods. Low-field single-sided NMR systems have built-in static gradients (SG) much stronger than typical PGSE maximum gradient strengths, which allows for the signal attenuation at extremely high <em>b</em>-values to be explored. Here, we perform SG spin echo (SGSE) and SG stimulated echo (SGSTE) diffusion measurements on biological cells, tissues, and gels. Measurements on fixed and live neonatal mouse spinal cord, lobster ventral nerve cord, and starved yeast cells all show multiexponential signal attenuation on a scale of <em>b</em> with significant signal fractions observed at <em>b</em> × <em>D</em>₀ ≫ 1 with <em>b</em> as high as 400 ms/μm². These persistent signal fractions trend with surface-to-volume ratios for these systems, as expected from porous media theory. An exception found for the case of fixed vs. live spinal cords was attributed to faster exchange or permeability in live spinal cords than in fixed spinal cords on the millisecond timescale. Data suggests the existence of multiple exchange processes in neural tissue, which may be relevant to the modeling of time-dependent diffusion in gray matter. The observed multi-exponential attenuation is from protons on water and not macromolecules because it remains proportional to the normalized signal when a specimen is washed with D₂O. The signal that persists to <em>b</em> × <em>D</em>₀ ≫ 1 is also drastically reduced after delipidation, indicating that it originates from lipid membranes that restrict water diffusion. The multi-exponential or stretched exponential character of the signal attenuation at <em>b</em> × <em>D</em>₀ ≫ 1 appears mono-exponential when viewed on a scale of <span><math><msup><mrow><mrow><mo>(</mo><mrow><mi>b</mi><mo>×</mo><msub><mrow><mi>D</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow><mo>)</mo></mrow></mrow><mrow><mn>1</mn><mo>/</mo><mn>3</mn></mrow></msup></math></span>, suggesting it may originate from localization or motional averaging of water near membranes on sub-micron length scales. To try to disambiguate these two contributions, signal attenuation curves were compared at varying temperatures. While the curves align when normalizing them using the localization length scale, they separate on a motional averaging length scale. This supports localization as the source of non-Gaussian displacements, but this interpretation is still provisional due to the possible confounds of heterogeneity, exchange, and relaxation. Measurements on two types of gel phantoms designed to mimic extracellular matrix, one with charged functional groups synthesized from polyacrylic acid (PAC) and another with uncharged functional groups synthesized from polyacrylamide (PAM), both exhibit signal at","PeriodicalId":93594,"journal":{"name":"Magnetic Resonance Letters","volume":"3 2","pages":"Pages 90-107"},"PeriodicalIF":0.0,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43472811","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"23Na relaxometry: An overview of theory and applications","authors":"Yifan Song ,&nbsp;Yu Yin ,&nbsp;Qinlong Chen ,&nbsp;Alessandro Marchetti ,&nbsp;Xueqian Kong","doi":"10.1016/j.mrl.2023.04.001","DOIUrl":"10.1016/j.mrl.2023.04.001","url":null,"abstract":"<div><p>²³Na is a nuclear magnetic resonance (NMR)-active isotope with a nuclear spin quantum number of 3/2. ²³Na relaxation phenomenon is at the core of ²³Na NMR measurement and analysis. Due to the dominance of quadrupolar interaction, the relaxation behavior of ²³Na is physically and mathematically more complex than that of a typical spin-1/2 isotope. In this review, we overview the semi-classical Redfield theory for deriving the formulations of ²³Na relaxation. We show that the relaxation behaviors of ²³Na can be quantitatively described by constructing the spectral density functions based on the second-order perturbation theory. In addition, we summarize the applications of ²³Na relaxometry in different research fields, including biomedicine, sodium ion batteries, and quantum information processing. Because sodium is an essential element in our body, food and industrial materials, the research on sodium by ²³Na NMR emerges as important future directions. The theoretical and practical understandings on ²³Na relaxation are the step stones for mastering advanced ²³Na NMR techniques.</p></div>","PeriodicalId":93594,"journal":{"name":"Magnetic Resonance Letters","volume":"3 2","pages":"Pages 150-174"},"PeriodicalIF":0.0,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46209216","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Probing electronic structures of transition metal complexes using electron paramagnetic resonance spectroscopy","authors":"Shengfa Ye","doi":"10.1016/j.mrl.2022.06.002","DOIUrl":"10.1016/j.mrl.2022.06.002","url":null,"abstract":"<div><p>Electron paramagnetic resonance (EPR) or electron spin resonance (ESR) has been widely employed to characterize transition metal complexes. However, because of the high degree of complexity of transition metal EPR spectra, how to extract the underlying electronic-structure information inevitably poses a major challenge to beginners, in particular for systems with <span><math><mrow><mi>S</mi><mo>&gt;</mo><mfrac><mn>1</mn><mn>2</mn></mfrac></mrow></math></span>. In fact, the physical principles of transition metal EPR have long been well-established and since 1970s a series of dedicated voluminous monographs have been published already. Not surprisingly, they are not appropriate stating points for novices to grasp a panorama of the profound theory prior to scrutinizing in-depth references. The present review aims to fill this gap to provide a perspective of transition metal EPR and unveil some peculiar subtleties thereof on the basis of our recent work.