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TODICA, M. "NMR OBSERVATION OF THE SPIN-LATTICE AND SPIN-SPIN RELAXATION IN SOME POLIBUTADIENES WITH DIFFERENT VINYL CONTENTS". International Journal of Modern Physics B 19, nr 13 (20.05.2005): 2167–74. http://dx.doi.org/10.1142/s0217979205029705.
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Some polybutadienes with different vinyl contents were observed by NMR methods in order to disclose the influence of the microstructure of the polymeric chains on the relaxation of the longitudinal and transverse magnetization. The relaxation process is correlated with the dynamic properties of the polymeric chains. The residual dipolar interaction determined by the rigidity of the polymeric chains is observed by the pseudo-solid echo method and is associated with the vinyl contents of the samples.
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Chance, Brent H., i Don E. Bray. "Nondestructive Monitoring of Stress Relaxation in Welded Steel Plates". Journal of Pressure Vessel Technology 124, nr 3 (26.07.2002): 343–48. http://dx.doi.org/10.1115/1.1491581.
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This study investigates transverse stress relaxation in welded steel plates. Two different methods of stress measurement were used; strain gages and critically refracted longitudinal LCR waves. The material investigated was ASTM 1008/1010 steel. T-shaped slots were cut from each edge of each specimen in order to provide a uniaxial tension stress field in the area of investigation. After the plates were stress-relieved by annealing, the transverse slots were then welded and allowed to cool. Strain gages were applied to the bridge area joining the middle of the plate and oriented parallel to the long side of the plate. Initial strain gage and ultrasonic measurements were then performed. At different time intervals, cutting through a sample plate’s welds relieved the stresses. Strain gage and ultrasonic measurements were then repeated. Both the strain gage and LCR methods indicate that there is a measurable stress relaxation in the plates, and that it occurs in a time-dependent and predictable manner.
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Wei, Mengmeng, Wenbin Yu, Min Zhou, Wei Huang, Yuanxing Liu i Xinye Xu. "Three techniques for measuring the transverse relaxation time of cesium atoms". AIP Advances 13, nr 3 (1.03.2023): 035327. http://dx.doi.org/10.1063/5.0140593.
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The transverse relaxation time ( T2) is an important indicator to determine the fundamental sensitivity limit of alkali-metal atomic magnetometers. We propose a method based on the principle of longitudinal field modulation that obtains T2 by scanning the transverse static magnetic field. The previous technique of extracting T2 from the linewidth of the modulation frequency and the traditional magnetic-resonance-broadening-fitting method are also described. The T2 measurements of Cesium (Cs) atoms are carried out through these three methods, whose operating environments are applicable to different atomic magnetometers, respectively. The method that we propose can be used for obtaining the T2 of Cs atoms as well as detecting the transverse static magnetic field and is customized for the study of the Cs–Xenon ensemble for the construction of nuclear magnetic resonance gyroscopes. Moreover, the relationship between the limit sensitivities and cell temperatures is further studied in the experiment.
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Monaretto, Tatiana, Tiago Bueno Moraes i Luiz Alberto Colnago. "Recent 1D and 2D TD–NMR Pulse Sequences for Plant Science". Plants 10, nr 5 (21.04.2021): 833. http://dx.doi.org/10.3390/plants10050833.
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Time domain nuclear magnetic resonance (TD–NMR) has been widely applied in plant science in the last four decades. Several TD–NMR instruments and methods have been developed for laboratory, green-house, and field studies. This mini-review focuses on the recent TD–NMR pulse sequences applied in plant science. One of the sequences measures the transverse relaxation time (T2) with minimal sample heating, using a lower refocusing flip angle and consequently lower specific absorption rate than that of conventional CPMG. Other sequences are based on a continuous wave free precession (CWFP) regime used to enhance the signal-to-noise ratio, to measure longitudinal (T1) and transverse relaxation time in a single shot experiment, and as alternative 2D pulse sequences to obtain T1–T2 and diffusion-T1 correlation maps. This review also presents some applications of these sequences in plant science.
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TODICA, M. "COMPARATIVE OBSERVATION OF THE NMR SPIN-LATTICE AND SPIN-SPIN RELAXATION IN MOLTEN AND CROSS-LINKED POLIBUTADIENE". International Journal of Modern Physics B 19, nr 10 (20.04.2005): 1771–81. http://dx.doi.org/10.1142/s0217979205029353.
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The molten and cross-linked polybutadiene were observed by NMR methods in order to disclose the influence of the presence of the temporary and permanent junctions between the polymeric chains on the relaxation of the longitudinal and transverse magnetization. The residual dipolar interaction determined by the entanglements of the polymeric chains is observed by the pseudo-solid echo method and is associated with the existence of the temporary network.
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Chen, Jianfei, Jingyu Chu, Wenchun Jiang, Bin Yao, Fan Zhou, Zhenbo Wang i Pengcheng Zhao. "Experimental and Numerical Simulation to Study the Reduction of Welding Residual Stress by Ultrasonic Impact Treatment". Materials 13, nr 4 (12.02.2020): 837. http://dx.doi.org/10.3390/ma13040837.
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In this study, the effects of ultrasonic impact treatment (UIT) on the residual stress in a repair welding joint are investigated by experimental and finite element methods. A three-dimensional numerical analysis approach including a thermomechanical-coupled welding simulation and dynamic elastic-plastic UIT simulation is developed, which has been validated by X-ray diffraction measurement and indentation strain method. The results show that longitudinal residual stresses basically turned into the small tensile stress state from the large tensile stress state, and transverse residual stresses have mainly turned into compressive stresses from large tensile stress after the UIT. In the thickness direction, the average decrease of longitudinal residual stress is 259.9 MPa, which is larger than the 149.1 MPa of transverse residual stress. The calculated residual stress distribution after the UIT of the thin plate is compared with that of the thick plate in the literature, with the results showing the stress accumulation layer inside the thick plate. The simulation results show that the elastic strains are decreased slightly and the equivalent plastic strain is increased markedly after UIT, which explains the mechanism of residual stress relaxation.
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Haribabu, Viswanathan, Palani Sharmiladevi, Najim Akhtar, Abubacker Sulaiman Farook, Koyeli Girigoswami i Agnishwar Girigoswami. "Label Free Ultrasmall Fluoromagnetic Ferrite-clusters for Targeted Cancer Imaging and Drug Delivery". Current Drug Delivery 16, nr 3 (1.02.2019): 233–41. http://dx.doi.org/10.2174/1567201816666181119112410.
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Objective: The label free ultrasmall fluorescent ferrite clusters have been engineered in a controlled fashion which was stabilized by serum protein and functionalized by folic acid for the application of targeted multimodal optical and Magnetic Resonance (MR) cancer imaging. Methods: The ultra-small manganese ferrite nanoclusters (PMNCs) with a diameter of 4 nm have a commendable effect on the longitudinal (T1) and transverse (T2) relaxation in MR imaging that was evident from the phantom and animal MRI. Results: The calculated longitudinal molar relaxivity of nanoclusters was found to be 6.9 ± 0.10 mM-1 S-1 which was exactly 2.22 times better than the conventional Gd-DOTA and their 4.01 ratio of the transverse (r2) and longitudinal (r1) relaxivities made them a potential candidate for both T1 and T2 contrast agents in MRI. In addition, the fluorescence-based small animal imaging showed folic acid driven accumulated fluorescent signal at the tumour site to conclude the capacity of PMNCs for targeted fluorescence imaging of cancer diagnosis. Conclusion: The cytotoxicity assay and histopathology studies were the evidence for their safe biodistribution in animal systems. Furthermore, the protein encapsulated clusters have the ability to deliver the anticancer drug Methotrexate (MTX) to the cancer tissues with a sustained manner. Therefore, one can conclude the remarkable efficacy of architect nanoclusters for theragnosis.
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Uddin, Md Nasir, R. Marc Lebel, Peter Seres, Gregg Blevins i Alan H. Wilman. "Spin echo transverse relaxation and atrophy in multiple sclerosis deep gray matter: A two-year longitudinal study". Multiple Sclerosis Journal 22, nr 9 (19.07.2016): 1133–43. http://dx.doi.org/10.1177/1352458515614091.
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Background: Deep gray matter (DGM) is affected in relapsing–remitting multiple sclerosis (RRMS) and may be studied using short-term longitudinal MRI. Objective: To investigate two-year changes in spin-echo transverse relaxation rate (R2) and atrophy in DGM, and its relationship with disease severity in RRMS patients. Methods: Twenty six RRMS patients and 26 matched controls were imaged at 4.7 T. Multiecho spin-echo R2 maps and atrophy measurements were obtained in DGM at baseline and two-year follow-up. Differences between MRI measures and correlations to disease severity were examined. Results: After two years, mean R2 values in the globus pallidus and pulvinar increased by ~4% ( p<0.001) in patients and <1.7% in controls. Two-year changes in R2 showed significant correlation to disease severity in the globus pallidus, pulvinar, substantia nigra, and thalamus. Multiple regression of the two-year R2 difference using these four DGM structures as variables, yielded high correlation with disease severity ( r=0.83, p<0.001). Two-year changes in volume and R2 showed significant correlation only for the globus pallidus in multiple sclerosis (MS) ( p<0.05). Conclusions: Two-year difference R2 measurements in DGM correlate to disease severity in MS. R2 mapping and atrophy measurements over two years can be used to identify changes in DGM in MS.
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Zhang, Yapeng, Jingjing Cheng i Wenzhong Liu. "Characterization and Relaxation Properties of a Series of Monodispersed Magnetic Nanoparticles". Sensors 19, nr 15 (2.08.2019): 3396. http://dx.doi.org/10.3390/s19153396.
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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.
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Wernersson, Sven, Göran Carlström, Andreas Jakobsson i Mikael Akke. "Rapid measurement of heteronuclear transverse relaxation rates using non-uniformly sampled <i>R</i><sub>1<i>ρ</i></sub> accordion experiments". Magnetic Resonance 2, nr 2 (12.07.2021): 571–87. http://dx.doi.org/10.5194/mr-2-571-2021.
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Abstract. Multidimensional, heteronuclear NMR relaxation methods are used extensively to characterize the dynamics of biological macromolecules. Acquisition of relaxation datasets on proteins typically requires significant measurement time, often several days. Accordion spectroscopy offers a powerful means to shorten relaxation rate measurements by encoding the “relaxation dimension” into the indirect evolution period in multidimensional experiments. Time savings can also be achieved by non-uniform sampling (NUS) of multidimensional NMR data, which is used increasingly to improve spectral resolution or increase sensitivity per unit time. However, NUS is not commonly implemented in relaxation experiments, because most reconstruction algorithms are inherently nonlinear, leading to problems when estimating signal intensities, relaxation rate constants and their error bounds. We have previously shown how to avoid these shortcomings by combining accordion spectroscopy with NUS, followed by data reconstruction using sparse exponential mode analysis, thereby achieving a dramatic decrease in the total length of longitudinal relaxation experiments. Here, we present the corresponding transverse relaxation experiment, taking into account the special considerations required for its successful implementation in the framework of the accordion-NUS approach. We attain the highest possible precision in the relaxation rate constants by optimizing the NUS scheme with respect to the Cramér–Rao lower bound of the variance of the estimated parameter, given the total number of sampling points and the spectrum-specific signal characteristics. The resulting accordion-NUS R1ρ relaxation experiment achieves comparable precision in the parameter estimates compared to conventional CPMG (Carr–Purcell–Meiboom–Gill) R2 or spin-lock R1ρ experiments while saving an order of magnitude in experiment time.
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Zhang, Yu, Jianxiang Zhao, Ying Gu, Yu Zhang, Yi Chen, Ping Song i Tao Yang. "A Methodology Study on the Optimal Detection of Oil and Moisture Content in Soybeans Using LF-NMR and Its 2D T1-T2 Nuclear Magnetic Technology". Agronomy 13, nr 4 (12.04.2023): 1102. http://dx.doi.org/10.3390/agronomy13041102.
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In this study, we aimed to provide an accurate method for the detection of oil and moisture content in soybeans. Introducing two-dimensional low-field nuclear magnetic resonance (LF-2D-NMR) qualitatively solved the problem of overlapping component signals that one-dimensional (1D) LF-NMR techniques cannot distinguish in soybean detection research. Soxhlet extraction, oven drying, LF-NMR spectrum, and LF-NMR oil and moisture content software were used to detect soybean oil and moisture content. The comparison showed that the LF-NMR oil and moisture content software was faster and more accurate than the other methods. The specific identification of the oil and moisture signals of soybean seeds using longitudinal relaxation time (T1) and transverse relaxation time (T2) successfully solved the problems of less mobile water, overlapping free water, and oil signals. Therefore, LF-2D-NMR can complement conventional LF-NMR assays, and this study provides a new method for the analysis and detection of moisture and oil in soybeans.
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Faas, Henryk M., James L. Krupa, Alexander J. Taylor, Francesco Zamberlan, Christopher J. Philp, Huw E. L. Williams, Simon R. Johnson, Galina E. Pavlovskaya, Neil R. Thomas i Thomas Meersmann. "Accelerated 19F·MRI Detection of Matrix Metalloproteinase-2/-9 through Responsive Deactivation of Paramagnetic Relaxation Enhancement". Contrast Media & Molecular Imaging 2019 (28.02.2019): 1–13. http://dx.doi.org/10.1155/2019/4826520.
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Paramagnetic gadolinium ions (GdIII), complexed within DOTA-based chelates, have become useful tools to increase the magnetic resonance imaging (MRI) contrast in tissues of interest. Recently, “on/off” probes serving as 19F·MRI biosensors for target enzymes have emerged that utilize the increase in transverse (T2∗ or T2) relaxation times upon cleavage of the paramagnetic GdIII centre. Molecular 19F·MRI has the advantage of high specificity due to the lack of background signal but suffers from low signal intensity that leads to low spatial resolution and long recording times. In this work, an “on/off” probe concept is introduced that utilizes responsive deactivation of paramagnetic relaxation enhancement (PRE) to generate 19F longitudinal (T1) relaxation contrast for accelerated molecular MRI. The probe concept is applied to matrix metalloproteinases (MMPs), a class of enzymes linked with many inflammatory diseases and cancer that modify bioactive extracellular substrates. The presence of these biomarkers in extracellular space makes MMPs an accessible target for responsive PRE deactivation probes. Responsive PRE deactivation in a 19F biosensor probe, selective for MMP-2 and MMP-9, is shown to enable molecular MRI contrast at significantly reduced experimental times compared to previous methods. PRE deactivation was caused by MMP through cleavage of a protease substrate that served as a linker between the fluorine-containing moiety and a paramagnetic GdIII-bound DOTA complex. Ultrashort echo time (UTE) MRI and, alternatively, short echo times in standard gradient echo (GE) MRI were employed to cope with the fast 19F transverse relaxation of the PRE active probe in its “on-state.” Upon responsive PRE deactivation, the 19F·MRI signal from the “off-state” probe diminished, thereby indicating the presence of the target enzyme through the associated negative MRI contrast. Null point 1H·MRI, obtainable within a short time course, was employed to identify false-positive 19F·MRI responses caused by dilution of the contrast agent.
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McCreary, Cheryl R., Marina Salluzzi, Linda B. Andersen, David Gobbi, Louis Lauzon, Feryal Saad, Eric E. Smith i Richard Frayne. "Calgary Normative Study: design of a prospective longitudinal study to characterise potential quantitative MR biomarkers of neurodegeneration over the adult lifespan". BMJ Open 10, nr 8 (sierpień 2020): e038120. http://dx.doi.org/10.1136/bmjopen-2020-038120.
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IntroductionA number of MRI methods have been proposed to be useful, quantitative biomarkers of neurodegeneration in ageing. The Calgary Normative Study (CNS) is an ongoing single-centre, prospective, longitudinal study that seeks to develop, test and assess quantitative magnetic resonance (MR) methods as potential biomarkers of neurodegeneration. The CNS has three objectives: first and foremost, to evaluate and characterise the dependence of the selected quantitative neuroimaging biomarkers on age over the adult lifespan; second, to evaluate the precision, variability and repeatability of quantitative neuroimaging biomarkers as part of biomarker validation providing proof-of-concept and proof-of-principle; and third, provide a shared repository of normative data for comparison to various disease cohorts.Methods and analysisQuantitative MR mapping of the brain including longitudinal relaxation time (T1), transverse relaxation time (T2), T2*, magnetic susceptibility (QSM), diffusion and perfusion measurements, as well as morphological assessments are performed. The Montreal Cognitive Assessment (MoCA) and a brief, self-report medical history will be collected. Mixed regression models will be used to characterise changes in quantitative MR biomarker measures over the adult lifespan. In this report, we describe the study design, strategies to recruit and perform changes to the acquisition protocol from inception to 31 December 2018, planned statistical approach and data sharing procedures for the study.Ethics and disseminationParticipants provide signed informed consent. Changes in quantitative MR biomarkers measured over the adult lifespan as well as estimates of measurement variance and repeatability will be disseminated through peer-reviewed scientific publication.