</p></div>","PeriodicalId":93594,"journal":{"name":"Magnetic Resonance Letters","volume":"3 1","pages":"Pages 43-60"},"PeriodicalIF":0.0,"publicationDate":"2023-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42687062","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Amide proton transfer imaging of Alzheimer's disease and Parkinson's disease","authors":"Chunmei Li ,&nbsp;Jinyuan Zhou ,&nbsp;Di Wang ,&nbsp;Xinyang Li ,&nbsp;Shanshan Jiang ,&nbsp;Yi Zhang ,&nbsp;Zhibo Wen ,&nbsp;Guangbin Wang ,&nbsp;Fuhua Yan ,&nbsp;Min Chen","doi":"10.1016/j.mrl.2022.10.002","DOIUrl":"10.1016/j.mrl.2022.10.002","url":null,"abstract":"<div><p>Amide proton transfer (APT) magnetic resonance imaging (MRI) is an important molecular imaging technique at the protein level in tissue. Neurodegenerative diseases have a high likelihood of causing abnormal protein accumulation in the brain, which can be detected by APT MRI. This article briefly introduces the principles and image processing technology of APT MRI, and reviews the current state of research on Alzheimer's disease and Parkinson's disease using this technique. Early applications of this approach in these two neurodegenerative diseases are encouraging, which also suggests continued technical development and larger clinical trials to gauge the value of this technique.</p></div>","PeriodicalId":93594,"journal":{"name":"Magnetic Resonance Letters","volume":"3 1","pages":"Pages 22-30"},"PeriodicalIF":0.0,"publicationDate":"2023-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44025986","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modulation mechanism of aquaporins by mercury revealed by solid-state NMR and molecular dynamics simulations","authors":"Shenlin Wang","doi":"10.1016/j.mrl.2022.12.002","DOIUrl":"10.1016/j.mrl.2022.12.002","url":null,"abstract":"","PeriodicalId":93594,"journal":{"name":"Magnetic Resonance Letters","volume":"3 1","pages":"Pages 85-86"},"PeriodicalIF":0.0,"publicationDate":"2023-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43139076","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Brain structural plasticity in rats subjected to early binocular enucleation characterized by high resolution anatomical magnetic resonance imaging and diffusion tensor imaging","authors":"Xuxia Wang,&nbsp;Fuchun Lin,&nbsp;Yan Kang,&nbsp;Hao Lei","doi":"10.1016/j.mrl.2022.10.001","DOIUrl":"10.1016/j.mrl.2022.10.001","url":null,"abstract":"<div><p>Visual deprivation leads to structural neuroplasticity in the blind subjects, including gray matter (GM) and white matter (WM) atrophy and alterations in structural connectivity. The rat model of binocular enucleation (BE) is a frequently used animal model for studying brain plasticity induced by early blindness. Yet few neuroimaging studies have been performed on this model to investigate whether or not the BE rats have image phenotypes similar to or comparable to, those observed in the early blind subjects. The current study aimed to assess brain structural plasticity in BE rats using anatomical magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI). The results demonstrated that early BE at postnatal day 4 (P4) caused almost complete degeneration of optic nerve (ON) and optic chiasma (OCH), atrophy in a number of visual and non-visual structures, including optic tract (OT), dorsal lateral geniculate nucleus (DLG) and corpus callosum (CC). The BE rats also exhibited impairments of WM microstructural integrity in the OT, and reduction of structural connectivity between the normal-appearing visual cortex (VC) and somatosensory/motor cortices at 4 months of age, likely as manifestations of deafferentation-induced maldevelopment. The structural neuroplasticity in BE rats observable to structural MRI parallels largely with what has been reported in blind subjects, suggesting that longitudinal neuroimaging studies on animal models of sensory deprivation can provide insights into how the brain changes its wiring and function during development/adaption in response to the lack of sensory stimuli.</p></div>","PeriodicalId":93594,"journal":{"name":"Magnetic Resonance Letters","volume":"3 1","pages":"Pages 14-21"},"PeriodicalIF":0.0,"publicationDate":"2023-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43913811","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Accurate surface normal representation to facilitate gradient coil optimization on curved surface","authors":"Hao Ren ,&nbsp;Hui Pan ,&nbsp;Feng Jia ,&nbsp;Jan G. Korvink ,&nbsp;Zhenyu Liu","doi":"10.1016/j.mrl.2022.05.001","DOIUrl":"10.1016/j.mrl.2022.05.001","url":null,"abstract":"<div><p>The design methods for gradient coils are mostly based on discrete extrinsic methods (e.g., the <em>Biot–Savart</em> integration calculation), for which the surface normal vector strongly influences any numerical calculation of the discretized surface. Previous studies are mostly based on regular or analytical surfaces, which allow normal vectors to be expressed analytically. For certain applications, design methods for extending current-carrying surfaces from developable or analytic geometries to arbitrary surfaces generated from a scanned point cloud are required. The key task is to correctly express the discretized normal vectors to ensure geometrical accuracy of the designed coils. Mathematically, it has been proven that applying a Delaunay triangulation to approximate a smooth surface can result in the discrete elemental normal vectors converging to those of the original surface. Accordingly, this article uses Delaunay triangulation to expand upon previous design methods so that they encompass arbitrary piecewise continuous surfaces. Two design methods, the stream function and the so-called solid isotropic material with penalization (SIMP) method, are used to design circumvolute and noncircumvolute gradient coils on general surfaces.</p></div>","PeriodicalId":93594,"journal":{"name":"Magnetic Resonance Letters","volume":"3 1","pages":"Pages 67-84"},"PeriodicalIF":0.0,"publicationDate":"2023-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47285271","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}