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MOJOVIĆ, MILOŠ, MARKO DAKOVIĆ, MIA OMERAŠEVIĆ, ZORICA MOJOVIĆ, PREDRAG BANKOVIĆ, ALEKSANDRA MILUTINOVIĆ-NIKOLIĆ i DUŠAN JOVANOVIĆ. "THE PARAMAGNETIC PILLARED BENTONITES AS DIGESTIVE TRACT MRI CONTRAST AGENTS". International Journal of Modern Physics B 24, nr 06n07 (20.03.2010): 780–87. http://dx.doi.org/10.1142/s0217979210064411.
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The increased use of imaging techniques in diagnostic studies, such as MRI, has contributed to the development of the wide range of new materials which could be successfully used as image improving agents. However, there is a lack of such substances in the area of gastrointestinal tract MRI. Many of the traditionally popular relaxation altering agents show poor results and disadvantages provoking black bowel, side effects of diarrhea and the presence of artifacts arising from clumping. Paramagnetic species seem to be potentially suitable agents for these studies, but contrast opacification has been reported and less than 60% of the gastrointestinal tract magnetic resonance scans showed improved delineation of abdominal pathologies. The new solution has been proposed as zeolites or smectite clays (hectorite and montmorillonite) enclosing of paramagnetic metal ions obtained by ion-exchange methods. However, such materials have problems of leakage of paramagnetic ions causing the appearance of the various side-effects. In this study we show that Co +2 and Dy +3 paramagnetic-pillared bentonites could be successfully used as MRI digestive tract non-leaching contrast agents, altering the longitudinal and transverse relaxation times of fluids in contact with the clay minerals.
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Tarasek, Matthew, Oguz Akin, Jeannette Roberts, Thomas Foo i Desmond Yeo. "Heat Modulation of Intrinsic MR Contrasts for Tumor Characterization". Cancers 14, nr 2 (14.01.2022): 405. http://dx.doi.org/10.3390/cancers14020405.
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(1) Background: The longitudinal relaxation time (T1), transverse relaxation time (T2), water proton chemical shift (CS), and apparent diffusion coefficient (ADC) are MR quantities that change with temperature. In this work, we investigate heat-induced intrinsic MR contrast types to add salient information to conventional MR imaging to improve tumor characterization. (2) Methods: Imaging tests were performed in vivo using different rat tumor models. The rats were cooled/heated to steady-state temperatures from 26–36 °C and quantitative measurements of T1, T2, and ADC were obtained. Temperature maps were measured using the proton resonance frequency shift (PRFS) method during the heating and cooling cycles. (3) Results: All tissue samples show repeatable relaxation parameter measurement over a range of 26–36 °C. Most notably, we observed a more than 3.3% change in T1/°C in breast adenocarcinoma tumors compared to a 1% change in benign breast fibroadenoma lesions. In addition, we note distinct values of T2/°C change for rat prostate carcinoma cells compared to benign tissue. (4) Conclusion: These findings suggest the possibility of improving MR imaging visualization and characterization of tissue with heat-induced contrast types. Specifically, these results suggest that the temporal thermal responses of heat-sensitive MR imaging contrast mechanisms in different tissue types contain information for improved (i) characterization of tumor/tissue boundaries for diagnostic and therapy purposes, and (ii) characterization of salient behavior of tissues, e.g., malignant versus benign tumors.
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Bogorad, Z., P. Mohanmurthy i J. A. Formaggio. "Ultracold neutron storage simulation using the Kassiopeia software package". New Journal of Physics 24, nr 2 (1.02.2022): 023007. http://dx.doi.org/10.1088/1367-2630/ac4ad4.
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Abstract The Kassiopeia software package was originally developed to simulate electromagnetic fields and charged particle trajectories for neutrino mass measurement experiments. Recent additions to Kassiopeia also allow it to simulate neutral particle trajectories in magnetic fields based on their magnetic moments. Two different methods were implemented: an exact method that can work for arbitrary fields and an adiabatic method that is limited to slowly-varying fields but is much faster for large precession frequencies. Additional interactions to simulate reflection of ultracold neutrons (UCNs) from material walls and to allow spin–flip pulses were also added. These tools were used to simulate neutron precession in a room temperature neutron electric dipole moment experiment and predict the values of the longitudinal and transverse relaxation times as well as the trapping lifetime. All three parameters are found to closely match the experimentally determined values when simulated with both the exact and adiabatic methods, confirming that Kassiopeia is able to accurately simulate neutral particles. This opens the door for future uses of Kassiopeia to prototype the next generation of atomic traps and UCN experiments.
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Davydov, Roman, Vadim Davydov, Nikita Myazin i Valentin Dudkin. "The Multifunctional Nuclear Magnetic Flowmeter for Control to the Consumption and Condition of Coolant in Nuclear Reactors". Energies 15, nr 5 (26.02.2022): 1748. http://dx.doi.org/10.3390/en15051748.
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The necessity of coolant flow consumption measurement accuracy increase in the nuclear reactor primary circuit has been substantiated. Additionally, the need to control the coolant condition in the current flow inside the pipeline is shown. Nowadays, the real-time coolant’s condition control function is not implemented at stationary nuclear power plants or mobile nuclear power plants used in moving objects. It is shown that a coolant consumption measurement error decreases and its condition data availability increases the heat transfer efficiency and the electrical energy generation (without the nuclear reactor and steam generator design change). Problems arising during coolant consumption control using various flowmeters models in the nuclear reactor primary circuit are considered. It has been found that nuclear magnetic flowmeters can solve these problems. New difficulties are noted as emerging when using pulsed nuclear magnetic flowmeters designs developed for measuring hydrocarbons, water, biological compounds consumption, and condition control. A new nuclear magnetic flowmeter design has been developed using a modulation technique for nuclear magnetic resonance signal recording. Methods for measuring the coolant flow’s longitudinal T1 and transverse T2 relaxation times are presented. Investigations of coolant flow parameters (consumption and relaxation times) inside the pipeline have been carried out. It is found that the measurement error for these parameters does not exceed 1%. The prospects of using the developed nuclear magnetic flowmeter-relaxometer design in the nuclear reactor first circuit are shown.
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Eckerbom, Per, Peter Hansell, Eleanor Cox, Charlotte Buchanan, Jan Weis, Fredrik Palm, Susan Francis i Per Liss. "Multiparametric assessment of renal physiology in healthy volunteers using noninvasive magnetic resonance imaging". American Journal of Physiology-Renal Physiology 316, nr 4 (1.04.2019): F693—F702. http://dx.doi.org/10.1152/ajprenal.00486.2018.
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Noninvasive methods of magnetic resonance imaging (MRI) can quantify parameters of kidney function. The main purpose of this study was to determine baseline values of such parameters in healthy volunteers. In 28 healthy volunteers (15 women and 13 men), arterial spin labeling to estimate regional renal perfusion, blood oxygen level-dependent transverse relaxation rate (R2*) to estimate oxygenation, and apparent diffusion coefficient (ADC), true diffusion (D), and longitudinal relaxation time (T1) to estimate tissue properties were determined bilaterally in the cortex and outer and inner medulla. Additionally, phase-contrast MRI was applied in the renal arteries to quantify total renal blood flow. The results demonstrated profound gradients of perfusion, ADC, and D with highest values in the kidney cortex and a decrease towards the inner medulla. R2* and T1 were lowest in kidney cortex and increased towards the inner medulla. Total renal blood flow correlated with body surface area, body mass index, and renal volume. Similar patterns in all investigated parameters were observed in women and men. In conclusion, noninvasive MRI provides useful tools to evaluate intrarenal differences in blood flow, perfusion, diffusion, oxygenation, and structural properties of the kidney tissue. As such, this experimental approach has the potential to advance our present understanding regarding normal physiology and the pathological processes associated with acute and chronic kidney disease.
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Myazin, Nikita Sergeevich, Vadim Vladimirovich Davydov, Victoria Valerevna Yushkova i Vasiliy Yurevich Rud'. "A new method of determining the state of water and agricultural areas in real time". Environmental Research, Engineering and Management 75, nr 2 (3.09.2019): 28–35. http://dx.doi.org/10.5755/j01.erem.75.2.22352.
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Paper discusses the technique of environmental condition monitoring based on the phenomenon of nuclear magnetic resonance (NMR). Express control is an integral part of agriculture, because when working on farms or in fields there are situations when it is physically impossible to deliver samples for research to a stationary laboratory (results are needed urgently or samples can change their properties during transportation). A brief review of the existing methods for monitoring the states of media in the express mode was carried out, their shortcomings were revealed and a new technical solution to this problem was proposed. For a small-sized NMR spectrometer, a new magnetic system and a signal registration circuit have been developed, which makes it possible to detect the NMR signal at different frequencies, thus registering the signal spectrum. In addition, this design also allows measuring the longitudinal and transverse relaxation times of the medium. With the help of the proposed technique, studies of various media have been carried out; the results of these studies are presented.
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Nagmutdinova, Anastasiia, Leonardo Brizi, Paola Fantazzini i Villiam Bortolotti. "Investigation of the First Sorption Cycle of White Portland Cement by 1H NMR". Applied Magnetic Resonance 52, nr 12 (23.10.2021): 1767–85. http://dx.doi.org/10.1007/s00723-021-01436-w.
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AbstractThis work is focused on the effects of drying/re-saturation cycles on the structure and components of White Portland Cement (WPC) samples. In particular, WPC of 0.5 water-to-cement ratio was studied by 1H Nuclear Magnetic Resonance (NMR) Relaxometry. A number of NMR sequences and different data processing methods were applied. Short (14 days of re-saturation) and long (6 months for the whole cycle) sorption cycles were investigated, using two drying methods: oven drying and drying under controlled relative humidity. The evolution during drying/re-saturation processes of interlayer space, gel pores, and bigger pores was followed by both the transverse relaxation times and the intensities of the nuclear magnetization. As a result of drying, reversible and irreversible changes in the pore structure, especially concerning the smaller porosity (interlayer and gel pores), were seen. Likewise, 1H signals in the crystalline phases of the cement were investigated by the standard Quadrature Echo method and by a more informative analysis based and a proper acquisition and processing of the longitudinal relaxation data. This analysis allowed the signal separation of 1H nuclei with higher and lower mobility (“solid” components). The NMR signal from this last component was analyzed on the basis of the Pake-Doublet theory in the time domain and two components were clearly detected, and assigned to 1H nuclei of crystalline water in Ettringite and OH groups in Portlandite. Reversible changes of the solid components of the cement samples were observed. This is a new method to deeply investigate the changes of solid components during sorption cycles.
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Laporte, John P., Mary E. Faulkner, Zhaoyuan Gong, Mohammad A. B. S. Akhonda, Luigi Ferrucci, Josephine M. Egan i Mustapha Bouhrara. "Hypertensive Adults Exhibit Lower Myelin Content: A Multicomponent Relaxometry and Diffusion Magnetic Resonance Imaging Study". Hypertension 80, nr 8 (sierpień 2023): 1728–38. http://dx.doi.org/10.1161/hypertensionaha.123.21012.
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BACKGROUND: It is unknown whether hypertension plays any role in cerebral myelination. To fill this knowledge gap, we studied 90 cognitively unimpaired adults, age range 40 to 94 years, who are participants in the Baltimore Longitudinal Study of Aging and the Genetic and Epigenetic Signatures of Translational Aging Laboratory Testing to look for potential associations between hypertension and cerebral myelin content across 14 white matter brain regions. METHODS: Myelin content was probed using our advanced multicomponent magnetic resonance relaxometry method of myelin water fraction, a direct and specific magnetic resonance imaging measure of myelin content, and longitudinal and transverse relaxation rates ( R 1 and R 2 ), 2 highly sensitive magnetic resonance imaging metrics of myelin content. We also applied diffusion tensor imaging magnetic resonance imaging to measure fractional anisotropy, mean diffusivity, radial diffusivity, and axial diffusivity values, which are metrics of cerebral microstructural tissue integrity, to provide context with previous magnetic resonance imaging findings. RESULTS: After adjustment of age, sex, systolic blood pressure, smoking status, diabetes status, and cholesterol level, our results indicated that participants with hypertension exhibited lower myelin water fraction, fractional anisotropy, R 1 and R 2 values and higher mean diffusivity, radial diffusivity, and axial diffusivity values, indicating lower myelin content and higher impairment to the brain microstructure. These associations were significant across several white matter regions, particularly in the corpus callosum, fronto-occipital fasciculus, temporal lobes, internal capsules, and corona radiata. CONCLUSIONS: These original findings suggest a direct association between myelin content and hypertension and form the basis for further investigations including longitudinal assessments of this relationship.
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Saidian, Milad, Torben Rasmussen, Mosab Nasser, Andres Mantilla i Rick Tobin. "Qualitative and quantitative reservoir bitumen characterization: A core to log correlation methodology". Interpretation 3, nr 1 (1.02.2015): SA143—SA158. http://dx.doi.org/10.1190/int-2014-0052.1.
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Reservoir bitumen is a highly viscous, asphaltene-rich hydrocarbon that can have important effects on reservoir performance. Discriminating between producible oil and reservoir bitumen is critical for recoverable hydrocarbon volume calculations and production planning, yet the lack of resistivity contrast between the two makes it difficult, if not impossible, to make such differentiation using conventional logs. However, the nuclear magnetic resonance (NMR) response in bitumen-rich zones is dominated by short transverse relaxation times ([Formula: see text]) and a low apparent fluid hydrogen index ([Formula: see text]), providing an opportunity to identify the presence of reservoir bitumen. Therefore, NMR logging technology becomes crucial in the characterization of reservoirs in which the presence of bitumen may be of concern. We used NMR and other log data to identify and quantify the occurrence of reservoir bitumen in a carbonate reservoir. A thorough petrophysical evaluation was performed using a full suite of logs, formation pressure measurements, and laboratory core analysis data. We discuss several quick methods to identify intervals with a higher chance of reservoir bitumen presence. The short transverse relaxation times ([Formula: see text]) and consequently lower [Formula: see text] logarithmic mean time values are characteristics of bitumen-rich zones. Another characteristic is low [Formula: see text] in these zones and consequently lower NMR porosity estimates when compared to porosity estimates from the density and neutron tools. We analyzed 2D longitudinal-transverse relaxation time ([Formula: see text]) maps for core samples at different depths to confirm the presence of reservoir bitumen in some wells using laboratory low-field NMR data. We observed a high [Formula: see text] ratio at various depths, which is an indication of high-molecular-weight hydrocarbons. The presence of bitumen at the same depths was confirmed by thin section analysis, and it is the likely cause for failed formation pressure testing attempts at those depth intervals. Partial cleaning of reservoir bitumen-rich core plugs results in helium-injection porosity estimates that are too low, and they are closer to the NMR porosity than to density porosity, the latter being more consistent with actual values. In addition, the grain density (GD) calculated by He injection is significantly lower than the GD estimated from elemental capture spectroscopy and X-ray diffraction techniques. Disregarding these effects complicates the core to log correlation, which is common practice for porosity calculations using the density log. A volumetric rock model was used to reconcile core and log data as well as to calculate the saturation of reservoir bitumen. The methodologies for reservoir bitumen characterization introduced here can be applied successfully in different reservoirs for more reliable and precise reservoir evaluation and production planning.
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Lee, Chena, Yoon Joo Choi, Kug Jin Jeon i Sang-Sun Han. "Synthetic magnetic resonance imaging for quantitative parameter evaluation of temporomandibular joint disorders". Dentomaxillofacial Radiology 50, nr 5 (1.07.2021): 20200584. http://dx.doi.org/10.1259/dmfr.20200584.
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Objective: This study investigated the usefulness of quantitative parameters [longitudinal relaxation (T1), transverse relaxation (T2), and proton density (PD)] obtained with synthetic magnetic resonance imaging (MRI) in assessing the progression of temporomandibular joint (TMJ) disorders. Methods: For individual TMJ disorder diagnoses, the presence of disc displacement in MRI and the osseous change in cone-beam CT were investigated. Joints were classified into three stages: (1) silent stage, no disc displacement or osseous change; (2) incipient stage, presence of disc displacement and absence of osseous change; and (3) progressed stage, both disc displacement and osseous change. In synthetic MRI, the T1, T2, and PD values of the condyle bone marrow were measured simultaneously. The median T1, T2, and PD values were analyzed according to disc displacement, osseous changes, and joint stage. Results: Significant differences were observed in the T1 and PD values of joints with disc displacement or condylar osseous change compared to normal joints. The T1 and PD values also differed between the silent and progressed stages. The PD value differed between the silent and incipient groups, while the T2 value did not differ significantly among the three groups. Conclusion: The PD and T1 values of condylar bone marrow obtained from synthetic MRI can be used as sensitive indicators of TMJ disorder progression. The PD value of the bone marrow showed potential as a useful biomarker for recognizing the initial stages of TMJ disorders. Synthetic MRI is useful for the simultaneous acquisition of effective MRI parameters for evaluating TMJ disorders.
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Reuter, Gilles, Emilie Lommers, Evelyne Balteau, Jessica Simon, Christophe Phillips, Felix Scholtes, Didier Martin, Arnaud Lombard i Pierre Maquet. "Multiparameter quantitative histological MRI values in high-grade gliomas: a potential biomarker of tumor progression". Neuro-Oncology Practice 7, nr 6 (15.08.2020): 646–55. http://dx.doi.org/10.1093/nop/npaa047.
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Abstract Background Conventional MRI poorly distinguishes brain parenchyma microscopically invaded by high-grade gliomas (HGGs) from the normal brain. By contrast, quantitative histological MRI (hMRI) measures brain microstructure in terms of physical MR parameters influenced by histochemical tissue composition. We aimed to determine the relationship between hMRI parameters in the area surrounding the surgical cavity and the presence of HGG recurrence. Methods Patients were scanned after surgery with an hMRI multiparameter protocol that allowed for estimations of longitudinal relaxation rate (R1) = 1/T1, effective transverse relaxation rate (R2)*=1/T2*, magnetization transfer saturation (MTsat), and proton density. The initial perioperative zone (IPZ) was segmented on the postoperative MRI. Once recurrence appeared on conventional MRI, the area of relapsing disease was delineated (extension zone, EZ). Conventional MRI showing recurrence and hMRI were coregistered, allowing for the extraction of parameters R1, R2*, MTsat, and PD in 3 areas: the overlap area between the IPZ and EZ (OZ), the peritumoral brain zone, PBZ (PBZ = IPZ – OZ), and the area of recurrence (RZ = EZ – OZ). Results Thirty-one patients with HGG who underwent gross-total resection were enrolled. MTsat and R1 were the most strongly associated with tumor progression. MTsat was significantly lower in the OZ and RZ, compared to PBZ. R1 was significantly lower in RZ compared to PBZ. PD was significantly higher in OZ compared to PBZ, and R2* was higher in OZ compared to PBZ or RZ. These changes were detected 4 to 120 weeks before recurrence recognition on conventional MRI. Conclusions HGG recurrence was associated with hMRI parameters’ variation after initial surgery, weeks to months before overt recurrence.
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Fang, Xiujie, Jin Li, Yanning Ma, Kai Wei, Wenfeng Fan, Yueyang Zhai, Wei Quan i Zhisong Xiao. "A Novel Measurement Method for Spin Polarization Three Axis Spatial Distribution in Spin-Exchange Relaxation Free Atomic Magnetometer". Photonics 10, nr 3 (20.03.2023): 332. http://dx.doi.org/10.3390/photonics10030332.
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The measurement of atomic spin polarization distribution in spin-exchange relaxation free (SERF) magnetometer is an important topic for improving the sensitivity and consistency of multi-channel magnetic field measurement applications. A novel spin polarization spatial distribution measurement method is presented based on the transient response of the magnetometer after modulating the pumped light with a chopper. Polarization is obtained by a slow-down factor based on the fast spin-exchange interaction effects. Longitudinal and transverse polarization distributions are measured simultaneously without interrupting the operation of the SERF status. Under different oscillating magnetic fields, the spin polarization is measured at the cell centroid. Residual magnetic field inside the magnetometer is obtained from the linear relationship between the precession frequency and the oscillating magnetic field. The one-dimensional polarization distributions in the x, y, and z axes are measured using a digital micromirror device with a resolution of 0.25 cm. The measurement results conform to the Lambert-Bier absorption law and the Gaussian distribution law. Furthermore, 7 × 7 two-dimensional spatial distribution measurements of polarization on the xy and yz planes are performed. Nonuniformity of 1.04 in the xy plane and 1.82 in the yz plane in the built magnetometer. Compared with other measurement methods, the distribution measurement method proposed is independent of optical depth and suitable for low polarization and high polarization applications. Based on the results of the proposed measurement method of spin polarization spatial distribution, further compensation can improve the application consistency of multi-channel magnetic field measurements and improve the sensitivity of single-channel differential measurements.
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Senesac, Claudia R., Donovan J. Lott, Sean C. Forbes, Sunita Mathur, Ishu Arpan, Emily S. Senesac, Glenn A. Walter i Krista Vandenborne. "Longitudinal Evaluation of Muscle Composition Using Magnetic Resonance in 4 Boys With Duchenne Muscular Dystrophy: Case Series". Physical Therapy 95, nr 7 (1.07.2015): 978–88. http://dx.doi.org/10.2522/ptj.20140234.
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Background Duchenne muscular dystrophy (DMD), an inherited recessive X chromosome-linked disease, is the most severe childhood form of muscular dystrophy. Boys with DMD experience muscle loss, with infiltration of intramuscular fat into muscles. Objectives This case series describes the progression of DMD in boys using magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS). Magnetic resonance results are then compared with an established functional timed test. Methods Four boys with DMD and 4 healthy age-matched controls were chosen from a larger cohort. Boys with DMD were assessed at 4 time points over 2 years, with controls assessed at baseline only. Progression of the disease was documented by assessing the plantar flexors using MRI and MRS techniques and by assessing ambulation using the 30-Foot Fast Walk Test. Results Transverse relaxation time (T2) values were elevated in all boys with DMD at baseline. The lipid ratio increased rapidly as the disease progressed in 2 boys. Discrete changes in T2 in the other 2 boys with DMD indicated a slower disease progression. Magnetic resonance imaging and MRS allowed monitoring of the disease over all time periods regardless of ambulation status. Limitations The magnetic resonance data were collected with 2 different magnets at 2 different field strengths (1.5 and 3.0 T). Although we corrected for this difference, care must be taken in interpreting data when different image collection systems are used. This was a case series of 4 boys with DMD taken from a larger cohort study. Conclusions Magnetic resonance imaging and MRS are objective, noninvasive techniques for measuring muscle pathology and can be used to detect discrete changes in both people who are ambulatory and those who are nonambulatory. These techniques should be considered when monitoring DMD progression and assessing efficacy of therapeutic interventions.
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Müller-Petke, Mike, Jan O. Walbrecker i Rosemary Knight. "The inversion of surface-NMR T1 data for improved aquifer characterization". GEOPHYSICS 78, nr 6 (1.11.2013): EN83—EN94. http://dx.doi.org/10.1190/geo2013-0035.1.
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A crucial component in sustainable freshwater management is the reliable and cost-effective characterization of groundwater aquifers. A technique that allows noninvasive characterization of shallow ([Formula: see text]) aquifers is surface nuclear magnetic resonance (surface NMR). The measured parameter longitudinal relaxation time [Formula: see text] provides a link to pore-scale properties and can be used to estimate the hydraulic conductivity of the sampled region. The recent development of an optimized acquisition scheme, phase-cycled pseudosaturation recovery (pcPSR), has significantly advanced our ability to acquire surface-NMR [Formula: see text] data. Building on these findings, we developed an inversion scheme that can reconstruct the depth-distribution of [Formula: see text] from pcPSR data. To stabilize the inversion, we took a staggered approach: We first determined the distribution of water content and effective transverse relaxation time [Formula: see text], and then we resolved the [Formula: see text] structure. We tested the capability of the inversion in a synthetic study using models containing an unconfined and confined aquifer under conditions of low and high levels of ambient electromagnetic noise. The results allowed us to optimize the design of pcPSR experiments, finding that acquiring pcPSR data at three interpulse delay times is the best choice when acquiring surface-NMR data in an area with no prior information. We have verified our inversion approach in a field study in Nebraska, USA, where we had access to borehole lithologic information and logging-NMR [Formula: see text] measurements. Although the structural details ([Formula: see text]) detected in logging NMR were not resolved in surface NMR — highlighting the general resolution limitation of surface NMR — the two methods consistently revealed a zone of elevated [Formula: see text] corresponding to a sand and gravel unit, overlying a zone of lower [Formula: see text] corresponding to a sand/sandstone unit. Our developed inversion scheme is an important step toward the reliable interpretation of surface-NMR [Formula: see text] data for aquifer characterization.
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Willcocks, Rebecca J., Alison M. Barnard, Ryan J. Wortman, Claudia R. Senesac, Donovan J. Lott, Ann T. Harrington, Kirsten L. Zilke i in. "Development of Contractures in DMD in Relation to MRI-Determined Muscle Quality and Ambulatory Function". Journal of Neuromuscular Diseases 9, nr 2 (1.03.2022): 289–302. http://dx.doi.org/10.3233/jnd-210731.
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Background: Joint contractures are common in boys and men with Duchenne muscular dystrophy (DMD), and management of contractures is an important part of care. The optimal methods to prevent and treat contractures are controversial, and the natural history of contracture development is understudied in glucocorticoid treated individuals at joints beyond the ankle. Objective: To describe the development of contractures over time in a large cohort of individuals with DMD in relation to ambulatory ability, functional performance, and muscle quality measured using magnetic resonance imaging (MRI) and spectroscopy (MRS). Methods: In this longitudinal study, range of motion (ROM) was measured annually at the hip, knee, and ankle, and at the elbow, forearm, and wrist at a subset of visits. Ambulatory function (10 meter walk/run and 6 minute walk test) and MR-determined muscle quality (transverse relaxation time (T2) and fat fraction) were measured at each visit. Results: In 178 boys with DMD, contracture prevalence and severity increased with age. Among ambulatory participants, more severe contractures (defined as greater loss of ROM) were significantly associated with worse ambulatory function, and across all participants, more severe contractures significantly associated with higher MRI T2 or MRS FF (ρ: 0.40–0.61 in the lower extremity; 0.20–0.47 in the upper extremity). Agonist/antagonist differences in MRI T2 were not strong predictors of ROM. Conclusions: Contracture severity increases with disease progression (increasing age and muscle involvement and decreasing functional ability), but is only moderately predicted by muscle fatty infiltration and MRI T2, suggesting that other changes in the muscle, tendon, or joint contribute meaningfully to contracture formation in DMD.
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Nikolova, Simona, Catherine Daniela Chong, Gina M. Dumkrieger, Jing Li, Teresa Wu i Todd J. Schwedt. "Longitudinal differences in iron deposition in periaqueductal gray matter and anterior cingulate cortex are associated with response to erenumab in migraine". Cephalalgia 43, nr 2 (luty 2023): 033310242211447. http://dx.doi.org/10.1177/03331024221144783.
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Objectives The objective of this longitudinal study was to determine whether brain iron accumulation, measured using magnetic resonance imaging magnetic transverse relaxation rates (T2*), is associated with response to erenumab for the treatment of migraine. Methods Participants (n = 28) with migraine, diagnosed using international classification of headache disorders 3rd edition criteria, were eligible if they had six to 25 migraine days during a four-week headache diary run-in phase. Participants received two treatments with 140 mg erenumab, one immediately following the pre-treatment run-in phase and a second treatment four weeks later. T2* data were collected immediately following the pre-treatment phase, and at two weeks and eight weeks following the first erenumab treatment. Patients were classified as erenumab responders if their migraine-day frequency at five-to-eight weeks post-initial treatment was reduced by at least 50% compared to the pre-treatment run-in phase. A longitudinal Sandwich estimator approach was used to compare longitudinal group differences (responders vs non-responders) in T2* values, associated with iron accumulation. Group visit effects were calculated with a significance threshold of p = 0.005 and cluster forming threshold of 250 voxels. T2* values of 19 healthy controls were used for a reference. The average of each significant region was compared between groups and visits with Bonferroni corrections for multiple comparisons with significance defined as p < 0.05. Results Pre- and post-treatment longitudinal imaging data were available from 28 participants with migraine for a total of 79 quantitative T2* images. Average subject age was 42 ± 13 years (25 female, three male). Of the 28 subjects studied, 53.6% were erenumab responders. Comparing longitudinal T2* between erenumab responders vs non-responders yielded two comparisons which survived the significance threshold of p < 0.05 after correction for multiple comparisons: the difference at eight weeks between the erenumab-responders and non-responders in the periaqueductal gray (mean ± standard error; responders 43 ± 1 ms vs non-responders 32.5 ± 1 ms, p = 0.002) and the anterior cingulate cortex (mean ± standard error; responders 50 ± 1 ms vs non-responders 40 ± 1 ms, p = 0.01). Conclusions Erenumab response is associated with higher T2* in the periaqueductal gray and anterior cingulate cortex, regions that participate in pain processing and modulation. T2* differences between erenumab responders vs non-responders, a measure of brain iron accumulation, are seen at eight weeks post-treatment. Less iron accumulation in the periaqueductal gray and anterior cingulate cortex might play a role in the therapeutic mechanisms of migraine reduction associated with erenumab.
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Davydov, Roman, Vadim Davydov i Valentin Dudkin. "The Nuclear Magnetic Flowmeter for Monitoring the Consumption and Composition of Oil and Its Complex Mixtures in Real-Time". Energies 15, nr 9 (29.04.2022): 3259. http://dx.doi.org/10.3390/en15093259.
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The necessity of increasing the efficiency of primary oil purification in a drilling station or an offshore platform has been substantiated. We consider the problems that arise during the primary processing of oil mixtures. Important conditions for increasing the efficiency of primary purification (separation) of oil mixtures include measuring the consumption and determining the content of various impurities (water, undissolved particles) and air in them, with an error of no more than 2%. We analyzed the possibilities of using various designs of flowmeters to measure the consumption of the oil mixture coming from a well. It is also necessary to use other measuring instruments to control the state of this mixture, which creates additional problems (searching for an appropriate locations to place them, providing the required operating conditions). Various designs of nuclear magnetic flowmeters–relaxometers were considered, making it possible to measure the consumption of a liquid medium and its times of longitudinal T1 and transverse T2 relaxation with one device. The measured values of T1 and T2 determine the state of the medium. The design of the industrial nuclear magnetic flowmeter–relaxometer M-Phase 5000, which is used to control the flow and quality of oil and oil products, was considered in more detail. Problems were identified that did not allow using this design of a nuclear magnetic flowmeter–relaxometer in a drilling rig or offshore platform. A new design of a nuclear magnetic flowmeter–relaxometer was developed, implementing the methods for measuring q, T1, and T2. These methods and various technical solutions make it possible to use this device at a drilling station or offshore platform. The measurement errors of the consumption q, T1, and T2 were determined. The results of various media studies are presented and compared with q, T1, and T2 measurements on other devices and measured volume (to confirm the adequacy of q measurements). The application scopes of the developed nuclear magnetic flowmeter–relaxometer were determined, in addition to the systems of primary oil processing.
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Hu, Kaifeng, Beat Vögeli i G. Marius Clore. "Interference between transverse cross-correlated relaxation and longitudinal relaxation affects apparent J-coupling and transverse cross-correlated relaxation". Chemical Physics Letters 423, nr 1-3 (maj 2006): 123–25. http://dx.doi.org/10.1016/j.cplett.2006.03.051.
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Malliavin, T. E., H. Desvaux i M. A. Delsuc. "Quantitative determination of longitudinal and transverse cross-relaxation rates". Journal de Chimie Physique et de Physico-Chimie Biologique 96, nr 9/10 (październik 1999): 1608–15. http://dx.doi.org/10.1051/jcp:1999238.
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ARDARAVICIUS, L., J. LIBERIS, A. MATULIONIS i M. RAMONAS. "ESTIMATION OF ELECTRON ENERGY RELAXATION TIME IN 2DEG CHANNELS FROM TRANSVERSE AND LONGITUDINAL NOISE". Fluctuation and Noise Letters 02, nr 01 (marzec 2002): L53—L63. http://dx.doi.org/10.1142/s0219477502000592.
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Microwave noise is investigated in heterostructures subjected to an electric field applied parallel to the interfaces. The longitudinal and transverse noise temperatures are measured and simulated in the plane of electron confinement in the directions perpendicular and parallel to the electric field. Monte Carlo simulation is performed for a subcritically doped InAlAs/InGaAs/InAlAs heterostructure containing a two-dimensional electron gas in a single channel. The simulated longitudinal noise temperature is found to be nearly the same as the transverse one in the field range where the interwell transfer of hot electrons is not important. The longitudinal noise temperature exceeds the transverse one considerably in a supercritically doped InAlAs/InGaAs/InAlAs/InP heterostructure containing three separate quantum-well channels, each accommodating a two-dimensional electron gas at equilibrium. The observed strong planar anisotropy is ascribed to the channel occupancy fluctuations caused by the interwell transfer of equilibrium electrons. A possibility to estimate energy relaxation time from the transverse and the longitudinal microwave noise measurements is discussed.
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Weaver, Daniel S., i Erik R. P. Zuiderweg. "ηz∕κ: A transverse relaxation optimized spectroscopy NMR experiment measuring longitudinal relaxation interference". Journal of Chemical Physics 128, nr 15 (21.04.2008): 155103. http://dx.doi.org/10.1063/1.2889923.
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Wood, John C., Michelle I. Aguilar, Maya Otto-Duessel, Hanspeter Nick, Marvin D. Nelson i Rex Moats. "Influence of Iron Chelation Therapy on R1 and R2 Calibration Curves in Gerbil Liver and Heart." Blood 108, nr 11 (16.11.2006): 1775. http://dx.doi.org/10.1182/blood.v108.11.1775.1775.
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Abstract Introduction: MRI is gaining increasing importance for the noninvasive quantification of organ iron burden. To date, MRI validation studies have not systematically examined the effects of different iron chelators. Since transverse relaxation rates depend on iron distribution as well as iron concentration, physiologic and pharmacologic processes that alter iron distribution could change MRI calibration curves. This paper compares the effect of three iron chelators, deferoxamine, deferiprone, and deferasirox on R1 and R2 calibration curves according to two loading and chelation strategies. Methods: 33 Mongolian gerbils underwent iron dextran 500 mg/kg/wk for 4 weeks followed by 4 weeks of chelation therapy using deferoxamine, deferiprone and defersirox. An additional 32 animals received less aggressive iron loading (200 mg/kg/week) for 10 weeks, followed by 12 weeks of chelation therapy. R1 and R2 measurements were obtained immediately post euthanasia using an NMR relaxometer. Calibration curves from 28 unchelated animals loaded with 200 mg/kg/week from 2 to 48 weeks were used as the reference standard for both chelated groups, using Bland-Altman analysis. Results: In the liver, R2-iron calibration became more variable over time regardless of whether chelation was performed or not (mean COV 28% versus 12%); no significant changes were observed in the heart R2-iron relationship. Variability in R1 measurements did not change for either heart or liver. Two systematic chelator-specific changes in liver iron calibration curves were noted:deferiprone treated animals exhibited signficantly higher R1 values (Figure 1) anddeferasirox treated animals demonstrated lower R2 values for given iron concentration (Figure 2). Both changes were associated with obvious changes in water content or iron distribution. Discussion: The acuity of the iron loading process affects the variability but not the bias of MRI-iron calibration curves. In contrast, iron chelation can produce systematic shifts in MRI calibration curves compared with the unchelated state, reflecting gross changes in tissue hydration and iron distribution. Since the rate of iron-loading and extraction performed in animals is more extreme than occurs in humans, limiting tissue requilibration, it is possible that the present studies overestimate the potential for chelator-specific calibration bias. Nonetheless, caution should be used in extrapolating calibration curves derived from patients using deferoxamine therapy to others being treated with deferiprone and deferasirox. Careful, longitudinal assessment of MRI calibration curves of patients receiving oral chelation therapies is warranted. Figure Figure Figure Figure
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Xu, Hong Yu, B. B. Xue, F. K. Cui i X. Q. Wang. "Reflection and Refraction of Coupled Transverse and Micro-Rotational Wave at Interface between Two Micropolar Elastic Solid". Advanced Materials Research 670 (marzec 2013): 193–201. http://dx.doi.org/10.4028/www.scientific.net/amr.670.193.
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Using the model of micropolar generalized magneto-thermo-elasticity, the coupled transverse and micro-rotational wave at an interface between two micropolar solid mediums is discussed in the presence of a constant magnetic field. The model can be applied to the coupled theory as well as to five generalizations: the Lord-Shulman theory with one relaxation time, the Green-Lindsay theory with two relaxation times, the Green-Naghdi theories of type II(without energy dissipation) and of type III, and the theory with dual-phase-lag. Using continuous conditions at the interface, the amplitude ratios of reflected and refracted longitudinal displacement waves, longitudinal micro-rotational waves and the coupled transverse and micro-rotational waves are studied for incident coupled transverse and micro-rotational wave. The effect of thermal relaxation is discussed for C-D theory, G-L theory and L-S theory. The numerical results show that the effects of thermal relaxation times are very significant on the amplitude ratios.
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Jiang, Yanfen, Valmik Bhargava i Ravinder K. Mittal. "Mechanism of stretch-activated excitatory and inhibitory responses in the lower esophageal sphincter". American Journal of Physiology-Gastrointestinal and Liver Physiology 297, nr 2 (sierpień 2009): G397—G405. http://dx.doi.org/10.1152/ajpgi.00108.2009.
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We recently found that an orally directed stretch of the esophagus activates a neurally mediated relaxation of the lower esophageal sphincter (LES). Goals of our study were to characterize the neural mechanisms responsible for axial and transverse stretch-activated responses in the LES. LES pressure was monitored in anesthetized and artificially ventilated mice. Sutures were placed in the esophagus to exert graded stretch in the longitudinal and transverse directions. Effects of bilateral vagotomy and pharmacological agents on the stretch-activated LES responses were investigated. The relationship between vagally stimulated axial stretch and LES relaxation was also studied. Stretch in the longitudinal and transverse directions caused a dose-dependent LES relaxation and contraction, respectively, that were not affected by bilateral vagotomy and sympathectomy but were blocked by tetrodotoxin. In bilateral vagotomized animals, hexamethonium, atropine, pyridoxalphosphate-6-azophenyl-2′,4′ disulfonic acid (PPADS), and ondansetron did not block the stretch-activated LES relaxation and contraction. Axial stretch-activated LES relaxation was blocked by nitric oxide inhibitor and transverse stretch-activated LES contraction was blocked by a combination of atropine and substance P antagonist. Electrical stimulation of the vagus nerve induced LES relaxation and axial stretch on the LES, both of which were blocked by rocuronium. Axial and transverse stretch-activated LES relaxation and contraction were present in the W/Wv mice that lack interstitial cells of Cajal (ICC). Stretch-activated LES relaxation and contraction are mediated through mechanosensitive neurons located in the myenteric plexus, which involves neither synaptic transmission nor ICC.
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Leeb, Sarah, Fan Yang, Mikael Oliveberg i Jens Danielsson. "Connecting Longitudinal and Transverse Relaxation Rates in Live-Cell NMR". Journal of Physical Chemistry B 124, nr 47 (12.11.2020): 10698–707. http://dx.doi.org/10.1021/acs.jpcb.0c08274.
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Brandt, E. H., i G. P. Mikitik. "Transverse and longitudinal vortex shaking and magnetic relaxation in superconductors". Physica C: Superconductivity 404, nr 1-4 (maj 2004): 69–73. http://dx.doi.org/10.1016/j.physc.2003.09.110.
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Hafner, A., W. von Philipsborn i A. Schwenk. "Mechanisms for the longitudinal and transverse relaxation of iron-57". Journal of Magnetic Resonance (1969) 74, nr 3 (październik 1987): 433–49. http://dx.doi.org/10.1016/0022-2364(87)90266-6.
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Foster, Richard J., Robin A. Damion, Thomas G. Baboolal, Stephen W. Smye i Michael E. Ries. "A nuclear magnetic resonance study of water in aggrecan solutions". Royal Society Open Science 3, nr 3 (marzec 2016): 150705. http://dx.doi.org/10.1098/rsos.150705.
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Aggrecan, a highly charged macromolecule found in articular cartilage, was investigated in aqueous salt solutions with proton nuclear magnetic resonance. The longitudinal and transverse relaxation rates were determined at two different field strengths, 9.4 T and 0.5 T, for a range of temperatures and aggrecan concentrations. The diffusion coefficients of the water molecules were also measured as a function of temperature and aggrecan concentration, using a pulsed field gradient technique at 9.4 T. Assuming an Arrhenius relationship, the activation energies for the various relaxation processes and the translational motion of the water molecules were determined from temperature dependencies as a function of aggrecan concentration in the range 0–5.3% w/w. The longitudinal relaxation rate and inverse diffusion coefficient were approximately equally dependent on concentration and only increased by upto 20% from that of the salt solution. The transverse relaxation rate at high field demonstrated greatest concentration dependence, changing by an order of magnitude across the concentration range examined. We attribute this primarily to chemical exchange. Activation energies appeared to be approximately independent of aggrecan concentration, except for that of the low-field transverse relaxation rate, which decreased with concentration.
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Goetz, Wolfgang A., Emmanuel Lansac, Hou-Sen Lim, Patricia A. Weber i Carlos M. G. Duran. "Left ventricular endocardial longitudinal and transverse changes during isovolumic contraction and relaxation: a challenge". American Journal of Physiology-Heart and Circulatory Physiology 289, nr 1 (lipiec 2005): H196—H201. http://dx.doi.org/10.1152/ajpheart.00867.2004.
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Left ventricular (LV) longitudinal and transverse geometric changes during isovolumic contraction and relaxation are still controversial. This confusion is compounded by traditional definitions of these phases of the cardiac cycle. High-resolution sonomicrometry studies might clarify these issues. Crystals were implanted in six sheep at the LV apex, fibrous trigones, lateral and posterior mitral annulus, base of the aortic right coronary sinus, anterior and septal endocardial wall, papillary muscle tips, and edge of the anterior and posterior mitral leaflets. Changes in distances were time related to LV and aortic pressures and to mitral valve opening. At the beginning of isovolumic contraction, while the mitral valve was still open, the LV endocardial transverse diameter started to shorten while the endocardial longitudinal diameter increased. During isovolumic relaxation, while the mitral valve was closed, LV transverse diameter started to increase while the longitudinal diameter continued to decrease. These findings are inconsistent with the classic definitions of the phases of the cardiac cycle.
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Houmard, J. A., R. Smith i G. L. Jendrasiak. "Relationship between MRI relaxation time and muscle fiber composition". Journal of Applied Physiology 78, nr 3 (1.03.1995): 807–9. http://dx.doi.org/10.1152/jappl.1995.78.3.807.
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The relationship between nuclear magnetic resonance relaxation time obtained with magnetic resonance imaging (MRI) and muscle fiber composition of the lateral gastrocnemius was examined in 13 men. There was a positive correlation (r = 0.80, P < or = 0.001) between longitudinal relaxation time and the relative percentage of slow-twitch muscle fibers (type I). There was no relationship between transverse relaxation time and type I percentage (r = 0.17, P = 0.57). These results suggest that MRI longitudinal relaxation time can be used for the noninvasive estimation of muscle fiber composition in humans.
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Peng, Jinpeng, Zhanchao Liu, Tengyue Wang, Yunkai Mao i Binquan Zhou. "Fast calibration of magnetic field coils in miniaturized NMRGs from Rabi oscillation of nuclear spins". AIP Advances 13, nr 2 (1.02.2023): 025037. http://dx.doi.org/10.1063/5.0137689.
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We propose a fast and accurate method for the in situ calibration of the transverse coils in miniaturized nuclear magnetic resonance gyroscopes based on the Rabi oscillation of hyperpolarized gaseous 129Xe nuclear spins. In contrast to the conventional method based on the free induction decay initial amplitude of different pulse durations, this method circumvents the error introduced by the frequency detuning of the transverse driving field. We experimentally confirm that the accuracy of the calibration is influenced by the longitudinal relaxation time T1, the transverse relaxation time T2, and the magnitude of the transverse driving field B1. Through the numerical simulation of Bloch equations, we show that the behavior of [Formula: see text] and M z can be completely specified by two dimensionless quantities a and b, and we provide a ready-to-use selection criterion of b ≥ 24 for choosing the proper B1. By switching the embedded magnetometer into the longitudinal mode, we demonstrate the effectiveness and efficiency of our new calibration method. Finally, we examine the effectiveness of the selection criterion with our new calibration method. This method is expected to improve the authenticity of coil calibration and relaxation measurement in a more efficient way.
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Weininger, Ulrich, Carl Diehl i Mikael Akke. "13C relaxation experiments for aromatic side chains employing longitudinal- and transverse-relaxation optimized NMR spectroscopy". Journal of Biomolecular NMR 53, nr 3 (lipiec 2012): 181–90. http://dx.doi.org/10.1007/s10858-012-9650-5.
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Su, Fu-Hu, Wang-Chuan Xiao, Sheann-Huei Lin i Qiyong Li. "Cross-linked polydimethylsiloxane colloid as novel contrast agent for gastrointestinal magnetic resonance imaging: Transient nuclear Overhauser effect within the interface". Journal of Biomaterials Applications 35, nr 2 (4.05.2020): 264–73. http://dx.doi.org/10.1177/0885328220921528.
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With good contrast in T1 and T2 weighted imaging as well as low toxicity in 3- (4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay, this work proposes the cross-linked polydimethylsiloxane colloids as a novel non-ionic contrast agent for gastrointestinal magnetic resonance imaging. The experiments of nuclear magnetic resonance spectra and relaxation show that within the interface of the colloids, there are nuclear Overhauser effect and transient nuclear Overhauser effect (cross-relaxation). Regarding the longitudinal relaxation experiments of CH2CH2O segments of Tween 80, a two spins system is found and modeled well by the equation [Formula: see text] which is deduced based on the transient nuclear Overhauser effect proposed by Solomon. The arbitrary constant X is additionally added with the initial conditions ( Iz − I0) t=0 = −2 XS0 and ( Sz − S0) t=0 = −2 S0. For the two spins system, D1 and T1 are corresponding to longitudinal relaxation times of the bound water and the CH2CH2O respectively. Concerning the transverse relaxation experiments of the CH2CH2O, they agree with the equation with three exponential decays, defined by three relaxation times, likely corresponding to three mechanisms. These mechanisms possibly are intramolecular and intermolecular dipole–dipole (DD) interactions and scalar coupling. Within the interface, hydrogen bonding causes the positive nuclear Overhauser effect of the CH2CH2O’s nuclear magnetic resonance spectra, the transient nuclear Overhauser effect of the CH2CH2O’s longitudinal relaxation experiments and the intermolecular dipole–dipole interactions of the CH2CH2O’s transverse relaxation experiments.
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Yamamoto, Ei, Kozaburo Hayashi i Noritaka Yamamoto. "Effects of Stress Shielding on the Transverse Mechanical Properties of Rabbit Patellar Tendons". Journal of Biomechanical Engineering 122, nr 6 (29.06.2000): 608–14. http://dx.doi.org/10.1115/1.1319660.
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With the aim of studying mechanisms of the remodeling of tendons and ligaments, the effects of stress shielding on the rabbit patellar tendon were studied by performing tensile and stress relaxation tests in the transverse direction. The tangent modulus, tensile strength, and strain at failure of non-treated, control patellar tendons in the transverse direction were 1272 kPa, 370 kPa, and 40.5 percent, respectively, whereas those of the tendons stress-shielded for 1 week were 299 kPa, 108 kPa, and 40.4 percent, respectively. Stress shielding markedly decreased tangent modulus and tensile strength in the transverse direction, and the decreases were larger than those in the longitudinal direction, which were determined in our previous study. For example, tensile strength in the transverse and longitudinal direction decreased to 29 and 50 percent of each control value, respectively, after 1 week stress shielding. In addition, the stress relaxation in the transverse direction of stress-shielded patellar tendons was much larger than that of non-treated, control ones. In contrast to longitudinal tensile tests for the behavior of collagen, transverse tests reflect the contributions of ground substances such as proteoglycans and mechanical interactions between collagen fibers. Ground substances provide lubrication and spacing between fibers, and also confer viscoelastic properties. Therefore, the results obtained from the present study suggest that ground substance matrix, and interfiber and fiber–matrix interactions have important roles in the remodeling response of tendons to stress. [S0148-0731(00)00806-2]
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Chen, Ming-Jye, Shu-Hsien Liao, Hong-Chang Yang, Hsin-Yi Lee, Yi-Jia Liu, Hsin-Hsien Chen, Herng-Er Horng i Shieh-Yueh Yang. "Characterizing longitudinal and transverse relaxation rates of ferrofluids in microtesla magnetic fields". Journal of Applied Physics 110, nr 12 (15.12.2011): 123911. http://dx.doi.org/10.1063/1.3671420.
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Dmitriev, Vladimir V., Ivan V. Kosarev, Norbert Mulders, Vladislav V. Zavjalov i Dmitry Ye Zmeev. "Measurements of longitudinal and transverse magnetic relaxation in superfluid confined to aerogel". Physica B: Condensed Matter 329-333 (maj 2003): 322–23. http://dx.doi.org/10.1016/s0921-4526(02)02070-7.
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Müller, Norbert. "Observation of multi-exponential longitudinal and transverse relaxation in two-dimensional NMR". Chemical Physics Letters 131, nr 3 (listopad 1986): 218–23. http://dx.doi.org/10.1016/0009-2614(86)80549-8.
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